Note: Descriptions are shown in the official language in which they were submitted.
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CYGROUND OF Ti~`lE INVENTION
~rhis invention relates ~enerally to ~erographic copying
apparatus and, more particularly, to a contact fusing system for
fixing electroscopic toner material to a support member.
In the process of xerography, a light image of an ori-
ginal 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 elec-
troscopic 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.
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.
i This action causes the toner to be absorbed to some extent into
the fibers of the support member which, in many instances, con-
stitutes 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
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xerographic as well as the electrographic recording arts, the use
of thermal energy for fixing toner images onto a support member
`~~ is old and well known.
One approach to thermal fusing 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 internally heated. During operation of a fusing
`l system of this type, the support member to which the toner images
are electrostatically adhered is moved through the nip formed be-
tween the rolls with the toner image contacting the fuser roll to
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thexeby effect heating of the toner images within the nip.
Heretofore, prior art fusers of the type described have
been constructed so that the roll members can be moved out of
contact wi~h each other during periods of non-use of the copier
apparatus, otherw~se flat areas may be formed on one or both of
the fuser members. Those skilled in this area of technology will
appreciate the complexity and the expense of the mechanism for
effecting such disengagement with the subsequent engagement of
the roll members. The desirability of eliminating such mechanisms
will also be appreciated by those skilled in this art.
BRIEF SUMMARY OF THE INVENTION
In accordance with one aspect of this invention there
is provided contact fusing system for fixing toner images to
copy sheets, said system comprising: a first roll structure;
a second roll structure; means for mounting said roll
structures for engagement whereby they cooperate to move said
copy sheets therebetween, said roll structures being permanent-
ly engaged; means for effecting rotational movement of said
roll structures; and means comprising a one-way clutch incor-
porated in said rotation effecting means for permitting rota-
tion of said roll structures independently of said rotation
effecting means whereby a copy~sheet can be manually moved
between said roll structures with simultaneous fixing of said
~, toner images to said copy sheet.
By way of added explanation, in accordance with this
invention in o~e of its aspects there is provided in a xero-
graphic reproducing apparatus a contact fuser system having a
pair of permanently nipped fuser roll members one of which is
heated for contacting toner images electrostatically adhered to
-~ 30 copy sheets. By permanently nipped, it is meant that the rolls
are not moved out of contact with each other.
The backup roll and its associated heated fuser roll
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member are operatively coupled to the main drive of the copier
apparatus via a one-way clutch which permits rotation of the
rolls independently of the main drive. The foregoing arrange-
ment enables a copy sheet, once it has started through the fuser
and in the event of a paper jam, to be manually pulled through
the fuser while simultaneously fusing the toner images carried
thereby. Accordingly, a copy which has started through the
fuser but has not been completely fused can be saved because it
can be fused notwithstanding a paper jam. In the typical prior
art roll contact fuser, for example, as described in U. S.
Patents 3,331,592 and 3,754,819, when a paper jam occurs, the
fuser roll members are automatically disengaged. Accordingly,
~ when the copy sheet is removed under such conditions it does
; not get fused.
Other objects and advantages of the present invention
will become apparent when read in conjunction with the accompany-
, ing drawings wherein:
Figure 1 is a schematic representation of a xerographic
~, reproducing apparatus incorporating the novel image fuser of the
present invention;
'~ Figure 2 is a top plan view of a fuser assembly incor-
1 porated in Figure l;
! Figure 3 is a right side elevational view of the fuser
.J assembly of Figure 2;
Figure 4 is a cross-sectional view taken on the line
~l IV-IV of Figure 3;
;~ Figure 5 is an enlarged fragmentary view in section of
- a release agent doctoring structure forming a part of the fuser
'i assembly of Figures 2 thru 4;
Figure 6 is a perspective view of the composite doctor-
ing structure of Figure 5;
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Figure 7 is an elevational view of the fuser assembly
as viewed from the left in Figure 3;
Figure 8 ~first page of drawings) is a perspective
view of a copy sheet stripper finger;
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Fiyure 9 is a cross-sectional view of a fuser roll system
showing a modified stripper fin~er arrangement and a backup roll
cleaniny structure;
Figure 10 is a cross-sectional view of a sprocket drive
and one-way clutch arrangement incorporated in the fuser assembly.
DETAILED DESCRIPTION OF T~E PREFERRED E~BODIMENT
,~ The reproducing machine illustrated in Figure 1 employs
an image recording drwm-like member 10 the outer periphery of
which is coated with a suitable photoconductive material 11. One
type of photoconductive material is disclosed in U.S. Patent No.
2,970,906 issued to Bixby in 1961. The drum 10 is suitably jour-
naled for rotation within a machine frame (not shown) by means of
a shaft 12 and rotates in the direction indicated by arrow 13, to
3 bring the image retaining surface thereon past a plurality ofxerographic processing stations. Suitable drive means (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
;I final support material such as paper or the like.
Since the practice of xerography is well known in the
art, the various processing stations for producing a copy of an
; original are herein represented in Figure 1 as blocks A to E.Initially, the drum moves photoconductive surface ll through a
l charging station A. At charging station A an electrostatic charge
1 is placed wniformly over the photoconductive surface 11 of the
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~ 25 drum 10 preparatory to imaging. The charging may be provided by
;~ a corona generating device of a type described in U.S. Patent No.
~ 2,836,725 iss~ed to Vyverberg in 1958.
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Thereafter, the drum 10 is rotated to exposure
station B where the charged photoconductive surface 11 is
exposed to a 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 ~orm of a latent electrostatic image. A
suitable exposure system may be of the type described in
U.S. Patent 3,832,057.
After exposure, drum 10 rotates the electrostatic
10 latent image recorded on the photoconductive surface 11 to
development station C, wherein a conventional developer mix
is applied to the photoconductive surface 11 of the drum 10
rendering the latent image visible. A suitable development
station is disclosed in Canadian Patent Application, Serial
No. 145,905. This application describes a magnetic brush
development system utilizing a magnetizable developer mix
having carrier granules and toner comprising electrophoto-
graphic resin plus colorant from dyes or pigments. A
developer mix is continually brought through a directional
20 flux field to form a brush thereof. The electrostatic
' latent image recorded on photoconductive surface 11 is
developed by bringing the brush of developer mix into
contact therewith. The developed image on the photoconduc-
tive surface 11 is then brought into contact with a sheet
of final support material 14 within a transfer station D
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and the toner image is transferred from the photoconductive
surface 11 to the contacting side of the final support
sheet 14. The final support material may be plain paper,
gummed labels, transparencie~ such as Polycarbonate, Poly-
30 sulfane and Mylar , etc., as desired.
* trade mark
~05957~3
After the toner image has been transferred to the
sheet of final support material 14, the sheet with the image
thereon is advanced to a suitable fuser assembl~ lS which
fuses the transfer powder image thereto. After the fusing
process, the final support material 14 is advanced by a series
of rolls 16 to a copy paper tray 17 for subsequent removal
therefrom by a machine operator.
Although a preponderance of the toner powder is
transferred to the final support material 14, invariably some
residual toner remains on the photoconductive surface 11 after
the transfer of the toner powder image to the final support -
material 14~ The residual toner particles remaining on the
photoconductive surface 11 after the transfer operation are
removed from the drum 10 as it moves through cleaning s*ation
~ E. Here the residual toner particles are first brought under
; the influence of a cleaning corona generating device (not
shown) adapted to neutralize the electrostatic charge remain-
ing on the toner particles. The neutralized toner particles
are then mechanically cleaned from the photoconductive surface
11 by conventional means as for example, the use of a resil-
iently biased knife blade as set forth in U. S. Patent No.
3,660,863 issued to Gerbasi in 1972.
The sheets of final support material 14 processed in
- the automatic xerographic reproducing device may be stored in
the machine within a removable paper cassette 18. A suitable
paper cassette is set forth în Canadian Patent Application,
Serial No. 148,892.
The copier can also have the capability of accept-
ing and processing copying sheets of varying lengths. The
30 length of the copy sheet, of course, being dictated by the ~-~
size of the original input scene information recorded on the
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photoconductive surface 11. To this end, the paper cassette
18 is preferably provided with an adjustable feature whereby
sheets of varying length and width can be conveniently accom-
modated therein.
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In operation, the casset~e 18 is filled with the stack
of ~inal support material 19 of pre-selected size and the cassette
18 is insertcd into thc machine by sliding along a bascplate (not
shown) which guides the cassette 18 into operable relationship
with a pair of feed rollers 20. When properly positioned in
communication with the feed rollers 20 the top sheet of the stack
19 is separated and forwarded from the stack 19 into the transfer
station D by means of registration rollers 21.
It is believed that the foregoing description is suf-
ficient for purposes of present application to illustrate the
general operation of an automatic xerographic copier which can
embody the teachings of the present invention.
The fuser assembly 15 as best illustrated in Figures 2
through 4 comprises a heated fuser roll structure 30 and a backup
roll 32 which cooperate to form a nip 33 therebetween through which
copy paper having toner images thereon passes with the toner images
contacting the fuser roll structure 30.
A channel shaped support base 34 (Figure 3) is provided
for supporting the fuser assembly 15 in the copier apparatus. The
backup roll 30 is supported by a pair of support brackets 36 which
are secured to the support base 34 by means of right angle brac-
- kets 38, the bases of which are spot welded or otherwise suitably
affixed to the support base 34. A pair of ball bearings 40 are
supported by the brackets 36 and are captivated in the brackets
by means of retaining rings 42. The backup roll structure may
comprise any suitable construction, for example, a steel cylinder,
but preferably comprises a rigid steel core or shaft 46 having a
~" Viton elastomer surface or layer 48 disposed thereover and affixed
thereto. A pair of shaft ends 49 of the core or shaft 46 are re--
; 30 ceived in the bearings 40 for supporting the backup roll 30. A
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suita~]e )~ackup rol~ has an overall dimension of approximately 1.55
inches including A O . 1 inch cover or layer of Viton elastomer or
othcr suitable hi~jh temperature elastomeric material, for example,
fluorosilicone or silicone ru~ber. The spccific dimensions of the
backup roll will be dictated by the requirements of the particular
copying apparatus wherein the fuser assembly 15 is employed, the
dimensions being greater or less depending upon the process speed
of the machine. In this embodiment the length of the roll is ap-
proximately 15 1/2 inches to accomodate various paper sizes.
A pair of support brackets 50 (Figure 2) having a gen-
erally E-shaped configuration similar to the support brackets 36
are provided for mounting the fuser roll structure in the fuser
assembly 15. To this end, a pair of ball bearings 52 one in each
of the support brackets 50 are provided, the bearings being re-
tained in the brackets by means of retaining rings 54. A pair of
end caps 55 are secured to a hollow cylinder or core 56 (Figures 3
and 4) forming a part of the fuser roll structure 30 and reduced
portions 57 thereof are received in the bearings 52 for supporting
the fuser roll structure. A heating element 58 is supported in-
ternally of the core 56 for providing thermal energy to elevate
the temperature of the core to operating limits. The heating
element may comprise any suitable type heater for elevating the
.
surface temperature of the cylinder to operational temperatures,
therefore 285-290F. For example, it may be a quartz envelope
having a tungsten resistance heating element disposed therein.
The cylinder or core 56 is fabricated from any suitable material
capable of efficiently conducting the heat to the external surface
of the core. Typical materials are anodized aluminum and alloys
thereof, steel, stainless steel, nickel and alloys thereof, nickel
plated c~pper, chrome plated copper, copper and alloys thereof.
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The resulting structure has an outside diameter on the order of
1.5 inches and has a length equal to that of the backup roll.
The power requirements for the foregoing are 420 watts peak
power with an average power of 320 watts and lO0 watts for
standby.
The heater element 58 is supported internally of the
core 56 by a pair of spring supports 60 which are mounted by in-
sulator blocks 62 to the support brackets 50. The free ends of
the springs supporting the heater element are each provided with
a locating ball 64 while the opposite end of the spring is dis-
posed in contact with an electrical terminal 66 to which elec-
trical wires (not shown) may be attached for supplying elec-
trical energy to the heater element. The terminal blocks can
be secured to the support brackets in any suitable manner, for
example, by screws. The spring supports and terminals are
preferably riveted to the terminal block.
The aforementioned materials from which the core 56 of
the fuser roll structure may be fabricated are relatively high
surface ener~y materials, consequently, hot toner material con-
tacting such surfaces would readily wet the surface of the fuserroll and it would be difficult to remove the toner therefrom.
Accordingly, there is provided a sump 68 (Figures 2 and 4) for
containing a material 69 capable of interacting with the core
in a manner described in Canadian Patent Application, Serial No.
, 198,048, Moser, et al and assigned to the same assignee as the
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instant application. The material is preferably a low molecular
weight substance which is solid at room temperature and which
has a relatively low viscosity at the operating temperatures of
the fuser roll structure. An example of such a material is
polyethylene homopolymer manufactured by Allied Chemical Co. and
having the designation AC-8 hopolymer.
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The sump 68 comprises a rear wall 70 having a generally
sloping portion connected to a generally vertical portion. The
rear wall is provided with a pair of apertured flanges 72 for
receiving supports 74 for mounting the sump 68 to the flanges 51
secured to the brackets 50 in a manner to allow pivotal movement
thereof. The sump also comprises a front wall (~igure 5) which
comprises a composite doctoring blade 78 including a base mer~er
80 with an elongated strip 82 secured to the base member. The
strip 82 is fabricated from a high tem~erature elastomeric material
which is compatible with the particular material 69, for example,
silicone rubber or Viton. By compatible with the strip it is meant
that the dimensions of the strip are not altered by contact with
the material.
The base member 80 and therefore the blade 78 is sup-
ported by the rear wall 70 by means of a rubber seal attached to a
lip 84 forming a part of the rear wall and a retainer 86 which is
suitably secured by, for example, screws 87, to the rear wall 70.
The base member 80 is provided with a plurality of slots 88 in
which the screws 87 ride to allow mounting of the base member in-
termediate the retainer 86 and the rear wall 70. The base member
is also provided with a plurality of apertures 90 disposed on the
- sides of the slots 88. The apertures receive dimples 92 forming
a part of the retainer 86. The slots and the apertures are over-
sized with respect to the dimples and screws so that the base mem-
ber can move due to thermal expansion without buckling thereof.
It will be appreciated that in addition to serving as a metering
blade the composite structure 78 serves to clean toner from the
fuser roll structure 30 and also act as a seal to prevent the
liquid or low viscosity polyethylene from leaking out of the sump
68. A pair of arcuate recesses 94 provided in the rear wall 70
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have disposed therein end seals 96 which contact the fuser roll
structure and thereby cooperate with the strip 82 to prevent leak-
age of polyethylene from the sump.
A pair of links 100 attached to extensions 101 of the
rear wall by retaining pins 102 have their ends threaded for re-
ceiving nuts 104. A tie bar 106 attached to the support brackets
50 support L-shaped brackets 108 having slots 110 therein. The
links 100 are received in the slots 110 to thereby provide means
for adjusting the pivotal orientation of the sump 68 to thereby
increase or decrease the pressure of the composite doctoring
structure 78 on the fuser roll structure to thereby control in
accordance with a predetermined amount, for example, a layer less
than 1 micron thick, the application of polyethylene to the fuser
roll structure. This is accomplished by tightening or loosening
, 15 of the nuts 104.
As mentioned hereinbefore, the polyethylene is solid
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at room temperature and is liquid at operational temperatures.
i The polyethylene in solid form is placed in the sump and is heated
~ by the thermal energy of the fusing roll structure and thereby
- 20 liquified. When the polyethylene resolidifies after the machine
~ has been inoperative for a period of time the polyethylene tends
,''7, to move away from the fuser roll structure consequently when the
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machine is restarted the polyethylene may not be applied to the
fuser roll structure immediately. This means that the fuser roll
~ 25 structure may not be properly protected against toner offsetting
f '~
'"'~1 to the bare metal. In order to safeguard against the foregoing,
~ the surface of the rear wall contacting the polyethylene is coated
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with a material that has a low affinity for the polyethylene,
for example, silicone rubber. In order to insure that the poly-
~ 30 ethylene is in contact with the fuser roll structure at the time
3 of restarting the machine, a collecting bar 111 is provided in the
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sump ancl attached thereto such that it is positioncd adjacent the
~user roll structure. I~ccorclingly, when the polyethylene resoli-
difies it will pull away from the rear wall 70 and it will solidify
on the collecting bar such that it is still in contact with the
fuser roll structure. This arrangement will insure proper opera-
tion of the fuser assembly until the bulk of the polyethylene is
melted in the sump.
The axis of the backup roll which should be apparent
from a consideration of its mounting as discussed above is fixed
relative to the support base 34. However, the fuser roll structure
is mounted such that it's pressure engagement with the backup
roll can be adjusted to thereby enable variation of the length of
the nip 33 formed between the two roll structures. To this end,
the fuser roll support brackets 50 are mounted to the backup roll
support brackets 36 by a pair of flexures 112 which are secured
to the support brackets 36 and 50 by means of retaining plates
114, dowl pins 116 and caps screws 118. The flexures 112 are
preferably fabricated from spring steel having a relatively small
thickness but sufficiently sturdy to hingedly mount the fuser roll
support brackets to the backup roll support brackets. A force at
the nip on the order of 150 pounds is provided by means of socket
head screws 120 and commercial compression springs 122 which are
supported by the upper flanges 51 secured to the fuser roll sup-
port brackets 50. The screws 120 are received in threaded lower
flanges 126 which are fixedly mounted to the backup roll support
brackets-36. It will be appreciated that by adjusting the socket
head screws 120 against the force exerted by the springs 122, the
nip pressure can be varied to produce the desired nip pressure.
The copy paper 14 carrying the fused images comprising
toner 124 is moved through a lower guide plate 128 (Figure 4)
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which is supported by mounting brackets 129 attached to the backup
roll supporting hrackets 36 and an upper guide plate 130 attached
to the tie bar 106. The upper guide pla-te is mounted to the tie
bar by mean~ of a generally U-shaped flange 132 having an open
area whlch is integral with the plate 130 and disposed at an acute
angle relative thereto. To insure that the copy paper follows
along a predetermined path including the space between the lower
and upper guide plates a plurality of generally L-shaped stripper
fingers 134 (Figures 4 and 8), preferably two in number, are pro-
vided. The leading edges of the stripper fingers are biased into~
engagement with the fuser roll structure 30 by means of a pair of
combination mounting brackets and bias member 136 in the form of
leaf springs. The leaf springs are mounted to the tie bar 106
such that a cantilevered portion 137 thereof engages a cam surface
138 of the stripper finger 134. Portions of the mounting bracket
136 are rolled as indicated at 140 to provide a bearing surface
'f for shafts 141 carried by the stripper fingers 134.
An alternate form of stripper finger may be employed
which comprises stripper fingers 142 (Figure 9) supported on a
, 20 shaft 143 which is supported indirectly by the support brackets
50 of the fuser roll structure 30. A counterweight 144 is pro-
vided for each of the stripper fingers 142 and is secured thereto
by means of a cap screw 145 which is threaded into the stripper
finger. The position of the counterweight can be varied relative
to the stripper finger to increase or decrease the amount of
l pressure which is applied by the stripper finger to the fuser roll
" structure. The position of the stripper fingers 142 are maintained
-~ on the shaft in a position relative to the longitudinal axis of
I the fuser roll structure 30 by grip rings 146. The grip rings
while maintaining the position of the stripper fingers fixed re-
lative the fusing roll structure 30 allow movement relative to the
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aforementioned aY~is o~ the stripper ~ingers with respect to the
fuser roll struct-lre so that the fuser stripper fingers can be
repositioned in the event of wear of the fuser roll structure.
The surface temperature of the fuser roll structure 30
is controlled by contacting the surface thereof with a thermistor
probe 148 of the type described in U.S. Patent 3,327,096, issued
in 1967 to sernous and incorporated herein by reference.
During operation of the fuser assembly 15, particularly
during duplex copying, toner accumulates on the backup roll struc-
ture 32. Accordingly! a backup roll cleaning structure or assembly
150 is provided which comprises a triangular shaped support member
152 having a wiper member 153 carried thereby. The cleaning assem-
bly is supported for movement in the direction of the backup roll
structure by a plurality of roller supports 154 and a spring member
156 supported by a member 158 urges the wiper surface into wiping
contact with the backup roll. As can be seen from the drawings,
the cleaning assembly is disposed adjacent the support base 34
so that toner removed from the backup roll will be deposited onto
l the support base. In operation it has been found that the toner
`~ 20 accumulates on the exit side of the nip formed between the backup
roll and the wiper member. The wiper member is preferably a high
temperature material with a high degree of resiliency and low af-
finity for toner particles and preferably comprises tetrafluoro-
ethylene, commonly referred to as TFE.
In order to accomplish rotational movement of the fuser
and backup rolls, the main machine drive is coupled to the fuser
~ roll structure via a drive sprocket 160, which is coupled to a
`l driven sprocket 161 by means of a one-way clutch 162, a bushing
164, and stub shaft 166. The driven sprocket 161 is coupled to
a sprocket 170 carried by the shaft of the fuser roll structure 30
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via a chain 172. The clutch 162 serves as a coupling between the
input from the main machine drive and the fuser roll structure,
which allows the fuser roll structure and backup roll to be rotated
independently of the sprockets provided for power driving the fuser
roll structure. In the event that a machine jam occurs, a sheet
of copy paper which has started through the nip of the fuser
assembly 15 can be manually moved out of the fuser assembly while
simultaneously fusing the toner images to the copy paper. Accord
ingly, unlike prior art fuser structures utilized in the xero-
graphic process, a copy which has started through the fuser but
has not been completely fused can be saved because it can be fused
notwithstanding a paper jam.
A cover structure 174 protects the fuser assembly from
contaminates. As viewed in Figure 7, the cover structure has a
bifurcated flange portion 176 which receives a pin member 178
carried by the bracket 50. There are two such flanges and pin
members, one on each side of the fuser assembly. A sidewardly
projecting flange 180 has an aperture through which a screw 181
is inserted and received in a threaded aperture in a flange 182
forming a part of the sump 68. The combination bifurcated flanges
- and pin members together with the screw 181 secures the cover in
place. As viewed in Figure 3, the cover has an inclined top sur-
face 184 and an opening 186 at the extreme right end thereof for
- directing vapors out of the fuser assembly. A pair of depending
flanges 190 cooperate with pins 192 carried by the tie bar 106
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to assist in maintaining the cover in place.
While the invention has been described with respect to
a preferred embodiment, it will be apparent that certain modi-
,
fications and changes can be made without departing from the
spirit and scope of the invention, for example, the images to be
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fused can be formed by other than the xerographic process dis-
closed and it is therefore intended that the foregoing disclosure
be limited only by the claims appended hereto.
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