JPH0481491B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] In order to streamline the connection work of CV cables,
The anti-corrosion layer and the reinforcing insulating layer may be formed using a heat-shrinkable tube instead of being wrapped with tape.

The present invention relates to a method for manufacturing a heat-shrinkable tube used in such cases, and particularly relates to a method for manufacturing a heat-shrinkable tube for use in such cases.
The present invention relates to a method for manufacturing a thin-walled, large-diameter heat-shrinkable tube.

[Prior Art] In FIG. 4, 10 is a lower core, and in this case, for example,
A CV cable core is used, and its conductor 12 is used as part of an electrical heating circuit as described later.

20 is an original tube made of, for example, crosslinked polyethylene.

Reference numeral 30 denotes a pressurizing cylinder, which is placed over the outside of the original tube 20, and sealed between it and the end of the original tube 20 by an O-ring.

32 is a metal fitting, which includes the lower core 10 and the original tube 2.
0 and is sealed with an O-ring. This metal fitting 32 and conductor 12
A conductor 34 is connected to the pressurizing cylinder 30, and a conductor 36 is connected to the pressure cylinder 30, thereby forming an electric circuit for heating the original tube. Note that the heating is performed using the pressure cylinder 30.
By heating with electricity.

38 is a wedge whose tip is pushed between the original tube 20 and the lower core 10, and for example, nitrogen gas is sent into the inside of the original tube 20 through the passage 40 to apply internal pressure to the original tube 20 and expand its diameter. .

Reference numeral 42 denotes a gas inlet/outlet, from which, for example, nitrogen gas is initially pressurized to apply external pressure to the former tube 20, and as the diameter of the former tube 20 expands,
I try to keep the external pressure constant by evacuation little by little.
(External pressure increases as the space between them shrinks).
Note that the reason for applying external pressure to the original tube 20 is to prevent foaming during heating and to prevent deterioration of the insulation properties.

[Problems to be Solved by the Invention] As mentioned above, when the original tube 20 is particularly long (for example, about 10 m), thin, and has a large diameter, it may not inflate uniformly. For example, if parts A and B in FIG.
It is cut off from. As a result, gas remains in portion C, resulting in a portion that does not inflate.

However, if a large number of gas inlets and outlets 42 are provided at minute intervals in the longitudinal direction of the pressurizing cylinder 30, the above problem will not occur. However, in this case, it becomes very difficult to apply a constant external pressure to the original tube 20 (to prevent foaming).

[Means for Solving the Problems] The present invention provides a gas leak means in the longitudinal direction on the inner surface of the pressurizing cylinder 30.
As mentioned above, even if the original tube 20 does not inflate uniformly, the gas is prevented from remaining.

[Description] (1) Fig. 1 shows a case where a cloth 50 is used as a gas leak means.

A cylindrical cloth 50 is attached to the inner surface of the pressure cylinder 30 by, for example, adhesive. As the cloth 50, a material that does not deteriorate even at the melting point of the original tube 20, such as canvas, is used.

In this way, when the original tube 20 is inflated, the cloth 50 is
be in contact with This allows gas to pass between the cloth 50 and the pressurizing cylinder 30, or even within the cloth 50 itself, so that even if there is a place where both sides are blocked, like the part C in FIG. 1, no gas remains.

(2) Figure 2 shows a case where a short thin-walled pipe 52 is used as the gas leak means.

This thin-walled pipe 52 is provided with a spigot 54 on one side and a socket 56 on the opposite side, as shown in FIG.
Let it be inscribed in 0.

Since the spigot 54 is simply inserted into the socket 56 and is not particularly sealed,
The gas passes between them, and then the thin walled pipe 5
2 and the pressurizing cylinder 30, the gas inlet/outlet 4
You can go out from 2.

Therefore, gas can be prevented from remaining and the diameter of the original tube 20 is uniformly expanded.

(3) FIG. 3 shows a case where a long thin-walled pipe 58 is used as the gas leak means.

This thin-walled pipe 58 has, as shown in FIG.
A narrow longitudinal groove 60 is provided on the inner surface.

Even if the original tube 20 swells and becomes inscribed in this thin-walled pipe 58 (at that time, the original tube 20 is heated and becomes very soft),
Due to surface tension, it does not penetrate into the groove 60.

Gas can therefore escape through this groove 60 and is prevented from remaining.

[Effects of the Invention] Since a longitudinal gas leak means is attached to the inner surface of the pressurizing tube 30, even if the source tube 20 is long, thin, and has a large diameter, as described above, gas will not leak out. There will be no areas where it remains and does not swell.

Therefore, the diameter of the original tube 20 is expanded uniformly.

[Brief explanation of drawings]

1, 2, and 3 are explanatory diagrams of different embodiments of the present invention, and FIG. 4 is an explanatory diagram of the prior art. 10... lower core, 20... former tube, 30...
... Pressure cylinder, 32 ... Metal fitting, 50 ... Cloth (an example of gas leak means), 52 ... Thin wall pipe (an example of gas leak means), 58 ... Thin wall pipe (an example of gas leak means).

Claims (1)

[Claims] 1. Cover the outside of the source tube 20 with the pressure tube 30, seal between it and the end of the source tube 20, and inject gas between the source tube 20 and the pressure tube 30. While applying external pressure to the original tube 20 after being press-fitted, the original tube 20 is heated and internal pressure is applied to it to expand its diameter.
With the diameter expansion of 0, the original tube 20 and the pressurizing tube 3
In the method for manufacturing a heat-shrinkable tube, in which the gas pressurized between 0 and 0 is discharged from both ends of the pressurizing tube 30 to maintain a constant external pressure applied to the original tube 20, the inner surface of the pressurizing tube 30 is A method for manufacturing a heat shrink tube, characterized in that a longitudinal gas leak means is provided.