JP3347288B2 - Tail clearance measurement device using incompressible fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tail clearance measuring apparatus utilizing an incompressible fluid, and more particularly, to a movable element which is loosely fitted to one end of an incompressible fluid-filled pipe provided on an inner surface of a skin plate. The present invention relates to an apparatus for measuring a tail clearance between an inner surface of a skin plate and an outer surface of a segment from a displacement of a piston fitted to the other end of the conduit between a time when the piston is positioned at a reference position and a time when the piston is brought into contact with a segment.

[0002]

2. Description of the Related Art As shown in FIG. 10, in a tunnel construction work for excavating with a shield machine (hereinafter referred to as shield work), a cylindrical shield skin plate (hereinafter, referred to as an outer peripheral wall) of the shield machine 1 is used. The shield segment 5 which becomes the tunnel wall after excavation is assembled inside the rear end of the skin plate 2.

At the time of assembling the segment 5, a minute gap called a tail clearance (L ₁ , L ₂ ,
L ₃ and L ₄ ) need to be managed. If the tail clearance is smaller than the predetermined gap, it becomes difficult to assemble the next segment 5 and the skin plate 2 may come into contact with the existing segment 5 and be damaged.
This causes problems such as difficulty in controlling the attitude of the user. For this reason, tail clearance is an important management item in shield construction.

In order to manage the tail clearance,
That measurement is necessary. In a conventional shield construction, a worker applies a scale or the like between the foremost part of the segment 5 and the skin plate 2 and directly measures the tail clearance by visual observation. On the other hand, JP-A-7-233695 and the like provide a distance sensor or the like based on a wave signal such as a light wave or an ultrasonic wave on the inner surface of a skin plate to be opposed to a segment, and measure a tail clearance by an electric output signal of the distance sensor or the like. It proposes a method to do so. Also, instead of directly measuring the tail clearance, for example, a method of measuring the segment inner diameter after assembly and indirectly measuring the tail clearance by a relatively complicated arithmetic processing based on the measured value of the segment inner diameter has been proposed. I have.

[0005]

However, the method of visually reading the tail clearance not only requires labor for reading, but also has a problem that an error in a read value by a measurer cannot be avoided. On the other hand, the tail clearance measuring method using the distance sensor or the like, although the distance sensor itself can be accurately measured in a laboratory, when used in a work environment of a shield construction, an electric signal of ambient noise is generated. However, there is a problem that an error due to the above-mentioned factors is likely to occur and a highly reliable measurement value cannot always be obtained, and there is also a problem that the electric sensor is weak in dirt and is easily broken, resulting in poor environmental resistance. In addition, the method of indirectly measuring the tail clearance has a problem in that errors are accumulated in the course of complicated arithmetic processing, and the reliability of the final measured value is reduced.

[0006] With the recent increase in the distance and speed of shield construction, there has been a strong demand for quick and automatic tail clearance measurement, and development of a highly reliable measuring device that can be used in a shield construction work environment. Is expected.

An object of the present invention is to provide a tail clearance measuring device capable of performing highly accurate measurement without being affected by the environment.

[0008]

With reference to the embodiment shown in FIG. 1, the tail clearance measuring apparatus using an incompressible fluid according to the present invention comprises a shield excavator 1 in which the inner surface of the skin plate 2 and the outer surface of the opposing segment 5 are connected. In the device for measuring the tail clearance between the segments, a cylindrical concave portion 10 formed in a predetermined portion of the inner surface of the skin plate 2 to face the segment 5, a sliding surface 15a fitted into the concave portion 10 and closely contacting the concave inner surface 10a and the segment. A movable element 12, having a top surface 13 to abut against 5,
Stop member 16 which the sliding of the movable element 12 in the recess 10 top surface 13 is limited to a position where a predetermined projection height L _0, the recess 10
1 from the bottom of the cylinder to the cylinder 20 in which the piston 21 is loosely fitted
8, an incompressible fluid 24 filled in the concave portion 10, the pipe 18 and the cylinder 20, and a pressing means 26 for pressing the piston 21 toward the pipe 18 side. position W of the piston 21 when the surface 13 has a predetermined projection height L _0
0 (see FIG. 1A) and the position W ₁ of the piston 21 when the top surface 13 of the movable element 12 is pressed by the outer surface of the segment 5 against the pressure of the pressing means 26 (see FIG. 1B). Displacement (W ₀ −
W ₁₎ from those obtained by measuring the tail clearance L _1.

A tail clearance measuring device utilizing an incompressible fluid according to the present invention shown in the embodiment of FIG. 4 is a device for measuring a tail clearance between the inner surface of the skin plate 2 of the shield machine 1 and the outer surface of the opposing segment 5. At
A cylindrical recess 10 formed in a predetermined portion of the inner surface of the skin plate 2 to be opposed to the segment 5, and a reduced-diameter hole for closing an entrance 11 of the recess 10.
A movable element 12 having a wall 35 with 35a, a base 39 loosely fitted in the recess 10, a reduced diameter portion 38 with a sliding surface 38a closely contacting the inner surface of the reduced diameter hole 35a, and a top surface 13 to be brought into contact with the segment 5; One end is communicated with each of the sliding limiting means 17 for limiting the sliding of the element 12 to the bottom of the concave portion 10 to a position where the top surface 13 closes the reduced diameter hole 35a, and the inlet side and the bottom side chambers 40a and 40b in the concave portion 10. The closed cylinder 20 in which the first conduit 41 and the second conduit 42 and the piston 21 are loosely fitted and the other end of the second conduit 42 communicates with one of the chambers 54a on both sides of the piston 21, The third conduit 43, one end of which communicates with the other 54b, the concave portion 10, the conduits 41, 42, 43 and the cylinder 20
And a fluid delivery device 45 with a delivery direction control valve 46 connected to the other end of the first pipeline 41 and the third pipeline 43. Fluid 24 to line 41
The position W ₂ of the piston 21 when the top surface 13 of the movable element 12 is brought into a position to close the reduced diameter hole 35a by the feeding of the piston 21 (see FIG. 4A).
And the position W ₃ of the piston 21 when the top surface 13 of the movable element 12 comes into contact with the outer surface of the segment 5 by the supply of the fluid 24 from the supply device 45 to the third conduit 43 (see FIG. 4B). Displacement (W ₃ −
The tail clearance is measured from W ₂ ).

Preferably, in the embodiment of FIG. 1 or FIG. 4, the cross-sectional area S ₂₀ of the cylinder ₂₀ is made sufficiently smaller than the cross-sectional area S ₁₀ of the cylindrical recess 10 to amplify the displacement of the movable element 12 and Displacement.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the embodiment of FIG. 1, a cylindrical recess 10 is formed at a predetermined position on the inner surface of a skin plate 2 to be opposed to a segment 5 at right angles to the inner surface of the skin plate 2 and separated from the recess 10. Hydraulic cylinders 20 for operation and measurement are appropriately arranged at a position on the inner surface of the skin plate 2. The concave portion 10 can be, for example, a hole formed in the inner surface of the skin plate 2 or a bottomed cylinder embedded in the skin plate 2. The bottom of the recess 10, which faces the entrance of the recess 10 on the inner surface of the skin plate 2, communicates with one end of the cylinder 20 through the conduit 18.

The cylinder 20 shown in FIG. 1 is disposed at a position opposite to the shield jack 3 when viewed from the cylindrical concave portion 10,
The installation position of the cylinder 20 is not limited to the illustrated example. Line 18
The cylinder 20 can be arranged at an arbitrary position on the inner surface of the skin plate 2 apart from the cylindrical concave portion 10 as long as the connection with the concave portion 10 is possible. For example, in the embodiment shown in FIG. 5, the cylinder 20 is disposed on the shield jack 3 side when viewed from the recess 10.

Although the pipe 18 in FIG. 1 is provided inside the thickness of the skin plate 2, the pipe 18 is connected to the culvert pipe on the inner side or the outer side of the skin plate unless it interferes with the shield work. can do. In addition, the pipe 18 can be a flexible pipe such as a rubber hose, for example. By making the pipe flexible, the degree of freedom of arrangement of the cylinder 20 can be increased.

As shown in FIG. 1, the movable element 12 having the sliding surface 15a is fitted to the entrance of the inner surface of the skin plate 2 of the cylindrical recess 10 and the piston 21 is loosely fitted to the cylinder 20. Movable element
A space in which both ends are closed by the piston 12 and the piston 21, that is, a space formed by the cylindrical concave portion 10, the pipe 18 and the cylinder 20, is filled with the incompressible fluid 24. The incompressible fluid 24 is a fluid having a sufficiently low compressibility, and may be, for example, hydraulic oil.

The movable element 12 is slidable in the recess 10 by the sliding surface 15.
The stop member 16 limits the top surface 13 of the movable element 12 to a position where the top surface 13 of the movable element 12 has a predetermined protrusion height L ₀ (see FIG. 1A). That is, the movable element 12 is
Is slidable between the bottom of the housing 10 and a position restricted by the stop member 16 on the entrance side of the recess 10.

In FIG. 1, the movable element 12 is provided with an enlarged diameter portion 15 having the same shape as the cross-sectional shape of the concave portion 10, and the concave inner surface 10 a of the enlarged diameter portion 15 is provided.
A stop member that limits the sliding of the movable element 12 toward the entrance by making contact with the top surface of the enlarged-diameter portion 15 as a sliding surface 15a opposite to the sliding surface 15a.
16 is fixed to the inner surface of the entrance of the recess 10. When the enlarged diameter portion 15 of the movable element 12 comes into contact with the stopper member 16, the top surface 13 of the movable element 12
There projects by a height L ₀ from the skin plate 2 internal surface. However, the shapes and positions of the movable element 12 and the stopper 16 are not limited to the illustrated example. Further, the cylindrical concave portion 10, the pipeline 18 and the cylinder 20 can each have an arbitrary cross-sectional shape, and for example, each can have a circular cross-sectional shape.

The pressing means 26 shown in FIG. 1 is disposed at a position where the free end of the force transmission rod integral with the piston 21 is fitted, and applies a predetermined pressing force in the direction in which the transmission rod is extended to the free end of the transmission rod. As a result, the piston 21 is moved closer to the pipe 18. The pressing means 26 in FIG. 1 is capable of accommodating a force transmission rod in accordance with the sliding of the piston 21. The displacement measuring device 28 in FIG. 1 can measure the displacement of the piston 21 from the extension length of the force transmission rod. However, pressing means 26 and displacement measuring instrument
The configuration and arrangement of 28 are not limited to the illustrated example.

The procedure for measuring the tail clearance by the measuring device of the present invention will be described with reference to the embodiment of FIG. First, before assembling the segment 5, a pressing force is applied from the pressing means 26 to the free end of the force transmitting rod, the piston 21 is moved toward the pipe 18, and the incompressible fluid 24 in the pipe 18 is removed from the cylinder 20. It is caused to flow toward the cylindrical recess 10. The movable element 12 in the cylindrical concave portion 10 is slid toward the inlet side of the concave portion 10 by the fluid 24 from the cylinder 20 to a position limited by the stopper member 16. FIG. 1 (A)
Stops the movable element 12 by the pressing force of the pressing means 26.
In slid until the limit, showing a state where the top surface 13 of the movable element 12 is protruded from the skin plate 2 the inner surface by a predetermined height L _0.

As shown in FIG. 1A, the position W of the piston 21 when the sliding of the movable element 12 is restricted by the stop member 16 is shown.
₀ is measured by, for example, the displacement measuring device 28 and is set as a reference position. FIG. 1 shows a movable element using a fluid 24 from a cylinder 20.
This shows a state in which the movable element 12 is pushed up from below, but the positional relationship between the movable element 12 and the incompressible fluid 24 is not limited to the illustrated example. The cylindrical concave portion 10 can be a concave portion of a lower entrance formed in an arbitrary portion on the inner peripheral surface of the skin plate 2, for example, a top portion, and in this case, the movable element 12 is pushed down from above by the fluid 24 from the cylinder 20. State.

On the other hand, after the assembly of the segment 5, the top surface 13 of the movable element 12 is pressed toward the inner surface of the skin plate 2 by the outer surface of the cement 5, and the movable element 12 is stopped against the pressing force of the pressing means 26. , That is, slides inward of the concave portion 10, and the incompressible fluid 24 flows from the cylindrical concave portion 10 side to the cylinder 20 side. The fluid 21 from the recess 10 causes the piston 21 in the cylinder 20 to slide toward the side opposite to the pipe 18. FIG.
(B) shows a state in which the top surface 13 of the movable element 12 is pressed by the segment 5. Top surface 13 pressed by segment 5
Protrusion height L ₁ of the tail clearance after segment assembly. As shown in FIG. 1 (B), the position W ₁ of the piston 21 pushed by the pressing of the segment 5, e.g., measured by the displacement meter 28.

Assuming that the compressibility of the incompressible fluid 24 is zero, the segment 5 projects from the top surface 13 of the movable element 12 to a height L _0.
The amount of fluid flowing from the cylindrical recess 10 during pressing to L ₁ to the conduit 18 from the product of the displacement of the sectional area S ₁₀ and top surface 13 of the cylindrical recess 10 (L ₀ -L ₁₎ ( S ₁₀ × (L ₀ −L ₁ )). On the other hand, the amount of fluid flowing out of the pipe 18 to the cylinder 20 during this time is determined by the product (S ₂₀ × (W ₀ −W ₁ ) of the sectional area S ₂₀ of the cylinder ₂₀ and the displacement (W ₀ −W ₁ ) of the piston 21. )). Since the inflow amount to the conduit 18 runoff equal, in the example of FIG. 1 can be calculated by the following equation (1) the tail clearance L ₁ after segment 5 assembly.

[0022]

L ₁ = L ₀ − {(W ₀ −W ₁ ) × (S ₂₀ / S ₁₀ )} (1)

Instead of the above equation (1), a relational expression between the displacement (L ₀ -L ₁ ) of the top surface 13 of the movable element 12 and the displacement (W ₀ -W ₁ ) of the piston 21 before the measurement of the tail clearance is started. the determined by the calibration, it is possible from the obtained relationship and displacement of the piston 21 (W ₀ -W ₁₎ and a predetermined height L ₀ Metropolitan Request tail clearance L _1.

In the present invention, since the tail clearance is measured using the incompressible fluid 24, there is no trouble that the measuring instrument (sensor) becomes inoperable due to muddy water even in the working environment in the shield work, and the skin plate is not affected. 2. The tail clearance at a predetermined portion of the inner surface 2 can be directly and accurately measured. Further, there is no need to interrupt the shield work for the measurement, and the tail clearance can be measured in real time when the segment 5 is assembled.

Thus, the object of the present invention is to provide a "tail clearance measuring device capable of performing highly accurate measurement without being affected by the environment".

[0026] Preferably, the ratio of the cross-sectional area S ₂₀ of the cylinder 20 to the cross-sectional area S ₁₀ of the cylindrical recess 10 in the formula (1) (S ₂₀ / S
₁₀ ) is made sufficiently small, and the displacement (L ₀ −L ₁ ) of the top surface 13 of the movable element 12 is amplified to be the displacement (W ₀ −W ₁ ) of the piston 21. If the displacement (W ₀ −W ₁ ) of the piston 21 can be amplified, even a slight displacement (L ₀ −L ₁ ) of the top surface 13 can be reliably detected, so that more accurate measurement of the tail clearance can be performed. Become.

As shown in FIG. 4, the pressing means 26 shown in FIG.
Instead of using a fluid feeder 45 with a feed direction control valve 46,
The fluid supply device 45 is connected to a first conduit 41 connecting the inlet-side chamber 40a in the recess 10 and a chamber 54b opposite to the conduit 18 (the second conduit 42 in FIG. 4) of the cylinder 20. By providing the third conduit 43, the position W ₂ of the piston 21 when the top surface 13 is positioned at the same height position as the inner surface of the skin plate 2 by the fluid supply from the supply device 45 to the first conduit 41. If the displacement between the position W ₃ of the piston 21 when brought into contact with the movable element top surface 13 to the segment 5 outer face by the fluid fed from the delivery device 45 to the third conduit 43 (W ₃ -W ₂₎ From, the tail clearance can be measured.

In the case of FIG. 4, the movable element 12 does not need to always protrude from the inner surface of the skin plate 2 as shown in FIG. 12 can be accommodated in the recess 10 (FIG. 4A)
reference). That is, in the embodiment of FIG. 4, it is sufficient that the movable element 12 protrudes from the inner surface of the skin plate 2 only at the time of measuring the tail clearance.

[0029]

FIG. 2 shows a supporting member 31 fixed to the inner surface of a skin plate 2 for supporting a piston 21 in a fixed direction, and a supporting member.
The embodiment of the pressing means 26 provided with an extension spring 33 interposed between the piston 31 and the piston 21 is shown. Pressing means 26 of FIG.
Referring to FIG. 2B, which is an enlarged view of a portion of a circle B including a circle, a support member 31 having one end fixed to the inner surface of the skin plate 2 is engaged with the free end of the force transmission rod of the piston 21. Board
Attach the extension spring 32 between the locking plate 32 and the support member 31.
To join. The extension spring 33 applies a pressing force to the locking plate 32 to bring the piston 21 closer to the pipeline 18 side, and the piston 21
Top 13 of movable element 12 in cylindrical recess 10 by fluid 24 from
Can be projected until limited by the stop member 16. However, the pressing means 26 of the present invention is not limited to the examples shown in FIGS. 1 and 2, but may be any as long as it presses the piston 21 toward the pipe 18 with a constant pressure.

FIG. 2 shows the displacement of the piston 21 in the axial direction of the cylinder 20 measured by a contact displacement measuring device 28 such as a linear encoder. The displacement measuring device 28 shown in FIG. 2 is arranged at a position facing the locking plate 32 attached to the free end of the force transmission rod of the piston 21 and is parallel to the skin plate axis O by the linear motor from the displacement measuring device 28 during measurement. Contact in the direction
The extension of the piston 21 is brought into contact with the locking plate 32, and the displacement of the piston 21 is measured from the change in the extension length of the contact 28a. For example, if the output value of the displacement measuring device 28 is offset to zero in the state before the assembly of the segment 5 shown in FIG. 1A, the displacement (W ₀ −) of the piston 21 after the assembly of the segment 5 shown in FIG. W ₁ ) can be obtained directly from the output of the displacement measuring device 28.

FIG. 3 shows an embodiment in which the top surface 13 of the movable element 12 can be brought into sliding contact with the outer surface of the segment 2. FIG. 3 (A)
Is a top surface 13 formed into the same curved surface as the outer diameter R of the segment 5.
FIG. 3B shows a top surface 13 provided with sliding means 14 such as a wheel device. By enabling the sliding contact between the top surface 13 of the movable element 12 and the outer surface of the segment 5, the tail clearance measurement by the device of the present invention can be continued even while the shield machine 1 is excavating.

FIG. 4 shows another embodiment of the present invention in which a fluid feeding device 45 with a feeding direction control valve 46 is used in place of the pressing means 26 shown in FIGS. In the embodiment of FIG. 4, the entrance 11 of the cylindrical concave portion 10 formed in a predetermined portion of the inner surface of the skin plate 2 is closed by the wall 35 having the reduced diameter hole 35 a, and the base portion 3 that is loosely fitted in the concave portion 10.
9 and a movable element 12 provided with a reduced diameter portion 38 having a sliding surface 38a in close contact with the inner surface of the reduced diameter hole 35a.
40a and a bottom chamber 40b are formed. Further, a closed cylinder 20 in which the piston 21 is loosely fitted and the chambers 54a and 54b are formed on both sides of the piston 21 is used instead of the cylinder 20 in FIG. Each of the cylindrical concave portion 10 and the cylinder 20 can be a hydraulic jack.

The inlet-side chamber 40a in the recess 10 and the fluid feeding device 4
5 is connected by a first conduit 41, a chamber 40b on the bottom side in the recess 10 and one chamber 54a of the cylinder 21 are communicated by a second conduit 42, and the other chamber 54b of the cylinder 21 is connected to the other chamber 54b. The inlet device 45 and the third conduit 43
Connect with. Each of the conduits 41, 42, and 43 can be a flexible conduit such as a rubber hose, for example, and the concave portion 10, the cylinder 21, and the fluid supply device 45 can be appropriately arranged at positions separated from each other. By disposing the cylinder 20 at a stable portion with little muddy water or vibration, damage to the displacement measuring device 28 can be reliably prevented. Recess 10 and each conduit 41, 42,
The 43 and the cylinder 20 are filled with the incompressible fluid 24.

As shown in FIG. 7, for example, as shown in FIG. 7, the fluid feeding device 45 includes a feeding direction switching valve 46 and a tank 4 for storing the fluid 24.
8, the fluid feed pipe 5 provided between the direction switching valve 46 and the tank 48
2 and fluid pump 47 provided on fluid return pipe 53 and fluid feed pipe 52
And a filter 49 and a valve 51, and a fluid feed pipe 52 and a fluid return pipe 53.
And a pressure control valve device 50 provided between the two.
The feed direction switching valve 46 switches between a phase in which the fluid feed pipe 52 is connected to the first pipe 41 and a phase in which the fluid feed pipe 52 is connected to the third pipe 43. Further, the pressure control valve device 50 has setting means and measuring means for setting the fluid pressure in the fluid feed pipe 52, compares the measured fluid pressure with the set fluid pressure, and determines that the measured fluid pressure is equal to or higher than the set fluid pressure. When it is confirmed, the pressure control valve is opened to maintain the fluid pressure in the fluid feed pipe 52 at the set fluid pressure.

The procedure of the tail clearance measurement according to the embodiment of FIG. 4 will be described. First, the feed direction control valve 46 is set to the phase at which the fluid feed pipe 52 is connected to the first conduit 41, and the feed device 45 is set.
Feeds the fluid 24 into the first conduit 41 from the
24 flows into the chamber 40a on the inlet side in the recess 10. The top surface 13 has a reduced diameter hole 35 for sliding the movable element 12 toward the bottom of the recess 10 in the recess 10.
Sliding restricting means 17 is provided for restricting the position of the movable element 12 to the position for closing a. The movable element 12 slides toward the bottom of the concave portion until the movable element 12 is restricted by the sliding restricting means 17 by the fluid 24 from the first conduit 41.

FIG. 4A shows a state in which the sliding of the movable element 12 is restricted by the sliding restriction means 17. In FIG. 4, the sliding limiting means 17 is the bottom surface of the concave portion 10, and the top surface 13 is positioned at the position where the top surface 13 closes the reduced diameter hole 35a when the movable element 12 contacts the bottom surface of the concave portion 10, that is, at the same height position as the inner surface of the skin plate 2. ing. However, the sliding restriction means 17 is not limited to the example of FIG. When the movable element 12 slides toward the bottom of the recess, the fluid is sent from the bottom chamber 40b in the recess 10 to the second pipe 42, and the fluid 24 in the second pipe 42 is transferred to the chamber 54a in the cylinder 20. The piston 21 flows and moves the piston 21 toward the chamber 54b. The position W ₂ of the piston 21 at this time is measured by the displacement meter 28.

Thereafter, the phase of the inlet direction control valve 46 is switched to the phase at which the fluid feed pipe 52 is connected to the third pipe 43,
The fluid 24 is delivered from the delivery device 45 to the third conduit 43. The fluid 24 in the third conduit 43 flows into the chamber 54b in the cylinder 20, moves the piston 21 toward the chamber 54a, and the fluid 24 in the chamber 54a in the cylinder 20 passes through the second conduit 42 into the concave portion 10. To the bottom chamber 40b. FIG. 4B shows a state in which the top surface 13 of the movable element 12 in the concave portion 10 protrudes by the fluid 24 from the cylinder 20 until the top surface 13 contacts the outer surface of the segment 5. The position W ₃ of the piston 21 at this time is measured by the displacement meter 28.

Assuming that the compressibility of the incompressible fluid 24 is zero, the outflow amount of fluid from the cylinder 20 and the inflow amount of fluid into the recess 10 are equal to each other. FIG using the cross-sectional area S ₂₀ of the cross-sectional area S ₁₀ and the cylinder 20 4
The tail clearance L of (B) can be calculated by the following equation (2). In Figure 4, since moving the top face 13 of the same height as the segment 2 the inner surface to a position abutting the segment 5 outer surface can be immediately calculated tail clearance L from the displacement of the piston 21 (W ₃ -W ₂₎ .

[0039]

L = (W ₃ −W ₂ ) × (S ₂₀ / S ₁₀ ) (2)

In the equation (2), as in the case of the equation (1), the amplification was performed by sufficiently reducing the ratio (S ₂₀ / S ₁₀ ) of the cross-sectional area S ₁₀ to the cross-sectional area S ₂₀ . Displacement (W ₃ −W ₂ ) is possible. Further, instead of the equation (2), the tail clearance can be obtained from the relational expression between the tail clearance L obtained by the calibration and the displacement (W ₃ −W ₂ ) of the piston 21.

FIGS. 5 and 6 show an embodiment of the present invention in which a nested hydraulic jack 34 is used instead of the cylindrical concave portion 10 and the movable element 12 shown in FIG. Nested hydraulic jack shown in FIG.
34 is a wall with fluid ports 44a, 44b for forming the cylindrical recess 10
The movable element 12 having a base portion 39 and a reduced diameter portion 38 is fitted into the cylindrical concave portion 10 in the wall body 36.

The movable element 12 shown in FIG. 6 includes a cylindrical through hole 60 penetrating the movable element 12 from the top surface to the other end, and a movable element having the through hole 60.
12 Wall 61 with reduced-diameter inner hole 61a that closes the top side mouth, through hole 6
A movable inner element 63 having a base 65 that loosely fits into the inner diameter of the inner element 63, a reduced-diameter section 64 with a sliding surface that is in close contact with the inner surface of the reduced-diameter inner hole 61a, and a top surface 13 to be brought into contact with the segment. Sliding restricting means 66 for restricting the sliding to the end side to a position where the top surface 13 of the inner element 63 closes the reduced-diameter inner hole 61a, and the chamber 67 in the through hole 60 to the inlet side chamber 40a in the recess 10 (FIG. 4), and a simultaneous sliding inhibiting means 70 for inhibiting simultaneous sliding of the movable element 12 and the inner element 63.

The operation of the telescopic jack 34 will be described with reference to FIG. The first conduit 41 is connected to the fluid port 44a, and the second conduit 42 is connected to the fluid port 44b. FIG.
(A) shows that when the fluid flows into the chamber 40a from the first conduit 41, the movable element 12 is moved by the sliding restricting means 17 (in FIG.
(Inner bottom surface) slides toward the chamber 40b side until restricted. The state in FIG. 6A corresponds to the state in FIG. At this time, the fluid also flows from the chamber 40a into the chamber 67 in the through hole 60 via the fluid passage 68, and the inner element 63 in the through hole 60 is provided with the sliding restriction means 66 (in FIG. 6, provided on the inner surface of the through hole 60). Until it is restricted by the locking means). That is, in FIG. 6A, the top surface 13 of the inner element 63 closes the reduced-diameter inner hole 61a on the top surface side of the movable element 12 of the through hole 60, that is, is positioned at the same height as the top surface of the movable element 12. .

FIG. 6 (B) shows a state in which the second port 42 is connected to the fluid port.
This shows a state in which the fluid is flowing into the bottom chamber 40b in the recess 10 via 44b. 6 not only restricts the sliding of the inner element 63 but also functions as a simultaneous sliding inhibiting means 70 for inhibiting the inner element 63 from sliding at the same time as the movable element 12. That is, the simultaneous sliding inhibition means 70 of FIG. 6 determines the static friction coefficient between the inner surface of the through hole 60 and the inner element 63 by the
The coefficient of static friction between the inner surface and the movable element 12 is made larger. Therefore, when the fluid flows into the chamber 40b,
First, the movable element 12 slides, and the sliding of the inner element 63 is suppressed. The top surface 13 of the inner element 63 projects at the same height as the top surface of the movable element 12, and the fluid in the chamber 40a is pushed out to the first conduit 41 via the fluid port 44a. However, the simultaneous sliding inhibition means 70 is not limited to the illustrated example.For example, it is assumed that the static friction coefficient between the inner surface of the through hole 60 and the inner element 63 is smaller than the static friction coefficient between the inner surface of the concave portion 10 and the movable element 12. be able to.

FIG. 6C shows a state in which the sliding of the inner element 63 is started after the sliding of the movable element 12 is restricted by the contact between the base 39 of the movable element 12 and the wall body 35 having the reduced diameter hole. Show. At this time, the top surface 13 of the inner element 63 projects from the movable element 12, and the fluid in the chamber 67 in the through hole 60 is pushed out to the first conduit 41 via the fluid passage 68 and the fluid port 44a. Top surface 13 of inner element 63
Are projected until they come into contact with the outer surface of the segment 5.

According to the telescopic hydraulic jack 34 shown in FIG.
The displacement width of the top surface 13 of the inner element 63 can be the sum of the sliding width of the movable element 12 and the sliding width of the inner element 63. For example, the hydraulic jack 34 has a low jack height and a short movable element 12.
Even when only the sliding width of the movable element 12 can be secured, the top surface 13 can be made to protrude beyond the sliding width of the movable element 12 by using the telescopic type. That is, according to the nesting type hydraulic jack 34 of FIG. 6, even when the sliding width of the movable element 12 is short, the protruding height of the top surface 13 can be increased as compared with the case of FIG. The jack height for securing the predetermined protrusion height can be kept low. The thickness of the skin plate 2 of the shield machine 1 is limited, and the nested hydraulic jack 34 capable of reducing the jack height is advantageous.

FIG. 6 shows a single inner element inside the movable element 12.
Although the telescopic hydraulic jack 34 provided with 63 is shown, two or more layers of inner elements 63a and 63b can be provided as shown in FIG. 5, and further reduction in the height of the jack can be expected. Nested hydraulic jack 34 with two or more inner elements 63a, 63b
Can be easily manufactured by those skilled in the art based on the example of FIG.

In the nested hydraulic jack 34 shown in FIG.
The top plate 74 fixed to the top surface 13 and the top plate 74
A spring 75 is provided for drawing inward. However, the top plate 74 and the spring 75 are not essential to the present invention.
In FIG. 5, the opening 8 penetrating the skin plate 2 is closed by an opening cover 9 from the outer surface of the skin plate, and a nested hydraulic jack 34 is disposed in the closed opening 8. However, the arrangement of the telescoping hydraulic jack 34 is not limited to the illustrated example, and the opening 8 and the opening cover 9 penetrating the skin plate 2 are not essential to the present invention.

In the embodiment of FIGS. 4, 5 and 6, preferably, as shown in FIG.
A communication path 56 for communicating between the chambers (40a, 40b) on both sides of the movable element 12 and the chambers (54a, 54b) on both sides of the piston 21;
58, a check valve device 57 that can be released in each communication path 56, 58,
59 will be provided. Since a fluid circuit is used in the present invention, it is preferable to bleed air from the piping as a preparation before the tail clearance measurement. Communication passage with check valve device 57, 59
56 and 58 enable air bleeding. The communication passage 56 is
For example, it can be connected between the communication port fluid ports 72a and 72b of the telescopic hydraulic jack 34 shown in FIG.

The procedure of tail clearance measurement including the air bleeding operation will be described below with reference to FIGS. In the embodiments shown in FIGS. 7 to 9, first, air bleeding (FIG. 7) is performed, and after the air bleeding is completed, the tail clearance measurement is performed in the order of zero adjustment (FIG. 8) and main measurement (FIG. 9).

[Air Vent] FIG. 7 shows a fluid circuit during the air bleed operation. During the air bleeding operation, as shown in FIG. 7, the check valves of the check valve devices 57 and 59 are released, and the communication in the communication passages 56 and 58 is ensured in both directions. For this reason the fluid 24 that is fed from the fluid delivery device 45 to the first conduit 41, as indicated by the arrows in FIG. 7, all rooms 40a in telescoping hydraulic jacks 34, 40b, 67 (see FIG. 6) Via all chambers 54a, 54b and all lines 41, 42, 43 in the cylinder 20
Te feed by Rukoto is circulated back to the input device 45, of which
Air in chambers 40a, 40b, 67, 54a, 54b and pipes 41, 42, 43
Can be eliminated .

Referring to FIG. 7, FIG. 4 and FIG. 6, at the time of bleeding, the movable element 12 in the recess 10 is moved to the side of the chamber 40a by the fluid 24 fed from the fluid feeding device 45 to the first conduit 41. The inner element 63 moves toward the chamber 67 in the through hole 60. This is because the areas in contact with the chambers 40a and 40b on both sides of the movable element 12 are different, and the areas in contact with the chambers 67 and 40b on both sides of the inner element 63 are also different. Thus, the movable element 12 and the inner element 63 each protrude until the top surface 13 contacts the segment 5. On the other hand, the piston 21 in the cylinder 20 moves toward the chamber 54b until the stroke limit is reached.

The above-described air bleeding operation is performed mainly for the purpose of eliminating air mixed in the incompressible fluid. This is because air is a compressible fluid, and mixing of air causes an increase in measurement error. In addition, the air bleeding operation of circulating the fluid 24 prevents local fluctuations in the temperature of the fluid in the piping, and prevents an increase in measurement error due to a change in the volume of the fluid 24 due to the temperature change. For example, air in the fluid is removed by performing air bleeding for about 5 minutes before the main measurement,
It is considered that local fluctuation of the fluid temperature can be prevented. During the air bleeding operation, the movable element 12 and the inner element 63 protrude from the inner surface of the skin plate 2.
It is preferable that the air bleeding operation time is not so long from the viewpoint of avoiding breakage or the like. However, the air bleeding operation time can be appropriately determined if breakage of the telescopic hydraulic jack 34 can be avoided separately.

[Zero Adjustment] After the air bleeding operation, zero adjustment is performed before measuring the clearance. Zero adjustment is performed by placing the top surface 13 of the movable element 12 (or the inner element 63) on the skin plate 2.
This is performed for the purpose of measuring the position W ₂ of the piston 21 (hereinafter, sometimes referred to as a reference position) with the displacement measuring device 28 in a state where the piston 21 is positioned at the same height position as the inner surface. FIG. 8 shows the fluid circuit at the time of zero adjustment.

As shown in FIG. 8, during the zero adjustment operation,
The check valve of the check valve device 57 of the communication passage 56 is operated, and the communication passage 56 is operated.
Is blocked from flowing from the chamber 40a to the chamber 40b. Therefore, the movable element 12 and the inner element 63 are moved toward the chamber 40b by the fluid 24 sent from the fluid inlet device 45 to the first conduit 41, and the top surface projecting from the inner surface of the skin plate 2 at the time of bleeding air.
13 gradually approaches the inner surface of the skin plate 2. Hereinafter, the approach of the top surface 13 to the inner surface of the skin plate 2 is referred to as the storage of the top surface 13 in the inner surface of the skin plate. On the other hand, the check valve device 59 of the communication passage 58 is kept released even at the time of zero adjustment to maintain the flow in both directions. For this reason, the piston 21 of the cylinder 20 that has moved until the stroke
Is maintained in that state even during the zero adjustment operation.

The movable element 12 and the inner element 63 are provided with a slip limiting means.
When the top surface 13 is completely accommodated in the inner surface of the skin plate, the movement of the piston 21 toward the chamber 54b is limited. In this state, when the fluid 24 is further supplied from the fluid supply device 45 to the first conduit 41, the pressure control valve device 50 of the fluid supply device 45 is operated, and the fluid pressure in the fluid circuit is maintained at the set fluid pressure. I do. That is, since the inside of the circuit reaches the set fluid pressure, it can be determined that the top surface 13 is completely housed in the skin plate inner surface. At this time, a displacement measuring instrument
Reference position the position W ₂ of the piston 21 which is measured at 28, for example to zero. The displacement measuring device 28 can be, for example, a linear encoder, an ultrasonic displacement meter, a laser displacement meter, or the like.

[Main Measurement] FIG. 9 shows a fluid circuit during the main measurement. In this measurement, the phase of the feed direction control valve 46 of the fluid feed device 45 is switched, and the fluid feed pipe 52 is connected to the third conduit 43. Also, the check valve of the check valve device 59 of the communication passage 58 is operated,
The flow from the chamber 54b to the chamber 54a in the communication passage 58 is blocked.

The piston 21 held at the stroke limit on the chamber 54b side is moved to the chamber 54a side by the fluid 24 sent from the fluid inlet device 45 to the third conduit 43, and the fluid 24
To the chamber 40b of the recess 10 via the second flow path 42, and the movable element 12
Then, the inner element 63 is moved to the chamber 40a and the chamber 67 side. At this time, the top surface 13 completely accommodated in the inner surface of the skin plate 2 at the time of the zero adjustment gradually projects from the inner surface of the skin plate 2.

If the surface 13 protrudes until it abuts the outer surface of the segment 5, the movement of the piston 21 is restricted. Further, when the fluid 24 is fed from the fluid feeder 45 to the third conduit 43, the pressure control valve device 50 of the fluid feeder 45 operates to maintain the fluid pressure in the fluid circuit at the set fluid pressure. That is, since the inside of the circuit reaches the set fluid pressure, the contact between the top surface 13 and the segment 5 can be determined. At this time, to measure the position W ₃ of the piston 21 by the displacement meter 28. Piston from the position W ₃ Metropolitan position W ₂ and the measurement time of the piston 21 of the zero adjustment when the piston 21
By obtaining the displacement (W ₃ −W ₂ ) of 21, the tail clearance L of FIG. 9 can be calculated based on the above equation (2), as in the case described with reference to FIG.

As described above, the measurement of the tail clearance at a predetermined portion on the inner surface of the skin plate 2 has been described.
Tail clearance measurement can be performed simultaneously for each part. That is, referring to FIGS. 10A and 10B which show a cross-sectional view including the skin plate axis O of the shield machine 1 and a cross-sectional view by a plane Fb orthogonal to the axis O, the skin plate axis O Cylindrical recesses 101 to _{1 at} a plurality of positions on an intersection line Cb between the plane Fb orthogonal to
0 ₄ bored, respectively diagrams each tubular recess 10 ₁ to 10 _4. 1 or 4
, The tail clearance is measured at a plurality of sites on the intersection line Cb. By obtaining the tail clearance at multiple locations on the intersection line Cb,
On Fb, the relative position of the outer surface of the segment 5 to the inner surface of the skin plate 2 can be grasped in real time.

Further, a plurality of cylindrical recesses 10 are provided on intersections Ca, Cb... Of a plurality of planes Fa, Fb... Orthogonal to the axis O at a predetermined distance in the direction of the axis O of the skin plate. , The tail clearance is measured at a plurality of portions on each intersection line Ca, Cb..., And the relative position of the outer surface of the segment 5 with respect to the inner surface of the skin plate 2 can be grasped on each of the planes Fa, Fb. By comparing the relative positions of the outer surfaces of the segments 5 on the respective planes Fa, Fb,..., The inclination of the segment 5 with respect to the skin plate 2 in the direction of the skin plate axis O can be obtained.

[0062]

As described above, in the tail clearance measuring apparatus using an incompressible fluid of the present invention, the movable element is loosely fitted to one end of the incompressible fluid-filled pipe provided on the inner surface of the skin plate. Since the tail clearance is measured from the displacement of the piston fitted to the other end of the pipeline between the time when the movable element is positioned at the reference position and the time when the movable element is brought into contact with the segment, the following remarkable effects are obtained.

(A) Even in the working environment of the shield work, an error is hardly generated in the measured value, and highly reliable tail clearance measurement can be performed. (B) The tail clearance at a predetermined site on the inner surface of the skin plate can be measured directly and accurately. (C) By making the cross-sectional area of the other end of the pipe sufficiently smaller than the cross-sectional area of one end, highly accurate tail clearance measurement can be performed.

(D) By using the fluid feeding device with the feeding direction control valve, the movable element can be made to protrude from the inner surface of the skin plate only at the time of measurement, and can be stored in the skin plate at the time of non-measurement. Damage can be avoided. (E) The movable element 12
, The stroke length of the top surface can be increased. For this reason, the jack height required for constant tail clearance measurement can be kept low. (F) The use of flexible pipes increases the degree of freedom in arranging both ends of pipes, and the displacement measuring instrument can be installed in a safe place with little muddy water and vibration, so that damage to the displacement measuring instrument is reliably prevented. Therefore, the reliability of the measurement can be kept high.

(G) Since the flexible conduit can be fastened along the inner surface of the skin plate, it is possible to prevent the work scaffold from being complicated. (H) It can be expected to be used for automation of tail clearance measurement, etc., corresponding to long distance and high speed construction of shield work. (I) Furthermore, wide utilization can be expected by combining it with an excavation operation support system or an automatic attitude control system in shield work.

[Brief description of the drawings]

FIG. 1 is an explanatory view of one embodiment of the present invention using a piston pressing means.

FIG. 2 is an explanatory view of a pressing means provided with an extension spring.

FIG. 3 is an explanatory view of a movable element whose top surface can be slid and contacted.

FIG. 4 is an explanatory view of an embodiment using a fluid feeding device with a feeding direction control valve.

FIG. 5 is an explanatory view of an embodiment using a fluid feeding device with a feeding direction control valve and a nested hydraulic jack.

FIG. 6 is an explanatory view of the internal structure of the telescopic hydraulic jack.

FIG. 7 is an explanatory diagram of a pipeline system during an air bleeding operation in the embodiment of FIG. 5;

FIG. 8 is an explanatory diagram of a pipeline system at the time of zero adjustment in the embodiment of FIG. 5;

FIG. 9 is an explanatory diagram of a pipeline system at the time of actual measurement in the embodiment of FIG. 5;

FIG. 10 is an explanatory view of a shield machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Shield excavator 2 ... Skin plate 3 ... Shield jack 5 ... Segment 8 ... Opening 9 ... Opening cover 10 ... Cylindrical recess 10a ... Recess inner surface 11 ... Recess entrance 12 ... Movable element 13 ... Top surface 14 ... Sliding means 15 … Enlarged diameter part 15a… sliding surface 16… stopping member 17… sliding restricting means 18… pipe line 20… cylinder 21… piston 24… incompressible fluid 26… pressing means 28… displacement measuring instrument 31… support member 32… lock Plate 33 ... Extension spring 34 ... Nesting type hydraulic jack 35 ... Wall with reduced diameter hole 35a ... Reduced diameter hole 36 ... Wall for forming concave part 38 ... Reduced diameter part 38a ... Sliding surface 39 ... Base 39a ... Sliding surface 40a, 40b ... chamber 41 ... first pipe 42 ... second pipe 43 ... third pipe 44a, 44b ... fluid inlet / outlet 45 ... fluid feeder 46 ... feed direction control valve 47 ... fluid pump 48 ... tank 49 ... filter 50 … Pressure control valve device 51… valve 52… fluid feed pipe 53… fluid return pipe 54a, 54b… chamber 55a, 55b… fluid inlet / outlet 56… communication path 57… reverse Valve device 58 ... Communication passage 59 ... Check valve device 60 ... Cylindrical through-hole 61 ... Wall with reduced inner diameter hole 63 ... Movable inner element 64 ... Reduced diameter portion 65 ... Base 66 ... Sliding limiting means 67 ... Chamber 68 ... Fluid passage 70: Simultaneous sliding inhibition means 72a, 72b: Fluid inlet / outlet for communication passage 74: Top plate 75: Spring

────────────────────────────────────────────────── ─── Continued on the front page (72) Kunihiro Nagamori, 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Masahiro Fukuda 1-2-7, Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Tsutomu Imagawa 1-2-7 Motoakasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Manabu Shibata 6-3-2 Toyo, Koto-ku, Tokyo Kashima Construction Co., Ltd. Company Kanto Branch (72) Inventor Hideaki Tanaka 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Tatsuro Sato 1-3-8 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. Company Tokyo Branch (56) References JP-A-5-202692 (JP, A) JP-A-4-31596 (JP, A) JP-A-1-137393 (JP, U) JP-A-2-1122791 (JP) , U) JP-A-2-116600 (JP, U) JP-A-4-82098 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) E21D 9/06 301

Claims (11)

(57) [Claims] An apparatus for measuring a tail clearance between an inner surface of a skin plate of a shield machine and an outer surface of a facing segment, wherein the cylindrical recess is formed in a predetermined portion of the inner surface of the skin plate to be opposed to the segment, and is fitted into the recess. A movable element having a sliding surface that fits and is in close contact with the inner surface of the concave portion and a top surface to be brought into contact with the segment; a stopper member that limits the sliding of the movable element in the concave portion to a position where the top surface has a predetermined height. A conduit extending from the bottom of the concave portion to the cylinder into which the piston is loosely fitted, an incompressible fluid filled in the concave portion, the conduit and the cylinder, and pressing means for pressing the piston toward the conduit side; The top of the element is pressed against the pressure of the pressing means by the position of the piston and the outer surface of the segment when the top of the element is brought to the predetermined projecting height by the pressure of the means. Incompressible fluid use of tail clearance measuring device comprising measuring the tail clearance from the displacement between the position of the piston when the. 2. The measuring device according to claim 1, wherein the pressing member is fixed to an inner surface of a skin plate for supporting the piston in a fixed direction, and an extension spring interposed between the supporting member and the piston. A tail clearance measuring device using an incompressible fluid, provided with a. 3. A tail clearance measuring device using an incompressible fluid, wherein the top surface of the movable element is slidably contactable with the outer surface of the segment. 4. An apparatus for measuring a tail clearance between an inner surface of a skin plate of a shield machine and an outer surface of an opposing segment, comprising: a cylindrical recess formed in a predetermined portion of an inner surface of the skin plate to be opposed to a segment; A wall having a reduced diameter hole to be closed, a movable element having a base loosely fitted in the concave portion, a reduced diameter portion with a sliding surface in close contact with the inner surface of the reduced diameter hole, and a top surface to be brought into contact with the segment; a concave portion of the movable element; Sliding restricting means for restricting sliding to the bottom side to a position where the top surface closes the reduced diameter hole, a first pipe and a second pipe each having one end communicating with the inlet side and the bottom side chamber in the recess. A closed cylinder in which the piston and the piston are loosely fitted and one end of the second conduit communicates with one of the chambers on both sides of the piston; a third conduit which has one end communicated with the other of the chambers on both sides of the piston; Fill pipes and cylinders Incompressible fluid that has, as well as the first
A fluid feeder with a feed direction control valve connected to the other end of the pipe and the third pipe, wherein the top surface of the movable element has a reduced diameter hole when the fluid is sent from the feeder to the first pipe. From the position of the piston when it comes to the position for closing and the displacement of the piston when the top surface of the movable element comes into contact with the outer surface of the segment by the fluid supply from the supply device to the third conduit. Tail clearance measurement device using incompressible fluid that measures tail clearance. 5. The measuring device according to claim 4, wherein a cylindrical through hole penetrating the movable element from a top surface to the other end, and a wall having a reduced-diameter inner hole closing an opening of the through hole on the movable element top surface side. A movable inner element having a base loosely fitted in the through-hole, a reduced-diameter portion with a sliding surface in close contact with the inner surface of the reduced-diameter inner hole, and a top surface to be brought into contact with the segment; Sliding restricting means for restricting the sliding to the side to a position where the inner element top surface closes the reduced diameter inner hole, a fluid passage communicating the chamber in the through hole with the inlet side chamber in the recess, and the movable An incompressible fluid in which simultaneous sliding inhibition means for inhibiting simultaneous sliding of the element and the inner element is provided, and the displacement of the top surface of the inner element is defined as the sum of the sliding width of the movable element and the sliding width of the inner element. Used tail clearance measurement device. 6. The measuring device according to claim 4, wherein the cylindrical concave portion and the cylinder are provided with communication passages with valves for communicating the chambers on both sides of the movable element and the chambers on both sides of the piston, respectively. the feed sent from the input device at the time of valve opening
By returning the circulated fluid to the inlet device via each chamber of the concave portion, each chamber of the cylinder, and the pipe, and circulating the fluid, air in each chamber and the pipe can be eliminated. Tail clearance measurement device using incompressible fluid. 7. The measuring device according to claim 1, wherein a cross-sectional area of the cylinder is sufficiently smaller than a cross-sectional area of the cylindrical concave portion, and a displacement of the movable element is amplified to amplify a displacement of the piston. Tail clearance measurement device using incompressible fluid. 8. The tail clearance measuring device using an incompressible fluid, wherein each of the conduits is provided inside a thickness of a skin plate according to any one of claims 1 to 7. 9. A tail clearance measuring apparatus using an incompressible fluid, wherein each of the conduits is a flexible conduit according to any one of claims 1 to 8. 10. The tail clearance measuring device according to claim 1, wherein the non-compressible fluid is used as a working oil. 11. The measuring device according to claim 1, wherein the cylindrical concave portion is formed at a plurality of portions on an intersection line between a plane orthogonal to the skin plate axis and an inner surface of the skin plate, and Tail clearance measurement device using incompressible fluid that measures tail clearance at the site.