US3828143A - Piezoelectric end capped cylinder assembly for use to the radial-mode resonance frequency - Google Patents

Piezoelectric end capped cylinder assembly for use to the radial-mode resonance frequency Download PDF

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Publication number
US3828143A
US3828143A US00265042A US26504272A US3828143A US 3828143 A US3828143 A US 3828143A US 00265042 A US00265042 A US 00265042A US 26504272 A US26504272 A US 26504272A US 3828143 A US3828143 A US 3828143A
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United States
Prior art keywords
radial
resonance frequency
mode resonance
transducer
end caps
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US00265042A
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A Tims
T Henriquez
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US Department of Navy
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US Department of Navy
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Priority to US00265042A priority Critical patent/US3828143A/en
Priority to CA169,681A priority patent/CA977454A/en
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H10N30/202—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using longitudinal or thickness displacement combined with bending, shear or torsion displacement
    • 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
    • B06B1/0644—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 a single piezoelectric element
    • B06B1/0655—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 a single piezoelectric element of cylindrical shape

Definitions

  • the element is usable with a much broader bandwidth up to the radial-mode resonance where prior art devices without the posts were usable only over about 60 percent of the possible usable range.
  • a cylindrical end capped piezoelectric transducer element provided with an interior post cemented to the end caps.
  • the structure prevents flexure resonance of the end caps to thus provide uniform, relatively flat responses to the radial-mode resonance frequency.
  • An object of the invention is to provide an improved end capped transducer.
  • Another object is the provision of an extended frequency range for end capped transducers.
  • Yet another object is to provide a transducer which can sustain greatly increased operating pressures.
  • FIG. 1 shows a section view of the cylindrical transducer preferred embodiment.
  • FIG. 2 shows a comparison of the sensitivity for a capped two element line with and without posts.
  • FIG. 1 shich shows a sectional side view of the transducer assembly, the transducer consists of a cylindrical piezoelectric ceramic element 1,
  • a glass post 4 of the exact length of the cylinder is concentrically mounted inside the cylindrical element 1 and is also epoxy bonded to the end caps 2.
  • the crosssectional area of the post is approximately 40 percent of that of the end cap.
  • the post allows the response of the transducer to be useful over a broad range of frequency up to the radialmode resonance while prior art transducers without such a structure were only usable to about 60 percent of the radial-mode resonance frequency.
  • the improved transducer is of great use in line arrays where previous transducers appeared to have a severe drop in sensitivity due to end flexure resonance and loss change in directivity characteristics.
  • the high-pressure capability of the transducer is improved as a result of the mechanical support that the post gives to the end caps. Further it should be noted the structure is mechanically sound with support passing through the end caps to supply support.
  • FIG. 2 shows a comparison of the sensitivity of a two element line with and without the post.
  • the sensitivity without the post curve 5 drops severely at about 30 kHz while the sensitivity with the post curve 6 remains relatively stable through the range of the element.
  • the use of the post is of great value in maintaining a broad frequency band of response.
  • An electroacoustic transducer which comprises:

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

A cylindrical end capped piezoelectric transducer element provided with a concentrically mounted interior post cemented to the end caps. The structure prevents resonance of the end caps to thus provide uniform, relatively flat response to the radial mode resonance frequency.

Description

Sttes tent 91 Tims et al.
[ Aug. 6, B974 PIEZOELECTRIC END CAPPED CYLINDER ASSEMBLY FOR USE TO THE RADIAL-MODE RESONANCE FREQUENCY [75] Inventors: Allan C. Tims; Theodore A.
Henriquez, both of Orlando, Fla.
[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.
22 Filed: June2l, 1972 21 Appl.No.:265,042
[52] US. Cl. 179/110 A, 340/10 [51] Int. Cl H04r 17/00 [58] Field of Search 189/110 A, 110 F; 310/82,
[56] References Cited UNITED STATES PATENTS 2,945,208 7/1960 Samsel 340/l0 3,437,171 4/1969 Davis et al. 340/10 Primary Examiner-Kathleen H. Claffy Assistant ExaminerThomas L. Kundert Attorney, Agent, or FirmR. S. Sciascia; Arthur L. Branning [5 7] ABSTRACT A cylindrical end capped piezoelectric transducer element provided with a concentrically mounted interior post cemented to the end caps. The structure prevents resonance of the end caps to thus provide uniform, relatively flat response to the radial mode resonance frequency.
3 Claims, 2 Drawing Figures PAIEN {En AUG 6 I914 DECIBELS RE I VOLT PER MICROPASCAL FREQUENCY IN kHz PIEZOELECTRIC END CAPPED CYLINDER ASSEMBLY FOR USE TO THE RADIAL-MODE RESONANCE FREQUENCY BACKGROUND OF THE INVENTION The resonance-free frequency band for a cylindrical piezoelectric ceramic element is a function of the largest dimension of the cylinder, which is usually the circumference; because the circumference is a function of the radius, the mean radius can be said to determine the first resonance called the radial-mode resonance. Although a smooth, relatively flat response should result at all frequencies up to that of the radialmode resonance, present capped cylinders operate smoothly only to frequencies between 40% and 60% of the radial-mode resonance frequency. The useful response terminates at a lower frequency, because the end caps of the cylinder break into flexure resonance causing a drop of several dB in sensitivity. When several of the transducers are formed into a closely spaced line array the resulting change in dB becomes greatly pronounced.
In tests a inch diameter cylinder without the posts showed end cap break up at 25 kHz while the radialmode resonance should occur at 50 kHz.
With a post the response of the transducer is relatively smooth and broadened up to the radial-mode resonance frequency.
Thus it is seen that with the use of the post the element is usable with a much broader bandwidth up to the radial-mode resonance where prior art devices without the posts were usable only over about 60 percent of the possible usable range.
SUMMARY OF THE INVENTION A cylindrical end capped piezoelectric transducer element provided with an interior post cemented to the end caps. The structure prevents flexure resonance of the end caps to thus provide uniform, relatively flat responses to the radial-mode resonance frequency.
OBJECTS OF THE INVENTION An object of the invention is to provide an improved end capped transducer.
Another object is the provision of an extended frequency range for end capped transducers.
Yet another object is to provide a transducer which can sustain greatly increased operating pressures.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a section view of the cylindrical transducer preferred embodiment.
FIG. 2 shows a comparison of the sensitivity for a capped two element line with and without posts.
PREFERRED EMBODIMENT OF THE INVENTION Now referring to FIG. 1 shich shows a sectional side view of the transducer assembly, the transducer consists of a cylindrical piezoelectric ceramic element 1,
having aluminum oxide or beryllium oxide end caps 2 bonded by an epoxy adhesive 3 to the ends of said element 1. A glass post 4 of the exact length of the cylinder is concentrically mounted inside the cylindrical element 1 and is also epoxy bonded to the end caps 2. The crosssectional area of the post is approximately 40 percent of that of the end cap.
The post allows the response of the transducer to be useful over a broad range of frequency up to the radialmode resonance while prior art transducers without such a structure were only usable to about 60 percent of the radial-mode resonance frequency.
The improved transducer is of great use in line arrays where previous transducers appeared to have a severe drop in sensitivity due to end flexure resonance and loss change in directivity characteristics.
Thus using the improved transducer line arrays with broad bandwidth relatively smooth response and predictable directivity are possible up to the radial-mode resonance frequency while retaining the well-known stability with temperature and pressure.
The high-pressure capability of the transducer is improved as a result of the mechanical support that the post gives to the end caps. Further it should be noted the structure is mechanically sound with support passing through the end caps to supply support.
FIG. 2 shows a comparison of the sensitivity of a two element line with and without the post. The sensitivity without the post curve 5 drops severely at about 30 kHz while the sensitivity with the post curve 6 remains relatively stable through the range of the element. As the severity of the sensitivity loss increases with the increase in the length of the line (apparently due to sympathetic resonance of end caps of other elements which are in a close proximity) the use of the post is of great value in maintaining a broad frequency band of response.
Of course many other materials can be used for the post and the end caps but optimum bandwidth has been achieved with the materials specified.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
What is claimed and desired to be secured by Letters Patent of the United States is:
1. An electroacoustic transducer which comprises:
a hollow cylindrical piezoelectric crystal;
a first end cap bonded to a first end of said crystal;
a second end cap bonded to a second end of said crystal; and,
a cylindrical post concentrically disposed within said crystal and bonded at each end to the internal side of said end caps.
2. The transducer of claim 1 wherein said end caps are composed of beryllium oxide.
3. The transducer of claim 1 wherein said end caps are composed of aluminum oxide.

Claims (3)

1. An electroacoustic transducer which comprises: a hollow cylindrical piezoelectric crystal; a first end cap bonded to a first end of said crystal; a second end cap bonded to a second end of said crystal; and, a cylindrical post concentrically disposed within said crystal and bonded at each end to the internal side of said end caps.
2. The transducer of claim 1 wherein said end caps are composed of beryllium oxide.
3. The transducer of claim 1 wherein said end caps are composed of aluminum oxide.
US00265042A 1972-06-21 1972-06-21 Piezoelectric end capped cylinder assembly for use to the radial-mode resonance frequency Expired - Lifetime US3828143A (en)

Priority Applications (2)

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US00265042A US3828143A (en) 1972-06-21 1972-06-21 Piezoelectric end capped cylinder assembly for use to the radial-mode resonance frequency
CA169,681A CA977454A (en) 1972-06-21 1973-04-26 Piezoelectric end capped cylinder assembly for use to the radial-mode resonance frequency

Applications Claiming Priority (1)

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US00265042A US3828143A (en) 1972-06-21 1972-06-21 Piezoelectric end capped cylinder assembly for use to the radial-mode resonance frequency

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0242844A1 (en) * 1986-04-23 1987-10-28 Laserdot Variable-surface mirror in an adaptive optical system
US4926396A (en) * 1989-10-10 1990-05-15 Teledyne Exploration High pressure transducer
USH1875H (en) * 1996-07-22 2000-10-03 Microtronic A/S Electroacoustic transducer

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2945208A (en) * 1951-01-05 1960-07-12 Gen Electric Compressional wave transducer
US3437171A (en) * 1967-11-03 1969-04-08 Texas Instruments Inc Marine hydrophone vibration isolation

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2945208A (en) * 1951-01-05 1960-07-12 Gen Electric Compressional wave transducer
US3437171A (en) * 1967-11-03 1969-04-08 Texas Instruments Inc Marine hydrophone vibration isolation

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0242844A1 (en) * 1986-04-23 1987-10-28 Laserdot Variable-surface mirror in an adaptive optical system
FR2597983A1 (en) * 1986-04-23 1987-10-30 Comp Generale Electricite MODULAR SURFACE MIRROR FOR WAVEFRONT ADAPTER OPTICAL SYSTEM
US4926396A (en) * 1989-10-10 1990-05-15 Teledyne Exploration High pressure transducer
USH1875H (en) * 1996-07-22 2000-10-03 Microtronic A/S Electroacoustic transducer

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CA977454A (en) 1975-11-04

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