Patent GB-964511-A (GB)
Title: Improvements in or relating to clutch operating mechanism for vehicles
Inventor: DAVIES DAVID AUBREY
IPC: B60K23/02
Filed: 1959-09-23
Abstract: 964,511. Fluid-pressure servomotor control systems. AUTOMOTIVE PRODUCTS CO. Ltd. Sept. 5,1960 [Sept. 23, 1959; Dec. 2, 1959], Nos. 32405/59 and 40998/59. Heading G3P. [Also in Division F2] A vehicle clutch is disengaged by a vacuum servomotor controlled by an operator controlled valve means and further valve means are provided which are controlled by an engine speed control device and control the rate of clutch engagement. As shown in Fig. 1 a vacuum operated servomotor 18 has a diaphragm 17 connected to a bellcrank lever 14 which is connected to a clutch throwout lever 12. As shown the clutch is engaged by springs,and to disengage, a pedal 39 is depressed thus raising a diaphragm 32 in a control valve 24 so that a head 36 of a double-headed valve member 34 closes an aperture 33 in the diaphragm and a head 35 uncovers a conduit 28 communicating with a vacuum reservoir 29, so that suction is applied to the working chamber 21 of the servomotor through a conduit 22, a non-return valve 23 in the conduit opening to allow free escape of air from the chamber, and the diaphragm 17 is moved to disengage the clutch. The body of the control valve 24 moves with the bell-crank lever 14 so that the valve head 35 tends to close the suction conduit 28. Thus the rate of clutch disengagement depends on the rate at which the pedal 39 is depressed. The pressure differential in the servomotor also acts on the valve diaphragm 32 so that the operator feels a reaction on the pedal 39 proportional to the thrust acting to disengage the clutch. When the pedal 39 is released,head 35 closes the suction conduit 28 and aperture 33 is opened, and air returns to the working chamber 21 from a port 31 and through the aperture 33. The non-return valve 23 closes and the air has to pass through a further valve means 44, the pressure in a chamber 48 of which builds up and unseats a valve member 52 so that air passes to the working chamber 21. As the clutch starts to engage the pressure differential across the valve member 52 drops and it is seated by a spring 53. Thereafter air enters the working chamber 21 through a restricted aperture 51 to give gradual engagement. During engagement the pressure in chamber 48 acts on a diaphragm 46 which engages the valve member 52 through a thrust rod 57. The other side of the diaphragm 46 is subject to the pressure of a spring 58 and to the pressure in the inlet manifold 55 of the engine. The opening thrust on the valve member 52 is therefore least when the engine throttle valve 59 is closed and greatest when it is wide open, so that seating of the valve member 52 is progressively retarded as the throttle is opened to increase the rate of clutch engagement. In the system of Fig. 2 a clutch 60 is disengaged by a vacuum servomotor 61 having a working chamber 72 selectively open to a vacuum reservoir 81 and to atmosphere under the control of a valve 62 actuated by movement of a gear change lever 63. Application of effort to the gear lever closes a switch which energizes a solenoid controlling the valve 62 so that suction is applied to the working chamber 72. When the gear lever is released the solenoid is de-energized and the suction connection closed. Air flows to the working chamber 72 through a further valve means 83 and the valve 62, and the rate of re-engagement is controlled as in Fig. 1. Specification 964,513 is referred to.