Patent Publication Number: US-11644352-B2

Title: Compact ultrasonic flowmeter

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/376,620, filed Apr. 5, 2019, which claims priority to European Application No. 18165942.6, filed Apr. 5, 2018, both of which are incorporated herein by reference in their entireties. 
     FIELD OF THE INVENTION 
     The present invention relates to ultrasonic flowmeters for measuring flowrate and other fluid related data, the flowmeters comprising a flow tube and a flowmeter housing containing flowmeter components including a printed circuit board with surface components on one side. 
     BACKGROUND OF THE INVENTION 
     Electronic or steady state flowmeters, such as ultrasonic flowmeters, are increasingly being used as utility meters for measuring water consumption. Compared to traditional mechanical flowmeters, an ultrasonic flowmeter provides the advantage of having no moving parts. Another advantage is the electronic nature of ultrasonic flowmeters. As ultrasonic flowmeters include a power source for powering the measurement circuit, often a battery, a radio communication device for external communication may also be integrated. Furthermore, ultrasonic flowmeters often include onboard processing capabilities, making data processing available in the meter. With an increasing focus on environmental issues, including water scarcity, water metering is on the rise resulting in more metering points on a global scale. Additionally, advancements in sensor technology and data processing have made it possible to gather new types of data and to use that data for new purposes, such as leak detection, water quality assessments, etc., rather than just water consumption. 
     With an increasing number of metering points, water meter manufacturability becomes an important factor and even minor improvements may have a significant impact on the total cost of a metering infrastructure including tenth of thousands of meters. Hence, an improved more compact and manufacturing friendly ultrasonic flowmeter would be advantageous. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to wholly or partly overcome disadvantages and drawbacks of the prior art. More specifically, it is an object to provide a compact and manufacturing friendly ultrasonic flowmeter. 
     Thus, the above described object and several other objects are intended to be obtained in a first embodiment of the invention by providing a compact ultrasonic flowmeter for measuring flowrate and other fluid related data, comprising: a flow tube with a flow bore for passage of the fluid between an inlet and an outlet; a flowmeter housing associated with the flow tube; a printed circuit board arranged in the flowmeter housing and including a processor for controlling operations of the flowmeter; a meter circuit including two or more ultrasonic transducers provided on the printed circuit board and configured for operating the ultrasonic transducers to transmit and receive ultrasonic wave packets through the fluid; a display mounted on the printed circuit board and configured for displaying a measured flowrate and other fluid related data; and one or more battery packs for powering flowmeter operations including at least the processor and the meter circuit and the display; wherein the processor and the ultrasonic transducers are surface mounted on a lower side of the printed circuit board and the display is mounted on an upper side of the printed circuit board. 
     By arranging surface mounted devices on one side of the printed circuit board and through hole components on the opposite side, an effective and reliable manufacturing process may be achieved. Additionally, by fitting electronic components associated with core flowmeter functionality onto one printed circuit board, a compact ultrasonic flowmeter is achievable. 
     In one embodiment, the flowmeter housing may be integrated with the flow tube, e.g. by being cast as a fully integrated monolithic component. Embodiments of the compact ultrasonic flowmeter may also be provided with a single printed circuit board wherein the processor and the ultrasonic transducers are surface mounted on a lower side of the single printed circuit board and the display is mounted on an upper side of the single printed circuit board. 
     By integrating the flowmeter housing with the flow tube and fitting all circuits and electronic components onto a single printed circuit board, a very compact and manufacturing friendly ultrasonic flowmeter is achieved. The compact ultrasonic flowmeter thus comprises only a single printed circuit board arranged in the flowmeter housing. 
     The ultrasonic flowmeter may further comprise a front plate provided with an opening for receiving a display, and the front plate may be arrange in flush with the display, such as 10-40 mm above the printed circuit board. Hereby the ultrasonic flowmeter is kept compact. 
     Additionally, the front plate may substantially cover the printed circuit board. Hereby the printed circuit board is shielded and protected by the front plate. The ultrasonic flowmeter described above may also comprise a container arranged on top of the printed circuit board, wherein the container is provided with a through-going opening  173  for receiving the display and configured to protect the printed circuit board and other components mounted thereon. 
     Moreover, the ultrasonic flowmeter may comprise a radio communication device mounted on the printed circuit board, wherein the radio communication device is electrically coupled to an antenna element via a radio circuit, and the antenna element is mounted on the container and releasably coupled to the radio circuit. Here, the antenna element may be mounted on a side face of the container. 
     Additionally, the radio communication device may be configured to detect whether it is electrically connected to the antenna element and the processor may be configured to determine that the container has been lifted above the printed circuit board based on input from the radio communication device, that the electrical connection to the antenna element has been disconnected. 
     The ability to determine whether the container has been lifted based on detection of the antenna element may provide a tamper detection functionality as the container and front plate shields and protects the printed circuit board including the metering circuit. 
     Further, the antenna element may be connected to the radio circuit via connectors provided on the printed circuit board and/or the antenna element. Also, the connectors and/or mating connector surfaces may be arranged on the printed circuit board along its periphery, corresponding to the position of the antenna element on the container. Such connectors may for example be of the spring contact connector type. 
     Additionally, the front plate may constitute a lid for the container and the container may contain a desiccant. 
     Furthermore, the ultrasonic transducers may be positioned on transducer areas provided on an outer surface of the flow tube, or on an upper surface of a bottom part of a separate flow meter housing mounted on a flow tube. 
     In one embodiment of the compact ultrasonic flowmeter described above, backing devices may be arranged on the printed circuit board opposite the transducers to providing a holding force pressing a lower side of the transducers against the transducer areas, i.e. the flow tube. Such backing devices may be mounted on top of the printed circuit board to apply the holding force to an area of the printed circuit board containing the ultrasonic transducers. The backing devices may comprise a backing element abutting the transducer and/or the printed circuit board and a restrained resilient member configured to provide the holding force. Furthermore, the backing device may include a bracket element arranged to displaceably receive the backing element and the resilient member in the form of a helical spring retained between the bracket element and the backing element. Additionally, a lower side of the ultrasonic transducers may be secured to the transducer areas by a non-hardening adhesive, such as a butyl containing adhesive. 
     Furthermore, the ultrasonic transducers may be mounted on islands provided in the printed circuit board being connected with the remaining printed circuit board via tongues of the printed circuit board containing copper traces for electrically connecting the ultrasonic transducers to the remaining meter circuit. Such design provides a certain resilience to the design and allows limited transducer displacement towards the flow tube. 
     Additionally, the ultrasonic flowmeter may be a utility meter for meter water consumption or a utility meter for metering fluid flow in a heat or cooling meter installation. The ultrasonic flowmeter described above may also additionally include a temperature probe for measuring the temperature of a fluid flowing through the flow tube. 
     Moreover, the ultrasonic flowmeter may be configured to include registers for storing meter data, such as flow-, volume- and/or consumption data. The ultrasonic flowmeter may also store other meter data, such as event- or performance data related to the operation of the meter or data related to other sensors (internal of external) connected to the meter. 
     The above described embodiments may each be combined with any of the other embodiments. These and other embodiments will be apparent from and elucidated with reference to the embodiments described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The compact ultrasonic flowmeter according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. 
         FIG.  1   a    shows a compact ultrasonic flowmeter, 
         FIG.  1   b    shows a transversal cross-section of an ultrasonic flowmeter, 
         FIG.  1   c    shows a longitudinal cross-section of an ultrasonic flowmeter, 
         FIG.  2    shows a compact ultrasonic flowmeter with an open flowmeter housing, 
         FIG.  3   a    shows the insides of the compact ultrasonic flowmeter, 
         FIG.  3   b    shows a longitudinal cross-section of the insides of the compact ultrasonic flowmeter, 
         FIG.  4    shows a printed circuit board of a compact ultrasonic flowmeter, 
         FIG.  5    shows a desiccant container including a front plate, 
         FIG.  6    shows a desiccant container without a front plate, 
         FIG.  7    shows an upper side of a printed circuit board of a compact ultrasonic flowmeter, 
         FIG.  8    shows a lower side of a printed circuit board of a compact ultrasonic flowmeter, and 
         FIG.  9    shows a cross-section of a transducer backing device. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1   a ,  1   b , and  1   c    illustrate a compact ultrasonic flowmeter  1  according to one embodiment of the invention. The flowmeter comprises a flow tube  11  with a flow bore  111  for passage of the fluid between an inlet  112  and an outlet  113 . A flowmeter housing  12  is formed as an integrated part of the flow tube thereby providing a compartment for meter components arranged at the flow tube to measure the flow rate of a fluid flowing in the flow bore. The flowmeter housing is closed-off by a lid  121  constituted by a locking ring  122  and a transparent cover element  124 . Between the lid and the flow meter housing a sealing element  123  is arranged to provide a hermetical seal. 
     Inside the flowmeter housing a printed circuit board (PCB)  13  including a processor  135  for controlling operations of the flowmeter is arranged. The PCB further includes a meter circuit (not shown) and two ultrasonic transducers  14  mounted on its lower side  131 . A lower side  141  of the ultrasonic transducers opposite an upper side connected to the PCB, is arranged against an outer surface of the flow tube  11 . The meter circuit is configured for operating the ultrasonic transducers to transmit and receive ultrasonic wave packets through the flow tube and a fluid present in the flow bore. On an upper side  132  of the PCB  13  a display  15 , configured for displaying a measured flowrate and other fluid related data, is mounted. A socket connector  155  and a set of diodes  156  configured for infra-red communications are also provide on an upper side of the PCB. 
     Referring to  FIGS.  7  and  8   , the lower side of the PCB contains the surface mounted devices (SMDs), such as the piezoelectric ultrasonic transducers  14  and the processor  135 , and the upper side of the PCB contains through hole components mounted by a selective soldering process. The upper side components, including the display, are provided with pins  151  which are arranged in through holes in the printed circuit board and selective soldered on the lower side of the PCB. By mounting SMDs on one side only, an effective and reliable manufacturing process may be achieved. Additionally, by mounting the through hole components on the upper side  132  and soldering these on the lower side, the manufacturing process may be further improved. However, the selective soldering process associated with the through hole components requires a certain spacing between SMDs and areas of the PCB in which selective soldering is used. 
     The flowmeter shown in  FIG.  1   a - 1   c    further includes two battery packs  16  for powering flowmeter operations including the processor, the meter circuit and the display. In alternative embodiments fewer or more battery packs may also be used. To effectuate a compact and handy design suitable for automated mass production, the battery packs are mounted directly on the PCB by battery pins  161  extending through plated through holes  161   a  in the PCB as shown in  FIG.  3   b    and  FIG.  4   . The battery pins are compliant pins that are deformed upon insertion into the plated through holes. The deformation of the battery pins ensure the necessary electrical contact between the pin and the PCB copper traces and secures the battery pact to the PCB. In the shown embodiment, the battery cells  162  are mounted in battery holders  163  including the battery pins. However, in alternative embodiments the battery pins may be fixed directly to the poles of the battery cells, e.g. by welding. Each of the battery holders comprises a rigid element  164  provided with two battery pins in opposite ends. A battery cell may be fixated between the pins as a sub-assembly, which subsequently can be mounted on a PCB. 
     As seen from  FIG.  1   a - c   , the battery packs are mounted on the lower side of the PCB and extend in a longitudinal direction of the flowmeter along the flow tube. With the PCB mounted in the housing, the battery packs are arranged on opposite sides of the flow tube providing a compact design. By arranging the batteries underneath the PCB, the space inside the housing is fully utilized. Further, the batteries are supported on a bottom face of the housing thereby maintaining the battery pins in the plated through holes  161   a.    
     The ultrasonic flowmeter further comprising a radio communication device  18  mounted on the lower side of the printed circuit board. The radio communication device is connected to a radio circuit implemented on the PCB. Via the radio circuit the communication device is electrically coupled to an antenna element  181  as will be further explained below. The radio communication device serves to transmit meter data via radio frequency communication to a back end- or head end system (HES) wherein meter data is stored and processed, such as for billing purposes. The radio communication device may provide both one-way and two-way communication between the flowmeter and head end system. Automated meter reading (AMR) advanced meter infrastructure (AMI) systems are commonly known for communicating with utility meters. In an AMI a communication path is established between the utility meter and the HES via a number of intermediate network devices such as data collectors, repeaters, routers gateways etc. The utility meters may deliver any data obtained by the meter or external sensors connected to it to the HES, however the capacity of the AMI and the battery capacity of the utility meters M will limit the amount of data that can be transmitted. The AMI may use any suitable technology for carrying data from the utility meter to the HES over one or more local area networks or wide area networks including connections to the open internet. The AMI may use any suitable wireless technology (e.g. wireless M-Bus, Narrow band IoT, SigFox, any cellular technologies or proprietary communication protocols) or any wired communication technologies (e.g. wired M-Bus, LON, Ethernet). 
     Still referring to  FIG.  1   a - 1   c   , a container  17  is provided on top of the PCB. The container comprises a compartment for containing a desiccant and the front plate  171  constitutes a lid for the container as seen from  FIGS.  5  and  6   . The desiccant ensures that moisture penetrating into the flowmeter housing, such as water molecules penetrating through its wall, are absorbed and thus does not negatively affect components arranged in the housing. The container further serves to protect or shield the PCB and components mounted thereon. As seen, only the display and diodes are visible as these are received in through-going openings  172 ,  173  provided in the container and the front plate. In an alternative embodiment no components or only the display may be received in openings in the container. 
     As seen from  FIGS.  3   a    and  5 , the container further includes an antenna element  181  mounted on its circumferential side face. In the shown embodiment, the antenna element is a piece of conducting material, such as a stamped out piece of metal, shaped to follow the outer contour of the container. In an alternative embodiment, the antenna element could be a patch antenna or a trace deposited directly on the side of the container. The antenna element  181  is connected to the radio circuit on the PCB via connectors  183 . The connectors engage with mating connector surfaces  184  arranged on the PCB, seen in  FIG.  4   . 
     The container and antenna element thus constitute an independent subassembly that may be manufactured and mounted in the housing during the final assembly of the flowmeter. Arranging the container on top of the PCB serves to protect the PCB and components mounted thereon. Further, a compact design is achieved as the container is designed to encompass components extending from the PCB. Also, the container serves to position the front plate 10-40 mm above the printed circuit board. 
     The radio communication device is configured to detect whether an electrical connection exists between the antenna element and its connectors  183  and the radio circuit. Based on input from the radio communication device, the meter processor  135  may thus determine whether the antenna element is connected to the radio circuit. Based on this determination, the processor may determine whether the container including the antenna element is properly mounted on top of the PCB or whether the container has been lifted above the PCB. Lifting of the container, i.e. disconnection of the antenna element, may indicate a tampering event or other unauthorized access to the meter electronics. If the processor determines that the antenna has been disconnected, the processor may store the event in a logger of the flowmeter and effectuate transmission, via the radio communication device, of an alarm or other information indicating a that a potential tampering event has taken place. The container subassembly thus also serves as a tamper detecting element designed to protect meter electronics and to warn about possible tampering. 
     As described above with reference to  FIG.  1   c   , a lower side  141  of the ultrasonic transducers are arranged against an outer surface of the flow tube  11 . The area of the flow tube receiving the transducers may be dedicated transducer areas wherein the thickness of the flow tube may be controlled to match the characteristics of the transducers. In alternative embodiments wherein the flowmeter housing constituted by a separate entity mounted on a flow tube (not shown), the transducers may be arranged against transducer areas provided on an upper or inside surface of a bottom part of the flow meter housing arranged to be in contact with a flowing medium in the flow tube, i.e. constituting part of the flow tube. 
     Referring to  FIG.  2    and  FIG.  4   , backing devices  19  are arranged on the PCB opposite the transducers. The backing devices are arranged to provide a holding force to the area of the PCB containing the ultrasonic transducers, thereby pressing the lower side of the transducers against the transducer areas, i.e. the flow tube. In  FIG.  2   , only one of two backing devices is shown to illustrate how the backing devices are mounted on mounting structures  125  extending from and integrated with the flow tube. By mounting the backing device directly to the flow tube, sufficient holding force may be obtained to keep the transducers in place for the duration of the lifetime of the meter. Each of the backing devices comprises a bracket element  192  fixed to the mounting structures and spring biased backing element  191  movable in a bore of the bracket element. A helical spring  193  is retained between the bracket element and the backing element providing the holding force. In the shown embodiment, the bracket element is fixed to the flow tube by screws but other fixing means may also be used, such as snap-mechanisms, etc. 
     Alternatively, the backing devices may be comprised by a resilient member secured to the mounting structure and an associated backing element abutting the printed circuit board. The resilient member may be a leaf spring or a piece of polymer or rubber material having a certain resilience. 
     Furthermore, a lower side of the ultrasonic transducers are secured to the transducer areas by a non-hardening adhesive, such as a butyl containing adhesive. The adhesive connects the transducers to the flow tube thereby improving the transfer of vibrations between the transducers and a fluid in the flow bore. The combined use of a backing device and a non-hardening adhesive ensure a durable construction wherein sufficient contact between the transducers and the flow tube is maintained for extended periods of operation. Good vibration- or signal transfer between the transducers and the fluid is important for the signal quality and may thus affect flow measurements. 
     As seen from  FIG.  7    and  FIG.  8    the ultrasonic transducers may additionally be mounted on displaceable islands  133  provided in the printed circuit board. The islands are connected with the remaining printed circuit board via tongues  134  of PCB containing providing a certain resilience. Hereby the part of the PCB containing the transducers may be displaced towards the flow tube to ensure good contact between the flow tube and the transducers. The resilience provided by the tongues also isolates the reminder of the PCB from transducer vibrations. Further, copper traces are provided on the PCB tongues to connect the transducers to the remaining meter circuit. 
     Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.