GB2128585A

GB2128585A - Flexible bulk containers

Info

Publication number: GB2128585A
Application number: GB08326761A
Authority: GB
Inventors: Dennis Pollitt
Original assignee: LOLIFT
Current assignee: LOLIFT
Priority date: 1982-10-08
Filing date: 1983-10-06
Publication date: 1984-05-02
Also published as: GB8326761D0

Abstract

A flexible bulk container has a base (1) from which upwardly extend a first pair of opposed wall sections (2, 3) and a second pair of opposed wall sections (4, 5). A first lifting band (7) extends between the upper edges of the side walls (2) and (3) and a second lifting band (8) extends between the upper edges of the side walls (4) and (5) and crosses the first lifting band. The two lifting bands are such that they are substantially equally stressed when the container is lifted by the bands under its rated load. <IMAGE>

Description

SPECIFICATION Flexible bulk containers This invention relates to flexible bulk containers.

Such containers are now commonly used for the transport of powdered or granular material, and are constructed to carry a given rated load, most commonly one tonne, with a factor of safety of at least five. One common form of container is constructed from woven fabric stitched into a boxshape and provided at the top of the container with lifting means. Various constructions have been proposed but there is a general need to reduce the cost of these containers to a figure where the container may be considered as readily disposable.

One of the main problems in reducing the cost of containers lies in the relationship and interconnection between the lifting means and the container body. The known forms of container require a heavy gauge of fabric for the container body to ensure that the area of the body to which the lifting load is transmitted exhibits sufficient strength to withstand that load without the fabric tearing, or without the lifting means pulling away from the fabric. The object of the present invention is to provide a container that is simple to manufacture and that enables a lighter gauge of fabric to be used, so reducing costs, while retaining the safety factors at the level required in the industry.

According to the invention, a flexible bulk container comprises a base, a first pair of opposed wall sections extending upwardly from the base, a second pair of opposed wall sections extending upwardly from the base and each joined to the wall sections of the first pair, a first lifting band extending between the upper edges of the wall sections of the first pair, a second lifting band extending between upper edges of the wall sections of the second pair and crossing the first lifting band, the two lifting bands being such that they are substantially equally stressed when the container is lifted by the bands under its rated load.

By utilising two crossed lifting bands that become substantially equally stressed when the container is lifted under rated load it will be understood that substantially equal loadings are transferred onto all four wall sections of the container so that the lifting load is distributed substantially equally over the whole of the wall area of the container. This will be facilitated if, as is preferred, each lifting band is of the same width as the wall sections that it joins, and if the wall sections of the two pairs are of substantially equal width. Previous container designs have transferred the lifting load principally to two opposed wall sections of the container or to localised wall regions. By providing this even distribution the fabric used may be of a lighter gauge than that previously adopted, with consequent cost reductions.

Preferably the coefficient of elongation of the first lifting band in the direction joining the first pair of wall sections is substantially equal to the coefficient of elongation of the second lifting band in the direction joining the second pair of wall sections, and the length of the first lifting band is equal to the length of the second lifting band within a tolerance of + 5%.

The tolerance is more preferably + 1%. Ideally, the two lifting bands will have identical coefficients of elongation and be of identical length. However, this may be difficult to achieve in practice and it is found that if nominally identical fabrics are used for the two lifting bands with the lengths being equal within the given tolerance then load transfer to the two bands is sufficiently equal for there to be stress transfer to substantially all areas of the bag wall. It is possible to select fabric for one of the lifting bands that has a substantially different coefficient of elongation to the fabric of the other bands and to adjust the lengths of the two bands in the relaxed state accordingly so that when the container is under rated load the two bands are substantially equally stressed.However, it is obviously more difficult to ensure substantially equal load distribution in such a construction.

The bag may be supplied to the user merely in the form already stated, leaving the user to gather together the two lifting bands and engage them at their centres onto a hook or other lifting device.

Alternatively, however, the container can be supplied in a form in which a lifting member passes around the under surfaces of the two lifting bands at the top of the container and projects above the lifting bands to provide a single lift point for the container. The lifting member is desirably an endless loop and conveniently is secured substantially centrally of each of the two lifting bands.

In this way the single central lift point is predefined for the user and it is a very straight forward matter to engage the lifting member with a crane hook, a tine of a fork-lift truck or any other lifting means.

Prefeably each lifting band is formed integrally with the two opposed wall sections which it joins.

The container is thus formed by stitching each edge of each wall section of the first pair to the adjacent edge of a respective one of the wall sections of the second pair along seams that extend upwardly from the base in the finished container. The base itself can be stitched into the container bottom or can be integral in whole or in part with any one of more of the wall sections. If the two lengths of fabric from which the lifting bands and wall sections are formed are of equal width it will be seen that a container of substantially square cross-section is obtained.

Other methods of constructing the container are of course possible and in one such arrangement the lifting bands and wall sections may be formed from a single piece of tubular woven fabric, the fabric being cut and stitched as necessary to form the lifting bands. A base will additionally be sewn into the container and such base may have any desired shape.

Generally, the container will be provided with an impervious inner liner enclosed within the container in order that the material is fully protected. For filling purposes an open neck of the inner liner may be passed through any of the spaces between the two lifting bands. After filling, the open neck of the liner can be tied off and then tucked down inside the container so that the liner is fully protected.

When the container is to be emptied a cut can be made in the bottom wall of the container, and of the inner liner if provided, so that the contents merely fail from the container, which can be disposed of. If the container is required to be reusable a discharge spout arrangement may be fitted to the bottom wall of the container, for example as described in patent specifications No. 1,431,582 or 1,536,237.

Particular embodiments of containers according to the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which Figure 1 is a perspective view from above of a first embodiment of container in accordance with the invention; Figure 2 illustrates a stage in one method of manufacturing the container of Figure 1; and Figures 3 and 4 show parts of the tops of two further embodiments of container.

As shown in Figure 1 a container according to the invention has a bottom wall 1, a first pair of opposed side walls 2 and 3 and a second pair of opposed side walls 4 and 5, all the side walls being of equal width. Each side wall is stitched to the adjacent two side walls along a seam 6 extending upwardly from the base of the container. The upper ends of the seam 6 can be taken as defining notional upper edges of the side walls, thus, for example the upper edge of the wall 2 can be considered as lying on the line X - Y and the upper edge of the side wall 4 as lying on the lineY-Y.

A first lifting band 7 extends between the upper edges of the side walls 2 and 3, and a second lifting band 8 extends between the upper edges of the side walls 4 and 5. Each lifting band is equal in width to the side walls that it joins. The second lifting band crosses the first lifting band and lies below the first lifting band. Each lifting band is gathered together at its respective centre and an endless lifting loop 9 passes around the undersurfaces of the two lifting bands at the top of the container and projects above the lifting bands to provide a single lift point for the container. The lifting loop may be secured substantially centrally of each of the two lifting bands by a suitable clip, tie or restraining member.

The two lifting bands 7 and 8 are such that they are substantially equally stressed when the container is lifted by the bands via the lifting loop 9 under its rated load. Thus, substantially equal loadings will be transferred into all four side walls of the container so that the lifting load is distributed substantially equally over the whole wall area of the container.

Desirably this is achieved by ensuring that the coefficient of elongation of the first lifting band 7 in a direction joining the upper edges of the wall sections 2 and 3 is substantially equal to the coefficient of elongation of the second lifting band 8 in the direction joining the upper edges of the side walls 4 and 5, the length of the first lifting band being equal to the second lifting band within a tolerance of 5%, more preferably 1%. Ideally the two bands will be of nominally identical fabric and of equal length within the normal sewing tolerance.

For example, a suitable container has been manufactured with the base 1, side walls 4 and 5 and second lifting band 8 formed from one length of fabric stitched at a convenient location on the base to form a continuous loop. The side walls 2 and 3 and the first lifting band 7 formed from a second length of fabric stitched to the first length of fabric along the seams 6 and also stitched to the base. The fabric of the two lengths is the same, the height of all the side walls is designed to be the same and the lengths of the two lifting bands are designed to be the same. A suitable fabric has been found to be woven polypropylene of 135 g/m2. Such a container, based on 89 cm square base and with a wall height of 11 5 cm has been tested to carry one tonne of powdered or comminuted material with a factor of safety in excess of 5.A fabric typical of that used in the prior art containers for the carriage of the same load in a container of similar size is woven polypropylene 240 g/m2 in weight, a much heavier fabric than need to be used in a container of the invention. The container of the invention can thus be made at a lower cost.

One method of manufacturing the container shown in Figure 1 is illustrated in Figure 2. A first length of fabric 10 of the desired width is passed through an endless lifting loop 11 and is itself formed into a continuous loop by stitiching together the edges DE and D"E" to form a seam.

A second length of fabric 1 2 is then passed through the loop 11 substantially at right angles to the first fabric length. Marked points A A' and B B' on the two fabric lengths are placed together and the two adjacent edges stitched together to form a seam. Marked points C C' and D D' are similarly placed together and the edges stitched to form a further seam. The edge B'Dt is then stitched to the edge BD" to form a base seam. Similar stitching is effected to the opposite side of the lifting loop to give a container in the form shown in Figure 1 with a lifting loop 11 positioned at the top of the container as part of the manufacturing operation.

Figure 2 illustrates only one possible method of manufacture. It results in a container having a continuous band with a seam positioned at one side of the base, but of course this seam could be positioned at any convenient location on that band. The base is formed from a single layer of fabric, however it is possible to use a longer second length 1 2 part of which also forms a base layer so that the base as a whole is formed by two thicknesses of fabric. Either a single or double base may be of plain form or may be gussetted as required. Any form of base may be provided with a discharge spout arrangement allowing the container to be emptied and re-used. Alternatively, no discharge spout is necessary, the container being disposable and the contents emptied merely by cutting the bottom of the container.Either or both lengths of fabric may be twisted through 1800 in the region where the fabric passes through the lifting loops 12 so forming a neck section at the centre of each lifting band. The lifting band need not be integral with the side walls and may be separate lengths of fabric stitched to the side walls. It is equally possible to manufacture the container from a single length of tubular fabric by making appropriate cuts longitudinally of the fabric at one end thereof and joining together the flaps so formed to constitute first and second crossed lifting bands. A base is then sewn into the opposite end of the tubular fabric length. Other possible forms of construction will readily be apparent. It will also be apparent that it is not essential to incorporate the lifting loop 11 to the container during stitching of the fabric to form the container.The stitching operations may be completed first and a suitable lifting loop then passed around the centre sections of the lifting bands.

Figures 3 and 4 show two forms of lifting loop.

The loop 1 3 of Figure 3 may be secured as shown to the lifting bands 14 and 15 after manufacture of the container and will generally be held in the position shown at the centre of the lifting bands by a clip or tie means (not shown) to hold it in its central position and prevent it from loosening and falling from the container. The lifting loop 1 6 shown in Figure 4 may be incorporated into the container during manufacture as previously described, the lifting bands 1 7 and 18 passing through the loop. Alternatively, the loop may be formed from a single length of material passed around the bunched centre parts of the lifting bands after manufacture, the ends of the lengths of material then being stitched together to form the continuous loop.In either case a clip or tie 19 may be used to secure the loop at the centre of the lifting band. The lifting loop may be formed of any one of a number of different materials, for example rope, webbing or a bunch of parallel fibres encased in a unitary plastics sheath.

Alternatively, the lifting loop may be a metal shackle or ring. Other alternatives will be apparent.

A container in any of the aforesaid forms may include an inner liner of impervious plastics material, desirably inserted into the container after manufacture through one of the spaces between the lifting bands. The neck of the liner may protrude through any of these spaces for filling purposes, to be tucked into the container after filling has been completed. It is not necessary for all the seams between the container side walls to extend to the same height. By bringing some seams higher than the others one or more of the openings between the lifting bands may be restricted so requiring access into the container and any liner therein through a particular opening.

Rather than have access into the container through an opening between lifting bands either or both of those bands may be formed with slots or other openings, desirably centrally thereof. The lifting loops will then need to be of such a length that will allow the lifting bands to be flattened out so that access is gained through the openings.

The materials and dimensions that have been exemplified herein may of course be changed to suit containers designed for any required load and purpose.

Claims

1. A flexible bulk container comprising a base, a first pair of opposed wall sections extending upwardly from the base, a second pair of opposed wall sections extending upwardly from the base and each joined to the wall sections of the first pair, a first lifting band extending between the upper edges of the wall sections of the first pair, a second lifting band extending between the upper edges of the wall sections of the second pair and crossing the first lifting band, the two lifting bands being such that they are substantially equally stressed when the container is lifted by the bands under its rated load.

2. A flexible bulk container according to claim 1 in which each lifting band is of the same width as the wall sections that it joins.

3. Aflexible bulk container according to claim 1 or claim 2 in which the wall sections of the two pairs are of substantially equal width.

4. A flexible bulk container according to any one of the preceding claims in which the coefficient of elongation of the first lifting band in the direction joining the first pair of wall sections is substantially equal to the coefficient of elongation of the second lifting band in the direction joining the second pair of wall sections, and the length of the first lifting band is equal to the length of the second lifting band within a tolerance of + 5%.

5. A flexible bulk container accordng.to claim 4 in which the tolerance is + 1%.

6. A flexible bulk container according to any one of the preceding claims in which a lifting member passes around the upper surfaces of the two lifting bands at the top of the container and projects above the lifting bands to provide a single lift point for the container.

7. A flexible bulk container according to claim 6 in which the lifting member is an endless loop.

8. A flexible bulk container according to claim 6 or claim 7 in which the lifting member is secured substantially centrally of each of the two lifting bands.

9. A flexible bulk container according to any one of the preceding claims in which each lifting band is twisted through 1 800 between the respective opposed wall sections.

10. A flexible bulk container according to any one of the preceding claims in which each lifting band is formed integrally with the two opposed wall sections which it joins.

1 A flexible bulk container according to any one of the preceding claims in which an impervious inner liner is enclosed within the container and has a neck which can project therefrom through a space between adjacent edges of the first and second lifting bands.

12. A flexible bulk container substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings, or to those Figures as modified by either Figure 3 or Figure 4 of the accompanying drawings.