| 摘要 |
1,158,019. Valves. MASCHINENFABRIK BURCKHARDT A.G. 22 Dec., 1967 [12 Jan., 1967], No. 58436/67. Heading F2V. [Also in Division F1] Safety valve for relieving excess pressure comprises a stepped piston valve member 3 slidable in a housing 2 and controlling flow from an inlet 1 to an outlet 10. The valve is moved to closed position manually by an actuator 20, 21 and loaded therein by air pressure supplied through a reducing valve 6 and restriction 7. Movement to the left owing to the area difference of lands 3a, 3b exhausts the loading pressure through the hollow interior of the valve member past a seat 8 and the valve quickly opens. A rubber abutment ring 24 reduces shock. In modifications, the seat 8 is replaced by an adjustable fixed piston (11) or cup (25) to variably retard opening. In another modification, excess pressure at either end of a doubleacting hydraulic cylinder is relieved to the opposite end by a piston valve member formed with three stepped lands (15, 16, 17), Fig. 4 (not shown), the difference in area between the respective outer lands and the middle land being the same and the said ends being connected on opposite sides of the middle land. |
