 |
Description  |
|
|
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to the concurrently filed U.S. patent
application Ser. No. 442,523, now U.S. Pat. No. 4,483,438.
TECHNICAL FIELD
This invention relates to apparatus and methods for securing together
overlapping portions of thermoplastic strap.
This invention further relates to chain assembly components and to methods
for fabricating chain assemblies. The chain assemblies may be incorporated
in, inter alia, strap securing apparatus.
BACKGROUND OF THE INVENTION AND TECHNICAL PROBLEMS POSED BY THE PRIOR ART
Friction-Fusion Welding Of Strap
A variety of methods have been marketed and/or proposed over the years for
securing together overlapping portions of a tensioned loop of
thermoplastic strap encircling an article. One method is effected by first
compressing the overlapping strap portions together and then creating a
unidirectional or multidirectional bodily sliding frictional movement
between the contacting surface regions of the overlapping strap portions
to melt interface regions of the overlapping strap portions. The melted
interface regions are allowed to solidify so as to bond the overlapping
strap portions together.
This process, which can be generally described by the term friction-fusion
welding, has proven to be especially effective with conventional
thermoplastic strap materials such as nylon, polyester, polypropylene, and
the like. Such conventional strap is typically provided in widths ranging
from 5 mm. to 9.525 mm. and has a thickness ranging between about 0.254 mm
and about 0.889 mm.
In conventional tools and machines for effecting a friction-fusion weld
between overlapping portions of thermoplastic strap, an engaging member is
provided for gripping the outwardly directed surface of one of the
overlapping strap portions and an anvil is provided for contacting the
outwardly directed surface of the other overlapping strap portion. The
strap engaging surface of the engaging member and of the anvil may each be
planar or may each be curved for receiving the overlapping strap portions.
Relative movement is effected between the engaging member and the anvil so
that at least some of the relative movement takes place in a planar or
curved locus conforming to the planar or curved interface between the two
overlapping strap portions.
Torsion Bar Friction-Fusion Strap Welding Machines
Conventional Torsion Bar Machine Design
A variety of mechanisms have been proposed for effecting the relative
motion necessary to friction-fusion welding techniques. Signode
Corporation, 3600 West Lake Avenue, Glenview, Ill. 60025 U.S.A. (the
assignee of the present invention), has developed and currently markets
friction-fusion strapping machines which incorporate torsion bar
assemblies. The torsion bar assembly is initially stressed and
subsequently released to oscillate the strap engaging member, as well as
the overlapping strap portion contacting the strap engaging member, for
thus effecting the necessary relative motion.
U.S. Pat. Nos. 3,494,280 and 3,548,740, also assigned to Signode
Corporation, disclose such torsion bar assemblies in strapping machines.
The torsion bar assemblies described in these patents have been further
developed and subsequently incorporated in strapping machines marketed by
Signode Corporation. Typical of such commercially available machines are
those sold under the designations "Power Strapping Machine Models MLN-2A,
ML2-EE, ML2-JE, and ML2-HG."
Problems With Low Amplitude Torsion Bar Oscillation
Although the above-described power strapping machines with torsion bar
assemblies work well in the many applications for which they were designed
to be employed, the inventor of the present invention has determined that
it would be desirable to provide an improved torsion bar assembly for use
in power strapping machines. The inventor has determined that if a
conventional torsion bar assembly design is employed with a relatively
short stroke (small oscillation amplitude), then the assembly must be
massive enough to accommodate the energy needed to properly form the
joint. However, a very short stroke (small oscillation amplitude) is more
easily damped out before a sufficient melting of the interface region
between the overlapping strap portions can be effected. Although this
tendency may be overcome by using a relatively large diameter torsion bar
with a small oscillation amplitude, more massive structural supports are
then required to accommodate such a design. The inventor of the present
invention has determined that, consistent with minimal supporting
structure, it is preferable to use a smaller diameter torsion bar with a
larger twist angle than to use a larger diameter torsion bar with a
smaller twist angle.
Problems With High Amplitude Strap Oscillation
In conventional torsion bar assemblies, the strap engaging member that is
oscillated by the torsion bar is part of, or is secured to, the torsion
bar. The strap engaging member includes an arm projecting radially
outwardly from the torsion bar. With a relatively small diameter torsion
bar and with a relatively large twist angle, such a strap engaging member
oscillates with a relatively large amplitude. However, in some
applications, the large oscillation amplitude causes an unduly large
movement of, and tension impact upon, the engaged strap.
The impact can be especially significant at the corners of the article
around which the strap has been tensioned. This impact, of course, can
place an undesirably high stress on the strap at the corner locations and
may also damage the strap and/or article. Accordingly, it has been
determined that, in some applications, a reduction in the amplitude or
stroke of the strap engaging member would be desirable so as to
substantially reduce, if not altogether eliminate, such problems.
As a way to reduce the stroke, the inventor of the present invention has
considered locating the strap contacting surface of the strap engaging
member as close as possible to the longitudinal axis of rotation of the
torsion bar. For example, a design might be considered wherein the
radially projecting arm of the strap engaging member is eliminated and
wherein the strap engaging member comprises the exterior cylindrical
surface of the torsion bar per se. With such a design, the actual
amplitude of strap oscillation will be considerably reduced even though
the twist angle of the torsion bar can remain relatively large (as desired
from the above-discussed standpoint of providing sufficient energy for the
friction-fusion weld in a manner that will produce a good weld and yet not
require execessive supporting structure for the torsion bar).
Although the above-postulated design of a torsion bar assembly appears, in
theory, to provide a solution to the problem of effecting a good weld with
sufficient energy and reduced strap movement amplitude, the design suffers
from practical drawbacks arising from conflicting design considerations.
In particular, with commercial strapping apparatus, especially with
strapping machines that automatically encircle an article with the strap,
sufficient space must be provided at the friction-fusion welding location
to accommodate the initial proper positioning of the overlapping strap
portions and the subsequent tensioning of the strap. In addition,
sufficient room must be provided to accommodate the various support
structures and mechanisms for initially forming the strap into the loop,
for gripping one or more portions of the strap, for stressing the torsion
bar assembly, and for cutting the welded strap loop from the trailing
portion of the strap.
Accordingly, the strap engaging member in a conventional torsion bar
strapping machine typically extends radially outwardly from the torsion
bar so that the strap engaging member contacts the strap at a location
spaced away from the torsion bar by an amount sufficient to provide the
required clearance for accommodating the above-described various
functions. Unfortunately, with such a design, the amplitude of oscillation
of the strap engaging member, and of the engaged strap, will necessarily
be relatively large when the torsion bar is stressed through a relatively
large twist angle. It would therefore be desirable to provide some
mechanism for reducing the amplitude of the oscillation of the strap
engaging member (and of the engaged strap) while permitting a relatively
small diameter torsion bar to be stressed through a relatively large twist
angle.
Problems With Curved Welding Areas
With the conventional torsion bar friction-fusion strapping machines
described above, the strap engaging member has a convex strap gripping
surface which presses the two overlapped strap portions against an anvil
having a generally concentric and concave bearing surface. The strap
engaging member and anvil are located in each machine at the bottom of the
package or article receiving area so that the bottom of the package or
article overlies, and is in close proximity to, the anvil and strap
engaging member. The anvil is disposed between the bottom of the article
and the strap path so that the overlapping strap portions can be pressed
into the concave bearing surface of the anvil by the convex strap engaging
member.
With many articles, the bottom of the article is flat and the portion of
the tensioned strap extending around the bottom of the article would
necessarily tend to conform to the flat bottom of the article. However,
because the anvil and strap engaging member are curved, the strap must
follow the curved, and longer, path defined between the anvil and the
strap engaging member. Thus, after the friction-fusion weld has been
completed and the strapped article removed from the machine, there will be
a slightly greater amount of slack in the tensioned loop compared to a
lesser amount of slack that would be introduced by a flat anvil.
Owing to the generally elastic nature of thermoplastic strap, the small
amount of additional slack introduced by the curved anvil is manifested in
a slightly reduced tension in the strap loop. This, of course, can be
accommodated by drawing a higher initial tension. However, from the
standpoint of minimizing the machine power requirements and the strap
tensile strength requirements, the inventor has determined that it would
be desirable to reduce, if not eliminate altogether, the concave curvature
of the anvil and conforming convex curvature of the strap engaging member.
Further, the inventor of the present invention has determined that it is
desirable, especially in welding overlapping portions of very thin strap
(film strap), to reduce the amount of curvature at the weld region so as
to be able to provide a weld extending for a greater distance along the
length of the strap than would otherwise be achievable on a practical
basis with a conventional curved weld region.
Accordingly, it would be advantageous to provide a torsion bar assembly
with a strap engaging member that would move in a relatively linear path
against a flat anvil parallel to the bottom of the article rather than in
the conventional path curving away from the article.
Chain Assemblies For Slip-Feed Strapping Machines
In the above-described torsion bar strapping machines the strap is
initially automatically formed into a loop about the article by a
loop-forming system. The system typically includes a main chain assembly
supported in a suitable framework to define a generally
rectangularly-shaped window or region around the article receiving station
in the machine. Fixed to the main chain assembly is a slip-feed strap
carrier, such as a pair of spaced-apart rollers, which engages the
trailing portion of the strap in a slip-feed manner and which is moved by
the main chain assembly around the article to form the strap into a tight
loop around the article. An example of such a system is disclosed in the
aforementioned U.S. Pat. No. 3,548,740. A modified system is disclosed in
the U.S. Pat. No. 4,393,763 assigned to the assignee of the present
invention.
The carrier main chain assemblies in such conventional systems are of the
well-known multiple strand, metal link and pin type that are guided, as
well as driven, by conventional metal sprockets. Although such
conventional carrier chain systems work extremely well, abnormally high
speed operation of the metal chain assemblies around metal sprockets can
produce high noise levels.
In order to increase the efficiency of automated assembly line article
strapping, it has become desirable to provide strapping machines with
higher and higher operating speeds. However, when strapping machines with
metal carrier chains and sprockets are operated at such very high speeds,
the operational noise levels become excessive.
In the United States of America the noise levels in work areas occupied by
employees are limited by various state and federal regulations.
Accordingly, it would be desirable to provide a strap transport system in
a power strapping machine that would have the strength and durability of a
metal chain but that would have the relatively low noise level associated
with nonmetallic belt drive assemblies. Further, with such an improved
strap transport system, it would be desirable to provide a structure that
could be relatively easily fabricated.
Friction-Fusion Welding Of Thin Film Wide Strap
Although conventional strap works well in a great many applications, the
inventor of the present invention believes that it would be highly
desirable to provide, in certain special applications, strap that is
considerably wider than conventional strap (e.g., two to eight times as
wide) and that is considerably thinner (e.g., less than 0.254 mm and
typically about 0.08 mm.).
Such strap could advantageously be used in certain applications, including
the binding of a stack of newspapers or magazines, and, preferably, may
also be transparent. The relatively wide strap would reduce the pressure
on the stack of newspapers or magazines, particularly at the corners, and
would thereby have less of a tendency to damage the newspapers or
magazines. Finally, a relatively thin, transparent, strap readily permits
viewing of the portion of the article which is covered by the strap.
With conventional thermoplastic strap having thicknesses of between about
0.254 mm. and about 0.889 mm., the overlapping strap portions are bonded
together in a friction-fusion weld to a thickness of between about 0.013
mm. and 0.051 mm. in each overlapping strap portion across the entire
width of the strap. Typically, the length of the friction-fusion bond
extends for about 10 mm. to about 35 mm. along the length of the
overlapping strap portions.
The inventor of the present invention has determined that conventional
friction-fusion techniques developed for strap of conventional thickness
are difficult to employ satisfactorily with thin film wide strap,
especially film strap having a thickness of less than 0.13 mm. and which
may be only about 0.08 mm. For one thing, much more energy would be
required to melt the entire surface areas of the overlapping wide strap
portions in the selected joint region. Further, control of the thickness
of the fused material in the thin strap would be difficult. Also, care
must be taken to avoid unwanted penetration of one or both of the
overlapping strap portions.
The inventor of the present invention has found that additional, unique
problems are presented by film strap fabricated from so-called "oriented"
materials, such as, for example, strap comprising linear crystallizable
polypropylene that has been worked into a thin film having planar
molecular orientation of the macromolecular chains with a uniplanar, axial
oriented crystalline structure through at least a major portion of the
film thickness. An attempt to produce a conventional friction-fusion weld
in such film strap across the full width of the strap may result in
reduced weld strength and can reduce the strap strength at the weld since
the strap orientation is destroyed in the fused region of the weld.
The inventor has thus determined that it would be desirable to provide a
method and apparatus for forming a friction-fusion joint or weld in
overlapping portions of the thin film strap whereby the overlapping strap
portions retain a sufficient amount of tensile strength after formation of
the friction-fusion weld to enable the strap to properly function in a
tensioned loop around an article at conventional strapping tensions for
the applications in which such thin film strap would be used. Such an
improved method and apparatus should desirably accommodate various means
for effecting the bodily sliding frictional of the overlapping strap
portions--including torsion bar actuted mechanisms as well as other
non-torsion bar actuated mechanisms.
SUMMARY OF THE INVENTION
Friction-Fusion Weld Pad Design
An apparatus is disclosed for securing a loop of thermoplastic strap around
an article so that two overlapping portions of the strap are bonded
together by means of a friction-fusion weld. The apparatus includes a
strap engaging member for pressing against and gripping the outwardly
directed surface of one of the overlapping strap portions. The strap
engaging member defines a plurality of spaced-apart, raised, ribs
extending parallel to the lengths of the overlapping strap portions. Each
rib presents a generally planar contacting surface.
The apparatus also includes an anvil defining a planar strap engaging
surface against which the outwardly directed surface of the other of the
overlapping strap portions is pressed. Means are provided for effecting
relative movement between the anvil and at least the strap engaging member
to compress the overlapping strap portions therebetween. Means are also
provided for moving the strap engaging member in contact with the strap
along a path of motion parallel to the lengths of the ribs.
According to the method for securing the strap, the straps are compressed
together between the anvil and the strap engaging member under the desired
amount of force and the strap engaging member is moved in a linear path,
with the ribs oriented parallel to the length of the strap, so as to cause
bodily sliding frictional movement between the overlapping strap portions
and a melting of interface regions which subsequently solidify.
Torsion Actuation System
The above-described welding process may be effected with a variety of means
for moving the strap engaging member. A novel means is disclosed herein
and may be used to effect the above-described strap welding process as
well as other strap welding processes. The novel means includes an
anchored torsion spring means for being torsionally stressed to store a
predetermined amount of energy. An arc of gear teeth is carried by the
torsion spring means for rotation with the torsion spring means about an
axis of rotation. Also provided is a strap engaging member with a row of
rack gear teeth. Means are provided for mounting the strap engaging member
with the rack gear teeth engaged with at least some of the teeth of the
arc of gear teeth on the torsion spring means. Finally, means are provided
for torsionally stressing and then removing the torsion stress from the
torsion spring means after the predetermined amount of energy has been
stored whereby the strap engaging member is oscillated on the mounting
means in linear motion against the overlapping strap portions as the arc
of gear teeth is rotated so as to effect the friction-fusion weld.
Lug and Chain Assembly
Embodiments of a novel driven lug for a chain assembly, along with a novel
chain assembly incorporating the lug, are disclosed with a method for
fabricating the chain assembly. The chain assembly is particularly well
suited for high speed operation as a strap carrier chain in an automatic
strapping machine.
The driven lug of the chain assembly includes a resilient mounting body
portion for being mounted between two adjacent cross members. The mounting
body portion defines a convex cavity on each of two opposite ends for
receiving a portion of one of the cross members. A driven body portion
extends from the mounting body portion and defines an engaging means for
being engaged by the selected drive means for driving the chain assembly.
An extension body portion projects from the mounting body portion opposite
the driven body portion. The extension body portion includes a tapered
portion decreasing in thickness with increasing distance from the mounting
body portion ends to faciliate insertion of the lug between the two
adjacent cross members. Preferably, the extension body portion further
includes a portion projecting from the distal end of the tapered portion.
According to the method for fabricating the chain assembly, a conventional
chain may be provided and the lug may be separately fabricated from a
resilient material. The tapered portion of the lug is inserted between the
two adjacent cross members and a pulling force is applied to the tapered
portion to force the tapered portion and the mounting body portion into
temporary compression between the two adjacent cross members to align the
mounting body portion cavities in receiving relationship with the cross
members.
Anvil, Gripper, and Cutter Assembly
Also disclosed herein is an assembly for use with a variety of
friction-fusion weld pad actuating systems in a strapping machine of the
type having (1) an anvil movable between an extended position for engaging
a first overlapping strap portion and a retracted position spaced away
from the first overlapping strap portion, (2) a strap engaging member for
pressing against and gripping the outwardly directed surface of a second
overlapping strap portion, (3) means for effecting relative movement
between the anvil and at least the strap engaging member to compress the
overlapping strap portions therebetween, and (4) means for moving the
strap engaging member to cause the bodily sliding frictional movement
between the overlapping strap portions.
The assembly includes a first carriage movable relative to the anvil
between a retracted position and an extended position. A second carriage
is provided and is movable relative to both the first carriage and the
anvil between a retracted position and an extended position.
A pair of grippers are pivotally mounted to the first carriage for pivoting
between an open position and a closed position against the sides of the
anvil to clamp an end of the strap against the anvil.
A pair of cutters are pivotally mounted to the first carriage for pivoting
between an open position and a closed position against, or partially
extending into, the sides of the anvil to sever the strap at the anvil.
Each gripper is provided with a gripper link pivotally connected to the
gripper and pivotally connected to the second carriage. Similarly, each
cutter is provided with a cutter link pivotally connected to the cutter
and pivotally connected to the second carriage.
Abutment surfaces are located to be engaged by a portion of each gripper
when each gripper is pivoted away from the open position with the first
carriage in the extended position.
Finally, means are provided for moving the second carriage from the
extended position to the retracted position after the friction-fusion weld
has been formed whereby rearward movement of the grippers and cutters is
initially prevented as the grippers engage and slide along the abutment
surfaces and pivot to the open positions and whereby the cutters,
grippers, and first carriage are retracted with the second carriage after
the grippers pivot to the fully opened positions and are disengaged from
the abutment surfaces.
Numerous other advantages and features of the present invention will become
readily apparent from the following detailed description of the invention,
from the claims, and from the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings forming part of the specification, in which
like numerals are employed to designate like parts throughout the same,
FIGS. 1, 2, 3, 4, 4A, 5, 6, and 7 are fragmentary, simplified, diagrammatic
views of the sequence of operation of a strapping apparatus and FIG. 1A
shows an enlarged, fragmentary, partial cross-sectional view of the strap
dispenser mechanism;
FIG. 8 is an enlarged, fragmentary, perspective view of the strap carrier
in a first embodiment of a main chain assembly;
FIG. 9 is a greatly enlarged, fragmentary, perspective view of a first
embodiment of one strand or chain assembly of the main chain assembly
shown engaged with a large drive sprocket;
FIG. 10 is a greatly enlarged side view of a first embodiment of a lug
forming part of the first embodiment of the chain assembly;
FIG. 11 is an end view of the lug of FIG. 10;
FIG. 12 is a fragmentary, partial cross-sectional view of the first
embodiment of the chain assembly trained between a guide V-pulley or
sheave and the drive sprocket;
FIG. 13 is a greatly enlarged, fragmentary, cross-sectional view taken
generally along the plane 13--13 in FIG. 12;
FIG. 14 is an enlarged, fragmentary, perspective view of a second
embodiment of one strand or chain assembly engaged with a large V-type
drive pulley or sheave;
FIG. 15 is a greatly enlarged side view of a second embodiment of a lug
forming part of the second embodiment of the chain assembly illustrated in
FIG. 14;
FIG. 16 is an end view of the second embodiment of the lug;
FIG. 17 is a fragmentary, partial cross-sectional view of the second
embodiment of the chain assembly trained between a guide V-pulley or
sheave and the larger V-type drive pulley or sheave;
FIG. 18 is a greatly enlarged, fragmentary, cross-sectional view taken
generally along the plane 18--18 in FIG. 17;
FIG. 19 is a fragmentary, plan view of the anvil, gripper, and cutter
assembly of the apparatus with the cover plate removed to show interior
mechanisms;
FIG. 20 is a fragmentary, side view of the anvil, gripper, and cutter
assembly;
FIG. 21 is a fragmentary, cross-sectional view taken generally along the
plane 21--21 in FIG. 20 showing in solid lines the opened grippers and
retracted anvil and showing in dashed lines the extended anvil;
FIG. 22 is a fragmentary, cross-sectional view taken generally along the
plane 22--22 in FIG. 19;
FIG. 23 is a view similar to FIG. 22, but showing the anvil extended;
FIG. 24 is a view similar to 23, but showing the gripper carriage and
cutter carriage also extended;
FIG. 25 is a view similar to FIG. 19 but showing the gripper carriage,
cutter carriage, and anvil in the extended positions as in FIG. 24, and
showing the cutters and grippers in the closed positions in solid lines
and in the open positions in dashed lines;
FIG. 26 is a view similar to FIG. 24, but showing the gripper carriage
being moved rearwardly to open the grippers;
FIG. 27 is a fragmentary, front end view taken along the plane 27--27 in
FIG. 25 to show the front of the anvil, gripper, and cutter assembly as
well as the torsion bar carriages below the anvil, gripper, and cutter
assembly;
FIG. 28 is an enlarged cross-sectional view taken generally along the plane
28--28 in FIG. 25;
FIG. 29 is enlarged, cross-sectional view taken generally along the plane
29--29 in FIG. 25;
FIG. 30 is a fragmentary, partial cross-sectional view of the anvil,
gripper, and cutter assembly overlying the torsion bar carriages and
showing overlapping strap portions being connected with a friction-fusion
weld;
FIGS. 31-33 are simplified, fragmentary, cross-sectional views taken
generally along the plane 31--31 in FIG. 30 to illustrate the sequence of
torsion bar operation (some of the structure unrelated to the torsion bar
operation being omitted from FIGS. 31-34 to better illustrate the torsion
bar operation);
FIG. 34 is a view similar to FIGS. 31-33, but taken in perspective, to
illustrate a further stage of operation of the strapping apparatus;
FIGS. 35-41 are fragmentary, partial cross-sectional views of the anvil,
gripper, and cutter assembly showing the sequence of operation with the
underlying torsion bar carriages;
FIG. 42 is a top plan view of the weld pad of the strap engaging member;
FIG. 43 is a greatly enlarged, fragmentary, cross-sectional view taken
generally along the plane 43--43 in FIG. 42 to illustrate the shape of the
weld pad teeth;
FIG. 44 is a view taken generally along the plane 44--44 in FIG. 43; and
FIG. 45, shown on the sheet of drawings with FIG. 30, is a reduced
cross-sectional view taken generally along the plane 45--45 in FIG. 30.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
While this invention is susceptible of embodiment in many different forms,
there are shown in the drawings and will herein be described in detail
various preferred embodiments of the invention. It will be understood,
however, that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not intended to
limit the invention to the embodiments illustrated.
The precise shapes and sizes of the components herein illustrated are not
essential to the disclosed apparatus and methods unless otherwise
indicated.
It will be understood that the apparatus disclosed herein has certain
conventional mechanisms, including drive mechanisms, control mechanisms,
and the like, the details of which, though not fully illustrated or
described, will be apparent to those having skill in the art and an
understanding of the necessary functions of such mechanisms.
General Arrangement Of The Apparatus
Referring now the drawings, the general arrangement and sequence of
operation of a novel article strapping apparatus can be best understood
with reference to FIGS. 1-7. The apparatus includes a main frame,
designated generally by reference numeral F in FIG. 1, which supports a
main chain assembly C defining a generally rectangularly shaped article
receiving window or station W that accommodates the article or package P
which is to be strapped. A support structure (not illustrated) underlies
the bottom of the receiving station W in a well known and conventional
manner to provide a guideway which receives the opposite ends of the strap
S forming a loop about the article P.
In the illustrated preferred embodiment of the article strapping apparatus,
the strap S is a wide, thin film strap (e.g., having a width greater than
about 10 mm. or more and having a thickness of less than about 0.254 mm.
The cross-sectional size of the strap S in the Figures is not to scale and
the strap thickness has been exaggerated for ease of illustration.
The main chain assembly C comprises at least two spaced-apart, parallel,
strands or chain assemblies C.sub.1 and C.sub.2 (FIG. 1). The frame F
supports the main chain assembly C in engagement with pairs of
spaced-apart, rotatable members M which hold the main chain assembly C in
the desired rectangular shape about the article receiving window W. Some
of the engaging members M may be positively driven by conventional means
(not illustrated) to drive the main carrier chain assembly clockwise or
counterclockwise about the article receiving window W.
Although only four pairs of chain assembly engaging members M are
illustrated in FIGS. 1-4, it is to be realized that additional pairs of
members M may be provided either inside or outside of the main chain
assembly loop. Depending upon the specific structure of the main chain
assembly C, the engaging members M may be V-pulleys (sheaves) or may be
toothed sprockets. A first embodiment of a main chain assembly for use
with toothed sprockets and a second embodiment of a main chain assembly
for use with V-pulleys are described in detail hereinafter.
Mounted to the main chain assembly C is a conventional strap carrier R
comprising two spaced-apart rollers R.sub.1 and R.sub.2. The rollers
R.sub.1 and R.sub.2 are mounted between the two spaced-apart strands or
chain assemblies C.sub.1 and C.sub.2. The strap S passes through the
carrier rollers R.sub.1 and R.sub.2 and thus has a portion which is guided
along the main chain assembly C around the outside of the engaging members
M. The two strands or chain assemblies C.sub.1 and C.sub.2 of the main
chain assembly C are typically joined in spaced-apart relationship by pins
or cross members (or, in some applications, by a center (third) chain
strand) which are not visible in FIGS. 1-4. Thus, the strap S is prevented
from sagging inwardly (between the two strands or chain assemblies C.sub.1
and C.sub.2) into the article receiving region W.
Typically, one or more of the chain assembly engaging members M are rotated
intermittently in one direction or the other by suitable conventional
drive means (not illustrated) to move the chain assembly and hence, the
strap carrier R, about the article receiving station W.
A variety of conventional designs may be employed for the specific
construction, number, and arrangement of the chain assembly engaging
members M, for the means for driving one or more of the chain assembly
engaging members M, and for the means for rotating one or more of the
chain assembly engaging members M. Reference is directed to U.S. Pat. No.
3,548,740 which shows the arrangement of sprockets with a two-strand chain
and to the recently allowed U.S. patent application Ser. No. 261,969 filed
on May 8, 1981 (assigned to the assignee of the present invention) which
discloses a three-strand chain assembly driven by sprockets.
The apparatus is illustrated in FIG. 1 in an initial position ready to
commence an operation cycle of receiving and strapping an article. The
free end of the strap S, having been severed from a loop of strap around a
previously strapped article, is already gripped by one of a pair of
grippers G against the side of an anvil A as best illustrated in FIG. 1
(where the right-hand gripper G is shown gripping the strap S on the
right-hand side of the anvil A). The anvil A defines a downwardly facing,
planar, strap engaging surface. The anvil and gripper mechanisms are
described in greater detail hereinafter.
The strap S extends outwardly (to the left as viewed in FIG. 1), between
the rollers R.sub.1 and R.sub.2 of the strap carrier R. The strap S
continues along the exterior of the chain assembly C and between a pair of
spaced-apart centering rollers 50 and 52 which allow for the feeding of
the strap in either strapping direction around the article P in the
article receiving station W. The frame F has a suitable portion (not
illustrated) to which the rollers 50 and 52 are mounted.
The strap S is fed to the centering rollers 50 and 52 from a strap
dispenser system D illustrated in FIGS. 1, 1A and 2. The system D includes
a strap reel 54 mounted for rotation about an axis 56. The strap S is
directed from the reel 54 around a dancer arm 58 and then through a series
of fixed pulleys 60 and a series of dispenser pull-off pulleys 62 which
are mounted on a movable carrier 64 which is biased downwardly by a
torsion spring 66. As the str | | |
