GB2132171A

GB2132171A - Flexible bulk container

Info

Publication number: GB2132171A
Application number: GB08333576A
Authority: GB
Inventors: Sydney Hardman
Original assignee: LOLIFT
Current assignee: LOLIFT
Priority date: 1982-12-23
Filing date: 1983-12-16
Publication date: 1984-07-04
Also published as: GB8333576D0; GB2132171B

Abstract

A flexible bulk container comprises a base and a wall structure (1 to 4) of flexible material extending upwardly from the base. Formed in the wall structure are a plurality of pockets (13 to 16) extending continuously between the top and bottom of the container. A plurality of lifting loops (9 to 12) are provided at the top of the container, each end of each lifting loop being secured to the wall structure in the area of a pocket. <IMAGE>

Description

SPECIFICATION Flexible bulk container This invention relates to flexible bulk containers such as are used in the storage and transport of particulate materials. Such containers are generally in the form of large bags or sacks, required to carry loads of up to one tonne or more, desirably with a considerable safety margin above the rated working load.

Many designs of such containers are now available and one common problem that arises is that of providing adequate strength, particularly at the area of attachment of lifting loops to the upper part of the container.

It has been proposed to make a flexible container from one or more lengths of textile material having at least one area which has been reinforced with interwoven additional reinforcing threads that are different from the threads of the body fabric in respect of count and/or textile material and/or tensile strength. Lifting means are than attached to the container by stitching at one or more areas of reinforcement. In another proposal reinforced areas of the container fabric are provided by increasing the number of warps of body thread per unit length to at least 1.4 times the number of warps per unit length in the rest of the fabric, a technique known as "cramming". Both these techniques have their disadvantages.The use of stronger additional reinforcing threads adds materially to the cost of the container, the majority of which can be manufactured from low-cost flat polyolefin tapes. The number of additional warp threads that can be incorporated by cramming is limited, particularly when flat tapes are used. The present invention seeks to overcome these disadvantages.

According to the present invention a flexible bulk container comprises a base, a wall structure of textile material extending upwardly from the base, the wall structure having a plurality of pockets extending continuously between the top and the bottom of the container, and a plurality of lifting loops at the top of the container, each end of each lifting loop being secured to the wall structure in the area of a pocket.

Although not so limited, the invention provides maximum advantage when the wall structure is formed from a woven fabric, and all threads extending between the top and the bottom of the container are of substantially identical material.

Preferably the woven fabric forming the wall structure has a first set of threads extending between the top and bottom of the container substantially uniformly in all regions of the wall structure and an additional set of threads extending between the top and bottom of the container in the region of each pocket, a single second set of threads being interwoven with the first and additional sets of threads. For maximum advantage the threads in the additional set are of substantially identical material to those in the first set. The first and additional sets of threads extending between the top and the bottom of the container are desirably warp threads, although they could be weft threads. All the threads are conveniently flat polyolefin tapes, the preferred polymer being polypropylene.

By forming a container in this way it will be seen that the pocket regions of the wall structure form regions where the wall structure is of double thickness. It is to this reinforced area that the lifting loops are secured, and they are thus able to transfer the lifting load to twice as many threads extending between the top and bottom of the bag as would be the case with a single thickness of fabric. As stated, the threads in both thicknesses of fabric in each pocket area are desirably of substantially identical material and the invention thus provides a simple way of doubling the number of threads to which the loops may be attached, thus providing more reinforcement that can be effected by cramming and achieving this without the need to use additional reinforcement threads of more expensive material.

If, as is preferred, each end of each lifting loop is inserted into an associated pocket before being stitched or otherwise secured to the wall structure then the invention provides a further very practical advantage during manufacture of the bag. Insertion of the end of the loop into the pocket ensures that there is positive location of the loop end so that connection is ensured between the loop end and the reinforced area. It would alternatively be possible to place the loop end outside the pocket on either face of the pocket area of the fabric, but the desired positive location is not then so readily achieved.

Containers according to the invention may be made in any of a number of different shapes. However, the preferred shape is for the container to comprise a rectangular, usually square, base, the wall structure being of corresponding rectangular cross-section and comprising four side walls. There are many known ways in which such containers may be constructed. As examples, the side walls may be formed from a single tubular woven length of fabric; may be formed from a single length of fabric folded to form the walls with the free ends of the fabric suitably stitched together; may be formed from two lengths of fabric each of which is folded to form part of at least two adjacent walls, the free ends of the two fabric lengths being stitched together; or may be formed from individual pieces of fabric, one for each side wall.A separate base may be stitched into any of the aforementioned wall structures, or the base may be made integral with one or more of the walls. A particularly suitable structure is to use one length of fabric folded to U-shape to form the base and two opposite side walls, the other two side walls being formed by individual lengths of fabric stitched to the base and to the first two side walls. If a container with a double thickness base is required then two oppositely disposed U-shaped pieces of fabric may be used, one piece forming a first base layer and two opposite side walls and the other piece forming a second base layer and the other two opposite side walls.

The lifting loops may be provided in a number of different ways. In the preferred arrangement, four lifting loops are provided each extending over a corner of the container with legs secured to each of the two adjacent walls which meet at that corner. In this arrangement each side wall will have two pockets extending continuously between the top and bottom of that side wall, the pockets being located towards the edges of the side wall. Alternatively, two lifting loops only may be provided, the legs of each loop being stitched or otherwise secured to each of two opposite side walls, or to each of two adjacent side walls.

As already stated, it is preferred that each end of each loop be received within the respective pocket, desirably through an open end of the pocket at the top of the container.

However, some or all loops can be inserted into the pocket through slits cut in one thickness of the fabric in the pocket region at any required height region of the container. The length of lifting loop material that is stitched to each pocket region will be chosen in accordance with the load that the container is designed to carry. For lighter loads relatively short lengths of lifting loop material may be stitched to the wall structure, for heavier loads longer lengths of loop material will need to be stitched to the wall structure. The lifting loops are suitably made of woven webbing, for example, webbing such as is commonly used for vehicle seat belts.

The invention will be better understood from the following description of specific embodiments thereof, given by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a first embodiment of container in accordance with the invention; Figure 2 is an exploded view of part of a wall section of the container of Fig. 1; Figure 3 is a cross-section on the line Ill-Ill of Fig. 1; Figures 4 to 7 are schematic top plan views of other embodiments of container; and Figures 8 and 9 are views of parts of yet further embodiments of containers.

Referring now to the drawings, Fig. 1 shows a flexible bulk container designed to carry one tonne of particulate material, with a safety factor of at least 4. The container is in the form of a bag having a square base from which extend four upstanding walls 1 to 4, to give a structure of substantially square crosssection. Corner seams 5 to 8 are formed between the edges of each pair of adjacent walls. The bag is of woven fabric, for example being woven from flat polypropylene tapes, and if desired the fabric may be sealed by a coating of suitable plastics material. The bag may conveniently be formed from three pieces of fabric, a substantially U-shaped portion forming the base and two opposite walls 1, 4 and two rectangular pieces each forming one of the other walls 2, 3 and being stitched to the base and to the walls 1 and 4.Other constructions are possible, as has already been discussed.

Four lifting loops 9 to 1 2 are attached to the upper part of the bag, each loop preferably being of webbing of the type commonly used for vehicle seat belts, for example woven polyethylene terephthalate approximately 5 cm wide. Each loop is attached to the walls in identical fashion and only the attachment for loop 10 will be described in detail, with further reference to Fig. 2 of the drawings.

The fabric forming each side wall of the bag is woven to have two pockets extending continuously between the top and bottom of the bag. Thus, side wall 2 has pockets 1 3 and 14, and side wall 4 has pockets 15 and 1 6.

The side walls 1 and 3 have similar pockets.

The pockets are formed during weaving of the fabric by any weaving technique compatible with the weave pattern used for the fabric itself. Plain woven fabric is commonly used for containers of this type and Fig. 2 shows schematically the weave of a fabric section incorporating a pocket. The wall fabric is formed from a first set of flat polypropylene tape warp threads 1 7 extending between the top and bottom of the container substantially uniformly in all regions of the wall structure and from additional warp threads 1 8 of identical flat polypropylene tape in the pocket regions. A first pair of weft threads a, b, again desirably of flat polypropylene tape, are interwoven with the warp threads 1 7 throughout the fabric. A second pair c, d of weft threads are interwoven with the warp threads 1 7 of the fabric except in the pocket regions, where they are interwoven with the additional warp threads 1 8. The pattern of wefts comprising threads a, b, c and d is repeated throughout the length of the fabric. Each leg of each lifting loop is inserted into an appropriate one of the pockets and each leg is stitched to the respective side wall by stitching through the two layers of fabric forming the pocket and through the loop material. The length of leg enclosed within and stitched to each pocket can be chosen as desired having regard to the required strength of the container.

Figs. 4 to 7 are schematic top plan views of other forms of container having walls formed with one or more pockets 20 which in each case extend the full height of the wall from the top to the bottom of the container and are formed during weaving of the wall fabric.

Lifting loops 21 are provided in different configurations, the ends of either one or more loops as appropriate being received in each pocket.

Fig. 8 shows one upper corner of a further form of container having two lifting loops 24, 25 each having legs received in appropriate pockets 26, 27 of the two adjacent walls. One loop is longer than the other and each corner of the container is provided with two loops in this manner. This increases the versatility of handling of the container.

Yet a further alternative is shown in Fig. 9 wherein one loop 30 is provided at the upper part of the container and has its legs received in the pockets of the two adjacent walls. A lower loop 31 had legs which enter the pockets through slits, the leg being stitched to the two thicknesses of pocket fabric in the same way as the legs of the upper loop. Again, if the container is provided with loops at high and low level at all four corners the handling versatility is increased.

It will be understood that there are many variations and modifications that can be made to the container shown, and indeed other forms of container can be constructed in accordance with the invention. The description given has been of a weaving technique which provides two overlying layers of fabric forming a single pocket layer between them. It will be understoof that structures are also possible comprising three overlying layers of material defining two pockets, one overlying the other, and both extending from the top to the bottom of the container. This will provide yet further reinforcement and indeed more than three layers could conceivably be used.

Claims

CLAIMS:

1. A flexible bulk container comprising a base, a wall structure of textile material extending upwardly from the base, the wall structure having a plurality of pockets extending continuously between the top and bottom of the container, and a plurality of lifting loops at the top of the container, each end of each lifting loop being secured to the wall structure in the area of a pocket.

2. A flexible bulk container according to claim 1 in which the wall structure is formed from a woven fabric, and all threads extending between the top and the bottom of the container are of substantially identical material.

3. A flexible bulk container according to claim 1 or claim 2 in which the wall structure is formed from a woven fabric having a first set of threads extending between the top and bottom of the container substantially uniformly in all regions of the wall structure and an additional set of threads extending between the top and bottom of the container in.

the region of each pocket, a single second set of threads being interwoven with the first and additional sets of threads.

.

4. A flexible bulk container according to claim 3 in which the first and additional sets of threads are warp threads and the second set of threads are weft threads.

5. A flexible bulk container according to any one of claims 1 to 4 in which all the threads of the woven fabric are flat polyolefin tapes.

6. A flexible bulk container according to any one of the preceding claims in which each end of each lifting loop is inserted into an associated pocket.

7. A flexible bulk container according to any one of the preceding claims in which the container comprises a rectangular base, the wall structure is of corresponding rectangular cross-section and comprises four side walls, each side wall has two pockets extending continuously between the top and bottom of the wall and located towards the edges of the wall, and four lifting loops are provided, each loop extending over a respective corner of the container and having legs secured to adjacent pocket areas of the walls that meet at that corner.

8. A flexible bulk container substantially as herein described with reference to Figs. 1 to 3 or to any one of Figs. 4 to 9 of the accompanying drawings.