Drug Delivery Device with Spring Mechanism

A drug delivery device comprises an housing, an axially displaceable piston rod, a rotatable drive member, a spring housing, a torsion drive spring coupled to the spring housing respectively the drive member, dose setting means allowing a user to simultaneously set a dose amount to be expelled and strain the torsion drive spring correspondingly by rotation of the drive member, and a release member being axially moveable relative to the housing between a proximal initial position and an actuated distal release position. The spring housing is helically coupled to the housing such that the spring exerts a tangential force on the spring housing to thereby bias the spring housing in the proximal direction, whereby the spring housing thereby exerts a proximally directed biasing force on the release member. The spring housing can be moved helically in the distal direction when a distally directed force is exerted on the release member.