There is provided a disposable scalpel having a retractable blade. The blade may be secured in any of three positions: 1) an intermediated retracted position for shipping, 2) an exposed position for use and 3) a permanently locked retracted position. A cap is provided to cover the openings on the scalpel...http://www.google.com.tw/patents/US5330493?utm_source=gb-gplus-share專利 US5330493 - Disposable scalpel
