Patent ID: 6942638

Claim:
A piston driven needle-less injector system for holding a medicament and delivering a stream of the medicament through an area of skin on an animal, the system comprising: A plunger, the plunger extending about an axis and having a first end, a second end, a mid-portion between the first end and the second end, and an external surface, the plunger including a concave rib that extends about the axis, expanding towards the first end of the plunger, the concave rib extending away from the external surface; An unrestrained ampule, the ampule comprising an elongated hollow body made from a polypropylene material, the elongated hollow body having a first end and a second end, the first end of the elongated hollow body including a nozzle, and the second end of the hollow body including an aperture adapted for accepting the plunger, the aperture for accepting the plunger extending from the second end of the hollow body towards the first end of the hollow body and being in fluid communication with the nozzle, the aperture being sized such that the concave rib produces an sealing fit with the hollow body, while the external surface remains spaced apart from the hollow body, when the concave rib is inserted into the aperture of the hollow body, the concave rib cooperating with the elongated hollow body by expanding and sealing the aperture in response to a deflection in the hollow body, so that deflections in the hollow body caused by a pressure force created as the medicament driven from the hollow body by the plunger are sealed by the concave rib.