FI58571B - METALLBORSTE FOER KOLLEKTOR- OCH KOMMUTATORMASKINER - Google Patents

Description

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Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 1763878.7 (71) Interelectric Sachseln AG, CH-6072 Sachseln / OW, Switzerland-Switzerland (CH) (72) Bodo Futterer, Lucerne, Hermann Sigrist, Gisvil, Switzerland-Switzerland (CH) ( Jk) Oy Borenius & Co Ab (5I +) Metal brush for collector and commutator machines - Metall-borste för kollektor- och kututatormaskiner

The invention relates to a metal brush for collector and commutator breakers, in particular for fast-rotating low-power DC machines.

In fast-rotating electrical machines, especially in commutator machines, the service life is shortened rapidly when the collector current load is 0.8 A or more. This is mainly due to commutation errors.

Attempts have already been made to avoid commutation errors by turning the collector with diamond. Nevertheless, it has been found that commutation errors occur due to certain corrugations in the surface of the collector lamellae.

The applicant has now found that the unfavorable effect of the corrugation of the collector surface can be avoided by making the brush in contact with the collector or the commutator made of metal and coating at least the 2 to 40 micron thick soft metal layer. In the range of 2 to 5 microns thick, the desired effect increases, and at a layer thickness of about 8 microns, achieves the most advantageous properties, while in the range of 20 to 40 microns, the effect gradually disappears again.

Coatings made of tin and / or lead or alloys of these metals have proven to be particularly advantageous, and 2,58571 pairs, silver, gold and cadmium or alloys thereof have a considerable, though not quite as beneficial, effect.

It is also possible to make the coating from the same metal as the brush itself, as long as care is taken to ensure that the coating has a soft texture, because based on the test results obtained so far, it seems important to obtain the softest possible coating.

The placement of the coating is suitably performed by Galvano-plastic or cathodic spraying, as this is the best way to control the thickness of the coating.

The invention will be explained in more detail below on the basis of an exemplary embodiment shown in the accompanying drawings.

Figure 1 shows in cross section a commutator of a fast rotating DC machine with one brush.

Fig. 2 shows a partial pattern corresponding to Fig. 1 of a collector brush arrangement after a certain operating time.

Figure 1 shows in cross-section a collector 1 of a rapidly rotating direct current machine with five collector lamellae 2 embedded in an insulating material piece 3 resting on the machine shaft 4. The surface of the collector is machined as evenly round and smooth as possible. Two metal brushes 5 are pressed into the collector, only one of which is shown in the figures. The metal brush 5 has a tin coating 6 with a thickness of 8 microns. The tin layer is galvanically formed.

Fig. 2 shows a part of the device according to Fig. 1 after a certain operating time of the collector and the brushes. It is noted that the tin layer has become ground at the point where the brush presses into the collector, so that the surface of the collector lamellae is for the most part in contact with the base metal of the brush 5. In the edge area, the tin coating is instead connected to the collector.

The metal brushes according to the invention achieve considerably better commutation than hitherto known brushes. The service life of the collector and the brushes is multiplied by collector currents exceeding 0.8 A. This advantageous effect is independent of the fact that the tin coating has already been abraded from the surfaces pressed against the collector after a short travel time.

Experiments have shown that the desired effect is also achieved when a soft metal coating exists in the area of the bearing surface between the brushes and the collector. It seems that the effect is not due to the attenuation of possible vibrations of the metal brushes.