Pen-type drug injection device with iris-style quick coupling for piston rod reset

摘要

A pen-type drug injection device (1) comprising a housing (2) having a longitudinal axis, a threaded piston rod (3), and a guide member for guiding the piston rod (3) during a drug dispensing operation ( 4) and a cartridge holder (5) for receiving the cartridge (6), the cartridge holder (5) being removable from the housing (2), the guide member (4) being threaded A pen-type drug injection device is disclosed that includes an iris-type aperture (40) defined by a pivotable segment (401). The drug delivery device (1) has an increased diameter of the aperture (40) when the cartridge holder (5) is removed from the housing (2), thereby causing the piston rod to engage the guide member (4; 401). The diameter is reduced when the cartridge holder is installed so that it can be freed from screw engagement and reset or pushed back to its initial position, so that the threads on the segment (401) Configured to re-engage.