Paired bags and method of making same

Abstract

A set of bags comprises a first lay-flat bag and a second lay-flat bag joined along their respective lengths. An end seal extending across both the first bag and the second bag. The first bag has a first side seal extending the length of the first bag, and the second bag has a second side-seal extending the length of the second bag. The first bag is connected with the second bag in an area between the first side-seal and the second side-sea. Both the first bag and the second bag having a total free shrink at 185° F. of at least 10 percent and a transverse free shrink at 185° F. which is greater than a longitudinal free shrink at 185° F.

Description

FIELD OF THE INVENTION [0001] The present invention relates to sets of bags made from a heat-shrinkable flexible packaging film. BACKGROUND OF THE INVENTION [0002] Heat-shrinkable bags made from flexible thermoplastic film have for some time been used for the packaging of various products, such as food products, especially meat. An “end-seal” bag is one such bag. In the making of heat-shrinkable end-seal bags, thermoplastic material is extruded from an annular die, in the form of a seamless tubing, with the extrudate (known as a “tape”) being relatively thick and relatively narrow. The annular extrudate is then quenched. Optionally, the tape can then be irradiated and / or coated with one or more additional layers containing thermoplastic polymer. The tape is then reheated to its softening point by exposure to hot water or steam (or other heating means) and is stretched in its longitudinal and transverse directions while the polymer remains in the solid state, resulting in heat-shrink...

AI Technical Summary

Benefits of technology

[0006] The present invention provides a set of heat-shrinkable bags and a process for making sets of such bags. In the process, the number of printing cycles, as well as the number of cycles used to make the transverse seals, can be cut in half, thirds, etc., while making the same total number of bags, thereby enabling a doubling, tripling, etc., of the number of bags per extrusion die, as well as per print cycle and per transverse seal cycle. In addition, the sets of heat-shrinkable bags have a lengthwise free shrink (i.e., shrink in the machine direction) which is less than the transverse free shrink (i.e., shrink across the width of the bags), so that during shrinking the heat-shrinkable bags have less tendency to distort flat, flexible, elongate products packaged in the bag.

[0007] The process can be used to produce sets of bags in which the bags of each set are connected with one another across the machine direction of the film being used to make the bags. Optionally, each set of bags can be provided with an appropriate number of longitudinal tear lines (i.e., tear lines running the length of the bags, i.e., in the machine direction) for ease in separating the bags from one another. In addition, because the bags are connected to one another, like a single bag the connected series of bags can be stretched out across the opening of a vacuum chamber without risk of overlap during sealing.

[0008] Moreover, the invention can be carried out so that each set of bags is connected to at least one other set of bags in a line of succession, e.g., resulting in a strand of paired bags, which can be of indeterminate length as it comes off of a production line. Optionally, this strand of sets of bags can be provided with transverse tear lines (i.e., a weakened region between the sets of bags, such as a line of perforations, etc.) so that each set of bags can be easily torn free of the strand of bags, as well as lengthwise (i.e., machine direction) tear lines between the bags of each set, so that the packaged product can be offered as singlets or any subset of the original set of bags.

[0009] In the sets of bags of the invention, the bag length of each of the bags in the set runs in the machine direction of the tubing. Likewise, the bag width of each of the bags in the set runs in the transverse direction, i.e., across the tubing. A greater free shrink in the transverse direction is desirable for the packaging of a wide variety of products, particularly food products which tend to distort by bending along the length of the bag in which they are packaged. Various meat products, such as small beef and pork cuts, for example, beef and pork tenderloin, eye of round, single ribs, beef spare ribs, split beef back ribs, and various lamb cuts, tend to distort (i.e., bend) if packaged in a shrink bag having a higher shrink along the length of the bag than across the width of the bag. Such package distortion is reduced or eliminated in the sets of bags of the invention, which have have greater free shrink across the bag than along the length of the bag.

Problems solved by technology

If two small bags are loaded into the same vacuum chamber at the same time, they may overlap and have weak seals.

However, if a single small bag is loaded into the large chamber, capacity is under-utilized and additional labor is required.

However, side-seal bags have a disadvantage of having a free shrink along the length of the side-seal bag (i.e., in the transverse direction of the length of the seamless tubing) which is higher than the free shrink across the width of the side-seal bag (i.e., corresponding with the length of the tubing).

Having a higher shrink across the tubing is detrimental to the packaging of relatively long, flat, flexible products in side-seal bags, as during subsequent bag-length shrinkage of a side-seal bag, the product can become distorted, i.e., “curved”, which lowers the appearance of the package to a consumer, and which is more difficult to box because of the curve in the package.

Moreover, paired side-seal bags cannot be provided as a continuous string of connected pairs, as to make the “pair” requires that the pair be separated from the remainder of side-seal bags formed from the tubing.

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