GB1211201A - Improvements relating to vehicle hydraulic brake control valve means - Google Patents

Abstract

1,211,201. Fluid pressure brakes; brake indicators. GIRLING Ltd. 23 Oct., 1967 [23 July, 1966], No. 33230/66. Addition to 1,079,505. Heading F2E and F2F. A control unit for an anti-skid braking system comprises an inertia controlled valve for insertion between a master cylinder and wheel cylinders, a differential piston operating in a stepped bore connected in parallel with the inertia valve and a by-pass valve also in parallel with the inertia valve. As shown in Fig. 2, fluid from the master cylinder enters the valve at 54 and passes via passages 40, 38 and lines 39, 51 to the front brake cylinders. Fluid from the master cylinder can also pass via a deceleration valve 30, and passages 34, 37 to the rear brake cylinders. A further passage between master cylinder and rear brake cylinders is available via the normally-open by-pass valve 44 and the passages 54, 40, 38, 39, 51, 50, 37. When the master cylinder pressure acting on the left hand side of a differential piston 41 is sufficient to overcome the force of springs 42, 43, the piston 41 is deflected to the right, so that spigot 52 allows spring 49 to close the by-pass ball valve 47. When the deceleration is sufficiently great, ball 30 moves to the left, closing the second path between master cylinder and rear brakes. Pressure from the master cylinder now acts on the right hand side of differential piston 41, so that the rate of increase in pressure on rear brake cylinders is less than that on the front brake cylinders. The valve may be inclined rearwardly so that the ball 30 is out of contact with the seating 33 or may be formed with an inclined lower surface to chamber 31. Fig. 3 (not shown) relates to an alternative arrangement in which the by-pass is formed by a passage (66) through the differential piston (41), the by-pass valve (63) being closed when the differential piston 41 is deflected by master cylinder pressure. Brake indicators.-A port 35 is provided for connection of a stop light switch. Fig. 1 shows an alternative by-pass valve in which the head 20 is normally biased away from the seating 22 by a spring 21, permitting flow of fluid from the master cylinder to the rear brakes via ports 25 and 26. When the pressure becomes sufficient to displace piston 18 to the left, valve 20 is closed so that the only communication between master cylinder and rear brakes is via a deceleration responsive valve and a pressure regulating piston in block 13.