Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to improved flared fuser
roll apparatus for fusing simplex and duplex co~ies produced
from a high speed copier/duplicator.
In copier/duplicator systems producing copies
wrinkled copies predominently occurring on the second
pass of the duplexed copy through the pressure heated
fusers have been a noticeable problem. The magnitude
and frequency of the wrinkle are known to be a function
of how long the copies are aged between simplex and duplex
passes, and are definitely affected by aging in a high
humidity environment. ~ormally, the paper wrinkle occurs
when the sheet of paper has become distorted before being
- processed on the second pass by the machine so that it is
no longer in a flat state. This is normally a result of
elongation of the edges of the copy sheet due to absorbtion
of moisture during the aging time between the simplex and
duplex passes. During the first pass, the entire sheet is
dried out, and because the copy sheet is part of a stack,
moisture re-absorbtion takes place primarily through the
edges. With the edges of the copy sheet being longer than
the center, wrinkles are formed as the copy sheet goes
through the roll nip during the duplex pass. It is also
possible to produce wrinkled copy on the first pass if the
paper is unpacked long enough prior to processing to permit
it to absorb sufficient moisture to result in edge elongation.
In accordance with this invention there is
- provided an improved pressure heated fusing apparatus
for a copier/duplicator machine capable of simplex and
duplex operation wherein the copy sheets make two passes
through processing station comprising: a first roll which
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is heated to a temperature sufficient to fuse toner images
onto paper support sheet material, a second roller arranged
axially parallel with said first roll to define a nip through
which the paper support sheet material bearing toner images
is passed, said first roll having a longitudinal cross-
sectional shape with a maximum diameter at the ends and a
minimum diameter at the center, said first roll being formed
with a taper at each end and having a center portion of
substantially uniform diameter extending longitudinally for
a predetermined distance between the taper ends.
This invention will be more apparent after
reading the following detailed description which refers to
accompanying drawings in which:
Figure 1 is a schematic view of a xerographic
copier/duplicator machine producing simplex and duplex
copies according to the present invention;
Figure 2 is a slde view of the improved roll
apparatus according to the present invention;
Figure 3 is a side view of an alternate roll
according to the invention.
Figure 1 shows a schematic of the copier/duplicator
system generally designated 2 including a copier machine 3,
which is a high speed copier/duplicator capable of producing
simplex or duplex copies at the option of a machine operator.
The copier machine 3 has a platen 4 for receiving documents
to be reproduced, and a control panel (not shown) which
includes various control knobs, buttons and switches for
selecting various modes of operation such as simplex and
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duplex copies and the number of copies to be reproduced.
The copier/duplicator system includes an automatic
xerographic apparatus which includes a photosensitive plate
including a photoconductive layer 10 that is placed over
a conductive backing. The plate is formed in the shape of
a drum 11 and the drum mounted upon a shaft 12 that is
journaled for rotation in the machine frame. Basically,
the xerographic drum is rotated in the direction indicated
so as to pass sequentially through a series of xerographic
processing stations. The photosensitive drum and the xero-
graphic processing apparatus are driven at predetermined
speeds relative to each other from a drive system (not shown)
and the operation thereof coordinated in order to produce
proper cooperation of the vario~s processing mechanisms.
The original, to be reproduced, is placed upon a
transparent horizontally supported platen 4 and the original
scanned by means of a moving optical scanning system and to
produce a flowing light image of the original. The scanning
system includes an elongated horizontal extended aperture
lamp 15 and a moveable lens element 18,
The lamp and lens element moves in coordination
across the object supported upon the platen to focus
successive incremental bans of illumination reflected from
the object onto the moving drum surface at synchronous speeds
therewith. The optical path is folded by means of a pair
of image mirrors 19 and 20 interposed between the lens and
the drum surface, the drum is first uniformly charged by
means of a corona generator 13 positioned on charging
station A. Under the influence of the flowing light image,
the uniformly charged photoconductive surface is selectively
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dissipated in the non-image areas to form what is commonly
known as a "latent electrostatic image".
The latent electrostatic image is carried on the
drum surface from the exposure station into the developing
station C. The developing station is primarily comprised
of a developer housing 22 adapted to support a supply of
two-component developer material 21 therein. The developer
material is transported by means of a bucket system 23 from
the bottom of the developer housing to an elevated position
where the material is delivered into the active development
zone. The developer material is caused to flow downwardly
in contact with the upwardly moving drum surface under
closely controlled conditions wherein charged toner particles
are attracted from the developer mix into the image areas
on the plate surface and thus making the image visible.
The moving drum surface next transports the de-
veloped xerographic image to a transfer station D. Cut
sheets of final support material are also moved into the
transfer station, the backside of the copy sheet is sprayed
with an ion discharge from a transfer corotron 25 inducing
on the sheet a charge having a polarity and magnitude
sufficient to attract the toner material from the drum
surface to the final support material. This induced charge
also electrostatically tacks the final support material to the
drum surface, In order to remove the copy sheet from the
drum surface a stripper finger 28 is positioned downstream
from the transfer corotron. The finger is arranged to move
between the drum surface and the copy sheet and lifts the
sheet from the drum surface and the copy sheet is directed
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along a predetermined path of travel into contact with a
stationary vacuum transport 29.
Although a preponderance of the toner material is
transferred from the drum surface to the copy sheet during
the transfer process, invariably some residual toner remains
behind on the drum surface after transfer. This residual
toner is transported on the drum surface into a cleaning
station E where it is brought under the influence of a
cleaning corotron 30 adapted to neutralize the electrostatic
charge tending to hold the residual toner to the drum surface,
The neutralized toner is mechanically cleaned from the
drum surface by means of a brush or the like and the toner
collected within a housing 31. A conveyor moving in an
endless loop through tubes 32 transports the collected
residual toner back to the developer housing where it is
deposited within the developer mix so that it can be once
again reused in the xerographic developing process,
The copy sheet, which has been removed from the
drum surface after the transfer operation is moved along
stationary transport 29 into fusing station F. The fuser 33
is basically made up of an upper roll 34 and a lower fuser
roll 35 mounted in operative relation to each other and the
pressure driving contact therebetween. The upper roll 34
has a metal core surrounded by a cylinder of silicone rubber.
The lower roll which is heated is a metal cylinder having a
coating made of polytetrafluorethylene as described, for
example, in U. SO Patent 3,834,861. The lower roll is wiped
with silicone oil to prevent image offset. As the heated
roll is rotated in the direction indicated the heated surface
of the lower roll is pressed into intimate contact with the
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image face of the copy sheet. Mechanical and heat energy
are transported from the roll surface to the copy sheet to
permanently bond the toner particles to the support material
while minimizing the effect of edge elongation of the copy
sheet passing through the rolls as will be explained more
fully hereinafter.
Upon leaving the fuser, the fixed copy sheet is
passed through a curvalinear sheet guide system, generally
referred to as 39, into cooperating advancing rolls 43 and
44O At this point, depending on the mode of operation
selected, the copy sheet is either forwarded directly to
the output tray 105 or into the upper supply tray 52 by
means of a movable sheet guide 45 for return through the
processing stations to produce duplex copies.
It is believed that the foregoing description is
sufficient for purposes of the present application to show
the general operation of a xerographic reproducing machine.
For a more detailed explanation of the copier/duplicator
xerographic components reference is made to U. S. Patent
No. 3,645,615 entitled Copying Apparatus.
Referring now to Figures 2 and 3 there is shown
the improved lower heated roll 35 according to the present
invention. It will be noted that the roll of Figure 2 is
flared or hourglass shaped with a single taper extending
from the center diameter x to the end diameter y. Figure 3
shows an alternative embodiment having a double taper ex-
tending from a flat section z at the central portion of the
roll. With the improved roll 35 of the invention it has
been found that diameter differences between x and y
desirably range from about .008 to about .024 inches and
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preferably between .016 to about .020 inches for copy
sheet lengths extending from 11 to 14 inches. Smaller
differences in the roll diameters will not correct the
wrinkle problem whereas too great a difference can result
in sheet distortion or curl. Also in the embodiment of
Figure 3 it has been found that section lengths z ranging
from about 4 to about 8 inches work well with this paper
length. The embodiment of Figure 3 is preferred because
of the tendency of the flared configuration Figure 2 to
drive the edges of the paper faster than the center which
can cause a distortion problem if the humidty is not
particularly high or the simplex mode of operation is
used and edge elongation of the copy sheet minimal.
While there have been shown and described and
pointed out the fundamental novel features of the invention
as applied to a preferred embodiment, it will be understood
that various omissions and substitutions and changes in the
form and details of the device illustrated and in its operation
may be made by those skilled in the art without departing
from the spirit of the invention.
