JPH11118083A - Electric heating mat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent short-circuit caused by contact of an electric heating wire. SOLUTION: A through hole 14 is provided in the approximately central part of a synthetic resin sheet 13, a spiral groove 15 around the through hole 14 is carved on one surface of the sheet 13, a heating die is pressed to the suitable part of the front surface of the sheet after inserting an electric heating wire 2 along the spiral groove 15, and an opening of the spiral groove 15 is partially blocked with molten resin. When a straight line extending along the front surface of the sheet 13 and passing the center of the through hole 14 is taken as a reference line X, more than three winds on the outermost peripheral side of the spiral groove 15 is crushed by the heating die over the width of 1/60 to 1/15 of the length of the circumference of the spiral groove 15, on the straight line with the through hole 14 as the center and inclined at 45 deg. in relation to the reference line X, and molten resin is filled in the spiral groove 15 to fix the electric heating wire 2.

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 the branch saddle 11
When the back surface of the branch saddle 11 is pressed against the outer peripheral surface of the synthetic resin tube 3 to perform fusion bonding, the back surface of the branch saddle 11 is in close contact with the outer peripheral surface of the synthetic resin tube 3 in the zones S1 and S2 shown in FIG. Is the back of the branch saddle 11 and the synthetic resin tube 3
Is considered to be due to the fact that the outer peripheral surface does not adhere.

That is, in the zones S1 and S2 in which the back surface of the branch saddle 11 is pressed against and adheres to the outer peripheral surface of the synthetic resin tube 3, the movement of the heating wire 2 is restricted by the resin. The heating wire 2 is not restrained by the resin at the portion where the back surface of the heating wire floats without adhering to the outer peripheral surface of the synthetic resin tube 3, so that the heating wire 2 is easily moved. Moreover, since the thermal expansion of the heating wire 2 is larger on the outer peripheral side, short-circuiting of the heating wire 2 is likely to occur on the outer peripheral side of the spiral, and the back surface of the saddle 11 does not adhere to the outer peripheral surface of the synthetic resin tube 3, that is, a floating portion. For example, it is considered that this occurs on a line inclined by 45 degrees with respect to the axis XX of the synthetic resin tube 3. In particular, the short circuit of the heating wire 2
It is considered that this is likely to occur due to a molding failure of the electrothermal mat 1a integrally fused to the back surface of the branch saddle 11.

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 equipped with a heating wire 2 is set in a mold, and an electric heating mat is provided 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 mold is pressed radially around the through hole 14 against the surface of the sheet 13, and the spiral groove 15 is formed with a molten resin. The opening is partially closed.

However, as shown in FIG. 7, when the opening of the spiral groove 15 is closed with the molten resin, if the molten resin is not sufficiently filled in the spiral groove 15, the heating wire 2 is fixed in a floating state. There is. When the space E is formed between the heating wire 2 and the bottom of the spiral groove 15, the heating wire 2 is not fixed but free, and the portion where the heating wire 2 is not fixed is located on the outermost peripheral side of the spiral groove. It is considered that a short circuit of the heating wire 2 occurs when the heating wire 2 is generated at a position of about 3 to 4 turns and at an angle of about 45 ° with respect to the axis X of the synthetic resin pipe 3.

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 an electric heating wire generates heat and thermally expands, the heating wires wound in a spiral form do not short-circuit. .

[0009]

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 was formed and a spiral groove centered on the through hole was formed on one side of the sheet, a heating wire was inserted along the spiral groove, and a heating mold was pressed into a proper position on the surface of the sheet and melted. When the opening of the spiral groove is partially closed with a resin, and a straight line that passes along the surface of the sheet and passes through the center of the through-hole is set as a reference line, the reference line is approximately 45 ° relative to the center of the through-hole. On the inclined straight line, three or more rounds on the outermost peripheral side of the spiral groove are crushed by a heating mold over a width of 1/60 to 1/15 of the circumferential length of the spiral groove on the outermost peripheral side, and the molten resin is swirled. The heating wire is fixed by filling the groove.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic plan view of an electric heating mat showing one embodiment of the present invention, FIG. 2 is a partial sectional view showing a state where a heating wire is inserted into a spiral groove, and FIG. 3 is a spiral groove formed by pressing a heating die against a synthetic resin sheet. FIG. 2 is a partial cross-sectional view showing a state in which an opening of the heating device is closed with a molten resin, in which 1a is an electric heating mat;
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.
Can be suitably used. A through hole 14 is provided substantially at the center of the sheet 13, and a spiral groove 15 having the through hole 14 as a center is formed on one surface of the sheet 13. Then, the heating wire 2 is inserted along the spiral groove 15, and terminal pins 21 are connected to both ends of the heating wire 2.

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.

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, when a straight line along the surface of the sheet 13 and passing through the center of the through hole 14 is set as the reference line X, the reference line X
The heating wire 2 inserted into the spiral groove 15 is fixed by eight molten resins extending radially along a straight line passing through the center of the through hole 14 and orthogonal to the reference line X and a straight line inclined at 45 °. . In the outermost three or four spiral grooves 15 on the outermost side, the interval between the eight molten resins is widened, so that the intermediate position may be closed with the molten resin extending radially.

On a straight line inclined at an angle of about 45 ° with respect to the reference line X about the through hole 14, a width W of 1/60 to 1/15 of the circumferential length of the spiral groove on the outermost peripheral side is formed. Three or more outermost circumferential sides of the spiral groove 15 are integrally crushed by a heating mold, and the molten resin is filled into each spiral groove 15 to fix the heating wire 2. At this time, if the width W crushed by the heating mold is smaller than 1/60 of the circumferential length of the spiral groove 15 on the outermost peripheral side, the amount of the molten resin filled in each spiral groove 15 is insufficient, so that the heating wire 2 Is weakened, and when the heating wire 2 generates heat, a short circuit may occur. Although the wider the crushing width W is, the better the result is obtained. However, in practice, it is experimentally confirmed that a sufficient effect can be obtained at 1/15 or less of the circumferential length of the spiral groove 15 on the outermost peripheral side. I was assured. still,
In the drawings, three spiral grooves 15 located on the outermost peripheral side are crushed integrally over a width W, and each spiral groove 15 is filled with a molten resin. The heating wire 2 may be fixed by filling the spiral groove 15 with the molten resin.

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. When the branch pipe joint is formed such that the reference line X of the electric heating mat 1a coincides with the axis XX of the connected pipe, a desired electro-fusion type branch pipe joint is formed. can get.

[0016]

As described in detail above, the electric heating mat according to the present invention has a structure in which the heating wire is likely to be short-circuited at the time of fusion bonding with the pipe to be connected, that is, approximately 45 ° to the pipe axis of the pipe to be connected.上 On a sloping straight line, three or more outermost circumferences of the spiral groove are crushed by a heating mold over a width of 1/60 to 1/15 of the circumferential length of the outermost spiral groove, and melted. Since the heating wire is fixed by filling the spiral groove with the resin, even if the heating wire generates heat and thermally expands, its movement is prevented. 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 an electric heating mat 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 partial cross-sectional view showing a state in which a heating die is pressed against a synthetic resin sheet to close an opening of a spiral groove with a molten resin.

FIG. 4 is a schematic plan view showing a conventional electric heating mat.

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.

FIG. 7 is a partial cross-sectional view of a conventional example showing a state in which a heating die is pressed against a synthetic resin sheet to close an opening of a spiral groove with a molten resin.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Branch saddle joint 11 Branch saddle 12 Branch pipe 13 Synthetic resin sheet 14 Through hole 15 Spiral groove 2 Heating wire 3 Synthetic resin pipe (connected 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 a heating wire is inserted along the spiral groove before the surface of the sheet. When the heating die is pressed in place and the melted resin partially closes the opening of the spiral groove, and when a straight line along the sheet surface and passing through the center of the through hole is used as a reference line, the reference line is 1/60 of the circumferential length of the outermost spiral groove on a straight line inclined approximately 45 ° about the through hole.
An electric heating mat characterized in that three or more outermost circumferential sides of a spiral groove are crushed by a heating mold over a width of up to 1/15, a molten resin is filled in the spiral groove, and a heating wire is fixed.