JPH08428B2 - Heating element for melting thermoplastic resin products - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element for melting and bonding a thermoplastic resin such as polyethylene resin which cannot be bonded with an adhesive.

[0002]

2. Description of the Related Art Conventionally, a current is applied to an electric resistance wire which is spirally wound in advance on an inner peripheral surface of a receiving end of a resin joint into which an end portion of a resin pipe is inserted to join the pipe and the joint. There was a technique for melting and joining parts.

[0003]

In the above prior art, since the electric resistance wire in which the electric resistance wire is covered with the thermoplastic resin layer is used, it is necessary to form a gap so as not to contact each other and to wind it in a spiral shape. , It is not possible to handle the electric resistance wire by itself at the time of molding the joint, and a resin collar for shape retention with a spiral groove is required, and it is troublesome to insert the electric resistance wire into the spiral groove of the resin collar. There was a problem that required a lot of work.

[0004]

SUMMARY OF THE INVENTION Therefore, according to the present invention, an electric resistance wire covered with an insulating layer of glass fiber and an electric resistance wire not covered with the glass fiber are integrally covered in parallel with a thermoplastic resin layer. The electric resistance wire covered with an insulating layer of glass fiber and the uncoated electric resistance element wire are spirally wound on a flat surface so that the electric resistance element wire and the uncoated electric resistance element wire are alternately positioned. On the winding start end side, the electric resistance element wire covered with an insulating layer of glass fiber and one end of the electric resistance element wire not covered are connected, and the electric resistance element wire covered with an insulating layer of glass fiber is covered. The other end of the electric resistance wire is formed in a flat plate shape extending from the outer peripheral side, and adjacent electric resistance wires are integrally joined to maintain the flat plate shape.

In addition, an electric resistance wire in which an electric resistance wire covered with an insulating layer of glass fiber and an electric resistance wire not covered with the glass fiber are integrally covered in parallel with a thermoplastic resin layer The electric resistance wire coated with layers and the uncoated electric resistance wire are spirally wound on the cylindrical surface so that the electric resistance wires are wound alternately. Connect one end of the electric resistance wire covered with a layer and one end of the electric resistance wire not covered, and connect the electric resistance wire covered with the insulating layer of glass fiber and the other end of the electric resistance wire not covered. The electrical resistance wire is formed into a tubular shape that is drawn out from the other end side, and adjacent electrical resistance wires are integrally joined to maintain the tubular shape.

[0006]

[Operation] Therefore, according to the present invention, the electric resistance wire alone has the flat shape of the electric resistance wire spirally wound or the cylindrical shape of the electric resistance wire spirally wound. Therefore, the electric resistance wire can be handled as a single unit during joint molding, no special shape-retaining member is required, and the electric resistance wire can be easily embedded or mounted in the joint during joint molding or fusion welding. is there.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is an overall front view of a plate-shaped heating element (H1), FIG. 2 is an overall side view of the same, FIG. 3 is an overall front view of a tubular heating element (H2), and FIG. 4 is an overall side view of the same. Each heating element (H1)
(H2) is composed of the electric resistance wire (1) alone.

FIG. 5 and FIG. 6 show each heating element (H1) (H2).
FIG. 3 is an explanatory view of the electric resistance wire (1) forming the electric resistance wire (1), which is covered with a mesh-shaped insulating layer (2) having a relatively large mesh woven with an insulating glass fiber. The first nickel wire (3), which is a resistive element wire, and the bare second nickel wire (4), which is not covered with the insulating layer (2), are parallel to each other, and the thermoplastic resin (melt-bonded resin product The same material is desirable.) A flexible structure in which the first nickel wire (3) and the second nickel wire (4) are integrally covered with a layer (5) and one end side of which is connected by a conductor (6). Is the code. Therefore, each heating element (H1) (H2) formed of the electric resistance wire (1) also has flexibility.

FIG. 7 is a manufacturing explanatory diagram of a flat plate-shaped heating element (H1), which is a cylindrical shaft-shaped core body (7) having an inner opening through which the rotary shaft (6) penetrates, and the core body (7). A first disc (8) integrally attached to one end side of the core body and a detachable attachment to the other end side of the core body (7) with a space substantially equal to the thickness of the electric resistance wire (1). A second disc (9) facing the first disc (8) and a reel (11) consisting of a holding bolt (10) for holding the end of the electric resistance wire (1).

Then, the reel (11) is set on the rotary shaft (6), and one end of the electric resistance wire (1) cut to a predetermined length is pressed through a holding bolt (10) to each disk (8) ( 9) The electric resistance wire (1) is fixed to the first nickel wire (1) by rotating the reel (11) with an appropriate tensile load applied to the end of the electric resistance wire (1). 3) and the second nickel wire (4) are spirally wound so that they are alternately located.

After that, the holding bolt (10) and the second disc (9) of the reel (11) are removed, and the heating element (H
1) One side surface is exposed, and the thermoplastic resin layer (5) of the adjacent electric resistance wire (1) is partially melted at a plurality of positions to temporarily fix (12) as shown by the phantom line in FIG. After the flat shape of the heating element (H1) is maintained, the heating element (H1) is removed from the reel (11) to manufacture the flat heating element (H1) shown in FIGS. It is a thing.

That is, the electric resistance element wire (3) covered with the insulating layer (2) of glass fiber and the electric resistance element wire (4) not covered with the thermoplastic resin layer (5) are integrated in parallel. The electric resistance wire (1) coated with the electric resistance wire (3) covered with the insulating layer (2) of glass fiber and the electric resistance wire (4) not covered with the electric resistance wire (4) are alternately located, An electric resistance element wire (3) which is wound in a spiral on a plane and is covered with an insulating layer (2) of glass fiber on the winding start end side of the electric resistance wire (1) and an electric resistance element wire which is not covered. A flat plate shape in which one end of (4) is connected and the electric resistance wire (3) covered with the insulating layer (2) of glass fiber and the other end of the electric resistance wire (4) not covered are drawn from the outer peripheral side. And the adjacent electric resistance wires (1) are integrally joined together to form a heating element (H1) having a flat plate shape.

The connection terminals (13) are provided at the ends of the nickel wires (3) and (4) exposed from one end of the electric resistance wire (1).
(14) is connected. This is after cutting the electric resistance wire (1) to a predetermined length before forming the flat heating element (H1), or by connecting the flat heating element (H1). Either may be performed after formation.

FIG. 8 is a manufacturing explanatory view of a cylindrical heating element (H2), which comprises a winding roll (16) having an inner opening through which the rotary shaft (15) passes.

Then, the electric resistance wire (1) cut into a predetermined length is sandwiched between the roll (16) and a fixing claw (17) projecting to the outer peripheral side at one end of the roll (16) to make electricity. An appropriate tensile load is applied to the end of the resistance wire (1) to rotate the roll (16), and the movement guide pin (18) on the outer peripheral side of the roll (16) is electrically resistance wire in the axial direction of the roll (16). By moving in the winding direction of (1), the first nickel wire (3) is formed on the outer peripheral surface of the roll (16).
And the second nickel wire (4) are spirally wound so that they are alternately located.

After that, as indicated by the phantom line in FIG. 3, the second of the adjacent electric resistance wires (1) is formed on the outer peripheral surface of the heating element (H2).
The thermoplastic resin layer (5) is partially welded at a plurality of positions to temporarily fix it (19) to retain the tubular shape of the heating element (H2), and then from the roll (16) to the heating element (H2). By removing the cylindrical heating element (H
2) is manufactured.

That is, the electric resistance element wire (3) coated with the insulating layer (2) of glass fiber and the electric resistance element wire (4) not covered with the glass fiber insulating layer (5) are integrated in parallel with the thermoplastic resin layer (5). The electric resistance wire (1) coated with the electric resistance wire (3) covered with the insulating layer (2) of glass fiber and the electric resistance wire (4) not covered with the electric resistance wire (4) are alternately located, An electric resistance element wire (3) which is spirally wound on the cylindrical surface and is covered with an insulating layer (2) of glass fiber at one end of the electric resistance wire (1).
And an electric resistance element wire (4) which is formed by connecting one end of the electric resistance element wire (4) which is not covered and is covered with an insulating layer (2) of glass fiber, and an electric resistance element wire (4) which is not covered. The other end is formed into a tubular shape in which an electric resistance wire is wound and drawn from the other end side, and adjacent electric resistance wires (1) are integrally joined to form a heating element (H2) having a cylindrical shape.

A connection terminal (20) is provided at one end of the nickel wire (3) (4) exposed from one end of the electric resistance wire (1).
(21) is connected, and this is a cylindrical heating element (H
It may be performed either after cutting the electric resistance wire (1) to a predetermined length before forming 2) or after forming the cylindrical heating element (H2).

As shown in FIGS. 9 to 11, a pipe (22) which is a thermoplastic resin product and a saddle type joint (23) for branching a pipe line from the middle of the pipe (22) are joined by fusion welding. The flat plate-shaped heat generating element (H1) is used for such a case, and the saddle type joint (23) is provided with a saddle type seat (24) to be placed on the outer peripheral surface of the tube (22). A through-hole (26) corresponding to the branch port (25) opened in the seat (24) is provided in the center of the seat (24), and a connecting tube (27) for connecting the branch pipe is provided in the center of the outer periphery of the seat (24). It is formed upright and the lower end of the connecting tube (27) communicates with the through hole (26).

FIG. 9 shows a flat heating element (H1) embedded in the seat (24) inner surface of the saddle type joint (23) by insert molding. As shown in FIG. In order to arrange the heating element (H1) on the outer peripheral side of 26), the heating element (H1) is embedded in the inner surface of the seat (24) of the saddle type joint (23), and from one end surface of the seat (24). Connection terminal (1
3) The tips of (14) are projected in parallel. One surface of the embedded heating element (H1) is exposed along the inner surface of the seat (24). When the seat (24) is placed on the pipe (22), one surface of the heating element (H1) and the heating element (H1) are exposed. Other than ()
The inner surface of the tube, that is, the non-melting surface (28), is connected to the pipe (2
The outer peripheral surface of 2) is closely attached. Also, circular grooves (2) extending along the inner and outer peripheral end surfaces of the heating element (H1) are used.
9) (29) is provided on the inner surface of the seat (24) and its groove (2
9) is formed to have a thickness of the heating element (H1), that is, a depth approximately half the diameter of the electric resistance wire (1), and the groove (29) is used to form the heating element (H1) and its outer peripheral side and inner peripheral side. Non-melting surface (2
8) and the non-melting surface (28) part is directly heated by the heating element (H1) to prevent melting, and the resin that expands at the time of melting is released to the groove (29) and collected. It is configured to prevent the molten resin from flowing out to the outside of the joint (23).

The heating element (H
As shown in FIG. 11, the saddle type joint (23) in which 1) is embedded is set on the pipe (22) and clamped by a clamp tool or the like, and then the heating element (H) is passed through the connection terminals (13) and (14).
The electric resistance wires (3) and (4) of (1) are energized to start heat generation, and a joint (joined to each thermoplastic resin layer (5) and the heating element (H1) of the electric resistance wire (1) ( After melting the thermoplastic resin on the side of 23) and the thermoplastic resin on the side of the pipe (22), turning off the electric current and hardening the molten resin, the pipe (22) and the saddle joint (23) are melted. It is the one that is bonded and joined.

Further, as shown in FIG. 10, a saddle type joint (2
The flat heating element (H1) can also be attached to the inner surface of the seat (24) of 3) during the fusion welding work. In that case, the inner surface of the seat (24) of the joint (23) can be the above-mentioned. Groove (2
In addition to 9), the plate-shaped heating element (H1) is provided with grooves (29) (2
9) A recess (30) having the same depth as the thickness of the heating element (H1) mounted between them, and the connection terminal (1) of the heating element (H1).
3) By forming the terminal grooves (31) and (32) into which the (14) is fitted at the time of molding the joint (23), the joint (23)
The same function as that of the insert-molded heating element (H1) can be achieved.

By the way, the flat heating element (H1)
After manufacturing, press the pipe (22) and joint (23)
The heating element (H1) is entirely heated on one side or both sides at the time of this press working to weld the resin of the thermoplastic resin layer (5) of the electric resistance wire (1). By doing so, the final stop is performed and the shape is maintained in the form of the actual use state.

The inner diameter of the flat plate-shaped heating element (H1) is adjusted by appropriately adjusting the diameter of the core body (7) of the reel (11) using a collar or the like, and the holding bolt (10) is adjusted to the first position. It can be adjusted by appropriately moving and adjusting the first and second discs (8) and (9) in the diametrical direction, and the outer diameter of the heating element (H1) can be adjusted by appropriately adjusting the length of the electric resistance wire (1) and the number of windings. The inner shape and outer shape of the heating element (H1) can be appropriately converted into a substantially perfect circle, an elliptical shape, or a polygonal shape depending on the outer shape of the core body (7) of the reel (11). The form of H1) is all selected and determined by the joint surface of the thermoplastic resin product such as the pipe (22) and the joint (23).

As shown in FIGS. 12 to 14, when a pipe (33) which is a thermoplastic resin product and a plug-in joint (34) into which the end portion of the pipe (33) is inserted are joined by fusion welding, etc. The cylindrical heating element (H2) is used.

In FIG. 12, the cylindrical heating element (H2) is embedded in the inner peripheral surface of each receiving port (35) of the plug-in joint (34) by insert molding, and the opening end face of each receiving port (35). The tips of the connection terminals (20) (21) of the heating element (H2) are projected in parallel from the above. As shown in FIG. 14, the heating element (H2) in the embedded state has an inner peripheral surface at each receiving port (35). The pipe (33) is exposed along the inner peripheral surface of the
When the end portion of is inserted, the joint surface between the inner peripheral surface of the heat generating element (H2) and the pipe (33) other than the heat generating element (H2) (the inner peripheral surface of the receiving end and the pipe end joining of the receiving inner end) Surface), that is, the non-melted surface (3
6) is in close contact with the outer peripheral surface and the end surface of the pipe (33). Further, circular grooves (37) (37) along both end surfaces of the heat generating element (H2) are provided on the inner peripheral surface of each receiving port (35), and the groove (37) is the thickness of the heat generating element (H2), that is, Formed to a depth of approximately half the thickness of the electric resistance wire (1),
The groove (37) separates the heating element (H2) from the non-melting surface (36) on both ends thereof, and the non-melting surface (36)
The molten resin is prevented from being directly heated by the heating element (H2) to be melted, and the resin that expands at the time of melting is escaped and accumulated in the groove (37), so that the molten resin is provided outside each receiving port (35) of the joint (34). It is configured to prevent spillage.

Then, the heating element (H
Each socket (35) of the plug-in type joint (34) in which 2) is embedded
After the end of the pipe (33) is inserted into and clamped with a clamp, the heating element (H) is passed through the connection terminals (20) and (21).
A joint (34) joined to the thermoplastic resin layer (5) and the heating element (H2) of the electric resistance wire (1) by energizing the electric resistance wires (3) and (4) of 2) to start heat generation. ) Side thermoplastic resin and the pipe (33) side thermoplastic resin are melted,
By turning off the power and hardening the molten resin, the pipe (3
The end of 3) and the socket (35) of the plug-in type joint (34) are fusion-bonded.

Further, as shown in FIG. 13, a cylindrical heating element (H2) is provided on the inner peripheral surface of the receiving port (35) of the plug-in type joint (34).
It can also be attached and used during fusion welding work,
In that case, in addition to the groove (37), a cylindrical heating element (H2) is formed on the inner peripheral surface of the receiving port (35) of the joint (34) in the groove (37).
A recess (38) having the same depth as the thickness of the heating element (H2) mounted between (37) and a terminal groove (39) (where the connection terminals (20) and (21) of the heating element (H2) are fitted. 40) and 40) are formed at the time of molding the joint (34), the same function as that of the heating element (H2) insert-molded in the joint (34) can be achieved.

The inner diameter of the cylindrical heating element (H2) can be adjusted by appropriately converting the roll (16) into one having a different diameter, and the length of the heating element (H2) can be adjusted by the electric resistance wire ( It can be adjusted by appropriately adjusting the length and the number of turns of 1), and the cross-section (end face) shape of the heating element (H2) can be appropriately converted into a substantially perfect circle, an ellipse or a polygon depending on the outer shape of the roll (16). The form of these heating elements (H2) is all selected and determined by the joint surface of the thermoplastic resin product such as the pipe (33) and the joint (34).

Each of the flat plate-shaped and cylindrical heating elements (H
1) Electric resistance wire (1) which is the only component of (H2)
Since not only the coating of the thermoplastic resin layer (5) but also the coating of the insulating layer (4) is applied to one of the nickel wires (3), in the state where the electric resistance wire (1) is closely attached, In the case of the heating element (H1), it can be spirally wound, and in the case of the heating element (H2), it can be spirally wound.
1) The (H2) can be composed of the electric resistance wire (1) alone, and can retain its predetermined shape. This makes it possible to easily manufacture each heating element (H1) (H2) itself. , Heating elements (H1) such as the joints (23) (34)
A thermoplastic resin product in which (H2) is embedded by insert molding can be easily formed, and the heating elements (H1) and (H2) can be used by being attached to the thermoplastic resin product during the welding operation. .

Further, since the heating elements (H1) and (H2) are composed of the electric resistance wire (1) alone, they are extremely flexible and have excellent followability to the melt-bonded surface and a thermoplastic resin. It is very easy to handle when it is embedded in the product in advance or when it is attached separately during the welding process.

When the thermoplastic resin layer (5) of the electric resistance wire (1) and the resin on the joint surface of the thermoplastic resin product are melted during the fusion welding operation, the electric resistance wires (3) and (4) are brought into mutual contact. There is a possibility that the electric resistance wire (3) (4)
One of the electric resistance wires (3) is covered with the insulating layer (4), so that no short circuit occurs.

In the case of a flat plate-shaped heating element (H1), both ends of the electric resistance wire (1) of each of the heating elements (H1) and (H2) are aligned and drawn out from the outer periphery to form a cylindrical heating element ( In the case of H2), the thermoplastic resin product can be connected to the connector of the controller that controls the heat generation amount of the heating elements (H1) and (H2) by pulling out the heating elements (H1) and (H2) from one end side.
1) (H2) connection terminals (13) (14), (20)
(21) can be properly arranged, and by dividing the electric resistance wire (1) into two in the lengthwise direction, in the case of a flat plate-shaped heating element (H1), it can be arranged in any direction from the outer peripheral side. Since it can be drawn out to both ends of the electric resistance wire (1), and in the case of a cylindrical heating element (H2), both ends of the electric resistance wire (1) can be drawn out in any direction from this one end side, thermoplastic resin The connection terminals (13) (14), (20) (2) are placed at optimum positions in accordance with the product type and form, and the welding work environment.
1) can be arranged freely, and this can be done without overlapping the electric resistance wire (1), so that each heating element (H1)
It is possible to prevent the electrical phenomenon of (H2) from being partially different, and to uniformly heat and melt the resin on the joint surface of the thermoplastic resin product to perform proper fusion bonding. If this point is ignored, there is no problem even if the electric resistance wire (1) is superposed because of the insulating effect.

When the flat plate-shaped heating element (H1) is manufactured, the heating elements (H1) are saddle-shaped from the beginning by bending the disks (8) and (9) of the reel (11) in parallel. The shape can be formed along the inner surface of the seat (24) of the joint (23).

As shown in FIG. 16, the plug-in joint (34)
Heating elements (H2) (H2) insert-molded into
By connecting one end of each electric resistance element wire (3) (4) integrally to form a “0” point, the individual heating element (H
2) It is not necessary to connect one end of each electric resistance wire (3) (4) of (H2).

Further, the electric resistance wire (1) has a quadrangular outer shape, whereby each heating element (H1) (H2) is formed.
The gap between the resin surface to be melted and the surface to be melted can be made extremely smaller than that of the electric resistance wire (1) having a circular outer shape, which is extremely advantageous in terms of heat conduction efficiency and can improve workability. Is.

[0037]

As is apparent from the above examples, according to the present invention, an electric resistance element wire (3) coated with an insulating layer (2) of glass fiber and an electric resistance element wire (4) not covered with the insulation layer (2) are provided. An electric resistance wire (1) integrally covered with a thermoplastic resin layer (5) in parallel, an electric resistance wire (3) covered with an insulating layer (2) of glass fiber, and an electric resistance wire not covered with the electric resistance wire (3). The electric resistance wire (4) is spirally wound on a plane so that the wires (4) are alternately located, and the electric resistance wire (1) is covered with an insulating layer (2) of glass fiber on the winding start end side of the electric resistance wire (1) ( 3) and one end of the uncoated electric resistance element wire (4) are connected, and the electric resistance element wire (3) covered with the insulating layer (2) of glass fiber and the uncoated electric resistance element wire (3) The other end of 4) is formed in a flat plate shape extending from the outer peripheral side, and adjacent electric resistance wires (1) are integrally joined to form a flat plate shape. In addition, since the electric resistance element wire (3) coated with the insulating layer (2) of glass fiber and the electric resistance element wire (4) not covered are parallel to each other, the thermoplastic resin layer (5) The electric resistance wire (1) integrally covered with the electric resistance wire (1) covered with an insulating layer (2) of glass fiber (3)
And spirally wound on the cylindrical surface so that the uncoated electric resistance wires (4) are alternately located, and the insulating layer of glass fiber ( The electric resistance elemental wire (3) covered with 2) is connected to one end of the electric resistance elemental wire (4) which is not covered, and an insulating layer (2) of glass fiber is connected.
The other ends of the electric resistance element wire (3) that is covered with the electric resistance wire and the electric resistance element wire (4) that is not covered are formed into a tubular shape by winding the electric resistance wire and drawing out from the other end side, and the adjacent electric resistance wires Since the cylindrical shape is maintained by integrally joining (1), the electric resistance wire (1) alone is spirally wound into a flat plate shape or spirally wound. Since the cylindrical shape of the electric resistance wire (1) is maintained, the electric resistance wire (1) can be handled as a single unit at the time of joint molding, and a special shape-retaining member is unnecessary, and the electric resistance wire (1) ) Can be easily embedded or mounted in the joint during joint molding or fusion welding work.

[Brief description of drawings]

FIG. 1 is an overall front view of a flat heating element.

FIG. 2 is an overall side view of a flat heating element.

FIG. 3 is an overall front view of a tubular heating element.

FIG. 4 is an overall side view of a tubular heating element.

FIG. 5 is an overall explanatory diagram of electric resistance wires.

FIG. 6 is an explanatory cross-sectional view of an electric resistance wire.

FIG. 7 is an explanatory diagram for manufacturing a flat plate-shaped heating element.

FIG. 8 is an explanatory view of manufacturing a cylindrical heating element.

FIG. 9 is an explanatory view of using a flat plate-shaped heating element.

FIG. 10 is an explanatory view of using a flat plate-shaped heating element.

FIG. 11 is an explanatory view of using a plate-shaped heating element.

FIG. 12 is an explanatory view of using a cylindrical heating element.

FIG. 13 is an explanatory view of using a tubular heating element.

FIG. 14 is an explanatory view of using a cylindrical heating element.

FIG. 15 is an enlarged cross-sectional view of a surface to be fused.

FIG. 16 is an explanatory view of connection of a heating element.

[Explanation of symbols]

 (H1) Flat heating element (H2) Cylindrical heating element (1) Electric resistance wire (2) Insulating layer (3) (4) Electric resistance wire (5) Thermoplastic resin layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-37496 (JP, A) JP-A-3-71824 (JP, A) JP-A-4-73493 (JP, A) JP-A-5- 263983 (JP, A) JP-A-6-249385 (JP, A) JP-B-49-27104 (JP, B1)

Claims (2)

[Claims] 1. An electric resistance wire in which an electric resistance wire covered with a glass fiber insulating layer and an electric resistance wire not covered with the glass fiber are integrally covered in parallel with a thermoplastic resin layer, Insulating layer of glass fiber on the starting end side of the winding of the electric resistance wire while spirally winding on a plane so that the electric resistance wire covered with a layer and the electric resistance wire not covered with the layer are alternately located. Connect one end of the electric resistance wire covered with and the one end of the electric resistance wire not covered, and the electric resistance wire covered with the insulating layer of glass fiber and the other end of the electric resistance wire not covered A heating element for melting of thermoplastic resin products, characterized in that it is formed in a flat plate shape drawn from the side, and adjacent electric resistance wires are integrally joined to maintain the flat plate shape. 2. An electric resistance wire in which an electric resistance wire covered with an insulating layer of glass fiber and an electric resistance wire not covered are integrally covered in parallel with a thermoplastic resin layer, The electric resistance wire coated with layers and the uncoated electric resistance wire are spirally wound on the cylindrical surface so that the electric resistance wires are wound alternately. Connect one end of the electric resistance wire covered with a layer and one end of the electric resistance wire not covered, and connect the electric resistance wire covered with the insulating layer of glass fiber and the other end of the electric resistance wire not covered. A heating element for melting of a thermoplastic resin product, characterized in that the electric resistance wire is wound into a tubular shape to be drawn out from the other end side, and adjacent electric resistance wires are integrally joined to maintain the tubular shape.