Patent ID: 7255690

Claim:
An infusion medium delivery device comprising: a reservoir for containing infusion medium under positive pressure; a drive device having: an inlet for receiving infusion medium under positive pressure; a piston channel for communication of infusion medium received by the inlet; a coil surrounding the piston channel; an armature disposed adjacent the coil, on one side of the piston channel; an outlet chamber disposed adjacent the coil, on the opposite side of the piston channel relative to the armature for receiving infusion medium from the channel; a piston located within the piston channel and moveable axially within the piston channel for allowing infusion medium to enter the outlet chamber under positive pressure; and an outlet in flow communication with the outlet chamber, for discharging a metered amount of infusion medium from the outlet chamber; a first valve member positioned downstream of the piston channel in a flow path of infusion medium, said first valve member moveable between opened and closed positions to selectively open and close one end of the piston channel to the outlet chamber, said one end of the piston channel closed to the outlet chamber when the first valve member is in the closed position; and a second valve member in fluid communication with the first valve member and positioned downstream of the first valve member in the flow path of infusion medium, the second valve member being moveable between opened and closed positions; wherein the first valve member is configured such that the first valve member is in the opened position at least when the metered amount of infusion medium beams to be discharged from the outlet chamber.