GB2143504A - Multi-layer plastics sack - Google Patents

Abstract

A multi-layer plastics sack has a substantially transparent outer layer or layers (14) and an opening (21) between this layer or these layers (14) and an inner layer (13) through which a label or card (22) can be inserted such that markings on the label or card (22) can easily be read or understood when the label or card (22) is viewed through the outer layer or layers (14). <IMAGE>

Description

SPECIFICATION Multi-layer plastics sack The present invention relates to multi-layer plastics sacks.

Plastics sacks made with a pair of opposed walls each formed of a plurality of layers of thermoplastics film material are known for various applications. The strengths of commonly used thermoplastics film materials is not linearly related to the gauge or thickness of the film. Thin films can be relatively stronger than would be expected in proportion to a thicker film. Accordingly, making a sack with several layers of thin films results in a stronger sack for the same weight of thermoplastics material, than using one thick film layer for the wall.

Such multi-layer plastics sacks are thus useful when strength is important, but use of such plastics packaging has not found favour in despatching or posting of goods because of the difficulty of affixing labels, stamps and the like to the plastics package. Labels applied to plastics film with commonly used gums and adhesives can readily be peeled off again and tend to become detached in the course of handling of the package.

According to the present invention, a multilayer plastics sack has a pair of opposed walls each formed of a plurality of layers of thermoplastics film material, the walls being separate at one edge of the sack to define the mouth of the sack, and an opening adjacent to the mouth to enable a card or label to be inserted between outer and inner layers of a wall of the sack, the outer layer or layers being substantially transparent to enable markings on the card or label to be identified when viewed through the layer or layers. In this way a multi-layer plastics sack can readily be labelled or marked in a secure way without the risk of the card or label becoming detached.

The card or label can be made of paper material and prepared in the usual way. For postal packages, the card or label would no maliy be pre-franked-before insertion between the layers of the wall. It is believed this multilayer plastics sack will find particular application in the mail order business where there is a substantial need for cheap but robust packaging.

Conveniently, the layers of each wall are sealed together adjacent the mouth of the sack and said opening is constituted by a slit through the outer layer or layers. It may be convenient to provide a slit forming a corresponding said opening in the outer layer or layers of each wall of the bag. Then, when the bags are being filled and cards or labels inserted, there will be no need to find out which side of the bag has the slit for insertion of the card or label. The card or label can be inserted on either side of the bag.

In a different arrangement, at least one pair of inner layers of the walls of the sack are formed of a longitudinally folded lay-flat tube of thermoplastics film material and at least an outermost layer of the walls is formed of a longitudinally folded single layer web of thermoplastics film material. Conveniently, then, the web of the outermost layer is narrower then the width of lay-flat tube. This construction avoids any need to seal the layers of the walls together adjacent the mouth of the bag.

It will commonly be convenient for at least the innermost layer of each wall to be substantially opaque, thereby hiding the contents.

The invention also envisages a sack as described above and including a card or label inserted behind the outer layer or layers of the wall of the sack.

It would be appreciated that it would normally be sufficient for the card or label to be inserted immediately behind the outermost layer.

The present invention also envisages a method of packaging goods using a multilayer plastics sack as described above and comprising preparing a label or identiffication card for the goods to be packaged; inserting the goods into the sack through the mouth and inserting the label or identification card through said opening to be viewable behind the outer layer or layers of one wall of the sack; and then heat sealing all the layers of both walls of the sack together across the width of the sack to close both the mouth of the sack and said opening. The steps of this method show how easily both the contents of the sack and the identification card or label can be enclosed and sealed in the sack simultaneously with one sealing operation.

In another aspect, the present invention provides a package comprising goods and a multi-layer plastics sack enclosing the goods, the sack having a pair of opposed walls each formed of a plurality of layers of thermoplastics film material with the goods enclosed between the walls, a label or identification card located between outer and inner layers of a wall of the sack, the outer layer or layers being substantially transparent to enable markings on the label or card to be identified when viewed through the layer or layers.

An example of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 illustrates a multi-layer plastics sack or package embodying the present invention; Figures 2, 3 and 4 illustrate a method of making the sacks shown in Figure 1; and Figure 5 illustrates as a different embodiment of sack made using a lay-flat tube.

Referring to Figure 1, a multi-layer plastics sack is illustrated comprising substantially flat multi-layer walls 10 and 11. The walls 10 and 11 are formed from three layers 12, 1 3 and 14 of thermoplastics film material, typi cally high density polyethylene film, folded in half at a fold 1 5 which forms a base of the finished sack. All layers of the two walls 10 and 11 are heat sealed together along side seams 16 and 17. The layers 12, 13 and 14 of each wall of the sack are heat sealed together at 1 8 and 1 9 adjacent the mouth 20 of the sack. Goods can be inserted into the sack through the mouth 20 so as to lie between the innermost layers 1 2 of the walls 10 and 11 of the sack.

The outermost layer 14 of at least the upper wall 10 as shown in Figure 1, is slit at 21 across the width of the bag just below the seal 1 9 relative to the mouth of the bag.

Through the opening provided by the slit 21, a label or card 22 is inserted between the outermost layer 1 4 and middle layer 1 3 of the wall 10 of the bag. The outermost layer 14 of the bag is made to be substantially transparent so that markings on the label or card 22 can easily be read or understood when the label or card is viewed through the layer 14.

The label or card 22 may for example be an address label with a postage paid franking mark 23 to enable the package to be sent through the mail.

The package can be closed once goods have been inserted into the sack through the mouth 20 and the label or card is located as shown in Figure 1 behind the outer layer 14, by a single sealing operation along the line 24. If this sealing operation is arranged to seal together all six layers of the walls of the bag, it can be seen that it simultaneously closes the mouth 20 of the bag to seal the goods therein but also closes the opening defined by the slit 21 so that the label or card 22 cannot fall out.

One method of assembling the multiple layers of the plastics sack is illustrated in Figure 2. In the illustration, three webs 30, 31 and 32 of thermoplastics film material are pulled from respective reels 33, 34 and 35 over a first common roller 36 where the layers are brought into contact and then over a centrefold bar 37 and a subsequent roller 38 which are arranged to fold all three layers in half along a centreline 39 of the web as illustrated. This method of assembling the multiple layers of plastics web material can be used provided the necessary width of the unfolded single layer webs 30, 31 and 32 is not excessive. However in some applications, where large size sacks are required, it is convenient to handle the web originally as a flattened two layer tube. A single centrefolded web is then produced by slitting the tube along one fold line.In order to assemble three layers from such separate centre folded webs, the individual webs must be opened and the inner webs inserted, using techniques which are known in the art.

Figures 3 and 4 illustrate the steps which may be used to form the multi-layer sacks from the continuous web 40. In this example, the web 40 is fed step wise through a slitting and welding station illustrated generally at 41. When the web 40 is correctly positioned it is held stationary in the welding station 41 and welding bars 42 and 43 are brought together on opposite sides of the web 40 to form transverse welds 44. The welds 44 form the side edges of the finished sack corre sponding to the seals 1 6 and 1 7 in Figure 1.

The welding operation may be continued also to cut right through the web so that not only are the side seals formed but the bags are separated one from another.

At the same time, as the transverse welds 44 are formed, welding bars 45 and 46 are brought together to seal the layers of the respective walls of the finished bag together adjacent the mouth of the bag. A separating bar 47 is provided to separate the layers of the web so that the mouth of the bag is left open.

A slitting knife 48 is also provided mounted on an arm 49 extending between the layers of the upper wall of the web so as to slit through only the uppermost layer of the upper wall as the web is moved along between welding operations. The knife is so positioned immediately adjacent the separating bar 47 so as to slit the outermost layer of the web to form the slits 21 in the finished sacks.

It will be appreciated that other methods of forming the multi-layer plastics sacks are possible. For example, as shown in Figure 5, the sacks may be made from a lay-flat tube 50 of thermoplastics film material which is longitudinally centre-folded at 51 inside a similarly centre-folded single layer web 52. The lay-flat tube 50 and web 52 may be centre-folded together in the manner shown in Figure 2.

Preferably the web 52 is slightly narrower than the tube 50 so that one or preferably both of the longitudinal edges 53 of the web 52 extend short of the side-folded edges 54 of the tube 50. The sacks are formed from the composite web by a single transverse welding operation with welding bars 55 to form the side welds of the sack corresponding to welds 1 6 and 1 7 of the sack shown in Figure 1. The side-folded edges 54 of the lay-flat tube 50 neatly define between them the mouth of the sack, and the edges 63 of the outer web 52 define openings to enable the insertion of a label or card behind the outer layer of the wall of the sack. As before, the web 52 is sufficiently transparent to enable markings on the label or card to be read, and the tube 50 may be made opaque.

Claims (9)

1. A multi-layer plastics sack having a pair of opposed walls each formed of a plurality of layers of thermoplastics film material, the walls being separate at one edge of the sack to define the mouth of the sack, and an opening adjacent the mouth to enable a card or label to be inserted between outer and inner layers of a wall of the sack, the outer layer or layers being substantially transparent to enable markings on the card or label to be identified when viewed through the layer or layers.

2. A sack as claimed in Claim 1 wherein the layers of each wall are sealed together adjacent the mouth of the sack and said opening is constituted by a slit through the outer layer or layers.

3. A sack as claimed in Claim 2 and including a slif forming a corresponding said opening in the outer layer or layers of each wall of the bag.

4. A sack as claimed in claim 1 wherein at least one pair of inner layers of the walls of the sack are formed of a longitudinally folded lay-flat tube of thermoplastics film material and at least an outermost layer of the walls is formed of a longitudinally folded single layer web of thermoplastics film material.

5. A sack as claimed in claim 5 wherein the web of the outermost layer is narrower than the width of lay-flat tube.

6. A sack as claimed in any preceding claim wherein at least the.innermost layer of each wall is substantially opaque.

7. A sack as claimed in any preceding claim and including a card or label inserted behind the outer layer or layers of a wall of the sack.

8. A method of packaging goods in a multilayer plastics sack as claimed in any preceding claim comprising preparing a label or identification card for the goods to be packaged; inserting the goods into the sack through the mouth and inserting the labe 1 or identification card through said opening to be viewable behind the outer layer or layers of one wall of the sack; and then heat sealing all the layers of both walls of the sack together across the width of the sack to close both the mouth of the sack and said opening.

9. A package comprising goods and a multi-layer plastics sack enclosing the goods, the sack having a pair of opposed walls each formed of a plurality of layers of thermoplastics film material with the goods enclosed between the walls, a label or identification card located between outer and inner layers of a wall of the sack, the outer layer or layers being substantially transparent to enable markings on the label or card to be identified when viewed through the layer or layers.