| 摘要 |
<p>1505417 Fluid pressure brakes; valves DEERE & CO 2 May 1975 [3 May 1974] 18378/75 Headings F2F and F2V A spring-loaded vehicle brake actuator 42 is released by fluid pressure from a pump 44, transmitted through valve 112 and line 146, when either of the service lines 54, 56 to a reversible motor 26 is pressurized. The valve 112 normally vents the brake actuator through bore 142 and exhaust 138. Pressure applied from service line 54 or 56 passes a shuttle valve 110 and at a first pressure lifts the ball 130 from its seat 132. The larger area of piston 148 is then available, and the valve will stay open, releasing the brake, until the service pressure falls to a lower pressure than the first pressure. The supply to the motor 26, which may drive one track of a track-laying vehicle, is controlled by a pair of poppet valves 62, 64, one for each service line. When e.g. the service line 54 is pressurized, pressure on the valve face 100 opens the valve seats 76, 78. Exhaust fluid passes through a bore 101 of the valve 64 and between ports 92, 90 of a counterbalancing valve 68 which is opened by the application of pressure from service line 54 to a pilot piston 84. When the motor 26 tends to overrun, e.g. downhill with low service line pressure, the valve 68 closes, pressure across the piston of the valve 64 equalizes because of the opening 101, and the valve 64 closes until pressure builds up in the service line 54 sufficient to open the valve 68.</p> |
