Patent ID: 7981107

Claim:
An implantable therapeutic substance delivery piston pump having a low profile inlet valve, comprising: a pump cylinder having an inlet enclosure with a therapeutic substance inlet coupled to a reservoir outlet and an outlet enclosure with an infusion outlet; a pump piston moveable within the pump cylinder, the pump piston having a piston fluid path, a piston inlet end and a piston outlet end, the pump piston forming an inlet chamber between the pump piston and the inlet enclosure and a pumping chamber between the pump piston and the outlet enclosure; an outlet valve carried on the outlet enclosure, the outlet valve configured to control the flow of therapeutic substance from the pumping chamber into the infusion outlet; and, a flat inlet valve carried on the pump piston in operating relation to the piston fluid path, the inlet valve having a valve element and valve spring configured to control the flow of the therapeutic substance from the piston outlet end into the inlet chamber, wherein the valve element comprises a valve surface facing the piston and wherein the valve surface closes the piston outlet end.