Apparatus for monitoring vibrations of a fan

Claim 1

APPARATUS FOR MONITORING VIBRATIONS OF A MEMBER COMPRISING A VIBRATION PICKUP HAVING AN OUTPUT PROPORTIONAL TO THE AMPLITUDE OF VIBRATIONS AND ADAPTED TO MEASURE VIBVRATIONS OF SAID MEMBER, A PHASE INVERTING TRANSFORMER CONNECTED TO THE OUTPUT OF SAID VIBRATION PICKUP, AN AMPLIFIER CONNECTED TO THE OUTPUT OF SAID TRANSFORMER, MEANS ASSOCIATED WITH SAID AMPLIFIER FOR PROVIDING AN ADJUSTABLE FEEDBACK VOLTAGE THERETO, A RECTIFIER CONNECTED TO THE OUTPUT OF SAID AMPLIFIER, A SELF-SATURATING MAGNETIC AMPLIFIER INCLUDING A CONTROL WINDING, A BIAS WINDING AND TWO LOAD WINDINGS CONNECTED IN PARALLEL, A RECTIFIER CONNECTED IN SERIES WITH EACH LOAD WINDING, THE LAST NAMED RECTIFIERS BEING OPPOSITELY DISPOSED WITH RESPECT TO ONE ANOTHER, MEANS CONNECTING THE UTPUT OF SAID FIRST NAMED RECTIFIER TO SAID CONTROL WINDING, AN INDUCTION RELAY CONNECTED TO AN A.C. POWER SOURCE IN SERIES WITH SAID LOAD WINDINGS AND LAST NAMED RECTIFIERS, AND MEANS OPERABLE BY SAID INDUCTION RELAY WHEN THE AMPLITUDE OF THE VIBRATIONS EXCEEDS A PREDETERMINED LEVEL.