GB575208A - Improvements in ball-bearing screw and nut gears - Google Patents

Abstract

575,208. Screw - and nut gearing. GENERAL MOTORS CORPORATION. March 6, 1944, No. 4109. Convention date, June 25, 1943. [Class 80 (iii)] In screw-and-nut gearing in which balls in the helical passage forming the threads are circulated through a transfer tube, means are provided to prevent jamming of the balls. According to the invention the transfer tube has substantially parallel arms which fit in the nut and each of which communicates with the helical passage through a rectilinear path in the nut, the axis of the path being tangential to the helical passage and lying at an angle to and in the same tangential plane as the axis of the arm. The screw 1 has a helical groove 2 and the nut 4 a helical groove 5 these grooves forming a helical passage 6 for the balls 7 which circulate through transfer passages 20, two separate trains of balls being provided. The paths by which the balls enter or leave the passage 6 are provided by holes such as 10, 10<1> which are bored with their axes a-b, Fig. 1, inclined at the angle of the thread in a plane c-d, Fig. 3, tangential thereto, each hole forming a straight continuation of the helical passage in a plane such as c, d. The inclined paths 10, 10<1> join continuations thereof provided by holes 30, 30<1> each bored with its axis e-f in a plane such as c-d and also in a plane normal. to the axis of the screw 1, in order to provide parallel passages for the ends 26, 26<1> of the U-shaped transfer tubes. The axes a-b and c-d of the two holes 10, 30 intersect at a point g at a distance k from the helical passage which is not less than 20 per cent nor more than 50 per cent of the ball-centre radius of the helical passage. A finger portion 35 serves to guide the balls. Specifications 518,405 and 539,176 are referred to.