.Iadd.An improved power-actuated tool having means for preventing firing if the tool is not properly aligned with the work surface. The tool housing member includes a slidably mounted firing mechanism having cocking means extending forwardly into engagement with a sensing means mounted in the barrel...http://www.google.es/patents/USRE30617?utm_source=gb-gplus-sharePatente USRE30617 - Power actuated tool
