A skin pricker has a barrel (1,11) in which a hammer (2,29) released by a trigger mechanism (32,34) can be shot forwards by a compressed spring (3,38) to impact on a lancet (24) and momentarily project its tip. The rear end of the spring acts against a barrier (4,39) adjustable axially of the barrel,...http://www.google.com.hk/patents/US7572269?utm_source=gb-gplus-share專利 US7572269 - Lancet
