Patent GB-647405-A (GB)
Title: Improvements in or relating to steering assemblies for dirigible vehicles and dirigible vehicles employing said steering assemblies
IPC: B62D11/08
Filed: 1947-11-25
Abstract: 647,405. Change-speed gear; friction clutches. THOMPSON PRODUCTS, Inc. Nov. 25, 1947, No. 31199. Convention date, March 26, 1947. [Class 80(ii)] [Also in Group XXXIV] A manually-controlled two-speed planetary gear for incorporation in the steering column of a vehicle, comprises a directdrive disc-clutch 40 and reduced drive disc-brake 60 jointly controlled so that both can never be simultaneously free. In addition, any drive-torque applied during a downshift automatically releases the direct-drive clutch as the reduced-drive brake engages, thereby avoiding a condition in which, for a brief interval during torque transmission, both clutch and brake might be simultaneously engaged, which would otherwise result in temporarily locking the steering mechanism. The oilsealed casing is designed for introduction into the lower end of the fixed casing of the existing steering-column, the input and output shafts 12a, 14a, of the gear being coupled respectively to the inner steering-shaft and the input shaft of the usual steering-box, Fig. 9 (not shown). The direct-drive clutch 40, normally kept in engagement by springs 46, directly connects an input sun 32 with an output planet-carrier 14c and is disengaged by application of the brake 60 to hold a freelymounted ring-gear 38 for reduced drive. Downshift is by pulling a manually-operable cable to turn a rock-shaft 72, a crankarm 72a on which turns a disc 70a carrying on radial spindles, four rollers 70b, Fig. 6, which, at their right sides bear on a flat thrust-washer 11, and at their left, ride up cam recesses in a cam-disc 70, which is thereby forced axially to the left, taking along a disc 68 to apply the reduced-drive brake 60, first through springs 68b, then positively through plungers 68a and, at a timed point in the latter action, acting through adjustable plungers 96 on a second cam-disc 80, radial cam recesses in which act on the roller-carrying forked ends of further plungers 54 which, through a ball thrust bearing 52 and thrust sleeve 39 apply a disengaging load to the springs 46 of the direct-drive clutch 40. Two conditions arise during the downshift, firstly if the shift is made whilst the steering shaft is idle, in which case the reduced-drive brake 60 becomes fully engaged and the direct-drive clutch 40 fully disengaged. Secondly if downshift is made whilst the gear is transmitting steering torque, in which case the initial application of the brake 60 causes the drive-torque to make the outer brakeshell 62, and with it the cam-disc 80, lag behind the ring-gear 38, this being permitted by lost-motion in their connecting splines 38d, so that the clutch-release plungers 54 ride up the cams of the now axiallyadvanced cam-ring 80, thus releasing the direct-drive clutch 40 as the reduced-drive brake 60 becomes effective and preventing any possibility of both being simultaneously engaged, which would otherwise result in locking the steering mechanism for a brief interval. To prevent re-engagement of the direct-drive clutch 40, should the direction of rotation of the input shaft be reversed, the ring-gear member 38 and outer brake-shell 62 are positively locked in the position of relative rotation which they have reached in this clutch-disengaging movement, thereby preventing the release plungers 54 from again riding down the cam-recesses of the disc 80 to permit re-engagement of the direct-drive clutch 40. For this purpose locking-segments 90, splined in the outer brake-shell 62 and connected by blade-springs 92 and axial adjusting bolts to the cam disc 80, are advanced axially by the axial movement of the cam-disc 80, in timed relation to the brake-engaging movement, whereby serrated locking-faces 90a, 38f on the locking segments 90 and ring-gear member 38 come into engagement, locking the members 38, 62 and positively preventing any further relative rotation therebetween. When the roller-ring 70 is manually turned back for upshift the clutch-springs 46 return all the parts to the position shown, for engagement of the direct-drive clutch 40 and release of the reduced-drive brake 60.