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| Number | Title | Issue Date |
| 4546607 | Pumping apparatus A pumping apparatus includes a reversible variable displacement drive pump having two ports and a lifting apparatus connected to one of the ports. The lifting apparatus is designed to fit on the well-head of an oil well and attach to the polish rod of the... | 10/15/1985 |
| 4438628 | Pump jack drive apparatus A pump jack drive apparatus includes a pair of hydraulic cylinders connected to a walking beam of the pump jack for reciprocating the horsehead, and a pair of microswitches or proximity switches which are closed by the walking beam at the limits of the st... | 03/27/1984 |
| 4187680 | Oil well pump drive An oil well pump drive including a drive unit that is hydraulically actuated by a double-acting hydraulic cylinder to reciprocate vertically. An endless chain is entrained over vertically spaced sprockets carried by the unit, with one flight of the chain ... | 02/12/1980 |
| 4136519 | Hydraulic cycloidal drive A transfer system having a transfer mechanism which is located directly on or adjacent the production machine. The transfer mechanism comprises a reciprocating workpiece shuttle driven by a hydraulic driving unit, specifically a hydraulic transfer cylinde... | 01/30/1979 |
| 4099447 | Hydraulically operated oil well pump jack A hydraulically operated oil well pump jack utilizing a double acting hydraulically operated piston and cylinder assembly for pivoting the walking beam of an oil well pump jack, a linkage mechanism for operating a reversing valve to cause extension and re... | 07/11/1978 |
| 3940930 | Hydraulic system for injection molding machine A fixed platen is supported in the machine frame, and a movable platen is connected to two parallel rods which project rearwardly through the fixed platen. Each rod carries a first piston and each piston is slidably received in a first cylinder. These cyl... | 03/02/1976 |
| 3932989 | Resonant gas-expansion engine with hydraulic energy conversion An illustrative system is disclosed for use as a rotary-drive engine, utilizing combustible fuel and a hydraulic system of energy conversion. An engine block defines a pair of expansion cylinders (combustion chambers) and an associated concentric pair of ... | 01/20/1976 |
