Brake mechanism with mechanical lock

Claim 1

A FLUID PRESSURE ACTUATOR FOR OPERATING VEHICLE BRAKES AND THE LIKE, COMPRISING A HOUSING HAVING A FIRST END WALL PROVIDED WITH A CENTRALLY ARRANGED OPENING, A BRAKE ACTUATING ROD EXTENDING FREELY THROUGH SAID OPENING AND MOVABLE AXIALLY OUTWARDLY FROM AN INNER INOPERATIVE POSITION, A SECOND END WALL HAVING AN INLET PORT FOR AN EMERGENCY SOURCE OF FLUID UNDER PRESSURE, FIRST AND SECOND CUP-SHAPED DIAPHRAGMS MARGINALLY ATTACHED TO SAID HOUSING AND MOVABLE RELATIVE THERETO AND TO EACH OTHER, THE EFFECTIVE AREA OF THE FIRST DIAPHRAGM BEING LESS THAN THE SECOND DIAPHRAGM, THE FIRST DIAPHRAGM DEFINING AN EMERGENCY PRESSURE CHAMBER BETWEEN ONE SIDE THEREOF AND SAID SECOND END WALL, AND BOTH DIAPHRAGMS DEFINING A SERVICE PRESSURE CHAMBER BETWEEN THE MARGINAL PORTIONS THEREOF, RESILIENT MEANS INTERPOSED BETWEEN THE FIRST END WALL AND THE BRAKE ACTUATING ROD FOR NORMALLY MAINTAINING THE LATTER IN ITS INOPERATIVE POSITION WITH THE INNER END THEREOF CONTACTING THE CENTRAL POSITION WITH THE INNER DIAPHRAGM, SAID RESILIENT MEANS NORMALLY MAINTAINING THE CENTRAL PORTIONS OF THE DIAPHRAGMS, IN CONTACTING RELATIONSHIP WITH A PORTION OF THE CENTRAL PORTION OF THE FIRST DIAPHRAGM IN ENGAGEMENT WITH SAID SECOND END WALL, SAID HOUSING HAVING A PORT FOR ADMITTING FLUID UNDER PRESSURE TO SAID SERVICE PRESSURE CHAMBER SPRING-APPLIED BRAKE LOCKING MEANS MOUNTED IN SAID HOUSING ADJACENT SAID FIRST END WALL FOR LOCKING SAID ROD AGAINST MOVEMENT TOWARD SAID SECOND END WALL AND A FLUID PRESSURE OPERATED DEVICE WITHIN THE HOUSING FOR RELEASING SAID LOCKING MEANS.