GB913388A - Improvements in or relating to screwdrivers and like tools - Google Patents

Abstract

913,388. Screw-drivers; wrenches. GENERAL ELECTRIC CO. Ltd., and SANDERS, T. J. Sept. 19, 1961 [Oct. 13, 1960], No. 35192/60. Class 61. A torque-indicating screw-driver or wrench comprises a shaft having at one end means to engage a screw, bolt, nut, &c. a driving handle and means to transmit driving torque from the handle to the shaft by way of a helical or other resilient spring so that it is deformed in the same way (e.g. by winding up in the case of a helical spring) irrespective of the sense of the torque transmitted. As shown, a screwdriver comprises a cylindrical body provided with a handle 1, the body being partially closed at the end adjacent the handle by a disc 6, partially closed at the other end by a disc 7 and having a ring 13 secured to the interior wall. The shaft 9 provided at one end with a screw-driver tip 10 is located relative to the body 4 by ball-races 11, 12 which cooperate with bearing surfaces formed on the shaft and on the disc portions 6, 7. The shaft 9 is formed with two disc portions 17, 18 which lie in the same general planes respectively as the ring 13 and disc 6. Connecting the disc portions 17, 18 is a stop-pin 19 and two eccentric pins 20, 21. The portion 24 of the pin 19 which lies between the discs 17, 18 is of cylindrical cross-section as are the corresponding portions 25 of the eccentric pins 20, 21. The portion 25 of each of the pins 21, 22 is off-set from the longitudinal axis of the remaining part. A helical spring 30 encircles the portion of the shaft which lies between discs 17, 18. The two ends 31, 32 of the wire forming the spring are straight, extend beyond the periphery of the spring and bear against the portions 25 of eccentric pins 20, 21 respectively, and also bear against further pins 33, 34 lying parallel to the pins 20, 21 and having their ends located respectively in the disc 6 and ring 13. The shaft 9 has secured thereto a drum 26 on which are engraved graduations which co-operated with an engraved mark on the body 4. In operation, when the shaft 9 is held still and the driving handle is rotated one of the eccentric pins secured to the driving handle will tend to push against the end of the spring whilst the other pin will tend to move away from the other end of the spring, the spring thus being wound up so that a torque is then applied to the shaft. On rotating the handle in the opposite direction the other eccentric pin winds-up the spring.