JP2001167838A - Power cord and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power cord and method of manufacturing the same that has high reliability, heat-resistance, and tracking-resistance properties without discupancy of plug blade distance during forming of blades and during the use of the plug. SOLUTION: Blades are connected to each of lead wires of a cord of which leading ends are exposed and are maintained at a predetermined distance. A base end of the blade and the leading ends of the cord are covered with synthetic resin to form a plug for manufacturing the cord. At a predetermined distance, the leading ends of the cord from base end of the blade and a base end is inserted and an insert core is inject molded with a hard substance of thermoplastic resin such as a polyamide resin, poly butadiene resin, polypropylene resin and after inserting the insert core, the plug is inject molded with soft substance of a thermoplastic resin such as vinyl chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power cord having a plug at one end of the cord and a method of manufacturing the power cord.

[0002]

2. Description of the Related Art In a power cord as described above, a plug blade is connected to each of a plurality of conductive wires protruding (exposed) from the tip of the cord, and the base side of the plug blade and the tip side of the cord are made of vinyl chloride. In some cases, the plug portion is formed by coating.

[0003] When the plug portion is formed of one kind of vinyl chloride, it has advantages such as good moldability and inexpensiveness. However, if this vinyl chloride plug is left in an outlet for a long period of time, the plug is It is said that the dust and moisture adhere between the blades and a minute current starts to flow, thereby destroying the tissue, forming a carbonized conductive path, causing a short circuit, and finally igniting, resulting in low reliability for tracking resistance. Has problems.

Further, since the plug portion is formed in a single forming step, sinks are liable to occur in a thick portion, and there is also a problem that the interval between the blades is disturbed.

Further, when the plug portion is formed of vinyl chloride, the vinyl chloride is relatively soft, so that it is easily deformed in the operation of insertion and removal from the outlet, and in this operation, the interval between the blades may be incorrect. There are also difficulties to do.

[0006]

SUMMARY OF THE INVENTION The present invention has high reliability with respect to tracking resistance, and maintains the interval arrangement of the blades without being disturbed by molding or operation of a plug. It is a main object of the present invention to provide a power cord having excellent operability or a method of manufacturing the same.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a blade is connected to each of a plurality of conductors exposed at the end of a cord, and these blades are held at a predetermined distance, and the base side of the wire and the cord are connected to each other. A power cord having a plug portion formed by coating the front end side with a synthetic resin, and inserting a base portion of the plug blade or a portion from the base portion to a tip end portion of the plug blade at a predetermined distance, to a polyamide resin (polyamide). 66, polyamide 4
6, polyamide 6, etc.), injection molding the core with a hard thermoplastic resin such as polybutadiene resin, polypropylene resin, etc., inserting the above core, and plugging with a suitable soft thermoplastic resin such as vinyl chloride. Is a power cord obtained by injection molding. When the core is formed of a thermoplastic resin such as a polyamide resin, a polybutadiene resin, or a polypropylene resin, these resins are hard and have excellent heat resistance, so that there is little internal deterioration due to heat. Can be held without deviating, and it is possible to prevent deformation and deviation in the operation of insertion and extraction with respect to the outlet.

In a preferred embodiment of the present invention, a core formed of a hard thermoplastic resin such as a polyamide resin, a polybutadiene resin, or a polypropylene resin is positioned at least on the front side of the plug portion, and Is formed so as to be exposed on the front surface of the plug portion. By forming the plug front part with a synthetic resin with good tracking properties such as the above polyamide resin, polybutadiene resin, polypropylene resin, etc., if dust or moisture adheres between the blades on the front of the plug part and a minute current starts flowing In addition, the microcurrent can prevent the tissue from being destroyed and the formation of a carbonized conductive path, and tracking ignition does not occur due to these causes, so that high reliability in tracking resistance can be obtained. Can be.

In a preferred embodiment of the present invention, a retaining structure is formed between the core and the plug to prevent the two from being separated by integrally forming the plug. With this retaining structure, even if the plug portion is roughly manipulated with respect to the outlet, a gap between the core and the plug portion is prevented or separated.

[0010] In the manufacturing method of the present invention, the base side of each of the blades connected to each of the plurality of conductors exposed at the end of the cord and held at a predetermined distance and the end of the cord are covered with a synthetic resin. And forming a plug portion by inserting a base portion of the blade or a portion from the base portion to a tip end portion of the cord at a predetermined distance from a polyamide resin (polyamide 66, polyamide 46, polyamide 6), a core forming step of injection molding a core with a hard thermoplastic resin such as a polybutadiene resin or a polypropylene resin, and a plug portion formed by inserting the core and inserting a suitable soft thermoplastic resin such as vinyl chloride. And a plug part forming step of performing injection molding. When the core is made of a thermoplastic resin such as a polyamide resin, a polybutadiene resin, or a polypropylene resin, since these resins are hard, they can be held without disturbing the disposition of the blades. In this case, the core can be easily held and can be formed without disturbing the arrangement of the blades.

Further, since the core has a structure covered with the outer shell of the plug portion and is formed in at least two steps, only a part of the core is thickened, so that sink occurs after the formation and the interval between the plug blades is changed. Inconvenience can also be prevented. In addition, since the thickness of the plug portion is small, the cooling time in the mold in each forming process can be short, so that the molding cycle time is short and economical. Similarly, it is more effective to position the core insert in the thick portion of the plug.

In the step of forming the plug portion, if the core is located on the front side of the plug portion, the plug portion can be formed in a state where the front surface of the core is in contact with the mold and held securely. Therefore, the interval between the blades can be maintained at a predetermined interval. Also, in the step of forming the plug portion, by forming a retaining structure between the core and the plug portion that prevents the two portions from being separated by integrally forming the plug portion, it is possible to surely secure the connection between the two. it can.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a perspective view of a power cord 1.
The power cord 1 has a shape in which the plug blades 3 and 3 connected to the tip of the cord 2 are protruded from the plug portion 4, and the plug portion 4 is formed by molding twice. In this embodiment, a power cord having two blades 3 and 3 will be described. However, the same applies to a power cord having a three-phase AC power supply.

Code 2 is, as shown in FIGS. 2 and 3,
The outer periphery of the conductor 2a (see FIG. 3) is
It is configured by covering with a rubber material such as P rubber and chlorosulfonated polyethylene rubber, or with an exterior material 2b such as an appropriate vinyl material.

The leading end of the cord 2 is divided into two parts by exposing the conducting wire 2a, and the conducting wire 2a is connected to the base 3a of the blade 3 by caulking or the like and integrated.

The tip of the blade 3 and the cord 2 are insert-molded on the core 5 at a predetermined distance. Then, FIG.
The outer shell 6 is formed by using the integrated core 5 and the plug blades 3 and 3 as inserts to form the plug portion 4 so as to be in the state shown in FIG.

Specifically, in order to obtain the core 3 in which the distal end portion of the blade 3 and the cord 2 in the state shown in FIG. 4 is inserted, as shown in FIG. The blades 3 are held between the upper die 7 and the lower die 8 with a predetermined distance between the upper blade 7 and the lower die 8 with the leading end of the lead wire 2a of the cord 2 connected thereto. Then, injection molding is performed with synthetic resin in this state. As the synthetic resin, a thermoplastic resin such as a polyamide resin (polyamide 66, polyamide 46, polyamide 6, or the like), a polybutadiene resin, a polypropylene resin, or the like is used. These synthetic resins are hard and have excellent heat resistance.

The shape of the core 5 is a shape located at least in the thick portion on the front side of the plug portion 4.
In this embodiment, the front surface of the core 5 is set to be exposed on the front surface of the plug portion 4. Although it is not necessary to expose the front surface of the core 5, it is better to expose the core 5, even if a synthetic resin that is not high in electrical insulation is used for the material of the outer cover 6, so that high security can be obtained. Good.

The core 5 has one protruding portion 5b at the center of the back surface of the front portion 5a having a substantially rectangular plate shape, and covers from both the base to the tip of the cord 2 on both sides thereof. Covering portions 5e, 5e whose end sides are bent in the convergence direction are continuously provided, and further, on the outer side, a step-preventing projection 5h whose front side is positioned inside the front surface 5a and is stepped is provided continuously. The retaining projection 5h has a retaining hole 5i formed therein. The size of the front surface 5a of the core 5 in the surface direction is larger than the width of the blade 3 in the vertical direction and the width of the blade 3 in the horizontal direction. The length is set to be longer than the interval, in other words, a size that can surround and hold the blade 3 in the separated arrangement state.

The protruding portion 5b protrudes toward the cord 2, and its thickness and width are appropriately set so that the thickness of the outer cover 6 to be formed later can be reduced. A hole 5c penetrating vertically is formed in the center.

Subsequently, to form the outer skin 6, the cord 2
5 with insert blade 3 integrated by insert molding
Is inserted between another upper mold 9 and a lower mold 10 having cavities of a predetermined shape, as shown in FIG. 6, and injection-molded with a synthetic resin. By this molding, the plug portion 4 is completed. As the synthetic resin, vinyl chloride or the like which is generally used for an insertion plug may be used. Note that, similarly to the core 5, a hard thermoplastic resin such as a polyamide resin, a polybutadiene resin, or a polypropylene resin may be used.

By the second molding, the injected synthetic resin flows into the hole 5c in the projecting portion 5b of the core 5, and is connected vertically and integrated as shown in FIG.
For this reason, separation of the core 5 and the outer skin 6 can be reliably prevented. That is, the hole 5c has a retaining structure.

Further, since the synthetic resin flows into the front surface of the retaining projection 5h and the synthetic resin also flows into the retaining hole 5i, a retaining effect is obtained, and the retaining projection 5h and the retaining The hole 5i has a retaining structure.

In addition to the above shape, for example, a convex or concave step may be formed at the edge of the front surface 5a of the core 5, or the protrusion 5
The outer peripheral portion of b may be formed in a jagged shape. In short,
What is necessary is just to have the shape which the synthetic resin which forms the outer skin 6 bites with a core.

As shown in FIG. 8, the core 5 may be provided with a root covering portion 5d for thinly covering the root of the blade 3 projecting from the plug portion 4 by a length of about several millimeters. When formed in this manner, the blade 3 is inserted into the outlet.
Can be prevented from directly adhering to the base of the base. For this reason, the effect of preventing tracking is enhanced, and the safety and reliability can be further improved.

FIG. 9 shows another example of the above-described retaining projection 5h. Since the configuration other than the retaining projection 5h is the same as the configuration described with reference to FIGS. Although a detailed description is omitted, the retaining projection 5h has a T-shape, and its front side is formed with a step located inside the front part 5a of the core 5, and the front side of the projection 5h is When the synthetic resin flows into both sides of the T-shape, a retaining action is obtained, and the T-shaped retaining protrusion 5h has a retaining structure.

(Second Embodiment) FIG. 10 is a perspective view showing the structure of a power cord 1 according to another example. In this power cord 1, when the plug blade 3 is insert-molded into the core 5, The shape of the core 5 is set so as to cover from the base 3 a of the blade 3 to the tip of the cord 2 with a different retaining structure. The manufacturing method is the same as that of the first embodiment. After the plug blade 3 is insert-molded into the core 5, the outer cover 6 is covered to form the plug portion 4.

That is, as shown in the side view of FIG. 11, the base 3a of the blade 3 and the cord 2 connected to this portion
And two covering portions 5e, 5e that cover up to the outer portion 2b at the end of the cord 2 projecting from the back surface of a rectangular front surface portion 5a whose front surface is exposed to the front surface of the plug portion 4. is there. The two covering portions 5e are bent rearward in the direction of convergence, and have a flange-like ridge 5f formed at the edge of the front surface portion 5a. These are retaining structures.

Insert molding of the blade 3 into the core 5 is performed in the same manner as described in the first embodiment. That is, as shown in FIG. 12, the blade 3 to which the cord 2 is connected is held between the upper die 7 and the lower die 8 in a predetermined spaced state, and injection molding is performed with synthetic resin in this state. As the synthetic resin, a thermoplastic resin such as the above-described polyamide resin, polybutadiene resin, or polypropylene resin is used. These synthetic resins are hard and have excellent heat resistance.

Subsequently, in order to form the outer skin 6 as shown in FIG. 13, the blade 3 and the core 5 integrated by insert molding are combined with each other into a predetermined shape as shown in FIG. Put between the upper die 9 and the lower die 10 with cavities,
Injection molding with synthetic resin. By this molding, the plug portion 4 is completed. As the synthetic resin, vinyl chloride or the like which is generally used for an insertion plug may be used. In addition, like the core 5, polyamide resin, polybutadiene resin,
A hard thermoplastic resin such as a polypropylene resin may be used.

By the second molding, the injected synthetic resin is engaged with the retaining structure, that is, the ridge 5f of the front surface 5a of the core 5 and the two covering portions 5e, and is integrated. For this reason, separation of the core 5 and the outer skin 6 can be reliably prevented.

As in the case of the first embodiment, the core 5 is provided with a root coating portion for thinly coating the root of the blade 3 projecting from the plug portion 4 by a length of several millimeters as shown in FIG. 5
d may be formed. When formed in this manner, it is possible to prevent dust and the like from directly adhering to the root of the blade 3 while being inserted into the outlet. For this reason, the effect of preventing tracking is enhanced, and the safety and reliability can be further improved.

Further, as shown in FIG.
The rear ends of the two covering portions 5e, 5e may be connected to the left and right by the connecting portion 5g. As a part of the retaining structure, the thickness of the outer cover 6 at the position corresponding to the connecting portion 5g is reduced, which contributes to preventing the occurrence of sink marks.

In any of the embodiments, the formation of the plug portion 4 may be performed not only twice but also three times.

[0035]

According to the present invention, a power plug having excellent tracking resistance and excellent heat resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a power cord according to a first embodiment.

FIG. 2 is a perspective view showing a main part of a power cord.

FIG. 3 is a cross-sectional view of a power cord.

FIG. 4 is a side view of a blade, a core, and a cord.

FIG. 5 is an explanatory view of a core forming step.

FIG. 6 is an explanatory view of a positive skin formation.

FIG. 7 is a longitudinal sectional view of a power cord.

FIG. 8 is a perspective view of a main part of a power cord according to another example.

FIG. 9 is a perspective view of a waist of a power cord showing another example of a retaining structure.

FIG. 10 is a perspective view of a main part of a power cord according to a second embodiment.

FIG. 11 is a side view of a main part of the power cord.

FIG. 12 is an explanatory view of a core forming step.

FIG. 13 is a cross-sectional view of the power cord.

FIG. 14 is an explanatory diagram of a skin forming step.

FIG. 15 is a perspective view of a main part of a power cord according to another example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power cord 2 ... Cord 2a ... Lead wire 3 ... Plug blade 3a ... Base 4 ... Plug part 5 ... Core 6 ... Outer shell 7, 9 ... Upper die 8, 10 ... Lower die

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Claims (7)

[Claims] 1. A plug blade is connected to each of a plurality of conductive wires exposed at the distal end of a cord, and these plug blades are held at a predetermined distance, and the base side and the distal end side of the cord are made of synthetic resin. A power cord having a plug portion formed by coating, wherein a predetermined portion of the power cord is inserted at a predetermined distance from the base of the blade or from the base to the tip of the cord to form a hard resin such as a polyamide resin, a polybutadiene resin, or a polypropylene resin. A power cord in which a core is injection-molded with a thermoplastic resin, and the core is inserted and a plug portion is injection-molded with a suitable soft thermoplastic resin such as vinyl chloride. 2. The power cord according to claim 1, wherein the core is formed at least on the front side of the plug portion so that the front surface of the core is exposed on the front surface of the plug portion. 3. The power cord according to claim 1, wherein a stopper structure is formed between the core and the plug portion to prevent the two portions from being separated by integrally forming the plug portion. 4. A base portion of each of the blades connected to each of a plurality of conductors exposed at the end of the cord and held at a predetermined distance and a tip side of the cord are covered with a synthetic resin to form a plug portion. A method of manufacturing a power cord to be formed, comprising inserting a base portion of the blade or a portion from the base portion to a tip portion of the cord in a predetermined spaced arrangement, and forming a rigid thermoplastic resin such as a polyamide resin, a polybutadiene resin, and a polypropylene resin. Multi-stage molding including a core forming step of injection-molding a core with a plug, and a plug part forming step of inserting the above-mentioned core and injecting a plug part with a suitable soft thermoplastic resin such as vinyl chloride. A method for manufacturing a power cord formed by the method described above. 5. The power cord according to claim 4, wherein, in the step of forming the plug portion, the core is formed at least at a front side of the plug portion so that a front surface of the core is exposed at a front surface of the plug portion. Production method. 6. The power cord according to claim 4, wherein in the plug forming step, a retaining structure is formed between the core and the plug portion to prevent the two portions from being separated by integrally forming the plug portion. Production method. 7. The method of manufacturing a power cord according to claim 4, wherein in the flag forming step, the core is formed so as to be located at least in a thick portion on the front side of the plug portion.