CA2544670A1 - System and method for pre-stretching plastic material - Google Patents
System and method for pre-stretching plastic material Download PDFInfo
- Publication number
- CA2544670A1 CA2544670A1 CA002544670A CA2544670A CA2544670A1 CA 2544670 A1 CA2544670 A1 CA 2544670A1 CA 002544670 A CA002544670 A CA 002544670A CA 2544670 A CA2544670 A CA 2544670A CA 2544670 A1 CA2544670 A1 CA 2544670A1
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- Prior art keywords
- assembly
- plastic material
- accumulator
- rollers
- accumulator wheel
- Prior art date
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- Abandoned
Links
- 239000000463 material Substances 0.000 title claims abstract description 74
- 239000004033 plastic Substances 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 25
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 claims 2
- 239000011248 coating agent Substances 0.000 claims 2
- 238000000576 coating method Methods 0.000 claims 2
- 238000011144 upstream manufacturing Methods 0.000 claims 2
- 230000037361 pathway Effects 0.000 claims 1
- 230000008569 process Effects 0.000 description 7
- 238000004806 packaging method and process Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229920006302 stretch film Polymers 0.000 description 4
- 239000000835 fiber Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 229920006311 Urethane elastomer Polymers 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920000728 polyester Polymers 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 230000036962 time dependent Effects 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000010073 coating (rubber) Methods 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
- B65B13/00—Bundling articles
- B65B13/18—Details of, or auxiliary devices used in, bundling machines or bundling tools
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
- B65B13/00—Bundling articles
- B65B13/18—Details of, or auxiliary devices used in, bundling machines or bundling tools
- B65B13/184—Strap accumulators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
- B65B11/00—Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material
- B65B2011/002—Prestretching mechanism in wrapping machines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
- B65B27/00—Bundling particular articles presenting special problems using string, wire, or narrow tape or band; Baling fibrous material, e.g. peat, not otherwise provided for
- B65B27/04—Bundling groups of cans or bottles
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Basic Packing Technique (AREA)
Abstract
A system and method are disclosed for pre-stretching plastic material that is later used in wrapping a plurality of objects. Plastic material is continuously or noncontinuously provided to a pre-stretching device including a plurality of rollers. The plastic material is passed around the plurality of rollers within the pre-stretching device and is then fed through an accumulator to a strapping device, The passing of the plastic material around the plurality of rollers causes the plastic material to stretch by a predetermined amount before entering the strapping device.
Description
Atty. Dkt. No.: 080573-0106 SYSTEM AND MET~IOD FOR PRE-STR»TCI~XNG Pr,ASTYC
N~A.TE~tIAL
GROSS-REFERENCE TO RE>:.ATED PATENT APPLICATIONS
[000X) This application claims priority from U.S. Provisional Patent Application Serial No. 60/6?3,029, Fled April 20, 2005 and herein incorporated by reference is its entirety.
FIELD OF THE INVENTION
N~A.TE~tIAL
GROSS-REFERENCE TO RE>:.ATED PATENT APPLICATIONS
[000X) This application claims priority from U.S. Provisional Patent Application Serial No. 60/6?3,029, Fled April 20, 2005 and herein incorporated by reference is its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the manufacture and use of strapping products.
More particularly, the present invention relates to the preparation of strapping materials for use in securing items such as plastic containers.
BACKGROUND OF THE INVENTION
More particularly, the present invention relates to the preparation of strapping materials for use in securing items such as plastic containers.
BACKGROUND OF THE INVENTION
[0003) The plastic container industry has utilized Strapping systems to unitize their products for over thirty years. In the past twenty years, This industry has migrated to plastic strapping systems to unitize their products, [0004) In recent years, the plastic container industry has undergone its own transformation. Plastic containers have become lighter and more cost efficient to manufacture. Additionally, the appearance, shape and desigtl of containers has become a t marketing tool. 'these changes to the plastic containers have creased packaging issues for the unitization of plastic bottles.
[0005] Historicahy, the amount of initial strap tension applied to a plastic container skid/unit was great enough to allow for the tension decay typical of plastic strapping, as well as the tension drop resulting from the shifting and shrinkage of individual plastic containers, while maintaining adequate package containment pressure to ensure proper unitization. New plastic container designs and increasing market pressure to produce' _1_ _.
Arty. bkt. I~o.: 080573-0106 containers at lower prices (meaning less resin per container), however, have created new challenges for the strapping process. In today's market, clew container designs often do not allow for initial strapping tension levels above about 65 lbs. For this reason, the tension levels that are used fall to about 40 lbs, At this level, strapping is unsuitable for maintaining adequate package containment pressure to ensure proper unitization of the plastic containers.
Arty. bkt. I~o.: 080573-0106 containers at lower prices (meaning less resin per container), however, have created new challenges for the strapping process. In today's market, clew container designs often do not allow for initial strapping tension levels above about 65 lbs. For this reason, the tension levels that are used fall to about 40 lbs, At this level, strapping is unsuitable for maintaining adequate package containment pressure to ensure proper unitization of the plastic containers.
[0006] Without an acceptable level of performance from strapping products, additional packaging products have been introduced to assist the packaging o~plastic containers. In particular, the use of plastic stretch film has been introduced to aid in packaging. With the introduction of stretch film, the industry found an improved process that provided the lEVel of unitization required to transport their plastic containers to'tlteir customer.
However, the introduction of stretch film to the unitization process for plastic containers also increased the cost of unitization by a multiple of about 2.5, Therefore, it would be desirable to develop a system and method for unitizing bundles of plastic containers that possess the benefits of stretch ~Im while also lowering the uniti2ation cost, SUMMARY OF THE INVENTTON
X4007] The present invention provides for an improved system and method of pre-stretching material for use in unitizing groups of plastic bottles. The present invention involves the use of a novel pre-stretching maehitte having a plurality of rollers. The rollers are used to pre-stretch tire plastic strapping, which is then transferred town accumulator before being used to package the respective containers.
[0008] The pz~e-stretch system and method of the present invention provides for the elimination of stretch film while producing higher retained strap tension that provides for a secure load of plastic containers. The present invention effectively eliminates the need for high tension of the package while providing a strap that is within the dynamic working range for retained tension. The plastic strapping can be pre-stretched without destroying the properties and characteristic of the plastic strappi~, instead only temporarily losing stability and rigidity in the strapping.
Atty, I~kt. No.: 08073-0106 (0009] These and other objects, advantages and features of the invention, together with the organization and manner of operation thereof', will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have Iike numerals throughout the several drawings described below.
BRrEp' bESCRIPTION OF THE'DRAW1NGS
[0010] FIG, 1 is a graph illustrating the relationship between strap Ioad vs eloxigation over time; ' (0011] FIG. 2 is a side vieww of a pre-stretching device, a material accumulator and a packaging machine according to one embodiment of the present invention;
[0012] FIG. 3 is a front view of pre-stretching device of FIG. 2, along with a representation of a portion of the material accumulator with the position of the accumulator wheel assembly, both according to one embodiment of the invention;
[0013] FIG. 4 is a side view of the pre-stretching device of FIG. 3;
[oolal FIG. 5 is a top view of the pre-stretclung device and material accumulator portion of FTG. 3; .
(0015] FIG. 6 is a graph illustrating the effect of pre-stretching on xetained tension; and [001C>] FIG. 7 is a graph illustrating the efFect of pre-stretching on stiffness.over time.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Plastic strapping is produced using a stretching process that is similar to that employed iz~ the production of fibers. This process results in the preferential orientation, of polymer molecules (or chains) along the strap length and a several-fold increase in tensile strength.
[00x8] Oriented plastic exhibits viscoelastic-plastic behavior in response to mechanical loading. Elastic deformation and recovery is pattly immediate and partly time dependent. Yielding occurs over a broad range rather than at a well defined point, and Atty. Dkt, No.:~080573-0106 the yield deformation itself is time dependent and only partly permanent (or "plastic"), the rest being recoverable over time. It is believed that the yield coxxesponds to plastic shearing between polymer chains corresponding to the disruption of secondary inter-chain bonds, fox example as discussed in Northolt, M.G_ et al_, Polyer Vol.
36, No. 18, pp. 3485-3492,1995, herein incorporated by reference, which provides a good description of the material mechanics and propose relevant theoretical models.
I
j0019] Figure 1 illustrates how upon loading, unloading and almost immediate reloading, the yield 'fee" in the load-elongation curve is no longer apparent.
Howevex, with a sufficient delay prior to reloading, the original yield characteristics return as the material seeks an equilibrium and secondary inter-chain bonds are re-established.
[0020] Being viscoelastic, plastic strapping is susceptible to tinne dependent relaxation upon loading. Plas'tie strap that is loaded and held at a constant elongation will undergo a lead decay (stress relaxation) while plastic strap that is under constant load will continue to elongate over time (creep). This behavior contrasts with that of steel, for example, where cxeep and stress relaxation are negligible.
[0020 As previqusly mentioned, stress relaxation can compromise pacl~age unitization.
Zt has been recognized that fibers which exhibit viscoelastic effects such as stress relaxation could be diminished by mechanical conditioning consisting of pre-loading the fibers to a load level that is higher than that used in the second loading.
This is discussed, for example, in Leaderman, H., Elastic and GYeep Properties of Filamentous Materials and Other High Polymers, 1943, herein incorporated by reference. The present invention makes use of this technique, hereafter referred to as "pre-stretching", to reduce the strap tension idsses that result from stress relaxation and package settling.
[0022] FIGS. 2-S show a pre-stretching device 100 and a material accumulator constructed according to one embodiment of the present invention, As shown in h'IGS. 2-5, the pre-stretching device 100 includes a bevel gear motor 110 that a used to provide power to a plurality of rollers 120. Although a bevel gear motor 110 is depicted in FIGS.
2-5, other types of motors may be used. A pair of polychains 130 are used to transfer the energy generated by the bevel gear motor 110 to the plurality of rollers 120.
Atty. Dkt. No.: 080573-0106 [0023] In the embodiment of the invention depicted in FTGS. 2-5, ten of the rollers 120 are included in the pre-stretching device 100, with the rollers 120 separated into a first roller gz~oup 1 ~0 and a second roller group 150.
[0021] ~'he path of material 160 from a coil 165 to be pre-stretched is shown in FIGS. 2 and 3. The material 160, which can comprise polyester or polypropylene strapping in various embodiments of the invention, is fed f~'om the,~coil 165 through an entrance point 170 on the pre-stretching device 100. In one embodiment of the invention, the material 160 passes over a preliminary tower 185 before reaching the entrance point 170. After passing through the entrance point 170, the material 160 passes around each of the rollers 120 in the firsi roller group 1 d0. Once the material 160 has passed around the last of the rollers 120 in the first roller group 140, it travels to the second roller group 150, where it passes around each of the remaining rollers 120 before exiting the pre-stretching device 100 through an exit point 180. rn one embodiment of the invention, the first roller group 140 and the second roller group 150 each comprise five of the rollers 120, [0025] Generahy, the material 160 can be pre-stretched to any elongation level that exceeds that which is applied to the package, but that is less than the break elongation of the strap. In one embodiment, for polyester strapping, the pre-stretch elongation level should be at least about 5% in order to reali2e a benefit to unitization and it should be no greater than about 10% so as to minimize the risk of the strap fracturing during pre-stretching. Within this range, higher pre-stretching levels offer greater potential benefits to unitization, but at the cost of Beater reductions to flexural rigidity and the resulting challenges to consistent feeding of the strap through large arches.
[0026] Figure 7 illustrates the effect of pre-stretching on stiffness of the strap. As can be seen from Figure 7, pre-stretching results in a lower bending load being necessary to achieve a particular deflection angle. The impact of the prestreching on stiffi~ess dissipates over time, as can be seen from the increase in stiffness from the 0.5 minute sample through to the 19 hour sample. In addition, a greater amount of pre-stretching will result in a greater reduction in stiffness as can be seen in the 10% pre-stretching sample in comparison io the non-stretched and the 7% pre-stretch samples.
Atty, Dkt. No.: 080573-0106 [0027] In one embodiment of the invention, the ratio of the roll surface speed of the second roller group 150 to that of the first roller group 140 is fixed at about 1.07:1. This causes the material I60 to be stretched by up to about seven percent over its original length. Importantly, this design maintains the original properties and characteristics of the material 160 and maintains the integrity of the material 160 due to the recovery of the pre-stretched strapping, ultimately creating a tighter ~t around the objects to be strapped during the unitization process. This embodiment of the present invention may be used in conjunction with a commercial strapping system to achieve improvement tension retention on PET bottle loads, as shown in Figure 3. Tt may be seen that one week following strap application, the tension loss in the pre-stretched straps was two thirds that of the straps that were not pr~stretched.
(0028] In one embodimart of the invention, each of the plurality o~rolle~rs 120 is preferably coated with urethane rubber. The urethane rubber coating provides a high friction surface which prevents the material 160 from slipping on the rollers ?~20. It will be evident to these skilled in the art that slippage could also be prevented by using other types of surface finish, or by increasing the wrap angle or the number of rollers, or perhaps by pre-stretching in a plurality of stages.
[0029] The material 160 can be fed through the pre-stretching device I00 at a variety of speeds. Tn one embodiment of the invention, the material 160 is routed through the pre-stretching device 100 at about five feet per second. rn another embodiment, the material 160 is routed through the pre-stretching device 100 at about four feet per second. At this speed, the material 160 is stretched by up to about eight percent over its original length.
Irrtportan~ly, this design maintains the original properties and characteristics of the material 160 and maintains the integrity of the material '160 due to the recovery of the pre stretch strapping, ultimately creating a tighter fit around the objects to be strapped during the unitization process.
[0030] After the material 160 exits the pre-stretching device 100 through the exit point 180, it enters the material accumulator 200 shown in FIGS. 2, 3 and 5, The material accumulator 200 includes a housing 210. The material accumulator 200 includes an Arty. Dkt_ No.: 080573-0106 accumulator entrance region 230 for the material 160. Substantially opposite the entrance region 230 is an exit region 240. The exit regiozt 240 includes an $ecumulator wheel assembly 265 which, in one embodiment of the invention, includes a wheel bracket 250 for mounting a ~Iat accumulator wheel 260 attd a flanged accumulator wheel 270.
The material 160 passes tluough the accumulator entrance region 230, across the material accumulator 200, and through the accumulator exit region 240 through the accumulator .
wheel assembly 265, particularly fhe flat accumulator wheel 260 and the flanged accumulator wheel 270. The flanges on the flanged accumulator wheel 270 act as a guide for the materia1.160.
[00371) In one embodiment of the invention, the accumulator wheel assembly 265 is positinnally adjustable. For example and as shown in FIG 2, the accumulator wheel assembly 265 is located at the top of the material accumulator 200. Iz~ FIG.
3, on the other hand, the accumulator wheel assembly 265 is positioned closer to the bottom of the material accumulator 200. The relative height of the accumulator wheel assembly 265 has a direct e~'ect on the speed at which the material 160 passes through the pre-stretching device 100 and the material accumulator 200. In particular, and in ore embodiment of the invention, the material 160 moves at a maximum speed when the accumulator wheel assembly z65 is located near the bottom of the material accumulator 200, with the accumulator wheel assembly 265 moving at progressively lower speeds as the accumulator wheel assembly 265 is raised.
[0032j After exiting the material accumulator 200 though the accumulator exit region 240, the matErial 160 is routed to a conventional strapping system 300, as shown in h'IG.
2.
[0033] In another embodiment of the invention (riot shown), a nan-continuous strap feed can be used. This embodiment allows for the momentary control of pre-stretch material 160 using an accumulator to "hold" the material 160 as it waits to move into active feeding around a skid of objects to be unitized.
[0034] The foregoing description of embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to be exhaustive _7_ Arty. Dkt, No.: 080573-0106 ox to Jirnit the present inventiozt to tb,e precise form disclosed, and modifications and variatioxys axe possible in light of the above teachings or may be acquired from practice of the present invention. The embodiments were chosen and described in order to explain the principles of the present invention and its practical application to enable one skilled in the art to utilize the present invention in various embodiments and with various modifications as are suited to the particular use contemplated.
_g_
However, the introduction of stretch film to the unitization process for plastic containers also increased the cost of unitization by a multiple of about 2.5, Therefore, it would be desirable to develop a system and method for unitizing bundles of plastic containers that possess the benefits of stretch ~Im while also lowering the uniti2ation cost, SUMMARY OF THE INVENTTON
X4007] The present invention provides for an improved system and method of pre-stretching material for use in unitizing groups of plastic bottles. The present invention involves the use of a novel pre-stretching maehitte having a plurality of rollers. The rollers are used to pre-stretch tire plastic strapping, which is then transferred town accumulator before being used to package the respective containers.
[0008] The pz~e-stretch system and method of the present invention provides for the elimination of stretch film while producing higher retained strap tension that provides for a secure load of plastic containers. The present invention effectively eliminates the need for high tension of the package while providing a strap that is within the dynamic working range for retained tension. The plastic strapping can be pre-stretched without destroying the properties and characteristic of the plastic strappi~, instead only temporarily losing stability and rigidity in the strapping.
Atty, I~kt. No.: 08073-0106 (0009] These and other objects, advantages and features of the invention, together with the organization and manner of operation thereof', will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have Iike numerals throughout the several drawings described below.
BRrEp' bESCRIPTION OF THE'DRAW1NGS
[0010] FIG, 1 is a graph illustrating the relationship between strap Ioad vs eloxigation over time; ' (0011] FIG. 2 is a side vieww of a pre-stretching device, a material accumulator and a packaging machine according to one embodiment of the present invention;
[0012] FIG. 3 is a front view of pre-stretching device of FIG. 2, along with a representation of a portion of the material accumulator with the position of the accumulator wheel assembly, both according to one embodiment of the invention;
[0013] FIG. 4 is a side view of the pre-stretching device of FIG. 3;
[oolal FIG. 5 is a top view of the pre-stretclung device and material accumulator portion of FTG. 3; .
(0015] FIG. 6 is a graph illustrating the effect of pre-stretching on xetained tension; and [001C>] FIG. 7 is a graph illustrating the efFect of pre-stretching on stiffness.over time.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Plastic strapping is produced using a stretching process that is similar to that employed iz~ the production of fibers. This process results in the preferential orientation, of polymer molecules (or chains) along the strap length and a several-fold increase in tensile strength.
[00x8] Oriented plastic exhibits viscoelastic-plastic behavior in response to mechanical loading. Elastic deformation and recovery is pattly immediate and partly time dependent. Yielding occurs over a broad range rather than at a well defined point, and Atty. Dkt, No.:~080573-0106 the yield deformation itself is time dependent and only partly permanent (or "plastic"), the rest being recoverable over time. It is believed that the yield coxxesponds to plastic shearing between polymer chains corresponding to the disruption of secondary inter-chain bonds, fox example as discussed in Northolt, M.G_ et al_, Polyer Vol.
36, No. 18, pp. 3485-3492,1995, herein incorporated by reference, which provides a good description of the material mechanics and propose relevant theoretical models.
I
j0019] Figure 1 illustrates how upon loading, unloading and almost immediate reloading, the yield 'fee" in the load-elongation curve is no longer apparent.
Howevex, with a sufficient delay prior to reloading, the original yield characteristics return as the material seeks an equilibrium and secondary inter-chain bonds are re-established.
[0020] Being viscoelastic, plastic strapping is susceptible to tinne dependent relaxation upon loading. Plas'tie strap that is loaded and held at a constant elongation will undergo a lead decay (stress relaxation) while plastic strap that is under constant load will continue to elongate over time (creep). This behavior contrasts with that of steel, for example, where cxeep and stress relaxation are negligible.
[0020 As previqusly mentioned, stress relaxation can compromise pacl~age unitization.
Zt has been recognized that fibers which exhibit viscoelastic effects such as stress relaxation could be diminished by mechanical conditioning consisting of pre-loading the fibers to a load level that is higher than that used in the second loading.
This is discussed, for example, in Leaderman, H., Elastic and GYeep Properties of Filamentous Materials and Other High Polymers, 1943, herein incorporated by reference. The present invention makes use of this technique, hereafter referred to as "pre-stretching", to reduce the strap tension idsses that result from stress relaxation and package settling.
[0022] FIGS. 2-S show a pre-stretching device 100 and a material accumulator constructed according to one embodiment of the present invention, As shown in h'IGS. 2-5, the pre-stretching device 100 includes a bevel gear motor 110 that a used to provide power to a plurality of rollers 120. Although a bevel gear motor 110 is depicted in FIGS.
2-5, other types of motors may be used. A pair of polychains 130 are used to transfer the energy generated by the bevel gear motor 110 to the plurality of rollers 120.
Atty. Dkt. No.: 080573-0106 [0023] In the embodiment of the invention depicted in FTGS. 2-5, ten of the rollers 120 are included in the pre-stretching device 100, with the rollers 120 separated into a first roller gz~oup 1 ~0 and a second roller group 150.
[0021] ~'he path of material 160 from a coil 165 to be pre-stretched is shown in FIGS. 2 and 3. The material 160, which can comprise polyester or polypropylene strapping in various embodiments of the invention, is fed f~'om the,~coil 165 through an entrance point 170 on the pre-stretching device 100. In one embodiment of the invention, the material 160 passes over a preliminary tower 185 before reaching the entrance point 170. After passing through the entrance point 170, the material 160 passes around each of the rollers 120 in the firsi roller group 1 d0. Once the material 160 has passed around the last of the rollers 120 in the first roller group 140, it travels to the second roller group 150, where it passes around each of the remaining rollers 120 before exiting the pre-stretching device 100 through an exit point 180. rn one embodiment of the invention, the first roller group 140 and the second roller group 150 each comprise five of the rollers 120, [0025] Generahy, the material 160 can be pre-stretched to any elongation level that exceeds that which is applied to the package, but that is less than the break elongation of the strap. In one embodiment, for polyester strapping, the pre-stretch elongation level should be at least about 5% in order to reali2e a benefit to unitization and it should be no greater than about 10% so as to minimize the risk of the strap fracturing during pre-stretching. Within this range, higher pre-stretching levels offer greater potential benefits to unitization, but at the cost of Beater reductions to flexural rigidity and the resulting challenges to consistent feeding of the strap through large arches.
[0026] Figure 7 illustrates the effect of pre-stretching on stiffness of the strap. As can be seen from Figure 7, pre-stretching results in a lower bending load being necessary to achieve a particular deflection angle. The impact of the prestreching on stiffi~ess dissipates over time, as can be seen from the increase in stiffness from the 0.5 minute sample through to the 19 hour sample. In addition, a greater amount of pre-stretching will result in a greater reduction in stiffness as can be seen in the 10% pre-stretching sample in comparison io the non-stretched and the 7% pre-stretch samples.
Atty, Dkt. No.: 080573-0106 [0027] In one embodiment of the invention, the ratio of the roll surface speed of the second roller group 150 to that of the first roller group 140 is fixed at about 1.07:1. This causes the material I60 to be stretched by up to about seven percent over its original length. Importantly, this design maintains the original properties and characteristics of the material 160 and maintains the integrity of the material 160 due to the recovery of the pre-stretched strapping, ultimately creating a tighter ~t around the objects to be strapped during the unitization process. This embodiment of the present invention may be used in conjunction with a commercial strapping system to achieve improvement tension retention on PET bottle loads, as shown in Figure 3. Tt may be seen that one week following strap application, the tension loss in the pre-stretched straps was two thirds that of the straps that were not pr~stretched.
(0028] In one embodimart of the invention, each of the plurality o~rolle~rs 120 is preferably coated with urethane rubber. The urethane rubber coating provides a high friction surface which prevents the material 160 from slipping on the rollers ?~20. It will be evident to these skilled in the art that slippage could also be prevented by using other types of surface finish, or by increasing the wrap angle or the number of rollers, or perhaps by pre-stretching in a plurality of stages.
[0029] The material 160 can be fed through the pre-stretching device I00 at a variety of speeds. Tn one embodiment of the invention, the material 160 is routed through the pre-stretching device 100 at about five feet per second. rn another embodiment, the material 160 is routed through the pre-stretching device 100 at about four feet per second. At this speed, the material 160 is stretched by up to about eight percent over its original length.
Irrtportan~ly, this design maintains the original properties and characteristics of the material 160 and maintains the integrity of the material '160 due to the recovery of the pre stretch strapping, ultimately creating a tighter fit around the objects to be strapped during the unitization process.
[0030] After the material 160 exits the pre-stretching device 100 through the exit point 180, it enters the material accumulator 200 shown in FIGS. 2, 3 and 5, The material accumulator 200 includes a housing 210. The material accumulator 200 includes an Arty. Dkt_ No.: 080573-0106 accumulator entrance region 230 for the material 160. Substantially opposite the entrance region 230 is an exit region 240. The exit regiozt 240 includes an $ecumulator wheel assembly 265 which, in one embodiment of the invention, includes a wheel bracket 250 for mounting a ~Iat accumulator wheel 260 attd a flanged accumulator wheel 270.
The material 160 passes tluough the accumulator entrance region 230, across the material accumulator 200, and through the accumulator exit region 240 through the accumulator .
wheel assembly 265, particularly fhe flat accumulator wheel 260 and the flanged accumulator wheel 270. The flanges on the flanged accumulator wheel 270 act as a guide for the materia1.160.
[00371) In one embodiment of the invention, the accumulator wheel assembly 265 is positinnally adjustable. For example and as shown in FIG 2, the accumulator wheel assembly 265 is located at the top of the material accumulator 200. Iz~ FIG.
3, on the other hand, the accumulator wheel assembly 265 is positioned closer to the bottom of the material accumulator 200. The relative height of the accumulator wheel assembly 265 has a direct e~'ect on the speed at which the material 160 passes through the pre-stretching device 100 and the material accumulator 200. In particular, and in ore embodiment of the invention, the material 160 moves at a maximum speed when the accumulator wheel assembly z65 is located near the bottom of the material accumulator 200, with the accumulator wheel assembly 265 moving at progressively lower speeds as the accumulator wheel assembly 265 is raised.
[0032j After exiting the material accumulator 200 though the accumulator exit region 240, the matErial 160 is routed to a conventional strapping system 300, as shown in h'IG.
2.
[0033] In another embodiment of the invention (riot shown), a nan-continuous strap feed can be used. This embodiment allows for the momentary control of pre-stretch material 160 using an accumulator to "hold" the material 160 as it waits to move into active feeding around a skid of objects to be unitized.
[0034] The foregoing description of embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to be exhaustive _7_ Arty. Dkt, No.: 080573-0106 ox to Jirnit the present inventiozt to tb,e precise form disclosed, and modifications and variatioxys axe possible in light of the above teachings or may be acquired from practice of the present invention. The embodiments were chosen and described in order to explain the principles of the present invention and its practical application to enable one skilled in the art to utilize the present invention in various embodiments and with various modifications as are suited to the particular use contemplated.
_g_
Claims (25)
1. A method of pre-stretching a plastic material for use in unitizing a plurality of objects, comprising:
providing the plastic material to a pre-stretching device including a plurality of rollers;
passing the plastic material around the plurality of rollers within the pre-stretching device; and feeding the plastic material from the pre-stretching, device to a strapping device, wherein the passing of the plastic material around the plurality of rollers cause the plastic material to stretch by a predetermined amount before entering the strapping device.
providing the plastic material to a pre-stretching device including a plurality of rollers;
passing the plastic material around the plurality of rollers within the pre-stretching device; and feeding the plastic material from the pre-stretching, device to a strapping device, wherein the passing of the plastic material around the plurality of rollers cause the plastic material to stretch by a predetermined amount before entering the strapping device.
2. The method of claim 1, wherein the plurality of ropers comprise two groups of rollers.
3. The method of claim 2, wherein each of the two groups of rollers comprise five rollers.
4. The method of claim 1, wherein each of the plurality of rollers include a urethane coating.
5. The method of claim 1, further comprising, before feeding the plastic material to the strapping device, passing the plastic material through an accumulator wheel assembly within an accumulator.
6. The method of claim 5, wherein the accumulator wheel assembly comprises:
an accumulator wheel bracket;
a flat accumulator wheel rotatably connected to the accumulator wheel bracket; and a flanged accumulator wheel rotatably connected to the accumulator wheel bracket and positioned relative to the flat accumulator wheel such that the flanged accumulator wheel and the flat accumulator wheel cooperate to guide the plastic material through the accumulator wheel assembly.
an accumulator wheel bracket;
a flat accumulator wheel rotatably connected to the accumulator wheel bracket; and a flanged accumulator wheel rotatably connected to the accumulator wheel bracket and positioned relative to the flat accumulator wheel such that the flanged accumulator wheel and the flat accumulator wheel cooperate to guide the plastic material through the accumulator wheel assembly.
7. The method of claim 5, wherein the position of the accumulator wheel assembly is adjustable relative to the remainder of the accumulator, and wherein the relative position of the accumulator wheel assembly affects the rate at which the plastic material enters the strapping device.
8. The method of claim 1, wherein the plastic material is passed around the plurality of rollers at about four feet per second.
9. The method of claim 1, wherein the plastic material is passed around the plurality of rollers at about five feet per second.
10. The method of claim 1, wherein the plastic material is stretched about five to about ten percent over its original length as it passes through the pre-stretching device,
11. The method of claim 1, wherein the plastic material is stretched about eight percent over its original length as it passes through the pre-stretching device.
12. The method of claim 1, wherein the plastic material is stretched about seven percent over its original length as it passes through the pre-stretching device.
13. An assembly for pre-stretching a plastic material for use in unitizing a plurality of objects, comprising:
a pre-stretching device including:
a pre-stretching device entrance region, a pre-stretching device exit region, a plurality of rollers positioned between the pre-stretching device entrance region and the pre-stretching device exit region, and an energy and torque source for driving each of the plurality of rollers at a predetermined rate, wherein the plurality of rollers are positioned to define a pathway for the plastic material through the pre-stretching device, and wherein the plastic material is stretched by a predetermined amount as it passes through the assembly before being fed to a strapping device.
a pre-stretching device including:
a pre-stretching device entrance region, a pre-stretching device exit region, a plurality of rollers positioned between the pre-stretching device entrance region and the pre-stretching device exit region, and an energy and torque source for driving each of the plurality of rollers at a predetermined rate, wherein the plurality of rollers are positioned to define a pathway for the plastic material through the pre-stretching device, and wherein the plastic material is stretched by a predetermined amount as it passes through the assembly before being fed to a strapping device.
14. The assembly of claim 13, wherein the plurality of rollers comprise two groups of rollers.
15. The assembly of claim 14, wherein each of the two groups of rollers comprise flue rollers.
16. The assembly of claim 13, wherein each of the plurality of rollers include a urethane coating.
17. The assembly of claim 13, further comprising an accumulator positioned downstream from the pre-stretching device, wherein the plastic material passes through an accumulator before reaching the strapping device.
18. The assembly of claim 17, wherein the accumulator includes an accumulator wheel assembly comprising:
an accumulator wheel bracket;
a flat accumulator wheel rotatably connected to the accumulator wheel bracket; and a flanged accumulator wheel rotatably connected to the accumulator wheel bracket and positioned relative to the flat accumulator wheel such that the flanged accumulator wheel and the flat accumulator wheel cooperate to guide the plastic material through the accumulator wheel assembly.
an accumulator wheel bracket;
a flat accumulator wheel rotatably connected to the accumulator wheel bracket; and a flanged accumulator wheel rotatably connected to the accumulator wheel bracket and positioned relative to the flat accumulator wheel such that the flanged accumulator wheel and the flat accumulator wheel cooperate to guide the plastic material through the accumulator wheel assembly.
19. The assembly of claim 18, wherein the position of the accumulator wheel assembly is adjustable relative to the remainder of the accumulator, and wherein the relative position of the accumulator wheel assembly affects the rate at which the plastic material enters the strapping device.
20. The assembly of claim 13, wherein the assembly is configured to stretch the plastic material between about five and ten percent over its original length as it passes through the assembly.
21. The assembly of claim 13, wherein the assembly is configured to stretch the plastic material about seven, percent over its original length as it passes through the assembly.
22. The assembly of claim 13, wherein the assembly is configured to pass the plastic material through the assembly at a rate of about four feet per second.
23. The assembly of claim 12, further comprising a preliminary tower positioned upstream of the pre-stretching device, the preliminary tower guiding the plastic material upstream of the pre-stretching device.
24. The assembly of claim 13, wherein the energy and torque source comprises a bevel gear motor.
25. The assembly of claim 13, wherein the assembly is configured to stretch the plastic material between about eight percent over its original length as it passes through the assembly.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US67302905P | 2005-04-20 | 2005-04-20 | |
| US60/673,029 | 2005-04-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2544670A1 true CA2544670A1 (en) | 2006-10-20 |
Family
ID=37114229
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002544670A Abandoned CA2544670A1 (en) | 2005-04-20 | 2006-04-20 | System and method for pre-stretching plastic material |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US20060254213A1 (en) |
| CA (1) | CA2544670A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113291520A (en) * | 2021-05-18 | 2021-08-24 | 浙江百事特包装科技股份有限公司 | Sword baling press is worn to anticollision formula |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL2033780B1 (en) * | 2022-12-21 | 2024-06-27 | Dutch Banding Company B V | Equipment for banding products |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4095318A (en) * | 1975-07-15 | 1978-06-20 | Allied Chemical Corporation | Controlled tow stretcher |
| US4706443A (en) * | 1982-05-04 | 1987-11-17 | International Packaging Machines, Inc. | Constant tension stretch wrapping machine |
| US5186981A (en) * | 1984-10-26 | 1993-02-16 | Lantech, Inc. | Rollers for prestretch film overwrap |
| US4934123A (en) * | 1988-02-25 | 1990-06-19 | Roy Salzsauler | Carriage |
| US4991381A (en) * | 1989-06-07 | 1991-02-12 | Liberty Industries | Stretch wrapped braking apparatus |
| US5014489A (en) * | 1989-09-07 | 1991-05-14 | Pacmac, Inc. | Film sheet feed for food tray film wrapping machine |
| US5673614A (en) * | 1996-02-20 | 1997-10-07 | H.W.J. Designs For Agribusiness | Wire tying device |
| US5644978A (en) * | 1996-02-29 | 1997-07-08 | H.W.J. Designs For Agribusiness | Wire tying apparatus for down-packer cotton press |
| FR2748734B1 (en) * | 1996-05-06 | 1998-07-31 | Thimon | OVERPACKING FILM, FILM PRE-STRETCHING DEVICE AND OVERPACKING PROCESS |
| FI101282B1 (en) * | 1996-12-02 | 1998-05-29 | Haloila M Oy Ab | wrapping machine |
| WO2000044620A1 (en) * | 1999-01-29 | 2000-08-03 | Jaenson Howard W | Automatic bale strapping system |
| US6185914B1 (en) * | 1999-09-10 | 2001-02-13 | 1137508 Ontario Ltd. | Pre-stretch web dispenser |
| US6487833B1 (en) * | 2000-01-29 | 2002-12-03 | Howard W. Jaenson | Strap welding system and method |
| GB0109646D0 (en) * | 2001-04-19 | 2001-06-13 | Itw Ltd | Web tensioning device |
| ITBO20030436A1 (en) * | 2003-07-22 | 2005-01-23 | Aetna Group Spa | EQUIPMENT FOR PRODUCT GROUPS. |
-
2006
- 2006-04-11 US US11/402,174 patent/US20060254213A1/en not_active Abandoned
- 2006-04-20 CA CA002544670A patent/CA2544670A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113291520A (en) * | 2021-05-18 | 2021-08-24 | 浙江百事特包装科技股份有限公司 | Sword baling press is worn to anticollision formula |
| CN113291520B (en) * | 2021-05-18 | 2022-07-19 | 浙江百事特包装科技股份有限公司 | Sword baling press is worn to anticollision formula |
Also Published As
| Publication number | Publication date |
|---|---|
| US20060254213A1 (en) | 2006-11-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |