Patent ID: 7084546

Claim:
A commutator comprising: a generally cylindrical dielectric body; and a plurality of commutator segments arranged along an outer peripheral surface of the dielectric body, wherein each commutator segment includes at least one ridge, which extends in a direction generally parallel to an axial direction of the commutator and radially inwardly projects into the dielectric body to secure the commutator segment relative to the dielectric body; each ridge includes a plurality of high projecting portions and a plurality of low projecting portions, wherein each high projecting portion has a projecting length, which is measured from abase end of the ridge in a projecting direction of the ridge and is longer than that of each low projecting portion; the high projecting portions and the low projecting portions of each ridge are alternately arranged in a longitudinal direction of the ridge; at least one of the low projecting portions of each ridge has at least one protrusion, which protrudes in a transverse direction that is perpendicular to the longitudinal direction of the ridge; each adjacent one of the high projecting portions of each ridge, which is adjacent to a corresponding one of the at least one of the low projecting portions of the ridge, includes: at least one groove that is obliquely angled relative to the longitudinal direction of the ridge; and at least one protrusion, each of which is bound with a corresponding one of the at least one groove and protrudes in an imaginary plane generally perpendicular to the projecting direction of the ridge over a corresponding adjacent one of the at least one protrusion of the adjacent low projecting portion, so that a first space is defined on one side of the adjacent protrusion of the low projecting portion, and a second space is defined on the other side of the adjacent protrusion of the low projecting portion between the adjacent protrusion of the low projecting portion and the protrusion of the high projecting portion; and at least a portion of the first space and at least a portion of the second space are placed along an imaginary line that is parallel to the projecting direction of the ridge.