JPH1032910A - Diameter expansion method for pre-molded rubber insulator - Google Patents

Abstract

(57) [Problem] To provide a method for expanding the diameter of a pre-molded rubber insulator in which the diameter of a pre-molded rubber insulator having a different inner diameter is reduced and the escape margin of a diameter-expanding jig is shortened. SOLUTION: When the left and right inner diameters of a pre-molded rubber insulator are different, first, a tapered insertion jig is attached to the tip of a small-diameter expanding jig from the small inner diameter side, and inserted.
Next, a method of expanding the diameter of the pre-molded rubber insulator, in which the diameter is increased by inserting a large-diameter expanding jig having a tapered portion formed at the tip from the large inner diameter side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for expanding a diameter of a pre-molded rubber insulator having different inner diameters.

[0002]

2. Description of the Related Art FIG. 3 is a longitudinal sectional view of a main part of a plastic power cable connecting portion such as a CV cable having different outer diameters of right and left cables to be connected. In the drawings, 1A is a small-diameter cable, 1B is a large-diameter cable,
B is a cable sheath of vinyl chloride, polyethylene, etc., 1
2A and 12B are insulating cores of a cable provided with a plastic insulator such as cross-linked polyethylene, and 13 is a conductor connecting portion. Reference numeral 2 denotes a semiconductive rubber internal electrode 22 on the inner peripheral portion of the insulating rubber portion 21 and an outer semiconductive layer 23 of semiconductive rubber on the outer peripheral portion.
Is a pre-molded rubber insulator that is integrally molded in advance,
The inner diameter of each insulating core 1 inserted into that part
The inner electrodes 22 are formed smaller than the outer diameters of the inner electrodes 2A and 12B. The inner electrodes 22 have inner diameters changed near the center in the length direction, and the insulating rubber portion 21 and the outer semiconductive layer 23 have different left and right inner diameters.

[0003] In forming the connection portion, a single diameter expanding jig is inserted into the inner diameter portion of the pre-molded rubber insulator 2 to increase the diameter, and the jig is inserted into one of the cable sheaths before connecting the cable conductor. After the cable conductor is connected, the pre-molded rubber insulator 2 is returned onto the conductor connection portion 13 and the diameter-expanding jig is pulled out to insulate the pre-molded rubber insulator 2 by the self-shrinkage force of the elastic force of the pre-molded rubber insulator 2. Core 1
2 are closely attached to each other to form a connection portion insulator.
An outer case 3 is provided outside the pre-molded rubber insulator 2.
The two ends are positioned on the cable sheath 11 and hermetically sealed.

[0004]

The conventional method for expanding the diameter of the pre-molded rubber insulator in forming the cable connection portions having different cable outer diameters as described above uses a single diameter-expanding jig and the inner diameter of the pre-molded rubber insulator. Since it is necessary to insert from one end of the part and expand the diameter and release it on one cable sheath in advance before connecting the conductor, it is necessary to expand the diameter of the pre-molded rubber insulator larger than the final shape, especially If the outer diameter of the cable insulator on the larger side of the insulator is larger than the outer diameter of the sheath on the smaller side, it is necessary to increase the diameter further. However, in such a case, the internal rubber defects of the pre-molded rubber insulator may be increased. Also, since the expanding jig is inserted from one direction of the pre-mold rubber insulator and pulled out in one direction, it is necessary to take a long allowance for the expanding jig, which is not suitable for assembly in a narrow space. There's a problem.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method of expanding the diameter of a pre-molded rubber insulator in which the diameter of the pre-molded rubber insulator is reduced and the escape allowance of the diameter-expanding jig is shortened. The feature is that when the left and right inner diameters of the pre-molded rubber insulator are different, first insert the tapered insertion jig from the small inner diameter side with the tapered insertion jig at the tip, then insert. An object of the present invention is to insert a large-diameter expanding jig having a tapered portion at the tip from the large inner diameter side to expand the diameter.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing a longitudinal section of a specific example of the diameter expanding method of the present invention. As shown in the drawing,
First, the small inner diameter side of the pre-mold rubber insulator 2 (left side in the figure)
Then, a taper-shaped insertion jig 31 is attached to the tip of the jig 30 having a small outer diameter, and the jig is inserted to expand the inner diameter side. At this time, the tapered insertion jig 31 is a large-diameter expanding jig 3.
The jig 30 is removed after the jig 30 is inserted into a predetermined position so as not to hinder the insertion of the zero. Subsequently, a large-diameter expanding jig 32 having a tapered portion 32a formed at the tip from the large-diameter side (right side in the drawing) is inserted until the tip thereof comes into contact with the step portion of the internal electrode 22, and the large-diameter side is inserted. Expand the diameter.

As described above, the pre-mold rubber insulator 2 is inserted into the small-diameter expanding jig 30 from the small inner side and the large-diameter expanding jig 32 from the large inner side to the pre-molded rubber insulator 2. The rate of expansion of the rubber insulator 2 on the small diameter side can be reduced, so that excessive stress is not applied to the pre-molded rubber insulator 2, and it is possible to suppress the increase of internal defects of the rubber and the occurrence of cracks. . Also, when removing the expanding jig, in order to escape the expanding jig to both sides of the pre-molded rubber insulator 2,
The escape allowance of the expanding jig can be shortened, which is effective for assembling in a narrow space.

FIG. 2 is an explanatory view showing a longitudinal section of another embodiment of the diameter expanding method of the present invention. When the difference between the left and right inner diameters of the pre-mold rubber insulator 2 is small, as shown in the drawing, first, a small outer diameter expanding jig 30 having a tapered insertion jig 31 attached to the tip from the small inner diameter side is used. After the insertion, the diameter of the small inner diameter side is expanded, and the insertion jig 31 is removed. Then, a large-diameter expanding jig 32 having a tapered portion 32a formed at the front end from the large-diameter side is inserted near the front end of the small-diameter expanding jig 30 at the front end to expand the large-diameter side.

[0009]

As described above, when the left and right inner diameters of the pre-molded rubber insulator of the present invention are different, the jig with the smaller outer diameter from the smaller inner diameter side and the jig with the larger outer diameter from the larger inner diameter side. The diameter of the pre-molded rubber insulator can be reduced by inserting the pre-molded rubber insulator to reduce the diameter expansion rate of the pre-molded rubber insulator, thereby suppressing an increase in internal defects of the rubber and the occurrence of cracks. Also, when removing the diameter-expanding jig, the diameter-expanding jig is made to escape to both sides of the pre-molded rubber insulator, so that the escape margin of the diameter-expanding jig can be shortened, which is effective for assembling in a narrow space. . Therefore, it is very effective when used for forming a plug-in connection portion of a plastic power cable such as a CV cable having different outer diameters of left and right cables to be connected.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a longitudinal section of a specific example of the diameter expanding method of the present invention.

FIG. 2 is an explanatory view showing a longitudinal section of another specific example of the diameter expanding method of the present invention.

FIG. 3 is a vertical cross-sectional view of a main part of a plastic power cable connecting portion having different outer diameters of left and right cables to be connected.

[Explanation of symbols]

 2 Pre-molded rubber insulator 21 Insulated rubber part 22 Internal electrode 23 External semiconductive layer 30 Small diameter expanding jig 31 Tapered insertion jig 32 Large diameter expanding jig 32a Tapered end

Claims (1)

[Claims] 1. A method for inserting a diameter increasing jig into an inner diameter portion of a pre-molded rubber insulator composed of an insulating rubber portion and a semiconductive rubber portion which are integrally formed in advance and expanding the inner diameter. When the inner diameter of the left and right sides of the pre-molded rubber insulator is different, first insert a jig with a small outer diameter from the smaller inner diameter side by attaching a tapered insertion jig to its tip, and then insert the tip from the larger inner diameter side. A method for expanding the diameter of a pre-molded rubber insulator, comprising inserting a large-diameter expanding jig having a tapered portion into the outer periphery thereof to increase the diameter.