US3536400A - Apparatus for cleaning the support of an electrophotographic member - Google Patents

Description

Oct. 27, 1970 T. G. GRIFFIN. JR 3,

APPARATUS FOR CLEANING THE SUPPORT OF AN ELECTROPHOTOGRAPHIC MEMBER 2 Sheets-Sheet 1 Filed Dec.

' THOMAS G. -GRIFFIN,JR.

INVENI'OR ATTORNEYS I Oct. 27; 1970 T. G. GRIFFIN, JR 3,536,400

APPARA FOR CLEANING THE SUPPORT OF AN ECTROPHOTOGRAPHIC MEMBER Filed Dec. 5, 1967 2 Sheets-Sheet 2 INVEN'IUR.

B) M v- I zfw dm ATTORNEYS THOMAS s. GRIFFIN,JR. j

United States Patent U.S. Cl. 355-15 7 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCES TO RELATED APPLICATIONS Reference is made to commonly assigned copending U.S. Pat. application Ser. No. 653,779 entitled Method of Repetitive Xerography Without Cleaning, filed July 17, 1967 in the names of James G. Jarvis and William C. York.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to a method and apparatus for cleaning a photoresponsive member in electrophotography. More specifically, this invention relates to cleaning the support or base of a flexible electrographic member to enable exposure therethrough.

Description of the prior art In certainforms of electrophotography, a photoelectroresponsive member is charged and exposed to an image of actinic radiation creating a corresponding charge image which is toned and utilized, commonly by transfer. The member is then cleaned and reused.

In the prior art the problem of cleaning has been extensively considered, see for example, U.S. Pat. No. 2,752,271, Walkup, issued on June 26, 195 6'. In this patent, a cylindrical brush having hair, fibers or the like on its outer surface is adapted to be placed in contact with a xerographic plate following transfer of a toner image therefrom in order to brush any residue of toner from the surface of the plate. In operation, a rotating cylindrical brush is urged against the surface of the plate to be cleaned. During the cleaning operation, the brush is driven in rotation in order to assist in the removal of toning material or the like from the brush after it has passed along .the photoresponsive surface. Vacuum can be applied to a hood surrounding the brush in order to draw air through the hood and subsequently to withdraw toning material from the fibers of the brush.

It is sometimes desirable to expose a photoelectroresponsive member through its base, see for example, U.S. Pats. No. 2,843,084 Hayford, issued July 15, 1958 and 3,166,418 Gundlach, issued J an. 19, 1965 and the previously mentioned Jarvis et al. application. As pointed out in said Jarvis et al. application, exposure through the base can be used in a system which eliminates the necessity to clean the photoconductor of a xerographic plate thereby reducing waste of toner and scratching and scumming of the photoconductor. If exposure is continually made through such a base in a machine using dry toner, it is advantageous to continuously clean the base for a clear exposure. If the sensitive member is a hard, continuous drum, an ordinary rotating brush in an exhaust hood will adequately clean it. However, when the sensitive member is a flexible web and/or has open spaces through which toner could escape from the toning station, the cleaning member can perform other functions according to the invention.

SUMMARY OF THE INVENTION It is an object of this invention to clean the support of an electrically photoresponsive member.

It is another object of the invention to provide a backing for a flexible photoelectroresponsive member during toning.

It is another object of the invention to provide a cleaning brush for removing material from the backing of photoelectroresponsive material in the form of an endless belt in which the various connected portions which make up the belt have openings therebetween.

In accordance with the invention, a brush disposed adjacent to the support side of an electrically photoresponsive member both cleans the support so that an exposure may be made through it and acts as a backing for the toning station itself supplying firmness to the member, if flexible, and preventing escape of toner from the toning station.

BRIEF DESCRIPTION OF THE DRAWINGS Additional objects and features of the invention will be understood from the following specification and from the drawings, in which:

FIG. 1 is a fragmentary verticle section view showing a photocopying apparatus employing an endless belt of photoresponsive segments and means for cleaning the surface of the segments opposite to that which receives toning material;

FIG. 2 is a fragmentary perspective view showing a portion of the endless belt of photoresponsive material shown in FIG. 1;

FIG. 3 is a vertical section view of the cleaning roller of the invention in engagement with and urging the photoresponsive material toward a toner brush; and

FIG. 4 is a perspective schematic drawing showing photocopying apparatus with which the brush of the invention can be used.

DESCRIPTION OF THE PREFERRED EMBODIMENT According to FIG. 1, an electrostatic image is formed on an electrically photosensitive member such as a flexible sheet 10 having a transparent conductive backing 10b and a photoconductive layer 10a by charging the photoconductive layer and exposing it through the backing 10b. Powdered toner is applied to the resulting electrostatic image on photoconductive layer 10a by a toner brush 12. In order to insure proper distribution of the toner material, it is necessary to control the depth of penetration of the flexible sheet 10 into the toner brush.

As shown in FIGS. 1 and 2, sheets 10 can be connected to one another to form an endless belt 13. End portions of each of the sheets are secured to rods 14 by hooks 15 which engage a plurality of corresponding openings 10d in the end portions of the sheets. Pairs of adjacent rods -14 are connected to one another by links 15 which in turn are attached to plated 16a of a roller chain 16.

Belt 13 is driven from left to right as viewed in FIG. 1. Sprockets 17 and 18 are adapted to engage end portions 14a of adjacent pairs of rods 14. Thus, along the reach Patented Oct. 27, 1970 of belt 13 shown in FIG. 1, the belt can be supported and tensioned by sprockets 17 and 18.

In addition to the previously mentioned problem of maintaining the proper engagement between the flexible sheet and the toner brush, it is also important to safeguard against the distribution of dust of fine toner particles upon the outer surface of the backing of the flexible sheet. If the optical image is to be projected through the transparent backing of the sheet 10, toner material, dust or other foreign material, if allowed to collect on the other surface of the transparent backing, would interfere with and be detrimental to the image. If the flexible sheet is to be advanced with respect to the toner brush at a relatively high speed in order to obtain a relatively high rate of production from the apparatus, the toner brush necessarily must rotate with a relatively high surface speed and consequently can throw off toner particles thereby causing a toner dust problem.

In order to remove dust from the surface of the trans parent backing 10b, there is provided cleaning brush 19 extending substantially transversely with respect to the belt, that is, at right angles to the path of its travel, and having its periphery adjacent to the surface of the sheets. Thus, brush 19 can be pivotally mounted in an adjustable manner by an arm 20 which is connected to a shaft 21 upon which the brush is pivotally mounted. A support 22 for the arm 20 is conditioned to position the arm 20 in an adjustable manner and thereby control the engagement of the periphery of the brush with the adjacent surface of the belt 13.

An outer surface or covering 19a of the brush is made of a material having high nap such as that of fur or fiber or a brush-type fabric which is suitable for the removing of fine toner particles are dust from the sheet. The covering 19a of the brush can be of a material having a location in the triboelectric order, such that in response to friction between the surface of the brush and the sheet, the toner particles and any possible dust will be attracted and held by the material forming the outer surface of the brush.

To facilitate the transfer of material from the surface of the sheet to the brush, the brush can be operated with a peripheral speed which is different than that of the sheet so that the resulting skid or slip of the brush with respect to the sheet will cause a scrubbing or brushing action which facilitates the cleaning of the sheet.

As shown in FIG. 3, brush 19 can be provided with a vacuum pickoff system 23 to remove toner which has been cleaned from the sheets by the covering of the cleaning brush. The vacuum pickoif system includes manifold 23a and conduit 23b containing an elongated slot exposed to the outer surface of the cleaning brush.

The rods 14 of the belt 13 extend above the surface of the sheets which is to be engaged by the cleaning brush 19 (FIG. 1). Since it is undesirable for the surface of the brush to contact the rods 14, brush 19 is provided with a relieved portion 19b which can accommodate the rods 14. Thus, the relieved portion interrupts the surface of the brush 19. In operation, the brush 19 is driven in synchronism with the belt 13 so that relieved portion 19b approaches belt 13 at the same time adjacent rods 14 are passing near to brush 19. In this way, the rods can pass through the opening of relieved portion 1912 without interfering with the operation of the cleaning brush.

In FIG. 3, the arc of relieved portion 19b is defined by the symbol 0. The radius of brush 19 to its outer periphery is defined by the symbol R, while the radius to the surface of relieved portion 19b is defined by the symbol R The diameter of rods 14 is defined by the symbol D The center line distance between successive leading or trailing bars 14 is defined by the symbol X. The distance between the opposite sides of rods 14 is defined by the symbol Y as shown in FIG. 1. Based upon the symbols defined above, the following dimensional relationships exist between belt 13, rods 14, and brush 19:

q 11 1 (Brushing action opposite 2? direction of belt).

Eq 2: R=X(1Q0|Slip (Brushing action in direc- As shown in FIG. 3, the cleaning brush 19 is positioned in alignment with the toning brush 12 with the centerline of brush 19 mounted substantially vertically above the centerline of the toning brush 12 and at a height which places the outer periphery of the cleaning brush 19 slightly below the normal line of travel of the sheet 10. By Way of example, the outer periphery of the brush can be approximately one-eighth of an inch below normal line 24. As a result, the surface of the brush is urged into engagement with the surface of the sheet and thereby provides positive contact which controls the engagement of the opposite side of the sheet with the toning brush 12. In this way, the cleaning brush 19 can serve the dual functions of cleaning one surface of the sheet and of controlling the engagement of the opposite surface of the sheet into the toner brush 12. In other words, brush 19' simultaneously serves as a cleaning brush and a back-up roll.

FIG. 4 shows a photocopying apparatus which can employ the cleaning brush 19 of the invention. A motor 26 serves as a constant-speed drive to a shaft 27 which is coupled to sprockets 28 in engagement with drive chains 16. Chains 16 advance an endless belt 13 above sprockets 28, 30, 31, 32, 39, 40, 45 and 46. Such sprockets are shown as circular discs in FIG. 4 for convenience, but are preferably relieved in the same manner as sprockets 17 and 18 in FIG. 1.

The chains advance the belt through a series of xerographic stations including a corona charger 29, an exposing station which includes a projector which directs light from an original 34 to a mirror 35 through a lens 36 to a mirror 37 to a mirror 38 and directed through a transparent backing 10b to a surface 10a of a sheet 10 of belt 13.

In order to expose sheet 10 to an optical image, it is necessary that the movement of the belt at the exposure station adjacent be terminated. In order to accomplish an interruption of the motion of the sheets at the exposure station, the endless belt is provided with a loop extending about sprockets 31 and 32. The loop returns to the main line of travel of the belt at sprockets 39. Beyond sprockets 39, the 'belt passes about sprockets '40 and then travels toward a toning station 41, including toner brushes 11 and 12.

Sprockets 30 and 39 have their supporting shafts connected to one another by links 42. The drive to sprocket 31 extending from shaft 27 includes a geneva 43 connected to sprocket 31. As a result, sprocket 31 is driven with an intermittent motion. Whenever the geneva is in a dwell position, sprockets 30 and 39 travel downwardly as viewed in FIG. 4 in response to the continuous drive of shaft 27. When the geneva enters upon its advancing position, chains 16 are moved with respect to sprockets 31 and 32 and as a result sprockets 30 and 39 travel upwardly as viewed in FIG. 4.

Upon exposure of sheet 10 to the optical image reflected from mirror 38, the exposed sheet bearing an electrostatic image corresponding to the exposed optical image is advanced by chains 16 along with endless belt 13 adjacent to sprockets 32, sprockets 39 and sprockets 40. Beyond sprockets 40 the sheet 10 is advanced between a toner brush 12 and cleaning brush 19. The

cleaning brush as described with respect to FIG. 3 urges sheet into the covering of toner brush 12 and at the same time removes any toner material or dust particles from the side of the sheet opposite the toner brushes.

Beyond the toning station the endless belt passes adjacent to sprockets 45 and 46 and then advances adjacent to a transfer station where the toned image on the sheet is transferred to a receiving surface such as a copy paper 47 from a paper supply 48. Copy paper 47 is advanced by a conveying belt 49 which is driven by a chain 50 extending about sprockets 5155. Beyond sprockets 51 belt 49 presses copy paper 47 against sheet 10 so that the electrostatic toned image on the sheet may be transferred to the copy paper in response to the charge applied to the sheet by corona generator 66. After the image is transferred, the copy paper is advanced beyond sprockets 54 and beneath a roller 65 to a surface 56. Surface 56 supports the copy paper with its toned image for travel through the fusing station including fuser unit 57. Beyond the fuser unit, a completed copy is discharged from the apparatus.

In accordance with the invention, the provision of cleaning brush 19 facilitates the toning operation performed by toner brush 12 in that the cleaning brush serves as a backup roller which urges sheet 10 into engagement with the surface of toner brush 12 and prevents escape of toner between sheets. In addition, it can be seen in FIG. 4 that cleaning brush 19 is available to maintain the surface of the endless belt disposed opposite the toner brushes free of unwanted toner material and any foreign material such as dust in order that the optical image can be projected through the transparent backing of the sheet.

Thus, the invention provides the advantages of enabling the cleaning brush to maintain the flatness of the sheet and its controlled engagement with the toning brush which at the same time enabling the side of the sheet opposite the toning brush to be continually cleaned.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be eifected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A photocopying apparatus comprising:

a reusable electrically photoresponsive member having first and second surfaces,

means for projecting a pattern of actinic radiation through said second surface to create an electrostatic image on said first surface,

means adjacent said first surface for toning said electrostatic image,

means adjacent said second surface for cleaning said second surface, said means for cleaning being positioned in opposed relationship to said toning means.

2. A photocopying apparatus according to claim 1 wherein:

said photoresponsive member is a flexible Web,

said toning means is adapted to contact said first surface during toning, and

said cleaning means provides a backing to support said photoresponsive member during toning.

3. A photocopying apparatus according to claim 1 wherein:

said photoresponsive member includes spaced photoresponsive sheets disposed in end-to-end relation, and

said cleaning means is positioned to prevent escape of toner between sheets.

4. A photocopying apparatus comprising:

a reusable electrically photoresponsive endless belt having first and second surfaces,

means for moving said belt through a series of stations,

a charging station for creating a uniform electrostatic charge on said first surface,

an exposing station for protecting a pattern of actinic radiation through said second surface to said first surface to create an electrostatic image on said first surface,

a toning station for applying toner to said electrostatic image to form a toner image defined by said electrostatic image,

a transfer station for transferring said toner image to a receiving medium, and

a cleaning station for cleaning said second surface positioned in opposed relationship to said toning station to provide a backup member for said belt at said toning station.

5. A photocopying apparatus according to claim 4 wherein:

said cleaning station includes a rotatable brush, and

means for applying a vacuum to the surface of said brush.

6. A photocopying apparatus according to claim 4 wherein said toning station includes a toning brush adapted to hold toner on its periphery triboelectrically and to rotatingly engage said first surface.

7. A photocopying apparatus according to claim 4 wherein said endless belt includes a plurality of photoresponsive sheets connected together in end-to-end spaced relation and said cleaning station comprises:

a rotatable brush having a longitudinal axis extending transversely with respect to the direction of motion of said belt and a periphery engaging said second surface of said belt, said brush having a relieved portion corresponding in length to the spacing between the spaced end portions of adjacent photoresponsive sheets, and

means for rotating said brush about its longitudinal axis in a predetermined phase relationship with respect to said belt, so that said relieved portion is in a facing relationship with said belt when said spaced end portions are adjacent said brush.

References Cited UNITED STATES PATENTS 2,820,716 1/1958 Harmon 355-17 3,084,061 4/1963 Hall 355 17 3,124,483 3/1964 Rheinfrank 355-14 3,438,706 4/1969 Tanaka 355 15 JOHN M. HORAN, Primary Examiner

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