Pneumatic fail-safe trailer brakes - with isolating valve to separate towing unit brakes when trailer brakes fail

摘要

The towing unit air reservoir is coupled to the trailer brakes via a control valve which regulates the trailer brake pressure w.r.t. towing unit brake pressure. An auxiliary air reservoir is fitted to the trailer and the trailer brakes are operated by pressure signals from the towing unit, using a control valve on the trailer. The towing unit control valve is improved by providing a further valve element to shut off the supply line to the trailer if the supply line pressure falls below a set value, or if the amount of airflow to the trailer exceeds a set value. This prevents the main air reservoir being drained if there is a leak in the trailer brakes.