Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3700324 A
Publication typeGrant
Publication dateOct 24, 1972
Filing dateJan 27, 1972
Priority dateJan 27, 1972
Also published asCA1005508A1, DE2251926A1, DE2251926B2, DE2251926C3
Publication numberUS 3700324 A, US 3700324A, US-A-3700324, US3700324 A, US3700324A
InventorsHerbert C Artelt Jr, Mark A Hutner, Neil A Polit, Donald W Watson
Original AssigneeXerox Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrophotographic printing systems
US 3700324 A
Abstract  available in
Images(5)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent Hutner et al.

[54] ELECTROPHOTOGRAPHIC PRINTING SYSTEMS [72] Inventors: Mark A. Hutner, Glenview; Neil A. Polit, Cary; Donald W. Watson, Arlington Heights; Herbert C. Artelt, Jr., Wildwood, all of ill.

[73] Assignee: Xerox Corporation, Stamford,

' Conn.

[22] Filed: Jan. 27, 1972 [211 App]. No.: 221,229

[52] US. Cl ..355/6, 355/7 [5 1] Int. Cl. ..G03g 15/00 [58] Field of Search ..355/6, 7

[56] References Cited UNITED STATES PATENTS 2,859,673 11/1958 Hix et al. ..355/6 2,927,516 3/1960 Hix ........355/6 Primary ExaminerRobert P. Greiner Attorney-James J. Ralabate et al.

[5 7] ABSTRACT Improved electrophotographic printing systems are provided in accordance with the teachings of the present invention wherein a plurality of coded data To Scanning 6 Selection Circuit Flq. 3

[ Oct. 24, 1972 records containing document information are scanned by code sensing devices and presented to electrophotographic imaging means at which the document information is imaged upon a photosensitive member and processed according to electrophotographic techniques for subsequent presentation to a transfer station. Code information from each of the plurality of data records scanned as provided by the code sensing devices is processed in accordance with selected conditions for printing and print and-skip information is generated in sequence therefrom. The sequence of print and skip information is propagated through logic circuitry at a rate corresponding to the rate at which document information from each of the plurality of coded data records is electrophotographically processed in such manner that each bit of information in the print and skip information sequence is present at a predetermined output of the logic circuitry at a time when document information from the data record associated therewith is presented to the transfer station. At the transfer station, a transfer member which is normally maintained in a position displaced from the photosensitive member is continuously charged by an ion charging device and a transfer member assembly is provided to selectively bring the transfer member from its displaced position into a transfer relationship with the photosensitive member in response to the presence of a bit representing a print signal at the predetermined output of the logic circuitry.

23 Claims, 12 Drawing Figures PATENTEU OCT 24 I972 sum 5 [IF 5 1 ELECTROPHOTOGRAPHIC PRINTING SYSTEMS BACKGROUND OF THE INVENTION This invention relates to electrophotographic printing techniques and more particularly to selective electrophotographic printing systems wherein desired conditions for printing may be set and document information present on a plurality of coded records may be selectively printed whenever the coded conditions of any such plurality of coded records meets the desired conditions set.

The widespread adoption of data processing techniques to all facets of business and commerce has rendered the storage of business records, mailing lists, employee files and the like on coded data records commonplace. Although the information stored in this form may be selectively retrieved by the utilization of data processing equipment, it is often desirable to directly provide the information present on the coded records retrieved in the conventional form of permanent documents which may be directly employed without further duplication. Where the coded data records take the form of a data card or the like which contains both a data area for coding'and an infonnation area wherein document information is contained in a form viewable by an observer but not readable by the data processing equipment, it was often necessary to first employ the data processing equipment for the purposes of selective retrieval and thereafter to utilize conventional copying equipment to duplicate the document information from each data card retrieved so that permanent documents which could be directly employed were obtained. As this multi-step mode of selective information retrieval was often time consuming, required the maintenance of costly specialized equipment which was frequently not utilized to its full potential and often failed to provide the information retrieved in a document format most suitable for utilization; the need became manifest for selective printing equipments capable of receiving coded data records in this format and directly printing the document information contained on any of such coded data records meeting the selection conditions set while providing a wide range of selectively.

For instance, although similar problems obtain wherever business records, personnel files or any other material which is to be selectively printed is stored on coded records of the foregoing kind, the need for selective printing equipment of the type mentioned above may be readily appreciated by a consideration of the specific case of mailing lists from which labels for addressing envelopes are prepared. In a typical case, addressing information for each individual present in a mailing list is maintained in document form on a codable data record or card and such data record or card is coded with information designating certain characteristics, i.e. business data, personal data, interest data personal and business, and the like, of the individual whose address is present on that record. These data records may be maintained in separate groups in accordance with preselected characteristics or may be individually retrieved in accordance with the characteristics selected for particular mailing by known data processing techniques assuming that the cost of the necessary data processing equipment therefor is justified by the frequency of its utilization. Thereafter, the data records selected may be loaded in bulk in electrophotographic printing apparatus which acts to retrieve information in bulk, such as the label printing apparatus disclosed in US. Pat. No. 3,674,352 issued July 4, 1972, to Raymond A. Wilmes and assigned to the Xerox Corporation. In the electrophotographic printing apparatus disclosed, a plurality of data cards in the form of address cards, microfiche or the like are loaded and processed on a continuous basis so that document information from each of the data cards loaded is sequentially reproduced on a paper web. Upon the completion of the run of selected data cards, the paper web may be removed from the electrophotographic printing apparatus and cut or torn along perforated portions of the web to obtain the desired label for addressing purposes from each of the data cards loaded. The electrophotographic printing apparatus disclosed in US. Pat. No. 3,674,352, supra, employs highly efficient continuous electrophotographic processing techniques wherein a photosensitive member in the form of a drum is relied upon and charging, exposure, development, transfer and cleaning stations are disposed about the periphery thereof so that continuous processing is achieved. Thus, as each of the plurality of data cards is fed toward the exposure station, a peripheral portion of the photosensitive member, whose area is sufficient to accommodate the document information on the data card, is sensitized at a charging station formed by conventional corotron apparatus and exposed to image radiation representing the document infonnation on the data card so that a latent electrostatic image is formed. Thereafter as the peripheral portion of the photosensitive member containing the latent electrostatic image formed rotates at a constant angular velocity toward the development station, a latent electrostatic image of the document information on the next data card is in the process of being formed on an adjacent peripheral portion of the photosensitive member. As each peripheral portion of the photosensitive member containing a latent electrostatic image rotates through the development station, conventional cascade development techniques are employed to cascade triboelectrically charged toner particles over the photosensitive member so that charged toner particles are deposited in a selective pattern on each peripheral image portion of the photosensitive member in accordance with the charge pattern exhibited by the latent electrostatic image formed. Upon the completion of rotation through the development station, each peripheral image portion of the photosensitive member rotates toward the transfer station wherein the toner image is transferred to a paper web or sheet. At the transfer station, corona charging techniques are employed to insure that high quality toner image transfer to the paper web or strip results while problems associated with the charging inefficiency, humidity sensitivity and susceptability to toner clogging upon a breakage of the transfer web inherent in other charging apparatus, such as transfer rollers, are avoided. In this apparatus, it should be noted, that corona charging techniques may be employed without difficulty because as each image formed on the photosensitive member is transferred, the transfer member may be continuously maintained in contact with the photosensitive member and hence problems associated with bringing a charged transfer member in contact with a photosensitive member are avoided. Upon completion of the image transfer, the toner image present on the paper web is fused to render it permanent while the peripheral. portion of the photosensitive member which has been processed through the transfer station rotates to a conventional cleaning station where the residual toner is removed so that such peripheral portion of the photosensitive member may again be employed in the formation of another latent electrostatic image when the rotation of the photosensitive drum next brings it into an operative relation with the charging and exposure stations associated with the latent electrostatic image formation to thereby achieve continuous electrographic processing.

Although the prior art, as exemplified by the DICK STRIP printing apparatus disclosed in US. Pat. No. 2,859,673 to I.M. Hix et al., has provided some highly specialized equipments which appear capable of providing successful selective printing operations for specified input and output conditions; such prior art has not, to the knowledge of the inventors herein, provided a generalized approach to selective electrophotographic printing systems which enable the high speed, high quality selective printing of document information present on coded data records taking any conventional format while allowing a relatively wide ambit of selectively with respect to the form of coding employed to be maintained. More particularly, the prior art selective printing apparatus of which the present inventors are aware has only provided highly specialized selective printing apparatus which has been unable to produce high quality toner images on a transfer member because highly efficient corona charging transfer techniques were considered unavailable due to problems associated with air gap ionization when a charged transfer member is selectively brought into contact with a toner image to be transferred. To avoid these problems lower efficiency charging techniques were employed which resulted in relatively low quality toner image formation on the transfer member as well as relatively long transfer intervals. Furthermore, the charging techniques employed tended to be highly susceptible to changing humidity conditions and whenever misfeed or breakage of the transfer member would occur, for instance in the case of a transfer roller, would directly act to remove toner from the photosensitive member and subsequently become clogged with toner. In addition, selection information generally was physically rotated with the photosensitive member so that only limited data processing functions were available and hence the selectivity associated with a given printing operation was highly restricted and only a limited number of control functions could be derived from the selection information which was processed.

Therefore, it is an object of the present invention to provide electrophotographic printing systems which enable high speed selective printing of document information present on coded data records which may take any conventional format.

It is a further object of the present invention to provide selective electrophotographic printing systems employing ion charging techniques at the transfer station thereof so that high quality toner images of document information which is selectively printed may be produced on a transfer member.

It is an additional object of the present invention to provide selective electrophotographic printing systems wherein a wide ambit of selectivity is available to an operator and may readily be increased or decreased to suit a specific need.

It is another object of the present invention to provide selective electrophotographic printing systems wherein selection information is logically processed independently of document information but propagated in a manner which relates in time to the processing of such document information whereby such logically processed selection information may be employed to control various operations in the processing of such document information.

It is a further object of the present invention to provide selective electrophotographic printing systems wherein document information from each of a plurality of coded data records is processed using continuous electrophotographic imaging techniques but only document information from selected ones of said coded data records is selectively transferred to a transfer member using improved transfer station charging and transfer member handling techniques.

Other objects and advantages of the present invention will become clear from the following detailed description of an exemplary embodiment thereof, and the novel features will be particularly pointed out in conjunction with the claims appended hereto.

In accordance with the teachings of the present invention, an electrophotographic printing system is provided wherein a plurality of coded data records containing document information are scanned by code sensing means and presented to electrophotographic imaging means whereat the document information therefrom is imaged upon a photosensitive member and processed according to electrophotographic techniques for subsequent presentation to a transfer station; code information from each of said plurality of data records scanned as provided by said sensing means is processed in accordance with selected conditions for selective printing and print and skip information is generated in sequence therefrom; said sequence of print and skip information is propagated through logic circuit means at a rate corresponding to the rate at which document information from each of said plurality of coded data records is electrophotographically processed in such manner that each bit of information in said print and skip information sequence is present at a predetermined output of said logic circuit means at a time when document information from the data record associated therewith is presented to said transfer station; at said transfer station, a transfer member which is normally maintained in a position displaced from said photosensitive member is continuously charged with ion charging means and means are provided to selectively bring said transfer member from said displaced position into a transfer relationship with said photosensitive member in response to the presence of a bit representing a print signal at said predetermined output of said logic circuit means.

The invention will be more clearly understood by reference to the following detailed description of an exemplary embodiment thereof in conjunction with the accompanying drawings in which:

FIG. 1 illustrates selective printing apparatus and associated components of an exemplary embodiment of a selective electrophotographic printing system in accordance with the teachings of the present invention;

FIGS. 2A 2D depict exemplary timing apparatus for the instant embodiment of the selective electrophotographic printing system;

FIG. 3 illustrates an exemplary embodiment of a scanning and selection circuit for the instant embodiment of the selective electrophotographic printing system;

FIG. 4 shows an exemplary embodiment of a logic and control circuit which may be employed in the instant embodiment of the selective electrophotographic printing system;

FIG. 5 is a detailed pictorial view of a portion of the selective transfer member mechanism illustrated in FIG. 1; and

FIGS. 6A6D illustrate the various relationships which obtain between the transfer member and the toner image to be transferred during a typical selective transfer operation in the embodiment of this invention shown in FIG. I wherein FIG. 6A depicts the relationship between the transfer member and the toner image at a point where selective transfer is initiated, FIG. 6B shows this relationship at a point where the selective transfer member has been brought into a transfer relationship with the toner image to be transferred, FIG.

6C depicts this relationship at a point when the transfer of the toner image from the photosensitive member to the transfer member has just been completed and FIG. 6D shows this relationship at a point where the transfer member is displaced from the photosensitive member at the completion of a selective transfer.

Referring now to the drawings and more particularly to FIG. 1 thereof, there is depicted a selective printing apparatus which constitutes that portion of the exemplary'embodiment of the instant invention that employs electrophotographic concepts originally disclosed in US. Pat. No. 2,297,691, issued to CF. Carlson on Oct. 6, 1942. Such selective printing apparatus is comprised of a continuously rotating photosensitive drum 20, having displaced along its periphery a charging station G, an exposure station C, a development station D, a transfer station E, and a cleaning station F.

Photosensitive drum 20 has been illustrated as a simple two layer drum including an insulating member 31 and conductive member 32. As the photosensitive drum 20 forms no part of the instant invention per se, it is here sufficient for an appropriate understanding of this disclosure to appreciate that if the selective printing apparatus is employed in conjunction with conventional electrophotographic techniques, the conductive member 32 may be formed of any suitable conductive material or a nonconductor overcoated with a conductive foil. Similarly, the insulating member 31 may be formed of a material displaying photoconductive characteristics such that the insulating member 31 is normally insulating and exhibits excellent charge retentivity but may be rendered selectively conductive by the application of electromagnetic radiation thereto through a light and dark pattern representing an object to be copied or, alternatively, freflection exposure techniques may be employed. The materials relied upon in the formation of the insulating member 31 may be selected from any of the well-known groupof materials conventionally employed in the electrophotographic processes:

form of a projection system 33 wherein optical transmission techniques are relied upon to sequentially image a light and dark pattern representing each data card 1 of a deck of data cards onto the surface of the insulating member 31. In FIG. 1, a slit exposure device 34 has been generally indicated, however, any optical system which relies upon lenses or the like may be readily employed. Additionally, although the exposure station C, illustrated in FIG. 1, has been shown positioned in such manner that the rotating photosensitive drum 20 is initially sensitized by the charging station G and subsequently exposed at station C, it will be apparent that the processing steps of charging and exposure may be carried out simultaneously by altering the position of the exposure station C and/or the charging station G. Furthermore, although only the simplified processing steps of a single charging operation and a single exposure are depicted in FIG. 1, it will be obvious that additional electrophotographic processing steps such as another charging operation may be employed in the formation of the latent electrostatic image or the latent electrostatic image formed may be reversed or otherwise altered by the use of such additional processing steps as is well known to those of ordinary skill in the art.

Development station D comprises hopper arrangement 35 suitable for subjecting incremental portions of the photosensitive drum 20 to a cascade development step or the like as is well known to those or ordinary skill in theart. For example, the hopper arrangement 35 driven by a developer motor 24 may take any of the conventional forms of devices generally employed in electrophotographic development equipment to flow charged, finely divided particles, known as toner, to the imaged area to deposit in a selective pattern of the electrostatic image previously formed.

Image transfer station E comprises a charging means 30 for imposing a predetermined charge on a portion of a transfer strip 9 within close proximity to the photosensitive drum 20 to thereby effect transfer of a toner image from the surface of the photosensitive drum 20 to the transfer strip 9 upon the latter engaging the former. The transfer strip 9 may be formed of suitable transfer material such as paper, plastic or any of the other well-known materials conventionally employed as transfer materials. The charging means such as those discussed in conjunction with the charging station G may be employed, it being appreciated that any charging means capable of imposing a predetermined charge level on the surface of the transfer strip 9 may be employed at the image transfer station E. The charging means 30 illustrated in FIG. 1 may be connected to a suitable source of potential, for example a conventional d.c. supply.

Cleaning station F may take the conventional form of rotating fur brush cleaning means, wiper means or cascade cleaning means which act in a well-known manner to remove residual toner from the surface of the photosensitive drum 20. As each of these techniques is well known to those of ordinary skill in the art, it is here sufficient to simply state that the cleaning station F acts to remove residual toner particles from the surface of the photosensitive drum 20 to thereby place the same condition for reuse.

A description of the remaining component parts of the selective printing apparatus depicted in FIG. 1, and in part in FIG. 2, is hereinafter set forth in conjunction with a general summary of the operation of such apparatus.

A plurality of data cards various ones of which are to be selectively printed are stacked in a feeder tray 2 and are fed, one by one, by means of a feeder roller 6 through a scanning station B and a projection system 33 to a restack tray 49. Coaxially mounted about a drive shaft of feeder roller 6 are two laterally displaced collars and 10'. Each of the collars 10 and 10' includes an adjustment screw 19 or 19' for enabling lateral and rotational adjustment along and about the drive shaft 5. Further, collars 10 and 10' have coaxially attached thereto timing discs 4 and 4, respectively. Coaxially mounted on collar 10 is a collar 11, and on collar 10' a collar 11'. Collars 11 and 11' include adjustment screws 21 and 21, respectively, for lateral and rotational adjustment along and about the collars l0 and 10, respectively. Coaxially attached to the collars l1 and 11' are, respectively, timing discs 3 and 3. Fixedly positioned between the disc combinations defined by discs 3 and 4, and 3 and 4, is a light source 7. On the side of the disc combination 3 and 4 remote from light source 7 is a photosensitive device 8, while on the side of disc combination 3' and 4 remote from light source 7 is a photosensitive device 8'. Upon each revolution of the feeder roller 6 in the clockwise direction, the open angular slot 0 as depicted in FIG. 28 will permit light radiation to pass between the light source 7 and the photosensitive device 8. Further, upon each such revolution of the feeder roller 6, the open angular slot 0 as depicted in FIG. 2C will permit light radiation to pass between the light source 7 and the photosensitive device 8. The photosensitive device 8 constitutes a portion of a system clock 70 of the logic and control circuit depicted in FIG. 4. As hereinafter described in detail with respect to the operation of such circuit, photosensitive device 8 generates for each revolution of the feeder roller 6 a dark edge triggering pulse the duration of which is determined by the preset displacement between the leading edge of disc 3 and the trailing edge of disc 4(360 0) as the feeder roller 6 is rotated in the clockwise direction. The photosensitive device 8' constitutes a portion of a selective transfer timing generator means 98 (also hereinafter describedwith respect to FIG. 4) which produces a clock pulse having a duration indicated by the interval (360 +0" defined by the leading edge of disc 3 and the trailing edge of disc 4' for each clockwise revolution ofthe feeder roller 6. Since the relative positions of discs 3and 4, and 31 and 4, are such that angle 0 is less tha n angle 6', and since the leading edge of disc 3 leads the leading edge of disc 3' by the angle 5 as indicated in FIG. 2D, it will be apparent that the pulses provided by photosensitive device 8 will be synchronized with the pulses provided by photosensitive device 8', but will be of lesser duration and lead the pulses provided by photosensitive device 8' by the time required for the disc 6 to rotate through an angle of :1: degrees. Accordingly, as hereinafter described with respect to the logic and control circuit depicted in FIG. 4, since a single revolution clutch 15, when energized, is responsive to the leading edge of the system clock 70, while the selective transfer means 25 is immediately activated thereafter by the pulse provided by the selective transfer timing generator means 98, the transfer strip 9 is brought to the speed of the photosensitive drum 20 prior at or to the strip engaging the toner image on the photosensitive drum 20 at transfer station E.

Scanning station B is located along the path of travel of the data cards 1 from the feeder tray 2 to the restack tray 49, at a position before the slit exposure device 34 of the projection system 33. It is from this station E that the scanning and selection circuit of FIG. 3 scans precoded information on the data cards 1 for providing to the logic and control circuit of FIG. 4 print and skip signals in a properly timed sequence representing the actual rate at which data cards are scanned at station B. It is noted that each such signal is a print signal only if the selection of particular preconditions as established in the scanning and selection circuit of FIG. 3 by the state of the selection modules therein, are satisfied by the pre-coded information scanned from the data card to which such signal relates by the determination of the presence of particular pre-coded information thereon and, when established, the absence of other particular pre-coded information thereon. Further, though such signal is derived almost simultaneously with the scanning of the data card to which it relates at scanning position B, and appears at the output of inverter and buffer stage 69 depicted in FIG. 3, it is utilized in a timed sequenced manner by the logic and control circuit of FIG. 4 for various coordinated control functions of the various elements of the selective printing apparatus of FIG. 1. More specifically, such circuit of FIG. 4 is adapted to receive and sequentially shift such signals in their timed sequence through a plurality of stages so that there is acquired a direct correspondence between the stage to which a particular signal has been shifted, and the position to which the image on the photosensitive drum 20 to which such signal pertains has been rotated. Thus, the type of signal (print or skip) at a particular stage may be utilized by logic circuitry connected to such stage to control functions desired at the corresponding position of the associated image.

To achieve the above-noted operations, there are provided a card edge detector 50 that generates a pulse upon the leading edge of each data card 1 coming into the detecting station B, and a plurality of scanning means 50-50C at the scanning station B which are so positioned as to sense pre-coded information on each data card as it reaches station B. It is noted in this regard that the data cards, for the purpose of this exemplary embodiment, are characterized by a physical format that includes a row of identical bit locations, aligned perpendicularly to the direction of card travel, for pre-coding such cards in accordance with a predetermined code as applied to the visible document manner, pre-coded information is made available for" scanning at the scanning station B as the bit locations of a data card pass immediately adjacent to the plurality of scanning means 50-50C. Further, to achieve scanning at scanning station B by means of scanning means 50A-50C only during that interval of time that the bit locations of the data card entering the scanning station B are immediately adjacent to the scanning means 50A-50C, the scanning and selection circuit of FIG. 3 as hereinafter described, utilizes the aforesaid pulse from edge detector 50 to provide a periodic scanning function delayed by that increment of time that it takes each data card to move from the position whereat its edge was detected to the position whereat the bit locations on such data card are immediately adjacent the scanning means 50A-50C.

Various alternative card formats as to bit locations, and selective rearrangements of the space relationship of the scanning means 50A-50C, will be apparent to those of ordinary skill in the'art. Further, it will be apparent to those of ordinary skill in the art that if the scanning and selection circuit of FIG. 3 is modified so as to achieve sequential scanning by a single scanning means, rather than simultaneous scanning by a plurality of scanning means 50A-50C, an appropriate data card format for the bit locations may include a column of bit locations aligned in the direction of the data card travel and provided with a clock track or external clocking means.

The sequential passage of data cards from the scanning station B through the projection system 33 to the restack tray 49 will cause optical images of the document information on each of the data cards passing through the slit exposure device 34, to be sequentially projected, by means of mirror and lens arrangements of the projection system 33, upon the surface of said photosensitive drum 20. Since the photosensitive drum 20 is continuously driven at a constant angular velocity such that the surface thereof is moving at a velocity equal to that of the data cards moving past the exposure devices 34, latent electrostatic images of the document information of the data cards are formed on successive incremental areas of the photosensitive drum 20 as they pass through the exposure station C. Further, as any data card scanned at scanning station B will require an increment of time to pass from station B to the slit exposure device 34, and since the various stations about the periphery of the photosensitive drum 20 are at fixed spatial positions, and the photosensitive drum 20 has a constant angular velocity, the aforementioned print or skip signal for each data card scanned precedes in time, and has a particular time relationship between, the formation of the latent electrostatic image associated with such data card,-and the subsequent operational steps affecting such incremental area upon which such image has been formed as such area is moved through the various peripheral stations D, E, F and G.

Accordingly, as described in detail hereinafter with respect to the logic and control circuit of FIG. 4, print or skip signals for the data cards scanned may be utilized by such circuit to provide a plurality of logic and control functions, so as to achieve optimized coordinated control operations at the development station D and the image transfer station E. Further, as disclosed in US. Pat. Application No. 221,193 filed concurrently with this application and assigned to the same assignee, such print or skip signals may be utilized by a novel fuser arrangement to achieve additional operational benefits. Since such fuser arrangement is not a necessary component of the present invention, but, rather, a preferred form of a fuser arrangement that may be utilized with the exemplary embodiment of this invention if toner fixing is desired, only a general reference thereto is made herein.

Difiiculties inherent to selective printers that form latent electrostatic images for each data card scanned but only transfer developed images on a selective basis, are background-toner buildup and excessive use of toner at the development stations. Background-toner buildup in any such printer often occurs because the latent electrostatic images sequentially formed on the rotating photosensitive drum are all sequentially developed atthe development station, and then only selective ones of such developed images are transferred at the image transfer station. Thus, the cleaning stations in any such printer is required not only to remove residual toner from those incremental areas from which toner has been transferredat the image transfer station but, also, all the toner from the incremental areas from which no toner has been removed at the prior image transfer station because of a skip condition for such incremental area. Since all cleaning stations are less than ideally efficient in their removal of all toner from the incremental areas passing therethrough, backgroundtoner will increase cumulatively for those incremental areas that may be successively skipped a number of rotations of the photosensitive drum.

To minimize the unnecessary use of toner, as well as background-toner buildup, the aforesaid print or skip signal for each data card scanned is utilized, as hereinafter described, by the logic and control circuit of FIG. 4, to energize the developer motor 24 just prior to the entry in the development station D of an incremental area having thereon a latent electrostatic image of a data card having a print signal associated therewith, and to maintain such developer motor 24 energized only so long as any such incremental area so identifiable with a print signal is within the chamber of the development station D. Thus, the hopper arrangement 35 will be operated in an intermittent manner to decrease the number of latent electrostatic images developed at station D whose toner is not to be subsequently transferred at the image transfer station E because of skip signals associated therewith. Since such intemiittent operation of the hopper arrangement 35 assures development of the least all the latent electrostatic images to be subsequently transferred at the image transfer station E, as well as providing a decrease in the unnecessarily developed images, the amount of toner expended is decreased while the backgroundtoner buildup is minimized, resulting in higher quality printing at decreased cost.

To achieve selective image transfer at station E in accordance with the aforesaid print or skip signals provided to the logic and control circuit of FIG. 4, the selective printing apparatus depicted in FIG. 1 may comprise a selective transfer mechanism, a strip drive mechanism and a strip restraining mechanism. The selective transfer mechanism 25 is preferably of a kind disclosed in US. Pat. Application No. 221,230 filed concurrently with this application and assigned to the same assignee and, as depicted in FIG. 1 and partially in FIG. 5 hereof, comprises a pair of parallel extending T shaped support members 25a, the horizontal portions of each of which is coupled at one end thereof to an anchor member.25b in a manner to permit pivotable movement about a fixed axis 25c which is parallel to the axis of rotation of photosensitive drum 20; a support shaft 25d extending between the central portions of T support members 25a and having a longitudinal axis which is parallel to axis of rotation of the photosensitive drum 20; a strip turn-around roller 25e concentrically positioned about support shaft 25 d and freely rotatable about their common longitudinal axis; a stripper bar 25f extending between the ends of the horizontal portions of the T support members 25a furthest removed from the anchor members 25b, and extending in a direction parallel to the axis of rotation of the photosensitive drum 20; a base member 25g upon which the vertical portions of T support members 25a are supported and fixedly attached; and a bistable drive 25h having one end thereof attached to the base member 25g and the other end thereof fixedly positioned, such bistable drive including a normally energized contraction solenoid 27 for maintaining the selective transfer mechanism 25 (more particularly, the strip turn-around roller 25e) at a position removed from the surface of the photosensitive drum 20, and an expansion spring 28 for pivotably impelling at a high velocity, the selective transfer mechanism 25 in an arched upward direction toward the photosensitive drum 20 upon the deenergization of the solenoid 27. The strip drive mechanism in the instant exemplary embodiment takes the form of a single revolution clutch 15, a strip advance pin wheel 16 the intermittent rotation of which is controlled by the clutch 15, and a strip alignment roller 17; while the strip restraining device takes the form of a friction drag 18. Clutch is of a type that rotates a fixed predetermined amount upon each activation thereof by the leading edge of a pulse derived from the system clock 70. Accordingly, upon each activation of the clutch 15, the strip advance pin wheel 16 is rotated a fixed amount which in turn cause the transfer strip 9 to move a fixed amount, during a single machine cycle of, for example, 332 milliseconds. Preferably, the lateral movement increment of transfer strip 9 for each machine cycle is made equal to the size of the developed image to be transferred, thus acquiring the economies associated with adjacent image printing on the transfer strip 9.

As depicted in FIG. 1, the strip 9 is threaded in such a manner as to pass from a strip supply 13, through the friction drag 18, around the turn-around roller 25e, under the stripper bar 25f, through a fuser 40 if toner fixing is desired, around the strip alignment roller 17, and about the pin wheel 16, and into a strip receiving tray 14. This arrangement normally maintains the strip 9 in a constant state of relatively high tension (for example 8 oz.), whether the transfer strip 9- is moving preparatory to or during selective transfer of the developed image at the image transfer stage E, or stationary during a skip condition; and whether the transfer strip 9 is moving toward or away from the photosensitive member 20 preparatory to or completion of, selective transfer.

Briefly, the operation of selective transfer mechanism 25 of FIG. 1 may be readily appreciated from a perusal of the print cycle diagrams of FIGS. 6A-6D. As previously noted, the logic and control circuit of FIG. 4 includes a plurality of stages to which print or skip signals are sequentially shifted in direct correspondence to the particularly spatial positions of the corresponding images on the photosensitive drum 20. At the time a developed image having associated therewith a print signal arrives at the position slightly prior to that indicated in FIG. 6A, the associated print signal has been shifted to a particular one of such plurality of stages which has connected thereto logic circuitry that (i) causes the single revolution clutch 15 to initiate clockwise rotation of the strip advance pin wheel 16 so as to promptly accelerate the velocity of the strip 9 to the surface velocity of the photosensitive drum 20; and (ii) after a short delay, to release a selective transfer relay 26 so as to deenergize the contraction solenoid 27. Upon such deenergization, the expansion spring 28 causes the T support members 25a to pivot upwardly and, in so doing, to cause the strip turnaround roller 25c and the stripper bar 25f to also move upwardly, the latter by a greater distance in view of its greater relative position from the pivot axis 25c. FIG. 6B indicates the event status at that time when the contraction solenoid 27 has fully released and allowed maximum contact between transfer strip 9 and photosensitive drum 20.

As the turn-around roller 25e is on the side of the photosensitive drum 20 closest to the pivot axis 250, and the stripper bar 25f is on the other side of such drum and thus closer to the strip alignment roller 17, the above-noted upward pivotable movement causes the strip 9 to engage the photosensitive drum 20 in an arc of contact because an adjustable spring stop 280 on rod 28b within the expansion spring 28 is adapted to permit a total upward stroke that carries the turnaround. roller 25s to a position that though removed from surface of the photosensitive member 20, causes the taut transfer strip 9 to move beyond a tangential relationship with the photosensitive member 20. In cooperation with the adjustable spring stop 28a, is an adjustable solenoid stop 27a that limits the downward movement of an armature 27b of the solenoid 27. By means of spring stop 28a and solenoid stop 270 the terminal positions of movement of the turn-around roller 25e may be clearly established and, if necessary, finely adjusted so as to acquire a controlled constant arc of contact whenever the transfer strip 9 is engaged with the photosensitive member 20 during a print mode, and to maintain the transfer strip 9 at a specific position in close proximity of the surface of the photosensitive member 20 during a skip mode. The total lack of engagement between the turn-around roller 25e and the surface of the photosensitive drum 20 under all conditions of operations enables high velocity movements of such roller toward the photosensitive drum 20 without fear of damage thereto. Since the transfer strip 9 is maintained in a condition of high tension and is brought from a disengaged position to a position of engagement with the photosensitive drum 20 in a very short interval of time (for example, a distance of Va of an inch in 30 ms) a constant arc of contact is achieved almost immediately upon deenergization of solenoid 27.

FIG. 68 illustrates the relative position of developed image to be printed and the engagement of the moving strip 9 with the surface of the photosensitive drum 20 in an arc of contact. In the exemplary case wherein the toner images are approximately 1 inch in length, such are of contact may have a length of approximately 3/10 of an inch. Since the toner transfer is practically instantaneous upon engagement of the transfer strip 9 and the photosensitive member 20, the transfer of toner for those incremental areas within the initially established are of contact is practically instantaneous. Notwithstanding that the charging means 30 may preferably be constantly energized, air gap ionization is avoided by the short time interval engagement and disengagement of the transfer strip 9 and the photosensitive member 20 during selective printing operations, as well as the positioning of the charging means 30 so that its effective radiation pattern does not include the entrance point of the aforesaid arc of contact. This is considered in detail in the aforesaid U. S. Pat. Application Ser. No. 221,230.

FIGS. 6C and 6D illustrate the conditions that pertain as the image being transferred moves through and away from the image transfer station B. As will be apparent from FIG. 6C, the further transfer of the developed image after the initial engagement of the strip 9 and the photosensitive drum 20 to form an arc of contact will be at the velocity of such drum and strip, since it is at this velocity that subsequent incremental areas of transfer strip 9 come into the arc of contact and then result in instantaneous toner transfer. FIG. 6C illustrates the conditions that pertain when the trailing edge of a toner image to be transferred is fully within the arc of contact between the transfer strip 9 and photosensitive drum 20; where, therefor if the next following toner image is not to be transfered, transfer strip 9 must be removed from the photosensitive drum 20 to avoid transfering any part of the next toner image. FIG. 6D shows the status of events which pertain when the single revolution clutch has moved one complete toner image increment and, thus, itself comes to a stop and thus stops the longitudinal motion of the transfer strip 9 while photosensitive drum continues to rotate. As hereinafter described with reference to the logic and control circuit of FIG. 4, the contraction solenoid 27 will be energized and the strip 9 returned to its normal disengaged position if the stage of such circuit preceding the stage referred to above with respect to FIG. 6A, has not received a print signal indicating that the following image on the photosensitive drum is also to be printed. With respect to the transition from the conditions that prevail as indicated in FIG. 6C and those that prevail in FIG. 6D, the energization of solenoid 27 will cause, in the exemplary case of 1 inch toner images the stripper bar f to move down and into engagement with transfer strip 9 in the vicinity of the beginning of the transferred image which usually does not include significant toner and thus does not result in: a smear problem. Such movement of the stripper 25f in conjunction with the downward movement of the tum-around roller 25c causes forces to be applied at two closely positioned locations on opposite sides of the transfer station E to overcome the electrostatic and other forces of attraction between the transfer strip 9 and the photosensitive member 20. In those situations wherein toner smear may be a significant problem, an alternative for the stripper bar 25f would be the substitution therefor of a vacuum bar extending in close proximity to the surface of the transfer strip 9 opposite to the surface upon which toner images are formed and activated during all non-print modes of operation.

An exemplary embodiment of the scanning and selection circuitry for association with the selective printing apparatus of the embodiment of this invention shown in FIG. 1 is schematically illustrated in FIG. 3

while an exemplary embodiment of the appropriate logic and control circuitry for association with such apparatus is depicted in FIG. 4. In the description of FIGS. 3 and 4 which follows, it has been assumed that conventional, commercially available TIL logic is utilized throughout for each of the gates, inverters, registers and flip-flops employed, while conventional integrated circuit operational amplifiers are relied upon for the amplifiers shown. Therefore, as will be apparent to those of ordinary skill in the art, complementary logic such as NOR elements are often relied upon to accomplish AND and/or OR functions so that design requirements can be optimized both in terms of a reliance upon logic elements which are readily available in the market place as well as the utilization of a minimum number of components. Accordingly, it will be appreciated by those of ordinary skill in the art that any of the specific logic components or arrangements described in conjunction with FIGS. 3 and 4 may be replaced by other components or groups thereof which produce similar outputconditions in response to similar input conditions even though the mode of logical operation employed thereby differs at the component level from that set forth in conjunction with FIGS. 3 and 4 so long as the resulting modification is calculated to achieve the same result or a slightly varied result directed to the same purpose. Furthermore, although 'I'IL logic and integrated circuit operational amplifiers, as mentioned above, are assumed to be utilized throughout the exemplary circuitry embodiments described in conjunction with FIGS. 3 and 4, MSI, individual circuit components or MOS implemented circuit chips may be readily substituted without any deviation from the inventive teachings contained herein.

Scanning and Selection Circuit Referring now to FIG. 3, there is shown a schematic representation of an exemplary scanning and selection circuit for the embodiment of the selective printing apparatus illustrated in FIG. 1. The exemplary scanning and selection circuit depicted in FIG. 3 comprises the card edge detector 50, the plurality of scanning means SOA-SOC, a plurality of data channels A-C associated therewith, a plurality of print selection modules 1-3, a decoder means formed by gating means 51 and 52, and gated output means 53. In a consistent manner with the description of the exemplary embodiment of the selective printing apparatus set forth above, it has been assumed that the raw data input which contains the document information to be selectively printed takes the form of individual data cards containing, in addition to visible document information, a row of 12 bit locations which are selectively encoded by marking or not marking each such bit location in accordance with a predetermined code applied to the document information contained in a given deck of such data cards. Additionally, it has been assumed that selection is achieved by scanning the mark or no mark information contained in a selected three of such 12 bit locations; however, as will be apparent to those of ordinary skill in the art from the symmetry of the exemplary circuit depicted in FIG. 3, any number of bit locations may be simultaneously scanned, depending upon the degree of selectivity required, by merely relying upon more or fewer scanning means 50A-50C associated with data channels A-C, or physically repositioning one or more of such scanning means over a different bit location. Accordingly, even though three scanning means 50A-50C and three data channels A-C are illustrated in FIG. 3, it will be appreciated by those of ordinary skill in the art that this showing is intended by way of illustration and not by way of limitation.

The document detector 50 and each of the plurality of data scanning means 50A-50C may take the form of individual photosensitive devices such as phototransistors, photodiodes or the like, physically positioned, as indicated in FIG. 1, at appropriate locations to detect the information sought to be obtained. The card edge detector 50 is positioned, as shown in FIG. 1, to detect the leading edge of each data card as it is fed from the feeder tray 2 toward the scanning station B, due to the radiation blockage achieved by the card edge. As the document detector 50 only acts to ascertain the presence of an edge of a data card, capacitive or mechanical detectors could be employed in place of the photosensitive device illustrated. Similarly, each of the plurality of data scanning means 50A-50C are positioned opposite the bit positions which are desired to be scanned when a data card is in the predetermined scanning position, station E, and produces a signal representative of the mark or no mark condition of the bit location being sensed due to the differential in the radiation level received by the photosensitive device when mark and no mark conditions are detected. Suitable preamplification stages, such as conventional transistor amplifiers or operational amplifiers, are included within the card edge detector 50 and each of the data scanning means 50A-50C so that the signals produced thereby, negatively directed pulses representing mark information in the case of phototransistors, are suitably amplified to selected logic levels prior to their application to the remaining circuit portions depicted in FIG. 3. Additionally suitable noise traps, such as d.c. shunts to ground, are also preferably provided to reduce noise and avoid spurious output signals.

The output of the card edge detector 50 is connected to the scanning window timing generator means 54 which acts in response to the receipt of each input pulse from the card edge detector 50 to generate a pulse having a sufficient duration, such as 25 milliseconds, for scanning and data utilization to take place after a delay interval, such as 120 milliseconds,

equal to the time interval necessary for a data card or the like whose leading edge has been detected by the card edge detector 50 to reach an appropriate scanning location beneath the plurality of data scanning means 50A-50C. Although the scanning window timing generator means 54 may conveniently take the form of a conventional monostable multivibrator having a duty cycle equal to the desired pulse duration, 25 milliseconds for the case stated above, which is arranged in a manner well-known to those of ordinary skill in the art, to be triggered through a conventional delay device which in this case would exhibit a delay interval equal to milliseconds; it is preferred that the design of the scanning window timing generator means 54 insure against spurious outputs due to. the detection of the trailing edge of the data card. This can be conveniently achieved by gating the triggering pulses for said monostable multivibrator through another monostable multivibrator whose duty cycle is equal to the desired delay and which thereby produces a pulse of proper duration whose trailing edge acts to trigger the monostable multivibrator having a duty cycle of 25 milliseconds. The output of the scanning window timing generator means 54 is connected through conductor 55 to the flip-flop 56, to a timing input relied upon in the circuitry indicated in FIG. 4, as indicated, and to each of the data channels A-C, where as shall be seen below, it acts to open and close the scanning window in an appropriately timed manner so that only data is scanned and utilized. The time during which the scanning window is opened, as aforesaid, is preferably made sufficiently long so that data is read even under conditions where the data card or mark information thereon is skewed within acceptable limits. The flip-flop 56 may take the form of .a conventional monostable multivibrator arranged to be triggered by the trailing edge of the pulse provided by the scanning window timing generator means 54 and has a duty cycle, sufficient to produce a pulse of appropriate duration such as 1% milliseconds, to apply a gating signal for the gated output means 53. The output of the flip-flop 56 is connected to a timing input of the gated output means 53 and also applied to the conductor 55 to extend the time the scanning window of data channels A-C is open by 1%. milliseconds. Although a monostable flip-flop 56 has been illustrated, it will be apparent to those of ordinary skill in the art that alternative gating arrangements may be employed to achieve the same result.

The output of each of the plurality of scanning means 50A-50C are each connected to their associated data channels A-C, respectively. As the data channels A-C are identical, only data channel A has been shown in detail while the corresponding structure of data channels B and C has been indicated in FIG. 3 by the appropriately annotated blocks. Data channel A, as shown in FIG. 3, comprises threshold amplifier means 57, inverter means 58, flip-flop 59 and an inverter and bufier stage indicated by block 60. All of the elements illustrated within data channel A, as indicated by the dashed block, may comprise conventional integrated circuit operational amplifiers and standard TTL components commercially available from semiconductor manufacturers such as Texas Instruments Corporation or Fairchild Electronics. The threshold amplifier means 57 is connected at the inverting input thereof to the output of scanning means 50A while the threshold level thereof is set at the input thereof connected to potentiometer 61. The threshold amplifier means 57 acts in the well-known manner to discriminate between negative going input pulses exceeding the thresholdsetting thereof and those which do not exceed such threshold so that only negatively directed pulses exceeding a predetermined level are inverted and applied to the output thereof. The threshold setting of the threshold amplifier means 57 is set to a level to insure that only negatively directed pulses representing true mark information reach the output thereof and in this manner provides noise isolation. Additional isolation from spurious inputs may be provided by a.c. coupling and noise suppression networks of the type well-known to those of ordinary skill in the art. Accordingly, a positively directed pulse at the output of the threshold amplifier means 57 is indicative that mark information is present, while the absence of a pulse at the output of the threshold amplifier means 57 is indicative that no mark information is present and hence if a bit location is being scanned at this time that no mark is present. The output of the threshold amplifier means 57 is connected to the input of the inverter means 58 which may take the form of a conventional TTL inverter. The output of the inverter means 58 is connected to the input of the flip-flop 59. The flip-flop 59 is conventional; however, the clear input thereof is connected to the output of the inverter means 58 while the preset input thereof is connected to receive timing pulses from the scanning window timing generator means 54 through conductor 55. Due to these connections, as well known to those of ordinary skill in the art, the flip-flop 59 will normally be held in a reset condition and hence may not be set by a negatively directed pulse from the inverter means 58 unless a timing pulse is present on conductor 55. Similarly, when the timing pulse on conductor 55 terminates, the flip-flop 59 will be returned to a reset condition and held in this state until the next timing pulse occurs regardless of the presence of spurious inputs from the inverter means 58. If the timing associated with the operation of the scanning window timing generator means 54 is recalled, it will be appreciated that the flip-flop 59 effectively acts as a scanning window whereby mark or no mark information may be stored therein only when the scanning window timing generator means 54 indicates that a data card is in a position for scanning by the production of a suitable timing pulse. The output of the flip-flop 59, wherein a positive or high level represents mark information while ground or a low level represents a no mark condition, is connected to the inverter and buffer stage 60. The inverter and buffer stage 60 may take the form of a conventional TTL inverter which exhibits a low output impedance and inverts the output levels of the flip-flop 59 applied thereto so that at the output thereof a low level represents mark information and a high level represents no mark information inthe bit locations sensed while the low impedance output insures against noise on the line. Although a plurality of signal inversions are employed in each of data channels A-C, it will be appreciated that this is merely a function of the logic arrangement employed and could be readily avoided by the utilization of other components and/or logic arrangements, such as deriving a low mark output level from the flip-flop 59.

The output of each of data channels A-C is connected from the inverter and buffer stage therein to each of the selection modules 1-3 in the manner indicated in FIG. 3. As the AND selection modules 1 and 2 are in all ways identical while OR selection module 3 varies from the AND selection modules 1 and 2 only by the substitution of a NAND gate for the single NOR gate employed therein and a slightly different data off condition, only the AND selection module 1 has been illustrated in detail in FIG. 3 while AND selection module 2 and the OR selection module 3 have been schematically indicated by the annotated blocks in FIG. 3. Therefore, although only AND selection module 1 is described in detail below, it will be appreciated that selection modules 2 and 3 take the same form and perform the same function except in areas specifically mentioned below.

The AND selection module 1 comprises a three positions switch means S S and S associated with each data channel A-C, respectively, a NOR gate 61 and a mode selection switch S Each of the three position switch means S S and S may take the form ofthe mechanical switch means shown and is employed to select whether mark or no mark information is to be detected from the data channel A-C associated therewith or alternatively a dont care condition may be selected by placing the switch means in the OFF position. The top position contact of each of the three position switch means S S and S annotated MARK, is employed when it is desired to select data cards having marks in the corresponding bit position scanned and is connected directly to the output of the inverter buffer stage 60 of the data channels A-C associated therewith in the manner indicated in FIG. 3. Thus, when a mark condition is scanned, a low level output will be present at the mark position contacts of each of the three position switch means S S while the detection of a no mark condition will be indicated by a high level output. The center position contact of each of the three position switch means S S and S annotated OFF, is utilized when the mark or no mark condition of the particular bit position being scanned is unimportant to the selection sequence being carried out. The off position contact of each of the three position switch means S S and S is connected to ground G through a conductor and hence this contact is maintained in a low condition regardless of the mark or no mark condition scanned. The bottom position contact of each of the three position switch means S S and S annotated NO MARK, is employed when it is desired to select a condition where the bit position being scanned does not contain a mark. This contact of each of the three position switch means S S and S is connected through an inverting gate 63A-63C, which may take the same form as the inverting gate 58, to the output of its associated data channel A-C. Thus, in the case of the NO MARK terminal of the three position Switch means S S a mark condition will be indicated by a high level output while the selected no mark condition is indicated by a low level output condition. Accordingly, it will be seen that at each of the three position switch means S S whenever the condition selected is present in the bit position of the data card being scanned, a low level output will be applied from the selected position contact of the three position switch means S S to the wiper contact thereof; however, when a non-selected condition is detected a high level output will be applied to the wiper contact from the selected contact.

The wiper contacts of each of the three position switch means S S are each connected through conductors 64A 64C, respectively, to the NOR gate 61. The NOR gate 61 may take the form of a conventional 'I'TL NOR gate; however, due to the input conditions employed, the NOR gate 61 functions in the same manner as an inverting AND gate. Thus, whenever all the inputs from the plurality of the three position switch means S S are low, indicating that the selected input conditions are satisfied by the bit positions of the data card being scanned, the AND input conditions for NOR gate 61 are satisfied and the output thereof goes high. However, when one or more of the inputs from the plurality of the three position switch means S S are high, indicating that the selected input conditions have not been satisfied by the bit positions of the data card being scanned, the AND input conditions for NOR gate 61 are not satisfied and the output thereof goes low. At this point in the description of FIG. 3, it will be appreciated that additional bit position selectivity is readily available and may be achieved merely by adding further data scanners SOD-Z, the data channels D-Z therefor as well as their associated inverter gates 63D 632, three position switch means S S and inputs 64D 642 to NOR gate 61.

The output of NOR gate 61 is connected through conductor 65 to terminals a and d of the mode selection switch S The mode selection switch S may take the form of a conventional double pole three position switch, such as a wafer switch or the like, wherein the wiper contacts are ganged as indicated for concurrent rotation. The upper and lower contacts a and d of the mode selection switch S are connected to the output of NOR gate 61, as aforesaid, while the central pair of contacts b and c are grounded as indicated in FIG. 3. The mode selection switch S is employed so that the mode of operation of the selective printing apparatus with respect to data cards meeting the AND data requirements set by the three position switch means S S may be selected. More particularly, the mode selection switch S may be employed to cause the printing, i.e., select, of the document information contained on data cards meeting the AND data requirements set by the three position switch means S S by setting the mode selection switch S to the SELECT position wherein contacts a and b are utilized; to cause the document information contained on data cards meeting the AND data requirements set by the three position switch means S S not to be printed, i.e., a skip, by setting the mode selection switch S to the SKIP position wherein contacts c and d are employed; and to disable the action of the AND selection module 1 by setting the mode selection switch S to the OFF position, wherein contacts b and c are employed, whereby any data conditions which may have been set by the three position switch means S S do not affect the printing or non-printing of the document information on a defined data card.

The upper wiper contact of the mode selection switch S is connected to the conductor annotated SELECT 1 indicating that the logic level on this conductor is associated with select or print information from the AND selection module 1, while the lower wiper contact thereof is connected to the conductor annotated SKIP 1, indicating that the logic level on this conductor is associated with skip or no print information. The manner is which the logic levels on the SELECT 1-3 and SKIP 1-3 conductors are utilized to control the operation of the selective printing apparatus according to the present invention will be explained below. Here, however, it is sufficient to appreciate that whenever the AND data conditions set by the three position switch means S S are present on a data card being scanned, a high level will be present at the output of NOR gate 61 while when such data conditions are not present a low level output will be present at the output of NOR gate 61. Thus, when the mode selection switch S is in the SELECT position, contacts a and b, conductor SKIP 1 will always have a low level thereon due to the grounded condition of contact b while conductor SELECT 1 may have a high or low logic level thereon depending upon whether or not the data card being scanned meets the AND data conditions set by the three position switch means S S Conversely, when the mode selection switch S is in the SKIP position, contacts c and d, conductor SELECT 1 will always have a low level thereon due to the grounded condition of contact c while conductor SKIP 1 may have a high or low logic level thereon depending upon whether or not the data card i being scanned meets the AND data conditions set by the three position switch means S S In the OFF position of the mode selection switch S both the SELECT l and SKIP l conductors are in a low logic condition due to the grounded condition of contacts b and c. Therefore, it will be seen that the AND selection module 1 allows for the selection of data cards coded via marks or no marks having all of up to three specified bit location criteria while the mode selection switch S allows the operator to define data cards so selected to be either selected for printing or skip mode operation.

The AND selection module 2 is identical, as aforesaid, to the AND selection module 1 and therefor allows for a second selection of data cards coded via marks or no marks having all of a second set of up to three specified bit location criteria while its mode selection switch S (not shown) allows the operator to define the second set of data cards so selected to be either selected for printing or skip mode operation. The OR selection module 3 differs from the AND selection module 1, described above, in that the OFF position of each of the three position switch means S S is tied to a high level rather than ground and a NAND gate is substituted for the NOR gate 61 wherein all of the connections to such NAND gate are the same as those specified in conjunction with NOR gate 61. The substituted NAND gate, as will be appreciated by those of ordinary skill in the art, acts as an inverting OR gate rather than an inverting AND gate and hence the substituted NAND gate will provide a high output level whenever any one of the specified bit conditions set on the three position switch means S S (not shown) is present while providing a low level output only when none of such specified data card bit conditions are present. The OFF position of each of the three position switch means S S is here tied to a high level so that a select will not occur whenever a dont care condition is specified in the absence of at least one of the specified criteria. Thus, the OR selection module 3 allows for a third selection of data cards coded via marks or no marks having any one of a third set of up to three specified bit location criteria while its mode selection switch S (not shown) allows the operator to define the third set of data cards so selected to be either selected for print or skipped. Although three selection modules 1-3 have been shown in FIG. 3, it will be apparent to those of ordinary skill in the art that a greater or lesser number of selection modules may be employed to provide the necessary selectivity for a desired application by merely adding or subtracting AND and/or OR selection modules to the cascaded selection modules depicted in FIG. 3.

The select conductors SELECT 1-3 of each of the selection modules 13 are connected to one of the logic inputs of NOR gate 51 while each of the skip conductors SKIP 1-3 are connected to one of the logic inputs of NOR gate 52. Additionally, another input to NOR gate 51 is connected to ground while the output of NOR gate 51 is connected to an input of NOR gate 52. The NOR gates 51 and 52 may take the same form as NOR gate 61; however, the input conditions of NOR gates 51 and 52 are such that NOR gate 51 is operated as an inverting OR gate while NOR gate 52 is operated as an inverting AND gate. The NOR gates 51 and 52 form a decoder circuit for the various select and skip logic inputs provided by the selection modules 1-3 which function in such manner that a skip input has priority so that document information from a scanned data card which produces a skip output from one of the selection modules l-3 and also produces a select output from another of the selection modules '1-3 will not be printed. The NOR gate 51 functions as an inverting OR gate, as aforesaid, and accordingly when any of the inputs thereto is at a high level, representing a select condition, the NOR gate 51 will produce a low level output which now represents a select level; however, a high level output from NOR gate 51, which now represents the absence of a select condition, is only reproduced when all of the inputs thereto are low. The NOR gate 52 functions as an inverting AND gate,.as aforesaid, and hence will only produce a high output level, which here represents a select or print condition, when all of the inputs thereto are low. However, when any of the inputs to NOR gate 52 are high, the output thereof will be low to thus indicate a no print or skip condition. As it will be recalled that a skip conditionis indicated on skip conductors SKIP 1-3 by a high level while a no skip condition is indicated on skip conductors SKIP 1-3 by a low level and the NOR gate 51 will only provide a low level output on conductor 66 when at least one high or select input is applied thereto; it will be seen that all of the inputs of NOR gate 52 will be low to thereby produce a high level select signal when at least one select level is applied to NOR gate 51 and no skip level on conductors SKIP l-3 is present. Under all other conditions, the output of the NOR gate 52 is low indicating a skip condition to thereby provide priority for 'skip signals which may be applied on conductors SKlP1-3. The input to NOR gate 67 is a force high input which is employed when all the data cards scanned are to be printed and acts when the Print ALL key (not shown) is depressed to force the output of NOR gate 52 high irrespective of any other inputs which may be applied thereto.

The output of NOR gate 52 is connected through conductor 68 to one input of AND gate 53 which may take the form of conventional AND gate means which produces a high output level only when both inputs thereto are high. The second or timing input to AND gate- 53 is connected to the flip-flop 56 which, as aforesaid, produces a 1% millisecond pulse at the termination of the timing pulse window. The output of the AND gate 53 is coupled through the inverter and buffer stage 69, which may take the same form as inverter and buffer stage 60, to the logic and control circuit illustrated in FIG. 4.

In considering the operation of the exemplary embodiment of the scanning and. selection circuit illustrated in FIG. 3, it willbe assumed that it is desired to print the document information from any data cards in a selected deck which have data combination 010 respectively in the three bit positions of the data cards present in the selected deck as we as document information from all data cards having a 1 in the first or third bit positions scanned except those having the combination 111, wherein mark information is taken as representing 1, no mark information is taken as representing a 0 and data channels A-C may be considered to be the first, second and third bit locations scanned, respectively. Under the exemplary select conditions specifiedthe three position switch means S and S and AND selection module 1 may each be set to their no mark positions while S is set to its mark position and the mode selection switch S is set to the SELECT position to thereby provide for the printing of data cards wherein the data combination 010 appears in the bit positions scanned. Similarly the three position switch means S and S present in OR selection module 3 would be set to their mark position while three position switch means S is set to its OFF or dont care position and the mode selection switch S is set to its select position to thereby provide select levels from all data cards scanned having a l in the first or third bit position scanned. The exemption, i.e., dont print 11 1, for the general OR condition specified is provided by setting each of the three position switch means S S in the AND selection module 2 to its mark position while setting the mode selection switch S to its skip position to thereby provide for a no print level in response to the detection of the exempted condition. Thereafter the selected deck of data cards may be loaded in the feeder tray and the start button for initiating a selective printing operation depressed.

In the operation of the exemplary embodiment of the scanning and selection circuit illustrated in FIG. 3, as each data card is fed into scanning station B, its leading edge is detected by the card edge detector 50, as aforesaid, and after a sufficient delay has elapsed for the data on the fed data card to reach a position beneath the scanning means 50A 50C, the scanning window timing generator means 54 will apply a pulse of sufficient duration to the flip-flop 59 in each data channel A-C to open the scanning window and maintain it in an open condition until the bit position data has been scanned and processed. Typical values for the delay provided between the detection of the leading edge of 23 the data card and the generation of the scanning window timing pulse may be of the order of 120 milliseconds while the duration of the scanning window timing pulse applied to conductor 55 may have an exemplary value of 25 milliseconds. When the scanning window is opened by the application of the timing pulse on conductor 55 to the preset input of flip-flop 59 in each of the data channels A-C, as aforesaid, the flipflops 59 will be released from their forced reset condition so that their logic state may be set. At this instant, the detected data card will be at the scanning station and hence the output condition of scanning means 50A-50C will represent the mark or no mark condition of the selected bit locations on the data card being scanned. After threshold discrimination and inversion by the threshold amplifier means 57 and the inverter means 58, the output condition of each of the scanning means 50A-SOC is applied as a setting input to the flipflops 59 in such manner that a negatively directed pulse, indicating mark information, acts to set each flip-flop S9 to its high level while the absence of such a pulse maintains the flip-flop 59 in its reset or low output condition. The output level of the flip-flops 59 in each of the data channels A-C is inverted and buffered by the inverter and buffer stage 60 and applied to all of the selection modules 1-3. Thus, each of the flip-flops 59, due to the scanning window timing pulses applied thereto, acts as a properly timed gating device while allows data to be inserted therein only when the scanning of bit information is assured while allowing the possible skew of such bit information within reasonable limits.

The output of the data channel A is directly applied to the mark contacts of the three position switch means S A S and is additionally inverted at the inverter 63A and applied to the NO-MARK contacts of switches S S Similarly, the output level of data channels B and C are applied to corresponding contacts of three position switch means S S and S S respectively in the same manner specified for the three position switch means S S The operation of the selection modules I3 and the decoder formed by NOR gates 51 and 52 will be explained in terms of the data conditions sought to be detected as set out above; however, it should be appreciated at the outset that as each data card is scanned under the control of the timing supplied by the scanning window timing generator means 54, the bit location information obtained will be compared with the conditions set in the selection modules 1-3 and thereafter decoded by NOR gates 51 and 52 so that either a select, a high level print signal, or a skip, a low level no print signal, is present at the output of the NOR gate 52 for each data card scanned. These select and skip signals at the output of NOR gate.52, which appear one at a time in sequence, are applied to AND gate 53 through conductor 68 and gated therethrough due to the action of flip-flop 56, as aforesaid, so that for each card scanned either a print or skip signal is applied to the print control circuit shown in FIG. 4 in a properly timed sequence representing the actual rate at which data cards are scanned at the scanning station B.

Under the exemplary conditions set forth above, whenever a data card having the data combination 010 is scanned, a high-low-high output level will be present at the outputs of data channels A-C, respectively, due to the inversion carried out by the buffer and inverter stages 60. As the three position switch means S S in AND selection module 1 are set to their NO-MARK, MARK and NO-MARK conditions, respectively, all of the inputs to NOR gate 61 on conductors 64A-64C will be low, due to the action of inverters 63A and 63C, satisfying the AND condition input requirements of this gate. Therefore, as the mode selection switch S is in its select condition, a high level output will be present on conductor SELECT 1 while a low level output will be present on conductor SKIP 1. In AND selection module 2, it will be recalled that all of the three position switch means S 8 are set to their mark condition for detecting a 111 condition and hence a highlow-high input condition will be applied to the inputs of the NOR gate 61 present in the AND selection module 2. Therefore, as the AND requirements of NOR gate 61 present in the AND selection module 2 are not met, both the outputs on conductors SELECT 2 and SKIP 2 will be low. Similarly in the OR selection module 2, three position switch means S and S are set to their mark condition while switch means S is set to its OFF or dont care position which in the case of the OR selection module 2 is a high level, as aforesaid, to prevent the NAND gate 61 from producing a high level due solely to the setting of this position. Therefore, as none of the OR requirements of NAND gate 61 present in the OR selection module 3 are met, as only high level inputs'are applied thereto, both the outputs on conductors SELECT 3 and SKIP 3 are low. Thus, when a 010 condition is scanned under the switch selection settings set forth above, conductor SELECT 1 has a high level thereon while conductors SELECT 2 and 3 and SKIP l- 3 are maintained at low level. NOR gate 51, as aforesaid, acts as an inverting OR gate and hence will produce a low output on conductor 66. Therefore, as a low level is present on conductor 66 as well as on all of the skip conductors SKIP 1-3, the AND conditions of NOR gate 52 are satisfied whereby the output of NOR gate 52 goes high producing a print signal for the selected condition which has been detected.

In a similar manner, whenever a data card having a l or a mark in the first and/or third position scanned bit location is detected, one of the following set of output conditions will be present at the outputs of data channels A-C due to the inversion carried out by the buffer and inverter stages 60:

1 high high low 2 high low low 3 low high high 4 low high low 5 low low high 6 low low low the table, except the last, the output from AND selection module 2 will be low on both the conductors SELECT 2 and SKIP 2 because the mode selection switch S is set to skip thereby grounding conductor SELECT 2 whilethe 111 or MARK-MARK-MARK setting of the three positive switch means S S will only satisfy the AND input condition required by the NOR gate 61 in response to a detection of the last datacondition listed in the table. Thus, for data combinations 1-5 listed in the table, conductors SELECT 2 and SKIP 2 will both reside at a low level while in response to the last data combination listed in the table conductor SELECT 2 will be low and conductor SKIP 2 will go high.

The three position switch means S S in the OR selection module 3 are set, as aforesaid, to MARK- OF F-MARK so that any low level received at the mark input of the three position switch means S or S will meet the OR condition of NAND gate 61 therein and results in the production of a high level at the output thereof. Therefore, as the mode selection switch S is in the select condition, receipt of any of the input conditions listed in the table will result in a high level on conductor SELECT 3 and a low level on conductor SKIP 3 as this conductor is grounded. Accordingly, it will be seen that for any of input conditions l-5 listed in the table, conductor SELECT 3 will be high while conductors SELECT l and 2 and SKIP 1-3 are low. This meets the OR conditions of NOR gate 51 which places a low level on conductor 66 so that all low inputs are applied to NOR gate 52 resulting in the production of a high select level at the output thereof. When, however, input condition 6 as listed in the table is detected, a high is present both on conductors SKIP 2 and SELECT 3 while low levels are present on all of the remaining conductors. The high level on conductor SELECT 3, meets the OR requirements of NOR gate 51 so that a low is again present on conductor 66. The high on conductor SKIP 2, however, violates the and condition required by NOR gate 52 so that a low level output is present on conductor 68 and selectively gated through AND gate 53. Thus it is seen that the exemplary conditions for printing set forth above, are satisfied by the described settings for the selection modules 1-3 and result in select or print signals being gated to the logic and control circuit of FIG. 4when the desired conditions are detected while skip signals are conveyed in response to the scanning of data cards not satisfying such conditions.

Logic and Control Circuit FIG. 4 schematically illustrates an exemplary embodiment of a logic and control circuit for the selective printing apparatus according to the teachings of the instant invention. In the description of the exemplary logic and control circuit illustrated in FIG. 4, it may be assumed that conventional TTL circuitry is utilized throughout unless otherwise specified. The exemplary logic and control circuit illustrated in FIG. 4 comprises system clock 70, start-stop signal generator means 71, OR gate 72, flip-flop buffer stage 73, shift register means 74, logic control means for the developer motor 75, logic control means for the single revolution clutch 76, logic control means 77 for the selective transfer release 101, and counter means 78 for controlling the 26 operation of the relay for the start stop signal generator 104. The system clock may take the form of a radiation actuated clocking device which provides a pulse of a selected duration at a time corresponding to the feeding of a data card toward the scanning and exposure stations from the feeder tray. Although the function of the system clock may be implemented in several ways, it has here been accomplished by deriving a photosensitive input from the timing discs 3 and 4 mounted for rotation on the drive shaft 5 of the feeder roller 6 shown in FIG. 1. Thus, as shown in FIG. 1, a light source 7 is mounted on one side of the timing discs 3 and .4 and a photosensitive device 8 such as a phototransistor, photodiode or the like is mounted on the other side of such timing discs 3 and 4. Therefore, for each revolution of the feeder roller 6 the photosensitive device 8 shown in FIG. 1 will receive a radiation input when the trailing edge of disc 4 rotates past the photosensitive device 8 and such radiation input will be maintained until the leading edge of the disc 3 again blocks the input radiation from the light source 7. Accordingly, the photosensitive device 8 will, in the well known manner, generate a negatively directed pulse for each revolution of the feeder roller 6, whether a data card is fed or not, which pulsehas a duration determined by the displacement 0 between the trailing edge of the second timing disc 4 and the leading edge of the first timing disc 3. Conversely, the output of the photosensitive device 8 will be high during the entire interval (360 0) that it is blocked by the leading edge of the first timing disc 3 until it is again unblocked by the trailing edge of second timing disc 4 and it is this interval (360 0) which is employed to determine the duration of the clock pulses produced by the system clock 70. Thus, dark edge triggering is employed to drive the system clock 70 from the photosensitive device 8 and the time occurrence of the leading edge of the clock pulse produced thereby is determined by the position of the leading edge of the first timing disc "3 on the shaft 5 while the duration of the clock pulse as determined by the time occurrence of trailing edge of such clock pulseis determined by the position of the trailing edge of timing disc 4. Therefore, if it is assumed that in the data card embodiment of this invention being described, approximately three cards are .fed per second, the feeder roller 6 may be treated as completing one revolution every 332 milliseconds to cause the photosensitive device 8 to produce one pulse for each revolution thereby defining a machine cycle time of 332 milliseconds. The system clock 70 may then take the form of a Schmitt trigger, flip-flop or other well known form of squaring circuit, arranged in the wellknown manner to follow the output of the photosensitive device 8 applied thereto and hence to be triggered by the positively directed leading edge of the pulse produced by such photosensitive device 8 and reset by the negatively directed trailing edge thereof. For a machine cycle time of 332 milliseconds a clock, pulse of approximately 230 milliseconds duration is appropriate and hence the displacement 0 between timing discs 3 and 4 may be considered to be appropriate to set and reset the system clock 70 so that clock pulses having a duration of approximately 230 milliseconds are produced in response to the interval (360 0) of blockage. Furthermore, although the clock pulse duration is here adjustable by the adjustable positioning of timing discs 3 and 4, it will be appreciated that fixed duration timing pulses could be obtained by employing monostable multivibrators and under these conditions the number of timing discs could be reduced. Thus, under the conditions specified above for each revolution of the feeder roller 6, the system clock 70 will produce a clock pulse whose duration is approximately 230 milliseconds and whose leading edge is timed with the occurrence of the leading edge of the first timing disc 3 on the feeder roller 6. Although a Schmitt trigger or flip-flop has been indicated as forming the clock pulse generator for the system clock 70, it will be appreciated that other gating arrangements may be utilized therefor and that if extremely well defined or clean clocking pulses are desired a pair of Schmitt triggers ma be employed to provide additional input definition. The output of the system clock 70 is connected through conductor 79 to a reset input for the flip-flop buffer stage 73, a clocking input for shift register means 74 and a timing input for the logic control means for the single revolution clutch 76 which controls the advancing of the transfer strip 9.

The start-stop signal generator means 71 comprises a relay which is actuated when the selective printing apparatus according to the instant invention is operating and deenergized to stop such selective printing apparatus. This relay is actuated bythe depression of a start button for the apparatus and deenergized in a manner that will be rendered apparent below in con junction with the description of the function of the counter means 78. Here, however, it is only important to note that whenever the relay in the start-stop signal generator is deenergized, a low logic level is present at the output thereof which acts to clear the shift register means 74 for the next operational run and inserts a low print signal into OR gate 72 so that a blank strip is printed in between selected printing runs of the apparatus according to the present invention. The output of the start-stop signal generator means 71 is connected through conductor 80 to a clear input of shift register means 74 and to one data input of OR gate 72 The OR gate 72 comprises a conventional OR logic element which acts in the well-known manner to produce a predetermined output level whenever a selected input level is applied to either of the inputs thereto. One input of OR gate 72 is connected, as aforesaid, to the output of the start-stop signal generator means 71, while a second input thereof, as indicated, is connected to the output of the buffer and in verter stage 69 of the exemplary scanning and selection circuit shown in FIG. 3 and, accordingly, receives a sequence of gated select and/or skip levels therefrom corresponding to the print or no-print sequence of the deck of data cards being scanned. A low level input to the OR gate 72 represents a select or print instruction while a high logic level represents a skip or no-print instruction. It may be noted that for any given run, the first input to OR gate 72 is a low level from the startstop signal generator 72 so that a blank strip print out initiates the print out sequence while the remaining inputs for the cycle are provided from inverter and buffer stage 69 in FIG. 3 and correspond to the print or noprint sequence associated with the deck of data cards being scanned. The output of the OR gate 72 is connected to the input of flip-flop bufier stage 73. The flipflop buffer stage 73 is a conventional flip-flop which is here employed to temporarily store each select or nonselect signal applied to OR gate 72 for subsequent insertion into shift register means 74. The input to the flip-flop buffer stage 73 from OR gate 72 is connected to the Preset input thereof while the D input of the flipflop is grounded, whereby a select or low input from OR gate 72 sets the flip-flop buffer stage 73 to a high state and the flip-flop is automatically reset to its low state on the application of a clock pulse thereto from the system clock 70. The output of the flip-flop 73 is connected to a data input of shift register means 74. The shift register means 74 may comprise a conventional 16 bit shift register used to clock select and skip levels through the system at the rate at which data cards are scanned and processed; however, as TTL logic is preferred, it will be appreciated that the 16 bit register is actually formed of two 8 bit register chips connected in series in a manner well known to those of ordinary skill in the art. In the shift register means 74, a high level as received from the flip-flop buffer stage 73 represents a select signal while a low level represents a skip. The shift register means 74 may be classified as a serial in, parallel out shifting configuration and only outputs 5-12 have been indicated in FIG. 4 as it is only these outputs which are here of interest. The clock input of the shift register means 74 is connected to the system clock 70, as aforesaid, while the clear input thereof is connected to the start-stop signal generator 71.

The relationship between the document information from a given card as it is processed according to the electrophotographic techniques employed by the present invention, as specified in conjunction with FIG. 1, and the scanned information from the data card resulting in a print or skip signal being shifted through shift register means 74 is such that when select or skip signal reaches output 5 of the shift register 74, the document information is being imaged on the photosensitive drum. The imaged information forming a latent electrostatic image enters the development station D at a point in time when its processed scanning information has been entered into the stage 6 of the shift register means 74 but has not yet propagated to stage 7. The image information is rotated through the development station D while scanning information from its data card is shifted through stages 7-9 and leaves the development station D about the time the scanning information from its data card has entered stage 10. When the scanning information reaches stage 12 of the shift register, the developed image has reached a point on the periphery of the drum, due to the rotation thereof, which is slightly ahead of the transfer station E. The presence of given bits of scanning information within certain stages of the shift register means 74 may thus be employed to control the selective operation of the developer motor 24, the single revolution clutch 15 and the selective transfer means 25.

Outputs 5-10 of the shift register means 74 are connected in parallel to the logic control means 75 for the developer motor 24. As was stated in conjunction with the description of FIG. 1, it is desirable to operate the developer 13 in a mode wherein it is normally off to conserve on the use of toner, etc. and thus to energize

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3975715 *Oct 25, 1973Aug 17, 1976Xerox CorporationScanning and selection methods and apparatus therefor
US4248528 *Apr 4, 1979Feb 3, 1981Xerox CorporationCopier with document sensing control
US4310235 *Mar 13, 1980Jan 12, 1982Xerox CorporationJob programming
US4678322 *May 30, 1986Jul 7, 1987Xerox CorporationMethod and apparatus for the prevention of unauthorized copying of documents
US4791449 *May 30, 1986Dec 13, 1988Xerox CorporationSystem for prevention of unauthorized copying
US5168313 *Apr 27, 1989Dec 1, 1992Kabushiki Kaisha ToshibaToner image transfer method and device for electrophotographic printing apparatus
US6370354Aug 8, 2000Apr 9, 2002Lexmark International, Inc.Method and apparatus for controlling media-to-image registration of a single-pass intermediate transfer member-based printing apparatus
EP0037561A2 *Apr 1, 1981Oct 14, 1981E.I. Du Pont De Nemours And CompanyAutomatic reference background monitoring network for a film processor
Classifications
U.S. Classification399/297, 399/84
International ClassificationG03G15/30, G03G15/36, G03G21/00, G03G15/16, G06K15/14, G03G15/08, G03G15/00, G03G15/22
Cooperative ClassificationG03G15/30, G06K15/14, G03G15/507
European ClassificationG03G15/50N2, G06K15/14, G03G15/30
Legal Events
DateCodeEventDescription
Jun 20, 1988ASAssignment
Owner name: VIDEOJET SYSTEMS INTERNATIONAL, INC., ELK GROVE VI
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:XEROX CORPORATION, A CORP. OF N.Y.;REEL/FRAME:004945/0373
Effective date: 19880608