| 摘要 |
PURPOSE:To move a photodetection part back aside after measurement is completed by fitting a ring fitted with the photodetection part, and a wire around a guide bar provided at right angles to a digger and driving the wire and allowing the photodetection part to reciprocate. CONSTITUTION:The ring body 3 is fitted around the guide bar 2 provided at right angles to the center shaft of the shield digger, the photodetection part 4 incorporating a servo-tracking mechanism and the wire 7 are fixed thereto, and the wire 7 is extended among sheaves 8 and a pulse motor 6. The motor 6 is rotated and reversed to move the photodetection part 4 forth and back and laser light from the front is measured to display the distance to the center shaft of the digger on a display part 10; and the photodetection part is moved aside after the measurement and a rear photodetection part takes a measurement. In this case, a measurement base point is reset with a limit switch 13 on every reciprocating operation and an error is corrected. Consequently, the front photodetection part 4 of two-stage constitution is moved back aside after the measurement. |
