Patent ID: 7419079

Claim:
A pneumatic tool comprising: a first cylinder having a first air inlet; a second cylinder having a second air inlet, said second air inlet also being an outlet so as to pass air in and out of said second cylinder; a first side channel connecting said first air inlet and said second air inlet; and an air inlet and outlet check valve placed on said first side channel so as to control air in and out of said second cylinder, said first side channel being in fluid connection with said second cylinder through said air inlet and outlet check valve, said air inlet and outlet check valve having an built-in check valve, said built-in check valve comprising: an internal valve base having an air inlet hole connected to a side channel thereof; an external valve base having an outlet hole connected to an external side thereof; and a traveling valve positioned so as to travel in an interval space between said internal valve base and said external valve base, wherein said internal valve base has an enlarged slot formed on an outside of said inlet hole thereof, said internal valve base having an annular oblique edge formed between said enlarged slot and said inlet hole thereof, said enlarged slot having an air hole connected to said second cylinder, said external valve base having a protruding tube formed inside said outlet hole thereof, said protruding tube extending to said enlarged slot of said internal valve base, said interval space defined by an opening between an inside of said protruding tube and said inlet hole of said internal valve base, said traveling valve having an internal tapered protruding end and an external tapered protruding end and a tapered loop edge, said internal tapered protruding end corresponding to said inlet hole of said internal valve base, said external protruding end corresponding to said protruding tube of said external valve base, said tapered loop edge corresponding to said annular oblique edge of said internal valve base.