U.S. patent number 3,918,809 [Application Number 05/482,726] was granted by the patent office on 1975-11-11 for apparatus for cleaning a surface support.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Stephen C. P. Hwa.
United States Patent |
3,918,809 |
Hwa |
November 11, 1975 |
Apparatus for cleaning a surface support
Abstract
An apparatus and method for cleaning liquid developer from
upwardly moving support surfaces, such as reusable surfaces used
for carrying latent electrostatic images is described. Surfaces are
cleaned by a wiper blade and at least one scraper blade adapted to
engage the support surface. The wiper blade acts upon the support
surface upstream of the scraper blade.
Inventors: |
Hwa; Stephen C. P. (Penfield,
NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
23917195 |
Appl.
No.: |
05/482,726 |
Filed: |
June 24, 1974 |
Current U.S.
Class: |
399/348; 118/70;
399/350 |
Current CPC
Class: |
G03G
21/0088 (20130101) |
Current International
Class: |
G03G
21/00 (20060101); G03G 021/00 () |
Field of
Search: |
;355/15,10,3R ;117/37LE
;118/DIG.23 ;15/256.51,1.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Moses; Richard L.
Attorney, Agent or Firm: Ralabate; James J. Kolasch; Donald
C. Chapman; Ernest F.
Claims
What is claimed is:
1. In an electrostatographic reproduction apparatus having a
movable support surface having a portion moving in operation in an
upward direction, means for forming a latent electrostatic image on
said surface, means for developing the latent image with liquid
developer, means for transferring the developed image to a sheet of
transfer material, a drive mechanism to move the support surface
past said means in succession, the improvement comprising cleaning
station means for removing liquid developer and debris from the
support surface, said cleaning station having at least one scraper
blade adapted to engage the support surface on said upwardly moving
portion, said scraper blade being a blade having a stem ending in a
tip portion in contact with the support surface, the stem extending
toward the tip in the upstream direction of the movement of the
support surface and exerting a chiselling action on the support
surface when pressed against the surface, and a wiper blade action
on the support surface upstream of the scraper blade, said wiper
blade being a blade having a stem extending in the downstream
direction of the support surface.
2. The apparatus of claim 1 wherein said scraper and wiper blades
are mounted to a single mounting block, said mounting block being
movable to move said blades out of engagement with said
support.
3. The apparatus of claim 1 further comprising a sump located below
the scraper blade and positioned to receive material scraped from
said surface by the wiper blade.
Description
BACKGROUND OF THE INVENTION
This invention relates to cleaning material from a support surface,
and more particularly, it relates to an apparatus and method for
removing liquid developer from a photoconductive or other
surface.
In the development of electrostatic latent images where liquid
developers are used to develop the image on the reusable
photoconductor surface or on a reusable interposition surface,
liquid developer remains on the surface after the developer image
is transferred to a substrate. In these processes and apparatuses
where the surface is reused to develop subsequent images, the
residual liquid developer must be removed therefrom to such an
extent that the residual developer will not interfere with
subsequent imaging causing streaks and other image or non-image
patterns and smudges of developer which transfer to subsequent
substrates. In order to accomplish sufficient removal of the
residual developer so that streaking and smudging of subsequent
prints is eliminated, several prior art methods have been
attempted, but they have resulted in failure. Wiper blades are
commonly used to remove the residual liquid developers from these
and other support surfaces.
U.S. Pat. No. 3,660,863 issued to Gerbasi on May 9, 1972, discloses
a scraper blade acting on a xerographic drum for removing
particulate toner material from the drum. In Gerbasi, the cutting
edge of the blade, that is, the edge of the blade formed by the
upper face surface or top surface and the front side surface, is
positioned slightly below the horizontal center line of the drum
and the cutting edge is held in a manner to readily cut or chisel
the particulate toner material from the drum surface. This
configuration is suitable for particulate toner material, however,
when used for cleaning liquid developers from a support surface
which in operation moves uphill, problems are encountered in
disposing of the liquid cleaned from the surface. The liquid runs
back over the uncleaned part of the surface and drips therefrom at
random positions.
Blade cleaning is also described by Royka et al in U.S. Pat. No.
3,552,850 wherein at least one self-adjusting flexible cleaning
blade for pressure contact cleaning of the imaging surface is
shown. In Royka et al, the leading edge of at least one cleaning
blade is preferably positioned to form an acute angle of less than
about 90.degree. and greater than about 20.degree. with the
confronting portion of the imaging surface or plane tangent to the
imaging surface at the line of blade contact to clean particulate
toner from photoconductive members when means to supply a dry solid
lubricant to the imaging surface are provided. This cleaning
technique which is primarily a wiping action, is operable for
particulate toner, but when liquid developers are used, streaking
of the support surface with developer due to the interference of
the intimate contact between the wiper blades and the support
surface from debris, remains a problem. Furthermore, the wiping
action does not suitably remove the liquid developers from the
surface.
In accordance with the present invention, cleaning blades may be
designated as scraper blades or wiper blades. A scraper blade is
defined as one wherein the stem extends towards the tip in the
upstream direction of the drum's movement and when pressed against
the drum exerts a chiselling action on the material (liquid
developer and debris) on the drum surface.
A blade which in operation is pressed against a support surface so
that it is bent along its length in the downstream direction of the
drum motion has a wiping action as it tends to be lifted up by
material moving with the drum surface. A wiper blade is defined in
accordance with the present invention as one in which the stem
extends in the downstream direction of the drum motion. As used
herein, upstream and downstream refer to drum motion.
OBJECTS OF THE INVENTION
It is an object of this invention to provide an apparatus and
method for improving the cleaning of resuable surfaces used in
electrostatic copying machines employing liquid developers for
development of the image.
Another object of this invention is to provide an apparatus and
method to improve the removal of liquid developer from reusable
surfaces when at least one scraper blade is used as the cleaning
blade at the upward or uphill portion of the reusable surface.
SUMMARY OF THE INVENTION
These and other objects are accomplished by providing an
electrostatographic reproduction apparatus having a movable support
surface, a portion of which moves in operation in an upward
direction, means for forming a latent electrostatic image on said
surface, means for presenting liquid developer to said latent image
to develop the image, means to transfer the developed image to a
sheet of support or transfer material and cleaning means to clean
material remaining on the support surface after transfer, and a
drive mechanism to move the support surface past said means in
succession, the cleaning means comprising at least one scraper
blade adapted to engage the support surface on said upwardly moving
portion and a wiper blade acting on the support surface upstream of
the scraper blade. A second and additional scraper blade may be
used to clean material from the support surface which has passed
between the first scraper blade and the support surface due to the
accumulation of debris between the first scraper blade and the
support surface.
According to the present invention, the dual blade system
eliminates the problem caused by the accumulated liquid developer
on the surface running back over the uncleaned part of the surface
and dripping off the surface at random positions. The wiper blade
catches the liquid developer scraped from the surface and diverts
it from the support surface to the wiper blade where it can be
collected in a sump or otherwise disposed of at one point.
There is also provided a method of cleaning liquid developer and
debris from the uphill portion of a support surface comprising the
steps of contacting the support surface having liquid developer
thereon with a wiper blade and thereafter contacting the support
surface with at least one scraper blade to divert the liquid
developer removed by the scraper blade from the surface to the side
of the wiper blade adjacent the scraper blade. This causes the
liquid developer to flow across the wiper blade so that it can be
collected in a sump or otherwise suitably disposed.
In essence, there is described a cleaning apparatus for cleaning
material from an upwardly moving support surface comprising a
scraper adapted to engage the support surface and a wiper blade
acting on the support surface upstream of the scraper blade.
By uphill portion of a support surface is meant that portion of a
support surface which moves in an upward direction when the support
surface is in motion.
Additional objects of this invention will become apparent to those
versed in the art of electrostatic copying machines in view of the
following detailed description of the method and apparatus taken in
conjunction with the accompanying drawings in which preferred
embodiments of the apparatus are shown.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a typical example in the form of a schematic sectional
view of an electrostatographic reproduction apparatus having a
single scraper blade and a single wiper blade.
FIG. 2 shows a schematic sectional view of an electrostatographic
reproduction apparatus having dual scraper blades and a single
wiper blade .
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the copying apparatus illustrated in FIGS. 1 and 2 a copying
drum 11 having a photoconductive surface is rotated in the
direction of the arrow about its axis past a number of processing
stations. The copy cycle starts at the charging station A wherein a
corona discharge device 12 is energized to a high potential to
apply charge to the drum surface. The drum then passes to the
exposure station B at which a flowing image of a document is
projected onto the charged drum surface by an optical system (not
shown) to produce an electrostatic latent image. The image flows so
that it moves in synchronism with the moving drum surface. The
latent image passes to the development station C at which liquid
developer is applied from a reservoir 15 by means of rolls 13 and
14. The roll 13 is a supply roll whose lower portion dips into the
liquid in the reservoir 15 and whose upper portion is spaced by
(for example) 0.25 mm from the upper roll 14 which has its surface
shaped with a helical groove. The roll 14 is provided with a
flexible doctor blade 16 which removes liquid from the groove to
below the groove upper edges due to the deformation of the blade
into the groove. The developer is attracted by electrostatic
attraction from the remote part of the groove to the latent image
across the gap between them to develop the image. An example of
this method of development is described in detail in U.S. Pat. NO.
3,084,043 issued to Robert W. Gundlach, which is incorporated
herein by reference, wherein there is claimed a method of
development in xerography comprising positioning close but spaced
from an electrostatic latent image on an image bearing surface a
substantially continuous film of electrically conductive ink
comprising a homogeneous liquid solution, providing flow aiding
elements in physical contact between said ink and said image
bearing surface, and applying a bias to said ink whereby ink moves
along said flow aiding elements and develops said electrostatic
latent image.
A sheet of paper is fed to a transfer station D by sheet feed
apparatus (not shown) to move in synchronism with the drum and is
pressed against the drum surface by a transfer roll 17 so that the
developed image is transferred to the paper which is then conveyed
away from the transfer station through a chute (not shown). Any
material remaining on the drum after the transfer station must now
be cleaned off at the cleaning station E. After cleaning,
electroluminescent strip 18 floods the drum surface with light to
discharge any remaining charges, so that the drum can pass onto the
charging station for the beginning of the next cycle. A drive
mechanism to move the support surface past the various stations in
succession and to move various other rolls is not shown. Means to
move these various surfaces can be readily provided by one skilled
in the art.
At the cleaning station in FIG. 1, there is provided scraper blade
21. The scraper blade is mounted on supporting block 24 which can
be moved so that scraper blade 21 can be disengaged from drum 11
when the blade is not in use. The arrows in supporting block 24 in
FIG. 1 indicate that it may be rotated to engage or disengage the
scraper blade and the support surface as desired. If the blade 21
is left pressing hard against the stationary drum 11, the
photoconductive surface may be deformed and the blade may acquire a
permanent set.
In FIG. 1, wiper blade 23 on support member 32 is positioned so
that it engages drum 11. As illustrated in FIG. 1, wiper blade 23
permanently engages drum 11, however, wiper blade 23 may be
suitably mounted to disengage from drum 11 as desired (not shown)
in FIG. 1. In the embodiment shown in FIG. 1, the wiper blade is
mounted in sump 25. Sump 25 is located below the scraper blade and
wiper blade to catch the liquid from the blades. When the wiper
blade 23 removes quantities of liquid developer from drum 11 so
that liquid developer flows upstream on drum 11 (in the direction
of the bottom of drum 11 in FIG. 1), it is preferred that sump 25
extend to the bottom center of the support surface on drum 11 to
collect the liquid developer which runs from the vicinity of wiper
blade 23 down the surface of the drum and drips into the sump below
it.
In accordance with the present invention the wiper blade 23 and
scraper blade 21 are mounted in the uphill direction of the drum
from bottom center of drum 11 to top center of drum 11 in the
direction of the arrow. Wiper blade 23 must engage the support
surface of drum 11 upstream from scraper blade 21 to effectively
remove the liquid developer and debris which the scraper blade
scrapes from the surface.
The surface of drum 11 is cleaned by contacting the uphill portion
of the support surface with a wiper blade and thereafter contacting
it with at least one scraper blade. In FIG. 1, as the scraper blade
21 cleans liquid developer and debris from the uphill portion of
the support surface on drum 11, the liquid developer collects and
accumulates on the upstream side of blade 21 until it runs down the
surface (upstream) where it collects on the downstream side of
wiper blade 23. The liquid developer accumulates on the downstream
side of wiper blade 23 until it runs down blade 23 and into sump
25. Thus, wiper blade 23 prevents liquid developer and debris
removed from the support surface by blade 21 from passing upstream
of the wiper blade.
At the cleaning station in FIG. 2, there are provided two scraper
blades 21 and 22. The scraper blades are mounted on supporting
block 24 which can be moved so that the scraper blades engage or
disengage drum 11. The arrows in block 24 in the drawing indicate
that the block may be rotated to engage or disengage the scraper
blades and the support surface as desired. If the blades are left
pressing hard against the stationary drum, the photoconductive
surface may be deformed, and the blades may acquire a permanent
set.
In FIG. 2, there is illustrated wiper blade 23 mounted on one edge
of sump 25 located below the scraper blades and the wiper blade to
catch liquid developer which drips from the blades. As illustrated
in FIG. 2, the edge of sump 25 opposite the edge upon which wiper
blade 23 is mounted, is supported by supporting block 24 at point
34 so that the engagement or disengagement of wiper blade 23 with
the support surface is controlled by the movement of supporting
block 24. Thus, means are provided for simultaneously moving the
scraper blade or scraper blades and the wiper blade out of
engagement with the support surface, or in the alternative for
moving said blades into engagement with said support surface. As
noted supra for FIG. 1, when wiper blade 23 causes liquid developer
to flow upstream on drum 11, it is preferred that sump 25 extend to
the bottom center of the support surface on drum 11 (not shown in
FIG. 2).
In addition to providing a method of preventing liquid developer
and debris from passing upstream of the wiper blades as described
supra for the embodiment of FIG. 1, the dual scraper blade
components illustrated in FIG. 2 wherein a second scraper blade is
located downstream from the first scraper blade, provide a method
of removing streaks of liquid developer from the support surface
which remain on the support surface upstream of the first scraper
blade due to the solid debris entrained between the first scraper
blade and the support surface. This action is described in my
copending applications.
The developer liquid remaining on the drum after the transfer
station D, together with any foreign matter such as paper fibers
reaches the wiper blade 23 first. The characteristics of the wiper
blade 23 are such that most of the material passes under the blade
unaffected.
The scraper blades 21 in FIG. 1 and 21 and 22 in FIG. 2 then scrape
the material from the drum 11 forming a bead at the end surface of
each blade. When this bead reaches a certain size, it will fall
into the sump or flow down the surface of the drum to the wiper
blade 23 which then deflects the flowing material into the sump
25.
Each scraper blade is preferably of polyurethane of 65 Shore A
hardness, however, scraper blades having a hardness up to about 90
Shore A or higher are also within the scope of the invention. The
scraper blades are preferably about three-fourths inch long and 80
thousandths of an inch thick. The blades are clamped in a
supporting block 24 preferably over about the first third of their
length. The ends of the blades are at 90.degree.. A much smaller
angle (such as 60.degree.) at the cutting edge leads to failure by
the edge becoming tucked under the blade by friction. The holder of
the blades extends at 20.degree. .+-. 5.degree. to the tangent to
the drum at the point of contact (a wider variation of angle being
possible to suit different combinations of blades, liquids and drum
surfaces), the blade preferably being slightly flexed against the
drum in operation by the supporting block 24, with a force of the
order of 10 grams per centimeter. In accordance with the present
invention, it is preferred that the scraper blades have a
rectangular longitudinal cross section.
Wiper blade 23 is preferably a 125 um blade, for example, of
polyethylene terephthalate, only very slightly flexed against the
support surface of drum 11. Suitable wiper blade materials, sizes
and position angles may be chosen by one skilled in the art.
Suitable non-metallic flexible cleaning blade materials are
described by Royka et al in U.S. Pat. No. 3,552,850 at column 14.
Stiffener plates and other improvements known and described in the
art can be used in mounting the wiper blades.
As used in this invention the distinction between scraper blade and
wiper blade set out supra in the background of the invention is
critical.
In accordance with the stated objects, the present invention
provides a suitable apparatus and method for cleaning liquid
developer from a surface capable of carrying electrostatic latent
images, and the removal of liquid developer from reusable surfaces
is improved when scraper blades are used as cleaning blades at the
uphill portion of the reusable surface. While this invention has
been described with reference to the structures and method steps
disclosed herein, it is not confined to the details set forth; and
this application is intended to cover such modifications or changes
as may come within the purposes of the improvements or the scope of
the following claims.
* * * * *