Ultrasonic detector

Claim 2

An ultrasonic acousto-electrical transducer comprising in combination a first amplifier stage having an input circuit and an output circuit; a second amplifier stage having an input circuit; and an ultrasonic coupling unit having two piezoelectric elements, each of said elements having two electrodes and developing potentials of opposite sign on said electrodes responsive to flexure, one of said elements being electrically connected in series with the output circuit of the first amplifier stage and the other of said elements being electrically connected in series with the input circuit of the second amplifier stage, said coupling unit having means for mounting the first and second elements for mechanical resonance at approximately the same frequency, said first and second elements being coupled vibrationally, whereby an electrical signal in the output of the first amplifier stage at the resonant frequency of the first element results in mechanical resonance of the first and second elements and the electrical potentials developed across the electrodes of the second element are impressed on the input circuit of the second amplifier stage, and an ultrasonic microphone having a piezoelectric element coupled electrically to the input circuit of the first amplifier stage, the piezoelectric element of said microphone having a mechanical frequency of resonance approximately equal to the mechanical frequency of resonance of the piezoelectric elements of the coupling unit.

Claim 3

An ultrasonic detector comprising the combination of claim 1 in combination with an audio responsive device electrically connected to the output of the second stage.

Claim 4

A vibration detector comprising a first amplifier state having an input circuit and an output circuit; a second amplifier stage having an input circuit; and an ultrasonic coupling unit having two piezoelectric elements, each of said elements having two electrodes and developing potentials of opposite sign on said electrodes responsive to flexure, one of said elements being electrically connected in series with the output circuit of the first amplifier stage and the other of said elements being electrically connected in series with the input circuit of the second amplifier stage, said coupling unit having means for mounting the first and second elements for mechanical resonance at approximately the same frequency, said first and second elements being coupled vibrationally, whereby an electrical signal in the output of the first amplifier stage at the resonant frequency of the first element results in mechanical resonance of the first and second elements and the electrical potentials developed across the electrodes of the second element are impressed on the input circuit of the second amplifier stage; and a probe transducer adapted to be placed in abutment with a surface having vibrations to be detected, said probe transducer having a piezoelectric element electrically connected to the input of the first stage and having a mechanical frequency of resonance approximately equal to the mechanical frequency of resonance of the piezoelectric elements of the coupling unit.

Claim 5

A vibration detector comprising a first amplifier state having an input circuit and an output circuit; a second amplifier stage having an input circuit; and an ultrasonic coupling unit having two piezoelectric elements, each of said elements having two electrodes and developing potentials of opposite sign on said electrodes responsive to flexure, one of said elements being electrically connected in series with the output circuit of the first amplifier stage and the other of said elements being electrically connected in series with the input circuit of the second amplifier stage, said coupling unit having means for mounting the first and second elements for mechanical resonance at approximately the same frequency, said first and second elements being coupled vibrationally, whereby an electrical signal in the output of the first amplifier stage at the resonant frequency of the first element results in mechanical resonance of the first and second elements and the electrical potentials developed across the electrodes of the second element are impressed on the input circuit of the second amplifier stage; and a probe transducer adapted to be placed in abutment with a surface having vibrations to be detected, said probe transducer having a piezoelectric element electrically connected to the input of the first stage and having a mechanical frequency of resonance approximately equal to the mechanical frequency of resonance of the piezoelectric elements of the coupling unit.

Claim 6

An ultrasonic detector comprising the combination of claim 1 wherein the first amplifier stage includes an electron valve having two terminals, electrons entering through the valve through the first terminal and leaving the valve through the second terminal, and the charge on the third terminal controlling the flow of electrons through the valve, one of the elements of the ultrasonic coupler being electrically connected to the first and second terminals of the electron valve and the other element of the ultrasonic coupler being electrically connected between the third and second terminals of the Electron valve, the electron valve and ultrasonic coupler being connected in an oscillator circuit having a resonant frequency controlled by the mechanical resonance of the piezoelectric elements of the ultrasonic coupler unit, whereby the stage functions as a mixer stage.