Brake pressure regulator

Claim 1

In a hydraulic brake pressure control system having a brake pressure regulator provided in a hydraulic line between a source of fluid under pressure and wheel brake means, and a load sensing means applying a force to the brake pressure regulator thereby controlling hydraulic brake pressure to the wheel brake means in dependence upon changes of the vehicle load, the improvement of said brake pressure regulator comprising, a cylinder housing, a differential piston reciprocally fitted within said housing and responsive to the force of said load sensing means in proportion to the vehicle load, a valve means for controlling fluid communication between said source of fluid under pressure and said wheel brake means via a first fluid passage, said valve means being operable by said differential piston and normally in the open position, sealing means mounted on said differential piston for normally preventing direct fluid flow through a second fluid passage between said source of fluid uNder pressure and said brake wheel means, and biasing means for urging said differential piston to move against the force of said load sensing means, whereby said differential piston and associated sealing means will move beyond their normal range of movement when there is considerable reduction of force by said load sensing means and for permitting direct fluid flow through the second fluid passage between said source of fluid under pressure and said wheel brake means, said valve means being closed when said differential piston moves beyond its normal range.