Road barrier power-on and -off automatic disengaging -and-engaging device

The utility model relates to an automatic disconnecting device for the switch on or off of a barrier, comprising an electromagnetic clutch 20 and a reversing frame 30, the electromagnetic clutch comprises a coilpanel 21, a sucker 22 and a connecting plate 23, the coilpanel and the sucker are respectively connected with the shell of a speed reducer and the output shaft of the speed reducer, the connecting plate is connected with the reversing frame 30. The reversing frame comprises a reversing disk 31, a shaft sleeve 32, a bearing 33 and a rotating arm 34, the shaft sleeve is sheathed on the output shaft 11 of the speed reducer, the reversing disk is arranged outside the shaft sleeve, the bearing is arranged between the shaft sleeve and the reversing disk, the rotating arm is vertically fixed on the neighboring edge of the reversing disk, the other end of the rotating arm is connected with a connecting rod 40 of the barrier. Under electrifying state, the electromagnetic clutch can be sucked mutually with the reversing frame for the automatic lifting of the barrier rod when the utility model is used, but the electromagnetic clutch and the reversing frame are separated each other under power-off state, thus the free lifting of the barrier rod can be implemented through manual mode, and any assisted device is not necessary during manual operation. Therefore, the utility model has the advantage of greatly convenient operation.