GB2130172A

GB2130172A - Flexible bulk container

Info

Publication number: GB2130172A
Application number: GB08232684A
Authority: GB
Inventors: Frank Nattrass
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-16
Filing date: 1982-11-16
Publication date: 1984-05-31
Also published as: GB2130172B

Abstract

A flexible bulk container has a base (1), side walls (2 to 5) lifting loops (7 to 10) extending from the upper parts of the side walls above the top of the container, and a reinforcing band (13) stitched to the bight and spaced legs of each of the loops and to the upper part of each side wall in the region between the closest legs of two adjacent loops. The band increases the resistance to damage caused by an attempt to lift the container on one loop only. <IMAGE>

Description

SPECIFICATION Flexible bulk container This invention relates to flexible bulk containers such as are used in the storage and transport of materials in granular, powder and other particulate forms.

Such containers are generally in the form of large bags or sacks which are often required to carry loads of up to one tonne or more, with considerable safety margin above this working load. The containers are commonly made from woven fabric, particularly woven polypropylene or other suitable synthetic material.

All flexible bulk containers of this type comprise a base and a wall structure extending upwardly from the base. The wall structure is generally tubular, fashioned to give a container crosssection that is usually square, but may be of circular or any other suitable form. Such containers can be looked upon as falling into one of two groups, according to the way in which the container is formed so that it may be lifted by a crane hook, tine of a fork-lift truck or other lifting means. In one group the fabric of one or more walls forming the wall structure is extended above the body of the container to form one or more bands which may be engaged by lifting means to lift the container. In the second group a plurality of lifting loops are joined to the wall structure at the upper part thereof, the loops being suitably spaced around the periphery of the upper part of the bag.

It is this second group of containers with which the present invention is concerned.

There have in the past been many proposals for providing lifting loops at the upper part of the wall structure of a container. In the most commonly used constructions the lifting loops are loops of high strength webbing, each loop having a bight and two spaced legs, each leg being stitched to the wall structure of the container, desirably so that there is reinforcement of the area where stitching occurs.For example, the fabric of the wall structure may be folded so that each leg is stitched to a plurality of thicknesses of material, each leg may be stitched to the wall structure in the region of a corner seam of that structure which may incorporate a strengthened selvedge of the fabric or each leg may be stitched to the wall structure in the region where the fabric of the wall structure is reinforced, for example by cramming extra threads into this region of the wall structure or by utilising in this region threads that are of higher tensile strength than the remaining threads of the wall structure. All such arrangements are more or less effective for transferring lifting load to the fabric forming the wall structure when the container is properly lifted on the loops.However, containers of this type are very commonly mishandled, and one particularly prevalent form of mishandling is an attempt to lift a container on one loop only, the container having been designed to be lifted on all the loops provided, which are usually four or two in number. The forces transmitted to the wall structure of the container in such improper lifting operation are such that the loop shears from the container so rendering this unfit for further use and possibly creating a hazardous situation. Attempts have been made to solve this problem by stitching a girth band around the upper part of the wall structure and by further reinforcing the region where the legs of the loops are joined to the wall structure.Some marginal improvement has been effected in this way, but the problem is still recognised as being one of the major areas of difficulty in the field of flexible bulk containers.

According to the present invention a flexible bulk container comprises a base, a wall structure extending upwardly from the base, a plurality of lifting loops each having a bight and two legs, each leg being joined to the wall structure and a band of reinforcing material secured to the lifting loops and to the upper region of the wall structure to extend along the bight of each loop, at least partially along each leg of each loop and from each such leg along the wall structure to the closest leg of the next adjacent lifting loop.

In such a container the presence of the band of reinforcing material does not affect the normal lifting behaviour when the container is properly lifted on all loops. However, should the container be improperly lifted on one loop then the presence of the reinforcing band will transmit stress directly form that one loop and through the reinforcing band to upper parts of the wall structure adjacent to that loop. Transmission of the stress will thus be into a much larger wall area of the fabric and by use of a reinforcing band of suitable strength it is found that containers can safely be lifted on one loop without that loop tearing away from the container.

The reinforcing band is preferably a single length of material secured to all the lifting loops and to every area of wall structure lying between the closest legs of adjacent loops. The two free ends of the reinforcing band may be butt-joined or overlapped, the joint or overlap desirably lying on the wall structure roughly midway between two adjacent loops. Rather than use a single reinforcing band the band may be interrupted and formed of a number of sections having free ends which are butt-joined or overlapped as required.

Desirably the reinforcing band extends around the uppermost part of the wall structure although it could be located a short distance down from the upper edge of the wall structure, for example no more than 5 cm down from the upper edge.

When the wall structure of the container is formed from woven fabric, as is usual, the reinforcing band may conveniently be a woven fabric webbing that is stitched to the lifting loops and to the fabric of the wall structure. It is preferred to use webbing that has an ultimate tensile strength of not less than 1 500 kg for a bag having a rated load of one tonne. However, significant improvement is achieved with webbing having ultimate tensile strength down to 750 kg.

Particularly suitable webbing is that of the type used for car seat belts.

The invention is advantageously applied to containers having either two lifting loops or four lifting loops. The latter is a more common form of container; such container conveniently has a square cross-section, the wall structure being comprised of four side walls, each loop extending across one corner of the container and having its two legs joined to two separate and adjacent side walls. Each leg is desirably joined to a reinforced area of the wall structure. As has already been pointed out, there are many ways in which such reinforcement can be effected. The assembly of base and wall structure is usually completed by a top or cover closing the top of the container and stitched or otherwise secured around the upper edge of the wall structure.A top closure is preferred in the container of the invention as when the container is lifted on a single loop it is found that some spillage of the contents would occur were such closure to be absent.

In order that the invention may be better understood embodiments of flexible bulk containers in accordance therewith will now be described in more detail, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a first embodiment of container; Figures 2 and 3 are respectively front and side elevations of the container of Figure 1 in one lifting condition; Figure 4 is a perspective view of a second embodiment of container; and Figures 5 and 6 are partial views of further embodiments of container.

Referring now to Figure 1 this shows a flexible bulk container of generally square cross-section comprising a base 1 from which a wall structure extends upwardly. The wall structure is composed of four side walls 2 to 5. Each side wall includes two reinforced strips 6 extending the full height of the side wail parallel to the side seams of the container. There are many different ways in which containers of this general nature can be formed, one example being given in our copending application No. 82.05961.

The container is formed with four individual lifting loops 7 to 10, each loop being integral with and an extension of the two reinforced strips 6 adjacent to the associated side seam of the container. Thus, for example, loop 10 is integral with the reinforced strips 6a and 6b and extends across the adjacent corner of the container. The top of the container is closed by a skirt 11 having a central opening 12 that may be closed by, for example, a drawstring.

In accordance with the invention a reinforcing band of webbing is stitched to the lifting loops and to the upper region of the wall structure. The reinforcing band is a single length of material having ends joined by an overlapping joint 14 lying between the closest legs of the adjacent loops 9 and 1 0. From the joint the band extends along one half of the upper part of the side wall area 2a lying between the closest legs of the loops 9 and 10, along the upper part of the first leg, the bight and the upper part of the second leg of the loop 10, along the upper part of the side wall area 3a laying between loops 10 and 7, along the upper part of one leg, the bight and the upper part of the second leg of the loop 7, along the upper part of the side wall area 4a lying between the loops 7 and 8, along the upper part of the first leg, the bight and upper part of the second leg of the loop 8, along the upper part of the side wall area 5a lying between the loops 8 and 9, along the upper part of one leg, the bight and the upper part of the second leg of the loop 9 and along the upper part of the second half of the side wall area 2a.

The container shown in Figure 1 is designed to be lifted on all four loops, either by engaging the tines or a fork-lift truck each with two loops at the same side of the bag, or by engaging all four loops with a hook of a crane or other hoist or attaching each loop to a hook on a spreader plate which is itself attached to a hoist. In any one of these lifting modes the lifting stress is transmitted by the loops to the reinforced strips in the side walls and the load is distributed over a considerable area of the and 3 respectively. It will be seen from these lifting of a container on one single loop and in this lifting mode the container takes up the form shown in the front and side elevations of Figures 2 and 3 respectively.If will be seen from these Figures that the loop on which the bag is lifted transmits its load into the bag fabric not only by the reinforced strips 6 but more importantly through the reinforcing band 1 3 extending to each side of the loop. The stitching of that band to the upper part of the side wall area transmits load from the reinforcing band into the fabric of the side wall and as a consequence the lifting force is distributed over a reasonable area of side wall.

Accordingly, the strain is accommodated without the lifting loop tearing from the container. Apart from being abie to withstand a pure lifting force on one loop the container is also capable of withstanding a horizontally applied force on one lifting loop, where again the force on the loop is transmitted into the reinforcing band and thence to the side wall fabric.

The material of the container may, in a preferred arrangements, be a woven fabric having polypropylene warp and weft yarns interwoven in any appropriate weaving pattern, usually smooth woven, although twill, basket and rib weaves could alternatively be used. In the region of the reinforcing bands 6a, Sb the reinforcement may be effected by cramming the warp threads, i.e. by making the warps per centimetre in the reinforced strip regions greater than the number of warps per centimetre in the base fabric used for the wall structure. Alternatively in the reinforced strips additional reinforcing warp threads may be interwoven with the polypropylene weft threads, the additional warp threads having a higher tensile strength than the base polypropylene warp threads. Such higher strength warp threads may replace entirely the warp threads of the base fabric in the strip areas or they may be used in addition to those warp threads. Reinforcing threads may be made from any suitable natural fibre or from a yarn of synthetic or semi-synthetic polymer, such as polyester, polyamide, pololefin, polyacrylic, or polypropylene having a higher tensile strength than the polypropylene yarn used for the base fabric. The material used for the reinforcement band 13 is conveniently webbing such as is used in car seat belts, the webbing being chosen to have an ultimate tensile strength of not less than 750 kg and desirably not less than 1 500 kg. The reinforcement band need not be a single length of material as shown in Figure 1, but may be made up of a number of lengths joined together, desirably in appropriate ones of the areas 2a to 5a.

The joints between the ends may be overlapping joints as shown at 1 4 or may be butt joints, and indeed where a single reinforcing band is used the joint 14 could be a butt joint rather than an overlapping joint. The webbing need not be of the same width as the material of the reinforced strips and lifting loops but will usually be no wider than the strips and loops. In the regions 2a to 5a the webbing desirably lies on the outer surface of the respective side wall as shown in Figure 1, although it could equally well lie on the inner surfaces of those side walls and thus on the face of each loop opposite to the face shown in Figure 1. In the areas 2a to 5a the reinforcing band need not be right at the upper edge of the container but may be spaced below this edge, desirably by no more than 5 cm.

Figure 4 shows the invention applied to a different type of container, although similar to that of Figure 1 in that it has a base 21, four side walls 23 to 25 and four lifting loops 27 to 30.

Each loop has a bight and two spaced legs and the two legs are stitched into a side seam construction such as 31 joining together two adjacent side walls. The panels of fabric forming the side walls have selvedges which are incorporated in the side seam structure, and this structure is thus a reinforced area to which the legs of the lifting loops are stitched. A reinforcing band 33 of webbing is stitched around the upper part of the container to extend along the top edge of each side wall and then partially up one leg along the bight and down the other leg of each lifting loop. The band 33 has its free ends joined by an overlapping joint 34. The container is closed by a lid 41 having a central opening 42.The presence of the reinforcing band, as with the container of Figure 1, allows the container to be lifted on one loop without that loop tearing from the container, load being transmitted through the reinforcing band into the wall fabric. Again, the construction and position of the reinforcing band may be modified.

Figure 5 shows the invention applied to a container having lifting loops 41 to 44, each having a bight and two spaced legs. Each leg is joined to the fabric of the container wall structure 45, in a region of the upper part of the wall structure where the fabric is folded to create a reinforced multi-layer fabric region. The legs of the loops are stitched to the multiple layers of fabric in those regions. A reinforcing band 46 extends around the upper part of the wall structure and also along part of one leg of each loop, along the bight and part of the other leg of the loop. Due to the twist in each loop the reinforcing band lies on the outer surface of the wall structure between loops 41 and 44 and between loops 42 and 43, whereas it lies on the inner face of the wall structure between loops 44 and 43 and 42 and 41.As with the previous embodiments the presence of the reinforcing band allows the container to be lifted on one loop without that loop tearing from the container.

Figure 6 shows the invention applied to a container having side walls 51 to 54, the opposing side walls 52 and 54 having reinforced strips 55.

The container has two lifting loops 56 and 57 each integral with and a continuation of the strips 55. A reinforcing band 58 extends along part of the top of the opposite side walls 52 and 54 between the two loops and along the first leg, the bight and the second leg of each of the two loops.

Free ends of the band 58 are overlap-jointed on the side wall 52.

In the container shown in Figures 1 and 6 the lifting loops are shown as integral continuations of the reinforced strips in the wall structure.

Alternatively, however, the loops may be separately constructed of any appropriate material, for example seat belt webbing, each leg of each loop extending downwardly from the upper edge of the respective wall and being stitched or otherwise secured to the reinforced strip of the wall.

The application of the invention to a number of different container constructions has been described, but it will be understood that there are many other different constructions of container having a plurality of lifting loops to which the concept of a reinforcing band incorporated in the loops and the upper part of the wall structure may be applied.

Claims

1. A flexible bulk container comprising a base, a wall structure extending upwardly from the base, a plurality of lifting loops each having a bight and two legs, each leg extending from the upper part of the wall structure above the top of the container, and a band of reinforcing material secured to the lifting loops and to the upper region of the wall structure to extend along the bight of each loop, at least partially along each leg of each loop and from each such leg along the wall structure to the closest leg of the next adjacent lifting loop.

2. A flexible bulk container according to claim 1 in which the reinforcing band is a single length of material secured to all the lifting loops and to every area of wall structure lying between the closest legs of adjacent loops.

3. A flexible bulk container according to claim 2 in which two free ends of the reinforcing band are joined or overlapped at a location on an area of the wall structure lying between the closest legs of adjacent loops.

4. A flexible bulk container according to any one of the preceding claims in which the reinforcing band is joined to the wall structure at a location no more than 5 cm down from the upper edge thereof.

5. A flexible bulk container according to claim 4 in which the reinforcing band is joined to the uppermost part of the wall structure.

6. A flexible bulk container according to any one of the preceding claims in which the wall structure is formed from woven fabric, and the reinforcing band is a woven fabric webbing that is stitched to the lifting loops and to the fabric of the wall structure.

7. A flexible bulk container according to claim 6 in which the webbing has an ultimate tensile strength of not less than 750 kg.

8. A flexible bulk container according to any one of the preceding claims, in which the container is formed with a top closure member.

9. A flexible bulk container substantially as herein described with reference to any one of Figures 4, 5 and 6 of the accompanying drawings.