U.S. patent application number 10/950952 was filed with the patent office on 2006-03-30 for vibrator assembly for strapping machine weld head.
This patent application is currently assigned to Illinois Tool Works, Inc.. Invention is credited to Timothy B. Pearson, Wayne J. Thas.
Application Number | 20060065135 10/950952 |
Document ID | / |
Family ID | 35539173 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060065135 |
Kind Code |
A1 |
Thas; Wayne J. ; et
al. |
March 30, 2006 |
VIBRATOR ASSEMBLY FOR STRAPPING MACHINE WELD HEAD
Abstract
A vibrator assembly is for use on a strapping head for a
strapping machine configured to position, tension and seal
strapping material around a load. The strapping head includes a
body, an anvil, and a welding motor having a rotating output shaft.
The vibrator assembly includes an eccentric element operably
mounted to the welding motor output shaft for rotation therewith. A
bearing is disposed about the eccentric element, A housing is
houses the eccentric element and bearing at least in part within
the housing. The housing defines a cup-shaped well having a first
axis length and a second axis length. The first axis length is
longer than the second axis length. The first axis length is in a
transverse direction, and the second axis length is in an
oscillating direction. The bearing is restrained in the oscillating
direction. A weld pad is operably connected to the housing by a
link. As the motor output shaft rotates, the eccentric element is
rotated and in turn rotates the bearing to impart oscillating
motion to the weld pad in the oscillating direction. The bearing is
restrained from moving in the transverse direction.
Inventors: |
Thas; Wayne J.; (Arlington
Heights, IL) ; Pearson; Timothy B.; (Antioch,
IL) |
Correspondence
Address: |
WELSH & KATZ, LTD. (ILLINOIS TOOL WORKS)
120 S. RIVERSIDE PLAZA
CHICAGO
IL
60606
US
|
Assignee: |
Illinois Tool Works, Inc.
Glenview
IL
|
Family ID: |
35539173 |
Appl. No.: |
10/950952 |
Filed: |
September 27, 2004 |
Current U.S.
Class: |
100/33PB ;
156/580 |
Current CPC
Class: |
B29C 66/4322 20130101;
B29C 66/1122 20130101; B29C 66/80 20130101; B65B 13/322 20130101;
B29C 65/069 20130101; B29C 66/4324 20130101; B29C 65/0618
20130101 |
Class at
Publication: |
100/033.0PB ;
156/580 |
International
Class: |
B65B 13/24 20060101
B65B013/24 |
Claims
1. A vibrator assembly for a strapping head for a strapping machine
configured to position, tension and seal strapping material around
a load, the strapping head including a body, an anvil, and a
welding motor having a rotating output shaft, the vibrator assembly
comprising: an eccentric element operably mounted to the welding
motor output shaft for rotation therewith; a bearing disposed about
the eccentric element; a housing, the eccentric element and the
bearing disposed at least in part within the housing, the housing
defining a cup-shaped well therein, the well having a first axis
length and a second axis length, the first axis length being longer
than the second axis length, the first axis length being in a
transverse direction, and the second axis length being in an
oscillating direction, the bearing being restrained in the
oscillating direction relative to the housing; and a weld pad
operably connected to the housing by a link, wherein as the motor
output shaft rotates, the eccentric element is rotated and in turn
rotates the bearing to impart oscillating motion to the weld pad in
the oscillating direction, and wherein the bearing is restrained
from moving in the transverse direction.
2. The vibrator assembly in accordance with claim 1 including a
seal disposed on the eccentric element configured for cooperating
with the housing to enclose the bearing and well.
3. The vibrator assembly in accordance with claim 1 including a key
and mating keyway one disposed on the housing and the other
disposed on the weld pad to restrain the weld pad from pivoting
about the link relative to the housing.
4. The vibrator assembly in accordance with claim 3 wherein the key
is disposed on the housing and the keyway is disposed on the weld
pad.
5. The vibrator assembly in accordance with claim 1 wherein the
housing well has an oval shape.
6. The vibrator assembly in accordance with claim 1 wherein the
link operably connecting the weld pad to the housing is a pin
fitted in respective openings in the housing and the weld pad.
7. The vibrator assembly in accordance with claim 1 including
friction reducing elements disposed in the well for contact with
the bearing.
8. The vibrator assembly in accordance with claim 7 wherein the
friction reducing elements are disposed in recesses formed in the
housing along the second axis.
9. A vibrator assembly for a strapping head for a strapping machine
configured to position, tension and seal strapping material around
a load, the strapping head including a body, an anvil, and a
welding motor having a rotating output shaft, the vibrator assembly
comprising: an eccentric element operably mounted to the welding
motor output shaft for rotation therewith; a bearing disposed about
the eccentric element; a housing, the eccentric element and the
bearing disposed at least in part within the housing, the housing
defining a cup-shaped well therein having an oval shape having a
first axis length and a second axis length, the first axis length
being longer than the second axis length, the first axis length
being in a transverse direction, and the second axis length being
in an oscillating direction, the bearing being restrained in the
oscillating direction relative to the housing; friction reducing
elements disposed in the well, in recesses formed in the housing,
for contact with the bearing, the friction reducing elements are
disposed along the second axis; a seal disposed on the eccentric
element configured for cooperating with the housing to enclose the
bearing and well; and a weld pad operably connected to the housing
by a link, wherein as the motor output shaft rotates, the eccentric
element is rotated and in turn rotates the bearing to impart
oscillating motion to the weld pad in the oscillating direction,
and wherein the bearing is restrained from moving in the transverse
direction.
10. The vibrator assembly in accordance with claim 9 including a
key disposed on the weld pad and a mating keyway disposed on the
housing to restrain the weld pad from pivoting about the link
relative to the housing.
11. A strapping head for a strapping machine configured to
position, tension and seal strapping material around a load,
comprising: a body; an anvil; a welding motor having a rotating
output shaft; a vibrator assembly having an eccentric element
operably mounted to the welding motor output shaft for rotation
therewith, a bearing disposed about the eccentric element, a
housing having the eccentric element and the bearing disposed at
least in part therein, the housing defining a cup-shaped well
having a first axis length and a second axis length, the first axis
length being longer than the second axis length, the first axis
length being in a transverse direction, and the second axis length
being in an oscillating direction, the bearing being restrained in
the oscillating direction relative to the housing; and a weld pad
operably connected to the housing by a link, wherein as the motor
output shaft rotates, the eccentric element is rotated and in turn
rotates the bearing to impart oscillating motion to the weld pad in
the oscillating direction, and wherein the bearing is restrained
from moving in the transverse direction.
12. The strapping head in accordance with claim 11 including
friction reducing elements disposed in the housing well, in
recesses formed in the housing, for contact with the bearing, the
friction reducing elements being disposed along the second
axis.
13. The strapping head in accordance with claim 11 including a seal
disposed on the eccentric element configured for cooperating with
the housing to enclose the bearing and well.
14. The strapping head in accordance with claim 11 including a key
disposed on the weld pad and a mating keyway disposed on the
housing to restrain the weld pad from pivoting about the link
relative to the housing.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention pertains to strapping machine weld
head vibrator assemblies. More particularly, the present invention
pertains to vibrator assemblies having a simplified, one-link
design.
[0002] Strapping machines are well known in the art. Typically
these machines are used for securing straps around loads. One type
of strapper is used with a plastic or polymeric strap and is a
stationary arrangement in which the strapper is included as part of
an overall manufacturing or packaging system.
[0003] A typical strapper includes a frame to which various
components are mounted. A chute is mounted to the frame through
which the strapping material is fed around a load. A strapping head
and a drive or feed mechanism are mounted to the frame. The
strapping material is fed from a source, by the feed assembly,
through the strapping head. The strapping material traverses around
the chute and back to the strapping head.
[0004] The strapping or welding head provides a number of
functions. The strapping head grips the strap during the course of
a strapping operation and cuts the strap from a strap source or
supply. In addition, the strapping head includes a sealer to seal
an overlying course of strapping material onto itself. This seal is
commonly referred to as a weld and is effected by heating one
course of the strap by use of a vibrating element.
[0005] Known strapping heads include a body and an anvil between
which the courses of strap materials traverse during a strapping
operation and between which the strapping material courses are held
during the welding operation. The anvil is maintained rigid and a
weld pad is brought into contact and applies pressure against the
strap. The pad is carried by an element that oscillates or vibrates
(and oscillates the pad) thus creating friction and heat to effect
the weld.
[0006] The drive for the vibrating element and pad is typically a
motor or other rotational drive. In order to impart vibrational
motion to the element, the rotational motion of the motor must be
transferred to linear motion. Known strappers include complex
linkages or eccentric shaft arrangements having open (elongated)
slots. While these arrangements function well for their intended
purposes (and particularly the eccentric arrangement), there are
drawbacks. For example, as with any complex linkage, problems can
occur at the linkage joints. As to the eccentric configurations,
there is always the potential for debris to accumulate in the
elongated slot (that receives the eccentric shaft). Such an
eccentric-containing configuration is disclosed in Gerhart et al.,
U.S. Pat. No. 6,532,722.
[0007] Accordingly, there exists a need for a simplified assembly
for a welding or strapping head weld pad. Desirably, such an
assembly eliminates the need for complex linkages and open regions
otherwise required to transfer rotational motion into linear
motion. More desirably, such an assembly is of a compact design and
readily permits removal for tool maintenance and inspection.
BRIEF SUMMARY OF THE INVENTION
[0008] A vibrator assembly is for use with a strapping machine
strapping or weld head. The strapping machine positions, tensions
and seals strapping material around a load. The strapping head
includes a body, an anvil, and a welding motor having a rotating
output shaft.
[0009] The vibrator assembly is a simplified design that eliminates
the need for complex linkages and open regions otherwise required
to transfer rotational motion into linear motion. Such an assembly
is of a compact design and readily permits removal for tool
maintenance and inspection.
[0010] The vibrator assembly includes an eccentric element operably
mounted to the welding motor output shaft for rotation with the
shaft. A bearing is disposed about the eccentric element.
[0011] The eccentric element and bearing are disposed, at least in
part, within a housing. The housing defines a cup-shaped well,
preferably, oval in shape. That is, the well has a first axis
length and a second axis length with the first axis length being
longer than the second axis length and with the first axis length
being in a transverse direction. Conversely, the second axis length
is in an oscillating direction. The bearing is restrained in the
oscillating direction.
[0012] A weld pad is operably connected to the housing by a link,
such as a pin. As the motor output shaft rotates, the eccentric
element is rotated and in turn rotates the bearing to impart
oscillating motion to the weld pad in the oscillating direction.
The bearing is restrained from moving in the transverse direction.
In a present assembly, friction reducing elements are disposed in
the well, in recesses formed in the housing along the second axis,
for contact with the bearing.
[0013] Preferably, a seal is disposed on the eccentric element for
cooperating with the housing to enclose the bearing and housing
well. A key is disposed on the weld pad and mating keyway is
disposed on the housing to restrain the weld pad from pivoting
about the link relative to the housing.
[0014] These and other features and advantages of the present
invention will be apparent from the following detailed description,
in conjunction with the appended claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0015] The benefits and advantages of the present invention will
become more readily apparent to those of ordinary skill in the
relevant art after reviewing the following detailed description and
accompanying drawings, wherein:
[0016] FIG. 1 is a perspective view of an exemplary strapping head
having a vibrator assembly embodying the principles of the present
invention;
[0017] FIG. 2 is an exploded view of the assembly and weld pad of
FIG. 1;
[0018] FIG. 3 is a top view of the assembly of FIG. 1; and
[0019] FIG. 4 is a cross-sectional view taken along line 4--4 of
FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0020] While the present invention is susceptible of embodiment in
various forms, there is shown in the drawings and will hereinafter
be described a presently preferred embodiment with the
understanding that the present disclosure is to be considered an
exemplification of the invention and is not intended to limit the
invention to the specific embodiment illustrated.
[0021] It should be further understood that the title of this
section of this specification, namely, "Detailed Description Of The
Invention", relates to a requirement of the United States Patent
Office, and does not imply, nor should be inferred to limit the
subject matter disclosed herein.
[0022] Referring to the figures and in particular FIG. 1, there is
shown a strapping machine strapping or weld head 10 having a
vibrator assembly 12, embodying the principles of the present
invention. The strapping head 10 includes generally, a body 14 and
an anvil 16. Internally, (not shown) a gripper assembly and a
cutter are carried by the body 14. As set forth in the above patent
to Gerhart et al., the cutter can be disposed within the gripper
assembly. The Gerhart et al. patent which is commonly assigned with
the present application is incorporated herein by reference.
[0023] In a typical strapper, the strap is welded to itself by the
action of a vibrating element or weld pad 18. The pad 18 is carried
by a carriage 20 that is moved in a linear or reciprocating motion
so as to fuse (by heat) the strap layer in contact with the pad 18
with an adjacent, confronting strap layer. The pad 18 can also be
formed as part of the carriage 20 (e.g., formed on a bottom surface
of the carriage 20 as seen in FIG. 4) as a unitary vibrator element
24. The carriage 20 and pad 18 together serve as the vibrator
element 24.
[0024] In order to provide linear movement to the element 24, the
strapping head 10 includes a weld or sealer motor 26. The motor 26
has a rotating output shaft 28 that is operably connected to the
element 24 by the vibrator assembly 12. To achieve the friction
necessary to form the strap seal, the element 24 moves at a rate of
about 10,000 to 15,000 movements or cycles per minute.
[0025] Known connecting arrangements use a crank-type connecting
rod extending between an eccentric pivot and the pad. The rod uses
two pins as links for transferring rotational movement of the motor
into reciprocating movement of the pad. One pin is on the carriage
and the other pin is on the eccentric shaft.
[0026] The physical distance between the pad and the eccentric is
short. As such, the angle that the connecting rod rotates through
is large (steep). The steep angle results in large side loads that
are induced on the pivot points of the connecting rod and on the
linear bearings (not shown but located as indicated at about 30 in
FIG. 2) of the pad (the linear bearings are positioned between the
sides of the pad and the carriage). These side loads result in high
frictional forces and loses. It was found that this required overly
frequent bearing and pivot pin lubrication for even minimal use. It
was further found that even with proper lubrication the 10,000
cycle per minute rate and the heat generated by the motor resulted
in excessive component aging and wear, and failure could occur as
frequently as within 10,000-15,000 cycles.
[0027] To overcome these friction-related problems, the present
vibrator assembly 12 eliminates the crank-type connection. An
eccentric cap 32 is fitted onto the motor output shaft 28. The cap
32 has a stepped configuration with a base flange 34, a central,
concentric cylindrical portion 36 (concentric with the flange 34
and motor shaft 28) and an eccentric stub 38. The stub 38 is
cylindrical, however, the longitudinal axis A.sub.38 of the stub 38
is offset from the longitudinal axis A.sub.28 of the motor shaft
28, flange 34 and central portion 36. A seal 40 is fitted over the
cap 32 around the central portion 36, resting on the flange 34.
[0028] A bearing 42 is fitted onto the eccentric stub 38 and is
retained on the stub 38 by a retaining clip or ring 44. In a
present assembly 12, the bearing 42 is a needle-type bearing that
is formed as a sleeve that fits onto the eccentric stub 38. In this
manner, although the bearing 42 and stub 38 are concentric with one
another, their shared axis (at A.sub.38) is offset from the
longitudinal axis A.sub.28 of the motor shaft 28, flange 34 and
central portion 36.
[0029] The bearing 42 is retained within a bearing housing 46. The
bearing housing 46 defines an inner cup-like portion or well 48 in
which the bearing 42 is positioned. As best seen in FIG. 3, the
well 48 has an elongated profile, being slightly oval-shaped. The
major axis A.sub.M is in the side-to-side direction and the minor
axis A.sub.N is in the front-to-rear (50-to-52, respectively)
direction. That is, the well is slightly larger side-to-side than
it is front-to-back (where front-to-back is the direction of
reciprocation as indicated by the arrow at 22). Pads 54 are
positioned within the well 48 at the front 50 and rear 52 for
"holding" the bearing 42 in place in the housing 46 and to reduce
the friction developed by the rotating bearing 42. The pads 54 are
fitted into recesses or channels 56 in the housing 46.
[0030] A present housing 46 is a two-part shell. A rear part 56a of
the shell forms a heel and a front portion 56b of the shell has a
connecting finger 58 that extends toward the element 24. The finger
58 defines a connecting portion 60 having an opening 62 therein. A
pin (such as a screw) 64 extends through the finger opening 62 and
a cooperating opening 66 in the element 24. This forms a single pin
link between the eccentric 32 and the element 24. The finger 58
includes a keyway or channel 68 that cooperates with a key 70
formed in the base of the element 24. This prevents the element 24
from rotating relative to the housing 46 about the pin 64, and thus
rigidly secures the housing 46 and element 24 to one another.
[0031] The front and rear housing parts 46a,b are secured to one
another by a plurality of fasteners 72. The entirety of the housing
46 serves as a grease pot. That is, the housing well 48 is filled
with lubricant to provide lubrication for the bearing 42. In that
the well 48 is oval rather than circular, there is space between
the bearing 42 and the wall of the housing 46 that also serves as a
region for accumulating lubricant. The seal 40 at the base of the
housing 46 (around the central portion 36 of the cap 32), closes
off and seals the housing 46. As a result of the oscillating action
of the bearing 42 relative to the housing 46, the lubricant is
forced around the housing 46 and into the bearing 42 to provide an
albeit minimally, pumped or forced lubricant circulating
system.
[0032] The present vibrator assembly 12 has a number of advantages
over the crank connecting rod assembly configuration. First, the
keyed 68, 70 arrangement of the element 24 and housing 46
eliminates a needle bearing, a pivot pin, and additional components
that would otherwise require lubrication. In that the element 24 is
restrained from moving in the side-to-side direction and is
restrained from pivoting (about the pin 64), less side loads are
induced on the linear bearings (those bearings between the element
24 and the head 10 at the anvil).
[0033] Moreover, because the well 48 within the housing 46 is oval
shaped, the space between the housing 46 and the bearing 42 permits
applying more lubricant around the bearing 42 than would a
tight-fitting arrangement. This, in conjunction with the seal 40,
shelters the bearing 42 and lubricant from contaminants.
[0034] In addition, the carbide pads or blanks 54 that are pocketed
into the front and rear of the housing 46 facilitate changing the
orbital motion of the eccentric 32 into linear motion with less
friction. This in turn results in less heat produced by the motor
26 and increases the life expectancy of the motor 26 and all of the
moving components attached to the vibrator assembly 12. The present
assembly 12 has been subjected to in excess of 150,000 cycles with
no additionally required lubrication and no component failures.
[0035] All patents referred to herein, are hereby incorporated
herein by reference, whether or not specifically done so within the
text of this disclosure.
[0036] In the present disclosure, the words "a" or "an" are to be
taken to include both the singular and the plural. Conversely, any
reference to plural items shall, where appropriate, include the
singular.
[0037] From the foregoing it will be observed that numerous
modifications and variations can be effectuated without departing
from the true spirit and scope of the novel concepts of the present
invention. It is to be understood that no limitation with respect
to the specific embodiments illustrated is intended or should be
inferred. The disclosure is intended to cover by the appended
claims all such modifications as fall within the scope of the
claims.
* * * * *