JPH0421408B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an improvement in a method for manufacturing an extrusion mold joint of an insulated cable, and particularly to cooling of the mold joint after extrusion molding. .

[Prior Art] In the extrusion process of an extrusion mold joint portion of an insulated cable, after injecting a polyethylene resin as an insulating resin into an extrusion mold, when the mold is rapidly cooled, a cavity is generated inside the extrusion mold. For this reason, the mold is slowly cooled, but merely slow cooling results in surface cracks due to non-uniform release from the mold.

In order to prevent this crack, it has been practiced to cool the polyethylene resin while applying gas pressure.

[Problems to be solved by the invention] However, if gas pressure is applied directly from the insulating resin injection port or overflow port, gas pressure is not applied to the interface between the mold and the insulating resin, and the inside of the insulating resin is There was a problem that gas entered the tank in a balloon shape. When gas pressure was applied through the ram, there was a problem that a cavity was generated directly under the ram during the cooling process. In order to prevent this, it may be possible to increase the gas pressure, but this also poses a problem from the viewpoint of the pressure resistance strength of the mold.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, to perform uniform cooling at normal gas working pressure without gas intrusion into the insulating resin, and to facilitate separation of the insulating resin from the mold. An object of the present invention is to provide a method for manufacturing an extrusion mold joint part of an insulated cable, which can be carried out to obtain stable and good quality.

[Means for Solving the Problems] The gist of the present invention is to provide a membrane with good separation properties on the inner surface of a mold, and then perform extrusion molding.

That is, the present invention provides a method for manufacturing an extrusion mold joint of an insulated cable, in which a membrane with good separability is laid on the inner surface of the extrusion mold except for the insulating resin injection port and its overflow port, and the extrusion mold Extrusion mold joint part of an insulated cable, characterized in that after injecting and filling the inside of the mold with an insulating resin, the mold joint part is cooled while applying gas pressure between the extrusion mold and a membrane with good separability. This is a manufacturing method.

In the present invention, a film with good separability is a film that has the property of being easily separated from molds, insulating resin, etc. without sticking to it, such as a fluororesin sheet or a silicone tube, and has a strength that does not easily break as a film. Anything is fine as long as it is. It includes not only single-layered membranes, but also many layered membranes and textile-like ones. In order to make the surface shape of the mold joint part more uniform, it is effective to use a membrane with good separability that has a checkered pattern with a separated non-membrane part.

In addition, when a membrane with good separability is laid on only the upper half of the mold, it has a considerable effect, and it is even more effective when it is laid on the entire inner surface of the mold.

As a method of cooling, of course a mold is used, but a method of cooling and circulating pressurized gas may also be used.

[Function] A film with good separability is placed on the inner surface of the extrusion mold, and by cooling while applying gas pressure between the two, the insulating resin filled in the mold is slowly released while being subjected to compressive stress. Moreover, since the entire surface is cooled uniformly, no cracks occur.
Furthermore, since gas pressure is applied through the membrane, gas does not partially intrude into the resin. Furthermore, when the mold is removed after cooling, it is easy to separate the mold from the insulating resin, resulting in a stable and high quality extrusion mold joint.

[Example] FIG. 1 is a diagram showing an embodiment of the present invention.

In FIG. 1, when manufacturing the extrusion mold joint part 4 of the CV cable connection part 3, the whole mold part of the mold 2 of the extrusion mold joint part 4 except the insulator resin injection port 5 and the overflow port 6 is shown. A fluororesin sheet was laid on the inner surface as a membrane 1 with good separability. Next, polyethylene resin was injected from the insulator resin injection port 5 and overflowed from the overflow port 6, thereby filling the inside of the mold 2 with the resin. During cooling, gas is supplied to the mold 2 from the gas injection ports 7a and 7b.
The extrusion mold joint part 4 was cooled while maintaining a pressure of 5 kg/cm ² by blowing between the inner surface of the membrane 1 and the fluororesin sheet having good separability. As a result, a high-quality extrusion mold joint 4 was manufactured without gas entering into the resin of the extrusion mold joint and without cracks.

FIG. 2 is a diagram showing another embodiment of the present invention.
FIGS. 3a and 3b are explanatory diagrams of two examples of the membrane 11 with good separation properties used in FIG. 2. In Figure 2,
When manufacturing the extrusion mold joint part 14 of the CV cable connection part 13, a film 11b having a checkered pattern with good separability as shown in FIG. It was laid. A feature of this film 11b is that non-film portions 18 are distributed in a checkered pattern. Further, overflow ports 16a, 16b, and 16c for insulating resin are provided at the positions of the non-film portions. In this case, a gas inlet for applying gas pressure is provided opposite the location where the membrane is present (not shown).

A silicon tube was used as the membrane 11b with good separation properties.

Insulator resin is injected into the mold 12 through the insulator resin injection port 15
Press-fit the overflow ports 16a, 16b,
The mold was filled with insulating resin by overflowing from 16c.

Next, gas was injected between the inner surface of the mold and the silicone tube from the gas inlet (not shown), and the gas pressure was 10.
Cooling was performed while pressurizing at Kg/cm ² . After the mold is removed after cooling, the shape of the extrusion mold joint part is more uniform as a whole because the insulating resin at the part corresponding to 18 is bonded to the inner surface of the mold in the open hole part where there is no film quality. The situation has become serious. Figure 3a
Like the membrane 11a, the overflow port hole 16a,
In the case of a film where almost the entire surface is flat except for those equipped with 16e and 16f, large undulations are likely to form on the surface because the insulating resin sinks uniformly due to its own weight over the entire film. . Membrane 11 with good separation properties
A film having a shape like b can improve this problem as described above.

[Effects of the invention] By installing the membrane with good separability of the present invention, gas intrusion and deformation into the insulating resin is eliminated, surface cracks do not occur, and the normal gas working pressure (0.5
~10Kg/cm ² ), it became possible to cool uniformly, the insulating resin and the mold could be easily separated, and it became possible to produce stable and high quality extrusion mold joints.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of one embodiment of the extrusion mold joint according to the present invention, Fig. 2 is a cross-sectional view of another embodiment of the present invention, and Fig. 3 is a cross-sectional view of an extrusion mold joint part according to an embodiment of the present invention. 2 is a perspective view of two examples of membranes; FIG. 1, 11, 11a, 11b... Membrane with good separation properties, 2, 12... Mold, 3, 13... CV cable connection part, 4, 14... Extrusion mold joint part, 5, 15... Insulation Body resin inlet, 6,16
a, 16b, 16c...Overflow port, 7
a, 7b...Gas inlet, 16d, 16e, 16
f...Overflow hole.

Claims (1)

[Claims] 1. In a method for manufacturing an extrusion mold joint portion of an insulated cable, a portion of the inner surface of the extrusion mold excluding an insulating resin injection port and its overflow port,
After installing a membrane with good separability and injecting insulating resin into the extrusion mold, the mold joint is cooled while applying gas pressure between the extrusion mold and the membrane with good separability. A method for manufacturing an extrusion mold joint of an insulated cable. 2. The method for manufacturing an extrusion mold joint portion of an insulated cable according to claim 1, wherein the membrane with good separability has a shape in which non-membrane parts are dispersed in a checkered pattern.