Patent ID: 7357031

Claim:
A precision sensor assembly for detecting vibrations in a machine tool having at least one rotatable rotor portion ( 2 a ) and at least one stationary stator portion ( 2 b ), said sensor assembly ( 1 ) comprising: a rotor unit ( 16 ) rigidly fixed to said rotor portion ( 2 a ); a stator unit ( 17 ) rigidly fixed to said stator portion ( 2 b ); means for perceiving vibrations of said rotor portion ( 2 a ) and adapted to emit signals correlated with said vibrations; and means for transmitting said signals; said rotor and stator units ( 16 , 17 ) being arranged separated from each other and said transmitting means including transmitting and receiving elements ( 10 , 11 ) located in said rotor unit ( 16 ) and stator unit ( 17 ), respectively, for contactless transmission of said signals between said units ( 16 , 17 ); wherein said means for perceiving said vibrations are disposed on said rotor unit ( 16 ) and comprise a piezoelectric sensitive element ( 6 ) and means for mechanical amplification of said vibrations, said mechanical amplification means comprising an elastic element ( 8 ) and a counter-mass ( 7 ) interposed between said elastic element ( 8 ) and said sensitive element ( 6 ); wherein said means for mechanical amplification of said vibrations comprise at least one mechanical resonant system, and wherein said at least one mechanical resonant system comprises said elastic element ( 8 ) and said counter-mass ( 7 ), said elastic element ( 8 ) and said counter-mass ( 7 ) being calibrated to oscillate in condition of mechanical resonance at a frequency substantially corresponding to a characteristic frequency of a frequency spectrum of said vibrations.