Patent ID: 8177750

Claim:
An implantable infusion pump for dispensing an active substance at one or varying flow rates to a patient comprising: a pump housing defining an upper surface, an active substance chamber, a propellant chamber separated from the active substance chamber by a first flexible membrane, a catheter, an exit opening in fluid communication with the active substance chamber and an entrance opening in fluid communication with the catheter; and a module attached to the pump housing, the module including a bottom surface contacting the upper surface of the pump housing, an entry formed in the bottom surface in fluid communication with the exit opening of the housing, an exit in fluid communication with the entrance opening of the housing, a valve portion having a longitudinally varying cross section along its length disposed within a valve body, a motor for longitudinally moving the valve portion within the valve body, a first pressure sensor for sensing the pressure of the active substance in the active substance chamber, and a second pressure sensor for sensing the pressure of the active substance downstream of the first pressure sensor, wherein during operation of the pump system, a fluid dispelled from the active substance chamber by a force from the propellant chamber passes through the exit opening of the housing, through the entry of the module, through the valve body of the module, through the exit of the module, through the entrance opening of the housing, and through the catheter.