Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
mis invention relates to a sheet feeding apparatus
for forming a buckle in a sheet and to a reproducing machine
employing such an apparatus and to the process.
It is known in the sheet feeding art that numerous
beneficial effects can be obtained by buckling a sheet during
feeding. Sheet buckling has been employed as a device for
improving sheet separation from a stack of sheets. A typical
example of such a use of sheet buckling would be the reverse
buckle sheet feeder wherein a sheet is first fed rearwardly
against a stop member to form a buckle to separate it from the
next adjacent sheet of the stack and then forwardly into the
appropriate sheet feed path. This type of approach is used
commercially as, for example, in the sheet feeder of the Xerox
3100 copier.
Yet another purpose of buckling sheets in a sheet
feeding environment is to remove residual skew which may have
occurred during initial feeding. Here again a sheet is buckled
up against a stop member. men it is gripped while buckled for
further feeding to eliminate residual skew. A typical example
of the implementation of this type of buckling approach is also
found in the Xerox 3100 copier wherein the sheet after feeding
from the stack is fed up against a registration gate and
forward buckled to remove residual skew.
It has been found that particularly when buckling
to achieve the removal of residual skew during sheet feeding
the buckle height must be controlled to obtain consistent
skew removal. A variety of approaches have been adopted by
the prior art for controlling buckle height. In the Xerox
3100 copier reverse buckle feeder fixed feeding times are
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utilized for controlling the buckle heights. This type of
approach has also been utilized in U. S. Patent No. 1,570,592
for a forward buckling type sheet feeding apparatus. These
approaches, while adequate for their intended purposes, leave
considerable room for improvement. Utilizing a fixed feeding
time for forming a buckle fails to take account of slippage
between the feeder and the sheet, and differences in the
position of the lead edge of the sheet at the time the feeding
cycle commences.
other approaches have been adopted in the prior art
for controlling buckle height in a sheet feeder which overcome
the problems of utilizing a fixed feeding time. In U. S.
Patent Nos. 3,241,831; 3,270,787, and 3,335,662, there are
disclosed apparatuses wherein the height of the buckle is
controlled by sensing the height electrically as by the use
of a photodetector or lever switch. After the appropriate
buckle height has been sensed the sheet is then fed in a
conventional manner.
The use of an optical sensor or a lever type switch
for sensing buckle height is disadvantageous because it is - :
difficult to accurately locate the sensor in the sheet feed
path. Further, it has been found that the buckle in different
kinds of sheets does not necessarily form at the same point
in the sheet feed path. An illustrative example of this
problem would be feeding a sheet of labels to an imaging
device such as a copier. A sheet of labels usually comprises
a flexible backing sheet with a plurality of labels adhesively
arranged on one side of the sheet. When buckling such a sheet
there is greater flexibility in those portions of the sheet
between label~ than in those portions of the sheet where a
^` 10393Z3
a label is present. Therefore, the buckle will often form
upstream or downstream of a buckle which would form in the
sheet if no labels were present.
SUMMARY OF THE INVENTION
.
In accordance with one aspect of this invention there
is provided in a sheet feeding apparatus for forming a buckle
in a sheet including; a stop member, and means for feeding said
sheet against said stop member to form a buckle in said sheet,
the improvement comprising: sensing means for sensing the
position of an edge of said sheet; timing means responsive to
said sensing means for timing a reference time interval from
the sensing of said edge, said timing means being coupled to
said feeding means and including means for stopping said feed-
ing means upon the expiration of said reference time interval,
said reference time interval being sufficiently long to allow
said feeding means to form said buckle in said sheet, and means
for adjusting the height of said buckle comprising means for
adjusting said timing means to allow said reference time inter-
val to be changed.
In accordance with another aspect of this invention
there is provided a sheet feeding process comprising: feeding
said sheet against a stop member to form a buckle in said sheet;
sensing the position of an edge of said sheet; timing reference
time interval from the sensing of said edge, said reference
time interval being sufficiently long to allow said sheet to be
buckled; adjusting the height of said buckle by varying said
reference time interval; and stopping the feeding of said sheet
upon the expiration of said reference time interval.
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It is also possible, in accordance with this
invention, to include a means for detecting a jam in the
apparatus. The jam detection means is coupled to the sensing
means for determining the presence or absence of the sheet
at the sensor at a given time.
This invention will become more apparent from the
following description and drawings.
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BRIEF DESCRIPTION OF THE DR~WINGS
Figure 1 is a perspective view of a sheet feeding
apparatus in accordance with one embodiment of the present
invention in its operative position.
Figure 2 is a perspective view of the sheet feeding
apparatus of Figure 1 with the paper drawer extended.
Figure 3 is a series of partial side views of the
sheet feeder of the present invention.
Figure 4 is a partial perspective view illustrating
the make-brake drive of the present invention.
Figure 5 is a series of partial side views illus-
trating the combination out of paper and drive make-brake
sensing switch of the present invention.
Figure 6 is a partial side view of the sheet feeder
of this invention.
Figure 7 is a partial side view of a sheet feeder in
accordance with this invention.
Figure 8 is a flow diagram for the electrical buckle
height control system.
Figure 9 is a schematic diagram of the electrical
buckle height control system of this invention.
Figure 10 is a timing diagram for the electrical
buckle height control system of this invention.
Figure 11 is a series of perspective views
illustrating the pivoting registration gate paper chute of
this invention.
Figure 12 is a partial side view of an alternative
embodiment of buckle assisting mechanism of this invention
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Figure 13 is a partial side view of the alternative
embodiment of Figure 12 illustrating its operation.
Figure 14 is a schematic side view of a reproducing
apparatus incorporating a bottom feeder and a top feeder in
accordance with this invention.
Figure 15 is a series of partial side views illus-
trating the operation of the feeders of Figure 14.
Figure 16 is a top and front view illustrating the
effect of a sheet being held simultaneously in registration
rolls and a separator.
Figure 17 is a top and front view illustrating the
effect of a pre-registration bump in the sheet feed path.
Figure 18 is a top and side view illustrating the use
of toes out registration rolls.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order to utilize a friction retard separator of the
type described in U. S. Patent No. 3,768,803, in a sheet feeder
which would be adapted for use in a compact reproducing machine
such as a compact xerographic copier, various improvements have
been provided to enable its efficient use. In a compact unit
the sheet feeder components, the registration mechanisms, and
the imaging device are all presented in a short paper path.
Therefore, a sheet being fed by the registration rolls may still
have a portion held within the nip of the separator. Since the
registration rolls feed the sheet to the imaging member, it is -
necessary that the action of the separator on the trailing
portion of the sheet not interfere with the smooth operation of
the registration rolls, and further, that it not interfere or
cause a force distribution which will result in rippling of the
; 10;~932:~
sheet particularly in the transverse direction. Such rippling
of the sheet results in copy quality defects in the form of
finger-like deletions in the resulting copy sheet.
Most xerographic type copiers use an on-center
separator, namely, a separator which feeds sheets from the
transverse center of the stack. The use of on-center feeding
requires center registration on the viewing platen for original
documents which are being copied. In newer machines such as
the Xerox 3100 compact copier, a corner registration arrangement
has been employed for original documents which has resulted in
the use of a sheet feeder arrangement wherein the stack is
registered against one side of the feeder. In this type of
device the sheet separator for many of the sheet sizes being
fed is off-center with respect to the stack.
It has been found that when a sheet separator of the
type described in the aforenoted patent is utilized for off-
center feeding. There is a tendency for the sheet being fed to
skew. This skewing tendency can be off-set to a great degree
by properly edge guiding of the sheets during feeding. The
skew which still persists can then be taken out by forward
buckling the sheet into a suitable registration gate.
The sheet feeding apparatus which will now be des-
cribed in detail has been designed for use in a compact
environment. It has been shown to be highly reliable with a
low propensity for jamming and misfeeding. The various
improvements which will be described hereinafter are shown in
an overall sheet feeding apparatus which compr~ses a pre-
ferred embodiment of this invention. It should be apparent,
however, that the~e improvements generally have wide application
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in the sheet feeding art and, therefore, are not necessarily
limited to the specific type of sheet feeding apparatus to be
described.
Referring now to Figures 1-3, the elements of the sheet
feeder 10 of this invention will be described. The feeder
includes a sheet support drawer 11 for supporting a stack of
sheets. While a top feeder is shown in these Figures the
various elements of the invention of this application are
generally applicable to bottom feeders as well as top feeders.
A friction retard separator 12 having a design similar
to that set forth in the above-noted U. S. Patent No. 3,768,803
is provided. The separator is supported in a pivoting frame
element 13 which pivots about the axis of a stub shaft 14. The
drive for the separator 12 is provided by means of a shaft 15
connected to the rear pulley 16 of the belt feeder 17 at one
end and which has a timing belt pulley 18 secured to its other
end. A second timing belt pulley 19 is journaled for rotation
about stub shaft 14, and a timing belt 20 connects both pulleys.
A drive gear 47 is secured to pulley 19 and is journaled about
shaft 14. A drive system 22 engages the gear 21 to drive the
belt feeder 17.
Following the separator 12, a pivoting registration
gate 80 and registration pinch rolls 24 are provided to first
enable a sheet to be forward buckled to remove any residual
skew, and to then feed the sheet in timed relation to a suitable
imaging member. A motor M is provided in the drive system 22 to
drive the registration rolls 24 by means of a chain drive 25
connected to the shaft 26 of the lower registration rolls 27.
The upper registration rolls 28 idle on shaft 29 against the
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lower registration rolls 27. A cam 30 and follower 31 arrange-
ment is utilized to pivot the registration gate 80 about the
axis of shaft 23 in and out of sheet blocking position in the
sheet feed path.
The feeder lO shown in adapted for use with a corner
registered reproducing machine and, therefore, the stack is
registered against a first stationary side guide 32. An
adJustable second side guide 33 is provided for engaging the
opposing side of the stack. Restraining means 34 are provided,
such as described in U.S. Patent No. 3,893,663 issued July 8, 1975,
and assigned to the assignee of the instant invention for restr-
aining the edges of the sheets in the stack in order to provide
efficient edge guiding of the sheets as they are fed by the
separator 12. As previously described depending on the width of
the sheets being fed, the feeder-separator will either be on-
center of off-center with respect to the transverse width of
the sheets in the stack and, therefore, proper edge guiding is
required to minimize skew due to the feeder. An imaging member
I such as a xerographic drum as shown in Figure 14 generally
follows the registration rolls 24 in the sheet feed path. The
imaging member I is not shown in Figure 1. Following the imaging
operation, a sheet transport 35 such as a vacuum transport is
utilized to carry the sheet away from the imaging member.
A stationary cam 36 and sliding follower 37 arrange-
ment are utilized for pivoting the separator 12 out of communi-
cation with the stack when the drawer 11 is withdrawn to its
extended position for loading and unloading sheets as well as
for clearning any jams or misfeeds which might have occurred.
Referring to ~igure 2, the paper drawer arrangement 11 is
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shown in its extended position. In the extended position the -:
paper drawer 11 has been withdrawn outwardly from its operative
position a sufficient distance to allow access to a stack of
sheets supported thereon. In addition, the separator 12 has
also been withdrawn to the extended position to allow access
to any sheets that might remain shingled in the nip of the
separator. The separator 12 is pivoted up to a position out
of contact with the stack by means of the action of the
follower 37 and cam 36 previously described. The separator 12,
as a unit comprising the belt feeder 17, and retard pad 38, is
secured to the top bar 39 of the pivoting frame 13 structure.
The side plates 40 and 41 are pivoted about the axis of the
shaft 14. The side plate 41 is suitably journaled for rotation
about the shaft 14 and the side plate 40 is pivotally pinned
to the drawer 11 frame, not shown.
One of the novel features of this invention comprises
the provision of a loading baffle 42 positioned to be pivoted
into operative position when the separator 12 is cammed out of
contact with the stack. The loading baffle 42 is supported
by the pivoting side plates 40 and 41 and in the embodiment shown
comprises an integral part of the lower paper chute 43. The
provision of a pivotal loading baffle 42 provides a convenient
means for registering the leading edge of a stack of sheet
material on the support tray 11. The stack is registered up
against the loading baffle 42 as well as the fixed side guide
32. The adjustable side guide 33 is then pushed into engage-
ment with the free side of the stack. This eliminates any
neces ity for having a support for the trailing edge of the
stack and provides a good means for accurately locating the
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lead edge of the stack with respect to the position of the
separator 12.
The pivotal operation of the loading baffle 42 of
this invention is~e~t illustrated in Figures 3A and 3B. In
Figure 3A the separator 12 in solid lines has been pivoted to
the loading position by the action of the cam 36 and follower
37. In this position the baffle 42 has a sufficient height
with respect to the support tray 44 so that the full height of
the paper stack P' to be employed can be placed against it.
The retard pad 38 of the separator 12 is positioned against
the back side of the baffle 42 and extends through a slot 45
in the baffle to be adjacent the stack. The baffle shown
extends across the length of the front edge of the stack. The
full range of motion of the separator 12 and baffle 42 is shown
in Figures 3A, while in Figure 3B, the separator and baffle are
shown in an operative position for an internediate stack height.
The shape of the lower paper chute 43 which is formed as an
integral part of the baffle 42 in the apparatus shown will be
described in greater detail later.
It is apparent from Figure 3 that the separator 12
is adapted to pivot through the full range of stack heights.
In the apparatus shown this range comprises about 13 from
the horizontal.
Referring now to Figures 2, 4, and 5, it is apparent
that since the separator 12 is carried along with the sheet
support drawer 11 to the extended position a make-brake drive
connection 46 is necessary for driving the belt of the feeder.
In the embodiment shown the make-brake drive 46 comprises a
pair of gears 47 and 48 which mesh when the paper drawer 11 is
in its operative or sheet feeding position, and which go out of
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mesh when the paper drawer is in its extended or reloading
position. The gear 48 is secured to the shaft 26 and the gear
47 is journaled about shaft 14. The gear 47 is coupled to the
pulley 19 through an electrically operated clutch 50. The
pulley 19 is coupled by means of timing belt 20 to the shaft
15 which is connected to the rear pulley 16 of the belt feeder
17.
The sheet support tray 11 is adapted to slide on rails
51 as shown in Figure 2 between the operative position and the
extended position. Adjustable abutment screws 52 at the ends
of the rails 51 provide a means for adjusting the position and
skew of the separator 12 with respect to the registration rolls
24 in the sheet feeding path.
Another of the improved elements of the present
invention is the utilization of a single switch actuator and
switch 53 for detecting both out of paper conditions as well as
meshing engagement of the make-brake drive mechanism 47 and 48.
Referring now to Figure 5a the gears 47 and 48 of the make-brake
drive are shown separated which would correspond to the extended
position for the paper drawer 11. In this position the micro-
switch 54 could not be actuated. This is the case even if a
paper stack were placed on the support tray and were caused to
depress the switch actuator 55 as shown by the dotted lines.
When the paper tray is pushed into the machine to its
operative position where sheet feeding can take place, the gears
47 and 48 are meshed as shown and the switch actuator 55 is in
position to engage the microswitch 54 detector. As shown in
Figure 5b, when no stack i8 present on the support tray, the
micro~witch 54 ic not actuated since the lever arm 56 of the
actuator 55 sticks up through the slot 57 in the tray. Upon
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placing a stack of sheets on the tray the arm 56 is depressed
as shown by the dotted lines which actuates the switch 54 and
provides a signal which indicates both that paper is present
and that the make-brake drive is engaged. Actuation of the
switch 54 requires concurrent engagement of the make-brake
drive 46 and presence of sheet material.
In order to accomplish this simultaneous operation,
the actuating lever 56 for the switch 54 is mounted to the
bottom side of the support tray while the switch itself is
mounted to a stationary feeder frame (not shown) upon which the
support tray slides. m e actuating lever itself has one end
pivotally mounted to the bottom of the support tray and the
other end arranged to protrude through the slot 57 in the
support tray when there is no stack of sheets supported on the
tray. At the end of the lever actuator adjacent to the pivot
~7 ~
A point, a cam portion~-7 is provided for engaging the switch 54
when the tray is in its operative position. The cam portion
pivots against the actuating button on the switch to open or
close the switch as desired. When the tray is withdrawn to its
extended position the cam portion~ of the lever 56 is with-
drawn from possible engagement with the switch 54. The lever
56 is adjustably mounted by means of the screw 58 to the bottom
~ 7~
of the support tray so that the cam~ can be positioned to
engage the switch button and actuate the switch 54 only when
the make-brake drive is in proper meshing engagement. In this
way tha switch is operative to detect both the drive connection
and an out of paper condition.
Another feature of the improved sheet feeding
apparatu~ of thi~ invention comprises the use of a toggling
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type retard pad. As previously described, the sheet separator
preferred for use with this invention is described in the
previously noted U. S. Patent No. 3,768,803. It employs a
queing throat into which the sheets are shingled in order to -
separate the top sheet from the remaining sheets. Since both
the belt feeder 17 and the retard pad 38 travel with the
support tray 11 to the extended position, and further since the
nip between the belt and the retard pad does not separate, it
is likely when changing sheet stacks that one or more sheets
will be shingled in the nip from between the belt feeder and the
retard pad. One of the principle reasons for desiring the sheet
separator 12 to extend from the reproducing machine in the same
manner as the paper drawer 11 is to provide access to such
shingled sheets. The nip force between the retard pad 38 and
the belt feeder 17 must be at some desired level in order to
provide sheet separation. This nip force has been found to
create some difficulty when pulling out sheets which are
shingled in the nip as, for example, when changing paper or
clearing jams.
Therefore, in accordance with this invention a means
has been provided for automatically reducing the nip force
between the retard pad 38 and the belt-feeder 17 when one is
attempting to remove sheets in a direction opposed to the
feeding direction and to automat cally increase the nip force
to the desired level when one is attempting to feed sheets in
the sheet feeding direction. In accordance with one embodiment
this is accomplished by a novel toggling linkage 60 for the
retard pad 38 which is best shown in Figure 6. As shown in
Figure 6, the retard pad 38 is pivoted about a pin 61 which
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extends transverse to the direction of sheet feed and transverse
to the belt feeder. The retard pad is supported by a member 62
which includes a slot 63 in which the pin 61 rides to pivotally
support the member 62. The pivot point for the retard support
plate 62 is off-center of the plate in the downstream direction
as shown. The support plate 62 is generally L-shaped with the
long first leg of the L including the retard pad 38 being
aligned with the belt feeder 17 and the short second leg of the
L being disposed substantially perpendicular thereto and
including the slot 63 defined by the fork-like projections which
project about the pin and provide the pivotable mounting.
A first adjustment screw 64 is provided in threaded
engagement with the bottom paper chute 44 of the pivoting frame
13 which abuts against the first leg of the plate 62 and -
provides the adjustment for the degree of pivoting motion to
be permitted when a sheet is pulled in a direction contrary to
the direction of sheet feeding. A second adjustment screw 65
is provided in one of the fork-like projections of the second
leg of the support plate 62. The second adjustment screw is
adapted to coact with a plate 66 fixed to the bottom of chute
44 as shown in order to adjust and limit the degree of motion for
the retard plate 62 when a sheet is being fed.
By providing the pivot point off-set from the center
of the retard pad in the direction of feed and by placing it
.A do w~sf~cg ~
~u~re~ of the center line of the plate 62, movement of a
sheet during ~heet feeding in the direction of feed will cause
the plate 62 to pivot or toggle in a counterclockwise direction
around the pin 61 and thereby increase the deflection of the
belt of the feeder 17 in the section between the pulleys, and
automatically increase the nip force between the feed belt 17
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and the retard pad 38 during sheet feeding. The degree of
rotation of the plate is determined by the adjustable stop
screw 65. Therefore, during sheet feeding a relatively higher
nip force between the belt and the pad is obtained by pivoting
the pad into the unsupported region of the belt and deflecting
the belt to a greater degree. When one is trying to clear
shingled sheets, or otherwise remove sheets from the nip of the
separator 12 pulling the sheet out causes the toggling plate
38 to rotate in a clockwise direction up against the screw 64
so as to reduce the deflection of the belt 17 in the unsupported
region and thereby reduce the nip force between the belt and the
retard pad. In this manner, one obtains automatically a
reduction in nip force when trying to pull out sheets from the
nip of the separator and an increase in nip force to a desired
level when one is attempting to feed sheets. Bu this simple
toggling type linkage for the retard pad 38, one is able to
eliminate the necessity for various approaches heretofore used
requiring the operator to pivot the pad away from engagement
with the feed means.
Yet another preferred feature of the paper drawer and
separator arrangement of the present invention, comprises an
upper paper chute 70 which is adapted to guide sheets which may
have curled edges. A problem associated with various copying
machines, particularly those utilizing radiant fusing, is
curl of the edges of the copy sheet. If one desires to refeed
these sheets through the copier or other reproducing machine in
order to obtain duplex copying or copying on both sides of the
sheet it is difficult to obtain reliable sheet feeding without
a high jam propensity. The upper paper chute 70 of the present
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feeder has been designed to take account of such curled type
sheets wherein when they are being fed for the second time
for copying on their second side, the curled edges would be
facing up. In order to accommodate these curled edges and
enable the sheets to be fed into the systems, dog-eared portions
71 are provided in the upper paper chute as shown in Figures 1,
2 ! and 7. The upstream corner portions 71 of the upper paper -'
chute 70 are bent upwardly to provide an increased gap between
the upper paper chute and the lower paper chute 44 to
accommodate the curl at the edges of the sheets. The upper
chute 70 shown is of a plate-like configuration which extends
t~ansversely across the sheet feed path and is generally co-
extensive with the belt feeder 17 in the sheet feeding direction.
The chute 70 is secured to the pivoting frame 13 by conven-
tional means (not shown). The upper paper chute 70 generally
conforms to the lower paper chute 44 in order to feed sheets
over the desired sheet feed path. The upwardly extending
dag-eared portions 71 enable the uniform feeding of sheets
having curled edges.
Referring now to Figure 7, following sheet separation
the sheet is fed along the sheet feed path defined by the
upper 70 and lower 44 paper chutes and then over the lower
paper chute until it reaches and engages a pivoting registra-
tion gate 80. The sheet continues to be fed until a
comparatively high forward buckle is obtained, as shown. The
large forward buckle formed generally has a height to length
betw,een constraining point ratio of about 1 to 4, and preferably
about 1 to 6 to eliminate any residual skew which may be
A t present due to the feeding of the sheet separator.~ ~b ~
obtain uniform buckle heights if the sheet feeder is to operate
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consistently to eliminate skew. It is recognized, of course,
that skew is bad for a reproducing machine since it results
in misregistered images and also in jamming of sheets in
downstream processing stations.
One of the problems with utilizing a belt and pad
friction retard separator wherein the next to be fed sheet
may be shingled in a queing throat, is that the lead edge of the
sheet is not at a definite location. Therefore, if one employs
a fixed time for buckle height formation, then depending on
where the lead edge of the sheet is in the nip prior to the
feed cycle, the resulting buckle height will vary to quite a
large extent. Detection of the actual buckle height is also
difficult because of the fact that the high point of the buckle
may appear at different locations along the sheet feed path
depending on the thickness of the material being fed, and also
on the type of material. For example, labels and other types
of similar materials buckle at odd positions as compared to
a paper sheet. Therefore, in accordance with a preferred
embodiment of this invention it is proposed to obtain uniform
buckle heights and, therefore, optimum results as far as skew
elimination is concerned by sensing the lead edge of the sheet
and then providing a desired time interval for buckle height
formation from the time the lead edge is sensed. To accomplish
this a switch 81 is placed in the sheet feed path which will
be intercepted prior to the lead edge of the sheet inter-
cepting the registration gate 80. The switch shown is shown
closely adjacent to the registration gate, however, that
position could be varied and the switch could have been placed
close to the separator, if desired. The lead edge of the
sheet being fed closes the switch 81 and causes a timer 82
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to count off a reference time interval during which the sheet
separator 12 continues to feed. After expiration, the reference
time interval the sheet separator 12 is deactivated by means
of the electric clutch 50. It should be apparent that while
a lever type switch 81 is shown as the lead edge sensor, other
types of detectors could be employed including photodetectors.
A lever switch has the advantage that it is not affected by
the feeding of transparent materials such as transparencies.
The timer 82 may be of any desired design. In accordance with
this invention it has been found to be preferable to incorporate
the timer into the machine control system in such a way that - -
an electronic timer is utilized.
Figure 8 represents a flow diagram for a control
system including an electronically timed buckle height contrDl.
Figure 8 represents an approach which could be utilized, for
example, with a Xerox "3100" copying machine. That machine
utilizes a scanning optical system for forming an image of an
original document placed on a transparent platen. The optical
image formed is then projected onto a xerographic drum. -
Further details of the process and apparatus will be described
later by reference to Figure 14.
Referring to Figure 8, following actuation of the
"print" switch 90 for the copier the machine control logic 91
and optics sensor 92 are initiated to provide optics ready and
machine ready signals, respectively, to the scanning logic
controller 93. This enables the scan controller 93 which in
turn enables the retard clutch S0 coupling the drive 22 to
the friction retard separator-feeder 12, and also enables the
scan solenoid 95 which causes the optics system 96 to scan
over its predetermined path and also cycles the registration
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1039323
system 80 for registering a copy sheet with respect to the
image projected on the drum. Enabling the retard clutch 50
causes a sheet to be fed by the separator 12 which in turn
actuates the sensor switch 81. Actuation of the sensor switch
81 provides a first signal A to the electronic timer 104 and
also an optional signal to the machine jam detection logic 101.
The master counter 102 which controls the timing of
the machi~ logic is coupled to a time delay logic circuit 103
to provide a time del~y signal to the electronic buckle control
system enabler 100 in order to prevent the enabler 100 from
providing the enable signal B to the timer 104 prior to the
clearing of the sensor switch 81 by the previously fed sheet.
This time delay is set at a time interval long enough for the
prior fed sheet to clear the sensor switch 81 before the
timer is enabled and short enough such that the newly fed
sheet will not reach the sensor switch before expiration of
the enabler time delay interval. Following this time delay
the buckle control system enable signal B is generated and
upon the concurrence of the register switch 81 sense signal A
the electronic timer 104 is actuated to count a reference time
interval during which the separator 12 continues to feed the
sheet to buckle it against the register gate 80. upon
expiration of the reference time interval the timer 104 provides
a disable signal C to the retard clutch S0 to disengage the
drive 22 from the separator 12.
The master counter 102 is reset to 0 after
each copy is made by a suitably timed signal ~ from the machine
controller 91. The master counter 102 generates a signal
E at an appropriate count to reset the buckle system enabler
100 .
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Optionally the master counter 102 can also signal
the jam logic 101 to enable it to interrogate the register
sensor switch 81 during an appropriate time interval when a
sheet should be present at the switch thereby ensuring that
sheet feeding has occurred. Should the jam logic 101 not
receive a register sensor switch signal so indicating, then
a signal is generated by the jam logic to the machine
disabling logic 105 to shut-off the machine. The jam logic
and disabling logic may be of any conventional design. For
example, one form of control logic for jam detection and
machine disablement is described in U. S. Patent ~o. 3,813,157,
assigned to the assignee of the instant invention.
Referring now to Figure 9, the elements of an
electronic timer and buckle control system 110 from Figure
8 which comprises the preferred embodiment of this invention is
shown in greater detail.
The sensor switch 81, as shown, comprises a single
pole double throw switch. Complementary output signals from
the sensor switch appear at terminals 111 and 112 which comprise
the inputs of a noise suppression circuit 113 which comprises
the resistors and capacitors in a conventional arrangement as
shown.
A D-latch 114 or flip-flop type circuit is included
as part of the noise suppression circuit. The set and reset
terminals of the latch 114 are coupled to the logic voltage
supply by separate pull up resistors R. Thus, one of the input
terminals of the latch is at a high logic level and the other
is at a low logic level depending on the position of switch 81.
Grounding a given terminal 111 or 112 by closing the switch
generates a low le~el signal. In the embodiment shown the
~ ' ' , :' ' ,, ' ' ,:
. .
~039323
switch 81 has not been activated by a sheet being fed and,
therefore, it is connected to the terminal 112 which provides
a low signal at the reset terminal D of the latch 114 and a
high signal at the set terminal. In this state the output
of the latch 114 comprises a low signal. When a sheet is
sensed the switch 81 connects terminal 111 to ground which
causes the set terminal of the latch 114 to go low and thereby
the output of the latch to go high. The output signal of the
latch 114 is applied to one input of a NAND gate 115. The other
input of the gate 115 is tied to a 60Hz. line. This NAND gate
is operative to gate in a 60 Hz. train of clock pulses to a
binary ring counter 116.
The master counter and decoder 117 which includes
elements 102 and 103 from Figure 8, is utilized to set and
reset a D-latch type flip-flop which comprises the buckle
system enabler 100. As previously described, the setting
signal for the enabler 100 is decoded after a suitable time
delay. The reset signal is generated when the master counter
and decoder 117 decodes a desired count corresponding to a
desired time interval for resetting the enabler. The output
of the.enabler D-latch 100 is high when it is set and low
when it is reset. The output is applied to one input of
a NAND gate 118. A second input to the ~AND gate 118 is
received through terminal 119 from the machine controller 91
of Figure 8, and comprises a cycle-up disable signal which
is low when the machine is cycling from its stand-by condition
to a machine ready condition and which is high when the machine
reaches the machine ready condition. A third input to this
NAND gate 118 is recieved through terminal 120 from the machine
controller and comprises a cycle-out disable signal which is
-23-
1(~39323
low when the machine is cycling from its machine ready condi-
tion to its machine stand-by condition, and is high when the
machine is in the machine ready condition. Upon the concurrence
of high signals at each of the inputs to the NAND gate 118 a
low signal is generated which enables the counter 116. The
counter 116 then counts the clock pulses which are gated to it
from the MAND gate 115 under the conditions previously described.
If desired, machine status need not be considered and
a suitable inverter circuit of conventional design could be
employed instead of the NAND gate 118 to change the output of
the enabler flip-flop 100 from a high to a low for enabling
the counter.
Four outputs from the binary ring counter 116 corres-
ponding to desired binary numbers are applied through switches
121-124 to respective inputs of a MAND gate decoder 125. Pull
up resistors 126 are provided in each input line between the
switch and the decoder 125 input to provide high signals at a
given input if the switch in the respective line is open. By
opening or closing the switches 121-124, one can decode any
desired count within the range of the counter to provide an
output signal from the decoder 125 indicating the end of the
reference time interval. The use of the in line switches,
as shown, therefore enables the reference time interval of
the timer 104 to be adjusted as desired. For the counter shown,
time intervals from 0 to 15 counts can be decoded which would
correspond to a time interval of 0 to .25 seconds. For example,
to decode a count of 8, switch 124 would be closed and the
others left open, while for a count of 15, all of the switches
121-124 would be closed.
-24-
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The output signal from the NAND gate decoder 125
which comprises the end of the reference time interval signal
is applied to set the input terminal of a D-latch 126 type
flip-flop. The D-latch 126 i5 reset by a signal F received at
terminal 128 from the scan controller 93 which is set forth
in Figure 8. The output of the D-latch 126 is applied to a
suitable latching switch circuit 127 which may be of any con-
ventional design such as, for example, one employing a silicon
controlled rectifier. The output of the latching switch is
effective to enable or disable the retard clutch. Resetting
the D-latch 126 causes the latching switch to enable the
retard clutch 50 whereas setting the latch disables the clutch.
Figure 10 shows a typical timing diagram for the
buckle height control system 110 of this invention. Actuation
of the "print" switch 90 for the copier at time toenables
the retard clutch for initiating sheet feeding. After a pre-
determined time delay tl-tOduring the sheet feeding interval,
the buckle system enabler D-latch 100 is enabled at time tl.
The lead edge sensor switch 81 is then actuated at time t2
to start the timer 104 and following the expiration of the
reference time interval t3-t2 at time t3 the timer disables
the retard clutch. At time t4 the buckle system enabler latch
100 is reset by the master counter 117. At time t5 the sheet
clears the sensor switch 81. When a second copy is initiated
at time to', the previously described timing cycle is repeated.
Having thus formed a forward buckle in the sheet
against the registration gate 80 it is now necessary to feed the
sheet to the nip of the registration rolls 24 and then to an
imaging member I. Since a relatively hia,h buckle has been
formed in the sheet, it has been found necessary and desirable
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in order to obtain sheet feeding without a high propensity for
jamming to assist the buckle in flattening out as the sheet is
fed by the registration roller.
As shown in Figures 7 and 11, the lead edge of the
sheet P at the time it intercepts the registration gate 80 rests
upon the lower registration rolls 27. The lower registration
rolls have a diameter which is greater than the diameter of
the upper registration rolls 28. The gate 80 in its sheet
blocking position is located just upstream of the nip of the
rolls 24, and close enough to the nip so that the lead edge
of the sheet as it engages the gate can rest against the lower
registration rolls. Since the rolls 24 are driven continuously
the effect of this arrangement is to have an assisting force
applied to the lead edge of the sheet to keep it in engagement
with the gate 80 as the gate pivots the lead edge into the
nip of the rolls 24. Further, this registration roll assist
also aids sheet feeding following the registration cycle,
since the sheet is already being acted upon by the lower
rolls 27 during the registration cycle.
The registration gate 80 shown in Figures 7 and 11,
also operates as an upper paper chute for the registration rolls
24. It extends substantially across the sheet. The portions of
the gate 80 which engage the lead edge of the sheet during
registration comprise tabs 130, the remaining plate-like face
portion 131 of the gate comprises the paper chute. As previously - -
noted, the lower registration roll assist helps to maintain engage-
ment between the lead edge of the sheet and the tabs 130. The
downstream side of the buckle which is formed in the sheet
engages the chute portion 131 of the registration gate 80. In
the embodiment Rhown, both the chute portion 131 and tab
-26-
,, , ', ' , ., , ':
.
~,
~ 103932:~
portions ~30 are formed as a single piece. Since the chute
portion 131 pivots as the sheet P passes into the nip of the
registration rolls 24 an assisting action on the front portion
of the sheet is provided to help carry it into the registration
901 4/qf~n 59i~ ~ckJ~
rollsA so as to reduce the tendency of the sheet to jam. If the
chute portion ]3] were stationary and only the tabs 130 pivoted,
then there would be a higher propensity for jamming. By pivoting
both the upper chute portion 131 and the registration tabs 130
jam propensity is substantially reduced. This occurs because
the chute portion which engages the buckle is moving in sub-
stantially the same direction as the sheet thereby reducing
the tendency of the sheet to bind against the chute.
To further assist in flattening out the buckle, as
shown in Figure 7, a plurality of transversely (normal to the
plane of the Figure) spaced apart buckle assist members 140
act on the upstream side of the buckle to push and flatten
the buckle as the sheet P is fed by the registration rolls 24.
The assist members comprise elongated elements pivoted so as to
be biased against the rearward or upstream side of the buckle.
The elements shown are formed of metal and are biased by
their own weight. Their weight provides sufficient assisting
force to provide the operative characteristics required.
Alternatively, the buckle assist members could comprise resilient
strips ]41 formed of Mylar or other suitable material which
could be mounted in cantilever fashion as in Figure 14. As
the buckle forms, it deflects the strips 141 in a spring-like
fashion. The strips then act like cantilever springs to force
the buckle to flatten as the sheet is being fed by the registra-
tion rolls. The use of Mylar fingers is a highly effective
approach when two feeders are employed which feed to the same
-27-
1039:~23
registration roll 24 and gate 80 arrangement.
Referring to Figure 15a, when the top feeder 150
is feeding the sheet P into the registration gate, the ~ylar
strip 141 is deflected upwardly by the upwardly forming buckle
and as the sheet is fed out by the registration rolls 24 it
acts upon the buckle to flatten it out. As shown in Figure
~5b, when the bottom feeder 160 is feeding, the ~ylar strip 141
is deflected in the opposing or downwardly direction by the
downwardly forming buckle and acts against the buckle to
flatten it out as the sheet P is fed.
Referring now to Figures 12 and 13, yet another
buckle flattening arrangement 170 is shown. In this embodi- -
ment the sheet feeder is positioned adjacent a xerographic
drum I. The registration gate 80' is positioned below the
sheet feed path. This gate 80' is also a pivoting type gate
which directs the lead edge of the sheet into the nip of the
registration rolls 24. A flexible sheet or multiple strip
like member 171 is connected between the gate 80' and the
retard pad supporting member 172. The member 171 thereby forms
the lower paper chute. When the gate 80' is in its operative
position to block sheet passage, there is sufficient slack in
the flexible member 171 to allow the formation of a downwardly
facing buckle. This would be the ~ eferred approach since it
allows easy access to the sheet for jam clearance. However,
this concept could be applied to an upwardly buckling
arrangement if desired. Following buckle formation, as shown
in Figure 13, to feed the sheet P and flatten the buckle,
the registration gate is pivoted out of its operative blocking
~osition to its inoperative position below the sheet feed
path and the slack in flexible member 171 is taken up so that
-28-
~039323
the member is held taut between the gate 80' and the retard
pad support member 172. The action of taking up the slack in
the member 171 assists in flattening the buckle in the same
manner to the concepts previously described.
Referring again to Figure 7, it is apparent that a
sheet P being fed by the friction retard separator 12 upon being
engaged by the registration rolls 24 is still held within the
nip of the friction retard separator. This arrangement, which
is desirable when the sheet feeder 12 is to be employed in a
compact environment wherein there is insufficient room to
separate the sheet registration and separation functions by
more than the length of a sheet, can result in significant
problems due to the interaction of these functions. The
frictional engagement between the registration rolls 24 and the
sheet and the torque supplied to the registration rolls must
be sufficient to overcome the nip drag between the belt feeder
17 and the retard pad 38 even though the belt feeder is free
wheeling since clutch 50 is disengaged and also the drag force
between the belt feeder and the stack P'.
One approach which could be employed to reduce the
nip force between the belt feeder ly and the retard pad 38
would be to separate the nip of the separator 12 when the
registration rolls feed the sheets P. However, this destroys
the queing and shingling function of the separator design 12
which is preferred. It is desirable in accordance with this
invention to maintain the closed nip of the separator 12 and
the retard pad in order to keep the appropriate queing throat
and shingling of the sheets in the throat. Therefore, it has
been determined that the best approach for reducing the drag on
the sheet P as it is being fed by the registration rolls 24
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9323
would be to reduce the drag due to the normal force of the
belt feeder 17 against the stack P'.
A specific approach for carrying this out has been
devised which is extremely simple in nature. It has been
noted that the friction retard separator 12 of this invention
including the feed belt 17 and retard pad 38 are pivoted about
the axis of shaft 14. Referring to Figure 6, the drive
pulley 19 rotates in a clockwise direction to advance the
timing belt 20 and separator belt 17 as shown by arrows 180
and 181. This results in an increase in normal force exerted
by the feeder 17 during feeding due to the addition of an
assisting pick force.
The assisting pick force which has been described is
believed to be a result of a reaction torque or resistance
torque about the pivot 14 of the separator 12. The normal
assisting force component contributed by this resistance torque
is a function of the input torque about the pivot point 14,
the length of the moment arm between the pivot point and the
point of application of the normal force to the stack P' and
the frictional resistance encountered by the belt 17. The
drive direction about the pivot point 14 should be in a direction
so as to cause the pick force to be exerted against the stack
P' rather than away from it. For example, if the feeder 17 were
rotated about the pivot 14 in the same direction as the drive
input 19, it should rotate against the stack.
In accordance with this invention, the normal force
with which the feeder 17 engages the stack P' during feeding
is comprised of two components, the first component comprises the
normal force which would be exerted by the belt feeder 17 against
-30-
,
" , .. . ..
,
9323
the stack when it is not being driven which can vary from zero
up to any desired level. In the embodiment of Figure 1 this
comprises the weight of the separator 12 frame 13, etc., as
counterbalanced by the spring 190. This component can be
relatively low, namely, a force sufficient to maintain friction
contact between the belt feeder 17 and the top of the stack.
Upon driving the belt feeder, an additional component of normal
force is imparted due to the resistance torque moment previously
described. This component in the embodiment shown in Figure 6
is substantially greater than the force of the first component.
Further, this component is self-compensating.
The amount of the resistance torque moment is believed
to be a function of the frictional resistance which the belt
encounters when it is being driven. A major component of the
frictional resistance is due to the nip friction between the
belt and the retard pad and a lessor component of the frictional
resistance is due to the friction between the belt and the
top sheet of the stack. The self-compensating effect results
as follows: If the sheets in the stack are not shingled
in the nip of the separator the frictional engagement between
the retard pad 38 and the belt 17 will be high, thereby
resulting in a high resistance torque and correspondingly
high normal assisting force applied to the stack. Thus, the
higher normal force required to separate and feed a sheet
from the stack would automatically be provided by the feeder
as proposed herein. There can be a reduction in normal force
applied where a sheet has already been shingled between the
nip of the belt and the retard pad. In this instance, to feed
the sheet a lower degree of normal force is required
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~39323
since it has already been separated from the stack. Since -
the sheet P has been shingled in the nip between the re-tard
pad 38 and the belt feeder 17, the frictional resistance of
that nip has been reduced, and consequently the normal assist-
ing or pick force component due to the resistance torque about
the pivot is also reduced. It is apparent then that the use
of the pick force herein as a normal assisting force during
feeding provides substantial advantages in enabling one to -
obtain automatic compensation in normal force for feeding
sheets under different conditions.
The amount of the normal force which results from
this additional resistance torque component can be adjusted by
adjusting the input torque about the pivot 14 and/or by adjust-
ing the length of the moment arm between the pivot and the
point of application of the normal force. -
While the use of this pick force has been shown by
reference to the use of a friction retard separator of the
belt and pad type, it should be apparent that it could also be
utilized with a friction retard separator of the roll type such
as the one described in U.S. Patent No. 3,883,133, issued
May 13, 1975, and assigned to the assignee of the instant invention. ;
If desired, the normal assisting force can be further
augmented by locating the feeder pivot 14 outwardly of the
plane of the sheet being fed as in U.S. Patent No. 3,048,393
to Furr et al. This configuration gives a pick force due to
the frictional resistance between the feeder and the sheet,
however, it varies with stack height.
The actual speed of the belt feeder may be modified
from the input torque supplied the pulley 19 by any desired
-32-
.. . . . . ....... .. . . .
,. ;, . .
1039323
means such as the use of varying sized pulleys 18, suitable
gearing or the like. It is essential, however, that the
drive about the pivot be in the proper direction, and,
therefore, it may be necessary to include additional idler
gears or the like to provide the appropriate input drive
direction.
The sheet separator 12 mounted as described is adapted
to apply a first high initial normal force against the stack
P' during feeding by the separator and then a substantially
lower normal force when the sheet P is being fed by the
registration rolls 24. This substantially reduced the drag
of the feeder on the sheet as it is fed by the registration
rolls 24.
Referring to Figure 14, the applicability of the
pick force principle to a bottom feeder 160 is also shown.
In Figure 14 two feeders 150 and 160 are employed. A top
feeder 150 is provided substantially as previously descirbed
with a difference being that the belt feeder 17' includes an
extra idler pulley 151 so that the circumference of the belt
is the same as the circumference of the belt utilized on the
bottom feeder 160. The belt portion between the idler pulley
151 and the rear belt pulley 16' operates as previously
described about axis 14'.
For the bottom feeder 160, however, wherein the belt
17'' feeds from the bottom of the stack P' a greater portion
of the feed belt between idler pulleys 161 and 162 engages
the bottom sheet to provide more efficient feeding. This is a
similar approach to that described in U.S. Patent No. 3,895,791,
issued July 22, 1975. The bottom feeder feed belt
-33-
, '' " ~ ,'' ' ",, ' "
'' ~ ,. ..
1039323
17'' and retard 38'' assembly are pivoted about a drive shaft
163 against the stack P'. The input drive gear 164 which
meshes with drive gear 48 (not shown) rotates in a counter-
clockwise direction. The rear pulley 16'' of the feeder 17''
is driven from the input drive gear 164 by a pulley and
timing belt arrangement similar to that previously described
with reference to the feeder 17 of Figure 6. In this manner
a pick force or normal assisting force is generated during
feeding. The pick force increases the normal force exerted
against the bottom of the stack substantially above that due
to the spring biasing 165 of the feeder head 17'' and 38''.
In the case of the top feeder 150 the stack support
tray provides a stop against which the pick force action of
the belt feeder 17' operates. In the case of the bottom
feeder 160 tray, however, no such stack stop is provided.
Therefore, in accordance with this invention, an
adjustable stop means 200 is provided against which the feed
belt 17'' acts. The adjustable stop means 200 comprises a
pivoting lever 201. The lever 201 has a pad 202 at one end for
contacting the stacX P' above the feed belt 17''. The other
end the lever is secured to a shaft 203 through a one way
clutch 204 which can be overridden by a desired degree of
force which is selected to be greater than the normal pick
force exerted by the bottom feeder 17''. The one way clutch
204 permits the lever 201 to move easily toward the stack
but will not allow it to move away from the stack except by
slipping upon the application of a relatively high force
#ubstantially greater than the pick force exerted against the
~tack by the feeder 17.
-34~
la3s323
In operation the adjustable stop lever 201 is raised to
load a sheet stack and is then lowered against the stack.
When a sheet P is being fed the high normal force due to the
pick force component acts against the pad 202 and lever 201
which restrains the stack from moving and allows the increase
in normal force to be applied to the stack. The bottom feeder
itself is biased with a low level of normal force against the
bottom of the stack by spring 165 even when no pick force is
provided.
It is a unique aspect of this invention that two sheet
feeders 150 and 160 can be provided which feed sheets to a
single set of registration rolls 24 wherein a sheet fed from
either feeder to the registration rolls is still in its
respective sheet separator at the time it is first fed by
the registration rolls. This is possible only because of
the highly compact nature of the sheet feeding apparatus of
this invention.
It should also be apparent that the belt feeders
17' and 17'' for the top feeder 150 and the bottom feeder 160
in Figure 14 are off-set from one another in a direction
transverse to the feeding direction.
One of the difficulties that arises when using a
single point separator 12 such as the friction retard separator
herein and multiple registration rolls 24 such as previously
described is an uneven force distribution in the sheet due to
the uneven tension in the sheet between the registration rolls
and the separator. This is belt illustrated by reference to Figure
16a. As the registration rolls 24 begin to advance the sheet
P and pull it from the nip of the separator 12, a force pattern
is created as shown in Figure 16a. This force pattern is quite
-35-
1()393Z3
non-uniform because of the fact that the registration rolls
extend across the transverse width of the sheet whereas the
separator is virtually at a single point. The result of this
non-uniform force distribution is a wrinkling of the sheet
as it is being fed by the registration rolls as shown in
Figure 16b. Feeding a sheet with a wrinkled lead edge or
wavey lead edge to an imaging member I results in deletions
in the resulting copy sheet where the sheet did not come into
contact with the imaging member due to its wavey surface.
These deletions extend like fingers in from the lead edge of
the sheet and may be characterized as finger-type deletions.
One approach to solving this pooblem is illustrated
in Figure 7 and comprises a bump 210 in the bottom of the
lower paper chute 43 which extends between the separator and the
registration rolls. The bump preferably should be relatively
sharp to cause a deflection in the sheet being fed which also
helps to initiate buckling. As the sheet P is being fed by the
registration rolls 24 while still being held in the separator
nip the bump results in a sharp bend 210' in the sheet as shown
in Figure 17a. m e effect of this bend in the sheet is to
provide a more uniform force distribution between the bend and
the registration rolls since the rolls pull against the line-like
bump 210. m e result of the bend in the sheet, as shown in
Figure 17b, is to provide a sheet without lead edge ripples or
wrinkles and thereby reduce or eliminate the finger-type dele-
tions previously described.
Yet another approach to eliminating wavey or wrinkled
lead edges for the sheet P being fed by the registration
-36-
103~32;1,
rolls 24 is shown in Figure 18a. In accordance with this
approach the registration rolls 220 and 221 which contact the
sheet near the opposing side edges of the sheet are toed out.
They are canted in generally opposing directions with respect
to the axis of the upper registration roll shaft 222. The
registration roll 221 on the right side of the sheet has its
axis of rotation canted or toes out to the right with respect to
the axis of shaft 222 and the registration roll on the left side
of the sheet has its acis of rotation canted or toed out to
the left with respect to the axis of shaft 222. The canting
of the rolls 220 and 221 may be obtained by providing an
eccentric bushing (not shown) for the shaft 222 about which the
rolls rotate. The details of this structure need not be shown
since any desired approach for toeing out the rolls 220 and 221
could be employed including bending the shaft 222 to the
desired canting angle. In the apparatus shown only the outer
top idler rolls 220 and 221 are toed out and the bottom rolls
27 which are driven are not toed out. If desired, both sets
of rolls could be canted. However, it has been found that
canting only the outer top rolls provides adequate results.
The effect of toeing out the rolls 220 and 221 is for each
roll to impart a force directed laterally outwardly of the
sheet feed direction on each side of the sheet so as to cause
any wrinkles or waveness in the sheet to be flattened out
by placing the sheet under tension along its transverse width.
The center registration roll 28 is shown, but need not be employed.
If a center roll is employed, it has been found desirable to
mount it so that it is not toed out in either direction, but
rather 80 that it i journaled concentrically with the axis
of shaft 222.
f, , ,' , ",.' , , ;", , ,'
lO~g3Z~ ,
It has been found that if a sheet is fed by the
separator without the benefit of the front portion 43' of the
lower paper chute that wrinkling of the leading portion of
the sheet can result. The portion of the sheet acted upon
by the separator follows the curved path of the separator
nip while the remaining portions of the sheet tries to go
in a straight path due to its inherent beam strength. This
can cause the leading portion of the sheet to wrinkle.
To eliminate this problem the portion 43' of the
lower chute 43 substantially co-extensive with the separator
12 is shaped to substantially conform along its transverse
width to the shape of the separator nip. This portion along
with the upper chute 70 causes the entire sheet to follow the
arcuate path of the separator nip and thereby reduces any
propensity for wrinkling the sheet.
The shape of the portion 43' is similar to, but
need not be identical to the shape of the nip. It should
have a sufficiently curved shape to guide the sheets over their
transverse width through substantially the same curved path
as the nip.
Referring again to the use of pick force as a
normal assisting force during feeding, it has been found that
particularly with a bottom feeder the first normal force
preferably is zero if desired and the entire normal force which
the feeder exerts against the stack should preferably comprise
the assisting force. This approach can also be applied to a
top feeder by providing sufficient counterbalancing to completely
overcome the weight of the feeder head. It has been found,
however, that the application of a small first normal force with
the top feeder provides good results.
-38-
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1039323
The pick force generated in accordance with the
feeding arrangement of this invention provides a very useful
side effect which comprises the breaking of the lead edge of
the stack due to its cyclic loading with the relatively high
pick force.
To further illustrate the use of pick force as a
normal assisting force the following calculated example is
presented for a feeder as shown in Figure 6 having the following
parameters:
1. The moment created by the weight of the
pivoting feeder head is about 1.15 inch
pounds.
2. The bearing friction which is assumed to
occur solely at pulley 16 is about .097
inch pounds.
3. The distance from the pivot axis 14 to
the point of contact with the stack in
the horizontal direction is about 4.56 -
inches and in the vertical direction is .
about .45 inches.
4. The wrap angle of the belt 17 about the
retard pad 38 is about 23.3 degrees.
5. The initial belt tension is about 1.5 lbs. -
6. That the diameter of pulley 19 is twice
the diameter of the drive hub of pulley
16 about the shaft 15, and that the
diameter of the pulley 16 is about .915
inche~.
-39-
10;~9323
7. The belt to retard pad coefficient of
friction is about 1.58; the paper-to-
paper coefficient of friction is about
.6, and the paper-to-retard apd coefficient
of friction is about 1.1.
Based on the above parameters, the following force
levels have been calculated. The normal force exerted by the
feeder against the stack when it is not running is about 0.25
pounds. In operation the assisting pick force raises the
normal force to about 0.65 pounds when no sheet is shingled
in the nip of the separator or to about 0.42 pounds if a sheet
is shingled in the nip. This illustrates the self-compensating
effect of the picking action of this invention.
In addition to the forces calculated above, the
following forces were calculated wi~h respect to the drag
force required to pull a sheet from the above feeder when it
is not running and the belt 17 is free wheeling.
The bearing drag force is about 0.21 lbs.
The feed belt to stack drag force is about 0.151 lbs.
The retard pad to belt nip drag force is about
0.666 lbs.
Providing a total drag force of about 1.03 lbs.
It is apparent that the drag force at the nip of the
separator is more than 4 times greater than the drag force
between the feed belt and the stack. Therefore, the pick
force which is generated is principally a function of the nip
friction.
It should also be apparent that if the full normal
force were applied to the feeder head instead of using a pick
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103g323
force assist then the belt-to-stack drag force would be
significantly higher.
This example is meant to illustrate, but one embodi-
ment of this invention ans i~ not intended to be limitive
of the invention. Feeders employing the principles disclosed
herein can utilize a wide range of parameters to get desired
force levels and other characteristics.
The sheet feeding apparatus lO of the present
invention is uniquely suited for use in a reproducing machine,
particularly reproducing machines of the xerographic type.
Its highly compact nature allows one to substantially reduce --
the space required for the sheet feeder. While the sheet -
feeders of this invention may be used with any desired
reproducing machine, a xerographic type reproducing machine
will be described by reference to Figure 14.
Referring now to Figure 14 there is shown by way
of example an electrostatographic reproducing machine 230 which
incorporates an improved sheet feeding apparatus 10 of the -- -
present invention. The reproducing machine 230 depicted
in Figure 14 illustrates the various components utilized
therein for xerographically producing copies from an original. -
Although the sheet feeding apparatus of the present invention
is particularly well adapted for use in an automatic xero-
graphic reproducing machine 230, it should become evident
from the following description that it is equally well suited
for use in a wide variety of electrostatographic systems and
other reproducing machines and is not necessarily limited in
its application to the particular embodiment shown herein.
m e reproducing machine illustrated in Figure 14
employs an image recording drum-like member 231, the outer
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periphery of which is coated with a suitable photoconductive
material. One type of suitable photoconductive material is
disclosed in U. S. Patent No. 2,970,906, issued to Bixby in
1961. The drum 231 is suitably journaled for rotation within
a machine frame (not shown) by means of a shaft 232 and rotates
in the direction indicated by arrow 233 to bring the image
retaining surface thereon past a plurality of xerographic
processing stations. Suitable drive means (not shown) are
provided to power and coordinate the motion of the various
cooperating machine components whereby a faithful reproduction
of the original input scene information is recorded upon a
sheet P of final support material such as paper or the like.
The practice of xerography is well-known in the
art, and is the subject of numerous patents and texts, including
Electrophotoqraphy by Schaffert, published in 1965, and
Xeroqraphy and Related Processes, by Dessauer and Clark,
published in 1965. The various processing stations for
producing a copy of an original are herein represented in -
Figure 14 as blocks 234-239.
Initially the drum 231 moves photoconductive surface
through charging station 234. In charging station 234 an
electrostatic charge is placed uniformly over the photoconduc-
tive surface of the drum 231 preparatory to imaging. The
charging may be provided by a corona generating device of
a type described in U. S. Patent No. 2,836,725, issued to
Vyverberg in 1958.
Thereafter, the drum 231 is rotated to exposure
station 235 where the charged photoconductive surface is
exposed to a light image of the original input scene information,
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whereby the charge is selectively dissipated in the light
exposed regions to record the original input scene in the
form of a latent electrostatic image. A suitable exposure
system may be of the type described in U.S. Patent No.
3,832,057, issued August 27, 1974.
After expsoure, drum 231 rotates the electrostatic
latent image recorded on the photoconductive surface to
development station 236 wherein a conventional developer mix
is applied to the photoconductive surface of the drum 231
rendering the latent image visible. A suitable development
station is disclosed in U.S. Patent No. 3,707,947 issued to
Reichart in 1973. This patent describes a magnetic brush
development system utilizing a magnitizable developer mix
having carrier granules and a toner colorent. The developer
mix is continuously brought through a directional flux field
to form a brush thereof. The electrostatic latent image
recorded on photoconductive surface is developed by bringing
the brush of developer mix into contact therewith.
The developed image on the photoconductive surface
is then brought into contact with a sheet P of final support
material wherein a transfer station 237 and the toner image
is transferred from the photoconductive surface to the con-
tacting side of the final support sheet. The final support
material may be paper, plastic, etc., as desired. After the
toner image has been transferred to the sheet of final support ~ -
material the sheet with the image thereon is advanced to a
suitable fuser 238 which coalesces the transferred powder
image thereto. One type of suitable fuser is described in
U.S. Patent No. 2,701,765, issued to Codichini, et al in 1955.
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Although a preponderance of the toner powder is
transferred to the final support material P, invariably some
residual toner remains on the photoconductive surface after
transfer. The residual toner particles remaining on the
photoconductive surface after transfer are removed from the
drum 231 as it moves through cleaning station 239. Here the
residual toner particles are first neutralized and then
mechanically cleaned from the photoconductive surface by
conventional means as, for example, the use of a resiliently
biased knife blade as set forth in U.S. Patent No. 3,660,863,
issued to Gerbasi in 1972.
It is believed that the foregoing description is
sufficient for purposes of the present application to illus-
trate the general operation of an automatic xerographic copier
which can embody the teachings of the present invention.
Unless otherwise specified or shown, shafts and other members
are suitabiy supported in appropriate machine frames by any
desired conventional means.
The term electrostatographic as employed in the
present application refçrs to the formation and utilization
of electrostatic charge patterns for the purpose of recording
and reproducing patterns in viewable form.
It is apparent that there have been provided in
accordance with this invention apparatuses which fully satisfy
the objects, means and advantages set forth hereinbefore.
While the invention has been described in conjunction with
specific embodiments therefor, it is evident that many
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alternatives, modifications and variations will be apparent
to those skilled in the art in light of the foregoing
description. 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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