GB1527902A - Skid control system - Google Patents

Abstract

1527902 Antiskid braking systems EATON CORP 16 Sept 1975 [26 Sept 1974] 38082/75 Addition to 1389845 Heading F2F A pressure modulating valve assembly 30 allows a rapid exhaust of brake pressure from a brake cylinder 14 when a sensor 40 detects an incipient skid followed by a rapid rise to a lower pressure than at first (see K in Fig. 6) followed by a further increase at a reduced rate on subsequent brake application. To this end the assembly 30 includes a relay valve 70 with a first piston portion 78 responsive to control pressure in an inlet chamber 44 and the opposed brake or outlet pressure in a chamber 46, a second piston portion 89, preferably of the same effective diameter as the first portion 78, responsive to a bias pressure in a chamber 52, and an opposed compensating pressure in a chamber 50 which communicates with the outlet or brake pressure through passages 98 and 99 and a valve 100 with a bleed hole 104 in parallel to a dump valve 108. This opens at a predetermined pressure differential to limit the differential between the chambers 46 and 50. In the absence of skidding the piston part 78 acts as a normal self-lapping relay valve, biased by a spring 90, in response to a control pressure from a drivers valve 24 communicated through an open modulating valve 62. Control pressure air passes through an orifice 97 and passage 96 to raise the bias chamber pressure to the control pressure. The spring 92 maintains the second piston portion 89 against a stop 94. In the skid mode the solenoid valve 62 closes the passage 58, which, while allowing the bias chamber pressure to increase, exhausts the chamber 44 through passage 60 and an exhaust port 68 allowing the piston portion 78 to rise and exhaust the brake cylinder through exhaust passage 122. On reapplication of the brakes the bias chamber pressure acting below the piston portion 89 is effective to close the inlet valve at successively lower pressures than before, the subsequent low rate of pressure rise (from the knee K of Fig. 6) occurring as the compensating chamber pressure differential bleeds through the valve 100 to the chamber 46.