A solenoid drive apparatus for driving a lead screw of an External Infusion Pump (1) having a housing (302), solenoid winding (356) within the housing (302), a solenoid armature (358) which is driven by the field of the solenoid winding (356), push rod (362) which is driven by the armature (358), pawn...http://www.google.com.au/patents/US4678408?utm_source=gb-gplus-sharePatent US4678408 - Solenoid drive apparatus for an external infusion pump
