JPH07151287A - Electric heating mat - Google Patents

Abstract

PURPOSE:To shape a branched pipe joint free from the danger of the short- circuit of an electric heating wire and the leak of the fluid in a pipe along the electric heating wire. CONSTITUTION:A through hole 11 is formed nearly at the center part of a synthetic resin sheet 1, and a spiral-shaped groove 12 is formed, having the through hole 11 as center, on one-side surface of the sheet 1, and an electric heating wire 2 whose outer peripheral surface is covered with synthetic resin is closely fitted free from gap in the groove 12. Further, a terminal pin 21 is connected at the end part of the electric heating wire 2 pulled out from the inner peripheral edge and the outer peripheral edge of the spiral-shaped groove 12. Accordingly, the generation of the bubbles in the vicinity of the electric heating wire is prevented, and the short-circuit of the electric heating wire is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating used for forming a branch pipe joint in which a branch pipe is integrally projected on the upper surface of a saddle curved in a substantially semi-circular shape, and a heating wire is embedded in the rear surface of the saddle. Regarding Matt.

[0002]

2. Description of the Related Art As an electric heating mat of this type, for example, in Japanese Patent Publication No. 62379/1990, a through hole is provided in a substantially central portion of a synthetic resin sheet, and a spiral continuous groove is provided around the through hole. At the same time, an electric heating mat having heating wires attached along the groove has been proposed.

[0003]

However, since the conventional electric heating mat has a gap between the spiral groove and the heating wire mounted in the groove, the electric heating mat is set in the mold. When a branched pipe joint was manufactured by injecting molten resin into the cavity, air was sometimes trapped in the spiral groove and air bubbles were generated in the vicinity of the heating wire.

For this reason, when the heating wire is heated and the synthetic resin pipe is fusion-bonded to the back surface of the saddle, the heating wire comes into contact with each other to cause a short circuit, or the fluid inside the pipe is discharged through bubbles existing along the heating wire. There was a risk of leakage. In addition, this electric heating mat is made of a synthetic resin sheet between the end of the heating wire drawn from the inner circumferential end of the spiral groove and the heating wire mounted in the spiral groove in order to prevent contact between them. However, there is also a problem that the structure becomes complicated and it takes time to manufacture the electric heating mat.

The present invention has solved the above problems and provides an electric heating mat capable of forming a branch pipe joint without the risk of short-circuiting of the heating wire or leakage of fluid in the pipe along the heating wire. is there.

[0006]

The electric heating mat of the present invention comprises:
A through hole is provided in the center of the synthetic resin sheet, and a spiral groove is provided around the through hole on one side of the sheet, and a heating wire whose outer circumferential surface is covered with synthetic resin is closely fitted to the groove. Let Further, it is characterized in that terminal pins are connected to the ends of the heating wire drawn out from the inner peripheral end and the outer peripheral end of the spiral groove.

[0007]

Since the heating wire whose outer peripheral surface is covered with the synthetic resin is closely fitted into the spiral groove without any clearance, no clearance can be formed between the spiral groove and the heating wire. Further, since the outer peripheral surface of the heating wire is covered with the synthetic resin, the heating wire drawn out from the inner peripheral end of the spiral groove does not short-circuit even if it comes into contact with the heating wire closely fitted in the spiral groove.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is a plan view of an electric heating mat showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1, FIG. 3 is a sectional view showing a state in which the electric heating mat is set in a mold, and FIG. YY in Figure 3
5 is a sectional view of a branch pipe joint obtained by injection molding. In the drawing, reference numeral 1 is a synthetic resin sheet, 2 is an outer peripheral surface of a metal wire such as a nichrome wire, polyethylene, polypropylene, polybutene, etc. Heating wire coated with synthetic resin,
Reference numeral 1a is an electric heating mat, and 3 is a branch pipe joint.

The synthetic resin sheet 1 is a thin sheet made of synthetic resin such as polyethylene, polypropylene, polybutene, etc., and a through hole 11 is provided at substantially the center of the sheet 1, and the through hole 11 is formed on one side of the sheet 1. A spiral groove 12 is provided around the center. Therefore, the heating wire 2 is closely fitted along the spiral groove 12 without any gap. Further, the heating wire 2 is drawn out from the inner peripheral end and the outer peripheral end of the spiral groove 12, and the resin at the tip end thereof is peeled off to connect the terminal pin 21.

It is preferable that the bottom of the spiral groove 12 has a trapezoidal cross section with a narrow width, and the heating wire 2 having a trapezoidal cross section of a coating resin is closely fitted to the groove 12. . The pitch P of the spiral grooves 12 can be appropriately set according to the wire diameter of the heating wire 2, etc., but the wire diameter is 0.3.
When the heating wire 2 having a thickness of up to 1.5 mm is used, the pitch P of the grooves 12 may be appropriately set within the range of 0.8 to 5.0 mm. Further, when the heating wire 2 is fitted into the spiral groove 12 and then the heater is applied to melt the coating resin of the sheet 1 and the heating wire 2 so as to be partially fusion bonded, the groove 12 is formed. The heating wire 2 does not protrude from the.

The electric heating mat 1a of the present invention has the above-mentioned structure. When this electric heating mat 1a is used to form a branch pipe joint in which the heating wire 2 is embedded in the back surface of the saddle, it is shown in FIG. As described above, the electric heating mat 1a is set in the mold. That is, the electric heating mat 1a is placed on the lower mold 4 with one surface on which the spiral groove 12 is formed facing upward, and the upper mold 5 and the core 7 are placed.
While closing the mold, the terminal holding plug 6 attached to the terminal pin 21 is fitted and fixed in the support hole 51 of the upper mold 5.

Then, when a molten resin such as polyethylene, polypropylene or polybutene is injected into the mold cavity, the molten resin is filled in the mold cavity, and the electric heating mat 1a and the molten resin are integrally fused and joined. At the time of this injection molding, since the heating wire 2 is closely fitted in the spiral groove 12, air is not trapped in the groove 12.
Therefore, when the mold is opened after waiting for the molten resin to solidify,
As shown in FIG. 5, the branch pipe joint 3 is obtained in which the branch pipe 32 integrally projects on the upper surface of the saddle 31 which is curved in a substantially semi-circular shape, and the heating wire 2 is embedded on the rear surface of the saddle 11.

[0013]

As described above in detail, according to the present invention, the heating wire whose outer peripheral surface is covered with the synthetic resin is closely fitted to the spiral groove provided on one side of the synthetic resin sheet without any gap. When the branch pipe joint is manufactured using the mat, air is not trapped in the spiral groove and bubbles are not generated in the vicinity of the heating wire. Further, since the outer peripheral surface of the heating wire is covered with the synthetic resin, the heating wire drawn from the inner peripheral end of the spiral groove comes into contact with the heating wire closely fitted in the spiral groove to cause a short circuit. Without fail, it is possible to manufacture a branch pipe joint with stable quality.

[Brief description of drawings]

FIG. 1 is a plan view of an electric heating mat showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a cross-sectional view of a state where an electric heating mat is set in a mold.

FIG. 4 is a sectional view taken along line YY of FIG.

FIG. 5 is a sectional view of a branch pipe joint obtained by injection molding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 synthetic resin sheet 2 heating wire 3 branch pipe joint 11 through hole 12 spiral groove 1a electric heating mat

Claims (1)

[Claims] 1. A branch pipe in which a branch pipe (32) is integrally projected on an upper surface of a saddle (31) which is curved in a substantially semi-circular shape, and a heating wire (2) is embedded on the back surface of the saddle (31). An electric heating mat (1a) used for molding a joint (3), wherein a through hole (1) is formed in a substantially central portion of a synthetic resin sheet (1).
1) and the through hole (1
A spiral groove (12) is provided around 1), and the groove (12)
A heating wire (2) whose outer peripheral surface is coated with a synthetic resin is closely fitted without a gap, and at the end of the heating wire (2) drawn from the inner peripheral edge and the outer peripheral edge of the spiral groove (12). An electric heating mat having terminal pins (21) connected thereto.