Dispensing speed control mechanism and injection device
The present invention relates to a dispensing speed control mechanism for use in an injection device. The injection device may have a housing ( 10, 30, 40; 40′; 40″; 40 ′″) and a drive member ( 70 ), which is driven by a power reservoir ( 100, 100 ′) and axially movable between a dose setting position, in which the drive member ( 70 ) is rotationally constrained to the housing ( 10, 30, 40; 40′; 40″; 40 ′″), and a dose dispensing position, in which the drive member ( 70 ) is rotationally de-coupled from the housing ( 10, 30, 40; 40′; 40″; 40 ′″). The speed control mechanism comprises friction means ( 42 ) for retarding the drive member ( 70 ) during dose dispensing depending on the axial position of the drive member ( 70 ). Further, the invention relates to an injection device with such a dispensing speed control mechanism.
1. A dispensing speed control mechanism for use in an injection device, the mechanism comprising:
a housing;
a drive member;
a power reservoir to drive the drive member, the power reservoir axially movable between a dose setting position in which the drive member is rotationally constrained to the housing, and a dose dispensing position in which the drive member is rotationally de-coupled from the housing; and
a friction member configured to retard the drive member during dose dispensing depending on the axial position of the drive member.
2. The mechanism according to claim 1 , wherein the friction member comprises a clicker mechanism comprising a clicker arm rotationally constrained to the housing, wherein the drive member comprises teeth interacting with the clicker arm in the dose dispensing position of the drive member.
3. The mechanism according to claim 2 , wherein the clicker arm is elastically displaceable in a radially outwards direction, wherein a stiffness of the clicker arm varies over a length of the clicker arm in the longitudinal direction.
4. A handheld injection device comprising:
a dispensing speed control mechanism comprising:
a housing;
a drive member;
a power reservoir to drive the drive member, the power reservoir axially movable between a dose setting position in which the drive member is rotationally constrained to the housing, and a dose dispensing position in which the drive member is rotationally de-coupled from the housing; and
a friction member configured to retard the drive member during dose dispensing depending on the axial position of the drive member; and
a release button displaceable to initiate dispensing of a set dose, wherein the drive member is coupled to the release button such that axial displacement of the release button is transferred to the drive member.
5. The injection device according to claim 4 , further comprising a dose setting member, wherein, during dose setting, the dose setting member rotates relative to the housing in a first direction, and wherein, during dose dispensing, the dose setting member rotates relative to the housing in a second opposite direction.
6. The injection device according to claim 5 , further comprising a limiter mechanism with a limiting element configured to limit the rotational movement of the dose setting member between a minimum dose position and a maximum dose position, wherein the limiting element is movable on a first path rotationally constrained and axially displaceable relative to at least one of the housing or the dose setting member, and is movable on a second, helical path relative to the other of the housing or the dose setting member, and wherein at least one of one of the first path and the second path has an end stop limiting the relative movement of the limiting element.
7. The injection device according to claim 5 , wherein the dose setting member is axially constrained within the housing.
8. The injection device according to claim 5 , further comprising a clutch provided interposed between the dose setting member and the drive member, wherein the clutch allows relative rotational movement between the dose setting member and the drive member during dose setting and prevents relative rotational movement between the dose setting member and the drive member during dose dispensing.
9. The injection device according to claim 4 , further comprising a piston rod, wherein the drive member is rotationally constrained and axially displaceable to the piston rod, and wherein the piston rod is in threaded engagement with the housing.
10. The injection device according to claim 4 , wherein at least the dose setting member is provided with markings visible from the outside of the housing.
11. The injection device according to claim 10 , further comprising a display wheel comprising markings visible from the outside of the housing, the display wheel coupled to the dose setting member by a gear wheel ( 140 ), wherein rotation of the gear wheel ( 140 ) causes intermitted rotation of the display wheel ( 130 ).
12. The injection device according to claim 10 , further comprising a last dose protection mechanism configured to prevent the setting of a dose which exceeds the amount of liquid left in a cartridge and a limiter interposed between the drive member and the dose setting member.
13. The injection device according to claim 4 comprising a cartridge containing a medicament.
14. The injection device according to claim 13 , wherein the power reservoir comprises a reverse wound flat spiral spring pre-tensioned to store energy required to dispense contents of the cartridge.
15. The injection device according to claim 13 , wherein the power reservoir comprises a torsion spring coupled to the dose setting member such that rotation of the dose setting member tensions the spring.