Dial-down mechanism for wind-up pen

摘要

The present invention relates to a dial-down mechanism for an injection device comprising a torsion spring for assisting injection of a dose of medicament from the injection device, the dial-down mechanism comprising a ratchet arm (21) engaging a ring element (10) and a reset element (30) which acts on a knob located on the periphery of the ratchet arm (21) to move the ratchet arm (21) out of engagement with the ring element (10) in order to allow the set dose to be reduced.

主权项

1. A dial-down mechanism for an injection device comprising a torsion spring which is strained when setting a dose by rotating a dose setting member (20) relatively to a housing in a first direction, and unstrained when rotating the dose setting member (20) in a second direction opposite the first direction, the torsion spring for storing energy to expel a dose from the injection device, the dial-down mechanism comprising:
a fixation element (10) coupled to the housing and having a plurality of inwardly pointing teeth (12), at least one ratchet arm (21) coupled to the dose setting member (20), wherein the at least one ratchet arm (21) engages the teeth (12) of the fixation element (10) and is shaped such that the dose setting member (20) is prevented from rotating in the second direction when the ratchet arm (21) engages the teeth (12) of the fixation element (10), the dial-down mechanism further comprises a reset member (30) configured for movement in a first direction and a second direction opposite the first direction, such that rotation of the reset member (30) in the first direction to set a dose is transformed directly to the dose setting member (20) and thereby rotates relatively to the fixation element (10), and rotation of the reset member (30) in the second direction activates the ratchet arm (21) to disengage the fixation element (10) and thereby allow the dose setting member (20) to rotate in the second direction by carrying at least one forward extending reset element (32) located distally to the reset member (30) and which acts on at least one part (25) of the ratchet arm to move the ratchet arm (21) out of engagement with the teeth (12) of the fixation element (10) thereby dialing down the set dose, wherein the reset member (30) is at least partially provided inside the dose setting tube (20) and axially retained by the dose setting member (20), and the ratchet arm (21) carries at least part (25) extending radially from the at least one ratchet arm (21) and having an outer radius from the centre axis of the injection device larger than the outer radius of the remaining part of the ratchet arm (21).