JP3375438B2 - Heating wire winding method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of injection-molding an electric fusion joint in which a heating wire is buried, in which the heating wire is closely adhered to the outer peripheral surface of a core. The present invention relates to a method for winding a heating wire that can be turned. 2. Description of the Related Art Conventionally, an electric fusion joint as shown in a sectional view of FIG. 3 has been used for connecting a synthetic resin gas pipe, a water supply / hot water supply pipe and the like. In the fusion joint, the heating wire 1 is wound in a coil shape a predetermined number of times on the outer peripheral surface of a core forming the inner peripheral surface of the joint, and terminal pins 2 are fixed to both ends thereof, and then the heating wire 1 is wound. The core is set in a mold and the molten resin is injected into a cavity formed between the core and the mold to produce the core. However, according to this conventional method, when a heating wire is wound around the outer peripheral surface of the core, FIG.
In some cases, a gap was formed between the heating wires 1 as shown in FIG. That is, the outer surface of the heating wire 1 made of a nichrome wire or the like is an insulating resin 1 such as polyethylene or polybutene.
1, if the thickness of the insulating resin 11 varies, the outer diameter d of the heating wire 1 fluctuates, and the feed pitch P of the heating wire 1 becomes constant according to the outer diameter d of the heating wire 1. Then
A gap may be formed between the heating wires 1 or the heating wires 1 may be overlapped and wound. For this reason, in the electric fusion joint obtained by injection molding, the depth and the interval of the heating wires are not uniform, and a strong fusion joint may not be obtained. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and a method for winding a heating wire in which a heating wire can be wound in close contact with an outer peripheral surface of a core and a reliable and strong fusion bonding can be obtained. Is provided. According to the present invention, when a heating wire is wound around an outer peripheral surface of a core forming an inner peripheral surface of an electrofusion joint, the core is rotated around an axis while rotating the heating wire. Measure the outer diameter of the heating wire wound around the outer peripheral surface. And this measurement is
The heating wire is wound by synchronizing the outer diameter of the heating wire and the pitch of the heating wire wound on the outer peripheral surface of the core by feeding back to the movement amount control device in the axial direction of the core or the feeding device of the heating wire. It is characterized by doing. As described above, since the outer diameter of the heating wire is synchronized with the pitch of the heating wire wound around the outer peripheral surface of the core, the heating wires are wound in close contact with each other. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic front view showing a step of winding a heating wire around an outer peripheral surface of a core, and FIG. 2 is a partial cross-sectional view showing a state in which the heating wire is closely wound. In the figure, reference numeral 1 denotes a heating wire such as a nichrome wire, and the outer surface of the heating wire 1 is covered with an insulating resin 11 such as polyethylene or polybutene. 2 is a terminal pin and 3 is a core. The core 3 forms the inner peripheral surface of the joint at the time of injection molding, and moves in the axial direction while rotating around the axis in cooperation with the control device 5. ing. In the present invention, when winding the heating wire 1 around the outer peripheral surface of the core 3, first, the insulating resin 11 covering the end of the heating wire 1 is peeled off, and the terminal pin 2 is caulked and fixed. Then, the terminal pin 2 is hooked on the tip of the locking tool 4 attached to one end of the core 3 and is moved in the axial direction while rotating the core 3 so that the heating wire 1 is coiled a predetermined number of times on the outer peripheral surface thereof. To wind. In the winding step, the outer diameter of the heating wire 1 is measured by the outer diameter measuring device 7 while sending out the heating wire 1 from the feeding device 6, and the measured value is fed back to the controller 5 of the core. The outer diameter d of the heating wire 1 and the pitch P of the heating wire 1 wound around the outer peripheral surface of the core are synchronized. That is, as shown in FIG. 2, when the outer diameter of the wound heating wire 1 is d1 and the outer diameter of the heating wire 1 wound closely thereto is d2, the pitch P is (d1 + d2) / 2. The amount of movement of the core 3 in the axial direction is controlled so that Further, the rotation of the core 3 is stopped at any time during the winding process, and an electric heating iron 8 is applied to the heating wire 1 wound around the outer peripheral surface of the core 3 to cover the outer peripheral surface of the heating wire 1. Partially melt the insulating resin. Then, as shown by the symbol W in FIG. 1, the adjacent heating wires 1 are fused and joined with the molten resin, so that the heating wires 1 are not displaced or loosened. After the heating wires 1 are wound in close contact with the outer peripheral surface of the core 3 in this manner, the terminal pins 2 are caulked and fixed to the rear end of the heating wire 1 wound on the core 3. Then, the core 3 around which the heating wire 1 is wound is set in a mold (not shown), and a molten resin such as polyethylene or polybutene is injected into a cavity formed by the core 3 and the mold. As shown in FIG. 3, an electric fusion joint in which the heating wire 1 is embedded is obtained. In the above embodiment, the method of moving the core 3 in the axial direction has been exemplified, but the present invention is not limited to this. The measured value of the outer diameter of the heating wire 1 measured by the outer diameter measuring device 7 is fed back to the feeding device 6 of the heating wire 1, and the feeding device 6 is moved in the axial direction of the core 3 to remove the outer diameter of the heating wire 1. d and the pitch P of the heating wire 1 wound around the outer peripheral surface of the core 3 may be synchronized. As described in detail above, according to the present invention, the outer diameter of the heating wire is synchronized with the pitch of the heating wire wound around the outer peripheral surface of the core. it can. Therefore,
It is possible to manufacture an electric fusion joint in which a reliable and strong fusion bonding can be obtained without forming a gap between the heating wires or being overlapped and wound.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic front view showing a winding step of the present invention. FIG. 2 is a partial cross-sectional view showing a state where a heating wire is wound in a state in which a heating wire is brought into close contact with an outer peripheral surface of a core. FIG. 3 is a cross-sectional view of the electric fusion joint. FIG. 4 is a partial cross-sectional view showing a state in which a heating wire is wound around an outer peripheral surface of a core in an irregular state. [Description of Signs] 1 Heating wire 2 Terminal pin 3 Core 4 Locking device 5 Control device 6 Feeding device 7 Outer diameter measuring device

Claims (1)

(57) [Claim 1] When winding a heating wire around an outer peripheral surface of a core forming an inner peripheral surface of a joint, the heating wire is wound around the outer peripheral surface while rotating the core around the axis. The outer diameter of the heating wire to be measured, and the measured value is fed back to the movement amount control device in the axial direction of the core , or the feeding device of the heating wire, and the outer diameter of the heating wire,
A method of winding a heating wire, wherein the heating wire is wound in synchronization with a pitch of the heating wire wound around the outer peripheral surface of the core.