阅读说明：本技术 流量计的流动管和壳体 (Flow tube and housing for a flowmeter ) 是由 彼得·施密特·劳森 马斯·安德森 于 2020-05-01 设计创作，主要内容包括：一种用于超声波流量计的流量计,包括：流动管,该流动管具有用于使流体在入口与出口之间通过的贯通开口,该流动管包括：比如金属的第一材料的流动管道,该流动管道在该入口与该出口之间延伸；比如基于聚合物的材料的第二材料的衬里,该衬里沿着该流动管道的内表面在该入口与该出口之间延伸；壳体,该壳体为换能器和计量电子器件提供隔间,其中该壳体通过安装在作为该衬里的一体部分的界面上而连接到该衬里。(A flow meter for an ultrasonic flow meter comprising: a flow tube having a through opening for passing fluid between an inlet and an outlet, the flow tube comprising: a flow conduit of a first material, such as 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 duct between the inlet and the outlet; a housing providing a compartment for the transducer and meter electronics, wherein the housing is connected to the liner by being mounted on an interface that is an integral part of the liner.)

1. An ultrasonic flow meter (1) comprising:

-a flow tube (2) having a through opening for passing a fluid between an inlet (21) and an outlet (22), comprising:

-a flow duct (3) of metallic material extending between the inlet (21) and the outlet (22); and

-a liner (4) of a first polymer-based material extending along an inner surface of the flow duct (3) between the inlet and the outlet;

a housing (5) providing a compartment for the transducer and meter electronics,

wherein the shell (5) is connected to the lining (4) by being mounted on an interface (25) which is an integral part of the lining (4).

2. The flowmeter of claim 1, wherein the first polymer-based material is based on one or more of the following polymers: polypropylene, PP; polycaprolactam, PA 6; polyethylene, PE; crosslinked polyethylene, PEX.

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

4. The flow meter according to any of the preceding claims, wherein the housing (5) is made of a second polymer-based material different from the first polymer-based material.

5. The flow meter of claim 4, wherein the second polymer-based material comprises PPS.

6. A meter according to claim 4 or 5, wherein the second polymer-based material is a composite material reinforced with one or more of the following fillers: graphite, carbon fiber, glass fiber, and metal powder.

7. A meter according to any of the preceding claims, wherein the interface (25) being an integral part of the liner comprises a thread (251) for mounting the casing (5).

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

9. A meter according to any of the preceding claims, wherein the casing (5) is locked to the interface (25) being an integral part of the liner (4) by one or more locking pins (81) received in openings in the interface (25).

10. A meter according to any of the preceding claims, wherein one or more sealing means are arranged between the interface (25) being an integral part of the liner and the casing (5).

11. A meter according to any of the preceding claims, wherein the liner (4) comprises sealing surfaces (201) arranged at the inlet (21) and outlet (22) of the flow pipe (2).

12. A meter according to claim 11, wherein the liner and the flow conduit each have a conical shape (202) at the inlet (21) and outlet (22) of the flow tube (2).

13. The flow meter according to any of the preceding claims, wherein the polymer-based first 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 any of claims 1 to 12, wherein the polymer-based first material comprises one or more polymers selected from the group consisting of: PEEK, PEKK, PEK, and wherein the polymer-based second 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 of the preceding claims, the method comprising the steps of:

-providing a metal flow conduit (3) comprising one or more openings (31) and a conical inner surface (202) at an inlet (21) and an outlet (22);

-arranging the flow duct (3) in an injection mould of a machine for overmoulding;

-injecting a polymer-based material into the injection mould to produce a flow tube (2) according to any one of claims 1 to 14, the flow tube comprising a liner (4) having an integral interface (25); and

the shell (5) is mounted on the interface (25) of the liner (4).

Technical Field

The present invention relates to an ultrasonic flow meter comprising a housing and a flow tube comprising an overmolded flow conduit.

Background

Ultrasonic flow meters utilize an ultrasonic transducer to transmit an ultrasonic signal through a flow passage to measure a flow rate. 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 rates and consumption of utilities such as water or district heating.

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 impervious to water 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 less expensive, but may have the disadvantage of being less robust. Also, the polymer flow pipe may have an effect that the metal pipes of the water supply are isolated from each other, which may be undesirable because the metal pipes of the water supply are sometimes used as a grounding system for electrical devices. Flow tubes based on metal tubing having 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 tubing.

Different ultrasonic flow meter concepts also exist as to how the transducer is mounted on the flow tube. Some flow meters are based on flow tubes provided with openings for receiving transducers, while others use a fully rectified tube with transducers mounted on the outer surface. However, flow meters with transducers mounted on the outer surface are particularly those with small flow tube diameters in the range of 5 to 15 millimeters (DN5 to DN15) and are only practically feasible when the flow tube is made of a polymer. In such meters, the ultrasonic signal is transmitted through the wall of the polymeric flow tube, thereby eliminating any need for sealing of the flow tube. For larger sized flow meters (e.g., from DN10, DN25 to DN50 and larger), the flow tube is typically made of metal and has openings for the transducers. Particularly those having a metallic flow tube, may have a liner covering the inner surface of the metallic flow conduit.

The flow meter also has a housing for enclosing the measurement circuitry, the battery, and optionally also the flow transducer. The housing must protect the elements enclosed by the housing from moisture, and in particular, water must be prevented or minimized from entering the housing. The housing is typically made of a polymer and the ultrasonic signal may be transmitted through the wall of the housing into the flow tube. The polymer is open to water diffusion and water may diffuse through the polymer wall of the housing and may damage the elements enclosed by the housing.

Therefore, there is a need for a flow meter comprising 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.

Disclosure of Invention

It is an object of the present invention to solve the above mentioned problems of the prior art and in particular to provide a flow meter comprising a housing preventing water ingress and a flow tube which utilizes the advantages of both metallic and polymeric flow tubes and which can be manufactured in a cost effective and versatile manner using materials. It is a further object of the present invention 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 tubes.

According to a first aspect of the present invention, an ultrasonic flow meter is provided. The flowmeter includes: a flow tube having a through opening for passing 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 along an inner surface of the flow conduit between the inlet and the outlet; a housing providing a compartment for the transducer and meter electronics, wherein the housing is connected to the liner by being mounted on an interface that is an integral part of the liner.

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

The liner protects the metal flow conduit from the fluid flowing in the flow conduit, thus preventing corrosion of the flow conduit. At the same time, metal from the flow conduit is prevented from dissolving in the fluid flowing in the flow conduit.

The interface as part of the liner has the advantage that a separate prefabricated shell can be mounted on the polymer liner: no elements for mounting the housing are required on the metal flow conduit. Further, the shell may be made of a different material than the liner containing the interface, which may be a metal or a polymer. The polymer-based material used for the shell may be different from the polymer-based material used for the liner. This has the advantage that different flow meters optimized for measuring different fluids under different conditions can be provided from different sets of pre-manufactured flow tubes and housings.

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

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

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 that includes a polymer and a filler.

Polymer-based materials that include fillers are also referred to as composites. In the context of the present invention, a polymer-based material (or simply polymer) should be construed as a composition comprising one or more polymers and optionally one or more fillers.

The polymer and polymer-based composite have different diffusion and hydrolysis resistances depending on the nature of the functional groups constituting the main chain of the polymer and the amount of any filler used therein. The addition of fillers such as carbon fibers to the polymer structure to improve its mechanical stability tends to reduce its stability to diffusion and hydrolysis. Thus, the hydrolysis and diffusion processes are facilitated by the addition of fillers to the polymer structure and even to what would otherwise be considered water impermeable, providing a route for water to enter the structure at the microscopic or even atomic level.

The flow tube with flow conduit and liner of the present invention solves this problem by providing a mechanically stable metal flow conduit and a polymer liner providing high hydrolysis and diffusion resistance, since in polymer based materials less filler can be provided. Also, by using a combination of metal flow pipe and polymer lining to provide strength, the polymer-based material used for the lining can be made from a wider range of inexpensive polymers.

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

The liners may be provided in a thermoplastic material such that they may be manufactured by injection moulding, and wherein the flow duct is moulded onto the liner to create a flow tube.

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

By applying such a 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 of simplifying production, as the interface can be provided in the same overmoulding process as the liner, which reduces production costs.

The first polymer-based material may be based on one or more of the following polymers: polypropylene, PP; polycaprolactam, PA 6; polyethylene, PE; crosslinked polyethylene, PEX. These polymers have the advantage of low cost and ease of use in the overmolding process. 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 with one or more of the following fillers: graphite, carbon fiber, glass fiber, and metal powder. The filler improves mechanical strength but also reduces diffusion resistance.

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

The polymer-based second material may be a composite material reinforced by one or more of the following fillers: graphite, carbon fiber, glass fiber, and metal powder. In particular PPS combined with the above-mentioned fillers shows a very high resistance to water diffusion. Such a flow meter may be particularly advantageous for use as a water meter that may be submerged or subject to condensation of water on the surface of the meter. This combination may also be advantageous for cold meters (cooling meters), which may also experience condensation of water on their outer surface.

The composition of the material may be different for the heat meter, as the lining needs to be adapted to a hot fluid which may also include some chemicals, whereas the heat meter is not submerged and is less likely to undergo condensation of water, and therefore the water impermeability of the housing is not critical. Thus, a heat meter having a lining made of a polymer based on one or more of PES, PSU, PPSU and a casing made of a polymer based on PA12, PPA or alternatively PPS may be advantageous, as PES, PSU, PPSU are suitable for protecting the flow conduit from the hot fluid flowing in the heating system, and in particular PA12 and PPA are low cost polymers which are lower cost than the polymer used for the lining.

For flow meters intended to measure the flow of fluids comprising more aggressive chemicals, the composition of the material may differ, as the lining needs to be adapted to protect the flow conduit from the more aggressive chemicals. Accordingly, flowmeters having a liner made from a PEEK, PEKK, or PEK based polymer and a casing made from a PA12, PPA, or alternatively PPS based polymer may be advantageous because PEEK, PEKK, or PEK may be resistant to corrosive chemicals, and particularly PA12 and PPA are low cost polymers that are less costly than the polymers used for the liner.

The liner may have sound absorbing properties and/or acoustic impedance that will deflect the ultrasonic waves, so that undesirable reflections are minimized and measurement accuracy is improved. For the choice of lining material with these properties, reference is made to EP 1387149 a 1.

The liner may include sealing surfaces disposed at the inlet and outlet of the flow tube. To increase the area of the sealing surface, it may be advantageous that the liner and the flow duct have a conical shape at the inlet and the outlet, respectively. A conical shape is fabricated on the inner surface of the flow conduit. When the flow conduit is overmolded, the liner will have a conical shape where it meets the conical inner surface of the flow conduit. This has the advantage of increasing the sealing surface without reducing the cross-sectional area of the flow passage. Further, the conical shape supports the liner to prevent it from being pressed back into the flow tube. The very thin wall of the flow conduit near the end of the conduit has the advantage that the liner-metal joint will move towards the periphery of the flow pipe, whereby it is protected from the mechanical forces of the fluid flowing in the flow pipe, which prevents the flow pipe from delaminating due to the fluid being pressed in between the liner and the flow conduit.

In a second aspect of the invention, a method of manufacturing a flow meter according to the first aspect, the method comprises the steps of: 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 mould of a machine for overmoulding; 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 the shell to the interface of the liner.

This method of production is particularly advantageous because the overmolding process is simplified by simply molding the interface for the shell rather than molding the shell as an integral part of the liner. Further, the conical inner surface of the flow duct has the advantage of reducing mechanical stresses in the flow duct due to shrinkage of the liner when it cools.

The polymer of the polymer-based material for the liner may be selected from the group consisting of: polysulfone (PSU), Polyethersulfone (PES), polyphenylene ether sulfone (PPSU), polyphenylene sulfide (PPS), Polyetherketone (PEK), Polyetheretherketone (PEEK), Polyetherketoneketone (PEKK), polypropylene (PP) and polycaprolactam (PA 6). Alternatively, if higher strength is desired in the liner, the polymer may be selected from the group consisting of: polysulfones (PSU), polyether sulfones (PES), polyphenylene sulfides (PPS), Polystyrenes (PS), polyphthalamides (PPA) and Polyamides (PA), in particular polyamide 12(PA12) prepared from 1, 12-dodecanedioic acid.

The polymer-based material for the casing may also be selected from the above-mentioned polymer group, and in particular PPS, PA12 and PPA may be advantageous for the casing.

Polysulfone is defined as a polymer in which the sulfone group (-S (O2) -) constitutes part of the backbone structure of the polymer. Examples include, but are not limited to, Polysulfone (PSU), polyphenylene ether sulfone (PPSU), and Polyethersulfone (PES).

Polysulfide is defined as a polymer in which sulfide groups (-S-) form part of the backbone structure of the polymer. An example thereof is polyphenylene sulfide (PPS).

Polyaryletherketones are defined as polymers in which a combination of an ether group (-O-) and a ketone group (-C (O) -) forms part of the backbone structure of the polymer. Examples include, but are not limited to, Polyetherketone (PEK), Polyetheretherketone (PEEK), and Polyetherketoneketone (PEKK).

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

The flow meter may be a consumption meter or a utility meter, e.g. a water meter, gas meter, heat meter, cold meter, energy meter or smart meter for cold and/or hot water.

Consumption meters may be used in conjunction with district heating, district cooling, and/or distributed water supply.

The consumption meter may be a legitimate meter, i.e. a meter subject to regulatory requirements. Such regulatory requirements may be requirements for measurement accuracy.

Further advantageous embodiments of the first and second aspect are disclosed in the description of the embodiments.

In general, the aspects of the invention may be combined and coupled in any way possible within the scope of the invention. These and other aspects, features and/or advantages of the invention will become apparent from and elucidated with reference to the embodiments described hereinafter.

Although the invention has been described in connection with specific embodiments, it should not be construed as being limited in any way to the examples given. The scope of the invention should be construed in accordance with the attached claims. In the context of the claims, the term "comprising" or "comprises" does not exclude other possible elements or steps. Furthermore, references to "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 not be construed as limiting the scope of the invention either. Furthermore, individual features mentioned in different claims may advantageously be combined, and the mentioning of these features in different claims does not exclude that: combinations of features are not possible and advantageous.

Drawings

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

fig. 1 illustrates an embodiment of an ultrasonic flow meter, comprising a housing mounted at the interface of a liner of a flow tube,

fig. 2 illustrates a flow tube, which contains a flow conduit and a liner providing an interface for installing a housing,

figure 3 shows a section through the flow tube of figure 2,

fig. 4 shows a cross-section of the flow meter of fig. 1, which contains a measurement conduit within the flow tube,

figure 5 is another illustration of a cross-section of the flow tube of figure 2,

figure 6 shows a flow duct which is shown,

fig. 7 illustrates an embodiment of an ultrasonic flow meter, comprising a housing fabricated as an integral part of a liner,

figure 8 shows a cross-section of the flow meter of figure 7,

fig. 9 illustrates another embodiment of an ultrasonic flow meter, comprising a housing mounted at the interface of a liner of a flow tube,

FIG. 10 shows a cross-section of the flow meter of FIG. 9 in the longitudinal direction, an

Figure 11 shows a cross-section of the flow meter of figure 9 in the transverse direction,

fig. 12A shows a cross-section of a flow tube, the flow tube having a liner that creates sealing surfaces at the inlet and outlet of the flow tube,

fig. 12B shows an enlarged view of the inlet/outlet of the flow tube of fig. 12A, where the liner has not cooled after overmolding, and has not shrunk,

fig. 12C shows an enlarged view of the inlet/outlet of the flow tube of fig. 12A, where the liner has cooled after overmolding, and has shrunk, thereby creating mechanical stress in the flow tube and deformation of the liner,

FIG. 13A shows a cross-section of a flow tube having conical interior surfaces at the ends of the flow conduit at the inlet and outlet of the flow tube, and a liner creating sealing surfaces at the inlet and outlet of the flow tube,

fig. 13B shows an enlarged view of the inlet/outlet of the flow tube of fig. 13A, where the liner has not cooled after overmolding, and has not shrunk,

fig. 13C shows an enlarged view of the inlet/outlet of the flow tube of fig. 13A, where the liner has cooled and has shrunk after overmolding, without mechanical stress or deformation of the liner being created in the flow tube,

FIG. 14 shows a cross-section of a flow meter having a housing, a flow tube, and a measurement conduit.

Detailed Description

Referring to fig. 1, 2 and 3, a flow meter 1 is shown comprising a housing 5 mounted on a flow tube 2. The flow duct 2 comprises a through opening for passing the fluid between the inlet 21 and the outlet 22. The through opening is also referred to as 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 arranged in alignment with the transducers of the ultrasonic flow meter arranged inside the housing.

The flow pipe 2 comprises a flow duct 3 and a liner 4 extending along the inner surface of the flow duct.

The flow duct is made of a metallic material, such as steel, stainless steel, cast iron, aluminum or brass, and comprises a plurality of through openings 31, as best seen in fig. 5 and 6. The flow conduits may be cast or made from standard lengths of tubing machined to contain the openings, threads and other geometries shown. The flow conduit may include threads 32 or a flange (not shown) for connecting the flow tube to a connecting conduit of a water distribution system.

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 a metal element 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 in an overmolding process with the remainder of the liner. The lining 4 containing the interface 25 extends from the inner surface of the flow duct 3, through one or more holes 31 in the flow duct, to the outside of the flow duct, where the interface 25 is arranged, and is an integral part of the lining. The interface includes one or more surfaces for disposing a sealing device, such as an O-ring or gasket (not shown), between the housing and the interface. The sealing means may preferably be arranged around two through openings 24 provided in the interface. Two through openings in the interface extend through the liner and the holes 31 in the flow duct, so that the flow channel 23 can be accessed directly 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. The sealing means between the housing 5 and the interface 25 is arranged to prevent fluid from escaping from the flow tube.

In the illustrated embodiment, the liner provides a water-impermeable membrane and completely covers the inner surface of the flow conduit. Thus, fluid flowing through the flow tube does not come into contact with the flow conduit. The liner protects the flow conduit from fluid flowing in the flow conduit and prevents corrosion of the flow conduit. Further, the liner prevents metal from the flow conduit from dissolving in the fluid. However, metal tubing that may be used in a water supply system in which the flow meter is installed may be connected to the metal flow tubing via threads 32. In this way, electrical connections to the conduits on each side of the flow meter are achieved. In some devices, galvanic isolation is not desirable. In another embodiment, the liner may be configured to cover only a portion of the flow conduit. Liners may be arranged at the inlet and outlet to create sealing surfaces for sealing the connection to the pipes of the water supply system, wherein the flow meter is mounted as illustrated in fig. 13A-13C.

The lining containing the interface is made of a polymer-based material. The polymer-based material may be a composite material comprising 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 inexpensive and easy to use in the overmolding process. The liner may comprise one or more of these polymers.

The housing 5 is mounted on the interface 25 as described above. The housing contains a cup-shaped element 51 provided with a cover 52. The cover may be provided with a transparent window. The housing is adapted to house the electrical components of the ultrasonic flow meter, including the piezoelectric transducer, control circuitry disposed on a Printed Circuit Board (PCB), a communication device for radio frequency communication, a battery pack providing a power source, and may further contain a display and other elements visible through the transparent window. The transducer is disposed within the housing to transmit an ultrasonic signal through the flow channel to generate a signal or value indicative of the flow rate of the fluid flowing through the flow tube. The transducer arranged inside the housing is in contact with the fluid in the flow tube through the through-openings in the wall of the housing and the interface, so that ultrasonic signals can be transmitted and received through the fluid inside the flow tube.

The housing is adapted to hold water away from components contained within the housing interior. The sealing means is disposed between the lid and the cup. The housing is made of a polymer-based material. The polymer-based material may be a composite material that includes 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 inside of the housing. Polyphenylene Sulfide (PPS) -based polymers are less diffusion open and have mechanical properties suitable for making housings. PPS is the preferred polymer material for the housing.

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

In fig. 4 and 14, the flow meter is shown as comprising a measurement conduit 6 arranged in the flow channel. The lining may be provided with recesses or protrusions for fixing the measuring pipe inside the flow tube. Alternatively, the liner may also provide a measuring pipe, as the measuring pipe is moulded as an integral part of the liner.

The measurement conduit may contain a flow straightener 61 configured to regulate fluid flow through the flow tube, for example, to reduce rotation, asymmetric flow profiles, or other unintended flow characteristics. The lining may be provided with recesses or protrusions for fixing the flow straightener inside the flow tube.

The flow meter may also contain 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 reflector may be overmolded by or molded into the liner. As a further alternative, the reflector may be omitted and the ultrasonic signal may be reflected by the metal wall of the flow conduit. If the reflector is 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 shown in fig. 14.

Referring to fig. 7 and 8, another embodiment of a flow meter is shown. In this embodiment, the shell 5 is made as an integral part of the liner 4, i.e. the liner is formed monolithically with the shell. Thus, the liner does not provide an interface 25 for mounting the shell. Since the shell is made as an integral part of the liner, no openings are provided in the flow tube, except for the inlet 21 and the outlet 22.

Fig. 9-11 illustrate another embodiment of an ultrasonic flow meter in which the case is attached to the interface of the liner and 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 liner interface. When the shell is mounted on the interface 25 of the liner, the locking pin extends through the opening in the liner and the opening in the shell, and the shell is locked to the interface of the liner. Alternatively, the housing 5 may be locked to the interface by using screws that extend through holes in the housing to holes 251 in the interface.

The flow meter may advantageously be an ultrasonic flow meter, such as a transit time flow meter, arranged to measure the flow rate of a fluid flowing in the flow channel 23 by using the operating principle of the transit time flow meter, i.e. wherein an ultrasonic signal is transmitted by one transducer and received by the other transducer, and wherein the time difference of arrival between counter-propagating signals is measured and converted into a flow rate.

The above-mentioned flow tube is advantageously manufactured on the basis of a flow conduit made of standard conduits, such as extruded, seamless or welded conduits. The standard pipe is cut and machined to a flow pipe as shown in fig. 6, containing threads and a plurality of openings.

The flow conduit is prepared for overmolding and is arranged in an injection mold designed for overmolding. Preparing the tube for overmolding may comprise one or more of the following steps: heating the pipe, cleaning the pipe, sandblasting the pipe coating or otherwise surface treating the pipe, especially to improve the adhesion of the lining. The lining is made by injection moulding and the melt is injected into the mould 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 melt into the flow conduit. The mould is designed with one or more cores so that flow channels 23 are provided. In one embodiment, the mold is designed such that the interface 25 for mounting the shell is created as an integral part of the liner. In other embodiments, the mold is designed such that the liner and shell are made as an integral part. Thus, a liner, which may contain a shell, is molded onto the flow conduit.

The liner is arranged to create sealing surfaces 201 at the inlet and outlet of the flow tube, which is illustrated in fig. 12-13. The sealing surface must be aligned with the end of the flow conduit and have a surface area that is large enough to provide an adequate seal when resting directly against the end of the connecting conduit or compressing the sealing device between the sealing surface and the end of the connecting conduit. To increase the surface area of the sealing surface, the size of the flow conduit is reduced at the end of the conduit to create an enlarged sealing surface 201 area without reducing the cross-sectional area of the flow passage 23. The liner is overmolded onto the flow conduit and will shrink upon cooling. If the liner extends around the ends of the flow pipe (FIG. 12B), or around sharp edges at each end of the flow, pipe stresses may develop in the flow pipe as the liner cools and hardens (FIG. 12C). To avoid such stresses, the flow conduit and liner may each have conical surfaces 202 facing each other at the inlet and outlet of the flow tube, and thus, a sealing surface with increased surface area may be created during the overmolding process without creating stresses in the flow tube (fig. 13B and 13C). In particular, the flow conduit may have conical inner surfaces and conduit ends at the inlet and outlet of the flow tube. The conical shape will have the effect that as the liner cools, hardens and contracts during the overmolding process, it will slide into the flow tube and align with the tube end without creating mechanical stress in the flow tube.

Although the invention has been described in connection with specific embodiments, it should not be construed as being limited in any way to the examples given. The invention may be practiced in any suitable manner; and the scope of the invention should be construed in accordance with the appended claims. Any reference signs in the claims shall not be construed as limiting the scope.