GB1441901A - Valve assembly for an anti-skid braking circuit - Google Patents

Abstract

1441901 Anti-skid braking systems SOC ANON DBA 3 Jan 1975 [15 Jan 1974] 303/75 Heading F2F In an anti-skid braking circuit with a pneumatic three-way valve relay 12 controlled by a pilot chamber 24 in response to a pneumatic (Fig. 1) or hydraulic (Fig. 2) valve assembly 32, the assembly 32 comprises a housing with an inlet 46 connected to an operator control 30, an outlet 48 to the pilot chamber 24 and a discharge outlet 74, the inlet 46 and outlet 48 being connected by a first passage including a chamber 51 with a differential pressure responsive isolating valve member 50 and a second or by-pass passage 64, 70, 49 including restrictions 66, 72 and a working chamber 52. A third passage 92 including a relief chamber 54 between the outlet 48 and the discharge outlet 74 is controlled by a relief valve member 88 which is openable by a solenoid valve 76 in response to an incipient skid condition when it seats the isolating valve member 50 through an abutment 90 and a valve member 82 between the chambers 52, 54. Figs. 1 and 2 show the normal braking condition but in an incipient skid condition the valve member 88 is shifted to the left closing the isolating valve member 50 and opening the discharge orifice 74 when the pilot chamber 24 is relieved through the orifice 48, the passage 92 and the chamber 54 and through the passage 70 and chambers 52 and 54 as the spring 98 holds the piston 56 from the valve 82. The rate of relief and brake pressure is determined by the constrictions 94 and 72. On de-energizing of the relief valve 76 the discharge orifice 74 is closed by the closure member 88 and the spring 98 pushes the piston 56 against the valve 82 separating the chambers 52 and 54 to provide in intermediate braking phase during which the pilot chamber 24 is replenished through the duct 64, adjustable constriction 66, chamber 52 and line 70. When the pressure in the chamber 52 has risen sufficiently the piston 56 is moved to the right with the valve member 82 and attached isolating valve member 50 when the full pressure is applied through the outlet 48 again. The line 70 may be eliminated to maintain the pressure during the intermediate phase if desired. In Fig. 2 the pilot chamber 24 is provided with a spring-loaded wall 102 to effectively increase its volume to prevent the pilot-pressure from dropping abruptly at the end of the relief phase.