Multidose jet injector

摘要

A multidose jet injector having a main cylindrical body assembly with a jet discharge orifice in its closed forward end and which encloses an internal injector piston element. The piston element can be cocked against heavy spring pressure and, in its cocked position, defines a medicament delivery chamber between the closed end of the main body assembly and the head of the piston. A reciprocative piston puller element is located within the main body assembly, rearward of the piston element, and is connected to a medicament pump cylinder which is enclosed within an elongated rearward tubular portion of the piston element. The puller element is used to pull the piston element to its cocked position and thereafter to reciprocate the medicament pump cylinder to first aspirate a controlled volume of medicament liquid from its supply vial to a medicament transfer chamber (formed within the rearward section of the tubular portion of the piston element) and then pump such medicament via a cannula passageway through the pump body and injector piston to the medicament delivery chamber. The main cylindrical body assembly includes a medicament apportionment mechanism which simultaneously adjusts the respective volumes of the medicament delivery chamber and medicament transfer chamber to allow for changes in desired medicament dosage quantities. Upon release of the injector piston from its cocked position, spring pressure imparts fast and powerful movement to such piston and medicament is ejected from the delivery chamber through the discharge orifice of the injector.