U.S. patent number 3,912,901 [Application Number 05/488,378] was granted by the patent office on 1975-10-14 for pfa teflon sleeved chow pressure roll.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to George R. Imperial, Joseph H. Moriconi, Stephen Strella.
United States Patent |
3,912,901 |
Strella , et al. |
October 14, 1975 |
PFA teflon sleeved chow pressure roll
Abstract
A backup roll for use in a roll fuser for fixing toner images to
copy sheets by the application of heat and pressure. The roll is
characterized by a rigid core covered with a relatively thick
elastomeric layer with a relatively thinner sleeve or layer of a
high flex life material forming an outer surface for the roll.
Inventors: |
Strella; Stephen (Pittsford,
NY), Imperial; George R. (Webster, NY), Moriconi; Joseph
H. (Rochester, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
23939505 |
Appl.
No.: |
05/488,378 |
Filed: |
July 15, 1974 |
Current U.S.
Class: |
219/216; 219/469;
432/60; 432/228; 100/327; 492/56 |
Current CPC
Class: |
F16C
13/00 (20130101); G03G 15/206 (20130101) |
Current International
Class: |
F16C
13/00 (20060101); G03G 15/20 (20060101); H05B
001/00 () |
Field of
Search: |
;219/216,469-471
;29/130,132 ;100/93RP ;432/60,228 ;161/189 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Albritton; C. L.
Claims
What is claimed is:
1. Fuser member for a roll fusing apparatus utilized in fixing
toner images to support sheets, said member comprising:
a rigid core;
a layer of resilient material adhered to said rigid core; and
an outer layer over said resilient layer, said outer layer
comprising a copolymer of perfluoroalkyl perfluorovinyl ether with
tetrafluoroethylene, said ether having the formula C.sub.n
F.sub.2n.sub.+1 --O--CF=CF.sub.2.
2. A fuser member according to claim 1 wherein n is a number from 1
to 5 inclusive.
3. Fuser apparatus for utilization in fixing toner images to copy
sheets, said apparatus comprising:
a heated fuser roll structure;
a backup roll supported for pressure engagement with said fuser
roll structure to thereby form a nip through which said copy sheets
pass with said images contacting said heated fuser roll
structure;
said backup roll comprising:
a rigid core;
a layer of resilient material adhered to said rigid core; and
an outer sleeve fabricated from a copolymer of perfluoroalkyl
perfluorovinyl ether with tetrafluoroethylene, said ether having
the formula C.sub.n F.sub.2n.sub.+1 --O--CF=CF.sub.2.
4. Apparatus according to claim 3 wherein n is a number from 1 to 5
inclusive.
5. Apparatus according to claim 4 wherein said fuser roll structure
is internally heated.
6. Copier apparatus including structure for forming toner images on
copy sheets and structure utilized in fixing the toner images to
the copy sheets wherein the latter structure comprises:
a backup roll comprising:
a rigid core;
a layer of resilient material adhered to said rigid core; and
an outer sleeve fabricated from a copolymer of perfluoroalkyl
perfluorovinyl ether with tetrafluoroethylene, said ether having
the formula C.sub.n F.sub.2n.sub.+1 --O--CF=CF.sub.2.
7. Apparatus according to claim 6 wherein n is a number from 1 to 5
inclusive.
8. Apparatus according to claim 7 including a fuser roll structure
supported for pressure engagement with said backup roll to thereby
form a nip through which said copy sheets are moved with said toner
images contacting said heater fuser roll structure.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to copier apparatus, and, more
particularly, to a roll fusing system for fixing electroscopic
toner material to a support member.
In the process of xerography, a light image of an original to be
copied is typically recorded in the form of a latent electrostatic
image upon a photosensitive member with subsequent rendering of the
latent image visible by the application of electroscopic marking
particles, commonly referred to as toner. The visual image can be
either fixed directly upon the photosensitive member or transferred
from the member to a sheet of plain paper with subsequent affixing
of the image thereto.
There are various ways of fusing or affixing the toner particles to
the support member, one of which is by the employment of heat. In
order to permanently affix or fuse electroscopic toner material
onto a support member by heat, it is necessary to elevate the
temperature of the toner material to a point at which the
constituents of the toner material coalesce and become tacky. This
action causes the toner to be absorbed to some extent into the
fibers of the support member which, in many instances, constitute
plain paper. Thereafter, as the toner material cools,
solidification of the toner material occurs causing the toner
material to be firmly bonded to the support member. In both the
xerographic as well as the electrographic recording arts, the use
of thermo energy for fixing toner images onto a support member is
old and well known.
One approach to thermofusing of electroscopic toner images onto a
support has been to pass the support with the toner images thereon
between a pair of opposed roller members, at least one of which is
either externally or 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 images contacting the fuser
roll to thereby effect heating of the toner images within the nip.
In order to enhance fusing of the toner images in the foregoing
manner, the backup roll of the fuser roll pair is usually
constructed so that the fuser roll creates a depression in the
backup roll as the result of a biasing force which forces the rolls
into engagement. To this end the backup roll comprises a rigid core
having a relatively thick elastomeric layer affixed thereto and an
outer layer or sleeve of abhesive material. The abhesive material
exhibits a low affinity for tackified toner. The aforementioned
depression is continually formed as different portions of the
backup roll move into and out of engagement resulting in a large
number of flexures of the outer layer. The useful life of such
backup rolls depends to a large degree on the ability of the
material forming the outer layer to withstand the strain of
continued flexing.
Accordingly, the principal object of this invention is to provide a
new and improved copying apparatus.
It is a more particular object of this invention to provide a new
and improved roll fusing apparatus for utilization in an
electrostatic copier apparatus.
Yet another object of this invention is to provide new and improved
backup roll for fusing apparatus.
A BRIEF SUMMARY OF THE INVENTION
Briefly, the above-cited objects are accomplished by the provision
of a backup roll which comprises a composite structure including a
rigid core supporting an outer layer of abhesive material and an
intermediate layer of silicone rubber. The thickness of the rubber
and the abhesive material are such as to readily yield to the force
of the fuser roll structure.
The outer layer comprises a fluorocarbon resin manufactured by E.
I. DuPont de Nemours and Co. (Inc.) which is designated "Teflon"
PFA Fluorocarbon Resin. This type of resin is a melt fabricable
perfluoropolymer which combines the carbon-fluorine backbone in the
main chain with perfluoroalkoxy side chains.
Other objects and advantages of the present invention will become
apparent when read in conjunction with the accompanying
drawings:
FIG. 1 is a schematic representation of a xerographic reproducing
apparatus incorporating the contact fusing system of this
invention;
FIG. 2 is a cross-sectional view of the fusing system forming this
invention;
FIG. 3 is a cross-sectional view taken along the line III--III of
FIG. 2;
FIG. 4 is a side elevational view of the fuser forming the present
invention with the backup roll and fuser rolls disengaged;
FIG. 5 is an elevational view of the fuser system similar to FIG. 4
but with the fuser roll and backup roll engaged;
FIG. 6 is a fragmentary view of a flexible drive coupling; and
FIG. 7 is a top plan view of the fuser assembly illustrated in FIG.
2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, especially FIG. 1, there is
disclosed an automatic xerographic reproducing machine 9
incorporating the roll fuser system of the present invention. The
automatic xerographic reproducing machine includes a xerographic
plate, or surface 10, formed in the shape of a drum. The plate has
a photoconductive layer or light sensitive surface on a conductive
backing journaled in a frame to rotate in a direction indicated by
the arrow. The rotation will cause the plate surface to
sequentially pass a series of xerographic processing stations.
For purposes of the present disclosure the several xerographic
processing stations in the path of movement of the plate surface
may be described functionally as follows:
a charging station A where a uniform electrostatic charge is
deposited onto the photoconductive plate;
an exposure station B, at which light or radiation patterns of
copies to be reproduced is projected onto the plate surface to
dissipate the charge in the exposed areas thereof, to thereby form
latent electrostatic images of the copies to be reproduced;
a developing station C, at which xerographic developing material
including toner particles having an electrostatic charge opposite
to that of the latent electrostatic images is cascaded over the
latent electrostatic images to form powder images in configuration
of the copy being reproduced;
a transfer station D, where the powder images are electrostatically
transferred from the plate surface to a transfer material such as
paper, which then is passed through a heated pressure fusing system
according to the present invention as will be described
hereinafter; and
a drum cleaning and discharge station E, at which the plate surface
is brushed to remove residual toner particles remaining thereon
after image transfer and at which the plate is exposed to a
relatively bright light source to effect substantially complete
discharge of any residual electrostatic charge remaining
thereon.
For further details of the xerographic processing stations
discussed above, reference may be had to U.S. Pat. No.
3,578,859.
A combination pressure and heat fusing system 12 as specifically
disclosed in FIGS. 2 and 3, comprises a heated fuser roll 16 and a
backup roll 18.
The fuser roll structure 16 comprises a rigid cylindrical member
20, preferably fabricated from steel, to which end caps or closures
22 and 22' have been affixed in any suitable manner, for example,
by brazing. The member 20 in one operative embodiment has an
outside diameter of 2 3/8 inches. The end cap or closure 22' (FIG.
2) is supported by a bearing 24 carried by a side frame member 26
of the roll fusing assembly 12. The end cap or closure 22 is
retained by the hub 28 of a fuser roll drive gear 30 which hub is,
in turn, retained or supported by a support bearing 32 disposed in
a side frame member 26'.
During operation of the fuser assembly 12 a support copy or sheet
34 (FIG. 3) is moved through the nip 36 formed by engagement of the
fuser roll structure 16 and the backup roll structure 18 such that
the toner images are contacted by the fuser roll structure 16. In
order to provide thermal energy for raising the temperature of the
toner particles to a suitable fusing temperature, a heater element
38 is supported internally of the cylindrical member 20 by heater
sockets 23 and 23'. The heater element may comprise a quartz heater
structure including a quartz envelope having a tungsten resistance
heating element disposed internally thereof. In practice power on
the order of 1,475 watts is supplied to the resistance heating
element via electrical connections 39 to thereby raise the surface
temperature of the fuser roll to approximately 380.degree.F.
In order to provide the fuser roll structure 16 with an outer
surface which has a relatively low affinity for tackified toner
particles, a fluorocarbon polymer layer 40 of, for example,
tetrafluoroethylene (abbreviated TFE) is provided on the rigid
cylindrical member 20. The TFE layer may be on the order of 1.2 -
1.5 mils thick and the member 20 is preferably fabricated from a
thermally conductive material such as copper or aluminum. When
copper is employed it should be coated with aluminum or nickel
prior to the application of the TFE. The particular manner in which
the fuser roll structure 16 is fabricated forms no part of the
present invention. Accordingly, such fabrication thereof may be in
accordance with well-known processes, for example, those set forth
in U.S. Pat. Nos. 3,437,032 and 3,776,760. While the fuser
structure is disclosed as having a TFE layer it may be fabricated
without the layer and may simply comprise a bare metal surface.
By controlling the heat transfer to the toner, virtually no offset
of the toner particles from the copy sheet to the fuser roll is
experienced under normal conditions. This is because the heat
applied to the surface of the roller is insufficient to raise the
temperature of the surface of the roller above the "hot offset"
temperature of the toner, whereat the toner particles in the image
areas of the toner would liquify and cause a shearing action in the
molten toner to thereby result in hot offset. Shearing occurs when
the interparticle or cohesive forces holding the viscous toner mass
together are less than the adhesive forces tending to offset it to
a contacting surface such as a fuser roll.
Occasionally, however, toner particles will be offset to the fuser
roll by an insufficient application of heat to the surface thereof
(i.e. "cold" offsetting); by imperfections in the properties of the
surface of the rolls; or by the toner particles insufficiently
adhering to the copy sheet by the electrostatic forces which
normally hold them there. In such a case, toner particles may be
transferred to the surface of the fuser roll with subsequent
transfer to the backup roll during periods of time when no copy
paper is in the nip.
Moreover, toner particles can be picked up by the fuser and/or
backup roll during fusing of duplex copies or simply from the
surroundings of the reproducing apparatus.
To minimize the chance of offsetting toner to the fuser roll a thin
layer of organosiloxane polymer or other suitable material is
applied to the surface of the fuser roll structure 16 to thereby
for an interface between the roll surface and the toner images
carried on the support material. Thus a low surface energy layer is
presented to the toner as it passes through the fuser nip and
thereby minimizes the degree of offsetting of toner to the fuser
roll surface.
For the purpose of applying the organosiloxane polymer material,
commonly known as silicone oil, to the fuser roll structure 16, a
quantity of silicon oil 42 is contained in a sump housing or oil
pan 44 forming a part of the fusing assembly 12. Approximately 0.65
liters of silicone oil in the sump provides a level therein which
extends to the tops of a plurality of rib members 45. An applicator
member 46 is supported within the housing 44 by means of a support
member 48 such that the applicator contacts both the silicone oil
and the surface of the fuser roll 16. As illustrated in FIG. 3, one
end of the applicator member is physically attached to the support
member 48 as indicated at 49 while the other end thereof extends
into the silicone oil and actually touches the bottom of the sump
44.
The applicator preferably comprises a material which is heat
resistant and which is capable of wicking silicone oil from the
sump to the fuser roll structure. To this end, the applicator
material is preferably a copolymer of meta-phenylenediamine and
isophthaloyl chloride which corresponds to a heatresistant nylon
material known under the trademark, Nomex (E. I. du Pont de Nemours
& Co.). In addition to applying silicone oil to the fuser roll,
the application cleans toner therefrom. It has been observed that
after extended operation, for example, fusing of 25 thousand
copies, the portion of the applicator contacting the fuser
structure becomes coated with toner but continues to apply silicone
oil to the fuser roll.
The support member 48 comprises an elongated construction which is
coextensive with the longitudinal axis of the fuser roll structure
16 and has a pair of sidewardly projecting pins 50 and 50' which
are received in a pair of upstanding ribs or channels 52 integrally
formed or otherwise provided in the sump 44, thereby locating the
support member 48 relative to the fuser roll structure. The ribs
prevent excessive surging of the oil in the oil pan when the pan is
moved and they also act as stiffeners for the oil pan. A pair of
bias springs 54 (only one being shown) are also received in the
channels 52 for biasing the support member upwardly with a total
force of approximately 6 pounds for effecting proper engagement of
the applicator with the fuser roll structure.
The periphery of the support member 48 is provided with a plurality
of concave areas or surfaces 56 each of which cooperates with only
a portion of the applicator 46. When the portion of the applicator
contacting the fuser roll becomes so toner laden as to lose its
effectiveness as either an applicator or a cleaner, the support
member 48 can be reoriented such that a clean portion of the
applicator is moved into alignment with the fuser roll structure.
To accomplish such reorientation the oil pan 44 is removed from the
fuser frame 57 by moving the pan from the right to left as viewed
in FIG. 3.
A doctor blade 58 and support 60 therefore are disposed within the
sump 44 such that the blade 58 contacts the fuser roll structure 16
after the oil has been applied by the applicator 46. The support 60
is provided with a pair of pin members 62 received in apertures in
the sump 44. Spring members 64 received in standoffs 65 serve to
bias the support 60 and therefore the blade 58 into contact with
the fuser roll with sufficient force (i.e. 8 lbs. total) that the
oil applied to the roll is metered to a thickness such that 6 .mu.
liters per copy of 8 1/2 .times. 11 inch paper is utilized. The
doctor blade which may be fabricated from any suitable material for
such purposes, for example, a fluorosilicone elastomer having a
durometer on the order of 80 Shore A, is received in an elongated
channel 66 of the support member.
The backup roll 18 (FIGS. 2 and 3) which has approximately the same
overall dimensions as the fuser roll structure 16 comprises a
rigid, generally cylindrical member 68 having an outside diameter
of 1 3/4 inches and a 3/16 of an inch wall thickness and a pair of
end caps 70 and 70' received in the terminal portions of the member
68. A 0.315 inch layer 72 of elastomeric material, preferably a
heat-resistant, organosiloxane polymer commonly known as silicone
rubber, is adhered to the member 68. A 0.019 inch outer layer or
sleeve 74 of high heat-resistant material having a relatively low
affinity for tackified toner is provided over the silicone rubber
layer. The combined thickness and durometer of the layers 72 and 74
is such as to allow for deformation thereof by the fuser roll
structure in order to yield a suitable length for the nip 36 (i.e.
an area coextensive with the concave portion of the backup roll). A
felt pad 75 and support 77 therefor are supported to the fuser
assembly frame so that the pad contacts the surface of the backup
roll. Thus, any contamination such as toner is removed from the
backup roll during its rotation.
It will be appreciated that as portions of the backup roll pass
through the nip area, the layers 72 and 74 are mechanically
stressed due to the flexing thereof. At the present time the useful
life of a structure such as the backup roll 18 appears to be
limited by the failure of the layer or sleeve 74, the main mode of
failure being the splitting or cracking thereof. Heretofore it has
been standard practice to utilize a heat resistant polymer material
such as fluoronated ethylene propylene (abbreviated FEP) for the
outer layer of the backup roll. For certain machines, the FEP
sleeves appear to be quite satisfactory. However, as operating
parameters of copiers, such as copier speed increase significantly,
it has been found that the flex fatigue life of FEP sleeves is not
satisfactory.
Flex fatigue life is defined as the number of cycles an FEP or
other material strip will undergo before splitting when flexed
90.degree. under 10 percent strain between two 20 mil radius
gripper jaws at 330.degree.F. Known materials such as the FEP
employed in the production of backup rolls provide rolls having
sleeves or outer layers whose flex life is on the order of 10K to
60K.
In order to improve the fatigue life of the backup roll of the
present invention, the layer or sleeve 74 has been fabricated from
a material having a flex life far in excess of the foregoing.
Accordingly, the sleeve 74 is fabricated from a copolymer of
perfluoroalkyl perfluorovinyl ether with tetrafluoroethylene
wherein the ether has the formula C.sub.n F.sub.2n.sub.+1
--O--CF=CF.sub.2 where n could probably be a number from 1-10
inclusive but is preferably 1-5 inclusive.
A backup roll 18 is fabricated with a layer of 74 PFA yielded 1.5
million flex fatigue cycles as compared to the 50 thousand cycles
obtained with the FEP sleeves.
The end caps 70 and 70' of the backup roll 18 are supported in a
pair of side frame or bracket members 76, 76' by bearings 78, 78'.
The backup roll together with the bearings and frame members can be
readily removed from the fuser assembly 12. To this end, the side
frames 76, 76' are provided in the uppermost portions thereof with
hook-like members 80, 80' which are received in recesses 82, 82'
provided in a pair of pivot arms 84, 84'. The pivot arms support
the backup roll for movement into and out of engagement with the
fuser roll structure 16 in a manner to be discussed hereinafter. A
pair of bolts 86, 86' fasten the lowermost portions of the side
frames to the pivot arms 84, 84'. The pivot arms are supported by
the machine frame through stub shafts 85.
To install the backup roll 18, the hook-like members 80, 81' are
inserted into the recesses 82, 82' with subsequent installation of
the bolts 86, 86'. To remove the backup roll the foregoing
procedure is simply reversed. Both installation and removal of the
backup roll can be accomplished quickly with a minimum of handling.
The hook-like members 80, 80' replace bolts similar to the bolts
86, 86'. It should be appreciated that during removal of the backup
roll when the bolts 86, 86' have been removed, the hook-like
members support the backup roll on the pivot arms 84, 84' so that
the backup roll need not be handled until after bolt removal. When
the backup roll is hot the foregoing aspect of the backup assembly
is significant. With prior art devices where four bolts are
employed, it is necessary to handle the backup roll while removing
the bolts.
As viewed in FIG. 4, the fuser roll structure 16 and the backup
roll 18 are supported out of engagement which corresponds to either
an inoperative condition of the copier apparatus 9 or a warmup
period which follows an initiation of the operation of the copier.
The warmup period is required among other things in order to allow
the fuser roll temperature to rise to a predetermined level
suitable for fusing toner particles on the support member 34. When
the rolls 16 and 18 are disengaged rotational movement of the
backup roll 18 is accomplished by means of a flexible shaft 90
which couples a drive gear 88 to the backup roll 18. Rotational
movement is imparted to the fuser roll structure 16 by virtue of
the driven gear 30 meshing with the drive gear 88. A shear pin 91
or other safety drive device secured in the hub of the gear 88 is
provided for drivingly coupling the gear to the main drive motor
(not shown) of the machine via a chain (also not shown).
The ends of the flexible drive shaft 90 which are rectangular in
cross-section are received in the end cap 70 and a clutch bearing
92, the latter of which is contained in the driven gear 88 for a
purpose to be discussed hereinafter.
The flexible drive shaft 90 allows for vertical displacement, as
viewed in FIG. 2, of the backup roll 18 which displacement is
effected by a latching mechanism generally indicated 94 (see FIGS.
4 and 5). During engagement of the backup roll and the fuser roll,
the backup roll is driven by the fuser roll and the one-way clutch
bearing 92 insures that the backup roll can be overdriven by the
fuser roll.
While other flexible shafts may be employed, the specific shaft 90
contemplated can be obtained from Stow Manufacturing Co. under the
designation Core No. Type 8990-100. This particular shaft is
fabricated by spirally winding wire rope to form a multi-layered
structure having a generally cylindrical cross section. The ends of
the shaft are crimped in order to form them into a generally square
configuration. In operation the rotation of the shaft is in a
direction which tends to tighten the windings thereof and therefore
render the shaft more rigid yet sufficiently flexible to allow for
the aforementioned displacement.
A modified form of the flexible coupling 90, as illustrated in FIG.
6, comprises a double slider coupling commonly referred to as an
Oldham coupling. In order to provide such an arrangement for
coupling the backup roll to a drive gear, the end cap 70 is
replaced by an end cap 96 having a slot 98 in the face thereof. A
shaft support disposed internally of the clutch bearing 92 is
replaced by coupling member 100 which has a slot 102 in the
circular face thereof similar to the slot 98 but oriented at a
90.degree. angle thereto. An interposer member 104 replaces the
shaft 90 and drivingly couples the end cap 96 to the coupling
member 100. To this end the interposer member comprises a generally
cylindrical body portion having a tongue portion 106, 106' formed
integrally with each of the faces thereof. This type of coupling
can, as in the case of the flexible shaft 90, permit displacement
of the backup roll 18, but it also permits quick removal of the
backup roll 18 from the fuser assembly.
The latching mechanism 94, as best viewed in FIGS. 4 and 5,
comprises a four pivot linkage arrangement which is actuated by
solenoid means 108 mounted on support bracket means 110 which is a
part of the side frame members 26, 26'. Each of the pivot arms 84
supports a differential screw 112 which in turn supports a moving
pivot member 114. The pivot member 114 operatively connects a link
116 to a link member 118 via a moving pivot 120 and a stationary
pivot 122. The stub shafts 85 supporting the pivot arms 84, 84' act
as a stationary pivot and form one of the four pivots of the
linkage arrangement.
The link 118 has affixed thereto a cam follower in the form of a
roller 124. The core 126 of the solenoid 108 acts as a cam, bearing
against the roller 124 to thereby effect clockwise rotation of the
link 118 about the pivot 122. Simultaneously, the moving pivot 120
moves to the right as viewed in FIG. 4 to a point that is
substantially in a straight line with a line drawn through the
center of the pivots 114 and 122. An adjustable bumper 128 acts as
stop member by virtue of its contacting the pivot arm 84 as viewed
in FIG. 5. In this manner the bumper 128 limits the degree of
travel of the pivot 120 to a position just to the left of the
aforementioned line drawn through the center of the pivots 114 and
122.
A pair of bias springs 130 (only one shown), one for each of the
pivot arms, assist the forces exerted by the fuser roll structure
16 to effect disengagement of the backup from the fuser roll when
the latching mechanism 94 is inoperative, in other words when the
solenoid means 108 is de-energized. The springs apply a total of
approximately 8 lbs. of force. It will be appreciated that the
amount of force required of the solenoid to maintain the backup and
fuser rolls in nip is quite small. The holding power requirement as
opposed to the latching power requirement for the solenoid is on
the order of 20 watts compared to 320 watts required for effecting
engagement between the rolls so as to create a total force of 800
lbs. during hot nip (i.e. when the fuser roll is at or near its
operating temperature). A second adjustable bumper or stop 132
integral with the link 118 limits the counterclockwise travel of
the link 118 through its engagement with the solenoid means
108.
Adjustment of the latching mechanism 94 is effected through
adjustment of the bumpers 128 and 132. With the solenoid energized
the bumper 128 should contact the pivot arms 84, 84' such that the
center of the pivot 120 is just to the left of the center line
through the pivots 114 and 122. If, when the solenoid is energized,
the foregoing is not the case then the bumper 128 can be moved
toward or away from the pivot arm, whichever is required.
Nip pressure can be varied through adjustment of the differential
screw 122 once the latching mechanism has been adjusted. Suitable
nip pressure is attained when the measured contact angle is equal
to 0.45 in. This can be done with standard carbon paper utilized in
accordance with established procedures for measuring the contact
arc between the backup roll and fuser roll structure.
It will be appreciated that the force exerted by the fuser roll
would normally tend to create a substantial shear force on the
bolts 86, 86'. Consequently, the side frame members 76, 76' are
constructed so as to direct the aforementioned shear forces through
the side frames in a direction so that these forces are directed
against inclined surfaces 134 of the pivot arms 84, 84'.
The solenoid means 108 may consist of a single D.C. solenoid, size
8EC available from Ledex Corporation or may consist of a pair of
D.C. solenoids, size 7EC also available from the Ledex
Corporation.
As illustrated in FIG. 7, a torque transmission shaft 136 couples
pivot arms 84, 84', to insure proper latching by the latch
mechanism 94. To this end, the lower portions of the pivot arms are
provided with castellated protrusions 138, 138' formed integrally
therewith. The shaft 136 supports a pair of castellated collars
140, 140' which cooperatively engage the protrusions 138, 138'
whereby motion imparted to either of the pivot arms is transmitted
to the other of the arms. The collar 140 is secured to the shaft by
a set screw 142 while the collar 140' carries a set screw 142'
which rides in a slot 144 provided in the shaft 136. A coil spring
146 engages a retaining ring 148 and the collar 140'in order to
bias the collars into engagement with the protrusions 138, 138'.
Removal of the shaft can be effected by simply moving it to the
right, as viewed in FIG. 7, against the force of the spring
146.
Also illustrated in FIG. 7 are a pair of fingers 150, 150' which as
viewed in FIG. 3 are positioned adjacent the exit of the nip 36.
The fingers effect removal of copy sheets 34 from the fuser roll
structure 16. As the copy sheet leaves the nip it follows the
rotation of the fuser roll structure, where it comes into contact
with the upper surface of the stripper fingers. The fingers thus
become interposed between the sheet and the fuser roll to thereby
redirect the sheet along a predetermined path of travel away from
the fuser roll so that it can be picked up by a transport (not
shown). The finger may be fabricated from a TFE material or the
upper surface thereof may be coated with TFE in order to minimize
tendency for the copy to stick thereon or for toner to be offset
thereto.
As illustrated in FIG. 3, a thermistor 152 and support 154 therefor
are pivotally supported in contact with the fuser roll structure
16. The thermistor may comprise any suitable construction, for
example, such as disclosed in U.S. suitable construction, for
example, such as disclosed in U.S. Pat. application Ser. No.
364,178, filed May 25, 1973 in the name of David K. Pearce and
assigned to the assignee of this invention. The temperature of the
fuser roll structure can be controlled in conjunction with the
output from the thermistor by a control circuit such as disclosed
in U.S. Pat. No. 3,327,096.
The entire fuser assembly 12 is supported within the apparatus 9 by
upper and lower slide structures and associated mounting brackets
and hardware. Only the upper slide 160 is illustrated. Suitable
slides are sold by the Accuride Co. and are identified by part
number C-301-17-LC. The slide structures and associated brackets
support the fuser assembly in a manner which enables sliding the
assembly into and out of the machine in a direction coincident with
the longitudinal extent of the rolls 16 and 18.
While the invention has been described with respect to the best
made contemplated, it will be appreciated that various
modifications may be made without departing from the spirit of the
invention. Accordingly, it is not intended that the scope of the
coverage sought be limited thereby.
* * * * *