Patent GB-453293-A (GB)
Title: Improvements in or relating to change-speed devices
IPC: F16H61/02
Filed: 1935-05-17
Abstract: 453,293. Change-speed gearing. PAVESI, U., 2, Via Palestro, Milan, Italy. May 17, 1935, No. 14522. Convention date, May 23, 1934. [Class 80 (ii)] Four forward and two reversed speeds are obtained from two epicyclic trains arranged in series, with their planet-carriers 4, 17 in invariable driving connection, by a cone friction clutch and brake 8, acting on a loose sunwheel 7 of the first train, and a synchronized positive clutch and brake 25, acting on a loose sun-wheel 24 of the second train, which latter is provided with an additional loose sun-wheel 23, locked for reverse by a positive detent, acting radially on a toothed disc 37 connected with the sun-wheel 23. The annulus 2 in the first train is integral with the driving shaft 1 and forms one element of the friction-clutch, the remaining sun-wheel 22 of the second train being rigidly connected to the driven shaft 3. The synchronizing arrangement in the second train comprises conical frictionsurfaces 32 for the positive brake 28, 29, and similar surfaces 31 between the two sun-wheels 23, 24, which latter surfaces tend to clutch the train solid before this is effected positively by engagement of the claw-element 26 with a toothed disc 27 on the planet-spindle. Synchronizing pressure is produced by a spring- loaded ball detent 34, the sun-wheel 24 being capable of slight axial movement, and carrying the claw-element 25 splined on its boss. Control may be manual or automatic. In the former case, preselection may be effected by using a pedal-control for the friction-cone 8, and a hand control for the positive-element 25 ; or in Fig. 9 (not shown), a single rotary cam-drum may control the positive-element directly and the friction cone through springs. The control-gear may act through solenoid or other electric means, or fluid-pressure or vacuum motors, or electric means for the positive-element and fluid-pressure for the friction - cone. The pressure - fluid may be supplied either by an air or liquid compresser, or by pressure-gas from the cylinders of the driving engine. In Fig. 1, fluid-actuated plungers 52, 53 and 55, 56 act in opposite directions on the friction-cone 8 and positiveelement 25 respectively, the cone 8 being actuated against a double-acting spring 49, which automatically neutralizes the gear when the fluid-pressure is relieved. A separate plunger, Fig. 2 (not shown), acts on the reverse detent. The fluid-pressure is controlled either by a multiple distributing-valve or by a series of cam-controlled piston-valves 67, Fig. 5, arranged at varying radii, corresponding to concentric cam-faces 74, 75, 76 on a rotary disc 77, which selectively moves the valves axially, against spring-pressure 78, so as to cut off communication between selected fluidducts 53<1> and the pressure-inlet 70, whilst simultaneously exhausting them at 72. Neutralization is effected at any time by leftward movement of a lever 79, which exhausts both power-cylinders 52, 53 of the friction-cone 8, and may be controlled by a pedal, replacing the usual clutch-pedal on a vehicle, and interconnected with the accelerator-pedal, so that release of the latter automatically neutralizes the gear. The friction-cone 8 is arranged to close after, and open before the positiveelement 25, by suitably designing the multiple distributing-valve or the selector-cam 77, and the size of the pressure cylinders and ducts. In the semi-automatic control shown in Fig. 3, upward changes of the selector-cam 77 are effected only automatically under the joint control of an engine-driven centrifugal governor and the position of the accelerator-pedal, downward changes being effected only by a complete downward stroke of the accelerator-pedal, which is possible only below a predetermined engine-speed. Connected with the selector cam-disc 77 is a ratchet-disc 80, urged in the clockwise direction, for upward changes, by a spiral spring 107, Fig. 5, and locked in steps by a double pawl 81, Fig. 3, which is released bv downward movement of a plunger 83, having a cam 85 engaging the pawl. A second pawl 86 ensures that the ratchet-disc 80 only moves one step at a time. The cam-plunger 83 is urged downwardly by the engine-driven centrifugal governor, acting through a lever 84, and is turned, to modify the action, by the accelerator-pedal, acting through a lever 94, cord 93 and pulley 92. The lever 94 is formed as a bell-crank, the other part of which bears at 91 on a plunger 87, carrying a pin 88, engaging the ratchet-disc 80, so that a complete downward stroke of the accelerator-pedal steps the ratchet-disc once in the downward direction. Such a downward stroke is positively prevented above a predetermined engine-speed by the conical end of the governor-controlled plunger 83, which advances a locking-plunger 96 obstructing a shoulder on the plunger 87. The latter may be operated through an electric or fluid-pressure servo.