Vehicle-trailer braking system

Claim 1

A braking system having a source of pressurized fluid, a reservoir, a hydraulic actuator, a brake, said actuator operable to cause engagement of said brake, a return and a supply line connecting said actuator with said reservoir and source of pressurized fluid, respectively, valve means for controlling flow through said supply and return lines including a body, a spool, said body having first and second ports therein, said first port connected to said supply line, said second port connected to said return line, said spool closing said first port when said second port is open and vice versa, a chamber formed between said spool and said body and means for biasing said spool including a first conduit connecting said chamber to said actuator for biasing said spool on said chamber side, and a second conduit between said actuator and said chamber to provide an unrestricted fluid path with said spool in said first position, a manual control device and a resilient connecting means between said manual control device and said spool to permit said manual control device to move said spool to a position opening said first port and then said conduit for biasing said spool, and said means for biasing said spool to then return said spool to a second position opening said second port and closing said first port to maintain a force on the brake system proportional to the force applied on said manual control device.