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Title:
A RESONATOR FOR THE ACOUSTIC TRANSMISSION OF INFORMATION AND A SYSTEM UTILIZING SAME
Document Type and Number:
WIPO Patent Application WO/1999/020987
Kind Code:
A1
Abstract:
The invention provides a resonator for converting an input of electric, information-carrying signals into an output of acoustic vibrations capable of propagating the information, including at least one element capable of converting electrical energy into acoustic vibrations, the element being at least indirectly seated on an elastically deformable element, an inertial mass mechanically coupled to the energy-converting element, pressure-applying means for mechanically coupling the inertial mass to the energy-converting element, and the energy-converting element to the elastically deformable element, wherein the inertial mass, the elastically deformable element and the energy-converting element constitute an oscilator, the resonance frequency of which is tunable by a controlled deformation of the elastically deformable element with the aid of the pressure-applying means.

Inventors:
Paz, Ilan (Ha'Rakefet Road 6 Alon Shvut Gush Etzion, 90433, IL)
Lehtzier, Yury (El'Azar 305/4 Gush Etzion, 90942, IL)
Application Number:
PCT/IL1998/000512
Publication Date:
April 29, 1999
Filing Date:
October 20, 1998
Export Citation:
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Assignee:
MAYCOM COMMUNICATIONS LTD. (P.O. Box 205 Alon Shvut Gush Etzion, 90433, IL)
Paz, Ilan (Ha'Rakefet Road 6 Alon Shvut Gush Etzion, 90433, IL)
Lehtzier, Yury (El'Azar 305/4 Gush Etzion, 90942, IL)
International Classes:
G10K9/122; H04B11/00; (IPC1-7): G01H11/08; G08C23/02; H04B11/00
Foreign References:
US5166907A
DE3028187A1
EP0033192A1
GB2258331A
DE4037600A1
US3663842A
Attorney, Agent or Firm:
Wolff, Bregman And Goller (P.O. Box 1352 Jerusalem, 91013, IL)
Download PDF:
Claims:
CLAIMS
1. l.
2. A resonator for converting an input of electric, informationcarrying signals into an output of acoustic vibrations capable of propagating said information, comprising: at least one element capable of converting electrical energy into acoustic vibrations, said element being at least indirectly seated on an elastically deformable element; an inertial mass mechanically coupled to said energyconverting element; pressureapplying means for mechanically coupling said inertial mass to said energyconverting element, and said energyconverting element to said elastically deformable element, characterized in that said inertial mass, said elastically deformable element and said energyconverting element constitute an oscillator, the resonance frequency of which is tunable by a controlled deformation of said elastically deformable element with the aid of said pressureapplying means.
3. A resonator for converting an input of acoustic vibrations into an output of electric, informationcarrying signals, comprising: at least one element capable of converting acoustic vibrations into electrical energy, said element being at least indirectly seated on an elastically deformable element; an inertial mass mechanically coupled to said energyconverting element; pressureapplying means for mechanically coupling said inertial mass to said energyconverting element, and said energyconverting element to said elastically deformable element, characterized in that said inertial mass, said elastically deformable element and said energyconverting element constitute an oscillator, the resonance frequency of which is tunable by a controlled deformation of said elastically deformable element with the aid of said pressureapplying means.
4. The resonator as claimed in claim 1, wherein said elastically deformable element is a cantilevered, elongated lug.
5. The resonator as claimed in claim 1, wherein said pressureapplying means is a threaded screw applicable against said inertial mass.
6. A resonator for converting an input of electric, informationcarrying signals into an output of acoustic vibrations capable of propagating said information, comprising: a housing accommodating, in superposition, at least one element seated at least indirectly on a lower portion of said housing and capable of converting electrical energy into acoustic vibrations; an inertial mass mechanically coupled to said energyconverting element; at least one elastically deformable element mechanically coupled to said inertial mass; a pluglike head piece for mechanically coupling said elastically deformable element to said inertial mass and said inertial mass to said energyconverting element; characterized in that said inertial mass, said elastically deformable element and said energyconverting element constitute an oscillator, the resonance frequency of which is tunable by a controlled deformation of said elastically deformable element with the aid of said pluglike head piece.
7. A resonator for converting an input of acoustic vibrations into an output of electric, informationcarrying signals, comprising: a housing accommodating, in superposition, at least one element seated at least indirectly on a lower portion of said housing and capable of converting acoustic vibrations into electrical energy; an inertial mass mechanically coupled to said energyconverting element; at least one elastically deformable element mechanically coupled to said inertial mass; a pluglike head piece for mechanically coupling said elastically deformable element to said inertial mass and said inertial mass to said energyconverting element; characterized in that said inertial mass, said elastically deformable element and said energyconverting element constitute an oscillator, the resonance frequency of which is tunable by a controlled deformation of said elastically deformable element with the aid of said pluglike head piece.
8. The resonator as claimed in claims 1,2,5 and 6, wherein said energy converting element is a piezoelectric element.
9. The resonator as claimed in claim 5, wherein said at least one elastically deformable element is a compression spring, abutting with one of its ends against said mass and with the other one of its ends against a pluglike head piece having, relative to said spring, at least one degree of freedom in movement, being the freedom in translation.
10. The resonator as claimed in claim 5, wherein the openend portion of said housing is provided with an internal thread.
11. The resonator as claimed in claims 5 and 9, wherein said pluglike head piece is provided with an external thread matching the internal thread of said housing and wherein, by rotating said pluglike head piece, deformation of said elastically deformable element can be controllably varied.
12. The resonator as claimed in claim 7, wherein said resonator comprises two or more stacked piezoelectric elements.
13. The resonator as claimed in claim 11, wherein said two or more piezoelectric elements are electrically seriesconnected.
14. The resonator as claimed in claim 11, wherein said two or more piezoelectric elements are electrically connected in parallel.
15. The resonator as claimed in claims 7 and 11, wherein said one or more piezoelectric elements operate in the flexure mode.
16. The resonator as claimed in claims 7 and 11, wherein said one or more piezoelectric elements operate in the compression mode.
17. A system for the acoustic transmission of information along a structural element, comprising: transmitter means consisting of a resonator capable of converting an input of signals produced by said information into an output of acoustic vibrations carrying said information; receiver means consisting of a resonator capable of converting an input of said informationcarrying acoustic vibrations into an output of signals rendering said information recoverable; first coupling means for mechanically coupling said transmitter means to said structural element, thereby passing on said acoustic vibrations to said structural element, and second coupling means for mechanically coupling said receiver means to said structural element, thereby picking up said acoustic vibrations from said transmitter means as propagated along said structural element; characterized in that the resonators of said transmitter means and said receiver means comprise a vibratory system consisting of a mass, an elastically deformable element and an energyconverting element mechanically coupled to said mass, and that the resonance frequency of said vibratory system is tunable by adjusting the force applied by said elastically deformable element, via said mass, to said energy converting element.
18. The system as claimed in claim 16, wherein the resonators of both said transmitter means and said receiver means are piezoelectric resonators.
19. The system as claimed in claim 16, wherein said structural element is a pipeline.
20. The system as claimed in claim 16, wherein said elastically deformable element consists of at least one lug of at least one pair of elongated lugs fixedly attached to said structural element at one of their ends.
21. The system as claimed in claim 16, wherein said first and second coupling means is a pair of rigid yokelike members clamped to said structural element and making contact with said element at a plurality of points located so as to restrict possible modes of vibration of said structural element.
22. The system as claimed in claim 20, wherein said resonators are rigidly mounted on at least one of said yokes at a point located in a plane symmetrical with said points of contact.
23. The system as claimed in claim 16, wherein said receiver means is mounted near the free end of a relatively long cantilever fixedly attached to, or integral with, a part of said second coupling means.
Description:
A RESONATOR FOR THE ACOUSTIC TRANSMISSION OF INFORMATION AND A SYSTEM UTILIZING SAME Technical Field The present invention relates to a resonator which can be tuned to produce acoustic vibrations over a wide range of frequencies. It also relates to a system for the acoustic transmission of information along a structural element.

Background Art Acquisition, for further processing, of measurement results relating to physical magnitudes such as, e. g., fluid flow in pipelines, is usually a very bothersome, time- consuming and labor-intensive affair. In order to properly bill their consumers, suppliers of water, for instance, must periodically read the meters of every single consumer, a task that requires a huge amount of manpower, so much so that some suppliers have taken to charging their clients not for actual consumption, but for averages calculated from past consumption and, from time to time, correcting the bills according to actual readings spaced apart by several months, a doubtful practice that has been known to give rise to frequent disputes. While such and similar measurement results could be collected automatically and channeled to a central location, this would require the use of either a wired connection, or of an RF (wireless) link. The disadvantages of these two alternatives are obvious. In addition to its costs, the RF link is unreliable, especially in surroundings consisting of metal structures such as chemical plants, ship's hulls and frames, etc.

Disclosure of the Invention It is thus one of the objects of the present invention to provide a resonator which can be tuned to produce acoustic vibrations over a wide range of frequencies.

It is equally an object of the present invention to provide a system for the acoustical transmission, with the aid of the above resonator, of information along a structural element.

According to the present invention, the above objects are achieved by providing a resonator for converting an input of electric, information-carrying signals into an output of acoustic vibrations capable of propagating said information. comprising at least one element capable of converting electrical energy into acoustic vibrations and vice-versa, at least indirectly seated on an elastically deformable element; an inertial mass mechanically coupled to said energy-converting element; pressure-applying means for mechanically coupling said inertial mass to said energy- converting element, and said energy-converting element to said elastically deformable element, characterized in that said inertial mass and said elastically deformable element constitute an oscillatory pendulum, the resonance frequency of which is tunable by a controlled deformation of said elastically deformable element with the aid of said pressure-applying means.

The invention further provides a system for the acoustic transmission of information along a structural element, comprising transmitter means consisting of a resonator capable of converting an input of signals representing information into an output of acoustic vibrations carrying said information, receiver means consisting of a resonator capable of converting an input of said information-carrying acoustic vibrations into an output of signals rendering said information recoverable; first coupling means for acoustically coupling said transmitter means to said structural element, thereby passing on said acoustic vibrations to said structural element, and second coupling means for acoustically coupling said receiver means to said structural element, thereby picking up said acoustic vibrations from said transmitter means as propagated along said structural element, characterized in that the resonators of said transmitter means and said receiver means comprise a vibratory system consisting of a mass and an elastically deformable element mechanically coupled to said mass, and that the resonance frequency of said vibratory system is tunable by adjusting the force applied by said elastically deformable element to said mass.

Brief Description of the Drawings The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

Fig. 1 is a schematic, cross-sectional view of a first embodiment of the resonator according to the invention, having a single element stressed in flexure; Fig. 2 is a similar cross-sectional view of a second embodiment of the resonator, comprising two elements connected in parallel and operating in the flexure mode; Fig. 3 shows a third embodiment of the resonator having two elements mounted in parallel and operating in the flexure mode; Fig. 4 represents a resonator with two series-connected elements operating in the flexure mode; Fig. 5 shows a resonator with stacked elements connected in parallel and operating in the compression mode; Fig. 6 illustrates an embodiment of a twin resonator in which the helical spring of the resonators of Figs. 1-5 has been replaced by lugs fixedly attached at one of their ends to the structural member, in this case, a pipeline; Figs. 7a and 7b illustrate two of the modes in which tubular members can be vibrationally elastically deformed at one point, with the deformation being propagated along the member; Fig. 8 is a cross-sectional view of part of the system according to the invention, comprising the resonator and a double-yoke-shaped clamp, coupling the resonator to the pipeline; Fig. 9 shows a similar clamp, with the two yokes hingedly articulated to one another on one side, and carrying two resonators, and Fig. 10 represents a cross-sectional view of a coupling arrangement for the resonator when acting as receiver.

Detailed Description Referring now to the drawings, there is seen in Fig. 1 a first embodiment of the resonator according to the invention. Resonator 2 which, in fact, is a piezoelectric transducer excited in a per se known manner, comprises a cup-shaped housing 4 made of a tough material and having a substantially cylindrical bore 6 ending in a shallow recess 8 of a diameter smaller than the diameter of bore 6, thus producing an annular shoulder 10. The open end of bore 6 is provided with an internal thread. Further seen is a threaded neck portion 12 of housing 4, serving for connection of resonator 2 to the coupling means seen in Figs. 8-10 and described further below.

On shoulder 10 is seated an elastic, metallic disk 14 which supports an element 16, e. g., a piezo element. Against the latter abuts an inertial, metallic mass 18, pressed down via a helical spring 20 by a threaded plug 22, the axial position of which can be adjusted with the aid of a hexagonal projection 24. Plug 22 and spring 20 are electrically insulated from each other by an insulating disk 26. Mass 18 is electrically insulated relative to housing 4 by means of a tubular insulator 28. One wire lead 30 is attached to mass 18, and the other lead 32, to housing 4. In this embodiment, due to the fact that elastic disk 14, seated on shoulder 10, is supported only along a peripheral zone, element 16, when excited, is stressed in flexure.

Spring 20 (with linear or non-linear elasticity), in combination with mass 18, element 16 and (in case of the piezoelements operating in the flexure mode) elastic disk 14, constitutes an oscillator, at least one elastic element of which must be non- linear (in flex-mode case, this may be elastic disk 14). The resonance frequency of this oscillator is a function of mass 18, the spring rate of spring 20 and the force exerted on the spring by plug 22. By appropriate selection of this mass and this spring, and by varying the force, it is therefore possible to vary the resonance frequency of the oscillator and the acoustical matching between piezoelement 16 and the signal-carrying structural element (the pipe), the importance of which possibilities will be explained further below. Varying of the force is carried out by rotation plug 22.

Fig. 2 represents a second embodiment of the resonator according to the invention, comprising two elements 16 connected in parallel and operating in the flexure mode. Lead 30 is connected to an electrode 34 located between elements 16, while lead 32 is again attached to housing 4.

Fig. 3 shows a third embodiment of the resonator in which two elements 16, connected in parallel, operate in the flexure mode. Elastic disks 14 are seated in an auxiliary mount 36, which also provides recesses 8'into which disks 14 will flex.

Fig. 4 illustrates a fourth embodiment of the resonator according to the invention, in which two series-connected elements 16 are used in the flexure mode.

While lower element 16 is mounted as seen in Fig. 1, upper element 16 is mounted on a second elastic disk 14 seated on shoulder 10'of an auxiliary mount 36 resting on the upper surface of lower element 16 and provided with a recess 8'. Elements 16 clearly operate in the flexure mode. Wire lead 30 enters the resonator through a hole 38 in plug 22 and is attached to mass 18, with wire lead 32 being attached to housing 4.

Fig. 5 represents a resonator with stacked elements 16 connected in parallel and working in the compression mode. Wire lead 30 is connected to all odd- numbered electrodes 34, and wire lead 32 to all even-numbered electrodes 34.

While, as will be shown, the resonators 2 seen in Figs. 1-5 are coupled to the structural elements intended to transmit certain information, e. g., pipelines, by special coupling means, resonators 2 in Fig. 6 do not use helical springs as the elastic elements, but are provided with elastically deformable lugs 40,40', which are directly welded to pipeline 42 at one of their ends. Near the other one of their ends, the upper lugs 40 are provided with electrically non-conductive inserts 44 with an internal thread, constituting the nuts for screws 46 that press upon mass 18. Thus, when screws 46 are tightened, each pair of lugs 40,40'is flexed apart, having the same effect as spring 20 when compressed by plug 22.

As indicated in the introductory section of the specification, the above- discussed resonators are intended to serve in a system for the acoustic transmission of information along a structural element, such as a pipeline. According to the invention, information, having been obtained by per se known means, is converted into electrical signals by equally known means and fed to a resonator of one of the above-mentioned types, acting as transmitter, causing the resonator to vibrate and, via an acoustic coupling element to be discussed further below, to transmit these vibratory signals along the structural element in the form of elastic deformations of the latter, being propagated at the speed of sound in the structural element. At a suitable remote point, there is mounted, on another coupling element, another resonator acting as receiver, the element of which, subjected to the arriving train of deformations, reconverts these deformations into an electrical signal.

As it is the aim of the present invention to transmit the signal over the structural element to the maximum possible distance while using a limited energy source, it is clearly necessary to transmit a maximum of vibratory energy yielded by the resonator operated by the signal at a given frequency and of limited strength.

These conditions are met by having the resonator operate at resonance and by acoustically matching the two vibratory systems: the resonator and a section of the structural element of a length of the order of the wavelength corresponding to that frequency. Where the resonator cannot be used in a pure resonance regime, the effectiveness will be maximized by being as close to resonance as possible. As the resonance frequency of this oscillator depends only on the relationship between the mass and the spring rate of the system, consisting of elastic disk 14 (in case of the piezoelements operating in the flexure mode), piezoelement 16 and spring 20, it is clear that resonance can be achieved by various combinations of the spring, the mass and the force acting thereon, and thus, on the piezoelement. The absolute magnitude of the amplitude depends on these parameters.

During acoustic transfer from one medium to another, the transfer coefficient increases when the acoustic impedance of the first medium is close to that of the second medium. In this particular case, this is expressed by the following relationship, in which the left term relates to the oscillator and the right term to the pipe: m F2 > EIpS wherein: m = mass k= spring rate F = force exerted by spring S = cross-sectional area of the pipe EI = flexural rigidity of the pipe p = mean density of pipe plus liquid Under the above conditions, a maximum of the vibratory energy of the oscillator passes into the vibrations of the pipe. Although the pipeline is usually massive and rigid in comparison to the oscillator, it is still possible to have the magnitude of the left term of the above expression approach that of the right term by means of F. While this causes some loss in the absolute amplitude of the oscillator vibrations, it provides a maximum of amplitude possible (with-as determined by the condition of resonance) by providing an appropriate F, a spring with a suitable spring rate and a mass of a suitable magnitude.

Conditions are different with the resonator operating as receiver. There, the source of the vibrations (of very low amplitudes) is the pipeline itself. In order to obtain an electric signal of maximum magnitude, the oscillator must enhance the amplitude of the movement of its vibrations relative to the vibrations at the source.

This means that while the receiving oscillator must be tuned to resonate with the received vibrations, F, m and k in this case must also provide a match between the oscillator and the resonator as a whole. Accordingly, while basically similar to the transmitting resonator, housing 4 and plug 22 are much lighter.

Figs. 7a and 7b illustrate two of a large number of possible vibrational modes of a pipe. Fig. 7a shows a bi-symmetrical mode (with the maximum deformation indicated by a dashed line) and Fig. 7b represents a tri-symmetrical mode. From the energy-saving point of view, the bi-symmetrical mode is superior to the higher-order symmetry modes and therefore the coupling elements to be discussed presently are designed to enforce the bi-symmetrical mode.

While a vibrational mode exists which is of a still lower, uni-symmetrical order and, theoretically, is thus superior from the energy point of view, it must be considered less suitable for the present purpose, as it is not only difficult to enforce, but, in any case, the co-appearance of the mode of Fig. 7a cannot be suppressed.

Fig. 8 shows a first embodiment of the coupling element according to the invention. The element consists of two yoke-like members 50,50'tightly clamped ont pipe 42 by means of bolts 52. Upper yoke 50 carries resonator 2. The slanting faces 54 are such that the angle a included between diagonals connecting the four points of contact A, B, C, D is less than 90°. Tightening of bolts 52 will impart to the pipe a preliminary deformation (exaggeratedly indicated by the dashed curve) which, even if small, will favor the bi-symmetrical deformation desired. Resolution of force F is indicated by arrows.

Fig. 9 illustrates a second embodiment of the coupling element, in which yokes 50,50'are articulated to one another by a hinge 56 located on one side, while clamping is effected by tightening bolt 52 on the other side. This particular embodiment carries two resonators 2.

Fig. 10 represents a coupling element particularly suitable for the receiving end of the system according to the invention. Seen are two clamp halves 58,60 almost completely surrounding pipe 42 and clamped onto the latter by means of bolts 52 indicated only by their center lines. One of the lugs of the upper clamp half 58 is elongated, constituting a cantilever 62 carrying resonator 2 at its end and thus acting as a mechanical amplifier for amplifying the amplitude.

The system according to the invention is envisaged to be adaptable also to potential information carriers other than pipelines, such as ship's frames and hulls, railway rails, and the like.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.