Patent GB-889469-A (GB)
Title: Devices for simultaneously measuring the velocity of rotation and the transmitted torque between two rotatable members
IPC: G01L5/26
Filed: 1960-02-26
Abstract: 889,469. Automatic torque-control systems. RECHERCHES ET ETUDES ELECTRONIQUES ET MECANIQUES. Feb. 25, 1960 [Feb. 26, 1959], No. 6617/60. Class 38 (4). [Also in Groups XIX and XXXVIII] In the measurement of the torque transmitted from a driving shaft to a driven shaft in terms of the angular displacement of one shaft relative to the other, this displacement is arranged to produce longitudinal movement of an element coaxial with both shafts, and the angular velocity of the shafts is measured simultaneously in terms of the rotation of the coaxial element. In Fig. 2, the driving shaft 1 carries splines 1a which engage a flange 7 on the end of a deformable member 3. The other end of this member consists of a sleeve 10 fitted with similar splines which engage corresponding splines on a socket 17, which in turn engages the driven shaft 4 in the same way. The centre portion of the member 3 comprises a number of longitudinal bars 15, 16 which are deformed into a helical configuration under the applied torque, and the sleeve 10 has a helical groove which co-operates with a finger 8 attached to a coaxial measuring element 5. The angular deformation of member 3 is thus converted into a proportional longitudinal displacement of element 5 and its attached lug 25, and is measured by means described below. The proportional relationship between the movements of 3 and 5 can be modified by changing the shape of the groove in sleeve 10. The socket 17 is attached to shafts 1 and 4 through bearings 21 and 22 and the longitudinal displacement of member 5 is thus unaffected by axial thrusts between the shafts. Backlash of the finger 8 is avoided by a spring 24 which urges the member 5 to the right. If axial thrusts can be absorbed in means external to the member 3, the assembly can be simplified by omission of the socket 17 (Fig. 3, not shown). In a modification (Fig. 4, not shown), the finger and groove are replaced by helical ramps which slide over one another. In another form (Fig. 5) the deformable member 33 consists of a flat helical spring (Fig. 6, not shown) whose inner end is driven by splines on shaft 1 and whose outer end is fastened to a flange 37 which similarly engages the shaft 4. This flange carries an extension 38a on which is mounted a finger 39 engaging a groove in a member 41 which can slide over the lower part of the member 33. As before, this finger and groove can be replaced by helical ramps. In a modification (Fig. 7, not shown) the member 41 has a bent portion by which the sensitivity can be adjusted. In another form (Fig. 8) a sleeve 50 attached to the driven shaft carries springs 56, 57 which engage arms 52, 53 mounted on the driving shaft 1 so that the torque compresses one half of each spring until the fingers 54, 55 touch the shoulders of the sleeve 50; further torque causes the arms 52, 53 to deform. By this means the sensitivity for low torques is increased. In Fig. 9 a pinion 66 on the driving-shaft 1 meshes with planetary gears 58, 59 on a carrier 58, which in turn engage toothed sectors 61, 62, on a sleeve 63 attached to the driven shaft. Torque causes the carrier 58 to turn and distort the tangentially-mounted blades 64, 65. Each of these deformable elements is associated with means for transforming the angular displacement into a longitudinal displacement as in Fig. 5. In each case movement of the member 5 can be measured electrically (see Group XXXVIII) and the resulting signal fed back to the power element driving- shaft 1 to maintain the torque within predetermined limits (Fig. 1, not shown). In one particular form of detector (Fig. 10) the member 5 moves a truncated cone 85 which is magnetized around its circumference with alternating N and S poles. As this cone rotates, it induces currents in coils 88, 89 whose amplitude depends on the air gap and hence on the axial position of the cone. The frequency of the currents represents the speed of rotation of the shafts.