Torsion spring mechanism for medicament delivery device, and medicament delivery device comprising said mechanism
A mechanism having a base structure; a plunger rod movable along a longitudinal axis; a driver rotatable about the longitudinal axis and engaging the plunger rod; a torsion spring connected to the driver and to the base structure, the torsion spring being arranged to rotationally drive the driver; and at least one support part arranged to support the torsion spring in a lateral direction; wherein the mechanism has at least one rotational interface between the driver and the base structure; and wherein the at least one rotational interface is positioned at between 0.5% and 99.5% of a length of the torsion spring; and/or wherein the at least one rotational interface has a first rotational interface positioned at less than 10% of the length of the torsion spring and a second rotational interface positioned at more than 90% of the length of the torsion spring.
1 . A mechanism for a medicament delivery device, the mechanism comprising:
a base structure;
a plunger rod movable relative to the base structure along a longitudinal axis;
a driver rotatable relative to the base structure about the longitudinal axis and engaging the plunger rod;
a torsion spring having a rotatable end connected to the driver and a base end connected to the base structure, the torsion spring being arranged to rotationally drive the driver; and
at least one support part arranged to support the torsion spring in a lateral direction with respect to the longitudinal axis, wherein the at least one support part comprises a second part, and a first part rotatable about the longitudinal axis relative to the base structure and relative to the second part,
wherein the mechanism comprises at least one rotational interface between the driver and the base structure, and
wherein the at least one rotational interface is positioned at between 0.5% and 99.5% of a length of the torsion spring along the longitudinal axis from the driver to the base structure.
2 . The mechanism according to claim 1 , wherein the torsion spring is a helical torsion spring.
3 . The mechanism according to claim 1 , wherein the driver threadingly engages the plunger rod.
4 . The mechanism according to claim 1 , wherein the at least one rotational interface comprises a first rotational interface positioned at less than 10% of the length of the torsion spring along the longitudinal axis from the driver to the base structure and a second rotational interface positioned at more than 90% of the length of the torsion spring along the longitudinal axis from the driver to the base structure.
5 . The mechanism according to claim 1 , wherein the first part is fixed to the driver.
6 . The mechanism according to claim 1 , wherein the second part is fixed to the base structure.
7 . The mechanism according to claim 1 , wherein a length of the first part along the longitudinal axis differs less than 20% from a length of the second part along the longitudinal axis.
8 . The mechanism according to claim 1 , wherein the at least one support part further comprises at least one intermediate part arranged between the first part and the second part, the at least one intermediate part being rotatable about the longitudinal axis relative to each of the first part and the second part.
9 . The mechanism according to claim 8 , wherein a length of the at least one intermediate part along the longitudinal axis differs less than 20% from each of a length of the first part along the longitudinal axis and a length of the second part along the longitudinal axis.
10 . The mechanism according to claim 1 , wherein the at least one support part is arranged inside the torsion spring with respect to the lateral direction.
11 . The mechanism according to claim 1 , wherein each of the at least one support part is cylindrical.
12 . The mechanism according to claim 1 , wherein each of the at least one support part is concentric with the longitudinal axis.
13 . The mechanism according to claim 1 , wherein the rotatable end comprises a first leg connected to the driver and extending in the lateral direction, and/or wherein the base end comprises an over center second leg connected to the base structure.
14 . The mechanism according to claim 1 , wherein the rotatable end is fixed to the driver and/or wherein the base end is fixed to the base structure.
15 . A medicament delivery device comprising the mechanism according to claim 1 , and a medicament container.
16 . A mechanism for a medicament delivery device, the mechanism comprising:
a base structure;
a plunger rod movable relative to the base structure along a longitudinal axis;
a driver rotatable relative to the base structure about the longitudinal axis while engaging the plunger rod;
a torsion spring arranged around a support part, where the torsion spring comprises a rotatable end connected to the driver and a base end connected to the base structure, where a release of tension of the torsion spring rotates the driver, wherein the support part comprises a first part and a second part, where the first part is fixed to the driver and rotates about the longitudinal axis relative to both the base structure and the second part that is fixed to base structure; and
a rotational interface located between the driver and the base structure, where the rotational interface is positioned at between 0.5% and 99.5% of a length of the torsion spring along the longitudinal axis from the driver to the base structure.
17 . The mechanism according to claim 16 , wherein the at rotational interface comprises a first rotational interface positioned at less than 10% of the length of the torsion spring along the longitudinal axis from the driver to the base structure and a second rotational interface positioned at more than 90% of the length of the torsion spring along the longitudinal axis from the driver to the base structure.
18 . The mechanism according to claim 16 , wherein a length of the first part along the longitudinal axis differs less than 20% from a length of the second part along the longitudinal axis.
19 . The mechanism according to claim 18 , wherein the support part further comprises an intermediate part arranged between the first part and the second part, the intermediate part rotates about the longitudinal axis relative to both the first part and the second part.
20 . The mechanism according to claim 16 , wherein the support part is concentric with the longitudinal axis.