JPS5923631B2 - Rubber, plastic wire and cable connection molds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for connecting rubber, plastic electric wires and cables.

Rubber or plastic cables, particularly CV cables having an insulating layer of cross-linked polyethylene, are easy to maintain and have recently been increasingly applied to high-voltage cables.

In response to this, higher reliability than ever is required for the connecting portions as well. To connect a high-voltage CV cable, wrap polyethylene, cross-linked polyethylene, ethylene propylene rubber (EP rubber), etc. in a tape shape around the insulating layer of the cable connection part, cast it using a mold, and then heat it. In many cases, a method is adopted in which the cable insulation is integrated with the cable insulation.

In these methods, if the insulating layer is applied by winding a tape, there is a risk that foreign matter undesirable in terms of electrical performance may be drawn in when the tape is wound, so a casting method using a mold is more preferable. However, this method using a mold has the problem that the conductor is pushed eccentrically by the injected resin that gets into the void during casting. The present invention has been made in view of the above.

That is, in the present invention, the injection port and overflow hole are arranged at symmetrical positions divided into two parts along the cylindrical axis of the mold, and the injection port is provided in the center of the mold and the overflow hole is provided on both ends of the mold. The object of the present invention is to provide a mold for connecting rubber and plastic electric wires and cables, which allows resin to flow easily within the mold and solves the above-mentioned problems. The present invention will be explained in detail using exemplary FIGS. 1 and 2. The mold 1 is split into two parts along the cylinder axis, each with an injection port 2 in the center, and the resin injection part near both ends.
A hole 3 for overflow is provided in each. Further, the mold fitting portion where the resin is injected is provided with a concave groove 4 and a convex striped protrusion 5 that matches the groove so as to fit therein. Furthermore, cable gripping portions 6 having a wall thickness thinner than that of the mold body are provided at both ends of the mold as necessary. By providing injection ports and overflow holes in each of the two molds as shown in the figure, resin can be injected from two symmetrical locations and overflow can occur, resulting in a symmetrical flow of resin within the mold. Therefore, the injected resin balances the force applied to the conductor and prevents deflection.

In particular, if the resin to be injected is polyethylene with a cross-linking agent, the temperature of the mold and resin cannot be increased to prevent the cross-linking agent from decomposing, and the resin will cool inside the mold unless the pouring speed is increased. There is the problem of creating voids, and in this case it becomes even more necessary to balance the forces applied to the conductor.

In addition, with this arrangement, the resin injected from the center of the mold sequentially pushes out the air in the mold through the overflow hole, thereby preventing the board from being caught in the insulating layer.

The reason why a concave groove 4 and a convex streak-like protrusion 5 are provided in the mold fitting part where the resin is poured is to prevent the injected resin from leaking from the mold joint. be.

When removing the mold after casting, it is necessary to cool the mold and the injected resin.

At this time, if resin leaks from the mold joint, cracks may appear in the insulation layer at the mold joint during cooling, or insufficient pressure may not be applied to the interface with the cable insulation layer, resulting in poor adhesion. do. In the mold according to the present invention, since the resin does not leak at the mold fitting portion, the above-mentioned cracks and poor adhesion can be prevented.

Furthermore, if cable gripping parts with a thinner wall thickness than the resin injection parts are provided at both ends of the mold, the center of the conductor can be set at the center of the mold (it can be set at the center in the radial direction). This is more desirable because it can reduce eccentricity and at the same time prevent deformation of the cable during pouring.

In the case of a cable with a thick conductor, the temperature of the cable will rise due to the spread of heat from the conductor, and there is a risk that the cable may become deformed at the end of the mold. By providing a thin cable gripping part, the mold temperature at both ends of the mold can be suppressed to a level that does not deform the cable, and because the mold end is located at the place where the cable temperature has dropped, the above deformation occurs. can be prevented. The thickness of the cable gripping part should be as thin as possible unless there is a problem in terms of strength, and the length of the gripping part depends on the thickness of the gripping part, but a sample length of 200 mm is sufficient. The connection portion insulating layer is molded using this mold in the following manner.

First, the connection part to which the conductor is connected is set in the mold, the two molds are brought together, and then firmly secured with a metal band or the like to prevent the resin injected from the mold fitting part from leaking.
Furthermore, after preheating the mold and the cable connection part, resin is injected from two opposing injection ports, and molded by pouring the resin until it overflows from the four overflow holes.

Here, in order to confirm the effects of the present invention, a cross-linked polyethylene insulated cable with an insulation thickness of 7 mm was used for a conductor of 150 m, and various molds were made with a thickness of 10 m and 71 L using polyethylene as an insulating layer at the connection part with a cross-linking agent (dicumyl peroxide). (Molded by heating 60 molecules in a mold at 110° C.), board curling, uneven thickness, and deformation of the cable at the end of the mold were compared.

Further, under nitrogen gas pressure (5k9/CTlL2), thermal crosslinking (heating at 20°C for 2 hours) was performed to compare the adhesion state at the interface with the cable insulation and electrical performance. As shown in Table 1, the results show that if the mold of the present invention is used, uneven thickness due to board entrainment will be avoided.
It was confirmed that a wire/cable connection with excellent electrical properties could be obtained without causing any deformation of the cable.

[Brief explanation of drawings]

Figure 1 is a longitudinal sectional front view of the mold of the present invention, Figure 2 is a sectional view taken along line A-A in Figure 1, and Figures 3 to 6 are of the mold used in experiments to confirm the effects of the present invention. In the longitudinal front view, Fig. 3 is the one used in Comparative Examples 1 and 2, Fig. 4 is the one used in Comparative Example 3,
FIG. 5 shows an example used in Example 1, and FIG. 6 shows an example used in Example 2. 1...Mold, 2...Pouring port, 3...
... Hole for overflow, 4 ... Concave groove, 5 ... Linear protrusion, 6 ... Cable gripping part.

Claims (1)

[Claims] 1. In the mold used to inject and mold the insulating layer of the connection part of rubber or plastic electric wire or cable using a rubber or plastic mold, the mold is divided into two along the cylinder axis. In each of these halves, a hole for injecting rubber and plastic is provided in the center part, and overflow holes for rubber and plastic are provided near both ends of the part where resin is injected, respectively, so that they are symmetrical with each other. Rubber/plastic electric wire/cable connection mold 2 characterized by having grooves and matching streak-like protrusions provided on the surface where the two halves of the rubber/plastic injection part fit together.From the rubber/plastic injection part. An electric wire with a thinner wall thickness, and a rubber according to claim 1, which has cable gripping portions at both ends.
Mold for connecting plastic wires and cables.