Apparatus for cleaning particles from a surface

Abstract: A cleaning apparatus (70) for removing particles (120) from a substrate surface (10) comprises a dual polarity, commutated roll (110) which attracts toner and debris particles (120) loosened into a particle cloud from the surface (10) by an acoustical horn (140). The particles are attracted to and adhere to the commutated roll, whether right or wrong sign (i.e. positive or negative), and are removed from the roll, as the roll rotates, by a scraper blade (150). The particles are collected in a waste container as the particles are removed from the roll surface by the scraper blade. The cleaning apparatus does not contact the surface, thus preventing wear thereof.

Description: This invention relates to an apparatus for cleaning particles from a surface, and more particularly, concerns a cleaning apparatus for an electrostatographic copier or printer. In a typical electrophotographic machine a charge retentive surface (i.e., photoreceptor) is electrostatically charged, and exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic latent image conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with the original, and may then be transferred to a substrate (e.g., paper) and affixed thereto to form a permanent record. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom. Conventional cleaning methods for cleaning this residual toner include contact cleaners (i.e. cleaners that frictionally contact the imaging surface) such as blades and brushes. The contact between these cleaners and the surface being cleaned decreases, through wear, the life of both the cleaner and the photoreceptor. This frictional contact can cause tearing and chipping to the cleaning blade edge which leads to cleaning failures and possible damage to the photoreceptor. The cleaning brushes often develop a set due to contact with the imaging surface, that affects the ability of the brush to clean the surface. US-A-3,257,224 discloses a magnetic roller that dips into developer powder contained in a trough beneath the roller. The iron filings, carrying the toner on their surfaces, adhere in brush-like formation to the magnetic poles of the roller and are applied in this form by rotation of the roller to the surface of a charged electrophotographic material which has been exposed imagewise and is traversed over the roller. The toner is attracted electrostatically from the magnet to the photoconductive coating of the electrophotographic material and a visible image is formed. US-A-4,111,546 discloses an electrostatographic reproducing apparatus and process that includes a system for ultrasonically cleaning residual material from the imaging surface. Ultrasonic vibratory energy is applied to the air space adjacent the imaging surface to excite the air molecules for dislodging the residual material from the imaging surface. Preferably pneumatic cleaning is employed simultaneously with the ultrasonic cleaning. Alternatively, a conventional mechanical cleaning system is augmented by localised vibration of the imaging surface at the cleaning station which are provided from behind the imaging surface. Xerox Disclosure Journal, volume 18, no. 3, May/June 1993, entitled "Acoustical Vacuum Cleaner Assist" discloses a high velocity and pressure vacuum that subsequently removes particles from the photoreceptor belt. The particles being previously dislodged by the vibratory action of an acoustical horn against the photoreceptor belt. In accordance with one aspect of the present invention, there is provided an apparatus for cleaning particles from a surface, comprising a device, in communication with the surface, for loosening the particles from the surface by vibration and, a member, positioned adjacent the surface, for attracting loosened particles thereto. The member including a plurality of segments with adjacent segments being of opposite polarities for attracting particles having opposite polarities thereto. The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of the present invention; and Figure 2 is a schematic illustration of a printing apparatus incorporating the inventive features of the present invention. In Figure 2, a reproduction machine, in which the present invention finds advantageous use, utilises a charge retentive member in the form of a photoconductive belt 10 mounted for movement past a charging station A, an exposure station B, developer stations C, transfer station D, fusing station E and cleaning station F. Belt 10 is entrained about a plurality of rollers 18, 20 and 22. Motor 23 rotates roller 20 to advance belt 10 in the direction of arrow 16 to advance successive portions thereof sequentially through the various processing stations disposed about the path of movement thereof. At charging station A, a corona discharge device 24 charges the belt 10 to a selectively high uniform positive or negative potential. Next, the charged portions of the photoconductive belt surface are advanced through exposure station B. At exposure station B, the uniformly charged belt surface 10 is exposed to a laser based input and/or output scanning device 25 which causes the photoconductive belt surface to be discharged in accordance with the output from the scanning device. The resulting photoconductive belt surface contains both charged-area images and discharged-area images. The photoconductive belt surface, when exposed at the exposure station B, is discharged to near zero or ground potential in the highlight (i.e. colour other than black) colour parts of the image. The photoconductive belt surface is also partially discharged in the background (white) image areas. After passing through the exposure station, the the belt surface contains charged areas and discharged areas which corresponding to two electrostatic latent images and to charged edges outside of the image areas. At development station C, a development system 30 advances developer materials into contact with the electrostatic latent images. The development system 30 comprises first and second developer apparatuses 32 and 34. The developer apparatus 32 comprises a housing containing a pair of magnetic brush rollers 35 and 36. The rollers advance developer material 40 into contact with the discharged areas of the latent images. The developer material 40, contains negatively charged color toner. Electrical biasing is accomplished via power supply 41 electrically connected to developer apparatus 32. A DC bias is applied to the rollers 35 and 36 via the power supply 41. The developer apparatus 34 comprises a housing containing a pair of magnetic brush rolls 37 and 38. The rollers advance developer material 42 into contact with the photoreceptor for developing the charged-area images. The developer material 42 contains positively charged black toner for developing the charged areas of the latent images. Appropriate electrical biasing is accomplished via power supply 43 electrically connected to developer apparatus 34. A DC bias is applied to the rollers 37 and 38 via the bias power supply 43. Because the composite image developed on the photoreceptor consists of both positive and negative toner, a pre-transfer corona discharge member 56 is provided to condition the toner for effective transfer to a substrate using corona discharge of a desired polarity, either negative or positive. Sheets of substrate 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 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 backup 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 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 cleaning apparatus 70. The photoconductive belt 10 is supported by an acoustic transfer assist device 130. Figure 1 shows an elevational view of the cleaning apparatus of the present invention. As non-transferred residual particles 120 remaining on the photoconductive belt 10 pass over the ATA (Acoustic Transfer Assist) device 130, the toner's attraction to the photoconductive belt 10 is substantially lessened due to the high frequency vibrations caused by the acoustical horn 140. The cleaning apparatus 70 comprises a dual polarity, commutated roll 110 that electrostatically attracts (both right and wrong signed) toner, after it has been loosened from the photoconductive belt 10 by the acoustical horn 140. The horn 140 may optionally be held in contact with the photoconductive belt 10 by suction. The high frequency vibration of the photoconductive belt 10 causes the toner particles 120 to form a particle cloud between the photoconductive belt 10 and the commutated roll 110. The voltage potentials on the commutated cleaning roll 110 are adjusted such that a more positive attraction (or negative attraction for wrong sign toner) is felt by the negatively charged toner on the grounded photoconductive belt. For example, a positive 250 volt potential on positive commutations of the cleaning roll create a strong attraction of the negatively charged toner setting on the grounded photoconductive belt towards the commutated cleaning roll 110. Conversely, a negative 250 volt potential on the negative commutations of the cleaning roll create a strong attraction of the positively charged (wrong sign) toner towards the commutated cleaning roll. With the assistance of the ATA providing the mechanical vibrations necessary to break the bond between the toner and the photoconductive belt and additionally bouncing the toner some distance "x" from the photoconductive belt surface, the attraction of the loose toner particles towards the commutated cleaning roll is complete. The commutated roll 110 attracts and causes both right and wrong sign toner to adhere to its surface as it rotates in a direction shown by arrow 115. A scraper blade 150 is placed in contact with the surface of the commutated roll 110 such that as the commutated roll rotates past the scraper blade 150, the particles adhering to the surface of the commutated roll 110 are scraped from the surface into a waste container (not shown). A vertical cleaner position allows the toner to "free fall" into a toner collection container due to gravity. The advantage of this apparatus over other cleaning systems is that no contact occurs between the commutated roll and the photoreceptor. With no contact, the life of the photoconductive belt is increased. The use of ATA device 130 yields greater than a 95% transfer efficiency in a cleaner configuration that allows the ATA to be operated at maximum potential. The acoustical horn 140 can be driven at maximum potential because toner registration is not a concern. This would allow for larger gaps between the roll 110 and photoconductive belt 10 thus, reducing the need for critical tolerances. The distance "x" of the commutated cleaning roll 110 from the surface of the photoconductive belt 10 is chosen to minimize the need for critical tolerances. The voltage potentials applied to the commutated cleaning roll are optimized such that the field strength between the commutated roll and the photoconductive belt are at a maximum and the air break down limit is not exceeded. In other words, the voltage is high enough to create a strong attraction of the toner from the photoconductive belt towards the commutated roll 110 but not strong enough to break down the air between the commutated roll 110 and photoconductive belt 10 and start arcing. For example, the voltage applied to the commutated roll 110 is in a range from approximately 100 volts (positive or negative) up to the air breakdown limit of approximately -100 volts. Thus, the voltage potentials and gap width would be chosen to maximize field strength and minimize the chance of entering the air breakdown limit. This is a non-contact cleaner because no part of the cleaner is in contact with the photoconductive belt 10 at any time. This non-contact cleaner eliminates motion quality problems, reduces photoconductive belt drag and reduces emissions. In a multi-pass copier (image-on-image), this cleaner would not have to retract from the photoconductive belt like conventional contact cleaners. Thus, reducing UMC (Unit Manufacturing Cost) and increasing reliability of the cleaner. Accordingly, the dual polarity, commutated roll of the present invention attracts toner and debris particles loosened into a particle cloud from the photoconductive belt surface by an acoustical horn. The particles adhere to the commutated roll, whether right or wrong sign (positively or negatively charged), and are removed form the roll, as the roll rotates, by a scraper blade. The particles are collected in a waste container as the particles are removed from the roll surface by the scraper blade.

Claims: An apparatus (70) for cleaning particles (120) from a substrate (10), comprising: a device (140), in communication with the substrate, for loosening the particles from the substrate by vibration; and a member (110), positioned adjacent the substrate, for attracting loosened particles thereto, said member including a plurality of segments with adjacent segments being of opposite polarities for attracting particles having opposite polarities thereto. An apparatus as recited in claim 1, wherein said substrate has first and second surfaces, and wherein the device applies vibratory energy to the first surface of the substrate. An apparatus as recited in claims 1 or 2, wherein said member comprises a roll. An apparatus as recited in claim 3, wherein said roll is positioned adjacent to and spaced from the second surface of the substrate. An apparatus as recited in any one of claims 3 or 4, wherein said device is an acoustical horn aligned with said roll. An apparatus as recited in claim 5, wherein said horn, in use, forms a cloud of particles in the space between said roll and the second surface of the substrate. An apparatus as recited in any one of claims 3 to 6, wherein the apparatus further comprises a scraper (150) contacting said roll to remove particles adhering thereto. An apparatus as recited in any of the preceding claims, wherein the particles include negatively charged particles and positively charged particles. An apparatus as recited in claim 8, wherein the negatively charged particles are attracted to the segments of said roll charged to a positive polarity; and wherein the positively charged particles are attracted to the segments of said roll charged to a negative polarity.

Inventors: BONISLAWSKI JOHN M JR, BONISLAWSKI, JOHN M., JR.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1995
Main classification: G03G21
IPC codes: G03G21