Abstract: The invention involves pressure-counterweighted oil-well pumping apparatus in which derrick structure of elemental simplicity involves components which are readily assembled and disassembled, such that a given pumping apparatus can be loaded on a single truck and transported from one to the next desired well-pumping location. For a given capacity pumping system, overall height requirements for the derrick structure are less than one half those of U.S. Pat. No. 4,631,918. And power-integrator complexity is substantially reduced by employment of a fixed-displacement variety in conjunction with a variable speed a-c motor as the prime mover, under control of solid-state devices and pressure-sensitive transducer elements which determine upper and lower limits of the reciprocating stroke.

Abstract: A three-chamber jack employs a telescoping relation between an outer cylinder and an intermediate cylinder, the closed outer ends of which cylinders continuously sustain lifting-load force. An annular piston is fixed to the inner end of the intermediate cylinder and has sealed sliding engagement to the bore of the outer cylinder. An inner cylinder is fixed to the closed outer and of the outer cylinder and extends concentrically within both the outer and the intermediate cylinder, and the inner cylinder has sealed sliding engagement with the bore of the annular piston. Three internal volumes are thus defined. Load-counterbalancing gas pressure is continuously operative within the first of those volumes, over the entire area of the annular piston, and hydraulic fluid contained within the second and third volumes is reversibly pumped from one to the other of the second and third volumes, to reversibly determine piston displacement.

Abstract: The invention contemplates hydraulic-lift mechanism which employs a power integrator in the connection between a charged hydraulic accumulator and the actuator for a vertically positionable load; the power integrator, additionally, has a prime-mover connection, and the pressurized charge of the accumulator is advisedly set to fully accommodate a preselected level of average load upon the actuator. The hydraulic circuit importantly includes check valves, with a pilot-operated check valve interposed between the power integrator and the accumulator and another pilot-operated check valve interposed between the power integrator and the load actuator. The pilot-operated check valves cooperate with other check valves to assure automatic transfer of hydraulic fluid under pressure from the accumulator to the load actuator, and vice versa, as may be determined by selected control of or via the power integrator.

Abstract: A battery-operated electric-motor driven hydraulic-lift mechanism for a fork-lift vehicle employs a hydraulic accumulator which serves an intertia-free counterweight function, designedly to the degree that such counterweight action is a direct offset of a predetermined average-load condition, as seen by the hydraulic-lift actuator of the system. Electric-motor drive is utilized for up/down operation of the fork lift, only to the extend needed to displace hydraulic fluid into or out of the "counterweighted" actuator. In some cases, such displacement will call for expending energy to add to or substract from the counterweight action; in other cases, the necessary fluid displacement results in an energy return to the system, i.e., in restoring energy to the battery.

Abstract: A prime-mover driven variable-rate pump of relatively great flow capacity is in delivery and return-circuit connection to an intermittently loaded hydraulic motor. A fixed-rate pump of substantially less capacity is continuously driven by the prime-mover, to charge a hydraulic accumulator, there being a safety relief to sump when a predetermined high-pressure threshold is reached. The accumulator is exclusively connected to the inlet of the variable-rate pump, being isolated by check valves from delivering any reverse flow to the fixed-rate pump and from delivering any reverse flow to the return portion of the motor-driving circuit. In said return portion, and between its check valve and the motor, a "dump" valve is operable for transient diversion of return flow to sump, thereby transiently enabling enhanced load-accelerating torque from the motor; this valve is preferably pressure-operated to "dump" position upon a load-reflecting pressure rise in the supply line from the variable-rate pump to the motor.

Abstract: A bridge-crane structure wherein major structural components to sustain loads imposed upon the span are also major functional components of hydraulically controlled hoist mechanism of the crane. Specifically, closed upper and lower elongate cylinders are rigidly laced by struts to define a bridge girder, of length corresponding to the length of the bridge; and these cylinders are charged with gas at elevated pressure and interconnected as major components of a hydraulic accumulator relied upon as a phantom counterweight in the hydraulic hoist mechanism.

Abstract: The invention contemplates hydraulic-lift mechanism which employs a power integrator in the connection between a charged hydraulic accumulator and the actuator for a vertically positionable load; the power integrator, additionally, has a prime-mover connection, and the pressurized charge of the accumulator is advisedly set to fully accommodate a preselected level of average load upon the actuator. The hydraulic circuit importantly includes check valves, with a pilot-operated check valve interposed between the power integrator and the accumulator and another pilot-operated check valve interposed between the power integrator and the load actuator. The pilot-operated check valves cooperate with other check valves to assure automatic transfer of hydraulic fluid under pressure from the accumulator to the load actuator, and vice versa, as may be determined by selected control of or via the power integrator.

Abstract: The invention contemplates a hydraulically operated twin-cable suspension for a clamshell or the like load-handling device. In a preferred embodiment, a charged accumulator is effectively a counterweight and is the source of all hydraulic fluid needed for the full range of actuation of two traction cylinders, one for each of the respective cables. Both cables automatically share the load, without slack, in any elevational situation, and simple hydraulic control circuitry selectively enables (a) an automated closing dig into loadable material and (b) a quick opening for load discharge. A single power integrator is interposed between the accumulator and the two traction cylinders for directionally controlling hydraulic-fluid displacement between the accumulator and the traction cylinders, as needed for all cable displacements.

Abstract: The invention in a preferred embodiment contemplates a dual-lift hydraulic arrangement in which each of two hydraulic-lift systems employs a power integrator in the connection between a charged hydraulic accumulator and a hydraulic actuator for cable suspension of a load. The accumulator may be a single device serving the respective hydraulic systems, each of which terminates in a traction cylinder for operating a cable lift for its end of the load suspension. A single prime mover serves both power integrators, and the pressurized charge of the accumulator is advisedly set to accommodate (counterbalance) a predetermined average of the combined load on the two actuators. The arrangement lends itself to single-handed control of both hydraulic systems and to the corrective tilt orientation of a load which may be relatively heavy at one end and relatively light at the other end.

Abstract: The invention contemplates oil-well pumping apparatus (a) in which a traction cylinder is mounted at the well-head for direct reciprocating operation of the polish rod from which a pumping piston is suspended in a well casing, and (b) in which hydraulic-counterweight principles of copending application, Ser. No. 601,481, filed Apr. 18, 1984 are employed to reduce lift-capacity requirements which would otherwise be imposed on the prime mover.