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过卷事故是提升卷扬机的最普遍,最严重的事故。按常规,乘人罐笼均设有二个过卷保护开关,一个装在机房内的深度指示器上,一个装在井架上。但不少矿山因井架上过卷保护开关安装维护困难而废弃不用,也有少数矿山由于疏忽,二个开关都失去了作用,问题更为突出。目前,井架及深度指示器上的二个过卷开关,都采用冲击式行程开关,用以断开安全闸接触器回路,再通过电磁铁带动四通阀,泄放安全闸油缸的油,施行紧急安全制
Over-winding accident is the most common and serious accident of hoisting winch. Conventionally, passenger cage are equipped with two over-roll protection switch, a depth indicator installed in the engine room, one mounted on the derrick. However, many mines were dismantled because of the difficulty of installation and maintenance of the overvoltage protection switch on the derrick. Because of negligence of a few mines, the two switches have lost their functions and the problems are more conspicuous. At present, two overvoltage switches on the derrick and depth indicator adopt an impulse stroke switch to disconnect the safety contactor circuit, and then the four-way valve is driven by the electromagnet to release the oil of the safety brake cylinder. Emergency safety system