Carbon brush with at least one pressed-in stranded copper wire

Details Carbon brush with at least one pressed-in stranded copper wire Carbon brush with at least one pressed-in stranded copper wire

2000-02-17

2001-08-21

Mullins, Burton S. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S248000, C174S09900B, C174S126100

Reexamination Certificate

active

06278215

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention is concerned with a carbon brush with at least one pressed-in stranded copper wire.
The stranded copper wires of such known carbon brushes are typically arranged as a plait-woven hollow stranded wire, and during their manufacture are subjected to heat treatment, namely sintering, whereby the temperature is typically from around 500° C. to 720° C. During this treatment, an almost complete recrystallisation of the copper takes place which results in an elastic, soft stranded copper wire. The latter properties of the stranded copper wire are desirable for their use in connection with carbon brushes in order for these to fulfil their function when installed in a motor, whereby any negative influence of the stranded copper wire on bringing the carbon brush into contact with a collector using static or dynamic spring pressure should be as small as possible.
In practise, however, the opposite requirement for stiffer stranded copper wire has arisen in part, particularly with respect to the manufacture of carbon brushes with pressed-in stranded copper wire and with the brush plates manufactured automatically from these. For the manufacture of the brush plates, the carbon brushes with pressed-in stranded copper wire are fed via an oscillating conveyor, whereby the individual carbon brushes circulate around a shaker several times. To avoid as far as possible any bending of the stranded copper wire and, as a result a failure of the brushes to be transported, or problems caused by the feed line to the carbon brush assembly area, a stiffer stranded copper wire is required.
SUMMARY OF THE INVENTION
This task is accomplished by means of a carbon brush containing a pressed-in stranded copper wire where the stranded copper wire has been recrystallized by a heat treatment, is formed from a plurality of copper strands, and contains at least one stiffening inner wire of diameter considerably greater that of any of the copper strands.
Surprisingly, it has been found that both for the operation of the carbon brushes with stranded copper wire and for their prior manufacture, a good compromise is achieved if the plait-woven hollow stranded wire made from stranded copper wires whose copper has been recrystallised by heat treatment and is therefore correspondingly soft is combined with an inner wire of considerably greater diameter than that of the individual wires making up the stranded copper wire, whereby the inner wire is comparatively stiff. The copper of the inner wire is also recrystallised. All in all, a targeted or defined stiffening the of copper wires combined in this way is achieved. The stiffness of these combined copper wires can be adjusted by a suitable combination of cross-sectional diameters of the stranded copper wire and the stiffening inner wire.
Advantageous for the manufacture is also the fact that the stranded copper wire, or the copper strands from which it is made, can be better aligned and need to be drawn only once.
In detail, as hitherto, hollow stranded wire of known dimensions made from copper strands each with a diameter of 0.05 to 0.1 mm can be advantageously combined with a stiffening single wire with a diameter of 0.1 to 0.5 mm. The diameter of the stiffening wire is thus at least twice that of the diameter of one of the copper wires making up the hollow stranded wire. On the whole, by selection of a suitable diameter of the stiffening inner wire, the stiffness of a stranded copper wire combined with this can be adjusted to meet the requirements for manufacture of the carbon brush or brush plate as well as the functional requirements for operation of such a carbon brush.


REFERENCES:
patent: 294148 (1884-02-01), Pope
patent: 1523599 (1925-01-01), Lindblade
patent: 1629875 (1927-05-01), Kerlin et al.
patent: 1885903 (1932-11-01), Eynon
patent: 2451839 (1948-10-01), Lemon
patent: 6140589 (2000-10-01), Blackmore

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