F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
F04B7/00—Piston machines or pumps characterised by having positively-driven valving
F04B7/04—Piston machines or pumps characterised by having positively-driven valving in which the valving is performed by pistons and cylinders coacting to open and close intake or outlet ports
F04B7/06—Piston machines or pumps characterised by having positively-driven valving in which the valving is performed by pistons and cylinders coacting to open and close intake or outlet ports the pistons and cylinders being relatively reciprocated and rotated