Medication dispensing apparatus with spring-driven locking feature enabled by administration of final dose
A medication dispensing apparatus with a spring-driven locking feature includes a drive member movable in a distal direction within a housing, and a fluid container with a piston that is advanceable by the drive member ( 60 ) when such drive member is moved distally by a driving means. The apparatus includes a latching element ( 180 ) having a skid ( 190 ) that is slidable along a surface of the drive member as the drive member passes distally during advancement. The drive member is arranged with the skid so as to maintain a latching lip of the latching element against a spring force in a first position free of the driving means during dose preparing and injecting prior to a final dose administration. The skid-engaging surface shifts distally of the skid such that the skid passes beyond a proximal end of that surface upon administration of a final dose, whereby the latching lip is urged by the spring force from the first position to a second position to physically lock the driving means to prevent further dose preparing and injecting.
1. A medication dispensing apparatus comprising:
a housing;
a drive member within said housing and movable in a distal direction;
a fluid container defining a medicine-filled reservoir with a movable piston at one end and an outlet at the other end, said piston engageable by said drive member to be advanced toward said outlet a distance equal to a distal movement of said drive member when said drive member is moved distally;
a plunger element;
a gear set including first and second pinions, said gear set pivotal on said plunger element and shiftable proximally and distally with the plunger element;
a first rack engaged with said first pinion and axially stationary within said housing;
a second rack engaged with said second pinion and movable within said housing on a piece clutchably connected to said drive member;
a latching element including a latching lip and a skid;
said drive member including an axially extending, skid-engaging surface along which said skid is slidable as said drive member passes distally during advancement during plunger element shifting in the distal direction, said skid-engaging surface having an axial length and a proximal end, said drive member along said axial length structured and arranged with said skid so as to maintain said latching lip against a spring force in a first position free of a latchable element disposed on said plunger element during dose preparing and injecting prior to a final dose administration; and
wherein said skid-engaging surface shifts distally of said skid such that said skid passes beyond the proximal end upon administration of a final dose allowing said latching lip to be urged by said spring force from said first position to a second position for engagement with said latchable element to physically lock said plunger element to prevent further dose preparing and injecting.
2. The medication dispensing apparatus of claim 1 wherein said proximal end of said skid-engaging surface comprises a proximal end of said drive member.
3. The medication dispensing apparatus of claim 1 wherein said skid is disposed distally of said latching lip.
4. The medication dispensing apparatus of claim 1 wherein said skid comprises a blade shape member that extends axially, and wherein said latching lip comprises a transversely extending flange.
5. The medication dispensing apparatus of claim 1 wherein said latchable element comprises a ramped distal face over which said latching lip is cammable to reach a latching engagement with said latchable element.
6. The medication dispensing apparatus of claim 1 wherein said latching element is axially fixed to said housing by at least one flange fit into a slot provided in said housing.
7. The medication dispensing apparatus of claim 1 wherein said spring force acting on said latching element comprises a resiliency of said latching element tending to return said latching lip to a neutral arrangement.
8. The medication dispensing apparatus of claim 7 wherein said latching element comprises a one piece metal stamping.
9. The medication dispensing apparatus of claim 1 wherein said skid-engaging surface is smooth.
10. The medication dispensing apparatus of claim 1 wherein said latching lip comprises a rim along an opening through which a latchable element extends to reach a latching engagement with said latching element.