Patent GB-408234-A (GB)
Title: Improvements in clutches and change-speed mechanisms
IPC: F16D43/202
Filed: 1932-09-27
Abstract: 408,234. Clutches; automatic variablespeed gearing. RICHARDS, C. H., 173, Harvard Avenue, Boston, U.S.A. Sept. 27, 1932, No. 26858. [Class 80 (ii).] Relates to a clutch which is automatically disengaged on easing the driving effort and the incorporation of such clutch in change-speed gearing. The clutch comprises a rotary member or planet-carrier i, Figs. 1 and 4, journalled loosely between coaxial driving and driven elements a, w and means transmitting the opposing driving and load torques to and through it such that the clutch normally transmits a steady drive, but upon any sudden unbalance between the said opposing torques, the drive is disrupted, in other words, the clutch is disengaged. In preferred forms, disruption of drive is accompanied by idle accelerated rotation of the carrier member i in the same direction as the drive. In the form shown in Fig. 4, planet toothed gears s, u fast on shafts h loose in the carrier i mesh respectively with a sun gear r fast on the driving-shaft a and with a sun gear v rigid with the load wheel w. The gear v is smaller than the gear r so that for idle running with the gear v stationary the carrier i must rotate faster in the direction of the drive. In a practical form, the gears r, s are all the same size and the diameter of the gear v is from 70 to 85 per cent of the diameter of the gear u. The device rotates solid, transmitting heavy steady loads, but, on upsetting the balance as by easing the throttle of a driving engine, the drive breaks down and the carrier i spins idly forward at increased speed. During the time that the carrier i is accelerating, a diminishing torque is actually transmitted so that the device then acts as a slipping or cushioning clutch. In the form shown in Fig. 1, the gear pairs are replaced by pairs of lever arms. Lever arms g, j rigid with the planetary shaft h engage arms f, n respectively secured to the driving- shaft a and to the load wheel w. The leverage is in favour of the load acting through the pair n, j, the arm n being shorter than the arm j, while the arms g and f are equal. A spring m is provided merely to prevent the planetary arms j, from flying out by centrifugal force on disrupted drive. This clutch normally rotates solid, transmitting a steady drive, but on introducing unbalance, the arm n slips under and clear of the arm j and in so doing accelerates the carrier i. As long as the drive is disrupted, the arm j clicks over the end of the arm n. To eliminate this clicking, the arms j, n may be formed as cams, as shown in Fig. 7, which glide over one another. A modification is described comprising a lever-arm train and a separate gear-wheel train upon the same carrier member. The former train has, on the load side, a planetary arm adapted to lock with or click over a driven lantern wheel, and, on the engine side, a pair of gears and an overrunning clutch. The latter train is like one of the trains of the arrangement of Fig. 4 with a lost-motion coupling between the two planet gears. A two-speed gear suitable for motorvehicles is shown in Fig. 13. The improved clutch is of the all-gear form and normally connects driving and driven shafts a, w in direct drive with a one-way clutch 45 in a countershaft reducing-train overrunning. By easing the throttle or engine clutch, not shown, the direct drive is disrupted, and the resistance to acceleration of the carrier i cushions the shock of changing down to the lower speed at which the one-way clutch 45 picks up the drive through a train 40, 41, 42, 45, 46, 48. An additional speed or speeds are obtained by an additional two-speed set or sets in series, there being suitable differences in the gear proportions in sets.