Study On No-connection Torque Protection Technology Of The Large Tower Crane

Tower cranes are major hoisting apparatus of the industrial or civil construction with traits of high working efficiency, wide range of uses, easy manipulation and convenient installation or dismantlement. With the development of the nuclear power station and the architecture industry in recent years, tower cranes are offered the best opportunities for developing which they have never met. But when the number of tower cranes increases rapidly, the number of the tower cranes accidents also increases in large quantity. Therefore it is urgent that the safety of tower cranes should be improved and the rate of tower crane accidents should be reduced.Crane torque limiter that is equipped on the crane is important overload protective device. It provides safeguard for the safety work of crane. Traditional torque protective device adopts a mechanical torque sensor, through making use of the machinery deformation to produce electric signal, then enlarge it in order to provide the operator with the protective signal. But this kind of no-connection torque protection has the inevitable error. To improve its reliability and accuracy, this paper is based on the deep comparison and analysis of the present domestic and foreign torque limiters, at the same time, make good use of its efficient experience which takes advantage of the technical achievements in the fields such as electronic, computer, sensing and controlling. At last, they brought forward the design idea of the no-connection type and carried out the research of the new-model tower crane torque limiter. The solving scheme in this system has the traits of general availability, high-accuracy and low cost and the like.The torque protective device in this paper adopts the design idea of the no-connection type, from weight and extent two sides to carry on the study of the signal detection, then examine whether the tower crane is reaching the limit or not. This can play the very important role in protecting the torque. As for the first aspect, that is, the weight examination, as all the work of the tower crane is from the electric energy, all the situations will be seen directly from the input power of the motor. Therefore in this paper we make use of the method of measuring the electric motor power signal instead of measuring the weight signal, and transfer it into the standard voltage signal by power transmitter, then transfer it to the interface of the computer. At last, check if the weight goes beyond the standard by use of the computer. On the other hand, for the amplitude detection, we adopt the revolution transformer to check the angle change of the jib loading boom on-line and transfer a signal to the computer to check if it extents over the limit. In this paper the collecting signal, that is, the simulated signal will be changed into the digital signal through the converter and then carry out processing the signal by use of the PLC. From the results of the experiment, we can see that having comparing with the traditional design idea, our design idea has the following advantages, such as, reducing the error measurement, improving the accuracy, which results in improving the stability of the whole system.