GB2373779A

GB2373779A - A reclosable sack

Info

Publication number: GB2373779A
Application number: GB0107729A
Authority: GB
Inventors: William Thomson
Original assignee: Linpac Containers Ltd
Current assignee: DS Smith Packaging Ltd
Priority date: 2001-03-28
Filing date: 2001-03-28
Publication date: 2002-10-02
Also published as: GB0107729D0

Abstract

A sack (21) comprising a pair of confronting walls (22,23) each of which has inner and outer surfaces and which define, at one end of the sack (21), a mouth (28) therefor, and a closure zipper (31) having two co-operable parts (32,33), wherein, at the mouth (28) of the sack (21), one wall extends beyond the other wall and wherein one part (66) of the closure zipper (31) is secured to the outer surface (24) of the shorter wall (22) and the other part of the zipper (31) is secured to the inner surface (54) of the longer wall (23).

Description

RECLOSABLE SACK DESCRIPTION This invention relates to a reclosable sack for the storage and transportation of materials in bulk and is especially, but not exclusively, related to such a sack with walls of multi-ply material, for example, walls having at least two plies of material. Also, the multi-ply walls of such a sack can be made of paper, plastics sheet, foil or any other suitable sheet material or any desired combination thereof. However, the walls of such a sack may be of single ply construction, with the sack being flat or gusseted.

Closure of the sack is achieved by means of a generally flat closure device, known as a"zipper". Such a zipper may comprise two extruded lengths of plastics material which close together by the interlocking action between complementary-shaped male and female extrusions. However, other forms of zipper may be used, for example, conventional fabric-backed, metal or plastics toothed zippers.

In one form of conventional reclosable paper or plastics sack, the top edges of the front and rear walls of the sack at its upper, open mouth are at substantially the same level, that is to say, they are flush-cut. A base web of one part of the zipper is secured to the outer surface of one of the front and rear walls of the sack, whilst the base web of the other part of the zipper is secured to the outer surface of the other wall of the sack. In some cases, one or both of the zipper base webs is folded inwardly through 1800, so that the complementary male and female extrusions can be interengaged with each other to close the otherwise open mouth of the sack.

This conventional arrangement of attachment of the zipper parts to the open mouth of the sack has several disadvantages, one being that the zipper

straddles the top of the flush-cut mouth of the sack, with the base webs of the two parts of the closure zipper being attached to respective outer surfaces of the walls of the sack, thereby making it difficult for a user to open the mouth of the sack when the zipper is opened.

It is an object of the invention to overcome, or at least substantially reduce, this disadvantage, as well as other disadvantages, associated with the conventional type of sack discussed above.

Accordingly, one aspect of the invention provides a sack comprising a pair of confronting walls each of which has inner and outer surfaces and which define, at one end of the sack, a mouth therefor, and a closure zipper having two cooperable parts, wherein, at the mouth of the sack, one wall extends beyond the other wall and wherein one part of the closure zipper is secured to the outer surface of the shorter wall and the other part of the zipper is secured to the inner surface of the longer wall.

The two walls of the sack may be single ply or may have two or more plies, in which case, at least one of the plies of the longer wall extends beyond the other, shorter wall.

In a preferred embodiment to be described in more details hereinbelow, each ply of the longer, multi-ply wall extends beyond the other, shorter wall. That other, shorter wall may, at the mouth of the sack, may have plies of different length, as may the longer wall.

In such an arrangement, one part, such as a base web, of the closure zipper is attached to the outer surface of at least one of the plies of the shorter wall of the sack, with the other part, such as the base web, of the closure zipper being attached to the inner surface of at least one of the plies of the longer sack wall.

A second aspect of the invention resides in a sack comprising two confronting walls each of which has respective inner and outer surfaces and which define, at an end of the sack, a mouth therefor, wherein, at the mouth one of the walls extends beyond the other wall, to expose the inner surface of that one wall.

Each wall of the sack may be single ply or have two or more plies, in which case, at least one of the plies of the longer wall extends beyond the shorter wall. Also, the plies of the shorter wall at the outer surface thereof may be of different lengths and the plies of the other, longer wall at the inner surface thereof may be of different length At the mouth of the sack, the outer surface of the shorter wall is arranged to have attached thereto one part of a two part closure zipper, whilst the inner surface of the other, longer wall may be arranged to have attached thereto the other part of such a closure zipper.

With a sack having a pair of multi-ply walls, the respective parts of any closure zipper may be secured to at least one of the plies of the corresponding wall.

The closure zipper preferably comprises a pair of complementaryshaped interchangeable sections, with respective base webs which are or can be attached to respective ones of the outer surface of the shorter sack wall and the inner surface of the longer sack wall.

The base webs of the two parts of the closure zipper may be secured to their respective walls by any suitable means, for example, by means of a suitable adhesive, such as a hot-melt adhesive. Also, and with a sack having multi-ply walls, the pair or at least one of adjacent pairs of plies can be glued

together in the region of the mouth of the sack, to provide a rigid structure to which the respective base webs of any closure zipper can be attached securely. Also, by bonding the wall plies together in this manner, the interior of the sack, and hence its contents, can be accessed readily via the mouth of the sack without damaging the plies of the sack walls.

In order that the invention may be more fully understood, a preferred embodiment of paper sack with multi-ply walls will now be described by way of example and in comparison with a prior art sack, with reference to the accompanying drawings in which Figure 1 is a sectional view of the mouth of a conventional paper sack, Figure 2 is a sectional view of the mouth of a sack in accordance with the invention, Figure 3 is a sectional view of the prior art sack shown in Figure 1 with a closure zipper attached thereto in a conventional manner, Figure 4 is a sectional view of a sack in accordance with the invention, as shown in Figure 2, with a closure zipper attached thereto, and Figure 5 is a front elevational view of part of a sack in accordance with the invention, as shown in Figure 2.

Referring firstly to Figures 1 and 3, a prior art paper sack indicated generally at 1, comprises a pair of walls indicated generally at 2 and 3, with the wall 2 constituting the front wall of the sack 1 and the wall 3 constituting the rear wall of the sack 1. Each of the front and rear walls 2,3 has three paper plies 4,5 and 6.

The tops of the two sack walls 2 and 3 are flush-cut, at 7, so that, at the mouth 8 of the sack 1, the two walls 2, 3 are of the same length.

As shown in Figure 3, a closure zipper, indicated generally at 11, comprises two parts, 12 and 13.

The closure zipper part 12 comprises a base web 14 and a male element 15, whilst the other closure zipper part 13 comprises a base web 16 with a female element 17 with which the male element 15 of the part 12 is interengaged.

The lower portion of the base web 14 of the part 12 is attached to the outer surface of the outer ply 4 of the sack wall 2 in the region of the sack mouth 8, whilst the lower region of the base web 16 of the other closure zipper 13 is attached to the outer surface of the outer ply 4 of the other wall 3.

The otherwise free end of the base web 16 is folded over through 1800 at 18, so that the complementary-shaped male and female elements 15,17 can interengage with each other, to close the mouth 8 of the sack 1, as shown in Figure 3, with the closure zipper 11 straddling the closed sack mouth 8.

Each closure zipper part 12,13 is extruded from a plastics material, with the lower regions of the respective base webs 14,16 being adhered to the respective outer surfaces of the plies 4 of the walls 2,3 by a hot-melt adhesive.

A tamper-evident device, in the form of a line of stitching 19 is provided below the interengaged male and female elements 15,17 and below the mouth 8 of the sack I This stitching 19 secures the front and rear walls 1 and 3, and hence their respective plies 4,5 and 6, together, so that access to the interior of the sack 1 is denied, if the closure zipper 11 is opened by separating the male element 15 from the female element 17.

Authorised removal of the stitched line 19 permits normal access to the interior of the sack 1 and, hence, the contents thereof Referring now to Figures 2,4 and 5, a paper sack, indicated generally at 21 and in accordance with the invention, comprises a pair of front and rear walls, indicated generally at 22 and 23 respectively, with the front wall indicated generally at 22 and the rear wall indicated generally at 23.

The front wall 22 has three paper plies, namely an outer paper ply 24, an inner paper ply 26 and an intermediate paper ply 25 The rear wall 23 also has these paper plies, namely an inner paper ply 44, an outer paper ply 46 and an intermediate paper ply 45 The plies 24,25 and 26 of the front wall 22 of the sack 21 are cut in a stepped configuration, such that the outer surfaces of the intermediate ply 25 and the inner ply 26 are exposed, as indicated at 35 and 36, respectively In accordance with the invention, the rear wall 23 extends beyond the front wall 22 of the sack 21.

The inner, intermediate and outer plies 44,45 and 46 of the rear wall 23 are also cut in a stepped configuration, such that the upper regions of the inner surfaces 55 and 56 of the intermediate and outer plies 45,46 of the rear wall 23 are exposed Also, as the rear wall 23 extends beyond the front wall 22, the upper region of the inner surface 54 of the inner ply 44 is also exposed above the level of the front wall 22.

As shown in Figure 4, a closure zipper, indicated generally at 31, comprises two extruded plastics parts, indicated generally at 32 and 33, respectively.

The first zipper part 32 comprises a base web 64 whose lower region is attached, by a hot-melt adhesive, to the upper region of the outer ply 24 of the front wall 22, as well as to the exposed surfaces 35 and 36 of plies 25 and 26, and which has a male element 65 interengaged with a female element 67 on a base web 66 of the other part 33 of the closure zipper 31 The base web 66 of the other zipper part 33 is attached, by hot-melt adhesive, to the upper region of the inner surface 54 of the inner ply 44, as well as the exposed inner surfaces 55 and 56 of the plies 45 and 46, of the rear wall 23.

In this manner, the mouth 28 of the sack 21 is closed to prevent access to the interior of the sack 21 and its contents.

Each end of the zipper 31 is sealed by heat or hot melt, with the two parts 32 and 33 secured together thereat, to prevent the ends of the zipper coming apart A tamper-evident line of stitching 39 is provided, as in the case of the stitching line 19 of the prior art sack 1 described above in relation to Figures I and 3, to secure the front and rear walls 22 and 23 together, so that, if the closure zipper 31 is opened, access to the interior of the sack 21 is prevented.

In authorised use of the sack 21, removal of the stitching 39 allows normal access to the interior of the sack 22 and its contents.

Because the rear wall 23 of the sack 22 extends beyond the front wall 22, access thereto by a user is facilitated for opening the closure zipper 31 by extracting the male element 65 from the female element 67 of the respective parts 32 and 33 of the zipper 31 across the width of the sack 22.

It is to be appreciated that the invention may employ sacks with single or multi-ply walls, the sacks being made of paper, plastics sheet, foil or any other suitable sheet material or any combination thereof. Also, the closure zippers are not limited to extruded plastics, two-part zippers and may be of any suitable two-part construction

Claims

CLAIMS 1. A sack comprising a pair of confronting walls each of which has inner and outer surfaces and which define, at one end of the sack, a mouth therefor, and a closure zipper having two cooperable parts, wherein, at the mouth of the sack, one wall extends beyond the other wall and wherein one part of the closure zipper is secured to the outer surface of the shorter wall and the other part of the zipper is secured to the inner surface of the longer wall.
2. A sack according to claim 1, wherein the two walls of the sack have two or more plies, with at least one of the plies of the longer wall extending beyond the other, shorter wall.
3. A sack according to claim 2, wherein each ply of the longer, multi-ply wall extends beyond the other, shorter wall.
4 A sack according to any preceding claim, wherein the other, shorter wall, at the mouth of the sack, has plies of different length.
5. A sack according to any preceding claim, wherein one part of the closure zipper is attached to the outer surface of at least one of the plies of the shorter wall of the sack, with the other part, such as the base web, of the closure zipper being attached to the inner surface of at least one of the plies of the longer sack wall.
6. A sack according to claim 5, wherein the one part of the closure zipper is a base web.
7. A sack according to claim 1. wherein the two walls of the sack are single ply.
8. A sack comprising two confronting walls each of which has respective inner and outer surfaces and which define, at an end of the sack, a mouth therefor, wherein, at the mouth, one of the walls extends beyond the other wall, to expose the inner surface of that one wall.
9. A sack according to claim 8, wherein each wall of the sack has two or more plies, with at least one of the plies of the longer wall extending beyond the shorter wall.
10. A sack according to claim 9, wherein the plies of the shorter wall at the outer surface thereof are of different lengths and the plies of the other, longer wall at the inner surface thereof are of different length.
11. A sack according to claim 8, wherein each wall of the sack is single ply.
12. A sack according to any of claims 8 to 11, wherein, at the mouth of the sack, the outer surface of the shorter wall is arranged to have attached thereto one part of a two part closure zipper, whilst the inner surface of the other, longer wall is arranged to have attached thereto the other part of such a closure zipper.
13. A sack according to claim 12 when dependent upon claim 9 or 10, wherein, the respective parts of the closure zipper are secured to at least one of the plies of the corresponding wall.
14. A sack according to claim 12 or 13, wherein the closure zipper comprises a pair of complementary-shaped interengageable sections, with respective base webs which are attachable to respective ones of the outer surface of the shorter sack wall and the inner surface of the longer sack wall.
15. A sack according to claim 14, wherein the base webs of the two parts of the closure zipper are secured to their respective walls.
16. A sack according to claim 15, wherein the base webs are secured by means of a suitable adhesive, such as a hot-melt adhesive.
17. A sack according to any of claims 1 to 6,8 to 10 and 12 to 16, wherein, the pair or at least one of adjacent pairs of plies are glued together in the region of the mouth of the sack, to provide a rigid structure to which the respective base webs of any closure zipper are attached securely.
18. A sack according to claim 17, wherein, when bonding the wall plies together in this manner, the interior of the sack, and hence its contents, can be accessed readily via the mouth of the sack without damaging the plies of the sack walls.
19. A sack substantially as hereinbefore described with reference to the accompanying drawings.