PURPOSE: To interrupt power transmission during an overload to an auger or the like by providing a flange in contact face to face to the drive shaft of an auger or block of a snowplow, inserting a bolt to a gap between one small- diameter flange and a guide ring and clamping it to other flange.

CONSTITUTION: A rigid shaft 2 is fixed by a key 3 to the shaft periphery of a transmission shaft 1 for transmitting rotation power from a snowplow main body side to a snowplow portion, and to its end portion, a fixed-side flange 5 is fixed. In opposite to the above, a rotation side flange 6 is provided on the transmission shaft for driving the auger and blower of the snowplow portion. And four bolts 9 are inserted to a gap 7 between a guide ring 8 arranged at the periphery of a fixed-side flange 5 and the fixed-side flange 5 and are tightened to the fixed-side flange 6 by nuts 12 through disc springs. In this way, if an overload occurs to the auger or blower, both the flanges slip thereby preventing breakage to the auger or blower.