Drive assembly and spacer for drug delivery system
A drug delivery system for injecting a medicament includes a housing, a container configured to receive a medicament including a stopper configured to move within the container and a closure, a needle in fluid communication with the container, a spacer configured to be engaged with the stopper, a first plunger, a first spring configured to bias the first plunger in an axial direction, second plunger disposed about the first plunger, a second spring configured to bias the second plunger in an axial direction. The first plunger is configured to move the spacer and the container relative to the housing via the first spring to establish fluid communication between the container and the patient needle, and the second plunger is configured to move the spacer and the stopper relative to the container via the second spring.
1. A drug delivery system for injecting a medicament, the system comprising:
a housing having a proximal end and a distal end;
a container configured to receive a medicament, the container comprising a stopper configured to move within the container and a closure;
a needle in fluid communication with the container;
a spacer configured to be engaged with the stopper;
a first plunger;
a first spring configured to bias the first plunger in an axial direction relative to the container;
a second plunger disposed about the first plunger; and
a second spring configured to bias the second plunger in the axial direction,
wherein the first plunger is configured to move the spacer and the container relative to the housing in the axial direction via the first spring,
wherein the second plunger is configured to move the spacer and the stopper relative to the container in the axial direction via the second spring, and
wherein the spacer comprises a body and a flange extending radially outward from the body, the body of the spacer configured to engage the first plunger, the flange of the spacer configured to engage the second plunger.
2. The system of claim 1 , wherein the second plunger comprises an outer plunger member and an inner plunger member, at least a portion of the inner plunger member received within the outer plunger member, the outer plunger member having an inwardly extending projection configured to engage an outwardly extending projection of the inner plunger member upon a predetermined axial displacement of the inner plunger member relative to the outer plunger member, and wherein the outer plunger member is configured to trigger withdrawal of the needle into the housing upon a predetermined axial displacement of the outer plunger member.
3. The system of claim 1 , wherein the first plunger includes a flange engaging a proximal end of the second spring.
4. The system of claim 3 , wherein the housing includes a stop, and wherein the flange of the first plunger is configured to engage the stop of the housing upon a predetermined axial displacement of the first plunger relative to the housing to limit axial displacement of the first plunger.
5. The system of claim 1 , wherein the first spring has a greater spring constant or greater spring force than the second spring.
6. The system of claim 1 , wherein the spacer includes a damping feature configured to dissipate energy of the second plunger during displacement of the second plunger relative to the spacer.
7. The system of claim 6 , wherein the damping feature comprises at least one resistance rib.