| 摘要 |
A hoisting system, particularly for automotive vehicles, includes a single command lever (17) coupled with a three-position rotary distributing valve (16) and a two-position slide valve (13), the former serving to select one of three modes of operation ("up," "down" or "lock") whereas the latter responds to a shifting of the lever between an "off" and an "on" position. A hydraulic pump (7) works into a high-pressure line with a first branch leading to a hoisting cylinder (1) for elevating the load and with a second branch traversing the two valves in series, this latter branch having an outlet terminating at a set of latching cylinders (5) whose pistons bear upon spring-loaded detents (4) for arresting the load at a selected level of elevation in the "lock" position of the rotary distributor. The connection between the command lever and the slide valve includes a lost-motion coupling (17', 18) whereby in an intermediate shifting position, in which the lever is stopped in the "up" position of the distributor, the slide valve remains closed while an electric switch (25) is actuated to start the pump motor (6) which operates until the lever is restored or the motor circuit is broken by a limit switch (24) tripped at the top of the hoisting stroke. Another switch (29) is closed momentarily upon passage of the rotary distributor into or out of its "lock" position to establish an alternate energizing circuit for the pump motor which raises the load to release the detents (4) if engaged, this alternate circuit including a further switch (28) for stopping the pump motor after the load has risen a short distance above its locking level.
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