EP2524384A1 - Electric contact element and method for producing an electric contact element - Google Patents

Abstract

The present invention relates to a method for producing an electric contact element from a semifinished product and to the electric contact element and the corresponding semifinished product. The method for producing an electric contact element (100), which can be electrically contacted by a mating contact, comprises the following steps: producing a wire (120) from a first electrically conductive material (112); coating the wire surface with a sheath (114) made of a second electrically conductive material; partially removing the sheath (114) in a direction along a longitudinal wire axis (118); forming at least one cylindrical semifinished product (110) by dividing the wire in a direction transverse to the longitudinal wire axis; fixing the semifinished product on a contact carrier (104) such that the second electrically conductive material is connected to the contact carrier; and reshaping the welded semifinished product so as to form the contact element (100), wherein a contact area (106), which is accessible for a mating contact, is formed by the first electrically conductive material.

Description

 Electric contact element and method for producing a

 electrical contact element

The present invention relates to a method for producing an electrical contact element from a semifinished product as well as to the electrical contact element and the corresponding semifinished product.

Electrical contacts are found in electrical appliances and switchgear, such as e.g. in light switches, circuit breakers or relays, diverse applications and are widely used. The components involved in the switching operations of an electrical contact, in particular to the contact layer, high demands are made in terms of electrical conductivity, wear resistance, mechanical stability and resistance to welding, especially at temperature effects. It has been shown that these choice of materials often contradictory requirements can be met particularly satisfactorily of precious metal / metal oxide composite materials.

Precisely because of their perspiration resistance, however, such noble metal / metal oxide composite materials, for example silver / tin oxide, can not be attached directly to a contact carrier material by welding.

Therefore, it is known to fasten the contacts by means of a riveting, as is the case for example in the so-called bimetal rivets, or to provide a weldable layer by constructing a multilayer contact. Here, the connection is made by cold welding or roll cladding. In these concepts, however, is a disadvantage that a high production cost is necessary and beyond a procedural minimum volume for the applied contact material must be required. In solid contacts or Drahtabschnittsnieten also a part of the precious metal is not used for the actual switching function and thus misused.

The object underlying the present invention can therefore be seen to provide a method for producing a contact element, on the one hand ensures optimum properties of the contact element during operation and on the other hand, a material-saving and cost-effective manufacturability. This object is solved by the subject matter of the independent patent claims. Advantageous developments of the present invention are the subject of the dependent claims.

The present invention is based on the idea that for the production of the actual contact as a semi-finished part of a wire of metal composite material is used as the first conductive material, which is provided with a metal coating as a second electrically conductive material, wherein the metal coating on a part the surface was removed again to expose the core of metal composite at the later contact surface.

The metal composite material may consist of a suitable metal, such as copper, copper-nickel alloy, chromium-nickel alloy or silver, which oxides such as tin oxide, zinc oxide, iron oxide such as Fe ₂ 03, copper oxide, cadmium oxide, indium oxide, antimony oxide, lanthanum oxide, magnesium oxide , Manganese oxide, bismuth oxide, tellurium oxide, carbon (in the form of carbon blacks, graphite or carbon fibers), or else nickel, if the metal is otherwise different from nickel. Particularly suitable as a metal composite material are described, for example, described in EP 508055, EP 1505164, EP 725154, EP 736885, EP 795367, DE 10012250, EP 1 142661, EP 1915765 and EP 2004349 and the documents cited therein. Particularly advantageous are the silver-based metal composites of EP 508055 and EP 1505164, to which reference is made. These are contact materials based on silver-tin oxide, which may additionally contain indium oxide, tellurium oxide, bismuth oxide, copper oxide, nickel oxide or mixtures thereof. Such materials can be produced by powder metallurgy or by internal oxidation.

The metal coating may consist of the same metal (s) as the metal composite forming the core, but does not contain any of the ingredients which cause the weld strength of the metal composite.

According to the present invention, the silver sheath of a silver tin oxide wire is removed from the region of the subsequent contact point by scraping or splitting. In this way, a minimum loss of precious metal is guaranteed and at the same time a contamination of the switching component with the noble metal in the region of the contact point is avoided and thus prevents welding of the switching contact.

On the other hand, by directly welding the silver tin oxide contact material to a contact carrier, the production can be greatly simplified and the manufacturing cost can be kept low. The use of precious metals is minimal because the precious metal does not have to be used for mechanical tasks. In the area of the switching point there is no weldable metallic precious metal.

According to an advantageous embodiment of the present invention, a part of the wire is scraped in an axial direction so that a segment is removed at the circular cross section of the wire. After dividing into cylindrical semi-finished products and forming into an electrical contact, the desired contact can be produced in a particularly simple manner and with comparatively little material loss in this way. If you want to remove more of the metallic shell, so further scraper steps can be performed in radially offset direction.

An embodiment in which there is no waste at all is given when the wire is split in the middle and both parts remain usable.

The advantageous properties of the present invention are particularly useful when the contact element according to the invention in a switching device, such as an electromagnetic relay, is used, since the problem of welding is particularly critical here.

For a better understanding of the present invention, this will be explained in more detail with reference to the embodiments illustrated in the following figures. The same parts are provided with the same reference numerals and the same component names. Furthermore, some features or combinations of features from the embodiments shown and described may also represent separate inventive or inventive solutions. Show it:

Fig. 1 is a schematic perspective view of a finished contact element; FIG. 2 shows a perspective view of the welded-on semifinished product according to the invention before forming; FIG.

Fig. 3 is a cross-section of the sheathed wire before cockroaches;

4 shows a cross section of the wire after a first scraping step;

5 shows a cross section of the wire after a splitting step;

Fig. 6 shows a cross section of the wire after performing several Schabeschritte.

1 shows a perspective view of the contact element 100 according to the invention using the example of a relay contact. The actual electrical contact 102 is connected to a contact carrier 104 shown here only schematically by welding. The contact surface 106, which comes into electrical connection with a mating contact during operation, is formed by a material which has no tendency to weld. According to the present embodiment, this is a silver-tin oxide composite material. But there are also other composite materials in question, for example, cadmium oxide, indium oxide, zinc oxide, copper oxide, antimony oxide, lanthanum oxide, magnesium oxide, manganese oxide, bismuth oxide, or tellurium oxide or a combination thereof. In the region of the weld 108 is a metal shell 1 14, in particular a noble metal sheath, in the present case, metallic silver, before, whereby the fixation of the contact 102 on the carrier 104 via a simple welding is possible.

2 shows a perspective view of a preliminary stage of the contact 100, in which the semifinished product 1 10 according to the invention is fixed on the contact carrier 104.

As indicated schematically in FIG. 2, the semifinished product consists of a cylindrical noble metal / metal oxide core 1 12 which is partially surrounded by a metallic noble metal shell 14. The jacket 1 14, which consists of a weldable material is arranged in particular in the region of the weld 108. In the area of the later contact point 106, however, the jacket is removed. By applying pressure in a direction 1 16 to the contact carrier 104, the semifinished product 1 10 is subsequently connected. ßend transformed into the actual contact 102. It should be noted that the preforming direction 1 16 extends transversely to a longitudinal axis 118 of the piece of wire.

FIGS. 3 to 6 explain various special possibilities for freeing the later contact region 106 from the metallic silver layer. In each case, a section through the wire 120, from which the semifinished product 110 is produced by cutting transversely to its longitudinal axis, is shown. Fig. 3 shows the blank, in which a core 1 12, which, as already mentioned, may for example consist of silver-tin oxide composite material, with a metallic noble metal sheath 1 14 is surrounded. The precious metal is, for example, metallic silver. As shown in Fig. 4, the partial removal of the metallic cladding layer 1 14 can be done by scraping a segment of the cross section.

Alternatively, either scraping to the center 122 of the wire 120 or splitting the wire into two halves, as shown in FIG. Although the variant shown in FIG. 5 offers the advantage, as semi-finished product, of offering the largest possible silver-free contact surface 106, it has the disadvantage that comparatively much material is lost if this cross section is produced by scraping. However, if a split method is used in which both halves of the wire remain usable, this variant represents the material-saving solution.

FIG. 6 shows an embodiment in which as much as possible of the metallic silver sheath 14 is removed from the later contact region by carrying out two further shaving steps in a radially offset direction to the first shaving step.

In the following Table 1, the respective material losses for the versions of FIGS. 4, 5 and 6 in relation to the cross-sectional area are compared in the case that a wire diameter of approximately 1.2 mm is considered with a silver coating of 40 μm. Table 1

As is clear from this overview, the least loss of material is recorded in the variant of FIG. 4, but the variant of FIG. 6 involves the most effective removal of the jacket material.

In summary, it can be stated that the production according to the invention of contact elements, for example for switching or leading contacts on relays, on the one hand allows easy manufacturability by the direct welding of the silver-tin oxide contact material, but on the other hand a particularly low tendency to weld in the region of the actual electrical Contact ensures. Through economical use of precious metal-containing raw materials, the costs can be further reduced.

Reference numeral Description

100 contact element

 102 electrical contact

104 contact carrier

 106 contact surface

 108 weld

 1 10 semifinished product

 1 12 core

 1 14 coat

 1 16 direction of the forming pressure

1 18 longitudinal axis of the wire

120 wire

 122 middle of the wire cross section

Claims

claims A method of making an electrical contact element (100) that is electrically contactable by a mating contact, the method comprising the steps of: Providing a wire (120) of a first electrically conductive material (1 12) with a jacket (1 14) of a second electrically conductive material; partially removing the jacket (1 14) in one direction along a wire longitudinal axis (1 18); Forming at least one cylindrical semi-finished product (110) by dividing the wire in a direction transverse to the wire longitudinal axis; Fixing the semifinished product on a contact carrier (104), so that the second electrically conductive material is connected to the contact carrier; Forming the welded semifinished product for forming the contact element (100), wherein a contact surface (106), which is accessible to a mating contact, is formed by the first electrically conductive material. 2. The method of claim 1, wherein the step of partially removing the shell (1 14) in a direction along a wire longitudinal axis (1 18) comprises: Scraping a part of the wire in an axial direction so that a segment is removed at the circular cross section of the wire. 3. The method of claim 2, wherein the step of partially removing the coating in a direction along a wire longitudinal axis comprises: Scraping off a portion of the wire in an axial direction offset from the previous scraping step by a defined radial angle such that at least one further segment is removed at the circular cross-section of the wire. 4. The method of claim 1, wherein the step of partially removing the coating in a direction along a wire longitudinal axis comprises: Splitting the wire in an axial direction, so that the circular cross-section of the wire is divided. 5. The method according to any one of the preceding claims, wherein the first conductive material is not weldable. 6. The method of claim 5, wherein the first conductive material comprises a noble metal / metal oxide alloy. A method according to any one of the preceding claims, wherein the second conductive material is weldable. 8. The method of claim 7, wherein the second conductive material comprises elemental noble metal. 9. The method according to any one of the preceding claims, wherein the contact element (100) is a contact for an electromagnetic relay. 10. The method according to any one of the preceding claims, wherein the step of fixing the semifinished product (1 10) on the contact carrier (104) by means of welding takes place. 1 1. A method according to any one of the preceding claims, wherein in the  Step of fixing the semifinished product on the contact carrier, the cylindrical semi-finished product (1 10) is fixed with its cylinder jacket surface on the contact carrier that the area in which the coating is removed, the contact carrier is remote. 12. An electrical contact element, which is electrically contacted by a mating contact, wherein the contact element (100) is made by a method according to one of the preceding claims. 13. Semifinished product for producing an electrical contact element, wherein the semifinished product has a core (1 12) made of a first electrically conductive material and a jacket (1 14) made of a second electrically conductive material and wherein the jacket is at least partially removed in a direction along a longitudinal axis (1 18) of the semifinished product. 14. A semifinished product according to claim 13, wherein the semifinished product has a cylindrical shape. 15. Use of the semifinished product according to claim 13 or 14 for the production of electrical contacts. 16. Electromagnetic relay with at least one switchable contact element according to claim 12.