| 摘要 |
<p>The rod included in each drill string component for transmission of striker energy to the drill crown at the strings lower end is surrounded by a tubular unit for transmission of rotation to the drill crown. The tubular unit produces a space for drilling fluid between it and the bar, and has two internal diameter reductions which are displaced towards the ends of it. The bar had radial projections which are displaced towards its end, whereby the internal dia. reductions and the radial projections are dimensioned to prevent the bar falling out of the tubular unit. The radial projections take the form of an all-round collar, and a transition part is arranged between the collar and the nearest free end of the bar. The corresp. dia, reduction are in the form of a seat hwich with the transition part is so formed that they and the transitioon part produce a check valve for drilling fluid when they are in contact with each other.</p> |
