WO2001054995A1

WO2001054995A1 - A valve bag and method of manufacturing

Info

Publication number: WO2001054995A1
Application number: PCT/FI2001/000071
Authority: WO
Inventors: Pentti Rikassaari; Valter Sievers
Original assignee: UPM Kymmene Oy
Current assignee: UPM Kymmene Oy
Priority date: 2000-01-28
Filing date: 2001-01-26
Publication date: 2001-08-02
Anticipated expiration: 2002-07-28
Also published as: FI20000169L; FI20000169A0; AU2001231788A1; FI20000169A7

Abstract

The application describes a valve bag made of paper, in which bag there is made a valve bottom by folding end flaps (5, 5') inwardly from the edges of a flattened tube-like blank, and by folding side flaps (12) from the blank sides on top of said end flaps. The bottom is provided, on the inside of the side flaps (12), with an inner bottom patch (7) that extends from one end flap (5) to the other (5'). The application also describes a method of manufacturing.

Description

_A valve bag and method of manufacturing .

FIELD OF THE INVENTION

The invention relates valve bags made of paper, and particularly to the making of the valve bottom. In particular, the invention relates to multilayer valve bags, where a barrier film is arranged in between the paper layers. In that case air can be exhausted from the bag during the filling process, so that air is conducted in between the barrier layer and the inner layer to the area of the bag bottoms, and further out thereof.

BACKGROUND OF THE INVENTION

Paper bags are manufactured by forming a paper web into a flattened tube, which is cut into blanks. At one end of the blank, there can be made a flat bottom by gluing, so that at the blank edges, triangular end flaps are folded inwards, and side flaps are folded on top of these. Generally a bottom patch is glued on top of this. In valve bags, both ends of the bag are closed, but at one end, there is made a filling valve by leaving the interval between the end flap and the side flaps unglued. At the valve end, there can additionally be attached, at a length from the edge of the end flap, a valve extension that improves the air-tightness of the bag. By this method, also multilayer bags can be manufactured.

Moisture-proof bags can be manufactured by placing a separate plastic barrier film between the paper layers. Particularly polyethylene has been used as the plastic material. A problem with this type of valve bags has been that air is not exhausted from the bag during the filling process. Therefore the barrier film has been perforated, which of course essentially weakens its sealing properties.

The exhaustion of air from a valve bag can also be arranged so that air is conducted in between the barrier film and the inner layer to the bag bottom area and further out via the bottom ends. This kind of bag is introduced in the Finnish patent publication FI-A-945831. In the Finnish patent publication FI-A-972664, there is described a similar bag, where the layer ends are laminated in order to improve the air-tightness. In both of these bags, air proceeds on one side of the bag only to one end, and on the opposite side of the bag only to the opposite end. At the valve end. air is exhausted only at the end opposite to the valve, when the filling valve is set tightly in place. GENERAL DESCRIPTION OF THE INVENTION

The present invention relates to a bag according to claim 1 , and to the manufacturing method and use of said bag. Preferred embodiments of the invention are described in the dependent claims.

In a bag according to the invention, the valve bottom is provided with an inner bottom patch placed under the side flaps and extending from one end flap to the other. The inner bottom patch makes the structure stronger and tighter as well as more solid.

An inner bottom patch is particularly advantageous in multilayer bags, where air is allowed to be exhausted from between the layers in the bag bottom area. In the arrangement according to the invention, air can also be exhausted at the valve bottom, via both ends of the bottom, so that air is exhausted in a very efficient way. Owing to the inner bottom patch, air can be conducted to the bottom at both ends of the bottom, too, which further improves air exhaustion.

DRAWINGS

The appended drawings form part of the detailed description of a preferred embodiment of the invention. They illustrate the making of the bag bottom step by step.

Figure 1 illustrates a blank where the end flaps are folded.

Figure 2 illustrates a blank to which an inner bottom patch is attached.

Figure 3 illustrates a blank provided with the necessary gluings required by the sealinog of the bottom.

Fi 'g6ure 4 illustrates how the bottom is sealed.

Figure 5 illustrates how the bottom patch is attached to the bottom.

Figure 6 illustrates a ready-made bag.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The bag according to the drawings is manufactured of a three-layered material. Innermost there is an inner layer 1 made of paper, further out a barrier layer 2 impermeable to air, and outermost an outer layer 3 made of paper. The inner layer 1 and the outer layer 3 can be made of a suitable bag paper (strength for example 95 give/⁾. The barrier layer 2 can be made of a suitable plastic film (for example. HDPE).

The inner layer 1 extends somewhat further than the barrier layer 2 and the outer layer 3.

In the vicinity of the head, the blank layers are attached together by means of a transversal point-by-point gluing. This improves the strength and also makes it easier to align the layers in the manufacturing process. In between the glue points, air can, however, flow out in between the inner layer 1 and the barrier layer 2. The best way to realize the gluing is to provide the barrier layer at the glue points with holes 4, through which the paper layers are glued together. Thus there can be used an ordinary paper glue that is easy to handle (for instance a starch glue). The holes in the plastic barrier layer can be made conveniently by melting with a hot pin.

At one edge of a flattened blank, there is inwardly folded an end flap 5. At the corners of the end flap, there are cut and turned open sealing flaps 6. At the opposite edge, there is folded a valve end flap 5'. Its corners are left uncut.

In the next step (Fig. 2), at the valve end of the blank, there is attached a rectangular inner bottom patch 7, which extends from the end flap 5 to the valve end flap 5'. The corners of the inner bottom patch extend somewhat over and outside the edges of the end flaps. The inner bottom patch is glued to the inner layer 1 of the end flap 5 by a uniform glue strip 8, and to the outer layer 3 by a uniform glue strip 9. Moreover, the inner bottom patch is glued at the edges to the end flaps and to the inner surface of the inner layer by uniform glue strips 10 extending from the end flap 5 to the valve end flap 5'. In the drawing, there are also marked the side folding lines 11, along which the side flaps 12 are folded. The glue strip 8 extends over the side folding line to the glue strips 10. The ends of the glue strip 9 are left inside the side foldin *og lines.

The gap between the valve end flap 5 ' and the inner bottom patch 7 is left open and forms a filling valve.

At the valve end of the inner bottom patch 7, there is made a folding 13 against the valve end flap 5' in order to improve solidity and rigidity.

In the next step (Fig. 3), there are made the glue strips 14 required for sealing the bottoms. The glue strip 14 extends from the inner bottom patch 7, from the side folding line 11, to the edge of the side flap 12. When the side flaps are folded against the inner bottom patch 7 (Fig. 4), the inner layer of the side flap that falls underneath is glued to the inner bottom patch. Also the inner edge of the side flap that falls on top is glued to the inner bottom patch, but its outer edge is glued to the inner layer of the side flap that is placed underneath. The edge of the topmost side flap is left at spaced apart from the edge of the barrier layer 2 of the lower side flap and of the edge of the outer layer 3. Thus air can flow at both ends between the inner layer and the outer layer.

Finally a bottom patch 15 (Fig. 5) can be glued to the bottom. The bottom patch is made of paper, it is of the same size as the bottom and rectangular in shape. At the side edges of the bottom patch, there are provided inwardly foldings 16, and at said foldings, the patch is glued with uniform glue strips 17.

The other end of the bag blank can be closed in similar fashion, but so that both ends are sealed by gluing.

As an alternative, one of the ends can be closed according to the method described in the publications FI-A-945481 and FI-A-972664.

The bag (Fig. 6) is filled through the valve by means of a pipe, which is pushed in an air-tight fashion between the valve end flap 5' and the inner bottom patches 7. When filling the bag, air is exhausted therefrom through the inner layer 1 to between the inner layer and the barrier layer 2. There it flows to the bag bottoms and is exhausted at both ends via both side flaps. When an inner bottom patch is provided at the bottom, air is exhausted on top of it, and to below a possible bottom patch 15. Because the bottom patch is glued by uniform sealings at the edges, air is exhausted from underneath the bottom patch at the bottom ends. Owing to the inner bottom patch, air can also be exhausted from the valve bottom at both ends thereof.

Moreover, the inner bottom patch also makes the bottom structure more air-tight.

In order to improve the flowing of air in between the inner layer 1 and the barrier layer 2, either the inner layer or the outer layer 3 can be provided with longitudinal grooves.

In order to further improve the exhaustion of air, the inner layer 1 can be suitably perforated. In the bag according to the above description, air is exhausted very efficiently, which reduces disturbances at the filling machine. Respectively, filling speeds can be further increased.

Claims

1. A valve bag made of paper, where a valve bottom is formed by folding end flaps (5, 5') inwardly from the edges of a flattened tube-like blank, and by folding side flaps (12) from the blank sides on top of said end flaps, and by leaving the gap between one of the end flaps (5') and the side flaps open, characterized in that the bottom is provided, on the inside of the side flaps (12), with an inner bottom patch (7) that extends from one end flap (5) to the other (5').

2. A bag according to claim 1 , where the inner bottom patch (7) is glued to the end flap (5).

3. A bag according to claim 1 , where the inner bottom patch (7) is glued to the side flap (12).

4. A bag according to any of the claims 1 - 3, where also the bottom opposite to the valve bottom is provided with an inner bottom patch.

5. A bag according to any of the claims 1 — 4, provided with several layers.

6. A bag according to claim 5, provided with an inner layer (1) permeable to air, outside it a barrier layer (2) impermeable to air, and further out an outer layer (3).

7. A bag according to claim 6, where the inner layer (1) arranged in the valve bottom is longer than the barrier layer (2) and the outer layer (3).

8. A bag according to any of the claims 1 - 7, where a bottom patch (15) is provided at the bottom, on top of the side flaps (12).

9. A method for manufacturing a valve bag made of paper, where there is formed a flattened tubular blank, end flaps (5, 5') are folded inwardly from the edges thereof, and on top of said end flaps, there are folded side flaps (12), characterized in that at the bottom, on the inside of the side flaps (12), there is attached an inner bottom patch (7) extending from one end flap (5) to the other (5').

10. A method for exhausting air from a multilayer valve bag comprising an inner layer, a barrier layer and an outer layer, in which method air is allowed to be exhausted from the bag to between the inner layer and the barrier layer, and further out at the edge of the layers at the bag bottom, characterized in that air is allowed to be exhausted at both ends of the bag, through the edges on both sides of the bag.