Cleaning apparatus for a moving belt surface

Abstract: An apparatus (10) and method for cleaning particles from a moving imaging surface (11). Backers (160,170) are retracted from a movable photoconductive belt (10) to release cleaning contact between the brushes (190,195) and the moving imaging surface during development of image-on-image in the multi-pass color printing cycle. After transfer of the multi-color developed image, the backers move into contact with one side of the photoconductive belt causing the moving imaging surface, on the other side of the photoconductive belt, to contact the cleaner brushes. The brushes clean the moving imaging surface of the photoconductive belt. The brushes are released from contact with the moving imaging surface when the backers are retracted, allowing the image-on-image multi-pass process to begin again. The brushes engage and disengage the photoconductive belt in the interdocument zone (i.e. between developed images) of the moving surface.

Description: This invention relates generally to a cleaning apparatus for a moving belt surface. In the image-on-image, multi-pass color, electrophotographic development process, four layers of color toner (black, cyan, yellow and magenta) are developed onto the photoreceptor before transfer to paper. A separate cycle of the photoreceptor is required to accomplish the development of each color toner layer. To avoid disturbance of these images as the color toner layers are being developed, the cleaning elements must be disengaged from the photoreceptor surface until after the four toner layers have been developed and transferred to paper. After the multi-layered toner image has been transferred to the paper, the cleaning elements must be re-engaged to the photoreceptor to clean any residual toner which failed to transfer. Several copiers presently use the multi-pass process before a single transfer step. For example, the Konica 9028 machine uses a blade cleaner which is retracted from the photoreceptor drum while the color images are being developed. The Panasonic FP-C1 machine uses a single electrostatic brush cleaner which is retracted by a cam from the drum photoreceptor. The Sharp CX7500 machine uses an intermediate belt and a dual blade cleaner which is retracted from the photoreceptor belt by a solenoid during color image development. The primary, high load, blade is also retracted when the photoreceptor seam passes under the blade to avoid a motion quality disturbance. All of these methods involve movement of the cleaning device into and out of contact with the photoreceptor. US-A-5,209,808 discloses an applicator system and method for automatically applying and securing an adhesive backed label onto a corner surface. The applicator head includes a backer plate and a tamping mechanism (or tamper plate) connected in spaced relationship through helical (or other) springs to the backer plate, whereby a label applied to the tamping mechanism is applied to the corner surface through spring force of the helical springs which press the label onto the corner surface but are sufficiently resilient to permit movement of the backer plate orthogonal to the tamper plate, and thus, relative to the corner surface. US-A-4,769,671 discloses an apparatus in which a tubular member mounted on a shaft moves linearly in response to rotation of the shaft. A cam is mounted on the shaft and in engagement with bearings mounted on the interior surface of the tubular member. As the shaft rotates, the cam moves in unison therewith to move the tubular member linearly. The linear movement of the tubular member moves a portion of a photoconductive belt between an operative position, adjacent a developer unit, and an inoperative position, spaced from the developer unit. US-A-4,669,864 discloses an image forming apparatus having a cleaning device arranged on the outer periphery of an image retainer, and bringing into and out of abutment against the image retainer, wherein the cleaning device comprises a first cleaning member and a second cleaning member arranged downstream of the first cleaning member in the moving direction of the surface of the image retainer. A cleaning operation of the second cleaning member against the image retainer is conducted according to a time at which the cleaning operation of the first cleaning member against the image retainer is conducted. US-A-4,230,406 discloses an apparatus which cleans particles from a photoconductive member arranged to advance along a predetermined path. When the photoconductive member is stationary, the particle cleaner and photoconductive member are spaced from one another. The photoconductive member is deflected into engagement with the particle cleaner in response to the photoconductive member advancing along the pre-determined path. In this manner, the particle cleaner removes residual particles from the photoconductive member during the movement thereof along the pre-determined path. From JP-A-58-016 277 a magnetic cleaner brush is known having a backer member in form of a metallic plate movable between a belt contact position and a non-contact position. In accordance with one aspect of the present invention, there is provided a cleaning apparatus for removing particles from an endless belt surface which moves along a predetermined path direction, comprising: a fixed cleaning means comprising a first brush and a second brush adjacent a first surface of the belt, said first brush being located upstream from said second brush in the direction of belt movement; and first and second positionable members adjacent a second, opposing, surface of the belt, said first and second positionable members being operatively associated with said first and second brush, respectively, said members being selectively independently movable between a first position spaced from the belt and a second position in contact with the second surface of the belt, the second position of each member moving the belt into contact with the cleaning brush associated with that member. The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic elevational view of a cleaner showing one of the two brushes with the backer engaged; Figure 2 is a schematic elevational view of a cleaner showing one of the two brushes with the backer retracted; Figure 3 is a schematic elevational view of a dual brush cleaner with both of the backers engaged; Figure 4 is a schematic elevational view of a dual brush cleaner with the first backer retracted and the second backer engaged; Figure 5 is a schematic elevational view of both backers retracted from the dual brush cleaner; Figure 6 is a schematic elevational view of a dual brush cleaner with the first backer engaged and the second backer retracted; and Figure 7 is a schematic illustration of a printing apparatus incorporating the inventive features of the present invention. For a general understanding of a color electrostatographic printing or copying machine in which the present invention may be incorporated, reference is made to U.S. Patents 4,599,285 and 4,679,929. In Figure 7, a reproduction machine, in which the present invention finds advantageous use, utilizes a charge retentive member in the form of the photoconductive belt 10 having a photoconductive surface 11 mounted for movement past charging station A, 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. At charging station A, a corona charge device 24 charges the belt 10 to a selectively high uniform positive or negative potential. This charging has to occur for every color. Any suitable control, well known in the art, may be employed for controlling the corona charge device 24. Next, the charged portions of the photoreceptor surface are advanced through exposure station B, where the uniformly charged photoconductive belt surface 11 is exposed to a laser based input and/or output scanning device 25 which causes the charged belt surface 11 to be discharged in accordance with the output from the scanning device (for example, a Raster Output Scanner (ROS)). At development station C, a development system 30, advances development materials into contact with the electrostatic latent images. The development system 30 comprises first and second developer apparatuses 32 and 34. (However, this number may increase depending upon the number of colors, i.e. for four colors there would be four developer housings.) The developer apparatus 32 comprises a housing containing a donor roll 35 and a magnetic roller 36. The developer apparatus 34 comprises a housing containing a donor roll 37 and a magnetic roller 38. The magnetic roller 36 develops toner onto donor roll 35. The donor roll 35 then develops the toner onto the belt surface 11. Both housings contain developer material 40, 42 of the selected colors. A D.C. bias is applied to the rollers 35 and 36 via the power supply 41, and a D.C. bias is applied to the rollers 37 and 38 via the bias power supply 43. Sheets of support material 58 are advanced to transfer station D from a supply tray, not shown. Sheets 58 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 64, which permanently affixes the transferred toner powder images to the sheets. Typically, 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. Residual toner and debris remaining on photoconductive belt 10 after each copy is made, may be removed at cleaning station F with a brush or other type of cleaning system 70. In the present invention, retractable cleaner backers 160,170 are used in the cleaning system. The cleaner backers are located under the portion of the photoconductive belt in alignment with fixed cleaning members, preferably rotatable brushes 190,195. The photoconductive belt 10 is also supported on the either side of the cleaning unit by adjustable backup rolls 165 and 175. This method reduces the complexity of the cleaner drive because no retraction motion of the cleaner is required. The portions of the retractable backers which contact the photoconductive belt are solid and substantially rigid to provide support for the flexible photoconductive belt especially when the belt and the cleaning members are in contact with each other. The backers are retracted from and engaged with the photoconductive belt using a solenoid or electrical motor or another electro-mechanical device 162 (see Figs. 1-6). In Figures 1 and 2, a single brush cleaner is shown schematically. The backer 160 is located on the opposite side of the photoconductive belt 10 from the imaging surface 11 thereof and directly opposite the fixed, rotatable brush 195. The cleaner brush 195 is partially enclosed in a housing 180. When the backer 160 moves into contact with one side of the photoconductive belt 10, the imaging surface 11 of the belt 10 is urged into cleaning contact with the cleaner brush 195, as shown in Figure 1. The direction of movement by the backer 160, into contact with the photoreceptor belt, is shown by arrow 12. Referring now to Figure 2, the backer 160 is retracted from the side of the photoconductive belt 10, opposite the imaging surface 11. This releases the imaging surface 11 of the photoconductive belt 10 from cleaning contact (i.e. the brush fibers remove particles from the belt surface when the brush rotates) with the cleaner brush 195. The direction of movement by the backer 160, away from contact with the photoconductive belt 10, is shown by arrow 14. The photoconductive belt 10 is supported by two back-up rollers 165, 175 on either side of the backer 160. The back-up rollers maintain the proper tension of the photoconductive belt 10 as the backer 160 moves into and out of contact with the photoconductive belt 10. The engagement (Figure 1) and disengagement (Figure 2) of the backer 160 and the cleaner brush 195 with opposite sides of the photoconductive belt 10 occur in the the region of the photoconductive belt surface 11 without an image to maintain a high productivity level. An embodiment of the present invention is shown in Figures 3-6, where two retracting backers (i.e. non-rotatable or rotatable) are used to engage and disengage the photoconductive belt surface with the cleaner brushes 190, 195. The repositioning of retractable cleaner backers 160, 170, rather than repositioning the cleaner brushes 190, 195, significantly reduces the complexity of the cleaner drive, because no retraction motion of the cleaner member is required. The cleaner brushes 190, 195 also have a larger mass than the photoreceptor backers 160, 170, which means that retracting the cleaner brushes 190, 195 would require more power and generate higher forces than the retraction mechanism of the present invention. The higher loads and more complex system result in a lower reliability for cleaner retraction when compared to photoreceptor backer retraction. These difficulties can be demonstrated on a cleaner system which retracts the electrostatic brush cleaner housing separately from the photoconductive belt. In such a cleaner system, a DC retraction motor is used to rotate two cam shafts, which retract the cleaner housings. A belt between the cam shafts maintains the retraction and engagement timing between the first cleaner housing and the second cleaner housing. A large cleaner housing surrounds two smaller cleaner housings to allow independent retraction of the two brushes by mounting pivot bearings and containing toner. In the present invention, the cleaner backers 160, 170 are retracted, allowing a single cleaner housing to be used and furthermore, pivot bearings and seals can be eliminated to reduce the cost of the cleaner. These cost reductions more than offset the cost associated with adding cleaner backer retraction to a photoconductive belt module. Furthermore, the effect of retracting cleaner backers on the steering of the photoconductive belt 10 and on photoconductive belt motion quality has been tested and analyzed. The analysis showed that the belt steering and motion quality disturbances caused by retracting the cleaner backers were small and within an acceptable motion quality tolerance, when tight tolerances were maintained on alignment of the moving backer with a high gain photoconductive belt drive servo system. Figures 3-6 show different positions of the backers 160, 170 during the cleaning operation of a dual electrostatic brush cleaner. In the image-on-image, multi-pass color development process, four layers of color toner (black, cyan, yellow and magenta) are developed onto the photoconductive belt surface before transfer to paper. A separate cycle of the photoconductive belt is required to accomplish the development of each color toner layer. To avoid disturbance of these images as the color toner layers are being developed, the cleaning elements must be disengaged from the photoconductive belt surface until after the four toner layers have been developed and transferred to paper. After the toner image has been transferred to the paper the cleaning brushes 190, 195 are re-engaged to the photoconductive belt surface to clean any residual toner which failed to transfer to the paper. In order to maintain a high productivity level, the cleaning elements should disengage and engage the photoconductive belt within the space of the interdocument zones. This requires that the disengagement and engagement occur over fairly short time periods which depend on the length of the interdocument zone and on the photoconductive belt process speed. For example, at photoconductive belt speeds of 40 ppm (prints per minute) and 65 ppm the estimated time for engagement or disengagement of the brushes 190, 195 is approximately 130 milliseconds (msec) and 80 msec, respectively. Dual electrostatic brush cleaners provide two brush cleaners biased to different polarities to clean particles of different polarities. In Figure 3, both backers 160, 170 are shown in contact with the side of the photoconductive belt 10 opposite the imaging surface 11. The backers 160, 170 are located directly opposite the cleaning brushes 190, 195, respectively, on the side of the photoconductive belt opposing the cleaner brushes 190, 195. The backers 160, 170 move into contact with the photoconductive belt 10 in the direction shown by arrows 12 causing the imaging surface 11 to make cleaning contact with the cleaning brushes 190, 195. The cleaning brushes 190, 195 are partially enclosed in a single housing 185. The backers 160, 170 are located between two back-up rolls 165, 175. These back-up rolls 165, 175 provide adequate tensioning for the photoconductive belt 10 as the backers 160, 170 move into and out of contact with the photoconductive belt 10. The backers 160, 170 are positioned such that the brush cleaners 190, 195 are in cleaning contact with the surface 11 (i.e. imaging and non-imaging regions) of the photoconductive belt 10 after transfer of the particles to the paper occurs. The cleaner brushes 190,195 engage and disengage the photoconductive belt in the interdocument zone (i.e. non-imaging region) (not shown). After the photoconductive belt 10 has completed a cleaning cycle past the cleaning brushes 190, 195 in the contact position shown in Figure 3, the backers 160, 170 are removed from contact with the photoconductive belt 10 to release the imaging surface 11 from cleaning contact with the cleaner brushes (see Figure 5). However, depending on the length of the interdocument zone, the backers 160, 170 may need to be removed from contact independently of each other (see Figures 4 and 6), if the interdocument zone can not accommodate both brushes simultaneously. In Figure 4, the first backer 160, in the direction of motion of the photoconductive belt 10, shown by arrow 16, is retracted away from the photoconductive belt 10, in the direction shown by arrow 14, when the interdocument zone 200 reaches the first backer 160, after a completed cleaning cycle. The second backer 170 remains in contact with the photoconductive belt 10 in the imaging region 210. As the photoconductive belt 10 continues movement in the direction shown by arrow 16, the second backer 170 will be retracted as the interdocument zone 200 reaches the second backer 170. Thus, both backers 160, 170 are retracted from the photoconductive belt 10, as shown in Figure 5, as image-on-image, multi-pass development takes place. Figure 6 shows the first backer 160 engaged and the second backer 170 retracted from the photoconductive belt 10. After single pass transfer of the developed image, the residual toner particles are cleaned from the imaging surface 11. The first backer 160 moves into contact with the photoconductive belt 10, shown by arrow 12, to move the imaging surface 11 of the photoconductive belt 10, into contact with the cleaner brush 195 while the cleaner brush 195 is in the interdocument zone 200. As the interdocument zone passes by the first brush 195, in contact with the surface 11, the interdocument zone 200 approaches the second brush 190 which is out of contact with the surface. The second backer 170 then moves the photoconductive belt 10 into contact with the second brush 190, as shown in Figure 3, to clean the imaging surface. The aforementioned sequence of Figures 3-6 described above is then repeated. In Figures 1-6, the cleaning devices are shown as (electrostatic) cleaner brushes. The cleaning devices, however, are not limited to electrostatic cleaning brushes. Other cleaning elements include magnetic and mechanical cleaning brushes, cleaning blades and cleaning webs. Therefore, the present invention provides a method and apparatus for bringing the photoconductive belt into and out of cleaning contact with the cleaning brushes using cleaner backers. The motion quality and belt steering concerns in using cleaner backers have been minimized. An advantage of moving the cleaner backers rather than the cleaning device, decreases the number of cleaning housings needed, thus reducing the cleaner cost.

Claims: A cleaning apparatus (70) for removing particles from an endless belt surface (11) which moves along a predetermined path direction, comprising: a fixed cleaning means comprising a first brush (190) and a second brush (195) adjacent a first surface (11) of the belt (10), said first brush being located upstream from said second brush in the direction of belt movement (16); and first and second positionable members (160, 170) adjacent a second, opposing, surface of the belt, said first and second positionable members (160, 170) being operatively associated with said first and second brush (190, 195), respectively, said members being selectively independently movable between a first position spaced from the belt and a second position in contact with the second surface of the belt, the second position of each member moving the belt into contact with the cleaning brush associated with that member. A cleaning apparatus as claimed in claim 1, wherein the cleaning means are rotatable brushes (190, 195), which are rotatably mounted in a housing (180, 185). A cleaning apparatus as claimed in claims 1 or 2, wherein the positionable members are non-rotating backers. A cleaning apparatus as claimed in any one of the preceding claims, wherein the cleaning apparatus further comprises at least one backup roller (165, 175) located adjacent the positionable members to maintain appropriate tension in the belt. A cleaning apparatus as claimed in any one of the preceding claims, wherein each positionable member is aligned with its respective cleaning brush on opposite sides of the belt. A cleaning apparatus as claimed in claims 1, 2 or 3, wherein the cleaning apparatus further comprises first and second backup rollers (165, 175) located on opposite sides of the positionable members, and in contact with the second surface of the belt to maintain appropriate tension in said belt. The cleaning apparatus as claimed in any one of the preceding claims, wherein the belt is a photoconductive belt in an electrographic machine and said particles to be removed from the surface thereof are residual toner particles. A method for cleaning particles from a moving belt (10) which moves along a predetermined path, comprising the steps of: fixing cleaning means comprising a first brush (190) and a second brush (195) adjacent a first surface (11) of the moving belt (10) which moves along a predetermined path and direction, said first brush being located upstream from said second brush in the direction of belt movement (16); providing first and second positionable members (160, 170) adjacent a second, opposing surface of the moving belt, said first and second positionable members (160, 170) being operatively associated with said first and second brush (190, 195) respectively, the positionable members being independently movable between a first position spaced from the second surface of the moving belt and a second position in contact with the second surface of the moving belt, the second position of each positionable member causing the first belt surface to contact the cleaning brush associated with that member and be cleaned thereby; and independently selectively moving the positionable members from the first position to the second position whenever cleaning of portions of the first surface of the belt is desired. A method for cleaning particles as claimed in claim 8, further comprising the step of maintaining tension in the moving belt by backup rollers (165, 175) whether the positionable member is in the first or second position.

Inventors: POZNIAKAS ROBERT S, ROLLINS DAVID E, THAYER BRUCE E, POZNIAKAS, ROBERT S., ROLLINS, DAVID E., THAYER, BRUCE E.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1995
Main classification: G03G21
IPC codes: G03G21, G03G15