Note: Descriptions are shown in the official language in which they were submitted.
~ I ~ 693~ ~
BACKGROUND OF THE INVENTION
The present invention generally relates to packaging
and more particularly to an apparatus and method for making
unitary packages which hold a plurality of components, each
package containing a load wrapped in a web of stretched film.
Case packing or boxing is a common way of shipping
- multiple unit products. The multiple unit products are
generally stacked in a corrugated box or are wrapped with kraft
paper with the ends of the kraft paper being glued or taped.
Another way of shipping such products is by putting a sleeve or
covering of heat shrinkable film around the products and
shrinking the sleeve to form a unitzed pacXage. The use of heat
shrinkable film is described in U.S. Patent Nos. 3,793,798;
3,626,645; 3,590,509 and 3,514,920. A discussion of this art is
set forth in U.S. Patent No. 3,867,806.
The use of spiral wrapping machinery is also well known
in the art. One such apparatus is shown by U.S. Patent No.
3,863,425 in which film is guided from a roLl and wrapped around
a cylindrical load in a sprial con~iguration. A carriage drives
the film roll adjacent the surface of the load to deposit a
spiral overwrap around the load and returns ln the opposite
direction to deposit another sprial overwrap around the load.
It has~previously been disclosed in~U.S. Patent No.
3,788,199 to spirally wind tapes in a manner that they overlap
25 each other to provide~eultable space therebetween when
breathabillty i9 required. In this refer~nce, a heavy duty bag
is prepared by spirally winding stretched tapes of synthetic
resin in opposite directions, so that they intersect each other
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to form a plurality of superimposed cylindrical bodies which are
bonded together to form a cylindrical network. The spirally
wound inner and outer tapes of the superimpos~d cyIindrical body
intersect each other at a suitable angle, depending upon the
application intended, the preferred embodiment having
substantially equal longitudinal transfer strength~ In this
preferred embodiment the tapes intersect each other at an angle
of about 90. The angle defined by the tapes constituting the
cylindrical network may be determined by varying the
interrelationship between the travelling speed of the endless
belts carrying the tape and the rotating speed of the bobbin
holders, which rotate a plurality of tape bobbins to deposit the
tape onto the moveable belt. The previously indicated patents
rely on heat shrink material, adhesives, a heat seal or the
tacky nature of the film to hold the outer layer of wrap in a
fixed position.
In U.S. Patent No. 3,003,297 a complex cutting and
holding mechanism is used to place tape on a box and cut it off
with the process being repeated for each box.
Additional references of interest which are pertinent
to rotatable drives for wrapping packages are disclosed in U.S.
Patent Nos. 3,820,451; 3,331,312; 3,324,789; 3,309,839;
3,207,060; 2,743,562; 2,630,751; 2,330,629; 2,054,603; and
~,124,770.
Other applications in packaging are shown by U.S.
Patent Nos. 3,514,920 and 3,793,798 in which heat shrink film is
wrapped around a pallet supporting a plurality of cartons. A
; similar full web apparatus using a tensioned cling film is shown
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by U.S. Patent No. 3,986,611 while another apparatus using a
tacky P.V.C. film ls disclosed in U.S. Patent No. 3,795,086.
The elasticity of the film or netting holds the product
under more tension than either the shrink wrap or the kraft
wrap, particularly with products which settle when packaged.
The effectiveness of stretched plastic film in holding a load
together is a function of the containment or stretch force being
placed on the load and the ultimate strength of the total
layered film wrap. These two functions are determined by the
modulus or hardness of the film after stretch has occurred and
the ultimate strength of the film after application~
Containment force is currently achieved by maximizing elongation
until just below a point where break of the film occurs.
Virtually all stretch films on the market today including
products of Mobil Chemical Company (Mobil X, Mobil C, Mobil H),
Borden Resinite Divislon (PS-26), Consolidated Thermoplastics,
Presto, PPD, and others consistently stretched less than 30~ in
field applications because of irregularities in film braking
systems. These systems depend upon friction either directly on
the film through a bar assembly such as that used by the Radient
Engineering Company or indirectly as that shown in Patent No.
3,867,B06 and No. 4,077,179.
All of these prior art apparatuses suffer from a severe
limitation which relates to cost per unit load for film
unitization. Friction brake devices do not maintain a
consistent force. These~ br~akes are subject to variation due to
their physical construction and their sensivitity to speed
change caused by passage of corners of the~load, and the
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resultant sudden speed up and slow speed down of film unwind. A
typical 40" x 48" pallet load will incur a surface speed change
of more than 40~ with each quarter turn. Higher turntable
speeds of 12-18RPM produce additional resonating forces which
change with a roll consumptlon and its resultant ~eight change.
Additional limitations on maximum elongation are caused by film
roll imperfections and gauge variations which accentuate the
force variations described above to produce film ruptures. Even
though all of the film previously described carrying
manufacturer's specified elongation rates above 300~, these
rates cannot be approached because of limitations imposed by
friction-type constant force devices~
One problem with shrink and non-cling stretch film
packaging in addition to the fact that they do not allow a load
to breathe is that the primary strength and reliability of the
package is determined by the consistent quality of the seal.
These seals depend on a careful maintenance of the sealing jaw
and are never as strong as the film itself. The time that it
takes to make the seals is a limiting factor on the possible
speeds of most shrink systems with the additional problem that
some stretchable materials, a~ for example, stretah netting, or
narrow film width cannot be effectively heat sealed.
In view of the previously stated characteristics of
; film the previously noted stretch machines including machines
manufactured by Lantech Inc., Infra-Pak; PS & D; Radient
Engineering, I.P.M.; and Mima have limited capabilities.
I 1 69.-34~
Stretch wrapping machines known in the art are
disclosed by machine Model Nos. SVS-80, SVSM-80, STVS-80,
STVSM-80 and SAHS-80, manufactured by Lantech Inc. Some full
web machines in effect have the carriage removed and these
machines are typified by Model Nos. S-65, SP-65 and SAH-70, also
manufactured hy Lantech Inc. A typical state of the art full
web machine is also discussed in U.S. Patent No. 3,8`67,806.
Other machines which could use the present invention are
machines which rotate the film around the load rather than
rotation of the turnable carrying the load. Such apparatus is
disclosed in U.S. Patent Nos. 4,05Q,220 and 4,110,957 and are
assigned to Lantech Inc.
When high elongation rates are attempted, the forces
frequently either distrupt the stacking pattern or pull the load
off of the turntable.
In addition non-vertical sides and corners on an
irregular load place extreme forces on a small area of film
during stretching, thereby causing a partial rupture at a point
well below the force achieveable on a flat side. This partial
- 20 rupture causes a transfer of force to the remaining portion of
the web. This force is frequently sufficient to produce a
"zippering" of the entire film web.
The present invention provides an apparatus and process
which prestretches film before wrapping the film around a load
so that the film may be stretched from 40 to 300% independently
of it being wrapped around the load so that it then holds the
load under compressive forces.
Most plastic films when stretched above their yield
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polnt gain significantly in modulus and ultimate strength. A
typical polyethylene will multiply three times the ultimate
strength in pounds per square inch of cross-sectional area after
being elongated approximately 300%. This significant increase
in strength begins approximately when the yeild point is
exceeded in elongation. Limitations of current friction-type
constant force devices prevent current stretch wrap applications
from achieving the higher levels of containment force and
ultimate strength available in most plastic films. Achieving
the higher elongation levels with the invention allows fewer
revolutions of film for equivalent holding power. These higher
levels of stretch not only allow fewer revolutions of film but
also less film by weight for each revolution. Cost savings of
more than 50% will requently result from using the present
invention.
When using the present invention, if irregular loads,
unstable loads, or crushable loads are met, the film leaving the
prestretching mechanism can be set to a surface speed equal to
or slightly faster than the average surface speed of the
pallet. Dramatic reduction of force on the film will give most
of the advantages of high elongation rates without its crushing
force. This reduction of force is caused by the non-elastic
strain recovery because the yield polnt is exceeded and the
rapid stress relaxation incurred at the high elongation level.
Very stable loads or loads not subject to crushing can
take advantage of the maximum strength of the film by slowing
the film leaving the prestretching mechanism to a surface speed
below the average speed of the pallet load, to produce
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additional stretch forces over and above those achieved during
the initial elongation.
Also, the present invention does not require the use of
a structural seal and therefore can use any type of s~retchable
material. The invention is designed to function with
stretchable film webs such as nylon, polypropylene, P.V.C.,
polybutylene, polyethylene or any copolymer or bLends of the
aforementioned stretchable films. However should a seal be
pxeferred, a fastening mechanism is also provided which
effectively fastens a wrapping of collapsed film to an adjacent
wrap while severing the trailing edge of the film web from the
load after the load has been spirally wrapped to form a package
overwrap.
SUMMA~Y OF THE INVE~TION
Process and apparatus are provided for appLying
stretchable plastic film to pallet loads for containment of the
loads using two connected sets of powered rollers driven at
different peripheral speeds to pre-stretch the plastic film
beyond its yield point and to then connect the film to a
- rotating pallet whose vertical surface is moving at
approximately the same rate as the surface of the faster and
final of the two sets of rollers. Where irreguIar or unstable
loads are~wrapped, ~the surface speed of the final roller can be
increased above the surface speed of the load thereby avoiding
disruptive forces on the load or tearing forces on the load or
tearing forces on the film. Relatively rigid and regular loads
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can utilize the maximum strength of the ~ilm by providing the
final roller with a surface speed less than that of the pallet
load, to incur additional elongation and unitizing ~orce. A
powered or force-loaded film accumulator such as a dancer bar
can be added to compensate for corners where significant
length-width distortions exist. A web narrowing device may be
placed upstream or downstream from the rollers to reduce the
hazard of edge tear under high elongation forces. Closure of
the film ends can be efficiently accomplished by a mechanical
closure mechanism.
The above mentioned purposes and operations of the
invention are more readily apparent when read in conjunction
with the following description of the drawings and the detailed
description of thP preferred embodiment of the present invention.
; 15 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of part of a preferred
embodiment of the inventive apparatus with a portion broken away;
~ Figure 2 is a plan view of the apparatus~including that
; part shown in Figure 1 as well as a turntable used to carry a
- 20 load to be wrapped;
Figure 3 is a reduced elevational front view of the
apparatus shown in Figure 2 (i.e~ looking from the bottom of
Figure 2);
Figure 4 is a side elevation view of another
embodiment of the apparatus which includes cutting and clamping
mechanisms;
Figure 5 is an enlarged partial top plan view partially
in section of the clamping assembly and of a tying assembly;
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Figure 6 is a side elevational view of the clamping
assembly shown in Figure 8 showing the position of the assembly
when rotated in phantom;
Figure 7 is an enlarged isolated perspective view of
the clamping assembly of the apparatus in an open position;
Figure 8 is a side elevational view of the clamping
assembly of the apparatus;
Figure 9 is a partial perspective of a web width
changing mechanism used in conjunction with the cutting and
clamping mechanisms and shown with the web in a full width open
position;
Figure 10 is a partial perspective view of the web
width changing mechanism after the mechanism has been rotated to
collapse the web into a rope:
Figure 11 is an enlarged side elevational view
partially in cross-section of the cutter and clamping
mechanisms; and
Figure 12 is a side elevational view of the cutter
mechanism housing.
DETAILED DESCRIPTION OF THE DRAWIN~S
The improved wrapping appara~us 10 is shown in Figures
1 through 12 with the preferred embodiment of the invention
being shown in Figures 1 through 4 and suitable mechanical
closures for use wlth the invention being shown in Figures 5
through 12. The operation and description of the apparatus and
its respective component parts are discussed in the following
description.
The powered stretch wrapping apparatus l0 comprises an
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upright frame 12 sitting on a base 14. In this, the pre~erred
embodiment of the invention, a carriage 15 is movably mounted on
frame 12 as is known to the art and is driven by r~ck and
pinion, chain or other suitable drive means. A rack type drive
is shown in Figure 3.
In the embodiment as most clearly shown in Figures 1
and 2, a support ~ar 20 is secured to the carriage walls 16 and
18 and pivotal support arms 22 and 24 are pivotally mounted to
brackets 26 and 28 respectively, which are in turn secured to
the side wall 17 of the carriage~ A rotatable shaft 30 is
mounted on the ends of the pivotal support arms and is adapted
to receive and hold a film roll 32.
The film roll is preferably a rolled ~ilm web 32 of
stretchable nature. Stretch films which can successfully be
used with the apparatus are Mobil X, Mobil C, Mobil H, Mobil Y,
Borden PS-26, Consolidated Thermoplastics EVA, Presto, St. Regis
and P.P.D. Bemis Stretch Net is also useable in the apparatus.
Excellent results have been achieved using linear low density
polyethylene.
An air cylinder 34 is mounted to the support bar 20 and
has an associated piston arm 36 which ls connected to arm 22 by
connector member 38. The air cylinder 14 is adapted to drive
arm 22 and film roll 32 forward to press the ~ilm roll a~ainst a
resilient rubber-type driver roller 40 constructed of
polyurethane, preferably having a durometer of between 42 and
52. Positioned adjacent to roller 40 i~s a second set of two
similarly constructed rollers 42 and 44O Roller 40 has a
sprocket 46 and roller 42 has a sprocket 48. The first roller
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40 and the second roller 42 are of similar diameter and have
different sized sprockets so that the surface movsmellt of the
first roller 40 is at least 40~ slower than that of the second
set of rollers 42,44. The sprockets are sized depending on the
amount of film elongation desired. Thus, the surface movement
of the first roller 40 can be about 40~, 75~, 200% or 300%
slower than the surface movement of the second set of rollers to
obtain prestretching of 40~, 75%, 200% or 300%. While
stretching normally ranges from 40 to 300%, excellent results
have been obtained when narrower ranges of prestretching are
required such as stretching the material 40% to 75%, 75% to
200%, 200% to 300%, and at least 100%. In certain instances,
prestretching has been successful at over 300% of stretch. The
rollexs 40 and 42 are connected by a drive chain or belt 50. As
best seen in Figure 3, both sets of rollers are driven by a
variable speed D.C. motor 52 through a reducer 54 connected to a
shaft 55 of roller 42. It is apparent that the reducer 54 could
be connected to either one of the rollers 42,44. The rollers
are provided with spur gears 56 and 5~ to accomplish the driving.
Alternate embodiments of the powered mechanical rollers
producing elongation of the film because of the different
surface speed of the rollers can be utilized in place of the
best mode of the invention which is disclosed in Figures 1 - 3.
For example, two sets of rollers having individual rollers
powered and connected by a belt or other suitable drive can be
used. The film web 33 ~Fig. 2) from film roll 32 could also be
drawn around idle rollers through the action of powered rollers
to get traction and elongate the film. Alternatively, one
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powered roller can pull the film web 33 from the film roll 32
directly with a brake engaging the film roll, holding it back so
it is elongated as it passes over the idle rollers. Thus, it
can be seen that the film is stretched between symmetrical round
rollers, rather than between the film roll and rectangular
pallet as has been the case in the previous prior art, to
stretch the film well above the yield point to take advantage of
the higher containment force and ultlmate s rength available.
Positioned adjacent to the second set of rollers, as
- 10 best shown in ~igures 1 through 3, is a horizontally movable,
vertically oriented accumulator mechanism 90. The accumulator
mechanism comprises two pivotable support arms 92 and 94 which
are respectively mounted to brackets 96 and 98 (Fig. 3). The
brackets are secured to side wall 19 on the carriage. An air
15 cylinder 100 is secured to a support bar 102 with the piston arm
` 104 of the air cylinder being connected to support arm by
connector member 106. A rotatable shaft 108 holds roller 110
for movement thereon so that film can be accumulated in
anticipation of corner passage of the film web around the pallet
load. The roller 110 is positioned to let out extra ~ilm as the
corner 131 ~Fig. 2) of the load 130 passes and regains the
excess film while the ~lat side 132 passes. This can be
accomplished positively by limit switch actuations on the
turntable. ThP accumulator can also hold a constant ~orce with
a spring or through air cylinder 100 thereby smoothing the
corner passage. An alternative mechanism to accomplish the same
result utilizes means to sense the corner passage of the pallet
and electrically determine the passage so that the speed o~ the
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D.C. motor is modified or changed. This changes the speeds of
both sets of rollers in unison so that the speed of the film
coming off the rollers is synchronized to compensate for the
corner passase of the load.
In operation of the apparatus l0, the film web 33 is
threaded around the first roller 40 and then between the second
set of rollers 42 and 44 around the accumulator roller 110, and
then attached to the pallet load 130 or turntable clamp (not
shown, but well known in the art). Tha turntable 120 (Fig. 2)
and roller drive is actuated si~ultaneously causing the film web33 to be unwound from the film roll 32 at controlled speed. The
second set of rollers 42,44 is mechanically interconnected to
rotate at a faster surface speed than rQller 40. The speed
difference of the interconnected rollers produces a precise
level of elongation independent of force required or gauge
variation. The film web 33 i9 supported over its full width by
smooth resilient parallel surfaces of the rollers. The
stretched film is then passed around the accumulator mechanism
90 to the load 130 without the need for relatively additional
- 20 stretch or additional force.
If irregular, unstable or crushable loads are
encountered, the second set of rollers 42,44 can be set to a
surface speed equal to or slightly faster than the average
surface speed of the load 130. A reduction of force on the film
will give most of the advantages of high elongation rates
without its crushing forceO This reduction of force lS caused
by the non-elastic strain recovery because the film web has
exceeded the yield point and the rapid stress relaxation
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incurred at the high elongation level.
Stab~e loads or loads not subject to crushing can takeadvantage of the maximum strength of the film by slowing the
second set of rollers to a surface speed below the average speed
of the pallet load, to produce additional stretch forces over
and above those achieved during the initial elongation.
In addition, certain types o~ high modulus films or
films stretched sign1ficantly above the yield point may require
positive corner compensation as provided by the accumulator
mechanism 90. The roller 110 is positioned to let out extra
film as the corner 131 passes and regain excess film while the
flat side 132 passes. This can be accomplished positively by
positioning limit switches on the turntable 120. Such
positioning is well known in the art. The accumulator can also
hold a constant force with a spring or air cylinder thereby
smoothing the corner passage.
The final film web end 33 can be brushed onto the
- underlying film layers on the load, tucked, heat sealed or
fastened by a mechanical closure mechanism. In the preferred
embodiment, the mechanical closure mechanism is utilized with
the invention~
It should be noted that film, film material and netting
are used interchangeably through the specification.
The invention has been described~with reference to
Figs. 1 to 4 and i ill be appreciated that the preferred
embodiment can~be used advantageously with associated parts to
enhance the wrapping efficiency. Such parts will now be
described.
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The film web 33 as it comes off the accumulator
mechanism 90 passes through a roper mechanism 50 shown in
figures 9 and 10. Mechanism 50 comprises a support plate 152
secured to the frame 12 and a rotatable support bar 154 having
one end rotatably mounted to the support plate, the other end
being secured to the web reduction member 156.
The web reduction member 156 comprises a rectangular
shaped bar which defines a rectangular aperture 157. The length
of the rectangular aperture is greater than the width of the web
of the material used for wrapping the load and the width of the
rectangular aperture is greater than the thickness of the web.
Preferably it is also equaI to the desired thickness of the web
when bunched or roped, so that when member 156 is rotated, web
material 22~ is roped into a diameter substantially equal to or
less than the width of aperture 157 as is best shown in Figure
10 .
A pneumatically activated cylinder 158 is secured to
the support plate 152 or the rame and has an end 159 of its
piston rod rotatably connected to drive bar 160 which is in turn
secured to the rotatable support bar 154. The cylinder 158 can
be energized by known fluid circuitry to move the rotatable
support bar, so that it rotates around pivot point 155 carrying
: the web reduction member 156 upward or downward in an
approximately 90 arc.~ This causes the material web to be
: 25 formed into a roped configuration 226 when the rectangular
member is parallel to the ground or alternatively allows free
flow of the open web through the:web reduction me=ber 15~ wh n
the web reduction member is positioned substantially
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perpendicular to the ground.
The material web when roped passes through a clamping
assembly 170 (Fig. 7) mounted on the edge of the turntable.
The clamp assembly 170 comprises a stationary arm
5 mechanism 172 and a rotatable clamp mechanism 174 mounted to a
shaft 176 which is rotated by a rotary pneumatic cylinder 178.
The stationary arm mechanism 172 comprises a support
block 180 mounted to turntable 308, a seat support 182 secured
to the support block 180 and a cylinder support subassembly 184
10 secured to the support block. The support block has its rear
portion 185 secured to the pneumatic cylinder and its forward
portion 186 secured to the stationary seat support 182. The
seat support 182 has a "U" shaped seat 188 with a resilient
friction member 190 made of rubber or other suitable resilient
t 15 material secured in the seat and extending above the legs 200
and 208 of the "U" shaped seat 182 for engagement with clamp arm
198 of the rotary clamp mechanism 174. The rotary clamp
mechanism 174 comprises a material guide member 192 of an
eccentric shape having a circular aperture 194 o~ suitable
20 diameter surrounding the pneumatic cylinder 174 so that the
guide member 192 can freely rotate around the pneumatic
cylinder. A curved surace notch 196 is cut inward from the
exterior edge of the ~aterial guide member 192 a suitable
distance which allows the notch to receive and guide the roped
25 material during the tying and severing operation of the
apparatus.
The clamp arm 198 is secured to a spacer bar 210 which
is secured in turn to the guide =ember 192. The clamp arm 198
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has a cut away segment 202 which approximates a curved "L"
shaped surface forming the contact surface for en~agemen~ with
the resilient friction member 190. The segment 202 has a planar
~ surface 204 adapted to engage the resilient friction member 190
to hold the roped material therebetween. ~he outwardly
extending leg 206 of the "L" is adapted to be positioned
adjacent the leg 208 of the seat 188 to engage the stretched
material at the smallest angle o extension from the wrapped
package.
A cutting mechanism 220 (Fig. 11) and tying mechanism
240 are secured to a moveable arm 212 which sequentially moves
the mechanisms into the path of the material for the severing
and tying steps. The arm 212 is rotatably mounted on support
structure 214 and is driven by pneumatic cylinder 216 secured to
the frame 222. Extension of the piston arm 217 of cylinder 216
drives the arm and the associated cutting and tying mechanism
into the material path so *hat the mechanism can perform its
desired function. Secured to the traversing arm 212 are a
perpendicularly extending arm 218 which holds the tying
mechanism 240 and a support structure 219 which is mounted to
the top of the arm and supports the cutting mechanism 220. The
; cutting mechanism 220 comprises an upright support plate 222 and
traverse brace 224 secured to the support plate and a piston 226
which is secured to the upright support plate 222. A piston arm
25 227 extends from the piston, the distal end of which is secured
to a cutting blade 228. The cutting blade 228 is reciprocally
positioned in a guillotlne sheath or housing 230, which is
secured to the end of~traversing arm 2120 The guillotine sheath
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2~0 comprises a plate structure having an inwardLy inclinednotch 233 (Fig. 12) cut into one side adapted to receive the
roped material and direct it into a center of the notch 234.
The roped material when held in cutting notch 234 is severed by
xeciprocating action of the cutting blade 228 striking the roped
material and cutting through the roped material.
A standard hog ringer device 242 (Fig. 11) such as that
made by ATR0 Company~ types I and C is secured to the lower part
of arm 219. A magazine 244 extends perpendicularly from the
mechanism to feed staples or hog rings into the mechanism. In
operation of such a standard hog ringer the shaped nose of the
hog ring engages the materials to be tied together and a ring or
staple is driven around the material held in the nose of the
ring and fastened around materials by bending the ring or staple
around the items to be tied. Thus, the two roped web layers
which have been placed side by side are fastened together
through the action of the hog ring passing a staple around both
of the ropes and fastening or tying them together through the
con~raction of the staple or bending of the staple or ring
around the materials,
- It should be noted that the steps of the wrapping
process can be interchangeable without departing from the scope
of the invention. Furthermore, these steps can be interchanged
and are equivalent.
In the foregoing description, the invention has been
described with reference to a particular preferred embodiment
although it is to be understood that the specific details shown
are merely illustrative and that the invention may be carried
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out in other ways without departing from the true spirit and
scope of the following claims.
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