GB578860A - Improvements in or relating to torque indicating or measuring devices - Google Patents

Abstract

578,860. Electric indicating systems. SHEPHERD, G. R. (Westinghouse Electric Jnternational Co.). April 13, 1944, No. 6853. [Class 40 (i)] [Also in Groups XIX and XXXVI] A device for indicating or measuring the torque of a shaft comprises a rotor assembly secured to rotate with the shaft of a stationary electromagnetic element, and at least one magnetic flux path linking said rotor assembly and said stationary element, characterised by means for producing an alternating magnetic flux in the magnetic flux path and means forming part of the rotor assembly responsive to the torque characteristics of the shaft for changing the value. of said alternating flux thereby inducing voltages in the stationary element indicative of the torque of said shaft. The rotor assembly 3, Fig. 1, comprises a pair of axially displaced torque rings 7 and 9 of magnetic material having axially extending fingers 7a and 9a. The rings 7 and 9 are mounted on non- magnetic bushings 11, 13 which are secured to rotate with the shaft 1. Between adjacent fingers 7a and 9a are airgaps 14. The stationary member 5 is annular in shape and forms two circular air gaps 21 and 23 with the torque rings 7 and 9 respectively. A coil 25 is secured within the annular recess of member 5 and is connected as one leg in a conventional bridge circuit 27 which is supplied with alternating current and adjusted to a balanced condition when the shaft is not loaded so that a voltage will not appear across the terminals of an indicating meter 29. When the coil 25 is energised a flux flowing in the clockwise direction as shown Fig. 1 is induced in the stationary member 5 and the rotor assembly 3. The flux path includes stationary member 5. air gaps 21, torque ring 7, finger 7a, an air gap 14, finger 9a, torque ring 9, air gap 23 and back to the stationary member 5. The size of the air gaps 14, 21, 23 and the shapes and sizes of the confronting faces across said air gaps are such as to compensate for end thrust in the shaft bending of the shaft and temperature variations in the shaft. If the shaft 1 is not transmitting a torque whether it is stationary or rotating the voltage in the coil 25 will remain constant. If, however, there is circumferential deflection of the shaft due to torque the air gaps 14 will increase or decrease depending on the direction of the distortion, the value of the circulating flux will be altered so that the voltage in the coil 25 will change thereby unbalancing the bridge current causing a voltage indicative of the torque to appear across the terminals of the indicating meter 29. Fig. 3 shows a further embodiment in which four coils 25a, 25b, 25e, 25d are used and a third ring 31 also secured to rotate with the shaft 1 and having axially extending fingers is provided. Further modifications are shown in the drawings. Specification 578,859, [Group XIX], is referred to.