Patent ID: 7201301

Claim:
A combustion-powered fastener-driving tool, comprising: a combustion-powered power source including a cylinder defining a path for a reciprocating piston and an attached driver blade; said piston reciprocating between a pre-firing position achieved prior to combustion and a bottom out position, upon combustion in said power source, said cylinder includes at least one exhaust valve which is a check valve configured for releasing combustion gases from said cylinder and preventing an influx of air in said cylinder through said valve, thus setting up a thermal vacuum in said cylinder after combustion; said at least one exhaust valve having at least one exhaust port being dimensioned as a function of a volume of a combustion chamber defined in part by an upper end of said piston so that sufficient gas is released to reduce combustion pressure in said cylinder to approximately one atmosphere in a designated time period available for said piston to travel past said at least one exhaust valve and return to said at least one exhaust valve.