Dose delivery mechanism
Abstract:
An injection device comprising a housing having a longitudinal axis, a dose selector (16) capable of being rotated about said longitudinal axis with respect to said housing by a user to set a dose of medicament to be ejected from the injection device and a spring (20) capable of storing energy necessary for ejecting the dose of medicament from the injection device. The spring is coupled to the dose selector such that a charging force can be transferred from the dose selector to the spring to increase the energy stored by the spring. The injection device further comprises a ratchet arrangement (25) moveable between an engaged state in which the spring is limited from unwinding from a currently selected dose and a disengaged state in which the spring is able to unwind and a drive assembly including a plunger element (23) capable of providing an axial force for ejecting a dose of medicament from the injection device. The drive assembly further comprises a drive clutch (21) moveable from a disengaged state in which a force path from the spring to the plunger element is interrupted and an engaged state in which the drive assembly can provide the axial force for ejecting a dose of medicament from the injection device via said force path.
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