Hand-held drug injection device and dose setting limiter mechanism therefor

1. A drive mechanism of a drug delivery device for dispensing of a dose of a medicament, the drive mechanism comprising:

a housing;

a piston rod extending in an axial direction to operably engage with a piston of a cartridge;

a drive sleeve rotatably supported in the housing, at least partially enclosing the piston rod, wherein the drive sleeve is operably releasable from the piston rod for setting of a dose and is operably engageable with the piston rod for dispensing of the dose;

a dose limiting member threadedly engaged with the drive sleeve, rotatably locked to the housing, and displaceable in the axial direction in response to a rotation of the drive sleeve relative to the piston rod; and

at least one stop member provided on the piston rod to engage with the dose limiting member for impeding a further displacement of the drive sleeve relative to the piston rod when a maximum dose configuration has been reached;

wherein the dose limiting member comprises at least one radially inwardly extending protrusion engaged with a correspondingly shaped and axially extending groove of the piston rod.

2. The drive mechanism according to claim 1 , wherein the dose limiting member is arranged radially between the drive sleeve and the piston rod.

3. The drive mechanism according to claim 1 , wherein the dose limiting member comprises a sleeve portion enclosing the piston rod.

4. The drive mechanism according to claim 3 , wherein the sleeve portion comprises an outer thread engaged with an inner thread of the drive sleeve.

5. The drive mechanism according to claim 1 , wherein the dose limiting member comprises a bracket portion extending in the axial direction and at least partially protruding from a proximal end of the drive sleeve.

6. The drive mechanism according to claim 5 , wherein the bracket portion comprises two axially extending and parallel oriented branches being mutually interconnected to form a closed frame structure operable to slidably receive a pin of the housing therein.

7. The drive mechanism according to claim 1 , wherein the at least one stop member comprises a radially outwardly extending flange portion at a proximal end of the piston rod.

8. The drive mechanism according to claim 1 , wherein the at least one stop member comprises a crown wheel facing in a distal direction to mate with a correspondingly geared proximal rim of the dose limiting member.

9. The drive mechanism according to claim 1 , wherein the drive sleeve is axially displaceable in a distal direction against the action of a spring, which is axially sandwiched between a proximal rim of the drive sleeve and a drive wheel rotatably engaged with the piston rod.

10. The drive mechanism according to claim 9 , wherein the drive wheel is threadedly engaged with the piston rod.

11. The drive mechanism according to claim 9 , wherein the drive sleeve comprises a crown wheel portion at a distal end face to mate with a correspondingly shaped crown wheel portion of the drive wheel.

12. The drive mechanism according to claim 9 , wherein the proximal rim of the drive sleeve is geared with a pinion of a drive spindle rotatably supported in the housing in a dose incrementing direction against the action of the spring.

13. The drive mechanism according to claim 9 , wherein the drive wheel comprises a geared rim engaged with a ratchet member of the housing operable to generate an audible click sound when the drive wheel rotates in a dose dispensing direction and being further operable to impede a rotation of the drive wheel in the opposite direction.

14. A drug delivery device for setting and dispensing of a dose of a medicament, the drug delivery device comprising:

a drive mechanism comprising:

a housing,

a piston rod extending in an axial direction to operably engage with a piston of a cartridge,

a drive sleeve rotatably supported in the housing, at least partially enclosing the piston rod, wherein the drive sleeve is operably releasable from the piston rod for setting of a dose and is operably engageable with the piston rod for dispensing of the dose,

a dose limiting member threadedly engaged with the drive sleeve, rotatably locked to the housing, and displaceable in the axial direction in response to a rotation of the drive sleeve relative to the piston rod, and

at least one stop member provided on the piston rod to engage with the dose limiting member for impeding a further displacement of the drive sleeve relative to the piston rod when a maximum dose configuration has been reached, wherein the dose limiting member comprises at least one radially inwardly extending protrusion engaged with a correspondingly shaped and axially extending groove of the piston rod; and

a cartridge containing the medicament and being arranged in the housing of the drive mechanism.

15. The drug delivery device according to claim 14 , wherein the dose limiting member is arranged radially between the drive sleeve and the piston rod.

16. The drug delivery device according to claim 14 , wherein the dose limiting member comprises a sleeve portion enclosing the piston rod.