Pipe joint with insertion port, and conversion joint

Abstract

To provide a pipe joint with an insertion port with improved pressure resistance of an insertion port pipe part.SOLUTION: A pipe joint (conversion joint 10) with an insertion port comprises a synthetic resin insertion port pipe part 14. The insertion port part includes a first pipe part 40, and a second pipe part 42 having the same outside diameter as the first pipe part and thickness larger than that of the first pipe part. The ends of the first and second pipe parts are connected with each other by an electric fusion socket part 44 having electric fusion sockets 46 at both ends. Axial length L1 of an exposure part 40c of the first pipe part is set to 0.6 or less times larger than insertion length L2, at which the first pipe part is inserted in the electric fusion socket.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a spigot pipe fitting and a conversion fitting, and more particularly to a spigot pipe fitting and a conversion fitting that include, for example, a fusion-weldable synthetic resin spigot pipe portion. [Background technology]

[0002] An example of this type of conventional spigot pipe joint (conversion joint) is disclosed in Patent Document 1. The conversion joint in Patent Document 1 includes a tubular joint body formed of metal and having a plastic pipe connection portion at one end, a plastic pipe (spigot pipe portion) one end of which is fitted onto the outside of the plastic pipe connection portion, and a ring that is fitted onto the outside of one end of the plastic pipe and presses the inner peripheral surface of one end of the plastic pipe against the outer peripheral surface of the plastic pipe connection portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-101250 A Summary of the Invention [Problem to be solved by the invention]

[0004] The spigot pipe fitting of Patent Document 1 is used for water piping and the like. In the case of a spigot pipe fitting for water piping, the spigot pipe part made of synthetic resin (made of polyethylene) has a pipe thickness specification of SDR11. On the other hand, high-pressure fire extinguishing piping is required to have a greater pressure resistance (internal pressure resistance characteristics) than water piping, and has a pipe thickness specification of SDR9. Note that SDR (Standard Dimension Ratio) is the value obtained by dividing the pipe outer diameter by the pipe thickness, and if this ratio is kept constant, the pressure resistance will be the same even if the pipe outer diameter changes.

[0005] If a spigot pipe fitting for water piping is applied to a high-pressure fire extinguishing piping as is, an SDR9 pipe component will be connected to the SDR11 spigot pipe section of the spigot pipe fitting, but in this state, the SDR11 spigot pipe section will not have sufficient pressure resistance, and there is a risk that it will not meet the pressure resistance standards for high-pressure fire extinguishing piping. In other words, in a pipe fitting or piping formed by connecting pipe components with different SDRs, there is a risk that the pressure resistance strength of the part with a large SDR (i.e., the pipe thickness) will be insufficient.

[0006] In addition, when applying a spigot pipe fitting for water piping to a high-pressure fire extinguishing piping, it is possible to change the spigot pipe part of the spigot pipe fitting from SDR11 to SDR9 (i.e., a pipe part with the same outer diameter but larger pipe thickness). However, changing to a spigot pipe part with a different SDR requires design changes to parts other than the spigot pipe part (the metal fitting body and ring in the case of a conversion fitting), which increases costs.

[0007] SUMMARY OF THE PRESENT EMBODIMENTS It is therefore a primary object of the present invention to provide a novel spigot and transition fitting.

[0008] Another object of the present invention is to provide a spigot pipe fitting and a conversion fitting in which the pressure resistance strength of the spigot pipe portion is improved. [Means for solving the problem]

[0009] The first invention is a spigot pipe fitting having a spigot pipe section made of synthetic resin, the spigot pipe section including a first pipe section and a second pipe section having the same outer diameter as the first pipe section but a larger pipe thickness than the first pipe section, the end of the first pipe section and the end of the second pipe section are connected by an electric fusion socket section having electric fusion ports at both ends, and the axial length of the exposed portion of the first pipe section is no more than 0.6 times the insertion length of the first pipe section inserted into the electric fusion port.

[0010] In a first aspect of the present invention, a spigot pipe fitting includes a spigot pipe section made of synthetic resin. The spigot pipe section includes a first pipe section and a second pipe section. The second pipe section has the same outer diameter as the first pipe section, and the pipe thickness of the second pipe section is greater than the pipe thickness of the first pipe section. The end of the first pipe section and the end of the second pipe section are connected by an electric fusion socket section having electric fusion sockets at both ends. The axial length of the exposed portion of the first pipe section is set to a value equal to or less than 0.6 times the insertion length of the first pipe section inserted into the electric fusion socket.

[0011] According to the first invention, the axial length of the exposed portion of the first pipe section, which has a smaller pipe thickness, is set to 0.6 times or less the insertion length into the electric fusion socket, thereby improving the pressure resistance of the first pipe section (and therefore the spigot pipe section). Also, since the end of the first pipe section and the end of the second pipe section are connected by an electric fusion socket section, the connection portion between the first pipe section and the second pipe section has increased rigidity and improved pressure resistance. Therefore, the pressure resistance of the spigot pipe section can be appropriately improved.

[0012] A second invention is dependent on the first invention, and the axial length of the exposed portion is 0.2 to 0.6 times the inner diameter of the first tubular portion.

[0013] According to the second aspect of the present invention, the pressure resistance of the spigot pipe portion can be improved more appropriately.

[0014] A third invention is according to the first or second invention, and the axial length of the exposed portion is 1.5 to 4.5 times the pipe thickness of the first pipe portion.

[0015] According to the third aspect of the present invention, the pressure resistance of the spigot pipe portion can be improved more appropriately.

[0016] A fourth invention is a conversion joint for connecting a metal pipe member and a synthetic resin pipe member, comprising a metal joint body having a spigot pipe connection portion at one end, a synthetic resin spigot pipe portion having one end fitted onto the spigot pipe connection portion, and a ring fitted onto one end of the spigot pipe portion to press the inner surface of the one end of the spigot pipe portion against the outer surface of the spigot pipe connection portion, the spigot pipe portion includes a first pipe portion and a second pipe portion having the same outer diameter as the first pipe portion and a larger pipe thickness than the first pipe portion, the end of the first pipe portion and the end of the second pipe portion are connected by an electric fusion socket portion having electric fusion ports at both ends, and the axial length of the exposed portion of the first pipe portion is 0.6 times or less the insertion length of the first pipe portion inserted into the electric fusion port.

[0017] In a fourth aspect of the present invention, the conversion joint includes a metal joint body having a spigot pipe connection part at one end, a synthetic resin spigot pipe part whose one end is fitted onto the spigot pipe connection part, and a ring fitted onto one end of the spigot pipe part to press the inner peripheral surface of the one end of the spigot pipe part against the outer peripheral surface of the spigot pipe connection part. The spigot pipe part includes a first pipe part and a second pipe part. The outer diameter of the second pipe part is the same as that of the first pipe part, and the pipe thickness of the first pipe part is larger than that of the first pipe part. The end of the first pipe part and the end of the second pipe part are connected by an electric fusion socket part having electric fusion sockets at both ends. The axial length of the exposed part of the first pipe part is set to be 0.6 times or less the insertion length of the first pipe part inserted into the electric fusion socket.

[0018] According to the fourth invention, the axial length of the exposed portion of the first pipe section, which has a smaller pipe thickness, is set to 0.6 times or less the insertion length into the electric fusion socket, thereby improving the pressure resistance of the first pipe section and, in turn, the spigot pipe section. Also, since the end of the first pipe section and the end of the second pipe section are connected by an electric fusion socket section, the connection portion between the first pipe section and the second pipe section has increased rigidity and improved pressure resistance. Therefore, the pressure resistance of the spigot pipe section can be appropriately improved.

[0019] Furthermore, the pressure resistance of the spigot pipe section can be improved without changing the design of the metal joint body and ring. In other words, the joint body and ring can be used for multiple applications requiring different pressure resistance, reducing the manufacturing cost of the conversion joint. Effect of the Invention

[0020] According to this invention, the pressure resistance strength of the spigot pipe portion of the spigot pipe fitting can be appropriately improved.

[0021] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings. [Brief description of the drawings]

[0022] [Figure 1] 1 is a plan view showing a conversion joint according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the conversion joint of FIG. [Diagram 3] 2 is a cross-sectional view showing a joint body provided in the conversion joint of FIG. 1. [Figure 4] 2 is a cross-sectional view showing a ring provided in the conversion joint of FIG. 1. [Diagram 5] 2 is a plan view showing a spigot pipe portion provided in the conversion joint of FIG. 1. [Figure 6] FIG. 6 is a cross-sectional view showing the spigot pipe portion of FIG. 5. [Figure 7] FIG. 11 is a plan view showing a conversion joint according to another embodiment of the present invention. [Figure 8] FIG. 11 is a plan view showing an electric fusion joint according to still another embodiment of the present invention. [Figure 9] FIG. 11 is a plan view showing a conversion joint according to still another embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing the conversion joint of FIG. 9. [Figure 11] 10 is a cross-sectional view showing a spigot pipe portion provided in the conversion joint of FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1 and 2, a conversion joint 10 (also referred to as a "dissimilar pipe joint") according to one embodiment of the present invention is a pipe joint for connecting metal pipe members such as steel pipes and valves to synthetic resin pipe members such as polyethylene pipes. The conversion joint 10 is an example of a spigot-equipped pipe joint having a synthetic resin spigot pipe portion.

[0024] The use and nominal diameter of the piping to be installed using the conversion joint 10 (pipe joint with spigot) are not particularly limited, but since the pressure resistance of the spigot pipe section 14 of the conversion joint 10 is improved as described below, the conversion joint 10 is preferably used for high-pressure fire piping for sprinkler equipment or fire hydrant equipment. The nominal diameter of the conversion joint 10 is, for example, 40 mm to 300 mm, and the following description will be given taking as an example a conversion joint 10 with a nominal diameter of 100 mm. The SDR (Standard Dimension Ratio) described later is the value obtained by dividing the pipe outer diameter by the pipe thickness, and the pressure resistance will be the same even if the pipe outer diameter changes as long as this ratio is kept constant.

[0025] 1 and 2, the conversion joint 10 comprises a metal joint body 12 having a first connection part 20 at one end, a synthetic resin spigot pipe part 14 having one end fitted onto the first connection part 20, and a metal ring 16 fitted onto one end of the spigot pipe part 14. The axial length of the conversion joint 10 is, for example, 560 mm.

[0026] 1 and 2 as well as FIG. 3, the joint body 12 is formed of a metal such as a copper alloy and iron. The joint body 12 includes a first connection part 20 formed at one end and a second connection part 22 formed at the other end, and is formed in a cylindrical shape as a whole. The first connection part 20 is a spigot pipe connection part (resin pipe connection part) into which one end of the spigot pipe part 14 is fitted, and is formed in a short cylindrical shape. On the outer circumferential surface of the first connection part 20, a plurality of annular projections 24 extending in the circumferential direction of the first connection part 20 are formed so as to be aligned at predetermined intervals in the axial direction of the first connection part 20. These annular projections 24 bite into the inner circumferential surface of the spigot pipe part 14, thereby reliably preventing the spigot pipe part 14 from coming off the first connection part 20. On the other hand, the second connection part 22 is a connection part (metal member connection part) with a metal pipe member, and is formed in a short cylindrical shape. In this embodiment, the second connection portion 22 has a socket structure, and a tapered female thread 26 is formed on the inner peripheral surface of the second connection portion 22. Also, a plurality of protrusions 28 (ribs) extending in the axial direction of the second connection portion 22 are formed on the outer peripheral surface of the second connection portion 22 so as to be aligned at predetermined intervals in the circumferential direction. Furthermore, a brim-shaped stopper 30 is formed on the outer peripheral surface of the connecting portion between the first connection portion 20 and the second connection portion 22.

[0027] As shown in Figs. 1 and 2, the spigot pipe section 14 is made of a polyolefin-based synthetic resin such as polyethylene and polybutene. In this embodiment, the spigot pipe section 14 is made of polyethylene (specifically, high-density polyethylene). One end of the spigot pipe section 14 is used as a connection section with the joint body 12 as described above, and is fitted onto the first connection section 20. Meanwhile, the other end of the spigot pipe section 14 is used as a connection section with a pipe member made of synthetic resin. For example, a pipe member made of the same material as the spigot pipe section 14 (made of polyethylene in this embodiment) is connected to the other end of the spigot pipe section 14 using an electric fusion joint and butt fusion. The specific configuration of the spigot pipe section 14 will be described later.

[0028] 1 and 2 as well as Fig. 4, the ring 16 is formed into a short cylinder shape from metal such as copper alloy and iron. A tapered resin escape portion 32 that expands in diameter toward the end face side is formed on the inner peripheral surface of one end (the end on the stopper 30 side) of the ring 16. Such a ring 16 tightens one end of the spigot pipe portion 14 fitted onto the first connecting portion 20 from the outside, and presses the inner peripheral surface of the spigot pipe portion 14 against the outer peripheral surface of the first connecting portion 20, thereby preventing the spigot pipe portion 14 from coming off.

[0029] Here, it is considered that the conversion joint (pipe joint with spigot) is used for various pipes such as water pipes and high-pressure fire extinguishing pipes. In this case, it is convenient if the conversion joint can be applied to other applications, for example, a conversion joint for water pipes to high-pressure fire extinguishing pipes. However, high-pressure fire extinguishing pipes are required to have a higher pressure resistance (internal pressure resistance characteristics) than water pipes. That is, while polyethylene pipes for water pipes have a pipe thickness specification of SDR11, high-pressure fire extinguishing pipes have a pipe thickness specification of SDR9. For this reason, if a conversion joint for water pipes is applied directly to high-pressure fire extinguishing pipes, the strength of the spigot pipe part made of synthetic resin (made of polyethylene) may be insufficient, and the pressure resistance standard for high-pressure fire extinguishing pipes may not be met. Therefore, a technology that can improve the pressure resistance strength of the spigot pipe part is required. In addition, from the viewpoint of manufacturing costs, it is preferable that parts can be shared between conversion joints for different applications.

[0030] Therefore, in this embodiment, the spigot pipe section 14 is constructed from two pipe members with different SDRs to shorten the portion with the thin pipe thickness, and these two pipe members are connected by an electric fusion joint, thereby making it possible to improve the pressure resistance of the spigot pipe section 14 while allowing the portions other than the spigot pipe section 14 (i.e., the joint body 12 and the ring 16) to be used for different purposes (for example, for water piping and high-pressure fire piping). The configuration of the spigot pipe section 14 will be specifically described below.

[0031] 5 and 6 together with FIG. 1 and FIG. 2, the spigot pipe section 14 includes a first pipe section 40 arranged on the joint body 12 side (one end side) and a second pipe section 42 arranged on the connecting pipe member side (the other end side). The second pipe section 42 has the same outer diameter as the first pipe section 40 and a larger pipe thickness than the first pipe section 40 (i.e., the SDR is smaller than that of the first pipe section 40). In this embodiment, the first pipe section 40 is made of a polyethylene short pipe with an SDR of 11, and the second pipe section 42 is made of a polyethylene short pipe with an SDR of 9. That is, in this embodiment, the outer diameters of the first pipe section 40 and the second pipe section 42 are 125 mm. The pipe thickness t1 of the first pipe section 40 is 11.4 mm, and the pipe thickness t2 of the second pipe section 42 is 14.0 mm. Furthermore, the inner diameter d1 of the first tubular portion 40 is 102.2 mm, and the inner diameter d2 of the second tubular portion 42 is 97.0 mm.

[0032] The end of the first tube section 40 and the end of the second tube section 42 are connected by an electric fusion socket section 44 made of polyethylene. The electric fusion socket section 44 has electric fusion receptacles 46 at both ends for receiving the respective ends of the first tube section 40 and the second tube section 42. An electric heating wire (not shown) is embedded so as to extend in a spiral shape near the inner surface of the electric fusion receptacle 46. Both ends of the electric heating wire are connected to a power supply connection terminal 48 formed so as to protrude from the outer circumferential surface of the electric fusion receptacle 46. The electric fusion receptacle 46 and the respective ends of the first tube section 40 and the second tube section 42 are fusion-joined by heat generated by passing an electric current through the electric heating wire from a power supply connected to the power supply connection terminal 48, which heats and melts the resin at the joining surfaces. By connecting the end of the first pipe section 40 and the end of the second pipe section 42 in this manner using the electric fusion socket section 44, the connection portion between the first pipe section 40 and the second pipe section 42 is made more rigid and has improved pressure resistance.

[0033] One end of the first pipe section 40 becomes one end of the spigot pipe section 14, i.e., the fitting section 40a sandwiched between the first connecting section 20 of the fitting body 12 and the ring 16. In this way, by using the SDR11 first pipe section 40 for the part connected to the fitting body 12, the fitting body 12 and the ring 16 can be of SDR11 specifications, i.e., those for water piping, as they are. The inner diameter d1 of the first pipe section 40 is set smaller than the outer diameter of the first connecting section 20, and when the fitting section 40a of the first pipe section 40 (i.e., one end of the spigot pipe section 14) is fitted onto the first connecting section 20, the first connecting section 20 is forced into the fitting section 40a. In addition, the inner diameter of the ring 16 is set smaller than the outer diameter of the fitting portion 40a when it is fitted onto the first connection portion 20, and when the ring 16 is fitted onto the fitting portion 40a, the fitting portion 40a is forced into the ring 16.

[0034] On the other hand, the other end of the first tube portion 40 serves as an insertion portion 40b to be inserted into the electric fusion socket 46, and an exposed portion 40c exposed to the outside is formed between the fitting portion 40a and the insertion portion 40b.

[0035] Here, from the viewpoint of the pressure resistance of the conversion joint 10, it is preferable not to form the exposed portion 40c in the first pipe portion 40, which has a smaller pipe thickness (i.e., pressure resistance) than the second pipe portion 42. However, as a result of intensive research by the inventors, it was found that even if the first pipe portion 40 has the exposed portion 40c, sufficient pressure resistance to meet the pressure resistance standard of the high-pressure fire extinguishing piping can be obtained by making the axial length L1 of the exposed portion 40c satisfy a predetermined condition. That is, it was found that the pressure resistance of the spigot pipe portion 14 (and therefore the conversion joint 10) can be sufficiently improved by setting the axial length L1 of the exposed portion 40c to a size of 0.6 times or less the insertion length L2 (i.e., the axial length of the insertion portion 40b) by which the first pipe portion 40 is inserted into the electric fusion socket 46, that is, by satisfying the condition of L1 / L2≦0.6. In this embodiment, the insertion length L2 is 79 mm, while the axial length L1 is 41 mm, and the value of L1 / L2 is 0.52.

[0036] According to a verification experiment (pressure resistance test) conducted by the inventors, in the case of a conversion joint 10 having an L1 / L2 value exceeding 0.6, the exposed portion 40c of the conversion joint 10 was destroyed when an internal pressure of 6.4MPa to 6.5MPa was applied. That is, the burst water pressure of the exposed portion 40c remained the same as the burst water pressure of a polyethylene pipe of SDR11 (about 6.4MPa), and there was no margin to meet the provisions of the pressure resistance standard for fire extinguishing piping. On the other hand, by setting the value of L1 / L2 to 0.6 or less, the burst water pressure of the exposed portion 40c became equal to or higher than the burst water pressure of a polyethylene pipe of SDR9 (about 7.0MPa), and it was confirmed that the pressure resistance standard for fire extinguishing piping was met with a sufficient margin. In addition, it was confirmed that the heat resistance of the conversion joint 10 was also improved by satisfying the condition of L1 / L2≦0.6.

[0037] Furthermore, it is preferable to set the axial length L1 of the exposed portion 40c to a value between 0.2 and 0.6 times the inner diameter d1 of the first pipe portion 40 while satisfying the condition L1 / L2≦0.6, in other words, to satisfy the condition 0.2≦L1 / d1≦0.6. This is because the pressure resistance of the spigot pipe portion 14 can be improved more appropriately.

[0038] Furthermore, it is preferable to set the axial length L1 of the exposed portion 40c to a value between 1.5 and 4.5 times the pipe thickness t1 of the first pipe portion 40, in other words, to satisfy the condition 1.5≦L1 / t1≦4.5. This is because the pressure resistance of the spigot pipe portion 14 can be improved more appropriately.

[0039] As described above, according to this embodiment, the axial length L1 of the exposed portion 40c of the first pipe section 40 is set to 0.6 times or less the insertion length L2 into the electric fusion socket 46, thereby improving the pressure resistance of the first pipe section 40 and, in turn, the spigot pipe section 14. In addition, the end of the first pipe section 40 and the end of the second pipe section 42 are connected by the electric fusion socket section 44, improving the pressure resistance of the connection portion between the first pipe section 40 and the second pipe section 42. Therefore, the pressure resistance of the spigot pipe section 14 can be appropriately improved.

[0040] Furthermore, according to this embodiment, the pressure resistance of the spigot pipe section 14 can be improved without changing the design of the metal joint body 12 and ring 16. In other words, the joint body 12 and ring 16 can be used for multiple applications requiring different pressure resistance (for example, water piping and high-pressure fire piping), so the manufacturing cost of the conversion joint 10 can be reduced.

[0041] The specific configuration of the conversion fitting 10 (fitting body 12, spigot pipe portion 14, and ring 16) described above is merely one example and can be modified as appropriate. For example, the arrangement of the annular projections 24 formed on the first connecting portion 20 of the fitting body 12, such as the number and shape, can be modified as appropriate. The second connecting portion 22 can also have a spigot structure or a union-type socket structure.

[0042] Also, as in the conversion joint 10 of the embodiment shown in FIG. 7, a third pipe section 52 having a larger diameter than the second pipe section 42 can be connected to the other end of the second pipe section 42 via a reducer section 50 by using butt welding or the like. The reducer section 50 and the third pipe section 52 are made of SDR9 polyethylene pipe members. That is, the conversion joint 10 may have a reducer structure on the other end side of the spigot pipe section 14. In the embodiment shown in FIG. 7, the spigot pipe section 14 is formed to satisfy the condition L1 / L2≦0.6, and has the same configuration as the embodiment shown in FIG. 1 except for having the reducer section 50 and the third pipe section 52.

[0043] Furthermore, in the above-mentioned embodiment, a conversion joint is shown as an example of a spigot pipe joint, but the configuration of the portion (main body portion) other than the spigot pipe portion of the spigot pipe joint is not particularly limited. For example, as in the embodiment shown in FIG. 8, the spigot pipe joint may be a Tee-type electric fusion joint 60. Briefly, the electric fusion joint 60 includes a joint body 62 having electric fusion receiving ports 64 at both ends, and a spigot pipe portion 66 (branch pipe portion) branching from the center of the joint body 62, and is formed of a polyolefin-based synthetic resin such as polyethylene. The spigot pipe portion 66 includes a first pipe portion 68 arranged on the joint body 62 side and a second pipe portion 70 arranged on the connecting pipe member side. The second pipe portion 70 has the same outer diameter as the first pipe portion 68 and has a pipe thickness larger than that of the first pipe portion 68. An end of the first pipe portion 68 and an end of the second pipe portion 70 are connected by an electric fusion socket portion 72, and the spigot pipe portion 66 is formed so as to satisfy the condition L1 / L2≦0.6.

[0044] Furthermore, in each of the above-mentioned embodiments, the first pipe section and the second pipe section are connected by an electric fusion socket section, and the spigot pipe section is formed so as to satisfy the condition L1 / L2≦0.6, thereby improving the pressure resistance of the spigot pipe section. In contrast, the following configuration can be adopted in the conversion joint to improve the pressure resistance of the spigot pipe section of the conversion joint. Other embodiments of the conversion joint will be described below with reference to Figs. 9 to 11. However, the parts other than the spigot pipe section (the joint body and the ring) are the same as those in the embodiment shown in Fig. 1, so that the overlapping description of the common parts will be omitted or simplified.

[0045] 9 and 10, the conversion joint 80 includes a metal joint body 82 having a first connection portion 90 and a second connection portion 92, a synthetic resin spigot pipe portion 84 having one end fitted onto the first connection portion 90, and a metal ring 86 fitted onto one end of the spigot pipe portion 84. Here, a conversion joint 80 having a nominal diameter of 100 mm will be described as an example. The axial length of the conversion joint 10 is, for example, 365 mm.

[0046] 11, the spigot pipe portion 84 is formed of a short pipe made of SDR9 polyethylene. That is, in this embodiment, the outer diameter of the spigot pipe portion 84 is 125 mm. The pipe thickness t3 of the spigot pipe portion 84 is 14.0 mm, and the inner diameter d3 is 97.0 mm.

[0047] In this embodiment, an annular recess 94 is formed by cutting or the like on one end of the spigot pipe section 84, i.e., on the inner circumferential surface of the fitting section 84a which fits onto the first connecting section 90 of the fitting body 82. This recess 94 has the same diameter as the inner diameter of an SDR11 polyethylene pipe. In other words, the portion of the spigot pipe section 84 where the recess 94 is formed, i.e., the fitting section 84a, is of the SDR11 specification, and its pipe thickness t4 and inner diameter d4 are 11.4 mm and 102.2 mm, respectively.

[0048] In such a conversion fitting 80, since the spigot pipe section 84 is formed from a short pipe made of SDR9 polyethylene, the pressure resistance of the spigot pipe section 84 can be appropriately improved and the pressure resistance standard for fire extinguishing piping can be met. Also, although the pipe thickness of the portion (fitting section 84a) where the recess 94 of the spigot pipe section 84 is formed is reduced, this fitting section 84a has sufficient pressure resistance because it is reinforced by being fitted onto the first connecting section 90 of the fitting body 82. Furthermore, since the fitting section 84a is of SDR11 specification, the fitting body 82 and ring 86 used for water piping can be used as they are.

[0049] 9, the pressure resistance of the spigot pipe section 84 can be appropriately improved with a simple configuration of forming the recess 94 at one end of the spigot pipe section 84. Furthermore, since the fitting body 82 and ring 86 can be used for a number of applications requiring different pressure resistance (for example, water piping and high-pressure fire piping), the manufacturing cost of the conversion fitting 80 can be reduced.

[0050] The specific configuration of the conversion fitting 80 (fitting body 82, spigot pipe portion 84, and ring 86) described above is merely one example and can be modified as appropriate. For example, the arrangement of the number, shape, and other aspects of the annular projections formed on the first connecting portion 90 of the fitting body 82 can be modified as appropriate, and the second connecting portion 92 may have a spigot structure or a union-type socket structure. In addition, the spigot pipe portion 84 may have a reducer structure.

[0051] Furthermore, the specific values ​​and specific configurations such as dimensions given above are merely examples and can be changed as appropriate according to the needs of product specifications, etc. [Explanation of symbols]

[0052] 10...Conversion joints (pipe joints with spigots) 12 ... Fitting body 14... Socket pipe part 16 ... Ring 20 ... First connection part (spigot pipe connection part) 22 … Second connection part 40 … First pipe section 42 …Second pipe section 44 ... Electric fusion socket part 46 ... Electric fusion socket 60... Electric fusion joint (pipe joint with spigot) 80...Conversion joint 94 ...Recess

Claims

1. A spigot pipe joint having a spigot pipe portion made of synthetic resin, The spigot pipe portion includes a first pipe portion and a second pipe portion having the same outer diameter as the first pipe portion and a larger pipe thickness than the first pipe portion, a spigot-equipped pipe fitting in which an end of the first pipe section and an end of the second pipe section are connected by an electric fusion socket section having electric fusion receiving ports at both ends, and the axial length of the exposed portion of the first pipe section is set to be 0.6 times or less the insertion length of the first pipe section inserted into the electric fusion receiving port.

2. 2. The spigot pipe fitting according to claim 1, wherein the axial length of said exposed portion is between 0.2 and 0.6 times the inner diameter of said first pipe portion.

3. 3. A spigot pipe fitting according to claim 1, wherein the axial length of said exposed portion is 1.5 to 4.5 times the pipe thickness of said first pipe portion.

4. A conversion joint for connecting a metal pipe member and a synthetic resin pipe member, A metal joint body having a spigot pipe connection portion at one end; a synthetic resin spigot pipe portion having one end fitted onto the spigot pipe connection portion; and a ring fitted onto one end of the spigot pipe portion to press an inner peripheral surface of the one end of the spigot pipe portion against an outer peripheral surface of the spigot pipe connecting portion; The spigot pipe portion includes a first pipe portion and a second pipe portion having the same outer diameter as the first pipe portion and a larger pipe thickness than the first pipe portion, A conversion joint in which an end of the first pipe section and an end of the second pipe section are connected by an electric fusion socket section having electric fusion receiving ports at both ends, and the axial length of the exposed portion of the first pipe section is set to be 0.6 times or less the insertion length of the first pipe section inserted into the electric fusion receiving port.

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