Variable load vehicle fluid pressure brake system

Claim 1

A VARIABLE LOAD VEHICLE FLUID PRESSURE BRAKE SYSTEM COMPRISING THE COMBINATION OF A BRAKE CYLINDER DEVICE OPERABLE RESPONSIVELY TO FLUID PRESSURE FOR EFFECTING A BRAKE APPLICATION ON THE VEHICLE ACCORDING TO THE DEGREE OF FLUID PRESSURE SUPPLIED THERETO, AN AIR SPRING CHARGEABLE WITH FLUID AT A PRESSURE CORRESPONDING TO THE LOAD ON THE VEHICLE, A SOURCE OF FLUID AT A CONTROLLED PRESSURE AND A RELAY VALVE DEVICE, SAID RELAY VALVE DEVICE COMPRISING: (A) A CASING, (B) A MOVABLE ABUTMENT MOUNTED IN SAID CASING AND FORMING THEREWITH A CONTROL CHAMBER AND A PRESSURE CHAMBER ON OPPOSITE SIDES RESPECTIVELY OF SAID MOVABLE ABUTMENT, SAID PRESSURE CHAMBER BEING CONNECTED TO SAID AIR SPRING AND BEING CHARGED WITH FLUID PRESSURE CORRESPONDING TO THAT IN THE AIR SPRING, (C) A SUPPLY VALVE NORMALLY OCCUPYING A SUPPLY POSITION, (D) AN EXHAUST VALVE NORMALLY OCCUPYING A CLOSED POSITION, (E) MEANS OPERATIVELY CONNECTING SAID MOVABLE ABUTMENT TO SAID SUPPLY VALVE AND SAID EXHAUST VALVE, (F) A MAIN SPRING DISPOSED IN SAID PRESSURE CHAMBER FOR EXERTING A PREDETERMINED FORCE, JOINTLY WITH THE AIR SPRING PRESSURE PREVAILING IN SAID PRESSURE CHAMBER, ON SAID MOVABLE ABUTMENT AND THEREBY URGING IT IN ONE DIRECTION TO OPERATE SAID SUPPLY VALVE TO ITS SUPPLY POSITION IN WHICH IT ESTABLISHES A COMMUNICATION VIA WHICH FLUID UNDER PRESSURE FLOWS FROM SAID SOURCE TO SAID BRAKE CYLINDER DEVICE, (G) PASSAGE MEANS VIA WHICH FLUID AT THE PRESSURE SUPPLIED TO SAID BRAKE CYLINDER DEVICE IS COMMUNICATED TO SAID CONTROL CHAMBER TO EXERT ON SAID MOVABLE ABUTMENT AN OPPOSITELY DIRECTED FORCE RELATIVE TO THE COMBINED FORCES OF SAID MAIN SPRING AND THE AIR SPRING PRESSURE PREVAILING IN SAID PRESSURE CHAMBER,