Patent GB-1022179-A (GB)
Title: Gear box control mechanism
IPC: F16H63/08
Filed: 1963-05-02
Abstract: 1,022,179. Change-speed control. J. L. GRATZMULLER. May 2, 1963 [May 10, 1962], No. 17403/63. Heading F2D. An hydraulic control system for a changespeed gear arrangement having ratio-establishing clutches selectively engaged by energization of individual hydraulic servos comprises an hydro-pneumatic accumulator 9, charged by a pump 10 from a sump 11 and feeding through a pipe 18 to the servos of series-arranged changespeed gears A ... D, each change-speed gear being controlled by selector valves 14A... 16A &c., conditioned to establish a desired ratio by automatic or manual rotation of a preselector cam drum 17, ratio establishment being obtained by the momentary opening of an electromagnetic valve 12 to supply a liquid pressure signal to the valves 14A . . 16A &c., the preselected valve or valves then opening to open further self-locking control valves and supply liquid under pressure direct from the accumulator 9 through pipes 18A ... 18D to the required servos. Each self-locking valve is of the type which is held in its open position by liquid pressure, e.g. in the servo to which it is connected. Each change-speed gear A &c. has its own interlocked liquid control circuit, which for a gear having two ratio establishing clutches may consist of two ratio-establishing servos 21 1 , 21 2 , Fig. 4 (not shown), fed from the accumulator 9 through the pipe 18 and selflocking control valves 22 1 , 22 2  opened on receipt of a momentary liquid pressure signal through alternatively opened selector valves 14, 15 and the electromagnetic valve 12. The control valves 22 1 , 22 2  are interlocked with each other through valves 23 1 , 23 2  and pipes 24 so arranged that the servo 21 1  can be vented only when the servo 21 2  is connected to pressure, and vice versa. For example, when the servo 211 is under pressure, this pressure is fed through the pipe 24 to the valve 23 2 , accordingly conditioned to its open position for slow release of control pressure applied to the valve 22 2 , which is also thereby opened to vent the servo 21 2 . When the selector valve 15 is opened and the ratio establishing signal is fed through the electromagnetic valve 12 to the control valve 22 2 , the latter is opened by a relatively large flow of liquid and connects the accumulator 9 through the pipe 18 directly to the servo 21 2 . Pressure builds up in the servo 21 2 , as the associated clutch engages, and ultimately opens the valve 231, so that the control valve 221 is in turn opened to vent the servo 21 1 . Thus engagement of one ratio-establishing clutch is effected concomitantly with disengagement of the other. In a form controlling two servos 21, 211, Fig. 5 (not shown), three selector valves 14 ... 16 and three self-locking control valves 22 1  ... 22 3  are provided, each control valve having two vent valves 23 3 , 23 3 <SP>1</SP> &c. opened when either of the other two control valves is closed. Each control valve 22 1  &c. is of the type having by-pass passages 25 1  &c. which feed-back liquid pressure to the valve, after it has been opened, to maintain it in open condition. Each change-speed gear A &c. comprises parallel input and output shaft, Fig. 1 (not shown), with two hydraulically controlled clutches and a ratchet clutch selectively engaged to establish three ratios.