GB425651A - Improvements in vehicle brake mechanism - Google Patents

Abstract

425,651. Fluid - actuated valves. HILL ENGINEERING CORPORATION, Mutual Building, Richmond, Virginia, U.S.A. April 23, 1934, No. 12202. Convention date, April 29, 1933. [Class 135] [See also Group XXXIV] A control valve for fluid-pressure brakes comprises two co-operating valve members, one actuated by the pedal to establish the operative pressure in the brake cylinder or actuator and the other by the pressure in the actuator to follow-up the movement of the first to lap the valve when the pressure established corresponds to the movement of the pedal. The operative pressure in the actuator is arranged to react upon the pedal. A valve for a vacuum brake is shown. The sleeve valve member 55 is actuated by the pedal through lever 104 and rod 99 and is connected to a diaphragm 53 subject on its two sides respectively to the pressure of the atmosphere through port 54<1> and to the vacuum in the brake actuator through passages 25, 109. The co-operating valve member 78 is connected to a diaphragm 72 which is subject on its two sides respectively to the pressure of the atmosphere through port 75 and to the vacuum in the actuator through passage 48. A spring 81 bears on the valve member 78. In the normal position shown, the brake actuator is connected to atmosphere through passages 25, 43, 47, ports 63, 62 in valve 55 and groove 80 in the valve 78. The vacuum source is connected at 38 and initial movement of the pedal to apply the brake registers the ports 60, 61 in valve 55 with groove 79 in valve 78 to connect the vacuum source to the actuator through passages 38, 47, 43. When the vacuum in the actuator acting on the diaphragm 72 is sufficient to bring the brake shoes into contact with the drums, it compresses the spring 81 and the valve 78 moves to the left to lap the valve ports. Further movement of the pedal and valve 55 results in corresponding movement of the valve 78 and the gradual application of the braking pressure. The vacuum in the actuator acting upon the diaphragm 53 reacts upon the pedal to indicate the braking pressure to the operator. The pedal is shown mounted freely upon the brake operating shaft and arranged to engage a lever thereon with lost motion to apply direct pressure to the brakes when desired.