GB2093437A - Sheet Stripping Apparatus and Method - Google Patents

Abstract

A sheet stripping apparatus and method used in a photocopying machine employ a resiliently biased sheet stripping element (48) in contact with the photosensitive surface (15) of the copier for detaching a leading edge of a copy sheet (40) as it moves toward the sheet stripping assembly. A moving deflection surface, such as a knurled roller (64) is positioned immediately adjacent the operative portion of the sheet stripping element for deflecting the detached leading edge of the copy sheet away from the sheet stripping element and toward an exit path. A friction roller (74) in juxtaposition to the deflection surface provides a nip for grabbing the copy sheet and directing it along the exit path. The friction roller is preferably driven at a velocity greater than or equal to the velocity of the photosensitive surface. <IMAGE>

Description

SPECIFICATION Sheet Stripping Apparatus and Method The invention relates generally to photocopiers and in particular to a method and apparatus for stripping sheets from a fragile photosensitive surface after transfer of a developed image from the surface to a copy sheet.

Background of the Invention A photocopier employs a moving photosensitive surface which is electrically charged and then exposed to an energy image, most often a light energy pattern generated by scanning an original document. The energy is focused on the charged surface to form a latent electrostatic image thereon. The latent image is developed, and the developed image is transferred to a copy sheet of transfer material brought into intimate contact with the surface portion bearing the developed image. The sheet is then stripped from the photosensitive surface and transported away from the surface along an exit path. A fixing or fusing station is typically provided along the exit path.

The copy sheet, when it is brought into contact with the photosensitive surface, ordinarily adheres tightly to it due to the electrostatic fields created during the photocopying and transfer processes and, in the case of liquid developer copiers, also because of the surface tension created by the liquid developer. The sheet must be stripped from the surface with a minimum of disturbance to the generally fragile developed image and with minimum or no damage to the fragile photosensitive surface. At least one commercially available dry copier directs a shortduration stream of air between the copy sheet and the photosensitive surface to separate the leading edge of the copy sheet so that it can be either later gripped or allowed to fall away from the photosensitive surface. The copy sheet is then conveyed to the fixing or fusing station.The air puffing method has the disadvantage of potentially disturbing the toner particles adhering to the copy sheet and of being very sensitive to the system operating parameters.

There also exist many different apparatus wherein a mechanical member makes actual contact with the fragile photosensitive surface.

One method, particularly useful in connection with liquid developer photocopiers and described more fully in U.S. Patent No. 4,000,942, provides for a stripping assembly having an elongated blade member in contact with a marginal edge of the photosensitive surface. When the copy sheet is fed toward the photosensitive surface, a marginal edge of the copy sheet slides along the stripping blade member. The member directs a forward portion of the leading edge of the copy sheet into engagement with a roller nip. A disadvantage of this approach is that an entire marginal edge of the copy sheet is prevented from contacting the photosensitive surface and is therefore unavailable for copying. The pressure of the member against the photosensitive surface also can wear or damage the surface therebeneath.

According to another method, generally used only with dry toner copiers, a mechanical member is either in constant contact with the surface or, to reduce the likelihood of damage to the surface, can be brought into timed engagement with the photosensitive surface without loss of image on the copy sheet. In either instance, the stripped paper is generally allowed to "fall" onto a conveyor system for removal to an exit station or is directed to rollers spaced some distance away from the surface. This apparatus has the disadvantage of potentially marring the image and, where movement is timed to the copy sheet, of requiring the device to be properly timed and precisely positioned so that it does not mar the photosensitive surface or the fragile image and so that sheet pick-off is reliably accomplisheci.

There also are described in the literature sheet stripping apparatus in which the sheet stripping mechanism is traversed across a limited portion of the drum in order to more dependably prevent damage to the drum photosensitive surface.

According to one such apparatus (U.S. Patent 4,1 68,902) the sheet stripping element is in continuous motion back and forth, oscillating, across a limited section of the width of the photosensitive drum surface. The actual sheet stripping element is designed to be pivoted away from the drum surface when the sheet, a relatively stiff member according to the patent, strikes it. In a second reference, U.S. 4,252,310, a sheet stripping mechanism is designed to traverse across a limited portion of the drum in small distance steps. The steps are controlled through a ratchet assembly and a smooth cam surface.

Typically, the sheet stripping element operates in timed relation to the arrival of the image transfer sheet so that the stripping element is pivoted down, into contact with the surface of the drum, just before the sheet arrives and pivots away from the drum after the sheet has been stripped from the drum. In both of these instances, the sheet is allowed to fall on what looks to be equivalent to a conveyor belt system for movement to the exit station.

The apparatus wherein a traversing sheet stripping member is employed appears to be used with dry toner developer and appears also to be directed to removing the stripping mechanism from the drum surface whenever it is not needed.

This requires additional mechanisms and timing which increases the complexity and cost of the sheet stripping mechanism. In addition, these prior art traversing mechanisms do not provide enough control over positioning of the sheet stripping element on the photosensitive member surface.

It is therefore a principal object of this invention to minimize interference with the photocopying process and reduce potential smudging or smearing of the copy sheet image while providing a long lasting and reliable sheet stripping apparatus. It is another important object of the invention to maximize the amount of copy sheet surface available for copying. A further object of the invention is a sheet stripping apparatus which is precise, stable, low in cost, durable, simple in construction, simple to install, and substantially maintenance free. A yet further object of the invention is a sheet stripping apparatus and method which can be particularly employed in liquid developer copiers.

Summary of the Invention The invention relates to a method and apparatus for removing copy sheet material from the photosensitive surface in a photocopying apparatus. The photocopying apparatus has a moving member having a photosensitive surface, elements for forming a developed image on the photosensitive surface, and a sheet feeding apparatus for feeding copy sheet material for contact with the photosensitive surface at a transfer station where transfer of the developed image onto the copy sheet material is accomplished.

The sheet removing assembly features a sheet stripping element having an operative portion resiliently biased against the photosensitive surface for contacting a leading edge of the copy sheet as it moves toward the sheet stripping element, and for detaching that leading edge of the copy sheet from the photosensitive surface.

The assembly further features a first movable deflection surface which has a surface portion closely adjacent the operative portion of the sheet stripping element and in the path of the detached leading edge for deflecting the detached edge away from the sheet stripping element and preferably toward a second movable friction surface. The invention further features drive elements for driving at least one of the first and second movable surfaces for directing the copy sheet material toward an exit path away from the photosensitive surface.

In another aspect, the invention relates to a method for removing copy sheet material from the photosensitive surface of a photocopying apparatus. The apparatus has elements for forming a developed image on the photosensitive surface, feed members for feeding a copy sheet material for contact with the photosensitive surface at a transfer station whereat the developed image is transferred to the copy sheet material, and sheet removal elements for removing the transfer sheet from the photosensitive surface. This aspect of the invention features the steps of resiliently biasing a sheet stripping member at an operative portion thereof against the photosensitive surface for contacting a leading edge of the copy sheet as it moves toward the sheet stripping element.The method further features detaching the leading edge of the copy sheet material from the photosensitive surface using the operative portion of the sheet stripping element and positioning a movable deflection surface adjacent the operative portion of the sheet stripping element for substantially immediately deflecting and maintaining the detached leading edge of the sheet material away from the sheet stripping element and toward the exit path. The method further features driving the moving deflection surface, for deflecting the copy sheet material away from the photosensitive surface, preferably at a velocity greater than the peripheral velocity of the photosensitive surface. Thus, the sheet is deflected away from the photosensitive surface away from the stripping member, and toward the exit path.

In yet another aspect, the invention has a sheet removing assembly which employs a sheet stripping element having an operative portion resiliently biased against the photosensitive surface for contacting a leading edge of the copy sheet as the sheet moves toward the sheet stripping element, and for detaching that leading edge of the copy sheet from the photosensitive surface. The assembly features a sheet stripping element drive unit for incrementally moving the element in a direction substantially parallel to the photosensitive surface.

In this aspect, the invention features a first circumferential surface having a plurality of discrete, operatively related positions for maintaining a positioning surface at a sequential plurality of selected positions. The invention further features an assembly for operatively connecting the stripping element to the positioning surface for movement in the direction of stripping element movement and a cam drive member for driving a second circumferential surface whereby the stripping element is moved to a new position relative to the photosensitive surface. The invention also features apparatus for actuating the cam drive member after a predetermined limit has been reached.

In a preferred embodiment, the invention features a drive unit having a cam element with a plurality of discrete, operatively related, position maintaining surfaces for positioning a camming surface at a plurality of sequential selected positions, and a resilient member for biasing the stripping element in the direction of stripping element movement and against the cam surface.

The drive unit further features a drive member operatively connected to a second plurality of position maintaining surfaces for moving the cam element whereby the stripping element is moved to a new position relative to the photosensitive surface. There is further featured a mechanism for actuating the drive member after a predetermined number of copies have been made whereby the stripping element does not rest, over the expected useful life of the surface, at one surface axial position long enough to adversely affect the photosensitive surface.

Brief Description of the Drawings Other objects, features and advantages of the invention will appear from the following description of particular preferred embodiments thereof and the drawings, in which: Fig. 1 is a schematic front elevation view of a photocopier in which the present invention is incorporated; Fig. 2 is an elevation view of the photosensitive surface and sheet stripping apparatus according to the invention with the copy sheet at the transfer station; Fig. 3 is an elevation view of the photosensitive surface and sheet stripping apparatus according to the invention with the copy sheet just having been picked off the photosensitive surface at its leading edge; Fig. 4 is an elevation view of the photosensitive surface and sheet stripping apparatus according to the invention with the copy sheet on its way along the exit path;; Fig. 5 is an enlarged view of the circled section of Fig. 2; Fig. 6 is an elevation view of the photosensitive surface and sheet stripping apparatus according to a second embodiment of the invention with the copy sheet at the transfer station; Fig. 7 is a schematic elevation view of the position of the sheet stripping element relative to the xerographic drum in a particular embodiment of the invention; Fig. 8 is an elevation view of the ratchet incrementing mechanism according to a preferred embodiment of the invention; Fig. 9 is a cross-sectional view of the interconnection of ratchet assembly and open face cam assembly according to a preferred embodiment of the invention; Fig. 10 is a quasi-sectional view showing the ratchet drive mechanism of Figure 8;; Fig. 11 is a sectional view of the resiliently biased sheet stripping assembly supporting and traversing element; and Fig. 1 2 is a graphical representation of the relative position of the sheet stripping element as a function of ratchet assembly rotation position.

Description of Particular Preferred Embodiments Referring to Fig. 1 , the invention is described in association with a liquid developer photocopier 12 having a rotatable drum 14 with a photosensitive surface 1 5 thereon. The invention is equally adaptable to non-drum apparatus such as belt configuration type copiers. The illustrated drum has a photosensitive selenium surface layer deposited on an aluminum substrate, and is rotated in the counterclockwise direction as indicated by the arrow 16, by a drive motor 17. A charge corona 18 charges the drum photosensitive surface 1 5 to about + 1 000 volts D.C. The charged drum surface 1 5 is exposed to an image at an exposure station 20.In the illustrated embodiment, the image is transmitted to the drum through a lens/mirror optical arrangement 22 from a document 24 illuminated by lamps 26.

The image is focused on the drum photosensitive surface 1 5 and thereupon the charge on the drum surface progressively forms an electrostatic latent image. The electrostatic latent image on the drum surface is brought to a development station 30 where a liquid developer 32, having negatively charged toner particles, contacts the electrostatic image to develop the image. The illustrated development station 30 includes a developer tank 34 and a development electrode 36. Developer 32 is introduced between the development electrode and the drum surface 1 5 to develop the electrostatic image. The drum surface 15, now wetted and carrying the developed image, is moved past a metering roll 38 which controls and limits the thickness of the liquid developer on the drum surface.

A copy sheet material 40 is fed toward the drum surface 1 5 to a transfer station 42. The sheet 40 is conveyed to the surface by, inter alia sheet registration rollers 44, as is well known, and contacts the drum surface, in this illustrated embodiment, just before a transfer corona 46. A positive charge from the transfer corona 46 is applied to the back of the copy sheet material 40, causing the transfer of toner particles from the developed image on the drum's surface 1 5 to the copy sheet 40. The sheet 40 is stripped off the drum surface by a pick-off assembly 48, according to the invention, which directs the copy sheet 40 along an exit path to driven rollers 54.

Rollers 54 transport the sheet toward a heating element for fixing the wet liquid image and then toward a copy receiving tray (not shown).

After transfer, there remains on the drum surface an undesirable residue of liquid that is removed by a surface contacting cleaning roller 56 and a cleaning blade 58. After cleaning, and prior to the next charging step, the drum surface is electrically neutralized by a high voltage A.C.

neutralizing charge from a corona 59.

Referring to Figs. 2-4, the illustrated pick-off assembly 48 according to the invention is incrementally traversed across the drum surface, parallel to the surface. The incremental translation of the assembly occurs in this illustrated embodiment at the beginning of a copy cycle. The illustrated pick-off assembly 48 has a planar mounting plate bracket member 60 affixed to a traversing drive mechanism 61 and on which are mounted a resiliently biased pivoting stripping element 62, first and second resiliently biased knurled rollers 64 and 65 connected respectively by link members 66, 67 for movement about the same pivot axis 68, and a third and a fourth positionally fixed knurled rollers 70 and 72 respectively.The knurled rollers 64 and 65 are resiliently biased against a rubber coated driven roller 74, and knurled rollers 70 and 72 are positionally spaced apart from the roller 74.

In the illustrated embodiment, element 62 is a planar element mounted for pivoting movement in a plane substantially normal to the axis of the rotating drum, i.e. aligned with the direction of movement of the photosensitive surface at their point of contact. Similarly, in the illustrated embodiment, the axes of rotation of the rollers are parallel to each other and to the pivot axis 68.

In its normal operating position, stripping element 62 resiliently engages the photosensitive surface 1 5 of drum 14. The stripping element 62 is resiliently pivoted about a pivot axis 80 under the influence of a spring element 82. Spring element 82 connects at one end to mounting bracket 60, is coiled around a shoulder screw 83, and rests at a second end in a groove 84 in element 62. The stripping element 62 is thus biased, in Figure 2, in a clockwise direction around pivot axis 80 which brings a tip 86 of stripping element 62 into operative resilient engagement with the photosensitive surface 15.

The pressure of tip 86 against surface 15 is thus controlled by the spring element 82.

According to the preferred embodiment of the invention, the pressure with which tip 86 bears against surface 1 5 is on the order of 3-4 grams.

In other embodiments, depending upon the operating system parameters, a lower pressure may be practical. According to the preferred embodiment of the invention, the forward facing or upstream facing angle made by the engaging surface 86a of tip 86 with a tangent to the drum at the point of contact of tip 86 and the drum surface, is in the range of about 52--73 0 and is, in the illustrated embodiment, 620. The location of the pivot axis 80, relative to the center of the drum, need not be precisely controlled; and in the illustrated embodiment, the axis location is at an angle past the top of the drum of 21.780 and at 14.980 above the tangent at the point of contact.

The detail of the blade element is illustrated in Figure 7.

Rollers 70 and 72 of assembly 48 are fixed in position as noted above, and are precisely mounted on plate 60 so as to be spaced apart from the surface 87 of roller 74. Illustrated roller 74 has a rubber coating 88 on a metal core 88a.

Illustrated knurled rollers 64 and 65 are, as noted above, resiliently biased, for independent movement relative to roller surface 87. Each of rollers 64 and 65 is guided by a slot 89 and 89a, respectively, in mounting plate 60. A resilient bias is applied to roller 64 by the action of a resilient spring 90 which is secured between the bracket member 60 and connection link 66. Rotation of connecting link 66 translates roller 64 in slot 89 about pivot axis 68. Similarly roller 65 is biased toward roller surface 87 by a resilient spring 93 secured between bracket 60 and connecting link 67. Rotation of connecting link 67 moves roller 65 in a slot 89a about pivot axis 68. Rollers 64 and 65 are driven by roller 74. All of the knurled rollers 64, 65, 70, and 72 are preferably of a medium knurl (21 pitch), standard face, and are commercially available.

Roller 74 is driven at a substantially constant speed by a connection to the drive system for the drum member. Preferably, the drive connection is adjusted so that roller surface 87 has a peripheral velocity just greater than that of the drum photosensitive surface 1 5. For example, the photosensitive surface velocity can be 492 inches per minute and the velocity of the surface 87 can be 516 inches per minute. (If the peripheral velocity of roller surface 87 is about equal to the velocity of the photosensitive surface, some buckling can occur along with smudging of the image.) However, in a second particular embodiment of the invention, as described below, the peripheral velocity of the roller surface 87 is selected to be substantially greater than that of the drum surface 1 5 to ensure that a copy sheet member is drawn away from stripping element 62 after a leading edge of the copy sheet element is captured by the roller 64 - roller 74 nip after removal from the photosensitive surface. In this latter embodiment, the roller 74 is driven through, for example, a slip clutch to ensure that the sheet material is not removed from the drum prior to image transfer.Thus, the sheet material leading edge is driven at an initial velocity substantially greater than the velocity of photosensitive surface; and after the "slack" is taken up, the sheet material leading edge velocity decreases to about that of the photosensitive surface. Also in this latter embodiment there is more freedom in setting the location of roller 64 relative to tip 86.

As noted above, in normal operation according to the invention, the stripping element tip 86 gently rests on the photosensitive surface 1 5 of the drum under the influence of spring biasing member 82. Therefore, in the illustrated embodiment, the pressure of the element tip 82 against the drum surface is easily and independently controlled. Furthermore, the stripping element 62 is configured so that the tip 86 rests on the photosensitive surface at its end (see Fig. 7) to more easily strip a copy sheet adhering to the drum surface. Illustrated element 62 is a planar mylar member having a thickness of .014 inches and lies in a plane substantially normal to the photosensitive surface.In other embodiments, element 62 could be made of any sufficiently rigid material (reinforced if necessary as in the illustrated embodiment) which will not damage the drum surface. Typical materials would be polypropylene, Lexan, Nylon, Teflon, etc. The thickness does not appear to be critical but is preferably as small as possible (consistent with a long lifetime in use) to reduce the likelihood of toner build-up on the blade tip which can result in marking the sheet during the sheet stripping step.

The stripping element 62 is advantageously placed in a position to contact and lift from the surface 1 5 a leading edge of a copy sheet at a corner thereof by deflecting the corner from the photosensitive surface and directing it, almost immediately, toward knurled roller 64. (See Fig.

3) The extent of tip 86, angle "a" in the illustrated embodiment of Fig. 7, is preferably about 55 .

And as noted above, the position of the tip relative to a tangent at the point of contact, downstream angle "b", is preferably about 1280.

Referring to Figure 7, the illustrated planar sheet stripping element 62 is preferably "sandwiched" between two thin metal support elements 200 (only one of which is shown in the figures). The illustrated sheet stripping element 62, in this configuration has the tip 86 extending beyond the metal support element 200. This helps to prevent toner build up on the metal support members. In the illustrated embodiment, the angle "a" is 550, as noted above. Other angles would be suitable depending upon the specific position of the sheet stripping element relative to the photosensitive surface from which a sheet material is removed.

As noted above, the sheet stripping element 62 is preferably mounted for movement along the direction normal to the movement of and parallel to the photosensitive surface. In the illustrated embodiment, this is along a direction parallel to the photocopier drum axis. As will become clear from the detailed description below, the sheet stripping element is traversed in small increments across the photosensitive surface by resiliently biasing the element against an open face cam element which is incrementally rotated about its axis. Thereby the illustrated spring biased blade element 62 is moved across the photosensitive surface in small precisely controlled increments approximately equal to twice the blade width.

Further, in accordance with the preferred embodiment of the invention, movement of the blade occurs prior to the occurrence of each sheet pickoff and in particular, incremental movement of the pickoff blade across the photosensitive surface occurs during the copy cycle but before pickoff is realized, that is the blade is moved near the beginning of each copy cycle. In other embodiments of the invention, the blade can be maintained in each fixed position for a predetermined operating limit, for example a number of copy cycles greater than one, and can be moved whenever the limit is achieved. If a time limit is imposed, the stripping element may stay at a given location for a fixed operating time (as opposed to number of cycles). Also the increment of movement can be greater or smaller than that in the illustrated embodiment.

Since the blade is being moved at the beginning of each copy cycle, it should be clear that over a typical drum life, more than 100,000 copies, a limit must be reached, even if the incremental distance is small, beyond which the blade cannot be moved in the same direction.

Indeed, in the preferred embodiment of the invention, the limit is set at approximately 0.3 inches. Thus, after the blade is moved in one direction approximately 0.3 inches, its direction is reversed (by an appropriate change in the surface of the open face cam which controls blade movement in the illustrated embodiment) and the blade is then moved in the opposite or reverse direction. Further, according to the invention, and as described in more detail below, better control of blade movement is effected by moving the blade in an interlaced pattern, that is, the positions of the blade moving in one direction interlace with the positions of the blade when it is moved in the opposite direction (see Fig. 12).

Referring now to Figures 8 and 9, the position of the stripping assembly is controlled by the position of the cam surface 201 of an open face cam member 202. Cam member 202 is secured to a hollow threaded shaft 204, at a keyed end 205, by a screw 206. The other keyed end 207 of shaft 204 carries a ratchet assembly 208 having a dual surface ratchet wheel 210 which is secured to the shaft by a screw 212. The cam element 202 and ratchet wheel 210 thus rotate together. Shaft 204 extends through and rotates in an opening 212 in a metal support frame element 214 using an oil-tight, self-lubricating bushing 216.

Turning first to the mechanism for rotating ratchet wheel 210, and referring in particular to Figures 8 and 10, the rotational position of ratchet wheel 210 is maintained by a series of circular depressions 220 which are periodically spaced around the circumference of a reduced diameter extending ring portion 222 of ratchet wheel 210. In the illustrated embodiment, the circular depressions 220 are spaced every 180 so that there are twenty depressions spaced around the circumference of ring portion 222. A pin 226 fixed to a pivoting arm 228, arm 228 pivoting around a pivot axis 230, holds the ratchet in position under the force applied by a resilient spring element 232. A second arm 234 also pivots about pivot axis 230.

Lever arm 234 is part of the actuating mechanism for incrementing the ratchet wheel 2,10 to a next incremental position (as determined by the depression 220). Lever arm 234 has a protruding cam follower 236 which is reciprocated at the beginning of a copy cycle by a cam actuating element 238 operated in synchronism with the paper feed section of the apparatus. Thus, when the paper feed section of the apparatus is operated, the cam actuating element 238, shown in outline in the figure, reciprocates the lever arm 234 around pivot axis 230. This causes a ratchet moving arm 240 to reciprocate so that it pulls, at a ratchet pulling end 242 against a ratchet tooth 244 of ratchet wheel 210. The resulting movement of ratchet tooth 244 causes ratchet wheel 210 to rotate about its axis 246 in a counterclockwise direction (Fig. 8).

As the ratchet wheel 210 rotates, the resiliently biased lever arm 228, and in particular pin 226, is forced radially away from axis 246, as arm 228 rotates in a clockwise direction about its pivot axis 230. Pin 226 is thus caused to move into a next sequential depression 220. When arm 234 returns to its original "at rest" position, ratchet pulling end 242 "climbs" over the ratchet tooth 244. Pin 226, in depression 220, maintains the ratchet wheel in a stable position.

Referring to Figure 8, as the arm 240 moves to the left under the influence of lever arm 234, thereby rotating ratchet wheel 210 in a counterclockwise direction, arm 240 slides past and on a standoff 248. When the cam actuator 238 returns to its original position, lever arm 234 and arm 240 are similarly urged to their respective starting positions by the restoring force of spring 232. Thus, as the cam follower returns to its original position, lever arm 234 rotates in the clockwise direction about axis 230 and arm 240 moves to a next ratchet depression 250. The ratchet pulling end 242 of arm 240 is inclined to more easily travel up and over a ratchet tooth 244. Arm 234 has a slotted opening 254 which accommodates the travel of a pin 256 of arm 240 as end 242 moves upward, over the ratchet teeth.

A corresponding slot 258 in arm 240 allows standoff 248 to travel therein. The entire ratchet actuating assembly 259 is supported on metal support plate 214 by standoffs 248 and 260. Arm 240 is spaced away from the frame element, plate 214, by spacers 261,262.

Referring to Figure 9, the open face cam 202 rotates or moves synchronously with the ratchet assembly 208. The open face cam is biased against the metal support 214 by a cam follower end 263 of an elongated member 264 (Fig. 11) as described in more detail below. To reduce the frictional contact of cam 202 with the metal support 214, cam 202 has, at its support contacting surface, a reduced area ring-shaped section 265 contacting member 214 along a small annulus. This significantly reduces the frictional resistance of the cam to rotational forces.

The "open face" of cam 202 provides the precision surface 201 for moving the sheet stripping element from operative position to operative position on the drum surface. Referring to Figure 11, the sheet removal assembly is mounted for movement in a direction parallel to the drum axis. The distance between the sheet stripping element 62 and, for example, a fixed side frame 280 of the copier, is controlled by the position of the open face cam element 202. The distance controlling mechanism employs the cam follower 263 (Figs. 9 and 11) resiliently biased in contact with the open face cam at its camming surface 201 The cam follower 263 is integral with elongated member 264 which are supported and guided by a sleeve 284 in which it may slide in the direction of an axis 286. Axis 286 is parallel to the drum rotation axis.Sleeve 284 threadingly engages a casting 288, at 290. The casting forms a fixed surface element of the sheet removal apparatus. The illustrated elongated member 264 further extends and supports one of the knurled rollers, roller 72, and is secured to the mounting plate bracket member 60 of the sheet stripping apparatus by an end cap 302 and nut 304.

A spring element 306 is constrained between an end of sleeve 284 and an E ring 308 securedly fastened to the elongated element 264 in a groove performed in element 264 for that purpose. Thus, the elements of the sheet removal apparatus are urged in a "downward" direction (in Fig. 11) so that the cam follower end 263 of the mechanism is urged against the open face of cam surface 201 of cam element 202.

In the normal operation of the traversing mechanism, the ratchet wheel 210 is incremented at the beginning of each copy cycle as described above. The surface of the open cam face is illustrated in Figure 12 as a function of the angular position of the cam. (It resembles an up and down staircase.) Note that generally, the maximum movement required in the cam surface structure is equal to a distance of "two" (these are of course relative differences and in the preferred embodiment of the invention, one unit equals 0.015" of movement). The direction of rotation of the cam element 202 need not be reversed to bring the traversing element back to its original position.

In typical operation of the sheet stripping portion of the sheet removal mechanism, according to a preferred embodiment of the invention, the knurled roller 64 engages the leading edge of the copy sheet 40 almost immediately after that leading edge is stripped from the photosensitive surface and the leading edge is thereby deflected and directed by the knurled roller into the nip between the knurled roller and the driven rubber roller surface 87.The knurled roller. as noted above is independently biased against the rubber roller surface and its position relative to the photosensitive surface 1 5 and the tip 86 is selected so that the leading edge of the stripped copy sheet substantially immediately contacts the roller 64 (Fig. 3). The knurled roller, which is being rotated, in this illustrated embodiment, by the roller 74, directs the copy sheet leading edge not only toward the nip 98 between the rollers 64, 74 but also away from the stripping element 62 (and tip 86) to prevent any disturbance to the image adhering to the underside of the copy sheet. Typically the knurled roller 64 bears against the roller 74 with a force of one to six ounces and is positioned immediately adjacent the surface 15, for example spaced 1/1 6 inches away therefrom.Thereby, the knurled roller 64 importantly deflects and directs the copy sheet away from the sheet stripping element and into a feed through mechanism whereby the remainder of the paper is pulled off the photosensitive surface and is directed and guided by the knurled rollers 65,70 and 72. The rollers 65, 70 and 72 effectively direct the copy sheet toward the fixing station and preferably also maintain the copy sheet safely spaced away from an edge 100 of mounting plate 60 (Fig. 4).

(Typically roller 65 bears on roller 74 with a force of two to seven ounces; and rollers 70 and 72 are spaced about 0.015 and 0.083 inches respectively from roller 74.) Only the leading edge of the copy sheet should be allowed to contact edge 100 if the fidelity of the image is to remain unimpaired. In this manner the image adhering to the copy sheet is not disturbed.

In the preferred embodiments rollers 64, 75, 70 and 72 are knurled rollers to prevent damaging the fragile toner image on the copy sheet. In other embodiments of the invention more or fewer rollers can be employed or other moving surfaces for example belts can be employed so long as the moving surface does not disturb the developed image on the copy sheet and so long as the function of roller 64, to substantially immediately deflect and direct the copy sheet away from the stripping element 62, is attained. Similarly roller 74 can be replaced by a belt or other moving surface.

In the embodiment just described, the velocity of the surface 87 of roller 74 is selected to be slightly greater than that of the photosensitive surface of the drum 14. In other embodiments, it is not necessary to rely upon the knurled roller 64 position and surface characteristic to ensure that the copy sheet is deflected away from the sheet stripping member 62. Thus, referring to Fig. 6, in another particular embodiment of the invention, the roller 74 is driven through a slip clutch 102 at an angular speed sufficient to ensure that the peripheral surface 87 has a velocity substantially greater than the velocity of the photosensitive surface. In this manner, the copy sheet tends to wrap more closely around the rubber roller 74 and is directed away from the stripping member 62.

In the illustrated embodiment, one traversing stripping assembly 48 is employed at a marginal edge of the copy sheet for initially detaching and gripping a corner of the copy sheet and directing it along an exit path. In other embodiments, a plurality of traversing assemblies 48 can be employed for example spaced apart along the drum width.

Advantages of the Invention and Non Obviousness The sheet stripping apparatus advantageously has a sheet pick-off mechanism for a photocopy apparatus which employs few parts, which is reliable, which avoids paper jams by picking off from the photosensitive surface all sheets thereon, including troublesome so-called "shingled" sheets, which provides an apparatus which is simple to manufacture and install from a technical standpoint, and which can use inexpensive materials and therefore has a low manufacturing cost. In addition, the claimed invention does not mar the image on the sheet nor does it adversely damage the photosensitive surface; and it does not rely upon complex timing mechanisms in order to remove the sheet (material) from the fragile photosensitive surface.

The properly dimensioned and positioned, resiliently biased stripping element by itself, and in combination with the incremental transverse movement, provide a mechanism wherein edge image deletion and even small corner area deletion simply need not occur, and wherein undue damage to the photosensitive surface is avoided for substantially the useful life of the photoconductor.

The various pick-off members shown in the prior art are more complex and typically have not employed a member always resting on the photosensitive drum. The prior art devices, such as U.S. Patent 3,649,11 5, are typically precisely timed devices having precision mechanical structures to avoid damaging the photosensitive surface. The claimed invention advantageously does not require these generally sophisticated timing mechanisms, for example either cam controlled, or mechanically or electrically actuated, which prior art apparatus employ.

With respect to those prior art devices wherein a mechanical structure is maintained in contact with or resting on the photosensitive drum, there is no device which either provides substantially full copy capability or which advantageously employs a cooperative deflection mechanism to substantially immediately deflect the copy sheet from the sheet stripping member to an exit path.

Thus, the references do not disclose the method and apparatus of the present invention.

The various pick-off members shown in the prior art which discloses traversing pick-offs (such as U.S. 4,168,902 and 4,252,310) have not employed a member always in contact with the photosensitive drum. With respect to those prior art devices wherein a mechanical structure is at least temporarily maintained in contact with or resting on the photosensitive drum, and which further traverse the drum, see, for example, U.S.

4,252,310, there is no device which provides the precise incremental operation described herein by the open face cam structure and pin positioning for accurately controlling the relationship of the blade and the photosensitive surface.

Further, references such as U.S. Patents 3,992,000; 3,885,786; 3,820,776; 3,450,402; 3,578,859; 3,844,252; 3,938,950; 3,991,999; 4,060,320; 4,072,307, and 4,261,560 do not disclose the method and apparatus of the present invention.

Additions, subtractions, deletions, and other modifications of the invention will be obvious to those practiced in the art and are within the scope of the following claims.

Claims (32)

Claims

1. A photocopying apparatus having a movable member (14) having a photosensitive surface (15), means for forming a developed latent image on said photosensitive surface (15), means (44) for feeding a copy sheet material (40) for contact with said photosensitive surface at a transfer station (42) for transferring said developed image onto said copy sheet material, and means (48) for removing said copy sheet from said photosensitive surface, characterized in that said sheet removing means comprises a sheet stripping element (62) having an operative portion resiliently biased against said photosensitive surface (15) for contacting a leading edge of said copy sheet (40) as it moves toward said sheet stripping element for detaching said leading edge of said copy sheet from said photosensitive surface (15), a moving deflection surface (64) positioned adjacent said operative portion of said sheet stripping element for substantially immediately deflecting said detached leading edge away from said sheet stripping element and toward an exit path, said moving surface thereby maintaining said copy sheet out of contact with said sheet stripping element, and means (74) for driving said moving surface for deflecting said copy sheet material toward said exit path and away from said photosensitive surface.

2. The apparatus of claim 1 characterized in that said deflection surface is a roller member surface, and further characterized by a driven roller member (74) in driving contact with said roller member surface, and resilient element (90) for biasing the sheet stripping element operative portion toward and in engagement with said photosensitive surface.

3. The apparatus of claim 1 further characterized by a driven surface (87) in driving contact with said deflection surface, and wherein said driving means drives said one of said deflection surface and said driven surface at a velocity greater than the peripheral velocity of said photosensitive surface (15).

4. The apparatus of claim 3 wherein said driving means is characterized by a slip element (102) for driving said driven surface at a velocity substantially greater than the velocity of said photosensitive surface.

5. The apparatus of claim 1 further characterized by a driven surface (87) in contact with said deflection surface, and wherein said driving means drives one of said deflection surface and said driven surface at a velocity substantially greater than the peripheral velocity of the photosensitive surface (15) for removing any slack in said detached copy sheet and at lower velocity after said slack has been removed.

6. A photocopying apparatus having a moving member (14) having a photosensitive surface (15), means for forming a developed latent image on said photosensitive surface (15), means (44) for feeding a copy sheet material (40) for contact with said photosensitive surface at a transfer station (42) for transferring said developed image onto said copy sheet material, and means (48) for removing said copy sheet from said photosensitive surface, characterized in that wherein said sheet removing means (48) comprises a sheet stripping element (62) having a tip portion its6) resiliently biased against said photosensitive surface for contacting a leading edge of said copy sheet (40) as it moves toward said sheet stripping element for detaching said leading edge of said copy sheet from said photosensitive surface (15), a deflection surface (64) mounted adjacent said tip portion (86) of said sheet stripping element for deflecting said detached leading edge away from said sheet stripping element and toward a nip formed by said deflection surface (64) and a movable friction surface (87), and means (102) for driving at least one of said deflection surface and said moving friction surface for passing said copy sheet material through the nip therebetween and directing it toward an exit path away from said photosensitive surface.

7. The apparatus of claim 6 characterized in that said deflection surface is the surface of a rotating deflection roller.

8. The apparatus of claim 7 characterized in that said moving friction surface is the surface of a driven roller member (74), said deflection roller is a knurled roller, and further characterized by first (82) and second (90) resilient elements for biasing respectively the sheet stripping element tip (86) toward said photosensitive surface and said knurled roller (64) toward said friction surface.

9. The apparatus of claim 8 further characterized by a second knurled roller (65), means for mounting said sheet stripping element and said first and second knurled rollers, and third resilient means (93) for biasing said second knurled roller (65) toward said friction surface, said second roller guiding said copy sheet material from said nip along said exit path.

10. The apparatus of claim 7 characterized in that said driving means drives said at least one of said deflection roller and said friction surface at a velocity greater than the peripheral velocity of said photosensitive surface.

11. The apparatus of claim 10 characterized in that said driving means includes a slip drive member (102) for driving movement of said friction surface at a velocity substantially greater than the velocity of said photosensitive surface.

1 2. The apparatus of claim 7 characterized in that said driving means drives one of said deflection roller and said driven surface at a velocity substantially greater than the peripheral velocity of the photosensitive surface (15) for removing any slack in said detached copy sheet and at lower velocity after said slack has been removed.

13. The apparatus of claim 8 further characterized by a third (70) and fourth (72) knurled rollers, wherein said third and fourth knurled rollers are spaced apart from said driven roller (74) for further guiding said copy sheet along the exit path.

14. A photocopying apparatus having a a movable member (14) having a photosensitive surface (15), means for forming a developed latent image on said photosensitive surface (15), means (44) for feeding a copy sheet material (40) for contact with said photosensitive surface at a transfer station (42) for transferring said developed image onto said copy sheet material, and means (48) for removing said copy sheet from said photosensitive surface, characterized in that said sheet removing means (48) comprises a sheet stripping element (62) having a tip portion (86) resiliently biased against said photosensitive surface for contacting a leading edge of said copy sheet (40) as it moves toward said sheet stripping element for detaching said leading edge of said copy sheet from said photosensitive surface (1 5), a rotatable knurled roller (64) having a knurled surface adjacent a tip portion (86) of said sheet stripping element for substantially immediately deflecting said detached leading edge away from said sheet stripping element (62), said knurled surface thereby maintaining said copy sheet out of contact with said sheet stripping element, a roller member (74) having a friction surface (87) in juxtaposition to the knurled surface for gripping in cooperation with said knurled surface the deflected leading edge of the copy sheet (40) and for guiding said leading edge along an exit path, and means (102) for rotating said roller member at a velocity sufficient to prevent marring of the developed image on said copy sheet.

1 5. The apparatus of claim 14 further characterized by first (82) and second (90) resilient elements for biasing respectively the sheet stripping element tip portion toward said photosensitive surface and said knurled roller toward said roller member.

1 6. The apparatus of claim 1 5 characterized in that said driving means drives said roller member (74) at a velocity greater than the peripheral velocity of said photosensitive surface, and further comprising a plurality of copy sheet guiding knurled rollers (65, 70, 72), each roller being mounted in an operative position opposite said roller member surface (87).

1 7. The apparatus of claim 1 6 characterized in that there are at least two copy sheet guiding rollers, one (65) of said rollers being resiliently biased into engagement with the surface of said roller member and a second (70, 72) of said rollers being spaced apart out of contact with said roller member surface.

18. The apparatus of claim 1 5 further characterized by means for mounting said sheet removing assembly in the path of a marginal edge of said copy sheet material.

1 9. The apparatus of claim 1 5 characterized in that said sheet stripping element comprises a planar member (62), and said sheet stripping assembly further comprises means for mounting said planar member in a plane substantially normal to the photosensitive surface.

20. The apparatus of claim 19 characterized in that said planar member has a mylar composition.

21. A method for removing a copy sheet material (40) from the photosensitive surface (15) of a photocopying apparatus, the photocopying apparatus having means for forming a developed image on the photosensitive surface (15), means (44) for feeding a copy sheet material for contact with the photosensitive surface at a transfer station (42) for transferring the developed image onto the copy sheet material, and means (48) for removing the copy sheet material from the photosensitive member, the method characterized by the steps of resiliently biasing a sheet stripping element (62) at a tip portion (86) against the photosensitive surface for contacting a leading edge of the copy sheet (40) as it moves toward the sheet stripping element, detaching a leading edge of the copy sheet (40) from the photosensitive surface using the tip portion (86) of the sheet stripping element, deflecting substantially immediately and maintaining the detached leading edge of the sheet material away from the sheet stripping element (62) and along an exit path, and driving a moving deflection surface (64) for deflecting the copy sheet material away from the photosensitive surface and the stripping member and toward the exit path.

22. The method of claim 21 further characterized by the step of directing said detached and deflected copy sheet material through a plurality of guiding roller members (65, 70, 72) for delivery to an exit path.

23. The method of claim 21 further characterized in that said driving step comprises the step of driving said deflection surface by a contacting driven surface (87), said deflection surface and said driven surface forming a nip for receiving said copy sheet.

24. The method of claim 23 further characterized in that said driving step comprises driving said driven surface at a velocity greater than the velocity of said photosensitive surface.

25. A photocopying apparatus having a movable member (14) having a photosensitive surface (1 5), means for forming a developed latent image on said photosensitive surface (15), means (44) for feeding a copy sheet material (40) for contact with said photosensitive surface (15) at a transfer station (42) for transferring said developed image onto said copy sheet material, and means (48) for removing said copy sheet from said photosensitive surface, said removing means including a sheet stripping element (62) having an operation portion (86) resiliently biased against said photosensitive surface (1 5) for contacting a leading edge of said copy sheet (40 as it moves toward said sheet stripping element and for detaching said leading edge of said copy sheet from said photosensitive surface, and a stripping element drive means for moving said element in a direction substantially parallel to the photosensitive surface, said drive means characterized by a first circumferential surface having a plurality of discrete, operatively related, positions (220) for maintaining a positioning surface (201) art a plurality of sequential selected positions, means (61) for operatively connecting said stripping element (62) to said positioning surface for movement in said direction of stripping element movement, a cam drive means (259) for driving a second circumferential surface to move said stripping element to a new position relative to said photosensitive surface, and means (238) for actuating said cam drive means after a predetermined limit has been reached.

26. A photocopying apparatus having a movable member (14) having a photosensitive surface (15), means for forming a developed latent image on said photosensitive surface (15), means (44) for feeding a copy sheet material (40) for contact with said photosensitive surface at a transfer station (42) for transferring said developed image onto said copy sheet material, and means (48) for removing said copy sheet from said photosensitive surface, said removing means including a sheet stripping element (62) having an operative portion (86) resiliently biased against said photosensitive surface (15) for contacting a leading edge of said copy sheet (40) as it moves toward said sheet stripping element and for detaching said leading edge of said copy sheet from said photosensitive surface, and a stripping element drive means for moving said element in a direction substantially parallel to the photosensitive surface, said drive means characterized by a cam element (202) having a plurality of discrete, operatively related, position maintaining surfaces (220) for maintaining a camming surface (201) at a plurality of sequential selected positions, resilient means (306) for biasing said stripping element, in said direction of stripping element movement, against said camming surface, drive means (259) operatively connected to a second plurality of position maintaining surfaces for driving said cam element to move said stripping element to a new position relative to said photosensitive surface, and means (238) for actuating said drive means after a predetermined number of copies have been made.

27. The apparatus of claim 26 further characterized in that said sheet removing means comprises: a moving deflection surface (64) positioned adjacent said operative portion of said sheet stripping element for substantially immediately deflecting said detached leading edge away from said sheet stripping element and toward an exit path, said moving surface thereby maintaining said copy sheet out of contact with said sheet stripping element, and second drive means (74) for driving said moving surface for deflecting said copy sheet material toward said exit path and away from said photosensitive surface.

28. The photocopying apparatus of claim 27 further characterized in that said cam element comprises a plurality of discrete, operatively related, surfaces (201) forming said camming surface and disposed sequentially about a circumference of said cam element, each surface having at least one neighboring surface wherein the distance in the movement direction between said operatively related surfaces is at least twice the width of the sheet stripping element.

29. The photocopying apparatus of claim 28 further characterized in that said drive means further comprises a supporting elongated member (264) having a longitudinal axis in said movement direction, means (302, 304, 60) for mounting said sheet stripping element in a fixed spatial relationship to said member, means (280, 284, 288) for positioning said member for an engaging relationship with said camming surface, and said resilient means biases a follower end (263) of said member against said camming surface.

30. The photocopying apparatus of claim 26 further characterized in that said camming surface (201) comprises a plurality of spaced apart, sequentially connected surfaces arranged in a staircase configuration for moving said stripping element in an interlaced pattern of positions.

31. A photocopying apparatus constructed and arranged substantially as herein described and shown in the drawings.

32. A method of removing a copy sheet material from the photosensitive surface of a photocopying apparatus, the method being substantially as herein described with reference to the drawings.