JPS5850485B2 - How to straighten plastic insulated cables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for straightening a plastic insulated cable, in which the cable is heated to a predetermined temperature and then a predetermined cooling time is elapsed before the straightening operation is performed.

When connecting plastic insulated cables, the cable may become curly in the drum and cannot be straightened, or if you try to bend it into a predetermined shape, it may not be possible to form it at room temperature.

In such cases, conventional methods have been used to soften the insulator by heating the conductor by heating it, or by wrapping a heater around the outside of the conductor, and then removing the curl.

However, this method has the disadvantage that the shielding copper tape wrapped around the outside of the plastic insulation will wrinkle if it is bent inadvertently during the straightening operation.

This phenomenon occurs because the insulator thermally expands during the previous heating and applies abnormal internal pressure to the shielding copper tape, making it impossible for the tape to escape in the cable axis direction at the overlapped part. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a cable straightening method that does not cause wrinkles in the copper tape even when the cable is heated to straighten the cable.

According to the present invention, the above purpose is to heat the cable to a temperature higher than that required for straightening the cable, cool it to some extent, and contract the insulator that expanded due to the previous heating, thereby creating an abnormal pressure between the insulator and the shielding copper tape. This can be achieved by removing the straightness after releasing the tape, thereby allowing the tape to escape in the cable axial direction at the overlapped portion.

Regarding the temperature range for heating and cooling at this time, the initial heating temperature must be below the allowable continuous use temperature of the insulator, and the temperature when removing the straightness must be above the temperature at which the straightness can be removed. It is necessary that there be.

Next, an example of a typical C■ cable among plastic insulated cables will be described.

The attached drawing shows the relationship between temperature and time for heating and cooling the cable.

In the drawing, the temperature range where the insulator can be straightened is T4~
It is between T1.

Here, a case will be described in which a heater is wound around the cable to heat it and the temperature is raised to T3 to remove the curl.

In this case, during the temperature rise of the cable (time A-B
) or even during the temperature maintenance (time B-C), the plastic is soft and can be straightened, but as mentioned above, the copper tape tends to wrinkle at the same time as the straightening.

Therefore, in the present invention, after heating the cable to a predetermined temperature, the cable is cooled to a certain extent (time (I)-E), and then the straightness is removed.

As a result, the pressing force from the insulator on the copper tape is released, and as a result, the copper tape can escape in the cable axial direction at its own overlapped portion.
It is possible to completely prevent wrinkles from forming on the copper tape.

In order to demonstrate the effects of the present invention, Table 1 shows experimental data obtained by bending C.
Shown below.

In the data in this table, the cable bending direction was opposite to the drum winding pattern, and the bending radius was 10d and 8d, where d was the cable diameter.

In the above table, the insulator surface temperature corresponds to T3, which is the temperature raised to remove the curl.

Also, data number 2 is in C in the diagram, number 3 is in D, and number 4 is in
corresponds to E.

Incidentally, if the relationship with the cable sheath surface temperature is investigated in advance, the insulator surface temperature can be easily known by looking at the sheath surface temperature.

As is clear from the tables and figures below, although wrinkles occur when straightening is performed under heating in the conventional method, according to the method of the present invention, wrinkles are removed as shown in data numbers 3 and 4. does not occur.

Note that the heating and cooling temperature of the cable varies depending on the type of cable, and is not limited to the range shown in the diagram.

[Brief explanation of the drawing]

The attached drawing is a graph showing the relationship between the temperature and time of the cable to be heated and cooled.

Claims (1)

[Claims] 1. A plastic insulated cable is heated, its cable insulator is heated to a predetermined temperature, and then it is cooled for a predetermined period of time, and after the temperature of the cable insulator is returned to the predetermined temperature, the straightening is performed. How to straighten plastic insulated cables.