U.S. patent number 3,788,275 [Application Number 05/266,905] was granted by the patent office on 1974-01-29 for magnetic shielding apparatus.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to William J. Hanson.
United States Patent |
3,788,275 |
Hanson |
January 29, 1974 |
MAGNETIC SHIELDING APPARATUS
Abstract
A device in which a magnetic flux field forms a shield of
magnetic granules about a shaft member journaled for rotary
movement. The shield is arranged to prevent contamination of the
shaft member. The foregoing abstract is neither intended to define
the invention disclosed in the specification nor is it intended to
be limiting as to the scope of the invention in any way.
Inventors: |
Hanson; William J. (Pittsford,
NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
23016475 |
Appl.
No.: |
05/266,905 |
Filed: |
June 28, 1972 |
Current U.S.
Class: |
399/104; 118/506;
277/410 |
Current CPC
Class: |
F16C
33/82 (20130101); F16C 33/72 (20130101); G03G
15/0942 (20130101); F16J 15/43 (20130101) |
Current International
Class: |
F16J
15/40 (20060101); F16J 15/43 (20060101); F16C
33/72 (20060101); G03G 15/09 (20060101); G03g
013/08 () |
Field of
Search: |
;118/637,308-312,506
;277/80 ;192/21.5 ;117/1NQ ;355/1NQ ;346/1NQ |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaplan; Morris
Attorney, Agent or Firm: James J. Ralabate et al.
Claims
What is claimed is:
1. A device for preventing magnetic granules from contaminating a
tubular shaft member journaled for rotary movement, including:
bearing means mounted on the shaft member; and
magnetic means disposed externally of and internally of said
tubular member, each said magnetic means being interposed between
said bearing means and the flow of magnetic granules, said magnetic
means producing a magnetic flux field entrapping and aligning the
granules into a shield located between the shaft member and said
magnetic means to prevent granules from contaminating said bearing
means.
2. A device as recited in claim 1, further including means for
impelling the granules entrapped by the shield formed by said
magnetic means in a direction substantially away from said bearing
means.
3. A device as recited in claim 2, further including a frame member
adapted to support said bearing means so as to enable the shaft
member to rotate relative thereto.
4. A device as recited in claim 3, wherein said magnetic means
includes a magnet member mounted on the shaft member spaced from
said frame member.
5. A device as recited in claim 4, wherein said impelling means
includes a threaded portion on said frame member aligned generally
opposed from said magnetic member and spaced therefrom, said
threaded portion being adapted to move the entrapped granules in a
direction substantially away from said bearing means as the shaft
member rotates.
6. A device as recited in claim 3, wherein said magnetic means
includes a magnet member mounted on said frame member spaced from
the shaft member.
7. A device as recited in claim 6, wherein said impelling means
includes a threaded portion on the shaft member aligned generally
opposed from said magnet member and spaced therefrom, said threaded
portion being adapted to move the entrapped granules in a direction
substantially away from said bearing means as the shaft member
rotates.
8. A development apparatus for an electrostatographic printing
machine of the type having conveyor means for transporting a
developer mix comprising magnetic carrier granules and toner
particles into contact with an electrostatic latent image to create
a toner powder image thereof, wherein the improvement includes:
a tubular rotary driven shaft member;
bearing means for rotatably supporting said shaft member; and
magnetic means disposed externally of and internally of said
tubular member, each said magnetic means being interposed between
said bearing means and the flow of carrier granules, said magnetic
means producing a magnetic flux field entrapping and aligning the
carrier granules into a shield located between said shaft member
and said magnetic means to prevent granules from contaminating said
bearing means.
9. An apparatus as recited in claim 8, further including means for
impelling the granules entrapped by the shield formed by said
magnetic means in a direction substantially away from said bearing
means.
10. An apparatus as recited in claim 9, further including a frame
member adapted to support said bearing means so as to enable said
shaft member to rotate relative thereto.
11. An apparatus as recited in claim 10, wherein said magnetic
means includes a magnet member mounted on said shaft member spaced
from said frame member.
12. An apparatus as recited in claim 11, wherein said impelling
means includes a threaded portion on said frame member aligned
generally opposed from said magnetic member and spaced therefrom,
said threaded portion being adopted to move the entrapped granules
in a direction substantially away from said bearing means as said
shaft member rotates.
13. An apparatus as recited in claim 10, wherein said magnetic
means includes a magnetic member mounted on said frame member
spaced from said shaft member.
14. An apparatus as recited in claim 13, wherein said impelling
means includes a threaded portion on said shaft member aligned
generally opposed from said magnetic member and spaced therefrom
said threaded portion being adapted to move the entrapped granules
in a direction substantially away from said bearing means as said
shaft member rotates.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to a development apparatus of an
electrostatographic printing machine, and more particularly
concerns a device for preventing contamination of the development
apparatus.
In the process of electrostatographic printing, an electrostatic
charge pattern corresponding to an original document to be
reproduced is recorded on an insulating medium. A viewable record
is produced by developing the electrostatic charge pattern with
particles to form a powder image thereof. Thereafter, the visible
powder image is fused to the insulating medium, or transferred to a
suitable support material and fused thereto.
The electrostatic charge pattern or latent image is developed by
bringing a developer mix into contact therewith. Various types of
developer mixes may be employed. However, generally, the developer
mix comprises dyed or colored thermoplastic particles, known in the
art as toner particles, which are mixed with coarser carrier
granules, such as ferromagnetic granules. The carrier granules
charge the toner particles to the correct polarity by
triboelectrification. As the developer mix is brought into contact
with the electrostatic latent image, the electric field exerts a
force on the charged toner particles. When this force is large
enough to break the carrier-to-toner bond, the toner particles then
attach themselves to the electrostatic latent image.
Development systems utilize suitable rotary impeller systems or
bucket conveyor systems to transport the developer mix from a sump
storing a supply thereof to the electrostatic latent image.
Impeller systems or conveyor systems generally include shaft
members journaled for rotary movement in suitable rolling contact
bearings, i.e., roller or ball bearings, to achieve the requisite
movement of developer mix.
The dynamic load characteristics of the bearing generally determine
its life expectancy. Defects in the bearings, mounting,
lubrication, or contamination may accelerate failure and shorten
bearing life. Magnetic carrier granules frequently enter the
bearing and act as a contaminant thereof. In this manner, the
carrier granules contaminate the bearings supporting the shaft for
rotary movement resulting in a reduction in the life expectancy
thereof. This substantially reduces the life expectancy of the
conveyor or impeller system and, in turn, that of the development
apparatus.
Accordingly, it is a primary object of the present invention to
improve the development apparatus by substantially reducing
contamination thereof.
SUMMARY OF THE INVENTION
Briefly stated, and in accordance with the present invention, there
is provided a device arranged to prevent contamination of a shaft
member journaled for rotary movement.
In the particular device illustrated, bearing means rotatably
support the shaft member with magnetic means being interposed
between the bearing means and a flow of magnetic granules. A
magnetic flux field produced by the magnetic means entraps and
aligns the magnetic granules into a shield. Thus, in accordance
with the present invention, the shield of granules located between
the shaft member and the magnetic means prevents subsequent
granules from contaminating the bearing means. Moreover, the
present invention also includes means for impelling the granules
entrapped by the shield in a direction substantially away from the
bearing means.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will become
apparent upon reading the following detailed description and upon
reference to the drawings, in which:
FIG. 1 is a sectional elevational view of a development apparatus
having the present invention therein and adapted for usage in an
electrostatographic printing machine; and
FIG. 2 is a partial, fragmentary sectional view of the shielding
device used in the development apparatus depicted in FIG. 1.
While the present invention will hereinafter be described in
connection with a preferred embodiment, it will be understood that
it is not intended to limit the invention to that embodiment. On
the contrary, it is intended to cover all alternatives,
modifications and equivalents as may be included within the spirit
and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
For a general understanding of the illustrated development
apparatus in which the present invention may be incorporated,
reference is had to the drawings wherein like reference numerals
have been used throughout to designate like elements. FIG. 1
schematically illustrates the development apparatus used in an
electrostatographic printing machine for producing copies from an
original document. As in all electrostatographic machines, an
electrostatic latent image is formed on an insulating medium.
Developer mix is brought into contact with the latent image and
toner particles deposited thereon to form a powder image thereof.
Thereafter, the powder image is transferred to a sheet of support
material to which it may be permanently adhered by a suitable
fusing device. This concept was originally disclosed in U.S. Pat.
No. 2,297,691 issued to Carlson in 1942.
The development unit depicted in FIG. 1 is of the type referred to
in the art as a "magnetic brush development system." In a magnetic
brush development system, a magnetizable developer mix having
carrier granules and toner particles is continually moved through a
directional flux field to form a brush of developer material. The
brush comprises a magnetic member with a mass of developer mix
adhering thereto by magnetic attraction. This chain-like
arrangement of developer mix simulates the fibers of a brush.
Development is achieved by bringing the brush of developer mix into
contact with the electrostatic latent image.
Referring once again to FIG. 1, the principle components of the
development unit depicted therein are developer housing 10,
conveyor means or paddle wheel 12, transport means or roll 14, and
developer means or roll 16. Paddle wheel 12 is a cylindrical member
with scoops or buckets 20 mounted around the periphery thereof. As
paddle wheel 12 rotates, it elevates developer mix 18 from the
lower region or sump of housing 10 to the upper region thereof.
When developer mix 18 reaches the upper region of housing 10, it is
lifted from buckets 20 to transport roll 14 by the magnetic flux
field produced by fixed magnets 22 disposed interiorly thereto.
Preferably, alternate buckets 20 of paddle wheel 12 have apertures
in the root diameters thereof enabling developer mix 18 carried in
those areas to fall back to the sump of developer housing 10. As
developer mix 18 falls back to the sump, it cascades over shroud 24
which is preferably a tubular member having an aperture or
longitudinally extending slot 26 in the lower region thereof. In
this way, developer mix 18 is recirculated such that the carrier
granules thereof are continually agitated to mix with fresh toner
particles and generate a strong triboelectric charge therebetween.
As developer mix 18, in buckets 20 of paddle wheel 12, approach
transport roll 14 the magnetic flux field produced by magnets 22
mounted fixedly therein attract developer mix 18 thereto. Transport
roll 14 moves developer mix 18 in an upwardly direction by the
frictional force exerted between the roll surface and developer mix
18. Metering blade 28 is provided to control the amount of
developer mix 18 carried over the top of transport roll 14. The
surplus developer mix is sheared from transport roll 14 and falls
in a downwardly direction toward paddle wheel 12. Surplus developer
mix falls through the apertures of paddle wheel 12 in a downwardly
direction into the sump of developer housing 10.
Developer mix 18, which passes metering blade 28, is carried over
transport roll 14 to developer roll 16 and into development zone 30
located between photoconductive surface 32 of drum 34 and developer
roll 16. The electrostatic latent image recorded on photoconductive
surface 32 is developed by contact with moving developer mix 18.
The charged areas of photoconductive surface 32 electrostatically
attract toner particles from the carrier granules of developer mix
18. At the exit of development zone 30, magnetic fields in a
direction generally tangential to developer roll 16 continue to
secure thereto denuded carrier granules (carrier granules which had
toner particles stripped therefrom) and unused developer mix. Upon
passing from development zone 30, the denuded carrier granules and
unused developer mix enter a region relatively free from magnetic
forces and fall from developer roll 16 in a downwardly direction
into the lower region of developer housing 10. As the denuded
carrier granules and unused developer mix descend, mixing baffle 36
diverts the flow from the ends toward the center of developer
housing 10 to provide mixing in this direction. Paddle wheel 12
includes a shaft member or hub 38 rotatably mounted on frame member
or developer housing 10. Buckets 20 are secured fixedly to hub
member 38.
Cylindrical shroud 24 serves to control the fall of unused
developer mix and denuded carrier granules such that they mix with
toner particles rather than simply falling into the sump of
developer housing 10. Furthermore, shroud 24 isolates, from
developer mix 18, an interior cylindrical enclosure which is used
to house toner dispenser 40. Toner dispenser 40 contains a fresh
supply of toner particles 42 arranged to pass through slot 26 in
shroud 24 and into the stream of developer mix 18. Having toner
particles introduced into the developer mix at this location
insures that the particles cannot be carried into development zone
30 without some degree of mixing with the carrier granules.
Additional toner particles are added to developer mix 18 in order
to replace the particles used in forming images so as to maintain
the concentration thereof substnatially constant providing
substantially uniform image developability.
Development begins when clutch gear 44 meshes with gear 46 which is
secured to paddle wheel 12. Clutch gear 44 rotates in the direction
of arrow 48 to drive gear 46 in the direction of arrow 50, thereby
causing paddle wheel 12 to also revolve in the direction of arrow
50. In operation, the development unit positions developer roll 16
adjacent the photoconductive surface 32 in operative communication
therewith to develop the electrostatic latent image formed thereon
with toner particles. Thereafter, toner particles are transferred
to the support material forming a toner powder image of the
original document thereon. In the preferred embodiment thereof,
development roll 16 includes stationary magnets 52 disposed
interiorly and arranged to attract developer mix 18 thereto from
transport roll 14.
As hereinbefore indicated paddle wheel 12 is journaled for rotary
movement by suitable bearing means such as roller bearings or ball
bearings mounted on opposed end portions of hub member 38 providing
support therefore. Carrier granules may contaminate the bearing
member and reduce the life expectancy of the paddle wheel assembly.
In order to preclude the occurrence of the aforementioned carrier
granule contamination, magnetic means are mounted on shroud 24 and
developer housing 10. The aforementioned relationship between the
magnetic means and bearing means is indicated more clearly in FIG.
2.
As shown in FIG. 2, developer housing 10 includes a generally
cylindrical interior surface for housing roller bearing 54. Outer
race 56 of roller bearing 54 is mounted on the cylindrical interior
surface of developer housing 10, while inner race 58 of bearing 54
is mounted on hub member 38 of paddle wheel 12. A pair of such
bearing members are mounted on hub member 38 in the region of
opposed end portions to provide a simple support therefore. Hence,
in this manner, paddle wheel 12 is journaled for rotary movement to
raise developer mix 18 from the lower region of developer housing
10 to the upper region thereof. Preferably, paddle wheel 10 is
interposed between shroud 24 and developer housing 10 and is
substantially concentric about the longitudinal axis of shroud 24.
In order to permit the addition of toner particles to toner
dispenser 40 or the replacement thereof, end cap 60 is removably
mounted on developer housing 10. As developer mix 18 is advanced in
an upwardly direction, magnetic carrier particles tend to move
toward bearing members 54 resulting in contamination thereof.
However, in the present invention, a shield of magnetic carrier
particle granules is formed via the utilization of magnetic means
operatively associated with impelling means to prevent carrier
granules from contaminating bearing 54. Magnetic means or ring
magnet 62 has the exterior circumferential surface thereof mounted
on developer housing 10 and is spaced axially from bearing member
54 by arcuate spacer 64. The interior circumferential surface of
magnetic means 62 is spaced from hub member 38. Hub member 38
includes a threaded portion 66 aligned so as to be opposed from
magnetic means 62. By way of example, threaded portion 66 may be a
suitable pipe thread. As carrier granules 68 advance toward bearing
member 54 they are attracted to magnetic means or ring magnet 62
via the magnetic flux field formed thereby. The magnetic flux field
is arranged to form a shield of carrier granules between hub member
38 and ring magnet 62. As hub member 38 rotates the exterior
threaded portion 66 thereof is arranged to impel carrier granules
68 in a direction substantially away from bearing member 54.
In order to further protect bearing member 54 from carrier granule
contamination an interior magnetic member 72 is mounted on shroud
24 in operative communication with internal threaded portion 74
e.g., a suitable pipe thread, of hub member 38. The magnetic means
or ring magnet 72 has the interior circumferential surface thereof
mounted on shroud 24. The exterior circumferential surface of ring
magnet 72 is spaced from hub member 38. The interior threaded
portion 74 of the hub member 38 is spaced from and aligned with the
exterior circumferential surface of ring magnet 72. As carrier
granules 68 advance toward bearing member 54, they are attracted to
ring magnet 72. Ring magnet 72 is arranged to form a magnetic flux
field which aligns and entraps carrier granules 68 to form shield
71 between the interior circumferential surface of hub member 38
and ring magnet 72. Hub member 38 includes an interior threaded
portion 74 substantially aligned with the exterior circumferential
surface of ring member 72. Threaded portion 74 is adapted to impel
carrier granules 68 away from bearing member 54 as hub member 38
rotates.
From the foregoing, it is apparent that the shielding arrangement
of the present device substantially improves the development
apparatus of an electrostatographic printing machine by reducing
contamination thereof. Furthermore, the carrier granules are
prevented from entering the bearing members supporting the paddle
wheel in rotary movement, thereby improving its life
expectancy.
It is, therefore, evident that there has been provided in
accordance with this invention, a device for substantially reducing
contamination of the development apparatus of an
electrostatographic printing machine that fully satisfies the
objects, aims and advantages set forth above. While this invention
has been described in conjunction with specific embodiments
thereof, it is evident that many alternatives, modifications and
variations will be apparent to those skilled in the art.
Accordingly, it is intended to embrace all alternatives,
modifications and variations that fall within the spirit and broad
scope of the appended claims.
* * * * *