GB1389005A - Fluid valves - Google Patents

Abstract

1389005 Controlling fluid pressure brakes HOPE TECHNICAL DEVELOPMENTS Ltd 26 May 1972 [5 March 1971] 6102/71 Heading F2F A brake control device for use for example with an anti-jack knife device such as that disclosed in Specification 1,075,802 comprises a housing 10 containing a regulator valve 18 having its outlet connected to the inlet of a control valve 14 the outlet of which is connected to the anti-jack knife device, the inlet of the control valve 14 receiving working fluid with the pressure at the outlet being dependent on the control signal applied to the device so that during operation a residual pressure prevails in the control valve inlet in the absence of a control signal such pressure being less than the maximum pressure of the working fluid but being sufficient to operate the anti-jack knife device. A double piston 12 disposed in a cylinder 11 has a rod 13 forming a spool valve 14 biased by a spring 30 and a second double piston 20 in a cylinder 15 is separated from a piston 16 by a spring 17 the piston 16 receiving the end of a plunger 47 operating valve 18. Each cylinder has an inlet channel 19, 19<SP>1</SP> which can receive a pneumatic auxiliary pressure signal and an inlet 21, 21<SP>1</SP> which can receive a pneumatic service pressure signal. A further inlet channel 22 constantly exposed to compressed air at about 120 p.s.i. extends into the inlet of valve 18, the arrangement being such that leakage air passes through the valve and pressurized air at about 40 p.s.i. enters the chamber 80 and acts against the inner face of piston 16. A further channel 24 extends from chamber 80 to an inlet 70 of valve 14. When valve 18 is nominally closed there is thus a residual pressure of about 40 p.s.i. in the channel 24 which can be applied to the anti-jack knife device.