Transfer Roller Assembly

Abstract

A transfer roller assembly including a transfer roller and a rotary cleaning brush for an electrostatographic machine. The transfer roller assembly is rotated about a support shaft and in pressure contact with the photoconductive surface during the image transfer mode therefor. The transfer roller assembly includes a rotating cleaning brush in cleaning contact with the transfer roller and is movable with the roller about the support shaft. Separate drive mechanisms from a single drive member on the assembly provide independent rotation to the roller and the brush.

Description

This invention relates to electrostatography, and more particularly, to a novel transfer roller assembly for an electrostatographic apparatus.

In the practice of electrostatography, as described in U.S. Pat. No. 2,297,691 to Chester F. Carlson, an electrostatographic plate having a surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image may then be developed by contacting it with a finely divided electrostatically attractable material, such as a resinous powder. The powder is held in the image areas by the electrostatic fields on the layer. Where the field is greatest, the greatest amount of material is deposited; and where the field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the copy being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably affixed to thereby form a permanent print.

The toner may be fixed by passing the sheet of paper or other surface including the transferred image between a heated roller and a second roller in pressure contact therewith whereby the toner becomes fused to the sheet of paper.

The image is generally transferred to an image receiving member by passing such a member between the photoconductive surface including the developed image and a roller in contact therewith. In order to provide quality copies during machine operation, there is need for continuous removal of unwanted toner deposits upon the transfer roller.

An object of this invention is to provide a novel, unitized transfer assembly.

Another object of this invention is to provide a novel transfer assembly including a cleaning roller which may be readily placed in operational contact with a transfer roller to be driven therewith and movable as a unit with the roller and drive means therefor.

These and other objects of the invention are obtained by providing a transfer assembly rotatably supported within the housing of an electrostatographic machine in juxtaposition to a photoconductive surface therefor. The transfer assembly is provided with a transfer roller, a rotary cleaning brush in brushing engagement with the surface of the roller. Both the brush and the roller are provided with separate motion imparting means. The assembly together with the transfer roller, the rotary brush, the separate motion imparting means are supported as a unit in the machine frame and may be moved as a unit out of the machine, or in contact with the photoconductive surface.

A better understanding of the present invention as well as other objects and further features thereof will become apparent upon consideration of the following detailed disclosure thereof, especially when taken with the accompanying drawings, wherein like numerals designate like parts throughout:

FIG. 1 is a schematic sectional view of an electrostatic reproduction machine embodying the principles of the invention;

FIG. 2 is a view of one end of the transfer assembly showing the motion imparting means for the transfer roller;

FIG. 3 is an isometric view (greatly simplified) of the transfer roller assembly;

FIG. 4 is a view of the other end of the assembly showing the motion imparting means for the rotary brush;

FIG. 5 is a rear view of the locking shaft assembly;

FIG. 6 is a side elevation view of a mounting frame for the transfer roller assembly; and

FIG. 7 is a side view of the transfer roller assembly illustrating the movement thereof when disposed in juxtaposition to a photoconductive belt of an electrostatographic machine.

For a general understanding of the illustrated copier/reproduction machine in which the invention may be incorporated, reference is had to FIG. 1 in which the various system components for the machines are schematically illustrated.

A document D to be copied is placed upon a transparent support platen P fixedly arranged in an illumination assembly, generally indicated by the reference numeral 10, positioned at the left end of the machine. Light rays from an illumination system are flashed upon the document to produce image rays corresponding to the informational areas. The image rays are projected by means of an optical system onto the photosensitive surface of a xerographic plate in the form of a flexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 14.

The belt 12 comprises a photoconductive layer of selenium which is the light receiving surface and imaging medium for the apparatus, on a conductive backing. The surface of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device or corotron 13.

The belt is journaled for continuous movement upon three rollers 20, 21 and 22 positioned with their axes in parallel. The photoconductive belt assembly 14 is slidably mounted upon two support shafts 23 and 24 with the roller 22 rotatably supported on the shaft 23 which is secured to the frame of the apparatus and is rotatably driven by a suitable motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the portion exposed is that portion of the belt running between rollers 20 and 21. During such movement of the belt 12, the reflected light image of such original document positioned on the platen is flashed on the surface of the belt to produce an electrostatic latent image thereon at exposure station A.

As the belt surface continues its movement, the electrostatic image passes through a developing station B in which there is positioned a developer assembly generally indicated by the reference numeral 15, and which provides development of the electrostatic image by means of multiple brushes 16 as the same moves through the development zone.

The developed electrostatic image is transported by the belt to a transfer station C wherein the present invention may be positioned and whereat a sheet of copy paper is moved between a transfer roller and the belt at a speed in synchronism with the moving belt in order to accomplish transfer of the developed image solely by an electrical bias on the transfer roller. There is provided at this station a sheet transport mechanism generally indicated at 17 adapted to transport sheets of paper from a paper handling mechanism generally indicated by the reference numeral 18 to the developed image on the belt at the station C.

After the sheet is stripped from the belt 12, it is conveyed into a fuser assembly, generally indicated by the reference numeral 19, wherein the developed and transferred xerographic powder image on the sheet material is permanently affixed thereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus.

Further details regarding the structure of the belt assembly 14 and other machine processing components so far outlined are not necessary as they form no part of the present invention.

Referring now to FIGS. 2, 3 and 4, there is illustrated a transfer assembly generally indicated as 30, having a transfer roller 32 secured to a shaft 34 which is mounted for rotation in suitable bearings supported in hub assemblies 36, 37. A pulley 38 is affixed to one end of the shaft 34 extending through the hub assembly 36 and engages an endless timing belt 40 entrained around an idler pulley 41 and a drive pulley 42. The pulley 42 is secured to one end of a drive shaft 44 which also supports the transfer assembly. The drive shaft 44 is mounted for rotation in the hub assemblies 36, 37 above the transfer roller 32 in parallel with the shaft 34 and extends outwardly beyond the hub assemblies 36, 37. The other end of the drive shaft 44 beyond the hub assembly 37 is suitably connected to the main drive system for the machine. Bearings 48 are positioned on the ends of the shaft 44 and are positioned in frame support assemblies, generally indicated as 50 and 52 (see FIGS. 5 and 6).

Each of the frame support assemblies 50 and 52 is comprised of a frame section 54 having a cylindrically shaped machined surface 56 for receiving the bearings 48 of the support shaft 44. An upwardly extending tab section 58 is formed on the frame section to receive a clamp 60 pivotally mounted to the tab section 58, such as by a pin 62. The clamp 60 is held in locking relationship to the frame section 54 by a screw 64. By virtue of the bearings 48, one mounted at each end of the shaft 44, the shaft supports the entire transfer assembly rocking movement upon the machine frame. This shaft also serves to drive the transfer roller and, as will be described, a rotary cleaning brush. The frame section 54 is provided with a shaft receiving opening 66 and mounting holes 68 for affixing the frame assembly 52 to the main body (not shown) of the electrostatographic machine. It is understood that the frame section 50 is similarly formed with respect to frame section 52 except that it is the mirror image thereof.

Referring now to FIG. 5, there is illustrated a locking shaft assembly, generally indicated as 70, comprised of a shaft 72, which is positioned for rotation in shaft receiving openings 66 of the frame sections 50 and 52. A handle 74 is affixed to the shaft 72 at an intermediate position thereof for rotation of the shaft to a locking attitude, as more fully hereinafter discussed. Positioned on either side of the shaft 72, there are affixed spring retaining asemblies 76 in which is positioned one end of springs 78. The other end of the springs 78 are affixed to lever elements 80 mounted for rotation about the shaft 72 and having an outwardly extending pin section 82. Each pin section 82 engages grooved sections 84 formed on an outer surface of the hub assemblies 36 (see FIGS. 2 and 7). THe handle 74 is positioned within a receiving plate 86 having a U-shaped opening 90 mounted to a hub assembly, generally indicated as 98, such as by screws 94.

Referring to FIG. 7, to place the transfer roller 32 in pressure contact with the photoconductive surface 12, the handle 74 is moved clockwise from its full line position to its dotted line position and locked against counterclockwise rotation in the lower notch 90a in the opening 90 of the receiving plate 86. This rotation causes rotation of the locking shaft 72. Such rotation of the locking shaft causes the lever elements to rotate clockwise about the shaft 72 forcing the pin section 82 thereof to press against one side of the cooperating grooves 84 on the hub assemblies thereby causing slight rocking movement or rotation of the entire transfer assembly about the shaft 44. This, in turn, forces under spring tension the transfer roller assembly 30 against the photoconductive surface 12. This relationship of pressure contact of the transfer roller 32 with the photoconductive member 12, facilitates image transfer and permits the transfer roller 32 and photoconductive member 12 to function as part of the transport system for image receiving members. Shifting of the handle 74 from the locking position back to its full line position wherein the handle is in the upper notch 90b of the opening 90 releases the forces that the pins 82 have upon the side of the grooves 84 causing counterclockwise rocking or rotation of the transfer assembly 30 on its supporting shaft 44. This rocking movement allows the assembly to move away from the photoconductive surface thereby facilitating the correction of paper jams and to permit removal of the photoconductive members from the machine.

Also mounted for rotation within the transfer assembly, as a movable part therewith is a cleaning brush 100 having stub shafts 102, one at each end thereof, extending into the hub assemblies 36, 37. The hub assembly 37, as shown in FIG. 4, includes the drive train for effecting rotation of the brush 100 in accordance with the transfer roller 32. A semi-cylindrical covering or housing 104 for containing the brush is suitably mounted in the hub assemblies 36, 37. The bristles of the brush are in interferring engagement with the surface of the roller 32 and upon relative rotation between the roller and the rotary brush, a sweeping action is accomplished. This sweeping action flicks into the housing 104, the loose toner particles which deposit upon the textured surface of the transfer roller and which may adhere to the back or non-transfer side of sheets of paper. The brushed away toner particles may adhere mechanically or electrostatically to the roller surface and if left unattended would accumulate and in time cause serious quality defects of the copies made by the machine. The housing 104 is connected by way of a vacuum duct 106 to a vacuum source in the machine so as to continuously clear the housing 104 of loose air-borne as well as bristle carrying toner particles. To aid in flicking accumulated toner out of the brush bristle is a flicker bar located such that flicked particles enter directly into the vacuum duct.

The drive train for producing rotation of the rotary brush 100 includes a drive gear 108 mounted on the drive shaft 44 to be driven thereby. The gear 108 is in mesh with an idler gear 110 which, in turn, is in mesh with a gear 112 secured to the adjacent stub shaft 102 for the rotary brush 100. With this gear arrangement, the transfer roller 32 and the brush 100 rotate in the same direction during brushing operation giving maximum difference in relative surface velocity. The relationship of the diameters of the gears 108, 110 and 112 is such as to provide an approximate ratio of 10:1 to the rotary speed relationship of the cleaning brush to the transfer roller, which ratio has been found to be optimum in cleaning efficiency. This provides an impact velocity for the brush bristles relative to the toner particles which is of sufficient force to dislodge the particles from the roller texture and overcome electrostatic forces effected by the roller surface.

From the foregoing, it will be apparent that the transfer assembly is adapted to be moved into and out of engagement with a photoreceptor member as a complete unit and that the cleaning brush for the transfer roller is made movable thereiwth. A single driving action is provided to imparting rotation to the transfer roller independently of the rotation imparted to the rotary cleaning brush. Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure which modifications are intended to be included within the scope of this invention.

Claims

What is claimed is:

1. In an electrostatographic machine having a movable photoconductive member:

a transfer assembly having a transfer roller mounted proximate to said photoconductive member, a rotary cleaning brush mounted adjacent said roller and having bristles in interferring engagement with the surface of said roller, said roller and said brush being mounted to rotate in the same direction, and means for pivotally supporting said assembly so that said roller can be moved into and out of contact with said photoconductive member, said pivotally supporting means permitting said roller and said brush to be moved as a unit.

2. The combination set forth in claim 1, wherein the ratio of the speed of rotation of said brush relative to that of said transfer roller is approximately 10:1.