Emergency non blocking brake for trailer - has emergency piston with smaller than combined area of relay and braking valves

摘要

The trailer pneumatic brakes are operated by a relay valve and a braking valve. In the event of brake line fracture, the loss in pressure operates an emergency piston valve to apply the trailer brakes. For a stable braking control, the area of the emergency piston is less than the combined area of the relay and braking valve. The emergency braking action is thus modulated w.r.t. the full braking capability. This prevents the trailer wheels from blocking and causing instability.