Aspirating plunger for power injector cartridges

In a self-aspirating hypodermic cartridge which contains an injectable fluid therein including a generally cylindrical barrel having a wall, and a plunger reciprocable in said barrel to aspirate the cartridge and to expel said injectable fluid therefrom, wherein the improvement comprising:

• the plunger having
• a female ring component, with a vertically oriented cylindrical hole, having a cylindrical flat bottom portion, a cylindrical flat top portion spaced from said cylindrical flat bottom portion, and a side portion connecting said cylindrical bottom and top portions and integral therewith, said side portion having a degree of incline with respect to a horizontal plane of from about 1.degree. to about 89.degree.;
• a mushroom-shaped component having a cylindrical plunger shaft slideably positioned into said female ring component, and a cone-shaped head at one end of the shaft and integral therewith having a degree of incline with respect to a horizontal plane of from about 1.degree. to about 89.degree.;
• and
• an elastomeric diaphragm-shell having a cylindrical bottom portion and a generally cone-shaped side portion integral therewith covering said male and female components, said cylindrical bottom portion forming a slideable seal between the female ring component and the wall of the cylindrical barrel when the plunger is placed in the barrel and said cone-shaped side portion forming a diaphragm whereby upon alternate exertion of pressure upon said plunger shaft and release thereof the deformation of the diaphragm reduces head space in the cylindrical barrel thereby expelling head space gas and upon release of pressure the diaphragm returns to its original shape resulting in aspiration.