JP3229579B2 - Screw member drop-off prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A device for preventing a screw member from falling off according to the present invention is provided at an end of the shield segment when assembling a shield segment that covers the inner peripheral surface of a tunnel hole having a circular cross section, excavated by a shield method. The screw member such as a stud or a bolt inserted into the through hole is used to prevent the screw member from dropping out of the through hole.

[0002]

2. Description of the Related Art When a tunnel is formed by a shield method, a hole having a circular cross section is excavated by an excavator, and the inner peripheral surface of the hole is covered with a concrete cylinder 1 as shown in FIG. This concrete cylinder 1 is constituted by connecting a large number of shield segments 2 and 2 to each other. Each shield segment 2, made of prestressed concrete,
As shown in FIGS. 17 and 18, 2 is formed in an arc shape obtained by cutting a part of the cylinder in the circumferential direction. A plurality of recesses 3 are formed on the inner peripheral surface of each shield segment 2, and through holes 5, 5 and 5 are provided between these recesses 3 and 3 and the axial end surfaces 4, 4 of the shield segment 2, respectively. Is formed. Further, through holes 7, 7 are formed between the concave portions 3, 3, which are located at both ends in the circumferential direction, and the circumferential end surfaces 6, 6, respectively.

When a concrete cylinder 1 as shown in FIG. 16 is constructed by combining a large number of the shield segments 2 and 2 described above, the axial direction of the shield segments 2 and 2 adjacent in the axial direction (or circumferential direction) is considered. The end faces 4, 4 (or the circumferential end faces 6, 6) abut each other, and the through holes 5, 5 (or 7, 7) formed in each shield segment 2, 2 are aligned. In this state, studs 9 having male screw portions 8 at both ends (or male screw portions at one end,
A pair of nuts 10 and 10 (see FIGS. 6 and 1 showing an embodiment of the present invention) are inserted with bolts each having a head at the other end and screwed to both ends of the stud 9 which is a screw member.
See 2. Alternatively, one nut), which is screwed to one end of a bolt which is also a screw member, is tightened.

As a result, each of the shield segments 2,
2, the concave portions 3 and 3 and the axial end surfaces 4 and 4
Are present between the pair of nuts 10, 10
And the shield segments 2 and 2 adjacent to each other are firmly connected to each other. When a concrete cylinder 1 as shown in FIG. 16 is actually constructed, a plurality of (in the illustrated case, 11) shield segments 2 are connected in the circumferential direction to form a short cylindrical shape. Cylindrical element 11, 1
After setting to 1, each of these cylinder elements 11, 11 is joined in the axial direction to obtain the concrete cylinder 1.

[0005] As described above, when a plurality of shield segments 2 and 2 are combined into a concrete cylinder 1, a screw member such as a stud 9 for connecting adjacent shield segments 2 and 2 with each other includes: After combining these shield segments 2, 2, they are inserted into the through holes 5, 7 prior to the connection and fixing. After the studs 9 and the like are inserted into the through holes 5 and 7 and before the studs 9 and the nut are tightened, the studs 9 and the like are forced by their own weight in the direction of coming out of the through holes 5 and 7. May be added. In order to assemble the concrete cylinder 1 efficiently and safely, regardless of the above-mentioned force,
It is necessary to prevent the studs 9 and the like from coming out of the through holes 5 and 7.

In view of such circumstances, utility model registration No. 2
JP-A-500905 describes a structure in which a rubber ring 13 is externally fitted to a bolt 12 which is a screw member, as shown in FIG. With the bolt 12 inserted into the through hole 5 (7), the rubber ring 13 is elastically compressed between the outer peripheral surface of the bolt 12 and the inner peripheral surface of the through hole 5 (7). Then, based on the frictional force acting between the inner and outer peripheral edges of the rubber ring 13 and the outer peripheral surface of the bolt 12 and the inner peripheral surface of the through hole 5 (7), the bolt 12 is removed from the through hole 5 (7). Prevents from getting out.

[0007]

In the case of the conventional structure shown in FIG. 19, the force required for inserting the bolt 12 into the through hole 5 (7) and the bolt 12 being pulled out from the through hole 5 (7). And the required force are equal to each other. On the other hand, the bolts 12 or studs 9 for connecting the shield segments 2, 2 are considerably large and heavy. Therefore, in order to reliably prevent the bolt 12 from coming out of the through hole 5 (7), the rubber is required to have a sufficiently large holding force for holding the bolt 12 in the through hole 5 (7). It is necessary to increase the frictional force acting between the inner and outer peripheral edges of the ring 13 and the outer peripheral surface of the bolt 12 and the inner peripheral surface of the through hole 5 (7).

As a result, in the case of the conventional structure, the force required to insert the bolt 12 into the through hole 5 (7) before combining the shield segments 2, 2 is large. Therefore, the operation of inserting the bolt 12 is troublesome. The present invention has been made in view of such circumstances.
While securely preventing the screw members such as the bolts 12 and the studs 9 from coming out of the through holes 5 (7),
(7) The invention has been devised so that the work of inserting a screw member into the inside can be easily performed.

[0009]

According to the present invention, there is provided an apparatus for preventing a screw member from falling off, comprising a screw member having a cylindrical shape and provided with an external thread portion on at least one outer peripheral surface thereof, and a member to be connected and fixed by the screw member. And a through-hole formed in the member to be coupled, and a holding ring made of an elastic material in an annular shape and elastically externally fitted to an intermediate portion of the screw member. Then, the screw member is prevented from falling out of the through hole based on the engagement between the retaining ring, the screw member, and the through hole. In particular, in the device for preventing a screw member from falling off according to the present invention, the holding ring is fixed to an inner peripheral surface of a locking groove provided in a part of the through hole; A holding ring portion provided on the inner diameter side of the portion and having an inner diameter in a free state smaller than the outer diameter of the intermediate portion of the screw member, an outer peripheral edge of the holding ring portion and an inner peripheral surface of the fitting fixing portion; And a connecting portion for connecting And, between the outer peripheral surface of the retaining ring and the screw member and the coupled member, the resistance to the elastic deformation of the retaining ring portion to one side in the axial direction is reduced,
A selection resistance portion is provided to increase resistance of the holding ring portion to elastic deformation on the other side in the axial direction.

[0010]

According to the device for preventing a screw member from dropping out according to the present invention as constructed above, the screw member can be easily inserted into the through-hole while reliably preventing the screw member from coming off. I can do it. For this reason, the work of inserting the screw member into the through-hole provided in the joined member can be easily performed while the assembly operation of joining the joined members can be performed efficiently and safely.

[0011]

1 to 6 show a first embodiment of the present invention, which corresponds to claim 2 of the present invention. The stud 9, which is a screw member, has a cylindrical shape as a whole, and is provided with male screw portions 8, 8 on the outer peripheral surfaces at both ends. The shield segments 2a and 2b, which are members to be coupled and fixed by the studs 9, respectively, are provided with through holes 5a and 5b through which the studs 9 can be loosely inserted. 2b are formed at positions matching each other when they are combined. One of the through holes 5a, 5b formed in the pair of shield segments 2a, 2b (to the right of FIGS. 1, 3, 5, and 6).
The outer end of the through hole 5a formed in the shield segment 2a (the end opposite to the other shield segment 2b) has a stepped engagement with a larger diameter than the other portion of the through hole 5a. The groove 14 is formed over the entire circumference. And
A retaining ring 15 is mounted in the locking groove 14. The holding ring 15 is integrally formed in an annular shape as a whole with an elastic material such as rubber, vinyl, or another elastomer, and can be elastically and externally fitted to an intermediate portion of the stud 9. The holding ring 15 and the stud 9
The stud 9 is prevented from coming out of the through hole 5a based on the engagement with the through hole 5a.

The holding ring 15 has a fitting fixing portion 16, and an outer peripheral surface and an inner end surface of the fitting fixing portion 16 (see FIGS.
6 is fixed to the inner peripheral surface and the rear end surface of the locking groove 14 by bonding. A holding ring 17 having an inner diameter in the free state smaller than the outer diameter of the intermediate portion of the stud 9 is disposed on the inner diameter side of the fitting / fixing portion 16. The inner peripheral surface of the fitting fixing portion 16 is connected by a connecting portion 18 which is thinner than the holding ring portion 17. Further, the thickness of the fitting / fixing portion 16 in the diameter direction is made different from the connecting portion 18 as a boundary. That is, a portion located on the inner side (left side in FIGS. 1 to 6) of the locking groove 14 when mounted on the locking groove 14, which is one side in the axial direction, is a thick portion 19 having a large thickness. Similarly, the opening side (the right side in FIGS. 1 to 6) of the locking groove 14 is a thin portion 20 having a small thickness. Also, the connecting portion 18
Is provided so as to be offset toward the thick portion 19 with respect to the holding ring portion 17.

Therefore, the outer half of the holding ring 17 (FIG. 1)
(Right half of Nos. 6 to 6) Between the outer peripheral surface and the inner peripheral surface of the thin portion 20, there is a concavity 21 in the form of a concave groove over the entire circumference.
Based on the presence of the constriction 21, the holding ring 17
Is easily elastically deformed on the side of the thin portion 20 (right side in FIGS. 1 to 6), but is hardly elastically deformed on the side of the thick portion 19 (left side in FIGS. 1 to 6). When the stud 9 is inserted into the inner diameter side of the holding ring 17, the inner diameter of the holding ring 17 is expanded elastically, and the holding ring 17 is elastically moved so as to fall in the insertion direction of the stud 9. Deform. The force required for the elastic deformation of the holding ring 17 in the falling direction depends on the direction as described above. Therefore, if the direction in which the stud 9 is inserted into the through hole 5a is set to a direction from the opening at the inner end (the end facing the other shield segment 2b) of the through hole 5a toward the opening at the outer end, the above-described holding is achieved. Ring 1
The portion including 7 functions as the selection resistance portion described in the claims.

According to the device for preventing the stud 9 from dropping out according to the present invention, the stud 9 is reliably prevented from coming off, and the stud 9 is inserted into each of the through holes 5a and 5b.
Can be easily inserted. Because of this,
The work of inserting the stud 9 into the through holes 5a, 5b provided in the shield segments 2a, 2b can be easily performed while the assembly work for connecting the shield segments 2a, 2b can be performed efficiently and safely. I can do it. Further, the nuts 10 and 10 are screwed to both ends of the stud 9 and the work of further tightening can be easily performed while effectively preventing the stud 9 from rotating together with the nuts 10 and 10 in a so-called manner. You.

[0015] This point will be described step by step. First, as shown in FIGS.
a, 2b, through-holes 5a formed in mutually matching portions,
The stud 9 is inserted into the through hole 5a in which the locking groove 14 is formed from the inner end side to the outer end side in FIG. At this time, the installation position (the direction of the through-hole 5a) of the locking groove 14 is regulated so that the stud 9 is inserted against the gravity (in the vertical direction). As described above, as the stud 9 is inserted into the through holes 5a and 5b, the holding ring portion 17 of the holding ring 15 is resiliently expanded in inner diameter by the stud 9 while the thin portion 20 Incline to the side. When the holding ring 17 is inclined toward the thin portion 20 in this manner, the width of the constricted portion 21 is elastically reduced. Therefore, the holding ring 17 is moved in this direction.
The force required to incline the stud 9 is relatively small, and the force required to insert the stud 9 into the through holes 5a and 5b is also small. The holding and fixing portion 16 of the holding ring 15
Is fixed to the inside of the locking groove 14 by bonding, so that the retaining ring 15 does not fall out of the locking groove 14 when the stud 9 is inserted. Further, when the holding ring portion 17 is inclined, a large force is not applied to the fitting / fixing portion 16 due to the presence of the constricted portion 21. Therefore, the bonding portion between the fitting fixing portion 16 and the inner surface of the locking groove 14 is not damaged.

The stud 9 is inserted into the through holes 5a and 5b.
When the force applied to the stud 9 is released while the stud 9 is inserted, the stud 9 loses its own weight (10 to 2 depending on the case).
(Approximately 0 kg), a force is applied in a direction (left direction in FIGS. 1 to 6) that comes out of both through holes 5 a and 5 b. As a result, the holding ring portion 17 is inclined toward the thick portion 19 based on friction with the outer peripheral surface of the stud 9. Then, as shown in FIGS. 3 and 4, the thick portion 19 and the holding ring 17 overlap, and a part of the holding ring 17 is strongly (with a large elastic force) pressed against the outer peripheral surface of the stud 9. Can be As a result, a large frictional force acts on the contact portion between the outer peripheral surface of the stud 9 and the holding ring portion 17, so that the stud 9 does not come out of the through holes 5a and 5b. When the through-holes 5a and 5b are arranged in an oblique direction and the like, the force applied to the stud 9 in the pull-out direction is small, as shown in FIG. Tilts only part way,
Before the retaining ring portion 17 and the thick portion 19 overlap, the stud 9 is prevented from coming off.

When the stud 9 is inserted through the through holes 5a and 5b as described above, the nut 10 is inserted into the male thread 8 at the tip of the stud 9 in the insertion direction as shown in FIG.
Screw. At this time, since the stud 9 is prevented from rotating based on the frictional engagement with the holding ring 15, the operation of screwing the nut 10 to the male screw portion 8 as described above is particularly necessary for the stud 9. It can be easily done without considering the rotation stop.

After the nut 10 has been screwed into the male thread 8 at the tip of the stud 9 in the insertion direction, the stud 9 is slightly returned to the rear in the insertion direction (left side in FIGS. 1 to 6). This returning operation is performed by applying an axial force to the front end surface of the stud 9 in the insertion direction (the right end surface in FIGS. 1 to 6). For example, the opening of a cylindrical cylinder with a bottomed cylinder that is in close contact with the outer surface is pressed against the outer surface of the shield segment 2a provided with the through hole 5a, and fluid pressure (for example, air pressure) is supplied into the cylinder. I do. As a result, the stud 9 is pushed rearward in the insertion direction with a force corresponding to the product of the cross-sectional area of the stud 9 and the fluid pressure, and the nut 10
And the outer surface of the shield segment 2a abuts. Since the force pushing the rear side in the insertion direction is larger than the force corresponding to the weight of the stud 9, regardless of the frictional force acting between the inner peripheral surface of the holding ring 15 and the outer peripheral surface of the stud 9, The stud 9 can be displaced rearward in the insertion direction. When the stud 9 is displaced by the fluid pressure, the holding ring 1
5 functions as a seal ring for sealing between the inner peripheral surface of the through hole 5a and the outer peripheral surface of the intermediate portion of the stud 9. At this time, the retaining ring 15 does not move irrespective of the axial movement of the stud 9 while being retained in the retaining groove 14. Accordingly, the holding ring 15 does not fall off from the inside of the through hole 5a as the stud 9 moves in the axial direction, and the function as the seal ring is reliably performed. On the other hand, in the case of the conventional structure shown in FIG. 19 described above, when the axial movement amount of the bolt 12 increases, the rubber ring 12 falls off from the through hole 5 (7), and the fluid pressure cannot be sealed. .

If the stud 9 is slightly returned to the rear side in the insertion direction in this manner, another male screw portion 8 provided on the rear side in the insertion direction is sufficiently protruded from the outer surface of the other shield segment 2b. As shown in FIG. 6, another nut 10 is screwed into the other male screw portion 8, and further tightened to couple and fix the pair of shield segments 2a and 2b.
In the process of returning the stud 9 to the rear side in the insertion direction, the holding ring portion 17 overlaps the thick portion 19 and strongly contacts the outer peripheral surface of the stud 9. Therefore, this stud 9
The stud 9 is reliably prevented from rotating when the other nut 10 is screwed and tightened. The device for preventing a screw member from falling off according to the present invention includes:
By operating as described above, the through holes 5a formed in the shield segments 2a, 2b can be efficiently and safely assembled to connect the pair of shield segments 2a, 2b. Inserting the studs 9 into the nuts 5 and 5b, and screwing and tightening the nuts 10 and 10 can be performed easily.

Next, FIGS. 7 to 12 show a second embodiment of the present invention corresponding to claim 3. FIG. In the case of this example, the backup ring 22 is provided on a part of the fitting fixing part 16a provided on the outer peripheral edge of the holding ring 15a and on the inner diameter side of the thick part 19a provided on the back side of the locking groove 14. I am wearing it. The backup ring 22 is provided adjacent to the holding ring 17a constituting the holding ring 15a, and functions as a backup for restricting the amount of elastic deformation of the holding ring 17a. The outer diameter of the backup ring 22 formed in an annular shape with a metal, a hard synthetic resin, or the like is large on the side of the holding ring portion 17a and small on the back side of the locking groove 14. The inner diameter of the thick portion 19a is also changed in the same manner as the outer diameter of the backup ring 22 so that the inner peripheral surface of the thick portion 19a and the outer peripheral surface of the backup ring 22 are meshed. Preferably, the outer peripheral surface of the backup ring 22 is
The inner peripheral surface a is elastically contacted. Such a backup ring 22 is mounted in the locking groove 14 together with the holding ring 15a.

In the structure of this embodiment incorporating the backup ring 22 as described above, a pair of shield segments 2a,
The operation of connecting and fixing the 2b is performed in the order shown in FIGS. 7 to 12 respectively correspond to FIGS. 1 to 6 of the first example described above. In particular, in this case,
In order to insert the stud 9 as a screw member into the through holes 5a and 5b, the stud 9 is inserted from the through hole 5b side into the through hole 5a.
7 and 8, the holding ring 17a and the backup ring 22 are separated from each other. Thereby, the contact pressure between the inner peripheral edge of the holding ring portion 17a and the outer peripheral surface of the stud 9 is reduced, and the force required to insert the stud 9 is reduced. When the stud 9 is inserted in this manner, the backup ring 22
Of the holding ring 15a.
The thick portion 19a is pressed down on the inner peripheral surface of the locking groove 14 to effectively prevent the retaining ring 15a from coming out of the locking groove 14.

On the contrary, the stud 9 is connected to the through hole 5
a and 5b, the holding ring portion 17a and the backup ring 2 as shown in FIGS.
2, the holding ring 17a is oscillated and displaced in a direction in which the stud 9 comes into contact with the stud 9 to increase the frictional force acting between the inner peripheral edge of the holding ring 17a and the outer peripheral surface of the intermediate portion of the stud 9. 9 is prevented from accidentally falling out of the through holes 5a and 5b. However, even when the frictional force acting between the inner peripheral edge of the holding ring portion 17a and the outer peripheral surface of the intermediate portion of the stud 9 is increased in this way, the frictional force is still equal to the first frictional force.
It is not as large as in the example. That is, the stud 9
Is likely to escape from the through holes 5a and 5b,
Since the holding ring portion 17a and the thick portion 19a do not overlap, the rise of the frictional force acting between the inner peripheral edge of the holding ring portion 17a and the outer peripheral surface of the stud 9 is suppressed to a certain extent. Can do things. Accordingly, it is possible to prevent the stud 9 from coming out of the through-holes 5a and 5b and to prevent an excessive force required to displace the stud 9 in the axial direction. Other configurations and operations are the same as those in the first example described above, and therefore, the same reference numerals are given to the same parts, and the duplicate description will be omitted.

Next, FIGS. 13 and 14 show third and fourth examples of the embodiment of the present invention, which also corresponds to claim 3. FIG. First, in the case of the structure of the third example shown in FIG. 13, the thick portion 1 forming the fitting and fixing portion 16b of the holding ring 15b is used.
9b is extended to the inner diameter side. The extended portion is overlapped with the outer diameter half of the holding ring 17a in the axial direction. The overlapped portion on the inner diameter side half of the thick portion 19a is made to function freely as a backup portion for limiting the elastic deformation of the holding ring portion 17a. In the case of the structure of the fourth example shown in FIG.
On the inner diameter side of the locking groove 14a, a protruding wall 23 that protrudes in the axial direction toward the holding ring portion 17a of the holding ring 15c is formed over the entire circumference. The distal end face of the protruding wall 23 is adjacent to the holding ring 17a, and can function freely as a backup part for limiting the elastic deformation of the holding ring 17a. Other configurations and operations are the same as those of the above-described second example.

Next, points to be noted when designing the device for preventing a screw member from falling off according to the present invention will be described with reference to FIG.
The points to be noted are as follows, and the corresponding parts of these points are denoted by reference numerals in FIG. As shown in FIGS. 7 and 8, when the stud is inserted into the inner diameter side of the retaining ring 15a, the retaining ring 15a does not fall out of the retaining groove 14 as shown in FIGS. Therefore, it is necessary to secure this bonding area. As shown in FIGS. 7 and 8, in order to reduce the force required to insert the stud into the inner diameter side of the holding ring 15a, the constricted portion 21 having a desired shape and width is replaced with the above-described stud. It is provided on the rear side with respect to the insertion direction. In the free state of the holding ring 15a, the outer diameter of the fitting fixing portion 16a and the inner diameter of the locking groove 14 are made substantially equal. The reason for such restriction is that these retaining rings 15a
This is to secure the adhesive strength between the groove and the locking groove 14. When the inner diameter of the locking groove 14 is larger than the outer diameter of the fitting fixing portion 16a,
The retaining ring 15a and the locking groove 14 cannot be bonded. On the other hand, if the inner diameter of the locking groove 14 is smaller than the outer diameter of the fitting and fixing portion 16a, it leaks from between the inner peripheral surface of the locking groove 14 and the outer peripheral surface of the fitting and fixing portion 16a during bonding. The amount of the adhesive increases, and the leaked adhesive is likely to adhere to other parts and cause a problem. The inner diameter and thickness of the retaining ring 17a The inner diameter and thickness of the retaining ring 17a are used to prevent the stud from coming off and the magnitude of the force required to insert the stud inside the retaining ring 17a. Greatly affects the magnitude of the force. Therefore, the inner diameter and the thickness of the holding ring 17a are regulated in accordance with the required magnitudes of the respective forces in relation to the elasticity of the elastic material constituting the holding ring 15a. Presence / absence of backup ring 22 and retaining ring 17a
The presence or absence of this backup ring 22 affects the magnitude of the force required to move the stud in the pull-out direction (backward in the insertion direction). Accordingly, in connection with the elasticity of the elastic material constituting the holding ring 15a, the backup ring 22 is provided depending on how much the force required to displace the stud in the pull-out direction during the tightening operation of the nut or the like is suppressed. Is determined. When the operation of returning the stud to the rear side in the insertion direction is performed by fluid pressure, the holding ring 17 is required.
Making a a withstand this fluid pressure is also a factor in determining whether or not to provide the backup ring 22.
In addition, in the case of providing, the thickness of the backup ring 22 and the distance between the backup ring 22 and the holding ring portion 17a are also restricted in accordance with the required magnitude of each of the above-mentioned forces in relation to the elasticity of the elastic material constituting the holding ring 15a. I do. Inner Diameter of Backup Ring 22 In the case where the backup ring 22 is provided and the operation of returning the stud to the rear side in the insertion direction is performed by fluid pressure, in order that the holding ring portion 17a can withstand this fluid pressure,
The relationship between the inner diameter of the backup ring 22 and the outer diameter of the stud is regulated by the relationship with the elasticity of the elastic material forming the holding ring 15a. Then, the so-called protrusion phenomenon, in which the inner peripheral edge of the holding ring 17a enters the gap between the inner peripheral edge of the backup ring 22 and the outer peripheral surface of the stud, is prevented. Relationship Between Inner Diameter of Thick Part 19a and Outer Diameter of Backup Ring 22 Preferably, the inner diameter and the outer diameter are set so that no gap is formed between the inner peripheral surface of the thick part 19a and the outer peripheral surface of the backup ring 22. And. However, if the irregularities formed on the inner peripheral surface of the thick portion 19a and the irregularities formed on the outer peripheral surface of the backup ring 22 mesh with each other and the backup ring 22 does not fall off the holding ring 15a, the inner diameter is set to be smaller than the outer diameter. May be slightly larger, and a slight gap may exist between the inner peripheral surface of the thick portion 19a and the outer peripheral surface of the backup ring 22.

[0025]

As described above, according to the screw member falling-off prevention device of the present invention, the operation of inserting the screw member into the through hole can be easily performed while reliably preventing the screw member from coming off. It can be done to. For this reason, the work of inserting the screw member into the through-hole provided in the joined member can be easily performed while the assembly operation of joining the joined members can be performed efficiently and safely. As a result, the work of connecting and fixing members to be connected such as shield segments can be facilitated, and the work of constructing various structures such as tunnels can be made more efficient.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a first example of an embodiment of the present invention in a state where a force is applied in a direction of inserting a stud into a through hole.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a partial cross-sectional view showing a first example of an embodiment of the present invention in a state where a force is applied in a direction in which a stud is pulled out from a through hole.

FIG. 4 is an enlarged view of a portion B in FIG. 3;

FIG. 5 is a partial cross-sectional view showing a state where a nut is screwed into one end of the stud.

FIG. 6 is a partial sectional view showing a state in which a nut is screwed to the other end.

FIG. 7 is a partial cross-sectional view showing a second example of the embodiment of the present invention in a state where a force is applied in a direction of inserting a stud into a through hole.

FIG. 8 is an enlarged view of a portion C in FIG. 7;

FIG. 9 is a partial cross-sectional view showing a second example of the embodiment of the present invention in a state where a force is applied in a direction in which a stud is pulled out from a through hole.

FIG. 10 is an enlarged view of a portion D in FIG. 9;

FIG. 11 is a partial cross-sectional view showing a state where a nut is screwed into one end of the stud.

FIG. 12 is a partial sectional view showing a state where a nut is screwed to the other end.

FIG. 13 shows a third example of the embodiment of the present invention.
FIG.

FIG. 14 is a view similar to FIG. 10, showing the fourth example.

FIG. 15 is a view similar to FIG. 10, but showing a state in which a stud is not inserted into the inside of the holding ring 15 for explaining points to be considered in designing the screw member drop prevention device of the present invention.

FIG. 16 is a perspective view showing a state where many shield segments are combined.

FIG. 17 is a front view showing an example of a shield segment.

FIG. 18 is a view as viewed from below in FIG. 17;

19A and 19B are partial cross-sectional views showing a conventional structure, wherein FIG. 19A shows a state before a bolt is inserted, and FIG. 19B shows a state after a bolt is inserted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Concrete cylinder 2, 2a, 2b Shield segment 3 Concave part 4 Axial end face 5, 5a, 5b Through hole 6 Circumferential end face 7 Through hole 8 Male thread part 9 Stud 10 Nut 11 Cylindrical element 12 Bolt 13 Rubber ring 14, 14a Stop groove 15, 15a, 15b, 15c Retaining ring 16, 16a, 16b Fitting fixing portion 17, 17a Retaining ring portion 18 Connecting portion 19, 19a, 19b Thick portion 20 Thin portion 21 Constricted portion 22 Backup ring 23 Projected wall

Continuation of the front page (72) Inventor Makoto Yamaguchi 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawa Shima-Harima Heavy Industries Co., Ltd. (56) References JP-A 7-119389 (JP, A) Kaihei 4-4995 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) E21D 11/04 E21D 11/08

Claims (3)

(57) [Claims] A screw member provided with a male screw portion on at least one end outer peripheral surface of a rod, a member to be connected and fixed by the screw member, a through hole formed in the member to be connected, and an elastic material. And a holding ring that is elastically externally fittable at an intermediate portion of the screw member. Based on the engagement of the holding ring with the screw member and the through hole, the screw member is In a device for preventing a screw member from dropping out of a hole, the holding ring is fixed to an inner peripheral surface of a locking groove provided in a part of the through hole; A holding ring portion provided on the inner diameter side of the fixing portion and having an inner diameter in a free state smaller than the outer diameter of the intermediate portion of the screw member; an outer peripheral edge of the holding ring portion and an inner peripheral surface of the fitting fixing portion; And a connecting portion for connecting the retaining ring to the retaining ring. Between the outer peripheral surface of the retaining member and the coupled member, the resistance to the elastic deformation of the holding ring in one axial direction is reduced, and the resistance to the elastic deformation of the holding ring in the other axial direction is reduced. A drop-off prevention device for a screw member, characterized in that a selection resistance portion for increasing the size is provided. 2. The method according to claim 1, wherein the thickness of the fitting fixing portion in one axial direction in the diametrical direction is increased, and the thickness in the other axial direction is also reduced.
By connecting the outer peripheral edge of the connecting portion, which is thinner than the retaining ring portion, to a portion between the one axial side and the other axial side of the fitting / fixing portion, the screw member is pivoted from one axial side of the retaining ring portion. The screw member according to claim 1, wherein the selective resistance portion reduces the force required for insertion toward the other side in the direction, and increases the force required for displacing the same from the other side in the axial direction toward the one side. Fall prevention device. 3. A backup portion is provided on a side adjacent to the holding ring portion where the screw member is inserted, and the holding ring portion is inserted when the screw member is inserted from one axial side to the other axial side of the holding ring portion. And the backup portion are separated from each other to reduce the force required to insert the screw member. Similarly, when displacing from the other side in the axial direction to one side in the axial direction, the holding ring portion and the backup portion are brought into contact with each other. The device for preventing a screw member from falling off according to claim 1 or 2, wherein the selective resistance portion is configured to increase a force required for displacing the screw member.