Full Title

Construction arrangement, or operation of valves incorporated in power brake systems and not covered by groups B60T11/00 or B60T13/00 (valve structures responsive to a speed condition B60T8/34; valves in general F16K) > Application and release valves > Triple or other relay valves which allow step-wise application or release and which are actuated by brake-pipe pressure variation to connect brake cylinders or equivalent to compressed air or vacuum source or atmosphere > controlled by three fluid pressures