Metal working – Method of mechanical manufacture – Electrical device making
Patent
1997-12-15
1999-12-07
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
310235, 310237, H01R 4308
Patent
active
059962100
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a process for manufacturing a flat commutator.
When a commutator is used in an environment that is aggressive for copper, for example, in a fuel containing methanol for motor vehicles, it is customary to designate carbon as the material for the commutator segments. These carbon segments must, however, be supported by segment supporting structures made of copper to be able to connect the coil ends of the rotor coil with the segments without a problem.
A process for manufacturing a carbon flat commutator is already known (DE 40 28 420 A1), which yields a commutator in which all the areas of the existing support body that are made of copper except the connecting hook are completely covered by the carbon segments and the molded plastic material. Therefore this commutator satisfies the highest demands. But its production is relatively expensive.
A known process of the type mentioned at the outset U.S. Pat. No. 5,255,426 is considerably more cost effective; in this process the ring wheel, which is made of carbon, is soldered on the segment supports after forming the hub on the support body, and then both the ring wheel and the support body are segmented by separating cuts. A disadvantage with this commutator is, however, that the cut edges of the support body, i.e., the lateral faces of the copper segment support parts, which border on the air gap, are exposed.
The problem of the invention is, therefore, to designate a process for manufacturing a flat commutator of the type mentioned that yields a commutator that is free of every disadvantage, but can still be designed inexpensively.
SUMMARY OF THE INVENTION
By virtue of the fact that the thickness of the support body is reduced until it results in the complete separation of the segment supporting structures from each other before the ring wheel is connected to the segment supporting structures, the separating cuts--through which the ring wheel is segmented--only need to separate the ring wheel. In addition, because the material parts of the molded plastic material, which fill in the grooves provided in the supporting body, have a larger width than the air gap formed when the ring wheel is segmented, these air gaps are connected to the molded plastic material between the segment supporting structures so the latter are not exposed by the separating cuts.
In a preferred working form the thickness reduction takes place by turning in the lathe. In so doing a centering bush for the ring wheel, which projects over the contact surface for the ring wheel, is formed advantageously from the material part of the molded plastic material covering the area of contact of the central bore--which contributes to a reduction of the production costs.
To be able to solder the ring wheel, which is made of carbon, to the segment supporting structures, it is necessary to metallize the side of the ring wheel turned toward the solder layer. Usually, in that connection, a thin copper layer is deposited by vapor. To avoid bringing this thin copper layer into contact with the aggressive environment of the commutator because it is exposed in the air gap, a silver layer instead of a copper layer is vapor or, deposited a silver layer is electroplated after depositing the copper layer. Likewise, the contact surface of the segment supporting structures is coated with a thin silver layer. As long uses silver solder is used, all contact between the aggressive environment and the copper forming the supporting part is ruled out.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated below in greater detail with the use of two working examples represented in the drawings.
FIG. 1 shows a longitudinal cut of a first working example.
FIG. 2 shows an incompletely represented top view of the surface shell of a first working example in the direction of arrow X of FIG. 1.
FIG. 3 shows a longitudinal cut of a second working example with metal layers that are greatly enlarged in the area of the connection between the carbon segments and the seg
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patent: 3478421 (1969-11-01), Preece
patent: 4035908 (1977-07-01), Ishi et al.
patent: 4283841 (1981-08-01), Kamiyama
patent: 4358319 (1982-11-01), Yoshida et al.
patent: 5157299 (1992-10-01), Gerlach
patent: 5245240 (1993-09-01), Takasaki
patent: 5400496 (1995-03-01), Kemmner et al.
International Search Report for PCT/EP96/02706.
Hall Carl E.
Kautt & Bux Commutator GmbH
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