GB2320933A

GB2320933A - Manufacture of wire rope

Info

Publication number: GB2320933A
Application number: GB9700070A
Authority: GB
Inventors: John Mawson Walton
Original assignee: Bridon PLC
Current assignee: Bridon PLC
Priority date: 1997-01-03
Filing date: 1997-01-03
Publication date: 1998-07-08
Anticipated expiration: 2017-01-03
Also published as: GB9700070D0; GB2320933B

Abstract

Each strand 5 of a wire rope is made by helically winding wires 2 around a grooved core 1 whose rounded grooves receive, and uniformly space, the wires. Strands 5 are helically wound around grooved core 8, which core may be replaced by a strand 5. The core grooves may be initially straight and twisted as the wires are wound. The core may be solid-state formed, e.g. by drawing. The strands may be rolled or swaged so that each has a non-circular profile, the resulting rope having a circular profile.

Description

Manufacture of Wire Rope This invention relates to wire rope, which consists of wire strands, each comprising helically wound wires.

The invention provides a method of manufacturing a wire rope, comprising helically winding a plurality of strands, wherein each strand is made by helically winding wires around a fluted centre member with rounded grooves extending continuously along it so that the wires are received in the grooves.

Accordingly, the invention provides a wire rope comprising a plurality of helical strands in which the wires are supported by a centre strength member which is fluted with rounded, e.g. circular, grooves prior to its introduction into the strands, the fluted profile corresponding to the size, number, and relative spacing of the surrounding wires.

Preferably, the grooves in the fluted member are initially straight and parallel to the longitudinal axis of the member, which is then twisted synchronously with the strand forming operation to bring the grooves into mesh with the surrounding wires at the desired helical lay.

The fluted member may comprise a solid monolithic member of material such as a polymer which has been subjected to solid-state forming to give a highly orientated structure and enhanced axial properties, the solid-state forming being based on draw ratios of at most 15, preferably 10 or less.

It is possible to achieve uniform spacing of the wires surrounding the fluted member, and the wires can be substantially out of contact with one another.

The outer strands may be rolled or swaged into a non-circular profile corresponding to a segment of a circle or circular annulus. This may be done before, during, or after the rope closing operation. The outer strands may be of alternate lay direction to give a high degree of line contact between the wires of adjacent strands.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a wire rope consisting of six outer strands wound on a core strand; Figure 2 is a cross-section through a wire rope consisting of eight outer strands wound on a fluted core; Figures 3 and 4 show alternative strands in cross-section; Figures 5 and 6 show wire rope constructions including shaped strands; Figure 7 is a graph showing the effect of solid-state drawing on the tensile strength of polypropylene rod; and Figure 8 is a graph showing the effect of solid-state drawing on the axial stiffness of polypropylene rod.

It is proposed to support the wires 2 in each strand in a wire rope with a high strength fluted member 1 in which the fluted shape is introduced prior to stranding the helical wires 2. In this way the gaps between the wires may be regularised and controlled to any desired level, without the risk of the strand becoming non-uniform.

Examples of strand cross-sections are illustrated in Figures 1 to 4, for single-layer strands 3-7 of circular cross-section. Where greater flexibility is required then strands having more than one layer of wires over the central member 1 of the strand can be considered, preferably in equal-lay constructions to ensure line contact between the adjacent layers By providing the fluted centre member 1 with a sufficiently high strength,one can ensure that it can withstand the rigours of a high-speed strand-forming operation without undue stretch. High strength may be achieved for example with solid-state forming of polymers using techniques which are already well known and understood and are described, for example, in GB-A-2 280 686. In this way it is possible to achieve tensile strength levels which are 10-20 times greater than those of the isotropic polymer, as illustrated in Figure 7. It is also possible to increase the axial stiffness by up to 10 times the isotropic state, as illustrated in Figure 8. When taken together in combination these two factors signify that the centre member 1 can contribute usefully to the breaking strength of the strand (and the rope). The exact level of contribution will depend primarily on the initial choice of material and the amount of solid-state deformation.

The graphs of Figures 7 and 8 exemplify the effect of solid-state drawing on polypropylene rod, although many other materials/polymers may also be considered suitable for similar treatment. Normally draw ratios of less than 15 and preferably less than 10 (and at least 4) are adequate to give the requisite properties, e.g. strength characteristics. If the level of drawing is excessive then the drawn member may be prone to axial delamination or splitting.

Strands 4 formed by laying a plurality of steel wires 2 over a fluted centre member 1 may be closed together into a rope as illustrated in Figure 1. The core 3 of the rope may be formed from a similar type of strand as the outer strands 4 but preferably differing in two important aspects. Firstly the size of the core strand 3 should be chosen to ensure adequate working clearances between the outer strands 4. In the case of a rope having six outer strands 4 this will mean having a core strand 3 which is larger than the outer strands 4 by, say, 20%. This may for example by achieved by increasing the number of wires and keeping the same wire diameter or vice versa. It will also be preferable, in the interests of load sharing, to have the wires in the core strand 3 laid up at a shorter pitch than the outer strands. For example, if the outer stands 4 are Ordinary laid, then the core strand 3 may be beneficially laid at a sufficiently short pitch to give line contact between the wires of the core strand 3 and the wires of the outer strands 4.

In another preferred form of rope, shown in Figure 2, the outer strands 5 may be supported by a fluted core 8, formed for example in accordance with GB-A-2 219 014 or GB-A-2 269 400. It may be noted that in this particular embodiment the steel wires 2 may be totally separated from one another so that inter-wire contact does not occur.

This results in an optimal tensile efficiency for the rope and good fatigue properties because of freedom from inter-wire fretting damage.

Other embodiments are illustrated in Figures 5 and 6 in which at least the outer strands 9 or 10 of the rope 11 or 12 are deformed, during or after stranding, to conform in cross-section to segments of the circular annulus that they will occupy in the rope.

(If the rope has no core, they will conform to segments of a circle.) Because of the relatively low stress required to cause this deformation, the re-shaping may also be effected during or after the closing operation of the rope. This ease of deformation comes from the low transverse stiffness of the fluted centre member 1, which will preferably be a solid member of highly orientated polymeric material, but may alternatively be formed from a malleable metal rod, for example made of aluminium alloy, which will also be effective in reducing the mass of the rope.

The shaping operation may be carried out by rolling or swaging the strands 9,10 either individually or in the finished rope.

The main core of the shaped strand ropes may be one of several types, of which two preferred forms are illustrated, a core strand 13 (consisting of wires 14 on a fluted member 15) in Figure 5 and a fluted core 16 in Figure 6.

The outer strands of the ropes may be arranged to have alternate (Langs and Ordinary) lay directions. This has the effect of bringing the inter-strand wire contacts into close alignment, and thereby minimising the contact stresses.

Claims

CLAIMS:

1. A method of manufacturing a wire rope, comprising helically winding a plurality of strands, wherein each strand is made by helically winding wires around a fluted centre member with rounded grooves extending continuously along it so that the wires are received in the grooves.

2. A method as claimed in claim 1, wherein the strands are wound around a core.

3. A method as claimed in claim 2, wherein the core is made by helically winding wires around a fluted centre member with rounded grooves extending continuously along it so that the wires are received in the grooves.

4. A method as claimed in any preceding claim, wherein the grooves are initially straight, including twisting the fluted centre member as the wires are wound around it.

5. A method as claimed in any preceding claim, wherein the fluted centre member comprises a solid member which has been subjected to solid-state forming.

6. A method as claimed in claim 5, wherein the solid-state forming comprises drawing with a draw ratio of at most 15, preferably at most 10.

7. A method as claimed in any preceding claim, wherein the wires are uniformly spaced around the fluted centre member.

8. A method as claimed in any preceding claim, wherein the wires in the strand are substantially out of contact with one another.

9. A method as claimed in any of claims 1 to 6, including shaping, e.g. rolling or swaging, the strands so that each outer strand of the rope has a non-circular profile corresponding to a segment of a circle or of a circular annulus.

10. A method as claimed in claim 9, wherein adjacent outer strands are of opposite lay direction.

11. A method of manufacturing a wire rope, substantially as described with reference to the accompanying drawings.

12. A wire rope made by a method according to any preceding claim.