Operating brake valve for an electrically and pneumatically actuated braking system in a motor vehicle

An operating brake valve for an electrically actuated braking system in a motor vehicle with a pneumatically actuated emergency braking system responsive to movement of a brake actuator pedal of the motor vehicle, the braking system including a brake actuating mechanism, comprising:

• a housing;
• a balance piston for movement in said housing in response to the movement of the motor vehicle's brake pedal;
• a graduated spring supporting said balance piston in said housing;
• a thrust piece movably supported on said balance piston, wherein said thrust piece is moveable along its length within said housing in response to movement of the brake pedal;
• an inlet and exhaust valve assembly mounted in said housing, wherein said valve assembly includes a compressed air reservoir, and wherein said valve assembly is actuated by said balance piston;
• a compressed air supply;
• a compressed air connecting line extending from said compressed air supply to said compressed air reservoir of said inlet and exhaust valve assembly:
• a position sensor for generating an electric signal to operate the brake actuating mechanism:
• a push rod, wherein said push rod depends from said thrust piece and extends toward said position sensor, wherein said push rod is moveable toward and away from said position sensor in response to the movement of said thrust piece with respect to said housing, and wherein said position sensor generates said electric signal in response to the movement of the push rod with respect to the position sensor;
• a compressed air control line extending from said inlet and exhaust valve assembly toward the brake actuating mechanism;
• a stop valve for controlling the supply of compressed air to the brake actuating mechanism through the brake valve, said stop valve having open and closed positions;
• a first electrically actuated solenoid valve for moving said stop valve into said open and closed positions;
• wherein said stop valve is initially held in its open position until a supply of compressed air is formed in said compressed air reservoir of said inlet and exhaust valve assembly and said first solenoid valve moves said stop valve into its closed position so that the brake actuating mechanism is operated by said electric signals generated from said position sensor, and said inlet and exhaust valve assembly is only actuated by said balance piston to pneumatically operate the braking mechanism of the motor vehicle in the event of an electrical failure in the motor vehicle.