Medication dispensing apparatus with triple screw threads for mechanical advantage

摘要

A medication dispensing apparatus that provides a mechanical advantage. During dose preparing, a nut rotating element ( 410 ) and a screw element ( 368 ) are in a first axial arrangement such that a screwing motion of the nut rotating element and screw element relative to the apparatus housing that moves the elements a first axial distance from a home position screws a nut ( 364 ) along a drive member threaded shaft ( 362 ) a second axial distance different than the first axial distance. During dose dispensing, the nut rotating element and the screw element are in a second axial arrangement, whereby a screwing motion of the screw element relative to the housing back toward the home position advances a plunger ( 366 ) in the distal direction to axially advance the nut and thereby the drive member and a fluid container piston to dispense medicine.