US3534427A

US3534427A - Cleaning apparatus for electrostatic printing machines

Info

Publication number: US3534427A
Application number: US713989A
Authority: US
Inventors: Gerard T Severynse
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1968-03-18
Filing date: 1968-03-18
Publication date: 1970-10-20
Anticipated expiration: 1987-10-20
Also published as: SU372853A3; FR2004161A1; CS157666B2; BE729977A; SE345533B; GB1238117A; NL6903868A; DE1913493A1; DE1913493B2; DE1913493C3

Description

Oct.- 20, 1970 I G. T. SEVERYNSE 3,534,427

' CLEANING APPARATUS FOR ELECTROSTATIC PRINTING MACHINES- Filed March. 18, 1968 3 Shee'is-Sheet 1 FIG. 1

' INVENTOR. GERARD T. SEV ERYNSE A RNEVS Oct. 20, 1970' G. T. SEVERYNSE CLEANIKG' APPARATUS FOR ELECTROSTATIC PRINTING MACHiNES Filed March 18, 19 68 5 Sheets-Sheet 2 FIG. 2

. INVENTOR.

GERARD T. SEVERYNSE ATTORNEYS Oct. 20, 1970' s. T. SEVERYNSE I 3,534,427

CLEANING'APPARATUS FOR ELECTROSTATIC PRINTING MACHINES Filed March 1a, 196 :5 Shets-Sheet s INVENTOR.

V ATTORNEYS United States Patent Oflice 3,534,427. Patented Oct. 20, 1970 3,534,427 CLEANING APPARATUS FOR ELECTROSTATIC PRINTING MACHINES Gerard T. Severynse, Fairport, N.Y., assignor to Xerox gorfioration, Rochester, N.Y., a corporation of New Filed Mar. 18, 1968, Ser. No. 713,989 Int. Cl. A471 /38, 13/40 US. Cl. -301 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to brush cleaning systems, and particularly, to improvements in a brush cleaner for particulate material that is particularly adapted for use with automatic copiers/reproducers capable of high speed operation.

As is well known in recent years, the steadily increasing size of various industries has required an enormous increase in the amount of paper work that must be accomplished, maintained, and made available for wide interplant circulation. With the present day commercial automatic copiers/reproduction machines that produce copies of between 5 and 60 8 x 11" sheets of copy per minute, the photoreceptor device is in the form of a drum which rotates in timed unison relative to a plurality of processing stations. In a large number of these reproducing machines, removal of residual toner particles from the photoreceptor drum is effected by wiping the drum with a rotating cylindrical brush which also beats against a flicker bar to remove the particles from the brush described more fully in US. Pat. 2,751,616, 3,062,109, and 3,278,972.

More recently increased speeds of the photoreceptor drum have required vast amounts of toner particles during development process. While the rotating brush and flicker bar arrangement cleans in one sense, it has not been entirely satisfactory in removing all the residual toner particles from the photoreceptor surface. The reason for this is that the toner particles accumulate on the brush and/or flicker bar and are then redeposited onto the photoreceptor surface from which they were originally removed.

\It is therefore the principal object of this invention to improve electrostatic reproduction machines.

It is another object of this invention to remove residual developing material from a photoreceptor surface with greater efliciency than heretofore.

It is a further object of this invention to remove toner particles from a photoreceptor surface by a brushing action without allowing the particles to redeposit on the surface.

These and other objects of this invention are achieved, generally speaking, by directing a high velocity fluid in opposition to the path of movement of the tips of bristles of a brush contacting a surface to be cleaned as they strike against a flicking device.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic sectional view of a reproduction machine incorporating a cleaning assembly according to the present invention with the processing components in section to better illustrate the environment for the pres ent invention;

FIG. 2 is an elevational view partly broken away in section of the cleaning assembly used in the machine;

FIG. 3 is a sectional view of the cleaning assembly taken along line 33 of FIG. 2;

FIG. 4 is a fragmentary sectional view taken along line 44 of FIG. 3 illustrating details of the high velocity fluid flow utilized in the cleaning assembly.

In FIG. 1 there is shown schematically a high speed automatic electrostatic or xerographic reproduction machine incorporating a cleaning assembly generally designated 10 according to the present invention.

The automatic xerographic reproducing machine comprises a xerographic plate 20 including a photoconductive layer or light-receiving surface on a conductive backing and formed in the shape of a drum, which is mounted on a shaft journaled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally, as follows:

A charging station, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station, at which a light or radiation pattern of copy to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof and thereby form a latent electrostatic image of the copy to be reproduced;

A developing station, at which a xerographic developing material including toner particles having an electrostatic charge opposite to that of the electrostatic latent image are cascaded over the drum surface, whereby the toner particles adhere to the electrostatic latent image to form a xerographic powdered image of the configuration of the copy being reproduced.

A transfer station, at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or a support surface; and,

A drum cleaning and discharge station, at which any residual toner particles remaining on the drum surface after image transfer are removed, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station located as indicated by reference character A includes a corona charging device 21 which comprises a corona discharge array of one or more corona discharge electrodes that extend transversely across the drum surface. The charging device is energized from a high potential source and is substantially closed within a shielding member.

Next subsequent thereto in the path of motion of the xerographic drum is an exposure station B. An optical scanning or projection system is provided to project a flowing image onto the surface of the photoconductive drum from a stationary original.

The optical scanning or projection assembbly comprises a stationary copyboard which consists of a transparent curved platen member 22, such as, for example, a glass plate or the like, positioned on the exterior of the cabinet, which is adapted to support a document to be reproduced, the document being uniformly illuminated and arranged in light projecting relation to the moving lightreceiving surface of the xerographic drum. Uniform lighting is provided by banks of lamps LMP1 arranged on opposite sides of the copyboard.

Scanning of the document on the stationary copyboard is accomplished by means of a mirror assembly which is oscillated relative to the copyboard in timed relation to the movement of the xerographic drum. The mirror assembly, which includes an object mirror 23, is mounted below the copyholder to reflect an image of the document through a lens 24 onto an image mirror 25, which, in turn, reflects the image onto the xerographic drum through a slot in a fixed light shield 26 positioned adjacent to the xerographic drum surface.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus 30 including a casing or housing having a lower or sump portion for accumulating developer material. A bucket type conveyor is used to carry the developing material to the upper part of the developer housing where it is cascaded over a hopper chute onto the xerographic drum to effect development. A toner dispenser 35 is used to accurately meter toner to the developing material as toner particles are consumed during the developing operation.

Positioned next and adjacent to the developing station is the image transfer station D which includes a sheet feeding arrangement adapted to feed sheets of sup port material, such as paper or the like, successively t the xerographic drum in coordination with the presentation of the developed image on the drum surface at the transfer station.

The sheet feeding mechanism includes a sheet feed device 40 adapted by means of vacuum feeders to feed the top sheet, of a stack of sheets on a tray 41, to rollers 42 cooperating with the belts of paper transport 44 for advancing the sheet sufliciently to be held by paper transport 44 which in turn, conveys the sheet to a sheet registration device 45 positioned adjacent the xerographic drum. The sheet registration device arrests and aligns each individual sheet of material and then in timed relation to the movement of the xerographic drum, advances the sheet material into contact with the xerographic drum in registration with a previously formed xerographic powder image on the drum.

The transfer of the xerographic powder image from the drum surface to the sheets of support material is effected by means of a corona transfer device 51 that is located at or immediately after the line of contact between the support material and the rotating drum. In operation, the electrostatic field created by the coronatransfer device is effective to tack the support material electrostatically to the drum surface, whereby the support material moves synchronously with the drum while in contact therewith. Simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and cause them to adhere electrostatically to the surface of the support material.

Immediately subsequent to the image transfer station, there is positioned a stripping apparatus to paper pick-off mechanism 52 for removing the sheets of support material from the drum surface. The device, which is of the type disclosed in Rutkus et al. US. Pat. 3,062,536, includes a plurality of small diameter orifices supplied With pressurized aeriform fluid by a suitable pulsator or other device. The pulsator is adapted to force jets of pressurized aeriform fluid through the outlet orifices into contact with the surface of the xerographic drum slightly in advance of the sheet of support material to strip the leading edge of the sheet from the drum surface and to direct it into an endless conveyor 55 whereby the sheet material is carried to a fixing device 60. At the fixing device, the transferred xerographic powder image on the sheet of support material is permanently fixed or fused thereto as by heat. After fusing, the reproduction is discharged from the apparatus at a suitable point for collection externally of the apparatus by means of the conveyor 65. In the embodiment shown,the reproductions are discharged from conveyor 65 into a receiving tray 61.

The next and final station in the device is a drum cleaning station E, having cleaning assembly 10 constructed in accordance with the invention which removes substantially all toner particles remaining on the xerographic drum after transfer in a manner to be described. Positioned adjacent to cleaning assembly 10 are a corona preclean device 66 and a discharge lamp LMP-2 which floods the xerographic drum with light to cause dissipation of any residual electrical charge remaining on the xerographic drum subsequent to cleaning.

Suitable drive means are provided to drive the drum, rotating mirror and sheet feed mechanism at predetermined speeds relative to each other, and to effect operation of the bucket-type conveyor and toner dispenser mechanism and the other operating mechanisms.

It is believed that the foregoing description is sufficient for the purposes of this application to show the general operation of a xerographic reproducing apparatus incorporating a brush cleaning apparatus constructed in accordance with the invention. For further details concerning the specific construction of the xerographic apparatus shown, reference is made to copending application, Ser. No. 400,363, filed on Sept. 30, 1964 in the name of R. F. Osborne et al.

Referring now to FIGS. 24, there is shown details of cleaning assembly 10 which includes a rotatable brush 71 of such construction so as to apply extremely light pressure to the photoconductive surface of the Xerographic plate to dislodge any toner particles which adhere to it. The brush may be made of any suitable material as, for example, synthetic fur, vegetable fibers, animal fur, and mixtures thereof. Synthetic fur is preferred because it is less expensive. Brush 71 is rotatably supported in a brush casing which consists of a right hand end frame 72 and left hand end frame 74 supporting therebetween upper and lower brush shields 76 and 77, respectively, and a vacuum duct 78. Both the right hand and left hand end frames 72 and 74 are provided with

semi-circular bosses

73 and 75, respectively, to which the above-described elements are attached, as by screws 79. The end frames 72 and 74 are formed with concave edge portions in conformity with the shape of the xerographic drum to permit the casing to be positioned closely adjacent to the xerographic drum while still substantially enclosing the brush.

The brush is supported at its right end by a truncated cone-shaped arbor 81 to support and rotate the brush, the arbor 81 being fixed on the shaft 82 of motor 83 mounted to end frame 72. At its opposite end, the brush is supported ;by another truncated cone-shaped arbor 84 that is rotatably and movably journaled by bearing 85 on shoulder bolt 86, the threaded portion of which extends through cover 87 and is secured thereto by nut 88. Bearing 85 and arbor 84 are resiliently biased toward the head of bolt 86 by spring 89 encircling the bolt and positioned between bearing washer 91 and cover 87.

Cover 87 is pivotally secured by pin 92 to the reduced bottom portion of end frame 74 and it is releasably secured in position to close the opening in this end frame by screw 93 which threads into a suitable aperture in the end frame. To aid in proper alignment of the cover, a tapered pin 94 extends from the end frame into a suitable aperture formed in the cover.

The vacuum duct 78 is provided with an'elonga'ted opening extending approximately the full length of the brush to permit removal of toner particles from the brush. The opening in the opposite end of vacuum duct 78 is in communication with an exhaust duct secured to the vacuum duct. The exhaust duct 105 is suitably connected to the filter box 106. A filter bag 107 is mounted within the filter box, with the mouth of the filter bag in communication with the exhaust duct. A motor driven fan unit 109, connected to the filter box, produces a flow of air through the filter box drawing air through the area surrounding the xerographic drum and the dust hood, the air entraining toner particles removed from the drum by the brush as the air flows through the dust hood. Toner particles are separated from the air as it flows through the filter bag so that only clean air is exhausted by the motor driven fan unit.

In order to aid in the removal of toner particles from the bristles of the brush 71 during rotation, cleaning apparatus is provided with a flicker rod or bar 110 mounted between the vacuum duct 101 and brush 71. Flicker bar 110 extends throughout the length of the brush parallel to the axis thereof and is supported by end frame 74 and the interior edge of a plate 112. The flicker bar is interposed in the path of movement of the bristles for brush 71 to an extent ranging from about .020 inch to about .200 inch, and preferably about .075 inch. In this manner toner particles on the brush are flicked from the brush in the vicinity of the vacuum duct. In using synthetic or other types of fur brushes to clean a xerographic plate moving at a high rate, there has been found severe filming of toner particles of the plate surface after a brief use. The cause of this filming has been traced to some degree to the impaction of toner particles onto the brush bristle tips which occurs where the bristles strike the flicker bar. It is believed that the filming is due to toner build-up on the flicker bar leading edge where it contacts the bristles. The toner build-up becomes tar-like after several cycles with the tar-like toner being transferred to the bristle tips and in turn to the xerographic surface being cleaned.

Another problem resulting from the use of the ordinary flicker bar with certain types of toner particles has involved the crystallization of some of the toner particles being flicked and the subsequent pulverization that occurs from this crystallization. In this case the toner material reclaimed is of little use for additional development.

In accordance with the invention flicker bar 110 is formed as a hollow member having a slot 114 arranged along the length thereof. In communication with slot 114 is a supply of compressed air which is accomplished in any suitable manner as by connecting a forced draft blower 116 to flicker bar 110 via a conduit 118 and valve 119. A high velocity jet of air escapes from slot 114 in the flicker bar causing substantially all the toner particles to be removed from the brush bristles and sucked into vacuum duct 78. Also due to the fact that the air jet is released in a direction counter to the rotation of the brush the impact of the bristles on the flicker bar is softened thereby lessening friction and minimizing heat build-up that ordinarily occurs during the flicking operation. It has been found that air velocities ranging from about 5 to about 100 liters per minute are suitable for the purpose intended depending upon the speed and power require ments of the machine. Under ordinary conditions velocities ranging from about 40 to 60 liters per minute are preferred.

It should be noted that the angle at which the air jet impinges on the bristles may vary from a direction nearly normal to the rotation of the brush as shown to a direction almost radially inward. To this end, the bar may be fixed in such a way as to enable different positions to be assumed as desired. It should be understood, however, that the position normal to the path of rotation of the brush is preferred due to its cushioning effect. Flicker bar 110 may be made of any suitable strength material, such as, aluminum, brass, steel, which may be uncoatedor coated with a low friction material as, for example, polytetrafluoroethylene. Slot 114 may have a width ranging from about .003 inch to about 0.10 inch.

Above is described a brush cleaning apparatus for continuously wiping off the residual toner particles resting upon a xerographic plate moving from the transfer station to the charging station of a reproduction machine. The residual toner particles are pulled off the surface of the plate by a brush and brought into contact with a jet of high velocity air issuing from a hollow flicker rod thereby causing the particles to be disengaged from the brush bristles and allowed to be sucked through a vacuum duct and into an exhaust duct. Heretofore, the toner particles deposited on the flicker bar as a film which was redeposited onto the xerographic plate. It can readily be appricated that with the present invention not only are substantially all the toner particles removed from the brush but that they are finally removed from the cleaning zone so as to prevent them from redepositing onto the xerographic plate being claimed.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration, and that the invention may be modified and embodied in various other forms without departing from the scope of the appended claims.

What is claimed is:

1. In a cleaning apparatus for removing electrostatically adhering particles from a xerographic plate Wherein a brush is rotatably mounted within a dust hood in a position such that at least a portion of the brush bristles project from an inlet opening in the hood into contact with the surface of the plate, and an elongated flicker member is positioned in the path of the brush bristles to contact the tips of the bristles, the improvement comprising said flicker member being formed as a hollow shape having a slot therein, said slot being located within the path of the brush bristles and means for introducing compressed air into said flicker member to cause high velocity air to be released through said slot against said bristles whereby substantially all the particles are removed therefrom without depositing onto said member as a film.

2. Apparatus according to claim 1 including an exhaust duct in communication with said housing to extract particles that are being flicked from said bristles.

3. Apparatus according to claim 2 wherein the high velocity air ranges from about 30 to about liters per minute.

4. Apparatus according to claim 1 wherein said slot is arranged in a direction substantially normal to the path of rotation of said bristles to cushion the impact of the bristles on said flicker member.

References Cited UNITED STATES PATENTS 2,482,781 9/1949 Knowlton et al. 15-308 X 3,278,972 10/1966 Hudson 15375 X ROBERT W. MICHELL, Primary Examiner US. Cl. X.R.