Propellant powered syringe with trigger

Abstract

A syringe propellable by propellant that boils at a predetermined temperature, the syringe including a barrel having an outlet at a front end, and a stopper axially moveable in the barrel. The stopper separates a first chamber and a second chamber, the first chamber being axially forwards of the stopper and being configured for containing a medicament, and the second chamber being axially rearwards of the stopper and being configured to receive propellant for acting on the stopper to move the stopper axially forwardly in the barrel to expel medicament through the outlet upon actuation of the syringe. The syringe further includes a third chamber for containing propellant. Upon actuation of the syringe, liquid propellant is released from the third chamber and boils outside of the third chamber at or above the predetermined temperature to provide an increasing vapor pressure in the second chamber that causes the stopper to move axially forwardly and begin to expel medicament through the outlet. At least one trigger for triggering an action is provided, the trigger activated in response to the pressure in the second chamber satisfying a predetermined condition.