Paper sheet feeding apparatus

Disclosed is a sheet feeder device including means for supporting a generally vertical stack of sheets. The supporting means include endless belts having an upper belt run position to extend across the bottom of the stack of sheets. A stationary gate forming member is provided which is positioned above the upper run of the belts and adjacent the forward side of the stack to define a nip which forms a gap between the gate forming member and the upper run for permitting the lowermost sheet of the stack to pass forwardly from the stack through the nip. The gate forming member is a cylindrical roll defining a central axis and an outer peripheral surface which is concentric to the central axis. The roll has a groove extending axially along the length thereof. An elastomeric bar is disposed in the groove, and the bar has a coefficient of friction which is higher than that of the material of the roll. Also, the bar is sized so as to extend radially beyond the peripheral surface. This portion of the bar includes a rearwardly facing edge surface which extends generally along a tangent to the outer peripheral surface of the roll. In operation, the lowermost sheet is fed by the endless belts through the nip without engaging the bar and without significant frictional resistance, while the sheet immediately above the lowermost sheet engages the bar and is retarded in its advance by its engagement with the material of the bar.

FIELD OF THE INVENTION 
This invention generally relates to paper feeding apparatus and, more 
particularly, to an apparatus for serially feeding flat sheets of paper 
from the bottom of a vertical stack of such sheets and so on to permit 
subsequent processing of each individual sheet. 
BACKGROUND OF THE INVENTION 
Generally, sheet feeding devices capable of high speed feeding are 
relatively complicated, and require a large number of complex and 
interrelated moving parts which are subject to wearing out and failure. 
Most known sheet feeders cannot dispense sheets in a shingled manner, but 
rather, only one sheet at a time. The ability to shingle sheets would 
greatly increase the efficiency of any feeder device, however, most feeder 
devices lack this ability. Also, most friction feed devices have problems 
feeding coated and slick stacks. 
Prior sheet feeder devices use suction cups to engage the bottom of the 
sheet being fed. The suction cups then pull the sheet downward and a 
separator member holds the sheet downward by inserting itself between the 
stack of sheets and the suctioned sheet. Then, a gripper arm member pulls 
the suctioned piece out and drops the sheet onto a conveyor belt for 
individual processing. The use of the suction cup presents numerous 
problems for different applications. For example, if the sheet being fed 
is a folded sheet of paper, the suction cup can adhere only to the lower 
portion of the folded paper. Consequently, the separator member does not 
separate between two separate sheets in the stack but rather between 
different folds of the same sheet. 
Another problem with the suction cup method is that it is unable to 
adequately perform when the sheets are made of a stiff material rather 
than a flexible material since the suction is not strong enough to bend 
the sheet. 
Yet another problem with prior sheet feeder devices is the wearing out of 
parts of the device. In devices with a stationary top roller, this top 
roller often wore out and was expensive and inconvenient to replace. 
Still another problem with earlier sheet feeders is the separation of 
sheets having a static electrical charge. These sheets tend to resist 
separation resulting in multiple sheets per package. 
An additional problem with prior devices includes the inability to use tall 
stacks of sheets because of the resulting increase in pressure upon sheets 
at the bottom of the stack. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide for a reliable and 
efficient sheet feeding apparatus of the described type. 
Another object of the present invention is to provide a sheet feeding 
apparatus capable of handling different types and sizes of paper sheets, 
including coated and slick sheets. 
It is yet another object of the present invention to provide a sheet 
feeding apparatus which can shingle feed the sheets. 
Still another object of the present invention is to provide a sheet feeding 
apparatus which can efficiently separate sheets bearing a static 
electrical charge. 
Yet another object of the invention is to provide a sheet feeding apparatus 
which allows for large sheet stacks. 
These and other objects and advantages of the present invention are 
achieved by the provision of an apparatus which comprises means for 
supporting a generally vertical stack of sheets so that the stack defines 
a forward side composed of aligned forward edges of the sheets and a 
bottom. The supporting means include endless belt means and means for 
mounting the endless belt means so as to have an upper belt run positioned 
to extend across the bottom of the stack of sheets. The apparatus also 
includes driving means for rotating the endless belt means so that the 
upper run moves in the forward direction. A stationary gate forming member 
is provided which is positioned above the upper run of the belt means and 
adjacent the forward side of the stack thereby defining a nip which forms 
a gap between the gate forming member and the upper run for permitting the 
lowermost sheet of the stack to pass forwardly from the stack through the 
nip. 
The gate forming member is preferably a cylindrical roll defining a central 
axis and an outer peripheral surface which is concentric to the central 
axis. The roll has a groove extending along the length thereof, and the 
groove is disposed so as to generally oppose the nip. The cylindrical roll 
also has a bar disposed in the groove. The bar is of a material having a 
higher coefficient of friction than the material of the cylinder. The bar 
is preferably of a trapezoid shape and one end portion of the bar extends 
beyond the outer peripheral surface of the cylinder. The surface portion 
extended beyond the roll surface includes a rearwardly facing and 
generally planar edge surface which extends generally along a tangent to 
the outer peripheral surface. 
In one preferred mode of operation, the gap formed between the bar and the 
upper rim of the belt means at the nip is adjusted to allow the lowermost 
sheet to freely pass therethrough, and so that the sheet above the 
lowermost sheet frictionally engages the rearwardly facing edge surface of 
the bar at the nip and is retarded thereby. When the lowermost sheet has 
been fed forwardly a sufficient distance to permit the overlying sheet to 
contact the endless belt means, the overlying sheet is then driven 
forwardly into the nip to form a tight fit, and which in turn causes the 
sheets to be shingled as they are fed from the stack. 
The sheet feeder device of the present invention may also include one or 
more guide means for ensuring that the sheet being fed is guided to its 
correct position on a conveyor belt or the like. The device may also 
include a photocell for sensing when a sheet is not in the process of 
being fed and then signaling the drive means to start the belt running so 
as to feed additional sheets.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring more particularly to the drawings, an apparatus for serially 
feeding sheets of paper from a bottom of a generally vertically stack of 
such sheets, and which embodies the features of the present invention, is 
indicated generally at 10. The apparatus 10 is shown in use as a part of a 
sheet feeding system, and wherein the sheets S are fed laterally from the 
bottom of the stack onto a moving conveyor belt B, and so that the sheets 
may be subsequently collated with other sheets, or placed in mailing 
envelopes, in a conventional manner. 
The apparatus 10 comprises a rigid frame 12 which includes a base plate 14, 
a pair of upright side plates 16 which are joined to the base plate, and a 
number of transverse rods 18 extending between and interconnecting the 
side plates. The transverse rods 18A and 18B are mounted by means of 
bearings 17 to the side walls, note FIG. 2, so as to permit the free 
rotation thereof. The remaining transverse rods are fixedly mounted to the 
side walls. Also, the frame includes a rear cover plate 20 which extends 
between the side plates 16 and is connected thereto at the rear portion of 
the frame. 
The apparatus 10 further comprises means for supporting a generally 
vertical stack of rectangular sheets S of paper. As best seen in FIG. 3, 
the supported stack defines a forward side 22 composed of aligned forward 
edges of the sheets, as well as the opposite rear side 24 composed of the 
aligned rearward edges of the sheets. The forward side of the stack is 
supported in the forward direction by a generally vertically extending 
front support plate 26. The front support plate includes in-turned 
opposite sides 25, which are fixedly secured to the frame by transverse 
rods 27. The upper portion of the support plate includes a generally 
horizontal mounting bracket 23 having a forwardly extending slot 23a for 
the purposes described below 
The means for supporting the vertical stack of paper sheets also includes a 
pair of vertical rods 28 which support respective opposite ends of the 
stack, and the rods are each mounted to the frame by an arm 29 which is 
fixed to the associated vertical rod, and which is coupled to a transverse 
rod 27 by an opening which receives the transverse rod, and a threaded 
member, so as to permit the separation of the rods 28 to be laterally 
adjusted. Thus the rods are able to accommodate stacks of sheets of 
different length therebetween. 
The stack supporting means further includes endless belt means, and which 
comprises, in the illustrated embodiment, three endless belts 30, and a 
pair of aligned support rolls 31 (FIG. 4) mounted on respective ones of 
said support shafts 18A, 18B for mounting each of said endless belts. A 
plurality of drive rolls 33 are mounted on each of said support shafts 
18A, 18B, with one of said drive rolls being positioned on each shaft 
between adjacent endless belts. The diameter of the support rolls 31 is 
less than the diameter of the drive rolls 33 so that said drive rolls have 
an outer surface which is substantially coextensive with the outer surface 
of said endless belts. The support rolls 31 are positioned such that the 
three belts 30 define coplanar upper runs which extend across the bottom 
of the stack. The belts 30 bridge the space between the drive rollers 33, 
and the belts 30 and drive rollers 33 serve to convey the sheets forwardly 
to the nip area in the manner further described below. 
The stack supporting means also includes a rear support member 34 which is 
positioned above the upper runs of the three belts and below the rear side 
of the stack of sheets. The rear support member includes a bracket 36 
which is releasably connected to the rear cover plate 20 by means of a 
threaded member 37 which extends through a slot 38 in the bracket and 
which threadedly engages a selected one of three threaded openings 39 in 
the rear cover plate. The bracket also includes four forwardly extending 
fingers 40 which underlie the rear side of the stack of sheets. The 
fingers each have an inclined forward edge as best seen in FIGS. 3 and 4, 
so as to lift the rear side of the stack upwardly from the upper run of 
the three belts. The lateral position of the bracket and the fingers is 
thereby adjustable so as to permit accommodation of sheets of differing 
widths. 
The three belts 30 and drive rollers 33 are rotated by a drive system 42 so 
that the upper runs move in a right to left (or forward) direction as seen 
for example in FIG. 4. This drive system includes an electric motor M 
which is mounted to the frame of the apparatus beneath the rear cover 
plate, and which includes an output drive pulley 43. The drive system 
further includes drive pulleys 44 fixedly mounted on each of the two 
transverse rods 18A and 18B, and an endless drive belt 46 entrained about 
the three drive pulleys. Also, a follower pulley 48 is provided which 
engages the belt at a location between the pulleys 43 and 44 to ensure 
proper and firm engagement therewith. 
The apparatus 10 further includes a stationary gate forming member 50 
positioned above the upper runs of the three belts, and adjacent the 
forward side of the stack of sheets, and so as to define a nip 52 between 
the gate forming member 50 and the upper runs of the belts 30 and the 
forward drive rollers 33 on the rod 18A. In the illustrated embodiment, 
the gate forming member comprises a generally cylindrical roll 51 defining 
a central axis 54 and an outer peripheral surface 56 which is concentric 
to the central axis. Also, the roll 51 has a groove 58 extending axially 
along the length thereof and which is positioned so as to generally oppose 
the nip. The groove 58 is of generally rectangular cross-section, and as 
best seen in FIG. 5, it includes opposing generally radially directed side 
walls, and a transverse bottom wall. 
The roll 51 has a bar 62 disposed in the groove 58. The bar 62 has a 
generally trapezoidal shape in cross-section, so as to define parallel 
side edges 62a and 62b, and oppositely inclined bottom and upper edges 62c 
and 62d respectively. The portion of the bar which includes the bottom 
edge 62c extends beyond the peripheral surface 56 at the nip, and such 
that the bottom edge 62c defines a rearwardly facing, generally planar 
edge surface which extends generally along a tangent to the outer 
peripheral surface 56. Also, the lowermost point of the edge surface 62c 
is positioned generally on a line which extends between the axis 54 of the 
roll 51 and the axis of the rod 18A, note FIG. 5. The bar is sized so that 
the bar's two side edges 62a, 62b are pressed into engagement with the 
opposing side walls of groove 58 and so as to permit the removal and 
replacement thereof so that the upper edge 62d extends from the groove 58 
and defines the rearwardly facing edge surface. This feature is 
advantageous in that it permits the bar to be repositioned to expose the 
edge 62d should the original edge 62c become worn in use. 
The bar 62 is composed of a material having a higher coefficient of 
friction than that of the material of the roll. 
In a preferred embodiment, the roll is formed of an acetal or metallic 
material having a coefficient of friction of about 0.15-0.35 and the bar 
is formed of an elastomeric material having a coefficient of friction of 
about 0.5-0.7. As those skilled in the art are aware, other materials for 
the roll and bar may also be used. This embodiment is especially suited 
for the processing of sheets bearing a static electrical charge or for 
operations where a large stack of sheets is being processed. Here, the 
elastomeric bar 62 provides a large surface to dissipate the sheets' 
charge before feeding, in contrast to the parent application cited above 
in which the rings do not provide such a large surface. For large stacks 
of sheets, the bar provides additional retarding surface to help overcome 
any additional pressure on the lowermost sheets. 
The apparatus includes means for mounting the roll 51 so as to permit the 
dimension of the nip 52 between the roll and endless belts 30 and rollers 
33 to be adjusted. The ability to adjust the nip allows for the single 
feeding of various thicknesses of sheets. More particularly, the roll 
includes a central portion 66 and a threaded radial opening 68 which 
extends into the central portion on the side opposite the bar, note FIG. 
6. Also, the opposite ends of the roll include coaxial mounting posts 70, 
which are received within respective ones of the vertically extending 
slots 72 in the sides 25 of the front support plate 26. A threaded rod 74 
is threadedly received in the opening 68, and the threaded rod includes an 
upper portion 76 which extends through the slot 23a in the mounting 
bracket 23. This upper end portion is formed with an internally threaded 
axial bore 78, and a sleeve 80 and a spring 82 coaxially surround the rod 
below the mounting bracket 23, with the sleeve having an upper end which 
engages the underside of the bracket 23. The spring is under compression, 
so as to bias the roll 51 downwardly with respect to the bracket. This 
downward movement is limited by a control knob 84 which has a threaded 
member engaged in the bore 78 at the upper portion of the rod, and an 
outer concentric sleeve 79 for engaging the upper side of the mounting 
bracket. Thus rotation of the control knob tends to raise or lower the 
roll with respect to the bracket, and to thus change the vertical 
dimension of the gap at the nip 52 formed between the roll 51 and the 
endless belts 30 and rollers 33. Also, the spring will be seen to bias the 
roll toward the nip and it permits limited upward movement of the roll 
away from the nip and against the force of the spring. 
The above-described mounting means for the roll 51 also permits the quick 
release and removal of the roll assembly which includes the roll 51, rod 
74, sleeve 80, and control knob 84, to thereby facilitate replacement or 
adjustment of the bar 62 as described above. More particularly, the 
assembly may be released and removed by lifting the roll 51 so that the 
mounting posts 70 are removed from the slots 72 in the sides 25 of the 
plate 26, and then slipped forward from the slot 23a. 
The apparatus further comprises sheet guide means 90 positioned downstream 
of and in registry with the nip for guiding the sheets forwardly after 
advancing through the nip. This sheet guide means, as seen in FIG. 2-4, 
comprises two laterally spaced apart guide roller segments 92 which are 
mounted for rotation about the transverse rod 94, which is disposed 
parallel to the axes of the rods 18A and 18B. The upper portions of the 
guide roller segments are substantially coplanar with the upper run of the 
three endless belts 30, and a transmission is provided for operatively 
connecting the drive motor with the guide roller segments, so that the 
guide roller segments rotate at a peripheral speed corresponding to the 
speed of the three endless belts 30 and rollers 33. This transmission 
comprises a pair of guide belts 96 entrained about each support roll 
segment and the adjacent roller 33 with the guide belts having an upper 
run which is substantially coplanar with the upper runs of the three 
endless belts. 
The sheet guide means 90 further comprises a pair of clamping roller 
segments 97, which are mounted on a support rod 98 which is positioned 
along an axis parallel to the axis of the guide roller segments 92 so that 
the clamping roller segments rest upon the peripheral surface of 
respective ones the guide roller segments. The clamping roller segments 
are freely rotatable, and the rod is supported by means of a pair of lever 
arms 99 which are pivotally mounted on respective posts 70 of the roll 51, 
as best seen in FIG. 1, and so that the clamping roller segments rest from 
their own weight upon the guide roller segments 92. 
To assist in properly delivering the sheets onto the conveyor belt B, at 
least one sheet guiding member 100 is positioned downstream of the nip and 
downstream of the sheet guiding means as seen in FIG. 1. The sheet guiding 
member is fixedly mounted above the conveyor belt, and it includes a 
downwardly inclined surface portion 102 for engaging the leading edge of 
each sheet and guiding the same towards an oscillating gripper 104 of 
conventional design. More particularly, the gripper is programmed to 
oscillate toward the clamping roller segments to engage the leading edge 
of each sheet, and then oscillate rearwardly while engaging the leading 
edge and so as to accurately position the sheet on the conveyor belt B. 
A photocell 110 is mounted on the apparatus to control the operation 
thereof. More particularly, in one possible mode of operation, when no 
sheet is detected by the photocell, the motor is actuated so as to rotate 
the endless belts 30 and drive rollers 33 a controlled distance which is 
calculated to deliver a single sheet through the nip. Concurrently, the 
gripper 104 is oscillated toward the apparatus to catch the leading edge 
of the sheet, and then oscillate rearwardly to its release position. The 
advancing sheet is detected by the photocell 110, which holds the motor 
deactivated until the sheet is moved by the conveyor beyond the site of 
the photocell. The sequence is then repeated to deliver another sheet from 
the stack onto the conveyor belt. 
Alternatively, the illustrated embodiment of the apparatus can be operated 
in a continuous fashion without the photocell or only using the photocell 
as a counter. In this mode, the speed of the drive means 42 and the 
conveyor belt B speed must be coordinated so that sheets fall on the belt 
at desired intervals. 
During the sheet feeding operation, it is preferred that the gap formed at 
the nip 52 be adjusted such that the lowermost sheet of the stack is free 
to pass through the nip 52 without engaging the bar 62 and thus without 
significant frictional resistance, while the sheet immediately above the 
lowermost sheet engages the bar 62 of the roll 51 and is retarded by the 
increased frictional resistance provided by the bar. Thus the sheets above 
the lowermost sheet are held substantially stationary in the stack. Also, 
the rear support member 34 is positioned so as to lift the rear side of 
the stack from the upper run of the three endless belts 30 and rollers 33 
such that the sheets in the stack above the lowermost sheet will only 
contact the upper run after the lowermost sheet has entered the nip. Thus 
the sheets are reliably fed in a serial manner from the bottom of the 
stack and until all of the sheets in the stack have been delivered onto 
the conveyor belt B. 
The apparatus may also be operated to provide for the shingling of the 
sheets being fed. In this regard, it will be understood that the 
peripheral surface on the side of the roll 51 facing the stack is smooth 
so as to offer very little resistance as the sheets form around the 
surface and are guided to the nip 52. The nip is adjusted to allow the 
lowermost sheet to freely pass between the bar 62 and the lower drive belt 
30 and rollers 33. The second sheet which is immediately above the 
lowermost sheet meets the resistance of the bar 62 at the nip and is held 
in place until the lower sheet has fed out enough to allow contact with 
the underlying drive belt system which then drives the second sheet 
forward into a tight fit in the nip. The trailing edge of the lowermost 
sheet passes the nip and the second sheet continues to drive forward, thus 
allowing shingling. This system makes this feeder very tolerant of open 
edge leading products and slick sheets. 
For shingling, the distance of the bar 62 from the drive rollers 33 is 
preferably about one and one-half times the thickness of the paper being 
fed. The bar thus retards the overlying second sheet while having minimum 
contact with the underlying first sheet. 
It will be apparent that the contact between the advancing sheets and the 
elastomeric bar 62 at the nip will in time cause the bar to wear and 
become less effective. One of the advantages of the present invention 
resides in the fact that the bar may be easily removed from the groove 58 
and replaced or may be removed, turned to the opposite side and reused. 
In the drawings and specification, there has been disclosed a preferred 
embodiment of the invention and, although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation, the scope of the invention being set forth in the following 
claims.