JP4016199B2 - Pipe fitting - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pipe joint for connecting, for example, a fluid tube through which fluid is introduced or led out.
[0002]
[Prior art]
Conventionally, pipe joints have been used to connect fluid tubes to fluid pressure devices such as cylinders. In this type of joint, a body into which the fluid tube is inserted is provided with a locking piece protruding by a predetermined length in the radially inward direction. Then, after inserting the fluid tube, the fluid tube is slightly pulled in the direction opposite to the insertion direction so that the tip of the locking piece is inserted into the outer peripheral surface of the fluid tube. It prevents the body from being removed. In addition, the said locking piece is hold | maintained by the engaging member with which the inside of the body was mounted | worn (for example, refer patent document 1).
[0003]
[Patent Document 1]
JP-A-8-178157 (page 4, right column to page 6, left column)
[0004]
[Problems to be solved by the invention]
By the way, in the pipe joint according to the prior art, for example, if it is attempted to increase the pulling strength that prevents the fluid tube from being pulled out of the body, the insertion amount of the locking piece with respect to the outer peripheral surface of the fluid tube May become excessive, and the fluid tube may be cut by the locking piece. On the other hand, if it is attempted to suppress the amount of the engaging piece inserted into the outer peripheral surface of the fluid tube, the pullout strength is reduced, and the fluid tube may be removed from the body.
[0005]
Moreover, in order to improve the assembly workability of the pipe joint, reduction of the number of parts is required.
[0006]
The present invention has been made in consideration of the above-mentioned various problems and the like, and improves the pull-out strength that prevents the fluid tube from being pulled out of the body and suppresses the amount of insertion of the locking claw. It is an object of the present invention to provide a pipe joint that can be used.
[0007]
[Means for Solving the Problems]
To achieve the above object, the present invention comprises a body into which a fluid tube is inserted;
A chuck that is disposed inside the body and holds the fluid tube via a locking claw inserted into an outer peripheral surface of the fluid tube;
An amount of insertion of the locking claw into the fluid tube , which is provided on the chuck, extends along the outer periphery of the fluid tube, has a concave portion formed in the vicinity of the locking claw, and And a stopper mechanism that can harmonize the pull-out strength of the fluid tube with the amount of insertion,
With
The stopper mechanism is characterized in that when the locking claw is inserted into the outer peripheral surface of the fluid tube, a part of the fluid tube enters the recess and contacts the inner wall surface. .
[0008]
According to the present invention, there is provided a stopper mechanism having a concave portion that extends along the outer periphery of the fluid tube and is curved in the vicinity of the locking claw . Their to, after inserting the fluid tube inside the body, by pulling the fluid tube slightly, with the fluid tube is held by the locking claw, the fluid in the recess of the stopper mechanism some of use tube enters, further ingress of the fluid tube by the inner wall surface of the concave portion by being blocked, the amount of insertion of the locking claw with respect to said fluid tube is restricted. Therefore, a stable holding state of the fluid tube can be obtained by harmonizing the insertion amount of the locking claw with respect to the fluid tube and the pulling strength of the fluid tube.
[0009]
Further, by providing an unlocking member for releasing the holding state of the fluid tube by the holding mechanism inside the body, the locking state of the fluid tube can be easily released.
[0010]
Furthermore, to press the chuck that holds the fluid tube under pressing action on the locking release member Gabo di side, by engaging claws of the chuck is displaced radially outwardly, conveniently the fluid tube Detachable from the body of the pipe joint.
[0011]
Furthermore, the chuck includes an inclined portion that gradually decreases in diameter in a direction in which the fluid tube is inserted. For this reason, when the fluid tube is pulled in a direction away from the body, the inclined portion comes into contact with the taper surface of the engagement member mounted inside the body, so that the chuck pulls the fluid tube. When displaced in the axial direction under the action, the displacement of the chuck is preferably regulated.
[0012]
Furthermore , the number of parts can be reduced by forming the chuck integrally with an unlocking member that releases the holding state of the fluid tube by the locking claws.
[0013]
The fluid tube is pulled by extending the stopper mechanism along the outer periphery of the fluid tube and providing a chamfered portion formed on the locking claw so as to face the fluid tube. At this time, since the chamfered portion prevents the locking claw from further entering the fluid tube, the amount of insertion of the locking claw into the fluid tube can be regulated.
[0015]
Furthermore, by forming the locking claw at the end of the curved portion that extends along the outer periphery of the fluid tube, the locking claw can be surely secured when the fluid tube is pulled. It is inserted into the surface.
[0016]
Still further, when a plurality of the locking claws are provided along the outer periphery of the fluid tube with a predetermined gap therebetween, the fluid tube can be held more firmly.
[0017]
In addition, by disposing a plurality of the locking claws at predetermined intervals along the axial direction of the body, it becomes possible to more reliably insert into the outer peripheral surface of the fluid tube by the plurality of locking claws. The fluid tube can be suitably held.
[0018]
Furthermore, by forming an arc portion having an arc cross section at the end portion of the locking claw, the end portion of the locking claw more preferably suppresses the amount of insertion into the outer peripheral surface of the fluid tube. Can do.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the pipe joint according to the present invention will be described below and described in detail with reference to the accompanying drawings.
[0020]
In FIG. 1, reference numeral 10 indicates a pipe joint according to the first embodiment of the present invention. This pipe joint 10 has a substantially cylindrical body 12 made of a resin material, and a connecting portion in which a threaded portion that is screwed into a port of a fluid device (not shown) is engraved on one end of the body 12. 14 is formed, a tightening portion 16 having a hexagonal cross section is provided at a substantially central portion of the outer peripheral surface along the axial direction, and a fluid tube 18 made of a resin material is provided on the other end side (FIGS. 8 to FIG. 8). 13) is inserted.
[0021]
Further, a passage 22 penetrating from one end side to the other end side is formed in the body 12. A first step portion 24 and a second step portion 26 are formed in the passage 22 in order from the connection portion 14 side. The first step portion 24 is engaged with a flange portion 30 of a sleeve 28 formed in a substantially cylindrical shape. Therefore, the sleeve 28 is prevented from being removed from the body 12. The sleeve 28 has a function of guiding the fluid tube 18 when the fluid tube 18 (see FIGS. 8 to 13) is inserted and when the fluid tube 18 is detached.
[0022]
A packing 32 protruding by a predetermined length on the inner peripheral side is attached to the second step portion 26 having a diameter larger than that of the first step portion 24. Since the packing 32 is engaged with the annular groove of the second step portion 26, the packing 32 is positioned with respect to the axial direction of the body 12.
[0023]
The body 12 is not limited to a resin material, and may be formed from a metal material.
[0024]
One end of the engaging member 33 is inserted into the opening 20 of the body 12 by a predetermined length. A bulging portion 34 that bulges radially outward is formed at one end of the engaging member 33 and is engaged with an annular groove 35 on the inner peripheral surface of the body 12. For this reason, the engaging member 33 is prevented from being removed from the body 12 and is integrally connected to the body 12.
[0025]
Further, the inner peripheral surface side of the bulging portion 34 of the engaging member 33 is a tapered surface 36 that gradually increases in diameter toward the other end portion side of the engaging member 33.
[0026]
Further, a locking portion 37 that contacts the end surface of the opening 20 of the body 12 is formed on the other end portion side of the engaging member 33 so as to protrude in a radially outward direction by a predetermined length.
[0027]
Furthermore, a guide portion 44 that protrudes radially inward is formed on the other end portion side of the engaging member 33.
[0028]
A part of a release bush (lock release member) 38 is inserted into the engagement member 33 so as to be displaceable along the axial direction. A plurality of slits (not shown) are formed at one end of the release bush 38 at a predetermined angle along the circumferential direction, bulge by a predetermined length in the radial outward direction, and gradually reduce in diameter toward the tip. A tip 40 is formed.
[0029]
Further, a flange portion 42 is formed on the other end portion of the release bush 38 so as to protrude outward in the radial direction.
[0030]
Further, the outer peripheral surface 43 of the release bush 38 is supported by the inner peripheral surface 45 of the guide portion 44 so as to be displaceable along the axial direction. The inner diameter A (see FIGS. 1 and 8) of the release bush 38 is slightly larger than the outer diameter B (see FIG. 8) of the fluid tube 18 inserted therein (A>). B).
[0031]
The chuck (holding mechanism) 46 is formed by pressing a thin plate member, and one end thereof is mounted between the inner peripheral surface 45 of the engaging member 33 and the outer peripheral surface 43 of the release bush 38.
[0032]
On one end portion side of the chuck 46, an engagement portion 48 is formed by bending in a substantially U-shaped cross section, and the inner peripheral surface of the engagement portion 48 slides along the outer peripheral surface 43 of the release bush 38. It is provided freely. A step portion 50 is formed between the distal end portion 40 of the release bush 38 and the outer peripheral surface 43 of the release bush 38. The stepped portion 50 is prevented from being pulled out of the body 12 by engaging the end portion of the engaging portion 48 under the displacement action along the axial direction of the chuck 46.
[0033]
Further, the chuck 46 extends in the direction of the connection portion 14 in a state in which the chuck 46 is inscribed in the inner peripheral surface 51 of the engagement member 33 from the engagement portion 48, and gradually in the radially outward direction inside the tightening portion 16. An inclined portion 52 that increases in diameter and an enlarged diameter portion 54 that extends substantially parallel to the inner peripheral surface of the tightening portion 16 of the body 12 are formed. A clearance is provided between the outer peripheral surface of the enlarged diameter portion 54 and the inner peripheral surface of the second step portion 26 of the body 12.
[0034]
A plurality of slits 56 a to 56 d are formed at the other end portion of the chuck 46 at a predetermined angle along the circumferential direction (see FIG. 4), and are substantially toward the inner circumferential side with respect to the enlarged diameter portion 54. A flat portion 58 bent so as to be orthogonal to each other, a locking claw 60 projecting from the inner peripheral end of the flat portion 58 at a predetermined angle toward the connecting portion 14, and the locking claw 60 And a concave portion (stopper mechanism) 63 formed by the curved portion 62. The curved portion 62 connects the locking claw 60 and the flat portion 58. And are provided.
[0035]
As shown in FIG. 3, the locking claw 60 of the chuck 46 is interposed via four support portions 65 a to 65 d that extend from the annular ring portion 64 at a predetermined interval in the circumferential direction. Thus, it can be elastically expanded and contracted.
[0036]
Further, as shown in FIGS. 5 and 6, the tip of the locking claw 60 is formed so that the concave portion 63 side corresponding to the inner peripheral side thereof has a substantially right-angle shape. It should be noted that there is a slight locking claw between both sides (see FIG. 6) in the vicinity of the slits 56a to 56d along the circumferential direction of the locking claw 60 and a substantially central portion (see FIG. 5) along the circumferential direction of the locking claw 60. The shape of 60 is formed differently.
[0037]
Specifically, a substantially right-angled blade edge portion 66 is formed at one corner portion provided on the concave portion 63 side. Further, as shown in FIG. 5, a chamfered chamfer 68 is formed at the other corner facing the fluid tube 18 at a substantially central portion along the circumferential direction of the locking claw 60. In addition, on both sides of the locking claw 60 in the vicinity of the slits 56a to 56d (see FIG. 4), as shown in FIG.
[0038]
The blade edge portion 66 is inserted into the outer peripheral surface of the fluid tube 18 when the fluid tube 18 is pulled.
[0039]
That is, by providing a chamfered portion 68 and a right angle portion 70 each having a different cross-sectional shape at a portion of the locking claw 60 facing the fluid tube 18, the right angle portion 70 has an acute outer periphery of the fluid tube 18. Simultaneously with the insertion into the surface, the chamfered portion 68 is pressed against the outer peripheral surface of the fluid tube 18, thereby providing resistance when the right-angled portion 70 is inserted into the fluid tube 18.
[0040]
As a result, by providing the chamfered portion 68 on the locking claw 60, there is an advantage that the amount of insertion into the outer peripheral surface of the fluid tube 18 is regulated. The amount of insertion into the outer peripheral surface of the fluid tube 18 can be adjusted by changing the distance along the circumferential direction of the chamfered portion 68 or the surface area of the chamfered portion 68.
[0041]
The locking claw 60 is formed to protrude slightly inward in the radial direction from the inner peripheral surface of the release bush 38.
[0042]
Further, a clearance is provided between the outer peripheral surface of the enlarged diameter portion 54 and the inner peripheral surface of the second step portion 26 of the body 12.
[0043]
The pipe joint 10 according to the first embodiment of the present invention is basically configured as described above. Next, the operation and effects thereof will be described.
[0044]
As shown in FIG. 1, in a state where the fluid tube 18 is not attached to the pipe joint 10, the fluid tube 18 connected to a fluid device or the like (not shown) is disposed along the sleeve 28 as shown in FIG. 8. Then, the one end surface of the fluid tube 18 is brought into contact with the flange portion 30 of the sleeve 28. At this time, the inner circumferential surface of the packing 32 comes into contact with the outer circumferential surface of the fluid tube 18 to surround the fluid tube 18, whereby the fluid inside the body 12 is kept airtight and the fluid flowing through the passage 22. Is prevented from leaking outside.
[0045]
Similarly, the other end of the chuck 46 is pushed outward in the radial direction (in the direction of arrow G in FIG. 8) by the outer peripheral surface of the fluid tube 18, so that the enlarged diameter portion 54 is placed inside the second step portion 26. While being displaced, the locking claw 60 is in contact with the outer peripheral surface of the fluid tube 18 (see FIG. 9).
[0046]
After the fluid tube 18 is inserted into the release bush 38, the fluid tube 18 is slightly moved in the direction of the flange portion 42 of the release bush 38 (arrow D direction) as shown in FIG. When pulled, the locking claw 60 that contacts the outer peripheral surface of the fluid tube 18 is inserted into the outer peripheral surface of the fluid tube 18 under the tensile action of the fluid tube 18 (see FIG. 11).
[0047]
Also, as shown in FIG. 11, the meat 72 on the outer peripheral surface of the fluid tube 18 enters the recess 63 along the upper surface of the locking claw 60 almost simultaneously by the locking claw 60. As a result, the fluid tube 18 is securely locked by the locking claw 60 inserted into the outer peripheral surface and the meat 72 entering the recess 63.
[0048]
Furthermore, as shown in FIG. 10, when the fluid tube 18 is to be pulled in the direction of the flange portion 42 of the release bush 38 (arrow D direction), the fluid tube is caused by the meat 72 that has entered the recess 63. It becomes resistance when 18 is displaced in the axial direction. Therefore, the fluid tube 18 is securely locked and prevented from being pulled out from the pipe joint 10, and the locking claw 60 is further prevented from being inserted into the fluid tube 18. .
[0049]
That is, when the meat 72 on the outer peripheral surface of the fluid tube 18 enters along the recess 63, the recess 63 serves as a wall and functions as a stopper, so that the locking claw 60 is inserted into the fluid tube 18. The amount is suppressed. By changing the inclination angle of the locking claw 60, the position of the concave portion 63 in the radial direction and the axial direction, the amount of depression of the concave portion 63, and the like, an appropriate amount of insertion of the locking claw 60 into the fluid tube 18 is achieved. Can be set.
[0050]
When the locking claw 60 is inserted into the outer peripheral surface of the fluid tube 18, the meat 72 on the outer peripheral surface of the fluid tube 18 enters the recess 63 along the upper surface of the locking claw 60. The escape of the meat 72 on the outer peripheral surface of the fluid tube 18 in the direction away from the side surface of the locking claw 60 on the concave portion 63 side can be prevented.
[0051]
Finally, when the fluid tube 18 is detached from the pipe joint 10, as shown in FIG. 12, the flange portion 42 of the release bush 38 is pressed toward the connecting portion 14 (arrow E direction). Under the pressing action of the flange portion 42, the distal end portion 40 of the release bush 38 presses the side surface of the bending portion 62 (see FIG. 13). Then, the depression 63 is displaced integrally with the bending portion 62 in the direction of the packing 32 (arrow E direction) under the pressing action by the tip portion 40, and the other end of the chuck 46 is forcibly displaced radially outward. . Therefore, the locking claw 60 inserted into the outer peripheral surface of the fluid tube 18 is separated from the outer peripheral surface of the fluid tube 18.
[0052]
As a result, since the locked state along the axial direction of the fluid tube 18 is released, the fluid tube 18 can be detached from the pipe joint 10 by pulling the fluid tube 18 in the axial direction.
[0053]
As described above, in the first embodiment, the locking claw 60 protruding to the inner peripheral side of the chuck 46 and the recess 63 in the vicinity of the locking claw 60 are provided, whereby the fluid tube 18 is pulled. When this occurs, the outer peripheral meat 72 of the fluid tube 18 enters the recess 63, and further entry is restricted by the inner wall surface of the recess 63. As a result, the amount of insertion of the locking claw 60 into the fluid tube 18 can be suppressed. Therefore, a stable holding state can always be maintained with respect to the pipe joint 10.
[0054]
Further, a chuck 46 having both a function of locking the fluid tube 18 between the engaging member 33 and the release bush 38 and a function of being held inside the engaging member 33 is provided. Therefore, the number of parts can be reduced, and the assembly workability of the pipe joint 10 can be improved.
[0055]
Next, the latching claw 80 according to the modification will be described.
[0056]
As shown in FIG. 7, the locking claw 80 according to the modified example is formed with an arc portion 84 having a circular arc cross section at the tip. The locking claw 80 is not provided with the chamfered portion 68 in the locking claw 60 of the first embodiment.
[0057]
By forming in this way, when the arc tube 84 is pressed against the outer peripheral surface of the fluid tube 18 by pulling the fluid tube 18, the arc portion 84 is inserted into the outer peripheral surface of the fluid tube 18. Is done. In that case, since the said circular arc part 84 is formed in the cross-sectional arc shape, the amount of insertion to the tube 18 for fluids of the said latching claw 80 can be suppressed. As a result, it is possible to maintain a stable holding state of the fluid tube 18 with respect to the pipe joint 10 at all times.
[0058]
Next, a pipe joint 100 according to a second embodiment of the present invention is shown in FIG. In the following embodiments, the same components as those of the pipe joint 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0059]
In the pipe joint 100 according to the second embodiment, the first locking claw 104 and the second locking claw 106 projecting at a predetermined interval on the inner peripheral surface of the chuck 102 are provided at two points. This is different from the pipe joint 10 according to the first embodiment.
[0060]
When the fluid tube 18 (see FIG. 8) inserted into the release bush 38 is pulled in the direction of the flange portion 42 of the release bush 38 (arrow D direction), the first locking claw 104 and the second engagement claw 104 are engaged. Since both the pawls 106 are inserted into the outer peripheral surface of the fluid tube 18, the fluid tube 18 can be locked even more firmly.
[0061]
Next, a pipe joint 120 according to a third embodiment of the present invention is shown in FIG.
[0062]
In the pipe joint 120 according to the third embodiment, an attaching / detaching member 122 integrally formed with the chuck 46 and the release bush 38 is provided on the inner peripheral side of the engaging member 33a, and the inner peripheral surface of the attaching / detaching member 122 is provided. It differs from the pipe joint 10 which concerns on 1st Embodiment by the point which has provided the 1st-3rd latching claw 104,106,124 which protruded.
[0063]
In this case, the number of parts can be reduced by integrally forming the chuck 46 and the release bush 38. When the fluid tube 18 (see FIG. 8) inserted in the release bush 38 is pulled in the direction of the flange portion 42 of the release bush 38 (arrow D direction), the first to third locking claws Since 104, 106, and 124 are respectively inserted into the outer peripheral surface of the fluid tube 18, the fluid tube 18 can be locked even more firmly.
[0064]
【The invention's effect】
That is, in the pipe joint according to the present invention, extends along the outer periphery of the fluid tube has a recess which is curved in the vicinity of the locking pawl, regulation of the amount of insertion of the locking claw by providing a possible stopper mechanism, it said part of the fluid tube is advanced into the recess of the stopper function, harmony and pullout strength of the locking claw of the amount of insertion and fluid tube with respect to said fluid tube Therefore, a stable holding state of the fluid tube can be obtained.
[0065]
Further, by extending the stopper mechanism along the outer periphery of the fluid tube and forming a concave portion curved in the vicinity of the locking claw, when the fluid tube is pulled, a part of the fluid tube is Since it introduce | transduces into a recessed part, the amount of insertion of the tube for fluids can be controlled.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view along the axial direction of a pipe joint according to a first embodiment of the present invention.
2 is an exploded perspective view of a vertical cross section of the pipe joint of FIG. 1;
FIG. 3 is a perspective view of a chuck constituting the pipe joint of FIG. 1;
4 is an arrow view seen from the direction of arrow F in FIG. 3;
5 is a partially enlarged longitudinal sectional view taken along line VV in FIG. 4. FIG.
6 is a partially enlarged longitudinal sectional view taken along line VI-VI in FIG. 4;
FIG. 7 is a partially enlarged longitudinal sectional view showing the vicinity of a locking claw according to a modification.
8 is a longitudinal sectional view showing a state in which a fluid tube is inserted into the pipe joint of FIG.
9 is a partially enlarged longitudinal sectional view in the vicinity of the locking claw in FIG. 8. FIG.
10 is a longitudinal sectional view showing a state where a fluid tube is locked to the pipe joint of FIG.
11 is a partially enlarged longitudinal sectional view in the vicinity of a locking claw in FIG.
12 is a longitudinal sectional view showing a state in which the fluid tube is unlocked from the pipe joint of FIG.
13 is a partially enlarged longitudinal sectional view in the vicinity of a locking claw in FIG. 12. FIG.
FIG. 14 is a longitudinal sectional view of a pipe joint according to a second embodiment of the present invention.
FIG. 15 is a longitudinal sectional view of a pipe joint according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10,100,120 ... Pipe joint 12 ... Body 14 ... Connection part 16 ... Fastening part 18 ... Fluid tube 20 ... Opening part 22 ... Passage 24 ... 1st step part 26 ... 2nd step part 28 ... Sleeve 30 ... Flange Part 32 ... Packing 36 ... Tapered surface 38 ... Release bush 40 ... Tip part 42 ... Flange part 44 ... Guide part 46 ... Chuck 48 ... Engagement part 50 ... Step part 52 ... Inclined part 54 ... Diameter expansion part 56a to 56d ... Slit 58... Plane portion 60, 80... Locking claw 62... Curved portion 63... Recess 64. Ring portion 104 .. first locking claw 106.

Claims (10)

A body into which the fluid tube is inserted;
A chuck that is disposed inside the body and holds the fluid tube via a locking claw inserted into an outer peripheral surface of the fluid tube;
An amount of insertion of the locking claw into the fluid tube , which is provided on the chuck, extends along the outer periphery of the fluid tube, has a concave portion formed in the vicinity of the locking claw, and And a stopper mechanism that can harmonize the pull-out strength of the fluid tube with the amount of insertion,
With
The stopper mechanism is characterized in that when the locking claw is inserted into the outer peripheral surface of the fluid tube, a part of the fluid tube enters the recess and contacts the inner wall surface. Pipe fittings. In the pipe joint according to claim 1,
The pipe joint according to claim 1, wherein a lock release member for releasing the holding state of the fluid tube by the chuck is provided inside the body. In the pipe joint according to claim 2,
The engagement release member presses a chuck that holds the fluid tube under a pressing action on the body side, and the engagement claw of the chuck is displaced radially outward. In the pipe joint according to claim 1,
The chuck includes an inclined portion that gradually decreases in diameter in a direction in which the fluid tube is inserted,
The pipe joint according to claim 1, wherein when the fluid tube is pulled in a direction away from the body, the inclined portion comes into contact with a taper surface of an engagement member mounted in the body. In the pipe joint according to claim 2,
The pipe joint according to claim 1, wherein the chuck is formed integrally with an unlocking member that releases the holding state of the fluid tube by the locking claws. In the pipe joint according to claim 1,
The said stopper mechanism is extended along the outer periphery of the said tube for fluids, The pipe joint characterized by including the chamfering part formed facing the said tube for fluids in the said latching claw. In the pipe joint according to claim 1,
The said latching claw is formed in the edge part of the curved part extended along the outer periphery of the said tube for fluids, The pipe joint characterized by the above-mentioned. In the pipe joint according to claim 1,
A plurality of the locking claws are provided with a plurality of slits spaced apart by a predetermined distance along the outer periphery of the fluid tube. The pipe joint according to claim 8,
A plurality of the locking claws are arranged at predetermined intervals along the axial direction of the body. In the pipe joint according to claim 1,
A pipe joint characterized in that an arc portion having an arc cross section is formed at an end portion of the locking claw.

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