Loading patent…
AssigneeCaterpillar Tractor Co.
InventorsJ. W. Burrows, Loyal O. Watts
Estimating the term…
PCT No. PCT/US79/00664 Sec. 371 Date Aug. 30, 1979 Sec. 102(e) Date Aug. 30, 1979 PCT Filed Aug. 30, 1979 PCT Pub. No. WO81/00600 PCT Pub. Date Mar. 5, 1981 A lock valve (10) for use in a hydraulic system (90) for positioning the work implement of an earth working machine which includes first and second check valves (28, 30) and a piston section (60, 70, 62, 72) for each operable by pilot fluid. In a first mode, the piston sections (60, 70, 62, 72) permit seating of both check valves, while in a second mode, the piston sections interlock so that only one check valve can seat. The lock valve (10) operates in a hydraulic system (90) to lock a work implement, such as a blade for a motor grader, in a fixed position during a first operating mode, while providing a connection from one end of an implement actuator to vent during a second operating mode to insure that a shock absorbing means for the implement hydraulic system maintains a full shock absorbing capacity.
An expandable piston lock valve (10) adapted to operate both as a lock valve and a longstem lock valve comprising a valve housing (12) defining an internal valve chamber (18), a pair of spaced valve inlet ports (24,26) in said valve housing (12) communicating with said valve chamber (18), a pair of spaced valve outlet ports (20,22) in said valve housing (12) communicating with said valve chamber (18), first normally closed check valve means (28) interposed between a first valve inlet and outlet port (24,20) to control the flow of fluid therebetween, second normally closed check valve means (30) interposed between a second valve inlet and outlet port (26,22) to control the flow of fluid therebetween, variable length piston means (58) mounted between said first and second check valve means (28,30) for operation in a first mode to permit both said first and second check valve means (28,30) to close simultaneously in the absence of fluid pressure supplied to either one of said pair of inlet ports (24,26) and in a second mode to prevent said first and second check valve means (28,30) from both closing simultaneously either in the presence or absence of fluid pressure supplied to either one of said pair of inlet ports (24,26), said variable length piston means (58) in said first mode having a first predetermined length and in said second mode expanding to a second predetermined length greater than said first predetermined length, and actuation means (68,78) for causing said variable length piston means (58) to expand from said first predetermined length to said second predetermined length.
A hydraulic system (90) for controlling the work element of an earth working machine comprising hydraulic motor means (102,104) for moving said work element, fluid source means (92,94,96,98) for providing fluid to said hydraulic motor means (102,104), shock absorbing means (140,142) including fluid accumulator means (140,142), and valve means (10a,10b,118) connected with said fluid source means (92,94,96,98) and said hydraulic motor means (102,104) and operative in a first mode to cause said hydraulic motor means to hold said work element in a fixed position and in a second mode to connect said hydraulic motor means to said fluid accumulator means (140,142), said valve means (10a,10b,118) including at least a first extendable piston lock valve means (10a) connected between said fluid source means (92,94,96) and said hydraulic motor means (102) and operative in said first mode to cause said hydraulic motor (102) means to hold said work element in a fixed position and in said second mode to relieve residual pressure on said hydraulic motor means, said first extendable piston lock valve means (10a) adapted to operate both as a lock valve and a longstem lock valve and including a valve housing (12) defining an internal valve chamber (18), a pair of spaced valve inlet ports (24,26) in said valve housing (12) communicating with said valve chamber (18), a pair of spaced valve outlet ports (20,22) in said valve housing (12) communicating with said valve chamber (18), first normally closed check valve means (28) interposed between a first valve inlet and outlet port (24,20) to control the flow of fluid therebetween, second normally closed check valve means (30) interposed between a second valve inlet and outlet port (26,22) to control the flow of fluid therebetween, variable length piston means (58) mounted between said first and second check valve means (28,30) for operation in a first mode to permit both said first and second check valve means (28,30) to close simultaneously in the absence of fluid pressure supplied to either one of said pair of inlet ports (24,26) and in a second mode to prevent said first and second check valve means (28,30) from both closing simultaneously either in the presence or absence of fluid pressure supplied to either one of said pair of inlet ports (24,26), said variable length piston means (58) in said first mode having a first predetermined length and in said second mode expanding to a second predetermined length greater than said first predetermined length, and actuation means (68,78) for causing said variable length piston means (58) to expand from said first predetermined length to said second predetermined length.
Dependencies are inferred from the claim text.