GB1214044A - Brake control assemblies - Google Patents

Abstract

1,214,044. Brake-valve control by master cylinders. LAMBERT BRAKE CORP. 10 Oct., 1968, No. 48090/68. Heading F2F. A brake control assembly having a master cylinder assembly and a control valve assembly located between a high-pressure fluid source and a brake has passages interconnecting the two assemblies and further passages connecting the control valve assembly between the source and the brake; pressurized fluid from the master cylinder moves a valve member of the control valve assembly which then permits some of the high-pressure fluid to flow to the brake until the pressure at it attains a value which is a particular multiple of the pressure of the pressurized fluid, the control valve assembly then automatically isolating the brake from the source, whilst maintaining the pressure at the brake: the valve member has further essential features. Preferably the high-pressure fluid source is a pump. As shown, a pedal 12, Fig. 1, serves to actuate a brake on the right hand side of the vehicle by means of a lever 30, push rod 34, part of a control assembly 16, and a brake line 18. Similarly, pedal 22 serves to actuate a brake on the left hand side of the vehicle. The control assembly 16 incorporates a master cylinder and an associated control valve for each brake, but it has a single reservoir 178, Fig. 4, for the two master cylinders, communicating with an auxiliary supply at 42, and a single inlet for high-pressure fluid at 46 from a pump, not shown. Fig. 7 is part of an unfolded cross-section of control assembly 16 and is orientated in the opposite direction to Fig. 1. In operation, when the left pedal 22 is depressed, push rod 36, Fig. 7, moves piston 92 inwards, causing flow of fluid (derived from reservoir 178) through apertures 218 and passage 212 into a chamber 62 behind a valve member 134. The valve member is thereby moved against the force of a spring 150 into the position shown, where a passage 260 in the valve member is in communication with the inlet 46 for high-pressure fluid. The high-pressure fluid passes from passage 260 along further passages 254, 258 in the valve member and thence along fixed passages 232, 230 to the brake line 26. Thereafter, the pressure builds up in the highpressure line between the pump and the brake cylinder, until a stage is reached where the force acting on the small annular surface 160 of valve member 134 exceeds the force acting on the end wall 154 of the valve member, whereupon spring 150 moves valve member 134 to the right, interrupting communication between passages 260 and 250 and thereby cutting off the highpressure fluid supply. The brake is now isolated from the pump, but the pressure in the brake line between brake and control valve is stabilized. The valve member remains in a stabilized condition until pedal pressure is decreased or further increased. Fig. 8 shows the assembly 16 in an emergency condition where the flow of high-pressure fluid from conduit 46 has been interrupted. When this occurs, the vehicle can be stopped by actuating both brake pedals. Loss of highpressure fluid enables valve members 134 and 164 to be moved further to the left than before, so that fluid from the master cylinder assemblies 14 (not shown) and 24 can flow through the passages 242 (not shown) and 234 respectively to the brake lines (26 being shown). The pressure in the brake lines is equalized by a passage 208, uncovered in this situation, so that the vehicle is stopped without swerving.