Testing the profiles of surface sections

Claim 1

APPARATUS FOR MEASURING AND INDICATING THE DEVIATIONS OF A SURFACE SECTION WITH RESPECT TO A BASIC CLOSED CURVE, COMPRISING A HOLDER FOR THE WORKPIECE, A FEELER IN ENGAGEMENT WITH THE SURFACE UNDER TEST, MEANS FOR MOUNTING THE FEELER TO PERMIT SUCH FEELER TO BE MOVABLE IN A DIRECTION APPROXIMATELY NORMAL TO THE SURFACE UNDER TEST, MEANS FOR RELATIVELY ROTATING THE FEELER MOUNTING MEANS AND THE WORKPIECE HOLDER, WHEREBY DURING SUCH ROTATIONAL MOVEMENT THE FEELER EXECUTES WORKING MOVEMENTS APPROXIMATELY NORMAL TO THE SURFACE SECTION UNDER TEST IN ACCORDANCE WITH THE SHAPE OF SUCH SURFACE SECTION, DETECTING MEANS CAPABLE OF TRANSLATING PHYSICAL MOVEMENTS INTO A REPRESENTATIVE ELECTRICAL SIGNAL, MEANS OPERATIVELY CONNECTING THE DETECTING MEANS TO THE FEELER, WHEREBY DURING THE RELATIVE ROTATIONAL MOVEMENT OF THE FEELER AND THE SURFACE UNDER TEST THE DETECTING MEANS PRODUCES A COMBINED A.C. AND D.C. ELECTRICAL SIGNAL OUTPUT REPRESENTING THE SHAPE OF THE SURFACE UNDER TEST, MEANS FOR AMPLIFYING SUCH ELECTRICAL SIGNAL OUTPUT, AN OUTPUT CIRCUIT FOR THE AMPLIFYING MEANS, AN EXTRACTING DEVICE IN CIRCUIT WITH THE OUTPUT CIRCUIT OF THE AMPLIFYING MEANS AND FOR DERIVING FROM THE AMPLIFIED SIGNAL OUTPUT AN A.C. SIGNAL EXTRACT EXCLUDING THE FOURIER D.C. COMPONENT OF SUCH SIGNAL OUTPUT AND THE FOURIER A.C. COMPONENTS OF SUCH SIGNAL OUTPUT ABOVE A CHOSEN HARMONIC, SUCH A.C. COMPONENT OR COMPONENTS INCLUDED IN SUCH A.C. SIGNAL EXTRACT HAVING THE SAME AMPLITUDE AS THE CORRESPONDING COMPONENT OR COMPONENTS IN THE AMPLIFIED SIGNAL OUTPUT, ELECTRICAL INTEGRATING MEANS IN CIRCUIT WITH THE OUTPUT CIRCUIT OF THE AMPLIFYING MEANS AND RESPONSIVE TO THE AMPLIFIED SIGNAL OUTPUT OVER AN INTEGRAL NUMBER OF COMPLETE RELATIVE ROTATIONS OF THE FEELER AND THE SURFACE UNDER TEST, OUTPUT MEANS FROM THE INTERGRATING MEANS FOR DELIVERING A STEADY D.C. SIGNAL EQUAL IN MAGNITUDE TO THE MEAN D.C. LEVEL OF THE SIGNAL OUTPUT, AN OUTPUT CIRCUIT CONNECTING THE OUTPUT SIDE OF THE EXTRACTING DEVICE AND THE OUTPUT SIDE OF THE INTEGRATING OUTPUT MEANS, WHEREBY THE A.C. SIGNAL EXTRACT AND THE STEADY D.C. SIGNAL ARE COMBINED TO PRODUCE A REFERENCE SIGNAL, VISUAL INDICATING MEANS, AN ELECTRICAL CONNECTION BETWEEN THE OUTPUT CIRCUIT OF THE AMPLIFYING MEANS AND THE VISUAL INDICATING MEANS FOR FEEDING THE AMPLIFIED SIGNAL OUTPUT OF THE DETECTING MEANS TO THE VISUAL INDICATING MEANS, AND AN ELECTRICAL CONNECTION BETWEEN THE OUTPUT CIRCUIT FOR THE REFERENCE SIGNAL AND THE VISUAL INDICATING MEANS FOR FEEDING THE REFERENCE SIGNAL TO THE VISUAL INDICATING MEANS IN PREDETERMINED PHASE RELATIVE TO THE AMPLIFIED SIGNAL OUTPUT FED THERETO, WHEREBY THERE IS PRODUCED IN SUPERIMPOSITION AT THE INDICATING MEANS A CURVE REPRESENTING THE ACTUAL SHAPE OF THE SURFACE SECTION UNDER TEST AND A REFERENCE CURVE FROM WHICH THE DEVIATIONS OF THE SURFACE SECTION UNDER TEST CAN BE MEASURED.