Trailer brake fluid system including a mechanical lock

Claim 1

IN A FLUID PRESSURE SAFETY BRAKE SYSTEM FOR A TRAILER OF THE TYPE HAVING A BRAKE ACTUATOR FOR APPLYING A TRAILER BRAKE, A RELAY EMERGENCY VALVE AND A FLUID PRESSURE RESERVOIR CHARGEABLE WITH FLUID UNDER PRESSURE THROUGH AN EMERGENCY LINE WHEN THE LATTER IS CONNECTED WITH A TRACTOR AND OPERATIVE TO CHARGE THE BRAKE ACTUATOR WITH FLUID UNDER PRESSURE TO APPLY THE TRAILER BRAKE WHEN THE EMERGENCY LINE IS DISCONNECTED FROM THE TRACTOR, SPRING APPLIED BRAKE LOCKING MEANS FOR LOCKING SAID ACTUATOR IN BRAKE APPLIED POSITION WHEN THE PRESSURE IN SAID RESERVOIR DROPS TO A PREDETERMINED VALUE, FLUID PRESSURE OPERATED RELEASE MEANS FOR MAINTAINING SAID LOCKING MEANS IN RELEASED CONDITION WHEN THE PRESSURE IN SAID RESERVOIR IS ABOVE SAID PREDETERMINED VALUE, AND MEANS FOR CONTROLLING SAID RELEASE MEANS AND FOR RELEASING THE TRAILER BRAKE COMPRISING VALVE MEANS HAVING A CASING PROVIDED WITH A VALVE ELEMENT SUPPORTED THEREIN, SAID ELEMENT BEING MOVABLE FROM A FIRST POSITION IN WHICH THE RESERVOIR IS CONNECTED WITH THE RELEASE MEANS TO MAINTAIN THE LOCKING MEANS IN RELEASED CONDITION WHEN THE PRESSURE IN SAID RESERVOIR IS ABOVE SAID PREDETERMINED VALUE TO A SECOND POSITION IN WHICH THE RESERVOIR IS CONNECTED DIRECTLY WITH THE ATMOSPHERE TO RELEASE THE BRAKE WHEN THE EMERGENCY LINE IS DISCONNECTED FROM THE TRACTOR, MEANS AFFORDING A RESTRICTED CONNECTION BETWEEN THE RELEASE MEANS AND THE ATMOSPHERE WHEN SAID VALVE ELEMENT OCCUPIES SAID SECOND POSITION, AND MEANS FOR AUTOMATICALLY MOVING SAID VALVE ELEMENT TO SAID FIRST POSITION WHEN THE PRESSURE IN SAID RELEASE MEANS DROPS TO A PREDETERMINED VALUE.