JP3735154B2 - Mold for cylindrical molded product and molding method thereof - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention is used in, for example, an electrofusion joint, that is, a piping work using a plastic pipe, and a mold used to mold an electrofusion joint in which a heating wire is embedded in a coil shape on a joint surface with the plastic pipe, and the mold Relates to a molding method.
[0002]
[Prior art]
There are various types of electrofusion joints, such as socket joints, elbow joints, cheese joints, reducer joints, and cap joints that are attached to the ends of pipes. It consists of a molded product in which a heating wire is embedded in a coil shape on the joint surface. And the fusion with the pipe is to heat and melt the joint surface with the plastic pipe by energization after inserting the plastic pipe from three sides, both sides or one side of the joint, or after pressing the joint against the outer peripheral surface of the plastic pipe. Is done.
[0003]
FIG. 1 shows a mold used for molding a socket joint among the above-described joints, and a core 2 connected in a separable manner by combining one side 2a and the other side 2b in a mold 1 divided into upper and lower parts. , And at the time of molding, each core 2a, 2b is wound with heating wire (usually coated heating wire 3 is used), set in the mold 1, and then injected into the cavity 5 through the gate 4. Is done.
[0004]
[Problems to be solved by the invention]
In addition to the above-described joints, many cylindrical electrofusion joints are required to have a perfect circle on the inner surface or outer surface. The mold shown in FIG. 1 also has a core formed in a perfect circle in order to obtain a joint having an inner diameter of a perfect circle, but the molded electrofusion joint is not removed from the core even if it is sufficiently cooled after molding. It tends to deform into an ellipse.
[0005]
The present invention has been made for the purpose of solving this problem, and an object of the present invention is to provide a mold capable of forming an electrofusion joint having a perfect inner diameter and a forming method using the mold. It is.
[0006]
[Means for solving problems]
The present inventors investigated the direction of the ellipse of the molded product in order to elucidate the reason why the inner diameter of the molded electrofusion joint becomes an ellipse, and the direction of the major axis after molding is the injection direction of the resin injected from the gate Found to match.
The present invention has been made based on this finding. As shown in FIG. 2, the core 11 has an elliptical shape, and the direction of the minor axis 2 coincides with the injection direction of the resin injected from the gate 12. It is set in the mold.
[0007]
That is, the present invention provides a slide core in which a core is disposed inside, a cylindrical cavity is formed around the core, and the core is capable of moving back and forth in the axial direction in a mold including a gate to the cavity, and a slide A sleeve core that is fitted into and attached to a core and wound with a heating wire or a covered heating wire, and the core is configured in an oval shape whose minor axis matches the injection direction of the resin injected from the gate. The second invention is characterized by injection molding using the mold of the first invention.
[0008]
According to the present invention, since the core is elliptical and its minor axis direction coincides with the injection direction of the resin injected from the gate, the molded electrofusion joint swells in the minor axis direction of the core and the inner diameter is a perfect circle. Turn into.
As shown in FIG. 5, the cavity in the mold becomes thicker on the opposite side of the gate 12 because the minor axis direction L of the core 11 coincides with the injection direction of the resin injected from the gate 12. As shown in FIG. 2, the thickness of the core 11 is thicker in the minor axis direction and thinner in the major axis direction, but not only the inner surface but also the outer surface is rounded, and the cavity 14 is formed to make the thickness uniform. As shown in FIG. 3, the inner surface of the mold is also preferably an ellipse similar to the core 11 so that the minor axis direction coincides with the injection direction of the resin injected from the gate.
[0009]
The core used in each of the above inventions includes a core 1 as shown in FIG. 1, that is, a core 2a, 2b divided on both right and left sides is solid and a covered heating wire 3 is wound around the core. In addition to this, as shown in FIG. 4, the core is divided into left and right parts, each of which is inserted into and inserted into each of the slide cores 16a and 16b which can advance and retreat in the axial direction, respectively. It is also possible to use the one composed of the sleeve core 18 on which the heating wire 17 (which may be a bare heating wire) is wound. According to the latter core, the sleeve core is thin and lightweight even if it is a large core and a heavy core. Therefore, it is easy to carry and handle when winding or mounting a mold. A large number of sleeves are available, and it is possible to replace the sleeve each time molding is completed, which increases productivity and makes it possible to automate, so that only the slide core can be cooled to cool the core. Since a simple structure is required, the cost can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The mold 13 shown in FIG. 5 is the same type of mold as shown in FIG. 1, and the core 11 has an elliptical shape and the minor axis direction coincides with the injection direction of the resin injected from the gate 12 (arrow direction in the figure). The mold 20 shown in FIG. 6 is the same as the mold shown in FIG. 5 except that the outer surface of the sleeve core 18 is elliptical and the minor axis direction is injected from the gate 19. The direction is the same.
[0011]
The above is an example of a mold for molding a socket joint of an electrofusion joint. However, in a mold for molding another insertion joint, a joint whose inner surface is rounded by configuring the core as described above. Can be obtained. The same applies to molds for molding other cylindrical molded products.
[0012]
【The invention's effect】
According to the mold of claim 1 and the molding method of claim 3, an electrofusion joint having an inner surface of a perfect circle or a substantially perfect circle is obtained by making the core into an oval shape in anticipation of deformation after molding. by can be Rukoto constitutes from slide core and the sleeve core, since it lighter and the sleeve core in thin, easily large diameter handling of the winding and the mold when worn even moldings, work It is possible to improve the performance, and it is possible to prepare a large number of wound sleeve cores, and it is possible to replace them in order, improving productivity, cooling only the slide core to cool, etc. Has an effect .
[0013]
According to the metal mold of claim 2, it is possible to obtain a cylindrical molded product having a uniform thickness in both the inner and outer true circles or the substantially true circles.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a mold.
FIG. 2 is a cross-sectional view of a molded product obtained by the method of the present invention.
FIG. 3 is a sectional view of a mold according to the present invention.
FIG. 4 is a cross-sectional view showing another example of a mold.
FIG. 5 is a sectional view of a mold according to the present invention.
FIG. 6 is a cross-sectional view of another mold according to the present invention.
[Explanation of symbols]
1, 13, 20 .. Die 2, 11... Core 3, 17 .. Covered heating wire 4, 12, 19... Gate 16 a, 16 b.

Claims (3)

The core is placed inside, to form a cylindrical cavity around the core, in a mold having a gate into the cavity, the slide core the core is movable back and forth in the axial direction,挿装wear fitted to slide core is made of a sleeve core heating wire or covering the heating wire is wound wire, electro fusion, characterized by being configured in an elliptical shape as to match the injection direction of the resin minor the core is injected from the gate Mold for fittings . 2. The mold for an electrofusion joint according to claim 1, wherein the inner surface of the mold forming the cavity is also an ellipse similar to the core, and the minor axis direction coincides with the injection direction of the resin injected from the gate.   2. A method for forming an electrofusion joint, wherein the mold according to claim 1 is used for injection molding.

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