Injection device for delivering a defined number of equal doses of a fluid substance

1. An injection device for delivering a defined number of equal doses of a fluid substance contained in a reservoir, the device having a housing within an arming mechanism and a dose delivery mechanism are arranged along a longitudinal axis of the housing, the housing being coupled to an enclosure adapted for receiving the reservoir with the fluid substance wherein

the arming mechanism comprises a setting sleeve which is axially non-displaceable and rotatable around said longitudinal axis of the housing in two opposite directions by a defined setting angle, the setting sleeve being coupled to a spring having a proximal end coupled to the housing so as to be strained by the rotation of the setting sleeve during arming of the device; and

the dose delivery mechanism comprises (i) a screw ring having an internal thread, (ii) a piston rod having an external thread and at least one longitudinal groove, and (iii) an immobilized blocking sleeve having at least one blocking projection engaging with the at least one longitudinal groove to prevent rotation of the piston rod, which is axially displaceable within the setting sleeve;

the screw ring is selectively engaged with the setting sleeve by projections and an elastic arm, the projections being arranged on an internal surface of the screw ring in equal distances defined by the defined setting angle and the elastic arm being located on a distal end of the setting sleeve, the elastic arm engaging one of said projections after each rotation by the defined setting angle,

wherein during arming of the device, the screw ring and the piston rod are immobilized by a trigger mechanism located on the housing, and

during delivery of each dose, the trigger mechanism is released allowing rotation of the screw ring and displacement of the piston rod along the housing by a defined distance due to unwinding of the spring, the displacement of the piston rod causing the fluid substance to be discharged from the reservoir,

wherein the device further comprises blocking means preventing arming of the device for delivery of a subsequent dose after said defined number of doses of the fluid substance have been delivered, the blocking means comprising at least one longitudinal protrusion located near the distal end of the setting sleeve on an inside surface of the setting sleeve, and at least one longitudinal arm located at a proximal end of the piston rod, the at least one longitudinal protrusion and the at least one longitudinal arm mutually blocking each other after said defined number of doses of the fluid substance have been delivered which prevents rotation of the setting sleeve by the defined setting angle in the arming direction.

2. The injection device according to claim 1 , wherein the spring is mounted on the setting sleeve and the arming mechanism further comprises a scale having a form of a sleeve surrounding the setting sleeve and the spring, wherein distal ends of the spring and of the scale are coupled in rotation with the setting sleeve, and wherein a proximal end of the spring is secured to the housing.

3. The injection device according to claim 1 , wherein the trigger mechanism comprises a trigger engaged with the housing, the trigger being moveable between a first position in which the trigger blocks the rotation of the screw ring and a second position in which the screw ring is free to rotate; the trigger mechanism further comprising a trigger slide which is displaceable along the housing and coupled with the trigger.

4. The injection device according to claim 3 , wherein the trigger comprises an elastic element enabling an automatic return of the trigger and the trigger slide to the first position in which the screw ring is blocked.

5. The injection device according to claim 3 , wherein the trigger comprises a projection which in the first position of the trigger, with the screw ring blocked, is engaged with a corresponding recess of the screw ring.

6. The injection device according to claim 5 , wherein the projection of the trigger engages the recess with a predetermined play.

7. The injection device according to claim 1 , wherein the trigger mechanism comprises a trigger engaged with the housing and being configured to move between two positions.

8. An injection device for delivering a defined number of equal doses of a fluid substance contained in a reservoir, the device comprising:

a housing;

an arming mechanism arranged along a longitudinal axis of the housing, wherein the arming mechanism comprises a setting sleeve which is axially non-displaceable and rotatable around said longitudinal axis of the housing in two opposite directions by a defined setting angle, the setting sleeve being coupled to a spring having a proximal end coupled to the housing so as to be strained by the rotation of the setting sleeve during arming of the device; and

a dose delivery mechanism arranged along the longitudinal axis of the housing, wherein the dose delivery mechanism comprises (i) a screw ring having an internal thread, (ii) a piston rod having an external thread and at least one longitudinal groove, and (iii) an immobilized blocking sleeve having at least one blocking projection engaging with the at least one longitudinal groove to prevent rotation of the piston rod, which is axially displaceable within the setting sleeve;

an enclosure coupled to the housing and configured to receive the reservoir with the fluid substance,

projections arranged on an internal surface of the screw ring in equal distances defined by the defined setting angle;

an elastic arm located on a distal end of the setting sleeve, wherein the screw ring is selectively engaged in rotation with the setting sleeve by the projections and the elastic arm, wherein the elastic arm is arranged to engage one of said projections after each rotation by the defined setting angle,

a trigger mechanism, located on the housing, for immobilizing the screw ring and the piston rod during arming of the device, wherein during delivery of each dose, the trigger mechanism is released allowing rotation of the screw ring and displacement of the piston rod along the housing by a defined distance due to unwinding of the spring, the displacement of the piston rod causing the fluid substance to be discharged from the reservoir; and

a blocking mechanism preventing arming of the device for delivery of a subsequent dose after said defined number of doses of the fluid substance have been delivered, the blocking mechanism comprising at least one longitudinal protrusion located near the distal end of the setting sleeve on an inside surface of the setting sleeve, and at least one longitudinal arm located at a proximal end of the piston rod, the at least one longitudinal protrusion and the at least one longitudinal arm mutually blocking each other after said defined number of doses of the fluid substance have been delivered to prevent rotation of the setting sleeve by the defined setting angle in the arming direction.

9. The injection device according to claim 8 , wherein the spring is mounted on the setting sleeve and the arming mechanism further comprises a scale having a form of a sleeve surrounding the setting sleeve and the spring, wherein distal ends of the spring and distal ends of the scale are coupled in rotation with the setting sleeve, and wherein a proximal end of the spring is secured to the housing.

10. The injection device according to claim 8 , wherein the trigger mechanism comprises a trigger engaged with the housing and a trigger slide which is displaceable along the housing and coupled with the trigger, wherein the trigger is moveable between a first position in which the trigger blocks the rotation of the screw ring and a second position in which the screw ring is free to rotate.

11. The injection device according to claim 10 , wherein the trigger comprises an elastic element enabling an automatic return of the trigger and the trigger slide to the first position in which the screw ring is blocked.

12. The injection device according to claim 10 , wherein the trigger comprises a projection which in the first position of the trigger, with the screw ring blocked, is engaged with a corresponding recess of the screw ring.

13. The injection device according to claim 12 , wherein the projection of the trigger engages the recess with a predetermined play.

14. The injection device according to claim 8 , wherein the trigger mechanism comprises a trigger engaged with the housing and being configured to move between two positions.