| 摘要 |
A syringe propellable by propellant that boils at a predetermined temperature, the syringe comprising a barrel having an outlet at a front end, and a stopper axially moveable in the barrel. The stopper defines and 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 comprises a rupturing portion and a third chamber for containing propellant where the third chamber is rupturable. The rupturing portion is configured to rupture the third chamber upon actuation of the syringe to fluidly connect the third chamber to the second chamber and release liquid propellant from the third chamber so that the pressure in the second chamber increases at or above the predetermined temperature causing the stopper to move axially forwardly and begin to expel medicament from the first chamber through the outlet. When propellant is released into the second chamber the pressure in the second chamber increases over a first time period to a first pressure causing the stopper to move axially forwardly to begin expulsion of medicament from the first chamber through the outlet. The syringe is configured such that while the medicament is expelled from the first chamber the pressure in the second chamber changes over a second time period from the first pressure to a second pressure. When substantially all the medicament has been expelled from the first chamber the pressure in the second chamber increases over a third time period towards a third pressure. The magnitude of the second pressure and the rate of increase of the pressure in the second chamber during the third time period are controlled by the thermal conductivity of the components of the syringe defining the second chamber, the rate of delivery of propellant to the second chamber, and the phase of the propellant during delivery into the second chamber. The third pressure is substantially equal to the vapour pressure of the propellant at ambient temperature at the instantaneous volume of the vaporised propellant, and at the third pressure the syringe contains liquid propellant. |
