Drive mechanism for a drug delivery device
A first input member and a second input member are arranged along a first axis and coupled in such a manner that a movement of the first input member along the first axis is converted into a rotational movement of the second input member with respect to the body . A first output member and a second output member are arranged along a second axis and coupled in such a manner that a rotational movement of the first output member is converted into a movement of the second output member along the second axis with respect to the body. The second input member and the first output member are releasably rotationally coupled.
1. A drive mechanism for a drug delivery device, comprising:
a body having a distal end and a proximal end, spaced apart in the direction of a first axis and a second axis that is parallel to the first axis,
a first input member and a second input member, arranged within the body along the first axis and coupled in such a manner that a movement of the first input member along the first axis is converted into a rotational movement of the second input member with respect to the body,
a first output member and a second output member, arranged within the body along the second axis and coupled in such a manner that a rotational movement of the first output member is converted into a movement of the second output member along the second axis with respect to the body,
the second input member and the first output member being releasably rotationally coupled when the first input member is moved in a distal direction,
a pinion member releasably rotationally coupling the second input member and the first output member,
a pawl member engaging with the pinion member allowing rotation of the pinion member in only one direction, and
a clutch coupling the second input member with the pinion member in a releasable fashion such that the clutch couples the second input member with the pinion member when a force is exerted on the first input member in the distal direction, and the second input member and the pinion member are not coupled when the first input member is being shifted in a proximal direction.
2. The drive mechanism according to claim 1 , further comprising:
the pinion member having notches, the pawl member being a hinged tongue or a resilient or resiliently mounted cantilever, and the pawl member having a tip or edge that engages the notches, thus preventing rotation of the pinion member in one direction.
3. The drive mechanism according to claim 1 , wherein
a set operation is performed by shifting the first input member in the proximal direction.
4. The drive mechanism according to claim 1 , wherein
a dispense operation is performed by shifting the first input member in the distal direction.
5. The drive mechanism according to claim 1 , wherein
the first input member is an input shaft, the input shaft being axially movable relatively to the body,
the second input member is an input sleeve, the input sleeve being rotatable around the first axis relatively to the body,
the first output member is an output sleeve, the output sleeve being rotatable around the second axis relatively to the body, and
the second output member is an output shaft, the output shaft being axially movable relatively to the body.
6. The drive mechanism according to claim 1 , further comprising:
a last-dose nut arranged within the body, the last-dose nut being movable relatively to the body along the first axis and being rotationally coupled with the first output member,
the last-dose nut and the second input member being coupled by a screw thread,
the screw thread generating a movement of the last-dose nut in either the distal or the proximal direction when a rotation of the second input member is generated by a shift of the first input member in the proximal direction, and
the body, the first output member or the second input member being provided with a stop element limiting the movement of the last-dose nut in the distal or the proximal direction.
7. The drive mechanism according to claim 1 , wherein the drive mechanism is provided for a fixed-dose drug delivery device.
8. The drive mechanism according to claim 7 , further comprising:
the body or the second input member being provided with a stop element, the stop element limiting the movement of the first input member in the proximal direction.
9. The drive mechanism according to claim 1 , further comprising:
a groove or track of the body locking the second output member rotationally to the body and allowing a shift of the second output member along the second axis.
10. A drug delivery device comprising a drive mechanism according to claim 1 , further comprising:
a compartment provided for a cartridge containing a drug and a piston that is provided to expel the drug from the cartridge, the piston being driven in the distal direction by the second output member.