U.S. patent number 3,724,422 [Application Number 05/097,856] was granted by the patent office on 1973-04-03 for magnetic brush developing apparatus.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Salvatore Latone, Michael R. Stanley.
United States Patent |
3,724,422 |
Latone , et al. |
April 3, 1973 |
MAGNETIC BRUSH DEVELOPING APPARATUS
Abstract
A magnetic brush developing apparatus for use in an
electrostatic printing machine having a plurality of brushes
arranged with their axes in parallel and in a plane inclined
relative to the horizontal and at such an angle as to allow
gravitational forces to return the developing material to a point
wherein the magnets associated with the brushes may continuously
form bristles thereon.
Inventors: |
Latone; Salvatore (Rochester,
NY), Stanley; Michael R. (Pittsford, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
22265461 |
Appl.
No.: |
05/097,856 |
Filed: |
December 14, 1970 |
Current U.S.
Class: |
399/269; 118/623;
222/DIG.1; 118/636 |
Current CPC
Class: |
G03G
15/09 (20130101); Y10S 222/01 (20130101) |
Current International
Class: |
G03G
15/09 (20060101); G03g 013/00 (); B05b
005/02 () |
Field of
Search: |
;118/636,637,623,624,DIG.24 ;117/17.5 ;222/56,57,DIG.1 ;355/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
H C. Medley, "Development of Electrostatic Images," IBM Digest,
Vol. 2, No. 2, August 1959..
|
Primary Examiner: Stein; Mervin
Assistant Examiner: Millstein; Leo
Claims
What is claimed is:
1. A magnetic brush apparatus for applying developing material to
electrostatic latent images in an electrostatic printing machine of
the type utilizing a moving, flexible photoreceptor plate having a
development portion thereof disposed at an angle relative to the
horizontal plane and wherein movement of the plate along the
portion is inclined upwardly comprising
a housing having a sump for containing developing material,
a plurality of magnetic developing brushes in said housing, each
having a roller with a periphery upon which bristles of magnetic
developing material are adapted to be formed.
said rollers each having an axis of rotation, said axes being
substantially parallel to the latent images surface of said plate
along said development portion,
a first of said brushes being arranged at the lower side of said
portion for receiving developing material from said sump and the
last of said brushes arranged at the upper side of said portion and
being adapted to direct unused material in said housing,
said brushes including means for forming a continuous path of
movement of the developing material from said first brush to the
last brush between said brushes and the photoreceptor plate,
and
means for directing the movement of said unused developing material
as it flows under the influence of gravity to the sump to be
received by said first brush.
2. The apparatus as claimed in claim 1 wherein said rollers for
said magnetic brushes are rotated in the same direction.
3. The apparatus in claim 2 wherein said rollers are rotated in the
direction of movement of the upwardly moving photoreceptor
plate.
4. A magnetic brush apparatus for applying developing material to
electrostatic latent images in an electrostatic printing machine of
the type utilizing a moving, flexible photoreceptor plate having a
development portion thereof disposed at an angle relative to the
horizontal plane and wherein movement of the plate along the
portion is inclined upwardly comprising
a housing having a sump for containing developing material,
a plurality of solely magnetic developing brushes in said housing,
each having a roller with a periphery upon which bristles of
magnetic developing material are adapted to be formed,
said rollers each having an axis of rotation, said axes being
substantially parallel to the latent image surface of said plate
along said development portion,
a first of said brushes being arranged at the lower side of said
portion for receiving developing material from said sump and the
last of said brushes arranged at the upper side of said portion and
being adapted to direct unused material in said housing,
means defining a path of flow for said unused developing material
between said last brush and said first brush, said path defining
means being formed to permit the flow of the material along said
path of flow under the influence of gravity, and
means positioned in said path of flow for subjecting the material
to a mixing action as the material moves under the influence of
gravity.
5. The apparatus of claim 4 wherein said development portion is
flat and wherein said roller axes lie substantially in a plane.
Description
This invention relates to improvements in developing apparatus for
electrostatic printing machines, and particularly to improvements
in magnetic brush developing devices for accomplishing highly
efficient, fast speed development during the printing of
electrostatically produced reproductions.
The invention has particular advantages for an electrostatic
copying machine of the type employing a photoreceptor in the form
of an endless belt. Generally, in endless belt printing machine
configurations which employ a plurality of magnetic brushes, the
brushes are arranged for developing purposes with a run of the belt
in the horizontal orientation. With the housing for the developing
apparatus having a plurality of magnetic brushes arranged in a line
generally parallel to the plane of the belt run, both of which are
in horizontal attitude, development material must be moved from the
finishing end of the housing to the starting end by means of
special conveying mechanisms such as conveying belts, augers,
material-throwing impellers and the like as well as special
arrangements for maintaining proper material mix and triboelectric
characteristics. These special devices also require drive
mechanisms for imparting the desired action. For large developing
apparatus employing two or more magnetic brushes, these special
provisions add considerable cost to the developing apparatus, take
up much needed space and require extra maintenance and cost.
Therefore, it is the principal object of the present invention to
improve electrostatic printing machines of the type utilizing an
endless belt photoreceptor and a plurality of magnetic brushes.
Another object of the invention is to maximize the use of
development material presented to an image to be developed in
electrostatic printing machines which employ magnetic brush
development.
These and other objects of the present invention are acquired by
the use of a photoreceptor endless belt having its development run
at an inclined plane and a plurality of magnetic brushes having
their axes arranged in parallel and in a plane generally parallel
to the plane of the photoreceptor belt at the zone of development
therefor. The brushes are arranged so that the developing material
in bristle form is moved up the incline plane whereupon, after
moving past the last brush in the string of brushes, the material
is returned for reuse to the beginning end of the string by gravity
forces. Enhancement is further provided by arranging the movement
of the electrostatic belt in an upward direction along this incline
plane and to impart a direction of rotation to the magnetic brushes
which is in the same direction as the movement of the belt.
A preferred form of the invention is shown in the accompanying
drawings in which:
FIG. 1 is a schematic sectional view of an electrostatic
reproduction machine embodying the principles of the invention;
FIG. 2 is an enlarged elevational view of a magnetic brush
developing apparatus utilized in the machine shown in FIG. 1, with
parts broken away;
FIG. 3 is a partial sectional view of the magnetic brush developing
system showing the recirculation flow path of developing
material;
FIG. 4 is an elevational view of another side of the housing shown
in FIG. 3 and showing the drive mechanism for the magnetic
brushes;
FIG. 5 is an isometric view of a cross-mixing baffle device
utilized in the flow path of the developing material; and
FIG. 6 is a top view of the cross-mixing baffle in relation to one
of the magnetic brushes.
For a general understanding of an electrostatic processing system
in which the invention may be incorporated, reference is had to
FIG. 1 in which various components of a system are schematically
illustrated. As in all electrostatic systems such as a xerographic
machine of the type illustrated, a light image of an original to be
reproduced is projected onto the sensitized surface of a
xerographic plate to form an electrostatic latent image thereon.
Thereafter, the latent image is developed with an oppositely
charged developing material comprising carrier beads and smaller
toner particles triboelectrically adhering thereto to form a
xerographic powder image, corresponding to the latent image on the
plate surface. The powder image is then electrostatically
transferred to a support surface to which it may be fixed by a
fusing device whereby the powder image is caused permanently to
adhere to the support surface.
The electrostatically attractable developing material commonly used
in magnetic brush developing apparatus comprises a pigmented
resinous powder referred to here as "toner" and a "carrier" of
larger granular beads formed with steel cores coated with a
material removed in the triboelectric series from the toner so that
a triboelectric charge is generated between the toner powder and
the granular carrier. The magnetizable carrier also provides
mechanical control for the formation of brush bristles by virtue of
magnetic fields so that the toner can be readily handled and
brought into contact with the exposed xerographic surface. The
toner is then attracted to the electrostatic latent image from the
carrier bristles to produce a visible powder image on an insulating
surface.
In the illustrated machine, an original 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. While upon the platen, an illumination system flashes light
rays upon the original thereby producing image rays corresponding
to the informational areas on the original. The image rays are
projected by means of an optical system 11 to an exposure station A
for exposing the photosensitive surface of a moving xerographic
plate in the form of a flexible photoconductive belt 12. In moving
in the direction indicated by the arrow, prior to reaching the
exposure station A, that portion of the belt being exposed would
have been uniformly charged by a corona device 13 located at a belt
run extending between belt supporting rollers 14 and 15. The
exposure station extends between the roller 14 and a third support
roller 16, and the belt run between these rollers is encompassed
entirely by the exposure station for minimizing the space needed
for the belt and its supporting rollers.
The exposure of the belt surface to the light image discharges the
photoconductive layer in the areas struck by light, whereby there
remains on the belt a latent electrostatic image in image
configuration corresponding to the light image projected from the
original on the supporting platen. As the belt surface continues
its movement, the electrostatic image passes around the roller 16
and through a developing station B located at a third run of the
belt and in which there is positioned a developing apparatus
generally indicated by the reference numeral 17. Suitable means
(not shown) such as, vacuum panels or tensioning means may be
utilized for maintaining the belt flat in all three belt runs, and
additionally, the belt run related to the development zone B is
maintained at an inclined plane. The developing apparatus 17
comprises a plurality of magnetic brushes which carry developing
material to the adjacent surface of the upwardly moving inclined
photoconductive belt 12 in order to provide development of the
electrostatic image.
As the developing material is applied to the xerographic belt,
toner particles in the development material are attracted
electrostatically to the belt surface to form powder images. As
toner powder images are formed additional toner particles are
supplied to the developing material in proportion to the amount of
toner deposited on the belt during xerographic processing. For this
purpose, a toner dispenser generally indicated by reference numeral
18 is used to accurately meter toner, upon demand, to the developer
material in the developing apparatus 17.
The developed electrostatic image is transported by the belt 12 to
a transfer station C located at a point of tangency on the belt as
it moves around the roller 15 whereat a sheet of copy paper is
moved at a speed in synchronism with the moving belt in order to
accomplish transfer of the developer image. There is provided at
this station a transfer roller 19 which is arranged on the frame of
the machine for contacting the non-transfer side of each sheet of
copy paper as the same is brought into transfer engagement with the
belt 12. The roller 19 is electrically biased with sufficient
voltage so that a developed image on the belt 12 may be
electrostatically transferred to the adjacent side of a sheet of
paper S as the same is brought into contact therewith, and also for
tacking the same on the roller 19. A stripping finger or air
puffing device 21 utilized for stripping the sheet from the roller
is provided to permit pick-up and continued movement of the sheet
by a vacuum conveying system 22. In tacking on the roller 19, each
sheet of paper travels only a short distance before being stripped
therefrom by the stripper 21. Devices such as gripper bars and
release elements mounted on the roller 19 may be utilized instead
of the stripper 21 for gripping the leading edge of each sheet of
copy paper to ensure proper positioning thereon and to effect the
release of a copy sheet at a precise time so as to strip the same
for pick-up by a conveying system. The timing of the release of
each edge relative to the sheet separation from the supply stack of
sheets may be for the same period of time.
There is also provided a suitable sheet transport mechanism adapted
to transport sheets of paper seriatim from a paper handling
mechanism generally indicated by the reference numeral 23 to the
developed image on the belt as the same is carried around the
roller 15. A programming device operatively connected to the
mechanism 23, the stripper device 21 and the illumination device
for producing an electrostatic latent image on the belt 12 is
effective to present a developed image at the transfer station C in
timed sequences with the arrival of a sheet of paper and being
coordinated with the activation of the stripper 21 at the precise
time that these elements are to function for their intended
purpose.
After the sheet is stripped from the belt 12, it is conveyed by the
conveying system 22 into a fuser assembly generally indicated by
the reference numeral 24 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. The remaining toner particles remaining as residue on
the developed images, background particles and those particles
otherwise not transferred are carried by the belt 12 to a cleaning
apparatus 25 positioned on the run of the belt between the rollers
14, 15 adjacent the charging device 13. The cleaning device
comprises a rotating brush, a corotron for neutralizing charges
remaining on the particles and discharge lamp for discharging any
remaining electrostatic charges on the belt. It will be appreciated
that the run of the belt adjacent the cleaning device is at an
incline angle relative to the horizontal as this run leaves the
uppermost roller 15 where a developed image is transferred. Such an
arrangement maintains the relatively straight line of copy sheet
movement which operatively cooperates with the printing belt 12 at
its highest point.
From the foregoing, it will be apparent that the configuration and
positioning of the processing devices for electrostatic
reproductions and the inclined angles of two of the runs are such
as to utilize fully all three runs of the photoconductive belt 12
so as to minimize its size as well as to optimize efficiency and
the utilization of machine space. The arrangement also results in a
machine which has a height that is ideal for operator that is,
waist high, especially in the provision of a paper path of movement
above the image processing apparatus. In this manner paper jams can
be attended to easily, without dismantling or involvement with
other apparatus in the machine, and without having to resort to
activities in the vicinity of the floor supporting the machine or
the lower regions thereof.
As shown in FIGS. 2 and 3, the developing apparatus comprises a
housing 26 having a generally rectangular cross section and a
length extending beyond the width of the belt 12. The housing 26 is
substantially closed except for an opening adjacent the
photoconductive belt 12 whereat development of the latent image is
effected. This housing serves as a container, closed at its ends,
by end walls 27 and 28 and supporting an inclined bottom wall 30
for containing developing material comprising carrier beads from
magnetizable material and colored electrostatic toner particles
which adhere electrostatically in great numbers to the carrier
beads.
Mounted for rotation within the developer housing are four magnetic
brushes 31, 32, 33, and 34 positioned with their axes in parallel
and below the selenium belt 12. The magnetic brush 31, comprising
outer cylinder 35, made of non-magnetizable material and extending
almost the length of the housing 26, is mounted for rotation by and
between the end walls 27, 28.
One end of the cylinder 35 is closed by a cap 36 which supports a
drive shaft 38 in axial alignment with the cylinder and is mounted
in suitable bearings on the end plate wall 27. The other end of the
cylinder is similarly supported by the wall 28. Within the cylinder
35 there is positioned elongated bar magnets 40, 41 extending
nearly the full length of the cylinder and being mounted therein by
means of suitable shafts (not shown) rotatably supported in the end
caps for the cylinder. These shafts on the magnets 40, 41 may be
adapted to be rotated by an external control device as will be
described hereinafter for rotating the bar magnets. In operation
during a development cycle, the brush cylinder 35 is rotated by way
of the drive shaft 38 and the magnets 40, 41 remain stationary.
The second, third and fourth magnetic brushes 32, 33 and 34 each
comprise a cylinder 42, 43, 44 respectively, end caps for the
respective cylinders, complement bar magnets and rotatably
supporting shafts therefor. Since each of the brushes 32, 33, 34 is
similar to the structure of the brush 31, further details are not
necessary to describe these brushes. Their only distinction lies in
the relative orientation of magnet polarities (see FIG. 3 for
preferred arrangement) and the inclusion of a pick-up magnetic
device 45 for the first brush 31. The pick-up device 45 includes
bar magnets supported by the magnets 40, 41 for the magnetic brush
31 for transporting developing material from the lower sump portion
of the housing 26 and to the adjacent periphery of the cylinder
35.
As shown in FIG. 3, the peripheral walls of the brush cylinder 35
and those for the other brushes are relatively close to each other.
During a development cycle when all cylinders are rotating in
unison in the same direction and with their respective magnetic
bars held stationary, the brush bristles produced by the influence
of the magnetic field emanating from the bar magnets acting upon
the magnetizable carrier beads in the developing material will form
on the upper region of the cylinder 35 between this cylinder and
the undersurface of the selenium belt 12. Bristles remain formed
during the developing cycle, being initiated by the influence of
the pick-up device 45 and maintained, during rotation of the
cylinder 35 produced by the magnetic field of the magnets 40, 41.
When bristles are moved out of the influence of the magnets 40, 41
beyond the closest distance between the belt 12 and the cylinder
35, they maintain formation by the influence of the magentic field
for the magnets associated with the brush 32, which influence is
stronger at this point than the diminished strength of the magnetic
field attributed to the magnets for the brush 31. The developing
material is carried during rotation of the cylinder 42 until they
in turn reach the stronger influence of the magnetic brush 33,
which effects the continued formation of bristles and movement of
the bristles until the influence of the last brush 34 is stronger
than the diminishing influence of the brush 33. After passing the
last brush 34, the cylinder 44 thereof transports the remaining
developing material around the same from which they will be
directed eventually to the sump of the housing 26 by gravity.
During movement of the carrier beads and toner through the
development zone B, the magnetic bristles and, therefore, the
development material, is in the form of a "magnetic blanket"
extending continuously over all of the brushes 31-34 for the entire
width of the development zone B wherein the material is disposed or
available to some degree for developing purposes. Control means,
not shown, may be operatively connected to the shafts associated
with each of the bar magnet pairs 40, 41 for each of the magnetic
brushes for rotating the pairs in unison in order to terminate the
formation of bristles on each of the brushes. In this manner, the
"magnetic blanket" over all of the brushes may be quickly
eliminated during the operating program for the reproduction
machine. Upon a restart of the machine, the control means may be
set to be activated as the machine is placed in standby condition
wherein all magnet pairs are oriented to operative positions. It
will be apparent that the width of the development zone B is larger
than the sum of the individual development zones for each of the
magnetic brushes. Further details regarding the formation and
effect of the "magnetic blanket" are described in the copending
application Ser. No. 830,285 assigned to the same assignee as the
present application.
Also mounted within the development housing 26 and below the
magnetic brush 31 is a paddle wheel impeller 46 having a plurality
of blades radially extending therefrom and having its ends
rotatably mounted in the end walls 27, 28 by means of a drive shaft
47. During a development cycle, the impeller 46 is rotated in the
direction shown by the arrow in FIG. 3 and serves to transport
development material toward the pick-up device adjacent the lower
surface of the magnetic brush 31 independent of the state of
levelness and the amount of carrier beads in the system. The
development material in this vicinity is picked up by the pick-up
magnet which commences the formation of bristles on the cylinder
35. As this cylinder rotates, the newly formed bristles come under
the influence of the magnets 40, 41 and the "magnetic blanket" for
the assembly 17 will be initiated.
The rotational motion for all of the rotary components of the
developing apparatus 17, as illustrated in FIG. 4, is derived by a
motor M-1 and a drive system comprising a pulley 48 secured to the
shaft of the motor, a smaller pulley 50 also secured to the shaft,
and timing belts 51, 52 for connecting the pulleys 48, 50
respectively, to the rotary components. Specifically, the belt 51
is drivingly engageable with suitable pulleys 53, 54 mounted on the
drive shafts for each of the magnetic brush cylinders 31, 32
respectively, an idler pulley 55 and pulleys 56, 57 secured to the
drive shafts for the magnetic brush cylinders 33, 34 respectively.
With this arrangement, the four magnetic brush cylinders rotate
with the same peripheral speeds, in the same direction and in a
direction which moves the "magnetic blanket" comprising magnetic
brush bristles upwardly in an inclined plane arranged at the same
angle as the angle of the plane which the belt 12 assumes in the
development run. The timing belt 52 connects the drive pulley 50
with a driven pulley 58 secured to the shaft 47 for the impeller 46
thereby assuring that the impeller and the magnetic brush cylinders
move in unison. The relative speed of the impeller 46 is slightly
less than the peripheral speeds of the magnetic brush cylinders but
incorporates a surface capacity which provides an excess of
development material being transported by the impeller which cannot
be picked up by the pick-up device 45 and will be carried around
the impeller and back into the sump of housing 26.
In order to optimize the length of the bristles during the
formation of the "magnetic blanket" upon the four cylinders, the
cylinder 35 has associated therewith a trimming blade 60 secured to
the end walls 27, 28 of the housing 26. This blade extends radially
toward the cylinder 35 and being spaced from the periphery thereof
a short distance equal to the desired length of the bristles to be
formed on each of the magnetic brush 31. The blade also smoothes
the developing material and contains the powder cloud in the
housing 26.
The depleted developing material which is carried beyond the
magnetic brush 34 or the last brush in the chain of magnetic
brushes that comprise the developing device, is conveyed back into
the housing 26 in order to be reused for development purposes. As
this material is moved by the cylinder 44, away from the
development zone B before being directed back into the sump of the
housing 26, it is directed by a longitudinal planar baffle plate 61
secured at its ends on the end walls 27, 28 for the developer
housing 26 to the upper end of a cross-mixing baffle generally
indicated by the numeral 62. Another baffle plate 63 mounted within
the housing 26 controls the movement of the development material
leaving the cross-mixing baffle 62 into working engagement with the
paddle wheel 46 for presenting the development material to the
pick-up magnet 45.
The cross-mixing baffle 62 is illustrated in FIGS. 5 and 6 and is
preferably formed from a single piece of metallic or plastic
material as by a single molding process. The baffle is formed with
a centrally disposed, longitudinal wall element 64 secured to and
spaced from the rear wall 30 of the developer housing 26 at an
angle slightly inclined to the vertical. The front side of the
central wall 64, or that side facing the magnetic brushes, is
formed with a plurality of deflector plates 65 which project
perpendicularly from the wall and are angled downwardly and
laterally relative to the vertical. In the illustrated baffle, six
of these deflector plates are provided and, in effect, form six
open-sided chutes for the flow of development material through this
side of the cross-mixing baffle. Similarly, the rear side of the
wall 64 is also formed with deflector plates, labeled 66, which
extend downwardly and laterally at an angle to the vertical that is
equal and opposite to that of the plates 65. Preferably, there are
enough deflectors 66 formed so as to provide seven conduits on the
rear of the wall 64 defined by the deflectors, the wall 64 and the
housing wall 30 so as to equalize cross flow in both
directions.
At the upper input end of the baffle 62 there is also formed as
integral structure a plurality of U-shaped guide elements which
serve as means for deflecting some developing material into the
front side of the baffle 62. Specifically, one of these guide
elements 67 receives some of the development material flowing
downwardly along the baffle 61 and directs this material along the
chute E defined by the two adjacent plates 65 near the end wall 27.
Similarly, another guide element 68 is arranged on the upper end of
the baffle 62 for directing development material down a chute
identified by the letter F. Extending along from the wall 27 toward
the wall 28, the cross-mixing baffle is also formed with additional
U-shaped guide elements 70, 71, 72, 73 which serve to collect and
direct development material into and downwardly into corresponding
chutes G, H, J and K. Within the confines of the guide element 73,
the end wall 28 and the housing wall 30 is an opening 74 provided
which serves to direct some development material into the chute
defined by the two adjacent plates 66 and the wall 30. This flow of
development material will be from left to right as viewed in FIGS.
5 and 6, as distinguished from the movement from right to left
produced by the chutes at the front side of the cross-mixing
baffle. Similarly, between the guides 72-73, 71-72, 70-71, 68-70
and 67-68, there are openings functionally similar to opening 74
for allowing the passage of development material therethrough for
directing this material into the chutes formed by two opposed
plates 66.
From the foregoing, it will be apparent that the development
material cascading down the baffle 61 will fall along the upper
longitudinal edge of the cross-mixing baffle 62 and that this
material will fall at random in fairly equal amounts through the
guides 67, 68, 70, 71, 72, 73 and through the openings therebetween
so that quantities of development material will be cascaded through
the baffle 62 on either side of the wall 64. That material which
falls through the baffle by virtue of the deflectors 65 on the
front side of the wall 64 will be moved or carried in successive
steps of movement from the right to the left, under action of
gravity. On the other hand, that development material which falls
between the wall 64 and the end wall 30 along the chutes defined by
the deflectors 66 will be carried along from the left to the right
in successive increments of movement.
From the illustrated cross-mixing baffle in FIGS. 5 and 6 with six
chutes on the front side of the wall 64 and seven chutes on the
back side of this wall so that exits of chutes are lined up with
the entrances of the next desired chutes, it will be appreciated
that during continuous recirculating movement of development
material throughout its flow path in the housing 26 comprising
movement around the paddle wheel 46, over the magnetic brushes 31,
32, 33, 34, across the baffle plate 61, and through the baffle 62,
13 such cycles of such movement of the material will result in any
quantity of the material being moved as viewed in FIG. 6, from the
housing wall 27 to the left to the wall 28 and back to the end wall
27 again. In FIG. 6, one of the magnetic brushes, labeled R, is
schematically illustrated in position relative to the baffle 62. In
this manner all of the development material utilized in the housing
26 may be carried from one side of the housing to the other
continuously thereby insuring at all times a homogenous mixture of
toner particles and carrier, and also to assure the presence of
fairly equal amounts of toner particles for each carrier particle.
Toner starvation, therefore, for any particular zone in a
transverse direction of the flow path in the developer housing will
be minimized. Such continuous cross-mixing of the developer mixture
will also enhance the triboelectric relationship between the
particles and carrier beads. It will also be appreciated that the
entire process of cross-mixing is accomplished by the action of
gravity upon the cross-mixing baffle 62 and without the need for
moving structural parts. By utilizing magnetic brushes having their
axes of rotation on an inclined plane and in parallel with the
inclined plane of a run of an endless photoreceptor belt,
recirculation of developing material in its continuous flow path is
accomplished by utilizing gravity instead of conveying devices,
mixing augers, throwing impellers, etc.
While the invention has been described with reference to the
structure disclosed, it is not confined to the details set forth;
but is intended to cover such modifications, or changes as may come
within the scope of the following claims.
* * * * *