Water cut-off structure for pipe joint and rubber ring used for the same

Abstract

To provide a water cut-off structure for a pipe joint enabling excellent construction performance and reconstruction without deteriorating water-tightness and a rubber ring used for the water cut-off structure.SOLUTION: A rubber ring 4 includes: a cylindrical-shaped cylindrical part having a tip part 41a inserted into a first space part; a tapered part 42 of which outer diameter expands from the other end part 41b side of the cylindrical part toward a direction opposite to the tip part 41a; and a reception part that receives a rubber packing 6. An inner diameter of the cylindrical part is larger than an outer diameter of an insertion port 3, and the tapered part 42 is formed so that wall thickness thereof gradually becomes thin from the other end part 41b to the tapered tip part. A push ring 5 pushes the rubber packing 6 against an end surface of the other end part 41b and an inner surface 42a of the tapered part 42. The tip part 41a of a rubber ring 4 is brought into close contact with an inner surface 21a of the first space part, and an outer surface 42b of the tapered part 42 is brought into close contact with an inner surface of a second space part.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a watertight structure for a pipe joint and a rubber ring used therefor. More specifically, the present invention relates to a watertight structure for a pipe joint in which the spigot of a ductile cast iron pipe is inserted into the spigot of another pipe, and a rubber ring attached to the outer surface of the spigot is pressed against the spigot by a pressure ring to stop water flow, and a rubber ring used therefor. [Background technology]

[0002] Conventionally, as a watertight structure for a pipe joint as described above, for example, the one described in Patent Document 1 is known. In such a watertight structure for a pipe joint for a ductile cast iron pipe, a rubber ring 4' as shown in Fig. 9 is used. Since the inner diameter D0 of this rubber ring 4' is smaller than the outer diameter of the insertion port 3, during construction, a lubricant or the like must be applied to the outer surface of the insertion port 3 and the inner surface of the rubber ring 4' to expand the rubber ring 4' and install it, which makes the work complicated.

[0003] Moreover, one end of this rubber ring 4' has a rounded portion 4'a, and as shown in Fig. 9, when the rubber ring 4' is attached to the insertion port 3, the outer diameter of the rounded portion 4'a is larger than the inner diameter of the first space 21' of the socket 2. Therefore, even if a lubricant is applied, it is difficult to push the rounded portion 4'a into the first space 21' with the press ring 5, and even if it is pushed in, the rubber ring 4' pulls the insertion port 3 further into the socket 2 than the intended joint position, so that skilled techniques are required for connection. Furthermore, when re-installing, even if the T-head bolt 9a and nut 9b are removed and the pipe joint is disassembled, it is difficult to remove the insertion port 3 and the pushed-in rubber ring 4' from the socket 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 6-69574 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above-mentioned conventional situation, the present invention aims to provide a water-stopping structure for a pipe joint that is easy to install and can be reinstalled without compromising watertightness, and a rubber ring to be used therewith. [Means for solving the problem]

[0006] In order to achieve the above object, the watertight structure of a pipe joint according to the present invention is characterized in that, in a configuration in which the socket of another pipe is inserted into the socket of a ductile cast iron pipe, and a rubber ring attached to the outer surface of the socket is pressed against the socket by a pressure ring to stop water, an annular rubber packing is further provided between the rubber ring and the pressure ring to be attached to the outer circumferential surface of the socket, the socket has a cylindrical first space portion and a second space portion whose inner diameter expands from the first space portion toward the opening, and the rubber ring has a cylindrical portion whose tip portion is inserted into the first space portion and a cylindrical portion whose other end portion expands outward in the opposite direction to the tip portion. The device comprises a tapered portion whose diameter expands, and a receiving portion which receives the rubber packing and is composed of the end face of the other end of the cylindrical portion and the inner surface of the tapered portion, the inner diameter of the cylindrical portion being larger than the outer diameter of the insertion port, and the tapered portion being formed so that its thickness gradually becomes thinner from the other end toward the tapered tip, and the pressure ring presses the rubber packing against the end face of the other end and the inner surface of the tapered portion, while tightly adhering the tip of the rubber ring to the inner surface of the first space and tightly adhering the outer surface of the tapered portion to the inner surface of the second space.

[0007] According to the above configuration, an annular rubber packing is further provided between the rubber ring and the press ring to be attached to the outer circumferential surface of the insertion hole. The receiving hole has a cylindrical first space and a second space whose inner diameter expands from the first space toward the opening. The rubber ring has a cylindrical cylindrical portion whose tip is inserted into the first space, a tapered portion whose outer diameter expands from the other end side of the cylindrical portion toward the opposite direction to the tip, and a receiving portion that is composed of the end face of the other end of the cylindrical portion and the inner surface of the tapered portion and that receives the rubber packing. The inner diameter of the cylindrical portion is larger than the outer diameter of the insertion hole, and the tapered portion is formed so that its thickness gradually becomes thinner from the other end toward the tapered tip. Therefore, it can be attached without applying a lubricant, and the insertion hole can be inserted in a temporary assembly state as shown in FIG. 6, for example, so that the workability is extremely high. In addition, since the tip can be attached (inserted) so as to follow the first space, the insertion port will not be pulled further into the receiving port than the intended joining position when pressed (joined) with the pressing ring. Moreover, by forming the tapered portion so that its thickness gradually decreases toward the tapered tip, the boundary portion (base) between the tip of the cylindrical portion and the tapered portion is made thick. This ensures the strength of the tip, and makes it easy to insert and remove the tip into and from the first space. And because of the shape of the tapered portion, the pressing ring presses the rubber packing against the end face of the other end and the inner surface of the tapered portion, and the tip of the rubber ring adheres closely to the inner surface of the first space, while the outer surface of the tapered portion adheres closely to the inner surface of the second space. This causes the rubber packing to be compressed and deformed along the tapered surface, ensuring watertightness.

[0008] In the above configuration, the outer diameter of the tip of the cylindrical portion is preferably slightly larger than the inner diameter of the first space portion, and the outer diameter of the tapered portion is preferably slightly larger than the inner diameter of the second space portion. This makes it necessary to reduce the diameters of the cylindrical portion and the tapered portion when fitting the rubber ring into the receiving port. Since the rubber ring is fitted by reducing its diameter, it is temporarily fixed to the receiving port by repulsive force after fitting. Therefore, there is no need to hold the rubber ring down after fitting, which improves workability.

[0009] In this configuration, the tapered tip may have a locking portion that locks onto the outer edge of the socket and a bulging portion that bulges inward from the locking portion, making it easier to keep the rubber packing concentric with other components during work.

[0010] In the above configuration, the inner surface of the bulge may be tapered so that the inner diameter of the bulge narrows toward the outside. This allows the inner surface of the bulge to be flattened after the rubber ring is attached to the receiving port, and improves workability without interfering with the insertion of the insertion port.

[0011] In the above configuration, the rubber ring may be made of a rubber material that is equal to or harder than the rubber packing. In this way, the rubber packing is mainly compressed and deformed by the pressure of the pressing ring, reducing its diameter and ensuring watertightness.

[0012] In this configuration, the rubber packing has a front surface facing the inner surface of the tapered portion and an inner peripheral surface facing the outer peripheral surface of the tube, and the front surface and the inner peripheral surface are preferably provided with a plurality of annular ridges at appropriate intervals. As a result, the annular ridges are compressed and deformed, the entire rubber packing is reduced in diameter, and the rubber ring and the insertion port are closely attached to ensure strong watertightness. In this case, the inclination angle of the inner surface of the tapered portion relative to the cylindrical portion is preferably larger than the inclination angle of the outer surface of the tapered portion relative to the cylindrical portion. In this way, in the above configuration, by increasing the inclination angle of the inner surface of the tapered portion, the rolling of the compressed deformation of the ridges on the front surface is promoted, making it easier to reduce the diameter. In addition, since the inclination angle of the inner surface is large, the rubber packing does not get clogged in front of the receiving portion of the rubber ring, and disassembly is also easy.

[0013] In the above configuration, the outer surface of the tapered portion may be provided with a plurality of annular projections at appropriate intervals, so that even if the tapered surface of the socket is scratched, the deformation of the annular projections fills the gaps caused by the scratches, ensuring watertightness.

[0014] In any of the above configurations, the socket of the ductile cast iron pipe is a K-shaped socket or a socket similar to a K-shaped socket. Sockets similar to a K-shaped socket include, for example, NS-shaped, S-shaped, US-shaped, UF-shaped, and U-shaped sockets. In the present invention, the ductile cast iron pipe also includes a deformed ductile cast iron pipe.

[0015] In order to achieve the above-mentioned object, the rubber ring of the present invention is characterized in that, in a configuration used in a water-stopping structure of a pipe fitting in which the socket of another pipe is inserted into the socket of a ductile cast iron pipe, the socket has a cylindrical first space and a second space whose inner diameter expands from the first space toward the opening, and the rubber ring has a cylindrical portion whose tip is inserted into the first space, a tapered portion whose outer diameter expands from the other end side of the cylindrical portion in the direction opposite the tip, and a receiving portion that receives the rubber gasket and is composed of the end face of the other end of the cylindrical portion and the inner surface of the tapered portion, and the inner diameter of the cylindrical portion is larger than the outer diameter of the socket, and the tapered portion is formed so that its thickness gradually becomes thinner from the other end toward the tapered tip. Effect of the Invention

[0016] According to the features of the watertight structure of the pipe joint and the rubber ring used therein of the present invention, excellent workability and re-workability are achieved without compromising watertightness.

[0017] Other objects, configurations and effects of the present invention will become apparent from the following detailed description of the preferred embodiments of the present invention. [Brief description of the drawings]

[0018] [Figure 1] 1 is a perspective view showing a waterproof structure for a pipe connection according to the present invention; [Diagram 2] FIG. 1 is a perspective view of a rubber ring according to the present invention. [Diagram 3] FIG. 1 is an enlarged longitudinal cross-sectional view of a rubber ring. [Figure 4] FIG. [Diagram 5]This is a view equivalent to FIG. 4, showing the state in which a rubber ring is attached to the receiving port. [Figure 6] This is a partially enlarged cross-sectional view showing the state in which the rubber gasket and the press ring are temporarily assembled to the receiving port with the rubber ring attached. [Figure 7] 7 is a view equivalent to FIG. 6 and showing the state in which the bolt and nut are tightened. FIG. [Figure 8] FIG. 11 is an enlarged longitudinal cross-sectional view showing a modified example of the rubber ring. [Figure 9] FIG. 11 is a partially enlarged cross-sectional view showing a water-stopping structure of a conventional pipe joint. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, the present invention will be described in more detail with reference to the accompanying drawings as appropriate. (Overview) 1, 6 and 7, the watertight structure 1 of a pipe fitting 10 according to the present invention generally comprises a socket 3 of another ductile cast iron pipe or the like inserted into a socket 2 of a ductile cast iron pipe, and a rubber ring 4 attached to the outer circumferential surface 3a of the socket 3 is pressed against the socket 2 by a pressure ring 5 to effect watertightness. In the present invention, the watertight structure 1 further comprises an annular rubber packing 6 attached to the outer circumferential surface 3a of the socket 3 between the rubber ring 4 and the pressure ring 5.

[0020] (Socket 2) 4, the socket 2 includes a cylindrical first space 21 and a second space 22 whose inner diameter D6 increases from the first space 21 toward the opening 23. A flange 24 is provided on the outside of the opening 23, and a through hole 25 for passing the T-head bolt 9a through is formed in approximately the center of the flange 24. In this embodiment, the socket 2 is, for example, a K-shaped socket for a ductile cast iron pipe.

[0021] (Rubber ring 4) As shown in Figures 2 and 3, the rubber ring 4 comprises a cylindrical portion 41 whose tip end 41a is inserted into the first space 21 of the receiving port 2, a tapered portion 42 whose outer diameter D3 expands from the other end 41b of the cylindrical portion 41 in the direction opposite the tip end 41a (the direction opposite to the insertion direction of the insertion port 3, rear of the other end 41b), and a receiving portion 43 constituted by an end face 41d of the other end 41b of the cylindrical portion 41 and an inner surface 42a of the tapered portion 42, and which receives the rubber gasket 6 described below.

[0022] The rubber ring 4 is formed of a rubber material that is equal to or harder than the rubber packing 6 described below. In this embodiment, for example, the rubber hardness of the rubber ring 4 is 75° to 85°, and the rubber hardness of the rubber packing 6 is 70°.

[0023] Here, the inner diameter D1 of the cylindrical portion 41 is larger than the outer diameter D0 of the insertion port 3. Therefore, there is no need to use a lubricant, and the insertion port 3 can be smoothly inserted in a temporary assembled state in which the rubber ring 4 is attached to the socket 2 in advance, as shown in Figure 6, for example, which provides excellent workability. In addition, the rubber ring 4 can be easily removed from the socket 2 and the insertion port 3 when re-installing.

[0024] Furthermore, the outer peripheral surface of tip 41a of cylindrical portion 41 is flat, and there is no rounded portion 4'a like in conventional rubber rings 4'. The thickness t of tip 41a is equivalent to height H of protrusion 26 that constitutes inner surface 21a of first space 21. This allows tip 41a to be inserted (attached) so as to fit along first space 21, so that when pressed (joined) with pressure ring 5, insertion port 3 is not pulled further into receiving port 3 than the planned joining position, improving ease of installation.

[0025] Furthermore, the outer diameter D2 of the tip 41a of the cylindrical portion 41 is formed slightly larger than the inner diameter D5 of the first space portion 21, and the outer diameter D3 of the tapered portion 42 is formed slightly larger than the inner diameter D6 of the second space portion 22. Therefore, when the rubber ring 4 is attached to the socket 2 as shown in FIG. 5, the cylindrical portion 41 and the tapered portion 42 must be reduced in diameter. The rubber ring 4 is temporarily fixed to the socket 2 by the repulsive force of the rubber caused by this reduction in diameter. Note that "slightly larger" means, for example, that the outer diameters D2, D3 of the rubber ring 4 are 1 to 3% larger than the inner diameter of the socket 2 (the inner diameters D5, D6 of the first and second spaces 21, 22).

[0026] The tapered portion 42 is formed such that its thickness T gradually becomes thinner from the other end 41b toward the tapered tip portion 42x. In addition, the outer side surface 42b of the tapered portion 42 is inclined at a predetermined outer inclination angle α with respect to the cylindrical portion 41, and the inner side surface 42a of the tapered portion 42 is inclined at a predetermined inner inclination angle β with respect to the cylindrical portion 41. The inner inclination angle β is larger than the outer inclination angle α, and in this embodiment, for example, the outer inclination angle α is 20.5° and the inner inclination angle β is 30°.

[0027] Here, in the case of the K-shaped receiving port 2, since the taper angle of the second space portion 22 is 20°, it is possible to set the inner inclination angle β of the rubber ring 4 to, for example, 20°, which is the same as the outer inclination angle α. However, in such a case, the tapered portion 42 becomes thin in order to secure the receiving portion 43, making it difficult to secure the strength of the cylindrical portion 41 and making it difficult to manufacture a rubber mold. Even if it could be manufactured, rubber is difficult to restore its original shape, and since the angle is small, the rubber packing is likely to get clogged at the corner tip, making it difficult to remove and unsuitable for re-installation. Furthermore, in order to facilitate the reduction in diameter due to the compression deformation of the front convex stripe 62a of the rubber packing 6 described later, it is necessary to set the inner inclination angle β to be larger than the outer inclination angle α, for example, to an inclination angle of 30°. This ensures that the rubber packing 6 can stop water.

[0028] In addition, in this embodiment, the tapered tip 42x of the tapered portion 42 is provided with a locking portion 44 that engages with the outer edge portion 2a of the receiving port 2 (outer surface 24a of the flange 24), and a bulge portion 45 that bulges inward (toward the central axis of the rubber ring 4) from the locking portion 44.

[0029] Moreover, the bulging portion 45 is formed in a tapered shape in which the inner diameter D4 of the bulging portion 45 narrows toward the outside (opening edge portion). As described above, the outer diameter D3 of the tapered portion 42 is formed slightly larger than the inner diameter D6 of the second space portion 22, so that the tapered portion 42 is reduced in diameter when the tapered portion 42 is attached to the second space portion 22. At this time, as shown in FIG. 5, the portion of the bulging portion 45 near the tapered portion 42 also slightly reduces in diameter due to the reduction in diameter of the tapered portion 42, so that the inner surface 45a becomes flat (parallel to the pipe axis) after the rubber ring 4 is reduced in diameter (the rubber ring 4 is attached to the receiving port 2). As a result, the contact between the outer edge portion 2a of the receiving port 2 and the contact surface 44a of the locking portion 44 is maintained, and the rubber ring 4 is stably attached to the receiving port 2.

[0030] (Push Ring 5) As shown in Figures 1, 6 and 7, the pressure ring 5 roughly has a ring-shaped main body 51 that surrounds the insertion port 3, a pressing portion 52 that protrudes from the main body 51 in the pipe axial direction and presses the rubber gasket 6 described later, and a through hole 53 through which the T-head bolt 9a passes.

[0031] (Rubber packing 6) 6 and 7, an inner peripheral surface 61 of the rubber packing 6 facing the outer surface 3a of the insertion port 3 is provided with a plurality of inner ridges 61a at appropriate intervals along the axial direction. A front surface 62 of the rubber packing 6 facing the tapered portion 42a is provided with a plurality of annular inner ridges 62a and annular inner recesses 62b alternately along the axial direction. A protrusion 63 that engages with the pressing portion 52 of the pressing ring 5 is formed at the rear end of the rubber packing 6. For example, a product as described in JP 2003-232476 A can be used as this type of rubber packing 6.

[0032] (Installation Procedure) Here, the procedure for constructing the pipe joint will be described with reference to FIGS. As shown in FIG. 5, first, the rubber ring 4 is attached to the socket 2. As described above, the outer diameter D2 of the tip 41a is slightly larger than the inner diameter D5 of the first space 21, and the outer diameter D3 of the tapered portion 42 is slightly larger than the inner diameter D6 of the second space 22. In addition, the inner surface 45a of the bulging portion 45 is formed in a tapered shape in which the inner diameter D4 of the bulging portion 45 narrows toward the outside. As a result, when the tip 41a and the tapered portion 42 are reduced in diameter to attach the rubber ring 4 to the socket 2, the tip 41a and the tapered portion 42 come into close contact with the inner surfaces 21a and 22a of the first and second spaces 21 and 22, and the abutment surface 44a abuts against the outer edge portion 2a of the socket 2, and the rubber ring 4 is temporarily fixed to the socket 2. Therefore, the worker does not need to hold the rubber ring 4 attached to the socket 2, which improves workability.

[0033] Then, as shown in FIG. 6, the rubber packing 6 and the pressure ring 5 are provisionally assembled to the socket 2 with the rubber ring 4 attached. Then, the protruding portion 63 of the rubber packing 6 is engaged with the pressing portion 52 of the pressure ring 5, and the spacer 8 is sandwiched between the flange 24 of the socket 2 and the main body portion 51 of the pressure ring 5, and the T-head bolt 9a and nut 9b are tightened to create a provisionally assembled state. This allows the rubber ring 4, the pressure ring 5, and the rubber packing 6 to be provisionally fixed to the socket 2, and the rubber packing 6 will not be pushed in during transportation to the construction site, etc. In addition, since the inner diameter D1 of the cylindrical portion 41 and the inner diameter D8 of the rubber packing 6 are larger than the outer diameter of the insertion hole 3, the insertion hole 3 can be easily inserted in the provisionally assembled state without using a lubricant, etc., and the construction is extremely easy.

[0034] Then, as shown in FIG. 7, the insertion port 3 is inserted to a predetermined position in the socket 2 in the above-mentioned provisionally assembled state, and then the spacer 8 is removed and the T-head bolt 9a and the nut 9b are tightened. As a result, the pressing portion 52 presses the rubber packing 6 toward the socket 2, but since the rubber ring 4 is made of a harder rubber material than the rubber packing 6, the rubber packing 6 is mainly deformed. Therefore, due to the pressing of the pressing portion 52, the front convex strip 62a is compressed and deformed by the inner surface 42a of the tapered portion 42, and the entire rubber packing 6 moves along the inner surface 42a toward the other end 41b side and shrinks in diameter. When further pressed, the rubber packing 6 rolls along the inner surface 42a and further shrinks in diameter, and the front surface 62 comes into close contact with the inner surface 42a, improving watertightness. The inner convex strip 61a of the inner peripheral surface 61 of the rubber packing 6 also acts in the same way, and is compressed and deformed by the outer peripheral surface 3a of the insertion port 3, so that the inner peripheral surface 61 comes into close contact with the outer peripheral surface 3a.

[0035] Furthermore, the pressure of the pressing portion 52 causes the rubber packing 6 to press the end face 41d of the other end portion 41b of the rubber ring 4 and the inner surface 42a of the tapered portion 42. This pressure of the rubber packing 6 causes the tip portion 41a of the rubber ring 4 to adhere closely to the inner surface 21a of the first space portion 21, and the outer surface 42b of the tapered portion 42 to adhere closely to the inner surface 22a of the second space portion 22. In this manner, the rubber ring 4 and the rubber packing 4 hold the insertion port 3 in the receiving port 2 and ensure watertightness of the pipe fitting 10.

[0036] Furthermore, when reinstalling, the T-head bolt 9a and nut 9b are loosened to disassemble the connections of the various components. At this time, the rubber ring 4 is made of a harder rubber material than the rubber packing 6, and the thickness t of the tip 41a is equal to the height H of the protruding portion 26 of the socket 2. Therefore, the rubber ring 4 is not excessively deformed, and can be easily removed from the socket 2, allowing reinstallation.

[0037] For example, for a pipe with a nominal diameter of 200, a tightening torque of about 20 Nm can ensure watertightness of 2 MPa. Furthermore, for a tightening torque of 60 Nm, the pipe (insertion port 3) can be easily removed from the fitting body (receiving port 2) by loosening the T-head bolt 9a and nut 9b and swinging the pipe fitting 10 by hand without using any tools. The removed pipe can then be inserted directly into the fitting body without resistance, making it possible to reinstall it. Note that for a tightening torque of 100 Nm, a tool must be used to remove the pipe from the fitting body, but reinstallation is possible in the same manner as above.

[0038] (Other embodiments) Finally, the possibility of other embodiments will be mentioned. Note that the same reference numerals are used to designate the same members as in the above embodiment.

[0039] In the above embodiment, the inner surface 45a of the bulging portion 45 of the rubber ring 4 is tapered so that the inner diameter D4 of the bulging portion 45 narrows toward the outside (opening edge). However, for example, as shown in Fig. 8(a), the inner surface 45a may be formed flat (parallel to the tube axis). However, forming the inner surface 45a of the bulging portion 45 into a narrowing tapered shape as in the above embodiment makes it less likely that a gap will be generated between the rubber packing 6 and the rubber ring 4, making it easier to insert the insertion port 3 and preventing misalignment of the cores of the respective components.

[0040] In the above embodiment, the outer surface 42b of the tapered portion 42 of the rubber ring 4 is not provided with any irregularities. However, for example, as shown in Fig. 8(b), a plurality of annular protrusions 47 may be provided at appropriate intervals on the outer surface 42b. As a result, even if the tapered inner surface 22a of the second space portion 22 is scratched, the deformation of the annular protrusions 47 can fill the gaps caused by the scratch, ensuring watertightness.

[0041] As shown in Fig. 1C, the locking portion 44 and the bulging portion 45 may be omitted. However, the embodiment in which the locking portion 44 and the bulging portion 45 are provided is superior in terms of keeping the rubber packing 6 concentric with other members.

[0042] In the above embodiment, the K-shaped socket of a ductile cast iron pipe is described as an example. Examples of applicable K-shaped sockets include the K-shaped socket of the joint type of ductile cast iron deformed pipe JIS G 5527, the socket of the K-shaped ductile cast iron deformed pipe for water supply described in JWWA G 113 ductile cast iron pipe for water supply and JWWA G 114 ductile cast iron deformed pipe for water supply (issued by the Japan Water Works Association), and the K-shaped socket of the joint type of JSWAS G-1 ductile cast iron pipe for sewerage (issued by the Japan Sewage Works Association). However, the present invention is not limited to these K-shaped sockets, and can also be applied to sockets similar to the K-shaped sockets. For example, the present invention can be applied to any of the sockets of NS, S, US, UF, and U shapes. The same is true for ductile cast iron deformed pipes.

[0043] In the above embodiment, the rubber ring 4 is formed from a rubber material harder than the rubber packing 6, and the rubber hardness of the rubber ring 4 is 75° to 85°, and the rubber hardness of the rubber packing 6 is 70°. However, the rubber hardness is not limited to the above values, and the rubber ring 4 may be formed from a rubber material having the same hardness as the rubber packing 6. For example, the rubber hardness of the rubber ring 4 may be 70° to 80°, and the rubber packing 6 may be formed from a rubber material having a rubber hardness of 70°. [Explanation of symbols]

[0044] 1: water-stopping structure, 2: receiving port, 2a: outer edge, 3: insertion port, 3a: outer periphery, 4, 4A, 4B, 4C: rubber ring, 5: pressing ring, 6: rubber packing, 8: spacer, 9a: T-head bolt, 9b: nut, 10: pipe joint, 21: first space, 21a: inner surface, 22: second space, 22a: inner surface, 23: opening, 24: flange, 24a: outer surface, 25: through hole, 26: protrusion, 40: main body, 41: cylindrical portion, 41a: tip, 41b: other end, 41c: outer surface of the other end, 41d: end surface, 42: tapered portion, 42a: inner surface, 42b: outer surface, 42x: tapered tip (end), 43: receiving portion, 4 4: engagement portion, 44a: abutment surface, 45: bulge portion, 45a: inner surface, 47: annular projection, 51: main body portion, 52: pressing portion, 53: through hole, 61: inner peripheral surface, 61a: inner ridge, 62: front surface, 62a: front ridge, 62b: front ridge, 63: protrusion, D0: outer diameter of insertion port, D1: inner diameter of cylindrical portion, D2: outer diameter of cylindrical portion, D3: outer diameter of tapered portion, D4: inner diameter of bulge portion, D5: inner diameter of first space portion, D6: inner diameter of second space portion, D7: outer diameter of rubber packing, D8: inner diameter of rubber packing, H: protrusion height, T: thickness of tapered portion, t: thickness of tip portion, α: inclination angle of outer surface, β: inclination angle of inner surface

Claims

1. A watertight structure for a pipe joint in which a slit of another pipe is inserted into a slit of a ductile cast iron pipe, and a rubber ring attached to the outer surface of the slit is pressed against the slit by a pressure ring to stop water flow, An annular rubber packing is further provided between the rubber ring and the pressing ring to be attached to the outer circumferential surface of the insertion hole, The socket includes a cylindrical first space and a second space whose inner diameter increases from the first space toward an opening thereof, The rubber ring includes a cylindrical portion having a tip portion inserted into the first space, a tapered portion whose outer diameter increases from the other end side of the cylindrical portion in a direction opposite to the tip portion, and a receiving portion that receives the rubber packing and is formed by the end face of the other end side of the cylindrical portion and the inner surface of the tapered portion, The inner diameter of the cylindrical portion is greater than the outer diameter of the insertion port, The tapered portion is formed so that its thickness gradually decreases from the other end toward the tapered tip portion, A waterproof structure for a pipe joint in which the pressure ring presses the rubber gasket against the end face of the other end and the inner surface of the tapered portion, while tightly sealing the tip of the rubber ring against the inner surface of the first space portion and tightly sealing the outer surface of the tapered portion against the inner surface of the second space portion.

2. 2. A water-stopping structure for a pipe joint according to claim 1, wherein the outer diameter of the tip of the cylindrical portion is slightly larger than the inner diameter of the first space, and the outer diameter of the tapered portion is slightly larger than the inner diameter of the second space.

3. 3. A waterproof structure for a pipe joint according to claim 2, wherein said tapered tip portion is provided with a locking portion that locks onto an outer edge of said socket and a bulging portion that bulges inwardly from said locking portion.

4. 4. A watertight structure for a pipe joint according to claim 3, wherein an inner surface of the bulge is tapered so that an inner diameter of the bulge narrows outward.

5. 2. A waterproof structure for a pipe joint according to claim 1, wherein said rubber ring is made of a rubber material that is equal to or harder than said rubber packing.

6. 6. A water-stopping structure for a pipe fitting as described in claim 5, wherein the rubber gasket has a front surface facing the inner surface of the tapered portion and an inner surface facing the outer surface of the pipe, and the front surface and the inner surface have a plurality of annular ridges provided at appropriate intervals.

7. 7. The watertight structure of a pipe joint according to claim 6, wherein an inclination angle of said inner surface of said tapered portion relative to said cylindrical portion is larger than an inclination angle of said outer surface of said tapered portion relative to said cylindrical portion.

8. 2. A waterproof structure for a pipe joint according to claim 1, wherein a plurality of annular projections are provided at appropriate intervals on the outer surface of the tapered portion.

9. 9. The water-stopping structure of a pipe joint according to claim 1, wherein the socket of the ductile cast iron pipe is a K-type socket or a socket similar to a K-type socket.

10. A rubber ring used in the watertight structure of a pipe joint in which the spigot of another pipe is inserted into the spigot of a ductile cast iron pipe, The socket includes a cylindrical first space and a second space whose inner diameter increases from the first space toward an opening thereof, The rubber ring includes a cylindrical portion having a tip portion inserted into the first space, a tapered portion whose outer diameter increases from the other end side of the cylindrical portion in a direction opposite to the tip portion, and a receiving portion that receives the rubber packing and is formed by the end face of the other end side of the cylindrical portion and the inner surface of the tapered portion, The inner diameter of the cylindrical portion is greater than the outer diameter of the insertion port, The tapered portion is a rubber ring formed so that its thickness gradually decreases from the other end toward the tip.

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