JP2012202492A - Method for manufacturing electric fusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electric fusion joint of high reliability ensuring the management of joining work by an indicator while enhancing manufacturing yield.SOLUTION: Molten resin is injected into an injection space formed by closing an inner mold fitted with a heating wire 3, and an outer mold comprising a bar-like indicator pin for forming a recess 8 and an indicator 13, to form a joint body 2 having the recess 8 and the indicator 13. At this time, an indicator forming hole recessed from the tip of the indicator pin toward the rear end side connected to the outer mold and filled with the molten resin to form the indicator 13 is formed so that the tip side is larger in diameter than the rear end side, and one end 13a side is formed with the indicator 13 having a large diameter part 15 larger in diameter than the other end 13b side with a step part 14 as a boundary.

Description

  The present invention relates to a method for manufacturing an electrofusion joint.

  Conventionally, a synthetic resin pipe such as a polyethylene pipe is frequently used for water pipes, gas pipes and the like because they are excellent in durability, corrosion resistance and flexibility, and are lightweight and excellent in workability (workability). In addition, as a joint for sockets, elbows, cheeses, saddles, etc., for joining this type of pipe material, it is possible to simply perform the joining work without using expensive tools, and there is no variation in joining quality and high reliability. Therefore, EF joints (electric fusion joints) are often used (see, for example, Patent Document 1).

  For example, as shown in FIG. 1, the EF joint 1 is formed using a synthetic resin such as polyethylene, and is formed by embedding a heating wire 3 such as a nichrome wire in a spiral shape on the inner peripheral surface 2 a side of the joint body 2. ing. Further, the EF joint 1 is formed by providing a pair of terminal pins 4 projecting radially outward from the outer peripheral surface 2 b on the joint body 2, and connecting both ends of the heating wire 3 to the terminal pins 4. .

  When the pipe members 5 and 6 are joined together using the EF joint 1, a controller (energization device) is connected to the pair of terminal pins 4 with the ends of the pipe members 5 and 6 fitted to the joint body 2. The cable connector is attached, and the heating wire 3 is energized to generate heat. Due to the heat generated by the heating wire 3, the inner peripheral surface 2 a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 can be fused, and the pipe members 5 and 6 can be joined to each other via the EF joint 1. .

  As shown in FIGS. 1 and 5, the EF joint 1 is provided with an indicator 7 for notifying that the inner peripheral surface 2a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 are properly fused. It has been. The indicator 7 is formed in a rod shape, and is provided in such a manner that one end 7 a is connected to the bottom surface 8 a of the recess 8 that is recessed in the radial direction from the outer peripheral surface 2 b of the joint body 2 and accommodated in the recess 8.

  On the indicator, the inner peripheral surface side of the joint body and the outer peripheral surface side of the pipe material are melted by the heat generated by the heating wire, and the expansion pressure of the melted resin acts. Then, when an expansion pressure necessary for properly fusing the inner peripheral surface side of the joint main body and the outer peripheral surface side of the pipe material acts, the indicator protrudes from the inside of the recess to the radially outer side of the joint main body, and is pushed out. Express from the place. Thereby, it becomes possible to join a pipe material reliably and easily using an EF joint, when an operator performs joining work, confirming the expression of an indicator visually.

  Further, when manufacturing such an EF joint, a heating wire insulatively coated with polyethylene, polybutene or the like is spirally wound around an inner mold (core mold), and a terminal pin is connected to the end of the heating wire. Next, the inner mold with the heating wires and terminal pins attached is conveyed to a predetermined set position, and the outer mold (cavity mold) is clamped. At this time, an indicator pin for forming the indicator and the recess is formed integrally with the outer mold or attached in a separable manner. The indicator pin is formed in a rod shape, and an indicator forming hole is formed which is recessed at the center of the axis from the front end toward the rear end connected to the outer mold.

  Then, the molten resin is injected into an injection space formed by clamping the inner mold and the outer mold, the molten resin is cooled and solidified, and the inner mold and the outer mold are released, whereby the EF joint is manufactured.

JP 2001-141168 A

  Here, as shown in FIG. 5 (and FIG. 1), the indicator 7 has an inner circumference of the joint body 2 as the radial distance L1 of the joint body 2 from the heating wire 3 to the bottom surface 8a of the recess 8 decreases. When the surface 2a side and the outer peripheral surface side of the pipe members 5 and 6 are melted, the surface 2a side protrudes from the inside of the recess 8 and is easily pushed out. For this reason, conventionally, by adjusting the distance L1 from the heating wire 3 to the bottom surface 8a of the recess 8 to manufacture the EF joint 1, the inner peripheral surface 2a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 are The indicator 7 is protruded from the recess 8 so as to be exposed outwardly while being properly fused.

  However, even if the distance L1 from the heating wire 3 to the bottom surface 8a of the recess 8 is adjusted, the indicator 7 is excessively raised due to external factors such as outside air temperature and water adhesion, and the resin melted from the recess 8 Erupted in some cases. Further, if the distance L1 from the heating wire 3 to the bottom surface 8a of the recess 8 is increased in order to prevent the molten resin from being ejected, the inner peripheral surface 2a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 are properly positioned. In spite of the expansion pressure necessary for fusing, the indicator 7 may not be sufficiently raised and it is very difficult to balance.

  On the other hand, by adjusting the distance L2 between the indicator 7 and the side surface (wall surface) 8b of the recess 8, the easiness of the indicator 7 to be raised can be changed.

  However, as shown in FIGS. 5 and 6A, when the distance L2 between the indicator 7 and the side surface 8b of the recess 8 is increased, the indicator 7 is easily raised and pushed out, but the surface area of the recess 8 is increased. Therefore, the vicinity of the corner 8c on the bottom surface 8a side of the recess 8 is broken by the action of the expansion pressure, and the molten resin is likely to be ejected. Further, by increasing the distance L2 between the indicator 7 and the side surface 8b of the recess 8, it becomes easy to be affected by external factors such as outside air temperature and water adhesion.

  Further, as shown in FIGS. 5 and 6 (b), if the distance L2 between the indicator 7 and the side surface 8b of the recess 8 is reduced in order to prevent the resin from being ejected, an indicator pin (for indicator formation) is formed during injection molding. ) Immediately becomes hot, and due to this, the cooling of the side surface 8b of the recess 8 is slower than the other portions. As a result, after a predetermined manufacturing cycle time has elapsed (cycle up) and the inner mold, the outer mold and the indicator pin are released, the side surface 8b of the recess 8 swells and welds to the indicator 7, There arises a disadvantage that the indicator 7 cannot be raised. For this reason, by simply adjusting the distance L2 between the indicator 7 and the side surface 8b of the recess 8, the inner peripheral surface 2a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 are properly fused. For this reason, it is difficult to achieve a balance so that the expansion pressure necessary for the operation acts and the indicator 7 is appropriately raised and exposed from the recess 8.

  Furthermore, in order to eliminate this inconvenience, it is conceivable that the inner mold, the outer mold and the indicator pin are released after waiting until the side surface of the recess is cooled to a state where it does not bulge. This leads to a significant decrease in manufacturing yield.

  In addition, using an indicator pin that can be separated from the outer mold, leaving the indicator pin, the inner mold and the outer mold are separated, and the EF joint with the indicator pin attached is transported to another place. It is also conceivable to remove the indicator pin when it is cooled to a state where it does not bulge. However, in this case, since the indicator pin cannot be diverted until the recess of each molded EF joint is cooled, it is necessary to prepare a large number of indicator pins. In addition, it is necessary to separately remove the indicator pin, which is a small mold, after cooling the recess, resulting in a decrease in manufacturing yield and a new inconvenience that it hinders manufacturing automation by the robot.

  In order to solve the above problems, the present invention provides the following means.

  The method for manufacturing an electrofusion joint according to claim 1 includes: a tubular joint body; a heating wire embedded in the joint body; and a bottom surface of a recess recessed from the outer peripheral surface of the joint body toward the inner peripheral surface side. A method of manufacturing an electric fusion joint comprising a rod-shaped indicator connected at one end and projecting in the recess for forming the inner mold to which the heating wire is attached, the recess and the indicator And injecting molten resin into an injection space formed by clamping an outer mold having a bar-shaped indicator pin to mold the joint body having the recess and the indicator, and from the tip of the indicator pin to the outer Recessed toward the rear end side connected to the mold, and formed with an indicator forming hole for filling the molten resin to form the indicator so that the front end side has a larger diameter than the rear end side do it Can, and forming said indicator having a large diameter portion having a larger diameter than the other end to said one end by the stepped portion as a boundary.

  In the method of manufacturing an electrofusion joint according to claim 1, by forming an indicator pin with a large diameter on the tip side of the indicator forming hole, a large diameter portion is formed on one end side connected to the bottom surface of the recess. The other end side from the step portion can be made smaller in diameter than the large diameter portion to form the indicator. For this reason, the distance between the one end side of the indicator and the side surface of the recess can be reduced by the large diameter portion, and the distance between the other end side and the side surface of the recess can be increased from the stepped portion of the indicator. .

  And since the distance between the one end side of an indicator and the side surface of a recess is small, it can prevent that an indicator protrudes too much in this part, and can prevent that resin protrudes while an indicator protrudes. In addition, it is possible to make the indicator less likely to be affected by external factors such as outside air temperature and water adhesion, and the indicator can be stably raised even when affected by external factors.

It is sectional drawing which shows the electric fusion joint which concerns on one Embodiment of this invention. It is a figure which shows the S section of FIG. 1, and is sectional drawing which shows the indicator part (indicator, recess) of the electrofusion joint which concerns on one Embodiment of this invention. It is a figure which shows the state which clamped the inner type | mold, the outer type | mold, and the indicator pin in the manufacturing method of the electrical fusion joint which concerns on one Embodiment of this invention. It is a figure which illustrates the extrusion amount of the indicator with respect to the environmental temperature of the electric fusion joint which concerns on one Embodiment of this invention, and the conventional electric fusion joint. It is a figure which shows the S section of FIG. 1, and is sectional drawing which shows the conventional indicator part (indicator, recess). It is sectional drawing which shows the conventional indicator part (an indicator, a recess).

  Hereinafter, with reference to FIG. 1 to FIG. 4, a method for manufacturing an EF joint (an electrofusion joint) according to an embodiment of the present invention will be described.

  As shown in FIG. 1, the EF joint A of the present embodiment is a socket and is formed using a synthetic resin such as polyethylene. The EF joint A includes a cylindrical joint body 2 formed by embedding a heating wire 3 such as a nichrome wire on the inner peripheral surface 2a side, and outer peripheral surfaces on both end sides in the axis O1 direction of the joint main body 2. 2b, and a terminal portion 10 for attaching a cable connector of the controller to flow a current through the heating wire 3, and an outer peripheral surface 2b on both ends of the joint body 2 in the direction of the axis O1. It is provided with an indicator portion 11 for notifying that the inner peripheral surface 2a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 are properly fused at the time of joining work for joining the pipe materials 5 and 6 together. Yes.

  The terminal portion 10 includes a terminal pin 4 projecting radially outward in the direction orthogonal to the axis O1 from the outer peripheral surface 2b of the joint body 2, and the joint body 2 so as to surround the terminal pin 4 around the terminal pin 4. And a connector mounting portion 12 that protrudes outward in the direction orthogonal to the axis O1 from the outer peripheral surface 2b. Further, the connector mounting portion 12 is formed in a cylindrical shape, and is integrally formed on the outer peripheral surface 2b of the joint body 2 so that the terminal pins 4 and the center axis of each other are coaxially arranged. The end of the heating wire 3 is connected to each terminal pin 4.

  As shown in FIGS. 1 and 2, the indicator portion 11 has a recess 8 that is recessed radially outward in the direction orthogonal to the axis O <b> 1 from the outer peripheral surface 2 b of the joint body 2, and one end 13 a on the bottom surface 8 a of the recess 8. And a substantially cylindrical bar-shaped indicator 13 projecting in a shape accommodated in the recess 8 in the direction orthogonal to the axis O1 along the side surface 8b of the recess 8.

  The indicator 13 is provided at the center of the recess 8 with the recess 8 and the center axis of each other being coaxially arranged. Further, the indicator 13 of the present embodiment is provided with a stepped portion 14 on the one end 13a (protruding direction base end) side, with the stepped portion 14 as a boundary, the one end 13a side on the large diameter portion 15 and the other end 13b (in the protruding direction The tip side is the small diameter portion 16.

  The indicator 13 is formed such that the large diameter portion 15 on the one end 13 a side has a larger diameter than the small diameter portion 16 on the other end 13 b side, and the large diameter portion 15 and the small diameter portion 16 are connected by the step portion 14. The large diameter portion 15 is formed with a substantially constant diameter from the one end 13a to the stepped portion 14. The small-diameter portion 16 is formed so that the other end 13b has a convex curved surface and the diameter is substantially constant from the step portion 14 to the vicinity of the other end 13b. And in this embodiment, the large diameter part 15 is formed so that distance (gap) L3 between the large diameter part 15 of the indicator 13 and the side surface (wall surface) 8b of the recess 8 may be 0.5 mm or less, for example. Yes. The small diameter portion 16 is formed so that the distance (gap) L4 between the small diameter portion 16 and the side surface 8b of the recess 8 is, for example, 1.0 mm or more. In addition, the large diameter part 15 may be formed so that the diameter may become small gradually as it goes to the step part 14 from the one end 13a.

  When manufacturing the EF joint A having the above configuration, as shown in FIG. 3 (and FIGS. 1 and 2), polyethylene, polybutene, or the like is formed on the outer peripheral surface 20a of the inner mold 20 which is a substantially cylindrical rod-shaped core mold. The heating wire 3 covered with insulation is wound in a spiral shape, and terminal pins 4 are connected to both ends of the heating wire 3, respectively. And the outer mold | type 21 which is a cavity metal mold | die is installed so that the inner mold | die 20 to which the heating wire 3 and the terminal pin 4 were attached may be clamped. In this way, the inner mold 20 and the outer mold 21 are clamped, and an injection space H having the same shape and size as the shape of the EF joint A is formed.

  At this time, the outer mold 21 is provided with a bar-shaped indicator pin 22 which is a mold for forming the recess 8 and the indicator 13 of the indicator portion 11 in a separable manner. The outer mold 21 is also provided with a mold (not shown) for forming the connector mounting portion 12 (terminal portion 10) in a separable manner. In addition, the mold for forming the indicator pin 22 and the connector mounting portion may be integrally formed with the outer mold 21.

  As shown in FIG. 3, the indicator pin 22 is formed in a substantially cylindrical bar shape, and is provided with an indicator forming hole 23 that is recessed from the front end 22 a toward the rear end 22 b connected to the outer mold 21 at the center of the axis. Yes. The indicator pin 22 is formed such that the indicator forming hole 23 is formed in the same shape and size as the indicator 13 and the front end 22a side is larger in diameter than the rear end 22b side. Further, the outer shape of the portion where the indicator forming hole 23 is formed is formed in the same shape and size as the recess 8. Furthermore, a deaeration hole 24 that opens to the rear end 22 b and communicates with the indicator formation hole 23 is formed on the rear end 22 b side of the indicator pin 22.

  Then, the molten resin is injected into an injection space H formed by clamping the inner mold 20 and the outer mold 21 provided with a mold for forming the indicator pin 22 and the connector mounting portion. At this time, the molten resin is filled in the indicator forming hole 23 of the indicator pin 22. At the time of injection molding, the plug member 25 is fitted into the deaeration hole 24 of the indicator pin 22, and air is exhausted from the indicator forming hole 23 through the inner surface of the deaeration hole 24 and the outer surface of the plug member 25. As a result, the indicator forming hole 23 is filled with the molten resin.

  Next, when the injected molten resin is cooled at a predetermined cycle time (when the cycle is UP), the outer mold 21 and the inner mold 20 are opened, and the EF joint A as a molded product is taken out. At this time, the indicator pin 22 is also released together with the outer mold 21.

  Here, if the wall thickness between the inner surface and the outer surface of the indicator forming hole 23 of the indicator pin 22, that is, the distance L4 between the indicator 13 and the side surface 8b of the recess 8 becomes too small, the indicator pin 22 at the time of injection molding. Immediately becomes hot, and cooling of the side surface 8b of the recess 8 becomes slower than the other portions. Due to this effect, the side surface 8b of the recess 8 is not sufficiently cooled even when the cycle is increased, and the side surface 8b of the recess 8 may swell and be welded to the indicator 13 after releasing (FIG. 6B). )reference).

  In contrast, in this embodiment, as shown in FIGS. 1 to 3, the indicator forming hole 23 of the indicator pin 22 is formed so that the tip 22a side has a larger diameter than the rear end 22b side. Thus, the indicator 13 includes a large diameter portion 15 on the one end 13a side, the distance L3 on the one end 13a side between the large diameter portion 15 and the side surface 8b of the recess 8 is small, and the small diameter from the step portion 14 to the other end 13b. The distance L4 between the portion 16 and the side surface 8b of the recess 8 is ensured to be large. For this reason, it is suppressed that the indicator pin 22 becomes hot immediately at the time of injection molding, and the side surface 8b of the recess 8 is sufficiently cooled in a cycle-up state. Thereby, after mold release, the side surface 8b of the recess 8 does not bulge.

  For this reason, it is not necessary to release the inner mold 20 and the outer mold 21 (and the indicator pin 22) after waiting until the side surface 8n of the recess 8 is cooled to a state where it does not bulge. Further, the inner mold 20 and the outer mold 21 are separated from each other while leaving the indicator pin 22, the EF joint A with the indicator pin 22 attached is conveyed to another place, cooled, and the indicator pin 22 is removed later. There is no need.

  And when joining pipe materials 5 and 6 using EF joint A manufactured as mentioned above, as shown in Drawing 1 and Drawing 2, the end of each pipe material 5 and 6 is a joint of EF joint A. The main body 2 is fitted to both end portions. Next, a cable connector of the controller is attached to the pair of terminal pins 4, and the heating wire 3 is energized to generate heat. Due to the heat generated by the heating wire 3, the inner peripheral surface 2 a side of the joint body 2 and the outer peripheral surface side of the pipe members 5 and 6 are respectively melted, and the expansion pressure of the melted resin acts on the indicator 13. Then, the expansion pressure necessary for proper fusion acts, and the indicator 13 protrudes from the inside of the recess 8 to the outside in the radial direction of the joint body 8 and is pushed out from the recess 8 to be exposed.

  At this time, since the distance L3 between the one end 13a side of the indicator 13 and the side surface 8b of the recess 8 is reduced by the large diameter portion 15, the indicator 13 is prevented from being raised excessively, and the molten resin is ejected. Is prevented from occurring. Further, as shown in FIG. 4, compared to the conventional case, the influence of external factors due to external temperature, water adhesion, etc. (environmental temperature) is reduced, and even if it is affected by external factors, the indicator 13 will rise stably.

  Even if the distance L3 between the one end 13a side of the indicator 13 and the side surface 8b of the recess 8 is reduced by the large diameter portion 15 to prevent the resin from being ejected, the step portion 14 of the indicator 13 is used. The distance L4 between the small diameter portion 16 on the other end 13b side and the side surface 8b of the recess 8 is ensured to be large. As a result, the expansion pressure necessary for proper fusion acts, and the indicator 13 is surely raised from the inside of the recess 8 to the outside in the radial direction of the joint body 2 and exposed from the recess 8. .

  Therefore, as shown in FIG. 2, in the manufacturing method of the EF joint A of the present embodiment, the recess 8 is formed by forming the indicator pin 22 with the tip 22a side of the indicator forming hole 23 having a large diameter. The indicator 13 can be formed by providing a large-diameter portion 15 on the one end 13 a side connected to the bottom surface 8 a and making the other end 13 b side from the step portion 14 smaller than the large-diameter portion 15. For this reason, the distance L3 between the one end 13a side of the indicator 13 and the side surface 8b of the recess 8 can be reduced by the large diameter portion 15, and the other end 13b side and the side surface of the recess 8 from the step portion 14 of the indicator 13. The distance L4 between 8b can be increased.

  And since the distance L3 between the one end 13a side of the indicator 13 and the side surface 8b of the recess 8 is small, it is possible to prevent the indicator 13 from rising too much at this portion, and the indicator 13 rises and the resin spouts out. Can be prevented. In addition, it is possible to make the indicator 13 less likely to be affected by external factors such as outside air temperature and water adhesion, and the indicator 13 can be stably raised even when affected by external factors.

  Further, when the distance L3 between the one end 13a side of the indicator 13 and the side surface 8b of the recess 8 is reduced by the large diameter portion 15, it is prevented that the indicator 13 is excessively raised and the resin is ejected. Even if it exists, since the distance L4 between the step portion 14 of the indicator 13 and the other end 13b side and the side surface 8b of the recess 8 is ensured, the indicator 13 is reliably raised so that it protrudes outward from the recess 8. It can be expressed.

  Further, as shown in FIGS. 2 and 3, the indicator pin 22 is immediately heated at the time of injection molding because the distance L4 between the step 14 of the indicator 13 and the other end 13b side and the side surface 8b of the recess 8 is large. This can be prevented, and the side surface 8b of the recess 8 can be efficiently cooled. For this reason, even if the inner mold 20 and the outer mold 21 (and the indicator pin 22) are released in a predetermined manufacturing cycle time, the side surface 8b of the recess 8 can be prevented from bulging, and the manufacturing yield can be improved. In addition, the side surface 8b of the recess 8 is not welded to the indicator 13, and the indicator 13 can be preferably formed.

  Therefore, according to the manufacturing method of the EF joint A of the present embodiment, the distance L3 between the one end 13b side of the indicator 13 and the side surface 8b of the recess 8 is adjusted by adjusting the diameter of the large diameter portion 15 of the indicator 13. By adjusting or adjusting the length (height) dimension of the large-diameter portion 15 in the central axis direction to adjust the region where the distance L3 between the indicator 13 and the side surface 8b of the recess 8 is small, the comparison It is possible to balance the indicator 13 so that the indicator 13 is raised and exposed from the recess 8 accurately and easily.

  And the influence of external factors, such as external temperature and water adhesion, can be suppressed small, it can prevent that the indicator 13 protrudes too much and a molten resin ejects from the recess 8, and the side surface 8b of the recess 8 bulges. Therefore, after waiting until the side surface 8b of the recess 8 is cooled to a state where it does not bulge, the inner mold 20, the outer mold 21 and the indicator pin 22 are released or the indicator pin 22 is attached. It is not necessary to transport the EF joint A to another place and cool it, and it becomes possible to increase the production yield and manufacture the highly reliable EF joint A. It is also possible to cope with manufacturing automation by a robot.

  As mentioned above, although one Embodiment of the manufacturing method of the electrofusion joint which concerns on this invention was described, this invention is not limited to said one Embodiment, It can change suitably in the range which does not deviate from the meaning. .

1 Conventional EF joint (electric fusion joint)
2 Joint body 2a Inner peripheral surface 2b Outer peripheral surface 3 Heating wire 4 Terminal pin 5 Tubing material 6 Tubing material 7 Conventional indicator 8 Recess 8a Bottom surface 8b Side surface (wall surface)
8c Corner portion 10 Terminal portion 11 Indicator portion 12 Connector mounting portion 13 Indicator 13a One end 13b Other end 14 Step portion 15 Large diameter portion 16 Small diameter portion 20 Inner mold 20a Outer surface 21 Outer mold 22 Indicator pin 23 Indicator formation hole 24 Deaeration Hole 25 Plug member A EF joint (electric fusion joint)
H Injection space O1 axis

Claims (1)

A cylindrical joint body, a heating wire embedded in the joint body, and a rod-like shape projecting in the recess by connecting one end to the bottom surface of the recess recessed from the outer peripheral surface to the inner peripheral surface side of the joint body A method of manufacturing an electric fusion joint comprising the indicator of:
Injecting molten resin into an injection space formed by clamping an inner mold to which the heating wire is attached and an outer mold having a bar-shaped indicator pin for forming the recess and the indicator, the recess and While molding the joint body having the indicator,
The indicator pin is recessed from the tip of the indicator pin toward the rear end connected to the outer mold, and has an indicator forming hole for filling the molten resin to form the indicator. Is also formed to be large diameter,
A method for producing an electrofusion joint, comprising: forming the indicator having a larger diameter portion on the one end side than on the other end side with a stepped portion as a boundary.

Images