GB245444A - Improvements in and relating to power actuators or servomotors - Google Patents

Abstract

245,444. Bragg, C. S., and Kliesrath, V. W. Jan. 5, 1925, [Convention date]. Fluid-pressure.-Ina power actuator or servomotor comprising a cylinder and double-acting piston with a connection to a vacuum-producing means, the parts are arranged so that a partial vacuum is maintained at both sides of the piston when it is in the normal inoperative position and the cylinder acts as a storage chamber, actuation of the piston being effected by admitting air to one end of the cylinder. The apparatus is adapted to be connected to the induction pipe of an internal combustion engine and used for operating the brakes of the vehicle carrying the engine. The supply pipe 62 of the servo-motor 1 is connected to a hollow rod 20 to which a brake lever is also secured. The rod 20 is connected by a collar 22 with a tube 20a sliding in the hollow piston rod 5 which is open to the air at 29 and has an eye for the connection of the brake lever. On the rod are two sets of two valves 40 - - 43 co-operating with seats 13 - - 16 in the boss of the piston, with a vacuum chamber 17 and passages leading to the cylinder. Each pair of valves has a central rubber or similar cushioning member 50 which retain the valves on their seats when the control rod is central in the piston. Movement of the control rod results, in consequence of the abutment of the collar 22, in one of the central valves 'being forced off its. seat to place one side of the cylinder in communication with the suction chamber 17 and one of the opposite outer valves also opens up the opposite side of the cylinder to the atmosphere. The seats 14, 15 have springs 51 which are stronger than the cushions 50 so that when the control is central in the piston; the valves 41, 42 will be off their seats and thus place both sides of the cylinder in communication with the suction chamber 17. Instead of the springs 51, the rubber valves 41, 42 may be formed with slight corrugations which provide for leakage except when flattened by pressure upon movement of the control rod. In the normal condition with the piston at the outer end of the cylinder, it is sufficient to open up the right hand side to the left hand side by a valve on the piston or external valve on a coupling pipe which valve is opened by contact with the cylinder or piston respectively when the piston is in the retracted position the outer end. In a modification the suction valves are unseated, in the retracted position, mechanically as by forming free flanges on the central collar which can be moved separately from the main control. Specification 226,514 is referred to.