A hydraulic engine having a frame on which a crankshaft is rotatably mounted between a plurality of cylinders. The individual cylinders are rockingly mounted on the frame arranged as opposed pairs of cylinders and their piston rods are operatively connected to cranks positioned 90.degree. apart upon the crankshaft. A power take-off shaft is also journalled on the frame and a drive train operatively connects the crankshaft to the power take-off shaft. The cylinders are connected by a fluid circuit to a motor-driven pump and included in the circuit are individual distribution valves for the cylinders. Operating plungers of the valves are connected by rods to eccentrics carried by the crankshaft and circumferentially positioned to extend and retract the several piston rods in a sequence which will rotate the crankshaft and deliver usable power to the takeoff shaft.

This invention relates to apparatus for controlling the inclination of a pivotable member relative to a fixed structure, in particular the inclination of the jib of a crane. Control is effected by two jacks, each being connected by one end to the jib and by the other end to the body of the crane. The points of attachment of the jacks to the jib and the pivot axis of the jib define the vertices of two deformable triangles, one preferably being right-angled when the other has been flattened to a straight line. The lifting torque of a crane can thereby be substantially constant for all values of jib inclination.

A vehicle stabilizer apparatus having a plurality of hydraulic stabilizer actuators with each actuator having an integral isolation valve effective to enable operation of a sequentially operable device such as a boom cylinder only after ground-engaging feet associated with the actuators have been brought into firm contact with the ground or other supporting surface. Each actuator is mounted for bodily movement between upper and lower positions on an associated vehicle supported mounting pin. The actuator is caused to move to its upper position when the associated ground-engaging foot engages the ground and through a plunger and plunger spring associated with the isolation valve the position of the actuator is sensed. The isolation valve is in a hydraulic circuit to prevent operation of the boom cylinder unless the actuator is in its upper position.

Backhoe swing apparatus including a backhoe swing bracket for supporting a backhoe for side-to-side swinging movement. A pair of hydraulic actuators are connected with the swing bracket for actuating the swing bracket in opposite directions. The hydraulic actuators are of the piston and cylinder type, and are controlled by a hydraulic system including a pair of hydraulic lines for conducting hydraulic fluid to and from each of the hydraulic actuators. A normally open pressure reducing valve in one of the hydraulic lines is operable to control pressure to one of the actuators to actuate the swing bracket in one direction and to thereby limit the pressure of fluid flowing to the actuator. Simultaneously, flow from the other actuator through the other hydraulic line is controlled by a first normally closed metering valve, which opens a permit such flow only when a predetermined minimum pressure exists in the other hydraulic line. A second normally closed metering valve controls flow of hydraulic fluid from the first hydraulic actuator when the swing bracket swings in the opposite direction, and permits such flow only when a predetermined minimum pressure exists in the other line.

A hydraulic system in a material handling device in which a movable member is rotated about a pivot point, by a pair of hydraulic motors reversibly operable in response to the selective application of hydraulic pressure thereto. The hydraulic pressure for operating the hydraulic motors is connected thereto through a hydraulic switching valve responsive to the position of said movable member where one hydraulic motor would normally oppose further rotation of the movable member to modify the hydraulic connections to that hydraulic motor in response to said member reaching that position whereby further rotation of the movable member is effected without opposition from the hydraulic motor.