CA1169349A - Stretch wrapping apparatus and process - Google Patents

Stretch wrapping apparatus and process

Info

Publication number
CA1169349A
CA1169349A CA000359938A CA359938A CA1169349A CA 1169349 A CA1169349 A CA 1169349A CA 000359938 A CA000359938 A CA 000359938A CA 359938 A CA359938 A CA 359938A CA 1169349 A CA1169349 A CA 1169349A
Authority
CA
Canada
Prior art keywords
film
load
web
speed
means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000359938A
Other languages
French (fr)
Inventor
William G. Lancaster
Patrick R. Lancaster, Iii
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lantech Inc
Original Assignee
Lantech Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US7478679A priority Critical
Priority to US074,786 priority
Application filed by Lantech Inc filed Critical Lantech Inc
Application granted granted Critical
Publication of CA1169349A publication Critical patent/CA1169349A/en
Application status is Expired legal-status Critical

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B65CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65BMACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
    • B65B11/00Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material
    • B65B11/04Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material the articles being rotated
    • B65B11/045Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material the articles being rotated by rotating platforms supporting the articles

Abstract

ABSTRACT OF THE DISCLOSURE
A process and apparatus for applying stretchable plastic film to loads for containment of the loads using two connected sets of powered rollers driven at different peripheral speeds to elongate the plastic film beyond its yield point and simultaneously connecting the stretched film to a rotating load whose surface is moving at approximately the same rate of speed as the surface of the faster and final of the two sets of rollers. A powered or force loaded film accumulator such as a dancer bar can be added to compensate for corners of the load where significant length-width distortions exist. In addition, 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 accomplished by a mechanical closure mechanism.

Description

~ 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 . . -1 ~ ~93~

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.

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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 : ~3 : : :

9 3 ~ 9 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 ~ _ 7 .~ ~
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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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~ I 1 693~9 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 _ g _ ' ~ :

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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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~ } ~ ~93~g 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 , ~;:
, ' , 93~9 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 6 ~

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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9 3 ~1 9 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 : - 15 -:

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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 1 3 ~

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 T~ ~

1 ~ 69~3 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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Claims (10)

THE EMBODIMENTS OF AN INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A repetitive commercial process of making a unitary package by wrapping a load consisting of a plurality of units with a stretched plastic film web overwrap and comprising the steps of:
a. placing the load on a rotatable support;
b. positioning a rolled stretchable plastic film web on a dispenser means adjacent to said support;
c. withdrawing a leading end of said web of plastic film from said dispenser means through a stretching means;
d. holding said leading end of plastic film web adjacent said load;
e. stretching the film web in said stretching means over one hundred percent and substantially above the yield point of the plastic material of the film web to permanently increase the modulus and strength of the plastic material in pounds per cross-sectional area by transporting the plastic film web through at least two different speeds, the second of which is faster than the first; and f. driving the support and load to rotate as the load is wrapped with more than one revolution of film web previously stretched substantially beyond its yield point, the load rotating at a speed sufficient to create a force in the film web adjacent the load which is substantially less than the force required to previously stretch the film so that the units of the load are held under a containment force by the wrapped film web.
2. A process of making a unitary package by wrapping a load consisting of a plurality of units with a stretched plastic film overwrap and comprising the steps of:
a. placing the load on a support;
b. positioning a roll of stretchable plastic film on a dispenser means adjacent to said support;
c. withdrawing a leading end of said plastic film from said dispenser means and passing said film through a powered prestretch device adapted to drive the film at a speed no greater than that of the surface speed of the load, said dispenser means comprising a powered roller assembly rotationally connected to at least one rotationally restrictive roller assembly, said rotationally restrictive roller assembly being retarded to a substantially constant relative speed to the rotationally powered roller assembly so that the film is elongated substantially above its yield point between the roller assemblies, thereby changing the film's strength characteristics and cross-sectional area;
d. holding said film adjacent said load and simultaneously causing relative rotation between said load and said dispenser means at a predetermined speed;
e. reducing the force on the film through inelastic strain recovery after it leaves the powered prestretch device; and f. wrapping the load with previously elongated film so that the units of the load are held under a compressive force. 21
3. A process of making a unitary package as claimed in claim 2 including the step after step (e) of compensating for a corner of said load by providing a relatively constant force on said film between the prestretch device and the load.
4. A process for spirially wrapping a web of stretched film on a load comprising a plurality of units to form a unitary package, which process is repeated in a commercial environment comprising the steps of:
a. withdrawing the web of film from a film roll through a powered prestretch means comprising a powered roller assembly and at least one restrictive roller assembly that is experiencing a retarding torque in the opposite direction to its direction of rotation interconnected by speed control means to maintain a substantially fixed relative speed, the speed of the restrictive roller assembly being less than said powered roller assembly, and holding the web of film adjacent to the load;
b. activating the powered prestretch means to drive the film web at an increased downstream speed from that of its upstream speed to produce film elongation above one hundred percent and the yield point of the film thereby changing the film's strength characteristics and cross-sectional area and to substantially reduce the film stress after the film leaves the powered prestretch means thereby isolating the maximum stretch force from the load while simultaneously causing relative rotation of the load and the powered prestretch means;
c. spirally wrapping the load;
d. fastening the leading web width of the film wrap to the trailing web width of the wrap; and e. severing said film web between the film roll and the fastened web sections.
5. A process for spirally wrapping a web of stretched plastic film on a substantially rectangular load comprising a plurality of units to form a unitary package comprising the steps of:
a. withdrawing the web of film from a film roll through not more than one powered roller assembly and holding the web of film adjacent a load;
b. activating the powered roller assembly to drive the film web at a speed which is substantially greater than an initial retarded speed at an upstream location sufficient to produce a film elongation above 100 percent and substantially above the yield point elongation of the film changing the film' s modulus and strength per cross-sectional area;
c. simultaneously initiating relative rotation of the load and the film roll to achieve a speed of the film web which is less than the previous faster speed of the film web to produce inelastic strain recovery of the film web as it is wrapped around the load;
d. spirally wrapping the load;
e. fastening the trailing end of the wrap to an underlying web layer; and f. severing the film web from the load.
6. A process for spirally wrapping a web of stretched material as claimed in Claim 4 wherein elongation of the material web is at least two hundred percent.
7. An apparatus for making a unitary package from a plurality of units forming a load using a single web of stretchable plastic film to form an overwrap comprising a frame, a dispensing means mounted to said frame, said dispensing means being adapted to hold a roll of stretchable plastic film material and including means for providing relative rotation between the load and the dispensing means, pre-elongation means positioned between said load, and said film dispenser, said pre-elongation means comprising a positive rotationally powered roller assembly speed controlled to a speed greater than the surface speed of the relatively rotating load and at least one rotationally restricted roller assembly speed retarded to a substantially proportional speed which is less than said powered roller assembly by speed control means connecting said assemblies, the web of plastic film material being withdrawn from said dispenser at a first speed and increased to a higher speed downstream causing it to be elongated substantially above its yield point so that the material is stretched past its yield point and wrapped around a load at a force less than its maximum stretch force incurred within said pre-elongation means.
8. An apparatus as claimed in claim 7 including means to sense the corner passage of the load and change the speed of a powered roller assembly.
9. A process of making a unitary load by wrapping a plurality of units with a stretched plastic film web overwrap forming a unitary load comprising the steps of:
a. elongating the film web in a stretching means comprising a powered roller means and a restrictive roller means at least fifty percent over the yield point while obtaining elongation of the film web over one hundred percent by subjecting the film web to differential surface speeds of said powered and restrictive roller means thereby gaining substantially in strentgh per cross-sectional area and modulus;
b. reducing the force on the film web substantially below the force necessary to stretch the film web while retaining at lest fifty percent of the elongation of the film web;
c. allowing inelastic strain recovery between the stretching means and the unitary load; and d. wrapping the load with a wrap of film web.
10. A unitary package comprising:
a load made up of a plurality of units stacked together;
a film wrapped about the load to retain the units in the stacked relationship, the film being in tension and having an enhanced modulus of elasticity caused by prestretching the film beyond the yield point before wrapping the film on to the load.
CA000359938A 1979-09-12 1980-09-09 Stretch wrapping apparatus and process Expired CA1169349A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US7478679A true 1979-09-12 1979-09-12
US074,786 1979-09-12

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CA1169349A true CA1169349A (en) 1984-06-19

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CA000359938A Expired CA1169349A (en) 1979-09-12 1980-09-09 Stretch wrapping apparatus and process

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JP (1) JPS5952087B2 (en)
AU (2) AU6238780A (en)
CA (1) CA1169349A (en)
FR (1) FR2468506B1 (en)
GB (1) GB2059906B (en)

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Also Published As

Publication number Publication date
AU6241480A (en) 1982-09-30
GB2059906B (en) 1984-04-04
AU538306B2 (en) 1984-08-09
JPS5664907A (en) 1981-06-02
AU6238780A (en) 1981-10-01
FR2468506A1 (en) 1981-05-08
CA1169349A1 (en)
JPS5952087B2 (en) 1984-12-18
FR2468506B1 (en) 1984-02-10
GB2059906A (en) 1981-04-29

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