Injection device having a thread having a variable pitch
The invention relates to an autoinjector for dispensing a liquid product, in particular a highly viscous medication, comprising: a housing, a product container, which is arranged in the housing and has a slidable piston, wherein the piston can be slid in a dispensing direction in order to dispense the product contained in the product container, a forward drive element, which acts on the piston as the product is being dispensed, a first spring, which is preloaded such that the product can be dispensed from the product container by the sliding of the forward drive element and the piston, and a rotation element, which is operatively coupled to the forward drive element, wherein the first spring acts on the rotation element in such a way that the rotation element is set into rotation in order to dispense the product, wherein the rotation element or the forward drive element has a thread having a variable pitch.
1. An autoinjector for dispensing a highly viscous liquid product, comprising:
a housing;
a product container comprising a displaceable piston arranged in the housing, wherein the piston is displaceable in a dispensing direction to dispense the product contained in the product container;
a drive member, which acts on the piston during product dispensing;
a first spring, wherein the first spring is preloaded for dispensing product from the product container; and
a rotation member operatively coupled to the drive member,
wherein the first spring acts on the rotation member such that the rotation member is set into rotation to cause displacement of the drive member and the piston to dispense the product, and
wherein the rotation member or the drive member comprises a thread having a variable pitch.
2. The autoinjector of claim 1 , wherein either the drive member comprises at least one thread segment and has a threaded connection to the rotation member, or the rotation member comprises at least one thread segment and has a threaded connection to the drive member.
3. The autoinjector of claim 2 , wherein a flank of the at least one thread segment of the drive member or of the rotation element comprises different pitch angles.
4. The autoinjector of claim 1 , wherein the rotation member comprises a thread start having an axial portion, and a distance between the drive element and the piston defines an acceleration path, wherein the axial portion is larger than the acceleration path.
5. The autoinjector of claim 1 , wherein the thread having the variable pitch comprises at least one region having a continuous pitch variation or/and a pitch variation of the thread having the variable pitch is discontinuous.
6. The autoinjector of claim 1 , wherein the thread having the variable pitch comprises a degressive thread pitch, whereby a decrease of spring torque during the dispensing can be compensated.
7. The autoinjector of claim 1 , wherein the rotation member comprises the thread having the variable pitch, wherein during a screwing movement between the rotation member and an at least one thread segment of the drive member, a flank of the at least one thread segment is screwed on the thread having the variable pitch of the rotation member, wherein different regions of the flank contact the thread having the variable pitch.
8. The autoinjector of claim 1 , wherein the drive member comprises a first threaded connection to the rotation member and a second threaded connection to one of the housing or an element fixed relative to the housing.
9. The autoinjector of claim 1 , wherein the first spring is a spiral spring.
10. The autoinjector of claim 1 , wherein the drive member is rotationally fixed relative to the housing, and wherein the rotation member is mounted axially fixedly in the housing and is coupled to the first spring such that a relaxation of the first spring causes rotation of the rotation member.
11. The autoinjector of claim 1 , wherein in a bearing position, axial forces arising from a thread transmission from a torque of the first spring are kept small by the thread having the variable pitch comprising a threaded connection at a point having a large pitch.
12. The autoinjector according to claim 1 , further comprising a retaining element, the retaining element comprising at least one axially directed arm, and a first engagement element and a second engagement element positioned on the at least one arm, and wherein the first engagement element releasably couples with a recess of the drive member, whereby the drive member is coupled axially fixedly to the retaining element, wherein the releasable coupling between the drive member and the retaining element is released when the retaining element disengages from the drive member, wherein the drive member is prevented by the releasable coupling from moving in the dispensing direction relative to the retaining element, wherein the releasable coupling can be released for product dispensing such that the first spring can drive the drive member relative to the retaining element in the dispensing direction.
13. The autoinjector of claim 12 , wherein the drive member is configured to move by the first spring in the distal direction relative to the retaining element when the releasable coupling between the first engagement element and the drive member is released and the second engagement element is engaged with a needle guard sleeve or a switching module.
14. The autoinjector of claim 13 , wherein the retaining element is engaged with the drive member and/or with the switching module.
15. The autoinjector of claim 12 , wherein the retaining element is configured for at least two of the following: to retain the drive member, to axially move to produce a start click signal, or to axially move to produce an end click signal.
16. The autoinjector of claim 1 , wherein the first spring is adapted to store the energy necessary for dispensing the product.
17. The autoinjector of claim 1 , wherein the product container is a syringe that has a container body and wherein an injection needle is fixedly arranged at the distal end of the body.
18. The autoinjector of claim 1 , wherein the variable pitch has various pitch angles, wherein the pitch varies along a length of the rotation member or the drive member.