Crane with automatic counterweight balancing device and method of arranging counterweight thereof

A crane with an automatic counterweight balancing device, comprising a main body and a counterweight device mounted on the main body, the main body comprising first and second racks that are arranged opposite to each other, first and second transmission devices that are respectively mounted to the first and second racks, and a carriage platform connected between the first and second transmission devices, the counterweight device comprising first and second magnetic field generators respectively mounted to the first and second racks and first and second permanent magnetic counterweight blocks respectively mounted to the first and second transmission devices;

• wherein the first transmission device comprises a first pulley, a first transmission belt that is provided in association with the first pulley, and a first servo motor that is in driving coupling with the first pulley, the second transmission device comprising a second pulley, a second transmission belt that is provided in association with the second pulley, and a second servo motor that is in driving coupling with the second pulley;
• wherein the first permanent magnetic counterweight block is mounted to the first transmission belt, the second permanent magnetic counterweight block being mounted to the second transmission belt;
• wherein the counterweight device comprises an electrical control device electrically connected to the first and second magnetic field generators, the electrical control device functioning to control magnetic field intensities of the first and second magnetic field generators;
• wherein the counterweight device comprises a transducer device electrically connected to the electrical control device, the transducer device functioning to monitor output torques of the first and second servo motors and transmitting the detected output torques to the electrical control device;
• and
• wherein the permanent magnetic counterweight blocks comprise permanent magnets.

A method of assembling a crane, comprising the following steps:

• (1) providing a crane main body and a counterweight device, wherein the crane main body comprises first and second racks that are arranged opposite to each other, first and second transmission devices that are respectively mounted to the first and second racks, and a carriage platform connected between the first and second transmission devices, the first transmission device comprising a first pulley, a first transmission belt that is provided in association with the first pulley, and a first servo motor that is in driving coupling with the first pulley, the second transmission device comprising a second pulley, a second transmission belt that is provided in association with the second pulley, and a second servo motor that is in driving coupling with the second pulley, the counterweight device comprising first and second magnetic field generators, first and second permanent magnetic counterweight blocks, an electrical control device, and a transducer device;
• (2) mounting the counterweight device to the crane main body, wherein the first magnetic field generators are mounted to two ends of the first rack, the first permanent magnetic counterweight block being mounted to the first transmission belt, the second magnetic field generators being mounted to two ends of the second rack, the second permanent magnetic counterweight block being mounted to the second transmission belt, the electrical control device being electrically connected to the first and second magnetic field generators, the transducer device being mounted to the first and second servo motors and electrically connected to the electrical control device;
• (3) the transducer device monitoring, in a real time manner, output torques of the first and second servo motors and transmitting the detected output torques to the electrical control device, the electrical control device comparing the output torques of the first and second servo motors with rating torques of the first and second servo motors that are previously loaded in the electrical control device;
• (4) the electrical control device controlling the first and second magnetic field generators to increase magnetic field intensities when the output torques of the first and second servo motors are greater than corresponding rating torques of the first and second servo motors, the first and second permanent magnetic counterweight blocks being subjected to an increased downward magnetic force thereby decreasing loading of the first and second servo motors, the output torques of the first and second servo motors being decreased with the decrease of the loading until the output torques are equal to the rating torques of the first and second servo motors;
• and
• (5) the electrical control device controlling the first and second magnetic field generators to decrease magnetic field intensities when the output torques of the first and second servo motors are less than the corresponding rating torques of the first and second servo motors, the first and second permanent magnetic counterweight blocks being subjected to a decreased downward magnetic force thereby increasing loading of the first and second servo motors, the output torques of the first and second servo motors being increased with the increase of the loading until the output torques are equal to the rating torques of the first and second servo motors.