Patent GB-721765-A (GB)
Title: Hydraulically operated clutch and gear change mechanisms for automobiles
Filed: 1952-02-12
Abstract: 721,765. Controlling change-speed gears and clutches. AUSTIN MOTOR CO., Ltd., WEAVING, J. H., PAYNE, E. R., and STUART, D. J. K. Feb. 11, 1953 [Feb. 12, 1952], No. 3661/52. Class 80 (2). In an automobile, gear shifting is initiated by movement of a selector valve which is mechanically linked to a main clutch controlling valve and to a gear executive piston, a hydraulic interlock valve being disposed between the clutch valve and the selector valve to cut off fluid supply to the selector valve and consequently prevent gear changing until the clutch is disengaged. As shown in Fig. I a double acting piston 1 in a cylinder 19 is centralized by springs 40, 41 but may be displaced hydraulically to actuate a gear executive lever 3. A single acting hydraulic piston 4 actuates the disengaging lever 6 of a spring- engaged friction clutch. In the preferred embodiment a driver-operated, steering - column - mounted, gear-change lever has up and down movement to engage the appropriate selector rod in the gearbox and turning movement about the column to actuate a selector valve 20. The valve 20 could, however, be actuated by a speed and torque responsive automatic mechanism. A valve 11 controls the admission and exhaust of fluid to and from the clutch actuating cylinder 8. An interlock valve 27 is normally maintained, by an adjustably preloaded spring 53 and fluid pressure in a space 54, in the position shown where the supply line 35 is cut off from the selector valve 20 but is open to a "holding line" 21. When the piston 1 is in either of its " in gear " positions, i.e. at the extreme right or left of its travel, parts 47 or 48 are open and fluid from the line 21 holds the piston in position with either spring 40 or 41 compressed. When the valve 11 is moved to the position shown pressure fluid is directed from a supply 14 to the cylinder 8 and the clutch is disengaged. Simultaneously the pressure of fluid in a space 60 rises as the clutch disengages until the interlock valve 27 moves against the spring 53, the space 54 being exhausted at 18 through the line 57 and valve 11, until the holding line 21 is exhausted through a throttle valve 33 and the supply line 35 is open to the selector valve 20. The piston 1 is then movable according to the position of the selector valve. A spring loaded ball 61 engages a groove 62 in the valve 27 to prevent oscillations of the valve spindle 28 and piston 1 during a change. The spring 53 is insufficient of itself to move the valve 27 back past the ball 61. After completion of the gear shift the valve 11 moves to an extreme end position whereupon the cylinder 8 and the space 60 are exhausted through a throttle valve 17. A supply line 55 is simultaneously opened to the space 54 and the valve 27 is returned to its interlocking position shown. The valve 20 is located in two " in gear" positions and in a central neutral position, by a spring-loaded ball 63. The rod 2 of the piston 1 is pivotally connected by a link 66 to one end of a lever 65 the other end of which is pivotally connected through a link 67 to the valve 11. A further link 69 having a stationary pivot at one end 71 is pivotally connected both to the link 65 at 68 and, by means of a link 70, to the valve 20. Operation. To initiate a gear shift the selector valve 20 is moved by the driver. The valve 11 simultaneously moves disengaging the clutch after which the interlock valve moves permitting fluid to flow through the selector valve 20. The piston 1 is actuated by this fluid to change the gear ratio and, through the linkage, restore the valve 11 to its initial position consequently exhausting the cylinder 8 and allowing the clutch to engage. The interlock valve 27 is moved during the final part of the movement of valve 11 to exhaust the selector valve 20 and hold the gear engaged by fluid supplied through the passage 21. In a modification, Figs. 8-11 (not shown), a linkage and clutch actuating valve are so arranged that the clutch is engaged in the neutral position of the piston 1 as well as in the " in gear " positions. A spring device may be inserted in the driver's control lever linkage whereby up and down movement of the lever would select a gear ratio and stress the spring which in turn would move a selector fork to engage the appropriate striker member when the actuating piston reached its neutral position. A piston 86 slidingly engaging the clutch disengaging piston 4 may be energized by pressure fluid from a passage 87 to disengage the clutch independently of the gear changing mechanism. The spring 53 is adjustable by a cap 72 to allow gear shifting at an optimum degree of clutch disengagement. Throttle valves 17 and 33 are adjustable to give the required rates of clutch re-engagement and gear-shifting.