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A fluid control system for selectively holding a work implement, such as a blade in a motor grader or the like, in a fixed position in a first operation mode, and for selectively providing a shock absorbing system (70,72) for the implement in a second operating mode. In the fixed position mode, lock

A fluid control system for selectively holding a work implement, such as a blade in a motor grader or the like, in a fixed position in a first operation mode, and for selectively providing a shock absorbing system (70,72) for the implement in a second operating mode. In the fixed position mode, lock valves (36,38,68) are operative to provide positive locking for an implement actuator (24,26), while in the shock absorbing mode, longstem lock valves (82,84) are operable to maintain one check valve (102) of a dual valve structure (96,98) unseated at all times. Each unseated check valve (102) provides a connection of one end of an implement actuator (24,26) to vent to insure that the shock absorbing system (70,72) maintains a full shock absorbing capacity.

대표청구항 ▼

A hydraulic system for controlling the work element of an earth working machine comprising hydraulic motor means (24,26) for moving said work element, said hydraulic motor means (24,26) including at least one lift jack (24) connected to move said work element, said lift jack (24) including a lift ja

A hydraulic system for controlling the work element of an earth working machine comprising hydraulic motor means (24,26) for moving said work element, said hydraulic motor means (24,26) including at least one lift jack (24) connected to move said work element, said lift jack (24) including a lift jack cylinder (30) and a piston (28) mounted for movement within said lift jack cylinder (30) which divides said lift jack cylinder (30) into a head end (32) and a rod end (34), fluid source means (10,12) for providing fluid to said hydraulic motor means (24,26), control means (14,16) connected to said fluid source means (10,12) for alternately directing a flow of fluid into and out of said head and rod ends (32,34) of said lift jack cylinder (30), shock absorbing means (70,72), including fluid accumulator means (70,72), and a lock valve system (36, 38, 68, 82,84) connected between said control means (14,16), said hydraulic motor means (24,26) and said shock absorbing means (70,72), said lock valve system (36,38,68,82,84) including first lock valve means (36,38) connected to said head and rod ends (32,34) of said lift jack cylinder (30), said first lock valve means (36,38) being selectively operable to permit or block fluid flow from said head and rod ends (32,34) of said lift jack cylinder (30) and said accumulator means (70,72), second lock valve means (68) being selectively operable to connect or disconnect said head end (32) of said lift jack cylinder (30) to said accumulator means (70,72), and longstem lock valve means (82,84) connected between said first lock valve means (36,38) and said control means (14,16), said longstem lock valve means (82,84) being operable in combination with said first lock valve means (36,38) to vent residual pressure at the head end (32) of said lift jack cylinder (30) when said head end (32) is connected to said accumulator means (70).