Electric fusion joint

Abstract

To provide an electric fusion joint capable of preventing a joint body and a fusion part of a resin pipe with an outer layer to be connected from deteriorating due to ultraviolet rays or the like, and capable of being easily manufactured.SOLUTION: An electric fusion joint 10 comprises a joint body 12 having an electric fusion socket 20. The joint body comprises an inner layer 12a, and a weather-resistant outer layer 12b that covers an outer peripheral surface of the inner layer. The electric fusion joint also comprises a cylindrical protective cover 14 having weather resistance and attached to an outer peripheral surface of the electric fusion socket so that one end part protrudes axially from an open end of the electric fusion socket.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to an electric fusion joint, and particularly, for example, to an electric fusion joint including a joint body having an electric fusion socket.

Background Art

[0002] An example of a conventional electric fusion joint is disclosed in Patent Document 1. The electric fusion joint of Patent Document 1 includes a joint body and a heat shrinkable tube covering the surface of the joint body, and is used for connecting coated polyethylene tubes (resin tubes with an outer layer). At both ends of the joint body, sockets (electric fusion sockets) for receiving the tube ends of the coated polyethylene tubes are formed. The heat shrinkable tube forms a coating layer (outer layer) on the surface of the joint body to prevent deterioration due to ultraviolet rays or the like, and flange portions are formed at both ends thereof. The flange portions project further in the axial direction from the open ends of the sockets of the joint body, and when the sockets of the joint body receive the tube ends of the coated polyethylene tubes, they cover the gaps formed between the open ends of the sockets and the outer layer of the coated polyethylene tubes. Thereby, the fusion part (the part where the coating layer is peeled off and the inner tube is exposed) of the coated polyethylene tube to be connected is prevented from being exposed to the outside, and deterioration of the fusion part due to ultraviolet rays or the like is prevented.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology of Patent Document 1, a heat-shrinkable tube is put on the entire joint body and heated and shrunk to form a coating layer on the surface of the joint body to prevent deterioration due to ultraviolet rays or the like. When heating and shrinking this heat-shrinkable tube, in order to avoid deformation of the joint body due to heat, a shrinkage prevention core is installed inside the receiving port and it is necessary to hold it until cooling is completed. However, cooling takes time, and in order to increase the production quantity of the electric fusion joint, it is necessary to prepare a large number of dedicated shrinkage prevention cores, so a large investment is required.

[0005] Therefore, the main object of this invention is to provide a novel electric fusion joint.

[0006] Another object of this invention is to provide an electric fusion joint that can prevent the fusion part of the joint body and the resin tube with an outer layer to be connected from deteriorating due to ultraviolet rays or the like and can be easily manufactured.

Means for Solving the Problems

[0007] The first invention is an electric fusion joint including a joint body having an electric fusion receiving port, wherein the joint body includes an inner layer and an outer layer having weather resistance covering the outer peripheral surface of the inner layer, and has weather resistance, and is provided with a cylindrical protective cover attached to the outer peripheral surface of the electric fusion receiving port so that one end portion protrudes axially from the opening end of the electric fusion receiving port.

[0008] In the first invention, the electric fusion joint includes a joint body having an electric fusion receiving port. This joint body has a two-layer structure including an inner layer and an outer layer, and the outer layer has weather resistance. Thereby, deterioration of the joint body due to ultraviolet rays or the like is prevented. Further, the electric fusion joint includes a cylindrical protective cover attached to the outer peripheral surface of the electric fusion receiving port. This protective cover has weather resistance, and one end portion protrudes axially outward from the opening end of the electric fusion receiving port. Thereby, even if the resin tube with an outer layer connected to the electric fusion receiving port expands and contracts due to temperature changes, the fusion part of the resin tube with an outer layer (the portion where the inner tube is exposed) is prevented from being exposed to the outside, and deterioration of the fusion part of the resin tube with an outer layer due to ultraviolet rays or the like is prevented.

[0009] According to the first invention, since the joint body is provided with an outer layer having weather resistance and a protective cover is attached to the electric fusion joint, it is possible to appropriately prevent the fusion part of the joint body and the resin pipe with an outer layer to be connected from being deteriorated by ultraviolet rays or the like. Further, since each of the joint body and the protective cover can be manufactured by injection molding, mass productivity is excellent, and an electric fusion joint can be easily manufactured only by combining them. Therefore, the productivity of the electric fusion joint is significantly increased.

[0010] The second invention is subordinate to the first invention. The joint body has a plurality of electric fusion joints, and a protective cover is attached to each of the plurality of electric fusion joints.

[0011] The third invention is subordinate to the first or second invention. The protective cover has an insertion hole into which a power connection terminal of the electric fusion joint is fitted.

[0012] According to the third invention, since the power connection terminal is fitted into the insertion hole, the protective cover is surely prevented from coming off from the electric fusion joint.

[0013] The fourth invention is subordinate to the first or second invention. The protruding length by which one end of the protective cover protrudes axially outward from the opening end of the electric fusion joint is in the range of 10 mm or more and 30 mm or less.

[0014] According to the fourth invention, even if the resin pipe with an outer layer expands and contracts due to temperature changes, the fusion part of the resin pipe with an outer layer can be appropriately covered with the protective cover.

[0015] The fifth invention is subordinate to the first or second invention. The protective cover has elasticity.

[0016] According to the fifth invention, the protective cover can be easily attached to the electric fusion joint.

Effects of the Invention

[0017] According to the present invention, it is possible to prevent the fusion part of the joint body and the resin pipe with an outer layer to be connected from deteriorating due to ultraviolet rays or the like, and it is possible to easily manufacture an electric fusion joint.

[0018] The above object, 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

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0020] Referring to FIGS. 1 and 8, an electric fusion joint 10 which is an embodiment of the present invention is a socket-type electric fusion joint (EF socket) for linearly connecting resin pipes 100 with outer layers such as coated polyethylene pipes, and includes a joint body 12 having an electric fusion receiving port 20. As will be described in detail later, the joint body 12 has a two-layer structure including an inner layer 12a and an outer layer 12b, and a protective cover 14 is attached to the outer peripheral surface of the electric fusion receiving port 20.

[0021] The use, nominal diameter, etc. of the pipe constructed using the electrofusion joint 10 are not particularly limited. However, the electrofusion joint 10 is basically used for water pipes (such as pipes attached to bridges or temporary pipes) that are exposed outdoors. Also, the nominal diameter of the pipe formed using the electrofusion joint 10 is, for example, 40 mm - 300 mm.

[0022] As shown in FIGS. 1 and 2, the electrofusion joint 10 includes a cylindrical joint body 12 and protective covers 14 attached to both ends of the joint body 12 (that is, the electrofusion receiving ports 20).

[0023] As shown in FIGS. 3 and 4, the joint body 12 is manufactured by injection molding a polyolefin-based synthetic resin such as polyethylene and polybutene. In this embodiment, the joint body 12 is made of polyethylene (specifically, low-density polyethylene).

[0024] At both ends of the joint body 12, electrofusion receiving ports 20 for receiving the ends of the resin pipe 100 with an outer layer are formed. Near the inner peripheral surface of the electrofusion receiving port 20, a heating wire 22 is embedded so as to extend spirally. Both ends of the heating wire 22 are connected to power connection terminals 24 formed so as to protrude from the outer peripheral surface of the electrofusion receiving port 20. When the power connection terminals 24 are connected to a power source and an electric current is passed through the heating wire, heat is generated. Due to this heat, the resin at the joint surface between the electrofusion receiving port 20 and the resin pipe 100 with an outer layer is heated and melted, so that the electrofusion receiving port 20 and the resin pipe 100 with an outer layer are fusion-bonded. Further, on the outer peripheral surface of the electrofusion receiving port 20, an indicator 26 is formed on the axially central side with respect to the power connection terminals 24. The indicator 26 is for indicating that the joint surface between the electrofusion receiving port 20 and the resin pipe 100 with an outer layer has been fused (or the progress of fusion). Also, on the outer peripheral surface of the tip of the electrofusion receiving port 20, a tapered surface 28 that becomes smaller in diameter toward the tip is formed. Further, on the inner peripheral surface of the central portion of the joint body 12, a stopper 30 for stopping the pipe end of the resin pipe 100 with an outer layer is formed.

[0025] Such an outer layer resin tube 100 is connected to the joint body 12 of the electric fusion joint 10 as described above. As shown in FIG. 5, the outer layer resin tube 100 has a two-layer structure including an inner tube 102 (tube body) and an outer layer 104 (coating layer). The inner tube 102 is a standard tube with a predetermined length (for example, 5 m or the like), and is formed of a polyolefin synthetic resin such as polyethylene and polybutene. The outer layer 104 is formed of a polyolefin synthetic resin such as polyethylene and polybutene, and is provided so as to cover the outer peripheral surface of the inner tube 102. The outer layer 104 is imparted with weather resistance by mixing (adding) carbon black into the synthetic resin as a raw material. By providing such an outer layer 104, damage to the inner tube 102 is prevented, and deterioration of the inner tube 102 (and thus the outer layer resin tube 100) due to ultraviolet rays and the like is prevented. In this embodiment, each of the outer layer resin tube 100, that is, the inner tube 102 and the outer layer 104, is made of polyethylene (specifically, low-density polyethylene), and the outer layer 104 is formed of polyethylene mixed with carbon black.

[0026] Also, at the end of the outer layer resin tube 100, that is, the fusion part 106 that is inserted into the electric fusion receiving port 20 of the electric fusion joint 10 and fusion-bonded, the inner tube 102 is exposed in order to appropriately perform the fusion bonding. That is, the outer peripheral surface (bonding surface) of the fusion part 106 that is fusion-bonded to the inner peripheral surface of the electric fusion receiving port 20 is the outer peripheral surface of the inner tube 102. This fusion part 106 is formed, for example, at the construction site by removing the outer layer 104 of the portion to be joined.

[0027] When such an electric fusion joint is exposed outdoors for piping, the joint body 12 may be deteriorated by ultraviolet rays or the like. Further, when the resin pipe 100 with an outer layer connected to the electric fusion joint expands and contracts due to temperature changes, the fusion part 106 (that is, the part without the weather-resistant outer layer 104) is exposed to the outside, and the resin pipe 100 with an outer layer may be deteriorated by ultraviolet rays or the like. In order to solve such problems, as in the invention of Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-167768) described above, it is also conceivable to attach a heat-shrinkable tube by heating and shrinking it to cover the entire outer peripheral surface of the joint body. However, this requires labor in the manufacture of the electric fusion joint and increases the cost.

[0028] Therefore, in this embodiment, an outer layer 12b having weather resistance is formed on the joint body 12, and the protective cover 14 is attached only to the outer peripheral surface of the electric fusion receiving port 20 that receives the fusion part 106 of the resin pipe 100 with an outer layer, so that the fusion part 106 of the resin pipe 100 with an outer layer to be connected is prevented from being exposed to the outside, and the electric fusion joint 10 can be easily manufactured. This will be specifically described below.

[0029] As shown in FIGS. 2 and 4, the joint body 12 has a two-layer structure including an inner layer 12a and an outer layer 12b that covers the outer peripheral surface of the inner layer 12a. The above-described heating wire 22 is provided at the boundary between the inner layer 12a and the outer layer 12b. The inner layer 12a is a part that contacts the fluid (tap water) flowing in the pipe and is also a part that is fusion-bonded to the fusion part 106 of the resin pipe 100 with an outer layer. The outer layer 12b is a part that constitutes the outer surface (that is, is exposed to the outside) of the joint body 12. In this embodiment, it is provided so as to cover the entire outer peripheral surface and end surface of the inner layer 12a. The outer layer 12b is provided with weather resistance in order to prevent deterioration of the joint body 12 due to ultraviolet rays or the like. Specifically, the outer layer 12b is formed of polyethylene mixed with carbon black. Note that the inner layer 12a is formed of polyethylene not mixed with carbon black. By providing the weather-resistant outer layer 12b, deterioration of the joint body 12 due to ultraviolet rays or the like is appropriately prevented.

[0030] Referring to FIGS. 6 and 7 together with FIGS. 1 and 2, the protective cover 14 is formed in a cylindrical shape and is attached to each of the electric fusion joints 20 of the joint body 12 such that one end portion projects axially outward from the open end of the electric fusion joint 20. The protective cover 14 is manufactured by injection molding a rubber material having weather resistance and stretchability such as ethylene propylene rubber. That is, the protective cover 14 has weather resistance and stretchability. The thickness of the protective cover 14 is, for example, 1.0 mm - 2.0 mm.

[0031] In this embodiment, the protective cover 14 includes a large-diameter portion 40, a tapered portion 42, and a small-diameter portion 44. The large-diameter portion 40 is a portion that is mounted on the outer peripheral surface of the electric fusion joint 20, and the inner diameter of the large-diameter portion 40 is set to be the same as or slightly smaller than the outer diameter of the electric fusion joint 20 in a state where no external force is applied. Therefore, when the protective cover 14 is attached to the electric fusion joint 20, the large-diameter portion 40 is in close contact with the outer peripheral surface of the electric fusion joint 20. The tapered portion 42 extends from one end of the large-diameter portion 40 and is formed so as to follow the tapered surface 28 of the electric fusion joint 20, that is, so as to decrease in diameter toward the small-diameter portion 44 side. The tapered portion 42 is a portion that is mounted on the tapered surface 28 of the outer peripheral surface of the electric fusion joint 20, and a part of the tapered portion 42 projects axially outward from the open end of the electric fusion joint 20. The small-diameter portion 44 extends from one end of the tapered portion 42 and is disposed axially outward of the open end of the electric fusion joint 20. That is, in this embodiment, a part of the large-diameter portion 40 and the tapered portion 42 serve as a mounting portion for the electric fusion joint 20, and the other part of the tapered portion 42 and the small-diameter portion 44 serve as a projecting portion that projects axially outward from the open end of the electric fusion joint 20.

[0032] The inner diameter of the small-diameter portion 44 of the protective cover 14 is preferably set to be larger than the inner diameter of the electric fusion joint receiving port 20 and smaller than the outer diameter of the electric fusion joint receiving port 20. Thereby, when connecting the resin tube 100 with an outer layer to the electric fusion joint receiving port 20, the protective cover 14 does not get in the way, and the protective cover 14 can be arranged near the outer peripheral surface of the resin tube 100 with an outer layer. Also, the protruding length L by which one end portion of the protective cover 14 protrudes axially outward from the open end of the electric fusion joint receiving port 20 is preferably set to a size of, for example, 10 mm or more and 30 mm or less. Thereby, even if the resin tube 100 with an outer layer connected to the electric fusion joint receiving port 20 expands and contracts due to temperature changes, the protective cover 14 can appropriately cover the periphery of the fusion portion 106 (the portion where the inner tube 102 is exposed) of the resin tube 100 with an outer layer.

[0033] Further, in the large-diameter portion 40 of the protective cover 14, a first insertion hole 46 into which the power connection terminal 24 of the electric fusion joint receiving port 20 is fitted and a second insertion hole 48 into which the indicator 26 is fitted are formed. When the protective cover 14 is attached to the electric fusion joint receiving port 20, the power connection terminal 24 is fitted into the insertion hole 46, so that the protective cover 14 is more reliably prevented from coming off.

[0034] When attaching the protective cover 14 to the electric fusion joint receiving port 20 of the joint body 12, the power connection terminal 24 and the indicator 26 are respectively fitted into the insertion holes 46 and 48 of the protective cover 14, and with this portion as a fulcrum, while expanding the large-diameter portion 40 using elasticity, it is preferably externally fitted to the electric fusion joint receiving port 20. In this way, since the protective cover 14 has elasticity, the protective cover 14 can be easily and closely attached to the electric fusion joint receiving port 20.

[0035] As shown in FIG. 8, a synthetic resin pipe (pipe line) is formed by inserting the end portion (fusion portion 106) of the resin pipe 100 with an outer layer into the electric fusion joint receiving port 20 of the electric fusion joint 10 and performing fusion bonding. At this time, one end portion of the protective cover 14 protrudes axially outward from the open end of the electric fusion joint receiving port 20 and covers the periphery of the resin pipe 100 with an outer layer near the electric fusion joint receiving port 20. Therefore, even if the resin pipe 100 with an outer layer expands and contracts due to temperature changes, it is possible to prevent the fusion portion 106 of the resin pipe 100 with an outer layer from being exposed to the outside.

[0036] As described above, according to this embodiment, since the joint body 12 includes the outer layer 12b having weather resistance, it is possible to appropriately prevent the deterioration of the joint body 12 due to ultraviolet rays or the like. Further, since the protective cover 14 attached to the outer peripheral surface of the electric fusion joint receiving port 20 protrudes axially outward from the open end of the electric fusion joint receiving port 20 at one end portion, it is possible to appropriately prevent the deterioration of the fusion portion 106 of the resin pipe 100 with an outer layer due to ultraviolet rays or the like. Therefore, the electric fusion joint 10 can be suitably used for outdoor exposed pipes.

[0037] In addition, since each of the joint body 12 and the protective cover 14 can be manufactured by injection molding, they have excellent mass productivity, and the electric fusion joint 10 can be easily manufactured only by combining them. Therefore, according to this embodiment, the productivity of the electric fusion joint is significantly increased.

[0038] In the above-described embodiment, the protective cover is formed of a rubber material having elasticity. However, the protective cover does not necessarily have to have elasticity, and the protective cover can also be formed of a synthetic resin such as polyethylene mixed with carbon black. In this case, a cut (slit) extending in the axial direction is formed in the protective cover, and when attaching the protective cover to the electric fusion joint receiving port of the joint body, it is advisable to externally fit it to the electric fusion joint receiving port while widening the cut. Further, locking claws may be formed on the protective cover, and the protective cover may be fixed to the electric fusion joint receiving port using the locking claws.

[0039] In addition, in the above-described embodiment, the large-diameter portion and the small-diameter portion of the protective cover are connected by a tapered portion (inclined wall), but they can also be connected by a stepped portion (orthogonal wall). Further, the protective cover can be formed with the same diameter over the entire axial length. Furthermore, in the above-described embodiment, the protective cover is attached to the electric fusion joint receiving port so as to cover the range axially inside the indicator, but as long as the protective cover can be attached so as not to fall off, the range in which the protective cover covers the outer peripheral surface of the electric fusion joint receiving port (that is, the axial length of the mounting portion) is not particularly limited. For example, the protective cover can also be attached to a portion on the tip side (axially outer side) of the power connection terminal of the electric fusion joint receiving port.

[0040] Furthermore, in the above-described embodiment, a socket-type electric fusion joint having electric fusion joint receiving ports at both ends is shown as an example of the electric fusion joint according to the present invention, but the joint body only needs to have at least one electric fusion joint receiving port, and the electric fusion joint may be a bend type, a cheese type, or the like.

[0041] Note that all of the specific numerical values and specific configurations such as the dimensions listed above are merely examples and can be appropriately changed according to the requirements such as the specifications of the product.

Explanation of Reference Numerals

[0042] 10... Electric fusion joint 12... Joint body 12a... Inner layer 12b... Outer layer 14... Protective cover 20... Electric fusion joint receiving port 24... Power connection terminal 46... Insertion hole

Claims

1. An electric fusion joint comprising a joint body having an electric fusion receiving port, wherein the joint body has an inner layer, and an outer layer having weather resistance that covers the outer peripheral surface of the inner layer, and an electric fusion joint comprising a cylindrical protective cover that has weather resistance and is attached to the outer peripheral surface of the electric fusion receiving port such that one end portion thereof protrudes axially outward from the open end of the electric fusion receiving port.

2. The joint body has a plurality of the electric fusion receiving ports, and the protective cover is attached to each of the plurality of the electric fusion receiving ports. The electric fusion joint according to Claim 1.

3. The protective cover has an insertion hole into which a power connection terminal of the electric fusion receiving port is fitted. The electric fusion joint according to Claim 1 or 2.

4. The protruding length by which one end portion of the protective cover protrudes axially outward from the open end of the electric fusion receiving port is in the range of 10 mm or more and 30 mm or less. The electric fusion joint according to Claim 1 or 2.

5. The protective cover has elasticity. The electric fusion joint according to Claim 1 or 2.

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