Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a fusing apparatus for
reproduction or copying machines, and more particularly, to
an improved fusing apparatus incorporating means to offset
spot or uneven wear of the fuser roll surface.
In order to fix, i.e. fuse, a toner developed
image, reproduction or copying machines incorporate a fixing
device, conventionally called a fuser. while the fuser may
take many forms, as, for example, a vapor fuser, heat or
combination heat-pressure type fusers appear today to be
most prevalent. One combination heat-pressure fuser consists
of the heated fusing roll in physical contact with a rela-
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tively soft pressure roll, these rolls cooperating to form afusing nip between which the copy material being fused pass.
To prevent offsetting of the toner onto the fuser rolls,
particularly the hot fusing roll, the roll surfaces are
preferably covered with a release material.
To assure removal of the fused material, for
example, copy sheets, from the fusing roll and to obviate
any tendency for the copy material to stick or adher to the
~ fusing roll surface, stripping fingers are often provided
f~ ' adjacent the fuser exit to strie the fused copy material
therefrom. To assure effective and reliable operation of
the stripper fingers, the fingers are normally biased or
otherwise held in operatite engageMent with the fusing roll
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periphery. Over a per-od of use, the constant rubbing cf
the stripper fingers against the roll perip~lery may wear
away the release material and result in lines or grooves
i; ~eing w~rn in the fusing roll surf~ce. In time, this may
have a deleterious effect on fuser operation. ~ '
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In a~similar vein, many t~sers incorporate a heat
detect~r or sens~r for the purpose of con~r~lling heat input
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to the fuser and to protect against dangerous over heating. ~ -
The aforesaid sensor may be arranged to rest or ride against
the fuser surface and this in turn may wear away a portion
of the release material.
In addition, it has been found that over an extend-
ed operating period, the copy material itself can cause
excessive wear on certain portions of the fusing roll surface, ;
most notably along the line where the relatively sharp edges
of the copy material contact the fusing roll. This problem
is perhaps furthered by the tendency in the industry toward
common sheet sizes, i.e. 11 inches.
In accordance with this invention there is provided
a reproduction machine for producing copies of documents, com-
prising in combination, a fuser for fixing the copy images
developed, the fuser having cooperating pressure and heated
fusing rolls forming there-between a nip through which copies
to be fused pass, bearing means supporting one of the rolls
for rotation, the bearing means being movable in an axial
direction to permit the one roller to be shifted axially where-
by to off~et spot wear on
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the surface of the one roll, and locking means for releasably
locking the bearing means and the one roll in selected position.
The present invention will be more apparent from the
ensuing description and drawings, in which:
Figure 1 is a schematic view of an exemplary repro-
duction or copying machine incorporating the improved fuser of
the present invention;
Figure 2 is an enlarged top plane view showing details
of the fuser roll support mechanism of the present invention;
and
Figure 3 is an enlarged side view in section of the
fuser shown in Figure 2.
( Referring particularly to Figure 1 of the drawings,
an exemplary copier/reproduction machine, designated generally
by the numeral 10 and incorporating the improved fuser 38 of
the present invention, is there shown. As in all electrostatic
systems such as the xerographic type machine illustrated, a
light image of a document to be reproduced is projected onto
the sensitized surface of a xerographic plate to form an
electrostatic latent image thereon. Thereafter, the latent
image is developed with an oppositely charged developing
material to form a xerographic powder or toner image, corres- -'
ponding to the latent image on the plate surface. The toner
image is then electrostatically transferred to a support or
copy material where it is fused by a fusing device so that the ;
toner image is permanently adhered to the copy material.
In machine 10, an original document ~2 to be copied
is placed upon a transparent support platen 14 fixedly ~
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arranged in an illumination assembly generally indIcated by
the reference numeral 15 and disposed at the left end of the
machine. While upon the platen, the document 12 is illumin-
ated. thereby producing image rays corresponding to the in-
formational areas on the oriqinal. The image rays are
projected by means of an optical system onto the photosensi-
tive sur~ace of a xerographic plate. In the exemplary copier/
reproduction machine 10, the xerographic plate is in the form
of a flexible photoconductive belt 17 supported in a belt
-~ assembly 18.
The support assembly 18 for photoconductive belt
17 includes three rollers 20, 21, and 22 located with parallel
i axes at approximately the apices of a triangle. The upper
roller 22 is rotatably driven by a suitable motor and drive
-~i means (not shown) to drive belt 17 in the direction shown by
the arrow in Figure 1. During this movemen. of the belt, the
~;~ xeflected light image of the original document 12 on platen
i 14 is flashed upon the photoreceptor surface of belt 17 at
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an exposure station 25 to produce an electrostatic latent
image thereon.
The continued movement of photoconductive belt 17
carries the electrostatic image through a developing station
26 in which there is positioned a developer assembly generally
indicated by the reference numeral 28~ There the latent
electrostatic image is de~eloped by means of toner throush
the use of a multiple magnetic brush system ~9.
The developed electrostatic image is carried ~y
belt 17 to the transfer station 30 where the developed image
is transferred to a copy material such as a sheet 31 of copy
p~per brought forward ~etween transfer loller 32 and b~l~ 17
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In order to accomplis~ transfer of the developcd image solely
by means of the electrical bias on transfer roller 32, the
copy sheet 31 is moved at substantially the same speed as
belt 17. A sheet transport mechanism generally indicated at
34 is provided to advance copy sheets 31 along a preset path
from a paper handling mechanism generally indicated by the
reference numeral 35 to transfer station 30 whereat the
developed image is transferred.
Following transfer, the copy sheet 31 is stripped
from belt 17 and conveyed by the sheet transport mechanism
34 through fuser 38 wherein the toner image is permanently
fused or affixed thereto. Foliowing fusing, the finished copy
is discharged into output tray 39.
While individual copy sheets 31 have been illus- -
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trated, it will be appreciated that endless o~ web-type copy
material may be used.
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Photoconductive belt 17 comprises a photoconductive
layer of selenium, which is the light receiving surface and
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imagang medium for the apparatus, on a conductive backing.
Further details r~garding the structu-e of the belt assembly
12 and its relationship with the machine and support therefor
~ may be found in United States Patent No. 3,730,623, issued
:( Ma~ 1, 1973, and assigned to the same assignee.
~user 38 includes a suitable housing 40 within
which is disposed a lower heated fuser roll 41 and an upper
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`~, back-up or pressure roll 42, rolls 41, 42 cooperating to
form a nip through which the copy sheets 31 pass. ~user
rolls 40, 41 are driven in the direction sh~o~ll b~ the solid
line arrows in Figur~ 3. ~o assure removal of sheets 31
~ therefrom, one or more stripper fingers 46 are rotatably
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supported as by shaft 47 in fuser housing 40 at the fuser
discharge side such that the leading edge 48 of fingers ride
or rest against the surface of fuser roll 41. To assure
sustained contact of fingers with the fuser roll surface,
suitable spring biasing means 49 are provided.
Pressure roll 42 includes a rigid internal core SO
; which may be steel, for example, over which a relatively
thick flexible sleeve-like cover 51 formed from a suitable
release material is disposed. Fuser roll 41 similarly has a
rigid internal core 54 which may, for example, be copper,
having a relatively thin coating 55 of a suitable release
material thereover. The relatively thin fuser roll coating
~` 55 may, for example, be applied by spray coating techniques.
One suitable release material for both pressure roll cover 51
and fuser roll coating 55 may comprise polytetrafluoroethylene.
Sleeve 51 of pressure roll 42 and coating 55 of
fuser roll 41 serve to prevent the toner on copy sheets 31
from offsetting onto the surface of either roll 41 or 42 as
well as to aid in preventing the sheets 31 themselves from
i sticking to one or the other of fuser and pressure rolls 41,
42, respectively. To heat f~9er roll 41, the cen~er of core
54 is hollow and a suitable heating lamp 56 is disposed
therewithin. Heating lamp 56 is connected to a suitable
source of electrical power (not shown). As will be under-
stood, heat from lamp 56 radiates to core 54 and is conducted
~i to the exterior coating 55 on the periphery thereof. The
heat from fuser roll 41 cooperates with whatever pressure
is excrted by pressure roll 42 to fuse the toner developed
~3: ~ imagés on copy sheets 31. Otller heating lamp arrangement~
or heatin~ sources may b~ ~lsed instead o~ the l~lmp arrangement
~llustrated.
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The metal cores 50, 54 of rolls 41, 42 are each
provided with projecting stub shafts 60, 60' and 61, 61',
respectively. In this connection, it will be understood that
stub shaft 61' of fuser roll 41 is hollow to accommodate
insertion and removal of heat lamp 5~ as well as the elec-
trical leads 64 thereto. The stub shafts of fuser and
pressure rolls 41, 42, respectively, are used to support
rolls 41, 42 in operative engagement with one another, stub
shafts 60, 60' of pressure roll 42 being suitably journaled
l in support arms 68 while stub shafts 61, 61' of fuser roll
41 are rotatably journaled by roller type bearings 74, 75 n
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fuser housing side walls 66, 67. The pressure roll support
arms 68 are pivotally mounted within fuser housing 40 by
suitable means (not shown) enabling pressure roll 42 to be
separated from fuser roll 41 when desired, i.e., as for
servicing of fuser 38, as more fully described in U. S.
Patent No. 3,754,819, issued August 28, 1973, and assigned
,
'l to the same assignee. Suitable bias means (not shown) are
provided to place pressure roll 42 in operating contact with
fuser roll 41.
Fuser roll bearings t.4, 75 ~re supported in side
walls 66, 67 of fuser housing 40. For this purpose, fuser
housing side walls 66, 67 each bave bearing bores 70, 70'
therethrough within which bearings 74, 75 rest, bores 70, ;
70' being slightly oversize to permit the supporting bearings
74, 75 for fuser roll 41 to slide axially therewithin.
Stub shafts 6C, 61, which project from one side of ;
3 pressure and fuser rolls 42 and 41, respectively, have
A~ meshing roll driv~ gears 76, 77 affixed to the ~erminal ends
thereof. Gears 76, 77 serve to drived1y ~nt~connect the
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fuser and pr~ssure rolls 41, 42 with each other. ~ suitable
fuser drive shaft 80 is provided to rotate the pressure roll
: gear 76 in.the direction indicated by the solid line arrow
in Figure 3, shaft 80 being drivingly connected to gear 76
by suitable means (not shown).
.. ~ As described, bearings 74, 75, which rotatably
. support fuser roll 41, are slideably disposed within bearing : .
bores 70, 70' of fuser housing walls 66, 67. To control the : . .
degree of fuser roll axial displacement and prevent unwar~
ranted axial displacements of the roll, the periphery of the . ~. .
. outer bearing race 82 of bearing 75 has a pair of spaced ..
grooves 84, 85 extending about the circumference thereof. ~.
The outer surface or boss 86 of the fuser housing wall 67
ad~oining the bearing bore is relatively flat to present a
`~ .stop or abutment surface O A bearing lock ring 87, which
conveniently may consist of cooperating ring halves, is
provided. The cross-sectional width of lock ring 87 is
~` slightly less than the width of grooves 84, 85 to permit
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-....... ring 87 to be inserted in one or the other as will appear. .:
The inner diameter of ring 87 is substantially equal to the
outer diameter of grooves 84, 85 while the outer diameter of ~
ring 87 is somewhat greater than the diameter of bearing ~.
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i bore 70'. By this construction, lock ring 87, w~hen inserted
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into one of the grooves 84, 85, projects radially outwardly
therefrom to prevent, in cooperation with boss 86 on wall
67, axial movement of fuser .roll 41 toward the opposite wall
66 (in the direotion shown by the solid line arrow in Figure
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~: :~ : An ou~er bearing cap ~0 is provi.ded havins an
ir.ternal bore 91 substantiaLly C~UDl to the diameter of
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bearing bore 70'. The outer dimen.sion of bearing cap 90 is
substantially grcater than the outer diameter of locking
ring 87 to permit cap 90 to overlay ring 87. Bearing cap
` 90, which is relied upon to prevent axial displacement of
fuser roll 41 in the opposite direction, is provided with a
relatively flat inside wall 92 adapted to abut boss 86 on
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wall 67. To accommodate lock ring 87, wall 92 of bearing
cap 90 is recessed at 9S. Screws 96 serve to releasably ~;
retain bearing cap 90 in place on the fuser housing wall 67. ~ ,
By the above-described construction, it will be
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understood that inter-engagement of lock ring ~7 with a
selected groove 84 or 85 in the outer bearing race 82 of
the fuser roll bearing 75 locates fuser roll 41 against ~ ;
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1 axial displacement in one direction, i.e., in the direction
J indicated by the so]id line arrow of Figure 2. Lock ring 87~ ;
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is in turn trapped between boss 86 on fuser housing wall 87
i and bearing cap 90 to prevent axial displacement of the outer
race 82 of bearing 75, and fuser roll 41, in the opposiie
;i4i . direction, i.e. the dotted line arrow shown in Figure 2.
As a result of the continual movement of copy
sheets 31 along the same path between fuser and pressure
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`l~ rolls 41, 42, the edges of sheets 31, which are relatively
harp, tend to wear away or erode the relatively thin coating
d 55 of release material on the metal core 54 of fuser roll 41.
This may result in the coating 55 belng worn off thc surface
of roll 91 in these areas wïth the result that toner may
adhere or offset onto the fuser roll surface at these points.
In a similar vein, contact of the stripper fingers
46 with the fuser roll surf~ce may in ti~e wear away the
sur~ace coating 55 on ruser roll ~1 where fin~ers 4b contact
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roll 41. ~s described, erosion of the release material
coating roll 41 may result in the ton~r offsetting ~nto the
roll surface with attendant degradation in the quality of the
copies produced.
In addition, the eroding or wearing away of the
release coating on fuser roll 41 may in time result in an
uneven or scored roll surface which itself may affect adverse-
ly fusing contact between rolls 41, 42 of fuser 38. ^
To obviate the above, fuser roll 41 is shiftedaxially to establish a different surface relationship between
fuser roll 41 and the copy sheets 31, as well as between the
surface of roll 41 and any other components such as stripper
fingers 46 in contact therewith. The aforesaid shifting or
fuser roll 41 may be undertaken in accordance with a pre-
determined servicing routine, i.e. after a preset number of
copies, or when inspection of the fuser roll 41 indicates
the desirability of doing so.
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~ Where it is desired to shift fuser roll 41 axially,
;~ bearing cap 90 is removed by removing attaching screws 96.
This permits loc~ ring 87 to be extracted from the groove 84
or 85 previously u9ed. The entire fuser roll 41 including
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' bearings 74, 75 may th~n be shifted axially until the unused
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,;;j groove 84 or 85 comes into operative position adjacent fuser
housina wall 67. Lock ring 87 may then be inserted into the
~;,5 new groove, and bearing cap 90 reins,~lled to lock fuser
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roll 41 in the new position. As can be appreciated from the
aforementioned description, the fuser roll 42 need not be
removed from the fuser housing 40 nor need f~lser 38 itself
~e otberwise dis-assembled. `~
~i ` ~o facilitate axi~l movement of fuser ro~l 41,
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pressurc betheen roll3 41, ~2 may be re3eased as described
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in the aforementioned U. S. Patent No. 3,754,819. ~nd to
facilitate proper location of the roll 41, lock ring 87 may
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be first inserted in the selected groove and thereafter
serve as a locating stop.
While fuser roll 41 has been described herein as
supported for movement, it wili be understood that pressure
roll 42 may instead or in addition be supported for axial
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displacement io accommoda.e spot wear on the pressure roll ~
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surface.
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~D While the invention has been described with
reference to the structure disclosed, it is not confined to
the details set forth, but is intended .o cover such
modifications or changes as may come within the scope of
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