Connecting pipe, resin joining pipe, and resin pipe joining method

Abstract

This invention provides a configuration that allows resin pipes, formed by extending at least the end portion including the joint in the circumferential direction, to be joined in the axial direction. [Solution] The connecting pipe 10 is made of resin and joins two resin pipes P by heat welding. The connecting pipe 10 has a heating wire 20 on the inner circumference side of the portion into which the resin pipe P is inserted, formed by extending the axial end including the joining portion in the circumferential direction. The heating wire 20 is configured to heat the resin pipe P at a position other than its axial end, and then heat the end.

Description

Technical Field

[0001] The present invention relates to a connecting pipe for connecting two resin pipes by heat welding, a resin joint pipe in which two resin pipes are connected by heat welding, and a method for joining resin pipes.

Background Art

[0002] There is known a resin joint pipe in which two resin pipes are connected by heat welding. In such a resin joint pipe, the two resin pipes are connected by heat welding using, for example, an electric fusion joint. For example, Patent Document 1 discloses an electric fusion joint in which an electric heating wire is inserted into a spiral groove formed on the inner peripheral surface of a resin pipe. In this electric fusion joint, by energizing the electric heating wire from a pair of connector pins provided on the outer peripheral surface of the electric fusion joint, the outer peripheral surface of a plastic pipe inserted into the resin pipe and the inner surface of the resin pipe are melted and fused.

[0003] On the other hand, as a resin pipe, a biaxially oriented pipe manufactured by stretching the pipe in the axial and circumferential directions is known. As such a biaxially oriented pipe, Patent Document 2 discloses a biaxially oriented polyethylene pipe manufactured by stretching a polyethylene pipe in the axial and circumferential directions.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the biaxially oriented tube disclosed in Patent Document 2, the tube is stretched in the axial and circumferential directions while being heated, and then rapidly cooled to fix it in the stretched size. Therefore, because strain remains inside the biaxially oriented tube, when heated above a predetermined temperature after stretching, it shrinks in an attempt to return to its original size. Consequently, when using an electrofusion joint as disclosed in Patent Document 1 to heat-weld the biaxially oriented tube disclosed in Patent Document 2, the biaxially oriented tube shrinks radially relative to the electrofusion joint, creating a distance between the electrofusion joint and the biaxially oriented tube. Therefore, there is a possibility that the biaxially oriented tube cannot be sufficiently heat-welded by the electrofusion joint.

[0006] In response to this, there is a need for a configuration that allows resin pipes, formed by extending at least the end portion including the joint in the circumferential direction, to be joined in the axial direction.

[0007] The object of the present invention is to realize a configuration that allows resin pipes, formed by extending at least the end portion including the joining portion in the circumferential direction, to be joined in the axial direction. [Means for solving the problem]

[0008] A connecting pipe according to one embodiment of the present invention is a resin pipe positioned to straddle the axial ends of two resin pipes that are joined together, and is joined to the two resin pipes by heat welding. The connecting pipe has a heating wire at a position that radially overlaps with the joint portion of the resin pipe, which is formed by extending at least the axial end of the two resin pipes, including the joint portion. The heating wire is configured to heat the resin pipe formed by extending at the circumferential direction at a position other than its axial end, and then heat at the end (first configuration).

[0009] If at least one of the two resin tubes to be joined is a resin tube formed by circumferentially extending at least its axial end, including the joining portion, then when attempting to join the two resin tubes to the connecting tube by heat welding, the axial end of at least one of the resin tubes, which is the circumferentially extended and expanded portion, will shrink in diameter due to the heat. As a result, it may not be possible to weld the two resin tubes to the connecting tube with sufficient strength.

[0010] In contrast, as described above, by passing an electric current through a heating element located on the inner circumference of the connecting pipe, the resin pipe inserted into the connecting pipe can be heated at positions other than its axial end, and then at its end. As a result, the connecting pipe joining the two resin pipes is heat-welded to at least one of the resin pipes at positions other than its axial end, and then heat-welded at its end. Therefore, the reduction in diameter of the joining portion of at least one of the resin pipes can be suppressed. That is, even if the parts of at least one of the resin pipes other than its end are heated, the other parts are not heated and do not reduce in diameter, so the parts other than the end can be heat-welded to the connecting pipe while suppressing the reduction in diameter of the end. Subsequently, with the reduction in diameter of the end suppressed by the heat welding of the parts other than the end, the resin pipe can be heat-welded to the connecting pipe.

[0011] Therefore, the at least one resin pipe can be joined to the connecting pipe while suppressing the reduction in diameter of the at least one resin pipe due to the heat during heat welding. Thus, a resin pipe formed by extending at least the end portion including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0012] The tip portion of the end does not need to be heated by the heating element.

[0013] In the first configuration described above, the heating wire has a first heating element that heats a position other than the axial end of the resin tube that is formed by extending it in the circumferential direction, and a second heating element that heats the end after the first heating element has started to heat up (second configuration).

[0014] As a result, by inserting a resin pipe, in which at least the axial end including the joint portion is extended in the circumferential direction, into a connecting pipe, and then heating the first heating element of the heating wire at a position other than the axial end of the resin pipe, followed by heating the second heating element of the heating wire at the end, it is possible to suppress the reduction in diameter of the joint portion of the resin pipe during heat welding. Therefore, a resin pipe formed by extending at least the end including the joint portion in the circumferential direction can be joined to another pipe by heat welding.

[0015] In the first configuration described above, the heating element constitutes a plurality of electrical circuits arranged in the axial direction of the resin tube. Each of these plurality of electrical circuits is configured to be energized (third configuration).

[0016] This allows electrical circuits to be energized and heated at multiple axial positions in the connecting pipe. Therefore, at least one of the resin pipes can be joined to the connecting pipe while suppressing the shrinkage of the diameter of at least one of the resin pipes due to the heat during heat welding. Thus, a resin pipe formed by extending at least the end portion including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0017] In the third configuration described above, the connecting tube is electrically connected to the plurality of electrical circuits and further has a plurality of pairs of terminals that protrude radially outward from the outer surface of the connecting tube. The plurality of pairs of terminals are arranged in the axial direction or the circumferential direction (fourth configuration).

[0018] As a result, a pair of terminals are electrically connected to each of the multiple electrical circuits, making it easy to switch the power supply to the multiple electrical circuits. Therefore, a configuration can be realized in which the connecting tube can be heated in the axial direction at multiple timings.

[0019] Furthermore, as described above, by arranging multiple pairs of terminals in an axial or circumferential direction, each pair of terminals can be easily identified when energizing the multiple electrical circuits through the multiple pairs of terminals at multiple timings. Therefore, the multiple electrical circuits can be easily energized.

[0020] Furthermore, when the multiple pairs of terminals are arranged axially on the connecting pipe, there is a possibility that the terminals may interfere with each other depending on the axial length of the connecting pipe. However, by arranging the multiple pairs of terminals circumferentially, interference between the terminals can be prevented.

[0021] In the first configuration described above, the internal resistance of the heating element changes depending on the axial position, by changing at least one of the thickness, length, or density of the heating element, so that the heating element is heated at a position other than the axial end of the resin tube and then heated at the end (fifth configuration).

[0022] This allows the internal resistance of the heating element to be varied according to the axial position, such that the heating element heats the resin pipe at a position other than the axial end, and then heats the end. Therefore, it is possible to join at least one of the resin pipes to the connecting pipe while suppressing the shrinkage of the diameter of at least one of the resin pipes due to the heat during heat welding. Thus, a resin pipe formed by extending at least the end including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0023] In the first configuration described above, the positions other than the end are positions where the end does not deform radially due to heat when the positions other than the end are heated relative to the resin tube formed by stretching in the circumferential direction (sixth configuration).

[0024] In this way, with the axial end portion of the resin tube, which includes at least the joint portion, formed by being stretched in the circumferential direction, being suppressed from reducing its diameter due to heating, the inner circumferential side of the connecting tube and the outer circumferential side of the resin tube can be heat-welded. Therefore, a resin tube, the end portion of which, including at least the joint portion, is formed by being stretched in the circumferential direction, can be joined to another tube by heat welding.

[0025] Note that the position that does not deform in the radial direction is preferably at a position of 20% or more of the outer diameter of the resin tube from the end portion of the resin tube, and more preferably 50% or more, but is not limited thereto. The position that does not deform in the radial direction may be appropriately set according to the amount of stretching in the circumferential direction of the resin tube.

[0026] In the first configuration, the connecting tube is cylindrical and covers the axial end portions to be joined in the two resin tubes from the radially outer side. The heating wire is provided on the inner circumferential side of the connecting tube (seventh configuration).

[0027] Thus, when the connecting tube is arranged on the radially outer side of the axial end portions to be joined in the two resin tubes, the joint portion of the resin tube, the axial end portion of which, including at least the joint portion, is formed by being stretched in the circumferential direction, is likely to reduce its diameter due to the heating of the heating wire.

[0028] On the other hand, as in the first configuration described above, by configuring the heating wire to heat the resin tube at a position other than the axial end portion and then heat the end portion, it is possible to suppress the resin tube formed by being stretched in the circumferential direction from reducing its diameter due to heat. Therefore, a resin tube, the end portion of which, including at least the joint portion, is formed by being stretched in the circumferential direction, can be joined to another tube by heat welding.

[0029] In the seventh configuration, at least a portion where the heating wire is provided in the connecting tube is made of resin (eighth configuration). Thereby, a part of the connecting tube can be melted by the heating of the heating wire and joined to the resin tube. Thus, the connecting tube and the resin tube can be joined more reliably.

[0030] A resin jointed pipe according to one embodiment of the present invention is a resin jointed pipe in which two resin pipes are joined by heat welding. The resin jointed pipe has a connecting pipe according to any one of the first to eighth configurations, which is positioned to straddle the axial ends of the two resin pipes that are joined, and joins the two resin pipes. At least one of the two resin pipes is formed by extending at least the axial end including the joining portion in the circumferential direction (ninth configuration).

[0031] Even in such resin-joined pipes, by joining two resin pipes using a connecting pipe described in any one of the first to eight configurations described above, it is possible to suppress the reduction in diameter of the joint portion of the resin pipes during heat welding. Therefore, a resin pipe formed by extending at least the end portion including the joint portion in the circumferential direction can be joined to another pipe by heat welding.

[0032] A resin pipe joining method according to one embodiment of the present invention is a method for joining two resin pipes by heat welding. At least one of the two resin pipes to be joined is formed by extending at least the end portion including the joining portion in the circumferential direction. The resin pipe joining method includes a connecting pipe placement step of arranging a connecting pipe so as to straddle the axial ends of the two resin pipes to be joined; a first heat welding step of heat welding the connecting pipe to at least one of the resin pipes at a position other than its axial end; and a second heat welding step of heat welding the connecting pipe to at least one of the resin pipes at its end (first method).

[0033] As described above, the connecting pipe that joins the two resin pipes is heat-welded to at least one of the resin pipes at a position other than its axial end, and then heat-welded at the end, thereby suppressing the reduction in diameter of the joining portion of at least one of the resin pipes. That is, even if the parts of at least one of the resin pipes other than the end are heated, the other parts are not heated and do not reduce in diameter, so that the parts other than the end can be heat-welded to the connecting pipe while suppressing the reduction in diameter of the end. Subsequently, with the reduction in diameter of the end suppressed by the heat welding of the parts other than the end, the end can be heat-welded to the connecting pipe.

[0034] Therefore, the at least one resin pipe can be joined to the connecting pipe while suppressing the reduction in diameter of the at least one resin pipe due to the heat during heat welding. Thus, a resin pipe formed by extending at least the end portion including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0035] In the second method described above, the connecting pipe is cylindrical in shape into which the two resin pipes can be inserted. In the connecting pipe placement step, the connecting pipe is placed on the outer circumferential surface of the axial ends that are joined together in the two resin pipes (second method).

[0036] When the inner circumference of the connecting pipe is joined to the outer circumference of the two resin pipes in this manner, the heat generated during heat welding can cause at least the end of the two resin pipes, including the joining portion, to stretch in the circumferential direction, resulting in a tendency for the formed resin pipe to shrink in diameter. Therefore, in the configuration described above, there is a possibility that the connecting pipe and the two resin pipes cannot be joined with sufficient strength.

[0037] In contrast, as in the first method, by heat-welding the connecting pipe to at least one of the resin pipes at a position other than its axial end, and then heat-welding it at the end, the reduction in diameter of the joint portion of at least one of the resin pipes can be suppressed. Therefore, a resin pipe formed by extending at least the end including the joint portion in the circumferential direction can be joined to another pipe by heat welding.

[0038] In the second method described above, the connecting pipe has a heating element on its inner circumference that can be heated at a position other than the axial end of the at least one of the resin pipes, and then heated at the end. In the first and second heat welding steps, the connecting pipe is heat-welded to the at least one of the resin pipes by heating with the heating element (third method).

[0039] This allows a resin pipe, formed by extending at least the end portion including the joint in the circumferential direction, to be heated by an electric heating wire at a position other than the axial end of the resin pipe, and then heated at the end. Thus, a first welding step of heat-welding the connecting pipe to the resin pipe at a position other than its axial end, and a second welding step of heat-welding the connecting pipe to the resin pipe at the end can be easily realized. [Effects of the Invention]

[0040] A connecting pipe according to one embodiment of the present invention has a heating wire positioned radially overlapping with the joint portion of a resin pipe, where at least the axial end of one of the two resin pipes, including the joint portion, is extended in the circumferential direction. The heating wire is configured to heat the resin pipe, which is formed by extending in the circumferential direction, at a position other than its axial end, and then at the end.

[0041] This allows the resin pipe to be joined to the connecting pipe while suppressing the shrinkage of the resin pipe due to the heat during heat welding. Therefore, a resin pipe formed by extending at least the end portion including the joining portion in the circumferential direction can be joined to another pipe by heat welding. [Brief explanation of the drawing]

[0042] [Figure 1] Figure 1 is a cross-sectional view showing a schematic configuration of a resin jointed tube according to an embodiment of the present invention. [Figure 2] Figure 2 is a flowchart showing the resin pipe joining method according to an embodiment. [Figure 3]Figure 3 is a diagram illustrating the thermal fusion process by the first heat-generating element. [Figure 4] Figure 4 is a diagram illustrating the thermal fusion process by the second heat-generating element. [Figure 5] Figure 5 is a cross-sectional view showing a schematic configuration of a resin jointed pipe according to another embodiment. [Figure 6] Figure 6 is a side view of a resin jointed pipe according to another embodiment. [Modes for carrying out the invention]

[0043] The following describes each embodiment with reference to the drawings. In each drawing, the same parts are denoted by the same reference numerals, and the description of those parts will not be repeated. Note that the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component.

[0044] Furthermore, in the following explanation, the expressions "fix," "connect," and "attach" (hereinafter referred to as "fixing, etc.") include not only cases where components are directly fixed to each other, but also cases where they are fixed to each other via other components. In other words, in the following explanation, the expressions "fixing, etc." include both direct and indirect fixing of components to each other.

[0045] (Resin joint pipe) Figure 1 is a cross-sectional view showing the schematic configuration of a resin jointed pipe 1 according to an embodiment of the present invention. The cross-sectional view shown in Figure 1 is a view of the resin jointed pipe 1 cut in the axial direction. The resin jointed pipe 1 is constructed by joining two resin pipes P,P to a resin connecting pipe 10. The connecting pipe 10 and the two resin pipes P,P are joined by heat welding at the joint portion 40. In the following description, the portion of the joint portion 40 on the connecting pipe 10 side will be referred to as the joint portion of the connecting pipe 10, and the portion of the joint portion 40 on the resin pipes P,P side will be referred to as the joint portion of the resin pipes P,P.

[0046] The resin pipe P is a biaxially stretched pipe formed by stretching in the circumferential and axial directions. That is, the resin pipe P is formed by stretching in the circumferential and axial directions while heated. The resin pipe P is a pipe made of a resin material, such as a polyethylene pipe or a pipe made of a polyolefin resin material such as polyethylene.

[0047] (Connecting pipe) The connecting pipe 10 is positioned radially outward relative to the two resin pipes P, P, so as to straddle the axial ends that are joined in the two resin pipes P, P, and connects the two resin pipes P, P. The connecting pipe 10 is a cylindrical resin member that covers the axial ends that are joined in the two resin pipes P, P from the radially outward direction.

[0048] The connecting pipe 10 has an inner diameter larger than the outer diameter of the two resin pipes P, P. That is, both axial ends of the connecting pipe 10 are configured to allow the ends of the two resin pipes P, P to be inserted. The connecting pipe 10 has a pair of resin pipe insertion sections 11, 11 at both axial ends into which the ends of the two resin pipes P, P can be inserted. In this embodiment, the pair of resin pipe insertion sections 11, 11 have the same length in the axial direction of the connecting pipe 10. However, the pair of resin pipe insertion sections 11, 11 may have different lengths in the axial direction of the connecting pipe 10.

[0049] Each of the pair of resin pipe insertion sections 11, 11 has a heating element 20 extending in the circumferential direction inside its inner circumference. Each heating element 20 is positioned in the resin pipe insertion section 11 so as to overlap radially with the joint portion of the two resin pipes P, P with respect to the connecting pipe 10. Each heating element 20 is arranged inside the resin pipe insertion section 11 so as to follow the inner surface of the resin pipe insertion section 11. The portion of the pair of resin pipe insertion sections 11, 11 where each heating element 20 is provided is made of resin. As a result, by passing an electric current through each heating element 20, the pair of resin pipe insertion sections 11, 11 can be melted and joined to the resin pipes P, P.

[0050] Although not specifically shown in the diagram, each heating element 20 has an insulating coating. This prevents short circuits even when the heating elements 20 are arranged so that they intersect with each other in the first heating element 21 and the second heating element 22, as will be described later.

[0051] Each heating element 20 within the pair of resin tube insertion sections 11, 11 is electrically connected to one another. The ends of the electrically connected heating elements 20 are electrically connected to terminals 32 that protrude radially outward from the axial central portion of the connecting tube 10. The terminals 32 are covered by cylindrical projections 31 that protrude radially outward from the connecting tube 10.

[0052] Each heating element 20 within the pair of resin tube insertion sections 11 is configured to generate heat at different timings depending on its axial position when an electric current is applied. In other words, each heating element 20 has multiple heating elements that generate heat at different timings when an electric current is applied. Specifically, in this embodiment, each heating element 20 has a first heating element 21 and a second heating element 22. In the first heating element 21 and the second heating element 22, the heating element 20 constitutes an electrical circuit. In other words, each heating element 20 constitutes multiple electrical circuits. The electrical circuit constituting the first heating element 21 and the electrical circuit constituting the second heating element 22 are aligned in the axial direction. The electrical circuit constituting the first heating element 21 and the electrical circuit constituting the second heating element 22 are each configured to be energized.

[0053] Each heating element 20 is configured to generate heat in the order of the first heating element 21 and then the second heating element 22 when current is applied. Each heating element 20 may be configured to generate heat in the order of the first heating element 21 and then the second heating element 22 by adjusting the internal resistance of each heating element 20, for example by changing the thickness, length, density, etc. of the heating element. That is, each heating element 20 may have its internal resistance changed by changing at least one of the thickness, length, or density of the heating element (for example, the number of heating elements per unit area, the axial pitch of the heating elements, etc.) depending on the axial position, so that it heats up at positions other than the axial ends of the resin pipes P, P, and then heats up at the ends. Alternatively, each heating element 20 may be part of an electrical circuit configured to partially pass current through the first heating element 21 and then the second heating element 22 in each heating element 20.

[0054] The first heating element 21 is located in the axial central portion of the resin pipe insertion section 11. The second heating element 22 is located on the open end side of the resin pipe insertion section 11 and on the axial central side of the connecting pipe 10, respectively. That is, the first heating element 21 is located between the second heating element 22 in the axial direction. Therefore, the first heating element 21 and the second heating element 22 are arranged in the order of second heating element 22, first heating element 21, and second heating element 22 in the axial direction from the open end of the resin pipe insertion section 11.

[0055] The first heating element 21 is provided to heat the resin pipe P at a position other than the axial end. The position other than the end is a position where, when the resin pipe P is heated at a position other than the end, the end does not deform radially due to the heat. In other words, the first heating element 21 is provided at a position such that, when heated, the portion of the resin pipe P located radially inward on the open end side of the resin pipe insertion portion 11 does not shrink in diameter due to the heat. This prevents the portion of the resin pipe P located radially inward on the open end side of the resin pipe insertion portion 11 from shrinking in diameter due to the heat generated by the first heating element 21.

[0056] The second heating element 22 is provided to heat the resin pipe P at the open end side of the resin pipe insertion section 11 and at the axial center side of the connecting pipe 10. That is, the resin pipe P is heated by the second heating element 22 at its axial end and at the portion opposite to the end in the axial direction relative to the portion heated by the first heating element 21. The axial tip portion of the end does not need to be heated (energized).

[0057] As described above, the multiple heating elements 21 and 22 on each heating element 20 are arranged axially, so that the axial central portion of the resin pipe insertion section 11 is first heated by the first heating element 21 and heat-welded to the resin pipe P. Subsequently, the open end side of the resin pipe insertion section 11 and the axial central side of the connecting pipe 10 are heated by the second heating element 22 and heat-welded to the resin pipe P. In this way, the heating element 20 is configured to heat the resin pipe P at positions other than its axial end, and then at the end.

[0058] As a result, when the axial central portion of the resin pipe insertion section 11 of the connecting pipe 10 is heated by the first heating element 21, the open end side of the resin pipe insertion section 11 and the axial central side of the connecting pipe 10 are not heated. Therefore, even if the heated portion of the resin pipe P attempts to shrink in diameter due to heat, the portions of the resin pipe P located radially inward on the open end side of the resin pipe insertion section 11 and the axial central side of the connecting pipe 10, respectively, do not shrink in diameter. Thus, the shrinkage of the heated portion of the resin pipe P is suppressed, and the axial central portion of the resin pipe insertion section 11 of the connecting pipe 10 can be heat-welded to the outer circumference of the resin pipe P.

[0059] Then, with the axial central portion of the resin pipe insertion portion 11 of the connecting pipe 10 heat-welded to the outer circumference of the resin pipe P, the open end side of the resin pipe insertion portion 11 and the axial central side of the connecting pipe 10 are heated by the second heating element 22, respectively. As a result, the portions located radially inward on the open end side of the resin pipe insertion portion 11 and the axial central side of the connecting pipe 10 are heat-welded to the open end side of the resin pipe insertion portion 11 while suppressing diameter reduction.

[0060] Therefore, with the above configuration, a resin pipe P, formed by extending at least the axial end including the joint portion in the circumferential direction, can be joined by heat welding using the connecting pipe 10.

[0061] The connecting pipe 10 according to this embodiment is made of resin and is positioned to straddle the axial ends of the two resin pipes P, P that are joined together, and joins the two resin pipes P, P by heat welding. The connecting pipe 10 has a heating wire 20 at a position that radially overlaps with the joining portion of the resin pipe P, which is formed by extending the axial end of at least the joining portion of the two resin pipes P, P in the circumferential direction. The heating wire 20 is configured to be heated with respect to the resin pipe P at a position other than its axial end, and then heated at the end.

[0062] If at least one of the two resin pipes P, P to be joined is a resin pipe P formed by stretching at least the axial end including the joining portion in the circumferential direction, then when the two resin pipes P, P are joined by heat welding, the joining portion of the resin pipe P will shrink in diameter due to the heat. As a result, there is a possibility that the two resin pipes P, P cannot be welded to the connecting pipe 10 with sufficient strength.

[0063] In contrast, as described above, by passing an electric current through the heating element 20 located on the inner circumference of the connecting pipe 10, the resin pipe P inserted into the connecting pipe 10 can be heated at positions other than its axial end, and then heated at the end. As a result, the connecting pipe 10 that joins the two resin pipes P, P is heat-welded to the resin pipe P at positions other than its axial end, and then heat-welded at the end. Therefore, the reduction in diameter of the joining portion of the resin pipe P can be suppressed. That is, even if the resin pipe P is heated at positions other than its end, the other parts are not heated and do not reduce in diameter, so the parts other than the end can be heat-welded to the connecting pipe 10 while suppressing the reduction in diameter of the end. Subsequently, with the reduction in diameter of the end suppressed by the heat welding of the parts other than the end, the end can be heat-welded to the connecting pipe 10.

[0064] Therefore, the resin pipe P can be joined to the connecting pipe 10 while suppressing the shrinkage of the resin pipe P due to the heat during heat welding. Thus, a resin pipe formed by extending at least the end portion including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0065] Furthermore, in this embodiment, the heating element 20 has a first heating element 21 that heats a position other than the axial end of the resin pipe P, and a second heating element 22 that heats the end after the first heating element 21 starts heating.

[0066] As a result, with the resin pipe P, whose axial end is extended in the circumferential direction, inserted into the connecting pipe 10, the first heating element 21 of the heating element 20 is heated relative to the resin pipe P at a position other than its axial end, and then the second heating element 22 of the heating element 20 is heated at the end, thereby suppressing the reduction in diameter of the joint portion of the resin pipe P during heat welding. Therefore, a resin pipe P formed with at least the end including the joint portion extended in the circumferential direction can be joined to another pipe by heat welding.

[0067] Furthermore, in this embodiment, the positions other than the end are positions where the end does not deform radially due to heat when the positions other than the end are heated relative to the resin pipe P.

[0068] This allows the inner circumference of the connecting pipe 10 and the outer circumference of the resin pipe P to be heat-welded together while suppressing the reduction in diameter of the axial end of the resin pipe P, which is formed by circumferentially extending at least the end including the joint portion, due to heating.

[0069] The resin joint pipe 1 of this embodiment has two resin pipes P, P and a connecting pipe 10 that is positioned to straddle the axial ends of the two resin pipes P, P that are joined together, and joins the two resin pipes P, P. At least one of the two resin pipes P, P is formed by extending at least the axial end including the joining portion in the circumferential direction.

[0070] Even in such a resin jointed pipe 1, by joining two resin pipes P, P using the connecting pipe 10 of this embodiment, it is possible to suppress the reduction in diameter of the joint portion of the resin pipe P during heat welding. Therefore, a resin pipe P formed by extending at least the end portion including the joint portion in the circumferential direction can be joined to another pipe by heat welding.

[0071] (Resin pipe joining method) Next, a method for joining resin pipes P, P using a connecting pipe 10 will be explained with reference to Figure 2. Figure 2 is a flowchart of the resin pipe joining method according to this embodiment.

[0072] When the flow shown in Figure 2 starts (START), first in step S1, the ends of two resin pipes P, P are inserted into the resin pipe insertion sections 11, 11 located at both axial ends of the connecting pipe 10, respectively.

[0073] In the following step S2, as shown in Figure 3, the output cable V of the fusion splicer W is electrically connected to the pair of terminals 32 of the connecting pipe 10.

[0074] Subsequently, when current is passed from the output cable V of the fusion splicer W to the pair of terminals 32, 32 of the connecting pipe 10, the heating element 20 inside the resin pipe insertion section 11 of the connecting pipe 10 is energized first, and the first heating element 21 generates heat (step S3). As a result, as shown in Figure 3, the portion of the resin pipe P located radially inward relative to the first heating element 21 (the portion other than the axial end) is heat-welded to the resin pipe insertion section 11 of the connecting pipe 10 (the portion enclosed by the dashed line in Figure 3). Thus, the axial central portion of the resin pipe insertion section 11 and the portion of the resin pipe P located radially inward relative to the axial central portion of the resin pipe insertion section 11 are heat-welded.

[0075] In this case, the open end side of the resin pipe insertion portion 11 and the axial center side of the connecting pipe 10 are not heated. Therefore, the portion of the resin pipe P inserted into the resin pipe insertion portion 11 that is located radially inward on the open end side and the axial center side does not shrink in diameter due to heating. This suppresses the shrinkage of the resin pipe P. Thus, as described above, the axial center portion of the resin pipe insertion portion 11 and the portion of the resin pipe P that is located radially inward relative to the axial center portion of the resin pipe insertion portion 11 can be joined by heat welding.

[0076] Subsequently, the power supply from the output cable V of the fusion splicer W to the first heating element 21 is terminated, and the portion that has been heat-welded by the first heating element 21 is cooled (step S4).

[0077] Next, as shown in Figure 4, the heating element 22 in the heating element 20 inside the resin pipe insertion section 11 of the connecting pipe 10 is energized, causing the second heating element 22 to heat up (step S5). As a result, the portion of the resin pipe P located radially inward relative to the second heating element 22 is heat-welded to the resin pipe insertion section 11 of the connecting pipe 10 (the portion enclosed by the dashed line in Figure 4). Thus, the open end side of the resin pipe insertion section 11 and the axial center side of the connecting pipe 10 are heat-welded to the portions of the resin pipe P located radially inward relative to the open end side and the axial center side of the resin pipe insertion section 11, respectively.

[0078] In this case, since the axial central portion of the resin pipe insertion section 11 in the connecting pipe 10 is joined to the resin pipe P, the reduction in diameter of the portion of the resin pipe P inserted into the resin pipe insertion section 11 that is located radially inward on the open end side and the axial central side is suppressed. Therefore, as described above, the open end side and the axial central side of the resin pipe insertion section 11 and the portion of the resin pipe P that is located radially inward with respect to the open end side and the axial central side of the resin pipe insertion section 11 can be joined by heat welding.

[0079] This allows the inner circumference of the resin pipe insertion portion 11 of the connecting pipe 10 and the outer circumference of the resin pipe P to be joined by heat welding.

[0080] Subsequently, the power supply to the second heating element 22 is terminated, and the portion heat-welded by the second heating element 22 is cooled (step S6). Then, the output cable V of the fusion splicer W is disconnected from the pair of terminals 32, 32 of the connecting pipe 10 (step S7). This process is completed (END).

[0081] In this embodiment, if the connecting pipe 10 has a pair of terminals 32, 32, it is preferable that the heating wire 20 has a configuration in which the energizing timing differs between the first heating section 21 and the second heating section 22, so that the joining method described above can be performed. That is, for example, the heating timing can be adjusted by changing the thickness or density of the heating wire between the first heating section 21 and the second heating section 22, or the output cable V of the fusion splicer W can be configured so that the energizing timing differs between V1, when the first heating section 21 generates heat (output where the second heating section 22 does not generate heat), and V2, when both the first heating section 21 and the second heating section 22 generate heat. In this example, two stages of energizing have been described, but the invention is not limited to this, and three or four stages of energizing can be selected as appropriate. In the case where a pair of terminals is connected to the first heating section 21 and the second heating section 22, the output cable V of the fusion splicer W can be connected to different pairs of terminals depending on whether the first heating section 21 or the second heating section 22 is energized.

[0082] Here, step S1 corresponds to the connecting pipe arrangement process, step S3 corresponds to the first heat welding process, and step S5 corresponds to the second heat welding process.

[0083] The resin pipe joining method of this embodiment is a method of joining two resin pipes P, P by heat welding. At least one of the two resin pipes P, P to be joined is formed by extending at least the end including the joining portion in the circumferential direction. The resin pipe joining method includes a connecting pipe placement step S1 in which a connecting pipe 10 is placed so as to straddle the axial ends of the two resin pipes P, P to be joined; a first heat welding step S3 in which the connecting pipe 10 is heat-welded to the resin pipe P at a position other than its axial end; and a second heat welding step S5 in which the connecting pipe 10 is heat-welded to the resin pipe P at the end.

[0084] As described above, the connecting pipe 10 that joins the two resin pipes P, P is heat-welded to the resin pipes P at positions other than its axial ends, and then heat-welded at the ends, thereby suppressing the reduction in diameter of the joining portion of the resin pipes P. That is, even if the parts of the resin pipe P other than the ends are heated, the other parts are not heated and do not reduce in diameter, so the parts other than the ends can be heat-welded to the connecting pipe 10 while suppressing the reduction in diameter of the ends. Subsequently, with the reduction in diameter of the ends suppressed by the heat welding of the parts other than the ends, the ends can be heat-welded to the connecting pipe 10.

[0085] Therefore, the resin pipe P can be joined to the connecting pipe 10 while suppressing the shrinkage of the resin pipe P due to the heat during heat welding. Thus, a resin pipe P formed by extending at least the end portion including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0086] In this embodiment, the connecting pipe 10 is cylindrical in shape into which two resin pipes P, P can be inserted. In the connecting pipe placement step S1, the connecting pipe 10 is placed on the outer circumferential surface of the axial ends of the two resin pipes P, P to be joined.

[0087] When the inner circumference of the connecting pipe 10 is joined to the outer circumference of the two resin pipes P, P in this manner, the heat of welding can cause at least the end of the two resin pipes P, P, including the joining portion, to stretch in the circumferential direction, resulting in a tendency for the resin pipe P to shrink in diameter. Therefore, in the configuration described above, there is a possibility that the connecting pipe 10 and the two resin pipes P, P cannot be joined with sufficient strength.

[0088] In contrast, as in the resin pipe joining method of this embodiment, by heat-welding the connecting pipe 10 to the resin pipe P at a position other than its axial end, and then heat-welding it at the end, the reduction in diameter of the joining portion of the resin pipe P can be suppressed. Therefore, a resin pipe P formed by extending at least the end including the joining portion in the circumferential direction can be joined to another pipe by heat welding.

[0089] Furthermore, in this embodiment, the connecting pipe 10 has a heating element 20 on its inner circumference that can be heated at a position other than the axial end of the resin pipe P, and then heated at the end. In the first heat welding step S3 and the second heat welding step S5, the connecting pipe 10 is welded to the resin pipe P by heating with the heating element 20.

[0090] This allows the electric heating wire 20 to heat a position other than the axial end of the resin pipe P, which is formed by extending at least the end including the joint in the circumferential direction, and then heat the end. Thus, a first heat welding step S3 in which the connecting pipe 10 is heat-welded to the resin pipe P at a position other than its axial end, and a second heat welding step S5 in which the connecting pipe 10 is heat-welded to the resin pipe P at the end can be easily realized.

[0091] (Other embodiments) Although embodiments of the present invention have been described above, the embodiments described above are merely examples for carrying out the present invention. Therefore, the invention is not limited to the embodiments described above, and it is possible to carry out the invention by appropriately modifying the embodiments described above without departing from the spirit of the invention.

[0092] In the above embodiment, both resin pipes P, P are biaxially stretched pipes formed by stretching in the circumferential and axial directions. However, only one of the resin pipes may be a biaxially stretched pipe formed by stretching in the circumferential and axial directions. In this case, the configuration of the above embodiment may be applied only to the portion where the biaxially stretched resin pipes are joined. Furthermore, only the ends of the resin pipes including the joining portion may be formed by stretching in the circumferential and axial directions, or the entire resin pipe may be formed by stretching in the circumferential and axial directions.

[0093] In the above embodiment, the connecting pipe 10 is positioned radially outward relative to the two resin pipes P, P so as to straddle the axial ends that are joined in the two resin pipes P, P, and connects the two resin pipes P, P. However, the connecting pipe may also be positioned radially inward relative to the two resin pipes to connect the two resin pipes. In this case, the heating element is located on the outer circumference side of the connecting pipe.

[0094] In the above embodiment, the heating element 20 of the connecting pipe 10 has a first heating element 21 and a second heating element 22. However, the heating element may have three or more heating elements. In this case as well, the heating element has multiple heating elements that heat up at different timings.

[0095] In the above embodiment, the connecting pipe 10 has a pair of resin pipe insertion portions 11, 11. Therefore, the two resin pipes P, P are inserted into the interior of both axial ends of the connecting pipe 10. However, the connecting pipe may have the resin pipe inserted into the interior of one axial end and the other axial end inserted into the end of the resin pipe. In this case, the heating wire is provided in the portion of the connecting pipe facing the resin pipe.

[0096] In the above embodiment, the first heating element 21 of the heating element 20 is located in the axial center of the resin pipe insertion section 11 of the connecting pipe 10. The second heating element 22 is located on the open end side of the resin pipe insertion section 11 and on the axial center side of the connecting pipe 10. However, the first heating element may be located on the axial center side of the connecting pipe in the resin pipe insertion section. The second heating element may be located on the open end side or the axial center of the resin pipe insertion section 11.

[0097] In the above embodiment, the connecting pipe 10 has heating wires 20 in each of the pair of resin pipe insertion portions 11, 11. However, the connecting pipe may have heating wires in only one of the pair of resin pipe insertion portions.

[0098] In the above embodiment, a groove extending in the circumferential direction may be provided on the inner circumference side of the resin pipe insertion portion 12 of the connecting pipe 10, and an annular sealing member may be placed in the groove. This allows the sealing member to seal the space between the inner circumference surface of the resin pipe insertion portion 11 of the connecting pipe 10 and the outer circumference surface of the resin pipes P, P inserted into the resin pipe insertion portion 11.

[0099] In the above embodiment, the heating element 20 of the connecting pipe 10 may be heated in stages in the circumferential direction.

[0100] In the above embodiment, the connecting pipe 10 has a pair of terminals 32, 32. However, the connecting pipe may have multiple pairs of terminals. For example, as shown in Figure 5, the connecting pipe 110 has a pair of terminals 32, 32 and another pair of terminals 132, 132. In the example shown in Figure 5, these terminals are aligned in the axial direction. In the example shown in Figure 5, the pair of terminals 32, 32 is positioned between the other pair of terminals 132, 132 in the axial direction. Note that the pair of terminals 32, 32 may be aligned in the axial direction, and another pair of terminals 132, 132 may be aligned in the axial direction at a position in the circumferential direction, either in the axial direction or in the axial direction relative to them. In other words, the terminals may be provided at any position as appropriate, depending on the size of the connecting pipe and the shape of the connecting pipe body.

[0101] A pair of terminals 32, 32 are electrically connected to the first heating element 21 of the heating wire 20. Another pair of terminals 132, 132 are electrically connected to the second heating element 22 of the heating wire 20. As a result, the first heating element 21 can be heated by connecting the output cable of the fusion splicer to the pair of terminals 32, 32 and passing current through it. Then, the second heating element 22 can be heated by connecting the output cable of the fusion splicer to the other pair of terminals 132, 132 and passing current through it. Thus, the heating wire 20 can be easily heated in the order of the first heating element 21 and then the second heating element 22. Alternatively, the pair of terminals 32, 32 may be electrically connected to the second heating element 22 of the heating wire 20, and the other pair of terminals 132, 132 may be electrically connected to the first heating element 21 of the heating wire 20. In Figure 5, reference numeral 101 denotes a resin jointing pipe, and reference numeral 131 denotes a protruding part.

[0102] Furthermore, as shown in Figure 6, the connecting pipe 210 has a pair of terminals 32, 32 and another pair of terminals 232, 232. In the example shown in Figure 6, the pair of terminals 32, 32 and the other pair of terminals 232, 232 are aligned in the circumferential direction. Each terminal of the pair of terminals 32, 32 is aligned in the axial direction. Each terminal of the other pair of terminals 232, 232 is aligned in the axial direction. Note that all terminals may be aligned in the circumferential direction, or the pair of terminals 32, 32 may be aligned in the circumferential direction, or the other pair of terminals 232, 232 may be aligned in the circumferential direction.

[0103] A pair of terminals 32, 32 are electrically connected to the first heating element of the heating wire. Another pair of terminals 232, 232 are electrically connected to the second heating element of the heating wire. As a result, the first heating element can be heated by connecting the output cable of the fusion splicer to the pair of terminals 32, 32 and passing current through it. Then, the second heating element can be heated by connecting the output cable of the fusion splicer to the other pair of terminals 232, 232 and passing current through it. Thus, the heating wire can be easily heated in the order of the first heating element and then the second heating element. Alternatively, the pair of terminals 32, 32 may be electrically connected to the second heating element of the heating wire, and the other pair of terminals 232, 232 may be electrically connected to the first heating element of the heating wire. In Figure 6, reference numeral 201 denotes a resin jointing pipe, and reference numeral 231 denotes a protruding part. [Industrial applicability]

[0104] The present invention can be used for a connecting pipe that joins two resin pipes by heat welding, a resin jointed pipe obtained thereby, and a resin pipe joining method. [Explanation of Symbols]

[0105] 1, 101, 201 Resin jointed pipe 10, 110, 210 connecting pipes 11. Resin tube insertion section 20 heating wire 21. First heat-generating section 22 Second Heat-Generating Section 31, 131, 231 protrusion 32, 132, 232 terminals 40 Joint P tube V output cable W Fusion Splicer

Claims

1. A resin connecting pipe positioned to straddle the axial ends of two resin pipes that are joined together, and joined to the two resin pipes by heat welding, At least one of the two resin tubes, including the joint portion, has an axial end that is extended in the circumferential direction, and the joint portion of the resin tube is positioned to overlap radially with the joint portion of the resin tube, The heating element is configured to heat the resin tube, which is formed by extending it in the circumferential direction, at a position other than its axial end, and then at the end. Connecting pipe.

2. In the connecting pipe according to claim 1, The aforementioned heating element is A first heating element is provided for a resin tube formed by extending it in the circumferential direction, which heats a position other than the axial end of the tube. A second heating element heats the end portion after the first heating element starts heating, Having, Connecting pipe.

3. In the connecting pipe according to claim 1, The heating element constitutes a plurality of electrical circuits arranged in the axial direction of the resin tube. Each of the aforementioned multiple electrical circuits is configured to be energized. Connecting pipe.

4. In the connecting pipe according to claim 3, The connecting tube is electrically connected to the aforementioned plurality of electrical circuits and further has a plurality of pairs of terminals that protrude radially outward from the outer surface of the connecting tube, The plurality of pairs of terminals are arranged side by side in the axial direction or the circumferential direction. Connecting pipe.

5. In the connecting pipe according to claim 1, The heating element is heated at a position other than the axial end of the resin tube, and then heated at the end, so that the internal resistance changes by changing at least one of the thickness, length, or density of the heating element depending on the axial position. Connecting pipe.

6. In the connecting pipe according to claim 1, The positions other than the aforementioned end are positions where, when the resin tube formed by stretching in the circumferential direction is heated, the end does not deform radially due to the heat. Connecting pipe.

7. In the connecting pipe according to claim 1, The connecting pipe is cylindrical in shape and covers the axial ends of the two resin pipes that are joined together from the radially outward direction. The heating element is provided on the inner circumference side of the connecting pipe. Connecting pipe.

8. In the connecting pipe according to claim 7, At least the portion where the heating element is provided is made of resin. Connecting pipe.

9. A resin jointed tube in which two resin tubes are joined by heat welding, The connecting pipe is positioned to straddle the axial ends of the two resin pipes that are joined together, and connects the two resin pipes, as described in any one of claims 1 to 8. Of the two resin tubes, at least one of them is formed by extending its axial end, including at least the joint portion, in the circumferential direction. Resin jointed pipe.

10. A resin pipe joining method that joins two resin pipes by heat welding, Of the two resin tubes to be joined, at least one of the resin tubes is formed by extending at least the end portion including the joining portion in the circumferential direction. The resin pipe joining method described above is: A connecting pipe arrangement step involves arranging the connecting pipe so as to straddle the axial ends of the two resin pipes that are joined together, A first heat welding step involves heat welding the connecting pipe to at least one of the resin pipes at a position other than its axial end, A second heat welding step involves heat welding the connecting pipe to at least one of the resin pipes at its end, Having, Resin pipe joining method.

11. In the resin pipe joining method according to claim 10, The connecting pipe is cylindrical in shape into which the two resin pipes can be inserted. In the connecting pipe arrangement step, the connecting pipe is placed on the outer circumferential surface of the axial end to be joined in the two resin pipes. Resin pipe joining method.

12. In the resin pipe joining method according to claim 11, The connecting pipe has an electric heating element on its inner circumference that can be heated at a position other than the axial end of at least one of the resin pipes, and then heated at the end. In the first and second heat welding steps, the connecting pipe is heat-welded to at least one of the resin pipes by heating with the electric heating element. Resin pipe joining method.

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