GB722937A - Improvements in and relating to the location of flaws in steel ropes and irregularities in metallic bodies - Google Patents

Abstract

722,937. Electric tests. COAL INDUSTRY (PATENTS), Ltd. June 18, 1953 [June 19, 1952], No. 15439/52. Class 37. Apparatus for testing for flaws in metallic bodies, e.g. wire ropes, wherein two search coils are inductively associated with the wire rope and connected in opposition to give no signal in the absence of flaws, is characterized in that the two search coils are separated by a distance approximately equal to one cycle length of a regular variation in the wire rope, so that regularly occurring variations do not produce a signal from the apparatus. As shown, two energizing coils F1, F2 and the two search coils S1, S2 and a balancing coil B are located in a former H, the distance between coils F1, S1 and F2, S2 being equal to one cycle length of a regular variation in wire rope R passing through the centre of former H. The energizing coils F1, F2 are fed from an oscillator O, and the search coils S2, S1 are connected in series opposition being initially balanced by coil B, so that their resultant output shown on meter I indicates the position and extent of irregularities in the wire rope. The test object may be magnetic when permeability variations are noted, or non-magnetic when conductivity variations are noted. In alternative arrangements the search coils need not be spaced by one cycle length, and auxiliary coupling coils produce a voltage which, when fed into the circuit, counterbalance signals produced by the regular variations. In this case only one search coil may be used.