JPH07308968A - Electric heating mat and manufacture of branch tube joint - Google Patents

Abstract

PURPOSE:To provide an electric heating mat and a method for manufacturing a branched tube joint using the mat in which an electric heating wire is not short-circuited by preventing a positional deviation, etc. CONSTITUTION:A through hole 11 is provided substantially at the center of a synthetic resin sheet 1, and an uneven part 110 is provided on the inner periphery of the hole 11. An electric heating mat 1a with a spiral groove 12 centering around the hole 11 on one side surface of the sheet 1, and which an electric heating wire 2 engaged closely along the groove 12 is set in molds, and then molten resin in injected in a cavity. Accordingly, when a branched tube joint is molded, the wire is not short-circuited.

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 in which a heating wire is embedded in a spiral shape, and a method for manufacturing a branch pipe joint using the electric heating mat.

[0002]

2. Description of the Related Art As an electric heating mat of this type, for example, in Japanese Utility Model Laid-Open No. 4-110297, 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, a heating wire is attached along the groove, and the end of the heating wire drawn out from the inner peripheral end of the spiral groove is supported at a predetermined height by a protrusion provided on the upper surface of the sheet, thereby forming a spiral shape. There has been proposed an electric heating mat in which a heating wire that crosses above the groove is not short-circuited with a heating wire mounted in the groove.

[0003]

However, since this conventional electric heating mat is not provided with the unevenness for positioning, when the branch pipe joint is formed using this electric heating mat, the heating wire may be short-circuited. there were. That is, when the electric heating mat is set in the mold cavity, a positional deviation may occur and the heating wire protruding from the spiral groove may short-circuit with the heating wire crossing over the spiral groove.

The present invention has been made to solve the above problems, and provides an electric heating mat that prevents occurrence of displacement and the like and does not short-circuit the heating wire, and a method for manufacturing a branch pipe joint using the electric heating mat. To do.

[0005]

According to a first aspect of the present invention, a synthetic resin sheet is provided with a through hole substantially in the center thereof, and an unevenness is provided on the inner periphery of the through hole, and the through hole is centered on one side of the sheet. It is characterized in that a spiral groove is provided in and the heating wire is closely fitted along the groove.

According to a second aspect of the present invention, a through hole is provided substantially in the center of the synthetic resin sheet, and an unevenness is provided on the inner periphery of the through hole, and a spiral groove centering on the through hole is formed on one surface of the sheet. An electric heating mat is provided in which heating wires are closely fitted along the groove, and the electric heating mat is placed on the lower mold and projections protruding from the upper surface thereof are inserted into the through holes and unevenness is formed. Fit and position. Then, the upper mold, the core, etc. are closed, and then the molten resin is injected into the mold cavity.

[0007]

Since the through hole is formed in the substantially central portion of the synthetic resin sheet and the inner circumference of the through hole is provided with the unevenness, the electric heating mat is placed on the lower mold and the projection protruding from the upper surface thereof is penetrated. When it is inserted into the hole and fitted with the concavo-convex, displacement and rotation do not occur when the molten resin is injected into the mold cavity.

[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 which reference numeral 1 is a synthetic resin sheet, 2 is a heating wire such as a nichrome wire, 1a is an electric heating mat, and 3 is a branch tube. It is a joint.

The synthetic resin sheet 1 is a thin sheet made of synthetic resin such as polyethylene, polypropylene or polybutene. A through hole 11 is provided at substantially the center of the sheet 1, and one sheet is provided on the inner periphery of the through hole 11. To a plurality of convex portions 110
To provide. The convex portion 110 is for preventing the positional displacement and rotation when the sheet 1 is set in the mold, and can have an appropriate shape as long as it has this function. Further, a concave portion may be provided instead of the convex portion 110.

Further, a spiral groove 12 is provided on one surface of the sheet 1 around the through hole 11, and the heating wire 2 is closely fitted along the groove 12. Then, the end of the heating wire 2 drawn from the inner peripheral end of the spiral groove 12 is hooked on the tip of the protrusion 13 provided on the upper surface of the sheet 1, and the end of the electric wire 2 is drawn to the outer peripheral side across the spiral groove 12 and the end thereof is drawn. The terminal pin 21 is connected to the part. Similarly, the terminal pin 21 is connected to the end of the heating wire 2 drawn from the outer peripheral end of the spiral groove 12.

The height of the protrusions 13 can be appropriately set according to the wire diameter of the heating wire 2 and the like.
When set to 10 mm, the heating wire 2 which is supported by the projection 13 and crosses over the spiral groove 12 does not short-circuit with the heating wire 2 mounted in the groove 12. On the other hand, the spiral groove 1
The pitch P of 2 can be appropriately set according to the wire diameter of the heating wire 2, etc., but the heating wire 2 having a wire diameter of 0.3 to 1.5 mm
In the case of using, the pitch P of the grooves 12 is 0.8 to 5.
It may be set appropriately in the range of 0 mm. Further, when the heating wire 2 is fitted into the spiral groove 12 and then the heater is applied to the sheet 1 to partially close the groove 12 with the melted resin, the heating wire 2 is removed from the groove 12. It is preferable because it can be prevented from protruding.

The electric heating mat 1a of the present invention has the above-mentioned structure. When a branch pipe joint is formed by using the electric heating mat 1a, the electric heating mat 1a as shown in FIG.
Is set in the mold. That is, the electric heating mat 1a is placed on the lower mold 4 curved in a semi-circular shape with one surface of the heating wire 2 fitted in the spiral groove 12 facing upward, and the protrusion 41 protruding from the upper surface of the lower mold 4. And the concave and convex 110
To fit. Therefore, the upper die 5 and the core 7 are closed, and the terminal holding plug 6 attached to the terminal pin 21 is fitted and fixed in the support hole 51 of the upper die 5.

Then, when a molten resin such as polyethylene, polypropylene or polybutene is injected into the mold cavity, the molten resin fills 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 projection 41 projecting from the upper surface of the lower mold 4 is fitted in the through hole 11 of the electric heating mat 1a, the electric heating mat 1a is prevented from being displaced or rotated and has a spiral shape. The heating wire 2 does not jump out from the groove 12 and short-circuit with the heating wire 2 that crosses above the groove 12. Therefore, when the mold is opened after waiting for the molten resin to solidify, the branch pipe 32 integrally projects on the upper surface of the saddle 31 which is curved in a substantially semi-arcuate shape as shown in FIG. A branch pipe joint 3 in which 2 is buried is obtained.

[0014]

As described above in detail, according to the present invention, the synthetic resin sheet forming the electric heating mat is provided with the through hole at the substantially central portion and the inner periphery of the through hole is provided with unevenness. When set in the mold, there is no displacement or rotation, and the heating wire does not jump out of the spiral groove and short-circuit with the heating wire that crosses above the groove. Therefore, if a branch pipe joint is molded using this electrothermal mat,
There is no risk of short-circuiting the heating wire, and a branch pipe joint of stable quality can be manufactured.

[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 4 lower mold 5 upper mold 11 through hole 12 spiral groove 13 protrusion 110 unevenness 1a electric heating mat

Claims (2)

[Claims] 1. A synthetic resin sheet (1) is provided with a through hole (11) at substantially the center thereof, and an unevenness (110) is provided on the inner periphery of the through hole (11). An electric heating mat, characterized in that a spiral groove (12) is provided around the through hole (11), and a heating wire (2) is closely fitted along the groove (12). 2. A synthetic resin sheet (1) is provided with a through hole (11) substantially at the center thereof, and an unevenness (110) is provided on the inner periphery of the through hole (11), and the sheet (1) is provided with the above-mentioned structure on one side thereof. A spiral groove (12) is provided around the through hole (11), and an electric heating mat (1a) in which a heating wire (2) is closely fitted along the groove (12) is prepared. (1
a) is placed on the lower mold (4) and the protrusion (41) protruding from the upper surface thereof is inserted into the through hole (11) and fitted with the concavo-convex (110) for positioning, and then the upper mold ( 5), a method for manufacturing a branch pipe joint, characterized in that the core (7) and the like are closed and then the molten resin is injected into the mold cavity.