Failure warning switch actuator with automatic reset and proportioner override

摘要

A dual circuit brake system has a failure warning section in which the pressures in each of the circuits are sensed by a pair of pistons having a switch actuating shuttle positioned between the pistons by a pair of springs. The ends of the shuttle are telescoped in the pistons for guidance and relative movement. The switch pistons are relatively small with little travel, minimizing displacement loss. The centering springs do not have sufficient load to force the shuttle to the off position once failure in one system has occurred and the pressure in the remaining system has been released. Repair of the failed system allows pressure actuation to move the shuttle back to the deactuated position for automatic reset. The proportioning valve for the rear brakes is so connected with the failure warning pistons that when the piston exposed to front brake pressure senses a pressure loss while rear brake pressure continues to act on the other piston, a proportioning valve element is moved away from its seat so that no proportioning action on the rear brake pressure can occur.