|Publication number||US3792913 A|
|Publication date||Feb 19, 1974|
|Filing date||May 12, 1972|
|Priority date||May 12, 1972|
|Publication number||US 3792913 A, US 3792913A, US-A-3792913, US3792913 A, US3792913A|
|Original Assignee||Xerox Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (19), Classifications (13)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1191 Simmons Feb. 19, 1974 [5 XEROGRAPHIC ERASE MECHANISM 3,671,121 6/1972 Albert 355 7  ento a y A S s Mac don NIY- 3,540,806 11/1970 Starkweather 355/8 X Assigneelv Xerox Corporation, Stamford, Primary ExaminerJoseph F. Peters, Jr. m Assistant Examiner-Michael L. Gellner  Filed: May 12, 1972 l 21 Appl. N011252,698 [571 ABSTRACT Apparatus suitable for use in an automatic xero- 52 us. c1. 355/7, 355/74 graphic repwqucing device for erasing aPomon 51 Int. Cl G03g 15/06 the electmstatlc charge recmded maged 58 Field of Search 355/3, 74, 7 mgraphic Plate the develoPmePt order to prevent development from occunng 1n at  Reerences Cited least one margin (iuiirtnagedd) rtegtilon thereofntfurther rneans are won e o a JUS e s1ze o e area 3 556 655 E I PATENTS 35 /55 erased in response to the size of the copy produced.
v ux et a 5 3,089,384 5/1963 Baasner 6 Claims, 5 Drawing Figures PATENTED FEB I 9 I974 SHEH 3 0F 3 FIG. 4
XEROGRAPHIC ERASE MECHANISM ious processing stations. The plate is first uniformly charged to a relatively high potential and the charge plate surface then exposed to a light image containing the original input scene information to be reproduced. Under the influence of the light image, the charge carried on the plate surface is selectivelydissipated in the light struck regions so as to record the original input scene information thereon in the form of a latent electrostatic image. The latent image is made visible by applying specially prepared electroscopic developer pow der, which is more generally known as toner, to the image bearing surface whereupon the toner particles are electrically attracted and loosely held in the more highly charged imaged areas thus rendering the electrical image visible.
Subsequent to the development operation, the visible toner image, which is loosely adhering to the plate surface, is generally transferred from the plate surface to a sheet of final support material such as paper or the like. One method for accomplishing image transfer is to place the final support sheet in overlying contact with the developed image and electrically treating the back side of the sheet'with corona thus causing the toner particles to be attracted from the plate surface to the contacting side of the final support sheet. Toner particles carried on the plate outside of the area contacted by the copy sheet, however, remain behind on the plate surface after completion of the transfer operation. This residual toner must be cleaned from the plate in some manner before a new copying cycle is initiated in order to prevent degrading subsequent produced copy.
Heretofore, plate cleaning did not pose a serious problem in the xerographic art simply because the copy sheet was usually of a size sufficient to cover the entire recorded original input scene information and most machines did not possess the capability for developing the large charged but unused margin region lying outside the domain of the original input scene information. However, with advances in the xerographic techniques, most of the newer xerographic copying machines in use today have such a solid area developing capability. As
'a consequence, it is now possible to develop the charged but unused margins surrounding the recorded input scene. These margins develop out as relatively large areas of highly dense toner concentration. Cleaning of'this large mass of toner from the plate surface not only places a heavy burden on the machines cleaning system, but also produces a great deal of unwanted dirt within the machine environments and is costly because of the sheer amount of wasted toner involved.
To avoid the above noted problems in machines having a solid area developing capability, erase lamps capable of discharging the plate surface in the initially charged but unimaged regions have been devised. Basically, this type oferase lamp is placed in a stationary position in regard to a moving photoconductive plate and the lamp is periodically energized to irradiate predetermined regions on the plate. The intensity and spectral output of the lamp is adapted so that the charge level in the irradiated zone is below the operating threshold level of the developing system thus preventing development. For further details and information concerning this type of erase mechanism reference is had to copending continuation application Ser. No. 145,013, filed in the name of Donohue. Although the Donohue type erase system has proven to be an efficient discharge device when employed in the normal Xerographic environment, it nevertheless does not readily lend itself to use in a machine where the size of the input scene information may vary between each imaging cycle.
It is therefore an object of the present invention to improve apparatus for erasing an electrostatic charge from a xerographic plate. I
It is a further object of this invention to provide apparatus for erasing the unused margin region of an exposed xerographic plate prior to development.
It is yet another object of this invention to provide an adjustable erase lamp capable of erasing varying mar gin widths along the side of a moving xerographic plate in response to the size of the copy sheet in process.
-Yet another object of this invention is to minimize the amount of unwanted development produced in an automatic xerographic reproducing machine.
A still further object of this invention is to reduce the amount of dirt produced in an automatic xerographic reroducing machine.
Yet another object of this invention is to reduce the amount of residual toner left on the photoconductive plate surface subsequent to the transferring of the image to a final support sheet.
These and other objects of the present invention are attained by means of an erase lamp mechanism posi tioned adjacent to a moving xerographic plate having a latent image recorded thereon. A lamp is arranged to irradiate a selected region alongat least one margin lying outside the imaged area to dissipate the plate charge below a level sufficient to sustain development. A shade is movably interposed in light blocking relationship between the erase lamp and the charged xerographic plate to block at leasta part of the illumination from irradiating the charged plate. The size of the copy sheet in process is sensed by means of a sheet sensing mechanism which is adapted to preposition the shade in relation to the lamp so that the charge in the unused margin region, that is, a region lying outside of the domain of the copy sheet, is erased prior to image development.
For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:
FIG. 1 is a schematic view showing the erase mechanism of the present invention embodied within an automatic xerographic processing machine;
margin of the moving xerographic recording plate found in the automatic machine illustrated in FIG. 1.
Referring now to the drawings, there is shown for the purposes of explanation an automatic xerographic reproducing machine incorporating the improved erase mechanism of the present invention. The copying ma- 7 chine employs a drum-like member 10, the outer periphery of which is furnished with a suitable xerographic imaging or photoconductive material 11 that is well-known and used to those skilled'in the art. Drum 10, which is suitably journaled for rotation within the machine frame by means ofa shaft 12, rotates in the direction indicated in FIG. 1 to bring the photoconductive image retaining surface 11 thereon past a plurality of xerographic processing stations. Suitable drive means (not shown) are also provided to power and coordinate. the motion of the various cooperating machine components to produce a faithful reproduction of the original input scene information.
I Since the practice of xerography is well-known in the art, the various processing stations for producing a copy of the original are herein represented as blocks A through E in FIG. 1. At station A, a uniform charge is placed upon the photoconductive surface of the drum. The charged drum surface is then passed to an exposure station B where at least a portion of the charged surface is exposed to a light image of the original input scene information so as to record the original input scene information thereon in the form of a latent electrostatic image. Developing means for applying toner material to the image bearing surface is provided at developing station C wherein the latent image is madevisible. The developed image is then brought into moving contact with a sheet of final support material 13 at a transfer station D wherein the toner image is electrically removed from the plate surface and placed in image configuration upon the contacting side of the final support sheet. Finally, at a cleaning station E, a cleaning mechanism, such as a fur brush or the like, is brought into operative contact with the photoconductive plate surface and the residual toner removed from the plate thereby placing the xerographic plate in a condition such that the plate can be again used in the xerographic process. I
It is herein contemplated that the sheets of final support material processed in the automatic xerographic reproducing device will be stored within the machine by means ofa removable paper cassette 14. It is further contemplated that the automatic reproducing machine will have the capability of accepting and processing copy sheets of varying lengths. The length of the copy sheet is dictated by the size of the original recorded upon the photoconductive plate with variations in length being perpendicular to the direction of sheet movement as it moves through the machine. To this end, the paper cassette is provided with an adjustable side margin so that sheets of varying lengths can be accommodated therein. In practice, the cassette is filled with a stack of paper 15 of a preselected size and the cassette inserted into the machine by sliding the cassette along a base plate 16 which guides the cassette into operable relationship with a pair of feed rolls 17. The feed roll mechanism is arranged to operate upon the uppermost sheet in the stack to separate the sheet from the remainder of the stack and to advance the separated sheet towards the transfer station. A registration mechanism 18 is interposed between the sheet supply station and the transfer station. The mechanism is arranged to momentarily intercept the leading edge of a sheet moving between the stations so as to align and register the sheet in relation to the developed xero' graphic image recorded on the drum surface. The copy sheet and the developed image are then advanced together through the transfer station wherein the image is placed upon the overlying sheet surface.
In operation, the top margin M of the xerographic image recorded upon the drum surface is registered in close parallel alignment with the upper edge 19 of the drum surface as seen in FIG. 2. The top side margin of the supply tray is also aligned'parallel with the end of the drum by means of an upright fixed margin guide 20 which serves to register the one side edge of the stack with the top edge of the image recorded on the drum. The right hand margin guide 21 of the cassette is adjustable so that the cassette can accommodate sheets of varying length therein.
The size of the copy sheet stored in the cassette is, of
course, dependent upon the size of the image recorded.
upon the xerographic drum. As can be seen, as the size of the recorded image varies in length, the width of the initially charged but unused margin region (X) along the bottom edge of the drum will also vary. Ordinarily, in a machine having a solid area developing capability, this charged but unimaged margin region will be developed with toner as the drum moves through the developing station. However, this toner will not be transferred to the final support sheet and will ultimately have to be cleaned from the drum before a new imaging cycle is initiated. The present invention is adapted to prevent this unwanted margin development from occurring and thus eliminating the added burden placed on the cleaning system as well as reducing the amount of dirt broadcast throughout the machine.
Positioned between the image exposure station B and the development station C is an erase lamp mechanism 25 capable of dissipating the initial charge created along the unused right hand margin of the drum. As noted, this unused drum region typically is that area on the drum surface which does not contain input data and as such does not come in contact with the copy sheet during transfer. By eliminating the charge in this unused region prior to development, the amount of plate cleaning necessary after image transfer is minimized and the amount of developer material required for each development cycle is considerably reduced.
The erase mechanism includes an electroluminescent panel 26 (FIG. 5) supported adjacent to and in close within a rigid holder 27 which serves to uniformly position the panel at a predetermined distance above the photosensitive surface. A shade member 28, the interior surface of which complements the exterior surfaces of-the panel and panel holder assembly, slidably encloses the panel in light-tight relationship therein. In this manner, the shade can be laterally repositioned in regard to the lamp so that margins of varying width (X) can be irradiated along the edge of the drum.
The slidable shade 28 is operatively connected to a sheet'sensing control mechanism 29, the operation of which will be explained in greater detail below, by means of an inextensiblecord 30 which is locked to the shade mechanism by suitable means as for example pin 35. In operation, the control mechanism senses the size or more particularly the length of the copy sheet being processed and slidably positions the shade in relation to the stationary erase lamp so that this unused margin region on the drum is irradiated with radiation to substantially reduce the charge in this area. In practice, the charge is reduced to a level below the development systems threshold potential level. As a result, the margin region remains undeveloped as it is moved through the subsequent developing station.
Referring more specifically to'FIGS. 2-4, there is illustrated a sheet sensing and control mechanism of the instant invention. The slidable shade 28 is normally mechanically biased to a rest position by means of a spring element 37 anchored in the left hand frame 38 (FIG. 2) of the machine. The spring exerts a force upon the inextensible cord 24-tending to pull the slide laterally along the lamp holder to a fully extended position against a stop 39 affixed in the lamp holder. Although the stop can be stationed anywhere along the lamp holder, it is desirable that it'be positioned in order to facilitate the smallest size exposure contemplated for processing in the automatic machine.
As can be seen in FIG. 2, cord 30, after passing through the slide mechanism, passes over a pairof small guide pulleys 40 mounted in the right hand frame 41 of the machine and then around a larger pulley 43 rotatably secured in horizontal mounting bracket 45 and finally the cord is secured to the free end of lever arm 46. The opposite end of the lever arm is movably supported within the sheet sensing mechanism of the instant invention, herein generally referenced by the numeral 29.
The sheet sensing mechanism is supported above the paper supply cassette upon the horizontal bracket 45 by means of a support bar 50 secured thereto in the manner best illustrated in FIGS. 3 and 4. Basically, the sensing mechanism generally includes a one way clutch mechanism 51, the previously noted lever arm 46, and a sheet sensing arm 52. The sheet sensing arm 52 is secured to the bottom portion of the clutch mechanism by means of a vertical shaft 54. A return spring 55 is wound about the shaft and is adapted to engage the sensing arm in a manner to continually urge the arm in a counter clockwise direction towards a home position wherein the sensing arm is normally positioned as illustrated in FIG. 3 with the free end of the arm extending beyond the adjustable right hand side margin guide 21 of the paper cassette.
A sensing arm actuator60 is rotatably pinned b means of a pivot 62 in the adjustable right hand margin guide 21 of the cassette. A clear square shaped aperture 61 is cut in the actuator through which passes a stationary pin 63 that is securely staked in the margin guide 21. A spring 65, also affixed to the margin guide and is arranged to continually force the bottom wall of the square apertureinto contact against the pin thus tending to normally support the actuator face 66 in a substantially vertical position.
In operation, when a cassette is inserted into the machine, actuator face 66 comes into moving contact with the free end of the sheet sending arm causing the arm to swing about its stationary pivot point in a clockwise direction as seen in FIG. 3. However, prior to the cassettes reaching its operative position in relation to the feed rolls, the actuator face releases the sensing arm thus allowing the arm to return to its normal home position. As can be seen, the degree of displacement of the sensing arm is dependent upon the position of the adjustable margin guide 21 in relation to the sensing arm pivot point. When relatively short sheets are stored in the stack the margin guide is positioned further away from the pivot point than when long sheets are stored therein. As a consequence, the degree of displacement of arm 52 is relatively small. Similarly when large sheets are stored in the cassette the margin guide is close to the pivot point and the displacement is relatively larger.
The movement of the sheet sensing arm is translated through the clutch mechanism to the lever arm 46 which is operatively attached to cord 30. As the sensing arm swings through its path of travel during the insertion of a cassette into the machine, the lever arm is caused to follow in a positive manner in'a clockwise direction. However, when the actuator face 66 releases the sensing arm, the clutch acts to lock the lever arm at its furthestmost point of rotation while, at the same time, freeing the sensing area to return to the home position. As can be seen, the position of the lever arm is therefore a direct indication of the size of the copy sheet being processed in the machine. This information is imparted directly to the shade mechanism via cord 30. By properly positioning the various elements, such as the pulley placements, the amount of angular displacement of the lever arm can be directly converted mechanically into a lever displacement of the lamp shade whereby a margin complimentary to the size of the copy sheet in process will be erased upon the drum surface.
Upon the removal of the cassette from the machine frame, a dog 68 engages a cam element 69 mounted on the sidewall of the cassette guide 16. The cam and dog imparts a horizontal motion to a slide member 70. The slide member, in turn, engages a lug 71 on the clutch mechanism mounted on the side of the sensing mechanism which acts to disengage the clutch releasing the lever arm and permitting the arm to return to its original starting position. A profile 72, machined on the working surface of the dog, is generated so that no motion is imparted to the slide mechanism by the cam when the cassette is inserted into the machine.
While this invention has been described with reference to the structure herein disclosed, it is not confined to the details as set forth and this application is intended to cover any modifications or changes that may come within the scope of the following claims.
What is claimed is:
1. A reproducing apparatus comprising: a photosensitive plate, means for forming a latent electrostatic image on said plate, means for reducing the charge in at least one unused margin region of said plate, means for developing said electrostatic latent image following said charge reduction in said marginal region, and means for transferring said image to a sheet of final support material, the improvement wherein said charge reduction means comprises:
a source of radiation capable of reducing the charge within said at least one margin region, said source being arranged to irradiate said at least one margin region;
adjustable shade means movably interposed in block- .ing relationship between said source and said plate to prevent at least partof the radiation from said source from irradiating said plate; and
means for adjusting the position of said shade in response to the size of the final support sheet.
2. An apparatus as in claim 1 wherein said shade is in sliding relationship with said source.
3. An apparatus as in claim 2 wherein said source comprises an electroluminescent lamp positioned adjacent to said plate.
4. in an automatic xerographic reproducing device of the type wherein a developed xerographic image is transferred from a moving photoreceptor surface to a final support sheet, apparatus to erase the charge along at least one side margin of the moving photoreceptor including,
an electroluminescent lamp positioned adjacent said moving member and being arranged to extend from one side margin of the member transverse said member to irradiate said charged member to dissipate the charge in the irradiated regions,
a movable shade mounted in light blocking relationship with said lamp and being arranged to move transverse to the direction of movement of said member whereby margins of varying widths are erasable on said member, and
means operable in response to the size of the final support sheet to position said shade whereby the charge in the margin of said member lying outside the imaged region is reduced to a level below the imaged development level.
5. In an automatic xerographic reproducing apparatus of the type having charging means to uniformly charge the entire image retaining surface of a moving photoconductive member, exposure means to selectively dissipate the charge on the plate to record original input scene information in the form ofa latent electrostatic image, the developing apparatus for making the latent image visible, and means to transfer the developed image to a sheet of final support material, the
an erase lamp positioned between the charging and vdeveloping means being arranged to illuminate at least one margin of said member to dissipate the charge thereon,
a movable shade arranged in light blocking relationship between the lamp and said member to vary the width of the margin erased,
sensing means to detect width of the final support sheet in process, and
means operatively connected to said sensing means to position said shade in response to the width sensed whereby the charge along said one margin lying outside the imaged region is reduced to a level below the image development level.
6. An automatic xerographic device of the type including means to move a uniformly charged xerographic plate through a series of processing stations including an exposure station wherein a latent electrostatic image is recorded on at least a portion of said plate surface, a development station wherein finely divided marking particles are attracted into the highly charged imaged areas on said plate thereby making the latent electrostatic image visible, and a transfer station wherein the developed image is transferred to a sheet of final support material brought into moving contact with said plate, apparatus for preventing unwanted development of the plate surface including an erase lamp positioned adjacent to the charged plate surface between the exposure station and the development station, said erase lamp being arranged to illuminate at least a portion of said charged plate surface to reduce the charge found thereon to a level sufficient to prevent development thereof,
a movable shade means interposed in light blocking relation between said erase lamp and the charged plate surface to prevent at least part of the illumination from said lamp from irradiating said plate whereby the charge on a preselected region of said plate is dissipated, and
control means to sense the size of the copy sheet moved into contact with said moving plate surface and to regulate the positioning of said movable shade in relation to said lamp whereby the charge on the plate surface moving through the transfer station lying outside of the sheet contact zone is reduced sufficiently to preclude subsequent develop-
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|U.S. Classification||399/190, 355/74|
|International Classification||G03G21/00, G03G15/00, G03G15/02, G03G15/047, G03G15/36, G03G21/10, G03G15/045|
|Cooperative Classification||G03G2215/0448, G03G2215/0443, G03G15/047|