| 摘要 |
1526948 Torque control of wrenches STANDARD PRESSED STEEL CO 19 Sept 1975 [19 Sept 1974] 38575/75 Heading G1N [Also in Divisions B3 and G3] Apparatus for measuring the stiffness of a bolt comprises means for determining the gradient of the torque/angle of rotation relationship, and is used to stop the tightening of the bolt when the gradient falls to half the maximum gradient, indicating that the bolt is approaching its yield point. In one embodiment, Fig. 2, a bolt is rotated by a tool 2 driven by a motor 10 through a spring coupling 11. The torque is measured by the difference between the rotation ° 1 at the input end, measured by a first toothed wheel encoder 9, and the rotation ° 2 at the output end, measured by a second toothed wheel encoder 6. The angular difference is continuously determined in a comparator 22, Fig. 3, where it is divided by ° 2 to obtain the torque curve gradient. The maximum value is stored at 24 and compared at 23 with the instantaneous gradient. When the latter falls to half the former a signal is produced to stop the motor 10. The output from the motor may be converted to a linear movement to determine the yield point of tensile samples. In another embodiment, Fig. 7, a wrench 50 comprises a driver bit 59 coupled to a motor 52 by a flexible part 64 carrying strain gauges 72 which measure the instantaneous torque. The angular rotation is measured by a pick-up 74 associated with a toothed member on the shaft, or the vanes 76 of the air motor 52. The rotation signals are used to sample the torque at equal intervals, the difference being determined at 94 and representing the torque/rotation gradient. The maximum value of the gradient signal is stored at 102 and a pre-set proportion, e.g. half, determined at 106 for comparison at 98 with the instantaneous gradient signal. When the former exceeds the latter the motor 52 is stopped. |
