Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates generally to flash fusing
and in particular to a method and apparatus for fusing toner
images onto flexible support materials. More specifically,
this invention relates to a xerographic flash fusing apparatus
and methods for rapidly and efficiently producing uniform
duplex image fixing on each side of support material.
In the xerographic process, a plate, generally
comprising a conductive backing upon which is placed a
photoconductive insulating surface, is uniformly charged and
the photoconductive surface then exposed to a light image of
an original to be reproduced. The photoconductive surface is
caused to become conductive under the influence of the light
image so as to selectively dissipate the electrostatic charge
found thereon to produce what is developed by means of a
variety of pigmented resin materials specifically made for
this purpose which are known in the xerographic art as
"toners". The toner material is electrostatically attracted
to the latent image areas on the plate in proportion to the
charge concentration found thereon. Areas of high charge
concentration become areas of high toner density while
correspondingly low charge image areas become proportionally
less dense. The developed image is transferred to a final
support material, typically paper, and fixed thereto to form
a permanent record or copy of the original.
3' 2S Many forms of image fixing techniques are known in
3 the prior art, the most prevalent of which are vapor fixing,
heat fixing, pressure fixing or a combination thereof as
described in U.S. Patent No. 3,539,161. Each of these
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techniques, by itself or in combination suffer from deficiencies
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`` 30 which make their use impractical or difficult for specific
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xerographic applications. In general, it has been difficult
to construct an entire~y satisfactory heat fuser having a
short warm-up time, high efficiency, and ease of control. A
further problem associated with heat fusers has been their
tendency to burn or scorch the support material. Pressure
fixing methods, whether hot or cold have created problems
with image offsetting, resolution degradation and producing
consistently a good class of fix. On the other hand, vapor
fixing, which typically employs a toxic solvent has proven
commercially unfeasible because of the health hazard involved.
Equipment to sufficiently isolate the fuser from the surrounding
ambient air must by its very nature be complex and costly.
With the advent of new materials and new xerographic
processing techniques, it is now feasible to construct auto-
matic xerographic reproducing apparatus capabLe of producing
copy at an extremely rapid rate. Radiant flash fusing is
one practical method of image fixing that will lend itself
readily to use in a high speed automatic process as described
in U.S. Patent 3,529,129. The main advantage of the flash
fuser over the other known methods is that the energy, which
~ is propagated in the form of electromagnetic waves, is
; instantaneously available and requires no intervening medium
for its propagation. As can be seen, such apparatus does not
require long warm-up periods nor does the energy have to be
transferred through a relatively slow conductive or convective
heat transfer mechanism.
- Although an extremely rapid transfer of energy
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between the source and the receiving body is afforded by
the flash fusing process, a major problem with flash fusing
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as applied to the xerographic fixing art, has been designing
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apparatus which can fully and efficiently utilize a preponder-
ance of the radiant energy emitted by the source during the
xelatively short flash period. The toner image typically con-
stitutes a relatively small percentage of the total area of
the copy receiving the radiant energy. Because of the properties
of most copy materials, as for example, paper, most of the
energy incident thereon is wasted by being transmitted through
the copy or by being reflected away from the fusing area.
Another disadvantage associated with the prior art flash fusing
10 apparatus has heretofore been the non-uniformity of image
fixing produced. This phenomena is primarily due to the fact
that it is difficult to produce highly uniform irradiance on
a large receiving surface as for example a sheet of paper,
from a relatively small source such as a flash lamp. This
; problem is further heightened in the case of duplex images on
both sides of the paper.
j While considerable effort has been expended in pro-
7 viding schemes for enhancing the efficiency and uniformity of
fix of electrographic flash fusing systems, most efforts have
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20 been directed toward the provision of specially contoured re-
~- flecting surfaces which are designed to at least partially
surround the flash lamp and thereby conserve energy via
multiple reflections as set forth in U.S. Patent 3,529,129.
In addition to being costly to fabricate, such reflecting
surfaces tend to become contaminated by loose toner particles
and thereby necessitate frequent cleaning operations.
In accordance with one aspect of this invention there
is provided an improved flash fusing apparatus for fusing toner
, images onto both sides of a flexible support material comprising:
'~ 30 a first elongated flash lamp, a second elongated flash lamp
positioned adjacent to said first lamp, and means for advancing
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said flexible supp~rt material bearing loose toner images along
a predetermined path substantially encircling each of said
first and second flash lamps along their longitudinal axis in
a manner to expose one side of said flexible support material
to radiant energy from said first elongated flash lamp and the
opposite side of said flexible support to radiant energy from
said second elongated flash lamp to thereby fuse the toner
images to said sides.
In accordance with another aspect of this invention
there is provided a method for flash fusing loose toner images
onto flexible support material on both sides thereof to produce
duplex copies comprising the steps of advancing a web of
support material bearing loose toner images on both sides there-
of along a predetermined path which encircles a first flash
lamp alony its longitudinal axis energizing the flash lamp to
efect uniform radiation to be received on all points of the
support material to fuse the image particles on one side thereof
and then ad~ancing support material past a second flash lamp
positioned adjacent said first lamp and arranged on the opposite
side of the web path and encircling said second lamp along its
longitudinal axis and flashing the second lamp to effect uniform
radiation to ~e received on the support material to fuse image
toner particles on the second side thereof.
For a better understanding of the invention reference
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is had to the following description wherein the Figure is a
side view of a web of support material bearing xerographic
toner images on each side thereof for fusing according to the
present invantion.
Referring now to the Figure in accordance with the
- 30 present invention, loose image toner particles 10 and 11 de-
posited onto a flexible support web 12 at developer stations
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14 and 15 respectively, are fused simultaneously. Web 12 is
transported about the axes of elongated sources of radiant
energy in the form of flash lamps 16 and 18. The web is
advanced along the curved path of a guide track 20 by a driven
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roller 22 which is rotated in a direction indicated by the
arrow. It will be appreciated that images 10 and 11 are moved
along a circular path in each fusing zone such that the toner
images are untouched and continuously face toward the center
of curvature of the path where flash fusing lamps 16 and 18
are situated. It will be further appreciated that each of
the flash fusing lamp fusing zones has a configuration which
is circular or cylindrical such that uniform irradiance is
insured to all points on the cylindrical surface from the par-
ticularflash lamp positioned along the central axis thereof.
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In this manner, it is not necessary to fuse the images onto
a support material in piece meal fashion by energizing the
lamp a number of times as different portions of the toner
images are transported past the flash lamp.
S Flash lamps 16 and 18 are energized at prede~ermined
intervals by a suitable control circuit. After simultaneous
fusing of the images onto the web, the web can be cut into
sheets and stacked by any suitable device.
It has been found that a Xenon flash lamp operating
at power levels between 800 and 1200 Joules produces very good
toner fusion. Pulse durations between 0.25 and 1.5 milli-
seconds were found to provide acceptable fusing with pulses
between 0.5 and 1.2 milliseconds giving better fusing results.
It has also been found that longer pulses of energy are re-
quired as the power level increases.
; The efficiency of the duplex fusing system of the
above-described invention can reduce the power required to
fuse ordinary simplex copies by as much as 50 percent. It
is believed that this is because of the unique configuration
~ 20 of the path through which the copy web is advanced past the
`` flash fusing lamps. It will be further appreciated that the
improved flash fusing system will provide improved efficiency
` even where images are on a single side of the web material.
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.
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