Vacuum belt sheet feeder device

In a sheet feeder device of the vacuum belt type, the vacuum belt moves in a pivotal manner between a generally horizontal sheet acquiring position, in which the lower face of the belt confronts the top surface of the top sheet, lying generally flat atop the underlying stack sheet; and a tilted position, in which the belt lifts the leading end of the acquired top sheet away from the underlying sheet, flexes it to insure its separation from the underlying sheet and delivers it endwise to a sheet receiving unit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improved vacuum belt feeder device for 
feeding successive sheets of paper or the like endwise from the top of a 
stack of sheets. More particularly, the invention relates to such a device 
in which the vacuum belt moves in a pivotal manner between a generally 
horizontal sheet acquiring position and a tilted sheet delivery position, 
whereby the belt lifts the leading end of the top sheet away from the 
underlying sheet and also flexes the top sheet to insure its separation 
from the underlying sheet. 
2. Description Relative to the Prior Art 
Many devices have been developed in the past to feed successive sheets 
endwise from the top of a stack of sheets, for example, to deliver the 
sheets one-at-a-time to a printer or copier apparatus. The well known type 
of such device to which the present invention is directed employs an 
endless belt to which the top sheet is adhered by vacuum or suction so 
that orbital movement of the belt moves the sheet endwise. Preferably, the 
belt holds the leading edge of the top sheet away from the next lower 
sheet and it is also advantageous that the top sheet be flexed centrally 
of the stack to further insure the proper separation of that sheet from 
the underlying sheet. 
The following prior art references disclose variation of the general type 
of sheet feeder device described above: 
U.S. Pat. No. 5,090,676 discloses a sheet feeder in which a vacuum belt is 
located above the topmost sheet of a pile of sheets and that sheet is 
moved upwardly into contact with the belt by a jet of air blown against 
the leading edge of the stack. The belt is perforated only in a specific 
region and the vacuum is controlled by the position of the perforated belt 
region relative to a plenum chamber. No means are provided for flexing the 
top sheet except for a sensor device that would appear to be relatively 
ineffective from the standpoint of sheet separation because of its close 
proximity to the trailing end of the sheet. 
U.S. Pat. No. 4,643,413 discloses a sheet feeder having a belt assembly 
comprising a plurality of spaced parallel belts located above a stack of 
paperboard sheets, with continuously evacuated suction chambers 
confronting the top sheet between the belts. The belt assembly is movable 
parallel to itself between lowered and raised positions. When the belt 
assembly is raised, it lifts the top sheet from the stack and the belt is 
then driven to move that sheet endwise into a nip between a pair of 
conveyor rolls. However, the sheet being transported is not flexed to 
insure its separation from the underlying sheet. 
U.S. Pat. No. 3,847,383 discloses a sheet feeder in which a belt assembly 
with a plurality of perforated vacuum belts is mounted with the belts 
permanently in sloped relation to the uppermost sheet in the sheet stack. 
Considerable air flow is therefore required to provide enough vacuum to 
lift and flex the top sheet into contact with the belts, which is 
cyclically prevented by a movable finger. The flexure region of the top 
sheet is not established by the vacuum belts, but, rather, by a buffer 
plate that is located adjacent the rearward or trailing belt rollers or 
idlers. 
U.S. Pat. No. 3,193,282 shows a device for feeding sheets off the bottom of 
a stack of sheets by means of a vacuum belt that shifts pivotally about 
the axis of one of the belt support rollers. However, the shifting of the 
belt does not move the engaged sheet away from the adjacent stack, but 
moves the belt from an operative position to a position beyond contact 
with the sheet with which it was engaged. 
U.S. Pat. No. 3,787,044 discloses a device for feeding sheets off the top 
of a stack, wherein a suction roller is lowered into contact with the top 
sheet and is then raised and rotated to advance the sheet endwise. A 
spring finger tends to establish a flexure region in the sheet being 
advanced. The covering and uncovering of the suction openings in the 
roller controls the up-and-down and rotational movements of the roller. 
SUMMARY OF THE INVENTION 
The present invention provides a novel improved sheet feeder device of the 
vacuum belt type in which the vacuum belt moves in a pivotal manner 
between a generally horizontal sheet acquiring position in which the lower 
face of the belt confronts the top surface of the top sheet and a tilted 
position in which the belt lifts the leading end of the acquired top sheet 
away from the underlying sheet, flexes it to insure its separation from 
the underlying sheet and delivers it endwise to a sheet receiving unit. 
In addition to being simple, reliable and relatively inexpensive, the novel 
sheet feeder device according to the present invention has the following 
specific advantages; 
1. The vacuum belt moves to the top sheet, resulting in positive pickup 
with a relatively low flow rate, which allows the use of a relatively 
small vacuum pump or the like and eliminates the need to turn the vacuum 
on and off. This low flow rate also allows the feeder to be quieter, and 
to use less power. 
2. No jets of air are used to separate the sheets, which also reduces noise 
and power consumption. 
3. No vacuum valve is required, thus providing a cost saving and a gain in 
reliability. 
4. The feeding motion is very simple and is not critical, thereby likewise 
resulting in cost savings and reliability improvement. 
5. The portion of the belt that flexes the sheet moves in the same 
direction and at the same speed as the sheet while the latter is being 
delivered, and therefore, does not tend to frictionally retard the sheet 
delivery. 
Various means for practicing the invention and other advantages and novel 
features thereof will be apparent from the following detailed description 
of illustrative preferred embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As best shown in FIG. 1, the first preferred embodiment of the invention 
comprises a frame 10 that includes front and rear angel corner guides 12 
and 14 for a stack of sheets 16 lying on a platen 18, the top or uppermost 
sheet being designated by numeral 20. The platen, in turn, can be raised 
and lowered by an elevator mechanism, depicted as a screw jack type of 
device 22, driven by a reversible electric motor 24. A bracket 26 is 
mounted to cross bar 28 of frame 10 above the stack of sheets and carries 
a vertically adjustable sheet sensor switch 30 that controls motor 24 to 
maintain the top of the stack at a predetermined level, as is well known 
in the art. 
The vacuum belt feeder unit 32 comprises a support plate 34 with depending 
ears 36 that are provided with bushings or bearings, not shown, that 
rotatably support the center shafts 38 and 40 of the respective; leading 
and trailing belt supporting rollers 42 and 44. The leading roller 42 is 
adapted to be driven by a gear reduction electric motor 46 mounted to 
plate 34 and connected to roller 42 by a gear belt or the like, not shown, 
which is enclosed in a housing 48. An endless flexible belt 50, provided 
with a pattern of perforations 52, is tensioned around rollers 42 and 44, 
with its inner lower surface 54 in contact with the open lower face of 
vacuum box 56. The vacuum box, in turn, is mounted to plate 34 by ears 58 
and is connected to a vacuum pump or the like, not shown, by a flexible 
hose 60. 
A pair of support arms 62 extend from cross bar 28 of frame 10 and straddle 
the trailing end of the belt unit. The center shaft 40 of the trailing 
roller 44 is received in arm bushings 64, thereby supporting the belt unit 
for pivotal movement about the axis of shaft 40. A bracket 66 projects 
upwardly from support plate 34 and is connected to the piston rod 68 of an 
air cylinder 70 or the like, which is similarly connected to a bracket 72 
attached to cross bar 28. By energizing air cylinder 70, by means of 
flexible air lines 74, the belt unit can by moved between its depicted 
generally horizontal position, in which the lower belt face is in close 
confronting relation to top sheet 20 of stack 16, as shown in FIGS. 1 and 
2b, and a tilted position in which the leading roller is raised above the 
stack, as shown in FIGS. 2a and 2c. Either the air cylinder itself or 
other appropriate stop means, not shown, can be used to establish the two 
extreme positions of the belt unit. 
Below the leading roller 42 of belt unit 32, an idler roller 76 is 
rotatably carried by a yoke member 78 pivoted to longitudinal bars 80 of 
frame 10 by studs 82. Springs 84, connected to extension arms 86 of yoke 
78 and to frame 10 bias the idler roller upwardly toward leading belt 
roller 42. 
FIG. 2a shows the feeder unit 32 and the idler roller 76 in the respective 
positions that they assume after a sheet has been delivered to a sheet 
receiving device depicted by guide members 88 and 90 and drive rollers 92 
and 94. To feed the next sheet, the belt unit and the idler roll are moved 
by air cylinder 70 to the position shown in FIGS. 1 and 2b, whereby the 
leading end of the top sheet 20 is acquired, i.e., is adhered to the lower 
face of the vacuum belt. After the the sheet is acquired, cylinder 70 
moves unit 32 to the position shown in FIG. 2c, and motor 46 is energized 
to drive roller 42 clockwise, as shown by arrow 96 in FIG. 2c. 
Accordingly, belt 50 raises the leading edge of the top sheet is above the 
upper sheet stop ends 98 of the front angle corner guides 12 of frame 10; 
and feeds the leading end of the sheet into the nip between the belt and 
idler roll 76, which helps guide the end of the sheet between guide 
members 88 and 90 and to drive rollers 92 and 94. At the same time, the 
region of the belt adjacent the trailing roller flexes the portion of the 
top sheet near the center of the stack to ensure the separation of the top 
sheet from the underlying sheet. It should be noted that, if the top sheet 
were to be flexed upwardly by its engagement with a stationary member, 
e.g. as in the device shown in the previously mentioned '383 patent, 
friction between that member and the sheet would tend to resist endwise 
movement of the latter. However, this is not the case with the subject 
device, because the sheet being delivered is flexed by the vacuum belt, 
which moves in the same direction and at the same speed as the sheet 
itself. 
After the top sheet has been delivered beyond engagement with the feeder 
unit, the latter is again moved by cylinder 70 from the position shown in 
FIG. 2a to the position shown in FIGS. 1 and 2b, whereby the vacuum belt 
acquires the next available sheet. 
As previously mentioned, because the lower face of the vacuum belt is in 
contact with or very close to the top sheet when the belt unit is in the 
position shown in FIGS. 1 and 2b, relatively little vacuum or suction is 
needed to insure that the belt will acquire the top sheet. Accordingly, 
the vacuum can remain turned on even when the belt is in the tilted 
position with no sheet covering its vacuum ports, without wasting 
excessive energy or creating excessive noise. 
The embodiment of the invention shown in FIGS. 3a and 3b is basically 
identical to the one described above, except that the shaft or stud member 
100 that define the pivot axis of feeder unit 32a are located somewhat 
rearwardly of the axis of the trailing roller shaft 40a. Consequently, 
when the vacuum belt unit 32a is moved to the position shown in FIG. 3b, 
the leading roller 42a and the idler roller 76a are raised to align the 
leading end of the sheet 20a with guide members 88 and 90; and the 
trailing roller 44a also moves slightly upwardly, but by a relatively much 
smaller amount, to insure that the top sheet is not pressed downwardly 
against the underlying sheet by the trailing roller portion of the belt, 
which might otherwise retard its endwise movement. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.