| 摘要 |
A rock drilling bit for a pneumatic percussion hammer has a bit head (11), its periphery (11a) substantially cylindrical and perpendicular to a working face (11b). An axial aperture from the top of the bit is in two diameters, the lower (21a) closely slidable on the bottom of an air exhaust tube (22) of the hammer, the upper (21) forming a high pressure air inlet connected to a series of primary and secondary air outlets (25, 26) from the periphery (11a) of the bit head (11), the primary air outlets (25) being connected through the bit to the air exhaust tube (22), the secondary air outlets (26) so directing air under pressure as to form a pressurized air shroud about the bit head (11). |
