GB540145A - Improvements in and relating to fluid pressure servo-operated devices - Google Patents

Abstract

540,145. Fluid-actuated valves. ASSOCIATED EQUIPMENT CO., Ltd., and PRIDDLE, A. T. C. April 5, 1940, No. 6192. [Class 135] [Also in Group XXXIV] A fluid-pressure servo system, particularly applicable to wheeled vehicle braking systems, including a manual or pedal control member and one or more pressureoperated members applying the operating effect is provided with means for grading the operating effect in such a way that it increases at a comparatively slow but steadily increasing rate during one part of the travel of the control member and increases at a steadily increasing higher rate during another part of the travel of the control member. In the servo-braking device shown a lever operated by a pedal acts upon the upper end of a variable-rate spring 1 by means of a member 2 guided in a casing 3 and a piston 4 is depressed against the action of a uniform-rate spring 5 by the lower end of the spring 1 to close an exhaust valve 6 and later to open a main valve 7 against the pressure of a spring 9 to admit pressure fluid through a port 71 to the brake-applying members by way of passages 18 and port 8 ; the valve 7 is connected for actuation to the valve 6 by members 10 and 11, carried by pistons 14 and 16 respectively, with a lost-motion connection 12. The admitted pressure raises piston 4 against the opposition of spring 1 so that the valve 7 is shut, the upward motion of the piston being opposed by the spring 1 and the brake pressure held until release of the pedal-operated lever allows the piston 4 to move upwards again until the springs 1 and 5 balance and the exhaust valve 6 opens. Specification 515,440, [Group XXXIV], is referred to.