Percussion tools incorporating a combustion cylinder for driving a reciprocable hammer piston

Claim 1

IN AN INTERNAL COMBUSTION PERCUSSION TOOL, A HOUSING, A COMBUSTION CYLINDER FORMING PART OF SAID HOUSING, A CAPTIVE PISTON IN SAID HOUSING RECIPROCABLE TO DEFINE GAS EXPANSION AND FLUID COMPRESSION IN SAID COMBUSTION CYLINDER, A FREE WORKING HAMMER PISTON IN SAID HOUSING RECIPROCABLE TO DEFINE GAS EXPANSION AND FLUID COMPRESSION IN SAID COMBUSTION CYLINDER, A FREE WORKING HAMMER PISTON IN SAID HOUSING RECIPROCABLE TO PERFORM A DOWNWARD PERCUSSION STROKE AND AN UPWARD RETURN STROKE WITH RESPECT TO SAID COMBUSTION CYLINDER, A PORTION OF SAID HAMMER PISTON BEING ACTUATED BY COMBUSTION GASES IN SAID COMBUSTION CYLINDER TO PRODUCE THE PERCUSSION STROKE OF THE HAMMER PISTON, A CYLINDER CHAMBER IN SAID HOUSING BETWEEN SAID HAMMER PISTON AND SAID HOUSING FOR ACTUATING THE HAMMER PISTON BY AN UPWARD THRUST THEREON TO PRODUCE THE RETURN STROKE, A PRESSURE FLUID SOURCE, MEANS FOR FEEDING PRESSURE FLUID FROM SAID SOURCE TO SAID CYLINDER CHAMBER, MEANS SEPARATE FROM SAID CYLINDER CHAMBER FOR GIVING SAID HAMMER PISTON AN ADDITIONAL UPWARD THRUST DURING ITS RECIPROCATION, AND MEANS FOR SUBSTANTIALLY REDUCING OR ELIMINATING SAID ADDITIONAL UPWARD THRUST DURING THE PERCUSSION STROKE AND THE RETURN STROKE