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US3872330A - High power acoustical transducer with elastic wave amplification - Google Patents

High power acoustical transducer with elastic wave amplification Download PDF

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Publication number
US3872330A
US3872330A US409534A US40953473A US3872330A US 3872330 A US3872330 A US 3872330A US 409534 A US409534 A US 409534A US 40953473 A US40953473 A US 40953473A US 3872330 A US3872330 A US 3872330A
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elements
elastic wave
discharging
control electrode
piezoelectric
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Darrow L Miller
William Y Wells
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Boeing North American Inc
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Rockwell International Corp
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Priority to US409534A priority Critical patent/US3872330A/en
Priority to NL7412063A priority patent/NL7412063A/xx
Priority to GB4112474A priority patent/GB1451247A/en
Priority to DE19742448318 priority patent/DE2448318A1/de
Priority to JP49122321A priority patent/JPS5075025A/ja
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B06B1/0215—Driving circuits for generating pulses, e.g. bursts of oscillations, envelopes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0607—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements
    • B06B1/0611—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements in a pile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/50—Application to a particular transducer type
    • B06B2201/55—Piezoelectric transducer

Definitions

  • ABSTRACT through a high impedance path over a relatively long period.
  • An electrical means is provided for discharging each in succession through a low impedance path. The stored energy is thereby released by each element in a very short time to provide an acoustical pulse of high peak power.
  • Each element is discharged with an electrical phase delay such that the elastic wave of each element adds in phase to the elastic wave of the 56 References Cited l I UNITED STATES PATENTS preceding element, resulting in an amplification of the acoustic wave as it progresses down the transmission g 2 path.
  • the entire sequence is repeated at a desired rate 2. reenspan c a 3.166.731 H1965 Joy 310/81 X to produce an dcousucll beam of hlgh peak power 3.243.648 3/1966 Yando 310/81 X 13 Claims, 7 Drawing Figures l m a. l
  • PATENTEU 8 I975 sumanrQ HIGH POWER ACOUSTICAL TRANSDUCER WITH ELASTIC WAVE AMPLIFICATION BACKGROUND OF THE INVENTION
  • This invention relates to a high power acoustical transducer, and more particularly to an electroacoustical transducer employing piezoelectric effects.
  • X rays have been used extensively in examination of the human body for bone fractures, tumors, and other defects, and will continue to be used in those cases where a quick look will suffice.
  • other examination techniques are required.
  • Ultrasonics is a useful technology for that purpose, as well as for therapy and dentristry.
  • the body tissues absorb a great amount of acoustic energy, particularly at high frequencies. Consequently, to find small defects, or otherwise observe small detail, ultrasonic transducers having higher transduction efficiencies at these high frequencies are necessary.
  • An improvement in the sound echo return from a defect interface, relative to the background spatial reflection noise, can be obtained by concentrating acoustical energy on the defect. This can be done by collimating or focusing the beam, but the round trip absorption loss in the material is a limiting factor. To overcome that limiting factor it is necessary to increase the energy content of the incident soundwave.
  • Some transducers such as electromagnetic transducers do not permit operation at high frequencies because of their mass. Magnetostriction devices are restricted to frequencies below 50 KHz because of eddy current losses. Some piezoelectric devices are small and are capable of being operated at high frequencies up to 25 MHz, but are limited in power.
  • the capacitance of a piezoelectric crystal quartz, Rochelle or lithium sulphate
  • thin layer of ferroelectric material barium titanate. lead titanate zirconate, lead metaniobate and the like
  • the capacitance is very high, particularly for the more efficient ceramic materials such as lead metaniobate or lead zirconate titanate, which have a high dielectric constant (250 to 1,700).
  • High capacitance. in turn. means low capacitive impedance.
  • a A X /8 inch lead metaniobate piezoelectric element with a dielectric constant of 250 typically has a capacitive impedance of approximately 10 ohms to a source of power applied to it.
  • a lead zirconate titanate transducer of the same size would have an even lower impedance in proportion to its much higher dielectric constant.
  • the circuit usually consists of an electrical storage capacitor (typically 330 pf) which is charged through a high resistance (typically 220 K ohms) over a relatively long period of time and then connected across a single piezoelectric element.
  • An electronic switch such as a gas thyraton or silicon controlled rec tifier (SCR) is employed to discharge the capacitor in a short period of time.
  • SCR silicon controlled rec tifier
  • Pulsing a plurality of piezoelectric elements in sequence to increase the potential power output would require a complicated highvoltage low-impedance pulsing system capable of operating at a pulsing frequency determined approximately by the velocity of the elastic wave divided by the wavelength in the piezoelectric material. If each unit were to be pulsed simultaneously to avoid the high frequency pulsing system, the resulting behavior (as in the prior art) would be similar to a low-frequency device with a characteristic frequency and behavior determined by its length and mass.
  • An object of this invention is to produce soundwaves the magnitude of which can be selectively increased or decreased as they progress in time through acoustically coupled piezoelectric crystals.
  • Another object of this invention is to provide a high power acoustic transducer.
  • Ahother object is to increase the available electrical transduction energy in an acoustically coupled piezoelectric elements as compared to pulsing methods and apparatus of the prior art.
  • a further object is to provide a number of piezoelectric elements acoustically coupled and to actuate some or all of the elements such that the elastic wave of each element actuated adds in phase with any portion thereof of the elastic wave progressing through the element thereby resulting in an amplification of the wave.
  • a further object is to provide a number of piezoelectric elements acoustically coupled and to actuate some or all of the elements such that the elastic wave of each element so actuated is out of phase with an thereby subtracts from the elastic wave progressing through the elements.
  • Still another object is to provide a series of acoustically coupled piezoelectric elements with means for pulsing the first element and means for subsequently using the previously generated elastic wave itself to trigger the remaining elements in sequence such that the elastic wave of each element coupled to the next adds in phase to the elastic wave generated in the next element.
  • a method and apparatus for charging over a relatively long period a group of piezoelectric elements which are polarized in a thickness mode d33 parallel to the sound transmission axis. (Alternatively they may be electrically polarized in another mode, such as a mode at a right angle to the transmission axis (c131) and arranged in series for mechanical expansion and contraction along the axis of sound transmission).
  • the piezoelectric elements are simultaneously charged through a high impedance means from a high voltage source.
  • the electrical energy stored in the capacitance of the piezoelectric elements is released over a relatively short period through a low impedance means to develop a high peak power conversion in each element discharged starting with the first element at one end of the group and proceeding through the group.
  • Each element is discharged at a rate that permits the elastic wave created by piezoelectric action during the extremely short discharge time of each preceding element to add in phase to (or subtract from if desired) the elastic wave produced by the piezoelectric element currently being discharged.
  • the result is a high-power acoustic (sonic or ultrasonic) wave propagated off the end of the last element discharged.
  • FIG. 1 illustrates partially in section a first embodi ment of the invention.
  • FIG. 2 illustrates the complete electrical circuit for driving the transducer of FIG. 1.
  • FIG. 3 illustrates a second embodiment of the present invention.
  • FIG. 4 illustrates still another embodiment to eliminate the requirement for insulation between the elements.
  • FIGS. 5 and 6 illustrates respective charged and discharged states of piezoelectric elements in the embodiment of FIG. 4.
  • FIG. 7 illustrates a third embodiment suitable for sonic frequency pulse operation.
  • FIG. 1 a first embodiment of the invention is shown using only three piezoelectric elements ll, 12, and 13. In practice, any number of elements may be used.
  • Each element is made of piezoelectric material, such as lead metaniobate, lead titanate zirconate, barium titanate, and the like, prepared in a known way by ceramic methods and made to have piezoelectric properties better than those of some natural crystals, such as quartz, by putting them through a cycle of polarization with a high electrostatic field.
  • piezoelectric ceramics are commercially available in a wide range of electromechanical transduction properties with dielectric constants ranging from 5 to 1,700 and in various sizes, shapes and thicknesses (half or full wavelength).
  • the material is usually selected with a dielectric constant, frequency constant, and electromechanical conversion parameters to provide an optimum length or thickness (measured along the axis of sound propagation, i.e., along the axis of desired piezoelectric mechanical strain), capacitance, and transduction performance for a specific design frequency.
  • the piezoelectric material is usually made in a slab configuration for polarization in the thickness mode.
  • a bar configuration is advantageously used for long wavelength elements.
  • the bar shaped piezoelectric elements are polarized in a right angle mode (d 31) for mechanical expansion and contraction at each end).
  • slabs are usually /2 wavelength thick. The exact thickness will depend on the frequency constant of the material.
  • the following table sets forth electromechanical properties of lead metaniobate available as Kezite K 81 from Keremos, Inc., Lizton, Indiana.
  • the halfwave thickness for the slab configuration would be about 0.025 inches and the capacitance about 1,000 pf for a inch diameter slab.
  • the piezoelectric slabs (or bars if the elements are polarized in a right angle mode) are arranged (stacked) along the axis of sound transmission and electrically insulated from each other with a low acoustical loss material as in the first embodiment of FIG. 1.
  • a second full-wave embodiment illustrated in FIG. 4 requires no insulation between elements. Before stacking the slabs, they are prepared with electrodes in the form of thin films of conductive material, such as vapor deposited silver, on both sides, with a small tab extending from the edge of each face through which electrical connections are made to a sequential trigger control circuit 14.
  • the cement successfully used was an epoxy type EC 1469 made by Minnesota Mining and Manufacturing Corporation. However, any epoxy or other cement may be used which can be applied in a liquid state and which sets in a solid state for form a good adhesive bond with a low interfacial acoustical loss. An epoxy is preferred for the additional insulating qualities of that material, but other types of cement may be used.
  • the material serves not only to hold the elements together with their electrical connecting tabs but also provides a low reflection, low loss acoustical transmission media between each element.
  • the scope of the present invention also includes other insulating materials such as oil or liquids which may be employed in a thin film to provide a low acoustical loss between elements.
  • an acoustical back wave damper 17 is cemented to the back of the first element.
  • a satisfactory acoustical damper for 2 A MHz operation consists of the metal loaded matrix material delineated in the following table.
  • the thickness of the damper is approximately /2 inch and comprises the bulk of the transducer height shown in FIG. 1. It should therefore be understood that the dimensions shown in that drawing are not proportional.
  • the dampened stack of piezoelectric elements is then placed in a housing open at one end with the third element flush with the opening. To secure the elements in place with the electrical leads passing through the housing as shown, the housing is filled with a plastic material.
  • the stack of piezoelectric elements may be potted" in plastic such that the plastic itself constitutes the housing, or they may be placed in a housing filled with oil to provide a thin insulating film between each element.
  • quick-disconnect receptacles may be provided for connecting the electrical leads to the outside so that the connections to the circuit 14 can be easily changed.
  • the completed threeelement high-power ultrasonic transducer is then ready to be placed on the object to be inspected.
  • a liquid, paste or other acoustical coupling media is employed to acoustically couple the transducer to the test article.
  • a suitable dry acoustical coupling matrix material is described in U.S. Pat. No. 3,663,842.
  • the sequential trigger control circuit for driving the transducer of FIG. 1 is shown in FIG. 2.
  • the piezoelectric elements are shown separated from each other although it is understood that they are acoustically coupled by an insulating medium. That coupling is represented by a dotted line from one element to the next.
  • a trigger pulse source transmits a single pulse for each time the transducer is to be actuated. Between trigger pulses, the elements are charged to a high voltage 250 V or greater from a source 21 through separate resistors 22, 23 and 24. These resistors are selected to be large (typically 150 K ohms) and the charge time is controlled (by varying a series resistor 25) to be shorter than the reciprocal of the trigger pulse rate. This assures maximum storage of energy for release in response to each trigger pulse.
  • a trigger pulse is coupled by a pulse transformer T to the gate electrode of a silicon controlled rectifier (SCR) 26 which then fires to provide a low impedance discharge path for the first element 11.
  • SCR silicon controlled rectifier
  • the electric wave produced by the sudden change in voltage across the element 11 causes a change in pressure across the next element 12.
  • the elastic wave resulting from the sudden discharge of element 11 will initially cause the next element [2 to be contracted even more in the vertical axis. This produces a transient increase in the voltage across element 12.
  • That transient is coupled by a capacitor 27 across a resistor 28 connected between the gate and cathode of an SCR 29 to trigger it, thus causing the next element to discharge and thereby produce an elastic wave or a portion thereof which adds in phase with the elastic wave from the first element.
  • a delay element 30 may be included as shown or the RC time constant of the capacitor 27 and resistor 28 can be adjusted such that the second element does not discharge until the elastic wave from the first element has traveled a sufficient distance to combine in phase with that from the second element.
  • the third element then discharges in sequence in a similar manner to complete one cycle of operation. Before the next trigger pulse from the source 20 occurs, all elements will be recharged in parallel for the next cycle.
  • the result is one acoustical energy burst for each trigger pulse, each element independently discharging in sequence with a traveling elastic wave initially generated by the electrical discharge of the first element. This process is repeated sequentially in time at a search pulse rate of 800 to 1,000 pps.
  • the scope of the present invention also includes having piezoelectric elements in the device which are not charged and/or discharged. Further, each piezoelectric element need not always be discharged in sequence (as to make a wider duration high energy pulse).
  • delay element 30 or RC time constant of capacitor 27 and resistor 28 can be adjusted such that the discharge of the second element combines out of phase with the elastic wave of the second element resulting in a net decrease in the magnitude of the traveling elastic wave at this position.
  • Transducers used in the ultrasonic frequency range have in the past been limited in power by their small physical size, half wave thickness and heat dissipation capabilities.
  • Single high frequency elements have been actuated by applying a short duration voltage pulse (about one microsecond) from a low impedance (50 ohm) source to the piezoelectric material. This technique is not very efficient and poor power transfer at ultrasonic frequencies results.
  • Stacked piezoelectric elements with electrical power inputs of l to 15 KW have been used as transducers to generate high acoustical power but only in the lower sonic frequency region (500 to 20 KHZ).
  • Some transducers consist of a group of transverse expander (45 Z cut) plates with interleaved foil electrodes electrically connected in parallel. The ends and not the faces of the plates of the stacked crystals act together simultaneously to form a single lateral expansion entirely different from this invention.
  • Another invention U.S. Pat. No. 3,693,415, employs multiple piezoelectric elements uniformly spaced in a row relative to the workpiece with successive units or groups energized in a manner so that successive foci are on a path on the outer surface of the workpiece. The angles are such that the pulses arrive substantially at the same time at a point within the workpiece.
  • Several transducers are employed and cover a substantial portion of the workpiece. This principle involves a number of transducers each acting independently at predetermined fixed angles. The amplitude output of one is not added to the next and to the next as a function of time as in the present invention. Conventional pulsing techniques are used. The longer acoustical path in the sample makes this possible. Similar techniques to the above are used in the prior art for scanning a large area with surface waves using sequentially operated multiple transducers. Another similar invention employs a liquid with multiple electrodes. These and other inventions of the prior art do not involve the principles disclosed in this invention.
  • the present invention is based upon simultaneously charging a number of elements through a high impedance from a common voltage source and then discharging the stored charges in the elements, each over a short period (less than one microsecond) through a low impedance path O.l ohm).
  • the same common high impedanace source is used, and each element charges independently over a relatively long period.
  • all of the piezoelectric elements are simultaneously recharged during the interval between acoustical search pulses from the source 20.
  • the charge time is relatively long (0.08 to 0.001 second) as compared to the envelope of the acoustical energy burst (0.2 to l microsecond).
  • the energy stored in the elements is transformed to mechanical energy which deforms the elements making them thicker or thinner, depending upon the polarization of the elements and the polarity of the power source.
  • the total energy stored in each unit is proportional to the square of the battery or power supply voltage and can be exceedingly high compared to conventional pulsing techniques where only a portion of the pulsing voltage is applied across the transducer. Since all of the stored energy can be released in about a microsecond or less, the result is a high peak acoustical power burst from each element in the stack: viz., watt seconds k CB where C is the capacitance of an element and E is the voltage of the source 21.
  • n elements are in the stack and each is shorted by an SCR switch at a period in time substantially in phase with the elastic wave from the preceding element, the amplitude of the elastic wave traveling down the stack is increased.
  • the battery voltage is thus effectively multiplied n times, and an elastic wave power gain will be obtained.
  • the sonic energy induced voltage in each piezoelectric element is used to trigger the SCR of the next element and the receiving element.
  • Recepticals 31 are provided to connect suitable recording or display apparatus. Both the transmitted signal and the echo return signal can be observed by using the last element 13 as a receiving as well as a transmitting piezoelectric transducer. With adjustable delay element in the gate circuits of the SCRs, it is possible to maximize the transmitted acoustic signal adjusting the delay elements 30 until maximum echo return from the defect is achieved in a standard environment.
  • the SCRs are triggered in sequence through separate multivibrators.
  • a pulse from the source 20 triggers a first multivibrator 32.
  • the leading edge of the positive going output from the true (1) output terminal is coupled by a differentiating circuit to the gate of the SCR 26.
  • the differentiating circuit is comprised of a capacitor 33 and a resistor 34 that actuates the first element 11.
  • the multivibrator 35 After a predetermined period, the multivibrator 35 resets and triggers a multivibrator 36 to activate the third element 13.
  • the periods of the multivibrators are set to cause the elements to be discharged sequentially and inphase with the traveling elastic wave generated by the first element.
  • Still other techniques may be devised for providing sequential trigger control.
  • a delay line with taps to each SCR may be used in place of a chain of multivibrator circuits.
  • digital techniques may be used employing a clock pulse source and a counter to time the periods between the activation of elements.
  • Analog techniques would provide as an advantage a static control signal for each element, rather than a sharp triggering pulse.
  • An advantage of a static control signal is that other electronic switching devices may then be used to discharge the element, such as a transistor switch which is turned on during the presence of the control signal. For higher discharge voltages, two transistor switches can be connected in series and turned on simultaneously by the same control signal. Still other possibilities will occur to those skilled in the art. All that is essential is that the elements be charged over a relatively long period from a common high impedance voltage source, and discharged in phase sequence through very low impedance switches. The shorter the discharge period, the greater the peak electrical power available for conversion to mechanical energy.
  • any number of elements can be used to further increase the power gain achieved upon actuating the elements in phase with the elastic wave from the first element. However, there is a maximum number of elements over which there would be no practical advantage due to the losses between the elements. This occurs when the nth element contributes only about 10 percent increase to the transmitted signal. Power out (P contributed by the nth element will then be (/100) of the input power P,.
  • n 1 The gain in db for n elements over a single element can be derived as follows, where n 1:
  • KP power from one element P power from two elements
  • elements are discharged in pairs.
  • the elements of a pair are connected to the power supply E oppositely. All elements in the stack are arranged with the same ferroelectric polarization as indicated by dots. Consequently, in a given pair, such as the first pair of elements 41 and 42, charging the elements will cause the element 41 to contract and the element 42 to expand longitudinally, i.e., along the axis of the stack, as shown in FIG. 5.
  • a switch S When a switch S is closed, the element 41 will expand and the element 42 will contract simultaneously.
  • the quiescent state of the first pair after the switch S is closed and the stored charge has been fully discharged is illustrated in FIG. 6.
  • the net effect is an elastic wave from the pair coupled to the next pair which is then actuated in phase sequence upon closing a switch S
  • the switches are here represented as mechanical switches, but it is understood that in practice they will be implemented with electronic devices, such as with SCRs.
  • piezoelectric elements said to be charged simultaneously and discharged in phase sequence can mean paired piezoelectric wafers, each pair constituting an element.
  • the principles and circuit techniques for sequential in phase discharge of elements is the same as for other embodiments.
  • the bottom piezoelectric element employed as a receiving transducer can be made from a high-voltage constant (G material to provide optimum receiving characteristics.
  • the other elements in the stack can be manufactured from a high-strain constant (D material to provide good electromechanical transduction.
  • the receiving element may conceivably be geometrically or ultrasonically phase isolated to provide excellent near surface resolution. It is practical for the solidstate switching circuitry to be integrated with the piezoelectric stack to form a composite transducer within one housing. This technique provides pulsing leads of minimum length, a prerequisite for ultra-high frequency performance. State-of-the-art microelectronic integrated circuit techniques are now developed sufficiently for this purpose.
  • each element is necessarily greater than at high frequencies due to the greater half or full wavelength. Consequently, the capacitance of each element would be too small to store the sufficient energy due to the greater distance between electrodes.
  • the present invention can still be practiced at low frequencies by effectively increasing the capacitance of each element. That is accomplished by dividing the thickness of each element into subelements, and constructing the subelements in the same manner as in the previously described embodiments, but electrically connecting the subelements in parallel. The paralleled subelements are then simultaneously triggered as a single element in phase with the elastic wave traveling down the stack from the adjacent paralleled subelements.
  • FIG. 7 illustrates this technique for the embodiment of FIGS. 1 to 3.
  • the same reference numerals are employed for corresponding elements with subscripts, a, b, c for components of subelements.
  • the same technique may be employed in an analogous manner to adapt the embodiment of FIGS. 4 to 6 to low frequencies.
  • a method of producing sonic or ultrasonic waves from a number of piezoelectric elements acoustically coupled, said elements being polarized for expansion and contraction along the axis of soundwave transmission comprising the steps of charging said elements simultaneously through a high impedance from a voltage source,
  • timing of the discharge of each succeeding element after the first is predetermined to occur in phase sequence such that the elastic wave or any portion thereof produced by each succeeding element is in phase with, and adds to, the elastic wave progressing through the group of elements.
  • timing of the discharge of each succeeding element after the first is predetermined to occur in phase sequence that the elastic wave or any portion thereof produced by each succeeding element is out of phase with, and subtracts from, the elastic wave progressing through said group of elements.
  • timing of the discharge in each succeeding element after the first is predetermined to occur in phase sequence such that the elastic wave or any portion thereof produced by one or more of the succeeding elements is in phase with and adds to the elastic wave progressing through said group of elements and the elastic wave produced by one or more of the succeeding elements is out of phase with and subtracts from the elastic wave progressing through said group of elements.
  • each element is comprised of a plurality of piezoelectric subelements acoustically coupled, and wherein subelements of each element are discharged simultaneously, thus providing a longer element for low frequency sonic waves of high energy.
  • Apparatus for producing an acoustical energy burst of high power ultrasonic soundwaves comprising a stack of piezoelectric elements acoustically coupled, each element comprising a slab of piezoelectric material polarized for operation in the thickness mode in a direction along an axis of said stack, said axis being perpendicular to flat sides of said stacked elements, and a separate conductive film on each side of each slab,
  • high impedance means for simultaneously charging the capacitance of said elements with an electrical charge across each of said elements
  • said discharging means comprising a separate low impedance electronic switch connected to each element, each switch having an anode connected to said conductive film on one side of an element, a cathode connected to said conductive film on the other side of said element, and a control electrode,
  • Apparatus for producing soundwaves comprising:
  • Apparatus for producing an acoustical energy burst of high power ultrasonic soundwaves comprising a plurality of piezoelectric elements acoustically coupled, each element comprising a slab of piezoelectric material polarized for operation in the thickness mode in a direction along an axis of said stack, said axis being perpendicular to flat sides of said stacked elements, and a separate conductive film on each side of each slab,
  • high impedance means for simultaneously charging the capacitance of said elements with an electrical charge across each of said elements
  • each controlled rectifier for discharging each element sequentially through a separate low impedance discharge path in phase relationship with the traveling elastic wave progressing along the sound axis, each controlled rectifier having an anode connected directly to a conductive film on one side of a unique one of said slabs, a cathode connected directly to a conductive film on the other side of said unique one of said slabs, and a control electrode connected to receive a triggering signal.
  • each of said elements includes a plurality of piezoelectric subelements, each with separate conductive film on each side, said subelements of an element acoustically coupled with a polarization for operation in said thickness mode along said axis, all of said subelements of an element being electrically connected in parallel for simultaneous charging, and electrically connected in parallel for simultaneous discharging by said means for discharging.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Transducers For Ultrasonic Waves (AREA)
US409534A 1973-10-25 1973-10-25 High power acoustical transducer with elastic wave amplification Expired - Lifetime US3872330A (en)

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Application Number Priority Date Filing Date Title
US409534A US3872330A (en) 1973-10-25 1973-10-25 High power acoustical transducer with elastic wave amplification
NL7412063A NL7412063A (nl) 1973-10-25 1974-09-11 Akoestische overdrager met hoog vermogen en elastische golfversterking.
GB4112474A GB1451247A (en) 1973-10-25 1974-09-20 Piezoelectric transducers
DE19742448318 DE2448318A1 (de) 1973-10-25 1974-10-10 Verfahren und vorrichtung zur erzeugung von schall- oder ultraschallwellen hoher leistung
JP49122321A JPS5075025A (de) 1973-10-25 1974-10-22

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US409534A US3872330A (en) 1973-10-25 1973-10-25 High power acoustical transducer with elastic wave amplification

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JP (1) JPS5075025A (de)
DE (1) DE2448318A1 (de)
GB (1) GB1451247A (de)
NL (1) NL7412063A (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4109174A (en) * 1976-02-24 1978-08-22 Lucas Industries Limited Drive circuits for a piezoelectric stack
US4433916A (en) 1982-11-02 1984-02-28 Hall Mark N Acoustic resonator having transducer pairs excited with phase-displaced energy
US4490640A (en) * 1983-09-22 1984-12-25 Keisuke Honda Multi-frequency ultrasonic transducer
US4529322A (en) * 1981-06-22 1985-07-16 Seiko Instruments & Electronics Ltd. Booster circuit for electronic watch elements
US5317229A (en) * 1991-11-27 1994-05-31 Siemens Aktiengesellschaft Pressure pulse source operable according to the traveling wave principle
US6111335A (en) * 1993-12-28 2000-08-29 Beniamin Acatrinei Piezoelectric interface analyzer
US20060012937A1 (en) * 2002-12-16 2006-01-19 Wac Data Service Co., Ltd. Piezoelectric actuator driver
CN101884974A (zh) * 2010-06-29 2010-11-17 深圳和而泰智能控制股份有限公司 超声波发生器
US20110162181A1 (en) * 2010-01-07 2011-07-07 Samsung Electro-Mechanics Co., Ltd. Device for polling piezoelectric element and polling method using the same
US20110237951A1 (en) * 2009-10-27 2011-09-29 Innurvation, Inc. Data Transmission Via Wide Band Acoustic Channels
US9880133B1 (en) * 2014-03-05 2018-01-30 Atlas Sensors, LLC Non-destructive ultrasonic yield strength measurement tool
US9976406B2 (en) 2011-12-13 2018-05-22 Piezotech Llc Enhanced bandwidth transducer method for well integrity measurement
EP3885055A1 (de) * 2020-03-24 2021-09-29 Imec VZW Verfahren zur erzeugung von ultraschall und ultraschallgenerator

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JPS5991798A (ja) * 1982-11-18 1984-05-26 Mitsubishi Electric Corp 超音波探触子

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US2921134A (en) * 1957-11-21 1960-01-12 Greenspan Martin Electrical-sonic transducers
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US3243648A (en) * 1962-03-28 1966-03-29 Gen Telephone & Elect Piezoelectric energy conversion and electroluminescent display device
US3292018A (en) * 1963-09-13 1966-12-13 Air Shields Transducers
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US2806155A (en) * 1952-07-09 1957-09-10 Rotkin Israel Piezoelectric crystal traveling-wave transducers
US2921134A (en) * 1957-11-21 1960-01-12 Greenspan Martin Electrical-sonic transducers
US3166731A (en) * 1959-11-24 1965-01-19 Chemetron Corp Ultrasonic testing device
US3243648A (en) * 1962-03-28 1966-03-29 Gen Telephone & Elect Piezoelectric energy conversion and electroluminescent display device
US3292018A (en) * 1963-09-13 1966-12-13 Air Shields Transducers
US3399314A (en) * 1965-11-12 1968-08-27 Hewlett Packard Co Ultrasonic signal apparatus

Cited By (17)

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Publication number Priority date Publication date Assignee Title
US4109174A (en) * 1976-02-24 1978-08-22 Lucas Industries Limited Drive circuits for a piezoelectric stack
US4529322A (en) * 1981-06-22 1985-07-16 Seiko Instruments & Electronics Ltd. Booster circuit for electronic watch elements
US4433916A (en) 1982-11-02 1984-02-28 Hall Mark N Acoustic resonator having transducer pairs excited with phase-displaced energy
US4490640A (en) * 1983-09-22 1984-12-25 Keisuke Honda Multi-frequency ultrasonic transducer
US5317229A (en) * 1991-11-27 1994-05-31 Siemens Aktiengesellschaft Pressure pulse source operable according to the traveling wave principle
US6111335A (en) * 1993-12-28 2000-08-29 Beniamin Acatrinei Piezoelectric interface analyzer
US20060012937A1 (en) * 2002-12-16 2006-01-19 Wac Data Service Co., Ltd. Piezoelectric actuator driver
US9192353B2 (en) * 2009-10-27 2015-11-24 Innurvation, Inc. Data transmission via wide band acoustic channels
US10092185B2 (en) * 2009-10-27 2018-10-09 Innurvation Inc. Data transmission via wide band acoustic channels
US20110237951A1 (en) * 2009-10-27 2011-09-29 Innurvation, Inc. Data Transmission Via Wide Band Acoustic Channels
US20110162181A1 (en) * 2010-01-07 2011-07-07 Samsung Electro-Mechanics Co., Ltd. Device for polling piezoelectric element and polling method using the same
CN101884974B (zh) * 2010-06-29 2011-11-23 深圳和而泰智能控制股份有限公司 超声波发生器
CN101884974A (zh) * 2010-06-29 2010-11-17 深圳和而泰智能控制股份有限公司 超声波发生器
US9976406B2 (en) 2011-12-13 2018-05-22 Piezotech Llc Enhanced bandwidth transducer method for well integrity measurement
US9880133B1 (en) * 2014-03-05 2018-01-30 Atlas Sensors, LLC Non-destructive ultrasonic yield strength measurement tool
EP3885055A1 (de) * 2020-03-24 2021-09-29 Imec VZW Verfahren zur erzeugung von ultraschall und ultraschallgenerator
US11799563B2 (en) 2020-03-24 2023-10-24 Imec Vzw Method of generating ultrasound and ultrasound generator

Also Published As

Publication number Publication date
NL7412063A (nl) 1975-04-29
JPS5075025A (de) 1975-06-20
GB1451247A (en) 1976-09-29
DE2448318A1 (de) 1975-05-07

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