Patent GB-872831-A (GB)
Title: A magnetostriction torque transducer
IPC: B06B1/08
Filed: 1959-03-06
Abstract: 872,831. Measuring torque. VYZKUMNY A ZKUSEBNI LETECKY USTAV. March 6, 1959 [March 9, 1958], No. 7853/59. Class 40 (1). [Also in Group XXXIX] The magnitude and direction of a torque is determined by applying it to the core of a magnetic amplifier wound with toroidal exciting and feedback windings, and a perpendicular, solenoid-wound, pick-up coil, the voltage induced in the pick-up coil being amplified by the magnetic amplifier through the feedback windings. The unit (Fig. 1) comprises four elements each consisting of a cylinder of mganetic material, with end flanges having apertures by which pins 19 mechanically couple the four elements together. One end of the assembly is secured to a base-plate 20, and the other end is attached to a flange 17 carrying a shaft 171 to which the test torque is applied. Each cylinder is wound with a solenoidal pick-up winding 41- 44, a toroidal polarizing winding 21-24, and an exciting winding 31-34. The upper pair of cylinders are also toroidally wound with a magnetizing winding 51, and a feedback winding 61, and similar toroidal windings 52, 62 are located on the lower pair of elements. As shown in Fig. 13, the exciting windings 31-34 are energized in series, with winding 31 opposed to winding 32, and 33 opposed to 34, so that no voltage is induced in windings 51, 52 or 61, 62. Equal voltages are however induced in the polarizing windings 21-24. With no torque applied to the transducer assembly, the four coils 31-34 are identical and no current flows through a motor-control winding 71 in the load joining the mid point of coils 31-34 to the centre tap of their A.C. supply. Also no voltages are induced in solenoidal pick-up coils 41- 44, and the voltages in polarizing windings 21- 24 are all equal, so that there is no potential difference between the centre point 40 of windings 21-24 and 41-44, and the centrally located slider 74 of a potentiometer 75 connected between the ends of these windings. When a torque T is applied, a voltage is induced in windings 41-44 whose magnitude is proportional to the value of T. This produces a D.C. voltage between centre point 40 and slider 74 which is fed through feedback windings 61-62, connected in series opposition. The four units are also supplied with a D.C. magnetic field by coils 51, 52 connected in series aiding, so that the resultant D.C. magnetic field in one pair of units is increased, and decreased in the other. Hence the impedance of one pair of exciting windings, say 31, 32, is increased and that of the other pair 33, 34 is decreased. This causes an unbalance current to flow through winding 71 of motor 70, which drives the slider 74 of potentiometer 75 to rebalance the system. The unbalance current is augmented due to the fact that the unbalance in windings 31-34 adds additional unbalance to the pick-up circuit by unbalancing the voltages induced in polarizing windings 21-24. In a modification (Fig. 2, not shown), both ends of the four unit assembly are anchored, and the torque is applied to the centre of the assembly, with the connections to windings 43, 44 reversed.