F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
F04C11/00—Combinations of two or more machines or pumps, each being of rotary-piston or oscillating-piston type; Pumping installations
F04C11/001—Combinations of two or more machines or pumps, each being of rotary-piston or oscillating-piston type; Pumping installations of similar working principle