PEN INJECTOR FOR A LIQUID INJECTION PREPARATION

摘要

Disclosed is a pen injector for a liquid injection preparation (3), particularly insulin, comprising a receptacle (2) for the injection preparation (3) and a plunger (6) that can be moved therein. The pen injector further comprises a displacer element (5), the displacement volume of which can be modified and which extends into the section of the receptacle (2) that is filled with the injection preparation (3). Furthermore, compensation means (8) are provided which control the movements of the plunger (6) at least in selected phases of operation in such a way that the plunger (6) simultaneously displaces an identical volume (13) of injection preparation or unblocks an identical spatial volume when the displacer element (5) unblocks a certain spatial volume (11) or displaces a certain volume of injection preparation, or vice versa. The displacer element (5) can be a threaded bar which penetrates a mating threaded hole in the plunger (6). The displacement volume of said threaded bar in the part of the receptacle (2) that is filled with injection preparation (3) can be modified by a rotational and/or an axial movement. Said measure is to prevent air from being sucked into the receptacle (2) when the displacer element (5) unblocks a spatial volume (11).