GB2068331A - Improvements in or relating to cargo lifting nets - Google Patents

Abstract

A cargo lifting net having a central cargo retaining part 11 comprised by a reticulated structure 12-15 has a substantial area of the cargo retaining part embedded in fabric-reinforced elastomeric material 22. One or more layers of reinforcing fabric may be used. <IMAGE>

Description

SPECIFICATION Improvements in or relating to cargo lifting nets THIS INVENTION relates to cargo lifting nets and is particularly concerned with heavy-duty cargo lifting nets such as are used for lifting and transporting loads by helicopter.

In helicopter aerial supply operations it is common to carry cargo in a large net suspended on a winch line under the helicopter.

Particularly for lifting heavy loads of up to 9,000 kilograms weight, such a cargo net comprises a complex reticulated structure of interwoven webbing straps which are fastened together at their cross-over positions. The complexity of this structure makes it difficult and hence costly to manufacture.

To assist in spreading the load over the net, and to protect the webbing straps from damage by portions of the cargo which may project through net interspaces, it is usual to lay a fibre matting, such as coconut matting, over at least the central area of the net before placing the cargo in position prior to lifting.

Disadvantages of this matting are that when laid upon a wet ground surface, or when exposed to rain, it soaks up water so that its weight is increased and, in due time, it supports the growth of vegetation.

According to the present invention a cargo lifting net having a central cargo retaining part comprised by a reticulated structure of webbing straps is characterised by having a substantial area of the central cargo retaining part embedded in fabric-reinforced elastomeric material.

Preferably that area of the central cargo retaining part which is embedded in fabricreinforced elastomeric material is medial of two layers of fabric reinforcing material.

The reinforcing fabric may be woven nylon cloth and the elastomeric material may be synthetic rubber or natural rubber.

The webbing straps are preferably manufactured from nylon although polyester may be used as an alternative material.

In one form of the invention the central cargo retaining part is substantially square in shape when the net is laid out flat, the side edge extremities being formed by four webbing straps which are joined at their ends to ring members. Additional webbing straps extend between adjacent side edge webbing straps, so as to intersect said side edge straps at included angles of substantially fortyfive degrees and are joined thereto by suitable means such as stitching. These additional webbing straps are also joined at their crossover positions by suitable means such as stitching.

A cargo net in this form of the invention may have a triangular-shaped lifting sling extending from each corner position of the central cargo retaining part. Each said lifting sling carries at its outermost apex and a ring member whereby the cargo net is attached to load lifting means such as, for example, a hook on a winch cable under a helicopter.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a view in plan on the cargo retaining part of a cargo net in accordance with one embodiment of the invention when the net is laid flat, and illustrates a lifting sling extending from one corner of the cargo retaining part; and Figure 2 is an enlarged transverse crosssection through a portion of the cargo retaining part of the cargo net shown in Fig. 1.

A cargo net 10 has a central cargo retaining part 11 which is square in shape when the net 10 is laid flat, as shown in Fig. 1. The cargo retaining part 11 is comprised by a reticulated structure of webbing straps, four such webbing straps 12, 13, 1 4 and 1 5 forming the major length of the side edge extremities of the cargo retaining part 11. The webbing straps 12, 1 3, 14 and 1 5 are joined at their ends to metal rings 1 6 by being passed through the rings 1 6 and fastened back on themselves using snap hooks (not shown). This simplifies replacement in the event of damage.Additional webbing straps 1 7 extend in spaced parallel relationship to each other between adjacent side edge webbing straps 1 2 and 1 3 and between adjacent side edge webbing straps 14 and 1 5. Similar webbing straps 1 8 extend in spaced parallel relationship to each other between adjacent side edge webbing straps 1 2 and 1 5 and between adjacent side edge webbing straps 1 3 and 14. The webbing straps 1 7 and 18 are interwoven with each other and are joined together by stitching at their cross-over positions.The webbing straps 1 7 and 1 8 intersect the side edge webbing straps 12, 13, 14 and 15, at an included angle of fortyfive degrees and joined thereto by stitching. The end portions of the straps 1 7 and 1 8 project beyond the side edge straps and are joined to metal rings 1 9 whereby the side edges may be laced together with the net is carrying cargo.

A triangular-shaped lifting sling 20 is shown extending from the lefthand corner of the cargo retaining part 11. It will be appreciated that a similar lifting sling will extend from each corner of the cargo retaining part 11. The sling 20 is comprised by webbing straps and is attached at its base to the metal rings 1 6. At its outer apex end the sling 20 carries a metal ring 21 whereby the cargo net 1 9 is attached to a load lifting device such as a hook on a winch cable under a helicopter.

In accordance with the present invention a substantial area of the central cargo retaining part 11 is embedded in fabric-reinforced elastomeric material 22, in this embodiment the elastomeric material being rubber. Four water drain holes 23 are provided at the centre area of the cargo retaining part. In this embodiment, as shown in Fig. 2, the webbing straps of the cargo retaining part 11 are medial of two layers of woven nylon fabric reinforcing material 24. In manufacture the webbing straps 12, 13, 14, 15, 17 and 18, which are preferably of woven nylon cords, are pretreated for rubber receptiveness over at least that area of the cargo retaining part 11 which is to be embedded in rubber. The two layers of nylon fabric-reinforcing material 24 are similarly pretreated for rubber receptiveness.

As such pretreatment techniques are well known in the art they will not be described herein. Each layer of nylon fabric reinforcing material 24 is next interposed between two sheets of uncured synthetic or natural rubber 25. One of these assemblies of rubber sheets 25 and nylon fabric reinforcing material 24 is positioned on each side of the cargo retaining part 11, and the total assembly is positioned in an autoclave where it is subjected to even pressure over both of its surfaces in order to bring the innermost rubber sheets into contact with the webbing straps as well as into contact with each other at the spaces between the webbing straps.Heat is applied to cure the rubber which permeates into the interstices between the threads of both the nylon fabric reinforcing material 24 and the webbing straps so that on removal from the press, after curing, the webbing straps are embedded in the fabric-reinforced rubber 22.

In use of the cargo net 10 to transport cargo, the layers of nylon reinforcing fabric 24 carry some of the load on the cargo retaining part 11 so that the number of webbing straps in the cargo retaining part 11 can be considerably reduced and the complexity of the reticulated structure formed by the webbing straps in prior art cargo nets can be replaced by a relatively simple open square weave as shown in the illustrated embodiment. Furthermore, the rubber provides protection for the webbing straps of cargo retaining area against wear and damage by cargo and, at the same time, is substantially impervious to water.

Of course, the embodiment hereinbefore described with reference to and shown in the accompanying drawings is by way of example and modifications are possible. For instance, only one layer of nylon reinforcing fabric need be used, this layer being positioned over the top of the webbing straps of the central cargo retaining part and these webbing straps being completely embedded in rubber. Moreover, the webbing straps may be joined to the metal rings by being passed through the metal rings, folded back on themselves, and fastened by stitching.

It will be appreciated that the invention is not limited to cargo nets for use in transporting loads by helicopter. It can be applied to cargo nets for use with other load lifting devices such as cranes.

Claims (11)

1. A cargo lifting net having a central cargo retaining part comprised by a reticulated structure of webbing straps charactersied in that a substantial area of the central cargo retaining part is embedded in fabric-reinforced elastomeric material.

2. A cargo lifting net as claimed in Claim 1, characterised in that the area of the central cargo retaining part which is embedded in fabric-reinforced elastomeric material is medial of two layers of fabric reinforcing material.

3. A cargo lifting net as claimed in either one of the preceding claims, characterised in that the reinforcing fabric comprises woven nylon cloth.

4. A cargo lifting net as claimed in any preceding claim, characterised in that the elastomeric material is rubber.

5. A cargo lifting net as claimed in any preceding claim, characterised in that the webbing straps are manufactured from nylon.

6. A cargo lifting net as claimed in any one of the preceding claims, characterised in that the central cargo retaining part is substantially square in shape when the net is laid out flat.

7. A cargo lifting net as claimed in Claim 6, characterised in that the side edge extremities of the central cargo retaining part are formed by four webbing straps joined at their ends to ring members.

8. A cargo lifting net as claimed in Claim 7, characterised in that additional webbing straps extend between side edge webbing straps so as to intersect the side edge webbing straps at included angles of substantially fortyfive degrees.

9. A cargo lifting net as claimed in any one of Claims 6, 7 or 8, characterised in that a triangular-shaped lifting sling extends from each corner portion of the central cargo retaining part.

1 0. A cargo lifting net as claimed in Claim 9, characterised in that each lifting sling is provided with a ring member at its outermost apex end.

11. A cargo lifting net substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 2. Every novel feature and every novel combination of features disclosed herein.