Patent ID: 7374252

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 and a wheel slip circuit comprising a wheel slip valve having release and lap valves, said wheel slip valve connecting a source of brake control pressure to the brake cylinders, exhausting the cylinders, or maintaining the pressure in the cylinders in response to signals from a wheel slip sensing unit, the improvement comprising: means for disabling the wheel slip valve; a timing reservoir in communication with the disabling means; and a check valve and choke circuit providing parallel connections between the output of the wheel slip valve and the timing reservoir having a first connection path comprising a check valve and charging choke and a second connection path comprising a dissipating choke such that flow from the output of the wheel slip valve passes through the check valve and charging choke to charge the reservoir when the brake cylinders are pressurized and opposite flow passes through the dissipating choke allowing the reservoir to discharge when the brake cylinders are exhausted, whereby if the reservoir pressure falls below a control pressure, the disabling means will disable the wheel slip valve and slip control will be interrupted.