JPH075353Y2 - Sealing structure for split split pipe fittings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a seal structure for a branched split type pipe joint, and in particular, the fluid flowing down the branch pipe through the perforation formed in the main pipe is The present invention relates to a seal structure that prevents the inconvenience of leaking to the outside through a gap between the inner surface of one joint member and the surface of a main pipe, which are arranged correspondingly, and preventing foreign matter from entering the inside through the gap.

[Prior Art] Generally, as shown in FIG. 8, a buried co-supply pipe for city gas has a configuration in which a branch pipe B from a main pipe A to a consumer is branched and connected to the main pipe A. The pipe B is branched and connected by using a branched split type pipe joint C.

That is, as shown in FIG. 5, the branched split type pipe joint C is composed of a pair of split joint members C1 and C2, and the inner surface Ca of one split joint member C1 is a perforation H formed in the main pipe A. Correspondingly, the split joint members C2 and C2 are arranged so as to face the inner surface Cb of the other split joint member C2, and a plurality of fastening points (for example, 4
5 (only two locations are shown in FIG. 5) are fastened together by fastening members D made up of bolts and nuts, and both C1 and C2 are integrally connected.

Further, the gas flowing down from the perforation H of the original pipe A toward the branch pipe B connected to the one split joint member C1 is discharged from the gap between the inner surface Ca of the one split joint member C1 and the surface of the original pipe A. The inner surface of one of the split joint members C1 in order to prevent the inconvenience of leakage to the outside or intrusion of foreign matter from the outside through the gap.
An annular fitting groove E is formed in Ca, an annular elastic seal member S is fitted in the fitting groove E, and the elastic seal member S surrounds the outer periphery of the perforation H and the surface of the original pipe A. The seal is made by pressing it against.

[Problems to be Solved by the Invention] As described above, in a gas piping system in which the branch pipe B is branched from the main pipe A to the branch pipe B by the branch split type pipe joint C and buried in the ground, for example, by arrow F1 due to ground subsidence. When the downward load shown in the drawing is applied to the branched split type pipe joint C and a force to bend the original pipe A as shown by the phantom line in FIG. 6 acts,
This bending force is also transmitted to the portion of the base pipe A held by the split joint members C1 and C2, and a compressive load acts above the horizontal neutral plane CF of FIG. A tensile load will act on the lower side.

In the portion of the base pipe A held by the split joint members C1 and C2, a perforation H is formed in the peripheral wall of the left half portion (left side of the vertical neutral plane CH) corresponding to the other joint member C2. Although it has high rigidity because it is not, since the peripheral wall of the right half portion (right side of the vertical neutral plane CH) corresponding to one joint member C1 is notched by forming a perforation H, it is more than the left half portion. Can be said to have a slightly low rigidity. Therefore, when the above-described compressive load and tensile load act, compressive strain and tensile strain are likely to occur in the right half portion having low rigidity.

Particularly, the compressive strain acts to reduce the pressure contact force of the annular elastic seal member S by causing the peripheral wall portion of the base pipe A to shrink radially inward. Since the amount of compressive strain gradually increases in accordance with the distance from the horizontal neutral surface CF to the upper skin side of the base pipe A, the pressure contact force of the annular elastic seal member S is at the distance from the horizontal neutral surface CF. It becomes smaller according to the size, and the pressure contact force at the upper end SH becomes the smallest.

However, in the conventional seal structure, the annular elastic seal member S having a uniform cross-sectional shape (for example, a regular circular cross-section) is fitted in the annular fitting groove E having a uniform cross-sectional shape, and the fastening member D is formed. Since the ring-shaped elastic seal member S is pressed against the surface of the base pipe A near the outer diameter of the hole H by the fastening force, the pressure contact force corresponds to the radially outer extension line of the horizontal neutral plane CF. The largest in the central part SC of the annular elastic seal member S,
It gradually decreases from here and becomes the smallest at the upper end SH. Since the pressure contact force of the annular elastic seal S is obtained by the fastening force of the fastening member D, the fastening force is large at the central portion SC acting toward the center P of the source pipe A in a normal time when no compressive strain is generated. , The upper end where the direction in which the fastening force acts deviates from the center P
It can be said that SH is slightly small, but due to the large compression strain, the pressure contact force becomes even smaller, and there is a risk that the sealability will deteriorate and gas leakage will occur.

Further, when a horizontal load indicated by arrow F2 in FIG. 5 is applied to the branch split joint C and a force to bend the base pipe A as shown by the phantom line in FIG. A compressive load acts on the right side of the surface CH (corresponding to the right half of FIG. 5),
A tensile load will act on the left side of the vertical neutral plane CH (corresponding to the left half of FIG. 5). The amount of compressive strain in this case is
Although the central portion SC of the annular elastic seal member S is maximized in the portion where the central portion SC is in pressure contact and the pressure contact force is reduced, as described above, the pressure contact force of the center portion SC is changed by the fastening force of the fastening member D. Since it is increased, even if the amount of compressive strain is large, it is possible to suppress the decrease in the pressure contact force and ensure excellent sealing properties. However, at the upper end portion SH, the lower end portion SL, and their vicinity where the pressure contact force is slightly small even in the normal state, even if the amount of compressive strain is small, the sealing property may be deteriorated and gas leakage may occur.

It should be noted that although the downward load F1 tends to cause tensile strain in the right half portion below the horizontal neutral plane CF in FIG. 5, this tensile strain causes the peripheral wall portion of the base pipe A to expand radially outward. As a result, since it acts so as to increase the pressure contact force of the annular elastic seal member S, the sealing performance does not deteriorate.

The present invention has been made in view of such circumstances, and when the load is applied to the split-branch pipe joint, the rigidity of the main pipe in one side region of the horizontal neutral plane is slightly reduced by the perforation. Even if a compressive strain is generated on the peripheral wall to reduce the pressure contact force of the annular elastic seal member, the amount of compression strain in this case is absorbed to compensate for the decrease in the pressure contact force, and a large pressure contact force is secured. It is an object of the present invention to provide a branch split type pipe joint seal structure capable of preventing a decrease in sealing performance and reliably preventing fluid (gas) leakage.

[Means for Solving the Problems] In order to achieve the above object, a first invention is an annular elastic seal which is pressed against one surface of the base pipe by one of the split joint members and surrounds the vicinity of the outer diameter of the perforation. The member has a cross-sectional shape in which the thickness dimension is set to be gradually larger than the width dimension in accordance with the distance from the horizontal neutral surface to the skin side with reference to the reference portion corresponding to the horizontal neutral surface of the original pipe. And the thickness direction is directed to the surface of the base pipe.

In order to achieve the above-mentioned object, the second invention is that an annular elastic seal member that is formed on one inner surface of the split joint member and surrounds the vicinity of the outer diameter of the hole formed in the base pipe is fitted. The depth of the annular fitting groove that press-contacts the annular elastic seal member with the surface of the base pipe is from the horizontal neutral plane with reference to the depth of the reference portion corresponding to the horizontal neutral plane of the base pipe. It is set to be gradually shallower according to the distance to the epidermis side.

[Operation] According to the first invention, a compressive strain is generated by a downward load on the peripheral wall of the upper pipe above the horizontal neutral surface, particularly in the region where the perforations are formed, and the compressive strain amount at this time is horizontal. Even if the distance gradually increases from the neutral surface toward the skin side of the main pipe, the cross-sectional shape of the annular elastic seal member is horizontal centered on the basis of the reference part corresponding to the horizontal neutral surface. Depending on the distance from the vertical surface to the skin side, the thickness dimension is set to be gradually larger than the width dimension, and the thickness direction is directed to the surface of the original pipe for pressure welding. Since the pressure contact force is gradually increased in accordance with the tendency of the amount of compressive strain to gradually increase, the pressure contact force is not reduced.

Then, a compressive strain is generated on the peripheral wall of the region where the perforations of the original pipe are formed by the load in the horizontal direction, and the amount of compressive strain at this time is from the vertical neutral plane orthogonal to the horizontal neutral plane to the skin side of the original pipe. Even if the distance gradually increases in accordance with the distance, the large fastening force of the fastening member acting toward the center of the original pipe causes
Since the central portion of the annular elastic seal member, that is, the reference portion corresponding to the horizontal neutral surface, can be pressed against the surface of the original pipe, the decrease in the pressure contact force can be suppressed even though the compression strain is large. At the same time, the upper and lower ends and the vicinity of the annular elastic seal member, which becomes slightly smaller because the acting direction of the fastening force deviates from the center of the original pipe, are horizontal with reference to the reference part corresponding to the horizontal neutral plane. Depending on the distance from the neutral surface to the skin side, the thickness dimension is gradually set larger than the width dimension, and the thickness direction is directed to the surface of the original pipe, so a large pressure contact force is applied. You can press it with.

Further, according to the second invention, a downward load causes a compressive strain on the peripheral wall of the upper side of the horizontal neutral surface of the original pipe, particularly in the region where the perforations are formed, and the compressive strain amount at this time is The depth of the annular fitting groove that fits the annular elastic seal member even if it gradually increases according to the distance from the vertical surface to the skin side of the original pipe is the standard corresponding to the horizontal neutral surface. Since the depth is set to be gradually shallower according to the distance remote from the horizontal neutral surface to the skin side based on the depth of the portion, the annular elastic seal member fitted in the annular fitting groove, Even if it has a normal uniform cross section, since it is gradually increased in accordance with the gradual increase tendency of the amount of compressive strain, the pressure contact force is not reduced.

Then, a compressive strain is generated on the peripheral wall of the region where the perforations of the original pipe are formed by the load in the horizontal direction, and the amount of compressive strain at this time is from the vertical neutral plane orthogonal to the horizontal neutral plane to the skin side of the original pipe. Even if the distance gradually increases in accordance with the distance, the large fastening force of the fastening member acting toward the center of the original pipe causes
Since the central portion of the annular elastic seal member, that is, the reference portion corresponding to the horizontal neutral surface, can be pressed against the surface of the original pipe, the decrease in the pressure contact force can be suppressed even though the compression strain is large. At the same time, the upper and lower ends of the annular fitting groove, which is slightly smaller because the acting direction of the fastening force deviates from the center of the original pipe, and the vicinity thereof are based on the depth of the reference part corresponding to the horizontal neutral plane. Since it is formed so as to be gradually shallower according to the distance from the horizontal neutral surface to the skin side, the annular elastic seal member fitted in this annular fitting groove has a normal uniform cross section. Even if it has, it can be pressed with a large pressing force.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a branched split type pipe joint to which an embodiment of the present invention is applied. In the figure, the branched split type pipe joint 1 is bolted to a main pipe 2 in a city gas pipe. Is composed of a pair of split joint members 11 and 12 which are joined together by a fastening member 4 made of the above, and one of the split joint members 11 corresponds to the perforation Q formed in the main pipe 2, and its inner surface The ring-shaped sealing member 3 fitted in the ring-shaped fitting groove 15 formed in the above is surrounded by the outer periphery of the perforation Q and pressed against the surface of the base pipe 2.

A branch pipe connection port 11B having an axis C1 is formed in one of the split joint members 11, and a perforation port for performing a perforation Q having an axis C2 intersecting with the axis C1 at a position near the outer diameter of the source pipe 2 is formed. 11A is formed. The axis C1 is orthogonal to the axis C3 of the base pipe 2 in the horizontal plane.

A female screw 11a is formed on the inner periphery of the hole 11A and is closed by screwing the plug 5 into the female screw 11a. A branch pipe 10 is connected to the branch pipe connection port 11B via a seal member 6, a retainer 7, a regulating member 8, a push ring 9 and the like in a hermetically sealed state and a regulated state.

The annular elastic seal member 3 is formed of an elastic material such as rubber, and as described above, it surrounds the vicinity of the outer diameter of the perforation Q and is pressed against the surface of the main pipe 2 to press the perforation Q from the main pipe 2.
And the gas flowing down to the branch pipe 10 through the one split joint member 11 is prevented from leaking to the outside through the gap between the inner surface of the one split joint member 11 and the surface of the original pipe 2, The foreign matter is prevented from entering through the gap.

The cross-sectional shape of the annular elastic seal member 3 is, as shown in FIG. 2, a vertical line L2 that passes through the center P and is orthogonal to the horizontal line L1 with reference to a regular circular reference portion on the horizontal line L1 that passes through the center P. It is formed in an oval shape in which the length of the major axis l2 is set to be gradually larger than the length of the minor axis 1 toward the intersecting position. In addition, for example, a protrusion 3A for positioning is provided on the surface of one of the regular circles.
And the annular elastic seal member 3 is fitted into the annular fitting groove 15 with the major axis l2 of the oval portion oriented toward the surface of the base pipe 2 as shown in FIG. After matching, the first
As shown in the drawing, one split joint member is fastened by the fastening member 4 in correspondence with the perforation Q, whereby the annular elastic seal member 3 is pressed against the surface of the base pipe 2.

When one split joint member 11 is attached to the base pipe 2, the annular fitting groove 15 is provided with a recess 15A on one side of both reference parts corresponding to an extension line of the horizontal neutral plane CF of the base pipe 2. Is forming. Further, the groove width is formed such that both the reference portions are small, and the width is gradually widened from here to both upper and lower end portions, and the depth thereof is set to be uniform. Therefore, if the annular elastic seal member 3 is fitted into the annular fitting groove 15 in a positioning state in which the positioning projection 3A protruding from the annular elastic seal member 3 is fitted in the recess 15A, it is inevitable. Specifically, the regular circular reference portion on the horizontal line L1 shown in FIG. 2 corresponds to the horizontal neutral plane CF of the source pipe 2 shown in FIG. As a result, based on the right circular reference portion corresponding to the horizontal neutral plane CF, according to the distance from the horizontal neutral plane CF to the surface side of the branch pipe 2, that is, the upper end side and the lower end side of the base pipe 2. The oval portion in which the length of the major axis l2 is set to be gradually larger than the length of the minor axis 1 is pressed into contact with the major axis l2 on the surface of the source tube 2. That is, near the outer diameters of the upper and lower ends of the perforation Q, the oval portion having the largest length of the major axis l2 with respect to the length of the minor axis 1 is pressed by the maximum pressing force.

In the above structure, the downward load indicated by the arrow F1 in FIG. 1 causes a force to bend the base pipe 2 as shown by the phantom line in FIG. 6, and this bending force acts on the split joint in the base pipe 2. When it is transmitted to the portion held by the members 11 and 12 and a compressive strain is generated in the peripheral wall of the base pipe 2 in the region where the perforations Q are formed, above the horizontal neutral plane CF in FIG. Although the amount of compressive strain increases gradually with the distance from the horizontal neutral plane CF toward the upper end of the main tube 2, that is, toward the skin side, the cross-sectional shape of the annular elastic seal member 3 is horizontal neutral. Oval cross section in which the length of the major axis l2 is set to be gradually larger than the length of the minor axis 1 according to the distance from the horizontal neutral plane CF to the skin side based on the reference circular part corresponding to the plane CF. Since the long axis l2 is directed toward the surface of the base pipe 2 and is pressed against the surface, the pressure contact force is Since the amount is gradually increased in accordance with the increasing tendency of the amount, a large pressure contact force can be obtained even in a region having a large amount of compressive strain.

That is, by the surface of the base pipe 2 and the groove bottom of the annular fitting groove 15,
By compressing the annular elastic seal member 3, the elastic compression amount of the annular elastic seal member 3 is gradually increased from the reference circular portion to the maximum oval portion, and the press contact force is increased accordingly, so that the compression strain amount is increased. Even large parts can be reliably sealed without lowering the pressure contact force.

Further, the horizontal load indicated by the arrow F2 causes a force to bend the base pipe 2 as shown by the phantom line in FIG. 7, and this bending force is caused by the split joint members 11 and 12 in the base pipe 2. Transmitting to the held portion, a compressive strain is generated in the peripheral wall of the region of the vertical neutral plane CH where the perforations Q are formed in FIG. 1, and the amount of compressive strain at this time is orthogonal to the horizontal neutral plane CF. Even if the distance gradually increases from the vertical neutral surface CH toward the skin side of the base tube 2, the large fastening force of the fastening member 4 acting toward the center P of the base tube 2 causes an annular shape. Since the central portion of the elastic seal member 3, that is, the reference portion corresponding to the horizontal neutral plane CF, can be brought into pressure contact with the surface of the base pipe 2, the reduction of the pressure contact force is suppressed even though the compression strain amount is large. At the same time, the acting direction of the fastening force deviates from the center of the main pipe 2 and thus becomes slightly smaller. The upper end and the lower end of the elastic seal member 3 and the vicinity thereof are based on a reference portion corresponding to the horizontal neutral plane CF, and the minor axis 1 depending on the distance from the horizontal neutral plane CF to the skin side. Since the length of the major axis l2, that is, the thickness dimension is set to be gradually larger than the length of the length dimension, that is, the width dimension, and the thickness direction is directed to the surface of the source tube 2, a large pressure welding is performed. It is possible to make a reliable seal by pressing it with force.

It should be noted that, in the above-mentioned embodiment, the explanation has been made by using the annular elastic seal member 3 having a circular cross-sectional shape, but the present invention is not limited to the above-mentioned embodiment, and, for example, the main pipe 2 The reference part corresponding to the horizontal neutral plane CF has a square cross section,
An annular elastic seal member having a rectangular cross section in which the thickness dimension is gradually increased with respect to the width dimension according to the distance from the horizontal neutral plane CF to the surface side of the main tube 2 may be used.
In short, the thickness dimension gradually increases with respect to the width dimension according to the distance from the horizontal neutral plane CF to the surface side of the original tube 2 with reference to the reference portion corresponding to the horizontal neutral plane CF of the original tube 2. If it is formed in the set shape, by directing the thickness direction to the surface of the base tube 2, it is possible to achieve the same effect as that of the above embodiment.

FIG. 4 is a branch split joint 1 to which the second embodiment of the present invention is applied.
Is a cross-sectional view of the embodiment, and the same or corresponding parts as those of the embodiment described in FIGS. 1 to 3 are designated by the same reference numerals, and the detailed description thereof will be omitted.

In this embodiment, the depth of the annular fitting groove 15 is based on the depth of the reference portion corresponding to the horizontal neutral plane CF of the base pipe 2, that is, the reference portion of the annular elastic seal member 3 is fitted. It is set to be gradually shallower in proportion to the distance from the horizontal neutral plane CF to the surface side, based on the depth of the part. That is, the annular fitting groove
The reference numeral 15 is formed so as to be gradually shallower toward both upper and lower end portions based on the depth of both reference portions.

In addition to the cross-sectional shape of the annular elastic seal member 3 fitted in the annular fitting groove 15, those having a regular circular cross section with a uniform outer diameter can be used in addition to those described in the above embodiment.

With this configuration, the downward load indicated by the arrow F1 in FIG. 4 causes a force to bend the base pipe 2 as shown by the phantom line in FIG. 6, and this bending force acts on the base pipe. 2 is also transmitted to the portion held by the split joint members 11 and 12, and particularly the perforation Q on the upper side of the horizontal neutral plane CF in FIG.
When compressive strain is generated in the peripheral wall of the base pipe 2 in the region where is formed, the amount of compressive strain at this time depends on the distance from the horizontal neutral plane CF toward the upper end of the base pipe 2, that is, toward the epidermis side. However, the depth of the annular fitting groove 15 into which the annular elastic seal member 3 is fitted is increased on the basis of the depth of the reference portion corresponding to the horizontal neutral surface CF. Since it is formed so as to be gradually shallower according to the distance from the surface to the surface layer side, the annular elastic seal member 3 fitted in the annular fitting groove 15 is formed.
However, even if it has a normal uniform cross section, its pressure contact force can be gradually increased in accordance with the tendency of the amount of compressive strain to increase. It can be surely sealed without causing it.

Further, the horizontal load indicated by the arrow F2 causes a force to bend the base pipe 2 as shown by the phantom line in FIG. 7, and this bending force is caused by the split joint members 11 and 12 in the base pipe 2. Transmitting to the held portion, a compressive strain is generated in the peripheral wall of the region of the vertical neutral plane CH where the perforations Q are formed in FIG. 4, and the amount of compressive strain at this time is orthogonal to the horizontal neutral plane CF. Even if the distance gradually increases from the vertical neutral surface CH toward the skin side of the base tube 2, the large fastening force of the fastening member 4 acting toward the center P of the base tube 2 causes an annular shape. Since the central portion of the elastic seal member 3, that is, the reference portion corresponding to the horizontal neutral plane CF, can be brought into pressure contact with the surface of the base pipe 2, the reduction of the pressure contact force is suppressed even though the compression strain amount is large. At the same time, the acting direction of the fastening force deviates from the center of the main pipe 2 and thus becomes slightly smaller. The upper end and the lower end and the vicinity thereof of the shape-like fitting groove 15 are based on the depth of the reference portion corresponding to the horizontal neutral plane CF, depending on the distance from the horizontal neutral plane CF to the epidermis side. Since it is formed so as to be gradually shallower, the annular elastic seal member 3 fitted in the annular fitting groove 15 is formed.
However, even if it has an ordinary uniform cross section, it is possible to bring it into pressure contact with a large pressure contact force for reliable sealing.

[Advantages of the Invention] Since the present invention is configured as described above, the following effects can be obtained.

According to the seal structure of the branched split type pipe joint of claim (1), the compressive strain that tends to reduce the pressure contact force of the annular elastic seal member to the peripheral wall of the former pipe in the region where the rigidity is slightly reduced due to the perforation. Even if occurs, the cross-sectional shape of the annular elastic seal member and the directivity with respect to the original pipe can gradually increase the pressure contact force in response to the gradual increase tendency of the compressive strain amount of the original pipe. However, without lowering the pressure contact force, it is possible to secure a high pressure contact force, prevent the deterioration of the sealing property, and reliably prevent the fluid leakage and the entry of foreign matter.

Further, according to the seal structure of the branched split type pipe joint of claim (2), the pressure contact force of the annular elastic seal member is reduced to the peripheral wall of the original pipe in the region where the rigidity is slightly reduced due to the perforation. Even if compressive strain occurs, it is possible to gradually increase the pressure contact force of the annular elastic seal member in accordance with the gradual increase in the compressive strain amount of the original pipe by changing the depth of the annular fitting groove. It is possible to secure a high pressure contact force and prevent the deterioration of the sealing performance without lowering the pressure contact force even in a portion having a large amount of strain, and it is possible to reliably prevent fluid leakage and foreign matter intrusion.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is a sectional view showing an example of a split split type pipe joint to which an embodiment of the present invention is applied, and FIG. 2 is an annular elastic seal member. FIG. 3 is a perspective view showing an example of a partial cross-section, FIG. 3 is an explanatory cross-sectional view showing a state before attachment to the original pipe, and FIG. 4 is an example of a split split type pipe joint to which the second embodiment of the present invention is applied. 5 is a sectional view showing a conventional seal structure applied to a split split pipe joint, FIG. 6 is a schematic left side view of FIG. 5, and FIG. 7 is a schematic plan view of FIG. Fig. 8 is a piping system diagram. 1 ... Branch split type pipe joint 2 ... Main pipe 3 ... Annular elastic seal member 4 ... Fastening member 11 ... One split joint member 12 ... Other split joint member 15 ... Annular fitting groove Q ... Perforation CF ... Original pipe Horizontal midplane

Claims (2)

[Scope of utility model registration request] 1. A pair of split joint members are arranged so as to oppose each other while holding a main pipe, and a plurality of fastening points of both split joint members are fastened by fastening members so that both split joint members are integrally joined. In the branched split type pipe joint, one of the pair of split joint members corresponds to the perforation formed in the base pipe, and the perforation is performed by being pressed against the surface of the base pipe by one of the split joint members. An annular elastic seal member surrounding the outside of the diameter is thicker than the width dimension according to the distance from the horizontal neutral surface to the skin side, with reference to the reference portion corresponding to the horizontal neutral surface of the original pipe. A branch split type pipe joint seal structure, characterized in that it is formed in a cross-sectional shape in which the length dimension is gradually increased and the thickness direction is directed to the surface of the original pipe. 2. A pair of split joint members are arranged so as to face each other so as to hold a main pipe, and a plurality of fastening points of both split joint members are fastened by fastening members to integrally join the split joint members. In the branched split type pipe joint, in which one of the pair of split joint members corresponds to the perforation formed in the base pipe, the branch joint is formed on one inner surface of the split joint member and is near the outer diameter of the perforation. A ring-shaped elastic seal member is fitted around the base pipe, and the depth of the ring-shaped fitting groove for pressing the ring-shaped elastic seal member against the surface of the base pipe corresponds to the horizontal neutral plane of the base pipe. The depth is set to be gradually shallower according to the distance from the horizontal neutral surface to the skin side, and the seal structure of the split pipe joint is characterized.