Power assisted master cylinder assemblies

Claim 1

A power assisted master cylinder assembly comprising a master cylinder which includes a body provided with a bore having inner and outer ends, a first piston moveable in said bore and having inner and outer portions, said inner portion bounding a pressure space inward of said piston for connection to a brake circuit, the outer portion of said piston being formed with an inwardly extending axial bore, a fixed sleeve slideably received in said bore, a pedal operated member extending through said fixed sleeve to directly engage said first piston, an annular closure member for closing the outer end of an annular space defined between said sleeve and said bore, first seal means between said piston outer portion, said sleeve and said bore, second seal means for sealing said closure member to said bore and said sleeve, said first and second seal means, said sleeve and said bore defining a sealed annular power chamber, an inlet to said power chamber for connection to a source of fluid under pressure and a control valve assembly which includes valve means for controlling the supply of fluid from said source to said power chamber, a second piston to operate said valve means, and means for transmitting movement of said first piston to said second piston; said pedaloperated member and pressure fluid in said power chamber acting in parallel on said first piston to prevent kick-back on said pedal-operated member on a rapid increase in pressure in said power chamber.