Patent GB-598066-A (GB)
Title: Improvements in variable speed mechanisms
IPC: F16H15/40
Filed: 1945-02-28
Abstract: 598,066. Variable-speed friction gearing. SPERRY GYROSCOPE CO., Inc. Feb. 28, 1945, No. 5069. Convention date, Feb. 28, 1944. [Class 80(ii)] Variable - speed friction gearing comprises a pair of idler balls 22, 23 in driving contact with each other, the ball 22 contacting a driving disc 13, Fig. 1, or cone 111, Figs. 6-8, whilst the ball 23 contacts a driven cylindrical roller 18, the ballsupporting means being such that a line joining the ball-centres is offset from the axis of the driven roller 18. Assembly and adjustment for wear are thereby simplified and many critical dimensions are avoided. In Fig. 1 the balls 22, 23 are carried between the side-faces 25 of a sliding carriage which is traversed radially of the driving disc 13 and parallel to the driven roller axis 18 by rack and pinion 32. The balls are supported radially of the driven roller 18 by two parallel guide-rollers 36, 37 journalled in the fixed main casing 11, or in the carriage 25, and friction pressure is applied by an adjustable spring 48, acting on a separate casing-part 12 carrying the driving disc 13 and fulcrummed on pointed screws 41 at each end of the main casing 13, which screws, together with additional screws 45 at right angles to them, can be used for initial adjustment of the position of the driving disc 13 and also for wear compensation, the casing-part 12 being urged against the screws 45 by a bent wire spring 167. The ball-carriage 25 is guided by a fixed rail 27, which it engages through spring-loaded rollers 28, 29, and by shrouds on the teeth of the rackengaging pinion 32. In Figs. 6 to 8 the friction gear comprises a driving cone 111, driven roller 126 and an interposed pair of contacting idler balls 124, 125, with offset centre-line as above, the balls being supported in a sliding carriage 138, guided by a rail 147, and traversed by a screw 141 engaging the carriage 138 through rollers 139, 142. The idler balls 124, 125 are supported radially and axially in the carriage by pairs of in clined rollers 151, 152 and 158, 159, the latter pair being carried by a pivotal member 155, pressed by a spring 163, which provides friction pressure, which increases with the load due to the wedging action of the ball 124 between the driving cone 111 and the ball 125. A modification of this form, Figs. 4 and 5, not shown, dispenses with the inclined rollers 151 &c., and supports the balls radially of the driven roller by guide-rollers similar to 36, 37 in Fig. 1, the upper roller being mounted in a pivoted member which is spring-pressed to apply friction pressure. Pairs of hard-surfaced buttons on the side faces of the carriage support the balls laterally at the poles of their axes of rotation. In Fig. 6, final drive is through a differential gear 119, not described, whereof the output member is connected to the final driven shaft 133; one input member 121 is driven directly by a wheel 118 on the driving shaft 116; whilst the other input member 131 is driven from the driving shaft 116 through bevels 117, the friction gear 111, 126 and toothed wheels 128,129, the latter, 129, being an idler and the arrangement being such that, with the friction gear in its central position, the differential input members rotate at equal opposite speeds so that the driven shaft 133 is stationary and forward and reverse speeds are obtained on either side of this position.