Combination push-pull valve assembly

摘要

A two knob control for tractor and trailer parking brakes providing single knob application of both tractor and trailer parking brakes. It also provides for maintaining the tractor parking brakes in the applied condition while charging the trailer brake air system and for applying the trailer brakes independently of the tractor brakes. Automatic application of trailer parking brakes is provided upon trailer breakaway or a significant reduction in tractor reservoir air pressure.