US Patent 10376641 Automatic injection device for administering a fixed dose

An injection device for administering a substance, including a housing, a plunger rod which can be moved relative to the housing, at least one retaining element associated with the rod to hold the rod relative to the housing, and a displaceable locking sleeve which can be displaced relative to the housing from one position in which the sleeve holds the at least one retaining element in a retaining position to a second position in which the at least one retaining element is released.