Abstract: PCT No. PCT/US79/00859 Sec. 371 Date Oct. 15, 1979 Sec. 102(e) Date Oct. 15, 1979 PCT Filed Oct. 15, 1979 PCT Pub. No. WO81/01034 PCT Pub. Date Apr. 16, 1981In prior art hydraulic systems, and in particular in hydraulic systems having a cylinder means for elevating and lowering a load, there exists the possibility that the hydraulic line from a control valve to the cylinder means could rupture, allowing the load to drop before the operator could react. The present invention solves this problem by providing a blocker valve (100) in the vent line (69) of a check valve (33,34) which check valve is interposed in the main line 27 between a cylinder means (12) and a control valve (21). The blocker valve (100) is responsive to the back pressure in the main line (27) from the check valve (33,34) to the control valve (27).

Abstract: A hydraulic control system having a plurality of hydraulic motors is provided with a sequencing control means for sequentially controlling or operating the motors from a single selector valve. The selector valve is operative to direct pilot fluid through a sequential controlling valve for pilot operation of separate pilot-operated control valves for the separate motors. The sequential control valve is operative to direct the fluid for operation of one of the control valves first for full operation of the first motor and then for directing pilot fluid to the second valve for operating the second motor. For operating the motors in the reverse direction, the second control valve is operative to control the second motor to its fully retracted position and then the first control valve becomes operative until the first motor is fully retracted.