GB1207573A - Improvements in and relating to fluid pressure operated servo motors - Google Patents

Abstract

1,207,573. Fluid-pressure brakes. AUTOMOTIVE PRODUCTS CO. Ltd. 14 Nov., 1968 [22 Jan., 1968], No. 3264/68. Heading F2F. In a fluid pressure operated servomotor for providing power assistance for fluid pressure braking systems, a casing 10 is divided into two chamber portions 13, 14 by a movable dividing member in the form of a diaphragm 15 and valve means 18 are carried by and movable with the moving dividing member such that the valve comprises a first valve closure member 43 (Fig. 2) co-operating with a seating 42 in a valve chamber 30, a second valve closure member 48, 49 co-operating with apertures 38 in a movable wall 31 of the valve and thrust means 45 interconnecting the valve closure members such that when the servomotor is operated the second valve closure member closes the apertures in the movable wall and the first valve member 43 is unseated so that the first and second chambers of the servomotor are interconnected as shown in the inoperative position of the servomotor shown in Fig. 1. In operation, when the operator depresses the brake pedal (not shown), the push rod 35 is moved to the right to close the first valve closure member 43 against its seat 42 to close off the interconnection between the chamber 13 and the chamber 14 of the vacuum-suspended servomotor. Continuing movement of the valve stem 32 allows the second valve means 48, 49 to be lifted off its seating against the movable wall 31 of the valve and atmospheric air is transferred via the apertures 38 and passageway 41 to the chamber 14 to allow the servomotor to operate and actuate the second push rod 53 to operate a master cylinder (not shown) to apply the hydraulic brakes of the vehicle. In an alternative embodiment (Fig. 3, not shown), the sealing member 43 includes a flexible diaphragm portion, the inner edge of which engages a groove (58) in the stem 32. Provision may be made for providing for the transmission of a reaction thrust to the operator proportional to the thrust exerted on the servomotor and this may be achieved by the provision of lever means 61 engaged by a cylindrical rim 64 carried by the output thrust member 53, as shown in Fig. 4.