Donor brush

A release agent management system including a metering roll supported for contact with release agent material contained in a sump. The metering roll also contacts a donor brush structure which, in turn, contacts a heated fuser roll member. The ends of the brush structure are provided with a pair of friction devices which contact the surface of the heated fuser roll member and do not contact the metering roll. Thus, the donor brush structure and the heated fuser roll member are frictionally coupled so that positive rotation of the heated fuser roll member imparts rotation to the donor brush structure.

BACKGROUND OF THE INVENTION 
The present invention relates to fuser apparatus for electrostatographic 
printing machines and in particular to release agent management (RAM) 
systems for a heat and pressure roll fuser. 
In imaging systems commonly used today, a charge retentive surface is 
typically charged to a uniform potential and thereafter exposed to a light 
source to thereby selectively discharge the charge retentive surface to 
form a latent electrostatic image thereon. The image may comprise either 
the discharged portions or the charged portions of the charge retentive 
surface. The light source may comprise any well known device such as a 
light lens scanning system or a laser beam. Subsequently, the 
electrostatic latent image on the charge retentive surface is rendered 
visible by developing the image with developer powder referred to in the 
art as toner. The most common development systems employ developer which 
comprises both charged carrier particles and charged toner particles which 
triboelectrically adhere to the carrier particles. During development, the 
toner particles are attracted from the carrier particles by the charged 
pattern of the image areas of the charge retentive surface to form a 
powder image thereon. This toner image may be subsequently transferred to 
a support surface such as plain paper to which it may be permanently 
affixed by heating or by the application of pressure or a combination of 
both. 
In order to fix or fuse the toner material onto a support member 
permanently by heat, it is necessary to elevate the temperature of the 
toner material to a point at which constituents of the toner material 
coalesce and become tacky. This action causes the toner to flow to some 
extent onto the fibers or pores of the support members or otherwise upon 
the surfaces thereof. Thereafter, as the toner material cools, 
solidification of the toner material occurs causing the toner material to 
be bonded firmly to the support member. 
One approach to thermal fusing of toner material images onto the supporting 
substrate has been to pass the substrate with the unfused toner images 
thereon between a pair of opposed roller members at least one of which is 
internally heated. During operation of a fusing system of this type, the 
support member to which the toner images are electrostatically adhered is 
moved through the nip formed between the rolls with the toner image 
contacting the heated fuser roll to thereby effect heating of the toner 
images within the nip. Typical of such fusing devices are two roll systems 
wherein the fusing roll is coated with an abhesive material, such as a 
silicone rubber or other low surface energy elastomer or, for example, 
tetrafluoroethylene resin sold by E. I. DuPont De Nemours under the 
trademark Teflon. In these fusing systems, however, since the toner image 
is tackified by heat it frequently happens that a part of the image 
carried on the supporting substrate will be retrained by the heated fuser 
roller and not penetrate into the substrate surface. The tackified toner 
may stick to the surface of the fuser roll and offset to a subsequent 
sheet of support substrate or offset to the pressure roll when there is no 
sheet passing through a fuser nip resulting in contamination of the 
pressure roll with subsequent offset of toner from the pressure roll to 
the image substrate. 
To obviate the foregoing toner offset problem it has been common practice 
to utilize toner release agents such as silicone oil, in particular, 
polydimethyl silicone oil, which is applied to the fuser roll surface to a 
thickness of the order of about 1 micron to act as a toner release 
material. These materials possess a relatively low surface energy and have 
been found to be materials that are suitable for use in the heated fuser 
roll environment. In practice, a thin layer of silicone oil is applied to 
the surface of the heated roll to form an interface between the roll 
surface and the toner image carried on the support material. Thus, a low 
surface energy, easily parted layer is presented to the toners that pass 
through the fuser nip and thereby prevents toner from adhering to the 
fuser roll surface. 
Various systems have been used to deliver release agent fluid to the fuser 
roll including the use of oil soaked rolls and wicks with and without 
supply sumps as well as oil impregnated webs. A another type of RAM system 
is disclosed in U.S. Pat. No. 4,214,549 granted to Rabin Moser on Jul. 29, 
1980. As disclosed therein, release agent material is contained in a sump 
from which it is dispensed using a metering roll and a donor roll, the 
former of which contacts the release agent material and the latter of 
which contacts the surface of the heated fuser roll. 
Xerox Disclosure Journal (XDJ) Volume 7, Number 3 dated May/June 1982 
discloses a release agent management system for a roll fuser apparatus. 
The apparatus comprises a fuser roll to which silicone oil is applied in 
order to counteract toner offset to the fuser roll. The fuser roll 
cooperates with a softer pressure roll to fuse toner images to a copy 
substrate such as plain paper. The silicone oil which is contained in a 
sump is applied to the surface of the fuser roll by means of a rotating 
brush which is adapted to be rotated in the opposite direction to that of 
the fuser roll. The brush engages one end of a wick while the other end of 
the wick is immersed in the silicone oil. Thus, the brush picks up 
silicone oil from the wick and conveys it to the fuser roll surface. Since 
the brush rotates counter to the fuser roll the brush bristles strip the 
lead edge of the copy and deflect it down and away from the fuser roll. 
The brush fibers undergo a snapping or flicking action as they move out of 
the nip formed between them and the fuser roll. It is this action which 
yields the stripping action. The oil application rate is controlled by the 
brush fiber density and the velocity of the fuser roll. 
U.S. Pat. No. 4,593,992 issued on Jun. 10, 1986 discloses an image forming 
apparatus for forming an unfixed image on a recording material including a 
fixing device having a pair of rotatable members for holding therebetween 
and conveying the recording material to fix the unfixed image on the 
recording material, speed control device for variably controlling the 
fixing rotational speed of the pair of rotatable members to a first fixing 
speed and a second fixing speed lower than the first fixing speed, 
application apparatus for intermittently supplying a parting agent to at 
least one of the pair of rotatable members and application control 
apparatus for variably controlling the application acting period of the 
application apparatus in accordance with the fixing rotational speed of 
the pair of rotatable members variably set by the speed control device. 
U.S. Pat. No. 4,496,234 issued on Jan. 29, 1985 discloses a release agent 
management (RAM) system for use with a heat and pressure fuser. The system 
is characterized by the use of a simple reciprocating, positive 
displacement pump for delivering silicone oil to the heated roll of the 
fuser. The pump is actuated in response to the fuser rolls being engaged 
and disengaged, such movement being adapted to act against one or the 
other of a pair of springs which in cooperation with the oil being pumped 
forms a damper system which is utilized to control the quantity of oil 
delivered. The springs and oil cause the velocity of the pump's piston to 
decay with time which results in more oil being pumped initially. 
U.S. Pat. No. 4,047,885 issued on Sep. 13, 1977 discloses contact fuser 
assembly for use in an electrostatic reproducing apparatus including an 
internally heated metal core cooperating with a resilient backup roll to 
form a nip through which substrates carrying toner images are moved with 
the toner images contacting the metal core. The fuser assembly is 
characterized by the provision of a sump of liquid release agent material 
which is provided for coating the surface of the fuser roll structure. In 
order to apply the liquid release agent material to the surface of the 
fuser roll structure there is provided a cylindrical applicator member 
which is partially submersed in the release agent material. A ratchet 
wheel and pawl arrangement is provided for periodically indexing or moving 
the applicator member in response to disengagement of the backup roll from 
the fuser roll through pivoting of an arm supporting the backup roll. To 
this end, the pawl member is pivotally supported by the pivot arm and 
actuates the ratchet wheel each time the pivot arm is moved for effecting 
disengagement of the backup roll from the fuser roll. 
Some of the RAM systems discussed above serve to dispense a fixed quantity 
of release agent material to a heated fuser roll member regardless of the 
desirability of dispensing different amounts of release agent material. 
Other systems such as the one disclosed in the XDJ noted above dispense 
more or less release agent material depending on the speed of the fuser 
roll contacted by the donor brush. 
U.S. patent application Ser. No. 07/798,379 filed in the name of Fromm et 
al on Nov. 26, 1991, now U.S. Pat. No. 5,200,786, discloses a release 
agent management (RAM) system for a heat and pressure fuser. The RAM 
system includes a metering roll and donor brush or equivalent structure 
for providing a low friction nip between it and a pressure or fuser rolls 
and also between it and the metering roll. The low friction nip allows 
rolls contacting the donor brush or its equivalent to be operated at 
different speeds. Thus, the metering roll can be rotated at different 
speeds for delivering different quantities of release agent material in 
accordance with different operating conditions of the imaging apparatus in 
which the RAM system is used. As disclosed in this application the donor 
brush is either connected to a separate drive or operatively coupled to 
the pressure or fuser roll for rotation therewith. 
Positive driving of machine components either by a dedicated drive 
arrangement or by some sort of mechanical coupling to other components add 
additional costs to one of the higher costing subsystems of xerographic 
printers and copiers. In addition to the added expense, such drive 
arrangements add complexity to the machine construction and servicing. 
While the donor roll of the '549 patent can be frictionally driven via one 
of the fuser members such friction driving is not feasible in a donor 
brush RAM system due to the low friction between the donor brush and the 
fuser member which it contacts. 
BRIEF SUMMARY OF THE INVENTION 
Briefly, the present invention comprises a RAM system including a metering 
roll supported for contact with release agent material contained in a 
sump. The metering roll also contacts a donor brush structure which, in 
turn, contacts a heated fuser roll member. 
The ends of the brush structure are provided with a pair of friction 
devices which contact the surface of the heated fuser roll member and do 
not contact the metering roll. To this end the donor brush structure is 
longer than the metering roll and shorter than the heated fuser roll 
member. Thus, the donor brush structure and the heated fuser roll member 
are frictionally coupled so that positive rotation of the heated fuser 
roll member imparts rotation to the donor brush structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
Referring now to FIG. 3, there is shown by way of example, an automatic 
electrostatographic reproducing machine 10 which includes a removable 
processing cartridge 12. The reproducing machine depicted in FIG. 3 
illustrates the various components utilized therein for producing copies 
from an original document. Although the invention is particularly well 
adapted for use in automatic electrostatographic reproducing machines, it 
should become evident from the following description that it is equally 
well suited for use in a wide variety of processing systems including 
other electrostatographic systems such as printers and is not necessarily 
limited in application to the particular embodiment shown herein. 
The reproducing machine 10 illustrated in FIG. 3 employs a removable 
processing cartridge 12 which may be inserted and withdrawn from the main 
machine frame. Cartridge 12 includes an image recording belt-like member 
14 the outer periphery of which is coated with a suitable photoconductive 
material 15. The belt or charge retentive member is suitably mounted for 
revolution within the cartridge about driven transport roll 16, around 
idler roll 18 and travels in the direction indicated by the arrows on the 
inner run of the belt to bring the image bearing surface thereon past a 
plurality of xerographic processing stations. Suitable drive means such as 
a motor, not shown, are provided to power and coordinate the motion of the 
various cooperating machine components whereby a faithful reproduction of 
the original input scene information is recorded upon a sheet of final 
support material 31, such as paper or the like. 
Initially, the belt 14 moves the photoconductive surface 15 through a 
charging station 19 wherein the belt is uniformly charged with an 
electrostatic charge placed on the photoconductive surface by charge 
corotron 20 in known manner preparatory to imaging. Thereafter, the 
uniformly charged portion of the belt 14 is moved to exposure station 21 
wherein the charged photoconductive surface 15 is exposed to the light 
image of the original input scene information, whereby the charge is 
selectively dissipated in the light exposed regions to record the original 
input scene in the form of an electrostatic latent image. 
The optical arrangement creating the latent image comprises a scanning 
optical system including lamp 17 and mirrors M1, M2, M3 mounted to a 
scanning carriage (not shown) to scan an original document D on an imaging 
platen 23. Lens 22 and mirrors M4, M5, M6 transmit the image to the 
photoconductive belt in known manner. The speed of the scanning carriage 
and the speed of the photoconductive belt are synchronized to provide 
faithful reproduction of the original document. After exposure of belt 14 
the electrostatic latent image recorded on the photoconductive surface 15 
is transported to development station 24, wherein developer is applied to 
the photoconductive surface 15 of the belt 14 rendering the latent image 
visible. The development station includes a magnetic brush development 
system including developer roll 25 utilizing a magnetizable developer mix 
having course magnetic carrier granules and toner colorant particles 
supplied from developer supply 11 and auger transport 37. 
Sheets 31 of final support material are supported in a stack arranged on 
elevator stack support tray 26. With the stack at its elevated position, a 
segmented feed and sheet separator roll 27 feeds individual sheets 
therefrom to a registration pinch roll pair 28. The sheet is then 
forwarded to a transfer station 29 in proper registration with the image 
on the belt and the developed image on the photoconductive surface 15 is 
brought into contact with the sheet 31 of final support material within 
the transfer station 29 and the toner image is transferred from the 
photoconductive surface 15 to the contacting side of the final support 
sheet 31 by means of transfer corotron 30. Following transfer of the 
image, the final support material which may be paper, plastic, etc., as 
desired, is separated from the belt due to the beam strength of the 
support material 31 as it passes around the idler roll 18. The sheet 
containing the toner image thereon is advanced to fixing station 41 
comprising heated fuser roll 52 and pressure roll 54 forming a nip 
therebetween wherein roll fuser 52 fixes the transferred powder image 
thereto. 
Although a preponderance of toner powder is transferred to the final 
support material 31, invariably some residual toner remains on the 
photoconductive surface 15 after the transfer of the toner powder image to 
the final support material. The residual toner particles remaining on the 
photoconductive surface after the transfer operation are removed from the 
belt 14 at a cleaning station 35 which comprises a cleaning blade 36 in 
scrapping contact with the outer periphery of the belt 14. The particles 
so removed are contained within cleaning housing (not shown) which has a 
cleaning seal 50 associated with the upstream opening of the cleaning 
housing. Alternatively, the toner particles may be mechanically cleaned 
from the photoconductive surface by a cleaning brush as is well known in 
the art. 
It is believed that the foregoing general description is sufficient for the 
purposes of the present invention to illustrate the general operation of 
an automatic xerographic copier 10 which can embody the apparatus in 
accordance with the present invention. 
Attention is now directed to FIG. 2 wherein the heat and pressure fuser 
apparatus comprising the fuser roll 52 and pressure roll 54 are 
illustrated together with a release agent management (RAM) system 56. As 
shown in FIG. 2, the fuser apparatus comprises the heated fuser roll 52 
which is composed of a core 58 having coated thereon a thin layer 60 of an 
elastomer. The core 58 may be made of various metals such as iron, 
aluminum, nickel, stainless steel, etc., and various synthetic resins. 
Aluminum is preferred as the material for the core 58, although this is 
not critical. The core 58 is hollow and a heating element 62 is generally 
positioned inside the hollow core to supply the heat for the fusing 
operation. Heating elements suitable for this purpose are known in the 
prior art and may comprise a quartz heater made of a quartz envelope 
having a tungsten resistance heating element disposed internally thereof. 
The method of providing the necessary heat is not critical to the present 
invention, and the fuser member can be heated by internal means, external 
means or a combination of both. Heating means are well known in the art 
for providing sufficient heat to fuse the toner to the support. The thin 
fusing elastomer layer may be made of any of the well known materials such 
as the RTV and HTV silicone elastomers as well as Viton (trademark of E.I. 
du Pont de Nemours & Co.). 
The fuser roll 52 is shown in a pressure contact arrangement with the 
backup or pressure roll 54. The pressure roll 54 comprises a metal core 64 
with a layer 66 of a heat-resistant material. In this assembly, both the 
fuser roll 52 and the pressure roll 54 are mounted on bearings (not shown) 
which are biased so that the fuser roll 52 and pressure roll 54 are 
pressed against each other under sufficient pressure to form a nip 68. It 
is in this nip that the fusing or fixing action takes place. The layer 66 
may be made of any of the well known materials such as fluorinated 
ethylene propylene copolymer or silicone rubber. 
The image receiving member or final support 31 having toner images 70 
thereon is moved through the nip 68 with the toner images contacting the 
heated fuser roll 52. The toner material forming the image 70 is prevented 
from offsetting to the surface of the fuser roll 52 by the application of 
a release agent material such as silicone oil 72 contained in sump 74. 
The sump 74 and silicone oil 72 form part of the RAM system 56. The RAM 
system 56, according to one embodiment of the invention, further comprises 
a metering roll 76 and a donor brush 78. The metering roll is supported 
partially immersed in the silicone oil 72 and contacts the donor brush for 
conveying silicone oil from the sump to the bristles of the donor brush 
78. The donor brush is rotatably supported for contact with the metering 
roll and also in contact with the pressure roll 54. While the donor brush 
is illustrated as contacting the pressure roll, it will be appreciated 
that, alternately, it may contact the fuser roll 52. Also, the positions 
of the fuser and pressure rolls may be reversed for use in other copiers 
or printers. A metering blade 84 supported in contact with the metering 
roll 76 serves to meter silicone oil to the required thickness on the 
metering roll. 
Whereas the contact of the donor roll of the '549 patent with its 
associated metering roll and the roll to which it delivers silicone oil is 
intimate (i.e. a high percentage of contact) the contact of the donor 
brush 78 with the pressure roll 54 and the metering roll 76 is only about 
10%. The low percentage of contact between the donor brush and the other 
rollers provides for low torque transmission form the donor brush to the 
metering and fuser rolls. In operation, the donor brush tends to slide 
relative to the metering and pressure rolls and the area of contact 
therebetween is very low, approximately 10%. 
A pair of wheels 90 attached to the core 92 of the donor brush structure 78 
engage the surface of the pressure roll 54. The wheels may be attached to 
the core in any suitable manner such as by pressing, by molding or gluing 
them thereto. The wheels are may be fabricated from any material such as 
rubber, plastic or metal which provides a high coefficient of friction 
between it and the pressure roll surface. The high coefficient of friction 
provides friction driving of the donor brush by the pressure which is 
positively driven via a motor 96 and suitable drive train, not shown. 
Thus, the donor brush comprises first and second members, bristles 101 and 
friction wheels 90, respectively, both of which contact the pressure roll 
54. The bristles contact the pressure roll with low friction while the 
friction wheels engagement it with a relatively high friction. 
As illustrated in FIG. 1, the donor brush structure 78 is longer than the 
metering roll structure 76 and shorter than the pressure roll 54. Such an 
arrangement permits contact of the friction wheels with the pressure roll 
while precluding contact between them and the metering roll thereby 
permitting driving of the donor brush by the pressure roll without 
engagement between the friction wheels and the metering roll. 
The metering roll is a smooth-surfaced metal roll on which the oil picked 
up from the sump is metered to the desired thickness by a metering blade 
84. The metering roll is adapted to be driven at different speeds to 
deliver different oil quantities of oil. To this end the motor 82 designed 
to rotate the metering roll in the order of 5 to 100 RPM which is about 1 
to 20% of the rotational speed of the pressure roll 54. The metering roll 
has a diameter of 20-75 mm and the donor brush has a diameter in the order 
of 20-40 mm. 
The bristle member 100 of the donor brush 78 is fabricated using 
heat-resistant fibers made of, by way of example, the copolymer of 
metaphenylenediamine and isophthaloyl chloride. A loading pressure of 0.5 
to 10 PSI causes the donor brush to conform to the surfaces of the 
pressure and metering rolls. At the aforementioned operating speeds of the 
metering roll, the brush fibers serve to deliver in the order of 1 to 6 
.mu.l of silicone oil. 
The speed of the metering roll is controlled by the motor 82 (FIG. 2) which 
is, in turn, controlled by the Electronic Subsystem (ESS) 100. The ESS 
comprises the necessary electronics and logic circuitry, well know in the 
art, to process control signals for controlling the rotational speeds of 
the motors 82 and 96. The speed of the metering roll causes the metering 
roll to deliver somewhere between 1 to 6 .mu.l of silicone oil to the 
donor brush in accordance with an algorithm forming a part of the ESS. 
While there has been illustrated and described what is at present 
considered to be a preferred embodiment of the present invention, it will 
be appreciated that numerous changes and modifications are likely to occur 
to those skilled in the art, and it is intended in the appended claims to 
cover all those changes and modifications which fall within the true 
spirit and scope of the present invention.