EP3411100A1 — A hypocycloid end-of-content mechanism

USPTO Abstract

The invention relates to a torsion spring driven injection device for delivering individually set doses of a liquid drug wherein a torsion spring is strained by rotation of a rotatable dose setting element and released by axial movement of a clutch which couples the dose setting element with the drive tube and the drive tube with a piston rod guide driving the piston rod. When straining the torsion spring the clutch is decoupled from a piston rod guide such that the piston rod guide is able to rotate independently and coupled to the dose setting element. During dose expelling the clutch is moved into engagement with the piston rod guide and out of engagement with the dose setting element such that the piston rod guide rotates with the clutch under influence of the torsion spring. The invention further relates to a non-axial movable End-of-Content mechanism preventing the user from setting a dose larger than the content of the injectable liquid drug remaining in the cartridge of the injection device.