Abstract: A master cylinder piston for use in a motor vehicle having a flap (22) that is biased towards a position to shut off a pressure-fluid passage (24) by a return spring (28) resting on a cage (30). A flange (38) on a cage (30)for the Spring (28) is located in an annular groove (44) provided in the housing (20) for the flap (22) when the cage (30) bears axially on an inner shoulder (64) of the housing (20).

Abstract: A master cylinder piston, more particularly for a motor vehicle, comprises a flap (22), biased towards a position in which it shuts off a pressure-fluid passage (24), by means of a return spring (28) resting on a cage (30), which includes retaining means (38, 40) under a permanent set for their accommodation in an annular groove (44) provided in the housing (20) of the flap, when the cage (30) bears axially on an inner shoulder (64) of the housing (20).

Abstract: A tandem master cylinder with a bore (1a) for retaining primary (3) and secondary (4) pistons. The secondary piston (4) has a bearing surface (40) for retaining a ring (10) slideably located between a first spring (8) and a seal (4b). The ring (10) pushes the seal (4b) back against a shoulder (41) on the secondary piston (4) in order to transmit a compressive force to seal (4b). The intensity of the compressive force varies with the force exerted on and transmitted by spring (8). The secondary piston (4) has a stop piece (42) for limiting the sliding of the ring (10) in the direction of the second seal (4b) in the bore (1a) of the master cylinder resulting in better sliding of seal (4b) within bore (1a). The functional relationship between the stop piece (42) and second seal (4b) provided for a substantially total reduction of any pressure difference between the pressurized fluid supplied to a primary and secondary circuits supplied by the master cylinder.

Abstract: Tandem master cylinder comprises primary and secondary pistons (3,4) moved apart by means of two springs (9, 10). Only one (9) of the two springs is prestressed in the rest position of the piston. The pressures in the primary 6 and secondary 7 chambers are thus very rapidly made similar to each other, without it being necessary to mount the springs in a cage of adjustable length.

Abstract: The invention relates to a master cylinder comprising a body (12) comprising a bore (14) in which slides, in leaktight manner, at least one piston (16, 18) movable between a rest position and at least one working position and defining at least one pressure chamber (20, 22) connected to an application fluid system, the piston (18) having a peripheral groove (44). According to the invention, a finger (42) actuated by an external mechanism (46) is capable of entering the groove (44) so as to lock the piston in one of its positions.