GB829399A - Means for measuring a torsional stress in a shaft of magnetostrictive material - Google Patents

Abstract

829,399. Measuring torsional stress. ALLMANNA SVENSKA ELEKTRISKA A.B. June 10, 1958 [June 26, 1957; May 13, 1958], No. 18466/58. Class 37. The torsional stress in a shaft of magnetostrictive material is measured with two similar magnetic cores having salient poles facing the shaft, displaced axially by a fixed distance and staggered circumferentially by half a pole spacing; when the shaft is rotating, the magnetic paths from any one pole and the two adjacent poles on the other core become unequal in reluctance due to torsional stress, and an A.C. signal fed into a coil on the one pole gives unequal pick-ups in coils on the other poles. In Fig. 1 one core 10 carries poles with energized windings 15, 16, 17, 18 and the other core behind it (not visible) carries poles with pick-up windings 25, 26, 27, 28. When the shaft 9 is at rest coil 16 (say) produces equal pick-ups in coils 26 and 27 and with the arrangement of Fig. 3 no output results from the circuit. The meter can be calibrated to read the torsional stress as a function of the unbalance current. In a preferred form (Fig. 7) the energized core has a pick-up core on each side of it, the eight windings thereof 25-28, 35-38 being connected as shown. For measuring stress in a hollow shaft the salient poles are mounted on a solid core situated inside the shaft (Fig. 5, not shown). The cores can be divided into two or more portions and need not be complete circles as long as there are at least three poles on the energized core and at least two on each of the pick-up cores. The whole device is magnetically shielded.