US2684901A - Image transfer device - Google Patents

Description

y 1954 E. R. SABEL ETI'AL 2,684,901

IMAGE TRANSFER DEVICE Filed Dec. 19, 1950 3 Sheets-Sheet 1 Fig. 4 as INVENTORS {pa/00p R- 6/9551- By CL)D R. H

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. IMAGE TRANSFER DEVICE Filed Dec. 19, 1950 3 Sheets-Sheet 2 HIGH vourAc:

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IMAGE TRANSFER DEVICE Filed Dec. 19, 1950 3 Sheets-Sheet 3 INVENTORS Patented July 27, 1954 IMAGE TRANSFER DEVICE Edward R. Sabel and C] N. Y., assignors to The yde R. Mayo, Rochester, Haloid Company, Rochester, N. Y., a corporation of New York Application December 19, 1950, Serial No. 201,534

6 Claims. 1

This invention relates to image transferring devices and particularly to devices for transferring image material electrostatically from one surface to another.

An important application of the devices herein disclosed is in the electrostatic transfer of powder images from electrophotographic plates and from other electrostatic image plates.

In the process of electrophotography, as described, for example, in Patent No. 2,297,891 issued to Chester F. Carlson, an electrophotographic plate comprising a layer of photoconductive insulating material on a conductive base is given an electrostatic charge, exposed to a light image to create an electrostatic latent image on its surface, and then dusted with an electroscopic powder to produce a powder image. "The apparatus of the present invention is useful in transferring such powder images to sheets of paper. paper offset mats, plastic sheets, and the like.

The devices of the present invention may also be used to transfer powder images formed on powder printing plate consisting of insulating images bonded to metal backings. With such plates powder images can be formed by simply charging the plate frfctionally or with an ion source to lay down an electrostatic charge on the insulating portions. Upon dusting with powder a powder image is deposited which can be transferred to paper or other sheets by the devices disclosed.

The devices herein disclosed are also useful in transferring other image materials which can be transferred electrostatically.

The devices of the present invention include mechanism for advancing an image plate under an ion source and means to feed a transfer sheet to the plate surface coincident with or prior to passage under the ion source. The invention also contemplates means for obtain ng registry the image on the transfer sheet. means for starting and stopping the plate advance and other features of control. Also contemplated are means to avoid bulges or blisters between the transfer sheet and the plate as they pass under the ion source.

The invention comprises the features of construction, combination of elements, arrangement of parts, and methods of operation referred to above or which will be brought out and exemplifled in the disclosure hereinafter set forth, including the illustrations in the drawing.

In the drawings:

Figure 1 is a top plan view of a transfer device embodying features of the present invention;

Figure 2 is a side elevation thereof;

Figure 3 is a vertical section on the line 33 of Figure 1;

Figure 4 is a vertical section on the line 4-4 of Figure 2;

Figure 5 is an enlarged detail view of the transfer sheet feed mechanism taken from the line 55 of Figure 2;

Figure 6 is a circuit diagram of the electrical controls for the device;

Figure 7 is a side elevation of a modified transfer sheet feed member; and

Figure 3 is a side elevation, partly in section, of a modified transfer device.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the construction and arrangement of parts in the method of operation without departing from the spirit of the invention. In the following description and in the claims parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts a the art will permit.

Referring to the drawings, the transfer device illustrated in Figures 1 to 5 inclusive for transferring powder images to individual sheets comprises a box-like base I 8 upon which is supported a feed chute mechanism H for transfer sheets, such as paper. The chute mechani m I i is supported by a pair of sheet metal standards i2 secured to the top surface of base ill. An ion source i3 comprising a grid of corona disch rge wires is bridged across the top surface of base l9 substantially midway between the ends of base Ill and is supported by a bridge-like rame'l i comprising a crosspiece and two v tical uprights supported near the edges of the top of base 5. The grid i3 is strung between insulating blocks BI and is shielded above by spaced sheet metal shield 62. A safety shield optionally protects against insertion of foreign obfects into the grid.

A pair of endless chains l5 and itpass over sprocket wheels ll which are mounted inside base in and extend through slots in its top surface. The chains slide over the top surface of base Ill optionally along a metal strip (not shown) to protect against wear, passing from one end to the other underneath sheet feed mechanism H and corona grid l3. Chain l5 passes under a drive sprocket is which is driven by an electric motor l8 through speed-reduction gearing.

A stop lever 2!] is also mounted inside the base it and provided with stop projections which extend up through the top of the base underneath the corona grid 13 to serve as positioning stops for an image plate and a sheet of transfer material. A solenoid H is provided for retracting the stop arm.

The circuit for energizing the corona grid i3, for starting and stopping electric motor 58, and for operating solenoid 2! to retract the stop arm is shown in Figure 6. The features of the con trol circuit, as well as specific details of the device, will be brought out more fully in the following description of the preferred mode of operation.

In operation, an image plate which may comprise a flexible plate or a rigid fiat metal plate carrying a powder image on its upper surface is laid on chains [5 and I6 where they rest on the top surface of base it and are underneath the transfer sheet feed mechanism l l. The plate is placed on the chains and slid forward manually to a position where the two corners of its leading edge are against stop pins 22 on step lever 23. The plate thus forms a bridge supported along its two edges on chains l5 and i6 and having its leading edge abutted against stop pins 22, and sides 12 provide lateral positioning or centering.

A transfer sheet, such as a sheet of paper, or a paper oifset master or other sheet transfer material, is placed on sheet feed mechanism H. Thi mechanism comprises means for supporting the edges of the transfer sheet consisting of a pair of L-shaped sheet metal channels 23' pivoted by hinges 24 to a pair of L-shaped sheet metal side members 25 as seen most clearly in Figures 3 and 5. Hinges 24 include coil springs (not shown) normally holding channels 23 in the position shown, with the upper edges of channels 23 abutting the inside faces of the flanges on members 25.

Transfer sheet feed mechanism Ii is provided with means to spread apart guide channels 23 to widen the gap between them and allow the body of the transfer sheet to fall against the surface of the image plate. This mechanism comprises a manually-operable lever 40 secured to a pivot shaft 61 carrying cam pins 42 which slide against cam surfaces 43 of channels 23 to swing them outwardly on their hinges 24. Cam surfaces 33 are formed by curving the hinge-attached faces of channels 23 outwardly at their upper ends adjacent cam pins 42 as seen most clearly in Figure 5. A pair of stops 44 is provided on the outer face of one of said members 25 to limit the travel or manual lever 40.

The side members 25 are secured to sheet metal uprights l2 so as to slant downwardly from the left-hand end of the device as seen in Figure 2 toward the position of the leading edge of an image plate when it is positioned against stop ins 22. Thus guide channels 23, which are supported by side members 25, form a paper chute sloping toward the leading edge of the image plate at a substantial angle. In practice an angle of 30 has been found to be suitable although in this embodiment of the invention the angle of the chute is not particularly critical and may be varied some without substantially changing the functioning of the device and will be varied to some extent depending on the nature of the transfer sheet.

The transfer sheet is selected of such width as to have its long edges resting on the sloping surfaces of guide channels 23 when positioned on the sheet feed mechanism. The sheet may then be advanced manually down the chute until its leading edge engages stop plate 26 also supported on stop arm 2% In the embodiment illustrated it is desired to index the transfer sheet with respect to the image plate so that the leading edge of the transfer sheet extends a short distance ahead of the leading edge of the image plate. However, it will be appreciated that, if desired, the image plate and transfer sheet can have their leading edges brought into register in which case stop pins 22 may be eliminated and stop plate 26 may serve as the indexing member for both the plate and the transfer sheet. Having advanced the transfer sheet into abutment with stop plate 26, the operator is now ready to start the transfer operation. At this time the transfer sheet is still suspended above the image plate and is in contact with it only along a narrow margin at the leading edge of the plate. This creates a curve or channel extending across the transfer sheet which tends to straighten out any bulges or kinks in the sheet material and causes the leading edge of the sheet to lie flat against the surface of the plate. In order to obtain a good electrostatic transfer of a powder image it is essential that there be intimate contact between the sheet material and the image-carrying surface throughout the area that passes under the ion source.

The operator now throws switch 21 to On position, if this has not already been done, and then momentarily presses start switch 36. This closes an energizing circuit (Figure 6) from the power source, such as a -volt A. C. line, through normally closed stop switch 29, start switch 28, lock-up relay winding 35] and Off-On switch 2'! to operate relay 3%] and close its holding contacts iii in parallel with switch 28 so that the circuit will remain closed when the operator manually releases start switch 28. A circuit is also completed through contacts 28 or St to a high voltage power supply unit 32 for energizing corona grid 53. Power supply 32 may comprise a step-up transformer and vacuum tube rectifier circuit of well-known design adapted to deliver a high potential, such as 6000-8000 volts D. C. to corona grid it, the opposite output terminal being connected to machine ground which includes chains 45 and it so that the image plate will be grounded when it is restin on the chains. A pilot light 33 bridged across the energizing circuit for the high voltage power supply is also turned on at this time to indicate to the operator that the corona grid is energized.

A circuit is also completed from contacts 28 or 35 through rectifier 3-1, rheostat 35, the parallel arrangement of high resistance relay winding 36 and condenser 3'1, and switch 27. Rheostat 35 has been preset to a resistance which adjusts the charging rate of condenser 37 to a value which introduces a predetermined time delay in the operation of relay 35 and the relay is marginally operating, requiring a certain minimum of current before it operates. This permits the high voltage power supply to warm up and grid 13 to become fully energized before operation of relay 36 which controls the drive motor i9 and solenoid 2|. The time delay additionally assures that the leading edge of the transfer sheet is adequately tacked down onto the image plate before the forward motion begins. When relay 36 operates it closes an energizing circuit from contacts 3| through the contacts of relay 3%, the winding of solenoid 2i and switch 2'3 to energize the solenoid. Relay 35 also closes the operating circuit to one terminal of motor 19 but the motor does not begin operation at this instant since its circuit is still incomplete.

Solenoid 2 i, in operating, pulls down its plunger against the compression of spring 38 and pulls down stop lever by link 39 connecting the solenoid plunger to the lever. This retracts stop pins 22 and stop plate 26 below the path of travel of the image plate. Operation of solenoid 2! also closes microswitch 45: which is controlled by lever 20, thus completin the return circuit from motor l8 through switch '2'! to power source and energizing motor iii to start the advance of the image plate and transfer sheet by chains :5 and I6.

In operation of the devi e the lever may be operated prior to start switch to drop the transfer sheet onto the image before the corona grid is energized, but in the preferred mode of operation the operator first presses the start switch 28 to energize the power supply which almost immediately places a charge on the leading edge or margin of the transfer sheet where it rests against the image plate thereby creating electrostatic adhesion of the tra fer sheet margin to the plate, The operator turns the lever so to drop the main body of L11 transfer sheet against the plate. This is preferred since it avoids the possibility that the transfer sheet may shift in position as it falls and thereby get out of register. The electrostatic adhesion prevent this.

As the image plate and transfer sheet pass under the corona grid iii an electric charge is sprayed onto the of transfer sheet progressively throughout its length to produce adhesion between the transfer sheet the underlying powder image. When the plate advances to end of the chain its leading edge projecting lever G5 comprising the operating arm of stop switch 29 which may be snap acting microswitch which is normally closed d which is opened by pressure on the actuati lever. Thus, when the plate engages lever step switch 29 is opened to deenergize power supply 32, release solenoid 2 i, stop motor l9, release relays 30 and 36, thereby unlocking the circuit and preparing it for subsequent manual initiation. The transfer sheet is now removed from the image plate, carrying with it the transferred powder image. The po vder can be fused onto the sheet in an oven or other fusing device. The image plate with any residual powder image it may carry, is now removed for cleaning and reuse. As soon as the plate is removed stop switch 29 closes its contacts but no energizing circuit is completed until start switch is again operated.

Figure '7 illustrates a modified sheet feed chute 46 comprising a broad and shallow metal channel 4! supported by sheet metal standards 48. This feed chute may be used in place of mechanism ll previously described where flexible transfer sheet materials are used. Since the sheet is supported by a solid metal channel it is not released to fall against the image plate in this case but is simply allowed to slide oif the sloping surface of channel t? when it is pulled along by the image plate due to the electrostatic adhesion produced by the corona discharge onto the leading edge of the transfer sheet.

Figure 8 illustrates a modified transfer device which includes a roller mechanism to between the sheet feed mechanism Ii and the corona grid l3. This mechanism comprises a pair of spaced parallel :netal levers 5i pivoted at one end at 52 and provided with aligned vertical notches 53 at their free ends. A rol er 54 which may preferably be formed of soft rubber but may be made of other materials such as metal, wood, plastic or the like, has an axial shaft 55 the ends of which are received in notches 53 so that the roller 56 is effectively positioned and guided by levers 5|. A pair of sheet metal standards 56 is mounted at the edges of base it beyond D the ends of shaft 55 and a shaft 5? is pivoted in aligned openings near the top of the standards and provided with manual lever at one end. An L-shaped link 53 is provided at each end of the roller, each of the links being pivoted at one end in the body of a lever 5i and at the other end to a crank lever to on shaft 5?. By manually rotating shaft 5? through an angle of approximately 90 levers 5i are lifted by links 53 to lift roller 54 to a position clearing the path of travel of the image plate. This renders the roller inoperative.

In operation, plate 83 is placed on the conveyor and manually advanced against stops and a transfer sheet 64 is advanced down t e chute of feed mechanism H underneath roller '5; until its leading edge is underneath corona grid i3 and in contact with stop 26. Manual rotation of shaft 51 in a counterclockwise direction as seen in Figure 8 will then lower roller 5d against the top face of the transfer sheet. Then, as the image plate is advanced under the corona grid i3, roller 5 serves to smooth down the shee before it under the corona grid. This roller is of particular advantage in the case of sheet materials which tend to be slightly irregular or which contain bulges or creases.

It has been seen that transfer mechanisms have been provided according to the present invention for transferring powder images electrostatically from rigid or flexible surfaces to individual sheets of paper, plastic and the like and to offset While the present invention, as to its objects and advantages, has been described nerein as carried out in specific embodiments thereof, is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

l. A transfer device for l -aterial from an image sheet, comp ing in combination,

an image plate, a transfer sta' to advance a plate on said support parallel to the plate so "ace pas said transfer ireeted toan acute respect to station, a sheet feed uide r .nio trans T18 on CL or c age 0 sheet may be electrostatically image plate while the major part of t1 2 is still at said acute angle to sa d ioage plate and a curved channel is for d for sheet to thereby eli "late bulges in the portion of the sheet clamped again t the image plate, means to retract s t feed guide means to drop the trailing tion of the transfer sheet onto image plate.

2. A transfer device for transferring an image material from an image plate to a transfer sheet, comprising in combination, a support for an image plate, a transfer station, drive means to advance a plate on said support in a path transparallel to the plate surface past said transfer station, a sheet feed guide directed toward said path of plate advance at an acute angle greater than 30 degrees with respect to the surface of said plate to feed a transfer sheet to the surface of a plate positioned. on said support at said acute angle and to a position in said path adjacent said transfer station, stop means to position the leading edges of said plate and transfer sheet prior to passing said transfer station, and means to retract said stop means and to energize said plate advance and discharge source, and an electric discharge source at said transfer station above said path of plate travel for producing an electric discharge onto the back of a transfer sheet overlying an image plate on said support, whereby the leading edge of a transfer sheet may be electrostatically clamped to an image plate while the major part of the sheet is still at said acute angle to said image plate and a curved channel is formed across the transfer sheet to thereby eliminate bulges in the portion of the sheet clamped against the image plate.

3. A transfer device for the electrostatic transfer of images comprising, in combination, an elec tric ion source, an electrically driven plate advance motor operatively connected to drive means to pass an image plate and superimposed transfer sheet under said source, a switch for initiating the energization of said ion source and said plate advance motor, a lock-up relay for maintaining said source and said advance motor energized, and a disconnect switch for deenergizing said lock-up relay to stop said motor and deenergize said ion source responsive to the completion of travel of an image plate under and beyond said source.

4. A transfer device for the electrostatic transfer of images comprising, in combination, .a corona discharge electrode and an energizing circuit therefor, an electrically driven plate advance motor operatively connected to drive means to pass an image plate and superimposed transfer sheet under said source, a manual switch for initiating the energization of said corona cir cuit and said plate advance motor, a lock-up relay for maintaining said corona circuit and said advance motor energized, and a disconnect switch for deenergizing said lock-up relay to stop said motor and deenergize said corona circuit responsive to the completion of travel of an image plate under and beyond said electrode.

5. A transfer device for the electrostatic transfer of images comprising, in combination, a corona discharge electrode, a motor driven plate advance mechanism to pass an image plate and superimposed transfer sheet under said electrode, a stop for indexing said image plate and transfer sheet with respect to each other prior to passage thereof under said electrode, an electromagnet for retracting said stop from its oper ative position, a manual switch for energizing said electromagnet and for initiating the energization of said corona electrode and said plate advance mechanism, a lock-up relay for maintaining said electromagnet, said electrode, and said mechanism energized, and a disconnect switch for deenergizing said lock-up to release said electromagnet, stop said mechanism and deenergize said electrode in response to the completion of travel of an image plate under said electrode.

6. A transfer device for the electrostatic transfer of images comprising, in combination, a grid of corona discharge wires, an electrically driven plate advance conveyor mechanism to pass an image plate and superimposed transfer sheet under said grid, 2, sheet feed chute for feeding a transfer sheet onto the face of said image plate prior to its passage under said grid, a stop for indexing said image plate and transfer sheet with respect to each other prior to passage thereof under said grid, an electromagnet for retracting said stop from its operative position, a manual switch for energizing said electromagnet and for initiating the energization of said corona grid and said plate advance mechanism, a lock-up relay for maintaining said electromagnet, said grid, and said motor energized, and a disconnect switch for deenergizing said lock-up relay to release said electromagnet, stop said mechanism and deenergize said grid in response to the completion of travel of an image plate under said grid.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 287,957 Osborne Nov. 6, 1883 1,077,818 Eagar Nov. 4, 1913 1,842,195 Pinder Jan. 19, 1932 2,058,732 Simon Oct. 27, 1936 2,095,502 Johnston Oct. 12, 1937 2,324,068 Crandell July 13, 1943 2,454,168 Hartwig Nov. 16, 1948 2,483,462 Huebner Oct. 4, 1949 2,486,703 Bishop Nov. 1, 1949 2,544,806 Ransburg Mar. 13, 1951 2,551,582 Carlson May 8, 1951 2,573,881 Walkup et a1 Nov. 6, 1951 2,576,047 Schaffert Nov. 20, i 2,576,882 Koole et al. Nov. 27, 1951

Claims (1)

1. A TRANSFER DEVICE FOR TRANSFERRING AN IMAGE MATERIAL FROM AN IMAGE PLATE TO A TRANSFER SHEET, COMPRISING IN COMBINATION, A SUPPORT FOR AN IMAGE PLATE, A TRANSFER STATION, DRIVE MEANS TO ADVANCE A PLATE ON SAID SUPPORT IN A PATH PARALLEL TO THE PLATE SURFACE PAST SAID TRANSFER STATION, A SHEET FEED GUIDE MEANS DIRECTED TOWARD SAID PATH OF PLATE ADVANCED AT AN ACUTE ANGLE GREATER THAN 30 DEGREES WITH RESPECT TO THE SURFACE OF SAID PLATE POSITIONED TO FEED A TRANSFER SHEET TO THE SURFACE OF A PLATE POSITIONED ON SAID SUPPORT AT SAID ACUTE ANGLE AND TO A POSITION IN SAID PATH ADJACENT SAID TRANSFER STATION, AN ELECTRIC DISCHARGE SOURCE AT SAID TRANSFER STATION ABOVE SAID PATH OF PLATE TRAVEL FOR PRODUCING AN ELECTRIC DISCHARGE ONTO THE BACK OF A TRANSFER SHEET OVERLYING AN IMAGE PLATE ON SAID SUPPORT, WHEREBY THE LEADING EDGE OF A TRANSFER SHEET MAY BE ELECTROSTATICALLY CLAMPED TO AN IMAGE PLATE WHILE THE MAJOR PART OF THE SHEET IS STILL AT SAID ACUTE ANGLE TO SAID IMAGE PLATE AND A CURVED CHANNEL IS FORMED ACROSS THE TRANSFER SHEET TO THEREBY ELIMINATE BULGES IN THE PORTION OF THE SHEET CLAMPED AGAINST THE IMAGE PLATE, AND MEANS TO RETRACT SAID SHEET FEED GUIDE MEANS TO DROP THE TRAILING PORTION OF THE TRANSFER SHEET ONTO THE IMAGE PLATE.

Images