Spring loaded oil distributing preheated donor roll

A release agent management (RAM) system including a metering roll supported for contact with release agent material contained in a sump. A donor roll is provided for applying oil deposited on its surface by the metering roll. Prior to fusing taking place, the donor roll is supported in pressure engagement with the fuser roll and out of contact with the metering roll. During fusing the donor roll is cammed into engagement with the metering roll.

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 the 
discharged portions and/or the charged portions of the charge retentive 
surface, the former in the case of tri-level imaging and the latter in the 
case of conventional xerography. 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 adhesive 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 retained 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. 
A common problem for prior art donor roll RAM systems is the poor 
distribution of oil within the first several copies. This can occur due to 
donor roll oil migration and roll slippage as the result of oil puddling. 
The problem becomes more difficult when dealing with slow process speeds 
and the high oil rates required for fusing of color images. 
BRIEF SUMMARY OF THE INVENTION 
Briefly, the present invention comprises a RAM system including a metering 
roll supported for contact with release agent material or oil contained in 
a sump and a donor roll which contacts the metering roll and a fuser roll. 
The oil is conveyed from the sump to the fuser roll via the donor roll. 
The donor roll is spring loaded or biased against the fuser roll during the 
pre run copy mode. At this same time, the donor roll does not contact the 
metering roll. As the heated fuser roll turns in contact with the donor 
roll the oil present on the donor roll surface is distributed between the 
two rolls. Also, during this time, the donor roll temperature becomes 
elevated thereby limiting the effects of oil viscosity due to temperature. 
Upon camming of the donor roll into contact with the metering roll the 
amount of slippage is minimized enalbling a uniformly oiled fuser roll 
thereby achieving the necessary properties necessary for fusing of color 
images. 
For a better understanding of the present invention, reference may be had 
to the accompanying drawings wherein the same reference numerals have been 
applied to like parts and wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
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. 
For a general understanding of the features of the present invention, 
reference is made to the drawings. In the drawings, like references have 
been used throughout to designate identical elements. FIG. 1 is a 
schematic elevational view of an illustrative electrophotographic machine 
incorporating the features of the present invention therein. It will 
become evident from the following discussion that the present invention is 
equally well suited for use in a wide variety of printing systems, and is 
not necessarily limited in its application to the particular system shown 
herein. 
Turning initially to FIG. 1, during operation of the printing system, a 
multi-color original document 38 is positioned on a raster input scanner 
(RIS), indicated generally by the reference numeral 10. The RIS contains 
document illumination lamps, optics, a mechanical scanning drive, and a 
charge coupled device (CCD array). The RIS captures the entire original 
document and converts it to a series of raster scan lines and measures a 
set of primary color densities, i.e. red, green and blue densities, at 
each point of the original document. This information is transmitted to an 
image processing system (IPS), indicated generally by the reference 
numeral 12. IPS 12 contains control electronics which prepare and manage 
the image data flow to a raster output scanner (ROS), indicated generally 
by the reference numeral 16. A user interface (UI), indicated generally by 
the reference numeral 14, is in communication with IPS 12. UI 14 enables 
an operator to control the various operator adjustable functions. The 
output signal from UI 14 is transmitted to IPS 12. A signal corresponding 
to the desired image is transmitted from IPS 12 to ROS 16, which creates 
the output copy image. ROS 16 lays out the image in a series of horizontal 
scan lines with each line having a specified number of pixels per inch. 
ROS 16 includes a laser having a rotating polygon mirror block associated 
therewith. ROS 16 exposes a charged photoconductive belt 20 of a printer 
or marking engine, indicated generally by the reference numeral 18, to 
achieve a set of subtractive primary latent images. The latent images are 
developed with cyan, magenta, and yellow developer material, respectively. 
These developed images are transferred to a copy sheet in superimposed 
registration with one another to form a multi-colored image on the copy 
sheet. This multi-colored image is then fused to the copy sheet forming a 
color copy. 
With continued reference to FIG. 1, printer or marking engine 18 is an 
electrophotographic printing machine. Photoconductive belt 20 of marking 
engine 18 is preferably made from a polychromatic photoconductive 
material. The photoconductive belt moves in the direction of arrow 22 to 
advance successive portions of the photoconductive surface sequentially 
through the various processing stations disposed about the path of 
movement thereof. Photoconductive belt 20 is entrained about transfer 
rollers 24 and 26, tensioning roller 28, and drive roller 30. Drive roller 
30 is rotated by a motor 32 coupled thereto by suitable means such as a 
belt drive. As roller 30 rotates, it advances belt 20 in the direction of 
arrow 22. 
Initially, a portion of photoconductive belt 20 passes through a charging 
station, indicated generally by the reference numeral 33. At charging 
station 33, a corona generating device 34 charges photoconductive belt 20 
to a relatively high, substantially uniform electrostatic potential. 
Next, the charged photoconductive surface is moved through an exposure 
station, indicated generally by the reference numeral 35. Exposure station 
35 receives a modulated light beam corresponding to information derived by 
RIS 10 having a multi-colored original document 38 positioned thereat. RIS 
10 captures the entire image from the original document 38 and converts it 
to a series of raster scan lines which are transmitted as electrical 
signals to IPS 12. The electrical signals from RIS 10 correspond to the 
red, green and blue densities at each point in the original document. IPS 
12 converts the set of red, green and blue density signals, i.e. the set 
of signals corresponding to the primary color densities of original 
document 38, to a set of colorimetric coordinates. The operator actuates 
the appropriate keys of UI 14 to adjust the parameters of the copy. UI 14 
may be a touch screen, or any other suitable control panel, providing an 
operator interface with the system. The output signals from UI 14 are 
transmitted to IPS 12. The IPS then transmits signals corresponding to the 
desired image to ROS 16. ROS 16 includes a laser with rotating polygon 
mirror blocks. Preferably, a nine facet polygon is used. ROS 16 
illuminates, via mirror 37, the charged portion of photoconductive belt 20 
at a rate of about 400 pixels per inch. The ROS will expose the 
photoconductive belt to record three latent images. One latent image is 
developed with cyan developer material. Another latent image is developed 
with magenta developer material and the third latent image is developed 
with yellow developer material. The latent images formed by ROS 16 on the 
photoconductive belt correspond to the signals transmitted from IPS 12. 
After the electrostatic latent images have been recorded on photoconductive 
belt 20, the belt advances such latent images to a development station, 
indicated generally by the reference numeral 39. The development station 
includes four individual developer units indicated by reference numerals 
40, 42, 44 and 46. The developer units are of a type generally referred to 
in the art as "magnetic brush development units." Typically, a magnetic 
brush development system employs a magnetizable developer material 
including magnetic carrier granules having toner particles adhering 
triboelectrically thereto. The developer material is continually brought 
through a directional flux field to form a brush of developer material. 
The developer material is constantly moving so as to continually provide 
the brush with fresh developer material. Development is achieved by 
bringing the brush of developer material into contact with the 
photoconductive surface. Developer units 40, 42, and 44, respectively, 
apply toner particles of a specific color which corresponds to the 
compliment of the specific color separated electrostatic latent image 
recorded on the photoconductive surface. The color of each of the toner 
particles is adapted to absorb light within a preselected spectral region 
of the electromagnetic wave spectrum. For example, an electrostatic latent 
image formed by discharging the portions of charge on the photoconductive 
belt corresponding to the green regions of the original document will 
record the red and blue portions as areas of relatively high charge 
density on photoconductive belt 20, while the green areas will be reduced 
to a voltage level ineffective for development. The charged areas are then 
made visible by having developer unit 40 apply green absorbing (magenta) 
toner particles onto the electrostatic latent image recorded on 
photoconductive belt 20. Similarly, a blue separation is developed by 
developer unit 42 with blue absorbing (yellow) toner particles, while the 
red separation is developed by developer unit 44 with red absorbing (cyan) 
toner particles. Developer unit 46 contains black toner particles and may 
be used to develop the electrostatic latent image formed from a black and 
white original document. Each of the developer units is moved into and out 
of an operative position. In the operative position, the magnetic brush is 
closely adjacent the photoconductive belt, while in the non-operative 
position, the magnetic brush is spaced therefrom. In FIG. 1, developer 
unit 40 is shown in the operative position with developer units 42, 44 and 
46 being in the non-operative position. During development of each 
electrostatic latent image, only one developer unit is in the operative 
position, the remaining developer units are in the non-operative position. 
This insures that each electrostatic latent image is developed with toner 
particles of the appropriate color without commingling. 
After development, the toner image is moved to a transfer station, 
indicated generally by the reference numeral 65. Transfer station 65 
includes a transfer zone, generally indicated by reference numeral 64. In 
transfer zone 64, the toner image is transferred to a sheet of support 
material, such as plain paper amongst others. At transfer station 65, a 
sheet transport apparatus, indicated generally by the reference numeral 
48, moves the sheet into contact with photoconductive belt 20. Sheet 
transport 48 has a pair of spaced belts 54 entrained about a pair of 
substantially cylindrical rollers 50 and 52. A sheet gripper (not shown) 
extends between belts 54 and moves in unison therewith. A sheet 25 is 
advanced from a stack of sheets 56 disposed on a tray. A friction retard 
feeder 58 advances the uppermost sheet from stack 56 onto a pre-transfer 
transport 60. Transport 60 advances sheet 25 to sheet transport 48. Sheet 
25 is advanced by transport 60 in synchroism with the movement of sheet 
gripper, not shown. In this way, the leading edge of sheet 25 arrives at a 
preselected position, i.e. a loading zone, to be received by the open 
sheet gripper. The sheet gripper then closes securing sheet 25 thereto for 
movement therewith in a recirculating path. The leading edge of sheet 25 
is secured releasably by the sheet gripper. As belts 54 move in the 
direction of arrow 62, the sheet moves into contact with the 
photoconductive belt, in synchronism with the toner image developed 
thereon. At transfer zone 64, a corona generating device 66 sprays ions 
onto the backside of the sheet so as to charge the sheet to the proper 
electrostatic voltage magnitude and polarity for attracting the toner 
image from photoconductive belt 20 thereto. The sheet remains secured to 
the sheet gripper so as to move in a recirculating path for three cycles. 
In this way, three different color toner images are transferred to the 
sheet in superimposed registration with one another. One skilled in the 
art will appreciate that the sheet may move in a recirculating path for 
four cycles when under color black removal is used and up to eight cycles 
when the information on two original documents is being merged onto a 
single copy sheet. Each of the electrostatic latent images recorded on the 
photoconductive surface is developed with the appropriately colored toner 
and transferred, in superimposed registration with one another, to the 
sheet to form the multi-color copy of the colored original document. 
After the last transfer operation, the sheet gripper opens and releases the 
sheet. A conveyor 68 transports the sheet, in the direction of arrow 70, 
to a fusing station, indicated generally by the reference numeral 71, 
where the transferred toner image is permanently fused to the sheet. The 
fusing station includes a heated fuser roll 74 and a pressure roll 72. The 
sheet passes through the nip defined by fuser roll 74 and pressure roll 
72. The toner image contacts fuser roll 74 so as to be affixed to the 
sheet. Thereafter, the sheet is advanced by a pair of rolls 76 to catch 
tray 78 for subsequent removal therefrom by the machine operator. 
The last processing station in the direction of movement of belt 20, as 
indicated by arrow 22, is a cleaning station, indicated generally by the 
reference numeral 79. A rotatably mounted fibrous brush 80 is positioned 
in the cleaning station and maintained in contact with photoconductive 
belt 20 to remove residual toner particles remaining after the transfer 
operation. Thereafter, lamp 82 illuminates photoconductive belt 20 to 
remove any residual charge remaining thereon prior to the start of the 
next successive cycle. 
Attention is now directed to FIG. 2 wherein the heat and pressure fuser 
apparatus comprising the fuser roll 74 and pressure roll 72 is illustrated 
together with a release agent management (RAM) system 90. As shown in FIG. 
2, the fuser apparatus comprises the heated fuser roll 74 which is 
composed of a core 92 having thereon a layer or layers 94 of a suitable 
elastomer. The core 92 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 92, although this is 
not critical. The core 92 is hollow and a heating element 96 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 fusing 
elastomer layer may be made of any of the well known materials such as the 
Viton and/or silicone rubber. 
The fuser roll 74 is shown in a pressure contact arrangement with the 
backup or pressure roll 72. The pressure roll 72 comprises a metal core 98 
with an outer layer 100 of a heat-resistant material. In this assembly, 
both the fuser roll 74 and the pressure roll 72 are mounted on bearings 
(not shown) which are biased so that the fuser roll 74 and pressure roll 
72 are pressed against each other under sufficient pressure to form a nip 
102. It is in this nip that the fusing or fixing action takes place. The 
layer 100 may be made of any of the well known materials such as Teflon a 
trademark of E.I. duPont. 
The image receiving member or final support 25 having toner images 104 
thereon is moved through the nip 102 with the toner images contacting the 
heated fuser roll 74. The toner material forming the image 104 is 
prevented from offsetting to the surface of the fuser roll 74 through the 
application of a release agent material such as silicone oil 106 contained 
in sump 108. 
The sump 108 and silicone oil 106 form part of the RAM system 90. The RAM 
system 90, according to one embodiment of the invention, further comprises 
a metering roll 110 and a donor roll 112. The metering roll is supported 
partially immersed in the silicone oil 106 and contacts the donor roll for 
conveying silicone oil from the sump to the surface of the donor roll 112. 
The donor roll is rotatably supported in contact with the metering roll 
and also in contact with the fuser roll 94. While the donor roll is 
illustrated as contacting the fuser roll, it will be appreciated that, 
alternately, it may contact the pressure roll 72. Also, the positions of 
the fuser and pressure rolls may be reversed for use in other copiers or 
printers. A metering blade 114 supported in contact with the metering roll 
110 serves to meter silicone oil to the required thickness on the metering 
roll. 
A cover member 120, only partially shown in FIGS. 3 and 4, is provided for 
the sump 108. The cover has attached to a bottom wall thereof, a pair of 
donor roll biasing members 122 (only one shown). The donor roll is 
supported, as shown in FIG. 3, by a pair of spring members 124 (only one 
shown) which are positioned adjacent the ends of the sump 108. To this 
end, the shaft ends 126 of the donor member are loosely received in the 
free ends of the springs 124. When the cover is installed the bias members 
122 urge the donor roll against the user roll 74. 
As can be seen from FIG. 3, the donor roll and the metering roll are 
disengaged from each other. This illustrates the orientation of the RAM 
members during the non-fusing or pre run mode. When the cover is installed 
on the sump the biasing members 122 serve to urge the donor roll against 
the fuser roll. 
The springs 124 which are secured to a pivotally mounted bracket structure 
129 are adapted for pivotal movement with the bracket structure in the 
counterclockwise direction as viewed in FIGS. 3 and 4 in order move the 
donor roll downwardly to effect engagement of the donor roll with the 
metering roll as illustrated in FIG. 4. Such engagement is effected 
through the movement of the bracket structure as it is cammed via a 
camming element 128 operatively connected to the bracket structure. The 
camming element 128 is a cam follower actuated by a cam, not shown. 
Camming action is initiated pursuant to the fusing of copies. The 
operative connection between the bracket and the cam follower 128 serves 
to allow pivoting of the bracket when the cam follower is moved in the 
downward direction.