JPH0972797A - Earth pressure meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure earth pressure even without increasing the mechanical assembly accuracy of an earth pressure meter by providing a pressure reception part and a pressure detection part. SOLUTION: When such pressure as earth pressure is applied to the entire surface of a pressure reception part 5 vertically, the pressure reception part 5 is recessed along an axial line L of a case body 3, thus shifting the short sides of a pressure detection part 12 mutually in parallel direction and hence curving a distorted part. The amount of distortion is transferred to a strain gauge 4 and is taken out externally from a cable 20 as an electrical signal corresponding to the amount of distortion. Even if such pressure as earth and sand is applied to the pressure reception part 5 in cantilever type, the reception part 5 vertically drops along the body 3 so that the detection part 12 is distorted and a strain gauge 14 can accurately detect the earth pressure. Also, a load cell for constituting the detection part 12 has a high sensitivity and improved linearity and is less subjected to the influence of an eccentric load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an earth pressure gauge, and more particularly, to an earth pressure gauge used for measuring the excavation earth pressure at the time of being attached to the tip of an excavator excavating in a tunnel. Regarding the structure.

[0002]

2. Description of the Related Art When excavating Tonuel on a hillside or seabed soil, the rotary excavating blade attached to the tip is rotated to dig into the soil. In this case, in order to control the traveling operation of the excavator, an earth pressure gauge is provided at the tip of the rotary excavating blade to constantly measure the pressure of earth and sand in front of the excavation.

As an earth pressure gauge that has been conventionally used, for example, the one described in JP-B-62-32412 can be mentioned. The structure of this earth pressure gauge is such that a cylindrical case projects in the direction of the earth surface from a substrate attached to the tip of the excavator, and a cup-shaped pressure receiving plate is placed inside the case.
The mouth is placed inside and slidably arranged. On the other hand, at the center of the cylindrical case, a flexure tube is erected from above the substrate. This strain tube is also formed in a deep cup shape, the cylindrical side wall is thick and has rigidity, and its mouth is fixed to the substrate. The bottom portion of the strain-flexing cylinder is formed thin, and the bottom portion faces the bottom portion of the pressure receiving plate, and they are connected by a screw rod. A strain gauge is attached to the bottom of the strain-flexing cylinder. The pressure plate is directed toward the soil surface and attached to the excavator to excavate the soil. During operation, when the pressure plate receives pressure from the soil surface, it retracts in the cylindrical case. This retracting force is transmitted from the screw rod to the bottom of the strain-flexing cylinder, and this portion is deformed in proportion to the earth pressure, and this deformation is detected by a strain gauge to measure the earth pressure.

[0004]

In the conventional earth pressure gauge as described above, since the bottom portion of the pressure receiving plate and the bottom portion of the strain-flexing cylinder are connected by one screw rod, the earth pressure can be accurately measured against the strain. The accurate earth pressure cannot be measured unless the mechanical precision of each part is improved in order to transmit to. Further, since the conventional one has the above-mentioned configuration, in order to minimize the measurement error due to the eccentric load, etc., these shapes are complicated, and there is a problem in reproducibility in mass production. There is. In addition, the strain gauge installation area is small and narrow, resulting in poor sensitivity and poor accuracy.

The present invention is intended to improve the above-mentioned conventional inconveniences, and an object thereof is to make it possible to accurately measure the earth pressure without increasing the mechanical assembly accuracy of the earth pressure gauge. An object of the present invention is to provide a pressure gauge, and to provide a structure of an earth pressure gauge capable of producing an earth pressure gauge having the same characteristics with high reproducibility and high sensitivity without requiring precise adjustment.

[0006]

In order to solve the above-mentioned problems, according to the present invention, an earth pressure gauge for detecting a pressure received from earth and sand by a strain amount of a strain gauge is attached to a substrate and oriented in a pressure receiving direction. A cylindrical case body, a pressure receiving portion having the same outer shape as the inner shape of the case body, slidably fitted on the inner surface of the case body, and interposed between the substrate and the pressure receiving portion, An earth pressure gauge, comprising: a pressure detecting unit having one end serving as a force acting end fixed to a pressure receiving unit and the other end serving as a force acting end fixed to a substrate. .

The pressure detector may be composed of a beam type load cell, and the load cell may be hermetically arranged in the case body. One end side, which is the force acting end of the pressure detecting portion, is fixed at a position eccentric from the center point of the pressure receiving portion. Particularly, it is preferable that the case body has a cylindrical shape.

In another embodiment, two pressure receiving portions are linearly arranged on the substrate, three pressure receiving portions are arranged in a star shape, or four pressure receiving portions are arranged in a cross shape.

In the earth pressure gauge according to the present invention thus constructed, when pressure such as earth and sand is applied to the pressure receiving portion, the pressure receiving portion is dented along the axis of the case body and transmitted to the pressure detecting portion. It This strain is transmitted to the strain gauge of the pressure detection unit and taken out from the cable as an electric signal to the outside.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of an earth pressure gauge according to the present invention, and FIG. 2 is an exploded perspective view thereof. In these figures, 1 is a disk-shaped substrate, and mounting holes 2 are formed at four positions. A cylindrical case body 3 is fixed to the substrate 1 by means such as welding. A pressure receiving element 4 is arranged inside the case body 3. As clearly shown in FIG. 2, the pressure receiving element 4 has a flat cylindrical pressure receiving portion 5. The pressure receiving portion 5 is slidably arranged inside the case body 3. An O-ring 7 is fitted in the depression 6 on the side of the pressure receiving portion 5,
The ring 7 is interposed between the case body 3 and the pressure receiving portion 5 to prevent intrusion of earth and sand into the interior.

The pressure receiving element 4 also has a ring-shaped mounting base 8. The mounting base 8 has a screw hole 9 for mounting on the substrate 1. Then, as shown in FIG. 1, the pressure receiving element 4 is attached to the substrate 1 in the case body 3 with the screw 10. A support pillar 11 is erected from the side of the mounting base 8, and one end of a pressure detection unit 12 is attached to the support pillar 11. In this pressure detection unit 12, four beams are combined into a quadrilateral, and thinly formed strained portions are formed on the long sides arranged in parallel, and the short sides are displaced in parallel to each other, and the strain of the strained portion is distorted. It is constituted by a so-called beam type load cell which measures the force applied to the short side by a quantity.

On the free short side of the pressure detector 12, the connecting column 1
3 is attached. Four strain gauges 14 are attached to the back side of the circular hole for forming the strained portion of the pressure detection portion 12, that is, the strained portion formed thinly. Four strain gauges 14 attached to the strained part
Are connected to a bridge circuit as indicated by a, b, c and d in FIG. The flat portion at the tip of the connecting column 13 is fixed to the portion near the back side peripheral edge of the pressure receiving portion 5 by brazing or welding.

As shown in FIG. 1, a through hole is provided in the center of the substrate 1, a terminal plate 15 is provided inside the through hole, and the input end and the output end of the bridge circuit shown in FIG. Derive to. A cover 16 is attached to the back surface of the substrate 1 with screws 17. 18 is an O-ring, cover 1
The inside of 6 is kept airtight. An electric wire penetrating piece 19 is attached to the center of the cover 16, and the cable 20 is hermetically introduced into the cover 16 and connected to the terminal plate 15 to lead out an electric signal obtained from the bridge to the outside. In addition, in FIG. 1, reference numerals 21, 22, and 23 are a gland washer, a gland packing, and a gland nut, respectively, which constitute the wire penetration metal piece 19. Further, FIG. 4 is a bottom view of the earth pressure gauge according to the present invention.

The earth pressure gauge constructed as described above is attached to the tip of a device such as a rotary excavating blade that requires earth pressure measurement. When the pressure such as earth and sand is applied to the entire surface of the pressure receiving portion 5 in the vertical direction, the pressure receiving portion 5 is recessed along the axis L of the case body 3, and the short sides of the pressure detecting portion 12 are displaced in parallel to each other. As a result, the strained portion is curved. This strain amount is transmitted to the strain gauge 14, and is taken out from the cable 20 as an electric signal corresponding to the strain amount.

Even if the pressure such as earth and sand is applied to the pressure receiving portion 5 in a cantilever manner, the pressure receiving portion 5 descends vertically along the case body 3, so that the pressure detecting portion 12 operates in the same manner as described above. The strain and strain gauge 14 accurately detect the earth pressure. Further, the load cell constituting the pressure detection unit 12 is, for example, the magazine “Measurement Technology” published by Nippon Kogyo Publishing Co., Ltd. September 1977 issue (Vol.
As described on pages 68 to 68, it has characteristics such as high sensitivity, excellent linearity, and less influence of eccentric load. Therefore, even if a large eccentric load is applied to the pressure receiving unit 5 of the vertical shaft, a large error does not occur in the detected pressure.

In the above-described embodiment, the O-ring 7 is only interposed between the case body 3 and the pressure receiving portion 5, so that the earth pressure gauge according to the present invention is used underwater. If a small gap is formed between the O-ring 7 and the inside of the case body 3, there is a risk that water will enter the pressure detection portion through this gap. FIG. 5 is a cross-sectional view showing another embodiment for eliminating such inconvenience. In this embodiment,
A separator plate 24 is provided on the lower surface of the pressure receiving unit 5. The separator 24 is fixed to the pressure receiving portion 5 with a screw 25, and a packing 26 for keeping airtightness is interposed between them. A bellows 27 is provided around the separating plate 24, and a peripheral edge of the bellows 27 is airtightly fixed to the inside of the case body 3 by welding or the like. Further, the tip of the connecting column 13 is fixed to the back side of the separator plate 24 by a method such as welding. Since the other configurations are the same as those in the above-described embodiment, the same reference numerals are given and the description thereof will be omitted. In this embodiment,
The space in which the pressure detection unit 12 is arranged can be shielded from the outside air. Moreover, since the bellows 27 is provided around the separator plate 24, the pressure received by the pressure receiving unit 5 is reliably and accurately transmitted to the pressure detecting unit 12.

In the embodiment of the invention described above, the number of load cells constituting the pressure detector 12 used is one, but
In the embodiment described below, a plurality of load cells are used. That is, in the structure shown in FIG. 6, the load cells 28 are linearly arranged, one end of each of the load cells is fixed to the supporting column 11 standing on the substrate 1, and the other end thereof is fixed to the connecting column 13. In the embodiment shown in FIG. 7, three load cells are arranged in a star shape, one end of each of the load cells is fixed to a supporting column 11 standing on the substrate 1, and the other end thereof is fixed to a connecting column 13. . In the embodiment shown in FIG. 8, four load cells are arranged in a cross shape, and one end of each of the load cells is provided with a support column 11 which is erected on the substrate 1.
, And the other ends are fixed to the connecting columns 13, respectively. By using a plurality of load cells in this way, it is possible to improve the earth pressure limit for maximum measurement and also improve the measurement sensitivity, and since the contacts between the pressure receiving unit 5 and the load cell are dispersed, the eccentric load It will also be less affected.

Although the present invention has been described with reference to the above embodiment, various modifications and applications are possible within the scope of the present invention, for example, changing the cross-sectional shape of the case body from a cylinder to a polygon. These modifications and applications are not excluded from the scope of the present invention.

[0019]

As described in detail above, according to the present invention, the pressure detecting portion for detecting the earth pressure can be semi-assembled before the earth pressure gauge is assembled, so that the mechanical assembling accuracy of the earth pressure gauge can be improved. An accurate earth pressure gauge can be assembled and the assembly process is simplified. Moreover, since the pressure detection unit whose adjustment is almost completed can be incorporated in the earth pressure gauge, the earth pressure gauge can be mass-produced with good reproducibility.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an earth pressure gauge according to the present invention.

FIG. 2 is an exploded perspective view of an earth pressure gauge according to the present invention.

FIG. 3 is a connection circuit diagram of a strain gauge.

FIG. 4 is a bottom view of the pressure receiving element.

FIG. 5 is a cross-sectional view of another embodiment of the present invention.

FIG. 6 is a cross-sectional view of another embodiment of the present invention.

FIG. 7 is a cross-sectional view of this other embodiment of the invention.

FIG. 8 is a cross-sectional view of another alternative embodiment of the present invention.

[Explanation of symbols]

 1 ... Substrate 2 ... Mounting hole 3 ... Case body 4 ... Pressure receiving element 5 ... Pressure receiving part 6 ... Dimple 7 ... ... O-ring 8 ... Mounting base 9 ... Screw hole 10 ... Screw 11 ... Support pillar 12 ... Pressure detection unit 13 ... -Connecting column 14-Strain gauge 15-Terminal plate 16-Cover 17-Screw 18-O-ring 19-Wire penetration 20-Cable 21-Gland washer 22-Gland packing 23-Gland nut 24-Separator 25-Screw 26- ..Packing 27 ... Bellows 28 ... Load cells

Claims (8)

[Claims] 1. An earth pressure gauge for detecting a pressure received from earth and sand by a strain gauge strain amount, which has a cylindrical case body attached to a substrate and oriented in a pressure receiving direction, and an outer shape which is the same as the inner shape of the case body. Then, the pressure receiving portion slidably fitted on the inner surface of the case body is interposed between the substrate and the pressure receiving portion, and one end side serving as a force acting end is fixed to the pressure receiving portion, An earth pressure gauge, comprising: a pressure detection unit having the other end side serving as a working end fixed to a substrate. 2. The earth pressure gauge according to claim 1, wherein the pressure detector is a beam type load cell. 3. The earth pressure gauge according to claim 2, wherein the load cell is airtightly arranged in the case body. 4. The earth pressure gauge according to claim 1, wherein one end side, which is a force acting end of the pressure detecting portion, is fixed at a position eccentric from a center point of the pressure receiving portion. 5. The earth pressure gauge according to claim 1, wherein the case body has a cylindrical shape. 6. The earth pressure gauge according to claim 1, wherein two pressure receiving portions are linearly arranged on the substrate. 7. The earth pressure gauge according to claim 1, wherein three pressure receiving parts are arranged in a star shape on the substrate. 8. The earth pressure gauge according to claim 1, wherein four pressure receiving portions are arranged in a cross shape on the substrate.