Medicament delivery device with a lead screw having a sensor

摘要

The present invention relates to a medicament delivery device such as a pen type injector used to expel medicament from a medicament cartridge under the action of a lead screw. The medicament cartridge typically comprises a cylinder having a displaceable piston at one end displacement causing medicament contained within the cartridge to be expelled. It is of advantage to know when the plunger contacts the displaceable piston since no delivery of medicament can occur before this point. A delivery device is disclosed in which a lead screw for a medicament delivery device comprises a shaft portion and a head portion, the head portion further comprising a fixed part, a displaceable part movable with respect to the fixed part, biasing means acting normally to urge the displaceable part away from the fixed part and a sensor to detect when the displaceable part moves towards the fixed part, one of the fixed part and the displaceable part being provided with a plurality of resilient fingers extending axially with respect to the lead screw, and the other of the fixed part and the displaceable part being provided with a plurality of opening, each of the resilient fingers extending within a corresponding opening.