GB968503A - Torquemeter - Google Patents

Abstract

968,503. Measuring electrically. DE HAVILLAND ENGINE CO. Ltd. Dec. 22, 1960 [Dec. 24, 1959], No. 43866/59. Heading G1N. A torquemeter comprises a shaft carrying two axially spaced elements each with a magnetisable cylindrical surface concentric with the shaft, a fixed pick-up device adjacent each element, a signal channel from each pick-up device which derives from picked-up signals square waves of substantially constant amplitude but having frequency and phase the same as those of the picked-up signals, and a device for comparing the square waves from the two channels. In Fig. 1, two aluminium support drums 12, 13 are mounted coaxially and in spaced apart relation on a shaft 11; alternatively they may be integral with the shaft. Thecurved peripheral surface of each drum carries an annular magnetizable element 14 in the form of a strip, layer, or wire of ferro-magnetic metal, an impregnated plastic strip, a sintered magnetic oxide material, etc.; if in layer form, the element may be applied by spraying. Adjacent each element is located one of two combined magnetizing, erasing and pick-up devices 15, 16 which, when a 7-contact 2-position switch 17 is in the position other than that shown, are connected in series (or, alternatively, in parallel) across a generator 32 coupled to the shaft 11 which is rotated under noload conditions so that each element 14 is similarly magnetised. Preferably the intensity of magnetization around the elements varies sinusoidally, but other wave-forms may be used. Switch 17 is then restored to the position shown. When shaft 11 rotates on load, the torsional twist therein causes a relative phase displacement between the outputs of pick-ups 15, 16, each output being supplied via a gain-stable amplifier 22, an amplitude limiter 23 and a gain-stable ring-ofthree amplifying unit 24 to an A.C. meter 27 which operates according to the algebraic sum of the signals. Alternatively, an oscilloscope may replace meter 27; also the resultant signal may be fed to apparatus 39 to control the speed of rotation or the load on the shaft. The elements 14 may be in the form of discs 41 secured to the sides of drums 12, 13. To mount the drums more closely together, one drum is mounted at one end of a sleeve which extends coaxially around the shaft and is attached thereto at its other end. A multiple torquemeter sensitive to the torque in two different portions of a rotating member comprises two torquemeters as described above, one of the magnetized elements being common to both torquemeters. The Provisional Specification describes a modification in which the outputs of pickup devices 15, 16 are supplied to the primary windings of two transformers, the secondary windings of which are connected in opposition to the meter; also a revolution meter comprises a single support drum holding magnetizable material, the magnitude or frequency of the picked-up signal being measured.