Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE I~VENTION
This invention relates generally to an electrostato- i
graphic printing machine, and more particularly concerns an
apparatus for periodically dispensing release material to a
` 5 heated fuser member.
~` In a typical electrostatographic printing machine, a
~; latent image is recorded on a surface and developed with chargedparticles. A sheet of support material is positioned closely
adjacent to the surface having the charged particles thereon.
The charged particles are transferred to the sheet of support
material in image configuration. After the particles are
transferred to the sheet of support material, they are per-
manently affixed thereto forming thereon a copy of the original
document. Electrophotographic printing and electrographic
printing are versions of electrostatographic printing. In the
process of electrophotographic printing, a photoconductive
member is charged to a substantially uniform level. A light
image of an original document irradiates the charged photo-
conductive member dissipating the charge in accordance with
the intensity thereof. This records an electrostatic latent
image on the photoconductive member corresponding to the original
document being reproduced. Electrographic printins differs
from electrophotographic printing in that neither a photocon-
ductive member nor a light image are required to create a latent
image of the original document. Generally, heat settable par-
ticles are employed in both of the foregoing processes to
develop the latent image. Heat is applied to these particles
permanently affixing them to the sheet of support material.
Different approaches have been employed for applying
heat to the particles adhering to the sheet of support material.
In one technique, the sheet of support material with the par-
ticles thereon pass between a pair of opposed rollers. At least
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one of these rollers is heated. The heated fuser roller has the
outer surface thereof covered with polytetrafluoroethylene,
commonly known as Teflon, to which a release agent such as
silicone oil is supplied. Preferably, the Teflon layer has a
thickness of about several mils with the thickness of oil being
less than one micron. Silicone based oil, which possess a
relatively low surface energy, has been found to be useful for
heated fuser rolls having an outer surface of Teflon. Generally,
a thin layer of silicone oil is applied to the surface of the
heated roller to form an interface between the roll surface
and powdered image carried on the sheet of support material.
The low surface energy of this layer prevents the particles
from transferring to the roller rather than remaining adhered
to the sheet of support material. In this manner, the particles
are permanently affixed to the sheet of support material,
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An alternate approach employs a bare metal heated
roller having low molecular weight polyethylene applied thereto
as a release agent. This release agent is generally a solid
at room temperature. Hereinbefore, the release agent has been
maintained in a sump adjacent the heated fuser roller. As the-
fuser roller reaches its operating temperature, the release
agent melts. The life expectancy of polyethylene release
material is greater in the solid state than in the liquid state, --
It is, therefore, evident that it is undesirable to maintain
the rèlease material in the liquid state an unnecessary duration
of time,
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In accordance with one aspect of this invention there
is provided in an electrostatographic printing machine, an
apparatus for dispensing a quantity of release material to a
heated fuser member operatively associated with a backup member
: wherein a sheet of support material having particles thereon
passes therebetween with the particles contacting the fuser
member, including: means for applying the release material
: to the surface of the fuser member; and means for automatically,
periodically moving the applying means into and out of engage-
ment with the surface of the continuously operating fuser
member to apply the release material thereto.
In accordance with another aspect of this invention
there is provided a fusing apparatus employed in an electro-
statographic printing machine for permanently affixing toner
particles to a sheet of support material, including: a heated
fuser roll; a backup roll operatively associated with said fuser
roll to enable the sheet of support material to pass there-
between with the toner particles contacting said fuser roll;
means for applying a release material to the surface of said
fuser roll; and means for automatically, periodically moving
said applying means into and out of engagement with the surface
of said continuously operating fuser roll to apply the release
material thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention will become more apparent upon read-
ing the following detailed description and upon reference to
the drawings, in which:
Figure 1 is a schematic elevational view of an
electrophotographic printing machine incorporating the features
of the present invention therein;
Figure 2 is a schematic elevational view of one
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embodiment of a release material dispenser employed in the
.; Figure 1 printing machine fuser; and
.. Figure 3 is a schematical elevational view of
another embodiment of a release material dispenser employed in
the Figure 1 printing machine fuser.
" While the present invention will hereinafter be
described in connection with various embodiments thereof, it
will be understood that it is not intended to limit the
invention to those embodiments. On the contrary, it is intended
to cover all alternatives, modifications and equivalents as
may l.e
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included within the spirit and scope of the invention as defined
by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
~; For a general understanding of an electrophotographicprinting machine in which the present invention may be incor-
porated, reference is had to Figure 1 which depicts schematically
the various components thereof. Hereinafter, like reference
numerals will be employed throughout to designate like elements.
Although the apparatus for dispensing the release material to
a fusing member employed in the electrophotographic printing
machine of Figure 1 is particularly well adapted for use therein,
it should become evident from the following discussion that it
is equally well suited for use in a wide variety of devices and
is not necessarily limited in its application to the particular
embodiment shown herein.
Since the practice of electrophotographic printing is
well known in the art, the various processing stations for pro-
ducing a copy of an original document are represented in
Figure 1 schematically by the reference letters A through F,
inclusive.
As in all electrophotographic printing machines of
the type illustrated; a drum 10 having a photoconductive surface
12 entrained about and secured to the exterior circumferential
surface thereof is rotated, in the direction of arrow 14, through
- 25 the various processing stations. One type of suitable photo-
conductive material is described in U.S. Patent No. 2,970,906
issued to Bixby in 1961. In general, photoconductive surface 12
is made from a selenium alloy.
Initially, drum 10 rotates photoconductive surface 12
through charging station A. At charging station A, a corona
generating device, indicated generally at 16, sensitizes photo-
conductive surface 12. Corona generating device 16 is
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positioned closely adjacent to photoconductive ~urface 12. When
corona generating device 16 i9 energized, photoconductive surface
12 is charged to a relatively high substantially uniform potential.
One type of suitable corona generating device is described in U.S.
Patent No. 2,836,725 issued to Vyverberg in 1958.
After a portion of photoconductive surface 12 is charged
to a substantially uniform potential, the charged portion thereof
is rotated to exposure station B. Exposure station B includes an
exposure mechanism, indicated generally by the reference numeral
18, having a stationary housing for supporting an original document
thereon. The housing comprises a transparent platen such as a glass
plate or the like having the original document disposed thereon.
Lamps illuminate the original document. Scanning of the original
document may be achieved by oscillating a mirror in a timed re-
lationship with the movement of drum 10. The light image of the
original document is reflected through a lens onto another mirror
which, in turn, transmits the light image through a slit onto the
charged portion of photoconductive surface 12. Irradiation of the
charged photoconductive surface 12 dissipates the charge thereon
recording an electrostatic latent image thereon corresponding to
the original document.
~hereafter, drum 10 rotates the electrostatic latent
image recorded on photoconductive surface 12 to development station
C. Development station C includes a developer unit 20 having a
housing with a supply of developer mix therein. The developer mix
comprises carrier granules with toner particles adhering thereto.
Preferably, the carrier granules are formed from magnetic material
with the toner particles being a heat settable plastic. Developer
unit 20 is, preferably, a magnetic brush development system. In
such a system, the developer mix is brought through a directional
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`- flux field to form a brush thereof. The brush of developer mix
contacts the electrostatic latent image recorded on photoconductive
surface 12. The latent image attracts electrostatically the toner
particles from the carrier granules forming a toner powder image on
`` 5 photoconductive surface 12.
Prior to continuing with the remaining processing sta-
tions, the sheet feeding path will be briefly described. With
continued reference to Figure 1, a sheet of support material is
advanced by sheet feeding apparatus 22 to transfer station D.
Sheet feeding apparatus 22 includes a feed roll 24 contacting the
uppermost sheet of the stack of sheets of support material 26.
Feed roll 24 rotates in the direction of arrow 28 to advance the
uppermost sheet from stack 26. Registration rolls 30, rotating in
the direction of arrow 32, align and forward the advancing sheet
of support material into chute 34. Chute 34 directs the advancing
sheet of support material into contact with photoconductive surface
12 in registration with the toner powder image developed thereon.
In this manner, the sheet of support material is positioned to
receive the toner powder image from photoconductive surface 12 at
transfer station D.
Transfer station D includes a corona generating device
36 adapted to apply a spray of ions onto the side of the sheet
of support material opposed from photoconductive surface 12. The
toner powder image adhering to photoconductive surface 12 is then
attracted therefrom to the sheet of support material in contact
therewith. After transferring the toner powder image to the sheet
of support material, the sheet of support material is advanced to
fusing station E.
Endless belt conveyor 38 advances the sheet of support
material with the toner powder image adhering thereon to fusing
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? station E. Fusing station E includes a fuser assembly, indicated generally by the reference numeral 40. Fuser assembly 40 heats
the transferred toner powder image permanently affixing it to the
sheet of support material. Fuser assembly 40 includes a heated
fuser member or roll, shown generally at 42 and a backup member or
roll indicated generally by the reference numeral 44. The sheet
of support material with the toner powder image thereon is inter-
posed betwaen fuser roll 42 and backup roll 44 with the toner pow-
der image contacting fuser roll 42. Dispenser 45 periodically
applies release material to fuser roll 42. Blade 46 adjusts the
thickness of the release material layer coating fuser roll 42. The
detailed structural configuration of fuser assembly 40 will be de-
scribed hereinafter with reference to Figures 2 and 3. After the
toner powder image is permanently affixed to the sheet of support
material, the sheet of support material is advanced by a series of
rollers 48 to catch tray 50 for subsequent removal therefrom by the
machine operator.
Invariably, after the sheet of support material is
separated from photoconductive surface 12, some residual toner
particles adhere thereto. These residual toner particles are re-
moved from photoconductive surface 12 at cleaning station F.
Cleaning station F includes a cleaning mechanism, designated
generally by the reference numeral 51. Cleaning mechanism 51 in-
cludes a corona generating device and a brush. Initially, toner
particles are brought under the influence of the corona generating
device to neutralize the remaining electrostatic charge on photo-
conductive surface 12 and the residual toner particles. The neu-
tralized toner particles are cleaned from photoconductive surface
12 by the rotatably mounted fibrous brush in contact therewith.
Subsequent to cleaning, a discharge lamp floods photoconductive
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surface 12 with light to dissipate any residual charge thereon.
In this manner, the charge on photoconductive surface 12 is returned
to the initial level prior to recharging photoconductive surface
; 12 for the next successive imaging cycle.
It is believed that the foregoing description is suf-
ficient for purposes of the present application to illustrate the
general operation of an electrophotographic printing machine em-
bodying the features of the present invention therein. Referring
now to the specific subject matter of the present invention,
Figure 2 depicts one embodiment of dispensing apparatus 45 asso-
ciated with fuser assembly 40.
Fuser assembly 40 comprises a heated fuser roll, indi-
cated generally by the reference numeral 42, and a backup roll,
indicated generally by the reference numeral 44. Fuser roll 42
cooperates with backup roll 44 to form a nip 52 therebetween
` through which the sheet of support material having a toner powder
image thereon passes therethrough. The sheet of support material
is arranged to have the toner powder thereon contacting fuser roll
42. A channel shaped base is provided for supporting fuser assembly
40 in the electrophotographic printing machine shown in Figure 1.
Backup roll 44 is mounted rotatably on a pair of brackets secured
to the channel shaped base by means of a right angle bracket. As
shown, backup roll 44 is adapted to rotate in the direction of
arrow 54. Preferably, backup roll 44 includes a rigid steel core
or shaft 56 having a Viton elastomeric surface or layer 58 dis-
posed thereover and affixed thereto. Shaft 56 is secured rotat-
ably on the brackets by a pair of bearings held in place by re-
- taining rings. By way of example, backup roll 44 has an overall
- dimension of approximately 1.55 inches with a 0.1 inch cover or
layer of Viton or other suitable high temperature elastomeric
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material, for example, fluorosilicone or silicone rubber. Backup
roll 44 is preferably 15 1/2 inches long to accommodate various
` widths of support material.
A pair of brackets having a generally E-shaped configura-
tion are provided for mounting fuser roll 42 rotatably in fuser
-; assembly 40. To this end, a pair of ball bearings, one in each of
the support brackets, are provided. The bearings are retained in
the brackets by means of retaining rings. A pair of end caps are
secured to a hollow cylinder or core 60 forming a part of fuser
roll 42. The end caps have reduced end portions so as to be mounted
in the bearings permitting fuser roll 42 to rotate in the direction
of arrow 62. A heating element 64 is supported internally of
cylinder 60 for providing thermal energy to cylinder 60 to the
operating temperature thereof. Heating element 64 employs a suit-
able type of heater for elevating the surface temperature of
` cylinder 60 to operational temperature, i.e. 285F to 295F. By
way of example, heating element 64 may include a quartz enevelope
having a tungsten resistance heating element disposed therein.
Preferably, cylinder 60 is fabricated from any suitable material
capable of efficiently conducting the heat to the external surface
thereof. For example, suitable materials are aluminum and alloys
thereof, steel, stainless steel, nickel and nickel alloys thereof,
nickel plated copper, chromium plated copper, copper and alloys
thereof. The resultant fuser roll 42 has an outside diameter pre-
ferably of about 1.5 inches with the length thereof about equal to
that of backup roll 44. In operation, fuser roll 42 requires about
420 watts peak power with the average power being about 320 watts,
and about 100 watts being provided for standby operation. Heating
element 64 is supported internally of cylinder 60 by a pair of
spring supports which are mounted in an insulator block secured to
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support brackets. The free ends of the spring supporting the
heating elements are provided with a locating ball while the
opposite end of the spring is disposed in contract with an
electrical terminal to which electrical wires may be attached
5 for applying electrical energy to heating element 64. The
insulator 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 insula-
ting block.
The aforementioned materials from which cylinder
60 are fabricated have a relatively high surface energy. Thus,
hot toner material contacting such surfaces would readily wet
the surface of cylinder 60. Toner wetting the surface of
cylinder 60 is difficult to remove therefrom. Accordingly,
15 there is provided a dispenser 44 containing a material capable
of interacting with cylinder 60 in a manner described in U. S.
Patent 3,937,637, issued February 10, 1976, Robin Moser et al.
The material is, preferably, a low molecular weight substance
which is a solid at room temperature and has a relatively low
20 viscosity at the operating temperature cylinder 60. An exam-
ple of such a material is polyethylene manufactured by Allied
Chemical Company and having a designation AC-8 homopolymer. -~
The foregoing polyethylene is employed in dispenser 45. As
shown in Figure 2, dispenser 45 includes a supply spool 66
25 mounted rotatably on a frame secured to the electrophotographic
machine. Take-up spool 68 is also mounted rotatably on the
frame and is spaced from supply spool 66. A web of flexible
material 70 is entrained about supply spool 66 and has the
leading edge thereof secured to take-up spool 68. A layer of
30 polyethylene material is coated on the surface of flexible
material 78 opposed from fuser roll 42. In the operative
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- position, the layer of polyethylene material coating web 78
contacts fuser roll 42. Web 78 is articulated so as to move
. periodically
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into and out of engagement with fuser roll 42. An indexing
motor operatively associated with take-up spool 68 intermit-
tently advances flexible material 78 so as to position new
portions of the polyethylene coating opposed from the surface
thereof having the polyethylene coating. Rod 80 is recipro-
cated to move the polyethylene coating on web 78 into and out
of contact with fuser roll 42. Articulation of rod 80 is
achieved by a bell crank mechanism 82 associated with drive
motor 84. By way of example, rod 80 may articulate at about
two revolutions per minute, thereby moving the polyethylene
coating on flexible material 78 into and out of contact with
fuser roll 42 two times per minute.
Blade 46 adjusts the thickness of the release
material layer coating fuser roll 42 so as to maintain a pre-
scribed thickness thereof. The detailed structural configu-
ration of blade 46 is described in U. S. Patent No. 3,935,836,
issued February 3, 1976.
Referring now to Figure 3, there is shown another
embodiment for release material dispenser 45. As shown there-
in, fuser roll 42 is operatively associated with backup roll44 and includes blade 46 adapted to adjust the thickness of
the release material layer applied thereto. Housing 70
defining an open ended compartment having a bar of polyethylene
material 72 disposed therein, is mounted slidably in frame 74
secured to the electrophotographic printing machine. Drive
motor 84 associated with bell crank mechanism 82 reciprocates
housing 70 in the direction of arrow 76. In this manner,
polyethylene bar 78 melts on contact with heat fuser roll 42
and forms a layer of release material on the outer surface
thereof. The thickness of the layer is adjusted by blade 46.
By way of example, a layer of less than one micron thick is
preferably applied thereto.
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In recapitulation, it is apparent that pursuant to the
features of the present invention, as heretofore described, the
dispensing apparatus includes a release material dispenser adapted
to reciprocate into and out of engagement with a heated fuser roll.
In this manner, the fuser roll is periodically coated with a layer
of release material. The thickness of the release material layer
-- is regulated by a blade in contact therewith. This type of system
insures that the prescribed amount of release material is applied
to the fuser roll and that the life of the polyethylene material
is optimized in that it remains in the solid state except for that
portion thereof contacting the heated fuser roll.
It is, therefore, evident that there has been provided,
in accordance with the present invention, an apparatus for dispen-
i
- sing release material to a fuser roll employed in an electrophoto-
graphic printing machine. The apparatus of the present invention
fully satisfies the objects, aims and advantages hereinbefore set
forth. While this invention has been described in conjunction
with specific embodiments thereof, it is evident that many alter-
: natives, modifications and variations will be apparent to those
skilled in the art. Accordingly, it is intended to embrace all
such alternatives, modifications and variations as fall within the
spirit and broad scope of the appended claims.
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