JP3004097B2 - Method of forming cable connection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily inserting a rubber molded stress cone around an insulator at the end of a rubber or plastic insulated cable to form a connection part having good performance.

[0002]

2. Description of the Related Art In recent years, in forming rubber, plastic insulated cables such as CV cables (cross-linked polyethylene insulated cables), straight connection parts, branch connection parts, terminal connection parts, and the like, reduction in size and labor saving of work. Alternatively, for the purpose of stabilizing performance, insulation treatment is performed using a stress cone (pre-mold stress cone) in which an insulating material such as rubber is molded in advance.

[0003] Such a rubber mold stress cone protrudes cylindrically forward from one of the tapered surfaces into a spindle-shaped insulating reinforcing body having tapered surfaces (inclined surfaces) formed on both sides of a central cylindrical portion. It is formed by forming a stress cone, and is formed so that the inner diameter is slightly smaller than the outer diameter of the cable insulator. If this is to be inserted around the outer periphery of the insulator at the end of the cable, apply a lubricant such as silicone oil or silicone grease to the surface of the cable insulator to reduce friction at the interface with the mold stress cone. The method of pushing by hand was adopted.

[0004]

However, in such a method, the mold stress cone is considerably thick even at the base ends (both ends) of the tapered portions on both sides, and the clamping force on the inside is large. It was difficult to move and insert on the body. In particular, when a large-diameter thick-walled mold stress cone is inserted into the cable having a large outer diameter, the operation is extremely difficult. In addition, since a method is employed in which an operator grips and pushes the mold stress cone from above by hand, there is a possibility that the outer peripheral surface of the mold stress cone may be damaged.

The present invention has been made in order to solve such a problem. Even if a large-diameter and thick rubber mold stress cone is used, it can be easily inserted into the outer periphery of the cable insulator without damaging the outer peripheral surface thereof. It is an object of the present invention to provide a method for forming a cable connection portion that can perform the above-described process and obtain a connection portion having excellent performance.

[0006]

According to the method of forming a cable connecting portion of the present invention, a rubber molded stress cone is inserted around an insulator around a rubber or plastic insulated cable end to form a cable connecting portion. After fitting the outer periphery of the rubber mold stress cone to be fitted with a splittable spindle-shaped body having a central portion and both ends having an inner diameter equal to the outer diameter of the central cylindrical portion and both ends of the mold stress cone, respectively. The cable is inserted from the end of the cable while the hollow portion of the mold stress cone is kept at atmospheric pressure, and the space between the tapered portions on both sides and the mold body is suctioned and depressurized.

[0007]

In the method of the present invention, first, a metal mold having the following shape is fitted to the outside of the rubber mold stress cone to be fitted. That is, a splittable metal mold body whose outer shape is a spindle shape, and whose inner diameters of the central straight pipe portion and both ends are equal to the outer diameter of the central cylindrical portion of the mold stress cone and the outer diameters of the tapered surface base ends at both ends, respectively, is fitted. You. Next, while maintaining the hollow portion of the mold stress cone at atmospheric pressure, the suction depressurizing mechanism attached to the metal mold body is operated, so that the gap between the mold stress cone and the mold body, that is, the mold stress cone is formed. The inside of the gap between the tapered portions on both sides of the mold and the outer peripheral surface of the mold inside is reduced in pressure. Due to such suction pressure reduction, the outside of the mold stress cone (pressure reduction) and the hollow part (atmospheric pressure)
The mold stress cone is pressed against the inner peripheral surface of the mold by this pressure difference. At this time, since the thickness of the rubber mold stress cone is thicker at the central cylindrical portion and becomes thinner toward both ends in the tapered portions on both sides, only the inner diameter of the thin portion at the base end of the tapered surface is widened.
Therefore, by inserting the mold stress cone in a state where the inner diameters of both end portions are widened in this manner, the force required for the operation can be reduced and the efficiency can be improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are longitudinal sectional views for explaining an embodiment of a method for forming a cable connecting portion according to the present invention.

In the embodiment, first, as shown in FIG. 1, a pair of cylindrical holding jigs 2 each having a tapered end are respectively inserted into a hollow portion of a rubber mold stress cone 1 to be inserted from both sides. The mold stress cone 1 is inserted and brought into close contact with the inner peripheral surface to support the mold stress cone 1 from the inside and hold the hollow portion at atmospheric pressure. Next, outside the mold stress cone 1, the whole is a spindle shape, and the central straight pipe portion and both end portions are equal to the outer diameter of the central cylindrical portion of the mold stress cone 1 and the tapered surface base end portions 3 on both sides, respectively. A metal mold body 4 having an inner diameter and configured to be dividable in the length direction is fitted. Then, from the suction port 5 attached to the tapered portion of the metal mold 4, a gap between the mold stress cone 1 and the metal mold 4, that is, both side tapered portions of the mold stress cone 1 and the metal mold outside the mold stress cone 1. The inside of the gap between the inner peripheral surface and the inner peripheral surface is suctioned and depressurized by a vacuum pump or the like. Due to such a suction pressure reduction, a pressure difference is generated between the pressure reduction outside the mold stress cone 1 and the atmospheric pressure in the hollow portion.
Is pressed against the inner peripheral surface. As a result, the inner diameter of the tapered surface base end 3 on both sides of the mold stress cone 1 is increased.

Next, after the holding jig 2 inserted into the hollow portion is removed, as shown in FIG. 2, the mold stress cone 1 in a state where the metal mold body 3 is kept covered is connected to the CV to be connected. The cable 6 is inserted from the stripped end and inserted around the outer periphery of the cable insulator 7. Next, after the metal mold body 4 is divided and removed, normal processing is performed on the inserted mold stress cone 1 to form a straight connection portion of the cable.

In the embodiment configured as described above,
The metal mold body 4 is fitted on the outer periphery of the rubber mold stress cone 1 and inserted from the end of the CV cable 6 in a state where the tapered surface base ends 3 are widened by suction and pressure reduction. No work is required and workability is high. Further, since the metal mold body 4 is fitted so as to be in close contact with the central cylindrical portion of the mold stress cone 1 and the outer peripheral surface of the upper portion of the taper on both sides, the force applied by the operator during the above-mentioned insertion is reduced. The work is efficiently transmitted to the stress cone 1, and the work of inserting the cable into the cable insulator 7 can be performed smoothly. Furthermore, after the mold stress cone 1 is inserted into a predetermined position and the metal mold body 4 is removed,
Since the depressurized state applied to the outer peripheral surface of the mold stress cone 1 is released, the tapered surface base end 3 returns to the original inner diameter by the elastic restoring force of rubber, and the inner peripheral surface is in contact with the outer peripheral surface of the cable insulator 7. Adhere well. Accordingly, the mold stress cone 1 can sufficiently follow the thermal expansion and contraction of the cable insulator 7 in the radial direction, and a connection portion with stable electrical characteristics is formed.

In addition, the thicker and larger-diameter mold stress cone 1 having a larger inner diameter has a greater effect of expanding the inner diameter of the thin portions at both ends by suction and pressure reduction, so that the insertion workability is further improved. Further, since the gap between the metal mold 4 and the mold stress cone 1 does not necessarily need to be kept at a vacuum but can be sufficiently improved only by reducing the pressure, the hermetic sealing inside the metal mold 4 can be achieved. Easy. In other words, the object can be achieved only by forming a general sealing structure at the divisional joint portion of the metal mold body 4 or the contact portion between the mold body and the mold stress cone 1.

[0014]

As described above, according to the method of the present invention, a rubber-molded stress cone is easily inserted with a relatively small force around the outer periphery of the insulator at the end of the rubber or plastic insulated cable, and a stable and good quality is obtained. A high performance cable connection can be formed.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view for explaining a method of fitting a metal mold body to a rubber mold stress cone and reducing the pressure by suction in an embodiment of the method for forming a cable connection portion of the present invention.

FIG. 2 is a longitudinal sectional view for explaining a method of inserting a rubber mold stress cone from an end of a cable in an embodiment of a method for forming a cable connection portion of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rubber mold stress cone 2 ... Holding jig 3 ... Base end part of taper surface 4 ... Metal mold body 5 ... Suction port 6 ... CV cable 7 ... Cable insulator

Claims (1)

(57) [Claims] 1. A rubber molded stress cone is inserted around the outer periphery of an insulator at the end of a rubber or plastic insulated cable to form a cable connection part. After fitting the splittable spindle-shaped body, each of which has an inner diameter equal to the outer diameter of the central cylindrical portion and both ends of the mold stress cone, the hollow portion of the mold stress cone is maintained at atmospheric pressure, A method of forming a cable connecting portion, wherein the cable connecting portion is inserted from an end of the cable while suction and pressure is reduced in a gap between both side tapered portions and the mold.