Spring Driven Injection Device

摘要

The present invention relates to an injection device for automatic torsion spring driven injection of a liquid drug. The injection device is of the type wherein a telescopically movable needle shield activates the release of the torque of the torsion spring to drive the injection when the needle shield is moved from its extended position to a retracted position. The injection device further has a needle holder carrying the injection needle, which needle holder is axially movable both in relation to the housing and in relation to the needle shield. It is therefore possible to retract the needle shield in relation to the housing and at the same time move the needle holder to its extended position such that the injection needle is presented outside the needle shield thereby providing for easy exchange of the injection needle.

主权项

1. A spring driven drug delivery device for delivering set doses of a liquid drug comprising:
a housing securing a cartridge containing the liquid drug and which cartridge is axially fixated to the housing, a dose setting arrangement for setting the size of the dose to be delivered, a torque spring drive mechanism for automatically driving the set dose out from the cartridge through an exchangeable injection needle mountable to the drug delivery device, the torque spring drive mechanism comprising a piston rod which is axially displaceable through engagement with a rotational piston rod guide rotational under the influence of a torsion spring, a telescopically movable needle shield for covering a distal end of the attached injection needle in an extended position and which needle shield when axially moved to a retracted position triggers the release of at least a portion of the torque of the torsion spring in order to perform an ejection of the liquid drug, and wherein a needle holder for carrying the exchangeable injection needle is axially movable relatively to both the housing and to the needle shield.