| Patents for F04C 23 - Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids (6,201) | |
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| 05/1976 | |
| 05/18/1976 | US3956904 Compressor-expander for refrigeration having dual rotor assembly |