Patent ID: 9539384
Date: 2017-01-10
CPC Classifications: A61M

Claim:
1. A medicament infusion device, comprising: a housing having an interior surface, the interior surface of the housing being at least partially threaded; a cavity within the housing configured to receive a cartridge, the cartridge having a reservoir for holding a medicament, a plunger for expelling the medicament from the reservoir, and an outlet port at a distal end of the housing; a drive mechanism disposed at a proximal end of the housing; a drive shaft in cooperation with the drive mechanism; a compound lead screw, the compound lead screw being essentially cylindrical and having at least a portion having a first diameter and at least a portion having a second diameter, wherein each of the portion having the first diameter and the portion having the second diameter are threaded, and the second diameter is greater than the first diameter; a piston having at least one threaded surface; at least one keyway, wherein the at least one keyway is configured to permit lateral motion of one of the compound lead screw or piston without permitting rotational motion; and and wherein the at least partially threaded interior surface of the housing engages the threaded second diameter of the compound lead screw and the compound lead screw moves relative to the at least partially threaded interior surface of the housing upon a rotation of the compound lead screw; wherein the threaded surface of the piston engages the threaded portion of the first diameter of the compound lead screw; and wherein the at least one threaded surface of the piston is an internal surface.