Patent GB-408309-A (GB)
Title: Improvements in or relating to clutch operating mechanism for motor vehicles
IPC: B60K23/02
Filed: 1932-10-01
Abstract: 408,309. Operating motor - vehicle clutches. BORG & BECK CO., 6558, South Menard Avenue, Chicago, U.S.A. Oct. I, 1932, No. 27343. Convention date, Jan. 19. [Class 80 (ii).] In engine-suction servomotor gear for operating motor-vehicle clutches, inflow of air during clutch engagement is cut off by a valve which closes automatically on initial contact of the clutch elements, independently of the point in the servomotor stroke at which that contact occurs, further inflow being restricted to that past a valve which is opened responsive to movement of the throttle. The servomotor comprises a chamber 18 with a flexible diaphragm 22 connected by a rod 33 and cable 40 to the clutch pedal 15, the control valve 49 being connected by linkage 56, 64, 62, rockshaft 60, arm 66, balljointed link 68, and rockshaft 71, carried in a swivelling bearing 74, to a crank 84 carrying a roller 83. A treadle 79 is so mounted by hinges 81, 82 that depression of its lower end actuates the crank 84 to raise the valve 49 against a torsion spring 61, while depression of its upper end independently operates the button 77 of the accelerator rod 76. When the valve 49 is so raised, its lower piston 51 masks ports 113, 106 in the valve casing 47 and its its upper piston 50 puts the chamber 18 into communication with the inlet manifold 11 by way of pipes 93, 92, 86 and the space around the valve stem 52, so that the rod 33 is lifted and the pedal 15 rapidly depressed. On release of the valve 49, the pipe 86 is connected to atmosphere by way of the port 113 and a port 114 in a supplementary valve casing 48, the supplementary piston valve 115 having been previously raised to uncover both ports by a pressure-responsive device comprising a flexible diaphragm 122 separating a chamber 129, constantly open to atmosphere by a passage 130, and a chamber 131 communicating by a pipe 90 with the chamber 18, the diaphragm being also pressed down by an adjustable spring 127, which is overcome when the pressure in the chamber 131 is low. When air rushes into the chamber 18, the increased pressure allows the valve 115 to fall and partially cover the ports 113, 114 to an extent determined by the area and speed of descent of the diaphragm 22 and the adjustment of the spring 127. When, on light contact of the clutch elements, the rod 33 is momentarily slowed up, the balance of the determining factors is sufficiently disturbed to cause complete masking of the ports 113, 114. The ports may, however, be of such smaller size that their partial covering by the valve 115 is unnecessary. The movement of the rod 33 is thus stopped, but if now the throttle is opened, the increased pressure in the manifold 11 is communicated by a pipe 97 to a chamber 111 separated by a flexible diaphragm 101 from a chamber 106<1> constantly open to atmosphere, the augmented pressure acting in conjunction with an adjustable spring 109 to lift a valve 104 and allow air to flow to the chamber 18 by way of an aperture 107 and the port 106. The degree of valve opening and hence the rapidity of the final engaging movement of the clutch are dependent on the throttle opening, so that slower engagement occurs when the throttle is gently opened on starting the vehicle in bottom gear than when it is more rapidly opened following a gear change. The further rise of pressure in the chambers 18, 131 depresses the valve 115 to the normal position shown in Fig. 3, where the ports 113, 114 communicate by a leak passage 116 to prevent upward " creep " of the diaphragm 22. Specification 408,308 is referred to.