Electrofusion joints

Abstract

To provide an electrofusion joint in which the pressure resistance strength of the socket pipe portion of the joint body has been improved. [Solution] The electrofusion joint 10 comprises a joint body 12, a conversion member 14, and a ring 16. The joint body has a main pipe section 20 that is electrofused to a first pipe member, and a junction pipe section 32 that branches off from the main pipe section. The conversion member has a first connecting section 40 that is fitted inside the tip of the junction pipe section of the joint body, and a second connecting section 42 that is connected to a second pipe member, and a ring 16 is fitted outside the tip of the junction pipe section of the joint body. The axial length L1 of the exposed portion 32b of the junction pipe section is set to 40 mm or less.

Description

Technical Field

[0001] This invention relates to an electric fusion joint, and particularly, for example, to a cheese-type electric fusion joint for connecting a first pipe member made of synthetic resin and a second pipe member made of metal.

Background Art

[0002] An example of a conventional cheese-type electric fusion joint is disclosed in Non-Patent Document 1. The male-threaded EF cheese disclosed in Non-Patent Document 1 includes a synthetic resin joint body having a main pipe portion that is electrically fusion-bonded to a first pipe member made of synthetic resin and a branch port pipe portion that branches from the main pipe portion, a first connection portion that is fitted inside the tip of the branch port pipe portion, a metal conversion member (thread member) having a second connection portion that is connected to a metal pipe member, and a metal ring that is fitted outside the tip of the branch port pipe portion.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The electrofusion joint (male threaded EF tee) described in Non-Patent Document 1 is used in water supply piping, etc. It would be convenient if electrofusion joints for water supply piping could be applied to high-pressure fire extinguishing piping, but high-pressure fire extinguishing piping requires greater pressure resistance (internal pressure resistance characteristics) than water supply piping. In this case, with a tee-type electrofusion joint, the pipe thickness of the socket pipe portion of the joint body is small, so a technology that can improve the pressure resistance of this portion is desired. To improve the pressure resistance of the socket pipe portion, one could consider increasing the pipe thickness of the socket pipe portion. However, increasing the pipe thickness of the socket pipe portion requires redesigning other parts of the electrofusion joint (especially the metal conversion member and ring), which increases costs.

[0005] Therefore, the primary objective of this invention is to provide a novel electrofusion joint.

[0006] Another object of this invention is to provide an electrofusion joint in which the pressure resistance strength of the socket pipe portion of the joint body is improved. [Means for solving the problem]

[0007] The first invention is an electrofusion joint comprising: a synthetic resin joint body having a first pipe member made of synthetic resin, a main pipe section to be electrofused and joined to the main pipe section, a metal conversion member having a first connecting section fitted internally to the tip of the spigot section and a second connecting section connected to a metal second pipe member, and a metal ring fitted externally to the tip of the spigot section, wherein the axial length of the exposed portion of the spigot section is 40 mm or less.

[0008] In the first invention, the electrofusion joint is constructed by attaching a metal conversion member and a ring to a joint body made of synthetic resin. The joint body has a main pipe section that is electrofused to a first pipe member made of synthetic resin, and a junction pipe section that branches off from the main pipe section. The conversion member has a first connecting section that is fitted internally to the tip of the junction pipe section of the joint body, and a second connecting section that is connected to a second pipe member made of metal, and the ring is fitted externally to the tip of the junction pipe section of the joint body. The axial length of the exposed portion of the junction pipe section of the joint body is set to 40 mm or less.

[0009] According to the first invention, with a simple configuration in which the axial length of the exposed portion of the splice pipe is 40 mm or less, the pressure resistance strength of the splice pipe (and by extension the electrofusion joint) can be appropriately improved, and the pressure resistance standards for high-pressure fire extinguishing piping can be met.

[0010] The second invention is subordinate to the first invention, and the axial length of the exposed portion of the ferrule is between 0.18 and 0.51 times the outer diameter of the main pipe.

[0011] According to the second invention, the pressure resistance strength of the socket pipe can be improved more effectively.

[0012] The third invention is dependent on the first or second invention, and the outer diameter of the spout section is between 0.09 and 0.12 times the axial length of the main section.

[0013] According to the third invention, the pressure resistance strength of the socket pipe can be improved more effectively. [Effects of the Invention]

[0014] According to this invention, the pressure resistance strength of the splice section of the joint body (and consequently the electrofusion joint) can be appropriately improved, and the pressure resistance standards for high-pressure fire extinguishing piping can be met.

[0015] The aforementioned objectives, other objectives, features, and advantages of this invention will become even clearer from the detailed description of the embodiments described below with reference to the drawings. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an example of a branch piping structure using an electrofusion joint, which is one embodiment of this invention. [Figure 2] This is a plan view showing an electrofusion joint. [Figure 3] This is a side view showing an electrofusion joint. [Figure 4]It is a cross-sectional view showing a cross-section of an electric fusion joint cut along line IV-IV of FIG. 3. [Figure 5] It is a plan view showing an electric fusion joint of another embodiment of this invention.

Mode for Carrying Out the Invention

[0017] Referring to FIG. 1, an electric fusion joint 10 according to an embodiment of this invention includes a joint body 12, a conversion member 14, and a ring 16. The electric fusion joint 10 is a cheese-type electric fusion joint (EF cheese with male threads) for connecting a first pipe member made of synthetic resin and a second pipe member made of metal, and forms a branch pipe structure 100 in which a metal branch pipe is connected to a synthetic resin pipe.

[0018] The use and diameter (nominal diameter) of this electric fusion joint 10 are not particularly limited. However, since the electric fusion joint 10 has improved pressure resistance (internal pressure resistance characteristics) as described later, it is suitably used for high-pressure fire pipes such as sprinkler equipment and fire hydrant equipment. Hereinafter, an electric fusion joint 10 that connects a polyethylene pipe member 102 (an example of the first pipe member) with a diameter of 100 mm and a cast iron drain valve 104 (an example of the second pipe member) with a diameter of 25 mm will be exemplified and described.

[0019] Referring to FIGS. 2 to 4 together with FIG. 1, the electric fusion joint 10 includes a joint body 12, a conversion member 14, and a ring 16, and has a configuration in which the conversion member 14 and the ring 16 are attached to the insertion pipe portion 32 of the cheese-type joint body 12. This will be specifically described below.

[0020] The joint body 12 includes a main pipe portion 20 and a branch pipe portion 22, and is formed of a polyolefin-based synthetic resin such as polyethylene and polybutene. In this embodiment, the joint body 12 is made of polyethylene (specifically, high-density polyethylene). Further, the diameter of the main pipe portion 20 is 100 mm, and the diameter of the branch pipe portion 22 is 25 mm.

[0021] The main pipe portion 20 has electric fusion sockets 24 at both ends for receiving the ends of pipe members 102 made of synthetic resin (polyethylene). Near the inner surface of each electric fusion socket 24, a heating wire (not shown) is embedded so as to extend spirally. The inner surface at the inner end of the electric fusion socket 24 is reduced in diameter in a stepped manner, and an annular stopper 24a is formed here. Also, both ends of the heating wire are connected to power connection terminals 26 formed to project from the top of the electric fusion socket 24. When the power connection terminals 26 are connected to a power source and current is passed through the heating wire, the resin at the joint surface between the electric fusion socket 24 and the pipe member 102 is heated and melted, so that the electric fusion socket 24 and the pipe member 102 are fusion-bonded. Further, an indicator 28 is formed at the top of the electric fusion socket 24, on the axially central side of the power connection terminals 26. The indicator 28 is for indicating that the joint surface between the electric fusion socket 24 and the pipe member 102 has been fusion-bonded (or the progress of fusion).

[0022] On the other hand, the branch pipe portion 22 is formed to project laterally from the central portion of the main pipe portion 20. The branch pipe portion 22 includes a base end portion 30 (thickened portion) formed at the peripheral edge of a branch opening formed in the main pipe portion 20, and a socket pipe portion 32 (straight portion) extending in the branch direction from the base end portion 30. The base end portion 30 is thicker than the socket pipe portion 32. In this embodiment, the outer peripheral surface of the branch pipe portion 22 is reduced in diameter in a stepped manner at the connecting portion between the base end portion 30 and the socket pipe portion 32. However, the base end portion 30 of the branch pipe portion 22 may be formed in a curved surface shape that smoothly continues with the socket pipe portion 32. In this case, the straight portion of the branch pipe portion 22 with a constant pipe thickness becomes the socket pipe portion 32.

[0023] The conversion member 14 is a member for connecting the joint body 12 and a second metal pipe member (in this embodiment, a drain valve 104), and is made of a metal such as copper alloy and iron. The conversion member 14 comprises a first connecting portion 40 formed at one end and a second connecting portion 42 formed at the other end, and is formed in a cylindrical shape overall. The first connecting portion 40 is a portion that is fitted inside the tip of the suction pipe portion 32 of the joint body 12, and is formed in a short cylindrical shape. Multiple annular protrusions extending in the circumferential direction are formed on the outer circumferential surface of the first connecting portion 40 so as to be arranged at predetermined intervals in the axial direction. These annular protrusions bite into the inner circumferential surface of the suction pipe portion 32, thereby reliably preventing the suction pipe portion 32 from coming off the first connecting portion 40. On the other hand, the second connecting portion 42 is a connecting portion with the second metal pipe member, and is formed in a short cylindrical shape. In this embodiment, the second connecting portion 42 is a male thread with screw threads (not shown) formed on its outer circumferential surface. Furthermore, a flange-shaped stopper 44 is formed on the outer circumferential surface of the connecting portion between the first connecting portion 40 and the second connecting portion 42.

[0024] The ring 16 is a component fitted to the tip of the socket pipe portion 32 of the joint body 12, and is formed in a short cylindrical shape from a metal such as copper alloy and iron. On the inner circumferential surface of one end of the ring 16 (the end on the stopper 44 side of the conversion member 14), a tapered resin relief portion is formed that widens toward the end face. In addition, multiple annular protrusions extending in the circumferential direction are formed on the inner circumferential surface of the ring 16 so as to be arranged at predetermined intervals in the axial direction. These annular protrusions bite into the outer circumferential surface of the socket pipe portion 32, thereby reliably preventing the ring 16 from coming off the socket pipe portion 32. Such a ring 16 tightens the tip of the socket pipe portion 32 of the joint body 12, into which the first connecting portion 40 of the conversion member 14 is fitted, from the outside, pressing the inner circumferential surface of the socket pipe portion 32 against the outer circumferential surface of the first connecting portion 40, thereby preventing the conversion member 14 from detaching from the socket pipe portion 32.

[0025] In such an electrofusion joint 10, the metal conversion member 14 and ring 16 have sufficient pressure resistance. Furthermore, although the main pipe section 20 of the joint body 12 is made of synthetic resin, its large pipe thickness ensures sufficient pressure resistance. Additionally, for the branch pipe section 22 of the joint body 12, the base end 30 has a large pipe thickness, and the tip 32a of the spigot pipe section 32 (the part where the ring 16 is fitted) is reinforced by the conversion member 14 and ring 16, thus ensuring sufficient pressure resistance. However, the exposed portion 32b of the spigot pipe section 32 that is exposed to the outside on the base end 30 side is made of synthetic resin and has a smaller pipe thickness, raising concerns about its pressure resistance compared to other parts. While the pressure resistance of this exposed portion 32b can be improved by increasing its pipe thickness, this would require redesigning other parts of the electrofusion joint 10 (especially the conversion member 14 and ring 16), resulting in increased costs.

[0026] Therefore, after diligent study by the inventors, they conceived the idea that the pressure resistance of the exposed portion 32b of the junction pipe section 32 could be improved by reducing its axial length L1. Verification experiments (destructive tests) were then conducted, and it was confirmed that by setting the axial length L1 of the exposed portion 32b to 40 mm or less, the pressure resistance standard for high-pressure fire extinguishing piping (6.4 MPa or higher) could be met even with the same pipe thickness (SDR11) as the conventional junction pipe section. In other words, it was found that it is good to set the axial length L of the exposed portion 32b of the junction pipe section 32 to 40 mm or less. In this embodiment, the axial length L1 of the exposed portion 32b is set to 31 mm.

[0027] If the axial length L1 of the exposed portion 32b of the socket pipe portion 32 is made too small, there will be no clearance for the ring 16 when attaching the conversion member 14 to the tip portion 32a of the socket pipe portion 32, making it difficult to attach the conversion member 14. For this reason, it is preferable that the axial length L1 of the exposed portion 32b be 20 mm or more. In this embodiment, the axial length of the ring 16 is made as small as possible without impairing the function of the ring 16, making it easier to make the axial length L1 of the exposed portion 32b smaller than in the conventional design. The axial length of the ring 16 in this embodiment is 11 mm.

[0028] Furthermore, it is preferable to satisfy the condition that the axial length L1 of the exposed portion 32b is 40 mm or less, and that the axial length L1 of the exposed portion 32b is set to a size of 0.18 times or more and 0.51 times or less the outer diameter L2 of the main pipe portion 20, that is, the condition 0.18 ≤ L1 / L2 ≤ 0.51 is satisfied. This is because the pressure resistance strength of the exposed portion 32b of the socket pipe portion 32 can be improved more appropriately. In this embodiment, the axial length L1 of the exposed portion 32b is 31 mm, while the outer diameter L2 of the main pipe portion 20 is 156 mm, and the value of L1 / L2 is set to 0.20.

[0029] Furthermore, it is preferable that the diameter of the socket pipe section 32 be small, and that the outer diameter W1 of the socket pipe section 32 be set to a size of 0.09 times or more and 0.12 times or less the axial length W2 of the main pipe section 20, that is, satisfying the condition 0.09 ≤ W1 / W2 ≤ 0.12. This is because it is possible to more appropriately improve the pressure resistance strength of the exposed portion 32b of the socket pipe section 32. In this embodiment, the outer diameter W1 of the socket pipe section 32 is 32 mm, while the axial length W2 of the main pipe section 20 is 270 mm, and the value of W1 / W2 is set to 0.27.

[0030] According to verification experiments conducted by these inventors, the electrofusion joint 10 of this embodiment has a pressure resistance strength of 7.4 MPa, and it was confirmed that it comfortably meets the pressure resistance standard for high-pressure fire extinguishing piping (6.4 MPa or higher).

[0031] As described above, according to this embodiment, the axial length L1 of the exposed portion 32b of the socket pipe portion 32 of the joint body 12 is set to 40 mm or less, so that the pressure resistance strength of the socket pipe portion 32 (and by extension the electrofusion joint) can be appropriately improved and the pressure resistance standards for high-pressure fire extinguishing piping can be met. Furthermore, by satisfying the conditions 0.18 ≤ L1 / L2 ≤ 0.51 and 0.09 ≤ W1 / W2 ≤ 0.12, the pressure resistance standards for high-pressure fire extinguishing piping can be met with a margin of safety.

[0032] The specific configuration of the electrofusion joint 10 described above, namely the joint body 12, the conversion member 14, and the ring 16, is merely an example and can be modified as appropriate.

[0033] For example, as shown in the embodiment in Figure 5, the second connecting portion 42 of the conversion member 14 may be a female thread with threads (not shown) formed on its inner circumferential surface. Also, although not shown, the main pipe portion 20 of the joint body 12 may have an electrofusion socket at only one end, or it may have a reducer structure with different diameters at both ends.

[0034] Please note that the specific dimensions and configurations mentioned above are merely examples and can be modified as needed according to product specifications and other requirements. [Explanation of Symbols]

[0035] 10 ... Electrofusion joints 12 ... Fitting body 14 ...Conversion member 16... ring 20 ... Main pipe section 22 ... Branch pipe section 32... Socket pipe part 32b...Exposed part 102 ... Pipe member (First pipe member) 104 ... Drain valve (second pipe component)

Claims

1. A synthetic resin joint body having a main pipe section that is electrofused to a first pipe member made of synthetic resin, and a spout pipe section that branches off from the main pipe section. A metal conversion member having a first connecting portion fitted inside the tip of the aforementioned ferrule pipe portion and a second connecting portion connected to a second metal pipe member, and The tip of the aforementioned ferrule section is fitted with a metal ring, An electrofusion joint in which the axial length of the exposed portion of the socket pipe is 40 mm or less.

2. The electrofusion joint according to claim 1, wherein the axial length of the exposed portion is 0.18 times or more and 0.51 times or less the outer diameter of the main pipe portion.

3. The electrofusion joint according to claim 1 or 2, wherein the outer diameter of the socket pipe portion is 0.09 times or more and 0.12 times or less the axial length of the main pipe portion.

Images