CA1056319A

CA1056319A - Easy open shrink wrap package

Info

Publication number: CA1056319A
Application number: CA232,625A
Authority: CA
Inventors: Frederick J. Doughty; Algimantas P. Urbutis
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1974-08-26
Filing date: 1975-07-31
Publication date: 1979-06-12
Also published as: ES440435A1; DK376775A; BR7505411A; ZA755409B; JPS5146292A; SE7509447L; DE2537669A1; DE2537669C3; BE832718A; FI752388A; AR206933A1; NO752922L; DE2537669B2; ATA655075A; AU8423075A; CH599882A5; MX143111A; ES445662A1; FR2283063A1; JPS559343B2

Abstract

ABSTRACT OF THE DISCLOSURE
A shrink wrap film package, such as a package of shirred sausage product casings, is provided with a wrap removal finger hole tearing grip pocket adjacent a tear initiating slit in a low stress area of the wrap, the combination defining a grip means which is easily pulled to tear the wrap and facilitate its removal from the packaged contents.

Description

~ 1os63l9 This invention relates to a package article, particularly to a shrink wrap package article, and more particularly to an easy to open shrink wrap pack-age article, such as a food product, or a package of shirred food casings of the type customarily used in the manufacture of meat sausage products, in which an assembly of the shirred casings are held securely for handling, shipping, and storage by an overwrap of resil- -ient shrink fitted film material.

Shrink wrap packaging techniques have found wide acceptance in industry and commerce, particularly in the food packaging industry where their adoption and use implement and facilitate maintenance of the essential and strictly imposed criteria of hygienic purity and package integrity, not only during packing operations as such, but also in the handling, shipping, storage, retail sale, and ultimate utilization of the packaged commodity - by the consumer. In the meat packing industry for instance, ' shrink wrap techniques are employed in the packaging of processed presliced and whole piece meats such as bacon, sausage products, ham, and rolled and loafed meats and the like. Food casings such as cellulose frankfurter casings are also shrink wrapped in assemblies of shirred and compressed lengths known in the industry as casing sticks. In U.S. Patent 3,764,351 to Whittington et al, package articles containing shrink wrap shirred food casing sticks are described and it is to such package articles, amongst others, that the present invention ` contributes significant ~mprovements.

Known shrink wrap package articles, because of their toughness and high structural integrity, do not, . .
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~056319 on experience, lend themselves to facile opening and removal of the shrink fitted overwrap. During the shrinking operation of the resilient film overwrap con-ventionally used, film sheet or sleeve edges unrestrained by the packaged article or articles shrink back and thicken, producing rim-like edges which are difficult to tear and sometimes even to cut. Where resilient film sheets are placed under and over a relatively flat meat article for instance, heat seamed and heat shrunk, the resulting heat seam bead around the package perimeter presents a formidable line of resistance to tear initiation in the shrink fitted overwrap. Where resilient film sleeves, either cut from continuous blowR extruded plastic film tubing or made up by heat seaming plastic film sheets, are used as the overwrap and the open sleeve ends are folded in over the articles, end panels, or other package elements, and the article heat shrunk, the edges of the heat shrunk sleeve are similarly tough and difficult to tear. A more explicit explanation of this phenomenon and of the cause of high and low tensile stress areas occurring in different areas of the shrink film wrap material is included hereinafter.

; Towards solving the problems attending opening shrink wrap package articles, the industry has tried and employed tabs extending exteriorly of heat seam bead lines such as commonly seen on film packaged bacon and the like articles, perforations or weakened points in the shrunk overwrap, tear tapes or strips imbedded in or disposed under the overwrap, and various other inovations and attempted panaceae, all with less than completely satisfactory results. Without belaboring this point, it .

10563~9 ` is enough for the purposes of this discussion to recog-nize the fact that most users eventually remove the over-wrap from a shrink wrap package article by piercing through the wrap with a cutting implement, at least to initiate a tear stripping point, and then randomly pull and tear the wrap off the package, perhaps cutting or piercing it again as necessary, to gain access to the packaged contents. As undesirable and uncomfortable as this mode of opening shrink wrap packages may be in a general sense, it quite factually is intolerable where the package contents are of a fragile nature, susceptible to surface damage and easily contam-inated, such as is the case with shirred food casing sticks. In such cases it is essential not only that the shirred sticks be available structurally undamaged, such as being scratch and pinhole free, but also that no con-taminating scraps of overwrap material be produced to interfere with the shirred sticks utilization.

The shirred casing or stick, is, it will be readily appreciated, a relatively fragile structure. Since the feeding of s~icks to the stuffing machines is most frequently an automatic operation involving the positioning of each stick in turn on the stuffing horn from a supply hopper, any structural irregularity in the stick such as curvature of the bore, bowing or other deformation causes breakage, ~ --jamming or other malfunction with consequent shutdown and loss of production time on the stuffing machine. It is therefore essential that the structural integrity and shape of the stick as it leaves the shirring machine be carefully maintained through handling, packaging, transportation, storage, and particularLy unpackaging, until the stick is in place on the horn of the stuffing machine. The benefit : ~;

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of the careful maintenance of casing stick structural integrity is lost and wasted i.f some of the sticks in a package are pierced, nicked, cut, or otherwîse damaged in openlng the stick package.

As noted above,' attempts at solvîng the problems attending openîng shrînk wrap package articles, particularly skîrred food casing stick packages, have ~een less than completeIy successful. Perforations, weakened lines, and ot~er such modes of di~nishing the structural integrity of the package în a shrink tî.ghtened high tensile stress area of the wrap film material frequently result in accîdental openings in handling, shipping, and such,' with' resultant contamination and loss of packaged product.
~mbedded tear tapes similarly occasîon accidental openings of packages, and are more costly to make. Tab-assisted '~
tearîng through a bead or h.eat se'am has provided a significant step towards solutîons of these probIems, but ; in opening shirred casing packages, th.e operator performing ~he unwrapping and hopper loading may have greasy, wet :
fingers or be wearing greasy, wet rubber gloves, which tend to slip off any sort of flat pulling tab.

With this being the state of the art, the' pres~ent invention was conceived and deveIoped to'make :' available to industry an easy to open shrink wrap package article.

A further ob.j':ect of the invention is to provide ' an easy to open shrink wrap package article'and technique . suitabIe for packaging perishable commoditîes, generally foods, partîcularly meat products and more partîcularly ~ food related products.
: ~ -5-1056~3~9 A further and more particular object of this invention is to provide an easy to open shrink wrap package article which is uniquely suitable for packaging fragile and contaminant-free, food-related c~mmodities such as shirred food casings or sticks.
A still further and important object of the present invention to provide a shrink wrap package article which maintains its structural integrity as it is made without any weak points or areas and which is readily and simply opened without piercing, cutting or otherwise endangering the contents thereof and which is free of tear tapes or similar ancillary elements used to facilitate opening in conventional such articles.

Another important object of the invention is to provide a shrink wrap shirred casing stick package having a positive grip finger-holed opening tab which can be effectively grasped and pulled with wet greasy fingers or glov~s to easily and effectively accomplish opening.

These and other objects will become the more readily apparent from the ensuing description and the appended drawings, wherein:
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Figure 1 is a perspective view of an assembly of casing sticks i~ the processes of being packaged accord-ing to the invention, shown with a finger hole forming dowel in place in the film wrap prior to heat shrinking;

Figure 2 is a perspective view of the Figure 1 assembly, shown subsequent heat shrinking of the package article, with the finger hole forming dowel still in place in the heat shrunk film wrap; and .~ .

Figure 3 is a perspective view of the Figure 2 assembly, shown with the finger hole forming dowel removed, and with a tear initiating slit made adjacent the dowel formed finger hole.

In general, the present invention is an improve-ment in a package article overwrapped with a resilient shrink fitted film material which, in place, has at least one area of low tensile stress relative to a tensile stress obtaining in another area thereof, the improvement comprising a package opening grip defined by a formed finger gripping hole through said material in said area of low tensile stress and, adjacent said hole, a tear initiating line in said material, extending from an exposed edge of said material into said area of low tensile stress.
The tear initiating line may be an elongate cut, or a row of perforations through the wrap film material, extending from an exposed edge of the material into less than completely through the low tensile stress area, or an end of a linearly extending seal comprised in the wrap, such as a heat seal made to form a sleeve from film sheet.

It is also possible within the scope of the in-vention to align the tear initiating line in parallel with one orien~ation direction of a biaxially oriented film, or with longitudinally extending heat seal, or to combine the various modes of cuts, perforations and seal seam lines, it being necessary only that the tear initiating line, of whatever form, is arranged adjacent the formed finger hole in a manner to define a grippable opening pull.

With reference to the drawings, Figure 1 shows a 30 package article 11 comprising a multipliçity of shirred -: . . - : - - . :

food casings or sticks 13 arrayed in a log pile arrangement so as to define a generally rectangular cross section package wrapped in a sheet of plastic film 15 which has been seamed longitudinally with a running heat seal 17 to define an open ended sleeve. End panels 19, 21 are inserted into the open ends of the film sleeve and pushed into abut- -ment with the stick ends. The sleeve ends extend over the end panels 19, 21 as edge portions or cuffs 23, 25. A
piercing dowel 27 is inserted through the cuff 23 film material adjacent the extending end of the heat seal 17 as shown. The dowel 27 may be of any suitable material, a 5/8 ineh diameter sharpened end wood dowel having been successfully used, it being desirable only that the dowel be of suitable size and diameter to form a finger size hole in the film material. A typical shrink fi~m for the illustrated embod~ment is plastic film material in the order of from about O.OS to about 0.08 millimeter thickness which may be employed in either sheet form or in sleeve form.
When tubular sleeves are used as the wrap, there is of course no heat seal 17.

After insertion of the piercing dowel 27 through the cuff 23, the cuffs are drawn down over the outer surfaces of the end panels 19, 21 and the assembly is heat shrunk, with the dowel left in place, to the condition shown in Figure 2 of the drawings. In the course of heat shrinking, or whatever other shrinking step employed, the edges of the film material cuffs 23, 25 shrinks and thickens. This shrinking and thickening occurs because the fi~m edges at ~he cuffs are virtually unrestrained by comparison wlth the areas of overwrap extending between the end panels 19, 21. Thus, in the wrap areas which are somewhat restrained at the time of the shrinking step, relatively high tensile .
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10563~9 stresses are developed in the film material, while in the areas where there is little or no restraint, such as at the cuff edges, only relatively low tensile stresses are developed. In these low tensile stress areas, the ab-sence of restraint allows relatively free pullback during shrinking and consequent thickening of the film material edge portions. In the drawings, the numeral 29 indicates such a relatively low tensile stress area and the numeral 31 indicates a relatively high tensile stress area. The shrinking and thickening of the film around the piercing dowel 27 forms a pocket or finger hole 33 which is shown more clearly in Figure 3.

Figure 3 shows the finished package article with the finger hole forming dowel 27 removed and with a tear initiating line, in the illustrated embodiment an elongate cut 35, made adjacent the finger hole 33, extending from the outer edge of the film material into, but less than completely through, the low tensile stress area 29. Here it is important to note that the tear initiating line may be any of several types. If the wrap is sheet material which has been seamed such as with a running heat seal to make a sleeve, the tear initiating line may be the end of the heat seal extending into and through the cuff 23 to its edge. If the tear initiating line is an elongate cut 35 or, alternatively, a row of perforations, it is important that such line extend from the film material only for enough into the low tensile stress area 2~ to facilitate tear initiation, and not into the high tensile stress area so as to raise the risk of accidental opening of the package.
The combination of the finger hole 33 and the tear initiating line, cut 35 for instance, defines a package opening grip 37, which can b~ firmly and positively grasped and pulled, without slipping or random tearing, to open the package.

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10563~9 While the foregoing description relates to shrink wrapped food casings packages, the invention is equally use-ful and applicable to any type of shrink wrapped article, and this whether the shrinking be effected by heat or any other mode. Numerous alternative modes of practicing the invention, but well within its scope, will, in the light of this disclosure, undoubtedly occur to persons conversant with the packaging arts. It is intended therefore that the . description herein be taken as illustrative only, and not construed in any limiting sense.

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Claims

What is claimed is:

1. In a package article overwrapped with a resilient shrink fitted film material which, in place, has at least one area of low tensile stress located contiguous to a shrink fitted edge of a sleeve form overwrap of resilient film material relative to a tensile stress obtaining in another area thereof, the improvement comprising a package opening grip defined by a formed finger gripping hole through said material in said area of low tensile stress and, adjacent said hole, a tear initiating line in said material, extending from an exposed edge of said material into said area of low tensile stress.

2. An improved package article according to claim 1 wherein said tear initiating line is an elongate cut extending from an exposed edge of said material into less then completely through said area of low tensile stress.

3. An improved package article according to claim 1 wherein said tear initiating line is an end of a linearly extending seal comprised in the overwrap of resilient shrink fitted film material.

4. An improved package article according to claim 1 wherein said tear initiating line is a row of perforations through said film material extending from an exposed edge of said material into less than completely through said area of low tensile stress.

5. An improved package article according to claim 2 wherein said elongate cut is disposed substantially parallel to one orientation direction of a biaxially oriented plastic film comprising the resilient shrink fitted film material.

6. An improved package article according to claim 3 wherein said linearly extending seal is a heat seal.

7. An improved package article according to claim 3 wherein said linearly extending seal is disposed substantially parallel to one orientation direction of a biaxially oriented plastic film comprising the resilient shrink fitted film material.

8. An improved package article according to claim 4 wherein said row of perforations is disposed substantially parallel to one orientation direction of a biaxially oriented plastic film comprising the resilient shrink fitted film material.

9. An improved package article according to claim 2 wherein said elongate cut is disposed in substantial alignment with a longitudinally extending seal comprised in the resilient shrink fitted film material.

10. An improved package article according to claim 9 wherein said longitudinally extending seal is a heat seal.

11. An improved package article according to claim 4 wherein said row of perforations is disposed in substantial alignment with a longitudinally extending seal comprised in the resilient shrink fitted film material.

12. An improved package article according to claim 11 wherein said longitudinally extending seal is a heat seal.

13. A method of making an opening grip in a package article overwrapped with a resilient shrink fitted film material which material, in place, has at least one area of low tensile stress relative to a tensile stress obtaining in another area thereof, which method comprises the steps of inserting a finger hole forming element through said film material at a point which, in the completed package article, will be in an area of low tensile stress, shrinking the film material overwrap onto the packaged article with the finger hole forming element in place in said material, removing the hole forming element from said material after the shrinking thereof to define a finger hole, and defining a tear initiating line in said material adjacent said finger hole.

14. The method according to claim 13 wherein the tear initiating line is defined by making an elongate cut extending from an edge of said material into less then completely through the area of low tensile stress.

15. The method according to claim 13 wherein the tear initiating line is defined by making a row of perforations through the material extending from an edge of said material into less than completely through the area of low tensile stress.