U.S. patent application number 09/453053 was filed with the patent office on 2002-06-27 for drawn, grooved stainless steel magnetic developer roll and process for making same.
Invention is credited to JUGLE, KIP L., MAGGIO, TIMOTHY M., ROSDAHL, ROBERT E. JR..
Application Number | 20020078568 09/453053 |
Document ID | / |
Family ID | 23799024 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020078568 |
Kind Code |
A1 |
MAGGIO, TIMOTHY M. ; et
al. |
June 27, 2002 |
DRAWN, GROOVED STAINLESS STEEL MAGNETIC DEVELOPER ROLL AND PROCESS
FOR MAKING SAME
Abstract
A drawn stainless steel magnetic development roll having a
coating-free developer-receptive surface, and a process for making
a development magnetic roll drawn from stainless steel and having a
developer-receptive, non-abrasive integral surface. The present
invention provides a process for making a novel magnetic roll by
cold drawing stainless steel rolls to have a desired grooved
surface finish, diameter, straightness, runout, and other
mechanical tolerance requirements.
Inventors: |
MAGGIO, TIMOTHY M.;
(ONTARIO, NY) ; ROSDAHL, ROBERT E. JR.; (ONTARIO,
NY) ; JUGLE, KIP L.; (BLOOMFIELD, NY) |
Correspondence
Address: |
THOMAS L TULLY
PERMAN & GREEN LLP
425 POST ROAD
FAIRFIELD
CT
06430
|
Family ID: |
23799024 |
Appl. No.: |
09/453053 |
Filed: |
December 2, 1999 |
Current U.S.
Class: |
29/895.3 ;
492/30; 492/36 |
Current CPC
Class: |
G03G 2215/0634 20130101;
G03G 15/0928 20130101; Y10T 29/4956 20150115 |
Class at
Publication: |
29/895.3 ;
492/30; 492/36 |
International
Class: |
B21D 053/00 |
Claims
What is claimed:
1. Hollow magnetic developer roll for use in an electrophotographic
imaging machine, comprising a drawn hollow non-magnetic stainless
steel roll having formed in the outer surface of the wall thereof a
plurality of narrow axial grooves, each having a maximum depth of
between about 0.01 mm and 0.5 mm, uniformly-spaced around the other
periphery of the roll.
2. A developer roll according to claim 1 in which said axial
grooves are hemispherical in cross-section.
3. A developer roll according to claim 2 in which said axial
grooves have a maximum depth between about 0.1 mm and 0.45 mm.
4. A developer roll according to claim 3 in which said arial
grooves have a maximum depth of about 0.4 mm.
5. A developer roll according to claim 1 in which said axial
grooves are uniformly spaced from each
other--,center-to-center,--by a distance between about 1.5 mm and
2.5 mm.
6. A developer roll according to claim 5 in which said axial
grooves are uniformly spaced by a distance of about 1.9 mm.
7. A developer roll according to claim 1 in which the opposed ends
of the hollow roll are counterbored inwardly a short distance to
render the wall thickness of the roll uniform at said ends.
8. A developer roll according to claim 1 in which the thickness of
the wall is between about 2.5 mm and 3.5 mm.
9. Process for producing a hollow stainless steel magnetic
developer roll for use in an electropholographic imaging machine
and having improved receptivity for electrophotographic developer
materials, comprising cold-drawing a hollow non-magnetic stainless
steel roll to the desired wall thickness, and cold-drawing a
plurality of narrow axial grooves in the outer surface of the wall
thereof, each having a maximum depth of between about 0.01 mm and
0.5 mm, uniformly spaced around the outer periphery of the
roll.
10. Process according to claim 9 in which said axial grooves are
formed by the displacement of stainless steel from the outer
surface of the roll during the cold-drawing step.
11. Process according to claim 9 which comprises cold-drawing axial
grooves which are hemispherical in cross-section.
12. Process according to claim 11 which comprises cold-drawing
axial grooves having a maximum depth between about 0.1 mm and 0.45
mm.
13. Process according to claim 12 which comprises cold drawing
axial grooves having a maximum depth of about 0.4 mm.
14. Process according to claim 9 which comprises spacing said axial
grooves by a distance between about 1.5 mm and 2.5 mm.
15. Process according to claim 14 which comprises spacing said
axial grooves by a distance of about 1.9 mm.
16. Process according to claim 9 which comprises the step of
counterboring the--inner surface at the--opposed ends of the
grooved roll inwardly a short distance to render the wall thickness
of the roll uniform at said ends.
17. Process according to claim 9 in which the thickness of the wall
is between about 2.5 mm and 3.5 mm.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to a development apparatus
for ionographic or electrophotographic imaging and printing
apparatuses and machines, and more particularly is directed to a
magnetic developer roll having a stainless steel sleeve.
[0002] Generally, the process of electrophotographic printing
includes charging a photoconductive member to a substantially
uniform potential to sensitize the surface thereof. The charged
portion of the photoconductive surface is exposed to a light image
from either a scanning laser beam, an LED source, or an original
document being reproduced. This records an electrostatic latent
image on the photoconductive surface. After the electrostatic
latent image is recorded on the photoconductive surface, the latent
image is developed. Two-component and single-component developer
materials are commonly used for development. A typical
two-component developer comprises magnetic carrier granules having
toner particles adhering triboelectrically thereto. A
single-component developer material typically comprises toner
particles. Toner particles are attracted to the latent image,
forming a toner powder image on the photoconductive surface. The
toner powder image is subsequently transferred to a copy sheet.
Finally, the toner powder image is heated to permanently fuse it to
the copy sheet in image configuration.
[0003] A non-interactive magnetic brush development method employs
permanently magnetized carrier beads operating with a rotating
multipole magnet within a conductive and nonmagnetic sleeve, such
as of aluminum or stainless steel. Magnetic field lines form arches
in the space above the sleeve surface and form chains of carrier
beads. The developer mass is held in contact with the sleeve and
out of direct contact with the photoreceptor by gradients provided
by the multipole magnet. As the core rotates in one direction
relative to the sleeve, the magnetic field lines beyond the sleeve
surface rotate in the opposite sense, moving carrier in a tumbling
action which transports developer material along the sleeve
surface. The strong mechanical agitation very effectively dislodges
toner particles generating a rich powder cloud which can be
developed to the adjacent photoreceptor surface under the influence
of development fields between the sleeve and the electrostatic
image.
[0004] In magnetic brush developing, a hollow tube or roll
containing fixed magnets is used to move the developer to the
photoreceptor. As the tube, such as of stainless steel, rotates
around the magnets and through a sump of developer, the magnets
attract the metallic carrier beads in the developer. The carrier
beads closest to the magnetic roll become magnetized, enabling more
carrier beads to stick. As a result, the developer builds up to
form bristles like a brush. This attraction of developer to the
magnetic roll is called a magnetic brush. The magnetic force on the
magnetic roll is just enough to allow the developer to build up on
the roll. As the magnetic roll or tube continues to rotate, it
moves the developer brush past a trim bar. The trim bar limits the
length of the brush by shearing off the portions of the developer
bristles that extend beyond a certain length. The trim bar ensures
that a desired bead height is obtained.
State of the Art
[0005] Conventional stainless steel developer rolls, sleeves or
tubes, generally extruded or drawn, have smooth surfaces which are
not sufficiently receptive to electrophotographic developer
materials. Therefore their manufacture requires the subsequent step
of overspraying the surface with a developer-receptive layer such
as of tungsten carbide. This substantially increases the material
cost and manufacturing cost of such rolls. In addition such
coatings are not wear/scratch resistant over extended time periods.
Thus, these coatings permit wear/scratching to form on the toner
transporting means, which in turn adversely affects image copy
quality. Also, toner particles can permanently adhere to the
surface of such coatings which can result in undesirable high
background deposits on the resulting developed images.
SUMMARY OF THE INVENTION
[0006] The present invention provides a process for making a drawn
stainless steel development magnetic roll having a coating-free
developer-receptive surface. The present invention provides a
process for making a development magnetic roll drawn from stainless
steel and having a developer-receptive, non-abrasive integral
surface.
[0007] The present invention further provides a process of making a
magnetic roll having improved stability, durability, toner tribo
charging characteristics and toner loading characteristics. The
invention provides an electrophotographic printing system having a
developer sump with an uncoated magnetic roll that is of lower cost
and ease to manufacture.
[0008] The present invention also provides a magnetic roll and a
process for making a magnetic roll by cold drawing stainless steel
rolls having a desired grooved surface finish, diameter,
straightness, runout, and other mechanical tolerance
requirements.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1 is a schematic elevational view of an illustrative
electrophotographic printing or imaging machine or apparatus
incorporating a development roll having the features of the present
invention therein;
[0010] FIG. 2 is a developer station of FIG. 1;
[0011] FIG. 3 is a schematic illustration of the cold-drawing of a
stainless steel developer roll, tube or sleeve by pulling it
through a die having surface-scoring members;
[0012] FIG. 4 is a plan view, in partial cross-section, of a
non-magnetic stainless steel developer roll, tube or sleeve
according to the present invention;
[0013] FIG. 5 is a cross-sectional view taken along the line 5-5 of
FIG. 4, and
[0014] FIG. 6 is a cross-sectional view of the section 6 of the
roll, tube or sleeve of FIG. 5.
[0015] Since the art of electrophotographic printing is well known,
the various processing stations employed in the printing machine
will be shown hereinafter schematically and their operation
described briefly with reference thereto.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0016] Referring to FIG. 1 of the drawings, there is shown a
xerographic type reproduction machine 8 incorporating the magnetic
grooved stainless steel roll of the present invention, designated
generally by the numeral 80. Machine 8 has a suitable frame (not
shown) on which the machine xerographic components are operatively
supported. Briefly, and as will be familiar to those skilled in the
art, the machine xerographic components include a recording member,
shown here in the form of a rotatable photoreceptor 14. In the
exemplary arrangement shown, photoreceptor 14 comprises a drum
having a photoconductive surface 16. Operatively disposed about the
periphery of photoreceptor 14 are a charge corotron 18 for placing
a uniform charge on the photoconductive surface 16 of photoreceptor
14; an exposure station 22 where the previously charged
photocontuctive surface 16 is exposed to image rays of a document 9
being copied or reproduced; development station 24 where the latent
electrostatic image created on photoconductive surface 16 is
developed by toner; and transfer detack corotrons 28 and 30 for
assisting transfer of the developed image to a suitable recording
substrate material such as a recording sheet 32 brought forward in
timed relation with the developed image on photoconductive surface
16. Residual toner is removed from the photoconductive surface at
cleaning station 34.
[0017] Recording sheets 32a are brought forward to the transfer
area by feed roll pair 40, sheet guides 42,43 serving to guide the
sheet through an approximately 180.degree. turn prior to the
transfer area. Following transfer, the sheet 32 is carried forward
to a fusing station 48 where the toner image is fixed by fusing
roll 49. After fusing, the recording sheet 32 is discharged to an
output tray.
[0018] Further details of the construction and operation of
development station 22 of the present invention are provided below
referring to FIG. 2. Development station 24 includes a developer
housing 65 in which a toner dispensing cartridge 66 is rotatably
mounted so as to dispense tone particles downward into a sump area
assisted by the augers 67 and 68.
[0019] Continuing with the description of operation of developing
station 24, a developing member 80 is disposed in predetermined
operative relation to the photoconductive surface 16 of
photoreceptor 14, the length of developing member 80 being equal to
or slightly greater than the width of photoconductive surface 16,
with the functional axis of developing member 80 parallel to the
photoconductive surface and oriented at a right angle with respect
to the path of photoreceptor 14. Advancement of developing member
80 carries the developer blanket into the development zone in
proximal relation with the photoconductive surface 16 of
photoreceptor 14 to develop the electrostatic image therein.
[0020] With continued reference to FIG. 2, augers 67 and 68, are
mounted rotatably to mix and transport developer material. The
augers have blades extending spirally outwardly from a shaft. The
blades are designed to advance the developer material in the axial
direction substantially parallel to the longitudinal axis of the
shaft. As successive electrostatic latent images are developed, the
toner particles within the developer material are depleted. Fresh
toner particles are furnished to the developer material in the
chamber from the toner dispenser. The augers in the chamber of the
housing mix the fresh toner particles with the remaining developer
material so that the resultant developer material therein is
substantially uniform with the concentration of toner particles
being optimized. In this manner, a substantially constant amount of
toner particles are maintained in the chamber of the developer
housing.
[0021] The present magnetic member 80 includes a hollow drawn
stainless steel tube or sleeve 78 enclosing a magnetic assembly 81
containing fixed magnets which are used to move the developer to
the photoreceptor. As the tube rotates about the magnets and
through a sump of developer, the magnets attract the metallic
carrier beads in the developer. The carrier beads closest to the
magnetic roll become magnetized, enabling more carrier beads to
stick. As a result, the developer builds up to from bristles like a
brush. This attraction of developer to the magnetic roll is called
a magnetic brush. The magnetic force on the magnetic roll is just
enough to allow the developer to build up on the roll. The magnetic
force has little effect on the charge either on the toner or on the
photoreceptor. As the magnetic roll or tube continues to rotate, it
moves the developer brush past a trim bar 90. The trim bar limits
the length of the brush by knocking off the portions of the
developer bristles that extend beyond a certain length. The trim
bar ensures that a desired bead height is obtained.
[0022] According to the present invention, and as illustrated by
FIG. 3, a non-magnetic 300 series stainless steel sleeve having the
desired inner and outer diameters is formed by a conventional
cold-drawing method and drawbench apparatus used for producing
hollow, tubular stainless steel pipes and conduits. In such process
a seamed or seamless stainless steel sleeve is first cold-drawn by
pulling it on a mandrel or table through a circular draw die 90 of
the desired diameter to simultaneously or subsequently form a
plurality of axial depressions or straight grooves 92 having the
desired depth and uniform spacing around the outer circumference of
the formed sleeve. The grooves 92 are formed by displacing material
on the outer surface of the sleeve 78 by a corresponding plurality
of metal displacement members 91 projecting from the inner surface
of the die 90, to form the grooves 92 as the sleeve 78 is
cold-drawn to the desired diameter.
[0023] The depth and radius of the grooves 92 generally is between
about 0.01 mm and 0.5 mm, preferably between about 0.1 mm and 0.45
mm, and most preferably about 0.4 mm, but deeper grooves can be
formed to allow for any secondary surface-machining operation
necessary to meet specifications.
[0024] As illustrated by FIGS. 4, 5 and 6, the present non-magnetic
stainless steel developer rolls 78 as illustrated have a length "L"
of about 412 mm, an outer diameter "O.D." of about 63.4 mm, an
inner diameter of about 60.4 mm, and a wall thickness of about 3 mm
in areas between the longitudinal grooves 92.
[0025] In the illustrated embodiment, the grooves 92 are
hemispherical in cross-section is shown in FIG. 6, have a depth "d"
of about 0.4 mm and are uniformly spaced from one-another,
center-to-center, by a space "s" of about 1.5 mm to 2.5 mm around
the circumference of the roll 78. Thus, with the dimensions given,
there are about 105 straight grooves 92 evenly spaced by about 1.9
mm and substantially parallel along the length of the roll.
[0026] The grooves 92 illustrated by FIG. 6 are formed as
illustrated by FIG. 3, using hemi-cylindrical metal displacement
members 91 which displace the cold drawn aluminum from the surface
of the roll to increase the wall thickness in areas underlying the
grooves. For this reason counterbores 93 are made inwardly from
each end of the drum, tube or sleeve 92 and extending a distance of
about 11 mm to provide uniform inner diameter portions of about
60.6 mm for mounting purposes. Generally the wall thickness is
between about 2.5 mm and 3.5 mm, most preferably about 3 mm.
[0027] The present process is quicker and less expensive than the
prior conventional method of machining the outer surface of
stainless steel sleeves or tubes, and then spraying with a tungsten
carbide layer in order to produce enough surface geometry or
roughness to help transport developer material. The present process
produces this desired result in an integral, un-coated drawn and
grooved stainless steel sleeve or tube, while avoiding the need for
abrasive coatings which can deteriorate, wear away and shed over
prolonged periods of use.
[0028] Also, the present cold-drawing process enables the reduction
of the thickness of the wall of the present stainless steel sleeves
or tubes, while meeting the requirements of high mechanical
strength.
[0029] Maximum Electrical Conductivity Requirements: The developer
roll has a requirement to be conductive, as cited below, but not
too conductive. The eddy current heating of the shell imposes this
limit. Eddy currents are the result of moving a conductor through a
magnetic field, similar to operation of an electrical
generator.
[0030] Eddy current heating scales with a) the square of the
relative speed between the magnet and the shell, b) with the square
of the radial component magnitude of the magnetic field, c)
approximately linear with the shell wall thickness, and d)
inversely linear with the electrical resistivity (linear with the
conductivity).
[0031] Higher speed machines, i.e., 100+ PPM process capability,
using two component development technologies, produce higher
developer roll rotational velocities. This in turn requires
stronger magnetic field profiles to maintain control over the
developer material. And both of these effects in turn result in
potentially higher eddy current losses or head loads with in the
developer housing.
[0032] For traditional aluminum developer rolls or shells,
experimental measurements indicated eddy current losses on the
order of 15 or more watts per developer roll. As a result,
non-magnetic stainless steel shells are preferred since they result
in significant reduction of the eddy current losses.
[0033] Recent modeling work indicates that for the developer
housing as in FIG. 2, magnetic configuration running at a surface
speed of 1270 mm/sec{50 ips}, the eddy current losses should be
about 16 watts for an aluminum shell and only about 4 watts for a
stainless steel shell.
[0034] Similar computations have been done for a TurboMaze type of
development system with eddy losses of 12 watts for an aluminum
shell and only 5 watts for a non-magnetic stainless steel shell.
This modeling assumed a 30.8 mm ID tube, with 0.9 mm thick walls, a
0.25 mm clearance to the mag roll assembly, 16 keystones poles each
22.5 degrees wide and 7 mm deep at a Br of 2.250 Koe, with the
magnet rotating relative to the shell at 1000 rpm.
[0035] Thin Wall Requirement: The thin wall requirement arises from
several objectives. First, the thinner the wall, the closer the
magnet assembly can be located relative to the developer material.
Since magnetic fields due to any magnetic assembly decrease at
least as rapidly as the 3.sup.rd power of the distance from the
magnetic, small changes in wall thickness are significant. Second,
the thinner the wall thickness, the lighter the overall part
weight. This provides benefits in a) lower start up inertial loads
hence lower initial drive torque requirements and b) in lower
system weight and hence potentially easier serviceability.
[0036] High Mechanical Strength: The mechanical strength
requirements arise from the need to maintain dimensional tolerances
over the entire length and circumference of the roll. The magnets
and developer material interact and effectively apply a significant
and non-uniform pressure on the exterior surface of the shell. With
the above cited desired thin walls, a high mechanical strength is
required to prevent deflection of the tube and maintain the
required xerographic tolerances.
[0037] Other embodiments and modifications of the present invention
may occur to those skilled in the art subsequent to a review of the
information presented herein; these embodiments and modifications,
as well as equivalents thereof, are also included within the scope
of this invention.
* * * * *