EP0288175A1

EP0288175A1 - Cleaning system

Info

Publication number: EP0288175A1
Application number: EP88302974A
Authority: EP
Inventors: Nero R. Lindblad; Henry R. Till; Charles A. Radulski
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1987-04-06
Filing date: 1988-03-31
Publication date: 1988-10-26
Also published as: JPS63261293A

Abstract

An apparatus (48) in which residual toner is removed from a photoconductive surface (10) after the transfer of a developed liquid image from the surface to a copy sheet. A porous roll (56) or belt (96) is employed to disturb the residual toner and detach it from the surface. Suction or electrical forces, cooperating with the porous roll or belt, attract the detached toner thereto for removal from the photoconductive surface.

Description

This invention relates generally to an electrophotographic printing machine, and more particularly concerns an apparatus for removing residual toner from a photoconductive member.
Generally, the process of electrophotographic printing includes charging a photoconductive member to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a liquid developer material into contact therewith. The liquid developer material comprises a liquid carrier having pigmented toner particles dispersed therein. The toner particles are deposited, in image configuration, on the photoconductive member. Thereafter, the developed image is transferred to the copy sheet. After transfer, heat is applied to the copy sheet to fuse the pigmented particles permanently to the copy sheet and vaporize the residual liquid carrier adhering thereto.
Invariably, after transfer, some of the liquid carrier and toner particles remain adhering to the photoconductive member. This residual material must be removed from the photoconductive member prior to the next successive imaging cycle. Presently, most electrophotographic printing machines use two cleaners to remove residual toner particles from the photoconductive member. For example, the Model No. 5040 and Model No. 8000 electrophotographic printing machines manufactured by the Savin Corporation use a rotating foam roll and a cleaning blade. Hereinbefore, various techniques have been devised for cleaning the residual toner particles from the photoconductive member. The following disclosures appear to be relevant:
US-A-4 016 812 discloses an apparatus for cleaning ink from the rolls of a printing machine. An endless web cleaning member is soaked in an ink solvent and engages the rolls that are to be cleaned. Ink is transferred from the rolls onto the cleaning web. A wiper assembly is further provided for cleaning the ink from the web.
US-A-4 279 501 describes an apparatus for cleaning toner from a photosensitive surface. A foamed polyurethane rubber roll and a scraping blade are employed in combination with a cleaning liquid to effect cleaning. The roller and blade are removable from their cleaning position with the photosensitive member to an inoperative position when the apparatus is not in operation.
US-A-4 344 361 teaches a device for cleaning debris from a blanket cylinder of an offset lithographic printing press. A cleaning cloth, with supply and take-up rolls, is provided in combination with a bladder member which is expanded by air under pressure. The expanded bladder member forces the cleaning cloth into engagement with the blanket cylinder in order to loosen the debris. A plurality of solvent dispensing tubes are used to provide a solvent to the cleaning cloth to aid in the cleaning process.
US-A-4 530 595 discloses a method and apparatus for cleaning toner from the surface of an electrostatic imaging member. A web-like film device comprises an outer electrically insulating side and an inner electrically conductive side. A voltage is impressed between the film member and the imaging surface. Subsequently, toner is removed from the imaging surface to the insulating side of the film member. Thereafter, toner is removed from the film member.
US-A-4 639 124 describes a cleaning apparatus for a multicolor electrophotographic printing machine. The cleaning system uses magnetically and electrically biased rolls to clean a photoconductive belt. Toner particles of a desired color may be recovered during the cleaning process for subsequent recycling and reuse in the printing machine.
In accordance with one aspect of the present invention, there is provided an apparatus for removing residual toner from a member after the transfer of a developed liquid image from the member to a copy sheet. The apparatus includes porous means for disturbing the residual toner and detaching the residual toner from the member. Means, cooperating with the porous means, attract the detached toner to the porous means.
Pursuant to another aspect of the features of the present invention, there is provided an electrophotographic printing machine of the type having a photoconductive member with residual toner adhering thereto after the transfer of a developed liquid image to the copy sheet, and a cleaning apparatus for removing the residual toner from the photoconductive member. The cleaning apparatus includes porous means for disturbing the residual toner and detaching the residual toner from the photoconductive member. Means, cooperating with the porous means, attract the detached toner to the porous means.
Other aspects of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which:

Figure 1 is a schematic elevational view showing an illustrative electrophotographic printing machine incorporating the features of the present invention therein;
Figure 2 is an elevational view depicting one embodiment of a cleaning system used in the Figure 1 printing machine;
Figure 3 is an elevational view showing another embodiment of a cleaning system used in the Figure 1 printing machine;
Figure 4 is an elevational view depicting still another embodiment of a cleaning system used in the Figure 1 printing machine; and
Figure 5 is an elevational view illustrating yet another embodiment of a cleaning system used in the Figure 1 printing machine.

Inasmuch as the art of electrophotographic printing is well known, the various processing stations employed in the Figure 1 printing machine will be shown hereinafter schematically and their operation described briefly with reference thereto.
Turning now to Figure 1, the electrophotographic printing machine employs a belt 10 having a photoconductive surface deposited on a conductive substrate. Preferably, the photoconductive surface is made from a selenium alloy, with the conductive substrate being made from an electrically grounded aluminum alloy. Other suitable photoconductive surfaces and conductive substrates may also be employed. Belt 10 moves in the direction of arrow 12 to advance successive portions of the photoconductive surface through the various processing stations disposed about the path of movement thereof. Belt 10 is supported by three rollers 14, 16, and 18 located with parallel axes at approximately the apexes of a triangle. Roller 14 is rotatably driven by a suitable motor associated with a drive (not shown) to move belt 10 in the direction of arrow 12.
Initially, a portion of belt 10 passes through charging station A. At charging station A, a corona-generating device, indicated generally by the reference numeral 20, charges the photoconductive surface of belt 10 to a relatively high, substantially uniform potential.
Next, the charged portion of the photoconductive surface is advanced through exposure station B. At exposure station B, an original document 22 is positioned face down upon a transparent platen 24. Lamps flash light rays onto original document 22. The light rays reflected from original document 22 are transmitted through a lens forming a light image thereof. The lens focuses the light image onto the charged portion of the photoconductive surface to dissipate the charge thereon selectively. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, belt 10 advances the electrostatic latent image recorded on the photoconductive surface to development station C.
At development station C, a developing liquid comprising an insulating carrier liquid and toner particles, is circulated from any suitable source (not shown) through pipe 26 into development tray 28 from which it is withdrawn through pipe 30 for recirculation. Development electrode 32, which may be appropriately electrically biased, assists in developing the electrostatic latent image with the toner particles, i.e. the pigmented particles dispersed in the liquid carrier, as it passes in contact with the developing liquid. The charged toner particles, disseminated throughout the carrier liquid, pass by electrophoresis to the electrostatic latent image. The charge of the toner particles is opposite in polarity to the charge on the photoconductive surface. By way of example, if the photoconductive surface is made from a selenium alloy, the photoconductive surface will be positively charged and the toner particles will be negatively charged. Alternatively, if the photoconductive surface is made from a cadmium sulfide material, the photoconductive surface will be negatively charged and the toner particles will be positively charged. Generally, the amount of liquid carrier on the photoconductive surface is too great. A roller (not shown) whose surface moves in a direction opposite to the direction of movement of the photoconductive surface, is spaced from the photoconductive surface and adapted to shear excessive liquid from the developed image without disturbing the image.
After development, belt 10 advances the developed image to transfer station D. At transfer station D, a sheet of support material 34, i.e. a copy sheet, is advanced from stack 36 by a sheet feeder, indicated generally by the reference numeral 38. The sheet of support material advances in synchronism with the movement of the developed image on belt 10 so as to arrive simultaneously therewith at transfer station D. Transfer station D includes a corona-generating device 40 which sprays ions onto the back of the copy sheet. This attracts the developed image from the photoconductive surface to the copy sheet. After transfer, the copy sheet continues to move onto conveyor 42 which advances the sheet to fusing station E.
Fusing station E includes a fusing system indicated generally by the reference numeral 44. The fuser assembly vaporizes the liquid carrier from the copy sheet and permanently fuses the toner particles, in image configuration, thereto. After fusing, the copy sheet is advanced to catch tray 46 for subsequent removal from the printing machine by the operator.
After the copy sheet is separated from the photoconductive surface of belt 10, some residual toner remains adhering thereto. This residual toner is removed from the photoconductive surface at cleaning station F. Cleaning station F includes a cleaning apparatus, indicated generally by the reference numeral 48, which removes residual toner adhering to the photoconductive surface of belt 10. In general, cleaning apparatus 48 disturbs the residual toner and detaches the residual toner from the photoconductive surface of belt 10. The detailed structure of the various embodiments of cleaning apparatus 48 are described hereinafter with reference to Figures 2 through 5, inclusive. Any residual charge left on the photoconductive surface is extinguished by flooding the photoconductive surface with light from lamp 50.
Preferably, the developer material includes a liquid insulating carrier having pigmented particles, i.e. toner particles dispersed therein A suitable insulating liquid carrier may be made from aliphatic hydrocarbon, such as an Isopar, which is a trademark of the Exxon Corporation, having a low boiling point. The toner particles include a pigment, such as carbon black, associated with the polymer. A suitable liquid developer material is described in US-A-4,582,774.
It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine incorporating the features of the present invention therein.
Referring now to Figure 2, there is shown one embodiment of cleaning apparatus 48. As shown thereat, cleaning apparatus 48 includes a roller 52 mounted rotatably, by suitable mean, such as ball bearings, on a shaft 54. A cylindrical, metal screen 56 is mounted interiorly of roller 52. Roller 52 rotates in the direction of arrow 58. A vacuum pump (not shown) is connected to the interior of screen 56 interior of roller 52. Roller 52 is made from a porous material. A pump (not shown) is coupled to pipe 60 to pump a cleaning fluid through pipe 60, in the direction of arrow 62, onto the photoconductive surface of belt 10 before roller 52. Preferably, roller 52 is made from a microporous polyurethane material, e.g. a foam material. In operation, as roller 52 rotates in the direction of arrow 58, the tangential velocity vector at the point of contact with the photoconductive surface of belt 10 is in an opposite direction to the direction of the velocity of belt 10. By abrasion, roller 52 disturbs and detaches the toner from the photoconductive surface of belt 10. The sub-atmospheric pressure maintained in the interior of screen 56 pulls the cleaning fluid and toner into the core of roller 52. The cleaning fluid is pumped from the cleaning apparatus to a liquid management station. Roller 52 is self sealing because of the vacuum, i.e. suction, applied to the foam. Preferably, the cleaning fluid applied on to the photoconductive surface of belt 10 is the liquid carrier employed in the developer material.
Turning now to Figure 3, there is shown another embodiment of cleaning apparatus 48. As depicted thereat, cleaning apparatus 48 includes a porous roller 64 mounted rotatably by suitable means, such as ball bearings, on shaft 66. Roller 64 is made from a thin, microporous polyurethane sleeve 68 mounted on a cylindrical, metal screen 70. As roller 64 rotates in the direction of arrow 76, the scrubbing action of sleeve 68, moving in the opposite direction to belt 10 at the point of contact therebetween, loosens the residual toner. A vacuum pump (not shown) is connected to the interior of screen 70. The vacuum, i.e. suction, at the interior of screen 70, pulls the residual toner into sleeve 68. At the top of cleaning apparatus 48, residual toner is flushed out of sleeve 68 through pipe 74. Cleaning fluid is introduced through pipe 72 for lubrication and to enhance cleaning. Preferably, the cleaning fluid is the liquid carrier used in the developer material. Screen 70 is electrically biased to a suitable voltage and magnitude to attract the dislodged residual toner to sleeve 68. It may not be necessary to utilize a vacuum interior of screen 70 when screen 70 is electrically biased to a suitable magnitude and polarity. In a cleaning apparatus of this type, sleeve 68 is continuously cleaned and it may be used to clean different color toner particles from the photoconductive surface of belt 10.
Another embodiment of cleaning apparatus 48 is illustrated in Figure 4. Cleaning apparatus 48 includes a roller 78 similar to roller 64 of Figure 3, being made from a sleeve of resilient, porous material fitting over a core of electrically conductive material. Roller 78 is mounted rotatably on shaft 80 by suitable means, such as ball bearings. As roller 78 rotates in the direction of arrow 82, since it is moving in an opposite direction to belt 10, the scrubbing action, at the contact point, disturbs the residual toner and dislodges it from the photoconductive surface. Roller 78 is electrically biased to a suitable polarity and magnitude to attract the detached toner thereto. Shield 89 prevents the toner adhering to roller 78 from being detached therefrom. Blade 86, which is made preferably from a stainless steel, contacts roller 78 to scrape the toner therefrom. Cleaning fluid from pipe 88 washes the toner from blade 86 onto belt 10. Preferably, the cleaning fluid is liquid carrier from the developer material. Blade 90 has its longitudinal axis extending in a transverse direction to belt 10, i.e. blade 90 is skewed, to seal the cleaning apparatus. By skewing blade 90, the cleaning fluid can be directed to the edge of the belt and then removed by using suction. Pipe 92 is connected to a vacuum pump to suck the cleaning fluid and toner away from belt 10, in the direction of arrow 94. In this way, the residual toner is removed from the vicinity of belt 10.
Figure 5 shows still another embodiment of cleaning apparatus 48. As depicted in Figure 5, cleaning apparatus 48 has a web 96 entrained about a pair of spaced rollers 98 and 100. Roller 100 is driven by a motor coupled thereto by suitable means, such as a belt or gear drive. Roller 100 rotates in the direction of arrow 102 and moves web 96. In this way, web 96 moves in the opposite direction to the direction of belt 10, as indicated by arrow 12, at the contact point. A cleaning fluid flows from pipe 104 onto web 96. Roll 100 is made from an electrically conductive material. a voltage source, coupled thereto, electrically biases roll 100 to a suitable polarity and magnitude so as to attract dislodged toner to web 96. The toner adhering to web 96 is washed therefrom by the cleaning fluid flowing from pipe 104. The residual toner and cleaning fluid flow through pipe 106 where the residual toner is reclaimed and the cleaning fluid returns to a liquid management system. Roll 98 may also be made from an electrically conductive material and may be electrically biased to a suitable magnitude and polarity to assist in cleaning the residual toner from web 96. Cleaning fluid flows from pipe 108 on to the photoconductive surface of belt 10 before the point of contact between web 96 and belt 10 in the direction of movement of belt 10, as indicated by arrow 12. Preferably, the cleaning fluid is the liquid carrier of the developer material. Web 96 is made preferably from a microporous, dielectric material. In operation, cleaning fluid flows from pipe 108 on to the photoconductive surface of belt 10 at the entrance to the cleaning zone. The cleaning fluid assists in removing the residual toner from the photoconductive surface, and lubricates the belt. At the contact point, web 96 scrubs belt 10 to detach the residual toner therefrom. The electrical field generated by roll 100 attracts the detached toner to web 96. Web 96 transports the toner to roll 98. At roll 98, cleaning fluid from pipe 104 flushes web 98 to remove the toner therefrom. Roll 98 may have an electrical field associated therewith to aid in the removal of the toner from web 96. The toner removed from web 96 and the cleaning fluid are sucked into pipe 106. Residual toner is reclaimed and the cleaning fluid returned to a liquid management system.
In recapitulation, it is clear that the cleaning apparatus of the present invention is adapted to detach residual toner from the photoconductive surface. The detached toner is removed. This is accomplished by the use of a porous roll or belt which scrubs the photoconductive surface of the belt to detach the residual toner therefrom. An electrical field and/or suction remove the detached toner from the photoconductive surface. Cleaning fluid is placed on the photoconductive surface to provide lubrication and to facilitate the cleaning action.

Claims

1. Apparatus for removing residual toner from a member after the transfer of a developed liquid image from the member to a copy sheet, including:
porous means for disturbing the residual toner and detaching it from the member; and
means, cooperating with the porous means, for attracting the detached toner to the porous means.

2. An apparatus according to claim , wherein the attracting means includes means for electrically biasing the porous means.

3. An apparatus according to claim 1 or 2, further including means for supplying a cleaning fluid to the member to assist in the removal of the residual toner therefrom.

4. An apparatus according to any preceding claim, wherein the porous means includes a foam roller.

5. An apparatus according to claims 2 and 4, wherein the electrical biasing means includes an electrically-conductive, substantially-cylindrical, sleeve disposed interiorly of the foam roller.

6. An apparatus according to any preceding claim, for removing residual toner from a movable member, including a blade having a free end thereof contacting the member downstream of the region in which it is contacted by the porous means.

7. An apparatus according to claim 3, wherein the porous means includes a porous belt.

8. An apparatus according to claim 7, wherein the attraction means includes a pair of electrically-conductive spaced rollers having the porous belt entrained thereabout.

9. An apparatus according to any preceding claim, wherein the toner-attraction means includes means for reducing the pressure in the porous means to attract the detached toner thereto.

10. An electrophotographic printing machine including residual toner removal apparatus as claimed in any preceding claim.