Laser reference level setting device

Details Laser reference level setting device Laser reference level setting device

1997-01-13

1998-11-24

Buczinski, Stephen C.

Optics: measuring and testing

Angle measuring or angular axial alignment

Photodetection of inclination from level or vertical

35613906, 35613908, G01B 1126, G01C 100

Patent

active

058415270

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a laser reference level setting device for setting a reference level, which serves as a reference for position, posture, etc. of concrete pipes when the concrete pipes are laid and buried underground, and in particular to a laser reference setting device, by which a target used for the laser reference level setting device and the center of the target are detected, and a laser beam is irradiated to the center of the target.


BACKGROUND ART

Typical operation in case concrete pipes are laid and buried underground is to dig the ground and to lay concrete pipes one after another into a ditch and to bury them.
For each linear section, the ground is dug down to the depth where concrete pipes are to be buried, and the concrete pipes are laid on a temporary base installed at the bottom of the ditch. In this case, adjustment is made in such manner that a direction and an inclination of the concrete pipes, in particular the lowermost position of inner side of each of the concrete pipes, are consistent with each other. Then, the concrete pipes are reburied.
These concrete pipes are used as passages for city water, sewage water or for passing other liquid and are laid with a certain inclination and without bending. If the buried concrete pipes are twisted and turned upward, downward, leftward or rightward, the liquid may stagnate or stop or leak into the soil, and the function as the passage cannot be fulfilled. Accordingly, an adequate reference line is required when the concrete pipes are to be laid.
A laser beam is suitable as such a reference line. The laser beam has no problem of slackening as in the case of threads even when used for a long distance, or the laser beam causes no hindrance to working. It is not cut of f due to interference with operators or concrete pipes.
To form a reference line by a laser beam for the purpose of laying concrete pipes, a laser reference level setting device is used.
The laser reference level setting device comprises a laser sighting device and a target. The laser sighting device is placed at a first manhole or at starting point of a ditch, and the target is positioned at the other end of the ditch. The target has a marking at the center to indicate the center position, and the target is placed in such manner that the center position of the target coincides with the center position of the concrete pipe to be laid. The center position of the target is determined by a measuring instrument such as a theodolite, etc.
Next, A laser beam is emitted from the laser sighting device, and the laser sighting device is adjusted so that the laser beam is irradiated toward the center of the target. When the adjustment is completed, the laser beam emitted from the laser sighting device serves as the reference line for laying the concrete pipes.
However, a vibration occurs during construction such as a vibration caused by construction work or by vehicles passing by, and a displacement often occurs due to the vibration. Therefore, re-adjustment must be made when the construction is stopped and so positions of the laser sighting device and the target must be adjusted rather frequently.
Then, the laser reference level setting device and the target are proposed to detect the center of the target.
The laser reference level setting device comprises a laser sighting device and a target. Further, the laser sighting device comprises a laser oscillating device rotatably supported and having an emitting means for emitting a polarized laser beam and a light receiving means for receiving a laser beam reflected from the target, a driving unit for rotating the laser oscillating device in upward, downward, leftward or rightward directions and a control unit for driving the driving unit depending upon a light receiving condition of the laser beam reflected from the target. A reflection surface of the target is designed as a retroreflection surface having a reflection layer comprising small spheres or small prisms. On its left or right half, a 1/4 .lambda.

REFERENCES:
patent: 3894805 (1975-07-01), Middleton
patent: 3907435 (1975-09-01), Roodvoets
patent: 4053238 (1977-10-01), George et al.
patent: 4457621 (1984-07-01), Harris et al.
patent: 4717251 (1988-01-01), Wells et al.
patent: 5098185 (1992-03-01), Watanabe
patent: 5621531 (1997-04-01), Van Adel

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