Fixed limit lifting jack

In a lifting jack comprising a frame, an elevating linkage pivotally mounted on the frame, a hydraulic housing on the frame having a hydraulic reservoir therein, and a hydraulic power cylinder operatively connected between said frame and said elevating linkage, the combination of a hydraulic network interconnecting said reservoir and said power cylinder and actuating means for said network, said network comprising a first bore in communication with said power cylinder and checked against return flow from said power cylinder, a second bore in communication with said reservoir and checked against flow to said reservoir, and a third bore in communication between said power cylinder and said reservoir, said third bore having an exposed outer end and a combined reverse action and load limit subassembly in said third bore, said actuating means comprising a pump and a pump actuator pivotally mounted on said frame, said pump actuator including reverse control for said elevating linkage, said pump having a pump chamber in communication jointly with said first and second bores, whereby to draw fluid from said reservoir and force fluid into said power cylinder, said load limit subassembly comprising a check valve seat and a load limit check valve element in said third bore seating in a direction to stop flow to said power cylinder, a bushing in fixed position closing the outer end of said third bore, a resilient actuator for said check valve element located between the load limit check valve element and said bushing, said reverse control comprising a stem member extending through said bushing into engagement with said resilient actuator, said stem member having an adjustment of position relative to said resilient actuator whereby to relieve tension in said resilient actuator to establish flow from said power cylinder to said reservoir and enable lowering of said elevating linkage.