Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND: OF TH-~ INVENTION
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This invention relates generally to sheet feeding
and separating apparatus, and more particularly, to c~mposi-
tions for the surfaces of sheet feeding and separating appara-
tus to improve serially feeding superposed sheets from a
stack of sheets to a xerographic machine. The invention further ~
relates to compositions for the surfaces of sheet retarding ~ -
devices in paper handling systems.
The development of high speed xerographic machines
has brought about the need for simple yet reIiable document i
feeder and separator apparatus capable of handling documents
(sheets) varying in length, width, thickness, weight, and ;
surface conditions. In order to serve in a wide variety of
applications these same machines require-that the feeder and
separator apparatus operate efficiently and reliably both as
an automatic feed on the one hand and as a manual input fffeder
on the other hand.
For example! in the automatic sheet feeder and
separator apparatus of the type disclosed in U.S. Patent No.
3,469,834 issued September 30, 1969, Stange, Lux and Michaels
and U.S. Patent No. 3,768,803 issued October 30, 1973, Stange,
there are described means for advancing and separating super- -
posed sheets having varied physical characteristics comprising
var~ous types of retarding members having frictional resistivity
surfaces thereon to cause good sheet separation of the super- -
posed sheets stacked in a holder for feeding into a xerographic
machine. The separation belt and retard member are employed f
in these patents for queuing and advancing the sheets andjor
separating them from the stack. In these patents, the region
of contact between the retarding member and the separation
belt form a sheet queuing throat which is able to "fan out"
or queue sheets passed through it. In U.S. Patent No. 3,768,803
the separation belt and retard ~ ~-
me~ber are positioned adjacent the edge of a stack of sheets, and
the sheets translate a very short distance before reaehing a sheet
queuing throat because the retard member is positioned close to the
edge of the stack.
In the above-cited references and in retard or retarding
members in general, the retard member may assume various shapes,
sizes, thicknesses, and configurations, including rolls, belts,
endless belts, shoes, pads, and the like, In U S. Patent No,
3,469,834 the retarding roll or abutment member has a frictional
member thereon which is formed of a resilient material having a lower
coefficient of friction than that of the separator feed belt, said
resilient material being mounted on a retarding roll or abutment
member in alignment and engagable with the separator feed beLt
In U. S. Patent No. 3,768,803 the retard surface is preferably a
soft rubber of about 40 durometer rating. This resiliency or softness
permits the lead edge of the sheets to "dig into" the retard means,
The retard means should not be too soft, however, or wear will be
excessive. For this reason, it is suggested that the retard means
be grooved to give it mechanical so~tness, resiliency or flexibility
while the durometer of the material is high to minimize wear.
Thus, the shortcomings of the retard surfaces of the prior art retard
members are a high wear rate when the retard surface is of a soft,
rubber material. When the hardness or durometer rating of the retard
surface is high to minimize the wear of the surface, the resulting
effect on the paper is lead edge delamination, Accordingly, a decrease
in retard wear rate impdlies an increase in lead edge delamination of the
sheets. Furthermore, dew-e~e~ in hardness of the retard surface
also result in sheet multifeeds,
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SUMMARY OF THE INVENTION ~O }~
In accordance with one aspect of this invention there
is provided in an apparatus for separating and feeding sheets
by means of a sheet separating and feeding device having a
retard member the surface of which is a friction member formed of
a resilient material, the surface comprising a microcellular
elastomer having a hardness of at least about 25 durometer.
In accordance with another aspect of this invention there
is provided in a method of separating superposed sheets by
providing a resilient surface having frictional contact with the
sheets, the improvement comprising using a microcellular elastomer
having a hardness of at least about 25 durometer as the surface in
frictional contact with the sheets whereby excellent sheet
separation is obtained without delamination of the sheets.
In accordance with another aspect of this invention there
is provided a retarding member for separating superposed sheets
without delamination of the lead edge of sheets and feeding said
sheets into a xerographic machine comprising a surface in friction-
al contact with the superposed sheets, the surface consisting of a
microcellular polyurethane subjected to a foaming process to re-
duce the hardness thereof to above at least about 25 durometer,
the microcellular polyurethane foam produced thereby having a
density of about 46.8 + 10 pounds/foot3, a tensile strength of at ~,
least about 180 pounds/inch2, a tear strength of at least about
8.0 pounds/inch, an ultimate elongation of at least about 230 per-
cent and 25 ~ercent compression deflection at about 50 - 15 pounds.
It was originally thought that an elastomeric material of
less than about 40 durometer rating would result in excessive wear
of the retard surface even though it would eliminate lead edge de-
lamination. However, the use of an elastomer having a durometerrating of at least about 25, unexpectedly resulted in a very low
retard wear rate when the elastomer comprised a microcellular struc-
ture. The microcellular elastomer having a hardness of at least
about 25 dur~meter rating performs far superior to solid elastomer
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.. . . . .
3~
materials having a hardness of about 40 durometer rating. Thus,the
microcellular structure of the elastomer is critical in providing a
surface ~or retard members in accordance ~Yith the present invention,
As used herein, durometer is defined as Shore A or Shore A durometer
Retard members, including retard rollers, belts,
endless belts, shoes, pads and the like having microcellular elasto- ~.
meric surfaces with a hardness of at least about 25 durometer rating
wear extremely well, separate ream interface slugs exceptionally~ ~
well and exhibit a substantially lower amount of lead edge delamination ~ .
than any of the solid (non-microcellular) elastomers of the prior ~ .
art having similar hardness durometer ratings ~: :
This in~ention will bec~me m~re readily apparent ~ :-
to those skilled in the art in view of the following detailed
description thereof, especially when read in conjunction with the .: .
accompanying drawing. .
BRIEF DESC~IPTION OF THE DRAWINGS
Figure 1 is a sectional view of a retard roll having a ...
microcellular elastomeric surface. .
. Figure 2 is a sectional view of a retard pad having a
microcellular elastomeric surface. :- ;
DESCRIPTION OF ~HE PREFERRED EMBODIMENTS
In a preferred embodiment in accordance with the present ..
f invention, a retarding member having a resilient surface for separating ..
superposed sheets without delamination of the sheets and for feeding
said sheets into a xerographic machine, comprises a microcellular
polyurethane subjected to a foaming process to reduce the hardness .
thereof to above at least about 25 durometer rating, the microcellular
polyurethane oam produced thereby having a density of about 36 pounds :
per cubic foot to about 52 pounds per cubic foot, a tensile strength
of at least about 180 pounds per square inch, a tear strength of at
least about 8 pounds per inch, an ultimate elongation of at least ;
about 230 percent and 25 percent compression deflection at about 35- ~.
65 pounds.
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It is also preferred in accordance with the present
invention that the microcellular elastomer including the micro-
cellular polyurethane described above, have a microcellular cell
size of about 0.005 inch. This is an average cell size, and as
used herein the cell size may ~ary as long as the effective durometer
of at least about 25 durometer is maintained. Thus, cell size is
important in the practice of the present invention, and variations
therein which result in an effective durometer hardness rating of
at least about 25, are within the scope of the invention. This micro-
cellular cell size is provided by the method of forming the cells
within the elastomer, and one skilled in the art can adjust the
cell size of the elastomer so that it is within the range of cell
sizes operable in accordance with the present invention, Furthermore,
it is not objectionable that the microcellular elastomer of the present
invention have voids or craters or other similar irregularities
spaced therethrough. These irregularities or voids result randomly
in the mierocellular elastomer during compounding of such micro-
cellular elastomeric materials Although there is no intention to
be held by the theory of operation of the microcellular elastomers
in accordance with the present invention, it is believed that the
microcellular formations within the elastomers, for example, the
~, microcellular polyurethane, prevents heat buildup during operation~
and accordingly, ~ the improved surface for separating and
feeding sheets from a stack. In the prior art solid (non-microcellular)
elastomers used as resilient surfaces with a hardness of about 40
durometer rating or higher, it is believed that there is an undesirable
heat buildup which causes malfunction of the sheet feeding devices,
Preferred modes upon which the microcellular polyurethane
surfaces of the present invention are operable for retard members,
in accordance with the present invention, are disclosed in U, S.
~.043~
Patent No. 3,469,834 issued to Stange, Lux, and Michaels on
September 30, 1969 for Sheet Feeder and Separator Apparatus.
Particularly therein, in Figures 3 and 8 are shown a friction
member 281 formed of a resilient material having a lower
coefficient of friction than that of a separator feed belt
260. The friction member 281 is mounted on retarding roll or
abutment member 282 in alignment and engagable with separator
feed belt 260. The microcellular elastomer having a hardness
of at least about 25 durometer rating of the present invention
may be used as resilient surface 281 a~ described in Column 7,
lines 25-31, and Column 15, lines 41-57 wherein is claimed
a means for advancing and separating superposed sheets having
varied physical characteristics comprising, a retarding member
having a curved frictional resistive surface thereon, means
supporting the retarding member, a pair of pulleys journaled
for rotation opposite the retarding member on either side
thereof in the direction of feed, a flexible endless belt mem-
ber entrained about the pulleys and forming an arcuate wrap
over the surface of the retarding member to define a throat,
means for supporting a stack of sheets adjacent the throat,
nudging means for advancing the uppermost sheet in the stack
into the throat, and drive means for driving the belt member
- and the nudging means in a direction to advance the uppermost
sheet from the staak and through the throat.
Another example of a retard surface which may be used
in accordance with the present invention, is disclosed in `~
U.S. 3,768,803 issued to Stange on October 30, 1973, claiming `- `
therein a sheet feeding and separating apparatus for feeding ~' -
and separating individual sheets from a stack of sheets at
an edge of the stack wherein the improvement comprises, an
endless sheet feeding and separating belt mounted for sheet
feeding engagement with the edge. ~
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104;~
of the stack of sheets; the feed belt being rotatably mounted ,
between spaced supports; a retard member having a supported
finitely curved frictional retard surface, said retard surface
deformably engaging said feed belt in the unsupported section
of the feed belt to form therewith a correspondingly curved
sheet queuing throat in which said retard surface in said belt
are continuously mechanically biased against one an~ther;
said sheet ~ueuing throat being positioned directly adjacent
the edge of the stack and said feed ~elt operatively extending
over only the edge of the stack, cooperatively preventing ' ,,
buckling of sheets fed from the stack by said feed belt into
said sheet queuing throat. In U.S. 3,768,803 a retard pad
having a surface 11 is shown in Figures 1, 3, 4, 5A, 5B,
6-16 which are amply described throughout the specification
thereof.
The novel use of the compositions in accordance with
the present invention are described with reference to Figures
1 and 2. In Figure 1 the retard member is in the form of a
retard roll having an outer resilient surface 1 of micro-
cellular elastomer having a hardness of at least about 25
durometer rating. The resilient, frictional microcellular
elastomer 1 is mounted upon retarding roll or abutment member ,
2. The retarding member is mounted by a bolt mounting member
designated by the numerals 3 and 4.
In Figure 2 the retard member is shown in the form ~
of a retard pad having a resilient, frictional surface compris- ' '
ing a microcellular elastomer having a hardness of at least about ,','
25 durometer rating designated by numeral 6, mounted upon a
rigid surface 5. The operation of the above-illustrated retard '
,members is shown in the above patents. One skilled in the ,,
art can provide grooved surfaces on the retard members of the -
present invention to reduce lead edge delamination.
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As described supra, one of thc prefcrred eornpositions,
which llas been foamed to form the microcellular elastomer in
accordance witll tl~e present invention and having a hardiless of at
least about 25 durometer rating, is polyurethane. However, any
microcellular elastomeric material may be used in accordance with
the present invention as long as ;t has the preferred characteristics
as set forth supra and including a hardness of at least- about 25
durometer rating, a density of about 46.8 + 10 younds/foot, a tensile
strength of at least about 180 pounds/inch , a tear strength of at
least about 8 pounds/inch, an ultimate elongation of at ]east about
230 percent, a 25 percent compression deflection at about 50 + lS
pounds and an average microcellular cell size of about U,005 inch.
As explained supra, variations in cell size which result in an
effective durometer hardness rating of at leas~ about 25, may be used
in accordance with the present invention. T]1US, the average cell size
may be greater than or less than about 0.005 inch. Furthermore, the
operative compositions of the present invention may also comprise voids
or craters or other irregularities spaced randomly therethrough.
One skilled in the art of compounding microcellular elastomers can
provide such materials having the above-described characteristics
without undue experimentation, }lowever, none of the limitations
set forth above are to be deemed within the scope of the present
invention if they reduce the durometer rating of the microcellular
elastomer below about 25,
The initiation or nucleation of cells capable of growth
to form the microcellular elastomers havillg the above-described
density, tensile strength, tear strength, cell size and the li~e can
be carried ou~ by one skilled in the art, The factors w}~ich merit
important consideration in preparing the proper cells in the
elastomers in aceordance with the presellt inve~tion include the type
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~W~
and amount of blowing agent, for example, the amount o~ gas
generated, the rate of generation, and the pressure which can be
developed to expand the polymer phase, the additives used in the
foaming system, for example, cell-control agents used to control the
surface tension of the system or to act as nucleating sites from
which cells may grow, or added to influence the mechanical stability
of the foam structure; and environmental factors such as temperature,
geometry of foam expansion, and pressure. The chemical stabilization
process is particularly useful in preparing polyurethane foams,
and are well known in the art
Examples of microcellular elastomers which may be used
in accordance with the present invention include polyurethanes, poly-
~vinyl chlorides), copolymers of styrene and acrylonitrile and poly-
ethylene, ther elastomers from which microcellular materials for
retard members can be made, include natural rubber, neoprene rub~er,
styrene/butadiene rubber, nitrile rubber, polychloroprene, chloro-
sulfonated polyethylene, butyl rubbers and the Like.
The thickness of the frictional, resilient material used
as the surface of a retard member, may be chosen in accordance with
a particular operation of the system for which it is utilized,
Furthermore, the retard memoer may consist entirely of the microcellular
elastomer or the microcellular elastomer having a hardness of at
least about 25 durometer rating may be a coating upon the surface of
a more rigid member. One skilled in the art can chose a suitable
thickness and/or member in accordanee with the particular system.
A microcellular polyurethane elastomer used as a surface
upon a retard roller, wore extremely well, separated ream interface
slugs excep~ionally well and exhibited very low lead edge delamination
in a high speed paper feeder when the elastomeric polyurethane had
the following physical characteristics in accordance with the present
~38;~ -
invention: a density of 46.8 + pounds per cubic foot, a 25 percent
compression defleetion at 50 pounds, a tensile strength of at
least 180 pounds/inch , an ultimate elongation of at least 230
percent, and a tear strength of at least 8 pounds~inch. A retard
belt having the above-described composition fed copies with no multi-
feeds attri~utable to the retard belt for in exeess of 250 7 000
cyclesO The microcellular polyurethane elastomer had a hardness
of about 30 durometer rating
A silicone rubber retard roll of a solid type (non-
microeellular) having a hardness of 50 Shore A and a tensile strength
of 700 pounds per square inch was only operable for 100,000 cycles.
Furthermore, a conventional polyurethane (non-microcellular) having
a hardness of 65 Shore A rating and a tensile strength of 4,000
'~ C~U5Q~
~ pounds per square inch ~sr~ leaa edge delamination of the sheets.
~h~ the retard roll having a silicone surface was used as described -
above, the silicone rubber was sheared by the lead edge o~ the
sheet causing excessive wear,
A microcellular polyurethane material used on the
surface of a retard pad, and having a hardness of 20 Shore A or
less, resulted in multifeed shut down rate increases and was
considered ineffective for high speed paper feed applications,
Solid polyurethanes having a hardness of 50 and 60
durometer ratings respectively, were used as surface materials upon
retard rolls in accordance with the present invention. The solid
polyurethane retard members had long lives, however, they were
characterized by a high rate of delamination of the lead edges of
sheets.
In accordance with the objects of the present invention
there has been described an apparatus and method for separating
superposed sheets and feeding said sheets into a xerographic
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machine by providing a resilient surface having frictional contact
with the sheets. the surface comprising a microcellular elastomer
having a hardness of at least about 25 durometer rating. The
compositions of the present invention produced excellent sheet
separation without delamination of the lead edges of the sheets,
without consistent or frequent multifeed and without excessive wear
of the resilient surface material, Accordingly, there has been
provided a retard surface which is soft to permit the lead edge of
the sheets to "dig into" the retard means without causing excessive
wear of the retard surface and without causing lead edge delamination
of the sheets,
While this invention has been disclosed with reference to
the compositions disclosed herein for use in retard members, it is not
necessarily confined to the details as set forth, and this application
is intended to cover such modifications or changes as may come within
the scope of the following claims,
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