by varying the relative eccentricity between two members, e.g. a cam and a drive shaft

Full Title

Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders (multi-stage pumps specially adapted for elastic fluids F04B25/00) > having cylinders in star- or fan-arrangement > Control > by varying the relative eccentricity between two members, e.g. a cam and a drive shaft