Flow meter flow tube and housing

Abstract

A flow meter for an ultrasonic flow meter, comprising: a flow tube having a through opening for passing a fluid between an inlet and an outlet, the flow tube comprising: a flow conduit of a first material, such as a metal, extending between the inlet and the outlet; a liner of a second material, such as a polymer-based material, extending along an inner surface of the flow conduit between the inlet and the outlet; a housing providing a compartment for a transducer and meter electronics, wherein the housing is connected to the liner by mounting on an interface that is an integral part of the liner.

Description

Technical Field

[0001] The invention relates to an ultrasonic flow meter, which comprises a housing and a flow tube, wherein the flow tube comprises an overmolded flow conduit. Background Art

[0002] Ultrasonic flow meters measure flow rate by using an ultrasonic transducer to transmit an ultrasonic signal through a flow channel. The operation of the ultrasonic transducer is controlled by an electrical circuit electrically connected to the transducer. Flow meters can be used to measure flow rate and consumption in utilities such as water or district heating.

[0003] There are different types of ultrasonic flow meters. Some ultrasonic flow meters are based on metal or brass flow tubes, and others are made entirely of polymers. Metal flow tubes have the advantage of being strong and impermeable, and can be used with hot liquids. However, metal flow tubes are also relatively expensive to produce, and may contain lead, which is generally considered undesirable. On the other hand, polymer-based flow tubes are generally cheaper, but may have the disadvantage of being less strong. Furthermore, polymer flow tubes may have the effect that the metal pipes supplying water are isolated from each other, which may be undesirable because the metal pipes supplying water are sometimes used as earthing (earthing or grounding) systems for electrical installations. Flow tubes based on metal pipes with a coated inner surface are known, but flow meters based on such flow tubes are still expensive to produce, especially due to the cost of the metal flow pipes.

[0004] There are also different concepts of ultrasonic flowmeters in terms of how the transducer is mounted on the flow tube. Some flowmeters are based on a flow tube provided with an opening for receiving the transducer, while other flowmeters use a complete flow tube with the transducer mounted on the outer surface. However, flowmeters with the transducer mounted on the outer surface are especially flowmeters with small flow tube diameters in the range of 5 to 15 mm (DN5 to DN15), and are only practically feasible when the flow tube is made of polymer. In such flowmeters, the ultrasonic signal is transmitted through the wall of the polymer flow tube, thereby eliminating any need for sealing the flow tube. For larger size flowmeters (for example, flowmeters from DN10, DN25 to DN50 and larger), the flow tube is typically made of metal and has an opening for the transducer. In particular, flowmeters with metal flow tubes can have a lining covering the inner surface of the metal flow conduit.

[0005] The flow meter also has a housing, which serves to enclose the measuring circuit, the battery and, optionally, the flow transducer. The housing must protect the components enclosed by the housing from moisture, and in particular, water must be prevented or minimized from entering the housing. The housing is usually made of a polymer, and the ultrasonic signal can be transmitted through the wall of the housing into the flow tube. The polymer is open to water diffusion, and water can diffuse through the polymer wall of the housing and can damage the components enclosed by the housing.

[0006] Therefore, there is a need for a flow meter that includes a flow tube that provides the advantages of both metallic and polymeric flow tubes and that can be combined with a housing that provides adequate protection against water ingress. Summary of the invention

[0007] An object of the present invention is to solve the above problems of the prior art and in particular to provide a flow meter comprising a housing that prevents water ingress and a flow tube that utilizes the advantages of both metal and polymer flow tubes and which can be manufactured using materials in a cost-effective and versatile manner. A further object of the present invention is to provide a flow meter having an extended life by improving the shielding of the electronic components from the measured fluid and water in the surrounding environment and preventing corrosion, hydrolysis and wear of the flow tube.

[0008] According to a first aspect of the present invention, there is provided an ultrasonic flow meter. The flow meter comprises: a flow tube having a through opening for passing a fluid between an inlet and an outlet, the flow tube comprising: a flow conduit of a metallic material extending between the inlet and the outlet; and a liner of a first polymer-based material extending between the inlet and the outlet along an inner surface of the flow conduit; a housing providing a compartment for a transducer and meter electronics, wherein the housing is connected to the liner by mounting on an interface that is an integral part of the liner.

[0009] An advantage of the present invention is that the metal flow conduit provides mechanical stability and the polymer liner provides high hydrolysis resistance and diffusion resistance. Due to the increased mechanical stability provided by the metal flow conduit, less filler can be provided in the polymer-based material used for the liner. Also, by using a combination of a metal flow conduit that provides strength and a polymer liner, the polymer-based material used for the liner can be made from a wider range of inexpensive polymers.

[0010] The lining protects the metal flow pipe from the fluid flowing in the flow pipe, thereby preventing corrosion of the flow pipe and, at the same time, preventing metal from the flow pipe from dissolving in the fluid flowing in the flow pipe.

[0011] The interface being part of the liner has the advantage that a separate prefabricated housing can be mounted on the polymer liner: no elements for mounting the housing are required on the metal flow pipe. Further, the housing can be made of a different material than the liner comprising the interface, which material can be metal or polymer. The polymer-based material for the housing can be different from the polymer-based material for the liner. This has the advantage that different flow meters optimized for measuring different fluids under different conditions can be provided from a collection of different prefabricated flow pipes and housings.

[0012] As an example, it may be advantageous to make the housing from a polymer-based material that has a higher resistance to water diffusion, so that the components enclosed by the housing are better protected. It should be noted that water diffusing into the housing is not limited to water flowing in the flow tube, but water in the surroundings of the housing will also diffuse through the walls of the diffusion-open meter housing. A flow meter such as a water meter may be submerged, or water may condense on the outer surface of the flow meter.

[0013] In the context of the present invention, a liner is to be understood as a covering of the inner surface of a flow tube which is otherwise exposed to the fluid. The interface is an integral part of the liner and is therefore to be understood as a part of the liner.

[0014] The flow conduit may be made of brass, steel, stainless steel, cast iron, aluminum, or any other suitable metal or alloy, and the liner may be made of a polymer-based material including a polymer and a filler.

[0015] Polymer based materials comprising fillers are also referred to as composite materials.In the context of the present invention, polymer based materials (or simply polymers) should be interpreted as compositions comprising one or more polymers and, where appropriate, one or more fillers.

[0016] Polymers and polymer-based composites have different resistances to diffusion and hydrolysis, depending on the nature of the functional groups constituting the backbone of the polymer and the amount of any fillers used therein. Adding fillers such as carbon fibers to a polymer structure to increase its mechanical stability tends to reduce its stability to diffusion and hydrolysis. Thus, the hydrolysis and diffusion processes are facilitated by adding fillers to polymer structures and even to polymer structures that are otherwise considered impermeable to water, providing a route for water to enter the structure at a microscopic or even atomic level.

[0017] The flow tube with flow conduit and liner of the present invention solves this problem by providing a metal flow conduit for mechanical stability and a polymer liner for high hydrolysis and diffusion resistance because less fillers can be provided in the polymer-based material. Also, by using a combination of a metal flow conduit for strength and a polymer liner, the polymer-based material for the liner can be made from a wider range of inexpensive polymers.

[0018] The polymer-based material for the liner may include fillers in a w / w ratio in the range of 1% to 20%, 1% to 10% or 1% to 5%. These relatively small amounts of fillers provide the liner material with excellent mechanical and chemical properties.

[0019] The liners may be provided in a thermoplastic material such that they can be manufactured by injection moulding and wherein the flow conduits are moulded onto the liners to create the flow tubes.

[0020] Thus, a flow meter can be obtained in an inexpensive manner which, by a suitable choice of the polymer-based first material, is sufficiently robust for handling and use.

[0021] By applying this so-called overmoulding, the flow tube can be manufactured in a very cost-effective manner. The interface being an integral part of the liner has the advantage that production is simplified, since the interface can be provided in the same overmoulding process as the liner, which reduces production costs.

[0022] The first polymer-based material may be based on one or more of the following polymers: polypropylene, PP; polycaprolactam, PA6; polyethylene, PE; cross-linked polyethylene, PEX. These polymers have the advantages of low cost and ease of use in overmolding processes. However, they do not have high mechanical strength and are to some extent open to water diffusion. The first polymer-based material may be a composite material reinforced by one or more of the following fillers: graphite, carbon, carbon fiber, glass fiber and metal powder. Fillers increase mechanical strength but also reduce diffusion resistance.

[0023] The flow meter may have a housing made of a second polymer-based material that is different from the first polymer-based material. Because the housing is not an integral part of the liner, it can be produced in a separate molding process using other materials and processes that are different from the materials and processes used to produce the liner. Therefore, it is advantageous to have a flow meter having a housing made of a second polymer-based material. It is particularly advantageous to provide a housing made of PPS. PPS has the advantages of high water diffusion resistance and high mechanical strength, however, is more expensive than PP, PA6, PE or PEX. Therefore, a flow meter comprising a combination of a liner made of a first polymer-based material including one or more of PP, PA6, PE or PEX and a housing made of a second polymer-based material including PPS provides an optimized solution, wherein the cost of the liner is reduced by using PP, PA6, PE or PEX, and the housing is optimized in terms of strength and minimizing water ingress into the housing by using PPS.

[0024] The second polymer-based material may be a composite material reinforced by one or more of the following fillers: graphite, carbon, carbon fiber, glass fiber and metal powder. In particular, PPS in combination with the above fillers exhibits extremely high resistance to water diffusion. Such a flow meter may be particularly useful as a water meter that may be submerged or susceptible to condensation of water on the surface of the meter. The combination may also be useful for cooling meters that may also experience condensation of water on their outer surfaces.

[0025] For heat meters the composition of the materials may be different, since the lining needs to be suitable for thermal fluids which may also include some chemicals, whereas the heat meter is not submerged and is unlikely to experience condensation of water, so the water-tightness of the shell is not so critical. Therefore, a heat meter having a lining made of a polymer based on one or more of PES, PSU, PPSU and a shell made of a polymer based on PA12, PPA or alternatively PPS may be advantageous, since PES, PSU, PPSU are suitable for protecting flow pipes from thermal fluids flowing in a heating system, and especially PA12 and PPA are low cost polymers that cost less than the polymer used for the lining.

[0026] For flow meters intended to measure flow of fluids including relatively aggressive chemicals, the composition of the materials may be different, as the liner needs to be suitable for protecting the flow conduit from the relatively aggressive chemicals. Thus, a flow meter having a liner made of a PEEK, PEKK or PEK based polymer and a housing made of a PA12, PPA or alternatively PPS based polymer may be advantageous, as PEEK, PEKK or PEK can resist aggressive chemicals, and especially PA12 and PPA are low cost polymers that cost less than the polymer used for the liner.

[0027] The lining may have sound absorbing properties and / or have an acoustic impedance that will deflect the ultrasound waves, so that undesirable reflections are minimized and the measurement accuracy is improved. For the selection of lining materials having these properties, reference is made to EP 1387149A1.

[0028] The liner may include sealing surfaces arranged at the inlet and outlet of the flow pipe. In order to increase the area of ​​the sealing surface, it may be advantageous that the liner and the flow pipe each have a conical shape at the inlet and outlet. The conical shape is manufactured on the inner surface of the flow pipe. When the flow pipe is overmolded, the liner will have a conical shape where it meets the conical inner surface of the flow pipe. This has the advantage of increasing the sealing surface without reducing the cross-sectional area of ​​the flow channel. Further, the conical shape supports the liner to prevent it from being pressed back into the flow pipe. The very thin wall of the flow pipe near the end of the pipe has the following advantage, the liner-metal joint will move towards the periphery of the flow pipe, so that it is protected from the mechanical forces of the fluid flowing in the flow pipe, which prevents the flow pipe from being delaminated due to the fluid being pressed between the liner and the flow pipe.

[0029] In a second aspect of the present invention, a method for manufacturing a flow meter according to the first aspect comprises the following steps: providing a metal flow conduit comprising one or more openings and a conical inner surface at an inlet and an outlet; arranging the flow conduit in an injection mold of a machine for overmolding; injecting a polymer-based material into the injection mold to produce a flow tube according to the present invention, the flow tube comprising a liner having an integral interface; and mounting a housing on the interface of the liner.

[0030] This production method is particularly advantageous because the overmoulding process is simplified by simply moulding the interface for the shell rather than moulding the shell as an integral part of the liner.Furthermore, the conical inner surface of the flow duct has the advantage of reducing mechanical stresses in the flow tube due to shrinkage of the liner as it cools.

[0031] The polymer of the polymer-based material used for the liner can be selected from the group consisting of: polysulfone (PSU), polyethersulfone (PES), polyphenylene ethersulfone (PPSU), polyphenylene sulfide (PPS), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polypropylene (PP) and polycaprolactam (PA6). Alternatively, if higher strength is required in the liner, the polymer can be selected from the group consisting of: polysulfone (PSU), polyethersulfone (PES), polyphenylene sulfide (PPS), polystyrene (PS), polyphthalamide (PPA) and polyamide (PA), especially polyamide 12 (PA12) prepared from 1,12-dodecanedioic acid.

[0032] The polymer-based material for the housing may also be selected from the above-mentioned group of polymers, especially PPS, PA12 and PPA may be advantageous for the housing.

[0033] Polysulfone is defined as a polymer in which the sulfone group (-S(O2)-) forms part of the main chain structure of the polymer. Examples include, but are not limited to, polysulfone (PSU), polyphenylene ether sulfone (PPSU) and polyether sulfone (PES).

[0034] Polysulfides are defined as polymers in which sulfide groups (-S-) form part of the main chain structure of the polymer. An example is polyphenylene sulfide (PPS).

[0035] Polyaryletherketone is defined as a polymer in which a combination of ether groups (—O—) and keto groups (—C(O)—) constitutes part of the main chain structure of the polymer. Examples include, but are not limited to, polyetherketone (PEK), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK).

[0036] The filler material of both the liner and the housing may be selected from the group consisting of graphite, carbon, carbon fiber, glass fiber and metal powder. The filler material constitutes a reinforcement and provides mechanical stability to the line and the housing, respectively.

[0037] The flow meter may be a consumption meter or a utility meter, such as a water meter, a gas meter, a heat meter, a cooling meter, an energy meter or a smart meter for chilled and / or hot water.

[0038] Consumption meters can be used in conjunction with district heating, district cooling and / or distributed water supply.

[0039] A consumption meter can be a legal meter, i.e. a meter that is subject to regulatory requirements. Such regulatory requirements may be requirements for measurement accuracy.

[0040] Further advantageous embodiments of the first and second aspects are disclosed in the description of embodiments.

[0041] In general, aspects of the invention may be combined and coupled in any possible way within the scope of the invention.These and other aspects, features and / or advantages of the invention will become clear from the embodiments described below and will be elucidated with reference thereto.

[0042] Although the present invention has been described in conjunction with specific embodiments, it should not be interpreted as being limited in any way to the examples given. The scope of the present invention should be interpreted in accordance with the appended claims. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. In addition, references such as "a" or "an" should not be interpreted as excluding multiple. The figure marks used in the claims for the elements indicated in the figures should not be interpreted as limiting the scope of the present invention. In addition, the individual features mentioned in different claims can be advantageously combined, and the mention of these features in different claims does not exclude that the combination of features is not possible and advantageous. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0044] Figure 1 An embodiment of an ultrasonic flow meter is presented, the ultrasonic flow meter comprising a housing mounted on an interface of a liner of a flow tube,

[0045] Figure 2 A flow tube is shown, the flow tube comprising a flow conduit and a liner providing an interface for mounting a housing,

[0046] Figure 3 Shows Figure 2 The cross section of the flow tube,

[0047] Figure 4 Shows Figure 1 The cross section of a flow meter comprising a measuring conduit within a flow tube,

[0048] Figure 5 yes Figure 2 Another display of a cross section of a flow tube,

[0049] Figure 6 The flow pipeline is shown,

[0050] Figure 7 An embodiment of an ultrasonic flow meter is presented, the ultrasonic flow meter comprising a housing made as an integral part of a liner,

[0051] Figure 8 Shows Figure 7 The cross section of the flow meter,

[0052] Fig. 9 Another embodiment of an ultrasonic flow meter is shown, the ultrasonic flow meter comprising a housing mounted on the interface of a liner of a flow tube,

[0053] Fig.10 Shows Fig. 9 The cross section of the flow meter in the longitudinal direction, and

[0054] Fig.11 Shows Fig. 9 The cross section of the flow meter in the transverse direction,

[0055] Fig. 12A shows a cross section of a flow tube having a liner creating sealing surfaces at the inlet and outlet of the flow tube,

[0056] Fig. 12B Shows Fig. 12A A magnified view of the inlet / outlet of the flow tube, where the liner has not yet cooled after overmolding and has not yet shrunk,

[0057] Fig. 12C Shows Fig. 12A Magnified view of the inlet / outlet of the flow tube, where the liner has cooled after overmolding and has shrunk, causing mechanical stresses in the flow tube and deformation of the liner,

[0058] Fig.13A showing a cross section of a flow tube having conical inner surfaces at the ends of the flow conduits at the inlet and outlet of the flow tube, and liners creating sealing surfaces at the inlet and outlet of the flow tube,

[0059] Fig. 13B Shows Fig.13A A magnified view of the inlet / outlet of the flow tube, where the liner has not yet cooled after overmolding and has not yet shrunk,

[0060] Fig. 13C Shows Fig.13A Magnified view of the inlet / outlet of the flow tube, where the liner has cooled after overmolding and has shrunk without mechanical stresses in the flow tube or deformation of the liner,

[0061] Fig.14 A cross section of a flow meter with a housing, a flow tube and a measuring conduit is shown. DETAILED DESCRIPTION

[0062] Reference Figure 1 , Figure 2 and Figure 3, shows a flow meter 1 comprising a housing 5 mounted on a flow tube 2. The flow tube 2 comprises a through opening for passing a fluid between an inlet 21 and an outlet 22. The through opening is also referred to as a flow channel 23. The flow tube further comprises an interface 25 for mounting the housing 5. The interface is provided with two through openings 24, which are arranged to align with the transducers of the ultrasonic flow meter arranged inside the housing.

[0063] The flow tube 2 includes a flow conduit 3 and a liner 4 extending along the inner surface of the flow conduit.

[0064] The flow conduit is made of a metal material (e.g., steel, stainless steel, cast iron, aluminum or brass) and comprises a plurality of through openings 31, such as Figure 5 and Figure 6 Best seen. The flow conduit may be cast or made from a standard length of pipe machined to include the openings, threads and other geometries shown. The flow conduit may include threads 32 or flanges (not shown) for connecting the flow tube to a connection conduit of a water distribution system.

[0065] The liner is cast or molded around the flow conduit (e.g., by a known overmolding process) to cover the inner surface of the flow conduit and provide an interface 25 for mounting the housing 5 on the outer surface of the flow conduit. The overmolding covers at least portions of the outer surface of the flow conduit. The interface may be provided with threads 251 for mounting the housing. Such threads may be provided by metal elements molded into the interface. The interface 25 is an integral part of the liner 4 and is made of the same material as the liner. The interface may be molded together with the rest of the liner in one overmolding process. The liner 4 including the interface 25 extends from the inner surface of the flow conduit 3, through one or more holes 31 in the flow conduit, to the outside of the flow conduit, where the interface 25 is arranged and is an integral part of the liner. The interface includes one or more surfaces for arranging a sealing device (e.g., an O-ring or a gasket (not shown)) between the housing and the interface. The sealing device may preferably be arranged around two through openings 24 provided in the interface. The two through openings in the interface extend through the holes 31 in the liner and the flow conduit, so that the flow channel 23 can be directly entered from the interface 25. When the housing is mounted on the interface, the housing is in direct contact with the flow channel and the fluid flowing in the flow channel. A sealing arrangement between the housing 5 and the interface 25 is arranged to prevent the fluid from escaping from the flow tube.

[0066] In the illustrated embodiment, the liner provides an impermeable membrane and completely covers the inner surface of the flow conduit. Therefore, the fluid flowing through the flow conduit does not come into contact with the flow conduit. The liner protects the flow conduit from the fluid flowing in the flow conduit and prevents corrosion of the flow conduit. Further, the liner prevents metal from the flow conduit from dissolving into the fluid. However, metal pipes that may be used in a water supply system in which the flow meter is installed can be connected to the metal flow conduit via threads 32. In this way, electrical connection of the pipes on each side of the flow meter is achieved. In some installations, galvanic isolation is not ideal. In another embodiment, the liner can be configured to cover only a portion of the flow conduit. The liner can be arranged at the inlet and outlet to create a sealing surface for sealing the connection to the pipe of the water supply system, where the flow meter is installed as FIG. 13A to FIG. 13C Installed as shown.

[0067] The liner comprising the interface is made of a polymer-based material. The polymer-based material may be a composite material including a filler, which increases the strength of the polymer-based material. Polypropylene (PP), polycaprolactam (PA6), polyethylene (PE) and cross-linked polyethylene (PEX) are preferred polymers for the liner because they are cheap and easy to use in the overmolding process. The liner may include one or more of these polymers.

[0068] The housing 5 is mounted on the interface 25 as described above. The housing includes a cup-shaped element 51 provided with a cover 52. The cover may be provided with a transparent window. The housing is adapted to accommodate the electrical components of the ultrasonic flow meter, including a piezoelectric transducer, a control circuit arranged on a printed circuit board (PCB), a communication device for radio frequency communication, a battery pack for providing power, and the housing may further contain a display and other components visible through the transparent window. The transducer is arranged inside the housing to transmit an ultrasonic signal through the flow channel to generate a signal or value indicating the flow rate of the fluid flowing through the flow tube. The transducer arranged inside the housing contacts the fluid in the flow tube through the through openings in the wall of the housing and the interface, and thus can transmit and receive ultrasonic signals through the fluid inside the flow tube.

[0069] The housing is adapted to keep water away from components contained inside the housing. A sealing device is provided between the lid and the cup. The housing is made of a polymer-based material. The polymer-based material may be a composite material including a filler to increase the strength of the polymer. The polymer is open to water diffusion. A desiccant may be contained inside the housing to absorb water that diffuses from the outside, through the walls of the housing, to the interior of the housing. Polyphenylene sulfide (PPS)-based polymers are less open to diffusion and have mechanical properties suitable for manufacturing the housing. PPS is a preferred polymer material for the housing.

[0070] The filler material of both the liner and the housing may be selected from the group consisting of graphite, carbon, carbon fiber, glass fiber and metal powder. The filler material constitutes a reinforcement and provides mechanical stability to the line and the housing, respectively.

[0071] exist Figure 4 and Fig.14 In FIG. 5 , the flow meter is shown to include a measuring conduit 6 arranged in the flow channel. The liner may be provided with recesses or protrusions for fixing the measuring conduit inside the flow tube. As an alternative, the liner may also provide the measuring conduit, in that the measuring conduit is molded as an integral part of the liner.

[0072] The measuring pipe may contain a flow straightener 61 arranged to condition the fluid flowing through the flow tube, for example to reduce rotation, asymmetric flow profiles or other unintended flow characteristics. The liner may be provided with recesses or protrusions for fixing the flow straightener inside the flow tube.

[0073] The flow meter may also include a flow insert (not shown) comprising two or more reflectors arranged in the flow channel to direct the ultrasonic signal from the transmitting piezoelectric transducer to the receiving piezoelectric transducer in such a way that the ultrasonic signal propagates parallel to the direction of the flow tube (i.e., parallel to the central axis of the flow tube). As an alternative to the flow insert, the reflectors may be overmolded by the liner or molded into the liner. As a further alternative, the reflectors may be omitted and the ultrasonic signal may be reflected by the metal wall of the flow conduit. If the reflectors are omitted, it may be advantageous to tilt the ultrasonic transducer at an oblique angle relative to the longitudinal direction of the flow tube. This is particularly advantageous in that the ultrasonic transducer may be inclined at an oblique angle relative to the longitudinal direction of the flow tube. Fig.14 Displayed in.

[0074] refer to Figure 7 and Figure 8 , shows another embodiment of a flow meter. In this embodiment, the housing 5 is made as an integral part of the liner 4, i.e. the liner is formed monolithically with the housing. Therefore, the liner does not provide an interface 25 for mounting the housing. Since the housing is made as an integral part of the liner, no openings are provided in the flow duct except for the inlet 21 and the outlet 22.

[0075] Figures 9 to 11 Another embodiment of an ultrasonic flow meter is shown in which the housing is connected to the interface of the liner and is held in place by a locking mechanism 8. The locking mechanism includes a plurality of locking pins 81 adapted to be received in openings in the interface of the liner. When the housing is mounted on the interface 25 of the liner, the locking pins extend through the openings in the liner and the openings in the housing, whereby the housing is locked to the interface of the liner. Alternatively, the housing 5 can be locked to the interface by using screws extending through holes in the housing to holes 251 in the interface.

[0076] The flow meter can advantageously be an ultrasonic flow meter, such as a through-time flow meter, which is arranged to measure the flow rate of the fluid flowing in the flow channel 23 by using the operating principle of a through-time flow meter, i.e., wherein an ultrasonic signal is emitted by one transducer and received by another transducer, and wherein the arrival time difference between the oppositely propagating signals is measured and converted into a flow rate.

[0077] The flow tubes are advantageously manufactured based on flow tubes made from standard pipes, such as extruded pipes, seamless pipes or welded pipes. The standard pipes are cut and processed as follows: Figure 6 A flow conduit is shown, comprising threads and a plurality of openings.

[0078] The flow duct is prepared for overmolding and is arranged in an injection mold designed for overmolding. Preparing the duct for overmolding may include one or more of the following steps: heating the duct, cleaning the duct, sandblasting the duct coating or otherwise surface treating the duct, in particular to improve the adhesion of the liner. The liner is made by injection molding, and the melt is injected into the mold and into the flow duct via a through opening 31 provided in the lower wall of the flow duct. In another embodiment, other or multiple openings may be used to inject the melt into the flow duct. The mold is designed with one or more cores so that a flow channel 23 is provided. In one embodiment, the mold is designed so that an interface 25 for mounting the housing is produced as an integral part of the liner. In other embodiments, the mold is designed so that the liner and the housing are made as an integral part. Therefore, the liner, which may include the housing, is molded onto the flow duct.

[0079] The liner is arranged to create sealing surfaces 201 at the inlet and outlet of the flow tube, which are illustrated in Figures 12-13. The sealing surface must be aligned with the end of the flow tube and have a surface area that is large enough to provide an adequate seal when placed directly against the end of the connecting tube or compressing the sealing device between the sealing surface and the end of the connecting tube. In order to increase the surface area of ​​the sealing surface, the size of the flow tube is reduced at the end of the tube to create an enlarged sealing surface 201 area without reducing the cross-sectional area of ​​the flow channel 23. The liner is overmolded onto the flow tube and will shrink when cooled. If the liner extends around the end of the flow tube ( Fig. 12B ), or extending around sharp edges at each end of the flow, then pipe stresses may develop in the flow tube as the liner cools and hardens ( Fig. 12C To avoid such stresses, the flow tube and the liner may each have conical inner surfaces 202 facing each other at the inlet and outlet of the flow tube, thereby creating a sealing surface with an increased surface area during the overmolding process without creating stresses in the flow tube ( Fig. 13Band Fig. 13C ). In particular, the flow duct may have conical inner surfaces and duct ends at the inlet and outlet of the flow duct. The conical shape will have the effect that when the liner cools, hardens and shrinks during the overmoulding process, it will slide into the flow duct and align with the duct ends without generating mechanical stresses in the flow duct.

[0080] Although the present invention has been described in conjunction with specific embodiments, it should not be construed as being limited in any way to the examples given. The present invention may be implemented in any suitable manner; and the scope of the present invention should be interpreted in accordance with the appended set of claims. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An ultrasonic flow meter (1), comprising: - a flow tube (2) having a through opening for the passage of a fluid between an inlet (21) and an outlet (22), comprising: - a flow duct (3) of metallic material, the flow duct extending between the inlet (21) and the outlet (22); and - a lining (4) of a first polymer-based material extending along the inner surface of the flow duct (3) between the inlet and the outlet; - a housing (5) which provides a compartment for the transducer and the meter electronics, Therein, the shell (5) is connected to the liner (4) by being mounted on an interface (25) which is an integral part of the liner (4).

2. The flow meter according to claim 1, wherein: The first polymer-based material is based on one or more of the following polymers: polypropylene, PP; polycaprolactam, PA6; polyethylene, PE; cross-linked polyethylene, PEX.

3. A flow meter according to any one of the preceding claims, wherein: The first polymer-based material is a composite material reinforced with one or more of the following fillers: graphite, carbon, carbon fiber, glass fiber, and metal powder.

4. The flow meter according to claim 1 or 2, wherein: The housing (5) is made of a second polymer-based material different from the first polymer-based material.

5. The flow meter according to claim 4, wherein: The second polymer-based material includes PPS.

6. The flow meter according to claim 5, wherein: The second polymer-based material is a composite material reinforced with one or more of the following fillers: graphite, carbon, carbon fibers, glass fibers, and metal powders.

7. The flow meter according to claim 5, wherein: The interface (25), being an integral part of the liner, comprises threads (251) for mounting the housing (5).

8. The flow meter according to claim 7, wherein: The threads (251) are provided by metal elements moulded into the interface (25).

9. The flow meter according to claim 5, wherein: The housing (5) is locked to the interface (25) which is an integral part of the liner (4) by one or more locking pins (81) received in openings in the interface (25).

10. The flow meter according to claim 5, wherein: One or more sealing means are arranged between the interface (25) which is an integral part of the liner and the housing (5).

11. The flow meter according to claim 5, wherein: The liner (4) includes sealing surfaces (201) arranged at the inlet (21) and outlet (22) of the flow tube (2).

12. The flow meter according to claim 11, wherein: The liner and the flow duct each have a conical inner surface (202) at the inlet (21) and outlet (22) of the flow tube (2).

13. The flow meter according to claim 4, wherein: The first polymer-based material comprises one or more polymers selected from the group consisting of: PES, PSU, PPSU, and wherein the second polymer-based material comprises one or more polymers selected from the group consisting of: PA12, PPA, PPS.

14. The flow meter according to claim 4, wherein: The first polymer-based material comprises one or more polymers selected from the group consisting of: PEEK, PEKK, PEK, and wherein the second polymer-based material comprises one or more polymers selected from the group consisting of: PA12, PPA, PPS.

15. A method of manufacturing a flow meter according to any one of the preceding claims, the method comprising the steps of: - providing a metal flow conduit (3) comprising one or more openings (31) and conical inner surfaces (202) at the inlet (21) and outlet (22); - arranging the flow duct (3) in an injection mold of a machine for overmolding; - injecting a polymer-based material into the injection mold to produce a flow tube (2) comprising a liner (4) having an integral interface (25); and The housing (5) is mounted on the interface (25) of the liner (4).

Images