Photoconductor-carrying Drum Assembly

Abstract

A photoconductor-carrying drum assembly is provided comprising a plurality of frame structures each with a pair of pivotal support members which normally mate together to define a curved surface with a flexible photoconductor element resting thereon. The support members of each frame structure swing inwardly when the structure reaches a predetermined angular position upon rotation of the drum assembly, whereby the photoconductor element assumes a substantially planar configuration for exposure. Each photoconductor element extends between supply and take-up spools carried by the frame structure together with a mechanism for periodically advancing the photoconductor in the imaging area.

Description

BACKGROUND OF THE INVENTION

The present invention is generally related to electrophotography and, more particularly, to a drum assembly for use with an electrophotographic reproduction apparatus and which carries an advanceable web of flexible photoconductor and includes means for flattening the photoconductor during exposure.

In recent years, various types of electrophotographic reproduction machines have been proposed or manufactured which utilize the well known principles of photoconductivity. Various plain paper type copiers have been provided which include drums with cylindrical photoconductive surfaces, such as selenium, which are exposed to the image of the original document to be copied to provide a latent image pattern. Typically, pattern is developed by the electrostatic application of toner particles which are ultimately transferred and fused to a plain paper copy. The use of a cylindrical drum with a photoconductive surface has the advantage of ease of disposition of the various process stations around the circumference of the drum. However, such drum structures are expensive to manufacture or replace, as is occasionally necessary. Furthermore, since the photoconductor surfaces are not flat, it is necessary to expose such progressively by line scanning the original document. Whatever means of scanning is employed, it necessarily contributes substantially to the cost of manufacture of the apparatus and significantly reduces the copy production rate.

In an attempt to increase the copy production rate, several plain paper copiers have been proposed which employ a flash exposure of the original onto a flat photoconductor surface, rather than a curved surface as provided with the earlier drum structures. One such proposed system includes an endless photoconductor belt or web, a portion of which assumes a planar configuration to accommodate imaging at a flash exposure station. Subsequent to exposure, the photoconductor web is advanced past the various process stations to ultimately produce a plain paper copy. Typically, the photoconductor web is of sufficient length to accommodate several image areas, whereby several copy processes may be carried out simultaneiously to further enhance the copy production rate. However, such endless belt arrangements require that the belt pass along a rather tortuous path in order to hold the size of the machine within reasonable dimensions. This subjects the belt to undesirable flexing and bending along its path around rollers of relatively small radious, which could eventually weaken the photoconductor support material to the point of breakage and possibly cause deterioration of the organic or inorganic photoconductor surface, necessitating replacement of the belt. Another problem is that the known photoconductor surfaces which are more suitable for withstanding the flexing have relatively short life spans in that they become fatigued within a relatively small number of copy cycles, thus requiring periodic replacement of the belt if quality copies are to be produced.

In attempts to overcome the above-mentioned problems presented by the endless photoconductor belt arrangement, various mechanical drum structures have been proposed which periodically flatten the photoconductor element for flash exposure. One such arrangement is disclosed by U.S. Pat. No. 3,584,947 to N. Mihalik and includes a cylindrical drum which carries several photoconductor plates around its circumference, each plate defining an image area. The plates are normally held in a curved configuration, but are periodically unwrapped from the drum surface to provide a planar configuration during exposure. Each plate is clamped, or otherwise held, along its opposite edges by a pair of lever mechanisms which are caused to move outwardly beyond the drum's circumference to flatten the associated photoconductor plate when the plate is positioned for exposure. Since each photoconductor plate periodically assumes a planar configuration, flash type exposure may be utilized, thereby providing relatively high speed copying. On the other hand, however, the mechanisms which effect unwrapping of the plates each include a considerable number of moving parts which are costly to manufacture and tend to decrease the overall liability of the machine. Also, since the levers move outwardly, considerable clearance must be provide around the drum making it necessary to increase the size of the machine and sacrifice compactness. Most important, is the fact that the photoconductor plates are susceptible to film build-ups and/or deterioration after a number of copy cycles, necessitating frequent servicing or replacement of the photoconductor plates, thus increasing the effective cost of operation.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel photoconductor-carrying drum assembly for use with an electrophotographic reproduction apparatus to provide the advantages of high speed copying and at the same time provide reliable operation requiring a minimum amount of servicing.

Another object of the present invention is to provide a versatile photoconductor-carrying drum assembly which is capable of periodically providing a portion of flattened photoconductor for flash exposure, yet is of relatively simple, highly reliable construction which is economical to manufacture and maintain.

It is a further object of the present invention to provide a unique drum assembly comprised of a plurality of frame structures, each carrying a photoconductor web extending between a supply spool and a take-up spool, whereby the web may be conveniently advanced a predetermined amount to replenish a fatigued or damaged portion of the photoconductor.

Still another object of the present invention is to provide a compact drum assembly comprising a pivotal support structure defining a normally curved support surface for a flexible photoconductor, the support structure being periodically pivoted inward toward the axis of drum rotation, whereby the photoconductor assumes a planar configuration for flash exposure.

Yet a further object of the present invention is to provide a photoconductor-carrying drum assembly including a pair of support doors which are folded inwardly in response to rotation of the drum assembly to a predetermined angular position, thereby presenting a flattened photoconductor element to a flash exposure station.

It is a further object of the present invention to provide a versatile drum assembly carrying at least one photoconductor web and including means for advancing the web a predetermined amount upon completion of a predetermined number of copy cycles.

Still another object of the present invention is to provide a unique photoconductor-carrying drum assembly including a mechanism for incrementally advancing or creeping the photoconductor element to incrementally remove fatigued portions of the photoconductor from the image area, each advancement occurring after a predetermined number of copy cycles.

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

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a typical electrophotographic reproduction machine employing the photoconductor-carrying drum assembly of the present invention;

FIG. 2 is an exploded perspective view of the drum assembly of the present invention with sections removed;

FIG. 3 is an end view of the drum assembly with portions shown in section and with one of the frame structures in a folded position to provide a flattened photoconductor element;

FIG. 4 is a partial plan view of the drum assembly taken along section 4--4 of FIG. 3;

FIG. 5 is a partial end view of the drum assembly showing the associated cam plates;

FIG. 6 is an exploded perspective view of a first embodiment of the photoconductor advance mechanism associated with the drum assembly;

FIG. 7 is a sectional view of the photoconductor advance mechanism illustrated in FIG. 6;

FIG. 8 is a simplified end view of the drum assembly as utilizing the advance mechanism shown in FIG. 6 together with an arcuate actuation member;

FIG. 9 is a partial side elevation of the drum assembly and actuator illustrated in FIG. 8;

FIG. 10 is an end view of a single frame structure of the drum assembly provided with a second embodiment of the advance mechanism;

FIG. 11 is an exploded perspective view of the frame structure and advance mechanism illustrated in FIG. 10;

FIG. 12 is a side elevation of the mechanical counter and advance ratchet illustrated in FIG. 11, with sections removed;

FIG. 13 is a sectional view of the tensioning mechanism associated with the supply spool shown in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now, more particularly, to FIG. 1 of the drawings, a typical electrophotographic reproduction apparatus is generally indicated by the numeral 20 and includes a rotatably supported drum assembly 22 mounted in a housing 24. The drum assembly is operatively connected to a drive motor, not illustrated, which effects controlled rotation of the drum assembly in a clockwise direction as indicated by arrow 26. The drum assembly is comprised of four quadrants or sections 28, 30, 32 and 34, each of which carries its own photoconductor element which defines a corresponding image area, as hereinafter explained.

Disposed about the periphery of the drum assembly 22 are a number of processing stations which carry out the conventional steps of the xerographic copying process. An initial charging station may be defined by a conventional corona discharge unit 36, or equivalent device, which provides a uniform charge on the surface of the photoconductor element prior to exposure. A flash exposure station, generally indicated by the number 38, is provided with a pair of flash lamps 40, preferably of the xenon type, which irradiates a document 42 resting upon a transparent window 44 in face-down orientation. This provides an image of light and shadow which is projected by a stationary lens 46 onto an image plane 48, which coinsides with the photoconductor element which is of a planar configuration during exposure.

The next station in the direction of rotation of drum assembly 22 is a developer unit 50, of a conventional type, which applies toner particles to the latent image pattern on the associated photoconductor element to define a developed image. Subsequent to development, the associated drum assembly quadrant is rotated to a transfer station, generally indicated by the numeral 52. Here the developed image on the photoconductor element is transferred to a sheet of copy material fed to the transfer station from a supply stack 54. Typically, the transfer of the developed image pattern is effected electrostatically and may be aided by the use of a transfer corona, not illustrated. The copy sheet is then separated from the drum quadrant by appropriate means and the toner image is fused to the copy sheet at a fusing station 56. The finished copy is then transported by appropriate means, not illustrated, to a output hopper, such as that indicated at 58. Various transfer and fusing techniques are well known to those skilled in the art of electrophotography, and a detailed description of such is deemed unnecessary for the purposes of this specification.

Since some residual toner remains on the photoconductor element, it is necessary to clean the element prior to re-exposure. Typically, this is achieved by a cleaning station including a pre-clean corona unit 60 which losens the remaining toner particles, and a cleaning unit 62 which brushes the toner particles from the surface of the photoconductor element.

It will be appreciated that the drum assembly of the present invention provides a plurality of image areas spaced around its circumference, whereby the various process stations may be operated concurrently to provide a high copy production rate. For example, when making multiple copies, the exposure operation can be carried out at quadrant 28 while the development operation is taking place at quadrant 30, together with the transfer and cleaning operations at quadrants 32 and 34, respectively. Since exposure is achieved by a flash, rather than scanning, the drum may be rotated at a high rate of speed which significantly enhances the copy production rate of the machine.

Referring now to FIG. 2 of the drawings, the preferred embodiment of the drum assembly may be seen in more detail. Each quadrant or section of the drum assembly is defined by an independent frame structure comprising a pair of rigid support members or doors 64 and 66, each pivotally mounted between a pair of rigid end plates 68 and 70 for controlled pivotal movement about axes 72 and 74, respectively. Normally, members 64 and 66 engage each other along line 76, such that they define a curved support surface for a flexible photoconductor element 78. Preferably, photoconductor element 78 is in the form of an elongated web extending between a supply location and a take-up location in the associated frame structure and includes a layer of organic photoconductor, such as polyvinyl benzocarbazole, on a base of alluminized Mylar of approximately 3 to 5 mils thickness. The portion of the photoconductor element which overlies support members 64 and 66 defines an image area which is normally of curved, part-cylindrical configuration. During the flash exposure operation support members 64 and 66 are moved inwardly, whereby the photoconductor element assumes a substantially planar configuration, as hereinafter explained.

Each of the frame structures is mounted to a common hub 92 which is provided with a pair of dovetails 94 and a group of key fins 96 which cooperate with key ways 98 and 100 in end plates 68 and 70. This provides convenient installation and removal of each frame structure from the hub permitting each frame structure to be removed independently of the others. Each frame structure may be secured in place against axial movement by a stop member 102 and lock tab 104, or other appropriate fastening means.

Preferably, the movement of the support members of each frame structure is achieved by way of cam followers 80 and 82 which are disposed outboard of end plate 68 and are carried by mounting pins 84 and 86 associated with support members 64 and 66, respectively. The mounting pins extend through appropriate slots 88 and 90 formed in the end plate.

With reference to FIGS. 3-5, the operation of each frame structure may be more clearly understood. As mentioned above, the support members are normally disposed in their outer positions, whereby they mate together to define the curved support surface for the photoconductor element. Preferably, each frame structure is provided with a pair of leaf-spring members 106 and 104 mounted to end plate 68 with movable end portions which retentively engage mounting pins 84 and 86 to normally retain the support members in their outer positions. Each of the cam followers 80 and 82 travel in circular path with the drum assembly until it engages a cam surface associated with a group of cam plates 110, 112, 114 and 116, illustrated in FIG. 4 and 5. The cam plates are effective to overcome the retaining forces of leaf-springs 106 and 108, allowing support members 64 and 66 to move inwardly toward the axis of drum rotation to a collapsed or folded position as illustrated in the uppermost quadrant of FIG. 3. Inward movement of the support members is accompanied by a corresponding disengagement from the intermediate portion of the photoconductor web 78, permitting it to assume a substantially planar configuration for flash exposure. Since the length of the intermediate portion of the photoconductor web is somewhat less when in the planar configuration than when in the curved configuration, appropriate tensioning means are provided for pulling the web taut during collapse of the support doors. Typical embodiments of the tensioning mechanism are hereinafter described.

With particular reference to FIG. 5, the arrangement of the cam surfaces which effect movement of the support members may be seen in more detail. Cam plates 110, 112, 114 and 116 are shown in solid line, while portions of the drum assembly being shown in phantom for the sake of clarity. The surfaces associated with the cam plates define a pair of distinct paths for followers 80 and 82 to appropriately time the opening and closing of support members 64 and 66 such that the photoconductor element assumes a planar configuration when the drum assembly is at a predetermined angular position corresponding to the exposure operation. In addition, the cam surfaces carefully control the movement of the doors relative to each other to assure clean engagement and disengagement therebetween.

It will be appreciated that as the drum assembly is rotated in a clockwise direction, as illustrated in FIG. 5, cam followers 80 and 82 enter the cam paths at an area generally indicated by the numeral 118. The folding operation is initiated by engagement of follower 80 with cam surface 120 defined by plate 110 and axially spaced from a corresponding cam surface 122 associated with cam plate 112. Since follower 80 engages the cam plate prior to follower 82, it may be referred to as the "leading" cam follower, with the corresponding cam surfaces being referred to as the "leading" cam surfaces. Similarly, follower 82 is herein referred to as the "trailing" cam follower, and the corresponding cam surfaces are referred to as the "trailing" cam surfaces.

Leading cam surface 120 curves radially inward toward the axis of drum rotation, whereby it is effective to influence leading follower 80 radially inward sufficiently to overcome the retaining forces of leaf-spring 106. Subsequent to release from leaf-spring, support member 66 continues to pivot inwardly under the influence of gravity with follower 80 riding along cam surface 124. The leading cam surface curves radially outward at a point indicated at 126 and is effective to influence follower 80 outwardly to return of support member 66 to its original position subsequent to exposure. Returned to the original position occurs when follower 80 reaches the apex of the leading cam surface as indicated at 128. At this position, leaf-spring 106 is effective to retain support member 66 in its outermost position during the development, transfer, and cleaning operations explained above.

Shortly after follower 80 initiates inward movement of support member 66, trailing follower 82 engages the trailing cam surface at 122 to initiate inward movement of trailing support member 64. As mentioned above, follower 82 is axially spaced from cam follower 80 and follows a path which is separate from the leading cam path. Plates 112 and 116 provide a pair of parallel cam surfaces, generally indicated by the numerals 130 and 132, which define the trailing path. Cam surface 132 is shaped to prevent trailing support member 64 from striking member 66 during each cycle for exposure. After exposure, the trailing cam surfaces influence follower 82 outward to return support member 64 to its original position in engagement wiht support member 66. It will be appreciated that the cam surfaces accurately control movement of the support members of each frame structure as the drum assembly is rotated. Of course, it is not intended that the present invention be limited to the cam configurations illustrated in FIG. 5 as various types of appropriate cams may be utilized, if desired.

With reference to FIGS. 6 and 7, a first embodiment of the photoconductor advance mechanism of the drum assembly is illustrated. Preferably, this mechanism is intended for advancing the photoconductor web an entire image area upon completion of a predetermined number of copy cycles. However, it will be appreciated that the mechanism may be readily adapted for advancing the photoconductor a lessor or greater distance than a single image area. The photoconductor web extends from a supply spool 134, through a pair of supply control rollers 136 and 138, over the support members 64 and 68, between take-up control rollers 140 and 142, to a take-up spool 144. Advance of the web is effected by controlled rotation of roller 142. Also, coller 142 serves to provide the appropriate tensioning of the web when the support members are folded inwardly during exposure, whereby the intermediate portion of the web assumes a substantially planar configuration. This tensioning is provided by a coil spring 146 with its inner end 148 affixed to shaft 150 by way of a slot 152, or other appropriate fastening means. Roller 142 is affixed to shaft 150 for rotation therewith, together with a gear 154 in meshing engagement with gear 156 associated with roller 140. Both roller 140 and gear 156 are rotatably mounted to a support shaft 158 by way of bearings, such as indicated at 160 in FIG. 7. Support member 66 is affixed to shaft 158 for pivotal movement therewith. The take-up control rollers 140 and 142 are provided with surfaces of resilient material such as rubber, and are biased toward each other, whereby the photoconductor web is pinched tightly between the rollers. As such, rotation of roller 142 effects a corresponding movement of the web.

When the support members are folded inwardly for exposure the excess intermediate portion of the web is taken up by spring 146 which rotates roller 142 in a clockwise direction. This maintains tension on the web to assure that such is in a planar configuration at the exposure station. When the support members are moved outwardly subsequent to exposure, tension on the web overcomes the forces of spring 146, whereby a length of the web is pulled back through rollers 142 and 140, permitting the web to assume its original curved configuration.

During cycling of the support members, the photoconductor web is prevented from creeping forward due to the pinching action of supply control rollers 136 and 138. Preferably, each of these rollers is provided with a resilient surface which frictionally engages and tightly grips the photoconductor, preventing movement thereof unless the rollers are rotated. Rotation of the supply control rollers is normally prevented by way of a drag brake mechanism, generally indicated by the numeral 161. Roller 136 is affixed to partially threaded shaft 162 held against rotation by way of flat 164 in engagement with end plate 70. An adjustable clamp nut 166 is threadedly mounted to the shaft and is tightened to bring a friction washer 168 in snug engagement with the end of roller 136 under the influence of a spring washer 170. The clamp nut 166 is adjusted to provide sufficient drag to prevent creeping of the photoconductor, yet allow advancement of the photoconductor under control of the advance mechanism, as hereinafter explained.

In order that the intermediate portion of the web is held taut during each exposure it is essential that spring 146 be sufficiently wound to effect take up of the excess when the doors are swung inwardly. This is achieved by winding the spring each time the support doors are cycled. An outer end portion 172 of the coil spring is fixed to a toothed drive pulley 174 for rotation therewith. A toothed belt 176 drivingly connects pulley 174 with a toothed advance pulley 178. Drive pulley 174 is rotatably mounted to the end of shaft 150 and is provided with a pin 180 which engages a corresponding finger 182, associated with shaft 150, when the spring is fully wound. Since the inner end 148 of the coil spring is affixed to shaft 150 and the outer end 172 is affixed to drive pulley 174, rotation of the drive pulley independent of shaft 150 is effective to wind the spring. After pulley 174 has been advanced a predetermined amount in a clockwise direction, pin 180 engages fingers 182 causing the drive pulley and shaft 150 to rotate in unison in a clockwise direction. This occurs during advance of the photoconductor, as hereinafter explained.

As mentioned above, the winding operation is initiated by the cycling of support members. Support member 66 is provided with a lever arm 184 which carries a pin 186 extending between the legs of a bifurcated member 188. A nylon bushing 190 is mounted to a shaft 192 and carries member 188 in frictional engagement under the influence of adjustable clamp bolt 194. Shaft 192 is supported by a one-way bearing 196, of a conventional type, which permits rotation of the shaft in a clockwise direction only. Shaft 192 is provided with a hollow or bore which is frictionally engaged by an expandable nylon shaft 198, as indicated at 200 in FIG. 7. This frictional engagement may be adjusted by a screw 202 which is threaded into shaft 198 such that tightening of the screw causes the shaft to expand outwardly to increase its frictional engagement with the interior of shaft 192. Shaft 198 is also provided with a pair of drive fingers 204 which operatively engage appropriate key ways 206 formed in take-up spool 144.

The spring winding operation may be described as follows. When the support members are folded inwardly for an exposure operation, bifurcated member 188 is rotated slightly counterclockwise. This movement is lost motion, as one-way bearing 196 prevents hollow shaft 192 from rotating in a counterclockwise direction. As the doors are returned to their original position, member 188 is rotated slightly in a clockwise direction. Normally, this motion is transmitted to shaft 192, which in turn causes rotation of advance pulley 178 and drive pulley 174 through belt 176. This movement winds the coil spring 146 in a clockwise direction. Each operation of the support door winds the spring slightly until pin 180 engages finger 182, at which time the spring is fully wound. Cycling of the doors subsequent to full winding of the spring causes bifurcated member 188 to slip on nylon bushing 190 in both the clockwise and counterclockwise directions.

It will be appreciated that clockwise advancement of shaft 192 will drive expandable shaft 198 in a clockwise direction which drives take-up spool 144 to remove any slack in the web between the take-up spool and take-up control rollers. Once the web is sufficiently tight, shaft 198 will slip with shaft 192 upon subsequent clockwise rotation. From the foregoing description, it will be appreciated that cycling of the support door keeps the coil spring in the fully wound condition and also prevents the accumulation of slack photoconductor within the frame structure.

In order to advance the photoconductor, drive pulley 174 is rotated in a clockwise direction, causing corresponding rotation of shaft 150 and roller 142. Rollers 140 and 142 rotate in unison through gears 154 and 156 to take up the desired length of photoconductor web. At the same time, pulley 178 is driven to rotate take-up spool 144 clockwise by way of shaft 198. Typically, the photoconductor web is advanced an entire image area after a predetermined number of copy cycles. When the advance operation has been completed, coil spring 146 is left in a fully wound condition, such that it is capable of pulling in the excess photoconductor on the first cycle of the support doors.

It will be appreciated that operation of the advance mechanism illustrated in FIGS. 6 and 7 may be effected in various manners. FIGS. 8 and 9 disclose a typical arrangement for effecting advancement of the photoconductor through rotation of drive pulley 174. An arcuate actuation member 208 is supported by appropriate means, not illustrated, and is operatively connected to a solenoid 210. A control circuit associated with the copy machine is connected to solenoid 210 by way of leads 212 for energization of the solenoid, for example, after a predetermined number of copy cycles. Of course, the control circuit may include means for otherwise energizing the solenoid, such as an "Advance" push button to effect manual advancement in the event of damage or excessive wear to the photoconductor.

Actuation member 208 is provided with a plurality of gear teeth 214 arcuately disposed on the lower side of the actuation member to define an arcuate rack. Drive pulley 174 is considerably wider than belt 176 to provide an exposed portion 216, illustrated in FIG. 9, which underlies actuation member 208. The actuation member is normally disposed in a position shown in solid line in FIG. 8. When solenoid 210 is energized, the actuation member is moved downward to a position shown in phantom in FIG. 8 at 208a. In this position, rack teeth 214 drivingly engage the teeth of drive pulley 174. With the drum assembly rotating in a counterclockwise direction, drive pulley 174 is driven in a clockwise direction. This operation effects advancement of the photoconductor, with the amount of advancement being determined by the length of the arcuate rack. The solenoid may be energized for an entire revolution of the drum assembly, whereby all four of the photoconductor webs are advanced in a single operation. On the other hand, if desired, the solenoid energization may be only mementary, whereby a single quadrant photoconductor is advanced. It will be appreciated that the photoconductor advance arrangement illustrated in FIGS. 8 and 9 is not limited to the actuation member being mounted directly above the drum assembly. It may be more suitable to mount the actuation member to one side or the other, or beneath the drum assembly, such that advancement occurs while the photoconductor is in the curved configuration.

Referring now, more particularly, to FIGS. 10 and 11, a second embodiment of the photoconductor advance and tensioning mechanism is illustrated. Typically, this mechanism advances the photoconductor web incrementally, or an amount less than an image area. Basically, each incremental advance is controlled by a mechanical counter and drive ratchet mechanism generally indicated by the numeral 218 which causes clockwise rotation of a drive shaft 220 to rotate a pair of pinch rollers 222 and 224, similar to the control rollers associated with the first embodiment. At the same time take-up spool 226 is driven in a counterclockwise direction to take up any slack photoconductor which has been advanced by rollers 222 and 224.

A drive ratchet 228 which is keyed or otherwise affixed to the drive shaft 220 to effect rotation thereof by way of a drive pawl 230 after the counter completes the preselected number of copy cycles. Pawl 230 is spring biased toward the teeth of ratchet 228, but normally is prevented from driving engagement therewith by a main counter wheel 232 provided with a single ratchet tooth 234. When counter wheel 232 is advanced to bring tooth 234 in alignment with drive pawl 230, the drive pawl is enabled to advance drive ratchet 228 upon the next cycle of the support doors. The mechanism is also provided with an adjustable advance cam 236 which determines the length of each incremental advancement of the photoconductor web. A pin or finger 240 is mounted on pawl 230 and rides on a cam surface 238 to prevent operative engagement of the drive pawl with the teeth of ratchet 228 through portion of the advance stroke. As pin 240 moves downwardly beyond the cam surface 238, drive pawl 230 is permitted to operatively engage the teeth of ratchet 228. That portion of the stroke during which the drive pawl is held inoperative may be set by adjusting the angular position of cam 236 by way of bolt 242 which cooperates with an arcuate slot 244 in the cam.

Drive pawl 230 is mounted to an advance shaft 246 carried by a pawl drive lever 248. A counter advance pawl 250 is also mounted to shaft 246 and is appropriately spring biased toward a counter advance ratchet 252. A drive gear 254 is attached to support door 66 for movement therewith and meshes with a driven gear 256 which is rotatably mounted about drive shaft 220 by way of a bushing 258, as best illustrated in FIG. 12. Drive lever 248 is mounted to bushing 258 and rotates with gear 256. Thus, cycling of the support door causes a corresponding reciprocation of lever 248, which in turn reciprocates pawls 230 and 250 along a predetermined arcuate path.

The gearing is such that when support door 66 is in its normal outer position, drive lever 248 is in its lower position as illustrated in FIG. 11. When the support doors are pivoted inward, drive lever 248 is pivoted in a counterclockwise direction to a position shown in dash line at 248a in FIG. 10. As the support doors move outwardly, pawls 230 and 250 are moved downward. Each downward stroke of the counter pawl 250 is effective to advance counter ratchet 252 a preselected number of teeth. A counter rate cam 259, similar to cam 236, engages a pin 260 of pawl 250 to prevent pawl's engagement with ratchet 252 during a portion of each stroke. The angular position of cam 258 may be adjusted by way of bolt 242. A pair of one-way pawls 262 and 264 are provided for preventing ratchets 228 and 252 from creeping backward in a counterclockwise direction. Main counter wheel 232 is affixed to counter ratchet wheel 252 for rotation therewith, such that each advancement of the counter ratchet moves ratchet tooth 234 closer to drive pawl 230. After a preselected number of counts or advancement of the counter ratchet, ratchet tooth 234 falls within the stroke area of tripawl 230, enabling the drive pawl on the next stroke.

When each incremental advancement is effected through mechanism 218, it is essential that the slack portion of photoconductor be wound onto take-up spool 226. This is achieved by way of tensioning lever 266 including a slot 268 which receives an extension of shaft 246 carried by drive lever 248. This mechanical arrangement is best illustrated in FIGS. 10 and 12. The tensioning lever is provided with a drive surface 270 which frictionally engages a corresponding surface 272 associated with take-up spool 226. The opposite end of the take-up spool is mounted to a one-way bearing 274 which permits rotation of the take-up spool is a counterclockwise direction only. Thus, as tensioning lever 266 is reciprocated, take-up spool 226 is rotated in a counterclockwise direction until the web is snugly wound and held in tension between the take-up spool and controller rollers 222 and 224. Subsequent reciprocation of the tensioning lever is accompanied by slippage at frictional surfaces 270 and 272. This slippage also occurs when the tensioning lever is pivoted in a clockwise direction due to the one-way bearing 274.

The second embodiment of the advance mechanism further differs from the first embodiment in that the imaging portion of the web is maintained in tension during exposure by a tensioning mechanism associated with the supply spool, rather than the take-up spool. The supply spool, indicated at 276, includes a notched disc 276 drivingly connected to a tensioning mechanism 280 by way of a connection pin 282. A housing 284 carries pin 282 and is attached to the outer end of a coil spring 286. A support shaft 290 rotatably supports one end of the take-up spool and is attached to the inner end of coil spring 286. A bushing 288 rotatably supports housing 284 to shaft 290. A friction clutch, generally indicated by the numeral 292, includes a stationary member 294 attached to the frame structures and plate 70. A moveable member 296 is keyed to shaft 290 and frictionally engages stationary member 294 along the area indicated at 298.

When the photoconductor is incrementally advanced, supply spool 276 is rotated in a counterclockwise direction, which in turn winds spring 286 by way of housing 284 and pin 282. If the spring is fully wound, shaft 290 is free to rotate through slip clutch 292. After the incremental advance is completed, spring 286 is left in a fully wound condition. When the support doors swing inward for the next exposure, the excess photoconductor is pulled in by clockwise rotation of take-up spool 276 under the influence of coil spring 286.

From the foregoing description, it will be appreciated that the second embodiment of the advance mechanism provides automatic incremental advance of the photoconductor web after a preselected number of copy cycles. By adjusting the position of cam 258, the number of copy cycles required before advancement may be conveniently selected. In addition, the length of incremental advancement may be adjusted by way of cam 236. Cycling of the support door advances the counter mechanism and effects advancement of the photoconductor upon reaching the preselected count. It will also be appreciated that cycling of the support doors maintains the photoconductor snugly wound on the take-up spool by way of tensioning lever 266, while the imaging portion of the web is automatically held in tension by way of the tensioning mechanism associated with the supply spool.

It is not intended that the second embodiment of the advance mechanism be limited to the mechanical counter illustrated in the drawings as other types of counters may be utilized, if practical to do so. Furthermore, the counting mechanism may be eliminated in lieu of very fine incremental advance which occurs on every copy cycle.

While the invention has been described with reference to the structure disclosed herein, it is not intended that the present invention be confined to the details set forth, and this application is intended to cover modifications or changes as may come within the scope of the following claims.

Claims

I claim:

1. A photoconductor-carrying assembly for use with an electrophotographic reproduction apparatus, said assembly comprising:

a frame structure including a normally curved support surface,

means for rotating said frame structure about an axis,

a flexible photoconductor element carried by said frame structure, a portion of said photoconductor element extending between first and second points of said frame structure and normally engaging said curved support surface to assume the configuration thereof, and

means for selectively moving at least a portion of said support surface inwardly toward said axis of rotation whereby said portion of said flexible photoconductor element assumes a generally planar configuration to define an imaging plane for exposure.

2. The assembly set forth in claim 1 together with means for holding said portion of said flexible photoconductor element in tension to maintain said photoconductor element in said planar configuration when said support surface is moved inwardly.

3. The assembly set forth in claim 2 wherein said support surface is normally of part cylindrical configuration.

4. The assembly set forth in claim 1 wherein said support surface is defined by at least one pivotally mounted support member operatively connected to said movement means for pivotal movement thereby between a normal position and a folded position.

5. The assembly set forth in claim 4 wherein said movement means includes actuation means operatively connected to said support member for effecting its pivotal inward movement to said folded position in response to rotation of said frame structure to a first predetermined angular position.

6. The assembly set forth in claim 5 wherein said actuation means also effects return of said support member to said normal position in response to rotation of said frame structure to a second predetermined angular position.

7. The assembly set forth in claim 6 wherein said actuation means includes a stationary cam member mounted adjacent said frame structure and a cam follower carried by said support member operatively engageable by said cam member.

8. The assembly set forth in claim 1 wherein said support surface is defined by a pair of normally mated pivotally mounted support members each operatively connected to said movement means for pivotal movement thereby between a normal position and a folded position.

9. The assembly set forth in claim 8 wherein said movement means includes actuation means operatively connected to said pair of support members for pivotally effecting their inward movement to said folded positions in response to rotation of said frame structure to a first predetermined angular position.

10. The assembly as set forth in claim 9 wherein said actuation means also effects return of said support members to their respective normal positions when said frame structure is rotated to a second predetermined angular position.

11. The assembly as set forth in claim 10 wherein said actuation means includes a pair of cam members mounted adjacent said frame structure and a cam follower carried by each of said support members operatively engageable by said cam member.

12. The assembly as set forth in claim 11 together with means for holding said portion of said flexible photoconductor element in tension to maintain said planar configuration when said support members are in said folded positions.

13. The assembly as set forth in claim 12 wherein said tensioning means is yieldable to allow the length of said portion of photoconductor element between said first and second points to vary under to influence of said support members.

14. A photoconductor-carrying assembly for use with an electrophotographic reproduction apparatus, said assembly comprising:

a frame structure including a support member defining a normally curved support surface,

motive means for rotating said frame structure about an axis,

a flexible photoconductor element comprising a web, with an intermediate portion extending between first and second spaced points associated with said frame structure and normally engaging said curved support surface to assume the configuration thereof,

supply means associated with said frame structure for storing a supply portion of said photoconductor web,

take-up means associated with said frame structure for advancing said web and storing a used portion thereof, said intermediate portion being between said supply portion and said used portion of photoconductor web and defining at least one image area, and

means associated with said frame structure for cyclicly substantially disengaging said intermediate portion of the photoconductor web from said support surface and allowing said intermediate portion of said frame structure to assume a substantially planar configuration and subsequently re-engaging said intermediate portion with said support surface.

15. The assembly set forth in claim 14 wherein said supply means and said take-up means are carried by said frame structure.

16. The assembly as set forth in claim 15 wherein said supply means and said take-up means include supply and take-up roller respectively mounted to said frame structure.

17. The assembly set forth in claim 16 together with means for applying tension to said intermediate portion of said photoconductor element when in said substantially planar configuration.

18. The assembly set forth in claim 17 wherein said tensioning means is operatively connected to at least one of said rollers.

19. The assembly set forth in claim 18 wherein the length of said intermediate portion of the photoconductor web between said first and second points when in said curved configuration is greater than when in said substantially planar configuration, said tensioning means including means for preventing slack in said photoconductor web between said first and second points when the configuration of the intermediate portion of the web is changed from curved to substantially planar by said disengagement means.

20. The assembly as set forth in claim 14 wherein said take-up means is operatively connected to said cyclic disengagement means for operation thereby.

21. The assembly as set forth in claim 14 wherein each actuation of said take-up means incrementally advances said web an amount less than one of said image areas.

22. The assembly as set forth in claim 21 wherein take-up means is actuated in response to completion of a predetermined number of operations of said cyclic disengagement means.

23. The assembly as set forth in claim 20 wherein said take-up means include means for effectively counting the number of cycles of said disengagement means to effect said selective advancement of said web upon reaching a predetermined count.

24. The assembly as set forth in claim 14 wherein said disengagement means is operatively connected to said support member to effect movement thereof from its normal position in one direction to substantially disengage said intermediate portion of photoconductor from said support surface to assume said planar configuration and subsequentially effect movement of said support member in the opposite direction for return to its normal position.

25. The assembly as set forth in claim 24 wherein said support member is pivotally mounted to said frame structure and moved pivotally by said disengagement means.

26. The assembly as set forth in claim 25 wherein said take-up means includes a take-up roller in operative engagement with said web, a main drive ratchet drivingly connected to said take-up roller and a drive pawl operatively connected to said support member for movement thereby, said counting means preventing driving engagement of said drive pawl with said drive ratchet until said predetermined count is reached.

27. A photoconductor-carrying assembly for use with an electrophotographic reproduction apparatus, said assembly comprising:

a stationary housing,

a frame structure rotatably mounted to said housing, said frame structure including a support surface,

motive means operatively connected to said frame structure for effecting rotation thereof about an axis relative to said housing,

an elongated photoconductor element carried by said frame structure and extending between a supply location and a take-up location with an intermediate portion normally engaging said support surface,

advance means operatively connected to said photoconductor element for advancing said photoconductor element over said support surface toward said take-up location from said supply location, said advance means including a rotatable drive element carried by said frame structure, said drive element moving in a circular path about said axis of rotation when said frame structure is rotated by said motive means, and

actuation means associated with said stationary housing and selectively movable between a normal retracted position and an advance position, said actuation means when in said advance position operatively engaging said drive element to effect rotation thereof to operate said advance means.

28. The assembly set forth in claim 27 wherein said actuation means includes a generally arcuate actuation member supported by said stationary housing, said actuation member intersecting said circular path when in said advanced position to engage drive element and effect rotation thereof due to rotation of said frame structure.

29. The assembly set forth in claim 28 wherein said drive element includes a gear teeth, said actuation member comprising a curved rack for operative engagement with said gear teeth when said rack is in said advance position.

30. The assembly set forth in claim 28 wherein said actuation means includes electromechanical means responsive to a photoconductor advance signal to move said actuation member to said advance position.

31. The assembly set forth in claim 30 wherein said drive element includes gear teeth, said actuation member comprising a curved rack for operative engagement with said gear teeth when said rack is in said advance position.

32. The assembly set forth in claim 31 wherein said advance means includes means for maintaining said intermediate portion of said photoconductor element in tension.