Method and apparatus for preventing motoring while braking

In a material handling machine including (a) a motor, (b) a motor controller configured to retard the machine by regenerative motor braking and having a fault terminal and a reset terminal, and (c) a manually-applied hydraulic brake for retarding the machine, the improvement comprising:

• a first relay responsive to a pressure-actuated switch for providing a controller-disabling fault signal to the fault terminal upon manual application of the brake;
• a sensor assembly emitting pulses during motor rotation;
• a pulse-receiving relay for determining motor speed;
• and,
• contacts actuated by the pulse-receiving relay for providing a signal to the reset terminal when the motor speed has decreased to a predetermined speed,
• whereby the controller operation is disabled to prevent the motor from driving through the brake and is subsequently restored when the motor speed has decreased to the predetermined speed.

In a material handling machine having (a) an electric motor and a motor controller configured to retard the machine by regenerative motor braking, (b) a manually-applied brake for retarding the machine, and (c) a manually operated speed control switch having a neutral position, an improved method for preventing machine "motoring" while braking including the steps of:

• applying the manual brake;
• generating a signal representing the motor speed;
• disabling the controller operation to prevent the motor from driving through the brake;
• and,
• restoring the controller operation when the motor reaches a relatively low speed;
• and wherein the operation-restoring step includes, in either order, the steps of:
• placing the speed control switch in the neutral position;
• and,
• generating a signal representing a relatively low motor speed.

In a material handling machine including (a) a drive motor, (b) a motor controller configured to retard the machine by regenerative motor braking and having a fault terminal, and (c) a manually-applied brake for retarding the machine, the improvement comprising:

• a motor speed signal generator coupled to the motor and providing an oscillating signal at a frequency related to the motor speed;
• a speed signal sensing relay coupled to the generator and including a pulse counter;
• and,
• signalling means for providing a fault signal to the terminal upon manual application of the brake,
• whereby the controller operation is disabled to prevent the motor from driving through the brake and the controller operation is restored at a relatively low motor speed.