GB2131389A

GB2131389A - Protective sleeve for fabric belts

Info

Publication number: GB2131389A
Application number: GB08324860A
Authority: GB
Inventors: Klaus Giesen; Wilfgang Scholz
Original assignee: Elastogran GmbH
Current assignee: BASF Polyurethanes GmbH
Priority date: 1982-09-18
Filing date: 1983-09-16
Publication date: 1984-06-20
Also published as: DE8226351U1; GB8324860D0

Abstract

A protective sleeve (1) for a fabric belt (2) consisting of natural and/or synthetic fibers or of wire or of wire rope, and for lifting belts, clamping belts and the like produced therefrom, has a generally rectangular inner profile (6) as well as a generally rectangular outer profile (5). The walls of the broader sides of the rectangles may be thicker than those on the narrower sides, and the edges of the profiles may be rounded. The internal height of the sleeve may narrow in its centre and the sleeve may be made of a polyurethane elastomer. <IMAGE>

Description

SPECIFICATION Protective sleeve for fabric belts The present invention relates to a protective sleeve for fabric belts which consist of natural and/or synthetic fibers or of wire or wire ropes. Such fabric belts are employed directly as lifting belts, clamping belts and the like.

The safety requirements and testing of lifting belts are set out in DIN 61,360, Part 2, Section 6.1.1, where it is stated that: "The lifting belts must be checked by a specialist once a year or more frequently. Moreover, depending on the conditions of use and on the operating conditions, intermediate checks should be carried out as required so that defective lifting belts can be excluded from use immediately".

It is obvious that the service life can be prolonged and hence costs saved if the fabric belts are protected against damage.

This is done by coating fabric belts directly with flexible plastic. However, this coating, too, can become defective, and then no longer fulfils its protective function.-The disadvantage in this case is that the service life of a directly coated fabric belt is no longer than that of the coating itself.

Fabric belts have also been covered with protective sleeves. These can be removed'before they are completely worn out, and can be replaced with fresh, undamaged protective sleeves. This increases the service life of the fabric belts. Conventionally used protective sleeves are those consisting of textile fabrics. Their disadvantage is that they are less hard-wearing than a coating of flexible plastic. Textile sleeves which are provided on one or both sides with a hard-wearing coating of flexible plastic are also known. The disadvantage of these can be described with reference to the example of a lifting belt produced from a fabric belt: According to DIN 61,360, Form B1 and Form B2, these lifting belts possess loops whose crosssection viewed end-on differs from that of the free clamping length in the middle of the lifting belt.The coated textile sleeve to be pulled on subsequently must fit this cross-section.

As the loop passes through the textile sleeve the latter assumes an approximately circular crosssection, after which it becomes flat. In this position the coated textile sleeve, which is itself soft, has the disadvantage that it does not exert a sufficiently high contact pressure to adhere firmly to the lifting belt. However, reliable protection of the lifting belt by the coated textile sleeve is achieved only when, during use of the lifting belt, the sleeve remains at that point of the lifting belt at which increased wear is to be expected as a result of, for example, contact with a sharp edge of a workpiece to be lifted.

Attempts have also been made to produce a protective sleeve from a sleeve consisting only of a flexible plastic and having a circular or approximately circular cross-section. Although this sleeve can be readily pulled over the lifting belts according to Form B1 and Form B2, it retains its circular or approximately circular cross-section after the loop has passed through. Hence, it never adheres firmly along the free clamping length of the lifting belt, which length comes into contact with the load.

It is an object of the present invention to provide a protective sleeve for fabric belts which lies on the fabric belt with an initial tension which is sufficiently high that, when the lifting belt, clamping belt or the like consisting of a fabric belt or produced from a fabric belt is used in the prescribed manner, the sleeve remains at the predetermined position.

We have found that good results are achieved, in accordance with the invention, if the protective sleeve has a generally rectangular cross-section. Advantageously, its inner profile as well as its outer profile is generally rectangular. Since the fabric belt, two, has a rectangular cross-section due to its method of manufacture, the protective sleeve comes into contact with the fabric belt on all sides, with the result that the firm adhesion between sleeve and belt, which is required in use, is achieved. The inner profile of the protective sleeve can be slightly larger than or the same size as the profile of the fabric belt, or can be slightly smaller than the profile of the fabric belt in one dimension.

When a fabric belt is used in the normal manner as a lifting belt, clamping belt or the like its broad side comes into contact with the object lifted. Hence, the protective function of a protective sleeve can be improved if its broad side, which comes into contact with the load, is thicker than its narrow side, which does not. A further advantage of this embodiment is that the rectangular hollow profile can be converted to a circular or approximately circular cross-section by applying pressure to the narrow side.

The reduced wall thickness of the narrow side of the protective sleeve also results in an increase in its flexibility at right angles to the narrow side. This flexibility is advantageous and desirable because fabric belts, or lifting belts, clamping belts or the like produced from them, frequently have to be bent into curves ofsmaller radius. The ratio of the wall thickness of the broad side, which comes into contact with the load, to that of the narrow side, which does not, is advantageously 2:1 or higher. The broad side is then from 2 to 10 mm thick.

It is advantageous if the protective sleeve has bevelled or rounded edges instead of sharp ones. If the outer profile has bevelled or rounded edges, the lifting belt, clamping belt or the like provided with the protective sleeve can be more easily pulled under and over the load to be fastened. Bevelled or rounded edges of the inner profile of the protective sleeve increase the clamping action at the edges of the lifting belt, clamping belt or the like consisting of or produced from a fabric belt.

The clamping action of the protective sleeve on the said lifting belt, clamping belt or the like can advantageously be increased if the inner profile of the protective sleeve differs from the outer profile of the said lifting belt, clamping belt or the like. In an advantageous embodiment, the internal height at the middle of the broad side of the protective sleeve is less than the corresponding height at the end of the broad side. The said lifting belt, clamping belt, etc. which is pulled into the protective sleeve expands the inner profile, leading inevitably to an increased clamping action.

The function of the protective sleeve is only fulfilled when it consists of a flexible material which resists stresses over long periods or permanently. Advantageously, the sleeve should be produced from a polyurethane elastomer. Such a material is flexible and has high tensile strength and elongation at break and low tear strength and abrasion. Such polyurethane elastomers can consist of polyesterpolyols and diphenylmethane diisocyanate. Their characteristic properties are as follows: Test according Property to DIN Unit Hardness 53,505 Shore A 75 85 Tensile strength 53,504 N/mm2 40 40 Elongation at break 53,504 O/o 500 500 Tear strength 53,515 N/mm 25 40 Abrasion 53,516 mm3 45 50 The accompanying drawings illustrate the invention.

Figure 1 of the drawings shows a perspective view of a protective sleeve 1, which has a rectangular cross-section and surrounds a lifting belt, clamping belt or the like consisting of or produced from a fabric belt 2.

Figure 2 of the drawings shows a cross-section through the protective sleeve 1. The thickness of its wall 3 at the broad side, which comes into contact with the load, is greater than the thickness of its wall 4 at the narrow side, which does not come into contact with the load.

Figure 3 of the drawings shows a cross-section through the protective sleeve 1, illustrating, by way of example, how the edges of its outer profile 5 and those of its inner profile 6 can be bevelled or rounded.

Figure 4 of the drawings shows a cross-section through the protective sleeve 1 in an embodiment where the internal height 7 in the middle of the inner profile is less than the corresponding height 8 at the end of the inner profile.

Claims

1. A protective sleeve for a fabric belt consisting of natural and/or synthetic fibers or of wire or wire rope, or for a lifting belt or clamping belt or the like produced therefrom, wherein both the inner profile and the outer profile of the sleeve are generally rectangular.

2. A protective sleeve as claimed in claim 1, wherein the walls of the broad side of the rectangle are thicker than those of the narrow side.

3. A protective sleeve as claimed in claim 1 or 2, wherein the edges of the outer profile and/or of the inner profile are bevelled or rounded.

4. A protective sleeve as claimed in any of claims 1 to 3, wherein the internal height in the middie of the broad side of the rectangle is less than the corresponding height at the end of the broad side.

5. A protective sleeve as claimed in any of claims 1 to 4, which is made of a polyurethane elastomer.

6. A protective sleeve for a fabric belt, or for a lifting belt or clamping belt or the like produced therefrom, substantially as hereinbefore described and illustrated in Figures 1 and 2, or Figure 3, or Figure 4, of the accompanying drawings.

7. A fabric belt, or a lifting belt, clamping belt or the like produced therefrom, which is protected within a protective sleeve as claimed in any of claims 1 to 6 extending over at least a major portion of its length.