| 摘要 |
<p>962,139. Valves. PARKER-HANNIFIN CORPORATION. Aug. 23, 1961 [Aug. 26, 1960], No. 30441/61. Heading F2V. The body of a sliding control valve has a bore 3 intersected by chambers 5, 9, 10, 14, 15, 18, 19, 20, chamber 5 being connected to supply, chambers 14, 15 to a doubleacting ram 54, chambers 10, 18, 19, 20 to a return passage 12, whilst chambers 5 and 9 are interconnected via a check valve. The chamber 5 is also provided with an adjustably spring-loaded relief valve, the discharge from which is led to chamber 18. A spool 4 slidable in the bore 3 has lands 31, 32A and 32B, 33A and 33B, 34, a spring centring means 35, and a ball detent-mechanism for holding the spool in a " float " position to the left of its neutral position; lands 31, 33B and 34 embody metering notches. In the neutral position chambers 14, 15 are prevented from communicating with chamber 9 by lands 32A, 32B and the supply chamber 5 is open to the return passage 12 via chamber 10. The spool is centred upon release of the actuating handle after each extension or retraction of the ram 54. In the " float " position chambers 5 and 10 are still in communication and land 32B prevents chamber 9 opening to either chamber 14 or 15. Inside the spool is check valve 5 which is unseated by the fluid displaced from the head of the ram 54 as the piston of the latter moves downwardly under the weight of the member operated thereby e.g. a dump truck body, the fluid passing from chamber 14 through radial passages 66 and an axial passage 67 in the spool to the rod end of the ram via chamber 15 and radial passages 68 so keeping that end of the ram filled with fluid. Excess fluid from the head end of the ram is returned to the passage 12 by orifices 69 in land 33B. A further detent mechanism may be provided to hold the spool in its other operating position; means not shown may be employed for automatically releasing the detent in response to a given pressure in the system or to a given position of the ram piston.</p> |
