U.S. patent number 3,638,614 [Application Number 04/855,002] was granted by the patent office on 1972-02-01 for electrostatic latent image development apparatus.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Ryland F. Rogers, Eugene F. Young.
United States Patent |
3,638,614 |
Young , et al. |
February 1, 1972 |
ELECTROSTATIC LATENT IMAGE DEVELOPMENT APPARATUS
Abstract
Apparatus for effecting development of an electrostatic latent
image comprising a plurality of magnetic developing rollers
positioned with intersecting magnetic force fields for effecting a
blanket of developing material extending about and between the
developing rollers adjacent an electrostatic latent image-bearing
surface. A cylindrical roller, which may be electrically biased, is
positioned between the magnetic developing rollers adjacent the
electrostatic latent image bearing surface to enhance image
development.
Inventors: |
Young; Eugene F. (Henrietta,
NY), Rogers; Ryland F. (Webster, NY) |
Assignee: |
Xerox Corporation (Rochester,
NY)
|
Family
ID: |
25320087 |
Appl.
No.: |
04/855,002 |
Filed: |
September 3, 1969 |
Current U.S.
Class: |
399/269;
399/270 |
Current CPC
Class: |
G03G
15/09 (20130101); B82Y 15/00 (20130101) |
Current International
Class: |
G03G
15/09 (20060101); G03g 013/00 () |
Field of
Search: |
;118/621,623,637
;117/17.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Medley, H. C. Development of Electrostatic Images. IBM Technical
Disclosure Bulletin, August 1959, Vol. 2, No. 2..
|
Primary Examiner: Stein; Mervin
Assistant Examiner: Millstein; Leo
Claims
What is claimed is:
1. Apparatus for developing a support surface carrying latent
electrical charges selectively retained in image configuration
including
a first magnetic field emitting means to convey a quantity of
magnetizable developer material in contact with a support surface
to be developed,
a second magnetic field emitting means spaced therefrom with the
respective magnetic fields intersecting to convey developer
material across the space therebetween in contact with the latent
electrical charges to effect the development thereof, and
means positioned between said first and second magnetic field
emitting means to support developer material conveyed across the
space therebetween in contact with the support surface.
2. Apparatus for developing a support surface having latent
electrical charges selectively retained in image configuration
including
a first magnetic field emitting means to move a quantity of
magnetizable developer material in contact with a support surface
having latent electrical charges selectively retained in image
configuration,
a second magnetic field emitting means spaced therefrom with the
respective emitted magnetic fields intersecting to move
magnetizable developer material in contact with the support surface
through the space between said first and second magnetic field
emitting means to effect the development of the latent electrical
charges selectively retained in image configuration, and
means positioned between said first and second magnetic field
emitting means to support developer material in contact with the
support surface as the developer material is moved between said
magnetic field emitting means in response to the intersecting of
their respective magnetic fields.
3. Apparatus for developing a support surface having latent
electrical charges selectively retained in image configuration
including
a plurality of spaced cylinders rotatably supported adjacent a
support surface having latent electrical charges selectively
retained in image configuration to convey a quantity of
magnetizable developer material thereto for effecting the
development thereof,
magnetic field producing means supported within each of said
cylinders to emit a magnetic field passing therethrough and
intersecting with the magnetic field emitted from within another of
said spaced cylinders,
means to rotate said cylinders to convey a magnetizable developer
material into contact with the support surface and across the space
between said cylinders in response to said intersecting magnetic
fields for effecting the development of the latent image on the
support surface, and
means positioned between said plurality of spaced cylinders
adjacent the support surface to support the magnetizable developer
material in brushlike tufts in response to the magnetic fields
emitted through said cylinders.
4. The apparatus of claim 3 wherein said means to support the
magnetizable developer material in brushlike tufts in response to
the magnetic field emitted through said cylinders includes
a rotatable cylinder supported adjacent the latent image bearing
support surface with the magnetizable developer material passing
therebetween.
5. Apparatus for developing a support surface having latent
electrical charges selectively retained in image configuration
including,
a plurality of spaced cylinders rotatably supported adjacent a
support surface having latent electrical charges selectively
retained in image configuration to convey a quantity of
magnetizable developer material thereto for effecting the
development thereof,
magnetic field producing means supported within each of said
cylinders to emit a magnetic field passing therethrough and
intersecting with the magnetic field emitted from within another of
said spaced cylinders,
means to rotate said cylinders to convey a magnetizable developer
material into contact with the support surface and across the space
between said cylinders in response to said intersecting magnetic
fields for effecting the development of the latent image on the
support surface, and
an electrically conductive rotatable cylinder supported adjacent
the latent image-bearing support surface between adjacent pairs of
said spaced cylinders to support the magnetizable developer
material in brushlike tufts in response to the magnetic fields
emitted through said cylinders.
6. The apparatus of claim 5 wherein said electrically conductive
cylinder is electrically biased to a potential of approximately 250
volts.
7. Apparatus for developing latent electrostatic charge patterns on
a support surface comprising,
a first magnetic field emitting means for conveying a quantity of
magnetizable developer material over the support surface to be
developed,
a second magnetic field emitting means for conveying a quantity of
magnetizable developer material from said first magnetic field
emitting means over the support surface to be developed, said
second magnetic field emitting means being spaced from said first
magnetic field emitting means such that the respective magnetic
fields are in overlapping relationship with each other, and
means positioned between said first magnetic field emitting means
and said second magnetic field emitting means for supporting
developer material conveyed from said first magnetic field emitting
means to said second magnetic field emitting means in contact with
the support surface to be developed.
8. Apparatus for developing latent electrostatic charge patterns on
a support surface comprising,
a first magnetic field emitting means for moving a quantity of
magnetizable developer material over the support surface to be
developed,
a second magnetic field emitting means for moving a quantity of
magnetizable developer material over the support surface to be
developed, said second magnetic field emitting means being spaced
from said first magnetic field emitting means with the respectively
emitted magnetic fields intersecting therebetween to support
magnetizable developer material across the space between said first
and said second magnetic field emitting means, and
means positioned between said first and said second magnetic field
emitting means for supporting developer material in contact with
the support surface to be developed as the developer material is
transported from said first magnetic field emitting means to said
second magnetic field emitting means.
9. Apparatus for developing latent electrostatic charge patterns on
a support surface comprising,
a first cylindrical member supported for rotation adjacent a
support surface having latent electrostatic charge patterns thereon
which are to be developed,
a first magnetic field producing means supported within said first
cylindrical member for attracting a quantity of magnetizable
developer material to the surface of said cylindrical member for
movement of said cylindrical member over said support surface,
a second cylindrical member supported for rotation adjacent said
support surface and spaced from said first cylindrical member,
a second magnetic field producing means supported within said
second cylindrical member, the field from said second magnetic
field producing means extending across the space between said first
and said second cylindrical members into the field of said first
magnetic field producing means to attract a quantity of
magnetizable developer material from the surface of said first
cylindrical member to the surface of said second cylindrical member
for movement by said second cylindrical member over said support
surface, and
means positioned between said first and said second cylindrical
members for supporting the magnetizable developer material
proximate to the support surface as the developer material is moved
across the space between said first and said second cylindrical
members.
10. Apparatus for developing latent electrostatic charge patterns
on a support surface comprising,
a first cylindrical member supported for rotation adjacent a
support surface having latent electrostatic charge patterns thereon
which are to be developed,
a first magnetic field producing means supported within said first
cylindrical member for attracting a quantity of magnetizable
developer material to the surface of said cylindrical member for
movement by said cylindrical member over said support surface,
a second cylindrical member supported for rotation adjacent said
support surface and spaced from said first cylindrical member,
a second magnetic field producing means supported within said
second cylindrical member, the field from said second magnetic
field producing means extending across the space between said first
and said second cylindrical members into the field of said first
magnetic field producing means to attract a quantity of
magnetizable developer material from the surface of said first
cylindrical member to the surface of said second cylindrical member
for movement by said second cylindrical member over said support
surface, and
a support member of generally cylindrical configuration positioned
intermediate said first and said second cylindrical members and
adapted for rotation to support the magnetizable developer material
proximate to the support surface as the developer material is moved
across the space between said first and said second cylindrical
members.
11. Apparatus for developing latent electrostatic charge patterns
on a support surface comprising,
a plurality of cylindrical members supported in spaced relationship
to each other adjacent said support surface for moving magnetizable
developer material over said support surface,
magnetic field producing means supported within said cylindrical
members, the respective fields from said magnetic field producing
means extending across the spaces between adjacent ones of said
cylindrical members in overlapping relationship to attract
magnetizable developer material from the surfaces of precedingly
adjacent cylindrical members to the surfaces of succeedingly
adjacent cylindrical members as the developer material is moved by
said cylindrical members over said support surface, and
means positioned between adjacent pairs of said cylindrical members
for supporting the magnetizable developer material proximate to the
support surface as the developer material is moved across the
spaces between said cylindrical members.
12. Apparatus for developing latent electrostatic charge patterns
on a support surface comprising,
a plurality of generally cylindrical members supported in rotatable
spaced relationship to each other adjacent said support surface for
moving magnetizable developer material in brushlike tufts over said
support surface,
magnetic field producing means supported within said cylindrical
members, the respective fields from said magnetic field producing
means extending across the spaces between adjacent ones of said
cylindrical members in overlapping relationship, said overlapping
fields forming brushlike tufts of magnetizable developer material
on the surfaces of said cylindrical members and attracting the
magnetizable developer material from the surfaces of precedingly
adjacent cylindrical members to the surfaces of succeedingly
adjacent cylindrical members as the developer material is moved by
said cylindrical members over said support surface, and
means positioned between adjacent pairs of said cylindrical members
for supporting the magnetizable developer material proximate to the
support surface as the developer material is moved across the
spaces between said cylindrical members.
Description
BACKGROUND OF THE INVENTION
This invention relates to the development of electrostatic latent
images and, in particular, to an apparatus for developing
electrostatic latent images utilizing a magnetizable carrier
material and an electroscopic toner powder.
More specifically, this invention relates to a magnetic brush
development apparatus having an extended development zone.
In the method of development of electrostatic latent images by the
application of electroscopic toner powder (for example, of the type
disclosed in Carlson U.S. Pat. No. 2,940,934) through the use of a
magnetizable carrier material, referred to in the art as magnetic
brush development, there is generally employed a single-magnetic
brush closely spaced adjacent a surface carrying latent electrical
charges in image configuration. As the electrostatographic art has
progressed, the time in which the latent image is in contact with
the development system has decreased because of the increased
linear speed of the latent image-bearing surface. Therefore, many
attempts have been made to increase the length of this development
zone. However, due to space constraints required of a commercial
reproducing apparatus the addition of a plurality of development
units has not been effective to solve this problem. One attempt to
increase the effective length of the development zone without
adding to the size of the development unit has been by positioning
two magnetic brush developing rollers adjacent each other and
adjacent an electrostatic latent image-bearing surface such that
the magnetic fields emitted from the development rollers intersect
to convey developer material across the space between the rollers
and in contact with the latent electrical charges on the
image-bearing surface. While such a system provides an increased
effective development zone and has proven to be very successful, it
has been found in certain applications wherein the magnetizable
carrier material is of a certain size, that the weight of the
developer material is such that gravitational forces overcome the
magnetic field emitted from the developing rollers and sufficient
contact is not maintained between the developer material and the
electrostatic latent image-bearing surface throughout the entire
development zone as is desired.
SUMMARY OF THE INVENTION
Therefore, it is an object of this invention to improve apparatus
for developing electrostatic latent images.
Another object of this invention is to increase the effective
development zone of developing apparatus.
A further object of this invention is to insure complete contact of
developer material with an electrostatic latent image-bearing
surface the development of which is effected by a plurality of
magnetic brush development rollers positioned adjacent one another
and the electrostatic latent image-bearing surface such that their
magnetic fields intersect to convey developer material across the
space therebetween in contact with the latent image-bearing
surface.
These and other objects are attained in accordance with the present
invention wherein there is provided a plurality of magnetic brush
developing units positioned adjacent each other and an
electrostatic latent image-bearing surface and including a
rotatable cylindrical member positioned between the developing
units and the latent image-bearing surface to effect image
development throughout the extended developing zone.
Further objects of this invention, together with additional
features contributing thereto and advantages accruing therefrom,
will be apparent from the following description of one embodiment
of the invention when read in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a mechanical schematic of an automatic xerographic
reproducing machine utilizing the invention of this
application;
FIG. 2 is a front perspective view of the developing apparatus to
better illustrate the developing units and the cylindrical roller
which enhances development of the electrostatic latent image
throughout the extended developing zone; and
FIG. 3 is a schematic section of the apparatus shown in FIG. 2
taken along lines 3--3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, there is illustrated a cross section mechanical
schematic of an automatic xerographic reproducing machine utilizing
this invention. As in all electrostatographic systems, illustrated
by the xerographic reproducing machine shown, a light image of a
document to be reproduced is projected 3 onto a photosensitive
surface 1 to form an electrostatic latent image thereon.
Thereafter, the latent image is developed 4 to form an
electroscopic toner powder image in the configuration of the latent
image on the photoreceptor surface. The powder image may then be
transferred 5 to a support material to which it may be permanently
fixed as by heat fusing, or the toner powder may be permanently
affixed to the photoreceptive surface depending on the method of
electrostatographic imaging employed as is well known in the
art.
Referring now to FIGS. 2 and 3, the developing apparatus 50 extends
the width of the photoreceptor 1 and is substantially enclosed
except for an opening adjacent the photoreceptor whereat
development of the latent electrostatic image is effected, and an
opening 11 upon which a toner powder dispenser 10 is positioned to
replenish the toner depleted from the developer mixture during
development of the electrostatic images. Within the housing of the
developer apparatus there is a sump 51 at the lowermost portion of
the housing containing developer material comprising magnetizable
carrier material and colored electroscopic toner particles. The
toner particles are many times smaller than the carrier material
and, due to a triboelectric relationship therebetween,
substantially uniformly coat the carrier material.
The developing apparatus 50 is positioned within the automatic
xerographic reproducing machine adjacent to the photoreceptor 1 by
suitable brackets and braces appropriately secured to the
developing apparatus and the frames of the machine. A suitable
mounting 12 is provided on the top of the developing apparatus
between cover plates 52 and 53 to position and retain the toner
powder dispenser 10.
Development of the electrostatic latent image is effected by a
blanket of developing material formed between a pair of adjacent
magnetic rollers 70 and 80 positioned such that their magnetic
force fields intersect to effect formation of a blanket of
developing material upon the rollers 70 and 80, and in the space
therebetween adjacent the photoreceptor 1. The magnetic rollers 70
and 80 comprise outer cylinders 71 and 81, respectively, of a
nonmagnetic material, such as aluminum, extending the width of the
developer housing with elongated bar magnets 72 and 82,
respectively, extending nearly the full length of each cylinder.
The bar magnets 72 and 82 are each supported, for example, on a
ferromagnetic bar 73 having rod 74 secured to each end, as by
welding, and securely fastened in mounting blocks 75 appropriately
secured to side frame plates 54 of the developer apparatus. The
outer cylinders 71 and 81 of nonmagnetic material are each mounted
for rotation within the developer housing by means of suitable
bearing surfaces 76 carried by the side frame plates 54 of the
developer housing (FIG. 2). One end of the cylinder is enclosed by
a cap 77 having a central opening therein, through which the rod
portion 74 passes, and is rotatably supported thereabout in the
frame plate 54 by the bearing 76. The driven end is enclosed by an
end cap 78 rotatably supported in suitable bearings in the side
frame plate 54 and having a drive gear 89 secured thereto to effect
rotation of each cylinder. The rotational drive for all other
rotary components of the developing apparatus 50 is derived from
drive gear 89 by means of a suitable timing belt (not shown)
engaging suitable drive connections on each component. In this
manner the outer cylinders may be rotatably driven about the
stationary elongated bar magnets 72 and 82. The polar orientation
of the elongated bar magnets is arranged such that the magnetic
force fields project through the walls of the nonmagnetic cylinders
71 and 81 to form the magnetizable carrier material into a
brushlike configuration in a manner well known in the art.
As best shown in FIGS. 2 and 3, the peripheral walls of the
cylinders 71 and 81 are positioned in closely spaced relationship
adjacent to one another. During a development cycle when both
cylinders are rotating in synchronism about their respective
stationary bar magnets 72 and 82, the brush bristles produced by
action of the magnetic field emanating from the magnets acting upon
the magnetizable carrier material will form on the upper region of
the cylinder 71 within the magnetic field emanating from magnets 72
and the under surface of the electrostatic image-bearing
photoreceptor 1. These bristles are formed during the developing
cycle, and are produced by the magnetic field from the bar magnets
72. When the bristles are moved by the cylinder 71 out of the
influence of magnet 72 beyond the closest distance between the
photoreceptor 1 and the cylinder 71, they are attracted by the
greater magnetic field of the magnet 82 which is stronger at this
point than the diminished strength of the magnetic field attributed
to the magnet 72. The developer material is carried therealong
during rotation of the cylinder 81 until the material reaches a
point beyond the development zone whereat the magnet field is
diminished and the carrier material and toner particles drop off
the cylinder 81 and back into the sump portion 51 of the developer
apparatus. A suitable stripping mechanism such as a nonmagnetizable
doctor blade 96 may be utilized to insure that the magnetizable
developer material is removed from the cylinder 81.
During movement of the developer material through the development
zone between the two cylinders 71 and 81, the magnetizable
developer material is in the form of a blanket extending the entire
distance (FIG. 3) between the two cylinders and in contact with the
photoreceptor 1. Therefore, the width of the development zone is
larger than the sum of the individual development zones for either
of the magnetic rollers 71 or 81.
In order to insure that the blanket of developer material contacts
the electrostatic latent image-bearing surface throughout the
extended development zone, a rotatable wire brush or other cylinder
60 is positioned between the magnetic developing rollers 70 and 80,
adjacent the latent image-bearing surface 1. The cylinder 60 is
rotatably supported in suitable bearing surfaces carried by side
frame plates 54 and may be positively driven, or act as an idler,
and functions to support the developer material as it passes from
cylinder 71 to cylinder 81. The cylinder 60 prevents the developer
tufts from collapsing under their own weight as they pass from the
magnetic field emanating from roller 70 into the magnetic field
emanating from roller 80. In addition to the cylinder 60 supporting
the developer material in brushlike tufts adjacent the latent
image-bearing surface, by applying a suitable electrical bias, such
as 250 volts, to the cylinder a development electrode effect will
occur to further enhance image development.
After the developer material has effected development of the latent
image on the photoreceptor surface, the material is removed from
the cylinder 81 and passed to the sump portion 51 of the developer
apparatus. A developer conveyor 20 is rotatably mounted within the
side frame plates 54 of the developer apparatus by suitable
bearings and carries the developer material from the sump portion
to be introduced to the magnetic developing rollers 70 and 80. The
developer conveyor comprises a plurality of spaced buckets 21
carried by a belt 22 appropriately driven by a shaft 23 rotatably
mounted in suitable bearing surfaces in the side frame plates 54
and driven by means of a gear (not shown) suitably secured to one
end of the shaft 23 and engaging a suitable drive system.
While there has been shown and described one embodiment of the
invention, it is intended that the invention be not limited to the
exact form shown and described or to anything less than the whole
of the invention as set forth in the appended claims.
* * * * *