Method of manufacturing commutator, apparatus for manufacturing commutator, and commutator

An apparatus for manufacturing commutator for punching a commutator forming plate of a predetermined length out of a plate member, said plate member having a plurality of projections formed at predetermined intervals in such a way that the projections extend in parallel to one another, wherein the commutator forming plate produced by said commutator manufacturing apparatus is capable of forming commutator pieces by forming the commutator forming plate into a cylindrical commutator forming plate wherein the projections are arranged on an inner surface of the cylindrical commutator forming plate, filling the interior of said cylindrical commutator forming plate with a molten resin, curing the resin, and segmenting the cylindrical commutator forming plate at predetermined angular distances after curing of said resin,

• wherein said commutator manufacturing apparatus comprises a first punch that has a plurality of recesses corresponding to said projections wherein said first punch has narrow portions formed at those portions of each recess that correspond to both corner portions of each projection in such a way that the narrow portions become narrower in a depth direction of that recess.

A method of manufacturing a commutator forming plate comprising the steps of:

• preparing a plate member having a plurality of projections formed at predetermined intervals in such a way that the projections extend in parallel to one another;
• and
• punching a commutator forming plate of a predetermined length out of said plate member using a first punch having a plurality of recesses corresponding to said projections and having narrow portions formed at those portions of each recess that correspond to both corner portions of each projection in such a way that the narrow portions become narrower in a depth direction of that recess.

An apparatus for manufacturing commutator forming plate for punching a commutator forming plate out of a plate member having a plurality of projections formed at predetermined intervals in such a way that the projections extend in parallel to one another, said apparatus comprising a first punch,

• said first punch having a plurality of recesses corresponding to said projections, and narrow portions formed at those portions of each recess which correspond to both corner portions of each projection in such a way that the narrow portions become narrower in a depth direction of that recess.