Hypodermic injector

Claim 1

A HYPODERMIC INJECTOR COMPRISING A BARREL, A HOUSING SECURED TO ONE END OF SAID BARREL AND DEFINING A RECESS FOR SUPPORTING AN AMPOULE SHELL AGAINST LATERAL DISTENTION WHEN PRESSURE IS APPLIED TO THE CONTENTS OF SAID SHELL, TWO PLUNGERS ARRANGED ONE WITHIN THE OTHER SLIDABLY MOUNTED IN SAID HOUSING TO ENGAGE THE CLOSED END OF AN AMPOULE SHELL WHEN SUPPORTED THEREIN, THE OUTER PLUNGER AT ITS OPERATIVE END BEING IN ADVANCE OF SAID INNER PLUNGER TO RECEIVE A PART OF AN AMPOULE SHELL OF REDUCED CROSS-SECTION FOR SUPPORTING SAID PART AGAINST LATERAL DISTENTION WHEN OPERATED UPON BY THE INNER PLUNGER, FIRST AND SECOND GUIDE MEMBERS SLIDABLY MOUNTED IN SAID BARREL BETWEEN SAID HOUSING AT ONE END AND FLANGE MEANS AT THE OTHER END, EACH OF SAID GUIDE MEMBERS HAVING A FLANGE ON ONE END, A COIL SPRING LOCATED IN SAID BARREL CONCENTRIC WITH SAID PLUNGERS AND BETWEEN SAID FLANGES ON SAID GUIDE MEMBERS, SAID GUIDE MEMBERS HAVING OPPOSED TUBULAR PARTS SLIDABLE ONE WITHIN THE OTHER, MEANS FOR RETAINING SAID GUIDE MEMBERS TOGETHER TO COMPRESS SAID SPRING BETWEEN SAID FLANGES AND MEANS FOR RELEASING SAID GUIDE MEMBERS AFTER SAID SPRING HAS BEEN COMPRESSED TO CAUSE ONE OF SAID GUIDE MEMBERS TO DRIVE FIRST, SAID INNER PLUNGER INTO SAID REDUCED PART OF THE AMPOULE SHELL UNTIL ITS OPERATIVE END IS LEVEL WITH THAT OF SAID OTHER PLUNGER AND THEN BOTH PLUNGERS TOGETHER INTO THE REMAINDER OF THE AMPOULE SHELL, TO CAUSE MEDICAMENT THEREIN TO BE DISCHARGED IN TWO PRESSURE STAGES.