Patent GB-846318-A (GB)
Title: Improvements in or relating to clutch operating mechanism for motor vehicles
Inventor: BLAND ALBERT NORMAN
IPC: F16D48/06
Filed: 1957-10-31
Abstract: 846,318. Clutch control. AUTOMOTIVE PRODUCTS CO. Ltd. Oct. 28, 1958 [Oct. 31, 1957], No. 34047/57. Class 80 (2). Operating mechanism for a vehicle clutch of the combined spring and centrifugal weight type, with the springs acting between a coverplate or other fixed abutment and a reactionplate, and the centrifugal weights acting between the reaction and pressure-plates, comprises release-levers acting on the reaction-plate and a release bearing 10 co-operating with the release-levers, the bearing 10 being connected through liquid-pressure means including master and slave piston-cylinder units 16, 17 and 21,19 to a power-actuating device 13 for releasing the clutch, the units having a stroke sufficient to move the clutch reaction plate from a position in which the clutch is fully engaged by its springs to a position in which it is fully released, and means to trap liquid in the slave cylinder and thereby limit movement of the clutch reactionplate to prevent engagement of the clutch by the springs alone. In the arrangement shown in Fig. 1 the power device 13 consists of a vacuum servomotor controlled by a solenoid valve 51, and the slave cylinder 21 incorporates a trap valve 22 seated by a spring-loaded pin 27 carried by slave piston 21, and unseated by a second pin 33 carried by a diaphragm 34, the chamber 35 of which may be placed, through a pipe 36 and a solenoid change-over valve 38, with an atmospheric port 43 or a vacuum source 42. An engine-driven governor 49 controls electric contacts 48 operating valve 38, and further contacts 55 in series with contacts 56 controlled by movement of diaphragm 34. Valve 51 is operated through a circuit including a battery 46 and a main or ignition switch 47, the circuit being completed through either of two .parallel circuits, the first of which includes the gear-change switch 54, while the second includes contacts 55, 56. With the vehicle stationary or moving at a speed below that at which governor 49 opens contacts 48, 55, the system is in the condition shown, valve 22 trapping liquid between itself and slave piston 21, thereby preventing movement of lever 11 and release bearing 10. When the speed exceeds this value valve 38 places chamber 35 in communication with vacuum and valve 22 is unseated to release the trapped liquid and allow spring engagement of the clutch independently of the centrifugal weights. Simultaneously contacts 56 are closed, so that if the speed falls below the selected value closure of contacts 55 causes operation of valve 51 and servomotor 13, to release the clutch. Subsequent closure of contacts 48 results in de-energization of servomotor 13 and the clutch moves towards the engaged position, until valve 22 is closed by pin 27, the clutch thus being held in position for centrifugal engagement. In a second embodiment, Fig. 2 (not shown), trapping of the liquid is controlled externally of the slave cylinder by a floating piston 62 in a cylinder mounted between the master and slave cylinders and bypassed by a conduit 64 controlled by a solenoid valve 65 operated by the contacts 48. The means for controlling re-engagement of the clutch after its release by servomotor 13 may be as described in Specifications 715,746 and 715,747.