US3741157A

US3741157A - Electrophotographic plate cleaning apparatus

Info

Publication number: US3741157A
Application number: US00888627A
Authority: US
Inventors: K Krause
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1969-12-29
Filing date: 1969-12-29
Publication date: 1973-06-26
Anticipated expiration: 1990-06-26
Also published as: FR2072209A5; BE758141A; GB1277173A; JPS5029652B1; DE2061666A1; CA923194A

Abstract

An electrophotographic plate cleaning apparatus utilizing air under pressure being directed through nozzles and onto the plate surface with vacuum means for drawing the removed material from the surface.

Description

United States Patent [191 3,741,157 Krause 1 June 26, 1973 [54] ELECTROPHOTOGRAPHIC PLATE 2,752,271 6/1956 Walkup et a1 118/637 UX CLEANING APPARATUS 2,818,595 1/1958 Rosewa1l...' 15/345 X 3,045,273 7/1962 Bruno 118/637 UX Inventor: Konrad e, Mount View, 3,239,863 3/1966 Gardner 15/345 x A Calif. 3,278,972 10/1966 Hudson 118/637 X 4 7 68' 1-1 [73] AS5191: lmemafim'al Busmess Mach'nes 1212176 6/1369 011111136121. 1 1 11/23? Corporation, Armonk, NY. [22] Fllefj: D 1969 Primary Examiner-James Kee Chi [21] Appl. No.: 888,627 Attorney-Hanifin and Jancin and Otto Schmid, Jr.

52 vs. Cl. 118/637, 15/345 [51] Int. Cl. 1305b 5/02, A471 5/14 57 ABSTRACT [58] Field of Search 118/637; l17/17.5;

96/1 R, 1 A, 1 E, 1 SD; 95/1 1 15/1-5, An electrophotographic plate cleaning apparatus utiliz I 345 ing air under pressure being directed through nozzles and onto the plate surface with vacuum means for 1 References Cited drawing the removed material from the surface.

UNITED STATES PATENTS 10 Claims, 8 Drawing Figures 2,576,047 11/1951 Schaffert 15/1.5X

PAIENIEmunes m3 3.741.157

sum 1 0f 3 III/IIffllf.

KONRAD A. KRAUSE H WM? ATTORNEY PATENTED M1126 I973 FIG. 7

FIG. 8

ELECTROPHOTOGRAPI-IIC PLATE CLEANING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to surface cleaning apparatus and more particularly to the removal of imagedeveloping powder from a photoconductive surface such as that used in an electrophotographic imaging system.

2. Description of the Prior Art In one method of electrophotography, a photoconductive member is charged electrostatically over its surface and then exposed to an opaque image to form the image in the electrostatic pattern on the surface. The areas of the photoconductive member exposed to the light image are discharged and the electrostatic latent image is created. Development of this electrostatic image then is achieved with an electrostatically charged material such as an electroscopic powder which is brought into surface contact with a photoconductive member and held thereon by the charge corresponding to the image. Thereafter, the material is transferred to a surface such as paper to which it may be fixed by heating or any other suitable means.

The transfer process normally removes only a portion of the powder leaving the remainder on the photoconductive member. This residual powder must be removed before a new image can be developed. Such removal is made difficult by the fact that the powder is held by an electrostatic charge and any direct contact with the electra photographic plate can result in damage to the plate s surface because the photographic materials used today are not resistant to abrasion.

It is the primary purpose of this invention to disclose an improved method for removing the charged material from a photoconductive surface in an efficient manner with little or no damage to the photographic member.

SUMMARY OF THE INVENTION A surface cleaning apparatus wherein a nozzle ass'embly positioned in spaced relationship to the surface directs a plurality ofjets of air under pressure onto the surface for sweeping away any residual powder with vacuum means adjacent the air jets to carry away the dislodged material. i

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustratedin the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 5 is a cross-sectional view of the embodiment of the subject invention shown in FIG. 4 wherein the additional cleaning apparatus is selectively operable;

FIG. 6 is a cross-sectional view of an additional embodiment of the subject invention utilizingan additional cleaning device comprising a selectively actuable cleaning apparatus;

FIG. 7 is a view showing apparatus for producing a lateral oscillatory motion of the cleaning apparatus comprising the invention;

FIG. 8 is a view showing apparatus for producing a combined lateral and angular oscillatory motion of the cleaning apparatus comprising the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is broadly applicable to all applications requiring cleaning particle material from surfaces. However, the embodiment of the invention described relates to an electrophotographic apparatus since the cleaning requirement in this apparatus presents stringent requirements due to the electrostatic attraction between the particles and the surface to be cleaned.

One example of a particular apparatus in which the subject invention is adapted for use is the electrophotographic apparatus shown in FIG. 1. In this apparatus, a rotatable drum 1 carries around its'periphery an electrophotographic photoconductive member 2 on which is directed an image which it is desired to be reproduced on the paper sheet 3. The surface of the photoconductor is uniformly charged to a predetermined polarity by corona discharge device 5. A document having the image to be copied is placed so that a suitable exposure means is operable to direct the image to expose station 4 onto the surface of the photoconductor 2. Relative motion is provided for the document at a speed synchronized with the surface speed of drum 1 in a manner known in the art. Where thephotoconductive surface is illuminated by the image, the surface is discharged leaving a charged pattern in aform of the image to be copied.

Thereafter, the drum passes a development station 10 at which a toner-carrier mixture 11 is cascaded across the electrostatic image on the surface of the photoconductor 2 as is known in the art. The toner, having a charge opposite from the polarity of the electrostatic image charge, is attracted to the drum surface to render the image visible.

Continuing the counterclockwise .-rotation of the drum 1', a copy paper 3 is fed into contact with the developed electrostatic image by the rollers 14. Preferably a corona unit 15 is disposed beneath the paper at the area of contact with-the drum. The corona has a polarity opposite that of the toner thereby attracting the toner to the copy paper. After this so-called corona transfer, the paper 3 is separated after the drum and fed past a fusing station which serves to fuse and permanently fix the toner to the paper. Since transfer of allthe image toner is not-usually accomplished, residual toner l6 usually remains on the drum surface after a transfer operation. The drum continuesto rotate past a cleaning apparatus 17 which cleans the surface of the an erase corona if desired, as known in the art, to aid in removal of the excess toner. This operation comof pressurized air onto the photoconductor surface to clean the residual toner from the surface. The force of the air pressure through the nozzles and the turbulence created by the directed streams of air striking the surface of the photoconductor produces a substantial lateral force on the toner particles which operates to dislodge the toner particles from the surface of the photoconductor. This action leads to improved cleaning efficiency and reduced filming of the photoconductor surface. Since no cleaning apparatus other than the air contacts the photoconductive surface, this factor also leads to reduced damage to the photoconductor surface and longer photoconductor-life.

In the embodiment shown, nozzle assembly 22 comprises an elongated air cylinder or conduit 28 having a plurality of nozzles 24 positioned to blow pressurized air which enters at one end of conduit 28 onto the photoconductor surface. Any suitable arrangement of nozzles 24 can be utilized, however, the preferred arrangement of nozzles is'a single line of orifices in air cylinder 28.Each orifice comprises a hole in the wall of air conspaced from the surface by a small amount. A supply duit' 28 which is preferably a countersunk inlet hole. In

the embodiment shown, a vacuum chamber is provided which substantially encloses the nozzle assembly 22 and is positioned close to the surface of the photoconductor so that by connecting a vacuum source to the-outlet 23 from vacuum chamber 30, the resultant airflow due to the pressure differential carries the dislodged toner particles away from the photoconductor surface. l

To provide greater turbu'lenceof the cleaning air as the air strikes the photoconductor surface, relative motion is provided between the streams of air issuing from the individual nozzles 24 and the photoconductor surface. This relative motion is accomplished by providing means for producing'relative lateral motion. Any suitable type of linear motion actuator can be-used. In the embodiment shown in- FIG. 7, the lateral motion means comprises a voice, coil linear ac tuator'26. The voice coil actuator comprises an annular magnetic path and a coil mounted for. linear 'motion' within the annularmagnetic path so that when the mechanism is energized with an alternating current voltagethe apparatus, produces a-reciprocating motion of air cylinder 28 at the frequency of the energizing voltage due to the mounting of air cylinder 28 by sleeve-bearings 25. The nozzle assembly 22 is coupled to the moving coil'portion of the voice coil actuator and nozzle assembly 22 is biased to 'the midpoint of its movement by means of springs 27. When actuator 26 is energized a reciprocating lateral motion of the nozzle assembly relative to the surface of the photoconductor 'isproduced so that increased turbulence of the air results which further improves the cleaning efficiency of the cleaning apparatus. In this manner, the same cleaning can be provided with a lower air pressure as compared to the previously described embodiment or a greater cleaning capacity can be obtained with the use of the same air pressure as the previous embodiment.

To provide still further increase in the efficiency of removing the residual toner from the surface of the 'ductor surface so that there is a' photoconductor, the nozzle assembly is moved in a lateral reciprocating motion as previously described, and at the same time the nozzle assembly is reciprocated on its axis in an angular fashion relative to the surface of the photoconductor. This operation provides still greater air'turbulence along the surface of the photoconductor which is operative to clean the surface with greater efficiency. The angular motion can be produced by any suitable means. In the embodiment of-the invention shown in FIG. 8, the angular motion is produced by a second voice coil linear actuator 29 which is operative to move the nozzle assembly in an angular movement relative to the photoconductive surface as the nozzle assembly is oscillated laterally with respect to the photoconductor surface. A mounting member 50 is fixed to conduit 28 and this mounting member terminates in a rounded end portion 52. The moving coil actuator 29 is coupled to a shaft having a bifurcated end portion 48 mounted for pivotally receiving end portion 52. Springs 51 are provided to bias cylinder 28 to a rest position in which the individual nozzles are facing substantially perpendicular to the photoconductor surface. This apparatus and the previously described lateral motion apparatus produced a combined lateral and angular movement of nozzleassembly 22. This operation has the effect of moving the individual air streams in an elliptical or circular path relative to the photoconduc tor surface due to the motion. v

The air jet cleaning. apparatus which has been described produces superior cleaning when compared to the prior art-brush cleaning method, .since the brush cleaning method, in addition to the problems relative to the cleaning and replacing of the brush, produces compound angular and linear filming of the photoconductor surface and some dam-1 brush cleaner assembly 32 is positioned adjacent the air jet cleaning apparatus. The airjet cleaning apparatus comprises a nozzle assembly 22- having a plurality of individual nozzles 24 substantially as described above. The brush cleaning assembly comprises a fiber brush 38 mounted for continuous rotation in a direction opposed to the movement of photoconductive member 2.

The brush is mounted so that it is in contact with photo-,

conductor member 2.'In this case the air pressure does not have to be as high as the embodiment in which the air jet cleaner is used along since an auxiliary cleaning apparatus is provided. In this embodiment the air jet cleaning system does the, main cleaning so the brush fibers do, not haveto transport as much toner as in conventional brush cleaning systems. For this reason, the brush can be rotated at a much slower speed as compared to conventional brush cleaning systems, which results in a reduction of the deformation of the fiber ends and, thus, does not require as frequent a replacement of brush 38. The slower speed of brush 38 also ie I duces local heating and deformation of the photoconcorresponding increase in the useful life of this member as compared to systems utilizing only brush cleaning.

In some cases it may be desirable to utilize the brush cleaner assembly only periodically to clean the photoconductive surface after a certain period of air jet cleaning. In the embodiment shown in FIG. 5 of the drawing, a brush 36 is mounted for selective movement to and from the position at which the brush is operative to clean the photoconductive surface by means of a selectively operable device. The selectively'operable de vice in the embodiment shown is a solenoid 34. The solenoid 34 is fixedly mounted to the machine frame and the armature is attached to a pivoted lever 40 to which is mounted the shaft of the rotating brush 36. The solenoid may be actuated by a suitable electrical signal CLEAN DRUM which can be generated in any suitable way. One suitable way in which the CLEAN DRUM signal can be generated is on the basis of a counted number of copy cycles. For example, at every 2,000 counts of a counter'a signal is produced which is effective to actuate solenoid 34 and the solenoid is maintained for apredetermined time in the operative position as shown dotted in FIG. 5 to remove any accumulated toner material.

An alternate embodiment of a selectively operable cleaning apparatus is shown in FIG. 6. In this embodiment an air jet cleaner is provided which operates as described above. This apparatus is operative to maintain the photoconductive surface in a clean condition for a substantial number of operative cycles. However, a supplemental cleaning apparatus 41 is provided which comprises a web cleaning member 42. Web member 42 is contained in a cartridge 44 and the cartridge is mounted so that in the inoperative position as shown in FIG. 6 the web is spaced a short distance from the photoconductor surface. Web cleaning member 42 may be composed of woven or nonwoven fibrous material, and the material may be impregnated with a wax material, a dry solvent material, liquid solvent material, an abrasive material or suitable combinations of these materials. In the preferred embodiment, web member 42 is impregnatedwith wax. Periodically, when the photoconductor surface is to. be wiped, a signal CLEAN DRUM is generated which actuates solenoid 46 to move the cartridge to the operative position as shown dotted in FIG. 6, so that the wax-impregnated web contacts the surface for a combined cleaning and polishing operation. The cleaning may be initiated in any suitable manner. One suitable technique for initiating a cleaning operation is on the basis of a counted number of copy cycles as previously described. The web renews the photoconductor surface by wiping off the film created by the residual toner and also waxes the surface of the photoconductor. If desired, the web may be driven from supply reel to take-up reel within cartridge 44 at a relatively slow speed while the web contacts the photoconductor surface so that a clean portion of the web continues to contact the photoconductor surface during the cleaning operation.

The velocity of the air stream emerging from the nozzle assembly to clean the photoconductive surface is determined by the air pressure applied, the velocity of the photoconductor surface and the size, number and type of individual nozzles provided in the air cylinder for directing the pressurized air onto the photoconductor surface. The nozzles must be close enough together when considering the spacing from the photoconductive surface so that the photoconductive surface is well covered, otherwise, the surface will not be uniformly cleaned and streaking of the copied image results. In a particular embodiment of the invention similar to the embodiment shown in FIG. 2, the individual nozzles comprise 0.005 holes spaced 0.030 of an inch apart and the air cylinder was spaced 0.020 of an inch from the photoconductive surface. In this embodiment an air pressure of 20 pounds per square inch was suitable for cleaning a surface moving at a velocity of 4 inches per second.

An embodiment of the apparatus shown in FIG. 8 wherein the air cylinder was moved in both a linear and an angular motion at a frequency of 60 cycles per second and an amplitude of 0.030 inches relative to the photoconductor surface, the photoconductive surface was cleaned sufficiently at higher speeds. Thus, it can be seen that the arrangement of the individual orifices and the pressure applied to the nozzles is selected on the basis of the velocity of the photoconductive surface to be cleaned, the degree of cleaning required and the gloss required on the photoconductive surface for the particular copying application.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a reproducing apparatus wherein an electrophotographic plate is passed through a series of process stations for transferring an image wherein one station includes the depositing of powder on the plate,

a plate cleaning station comprising a supply of pressurized gas,

a nozzle assembly positioned adjacent, but spaced from, said plate,

means for effecting relative movement between said plate and nozzle assembly; means for connecting the nozzle assembly to said gas supply, said nozzle assembly comprising a plurality of individual nozzles designed for receiving and directing the pressurized gas onto said plate to clean the powder therefrom; and

means for continuously oscillating said nozzle assembly laterally with respect to said plate to increase the turbulence produced by said pressured gas contacting said plate.

2. The plate cleaning apparatus according to claim 2 additionally comprising means for oscillating said nozzle assembly angularly with respect to said plate to increase the turbulence caused by said pressured gas contacting said plate.

3. The plate cleaning apparatus according to claim 1 additionally comprising a vacuum chamber surrounding said nozzle assembly; and

means for producing a reduced pressure within said chamber so that the powder cleaned from said plate is removed through said vacuum chamber.

4. The plate cleaning apparatus according to claim 1 wherein-said nozzle assembly comprises an air cylinder and said individual nozzles comprise countersunk holes spaced along said air cylinder.

5. The plate cleaning apparatus according to claim 4 wherein said countersunk holes comprising said individual nozzles are in line in said air cylinder.

6. The plate cleaning apparatus according to claim 5 wherein said individual nozzles are positioned to direct said pressured gas substantially perpendicularly to the surface of said plate.

7. In a reproducing apparatus wherein an electrophotographic plate is passed through a series of process stations for transferring an image wherein one station includes the depositing of powder on a plate,

a first and a second plate cleaning apparatus,

means for effecting relative movement between said plate and said plate cleaning apparatus,

said first plate cleaning apparatus comprising a supply of pressured gas,

a nozzle assembly positioned adjacent, but spaced from, said plate,

means for connecting the nozzle assembly to said gas 1 supply, said nozzle assembly comprising a plurality of individual nozzles'designed for receiving and directing the pressured gas onto said plate to clear the powder therefrom,

said second plate cleaning apparatus comprising cleaning means mounted for movement from an idle position adjacent to but not contacting the plate and a cleaning position contacting said plate; and I means for selectively moving said second plate cleaning means from the idle to the cleaning position.

8. The plate cleaning apparatus according to claim 7 wherein said cleaning means comprises a rotating cleaning brush.

9. The plate cleaning apparatus according to claim 7 wherein said cleaning means comprises a web cleaning member.

10. The plate cleaning apparatus according to claim 9 wherein said web cleaning member is impregnated with a wax substance.

Claims

1. In a reproducing apparatus wherein an electrophotographic plate is passed through a series of process stations for transferring an image wherein one station includes the depositing of powder on the plate, a plate cleaning station comprising a supply of pressurized gas, a nozzle assembly positioned adjacent, but spaced from, said plate, means for effecting relative movement between said plate and nozzle assembly; means for connecting the nozzle assembly to said gas supply, said nozzle assembly comprising a plurality of individual nozzles designed for receiving and directing the pressurized gas onto said plate to clean the powder therefrom; and means for continuously oscillating said nozzle assembly laterally with respect to said plate to increase the turbulence produced by said pressured gas contacting said plate.

3. The plate cleaning apparatus according to claim 1 additionally comprising a vacuum chamber surrounding said nozzle assembly; and means for producing a reduced pressure within said chamber so that the powder cleaned from said plate is removed through said vacuum chamber.

4. The plate cleaning apparatus according to claim 1 wherein said nozzle assembly comprises an air cylinder and said individual nozzles comprise countersunk holes spaced along said air cylinder.

7. In a reproducing apparatus wherein an electrophotographic plate is passed through a series of process stations for transferring an image wherein one station includes the depositing of powder on a plate, a first and a second plate cleaning apparatus, means for effecting relative movement between said plate and said plate cleaning apparatus, said first plate cleaning apparatus comprising a supply of pressured gas, a nozzle assembly positioned adjacent, but spaced from, said plate, means for connecting the nozzle assembly to said gas supply, said nozzle assembly comprising a plurality of individual nozzles designed for receiving and directing the pressured gas onto said plate to clear the powder therefrom, said second plate cleaning apparatus comprising cleaning means mounted for movement from an idle position adjacent to but not contacting the plate and a cleaning position contacting said plate; and means for selectively moving said second plate cleaning means from the idle to the cleaning position.