GB2226541A

GB2226541A - Waste disposal bag

Info

Publication number: GB2226541A
Application number: GB8826265A
Authority: GB
Inventors: Paul Richard Baldwin
Original assignee: INTERPOLY Ltd
Current assignee: INTERPOLY Ltd
Priority date: 1988-11-09
Filing date: 1988-11-09
Publication date: 1990-07-04
Also published as: GB8826265D0

Abstract

A side gusseted bag of flexible plastics material has an open end (22) and a heat sealed closure (6) at the other end. The sealed end portion is also folded over (20) and a further heat seal (18) formed midway between the fold (20) and the end seal (6) so that the bag can be opened out into a box shape. A series of such bags are formed from a tube blown from a film. <IMAGE>

Description

"Waste Disposal Bag This invention relates to waste disposal bags, and particularly to bags which are manufactured from a blown film of flexible plastics material such as polyethylene.

Bags of this general kind are described in our British patent applications nos. 8703508 and 8726038. These applications are particularly directed to the arrangements for closing the open end of the bag, in which (for example) a layer of pressure sensitive adhesive is applied to a closure strip having a first portion secured across one outer face of the bag and a second portion overlying said face adjacent the open end of the bag, the overlaid area of the face carrying a layer of silicone so that the pressure sensitive adhesive adheres temporarily to the overlaid area.

The closure strip is then peeled from the overlaid area, and the open end of the bag is folded so that its edges underlie and are sealed by the closure strip, after the bag has been used.

By means of this type of arrangement, it is possible to provide quite secure closure of the open end of the bag after use. The present invention relates to an improved heat-sealed closure of the other end of the bag, i.e. the "bottom" end.

The present invention provides a gusseted bag of flexible plastics material having an open end and a heat sealed closure at the other end, and in which the said other end is subsequently folded over, and a further heat seal is applied across the folded over portion, between the fold and the already sealed extreme end.

Preferably, the further heat seal is formed approximately midway between the fold and the already.heat sealed end, and in a preferred embodiment of the invention, the length of the bottom end of the bag which is folded over is equal to the total width of the gusset, so that when the resulting bag is opened out it falls naturally into a free standing, open box shape. When the additional seal is made in this way, and at the preferred spacing of halfway between the fold and the already sealed end, the additional layering forms a relatively rigid base for the bag so that it can stand freely on a flat surface, even if it is made from very thin plastics film material. Furthermore, the trapped pockets of air between the seals provide extra protection against possible bursting or leakage.

The invention also extends to a method of making a bag from a film of flexible plastics material, the method comprising the steps of blowing a film into a tube shape, continuously folding the side of the tube to form gussets so that it can be flattened, forming a heat seal across the width of the flattened tube at intervals and then shearing the tube close to the seal, so as to form a series of separate open ended bags; and subsequently, folding over the sealed end of the bag and forming a further heat seal to hold down the folded over flap, between the fold and the already heat sealed end. Preferably, the length of the bag which is folded over is made equal to the total width of the gusset, and the further heat seal is made midway between the folded over portion and the already sealed end.

One embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a flexible plastics bag of conventional construction, in a partially opened condition; Figure 2 is a plan view of the bag of Figure 1, in a flattened condition, so as to show the positions of the gussets; Figure 3 is an edge view of a bag of the kind shown in Figure 2, illustrating how the sealed end is folded over in accordance with the invention; Figure 4 is a perspective view of a bag made in accordance with the invention, in a free standing open condition; and Figure 5 is a top plan view taken into the open end of the bag of Figure 4.

Referring to Figure 1, a conventional bag 2 is made from flexible plastics material such as polyethylene, by blowing the film into a tube, gussetting the sides as indicated at 4, making a heat seal across the width of the bag as indicated at 6 and subsequently, shearing the tube at 8, adjacent the heat seal line 6, so as to form it into separate bags.

It will be appreciated that the resulting bag is not at all rigid, and tends to collapse back into a flat condition, even from the semi-open condition shown in Figure 1. Furthermore, because of the positions of the gusset folds 10, indicated in the plan view of Figure 2, the thickness of the flattened end of the bag changes from four layers of material, in the gussetted outer edge portions 12, to only two layers at the inner region 14. Accordingly, when the heat seal 6 is made across the width, there are two points 16 at which there is an abrupt change of thickness, and it is almost impossible to prevent the formation of pin holes at these regions, so that it is very difficult to form a completely watertight bag in this way.

As illustrated in Figure 3, this construction can be improved in accordance with the principles of the present invention by folding over the already sealed end 6 of the bag, by an amount which is equalsto the total (opened out) width of the gusset, and then forming a further heat seal at a position 18, midway between the fold 20 and the end 6.

When the resulting bag is opened out to the condition illustrated in Figure 4, the folded over portion forms a natural base for the opened out bag, so that it can.easily stand in a balanced condition on a flat surface, with the aperture 22 held open for easy access. The plan view of Figure 5 illustrates how the gussetted portions 4 fall into a naturally triangularly folded shape at the base of the bag, when it is standing in the open condition illustrated in Figure 4. It will be appreciated that, because of the large number of layers of folded material then formed in the base of the open bag, a strong and watertight construction is provided, which can easily stand up on a flat surface even if it is made from a very thin flexible film material.

Consequently, the principles of the invention provide a bag having considerably wider applications than previous bags made of material of this kind.

It will, of course, be appreciated that the closure of the upper end of the bag may be of any suitable type, and it may for example be of thetadhesive type illustrated in our British patent applications nos. 8703508 or 8726038.

Claims

CLAIHS

1. A side gusseted bag of flexible plastics material having an open end and a heat sealed closure at the other end, and in which the said other end is subsequently folded over, a further heat seal then being applied across the folded over portion, between the fold and the already sealed extreme end.

2. A bag according to claim 1 in which the said further heat seal is formed in a region midway between the fold and the already heat-sealed end.

3. A bag according to claim 1 or claim 2 in which the length of the folded over part of the bottom end of the bag is equal to the total width of the side gusset.

4. A bag according to claim 2 or claim 3 in which the bag is opened out into a rectangular box formation after heat-sealing, so that the folded portions of the end of the bag form a rectangular base.

5. A method of forming a bag from a film of flexible plastics material, the method comprising the steps of blowing a film into a tube shape, continuously folding opposite sides of the tube to form gussets so that it can be flattened, forming a heat seal across the width of the flattened tube at intervals and then shearing the tube close to the seal, so as to form a series of separate open ended bags; and subsequently, folding over the sealed end of each bag and forming a further heat seal to hold down the folded over flap, between the fold and the already heat sealed end.

6. A method according to claim 5 in which the length of the bag which is folded over is made equal to the total width of the gusset, and the further heat seal is made midway between the folded over portion and the already sealed end.

7. A bag substantially as herein described with reference to the accompanying drawings.

8. A method of making bags from flexible film, the method being in accordance with claim 5 or claim 6 and substantially as herein described.