GB2090577A

GB2090577A - Double layer bag

Info

Publication number: GB2090577A
Application number: GB8038403A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-11-29
Filing date: 1980-11-29
Publication date: 1982-07-14
Also published as: GB2090577B

Abstract

A sealable vacuum-tight double layer block-base bag has an inner layer (2) of heat-sealable flexible material and an outer layer (1) of paper or the like which is connected to the inner layer, by glueing or heat- sealing at separate spaced apart points (3, 4, 5, 6) in the region of the bottom and upper edge of the bag. The inner layer (2) has a longitudinal seam (22) which is staggered relative to a longitudinal glue seam (11) in the outer layer(1). <IMAGE>

Description

SPECIFICATION Double layer bag This invention relates to a sealable vacuumtight double layer bag having a stable block-base bag and foldable bottom and side walls, the inner layer of the said bag comprising a heat-sealable, flexible material and the outer layer comprising paper or like material.

Air-tight packages are often used for loose goods such as food and semi-luxuries, particularly for roasted ground coffee beans. Such bags usually consist of one or more layers of a flexible, air-tight sheet material which can be heat-sealed, at least on the inside. The sheet materials are fed in the form of a continuous sheet into a packing machine where they are made into a tube, or they are fed into a packing machine already pre-shaped into a tube where they are transversely sealed, thereby forming a sealed closure at one end. This tube-shaped bag is then cut off, filled, evacuated and sealed again in a vacuum. In this way a firm block is formed and the creases or folds of the surplus sheet material usually drag between the transverse seal seam and the cutting edge.This makes the block-shaped package unstable and it is, because of its unevenness, not very attractive to sell. If the outer layer were printed the creases and folds of the irregular package would distort the printed matter, such as a picture, name, etc. It has therefore been necessary up to now to place the air-tight package inside an additional outer package which could, for example, be a folding carton printed with advertising matter, to conceal the creased appearance of the air-tight package.

Alternatively another bag could be used as an outer package. The use of an additional outer package adds to the packaging cost, and the stability of the bag is not improved. A block-base bag is in this case very useful. But it is difficult to produce an air-tight block-base bag.

Air-tight and double layer block-base bags commonly used up to now have longitudinal seal seams in the inner layer and longitudinal- or glued seams in the outer layer which are directly superimposed, these seams being on one side or the other of the bag or on the back of the bag. This means that the longitudinal seal seam runs in the base area paralle! to the base-flap-turnover of the usual base fold of the bag, so that in the intersection area between the longitudinal seal seam and the base seal seam an air tight seal is very difficult or almost impossible to achieve, because of the directly adjacent folds of the seal flaps.

Another problem arises in sealing the top edges of such bags after they have been filled, due to the fact that the sealing jaws of the sealing machine have to seal together, in the area of one of the side pleats of the bag across the longitudinal seal seam, six thicknesses of the sheet packaging material, in the area of the other side pleat, four such thicknesses and in the central area of the bag two such thicknesses. Because of these varying thicknesses of the sheet material (that is, 6, 4 and 2 thicknesses) across the area to be sealed, it is not possible to ensure effective air-tight closure of the packages so formed, using present-day sealing machines.

The object of this invention is to eliminate the aforementioned disadvantages of presently used vacuum packages by providing a special blockbase bag.

According to the present invention there is provided a sealable vacuum-tight double layer and stable blocl < -base bag with folded bottom and side walls, comprising an inner layer of a heat-sealable, flexible material and an outer layer of paper or like material, in which the inner layer is connected to the outer layer only in the region of the bottom and upper edge of the bag by means of glueing or heat-sealing the inner layer having a longitudinal seal seam which is staggered relative to a longitudinal glue seam in the outer layer.

This glueing or heat-sealing between the layers should be suitably intermittent so that the space between the two layers, after the creation of the vacuum within the inner layer, and after closing the block-base bag, can be in contact with the outside air, which ensures that the smooth outer layer, which in most cases consists of paper, conceals all irregularities of the air-tight inner layer and also provides the blocl < -base bag, through the additional material reinforcement at the bottom, with a good firm stand. The sealing of the longitudinal seal seam with the base seal seam in the intersection area no longer presents a problem, as the impairment of the fold of the bottom flap no longer applies.Furthermore the bag according to the invention has around its top edge a uniform thickness made up of four layer thicknesses, as compared with the thickness varying from 6 to 2 layers which is characteristic of the previously known bag referred to earlier.

This is an important advantage for the air-tight sealing of the bag. Only the bag according to this invention ensures the manufacture of a rigid and firm-standing block-base bag with a smooth outer layer after evacuation and a sufficiently air-tight closure.

The invention also provides, according to another aspect, a method of filling a bag as previously defined, in which the bag is opened and filled with loose goods, following which only the inner layer of the bag is evacuated and sealed under a vacuum.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a front elevation of a block-base bag according to one embodiment of the invention, in a folded state before filling; Figure 2 is a rear elevation of the bag shown in Figure 1; Figure 3 shows a filled and sealed block-base bag ready for sale and Figure 4 shows the same bag as shown in Figure 3, but with part of its outer layer torn open to show part of the inner layer.

The block-base bag consists of an outer layer 1, of paper or like material and an air-tight, flexible, heat-sealable inner layer 2 which is connected to the outer layer 1 at points 3, 4 and 5 by means of glueing or heat-sealing. In addition the inner layer 2 is glued or sealed to the outer layer 1 near the top edge of the bag by an intermittent transverse seam 6. A seal seam 7 is provided at the bottom part of the block-base bag. A glue seam 11 of the outer layer 1 can be seen on the back of the bag (Fig. 2). A further seal seam 22 of the inner layer, which also runs in a longitudinal direction, is not visible from the outside and is therefore represented by a broken line in Figure 2. The seam 22 is staggered relative to the glued seam 11 and is arranged in the central area of the back of the bag.

The block-base bag is opened in the normal use of a filling machine which fills the bag with loose goods such as, for example, ground coffee. After filling, the vacuum-tight inner layer 2 of the bag is located at a vacuum-station, where it is evacuated and then vacuum-sealed along a seai-seam 9. This causes the inner layer 2 to shrink with its contents to form a square shaped block. After removing the bag from the vacuum-station, normal air pressure prevails between the outer layer 1 and the inner layer 2 of the bag. As a result the outer layer 1 remains smooth, concealing any creases or unevennesses formed in the inner layer 2 during the process of evacuation. The package therefore takes on the smooth, square shape shown in Figure 3, which is attractive as well as stable and uniform.

Figure 4 shows a filled and evacuated inner layer 2 with a partially torn-away outer layer 1 in order to show the creased condition of the inner layer 2 after the filling and evacuation with its upper folded parts, which forms a so-called cover flap 8, turned up in order to reveal part of the longitudinal seal seam 22 of the inner layer 2 and to show diagrammatically the position of the seal seam 9 of the inner layer 2. The cut edge 10 of the open end of the bag shows the structure of the block-base bag, revealing the outer layer 1 and the inner layer 2.

The invention has the further advantage of not needing an additional outer package or cover, which saves on manufacturing costs, because the outer layer 1 and the inner layer 2 are already connected with one another at the seal- or glue points 3, 4 and 5 before the bag is shaped.

Furthermore the usual sequence of operations for the attachment of special outer packages, which obviously adds to the overail cost, including the cost of folded cartons or wrapping material, is dispensed with, so that the entire wrapping operation is considerably rationalised.

A double layer, heat-sealable block-base bag according to the present invention can be prefabricated in block-base bag-forming machines and fed to a filling machine, or lined-up with or integrated with a forming machine in order to be glued or sealed as previously described.

Claims

1. A sealable vacuum-tight double layer and stable block-base bag with folded bottom and side walls, comprising an inner layer of a heat-sealable, flexible material and an outer layer of paper or like material, in which the inner layer is connected to the outer layer only in the region of the bottom and upper edge of the bag by means of glueing or heat-sealing the inner layer having a longitudinal seal seam which is staggered relative to a longitudinal glue seam in the outer layer.

2. A bag according to Claim 1, in which the longitudinal seal seam of the inner layer is disposed centrally of one side of the bag, between the two side walls thereof.

3. A bag according to Claim 1 or Claim 2, in which the glueing or heat-sealing of the inner layer to the outer layer is effected at several separate points.

4. A bag according to Claim 1, Claim 2 or Claim 3, in which the glueing or heat-sealing in the region of the upper edge of the bag is intermittent.

5. A method for filling a bag according to any one of the preceding claims in which the bag is opened and filled with loose goods, following which only the inner layer of the bag is evacuated and sealed under a vacuum.

6. A sealable, vacuum-tight double layer bag substantially as herein described with reference to and as shown in the accompanying drawings.