Pressurized gas powered liquid transfer device and system

A transfer device for transferring a medical fluid from a vial to a medical fluid injection device comprising:

• a) a vial elevator configured to receive a vial containing a medical fluid;
• b) a vial elevator shaft within which the vial elevator moves between an extended position and a retracted position;
• c) a vial spike positioned within the vial elevator shaft so that the vial spike is positioned within the vial when the vial elevator is in the retracted position;
• d) an expansion chamber in fluid communication with the vial spike via a gas passage;
• e) an injection device port in fluid communication with the vial spike via a liquid passage;
• f) a pressurized gas cartridge positioned with the expansion chamber;
• g) a puncture tip;
• h) a trigger spring having a hammer, said trigger spring configured to be deflected and released as the vial elevator moves from the extended position into the retracted position;
• and
• i) a flexible wall portion positioned adjacent to the pressurized gas cartridge or the puncture tip and configured to be engaged by the hammer of the trigger spring upon release of the trigger spring after deflection so that the flexible wall portion causes the puncture tip to puncture the pressurized gas cartridge so as to pressurize the expansion chamber.