US3497297A

US3497297A - Segmented platen for electrostatic printing

Info

Publication number: US3497297A
Application number: US665914A
Authority: US
Inventors: Gene H Robinson; Theodore H Morse
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1967-09-06
Filing date: 1967-09-06
Publication date: 1970-02-24
Anticipated expiration: 1987-02-24
Also published as: FR1599752A; DE1797249B2; GB1244855A; DE1797249A1

Description

SEGMENTED PLATEN FOR ELECTROSTATIC PRINTING Filed Sept. 6 1967 .G. H. ROBINSON ET AL Feb.

2 Sheets-Sheet 1 F5050 QSIUEEM GENE H. ROBINSON THEODORE H. MORSE INVENTORS' I frfu/fi dz.

' ATTORNEYS United States Patent 3,497,297 SEGMENTED PLATEN FOR ELECTROSTATIC PRINTING Gene H. Robinson and Theodore H. Morse, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Sept. 6, 1967, Ser. No. 665,914 Int. Cl. G03g 5/02 US. Cl. 355-16 Claims ABSTRACT OF THE DISCLOSURE An electrically conductive platen, for supporting a receiver sheet of variable size, is divided into conductive segments electrically insulated from each other. The segments may be selectively connected to a power supply so that an electrical potential is established between the segments over which the receiver sheet extends and a photoconductive element positioned above the sheet. The segments which are not covered by the receiver sheet are electrically connected to the photoconductive element so that no short circuit will be created therebetween. A receiver sheet which covers more than one segment is sufliciently conductive to bridge the gap between adjacent segrnents so that no trace of the gap shows on the developed image.

BACKGROUND OF THE INVENTION This invention relates to an apparatus for carrying out a process wherein an electrostatic charge is altered by the action of actinic radiation, such as light, during exposure to a pattern of actinic radiation and the application of an electrical field between a photoconductive element and a receiving material, where the exposure may take place simultaneously or immediately after the application of the electrical field. To accomplish this, a receiving sheet is placed between a photoconductive element, including a suitable support bearing a conductive layer which in turn has a photoconductive layer thereon, and a conductive platen. At the same time that the photoconductive element is exposed to a radiation pattern, an electrical field is created between its conductive backing and the platen so that an electrostatic image is placed on the receiving sheet corresponding to the pattern.

In most prior-art devices, prints are made on only one size sheet of paper or receiver wherein the paper is supplied to the machine in sheet form or on a roll which is cut to a preselected length. Other machines are adapted to utilize sheets of difierent sizes but are not adaptable to the special problems which occur when receiver sheets of varying size are charged and exposed at the same station. In this situation, the platen with the receiver sheet resting thereon is covered by a photoconductive element. However, if the receiver sheet is smaller than the platen and photoconductive element, direct contact will occur between the later two causing a short circuit and damage to the photoconductive element.

SUMMARY OF THE INVENTION The above-mentioned difliculties can be overcome by utilizing the present invention, which, in the embodiment shown, provides a roll of receiver-sheet material which is fed onto a segmented platen. There it may be cut to any one of several preselected sizes corresponding to the size of one or more adjacent conductive platen segments. The segments are electrically insulated from each other and are connected to one terminal of a DC voltage source. The other terminal is connected to a photoconductive element which may be placed down upon the receiver sheet during charging and exposure to a light image. By

segmenting the platen, only those sections which are under the receiver sheet are connected to the voltage source during an exposure. Those segments, which are not under the receiving sheet or receiving paper, but are in direct contact with the photoconductive layer, are electrically connected to the same potential as the photoconductive layer. As a result, no short circuit is created between the photoconductive layer and the platen during charging. The receiver has a conductive backing which bridges the gap between the platen segments so that an image is placed on the receiver sheet across the gaps. Thus, these gaps do not show up on the receiver sheet when it is developed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, fragmentary, side-elevation of a printer in which the novel segmented platen of this invention may be utilized;

FIG. 2 is a greatly enlarged cross-section of the photoconductive element, receiver and segmented platen showing further details of the platen; and

FIG. 3 is a top plan view of the segmented platen of FIG. 2, taken along line 33 of FIG. 2, showing the electrical connection for placing the various platen segments in the circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with this invention, a novel segmented platen S may be used in an electrophotographic apparatus, such as the electrostatic printer shown in FIG. 1. A receiving sheet R which is made of paper 10, having an insulating coating 11 on one side and a conducting material, such as layer 12 on the opposite side, a best seen in FIG. 2. It will be understood that conductive layer 12 does not have to be a discrete layer, but may be a conductive material within paper 10. It may be fed from a supply roll 13, see FIG. I, mounted for rotation about a horizontal axis 14 in housing H and then through a pair of horizontal feed rollers 15 and 16 and onto a support or platen S. The feed rollers may be driven in any suitable manner, such as by paper feed motor 17 connected to roller 16 by belt 18. This platen may be made up of several adjacent segments having areas for supporting a receiver, such as

segments

19, 20, 21, 22, 23 and 24, as best seen in FIG. 3, mounted in a base 25 made of insulating material and having

transverse ribs

26 and 27 and longitudinal rib 28 between the segments to insulate them electrically, as shown.

A photoconductive sheet P, which is shown as a flexible sheet but could be made of a rigid material, is supported at opposite ends of platen S by means of spaced brackets 29 and 30. As seen in FIG. 2, photoconductive element or sheet P includes a photoconductive coating or layer 31 on a transparent conductive layer 32 carried by a transparent support 32'. Conveniently, the ends of photoconductive sheet P may be attached to rods 33 and 34 which are received in brackets 29 and 30, respectively. At least rod 34 is made of conductive material and is in electrical contact with conductive layer 32. This completes the electrical circuit through wire 35 to a DC voltage source 36. The opposite side of voltage source 36 is connected through a switching circuit 37 by means of

wires

38, 39 and 40 to

platen segments

19, 20 and 21, respectively as further described below.

Bracket 29, which holds one end of the photoconductive element, is mounted on the upper end of front vertical arm 41 at the front of platen S whereas bracket 30 is attached to the upper end of a rear vertical arm 42. These arms are each arranged for vertical movement, as shown, and front arm 41 carries a knife blade 43 which cooperates with a stationary cutter 44 at the front end or platen S to cut receiver R to a proper-length sheet after it has been fed onto the platen. Vertical arms 41 and 42 are connected through a suitable linkage mechanism (not shown) to a motor (not shown) so that photoconductive element P may be lowered onto the receiver R before exposure and raised when the receiver is moved across platen S. When the photoconductive element P is superimposed on a severed receiving sheet supported by platen S, the photoconductive element is ready to be exposed to a light image and charged. Conveniently, as the receiver R is fed onto platen S, it may be cut to correspond to the length of segment 19, which might be some standard length, such as 11 inches, or the receiver might be cut to the length of segment 19 and combined, which again could be a convenient length, such as 13 inches. Finally, the receiver may be cut so as to cover the entire platen, including

segments

19, 20* and 21, for some still-further desirable length, such as 14 inches. Similarly, the width of the receiver might be varied. For example, roll 13 might be 8% inches wide so as to cover only

platen segments

19, 20 and 21 or it could be 11 inches wide, for example, so as to cover

segments

22, 23 and 24 also. It will be understood that the sizes mentioned are arbitrary and that other sizes may be chosen as conditions require. Also, a greater or lesser number of platen segments may be provided to facilitate the use of a greater or smaller number of receiver sizes. By looking at FIGS. 1 and 2, it can be readily seen that, unless the receiving sheet extends across all of the platen segments, a short circuit would be created between the photoconductive layer and the uncovered platen segments, thereby making the device inoperative.

However, by utilizing switching circuit 37, this problem can be overcome. Thus, turning to FIG. 3,

gang switches

45, 46 and 47 may be provided, which are connected to a knob (not shown) on the front of housing H. Suitable indicia may be provided thereon to indicate the length of paper desired. Thus, by merely turning the knob, the operator can accomplish two things. He can adjust the paper feed mechanism through switch 45 so that the proper length of receiver will be fed onto the platen. Thus, when switch 45 is in the position shown, the paper feed motor 17 will be connected so as to advance receiverR so that it covers segment 19 only. Secondly, segment 20, which is not covered by the receiver, will be connected through wire 48, switch 46 and wires 49, 50 and to conductive layer 32 so that no short circuit will be created therebetween. Similarly, uncovered segment 21 will be connected through wire 51, switch 47 and

wires

52, 50 and 35 to conductive layer 32.

If switch 45 is advanced to the next position to cause a longer length of paper to be fed, switches 46 and 47 will also be advanced to the next position. This will place platen segment 20 in the circuit through wire 48, switch 46 and

wires

53 and 38. On the other hand, segment 21, which still remains uncovered, will be connected through wire '51, switch 47 and

wires

52, 50 and 35 to the conductive layer 32. If switch 45 is advanced to the third position, so that a still-longer length of receiving sheet is fed onto the platen which will cover all of

segments

19, 20 and 21, the circuit to platen segment 20 will still be completed, but this time it will be completed throughwire 48, switch 46, and

wires

54 and 38. The circuit to platen segment 21 will now be completed through wire 51, switch 47 and

wires

55 and 38.

Whenever a receiving sheet is used having a width no greater than

platen segment

19, 20 and 21, gang switches 56, 57 and 58 will be placed in the position shown in FIG. 3. Thus, segment 22 is connected by wire 59, switch 56 and

wires

60, 50 and 35 to conductive layer 32 to prevent a short circuit therebetween and to maintain both at the same electrical potential. Similiarly, segment 23 is connected to the conductive layer 32 by wire 61, switch 57 and

wires

62, 50 and 35, and segment 24 is connected by wire 63, switch 58 and

wires

64, 50 and 35. 'However, by moving the gang switches to the alternative position,

segments

22, 23 and 24 can be connected into the circuit whenever

segments

19, 20, and 21, respectively, are connected in the circuit. Therefore, in this alternative position, segment 22 will be connected through wire 59, switch 56 and

wires

65 and 38 to voltage source 36. On the other hand, segment 23 will be connected through wire 61, switch 57 and

wires

66 and 48 to switch 46 so that it will be placed in the circuit whenever segment 20 is placed therein. Similarly, segment 24 will be connected through wire 63, switch 58 and

wires

67 and 51 to switch 47 so that it will be placed in the circuit whenever segment 21 is. Of course, it will be understood that additional segments, either longitudinally or laterally, could be provided, as needed, with additional switching circuits. Likewise, fewer segments and switching circuits could be provided, if desired.

When receiver R is large enough to extend across more than one segment, as in FIG. 2, conductive backing 12 will electrically bridge the gap, as across

ribs

26 and 27 between

segments

19 and 20 and segments 20* and 21, respectively. Thus, an electrostatic image or charge pattern placed on insulating layer 11 will be formed on the portion thereof extending across

ribs

26 and 27. This has been found to be true for gaps as large as inch.

After leaving the platen, the receiving sheet, which now carries an electrostatic image, is passed around a roller 68 and between it and a pressure roller 69 into a developing tank 70 having guide means 71 therein for directing the receiving sheet through a toner liquid. Of course, it will be understood that a dry toner system such as a cascade or cloud system could be used. However, in the examples shown, after the receiving sheet passes through developing tank 70, it passes over roller 72 and between squeegee rollers 73 and 74 and pressure rollers 75 and 76, which squeeze excess toner liquid from the paper, and past IR lamp 77 to dry the paper and aflix the image thereto. Finally, the sheet is fed through slot 78 in housing H for use.

From the foregoing, it can be seen that the segmented platen of this invention may be used with receiving sheets of varying length having a conductive backing which will bridge the gap between adjacent segments selectively connected in an electrical circuit to create an electric field between the photoconductive layer and only those segments which are under a receiving sheet. Any other segments will be electrically connected directly to the conductive layer so that no short circuit will be created between the photoconductive layer and these other segments.

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 affected within the spirit and scope of the invention We claim:

1. A platen for supporting receiving sheets of varying size in an electrostatic printer, wherein a photoconductive element is positionable over a receiving sheet on the platen'and exposable to a light image so that an electrostatic image is placed on the sheet, said platen comprismg:

a base; and

a plurality of adjacent, spaced, conductive segments mounted on said base, said segments having substantial areas for supporting the receiving sheet, and being electrically insulated from each other.

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

insulating material between said segments.

3. A platen, as set forth in claim 1, including:

two segments in adjacent end-to-end relationship and having a common centerline; and

a third segment adjacent to at least one of said two segments, said third segment having a centerline generally parallel to said common centerline.

4. In an electrostatic printer including:

a platen for supporting receiving sheets of varying size;

a photoconductive element positionable over a receiving sheet on said platen;

a voltage source electrically connected between said platen and said photoconductive element; and

means for advancing a receiving sheet onto said platen to selectable lengths;

the improvement comprising;

said platen including a plurality of adjacent, spaced,

conductive segments, each segment having a substantial surface area for supporting a receiving sheet, and being electrically insulated from each other; and

switch means connected between said segments and said voltage source for selectively creating an electrical potential between said photoconductive element and one or more of said segments.

5. In an electrostatic printer, as set forth in claim 4,

the further improvement wherein:

said switch means is responsive to said advancing means so that said electrical potential is created between said photoconductive element and those segments eoverable by a selected receiving sheet length.

6. In an electrostatic printer, as set forth in claim 4,

the improvement further comprising:

the improvement further including:

a receiving sheet supportable on said segmented platen and having a conductive backing which forms an electrical bridge between adjacent segments covered by said receiving sheet so that an electrostatic image can be formed on said receiving sheet across the spaces between said segments.

8. In an electrophotographic apparatus including:

a first conductive layer;

a photoconductive layer having a first and second surface, said first surface being in face-to-face contact with said first conductive layer;

a second conductive layer in face-to-face contact with said second surface of said photoconductive layer, said photoconductive layer and said second conductive layer adapted to receive a receiving sheet therebetween, said receiving sheet having an insulating surface positionable in virtual contact with said photoconductive layer;

means for creating a charge patten on said insulating surface to exposure of said photoconductive layer to an actinic radiation image; and

means for applying an electrical potential between said conductive layers to create an electrical field therebetween;

the improvement comprising:

said second conductive layer having a plurality of spaced, conductive segments which are electrically insulated from each other; and

means connected to said segments for applying a first potential to segments not coverable by said receiving sheet and said for applying a second potential to segments eoverable by said receiving sheet, so that a charge pattern may be placed on receiving sheet, said receiving sheets having at least one dimension shorter than the corresponding dimension of said photoconductive layer and first conductive layer without creating a short circuit between the first and second conductive layers.

9. In an electrophotographic apparatus, as set forth in claim 8, the further improvement wherein:

said first potential is the same as the potential on said first conductive layer. 10. In an electrophotographic apparatus, as set forth in claim 8, the improvement further including:

a receiving sheet interposable between said photoconductive layer and said second conductive layer, said receiving sheet having:

a conductive material on one side thereof extendable between those segments covered by said receiving sheet to provide electrical contact therebetween so that said charge pattern, will be formed on said receiving sheet between said segments.

References Cited UNITED STATES PATENTS 3,003,404 10/1961 Metcalfe et al 355-16 X 3,057,275 10/1962 Walkup et al. 35515 3,288,602 11/1966 Snelling et al. 96l 3,393,617 7/1968 Gaynor 355-3 JOHN M. HORAN, Primary Examiner A. MATHEWS, Assistant Examiner