Pen needle assembly for intradermal injection

1. A pen needle assembly, comprising:

an outer shell having a first end configured to engage the skin of a patient and a second end;

an inner shell disposed within said outer shell and engageable with a drug delivery device, said inner shell being slidable within said outer shell and having a first end and a second end,

a hub movably disposed within said outer shell and being movable relative to said outer shell and inner shell;

a needle rigidly fixed to said hub;

an adhesive layer disposed on said hub;

a first spring coupled to said outer shell and to said inner shell to retract said inner shell toward said second end of said outer shell;

a second spring extending between said inner shell and hub to bias said hub away from said first end of said inner shell;

wherein said hub and inner shell move downwardly relative to said outer shell during an injection to adhere said adhesive layer on a patient's skin and move upwardly relative to said outer shell to raise the patient's skin to facilitate the injection.

2. A pen needle assembly according to claim 1 , wherein

a tab disposed on an inner surface of said outer shell engages a projection disposed on said hub, thereby preventing upward movement of said hub after an injection such that the pen needle assembly cannot be re-used.

3. A pen needle assembly according to claim 1 , further comprising

a safety cap removably connected to said outer shell.

4. A pen needle assembly according to claim 1 , wherein

said inner shell has an outwardly extending flange with a top face and a bottom face, said first spring being connected to said top face and to said outer shell, and said second spring has a first end contacting said bottom face and a second end contacting said hub.

5. The pen needle assembly according to claim 4 , further comprising

a latch hook having one end coupled to said hub, and a second end with a hook engaging a prong on said inner shell, said second spring biasing said hub away from said inner shell when said hook disengages from said prong.

6. The pen needle assembly according to claim 5 , wherein

said prong extends from said bottom face of said flange toward said hub, and where said outer shell and inwardly extending tab coupled to an outwardly extending protrusion on said hub, and where downward movement of said inner shell contacts said hub to disengage said tab with said prong whereby said second spring biases said hub away from said inner shell.

7. A pen needle assembly, comprising:

an outer shell having a first end adapted to engage a patient's skin at an injection site;

a hub movably disposed within said outer shell;

a needle fixed to said hub and having a patient end for piercing the skin at the injection site;

an inner shell disposed within said outer shell and engageable with a drug delivery pen, said hub being movable relative to the inner shell;

a first spring having a first end connected to said outer shell and a second end connected to said inner shell;

a second spring having a first end connected to said inner shell and a second end connected to said hub;

an adhesive layer disposed on said movable hub for contacting and raising the skin at the injection site; and

a retaining latch disposed between said hub and said inner shell to prevent movement of said hub relative to said inner shell when said retaining latch is engaged with said inner shell.

8. A pen needle assembly according to claim 7 , further comprising

a safety cap removably connected to said outer shell and covering said patient end of said needle.

9. A pen needle assembly according to claim 7 , wherein

said inner shell has a locking prong engaged by said retaining latch.

10. A pen needle assembly according to claim 7 , wherein

a projection on said hub engages a tab on said outer shell, thereby preventing upward movement of said hub after an injection such that the pen needle assembly cannot be re-used.

11. A pen needle assembly according to claim 7 , wherein

said first spring is not compressed between said outer shell and said inner shell when said retaining latch is engaged with said inner shell.

12. A pen needle assembly according to claim 7 , wherein

said second spring is compressed between said inner shell and said hub when said retaining latch is engaged with said inner shell.

13. A drug delivery pen, comprising:

a medicament cartridge;

an outer shell having a first end adapted to engage a patient's skin at an injection site;

a hub movably disposed within said outer shell;

a needle fixed to said movable hub and having a patient end for piercing the skin at the injection site;

an inner shell disposed within said outer shell and adapted to engage said a lower housing of the drug delivery pen;

a first spring having a first end connected to said outer shell and a second end connected to said inner shell to retract said inner shell and hub with respect to said outer shell;

a second spring having a first end connected to said inner shell and a second end connected to said hub to bias said hub away from said inner shell; and

an adhesive layer disposed on said movable hub for contacting and raising the skin at the injection site.

14. A drug delivery pen according to claim 13 , further comprising

a safety cap removably connected to said outer shell and covering said patient end of said needle.

15. A drug delivery pen according to claim 13 , wherein

a retaining latch disposed between said hub and said inner shell prevents movement of said hub relative to said inner shell when said retaining latch is engaged with said inner shell.

16. A drug delivery pen according to claim 15 , wherein

said inner shell has a locking prong engaged by said retaining latch.

17. A drug delivery pen according to claim 13 , wherein

a projection on said hub engages a tab on said outer shell, thereby preventing upward movement of said hub after an injection such that the pen needle assembly cannot be re-used.

18. A method of facilitating medicament injection, comprising the steps of:

moving an outer shell of a pen needle assembly upwardly relative to an inner shell and a needle hub by pushing downwardly on a pen needle assembly on a patient's skin at an injection site;

flexing a projection of the hub of the pen needle assembly inwardly responsive to the upward movement of the outer shell to unlock the hub from the inner shell;

moving the hub downwardly responsive to the unlocking of the hub relative to the inner shell and outer shell to contact an adhesive layer disposed on the hub with the patient's skin at the injection site; and

retracting the inner shell and hub relative to the outer shell and raising the skin at the injection site upwardly, thereby facilitating the injection.

19. A method of facilitating medicament injection according to claim 18 , further comprising

moving the hub downwardly with respect to the outer shell and inner shell by a spring disposed between the inner shell and the hub to bias the hub away from the inner shell.

20. A method of facilitating medicament injection according to claim 18 , further comprising

moving the hub and inner shell upwardly with respect to the outer shell by a spring disposed between the inner shell and the outer shell to retract the inner shell and hub with respect to the outer shell.

21. A method of facilitating medicament injection according to claim 18 , wherein

flexing the projection inwardly disengages a latching hook from a locking prong on the inner shell to allow movement of the hub relative to the inner shell.

22. A method of facilitating medicament injection according to claim 18 , further comprising

limiting upward movement of the hub relative to the outer shell to prevent re-use of the pen needle assembly after an injection.