U.S. patent number 3,847,119 [Application Number 05/238,045] was granted by the patent office on 1974-11-12 for transfer roller assembly.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Daniel S. Hoffman, Gilbert E. Koch.
United States Patent |
3,847,119 |
Hoffman , et al. |
November 12, 1974 |
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.
Inventors: |
Hoffman; Daniel S. (Rochester,
NY), Koch; Gilbert E. (Rochester, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
22896274 |
Appl.
No.: |
05/238,045 |
Filed: |
March 27, 1972 |
Current U.S.
Class: |
399/101;
118/262 |
Current CPC
Class: |
G03G
15/168 (20130101) |
Current International
Class: |
G03G
15/16 (20060101); G03g 013/00 () |
Field of
Search: |
;118/247,249,262,637,261,203,204,70 ;355/3,12,15 ;96/1.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
D J. Oldenboom, "Electromechanical Transfer Mechanism", IBM Tech.
Disclosure, Vol. 1, No. 3, Oct 1958..
|
Primary Examiner: Reynolds; W. C.
Assistant Examiner: Millstein; Leo
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.
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.
* * * * *