GB529607A - Improvements relating to hydraulic control mechanism - Google Patents

Abstract

529,607. Hydraulic brakes. PRATT, J. H., MANLEY, G. E., and GIRLING, A. H. G. June 5, 1939, No. 16401. [Class 103 (i)] Relates to hydraulic control mechanism comprising a master cylinder incorporating a valve mechanism which permits communication between the liquid reservoir and the master cylinder when the master piston is returned to its initial position after a control operation but which cuts off communication between the reservoir and master cylinder immediately a control movement is initiated. In order that closing of the valve mechanism may not be prevented by dirt &c. in the liquid one or other of the co-operating parts of the valve is formed of a soft and resilient material such as rubber and the movable valve element has a relatively large acting surface; a spring for continually exerting a closing influence on the valve is made insufficiently strong to overcome the influence of atmospheric pressure on the acting face of the valve. In the construction shown in Fig. 1, the closed end of the master cylinder 3 communicates with the reservoir through an axial passage 3a controlled by a soft rubber valve head 5 with a concave acting face 5a, the valve head being contained in a cage 10 against the top of which the valve-closing spring 11 bears. The valve head 5 is carried on a stem 6 with an enlarged head 6a working in an axial hole of the master piston 7, the closing cap of the axial-hole abutting against the head 6a when the piston 7 returns to the out-of-action position as shown and lifting the valve head 5 off its seat. In another embodiment of the invention the open portion of the master cylinder is placed within the reservoir, the controlling valve and its port being at this end of the cylinder and a link and crank arm for actuating the piston being also within the reservoir.