JPH11141786A - Electric heating mat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strongly fix an electric heating wire, and surely prevent short circuit of the electric heating wire by inscribing a spiral groove for inserting a electric heating wire around a penetrating hole on one surface of a synthetic resin made sheet provided with the penetrating hole on a nearly center part, and penetrating small holes on a bottom part of the spiral groove at a predetermined interval. SOLUTION: A heating mat 1a is formed by spirally mounting a electric heating wire 2 on a synthetic resin made sheet 13, and a spiral groove 15 is inscribed around a penetrating hole 14 on one surface of the sheet 13. Small holes 16 are arranged on a bottom part of the spiral groove 15 at a predetermined interval, the electric heating wire 2 is inserted along the spiral groove 15, and terminal pins 21 are connected to both ends of the heating wire 2. A heating mold is pushed down on a suitable position of the sheet 13, and an opening part of the spiral groove 15 is partially blocked by fused resin. When the electric heating mat 1a is fused integratedly with a back surface of the branch saddle 11, air stagnated in the spiral groove 15 is discharged from the small holes 16, and thereby, the electric heating wire 2 is strongly fixed by fused resin filled in the spiral groove 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating mat which is integrally fused to a back surface of a branch saddle which is curved in a substantially semicircular arc when an electric fusion type branch pipe joint is injection-molded.

[0002]

2. Description of the Related Art When a branch pipe is taken out from a polyethylene gas pipe or a hot water supply pipe, an electrofusion type branch pipe joint shown in a sectional view in FIG. 4 is used. In this branch pipe joint 1, a branch pipe 12 is integrally protruded from the upper surface of a branch saddle 11 curved in a substantially semicircular arc shape. Both ends of the heating wire 2 are connected to terminal pins 21 protruding from the upper surface of the saddle 11. When connecting the branch pipe joint 1 to the synthetic resin pipe 3,
Electric current was supplied to the heating wire 2 while pressing the back surface of the saddle 11 against the outer peripheral surface of the synthetic resin tube 3, and the two were fused and joined by the heating wire 2 that generated heat.

[0003]

However, in the conventional electric fusion type branch pipe joint, when the heating wire 2 generates heat, the adjacent heating wires 2 and 2 may come into contact with each other. FIG. 5 is a state view of the branch saddle 11 as viewed from the back side.
When the heating wire 2 generates heat and thermally expands, a partial bulge T occurs in the outer peripheral direction, and this bulge T comes into contact with the adjacent outer heating wire 2 to cause a short circuit.

In particular, short-circuiting of the heating wire 2 tends to occur more easily on the outer periphery than on the inner periphery of the spiral, and tends to occur at a position inclined at 45 degrees with respect to the axis XX of the synthetic resin tube 3. Was. One of the causes is that air is formed around the heating wire 2 when the electric fusion type branch pipe joint is injection-molded.

In general, an electric fusion type branch pipe joint is integrally formed by injection. At the time of injection molding, an electric heating mat 1a having a heating wire 2 is set in a mold, and an electric heating mat is placed on the back surface of the branch saddle 11. The mat 1a is integrally fused. As shown in FIG. 6, the electric heating mat 1 a has a through hole 14 at a substantially central portion of a synthetic resin sheet 13 made of polyethylene or the like, and a spiral groove around the through hole 14 on one surface of the sheet 13. 15, the heating wire 2 is inserted along the spiral groove 15, and then a heating die is pressed radially around the through hole 14 against the surface of the sheet 13, and the spiral groove 15 is formed of molten resin. The heating wire 2 is temporarily fixed by partially closing the opening.

When the electric heating mat 1a is set in a mold and the molten resin is injected into the cavity, if the molten resin does not spread to all corners of the spiral groove 15 into which the electric heating wire 2 is inserted, the periphery of the electric heating wire 2 There is a pool of air. Heating wire 2
When the heating wire 2 generates heat and thermally expands, the movement of the heating wire 2 becomes easy, and the thermal expansion of the heating wire 2 is larger on the outer peripheral side of the spiral.
It is considered that the heating wire 2 is short-circuited on the outer peripheral side of the spiral.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an electric heating mat in which, when the electric heating wire generates heat and thermally expands, the heating wires wound in a spiral form do not short-circuit. .

[0008]

SUMMARY OF THE INVENTION The present invention relates to an electric heating mat which is integrally fused to the back surface of a synthetic resin branch saddle curved in a substantially semicircular arc shape, and penetrates a substantially central portion of a synthetic resin sheet. A hole is provided, and a spiral groove centered on the through hole is formed on one surface of the sheet. Small holes are provided at predetermined intervals at the bottom of the spiral groove, and then heating wires are formed along the spiral groove. Is inserted.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic plan view of a synthetic resin sheet showing one embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing a state where a heating wire is inserted into a spiral groove, and FIG. 3 is an electrofusion type obtained by injection molding. It is sectional drawing of the principal part of a branch pipe joint, 1a is a heating mat in the figure, 2 is a heating wire.

The heating mat 1a is formed by spirally mounting the heating wire 2 on a synthetic resin sheet 13 such as polyethylene or polybutene. The synthetic resin sheet 13 has a thickness of 1 to 4 mm.
The through-hole 14 is provided substantially at the center of the sheet 13, and a spiral groove 15 centered on the through-hole 14 is formed on one surface of the sheet 13. Then, small holes 16 penetrating the sheet 13 are provided at predetermined intervals at the bottom of the spiral groove 15, and the heating wire 2 is inserted along the spiral groove 15, and terminal pins 21 are provided at both ends of the heating wire 2.
Are connected.

The heating wire 2 can be appropriately selected according to the diameter and the like of a synthetic resin pipe (connected pipe) to which the branch saddle 11 is connected. In general, a nichrome wire having a wire diameter of 0.3 to 1.5 mm, A copper nickel wire or the like can be suitably used. Further, the interval between the heating wires 2 wound in a spiral shape is set at 0.1 mm according to the wire diameter or the like.
It can be set within a range of 6 to 5.0 mm. At this time, the width H of the spiral groove 15 is substantially equal to the diameter of the heating wire 2,
The depth D is preferably set slightly larger than the diameter of the heating wire 2. Further, a small hole 1 provided at the bottom of the spiral groove 15
6 is preferably slightly smaller than the diameter of the heating wire 2.

After the heating wire 2 is inserted along the spiral groove 15, a heating die (not shown) is pressed to an appropriate position on the surface of the sheet 13, and the opening of the spiral groove 15 is partially closed with a resin melted. At this time, as in the conventional example shown in FIG.
The heating wire 2 inserted into the spiral groove 15 may be temporarily fixed by a plurality of molten resins extending radially with the center of the heating wire 4.

The above-described electric heating mat 1a according to the present invention is shown in FIG.
When the branch pipe joint in which the branch pipe 12 integrally protrudes from the upper surface of the branch saddle 11 which is curved in a substantially semicircular arc like the conventional branch pipe joint shown in FIG. It is what is fused. The air staying in the spiral groove 15 during this injection molding is discharged from the small hole 16, so that the heating wire 2 is
Without being fixed in a state of rising from the bottom of the
As shown in FIG. 3, the heating wire 2 is firmly fixed by filling the spiral groove 15 with the molten resin.

[0014]

As described in detail above, the electric heating mat of the present invention has a small hole at the bottom of the spiral groove into which the heating wire is inserted so that the air can be discharged smoothly. At this time, the heating wire is not fixed in a state where it rises from the bottom of the spiral groove, and the heating wire fills the spiral groove and is firmly fixed by the molten resin. For this reason, the electric fusion type branch pipe joint using the electric heating mat of the present invention can provide a reliable and strong fusion bonding without short-circuiting of the heating wire.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a synthetic resin sheet showing one embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a state in which a heating wire is inserted into a spiral groove.

FIG. 3 is a cross-sectional view of a main part of an electrofusion type branch pipe joint obtained by injection molding.

FIG. 4 is a schematic sectional view showing a conventional electro-fusion type branch pipe joint.

FIG. 5 is a state diagram of a conventional branch pipe joint viewed from the back side of a saddle.

FIG. 6 is a schematic plan view of a conventional electric heating mat.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric fusion type branch saddle joint 11 Branch saddle 12 Branch pipe 13 Synthetic resin sheet 14 Through hole 15 Spiral groove 16 Small hole 2 Heating wire 3 Synthetic resin pipe

Claims (1)

[Claims] 1. An electrothermal mat integrally fused to a back surface of a synthetic resin branch saddle curved in a substantially semicircular arc shape,
A through hole is provided substantially at the center of the synthetic resin sheet, and a spiral groove centered on the through hole is formed on one surface of the sheet, and small holes are formed at predetermined intervals at the bottom of the spiral groove. An electric heating mat characterized by inserting a heating wire along the spiral groove afterwards.