在地面用按钮操作的单梁吊车,由于操作人员不固定,维护保养较差,经常发生接触器触头粘连或按钮受潮连电现象.在这种情况下,天车失控,即使停止操作,天车仍继续运行,挣断钢丝绳,或被吊重物撞坏其它设备。为了防止这类事故的发生,有的起重机生产厂家在按钮盒上增加了总电源停送开关。但这种操作方式有两个缺点:(1)操作人员不固定,很难做到使用完毕就断开总 Single-girder crane operating on the ground with a button often causes contactor contact sticking or button damp electricity connection due to unfixed operator’s maintenance and poor maintenance In this case, the crane runs out of control, and even if the operation is stopped, the day The car is still running, breaking the wire rope, or being hit by heavy objects and crashes on other equipment. In order to prevent such accidents, some crane manufacturers in the button box to increase the total power off switch. However, this mode of operation has two drawbacks: (1) the operator is not fixed, it is difficult to be completed on the use of the total off