Abstract: A vehicle comprises an engine compartment and a passenger space which are separated by an apron (76), and a pneumatic brake booster comprises a casing (10) formed of a front shell (10a) and a back shell (10b) inside which is located a piston (20) including a back tubular part (22) and supporting a skirt (14) which, with the aid of an unrolling membrane (12), defines a first chamber (16), or front chamber, connected permanently to a source of partial vacuum and a second chamber (18), or back chamber, connected selectively to the front chamber (16) or to atmosphere by a valve mechanism (40) actuated by a control rod (34), the casing (10) of the booster comprising a mechanism (74) for securing the booster to the apron (76) of the vehicle.

Abstract: The servomotor incorporates a component (50, 51) for retaining and positioning the plunger (12) forming the movable seat (11) for the valve mechanism (9) of the servomotor, the retaining component incorporating a cylindrical component (50) pivoting in the valve body (8) about an axis perpendicular to the direction of movement of the plunger (12), provided with a longitudinal groove (57) bounded by a first cam surface (58) cooperating with a shoulder (47) of the plunger (12) and a follower lever (51) outside the valve body (8) and incorporating a profiled edge (60) cooperating, on the return of the servomotor towards its rest position, with a ring (43) mounted in the neck (21) of the casing (1).