Clamp for sheathed rod, strand or rope

#This invention relates to a clamp for application, at an intermediate or terminal position, to a rod, wire strand, or wire rope, sheathed with plastics material. The invention is particularly, but not solely, concerned with steel rod, steel wire strand, and steel wire rope which are to be used as stressing members, especially strands and ropes comprising helically spun filaments of cold-drawn high-tensile carbon steel which, after spinning, are subjected to radial compaction and/or isothermal treatment.

#In this specification, for ease of description, stands and ropes will be referred to generically as "cables", and rods an cables will be referred to generically as "lines".

#The application of a continuous sheathing of plastics material (e.g. thermoplastic) to a cable to achieve such desirable features as protection against mechanical damage and the effects of exposure to a harmful environment is well known. In applying a clamp to a sheathed cable, the following desiderata, amongst others, are aimed at: an intermediate or terminal clamp should provide positive location and holding, enabling it to sustain loads equal to or in excess of the breaking load of the cable to which it is applied; those areas (if any) where the sheathing has been removed from the cable to allow physical engagement between the clamp and the cable should be sealed off from the exterior with regard to penetration and attack by environmental corrosive agents; the clamp should be able to accommodate a cable without its having to be threaded through a hole bored in the body of the clamp

#The invention is described further, by way of example only, with reference to the accompanying drawings, in which:

#FIG. 1 is a perspective view of a portion of bared cable with a hard tubular element held in position by a circlip;

#FIG. 2a is an end view of the tubular element;

#The clamp illustrated in FIGS. 1 to 3 includes an elongate ductile aluminium body which has a rounded channel 2 providing a basically U-shaped cross-section. The side walls 4 progressively thicken from the common semi-circular base 3 to the top where the inner and outer faces of each wall merge into arcs 6 of equal radius.

#The plastics-sheathed compacted high-tensile carbon-steelwire cable 7 to be clamped is prepared at the appropriate position by removing a section of sheathing slightly longer than the overall length of a hardened steel tubular element 8 consisting of a parallel-walled hardened steel tube with tapered ends 10 and a serrated bore 5; the element 8 is divided longitudinally into two halves 9, which are held together by a circlip 11 located mid-length in a peripheral recess 12 (see FIGS. 2a and 2b).

#The prepared cable 7 is positioned in the clamp body 1 as shown in FIG. 3, with the tubular element 8 located mid-way along the longitudinal axis of the channel 2, at this stage there is a gap between the two halves 9 of the tubular element. This assembly, when placed in a suitable die set (not shown) and subjected to radial pressure via a hydraulic press, undergoes a progression of mechanical changes. Initially the walls 4 of the channel 2 are displaced inwardly to make physical contact with the tubular element 8, whereupon, because the hardened steel tubular element is relatively incompressible, the pressure is transmitted to the surface of the underlying area of cable, deforming it to the point at which it is fully indented and gripped by the serrated bore of the tubular element 8 (whose two halves 9 are now in contact with each other). Having fully consolidated the tubular element 8 onto the cable 7, continued radial pressure promotes further plastic flow and deformation, closing the mouth of the channel 2. The clamp body, externally, takes the form of a cylinder 13 (FIG. 4) with, midway along its length, a peripheral ridge 14 projecting at right angles to its longitudinal axis; this shape is formed by the die set.