Patent ID: 7520574

Claim:
In a pneumatic brake cylinder control circuit for controlling the supply of pressurized air to brake cylinders, said circuit having a main source of pressurized air which drops in an emergency and having a modulated pressure source, the output of which is supplied to the brake cylinders, the improvement comprising: a pneumatic emergency brake release timer comprising: a high capacity transfer valve connected in a first position to the output of the modulated pressure source and in a second position connected to a source of emergency braking air pressure, the high capacity transfer valve being biased in the second position to provide communication between the emergency braking air pressure and the brake cylinders, the high capacity transfer valve being forced to the first position by a preset pilot pressure at the pilot port; a timing reservoir in communication with the pilot port of the high capacity transfer valve; and a check valve and a choke circuit providing parallel connections between the main source of pressure and the timing reservoir through said check valve and opposite flow through a dissipating choke, whereby after a period of time for the timing reservoir to at least partially discharge through the choke circuit, the high capacity transfer valve will place the source of emergency braking air pressure in communication with the brake cylinders.