Drive mechanism for a drug delivery device

摘要

A drive mechanism for a drug delivery device having a rotationally fixed plunger rod driven by a lead screw. The lead screw engages a free lock which is coupled to a release knob. A dose setting dial cooperates with an inner cylinder using a clutch to establish the axial movement of the plunger rod during dose setting and dispensing.

主权项

1. A drive mechanism for use in a drug delivery device comprising:
a plunger rod having a non-circular perimeter and being hollow, said plunger rod being prevented from rotation during both setting and dispensing a dose of said drug and having a distal end configured to abut and engage a cartridge piston; a lead screw engaged with said plunger rod and is configured to rotate relative to the plunger rod during dose setting; a hollow cylindrically shaped dose setting dial configured to simultaneously rotate and traverse axially towards the proximal end during dose setting and to simultaneously rotate and traverse axially towards the distal end during dose dispensing; an inner cylinder being releasably connected to the dose setting dial, such that relative rotation between said dose setting dial and said inner cylinder is prevented during dose setting but is allowed during dose dispensing; and a plunger rod holder, which prevents said plunger rod from moving towards the proximal end during dose setting, but allows said plunger rod to move towards the distal end during dose dispensing.