| 摘要 |
In apparatus for controlling the position of a drift advancing machine having a longitudinal axis: two light beam sources or laser beam sources spaced longitudinally from the machine, the sources emitting beams which are parallel to each other and to the drift axis and which are in different vertical planes extending longitudinally of the drift; and two beam receivers arranged on the machine, the receivers being in transversely spaced apart positions relative to the longitudinal axis of the machine, and the transverse distance between the receivers corresponding to the transverse distance between the two beams. |
