Method and apparatus for controlling a bucket hoist

A control system for a hoist having a load handling member having a first block and a second block, wherein relative motion between the first block and the second block causes the load handling member to open or close and wherein motion by both the first block and the second block in the same direction causes the load handling member to raise or lower, the control system comprising:

• an operator interface configured to receive a plurality of commands from an operator and, in response to the plurality of commands from the operator, configured to generate a first raise signal, a second raise signal, a first lower signal, and a second lower signal, wherein:
• the first raise signal commands a closing motor operatively connected to the second block on the load handling member to rotate in a first direction,
• the second raise signal commands a holding motor operatively connected to the first block on the load handling member to rotate in the first direction,
• the first lower signal commands the closing motor operatively connected to the second block on the load handling member to rotate in a second direction, and
• the second lower signal commands the holding motor operatively connected to the first block on the load handling member to rotate in the second direction;
• a first motor controller in communication with the operator interface to receive the first raise signal and the first lower signal, the first motor controller configured to rotate the closing motor in the first direction responsive to the first raise signal and to rotate the closing motor in the second direction responsive to the first lower signal;
• and
• a second motor controller in communication with the operator interface to receive the second raise signal and the second lower signal, the second motor controller configured to rotate the holding motor in a first direction responsive to the second raise signal, and to rotate the holding motor in a second direction responsive to the second lower signal, wherein the second motor controller is further operative to output a torque command to the holding motor responsive to the first raise signal.

A method of closing a load handling member from an open position, wherein the load handling member includes a first block and a second block and relative motion between the first block and second block causes the load handling member to open and close and wherein motion by both the first block and the second block in the same direction causes the load handling member to raise and lower, the method comprising the steps of:

• generating a command signal with a master switch, wherein the command signal is operative to cause the load handling member to close;
• rotating a closing motor via a first motor controller to bring the second block closer to the first block, thereby closing the load handling member responsive to the command signal;
• and
• supplying a current to a holding motor via a second motor controller responsive to the command signal, wherein the current is regulated such that the holding motor generates a predefined torque at an output shaft of the holding motor and the predefined torque is less than a magnitude of torque required to suspend a weight of the load handling member.