| 主权项 |
1. A drive mechanism for an injection device configured for setting and expelling set doses of a drug from a drug-filled cartridge, the drive mechanism comprising:
a piston driver configured for rotation around and axis and for axially driving forward a piston accommodated in a cartridge, the piston driver comprising a piston driver thread that engages a thread of a further component of the injection device, wherein the piston driver during dose setting rotates and moves in an axial direction, a piston rod coupling movement of the piston driver with movements of the piston during expelling of a set dose, the piston rod and the piston driver being coupled so as to enable telescopically lengthening of the piston rod and the piston driver during dose setting, a rotatable counter-element arranged coaxially with the piston driver, the piston driver and the counter-element being configured for relative axial movement during dose setting from a minimum dose state to a maximum dose state, and a spring device arranged between the piston driver and the counter-element, the spring device being increasingly tensioned when the dose setting is changed from the minimum dose setting state to the maximum dose setting state, said tension being releasable for driving forward the piston during dose expelling,wherein one of the piston driver and the counter-element defines a longitudinal track extending along said axis and the other of the piston driver and the counter-element defines a track follower adapted to engage the longitudinal track, wherein the longitudinal track and the track follower controls the relative rotational position between the piston driver and the counter-element for relative axial positions between the piston driver and the counter-element from the minimum dose setting state to the maximum dose state, andwherein a releasable interlock is provided that, when activated, maintains the piston driver and the counter-element in an interlocked state where the relative axial position between the piston driver and the counter-element is fixed, and wherein the releasable interlock is so configured that activation and/or release of the interlock requires the spring device to be tensioned further than at the maximum dose setting state. |
