WO2018136044A1

WO2018136044A1 - Ultrasonic transducer and method of assembling the same

Info

Publication number: WO2018136044A1
Application number: PCT/US2017/013900
Authority: WO
Inventors: Daniel Roehrig; Robert Schaefer; Joespeh WUTHIJAROEN; Michael Keenan
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-01-18
Filing date: 2017-01-18
Publication date: 2018-07-26

Abstract

An ultrasonic transducer and a method of assembling components of the ultrasonic transducer are provided. The method comprises installing a dry film adhesive, a plurality of crystal components, a plurality of crystal loading components, a plurality of sleeve loading components in a transducer body and installing a retaining ring on the plurality of sleeve loading components in the transducer body. The method further comprises loading the dry film adhesive, the plurality of crystal components, the plurality of crystal loading components and the plurality of sleeve loading components to form an assembly therefrom by subjecting all the components of the ultrasonic transducer to a non-torsional spring force due to compression of springs caused by installing of the retaining ring such that the assembly is locked in place.

Description

ULTRASONIC TRANSDUCER AND METHOD OF ASSEMBLING THE SAME

BACKGROUND

1. Field

[0001] Aspects of the present invention generally relate to a transducer such as an ultrasonic transducer and more specifically relate to assembling components of an ultrasonic transducer.

2. Description of the Related Art

[0002] Ultrasonic flow meters are used for the measurement of fluid flow in day-today applications involving both liquids and gases. Ultrasonic flow meters have the advantage that they have no moving parts that can fail, introduce very little pressure drop, and offer a high turndown ratio.

[0003] Ultrasonic flow meters use two transducers for transmitting and receiving signals in opposite directions (i.e., upstream and downstream) to derive the transit-time difference used to determine the fluid flow velocity. Main applications include the measurement of volume flow within the general, petrochemical and chemical industries, power engineering and water and waste water.

[0004] Ultrasonic transit-time transducers installed in hazardous area locations often require electrical isolation of a piezo-ceramic crystal's front face electrode, while also maintaining efficient and reliable acoustic coupling to a metallic window in contact with the process fluid. Grease is commonly used for the acoustic coupling of these crystals, making it difficult to ensure the required 500 VAC electrical isolation. In addition, the dimensions of the gap between the piezo element and the metallic surface must be well controlled. The edges of the piezo ceramic element must also be electrically isolated from any other conductive surfaces.

[0005] Existing solutions include the use of grease coupling with an intermediate insulating disk to ensure the required 500 VAC electrical isolation. However, this arrangement introduces multiple grease coupled acoustic interfaces which can create additional resonances as well as reduced signal transmission. Another approach may involve the complete isolation of the metallic transducer housing from the pipe section, but this isolation can be defeated by foreign debris, such as metal fillings, becoming trapped between the transducer housing and the installation port. The use of liquid epoxies, to acoustically couple and isolate the crystals, may also be considered, however it is difficult to control the epoxy thickness and also ensure that no air pockets exist which can reduce signal amplitude and defeat the required 500 VAC electrical isolation.

[0006] Therefore, there is a need for an assembly method having an ease of fabrication and such a method of assembling components of a transducer that will also reduce cost.

SUMMARY

[0007] Briefly described, aspects of the present invention relate to a method of assembling components of an ultrasonic transducer. A dry film adhesive or epoxy has been selected to achieve consistent bond line thickness. A pre-cured load on a crystal relative to an epoxy bond is carefully controlled. In addition, an isolation sleeve surrounding the crystal is subsequently bonded with a lighter load. Wave spring washers are used to form two independent spring stacks, one for loading the crystal and a second for loading the isolation sleeve. The method first loads the crystal, excluding air from that bond, and then applies the final loading to the isolation sleeve. Use of wave spring washers eliminates the torsional stresses.

[0008] In accordance with one illustrative embodiment of the present invention, a method of assembling components of an ultrasonic transducer is provided. The method comprises installing a dry film adhesive in a transducer body of the ultrasonic transducer, installing a plurality of crystal components, including a crystal and an isolation sleeve, on the dry film adhesive in the transducer body, installing a plurality of crystal loading components on the plurality of crystal components in the transducer body, installing a plurality of sleeve loading components on the plurality of crystal loading components in the transducer body and installing a retaining ring on the plurality of sleeve loading components in the transducer body. The method further comprises loading the dry film adhesive, the plurality of crystal components, the plurality of crystal loading components and the plurality of sleeve loading components to form an assembly therefrom by subjecting all the components of the ultrasonic transducer to a non-torsional spring force due to compression of springs caused by installing of the retaining ring such that the assembly is locked in place.

[0009] In accordance with another illustrative embodiment of the present invention, an ultrasonic transducer is provided. The ultrasonic transducer comprises a transducer body, a dry film adhesive disposed in the transducer body and a plurality of crystal components including a crystal and an isolation sleeve disposed on the dry film adhesive. The method of assembling components of the ultrasonic transducer comprises the steps of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 illustrates an exploded view of an assembly of all the components of an ultrasonic transducer in accordance with an exemplary embodiment of the present invention.

[0011] FIG. 2 illustrates a cross-sectional view of the assembly of all the components of the ultrasonic transducer at a line A-A in FIG. 1 in accordance with an exemplary embodiment of the present invention.

[0012] FIG. 3 illustrates a fully compressed view of the assembly of all the components of the ultrasonic transducer of FIG. 1 in accordance with an exemplary embodiment of the present invention.

[0013] FIG. 4 illustrates a cross-sectional view of the fully compressed assembly of all the components of the ultrasonic transducer of FIG. 3 at a line B-B in FIG. 3 in accordance with an exemplary embodiment of the present invention.

[0014] FIG. 5 illustrates a flow chart of a method of assembling components of an ultrasonic transducer according to an exemplary embodiment of the present invention.

[0015] FIG. 6 illustrates a flow chart of a method of assembling options of an ultrasonic transducer according to an exemplary embodiment of the present invention.

[0016] FIG. 7 illustrates an in-line meter body in which the ultrasonic transducer 7 of FIG. 1 is installed in accordance with an exemplary embodiment of the present invention.

[0017] FIG. 8 illustrates a cross-sectional view of the in-line meter body of FIG. 7 at a line C-C in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0018] To facilitate an understanding of embodiments, principles, and features of the present invention, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of an ultrasonic transducer and a method of assembling components of the ultrasonic transducer. Embodiments of the present invention, however, are not limited to use in the described devices or methods.

[0019] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present invention.

[0020] Consistent with an exemplary embodiment of the present invention, FIG. 1 represents an exploded view of an assembly 5 of all the components of an ultrasonic transducer 7.

[0021] By subjecting all the components of the ultrasonic transducer 7 to a non- torsional spring force due to compression of springs the assembly 5 is formed and locked in place. The idea is to use a special type of spring that does not exert a torsional force when compressed with a normal load. Coil springs have this problem, therefore an alternative approach is developed using a type of wave spring.

[0022] The assembly 5 is compressed by an arbor tool 10 to form the ultrasonic transducer 7. The arbor tool 10 has a shaft or an arbor via which it is mounted on the assembly 5. The arbor tool 10 provides a tool component that assembles the components of the assembly 5 together to form the ultrasonic transducer 7.

[0023] Referring to FIG. 2, it illustrates a cross-sectional view of the assembly 5 of all the components of the ultrasonic transducer 7 at a line A-A in FIG. 1 in accordance with an exemplary embodiment of the present invention. The assembly 5 includes a transducer body 212 of the ultrasonic transducer 7. The assembly 5 further includes a dry film adhesive 215, a plurality of crystal components 217, a plurality of crystal loading components 220, a plurality of sleeve loading components 222, and a retaining ring 225. In one embodiment, the dry film adhesive 215 is a pre-cut dry film epoxy.

[0024] The plurality of crystal components 217 includes a crystal isolation sleeve 230, a crystal 232 and a crystal loading ring 235. In one embodiment, the crystal 232 is a piezo-ceramic crystal element having a front face electrode such that the front face electrode is a component of the ultrasonic transducer 7 that requires electrical isolation. The assembly provides this component of the ultrasonic transducer 7 a desired level of the electrical isolation. In use, the assembly 5 of the ultrasonic transducer 7 provides an efficient and reliable acoustic coupling of the piezo-ceramic crystal element to a metallic window in contact with a process fluid in an in-line meter body. This ultrasonic transducer 7 may be a transducer suitable for installation in a hazardous area location.

[0025] The plurality of crystal loading components 220 includes crystal springs 240 and a plunger 242. The plurality of sleeve loading components 222 includes sleeve springs 245 and a washer 250.

[0026] Turning now to FIG. 3, it illustrates a fully compressed view of the assembly 5 of all the components of the ultrasonic transducer 7 of FIG. 2 in accordance with an exemplary embodiment of the present invention.

[0027] FIG. 4 illustrates a cross-sectional view of the fully compressed assembly 5 of all the components of the ultrasonic transducer 7 of FIG. 3 at a line B-B in FIG. 3 in accordance with an exemplary embodiment of the present invention. The transducer body 212 includes a groove 400. When fully compressed, the retaining ring 225 snaps into the groove 400. This locks the assembly 5 in place.

[0028] As seen in FIG. 5, it illustrates a flow chart of a method 500 of assembling components of the ultrasonic transducer 7 according to an exemplary embodiment of the present invention. Reference is made to the elements and features described in FIGs. 1-4. It should be appreciated that some steps are not required to be performed in any particular order, and that some steps are optional.

[0029] The method 500, in step 505, includes installing the dry film adhesive 215 in the transducer body 212 of the ultrasonic transducer 7. The method 500, in step 510, further includes installing the plurality of crystal components 217, including the crystal 232 and the isolation sleeve 230, on the dry film adhesive 215 in the transducer body 212. The method 500, in step 515, further includes installing the plurality of crystal loading components 220 on the plurality of crystal components 217 in the transducer body 212. The method 500, in step 520, further includes installing the plurality of sleeve loading components 222 on the plurality of crystal loading components 220 in the transducer body 212. Between the step 515 and the step 520 two sets of spring stacks are selected to maintain an optimum pressure on the dry film adhesive 215. Both under the crystal 232 (large area) and under the isolation sleeve 230 (small area).

[0030] The method 500, in step 525, further includes installing the retaining ring 225 on the plurality of sleeve loading components 222 in the transducer body 212. The retaining ring 225 secures both the sleeve loading components 222 and the plurality of crystal loading components 220. The method 500, in step 530, further includes loading the dry film adhesive 215, the plurality of crystal components 217, the plurality of crystal loading components 220 and the plurality of sleeve loading components 222 to form the assembly 5 therefrom by subjecting all the components of the ultrasonic transducer 7 to a non-torsional spring force due to compression of springs caused by installing of the retaining ring 225 such that the assembly 5 is locked in place.

[0031] The method 500 further includes compressing the retaining ring 225 with the arbor tool 100 to snap the retaining ring 225 into the groove 400 situated in an inner hollow side of a tubular shape of the transducer body 212.

[0032] After loading the retaining ring 225, the arbor tool 10 is used such that the crystal 232 is loaded to an optimum pressure by the arbor tool 10 before any pressure is applied to the isolation sleeve 230. All components are loose until subjected to spring forces to lock in the assembly 5. The retaining ring 225 captures the assembly 5 in place.

[0033] The spring selection is critical in this assembly 5. To avoid a torsional force on the assembly 5 and especially on the dry film adhesive 215 during curing wave washers are selected as they can be easily stacked with flat washers in between.

[0034] In this way, a method of bonding the crystal 232 to the transducer body 212 with a paper thin adhesive is provided in which a specific order of loading the components is used. It is a two stage process which uses controlled loading. Two co- centric spring stacks are removed in this method. [0035] As shown in FIG. 6, it illustrates a flow chart of a method 600 of assembling options of the ultrasonic transducer 7 according to an exemplary embodiment of the present invention. The method 600, in step 605, includes a final assembly step. After the final assembly step 605 one has two options. In option 1, step 610, the method 600 includes removing assembly components to be used in the next assembly. The components of the assembly 5 to be removed are: the arbor tool 10, the retaining ring 225, the plurality of sleeve loading components 222, the plurality of crystal loading components 220 and the crystal loading ring 235.

[0036] The method 600 includes removing first the retaining ring 225 from the assembly 5 after curing of the dry film adhesive 215, removing thereafter the plurality of sleeve loading components 222 and the plurality of crystal loading components 220 and removing last the crystal loading ring 235 from the assembly 5.

[0037] In option 1, if we were to remove the assembly components of the assembly 5, after curing, instead of using the retaining ring 225 the loading components may be attached to a fixture that would be clamped in place until the curing is done, at which point, the clamp would be released and all the loading components would come out, to be used on the next set of parts. So there is a possibility of using a fixture to hold down the assembly 5 during curing and removing the loading components after the assembly 5 had cured. The retaining ring 225 is replaced by the clamping element of the fixture. Therefore, one alternate assembly method is clamping in place through cure in place of holding with the retaining ring 225.

[0038] In option 2, step 615, the method 600 includes leaving all the components in the assembly 5 as is. That is, leaving all the components of the ultrasonic transducer 7 in place as is as a permanent part of the assembly 5.

[0039] The ultrasonic transducer 7 may be used for flow rate measurement in conduits and channels with large cross section. The ultrasonic transducer 7 has many advantages e.g. no pressure loss, high accuracy and the possibility to be installed on existing conduits and channels. This type of flow meter is based on the principle that the ultrasonic pulse traveling along an acoustic path is altered by the fluid velocity. An ultrasonic pulse propagates at a slower speed in the upstream direction than it does in the downstream direction, such that the time difference is proportional to the velocity of flow inside the measurement section.

[0040] FIG. 7 illustrates an in-line meter body 700 in which an ultrasonic transit time transducer 705 of FIG. 1 is installed in accordance with an exemplary embodiment of the present invention. The in-line meter body 700 is an in-line measuring element which is used to measure the volume flow of liquids or gases. It can be used with both conductive and non-conductive liquids.

[0041] In the in-line meter body 700, a signal is sent directly and without reflection, between the transmitting and receiving transducers. The advantage gained sending signals from point to point is an extremely good signal strength for the signal processing. A sound wave traveling in the same direction as the liquid flow arrives at a point B from a point A in a shorter time than the sound wave traveling against the direction of flow (from point B to A). The difference in sound transit time indicates the flow velocity in the pipe.

[0042] With regard to FIG. 8, it illustrates a cross-sectional view of the in-line meter body 700 of FIG. 7 at a line C-C in accordance with an exemplary embodiment of the present invention.

[0043] In the in-line meter body 700, two ultrasonic transducers 705(1-2) of four ultrasonic transducers 705(1-4) are placed at an angle in relation to a pipe axis. This may be an in-line (non-refractive) flowmeter. The measuring principle of the in-line (non- refractive) flowmeter offers the advantage that it is independent of variations in the actual sound velocity of the liquid, i.e. independent of the temperature.

[0044] Depending on the upstream pipe configuration, fluid flows through the meter body may have a tendency to swirl and/or exhibit an asymmetrical flow profile. Therefore two or more tracks may be needed to provide the required flow accuracy. A multi-track system offers reduced sensitivity to upstream obstruction like bends, pumps or valves and improved security in the measurements as the meter continues to measure even if one track stops working.

[0045] While particular embodiments are described in terms of an in-line meter body, the techniques described herein are not limited to in-line meter body but can also be used in other configurations, such as open channel flow meters.

[0046] While embodiments of the present invention have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.

[0047] Embodiments and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components and equipment are omitted so as not to unnecessarily obscure embodiments in detail. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.

[0048] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus.

[0049] Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead, these examples or illustrations are to be regarded as being described with respect to one particular embodiment and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized will encompass other embodiments which may or may not be given therewith or elsewhere in the specification and all such embodiments are intended to be included within the scope of that term or terms.

[0050] In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

[0051] Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of the invention. The description herein of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein (and in particular, the inclusion of any particular embodiment, feature or function is not intended to limit the scope of the invention to such embodiment, feature or function). Rather, the description is intended to describe illustrative embodiments, features and functions in order to provide a person of ordinary skill in the art context to understand the invention without limiting the invention to any particularly described embodiment, feature or function. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the invention in light of the foregoing description of illustrated embodiments of the invention and are to be included within the spirit and scope of the invention. Thus, while the invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the invention.

[0052] Respective appearances of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" or similar terminology in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any particular embodiment may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the invention.

[0053] In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that an embodiment may be able to be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the invention. While the invention may be illustrated by using a particular embodiment, this is not and does not limit the invention to any particular embodiment and a person of ordinary skill in the art will recognize that additional embodiments are readily understandable and are a part of this invention.

[0054] It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.

[0055] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component.

Claims

What is claimed is:

1. A method of assembling components of an ultrasonic transducer, the method comprising:

installing a dry film adhesive in a transducer body of the ultrasonic transducer; installing a plurality of crystal components, including a crystal and an isolation sleeve, on the dry film adhesive in the transducer body;

installing a plurality of crystal loading components on the plurality of crystal components in the transducer body;

installing a plurality of sleeve loading components on the plurality of crystal loading components in the transducer body;

installing a retaining ring on the plurality of sleeve loading components in the transducer body; and

loading the dry film adhesive, the plurality of crystal components, the plurality of crystal loading components and the plurality of sleeve loading components to form an assembly therefrom by subjecting all the components of the ultrasonic transducer to a non-torsional spring force due to compression of springs caused by installing of the retaining ring such that the assembly is locked in place.

2. The method of claim 1, wherein the crystal is a piezo-ceramic crystal element having a front face electrode such that the front face electrode is a component of the ultrasonic transducer that requires electrical isolation, wherein the assembly provides the component of the ultrasonic transducer a desired level of the electrical isolation.

3. The method of claim 1, wherein in use the assembly of the ultrasonic transducer provides an efficient and reliable acoustic coupling of the piezo-ceramic crystal element to a metallic window in contact with a process fluid.

4. The method of claim 1, further comprising:

compressing the retaining ring with an arbor tool to snap the retaining ring into a groove situated in an inner hollow side of a tubular shape of the transducer body.

5. The method of claim 4, further comprising:

removing first the retaining ring from the assembly after curing of the dry film adhesive;

removing thereafter the plurality of sleeve loading components and the plurality of crystal loading components; and

removing last a crystal loading ring from the assembly.

6. The method of claim 4, further comprising:

leaving all the components of the ultrasonic transducer in place as is as a permanent part of the assembly.

7. The method of claim 1, wherein the dry film adhesive is a pre-cut dry film epoxy.

8. The method of claim 7, wherein the plurality of crystal components include a crystal loading ring.

9. The method of claim 8, wherein the plurality of crystal loading components include a crystal spring and a plunger.

10. The method of claim 9, wherein the plurality of sleeve loading components include a sleeve spring and a washer.

11. An ultrasonic transducer, comprising:

a transducer body;

a dry film adhesive disposed in the transducer body; and

a plurality of crystal components including a crystal and an isolation sleeve disposed on the dry film adhesive, wherein a method of assembling components of the ultrasonic transducer comprising:

installing the dry film adhesive in the transducer body of the ultrasonic transducer; installing the plurality of crystal components on the dry film adhesive in the transducer body;

12. The ultrasonic transducer of claim 11, wherein the crystal is a piezo-ceramic crystal element having a front face electrode such that the front face electrode is a component of the ultrasonic transducer that requires electrical isolation, wherein the assembly provides the component of the ultrasonic transducer a desired level of the electrical isolation.

13. The ultrasonic transducer of claim 11, wherein in use the assembly of the ultrasonic transducer provides an efficient and reliable acoustic coupling of the piezo- ceramic crystal element to a metallic window in contact with a process fluid.

14. The ultrasonic transducer of claim 11, wherein the method further comprising: compressing the retaining ring with an arbor tool to snap the retaining ring into a groove situated an inner hollow side of a tubular shape of the transducer body.

15. The ultrasonic transducer of claim 14, wherein the method further comprising: removing first the retaining ring from the assembly after curing of the dry film adhesive; removing thereafter the plurality of sleeve loading components and the plurality of crystal loading components; and

removing last a crystal loading ring from the assembly.

16. The ultrasonic transducer of claim 14, wherein the method further comprising: leaving all the components of the ultrasonic transducer in place as is as a permanent part of the assembly.

17. The ultrasonic transducer of claim 11, wherein the dry film adhesive is a pre-cut dry film epoxy.

18. The ultrasonic transducer of claim 17, wherein the plurality of crystal components include a crystal loading ring.

19. The ultrasonic transducer of claim 18, wherein the plurality of crystal loading components include a crystal spring and a plunger.

20. The ultrasonic transducer of claim 19, wherein the plurality of sleeve loading components include a sleeve spring and a washer.