GB837130A - A motion transmitting device - Google Patents

Abstract

837,130. Friction gearing; screw-and-nut gearing. ANDERSON CO. July 31, 1957, No. 24265/57. Classes 80 (1) and 80 (3). In motor-driven screw-and-nut mechanism for longitudinally moving a tubular member 15, the screw 43 is driven by the motor shaft 20 through epicyclic friction gearing 16 which slips on overload to prevent damage should the member 15 be held stationary while the motor (not shown) is running, the pressure between the frictionally engaging parts being adjustable. The friction gearing 16 comprises planetary elements 27 which are rotatably mounted in cruciform openings in a tubular cage 41 of brass or nylon secured to the driven screw 43. Each element 27 has two radially enlarged toroidal portions engaging grooves in an inner race 25 secured to the driving shaft 20 and grooves in a split outer reaction race 26a, 26b. The non-rotatable race parts 26a, 26b are slidable in a fixed casing part 21b and are urged towards each other by spring 31, 33 adjusted respectively by rotation of a threaded casing part 21a and of a threaded member 34. An opening 39 allows insertion of a tool to engage recesses in the circumference of the member 34 to effect adjustment thereof. The screw 43 may drive the member 15 through an ordinary non- rotatable nut, but as shown the screw 43 engages planetary elements 51 which are rotatably mounted in a freely rotatable cage 50 and which engage annular grooves 53 in the member 15. The elements 51 have unequally spaced radially enlarged surfaces 52. Axial movement of the cage 50 is limited by stops 54, 55 on the screw 43. The member 15 is guided by a cup-shaped plate, which may be of nylon held by the stop 55. In modifications of the friction gearing 16 the spring 31 is dispensed with and the race part 26a bears against a fixed flange, the single loading spring 33 being adjusted by the member 34, or by an internally threaded member replacing the member 34. Alternatively the race part 26a may bear directly against the flange of an adjustable casing part 21a, the single spring 33 bear directly on the motor housing 18, and the inner race 25 be slidably keyed on the shaft 20 so that adjustment of the spring 33 is obtained by rotation of the casing part 21a. In a further modification both the inner and outer races are split and are loaded by respective adjustable springs. It is stated that the mechanism may be used in reverse to rotate a shaft 20 by axial movement of the member 15. It is also stated that the gearing 16 may be used, without the screw and nut mechanism, to convey drive between the shaft 20 and a pulley mounted on the cage 41, said gearing slipping on overload.