| 摘要 |
A vehicle convertible top (16) is moved by hydraulic cylinders (29) between extreme raised and lowered positions. The cylinder ends are connected (26, 28) to ports (60, 60') in a reversible hydraulic pump (36) in one end of an elongated housing (34), which has a reservoir (40) in the other end, separated by a pump cover (42). The pump cover (42) houses two fluid circuits (60-88 and 60'-88') connecting the pump (36) to the ends of the cylinders (29). Each circuit has an end of cycle hydraulic locking device (78, 80, 98 and 78', 80', 98') comprising a normally-closed valve (78, 80 and 78', 80') and a valve actuator (90 and 90'). The circuit valves (78, 80 and 78', 80') are alternately opened by pump pressure to pressurize one end of the cylinders (29) to alternately raise and lower the top (16). The opened valve (78, 80 or 78', 80') closes when the pump (36) ceases operation, preventing fluid backflow through that circuit to the pump (36). This hydraulically locks the top (16) in extreme raised and lowered positions to facilitate top latching and tonneau installation. A groove (83) in the valve seat (78) forms a leakage path which bypasses the closed valve to slowly reduce hydraulic pressure in the actuator (29) at a predetermined rate until pressure is relieved after a predetermined period of time sufficient to accomplish top latching or tonneau installation. A manually-operated pump bypass (120-140) in the pump cover (42) vents both circuits to the reservoir (40) to enable manual top operation when the pump (36) is inoperative. The pump cap (42) includes makeup valving (150-156 and 150'-156') for accommodating the displacement differential in the cylinders (29). |
