To improve assembly structure in order to enhance the reliability of "open" and "close" detection action in a switch mechanism for blade opening and closing detection installed in a disconnector.

This is a disconnector for electric power in which limit switches 14B, 14A for detecting "open" and "close" position of a blade are installed opposed to each other at the shaft end of a blade opening and closing shaft 5 incorporated in the base of the disconnector, and a plate cam is installed at the shaft end of the blade opening and closing shaft as an actuator for switch operation, and the "open" and "close"position detecting limit switch is made "ON" action according to the open and close operation of the blade. The plate cam is constructed of two sheets of plate cams 9A, 9B corresponding individually to the "close" and "open" detecting limit switches 14A, 14B, and action point of each limit switch is made capable of adjusting individually, then, each plate cam is overlapped at the shaft end of the blade opening and closing shaft 5 and fastened by a bolt 15 and, further, by driving in a spring pin 16, rotation stopper is made.