JPH09306581A - Double insulated electric power source plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel double-insulation power supply plug excellent in safety and reliability by surely preventing an electric hazard or tracking due to stray wires. SOLUTION: Plug blades 4, 4 are respectively connected to a plurality of insulated electric wires 2, 2 exposed out of an end part of an electric power source cord 1 and at the same time the insulated electric wires 2, 2 together with the connection parts 5, 5 of the plug blades 4, 4 are coated with a primary insulator 7 of a thermoplastic resin and further the circumference of the primary insulator 7 is unitedly coated with a secondary insulator 6 by mold coating, so that the plug blades 4, 4 are fixed at a prescribed gap from each other. Consequently, danger such as electric shock hazard, tracking, etc., due to stray wires can be easily and reliably prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded insulating power plug which is detachably inserted into an outlet and used.

[0002]

2. Description of the Related Art Generally, an insulated power plug having a structure as shown in FIG. 5 is used as a power plug used in household electric appliances and the like.

As shown in the figure, the insulated power plug is a pair of insulated wires 2 and 2 exposed at the end of the power cord 1.
After connecting the connection portions 5 and 5 of the plug blades 4 and 4 to the conductors (strands) 3 and 3 by crimping, spot welding, soldering, etc., the intervals between the plug blades 4 and 4 are fixed to be constant. Insulator 6 made of soft polyvinyl chloride compound (PVC) or the like around the connecting portions 5 and 5
It is formed by integral mold coating with.

[0004]

By the way, in the conventional insulated power source plug as described above, the insulation of the connection portions 5 and 5 between the plug blades 4 and 4 and the insulated wires 2 and 2 is performed only by the insulator 6. Since it is insulation (integral molding only), the Hagre wire (st
ray strands) was easy to occur. Further, since it is difficult to detect the haggle line, a part of the haggle line may be exposed on the surface of the insulator 6 after the insulator 6 is mold-coated, so that when the plug is touched, There was a possibility of electric shock. Similarly, in the conventional insulated power plug, the roots 4a of the plug blades 4 and 4 exposed from the plug end surface 6a of the insulator 6 are continuously used for a long time.
There is a possibility that a short circuit due to tracking may be caused by dust or the like adhering to the portion. Further, if the connection portion 5 between the plug blade 4 and the conductor 3 has a poor connection, the resistance of the connection portion 5 increases and the state becomes overheated, so that the insulator 6 is softened and deformed. there were.

Therefore, the present invention has been devised to effectively solve such a problem, and the purpose thereof is to satisfactorily connect the plug blade and the conductor, thereby causing a risk of electric shock or tracking. The present invention provides a safe double-insulated power plug that can prevent the above.

[0006]

In order to solve the above problems, the present invention is to connect plug blades to a plurality of insulated wires exposed from the end of a power cord, and to connect these insulated wires to the plug blades. Is covered with a primary insulator made of a thermoplastic resin, the periphery of this primary insulator is integrally mold-coated with a secondary insulator, and these plug blades are fixed at a predetermined interval. is there.

That is, in the insulated power supply plug according to the present invention, first, the connection portion between the insulated wire and the plug blade is covered and insulated with the primary insulator, and then the periphery thereof is further covered with the secondary insulator. Even if the above-mentioned Hagure line is generated in the connection portion in the manufacturing process, it is not exposed to the surface of the secondary insulator, and the risk of electric shock can be avoided.

Further, by exposing the primary insulator covering the base portion of the plug blade by 2 mm to 4 mm from the plug end surface, it can be used for a long time as a power plug of a refrigerator or the like, and dust or moisture can be applied to the plug end surface. Even if is attached, since the root portion of each plug blade is insulated by these insulators, it is possible to prevent a short circuit due to tracking.

Further, as the primary insulator, the heat distortion temperature is 200 ° C. or more, the notched Izod impact strength is 20 kg.
By using the polyamide of f / cm / cm (at 23 ° C.) or more, the secondary insulator provided on the surface is not easily softened and deformed. That is, this polyamide is one of the non-halogen flame-retardant materials, and it exhibits excellent heat resistance even if heat is generated due to poor connection at the connection part between the insulated wire and the plug blade, and it will burn. There is no.

Further, by using the soft polyvinyl chloride compound as the secondary insulator, the plug body can exhibit good workability and insulating properties.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a double insulated power plug according to the present invention. As shown in the figure, this double-insulated power plug is attached to the conductors (strands) 3 and 3 of a pair of insulated wires 2 and 2 exposed at the end of a power cord 1 with an insulation coating, and plug blades 4 and 4, respectively. Connection part 5, 5
Are connected by crimping, spot welding, soldering, or the like.
The periphery of 5 is insulation-coated with primary insulators 7 made of thermoplastic polyamide. Further, a soft polyvinyl chloride compound (PV) is provided around the primary insulators 7 and 7 so that the plug blades 4 and 4 are held parallel to each other and their intervals are kept constant.
It is mold-coated with a secondary insulator 6 made of C).
When the mold is coated with the secondary insulator 6,
The ends of the primary insulators 7, 7 covering the roots 4a, 4a of the plug blades 4, 4 are the plug end faces 6a of the secondary insulator 6.
The exposed state is about 2 mm to 4 mm.

In the double-insulated power source plug of the present invention thus formed, the primary insulator 7 made of polyamide is used.
Since the connecting portions 5 and 5 of the plug blades 4 and 4 are covered by the plug blades 4 and 4, the connecting portions 5 and 5 are conductors 3 and 3 which are stranded wires.
Even if a haggle line is generated due to the scattering, most of the haggle line is suppressed in the primary insulator 7, and even if the haggle line is exposed on the surface of the primary insulator 7, the primary insulator 7 is still further exposed. The secondary insulator 6 that is covered around the inner circumference of the inner wall of the inner wall 6 keeps the inner portion of the inner wall of the inner wall of the inner wall of the inner wall of the inner wall of the inner wall of the secondary insulator 6. Therefore, it is possible to easily and surely avoid the risk that a part of the Hagley line, which is difficult to detect as in the conventional case, is exposed on the surface of the secondary insulator 6 and an electric shock is caused. In addition, as the polyamide that constitutes the primary insulators 7, 7, as described above, the heat distortion temperature 2
Izod impact strength with notch 20 kgf /
By using a material having excellent heat resistance and strength of cm / cm (at 23 ° C.) or more, even if heat is generated due to a poor connection between the connecting portions 5 and 5, this can be easily melted or burned. Absent. Moreover, by providing this level of strength, it will not break or be damaged even by the impact of ordinary people hitting it with a hammer etc., and it will also exhibit excellent durability and reliability. it can.
In addition, in selecting the material for the primary insulator 7, in addition to the polyamide as described above, polycarbonate (PC), polyphenylene oxide (PPO), and polyphenylene ether (PPE) were also examined, but these were all hydrolyzed. And stress cracking against chemicals occurred, so it could not be adopted.

Further, as shown in the figure, a part of the primary insulator 7 is exposed from the plug end surface 6a by about 2 mm to 4 mm so as to cover the root portion of the plug blade 4, thereby increasing the creepage distance. The occurrence of tracking is prevented in advance.

If the exposed length is less than 2 mm, the effect of suppressing tracking is not recognized.

Using such a double insulated power supply plug of the present invention and a conventional insulated power supply plug as shown in FIGS. 5 and 6, a 100 ° C. static load test ( 100 ° C x 20N x 1 hour (entire plug), 100 ° C x 100N x 1 hour (plug blade))
As a result, the conventional insulated power plug was
It failed the withstand voltage test of 2500 V / min, and the amount of the plug blade coming off from the plug end face was 15 mm or more, which was not practical. On the other hand, it was found that the double insulated power supply plug according to the present invention passed the same withstand voltage test and had a plug blade withdrawal amount of only 0.5 mm, which was sufficiently practical. In this test method, the sample and the sample jig were left in a constant temperature bath at 100 ° C. for 1 hour or more, and then a specified load was applied for 1 hour.

Similarly, the double insulated power supply plug of the present invention and the conventional insulated power supply plug are used, and ammonium chloride (NH ₄ C) having a concentration of 0.2% is provided between these plug blades 4 and _4.
l) An aqueous solution of 20 mm ³ was dropped at intervals of 5 minutes, and a tracking test in which an AC voltage of 125 V was applied between the plug blades 4 and 4 was tried. As a result, in the conventional plug, 100 to 150 drops caused ignition by tracking. On the other hand, in the double insulated power supply plug of the present invention, no ignition was observed even when the number of droppings exceeded 250 times.

Next, FIGS. 3 and 4 show another embodiment of the double insulated power plug according to the present invention. That is, in the present embodiment, as shown in the above-described embodiment, unlike the case where the individual connecting portions 5 and 5 are covered with the primary insulators 7 and 7, respectively, the individual connecting portions 5 and 5 are different from each other.
5 is integrally coated and fixed with a primary insulating material 8 also made of polyamide, and then a secondary insulating material 6 is mold-coated around the primary insulating material 8 and configured as in the present embodiment. However, it is possible to obtain the same effect as that of the above embodiment. In each of the above-described embodiments, the case where two plug blades are used has been described, but the present invention is not limited to this. For example, an insulated power plug used for a three-phase AC power supply or the like may be used. Needless to say, the present invention can also be applied to an insulating plug using three or more plug blades. Further, even if the root portion 4a of the plug blade is covered with the secondary insulator 6 side, tracking can be effectively prevented in the same manner as above.

[0019]

In summary, according to the present invention, the plug blade connecting portion is doubly covered with two insulating materials, and the base portion of the plug blade is covered with an insulating material. Since the tracking can be reliably prevented, it is possible to exhibit excellent effects such as a great improvement in safety and reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a double insulated power plug according to the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a sectional view showing another embodiment of the double-insulated power plug according to the present invention.

4 is a cross-sectional view taken along the line AA in FIG.

FIG. 5 is a sectional view showing an example of a conventional insulated power plug.

FIG. 6 is a sectional view taken along the line AA in FIG. 5;

[Explanation of symbols]

 1 Power Cord 2 Insulated Wire 3 Conductor 4 Plug Blade 4a Plug Blade End Face 5 Connection Part 6 Secondary Insulator 6a Plug End Face 7,8 Primary Insulator

Front page continued (72) Inventor Zensuke Araki 4-10-1 Kawajiri-cho, Hitachi-shi, Ibaraki Hitachi Cable Processing Co., Ltd. (72) Inventor Masaaki Inada 4--10-1 Kawajiri-cho, Hitachi-shi, Ibaraki Hitachi Cable Inside Machining Co., Ltd. (72) Inventor Satoshi Sakuma 4-10-1 Kawajiri-cho, Hitachi-shi, Ibaraki Hitachi Cable Manufacturing Co., Ltd.

Claims (4)

[Claims] 1. A plug blade is connected to each of a plurality of insulated wires exposed from an end of a power cord, and a connecting portion between the insulated wire and the plug blade is covered with a primary insulator made of a thermoplastic resin. A double-insulated power plug, characterized in that the periphery of a primary insulator is integrally mold-coated with a secondary insulator, and these plug blades are fixed at predetermined intervals. 2. The double-insulated power plug according to claim 1, wherein the primary insulator covering the root portion of the plug blade is exposed from the end face of the plug by 2 mm to 4 mm. 3. A heat distortion temperature of 20 as the primary insulator.
Izod impact strength with notch at 0 ° C or higher 20 kgf / c
The double-insulated power plug according to claim 1 or 2, wherein a polyamide having a m / cm (at 23 ° C) or higher is used. 4. The double-insulated power plug according to claim 1, wherein a soft polyvinyl chloride compound is used as the secondary insulator.