| 摘要 |
<p>A pneumatic brake system is provided for tractor-trailer vehicles which permits air to be supplied to the trailer while both tractor and trailer brakes remain set when the rig is parked. The system includes a park valve which, by itself, is operable to always set the tractor-trailer brakes when the vehicle is parked and release same when the vehicle is to be driven. A control valve is provided in the system which, when optionally operated, supplies air to the trailer while automatic valve means respond to the position of the control and park valves to maintain the tractor parking brakes and trailer service brakes set during trailer fill operation.</p> |
