Method and apparatus for ultrasonic transducer protection

Claim 2

Apparatus for the protection of an ultrasonic transducer designed to operate while immersed in a liquid, said apparatus comprising: first electrical means coupled with the transducer, for detecting surface motion of the liquid; and second electrical means coupled with said first electrical means, for switching the transducer off when surface motion of the liquid cannot be detected, whereby the non-existence of surface motion in the liquid when the transducer is in an on condition indicates that liquid is not present and that the transducer is therefore subject to damage or destruction.

Claim 3

Apparatus as set forth in claim 1, wherein: said first electrical means monitors a radio-frequency signal applied to energize the transducer; and said first electrical means includes rectifying and filtering means for removing radio-frequency components of the monitored signal, peak detection means for detecting a peak value of random amplitude variations in the monitored signal, and comparator means for comparing the detected peak value with a fixed threshold level; whereby significant surface motion of the liquid causes random variations in the pattern of ultrasonic energy reflected back from the surface, which in turn causes random variations in the acoustic impedance and the electrical impedance of the transducer, thereby generating random amplitude variations in the electrical voltage between the transducer terminals.

Claim 4

Apparatus as set forth in claim 1, and further including means for locking the transducer in an off condition after switching off by said second electrical means, whereby the transducer can be switched on again only by removal and reapplication of electrical power to said apparatus.

Claim 5

Apparatus as set forth in claim 1, and further including means for overriding said first electrical means and switching the transducer on for at least a brief period of time when electrical power is first applied to said apparatus, whereby, if liquid is present, surface motion will be detected during said brief period of time, and said first electrical means will hold the transducer in an on condition after said brief period of time has elapsed.

Claim 6

Apparatus for the automatic protection of an ultrasonic transducer which is operated immersed in a liquid, said apparatus comprising: surface motion detection means coupled to the transducer and operable to generate an electrical signal when the surface motion of the liquid exceeds a predetermined threshold level; transducer temperature detection means, including means for generating a first temperature signal if the transducer temperature exceeds a first predetermined value, and means for generating a second temperature signal if the transducer temperature exceeds a second predetermined value greater than the first predetermined value; and electrical means coupled with said surface motion detection means and said temperature detection means, for switching the transducer to an off condition if the transducer temperature exceeds the first predetermined value and no surface motion is detected, or if the transducer temperature exceeds the second predetermined value; whereby the transducer is permitted to remain in an on condition if its temperature is below the first predetermined value, even if there is no surface motion, in order to permit adjustment of the transducer without its being automatically turned off when surface motion stops.

Claim 7

Apparatus for the automatic protection of an ultrasonic transducer which is operated immersed in a liquid, said apparatus comprising: surface motion detection means coupled to the transducer and operable to generate an electrical signal when the surface motion of the liquid exceeds a predetermined threshold level; transducer temperature detection means, including means for generating a first temperature signal if the transducer temperature exceeds a first predetermined value, and means for generating a second temperature signal if the transducer temperature exceeds a second predetermined value greater than the first predetermined value; and electrical means coupled with said surface motion detection means and said temperature detection means, for switching the transducer to an off condition if the transducer temperature exceeds the first predetermined value and no surface motion is detected, or if the transducer temperature exceeds the second predetermined value; whereby the transducer is permitted to remain in an on condition if its temperature is below the first predetermined value, even if there is no surface motion, in order to permit adjustment of the transducer without its being automatically turned off when surface motion stops.

Claim 8

Apparatus as set forth in claim 5, and further including means for locking the transducer in the off condition after switching off by said electrical means, whereby the transducer will remain switched off even if surface motion should be subsequently detected or if the transducer temperature should subsequently fall below the second or first predetermined values.

Claim 9

Apparatus as set forth in claim 5, and further including means for overriding said electrical means and switching the transducer on for at least a brief period of time when electrical power is initially applied to said apparatus, whereby the transducer may be switched on when surface motion is initially absent and the transducer temperature is above the first predetermined level, and whereby the transducer will remain in the on condition after the brief period of time provided surface motion is detected during that time and the transducer temperature does not exceed the second predetermined level.

Claim 10

Apparatus as set forth in claim 5, and further including alarm indication means coupled with said electrical means, for indicating that the transducer has been switched off because of lack of surface motion or because of high temperature.

Claim 11

Apparatus as set forth in claim 5, wherein said surface motion detection means includes: rectifying and filtering means coupled to the transducer, for removing radio-frequency components in the electrical voltage as monitored at the transducer terminals; peak detection means for detecting peak values of random amplitude variations in the voltage signal across the transducer terminals; and comparator means for comparing the detected peak values of random amplitude variations with a fixed threshold value, and thereby generating a signal indicative of the presence or absence of surface motion in the liquid.

Claim 12

Apparatus for the automatic protection of an ultrasonic transducer which is operated immersed in a liquid, said apparatus comprising: surface motion detection means coupled to the transducer and operable to generate an electrical signal when the surface motion of the liquid exceeds a predetermined threshold level; transducer temperature detection means, including means for generating a first temperature signal if the transducer temperature exceeds a first predetermined value, and means for generating a second temperature signal if the transducer temperature exceeds a second predetermined value greater than the first predetermined value; electrical means coupled with said surface motion detection means and said temperature detection means, for switching the transducer to an off condition if the transducer temperature exceeds the first predetermined value and no surface motion is detected, or if the transducer temperature exceeds the second predetermined value, whereby the transducer is permitted to remain in an on condition if its temperature is below the first predetermined value, even if there is no surface motion, in order to permit adjustment of the transducer without its being automatically turned off when surface motion stops; means for locking the transducer in the off condition after switching off by said electrical means, whereby the transducer will remain switched off even if surface motion should be subsequently detected or if the transducer temperature should subsequently fall below the second or first predetermined values; means for overriding said electrical means and switching the transducer on for at least a brief period of time when electrical power is initially applied to said apparatus, whereby the transducer may be switched on when surface motion is initially absent and the transducer temperature is above the first predetermined level, and whereby the transducer will remain in the on condition after the brief period of time provided surface motion is detected during that time and the transducer temperature does not exceed the second predetermined level; and alarm indication means coupled with said electrical means, for indicating that the transducer has been switched off because of lack of surface motion or because of high temperature.

Claim 13

Apparatus for the automatic protection of an ultrasonic transducer which is operated immersed in a liquid, said apparatus comprising: surface motion detection means coupled to the transducer and operable to generate an electrical signal when the surface motion of the liquid exceeds a predetermined threshold level; transducer temperature detection means, including means for generating a first temperature signal if the transducer temperature exceeds a first predetermined value, and means for generating a second temperature signal if the transducer temperature exceeds a second predetermined value greater than the first predetermined value; electrical means coupled with said surface motion detection means and said temperature detection means, for switching the transducer to an off condition if the transducer temperature exceeds the first predetermined value and no surface motion is detected, or if the transducer temperature exceeds the second predetermined value, whereby the transducer is permitted to remain in an on condition if its temperature is below the first predetermined value, even if there is no surface motion, in order to permit adjustment of the transducer without its being automatically turned off when surface motion stops; means for locking the transducer in the off condition after switching off by said electrical means, whereby the transducer will remain switched off even if surface motion should be subsequently detected or if the transducer temperature should subsequently fall below the second or first predetermined values; means for overriding said electrical means and switching the transducer on for at least a brief period of time when electrical power is initially applied to said apparatus, whereby the transducer may be switched on when surface motion is initially absent and the transducer temperature is above the first predetermined level, and whereby the transducer will remain in the on condition after the brief period of time provided surface motion is detected during that time and the transducer temperature does not exceed the second predetermined level; and alarm indication means coupled with said electrical means, for indicating that the transducer has been switched off because of lack of surface motion or because of high temperature.

Claim 16

A method as set forth in claim 11 wherein said detecting step includes: rectifying and filtering the voltage across the transducer terminals to remove radio-frequency components; detecting peak values of random variations in the signal remaining after rectifying and filtering if surface motion is present; and comparing the detected peak values with a fixed threshold value to determine whether or not there is surface motion on the liquid.

Claim 17

A method as set forth in claim 11, and further including the step of locking the transducer in an off condition after turning off by said switching step, thereby preventing re-energization of the transducer until electrical power has been removed and reapplied.

Claim 18

A method as set forth in claim 11, and further including the step of initially overriding said step of switching the transducer off, and switching the transducer on during the initial application of electrical power for a short period of time, whereby the transducer may be initially energized although surface motion will be absent, and will remain energized if surface motion is detected during the brief period of time.

Claim 21

A method as set forth in claim 15, and further including the step of locking the transducer in an off condition after switching off by said switching step, whereby the transducer will remain in the off condition even if surface motion is resumed and the transducer temperature falls below the second or first predetermined values.

Claim 22

A method as set forth in claim 15, and further including the step of switching the transducer on initially at least for a brief period of time, said step of switching on overriding said step of switching for the brief period of time, whereby the transducer will remain in the on condition if the transducer temperature falls below the second predetermined value, and if surface motion begins or the transducer temperature falls below the first predetermined value, all during the brief time period.

Claim 23

A method as set forth in claim 15, and further including a step of actuating an alarm signal whenever said step of switching off the transducer takes place, whereby the condition which caused switching off of the transducer may be brought to the attention of an operator and corrected.

Claim 24

A method as set forth in claim 15, wherein said step of detecting surface motion of the liquid includes: rectifying and filtering the voltage signal across the transducer to remove radio-frequency components thereof; detecting peak values in the remaining signal due to random variations in signal amplitude caused by surface motion; and comparing the detected peak values with a fixed threshold value to determine whether or not surface motion exists.