Pneumatic servomotor comprising a diaphragm and/or a joint which is overmoulded onto the skirt

A pneumatic servomotor (12) for assisted braking comprising a rigid axial casing (16), in which a substantially truncated-cone shaped transverse skirt (18) is movable and integral with a piston (20) for the actuation of an associated master cylinder (14), said skirt defining two pressure chambers (24, 26) inside the casing in which a substantially annular sealing diaphragm (30) made of an elastomeric material is interposed between the casing (16) and an outer peripheral area (32) of the skirt (18);

• and in which a substantially annular seal (34) made of an elastomeric material is interposed between an inner area (36) of the skirt (18) and the piston (20), characterized in that the sealing diaphragm (30) and/or the seal (34) comprise(s) a portion, which is moulded over the skirt (18), said portion including an annular portion (44) of the diaphragm (30), that faces the axis of the servomotor (12), covers both sides (31, 33) of an outer peripheral truncated-cone shaped area (32) of the skirt (18), and fills at least a first through thickness channel (46) provided in said outer peripheral area (32) of the skirt (18), so as to ensure a continuity of the elastomeric material of the diaphragm (30), said channel (46) is situated facing a projection (48), formed in the outer peripheral truncated-cone shaped area (32) of the skirt (18), creating an accumulation area (49) for the elastomeric material of the diaphragm (30) to provide more reliable strength of said elastomeric material close to the channel (46).