Patent ID: 7867221

Claim:
An implantable infusion device, comprising: a collapsible member defining a reservoir for containing a variable volume of fluid therein, wherein the collapsible member comprises a reservoir surface that moves between a full position and a refill position in response to a change in volume of the fluid contained in the reservoir; a housing connected to the collapsible member, the housing defining: a refill port for receiving the fluid; and a refill passageway connecting the refill port to the reservoir; a valve plunger for selectively occluding the refill passageway, wherein the valve plunger comprises a free distal end configured to abut the reservoir surface of the collapsible member during movement between the full position and the refill position; and a displacement sensor coupled to the housing and operable to detect a position of the free distal end of the valve plunger at any time during movement of the reservoir surface between the full position and the refill position, the displacement sensor electrically coupled to electronics configured to provide feedback corresponding to the detected position of the free distal end.