Hypodermic injection device having means for varying the medicament capacity thereof

摘要

A hypodermic injection device comprising a cartridge holder having a cylindrical body open at one end and closed at the other end, the closed end being provided with an aperture, a cartridge with the holder, the cartridge including an ampoule having a cylindrical sleeve open at one end and having a necked portion at the other end to receive a hub mounting a cannula, the cannula facing the apertured end of the cylindrical body, a piston slidably carried within the sleeve adjacent the open end thereof to define a medicament chamber between the piston and cannula, fluid medicament in the medicament chamber, the piston having a concave face on the side forming one end of the medicament chamber, a spring power assembly adjacent the open end of the ampoule sleeve for moving the cartridge forward and for injecting the fluid medicament, spacer means positionable between the outer face of the piston and the adjacent spring power means to vary the position of the piston within the ampoule sleeve and thereby control the volume of the medicament chamber and the medicament carried therein, a safety assembly for controlling actuation of the spring power assembly, and a resilient sheath covering the cannula to maintain the cannula in sterile condition.