Note: Descriptions are shown in the official language in which they were submitted.
~04Z65S
1 Specification
In well-known electrostatic printing processes, a surface bearing
a latent electrostatic image is developed by applying a developer
material comprising toner and a carrier material to the surface.
The small toner particles are held onto the surfaces of the relatively
larger carrier particles by electrostatic forces, which develop from
the contact between the toner and carrier particles producing tri-
boelectric charging of the toner and carrier to opposite polarities.
A portion of the applied triboelectrically charged toner is selec-
tively attracted to the image areas of the surface, and the remainderof the developer material is removed and allowed to recirculate to form
subsequent images.
In order to assure clear, sharp images, it is necessary that the
toner obtain a high triboelectric charge prior to development. This
has generally been effected in prior devices by selecting toner and
carrier materials which are widely separated in the triboelectric
series and by causing agitation and stirring of the developer material
prior to development. Further, the ratio of toner to carrier in the
developer material or mix is closely controlled. However, even when
the most optimum materials and mixing devices are utilized, the
triboelectric charge of the toner for a given toner-carrier ratio is
often insufficient to provide uniform high quality copy output.
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1 Various prior art developing mechanisms ;ncorporate a magnetic
brush comprising a cylindrical member or roll rotatably mounted relative
to a fixed magnetic field generating means onto which multicomponent
magnetic developer material is delivered. The magnetic field generating
means creates a magnetic field causing the magnetic developer to form
in bristle-like arrays over the surface of the cylindrical member or
roll as it is rotated into contact with an electrostatic latent image-
bearing surface.
For the surface of a magnetic brush roll to transport the mag-
netic developer to an electrostatic latent image-bearing surface, it
has previously been suggested in U.S. patent 3,040,704 to Bliss to
form the roll with a roughened external surface. However, attempts
to roughen the surface of the roll, which is formed of a non-magnetic
material such as aluminum, brass, or other soft alloy, by cutting
grooves, serrations, or knurls therein have resulted in the surface
being rapidly worn down by the abrasive action of the developer
material.
It also has been previously suggested in U.S. patent 3,219,014
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1 to Mott et al to sandblast the surface of a magnetic brush roll to
roughen the surface in a uniform pattern. However, sandblasting does
not make the surface rough enough. Furthermore, the wear of the sand-
blasted surface results in polished high spots to reduce the transport
capability for the developer material by the sandblasted surface.
Instead of forming the roughened surface directly in the magnetic
brush roll by grooves, serrations, knurls, or sandblasting, it has
previously been suggested in U.S. patent 3,246,629 to Shelffo to bond
a layer of irregular shaped particles to the surface of the magnetic
brush roll. This provides a random roughened surface.
In transporting the developer material to the electrostatic
latent image-bearing surface, the developer material is moved either
uphill or downhill depending on how the entire machine is arranged.
When the developer material is moved uphill, the surface of the
magnetic brush roll must be rough enough to enable the carrier par-
ticles to not slide relative thereto while being advanced uphill by
the magnetic brush roll.
While the magnetic brush roll of the aforesaid Shelffo patent
provides a roughened surface, this surface lacks the desired properties
of being non-abrasive and resilient. The abrasive surface of the
magnetic brush roll of the aforesaid Shelffo patent causes wear on
the carrier particles of the developer material, particularly in the
slight clearance area between the magnetic brush roll and the electro-
static latent image-bearing surface since the abrasive surface causes
the carrier particles to rub against each other and against the surface
of the magnetic brush roll. Lack or resiliency in the surface of the
magnetic brush roll of the aforesaid Shelffo patent prevents the sur-
face of the magnetic brush roll from giving to a slight degree when a
plurality of the carrier particles are disposed in engagement with
each other between the magnetic brush roll and the electrostatic latent
image-bearing surface with a slightly greater overall distance than
the clearance.
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1 The present invention satisfactorily solves the foregoing pro-
blems by providing a roughened surface which is both resilient and
non-abrasive as well as being abrasion resistant. The resilient and
non-abrasive surface of the magnetic brush roll of the present in-
vention increases the life of the carrier particles by reducing wear
of the carrier particles. Thus, wear on the carrier particles is
reduced not only by the non-abrasive surface of the magnetic brush
roll of the present invention, but its resiliency prevents wear when
the carrier particles are within the clearance area in which they
tend to have the greatest rubbing relation with the magnetic brush
roll and with each other.
Even though the surface of the magnetic brush roll of the present
invention is both resilient and non-abrasive~ it still is rough. As
a result, it provides the desired surface to enable the magnet;c
brush roll to advance the developer material or mix in an uphill
direction so that the carrier particles, which have the toner par-
ticles thereon, are advanced to the clearance area between the mag-
netic brush roll and the electrostatic latent image-bearing surface.
The present invention provides the improved magnetic brush roll
through having a resilient polymeric material secured to a non-magnetic
core. Because it is necessary to have a bias on the magnetic brush
roll, at least the surface of the resilient polymeric material must
be conductive. In its preferred form, the resilient polymeric
material of the magnetic brush roll of the present invention is homo-
geneous and conductive throughout.
An object of this invention is to provide a magnetic brush roll
having a non-abrasive and resilient surface that is rough or tex-
tured.
Another object of this invention is to provide a magnetic brush
roll having a resilient polymeric material as its surface.
The foregoing and other objects, features, and advantages of
the invention will be apparent from the following more particular
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1 description of preferred embodiments of the invention, as illustrated
in the accompanying drawing.
In the drawing:
FIGURE 1 is a schematic sectional view of a portion of an electro-
static reproduction machine having the magnetic brush roll of the
present invention.
FIGURE 2 is a fragmentary perspective view of a portion of one
form of the magnetic brush roll of the present invention.
FIGURE 3 is a fragmentary sectional view of another form of the
magnetic brush roll of the present invention.
Referring to the drawing and particularly FIGURE 1, there is
shown a portion of an electrostatic reproduction machine 10 having a
photoconductor drum 11, which functions as the electrostatic latent
image-bearing surface. The photoconductor drum 11 is rotated clock-
wise by being driven from a main power source.
The developer material, which comprises a mix of carrier parti-
cles and toner part;cles, is stored in a sump portion 14 of a magnetic
brush developer station 15. The toner particles are supplied to the
sump portion 14 from a toner cartridge (not shown) by a metering
cylinder (not shown) of a replenisher (not shown), which has an
agitator (not shown), through an opening 16 in the magnetic brush
developer station 15 to the sump portion 14 of the magnetic brush
developer station 15. Counter rotating augers 17 and 18 stir the
freshly added toner with the developer material in the sump portion
14 to assure complete mixing thereof as well as to enhance the
triboelectric charging of the developer material.
The developer material is metered from the sump portion 14 to a
transport portion 19 of the magnetic brush developer station 15 by a
metering gate 20. The transport portion 19 of the magnetic brush
developer station 15 ~as a transport roll 21 disposed therein beneath
a magnetic brush roll 22.
The transport roll 21, which rotates at a speed less than the
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~042655
rotational speed of the magnetic brush roll 22 to provide a surface
velocity of the transport roll 21 no greater than the surface velo-
city of the magnetic brush roll 22, rotates clockwise while the mag-
netic brush roll 22 rotates counterclockwise. The transport roll 21
surrounds a fixed drum 23 which has magnets 24 on a portion of the
surface thereof to aid in holding the developer material on the trans-
port roll 21 until the developer material is advanced to a position
adjacent the oppositely rotating magnetic brush roll 22.
As the developer material is advanced by the transport roll 21
to the magnetic brush roll 22, the developer material is attracted
to the magnetic brush roll 22 by magnets 25, which are fixed and
disposed within the magnetic brush roll 22. The magnets 25 may be
of any suitable type as long as they cause the developer material to
adhere to the magnetic brush roll 22 and have a bristle-like array
adjacent the photoconductor 11.
As shown in FIGURE 2, the magnetic brush roll 22 includes a core
26 of a non-magnetic material such as aluminum, for example. The core
26 is closed at its ends by plates 27.
A shaft 28 extends from the plate 27 at one end of the core 26
and is driven from a main power source by a chain passing around
a sprocket on the shaft 28. The transport roll 21 is driven in unison
with the magnetic brush roll 22 through the same chain cooperating
with a shaft 29 of the transport roll 21. The other plate 27 is
rotatably supported by a bearing on a fixed shaft 30 (see FIGURE 1)
on which the magnets 25 are supported.
The core 26 of the magnetic brush roll 22 has a sleeve 31 of
a resilient polymeric material secured thereto. The sleeve 31 has its
surface textured so as to be roughened to a desired extent. The
roughness pattern in the sleeve 31 can be uniform or non-uniform.
One suitable example of the resilient polymeric material of
the sleeve 31 is polyurethane. The sleeve 31 is homogeneous and is
conductive so that a desired bias can be applied to the magnetic
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1 brush roll 22. ~hile polyurethane is not conductive, carbon is added
thereto to insure that the sleeve 31 is conductive.
One means of forming the sleeve 3i is to use Norton Company's
AH299 grinding tube as a mold. The tube is machined to an outer
diameter of 2.4 inches and then grit blasted to produce a random,
textured surface on the tube as the mold. Then, DuPont 958-202 steel
blue Teflon** release coat is applied to the surface of the mold.
The mold is then dip coated twelve times within a conductive
polyurethane solution with the mold being inverted after each of
the dips. The conductive polyurethane solution is prepared by
adding one hundred parts by weight of Hughson Chemical Company's
TS-1525-37 urethane lacquer resin, 8.3 parts by weight of Cabot
Corporation's Vulcan* XC-72 conductive carbon black, 100 parts by
weight of toluene, and 100 parts by weight of isopropyl alchohol with-
in an attritor and running the attritor at full speed for one hour~
After each coating of the conductive polyurethane solution is
formed on the mold, it is air dryed for at least fifteen minutes
before an additional coat is applied by dipping. After every fourth
dip and after air drying, the mold is placed in an air circulating
oven and allowed to dry for at least fifteen minutes at 150 F to
remove any residual solvent.
This forms the sleeve 31, which is removed from the mold. After
turning the sleeve 31 inside out, the sleeve 31 is deposited over the
core 26, which has been adhesive coated by spray coating with EC2290
modified epoxy adhesive of 3M and completely dried. The sleeve 31 is
expanded by air to be able to fit over the core 26. After the sleeve
31 has been disposed over the core 26, it is cured for one hour at 300 F.
Tests have indicated that the tensile strength of the sleeve 31
is 4,000 p.s.i. with an ultimate elongation in excess of 800 per cent.0
The tear strength of the sleeve 31 is 330 pounds per inch thickness,
* Trade Mark
*** Registered Trade Mark
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~04Z655
1 and it has a hardness of 65 on a shore A durometer. Its volume resisti-
vity is 104 ohm-cm.
Accordingly, the magnetic brush roll 22 has a surface, which is
rough or textured, non-abrasive, and abrasion resistant. At the same
time, the sleeve 31 is resilient and is conductive throughout. This
permits the required bias to be applied to the magnetic brush roll 22.
As the magnetic brush roll 22 advances the developer material
toward the photoconductor drum 11, it passes a bead control device
32. The bead control device 32 limits the thickness of the developer
material on the magnetic brush roll 22 prior to being advanced into
the position adjacent the photoconductor drum 11.
The magnetic brush developer station 15 supports a pile fabric
seal 33, which is made of a material such as Kodel*, for example. The
purpose of the seal 33, which engages the photoconductor drum 11, is
to prevent a toner cloud from escaping from the magnetic brush develo-
per station 15.
After the magnetic brush roll 22 has advanced the developer
material past the photoconductor drum 11, the developer material
remaining on the magnetic brush roll 22 is released after passing
the last of the magnets 25 and returned to the sump portion 14 of
the magnetic brush developer station 15.
The magnetic brush developer station 15 also supports a blade
scraper 34, which is conductive coated Mylar, adjacent the photo-
conductor drum 11 and spaced slightly therefrom. The purpose of the
blade scraper 34 is to keep the toner and carrier particles from
escaping from the magnetic brush deve10per station 15.
A seal 35, which is spaced slightly from the photoconductor
drum 11, also is supported by the magnetic brush developer station 15
and is passed by the photoconductor drum 11 after the photoconductor
drum 11 moves past the scraper 34. The seal 35, which also is
* Trade Mark
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1 conductive coated Mylar**, likewise functions to keep the toner and
carrier particles from escaping from the magnetic brush developer sta-
tion 15.
Instead of the magnetic brush roll 22 having the sleeve 31, which
is homogeneous polyurethane with carbon, a magnetic brush roll 37
(see FIGURE 3) could be employed in which the core 26 would again be
used. The core 26 would have a layer 38 of polyurethane without
carbon thereon so that the layer 38 would not be conductive. Then, a
layer 39 of polyurethane with carbon could be applied to the layer
38 by being painted thereon. The layer 39 would need to be only about
.001" thick.
Thus, the magnetic brush roll 37 would be conductive only along
its surface. However, this is sufficient to provide the desired
bias thereon.
The sleeve 31 of the magnetic brush roll 22 or the layer 38 of
the magnetic brush roll 37 must be at least .010" thick and is pre-
ferably at least .015" thick. While the sleeve 31 of the magnetic
brush roll 22 or the layer 39 of the magnetic brush roll 37 has a
hardness of 65 on a Shore A durometer, it should be understood that
either could have a hardness up to 95 on a Shore A durometer and still
have sufficient resiliency.
While the resilient polymeric material has been described as being
polyurethane, it should be understood that any other resilient poly-
meric material having the desired properties could be employed. This
includes the capability of having a conductive material such as carbon,
for example, added without the material losing its other desired pro-
perties of being resilient, non-abrasive, and abrasion resistant. Thus,
any synthetic rubber having the properties of being resilient, non-
abrasive, and abrasion resistant could be utilized, for example, The
rubber could be dip-coated on a textured core of a non-magnetic material,
for example, to have the desired roughness. It is necessary that any
** Registered Trade Mark
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1 resilient polymeric material be non-abrasive and abrasion resistant
as well as having a sufficient roughness to permit the developer
material to have a foothold on the magnetic brush roll.
While the roughness of the material can be within varying ranges,
it is preferred that the roughness be no greater than that produced by
a molding from a fifty grit sandpaper. The roughness preferably is no
less than that produced by ninety grit sandpaper.
While the sleeve 31 has been described as being formed through
a dipping process on a mold and then removing the sleeve 31 for appli-
cation on the core 26, it should be understood that any other suitable
process could be employed. For example, the material could be injection
molded around a core or a sleeve could be extruded with the material
having to be thermoplastic in nature to allow the desired roughness
to be embossed in its surface.
While the present invention has been shown and described as
having the developer material moved uphill by the magnetic brush roll,
it should be understood that the magnetic brush roll of the present
invention could be utilized where the developer material is moved
downhill. This would be particularly useful in a relatively high
speed machine.
An advantage of this invention is that it reduces the wear of the
developer material. Another advantage of this invention is that it is
particularly useful in moving a material uphill to an electrostatic
latent image-bearing surface.
While the invention has been particularly shown and described
with reference to preferred embodiments thereof, it will be under-
stood by those skilled in the art that the foregoing and other
changes in form and details may be made therein without departing from
the spirit and scope of the invention.
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