PURPOSE: To secure the detection that the stocking quantity has reached the fixed amount by hanging down the sensor rod from the ceiling of the grain tank and then closing the signal circuit when the sensor rod stand still with an inclination.

CONSTITUTION: Support barrel 3 is fixed to the ceiling of the grain tank to hang down sensor rod 1 in a free-swing way, and wing 4 is attached radially to the lower half part of rod 1. Limit switch S is conneted to the signal circuit via the timer. Now the grain is stocked into the grain tank by scattering, and thus the grain hits wing 4 intermittently to swing rod 1 right and left and back and forth. The push button of switch S is turned on and off by swinging of rod 1, but the signal circuit is not actuated if the ON and OFF of the switch is in a short time. When the stocking amount of the grain increases up to the fixed level and the lower end of rod 1 touches the grain stock, rod 1 inclines gradually and then stops to keep push-button 2 on. As a result, the signal circuit is closed to inform the operator that the amount of the grain has reached the limit level.