JPS646604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheath connection method by on-site welding of a conduit aerial cable using a sheath expansion method.

Pipeline aerial cables have a conductor supported in a metal cylindrical sheath coaxially with the center axis of the sheath using spacers, and the space is filled with an insulating gas such as SF ₆ (sulfur hexafluoride). This structure is used as a high-voltage, large-current power transmission line. This conduit aerial cable is manufactured in short units at a factory, transported to the line installation site, and successively connected by welding or the like and installed at the site. In the case of on-site connection of the sheath, it is important to maintain the sheath airtight against the SF ₆ sealed inside, so it is connected by reliable and complete welding.
The sheath is usually a large-diameter pipe made of aluminum or stainless steel with a diameter of 300 mm to 1,200 mm, and because it is easily distorted, a method of connecting it with a flange at the end was used, but the flange method requires processing and other costs. Because of the high cost, from the point of view of economy, connections are often made by the tube expansion method in which the diameter of the end of the sheath itself is increased. To connect the sheath by the conventional tube expansion method, as shown in Figs. 1 and 2, a tube expansion part 5 parallel to the axis of a small proportion is inserted at the end of the sheath 1 on one side so that it will be inside during insertion. Similarly, at the end of the sheath 2 on the other side, a relatively large enlarged tube portion 6 parallel to the outer axis is provided. To connect the conduit aerial cable, the conductors 3 are connected by plug-in contacts 4, the expanded tube portions of the sheaths on both sides are fitted into each other, and both expanded tube portions are welded 8. Expanding the ends of the sheath changes the diameter of the sheath so that both ends can fit into each other, and by expanding the sheath, the ends become more resistant to deformation, improving roundness and making the mutual gap G small and uniform. This is to enable welding to be performed easily and reliably. However, in the pipe expansion process, it is difficult to precisely process the roundness and diameter of the expanded part.
In other words, in order to be able to fit in either case, it is necessary to process it to a standard size that creates a gap of 3 to 5 mm. Therefore, on-site welding is very difficult, and especially in the case of automatic welding which is sensitive to the gap dimensions, this welding is practically impossible.

The object of the present invention is to provide a connection method that eliminates the above-mentioned drawbacks by providing a tapered part in the expanded part of the sheath that goes inside when connecting sheaths on-site by the pipe expansion method of a conduit aerial cable. It is something.

The present invention will be explained below with reference to the drawings.

In the present invention, as shown in FIG. 3, when fitted, the inner sheath 1 is expanded to a larger extent than in the conventional method so that the inner diameter is slightly larger than the inner diameter of the expanded tube portion 6 of the outer sheath 2. Next, the distal end of the tube expansion section 5 that becomes the inner side is made into an axis-parallel section 11 having a diameter smaller than that of the tube expansion section 6, and a tapered section 9 is formed between this section and the outside of the tube expansion section 5 by mechanical cutting. Cut. When the sheath 1 having the expanded tube part with the tapered part 9 cut in this way is used to fit the sheath expanded tube part 6 on the other side, there will be a large gap between the parallel part 11 and the inside of the expanded tube part 6 at the time of fitting. Therefore, it is easy to fit in, and as the fitting progresses, the tip of the expanded tube portion 6 hits the surface of the tapered portion 9, and it will not advance any further. At that position, there is almost no welding gap between the inner sheath expanded tube part and the outer sheath expanded tube part, so welding becomes very easy, and automatic welding is also easily possible. Even if the roundness of the expanded portion of the outer sheath is slightly poor, it is corrected when the outer sheath 6 is pushed along the tapered portion 9 during fitting, and it naturally adheres to the surface of the tapered portion 9, resulting in an automatic centering effect. be.

In general, since the sheath is a large-diameter metal tube, it is difficult to expand the sheath, and a considerable tolerance with respect to the standard diameter is required during processing. Therefore, in the sheath tube expansion and connection method of the present invention, as shown in FIG.
Therefore, the expanded tube part 6 is machined to a standard dimension in which it abuts against the tapered part 9, but as shown in FIG. 4, the outer diameter do of the expanded tube part 5 has the maximum negative tolerance, When the positive tolerance is the maximum, the dimensions and tolerances may have to be selected so that the expanded tube portion 6 does not hit the tapered portion 9 but lies outside the expanded tube portion 5. In that case, the fifth
If the gap g shown in the figure is selected to be smaller than the size required for welding, the welding operation will always be easy and automatic welding can be used.

As explained above, in the sheath expansion connection method for conduit aerial cables of the present invention, a tapered part is provided in the inner sheath expansion part when connecting, and the sheaths are fitted into each other and welded, so fitting is easy and on-site. This is an effective method that allows for reliable welding and can also be used with automatic welding.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a conventional method for expanding and connecting the sheath of an aerial cable, and FIG. 2 is a detailed cross-sectional view of section A of the same. FIGS. 3 and 4 are cross-sectional views showing embodiments of the present invention. 1, 2...Sheath, 3...Conductor, 4...Plug-in contact, 5...Inner sheath expansion section, 6...
... Outer sheath expanded tube part, 7... SF ₆ gas, 8... Welded part, 9... Tapered part, 11... Parallel tip part.

Claims (1)

[Scope of Claims] 1. In the sheath expansion connection method in which the ends of the sheaths on both sides of a conduit aerial cable are expanded, fitted into each other, and connected by welding, (a) up to the tip of the end of the sheath that becomes inside, (b) Create an expanded tube section with an outer diameter larger than the inner diameter of the expanded tube section of the sheath that will become the outer side;
Cutting is performed to form a tapered part that connects the outer surfaces of the parallel part and the expanded tube part, and (c) the processed part is fitted into the expanded tube part of the outer sheath up to the tapered part, and both are welded. How to connect a conduit aerial cable. 2 In the tube expansion process, the tube is expanded to a standard dimension in which the outer diameter of the inner sheath tube expansion section is larger than the inner diameter of the outer sheath tube expansion section. The pipe is expanded with a tolerance such that when the inner diameter of the expanded sheath tube portion is the maximum plus tolerance, the outer diameter of the expanded tube portion of the inner sheath is not smaller than the inner diameter of the expanded tube portion of the outer sheath by 5 mm or more. A method for connecting a conduit aerial cable according to claim 1.