JP4444886B2 - Low voltage underground fuse - Google Patents

Description

  The present invention relates to a low-voltage underground lead-in fuse used for underground distribution lines, and more particularly to improvement of chemical resistance, more specifically alkali resistance.

  The low-voltage underground lead-in fuses used for underground distribution lines are installed in concrete manholes or fences. Concrete is produced by the hydration reaction of cement, and initially exhibits strong alkalinity of pH 12 or more due to calcium hydroxide contained therein, etc., but the cement hardens over time, reacts with carbon dioxide in the air, and from the surface Neutralize. When installing manholes and fences, more concrete may be placed on site to adjust the level of equipment installed. In such a case, if the rainwater flows into the manhole or dredging before the cement hardens, or if there is scattering inflow of cement powder, the low-pressure underground lead-in fuse installed inside will come into contact with strong alkaline water, It will be submerged in strong alkaline water. In addition, at the site of alkaline soil, manholes and ridges may be strongly alkaline due to the inflow of groundwater and rainwater.

The idea of improving the water tightness of the low-voltage underground lead-in fuse has been made for some time. FIGS. 5 to 7 show an example of a low-voltage underground pull-in fuse that has been used so far. An inner cylinder is arranged in an outer cylinder 1 made of polycarbonate resin, and leads are provided outside the outer cylinder 1 in the axial direction. The fusible body connected to the wire 2 is housed in the inner cylinder, the both ends of the outer cylinder 1 are sealed with the cap 3, and the resin mold 4 is applied to the portion extending from the outer surface of the cap to the lead wire. The outer side is covered with an electrically insulating cover 11 made of soft vinyl chloride, and the watertightness is enhanced by the resin mold 4 and the electrically insulating cover 11. Increasing water tightness with a resin mold and an electrically insulating cover is as disclosed in Patent Document 1.
Real fairness 4-24589

By the way, polycarbonate resin is used for the outer cylinder in the low-voltage underground lead fuse because it has advantages such as impact resistance, heat resistance, and high transparency. The cap is also made of polycarbonate resin, and the outer cylinder and the cap are fixed with ultrasonic welding 12 or screwing while maintaining watertightness. However, the chemical durability of polycarbonate resin is relatively strong against acidic liquids, but is weak against alkaline liquids and solvents, and therefore has a property of being easily chemically deteriorated. In addition, when the residual stress generated when the outer cylinder and the cap are fixed by ultrasonic welding or screwing is large, the welded part or screwed part is easily affected by chemical deterioration. Contacting or immersing strong alkaline water in concrete manholes or cages would cause cracks in the outer cylinder and cap, and strong alkaline water could enter the interior and damage the fuse.
In addition, a polyurethane resin is used as the resin mold, but when exposed to strong alkaline water for a long time, a further measure against alkali resistance has been desired.

  Therefore, the object of the present invention is excellent in alkali resistance, and even when exposed to strong alkaline water for a long time in a manhole or a cage, the outer tube and the cap are not cracked and watertight. Therefore, it is an object of the present invention to provide a low-voltage underground pull-in fuse that can maintain its characteristics and can exhibit its original fuse function for a long period of time.

In order to achieve the above object, the low-voltage underground lead-in fuse according to the present invention is characterized in that a coating having a good chemical resistance is applied to the entire outside of the low-voltage underground lead-in fuse according to the same configuration as the conventional one. Is.
That is, the low-voltage underground lead-in fuse according to the present invention has an inner cylinder placed in an outer cylinder made of polycarbonate resin, and a fusible body connected to a lead wire on the outer side in the axial direction of the outer cylinder is sealed in the inner cylinder. In the fuse for low-voltage undergrounding, in which both ends of the outer cylinder are sealed with caps, a resin mold is applied to the part extending from the outer surface of the cap to the lead wire, and the outside of the resin mold is covered with an electrically insulating cover The outer cylinder is covered with an electrically insulating coating with good chemical resistance and the resin insulation cover covering the outer periphery of the resin mold is a molded product made of vinyl chloride with good chemical resistance, and is electrically insulated from the outer periphery of the resin mold. It covers the both ends of the conductive coating, and the externally exposed end surface of the resin mold is coated with an electrically insulating sealing agent having good chemical resistance.

As the electrically insulating coating with good chemical resistance for covering the outer cylinder, a cylinder made of transparent hard vinyl chloride or a transparent polyester tape wrapped around which the operating state of the fusible body can be visually observed from outside is desirable. In the case where the residual stress is small and it is difficult to be affected by the alkaline liquid, an electrically insulating coating made of polycarbonate resin may be used.
Semi-rigid or rigid vinyl chloride molded product that is difficult to deform as an electrically insulating cover that covers the outer periphery of the resin mold from both ends of the electrically insulating coating, and can be used as a mold for filling the resin mold. Is desirable.

  In the case where the electrically insulating coating covering the outer cylinder is made of a transparent rigid polyvinyl chloride cylinder, the outer casing is covered from the outer peripheral surface of the cap, and the electric insulating cover is covered from the outer peripheral portion of the resin mold. It covers over both ends. Specifically, an electrical insulating cover shall be fitted to both ends of the electrical insulating coating and fixed with vinyl chloride adhesive.

  The resin mold is fluid in the initial stage and hardens and solidifies over time, so that the resin mold does not leak onto the outer cylinder surface through the gap between the electrical insulation coating and the cap. In this case, a structure in which an elastic packing such as silicon resin for preventing leakage of the resin mold is provided is desirable.

  In addition, when the electrically insulating coating covering the outer cylinder is a coating wrapped with a transparent polyester tape, it is configured to cover from the outer cylinder to the outer peripheral surface of the cap, and the electric insulating cover is insulated from the outer peripheral portion of the resin mold. It covers over both ends. Further, the insulating coating covering the outer cylinder may be constituted by a coating around which a transparent polyester tape is wound, and a resin mold covering the boundary between the outer cylinder and the cap. The outer peripheral surface of the resin mold that covers the boundary portion from the outer peripheral portion, that is, covers both ends of the electrically insulating coating. In this case as well, the electrically insulating cover is fixed to the both ends of the electrically insulating coating with an adhesive for vinyl chloride.

  Silicone with good chemical resistance and stretchability is used as an electrical insulating sealant to cover the resin mold applied to the lead wire connection and the externally exposed end surface of the resin mold that covers the boundary between the outer cylinder and the cap. Resin is desirable.

  As described above, the low-voltage underground lead-in fuse according to the present invention covers the outer cylinder with an electrically insulating coating having good chemical resistance and extends from the outer periphery of the resin mold to both ends of the electrically insulating coating. Because it is covered with an electrically insulating cover made of a vinyl chloride molded product, it is resistant to strong alkaline water, and because it has high impact resistance, heat resistance, and transparency, the polycarbonate resin that it is desired to use is used. It can be used as it is for outer cylinders and caps, and the outer end surface of the resin mold is coated with an electrically insulating sealant with good chemical resistance, so the durability against strong alkaline water is improved and the entire fuse is Even if it may be submerged in strong alkaline water, the watertightness is not impaired over a long period of time and the deterioration over time is small. Therefore, it was possible to extend the lifetime of low-voltage underground fuses installed in concrete manholes and fences.

  In addition, since it is the structure which coat | covers the outer peripheral part of a resin mold with the electrically insulating cover which consists of a semi-rigid or hard vinyl chloride molded product, when applying a resin mold, this electrically insulating cover is also used as a mold mold. Can be used as a frame and caps a cylindrical mold envelope to apply a resin mold, like a conventional low-voltage underground lead-in fuse that uses an electrically insulating cover made of soft vinyl chloride There is no need to provide the outer surface, and the number of parts can be reduced.

Embodiments of the low-voltage underground lead-in fuse according to the present invention will be described below.
FIG. 1 is an external front view showing an embodiment of a low-voltage underground lead-in fuse according to the present invention, and FIG. 2 is a longitudinal sectional view. The structure of the fuse body is almost the same as that of a conventional fuse, and a transparent, electrically-insulating inner cylinder (not shown) is arranged in an outer cylinder 1 made of transparent polycarbonate resin, The fusible body connected to the lead wire 2 is stored in the inner cylinder in a sealed state, and both ends of the outer cylinder 1 are sealed with a cap 3 made of polycarbonate resin, and the portion extending from the outer surface of the cap 3 to the lead wire 2 is sealed. Resin mold 4 is applied. The fusible body and the lead wire are connected via a compression sleeve 5.

  Reference numeral 6 denotes an electrically insulating coating with good chemical resistance, which covers from the outer cylinder 1 to the outer peripheral surface of the cap 3, and in this example, is constituted by a cylinder made of transparent hard vinyl chloride. As shown in FIG. 3, this cylindrical body is composed of a cylindrical portion 6 a that covers the outer periphery of the outer cylinder 1 and a slightly large-diameter cylindrical portion 6 b that covers the outer periphery of the cap 3. 7 is an electrical insulating cover that covers from the outer peripheral portion of the resin mold 4 to the outer peripheral portion of the cylindrical portion 6b of the electrical insulating coating 6, that is, both ends of the electrical insulating coating 6, and has good chemical resistance. This is a semi-rigid or hard vinyl chloride molded product, fitted to both ends of the electrically insulating coating 6, and fixed with an adhesive for vinyl chloride.

  The resin mold 4 is made of polyurethane resin, and the outer cylinder 1 and the outer periphery of the cap 3 are covered with a cylindrical body made of transparent hard vinyl chloride as an electrically insulating coating 6, and the end of the cylinder body from the axial outer peripheral surface of the cap 3. After the resin mold is once applied to the part extending over the inner peripheral surface of the part, the electrically insulating cover 7 is fitted to both ends of the electrically insulating coating 6 and fixed with an adhesive for vinyl chloride. The remaining resin mold is applied while being used as a mold for molding.

  A primer is preferably applied to the inner surface of the cylindrical portion 6b of the electrically insulating coating 6 so that a strong adhesion to the resin mold can be obtained. The externally exposed end face of the resin mold 4 is coated with an electrically insulating sealing agent 8 having good chemical resistance such as silicon resin in order to avoid contact with alkaline water. Note that the boundary between the outer cylinder 1 and the cap 3, in this example, the cylinder of the electric insulating coating 6, so that the resin mold does not leak to the surface of the outer cylinder 1 through between the electric insulating coating 6 and the cap 3. An elastic packing 9 made of silicon resin is disposed between the inner end wall of the shaped portion 6b and the inner end face of the cap 3 to prevent the resin mold from leaking.

  FIG. 4 is a schematic front view showing another embodiment of the low voltage underground lead-in fuse according to the present invention. The difference from the above embodiment is that the transparent polyester tape is used as the electrically insulating coating 6 covering the outer peripheral surface of the outer cylinder 1. And a resin mold 4 that covers the boundary between the outer cylinder 1 and the cap 3. That is, a transparent polyester tape with good chemical resistance is wound around the outer peripheral surface of the outer cylinder 1 and the boundary portion between the outer cylinder 1 and the cap 3 is covered with a resin mold 4 to cause deterioration due to contact with alkaline water. It is intended to prevent.

  The electrically insulating cover 7 covers the outer peripheral surface of the resin mold 4 that covers the boundary portion from the outer peripheral portion of the resin mold 4 at the lead wire connecting portion, that is, the both ends of the electrically insulating coating 6. In order to prevent contact between the resin mold and the alkaline water, an electrically insulating sealant 8 with good chemical resistance such as a silicone resin that seals the externally exposed end surface of the resin mold 4 is used in the same manner as in the above embodiment. In addition to being provided on the externally exposed end face of the resin mold 4 at the connecting portion, it is also provided on the externally exposed end of the resin mold 4 applied to the boundary portion between the outer cylinder 1 and the cap 3.

  Note that it is desirable to seal the winding end portion of the transparent polyester tape with a silicone resin. In addition, when the transparent polyester tape is wound not only on the outer peripheral portion of the outer cylinder 1 but also on the outer peripheral portion of the cap 3, the electrically insulating coating 6 covering the outer peripheral surface of the cap from the outer cylinder is used. The resin mold applied to the boundary between the cap 3 and the cap 3 may be omitted. In this case, the inner end of the electrically insulating cover 7 only needs to reach a position that covers both ends of the electrically insulating coating 6 that covers the outer periphery of the cap.

1 is an external front view showing an embodiment of a low-voltage underground lead-in fuse according to the present invention. Same longitudinal section Cross section of a transparent rigid vinyl chloride cylinder used as an electrical insulation coating Schematic front view showing another embodiment of a low-voltage underground lead-in fuse according to the present invention Front view showing an example of a conventional low-voltage underground lead-in fuse Same longitudinal section The longitudinal cross-sectional view in the state which removed the electrically insulating cover which covers the outer side of the resin mold part

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder 2 ... Lead wire 3 ... Cap 4 ... Resin mold 6 ... Electrical insulation coating 7 ... Electrical insulation cover 8 ... Electrical insulation sealing agent

Claims (6)

An inner cylinder is placed inside an outer cylinder made of polycarbonate resin, a fusible body connected to a lead wire on the outer side in the axial direction of the outer cylinder is stored in a sealed state in the inner cylinder, and both ends of the outer cylinder are sealed with caps In a low-voltage underground lead-in fuse in which a resin mold is applied to the part extending from the outer surface of the cap to the lead wire, and the outer side of the resin mold is covered with an electrically insulating cover, the outer cylinder is electrically insulated with good chemical resistance. The resin insulation cover that covers the outer periphery of the resin mold and the molded product made of vinyl chloride with good chemical resistance is covered from the outer periphery of the resin mold to both ends of the electric insulation coating. A low-voltage underground lead-in fuse with an externally exposed end face covered with an electrically insulating sealant with good chemical resistance. The electrically insulating coating covering the outer cylinder is made of a transparent rigid polyvinyl chloride cylinder covering the outer cylinder from the outer cylinder to the outer peripheral surface of the cap, and the electric insulating cover is electrically insulated from the outer periphery of the resin mold. 2. The low-voltage underground lead-in fuse according to claim 1, wherein the fuse is covered over both ends. 3. An elastic packing for preventing leakage of the resin mold is disposed between the electrical insulation coating and the cap, and a semi-rigid or hard electrical insulation cover is fitted and fixed to both ends of the electrical insulation coating. The low-voltage underground lead-in fuse described. The electrically insulating coating covering the outer cylinder is composed of a coating wrapped with a transparent polyester tape, covering the outer cylinder from the outer cylinder to the outer peripheral surface of the cap, and the electric insulating cover from the outer periphery of the resin mold to both ends of the insulating coating. 2. The low-voltage underground lead-in fuse according to claim 1, wherein the fuse is covered over a portion. The electrically insulating coating covering the outer cylinder is composed of a coating wrapped with a transparent polyester tape and a resin mold covering the boundary between the outer cylinder and the cap, and the electric insulating cover extends from the outer periphery of the resin mold at the lead wire connecting portion to the boundary. The low-voltage underground lead-in fuse according to claim 1, wherein the fuse is covered over an outer peripheral surface of a resin mold covering the portion. 6. The low-voltage underground lead-in fuse according to claim 1, wherein the electrically insulating sealing agent covering the externally exposed end surface of the resin mold is a silicon resin.

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