Automatic injector with kickback attenuation

1. An auto-injector comprising:

a housing having a retention step formed on an inner surface of the housing, the housing having no surface operative to contact an injection site during a medicament dispensing operation;

a cartridge having an opening therein and containing a medicament, the medicament rearwardly confined by a plunger received through the opening, the cartridge including a needle assembly operative to dispense the medicament there through during a medicament dispensing operation, the needle assembly including a needle;

a cartridge container disposed within the housing and operative to receive the cartridge therein, the cartridge container having a ledge that abuts the retention step of the housing to limit movement of the cartridge container within the housing, the cartridge container having a closed front end except for an opening therein sized to receive the needle there through during a medicament dispensing operation, the closed front end operative to engage the cartridge and oppose continued movement of the cartridge after the needle passes through the front end opening;

an actuation assembly providing a stored energy source capable of driving the plunger within the cartridge to dispense the medicament through the needle assembly, the actuation assembly secured to the housing; and

a needle cover at least partially received within the housing and positioned between the housing and the cartridge container, the needle cover having an opening formed therein sized to receive the needle there through during a medicament dispensing operation, the needle cover having a first locked retracted position and a second locked extended position, the needle cover extending beyond the housing in the first locked retracted position; whereby:

energy released from the stored energy source to drive the needle and cartridge during the medicament dispensing operation is not transmitted to the needle cover.

2. The auto-injector of claim 1 wherein the needle cover has a surface operative to contact an injection site prior to a medicament dispensing operation, the surface having the opening to receive the needle there through during a medicament dispensing operation.

3. The auto-injector of claim 1 wherein the actuation assembly is secured to the housing via projections formed on an outer surface of the actuation assembly that are snap fit into respective openings in the housing.

4. The auto-injector of claim 1 further comprising a needle cover spring positioned inside the needle cover between an end surface of the needle cover and the front end of the cartridge container.

5. The auto-injector of claim 4 wherein the front end of the cartridge container is tapered, the cartridge container comprising a plurality of ribs formed on the outer surface of the tapered front end, the needle cover spring disposed about the plurality of ribs.

6. The auto-injector of claim 1 wherein the cartridge further comprises a needle sheath disposed about the needle, the needle sheath being compressed between the cartridge container and the cartridge during the medicament dispensing operation.

7. The auto-injector of claim 1 further comprising a locking mechanism for selectively holding the needle cover in the first locked position and in the second locked position, the locking mechanism located within the housing to protect against tampering and dirt ingress.

8. The auto-injector of claim 1 wherein the stored energy source is a spring.

9. The auto-injector of claim 1 wherein the ledge of the cartridge container is located on an end opposite the closed front end.

10. An auto-injector comprising:

a housing;

a cartridge having an opening therein and containing a medicament, the medicament rearwardly confined by a plunger received through the opening, the cartridge including a needle assembly operative to dispense the medicament there through during a medicament dispensing operation, the needle assembly including a needle;

a cartridge container disposed within the housing and operative to receive the cartridge therein, the cartridge container having an annular structure that engages an inner surface of the housing to limit movement of the cartridge container within the housing, the cartridge container having a closed front end except for an opening therein sized to receive the needle there through during the medicament dispensing operation, the closed front end operative to engage the cartridge and oppose continued movement of the cartridge after the needle passes through the front end opening;

an actuation assembly providing a stored energy source capable of driving the plunger within the cartridge to dispense the medicament through the needle assembly, the actuation assembly secured to the housing; and

a needle cover at least partially received within the housing and operative to receive therein at least the front end of the cartridge container, the needle cover having an opening formed therein sized to receive the needle there through during the medicament dispensing operation, the needle cover having a first locked retracted position and a second locked extended position, the needle cover having a surface operative to contact an injection site prior to a medicament dispensing operation, the surface having the opening to receive the needle there through; whereby:

residual force from the energy source after activation of the medicament dispensing operation is contained by the cartridge container, the cartridge, the housing, and the actuation assembly to prevent kickback of the auto-injector during the dispensing operation.

11. The auto-injector of claim 10 wherein the annular structure of the cartridge container is a ledge located on an end opposite the closed front end.

12. The auto-injector of claim 10 wherein the needle cover extends beyond the housing in the first locked retracted position.

13. The auto-injector of claim 10 wherein the actuation assembly is secured to the housing via projections formed on an outer surface of the actuation assembly that are snap fit into respective openings in the housing.

14. The auto-injector of claim 10 further comprising a needle cover spring positioned inside the needle cover between an end surface of the needle cover and the front end of the cartridge container.

15. The auto-injector of claim 14 wherein the front end of the cartridge container is tapered, the cartridge container comprising a plurality of ribs formed on the outer surface of the tapered front end, the needle cover spring disposed about the plurality of ribs.

16. The auto-injector of claim 10 wherein the cartridge further comprises a needle sheath disposed about the needle, the needle sheath being compressed between the cartridge container and the cartridge during a medicament dispensing operation.

17. The auto-injector of claim 10 further comprising a locking mechanism for selectively holding the needle cover in the first locked position and in the second locked position, the locking mechanism located within the housing to protect against tampering and dirt ingress.

18. The auto-injector of claim 10 wherein the stored energy source is a spring.

19. An auto-injector comprising:

a housing;

a cartridge having an opening therein and containing a medicament, the medicament rearwardly confined by a plunger, the cartridge including a needle assembly operative to dispense the medicament there through during a medicament dispensing operation, the needle assembly including a needle;

a cartridge container disposed within the housing and operative to receive the cartridge therein;

an actuation assembly providing a stored energy source capable of driving the plunger within the cartridge to dispense the medicament through the needle assembly, the actuation assembly secured to the housing; and

a needle cover at least partially received within the housing and positioned between the housing and the cartridge container, the needle cover having an opening formed therein, the needle cover having a first locked retracted position and a second locked extended position, the needle cover extending beyond the housing in the first locked retracted position; wherein:

the housing has no surface operative to contact an injection site; and

energy released from the stored energy source to drive the needle during the medicament dispensing operation is not transferred to the needle cover.

20. A method of attenuating kickback in an auto-injector, the method comprising:

securing an actuation assembly to a housing, the actuation assembly comprising a stored energy source;

receiving a cartridge within a cartridge container, the cartridge including a needle assembly that includes a needle, the cartridge container having a front end;

receiving the cartridge container within the housing;

receiving a needle cover within the housing, the needle cover extending beyond the housing and having an end surface operative to contact an injection site prior to a medicament dispensing operation, the needle cover operative to receive the front end of the cartridge container; and

containing residual force from the stored energy source within the cartridge container, the cartridge, the housing, and the actuation assembly after activating the auto-injector to prevent transfer of the residual force to the needle cover.

21. An auto-injector comprising:

a housing;

a cartridge having an opening therein and containing a medicament, the medicament rearwardly confined by a plunger, the cartridge including a needle assembly operative to dispense the medicament there through during a medicament dispensing operation, the needle assembly including a needle;

a cartridge container disposed within the housing and operative to receive the cartridge therein;

an actuation assembly providing a stored energy source capable of driving the plunger within the cartridge to dispense the medicament through the needle assembly, the actuation assembly secured to the housing; and

a needle cover at least partially received within the housing and positioned between the housing and the cartridge container, the needle cover having an opening formed therein, the needle cover having a first locked retracted position and a second locked extended position, the needle cover extending beyond the housing in the first locked retracted position; wherein:

the needle cover has a surface operative to contact an injection site prior to a medicament dispensing operation; and

energy released from the stored energy source to drive the needle during the medicament dispensing operation is not transferred to the needle cover.