Ramped backer and shock absorbing material for reduced photoreceptor impact in a retractable cleaner

Abstract: An apparatus, method and printing machine that utilizes a ramped backer and/or a shock absorbing material in a cleaner subsystem to reduce or prevent photoreceptor motion quality disturbances. The shock absorbing material (180) prevents an instantaneous high impact force between the spacer wheel and the photoreceptor backer bar (115) that can cause photoreceptor motion quality disturbance. The ramped backer prevents the instantaneous deceleration of the spacer wheel (100) with the backer that causes motion quality disturbance due to the shaking of the photoreceptor belt from the impact on contact. The combination of the shock absorbing material and the ramped backer create a preferred embodiment to prevent photoreceptor motion quality disturbance by the cleaner system.

Description: This invention relates generally to an electrostatographic printer and copier, and more particularly, a cleaning system that reduces photoreceptor motion quality impact and sets a proper brush to photoreceptor interference (BPI). A multipass IOI xerographic system requires a cleaning subsystem which is able to engage and retract from the photoreceptor. Since the cleaner must remove all untransferred toner, while not disturbing the new, pre-transferred images, the engagement motion must occur during the interdocument zone. In order to place the cleaner in a typical 50 mm interdocument zone, high engagement speeds must be used. BPI is one of the key critical parameters in any cleaner, and is directly related to the cleaning performance. The mass of the cleaner, combined with the fast engagement speeds, causes the cleaner spacer wheels to impact the backer bars with a large transient force. This impact force disturbs image quality by effectively shaking the photoreceptor belt module with respect to the ROS. A method and/or apparatus is needed to reduce or prevent the disturbance of image quality. Furthermore, a multipass IOI xerographic system requires a cleaning subsystem which retracts. In addition to the requirement for acceptable cleaning of toner off of the photoreceptor, the cleaner must have a low impact force on the photoreceptor belt module in order to not disturb image quality. Traditional photoreceptor backers for retracting cleaners have consisted of a single contact point to set the cleaner position as it engages. This configuration serves to decelerate the cleaner engagement motion instantaneously causing a jarring impact to the photoreceptor backer and a ringing vibration to the photoreceptor module. US 5,669,055 describes a dual brush cleaner retraction mechanism and variable inertia drift controller for a retractable cleaner. The apparatus comprises a number of mechanical components to activate and control the engaging movement of two cleaner rollers. A damping member that comprises a material that includes a shock absorbing component is not described. Patent abstract of Japan, Vol. 012, No. 235, July 6, 1988 & JP 63026678 A (Konica Corporation, February 4, 1988) describes a cleaning device comprising an oscillating member to which a cleaning roller is attached and pressed against an image carrying body. A spring detained to the tip of the oscillating member works so as to soften a shock. A damping member comprising a material that has a shock absorbing component is not disclosed. It is the object of the present invention to improve a retractable cleaner member with regard to lowering interference of the retractable cleaner member to the photoreceptor. This object is achieved by providing an apparatus according to claim 1. Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which: Figure 1 is a prior art schematic view of a spacer wheel controlling brush to photoreceptor interference (BPI) against a backer bar; Figure 2 is a perspective view of an O-ring inserted into a groove on the edge of a spacer wheel; Figure 3A is a schematic view of a foam coated spacer wheel out of contact with the photoreceptor; Figure 3B is a schematic view of a foam coated spacer wheel compressing and decelerating upon contact with the photoreceptor; Figure 3C is a schematic of a foam coated spacer wheel maintaining a fixed BPI; Figure 4 is a schematic of the brush with raised fibers to cushion the cleaner landing; Figure 5 is a prior art schematic of a flat backer used as a stop for the retractable cleaner spacer wheel; Figure 6 is a schematic of a ramped backer that decelerates the retractable cleaner as it moves toward contact with the photoreceptor; Figure 7 is a schematic of a preferred embodiment of the present invention combining the ramped backer with a dampening material; Figure 8 is a schematic of an alternate ramped backer embodiment with a retractable cleaner; Figure 9 is a schematic of an alternate ramped backer embodiment in combination with a dampening material; and Figure 10 is a schematic illustration of a printing apparatus incorporating the inventive features of the present invention. Referring now to the drawings, where the showings are for the purpose of describing a preferred embodiment of the invention and not for limiting same, the various processing stations employed in the reproduction machine illustrated in Figure 10 will be briefly described. A reproduction machine, from which the present invention finds advantageous use, utilizes a charge retentive member in the form of the photoconductive belt 10 consisting of a photoconductive surface and an electrically conductive, light transmissive substrate mounted for movement past charging station A, and exposure station B, developer stations C, transfer station D, fusing station E and cleaning station F. Belt 10 moves in the direction of arrow 16 to advance successive portions thereof sequentially through the various processing stations disposed about the path of movement thereof. Belt 10 is entrained about a plurality of rollers 18, 20 and 22, the former of which can be used to provide suitable tensioning of the photoreceptor belt 10. Motor 23 rotates roller 20 to advance belt 10 in the direction of arrow 16. Roller 20 is coupled to motor 23 by suitable means such as a belt drive. As can be seen by further reference to Figure 10, initially successive portions of belt 10 pass through charging station A. At charging station A, a corona device such as a scorotron, corotron or dicorotron indicated generally by the reference numeral 24, charges the belt 10 to a selectively high uniform positive or negative potential. Any suitable control, well known in the art, may be employed for controlling the corona device 24. Next, the charged portions of the photoreceptor surface are advanced through exposure station B. At exposure station B, the uniformly charged photoreceptor or charge retentive surface 10 is exposed to a laser based input and/or output scanning device 25 which causes the charge retentive surface to be discharged in accordance with the output from the scanning device (for example, a two level .Raster Output Scanner (ROS)). The photoreceptor, which is initially charged to a voltage, undergoes dark decay to a voltage level. When exposed at the exposure station B it is discharged to near zero or ground potential for the image area in all colors. At development station C, a development system, indicated generally by the reference numeral 30, advances development materials into contact with the electrostatic latent images. The development system 30 comprises first 42, second 40, third 34 and fourth 32 developer apparatuses. (However, this number may increase or decrease depending upon the number of colors, i.e. here four colors are referred to, thus, there are four developer housings.) The first developer apparatus 42 comprises a housing containing a donor roll 47, a magnetic roller 48, and developer material 46. The second developer apparatus 40 comprises a housing containing a donor roll 43, a magnetic roller 44, and developer material 45. The third developer apparatus 34 comprises a housing containing a donor roll 37, a magnetic roller 38, and developer material 39. The fourth developer apparatus 32 comprises a housing containing a donor roll 35, a magnetic roller 36, and developer material 33. The magnetic rollers 36, 38, 44, and 48 develop toner onto donor rolls 35, 37, 43 and 47, respectively. The donor rolls 35, 37, 43, and 47 then develop the toner onto the imaging surface 11. It is noted that development housings 32, 34, 40, 42, and any subsequent development housings must be scavengeless so as not to disturb the image formed by the previous development apparatus. All four housings contain developer material 33, 39, 45, 46 of selected colors. Electrical biasing is accomplished via power supply 41, electrically connected to developer apparatuses 32, 34, 40 and 42. Sheets of substrate or support material 58 are advanced to transfer station D from a supply tray, not shown. Sheets are fed from the tray by a sheet feeder, also not shown, and advanced to transfer station D through a corona charging device 60. After transfer, the sheet continues to move in the direction of arrow 62, to fusing station E. Fusing station E includes a fuser assembly, indicated generally by the reference numeral 64, which permanently affixes the transferred toner powder images to the sheets. Preferably, fuser assembly 64 includes a heated fuser roller 66 adapted to be pressure engaged with a back-up roller 68 with the toner powder images contacting fuser roller 66. In this manner, the toner powder image is permanently affixed to the sheet. After fusing, copy sheets are directed to a catch tray, not shown, or a finishing station for binding, stapling, collating, etc., and removal from the machine by the operator. Alternatively, the sheet may be advanced to a duplex tray (not shown) from which it will be returned to the processor for receiving a second side copy. A lead edge to trail edge reversal and an odd number of sheet inversions is generally required for presentation of the second side for copying. However, if overlay information in the form of additional or second color information is desirable on the first side of the sheet, no lead edge to trail edge reversal is required. Of course, the return of the sheets for duplex or overlay copying may also be accomplished manually. Residual toner and debris remaining on photoreceptor belt 10 after each copy is made, may be removed at cleaning station F with a brush, blade or other type of cleaning system 70. A preclean corotron 161 is located upstream from the cleaning system 70. In a full color, multipass Image on Image (IOI) xerographic machine, it is necessary to have a cleaner which can retract from and engage the photoreceptor (e.g. imaging surface). Since the cleaner must remove all untransferred toner, while not disturbing the new, pre-transferred images, the engagement motion must occur during the interdocument zone. In order to place the cleaner in a typical 50 mm interdocument zone, high engagement speeds must be used. This speed requirement increases as the cleaner is retracted farther from the photoreceptor. In machines where it is necessary to remove the cleaner or photoreceptor for maintenance, an inherent variability in the spacing between the cleaner and the photoreceptor exists. In order to accommodate this variability, the cleaner has a wide latitude (+/-3 mm) where it can expect the photoreceptor to be. In order to always set a proper cleaner brush to photoreceptor interference (BPI), the cleaner brushes are equipped with spacer wheels. The spacer wheels contact backer bars outside of the photoreceptor (but part of the photoreceptor belt module) and set the BPI. Due to locational tolerances some amount of overtravel (i.e. the cleaner brush travels beyond the nominal photoreceptor backer bar position) of the cleaner is required for the spacer wheels to locate against the backers. Cleaner springs are compressed when the spacer wheels contact the photoreceptor backers during the overtravel portion of the engagement cycle. BPI is one of the key critical parameters in any cleaner, and is directly related to the cleaning performance. Ideally, the BPI is a fixed, predetermined value. If the retracting cleaner locational tolerances are large, then overtravel springs and spacer wheels become necessary to ensure a proper BPI. In Figure 1, a spacer wheel 100 is shown in contact with a backer bar 110. The fibers 95 of a cleaner brush are shown extending radially beyond the diameter of the spacer wheel 100. The mass of the cleaner, combined with the fast engagement speeds, causes the cleaner spacer wheels to impact the backer bars with a large transient force. This impact force disturbs image quality by effectively shaking the photoreceptor belt module with respect to the ROS (Raster Output Scanner). In order to minimize motion quality impacts from the cleaner as it engages the photoreceptor, the present invention provides several methods of adding shock-absorbing material to the cleaner brush. These methods cushion the brush impact, while maintaining a proper spacing relationship between the brush and the photoreceptor. Minimization of the motion quality impacts enables the creation of high quality images since the photoreceptor is not shaken with respect to the ROS. The spacer wheels must be made of a rigid material, that is any material which is substantially rigid with a preference in this application to light materials. The rigidity is required in order to maintain a constant and predictable BPI. Soft spacer wheels can cause unacceptable BPI variance. Reference is now made to Figure 2, which shows an embodiment of the present invention. This embodiment proposes adding a shock absorbing material (e.g. urethane, fiber, foam, elastomer, etc.) to the rigid spacer wheel 100 or the cleaner brush. A thin layer of soft material (e.g. urethane, fiber, foam, elastomer, etc.) could be coated on or slipped over the existing spacer wheels. On impact, the soft material absorbs the bulk of the impact force. The soft material then compresses, decelerating the cleaner without a high impact force, and allows the rigid material inside of the spacer wheel 100 to set the BPI. This can be accomplished in a variety of ways, including: 1) Adding a groove on the edge of the spacer wheel and inserting and O-ring 120 as shown in Figure 2. The material properties of the O-ring 120, the thickness, elasticity, depth and shape of the groove in the spacer wheel may be optimized to provide minimal motion quality impact, while providing a proper BPI. 2) A second implementation is to use a foam ring to cover the contacting surface of the spacer wheel, as shown in Figures 3A-3C. This foam covering 130 may be closed or open celled, depending upon the type of properties desired for an application. The foam 130 operates similar to the rubber O-ring by dampening the impact force of the spacer wheel as the cleaner engages the photoreceptor. Figures 3A-3C show the steps of operation of the foam coated spacer wheel. Figure 3A shows the foam coated spacer wheel 100 moving toward the backer 110 for the engagement of the cleaner with the photoreceptor (not shown). Figure 3B shows spacer wheel 100 with the foam coating 130 at the beginning of compressing and decelerating to prevent the high impact force. Figure 3C shows the spacer wheel 100 with the foam 130 coating compressed and a fixed BPI being maintained. Reference is now made to Figure 4, which shows another embodiment of the present invention. Another method of adding a shock absorbing material to a retracting brush cleaner, is to shear the ends of the electrostatic brush 140 longer than the normal brush pile height. The retraction and engagement motion of the brush 140 is shown by arrow 105. For example, if a spacer wheel 100 is currently used to set at 2 mm BPI, the brush fibers 150 will extend 2 mm beyond the spacer wheel 100 in a radial direction. As the spacer wheel 100 moves towards the photoreceptor backers 110, the 2 mm of brush 140 will impact the photoreceptor 10 before the spacer wheels 100 contact the backers 110. By increasing the brush pile height on the ends of the brush, the shock absorption of the brush is increased, outside of the image area, so the cleaner operation is unaffected. After the longer fibers 150 compress, the hard spacer wheel maintains the proper BPI in the image area. Figure 4 shows a version of a cleaner brush with raised fibers to cushion (e.g. dampen) the cleaner landing. The above stated methods have the advantage of being easily implemented into existing design. These embodiments can also be applied to spacer stops with shapes other than wheels. A multipass xerographic system requires a cleaning subsystem which retracts. In addition to the requirement for acceptable cleaning of toner off of the photoreceptor, the cleaner must have a low impact force on the photoreceptor belt module in order to not disturb image quality. Traditional photoreceptor backers for retracting cleaners have consisted of a single contact point to set the cleaner position as it engages. This apparatus decelerates the cleaner engagement motion instantaneously causing a high impact force on the photoreceptor. Figure 5 shows the prior art of current configuration where a flat backer 110 is used to stop the spacer wheel 110 allowing a high impact force between the cleaner and the photoreceptor causing an image quality disturbance. Reference is now made to Figure 6 which shows another embodiment of a backer and spacer system, which is not part of the present invention. Figure 6 shows a ramped backer 115 to decelerate the cleaner (not shown) as it engages the photoreceptor. In this embodiment, ramping the backer bar avoids the instantaneous deceleration of the spacer wheel 100 by the photoreceptor backer bar(s) shown in Figure 5. By using a ramped backer 115 to gently decelerate the cleaner, the impact force that disturbs the image quality by shaking the photoreceptor belt module is eliminated. The angle of the "ramped" portion of the backer is sufficient to prevent instantaneous impact between the spacer wheel 100 and the backer. The ramped backer 115 provides a gradual increase in interference with the spacer wheel 100 to the full BPI at the home position, causing the cleaner to decelerate with minimum impact force into an engaged position with the photoreceptor. The movement of the spacer wheel 100 is controlled by the movement of the retraction arm 170. The direction of movement of the retraction arm 170 about a pivot 171 is shown by the arrows 105. The resulting advantage is improved photoreceptor motion quality for the imaging system. This embodiment is inexpensive, easy to manufacture, and easily implemented on current retracting cleaners. The invention could also apply to other subsystems which have similar engage/retract requirements with the photoreceptor. Figure 8 shows an alternate embodiment of a ramped backer 125 in a cleaner subsystem similar to that shown in Figure 6. Ramped backer 125 has a lever section 126 that is of a thin material thickness to allow the backer bar deflection as the spacer wheel 100 travels to a seated position. This prevents binding of the cleaner brush assembly. Reference is now made to Figure 7, which shows another embodiment of the invention, where a ramped backer is combined with a shock absorbing material. The combination of a ramped backer 115 and a spacer wheel 100 that has a shock absorbing material 180 prevents an instantaneous deceleration of the spacer wheel 110 with the ramped backer 115. The shock absorbing material 180 includes the O-ring, foam coating and raised brush fibers referred to in Figures 2, 3 and 4. Figure 9 shows an alternate embodiment of the ramped backer 125 in a cleaner subsystem similar to that shown in Figure 7. In recapitulation, the present invention utilizes a shock absorbing material in a cleaner subsystem to reduce or prevent photoreceptor motion quality disturbances. The shock absorbing material prevents an instantaneous high impact force between the spacer wheel and the backer bar that can cause photoreceptor motion quality disturbance. The combination of the shock absorbing material and a ramped backer create a preferred embodiment of the present invention to prevent photoreceptor motion quality disturbance by the cleaner system.

Claims: An apparatus for reducing and preventing motion quality defects of an imaging surface by a cleaning subsystem comprising: a retractable cleaner member (170), having a first position and a second position, for cleaning the imaging surface, the retractable cleaner member being movable between the first position and the second position; a spacer member (100) to maintain a desired distance between the imaging surface and the retractable cleaner member (170) during engagement therebetween; a backer member (110) being positioned opposite said spacer member (100) to decelerate said spacer member, said backer member (110) and said spacer member (100) preventing an instantaneous high impact contact therebetween to prevent a motion quality disturbance of the imaging surface by the cleaning subsystem; and characterized by a dampening member (120, 180) provided on or adjacent the spacer member to prevent a high instantaneous impact force between said spacer member and said backer member, wherein said dampening member comprises a material that has a shock absorbing component. An apparatus as recited in claim 1, wherein said first position comprises said retractable cleaner member (170) being out of contact with the imaging surface. An apparatus according to claims 1 or 2, wherein said second position comprises said retractable cleaner member (170) engagingly contacting the image surface. An apparatus according to any one of the preceding claims 1-3, wherein said spacer member comprises a spacer wheel (100). An apparatus according to claim 4, wherein said spacer wheel (100) includes an outer surface that contacts said backer member (110). An apparatus according to claims 4 or 5, wherein said spacer wheel comprises: a grooved edge along the outer surface of said spacer wheel (100); and said dampening member (120) being inserted into said groove edge of said spacer wheel (100) to prevent the high instantaneous impact force between said spacer wheel and said backer member (110). An apparatus according to any of claims 1 to 6, wherein said dampening member (120,180) comprises an O-ring. An apparatus according to any of claims 4 to 5, wherein said dampening member (120,180) comprises a foam coating about the outer surface of said spacer wheel. An apparatus according to claim 1, wherein said dampening member (120,180) comprises: said cleaner member (170) being a brush cleaner having fibers extending radially from a core, said brush cleaner having a center region between two ends, said fibers having a longer brush pile height on the ends of said brush cleaner than in the center region; and said longer brush height fibers (170) extend radially longer than said spacer member (100), said longer brush pile height fibers compressing as the cleaner brush moves from the first position to the second position absorbing the impact force of contact between said backer member and said spacer member (100). An apparatus according to any of claims 1 to 9, further comprising a ramped entry to said backer member (110), said ramped entry guiding said spacer member (100) to said backer member (110) as said cleaner member moves from the first position to the second position.

Inventors: AUTY RONALD E, FORNALIK ANTHONY C, LATOUR NORMAN E, MILLER CHRISTOPHER B, SOURES NICHOLAS M, THAYER BRUCE E, AUTY, RONALD E., FORNALIK, ANTHONY C., LATOUR, NORMAN E, MILLER, CHRISTOPHER B., SOURES, NICHOLAS M., THAYER, BRUCE E.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1998
Main classification: G03G21
IPC codes: G03G21