Locomotive parking brake
A railway vehicle parking brake that can provide the appropriate tension to the braking system using a motor, a brake chain drum interconnected to the motor to take up or release a brake chain, a load arm deflects in response to tension in the brake chain, and a switch that is closed by the load arm when it deflects. A movable sheave interconnects the brake chain and the load arm and is positioned between the brake chain drum and a fixed sheave over which the brake chain is looped. A control method considers the position of the first switch to determine whether to the motor off when applying the brakes and the amount of current being drawn by the motor to determine whether to the motor off because of a system failure.
1. A method of controlling a parking brake, comprising:
providing a motorized parking brake having a motor, a brake chain drum interconnected to the motor to take up or release a brake chain, a load arm that is deflected based on tension in the brake chain to close a first switch, a cam coupled to a first end of the brake chain for rotation when the brake chain is taken up or released by the brake chain drum, and a second switch associated with the cam so that when the brake chain drum drives the brake chain into a fully released position the cam closes the second switch;
checking for a first signal from the first switch indicating that the brake chain in under a predetermined level of tension;
receiving a second signal from the motor indicating an amount of current being provided to the motor; and
stopping the motor if the first signal is received or if the second signal indicates that the amount of current being provided to the motor is over a predetermined threshold.
2. The method of claim 1 , further comprising the step of stopping the motor if the amount of current being provided to the motor exceeds a second threshold.
3. The method of claim 2 , wherein the motorized parking brake further includes a first sheave that engages the brake chain and moves away from the brake chain into the load arm in response to tension in the brake chain.
4. The method of claim 3 , wherein the motorized parking brake further includes a second sheave positioned apart from and in alignment with the brake chain drum to define a section of brake chain therebetween that engages the first sheave.
5. The method of claim 4 , wherein the brake chain extends from the first end over the brake chain drum and between the first and second sheaves to a second end for coupling to a brake rigging of a railway vehicle.