Speed drop detector for high-speed bucket belt conveyor

Claim 1

A speed drop detector for a high-speed bucket belt conveyor constructed of a series of buckets attached to an endless moving belt at regular intervals, which detector comprises: an electromagnetic induction sensor for detecting the passage of a bucket, a speed setter for generating a sawtooth voltage which rises with an adjustable gradient and falls sharply upon receipt of a signal from said sensor, a speed drop rate setting circuit for generating a reference voltage that is individually drawn in accordance with one or more set speed drop rates and is increased with respect to the maximum value of said sawtooth voltage at a working speed of the high-speed bucket belt conveyor, said increase being in inverse proportion to a speed corresponding to the set speed drop rate, a comparator for comparing the sawtooth and reference voltages and producing a speed-down signal when the sawtooth voltage reaches the reference voltage, an alarm output circuit actuated by a speed-down signal for a minute speed drop rate which requires no stoppage of the high-speed bucket belt conveyor, and a logic circuit for actuating a stop control output circuit by inputting a speed-down signal for an ordinary speed drop rate which does require the stoppage of the conveyor, the logic circuit having a first and a second quarter divider respectively dividing the sensor and speed-down signals, the first quarter divider being reset by the speed-down signal, and the second quarter divider being reset by a set output of the first quarter divider, the second quarter divider having a forced set terminal, and actuating the stop control output circuit with a set output thereof.