US3672758A - Device and method for handling a flexible photoconductor - Google Patents

Abstract

A FLEXIBLE PHOTOCONDUCTIVE SHEET SUPPORTED BY OPPOSITE ENDS OVER A PLATEN FOR SUPPORTING A RECEIVING SHEET WHEREIN THE PHOTO CONDUCTIVE SHEET IS LOWERED WHILE AN ELECTRIC POTENTIAL IS APPLIED BETWEEN IT AND THE PLATEN TO CREATE AN ELECTRIC FIELD THEREBETWEEN. FIRST, ONE END OF THE PHOTOCONDUCTIVE SHEET IS BROUGHT INTO LINE CONTACT WITH THE RECEIVING SHEET AND HELD THERE-AGAINST BY ELECTROSTATIC FORCE. THEN, AS THE OTHER END IS LOWERED, THE PHOTOCONDUCTIVE SHEET PROGRESSIVELY CONTACTS THE RECEIVING SHEET, FORCING ANY AIR OUT FROM BE TWEEN THE SHEETS SO THAT THEY ARE HELD IN INTIMATE CONTACT BY THE ELECTROSTATIC FORCE. A CLAMPING MECHANISM IS USED TO HOLD THE RECEIVING SHEET DURING SEPARATION FROM THE PHOTOCONDUCTIVE SHEET FOLLOWING EXPOSURE TO AN ELECTROSTATIC IMAGE.

Description

June 27, 1972 w MacD N LD, JR

DEVICE AND METHOD FOR HANDLING A FLEXIBLE PHOTOCONDUCTOR Filed April 24, 1970 3 ShBGtS-SIXOQ'B 1 FIG.

WILLIAM A. MAC DONALQJR INVENTOR.

19. Jig/4Z4 fa WW A TTORNE YS June 27, 1972 W. A. Ma DONALD, JR 3,672,758

DEVICE AND METHOD FOR HANDLING A FLEXIBLE PHOTOCONDUCTOR 3 Sheets-Sheet 2 INVENTOR BY M J fiMm/M AT TORNE YS FIG. 7

WILLIAM A. MAC DONALD JR omvxcm AND mawuon won HANDLING A maxzsw raowocounucwon Filed April 24, 1970 June 27, 1972 w. A. MMDONALD, JR

3 Shah-Shut 5 WILLIAM A. MAC DONALDJR,

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INVENTOR. i A 54944. XMQ/A M AT TORNE YS United States Patent Office 3,672,758 Patented June 27, 1972 Int. Cl. 603g /00 US. Cl. 355-3 17 Claims ABSTRACT OF THE DISCLOSURE A flexible photoconductive sheet supported by opposite ends over a platen for supporting a receiving sheet wherein the photo conductive sheet is lowered while an electric potential is applied between it and the platen to create an electric field therebetween. First, one end of the photoconductive sheet is brought into line contact with the receiving sheet and held there-against by electrostatic force. Then, as the other end is lowered, the photoconductive sheet progressively contacts the receiving sheet, forcing any air out from between the sheets so that they are held in intimate contact by the electrostatic force. A clamping mechanism is used to hold the receiving sheet during separation from the photoconductive sheet following exposure to an electrostatic image.

This application is a continuated of application Ser. No. 665,915 filed Sept. 6, 1967, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to an apparatus for positioning a photoconductive sheet on a receiving sheet, and more particularly to a device for lowering a flexible photoconductive sheet onto a receiving sheet on a platen in the presence of an electric field, prior to exposing the photoconductor to an actinic radiation pattern.

Background of the invention Several devices are available for bringing a photoconductive member and receiving sheet together either prior to or simultaneously with the exposure of the photoconductive member to an actinic radiation pattern. However, most of these systems are designed primarily for use with rigid planar photoconductors and platens or with rotating drums, one of which acts as a platen and the other of which carries a photoconductive surface. None of these devices are suitable for positioning a flexible photoconductor member on a receiving sheet carried on a planar platen.

A difficulty encountered with a flexible photo conductor is that of preventing air bubbles from forming when the photoconductor is laid down on the platen. This is especially true when an electrostatic force is applied between the platen and the photoconductor. If any wrinkle or irregularities occur in the photoconductor, the electrostatic force will pull those portions of the photoconductor which are closest to the platen into contact with the receiving sheet leaving air bubble in the areas between. If this occurs a satisfactory electrostatic image will not be formed on the receiving sheet.

SUMMARY OF THE INVENTION In the present inevntion, a sheet having photoconductive surface on a conductive backing is suspended in a spaced relation to a conductive means or platen by two reciprocal members to which opposite ends of a photoconductor or photoconductive sheet are attached. A receiving sheet having an insulating surface may be fed onto the platen so that it lies between the platen and the photoconductive sheet suspended thereabove. An electrostatic force is created between the photoconductor and the platen, by applying a potential therebetween, as the photoconductor is lowered, such as one end at a time. Conveniently, the first end to be lowered may carry a cutter for severing the portion of the receiving sheet on the platen from a roll of receiving material. As the other end of the photoconductor is lowered, the catenary curve which the photoconductor normally takes, will cause it to first engage the platen in a line contact thereacross. As the end of the photoconductor continues to be lowered, progressive contact between the photoconductor and receiving sheet will occur as the electrostatic force pulls the two into intimate contact. At this point, the opposite end of the photoconductor is lowered so that the progressive contact between the two sheets proceeds in the opposite direction forcing any air out from between them. Thus, no wrinkles can occur in the flexible photoconductor to cause air to be trapped between the photoconductive and receiving sheets. The photoconductor is then exposed to an actinic radiation pattern, thereby placing an electrostatic image on the receiver. The electrostatic force is then discontinued and the edges of the receiving sheet are clamped to hold the receiving sheet in place as the photoconductor is separated from the receiver. During separation, both ends of the photoconductor may be raised simultaneously or sequentially, as desired. The clamping means can then be released so that the receiving sheet may be removed from the platen and the electrostatic image thereon developed in any suitable well-known manner.

Additional novel features of this invention will become apparent from the description which follows, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic, fragmentary, vertical section of a printer utilizing the novel, flexible photoconductor handling device of this invention, showing a photoconductor supported in raised position;

FIG. 2 is an enlarged, fragmentary perspective view showing further details of the photoconductor handling mechanism and a receiving sheet clamp-down mechanism of this invention;

FIG. 3 is a fragmentary, enlarged side elevation of the photoconductor handling mechanism of this invention with one end of the mechanism lowered so that the photoconductor is in partial contact with the receiving sheet;

FIG. 4 is an enlarged fragmentary side elevation, similar to FIG. 3, but showing the photoconductor handling mechanism in its lowered position so that the photoconductor is in intimate contact with the receiving sheet through its length;

FIG. 5 is a fragmentary, vertical section, taken along line 55 of FIG. 1, (showing details of the clamping mechanism for the receiving sheet in raised position;

FIG. 6 is a fragmentary, vertical section, similar to FIG. 5, but showing the clamping mechanism in clamping relationship; and

FIG. 7 is a fragmentary vertical section, taken along line 77 of FIG. 1, showing details of the center feedroll mechanism and clamping means.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with this invention, an electrostatic printer having a housing H, as shown in FIG. 1, may be provided wherein a receiving sheet 10 may be fed from a roll 11 through a pair of feed rollers 12 and 13 and onto a conductive means, such as platen 14. Conveniently, the receiving sheet may be of the type having an insulating coating on one side and a conductive backing or layer on the back side. The platen is connected by a wire through a switch 16 to a DC voltage source 17.

A flexible photoconductor or photoconductive sheet 18, which may include a coating or layer of photoconductive material on one side of a transparent support and a transparent conductive layer on the opposite side of the support, is supported from opposite ends by the photoconductive handling device D. For this purpose, rods 19 and 20 are respectively attached to opposite ends of the photoconductive sheet 18 and received in pairs of brackets 21 and 22, respectively. One of the rods, such as rod 20 is made of conductive material and is in electrical contact with the metallic backing of the photoconductive sheet 18. When mounted in brackets 22, the electrical circuit is completed through wire 23 to voltage source 17. By this means an electrical potential may be applied between the platen and photoconductor to create an electric field therebetween so that an electrostatic force is created which tends to attract the photoconductor to ward a receiving sheet on the platen.

As best seen in FIG. 2, front brackets 21 are mounted on a cross-member 24, interconnecting a pair of upstanding arms 25 and 26, respectively, which are connected to generally U-shaped cam followers 27 and 28. Within the flanges of the cam followers are cams 29 and 30, respectively, which are interconnected by a rotatable rod 31 extending through opposite side walls 32 and 33 of a U-shaped frame P which includes a bottom wall 34. A fixed cutting bar 35 is attached to the end of platen 14 adjacent arms 25 and 26 and is adapted to be engaged by an angular cutting blade 36 connected to and movable with the arms. One end of cutting blade 36 terminates in a downwardly extending flange 37 attached to the upper end of arm 26 and the other end terminates in an angular portion 38 and a downwardly extending flange 39 which is attached to arm 25. Therefore, as shaft 31 is rotated, as by motor 40 connected thereto by a belt 4! extending around pulleys 42 and 43, arms 25 and 26 will move downwardly so that blade 36 engages cutter bar 35 severing receiver 10 which has previously been fed onto platen 14. Angular portion 37 of cutter blade 36 is provided so that the sheet may easily be fed under the cutter blade in the vicinity of flange 38 without unduly extending the length thereof. By making the cutter blade higher at one end than at the other, a traveling point contact will be obtained between the cutter blade, including angular portion 37, and the cutter bar to provide a scissors-like cutting action across the receiver.

Brackets 22 which support the opposite end of photoconducting sheet 18 are attached to a crossbar 44 having downwardly extending arms or ends 45 and 46, as shown in FIG. 2, pivoted to links 47 and 48. The Opposite ends of the links are pivoted to shafts 49 and 50 extending from side walls 32 and 33 of frame F. In order to maintain photoconductive sheet 18 under tension so that it is properly positioned with respect to the platen in the raised position and during lowering, spring 52 extends between arm 45 and shafts 49 and spring 53 extends between arm 46 and shaft 50. At least link 48 is provided with a cam follower intermediate its ends, such as roller 54, which rides on a rotatable cam 55 mounted on a shaft 56 extending through the side walls of frame F. The shaft and consequently cam 55 are driven by a suitable drive means, such as motor 40, connected thereto by a belt 57 extending around pulley 58 on the motor shaft and pulley 59 on shaft 56.

The rotation of shafts 31 and 56 is synchronized so that the forward end of the receiver is lowered first as cams 29 and 30 rotate, then as cam 55 is rotated, roller 54 will ride into the relief portion thereof, as shown in FIG. 4, to lower the other end.

The downward movement of the forward end of conductive sheet 18, as shown in FIG. 3, will cause initial line contact, which is illustrated as being at the end, but

it will be understood that depending on the geometry of the parts and the amount of tension applied to photoconductive sheet by springs 52 and 53, this initial contact could occur intermediate the ends followed by progressive contact across the sheet forcing air out ahead of the photoconductive element as it is lowered.

Switch 16 may be closed prior to or during the lowering of the photoconductive sheet to create an electrostatic force between the platen and the photoconductor so that the latter is attracted to the receiving sheet. As the rear end is lowered, the line contact between photoconductive sheet 18 and receiver 10 will proceed rearwardly forcing the air out from between the two sheets and the electrostatic force between the platen and the photoconductive sheet 18 will cause the photoconductive sheet to be pulled into intimate contact with the receiver without wrinkling. Thus, by holding photoconductive sheet 18 under tension and lowering it as described above, the electrodstatic force will pull it into intimate contact with receiving sheet 10-.

While the photoconductive element 18 is in the lowered position shown in FIG. 4, it may be exposed to a patttrn of actinic radiation of known type, such as, for example scanning, projection or flash exposure stations, so that an electrostatic image will be formed on receiver 10. One position for such an exposure station is diagrammatically illustrated in FIG. 1. Switch 16 is then opened so that no potential is applied between the photoconductive sheet 18 and platen 14 so the photoconductor can be raised.

Because of the electrostatic attraction between receiver 10 and photoconductive sheet 18, the sheet must be held against the platen during the raising operation. This is accomplished by the clamping device C, best seen in FIGS. 2 and 5-7. Conveniently, platen 14 may be supported on a pair of spaced frame members, such as extrusions 60 each of which has an inwardly extending flange 61 on which the platen rests. The extrusion also includes a downwardly extending flange 62, an upwardly extending ridge 63 and an object upwardly extending flange 64. Ridge 63 serves as a fulcrum for an angular clamp 65 having an inwardly extending flange 66 and upwardly extending flange 67. Clamp 65 is held on ridge 63 by a plurality of spaced, spring clips 68 extending over flange 67 of the clamp and over downwardly extending flange 62 of extrusion 60, as shown. Clamp 65 is operated by an outwardly extending arm 69 attached to flange 66, as by welding, and having a rod 70 extending through the outer end thereof. Rod 70 has a pair of spaced stops 71 at the upper end to limit the movement of arm 69 along the rod 70. The lower end of rod 70 extends through flange 72 on arm 73 and is held in place by spaced stops 74.

Arm 73 is pivoted intermediate its ends on a pin 75, as in FIG. 4, one end thereof being urged downwardly by spring 76 extending from post 77 on the arm to the side wall of frame F. The opposite end is provided with a cam follower 78 which engages cam 79 mounted on shaft 56, between the side wall of frame F and cam 55. The cam is so shaped and so positioned on shaft 56, that it rides up on the lobe of the cam, as in FIG. 4 just prior to the raising of photoconductor 18. Thus, just before the photoconductor is raised, rod 70 will be moved upwardly to pivot clamp 65 about ridge 63 as a fulcrum so that inwardly extending flange 66 thereof clamps the edge of receiving sheet 10, as seen in FIG. 6. While in this position, earns 29 and 30 as well as cam 55 will rotate so as to raise both ends of the photoconductive sheet 18 simultaneously, thereby stripping it from receiver 10. Following the separation of the photoconductive sheet from the receiver, rod 70 will move downwardly as cam follower 78 rides oil of the lobe of cam 79 thereby pivoting clamp 65 from the position of FIG. 6 to the position of FIG, 5 to release receiving sheet 10 so that it may be fed by upper pressure roller 80 and lower drive roller 81, shown in FIG. 7, which is driven through shaft 82 by a suitable drive means (not shown). Conveniently, these rollers are mounted intermediate the ends of platen 14, with pressure roller 80 extending through a slot in flange 66 of clamp 65. Alternatively, separate clamps could be utilized on opposite sides of the rollers, in which case additional control mechanism for operating them would be required.

The receiving sheet 10, which now carries an electrostatic image thereon, is fed around roller 83 of FIG. 1, after photoconductive sheet 18 has been raised, and past roller 84 into a toner tray 85 having guide 86 thereon. Although a liquid toner station has been shown, it will be understood that powder could be used as well. The toner contains particles charged with a potential opposite that of either the image or the background area so that they are attracted to and stick to one area and are repelled from the other. As the receiver leaves the toner tray, it may pass over a roller 87 and through a drying station having a plurality of closely spaced compression rollers, such as rollers 88 and 89 and rollers 90 and 91. Finally, the receiver may pass an infrared lamp 92, which completes the drying, and then out of the housing H through a slot 93, after which it is ready for use.

It will be understood that all of the operations described may be accomplished through a control mechanism including a single power source, such as motor 40, or separate power sources having suitable circuits and switching mechanisms could be provided as will be apparent to one skilled in the art.

From the foregoing, it can be seen that the novel features of this invention have been fulfilled to a marked degree. The photoconductive sheet handling device D permits one end of the photoconductive sheet to be lowered before the other end is lowered so that an electrostatic charge between the sheet and the platen underneath the receiver will cause a progressive line contact between the photoconductive sheet and the receiver as the photoconductive sheet is lowered. After the photoconductive sheet has been exposed to an actinic radiation pattern to place an electrostatic charge on the receiver, the electrostatic field is discontinued and the clamping device C engages the edges of the paper while the photoconductive sheet is stripped from the receiver. After the stripping operation, the clamps release the paper which is then fed by central guide rollers to the toning and drying stations, respectively.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim: 1. A device for selectively positioning a flexible photoconductive sheet, which has a conductive backing, including:

a generally planar platen made of conductive material and having two ends, said platen adapted to support a receiving sheet;

first and second photoconductive sheet supporting means adjacent opposite ends of said platen, movable toward and away from said platen;

means for applying an electrical potential between said platen and the conductive backing of a photoconductive sheet mounted on said supporting means, for creating an electrostatic force between said platen and said photoconductive sheet;

actuatable clamping means engageable with said platen for holding said receiving sheet therebetween; and moving means coupled to each of said supporting means and said clamping means for sequentially moving each of said supporting means toward said platen so that initially a line contact is made between a photoconductive sheet connected to said supports and a receiving sheet on said platen followed by progressive contact, said electrostatic force pulling said sheets into intimate contact across coextensive portions of their surfaces, and for simultaneously actuating said clamping means and moving said supporting means away from said platen so that said photoconductive sheet will be stripped from said receiving sheet.

2. A device, as set forth in claim 1, further including:

drive means intermediate said ends of said platen for moving said receiver off of said platen after said supporting means are moved away from said platen.

3. A device, as set forth in claim 1, wherein said moving means includes:

a cam follower connected to each of said supporting means; and

cam means engageable with said cam followers to move said support means toward and away from said platen in response to movement of said cam means.

. 4. A device, as set forth in claim 1, further including:

means biasing one of said supporting means away from the other of said supporting means so that when a photoconductive sheet is extended between said support means, the sheet is held under tension.

5. A device, as set forth in claim 1, further including:

cutting means coupled to one of said support means to out said receiving sheet to length when said supporting means move toward said platen.

6. A device, as set forth in claim 5, wherein said cutting means includes:

a cutting bar mounted at one end of said platen;

a cutting blade attached to said supporting means at said one end engageable with said cutting bar when said supporting means at said one end is moved toward said platen to out said receiving sheet.

7. A device, as set forth in claim 1, wherein one of said supporting means further includes:

a conductive portion connected to said voltage applying means and connectable to the conductive backing of said photoconductive sheet.

8. A device, as set forth in claim 1, wherein said clamping means includes:

a pivotal clamp movable between a released position and a receiving sheet engaging position;

biasing means, connected to said clamp for exerting a force to urge said clamp toward one of said positions; and

means engageable with said clamp for moving said clamp toward the other of said positions against the force of said biasing means.

9. A device, as set forth in claim 8, further including:

a frame on which said platen is mounted, said clamp being pivotally mounted on said frame; and

said biasing means includes a spring clip engaging said frame and said clamp.

10. A device, as set forth in claim 8, wherein:

said biasing means is arranged for urging said clamp toward said released position; and

said engageable means is arranged for urging said clamp toward said receiving sheet engaging position.

11. A device, as set forth in claim 1, further including:

a first cam follower connected to each of said supporting means;

first cam means engageable with said first cam follower to move said support means toward and away from said platen in response to movement of said first cam means;

said clamping means further including:

a pivotal clamp movable between a released position and a receiving sheet engaging position;

a second cam follower connected to said clamp;

a second cam means engageable with said second cam follower and interconnected with said first cam means so that said clamp is in said receiving sheet engaging position when said supporting means are moved away from said platen and is moved to said released position after said supporting means are moved away from said platen upon movement of said first and second cams. 12. A method of applying a flexible photoconductive sheet, having a conductive backing, to a receiving sheet on a platen to facilitate formation of an electrostatic image, including the steps of:

feeding a receiving sheet onto said platen; applying a potential between said platen and said conductive backing to create an electrostatic force between said platen and said photoconductor; supporting said photoconductive sheet at opposite ends adjacent said platen; moving one end of said photoconductive sheet toward said platen so that said sheet initially engages a receiving sheet on said platen in a line contact; and

moving the other end of said photoconductive sheet toward said receiving sheet so that said electrostatic force pulls said photoconductive sheet and said receiving sheet together causing progressive contact across said sheets until they are in facc-to-face contact.

13. A method, as set forth in claim 12, including the further steps of:

discontinuing the application of said potential;

clamping said receiving sheet against said platen; and

moving said photoconductive sheet away from said platen to separate said photoconductive sheet from said receiving sheet.

14. A device for selectively positioning a flexible photoconductor, having a conductive backing, said device including:

conductive means for supporting an insulating surface;

first and second spaced photoconductor supporting means adjacent said conductive means for supporting said photoconductor for movement toward and away from said conductive means;

means for applying an electrical potential between said conductive means and said conductive backing of said flexible photoconductor, said photoconductor having opposite ends mountable in said first and second supporting means, for creating an electrostatic force between said conductive means and said photoconductor; and

means coupled to said supporting means for moving said photoconductor toward said conductive means to initially make line contact between said photoconductor and said insulating surface followed by progressive surface contact, wherein said electrostatic force pulls said photoconductor and said insulating surface into intimate contact across coextensive por- 5 tions thereof, and for moving said photoconductor away from said conductive means to strip said photoconductor from said insulating surface. 15. A method of positioning a flexible photoconductor, having a conductive backing, on an insulating surface supported by a conductive platen to facilitate an electrostatic image, said method including:

applying a potential between said platen and said conductive backing to create an electrostatic force between said platen and said photoconductor;

supporting said photoconductor in spaced position from said platen; and

moving said photoconductor toward said platen to initially make line contact between said photoconductor and said insulating surface wherein said electrostatic force pulls said photoconductor and said insulating surface together in progressive contact until they are in face-to-face contact.

16. A method, as claimed in claim 15, including the further steps of:

discontinuing the application of said potential; and

moving said photoconductor away from said platen to strip said photoconductor from said insulating surface. 17. A method of positioning a flexible photoconductor, having a conductive backing, on an insulating surface supported by a conductive platen to facilitate formation of an electrostatic image, said method including:

applying a potential between said platen and said conductive backing to create an electrostatic force between said platen and said photoconductor;

supporting said photoconductor in spaced position from said platen, and

moving said photoconductor or said platen to initially make a line contact between said photoconductor and said insulating surface and further moving said photoconductor or said platen to allow said electrostatic force to pull said photoconductor and said insulating surface together in progressive contact until they are in face-to-face contact.

References Cited UNITED STATES PATENTS 2,600,580 6/1952 Sabel et al 35512 3,437,336 4/1969 Enke et al 355-3 X 3,309,960 3/1967 Delplanque 355-3 2,672,787 3/1954 Schreiber et al 35572 FOREIGN PATENTS 1,026,180 4/1953 France 355-72 SAMUEL S. MATTHEWS, Primary Examiner R. P. GREINER, Assistant Examiner US. Cl. X.R. 355-16, 72

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