Overhead traveling crane system

A lifting device of an overhead traveling crane system of the type having a moving device movable on an upper track and suspending the lifting device from the moving device through motor-driven wires so as to ascend and descend with respect to a reference position on the ground, wherein said lifting device is used to position one or more magnetic sensors in a given position for detecting a magnetic condition of a target at the reference position on the ground, comprising:

• at least two spaced-apart locking members slidably engaged on respective opposing ends of a lower part of the lifting device so as to be slidable in up and down directions with respect to each lifting device end, wherein a stopper is attached to an upper end of each of the locking members in order to prevent it from disengaging from the lifting device, and a contacting means is fixed to a lower end of each of the locking members in order to cause it to stop descending and slide relative to the lifting device when the contacting means comes into contact with the target at the reference position on the ground,
• one or more sensing devices attached to given positions on the lifting device adjacent each locking member, and a sensor element fixed at a predetermined position on each locking member for providing a motor-control signal to control or stop the descent of the lifting device when the sensor element is moved in proximity to the sensing devices during sliding movement of the locking member relative to the lifting device,
• wherein each of the locking members is stopped from descending when the contacting means make contact with the target at the reference position, and the respective end of the lifting device can continue to descend until the sensing devices attached to the lifting device can sense the sensor element attached to each locking member and provide the motor-control signal to cause the lifting device to stop descending, and
• wherein the one or more magnetic sensors are suspended from and supported on the lower part of the lifting device and become positioned precisely for detecting a magnetic condition of the target at the reference position when the sensing devices sense the sensor elements attached to the locking members and provide the motor-control signal to cause the lifting device to stop descending.