Improvements in or relating to apparatus for improving the tensile properties of steel wire

摘要

PICT:1114261/C6-C7/1 Apparatus for improving tensile properties of steel wire comprises one or more rotary members 11, 12, 21 around which wire is passed and means for passing a heating current from at least one rotary member, e.g. member 11 and 21, along a length of wire 23a, b under tension to effect its permanent elongation, the or each rotary member connected to the heating current supply circuit comprising a set of spaced commutator segments (see Figs.5 and 7, not shown) forming the wire engaging periphery 32 of the rotary member and one or more current carrying brushes 27-30 arranged to contact the segments at a circumferential position spaced from that portion of the periphery A, B, C, D on to or off which the length of wire being heated momentarily passes, so that current flows between each brush and only those segments connected to part of the periphery with which the wire is momentarily in pressure engagement. Thus local martensite formation is avoided by precluding overheating due to sparking or arcing at the points A, B, C, D. Preferably, the circumferential width of each brush does not exceed the circumferential length of each commutator segment, and the current supply path to each brush is of a different electrical resistance, a maximum circumferentially nearest to the points A, B, C, D and least furthest from such points so that current flow is uniform along the wire between the segments and the wire surface. As shown, wire 23 initially passes around pre-tensioning reel 25, then around member 12 (not connected to the current supply circuit), then member 11, back to member 12 and so on prior to being heated, each member being provided with V grooves for wire advancement as described in Specification 969,191. Pulley 42 is a tension measuring device. The length of heated wire 23b may be cooled before passing on to member 11 as described in Specification 748,357.