| 摘要 |
<p>1,252,169. Brake valves. BENDIX-WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. 25 Sept., 1969 [3 Oct., 1968], No. 47139. Heading F2F. In a duct circuit fluid pressure braking system in which an emergency brake is spring applied and fluid pressure released, a valve 46 provides for controlled release of pressure to the brake when a leak develops in the system. Fluid pressure is supplied from reservoirs 10, 14 through conduits 18, 19 to the upper and lower halves 20, 21 of a dual pressure brake valve 22 connected respectively via pipes 24, 26 to the rear and front service brakes of a trailer, the rear brake 27 having a chamber 28 and push rod 30 and including a spring operated brake 32 with a release chamber 34. Fluid passes from pipe 24 to a chamber 97 of valve 46 by way of conduit 100 and port 98, and to chamber 34 from reservoirs 10, 14 past a pressure protection valve 16 and a check valve 12, a parking valve 90, inlet port 87 and cavity 52 a centrally located inlet port 60 and delivery cavity 48. A combined inlet and exhaust valve member 64 engages a seat 62 to disconnect cavities 48, 52 and is urged into its closed position by a spring 84 surrounding a sleeve 76 through which extends a plunger 114 having an upper piston 106 and engaging at its lower end a piston 68. In normal operation a manually or hydraulically operated handle 92 opens a valve 90 to admit fluid pressure to chamber 34 to hold the brakes released. On actuation of valve 21 the brakes are operated, fluid pressure also passing to ports 104 and 98 to equalize pressure acting oppositely on pistons 106, 68. When pressure is lost in pipe 24, valves 12, 16 close and if the valve 20 is actuated the combined downward pressure of fluid acting on pistons 106 and 68 being greater than that acting upwardly on piston 68 causes the latter to move downwardly against the action of spring 70 to close off the inlet port 60 and to cause valve member 64 to disengage seat 66 and partially exhaust pressure in line 36 via chambers 74, 78 and port 80. Spring 70 then causes valve 64 to be engaged by seat 66 again to momentarily trap pressure in chamber 34. On further application of the brakes the piston again moves downwardly and the sequence of opening and closing valve member 64 continues to give controlled application of the emergency brakes. In a further embodiment the service pressure is fed to the underside of the upper piston, and in normal operation the inlet and delivery are disconnected and the inlet and exhaust valves are lapped. In this embodiment the lower piston is made responsive to a selected pressure by means of an adjusting bolt urging the spring.</p> |
