Eddy current inspection system

Claim 1

AN APPARATUS FOR DETERMINING THE PRESENCE OF FLAWS IN WORKPIECES, SAID APPARATUS COMPRISING: (A) A FLAW PICK-UP UNIT ARRANGED FOR MOVEMENT RELATIVE TO A WORKPIECE TO INSPECT THE WORKPIECE FOR FLAWS; (B) ENERGIZING MEANS FOR INDUCING A HIGH FREQUENCY CURRENT SIGNAL IN THE WORKPIECE SO AS TO PRODUCE A HIGH FREQUENCY CARRIER SIGNAL IN THE PICK-UP UNIT; (C) AN AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT HAVING ALIMITER INPUT, AND REFERENCE INPUT, AND AN OUTPUT; (D) FIRST CIRCUIT MEANS CONNECTING THE OUTPUT OF THE PICK-UP UNIT TO THE LIMITER INPUT OF THE AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT TO PROVIDE A DEFECT INFORMATION CARRIER SIGNAL TO THE LIMITER INPUT; (E) SECOND CIRCUIT MEANS CONNECTING THE REFERENCE INPUT TO THE ENERGIZING MEANS TO PROVIDE A REFERENCE SIGNAL TO THE REFERENCE INPUT; (F) AT LEAST ONE OF SAID CIRCUIT MEANS INCLUDING PHASE SHIFTING MEANS FOR SHIFTING THE PHASE OF THE SIGNALS APPLIED TO SAID INPUTS; (G) SAID AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT BEING RELATIVELY UNRESPONSIVE TO CHANGES IN AMPLITUDE OF THE DEFECT INFORMATION CARRIER SIGNAL AND BEING RESPONSIVE TO PHASE FLUCTUATIONS OF THE CARRIER SIGNAL CAUSED BY DEFECTS IN A WORKPIECE TO PROVIDE A DEFECT SIGNAL AT ITS OUTPUT EACH TIME THE CARRIER SIGNAL UNDERGOES A PREDETERMINED PHASE FLUCTUATIONS; AND, (H) ADJUSTABLE VOLTAGE MEANS CONNECTED TO SAID ENERGIZING MEANS AND TO SAID PICK-UP UNIT FOR PROVIDING SAID HIGH FREQUENCY CURRENT SIGNAL TO SAID PICK-UP UNIT AT A PREDETERMINED PHASE AND AMPLITUDE SO AS TO ASSURE THAT THE CARRIER SIGNAL IS PROVIDED CONTINUOUSLY TO THE LIMITER INPUT OF THE AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT.

Claim 2

AN APPARATUS FOR DETERMINING THE PRESENCE OF FLAWS IN WORKPIECES, SAID APPARATUS COMPRISING: (A) A FLAW PICK-UP UNIT ARRANGED FOR MOVEMENT RELATIVE TO A WORKPIECE TO INSPECT THE WORKPIECE FOR FLAWS; (B) ENERGIZING MEANS FOR INDUCING A HIGH FREQUENCY CURRENT SIGNAL IN THE WORKPIECE SO AS TO PRODUCE A HIGH FREQUENCY CARRIER SIGNAL IN THE PICK-UP UNIT; (C) AN AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT HAVING ALIMITER INPUT, AND REFERENCE INPUT, AND AN OUTPUT; (D) FIRST CIRCUIT MEANS CONNECTING THE OUTPUT OF THE PICK-UP UNIT TO THE LIMITER INPUT OF THE AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT TO PROVIDE A DEFECT INFORMATION CARRIER SIGNAL TO THE LIMITER INPUT; (E) SECOND CIRCUIT MEANS CONNECTING THE REFERENCE INPUT TO THE ENERGIZING MEANS TO PROVIDE A REFERENCE SIGNAL TO THE REFERENCE INPUT; (F) AT LEAST ONE OF SAID CIRCUIT MEANS INCLUDING PHASE SHIFTING MEANS FOR SHIFTING THE PHASE OF THE SIGNALS APPLIED TO SAID INPUTS; (G) SAID AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT BEING RELATIVELY UNRESPONSIVE TO CHANGES IN AMPLITUDE OF THE DEFECT INFORMATION CARRIER SIGNAL AND BEING RESPONSIVE TO PHASE FLUCTUATIONS OF THE CARRIER SIGNAL CAUSED BY DEFECTS IN A WORKPIECE TO PROVIDE A DEFECT SIGNAL AT ITS OUTPUT EACH TIME THE CARRIER SIGNAL UNDERGOES A PREDETERMINED PHASE FLUCTUATIONS; AND, (H) ADJUSTABLE VOLTAGE MEANS CONNECTED TO SAID ENERGIZING MEANS AND TO SAID PICK-UP UNIT FOR PROVIDING SAID HIGH FREQUENCY CURRENT SIGNAL TO SAID PICK-UP UNIT AT A PREDETERMINED PHASE AND AMPLITUDE SO AS TO ASSURE THAT THE CARRIER SIGNAL IS PROVIDED CONTINUOUSLY TO THE LIMITER INPUT OF THE AMPLITUDE LIMITING AND PHASE DETECTING CIRCUIT.