DOWNHOLE AIR HAMMER WITH COMBINATION DRILLING TOOL Russian patent published in 1995 - IPC

FIELD: mining. SUBSTANCE: downhole air hammer with combination drilling tool includes body, hammer with central exhaust channel separating body hollow into chamber of working and idle strokes and combination tool which consists of detachable bit with skirt and shank having leading spline thread and centering bead. Body front part has open recess to receive sealing and centering bushing installed movably relative to body and shank. Sealing and centering bushing thrusts end face of bit skirt. Shank centering bead has lock spline thread shifted through one half of step relative to leading spline thread. Bit skirt and body ends have local stiffening ribs inscribed into circumference whose diameter equals the diameter of drill bit. EFFECT: higher efficiency. 8 dwg