Abstract: To protect the space within which the slip rings (20a, 20 b) of a vehicular-type alternator operate, against extraneous contamination, a plastic sleeve (29) with an axially extending gap (35) is snap-connected with the inner wall defining an opening (28b) of a connection plate (23) already present in the alternator; this retains the sleeve (29), preferably of plastic, within the alternator, the other axial end thereof being secured to an internally extending projection from the B-end shield (15), either formed by a plastic bushing (19) surrounding the B-bearing (18) or an internal flange (36) already present on the end shield (15).