Patent ID: RE44677

Claim:
A brake system comprising: a normal source of pressurized hydraulic brake fluid; a backup source of pressurized hydraulic brake fluid; a vehicle brake which is operated by application of pressurized hydraulic brake fluid thereto; a valve for selectively preventing the flow of hydraulic brake fluid between the backup source and said vehicle brake; a fluid conduit in fluid communication with said backup source; a pedal simulator in fluid communication with said backup source via said fluid conduit, said pedal simulator including a spring and a piston acting to compress said spring under the influence of pressurized hydraulic fluid from said backup source exceeding a first pressure; and a fluid separator unit for maintaining the integrity of said backup source of pressurized fluid and preventing intermixing of the hydraulic brake fluid of said normal source and the hydraulic brake fluid of said backup source and having a movable pressure boundary which enables, through movement thereof, said normal source of pressurized hydraulic brake fluid to selectively act upon said vehicle brake via a portion of said backup source when said valve is shut.