Patent GB-840261-A (GB)
Title: Improved clutch assembly
Inventor: BIRABEN HENRI EMILE
IPC: F16D48/06
Filed: 1957-10-01
Abstract: 840,261. Clutch control; friction clutches. VAUXHALL MOTORS Ltd. Aug. 27, 1958 [Oct. 1, 1957; Jan. 30, 1958], Nos. 30631/57 and 3121/58. Class 80 (2). A centrifugal clutch 2 for a motor vehicle, which can also be disengaged at will (by gear shift) and automatically below a predetermined engine speed by energizing a vacuum servomotor 24, acting through linkage 22 on a clutch release-collar 19, has also a manual override 50 for its engaging masses 6 which permits engagement of the clutch at rest (e.g. for engine braking and push start) by movement of the release collar 19 beyond the normal disengagement position determined by the vacuum motor 24; and in addition the override 50 also opens a valve 49 venting the vacuum motor 24, or the source 28 of vacuum which energizes it. The clutch comprises centrifugal masses 6, Fig. 1, each carried on a bell-crank 3 pivoted on an input casing 1 and having an inner arm 4 thrusting through brackets 12 on a ring 9 which, in pockets 11, carries springs 10 bearing on the presser plate 8 of the clutch whereby centrifugal outward movement of the masses 6 engages the clutch through the springs 10. The clutch can be disengaged at will by manual leftward movement of the release collar 19, which acts on the presser plate 8 through radial levers 18 pivoting on the cover 1. Pivoted on the presser plate 8 are bolts 13 adjustably carrying stops 15 which pass through clearance openings on the arms 4 of the bell-cranks 3. Springs 16 urge the bolts 13 pivotally inwards, but in the normal operating positions of the release collar 19, centrifugal force initially takes the bolts 13 outwards to the position shown, in which the stops 15 lie on the outer sides of the bell-crank arms 4 whereafter the reaction of the main springs 10 hold the stops 15 against the said arms and the stops limit engaging movement of the presser plate 8, thereby preventing engagement of the clutch except by the centrifugal masses. When at rest the manual override 50 is operated to move the release-collar 19 leftwards, Fig. 1, beyond the normalclutch disengaged position, the consequent additional rightward movement of the presser plate 18 releases the pressure of the boltstops 15 on the bell-crank arms 4 whereupon the spring 16 pivots the bolts 13 inwards to a position in which their stops 15 can pass freely through the clearance holes in the bell-crank arms 4, thus permitting the main spring 10 to thrust the presser plate 8 to the clutch-engaged position. In the collar operating linkage, Fig. 5, the clutch release collar 19 is moved right to disengage the clutch by rightward movement of a piston rod 65 of the servo 24 energized through a double valve 26 which is normally conditioned as shown, Fig. 4, with two valves 35, 36 in their lower positions connecting the servo-duct 25 through a chamber 39 and bleed hole 40 to a reservoir duct 27. As the engine reaches a predetermined speed a voltage-sensitive relay 45 is energized by an engine-driven generator 46 to close a switch whereupon a solenoid 38 is energized by the generator, opening the valve 36 and connecting the chamber 39 to an air intake 31 which brakes the vacuum in the servo 24, permitting the piston rod 65 to move left under spring loading which moves the release collar 19 to the clutch-engaged position, and the clutch is gradually engaged by the centrifugal masses 6. Movement of the gear-shift lever 44 closes a touch-sensitive switch 43 energizing a solenoid 37 which raises the valve 35 connecting the servo 24 directly to the vacuum reservoir 28 for clutch disengagement. Override clutch engagement with the vehicle at rest and engine stationary is effected by movement of the inner core 47 of a Bowden cable 50, the opposite movement of the outer sheath of which is first used to open the valve 49 (also in Fig. 6, not shown) to vent the vacuum reservoir 28, whilst the inner core 47 moves the release collar 19 right beyond the normal clutch disengagement position. In Figs. 9 to 11, not shown, the vacuum release valve 49 of Fig. 5 is incorporated in the piston rod of the servo 24.