GB2226053A

GB2226053A - Leno-woven sling

Info

Publication number: GB2226053A
Application number: GB8828755A
Authority: GB
Inventors: William Samuel Bleakley
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-12-08
Filing date: 1988-12-08
Publication date: 1990-06-20
Anticipated expiration: 2008-12-08
Also published as: AU2904589A; GB8828755D0; WO1989005276A1; GB2226053B; GB8728699D0

Abstract

A method of making an elongate and flexible load bearing element, for example a sling used to lift heavy or awkward shapes, is disclosed. The method comprises the steps of twisting two lengths of, e.g., stranded wire (4) together to make a warp assembly (3), each assembly (3) having a plurality of longitudinally spaced apart loops (7), arranging two such assemblies side-by-side with the loops (7) thereof in sideways alignment to form a plurality of spaced "sheds" (8), and threading a weft length (9) through the sheds (8) to hold the assemblies (3) together. A sling may be formed by providing an eye (2) at each end of the element.

Description

LOAD BEARING ELEMENT The invention relates to an elongate, flexible and substantially flat load bearing element, and in particular to a lifting sling of the type used to lift heavy or awkwardly shaped loads using a crane or the like. For convenience the invention will be described in relation to such a sling.

A known lifting sling comprises an elongate and flat band having an eye at each end. It is known to form the band by braiding or plaiting strands of wire together by hand and then forming the eyes, e.g. by interweaving the outermost ends of the strands back into the band. This method of manufacture is time consulting especially if a large sling, e.g. greater than about 10cm wide, or greater than about 1.5m long is required.

The maximum load capacity of a sling made by this method is limited because of the difficulties in plaiting especially strong lengths of thick wire rope.

The invention is based upon the realisation that there is no need to plait or braid together lengths to form the band, but rather that by twisting lengths together a series of loops can be formed which can be used as part of the means to hold the band together.

As used herein, the term "warp" defines the lengths which extend along the longitudinal axis of the element, and "weft" defines the lengths which are transverse to the axis. When a pair of lengths is twisted together, a plurality of longitudinally spaced apart loops is formed. When two or more such twisted pairs are arranged side-by-side, the term "shed" defines a row of aligned loops which extends between the twisted pairs.

According to a first aspect of the invention, there is provided a method of making an elongate, flexible and substantially flat load bearing element, comprising the steps of; twisting at least two lengths of material together to form a warp assembly including a plurality of longitudinally spaced apart loops; arranging two such warp assemblies in side-by-side relation with the loops thereof in alignment to form a plurality of sheds; threading a weft length of material through the sheds to hold the warp assemblies together.

In a preferred aspect, there is provided a method of making a sling comprising the method as defined followed by the additional step of providing an eye at each end of the sling.

The warp and weft lengths preferably comprise stranded steel or like wire, but may instead comprise lengths of single wire, or natural or synthetic textile or textile like material.

Preferably at least one further warp assembly, formed from twisted lengths of textile like material of a diameter greater than that of the other warp assemblies, is arranged side-by-side with those warp assemblies prior to the step of threading the weft length through the sheds. In this way, the textile stands proud of the wire and the formed sling is protected from damage, e.g. by abrasion, and the carried loads are protected from damage by the wires.

In another aspect of the invention, there is provided a load bearing element comprising an elongate and flat band optionally having an eye at each end of the element, wherein the band comprises at least two warp assemblies arranged side-by-side, each warp assembly comprising at least a pair of flexible lengths twisted together, and a weft length which passes through the sheds to hold the warp assemblies together.

In order that the invention may be better understood, it will now be described by way of example with reference to the accompanying diagramatic drawings, in which: FIG. 1 is a plan view of a lifting. sling manufactured according to a method of the invention; FIG. 2 is a side elevation of the sling of FIG. 1; and FIG. 3 is a partial plan view of a sling according to FIG.1 to an enlarged scale, but omitting the textile lengths for clarity.

As shown in the drawings, a lifting sling comprises an elongate and substantially flat band 1 having an eye 2 at each end. The band 1 comprises four warp assemblies 3 disposed in generally parallel sideby-side relation. Each assembly comprises two warp lengths 4 twisted together. Each warp length 4 is formed of single or multi-stranded steel or like wire.

Two further warp assemblies 5 are present, one on each side of the wire warp assemblies 3. The warp assemblies 5 each comprise a twisted pair of lengths of a natural or synthetic textile 6, e.g. polypropylene rope, of a diameter greater than that of the wire. As a result of the twisting of the lengths 4, 6 a series of longitudinally spaced apart loops 7 is formed in each assembly 3, 5. A plurality of longitudinally spaced sheds 8 is present which are formed by the aligned loops 7 of each assembly 3, 5.

As best shown in FIG.3, (from which the textile warp assemblies 5 have been omitted) a weft length 9 comprising a length of single or multi-stranded steel or like wire is present within the sheds 8 to hold the arranged warp assemblies 3, 5 together.

The sling is formed by firstly providing lengths of stranded steel wire 4. Two such lengths 4 are twisted together to make a warp assembly 3 having a plurality of spaced loops 7. The twisting may be done mechanically to ensure that there is a fixed number of loops 7 per unit length. Alternatively, pre-twisted pairs of wires may be supplied from a drum and cut to the desired length as required. The textile warp assemblies 5 are made in a similar manner from a length of polypropylene rope or the like and have the same number of twists per unit length as the wire warp assemblies 3.

The sling shown in the drawings is formed by arranging four wire warp assemblies 3 on the ground in parallel side-by-side relation and then temporarily clamping or tying the arranged assemblies together at the desired length of the band 1. Two textile warp assemblies 5 are then arranged in parallel, one on each side of the wire assemblies 3, so that the loops 7 on each assembly 3, 5 are in alignment to form the sheds 8.

The weft length 9 is then threaded through a shed 8 at one end of the band 1 from one side of the arranged assemblies 3, 5 to the other side. The free ends of the weft are then both threaded through the next longitudinally spaced along shed 8, one free end being threaded from each side of the arranged assemblies.

This step is repeated along the length of the band to hold the assemblies 3, 5 together. At the further end of the band 1, the remaining free ends of the weft are secured, e.g. by threading them back into the band 1.

As described above the formed assemblies 3, 5 are arranged on the ground. In another method, the assemblies 3, 5 are rolled up side-by-side on a drum, and the sling-maker may work from a seated position merely having to unroll the drum as he threads the weft 9.

In this way, the band 1 is formed. The eyes 2 are then formed at each end of the sling in known manner.

The eyes 2 shown in FIGS. 1 and 2 are formed by bending the free ends of the warp lengths 4 to form a bight, and then clamping them by means of a steel ferrule 10.

In a first modification (not shown), a sling can be made from seven, eight, fourteen or sixteen wire warp assemblies of a length greater than twice the length of the sling to be formed, the assemblies being bent at mid-way of their length so that the band will be formed of fourteen, sixteen, twenty-eight or thirty-two assemblies, the bent end forming one eye with the other eye at the opposite end being formed by the ends of the seven, eight, fourteen or sixteen warp assemblies being laid on top of the other and being clamped together by means of steel ferrules at the ends. Textile warp assemblies of substantially the same length as the band can be included in the band. The eyes so formed can be bound with a suitable material. This modified sling is advantageous since it has one end without ferrules whereby to allow that end to pass under a load which a ferruled end could not.

Each wire warp assembly can be formed of more than two lengths of wire, for example three or four lengths.

Initially, the two length assembly is formed and the additional lengths are then laid into it.

The simple and versatile method of construction and assembly ensures that long or wide slings can be made merely by using two or more warp assemblies in parallel without the need for braiding and plaiting. It is also possible to produce a high load capacity sling by using large diameter steel ropes. In the past, such rope has proved very difficult to plait or braid. The method of the invention has the further advantage that the textile rope, in two or more warp assemblies, may easily be included at the time of manufacture. With the known methods, the textile rope must be interwoven into the band afterwards. A sling made according to the invention has a lower stretch factor than the known braided or plaited slings and is flatter.

Claims

CLAIMS:

1. A method of making an elongate flexible and substantially flat load bearing element, comprising the steps of; twisting at least two lengths of material together to form a warp assembly including a plurality of longitudinally spaced loops; arranging two such warp assemblies in side-by-side relation with loops thereof in alignment to form a plurality of sheds; and threading a weft length of material through the sheds to hold the warp assemblies together.

2. A method as claimed in Claim 1, wherein the additional step of providing an eye at each end of the element to form a sling.

3. A method as claimed in Claim 1 or 2, wherein at least one further warp assembly formed from twisted lengths of textile-like material of a diameter greater than that of the other warp assemblies, is arranged side-by-side with those warp assemblies prior to the step of threading the weft length through the sheds.

4. A method as claimed in any preceding Claim, wherein the warp and weft lengths comprise single or multi-stranded steel wire.

5. A method as claimed in any preceding Claim, wherein the further warp assembly is formed from lengths of polypropylene rope twisted together.

6. A load bearing element comprising an elongate and flat band optionally having an eye at each end of the element wherein the band comprises at least two warp assemblies arranged side-by-side to form a plurality of longitudinally spaced apart sheds, each warp assembly comprising two lengths of material twisted together, and a weft length which passes through the sheds to hold the warp assemblies together.

7. A method of making a flat load bearing element substantially as hereinbefore described.

8. A load bearing element substantially as hereinbefore described with reference to the accompanying drawings.