Patent GB-598186-A (GB)
Title: Improvements in or relating to torque measuring devices
IPC: G01L3/10
Filed: 1945-03-15
Abstract: 598,186. Dynamometers. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. March 15, 1845. No. 6521. Convention date, Oct. 29, 1943. [Class 106 (ii)] [Also in Group XXXVIII] Apparatus for indicating or measuring the torque of a rotating shaft comprises a rotor assembly secured to rotate with the shaft, a stationary electromagnetic element, the rotor assembly and the stationary element being linked by at least one magnetic flux path, means for producing an alternating flux in the magnetic flux path or paths, means forming part of the rotor assembly responsive to the torque of the shaft for changing the value of said alternating magnetic flux, said stationary element including a member disposed to be linked by the said alternating magnetic flux adjacent the rotor assembly. A shaft 1, Fig. 1, subject to a load, has secured thereto a rotor assembly 3 comprising a pair of magnetic torque rings 7 and 9 spaced a known axial distance apart and mounted on non-magnetic bushings 11 and 13 secured on flanges 11a and 13a. The bushings 11 and 13 are provided with sleeves 11b and 13b which extend axially of the shaft 1 between the shaft and the rotor assembly. A reference ring 33, mounted on a non-magnetic bushing centrally between the rings 7 and 9, is provided with axially extending fingers 33c which are in interlocking relationship with axial fingers 7a and 9a of the rings 7 and 9 forming the air-gaps 14a and 14b as shown. The arrangement is such that when the shaft is subject to torque the air-gap 14a increases proportionally to the torque while the air-gap 14b decreases proportionally to the torque or vice versa depending on the direction of the torque. Surrounding the rotor assembly 3 is an annular stator member 5 comprising a pair of annular magnetizing coils 25a and 25b enclosed in housings 24a and 24b which form circular air-gaps 21, 23 and 27 with the rings 7, 9 and 33 respectively. The housings 24a and 24b are each provided with an opening adjacent the air-gaps 14a and 14b within which openings are positioned annular coils 25c and 25d. The coils 25a and 25b are energized from a suitable source of alternating current whereupon an alternating magnetic flux flows in the indicated path linking the coils 25c and 25d, the sleeves 11b and 13b serving to keep the flux to the path. If the shaft 1 is transmitting torque, the air-gaps 14a, 14b alter as above described and cause the voltage induced in the coils 25c and 25d to change by an amount corresponding to the torque and this change is indicated by a meter to which the coils 25c and 25d are connected. In another embodiment, Fig. 3, the reference ring 7 is omitted and therefore the torque acts only on one set of air-gaps 14b. The coil 25b is wound on an annular ring 26 and is connected as one leg in the shown Wheatstone bridge circuit which is balanced for a condition of no torque on the shaft 1 when the coil 25b is energized. When the shaft 1 is subject to torque, the air-gaps. 14b alter, as before, producing corresponding changes in the alternating magnetic flux path and as a result unbalancing the bridge circuit by an amount proportional to the torque. The meter M therefore gives an indication of the torque of the shaft. Specifications 578,860 and 579,451 are referred to.