Patent Description:
Fluid flow measurement is required in a variety of applications, such as gas and water supply measurements used by energy suppliers. Depending on the environmental conditions and the characteristics of the fluid to be measured, there are multiple ways of metering a fluid flow. Some flow measurement devices, such as mechanical flow meters, are in direct contact with the fluid to be measured and therefore influence the fluid flow, at least to some extent. Other flow measurement devices do not interact with the fluid and may thus be considered to be non-invasive. Examples for such non-invasive flow meters are magnetic, optical, or ultrasonic flow meters.

The present disclosure relates to coupling members for ultrasonic flow meters. Ultrasonic flow meters utilise the fact that sound waves move faster when travelling in the same direction as a flowing medium, and slower when travelling against the flow. This principle is not only used to accurately measure the flow of liquids and gases but also helps derive parameters like density and viscosity of the flowing medium.

Ultrasonic flow meters use one of two measurement principles, namely transit-time versus Doppler effect measurements. Doppler effect flow meters include a continuous ultrasonic wave transmitter, and a receiver detecting parts of the continuous ultrasonic waves that are scattered from particles suspended in the fluid medium. The received ultrasonic wave has a frequency shift (Doppler frequency shift), which is directly proportional to the flow.

In transit-time flow measurement, a pair of ultrasonic transducers is used where both function as a transmitter as well as the receiver. The flow meter operates by alternately transmitting and receiving bursts of ultrasonic waves between the two transducers and measuring the transit time for set waves to travel between the two transducers. Ultrasonic waves travelling with the fluid flow will result in shorter transit times, whereas waves travelling against the flow will have longer transit times. The difference in the transit time measured is directly proportional to the velocity of the fluid in the pipe.

The transducers for transit-time flow meters can be mounted to the fluid conduit in various different ways, all of which include at least a pair of transducers that are offset from each other along the flow axis of the fluid conduit. Three main arrangements that can be utilised in flow measurements are the "Z-method", the "V-method", and the "W-method". In the "Z-method", the two transducers are mounted on opposite sides of the pipe and the sound pulses cross the pipe flow once. This method can be used for larger pipe sizes.

With the "V-method" and the "W-method", the two transducers are mounted on the same side of the pipe and the sound pulse is reflected on the opposite of the pipe, such that the sound pulse crosses the pipe twice (V-method) or four times (W-method) before reaching the respective other transducer.

A schematic view of a flow metering device set-up according to the V-method is shown in <FIG>. The flow metering device <NUM> includes a housing <NUM>, which is attached to a fluid conduit <NUM> for measuring a corresponding fluid flow <NUM> within said conduit <NUM>. The flow measurement device <NUM> comprises a first ultrasonic transducer <NUM> and a second ultrasonic transducer <NUM> received within the housing <NUM>. Both the first and second ultrasonic transducers <NUM> and <NUM> are configured to transmit and receive ultrasonic waves.

The first and second ultrasonic transducers <NUM> and <NUM> are coupled to the fluid conduit <NUM>. A contact gel (not shown) is typically provided between an outer surface of the fluid conduit <NUM> and the transducers <NUM>, <NUM> to avoid air gaps between the transducers <NUM>,<NUM> and said outer surface of the fluid conduit <NUM>. By eliminating air gaps between the transducers <NUM>,<NUM> and the fluid conduit <NUM>, inadvertent signal losses can be reduced.

<FIG> shows a first sound path <NUM> of an ultrasonic wave travelling from the second transducer <NUM> towards the first transducer <NUM>. As is directly derivable from <FIG>, the signal path <NUM> is substantially V-shaped. The sound signal enters the fluid conduit <NUM> at the top surface of the fluid conduit <NUM>, as is shown in <FIG>, and propagates through the pipe until it is reflected by an opposite, lower end of the fluid conduit <NUM>, The signal is then reflected back towards the first transducer <NUM>. It should be noted that the angle α, at which the ultrasonic signal impacts the lower end of the fluid conduit <NUM>, is usually predetermined and important for effective flow measurement. Another constant is the diameter D of the transducers <NUM> and <NUM>. The diameter D is usually set by the strength of the ultrasonic wave signal required, which in turn is dependent on the type of fluid measured. With the angle α and diameter D being fixed, a distance d between the first and second transducers mainly depends on the diameter of the fluid conduit <NUM>. Accordingly, fluid conduits with smaller diameters result in a shorter distance d, whereas fluid conduits with a larger diameter require an increased distance d between the two transducers <NUM>, <NUM>. Yet, it should be noted that transducers that are arranged at a fixed distance d may still be used to measure fluid conduits of various diameters, e.g. within a range of <NUM>.

Particularly when measuring fluid conduits of smaller diameters, such as the one shown in <FIG>, the distance d between the first and second transducers reduces so much that the transducers <NUM>, <NUM> contact each other in the centre <NUM>, between the first and second transducers <NUM>, <NUM>. Such contact can result in a significant increase of crosstalk between the first and second transducers <NUM> and <NUM>. Such crosstalk results in noise signals <NUM> created by sound waves travelling along the outer surface of the fluid conduit, directly between the first and second transducers <NUM>, <NUM>. Noise signals <NUM>, therefore, do not cross the flow conduit. Of course, said noise signals <NUM> will reduce the quality of the ultrasonic signal <NUM> used for flow measurement and thus should be avoided or reduced.

In view of the aforementioned problem, it is an object of one or more embodiments of the present disclosure to reduce inadvertent crosstalk between the transducers, even when measuring on small diameter fluid conduits.

<CIT>) discloses a coupling element for an ultrasonic flow meter, which has a pedestal with a contact surface, on which contact surface a piezoelectric element is applied and which pedestal is an integral part of the coupling element.

According to the present disclosure, there is provided an ultrasonic flow metering device according to claim <NUM>, featuring two coupling members of the subsequently described type, the coupling member being elastic and configured for acoustically coupling an ultrasonic transducer to a fluid conduit. The coupling member comprises a first face adapted to be connected to an ultrasonic transducer and a second face adapted to a be connected to a fluid conduit. The coupling member further comprises at least one sidewall connecting the first and second faces, wherein the at least one sidewall comprises a first recess extending from the second face.

The coupling member of the present invention provides an interface between corresponding transducers and the fluid conduit that helps to reduce reflection of the acoustic wave signal produced by the transducers on the outer surface of the fluid conduit. The coupling member is also elastic. Producing the coupling member in an elastic form (e.g. by using elastic materials to form the coupling member) reduces the chance of air gaps being created between the transducers and the outer surface of the fluid conduit.

This is particularly the case if the coupling members are used in clamp on flow metering devices, in which the coupling members are squeezed onto the outer surface of the fluid conduit. The elastic coupling member also reduces the likelihood of inadvertent displacement of the latter under operation, thanks to its increased friction on the pipe wall. The coupling member of the present disclosure removes the requirement of adding a contact gel, grease, epoxy or glue between the transducers and the outer surface of the fluid conduit. The elastic coupling member may be configured such that the coupling member will elastically deform when in use. In particular, the elasticity of the coupling member may be chosen such that the coupling member will deform under a force that pushes/squeezes the coupling member onto the outer surface of a corresponding fluid conduit. Such deformation can reduce, and potentially eliminate, any air gap between the coupling member and the outer surface of the fluid conduit.

The recess arranged on the sidewall and extending from the second face can be used to create an attenuating air gap between adjacent coupling members when used in a corresponding flow meter, particularly in V-method ultrasonic flow meters, even when applied to flow tubes of very small diameter, such as diameters of <NUM> or less.

As will be described in more detail below, contact between sidewalls of two adjacent coupling members, along their respective second faces, could create inadvertent or undesired contact between two coupling members. Adding a recess to the sidewall along the second face of the coupling member will help to avoid said contact and create an air gap, which acts to attenuate noise signals/crosstalk between the first and second transducers.

The recess may have any shape or form. For example, it may be in the form of any one or more of a flat, concave, stepped, straight or angled surface. As will be clear from the following description, the recess refers to any partial removal of a sidewall connecting the first or second face of the coupling member. It may be created by moulding or by removing a part of a smooth side wall by means of cutting or machining parts of said side wall.

In an embodiment of the present disclosure, the coupling member is configured such that ultrasonic signals entering the coupling member at the first face propagate obliquely into the second face of the coupling member. In other words, the coupling member of the present disclosure not only acts as a means for avoiding air gaps between an outer surface of the fluid conduit and the transducers. Rather, the coupling member also acts as a propagation aid, which is designed such that the ultrasonic sound wave created by the respective transducer is refracted, when entering the first face of the coupling member, so as to exit the second face at an oblique angle, which is preferably also oblique to an outer face of the fluid conduit. The coupling member may thus be the only part situated between the transducer and the fluid pipe.

The first face may be directly connected to a transducer, whereas the second face may be directly connected to an outer surface of a corresponding fluid conduit. The first face may be directly moulded onto a corresponding surface of the transducer. In other embodiments, the first face may be connected to the corresponding surface of the transducer by means of an adhesive, such as Cyanoacrylate adhesive. However, it will be understood that application of any other adhesive is also feasible for as long as it does not significantly affect the ultrasonic signal.

In another embodiment, the coupling member is made from a material having a refractive index that substantially matches a refractive index of a flow medium to be measured. By matching the refractive index of the coupling member to the refractive index of the flow medium, the amount of refraction is reduced rendering the signal path more easily controllable.

The recess extending from the second face may be a retracted flat. In one embodiment, the recess may extend in a direction substantially orthogonal to the second face.

In another embodiment, at least parts of the sidewall extend substantially orthogonal to the first face. Accordingly, said orthogonal parts of the sidewall are aligned with a main direction of propagation of the ultrasonic signal. In other words, the sidewalls of the coupling member extend in a preferred direction of the ultrasonic signal to support propagation of said signal in a desired direction and to attenuate parts of the signal that divert from said preferred signal path.

The coupling member may be prism shaped. In particular, the coupling member may be a truncated, cylindrical prism with the first face being truncated at an oblique angle.

The coupling member may be made from a polymeric material.

In yet another embodiment, the recess does not intersect the first face of the coupling member. Creating a recess that would reduce the surface area of the first face of the coupling member can result in significant parts of the relevant ultrasonic signal being lost.

By creating a recess that does not intersect with the first face, the recessed coupling member of the present disclosure does not significantly affect the amount of ultrasonic signal being introduced into the coupling member and, at the same time, avoids inadvertent contact between corresponding coupling members.

The recess may comprise a plurality of concave recesses. This arrangement further assists in attenuating unwanted noise between the respective transducers.

In another embodiment, the coupling member comprises an anti-rotation member. The anti-rotation member may be formed in one piece with the coupling member and may protrude from its sidewall on an opposite end to the recess. In some embodiments, the coupling member comprises a plurality of anti-rotation members protruding from the sidewall. For example, a first anti-rotation member may protrude from the sidewall on an opposite end to the recess, whereas second and third anti-rotation members are spaced circumferentially at around <NUM> degrees from the first anti-rotation member. The second and third anti-rotation members may be arranged at opposite ends of the sidewall.

According to the invention, there is provided a clamp on flow metering device comprising first and second coupling members as described above. First and second coupling members are arranged with respect to each other such that their respective recesses face each other and form a gap between the coupling members.

The gap may be filled with a spacer element. The spacer element may be made from a material that is stiffer than a material of the first and second coupling members. Rather than using an air gap to separate the first and the second coupling members from each other, a spacer element may be inserted to maintain the distance between the respective coupling members. As such, the spacer element, which is stiffer than the coupling members, will not deform even if the coupling members are pushed towards each other, e.g. when fixing the flow metering device to the respective fluid conduit.

The spacer element may be made from any highly sound attenuating material. In one embodiment, the spacer element is made from cork or graphite. The spacer element may be solid or hollow for as long as the stiffness is sufficient to maintain the distance or gap between the coupling members.

In another embodiment, the coupling member comprises an anti-rotation member protruding from a sidewall of the coupling member. The anti-rotation member may be ranged on a side of the coupling member, which is opposite to the recess. The anti-rotation member may be an integral part of the coupling member. The anti-rotation member detains correct alignment of the recess within the ultrasonic flow metering device.

The anti-rotation members of the first and second coupling members protrude from their respective sidewalls in substantially opposite directions.

In another embodiment, the ultrasonic flow metering device may be a clamp on flow meter. In yet another embodiment, the ultrasonic flow metering device may be a "V-method" flow meter.

The coupling member of the present disclosure may be produced by a moulding process, e.g. liquid injection moulding. The coupling member may be directly moulded onto a corresponding surface of a respective transducer.

Alternatively, the coupling member of the present disclosure may be manufactured in successive layers on basis of layered model data by means of an additive manufacturing device. In this case, there may be provided a computer readable medium comprising instructions which, when the instructions are executed by an additive manufacturing device, cause the additive manufacturing device to carry out said additive manufacturing method.

The above layered model data may be created, comprising:.

Not according to the claimed invention, there is provided a method of manufacturing a flow metering device, the flow metering device comprising an ultrasonic transducer, the method comprising:
moulding an elastic coupling member directly onto a coupling surface of the ultrasonic transducer.

Moulding an elastic coupling member directly onto a coupling surface of the ultrasonic transducer reduces the introduction of air gaps between the coupling surface and a corresponding first face of the coupling member. Air gaps may attenuate the acoustic signal produced by the transducers. Due to the reduced number or size of air gaps achieved by the above moulding process, the SNR (signal-to-noise ratio) of the acoustic signal may increase.

The elastic coupling member may be injection moulded onto the ultrasonic transducer. It should be noted that the elastic coupling member of this method may have any mouldable shape and therefore may or may not include the recess described in connection with the specific coupling member described above.

The method may further comprise preparing the coupling surface with a primer before the moulding step. The primer may be any primer facilitating adhesion between the coupling surface of the transducer and the corresponding face of the coupling member during the moulding process.

The primer may be a shellac resin. In one example, the primer may be a spray-on primer.

The scope of the present invention is defined by the appended claims, while embodiments and all features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:.

Turning to <FIG>, there are shown different views of a coupling member for flow metering devices according to an embodiment of the present disclosure. The illustrated coupling member <NUM> comprises a first face <NUM>. The first face <NUM> is configured to be connected to ultrasonic transducer <NUM> as indicated by the dash lines in <FIG>. To this end, the first face may have a shape that matches the corresponding surface of the transducer <NUM>. In one embodiment, said shape is a flat first face <NUM> that corresponds to a flat face of the transducer <NUM>. In other embodiments, the face of the transducer may be uneven, e.g. it may comprise a shoulder portion along its circumferential edge, in which case the first face of the coupling member would match the shape of the shoulder portion inversely.

The coupling member <NUM> comprises a second face <NUM>. The second face <NUM> is configured for connecting the coupling member to a fluid conduit (see <FIG>). The second face <NUM> of the embodiment shown in <FIG> has a curved shape. The curved shape is provided to match an outer surface of a variety of tubular conduits of different diameters. As is indicated in <FIG>, the radius R of the curvature of the second face <NUM> relates to the radius R of a maximum conduit size to be contacted by the coupling member <NUM>. It will, however, be understood that the coupling member with radius R may also be used for fluid conduits of significantly smaller radius than R.

The first face <NUM> and the second face <NUM> are arranged on opposite ends of the coupling member <NUM>. In the illustration of <FIG>, the first face <NUM> is an upper face of the coupling member <NUM>, whereas the second face <NUM> is a lower face. The first and second faces <NUM>, <NUM> are connected via sidewalls <NUM>, <NUM>, <NUM>, and <NUM>.

In the embodiment illustrated in <FIG>, the coupling member <NUM> is prism shaped. More particularly, the coupling member <NUM> is a truncated, cylindrical prism with the first face <NUM> being truncated at an oblique angle. The second face <NUM>, on the other hand, extends substantially horizontally in the flow direction.

The coupling member <NUM> of this embodiment is a substantially cylindrical prism with the exception of a protrusion <NUM>, which extends from circumferential sidewall <NUM>. The protrusion <NUM> defines three further sidewalls <NUM>, <NUM>, and <NUM> connecting the first face <NUM> with the second face <NUM> that is derivable from <FIG>, for example.

Turning to <FIG>, it will be appreciated that at least parts of sidewall <NUM> extend perpendicular to the first face <NUM>. These parts of sidewall <NUM>, therefore, run parallel with an axis A that indicates a main line of propagation for sound waves created by the transducer <NUM>. However, rather than the sidewall <NUM> extending in a perpendicular direction with respect to the first face <NUM> all the way to the second face <NUM>, parts of sidewall <NUM> (left part in <FIG>/front part in <FIG>) comprise a recess <NUM> extending from the second face <NUM>.

In the illustrated embodiment, recess <NUM> is a retracted flat. The recess <NUM> in the form of a retracted flat extends in a direction, which is substantially perpendicular to the second face <NUM>.

The recess <NUM> shortens the extent of the second face <NUM> as compared to an entirely straight sidewall <NUM> as indicated by the dashed lines in <FIG>. As will be described in more detail with reference to <FIG>, the recess, therefore, facilitates the provision of an air gap between two coupling members arranged on the same side of a fluid conduit.

It should be understood that the recess <NUM> does not necessarily need to be in the form of a retracted flat. Rather, other embodiments might include a curved, stepped surface. As highlighted by the dashed line in <FIG>, the recess <NUM> refers to any partial removal of a smooth sidewall connecting the first or second face <NUM>, <NUM> of the coupling member <NUM>. It may be created by moulding or by means of cutting or machining parts of said side wall to create a corresponding cut-out.

In <FIG>, the dashed line together with the upper-left part of side wall <NUM> (the part that is perpendicular to first face <NUM>) shows an example of what is meant by the term "smooth side wall". In this case, a "smooth side wall" would extend in a straight line between edges of the first and second face. It will be appreciated that a smooth side wall may also be curved rather than straight but does not include any sharp edges. Accordingly, the term "smooth" may be interpreted in a mathematical sense.

The recess <NUM> changes the direction of the sidewall and thus introduces a sharp turning point <NUM> into the cross-section of side wall <NUM>.

Expressed in an alternative way, the recess changes the direction of at least parts of the side wall <NUM> in such a way that the size of the second face <NUM> is reduced as compared to the straight or smooth extend of the side wall, indicated by the dashed line on the bottom-left corner of <FIG>.

<FIG> shows a bottom plan view of the coupling member <NUM>. From this illustration, it is visible that the protrusion <NUM> has a dove tail shape and includes a second recess <NUM> extending from the second face <NUM> and creating a receptacle for a variety of sensors, such as temperature sensors for measuring the temperature of the outer surface of the fluid conduit, which is a measure for the temperature of the fluid within the conduit. The second recess is arranged on the second face <NUM>, such that the elastic nature of the coupling member <NUM> will push a corresponding temperature sensor against the outer surface of the fluid conduit as the flow metering device is attached to the latter, thereby preventing air gaps between the temperature sensor and the conduit. At the same time, the dove tail shaped protrusion <NUM> may be used as an anti-rotation element to facilitate correct alignment of the coupling member <NUM> in a housing of a corresponding flow metering device.

Turning to <FIG>, there is shown a range of possible extents for the recess <NUM>. The range is defined by limits <NUM> and <NUM> shown in <FIG>. The first threshold <NUM> relates to a case in which the sidewall <NUM> is cylindrical all the way between the first face <NUM> and second face <NUM>. It will be understood that in this scenario shown in <FIG>, no recess will be created.

<FIG> shows a recess <NUM> per the embodiment shown in <FIG>, which is situated between the first and second limits <NUM> and <NUM>. The second limit <NUM> is set to ensure that the recess <NUM> will not intersect the first face <NUM> of the coupling member <NUM>. If the recess <NUM> went beyond the second limit <NUM> and therefore intersected the first face <NUM>, the ultrasonic signal created by the transducer <NUM> (<FIG>) would be significantly affected, resulting in an increased risk of receiving non-usable signals at a corresponding, receiving transducer.

The recessed shape of the coupling member of the present disclosure also has advantages when the coupling member is compressed. It will be understood that compression of the coupling member can occur when a corresponding flow metering device, and in particular a clamp-on flow metering device, is attached to the outer surface of a respective fluid conduit. This will result in compressing the elastic coupling member, which is located between the transducer and the fluid conduit, against the outer surface of the fluid conduit to close potential air gaps between the second face of the latter and an outer surface of the fluid conduit.

<FIG> shows, schematically, the effect of compressing the coupling member <NUM> according to the embodiment shown in <FIG>. As a force is applied on coupling member <NUM>, pushing the first face <NUM> and the second face <NUM> closer together, expansion of the sidewall <NUM> in a direction mainly perpendicular to the direction of the compressive force occurs. It has been found that, due to the provision of the recess <NUM> along sidewall <NUM>, expansion of the coupling member <NUM> in the lateral direction mainly occurs in parts of the sidewall <NUM>, which are not recessed, as can be derived from the dashed line in <FIG>. In other words, most of the expansion occurs in the section of the sidewall <NUM>, which is not recessed and arranged adjacent to the first face <NUM>. The recessed surface, which extends from the second face <NUM>, does not expand significantly compared to the non-recessed part of the sidewall <NUM>. This phenomenon is particularly prominent in embodiments in which the recess <NUM> extends substantially perpendicular to the second face <NUM>. As mentioned above, by inhibiting expansion of the coupling member, particularly in regions close to the second face <NUM>, it is possible to avoid inadvertent contact between two adjacent coupling members, which would otherwise result in increased cross-talk.

Turning to <FIG>, there is shown a side view of a coupling member for flow metering devices according to another embodiment of the present disclosure. It will be appreciated that the coupling member <NUM> is mostly identical to the coupling member <NUM> of <FIG> except for the recess <NUM>.

The illustrated coupling member <NUM> comprises a first face <NUM>. The first face <NUM> is configured to be connected to ultrasonic transducer <NUM> as indicated by the dash lines in <FIG>. To this end, the first face <NUM> may have a shape that matches the corresponding surface of the transducer <NUM>. In the present embodiment, said shape is a flat first face <NUM> that corresponds to a flat face of the transducer <NUM>.

The coupling member <NUM> comprises a second face <NUM>. The second face <NUM> is configured for connecting the coupling member to a fluid conduit (see <FIG>). The second face <NUM> has a curved shape. The curved shape is provided to match an outer surface of a variety of tubular conduits of different diameters.

The first face <NUM> and the second face <NUM> are arranged on opposite ends of the coupling member <NUM>. In the illustration of <FIG>, the first face <NUM> is an upper face of the coupling member <NUM>, whereas the second face <NUM> is a lower face. The first and second faces <NUM>, <NUM> are connected via sidewall <NUM>.

At least parts of sidewall <NUM> extend perpendicular to the first face <NUM>. These parts of sidewall <NUM>, therefore, run parallel with an axis A1 that indicates a main line of propagation for sound waves created by the transducer <NUM>. However, rather than the sidewall <NUM> extending in a perpendicular direction with respect to the first face <NUM> all the way to the second face <NUM>, parts of sidewall <NUM> comprise a recess <NUM> extending from the second face <NUM>.

In the embodiment of <FIG>, recess <NUM> is a curved recess. The curved recess <NUM> shortens the extent of the second face <NUM> as compared to an entirely straight sidewall <NUM>. Therefore, the recess <NUM> facilitates the provision of an air gap between two coupling members arranged on the same side of a fluid conduit.

It should be understood that the recess <NUM> does not necessarily need to be in the form shown in <FIG>. In some embodiments, the recess <NUM> can include any curved, stepped surface. The recess <NUM> can refer to any partial removal of a smooth sidewall connecting the first and second face <NUM>, <NUM> of the coupling member <NUM>. It may be created by moulding or by means of cutting or machining parts of said side wall to create a corresponding cut-out.

The recess <NUM> changes the direction of the sidewall <NUM> and, in this example, introduces a sharp turning point <NUM> into the cross-section of side wall <NUM>. The recess <NUM> changes the direction of at least parts of the side wall <NUM> in such a way that the size of the second face <NUM> is reduced as compared to a straight or "smooth" non-recessed side wall. The recess <NUM> can also be considered as defining a surface that is obliquely angled with reference to the axis A1 that indicates the main line of propagation for sound waves through the coupling member <NUM>.

<FIG> shows a front view of a coupling member <NUM> according to another embodiment of the present disclosure. The coupling member <NUM> shown in <FIG> includes a first face <NUM> adapted for connection to an ultrasonic transducer and an opposite second face <NUM> configured for connection to the outer surface of a fluid conduit. A sidewall <NUM> connects the first face <NUM> to the second face <NUM>. At least parts of the sidewall <NUM> include a recess <NUM>, similar to recess <NUM> described with respect to the embodiment shown in <FIG>. However, in contrast to recess <NUM>, recess <NUM> comprises a plurality of concave recesses <NUM>. Accordingly recess <NUM> creates a surface, which is comparable to a golf ball, with the exception that the concave recesses <NUM> may have varying diameters. The additional concave recesses <NUM> further attenuate noise signals and are shaped to trap the sound waves of the noise signal within them. It will be appreciated that other shapes, such as a plurality of triangular recesses (not shown), may alternatively also be used to further reduce the noise signals.

Turning to <FIG>, there are shown two embodiments of an ultrasonic flow metering device in accordance with the present disclosure.

In a first embodiment shown in <FIG>, the ultrasonic flow metering device <NUM> includes a housing <NUM> for supporting first and second transducers <NUM>, <NUM> and respective first and second coupling members <NUM>, <NUM>. The coupling members <NUM> and <NUM> in this embodiment are both shaped per the embodiment shown in <FIG>.

The first transducer <NUM> is arranged within the housing <NUM> in such a way that it is directly connected to the first face of the first coupling member <NUM>. The second transducer <NUM> is received within the housing <NUM> such that it is directly connected to the first face of the second coupling member <NUM>. The second faces of the two coupling members <NUM>, <NUM> are pressed against the outer surface of a fluid conduit <NUM>. The first and second transducers <NUM>, <NUM> are arranged on the same side of the fluid conduit <NUM> and offset along the longitudinal direction of said fluid conduit <NUM>.

The first and second coupling members, <NUM>, <NUM> are arranged within the housing <NUM> such that their respective recesses <NUM>, <NUM> face each other and create a gap <NUM> there between. In this embodiment, gap <NUM> is an air gap, which acts to weaken unwanted noise signals <NUM> that do not enter flow conduit <NUM> before being received by the respective other transducer. Only ultrasonic wave signals <NUM> that enter the conduit <NUM> and are reflected back to the receiving transducer will cross the air gap with full signal strength. The gap <NUM> shown in <FIG> can, therefore, be considered as an attenuating gap acting to reduce noise signals <NUM> and improve the quality of the ultrasonic signal received by the transducers <NUM>, <NUM>.

It will be understood that both transducers <NUM> and <NUM> may work as both transmitters and receivers, at different times during the flow metering process. Both transducers <NUM> and <NUM> of the depicted embodiment can, therefore, also be described as transceivers. Accordingly, signals <NUM> and <NUM> also travel in a direction opposite to the arrows shown in <FIG>.

It should also be understood that the housing <NUM> is only represented as a transparent black box and may include further components such as power supply and signal lines for connecting the transducers <NUM> and <NUM> to a control unit not shown. Of course, the connection between the transducers <NUM> and <NUM> and a corresponding control unit may also be realised wirelessly, in which case the housing <NUM> further includes a wireless communication device connected to the transducers <NUM>, <NUM>.

Finally, <FIG> shows that the protrusions of the two coupling members <NUM>, <NUM> extend in substantially opposite directions. The protrusions are fixed within the housing such that they act as anti-rotation members ensuring that the coupling members <NUM> and <NUM> are always aligned with each other in such a way that the recessed surfaces face each other.

Another embodiment of an ultrasonic flow metering device <NUM> according to the present disclosure is shown in <FIG>. The ultrasonic flow metering device <NUM> of <FIG> is substantially identical to the flow metering device <NUM> of <FIG>. However, rather than providing an air gap <NUM> between the coupling members, a spacer element <NUM> is arranged within the gap. The spacer element may be made from a material that is stiffer than a material of the first and second coupling members <NUM>, <NUM>. Accordingly, the spacer element <NUM> will ensure that the gap between the first and second coupling members <NUM>, <NUM> will be maintained even if the coupling members <NUM>, <NUM> are compressed and try to expand towards each other. At the same time, the spacer element <NUM> acts to attenuate the noise signals, due to its shape and material. The spacer element <NUM> may be a hollow box and made from a highly attenuating material, such as cork.

<FIG> schematically illustrate a method for manufacturing a flow metering device. In particular, the steps shown in <FIG> schematically illustrate a method for moulding an elastic coupling member directly onto a corresponding transducer to form a transducer module. Moulding the elastic coupling member directly onto the transducer may advantageously reduce the number and / or volume of air gaps between the transducer and the coupling member. Air gaps may attenuate the acoustic signal produced by the transducers. Due to the reduced number or size of air gaps achieved by the described method, the SNR (signal-to-noise ratio) of the acoustic signal may increase.

Turning to <FIG>, there is shown a schematic representation of an A-plate <NUM> that forms part of a mould. The A-plate <NUM> comprises a first cavity <NUM>. The first cavity <NUM> is sized and shaped to receive a transducer <NUM> of the flow metering device. In other words, the shape of the first cavity <NUM> of the A-plate <NUM> matches the shape of the transducer <NUM>.

The transducer <NUM> is inserted and held within the first cavity <NUM> of the A-plate <NUM>. The transducer <NUM> may be retained within the first cavity <NUM> by any known means, such as fastening members, particularly fastening screws or bolts arranged on the A-plate <NUM>. Of course it may also be possible to retain the transducer in other ways, such as by means of a press-fit between the cavity and the transducer or geometric retaining structures, such as back tapers.

<FIG> illustrates a second step, in which a coupling surface <NUM> of the transducer is prepared for the moulding process with a primer <NUM>. In the illustration of <FIG>, the primer is a spray-on primer, such as Shellac resin. The primer may be automatically or manually applied to the coupling surface <NUM> of the transducer <NUM>. Of course, any other form of primer may be used to prepare the coupling surface <NUM>. In some embodiments, a primer may not be required at all.

Turning to <FIG>, the A-plate <NUM> of the mould is connected with a B-plate <NUM> to form the mould for adding the elastic coupling member to the coupling surface <NUM> of the transducer <NUM>. The B-plate <NUM> comprises a second cavity <NUM> with an opening facing the coupling side <NUM> of the transducer <NUM>. As will be appreciated, the shape of the second cavity <NUM> represents an inverse of the shape of a desired coupling member. The second cavity <NUM> may be connected, in a known way, to a runner <NUM> for injecting elastomeric material into the second cavity <NUM>. Once the elastomeric material is injected into the second cavity <NUM>, the elastic coupling member is formed and, at the same time, connected to the coupling surface <NUM> of the transducer <NUM>.

When the injected elastomeric material has set, the transducer module comprising the transducer <NUM> and a corresponding coupling member (e.g. coupling member <NUM> shown in <FIG>), is ejected from the mould. The transducer module may then be inserted into a housing of the flow metering device, as will be described in more detail with reference to <FIG>.

<FIG> schematically shows parts of a flow metering device of the present disclosure. <FIG> shows a part of a housing <NUM> of a flow metering device in which a first transducer module comprising the transducer <NUM> and the coupling member <NUM> is received. Similar to the embodiments described with reference to <FIG>, the housing <NUM> may also comprise a second transducer module, which is not shown in <FIG> for simplicity. The transducer module produced by the injection moulding process illustrated in <FIG> may be inserted into corresponding cavities of the housing <NUM>. The cavities may match the shape of the transducer module.

Claim 1:
An ultrasonic flow metering device (<NUM>) comprising:
a first coupling member (<NUM>), the first coupling member (<NUM>) being configured for acoustically coupling a first ultrasonic transducer (<NUM>) to a fluid conduit (<NUM>), the first coupling member comprising:
a first face (<NUM>) adapted to be connected to the first ultrasonic transducer (<NUM>) and a second face (<NUM>) adapted to be connected to the fluid conduit (<NUM>); and
at least one sidewall (<NUM>) connecting the first and second faces (<NUM>, <NUM>), wherein the at least one sidewall (<NUM>) comprises a recess (<NUM>; <NUM>) extending from the second face (<NUM>);
a second coupling member (<NUM>), the second coupling member (<NUM>) being configured for acoustically coupling a second ultrasonic transducer (<NUM>) to the fluid conduit (<NUM>), the second coupling member (<NUM>) comprising:
a first face (<NUM>) adapted to be connected to the second ultrasonic transducer (<NUM>) and a second face (<NUM>) adapted to be connected to the fluid conduit (<NUM>); and
at least one sidewall (<NUM>) connecting the first and second faces (<NUM>,<NUM>), wherein the at least one sidewall (<NUM>) comprises a recess (<NUM>; <NUM>) extending from the second face (<NUM>);
characterized in that the first and second coupling members (<NUM>, <NUM>) are elastic and arranged with respect to each other such that their respective recesses (<NUM>, <NUM>) face each other and form a gap (<NUM>) between the coupling members (<NUM>, <NUM>), and such that contact between the first and second coupling members, that would occur if there were no recesses, is avoided.