EP0030442B1

EP0030442B1 - Flexible container for bulk material

Info

Publication number: EP0030442B1
Application number: EP80304322A
Authority: EP
Inventors: Charles Sydney Futerman
Original assignee: Miller Weblift Ltd
Current assignee: MARLING EUROPE LIMITED TE LONDEN, GROOT-BRITTANNIE
Priority date: 1979-12-05
Filing date: 1980-12-02
Publication date: 1984-07-11
Also published as: GB2063816B; DK148880C; NO803643L; DK148880B; EP0030442A1; DK510980A; NO152160B; DE3068560D1; GB2063816A; ATE8375T1; NO152160C

Abstract

Intermediate bulk containers (14) comprise a bag portion (15) of woven polyethylene or polypropylene tapes for containing bulk material and lifting loops (16) of sufficient stiffness to stand proud of the container and offer access to the tines (18) of a fork-lift truck. The loops (16) are of woven nylon webbing, stiffened for example by sewing, stapling, stitching or the like, strips of plastic material thereto. This construction allows lifting of the containers by one operative in a fork-lift truck without requiring a second operative to hold up the lifting loops to receive the tines of the truck.

Description

This invention relates to flexible containers for bulk material, particularly for particulate or pulverulent material, hereinafter referred to as intermediate bulk containers (IBS's).
Currently, intermediate bulk containers are of two main kinds. The first kind is where the container has lifting means, such as straps, ropes or metal rings, attached to the top of the material forming the container; and the second kind is where the container may be lifted by means of webbing, rope or the like passing beneath the container. The second kind, or 'underslung', container is still lifted from above but most of the stress is carried by the webbing or rope rather than the container material itself. The most common type of lifting means comprises loops of webbing.
A further type of IBC is illustrated in our Belgian Patent No. 862794, which comprises a bag portion for containing the material, and lifting loops comprising woven webbings of high tensile synthetic fibres at the top of the bag portion, each bag including a bight portion. The loops are stitched to reinforced- areas woven into the bag fabric itself. US-A-4010784 discloses another form of IBC in which the lifting loops are attached to a folded portion of the bag fabric in order to improve the load carrying capacity of the IBC. As before the lifting loops are of woven webbing, of polyethylene terephthalate of the type used for vehicle seat belts. Indeed where webbing lifting loops are used woven nylon or polyester seat belt webbings are almost always employed. These of course have little or no resilience or stiffness despite the schematic drawings in the patent specifications referred to above which show them in an upright position. Such containers may be lifted, for instance on to a freight transporter, by means of hooks slung from cranes passing through the lifting loops. However a great deal of loading, stacking and the like of IBC's can advantageously be done with a fork-lift truck, the tines of which pass through the lifting loops. This is a very simple and convenient way of handling bulk material and to some extent explains why the use of IBC's has expanded over the past few years. In practice, one operative holds up the lifting loops of the IBC while a second in the truck manoeuvres the tines of the fork-lift into the loops, after which the IBC can be lifted and moved by the truck.
The invention seeks to provide a bulk material container the handling of which by fork-lift truck or the like is facilitated, and which can conveniently be handled by one operative alone.
According to the present invention there is provided a flexible container for bulk material intended to be handled by a fork lift truck which comprises a bag portion for containing the material and lifting loops comprising woven webbings of high tensile synthetic fibres at the top of the bag portion each including-a bight portion, characterised by the lifting loops over a substantial part of the length of each bight portion being associated with resilient means of such stiffness that the loops stand proud of the container and offer access to the lifting means without further manipulation and of sufficient resilience so that they return to the upright position after being pressed flat.
IBC's may be divided into two types: single trip and reusable. The single trip IBC is generally of the kind referred to above in which the lifting means is attached to the top of the bag, and is relatively inexpensive to produce and may thus be treated as expendable after being used once. Reusable IBC's are generally of the second kind referred to -above, i.e. underslung, and are far more expensive to produce. The invention may be applied to either kind of IBC but is especially useful with single trip IBC's as the stiffened loops will only be handled a relatively few times and the possibility of the loops being flattened in use will be reduced.
The container may be made from any suitable strong flexible material, but is preferably made from a woven fabric. Preferably the fabric is a plain weave, but naturally other weaves may be employed if desired, for example twill, basket or ribbed weave.
The yarns from which the bag is woven may in general be of any textile or non-textile fibre, natural or synthetic, staple or continuous filament, e.g. polyamide, polyester, acrylic, olefin, natural or regenerated cellulosic, keratinous, glass, metal or mineral. For reasons of strength, economy and durability however, it is prefereed to use continuous filaments or tapes of polyethylene or polypropylene.
The weaving density will depend on factors such as the type and count of the yarns selected, the desired covering power and fabric weight required. However for the preferred polyethylene or polypropylene tapes, fabrics having between 10 and 25 ends per inch and between 10 and 15 picks per inch have proved suitable, using tapes with counts in the range 750 to 2000 denier.
If desired the bag may be provided with a weatherproof liner. The liner may be of any suitable impermeable material, e.g. treated paper or plastics material, and is preferably a plastics material, e.g. a polyethylene, sheet. In the latter case the sheet may be suitably in the range 85 to 150 micron, although it is preferred to use thicknesses towards the upper end of the range of added durability. To accommodate types of container with an outlet spout, the liner may also have matching outlet spouts.
The supporting means, of slings, may comprise straps, webbings, ropes or the like, which are sufficiently strong to support the weight of the container and its contents. Particularly preferred supporting means are woven webbings of high tensile synthetic fibres, e.g. polyesters or polyamides. The preferred polyethylene or polypropylene tapes of the outer bag fabric have a tensile strength in the region of 5-6 gms per denier, and thus an inch wide strip of a 15 x 12 woven fabric of 2000 denier polypropylene will support above 150 kg in the warp direction. However, in containers of the kind to which the invention relates the greater part of the stress in lifting a full container is taken by the supporting means. Consequently it is preferred to use webbing material with a breaking load of at least 1000 kg. Especially suitable webbings include, for example, 1 inch wide webbing woven from about 115 ends of 1880 decitex nylon tapes with 17-18 picks per inch having a breaking strength of about 1500 kg; or 2 inch webbing woven from 156 ends of 1990 decitex nylon tapes with 17-18 picks per inch and having a breaking strength of about 2000 kg.
The lifting loops according to the invention should be of such a stiffness that they stand proud of the container and offer access to, e.g. the tines of a fork-lift truck without needing manual handling of the loops. The lifting loops can themselves be made of a material of suitable stiffness, but if the preferred woven webbings referred to above are employed then additional stiffening means may be employed. For example, a strip, wire or rod of material of suitable stiffness may be attached to the webbing comprising each loop, especially in the area of the bight of the loop, by any suitable means such as stitching, stapling, adhesively fixing or tying. Alternatively, the webbing may be formed with channels or pockets therein, into which the stiffening may be placed.
As examples of materials of suitable stiffness we have achieved good results with semi-rigid plastics materials such as nylon, polyethylene, polypropylene and the like, although other materials, such as paraweb or even knitted wire, give acceptable results.
In order to ensure that the loop stands up from the bag and will return to this position after flattening, the stiffener should preferably extend around the entire bight of the loop into the attachment points of each end of the loop to the container body, e.g. box and cross pattern stitching. So that the webbing takes the strain of lifting without affecting the stiffener, it is preferred to attach the stiffener on the upper faces of the loops, i.e. where the stiffener will not be in direct contact with the tines of the lifting means. Further, it is desirable to use a stiffener material that has an elongation characteristic at least as great as that of the loops so that stretching of the latter during lifting will not affect the stiffener. Alternatively, the stiffener may be over-fed when attaching to the loop webbing so that there is sufficient stiffener there to accommodate the elongation of the webbing (which may be in the order of 10% for the preferred webbing referred to above when lifting loads in the range t to 2 tonnes). However, where the stiffening is in a channel or pocket in the loop it need not be sewn or adhered to the loop at all and so takes none of the strain of lifting. Another alternative is to stiffen the preferred webbing, e.g. by application of a synthetic resin or prepolymer curable to a material of the required stiffness. For instance, an acrylate, an acrylonitrile-butadienestyrene copolymer or another suitable polymer could be applied, e.g. from a solution or dispersion, to the webbing either batch-wise or continuously and cured or allowed to cure. For reasons of economy an acrylate emulsion may be preferred. This may be applied continuously, e.g. by means of a pad-mangle and, preferably, passed through a heating zone to effect drying and curing, to produce a webbing which is undiminished in strength but has the necessary stiffness characteristics according to the invention. Alternatively a hot melt thermoplastic resin could be applied to the webbing and allowed to set.
Although the invention is applicable to all types of IBC having lifting loops, especially advantageous results are obtained when it is employed with IBC's having lifting loops attached to reinforced areas in the container fabric, as disclosed in our Belgian Patent No. 862794.
The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a conventional IBC with lifting loops;
Figure 2 is a perspective view of an IBC according to the invention;
Figures 3(a) to 3(c) illustrate lengths of lifting loop material having stiffening portions attached thereto in differing ways.

Figure 1 illustrates an IBC 10 having conventional webbing strap lifting loops 12, and it can be seen that the loops hang down or lie on the container body, and would need to be held up to allow a fork-lift tines to enter them.
Figure 2, on the other hand shows an IBC 14 with a bag portion 15 having stiffened lifting loops 16 according to the invention which stand proud of the container and offer access to the tines 18 of a fork-lift truck. As shown in dotted lines in Figure 2 the tines 18 can be aligned and inserted into the loops 16 by a single operator driving the fork-lift truck with no need of second operative to hold up the lifting loops. The container illustrated has webbing loops 16 of woven nylon attached, by a 'box and cross' stitching pattern 20 to reinforced bands 22 of interwoven high tensile yarns as described in our aforementioned Belgian patent. Each webbing loop 16 is stiffened around the entire bight of the loop to points 24, 26 below the attachment points 20.
Figure 3(a) shows a webbing strap 28, suitable for use as a lifting loop 16, having a strip of stiff plastics material 30 attached thereto on the upper side by stitching 32. In Figure 3(b) a stiffener 28 is slipped into a pocketed webbing strap 34. Figure 3(c) illustrates a plastics strip 30 being tied to the webbing 28 by means of a cord 36.
The number of, and positioning of, the lifting loops 16 is a matter for choice according to exact lifting means intended to be used.
The configuration illustrated, with four open ended loops across the corners of the bag is convenient, but other positions may be used, e.g. as illustrated in our Belgian Patent No. 862794.
An important feature of the invention is that the stiffener should be sufficiently resilient to recover from flattening since, in use, it is likely that the IBC's will be stacked one on top of the other. Thus the loop in this condition should lie flat, and recover from the stacking forces to stand upright again once the weight is removed.

Claims

1. A flexible container (10) for bulk material intended to be handled by a fork-lift truck (18) which comprises a bag portion (15) for containing the material and lifting loops (16) comprising woven webbings (28) of high tensile synthetic fibres at the top of the bag portion each including a bight portion, characterised by the lifting loops (16) over a substantial part of the length of each bight portion being associated with resilient means (30) of such stiffness that the loops (16) stand proud of the container (10) and offer access to the lifting means (18) without further manipulation and of sufficient resilience so that they return to the upright position after being pressed flat.

2. A container as claimed in claim 1 in which the bag portion (15) is made of woven fabric.

3. A container as claimed in claim 2 in which the bag portion (15) is woven from polyethylene of polypropylene tapes.

4. A container as claimed in either claim 1 or 2 in which the bag portion. (15) contains reinforced areas of interwoven high tensile yarns to which the lifting loops are attached.

5. A container as claimed in any of claims 1 to 4 in which the lifting loops (16) are nylon webbings.

6. A container as claimed in any of claims 1 to 5 in which the lifting loops (16) are stiffened by including a strip, wire or rod of resilient material.

7. A container as claimed in claim 6 in which the material (30) is stitched to the loop (16).

8. A container as claimed in claim 6 in which the material (30) is stapled to the loop (16).

9. A container as claimed in claim 6 in which the material (30) is adhesively bonded to the loop (16).

10. A container as claimed in claim 6 in which the material (30) is tied to the loop (16).

11. A container as claimed in claim 6 in which the material is placed within a pocket or channel in the loop (16).

12. A container as claimed in any of claims 6 to 10 in which the material is attached to the upper face of the loop.

13. A container as claimed in any of claims 6 to 12 in which the stiffener material (30) extends around the entire bight of each loop and into the points of attachment (20) of the loop (16) to the bag (10).

14. A container as claimed in any of claims 7 to 13 in which the stiffener material (30) comprises a semi-rigid plastics material.

15. A container as claimed in claim 14 in which the stiffener material (30) is polyethylene, polypropylene or nylon.

16. A container as claimed in any of claims 5 to 15 in which the stiffener material (30) has an elastic elongation characteristic at least as great as that of the lifting loops.

17. A container as claimed in any of claims 1 to 5 in which the resilient means comprises a resin or polymer impregnated within the woven webbing (28) to render the webbing semi-rigid.

18. A container as claimed in claim 17 in which the webbing (28) is stiffened by immersing it in a solution or dispersion of a synthetic resin and curing the resin or allowing it to cure.

19. A container as claimed in claim 18 in which the resin is an acrylate, or an acrylonitrile-butadiene-styrene copolymer.