Ventilated brush holder

In combination, a dynamoelectric machine having an end frame and a rotor, said rotor having a rotor shaft, a slip ring assembly carried by said rotor shaft having a pair of axially spaced metallic slip rings, a fan rotatably driven by said rotor shaft that is axially spaced from said slip ring assembly, an opening in said end frame having an internal surface, a ball bearing having an outer race located in said opening, said rotor shaft having a portion that is rotatably supported by the inner race of said ball bearing, said slip ring assembly located at one side of said frame and said fan located on an opposite side of said frame, a brush holder having a tubular shield portion, a brush holding portion and a tubular bearing retainer portion, said tubular shield portion having an open end that forms an air inlet, said tubular bearing retainer portion disposed between and engaging respectively said internal surface of said opening in said frame and the outer surface of said outer race of said ball bearing, said tubular shield portion being positioned to enclose said slip rings, brushes slidably supported by said brush holding portion, said brushes projecting into the interior of said tubular shield portion and having end surfaces that respectively engage said slip rings, and a plurality of circumferentially spaced and axially extending air passages disposed about said outer race of said ball bearing, said air passages connecting the interior of said tubular shield portion to an area adjacent said fan, said air passages comprising a plurality of circumferentially spaced and axially extending slots formed in said bearing retainer portion.