JPH077071B2 - Marker for detecting underground buried objects - Google Patents

Description

TECHNICAL FIELD The present invention relates to a marker used for detecting an object buried in the ground by using radio waves (signals) from the ground, and particularly to a marker such as a synthetic resin. It is suitable to be used by arranging it just above a conduit made of a non-conductive member.

(Prior Art) For an object buried in the ground, such as a water pipe, a gas pipe, and a cable pipe, it is necessary to dig up the buried pipe in order to perform extension work, repair work, or branch work. At this time, underground pipes in the city are complicated by various pipelines, and in order to dig up only the target pipe, a detection marker is buried along the pipeline and this marker is detected from the ground by a detector. Is being detected to confirm the buried position of the pipeline.

For example, U.S. Pat. No. 4,334,227 discloses an invention relating to a marker in which a resonant element including a coil and a capacitor is embedded in an annular frame made of synthetic resin. The markers are installed, for example, directly above the underground buried pipe at intervals, and the marker can be detected by a detector from the ground to know the buried position of the underground buried pipe. To detect a marker, a signal with a frequency equal to the resonance frequency of the marker is sent to the transmitter coil of the detector by current, and when the transmission operation is stopped, the signal emitted from the marker due to the resonance of the marker is received by the detector. The coil receives the signal, and the voltage generated in the receiving coil is detected and output as a meter or speaker sound.
By repeating this transmission and reception and connecting the positions where the output is maximum, the installation position of the pipeline can be confirmed.

(Problems to be solved by the invention) However, in the above-mentioned marker, the transmitted and received signals are weakened by the influence of the electromagnetic field in the ground and diverge into the ground, so that the detection range is narrow and the accuracy is poor. There is. In order to widen the detection range and increase the accuracy, it is sufficient to increase the power of the transmission signal, but if strong radio waves are used, there is a problem that the detection work cannot be performed freely under the regulations of the Radio Law.

(Means for Solving Problems) The present invention solves the above-mentioned drawbacks of a marker having a resonance element and provides a marker for detecting an underground buried object capable of accurately detecting even a weak radio wave. The gist of the invention is that the resonant element is mounted on a non-magnetic plate-like body.

(Function) Since the marker of the present invention has the resonant element mounted on the non-permeable magnetic plate-like body, if the resonant element is installed on the underground buried object so that it faces the ground, The magnetic plate can block the electromagnetic field in the ground to reduce the influence of the electromagnetic field, prevent the emission signal from the detector on the ground to be diverged, and increase the coercive force, as well as the received signal to the ground. The direct effect of the electromagnetic field can be reduced, and weak radio waves can be accurately detected over a wide range.

(Example) Next, the marker of this invention is demonstrated with reference to drawings.

FIG. 1 is a perspective view showing an example of the marker of the present invention.
Is a resonance element, and 2 is a non-magnetic plate-like body. The resonance element 1 is one in which a capacitor is connected to both ends of a coil to form a resonance circuit, and has a unique resonance frequency depending on the wire material of the coil, the winding diameter, the number of windings, the winding method, and the capacitance of the capacitor. To be done. The resonance frequency is preferably in the range of 50 to 200 KHz.

Further, the non-magnetic plate-shaped body 2 may be a plate-shaped body made of a non-magnetic material, and for example, a pure iron plate (having a purity of 99.9% or more), a copper plate or the like can be used. The plate-like body 2 may have any thickness as long as it has a strength not to be deformed even if it is buried in the ground as a plate-like body, and the size is preferably as large as possible, but at least the coil of the resonance element is required. It should be larger than the outer diameter, and if it does not hinder handling, it should be larger than or equal to the size of the underground buried object, for example, in the case of a pipe, larger than the outer diameter of the pipe. Further, the shape is preferably circular so that the outer edge is at the same distance from the resonant element, and particularly, the surface on which the resonant element 1 is mounted is preferably a concave spherical surface like the concave spherical antenna. If the plate-like body 2 has a structure in which a glass powder layer 3 is formed as an intermediate layer between two non-magnetic plate-like bodies and integrated, the glass powder layer is generated by a magnetic field in the ground. Since the eddy current that is generated is cut, the marker detection accuracy is improved.

Then, the resonance element 1 is attached to the plate-like body 2 so that the center of the coil coincides with the center of the plate-like body 2 to form the marker of the present invention. The resonant element 1 may be attached to the plate-shaped body 2 as long as the marker is not separated when it is embedded in the ground, whether it is adhered with an adhesive or fixed with a stopper. Good. Further, since the resonance element 1 and the plate-shaped body 2 are buried in the ground, it is preferable that they are moisture-proofed. This moisture-proof treatment makes it easy to wrap the entire marker with a plastic coating.

The sensitivity of the coil of the resonance element 1 decreases when the winding diameter is small, but it is difficult to handle when the winding diameter is large. Therefore, it is preferable to set the coil to 50 to 200 mm or so. Is preferred. Further, a crystal oscillator may be used instead of the capacitor to form the resonance element 1.

The marker of the present invention configured as described above is used by embedding the resonance element 1 facing the ground and the non-magnetic plate-shaped body 2 in parallel with the ground directly above the underground buried object. It
In the case of a buried pipe, if it is buried along the pipe, the condition of the buried pipe such as the direction of the pipe and the position of the branch can be confirmed.

In addition, if you prepare several types that use resonance elements with different resonance frequencies, even if multiple piping systems are embedded side by side, you can distinguish by simply embedding markers with different resonance frequencies in each. .

(Effect of the Invention) The marker of the present invention has the above-described configuration, and since the resonant element is mounted on the non-magnetic plate-like body, the resonant element is installed on the underground buried object so as to face the ground. When it is used, the non-magnetic plate-like body can block the electromagnetic field in the ground to reduce the influence of the electromagnetic field, prevent the divergence of the transmission signal from the detector on the ground and prevent the direct transmission of the underground electromagnetic field to the reception signal. It is a marker that can reduce the influence and can detect with sufficient accuracy with the electric field strength within the range of the radio station that does not require a license under the Radio Law.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of the marker of the present invention in a partial cross section. 1 ... Resonance element, 2 ... Non-permeable plate-like body, 3 ... Glass powder layer.

Claims (4)

[Claims] 1. A marker for detecting an underground buried object, comprising a resonant element mounted on a non-magnetic plate-like body. 2. The marker according to claim 1, wherein the non-permeable plate is a pure iron plate or a copper plate. 3. The marker according to claim 2, wherein a glass powder layer is formed as an intermediate layer of the non-magnetic plate-like body. 4. The marker according to claim 1, 2, or 3, wherein the resonance element comprises a coil and a capacitor.