Motorized drug delivery device

1. A motorized drug delivery device configured to administer at least one pre-set dose of a medicament contained within a medicament container, the delivery device comprising:

a user activation system;

a motor;

a gear train operatively coupled to the user activation system and the motor;

a piston plunger system operatively coupled to the gear train, the piston plunger system comprising a piston plunger and at least one plunger extension for extending a length of the piston plunger;

wherein the piston plunger system is configured to act on a stopper contained within the medicament container to deliver at least one pre-set dose of medicament,

wherein the user activation system comprises a mechanical automatic reset activation system that automatically resets the drug delivery device after administration of the pre-set dose, and wherein the mechanical automatic reset activation system includes a dispense button operatively coupled to a hook release.

2. The drug delivery device of claim 1 , wherein the activation system further comprises a spring disposed about a proximal end of the hook release.

3. The drug delivery device of claim 2 , further comprising a connection rod engaged with the proximal end of the hook release.

4. The drug delivery device of claim 3 , wherein the gear train comprises

a gear disc, a driving gear, a transfer gear, and a driven gear.

5. The drug delivery device of claim 4 wherein the gear disc is operatively coupled to an output shaft of the motor.

6. The drug delivery device of claim 5 , wherein the gear disc comprises a first inclined wall.

7. The drug delivery device of claim 6 , wherein the first inclined wall of the gear disc is operatively coupled to the connection rod during dose administration.

8. The drug delivery device of claim 7 , wherein when the first inclined wall of the gear disc is operatively coupled to the connection rod, an injection circuit is completed so as to initiate dose administration.

9. The drug delivery device of claim 4 , wherein

the transfer gear is operatively coupled between the driving gear and the driven gear.

10. The drug delivery device of claim 4 , wherein

the driven gear comprises a threaded interior.

11. The drug delivery device of claim 10 , wherein the threaded interior engages a groove provided on an outer surface of the piston plunger.

12. The drug delivery device of claim 4 ,

wherein rotation of the driven gear drives the piston plunger.

13. The drug delivery device of claim 12 , wherein rotation of the driven gear drives the piston plunger in a distal direction during dose administration.

14. The drug delivery device of claim 1 , wherein the piston plunger system comprising the piston plunger and at least one plunger extension for extending the length of the piston plunger comprises:

a first plunger extension and a second plunger extension.

15. The drug delivery device of claim 14 , wherein the first and second plunger extensions are configured to be inter-connectable to each other for forming an elongated piston plunger.

16. The drug delivery device of claim 15 , wherein the first and second plunger extensions are interconnected during dose administration.

17. The drug delivery device of claim 15 , wherein the piston plunger system further comprises a magazine stack,

wherein the first and second plunger extensions are arranged in the magazine stack.

18. The drug delivery device of claim 17 , further comprising

a magazine spring for exerting a biased force onto one of the first or second plunger extensions so as to maintain an urging force upon the first and second plunger extensions.

19. The drug delivery device of claim 18 , wherein the magazine spring comprises a flat band spring.