| 摘要 |
The drill bit skirt (20) contains a concave peripheral cavity (23) whose front end is adjacent to a web (22) located in a region (X) defined between two planes (26, 27) coincidental with the front and rear axial ends of the peripheral pins (19). A rock drill bit (11) for percussion drilling, especially for a water-driven sinking drill hammer, comprises a shaft, a drill head (16) at the front end of the shaft, an elongated mantle surface or skirt, and a number of hard metal pins mounted in the front face (17) of the drill head, and peripheral pins (19) mounted in a peripheral flange. The skirt contains a concave peripheral cavity for reducing its rear axial diameter. The front of the cavity is adjacent to a web located in a region defined between two planes coincidental with the front and rear axial ends of the peripheral pins. |
