Particle separating device

Abstract

Comingled particles, such as nut meats and shell fragments, are segregated by directing the particles one after the other onto a sounding plate, from which they deflect into a rebound trajectory. Each particle upon striking the plate imparts ultrasonic vibrations to the plate, and these vibrations are converted by a transducer into an electrical input signal that oscillates at the frequency of the vibrations and undergoes corresponding changes in amplitude. After amplifying the input signal and filtering low frequency signals from it, a comparator converts those original oscillations which exceed a predetermined threshold amplitude into voltage pulses that are counted in a counter. If the count exceeds a minimum set into the counter, the counter produces a signal itself. This signal initiates an output signal of predetermined duration, which after undergoing a delay, operates an air valve that is connected with an air nozzle located along the rebound trajectory. As a result, an air blast issues from the nozzle. The delay is such that the air blast occurs just when the particle that caused it is opposite the nozzle, so that the air blast deflects the particle out of the rebound trajectory and into a reject trajectory. On the other hand, oscillations in the input signal that exceed another and higher threshold amplitude may be converted into pulses which themselves initiate the output signal without being counted. In this instance the signal that is produced overrides the output signal derived from the counter and is of longer duration, so that a longer air blast occurs. This air blast is normally of sufficient duration to deflect the heavier particles into the reject trajectory.