GB1002091A - Tandem pressure fluid control valves - Google Patents

Abstract

1,002,091. Valves; compressed air brakes. WAGNER ELECTRIC CORPORATION. April 3, 1964, No. 13963/64. Headings F2F and F2V. A reaction piston 79 and a relay piston 72 are moved downward upon depressing a brake pedal so that a valve member 85 closes an outlet chamber 54 from atmosphere; further movement of piston 79 causes unseating of an inlet valve 62 so that pressure fluid from the reservoir 10 flows through chamber 54 and operates slack adjuster 14. Concomitantly pressure fluid in chamber 54 traverses a passage 86 in the stem of valve 62 and enters an application chamber 87 as well as flowing via a line 19 and a ratio-adjusting valve 20 into a ratio chamber 93 whereby the relay piston 72 is independently lowered to first isolate another outlet chamber 35 from atmosphere; further movement of the piston 72 unseats another inlet valve 43 and interconnects a further reservoir 4 to chamber 35 whereby another set of slack adjusters 9 are operated. When the reaction force created by the fluid in chambers 87, 93 equals the manual force on the piston 79 the latter moves up against a metering spring so that the inlet valve 62 is lapped and direct " feel " of the braking effort is afforded the operator; the inlet valve 43 is also lapped by the pressure in chamber 35 acting on the piston 72. Upon removing the manual force on the brake pedal the adjuster actuators 8, 13' are exhausted through ports 40 and 61 and the parts return to the positions shown. Since the effective areas of chambers 87, 93 are equal and opposite to that of the piston 72 in chamber 35 a 1: 1 ratio between the pressure in the branches 2, 3 is realized. Rotation of valve 20 reduces this ratio by venting chamber 93. Failure of one branch 2, 3 does not prevent the other one from operating with appropriate " feel " and a minimum of lost stroke. Valve 20 also provides for sequential operation of each set of brakes. In another form the stem of valve 62 consists of two separate axial parts between which is formed the exhaust valve which controls the venting of chamber 54 to atmosphere.