GB1411981A - Flow control valve for a braking system - Google Patents

Abstract

1411981 Tractor/trailer braking systems EATON CORP 16 Dot 1972 [26 Oct 1971] 47595/72 Heading F2F A relay valve 26 for use in a tractor/trailer braking system controls the application of the trailer brakes 24 in the event of pressure in an emergency line 38 falling below a predetermined level. During start-up of the vehicle a compressor driven reservoir supplies compressed air, to an inlet 38 of valve 26 by way of line 38, air then flowing past a check valve 102, passages 94, 72 respectively formed in a check valve assembly 88 and spool 70, passages 69 in a bobbin 64 and port 52 to charge a reservoir 28. As pressure builds up check valve assembly 88 moves rightwardly causing a nose portion 86 to firstly seat against seal 76 thereby closing communication between port 52 and a port 56 leading to an application line 42 and thereafter to unseat seal 76 from a shoulder 80 to establish communication between a port 50 and port 56. To initiate a braking application a treadle valve 16 is operated thereby passing air from reservoir 14 to port 50, and hence port 56 by way of a service line 40. The pressure in application line 44 then operates a valve 30 and air is allowed to pass from reservoir 28 to actuate brakes 24 by way of ports 52, 54, a supply line 44 and valve 30. If emergency line pressure is lost, for example by disconnection of the emergency line after the trailer is parked, a spring 106 shifts check valve assembly 88 leftwardly and spool 70 also moves leftwardly to isolate port 50 from port 56. Thereafter nose portion 86 moves away from seal 76 thereby establishing communication between ports 52, 56 and allowing the reservoir pressure to actuate valve 30 so that the brakes may be actuated through pressure in line 44. Valve 30 is solenoid operated under the control of an antiskid circuit 31 to relieve the braking pressure under skid conditions. In the construction shown in Fig. 3 comprising the subject matter claimed in which the brakes include a spring applied, air pressure released portion emergency actuator valve 26 is fitted with a cartridge 110, having a further check valve assembly 118 which during normal braking permits passage of air to the pressure hold-off chamber 140 of the brake. If the emergency line 38 pressure fails this assembly (118) shifts leftwardly causing a check valve plate 124 therein to engage a projection 132 whereby the pressure in the hold-off chamber is released gradually to cause the brake to be spring applied at the same time as the normal apply pressure in apply chamber 142 of the brake decreases. The claims are directed to the Fig. 3 embodiment of valve 26.