US Patent 7573174 Universal motor with a device for removing dust

A universal motor (2) includes at least two carbon brushes (36) contacting the commutator (14), a ventilation device (12) for producing a cooling flow (K), and a dust protection arrangement for preventing penetration of material particles (M) into the commutation region (34) and including at least one guide member (26) that provides for delivering of the material particles (M) in the cooling flow (K), with the at least one guide member (26) having a smooth concave guide surface (28) located between the two carbon brushes (36) and extending adjacent to an outer surface (30) of the commutator (14) and toward a suction opening (22) connected with the cooling flow path (24).