JPH0143432B2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Objectives of the Invention] The present invention relates to a cross-linked polyethylene insulated cable (hereinafter referred to as
This article relates to a method for manufacturing the connection part of a CV cable (referred to as a CV cable).

CV cable connections are manufactured by extruding or tape-wrapping polyethylene containing a cross-linking agent, and integrating it with the cable insulation using heat molding. In this case, when a crosslinking reaction occurs due to heating, a reaction gas is generated, but if this is left untreated, the insulator may foam.To prevent this, it is recommended to apply gas pressure to the insulator and pressurize its surface. It's normal. This gas pressure is removed after the crosslinking reaction is completed, but if the insulator near the cable conductor is not sufficiently cooled even after the reaction is completed, foaming may still occur due to the removal of the gas pressure. Therefore, a sufficiently long cooling time is provided and the gas pressure is released after the conductor has completely reached ambient temperature. However, the cooling time required for this method is extremely long;
Another problem was that it was difficult to control the gas pressure at a constant level over such a long cooling process.

An object of the present invention is to provide a method for manufacturing a connection portion of a CV cable, in which the cooling time of the insulator is sufficiently shortened, and the problem of foaming does not occur, in contrast to the conventional method described above.

[Summary of the invention]

According to the present invention, the connection portion insulator surface temperature and/or
Alternatively, the above object is achieved by measuring the surface temperature of the cable insulator, estimating the temperature of the cable conductor from this, and releasing the gas pressure when the conductor temperature becomes below the melting point of the insulator.

〔Example〕

FIG. 1 shows a thermal equivalent circuit of a CV cable and its connection.

In Figure 1, Ta is the insulator surface temperature,
This can be measured. R is the thermal resistance of the insulator, r
is the thermal resistance of the cable conductor, C is the heat capacity of the insulator,
And c is the heat capacity of the conductor, all of which can be known in advance. Therefore, it is easy for those skilled in the art to derive the conductor temperature Tc from these values. By providing a plurality of such measurement systems around the connection portion, the conductor temperature Tc can be determined correctly.

FIG. 2 is a schematic diagram showing an embodiment of an apparatus for carrying out the method of the invention.

In FIG. 2, temperature sensors 2 are placed at appropriate locations on the connection bridging mold 5 and the cable 6. An appropriate gas is supplied to the mold 5 from a gas cylinder 4 via a gas pressure control valve 3 to pressurize the inside of the mold. This control valve 3 is controlled by a control computer 1.

The temperature sensor 2 is connected to the control computer 1, and this control computer calculates the conductor temperature Tc ₁ ......Tc ₃ at each location from the insulator surface temperature Ta ₁ , ......Ta ₃ measured by the temperature sensor 2. , and further calculate the average temperature of the conductor at the connection. This allows the temperature of the insulator near the conductor to be known.

When this temperature drops below the melting point of the insulator or the temperature at which its physical properties suddenly change (approximately 100°C in the case of polyethylene), the control computer 1 controls the gas pressure control valve 3 to close, and Release the gas pressure. Thereafter, by dismantling the mold 5 and performing air cooling or water cooling, rapid cooling of the connecting portion can be easily performed.

A program for such processing by the control computer 1 can be created extremely easily, and therefore will not be described in detail.

〔Effect of the invention〕

According to the method of the present invention, the connection part, which takes the longest time in CV cable connection work, can be cooled in an extremely short time, and problems such as foaming and cracking of the insulator at the connection part can be completely eliminated by stable insulation. It is possible to manufacture connections with performance.

[Brief explanation of drawings]

FIG. 1 is a thermally equivalent circuit for an insulator and a conductor, and FIG. 2 is a schematic diagram of an embodiment of a device for carrying out the method of the invention. 1... Control computer, 2... Temperature sensor, 3... Gas pressure control valve, 4... Gas cylinder, 5
...Bridging mold, 6...CV cable.

Claims (1)

[Claims] 1 After forming the insulator at the connection part of a cross-linked polyethylene insulated cable by extrusion molding or wrapping it with tape, that part is heated while being pressurized with air, nitrogen gas, SF ₆ gas, etc., and the insulation of the cable is formed by a cross-linking reaction. In the method of manufacturing a connection part that is made to become integrated with the body, the temperature of the cable conductor is determined in the cooling process after the completion of the crosslinking reaction,
A method for manufacturing a connection part for a cross-linked polyethylene insulated cable, characterized in that the pressure of the gas is removed when the temperature drops below the melting point of the insulator of the connection part.