| 摘要 |
PCT No. PCT/US80/00321 Sec. 371 Date Mar. 24, 1980 Sec. 102(e) Date Mar. 24, 1980 PCT Filed Mar. 24, 1980 PCT Pub. No. WO81/02768 PCT Pub. Date Oct. 1, 1981.A load check valve is normally employed in association with a double-acting hydraulic cylinder, such as the type used to raise and lower the boom of a construction vehicle. Conventional check valves of the poppet type are difficult to modulate whereas check valves of the spool type generally do not insure leakage control at an acceptable rate during normal operation. The spool-type load check valve (20) of this invention, used in conjunction with additional check valves (60,61), overcomes the latter problem by providing a series of interconnecting passages and chambers (36) for communicating equalized fluid pressure from a cylinder (11) to either end of the spool (27) thereof to provide for minimal leakage. When a pair of such cylinders (11,12) are utilized, the load check valves (20,20') associated therewith are interconnected by a balance line (50) and resolver valves (47') to insure equalization of fluid pressure in the cylinders upon actuation thereof and to further insure a gradual descent of a load carried by the cylinders upon loss of fluid pressure between the check valves.
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