Pneumatic brake system for a tractor-trailer vehicle including an anti-lock control valve in the trailer brake system

Claim 1

A vehicle brake system for braking a tractor coupled to a towed trailer by means of a source of fluid supplied to said system under supply and variable signal pressures, said trailer adapted to be equipped with associated, fluid-operated devices, said system compriSing: a plurality of spring-set brake actuators on said tractor and trailer, each actuator having a first chamber operable by said source under signal pressure to normally brake said tractor and trailer, spring means operable in a release position to brake said vehicle in an emergency condition and a second chamber operable by said source under supply pressure to maintain said spring means in a compressed inoperable manner under normal operating conditions; trailer valve means on said trailer including first and second brake lines and a relay valve, said trailer valve means operable in a normal position by fluid under supply pressure in said first line to communicate fluid in said second line under signal pressure to said trailer brake actuators and automatically shifted to an emergency position upon sensing a drop in pressure of said fluid in said first line to actuate said trailer brake actuators; a manually operable park valve on said tractor having an inlet connected to said source under supply pressure, an outlet and a vent, said park valve having a released position communicating its inlet with its outlet and an applied position communicating its outlet with its vent effective to actuate said spring means; control valve means including a control valve on said tractor having a first inlet in communication with said source under supply pressure, a second inlet in communication with said outlet of said park valve, and at least a first outlet, said control valve means manually operable to a fill position when said park valve is in its applied position to communicate said first inlet with said first outlet of said control valve; automatic valve means on said tractor in fluid communication with said outlet of said control valve and in fluid communication with said trailer valve means, said automatic valve means operable when said park valve is in its applied position and said control valve means is in its fill position to port fluid under supply pressure to both said first and second brake lines of said trailer valve means whereby said trailer brake actuators are actuated while said first line may be adapted to simultaneously operate said associated devices; and said trailer valve means includes a first reservoir, said relay valve associated with said first reservoir and in communication with said second chamber of said actuator and said first brake line, a second reservoir and an antilock valve associated with said second reservoir and in fluid communication with said second brake line and said first chamber of said actuator, said trailer valve means further operable with said control valve means in said fill position and said park valve in said applied position to maintain said trailer brake actuators in a fully actuated position while said trailer reservoirs are being pressurized with fluid at supply pressure.