Portable power tool with improved combustion chamber charging means

A portable power tool comprising:

• a body defining a cylindrical bore;
• a piston, slidably and sealingly housed within said cylindrical bore, for a movement in one direction from a first position through a power stroke into a second position and in an opposite direction through a return stroke;
• a combustion chamber, formed in said body, associated with and arranged for communication with said cylindrical bore at an end remote from said second position of said piston, said combustion chamber being receivable of a gaseous fuel mixture for ignition and combustion;
• at least one double function opening means, provided in said body and communicating with said combustion chamber, for admission of said fuel mixture to said combustion chamber and emission of a residual gas therefrom;
• valve means, mounted within said body, for movement between an open condition and a closed condition relative to said double function opening means;
• fuel supply means for supplying said fuel mixture to said double function opening means;
• exhaust means for removing said residual gas from said double function opening means;
• said valve means, said double function opening means, said combustion chamber, said fuel supply means and said exhaust means cooperating so that when said valve means is in said open condition and said piston at its first position, said fuel mixture is directed into and around said combustion chamber in a manner scouring the combustion chamber of residual gases from a preceding cycle of operation of the tool and sweeping said residual gases out through said double function opening means prior to movement of the valve means to its closed condition;
• ignition means for igniting said fuel mixture in said combustion chamber with said valve means in said closed condition;
• whereby subsequent combustion of said fuel mixture creates an elevated pressure condition within said combustion chamber and such elevated pressure can be passed to said cylindrical bore land said piston therein to cause rapid movement under power of said piston, through said power stroke towards said second position, said piston being arranged to effect a required power assisted operation.