Abstract: The piston of the generator (6, 8) has a smooth lateral surface and cooperates in sliding sealing engagement with a pair of seals (9a, 9b) fixedly mounted in annular grooves formed in the interior surface of the single bore (2) of the tubular body (1) of the generator. The bore opens at either end of the body and comprises, in its interior surface, at least one longitudinal groove (17) extending over the entire length of the bore, the bore being closed at one end by an obturator element (4) fitted onto the body (1).

Abstract: The distributor comprises a star-shaped rotor (2) arranged between two concentric components which are spaced axially and are fixed in rotation to a second valve portion (60); a C-shaped centering return spring (40) is arranged around the rotor (2) and cooperates, by its facing ends, with a projection (100) of one of the arms (10.sub.1) of the rotor and with adjacent projections of the second valve portion.

Abstract: The device comprises a hydraulic operating actuator (5), associated with a friction element (4) and capable of being operated by a liquid under pressure to bring the friction element into frictional contact with the component to be braked (2); and a pneumatic actuator means (10), incorporating a hydraulic chamber (20), joined to the hydraulic actuator (5), and a pneumatic chamber (14) capable of being joined to a source of gas under pressure, the two chambers being separated by a movable wall structure forming a piston, the hydraulic chamber (20) being at least partially defined by a flexible elastic envelope (21) arranged in the immediate vicinity of the hydraulic operating actuator.