U.S. patent application number 10/006058 was filed with the patent office on 2003-06-12 for gripper bar for die cutting machine.
Invention is credited to Oetlinger, Frank E..
Application Number | 20030107167 10/006058 |
Document ID | / |
Family ID | 21719082 |
Filed Date | 2003-06-12 |
United States Patent
Application |
20030107167 |
Kind Code |
A1 |
Oetlinger, Frank E. |
June 12, 2003 |
Gripper bar for die cutting machine
Abstract
A hollow gripper bar having a hexagonal profile which reduces
the bending and torsional stresses applied thereto by the
acceleration and deceleration of the bar in a die cutting machine.
The gripper bar includes an upper wall, a spaced lower wall, a
leading wall and a trailing wall extending between the upper and
lower walls. The leading wall includes a front top portion
extending transversely from the upper wall and a front bottom
portion disposed at an acute angle with respect to the front top
wall portion. The trailing wall is similar in design to the leading
wall and includes a rear top portion extending transversely from
the upper wall and a rear bottom portion disposed at an acute angle
with respect to the rear top portion. Both the front top portion
and rear top portion have a thickness that is greater than the
thickness of the upper wall. In addition, the front bottom portion
as well as the rear bottom portion have a tapered thickness that
gradually decreases from the front top portion and rear top
portion, respectively, to the lower wall.
Inventors: |
Oetlinger, Frank E.;
(Grafton, WI) |
Correspondence
Address: |
ANDRUS, SCEALES, STARKE & SAWALL, LLP
Suite 1100
100 East Wisconsin Avenue
Milwaukee
WI
53202-4178
US
|
Family ID: |
21719082 |
Appl. No.: |
10/006058 |
Filed: |
December 6, 2001 |
Current U.S.
Class: |
271/204 |
Current CPC
Class: |
B65H 29/045 20130101;
B65H 2701/1764 20130101; B65H 2801/42 20130101; B65H 29/044
20130101 |
Class at
Publication: |
271/204 |
International
Class: |
B65H 029/04 |
Claims
I claim:
1. A gripper bar for gripping a sheet of paper material in a die
cutting machine that processes said sheet into a box blank,
comprising: a longitudinally extending hollow bar which includes an
upper wall having a leading end and a trailing end which define a
width for said bar, a lower wall spaced from said upper wall to
define a height for said bar, said lower wall having a leading end
and a trailing end which define a width for said lower wall which
is less than the width of said bar, a leading wall extending
between and integral with the leading ends of said upper and lower
walls, said leading wall including a front top wall portion
extending transversely from the leading end of said upper wall to a
front lower end which defines a height for said front top wall
portion which is less than the height of said bar, and a front
bottom wall portion extending between the front lower end of said
front top wall portion and the leading end of said lower wall, said
front bottom wall portion disposed at a first acute angle with
respect to said front top wall portion, and a trailing wall
extending between and integral with the trailing ends of said upper
and lower walls, said trailing wall including a rear top wall
portion extending transversely from the trailing end of said upper
wall to a rear lower end which defines a height for said rear top
wall portion which is less than the height of said bar, and a rear
bottom wall portion extending between the rear lower end of said
rear top wall portion and the trailing end of said lower wall, said
rear bottom wall portion disposed at a second acute angle with
respect to said rear top wall portion; and a plurality of grippers
disposed on said bar and spaced at regular intervals along its
longitudinal length.
2. The gripper bar of claim 1 wherein said upper and lower walls
are parallel.
3. The gripper bar of claim 1 wherein said upper and lower walls
are planar.
4. The gripper bar of claim 1 wherein said upper and lower walls
are of equal thickness.
5. The gripper bar of claim 1 wherein said front and rear top wall
portions are parallel.
6. The gripper bar of claim 1 wherein said front and rear top wall
portions are planar.
7. The gripper bar of claim 1 wherein said front and rear top wall
portions are of equal thickness.
8. The gripper bar of claim 1 wherein the height of said front top
wall portion is equal to the height of said rear top wall
portion.
9. The gripper bar of claim 1 wherein said first and second acute
angles range from about 30.degree. to about 80.degree..
10. The gripper bar of claim 1 wherein said first and second acute
angles are equal.
11. The gripper bar of claim 1 wherein said first and second acute
angles are both about 74.degree..
12. The gripper bar of claim 1 wherein said upper wall has a
thickness, and said front top wall portion has a thickness greater
than the thickness of said upper wall.
13. The gripper bar of claim 1 wherein said upper wall has a
thickness, and said rear top wall portion has a thickness greater
than the thickness of said upper wall.
14. The gripper bar of claim 1 wherein said upper wall has a
thickness, and said front and rear top wall portions each has a
thickness greater than the thickness of said upper wall.
15. The gripper bar of claim 14 wherein a ratio of the thicknesses
of said front and rear top wall portions to the thickness of said
upper wall ranges from about 1.01 to 1 to about 2 to 1.
16. The gripper bar of claim 15 wherein said ratio is from about
1.1 to 1 to about 1.5 to 1.
17. The gripper bar of claim 15 wherein said ratio is about 1.2 to
1.
18. The gripper bar of claim 1 wherein said front bottom wall
portion has a tapered thickness that gradually decreases from the
front lower end of said front top wall portion to the leading end
of said lower wall.
19. The gripper bar of claim 1 wherein said rear bottom wall
portion has a tapered thickness that gradually decreases from the
rear lower end of said rear top wall portion to the trailing end of
said lower wall.
20. The gripper bar of claim 1 wherein said front bottom wall
portion has a tapered thickness that gradually decreases from the
front lower end of said front top wall portion to the leading end
of said lower wall and said rear bottom wall portion has a tapered
thickness that gradually decreases from the rear lower end of said
rear top wall portion to the trailing end of said lower wall.
21. The gripper bar of claim 20 wherein the tapered thickness of
said front and rear bottom wall portions is at an angle of from
about 1.degree. to about 10.degree..
22. The gripper bar of claim 21 wherein the angle is about
5.degree. for both said front and said rear bottom wall
portions.
23. The gripper bar of claim 1 wherein the hollow bar is composed
of aluminum.
24. A gripper bar for gripping a sheet of paper material in a die
cutting machine that processes said sheet into a box blank,
comprising: a hollow bar defining a longitudinal axis; a plurality
of grippers disposed on said bar and spaced at regular intervals
along said longitudinal axis and movable between open and closed
positions; a longitudinally extending axle rotatably mounted within
said hollow bar for movement between a first position wherein said
grippers are closed and a second position wherein said grippers are
open; a plurality of actuators mounted on said axle and spaced at
regular intervals to correspond with said grippers, said actuators
rotatable with said axle to open and close said grippers; a lever
disposed at one end of said axle operable to rotate said axle
between said first and second positions; and mounting means for
mounting said lever on said axle, said mounting means comprising a
key formed on said axle, a key-receiving opening formed in said
lever, and a clamp for clamping said lever on said axle.
25. The gripper bar of claim 24 wherein said key comprises a flat
area formed in said axle and said key-receiving opening includes a
matching flat section corresponding thereto.
26. The gripper bar of claim 24 wherein said clamp comprises a pair
of opposing jaws surrounding said axle.
27. The gripper bar of claim 26 wherein said clamp further includes
a retainer for pinching said jaws together about said axle.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to die cutting machines for
making box blanks, and more particularly to a gripper bar for use
in a die cutting machine.
[0002] Gripper bars are used in die cutting machines to pull sheets
of paper material through the machine, and properly position the
sheets at various successive processing stations where the sheet
may be printed, cut, embossed, creased, and/or stripped of waste.
Gripper bars are generally fitted on two lateral chains at regular
spaced distances in the machine and extend crosswise to the machine
direction, i.e. the traveling direction of the sheets of paper
material in the machine. The gripper bars and sheets of paper
material follow a circuit composed of successive horizontal
intermittent movement from a starting position through the various
processing stations. At the downstream end of the machine, the
gripper bars move in an upward arc to a return path which then
terminates in a downward arc to the starting position where the
gripper bar is once again ready to accept a sheet of material and
to proceed through the successive processing stations of the
machine.
[0003] When the gripper bar is in the starting position, it is
properly aligned with a feeder table as well as the various
downstream processing stations referred to above. When a sheet of
paper material to be processed is pushed from the feeder table,
grippers on the gripper bar are closed about the edge of the sheet
and the sheet is carried to the first processing station within the
machine. Thus, as the sheet is transferred from one station to the
next in order to permit cutting, creasing, waste stripping and the
like, the gripper bar successively moves between combinations of
acceleration, deceleration, dwell, and/or standstill
operations.
[0004] As the production speeds of machines increase, a
corresponding shorter operating cycle for the gripper bar and sheet
of paper material results. For example, it is possible to reach a
throughput and production speed of more than 9,000 pieces per hour
with a cycle duration at each station of about 0.4 seconds, of
which about 0.3 seconds are taken up by movement of the sheet of
material and the gripper bar from one station to the next,
typically a length of about 1 meter. Since the gripper bars are
connected only at their ends to drive chains in the machine, the
bending and torsional stresses applied to the gripper bars by
acceleration and deceleration are extreme. In addition, the
moveable assembly comprising the gripper bar, the grippers
themselves, and the accompanying elements for actuating the
grippers which are carried on the gripper bar, is relatively heavy
which results in a massive high inertia momentum which adds to the
bending and torsional stresses applied to the gripper bar.
Obviously, over time, the gripper bars become stressed, and should
the bar fracture, the resulting damage to the machine and machine
downtime is very costly.
[0005] Gripper bars are typically formed to have a hollow
cross-sectional profile through which a gripper opening axle
extends. The gripper opening axle, which is rotatably mounted in
the bar, is driven to open and close the grippers. The gripper
opening axle is rotated by means of a lever attached at one end
thereof which typically engages a cam mechanism at the above noted
starting position to open the grippers. In order to insure that the
grippers close tightly about the edge of a sheet of paper material
to be processed, a relatively strong spring force is utilized to
insure the necessary gripper action against the sheet of material.
Consequently, a very strong opening torque is applied to the axle
via the lever to open the gripper fingers against the spring force.
This strong opening torque provides a stress on the mounting
arrangement of the lever on the axle. In the past, this stress has
eventually led to a loosening of the lever mounting on the axle
resulting in a reduction or the complete elimination of the travel
of the tips of the gripper fingers. Obviously, if the gripper
fingers do not open, the gripper bar cannot accept a new sheet of
paper material at the starting position in the machine. This again
results in potential damage and machine downtime.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
gripper bar having a profile which reduces the bending and
torsional stresses applied thereto by the acceleration and
deceleration of the bar in a die cutting machine.
[0007] It is another object of the invention to provide a gripper
bar whose weight will be reduced so as to further reduce the stress
caused by the relatively high inertia momentum of prior art
devices.
[0008] Yet another object of the invention is to provide a gripper
opening arrangement which utilizes a lever that will not loosen to
thereby insure proper travel for the tips of the gripper
fingers.
[0009] In order to accomplish the above objects, the present
invention provides a hollow gripper bar with a unique profile. The
gripper bar includes an upper wall, a spaced lower wall, a leading
wall and a trailing wall extending between the upper and lower
walls. The leading wall includes a front top portion extending
transversely from the upper wall and a front bottom portion
disposed at an acute angle with respect to the front top wall
portion. The trailing wall is similar in design to the leading wall
and includes a rear top portion extending transversely from the
upper wall and a rear bottom portion disposed at an acute angle
with respect to the rear top portion. In a preferred embodiment,
both the front top portion and rear top portion have a thickness
that is greater than the thickness of the upper wall. The ratio of
the thickness of the front and rear top portions to the thickness
of the upper wall ranges from about 1.01 to 1 to about 2 to 1,
preferably from about 1.1 to 1 to about 1.5 to 1, and most
preferably about 1.2 to 1. In addition, the front bottom portion as
well as the rear bottom portion have a tapered thickness that
gradually decreases from the front top portion and rear top
portion, respectively, to the lower wall. The tapered thickness of
the front and rear bottom portions range from an angle of about
1.degree. to about 10.degree., with 5.degree. degrees being
preferred.
[0010] In another embodiment, the gripper bar includes an improved
mounting for the lever on the gripper opening axle. In this
embodiment, the gripper bar includes an elongate bar in the form of
a hollow shell defining a longitudinal axis, a plurality of
grippers disposed on the bar and spaced at regular intervals along
the longitudinal axis and moveable between open and closed
positions, a longitudinally extending axle rotatably mounted within
the hollow bar for movement between a first position wherein the
grippers are closed and a second position where the grippers are
open, a plurality of actuators mounted on the axle and spaced at
regular intervals to correspond with the grippers so as to be
rotatable with said axle to open and close the grippers, a lever
disposed at one end of the axle operable to rotate the axle between
its first and second positions, and the mounting for the lever on
the axle comprises a key formed on the axle, a key-receiving
opening formed in the lever, and a clamp for clamping the lever on
the axle. Preferably, the key comprises a flat area formed on the
outer surface of the axle and the key-receiving opening includes a
matching flat section corresponding thereto. The clamp preferably
comprises a pair of opposing jaws surrounding the axle, and a
retainer such as a bolt for pinching the jaws together to securely
mount the lever on the axle.
[0011] Other advantages and features of the invention will be
readily apparent from the description of the preferred embodiments,
the drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The drawings illustrate the best mode presently contemplated
of carrying out the invention.
[0013] In the drawings:
[0014] FIG. 1 is a crosswise elevational view of a gripper bar
constructed in accordance with the present invention illustrated
partially in section and partially in full;
[0015] FIG. 2 is a top plan view of the gripper bar of FIG. 1 also
shown partially in section and partially in full;
[0016] FIG. 3 is an enlarged cross-sectional view of the gripper
bar taken along the line 3-3 shown in FIGS. 1 and 2;
[0017] FIG. 4 is an enlarged cross-sectional view of the gripper
bar taken along the lines 4-4 shown in FIGS. 1 and 2.;
[0018] FIG. 5 is an enlarged exploded view of a gripper opening
axle and accompanying lever for rotating the axle; and
[0019] FIG. 6 is an enlarged cross-sectional view showing the
mounting arrangement for the lever on the gripper opening axle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Referring now to the drawings, FIGS. 1 and 2 illustrate a
gripper bar generally designated by the numeral 1 which is used in
a die cutting machine for converting or processing a sheet of paper
material into a box blank. These machines are used to cut one or
several blanks into each sheet of paper material which, after
folding and gluing may be formed into boxes. The gripper bar 1
enables the pulling and positioning of the sheets of paper material
within the machine as they are carried through various sequences of
printing, cutting, embossing, creasing, waste stripping and/or
blanking stations.
[0021] The die cutting machine usually is formed by a series of
stations with the first station being a starting position or input
station in which the sheets, which may be pre-printed if desired,
are taken one by one from the top of a stack to a feed table where
they are placed in position against frontal and side guides. The
sheet can then be grasped by the gripper bar, which extends
longitudinally crosswise of the machine direction. The gripper bar
is attached at its opposite ends to a pair of lateral chains which
lead the bar, and thus the sheet of paper material in the machine
direction or downstream into subsequent processing stations.
Typically, the sheet is first conveyed into a cutting station where
the box blanks of a desired size are cut into the sheet. These
blanks are held to the sheet by nicks which are arranged along the
cut edges of the blanks. This cutting station is usually comprised
of upper and lower tools one of which is provided with a plurality
of line-shaped straight and curved die cutting blades. If desired,
the cutting station may be preceded by a printing station, or as
noted above, the sheets may be pre-printed. After cutting, the
sheet is then lead to a stripping station where the waste, i.e. the
unused scrap between the various box blanks, are grasped by upper
lower pins in order to be lead downward into a waste container. The
sheet is then fed into a blank separating station where the fasten
points or nicks between the blanks and the sheet are broken by a
tool so that each of the blanks are released and falls onto a stack
of blanks below the tool. Finally, the residual or remaining
portion of the sheet is carried into a delivery or exit station
where it is released by the gripper bar 1.
[0022] A plurality of gripper bars 1 are generally fitted onto two
lateral chains (not shown) at regular intervals depending on the
length of each sheet of material and extend crosswise to the
machine direction or downstream direction of the sheets. As noted
above, the chains and attached gripper bars 1 follow an
elliptical-like circuit inside the die cutting machine initially
composed of successive horizontal translation movements from the
starting position or input station along a horizontal path through
the various sequential processing stations and then, at the end of
the path, i.e. the downstream or exit end, move in an upward arc to
a return path which moves the gripper bars 1 back upstream and then
terminates in a downward arc to once again be located at the
starting position or input station. When the gripper bar 1 is in
its starting position or input station, it is aligned with the
feeder table and at this stage, the grippers (hereinafter to be
described) are opened to receive a sheet of paper material pushed
downstream from the feeder table into the input station. Once
properly located between the grippers of the gripper bar 1, the
grippers close to grasp the front or leading edge of the sheet
whereupon the sheet is carried downstream to the first processing
station which, as noted above, is typically either a printing
station or a cutting station. Although the die cutting machine is
not illustrated in detail herein, the machine and its operation is
well known to those skilled in the art and therefore it is believed
not necessary to illustrate the machine in detail herein.
[0023] As used herein, the terms "upstream" and "downstream" are
used in reference to the direction of displacement of the sheet of
paper material, which is shown by arrow 2 in FIG. 2. Arrow 2
illustrates the machine direction, i.e. the downstream or material
processing direction for the sheet. Thus, upstream typically refers
to a direction toward the entrance of the machine whereas
downstream refers to a direction leading to the exit of the
machine. Likewise, the term "leading" refers to the downstream side
of an element wherein the term "trailing" refers to the upstream
side of the element. In a similar manner, the expression
"crosswise" refers to a direction transverse to the machine
direction indicated by arrow 2. The term "sheet of paper material"
refers to flat , plate-like work pieces or elements, such as planar
sheets of paper, cardboard, paperboard, and the like, typically
processed into packaging, particularly boxes.
[0024] Referring again to FIGS. 1 and 2, gripper bar 1 defines a
longitudinal axis which extends crosswise with respect to the
machine direction 2. As shown, gripper bar 1 has a hollow hexagonal
profile defined by an outer shell having an upper wall 3, a lower
wall 4, a leading wall 5 and a trailing wall 6 (see FIG. 3).
Opposite ends of gripper bar 1 are attached by mounting plates 7
and 8 to drive chains (not shown) of the die cutting machine in a
conventional manner.
[0025] A plurality of grippers 9 are disposed on bar 1 and spaced
at regular intervals along its longitudinal axis. Grippers 9 are
moveable between open and closed positions to grasp the leading
edge of a sheet of paper material at the input station to pull the
sheet through the machine and to release the sheet at the exit end
of the machine. As shown best in FIGS. 3 and 4, each gripper 9
includes an upper finger 10 and a lower finger 11. Upper finger 10
is mounted at its leading end to leading wall 5 by means of a pair
of screws 12. Finger 10 also includes an S-shaped portion 13 which
leads to a horizontal portion 14 which extends across the outer
flat surface of upper wall 3 of gripper bar 1 and extends upstream
or rearwardly to a knuckled tip portion 15 which projects
rearwardly beyond trailing wall 6. Lower finger 11 is in the form
of a right angled member having a vertical leg portion secured by
screw 16 to trailing wall 6. Finger 11 includes a horizontal leg
portion 17 extending rearwardly from wall 6 and leading to a
serrated tip portion 18. The serrated tip portion 18 interacts with
the knuckled tip portion 15 to securely grasp a sheet of paper
material therebetween due to the spring force provided by S-shaped
portion 13 of upper finger 10.
[0026] As shown best in FIG. 3, tip portions 15 and 18 open
sufficiently to provide a tip travel or gap 19 having sufficient
height to receive the leading edge of a sheet of paper material
therebetween. In order to provide for the opening and closing
movement of fingers 10 and 11, gripper bar 1 includes a
longitudinally extending axle 20 rotatably mounted within the
hollow profile of gripper bar 1 for movement between a first
position wherein fingers 10 and 11 are closed and a second position
wherein fingers 10 and 11 are open. Axle 20 is rotatably mounted at
its opposite ends via bearings 21 and 22 formed in mounting plates
7 and 8 respectively. As shown best in FIG. 3, axle 20 is tubular
in shape and extends longitudinally along the longitudinal axis of
gripper bar 1 and is typically composed of an aluminum material. In
order to rotate axle 20 between its first and second positions for
closing and opening fingers 10 and 11, there are provided two
levers 23 and 24 securely mounted thereto at opposite ends thereof.
Levers 23 and 24 each include a roller 25 and 26, respectively,
which engages a cam or other element (not shown) in the machine to
raise or lower levers 23 and 24, which in turn rotates axle 20,
depending upon whether fingers 10 and 11 need to be open at the
input station for receiving a sheet of paper material or closed
during subsequent stations for processing of the sheet. As shown
best in FIG. 4, each roller 25 and 26 is mounted for rotation via
pin 27 which is held in place by a snap ring 28.
[0027] A plurality of actuators or arms 29 are mounted on axle 20
and spaced at regular intervals to correspond with the location of
grippers 9. Each actuator includes a roller 30 at its outer end
which extends through an opening 31 formed in upper wall 3 of
gripper bar 1 to engage the underside of upper finger 10 and move
finger 10 upwardly through its travel to form gap 19 when axle 20
is rotated between its first and second positions. The movement of
levers 23 and 24 resulting in the rotation of axle 20 and movement
of actuators 29, must be properly coordinated in order to open and
close fingers 10 and 11 at the appropriate locations and times and
to provide the proper travel or gap 19.
[0028] Referring now specifically to FIG. 3, there is illustrated
the hollow hexagonal-shaped profile of gripper bar 1. As
illustrated, upper wall 3 and lower wall 4 are parallel to one
another, are substantially flat or planar in shape, and have a
constant equal thickness of approximately 5 mm. Upper wall 3 has a
leading end 32 and a trailing end 33 which define a width for
gripper bar 1. Lower wall 4 is spaced from upper wall 3 to define a
height for gripper bar 1 which is sufficient to accommodate axle 20
and actuators 29. Lower wall 4 has a leading end 34 and a trailing
end 35 which define a width for lower wall 4 which is less than the
width of upper wall 3. Leading wall 5 extends between and is
integral with the leading ends 32 and 34 of the upper and lower
walls 3 and 4 respectively. Leading wall 5 includes a front top
wall portion 36 which extends transversely or downwardly from the
leading end 32 of upper wall 3 to a front lower end 37 which
defines a height for the front top wall portion 36 which is less
than the height of bar 1. Leading wall 5 also includes a front
bottom wall portion 38 which extends between the front lower end 37
of front top wall portion 36 and the leading end 34 of lower wall
4. As shown best in FIG. 3, the front bottom wall portion 38 is
disposed at a first acute angle A1 with respect to the front top
wall portion 36. This acute angle A1 preferably ranges from
30.degree. to 80.degree. and is most preferably 74.degree.. The
trailing wall 6 extends between and is integral with the trailing
ends 33 and 35 of the upper and lower walls 3 and 4 respectively.
The trailing wall 6 includes a rear top wall portion 39 extending
transversely or downwardly from the trailing end 33 of upper wall 3
to a rear lower end 40 which defines a height for rear top wall
portion 39 which is less than the height of bar 1, but equal to the
height of front top wall portion 36. Trailing wall 6 also includes
a rear bottom wall portion 41 which extends between the rear lower
end 40 of the rear top wall portion 39 and the trailing end 35 of
lower wall 4. The rear bottom wall portion 41 is disposed at a
second acute angle A2 with respect to rear top wall portion 39. As
with angle A1, angle A2 is preferably between 30.degree. to
80.degree., but is most preferably equal to angle A1 and has an
angle of 74.degree..
[0029] Gripper bar 1 is preferably composed of aluminum, and in
order to provide sufficient resistance to bending and torsional
forces applied during processing of a sheet of paper material,
front top wall portion 36 and rear top wall portion 39 both have a
thickness greater than the thickness of upper wall 3 and lower wall
4. As illustrated, the front top wall portion 36 and rear top wall
portion 39 have a thickness of about 6 mm. However, the ratio of
the thickness of wall portions 36 and 39 with respect to upper
lower walls 3 and 4 may range from 1.01 to 1 to about 2 to 1,
preferably 1.1 to 1 to about 1.5 to 1, and most preferably 1.2 to
1. In addition, it can be seen that front bottom wall portion 38
and rear bottom wall 41 both have tapered thicknesses that
gradually decrease from the lower ends 37 and 40 of wall portions
36 and 39 respectively to the leading end 34 and trailing end 35,
respectively, of lower wall 4. As illustrated in FIG. 3, the
tapered thickness of bottom wall portions 38 and 41 is at an angle
of about 5.degree., but may range between an angle of about
1.degree. to about 10.degree.. These angles are designated as B1
and B2 in FIG. 3. Thus, the increased thickness of top wall
portions 36 and 39 with respect to upper and lower walls 3 and 4,
together with the tapered thickness of bottom wall portions 38 and
41 serve to minimize stresses applied to gripper bar 1 as gripper
bar 1 proceeds in the machine direction between the processing
stations. As a result of less stress, gripper bar 1 is less likely
to fracture and/or crack.
[0030] Referring now to FIGS. 5 and 6, lever 24 is illustrated in
more detail. Lever 24 is identical to lever 23 and thus the
following description relating to FIGS. 5 and 6 apply equally to
the structure of lever 23. As illustrated, axle 20 has a key or
flat area 42 formed in its outer surface at the end thereof. Lever
24 in turn includes a key-receiving opening 43 formed therein which
receives the end of axle 20 and includes a matching flat section 44
formed on the inner surface of opening 43 which corresponds in size
and dimensions to key 42. In addition to opening 43, lever 24
includes a pair of spaced ears 45 and 46 for mounting roller 26
therebetween (shown in FIG. 1 but not in FIGS. 5 and 6). In order
to securely mounting lever 24 on axle 20, lever 24 includes a pair
of opposing jaws 47 and 48 surrounding axle 20. Jaws 47 and 48
extend in the opposite direction from ears 45 and 46 and project
beyond the circumference of axle 20 to provide a clamp for clamping
lever 24 onto axle 20. In order to accomplish this, each jaw 47 and
48 includes a threaded opening 49 and 50 respectively, which
receives a retainer or bolt 51 therein. When tightened, bolt 51
securely clamps lever 24 onto axle 20. This clamping action
together with the key arrangement formed between axle 20 and lever
24 substantially prevents lever 24 from loosening on axle 20. Thus,
this mounting arrangement minimizes the possibility of lever 24
loosening on axle 20.
* * * * *