Patent ID: 7896866

Claim:
An implantable drug pump device for providing infusate to a patient, comprising: a housing; a refill port for transferring infusate into the device, the refill port extending through the housing into an interior space of the housing; a septum within the refill port for sealing the refill port and for receiving a needle; a reservoir for storing infusate within the housing, wherein the reservoir comprises a top plate, a bottom plate, and a bellows connecting the top plate and the bottom plate, wherein the bellows expands when infusate is provided through the refill port and the bellows collapses upon discharge of infusate from the reservoir; and an extensible structure connected to the bottom plate of the reservoir, wherein (i) the extensible structure is substantially collapsed when the bellows is substantially expanded, and (ii) the extensible structure is substantially expanded away from the bottom plate when the bellows is substantially collapsed; wherein, when the reservoir is substantially empty, (i) the bottom plate of the reservoir is disposed above a portion of the refill port that is disposed farthest within the interior space of the housing and (ii) the extensible structure extends about the refill port.