| 摘要 |
A rotary roller bit for drilling earth and rock formations, having a main body and three legs extending outwardly therefrom. Each of the legs carries a conical roller cutter with internal bearings and there is a seal around the periphery of the top of the roller cutter. The periphery of the roller cutter is spaced from the adjacent portion of the leg so as to provide a jet slot for the discharge of air. Adjacent the slot and radially inwardly is an air chamber which is formed between an annular surface of the leg and a seal ring. The air chamber is substantially greater in its dimension axially of the roller cutter and air is supplied to it under sufficient pressure to cause a jet of air to flow from the jet slot at a sufficient rate to prevent the entry of rock particles and dirt into the roller cutter. |
