GB1389845A - Relay compensator valve - Google Patents

Abstract

1389845 Antiskid braking systems EATON CORP 16 March 1972 [17 March 1971] 12239/72 Heading F2F A pressure modulating valve 30 for use in an antiskid braking system allows a rapid exhaust rate from a brake cylinder 14, when a skid is detected by a sensor 40, and an initially rapid rise in pressure to a level lower than the previous maximum pressure and a second stage rise in pressure at a substantially lower rate on brake reapplication. On operation of a treadle operated valve 24 air passes from an air reservoir 22 to a control chamber 52 via passages 72, 74 an open three-way solenoid valve 50 and a passage 76. During normal braking valve 30 acts as a relay and with valve 50 open the pressure in chamber 52 acts downwardly via a diaphragm 44 on a primary piston 78 causing a seal 88 to be unseated from a lip 90 allowing air to pass from the reservoir 22 to a chamber 54 via chamber 56, and then to the brake cylinder 14. As pressure builds up in chamber 54 the differential pressure across diaphragm 44 is equalized and a spring 93 causes piston 78 to move upwardly and re-seat seal 88. The brake pressure therefore rises in stages as valve 24 is progressively opened. Antiskid operation.-During brake application if the brake pressure overshoots that required for wheel lock wheel lock sensor 40 transmits a signal to solenoid valve 50 which closes communication between reservoir 22 and chamber 52 and opens the latter to exhaust. Pressure in chamber 54 forces diaphragm 44 apart from piston 78 allowing air to be discharged through orifices in a disc portion 86 of piston 78 and via passage 76 to exhaust. The pressure in a chamber 58 is also discharged through passage 102, an orifice and check valve assembly 48 comprising a washer 104 having an orifice 106, passage 100 and chamber 54. A pressure imbalance across a disc portion 97 of a secondary piston 80 is thereby created as pressure continues to build up in a chamber 60 through orifice 116 and passage 118 causing secondary piston 80 to move upwardly so that seal 88 is seated. The wheel then commences to reaccelerate and the solenoid valve 50 is released thereby reapplying brake pressure very rapidly. The pressure in chamber 54 then causes piston 78 to move upwardly and seat seal 88. The next stage of brake pressure rise occurs at a substantially slower rate since the bleeding of pressure into chamber 58 through orifice 104 reduces the pressure differential across diaphragm 46 so that the piston 78 is moved downward slightly to allow air to bleed from high pressure chamber 56 through passage 84 into chamber 54 the rate of rise in which is determined by the pressure rise in chamber 58. The brake pressure will thus rise slowly until the skid sensor 40 again detects wheel lock and the valve will be recycled.