Pipe joint

Abstract

To provide a pipe joint improved in the pressure resistance of a straight pipe part.SOLUTION: A pipe joint includes a straight pipe part 16 including a first pipe part 40 and a second pipe part 42 having an outer diameter equal to that of the first pipe part and a pipe thickness larger than that of the first pipe part. A second pipe part has an annular recess 46 having a diameter equal to an inner diameter of the first pipe part and formed on an inner peripheral surface in an end part thereof in a side of the first pipe part. The first pipe part and the second pipe part are connected with butt fusion.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a pipe joint, and more particularly to a pipe joint having a straight pipe section made of synthetic resin and formed by butt welding, for example. [Background technology]

[0002] An example of a technique related to a pipe member formed by using conventional butt welding is disclosed in Patent Document 1. The technique of Patent Document 1 relates to a fused pipe in which a first resin pipe and a second resin pipe are connected by fusion, and an inner circumferential bead is formed on the inner circumferential surface of the connection part between the first resin pipe and the second resin pipe, and the inner circumferential bead has a first convex part on the first resin pipe side and a second convex part on the second resin pipe side. The ratio of the maximum inner diameter at the end of the first resin pipe in the region where the inner circumferential bead is not formed to the maximum inner diameter at the end of the second resin pipe in the region where the inner circumferential bead is not formed is 1.02 or more and 1.15 or less, and the inner diameter of the first resin pipe at the maximum height position of the first convex part is larger than the inner diameter of the second resin pipe at the maximum height position of the second convex part. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-122516 A Summary of the Invention [Problem to be solved by the invention]

[0004] In pipe fittings such as EF tee and reducers, straight pipe sections may be formed using butt welding. In this case, it is standard to connect pipe members with the same SDR to form a straight pipe section, but as in the technology of Patent Document 1, pipe members with different SDRs (i.e., the same outer diameter but different pipe thicknesses) may be connected to each other. 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 even if the pipe outer diameter changes, the pressure resistance will be the same.

[0005] However, in the technology of Patent Document 1, pipe members with different SDRs are simply butt-welded together, and the sizes of the butted end faces are different, which may reduce the joint strength (and therefore the pressure resistance of the straight pipe section).In addition, in the technology of Patent Document 1, the bead section formed by butt welding protrudes significantly from the pipe inner surface (especially the inner surface of the second resin pipe, which has a thicker pipe thickness), which causes a large pressure loss in this section.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS It is therefore a primary object of the present invention to provide a novel pipe joint.

[0007] Another object of the present invention is to provide a pipe fitting which can reduce pressure loss while improving the pressure resistance of a straight pipe section, even in a case where the straight pipe section is formed by butt welding pipe members with different SDRs. [Means for solving the problem]

[0008] The first invention is a pipe fitting having a straight pipe section made of synthetic resin, the straight 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, an annular recess having the same diameter as the inner diameter of the first pipe section is formed on the inner surface of the end of the second pipe section facing the first pipe section, and the first pipe section and the second pipe section are connected by butt welding.

[0009] In a first aspect of the present invention, the pipe joint comprises a straight pipe section made of synthetic resin. The straight pipe section includes a first pipe section and a second pipe section having the same outer diameter as the first pipe section and a larger pipe thickness than the first pipe section. An annular recess having the same diameter as the inner diameter of the first pipe section is formed on the inner peripheral surface of the end section of the second pipe section on the first pipe section side, and the first pipe section and the second pipe section are connected by butt welding. That is, the first pipe section and the second pipe section are butt fused with the shape and size of their end faces matching each other.

[0010] According to the first invention, the end faces of the first and second pipe sections are butt-welded with the same shape and size, so that optimal joint strength can be obtained. In addition, the bead portion does not protrude beyond the inner peripheral surface of the second pipe section, so that pressure loss occurring at the joint between the first and second pipe sections can be reduced. Therefore, even when a straight pipe section is formed by butt-welding the first and second pipe sections with different pipe thicknesses, the pressure resistance of the straight pipe section and therefore the pipe joint can be appropriately improved while reducing pressure loss.

[0011] A second invention is dependent on the first invention, and includes a long strip-shaped reinforcing fiber wound around an outer circumferential surface of the first pipe portion and an outer circumferential surface of an end portion of the second pipe portion on the first pipe portion side.

[0012] According to the second invention, the portion of the straight pipe section where the pipe thickness is small is appropriately reinforced, so that the pressure resistance of the straight pipe section and therefore the pipe joint can be appropriately improved.

[0013] A third invention is according to the first or second invention, and has a tapered portion formed on a wall portion of the recess opposite to the first tubular portion, the tapered portion having a diameter decreasing with increasing distance from the first tubular portion.

[0014] According to the third aspect of the present invention, the pressure loss occurring at the connecting portion between the first pipe section and the second pipe section can be more appropriately reduced.

[0015] The fourth invention is dependent on the second invention and has a tapered portion formed in the wall portion opposite the first pipe portion of the recess and having a diameter that decreases with increasing distance from the first pipe portion, and the reinforcing fibers are arranged at the end of the second pipe portion on the first pipe portion side so as to cover at least the outer peripheral surface of the portion where the recess and the tapered portion of the second pipe portion are formed.

[0016] According to the fourth aspect of the present invention, the pressure loss occurring at the joint between the first pipe section and the second pipe section can be more appropriately reduced. Also, the thin pipe wall portion of the straight pipe section is appropriately reinforced, so that the pressure resistance of the straight pipe section and therefore the pipe joint can be appropriately improved.

[0017] The fifth invention is dependent on the fourth invention, and the reinforcing fibers are arranged at the end of the second tubular section on the first tubular section side, extending from the edge of the tapered section opposite the first tubular section to a section 5 mm to 50 mm away from the first tubular section.

[0018] According to the fifth aspect of the present invention, the straight pipe portion is more appropriately reinforced, so that the pressure resistance of the straight pipe portion and therefore the pipe joint can be appropriately improved.

[0019] A sixth invention is according to the first or second invention, wherein the axial length of the recess is 0.03 to 0.60 times the diameter of the recess.

[0020] According to the sixth aspect of the present invention, the pressure loss occurring at the connecting portion between the first pipe section and the second pipe section can be more appropriately reduced.

[0021] A seventh invention is dependent on the third invention, and the inclination angle of the tapered portion with respect to the axial direction is equal to or greater than 25 degrees and equal to or less than 45 degrees.

[0022] According to the seventh aspect of the present invention, the stress in the tapered portion is effectively reduced, and a decrease in strength of the connecting portion between the first pipe portion and the second pipe portion is suppressed.

[0023] An eighth invention is according to the first or second invention, wherein the axial length of the recess is 0.3 to 4.5 times the pipe thickness of the second pipe portion at the portion where the recess is formed.

[0024] According to the eighth aspect of the present invention, the pressure loss occurring at the connecting portion between the first pipe section and the second pipe section can be more appropriately reduced. Effect of the Invention

[0025] According to this invention, even when a straight pipe section is formed by butt welding a first pipe section and a second pipe section having different pipe thicknesses, the pressure resistance of the straight pipe section and therefore the pipe joint can be appropriately improved while reducing pressure loss.

[0026] 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]

[0027] [Figure 1] 1 is a plan view showing an electric fusion joint according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view showing a branch joint body of an electric fusion joint. [Diagram 3] FIG. 4 is a half-sectional view showing a branch pipe portion of an electric fusion joint. [Figure 4] FIG. 4 is an enlarged partial cross-sectional view of a part of FIG. [Diagram 5] FIG. 11 is a plan view showing a reducer according to another embodiment of the present invention. [Figure 6] FIG. 11 is a plan view showing a conversion joint according to still another embodiment of the present invention. [Figure 7] FIG. 11 is a plan view showing a conversion joint according to still another embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view showing the conversion joint of FIG. [Figure 9] 8 is a cross-sectional view showing a straight pipe portion provided in the conversion joint of FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] 1, an electrofusion joint 10 according to one embodiment of the present invention is a Tee-type electrofusion joint (EF Tee), and includes a branch joint body 12 having a main pipe section 14 and a branch pipe section 16. The electrofusion joint 10 is an example of a pipe joint according to the present invention, and the branch pipe section 16 is an example of a straight pipe section made of synthetic resin. As will be described in detail later, the branch pipe section 16 (straight pipe section) included in the electrofusion joint 10 is formed by butt welding a first pipe section 40 and a second pipe section 42. In addition, a second reinforcing fiber 20, which is an example of a reinforcing fiber, is wound around the branch pipe section 16, thereby increasing the pressure resistance (internal pressure resistance characteristic).

[0029] The use and nominal diameter of the piping constructed using the electric fusion joint 10 (pipe joint) are not particularly limited, but since the electric fusion joint 10 has improved pressure resistance as described below, it is suitable for use in high-pressure fire piping for sprinkler equipment or fire hydrant equipment. The nominal diameter (inner diameter) of the piping formed using the electric fusion joint 10 is, for example, 40 mm to 300 mm. In the following, an electric fusion joint 10 provided at a branching portion where a pipe with a nominal diameter of 100 mm branches into a pipe with a nominal diameter of 100 mm, that is, an electric fusion joint 10 in which the nominal diameters of the main pipe section 14 and the branch pipe section 16 are both 100 mm, will be described as an example. The SDR (Standard Dimension Ratio) described later is a value obtained by dividing the pipe outer diameter by the pipe thickness, and if this ratio is constant, the pressure resistance will be the same even if the pipe outer diameter changes.

[0030] 1, the electric fusion joint 10 includes a branch joint body 12 having a main pipe section 14 and a branch pipe section 16. The electric fusion joint 10 also includes a first reinforcing fiber 18 wound around the outer circumferential surface of the main pipe section 14, and a second reinforcing fiber 20 wound around the outer circumferential surface of the branch pipe section 16.

[0031] 2, the branch joint body 12 includes a main pipe portion 14 and a branch pipe portion 16, and is made of a polyolefin-based synthetic resin such as polyethylene or polybutene. In this embodiment, the branch joint body 12 is made of polyethylene (specifically, high-density polyethylene).

[0032] The main pipe section 14 has electric fusion sockets 30 at both ends for receiving the ends of a pipe member (not shown) made of synthetic resin. A heating wire (not shown) is embedded in the vicinity of the inner peripheral surface of the electric fusion socket 30 so as to extend in a spiral shape. Both ends of the heating wire are connected to power supply connection terminals 32 formed to protrude from the outer peripheral surface of the electric fusion socket 30. When the power supply connection terminals 32 are connected to a power supply and an electric current is passed through the heating wire, heat is generated. The resin on the joint surface between the electric fusion socket 30 and the pipe member is heated and melted by this heat, and the electric fusion socket 30 and the pipe member are fused and joined. Furthermore, an indicator 34 is formed on the outer peripheral surface of the electric fusion socket 30, closer to the center in the axial direction than the power supply connection terminals 32. The indicator 34 is for indicating that the joint surface between the electric fusion socket 30 and the pipe member has been fused (or the progress of fusion).

[0033] The branch pipe section 16 is formed by protruding from the center of the main pipe section 14. As will be described in detail later, the branch pipe section 16 in this embodiment includes a first pipe section 40 and a second pipe section 42 that has the same outer diameter as the first pipe section 40 and a larger pipe thickness than the first pipe section 40, and is formed by butt welding these sections. Therefore, a bead section 44 is formed at the connecting portion between the first pipe section 40 and the second pipe section 42.

[0034] Returning to Fig. 1, the electric fusion joint 10 includes a long strip-like first reinforcing fiber 18 wound around the outer circumferential surface of the main pipe section 14. The first reinforcing fiber 18 is made of high-strength fibers such as polyarylate fibers, aramid fibers, carbon fibers, and ultra-high molecular weight polyethylene fibers. In this embodiment, the first reinforcing fiber 18 is made of polyarylate fiber, Vectran (registered trademark) manufactured by Kuraray Co., Ltd., and has a tensile strength of 290 kg / mm 2 ].

[0035] The first reinforcing fiber 18 is wound around the main pipe portion 14 so that the power connection terminal 32 and the indicator 34 of the electric fusion socket 30 are exposed. This allows other pipe members to be connected to the electric fusion socket 30 in the same way as a joint that does not have the first reinforcing fiber 18. The first reinforcing fiber 18 is composed of a single strip of material that is continuous in the circumferential direction (i.e., not cut in the longitudinal direction). This allows the expansion of the main pipe portion 14 due to internal pressure to be appropriately suppressed (i.e., pressure resistance to be increased). The width of the first reinforcing fiber 18 is preferably 50 mm to 70 mm, for example, and is 60 mm in this embodiment.

[0036] In addition, the first reinforcing fiber 18 is preferably wound around both ends of the main pipe portion 14 over at least the entire circumferential length (i.e., one or more turns). In addition, it is preferable to wind the first reinforcing fiber 18 three or more times around the branch intersection portion 14a. The branch intersection portion 14a is a portion with low pressure resistance because a branch hole communicating with the branch pipe portion 16 is formed therein. However, by winding the first reinforcing fiber 18 three or more times around the branch intersection portion 14a, the pressure resistance of the branch intersection portion 14a (and thus the electric fusion joint 10) can be appropriately improved. In particular, the effect of improving pressure resistance is greatly exhibited in the electric fusion joint 10 in which the main pipe portion 14 and the branch pipe portion 16 have the same diameter and the opening area of ​​the branch hole is large. According to a verification experiment by the inventors, it was confirmed that the main pipe portion 14 satisfies the pressure resistance standard (6.5 MPa) for high-pressure fire extinguishing piping with a sufficient margin by winding the first reinforcing fiber 18 three times around the branch intersection portion 14a.

[0037] In addition, the first reinforcing fiber 18 is preferably wound in a diagonal direction with respect to the axial center of the main pipe section 14 so that it overlaps the base end section 16a (rising section) of the branch pipe section 16 and also overlaps the branch opposing center section 14b, which is an extension of the axial center of the branch pipe section 16, at the branch intersection section 14a. This allows the base end section 16a of the branch pipe section 16, i.e., the peripheral section of the branch hole formed in the main pipe section 14, to be appropriately reinforced. Furthermore, the first reinforcing fiber 18 wound in multiple layers (i.e., multiple windings) at the branch intersection section 14a is preferably wound so as not to shift in the width direction as much as possible, but it can also be wound so as to shift in the width direction. However, it is preferable that the overlap width between the first and second layers and the overlap width between the second and third layers of the first reinforcing fiber 18 at the branch intersection section 14a are at least half the width of the first reinforcing fiber 18. In other words, the offset width between vertically overlapping first reinforcing fibers 18 is preferably less than half the width of the first reinforcing fibers 18 (60 mm in this embodiment) (less than 30 mm in this embodiment).

[0038] 2-4 together with FIG. 1, the branch pipe section 16 of this embodiment includes a first pipe section 40 formed on the base end side and a second pipe section 42 formed on the tip end side, and is formed by butt welding these. The second pipe section 42 has the same outer diameter as the first pipe section 40 and a pipe thickness larger than that of the first pipe section 40. In other words, the branch pipe section 16 is formed by connecting pipe sections with different SDRs, and the second pipe section 42 has a smaller SDR than the first pipe section 40. In this embodiment, the outer diameters of the first pipe section 40 and the second pipe section 42 are each 125 mm. The first pipe section 40 has a pipe thickness specification of SDR11, and its pipe thickness t1 is, for example, 11.4 mm, and its inner diameter d1 is, for example, 102 mm. On the other hand, the second pipe portion 42 has a pipe thickness specification of SDR9, the pipe thickness t2 is, for example, 14.0 mm, and the inside diameter d2 is, for example, 97 mm.

[0039] In this embodiment, an annular recess 46 having a diameter d3 equal to the inner diameter d1 of the first pipe section 40 is formed on the inner circumferential surface of the end of the second pipe section 42 on the first pipe section 40 side. That is, the pipe thickness t3 of the portion of the second pipe section 42 where the recess 46 is formed (the end of the second pipe section 40 side) is equal to the pipe thickness t1 of the first pipe section 40. By forming such a recess 46 in the second pipe section 42 and then connecting the first pipe section 40 and the second pipe section 42 by butt welding, the shapes and sizes of the end faces of the first pipe section 40 and the second pipe section 42 match, so that optimal joint strength can be obtained. That is, the first pipe section 40 and the second pipe section 42 are butt-welded in a state in which the shapes and sizes of the end faces match, so that they are firmly joined. Furthermore, since the bead portion 44 does not protrude significantly beyond the inner peripheral surface of the second pipe portion 42, pressure loss occurring at the connecting portion between the first pipe portion 40 and the second pipe portion 42 can be reduced.

[0040] The size of the recess 46 is not particularly limited, but the axial length A of the recess 46 is preferably 0.03 to 0.60 times the diameter d3 of the recess 46. The axial length A of the recess 46 is preferably 0.3 to 4.5 times the pipe thickness t3 of the portion of the second pipe section 42 where the recess 46 is formed. This is because the pressure loss occurring at the connecting portion between the first pipe section 40 and the second pipe section 42 can be more appropriately reduced.

[0041] Furthermore, a tapered section 48 is formed on the wall of the recess 46 on the opposite side to the first pipe section 40 (i.e., the downstream side), the diameter of which decreases with increasing distance from the first pipe section 40. By providing the tapered section 48, pressure loss can be reduced more appropriately. The inclination angle θ of the tapered section 48 with respect to the axial direction is not particularly limited, but is preferably set to 25 degrees or more and 45 degrees or less. By setting the inclination angle θ of the tapered section 48 within this range, the stress in the tapered section 48 is effectively reduced, and a reduction in the strength of the connecting portion between the first pipe section 40 and the second pipe section 42 can be suppressed.

[0042] As described above, the electric fusion joint 10 includes the long strip-shaped second reinforcing fiber 20 wound around the outer circumferential surface of the branch pipe section 16. In this embodiment, the second reinforcing fiber 20 is wound so as to cover the outer circumferential surface of the first pipe section 40 and the outer circumferential surface of the end of the second pipe section 42 on the first pipe section 40 side. The second reinforcing fiber 20, like the first reinforcing fiber 18, is made of high-strength fibers such as polyarylate fibers, aramid fibers, carbon fibers, and ultra-high molecular weight polyethylene fibers. In this embodiment, Vectran (registered trademark) manufactured by Kuraray Co., Ltd., which is a polyarylate fiber, is used as the second reinforcing fiber 20, and its tensile strength is 290 [kg / mm 2 The width of the second reinforcing fibers 20 is preferably, for example, 50 mm to 70 mm, and is 60 mm in this embodiment.

[0043] The second reinforcing fiber 20 to be wound around the outer peripheral surface of the branch pipe section 16 may be wound in the circumferential direction (spiral shape) since there is no obstruction like the main pipe section 14. In this case, the second reinforcing fiber 20 may be wound around the branch pipe section 16 at least once in the circumferential direction, and preferably in two or three layers.

[0044] In addition, when the second reinforcing fiber 20 is wound around the end of the second pipe section 42 on the side of the first pipe section 40, it is preferable to wind the second reinforcing fiber 20 so as to include at least the portion where the recessed portion 46 and the tapered portion 48 are formed. This appropriately reinforces the portion where the pipe thickness of the branch pipe section 16 is thin, and therefore the pressure resistance of the branch pipe section 16 and the electric fusion joint 10 can be appropriately improved. According to a verification experiment by the inventors, it was confirmed that the branch pipe section 16 satisfies the pressure resistance standard (6.5 MPa) for fire extinguishing piping with a sufficient margin by winding the second reinforcing fiber 20 around the outer circumferential surface of the first pipe section 40 and the outer circumferential surface of the end of the second pipe section 42 on the side of the first pipe section 40 one or more times so as to include the portion where the recessed portion 46 and the tapered portion 48 are formed.

[0045] Furthermore, when the second reinforcing fiber 20 is wound around the end of the second pipe section 42 on the first pipe section 40 side, it is preferable to wind it so that it extends from the edge of the tapered section 48 on the opposite side to the first pipe section 40 to a portion 5 mm to 50 mm on the opposite side to the first pipe section 40. In other words, when the axial length of the recessed section 46 is A, the axial length of the tapered section 48 is B, and the axial length from the edge of the recessed section 46 on the first pipe section 40 side to the tip of the second reinforcing fiber 20 is C, it is preferable to wind the second reinforcing fiber 20 around the branch pipe section 16 so that the relationship 5≦C-(A+B)≦50 [mm] is satisfied. This allows the branch pipe section 16 to be reinforced more appropriately.

[0046] Although not shown in the drawings, it is preferable to wrap protective tape around the outer circumferential surfaces of the first reinforcing fiber 18 and the second reinforcing fiber 20. The protective tape is a member for protecting the first reinforcing fiber 18 and the second reinforcing fiber 20 from ultraviolet rays, external damage, and the like. As the protective tape, for example, VALCO TAPE (registered trademark) manufactured by Furukawa Electric Co., Ltd. may be used.

[0047] When the protective tape is wound around the outer peripheral surface of the first reinforcing fiber 18 and the second reinforcing fiber 20, a part of the first reinforcing fiber 18 or the second reinforcing fiber 20 may be exposed, but it is preferable to provide the protective tape so as to cover the entire outer peripheral surface of the first reinforcing fiber 18 and the second reinforcing fiber 20. In addition, when the protective tape is wound around the outer peripheral surface of the first reinforcing fiber 18, it is preferable to expose the power connection terminal 32 and the indicator 34 of the electric fusion socket 30. As a result, even when the protective tape is provided, other pipe members can be connected to the electric fusion socket 30 in the same way as a joint without the protective tape. In this way, by providing the electric fusion joint 10 with the protective tape in advance, it is possible to appropriately prevent the first reinforcing fiber 18 and the second reinforcing fiber 20 from being deteriorated or damaged by ultraviolet rays while maintaining the workability of the electric fusion joint 10.

[0048] As described above, according to this embodiment, the recess 46 is formed on the inner peripheral surface of the second pipe section 42, and the first pipe section 40 and the second pipe section 42 are connected by butt welding, so that the end faces of the first pipe section 40 and the second pipe section 42 can be firmly fusion-joined. In addition, since the bead section 44 does not protrude significantly beyond the inner peripheral surface of the second pipe section 42, pressure loss occurring at the connection section between the first pipe section 40 and the second pipe section 42 can be reduced. Therefore, even when the branch pipe section 16 (straight pipe section) is formed by butt welding the first pipe section 40 and the second pipe section 42 having different pipe thicknesses, the pressure loss can be reduced while the pressure resistance of the branch pipe section 16 can be appropriately improved.

[0049] Furthermore, according to this embodiment, the second reinforcing fiber 20 (reinforcing fiber) is wound around the outer peripheral surface of the first pipe section 40 and the outer peripheral surface of the end of the second pipe section 42 on the first pipe section 40 side, thereby more appropriately improving the pressure resistance of the branch pipe section 16 and, by extension, the electric fusion joint 10.

[0050] In the above-described embodiment, a Tee-type electric fusion joint (EF Tee) was shown as an example of a pipe joint according to the present invention, but the configuration of the parts other than the straight pipe section of the pipe joint is not particularly limited, and the present invention can be applied to various types of pipe joints.

[0051] 5 shows another embodiment in which the present invention is applied to a reducer 50. A small diameter pipe section 54, which will be described later, is an example of a straight pipe section made of synthetic resin. The same reference numerals are used for the same parts as in the above-described embodiment, and duplicated descriptions will be omitted or simplified.

[0052] As shown in FIG. 5, the reducer 50 includes a large diameter pipe section 52 formed at one end, a small diameter pipe section 54 formed at the other end, and a tapered pipe section 56 connecting them. The small diameter pipe section 54 includes a first pipe section 40 formed on the base end side and a second pipe section 42 formed on the tip end side, and is formed by butt welding these. The second pipe section 42 has the same outer diameter as the first pipe section 40 and a pipe thickness larger than that of the first pipe section 40. An annular recess 46 having a diameter d3 the same as the inner diameter d1 of the first pipe section 40 and a tapered section 48 are formed on the inner peripheral surface of the end section of the second pipe section 42 on the first pipe section 40 side. In addition, a second reinforcing fiber 20 is wound around the outer peripheral surface of the first pipe section 40 and the outer peripheral surface of the end section of the second pipe section 42 on the first pipe section 40 side.

[0053] 6 shows yet another embodiment in which the present invention is applied to a conversion joint 60. A resin pipe section 64, which will be described later, is an example of a straight pipe section made of synthetic resin. The same reference numbers are used for parts similar to those in the above-described embodiment, and duplicated descriptions will be omitted or simplified.

[0054] As shown in FIG. 6, the conversion joint 60 is a pipe joint for connecting a metal pipe member (not shown) such as a steel pipe and a valve to a synthetic resin pipe member (not shown) such as a polyethylene pipe. The conversion joint 60 includes a metal joint body 62 having a first connection part 70 and a second connection part 72, a resin pipe part 64 having one end fitted onto the first connection part 70, and a metal ring 66 fitted onto one end of the resin pipe part 64. A synthetic resin pipe member is connected to the other end of the resin pipe part 64 via an EF socket or the like. On the other hand, a metal pipe member such as a steel pipe and a valve is connected to the second connection part 72 of the joint body 62.

[0055] The resin pipe section 64 includes a first pipe section 40 formed on the base end side and a second pipe section 42 formed on the tip end side, and is formed by butt welding these. The second pipe section 42 has the same outer diameter as the first pipe section 40 and a pipe thickness larger than that of the first pipe section 40. An annular recess 46 having a diameter d3 the same as the inner diameter d1 of the first pipe section 40 and a tapered section 48 are formed on the inner peripheral surface of the end section of the second pipe section 42 on the first pipe section 40 side. A second reinforcing fiber 20 is wound around the outer peripheral surface of the first pipe section 40 and the outer peripheral surface of the end section of the second pipe section 42 on the first pipe section 40 side.

[0056] 5 and 6, similarly to the embodiment shown in Fig. 1, even when a straight pipe section (small diameter pipe section 54, resin pipe section 64) is formed by butt welding a first pipe section 40 and a second pipe section 42 having different pipe thicknesses, the pressure resistance of the straight pipe section can be appropriately improved while reducing pressure loss. Furthermore, since the second reinforcing fiber 20 is provided, the pressure resistance of the straight pipe section and therefore the pipe joint (reducer 50, conversion joint 60) can be more appropriately improved.

[0057] Instead of the above-mentioned configuration, the pressure resistance of the resin pipe part of the conversion joint can be improved by adopting the following configuration to the conversion joint. Hereinafter, other embodiments of the conversion joint will be described with reference to Figs. 7 to 9.

[0058] 7 and 8, the conversion joint 80 includes a metal joint body 82 having a first connection portion 90 and a second connection portion 92, a plastic pipe portion 84 having one end fitted onto the outside of the first connection portion 90, and a metal ring 86 fitted onto one end of the plastic 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 80 is, for example, 365 mm.

[0059] 9, the resin pipe portion 84 is constituted by a short pipe made of SDR9 polyethylene. That is, in this embodiment, the outer diameter of the resin pipe portion 84 is 125 mm. The pipe thickness t4 of the resin pipe portion 84 is 14.0 mm, and the inner diameter d4 is 97.0 mm.

[0060] In this embodiment, an annular recess 94 is formed by cutting or the like on one end of the resin pipe section 84, i.e., on the inner peripheral surface of the fitting section 84a which fits onto the first connecting section 90 of the joint 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 resin pipe section 84 where the recess 94 is formed, i.e., the fitting section 84a, is of the SDR11 specification, and its pipe thickness t5 and inner diameter d5 are 11.4 mm and 102.2 mm, respectively.

[0061] In such a conversion joint 80, since the plastic pipe section 84 is composed of a short pipe made of SDR9 polyethylene, the pressure resistance of the plastic pipe section 84 can be appropriately improved and the pressure resistance standard for fire extinguishing piping can be satisfied. Also, although the pipe thickness of the part (fitting section 84a) where the recess 94 of the plastic 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 joint body 82. Furthermore, since the fitting section 84a is of SDR11 specification, the joint body 82 and the ring 86 for water piping can be used as they are.

[0062] 7, the pressure resistance of the resin pipe section 84 can be appropriately improved with a simple configuration of forming the recess 94 at one end of the resin pipe section 84. In addition, since the joint body 82 and the ring 86 can be used for multiple applications requiring different pressure resistance (for example, water piping and high-pressure fire piping), the manufacturing cost of the conversion joint 80 can be reduced.

[0063] It should be noted that the specific values ​​such as dimensions and specific configurations given above are merely examples and can be changed as appropriate according to the needs of product specifications, etc. [Explanation of symbols]

[0064] 10... Electric fusion joint (pipe joint) 12 …Branch joint body 14 …Main Division 16 … Branch pipe section (straight pipe section) 18...First reinforcing fiber 20 ... Second reinforcing fiber (reinforcing fiber) 46 ... Recess 48 …Tapered section 50...Reducer (another example of a pipe fitting) 60...Conversion fittings (another example of pipe fittings)

Claims

1. A pipe joint having a straight pipe portion made of synthetic resin, The straight 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 ring-shaped recess having the same diameter as the inner diameter of the first pipe portion is formed on an inner surface of an end of the second pipe portion facing the first pipe portion, and the first pipe portion and the second pipe portion are connected by butt fusion.

2. 2. The pipe joint according to claim 1, further comprising a long strip-shaped reinforcing fiber wound around an outer circumferential surface of the first pipe portion and an outer circumferential surface of an end portion of the second pipe portion on the first pipe portion side.

3. 3. The pipe joint according to claim 1, further comprising a tapered portion formed in a wall of said recess opposite said first pipe portion, said tapered portion having a diameter decreasing with increasing distance from said first pipe portion.

4. a tapered portion formed on a wall portion of the recess opposite to the first pipe portion, the tapered portion having a diameter decreasing with increasing distance from the first pipe portion; 3. The pipe fitting according to claim 2, wherein the reinforcing fibers are provided at an end of the second pipe portion on the first pipe portion side so as to cover at least an outer peripheral surface of a portion of the second pipe portion which forms the recess and the tapered portion.

5. 5. The pipe fitting according to claim 4, wherein the reinforcing fibers are provided at an end of the second pipe portion on the first pipe portion side, extending from an edge of the tapered portion opposite the first pipe portion to a portion that is 5 mm to 50 mm away from the first pipe portion.

6. 3. A pipe joint according to claim 1, wherein the axial length of said recess is equal to or greater than 0.03 times and equal to or less than 0.60 times the diameter of said recess.

7. 4. The pipe joint according to claim 3, wherein an inclination angle of said tapered portion with respect to an axial direction is equal to or greater than 25 degrees and equal to or less than 45 degrees.

8. 3. A pipe joint according to claim 1, wherein the axial length of the recess is between 0.3 and 4.5 times the pipe thickness of the second pipe portion at the portion where the recess is formed.

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