Patent GB-628857-A (GB)
Title: Improvements in or relating to actuating mechanism applicable to vehicle brakes and the like
IPC: B60T13/72
Filed: 1947-03-18
Abstract: 628,857. Fluid-pressure servomotor-control systems. SHELTON, H. March 18, 1947, No. 7457. Convention date, March 18, 1946. [Class 135] [Also in Groups XXXI and XXXIV] A servo assisted control mechanism for vehicle brakes comprises a vacuum cylinder, the electromagneticallyoperated valves for which are controlled by a central contact moved by a manual control member and co-operating with contacts that are moved by the piston so as to give a " follow-up action. The suction valve may be caused automatically to oscillate to moderate the application. The vacuum cylinder 38 has a piston-rod 36 connected to the brake pedal by a chain 34. A solenoid-operated valve mechanism is mounted above the cylinder and is controlled by an annular earthed contact 18, Fig. 3, axially movable on the steering column 12 by the telescopic spokes 3 of a manuallycontrolled ring 1 mounted above or below the steering wheel 2, said contact being located normally between further contacts 19 and 20, 21 as shown in Fig. 3. The contacts 20, 21 are slidably-mounted in a housing 23 and connected to the brake pedal by a rod 25, a cranked lever 26 pivoted on the steering column at 27 and a rod 28. Downward axial movement of the ring 1 engages the contact 18 with the contact 20 to energize a solenoid 48 and cause an armature 47 and valve 45 to move against the action of a spring 49 to open the port 44 and so connect the cylinder 38 to the vacuum source to effect actuation of the brake pedal 29. After a limited movement of the pedal to the right a stop 32 on the rod 28 engages the cranked arm 26 and causes it to rock about the pivot 27 with a resulting downward movement of the rod 25 which separates the contacts 18 and 20. The solenoid is thus de-energized and the valve 45 closes so that the brakes are held stationary. Increased braking action is obtained by further downward movement of the ring 1. Smoothness of control is obtained by connecting the contact 20 with the solenoid 48 through a trembler switch 51 attracted by a pole-piece 50 and having contacts 52, 53 normally held in engagement by the spring- loaded rod 56 of a piston 57. Suction in the passage 43 draws the piston 57 to the right and breaks the circuit to the solenoid 48 to cause rapid oscillation of the valve 45. Oscillating movement of the valve is also achieved by connecting a byepass 77 from the suction side of the cylinder 38 to a sealed diaphragm 80 attached to the lower end of the rod 25 to cause make-and-break contact of the contacts 18, 20. A contact 21 is positioned at a lower level than the yieldingly-mounted contact 20 and is connected directly to the solenoid 48 to complete an emergency circuit in the event of failure of the circuit containing the contacts 52, 53. The brakes are released by upward movement of the ring 1 which first disengages the contacts 18, 20 and allows the valve 45 to close and then closes the contacts 18, 19 to energize a further solenoid 64. This solenoid moves a spring-loaded armature 65 and a valve 66 to the right to admit atmosphere to the cylinder 38 through a metering passage 70. Emergency release of the brakes may be effected by a manually-controlled valve 73 which may be connected to the throttle linkage.