JPH01145113A - Manufacture of electrofusion coupling - Google Patents

Abstract

PURPOSE:To enable elimination of a press hole, by a method wherein a core is fitted with a molded sheet with a built-in heating wire and positioning of the same is performed by pressing a necessary part against the core by a press bar comprised of thermoplastic resin. CONSTITUTION:When a sheet 1, where a vertical groove is cut on the surface, a through-hole 2 is formed on the central part and a heating wire 3 has been pressed in the groove on the circumference of the hole 2, is bent into a semicircle and put over a core 4, a gap is made between them. A pair of press bars 7 made of thermoplastic resin is fitted to a mold 6 on symmetrical positions, at the time of combination, this press bar 7 presses in the sheet 1 on the circumference of the through-hole 2 and stuck close to the core 4. Molten resin is pressed into a cavity 5 for filling. The press bar 7 is melted according to this and integrated with the cast molten resin. With this construction, neither a hole is left behind in a molded product nor back-filling of the hole becomes necessary. Then it becomes possible to perform confirmation of fusing by peeping into the hole by constituting so that the hole is formed after the press bar 7 has been drawn out.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is used to connect plastic pipes, and is applicable to electrofusion joints such as socket-shaped pipe joints and saddle joints in which heating wires are embedded in the contact surface with the pipes. Regarding manufacturing methods.

Conventional technology Electrofusion fittings are recently developed as pipe fittings and saddle fittings for plastic pipes used in water and sewage pipes, gas pipes, etc. 0 The illustration shows an electrofusion fitting used as a saddle fitting. It consists of a molded product with heating wires embedded in the joint surface with the pipe, and the fusion with the pipe is achieved by pressing it against the side of the pipe and applying electricity once.
This is done by heating and melting the contact surface. The manufacturing methods for such saddle joints include a process of winding a coated heating wire into a spiral, a process of heating and compressing the spirally wound coated heating wire and forming it into a sheet, and a process of forming a spiral formed into a sheet. The heating wire is bent into a semicircular shape and placed inside the mold.
A method involving injection molding is known, and a method for pipe joints is also known, in which a heating wire is spirally wound around a sleeve made of thermoplastic resin and then placed in a mold and then injection molded.

Problems to be Solved by the Invention Regarding pipe joints, similar to saddle joints, heating wires bent into a deformed spiral shape, zigzag shape, etc. are formed into a sheet, which is then wrapped around a cylindrical core and injection molded. is possible. In order to obtain saddle joints and pipe joints using the methods described above, it is necessary to position the sheet in close contact with the core during molding. must be kept.

To solve this problem, the present invention uses a presser bar to press down the sheet at desired locations, but the problem is that holes are created in the molded product after the presser bar is pulled out.

Means for Solving the Problems In the first invention, the presser bar is made of thermoplastic resin so that it is melted during molding and integrated with the molding material, thereby preventing holes from forming in the molded product. That is, the first invention provides a sheet in which a heating wire is formed into a spiral shape, a deformed spiral shape, a zigzag shape with a constant or variable swing width, or a combination thereof, and then this sheet is attached to a semicircular or circular core. This is characterized in that the required portions are pressed against the core using a presser rod made of thermoplastic resin to position them, set, and then injection molded.

To obtain a sheet, for example, a method is used in which a coated heating wire is bent into a spiral shape, a zigzag shape, etc. and then heated and pressed to form it into a sheet shape;
There are methods such as pushing a heating wire into a groove formed in a sheet made of thermoplastic resin, or pushing a heating wire into a sheet and fusing it.

To attach a sheet to a core, the sheet is usually formed into a semicircular shape in advance and then fitted onto the core (if the sheet is circular, it is forcibly expanded once and then fitted).
Alternatively, it may be bent along the circumferential surface of the core. When the sheet is previously formed into a semicircular or substantially circular shape, it is preferably formed so that its radius of curvature is slightly smaller than the radius of curvature of the core. Forcibly expanding and fitting increases the degree of adhesion to the core, and in the case of a semicircular sheet, by pressing the center part,
This is because, in the case of a circular sheet, by pressing the joint portion of the sheet around the core, the sheet can be firmly held in close contact with the core without shifting.

The presser bar does not have to be the same material as the molding material as long as it melts during molding, but it is preferably made of the same material.

The second invention is to leave the hole formed after the presser bar is removed and use it as an inspection hole to check whether there is fusion between the plastic pipe and the electrofusion joint. .

Therefore, the second invention provides a sheet in which a heating wire is formed into a spiral shape, a deformed spiral shape, a zigzag shape with constant or deformed swing 111, or a combination thereof, and then this sheet is attached to a semicircular or circular core. The desired part is pressed against the core with a presser bar to position it, set, and then injection molded, and after the presser bar is pulled out after molding, a hole is formed that reaches the sheet from the outside surface. That is.

Embodiment Figures 1 to 3 show the manufacturing method of the saddle joint.
First, a spiral groove is cut on the surface of a thermoplastic resin sheet 1, a through hole 2 is formed in the center, and a heating wire 3 is pushed into the groove around the hole (Fig. 1). 1 is bent into a semicircular shape, and its radius of curvature is formed to be smaller than the radius of curvature of the core 4, which has a semicircular cross section. The sheet 1 is then placed over the core 4 (FIG. 2). In this state, the sheet 1 has a smaller radius of curvature than the core, so it is installed in a swollen state over the core 4, leaving a gap between it and the core. Subsequently, a mold 6 that cooperates with the core 4 to form a saddle joint-like cavity 5 is assembled and connected, but prior to assembly, the mold 6 is made of thermoplastic resin, preferably the same material as the molding material. Presser bar 7
A pair of presser feet 7 are installed in symmetrical positions, and when assembled, the presser foot 7 presses down the sheet 1 around the through hole 2 and brings it into close contact with the core 4 (Fig. 3). Molten resin is press-fitted and filled. Along with this, the presser bar 7 is melted and integrated with the injected molten resin. Note that even if the presser rod 7 melts and loses its function of pressing the sheet 1, the sheet will not swell due to the pressure of the molten resin. Also, during molding, the attachment part T of the presser bar 7 to the mold 6
The molded product is also melted, so that a mounting portion T for the presser bar protrudes from the molded product, but this portion is cut out if necessary.

Figures 4 to 6 show a method for manufacturing a socket-shaped pipe joint, in which a zigzag groove is cut on the surface of a thermoplastic resin sheet 11, a heating wire 12 is pushed into the groove (Figure 4), and then This sheet 11 is bent into a circle with a diameter one smaller than the core 13 with a circular cross section.Then, it is forcibly expanded as shown in FIG. Rotate it a half turn until it is at the upper end as shown in the figure. Next, the upper mold 16 is assembled on the fixed lower mold 15,
Prior to assembly, a plurality of presser rods 17 made of thermoplastic resin are attached to the upper mold 16 in rows arranged in the axial direction.
During assembly, this presser bar 17 presses the joints of the sheets 11 and tightly fixes the sheets 11 to the core 13 (Fig. 6).
The molten resin is press-fitted into the cavity 18 formed around the core 13 and filled.

In each of the above embodiments, the presser bar 7 or 17 is made of thermoplastic resin and is melted during molding.
In other embodiments, the material is non-meltable, such as the mold 6 or 1.
It is made of the same material as 6 and fixed to the mold, and a hole is formed in the molded product after the presser rod that reaches the sheet from the outside surface is removed, and by looking into the hole, the plastic tube and electrofusion are formed. Check whether fusion with the joint has been performed. That is, when fusion is performed, the fusion can be confirmed by partially or most of the hole being filled.

In the above embodiment, a sheet into which heating wires are pressed is used, and this is bent into a semicircular or circular shape and attached to the core, but the heating wires are attached by being fused to the sheet. Alternatively, you can use a sheet made by bending the coated heating wire into a spiral shape, zigzag shape, etc. and heat-pressing it without using a sheet, or by forming the sheet into a semicircle or circle in advance. Instead of bending it, it can also be attached by bending it along the circumference of the core.

Effects of the Invention According to the first invention, the presser rod that presses and positions the desired part of the sheet is made of thermoplastic resin and is melted during molding, so no holes remain in the molded product and there is no need to backfill the holes. It disappears.

According to the second invention, a hole is formed in the molded product that reaches the sheet from the outer surface, and by looking through the hole, it is possible to confirm whether or not the plastic pipe and the electrofusion joint have been fused. It becomes easy to do.

[Brief explanation of the drawing]

Figures 1 to 3 show the manufacturing method of the saddle joint. Figure 1 is a plan view of a sheet with heating wires attached in a spiral shape,
3 is a sectional view showing a state in which the sheet is folded into a semicircular shape and placed over a core, and FIG. 3 is a sectional view showing a state in which a mold is assembled. Figures 4 to 6 show the manufacturing method of socket-shaped pipe joints. Figure 4 is a plan view of a sheet with heating wires attached in a zigzag shape, and Figure 5 is a diagram showing how the sheet is fitted to the core. FIG. 6 is a sectional view showing the state in which the upper and lower molds are combined. 1.11... Thermoplastic resin sheet 3.12... Heating wire 4.13... Core 5.18...
Cavity 6.15.16... Mold 7.17... Presser bar Applicant Mitsui Petrochemical Industries Co., Ltd. Agent Patent Attorney Akira Sato - 3 sales (1 in heavy industry (method)) February 26, 1988 Director General of the Patent Office Kunio Ogawa1, Indication of the case 1988 Patent Application No. 3039252, Title of the invention Method for manufacturing electrofusion kumite3, Relationship with the person making the amendment ()1 Residence of the patent applicant Address: 3-2-5 Kasumigaseki, Chiyoda-ku, Tokyo Name: Mitsui Petrochemical Industries Co., Ltd. Representative: Takebayashi Sho No 4 Address: 7-3-12-5, Chuo, Okiichi, 737 Japan
Date of amendment order: February 3, 1986 (all sending dates)
(February 23, 1988) 6. Subject of amendment: Brief description of drawings in specification and document certifying authority of representation 7. Contents of amendment +11 Specifications;! ) On page 11, line 3, correct “2nd wa” to “2nd wa”.

Claims (9)

[Claims] (1) Obtain a sheet of heating wire formed into a spiral shape, a deformed spiral shape, a zigzag shape with a constant or variable swing width, or a combination of these shapes, and then attach this to a semicircular or circular core to form the desired part. A manufacturing method for an electrofusion joint, which is characterized by pressing and positioning the core against the core with a presser rod made of thermoplastic resin, setting it, and then injection molding it. (2) The method for producing an electrofusion joint according to claim 1, wherein the sheet is obtained by heat-pressing coated heating wires bent in a spiral shape, a deformed spiral shape, a zigzag shape, etc. (3) The method for manufacturing an electrofusion joint according to claim 1, wherein the sheet is made of a thermoplastic resin fastening sheet with grooves cut on the surface and heating wires pushed into the grooves. (4) The method for producing an electrofusion joint according to claim 1, wherein the sheet is made of a thermoplastic resin sheet with heating wires pressed into the surface and fused. (5) The method for manufacturing an electrofusion joint according to claim 1, wherein the sheet is formed into a semicircular or circular shape and then fitted into the core. (6) The method for manufacturing an electrofusion joint according to claim 5, wherein the sheet is formed to have a smaller radius of curvature than the core. (7) The method for manufacturing an electrofusion joint according to claim 1, wherein the sheet is bent while following the circumferential surface of the core. (8) The method for manufacturing an electrofusion joint according to claim 1, wherein the push rod is made of the same material as the molding material. (9) Obtain a sheet of heating wire formed into a spiral shape, a deformed spiral shape, a zigzag shape with a constant width or a modified width, or a combination thereof, and then attach this to a semicircular or circular core to form the desired part. Manufacture of an electrofusion joint, characterized in that the core is pressed against the core with a presser rod for positioning, set, and then injection molded, and after the presser rod is pulled out after molding, a hole is formed that reaches the sheet from the outer surface. law