U.S. patent number 3,700,328 [Application Number 05/210,756] was granted by the patent office on 1972-10-24 for magnetic brush cleaning system.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Ronald V. Davidge, Henry C. Locklar, James C. Ralston, Robert T. Ritchie.
United States Patent |
3,700,328 |
Davidge , et al. |
October 24, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
MAGNETIC BRUSH CLEANING SYSTEM
Abstract
The present case concerns several systems for cleaning a
photoconductor of residual toner at a cleaning station and
recirculating the toner to a developer station in a copier machine.
One embodiment contemplates a fairly continuous accumulation of
residual toner in the cleaning unit and a periodic recirculation of
the toner to the developer unit. Another embodiment makes use of a
cleaning station for performing cleaning of toner from an imaging
portion of a photoconductor drum member and concurrent conveyance
of residual toner from the cleaning station back to the developer
station by another portion of the photoconductor. In still another
version, recirculation is performed by augers. In some cases,
recirculation is initiated by counter means operative after a
predetermined number of cycles.
Inventors: |
Davidge; Ronald V. (Lexington,
KY), Locklar; Henry C. (Lexington, KY), Ralston; James
C. (Lexington, KY), Ritchie; Robert T. (Lexington,
KY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
22784152 |
Appl.
No.: |
05/210,756 |
Filed: |
December 22, 1971 |
Current U.S.
Class: |
399/359;
399/353 |
Current CPC
Class: |
G03G
21/0047 (20130101); G03G 21/105 (20130101); G03G
2221/0005 (20130101) |
Current International
Class: |
G03G
21/00 (20060101); G03G 21/10 (20060101); G03g
015/00 () |
Field of
Search: |
;355/3,10,14,15,17
;118/637 ;117/17.5,37LE |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Mathews; Alan A.
Claims
What is claimed is:
1. A cleaning and recirculation system for a copier machine having
a photoconductor member and charging, imaging and transfer
stations, arranged for processing of images on said photoconductor
member, comprising:
a developer station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to develop images on
said photoconductor by deposition of toner on said photoconductor
member following imaging thereof at said imaging station;
cleaning station positioned adjacent said photoconductor member and
having a magnetic brush normally operable to clean residual toner
from said photoconductor member following transfer of an image from
said photoconductor member to a receiving surface at said transfer
station; and
circuit means operable in a first mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing and cleaning by said brushes as set
forth and said circuit means being operable in a second mode to
supply second predetermined bias potentials to the various stations
in said system to effect transfer of residual toner from said
cleaning station to said photoconductor member, and conveyance of
said residual toner by said photoconductor member back to said
developer station for re-use.
2. The system of claim 1 further comprising:
recirculation control means for monitoring developing and cleaning
cycles of said system and operable upon occurrence of a
predetermined number of cycles to initiate said second mode of
operation of said circuit means.
3. The system of claim 2 further comprising:
counter means operable to count said predetermined number of
cycles.
4. A cleaning and recirculation system for a copier machine having
a photoconductor member, and various stations, arranged for
processing of images on said photoconductor member, comprising:
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a first erase station;
a developer station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to develop images on
said photoconductor by deposition of toner on said photoconductor
member following imaging thereof at said imaging station;
a transfer station operable to effect transfer of an image
developed on said photoconductor to a receiving surface;
a second erase station;
a cleaning station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to clean residual
toner from said photoconductor member following transfer of an
image from said photoconductor to a receiving surface at said
transfer station; and
circuit means operable in a first mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing and cleaning by said brushes as set
forth and said circuit means being operable in a second mode to
supply second predetermined bias potentials to the various stations
in said system to effect transfer of residual toner from said
cleaning station to said photoconductor member, and conveyance of
said residual toner by said photoconductor member back to said
developer station for re-use.
5. A cleaning and recirculation system for a copier machine having
a photoconductor member, and various stations arranged for
processing of images on said photoconductor member, comprising:
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a first erase station;
a developer station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to develop images on
said photoconductor by deposition of toner on said photoconductor
member following imaging thereof at said imaging station;
a transfer station operable to effect transfer of an image
developed on said photoconductor to a receiving surface;
a second erase station;
a cleaning station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to clean residual
toner from said photoconductor member following transfer of an
image from said photoconductor to a receiving surface at said
transfer station; and
circuit means operable in a first mode to supply first
predetermined bias potentials and gating signals to the various
stations in said system to effect developing and cleaning by said
brushes as set forth comprising;
supplying positive potentials to said charging station and said
cleaning stations and minus potentials to said developing and
transfer stations, an a-c potential to said second erase station
and concurrently gating off said first erase station;
and said circuit means being operable in a second mode to supply
second predetermined bias potentials and gating signals to the
various stations in said system to effect transfer of residual
toner from said cleaning station to said photoconductor member, and
conveyance of said residual toner by said photoconductor member
back to said developer station for re-use comprising:
supplying a positive potential to said transfer station, a negative
potential to said cleaning station and a higher negative potential
to said developing station, an a-c potential to said first erase
station, and concurrently gating off said charging station, said
imaging station, and said second erase station.
6. A cleaning and recirculation system for a copier machine having
various stations arranged for processing of images member,
comprising:
a photoconductor member, said photoconductor member having at least
one image area and at least one inter-image area;
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a developer station positioned adjacent said photoconductor member
and normally operable to develop images in the image area on said
photoconductor by deposition of toner on said photoconductor member
following imaging thereof at said imaging station;
a transfer station operable to effect transfer of an image
developer on said photoconductor to a receiving surface;
a cleaning station positioned adjacent said photoconductor member
and normally operable to clean residual toner from the image area
on said photoconductor member following transfer of an image from
said photoconductor member to a receiving surface at said transfer
station; and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing and cleaning of said image area as set
forth and said circuit means being further operable in a
recirculate mode to supply second predetermined bias potentials to
the various stations in said system to effect transfer of residual
toner from said cleaning station to the inter-image area on said
photoconductor member in an alternating fashion with said
copy-making mode, and conveyance of said residual toner by said
photoconductor member back to said developer station for
re-use.
7. A cleaning and recirculation system for a copier machine having
various stations arranged for processing of images, comprising:
a photoconductor member, said photoconductor member having at least
one image area and at least one inter-image area;
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a developer station positioned adjacent to said photoconductor
member and having a magnetic brush normally operable to develop
images in the image area on said photoconductor by deposition of
toner on said photoconductor member following imaging thereof at
said imaging station;
a transfer station operable to effect transfer of an image
developed on said photoconductor to a receiving surface;
a cleaning station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to clean residual
toner from the image area on said photoconductor member following
transfer of an image from said photoconductor to a receiving
surface at said transfer station; and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing and cleaning of said image area by said
brushes as set forth and said circuit means being further operable
in a recirculate mode to supply second predetermined bias
potentials to the various stations in said system to effect
transfer of residual toner from said cleaning station to said
inter-image area on said photoconductor member in an alternating
fashion with said copy-making mode, and conveyance of said residual
toner by said photoconductor member back to said developer station
for re-use.
8. The system of claim 7 further comprising:
means mounting said photoconductor member for relative movement
with respect to said stations; and
means mounting said circuit means for operation in timed relation
with relative movement of said photoconductor member and said
stations to effect copy-making and recirculate modes in proper
synchronism with respect to said image and inter-image areas on
said photoconductor member.
9. The system of claim 8 wherein said photoconductor comprises a
drum member and said circuit means comprises a cam member and a
switch member and further comprising:
a common shaft means mounting said drum member and said cam member
for synchronized rotation.
10. A cleaning and recirculation system for a copier machine having
various stations arranged for processing of images member,
comprising:
a photoconductor member, said photoconductor member having a
plurality of image areas and inter-image areas interspersed between
said image areas;
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a developer station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to develop images in
the image areas on said photoconductor by deposition of toner on
said photoconductor member following imaging thereof at said
imaging station;
a transfer station operable to effect transfer of an image
developed on said photoconductor to a receiving surface;
a cleaning station positioned adjacent said photoconductor member
and having a magnetic brush normally operable to clean residual
toner from the image areas on said photoconductor member following
transfer of an image from said photoconductor to a receiving
surface at said transfer station; and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing and cleaning of said image areas by
said brushes as set forth and said circuit means being further
operable to supply second predetermined bias potentials to the
various stations in said system to effect transfer of residual
toner from said cleaning station to the inter-image areas on said
photoconductor member in an alternating fashion with said
copy-making mode, and conveyance of said residual toner by said
photoconductor member back to said developer station for
re-use.
11. A cleaning and recirculation system for a copier machine having
a photoconductor member with first and second portions and
charging, imaging and transfer stations arranged for processing of
images on said photoconductor member, comprising:
a developer station positioned adjacent said photoconductor member
and normally operable to develop images on said photoconductor
member by deposition of toner on said photoconductor member
following imaging thereof at said imaging station;
a cleaning station incorporating a magnetic brush member, said
magnetic brush member having a first portion positioned adjacent
the first portion of said photoconductor member, and normally
operable to clean residual toner from said photoconductor member
following transfer of an image from said photoconductor to a
receiving surface at said transfer station and said magnetic brush
member having a second portion positioned adjacent the second
portion of said photoconductor member operable to convey residual
toner onto the second portion of said photoconductor member;
and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing, and cleaning by said first magnetic
brush portion and said circuit means further being operable to
supply second predetermined bias potentials to the various stations
in said system to effect transfer of residual toner from said
cleaning station by said second magnetic brush portion to said
photoconductor member, and conveyance of said residual toner by
said photoconductor member back to said developer station for
re-use concurrently with said copy-making mode.
12. A cleaning and recirculation system for a copier machine having
a photoconductor member with first and second portions and
charging, imaging and transfer stations, arranged for processing of
images on said photoconductor member, comprising:
a magnetic brush developer station positioned adjacent said
photoconductor member and normally operable to develop images on
said photoconductor by deposition of toner on said photoconductor
member following imaging thereof at said imaging station;
a cleaning station incorporating a magnetic brush member said
magnetic brush member having a first portion positioned adjacent
the first portion of said photoconductor member, and normally
operable to clean residual toner from said photoconductor member
following transfer of an image from said photoconductor member to a
receiving surface at said transfer station and said magnetic brush
member having a second portion positioned adjacent the second
portion of said photoconductor member and operable to convey
residual toner onto the second portion of said photoconductor
member; and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing, and cleaning by said first magnetic
brush portion and said circuit means further being operable to
supply second predetermined bias potentials to the various stations
in said system to effect transfer of residual toner from said
cleaning station by said second magnetic brush portion to said
photoconductor member, and conveyance of said residual toner by
said photoconductor member back to said developer station for
re-use concurrently with said copy-making mode.
13. A cleaning and recirculation system for a copier machine having
a photoconductor member with first and second portions and
charging, imaging and transfer stations, arranged for processing of
images on said photoconductor member, comprising:
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a first erase station positioned adjacent the first portion of said
photoconductor member;
a magnetic brush developer station positioned adjacent said
photoconductor member and normally operable to develop images on
said photoconductor member by deposition of toner on said
photoconductor member following imaging thereof at said imaging
station;
a transfer station operable to effect transfer of an image
developed on said photoconductor to a receiving surface;
a second erase station positioned adjacent the second portion of
said photoconductor member;
a cleaning station incorporating a magnetic brush member, said
magnetic brush member having a first portion positioned adjacent
the first portion of said photoconductor member, and normally
operable to clean residual toner from said photoconductor member
following transfer of an image from said photoconductor to a
receiving surface at said transfer station, and said magnetic brush
member having a second portion positioned adjacent the second
portion of said photoconductor member and operable to convey
residual toner onto the second portion of said photoconductor
member; and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing, and cleaning by said first magnetic
brush portion comprising supplying positive potentials to said
charging station and said cleaning station and minus potentials to
said developing and transfer stations, and an a-c potential to said
first erase station;
and said circuit means further being operable to supply second
predetermined bias potentials to the various stations in said
system to effect transfer of residual toner from said cleaning
station by said second magnetic brush portion to said
photoconductor member, and conveyance of said residual toner by
said photoconductor member back to said developer station for
re-use concurrently with said copy-making mode, comprising:
supplying positive potential to said transfer stations, a negative
potential to said cleaning station, and a higher negative potential
to said developing station, and an a-c potential to said second
erase station.
14. A cleaning and recirculation system for a copier machine having
various stations arranged for processing of images, comprising:
a photoconductor member;
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a developing station positioned adjacent said photoconductor member
and normally operable to develop images in the image areas on said
photoconductor deposition of toner on said photoconductor member
following imaging thereof at said imaging station;
a cleaning station positioned adjacent said photoconductor member
and normally operable to clean residual toner from said
photoconductor member following transfer of an image from said
photoconductor to a receiving surface at said transfer station;
and
circuit means operable in a copy-making mode to supply first
predetermined bias potential to the various stations in said system
to effect developing and cleaning as set forth; and
auger means interconnecting said developer station and said
cleaning station and operable concurrently with copy-making
operations to effect transfer of residual toner from said cleaning
station to said developer station for re-use.
15. A cleaning and recirculation system for a copier machine having
a photoconductor member and charging, imaging and transfer stations
arranged for processing of images on said photoconductor member,
comprising:
an auxiliary member associated with said photoconductor member;
a charging station operable to uniformly charge said photoconductor
member;
an imaging station to discharge said photoconductor member in
accordance with light patterns derived from an original
document;
a first discharge station position adjacent said photoconductor
member;
a magnetic brush developer station positioned adjacent said
photoconductor member and normally operable to develop images on
said photoconductor member by deposition of toner on said
photoconductor member following imaging thereof at said imaging
station;
a transfer station operable to effect transfer of an image
developed on said photoconductor member to a receiving surface;
a second discharge station positioned adjacent the said auxiliary
member;
a cleaning station incorporating a magnetic brush member, said
magnetic brush member having a first portion positioned adjacent
said photoconductor member, and normally operable to clean residual
toner from said photoconductor member following transfer of an
image from said photoconductor to a receiving surface at said
transfer station, and said magnetic brush member having a second
portion positioned adjacent said auxiliary member and operable to
convey residual toner onto said auxiliary member; and
circuit means operable in a copy-making mode to supply first
predetermined bias potentials to the various stations in said
system to effect developing, and cleaning by said first magnetic
brush portion;
and said circuit means further being operable to supply second
predetermined bias potentials to the various stations in said
system to effect transfer of residual toner from said cleaning
station by said second magnetic brush portion to said auxiliary
member, and conveyance of said residual toner by said auxiliary
member back to said developer station for re-use concurrently with
said copy-making mode.
Description
BACKGROUND OF INVENTION, FIELD, AND PRIOR ART
A variety of techniques have been described in the prior art for
cleaning of a photoconductor in a copier machine and in some
circumstances, recirculation of residual toner. However, none of
the prior art to be discussed is considered anticipatory of the
present arrangements.
U. S. Pat. No. 2,757,635 and United Kingdom patent 1,059,649 are
representative of toner recirculation systems using blowers or air
flow. The U. S. Pat. Nos. 3,306,193; 3,333,572; 3,405,682; and
3,438,706 are representative of patents showing the use of separate
belt members, or the like, for conveyance of toner in the system in
a recirculation mode, or simply for the purpose of cleaning,
without recirculation. The U. S. Pat. No. 2,874,063 is an early
teaching of the use of a magnetic member for cleaning of a
photosensitive surface. The U. S. Pat. No. 3,357,402 describes the
use of fur brushes for both developing and cleaning of a
photoconductor. The U. S. Pat. No. 3,552,850 describes a cascade
developer with a scraper member for cleaning and effects some
transportation of residual toner particles on the photoconductor
surface.
SUMMARY OF THE INVENTION
The invention, in its various forms, is set in a copier machine
making use of a drum photoconductor member. In a first embodiment,
various stations are arranged around the periphery of the drum
including a charging station, an imaging station, an erasing
station, a developing station, a transfer station, and a cleaning
station. In one form, the developing and cleaning stations comprise
magnetic brush members operable to attract and repel toner
particles relative to the drum photoconductor surface. Electrical
circuit means is provided that is operable in a first mode to
provide appropriate biasing signals to effect charging, imaging,
developing, transferring, and cleaning of images with accumulation
of residual toner particles at the cleaning station. In another
mode, the electrical circuit means is effective to establish
appropriate biasing so that residual toner particles are attracted
from the cleaning unit onto the surface of the drum, conveyed by
the drum to the developing station and deposited therein. A counter
controls the timing or institution of the recirculation cycle.
In another form of the invention, inter-image areas are provided on
the surface of the drum between each succeeding image area, and cam
members are located in operable relation with respect to the drum
to effect changes in bias of the various stations to convey toner
from the cleaning station to the developing station in the
inter-image areas concurrently with imaging and copy making. Thus,
recirculation is effected concurrently with the copy making process
and a separate recirculation cycle is not required in this
version.
In another form of the invention, a magnetic brush member has a
first cleaning portion operable to remove residual toner particles
from the surface of the photoconductor drum and a second portion
insulated from the first portion and operable to convey residual
particles from the cleaning station back onto the drum for
conveyance back to the developer station. In this version, the
recirculation of toner particles also takes place concurrently with
the normal copy making processes in the machine. As before,
appropriate biasing potentials are provided in the system to effect
the removal and transportation of toner particles.
In still another version, cleaning and developing stations are
provided adjacent the drum photoconductor member and recirculation
of toner particles is effected essentially in a mechanical fashion
by the use of auger means arranged in such a fashion that toner
particles may be conveyed from the developer station to the
cleaning station, or vice versa.
OBJECTS
Accordingly, a primary object of the present invention is to
provide a cleaning system for a copier machine with the capability
of recirculating residual toner in a highly efficient manner to the
developing station in the machine for reuse.
Another object of the present invention is to provide a cleaning
and recirculating system for a copier machine wherein the system is
normally operable to develop and clean a photoconductor member
during a copy making mode and is periodically operable in a
recirculating mode to transfer residual toner from the cleaning
station to the developing station.
Still another object of the present invention is to provide a
system of this nature in which recirculation of residual toner from
a cleaning station to a developing station is effected concurrently
with copy making operations, thereby eliminating the requirement
for a separate independent recirculation cycle.
A further object of the present invention is to provide a cleaning
and recirculating system for a copier machine in which a
recirculation cycle is initiated upon occurrance of a predetermined
number of developing and cleaning cycles during copy making
operations.
A still further object of the present invention is to provide a
combined cleaning member having a first portion operable to remove
residual toner from a photoconductor member during cleaning
operations and a second portion operable to return residual toner
to said photoconductor member for transportation to the developing
station in said system.
Also, an object of the present invention is to provide a cleaning
and recirculating system for a copier machine making use of
mechanical means to effect the recirculation of residual toner in
the system.
The foregoing and other objects, features, and advantages of the
invention will be apparent from the following more particular
description of various embodiments of the invention as illustrated
in the accompanying drawings.
DRAWINGS
In the Drawings:
FIG. 1 represents a copier machine incorporating a cleaning and
recirculating system in accordance with the present invention in
which developing and cleaning cycles are normally effected during
copy making operations and having provision for periodically
recirculating residual toner from a cleaning station to a
developing station with the photoconductor member serving as the
transport means in the system. A counter is provided to recognize
the occurrance of a predetermined number of cycles to initiate the
recirculating cycle.
FIG. 2 represents a cleaning and recirculating system in which a
photoconductor member has a plurality of image areas, each
separated by an inter-image area and having facilities for imaging,
developing, transferring, and cleaning the image areas in a normal
copy making mode while concurrently providing appropriate
potentials to effect recirculation of toner from the cleaning
station to the developing station by deposition in the inter-image
areas.
FIGS. 3 and 4 represent another version of the invention in which
the cleaning station comprises a magnetic brush member having a
first portion for cleaning of residual toner from the
photoconductor member and a second portion for transfer of residual
toner onto a special area of the photoconductor member for
transportation back to the developing station concurrently with
copy making operations.
FIG. 5 represents a cleaning and recirculating system having a
developing station and a cleaning station and mechanical means in
the form of augers for effecting recirculation of toner back and
forth between the stations, as required.
DETAILED DESCRIPTION
Cleaning System
The system includes a separate magnetic brush cleaning station with
means for recirculating toner from the cleaning station to the
developing unit.
FIG. 1 shows schematically a copying machine having a developer 1
in which magnetic brush 2 rotates as shown and a separate cleaning
station 3 in which magnetic brush 4 rotates as shown. The units
have bucket systems 5 and 6 which transport mixtures of toner and
magnetic carrier upward into reservoirs placed atop the magnetic
brush drums. These drums contain stationery magnets in core
assemblies (not shown) which attract the magnetic carriers so the
mixtures are carried past the photoconductor on drum 7 by the
abrasive surfaces of the magnetic brush drums. Developer unit 1
also includes a replenisher unit 8 which adds toner to the system
and a mixing auger 9a which mixes carrier and toner. This machine
has two modes of operation.
In the development mode, toner is placed on the photoconductor
surface and appropriate areas by development magnetic brush 2. Most
of this toner is subsequently transferred to paper 9 supplied by
paper feed unit 10 at transfer station 11. This paper is
subsequently fed through fuser 12 to stack 13. Residual toned
images left on the photoconductor after transfer are subsequently
removed by cleaner magnetic brush 4. Operation in this mode can
continue until the concentration of toner in the cleaner unit 3
reaches a level which prevents effective cleaning. When this occurs
a recirculation cycle is obtained by the operation of relay coil
14, the contacts of which change the electrical bias applied to
various components so that toner is deposited on the photoconductor
surface by cleaner magnetic brush 4 to be subsequently carried by
the revolution of drum 7 to developer magnetic brush 2 which
attracts and removes this toner. The following discussion of both
modes of operation assumes that the carrier in developer unit 1 is
coated with a material such as tetrafluoroethylene which
triboelectrically places a positive charge on the toner particles
and that the carrier in cleaner unit 3 is coated with a material
such as ethyl cellulose which triboelectrically places a negative
charge on the toner particles. This combination produces effective
cleaning.
In the development mode, the photoconductor surface is first
charged negatively by charge corona wires 15 operating in
conjunction with grid wires 16. The photoconductor is subsequently
discharged in areas corresponding to the light areas of document 17
placed atop a glass plate traveling in the direction shown and
illuminated by lamps 18 which expose photoconductor through lens
assembly 19 and aperture 20. Erase lamp 21 is not used in this
mode. A negative bias is applied through contact 52 associated with
coil 14 to provide the conventional development electrode effect
which prevents the toning of background areas of the
photoconductor. Triboelectrically positively charged toner
particles from the mixture being carried by developer magnetic
brush 2 are deposited on the areas of the photoconductor which have
not been fully discharged. Most of these particles are subsequently
transferred to the surface of paper 9 with the aid of an
electrostatic field produced by the application of a negative
voltage to transfer corona wire 22. The photoconductor is
subsequently discharged by a fluorescent erase lamp 23 driven by
ballast 24 which is in turn activated by the AC line through
contact 25 of the relay. Subsequently toner particles remaining on
the photoconductor are triboelectrically charged negatively by
contact with the carrier in cleaner unit 3 and are attracted by the
electrostatic field produced through the application of a positive
electrical bias to the unit through relay contact 25.
In the recirculation mode, the transfer of relay contact 25 shuts
off the mechanical drive in paper feed unit 10 and turns off erase
lamp 23. The transfer of relay contact 27 applies a positive
voltage to corona wire 22 which in turn charges the photoconductor
positively. The transfer of relay contact 26 applies a negative
bias to cleaner unit 3. The electrostatic field thus produced
transfers triboelectrically negatively charged toner particles from
the mixture traveling on cleaner magnetic brush 4 to the
photoconductor surface. The transfer of contacts 28 and 29 prevent
the application of voltage to corona wires 15 and grid wires 16
preventing the deposition of toner on these wires. The transfer of
contact 25 applies an AC voltage to ballast 30 which drives
fluorescent erase lamp 21 discharging the photoconductor. The
transfer of relay contact 52 applies a higher negative bias to
developer unit 1 so that toner particles on the photoconductor
surface which are triboelectrically charged positively by contact
with the carrier transported by developer magnetic brush 2 are
removed from the photoconductor surface.
During the operation of the machine in the development mode, each
rotation of cam 31 with drum 7 transfers contact 32 applying the AC
line voltage to line 33 advancing counter 34, which is designed to
close contact 35 when the number of revolutions taken by drum 7
indicates that the toner concentration in cleaning unit 3 may be
reaching a level that prevents efficient cleaning. The closure of
contact 35 then applies AC line voltage to relay coil 14 and the
closure of its associated contact 36 holds this voltage on the coil
through contact 32 when this contact transfers. At this time the
transfer of contact 37 also applies the line voltage coming through
contact 32 and 36 to line 38 resetting counter 34. When contact 32
transfers again after one revolution of drum 7 the circuit path by
which coil 14 is held and through which the voltage is applied to
line 38 is broken. Since the counter has been reset by this time,
contact 35 has opened so that coil 14 is dropped. Thus, when
counter 34 reaches the count for which it was designed relay coil
14 is actuated and held for a single revolution of drum 7 producing
the required toner recycling operation.
Alternately and more desirably a means for sensing toner
concentration within the cleaner unit 3 may be provided so that a
toner recirculation cycle is automatically provided when and only
when this concentration reaches a level at which effective cleaning
is jeopardized. In any case, the recirculation cycle may be
automatically provided when required at the end of copy run rather
than during them. Operation intervention can also be used to start
a recirculation cycle when cleaning appears to be a problem.
FIG. 2 shows schematically alternate means for providing for the
transfer of toner from cleaner unit 3 to developer unit 1. The
motion of document 17 and the operation of paper feed unit 10 are
synchronized with the rotation of photoconductor drum 7 so that
images to be copied are placed on defined areas of the
photoconductor surface. Cam surfaces 39, which rotate with the
photoconductor drum define the photoconductor areas between these
image areas. These surfaces move segments 40, transferring contacts
which switch the operation of components as described in reference
to FIG. 1 so that toner is deposited on these areas by cleaner
magnetic brush 4 and picked up from these areas by developer
magnetic brush 2. This configuration has the advantage of not
requiring a separate recirculation cycle and of maintaining a low
toner concentration in the cleaner by recirculating toner after
cleaning residual toner from each image area, but sufficient space
for this operation must be provided between image areas on the
photoconductor.
FIGS. 3 and 4, which are partial sectional views taken as shown by
section lines 3--3 and 4--4 respectively in FIG. 1, show alternate
means of providing for toner recirculation in which the circuits
for switching the operation of components are eliminated. The
cleaner magnetic brush 4 is divided into two sections 4a and 4b
turning together but separated by an insulating section 4c. An
electrical bias favorable to the removal of toner from the
photoconductor is placed on section 4a, which covers the width of
the photoconductor on which images are placed as defined by the
slot in aperture 20 and the position of paper 9, while an
electrical bias favorable to the deposition of toner on the
photoconductor from cleaner magnetic brush section 4b is applied to
this section. Charging corona wires 15, associated grid wires 16,
transfer corona wire 22, and erase lamp 23a extend across the
photoconductor width used for imaging. Erase lamp 21a and an
additional charging corona wire 41 are placed between the developer
and cleaner units, to which a voltage is applied so that the
photoconductor is charged in a manner favorable to the transfer of
toner from cleaner magnetic brush section 4b to the surface of the
photoconductor, extend across the photoconductor width used for
toner recirculation. Augers may be included in cleaner unit 3 to
aid in the circulation of carrier and toner within the unit. This
configuration provides for continuous development and toner
recirculation by photoconductor charging and discharging and by
toner transfer mechanisms as described in reference to FIG. 1.
Alternately another material capable of being charged and
discharged by corona units may be used in place of the extra
photoconductor width.
FIG. 5 shows alternate means for providing for the circulation of
toner. The mixture of carrier and toner from developer unit 39 and
cleaner unit 40 is continuously circulated by augers 42 and 43
operating in the reservoirs of the units and by augers 44 and 45
connecting the units. Because of the large quantities of material
in the units, a relatively slow rate of material transport between
the units is required to maintain approximately the same toner
concentration in both units. The photoconductor drum 7 and
conventional means for charging and imaging the photoconductor on
its surface and conventional means for transferring toner images
from its surface to paper (not shown) are provided as described
before. Assuming that a magnetic carrier coated with a material
such as tetrafluoroethylene which triboelectrically places a
positive charge on toner particles is used, a negative electrical
bias is placed on the developing unit to provide the development
electrode effect which prevents toning background areas. A positive
preclean corona wire 45a is used to discharge the photoconductor
before it passes by the cleaning station. The use of this wire may
be considered an alternative to the use of an erase lamp as
previously described in reference to FIG. 1. A negative bias which
may be higher than that applied to developer unit 39 is applied to
cleaner unit 40. Since the photoconductor has been discharged this
bias produces an electrostatic field which effects the removal of
triboelectrically positively charged toner particles from the
photoconductor to the carrier mixture in the cleaner unit.
The systems described in this disclosure have advantages over
conventional cleaning methods of eliminating the air system with
its filter replacement and noise problems and of recirculating the
toner picked up by the cleaning station reducing the rate of toner
usage. The configuration shown in FIGS. 1 through 4 have the
advantage over that shown in FIG. 5 of allowing a wide choice of
carrier coatings for use in the cleaner unit, which appears
desirable. The configurations shown in FIGS. 2 through 5 have the
advantage over that shown in FIG. 1 of allowing continuous
operation without separate recirculation cycles. The configurations
shown in FIGS. 3 and 4 require additional areas on the
photoconductor or other material for toner recirculation.
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