Sheet feeding apparatus

A sheet feeding apparatus capable of feeding corrugated cardboard sheet without the need for feed rolls which comprises a support for sheet having a feed end and a delivery end. The support further includes feed elements comprising at least one feed element driven at a variable speed and at least one feed element driven at a constant speed. The variable speed feed element transfers the sheet from the feed end to the constant speed feed element. The constant speed feed element transfers the sheet from the variable speed feed element to the delivery end. The variable speed feed element is driven by a variable speed generating mechanism which generates a motion cycle including a constant speed output segment which is equal to the constant speed of the constant speed feed element. The sheet feeding apparatus provides a smooth continuous, controlled transfer of the sheet from the feed end to the delivery end of the apparatus.

FIELD OF THE INVENTION 
This invention relates to apparatus for feeding paperboard sheets, and 
particularly corrugated paperboard sheets, to sheet-handling apparatus. 
This feeding apparatus can also be used to feed solid fiber or 
non-corrugated sheets. 
RELATED ART 
Paperboard sheets, and particularly corrugated paperboard or cardboard 
sheets, are widely used in a variety of industries. Corrugated paperboard 
typically comprises a laminate of several layers of thin paperboard. The 
internal layer or layers of the paperboard are corrugated, i.e., comprised 
of paperboard which has parallel and alternating grooves therein. While 
these grooves lend strength to the cardboard without adding excess weight, 
they are very susceptible to being crushed when excess force is applied to 
the sheet. 
Corrugated paperboard is manufactured in a paper-making plant and is then 
typically shipped as large flat sheets or "blanks" to box manufacturers 
who use the paperboard sheets to form boxes. The box manufacturer 
typically has machinery for printing desired information on the sheet and 
for forming the sheet into a flattened box ready for shipment to the 
customer, who then purchases the flattened boxes for later assembly and 
packaging of the customers product. 
Sheet feeders are used in these industries where it is desirable to feed 
paperboard sheets to machinery for subsequent treatment thereof. Such 
sheet feeders are commonly used in the box-making industry, at the very 
beginning of the box manufacturing process, to feed corrugated paperboard 
sheets to an entire manufacturing line of machinery, which follows the 
sheet feeder, for treating the sheet. This machinery may comprise a 
variety of known sheet treatment machines for example a rotary die cutter 
or flexo-folder-gluer. 
One common example of a manufacturing line for treating corrugated 
cardboard sheets includes a series of print and impression cylinders which 
provide printed matter on the sheet. These cylinders are commonly followed 
by a slotter which provides cuts in the sheet at which the sheet may be 
later folded for assembly into a box. The slotter may be followed by a 
gluer which provides adhesive on selected areas of the sheet so that when 
the sheet is later assembled into a box, selected areas of the sheet are 
adhered to one another. 
The gluer may be followed by a folder which folds the peripheral ends of 
the sheet along the cuts created by the slotter so that ends of the sheet 
are positioned one on top of the other. Folding the sheet causes the areas 
of the sheet having adhesive thereon to be in register with one another. 
The folder may then stack the folded sheets on top of each other until a 
predetermined amount have been stacked. The stack of folded sheets is then 
bundled and shipped to the customer. Typically, the customer will assemble 
the folded sheet into a box, fill the box with its product and then sell 
the product contained in the box to the ultimate end user of the product. 
Because the sheet feeder is but a small part at the very beginning of a 
much larger manufacturing line, it is essential that the sheet feeder 
transfer the sheet to the manufacturing line in precise sequence and at 
the same speed that the manufacturing line is processing the sheets. That 
is, each sheet must reach the manufacturing line at exactly the same point 
in the machine cycle of that line. When each sheet is not fed at exactly 
the same point in the cycle, the result is commonly refered to as 
misfeeding. Misfeeding causes the sheets to be treated in a non-uniform 
manner by the machinery. Sheets which are not treated uniformly end up as 
inferior "seconds" which may not be acceptable to the customer. Such 
seconds often have to be sold at a loss to the manufacturer. Losses to the 
manufacturer may ultimately be passed on to the customer in the form of 
higher prices for the treated sheets. 
Sheet feeders of conventional design for timely feeding paperboard sheets 
to sheet-handling apparatus use vacuum assisted feeding elements such as 
suction cups, belts or wheels to transfer the sheet from a stack of sheets 
to a pair of heavy weight feed rolls or cylinders. The sheet is 
transferred by the feed rolls to the subsequent sheet-handling apparatus 
of the manufacturing line. 
The feed rolls are arranged one on top of the other and are spaced slightly 
apart from each other. Typically, the feed rolls are spaced apart at a 
distance which is slightly smaller than the thickness of the sheet being 
fed. The small distance between the feed rolls through which the sheet 
passes is commonly refereed to in the art as the "nip". One feed roll is 
rotated in a clockwise direction while the other feed roll is rotated in a 
counter-clockwise direction. When the sheet reaches the nip it is grabbed 
between the oppositely rotating feed rolls. Because the nip is typically 
smaller than the thickness of the sheet, if the sheet is corrugated, the 
corrugations of the sheet may be crushed as it is grabbed by the feed 
rolls. 
Examples of conventional sheet feeders which include feed rolls are 
disclosed in U.S. Pat. No. 4,494,745 to Ward Sr. et al., and U.S. Pat. No. 
4,681,311 to Sardella. These conventional designs generate an intense 
vacuum force from underneath the sheet which pulls the sheet against the 
feed elements. In order for the feed rolls to grip the sheet and pull it 
from the control of the vacuum assisted feed elements, the nip between the 
feed rolls must be relatively small. Once the sheet has been gripped by 
the feed rolls it is then fed to the subsequent sheet-handling machinery. 
It is an essential part of this conventional design to make the nip of the 
feed rolls relatively small to ensure that the sheet is under the control 
of the feed rolls before it is transferred to the subsequent machinery. If 
the sheet is not under control of the feed rolls the sheet may not be fed 
to the machinery in precise sequence. Therefore, it is common with these 
conventional designs to make the distance between the feed rolls so small 
that the corrugated layer of the sheet is crushed by the feed rolls as it 
is gripped by them. 
As discussed above, crushing the corrugations is highly undesirable because 
the structural strength, integrity and appearance of the ultimate 
corrugated end product is considerably reduced. Inferior end products 
cause increased waste and excess cost to the manufacturer and ultimately 
the consumer, as well as cause consumer dissatisfaction. 
Several sheet feeders have attempted to overcome the crushing problems 
associated with feed rolls. Although such feeders may avoid the problems 
associated with feed rolls, they suffer from their own problems and 
deficiencies. For example, these prior sheet feeders fail to provide a 
smooth, continuous, controlled transfer of the sheet. 
One example of such prior sheet feeders is described in U.S. Pat. No. 
4,363,478 to Tsukasaki. This feeder employs a kicker element which is 
reciprocated to engage the trailing edge of the bottommost sheet from a 
stack of sheets. The kicker element pushes the sheet onto a vacuum 
assisted conveyor belt which replaces conventional feed rolls. The speed 
at which the kicker advances toward the sheet is equal to the 
circumferential speed of the conveyor belt. Because the kicker element 
abruptly pushes the sheet onto the conveyor belt, this sheet feeder does 
not provide a smooth and continuous controlled transfer the sheet. 
Furthermore, this type of sheet feeder has been known to jam or misfeed 
if, among other reasons, a sheet is warped or the edge of the sheet is 
crushed or ragged. Such jams may cause significant production delays which 
increases manufacturing costs. As discussed previously, misfeeding is 
known to produce an inferior, non-uniform end product which is 
unacceptable to consumers. 
Another example of a prior art sheet feeder which has attempted to overcome 
the crushing problems associated with feed rolls is described in U.S. Pat. 
No. 4,236,708 to Matsuo. The sheet feeder of this patent employs two sets 
of vacuum assisted conveyor belts to feed corrugated cardboard sheets to a 
die cutter. Each set of belts is arranged along the sheet feeder in a 
longitudinal direction to the direction of travel of the sheet. The first 
set of belts advances the sheet from rest up to line speed of the 
subsequent sheet handling machinery. The first set of belts then feeds the 
sheet to the second set of belts which is traveling at line speed. 
The Matsuo patent, although avoiding the problems associated with feed 
rolls, has several disadvantages. First, the speed between the two sets of 
belts is matched for only an instant during the period when the sheet is 
fed from the first set of belts to the second. Therefore, for some finite 
time, the sheet is under the control of at least two belts which are not 
traveling at a matched speed. This unequal rate of speed between the two 
belts does not produce a smooth, continuous transfer of the sheet. 
Moreover, an unequal rate of speed can cause the belts to lose control of 
the sheet which would not be acceptable for heavyweight corrugated sheets. 
Lack of a smooth transfer and loss of control of the sheet by the feed 
belts can cause the sheet to be fed out of sequence to the subsequent 
sheet handling machinery. Feeding out of sequence or misfeeding, as 
discussed above, is known to result in an inferior, non-uniform end 
product. 
Furthermore, the vacuum area of the Matsuo sheet feeder is not constant 
during the time when the sheet is in transition between the belt sets. As 
a result, the sheet may not remain in contact with the belts during the 
transfer. Naturally, this too can cause a loss of control of the sheet 
which can cause the sheet to be fed out of sequence to the subsequent 
sheet handling machinery, resulting in an inferior, non-uniform end 
product. 
In general, the Matsuo sheet feeder can produce a discrete, abrupt transfer 
of the sheet from the first set of belts to the second set, which may 
result in the sheet being essentially "thrown" from one feeding element to 
the next. This throwing motion may ultimately result in a poor quality end 
product, since once the sheet has been uncontrollably fed to the second 
set of belts, it is likely to be misfed to the subsequent machinery as 
well. 
Therefore, the need exists for a sheet-feeding apparatus that eliminates 
the crushing problems associated with feed rolls and provides a smooth, 
continuous, controlled transfer of a sheet to sheet handling machinery. 
SUMMARY OF THE INVENTION 
The present invention overcomes the problems and deficiencies discussed 
above by providing a sheet-feeding apparatus capable of feeding corrugated 
sheets without the need for feed rolls. The apparatus comprises a support 
for a sheet having a first plurality of feed elements driven at a variable 
speed and second plurality of feed elements driven at a constant speed. 
The feed elements are preferably arranged in transverse rows. The feed 
elements preferably comprise feed wheels. 
The variable speed feed elements are driven by a variable-speed generating 
mechanism. The variable-speed generating mechanism generates a motion 
cycle which preferably comprises an acceleration segment, a constant-speed 
output segment, and a deceleration segment. The constant-speed output 
segment is substantially equal to the constant speed of the constant speed 
feed elements. 
The variable-speed generating mechanism may comprise a driver element and a 
driven element, both having geared portions which intermesh to create the 
constant-speed output segment. The constant-speed output segment of the 
variable-speed generating mechanism may begin before the leading edge of 
the sheet contacts the variable-speed feed elements, and may be maintained 
until the trailing edge of the sheet has contacted the constant-speed feed 
element closest to the variable speed feed elements. When the leading edge 
of the sheet contacts one of the constant-speed feed elements adjacent the 
delivery end of the apparatus, the deceleration segment may begin. The 
deceleration segment may be created by the driver element including a 
roller which is received in a slot of the driven element. 
An output gate may be provided above the variable speed feed elements to 
define a gap for limiting the number of sheets transferred at one time by 
the feed elements to the delivery end. A vacuum chamber may be provided 
adjacent the feed elements for creating a constant vacuum pressure which 
maintains the sheet in contact with the feed elements at all times during 
sheet transfer. The vacuum chamber may include vacuum partitions for 
allowing vacuum pressure to be provided adjacent selected feed elements. 
A clearing mechanism may be provided adjacent the variable speed feed 
elements. The clearing mechanism may comprise a lowering mechanism, an 
actuator, and a clearing cam. Interaction between the clearing cam and 
actuator causes the lowering mechanism to move vertically and selectively 
prevent the sheet from contacting the feed elements. 
The sheet feeding apparatus provides a smooth, continuous controlled 
transfer of a sheet, a corrugated sheet in particular, from one end of the 
feed apparatus to the other. Due to the absence of feed rolls, the sheet 
is fed without crushing the corrugations. The sheet remains under the 
control of a plurality of feed elements traveling at matched speed, which 
allows improved control of the sheet throughout sheet transfer. 
Maintaining the constant speed output segment of the variable speed feed 
elements until the sheet has been transferred to the control of the 
constant speed feed elements provides accurate feeding of the sheet to 
subsequent sheet-handling apparatus. As each successive feed element row 
assumes control of the leading edge of the sheet, a feed element row at 
the trailing edge of the sheet relinquishes control. This provides a 
smooth, continuous controlled transfer of the sheet as it is fed by the 
feeding apparatus. 
These and other features and advantages of the invention will become 
apparent from the following description of a preferred embodiment of the 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings in which similar reference numerals have been 
used to refer to similar elements, and in particular to FIG. 1, the 
present invention comprises a sheet feeder, shown generally by reference 
numeral 10, for feeding a paperboard sheet from a stack of sheets. The 
sheet feeder 10 is designed to transfer an individual sheet to a variety 
of subsequent sheet handling machinery, designated by the dotted outline 
box labeled M. Machinery M may comprise for example: a die cutter; a 
slotter; a folder; a gluer; print and impression cylinders; as well as any 
combination of the same. The machinery M is driven at a continuous speed 
which is hereinafter referred to as the line speed, but does not form a 
part of the present invention. Furthermore, it is not essential to the 
present invention that sheet feeder 10 be as wide as machine M. 
Sheet feeder 10 of the present invention comprises a series of feed wheels 
19, a drive train located in housing 44, a vacuum mechanism located within 
wheel box 34 underneath feed wheels 19, and a clearing mechanism, a 
portion of which is located within wheel box 34, which cooperate to 
smoothly transfer a sheet to machine M. Each of the components will be 
discussed in turn in detail below. 
Feed wheels 19 provide support for a sheet as it is transferred by sheet 
feeder 10, and preferably are comprised of high-friction urethane. 
However, other materials having a high coefficient of friction may be used 
as well. Feed wheels 19 are arranged in wheel box 34. Wheel box 34 has a 
feed end 38, a center portion 40, and a delivery end 42. The sides of 
wheel box 34 are shown generally in FIG. 1 as the operator side 0 and 
drive side D. 
With continuing reference to FIG. 1, a plurality of feed wheels 19 are 
arranged along feed wheel shafts 21, 23, 25, 27, 29, 31 and 33. Shafts 21, 
23, 25, 27, 29, 31 and 33 are arranged in horizontal rows within wheel box 
34 from feed end 38 to delivery end 42. Shafts 21, 23, 25, 27, 29, 31 and 
33 extend across wheel box 34 from operator side 0 to the drive side D and 
are transverse to the direction of travel of a sheet from feed end 38 to 
delivery end 42. Feed wheels 19 are preferably arranged so that they do 
not contact one another. However, it is possible that shafts 21, 23, 25, 
27, 29, 31 and 33 may be positioned so that wheels 19 of adjacent shafts 
are interleaved in order to conserve space by making the distance between 
feed end 38 and delivery end 42 shorter. 
Referring now to FIG. 6, in which feeder 10 is shown just prior to transfer 
of a sheet S from stack SS to machine M, Sheet S is supported by feed 
wheels 19 on shafts 21, 23 and 25. A feed gate 14 is provided above center 
portion 40. Gate 14 is a rigid plate which extends from operator side 0 to 
drive side D of wheel box 34. Gate 14 acts as a front stop by preventing 
stack SS from moving toward delivery end 42. Sheet S has a leading edge L 
and a trailing edge T. A gap 15 is formed between the bottom of gate 14 
and center portion 40. Gap 15 selectively allows only one sheet S at a 
time to pass from stack SS towards delivery end 42, and can be adjusted to 
accommodate for a variety of sheet thicknesses. 
Feed wheels 19 are divided into two sets. The first set (plurality) 
comprises the transverse rows of shafts 21, 23, 25, and 27 in which the 
feed wheels 19 rotate at a variable speed. Shafts 21, 23 and 25 are 
disposed between feed end 38 and gate 14. Shaft 27 is disposed between 
gate 14 and delivery end 42. The second set (plurality) comprises the 
transverse rows of shafts 29, 31, and 33 in which the feed wheels 19 
rotate at a constant speed. Shafts 29, 31 and 33 are disposed between 
shaft 27 and delivery end 42. 
As will become apparent from the discussion below of the operation of sheet 
feeder 10, it is preferred that the constant speed at which feed wheels 19 
of shafts 29, 31 and 33 are driven be equal to the line speed of machine M 
to ensure accurate feeding of sheet S to Machine M and therefore, uniform 
treatment of sheet S. 
While individual feed wheels on shafts have been shown in the drawings, 
sheet feeder 10 could alternately comprise individual belts driven by 
pulleys, or any other known feed element means for transferring paperboard 
sheets. The belts, for example, may be arranged similar to the wheels 
shown in the drawings. That is, there could be seven transverse rows of 
individual belts extending from feed end 38 to delivery end 42 of feeder 
10. Three transverse rows of belts driven at a variable speed may be 
provided between feed end 38 and gate 14. One transverse row of belts 
driven at a variable speed may be provided between gate 14 and delivery 
end 42. Three transverse rows of belts driven at a constant speed may be 
provided between the four belts driven at a variable speed and delivery 
end 42 of feeder 10. 
Furthermore, while four rows of feed wheels 19 rotating at a variable speed 
and three rows of feed wheels 19 rotating at a constant speed have been 
shown in the figures, it is contemplated that sheet feeder 10 could 
comprise more or less than the number of rows shown. In addition, it is 
possible that sheet feeder 10 could employ a single row of feed elements 
rotating at variable speed and a single row of feed elements rotating at 
constant speed. Furthermore, while feed wheels having a continuous surface 
have been shown in the drawings, it is possible that feed wheels having a 
partially relieved surface, as in known in the art, could also be employed 
with the present invention. 
Referring now to FIG. 2, a drive train for rotating feed elements 19 of 
sheet feeder 10 is shown generally at 43. Drive train 43 is disposed 
within housing 45 preferably mounted at drive side D of wheel box 34. 
Drive train 43 comprises a variable-speed drive train shown generally at 
45 and a constant-speed drive train shown generally at 46. 
Variable-speed drive train 45 causes feed wheels 19 on shafts 21, 23, 25 
and 27 to rotate, and comprises a variable-speed drive gear 50 rotating 
counterclockwise, a first variable-speed idler gear 51, and a second 
variable-speed idler gear 52. Both idler gears 51 and 52 are driven by the 
variable-speed drive gear 50. Additionally, variable-speed drive train 45 
comprises variable-speed pinion gears 53, 54, 55, and 56 which are 
provided on feed element shafts 21, 23, 25 and 27 respectively. Gears 53 
and 54 are driven by idler gear 51, while gears 55 and 56 are driven by 
idler gear 52. Rotation of pinion gears 53-56 by variable-speed idler 
gears 51 and 52 causes the variable-speed feed element shafts 21, 23, 25 
and 27 to rotate, thereby causing feed wheels 19 located thereon to 
rotate. Contact between the rotating feed wheels 19 and sheet S causes 
sheet S to be transferred from feed end 38 toward delivery end 42. 
With continued reference to FIG. 2, constant-speed drive train 46 comprises 
a constant-speed drive gear 84 which rotates clockwise, to drive 
constant-speed pinion gears 57 and 58 provided on shafts 29 and 30, 
respectively. Additionally, constant-speed gear train 46 comprises a 
constant-speed idler gear 86 which, driven by gear 58, drives 
constant-speed pinion gear 59 provided on shaft 31. Rotation of 
constant-speed pinion gears 57, 58 and 59 by drive gear 84 and idler gear 
86 causes feed wheels 19 on shafts 29, 31, and 33 to rotate. Contact 
between the rotating feed wheels 19 and sheet S causes sheet S to be 
transferred from the feed wheels 19 of shafts 21, 23, 25 and 27 to 
delivery end 42 of feeder 10. 
Constant-speed drive gear 84 may be driven independently of sheet feeder 
10. However, as discussed above, it is preferable that feed wheels 19 on 
shafts 29, 31 and 33 are driven at the same line speed as machine M. 
Therefore, constant-speed drive gear 84 could be driven by machine M. 
Variable-speed drive gear 50 is driven in the motion cycle shown in FIGS. 3 
and 4. FIGS. 3 and 4 show the relationship between the output velocity or 
line speed of feed elements 19 on shafts 21, 23, 25, and 27 and machine 
rotation of sheet feeder 10. That is, it shows the line speed of the feed 
wheels 19 during the time it takes for sheet feeder 10 to go through one 
complete feed cycle (360.degree.). 
Referring now to FIG. 3, which shows a single feed operation where one 
sheet S is fed per machine cycle, the motion cycle of variable-speed drive 
train 45 is divided into three segments A, B, and C. The first is 
acceleration segment A. During acceleration segment A, the speed of the 
feed wheels 19 on shafts 21, 23, 25, and 27 accelerates from zero velocity 
to 100% velocity, which is equivalent to the line speed of machine M. 
Segment B is the constant-speed output segment. During segment B, feed 
wheels 19 on shafts 21, 23, 25 and 27 are maintained at line speed. 
Segment B continues approximately until lead edge L of sheet S has been 
transferred from feed elements 19 of shaft 25 toward delivery end 42 and 
has contacted the feed wheels 19 of shaft 33. At this point in the feed 
cycle, sheet S is under the control of feed wheels 19 on shafts 29, 31 and 
33. 
The third segment C is a non-critical segment during which the speed of 
feed wheels 19 on shafts 21, 23, 25 and 27 may increase or decrease 
without an effect on sheet S due to a clearing mechanism (FIGS. 6-10). The 
clearing mechanism maintains stack SS out of contact with feed wheels 19 
on shafts 21, 23, 25 and 27 when it is desired that no sheet S be 
transferred from stack SS. The preferred non-critical segment C, shown in 
dotted lines in FIG. 3, is generated by a mechanism which is to be 
discussed in greater detail below. As shown in FIG. 3, the velocity at the 
end of segment C may, if desired, be zero. 
FIG. 4 shows the relationship between output velocity of the feed elements 
19 on shafts 21, 23, 25 and 27 and machine rotation (360.degree.) of sheet 
feeder 10 during a double feed operation when two sheets are fed per 
machine rotation. That is, where the first sheet is fed when the machine 
rotation is at 0.degree. and the second sheet is fed when the machine 
rotation is at 180.degree.. During a double feed operation, the motion 
cycle goes through six segments A', B', C', A', B', and C'. 
Segment A' is an acceleration segment. During segment A', feed wheels 19 on 
shafts 21, 23, 25 and 27 are accelerated from zero velocity to line speed. 
Segment A' is substantially identical to segment A of the single feed 
operation (FIG. 3). Segment B', the constant-speed output segment, is 
substantially identical to segment B of the single feed operation (FIG. 
3). During segment B', feed wheels 19 on shafts 21, 23, 25 and 27 are 
maintained at 100% line speed, preferably until lead edge L of sheet S has 
reached feed wheels 19 on shafts 29, 31 and 33. At this point in the feed 
cycle, sheet S is preferably under the control of feed element 19 on 
shafts 27, 31 and 33. 
The third segment C' is the noncritical segment for the double feed 
operation. Similar to non-critical segment C (FIG. 3), the output velocity 
of feed wheels 19 on shafts 21, 23, 25 and 27 may increase or decrease 
without an effect on stack SS due to the clearing mechanism (FIGS. 6-10) 
which maintains stack SS out of contact with feed wheels 19 on shafts 21, 
23, 25, and 27. Non-critical segment C' extends until 180.degree. of a 
machine rotation, at which point in the feed cycle, a second acceleration 
segment A', identical to the first A' begins, followed by a second 
identical constant-speed output segment B', which is followed by a second 
non-critical segment C'. Both preferred non-critical segments C' are shown 
in dotted lines in FIG. 4. 
A variable-speed generating mechanism which is capable of generating the 
preferred motion cycles shown in FIG. 3 is shown generally at 60 in FIG. 
5. This mechanism is available from Cyclo Index, a division of Leggett & 
Platt, Inc., Carthage, Missouri. Mechanism 60, for performing the single 
feed operation of FIG. 3, is available as Part No. 6410-240-1/2. The 
preferred mechanism (not shown) for performing the double feed operation 
of FIG. 4 is available as part No. 6420-170-1/3. 
Variable-speed generating mechanism 60 comprises a driver element 61 and a 
driven element 66 which cooperate to produce a variable-speed motion 
cycle. Driver element 61 comprises a geared portion 62; an acceleration 
roller 63; a deceleration roller 64; and a circumferential portion 65. 
Driven element 66 comprises two geared portions 67 and 68 each having 
teeth; four slots 70, 71, 72, and 73; and four rollers 74, 75, 76, and 77. 
During segment A (FIG. 3) acceleration roller 63 is disposed within slot 70 
and mechanism 60 functions similar to a conventional Geneva mechanism. As 
driver element 61 is rotated in a clockwise motion (by a constant driving 
force not shown), contact of roller 63 within slot 70 forces driven 
element 66 to rotate in a counterclockwise direction. Rotation of element 
66 causes variable-speed gear train 45 (FIG. 2) to rotate which in turn 
causes variable-speed feed wheels 19 on shafts 21, 23, 25 and 27 to 
rotate. Rotation of feed wheels 19, as discussed above, causes sheet S to 
be transferred through sheet feeder 10. 
FIG. 5 shows mechanism 60 during a portion of the constant-speed output 
segment B (FIG. 3), during which, the teeth of geared portion 62 of driver 
element 61 are intermeshing with the teeth of geared portion 68 of driven 
element 66. As driver element 61 continues to rotate clockwise, the teeth 
of geared portions 62 and 68 intermesh causing driven element 66 to rotate 
counterclockwise. This constant and continuous intermeshing of geared 
portions 62 and 68 causes variable-speed gear train 45 to rotate at a 
constant speed and thereby causes feed wheels 19 on shafts 21, 23, 25 and 
27 to rotate at a constant speed. 
Once the last tooth of each geared portion 62 and 68 have intermeshed, 
deceleration roller 64 on driver element 61 engages slot 77 and the 
deceleration segment begins (dotted line in FIG. 3). As driver 61 
continues to rotate clockwise, the only contact between driver 61 and 
driven element 66 is rollers 76 and 77 which roll along the surface of 
surface 65 of driver 61. Driven element 66 is in a dwell period in which 
it is maintained in a stationary position relative to driver element 61 by 
rollers 74 and 75. As shown in FIG. 3, deceleration of mechanism 60 occurs 
during the non-critical segment C. Although mechanism 60 provides a dwell 
period, it is not critical to the present invention that a dwell period be 
a part of the motion cycle. 
As discussed above, variable-speed generating mechanism 60 shown in FIG. 5 
can be used to rotate the variable-speed drive gear 50 (FIG. 2). While 
this is the preferred mechanism for generating the required motion cycle 
shown in FIG. 3, the present invention may be practiced with a variety of 
other conventional mechanisms which are capable of generating the desired 
variable speed motion cycle. Examples of such alternative variable-speed 
generating mechanisms which are capable of generating the required 
segments A and B include: a conventional indexing mechanism with a 
conventional differential; a conventional Geneva drive with a conventional 
differential; a five-bar dwell mechanism with a conventional differential; 
and a variable-speed motor. 
Furthermore, although driven element 66 of mechanism 60 only achieves 1/2 a 
revolution per one revolution of driver 61, this ratio is not essential to 
the present invention. Alternative mechanisms which for example provide a 
1:1 ratio or integer or fraction thereof would also be acceptable. 
It should be understood that the preferred mechanism for driving the 
variable-speed drive gear 50 in a double feed operation would comprise a 
drive gear having two identical geared portions and rollers. Geared 
portions similar to portion 62 would, however, include fewer teeth than 
portion 62 shown in FIG. 5, and rollers 63 and 64 would be approximately 
90.degree. apart. 
Referring now to FIG. 7, the vacuum mechanism will now be discussed. The 
vacuum mechanism maintains sheet S in constant contact with feed wheels 19 
while sheet S is being transferred from feed end 38 to delivery end 42 of 
sheet feeder 10. 
The vacuum mechanism more particularly comprises a vacuum chamber 94 
located within wheel box 34 underneath feed wheels 19. Vacuum chamber 94 
further includes alternating vacuum partitions 96 and bearing supports 98 
(FIG. 1). Bearing supports 98 include bearing surfaces for supporting 
shafts 21, 23, 25, 27, 29, 31 and 33, and act as vacuum partitions. 
Vacuum chamber 94 is connected at its bottom portion to a fan (not shown) 
which generates a constant negative vacuum pressure shown by arrows V in 
FIG. 7. Vacuum pressure V is applied to the underside of feed wheels 19 as 
they are supported across wheel box 34. Vacuum pressure V pulls sheet S 
against feed wheels 19 as sheet S is transferred along them. When a sheet 
narrower than the width of the wheel box 34, the width being defined by 
the distance between operator side 0 and the drive D side, is fed by sheet 
feeder 10, it is possible to close off vacuum pressure V to selected areas 
of vacuum chamber 94 which are not contacted by sheet S. This is possible 
by providing shut-off means 95 between portions of vacuum chamber 94, 
defined by partitions 96 and supports 98, and the fan. While a damper-like 
sliding plate has been shown in the figures as the preferred shut-off 
means, a valve, for example, would also be satisfactory. 
A baffle 16 is provided above feed elements 19 on shafts 27, 29, 31 and 33 
between gate 14 and delivery end 42. Baffle 16, which may be a horizontal 
flexible plate supported by vertical support 17, extends from operator 
side 0 to drive side D of sheet feeder 10. Baffle 16 is fixed at a height 
just above the height of sheet S as it passes thereunder. Baffle 16 serves 
to minimize air leakage into vacuum chamber 94 which might otherwise 
reduce the efficiency of the vacuum mechanism. 
Although a single vacuum chamber 94 has been shown extending from feed end 
38 to delivery end 42, individual vacuum chambers and fans could be 
provided for each row of feed wheels or the alternative feed elements 
discussed above. This would increase efficiency of the vacuum mechanism 
because any leakages of air associated with one chamber would not effect 
any of the other chambers. Furthermore, it is possible to provide one 
vacuum chamber for the rows of shafts 21, 23, 25 and 27 and a second 
vacuum chamber for the rows of shafts 29, 31, and 33; or to provide one 
vacuum chamber for the rows of shafts 21, 23 and 25 and a second vacuum 
chamber for the rows of shafts 27, 29, 31 and 33. Moreover, any 
alternative arrangement of vacuum chambers and fans which will achieve the 
desired result of minimizing air leakage may also be employed with the 
present invention. 
FIGS. 6-10 show a clearing mechanism which is employed with sheet feeder 10 
of the present invention. The clearing mechanism selectively prevents 
sheet S from contacting feed wheels 19 on shafts 21, 23, 25 and 27. The 
clearing mechanism comprises a lowering mechanism shown generally at 102, 
an actuator shown generally at 103, and a clearing cam 126. Lowering 
mechanism 102 is moved vertically by the interaction of actuator 103 and 
clearing cam 126, as will be discussed below. 
One lowering mechanism 102 is shown provided adjacent each feed wheels 19 
on each of shafts 21, 23, 25 and 27. Each lowering mechanism 102 includes 
a pad 104 which is provided on each side of each feed wheel 19. Pad 104 is 
disposed on the top of a block 106. A cylindrical clearing pad rod 108 is 
provided at the bottom of block 106 opposite pad 104. A linear bearing 
110, disposed within wheel box 34, maintains the vertical movement of rod 
108 and therefore of lowering mechanism 102. The end of rod 108, opposite 
block 106, is hemispherical. 
Actuator 103 comprises a push lever 114 (FIG. 7), actuating lever 122 and 
cam follower 118 (FIG. 8). One end of push lever 114 is in contact with 
the hemispherical end of rod 108. The other end of push lever 114 is 
rigidly fixed to a clearing shaft 116. Each clearing shaft 116 extends 
from housing 136 on operator side 0 to drive side D of feeder 10. Cam 
follower 118 is rotatably attached to actuating lever 122 by a cam 
follower pin 120. 
Referring now to FIGS. 8-10, clearing cams 126 are provided in housing 130. 
One cam 126 is provided for each row of feed wheels 19 on shafts 21, 23, 
25 and 27. Cams 126 are disposed on cam shaft 127 which rotates at a 
constant angular speed preferably equal to the constant angular speed of 
driver 61 (FIG. 5). If an alternative variable-speed mechanism is selected 
to drive the variable-speed feed elements 19 of shafts 21, 23, 25 and 27, 
it is preferred that cams 126 be at a 1:1 ratio with the output element of 
the mechanism. 
Each cam 126 has a profile including a relieved surface 125 and a 
non-relieved surface 129 (FIG. 8). Each cam follower 118 follows the 
profile of its associated clearing cam 126. A compression spring 117 is 
provided on rod 108 to provide a downward force on clearing shaft 116 to 
help ensure constant contact between each cam follower 118 and its 
associated clearing cam 126. 
When cam followers 118 are in contact with the relieved surfaces 125 of 
clearing cam 126, lowering mechanisms 102 are in the down position during 
which time the bottommost sheets of stack SS is in contact with feed 
wheels 19 on shafts 21, 23, and 25 (FIG. 7). As cams 126 rotate and cams 
follower 118 contacts the non-relieved surface 129 of cams 126, shafts 116 
pivots causing actuator 114 to pivot thereby moving rod 108 and therefore 
lowering mechanisms 102 vertically into the up position. During the up 
position, pads 104 are at a position higher than the top surface of feed 
wheels 19 on shafts 21, 23, 25 and 27, thereby preventing the bottommost 
sheet in stack SS from contacting feed wheels 19. 
Referring now to FIGS. 9 and 10, actuators 103 and clearing cams 126 are 
disposed in clearing mechanism housing 130. Housing 130 preferably 
comprises the sheet feeder inner frame 132, a bottom plate 134, an end 
plate 136, and a top plate 138. Inner frame 132 provides a bearing surface 
133 which supports clearing shafts 116, and a bearing surface 135 (shown 
in phantom in FIG. 9)which supports clearing cam shaft 127. A drive means 
DM for driving shaft 127 is shown in dotted outline in FIG. 9. 
Alternatively, shaft 127 may extend to drive side D of feeder 10 and may 
be driven by drive train 43. The end plate 136 of housing 103 also 
provides a bearing support 137 (shown in phantom) for clearing cam shaft 
127. 
Additionally, end plate 136 provides apertures 140 for supporting 
interrupter mechanisms shown generally at 128. One interrupter 128 is 
provided for each actuator 122. Each interrupter 128 acts as a latch by 
maintaining the clearing mechanism in the up position. Each interrupter 
128 preferably comprises a double-acting air cylinder 142 which cooperates 
with an actuating lever 122. Air cylinder 142 includes an 
operator-selectable switch (not shown) which causes pressurized air 
supplied to air cylinder 142 to extend the tapered end 144 of air cylinder 
142. When tapered end 144 is extended, it is received within a tapered 
hole 124 on actuating lever 122 (FIG. 8). Tapered end 144 and tapered hole 
124 are in alignment only when roller 118 is on surface 129 of cam 126; 
therefore, interrupter 128 should only be activated when roller 118 is on 
raised surface 129 of cams 126. The presence of tapered end 144 within 
tapered hole 124 slightly raises actuating lever 122 and prevents it from 
further pivoting which prevents rod 108 from moving vertically. When 
deactivation of interrupter 128 is desired, the operator-selectable switch 
is activated in the opposite direction causing tapered end 144 to retract 
from tapered hole 124. Preferably deactivation is accomplished when roller 
118 is in contact with surface 129 of cam 126. Once deactivated, actuator 
122 is allowed to pivot freely and therefore rod 108 is again allowed to 
move vertically. 
Several lowering mechanisms 102 are provided along each shaft 21, 23, 25, 
and 27. An individual actuator 122, clearing cam 126 and interrupter 128 
is provided for each shaft 21, 23, 25 and 27. Each clearing cam 126 has a 
cam profile which raises the lowering mechanisms for each row into the up 
position when trailing edge T of sheet S has been transferred to the next 
subsequent row of feed wheels 19. At the beginning of a feed cycle, the 
cams may lower all of the rods 108 in unison. However, it is also possible 
that rods 108 associated with feed elements 19 of shafts 21, 23 and 27 
could lower in unison before rods 108 for shaft 29 are lowered. This would 
be useful if sheet S is particularly long. 
Although the particular clearing mechanism shown in the Figures has been 
described with regard to the present invention, many other known clearing 
mechanisms could be used. Any conventional clearing mechanism which is 
capable of changing the relationship of stack SS and feed elements 19 
would be suitable for incorporation with the present invention. For 
example, a clearing mechanism which lowers the feed wheels or elements, 
feed wheels having a relieved surface as discussed above; and an outer 
shell rotatably mounted over the sheet support which blocks contact of the 
feed elements with the sheet could alternatively be used. 
In operation of the preferred embodiment of sheet feeder 10 during a single 
feed operation of the present invention, stack SS is placed on the feed 
end of sheet feeder 10 and is supported by the clearing mechanism which is 
in the up position, preventing the bottommost sheet in stack SS from 
contacting feed wheels 19 on shafts 21, 23, 25 and 27. Gate 14 prevents 
stack SS from moving beyond center portion 40. 
Feed wheels 19 on shafts 29, 31, and 33 are rotating at constant machine 
speed which is equal to the line speed of machine M. The vacuum mechanism 
is activated and provides constant vacuum pressure V in chamber 94 
underneath the feed wheels 19. When it is desired to start feeding, the 
operator activates the switch on each interrupter 128 allowing rollers 118 
to contact cams 126. The clearing mechanism begins to move towards the 
down position (FIG. 7) and variable-speed generating mechanism 60 begins 
acceleration segment A (FIG. 3) As sheet S contacts feed wheels 19 on 
shafts 21, 23, 25, and 27 they begin rotating counterclockwise in unison. 
Sheet S begins movement from feed end 38 towards delivery end 42. 
Sheet S is now under the control of the feed wheels 19 on shafts 21, 23, 
and 25, rotating at identical or matched speed. Lead edge L of sheet S 
then passes under gate 14 and through gap 15. As lead edge L of sheet S 
contacts feed wheels 19 on shaft 27, lowering mechanism 102 for shaft 21 
is raised to the up position. By the time sheet S is ready to be 
transferred from feed wheels 19 on shaft 27 to shaft 29, feed wheels 19 of 
shaft 27, and therefore sheet S, has reached 100% line speed. When lead 
edge L contacts feed wheels 19 on shaft 29, lowering mechanism 102 for 
shaft 29 is raised to the up position. When lead edge L contacts feed 
wheels 19 on shaft 31, lowering mechanism 102 for shaft 25 is raised to 
the up position. Finally, when lead edge L reaches feed wheels 19 on shaft 
33, lowering mechanism 102 for shaft 27 is raised to the up position. 
Constant-speed output segment B has begun (FIG. 3) and is maintained until 
lead edge L of sheet S has contacted feed wheels 19 on shaft 33, or until 
sheet S is contacting the minimum number of rows of constant-speed feed 
wheels 19 necessary to control sheet S. In the preferred embodiment this 
minimum number is preferable three. 
At this point in the feed cycle, all of the lowering mechanisms 102 are in 
the up position and sheet S is no longer contacting feed wheels 19 on 
shafts 21, 23, 25 and 27. The motion cycle of the variable-speed 
generating mechanism 60 is now in the non-critical segment C. Sheet S 
continues towards delivery end 42, under the control of feed elements 19 
on shafts 29, 31, and 33, where sheet S is smoothly and continuously 
transferred to machine M while it is traveling at a 100% matched speed to 
the line speed of machine M. 
The result is a smooth, continuous transfer of sheet S from one row of feed 
wheels 19 to the next row of feed wheels 19 where each successive row of 
feed wheels 19 which is contacting sheet S is traveling at the same speed 
as sheet S. This ensures that sheet S is controlled at all times 
throughout the feed cycle by preferably three rows of feed wheels 19 
traveling at matched speed. 
It should be understood that the foregoing disclosure relates only to 
presently preferred embodiments, and that it is intended to cover all 
changes and modifications of the invention herein chosen for the purpose 
of the disclosure which do not constitute departures from the spirit and 
scope of the invention as set forth in the appended claims.