GB1183523A - Improvements in or relating to hydraulic brake pressure control devices - Google Patents

Abstract

1,183,523. Brake control valves; valves. GIRLING Ltd. 14 June, 1967 [11 July, 1966], No. 30967/66. Headings F2F and F2V. In a brake control valve whose outlet pressure at 3, Fig. 1, is reduced relatively to its inlet pressure at 2 as the latter increases, by repeated opening and closing of a valve closure assembly, the assembly comprises a resilient seal 12 and a support member 14 arranged to support the seal against the pressure difference across it during and after closure of the valve, to avoid damage from extrusion or attrition of the seal. As inlet 2 pressure increases, a piston 8 is forced to the left against a control spring 18, a head 9 on the piston forcing seal 12 against a seat 6 to close the valve and the support member 14 is urged by a spring 17 in the same direction to engage the seat 6 before the seal engages it to prevent extrusion of the latter. Further increase in inlet pressure moves the piston to the right, and the cycle repeats. On release of inlet pressure, leakage through channels 11, 16, 19 equalizes the pressures. and the piston returns to the open position. The valves of Figs. 2 and 3 (not shown), are similar to the above, the load-sensitive valve of Fig. 3 having a cap (31) subject to, for example, rear axle loading which acts to assist the control spring (18A). In another embodiment (Fig. 4, not shown) valve closure is effected by a cup washer type of seal (12) being forced into a bore (5), a support member (14) moving with it to engage a shoulder (6) and provide a smooth passage for the seal across the shoulder (6). In another embodiment (Fig. 5, not shown) valve closure is effected by movement of a piston (4) into a stationary seal (12), smooth entry being achieved by arranging inside the seal a support member (34) which is of the same external diameter as the piston (4) and which is engaged by the piston before the latter enters the seal.