A needleless injection device includes an initiator valve controlling flow of compressed gas into a reservoir. A poppet valve connecting to the reservoir has a gas pressure regulation end to regulate flow from the initiator valve into the reservoir. A clamp piston is driven forward by gas pressure from...http://www.google.de/patents/US5399163?utm_source=gb-gplus-sharePatent US5399163 - Needleless hypodermic injection methods and device
