Drug delivery device

1. A drug delivery device comprising:

a syringe from which a needle extends;

an inner sheath adapted to be movable between a retracted position in which the needle projects beyond a distal end of the inner sheath and an extended position in which the needle is covered by the inner sheath;

a support sheath adapted to hold the syringe and to hold the inner sheath in the retracted position as well as in the extended position;

a piston rod that is movable from a first position in which the piston rod is retracted, to a second position in which a drug delivery process is finished;

an actuation head that is coupled on a proximal end of the piston rod;

a first locking element formed by an end portion of the actuation head, the first locking element extending in a distal direction, the first locking element having one or more latching elements arranged on an inner surface of an outer wall of the actuation head; and

a second locking element formed by a proximal section of the support sheath, the second locking element extending in a proximal direction, the second locking element having a plurality of latching recesses formed on an outer surface of the proximal section of the support sheath, each latching recess being spaced apart from other latching recesses of the plurality of latching recesses,

wherein the plurality of latching recesses are adapted to receive the one or more latching elements when the piston rod is in the second position.

2. The drug delivery device of claim 1 , wherein when the piston rod is in the second position, the latching elements are locked with respect to the latching recesses to prevent a reuse of the drug delivery device.

3. The drug delivery device of claim 1 , wherein the second locking element has a first plurality of curved portions, wherein each latching recess of the plurality of latching recesses is formed on a respective curved portion of the first plurality of curved portions.

4. The drug delivery device of claim 3 , wherein an outer wall of the second locking element defines the first plurality of curved portions,

wherein an outer wall of the first locking element has an inner circumference larger than an outer circumference of the outer wall of the second locking element, and

wherein the outer wall of the first locking element has a second plurality of curved portions that abut against the first plurality of curved portions when the piston rod is in the second position.

5. The drug delivery device of claim 3 , wherein the first locking element comprises an inner wall comprising an outer circumference smaller than an inner circumference of the second locking element, and

wherein the inner wall of the first locking element has a third plurality of curved portions with curvatures that correspond to curvatures of the first plurality of curved portions of the second locking element.

6. The drug delivery device of claim 1 , wherein the first locking element has a double wall comprising an inner wall and an outer wall, the inner wall having an outer circumference smaller than an inner circumference of the second locking element, and the outer wall having an inner circumference larger than an outer circumference of the second locking element,

wherein a recess arranged between the outer wall and the inner wall of the first locking element is configured to receive the second locking element when the piston rod is in the second position.

7. The drug delivery device of claim 1 , wherein at least two of the latching recesses are arranged opposite one another about a circumference of the second locking element.

8. The drug delivery device of claim 1 , wherein the one or more latching elements of the first locking element comprise a plurality of latching noses, each latching nose being received by a respective latching recess when the piston rod is in the second position.

9. The drug delivery device of claim 1 , wherein the one or more latching elements of the first locking element comprise a circumferential projection configured to be received by one of the plurality of latching recesses when the piston rod is in the second position.

10. The drug delivery device of claim 1 , wherein the actuation head includes one or more fragmented markings that are viewable through the proximal section of the support sheath when the piston rod is in the second position.

11. The drug delivery device of claim 10 , wherein the one or more fragmented marking are viewable through a transparent portion of the proximal section of the support sheath when the piston rod is in the second position.

12. The drug delivery device of claim 1 , wherein the first locking element has an outer circumference smaller than an inner circumference of the second locking element, and

wherein the first locking element comprises a substantially annular portion that extends perpendicular with respect to a longitudinal axis of the drug delivery device such that a circumference of the annular portion is equal to or larger than an outer circumference of the second locking element.

13. The drug delivery device of claim 12 , wherein in the second position the annular portion abuts against the second locking element or the annular portion remains axially spaced from the second locking element by no more than 3 millimeters.

14. The drug delivery device of claim 1 , wherein the second locking element comprises a spring element suitable for being deactivated to retain the inner sheath in the retracted position inside the support sheath and for being activated to allow the inner sheath to move in the distal direction into the extended position.

15. The drug delivery device of claim 14 , wherein the spring element is designed as a first resilient tongue that is integral with an inner surface of the second locking element.

16. The drug delivery device of claim 15 , wherein the first resilient tongue abuts against a second spring element arranged on the inner sheath.

17. The drug delivery device of claim 1 , wherein the syringe contains a medicament.

18. The drug delivery device of claim 1 , further comprising a flange arranged on the support sheath to extend perpendicular with respect to a longitudinal axis of the drug delivery device,

wherein when the piston rod is in the second position the flange abuts against the first locking element or the flange remains axially spaced from the first locking element by no more than 3 millimeters.

19. The drug delivery device of claim 1 , wherein an inner diameter of the outer wall is larger than an outer diameter of the second locking element such that the first locking element at least partially surrounds the second locking element when the piston rod is in the second position.

20. A drug delivery device comprising:

a syringe from which a needle extends;

an inner sheath adapted to be movable between a retracted position in which the needle projects beyond a distal end of the inner sheath and an extended position in which the needle is covered by the inner sheath;

a support sheath adapted to hold the syringe and to hold the inner sheath in the retracted position as well as in the extended position;

a piston rod that is movable from a first position in which the piston rod is retracted, to a second position in which a drug delivery process is finished, and

an actuation head that is coupled on a proximal end of the piston rod;

a first locking element formed by a circumferential end portion of the actuation head, the first locking element extending in a distal direction, the first locking element having one or more latching elements; and

a second locking element formed by a proximal section of the support sheath, the second locking element extending in a proximal direction,

wherein the second locking element has a plurality of latching recesses designed on a plurality of curved portions formed on an outer wall of the second locking element, each latching recess being spaced apart from other latching recesses of the plurality of latching recesses and being formed on a respective curved portion of the plurality of curved portions,

wherein the first locking element has a double wall comprising a first inner wall and a first outer wall, the first inner wall having an outer circumference smaller than an inner circumference of the outer wall of the second locking element, and the first outer wall having an inner circumference larger than an outer circumference of the outer wall of the second locking element, and

wherein, when the piston rod is in the second position, a recess arranged between the first outer wall and the first inner wall of the first locking element is configured to receive the outer wall of the second locking element so that each of the latching recesses of the second locking element receives a respective latching element of the first locking element.

21. A method of delivering drug, the method comprising:

moving a piston rod of a drug delivery device from a first position with respect to a syringe to a second position with respect to the syringe to dispense a drug from the syringe through a needle connected to the syringe; and

locking an actuation head coupled on a proximal end of the piston rod when the piston rod reaches the second position, by engaging one or more latching elements arranged on an inner surface of an outer wall of the actuation head with a plurality of latching recesses formed on an outer surface of a support sheath that holds the syringe, and

wherein moving the piston rod from the first position to the second position causes an inner sheath of the drug delivery device to move from a retracted position in which the needle projects beyond a distal end of the inner sheath to an extended position in which the needle is covered by the inner sheath.

22. The drug delivery device of claim 20 , wherein the one or more latching elements are arranged on an inner surface of the outer wall of the actuation head and the plurality of latching recesses are formed on an outer surface of the proximal section of the support sheath.