Patent ID: 8696631
Filing Date: 2014-04-15
Classification: A61M,F04B

Abstract:
1. A drive mechanism for delivery of infusion medium comprising: an inlet for receiving infusion medium; an outlet for discharging infusion medium; a piston channel having a generally annular wall with an axial length defined between an open inlet end on a same side of the drive mechanism as the inlet and an open outlet end on a same side of the drive mechanism as the outlet; a piston within an interior of the generally annular wall along the axial length of the piston channel and moveable axially between a retracted position and a forward position to drive infusion medium toward the outlet; a clearance between the interior of the generally annular wall and the piston along the axial length of the piston channel; an armature located proximate to the open inlet end of the piston channel and moveable between a retracted position and a forward position; a spring around and coaxial with the piston and between the armature and a shoulder within the interior of the generally annular wall of the piston channel to exert a spring force to urge the armature toward its retracted position; a coil located coaxial with the piston and in a position relative to the armature to generate an electromagnetic field upon energization sufficient to overcome the spring force and cause the armature and piston to move from their retracted positions to their forward positions; and a valve assembly having a valve cap and a valve member, the valve member being supported on the valve cap for movement relative to the valve cap and being moveable between open and closed positions to selectively open and close the open outlet end of the piston channel to an outlet chamber, the valve member being moveable in response to axial movement of the piston within the piston channel, the valve cap being free of any fluid flow opening therethrough; and the inlet, piston channel, outlet chamber and outlet defining a fluid flow direction from the inlet, then through the clearance along the axial length of the piston channel from the open inlet end to the open outlet end, and then through the outlet chamber and the outlet, for communication of infusion medium during operation of the drive mechanism.