Injector for preventing accidental needle sticks

1. An injector for preventing accidental needle sticks, comprising:

a cylinder extending along a longitudinal axis, an inner wall and an outer wall, the cylinder having an outlet at an outlet end opposite an actuating end and a finger grip on the outer wall, which finger grip is positioned between the outlet end and the actuating end;

a piston having a piston body and a deformable sealing element, which deformable sealing element abuts the inner wall of the cylinder at an abutting interface and seals an annular gap between the piston body and the inner wall of the cylinder when the piston is inserted in the cylinder;

a needle guard for mounting on the outside of the cylinder from the outlet end or the actuating end, which needle guard comprises a barrel with a mounting end opposite an operating end, the barrel having a slot for receiving the finger grip of the cylinder when the needle guard is mounted on the cylinder, which slot extends from the mounting end towards the operating end;

wherein when the needle guard is mounted on the outside of the cylinder from the outlet end, the finger grip is received in the slot for receiving the finger grip; and

wherein when the needle guard is mounted on the cylinder from the actuating end in a protective position, the barrel extends along the longitudinal axis and projects beyond the outlet end of the cylinder so that when a hypodermic needle is attached at the outlet end, the barrel protects a user from accidental needle sticks.

2. The injector according to claim 1 , further comprising a hypodermic needle.

3. The injector according to claim 1 , wherein the needle guard is provided with a device for actuating the piston, which can move the piston from the actuating end towards the outlet end of the cylinder when the needle guard is mounted on the cylinder from the actuating end.

4. The injector according to claim 3 , wherein the device for actuating the piston is a compression spring arranged at the operating end of the needle guard.

5. The injector according to claim 4 , wherein the compression spring is a helical compression spring.

6. The injector according to claim 4 , wherein the compression spring has a compression constant, k, in the range of 0.01 N/mm to 1 N/mm, as determined from the relation: k=F/X, where F is the force applied and X is the displacement of the compression spring.

7. The injector according to claim 3 , wherein the device for actuating the piston is a needle cap having a tubular section with a fastening end comprising a device for fastening the needle cap to an inside wall of the barrel, which needle cap has a length, which is equal to or larger than an operating length of the cylinder defined by the distance from the actuating end of the cylinder to the outlet end of the cylinder minus the dimension of the piston parallel with the longitudinal axis.

8. The injector according to claim 7 , wherein the barrel is flexible in a transverse direction, and the needle cap at the fastening end has a fastening device for engaging a complementary fastening device on the inside wall of the barrel, which provide the device for fastening the needle cap to the inside wall of the barrel, wherein the fastening is releasable.

9. The injector according to claim 8 , wherein the barrel has an oval transverse cross section.

10. The injector according to claim 1 , wherein the piston is injection moulded from a TPE.

11. The injector according to claim 10 , wherein the piston has a Shore A hardness in the range of 50 to 90.

12. The injector according to claim 10 , wherein the injector does not comprise a lubricant.

13. The injector according to claim 10 , wherein the cylinder is prefilled with a pharmaceutical composition.

14. The injector according to claim 1 , wherein when the needle guard is mounted on the cylinder from the outlet end in a storage position the barrel shields the user of the injector from a hypodermic needle, when a hypodermic needle is attached to the outlet of cylinder.