GB2301087A

GB2301087A - Transport sack

Info

Publication number: GB2301087A
Application number: GB9610951A
Authority: GB
Inventors: Wolf-Dieter Haberl
Original assignee: Storsack Austria GmbH
Current assignee: Storsack Austria GmbH
Priority date: 1995-05-24
Filing date: 1996-05-24
Publication date: 1996-11-27
Anticipated expiration: 2016-05-24
Also published as: ATA88095A; NL1003204A1; DE19620372B4; NL1003204C2; GB2301087B; BE1012524A3; GB9610951D0; AT403155B; DE19620372A1

Description

TRANSPORT SACK The invention concerns a transport sack which is formed by

sewing up one or several fabric webs. The invention also relates to a method for manufacturing the transport sack and the apparatus for this purpose. Such a type of transport sack is also called a "big bag".

Transport sacks of this kind are a cheap and a frequently used transport medium for pourable materials. One bag is capable of taking loads of up to several tons.

In the case of a powdery pourable material, it is necessary to design the transport sack to be as near as possible leakproof. Mostly one uses, as the material for the transport sack, coated fabrics, for example, polypropylene webs with a polypropylene coating or polyethylene webs with a polyethylene coating. In the case of transport sacks of this kind designed to be leakproof, the problem arises during filling that the air situated in the sack must escape at high pressure and at a high speed, in particular in the case of fast filling processes. The high pressure and the fast rate of flow produce the effect that even small holes allow the emergence of dust. A weak point is formed in this respect, in particular by the seams at which the various fabric webs are sewn together to form the transport sack. The high filling pressure and the tensional stress of the walls at the edge seams or web seams lead to a widening of the stitch holes which, like jet-type openings, allow fine dusts to emerge.

To remedy this drawback, it has already been known to seal the seam zone in that a strip of material, or a strip of felt, is folded over round the edge to be sewn up and is sewn up on the outside with the fabric webs. This solution is very expensive since the strip has to be relatively wide and 2 is expensive. The input of labour is also high.

The known literature shows the sealing of flat seams, in which case very special applications are partly concerned. Thus DE-A-2751162 discloses the sealing of seams on folding tops of motor vehicles and DE-B-3209054 discloses the watertight connection of plastic-coated fabric parts. FR-A2634468 admittedly describes a transport sack, but of the type wherein the seal is provided by an inserted leakproof sack, in which arrangement the problem on which the invention is based cannot occur at all.

In accordance with a first aspect of the present invention there is provided a transport sack, formed by sewing up one or several fabric webs or sheets by means of edge seams, wherein in order to form a leakproof seam, a sealing strip is provided between the fabric webs in the seam zone and is sewn up jointly with the fabric webs, and wherein the sealing strip consists of a flexible material and at the side of the seam projects into the interior of the transport sack. This sealing strip preferably consists of a flexible material and, at the side of the seam, projects into the inside of the transport sack. In a particularly preferred embodiment, the sealing strip consists of a loosely plaited or woven or knitted wad such as a multifilament wad or tow, or a felt strip.

A second aspect of the invention provides a method of sewing a transport sack of the first aspect, wherein, during the sewing together of the respective two fabric webs to form a seam, a sealing strip is laterally fed between them from the inside into the seam zone and is sewn in.

For an additional sealing effect, a further sealing strip may be additionally sewn on jointly from the outside at one or both of the two sides of the seam.

Seams formed in this way are very leak-tight and the costs of manufacture amount to one tenth as compared with the method described above.

in a preferred mode, the sealing strip is a woven, knitted or plaited strip, as for example, a polypropylene multifilament wick. Such a wick is very soft and flexible. A preferred wick has cross-sectional dimensions of approximately 15 =m in width and is 4 nm thick. Circular section wicks may also be used.

The effect lies above all in the fact that the flexible sealing strip extends inwards into the interior of the transport sack and during the filling positions itself in front of the edge shape and thus exerts a sealing function which even takes place ahead of the formation of the stitch holes. If a wick strip or felt strip is used as the material, as is preferred, the air can escape through the seam zone but the particles are nevertheless prevented from escaping. There thus occurs a filter effect.

During manufacture it is necessary to insert the sealing strip between the fabric webs, and to guide it in such a way that the sealing strip is securely sewn on at the same time. When the sealing strip is fed manually, in the event of careless handling, it may happen that this sewing together may not take place in an accurate manner and the sealing strip may migrate somewhat towards the inside. Such a point in the seam would not be leakproof.

To ensure the correct feeding and sewing, a third aspect of the invention provides an apparatus for sewing a transport sack of the first aspect, wherein a laterally pivotable guide lever is arranged on the sewing table and has a guide means at its guiding end. In the swung-in state of the guide lever the guide means lies between the fabric webs to be sewn 4 together and ensures the exact feeding of the sealing strip into the seam.

The invention will be described in greater detail below with reference to the accompanying schematic drawings.

Figure 1 shows the basic structure of a transport sack; Figures 2, 3 and 4 each show a section through the sewn up edge zone of the sack at different times; Figure 5 is a perspective view showing schematically the process of the sewing by means of the apparatus in accordance with the invention; and Figures 6 and 7 show two different forms of a transport sack in a schematic representation.

According to Figure 1, the conventional transport sack consists of, for example, the four side walls 1, the bottom 2 and the cover 3. At the edges, the fabric webs are sewn together by means of one seam 4 each, so as to leave outwardly projecting strips 5.

The cover 3 has a pouring opening with a sleeve 6. The bottom 2 may be closed to the exterior or be provided with an appropriate discharge opening. Loops 25 may be provided at all four corners to allow the sack to be lifted and held. The formation of the seams 4 and of all remaining seams of the finished transport sack is a preferred object of the present invention.

In the sewing process shown in Figure 2, two superposed fabric webs 7 are sewn together in the edge zone by means of the seam 4, in which process the sealing strip 8 is arranged between the two fabric webs 7. As may be seen in Figure 2, the sealing strip 8 is sewn up jointly with the seam 4 and, in any case, also projects inwards into the interior of the sack.

Figure 3 shows the behaviour of the seam zone during the filling of the erected sack in which the two fabric webs 7 are pulled apart with a high force and the seam 4 is subjected to high stresses. The stitch holes which might tend to open in this process are closed by the sealing strip 8 or are sealed in the manner of a filter, since the flexibility of the sealing strip produces a sealing effect, so that fine dusts cannot escape through the stitch holes of the seam 4.

Figure 4 shows a seam formation wherein, additionally to the sealing strip 8 arranged between the fabric webs, on one or both sides a further sealing strip 26 is on the outside, which reinforces the seal still further.

Figure 5 shows schematically the apparatus for forming the sealed seam. The sewing machine 9 is disposed on a sewing table 10. The thread 11 runs, to the needle 12, over the usual guide and tensioning devices. The sewing foot 14, secured on the sewing foot holder 13 and pressed downwards, bears on the upper fabric web 7. The sealing strip 8 is inserted and fed between the upper and lower fabric webs 7 in such a way that it is sewn in jointly with the formed seam 4.

The feeding and lateral guidance of the sealing strip 8 is effected by means of the guide lever 15 which is pivotable about the pin 16 on the sewing table 10. A guide hook 18, provided on the guiding end 17, guides the sealing strip 8 during the sewing process and in particular prevents it from migrating into the inside of the sack. Instead of the guide hook, other guide means such as a guide eyelet may be provided.

The insertion of the sealing strip 8 into the guide hook 18 is effected when the guide lever 15 is in the position shown in Figure 5. Before the sewing process starts, the guide lever 15 is pivoted in the direction of arrow 19 until it bears on the sewing table 10 and guides the sealing strip 8 up to a short distance ahead of the sewing foot 14.

When the end zone of a seam has been reached, the guide lever 15 can be again swung outwards, and the sealing strip 8 can be cut off appropriately and the sewing of the seam can be finished.

In the case where, in addition to the sealing strip 8, additional sealing strips are also to be sewn in from the outside, the additional sealing strips 26 (shown in Figure 4) can be fed from below via the eyelet 20 on the sewing foot 14 and via an appropriate further guide eyelet of the sewing table.

Figure 6 shows schematically an arrangement of fabric webs in which two opposite side walls and the bottom are formed from a single fabric web 21 folded into a U shape, and two further fabric sheets 22 complete the side walls. If required, a separate cover can also be additionally fitted from the top and be sewn up.

in the design shown in Figure 7 there are two fabric webs 23, 24, both folded into a U-shape, which are sewn up together in the configuration shown. This design has the advantage that a completely closed transport sack, which can be provided at the top and bottom with the appropriate filling and emptying openings, can be manufactured with a single leakproof seam.

All the seams required for this purpose can in accordance with the invention be sewn with a sealing strip.

The seams 4 are preferably chain stitch seams, but may also be in the form of a lock stitch seam.

8 -

Claims

C L A I M S

1. A transport sack, formed by sewing up one or several fabric webs or sheets by means of edge seams, wherein in order to form a leakproof seam, a sealing strip is provided between the fabric webs in the seam zone and is sewn up jointly with the fabric webs, and wherein the sealing strip consists of a flexible material and at the side of the seam projects into the interior of the transport sack.

2. A transport sack according to claim 1, wherein the sealing strip consists of a loosely plaited or woven or knitted multifilament elongate wad or a flexible felt strip.

3. A transport sack according to either of claims 1 or 2 wherein, in addition to the sealing strip between the fabric webs, one or a respective further sealing strip is arranged and sewn jointly at one or both of the two outer sides of the fabric webs.

4. A transport sack according to any one of claims 1 to 3, wherein its side faces and the bottom are formed from a fabric web folded into a U shape and from two separate side face sheets.

5. A transport sack according to any one of claims 1 to 3, wherein the sack includes a cover, and wherein the side faces, the bottom and the cover are formed from two fabric webs folded into a U shape, and the sack is sewn up with a single continuous seam.

6. A transport sack according to any one of claims 1 to 5, wherein the seams are formed by one or several chain stitch seams.

7.

A transport sack substantially as hereinbefore 9 - described with reference to, and as illustrated in, Figures 1 to 3 of the accompanying drawings.

8. A transport sack according to claim 7, when modified as shown in Figure 4, or Figure 6 or Figure 7 of the accompanying drawings.

9. A method for sewing a transport sack according to any one of the preceding claims wherein, during the sewing together of the respective two fabric webs to form a seam, a sealing strip is laterally fed between them from the inside into the seam zone and is sewn in.

10. A method of sewing a transport sack substantially as hereinbefore described with reference to the accompanying drawings.

11. An apparatus for sewing a transport sack according to any one of the preceding claims, wherein a laterally pivotable guide lever is arranged on the sewing table and has a guide means at its guiding end.

12. An apparatus according to claim 11, wherein said guiding means comprise a guide hook or a guide eyelet.

13. An apparatus for sewing a transport sack, substantially as hereinbefore described with reference to, and as illustrated in, Figure 5 of the accompanying drawings.