Patent ID: 8176995

Claim:
A pneumatic hammer drill with a reduced-impact sliding pressure control valve, comprising: a cylindrical casing; an air feed tube, supported along the central axis of the casing, with at least one air distribution slot cut into the distal end of the feed tube; a reciprocating piston, comprising: a front end face and a rear end face, disposed inside the casing; a central bore hole sized to fit closely over the feed tube that allows the piston to reciprocate forward and back along the air feed tube; a rear supply port fluidically connected to the rear end face and to a rear supply port side-hole in the piston that is fluidically connected to the central bore hole; a front supply port fluidically connected to the front face and to a front supply port side-hole in the piston on the opposite side circumferentially from the rear supply port side-hole, that is fluidically connected to the central bore hole; a front piston inner shoulder; and a rear piston inner shoulder; and a reduced-impact sliding spool valve disposed over the air feed tube, inside of the piston, with forward and rear limit stop positions defined by the front piston inner shoulder and by the rear piston inner shoulder, respectively; wherein the reduced-impact sliding spool valve comprises a thin metallic shell filled with particles or balls.