Injector for throw-away ampoules - has trigger operated to move ampoule piston forward and released to retract it for aspiration check

摘要

The mechanism is intended for administering an injection using a throw-away ampoule. It is provided with means which permit automatic aspiration (withdrawal of ampoule piston to check whether the injection needle has entered a blood vessel). Aspiration can be effected at any point over the entire stroke of the piston without this affecting the position of the needle. The mechanism may comprise a trigger-operated push rod with barbed plunger to engage the piston, the trigger operating the rod via a spring-loaded friction element during the injection stroke, whilst a further spring-loaded friction element retracts the rod when the trigger is released to aspirate.