Medicament delivery device
A dose setting mechanism for a medicament delivery device is presented having a pinion mounted to a locking member where the axis of rotation of the pinion is offset and parallel to the longitudinal axis of the housing containing the dose setting components. Primary and secondary dose members are engaged with the pinion to indicate a set dose of medicament.
1. A dose setting mechanism for a medicament delivery device comprising,
a housing having a longitudinal axis;
a locking member rotationally and slidably fixed to the housing and releasably engaged with a lead screw;
a dose member arranged coaxially and slidable with respect to the lead screw such that the dose member is rotatable relative to the lead screw when the dose setting mechanism is in a non-activated state and where the dose member is slidably connected and rotatably fixed to the lead screw when the dose setting mechanism is in an activated state;
the lead screw is coaxially arranged and engaged with the locking member when dose setting mechanism is in the non-activated state;
a plunger rod rotationally fixed to the lead screw;
a nut threadedly connected to the plunger rod and slidably locked to the lead screw; and
a dose knob rotationally fixed to the dose member that is in clutched engagement with the lead screw, where the dose knob and dose member are rotationally fixed to the lead screw when the dose setting mechanism is in the activated state, and
wherein the locking member is disengaged from the lead screw when the dose setting mechanism is in the activated state and the locking member is engaged with the lead screw when the dose setting mechanism is in the non-activated state.
2. The dose setting mechanism of claim 1 where the dose setting knob is connected to the dose member such that when the dose setting mechanism is transformed from the non-activated state to the activated state, the dose setting knob is manually manipulated in a pre-determined direction, whereby the locking member is released and the lead screw member is distally moved a pre-determined distance by a biasing force independent of the size of a dose to be set.
3. The dose setting mechanism of claim 2 where the biasing force is in a distal direction and is generated by a compression spring in a pre-tensioned state.
4. The dose setting mechanism of claim 1 further characterized in that the locking member comprises a flexible lever configured to engage a ledge on the lead screw when the dose setting mechanism is in the non-activated state.
5. The dose setting mechanism of claim 1 further characterized in that the locking member has a proximal enlarged plate with a distally projecting stop member.
6. The dose setting mechanism of claim 5 further characterized in that the dose member has a stop member that interacts with distally projecting stop member on the locking member during dose setting.
7. The dose setting mechanism of claim 1 further characterized in that the lead screw and the dose member are arranged and configured such that the lead screw can slide axially relative to the dose member during transition from the non-activated state to the activated state.
8. The dose setting mechanism of claim 1 further characterized in that a ratchet is between proximal end of the lead screw and the nut such that rotational movement of the lead screw relative to nut generates an audible signal during dose setting.
9. The dose setting mechanism of claim 8 where the audible signal is directly related to each unit dose set.
10. The dose setting mechanism of claim 1 further characterized in that the nut comprises grooves on an outer circumferential side face that engage longitudinal ribs on an inner surface of the housing to rotationally lock the nut to the housing and allow the nut to slide relative to the housing when the dose setting mechanism transitions from the non-activated state to the activated state.
11. The dose setting mechanism of claim 1 further comprising a biasing member that is a spring located between an inner wall of the housing and a proximal end of the nut and is in a pre-tensioned state when the dose setting mechanism is in the non-activated state and the locking member is engaged with the lead screw.
12. The dose setting mechanism of claim 1 further characterized in that the dose member is arranged with a circumferential band containing indicia indicative of a set dose.
13. The dose setting mechanism of claim 12 where the housing further comprises a dose window that is configured to allow viewing of the indicia.