JPS643133Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an internally cooled cable for supplying power to electric furnaces and the like.

[Conventional technology]

Conventionally, as internally cooled cables for electric furnaces, etc., multiple tinned copper wires are twisted together as conductors around the outer periphery of a helical tube made of a steel strip or hard copper strip formed into a hollow helical tube shape, and then an insulating layer and a protective layer are placed on the outer circumference of the helical tube. A material with layers etc. is used. The above cable cools the cable conductor by passing a cooling medium such as industrial water inside the helical tube and increases the power transmission capacity. The problem is that it occurs at an early stage and the cable life is short.

In order to stabilize the lifespan of such cables over the long term, the inventor of the present invention first studied the causes of short-term breakage of the tinted copper wire of conventional cables, and as a result, obtained the following knowledge.

In other words, in the case of internally cooled cables for electric furnaces, etc., the work of casting molten metal, etc. inside the electric furnace to the outside of the furnace is repeated. The cable itself is also subjected to repeated bending stress. As a result, the wires in the cable are subjected to friction against each other, but the tin plating layer wears out relatively quickly and eventually peels off, exposing the copper. In this state, it is thought that the water acting as a cooling medium causes corrosion of the copper itself, eventually leading to wire breakage.

In addition, corrosion of the sparrow layer itself due to various ions contained in the cooling water used is also considered.
It is thought that the corrosion of the plating layer is accelerated by the mutual interaction between wear and corrosion, and that the portions to which bending stress is applied will clearly reach wire breakage earlier than other portions.

Furthermore, it has been found that galvanic corrosion occurs at the interface between the exposed copper and the tin-plated layer, and that the tin-plated copper wire is severely eroded by this action.

[Disclosure of invention]

Based on the above-mentioned new knowledge, the inventor of the present invention investigated various structures and decided on a structure in which a plurality of nickel-plated copper wires are provided around the outer periphery of a spiral tube through which the cooling medium is inserted, in which a metal band is formed into a hollow spiral tube shape. As a result, the cable can be stabilized for a long period of time, and the invention of the present application has been completed.

The internally cooled cable of the present invention will be explained below with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of an internally cooled cable according to the present invention.

1 is a steel strip or hard copper strip wound spirally with appropriate intervals, for example, with an inner diameter of about 10 to 30 mm.
a hollow helical tube; 2 is a nickel-plated copper wire twisted in one or more layers around the outer periphery of the hollow helical tube 1; 3 is a separator tape made of glass fiber or paper provided as appropriate on the outer periphery of the nickel-plated copper wire 2; 4 is an insulating layer made of butyl rubber or the like provided on the outer periphery of the separator tape 3;
6 is a reinforcing embedded braid, and 6 is a protective layer made of chloroprene rubber or the like.

As the nickel-plated copper wire 2 in the present invention, for example, a copper wire having a diameter of about 0.2 to 1 mm and electrically nickel plated to a thickness of about 0.1 to 2.0 μm can be appropriately used.

In addition, in order to twist the above-mentioned nickel-plated copper wires around the outer periphery of the hollow helical tube 1, several sets of strands of nickel-plated copper wires, each consisting of several to several tens of nickel-plated copper wires, are used. The wires may be twisted around the outer circumference of the helical tube 1, or the wires may be twisted so as to be arranged at a fixed pitch around the outer circumference of the helical tube 1 without being twisted in advance.

Although the internally cooled cable of the present invention has the above-mentioned configuration, the effects of the internally cooled cable of the present invention will become clearer from the following examples.

〔Example〕

A hard copper strip with a width of 8 mm and a thickness of 1 mm is formed into a helical tube shape (inner diameter of the helical tube: 12 mm) as shown in Figure 1, and a nickel-plated copper wire with a wire diameter of 0.45 mm (plated thickness :1μm) After twisting 19 strands of 34 strands together,
The test sample was a cable wrapped with 0.25 mm thick cloth tape and coated with 2.5 mm thick butyl rubber insulation.
As a comparative example, a cable having the same structure as the above cable except that the conductor was a tin-plated copper wire (plating thickness: 1 μm) was used as a sample.

A fatigue test was conducted on each of the above samples using a cable fatigue tester shown in FIG.

Figure 2 is a side view of a fatigue testing machine for observing the degree of fatigue due to repeated bending of cables, and a cable sample piece to be measured attached to the testing machine.
On the upper surface, a fixed support 11 (length: 1.2 m) and a movable support 12 (length: 1.2 m) are erected perpendicularly to the base 10. Here, the distance between the fixed support 11 and the movable support 12 is 65 cm. The movable column 12 is the fulcrum 1
3, and has a structure that allows it to lean toward the fixed support 11.

The test was carried out by attaching both ends of the cable sample 14 to be measured to the supports 15 and 16 installed on the fixed column 11 and the movable column 12, respectively.
2 in the illustrated direction, that is, in the direction of the fixed column 11, to fatigue the bent portion of the cable sample to be measured, and observe the fatigue state.

The conditions for the test were that the length of the sample was 1.5 m, the bending angle θ of the movable support 12 was 15°, and the number of bends was 5000 reciprocations. Then, water was introduced into the helical tube of sample 14 as a cooling medium, and both ends of the tube were sealed with tape to prevent water leakage.

After conducting the test under the above conditions, the water inside the helical tube was drained, the bent portion of the cable was disassembled in the longitudinal direction, and the corrosion state of the plating layer of the plating copper wire and the copper portion was observed.

The tin-plated copper wire of the comparative example cable had some parts where the tin-plated layer remained, but most of it had peeled off due to wear and corrosion between the strands, exposing the underlying copper wire. Wire breaks occurred in dozens of locations.

In comparison, in the nickel-plated copper wire of the cable of the present invention, there were no parts where the plating layer peeled off and the underlying copper wire was exposed, and there were no broken wires. Therefore, the internally cooled cable of the present invention is considered to be able to withstand use for a longer period of time than the comparative example.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of an internally cooled cable according to the present invention. FIG. 2 is an explanatory diagram showing a fatigue testing machine for internally cooled cables. Explanation of symbols: 1... Spiral tube, 2... Nickel-metsuki copper wire.

Claims (1)

[Scope of utility model registration request] An internally cooled cable characterized by having a plurality of nickel-plated copper wires on the outer periphery of a helical tube through which a cooling medium is inserted, which is formed by forming a metal band into a hollow helical tube shape.