Patent GB-998561-A (GB)
Title: Improvements in or relating to change speed gearing
IPC: F16H61/02
Filed: 1962-11-05
Abstract: 998,561. Controlling epicyclic change-speed gearing; friction clutches. ATELIERS DE CONSTRUCTIONS MECANIQUES DE VEVEY S.A. Nov. 5, 1962 [Nov. 17, 1961], No. 41726/62. Headings F2C and F2D. A change-speed gear comprising gear trains engaged by fluid pressure servo-operated friction clutch devices for change of ratio and for change of direction from neutral has at least one distributer for distribution of the fluid to the servomotor. A tractor drive comprises an engine 8 driving a direct, reduced forward and reduced reverse epicyclic gear 3, 5, 7 through countershaft gears a, b, c, d, and clutches 1, 2, the output from the forward and reverse gearing passing through a two-speed epicyclic gear 4, 7 to a differential 12 and wheels 15a. The clutches 1, 2 and the direct drive clutches, 3, 4 of the epicyclic units which are similar, have input 21 and output shafts 22, Fig. 2, connectable by a stack of clutch plates 31, 32 splined to output and input members rigid with the shafts. The plates are engaged by fluid pressure acting in a sliding cylinder 26 against an axially fixed piston 29 against release springs 28. Cushioning of clutch engagement is obtained by bleeding fluid from the cylinder through a passage 34 leading to concentric holes 35, 36 in the clutch plates. As the plates near synchronism the flow through the holes decreases and allows build-up in the actuating chamber 20. Excess fluid lubricates the clutch. The epicyclic gear 4, 7 (Fig. 4), provides direct drive between shafts 49, 45 on engagement of the fluid-operated clutch plates 48 and reduced drive on engagement of a fluid pressureoperated band brake 7 to arrest the ring gear L of a three element epicyclic gear having a run M, stepped planets j, k and output planet carrier 44 on the shaft 45. The direct and reduced forward and reverse epicyclic gear 3, 5, 6 (Fig. 6), provides direct, drive between shafts 69, 65 by engagement of the fluid-pressure clutch 61, 68; reduced forward drive by engagement of a band brake 5 to arrest a ring gear g of the gear having a sun gear e, interengaged planet gears f 1 , f 2  on output planet carrier 66 and a second sun gear h which may be held by brake 6 for reverse. Eight forward speeds, neutral and four reverse speeds may be obtained by selective engagement of the fluid-pressure clutches and brakes under the control of a multiport rotary valve 83 distributing fluid from a bore 87 to the appropriate clutch device through passages 1-7, and connecting the remainder of the clutch devices to exhaust through a passage 86. In a modification, two rotary valves may be used for speed change and direction change respectively, it being possible to select any speed ratio on one valve and engage that ratio in forward or reverse from neutral on the other valve. In another embodiment, the rotary valves may be replaced by solenoid-operated ball valves 1-7 (Fig. 10a), controlled through a circuit providing a forward, neutral, reverse controller A, a speed ratio control B for forward speeds and a speed ratio control C for reverse speeds. This allows the engagement of any ratio forward or reverse ratio pre-selected on controls B or C by movement of the controller A. The solenoid-operated ball valves 118 (Fig. 11a may be mounted in pairs in a housing 110 containing two hydraulically interlocking shuttle valves 112a to prevent simultaneous engagement of two ratios by pressure build-up in chambers 119. In another embodiment (Fig. 12), an acoustic ratio change may be made by high and lowfrequency whistle signals received by a microphone 132 feeding low and high-pass filters 134, 135 to actuate relays 140, 141 controlling the forward, neutral, reverse switch 142 corresponding to the controller A of the embodiment shown in Fig. 10a.