Flexible Pilfer Proof Closure Construction For Bags

Abstract

A thin plastic film bag having openable pressure releasable rib and groove elements and closure strips at the top for closing a top side opening with the first strip having a marginal portion extending downwardly and attached to the bag wall and the second strip having a marginal portion extending upwardly and attached to the bag wall, and the first strip having a flange extending upwardly attached to the marginal portion of the second strip and having a tear line for releasing the flange so that it can be used to pull open the bag by separating the rib and groove elements.

Parent Case Text

REFERENCE TO OTHER CASES

The present application is a continuation-in-part of my copending application, U.S. Ser. No. 12,187, filed Feb. 18, 1970, now U.S. Pat. No. 3,608,439.

Description

BACKGROUND OF THE INVENTION

Closure elements in which the closures are provided by interengaging strips of plastic material have become very commonplace. One of the most common types of configurations for such strips is illustrated in Madsen U.S. Pat. No. 2,613,421 owned by the assignee of the present application.

The present invention is directed to an improved bag construction having a closure which is substantially pilfer-proof in that the reclosable closure element is not directly accessible from the exterior of the bag, but requires separating or tearing a plastic strip to make it accessible.

The method of the present invention involves the simultaneous formation of a plurality of closure tubes from which individual bags or pouches can be made.

The invention particularly contemplates provision of closure strips for use on various types of pouches or bags such as those utilized for packaging merchandise marketed in stores. The reclosable pouches are particularly desirable for this use since they can be reused either with a commodity within the pouch or for additional purposes, thus extending their usefulness. The type of closure strip well suited for this type of pouch is one which has releasably interlocking rib and groove elements extending therealong which adhere together when an external pressure is applied to the strips and which release when they are forcibly pulled apart. However, this type of closure permits preliminary opening and possible tampering with the contents. For example, in a retail store, containers of the types heretofore provided could be opened and the contents removed in part, or the contents could be contaminated or foreign elements placed in the container. In this type of container, bulky contents or objects are frequently displayed and sold which bulge the container and place a strain upon the reclosable fastener elements.

The structure provided in accordance with the principles of the present invention employs a fastener at the top side of a bag particularly constructed to prevent accidental opening, and is the type generally disclosed and claimed in my U.S. Pat. No. 2,780,261. An opening flange is provided along the top of one of the fastener interlocking elements for pulling apart said elements and this opening flange is sealed to a marginal portion on the other fastener element which in turn is also connected to the rear wall of the bag. Below this seal is a frangible tear line. This arrangement prevents accidental opening and positively prevents the entry of any dust, moisture or foreign elements into the bag until the tear line is forcibly opened. Said arrangement is also provided with a bead at the top or an additional reversibly folded tab to aid in rupturing the tear line.

Accordingly, it is an object of the present invention to provide an improved container with an interlocking closure that has an additional impenetrable seal protecting the contents of the bag until it is to be used and which can be, at that time, torn to provide access to the bag and to the reclosable closure elements of the bag.

In the method of manufacturing bags with reclosable openings, a sheet of heat sealable material in the form of an open tube is positioned with its marginal edges in spaced opposed relationship. A closure strip is placed over the marginal edges of the sheet, the closure strip having opposite edges overlying the marginal edges of the sheet and including interjoined webs between releasably interlocking rib and groove elements adjacent the opposite edges of the closure strip, and including preformed tear lines between the interlocking elements. The edges of the strip are secured to the underlying marginal edges of the sheet and then the webs of the closure strip are heat sealed together between the interlocking rib and groove elements. Simultaneously with or after the heat sealing of the webs, the resulting structure is severed along the area of heat sealing to provide two tubes from which the individual bags may be formed.

Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat schematic illustration of extrusion dies which can be used to form the elements making up the closure strip of the present invention;

FIG. 2 is a somewhat schematic view of the assembly after the closure strip has been applied to the bag-forming split tube and prior to the heat sealing operation;

FIG. 3 is a view on a somewhat larger scale than FIG. 2, illustrating the assembly after heat sealing and severing in the heat sealed area has been accomplished;

FIG. 4 is a fragmentary view of one of the bag elements, illustrating the manner in which the outer web of the closure member can be flexed and separated to provide access to the closure elements; and

FIG. 5 is a view of a modified form of the invention in which a tab is employed to facilitate tearing open the outer closure strip to provide access to the closure elements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The features of the invention pertain primarily to the structure of the bag as illustrated in FIGS. 3 through 5, but for explanation of the structure, a brief description of the method of making will first be provided.

In FIG. 1, reference numbers 10, 11 and 12 indicate generally extrusion dies for forming continuous strips of heat sealable material in making up the closure strip of the present invention. The individual strips are made up of a suitable resinous material which is resilient and flexible. The vinyl resins such as polyvinyl chloride, polyvinyl acetate, or copolymers thereof, or polyethylene are particularly suitable for this use.

The extrusion die 10 has a cavity 13 therein in which the plastic material is formed into the shape shown in succeeding figures. The die 10 also includes a knife edge 14 which extends into the cavity 13 to provide a preformed line of weakness for tearing purposes, as will be apparent from the succeeding description.

Die 12 is similar to die 10 in that it includes an extrusion cavity 15 and a knife edge 16 extending therein to provide the preformed line of weakness in the extruded strip.

As seen in FIG. 2 particularly, the strip resulting from the extrusion in die 10 has a flat marginal end portion 17, a pair of ribs and grooves 18 forming part of the separable closure elements, and a preformed tear line 19 resulting from the presence of the knife edge 14 in the die. Similarly, the strip produced in the die 12 has a flat marginal end portion 20, integral ribs and grooves 21 and a tear line 22. The two extruded strips from the dies 10 and 12 which we shall call the outer webs for purposes of convenience, are shown in FIG. 2, to be in abutting relation but they can also be overlapped or even separated by a small distance provided that the inner ends of the two web portions are sufficiently close so that they are within the subsequently applied heat sealing field where they are subject to plastic flow. Additionally, dies 10 and 12 can be combined into one die resulting in a single strip.

The other portion of the closure element which we shall call the inner web for purposes of convenience is formed in the die member 11. As seen in FIG. 1, die member 11 has a pair of opposed extrusion cavities 23 and 24 for forming complementary rib and groove type closure elements, with a web-forming cavity 25 therebetween. The extrusion die may also be provided with a centrally disposed recess 26 so that the central portion of the web formed in the die is thickened. As seen in FIG. 2, the inner web which results from the extrusion material in die 11 has rib and groove portions 26 which are releasably engageable with the complementary rib and groove portions 18 of one outer web, and rib and groove portions 27 which are releasably engageable with the ribs and grooves 21 in the other outer web member. The two rib and groove portions of the inner web are connected by means of web portion 28 having a thickened central portion 29 due to the presence of the cavity 26 in the extrusion die.

The marginal edges 17 and 20 of the two outer strips which combine to form the outer webs of the entire closure element are heat sealed or otherwise secured to a sheet 30 of heat sealable resinous material which is arranged in the form of a flattened, open tube with its marginal edges 31 and 32 in spaced opposed relationship.

The next step consists in gathering the 3 ply structure shown in FIG. 2 together for the purpose of providing a heat sealed seam running the length of the assembly. To accomplish this, there is provided a heat sealing element 33 on one side of the assembly, and an anvil 34 on the opposite side. The heat sealing element 33 which may be heated by any suitable means, including high frequency induction fields, may also be provided with a knife edge 35 so that heat sealing may be accomplished simultaneously with slitting of the assembly into separate tubes, as shown in FIG. 3 of the drawings. Alternatively, however, the knife edge 35 may be replaced by a spaced series of slitting or perforating means to provide a line of weakness running the length of the finished assembly so that severing can be carried out after the thermoplastic material has been removed from the heat sealing station.

Severing of the assembly, as illustrated in FIG. 3 results in the production of two continuous collapsed reclosable fastener tubes wherein the individual upper webs making up the upper assembly are gathered and formed into beads 36 and 37 which form the top of the closure for the finished bags.

The tubes produced by the process described are then severed crosswise and heat sealed to produce individual bags of the desired size.

Bags of unique construction have been provided as illustrated in the form shown by FIGS. 3 and 4 and the alternative form shown by FIG. 5. In the arrangement of FIGS. 3 and 4, the bag wall 30 is formed of a thin lightweight film with the closure strips 40 and 41 attached to the front wall 43 and the rear wall 30 of the bag. While the bag is constructed in a preferred method as described above, it will be understood that other methods of construction may be employed and the bag and fastener strips may be extruded in a single operation. For example, the front wall 43 and the closure strip 40 may be of one integral part as well as the back wall 30 and the closure strip 41. The frangible connection which is formed between the flange 42 and the back wall 30 at the bead 36 would then have to be formed by a separate operation. The tear line 19, of course, would have to be present.

In the structure as completed, as illustrated in FIGS. 3 and 4, the front and rear closure strips 40 and 41 are attached to the bag walls, and the front closure strip 40 has a downwardly extending marginal portion 17 which is attached to the front wall 43 of the bag.

The rear closure strip 41 has an upwardly extending marginal portion 28 which is attached to the rear wall 30 of the bag at the bead 36. The front closure strip 40 has an upwardly extending flange portion 42 which contains the tear line 19 and which is also attached to the rear wall 30 of the bag at the bead 36.

The bead provides a convenient hinge point for bending and tearing the tear line 19. It also particularly provides an excellent grasping location for the user to separate the fastener strips 40 and 41 dislocating the ribs 26 from the grooves 18. When the tear line 19 is ruptured and the flange 42 is freed, the user grasps the flange 42 and the bead 36 and pulls the strips 40 and 41 apart.

In the arrangement of FIG. 5, a pull tab 38 is provided to aid in performing the initial rupture of the tear line 19. The pull tab 38 also provides additional gripping area for gripping the front flange 42.

It has been discovered that by breaking the connection of the flange 42 to the bead 36 along the tear line 19 a somewhat uneven edge results. This is particularly true where a plastic material such as polyethylene is employed and the material tends to stretch just before breaking occurs, so that a somewhat scalloped or ruffled edge results at the tear line 19. Where a clear polyethylene material is used, the broken edge has a contrasting white color. The color difference combined with the torn edge improves the ability of the user to see the edge of the flange 42 and to grip it. In these bags having very small parts, it is somewhat difficult to see the flange 42 and to easily grip it and the torn edge facilitates this identification.

The structure of the present invention thus provides an improved reclosable bag wherein the contents are protected until the bag is to be used and wherein an improved reclosable bag is obtained.

Claims

I claim as my invention:

1. A closure structure for a plastic film bag or the like comprising opposed front and back closure strips having facing complementary shaped separable pressure interlocking rib and groove elements thereon, the front strip having an upwardly extending flange portion above the rib and groove elements, and a downwardly extending marginal portion below the elements, the back strip having an upwardly extending marginal portion with the rear wall of the bag joined to said marginal portion, the flange portion of the front strip and the marginal portion of the back strip being joined to each other by a fluid impervious frangible means, so that they will remain attached until forcibly separated so as to allow gripping of the flange portion and thereby separating the rib and groove elements.

2. A closure structure for a plastic film bag or the like in accordance with claim 1 wherein said frangible means comprises a groove in the flange portion of the front strip.

3. A closure structure for a plastic film bag or the like in accordance with claim 1 and including a pull tab on the flange on the front strip located below the frangible element.

4. A closure structure for a plastic film bag or the like in accordance with claim 1 and including a bead formed at the juncture between said flange, said bag rear wall and said marginal portion of the back strip.

5. A closure structure for a plastic film bag or the like constructed in accordance with claim 1 wherein the flange and rear marginal portion of the back strip and said rear wall of the bag are joined at the same location.

6. A closure structure for a plastic film bag or the like constructed in accordance with claim 5 with said location being formed by a relatively heavy weld bead.

7. A structure for making two separate bags in a single manufacturing operation which comprises an upper closure strip and a lower closure strip, said strips having separated parallel facing releasably interlocked rib and groove elements thereon, each of said strips having a web portion intermediate the rib and groove elements, the upper strip having marginal portions outwardly of the rib and groove elements, a film sheet underlying said strips with the edges turned inwardly and attached to said marginal portions, and tear lines in the web portion of the upper strip spaced on each side of the center thereof and extending parallel along the strip whereby plural bags may be formed by forming a weld joining the strips and the sheet along an area between the tear lines.

8. A structure in accordance with claim 7 wherein the lower strip has a thickened portion in the center of the web portion at the location where the weld is to be made.

9. A construction in accordance with claim 7 wherein the upper strip is formed in two sections separated along the center between the tear lines.

10. A construction in accordance with claim 7 wherein a weld is formed joining the upper and lower strips and the sheet whereby the structure may be severed on the center of the weld for forming separate bags.