Tractor protection valve assembly

Claim 1

A TRACTOR PROTECTION VALVE ASSEMBLY INCLUDING A HOUSING, AN ELONGATED CHAMBER IN SAID HOUSING, SAID CHAMBER HAVING AN ENLARGED END PORTION, A PISTON MEMBER HAVING A PISTON PORTION RECIPROCAL IN SAID ENLARGED CHAMBER PORTION, SAID PISTON MEMBER HAVING A REDUCED, SHAFTLIKE EXTENSION EXTENDING THROUGH SUBSTANTIALLY THE ENTIRE REMAINDER OF SAID CHAMBER, SAID EXTENSION HAVING A DIAMETER LESS THAN THAT OF SAID CHAMBER REMAINDER, AN ENLARGEMENT INTERMEDIATE THE ENDS OF SAID EXTENSION, A SEAL CARRIED BY SAID ENLARGEMENT AND ENGAGING AN INTERMEDIATE PORTION OF THE WALL OF SAID CHAMBER REMAINDER TO DIVIDE THE SAME INTO A FIRST AND A SECOND CHAMBER REMAINDER PORTION, AN EMERGENCY FLUID PRESSURE INLET COMMUNICATING WITH SAID FIRST REMAINDER PORTION, AN EMERGENCY FLUID PRESSURE OUTLET COMMUNICATING WITH SAID FIRST REMAINDER PORTION AND WITH SAID EMERGENCY FLUID PRESSURE INLET AT ALL POSITIONS OF SAID PISTON MEMBER, SAID PISTON PORTION BEING SUBJECT TO EMERGENCY FLUID PRESSURE IN SAID FIRST REMAINDER PORTION AT ALL POSITIONS OF SAID PISTON MEMBER, A VALVE MEMBER CARRIED AT THE DISTAL END OF SAID EXTENSION BEYOND SAID INTERMEDIATE EXTENSION ENLARGEMENT, A SERVICE FLUID PRESSURE INLET FORMED IN THE END WALL OF SECOND REMAINDER PORTION, SAID VALVE MEMBER BEING POSITIONED TO CLOSE SAID SERVICE FLUID PRESSURE INLET WHEN SAID PISTON MEMBER IS IN ONE POSITION, A SERVICE FLUID PRESSURE OUTLET COMMUNICATING WITH SAID SECOND REMAINDER PORTION, YIELDING MEANS ENGAGING SAID PISTON PORTION AND HOUSING TO URGE SAID PISTON MEMBER TOWARD SAID ONE POSITION, SAID PISTON MEMBER BEING URGED IN THE OPPOSITE DIRECTION BY EMERGENCY FLUID PRESSURE ABOVE A PREDETERMINED AMOUNT IN SAID FIRST REMAINDER PORTION TO UNSEAT SAID VALVE MEMBER AND OPEN COMMUNICATION BETWEEN SAID SERVICE FLUID PRESSURE INLET AND SERVICE FLUID PRESSURE OUTLET THROUGH SAID SECOND REMAINDER PORTION, SAID PISTON PORTION HAVING A DIAMETER SUBSTANTIALLY GREATER THAN THOSE OF SAID ENLARGEMENT AND SAID VALVE MEMBER.