US 3809472 A
A pre-development exposure assembly is provided within an electrostatic reproduction machine transverse to the photoconductive surface thereof to selectively expose side portions of the photoconductive surface in response to a signal generated by a switch associated with the paper supply assembly responsive to paper size therein.
Claims available in
Description (OCR text may contain errors)
vO Umted States Patent 1 1 1111 3,809,472 Liechty  M 7, 1974 PRE-DEVELOPMENT EXPOSURE 3,685,894 8/1972 Lux et a1 355/3 ASSEMBLY 3133155; 13/1325 81*? 322132;
, ar 1 lnvemori Karl y, Pittsford, 3,122,455 2/1964 Grimm et a1 355/3 x Assigneez xerox Corporation, Stamford 3556.655 l/1971 Lux et a1 355/51 X Conn. Primary ExaminerRobert P. Greiner  Flled: 1971 Attorney, Agent, or Firm lames J. 'Ralabate  Appl. No.: 214,244
'  ABSTRACT  US. Cl 355/3 R, 355/16, 355/125 [51 Int. Cl. G03b 15/00 Predevelopmem .exposure assembly provlded  Field of Search 355/3 14 16 7 74 125 wlthm an electrostanc reproducnon machme trans- 5 verse to the photoconductive surface thereof to selectively expose side portions of the photoconductive sur- 56] References Cited face in response to a signal generated by a switch associated with the paper supply assembly responsive to I UNITED STATES PATENTS paper Size therein. 3,687,538 8/1972 Matsumoto 355/3 3,724,940 4/1973 Koizumi 355/3 5 Claims, 3 Drawing Figures T 42 a; 52 a 3- 5:-) 56 u 50 i (=3? E H \J V V 58 (i 1 k c. 4
1 PRE-DEVELOPMENT EXPOSURE ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to electrostatography, and more particularly to improvements in the control of development' with particulate toner material that is adapted for use in electrostatographic apparatus.
In the practice of xerography as described in U.S. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer .thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.
The latent electrostatic image may then be developed by contacting it with a finely divided electrostatically attractable material, such as a resinous powder; The powder is held in the image areas by the electrostatic fields on the layer. Where the field is greatest, the greatest amount of material is deposited; and where the field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the copy being reproduced. The powder is subsequently transferred to a sheet of ,paper or other surface and suitably affixed to thereby form a permanent print. i
The latest machine concept for copiers utilizes flash exposure of a document and the arrangement ofa mov-' ing photoconductor material in'the form of an endless belt. Additionally, the photoconductive surface of such a machine is continuously charged. In order to effectively develop the latent image produced in such machine with the provision for solid area coverage, a developing system is employed which supplies toner particles in relatively large quantities. Additionally, high production rates are more readily achievable by passing the image receiving member sideways through the transfer and fixing stations as distinguished from length-wise transit as performed by most prior art devices, e.g. line copy would be parallel to the direction of rotation of the photoconductive belt.
Such high-speed machines are also being provided with image reducing capabilities. Exposure of a translucent document on a platen to be reproduced in reduced size, results in unexposed planes on each side of the photoconductive surface, assuming alignment of the document as distinguished from edge alignment on the machine. Such planes, after passage through a solid area developing station, would contain a'high concentration of toner particles, i.e in effect, a'developed solid area image, although not in response to exposure of such area imagewise to light of an image to be reproduced. If the photoconductive belt is passed through a transfer station in contact with an image receiving member ofa length equal to the original document, the top and bottom of the receiving member will have a margin of .solid area coverage. If the receiving member is of a length corresponding to the length of the reduced image or less, the toner particles will pass through such station, with a portion adhering to the OBJECTS OF THE INVENTION It is an object of this invention to improve electrostatic reproduction machines for effecting high speed development of line copy and solid area with minimum waste of developing material.
Another object of this invention is to permit continuous operation of an electrostatic charging device in an electrostatic reproduction machine thereby allowing the high speed operation thereof.
SUMMARY OF THE INVENTION These and other objects of the invention are obtained by a pre-development exposure assembly disposed transverse to a photoconductive surface. The predevelopment exposure assembly is provided with pairs of cooperating slits and a discharge device positioned within the assembly and associated with each pair of slits for selective discharging of a moving photoconductor surface prior to development of an electrostatic latent image thereon. A control circuit is associated with each discharge device and is arranged to control the energization thereof in response to a signal generated by the interaction between a reduced magnification mode and a switch provided on a paper assembly actuated in response tothe length of paper thereon. The energization of the respective discharge devices dissipates the charged areas along selective areas on the photoconductive surface not exposed imagewise to a light pattern as hereinbelow discussed.
DESCRIPTION OF THE DRAWINGS A better understanding of the present invention as well as other objects and further features thereof will become apparent upon consideration of the following detailed disclosure thereof, especially when taken with the accompanying drawings, wherein like numerals designate like parts throughout.
FIG. 1 is a schematic sectional view of an electrostatic reproduction machine embodying the principles of the invention;
FIG. 2 is a plane view of the pre-development exposure assembly;
FIG. 3 is a cross-sectional view of the predevelopment exposure assembly taken along the lines of 3-3 of FIG. 2.
For a general understanding of the illustrated copier/reproduction machine in which the invention may be incorporated, reference is had to FIG. 1 in which the various system components for the machine are schematically illustrated. A document D to be cop- .ied is placed upon a transparent support platen P belt 12 arranged on a belt'assembly, generally indicated by the reference numeral 14.
The belt 12 comprises a photoconductive layer of selenium which is the light receiving surface and imaging medium for the apparatus, on a conductive backing. The surface of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device or corotron 13.
The belt is journaled for continuous movement upon three rollers 20, 21 and 22 positioned with their axes in parallel. The photoconductive belt assembly 14 is slidably mounted upon two support shafts 23 and 24 with the roller 22 rotatably supported on the shaft 23 which is secured to the frame of the apparatus and is rotatably driven by a suitable motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the portion exposed is that portion of the belt running between rollers and 21. During such movement of the belt 12, the reflected light image of such original document positioned on the platen is flashed on the surface of the belt to produce an electrostatic latent image thereon at exposure station A.
As the'belt surface continues its movement, the electrostatic image passes through a developing station B in which there is positioned a developer assembly generally indicated by the reference numeral 15, and which provides development of the electrostatic image by means of multiple brushes 16 as the same moves through the development zone.
The developed electrostatic image is transported by the'belt to a transfer station C whereat a sheet of copy paper is moved between a transfer roller and the belt at a speed in synchronism with the moving belt in order to accomplish transfer of the developed image solely by an electrical bias on the transfer roller. There is provided at this station a sheet transport mechanism generally indicated at 17 adapted to transport sheets of paper from a paper handling mechanism generally indicated by the reference numeral l8'to the developed image on the belt at the station C.
After the sheet is stripped from the belt 12, it is conveyed into a fuser assembly, generally indicated by the reference numeral 19, wherein the developed and transferred xerographic powder image on the sheet material is permanently affixed thereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus.
Further details regarding the structure of the belt assembly l4 and its relationship with the machine and support therefor may be found in the copending Application Ser. No: 102,312 filed Dec. 29, 1970 assigned to the same assignee, now U.S. Pat. No. 3,730,623, issued May 1, 1973.
The predevelopment exposure assembly of the present invention, generally indicated as 30, is positioned within the lower portion of the reproduction machine between the exposure station A and the developing station B, as illustrated in FIG. 1. Referring now to FIGS. 2 and 3, the pre-development assembly is comprised of a molded housing 32, a base 34 and discharge devices, such as fluorescent lamps 36'and 38 activated by a conventional energizing means (not shown).. The housing 32 is formed with a top wall 40, side walls 42 and 44, and end walls 46 and 48. Within the housing 32, there is provided an intermediate wall 50 forming chambers 52 and 54 in which fluorescent lamps 36 and 38, respectively are disposed. The top wall 40 of the housing 32 is formed with pairs of cooperating slits 56 and 58 which permit the passage of actinic radiation therethrough from fluorescent lamps 36 and38, respectively. The pre-development exposure assembly 30 is provided with a bracket means, generally indicated as 60, for mounting the assembly 60' within the electrostatic machine. i
Each of the fluorescent lamps 36 and 38 may be provided with a control circuit the numeral 62, such as described in copending application Ser. No. 145,013, tiled May 19, 1971, whichis a continuation of application Ser. No. 73l,967, filed May 24, 1968, now abandoned, filed by James M. Donohue, entitled SELEC- TIVE DEVELOPMENT CONTROL FOR ELECTRO- STATIC REPRODUCTION MACHINES, each of which control circuits being energized by a signal from a switch the numeral 64 provided on the paper supply elevator assembly, as described in copending application Ser. No. 214,345 filed Dec. 30, 1971 by Sission, et al relating to paper dimension sensing. The control circuits may also be energized by an operator through a reduced magnification mode of the machine.
In operation of a copier/reproduction machine, as hereinabove described, the endless photoconductive belt is continuously charged, for example, by corona charging from a coronode array, such as disclosed in U. S. Pat. No. 2,588,698 to Carlson. If in one mode, for example, the maximum dimension of paper in the supply assembly correspondsto that of the document to be copied, neither of the control circuits associated with the respective fluorescent lamps will be energized.
Should a signal be developed by a switch disposed on the supply assembly; sensing that the supply paper is of smaller dimension than the designed maximum dimension of the supply assembly, a corresponding control system is energized thereby illuminating the respective fluorescent lamp to expose continuously the side portions (i.e. cylindrical planes at the roller 21) of the photoconductive surface corresponding to an area determined by the width of the pair of slits through which the light passes. Alternatively, a fluorescent lamp may be activated in response to a signal indicative of a reduced magnification mode of the machine by the depression by an operator of an appropriate selection device. I
It will be appreciated that in the absence of such exposure, that developer particles will adhere to planes on the sides of the photoconductive surface. There being no image receiving surface of sufficient dimension at the transfer station D, some of the toner particles will attach .to the transfer roller with the subsequent requirementof transfer roller cleanup, while the remaining portion of the toner particles adhering to the belt will be removed by a toner clean-up brush, such as illustrated as 26 in FIG. 1. Thus without the present invention, it can be readily appreciated that excessive steps must be taken to provide for toner clean-up within such a copier/reproduction machine thereby presenting a serious solids handling problem, with a concomitant excessive consumption of toner particles.
While the present invention has been described with reference to the incorporation of two pairs of slits in .the pre-development exposure assembly, it will be understood that one, or three or more slits may be pro- 'ing slits at one end thereof instead of at both ends dependent'on the reference positioning of the document on the platen as well as the optic system to be employed in the machine. The principle of the present invention, while discussed with reference to a high speed machine employing an endless photoconductive belt being continuously charged, is applicable to high-speed drumtype electrostatographic machines regardless of the orientation in which the receiving members are transported therethrough. Discharge devices, other than fluorescent lamps may be employed in the present invention, e.g. corotrons, and the like.
While the instant invention as to its objects and advantages has been described herein as carried in specific embodiments thereof, it is not desired to be limited thereby, but it is intended to cover the invention broadly within the scope of the appended claims.
What is claimed is:
1. In an electrostatic reproduction machine havinga moving photoconductive surface adapted to be charged and to carry an electrostatic latent image thereon, and developing means positioned at a development zone to develop the moving electrostatic image on said surface, the developed-image being adapted for transfer to a suitable receiving member, the combination comprising:
a discharge device adapted when activated to discharge a charged area on a side portion of said surface, said device being positioned to discharge portions of said surface prior to development thereof;
meansadapted on a control signal to actuate said discharge device; and control means responsive to the size of the receiving member operative on a predetermined receiving member size to provide said control signal whereby said discharge "device is activated to remove the charge on the side portion of said surface extending beyond the edges of said receiving member.
2, In the electrostatic reproduction machine as defined in claim 1 wherein said device discharges charged areas on either side portions of said photoconductive surface.
3. The electrostatic reproduction machine as defined in claim 1 wherein said discharge means is a fluorescent lamp.
4. In an electrostatic reproduction machine having a moving photoconductive surface adapted to be charged and to carry an electrostatic latent image thereon, and developing means positioned at a development zone to develop the moving electrostatic image on said surface, the developed image being adapted for transfer to a suitable receiver member, the combination comprising:
means to provide an uncharged strip along the edge portion of 'said surface prior to development thereof;
means adapted to a control signal to actuate said first mentioned means; and
control means responsive to the size of the receiver member operative on a predetermined receiver member size to provide said control signal whereby said uncharged strip is provided between the edge of said receiving member and the edge of said surface.
5. An electrostatic reproduction machine as defined in claim 4 wherein said means to provide an uncharged strip is adapted to provide the uncharged strip on either side portion of said photoconductive surface.
I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 09 472 Dated May 7 1974 Invent Karl E. Liechty It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 6, claim 4, line 24, change 'to" (first occurrence) to on.
Signed and sealed this 24th day of September 1974.
McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMM-DC wan-Poo 9 Us, GOVERNMENT PRINTING OFFICE HID 0-366-334,