Patent ID: 8197440

Claim:
A needleless injection device comprising: an energy source adjacent a first end of the injection device; a reservoir blocked by a movable upstream stopper and a movable downstream stopper between which a liquid active principle is housed, said movable upstream stopper being disposed adjacent said first end; and an injection nozzle disposed adjacent said second end and further equipped with a receptacle and at least one injection duct, said receptacle containing a cavity with a height equal to a distance covered by the movable downstream stopper before opening each injection duct, wherein the needleless injection device is shaped such that: a height of the cavity in millimeters is between a minimum height and a maximum height respectively defined by the following equations: •minimum height=3 •maximum height=15×exp(−( V/ 9) 2 )+10 where V is a speed of an initial increase in a pressure profile expressed in bars per microsecond; a ratio between a length of each injection duct and the height of the cavity is between 1 and 2.