Patent Application
20230317319
This application claims priority to DE Application No. 10 2022 203 351.5, having a filing date of Apr. 5, 2022, the entire contents of which are hereby incorporated by reference.
The following relates to a novel method for producing an electrical contact assembly and to an electrical contact assembly.
In electrical installations, there are often particular requirements for electrical contacts, in particular the contacts that form a switching pole in switching elements. These requirements may be for example: a high conductivity, a specific hardness, a high resistance to burn-up in switching operations and/or a specific temperature resistance.
Suitable materials in this case often do not meet all the requirements equally well. For example, there are materials which have a high conductivity, but are relatively soft. Many materials that are well suited for contacting are not at the same time suitable for forming the element that mechanically carries the contact, and/or are comparatively expensive. Typical contact materials are in this case silver-based materials with a high silver content, such as for example silver graphite, in particular with graphite contents of 2 to 5 percent by weight (% by weight) and hardnesses of 35 to 60 HV 10.
It is usual to connect contact material supports formed from such contact materials to a carrier to form a contact assembly. It is known in this case to apply the contact material to the carrier by means of soldering or welding or to introduce it into an opening in the carrier as a contact rivet.
A disadvantage of the material-bonding production methods of soldering and welding is that, over the course of time and/or due to mechanical and/or thermal loading of the contact, delamination can occur in the connecting zone between the contact and the carrier, as a result of which the contact becomes unusable or unsafe. In particular in the latter case, there may be significantly increased electrical resistances in the contact region, which can result in undesirable heating up, even to the extent of causing fires.
A disadvantage of the contact rivets is that, likewise due to mechanical and/or thermal loading, settlements can occur within the riveted connection and result in the frictional and/or interlocking engagement of the riveted connection being lost, with the adverse effects described above.
An aspect relates to provide a novel method for producing an electrical contact assembly and also to provide a novel electrical contact assembly.
One advantage of embodiments of the present invention is that a connection comprising both material bonding and frictional or interlocking engagement, a connection comprising frictional and interlocking engagement, is produced between the contact and the contact carrier in one working step. Consequently, the method is only a little more complex than conventional methods, but produces a significantly more robust connection which, as compared with riveted connections, additionally comprises material bonding and, as compared with soldered or welded connections, additionally comprises interlocking and/or frictional engagement. In this way, embodiments of the present invention avoids the disadvantages mentioned at the beginning.
Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:
At least in the region of the through-opening 11, the contact carrier 10 is suitable for material bonding and riveting, i.e., at least in this region it at least partially consists of a material or is at least partially coated with a material which can enter into a material bond with the material of the contact material support 20. Conversely, the contact material support 20 consists of a material which in the region of the joint can enter into a material bond with the (surface) material of the contact carrier 10.
Suitable materials for the contact material support 20 are for example silver graphite, in particular in the specific form of AgC4, and other silver- or copper-based materials, in exemplary embodiments comprising organic or inorganic constituents such as for example carbon C, tungsten W, tungsten carbide WC and/or tin oxide SnO2.
Suitable materials for the contact carrier 10 and/or its surface coating in the region of the joint with the contact material support are for example copper, brass or steel. If, for example for reasons of strength, the carrier consists of a material which cannot enter into a material bond with the material of the contact piece, chosen for example because of its electrical properties, or can only enter into a material bond with it to a slight extent, it is for example possible to use plating or a chemical process to apply to the carrier 10 a thin layer capable of material bonding. In this case, the thin layer may be confined to the region of the material bond 41 to be produced (see
After aligning the workpieces 10, 20 and the electrodes 31, 32, so as to be concentric to the opening 11, a voltage is applied to the electrodes and a joining force is exerted, indicated by arrows A and B. The voltage, to be precise the variation in the voltage over time, is in this case chosen such that a current flowing through the contact material support 20 and the contact carrier 10 has a variation over time which, together with the variation over time of the forces A and/or B, makes possible a material-bonding connection of the contact 21 (
In this case, the voltage or the current may for example be chosen at first to be high, in order to bring the contact material support 20 and the joining region of the contact carrier 10 from the solid state to a deformable state by heating. In this case, the material does not have to be heated up to the melting point, it is sufficient if deformation without tearing is made possible under the effect of force. In this state, the contact material support 20 is pressed by the effect of force A, B to form the contact 21 in the opening 10. Subsequently or during this operation, the process parameters, such as for example the current intensity and its variation over time and also the forces A and/or B and their variation over time, may be chosen such that in the contact region 41 welding is brought about between the contact material support 20 or the contact 21 and the opening 10, i.e. a material-bonding unification of the contact 21 and the carrier 10 is brought about in the region of the areas where they touch.
The result of this operation is shown in
For the forming of this rivet head, or in more general terms a widening of the contact material in the region 43, it may be sufficient to utilize the properties of the carrier 10. Specifically, when the carrier is heated up by the flowing current, these properties bring about a softening of the carrier material from the outside to the core and, together with the effect of force A, B, consequently promote the forming of the shape represented in
The forming of the widening of the contact 21 in the region 43 can be promoted by the aperture being provided with a larger cross section on the side of the carrier 10 that is facing away from the contact area 22 than on the side that is facing the contact area 22.
In other exemplary embodiments, it may be sufficient for there to be a connection comprising material bonding and predominantly interlocking engagement, without the material of the carrier 10 being appreciably deformed in the region of the joint.
In further exemplary embodiments of the present invention, two contact material supports may be provided (not represented), a second contact material support being placed into or onto the electrode 32 on the side of the carrier facing away from the first contact material support before the beginning of the joining process. In this way, a two-sided contact can also be produced for example, by the lower electrode 32 being designed by analogy with the electrode 31 and by the contact material supports (which are generally softer than the carrier material) being welded or fused to one another in the opening 11 during the joining process.
In exemplary embodiments of the present invention, the opening 11 may be a through-opening, for example be formed cylindrically, or have other contours, for example as an elongated hole or oval or droplet-shaped. In other exemplary embodiments, the opening 11 is a depression, i.e. for example a blind hole, with one of the aforementioned contours or cross sections.
In this case it is possible to connect a correspondingly larger contact to the carrier by means of two or more openings or depressions.
It should finally be pointed out that the exemplary embodiments described above can be combined with one another as desired.
Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 203 351.5 | Apr 2022 | DE | national |
