A spring assisted drug delivery device is provided comprising a housing and a lead screw having a longitudinal axis, a distal end and a proximal end that is rotatably fixed during dose setting and dose delivery and axially movable in a distal direction relative to the housing. The device further comprises a drive nut threadedly engaged and screwable along the lead screw threaded shaft and a number sleeve threadedly engaged with the housing to be screwable relative to the housing. A dial link is connected with the drive nut and axially movable and rotatably fixed relative to the drive nut and an inner sleeve is threadedly engaged with the number sleeve, the inner sleeve being axially movable and rotatably fixed relative to the housing. A mid-body is axially fixed inside of the housing. A spring is provided that assists a user of the device during a dose administration step.
