WO1999022207A1

WO1999022207A1 - Ultrasonic gas meter silencer and method

Info

Publication number: WO1999022207A1
Application number: PCT/US1998/022675
Authority: WO
Inventors: Winsor Letton; Klaus J. Zanker
Original assignee: Daniel Industries, Inc.
Priority date: 1997-10-24
Filing date: 1998-10-23
Publication date: 1999-05-06

Abstract

A silencer for use with an ultrasonic flow meter for measuring a stream of fluid in a pipe. The silencer is for reducing the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment such that the wavelengths associated with the silencer are short with respect to the dimensions of the associated equipment. In one of various embodiments, a plurality of plates having apertures are provided. The apertures in the plates are sized and shaped for maximum passage of fluid and for minimum passage of noise in the ultrasonic range of frequencies caused by the flow control valves and related equipement. Alternate embodiments include off-setting plates, open-cell foam plugs, closed cell foam linings, off-line assemblies using visco-elastic absorbing material and semi-circular plates oriented in longitudinal relationship within the pipe.

Description

ULTRASONIC GAS METER SILENCER AND METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional patent application 60/062.773 "Ultrasonic Gas Meter Silencer and Method," filed 10/24/97. STATEMENT REGARDING FEDERALLY SPONSORED

RESEARCH OR DEVELOPMENT

Not Applicable.

FIELD OF THE INVENTION The present invention relates generally to a silencer and method for use with an ultrasonic gas flow meter. Specifically, the present invention relates to a silencer and method for use with an ultrasonic gas flow meter for reducing noise in the ultrasonic range of frequencies caused by related equipment in the flow stream.

BACKGROUND OF THE INVENTION

Ultrasonic flow meters have great utility for the measurement of fluids. Of primary concern with respect to the use of ultrasonic flow meters is the reduction of noise caused by equipment in the flow stream that affects the operation of the ultrasonic flow meter. Equipment in the flow stream that affects the operation of the ultrasonic flow meter may be. for example, a flow control valve.

It is, therefore, a feature of the present invention to provide a silencer and method for use with an ultrasonic gas flow meter which reduces the noise in the ultrasonic range of frequencies caused by related equipment in the flow stream.

A feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter that can be placed in-line with the meter.

Another feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter that is effective at frequencies of approximately between 50 and 300 kHz. and preferably between 80 kHz and 180 kHz.

Still another feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter such that the wavelengths associated with the present invention are short with respect to the dimensions of the associated devices. Still another feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter that is effective at pressure drops of approximately greater than 10 bar across the flow control valve.

- 1 - Another feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter that is placed intermediate of an upstream ultrasonic gas flow meter and a downstream flow control valve.

Yet another feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter that is placed intermediate of an downstream ultrasonic gas flow meter and a upstream flow control valve.

Yet another feature of the present invention is to provide a silencer and associated method for use with an ultrasonic gas flow meter wherein the power levels associated with the invention are substantially different than associated with prior devices. Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.

SUMMARY OF THE INVENTION To achieve the foregoing objects, features, and advantages and in accordance with the purpose of the invention as embodied and broadly described herein, a silencer for use with an ultrasonic flow meter for measuring a stream of fluid in a pipe is provided for reducing the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment, such that the wavelengths associated with the present invention are short with respect to the dimensions of the associated devices. Also, the power levels associated with the silencer of the present invention are substantially different than associated with prior devices.

In one embodiment, a silencer is provided comprising a plurality of plates and a separation means. The plates have apertures such that the apertures in the plates are sized and shaped for maximum passage of fluid and for minimum passage of noise in the ultrasonic range of frequencies caused by flow control valves and related equipment. The separation means maintains the plates at a predetermined distance one from the other such that the distance between the plates is spaced for maximum passage of fluid and for minimum passage of noise in the ultrasonic range of frequencies caused by flow control valves and related equipment.

In another embodiment, a silencer is provided comprising a first plate, a second plate and a sleeve. The first plate has a first side positioned to receive the noise, an inside circumference defining an aperture, and a plurality of grooves on the first side of the first plate for dispersing and dissipating the noise impinging on the plate. The second plate is downhoise from the first pate and disposed to disperse and dissipate noise impinging on it. The sleeve connects the first plate to the second plate and has a plurality of apertures therein for freely passing the fluid such that the noise

- 2 - in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced.

In yet another embodiment, a silencer is provided having a first plate, a second plate and a plurality of stanchions. The second plate is downnoise from the first plate and is disposed to disperse and dissipate noise impinging on it. A plurality of stanchions connect the first plate to the second plate. The stanchions are positioned for freely passing the fluid there between such that the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced.

In yet another embodiment, a silencer is provided comprising a cylindrical member and a plurality of semi-circular plates. The semi-circular plates are arranged within the cylindrical member in an offsetting orientation such that the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced.

Also, an improved silencer is provided for use with an ultrasonic flow meter, the silencer reducing the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment. The improvement is placing a visco-elastic member in the pipe having characteristics such that the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced and the flow of fluid is unfettered.

In still another embodiment, a silencer is provided comprising a plurality of members disposed along the interior surface of the pipe aligned in a radial direction toward the center of the pipe, and a lining engaged with the members and the interior surface of the pipe. The lining is made of closed-cell foam material. The noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced by continual engagement with the lining and members.

In still another embodiment, a silencer is provided comprising a visco-elastic absorbing member disposed along the central axis of the pipe containing the flow control valves and related equipment. The visco-elastic absorbing member is oriented for linear engagement of the noise. The ultrasonic flow meter is oriented at an angular position remote from the flow control valves and related equipment so as not to be in a linear relationship with the noise emitted from the flow control valves and related equipment. The noise in the ultrasonic range of frequencies caused by the flow control valves and related equipment is reduced by linear engagement with the visco-elastic absorbing member. Alternately, the visco-elastic absorbing member may be a plurality of conical elements with the apex of the conical elements oriented toward the flow control valves and related equipment and the base remote therefrom.

Thus, the present invention comprises a combination of features and advantages which enable it to overcome various problems of prior devices. The various characteristics described

- 3 - above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings which are incorporated in and constitute a part of the specification, illustrate a preferred embodiment of the invention and together with the general description of the invention given above and the detailed description of the preferred embodiment given below, serve to explain the principles of the invention.

FIGS. 1 and 2 are schematic illustrations of the prior art placement of a flow control valve in the vicinity of an ultrasonic gas flow meter.

FIG. 3 is a schematic illustration of the present invention with an ultrasonic gas flow meter placed upstream of a flow control valve and a silencer placed intermediate there between.

FIG. 4 is a schematic illustration of another embodiment of the present invention with the ultrasonic gas flow meter placed downstream of a flow control valve and a silencer placed intermediate there between.

FIG. 5 is a schematic illustration of yet another embodiment of the present invention with the ultrasonic gas flow meter placed downstream of the flow control valve and the silencer placed at a blind-T location there between.

FIG. 6 is a schematic illustration of another embodiment of the present invention with the ultrasonic gas flow meter placed upstream of the flow control valve and the silencer placed at a blind-T location there between.

FIG. 7 is plan view of one embodiment of the present invention incorporating a plurality of perforated plates.

FIG. 8 is a perspective view of the embodiment of the present invention using a plurality of perforated plates illustrated in FIG. 7.

FIG. 9 is an end view of one embodiment of the present invention using recessed plates. FIG. 10 is a cross-sectional view of the embodiment of the present invention using recessed plates as illustrated in FIG. 9 taken along the section line 10-10.

FIG. 11 is an end view of one embodiment of the present invention using displaced plates. FIG. 12 is a perspective view of the embodiment of the present invention using displaced plates as illustrated in FIG. 11 taken along the section line 12-12.

FIG. 13 is an end view of an embodiment of the present invention using a plurality semi-circular plates.

FIG. 14 is a perspective, sectional view of an embodiment of the present invention using a plurality of semi-circular plates as illustrated in FIG. 13.

- 4 - FIG. 15 is a sectional view of the silencer illustrated in FIGS. 13 and 14 taken along the section line 15-15 in FIG. 14.

FIG. 16 is a schematic illustration of yet another silencer of the present invention utilizing a visco-elastic material sufficiently porous to allow through flow. FIG. 17 is a cross-sectional illustration of a maze-type silencer of the present invention which maze silencer is lined with absorbing material.

FIG. 18 is a schematic illustration of a silencer as practiced by the present invention using a blind-T configuration/

FIG. 19 is a schematic illustration of yet another embodiment of a silencer of the present invention using a blind-T configuration.

FIG. 20 is a perspective, sectional view of an embodiment of the present invention using a plurality of semi-circular plates.

The above general description and the following detailed description are merely illustrative of the generic invention, and additional modes, advantages, and particulars of this invention will be readily suggested to those skilled in the art without departing from the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made in detail to the present preferred embodiments of the invention as described in the accompanying drawings. FIG. 1 illustrates a prior art arrangement of an ultrasonic gas meter 10 in conjunction with a flow control valve 20. The ultrasonic gas meter 10 is upstream of the flow control valve 20. When the flow control valve 20 is actuated, the ultrasonic gas meter 10 is affected by the noise associated with the closing and opening of the valve.

FIG. 2 is a schematic illustration of a prior art arrangement with a flow control valve 20 upstream of an ultrasonic gas meter 10. The importance of moving the valve is the production of a pressure drop. When the flow control valve is actuated, and the valve is opened or closed, the noise associated with the valve affects the ultrasonic gas meter 10.

FIG. 3 is a schematic illustration of the present invention with the ultrasonic gas meter 10 upstream of the flow control valve 20. Disposed between the ultrasonic gas meter 10 and the flow control valve 20 is a silencer 100. The silencer 100 acts to prevent the noise associated with the opening and closing of the flow control valve 20 from affecting the ultrasonic gas meter 10.

FIG. 4 is a schematic illustration of another embodiment of the present invention where the flow control valve 20 is upstream of the ultrasonic gas meter 10, and the silencer 100 is disposed, relatively, closer to the flow control valve 20 than the ultrasonic gas meter 10. The up stream silencer 100 must not disturb the flow into the meter 10.

- 5 - FIG. 5 is a schematic illustration of yet another embodiment of the present invention with a flow control valve 20 upstream of an ultrasonic gas meter 10 whereby the flow control valve 20 and the ultrasonic gas meter 10 are separated by an angle, such as for example, a 90 degree angle. The silencer 100 is disposed in a linear relationship with the flow control valve 20. Thus, the flow control valve 20 is at an angular relationship with the ultrasonic gas meter 10, and the ultrasonic gas meter 10 is at an angular relationship with the silencer 100.

FIG. 6 is a schematic representation of another embodiment of the present invention with the ultrasonic gas meter 10 upstream of the flow control valve 20. The silencer 100 is in a downstream angular relationship to the ultrasonic gas meter 10 and in a linear relationship with the downstream flow control valve 20. In FIGS. 3 through 6, the wavelengths associated with the silencer are short with respect to the dimensions of the associated devices, namely, the flow control valve, the ultrasonic gas meter, the silencer, the pipe, etc. Also, the power levels associated with the silencer are substantially different than the power levels associated with prior devices.

FIG. 7 is an end view of another embodiment of the silencer of the present invention incorporating a plurality of perforated plates. FIG. 7 illustrates the silencer 200 having a first plate 212. a second plate 222. a third plate 232 and a plurality of stanchions 242. The first plate 212 of the silencer 200 has a plurality of apertures 214 there through. The aperture may be beveled as illustrated in FIG. 7, alternately the apertures may be cylindrical, or some other configuration, as may be required. FIG. 8 is an illustration of the perforated plate silencer 200 illustrated in FIG. 7. The silencer 200 in FIG. 8 illustrates the separation of the first plate 212 from the second plate 222 from the third plate 232. It can be appreciated by those skilled in the art that various numbers of plates may be appropriate for a silencer of the type illustrated in FIGS. 7 and 8. For example, such a silencer 200 may just have two plates, or a silencer 200 may be required which would have any number of plates depending on the effectiveness of the silencer 200 and the phenomena being addressed by the silencer 200.

FIG. 8 illustrates the plates 212, 222, 232 dispersed at equal distances. Particularly, the first plate 212 and the second plate 222 are displaced by a distance d|. The second plate 222 and the third plate 232 are displaced by a distance d . It is appreciated by those skilled in the art that the varying plate distances may be based upon the physical phenomena being addressed by the silencer 200. For example, the spacing of the plates may be made such that the distance d| or d₂ is a function of the wave length of the dominant frequencies associated with the flow control valve or some multiple of a frequency associated therewith. It can be appreciated that varying the distance between the plates can have an appreciable effect on the effectiveness of the silencer 200. Also, the configuration of the apertures 214 in the first plate 212 and the respective apertures 224, 234 in the

- 6 - subsequent plates 222. 232, respectively, can have differing configurations from plate to plate to be effective for addressing the silencing problem being addressed.

FIG. 9 is an end view of another silencer 300 embodied by the present invention utilizing recessed plate. The silencer 300 has a first plate 312 and a second plate 322. The first plate 312 and the second plate 322 are displaced by a cylindrical separator 332. The first plate 312 has at its radial extremity, a plurality of grooves 314. The plurality of grooves 314 are effective for dispersing the sound waves received from a flow control valve 20. Further, it should be appreciated that the example of using grooves is merely illustrative and the present invention incorporates using any rough surface for the effective dispersion of the undesirable sound waves. FIG. 10 is an illustration of the silencer 300 illustrated in FIG. 9 taken along the section line

10-10. The silencer 300 is illustrated in FIG. 10 whereby the first plate 312 is separated from the second plate 322 by a distance d₃. The distance d also defines the length of the central axis associated with the cylindrical separator 332. The cylindrical separator 332 has a plurality of apertures 334 therein. The number, size and shape of the apertures 334 in the cylindrical separator 332 varies with respect to the noise problem for which the silencer 300 is being used. Also, the distance d₃ between the first plate 312 and the second plate 322 can be changed according to the noise being seen by the silencer 300.

FIG. 11 is an end view of yet another embodiment of the present invention illustrating a silencer 400 using displaced plates 412, 422. The silencer 400 has a first plate 412. a second plate 422 and a plurality of stanchions 432. The first plate 412 has a plurality of grooves 414 located at its axial extremity. The grooves 414 are effective for baffling and dissipating noise which engages the surface of the first plate 412. Although the grooves 414 are illustrated at the axial extremity of the first plate 412. it can be appreciated that the grooves 414 may be located at any location upon the surface of the first plate 412, as the need arises. Further, it-should be appreciated that the example of using grooves is merely illustrative and the present invention incorporates using any rough surface for the effective dispersion of the undesirable sound waves.

FIG. 12 is a perspective view of the silencer 400 illustrated in FIG. 11 taken along the section line 12-12. FIG. 12 illustrates the first plate 412 being separated from the second plate 422 by a distance ds.. The distance c can be varied depending upon the noise problem being solved by the silencer 400. The first plate 412 and the second plate 432 are held, one disposed from the other, by a plurality of stanchions 432. The stanchions 432 have a length which is essentially the distance d4 between the first plate 412 and the second plate 422. The first plate 412 has therein an aperture 416. The aperture 416 in the first plate 412 is defined by an interior diameter surface 418 of the first plate 412. The size of the aperture 416 in the first plate 412 can be varied depending on the application of the silencer 400.

- 7 - FIGS. 13, 14 and 15 illustrate yet another embodiment of the silencer 500 of the present invention utilizing semi circular plates. FIG. 13 is an end view of the semi circular embodiment of the silencer 500 of the present invention. The figures illustrates the application of semi-circular plates A, B, C and D. It can be appreciated the additional semi-circular plates are readily to practice the present invention, as well as fewer plates than illustrated in FIGS. 13, 14 and 15.

FIG. 13 is an end view of the silencer 500 illustrated in FIGS. 13, 14 and 15. The silencer 500 is illustrated showing a first semi-circular plate 510 and a second semi-circular plate 520. Particularly, FIG. 13 illustrates the straight edge 512 of the first semi-circular 510 in a horizontal arrangement with respect to the silencer 500. Similarly, the straight edge 522 of the second semi-circular plate 520 is illustrated in a vertical arrangement with respect to the silencer 500. The straight edge 522 as illustrated in FIG. 13 is only visible in the lower portion of the end view of FIG. 13.

FIG. 14 is a perspective, cut-away view of the semi-circular plate silencer 500 of the present invention. The semi-circular plates A, B, C, D are illustrated being arranged within a cylindrical member 502. The first plate A and the second plate B are separated by a distance d₅ι.

The second plate B and the third plate C are separated by a distance d₅₂. Similarly, the third plate C and the fourth plate D are separated by a distance ds₃. More particularly, the first semi-circular plate A has a first surface 510 bounded by a straight edge 512 and a curved edge 514. The second semi-circular plate B has a planar surface 520 bounded by a straight edge 522 and a curved edge 524. Similarly, the third semi-circular plate C and the fourth semi-circular D have respective planar surfaces 530. 540, and straight edges 532. 542, and curved edges 534, 544.

FIG. 15 is a sectional view of the silencer 500 illustrated in FIGS. 13 and 14 taken along the section line 15-15 in FIG. 14. Each semi-circular plate A, B, C, D is illustrated displaced by the distances d.₅₁, d₅₂ and ds , respectively. The first semi-circular plate A is illustrated in the lower portion of the cylindrical member 502. The second semi-circular plate B is illustrated traversing the cylindrical member 502 from the illustrated top to the illustrated bottom. The third semi-circular plate C is illustrated in the lower portion of the cylindrical member 502 of the silencer 500. The fourth semi-circular plate D is illustrated traversing the entire diameter of the cylindrical member 502 associated with the silencer 500 of the present invention. Alternately, the plates may be sequenced in a different order, or in different positions, such as first semi-circular plate A being located in the top portion of the cylindrical member 502 as shown in Figure 20.

FIG. 16 is a schematic illustration of yet another silencer 600 of the present invention utilizing a visco-elastic material. The visco-elastic material 602 is illustrated disposed within the pipe 60 for providing a silencer 600. In the embodiment of the silencer 600 illustrated in FIG. 16, it is appropriate to match the acoustic impedance associated with the visco-elastic material 602 with

- 8- the frequencies which are desired to be absorbed. The impedance has to be matched to the gas to prevent the noise from reflecting from the visco-elastic material. Typically, for example, open-cell foam would be appropriate for use with clean gas. In this embodiment of the present invention, the open cell foam is necessary to allow through flow, but the foam acts as a filter and sponge, hence clean gas. Further, with respect to the silencer 600 illustrated in FIG. 16, it is appropriate to match the damping characteristics as well as the frequency. The damping is achieved by the "visco" portion of the material, and the frequency matching is achieved by the "elastic" part of the material. Apart from the visco-elastic properties of the foam there are other mechanisms for absorbing the energy. If the cell size of the foam is close to the wavelength of the ultrasound, some resonance effects can increase the absorption, and the flow through these small passages (cells) leads to normal viscous dissipation that further increases absorption.

FIG. 17 is a cross-sectional illustration of a maze-type silencer 700 of the present invention. The maze silencer 700 provides a closed-cell arrangement defined by the supports 710 running perpendicularly to the pipe 70. In a more particular embodiment of the invention illustrated in FIG. 17, the supports 710 have associated a foam material 730. The foam material 730 is also preferably affixed to the inside of the pipe 70. The foam 730 associated with the support 710 can have parallel sides 732 and angled ends 734. However, it can be appreciated that various types of foam 740 can be used. For example, the maze is lined with a closed cell foam because the maze does not need to be open cell. No through flow is required with respect to the foam of the present embodiment and the foam does not suffer from being a filter or sponge. Also, various shapes of support 710 are readily adaptable by those skilled in the art dependent upon the noise problem being solved by the silencer 700. Also, the shape of the foam 740 around the support 710 and along the inside walls of the pipe 70 can be changed depending on the problem being solved by the silencer 700. FIG. 18 is a schematic illustration of another silencer 800 as practiced by the present invention using a blind-T configuration. The silencer 800 illustrated in FIG. 18 shows a flow control valve 20 upstream of the silencer 800. The ultrasonic gas meter (not illustrated in FIG. 18) is downstream or upstream of the flow control valve 20. The noise emanating from the flow control valve 20 is oriented so as to impinge on the silencer 800. The silencer 800 comprises a visco-elastic absorbing material 802. The absorbing material 802 is affixed in the pipe 80 using a flange 804. The absorbing material 802 is oriented so that the noise is impaled there against in a direct manner. The pipe 80 comprises a first section 82 containing the flow control valve 20 and the silencer 800. Also, the pipe 80 has a second section 84 in which the ultrasonic gas meter is located albeit not illustrated.

- 9 - FIG. 19 is a schematic illustration of yet another embodiment of a silencer 900 of the present invention using another blind-T configuration. The silencer 900 illustrated in FIG. 19 comprises a visco-elastic absorbing material 902. The visco-elastic material 902 is arranged in a plurality of conical members 904. The conical members 904 extend from a wide base portion to a narrow pointed portion. The flow control valve 20 is located within the pipe 90 such that the noise is propagated directly toward the narrow pointed portion of the conical members 904. The flow control valve 20 and the silencer 900 are disposed within a first section 92 of the pipe 90. The ultrasonic gas meter (not illustrated) is disposed within a second section 94 of the pipe 90.

In FIGS. 7 through 19. the wavelengths associated with the silencer are short with respect to the dimensions of the associated devices, namely, the flow control valve, the ultrasonic gas meter, the silencer, the pipe, etc. It should be noted, however, that the open cell foam of the embodiment shown in Figure 16 may have cells of similar dimension to a wavelength. Also, the power levels associated with the silencer of the present invention are substantially different than the power levels associated with prior devices. With respect to the baffle-design embodiments of the present invention, the noise is essentially reflected. The noise is reflected by scattering, refraction and dispersion to produce destructive interference. The destructive interference, and its magnitude, is produced by scattering, refraction and dispersion which is controlled by geometry, including the surface roughness. Thus, the structural limitations of the present invention are related to the wavelengths being scattered, refracted and dispersed. Such wavelengths are short with respect to the dimensions of the associated structures and devices.

With respect to the visco-elastic embodiments of the present invention, the basic idea is to absorb and dissipate the noise, i.e.. convert the noise to heat. The visco-elastic material has to be impedance matched to the gas to avoid reflection. Acoustic impedance is defined as: Z = (d)(c) where d = density of material and c = speed of sound in the material. It is difficult to find materials with the same acoustic impedance, Z, as gas. Since foams have been determined to have the required acoustic impedance, foams comply with the scope of the present invention. For example, open cell foams are good for absorption, but poor in dirty wet gas because they act as filters and sponges. Also by way of example, closed cell foams overcome the filter/sponge problems and hence are more practical materials. As previously discussed, the elastic properties are matched to the frequency of the noise and the visco properties are matched to damp the noise.

The silencer designs of the present invention illustrated in FIGS. 7, 8, 13, 14, 15,16 and 17 are symmetrical and hence can be used with the flow and noise in either direction, i.e., these embodiments of the present invention are completely reversible. The silencer design of the present

- 10 - invention illustrated in FIGS. 9 and 10 is not symmetrical, but it can be used in both directions by placing roughness on either or both faces 312, 322. Similarly, the silencer design in FIGS. 11 and 12 is not symmetrical, but can be completely reversible by placing roughness on either or both faces 412, 422.

Additional advantages and modification will readily occur to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus, and the illustrative examples shown and described herein. Accordingly, the departures may be made from the details without departing from the spirit or scope of the disclosed general inventive concept.

- 11 -

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A silencer for use with an ultrasonic flow meter, the silencer suitable to reduce the noise in the ultrasonic range of frequencies comprising: (a) a plurality of plates having apertures therein such that the apertures in the plates are sized and shaped for maximum passage of fluid and for minimum passage of noise in the ultrasonic range of frequencies caused by flow control valves and related equipment, and

(b) separators maintaining the plates at a predetermined distance one from the other such that the distance between the plates is spaced for maximum passage of fluid and for minimum passage of noise in the ultrasonic range of frequencies caused by flow control valves and related equipment such that the wavelengths associated with the silencer are short with respect to the dimensions of the associated devices.

2. A silencer for use with an ultrasonic flow meter, the silencer suitable to reduce noise in the ultrasonic range of frequencies:

(a) a first plate comprising

(1) a first side positioned to receive the noise in the ultrasonic range of frequencies,

(2) an inside circumference defining an aperture, and (3) means for roughing the first side of the first plate for dispersing and dissipating the noise impinging thereupon,

(b) a second plate downnoise from the first pate and disposed to disperse and dissipate noise impinging thereupon, and

(c) a sleeve connecting the first plate to the second plate, the sleeve having a plurality of apertures therein for freely passing fluid there through such that the noise in the ultrasonic range of frequencies.

3. The silencer of claim 2, wherein said sleeve is a plurality of stanchions connecting the first plate to the second plate, the stanchions positioned for freely passing the fluid there between such that the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced.

4. A silencer for use with an ultrasonic flow meter for measuring a stream of fluid¹ in a pipe, the silencer for reducing the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment comprising:

(a) a cylindrical member, and (b) a plurality of semi-circular plates,

- 12 - the semi-circular plates are arranged within the cylindrical member^~╧èn an offsetting orientation such that the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced such that the wavelengths associated with the silencer are short with respect to the dimensions of the associated devices.

5. An improved silencer for use with an ultrasonic flow meter, the silencer reducing the noise in the ultrasonic range of frequencies, the improvement comprising placing a cellular visco-elastic member in the pipe having characteristics such that the noise is reduced and the flow is unfettered.

6. A silencer for use with an ultrasonic flow meter for measuring a stream of fluid in a pipe, the pipe having an interior surface, the silencer for reducing the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment comprising:

(a) a plurality of members disposed along the interior surface of the pipe aligned in a radial direction toward the center of the pipe: and

(b) a lining engaged with the members and the interior surface of the pipe, the lining comprised of closed-cell foam material, such that the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment is reduced by continual engagement with the lining and members such that the wavelengths associated with the silencer are short with respect to the dimensions of the associated devices.

7. A silencer for use with an ultrasonic flow meter for measuring a stream of fluid in a pipe, the pipe having an interior surface and a central axis, the silencer for reducing the noise in the ultrasonic range of frequencies caused by flow control valves and related equipment comprising: a visco-elastic absorbing member disposed along the central axis of the pipe containing the flow control valves and related equipment for linear engagement of the noise emitted therefrom with the visco-elastic absorbing member, the ultrasonic flow meter oriented at an angular position remote from the flow control valves and related equipment so as not to be in a linear relationship with the noise emitted from the flow control valves and related equipment, such that the noise in the ultrasonic range of frequencies caused by the flow control valves and related equipment is reduced by linear engagement with the visco-elastic absorbing member.

8. The silencer of claim 7, wherein said absorbing member comprises a plurality of conical elements with the apex of the conical elements oriented toward the flow control valves and related equipment and the base remote therefrom.

- 13 -