Magnetic inductive flowmeter

Abstract

The invention relates to a magnetic-inductive flowmeter, comprising a housing, a replaceable measuring tube for conducting a flowable medium, at least two measuring electrodes which are mounted in the measuring tube, each having a front region which is in galvanic contact with the medium, a magnetic field generating device for generating a magnetic field which permeates the measuring tube, the magnetic field generating device comprising at least a first coil which surrounds a first coil core and a second coil which surrounds a second coil core, and at least two connection contacts which are arranged in a first housing part or a second housing part, each being electrically connected to a measuring circuit which is preferably arranged in the housing, characterized in that the housing has a two-part design and comprises a first housing part and a second housing part, the first coil and the first coil core being arranged in the first part, the second coil and the second coil core being arranged in the second part, wherein the measuring tube is interlocked and / or frictionally arranged between the first part and the second part of the housing, wherein the first part and the second part of the housing are interconnected by a linear guide element, the distance of the second housing part from the first housing part being linearly adjustable by the linear guide element.

Description

Background Art

[0001] Magnetic-inductive flowmeters are used to determine the flow rate and volume flow of a flowing medium in a pipeline. They have a magnet system that generates a magnetic field perpendicular to the flow direction of the flowing medium. A single coil is typically used for this purpose. To achieve a predominantly uniform magnetic field, pole pieces are additionally formed and attached so that the magnetic field lines extend substantially perpendicular to the horizontal axis or parallel to the vertical axis of the measuring pipe over the entire pipe cross-section. A pair of measuring electrodes attached to the lateral surface of the measuring pipe taps an electrical measurement voltage or potential difference that is applied perpendicular to the flow direction and the magnetic field and occurs when the conductive medium flows in the flow direction when the magnetic field is applied. Since the tapped measurement voltage, according to Faraday's law of induction, depends on the velocity of the flowing medium, a flow measurement value can be determined from the induced measurement voltage u. Depending on the application, this flow measurement value includes the flow rate u, an additional known pipe cross-section, the volume flow rate V, or an additional medium density, the mass flow rate m.

[0002] Magnetic-inductive flowmeters (which use exchangeable measuring tubes) are known and are taught, for example, in DE 102016 118 064A1.

[0003] DE 10 2010 031 433 A1 teaches a replaceable, partially U-shaped disposable insert with at least three measuring electrodes, designed for use in the measuring tube of a conventional magnetic-inductive flowmeter. Two of the at least three measuring electrodes are contacted via measuring electrodes installed in the measuring tube and connected to a measuring circuit. The magnetic field generated by the magnet system of the magnetic-inductive flowmeter penetrates the walls of the measuring tube and the disposable insert, generating a charge separation in the medium flowing through the disposable insert. This charge separation is tapped as a measuring voltage by the at least three measuring electrodes. However, a disadvantage of this invention is that installing the disposable insert in the measuring tube is very laborious, especially under cleanroom conditions. Summary of the Invention

[0004] The invention is based on the object of providing a magneto-inductive flowmeter which, under clean room conditions, enables a simple replacement of the measuring tube or a simple insertion of the measuring tube into the measuring system.

[0005] This object is achieved by the magnetic-inductive flowmeter according to the present invention.

[0006] The magnetic induction flowmeter according to the present invention comprises:

[0007] -shell;

[0008] a measuring tube for guiding the flowable medium;

[0009] - at least two measuring electrodes, which are mounted in the measuring tube,

[0010] wherein the measuring electrodes each have a front region for making galvanic contact with the medium;

[0011] - a magnetic field generating device for generating a magnetic field which permeates the measuring tube,

[0012] wherein the magnetic field generating device comprises a first coil and a second coil,

[0013] wherein the first coil surrounds a first coil core,

[0014] the second coil surrounds a second coil core;

[0015] - at least two connection contacts, which are each electrically connected to a measuring circuit, which is preferably arranged in the housing;

[0016] and characterized in that

[0017] the housing has a two-part design and comprises a first housing part and a second housing part,

[0018] wherein the first coil and the first coil core are arranged in the first housing part,

[0019] wherein the second coil and the second coil core are arranged in the second housing part,

[0020] wherein the measuring tube is arranged in a form-locked or press-fit manner between the first housing part and the second housing part, and

[0021] the first housing part and the second housing part are interconnected by means of a guide element,

[0022] wherein the distance between the two housing parts can be linearly adjusted by means of the guide element.

[0023] Up to now, the replaceable measuring tube had to be inserted into a receptacle, which was realized in the form of a U-shaped receptacle or an opening in the housing or in the form of a measuring tube inlet of a conventional flowmeter. In order to make it easier to install the measuring tube, the receptacle or the opening cannot be further enlarged afterwards.

[0024] The two-part design of the housing and the connection of the two parts to the guide element allow an easy-to-handle solution to be achieved. Before the insertion of the measuring tube, the distance between the two parts of the housing can be increased, so that the opening formed by the two housing parts expands and the measuring tube can be easily inserted. After the insertion of the measuring tube, the distance between the two housing parts can be reduced again via the guide element, so that the measuring tube is arranged in a form-locked or press-fit manner between the first housing part and the second housing part.

[0025] The guide element used in mechanical engineering makes it possible to guide an object or a point of an object on a predetermined path. It is particularly advantageous for the present application that the guide element facilitates the linear movement of at least one housing part. Linear guides or straight guides are suitable for this purpose. Examples of linear positioning and handling systems are single-axis systems, two-axis systems, multi-axis systems or electromechanical cylinders. Furthermore, the guide element also comprises a drive unit, such as a linear motor, a pneumatic cylinder and a hydraulic cylinder.

[0026] The adjustment of the distance between the two housing parts can be achieved in such a way that the two housing parts are each moved linearly towards or away from each other along the guide element. It is particularly advantageous if one of the two housing parts is fixed and only the other housing part is linearly adjustable.

[0027] The guide element has a guide body. This can be designed as a rail, in particular a round rail or a roller guide, in particular a profile rail guide or a car rail guide.

[0028] Advantageous embodiments of the application are as follows.

[0029] One embodiment provides that the guide element is formed by at least one guide body, in particular at least partially cylindrical, and a spring, in particular a helical spring,

[0030] wherein the spring, which is designed in particular as a tension spring or a compression spring, is arranged on the guide body such that the spring of one of the two housing parts presses against the other housing part or pulls the two housing parts together.

[0031] It is advantageous if the guide element has at least one spring which pushes or pulls the two housing parts together. This is a compression or tension spring. When the measuring tube is being installed, the housing parts are moved along the guide body, so that the spring is compressed or pulled apart. A force has to be exerted for this to happen and to keep the moving housing parts in place. This force can be exerted, for example, by an assembler or with the aid of a drive unit.

[0032] If the measuring tube is in the mounted position, the force can be reduced, which causes the spring to bring the two housing parts together again so that the measuring tube is fixed in the two housing parts in a press fit.

[0033] For applications in clean room areas, it is particularly meaningful to realize the guide element by means of a guide body and a spring, since thereby impurities due to wear or hydraulic oil are avoided.

[0034] One embodiment provides that the first return body is arranged in the first housing part,

[0035] wherein the second return body is arranged in the second housing part,

[0036] wherein the return bodies each have two legs and a base,

[0037] wherein the base covers the respective coil core at the end,

[0038] wherein the legs extend laterally to the respective coil and are inclined towards the measuring tube.

[0039] The return bodies serve to collect the magnetic field lines that leave the coil core but do not intersect the measuring tube or only partially intersect the measuring tube and to guide these magnetic field lines to the opposite pole with as little loss as possible. Thus, in each case, the return bodies ideally contact the two coil cores on the side facing away from the measuring tube. The return bodies are usually formed from a plurality of interconnected metal sheets, which are preferably produced by stamping packaging. However, return bodies formed from a single metal sheet part or a single layer of metal sheet parts are known.

[0040] The return bodies are usually embodied in the mounted state so that they completely enclose the measuring tube in the cross section of the partial area of the measuring tube. Usually, the return bodies are formed in two parts, wherein the two parts overlap and are interconnected. The two return bodies are fixed to one another by means of screws or a snap lock, thus ensuring the contact.

[0041] According to the application, the return bodies have a base and two legs. Ideally, a U shape is thereby formed. Similar forms are known from DE 10 2011 079 352 A1. The return bodies can be formed in one piece or also in multiple pieces, in particular two pieces. In this case, the return bodies consist of two L-shaped parts, which together essentially form a U shape. The two return bodies form a return device. On the one hand, the two return bodies can contact when the flowmeter is in the closed state. For this purpose, an opening in the housing is necessary, through which at least one of the return bodies extends. However, depending on the application, the contact between the two return bodies can be dispensed with. In this case, the respective return body is separated by the wall of the two housing parts.

[0042] One embodiment provides that, in particular, the closure element attached to the housing is designed to connect the first return body to the second return body,

[0043] wherein the closure element is implemented in the form of a pivotable flap or in the form of a linearly displaceable sheet metal part.

[0044] It is advantageous that, in addition to the spring ensuring the press-fit connection of the measuring tube between the two housing parts, a closure element is arranged by means of which an additional securing is achieved. In particular in the case of applications using flexible hoses and / or plastic pipe systems, there is a risk that, when forces transmitted via the pipe system pull the spring apart or compress the spring and thus misalign the measuring tube in its installed position, which leads to a loss of electrical contact between the connection contact and the measuring electrode, the measurement values are distorted.

[0045] The closure element preferably comprises at least one rotary joint, a locking bolt and a closure flap. The closure flap is movably connected to the rotary joint and rotates about an axis of rotation defined by the rotary joint. The rotary joint is attached to one of the two parts of the housing. The locking bolt is attached to the respective other housing part. When the closure element is closed, the closure flap rotates about the rotary joint until the locking bolt fits tightly in a molding introduced into the closure flap. In this state, the two housing parts cannot be detached. Without previously reopening the closure element, the measuring tube cannot be removed from its installed position.

[0046] It is particularly advantageous that the closure element not only ensures the securing of the measuring tube between the housing parts, but also establishes a connection between the two return bodies in the closed state. This can take place, for example, by means of a rotary joint and a locking bolt, both of which are in contact with one of the two return bodies. If the closure flap is closed, a closed contact is formed between the two return bodies via the closure unit. If the closure unit is made of a ferromagnetic material, it is additionally designed to guide a magnetic field from the first return body to the second return body and vice versa.

[0047] Alternatively, the two return bodies can also be connected via a linearly displaceable sheet metal part attached to one of the two housing parts. Before the measuring tube is guided through the opening, the sheet metal part is displaced. If the measuring tube is in the installed position, the sheet metal part is moved again along the opening until it contacts the two return bodies.

[0048] One embodiment provides that a first plug-in connection is arranged in the first housing part, which is electrically connected to the operating circuit,

[0049] wherein the second plug connection is arranged in the second housing part, said second plug connection being designed to be complementary to the first plug connection and to be electrically connected to the second coil

[0050] wherein, in the closed state of the magnetic inductive flowmeter, an electrical connection is established between the first plug connector and the second plug connector.

[0051] The fact that the housing is formed in two parts raises the problem of electrically connecting the individual coils to an operating circuit which is configured to supply the coils with power. It is therefore advantageous if both housing parts have plug connections which are designed to be complementary to one another, such that in the closed state an electrical connection is achieved between the operating circuit and the individual coils.

[0052] If the operating circuit is arranged in the first housing part, the electrical connection of the operating circuit to the first coil is not critical. It is possible to provide an opening in both housing parts, for example, through which an electrical cable extends to supply the second coil with power. However, since the two housing parts are designed to be able to be moved or partially moved via the linear guide element, the electrical cable can quickly be damaged.

[0053] It is therefore advantageous if the two housing parts have complementary plug connections. This thus avoids the electrical cable extending outside the housing and additionally ensures that the meter only operates when it is also in the closed state.

[0054] The operating circuit does not have to be arranged in the first housing part, but can also be located outside the housing and connected to the coil located there via a plug connector which is arranged in one of the two housing parts.

[0055] One embodiment provides that the housing parts each have at least one surface which faces a surface of the respective other housing part,

[0056] wherein the connection contact is arranged on the surface and protrudes from the surface,

[0057] wherein the connection contact is resilient.

[0058] In a conventional measuring tube, the measuring electrodes are arranged diametrically and connected to a measuring circuit via a contact body, for example a cable. The cable extends along the outer wall of the measuring tube to the coil core, where it runs between the coil core and the coil sleeve to the end region of the coil core (cf. DE 20 2014 103 426 U1). The entire arrangement of the cable is as symmetrical as possible with respect to the longitudinal plane of the measuring tube extending through the two coils. The cable extends from the end of the coil core all the way to the measuring circuit. However, with a replaceable measuring tube, wiring the measuring electrodes again and again is laborious. It is therefore advantageous if a connection contact is provided in the housing, which connection contact is itself electrically connected to the measuring circuit and has electrical contact with the measuring electrodes in the measuring tube in the installed state of the measuring tube.

[0059] Due to the fact that the connection contact is resilient, wear of the contact during repeated insertion and removal of the replaceable measuring tube can be minimized.

[0060] Measuring circuits in the field of flow measurement technology are sufficiently known. The purpose of the measuring circuit is to detect very small absolute values and changes in the respective measured variable. There are a number of different embodiments, each with their advantages and disadvantages.

[0061] On the one hand, the measuring circuit can be configured to tap the potential at one of the measuring electrodes with respect to a reference potential. Thus, even if one of the two measuring electrodes fails, the flow rate can still be determined on the basis of the determined potential. The housing potential or the ground potential is suitable as the reference potential. A magnetic inductive flowmeter can have a ground electrode connected to the reference potential. Thus, the two measured variables can be the potential present and determined at each of the two measuring electrodes.

[0062] On the other hand, the measuring circuit can be designed to detect and record the potential difference present between the two measuring electrodes.

[0063] The measuring circuit thus comprises an analog / digital converter, which converts the incoming signal, in this case the potential difference present at the respective measuring electrode pair or the potential present at the respective measuring electrode, into digital data, which are then further processed or stored by the evaluation circuit. However, other measuring converters or measuring transducers from the field of digital measurement technology are also known and suitable for detecting a measurement voltage or potential.

[0064] The evaluation circuit is configured to process the measured values of the respective measured variables measured by the measuring circuit and to determine the sought measured variable. The evaluation circuit thus usually comprises a microprocessor, amplifiers and noise filters. The measuring and evaluation circuit can be of modular design and can communicate by means of a wireless connection, or can be part of a single electronic measuring and evaluation unit arranged in the housing of the flowmeter.

[0065] One embodiment provides that the measuring electrodes are arranged on opposite sides of the measuring tube,

[0066] wherein the measuring electrodes are pin-shaped and have a recess at the respective end, which is embodied as a receptacle for the connection contact.

[0067] In conventional measuring tubes, the measuring electrodes are arranged diametrically. The front surface of the measuring electrodes is usually designed to form current contact with the flowing medium. However, measuring tubes with measuring electrodes are also known, the side surfaces of which form current contact with the medium.

[0068] It is particularly advantageous if the end of the measuring electrode has a recess which is complementarily formed to the resilient connection contact. Thereby, a sufficient contact of the measuring electrode can be ensured. When inserted into the measuring tube, the resilient connection contact is first displaced and then snaps into the receptacle.

[0069] One embodiment provides that the measuring electrodes are mounted in a section plane of the measuring tube,

[0070] wherein a ground electrode for forming current contact with the medium relative to the section plane is attached in the measuring tube at a distance,

[0071] wherein a connection contact for electrically connecting to a reference potential, in particular to a ground potential, is arranged in the first housing part or in the second housing part.

[0072] A flowmeter with a measuring tube designed to be electrically insulated requires a sufficient grounding in the form of a ground ring or a ground electrode. For a more compact design of a magnetic inductive flowmeter, it is advantageous if the ground electrode is configured offset relative to a section plane intersecting the measuring electrodes, since in this way the connection contacts of the magnetic field generating means and the ground electrode do not hinder each other. Preferably, the section plane intersecting the ground electrode in the flow direction is arranged downstream of the section plane to which the measuring electrodes are attached. The offset arrangement of the ground electrode is also part of an error-proof system, thus avoiding a defective installation of the measuring tube in the magnetic inductive flowmeter.

[0073] One embodiment provides that at least one housing part has a front surface,

[0074] wherein the normal vector of the front surface consists of a vector parallel to the longitudinal axis of the guide element and a vector parallel to the transverse axis of the measuring tube connecting the two measuring electrodes,

[0075] wherein the front surface is configured to convert a force acting on the front surface into a linear movement of the housing part away from the respective other housing part when the measuring tube is being inserted.

[0076] It is particularly advantageous if the housing in the front region has a front surface which is inclined with respect to the insertion direction of the measuring tube such that, when the measuring tube is being inserted between the two housing parts and pressed against the front surface, a force acting in the insertion direction is deflected into a force parallel to the longitudinal direction of the linear guide element. This has the effect that the spring is pressed open or compressed by pressing the measuring tube against the front surface, as a result of which the distance between the two housing parts increases. The distance increases until the measuring tube has reached the installed position. The distance then decreases again and the measuring tube is attached between the two housing parts not only in a form-locked manner but also in a press-fit manner. This simplifies the insertion of the measuring tube, so that it is not necessary to first pull the housing parts apart before the measuring tube is inserted. It is sufficient to press the measuring tube against the front surface.

[0077] One embodiment provides that the measuring electrodes each have a measuring electrode body which is in particular L-shaped.

[0078] The L-shaped measuring electrode body ensures that the contact point between the measuring electrode and the connection contact is located close to the housing. This prevents the connection contact from obstructing the insertion of the measuring tube.

[0079] The measuring tube body of the measuring tube is preferably produced in one piece by a one-shot forming process, in particular by injection molding. In the same process, the measuring electrodes can also be arranged in the measuring tube and overmolded with the material of the measuring tube body. It is therefore advantageous if the measuring electrodes are also formed in one piece, since production steps can thus be saved.

[0080] One embodiment provides that the measuring electrode body is formed from two parts,

[0081] wherein the end region of the first part is formed complementarily to the front region of the second part,

[0082] wherein the second part is connected to the first part in a form-locked manner.

[0083] Although an additional installation step is required to insert the second part of the measuring electrode body into a receptacle provided in the measuring tube body, the measuring electrode body does not have to be first reformed into an L shape by a reforming process, in particular by a bending process. This can lead to defects, in particular in measuring electrodes having a small cross section.

[0084] One embodiment provides that the measuring tube comprises at least two guide discs as positioning means,

[0085] wherein the guide discs each have a contact surface,

[0086] wherein the guide discs are attached to the measuring tube such that the contact surfaces face each other,

[0087] wherein the guide discs are spaced apart and the contact surfaces are in contact with the housing.

[0088] The guide discs ensure that the measuring tube is inserted into the measuring tube to fit precisely into the intended installation position and ensure that the measuring electrode and the connection contact lie in a common plane, thereby preventing false contacts. Furthermore, displacement of the measuring tube in the longitudinal direction is prevented.

[0089] Further structures in the measuring tube body are based on the error prevention principle, ensuring that there is only one installation option for the measuring tube, so that it is always ensured that the measuring electrode and the ground electrode are contacted by the connection contact.

[0090] One embodiment provides that the magnetic field generating device, in particular the pole shoes of the magnetic field generating device, are separated from the measuring tube by the wall of the housing.

[0091] One embodiment provides that the first housing part and the second housing part each have an opening,

[0092] wherein the legs of the first return body and / or the second return body extend through the respective openings,

[0093] wherein, in the closed state of the magnetic inductive flowmeter, contact between the first return body and the second return body is produced.

[0094] The typical flowmeter with exchangeable measuring tube has a highly simplified magnet system. As a result, the measurement error is also within a single percentage. It is therefore particularly advantageous that the two return bodies are interconnected, since stray fields can thereby be reduced.

[0095] It is therefore particularly advantageous to introduce openings in the two housing parts through which the return bodies extend. In the open state, the return bodies do not contact each other and the measuring tube can be inserted between the two housing parts. In the closed state, the two return bodies contact each other and the path of the magnetic field lines is closed again along the return bodies.

[0096] One embodiment provides that the measuring tube is made of an insulating material, in particular of plastic, and preferably of polyether ether ketone (PEEK), polyaryletherketone (PAEK), polyphenylsulfone (PPSU), polyethersulfone (PESU), polysulfone (PSU), polyarylamide (PARA), glass and / or ceramic.

[0097] Flowmeters with disposable measuring tubes are required for biopharmaceutical applications. For this purpose, the materials in contact with the medium must be biocompatible and gamma sterilizable. It is therefore particularly advantageous if the measuring tube is made of one of the aforementioned materials, since these materials meet the biopharmaceutical requirements. BRIEF DESCRIPTION OF DRAWINGS

[0098] The application is explained in more detail with reference to the following figures. As shown below:

[0099] Figure 1 is a cross section of the measuring device of the measuring tube;

[0100] Figure 2 is a longitudinal section of the measuring device of the measuring tube;

[0101] Figure 3 is a longitudinal section of the housing;

[0102] Figure 4 is a perspective view of the measuring device housing with the measuring tube inserted;

[0103] Figure 5 is a perspective view of the measuring device with the closure element in the open and closed state;

[0104] Figure 6 is a perspective view of the measuring device with an eccentric rod;

[0105] Figure 7 is a separate step in which the measuring tube is inserted into the housing in cross-sectional view; and

[0106] Figure 8 is an embodiment of the replaceable measuring tube with an L-shaped measuring electrode body. DETAILED DESCRIPTION

[0107] The structure and the measuring principle of a magnetic inductive flowmeter are known in principle. Figure 1An embodiment of a magnetic inductive flowmeter according to the application is shown. A medium having electrical conductivity is conducted through a replaceable measuring tube 2. A magnetic field generating device is arranged in a housing 1 such that the magnetic field lines are oriented essentially perpendicular to a longitudinal direction defined by the measuring tube axis. A saddle coil or pole shoe 24 with attached coil device 5 and coil core 6 is preferably suitable as the magnetic field generating device. When a magnetic field is applied, a potential distribution depending on the flow rate is generated in the measuring tube 2 and tapped with two opposing measuring electrodes 3 attached to the inner wall of the measuring tube 2. Typically, they are arranged diametrically and form an electrode axis or intersect with a transverse axis which extends perpendicular to the magnetic field lines and the longitudinal axis of the tube. Based on the tapped measuring voltage U, the volume flow V of the medium is determined, taking into account the magnetic flux density, the flow rate u and, in addition, the tube cross section. If the medium density is additionally known, the mass flow m can also be monitored. In order to prevent the measuring voltage applied to the first and second measuring electrodes 3 from being conducted away via the tube, the inner wall is lined with an insulating material, for example a plastic lining. In a measuring tube made of insulating material, it is not necessary to apply an insulating coating. A measuring circuit 8 is configured to detect the measuring voltage applied to the measuring electrodes 3. An evaluation circuit is designed to determine a flow measurement value of the medium from the detected measuring voltage. The magnetic field generating device is controlled via an operating circuit 17. In addition to the measuring electrodes, commercially available magnetic inductive flowmeters also have two further electrodes. On the one hand, a fill level monitoring electrode, which is optimally attached to the highest point in the measuring tube 2, serves to detect partial filling of the measuring tube and is configured to pass this information on to the user and / or to take this fill level into account when determining the volume flow. In addition, a grounding electrode 20 (in this embodiment attached at the highest point of the tube cross section instead of the fill level electrode) serves to ensure sufficient grounding of the medium. This is particularly necessary in a measuring tube 2 having an electrically insulating measuring tube body 31.

[0108] The magnetic field generating device and the separate circuits 8, 17 are accommodated in the housing 1. However, it is also possible to arrange the separate circuits outside the housing 1, for example in a control system, and to enable the connection via a connector 26 which is preferably designed as a plug connector.

[0109] Generally, the measuring electrodes 3 extend from inside the measuring tube through the measuring tube body 31 to the inside of the housing, where they are electrically connected to the measuring circuit 8. In the present embodiment, no measuring electrodes 3 are arranged in the housing 1. Instead, the housing 1 has connection contacts 7 which are configured to contact the measuring electrodes 3 of the measuring tube 2 and thus to produce an electrical contact between the measuring electrodes 3 and the measuring circuit 8. The connection contacts 7 can be resilient. They extend through the housing wall 25 of one of the two housing parts 1.1, 1.2. The measuring electrodes each have a front region 4 which contacts the flow medium. The front region 4 can have a mushroom shape, a pointed head, a flat head, a cylindrical shape, a conical shape or a pin shape. The side surface of the measuring electrode extends in the measuring tube body 31 and does not contact the medium. Furthermore, the measuring electrode body 22 of the respective measuring electrode 3 is formed in two pieces. A first part of the measuring electrode body 22 comprises the front region 4 and additionally comprises a receptacle 19 for a second part of the measuring electrode body 22. The second part of the measuring electrode body 22 has a front region which is complementary to the receptacle 19, thus achieving a form-locked connection. The end region of the second part of the measuring electrode body 22 is formed complementarily to the connection contacts 7. The second part of the measuring electrode body 22 is inserted into the receptacle of the measuring tube body 31. The two housing parts 1.1, 1.2 each have at least one surface 18 which faces a surface of the respective other housing part. The surface 18 contacts the measuring tube 2. One of the two surfaces comprises the connection contacts 7.

[0110] According to the application, the housing 1 has a two-part design. The first housing part 1.1 has a first coil 5.1 with a first coil core 6.1 and the second housing part 1.2 has a second coil 5.2 with a second coil core 6.2. In this embodiment, the pole shoes 24 and the coil cores 6 are formed integrally. The pole shoes 24 rest against the inner side of the respective housing wall 25. The return means 12 are arranged in each housing part. The return means 12 comprise two return bodies 12.1, 12.2, each of which consists of a single bent sheet metal part or a bent sheet metal part formed from multiple layers. The return bodies 12.1, 12.2 are each U-shaped. This means that these return bodies have a region shaped as a base 14 and two regions shaped as legs 13. The base 14 contacts the side of the coil core 6 facing away from the measuring tube and the legs 13 extend along the coil arrangement 5 in the direction of the longitudinal plane intersecting the two measuring electrodes 3. However, the two return bodies 12.1, 12.2 do not contact. Not shown in the embodiment but also claimed is an opening in the two housing parts 1.1, 1.2 through which at least one of the two return bodies 12.1, 12.2 extends, whereby, in the closed state of the measuring system, contact between the two return bodies 12.1, 12.2 is achieved. According to this embodiment, the second housing part 1.2 can be moved away from the first housing part 1.1 so that the measuring tube is inserted into the mounting position and is not obstructed by the return means 12.

[0111] The two housing parts 1.1, 1.2 are interconnected via a linear guide element 9. The guide element 9 comprises two guide bodies 10 and a spring 11 in each case. The spring 11 is a cylindrical helical compression spring. The two guide bodies 10 are cylindrical round tracks. If the second housing part 1.2 is moved, the spring 11 is compressed. The opening for the measuring tube 2 formed by the two housing parts 1.1, 1.2 is too small for the measuring tube 2. The second housing part 1.2 has to be moved by the guide element 9 so that the opening is large enough for the measuring tube 2. Furthermore, at least one housing part 1.1, 1.2 has a front surface 21 which is shaped so that when the measuring tube 2 is pressed against the front surface 21, the second housing part 1.2 is moved along the guide element 9 and can insert the measuring tube 2 into the mounting position. To this end, the surface 18 has a solder which is neither perpendicular nor parallel to the longitudinal axis of the guide element 9, but is inclined towards the mounting direction of the measuring tube 2. Thus, the second housing part 1.2 is displaced by pressing the measuring tube 2 and only moves back in the direction of the starting position when the opening is large enough for the measuring tube 2 to fit through. A form-locking and / or press-fit connection between the housing 1 and the measuring tube 2 is thus achieved.

[0112] The two housing parts 1.1, 1.2 both have plug connections 16 which are designed to be complementary to one another. As a result, an electrical connection between the operating circuit 17 and the second coil 5.2 arranged in the second housing part 1.2 is ensured without additional cables having to extend outside the two housing parts 1.1, 1.2. In the open state, the connection between the two plug connections 16 is broken and the supply to the second coil 5.2 is interrupted.

[0113] Figure 2 A longitudinal section along the measuring tube 2 is shown. In the first housing part 1.1 is a connection contact 7 for a grounding electrode 20, which is arranged in the measuring tube 2 and is configured to ensure a controlled potential in the medium. The connection contact 7 is connected to a reference potential, for example a ground potential. The grounding electrode 20 is arranged offset in the longitudinal direction with respect to the section plane of the measuring tube 2 which intersects the two measuring electrodes 3.

[0114] Furthermore, the measuring tube 2 has two guide discs 23 which each have two opposite sides which contact the side surfaces of the two housing parts 1.1, 1.2. This results in a precise fit installation of the measuring tube 2.

[0115] Figure 3 A longitudinal section along the housing 1 is shown. The two guide bodies 10 extend along the receptacles in the two housing parts 1.1, 1.2, wherein the receptacle in the first housing part 1.1 is embodied as a blind hole and the receptacle in the second housing part 1.2 is embodied as a through-hole. The first housing part 1.1 rests on the guide body 10, in particular on the respective front surface, wherein the second housing part 1.2 can be moved linearly along the guide body 10. Furthermore, the two guide elements 9 each have a spring 11. The spring 11 is attached to the guide body 10 such that guiding the second housing part 1.2 along the guide body 10 results in the compression of the spring 11. For this purpose, the guide body 10 has a support surface for the spring 11 in the end region, the cross-sectional area of which is greater than the cross-sectional area along the region in which the spring 11 is arranged. If the second housing part 1.2 is moved, then the outer wall of the second housing part 1.2 or a stop arranged in the receptacle of the guide body presses against the two springs 11 and ensures the compression of the two springs 11.

[0116] Figure 4A perspective view of an embodiment of a magnetic inductive flowmeter according to the application is shown, wherein the measuring tube 2 is in the installed state. The measuring tube can be inserted into the opening formed by the two housing parts 1.1, 1.2 until the measuring tube abuts against the front surface 21. If the measuring tube 2 is pressed further in the direction perpendicular to the longitudinal axis of the guide body 10, the force acting is converted into a force parallel to the longitudinal axis of the guide body 10 and guides the second housing part 1.2 along the guide body 10. The magnitude of the force required to move the second housing part 1.2 depends on the spring constant of the respective spring 11.

[0117] In this embodiment, the measuring electrode 3 has a one-piece design and has a receptacle for the associated connection contact 7. The connection contact 7 is elastic and can be lowered when the measuring tube 2 is inserted into the first housing part 1.1.

[0118] Figure 5 A perspective view of a further embodiment of a magnetic inductive flowmeter according to the application is shown, which has a closure element 15. The closure element 15 has two rotary joints 28, a locking bolt 29 and a closure flap 30. The closure flap 30 can be moved about a rotation axis defined by the rotary joints 28. In the closed state, a molding in the closure flap 30 encloses the locking bolt 30. In this state, the two housing parts 1.1, 1.2 cannot be pulled apart and thus the measuring tube 2 cannot be removed.

[0119] Figure 6 A perspective view of a further embodiment of a magnetic inductive flowmeter according to the application is shown, which has an eccentric lever 27. If the measuring tube 2 is arranged between the two housing parts 1.1, 1.2, a further stabilization of the measuring device is ensured by the fixation of the eccentric lever 27, which has a rotation axis offset with respect to the central axis. The fixation is carried out by throwing the eccentric lever 27, which has a rotation axis offset with respect to the central axis. In this case, the second housing part is pressed further in the direction of the first housing part and the measuring tube is fixed more firmly. This embodiment is particularly advantageous when the measuring tube 2 has a special form-locking arrangement between the two housing parts 1.1, 1.2.

[0120] Figure 7 Three individual steps for the installation of the measuring tube 2 into the opening between the two housing parts 1.1, 1.2 are shown in sectional representation. In the first step, the second housing part 1.2 is moved away from the first housing part 1.1, wherein the second housing part 1.2 is guided along the linear guide body 10. In the first step, the spring 11 is compressed.

[0121] In a second step, the measuring tube 2 is inserted into the opening. The arrow indicates the preferred installation direction. The shape of the measuring tube body ensures that the preferred installation direction is maintained and that incorrect installation positions, in which insufficient contact between the measuring electrode and the connection contacts is not possible, are avoided.

[0122] In a third step, the spring is released again and the second housing part 1.2 returns to its starting position. This results in a form-locking and / or force-fit connection between the measuring tube 2 and the two housing parts 1.1, 1.2.

[0123] Figure 8 Another embodiment of a replaceable measuring tube 2 is shown. The measuring tube 2 has two measuring electrodes 3, each with an L-shaped measuring electrode body 22. The measuring electrode bodies 22 are bent using a bending process and placed in this form in a mold along with the material of the measuring tube body. A pin-shaped grounding electrode 20 is arranged offset from the transverse axis of the measuring electrodes 3. The measuring electrodes 3 and grounding electrode 20 have open ends that are formed to complement the front areas of the connection contacts in the housing (not shown).

[0124] Reference Signs List

[0125] 1. Housing

[0126] 1.1 First housing component

[0127] 1.2 Second housing component

[0128] 2 Measuring tube

[0129] 3 Measuring electrodes

[0130] 4 Front area

[0131] 5 Coil device

[0132] 5.1 First Coil

[0133] 5.2 Second Coil

[0134] 6 Coil core

[0135] 6.1 First coil core

[0136] 6.2 Second coil core

[0137] 7 Connector contacts

[0138] 8 Measurement circuit

[0139] 9 Guide element

[0140] 10 Guide body

[0141] 11 Spring

[0142] 12 return means

[0143] 12.1 first return body

[0144] 12.2 second return body

[0145] 13 leg

[0146] 14 base

[0147] 15 closure element

[0148] 16 plug connection

[0149] 16.1 first plug connection

[0150] 16.2 second plug connection

[0151] 17 operating circuit

[0152] 18 surface

[0153] 19 accommodation

[0154] 20 ground electrode

[0155] 21 front surface

[0156] 22 measuring electrode body

[0157] 23 guide disc

[0158] 24 pole shoe

[0159] 25 housing wall

[0160] 26 connector

[0161] 27 eccentric lever

[0162] 28 rotary joint

[0163] 29 locking bolt

[0164] 30 closure flap

[0165] 31 measuring tube body

Claims

1. Magnetic inductive flowmeter, comprising: - a housing (1), - a measuring tube (2) for conducting a flowable medium, - at least two measuring electrodes (3) which are mounted in the measuring tube (2), wherein the measuring electrodes (3) each have a front region (4) for making galvanic contact with the medium, - magnetic field generating means for generating a magnetic field which passes through the measuring tube (2), wherein the magnetic field generating means comprise a first coil (5.1) and a second coil (5.2), wherein the first coil (5.1) surrounds a first coil core (6.1), wherein the second coil (5.2) surrounds a second coil core (6.2), - at least two connection contacts (7), wherein the connection contacts (7) are each electrically connected to a measuring circuit (8), characterized in that the housing (1) has a two-part design and comprises a first housing part (1.1) and a second housing part (1.2), wherein the first coil (5.1) and the first coil core (6.1) are arranged in the first housing part (1.1), wherein the second coil (5.2) and the second coil core (6.2) are arranged in the second housing part (1.2), the measuring tube (2) is arranged between the first housing part (1.1) and the second housing part (1.2) in a form-locked or press-fit manner, and the first housing part (1.1) and the second housing part (1.2) are interconnected by means of a guide element (9), wherein the distance between the two housing parts (1.1, 1.2) can be linearly adjusted by means of the guide element (9), wherein the two housing parts (1.1, 1.2) each have at least one surface (18) which faces a surface (18) of the respective other housing part (1.1, 1.2), wherein the connection contacts (7) are located on the surfaces (18) and protrude from the surfaces, wherein the connection contacts (7) are resilient.

2. Flowmeter according to claim 1, wherein, the measuring circuit (8) is arranged in the housing (1).

3. Flowmeter according to claim 1, wherein, the guide element (9) is formed by at least one guide body (10) and a spring (11), wherein the spring (11) is arranged on the guide body (10) such that the spring (11) of one of the two housing parts (1.1, 1.2) presses against the respective other housing part (1.1, 1.2) or pulls the two housing parts (1.1, 1.2) together.

4. Flowmeter according to claim 3, wherein, the guide body (10) is at least partially cylindrical.

5. Flowmeter according to claim 3, wherein the spring (11) is a helical spring.

6. Flowmeter according to claim 3, wherein, the spring (11) is designed as a tension spring or a compression spring.

7. Flowmeter according to claim 1, wherein, a first return body (12.1) is arranged in the first housing part (1.1), wherein a second return body (12.2) is arranged in the second housing part (1.2), wherein the return bodies (12.1, 12.2) each have two legs (13) and a base (14), wherein the base (14) covers the respective coil core (6.1, 6.2) at the end, wherein the legs (13) extend laterally to the respective coil (5.1, 5.2) and are inclined towards the measuring tube (2).

8. The flowmeter according to claim 7, wherein a closure element (15) is designed to connect the first return body (12.1) to the second return body (12.2), wherein the closure element (15) is realized in the form of a pivotable flap or in the form of a linearly displaceable sheet metal part.

9. The flowmeter according to claim 8, wherein the closure element (15) is attached to the housing.

10. The flowmeter according to any one of claims 1 to 9, wherein a first plug connection (16.1) is arranged in the first housing part (1.1), which is electrically connected to an operating circuit (17), wherein a second plug connection (16.2) is arranged in the second housing part (1.2), which is designed to be complementary to the first plug connection (16.1) and is electrically connected to the second coil (5.2) wherein, in the closed state of the magnetic-inductive flowmeter, an electrical connection is established between the first plug connection (16.1) and the second plug connection (16.2).

11. The flowmeter according to any one of claims 1 to 9, wherein the measuring electrodes (3) are arranged on opposite sides of the measuring tube (2), wherein the measuring electrodes (3) are pin-shaped and have a recess at the respective end, which is embodied as a receptacle (19) for the connection contact (7).

12. The flowmeter according to any one of claims 1 to 9, wherein, the measuring electrodes (3) are attached on a cut plane of the measuring tube (2), wherein a ground electrode (20) for making galvanic contact with the medium relative to the cut plane is attached in the measuring tube (2) at a distance, wherein a connection contact (7) is arranged in the first housing part (1.1) or in the second housing part (1.2), wherein the connection contact (7) is embodied to electrically connect the ground electrode (20) to a reference potential.

13. The flowmeter according to claim 12, wherein, the connection contact (7) is embodied to electrically connect the ground electrode (20) to a ground potential.

14. The flowmeter according to any one of claims 1 to 9, wherein, at least one housing part (1.1, 1.2) has a front surface (21), wherein the normal vector of the front surface (21) consists of a vector parallel to the longitudinal axis of the guide element (9) and a vector parallel to the transverse axis of the measuring tube (2) connecting the two measuring electrodes (3), wherein the front surface (21) is configured to convert a force acting on the front surface (21) into a linear movement of the housing part (1.1, 1.2) away from the respective other housing part (1.1, 1.2) upon positive insertion of the measuring tube (2).

15. The flowmeter according to any one of claims 1 to 9, wherein, The measuring electrode (3) has in each case a measuring electrode body (22) which is L-shaped.

16. The flowmeter according to claim 15, wherein The measuring electrode body (22) is formed from two parts, wherein an end region of the first part is formed complementarily to a front region of the second part, wherein the second part is connected to the first part in a form-locked manner.

17. The flowmeter according to any one of claims 1 to 9, wherein The measuring tube (2) has at least two guide discs (23) which serve as positioning means, wherein the guide discs (23) each have a contact surface, wherein the guide discs (23) are attached to the measuring tube (2) such that the contact surfaces face one another, wherein the guide discs (23) are spaced apart and the contact surfaces are in contact with the housing (1).

18. The flowmeter according to any one of claims 1 to 9, wherein, The magnetic field generating means are separated from the measuring tube (2) by a wall (25) of the housing (1).

19. The flowmeter according to claim 18, wherein, The pole piece (24) of the magnetic field generating means is separated from the measuring tube (2) by the wall (25) of the housing (1).

20. The flowmeter according to claim 7 or 8, wherein, The first housing part (1.1) and the second housing part (1.2) each have an opening, wherein a leg of the first return body (12.1) and / or the second return body (12.2) extends through the respective opening, wherein, in the closed state of the magnetic-inductive flowmeter, contact between the first return body (12.1) and the second return body (12.2) is produced.

21. The flowmeter according to any one of claims 1 to 9, wherein, The measuring tube (2) is made of an insulating material.

22. The flowmeter according to claim 21, wherein The measuring tube (2) is made of plastic.

23. The flowmeter according to claim 22, wherein The measuring tube (2) is made of polyether ether ketone (PEEK), polyaryletherketone (PAEK), polyphenylsulfone (PPSU), polyethersulfone (PESU), polysulfone (PSU), polyarylamide (PARA), glass and / or ceramic.

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