GB1498401A - Drive arrangements - Google Patents

Abstract

1498401 Torsionally resilient drive mechanism ELEKTROGERATEWERK SUHL VEB 23 Dec 1974 [27 Dec 1973 2 Sept 1974 (3)] 55367/74 Headings F2U and F2Q [Also in Division B1] A drive arrangement for preventing the destruction of gearing teeth due to excess loading whilst providing efficient drive at low loads comprises, between an input drive member and an output drive member, a first drive means including gear means and a torsion spring coupling and a second drive means including gear means and a lost-motion connection so that drive passes through the second drive means as well as the first only after the torsion spring coupling has been stressed sufficiently by the load to close up the lost-motion connection, the area of input gear or output gear teeth which transmits the drive being greater when both drive means participate. In the arrangement illustrated in Figs. 1, 4 and 6, a driving worm 6 engages a wormwheel 4 rotatably mounted on a shaft 1 and a wormwheel 8 fixed on a shaft 10, the worm-wheel 4 driving a spur gear 5 through a spring 13 and the wormwheel 8 having an arcuate slot 84 into which extends a pin 83 protruding from a spur gear 7 rotatably mounted on shaft 10. If the load on an output shaft fixed to shaft 1 increases above a limit set by the spring 13 the relative movement between wormwheel 4 and spur gear 5 causes the pin 83 to engage an end of slot 84 so that drive passes through both worm-wheels. The spring 13 can be a helical spring (as shown), or it can be of resilient material, or it can be a spiral spring (Fig. 13, not shown), or there may be a pair of compression springs (Fig. 11, not shown) or tension springs (Fig. 12, not shown), a resilient plate (Fig. 14, not shown), a set of internested helical springs (Fig. 35, not shown) or a set of spiral springs (Fig. 34, not shown). To allow for the greater torsion angle of the lastmentioned embodiments the slot in the wormwheel 8 may be a spiral and the pin may be guided in a radail groove in the spur gear (Fig. 28, not shown) or the slot may be a screw in a cylinder with the pin guided in an axial slot (Fig. 31, not shown) or there may be a stack of plates with spiral grooves (Fig. 30, not shown) or an internested set of screwed cylinders (Fig. 32, not shown). The worm drive may be replaced by spur gear drives to outer and inner teeth of an output ring gear (Fig. 44, not shown), or as shown in Fig. 45, there may be an input shaft 1 having a driving member 136 fixed to it which drives a gear 138 through the spring 13, a second gear 133 being driven through the pin-and-slot lost-motion connection when the load, driven by an internally toothed rim 127, increases above a set amount. The lost-motion connection can comprise a roller or ball engaging grooves in the worm gear 8 and spur gear 7 (Figs. 8, 9, not shown). Wormwheels and spur gears can be of plastics material. A corrugated compression spring 25 (Fig. 45) provides damping of the torsional movement. The drive may be for driving accessories of a handheld beater or stirrer.