GB2047199A

GB2047199A - Reinforced gusseted bag

Info

Publication number: GB2047199A
Application number: GB8010438A
Authority: GB
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1979-03-30
Filing date: 1980-03-28
Publication date: 1980-11-26
Also published as: NO800863L; NZ193294A; AU539227B2; IT1188983B; BE882516A; FI800958A; AU5693780A; GB2047199B; NL8001858A; IT8048275A0; SE8002383L; CA1171822A; FR2452434A1; FR2452434B1; DK136080A; CH637078A5; DE3011442A1

Abstract

A plastics bag includes a gusseted portion (12) and a spot heat sealed region (16) joining together all four layers of the bag comprising the layers of the gusset fold and wall portions delimiting the gusset fold, in order to reinforce the gusseted portion. <IMAGE>

Description

SPECIFICATION Reinforced gusseted bag and method for manufacturing same The invention relates to a plastics bag of a heat sealable material including a gusseted portion and to a method of forming same.

Methods for making bottom and side gusseted plastics bags are well-known in the art. The following patents show some of the typical prior art methods for making gusseted plastics bags and these patents are incorporated herein by reference.

These patents are U.S. patent no. 4,046,065, U.S.

patent no. 3,980,225, U.S. patent no.3,319,540, U.S.

patent no.3,395,622, and U.S. patent no.3,839,128.

In the prior art, it was found that the bottom gusseted plastics bags had two weak points, one at each of the intersections of the center line fold of the gusset and the side edges. One prior art solution to this problem has been the use of diagonal heat seal regions extending from the weak points down to the bottom of the bag at an angle to the bag bottom. The diagonal heat seals can have two different forms. If the diagonal heat seal joins together the four layers of the bag, then the gusset becomes restricted and the bag cannot be opened fully so that the bag capacity as well as the stand-up qualities of the bag becomes impaired.

If the diagonal heat seals are made to seal only the two adjacent layers of the bag rather than all four layers, a separator plate must be used in the sealing process. The use of a separator plate between the layers keeps the diagonal heat seal from reaching and reinforcing the weak seal points so that the effectiveness of the diagonal seal is not fully obtainable. Furthermore, the use of a separator plate requires that the heat sealing be separately accomplished on each side of the bag so that an increase in equipment and manufacturing costs results.

Similarly, weak points have been found in side gusseted bags and these have been dealt with by the use of diagonal heat sealing also.

The instant invention can be carried out economically and is surprisingly effective in improving the strength of the gusseted plastic bag.

One of the embodiments of the instant invention is a plastics bag comprising two side walls of a heat sealable material, the side walls being connected together by an inwardly folded portion of material which is folded along a center line fold and outer line folds to define a gusseted portion, the side walls being heat sealed together at least along an edge generally perpendicular to the center line fold to define the bag, and a spot heat sealed region spaced from the outer line folds and located at the intersection of the center line fold and the edge for joining together all four of the layers of the material.

Another embodiment of the instant invention is a plastics bag comprising two side walls of a heat sealable material, the side walls being connected together by an inwardly folded portion of material which is folded along a longitudinal center line fold to define a gusseted bottom, the side walls being heat sealed together along opposite sides of the bag to define side edges of the bag, and a spot heat sealed region spaced from the bottom of the bag and located at each of the intersections of the center line fold and the side edges for joining together all four of the layers of the material.

Generally, each spot heat sealed region is preferably a semi-circle positioned with a diameter along the side edge and substantially bisected by the center line fold. Other shapes for the heat sealed region can be used such as rings, triangles, hexagons and other polygons.

The plastics bag can include a closure device suitable for opening and closing the bag in accordance with the prior art or as shown in the co-pending patent application serial no.892,432 filed March 31, 1978 and assigned to the assignee of the instant application.

Another embodiment of the invention is a method of forming a reinforced gusseted plastics bag, comprising the steps of supplying heat sealable material, inwardly folding a portion of the material along a center line fold and outer line folds to define a gusseted portion, and heat sealing at least along an edge generally perpendicular to the center line fold to define a bag, wherein the improvement comprises spot heat sealing a region spaced from the outer line folds located at the intersection of the center line fold and the edge for joining together all four of the layers of the material.

Another embodiment of the invention is a method of forming a reinforced bottom gusseted plastics bag, comprising the steps of supplying a heat sealable plastics film web in the form of a continuous sheet having substantially parallel sheet edges, folding the film web so that the sheet edges of the film web are near each other and substantially parallel to each other, inwardly folding a portion of the film web to establish a longitudinal center line fold to define a gusset, spot heat sealing regions to join together all four layers of the material at spaced locations along the center line fold, and seversealing the film web transversely to intercept the heat sealed regions to define side edges for the bag.

Preferably, the heat sealed regions are spaced apart a predetermined distance equal to the width of the bag and preferably the heat sealed regions are circular.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which: Fig. 1 is a front elevational view of a plastics bag in accordance with the invention; Fig. 2 is a sectional view along the line 2-2 of Fig. 1; Fig. 3 is a perspective view of the plastics bag of Fig. 1 in an open state; Fig. 4 is a block diagram of the apparatus for carrying out the method of the invention; and Fig. 5 shows a portion of the operations shown in Fig.4,and Fig. 6 is a front elevational view of another plastics bag in accordance with the invention.

In carrying the invention into effect, certain embodiments have been selected for illustration in the accompanying drawings and for description in the specification, reference being had to Figs. 1 to 6.

A plastics bag in accordance with the instant invention optionally includes a closure device at the opening of the bag. Fig. 1 shows one embodiment of the invention which includes a closure device 10.

The side walls 11 are of a heat sealable material and the gusseted bottom 12 can be seen from Fig. 2 as being an inwardly folded portion of the material which is folded along a longitudinal center line fold 13 and outer line folds 15.

The side edges 14 are formed by a sever-sealing operation, as in the prior art, and spot heat sealed regions 16 are located at the intersections of the center line fold 13 and the side edges 14 in order to provide reinforcement for the gusseted bottom 12, particularly when the bag is opened and loaded and the gusset bottom 12 is stressed. The heat sealed region 16 join together the four layers at the gusseted bottom 12 as can be appreciated by reference to Figs.2 and 3.

Fig. 4 shows a block diagram of the apparatus for carrying out the method of the invention for producing a plastics bag in accordance with the invention.

Generally, the production of a plastics bag having a gusseted bottom is known from the prior art.

Plastic film webs 17 is supplied, for example, from a roll 18 of the heat sealable material. In its simplest form, the plastics film web 17 can be a single layer.

Plastics film web 17, however, could also be a mul tilayerfilm web, provided that both of the outside layers are heat sealable so that the plastics bag of the invention can be formed. Unit 19 folds the film web 17 in half and forms an inwardly folded portion along a longitudinal center line to define a gusset portion. Unit 19 is well-known from the prior art, such as U.S. patent no.3,059,549. Preferably the film web 17'is folded in half, but it may be desirable for certain uses to fold the film web so that the plastics bag finally obtained will have one side wall extending beyond the other side wall.

The folded film web 21 from unit 19 can have a closure device bonded to it in unit 22 in accordance with prior art methods, or go directly to unit 23 for spot heat sealing regions for reinforcing the gusseted bottom. The method of establishing spot heat sealing is well-known in the prior art. The spot heat sealing regions 25 are spaced apart a distance equal to the width of the bags being produced. The spot heat sealed film web 24 is thereafter sever-sealed in unit 26 to produce the plastics bag according to the invention.

Fig. 5 shows the spot heat sealed film web 24 which is moved into the unit 26, and bag 27 which is ejected by the unit 26. The sever-sealing operations substantial bisect the spot heat sealed regions 25 as shown in Fig. 5.

The surprising improvement obtained by the instant invention can be appreciated by the follow ing test results.

Bottom gusseted bags were made in the so-called "5 quart size". The bags were made from low density polyethylene film having a thickness of 1.75 mil (0.00254 cm). The dimensions were 10-1/2 inches (26.67 cm) wide and 11 inches (27.74 cm) deep with a bottom gusset 2 inches (5.08 cm) deep. The bags included interlocking closures. Of the 104 bags, half were in accordance with the invention while the other half did not include reinforcing and were according to prior art.

Each bag was loaded with a liter of water, sealed with the interlocking closure, and dropped in an upright position from a height of 4 feet (1.22 metres) onto a hard surface. Thereafter, each bag was inspected for damage.

The 52 bags according to the invention has a single bag failure while the 52 bags according to the prior art had 10 bag failures.

These results show that the bags according to the invention are substantially superior to the prior art bags without the spot heat sealing reinforcing.

Fig. 6 shows another embodiment of the invention for a plastic bag having side gussets. The side walls 30 are of a heat sealable material. The gusseted sides 31 have been formed by inwardly folding the material along center line folds 32 and outer line folds 33. As prior art practice, an edge seal 34 is formed with a skirt 36. The spot heat sealed regions 37 are located at the intersections of the center line folds 32 and the edge seal 34 in order to provide reinforcement for the respective gusseted sides 31.

It is understood that the invention is not limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Claims

1. A plastics bag comprising two side walls of a heat sealable material; said side walls being connected together by an inwardly folded portion of material which is folded along a center line fold and outer line folds to define a gusseted portion; said side walls being heat sealed together at least along an edge generally perpendicular to said outer line fold to define said bag; and a spot heat sealed region spaced from said outer line folds and located at the intersection of said center line fold and said edge for joining together all four of the layers of the material.

2. The plastics bag of claim 1 or 2, wherein said comprising a closure device near the opening of said bag.

3. The plastics bag of claim 1, wherein said spot heat sealed region has the shape of at least a portion of a circle.

4. The plastics bag of claim 1 or 2, wherein said spot heat sealed region has the shape of a triangle or rectangle or other polygon.

5. The plastics bag of claim 1 or 2, wherein said spot heat sealed region has the shape of a semicircle and is positioned with the diameter of said semi-circle along said edge.

6. A plastics bag comprising two side walls of a heat sealable material; said side walls being connected together by an inwardly folded portion of material which is folded along a longitudinal center line fold to define a gusseted bottom; said side walls being heat sealed together along opposite sides of the bag to define side edges of the bag; and a spot heat sealed region spaced from the bottom of the bag and located at each of the intersections of said center line fold and said side edges for joining together all four of the layers of said material.

7. The plastics bag of claim 6, further comprising a closure device near the opening of said bag.

8. The plastics bag of claim 6 or 7, wherein said spot heat sealed region has the shape of at least a portion of a circle.

9. The plastics bag of claim 6 or 7, wherein said spot heat sealed region has the shape of a semicircle and is positioned with the diameter of the semi-circle along the proximate side edge;

10. The plastics bag of claim 6 or 7, wherein said heat sealed region has the shape of a triangle or rectangle or other polygon.

11. A plastics bag comprising two side walls of heat sealable material; said side walls being connected together at opposite sides by inwardly folded portions of material each of which is folded along a center line fold and outer line folds to define gusseted sides; said side walls being heat sealed together to define a bottom edge; and a spot heat sealed region spaced from said outer line folds and located at each of the intersections of said center line fold and said bottom edge for joining together all four of the layers of said material.

12. The plastics bag of claim 11, wherein said bag includes a skirt portion extending beyond said bottom edge.

13. The plastics bag of claim 11 or 12, wherein spot heat sealed region has the shape of at least a portion of a circle.

14. The plastics bag of claim 11 or 12, wherein said spot heat sealed region has the shape of a triangle or rectangle or other polygon.

15. A method of forming a reinforced gusseted plastic bag, comprising the steps of supplying heat sealable material; inwardly folding a portion of the material along a center line fold and outer line folds to define a gusseted portion; and heat sealing at least along an edge generally perpendicular to said center line fold to define a bag; wherein a region is spot heat sealed, the region being spaced from said outer line folds and located at the intersection of said center line fold and said edge for joining together all four layers of said material.

16. A method of forming a reinforced bottom gusseted plastics bag, comprising the steps of supplying a heat sealable plastic film web of a continuous sheet having substantially parallel sheet edges; folding said film web so that the sheet edges of said film web are near each other and substantially parallel to each other, inwardly folding a portion of said film web to establish a longitudinal center line fold to define a gusset; spot heat sealing regions to join together all four layers of said material at spaced apart locations along said center line fold, and sever-sealing said film web transversely to intercept said heat sealed regions to define side edges for said bag.

17. The method of claim 16, further comprising the step of connecting a closure device to said film web so that said bag is produced as a reclosable bag.

18. The method of claim 16 or 17,wherein said spot sealing regions have the shape of a circle and the sever-sealing step substantially bisects said spot sealing regions.

19. The method of claim 16 or 17, wherein said spot sealing regions have the shape of triangles or rectangles or other polygons.

20. A method of forming a plastics bag, substantially as hereinbefore described with reference to Figures 1 to 5 or to Figure 6 of the accompanying drawings.

21. A plastics bag substantially as hereinbefore described with reference to Figures 1 to 3 and 5 or to Figure 6 of the accompanying drawings.

22. A plastics bag whenever produced by the method of any of claims 15 to 20.