Pressurized brake cylinder using inlet pressure as a boost

Claim 1

A BRAKE ACTUATOR INCLUDING A HOUSING, A MOVABLE WALL DIVIDING SAID HOUSING INTO AN AIR CHAMBER AND A SPRING CHAMBER, AN INLET IN SAID AIR CHAMBER, A FIRST PASSAGE COMMUNICATING SAID INLET WITH SAID AIR CHAMBER, A SECOND PASSAGE COMMUNICATING SAID SPRING CHAMBER WITH SAID AIR CHAMBER THROUGH SAID FIRST PASSAGE, A VALVE MEMBER AT SAID INLET, SAID VALVE MEMBER BEING MOVABLE INTO A FIRST POSITION CLOSING COMMUNICATION BETWEEN SAID FIRST AND SECOND PASSAGES AND OPENING COMMUNICATION BETWEEN SAID FIRST PASSAGE AND SAID INLEY IN RESPONSE TO AIR ENTERING SAID INLET UNDER A PRESSURE GREATER THAN THE PRESSURE IN SAID AIR CHAMBER, SAID VALVE MEMBER BEING MOVABLE INTO A SECOND POSITION CLOSING SAID INLET AND OPENING COMMUNICATION BETWEEN SAID FIRST AND SECOND PASSAGES TO COMMUNICATE SAID AIR CHAMBER WITH SAID SPRING CHAMBER IN RESPONSE TO DIMINUTION OF PRESSURE AT SAID INLET BELOW THE PRESSURE IN SAID AIR CHAMBER, AND MEANS EXHAUSTING AIR ABOVE A PREDETERMINED PRESSURE FROM SAID SPRING CHAMBER TO ATMOSPHERE.