| US 7,520,574 B2 | ||
| Pneumatic emergency brake release timer | ||
| David E. Schweikert, Duncan, S.C. (US); Robert N. Scharpf, Greer, S.C. (US); and James A. Wood, Spartanburg, S.C. (US) | ||
| Assigned to Wabtec Holding Corporation, Wilmerding, Pa. (US) | ||
| Filed on Mar. 28, 2006, as Appl. No. 11/391,536. | ||
| Prior Publication US 2007/0236077 A1, Oct. 11, 2007 | ||
| Int. Cl. B60T 8/34 (2006.01) | ||
| U.S. Cl. 303—128 [303/22.6] | 4 Claims |
| 1. 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.
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