KR101780462B1 - Centralizer having variable bow - Google Patents

Abstract

The present invention provides a centralizer with variable arms capable of fixating a sonde at a central part of a drilling hole by being inserted into the drilling hole. The centralizer with the variable arms includes: a pair of body members having a locking protrusion in one end, a male screw thread in one side of the locking protrusion, multiple inner fitting grooves at constant intervals in a longitudinal direction in an outer circumference, and multiple fixating holes where some parts of the inner fitting grooves are exposed and facing each other to make the fixating holes symmetric; multiple center fixating members having multiple fixating protrusions to fit and fixate the fixating protrusions into the fixating holes while covering the outer circumferences of the body members; a pair of nut members coupled to rotate along the male screw thread by being inserted into the other end of the body member, having multiple outer fitting grooves at constant intervals in an inner circumference, arranged to form arm fitting grooves by facing the inner fitting grooves, and having a polygonal surface on an outer circumference; and the multiple arms of which both ends are inserted and fixated into the arm fitting grooves, formed to become curved to a central part, and supporting the body members while being in face-contact with an inner circumference of the drilling hole by having an elastic force. Accordingly, it is possible to check that the arms are inserted and fixated into the drilling hole with the unaided eye unlike an existing centralizer which is impossible to check whether arms are properly inserted and fixated or not.

Description

Centralizer having variable bow < RTI ID = 0.0 >

The present invention relates to a central riser to be inserted into a borehole for geological exploration and the like. More particularly, the present invention relates to a central riser for supporting a measuring device when a sensor measuring device such as a sonde is inserted, To a central riser.

In general, for the exploration of the ground such as mineral resource exploration, groundwater development, and the design of the ground for the design of buildings, a borehole is drilled in the borehole, and the physical property of the rock is determined in depth by inserting a measuring device called sonde Followed by continuous measurement.

The size of the borehole is designed to be 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, depending on the depth or properties of the ground to be drilled. When the borehole is secured, the sonde is lowered to the bottom of the borehole to perform imaging of the borehole and physical property measurement of the ground.

At this time, the descending sonde should descend along the center of the inner diameter of the borehole without shaking to increase the accuracy of measurement and obtain stable and continuous data.

To this end, a centralizer at the top and bottom of the sonde uses a guide.

Typically, the central riser supports the sonde at the top and bottom, and a plurality of bows in the center are brought into close contact with the inner circumference of the borehole so that the sonde is positioned at the center of the borehole.

While various types of central risers are used, if the diameter of the borehole is different or the measurement conditions are changed, it is necessary to replace the central riser or replace the parts such as the bows.

In addition, it is necessary to disassemble and reassemble the central riser in order to replace the parts other than the bow, but the conventional central riser is fixed by fixing the bow between the upper and lower ends, and it is impossible to disassemble and reassembly is also difficult.

Therefore, a central riser is required to easily replace a part such as a bow, selectively apply according to the diameter of the borehole and the borehole, and to increase the efficiency by reusing it.

As a prior art related to this, Korean Utility Model No. 0200714 Teletube Viewer Logger Centralizer is disclosed.

Korea Utility Model No. 0200714

Accordingly, it is an object of the present invention to provide an adjustable barb that can be accurately positioned, replaced, easily disassembled and reassembled, conveyed conveniently, and free of protruding parts from the body, And a central riser.

The problems to be solved by the present invention are not limited to the above-mentioned problem (s), and another problem (s) not mentioned can be understood by those skilled in the art from the following description.

In order to solve the above-described problems, the present invention provides a central riser inserted into a borehole to fix a sonde at a central position of a borehole, the central riser having a catching jaw at one end, a male thread formed at one side of the catching jaw , A plurality of inner fitting grooves spaced apart from each other in the longitudinal direction are formed on the outer circumferential surface thereof, and a plurality of fixing holes having a part of the inner fitting groove opened at the other end thereof, Body member; A plurality of center fixing members, each of which has a plurality of fixing protrusions provided at both ends thereof to surround and fix the outer circumferential surface of the body member, the fixing protrusions being inserted into the fixing holes; A plurality of outer fitting grooves inserted at the other end of the body member and rotatably coupled along the male thread, the outer fitting grooves being uniformly spaced along the inner circumferential surface of the body member, A pair of nut members having a polygonal surface on an outer peripheral surface; And a variable rib that includes both ends thereof inserted and fixed in the bow-in groove and bent toward an upper portion of the bow, and has a plurality of ribs which are provided with an elastic force to support the bow member in an inner peripheral surface of the borehole, And a variable rib according to the present invention.

The body member and the nut member may be transparent plastic.

Further, the nut member may have a polygonal surface on the outer circumferential surface.

The body member has a second female thread formed on the inner side of the engaging jaw, a second male thread formed on the outer circumferential surface thereof and fastened and fixed to the second female threads, a polygonal surface is formed on the outer circumferential surface, And a fixing member to which the pusher is inserted and fixed.

Further, the pusher is provided as a hollow circular ring, and when the fixing member is rotated, the pusher is brought into close contact with the body member so as to press the rubber ring to enlarge the diameter of the rubber ring.

Further, the body member may be provided with a scale on one side of the male thread.

Further, the plurality of center fixing members may further include a plurality of buckle belts which surround and clamp the outer circumferential surfaces of the plurality of center fixing members.

In addition, both ends of the barb are inserted into the bow-engaging groove to fix the nut member to the body member.

Further, the barb is provided with an elastic force so as to bend outwardly from the central portion, and the degree of bending can be adjusted according to the rotation of the nut member.

Further, the nut member may be provided with a marking line along the outer circumferential surface of the nut member.

According to the present invention, it can not be confirmed that the bow is properly inserted and fixed in the conventional central riser, but it is visually confirmed that the bow is inserted and fixed.

In addition, since the degree of bowing can be precisely checked and adjusted, it is possible to accurately position the sonde at the center of the borehole, and it is very easy to replace even if the bowstring is broken.

In addition, the conventional central riser has a protrusion such as a screw for fixing the bow at the upper and lower ends of the body. However, since the protrusion is not formed by inserting and fixing the fixing member into the body member, the convenience of operation is greatly increased.

In addition, the conventional central riser can not be adjusted again by separating the bows. However, the present invention can replace the bobbin, moving the nut member precisely based on the center portion of the bobbin to precisely control the bending and bending degree of the bobbin .

Further, the central riser according to the present invention can be separated and quickly reassembled, so that it is convenient to store and transport, and there is no need to replace or adjust the components depending on the type of borehole.

1 is an exploded perspective view of a central riser having a variable rib according to an embodiment of the present invention.
Fig. 2 is a perspective view of a body member of a central riser having a variable-type barb according to Fig. 1. Fig.
3 is a front cross-sectional view of a body member of a central riser having a variable rib according to Fig.
4 is a perspective view of a center fixing member of a central riser having a variable rod according to FIG.
FIG. 5 is a perspective view of a center fixing member to which a buckle belt of a central riser having a variable rib according to FIG. 1 is fastened.
6 is a perspective view of a nut member of a central riser having a variable rib according to FIG.
FIG. 7 is a perspective view of a central riser having a variable rib according to an embodiment of the present invention. FIG.
8 is a sectional view taken along the line VIII-VIII in Fig.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving it will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings.

The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is an exploded perspective view of a central riser having a variable rib according to an embodiment of the present invention.

Referring to FIG. 1, a central riser having a variable rib according to the present invention includes a body member 100, a center fixing member 200, a nut member 300, and a rib 400.

The central riser having the variable beam is inserted into a borehole to fix the sonde to the center of the borehole.

The sonde includes various sensor devices, is inserted into a borehole for the purpose of geological survey, and is precisely disposed at the center of the borehole so as not to collide with the borehole.

The body member 100 is provided with a locking step 110 at one end thereof, a male thread 120 is formed at one side of the locking step 110, and a plurality of inner fitting grooves 120, A plurality of fixing holes 140 are formed at the other end of the inner fitting groove 130 and the fixing holes 140 are symmetrically opposed to each other.

The body members 100 are provided in a pair, and one of the body members 100 and the other body member 100 have the same structure and exhibit the same function.

The central riser having the variable ribs has the nut member 300 fastened to one side of the body member 100 and the rib 400 is inserted and fixed to the nut member 300.

Fig. 2 is a perspective view of a body member of a central riser having a variable-type barb according to Fig. 1. Fig.

Referring to FIG. 2, the body member 100 has a plurality of inner fitting grooves 130, which are cylindrically shaped and are uniformly spaced in the longitudinal direction of the outer peripheral surface.

The inner fitting groove 130 provides a space into which one end of the barb 400 is inserted.

The locking jaw 110 provides a space in which the fixing member 500 to be described later is inserted and fixed and the nut member 300 is fastened to the body member 100, .

The male thread 120 is formed at one end of the outer circumferential surface of the body member 100 and is disposed at one side of the engaging jaw 110.

The male screw thread 120 is fastened to the female thread 340 formed on the inner circumferential surface of the nut member 300 to provide fastening means for fastening the nut member 300 to the body member 100.

The inner fitting groove 130 is formed in the longitudinal direction of the outer peripheral surface of the body member 100 and a fixing hole 140 partially opened at the other end of the body member 100 is formed.

The fixing hole 140 may be formed by a plurality of fixing holes 140. The fixing hole 140 may be formed by inserting the fixing protrusions 210 of the center fixing member 210 into the pair of body members 100, .

The fixing hole 140 is formed at the other end of the body member 100 and the pair of body members 100 are disposed to face each other such that the fixing holes are symmetrical with respect to each other to use the center fixing member 200 So that the pair of body members 100 can be fastened together.

The pair of body members 100 may be separately stored when the central fixing member 200 is detached.

Meanwhile, the body member 100 and the nut member 300 may be made of transparent plastic.

Particularly, the body member 100 and the nut member 300 are made of a PVC material that supports the sonde and does not cause damage even if the bar 400 is inserted and fixed, but the present invention is not limited thereto.

When the body member 100 and the nut member 300 are made of a transparent material, it is easy to check whether the barb 400 is inserted and fixed accurately. When the bar member 100 and the nut member 300 are moved, It is very advantageous that the degree of bending of the accurate barb 400 can be grasped.

3 is a front cross-sectional view of a body member of a central riser having a variable rib according to Fig.

Referring to FIG. 3, a fixing member 500 may be inserted and fixed to one side of the body member 100.

A second female thread (150) is formed inside the engaging step (110).

A second male thread 150 is formed on the outer circumferential surface of the fixing member 500 and is fastened and fixed to the second female thread 150.

The fixing member 500 has a polygonal surface at one end and a rubber ring 520 and a pusher 510 at the other end.

The pusher 510 is provided as a hollow circular ring to closely contact the body member 100 when the fixing member 500 is rotated to press the rubber ring 520 to expand the diameter of the rubber ring 520 .

The sonde is to be fixed after being inserted into the body member 100.

Therefore, when the sonde is inserted and fixed inside the body member 100, the center portion of the barb 400 is brought into close contact with the inner circumferential surface of the borehole so that the sonde can be always disposed at the center of the borehole.

The fixing member 500 is rotated to move the fixing member 500 toward the body member 100 and apply pressure to the rubber ring 520 and then push the other rubber ring 520 by the pusher 510, (520).

When the fixing member 500 applies pressure to the plurality of rubber rings 520, the diameter of the rubber ring 520 is enlarged and the frictional force with the outer circumferential surface of the sonde is greatly increased so that the body member 100 is firmly fixed to one end of the sonde Can be fixed.

In the conventional central riser, the band surrounding the outer periphery of the sonde is fixed with screws, but in this case, the efficiency of the work is greatly reduced by the protruding screws, and the worker's safety can be reduced.

Therefore, when the fixing member 500 is rotated and inserted and the sonde is fixed to the inner rubber ring 520 by using the pressure, there is an advantage that no projecting portion like a screw is formed.

The fixing member 500 has a plurality of outer circumferential surfaces and can be easily rotated by holding by the operator.

Although it is preferable that the outer circumferential surface of the fixing member 500 is formed as a polygonal surface, it is also possible to have a configuration such as a ridge (not shown) in which the fixing member 500 can be rotated by friction.

On the other hand, the body member 100 may be provided with a scale on one side of the male threads.

Referring to FIG. 2, the scale 160 is provided on the outer circumferential surface of the body member 100 and is provided as one side of the male thread 120.

When the nut member 300 is rotated and moved by the scale 160, it is possible to accurately grasp the lengthwise movement of the body member 100.

Therefore, even when the diameter of the borehole is deformed, the body member 100 can be positioned at the borehole center only by moving the nut member 300 and changing the degree of bending of the boulder 400.

4 is a perspective view of a center fixing member of a central riser having a variable rod according to FIG.

Referring to FIG. 4, the center fixing member 200 includes a plurality of fixing protrusions 210 at both ends thereof to surround and fix the outer circumferential surface of the body member 100, and fixing protrusions 210 ) Are inserted and fixed.

Since the center fixing member 200 is formed to surround the outer circumference of the body member 100, the center fixing member 200 may be provided in a shape of a circular arc cut according to the shape of the body member 100.

The fixing protrusion 210 is disposed at the inner side edge of the center fixing member 200 and the fixing protrusion 210 is inserted and fixed in the fixing hole 140.

The fixing protrusion 210 may have a rectangular shape and may protrude from the other central fixing portion 210 when the fixing protrusion 210 is half the length of one side of the fixing hole 210 and one side of the fixing hole 140. [ And is engaged with the fixing protrusion 210 of the member 200 and inserted into the fixing hole 140 to maintain the frictional force.

Therefore, the center fixing member 200 is disposed between the pair of the body members 100 to connect the body members 100 to each other and fix the body member 100 firmly.

It is preferable that the center fixing member 200 is provided to cover the body member 100. In a case where the pair of body members 100 can be wrapped and fixed, two or three body members 100 may be provided.

FIG. 5 is a perspective view of a center fixing member to which a buckle belt of a central riser having a variable rib according to FIG. 1 is fastened.

Referring to FIG. 5, the plurality of center fixing members 200 may further include a plurality of buckle belts 220 that surround and clamp the outer circumferential surfaces of the plurality of center fixing members 200.

When the center fixing member 200 is fixed once more by being wrapped around the body member 100 and then fixed by the plurality of buckle belts 220, the pair of body members 100 are separated from each other Can be prevented very effectively.

6 is a perspective view of a nut member of a central riser having a variable rib according to Fig.

5, the nut member 300 is inserted from the other end of the body member 100 and is rotatably coupled along the male screw thread 120. The nut member 300 includes a plurality of outer fitting grooves 300, (310) is formed on the inner fitting groove (130), and the insertion fitting groove (410) is formed to face the inner fitting groove (130).

The nut member 300 may be rotated along the male threads 120.

Since the body members 100 are opposed to each other and are provided in a pair, the nut members 300 are also fastened to the respective body members 100 and are provided in pairs.

The spacing between the nut members 300 can be adjusted by rotating the pair of nut members 300 along the male threads 120.

FIG. 7 is a perspective view of a central riser having a variable rib according to an embodiment of the present invention. FIG.

7, both ends of the barb 400 are inserted into and fixed to the bow-insertion groove, and are bent to move toward the central portion. The barb 400 is fitted to the inner peripheral surface of the borehole with an elastic force, Or the like.

The barb 400 is provided with an elastic force so as to bend outwardly from the center portion, and the degree of bending is adjusted according to the rotation of the nut member 300.

The barb member 100 may be disposed at the center of the borehole by supporting the saddle due to the change of the position of the nut member 300 because the barb 400 has an elastic force and can be bent.

8 is a sectional view taken along the line VIII-VIII in Fig.

8, when the outer fitting groove 310 formed on the inner side of the nut member 300 and the inner fitting groove 130 formed on the outer peripheral surface of the body member 100 face each other, .

When the insert bar 410 is formed, both ends of the barb are inserted into the insert bar 410 to fix the nut member 300 to the barrel member 100.

Meanwhile, in the case of the conventional central riser, an insertion groove is formed at an upper end and a lower end to be inserted into the sonde so that the bow is forcibly fitted. In this case, it is very difficult to accurately insert the bow according to the depth width of the insertion groove, There is a problem that the bow can not be inserted well due to the air pressure.

Therefore, when the outer fitting groove 310 is formed inside the nut member 300 and the inner fitting groove 130 of the body member 100 is formed and the bow fitting groove 410 is formed to face each other, The bow-fitting groove 410 is not closed as in the case of the insertion groove, so that the bowstring 400 can be easily inserted and fixed.

When the both ends of the barb 400 are inserted into the bow-insertion groove 410, the barb 400 is inserted into the nut member (not shown) 300 can be prevented from rotating and can be firmly fixed to the body member 100.

The nut member 300 is positioned after the nut member 300 moves along the male thread 120 of the body member 100 and when the rod member 400 is inserted, The nut member 300 can be accurately fixed at a predetermined position of the body member 100. Therefore,

When one of the nut members 300 of the pair of body members 100 is positioned, only the nut members 300 are positioned and the nut members 300 300 can be fixed to the body member and the degree of bending of the ribs 400 can be accurately determined according to the distance between the pair of nut members 300.

The conventional bow can not be changed in accordance with the diameter of the borehole and the bending of the bow can not be changed. However, it is possible to easily insert and fix the bar 400 using the nut member 300, 400 can be bent so as to determine the degree of bending of the barb 400.

The plurality of barbets 400 may be disposed at intervals of 90 ° or 60 ° along the outer circumferential surface of the body member 100. However, when the body member 100 is constantly positioned at the center of the borehole And is not particularly limited when it can be positioned.

On the other hand, the nut member 300 has a polygonal surface 320 formed on the outer circumferential surface thereof.

The polygonal surface 320 is preferably formed in an octagonal or hexagonal shape, but is not limited to the number of the polygonal surface as long as it can be gripped and rotated by an operator.

The operator can easily determine the position of the nut member 300 in the body member 100 by rotating the nut member 300 when a polygonal surface is formed on the outer circumferential surface of the nut member 300.

Here, the nut member 300 may be provided with a display line 330 along an outer circumferential surface thereof.

The indicator line 330 can read the scale 160 of the body member 100 and accurately indicate the position of the nut member when the nut member 300 is made of transparent plastic.

Accordingly, the degree of bending of the center of the barb 100 can be determined according to the position of the nut member 300 rotated while rotating the nut member 300. At this time, The height of the central portion of the bobbin 400 is determined by checking the height of the central portion of the bobbin 400. Therefore, even if the diameter of the borehole changes, the bobbin 400 having different bending degrees is not required, It is possible to cope with various boreholes by varying the degree of bending.

Hereinafter, an operation method of the central riser having the variable rib according to the present invention will be described with reference to the accompanying drawings.

The sonde is prepared, and the fixing member 500, in which the rubber ring 520 and the pusher 510 are fitted, is inserted into the sonde.

The saddle with the fixing member 500 inserted is inserted into one end of the body member 100.

The nut member 300 is fastened along the male threads of the body member 100.

Another body member 100 having the nut member 300 fastened thereto is prepared and the body member 100 is inserted with one end of the body member 100 facing away from the other body member 100, Wrap it.

A fixing member having a rubber ring 520 and a pusher 510 inserted therein is further inserted into the newly fitted body member 100.

When the outer circumferential surface of the fixing member 500 is gripped and rotated, the rubber ring 520 is squeezed to increase frictional force with the outer circumferential surface of the sonde so that the fixing member 500 is firmly fixed to the sonde.

After the body member 100 is fixed to the saddle by rotating all of the fixing members 500 inserted into the pair of body members 100, 200 are inserted.

The center fixing member 200 tightly fixes the portions where the pair of the body members 100 are connected by the friction between the fixing protrusions 210 and the fixing holes 140. [

Thereafter, the scale 160 of the body member 100 is checked while the nut member 300 is rotated.

In one embodiment of the present invention, when the nut member 300 is moved a mm along the scale 160 of the body member 100 and the facing nut member 300 is also moved a mm toward the center, A change in b value with respect to a value is continuously recorded by recording the height of the bent portion on the central portion of the barb 400 at b mm in the member 100. Based on this, The distance from the center of the body member 100 to the inner peripheral surface of the borehole is determined.

Therefore, even if the diameter of the borehole changes, the body member 100 can be positioned at the center of the borehole by only adjusting the nut member 300.

The conventional central riser is very difficult to adjust the bending degree of the bow to fit the inner wall of the borehole. However, the present invention can determine the degree of bending of the boulder 400 according to the movement of the nut member 300, .

When the position of the nut member 300 is determined, the barb 400 is inserted and fixed along the outer peripheral surface of the body member 100.

Both ends of the barb 400 are inserted into the insertion groove 410 formed by the inner fitting groove 130 of the body member 100 and the outer fitting groove 310 of the nut member 300.

When the both ends of the barb are inserted into the bow-insertion groove 410, the nut member 300 is accurately caught at both ends of the barb 400 and can not rotate any more.

The fixed barb 400 can support the body member 100 at a center of the borehole.

After the sonde has been recovered from the borehole after the inspection or the like, the nut member 300 is rotated in the reverse order of assembly toward the catching jaw 110 at one end of the body member 100, And the body member 100 can be separated by separating the center fixing member 200 from each other.

Since the respective components can be quickly separated from the conventional central riser, the separate storage and transportation are very convenient.

When the sonde is inserted into the borehole of the same diameter, the nut member 300 may be rotated without rotating the fixing member 500, so that only the body member 100 may be detached from the sonde. In this case, Since the barb 400 is fixed even when it is separated from the sonde, there is no inconvenience that the barb 400 is adjusted again to fit the borehole.

While the present invention has been described with respect to specific embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications may be made without departing from the scope of the present invention.

Therefore, the scope of the present invention should not be construed as limited to the embodiments described, but should be determined by the scope of the appended claims, as well as the claims.

It is to be understood that the foregoing embodiments are illustrative and not restrictive in all respects and that the scope of the present invention is indicated by the appended claims rather than the foregoing description, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

100: body member 110:
120: male threads 130: inner fitting groove
140: Fixing hole 150: Second arm thread
160: scale 200: center fixing member
210: fixing protrusion 220: buckle belt
300: nut member 310: outer fitting groove
320: polygon 330: line
340: Female thread 400: Ribbon
410: Bow insertion slot 500: Fixing member
510: pusher 520: rubber ring
530: Second male thread

Claims (10)

A central riser inserted in a borehole to fix a sonde to the center of the borehole,
A plurality of inner fitting grooves spaced apart from each other in the longitudinal direction are formed on the outer circumferential surface and a plurality of inner fitting grooves formed on the outer circumferential surface of the inner fitting groove, A pair of body members having a plurality of fixing holes, the pair of body members facing each other such that the fixing holes are symmetrical;
A plurality of center fixing members, each of which has a plurality of fixing protrusions provided at both ends thereof to surround and fix the outer circumferential surface of the body member, the fixing protrusions being inserted into and fixed to the fixing holes;
A plurality of outer fitting grooves inserted at the other end of the body member and rotatably coupled along the male thread, the outer fitting grooves being uniformly spaced along the inner circumferential surface of the body member, A pair of nut members having a polygonal surface on an outer peripheral surface; And
And a plurality of ribs which are inserted and fixed at both ends of the bow into the bow, and which are formed to bend toward the center and support the bow at an inner peripheral surface of the borehole with an elastic force.
The method according to claim 1,
The body member and the nut member
Characterized in that it is made of transparent plastic.
The method according to claim 1,
The nut member
And a polygonal surface is formed on an outer circumferential surface of the central riser.
The method according to claim 1,
The body member
A second female thread is formed inside the engaging jaw,
And a movable member having a second male thread formed on the outer circumferential surface thereof and fastened and fixed to the second female thread and having a polygonal surface on one end and a rubber ring and a pusher fitted on the other end, Central riser.
5. The method of claim 4,
The pusher
Wherein the rubber ring is provided with a hollow circular ring, and when the fixing member is rotated, the rubber ring is pressed toward the body member to press the rubber ring to expand the diameter of the rubber ring.
The method according to claim 1,
The body member
And a scale is provided on one side of the male screw thread.
The method according to claim 1,
The plurality of center fixing members
Further comprising a plurality of buckle belts that wrap around and support the outer circumferential surfaces of the plurality of center fixing members.
The method according to claim 1,
The ribbing
And the nut member is fixed to the body member by inserting the both ends into the bow-engaging groove, thereby fixing the nut member to the body member.
The method according to claim 1,
The ribbing
And is provided with an elastic force so as to bend outward from the central portion,
And the degree of bending of the nut is adjusted according to the rotation of the nut member.
The method according to claim 1,
The nut member
And a display line is provided along the outer circumferential surface of the nut member.

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