443,039. Operating clutches. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. Sept. 24, 1934, No. 27354. Convention date, Sept. 23, 1933. [Class 80 (ii)] In a fluid-pressure servomotor for operating the clutch of a motor - vehicle under the control of a valve, further valve means are provided for selectively varying the clutch disengaging stroke of the servo piston so as to be alternatively short or long at the will of the driver. Slide valves 78 and 80, Figs. 5, 8 and 9, are arranged in bores in a casing 76, the valve 78 being connected to the accelerator 90, Fig. 1, and the valve 80 being controlled by manually-operable Bowden mechanism 82 so as to occupy any one of three positions. With the valve 80 in the first position shown in Fig. 5, the left-hand end of the servo cylinder 50 is, upon release of the accelerator, put into communication with the engine intake manifold 74 through a port 104 in the end of the cylinder 50, a conduit 108, a port 100 in the casing 76, an annular recess 112 and a longitudinal groove 114 in the valve 80, a passage 116 in the casing 76, an annular recess 118 in the valve 78, a port 94 in the casing 76, and a conduit 96, whereby the servo piston 54 is drawn fully to the left to retract the clutch presser plate 28, Fig. 2, through the piston rod 56, arm 58, slidable collar 60 and radial levers 62. Upon initial depression of the accelerator, the valve 78 moves to the left to close the port 94 and bring the passage 116 into communication with a longitudinal groove 128 in the valve 68, which groove is in communication with a port 106 in the side of the cylinder 50 through a conduit 110, a port 102 in the casing 76, an annular recess 124 in the valve 80, and a passage 126 in the casing 76. The lefthand end of the cylinder is thus put into communication with the right-hand end, which is open to the atmosphere through a port 120, and the piston 54 moves rapidly to the right under the action of the clutch springs until the port 106 is closed by the piston, when its movement is arrested, in which position the clutch remains just out of engagement. Upon further depression of the accelerator, the valve 78 moves further to the left to open a passage 132 in the valve 78 to an air inlet port 98, the passage 132 leading from the groove 128, and the piston thus completes its engaging stroke at a slow speed determined by an adjustable bleed valve 138 controlling the passage 132. With the valve 80 in the second position shown in Fig. 8, the port 100 is blocked. Thus, upon release of the accelerator, the port 106 is put into communication with the manifold 74 through conduit 110, port 102, annular recess 140 in valve 80, groove 114, passage 116, recess 118, port 94, and conduit 96, and the piston moves to the left only until it closes the port 106, when its movement is arrested. Upon depressing the accelerator to open the passage 132, the piston moves to the right at a speed determined by the valve 138. With the valve 80 in the third position shown in Fig. 9, the servo is inoperative, the passage 116 being closed and the port 100 being opened to atmosphere, and the clutch is then controlled only by the customary pedal 68, which co-operates with the collar 60 through links 70. The foot-shaped shanks 42, Fig. 2, of weights 40 may extend through the presser plate 28, which rotates with the driving flywheel 20, into engagement with a ring 34 which rotates with the plate 28, is urged towards the latter by springs 44, and is interposed between the plate 28 and the driven plate 22, whereby the centrifugal action of the weights augments the action of the clutch springs above a critical speed. In this case, with the valve 80 in the position shown in Fig. 5, the weights are, when the accelerator is released, ineffective to produce clutch engagement, but, on depression of the accelerator, the effect of the weights precedes that of the clutch springs ; with the valve 80 in the position shown in Fig. 8, however, the weights are, when the accelerator is released, still effective to produce engagement above the critical speed. A lockable free-wheel clutch 18, Fig. 1, may be arranged between the gear-box 14 and the propeller shaft 16.