The invention herewith defended, consists of an overvoltage discharger, of the type which, in compliance with the electrical standards for said elements, includes varistors in alignment, with end exterior contacts and an isolating means of the exterior isolating casing, said casing being constructed of a non conductive material.

The invention is characterized by compression means of the varistor assembly, new external components and other diverse improvements of the end contact parts and of the joining means of the discharger, as well as other means which assure the watertightness of the assembly.

The limiters of the amplitude and of the duration of the overvoltages in the high voltage electric lines, popularly called arresters, are well known and are perfectly controlled and standardized; that is why their fundamental construction reaffirms a series of elements and an arrangement which not only corresponds to the state of the art but is also mandatory.

As regards their outside layer, in recent times they have passed from being porcelain layers to rubber layers, due to diverse and complex reasons, among which must be emphasized the lighter weight and the improved humidity and environmental dirt repellant behaviour of the rubber, though to the detriment of the mechanical strength of the discharger.

Diverse constructions of dischargers exist with rubber isolators and metallic contact parts with an annular recess of polygonal internal finish, with an intermediate isolator tape attachment, which are simply self-carrying and do not present any mechanical strength, for example, versus false handlings or when an operator has to grip them accidentally.

The applicant is not aware of the existance of overvoltage dischargers which include tensing means of the contact parts located at the ends, internally to the contacts, in such a manner, that the intermediate aligned varistors are grouped and solidified with sufficient stiffness to compensate the lesser mechanical strength of the new rubber isolators.

The invention which is the object of the present specification, refers to an overvoltage discharger of the type which, according to the electrical standard for said elements, includes varistors in alignment, with end exterior contacts and an isolation means of the exterior isolating casing, said casing constructed of non conductive material, at present of rubber.

The varistors or "chips", in the language of the speciality, are cylindrical disks of metallic oxides, with a very high threshold of current pass, which is variable according to the included product and to the manufacturer, which may be established in numbers comprised between 1 and 4 kV per disk.

The exterior contacts of the disks are made highly complex, due to which contact parts are required, which are metallic, cylindrical and of the same diameter as the varistors, which stiffen the disk assembly and make possible an improved electric connection among them.

The invention is characterized by compression means of the varistor assembly, based on double consecutive recesses of the contact metallic parts in annular construction and with knurled internal finish, in order that the grip of the compression tape is increased on the same, said parts being joined to the end connection studs, by means of fastening elements, all of them conventional.

The assembly of varistors and contact parts is taped with a waterproof ply with adhesive on both sides, which prevents ingress of humidity or environmental dust or other residues into the contact zone between varistors, either between the opposite sides of the same or between the external sides of the exterior chips and the internal sides of the contact parts, extending towards the edge of the first annular recess of each contact part.

Next, another fabric is placed, which wraps the waterproof ply and remains adherred onto the adhesive of its exterior side, said fabric being of grated construction, in glass fibre material and with sufficient pitch to make possible a disintegration of the oxides of the varistors, without explosion, in such a manner, that during the destructive tests with 12.000 A or more, a wearing away of the chips is produced within a very restricted area, instead of a violent expulsion of the material, this mesh fabric equally extending towards the edge of the first annular recess of each contact part.

Next, a third layer of helicoidal configuration is placed, of resined fabric, for example of glass fibre, in such a manner, that its placement starts at the most internal annular recess, until it fills it up, and after reaching the opposite recess, being perfectly tensed, it configurates again another helix, transversal to the former, returns to the most external recess of the first contact part, and after tensing and filling up the annular area, finally returns to the most external recess of the opposite one, tensing and filling up this area.

Alternately, after conducting the first twist, the second annular area is filled up, and from it, one single tensing twist is conducted on the second area of the first contact part, also transversally to the former.

Finally, an additional resin coating is conducted, and an ovening of the thus formed part at the temperature of the rubber injection and a molding of the exterior insulator.

Grounding disconnectors or operation indicators may be placed, at the criteria of the user, on the exterior threaded studs.

Also, circular grooves or splines have been provided on the outside contact parts, on their exterior sides, in such a manner, that when the external cover is placed and tightened by means of the action of a nut, of the disconnector or indicator which are threaded on the connection stud, the rubber enveloper is compressed on said spline, thus assuring even more, the already in itself, good watertightness of the assembly.

In order to complement the description being conducted herewith, and with the object of helping to a better and easier understanding of the characteristics of the invention, the present Specification is enclosed, forming integral part of the same, with a set of drawings in which, with illustrative and never limitative character, the following has been represented:

• Figure 1 is a view of the overvoltage discharger, with a partially stepped cross section of the same, showing its internal elements.
• Figure 2 is an idealized view of the final double taping showing the tensing of the internal elements of this discharger.

In view of the previous description, the present invention refers to an overvoltage discharger of the type which includes, between two contact parts which are joined by connection elements to the end studs of the discharger with or without grounding disconnectors or operation indicators, an alignment of varistors, said varistors covered by diverse layers of non conductive material, with exterior resin coating and an exterior rubber insulating casing which esssentially characterises tensing means of the varistor assembly, based on double recesses (1.1) and (1.1'), as well as the (2.1) and the (2.1') consecutively, respectively to metallic contact parts (1) and (2), of annular construction and with internal knurled finish (3) to improve the grip, a waterproof sealing ply (4) with adhesive (4') on both sides, and which extends towards the edge of the first recess (1.1) and (2.1) of each part (1) and (2), wrapped in another grated fabric (5) with pitch and equally up to the edge of the recess (1.1) and (2.1), as well as a third layer, helicoidal, of resined fabric (6).

A first layer, helicoidally tensed, of fabric (6), covers the interior and intermediate space of opposed recesses (1.1) and (2.1), followed by a second layer of this fabric (6), helicoidally tensed and in opposite direction, from recess (2.1) to recess (1.1') of the part (1), covering its internal space, and a third layer, helicoidally tensed in the same direction as the first and equally filled in up to recess (2.1').

Alternatively, the fabric (6) is only provided with two helicoidal layers with opposed twisting direction, the first fills in annular recesses (1.1), (2.1) and (2.1'), and the second layer reaches from the latter up to recess (1.1').

A recess (7), conventionally watertightened, of the external face of the contact metallic parts (1) and (2), facilitates the sealing of the overvoltage discharger, with the collaboration of the external cover (8) which, by means of the action of a female threaded part such as a nut, the disconnector or the indicator, compresses the rubber (9) of the exterior casing, against the recess (7)

This description is not made more extensive with the understanding that any expert in the art shall have sufficient information in order to understand the scope of the invention and the advantages derived thereof, as well as to proceed to reproduce the same.

It is understood, that if the essentiality of the invention is not altered, the variations both in materials as well as in the shape, size and arrangement of the elements are capable of changes, characterized within the same.

The terms used during the description and the meaning of the same shall always be considered in a non limitative manner.