Multidose jet injector

Claim 1

AN INJECTOR INSTRUMENT COMPRISING A BODY DEFINING AT ONE END A MEDICAMENT CHAMBER HAVING A DISCHARGE ORIFICE, A PLUNGER CARRIED WITHIN SAID BODY AND ENTERING SAID MEDICAMENT CHAMBER, A SPRING ASSEMBLY FOR MOVING SAID PLUNGER AND THEREBY EXPELLING MEDICAMENT THROUGH SAID ORIFICE, SAID SPRING ASSEMBLY COMPRISING A PAIR OF CUPLIKE SLEEVES TELESCOPICALLY RELATED TO EACH OTHER AND SLIDABLE IN SAID BODY, A COMPRESSION SPRING CONTAINED IN SAID SLEEVES AND CONNECTING MEANS BETWEEN THE CUP BOTTOMS TO RETAIN SAID SPRING PRELOADED, A LATCH FOR SAID SPRING ASSEMBLY AND CARRIED BY SAID BODY TO LOCK SAID ASSEMBLY IN A POSITION SLIGHTLY SPACED FROM SAID PLUNGER WHEN THE LATTER IS IN RETRACTED POSITION, A ROLLER CARRIED BY SAID SPRING ASSEMBLY, A CAM SHAFT ROTATABLY CARRIED BY SAID BODY AND HAVING A CAM COACTING WITH SAID ROLLER, AND A LEVER FOR ROTATING SAID CAM SHAFT AND CAM FOR COMPRESSING SAID SPRING ASSEMBLY WHEREBY UPON RELEASE OF SAID LATCH SAID SPRING ASSEMBLY EXPANDS TO IMPART AN INITIAL ADVANCING FORCE TO SAID PLUNGER AND THEREAFTER CONTINUES TO APPLY ADVANCING FORCE FOR EJECTING THE MEDICAMENT.