CA1090694A - Transducer assembly, ultrasonic atomizer and fuel burner - Google Patents
Transducer assembly, ultrasonic atomizer and fuel burnerInfo
- Publication number
- CA1090694A CA1090694A CA336,571A CA336571A CA1090694A CA 1090694 A CA1090694 A CA 1090694A CA 336571 A CA336571 A CA 336571A CA 1090694 A CA1090694 A CA 1090694A
- Authority
- CA
- Canada
- Prior art keywords
- section
- flange
- fuel
- atomizing
- liquid
- 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
Links
Landscapes
- Special Spraying Apparatus (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A transducer assembly includes a first half wavelength double-dummy section having a pair of quarter wavelength ultrasonic horns and a driving element sandwiched therebetween. A second half wavelength stepped amplifying section extends from one end of the first section and has a theoretical reso-nant frequency equal to the actual resonant frequency of the first section.
When used as a liquid atomizer, the small diameter portion of the stepped amplifying section has a flanged tip to provide an atomizing surface of in-creased area. To maintain efficiency, the length of the small diameter por-tion of the second section with a flange should be less than its length with-out a flange. A decoupling sleeve within an axial liquid passageway elimi-nates premature atomization of the liquid before reaching the atomizing sur-face.
A transducer assembly includes a first half wavelength double-dummy section having a pair of quarter wavelength ultrasonic horns and a driving element sandwiched therebetween. A second half wavelength stepped amplifying section extends from one end of the first section and has a theoretical reso-nant frequency equal to the actual resonant frequency of the first section.
When used as a liquid atomizer, the small diameter portion of the stepped amplifying section has a flanged tip to provide an atomizing surface of in-creased area. To maintain efficiency, the length of the small diameter por-tion of the second section with a flange should be less than its length with-out a flange. A decoupling sleeve within an axial liquid passageway elimi-nates premature atomization of the liquid before reaching the atomizing sur-face.
Description
i9~
This application is a division of application 290,308, filed November 7, 1977.
The present invention relates to transducer assemblies and to apparatus employing same for achieving efficient combustion of fuels. An example of same is found in the United States patent to H. L. Berger, 3,861,852, issued January 21, 1975.
One problem associated with transducer assemblies of the type used in apparatus for achieving combustion of fuels is the non-uniform delivery of fuel to the atomizing surface with consequent non-uniform distribution of fuel from same. It has been discovered that with such prior art assemblies, fuels which have low surface tension as, for example, hydrocarbon fuels, begin to atomize within the fuel passage leading to the atomizing surface. This premature atomization creates bubbles within the fuel passage. The bubbles eventually work their way to the atomizing surface, but their arrival at the atomizing surface results in a temporary interruption in fuel flow to portions of the surface and, as a result, non-uniform distribution of fuel over the surface. The bubble remains intact for a short period of time on the atomiz-ing surface and thus the surface area beneath the bubble during the interval is not wet with fuel.
According to the present invention there is provided an ultrasonic transducer having an elongated, longitudinally vibrating probe with a flanged tip, said flanged tip comprising a vibrating surface capable of causing atom-ization of a liquid, the transducer further comprising a liquid delivery pas-sage extending axially through said probe to said atomizing surface and a decoupling sleeve mounted within said passage and extending to said atomizing surface for acoustically isolating the interior surface of said passage from liquid flowing therethrough.
In the accompanying drawings, which illustrate an exemplary embodi-ment of the present invention and related structures that may advantageously ~t~ - 1- ~, - -, .~ .
.. . . . . .
., -- :, -' .
10~ 9~
be used in conJunction therewith:
Figure 1 is a cross sectional view of a first section of a transduc-er assembly;
Figure 2 is a cross sectional view of a second section Or the trans-ducer assembly; and Figure 3 is a cross sectional view of a complete transducer assem~
bly: -~eferring to the dra~ing, the design oP a transducer assembly may be optimized, for among other things, maximum Q, by con~tructing a first transducer assembly section comprising a driving element and t~o identical horn sections (Figure 1) such that the resulting structure forms a symmetric geometry with respect to the longitudinal axis. This first assembly section is referred to as a double-dummy ultrasonic horn. In the next operation the resonant frequency of the first section is measured, and a second section is added (Figure 2) that includes an amplification step and an atomizing sur-face, and whose theoretical resonant frequency matches the empirically mea~ured frequency of the first section, thereby forming a complete trans-ducer assembly (Figure 3) designed for maximum Q and for use in achieving efficient c bustion of fuels.
Referring first to Figure 1 the first section 11 of the transducer assembly i8 seen a8 including front 12A and rear 13 ultrasonic horn sections and a driving element 14 comprising a pair of piezoelectric discs 15, 16 and an electrode (not shown) positioned therebetween, excited by bigh frequency electrical energy fed thereto from a te i nal lô.
Driving element 1~ is sandwiched between flanged portions 19, 20 of horn sections 12A, 13 and securely clamped therein by mean~ of a clamping assembly that includes a mounting ring 21 (for secur~ng the assembly to other apparatus) and a plurality of assembly bolts 22 which pass through holes in , - . . . .
,' " - ,. :- "i - ......................... - `
- .
" . - .:.iW~
1~13~;9~
terminal 18, flange sections 19 and 20 into threaded openings in mounting ring 21. The assembly bolts 22 are electrically isolated from the terminal 18 by means of insulators 23.
The first section 11 further includes a fuel tube 24 for introduc-ing fuel into a channel within the transducer assembly and a pair of sealing gaskets 26, 27 compressed between horn flange sections 19, 20.
In a typical embodiment: the horn sections 12A, 13 and flange sections 19, 20 are preferably of good acoustic conducting material such as aluminum, titanium or magnesium; or alloys thereof such as Ti-6A R-4v titanium-aluminum alloy, 6061-T6 aluminum alloy, 7025 high strength aluminum alloy, AZ 61 magnesium alloy and the like; the discs 15, 16 are of lead-zirconate-titanate such as those manufactured by Vernitron Corporation or of lithium miobate such as those manufactured by Valtec Corporation; the elec-trode is of copper; the terminal 18, mounting ring 21, and assembly bolts 22 are of steel; the insulators 23 are of nylon, polytetrafluoroethylene ~such as sold by Dupont under the trade mark Teflon) or some plastic with good electrical insulating properties; and, the sealing gaskets 26, 27 are of silicone rubber.
The first section 11 is seen to have symmetric half-wavelength geometry, yet it contains all the ana lous features of the transducer assem-bly, i.e. clamping at non-nodal planes, copper electrode, screw clamping and mounting bracket. The properties of this first section are established and its characteristic frequency, for maximum Q, quantitatively measured. Typical-ly the frequency is measured and found to be 85KHZ. This completes the first step in the design of the transducer assembly.
Referring to Figure 2, another half-wave section 29 is added to the first section 11. The section 29 is seen as including a large diameter seg-ment 12B, a small diameter segment 30 so as to form an amplification step 31, a flanged tip 32 with atomizing surface 33, a central passage 34 for .~.
~ --3--: . ~ :: . - : .
: ` ~ . ' :
10!~ 9~
delivering fuel to the atomizing surface 33 and internally mounted decoupling sleeve 35. The decoupling 81eeve i8 a substance such as Te n on which does not couple well acoustically to the fuel hole.
It will be observed by those skilled in the art that this section contains few anamolies since it is a pure theoretical structure as well. Its characteristic frequency for maximum Q is computed and selected 80 as to match that of the first section 11.
In order to complete the design, the two sections 11 and 29 are formed integrally so as to yield a transducer assembly (Figure 3) optimized for maximum Q and for use in achieving efficient combustion of fuels.
Prior art transducer assemblies used for ultrasonic atomization of fuel have, in the past, typically employed a flanged tip 32 with atomization surface 33. The presence of the flanged tip with its atomization surface 33 increases atomization capabilities due to increased atomizing surface area.
The addition of such flange has been at the expense of atomizer efficiency.
Referring to Figure 2, let A = length of horn front section 12B, B ~ length of small diameter segment 30 and C = thickness of flanged tip sec-tion 32.
In prior art assemblies that do not use a flange, A = 1 since they are both quarter wave length sections.
In prior art assemblies utilizing a flange A = 1.
BIC
It has been determined that maintaining the ratio at 1, even a M er addition o~ the flange, is inefficient and reduces power transfer, but by maintaining the ratio A ~ 1 efficiency levels can be maintainea at pre-~C
flange addition levels. Thus, for example, if ~3 = diameter of flange section 32 _ ~ _ ~ -. .
~0~;~4 D2 = diameter of small diameter segment 30 for 3 = 1.53 ~2 A (without flange) = A = 1 B+C B
and A (with flange) = 1.12 B+C
and the efficiency levels achieved with the flange match those of the assembly with the flange. .
~ he foregoing analysis applies to assemblies of aluminum, titanium, magnesium and previously mentioned alloys, and assumes that for both mate-rials the velocity of sound in same is approximately the same. For other 0 materisls with different velocities of sound the ratio A will differ, but BIC
always be greater than 1.
The long-term reliability of the device is dramatically enhanced by sealing the discs 15 since fuel contamination is no longer possible. The space between the clamping flange sections 19, 20 is filled with a silicone rubber compound as by sealing gaskets 26, 27. In the past, fuel creepage onto the faces of the discs 15, 16 has caused degradation of sPm~ and has resulted in poor long-term atomizer performance. The phenomenon causes a 1088 in mechanical coupling between elements of the horn. The gaskets 26, 27 solve the problem and atomizer performance is not affected by the added mass as has been confixmed by before and after measurement of impedance, operating fre-quency and flange displacement. The slightly higher internal heating caused by sealing the discs 15 does not reduce the atomizer's useful life since internal temperatures are still well below the m~ximum operating temperature for piezoelectric crystals. The gaskets 26, 27 are of a compressible material and have an inner periphery conforming to but initially sl~ghtly greater than the outer circumference of the discs 15, 16. Upon clamping the inner periph-ery of gaskets 26, 2~ come into light contact with the outer circumference of ,~ ~, : ' 10~ i9~
the discs 15, 16.
The present application is concerned with the elimination of pre-mature atomization Or fuel in the fuel passage leading to the atomizing sur-fsce. As noted previously, in prior art structures the fuel can begin to atomize within the fuel passage leading to the atomizing surface. This pre-mature atomization creates voids within the fuel passage at the fuel-wall interface which leads to the formation of bubbles within the fuel passage.
The bubbles eventually work their way to the atomizing surface, but their arrival at the atomizing surface results in a temporary interruption in fuel flow to a portion of the surface and as a result, non-uniform distribution of fuel over the surface. The bubble remains intact for a short period of time on the atomizing surface and thus the surface area beneath the bubble during that interval is not wet with fuel. The net effect of thls non-uniform and constantly varying distribution of fuel on the surface is a spatially un-stable spray of fuel, a condition which leads to unstable combustion.
The foregoing problem is eliminated by the provision of a decoupling sleeve 35 within the fuel passage 3~l that extends up to, say within 1/32 of an inch of the atomizing surface 33. The sleeve is typically i e of plastic and press fit into passage 34 extending inwardly to large diameter segment 12b. The difference in acoustical transmitting properties between the mate-rial of the sleeve 35 and the horn section 29 is such that the vibrating motion of section 29 is not imparted to the fuel within the fuel passage 3 encompassed by the sleeve 35.
.~.. .. . . . .
.' ' "' .. ~ , .
.
This application is a division of application 290,308, filed November 7, 1977.
The present invention relates to transducer assemblies and to apparatus employing same for achieving efficient combustion of fuels. An example of same is found in the United States patent to H. L. Berger, 3,861,852, issued January 21, 1975.
One problem associated with transducer assemblies of the type used in apparatus for achieving combustion of fuels is the non-uniform delivery of fuel to the atomizing surface with consequent non-uniform distribution of fuel from same. It has been discovered that with such prior art assemblies, fuels which have low surface tension as, for example, hydrocarbon fuels, begin to atomize within the fuel passage leading to the atomizing surface. This premature atomization creates bubbles within the fuel passage. The bubbles eventually work their way to the atomizing surface, but their arrival at the atomizing surface results in a temporary interruption in fuel flow to portions of the surface and, as a result, non-uniform distribution of fuel over the surface. The bubble remains intact for a short period of time on the atomiz-ing surface and thus the surface area beneath the bubble during the interval is not wet with fuel.
According to the present invention there is provided an ultrasonic transducer having an elongated, longitudinally vibrating probe with a flanged tip, said flanged tip comprising a vibrating surface capable of causing atom-ization of a liquid, the transducer further comprising a liquid delivery pas-sage extending axially through said probe to said atomizing surface and a decoupling sleeve mounted within said passage and extending to said atomizing surface for acoustically isolating the interior surface of said passage from liquid flowing therethrough.
In the accompanying drawings, which illustrate an exemplary embodi-ment of the present invention and related structures that may advantageously ~t~ - 1- ~, - -, .~ .
.. . . . . .
., -- :, -' .
10~ 9~
be used in conJunction therewith:
Figure 1 is a cross sectional view of a first section of a transduc-er assembly;
Figure 2 is a cross sectional view of a second section Or the trans-ducer assembly; and Figure 3 is a cross sectional view of a complete transducer assem~
bly: -~eferring to the dra~ing, the design oP a transducer assembly may be optimized, for among other things, maximum Q, by con~tructing a first transducer assembly section comprising a driving element and t~o identical horn sections (Figure 1) such that the resulting structure forms a symmetric geometry with respect to the longitudinal axis. This first assembly section is referred to as a double-dummy ultrasonic horn. In the next operation the resonant frequency of the first section is measured, and a second section is added (Figure 2) that includes an amplification step and an atomizing sur-face, and whose theoretical resonant frequency matches the empirically mea~ured frequency of the first section, thereby forming a complete trans-ducer assembly (Figure 3) designed for maximum Q and for use in achieving efficient c bustion of fuels.
Referring first to Figure 1 the first section 11 of the transducer assembly i8 seen a8 including front 12A and rear 13 ultrasonic horn sections and a driving element 14 comprising a pair of piezoelectric discs 15, 16 and an electrode (not shown) positioned therebetween, excited by bigh frequency electrical energy fed thereto from a te i nal lô.
Driving element 1~ is sandwiched between flanged portions 19, 20 of horn sections 12A, 13 and securely clamped therein by mean~ of a clamping assembly that includes a mounting ring 21 (for secur~ng the assembly to other apparatus) and a plurality of assembly bolts 22 which pass through holes in , - . . . .
,' " - ,. :- "i - ......................... - `
- .
" . - .:.iW~
1~13~;9~
terminal 18, flange sections 19 and 20 into threaded openings in mounting ring 21. The assembly bolts 22 are electrically isolated from the terminal 18 by means of insulators 23.
The first section 11 further includes a fuel tube 24 for introduc-ing fuel into a channel within the transducer assembly and a pair of sealing gaskets 26, 27 compressed between horn flange sections 19, 20.
In a typical embodiment: the horn sections 12A, 13 and flange sections 19, 20 are preferably of good acoustic conducting material such as aluminum, titanium or magnesium; or alloys thereof such as Ti-6A R-4v titanium-aluminum alloy, 6061-T6 aluminum alloy, 7025 high strength aluminum alloy, AZ 61 magnesium alloy and the like; the discs 15, 16 are of lead-zirconate-titanate such as those manufactured by Vernitron Corporation or of lithium miobate such as those manufactured by Valtec Corporation; the elec-trode is of copper; the terminal 18, mounting ring 21, and assembly bolts 22 are of steel; the insulators 23 are of nylon, polytetrafluoroethylene ~such as sold by Dupont under the trade mark Teflon) or some plastic with good electrical insulating properties; and, the sealing gaskets 26, 27 are of silicone rubber.
The first section 11 is seen to have symmetric half-wavelength geometry, yet it contains all the ana lous features of the transducer assem-bly, i.e. clamping at non-nodal planes, copper electrode, screw clamping and mounting bracket. The properties of this first section are established and its characteristic frequency, for maximum Q, quantitatively measured. Typical-ly the frequency is measured and found to be 85KHZ. This completes the first step in the design of the transducer assembly.
Referring to Figure 2, another half-wave section 29 is added to the first section 11. The section 29 is seen as including a large diameter seg-ment 12B, a small diameter segment 30 so as to form an amplification step 31, a flanged tip 32 with atomizing surface 33, a central passage 34 for .~.
~ --3--: . ~ :: . - : .
: ` ~ . ' :
10!~ 9~
delivering fuel to the atomizing surface 33 and internally mounted decoupling sleeve 35. The decoupling 81eeve i8 a substance such as Te n on which does not couple well acoustically to the fuel hole.
It will be observed by those skilled in the art that this section contains few anamolies since it is a pure theoretical structure as well. Its characteristic frequency for maximum Q is computed and selected 80 as to match that of the first section 11.
In order to complete the design, the two sections 11 and 29 are formed integrally so as to yield a transducer assembly (Figure 3) optimized for maximum Q and for use in achieving efficient combustion of fuels.
Prior art transducer assemblies used for ultrasonic atomization of fuel have, in the past, typically employed a flanged tip 32 with atomization surface 33. The presence of the flanged tip with its atomization surface 33 increases atomization capabilities due to increased atomizing surface area.
The addition of such flange has been at the expense of atomizer efficiency.
Referring to Figure 2, let A = length of horn front section 12B, B ~ length of small diameter segment 30 and C = thickness of flanged tip sec-tion 32.
In prior art assemblies that do not use a flange, A = 1 since they are both quarter wave length sections.
In prior art assemblies utilizing a flange A = 1.
BIC
It has been determined that maintaining the ratio at 1, even a M er addition o~ the flange, is inefficient and reduces power transfer, but by maintaining the ratio A ~ 1 efficiency levels can be maintainea at pre-~C
flange addition levels. Thus, for example, if ~3 = diameter of flange section 32 _ ~ _ ~ -. .
~0~;~4 D2 = diameter of small diameter segment 30 for 3 = 1.53 ~2 A (without flange) = A = 1 B+C B
and A (with flange) = 1.12 B+C
and the efficiency levels achieved with the flange match those of the assembly with the flange. .
~ he foregoing analysis applies to assemblies of aluminum, titanium, magnesium and previously mentioned alloys, and assumes that for both mate-rials the velocity of sound in same is approximately the same. For other 0 materisls with different velocities of sound the ratio A will differ, but BIC
always be greater than 1.
The long-term reliability of the device is dramatically enhanced by sealing the discs 15 since fuel contamination is no longer possible. The space between the clamping flange sections 19, 20 is filled with a silicone rubber compound as by sealing gaskets 26, 27. In the past, fuel creepage onto the faces of the discs 15, 16 has caused degradation of sPm~ and has resulted in poor long-term atomizer performance. The phenomenon causes a 1088 in mechanical coupling between elements of the horn. The gaskets 26, 27 solve the problem and atomizer performance is not affected by the added mass as has been confixmed by before and after measurement of impedance, operating fre-quency and flange displacement. The slightly higher internal heating caused by sealing the discs 15 does not reduce the atomizer's useful life since internal temperatures are still well below the m~ximum operating temperature for piezoelectric crystals. The gaskets 26, 27 are of a compressible material and have an inner periphery conforming to but initially sl~ghtly greater than the outer circumference of the discs 15, 16. Upon clamping the inner periph-ery of gaskets 26, 2~ come into light contact with the outer circumference of ,~ ~, : ' 10~ i9~
the discs 15, 16.
The present application is concerned with the elimination of pre-mature atomization Or fuel in the fuel passage leading to the atomizing sur-fsce. As noted previously, in prior art structures the fuel can begin to atomize within the fuel passage leading to the atomizing surface. This pre-mature atomization creates voids within the fuel passage at the fuel-wall interface which leads to the formation of bubbles within the fuel passage.
The bubbles eventually work their way to the atomizing surface, but their arrival at the atomizing surface results in a temporary interruption in fuel flow to a portion of the surface and as a result, non-uniform distribution of fuel over the surface. The bubble remains intact for a short period of time on the atomizing surface and thus the surface area beneath the bubble during that interval is not wet with fuel. The net effect of thls non-uniform and constantly varying distribution of fuel on the surface is a spatially un-stable spray of fuel, a condition which leads to unstable combustion.
The foregoing problem is eliminated by the provision of a decoupling sleeve 35 within the fuel passage 3~l that extends up to, say within 1/32 of an inch of the atomizing surface 33. The sleeve is typically i e of plastic and press fit into passage 34 extending inwardly to large diameter segment 12b. The difference in acoustical transmitting properties between the mate-rial of the sleeve 35 and the horn section 29 is such that the vibrating motion of section 29 is not imparted to the fuel within the fuel passage 3 encompassed by the sleeve 35.
.~.. .. . . . .
.' ' "' .. ~ , .
.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An ultrasonic transducer having an elongated, longitudinally vibrat-ing probe with a flanged tip, said flanged tip comprising a vibrating surface capable of causing atomization of a liquid, the transducer further comprising a liquid delivery passage extending axially through said probe to said atom-izing surface and a decoupling sleeve mounted within said passage and extend-ing to said atomizing surface for acoustically isolating the interior surface of said passage from liquid flowing therethrough.
2. An ultrasonic transducer according to claim 1 wherein said decou-pling sleeve is a plastic material which does not couple well acoustically with the material of the transducer probe.
3. An ultrasonic transducer according to claim 2 wherein the material of the decoupling sleeve is nylon.
4. An ultrasonic transducer according to claim 2 wherein the material of the decoupling sleeve is polytetrafluoroethylene.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA336,571A CA1090694A (en) | 1976-11-08 | 1979-09-28 | Transducer assembly, ultrasonic atomizer and fuel burner |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US739,812 | 1976-11-08 | ||
| US05/739,812 US4153201A (en) | 1976-11-08 | 1976-11-08 | Transducer assembly, ultrasonic atomizer and fuel burner |
| CA290,308A CA1071997A (en) | 1976-11-08 | 1977-11-07 | Transducer assembly, ultrasonic atomizer and fuel burner |
| CA336,571A CA1090694A (en) | 1976-11-08 | 1979-09-28 | Transducer assembly, ultrasonic atomizer and fuel burner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1090694A true CA1090694A (en) | 1980-12-02 |
Family
ID=27165366
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA336,571A Expired CA1090694A (en) | 1976-11-08 | 1979-09-28 | Transducer assembly, ultrasonic atomizer and fuel burner |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1090694A (en) |
-
1979
- 1979-09-28 CA CA336,571A patent/CA1090694A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| GB1595716A (en) | Ultrasonic transducer | |
| US3861852A (en) | Fuel burner with improved ultrasonic atomizer | |
| US4474326A (en) | Ultrasonic atomizing device | |
| US3400892A (en) | Resonant vibratory apparatus | |
| US4978067A (en) | Unitary axial flow tube ultrasonic atomizer with enhanced sealing | |
| US5330100A (en) | Ultrasonic fuel injector | |
| CA2029041C (en) | Piezoelectric pressure sensor | |
| US4301968A (en) | Transducer assembly, ultrasonic atomizer and fuel burner | |
| US20100020646A1 (en) | Ultrasonic transducer with improved method of beam angle control | |
| US3964308A (en) | Ultrasonic flowmeter | |
| WO2011090484A1 (en) | Hidden ultrasonic transducer | |
| US4245225A (en) | Ink jet head | |
| EP0192074B1 (en) | Fuel atomizer | |
| JPH0367747B2 (en) | ||
| US5364005A (en) | Ultrasonic transducer and mount | |
| CA1090694A (en) | Transducer assembly, ultrasonic atomizer and fuel burner | |
| US4439847A (en) | High efficiency broadband directional sonar transducer | |
| US4646967A (en) | Ultrasonic water jet having electromagnetic interference shielding | |
| JPS6197538A (en) | Shock wave sensor | |
| JPH0651141B2 (en) | Ultrasonic vibration type fuel injection valve | |
| CA1090695A (en) | Transducer assembly, ultrasonic atomizer and fuel burner | |
| CN115790749A (en) | Transducer, manufacturing method and flow measuring device | |
| US4135109A (en) | High powered piezoelectric cylindrical transducer with threads cut into the wall | |
| JPH1164058A (en) | Ultrasonic flowmeter | |
| EP0245671B1 (en) | Central bolt ultrasonic atomizer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |