Device for detecting nonmagnetic or magnetic conducting bodies for conveyors using coils whose projection on the conveyors are essentially trapezoidal

Abstract

Abstract THIS INVENTION RELATES TO A METHOD AND A DEVICE FOR DETECTING ELECTROMAGNETICALLY NONMAGNETIC OR MAGNETIC CONDUCTING BODIES, E.G. MEAL BODIES, FROM A MEDIUM (SURROUNDING MATERIAL) DIFFERENTIAL FROM THE MATERIAL OF THE BODIES, APPLIED PARTICULARLY FOR DETECTING MAGNETIC AND NON MAGNETIC METAL SCRAP FROM BELT CONVEYED MAGNETIC AND/OR CODUCTING ORE OR ORE PRODUCT. THE OPERATION OF THE METAL DETECTOR ACCORDING TO THE INVENTION IS BASED ON THE DIFFERENT CONDUCTIVITY OF ORES AND METALS BY DETECTING SUCH A COMPONENT OF THE SECONDARY FIELD CAUSED BY A BODY IN AN ELECTROMAGNETIC ALTERNATING FIELD, AS IS SMALL FOR THE ORE MATERIAL BUT LARGE FOR METALS BECAUSE OF THEIR GOOD CONDUCTIVITY. THE DETECTOR COMPRISES AN AUDIO FREQUENCY TRANSMITTING SYSTEM, A RECEIVING SYSTEM TO DETECT THE FIELD CAUSED BY THE METAL BODIES, A SIGNAL AMPLIFIER, A COHERENT DETECTOR WHICH SEPARATES A COMPONENT OF CERTAIN PHASE FROM THE SIGNAL RECEIVED AND FINALLY A MONITOR CIRCUITRY FOR THE ANALYSIS OF THE SIGNAL OBSERVED AND FOR THE FORMING OF AN ALARM SIGNAL. THE TRANSMITTER IS CONSTRUCTED TO PRODUCE A FIELD WHICH VARIES IN DIRECTION AS A FUNCTION OF POSITION IN THE FIELD SO THAT A DETECTABLE SIGNAL IS RECEIVED AT ONE POINT AT LEAST OF THE INFLUENCE AREA, IRRESPECTIVE OF THE SHAPE, DIRECTION AND POSITION OF THE BODY ON THE BELT WHEN THE BODY MOVES THROUGH THE INFLUENCE AREA OF THE INSTRUMENT (USUALLY THAT OF A COIL SYSTEM). THE SIGNALS CAUSED IN THE RECEIVING SYSTEM BY THE TRANSMITTER AND THE EVENTLY DISTRIBUTED SURROUNDING (ORE) MATERIAL ARE MADE ZERO EITHER BY USING A BRIDGE CONNECTION OF THE COILS OR BY A SUITBLE CONSTRUCTION OF THE RECEIVING COIL SYSTEM.

Inventors

• 👤 Kai B Fallenius
• 👤 Keijo A Varmola

Bibliographic Details