U.S. patent number 3,678,896 [Application Number 05/110,435] was granted by the patent office on 1972-07-25 for conveyor system.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Robert E. Hewitt.
United States Patent |
3,678,896 |
Hewitt |
July 25, 1972 |
CONVEYOR SYSTEM
Abstract
Apparatus for use in an automatic xerographic reproducing
apparatus for cleaning residual toner material from the
photoconductive surface after the image has been transferred to a
final support material for returning the residual toner to a
xerographic developing station via a chain conveyor of improved
construction for reuse in the xerographic process.
Inventors: |
Hewitt; Robert E. (Ontario,
NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
22332995 |
Appl.
No.: |
05/110,435 |
Filed: |
January 28, 1971 |
Current U.S.
Class: |
399/359 |
Current CPC
Class: |
G03G
21/105 (20130101) |
Current International
Class: |
G03G
21/10 (20060101); G03g 013/00 () |
Field of
Search: |
;118/637 ;117/17.5
;198/168 ;355/15 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stein; Mervin
Assistant Examiner: Millstein; Leo
Claims
What is claimed is:
1. In apparatus for returning the residual particulate toner
remaining on a photoconductive surface after image transfer to a
remote developer housing for reuse in the xerographic developing
process wherein residual particulate toner is removed from the
photoconductive surface and collected and then returned by a
tubular conduit connecting said collecting means and the developer
housing, an endless chain means being arranged to be driven
sequentially through said collected toner and then a tubular
conduit in communication with the developer housing, the
improvement comprising
said endless chain means comprising spherically shaped hollow
members formed with two small oppositely faced apertures in the
surface thereof and elongated members each received through a one
of said apertures on adjacent hollow members and formed with belled
end portions,
drive means to drive the chain means including a drive sprocket to
positively engage the hollow members,
said hollow members being formed with at least one relatively large
opening at substantially right angles to said apertures whereby
upon bending movement of said chain means around said sprocket
residual toner material filling said hollow members may be
discharged to enable relative movement between said elongated
members and said hollow members.
2. Apparatus according to claim 1 wherein the ratio of the area of
said relatively large openings to the surface area of said hollow
members ranges from about 1 to 20 to about 1 to 5.
Description
This invention relates to xerographic apparatus and, in particular,
to recovering unused toner material from a photoconductive surface
after the xerographic image has been transferred and reusing the
recovered toner once again in the xerographic development
process.
In the art of xerography, as originally disclosed by Carlson in
U.S. Pat. No. 2,297,691, a xerographic plate, which is formed of a
conductive backing upon which is placed a photoconductive
insulating material, is charged uniformly and the surface of the
plate exposed to a light image of an original to be reproduced. The
photoconductive coating is caused to become conductive under the
influence of the light image so as to selectively dissipate the
electrostatic charge found thereon thus producing an electrostatic
latent image. The latent image is made visible by developing the
image with any one of a variety of pigmented resins which have been
specifically developed for this purpose. In the xerographic
process, the pigmented resin material, or toner, is
electrostatically attracted to the latent image on the
photoconductive surface in proportion to the amount of charge found
thereon. Areas of small charge concentration become areas of low
toner density while areas of greater charge concentration become
proportionally more dense. The fully developed image is then
transferred from the plate surface to a final support material, as
for example, paper, and the image fixed thereto to form a permanent
record of the original copy.
A preponderance of the toner material is transferred from the
photoconductive surface to the final support material during the
transfer operation. However, it has been found that the forces
bonding some of the toner particles to the photoconductive surface
are stronger than the transfer forces involved and therefore some
particulate material remains on the photoconductive surface after
the xerographic image is transferred. This residual toner, if not
cleaned from the xerographic plate in some manner, will have a
deleterious effect on subsequent images processed on the plate.
Plate cleaning in automatic xerographic machines in which the plate
is continually reused in the xerographic process is accomplished by
various devices such as fiber brushes, cleaning webs, wiper blades
or the like. The toner material so removed is usually collected and
stored in the machine and then periodically removed and discarded.
However, most of the commercially accepted methods of cleaning a
photoconductive surface in automatic xerographic machines have been
found to be dirt producing and wasteful. The fine residual toner
material removed from the plate surface is extremely difficult to
handle and the material often migrates from the cleaning system
into other areas of the machine to contaminate the machine
component parts. It has also been found that the residual toner
removed from the xerographic plate surface constitutes an extremely
high percentage of the total toner used in the xerographic
process.
Recently a system of recovering the residual toner for reuse in the
development zone has been accomplished effectively by passing a
bead chain conveyor between a cleaning station and the development
station as described in copending application Ser. No. 838,816,
filed on July 3, 1969, and commonly assigned with the instant
application. The present invention is an improvement to the bead
chain conveyor which must return the residual toner material for
reuse in the system.
It is therefore an object of this invention to improve xerography,
and in particular, automatic xerographic reproducing apparatus.
A further object of this invention is to reduce toner waste in an
automatic xerographic reproducing apparatus.
A still further object of this invention is to reclaim residual
toner left in a xerographic plate after the transfer operation so
that the toner can be reused in the xerographic develop
process.
A still further object of the invention is to improve bead chain
conveyor for the transport of powder materials.
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
connection with the accompanying drawings, wherein:
FIG. 1 illustrates schematically an automatic xerographic
reproducing apparatus employing the toner reclaiming system of the
present invention;
FIG. 2 is a side elevation in partial section showing the drum
cleaning station, the improved bead chain construction according to
the invention and bead chain drive, the xerographic development
system, and the associated elements of the toner reclaiming system
shown in FIG. 1;
FIG. 3 is a partial top view of the toner reclaiming system shown
in FIG. 2;
FIG. 4 is an enlarged sectional view illustrating details of the
improved chain construction according to the present invention;
FIG. 5 is an enlarged elevation sectional view of improved chain
construction winding around its capstan drive; and
FIG. 6 is an enlarged perspective view of the improved bead chain
and tubular conduit having metering means associated therewith to
distribute toner material evenly throughout the developer
housing.
As shown, the automatic xerographic reproducing apparatus comprises
a xerographic plate including a photoconductive layer of a light
receiving surface on a conductive backing and formed in the shape
of a drum, generally numerically designated 10 which is journaled
in the frame of the machine by means of shaft 11. The xerographic
plate is rotated in the direction indicated in FIG. 1 to cause the
drum surface to pass sequentially through 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 A, in which a uniform electrostatic charge is
deposited on the photoconductive layer of the xerographic drum;
An exposure station B wherein a light or radiation pattern of an
original document to be reproduced is projected onto the drum
surface to dissipate the charge found thereon in the exposed areas
to form a latent electrostatic image;
A development station C, at which a xerographic developing material
having toner particles possessing an electrostatic charge opposite
to the charge found on the drum surface in the latent image areas
are cascaded over the moving drum surface whereby the toner
particles adhere to the electrostatic latent image to make visible
the image in the configuration of the original document to be
reproduced;
A transfer station D, in which the xerographic powder image is
electrostatically transferred from the drum surface to a final
support material; and
A drum cleaning and toner collecting station E, wherein the drum
surface is first charged and then wiped with a doctor blade to
remove residual toner particles remaining thereon after image
transfer and wherein the removed toner is collected for reuse in
the xerographic process and in which the drum surface is exposed to
an incandescent panel to effect substantially complete discharge of
any residual electrostatic charge remaining thereon.
The charging station is preferably located at the bottom of the
drum in the position indicated by reference character A in FIG. 1.
The charging arrangement consists of a corona charging device 13
which includes a corona discharge array of one or more corona
discharge electrodes that extend transversely across the drum
surface and are energized from a high potential source. The corona
discharge electrode is substantially enclosed within a shielding
member and is adapted to generate a charge confined within this
specific area.
Next subsequent thereto in the path of travel of the xerographic
drum is an exposure station B wherein a flowing light image of a
stationary original is placed on the moving drum surface.
Basically, the optical scanning and projecting assembly comprises a
stationary transparent copy board 14 adapted to support the
original to be copied; an illuminating means LMP-1 to illuminate
uniformly the original supported on the copy board; a folded
optical system including an object mirror 16, a movable lens system
17, and an image mirror 18 arranged in light projecting
relationship with the moving drum surface to project successive
illuminated incremental areas on the original document onto the
drum surface to form a flowing light image thereon. The lens
element is positioned beneath the copy board and is arranged to
move through a path of travel parallel to the plane of the copy
board whereby the subject image of the original is scanned in timed
relation to the movement of the light receiving surface on the
xerographic drum.
Positioned adjacent to the exposure station is a fade out panel 19
arranged to discharge or expose the drum surface in the areas
between copies to a level below that required for xerographic
development so that these charged but non-imaged areas will not be
developed as the drum moves through the subsequent developing
station.
Next adjacent to the exposure station is a developing station C in
which is positioned developing apparatus 20 including a housing 28
having a lower sump portion therein capable of supporting a
quantity of two component developer material. A bucket type
conveyor 27, having any suitable drive means, is employed to carry
the developer material from the lower sump area to the upper part
of the developer housing where it is deposited in hopper 29. The
developer material moves downwardly into contact with the upwardly
moving photoconductive drum surface. Toner particles are deposited
in the image areas on the drum surface in relation to the charge
pattern found thereon to form a developed xerographic image. The
unused developer material passes from the development zone back
into the lower portion of the developer housing. Fresh xerographic
toner material is supplied to the developer mix in proportion to
the amount of toner deposited on the drum surface by means of
dispensing apparatus positioned in the lower portion of toner
dispensing bottle 21.
Positioned next and adjacent to the developing station is the image
transfer station D. Individual sheets of final support material are
fed seriatim into sheet registering and forwarding apparatus 22
from either upper feed tray 35 or lower feed tray 34. The properly
registered sheets are then forwarded into moving contact with the
moving drum surface and the developed image electrostatically
transferred from the drum to the final support material by means of
transfer corotron 24. In operation, the electrostatic field created
by the corona discharge device electrostatically tacks the transfer
material to the drum surface whereby the transfer material moves
synchronously with the drum while in contact therewith.
A mechanical stripper finger 25 is pivotally mounted in close
proximity to the drum surface immediately adjacent to the transfer
corotron. The finger is arranged to move into contact with the drum
surface prior to the arrival of the leading edge of the support
material. The arcuate shaped stripper finger moves between the drum
surface and the leading edge of the final support material to
mechanically break the electrostatic bond holding the material to
the drum surface. Because of the positioning and the shape of the
finger, the leading edge portion of the sheet of final support
material is directed upwardly into contact with stationary vacuum
transport 26. The trailing edge of the support material, which at
this time is still electrostatically tacked to the drum surface,
continues to drive the support material forward so that it moves
along the bottom surface of the vacuum transport towards fuser
assembly 30.
The image bearing support material moving along the stationary
vacuum transport moves into the nip between upper fuser roll 31 and
lower fuser roll 32 of fuser assembly 30. The two rolls coact to
deliver pressure driving force to the sheet of support material
positioned therebetween. A radiant heat source of heat energy 33
extends transverse to the lower roll surface and transfers heat
energy to the roll. The roll is specifically coated so that the
heat energy transferred thereto is stored on the outer surface of
the roll. As the roll rotates in the direction indicated, the heat
energy stored there is brought into rubbing contact with the image
bearing support material passing through the nip between the two
rolls where image fixing is accomplished by delivering a
combination of heat and pressure energy to the image bearing
support material.
After leaving the fuser assembly, the fixed copy is transported
through a circular paper path into a movable guide and drive roll
assembly 36. The movable guides can be prepositioned to either feed
the paper delivered from the fuser into upper feed tray 35 or into
discharge catch tray 37. The apparatus can be programmed by means
of the machine control logic system to precondition the paper
handling equipment to accept simplex copies in upper feed tray 35.
The simplex copy is then once again reprocessed through the
xerographic transfer station to form a duplex image and then
discharge from the machine as described above.
The next and final station in the automatic xerographic reproducing
apparatus is a drum cleaning and toner recovery station E at which
cleaning apparatus constructed in accordance with the present
invention removes substantially all residual toner particles
remaining on the xerographic drum surface after image transfer
recovers the residual toner removed for reuse in the automatic
reproducing apparatus in a manner to be described below.
A rectangular shaped flexible blade is utilized in the preferred
embodiment of the present invention to remove residual toner from
the moving drum surface. The blade is mounted in blade holder 51
forming one wall of cleaning and collection apparatus 40 (FIG. 1)
so that it normally rests transversely in a pressure contact with
the photoconductive layer on the drum with the edge of the blade
formed by the joinder of upper face surface 47 and front side
surface 48 being positioned slightly below the horizontal
centerline of the drum. It should be noted that the blade is
positioned so that the contacting edge cuts or chissels toner
material from the drum surface much like a lathe cutting tool
removes material. In fact, it has been found that the forces
experienced by the blade are quite similar to the forces
encountered by the lathe cutting tool. The blade is best supported
in a tool-like fashion having an end relief angle and a slight back
rate angle. The end relief angle, that is, the angle between the
front side 48 of the blade and a plane tangent to the drum surface
at the point of lead edge contact, can be varied for different
blade materials to effectively eliminate blade chatter and other
undersirable effects associated with improper blade positioning.
Although not essential for the practice of the present invention,
it is desirable to provide a slight back rack on face surface 47 so
that a sharper cutting edge is presented to the drum surface
resulting in more efficient drum cleaning.
Any suitable non-metallic flexible cleaning blade material may be
employed in the cleaning system of the present invention. Typical
non-metallic flexible materials include: polysiloxane rubber,
polyurethane rubber, polytetrafluoroethylene resin,
polytrifluorochloroethylene resin, styrenebutadiene rubber, nitrile
rubber, nitro-silicone rubber, flexinle polyurethane foam,
polyethylene resin, and blends, mixtures and copolymers thereof.
The blade should be sufficiently soft to minimize plate abrasion
and particularly abrasion to a selenium type imaging surface.
Preferably, the blade material should have a Shore hardness of less
than 65 durometers. Tests have shown that a relatively wide
latitude in blade thickness can be employed in the present
apparatus with no noticeable change in the cleaning process.
It should be clear that by the doctor blades slightly below the
horizontal centerline of the drum surface and providing the blade
with a slight back rack, the removed residual toner material will
be forced to fall to the backside of the blade, that is to the side
away from the photoconductive drum surface. The removed residual
toner is thus prevented from recontacting and rebonding itself once
again to the drum surface. As illustrated in FIGS. 2 and 3, the
removed toner falls into an open side channel 53 adjacent to and
running longitudinally along the drum surface. A screw type
conveyor 55 mounted upon shaft 54 is journaled for rotation in end
plate 56 and cover plate 62. The conveyor is supported in the open
side channel in substantially parallel relation to the doctor blade
and is arranged to convey the toner particles removed from the drum
surface towards toner recovery drive housing 61.
The open side channel 53 is closed at one end by means of end plate
56 while the opposite end of the channel is securely mounted in
drive housing 61. The channel communicates with a reservoir or
collecting area, generally referred to as 57, in the housing. A top
portion of shaft 54 as seen in FIG. 3, extends through end plate 56
and has rigidly affixed thereto driving gear 85. Although not
shown, driving gear 85 is driven from the machine main drive system
to rotate the auger in a direction whereby the screw conveyor
transports toner material laterally behind the blade into reservoir
area 57 where the residual toner is collected. The residual toner
which is collected in reservoir area 57 of the drive housing 61 is
transported back to the developer housing by means of a conveyor
system made up of supply and return tubing 66, 67; developer
housing connector 70; and toner metering and return loop 71. The
various parts making up the conveyor system are mated together so
that a continuous substantially closed circuit conduit having a
uniform inside diameter runs from reservoir area 57 across the
width of the developer housing and returns once again to said
reservoir.
An endless chain generally designated 90 according to the invention
as will be more fully described hereinafter moves downwardly
through the collected toner material in reservoir area 57. The
chain beads mechanically force the particulate toner material
downwardly into supply tubing 66. The tubing is maintained in
operative relation with the drive housing by pressing the tubing
firmly into the adapter positioned in the bottom of the drive
housing plate 65. The opposite end of tubing 66 is similarly
connected in developer housing connector 70. Supply tubing 66 and
the return tubing 67 are preferably constructed of a flexible
plastic material which, as shown in FIG. 1, is conveniently routed
from the toner cleaning and collecting apparatus 40 to the
developer housing 20 through the machine so as to avoid the
stationary machine components.
New toner is dispensed in the present apparatus by means of a roll
dispenser (not shown) positioned in the bottom portion of toner
dispensing bottle 75. The bottle is seated between rails 73, 74
extending laterally across the dispensing opening provided in the
developer housing. The bottle is adapted to dispense toner at a
predetermined rate directly into the developer housing as
dispensing roll is rotated in the direction indicated. Developer
housing connector 70 is secured to the developer housing by
affixing embossed sections 72 thereon to rails 73, 74 as for
example, by screws. The bead chain which has transporting toner
material through supply tubing 66, is guided through approximately
a 90.degree. turn as the chain passes through connector 70 so that
the chain leaves the connector along a path of travel substantially
parallel to rail 73. Loop 71, which is also fabricated of a
relatively rigid plastic material, is supported in the connector 70
so that the loop is suspended just below the toner dispenser bottle
and runs substantially around the outer periphery of the bottle in
parallel relation to the support rails. The bead chain entering the
dispensing area of the developer housing first passes through a
portion of tubing having a series of step-like cutouts 80 formed in
the side wall thereof. As illustrated in FIG. 6, the step-like
cutouts are progressively lowered in equal increments as the tubing
extends across the width of the developer housing from a starting
point substantially high on the side wall of the tube to a point
whereby the entire side wall of the tube is removed. As the chain
transports toner across the width of the developer housing, the
toner is incrementally dispensed in substantially equal quantities
across the developer housing. The bead chain continues around the
loop and once again makes a 90.degree. turn through connector 70
and returns once again to drive housing 61 through return tube
67.
Although not shown, seals are provided between the open side
channel 53 and the rotating drum surface to prevent residual toner
material from escaping from the toner cleaning and collecting
apparatus 40. As can be seen, because a close system is thus
provided, little or no free toner material is permitted to escape
to the surrounding machine areas. The toner cleaning and recovery
system as herein disclosed is not only extremely clean to operate
but also protects the surrounding machine components from being
contaminated by loose or free toner particles. The entire cleaning
and collecting apparatus 40 (FIG. 1) is pivotally supported upon
pivot arms 58 mounted on tie rod 59 which is locked to the machine
frame. To facilitate drum removal, the entire assembly 40 is swung
downwardly about rod 59 away from the drum surface. As can be seen,
open side channel 53 pivotes downwardly to form a trough capable of
containing any loose toner particles which may be in process in the
system at this time. When the assembly is moved to the operative
position as shown in FIG. 2, a spring biased latch 86 is locked in
supporting engagement with latch pan 87 by means of locking
mechanism 88 whereby the cleaning edge of the flexible
self-adjusting cleaning blade is placed in pressure contact with
the rotating drum surface.
A drive sprocket 63 is rotatably mounted on shaft 82 which is
journaled for rotation in drive housing 61. The drive sprocket is
driven directly from the main machine drive through screw conveyor
shaft 54. Driven gear 84, mounted on the bottom end shaft 54, as
shown in FIG. 3, turns intermediate gear 83 which in turn drives
sprocket drive gear 81 in the desired direction shown in FIG. 2.
Passing over the rim of the drive sprocket 63 is endless bead chain
generally designated 90. The drive sprocket is arranged to engage
and guide the chain to move the chain in the direction indicated.
In the past, difficulty has been experienced in bending
conventional type bead chain around sprocket 63 due to the fact
that residual toner material fills the chain beads causing a
stiffness in the chain which may result in a malfunction.
In accordance with the present invention, the chain 90 remains
flexible throughout its circuitous path. The chain is formed by
hollowed spherically shaped members 93 which have apertures 95
formed therein through which link members 97 are received to form a
continuous chain. In the past, it has been found that toner
material has entered spherical members 93 through apertures 95
whereby link members 97 have been prevented from moving relative to
the spherical members around bends as where the chain passes around
drive sprocket 63. As best shown in FIGS. 4 and 5 relatively large
openings 100 are formed in the surface of member 93 at right angles
to the link members 97. By the arrangement any toner material
trapped in the spherical members 93 is discharged through openings
100 due to a pumping action carried out by the belled end portion
101 of link members 97 as spherical members 93 rotate on their axes
as best seen in FIG. 5. Now it can be understood that the coaction
of the link members 97 on the toner material discharges the
material maintaining a flexibility in the chain structure.
Openings 100 should be sufficiently large to adequately expel toner
material for chain flexibility but not sufficiently small such that
the strength of the chain is not weakened. Under these
circumstances, it has been found that the ratio of the area of
openings 100 to the surface area of the spherical members 93 may
range from about 1 to 20 to about 1 to 5.
While this invention has been described with reference to the
structure 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 scope of the following
claims.
* * * * *