Sheet feeding and separating apparatus adapted to separate a single sheet from a stack of sheets and forward the separate sheet away from the stack for subsequent processing. The apparatus includes a feed belt disposed adjacent the stack for contact with the top sheet to separate the sheet therefrom. A retard shoe is spring biased into engagement with the feed belt. Actuation of the feed belt and engagement of the retard shoe with the sheets provide a rotating and locking relation with the mounting member of the retard shoe thereby preventing passage of multiple sheets by the feed belt but allowing the fed sheet to be pulled from the apparatus by a low value of pull force.

The invention relates in general to the feeding of sheet material and, more 
particularly, to improved sheet separating apparatus for reliably 
separating sheet material fed from a superimposed stack. 
The advent of programmable printing machines, such as automatic typewriters 
in word processing systems, has been very popular among businesses because 
of the speed and accuracy with which documents may be prepared, and for 
some printing operations the system may operate without an operator in 
attendance. The result of the popularity of the word processing systems 
has been the creation of a need for more rapid and reliable means of 
automatically feeding paper to the printers of the systems. Of course, 
there has always been a need for rapid and reliable means of automatically 
feeding paper in and to large high-speed printers, sorters, collators, 
reproduction machines, etc. A sheet misfed or multifed sheets usually 
seriously impair the operation of the machine and/or system. 
Apparatus and methods for separating sheet material from a stack and 
serially feeding discrete pieces of sheet material to a machine are known 
in the art. As disclosed in U.S. Pat. No. 3,260,521, a drive roller is 
rotatably supported so that the drive roller is engaged by the leading 
edge of the outside article in the stack under the force of a spring 
forcing the stack in the direction of the drive roller. A blade-like stop 
abuts the roller as a barrier to the passage of sheets from the stack with 
the blade-like stop being forced against the drive roller by spring means. 
The abutting edge of the blade-like stop is beveled to provide an inclined 
surface facing the stack. The sheet of paper will strike the incline, 
force the stop away from the drive roller and be fed between the stop and 
the drive roller. Multifeeds are minimized by using a heavy spring to 
force the blade-like stop against the drive roller together with provision 
of a large force to rotate the drive roller. 
U.S. Pat. No. 3,941,373 discloses a feed belt for feeding sheets from a 
stack. A low-friction feed gate is disposed adjacent the front edge of the 
stack and is spring biased into engagement with the feed belt. The gate 
acts to maintain the forward edge of the stack in alignment and prevent 
the passage of more than one sheet at a time between the gate edge and the 
feed belt. Again, multifeeds are minimized by using a heavy spring to 
force the gate against the feed belt while providing a large force to 
drive the feed belt. 
U.S. Pat. No. 3,768,803 discloses a separator in which a feed belt is 
supported for movement about a pair of pulleys. A curved retard means is 
stationarily positioned against a section of the belt between the pulleys 
to form a sheet queuing throat. The feed belt contacts the stack near the 
edge, and the throat acts to queue or align the sheets for advancement 
into a sheet handling system. In this system, only the topmost sheet is 
fed through the separator. However, adjacent sheets are shingled in the 
throat formed between the belt and the stationary retard pad. 
In all these prior art sheet-feed apparatus, the amount of force available 
to pull the sheet past the retard mechanism and separate a single sheet 
from the stack has not been a concern or a problem. When a sheet feeder is 
employed in conjunction with a conventional printer in an automatic 
typewriter, the amount of force available to pull the sheet material from 
the sheet-feed apparatus and the retard mechanism may be of concern and of 
prime importance because the amount of force is normally low and of 
limited amount. This is particularly true of low-cost printers and some 
printers, which are already in the marketplace. Reliability of proper 
paper feed to the printer during automatic printing is a high priority, 
espeically when the printing is occurring automatically by an unattended 
machine. Normally the platen of the automatic printer provides the force 
required to pull the sheet of paper from the retard mechanism in the sheet 
feeder, and the platen force available for this function is limited in 
present-day printers. 
The invention as claimed is intended to provide a remedy for unreliable 
paper feed, e.g., misfeed or multifeed, to an automatic printer when the 
available force supplied by the platen and feed rollers of the automatic 
printer is limited. 
The invention provides reliable paper feeding to the automatic printer 
thereby increasing the throughput of the system by reducing delays because 
of paper jams caused by improperly fed sheets and the absence of paper 
caused by misfeeds. Available printers need not be modified to increase 
the torque available to the platen drive system. One advantage offered by 
the present invention is the low amount of force required to pull a sheet 
of material through the friction retard separator. 
Although the invention is appicable to any sheet-feed environment utilizing 
low value of pull force, it has been found particularly useful in the 
environment of a paper feeder for a printer system having limited amount 
of platen pull force; therefore, without limiting the bounds of the 
invention, the invention will be described in this environment.

Referring now to FIG. 1, a simplified view of a sheet-feed apparatus 10 
embodying the present invention is illustrated. Mounted to frame 12 by 
pivot means 13 is an input tray 14 for receiving a stack of sheet material 
therein. As seen in FIG. 2, spring means 16 forces the stack of sheet 
material or paper sheets 18 against a sheet feeding and separating belt 20 
of paper-feed assembly 22. Sheet 18 could be a single sheet or multiple 
sheets. The sheet feeding and separating belt 20 is driven by stepper 
drive motor 24 through the pulley-belt assembly 26, shaft 28 and one-way 
clutch 29. Stepper drive motor 24 is controlled via signals applied to 
terminals 30. There are two guide plates 32 and 34; guide plate 32 is 
stationary and guide plate 34 is pivotable. Guide plates 32 and 34 tend to 
guide the sheet material 18 after it leaves the paper-feed assembly 22 on 
its path of travel to the printer (not shown). The top edge of guide plate 
34 is removably attached to rod 36 by spring clips 38 and is pivoted at 
its lower portion by pivot means (not shown). This means of mounting plate 
34 allows the plate 34 to pivot away from the sheet-feed apparatus 10 and 
guide plate 32 to provide for clearing of any paper jams, etc. Guide plate 
32 is removably attached to frame 12 by fasteners 39. 
Referring now to FIG. 2, the paper-feed assembly 22 includes a sheet 
feeding and separating belt 20 mounted for movement about rollers 40 and 
42 together with spring-loaded friction retard separator 44. Rollers 40 
and 42 rotate about shafts 46 and 48, respectively, in a clockwise 
direction as does the sheet feeding and separating belt 20. The 
spring-loaded friction retard separator 44 includes retard pad or shoe 46 
attached to a generally L-shaped mounting block 48. Mounting block 48 is 
positioned within and guided within predetermined limits by guide 50. 
Compression spring 52 mounted within opening 53 in guide 50 tends to force 
mounting block 48 and attached retard pad 46 toward the sheet feeding and 
separating belt 20 such that the retard pad 46 is in contact with belt 20 
and is raised from contact with top surface 51 of guide 50. Mounting block 
48 is free to move up and down with respect to guide 50 and support member 
54. Dimension "a" is 0.020 inch .+-.0.010 inch. Guide 50 is attached to 
support member 54 by suitable means, such as bolts or rivets (not shown). 
Support member 54 also functions as a front support wall for input tray 
14. Upper edge 56 of support member 54 is positioned with respect to the 
sheet feeding and separating belt 20 to limit the number of sheets 18 that 
could traverse the opening therebetween. Spring 16 forces the forward edge 
of input tray 14 toward paper-feed assembly 22 such that the top sheet of 
material or paper 18 is positioned in contact with the sheet feeding and 
separating belt 20. Support member 58 supports the sheet 18 as it exits 
the paper-feed assembly 22. 
The sheet feeding and separating belt 20 is formed from isoprene stretch 
material. The isoprene stretch material has a high coefficient of friction 
in the order of 2 or greater. The retard pad or shoe 46 is formed from 
silicone rubber, which has a lower coefficient of friction, i.e., 1.5, 
than the isoprene stretch mateial. Sheet material 18 has a coefficient of 
friction, which is less than either the isoprene stretch material or the 
silicone rubber. Mounting block 48 is machined from aluminum, and guide 50 
is molded from glass-reinforced polycarbonate. Guide 50 may also be 
machined from aluminum, which works even better than the glass-reinforced 
polycarbonate but is more expensive to fabricate. Compression spring 52 is 
available from Associated Spring Corporation as part No. CO 300-022-0880S. 
During normal feed operation when one sheet 18 only is being fed, the 
force of spring 52 is essentially equal to the locking force (to be 
discussed below) supplied by mounting block 48 plus the force of gravity 
as applied to mounting block 48. 
The relative position of the sheet feeding and separating belt 20 and the 
retard pad or shoe 46 is important. The retard pad or shoe 46 is 
positioned at a location near the roller 40 such that when a normal force 
is applied to the sheet feeding and separating belt 20 in the area 60 of 
the back portion of the retard pad or shoe 46 by sheet material 18 being 
fed therebetween, the sheet feeding and separating belt 20 is compressed 
thereby limiting the deflection of belt 20 upward between rollers 40 and 
42. 
Referring now to FIGS. 3 and 4, a side and rear view of the mounting block 
48 and the retard pad or shoe 46 are shown. The outer curved surface 62 of 
the retard pad or shoe 46 is formed on a three inch radius. Beveled face 
64 is generally formed at a 30 degree angle from surface 62. Grooves 66 
are formed in surface 62. 
Referring to FIGS. 5 and 6, a top and rear view of guide 50 is shown. Lugs 
68 and 70 through which openings 72 and 74 are formed, respectively, 
provide mounting means, together with appropriate fasteners, to mount 
guide 50 to support member 54 (FIG. 2). Spring 52 (see FIG. 2) is mounted 
within opening 53. The vertical portion of mounting block 48 is positioned 
within cutout 76. 
In operation of the specific embodiment employing the present invention and 
with reference to FIG. 2, paper feed is initiated by rotation of the sheet 
feeding and separating belt 20 in a clockwise direction. Since the sheet 
feeding and separating belt 20 is in contact with sheets 18 and retard 
shoe 46, the movement of belt 20 causes two things to happen essentially 
at the same time. Curved surface 62 of the retard shoe 46 is forced to the 
left causing a rotation or cocking of mounting block 48 with respect to 
guide 50 and support member 54. Moment point 78 between mounting block 48 
and guide 50, together with contact point 80 between mounting block 48 and 
support member 54, provide the contact surface areas between the mounting 
block 48, guide 50 and support member 54. The mounting block 48 is locked 
or wedged in this position, and the force of spring 52, together with the 
frictional forces at moment point 78 and contact point 80, keeps the 
retard shoe 46, together with mounting block 48, from being depressed away 
from the sheet feeding and separating belt 20. At the same time, the 
moment of the sheet feeding and separating belt 20 over the stack of 
sheets 18 causes the outer or uppermost sheets 18 to be pulled toward the 
throat formed by the belt 20 and the upper edge of support member 54 and 
retard shoe 46. The separated sheets 18 are immediately subjected to the 
queuing operation of the throat area and the beveled face 64 of retard 
shoe 46. The queuing process relies on the fact that the coupling forces 
between the belt 20 and the outermost sheets 18 are greater than the 
coupling forces between the other sheets 18. Any underlying sheets 18 
pulled along are stopped by support member 54 and beveled face 64. If 
multisheets 18 tried to pass through between the curved surface 62 of 
retard shoe 46 and belt 20, the mounting block 48 with retard shoe 46 
locks even tighter (the larger the wedge of paper, the greater the locking 
force), and only one sheet 18 is allowed to pass through the paper-feed 
assembly 22. The leading edge of sheet 18 passes through the paper-feed 
assembly 22 and on to the platen and feed-roll assembly (not shown) of the 
printer. The paper-feed assembly 22 stops feeding the sheet 18 at this 
time even though the rear portion of sheet 18 remains between belt 20 and 
retard shoe 46. Because of the locking action of the invention, the force 
of spring 52 can be made very low, which results in a very low force being 
required by the platen (not shown) to pull the sheet from the paper-feed 
assembly 22. As the sheet 18 is being pulled from the paper-feed assembly 
22, one-way clutch 29 (FIG. 1) essentially disconnects stepper drive motor 
24 from the paper-feed assembly 22 to allow sheet 18 to be removed by the 
platen. The paper-feed assembly 22 is then started, and the next sheet is 
fed to the printer. 
As previously noted, the location of the retard shoe 46 relative to the 
roller 40, together with the locking action of the mounting block 48 and 
attached retard shoe 46, is most important. If more than one sheet 18 is 
attempted to be fed past the retard shoe 46, the sheet feeding and 
separating belt 20 is compressed rather than deflected (with respect to 
the retard shoe 46). The force provided by multiple sheets 18 attempting 
to be fed across the retard shoe 46 increases the force of the locking 
mechanism thereby preventing the depression of the retard shoe 46. The net 
result is an infinitely adjustable retard mechanism ensuring single sheet 
feed with minimal force required by the platen to remove the sheet 18 from 
the paper-feed assembly 22. 
Another advantage of the present invention is the self-adjusting feature. 
As the curved surface 62 of the retard shoe 46 wears out, spring 52 
automatically pushes the mounting block 48 further in an upward direction 
such as to maintain contact between the curved surface 62 of the retard 
shoe 46 and the surface of the sheet feeding and separating belt 20. 
Although the present invention has been described with reference to a 
presently preferred embodiment, it will be appreciated by those skilled in 
the art that various modifications, alternatives, variations, etc., may be 
made without departing from the spirit and scope of the invention as 
defined in the appended claims.