CH660643A5 - METHOD FOR PRODUCING A CAST RESIN ISOLATOR WITH CAPACITIVE FIELD CONTROL INSERTS. - Google Patents

Description

The invention relates to a method for producing a cast resin isolator with capacitive field control inserts according to the preamble of claim 1. It is particularly suitable for the production of insulators for cable fittings, in particular terminations of high-voltage cables.

It is known to produce such fittings from cast resin cast in appropriately recessed molds. For example, reference is made to DE-PS 1 590 294, which relates to an electrical insulating body made of cast resin, in particular for sleeves and terminations of electrical cables, with at least one field control electrode made of wire mesh cast therein, the wire mesh gaps of which are bridged by electrically conductive casting resin. However, the production of this insulating body, in particular the field control electrode cast in it, which is designed in such a way that stresses in the insulating body caused by shrinkage or by changing the temperature as well as field tip effects on the electrode surface are avoided.

This is possible from DE-AS l 120 003, in which various types of the production of cast resin insulators with capacitive control inserts are described, the respective disadvantage of which is indicated. According to the teaching of this design specification, these disadvantages are to be avoided by the fact that the capacitive control inserts to create expansion reserves between the individual layers of insulating material cast on one after the other consist entirely or partially of a compressible-elastic material which either itself is electrically conductive or has interconnected electrically conductive surfaces is. For the production of this known casting resin isolator, several casting processes, namely a special casting for each capacitive insert, are necessary. It goes without saying that this method is particularly complex if the insulating body produced in this way, depending on the voltage level, has a plurality of capacitive control deposits, e.g. 5 to 20, should contain, as is required for example for use with a maximum voltage set.

The invention has for its object to provide a method for producing a casting resin isolator of high mechanical and electrical strength with more than two capacitive field control inserts, which can be carried out in a simple manner in a cost-saving manner and only requires two casting processes. This object is achieved by the invention specified in claim 1.

What is important for this is the special shape of the outer surface of the preform with the ring pockets, which are designed and dimensioned such that they are produced as recesses of the preform, which is cast in one piece by a single casting in a hollow mold, and can then be easily coated with the conductive coating, e.g. can be provided by metallizing the outer body surface. After the casting resin covering has been applied, this forms the capacitive field control deposits which overlap at a distance by a final second potting of this insulating body.

In a particularly advantageous manner, the dimensions of the core, the pockets and the ring webs that delimit them, and the thickness of the casting resin shell, which then surrounds the preform with a single potting and fills its pockets, can be selected such that, taking into account the shrinkage of the second potting, quasi one-piece, mechanically strong and tension-free and electrically high-quality insulating body is created.

Advantageous developments of the invention are specified in the dependent claims 2 to 4, which relate to different variations in the pouring of additional metallic devices into this insulating body. These are devices for holding the head and / or foot fitting and for holding the insulating body. These are poured into the insulating body produced in this way by appropriate arrangement before the casting of the preform or before the subsequent casting of the same with the same casting resin in such a way that they form firmly anchored, quasi one-piece parts of the same, which mechanically and / / or perform electrical functions of the same.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawing. Show it:

1 shows a semi-section of a preform with a metallized lateral surface, before the removal of its ring land adapters, in a longitudinal section;

2 shows in half section an embodiment variant of a cast resin isolator produced by the described method;

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3 and 4 also in half section various other versions of this isolator.

As can be clearly seen in FIGS. 2, 3 and 4, the insulator produced according to the new method is composed of a preform 1 made of cast resin and a cast resin shell 2 which supplements this for its form of use, which e.g. conical with a simply curved, smooth or corrugated outer surface or with recesses and / or projections of the same, e.g. can be designed with umbrellas for outdoor use. The one with the first step in a e.g. two-part hollow mold poured pre-body 1 has on its outer surface cascading ring pockets 3, which are delimited by ring webs 5. These are made electrically conductive, e.g. metallized or provided with a conductive coating applied in any way, such as painting, spraying, flame spraying or the like. This advantageously takes place immediately after the preform 1 has been removed from its casting mold, preferably while it is still warm and not shrunk, as a result of which the adhesion of the conductive covering, e.g. also a graphite layer, improved and this is compressed. Thereafter, the edges 5a of all the ring webs 5 are removed mechanically, e.g. cut off, whereby the previously made lateral surface of the pre-body 1 is divided into a number of electrodes which overlap each other and correspond to the previously formed number of ring pockets 3 and which form separate capacitive field control inserts 4 of the casting resin insulator, which is finished with a further potting in its final form.

As shown in FIGS. 2 to 4, a head fitting connection ring 7 and a cylindrical extension 8 of a foot fitting flange 6 made of metal can also be cast in the smaller end area coaxially to its longitudinal axis when the preform 1 is cast. Here, the head fitting connection ring 7 is already insulated from the outer surface when the preform 1 is poured out, and then the conductive coating is applied to it only up to an area thereof, which lies away from the connection ring 7. At the same time, however, the conductive covering at the other end of the preform 1 extends beyond the extension 8 of the foot fitting flange 6 cast therein.

contacting it so well in an electrically conductive manner. This combines the advantage of a particularly simple casting of the outer casting resin casing 2 which isolates the electrodes with good grounding of the bottom or outermost field control electrode, with a simultaneous capacitive effect of all other field control inserts 4. This brings with it the advantage of a particularly compact and space-saving and mechanically solid construction itself, as can be seen from FIG. 2 to 5.

According to another process variant which is particularly advantageous in terms of process technology, prior to casting the preform 1, which is formed solely with the ring pockets 3, after it has been provided with the conductive coating, a head fitting connecting ring 7, which is designed as an inwardly stepped cylinder body, is placed on its head end. and arranged at the same distance around the foot end of the pre-body 1 of the foot fitting flange 6 with the cylindrical extension 8 in a coaxial position. These devices are then - insulated from the field control deposits 4 - cast into the cast resin shell 2. This leads in a particularly simple manner to a cast resin insulator with end fittings, the inside and outside surfaces of which are included in the capacitive field control.

According to one of the previously described similar process variants, a metal ring 9, which contacts the bottom field control insert 4 and which is formed in one piece with a cable entry 10 or is firmly connected, is placed in the area of the outer surface before the casting of the preform 1 with the casing body 2 instead of the insulated foot fitting flange 6 the cast resin shell 2 to be produced at a distance above the metal ring 9, a retaining ring 11 for insulated fastening of the insulator to a base plate 12, but also in the manner described above, the head fitting connection ring 7 at the head end of the insulator thus produced. This leads to an isolator according to FIG. 4, which combines the advantages of cost-effective production with that of a versatile application with different cable terminations and their simple assembly. The outermost field control electrode 4 can be grounded via the metal ring 9, which is conductively connected to the metal sheath 13 of a cable to be sealed via the lead-in 10 and a solder seal 14.

The preform 1 can also be cast in a hollow cone in its lower region, as indicated in FIGS. 3 and 4, for receiving a central electrode part 15, which is made separately, for example, from a conductive elastomer. This considerably increases the versatility of the possible uses of such a device produced cast resin isoator.

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Claims (4)

660 643 1. A method for producing a cast resin isolator with capacitive field control inserts, a cast body (1) first being cast from the cast resin, then the outer surface of which is at least partially provided with an electrically conductive coating and finally cast with an outer cast resin shell (2), characterized in that the preliminary body (1) is cast with ring pockets (3) overlapping one another in cascade fashion, after the application of the conductive covering the edge (5a) is removed from the upright ring webs (5) delimiting the ring pockets (3) and the Conductive covering is divided into mutually overlapping, separate field control inserts (4), and these are embedded in the casting resin in the subsequent casting of the preform (1), which also fills the ring pockets (3), with the casting resin shell (2) and insulated therein . 2. The method according to claim 1, characterized in that when casting the pre-body (1) coaxially to its longitudinal axis, a head fitting connection ring (7) and a cylindrical extension (8) of a foot fitting flange (6) are cast in with metal, the head fitting Connection ring (7) isolated from the outer surface of the pre-body (1), on the other hand the cylinder extension (8) is exposed and when applying the conductive covering, contacting this is included with this (Fig. 2). 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that before the casting of the pre-body (1) on the head end of a head fitting connection ring (7) and at a uniform distance around its foot end a foot fitting flange (6) with cylindrical extension (8) in coaxial Layer arranged and - isolated from the field control inserts (4) - also cast in the cast resin shell (2) (Fig. 3). 4. The method according to claim 1, characterized in that a lowermost field control insert (4) contacting metal ring (9) which is integrally formed with a cable entry (10) or fixedly connected, and in the area of the outer surface of the cast resin shell (2) in Distance above the metal ring (9), a retaining ring (11) for insulated fastening of the insulator (1, 2) to a base plate (12) are also cast in (FIG. 4).