US3487137A - Method of producing ultrasonic energy absorbing material - Google Patents
Method of producing ultrasonic energy absorbing material Download PDFInfo
- Publication number
- US3487137A US3487137A US725478A US3487137DA US3487137A US 3487137 A US3487137 A US 3487137A US 725478 A US725478 A US 725478A US 3487137D A US3487137D A US 3487137DA US 3487137 A US3487137 A US 3487137A
- Authority
- US
- United States
- Prior art keywords
- acoustic impedance
- binder
- matrix
- load
- acoustic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title description 6
- 239000011358 absorbing material Substances 0.000 title 1
- 239000011159 matrix material Substances 0.000 description 19
- 239000011230 binding agent Substances 0.000 description 15
- 239000007788 liquid Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 239000004593 Epoxy Substances 0.000 description 8
- 239000002923 metal particle Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 5
- 238000003825 pressing Methods 0.000 description 5
- 229920005989 resin Polymers 0.000 description 5
- 239000011347 resin Substances 0.000 description 5
- 239000003822 epoxy resin Substances 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 229920000647 polyepoxide Polymers 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241001605719 Appias drusilla Species 0.000 description 1
- 244000304337 Cuminum cyminum Species 0.000 description 1
- 235000007129 Cuminum cyminum Nutrition 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 1
- 229910002113 barium titanate Inorganic materials 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/002—Devices for damping, suppressing, obstructing or conducting sound in acoustic devices
-
- 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
- B06B1/0662—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 with an electrode on the sensitive surface
- B06B1/0681—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 with an electrode on the sensitive surface and a damping structure
Definitions
- the desired impedance of the load is determined by the pressure applied during or prior to the curing of the binder.
- Ultrasonic transducers are commonly used to convert electrical signals into bursts of ultrasonic vibrations for use in industrial and medical applications. It is generally essential that the ultrasonic vibrations emanate from only one surface of the transducer and, therefore, that ultrasonic vibrations emanating from other surfaces of the transducer be absorbed. Undesirable vibrations from an ultrasonic transducer are conventionally absorbed by a matrix structure which includes metal particles in a binder and which is acoustically coupled to receive and absorb the undesirable ultrasonic vibrations. However, mismatches in the coupling of ultrasonic vibrations to the absorptive load produce undesirable reflections at the interfaces of acoustic media of dilferent acoustic impedances.
- mismatches in the coupling to an absorptive load are substantially eliminated by forming the load in accordance with the process of the present invention to have an acoustic impedance which substantially equals the acoustic impedance of the ultrasonic transducer.
- the acoustic impedance of the load is altered by altering the density of the matrix structure which forms the load.
- the acoustic impedance of the cured, unpressed material is much lower than the acoustic impedance of the piezoelectric material it is intended to match.
- the liquid matrix material is loaded into a mold of suitable shape and is pressed to expel about half of the initial amount of the epoxy binder and to orient the metal particles in close contact throughout the volume of the mold.
- the mold may be of conventional design with suflicient differences in the dimensions of mating surfaces to allow excess epoxy to escape from the mold. This step of pressing out the excess epoxy increases the density and the stiffness, and, hence, the acoustic impedance of the matrix material in the mold.
- the pressure on the matrix material in the mold may be maintained during the curing cycle of the epoxy or it may simply be maintained only long enough to expel the excess epoxy prior to its curing cycle.
- the pressed and cured matrix material has been found to have an acoustic impedance which is typically twice as great as the acoustic impedance of similar types of acoustic load materials which are made without pressing or other means of compaction before or during the epoxy curing cycle.
- the acoustic impedance of the absorptive load may be varied in accordance with the present invention over a range of values from about 10 to 25 simply by altering the pressure applied to the liquid matrix material in a mold to expel a certain amount of excess binder material.
- a few tests at various molding pressures exerted on selected formulations of matrix materials may thus pro vide sufiiicient data for selecting the matrix material formulation and molding pressure required to produce an absorptive load having an acoustic impedance which matches, typically within five percent, the acoustic impedanee of a given piezoelectric material.
- step (d) curing said liquid resin binder remaining in said matrix to a solid state to produce said absorptive load; said acoustic impedance in said produce load being determined by the pressing as applied in above step (c).
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Mechanical Engineering (AREA)
- Transducers For Ultrasonic Waves (AREA)
- Casting Or Compression Moulding Of Plastics Or The Like (AREA)
Description
United States Patent U.S. Cl. 264111 2 Claims ABSTRACT OF THE DISCLOSURE A method of making an acoustic absorptive load for a piezoelectric vibrator in which a mixture of metal particles and a liquid epoxy binder are pressed in a mold to expel excess binder, and then curing the binder. The desired impedance of the load is determined by the pressure applied during or prior to the curing of the binder.
BACKGROUND OF THE INVENTION Ultrasonic transducers are commonly used to convert electrical signals into bursts of ultrasonic vibrations for use in industrial and medical applications. It is generally essential that the ultrasonic vibrations emanate from only one surface of the transducer and, therefore, that ultrasonic vibrations emanating from other surfaces of the transducer be absorbed. Undesirable vibrations from an ultrasonic transducer are conventionally absorbed by a matrix structure which includes metal particles in a binder and which is acoustically coupled to receive and absorb the undesirable ultrasonic vibrations. However, mismatches in the coupling of ultrasonic vibrations to the absorptive load produce undesirable reflections at the interfaces of acoustic media of dilferent acoustic impedances.
SUMMARY OF THE INVENTION Accordingly, mismatches in the coupling to an absorptive load are substantially eliminated by forming the load in accordance with the process of the present invention to have an acoustic impedance which substantially equals the acoustic impedance of the ultrasonic transducer. The acoustic impedance of the load is altered by altering the density of the matrix structure which forms the load.
DESCRIPTION OF THE PREFERRED EMBODIMENT In the method of forming an absorptive load for an ultrasonic transducer in accordance with the present invention, a mixture of particles of a metal such as molybdenum, iron or tungsten, or the like (acoustic impedances typically greater than 45 in a system of units for which the acoustic impedance of water=l.5), and a suitable liquid binder such as epoxy resin is prepared in a ratio of materials which contains about twice the epoxy resin desired to have present in the finished material. The final matching of the acoustic impedances is accomplished according to the present invention by exerting pressure on the uncured volume of matrix materials causing about half of the uncured binder to be expelled from the mold used to hold the matrix materials during the pressing process. Thus, to match the acoustic impedance of an utrasonic vibrator element formed of a piezoelectric material such as barium titanate (acoustic impedance=24 in a system of units for which the acoustic impedance of water=1.5), or lead rnetaniobate (acoustic impedance=17,) the matrix material may be prepared using tungsten particles (specific gravity=l9) of about 4 to 6 micron size and liquid, uncured epoxy in a ratio by weight of less than about 12 parts tungsten to one part epoxy resin (for example, Eccogel 1265, distributed by Emerson & Cumin Company).
In the above formulation of the matrix material, the acoustic impedance of the cured, unpressed material is much lower than the acoustic impedance of the piezoelectric material it is intended to match. To obtain an acoustic impedance which matches the piezoelectric material, the liquid matrix material is loaded into a mold of suitable shape and is pressed to expel about half of the initial amount of the epoxy binder and to orient the metal particles in close contact throughout the volume of the mold. The mold may be of conventional design with suflicient differences in the dimensions of mating surfaces to allow excess epoxy to escape from the mold. This step of pressing out the excess epoxy increases the density and the stiffness, and, hence, the acoustic impedance of the matrix material in the mold. The pressure on the matrix material in the mold may be maintained during the curing cycle of the epoxy or it may simply be maintained only long enough to expel the excess epoxy prior to its curing cycle. The pressed and cured matrix material has been found to have an acoustic impedance which is typically twice as great as the acoustic impedance of similar types of acoustic load materials which are made without pressing or other means of compaction before or during the epoxy curing cycle.
The acoustic impedance of the absorptive load may be varied in accordance with the present invention over a range of values from about 10 to 25 simply by altering the pressure applied to the liquid matrix material in a mold to expel a certain amount of excess binder material. A few tests at various molding pressures exerted on selected formulations of matrix materials may thus pro vide sufiiicient data for selecting the matrix material formulation and molding pressure required to produce an absorptive load having an acoustic impedance which matches, typically within five percent, the acoustic impedanee of a given piezoelectric material.
I claim:
1. A method of producing an acoustic absorptive load for a piezoelectric vibrator, said load having a desired acoustic impedance and consisting of metal particles and a liquid resin binder curable to a solid. state, comprising:
(a) preparing a matrix of said metal particles with an amount of said liquid resin binder in excess of the resin binder in the prepared load,
(b) placing said matrix within a mold,
(c) pressing said matrix to expel a portion of said liquid resin from said matrix while increasing the density and stifiness of said matrix, and
(d) curing said liquid resin binder remaining in said matrix to a solid state to produce said absorptive load; said acoustic impedance in said produce load being determined by the pressing as applied in above step (c).
2. The method as in claim 1 wherein the metal particles and liquid binder combined in the'first-named step are combined in a ratio by weight of metal particles to binder less than about 12:1 for particles of metal having a specific gravity greater than 18.
References Cited UNITED STATES PATENTS 2,707,755 5/1955 Hardie et al. 310-82 2,881,336 4/1959 Elion 3108.2 3,403,271 9/1968 Lobdell et al. 3l08.2
ROBERT F. WHITE, Primary Examiner J. R. HALL, Assistant Examiner US! C X-R' 310-82
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US72547868A | 1968-04-30 | 1968-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3487137A true US3487137A (en) | 1969-12-30 |
Family
ID=24914726
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US725478A Expired - Lifetime US3487137A (en) | 1968-04-30 | 1968-04-30 | Method of producing ultrasonic energy absorbing material |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3487137A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3821834A (en) * | 1972-07-18 | 1974-07-02 | Automation Ind Inc | Method of making an ultrasonic search unit |
| US3943217A (en) * | 1970-06-11 | 1976-03-09 | Franz Rother | Process for manufacturing bodies of various shapes from inorganic powders |
| US4018861A (en) * | 1972-03-29 | 1977-04-19 | Great Canadian Oil Sands Limited | Method for preparing consumable electroslag guide nozzle |
| US4037180A (en) * | 1975-03-06 | 1977-07-19 | U.S. Philips Corporation | Electro-mechanical filter |
| EP0142318A2 (en) * | 1983-11-09 | 1985-05-22 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic probe |
| US5988689A (en) * | 1997-12-26 | 1999-11-23 | Central Plastics Company | Heat-shrinkable electrofusion fittings and methods |
| US20040200056A1 (en) * | 2001-02-28 | 2004-10-14 | Masushita Electric Industrial Co., Ltd. | Ultrasonic transducer, method for manufacturing ultrasonic transducer, and ultrasonic flowmeter |
| US9880671B2 (en) | 2013-10-08 | 2018-01-30 | Sentons Inc. | Damping vibrational wave reflections |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2707755A (en) * | 1950-07-20 | 1955-05-03 | Sperry Prod Inc | High absorption backings for ultrasonic crystals |
| US2881336A (en) * | 1956-05-04 | 1959-04-07 | Sperry Prod Inc | Damping means for piezo-electric crystals |
| US3403271A (en) * | 1966-02-09 | 1968-09-24 | Hewlett Packard Co | Ultrasonic transducer with absorptive load |
-
1968
- 1968-04-30 US US725478A patent/US3487137A/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2707755A (en) * | 1950-07-20 | 1955-05-03 | Sperry Prod Inc | High absorption backings for ultrasonic crystals |
| US2881336A (en) * | 1956-05-04 | 1959-04-07 | Sperry Prod Inc | Damping means for piezo-electric crystals |
| US3403271A (en) * | 1966-02-09 | 1968-09-24 | Hewlett Packard Co | Ultrasonic transducer with absorptive load |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3943217A (en) * | 1970-06-11 | 1976-03-09 | Franz Rother | Process for manufacturing bodies of various shapes from inorganic powders |
| US4018861A (en) * | 1972-03-29 | 1977-04-19 | Great Canadian Oil Sands Limited | Method for preparing consumable electroslag guide nozzle |
| US3821834A (en) * | 1972-07-18 | 1974-07-02 | Automation Ind Inc | Method of making an ultrasonic search unit |
| US4037180A (en) * | 1975-03-06 | 1977-07-19 | U.S. Philips Corporation | Electro-mechanical filter |
| EP0142318A2 (en) * | 1983-11-09 | 1985-05-22 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic probe |
| EP0142318A3 (en) * | 1983-11-09 | 1987-03-11 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic probe |
| US5988689A (en) * | 1997-12-26 | 1999-11-23 | Central Plastics Company | Heat-shrinkable electrofusion fittings and methods |
| US20040200056A1 (en) * | 2001-02-28 | 2004-10-14 | Masushita Electric Industrial Co., Ltd. | Ultrasonic transducer, method for manufacturing ultrasonic transducer, and ultrasonic flowmeter |
| US7087264B2 (en) * | 2001-02-28 | 2006-08-08 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic transducer, method for manufacturing ultrasonic transducer, and ultrasonic flowmeter |
| US9880671B2 (en) | 2013-10-08 | 2018-01-30 | Sentons Inc. | Damping vibrational wave reflections |
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