Variable force sheets or set ejector

In an output sheet handling system for a reproduction apparatus, for selective stacking of the output sheets into at least one stacking tray, with a sheet ejection system for gripping and ejection of the output of the printed sheets into a stacking tray sequentially as individual output sheets or as a compiled stack of sheets, the sheet ejection system includes an automatic variable normal force system automatically providing a substantially higher gripping normal force for ejection of a compiled stack of sheets than for ejection of individual output sheets. The ejection system preferably increases the gripping normal force for the set ejection in proportion to the thickness of the compiled stack being ejected, and feeds individual delicate sheets through a nip with an automatically substantially lower normal force.

There is disclosed in the embodiments herein an improved, low cost and 
simple system for ejecting varying numbers of printed sheets of various 
weights without requiring a high power, high torque drive, and yet also 
providing for the protection of delicate sheets such as carbonless 
pressure-sensitive paper or other special paper stocks easily marked or 
wrinkled. 
By way of background, on-line set compiling and finishing is very 
desirable, particularly for the job sets printed precollated by many 
modern high volume printers, copiers and other reproduction apparatus. 
Precollated copy sets output can be provided by an electronic printer with 
automatic page reordering, or a recirculating document handler, both well 
known per se. A single or plural tray compiler may be used to stack and 
align sheets therein, one at a time, and, if desired, also stapling or 
otherwise finishing each collated job or copy set. Single or partial tray 
compiler/staplers are disclosed, for example, in U.S. Pat. Nos. 5,098,074; 
4,417,801; 4,541,626; 5,098,074; 5,120,047; 5,201,517; 5,288,062; 
5,308,058; 5,289,251; and 5,328,169 (the latter, and U.S. Pat. No. 
5,308,058, FIG. 2 compiler is like that of FIG. 2 herein). In the system 
examples illustrated hereinbelow, a compiler tray may be a part of, or 
have a sheet input path directly or indirectly from, a reproduction 
apparatus sequentially providing output sheets, to compile sets of those 
sheets, as is generally known. 
It is also well known in this art, for better stacking registration, to 
sequentially deposit the outputted sheets for stacking onto an inclined 
surface. That allows different sizes of sheets to be stacked using the 
same paper path and the same tray system, using partially gravity assisted 
stacking against a simple inboard or outboard registration wall or 
surface. However, active stacking registration/alignment assistance 
systems, such as scuffers, flappers, tampers, joggers, etc., can be 
additionally provided for stacking and registration assistance. E.g., the 
illustrated "floppy belt" type reverse feeding top sheet jogger for 
initial uphill stacking thereover, with jogged registration at the 
downhill inboard end of the tray, as shown in U.S. Pat. Nos. 4,883,265; 
5,098,074; 5,137,265; 5,288,062; 5,308,058; 5,328,169; etc. 
It is known that compilers may be equipped to automatically eject each 
compiled sheet set into a downstream stacking tray or bin with a set 
ejector of some sort, such as the closable driven roll nips illustrated 
herein and in above-cited art. However, with downhill inboard 
registration, as is also illustrated in the compiler examples herein, the 
compiled set must be ejected uphill, partially against gravity, into its 
stacking tray or bin. That makes set ejection more difficult, especially 
for heavy or thick compiled sets. The present system is directed to 
improvements as to these and other problems. 
Further by way of background, it is also known that various known lateral 
or side edge sheet registration systems, such as lateral joggers, tampers, 
and/or edge guides, may be compatibly provided in compiler systems. Some 
examples are in U.S. Pat. No. 5,044,625 (D/87242), art cited therein, and 
various other art cited herein. Accordingly, there is no need to 
illustrate examples here. It is also known that during the compiling 
operation, the compiler shelf or tray need only support part of the 
sheets, with part of the sheets being compiled partially extending into 
the stacking bin or tray, on top of the bin, tray, or prior sets stacked 
therein, as disclosed in U.S. Pat. Nos. 5,098,074; 5,137,265; 5,201,517, 
5,328,169; and other art cited herein. 
Another potential application of the present system is in or as part of a 
"mailboxing" system. That is, an output system capable of independently 
handling and separating different jobs for different users or addressees 
automatically and simply. Sets or jobs of plural physical sheets outputted 
by a printer are variously directed into particular "mailbox" bins or sets 
of bins. This allows plural users to share a printer yet have the 
different users outputs automatically placed into different "mailboxes" or 
bins. "Mailboxing" is further described for example in Xerox Corporation 
U.S. Pat. No. 5,308,058 issued May 3, 1994, or U.S. Pat. No. 5,328,169 
issued Jul. 12, 1994; U.S. Pat. No. 5,098,074 issued Mar. 24, 1992 and EPO 
application No. 0 241 273 published Oct. 14, 1987, and other art cited 
therein. 
Job set ejection into the final output bin or tray presents special 
difficulties. As disclosed in said U.S. Pat. Nos. 5,308,058 and 5,098,074, 
a desirable feature for mailboxing systems is to optionally collate and 
staple or otherwise bind, fasten or finish the sheets of each user job 
together, so that plural finished sets may be stacked in the users bins, 
maintained separated from other job sets therein by being so fastened. 
This can be done by pre-compiling and stapling each set before they are 
placed into mailbox bins, such as with a moving compiler/stapler unit 
repositionable adjacent the user bin to be loaded, as described in the 
above-cited patents, and shown in FIG. 2 here. In-bin stapling in the 
output bins themselves is an alternative. 
Further by way of background, as is also shown in the art, the stacking 
tray or bin into which job sets are ejected from a compiler may be an 
elevator type, in which the tray moving down as it fills to maintain the 
top of the stack slightly below the compiler exit level. Conventional 
elevator-moved stacking trays can be used, like those described in the 
above-cited U.S. Pat. Nos. 5,098,074 or 5,137,265; 5,026,034; 4,541,763; 
or 4,880,350. Alternatively, especially in a mailboxing system, 
compiler/stapler units can move or reposition as an output stacking tray 
fills. This desirably allows a simple fixed tray to be used, with no 
elevator mechanism for that tray, by using the same indexing elevator 
system as is used to direct jobs from the compiler unit to selected 
mailbox bins. 
The presently disclosed apparatus may be readily operated and controlled 
with conventional control systems. It is well known in general and 
preferable to program and execute such control functions and logic with 
conventional software instructions for conventional microprocessors. This 
is taught by various patents such as those cited above or U.S. Pat. No. 
4,475,156 and art cited therein, and various commercial facsimile 
machines, copiers and sorters. Such software may of course vary 
considerably depending on the particular function and the particular 
software and the particular microprocessor being utilized, but will be 
available to or readily programmable by those skilled in the applicable 
arts without undue experimentation from either verbal functional 
descriptions, such as those provided herein, or prior knowledge of those 
functions which are conventional, together with general knowledge in the 
software and computer arts. Controls may alternatively be provided 
utilizing various other known or suitable hard-wired logic or switching 
systems. 
A specific feature of the specific embodiments disclosed herein is to 
provide in an output sheet handling system for a reproduction apparatus, 
for selective stacking of the output sheets into at least one stacking 
tray, with a sheet ejection system for gripping and ejection of the output 
of the printed sheets from said reproduction apparatus into said stacking 
tray sequentially as individual output sheets or as a compiled stack of 
plural output sheets, the improvement wherein said sheet ejection system 
includes an automatic variable normal force system automatically providing 
a substantially higher gripping normal force for said ejection of said 
compiled stack of plural output sheets than for said ejection of said 
individual output sheets. 
Further specific features provided by the system disclosed herein, 
individually or in combination, include those wherein said output sheet 
handling system includes a compiled sheets set stapling system, and 
wherein said sheet ejection system provides ejection of the output of 
printed sheets as a compiled and stapled stack of plural said output 
sheets from said reproduction apparatus, ejected by said sheet ejection 
system into said stacking tray as a stapled set of plural output sheets; 
and/or wherein said sheet ejection system increases said gripping normal 
force for said ejection in proportion to the thickness of said compiled 
stack of plural output sheets being ejected; and/or wherein said sheet 
ejection system comprises a closable sheet feeding nip providing said 
gripping normal force and said ejection and with at least two different 
operating modes; a first closed nip mode for said ejection of the output 
of printed sheets into said stacking tray as a previously compiled stack 
of plural said output sheets through said nip with said substantially 
higher gripping normal force in said nip, and a second closed nip mode for 
feeding individual delicate sheets through said nip with an automatically 
substantially lower said gripping normal force in said nip than in said 
first mode; and/or wherein said output sheet handling system includes a 
compiled sheets set stapling system, and wherein in said first mode said 
sheet ejection system provides ejection of the output of printed sheets as 
a compiled and stapled stack of plural said output sheets from said 
reproduction apparatus, ejected by said sheet ejection system into said 
stacking tray as a stapled set of plural output sheets; and/or in which 
said gripping normal force of said nip has a maximum force limit set to 
protect an object improperly inserted therein; and/or further including a 
third operating mode of said sheet ejection system in which said closable 
sheet feeding nip is open, with no sheet gripping normal force, to provide 
unobstructed sheet compiling prior to said sheet stack ejection with the 
sheets being compiled partially extending through said open nip; and/or 
further including a fourth operating mode of said sheet ejection system in 
which said closable sheet feeding nip is opened automatically in response 
to a sheet jam signal for sheet jam clearance; and/or wherein said sheet 
ejection system includes a nip opening and closing drive system for said 
closable sheet feeding nip, and an associated spring force system actuated 
to provide said substantially higher gripping normal force in said nip in 
said first mode in response to said drive system continuing to operate 
after closing said sheet feeding nip. 
In the description herein the term "sheet" refers to a usually flimsy sheet 
of paper, plastic, or other such conventional individual image substrate. 
The "copy sheet" may be abbreviated as the "copy". A "job" is a set of 
related sheets, usually a collated copy set copied from a set of original 
document sheets or electronic page images from a particular user or 
otherwise related. 
As to specific hardware components of the subject apparatus, or 
alternatives therefor, it will be appreciated that, as is normally the 
case, some such specific hardware components are known per se in other 
apparatus or applications which may be additionally or alternatively used 
herein, including those from art cited herein. All references cited in 
this specification, and their references, are incorporated by reference 
herein where appropriate for appropriate teachings of additional or 
alternative details, features, and/or technical background.

Describing now in further detail the exemplary embodiment with reference to 
the Figures, the examples here of an output sheet compiling and/or 
stapling and ejecting system for a reproduction apparatus may be, for 
example, similar to but an improvement over, that disclosed and described 
in the above-cited Xerox Corporation patents such as U.S. Pat. No. 
5,288,062 issued Feb. 22, 1994 (re FIG. 3) or U.S. Pat. No. 5,308,058 (re 
FIG. 2). Accordingly, common elements need not be re-described in detail 
herein. For clarity, common reference numbers, except that they are 
primed, are used in said different embodiments illustrated herein. A 
selectable sheet deflecting or bin gating input system 40 is also shown in 
the FIG. 2 embodiment. The sequentially incoming output sheets 12 from 
almost any reproduction apparatus may pass through almost any desired 
input feeder or gating system to the compiler, and thus need not be 
illustrated. All the incoming sheets 12 in the embodiments herein are 
first fed via an input feeding rollers nip 42 into a compiler unit 16. The 
compiler unit 16 here includes a partial compiler tray 15 and an integral 
stapling system 17. 
However, in a bypass or sorting mode individual sheets may be fed directly 
through the compiler/stapler unit 16 directly on into the adjacent output 
stacking bin or tray 18, without compiling in tray 15 or stapling, as 
shown for example in the darker dashed line path with arrows in FIG. 2. In 
this mode, a sheet ejection system 20 has its arm unit 22 moved down so 
that the upper ejection nip rollers 24 on the end of this arm 22 are held 
down in engagement with lower ejection nip rollers 26, to feed out the 
individual sheet into stacking tray 18. 
Alternatively, the incoming sheets 12 may be compiled as a compiled set 
stack 14 in compiler tray 15, before being ejected from the compiler unit 
16 as a plural sheet compiled set to be stacked in the output stacking bin 
or tray 18 on top of other plural sheet compiled sets. This may be done by 
dropping each incoming sheet 12 and feeding it backwards to register 
against the downhill stacking rear registration wall 15a or fingers of the 
compiling tray 15, on top of prior such stacked sheets. Once the incoming 
sheet has been discharged from the sheet entrance rolls nip 42 and drops 
onto partial compiler tray 15, it slides back downhill, and its upper 
surface is also contacted by a rotatable frictional flexible compiler 
jogger belt 44, causing the sheet to be driven back and downhill until it 
is fully registered against the upstanding rear wall 15a of the tray 15. 
This type of compressible open or "floppy belt" 44 jogger or compiler 
assistance is further disclosed in the above-cited U.S. Pat. Nos. 
4,883,265 and 5,137,265, etc.. Each subsequent job sheet is compiled on 
top of the prior sheets on tray 15 in this manner, until one complete job 
set is compiled (a collated document copy set, faximile document, or 
whatever). 
During this set compiling and registration mode, the set discharge system 
20 has its arm unit 22 moved up, so that the nip is held open between the 
upper rollers 24 and the lower rollers 26, i.e., in an up position out of 
contact. That is, during this compiling cycle, the sheet ejection system 
20 is not attempting to eject any of the sheets in the compiling tray 15, 
and the open nip allows the compiling set to stack therethrough, extending 
out partially through the open nip into the stacking tray 18. That is, 
during this compiling operation the sheets partially extended and hang out 
into the adjacent bin 18, saving overall dimensional space. That is, this 
particular illustrated compiler tray 15 is only a partial sheet supporting 
shelf for most sizes of sheets, as in the above-cited U.S. Pat. Nos. 
5,098,074, 5,137,265, etc. 
A conventional lateral registration tamper or jogger may also be provided 
in this compile mode, as in the cited art thereon. That is, once, or 
while, each incoming sheet is rear registered by the rotation of the 
floppy registration belts 44 thereagainst, a lateral tamper or jogger 
mechanism may engage each sheet to shift each sheet towards a lateral 
registration edge as is shown in the tray 15. Because the floppy 
registration belts 44 are so flexible, they are easily deformed in the 
lateral direction and do not resist such sideways movement of the sheet. 
In the compile mode, once the reproduction apparatus controller 100 or 
other signal source indicates the end or last sheet being compiled of that 
job set, if a stapling signal is also provided, then the compiled set may 
be stapled in one or more positions by the stapling system 17 before the 
set is ejected. 
Once the stapled (or unstapled) compiled set is fully compiled, it may be 
ejected, to feed out the set fully into stacking tray 18. The set ejection 
or discharge system 20 arm unit 22 moves down to close the nip on the set 
with an appropriate nip or normal force so that the set is fed out between 
the upper rollers 24 and the lower rollers 26. Note that this is feeding 
the set uphill, against gravity. In this mode, the set to be fed out is 
often much heavier than a single sheet, and with a different nip spacing 
depending on the set thickness. 
As illustrated in the successive positional views of FIG. 1 A-D, there are 
three basic modes of operation of the illustrated plural mode sheet or set 
ejection system. As in FIG. 1A, an open nip 24, 26 mode of the sheet 
ejection unit 20 may be provided in which the arm unit 22 is raised. In 
this mode, sheet stacking is provided unobstructedly into the compiler. 
This is because this particular illustrated embodiment has a short 
compiler tray and part of the sheets stacking in the compiler extend into 
the associated output stacking tray adjacent thereto, as described in the 
cited references thereon. 
In another two modes of operation, there is provided a closed ejection nip 
24, 26. This nip is closed in the FIG. 1 embodiment by a variable force 
system 30 including a nip opening and closing drive system 31 driven by 
motor M1 here through a drive linkage 32 via a camming lever 33 and a cam 
engagement surface 34. In the initial closed nip mode of FIG. 1B, a very 
light nip normal force may be provided for appropriately feeding 
individual delicate sheets, such as carbonless transfer paper which is 
pressure sensitive, through the nip 24, 26 directly to the stacking tray 
18 without compiling, i.e., bypassing the compiler tray 15. 
In the other closed nip mode of operation, as in FIG. 1C, a closed nip is 
provided with a heavy nip or normal force for feeding out a stack of 
sheets which have been compiled in the compiler tray 15. This greatly 
increased normal force for heavy set ejection is also provided by the 
variable normal force system 30, as will be further described below. 
Typically, such ejected compiled sets in this mode will also have been 
stapled in the compiler unit 16 by an integral set stapling system 17, and 
thus are particularly susceptible to disheveling or tearing the top or 
bottom sheet of the stapled set during ejection if proper normal force is 
not applied to provide for non-slip feeding of the entire stack set. 
In addition to the three operational modes described above, and further 
described below, an additional desired design criteria is to provide nip 
force application means having a large amount of overtravel, or to 
otherwise provide for safety considerations. That is, if something were 
somehow under the eject arm 22 or eject roller 24 when the system is 
closing, the closing force should be limited. The closing movement should 
not, for example, fully deflect a spring and "bottom out" until the motor 
stalls out with an unacceptably high force. It is also desirable that the 
eject arm 22 should open or lift for jam clearance as part of the shut 
down procedure of the system after certain faults, although it does not 
have to open simply when power is removed. The cited references teach jam 
detectors which can be conventionally connected to motor M1 via controller 
100 here. 
To summarize said three modes of operation there are at least three 
different desired eject nip pinch forces to be provided, all with low 
power consumption, for varying print media feeding requirements, by the 
variable force system 30. One is zero pinch force with an open nip to 
allow sheets to reverse between the exit pinch rolls 24, 26 for 
registration in the compiler. Another is a low pinch force to avoid 
marking carbonless sheets or other delicate individual sheet alternatively 
being fed by the same nip. Another is a high nip force to maintain stack 
integrity during stack ejection, by high paper-to-paper or intersheet 
friction when ejecting a stacked set. This high force on the nip during 
thick set ejection is needed to ensure that a complete set can be driven 
out without shingling or tearing the outermost sheets, as noted. 
Referring further to details of the embodiment of FIG. 1, it may be seen 
that this system 30 requires less power by requiring the motor M1 to only 
work against spring force 35 only in the closed nip position for stack 
ejection, rather than during the entire nip opening or closing operation. 
This is a significant improvement over prior systems, such as that shown 
in FIG. 2, in which the eject arm is spring loaded into the closed 
position and is opened by a motor driven cam always working against that 
spring force to open the eject nip. Such prior art systems also have 
excessive nip normal force for individual sheets or small sets. 
Furthermore, this nip force in the present system is self-adjusting based 
on the stack thickness, i.e., increasing automatically with the increase 
in thickness of the set to be ejected form the compiler. The high nip 
force is generated here only in the primary or set ejection mode. The 
spring 35 load is applied here only after the eject nip 24, 26 has been 
fully closed onto the sheets between rolls 24 and 26 by full downward 
movement of the sheet ejector arm unit 22. This drastically reduces the 
drive torque and power required to operate the system. The system here 
also optionally allows the final applied nip force to be varied by 
stopping the drive system in two or more different positions. 
As the motor M1 rotates the nip opening and closing drive system 31, here 
this reciprocally moves the crank arm or drive linkage 32, which is in 
turn oscillates the pivot arm or camming lever 33 here. The illustrated 
right angle extension of the pivoted camming lever 33 here is adapted to 
intermittently engage a cam engagement or lifting surface 34 on the sheet 
ejector arm unit 22. 
As shown, one end of spring 35 is connected to the end of the set ejector 
arm unit 22 opposite the pinch roll 24. The other end of spring 35 is 
connected to, and moves with, camming lever 33. The spring 35 can 
partially pull the ejection arm 22 towards the camming lever or pivot arm 
33, but the spring 35 only deflects to generate counter nip force only 
after the nip has been fully closed, as will be described. 
As the nip opening and closing drive system 31 rotates, its position may be 
detected by suitable means, such as the illustrated extending rotating 
flag 36 successively actuating rotation sensors 37, 38 and 39. Note that a 
single sensor plus a simple timing algorithm could be used in place of the 
three sensors 37, 38 and 39 illustrated here. Alternatively, a single 
sensor and a signal from an "arm closed" interlock switch, as in FIG. 4, 
may be used. Or, two separate flags may be used with two sensors, to 
provide four states of position detection from the respective switch 
activations or non-activations, i.e., 00, 01, 10 and 11. 
As shown in the respective illustrated positions of FIG. 1, in FIG. 1A the 
ejection arm 22 is just starting to close. The opening and closing drive 
system 31 is not working against any spring load from the spring system 
35. In FIG. 1B, the ejection arm 22 has closed to close the nip 24, 26, 
and drive system 31 has been stopped with the flag 36 blocking the first 
sensor 38. A low nip force is generated in this drive system 31 position 
in the nip between rollers 24 and 26. This is the position for feeding 
delicate single sheets through the system. Note that in this position the 
cam engagement surface 34 is not contacted by the camming lever 33 and 
only the spring 35 is acting to provide normal force (in addition to 
gravity) to the nip 24, 26. That is, the cam engagement surface 34 is 
fully disengaged from the camming lever 33 in this position. 
Referring to the next Figure, 1C, the drive system 31 is driven further or 
not stopped until flag 36 reaches the second sensor 37 position. In this 
position and mode, the variable normal force system 30 has increased the 
normal force substantially, for set ejection, because the drive linkage 32 
has now been rotated further to further rotate the camming lever 33 and to 
also pull the end of the spring 35 connected thereto to thereby 
substantially increase the spring force applied to the ejector arm unit 22 
by tensioning spring 35. The machine controller 100 knows whether set 
compilation or single sheet outputting has been selected and controls the 
drive system 31 to stop at the corresponding desired sensor position. 
In the next step, illustrated in FIG. 1D, there is illustrated the lifting 
or opening of the ejector arm unit 22 by further rotation of the nip 
opening and closing drive system 31, which now oscillates the camming 
lever 33 in the opposite direction so that the cam engagement surface 34 
is now engaged and lifted by this movement of the camming lever 33. This 
position can be signaled by a sensor 39. Note that in this position the 
drive system 31 is not working against any spring load from the spring 
force system 35 because the cam engagement surface is now resisting the 
load from the spring (which is still in tension) and the camming lever 33 
and the ejection arm 22 act as a single freely pivoting solid body. 
Referring further now to the FIG. 4 embodiment, here after a set has been 
compiled and stapled, it is ejected using a similar eject roller nip 70 
(in its closed or phantom line position). The nip 70 is closed using a DC 
motor 71 driving a linkage 72 attached to the eject arm 73 as shown. The 
mechanism that opens and closes the eject arm 73 can be stopped in the 
upper (or open) (solid line) position, or in one of two closed positions, 
as in the other embodiments. The signal from a home sensor 76 here is used 
in conjunction with a signal from an interlock switch 78 to stop the eject 
arm 73 in the correct location. (See the table below for further details.) 
When the eject arm 73 is in the first closed position, the nip 70 is 
loaded with a low nip force of approximately 4.0 N. This position is used 
to transport single sheets in non-stapling modes. In the second closed 
position, nip 70 is loaded with a high nip force of approximately 7.0 N. 
This higher force is sufficient to eject stapled sets without slip at the 
sheet-to-sheet interfaces. 
The upper rolls 80 of nip 70 are elastomer drive rolls and the lower rolls 
82 are idlers. The idler rolls 82 may be shaped to provide corrugation to 
the sheets or sets passing through the nip. If the 70 nip is driven by the 
same motor (not shown here) as the upstream or feed-in drive nip (not 
shown here) that upstream nip may be released during set ejection so that 
the lead edge of the next incoming sheet can enter without velocity 
mismatch problems. The set ejection arm is preferably always left in the 
closed position between jobs to provide a physical barrier preventing 
operators from inserting their fingers into the compiler area during 
movement of the finishing carriage. The interlock switch 78 prevents the 
stapler motor and the carriage vertical drive motor from operating when 
the eject arm 73 is open. At the start of each job, the eject arm is 
initialized to the low force closed position. This initialization 
procedure is accomplished by running the eject arm motor 71 until sensor 
78 is blocked while interlock switch 78 is in the open state, as in the 
Table. 
TABLE 
______________________________________ 
EJECT ARM POSITIONING 
[To stop the eject arm 73 in desired 
position, drive motor 71 until sensor 
76 transition occurs with switch 78 
at state listed, wait specified 
time delay and stop motor 71 using 
DC braking] 
DESIRED STOP Sensor 76 Interlock 
POSITION TRANSITION Switch 78 STATE 
______________________________________ 
Open Blocked Not Actuated 
(contacts closed) 
Closed Blocked Actuated 
(low force) (contacts open) 
Closed Unblocked Actuated 
(high force) (contacts open) 
______________________________________ 
It will be appreciated that there are a number of other possible 
alternative mechanisms to achieve the functions described herein. For 
example, the crank arm 32 could be replaced by a pin in an eccentric cam 
track or an eccentrically mounted cam on a motor shaft inside a yoke which 
is U-shaped, C-shaped, or elongated. The cam can engage one side of the 
yoke to lift up the arm in one rotary position, but then in intermediate 
positions of the eccentric cam rotation not engage the yoke, and thus 
allow the arm to drop so that the weight of the arm holding the ejector 
rollers would provide the light, normal force of the second mode for 
single delicate sheets. This could be assisted with a partial 
counter-balanced spring. Then, further rotation of the eccentric cam could 
engage the other side of the oversized yoke to press down the arm with the 
desired higher normal force, preferably indirectly through a spring. 
While the embodiments disclosed herein are preferred, it will be 
appreciated from this teaching that various alternatives, modifications, 
variations or improvements therein may be made by those skilled in the 
art, which are intended to be encompassed by the following claims: