US3644035A

US3644035A - Flat plate traveling roller imaging system

Info

Publication number: US3644035A
Application number: US876848A
Authority: US
Inventors: Raymond K Egnaczak; Gino F Squassoni
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1969-11-14
Filing date: 1969-11-14
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22
Also published as: PL82860B1; NL7016549A; CA923356A; JPS4913338B1; CH528763A; DE2055509A1; BE758904A; SE367074B; FR2069732A5; GB1335051A; ES385454A1; SU404290A3

Abstract

A photoelectrophoretic imaging machine employing a stationary electrode over which two imaging and one transfer roller electrode travels to form and transfer an image formed from photoelectrophoretic ink exposed to light and subjected to electric field. The roller electrodes are journaled in two separate carriages with one drive mechanism employed to propel the carriages and a second drive mechanism employed to rotate the roller electrodes. The roller electrodes are lowered into contact with the stationary electrode by an elevator mechanism that enables the forces exerted on the roller to be varied from one end of a roller to the other. Means are provided for loading and ejecting a record sheet from the surface of the transfer roller. An auxiliary drive mechanism and cleaning station are positioned to engage the imaging roller electrodes after they pass over the stationary electrode.

Description

United States Patent Egnaczak et al.

[54] FLAT PLATE TRAVELING ROLLER IMAGING SYSTEM [72] Inventors: Raymond-K. Egnaczak, Williamson; Gino F. Squassoni, Pittsford, both of NY.

[73] Assignee: Xerox Corporation, Rochester, N.Y.

[22] Filed: Nov. 14, 1969 211 App]. No.: 876,848

gllll Primary Examiner-Samuel S. Matthews Assistant Examiner-Robert P. Greiner Attorney-James J. Ralabate, David C. Petre and Michael H.

Shanahan [57] ABSTRACT A photoelectrophoretic imaging machine employing a stationary electrode over which two imaging and one transfer roller electrode travels to form and transfer an image formed from photoelectrophoretic ink exposed to light and subjected to electric field. The roller electrodes are joumaled in two separate carriages with one drive mechanism employed to propel the carriages and a second drive mechanism employed to rotate the roller electrodes. The roller electrodes are lowered into contact with the stationary electrode by an elevator mechanism that enables the forces exerted on the roller to be varied from one end of a roller to the other. Means are provided for loading and ejecting a record sheet from the surface of the transfer roller. An auxiliary drive mechanism and cleaning station are positioned to engage the imaging roller electrodes after they pass over the stationary electrode.

19 Claims, 6 Drawing Figures PATENTEnmzz I972 3,644,035

SHEET 1 [IF 4 I N VENTORS RAYMOND K. 56 CZAK BY NO SW ATTORNEY PATENIEDFEB22 m2 3, 644,035

SHEET 2 UF 4 FIG. 2

PATENTEDFEB 22 I972 SHEET R []F 4 BACKGROUND OF THE INVENTION This invention relates generally to an imaging system and in particular to a photoelectrophoretic imaging system. More specifically, the invention relates to new and improved methods and apparatus for implementing the photoelectric imaging process.

In the photoelectrophoretic imaging process, an image is formed from an imaging suspension or ink by subjecting the ink to an electric field and exposing it to activating electromagnetic radiation, e.g., visible light. The imaging suspension is comprised of photosensitive particles suspended within an insulating liquid carrier. The particles are believed to bear a net electrical charge while in suspension. Normally, the ink is placed between injecting and blocking electrodes used to establish the electric field and is exposed to a light image through one of the electrodes which is at least partially transparent. According to one theory, particles attracted to the injecting electrode by the electric field exchange charge with the injecting electrode when exposed to light and migrate under the influence of the field through the liquid carrier to the blocking electrode. As a result of the migration, positive and negative images are formed on the two electrodes. The blocking electrode is.covered with a dielectric material to prevent charge exchange with the particles and thereby prevent the particles from oscillating back and forth between the two electrodes.

The photoelectrophoretic imaging process is either monochromatic or polychromatic depending upon whether the light-sensitive particles within the liquid carrier are responsive to the same or different portions of the light spectrum. A full-color polychromatic system is obtained, for example, by using cyan, magenta and yellow-colored particles which are responsive to red, green and blue light respectively. An extensive and detailed description of the photoelectrophoretic process is found in U.S. Pat. Nos. 3,384,565 and 3,384,488 to Tulagin and Carreira, 3,383,993 to Yeh and 3,384,566 to Clark.

The photoelectrophoretic imaging system disclosed in the above-identified patents utilizes a transparent flat plate configuration for one of the electrodes used in establishing the electric field across the imaging suspension. However, these patents do not discuss an imaging system adapted for the rapid production of images in a sequential manner as is desirable for a commercial application of the photoelectrophoretic process.

The present imaging system employs a stationary flat plate electrode over which first and second imaging roller electrodes are passed to form an image from photoelectrophoretic ink present between the electrodes. The image formed from the ink is transferred to a record sheet loaded onto the surface of a transfer roller electrode and passed over the stationary electrode. The roller electrodes are mounted on carriages which are shuttled back and forth over the stationary electrode by novel drive means permitting the rapid and efficient formation of a plurality of images. The imaging and transfer roller electrodes are coupled to their respective carriages by elevator mechanisms. Each elevator mechanism can vary the elevation of a roller relative to the stationary electrode over a continuous range and can position the ends of a roller at different elevations. These abilities enable the elevator mechanisms to vary the shape of the interface or nip between a roller and the stationary electrode. Image formation and transfer occurs substantially in the nip and controlling its shape helps control the image forming and transferring operations. Furthermore, a novel auxiliary drive mechanism is used in combination with separate cleaning assembly to clean the surfaces of the imaging roller electrodes.

Accordingly, it is an object of the present invention to improve photoelectrophoretic imaging systems.

More specifically, it is an object of the invention to devise novel apparatus for effecting the rapid and efficient production of photoelectrophoretic images using traveling roller electrodes and a stationary flat plate electrode.

Another object of the invention is to devise novel means and methods for compressing the injecting and blocking electrodes of a photoelectrophoretic imaging system.

Another object of the invention is to control the configuration of the nip between injecting and blocking electrodes of a photoelectrophoretic imaging system.

Another object of the invention is to devise novel means for effecting translation and rotation of a roller electrode used in a photoelectrophoretic imaging machine.

Yet another object of this invention is to devise novel means for handling a record sheet to which a photoelectrophoretic image is transferred.

DESCRIPTION OF THE DRAWINGS Other objects and features of the present invention will be apparent from a further reading of the instant description of the invention and the drawings which are:

FIG. 1 is a perspective view of a photoelectrophoretic imaging machine according to the present invention;

FIG. 2 is a cross-sectional elevation view of the imaging machine taken along lines 2-2 in FIG. 1;

FIG. 3 is a schematic illustration of a sheet-handling system in side elevation and the transfer roller electrode used in the machine of FIG. 1;

FIG. 4 is a side elevation view of the auxiliary drive mechanism used by the machine of FIG. 1;

FIG. 5 is a perspective isolated view of the drive mechanism for propelling the carriages used by the machine of FIG. 1; and

FIG. 6 is a perspective isolated view of a rotational gear rack and associated apparatus used with the transfer roller on the machine of FIG. 1.

DESCRIPTION OF THE INVENTION roller electrode 3 is a blocking electrode of conventional design having a conductive core overcoated with an electrically insulating material. An image is formed on the stationary electrode by coating the roller electrode 3 or the stationary electrode 2 with a photoelectrophoretic ink and by passing the roller electrode over the stationary electrode. Typically, the stationary electrode is electrically grounded and the roller electrode is coupled to voltage source of at least :L-3,000 volts, as an example. The electric field established between the electrodes by the voltage potentials causes the photosensitive ink particles exposed to light to migrate away from the stationary electrode. The ink particles remaining on the stationary electrode form the desired image. The ink is exposed to electromagnetic radiation to which it is responsive, such as visible light, through the stationary electrode by means of the exposure mechanism 5.

Roller exposure 7 is also a blocking electrode being composed of an electrically insulating material overcoating a conductive inner core. This second roller electrode 7 is passed over the stationary electrode in the same manner as the first roller electrode 3. The second roller is also coupled to a highvoltage source but not necessarily of the same potential. The second roller is not coated with ink but is used as a means to subject to a field the ink subjected to a field during the passage of the first roller electrode. This subsequent subjection of the ink to an electric field is accomplished by exposure of the ink to light and is found to improve the quality of the image.

The image formed on the stationary electrode is transferred to a recording sheet by means of the transfer roller electrode 8. The sheet is typically a paper material made from cloth or wood fibers and of a quality selected to suit the needs of a particular user. The details of the sheet-feeding mechanism are not shown in FIG. 1 in order to simplify that drawing. FIG. 4 illustrates schematically the details of the sheet-handling apparatus which are discussed in more detail later. The transfer roller electrode is-also a blocking electrode comprising an electrically insulating layer over a conductive core. A portion of the cylindrical roller is cut away as indicated in FIG. 3 to accommodate loading and unloading a sheet around the periphery of the roller. Again this is discussed in more detail later. The image is transferred to the sheet by coupling a high voltage to the transfer roller of a polarity opposite to that coupled to the first and second rollers 3 and 7. The field established between the transfer and stationary electrodes is therefore such to effect the migration to the sheet of all the ink particles forming the image. The foregoing operation takes place as the transfer roller is passed over the image.

The transfer of an image is normally made in the absence of light. Imagewise light, i.e., light in the same configuration as used to form the image, can be used in the transfer operation without making any substantial alternations to the system. If white light, i.e., radiation including all wavelength to which the ink is exposed, is used the polarity of the voltage coupled to the transfer electrode is changed to be the same as that coupled to the first and second roller electrodes. It is noted that the present machine is particularly adapted for the use of light during transfer of an image. This is true for any type of illumination or exposure means employed whether full frame or scan type or using transparency or opaque originals. The reason is that image transfer takes place substantially at the same locations as image formation. Consequently, no particular mechanical alternation need be made to the exposure mechanism or other parts of the system to make light available during transfer.

Machine 1 includes a frame 9 on which the stationary electrode 3 is rigidly' supported. The imaging roller electrodes 3 and 7 are journaled for rotation in carriage while the transfer roller electrode 8 is journaled for rotation in carriage 11. Carriages 10 and 11 are slidably supported on the frame 9, as shown in FIG. 2, by the

rails

13, 14, 15 and 16 and an appropriate number of wheels of which the wheels 17, l8, l9 and are typical.

Wheels

17 and 19 are rotatably coupled to the carriages for rotation about a horizontal axis and ride in

tracks

13 and 15 to stabilize the carriages in a vertical plane.

Wheels

18 and 20 are rotatably coupled to the carriages for rotation about a vertical axis and ride in tracks14 and 16 to stabilize the carriage in a horizontal plane.

The carriages include bearing mounts 21-26 (FIG. 1) mounted on either side of the carriages for raising and lowering the rollers 3, 7 and 8. The bearing mounts constitute an elevator mechanism for moving the rollers between an elevation atwhich they contact the stationary electrode and an elevation at which they clear the stationary electrode. In addition, each bearing mount operates independently so the ends of a roller can be positioned at a different elevation from the stationary electrode. The bearing mounts, of which mounts 25 and 26 in FIG. 2 'are typical, are coupled to the walls of the carriages by coil springs 29 and the fluid-operated cylinders 30. The axle 31 of a roller electrode, e.g., roller 3, is journaled by a bearing 32 in the plate 33 made from an electrically insulating material. A voltage potential is coupled to a roller electrode through its axle by means of an electrical lead 35 and a conductive brush 36 that rides on the surface of an axle.

The insulating plate 33 is coupled to springs 29 and a cylinder with the springs acting as a mechanical bias that forces the plate 33 upward to hold a roller at an elevation out of contact with the stationary electrode. The cylinder barrel 37 is coupled to the wall of a carriage and the piston rod 38 is coupled to a plate 33. The springs 29 force the piston rod up into the barrel to expel any fluid in the cavity behind the piston 38 through the orifice 39. The orifice is coupled by appropriate valves and pumping to a fluid pump which pumps a fluid into the cylinder to extend the piston rod. The extended piston rod in turn forces the plate 33 downward compressing spring 29. The stroke of the piston, i.e., the distance it moves downward, is selected to move the bearing mount and therefore theroller into contact with the stationary electrode.

The roller electrodes 3, 7 and 8 are compressible at least to some degree so that when forced downward against the stationary electrode they flatten over some finite area hereafter referred to as a nip. Image formation and transfer takes place substantially in the nip because, for one reason, that is the area in which the electric field is the strongest. The elevator mechanism, i.e., the cylinders, enable the geometry of the nip to be conveniently varied to effect some variation in an image either during formation or transfer of the image. The width of the nip is varied by uniformly increasing or decreasing the fluid pressure in the cylinders at opposite ends of a roller. The nip can be rendered substantially trapezoidal or triangular by making the fluid pressure in a cylinder at one end of a roller greater than that in the cylinder at the other end of a roller.

The cylinders 30 on the left and right sides of a roller electrode are squeeze means for controlling the force exerted between roller and stationary electrodes. The force exerted between the electrodes establishes the shape of the nip between them. The force and thereby nip shape is controlled by varying the fluid pressure inthe cylinders. The fluid may be either a gas or a liquid and its pressure is controlled by an appropriate valve or other fluid pressure control device such as a variable displacement pump. The fluid-operated cylinder provides excellent force control over a continuous range of forces. In addition, since the piston rod of a cylinder extends when the load is moved, the fluid-operated cylinders 30 also provide means for insuring constant and uniform forces between the roller and stationary electrodes.

The carriages are propelled past the stationary electrode between starting or park positions on the left side of electrode 2 (FIG. 1) and turn positions on the right side of electrode 2. The drive mechanism for propelling the carriages (FIG. 5) include the drive rack gears 43 and 44 which are rigidly coupled to carriages l0 and 11 respectively and slidably supported on frame 9. The

gears

45 and 46 mate with the drive racks 43 and 44 respectively to propel the drive racks and therefore the carriages back and forth along the frame.

Gears

45 and 46 are powered by

electric motors

49 and 50 respectively to which they are coupled by

appropriate shafts

47 and 48 and

appropriate gear mechanisms

51 and 52 respectively.

The roller electrodes 3, 7 and 8 are rotated at an angular velocity to establish substantially a zero relative velocity between points on the peripheries of the rollers and points on the surface of the stationary electrode 2. The zero relative velocity between roller and stationary electrodes prevents ink from being smeared or otherwise adversely affected by the rollers. Each roller is rotated by a gear and rack assembly typical of which is the gear and rack assembly for the first roller electrode 3 shown in FIG. 2. The diameter of the rollers, speed of the carriages and gear ratios are selected to obtain the desired zero relative velocity. The rotational rack gears 55, 56 and 57 are coupled to the frame 9 being braced against sliding movement and biased by coil springs 58 upward into contact with a mating pinion gear, of which gear 59 for roller 3 is typical. The spring mounts for the rotational drive racks enable them to remain engaged with the mating pinion gears (such as gear 59) whether or not the rollers are positioned by the elevator mechanisms at an elevation for contacting or clearing the stationary electrode.

The rotational pinion gears, e.g., gear 59, are coupled to the axle of a roller, e.g., axle 31, by means of an override clutch, e.g., clutch 62. The override clutch is functionally equivalent to a ratchet and pawl mechanism where a circular ratchet is coupled to the axle 31 and the pawl is coupled to a gear such as gear 59. The pawl engages a tooth on the ratchet when carriages l0 and 11 move from the park to the turn positions causing a roller to be rotated. The pawl slides over the teeth on the ratchet when the carriages travel from the turn to the park positions preventing rotation of a roller. The gear cou pled to the roller, e.g., gear 59, is rotated during the turn to park travel because it is always operatively engaged with the rotational rack gear, e.g., rack gear 56. However the override clutch disengages a gear, e.g., gear 59, from an axle, e.g., axle 31 during the turn to park travel.

The rotational rack gear 55 used to rotate the transfer roller includes an additional feature. The rack gear 55 is normally braced against sliding movement relative to the frame 9. However, the shorten the overall length of machine 1, the rack is coupled to fluid-operated cylinder 63 (FIG. 6) which pulls the rack 55 toward the park position after carriage 11 has traveled past the stationary electrode and come to a stop. The circumference of the transfer roller is sufficiently large to have an entire image on the stationary electrode transferred to a sheet on its surface when it has been rotated less than 360. Once the image is transferred to the sheet the carriage can stop. However, to eject the sheet from the transfer roller it must be rotated through an additional angular displacement. The transfer roller is rotated the additional amount by pulling the rack gear 55 back toward the park position to rotate the pinion gear (similar to gear 59) coupled through an override clutch (similar to clutch 62) to the axle (similar to axle 31) of the transfer roller 8.

Referring now to FIG. 6, the rack gear 55 is supported by bias springs 58 above the slide member 64. Member 64 is supported for sliding movement relative to frame 9. The piston rod 66 of cylinder 63 is coupled by appropriate means to the slide member 64 and is normally substantially fully extended out of barrel 65. A fluid is pumped into the cylinder barrel 65 via conduit 67 to force the piston rod and slide member to the left, i.e., toward the park piston. This movement of the slide member 64 effects the ejectment of a sheet from the transfer roller to an output tray. Thereafter, a fluid is pumped into the cylinder barrel 65 via conduit 68 to return'the rack member to its starting position. This movement of the rack 55 toward the turn position does not rotate the transfer roller 8 because of the override clutch (such as clutch 62) coupled to the axle of the transfer roller.

The sheet-handling apparatus associated with the transfer roller is schematically illustrated in FIG. 3. An input tray 70 supports the stack of sheets 71. The top sheet in the stack is fed to the buckle mechanism comprising the buckle cams 72 and the release cam 73. Cam 72 is a friction device which is normally rotated to the portion shown to permit a sheet to be fed onto the table 74. The sheet fed onto the table is restrained from further advancement by the stop pad 75 on the release cam 73. The buckle cam 72 is then rotated counterclockwise substantially 360. The cam 72 engages the sheet fed onto the table and forces it against the stop pad 75 causing it to buckle in the manner shown. Meanwhile, the transfer roller 8 is rotated until the gripper fingers 78 are positioned near the release cam 72. The fingers 78 are mounted on a shaft 79 that is appropriately torque biased to maintain the gripper fingers closed, i.e., in contact with the periphery of the roller. A trip device 80 is rigidly coupled to the shaft and rotates the shaft clockwise against the bias when an interposer member 81 is placed in its path. The interposer 81 is a shaft coupled to the piston rod of a cylinder. The cylinder is coupled to the carriage and is positioned relative to the trip device 80 to place the interposer in the path of the trip device when the piston rod is extended. The interposer is positioned relative to the transfer roller to open the gripper fingers (i.e., move them to the position shown) when they approach the release cam.

The stop pad 75 is lifted to allow the buckled sheet to shoot forward into the open gripper fingers. Once the gripper fingers have rotated with roller 8 past the interposer 81, they close on the sheet. The sheet is pulled around the periphery of the roller by the gripper fingers with the image on the stationary electrode being transferred to it in the process. The high-voltage potential coupled to the roller not only attracts the ink particles from the grounded stationary electrode but also acts to electrostatically tack the sheet to the roller.

After the image is transferred to the sheet the carriage comes to a stop with the roller 8 in substantially the same angular position as shown in FIG. 3. At this point cylinder 63 in FIG. 6 is activated to pull the rack 55 toward the park position. Once again the interposer 81 is inserted into the path of the trip device 80 to open the gripper fingers. This time the gripper fingers are opened to release the sheet on the surface of the roller. The separator fingers 87 are normally at the position shown and are coupled to shaft 88 which is in turn rotatably supported by carriage 11. The shaft 88 is rotated by appropriate means counterclockwise to lower the fingers into the cutout 89 in the roller 8. The separator fingers deflect the sheet into the bite of friction feed rollers 90 which advance the sheet onto the output tray 90a. The movement of rack 55 continues toward the park position until the roller 8 returns to substantially that angular position shown in FIG. 3. The transfer roller remains in this angular position when the carriage is returned to the park position because of the override clutch (like clutch 59) coupled to its axle and the gear (like gear 59) mated with the rotation drive rack 55. A plurality of cam-operated switches 60 (FIG. 5) are activated by the movement of the carriages to generate electrical and mechanical timing signals for apparatus such as buckle cam 72, release cam 73 and interposer 81. The timing signals enable the various machine operations to occur at the proper instant in time.

The first and second imaging rollers 3 and 7 respectively have their surfaces cleaned by the cleaning assembly 91 when carriage 10 is at the'turn position. The cleaning tank 92 contains a cleaning fluid (normally the same material as the insulating fluid used in the photoelectrophoretic ink) and

brush rollers

93 and 94. The

rollers

93 and 94 are journaled for rota tion in the tank 92 and are rotated by appropriate motors and drive means. The outer surface of each brush roller is a fiber material which is wetted by the cleaning fluid as the brush rollers rotate. The tank 92 and brush rollers are raised by hoist means to an elevation at which the

brush rollers

93 and 94 contact the imaging rollers 3 and 7 respectively. The rollers 3 and 7 are maintained at their uppermost position by the cylinders 30 at this time.

The cleaning assembly includes the tank 92 which is slidably supported by the standards 95 and 96. The threaded shaft 97 is engaged with mated thread in the floor of the tank. Motor 98 is coupled to shaft 97 by appropriate gear means 99 for rotating the shaft. The shaft is rotated clockwise to raise the tank 92 and counterclockwise to lower it.

The imaging rollers 3 and 7 are rotated by the auxiliary drum mechanism 10] shown in FIGS. 1 and 4 when carriage 10 is at the turn position. The auxiliary drive mechanism has the

concave members

102 and 103 coupled to the piston rods of fluid-operated

cylinders

104 and 105. The

concave members

102 and 103 are extended into friction engagement with mating convex members coupled to the axles of rollers 3 and 7 when carriage 10 is at the turn position and the rollers are held at their highest elevation by the bias springs 29. Convex member 108 (FIG. 2) coupled to axle 31 of the first imaging roller electrode 3 is typical of a like convex member coupled to the axle of the second imaging roller 7. The

concave members

102 and 103 are rotated in the same direction the imaging electrodes are rotated when moving over the stationary electrode. The override clutch permits the axle of the rollers 3 and 7 to be rotated without rotating the gears engaged with rotational rack gears 56 and 57.

The

concave members

102 and 103 and associated apparatus are substantially identical and for this reason the description of one suffices for the other. Accordingly, convex member 103 (FIG. 4) is coupled to a keyed shaft 109 which is journaled for rotation in pillow blocks 10. The keyed shaft 109 has a groove extending parallel to its axis of rotation. The pulley 111 is coupled to shaft 109 by a key member rigidly coupled to the pulley and slidably fit into the groove. The key member on the pulley transmits the rotation of the pulley to the keyed shaft and permits shaft 109 to slide along its axes while being rotated. Accordingly, the concave member 103 can be slid into and out of engagement with the convex member 108. The pulleys 111 are driven by an electric motor 112 through appropriately connected pulley and belts including pulley 113 and continuous belt 1 14. The keyed shaft 109 is coupled to the piston rod 117 of cylinder 105. Cylinder is a double-acting cylinder that extends piston rod 117 when a fluid is pumped into barrel 118 through orifice 119 and retracts the piston rod when fluid is pumped into the barrel through orifice 120.

The auxiliary drive mechanism 101 cooperates with the cleaning assembly to remove unused ink and other materials from the surfaces of the imaging rollers 3 and 7, The

concave members

102 and 103 are extended and rotated to rotate the rollers 3 and 7. The cleaning tank 92 is raised to bring the

brush rollers

93 and 94 into contact with rollers 3 and 7. The fiber material on the brush rollers wet and scrub the surfaces of rollers 3 and 7. The cleaning assembly 91 and auxiliary drive mechanism are retracted from the rollers after the cleaning operation is over. Squeegees can be pressed against the surfaces of the rollers 3 and 7 to remove any remaining cleaning fluid if so desired.

The inking of the stationary electrode and/or the first imaging electrode can be accomplished by pouring a photoelectrophoretic ink onto the surface of roller 3 or electrode 2 since both are accessible for this purpose. Alternately, appropriate inking means can be placed near either the park or the turn positions to mechanically coat the surface of the roller electrode with an ink. Typical means might include a wetting roller such as the brush rollers 92 and 93 submerged in an ink bath and positioned to contact the roller 3. Also, such a mechanism could be coupled to carriage in front of the roller 3 to coat the electrode 2 with ink as the carriage travels over it.

The exposure mechanism 5 used to expose the ink between the roller and stationary electrodes (regardless how the ink arrived there) includes the transparency projector 123 of conventional design and the plane mirror 124. The projector includes means for holding a transparency, for illuminating the transparency, for collecting the radiation passing through the transparency and for focusing a light image of the transparency onto the interface or nip between the roller and stationary electrodes. The projector and mirror are mounted on the frame with the projector aimed generally at right angles to the path traveled by the rollers 3, 7 and 8. This enables the projector to be positioned at a convenient access location on the frame. in addition, the exposure mechanism is physically out of the way of the carriages and other moving parts and enables the overall machine size to be minimized.

The mirror 124 converts the right reading light image of a transparency to a reverse reading light image. This results in the formation of a reverse reading image on the stationary electrode (as viewed looking downward onto the stationary electrode). The reverse reading image is once again right reading, however, after the image is transferred to a sheet. and

What is claimed is:

l. imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes,

a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller,

translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions,

rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image; and,

elevator means for moving a roller electrode into contact with the stationary electrode as it travels thereby and for controlling the force exerted by the roller electrode along its length on the stationary electrode.

2. The apparatus of claim 1 wherein said elevator means includes means to hold a roller electrode at a first elevation relative to the stationary electrode and means for independently moving each end of a roller electrode from that first position.

3. The apparatus of claim 1 wherein said elevator means includes bias means for holding a roller electrode at an elevation out of contact with the stationary electrode and first and second means coupled to each end of the roller electrode for moving an end of a roller electrode toward the stationary electrode.

4. The apparatus of claim 1 wherein said elevator means includes left and right bearing mounts between which a roller electrode is journaled, left and right bias means for urging the left and right bearing mounts respectively away from the stationary electrode and left and right squeeze means for moving the left and right bearing mounts respectively toward the stationary electrode against the force exerted by the bias means.

5. The apparatus of claim 4 wherein said squeeze means include fluid-operated cylinders.

6. imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions,

rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for affecting formation and transfer of an image; and,

handling means for loading a sheet onto the surface of the transfer roller prior to passing over the stationary electrode and for ejecting the sheet from the roller after an image has been transferred to the sheet.

7. The apparatus of claim 6 wherein said sheet-handling means includes gripper means for holding a sheet to the transfer roller, input means for feeding a sheet into the gripper means and separator means for deflecting a sheet released by the gripper means from the roller to an output tray.

8. The apparatus of claim 7 wherein said input means includes a buckle means for buckling a sheet against a stop and a release means for moving the stop pad to allow the tension of a buckled sheet to advance the sheet to the gripper means.

9. The apparatus of claim 7 further including an input tray for supporting a stack of sheets and means for feeding a single sheet from the stack to the buckle means.

10. imaging apparatus comprising 7 a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to elec tromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes,

translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions; and,

rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image, wherein said rotational drive means includes means to rotate said transfer roller after it has traveled past the stationary electrode for ejecting from the transfer roller a record sheet to which an image has been transferred.

11. lmaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied between said r oller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes,

translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions, and

rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image, wherein said translational drive means includes at least one carriage supported for travel past said stationary electrode and means for stabilizing the carriage in horizontal and vertical planes.

12. The apparatus of claim 11 wherein said translational drive means further includes rack gears rigidly coupled to said carriage and supported for movement upon rotation of a pinion gear operatively engaged therewith.

13. lmaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions,

rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image, wherein said rotational drive means includes first and transfer rack gears supported adjacent the stationary electrode and operatively engaged with pinion gears coupled to said at least first electrode and transfer roller electrode respectively by override clutches that permit rotation of a roller during park to turn travel.

14. The apparatus of claim 13 further including elevator means for varying the elevation of a roller electrode relative to the stationary electrode and bias means for maintaining engagement between a pinion and rack gear for rotating a roller regardless of the elevation of the roller electrode.

15. The apparatus of claim 13 wherein said rotational drive means further includes means for pulling said transfer rack gear toward the park position after the transfer roller has traveled past said stationary electrode for ejecting a record sheet from the transfer roller after an image has been transferred thereto.

16. Imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions,

cleaning means positioned adjacent said turn position to clean the first roller electrode after the formation of an image.

17. The apparatus of claim 16 further including auxiliary drive means for rotating said first roller electrode independently of said rotational drive means for assisting the cleaning means in cleaning the first roller electrode.

18. The apparatus of claim 16 wherein said rotational drive means for rotating said first roller electrode includes an override clutch and said auxiliary drive means includes a first friction member slidably and rotatably supported for engaging a second friction member coupled to said first roller electrode for rotation of the roller electrode in a direction permitted by the override clutch.

19. In a photoelectrophoretic imaging system of the type wherein roller and second electrodes are supported for relative movement to form an image from photoelectrophoretic ink present in the nip formed between the electrodes exposed to electromagnetic radiation and subjected to an electric field established by voltages coupled to the electrodes, an elevator mechanism for controlling the shape of the nip between the electrodes comprising bias means to hold one electrode at a first elevation relative to the other,

i left and right squeeze means coupled to the ends of one electrode to force the electrodes together against the force of the bias means,

said bias means coupled to left and right bearing mounts supporting said roller electrode urging the roller electrode to an out of contact elevation with the second electrode and wherein said left and right squeeze means include fluid operated cylinders coupled to the left and right bearing mounts respectively to force the roller and second electrodes into contact.

Claims

1. Imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions, exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes, a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller, translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions, rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image; and, elevator means for moving a roller electrode into contact with the stationary electrode as it travels thereby and for controlling the force exerted by the roller electrode along its length on the stationary electrode.

6. Imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions, exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes, a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller, translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions, rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for affecting formation and transfer of an image; and, handling means for loading a sheet onto the surface of the transfer roller prior to passing over the stationary electrode and for ejecting the sheet from the roller after an image has been transferred to the sheet.

10. Imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions, exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes, a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller, translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions; and, rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image, wherein said rotational drive means includes means to rotate said transfer roller after it has traveled past the stationary electrode for ejecting from the transfer roller a record sheet to which an image has been transferred.

11. Imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions, exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes, a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller, translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions, and rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image, wherein said translational drive means includes at least one carriage supported for travel past said stationary electrode and means for stabilizing the carriage in horizontal and vertical planes.

13. Imaging apparatus comprising a stationary transparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions, exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes, a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller, translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions, rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image, wherein said rotational drive means includes first and transfer rack gears supported adjacent the stationary electrode and operatively engaged with pinion gears coupled to said at least first electrode and transfer roller electrode respectively by override clutches that permit rotation of a roller during park to turn travel.

16. Imaging apparatus comprising a stationary trAnsparent electrode and at least a first roller electrode supported for travel past the stationary electrode between park and turn positions, exposure means for exposing photoelectrophoretic ink applied between said roller and stationary electrode to electromagnetic radiation in imagewise configuration to form an image on the stationary electrode from ink exposed to radiation and subjected to an electric field established between the electrodes, a transfer roller electrode supported for travel past the stationary electrode over substantially the same path traveled by said first roller electrode to transfer an image formed on the stationary electrode to a record sheet carried by the transfer roller, translational drive means for propelling said at least first roller electrode and said transfer roller electrode past said stationary electrode between park and turn positions, rotational drive means for rotating said at least first roller electrode only as it travels past the stationary electrode from park to turn positions for effecting formation and transfer of an image; and, cleaning means positioned adjacent said turn position to clean the first roller electrode after the formation of an image.

19. In a photoelectrophoretic imaging system of the type wherein roller and second electrodes are supported for relative movement to form an image from photoelectrophoretic ink present in the nip formed between the electrodes exposed to electromagnetic radiation and subjected to an electric field established by voltages coupled to the electrodes, an elevator mechanism for controlling the shape of the nip between the electrodes comprising bias means to hold one electrode at a first elevation relative to the other, left and right squeeze means coupled to the ends of one electrode to force the electrodes together against the force of the bias means, said bias means coupled to left and right bearing mounts supporting said roller electrode urging the roller electrode to an out of contact elevation with the second electrode and wherein said left and right squeeze means include fluid operated cylinders coupled to the left and right bearing mounts respectively to force the roller and second electrodes into contact.