Note: Descriptions are shown in the official language in which they were submitted.
ARTICLE STRAPPING METHOD AND APPARATUS
The present invention is directed to an improved
method and apparatus for applying a tensioned strap loop
about an article.
Known in the art are automatic article strapping
machines which include a yoke that communicates with a
strapping mechanism and which together provide a gen-
erally continuous strap passage. In such machines,
strap is fed from a supply into and along such passage
to provide a loop in which leading end and feed portions
of the strap are in overlying relationship. After the
leading end portion of such strap loop is gripped, a
pulling force is imposed on the feed portion of the
strap to withdraw the strap from the passage as a loop
and to apply the same in a tensioned condition about an
article which is being strapped. The feed portion of
the strap is then gripped and overlying leading end and
feed portions of the strap loop are sealed together.
Known also in the art are semi-automatic strapping
machines which include no yoke and in which the leading
end portion of a strap fed from a supply is manually
laced about an article which is being s~rapped and then
inserted into position for gripping. Once such gripping
occurs, the strap is tensioned as a loop onto the
article by a pulling force applied to the feed portion
of the strap, after which the leading end and feed
portions of the tensioned strap loop are sealed together.
For simplicity and use of description, ~strapping
mechanism" or simply "mechanism" as employed herein
encompass such mechanisms as include at least means for
gripping the leading end portion of a strap after it has
been looped or laced about an article to be strapped.
Desirably, but not necessarily, means for sealing
the overlying leading end and feed portions of the strap
liZ7~S7
loop after tensioning thereof is completed are included
as part of such mechanism. Means for holding or grip-
ping the feed portion of the strap and for feeding and
tensioning of the strap are of course necessary in the
apparatus of this in~ention and may be mounted on
portions of the apparatus separate from the strapping
mechanism. In certain embodiments hereafter described
one of such gripping, feeding and tensioning means is
included as part of the strapping mechanism, while in
still other described embodiments, all of such means are
part of the strapping mechanism. A typical example of
such strapping mechanisms which includes means for
feeding snd tensioning of strap, for gripping the strap
before and after the tensioning thereof, and for sealing
of overlying portions thereof is described, for example,
in Vnited States patent 3,759,169, issued September 18,
1973 to G. F. Goodley.
Strapping mechanisms as described above may be
housed below an article supporting table, as described
in the cited Goodley patent, or as incorporated in
conventional semi-automatic strapping machines, so that
the strapped article has a bottom strap seal; that is,
with overlying strap portions being sealed adjacent to
the bottom of such article. Such strapping mechanism
may also be oriented relative to the article supporting
table so as to provide a tensioned strap loop having a
seal along the top or side of the article or be employed
in a pallet strapping machine or a horizontal strapping
machine, for example as disclosed in ~nited States
patents 3,949,662, issued April 13, 1976 to W. H. Woomer,
and 4,005,647, issued February 1, 1977 to Goodley et
al., respectively, to provide an article with a side-
sealed tensioned strap.
~Z7~57
In accordance with the present invention, there is
provided an improved strapping method and apparatus in
which a strap loop is disposed about an article and
tensioned to a high degree by imposing a pulling force
on the leading end portion as well as to a feed portion
thereof, after which overlying leading end and feed
portions of the strap are sealed together to retain the
strap loop in its tensioned condition about the article.
While the prior art strapping machines described
above perform weil, the application to articles of strap
loops which are under still greater tension, without any
or significant sacrifice in the advantages now provided
by such machines, is desirable, if not essential, in
certain article strapping operations. Accordingly, a
primary advantage of this invention is to provide an
improved strapping method and apparatus for applying
tensioned strap loops about articles.
Another advantage is the provision of an improved
method and apparatus for strapping of articles with
tensioned strap loops in which tension variations along
the length thereof are reduced or minimized during the
application thereof.
Still another advantage is the provision of an
improved method and apparatus for strapping of articles
with tensioned strap loops which exhibit better tension
maintenance characteristics.
A still further advantage is the provision of an
improved article strapping method and apparatus in which
friction encountered during tensioning of a strap loop
about an article is significantly overcome.
A still further advantage is the provision of an
improved article strapping method and apparatus which is
adapted to apply a highly tensioned strap loop that is
sealed along the bottom, top, or side of an article.
It will be understood that the terminology
~imposing a pulling force~, and similar language employed
~iZ7~57
-- 4 --
in the description and claims, involves the application
of a pull on the feed and/or leading end portions of the
strap that is looped about the article to be strapped so
as to tension or still further tension the strap loop.
For example, w~th a strap looped or laced about an
article and gripped at its leading end portion, imposing
a pulling force on the feed portion of the strap so as
to move or retract the same will tension the strap loop
onto the article and, while at least maintaining the
tension in such strap loop, imposing a pulling force on
the leading end portion of the strap as to move the same
will still further tension the strap loop.
More particularly, as in conventional strapping
procedures, the method of this invention involves
feeding a strap longitudinally from a supply, lacing
the same either through a yoke or manually along a path
disposed in a plane and extending about an article which
is to be strapped to provide a strap loop having the
strap leading end and feed portions thereof in overlying
relationship. While in conventional procedures tension-
ing of the strap loop is achieved by simply imposing a
pulling force on the feed portion of the strap while the
leading end portion of the strap is gripped, by the
method of this invention the strap loop is tensioned
about the article by imposing pulling forces on both the
leading end and feed portions of the strap. Thus, by
the method here described, a strap loop which has been
tensioned about an article by imposing a pulling force
on one of the leading end and feed portions thereof, is
still further tensioned by imposing a pulling force on
the other of such leading end and feed portions, after
which the overlying leading end and feed portions of the
now highly tensioned strap loop are sealed together.
In conventional strapping procedures, during the
tensioning of a strap looped about an article, the
movement of the successive strap segments which are
l~Z7957
-- 5 --
between the feed and leading end portions thereof is
progressively retarded by the cumulative friction that
is developed. As a result, the leading end and feed
portions of such tensioned strap are under significantly
different tensions. Thus, a tension intermediate of
these different tensions will exist in the strap length
which is provided upon sealing of such leading end and
feed portions. Moreover, the tension in this particular
length of the applied strap loop will differ from those
10 which exist in the strap lengths that are engaged with
other faces of the strapped article, and especially the
ætrap length which i8 most remote thereto. For example,
in a strap loop applied to an article of rectangular
configuration, that length of the applied strap loop
15 which includes the sealed strap portions will be under a
substantially greater tension than that existing in the
strap length engaged with an article face opposite
thereto. The different tensions along these lengths of
the applied strap loop tend to equalize with time and/or
20 movement of the strapped article, as during storage
and/or shipment thereof, so that the entire applied
strap loop may slacken somewhat.
On the other hand, by imposing a pulling force on
the leading end portion of the strap loop, as well as
feed portion thereof, in accordance with the method of
this invention, the frictional forces acting upon the
strap loop may be largely overcome. As a result, the
tension in the strap length which is provided upon the
sealing of such leading end and feed portions will be
30 greater than that which is achieved by conventional
procedures; that is, will more closely approach, or be
equal to, or even exceed the tension which is applied to
the feed portion of a strap loop by such conventional
procedures. Moreover, by the method of this invention
1~279S7
greater lengths of the applied strap loop are initially
under tensions which at least approach the imposed
pulling forces. Thus, as the overall initial tension in
the strap loop is higher than is achieved by conventional
procedures, and as a lesser degree of tension equaliza-
tion can occur in the strap loop after overlying portions
thereof are sealed together, the applied strap loop is
retained snugly against the strapped article under a
comparatively high tension.
As heretofore mentioned, in the method of the
present invention, pulling forces are imposed on both
the leading end and feed portions of the strap. These
pulling forces are desirably imposed, at least in part,
in sequence, and while the pulling force may be at least
initially imposed on either the leading end or feed
portion of the strap, it is most practical, and thus
preferred, that a pulling force be imposed first on the
feed portion of the strap. As such pulling force is
imposed on the feed portion of the strap, the leading
end portion of the strap is fixed to tension the feed
portion of the strap and the strap looped about the
article. As in conventional procedures, frictional
forces retard the movement of the strap relative to the
article and thus at this stage the tension in the feed
portion of the tensioned strap loop will be greater than
that in the leading end portion of such tensioned
loop.
With the tension in the feed portion of the ten-
sioned strap loop now being at least maintained, imposing
a pulling force on the leading end portion of the
strap will increase the tension in the strap loop. The
pulling force imposed on the leading end portion of the
strap may be less than, equal to, or greater than that
imposed on the feed portion. Thus, if the pulling force
imposed on the strap feed portion is simply maintained
after the strap loop has been tensioned about an article,
l~Z7g57
the pulling force imposed on the leading end portion may
be: (a) less than that imposed on the feed portion of
the strap so as to provide for some increase in the
tension in the strap loop; (b) or may be essentially
equal to that imposed on the feed portion of the strap;
(c) or may be greater than that imposed on the feed
portion of the strap but should not be of such magnitude
as to cause the tensioned strap loop to simply move as a
unit relative to the article.
Alternatively, once the pulling force imposed
upon the feed portion of the strap tensions the strap
loop about the article, such pulling force may be
continued and increased while a pulling force is imposed
on the leading end portion of the strap. In this
instance, the pulling force applied to the leading end
and feed portions of the strap may differ as heretofore
described.
As a still further alternative, the feed portion
of the strap may be fixed or held after a pulling
force is imposed thereon to tension the strap loop
about the article and the pulling force then imposed
on the leading end portion of the strap may be less
than, equal to, or greater than that imposed on the
feed portion of the strap. In this instance, as
the feed portion of the strap is fixed, the pulling
force imposed on the leading end portion of the strap
may significantly exceed the pulling force imposed on
the feed portion of the strap without shifting of the
tensioned strap loop and unit relative to the article.
Preferably, the leading end and feed portions
of the strap are so gripped that, after tensioning of
the strap loop is completed, overlying leading end and
feed portions of the strap which are to be sealed are
directly adjacent to the tensioned strap loop and are in
a relaxed or only slightly tensioned condition. Thus,
the sealed portion of the applied strap loop will be
1~27gs7
under a tension which may be less than, equal to or
greater than that imposed on the feed portion of the
strap loop prior to the sealing thereof, and in all
instances will be greater than that achieved by conven-
tional procedures.
As conventional strapping procedures involvefeeding or lacing a strap along a path spaced from the
article which is to be strapped, the leading end and
feed portions of the strap loop will overlie and are
normally sealed ~ogether at a location which is spaced
from the strapped article. Thus, when such sealed strap
portions are released from the position of sealing, the
tension in the strap loop draws the same against the
strapped article. Of course, this results in some
sacrifice in the overall tension in the applied strap
loop which may be tolerable, as when employing a semi-
automatic strapping machine, or rather significant, as
in strapping of pallet-supported articles where strap
sealing generally occurs at a location spaced perhaps 3
or more inches away from the article.
Accordingly, in some embodiments of the method of
this invention, it is preferred that, prior to imposing
any tension onto a strap loop or during such tensioning,
the overlying leading end and feed portions thereof are
together moved a predetermined distance toward, and
desirably directly adjacent to the article which is to
be strapped. In this manner, the subsequently tensioned
and sealed strap loop more closely approaches the
perimeter of the article to which it is applied so that
sacrifice in the overall tension in such strap loop is
certainly minimized.
The apparatus of the present invention is similar
to conventional strapping machines in that it includes a
support, means for feeding a strap having leading end
and feed portions for looping about an article which is
to be strapped, and a strapping mechanism which includes
li2~9~7
at least means for gripping the leading end of a strap.
As also present in such known machines, the apparatus
of this invention includes tensioning means for impos-
ing a pulling force on the feed portion of a strap
looped about an article, means for use in holding or
gripping such strap feed portion to maintain tension
in a strap loop, and means for sealing overlying leading
end and feed por'ions of a strap.
As such conventional machines generally include
a housing, which is part of the machine frame, for
containing the strapping mechanism, the apparatus of
this invention is hereafter described as also including
such housing as part of the support of the apparatus.
Further, in both known strapping machines and in the
apparatus of this invention strap guide means are
provided which define a strap passage disposed in a
plane. In the case of a semi-automatic strapping machine,
such guide means assists in positioning the leading end
portion of a strap for access and manual lacing as a
loop about an article which is to be strapped, while in
an automatic strapping machine, the guide means would
include at least a yoke, and perhaps a lance in a pallet
strapping apparatus, for lacing a strap as a loop about
an article which is to be strappedO In both semi-
automatic and automatic strapping machines, the strap islaced as a loop, preferably in the plane of the passage
as defined by the guide means, with strap leading end
and feed portions disposed in overlying relationship.
Distinguishing the apparatus of this invention
from those known in the art is that the strapping
mechanism is mounted for movement relative to the
apparatus support or housing in the plane defined by the
strap guide means. Further, the apparatus includes
means for moving such mechanism between retracted and
projected positions so that a pulling force may be
imposed on the leading end portion which is gripped by
1~27957
-- 10 --
the gripping means of such mechanism. Thus, with the
apparatus of this invention, pulling forces of different
magnitude may be imposed on the leading end and feed
portions of a strap, and may be imposed sequentially
so that a strap looped about an article may be ten-
sioned about the article by imposing one of such pul-
ling forces and then still further tensioned by im-
posing the other of such pulling forces.
The support of certain embodiments of the apparatus
of this invention also differs from those of conventional
machines in that it includes a fixed structure and a
carriage. In such embodiments, the strapping mechanism
and its housing are mounted on the carriage and means
are provided for moving the carriage between retracted
and projected positions, the latter of which is located
near and desirably directly adjacent to the article
which is to be strapped.
More specifically, in the apparatus of this inven-
tion, movement of the strapping mechanism between its
retracted and projected positions is in the plane of the
strap passage, and is achieved by a separate drive means.
For example, in apparatus for strapping articles
with side-sealed strap loops, such as with pallet
strapping apparatus constructed in accordance with the
present invention, movement of the strapping mechanism
relative to its housing occurs along the vertical plane
within which is disposed the strap passage, and is
preferably achieved in at least one of its directions of
movement by a drive means. Thus, if in such apparatus
the strap loop within the strap passage is such that a
downward pulling force is to be imposed on the leading
end portion thereof during tensioning of the strap loop,
part or all of the weight of the strapping mechanism may
be relied upon to urge the same into its projected
position to impose such pulling force. In this instance,
the drive means may be used so as to supplement the
1~2~
gravitational force acting on the strapping mechanism
and would also serve to elevate such into its initial
retracted position after strap loop sealing is completed
Alternatively, if in such apparatus the strap loop is
such that during tensioning an upward pulling force is
to be imposed on the leading end portion thereof, the
drive means projects the strapping mechanism in such
upward direction relative to its housing with a force
such that its weight is more than counterbalanced. In
this instance, the strapping mechanism may be returned
to its initial retracted position by gravity after strap
loop sealing has been completed.
Regardless of the direction and/or manner of
movement of the strapping mechanism relative to its
housing, during tensioning of the strap loop, it is
preferred that the strap tensioning means first performs
its intended tensioning function on the feed portion of
the strap loop and then at least maintains such tension
while and until the pulling force imposed on the leading
end portion of such tensioned strap loop achieves the
intended supplemental loop tensioning. This sequence is
most practical as it insures that the pulling force
imposed on the leading end portion of the strap loop
does not assume all or part of the function of the strap
tensioning means and is not merely compensated by
tension relaxation along feed portion thereof but does,
in fact, achieve increased tension in the strap loop.
As mentioned, in certain embodiments of this inven-
tion the strapping mechanism and its housing are sup-
ported by a carriage which is also capable of movementin the plane of the strap passage, but in a direction
generally perpendicular to the direction of movement of
the strapping mechanism relative to its housing. For
example, in a pallet strapping apparatus, as the
~127~S7
strapping mechanism would be moved vertically along the
plane of the strap passage to impose a pulling force on
the leading end of a strap loop, as described above, the
carriage would also be moved within this same plane, but
in a horizontal direction. The function of such car-
riages is to position the strapping mechanism close
to and desirably directly adjacent to the article which
is being strapped. Thus, in such pallet strapping
apparatus, in the retracted position of the carriage the
strapping mech~nism and housing are aligned with a yoke
and together define a strap passage, while in a pro-
jected position of the carriage the strapping mechanism
is close to the article which is being strapped.
In a horizontal strapping apparatus constructed in
accordance with present invention, tne carriage would
likewise serve to project the sealing mechanism directly
adjacent to the article which is to be strapped.
Movement of the carriage between its retracted and
projected positions would occur in the horizontal plane
of the strap guide means and would be in a direction
perpendicular to the movement of the strapping mechanism
in such same horizontal plane.
The presence of the carriage in such embodiments of
the apparatus of this invention in no way interferes
with the feeding of strap into and along the strap
passage or in the delivery of articles into and/or
from the apparatus, yet it facilitates the application
of tensioned strap loops which more snugly grip the
strapped article. In general, carriage movement between
retracted and projected positions of from about 3 to 12
inches is desirable and, preferably, control means are
provided to insure that tensioning of a strap loop
occurs only after such carriage has assumed its pro-
jected position.
The method and apparatus of the present invention
are applicable for use with a variety of articles which
~1Z7957
may vary in size and/or shape and which may consist, for
example, of a single unit or package or a series of
units or packages in a stacked array.
The term "strap" and "strapping" as used herein are
intended to include conventional flat, narrow elongated
flexible structures which are capable of being fed
longitudinally, and particularly but not limited to,
structures which are formed of synthetic thermoplastic
materials, such as, polypropylene, nylon, and poly-
esters, which have been stretched and/or rolled toorient the molecules thereof. Further, the term
~sealing~ as employed herein includes connecting
of overlying strap portions, as by thermal welding,
metallic seals, adhesives, and the like. Preferably,
lS but not ~y way of limitation, thermal softening of
opposing surfaces of overlying portions of plastic strap
is achieved as described in the above cited Goodley
patent.
For the sake of simplicity and ease of description,
the present invention is hereafter described in detail
as employed in strapping of pallet-supported articles
and, more particularly, employing a machine as disclosed
in the above cited Woomer patent, into which are incor-
porated the teachings of the present invention. In
addition, embodiments of semi-automatic strapping
apparatus incorporating the teachings of this invention
are described to illustrate the wide applicability of
this invention.
In the drawings, Figure 1 i5 a side view of one
embodiment of the apparatus of the present invention,
with portions thereof broken away;
Figure 2, illustrates on an en~arged scale,
a portion of the apparatus shown in Figure 1 in its
operative position;
Figures 3 and 4 are fragmentary views of a
portion of the apparatus as seen in the direction of
1~27957
- 14 -
arrows III-III and IV-IV, respectively, in Figure 1;
Figure 5 is a partial side view showing
elements of the strapping mechanism as seen from the
side opposite that shown in Figures 1 and 2;
Figures 6 and 7 are fragmentary diagrammatic
views showing details of the strapping mechanism illu-
strated in Figure 5;
Figure 8 is a diagram of a pneumatic system
incorporated in the apparatus shown in Figure 1;
Figures g and 10 together are a diagram of the
electrical system of the apparatus shown in Figure 1;
Figur~s 11, 12, and 13 are schematic views
showing the apparatus of this invention during various
stages of its operation; and
Figures 14, 1S and 16 are embodiments of
semi-automatic strapping machine incorporating the
present invention.
The apparatus of Figures 1-13 is adapted to be
integrated into a production or packaging system and
is illustrated in Figures 1 and 2, in position to apply
tensioned strap loops about articles A which are carried
by pallets P and delivered by a conventional roll
conveyor C. The pallet P is of the conventional two-
deck construction having a lower deck 15 and an upper
deck 17 which are secured to spacers disposed between
such decks.
The overall appearance of this apparatus and
certain stages of its operation are similar to the
pallet strapping machine disclosed in United States
3~ patent 3,949,662, issued to W. H. Woomer. Thus, where
such similarities exist reference will be made to this
cited Woomer patent for the sake of brevity.
Turning to Figures 1-3 of the drawing, the appar-
atus has an appropriate support or framework which
includes a base 19, a pair of laterally spaced columns
21, a pair of laterally spaced uprights 25 and a channel
~27957
27 connected inwardly of its ends to the columns 21 and
uprights 25 with web 29 and flanges 31 disposed as shown
in Figure 3. Means for guiding strap about an article A
includes yoke sections 33, 35, 37 and 39 and a lance 41,
the latter of which is supported and reciprocated
between a retracted position and a projected position,
as indicated by broken and solid lines as shown in
Figure 1, by a shaft 43. Rotation of the shaft 43 is
by a mechanism as indicated at 45 which includes an
lO electric motor 47 and a chain 49.
Strap S which is to be applied to article A is
drawn from a supply coil which is carried by a suitable
dispenser 51 fixed to the channel 27. As strap S is
drawn from the supply coil, it is passed about a dancer
15 arm roll 53 led by rolls into and through a strap
accumulator 55 and into a strapping mechanism which is
indicated generally by the character 57. In this
embodiment, and as hereafter described in detail, the
strapping mechanism includes means for gripping both
20 the leading end and feed portions of strap, means
for feeding and applying tension to the feed portion
thereof, and means for sealing overlying portions of the
strap after pulling forces are applied to its feed and
leading end portions.
The apparatus of the present invention thus far
described in detail is generally similar to known pallet
strapping machines, such as that disclosed in the cited
Woomer patent 3,949,662~ However, differing signifi-
cantly from such known machines is that the strapping
3~ mechanism 57 of the apparatus of the present invention
is mounted for vertical movement relative to a housing,
which is indicated generally at 59, and that such
housing 59 is in turn supported on a carriage ~1 which
is movable horizontally between a retracted and a
35 projected position as shown in Figures 1 and 2. In this
embodiment, both the housing 59 and carriage 61 are
~1279~7
- 16 -
considered to be part of the apparatus support.
More specifically, as best shown in Figures 2 and 3
the carriage 61 includes a slide plate 63 which is
stiffened by bars 65 and is supported and guided for
horizontal movement by a series of rollers 67 and 69.
Roller spindles 71 are mounted on plates 73 which are
bolted at 75 to the vertical flanges 31 of the channel
27. The rollers 69 project through suitable openings in
the channel web 29 to elevate and thus provide for free
movement of the slide plate 63 relative to such web 29.
l0 Angle members 77 are also fixed to the plates 73 to
provide a guard for rollers 67. Linear movement is
imparted to the carriage 61 by a conventional pneumatic
cylinder assembly having a piston rod 79 pivoted at 81
to the channel 27 and a cylinder 83 pivoted at 85 to the
15 slide plate 63.
The housing 59 may consist simply of a top plate 87
and corner angle sections 89 which are fixed to the
carriage 61, while the strapping mechanism 57, includes
top and bottom plates 91 and 93 which extend laterally
20 beyond the remainder of such mechanism. Rod 95 is fixed
to the top plate 91 of the strapping mechanism 57 and
extends freely through an opening in the housing top
plate 87 and similar rods 97 are fixed to the carriage
slide plate 63 and project through openings 99 in the
25 bottom plate 93 of the strapping mechanism 57 for
guiding the same during its movement in a vertical
direction, as hereafter described. Obviously, the area
between the strapping mechanism 57 and the article A
must be unobstructed and thus the channel web 29,
30 carriage slide plate 63 and the bottom plate 93 of such
strapping mechanism 57 are provided, respectively, with
slots 101, 103, and 105 which are aligned w~th each
other, with a similar slot being formed also in the top
plate 87 of the respective housing 59.
11;~7957
-- 17 --
As shown in Figure 1, in the retracted position of
the carriage 61, the yoke sections 33, 35, 37 and 39 and
the lance 41 cooperate with the strapping mechanism 57
to provide a generally continuous passage through which
5 the strap S may be longitudinally fed to form a strap
loop about the article A. The yoke section 33 is fixed
to the base 19 and by braces 107 to the uprights 25,
while the yoke section 35 is hinged at 109 for swinging
movement as indicated by broken lines. Under the action
of a torsion sp-ring 111 the yoke section 35 normally
assumes its position as shown in solid lines in which it
bears against a stop pin 1 13.
During lacing, the leading end portion of the strap
fed by the strapping mechanism 57 is guided into the
15 yoke section 3 5 by the yoke sect ion 37 and, after
travelling along the yoke section 33 and the lance 41,
is returned into the strapping mechanism 57 by the yoke
section 39. Turning to Figure 5, the yoke sections 37
and 39 are fixed only to the strapping mechanism 57 and
20 are free to move relative to the slide plate 63 and the
top plate 87 of the housing during vertical travel of
such strapping mechanism.
The yoke sections 33, 35, 37 and 39 are of conven-
tional construction, and typical of such construction is
25 the yoke section 37 shown in Figure 4. This yoke
section 37 includes a beam 115, gates 117, a gate
retainer bolt 119 and nut 121, springs 123 and spring
cups 125. The gates 117 are pivoted at 127 to the beam
115 and together with the beam flange 129 define a
30 passage 131 for the strap S. During tensioning of strap
laced through the yoke section, the gates 117 are
pivoted apart by the tensioned strap, the strap is
released, and the springs 123 return the gates 117 to
their illustrated positions, with their movement beinq
35 dampened by resilient inserts 133.
S7
- 18 -
The strapping mechanism 57, except for its capabil-
ity of moving vertically relative to the housing 59, and
certain control aspects, is essentially the same as
disclosed in the cited Woomer patent. Only such details
of the strapping mechanism 57, including its control
systems, sufficient to provide an understanding of the
invention will be described herein.
The strapp~ng mechanism 57, as shown in Figure 5,
includes strap feed and tensioning means indicated at
135 which serves to draw strap from the supply coil, and
feed the same longitudinally through a gripper assembly
137 and up into and through the yoke segment 37. After
travelling sequentially along the sections 35 and 33 and
the extended lance 41, and the yoke section 39, the
leading end portion of the loop of strap thus fed about
the article A returns to the strapping mechanism 57 and
is gripped by the gripper assembly 137. During subse-
quent tensioning, the strap loop is pulled snugly
against the article A, with the strap that is withdrawn
during such tensioning being collected within the
accummulator 55.
More specifically, and with reference to Figures
5-7, the strap feed and tensioning means 135 includes
tensioning and feed wheels 139 and 141 which are mounted
on shafts 143 and 145, re~pectively, and geared together
by gears, not shown. The shaft 143 is driven by a chain
147 passing around a sprocket 149 fixed to such shaft
143 and a sprocket 151 fixed to a shaft 153 of a rever-
sible air motor 155. By means including an idler
sprocket 157 and pivot arm 159, the tension in the lower
reach 161 of the chain 147 is sensed so as to actuate a
tension switch TS, and cause the air motor 155 ~o stall
when the strap loop being applied to the article A is
under a predetermined tension, as hereafter described in
detail.
The gripping assembly 137, as best shown in Figures
and 7 includes front and rear grippers or holding
llZ7~
- 19 -
means 163 and 165, respectively. During initial feeding,
the strap S passes through an aperture 167 in the front
gripper 163, an aperture 169 in a fixed shear plate 171,
past a cutoff knife 173, between a movable sealing
platen 175 and a retractable tongue 177 and between the
rear gripper 165 and a retractable anvil 179. With
continued feeding of the strap along the generally
continuous passage as heretofore described, the leading
end portion 18i of the strap passes between the front
gripper 163 and the anvil 179 and between the tongue 177
and such anvi~ 179 until it strikes a stop 183. The
rotation of the wheels 139 and 141 continues but as an
overfeed loop of strap develops at the tension wheel
139, a pivot flag 185 is moved to operate a strap limit
valve SV which causes the front gripper 163 to close and
grip the strap leading end portion 181 and stop the air
motor 155.
The elements of the strapping mechanism 57 de-
scribed above relating to the feeding, gripping, sealing
and cutting of the strap are essentially the same as
described in the cited Goodley and Woomer patents and,
preferably, the operation of these elements is effected
by the linear activator LA and cam assembly LC as
described in these cited patents.
In the illustrated embodiment, this upward movement
of the strapping mechanism 57 into a projected position
is achieved by a pneumatic means which includes an air
cylinder 187 fixed to the housing top plate 87 and a
piston having an operating rod 189 connected to the top
plate 91 of such strapping mechanism 57.
In describing the se~uence of an operational cycle
in accordance with the preferred method of this inven-
tion, reference is made primarily to Figures 8-1 n and to
the schematic views shown in Figures 11-13. To better
appreciate the functions of the various control ele-
ments, it will be understood that the apparatus is in
condition for performing an operational cycle when the
1127957
- 20 -
strapping mechanism 57 in its home or retreat position,
the carriage 61 also in its home or retracted position
and the strap S having been pre-fed along the yoke
sections 37, 35 and 33.
To assist in the understanding of the operational
cycle, the function of certain of the limit and pressure
electric switches is provided as follows:
Limit Switches
Limit switches LS-1 and LS-2 control the motor 47
for extension and retraction of the carriage lance
mechanis~ 45 by deenergizing motor starter relay ME
(motor extend) and motor starter relay MR (motor
retract) respectively.
The horizontal home limit switch 191 indicates the
position of the carriage 63. When the carriage is fully
retracted, it deenergizes relay R-7 to allow strap
feeding through the yoke at the beginning of a machine
cycle or at the end of a strapping cycle to pre-feed the
yoke.
The top plate limit switch 195 when actuated
energizes the solenoid S-1 carriage stop solenoid valve
197 to stop movement of the carriage 63 and initiates
strap tensioning.
The cam limit switch 199 controls the descent of
strapping mechanism 57 and retraction of the carriage 63
Pressure Electric Switches - PE
Switch PE-l initiates extension of the carriage 63.
Switch PE-2 is actuated when the strap is fully ten-
sioned and controls dwell of the linear cam LC. In the
preferred embodiment here described, the switch PE-3
controls relay R-6 which will not energize and allow
vertical floating or driving of the strapping mechanism
57 should the carriage 63 not move a predetermined
distance toward the article A~
In Figure 8, compressed air is supplied at AS, and
in Figure 9 electric supply is indicated at ES. Shown
in Figure 9 is a switch SW-1 which can be set for either
11~79S7
- 21 -
automatic or manual operation, whereby the respective
lights AL and ML are illuminated, and as illustrated
this switch SW-1 is set for automatic operation.
Initiation of a machine cycle begins by either depres-
sing the Cycle Start pushbutton 201 or by an inputsignal energizing relay R-1. This will energize the
machine cycle timer TDR-4, set the lance extend-retract
switch SW-2 in~ iss extend position and the strap feed
and tension swicch SW-3 in its feed position as shown in
Figure 9, and energize the motor starter relay ME (motor
extend) starting the motor 47 and causing the lance 41
to extend through the void in the pallet P. Upon lance
extension of approximately one inch, the rear limit
switch LS-2 is closed, energizing the relay R-5 which
causes the "lance retracted" light 203 to be extin-
guished, energizes the lance blockage timer TDR-2,
and prepares the motor starter relay MR (motor retract)
for retracting the lance 41 at the end of the strapping
cycle.
Upon full extension of the lance 41, the front
limit switch LS-1 will close, thereby energizing the
relay R-4 and illuminating the "lance extended" light
205 and deenergizing the lance delayed timer TDR-2. In
the event that the front limit switch LS-1 does not
close, as when the lance 41 is blocked during its
extension, the relay R-4 will not be energized and the
lance delayed timer TDR-2 will time out, illuminating
the ~trouble" light 207 and energizing the relay R-3.
This, in turn, deenergizes the relay R-1 and halts the
machine cycle. Upon depression of the reset 209 button,
the lance 41 will be retracted into its original stowed
position.
With the energization of the relay R-4 as described
above, the motor starter relay ME (motor extend) will be
~5 deenergized thereby stopping the motor 47. At this time
the solenoid S-3 of the valve V-6 will actuate the valve
V-4 so as to direct air into the air motor and cause
liZ7957
- 22 -
strap S to feed through the strapping mechanism 57 and
along the yoke sections 37, 35 and 33, the lance 41 and
the yoke section 39 until its free end 181 contacts the
stop 183. The strap S then starts to buckle and a loop
of strap develops at the tension wheel 139, causing the
flag 185 to pivot actuating the strap limit valve SV
which shifts the valve V-l. Air is now directed to the
front gripper 163 which grips the strap free end portion
181 against the anvil 179.
At this tim~, the pressure electric switch PE-l is
activated, energizing the solenoid S-4 carriage projection
valve 211 which directs air to the piston side of the air
cylinder 83 and causes the carriage 61 to be projected
t~ward the article A which is to be strapped. Upon a
predetermined travel of the carriage 61, the carriage
limit valve 213 opens to the atmosphere, exhausting air
from the piston side of the ver~ical float/drive cylinder
187 and activating the switch PE-3. As the switch PE-3
i8 closed, the relay R-6 is energized, thereby activating
the solenoid S-5 of vertical float valve 215. The air
pressure is regulated by the float pressure regulator 217
at such pressure as to provide a force to the cylinder
rod 189 as might be necessary to counterbalance the
weight of the entire strapping mechanism 57, thus this
mechanism 57 is prepared for counterbalancing after the
pulling force applied to the feed portion of the strap S.
Hinged at 191 to the housing 59 are top plates 193
which, when engaged with the article A during carriage
projection, pivot and actuate a top plate limit switch
~95 that energizes the carriage stop solenoid S-1 and
energizes the solenoid S-6 of the valve V-5. At this
stage, with the horizontal traverse or projection of the
carriage 61 now halted, the solenoid valve V-5 directs
air into the air motor for strap tensioning. When this
strap is tightened sufficiently around the article A to
move the idler sprocket 157, shown in Figure 5, the
tension limit switch TS is disengaged, thus closing its
~27~
- 23 -
contact and the relay R-2. This stage is illustrated in
Figure 11 and shows the strap as would be tensioned to
its maximum degree by conventional strapping methods and
machines. However, with the embodiment of the apparatus
of this invention here described in detail, closing of
the relay R-2 energizes the tension delay timer TDR-5 and
the solenoid S-7 vertical drive solenoid valve 219 which
pressurizes the cylinder rod side of the vertical float/
drive air cylinder 187. The air input is regulated by
the drive regulator 221 which is set at a pressure which
will provide a force to the cylinder rod 189 such that,
taken with any upward force exerted on the mechanism 57
by the tensioned strap, the weight of the entire strapping
mechanism 57 is counter-balanced.
When the drive regulator is set such that the force
applied to the cylinder rod 189 provides for counter-
balancing the weight of the strapping mechanism 57, the
apparatus is now conditioned to impose a pulling force
on the leading end portion of the strap which at least
more closely approaches, and desirably equals the pull-
ing force applied to the feed portion of the strap loop
so that the tensions in such strap portions, are gener-
ally the same. This stage is shown in Figure 12.
Thus, when the drive regulator 219 is set so that
the force applied to the cylinder rod 189 is greater than
that necesary to counterbalance the strapping mechanism
57, the mechanism 57 is driven upwardly with a force
such that the pulling force acting on the leading end
portion 1~1 of the strap loop more closely approaches or
equals that acting upon the feed position of such strap
loops. This stage is illustrated in Figure 13.
As the solenoid valve V~5 is still energized, the
air motor continues to tension the strap, stalling the
air motor 155. The tension regulator 223 regulates the
air pressure through the solenoid valve V-5 which, in
turn, regulates the amount of torque the air motor 155
will provide. Once the tension delay timer TDR-5 times
l~Z7957
- 24 -
out, the solenoid valve V-10 is energized providing air
to shift the valve V-2 which, simultaneously, actuates
the switch PE-2 to deenergize the valve V-5. As a
result, strap tensioning is stopped, the linear cam dwell
timer TDR-1 is energized, the rear gripper 165 is actuated
to clamp and hold the feed portion of the strap loop
against the anvil 179, and air is directed to the piston
side of the linQar cam cylinder which extends the linear
cam.
As this linear cam extends, the cam limit switch
199 closes and after the tensioned strap is cut and
sealed by a heated blade 225, the linear cam dwell timer
TDR-1 times out and deenergizes the relay R-l. The motor
starter relay MR (motor retract) is thereby energized so
that the lance 41 is withdrawn, and the relay R-2 is also
deenergized, as are the vertical drive solenoid valve 219
and the tension delay timer TDR-5. The latter deenergizes
the solenoid S-8 of the valve V-10.
The timing out of the linear cam dwell timer TDR-1
also energizes the relay R-8 which holds itself in, and
also deenergized by the relay R-l is the solenoid valve
V-6 so that air passes thro~gh solenoid valve ~-6 to
shift the valves ~-1 and V-2. Once shifted, the valve
V-2 exhausts air from the rear gripper 165 and directs
air to the rod side of the linear cam cylinder, retracting
the cam and thus opening the anvil 179 to eject the strap
and open the cam limit switch 199. In addition, its
switch PE-2 returns to its normal position. The shifted
valve V-l exhausts air from the front gripper 163 and
allows the switch PE-l to return to its normally open
position~
The carriage projecting solenoid valve 211, the
carriage stop solenoid valve 197, and the vertical float
solenoid valve 215 are now deenergized, but the carriage
61 will not retract until the strapping mechanism descends
to close the vertical home limit valve 227. Once this
has been achie~ed, and the carriage 61 is retracting, the
-
~1279~7
- 25 -
carriage limit valve will actuate 213, pressurizing the
piston side of the vertical float/drive cylinder, and the
switch PE-3 deenergizes the relay R-6.
Upon full retraction of the carriage 61, the hori-
zontal home limit switch 191 is actuated, deenergizingthe relay R-7 which, in turn, energizes the pre-feed
cycle timer TDR-3 and the solenoid valve V-6. Air is now
directed to the pilot of the valve V-4 which actuates and
directs air to the air motor 155, again feeding strap
S through the strapping mechanism and yoke sections 37,
35 and 33. When the pre-feed cycle timer TDR-3 times out,
it denergizes the relay R-8 which, in turn, deenergizes
the pre-feed cycle TDR-3 and solenoid valve V-6 which
stops the air motor 155 and halts the feeding of strap.
Turning again to Figures 11-13, at the stage shown
in Figure 11, the strapping mechanism 57 is disposed
directly adjacent to the article A which is being
strapped, the leading end portion 181 of the strap loop
is gripped and such loop is being tensioned onto the
article A by the tensioning means 135. The tension in
the respective portions or legs 197, 199, 201, 203, and
205 of the applied strap loop are indicated at T1, T2,
T3, T4 and T5, with the frictional forces which retard
the movement of the strap loop during tensioning,
particularly at the article corners, are indicated as
F1, F2, F3 and ~4.
Obviously, the tension in the ~trap loop decreases
progressively along the length thereof, from a maximum
tension T1 to a minimum T5. As the tension T5=T1-F1-F2-
F3-F4, if the leading end and feed portions of the
applied strap loop were to be sealed at this stage, the
tension in the side of such sealed strap loop formed by
the legs 197 and 205 would be intermediate to that of T1
and T5.
In accordance with this embodiment of the present
invention, and as illustrated in Figure 12, after and
during continued tensioning of the strap loop by the
11~Z7957
tensioning means 135, the strapping mechanism 57 is
urged upwardly with such force that its weight is
counterbalanced as indicated by the arrow 209.
By applying an upward force to the strapping
mechanism 57 which is greater than the weight of such
mechanism 57, as indicated by the arrow 211 in Figure
13, the legs 197 and 199 of the strap loop are under
tensions T1 and T2, as developed by the pulling force
imposed by the tensioning means 135. The legs 205 and
203 are under tensions T5 and T4 which are applied by
the projected strapping mechanism 57 and, desirably
approach or are equal to the respective tensions T1 and
T2, while the tension T3 in the leg 201 of the strap
loop is that which extends generally equally toward
opposite ends thereof, as applied by the tensioning
means 135 and the projected strapping mechanism 57.
More specifically, desirably T1=T5 and T2=T1-F1=T4=T5-F4,
while T3=T2-F2=T4-F3 and is greater than that achieved
in Figure 11.
Upon sealing of the legs 197 and 205 of the strap
loop, the tension in the resulting side of applied strap
will be equal to the tension originally existing in such
legs or T1 which is equal to T5.
The upward driving force imposed on the strapping
mechanism 57, as indicated by the arrow 211 in Figure
13, will depend upon the frictional forces which are
encountered during the strapping of a particular article
A and which, in turn, depend on the characteristics of
the strap S which is being applied, such as its lubricity
and surfaced smoothness. Obviously, frictional forces,
such as Fl, F2, F3 and F4, will exist and, while the
strapping mechanism 57 may be driven upwardly with a
force which is greater than the weight of such mechanism,
such upward driving force should not be such as to lift
the article A or to exceed the retarding frictional
forces, such as F1, F2, F3 and F4, so as to cause the
loop of strap to slide as a unit relative to the article
957
- 27 -
A.
While the preferred operational sequence of the
embodiment of the invention shown in Figures 1-13 has
been described in detail, the described apparatus may be
operated without projection of the carriage 61. In this
instance, the upward movement of the strapping mechanism
57, under a force equal to or greater than its weight,
will cause the yoke section 37 which is carried thereby
to deflect the yoke section 35 as indicated by broken
lines in Figure 1. Upon the subsequent sealing of the
leading end and feed portions of the strap loop, the
sealed side thereof is urged against the side of the
strapped article in much the same manner as with con-
ventional apparatus. Yet, insofar as the leading end
and feed portions of the strap loop are under tensions
which at least approach each other prior to the sealing
thereof, the overall tension in the applied strap loop
is greater than that which is achieved with such conven-
tional apparatus.
In the embodiment of the invention described in
detail, the tensioning means 135 is operated to tension
the strap loop onto the article A, as shown in Figure
11, and is kept in operation to maintain the tension in
such strap loop while a pulling force is applied to the
leading end portion or leg 205 of the strap loop in a
manner as illustrated in Figures 12 and 13. Maintenance
of the tension developed in the strap loop by the
tensioning means 135 can also be achieved by gripping
the feed portion or leg 197 of the tensioned strap loop
at some location outwardly of the strapping machanism
57, after which operation of the tensioning means may be
discontinued.
Reference is now made to Figures 14-16 which illu-
strate further embodiments of the present invention and
3~ in which li~e elements are denoted by the same reference
characters.
9~7
- 28 -
Shown in Figure 14 are those elements of a semi-
automatic strapping machine which are necessary for
understanding the present invention, including a support
or framework 213, having a table 215 and a fixed guide
217, and a strapping mechanism 219. Article stops 221
and 223 are disposed laterally of a strap path, as
hereafter described, and adjustable relative to each
other to accommodate articles of different sizes.
The strapping mechanism 219 shown in Figure 14 is
supported on the guide 217 by bearings 225 and includes
gripping means 227 and holding means 229 for fixing the
respective leading end and feed portions of a strap S,
means 231 for sealing overlying strap portions, and
strap feed and tensioning means 233 which wheels 235 and
237. When using a strap S formed of thermoplastic
material, all such means 227, 229, 231, and 233 may be
of a construction and operate in a manner as described
in the cited Goodley patent. A rack 239 is fixed to the
strapping mechanism 219 and is engaged by a pinion 241
which is driven by a motor, not shown. Movement of the
strapping mechanism 219 to the left, as viewed in Figure
14, is limited by a stop 243.
In the use of this embodiment, a predetermined
length of strap S is fed from a supply, not shown, by
the feed means 233 so that its leading end portion 244
is accessible for gripping and manual lacing as a loop
about the article A. As in conventional semi-automatic
strapping machines, insertion of the leading end portion
244 into the gripping means 227 actuates a switch, not
shown, which initiates a sequence of operations. More
particularly, in such sequence of operations, the
gripping means 227 is first caused to engage and fix the
leading end portion of the strap S, after which the
tensioning means 233 is operated to apply the strap S
onto the article A as a tensioned loop. As thus far
described, the apparatus shown in Figure 14 functions in
the same manner as conventional strapping machines.
957
- 29 -
However, with the apparatus of this invention, after the
tensioned strap loop is applied to the article A, the
operation of the tensioning means 233 is continued so as
to maintain the tension in the strap loop while movement
is imparted to the stapping mechanism 219 in the direc-
tion indicated by arrow 245 by the rack 239 and 241.
Thus, with this embodiment, the tension developed
on the leading end portion of the strap loop by the
pulling force imposed thereon may be less than and
approach or equai that which is provided by the pulling
force imposed on the feed portion of such loop.
The embodiment of the apparatus shown in Figure
15 differs from that illustrated in Figure 14 only by
having the strap feed and tensioning means 233 positioned
separate from the strapping mechanism 219. With this
arrangement, movement of the strapping mechanism 219 in
the direction of the arrow 245 is achieved by driving
the rack 239 by the pinion 241, with a pulling force
imposed on the leading end portion of the strap which is
less than or equal to that imposed by the means 233 and,
if the feed portion of the strap does not slip relative
to such means 233, the pulling force imposed on the
leading end portion of the strap may exceed that imposed
on the feed portion thereof.
In the embodiment of the apparatus shown in Figure
16, a sub-frame 247 is fixed to the underside of the
table 215 and carries the guide 217 and strap feed and
tensioning means 233. As thus far described, the
apparatus shown in Figures 15 and 16 are essentially the
same. In the latter apparatus, however, an auxiliary
gripping or holding means 251, which is not part of the
strapping mechanism 219, is fixed to the table 215.
In the operation of this embodiment, the strap S
laced about the article A and held by the gripping means
227 is tensioned onto the article A by the tensioning
means 233, after which the feed portion of the strap is
fixed by the holding means 251. Such operation is
1~7957
- 30 -
similar with that of certain known strapping machines.
However, with the embodiment shown in Figure 16, prior
to sealing of overlying strap portions, the strapping
mechanism 219 is urged by the rack 239 and pinion 241 in
the direction of arrow 245 to impose a pulling force on
the leading end of the strap loop to thereby further
tension the same. In this instance, the pulling force
imposed on the leading end position of the strap may be
less than, or equal to, or greater than that imposed on
the feed portion of the strap. Once such tensioning is
completed, the gripping means 229 is operated to hold
the feed portion of the strap, after which the gripping
means 251 is released and the overlying strap portions
of the applied loop are sealed together.
