Abstract: A sealing device is mounted in the bore of a housing in which a piston is slidably mounted. A fluid tight seal is mounted between a shoulder of the housing and a washer circumscribing the piston. The washer has an outer diameter substantially equal to that of the bore and comprises an outer annular groove in which at least one fixing element is disposed. Each fixing element comprises a tongue-shaped portion penetrating through a corresponding radial bore defined at the bottom of the annular groove. When the piston is inserted through the washer, the fixing elements are moved radially towards the outside of the washer through the tongue-shaped portions and penetrate into a facing annular groove formed in the bore.

Abstract: The invention relates to a master-cylinder having a two-part cylinder, one part being of narrower diameter than the other, and a two-part piston slidable in the cylinder. Two pressure chambers are defined by the cylinder and the piston. Advance of the piston reduces the volume of both. One, the high pressure chamber feeds an external pressure system, and is itself fed by the other chamber through a valve system during an initial phase of the piston stroke. In a later phase the feed from the second in the first chamber ceases and instead the second chamber feeds the fluid reservoir through a control valve. Pressure-transmitting means such as a rod is arranged between the high pressure chamber and the control valve to open the control valve when the pressure in the high pressure chamber exceeds a predetermined value.