Field device for process automation

Abstract

The invention relates to a field device for process automation (1), comprising: - a measuring tube (2) for conveying a flowable medium; - a sensor (3) for determining a physical and / or chemical measured variable; - a plastics housing (4) for protecting the sensor (3), wherein the plastics housing (4) comprises individual housing parts (30, 31), wherein the plastics housing (4) comprises a housing interior (4*) in which at least part of the sensor (3) is arranged; - a heating device (5), characterised in that an integral fusion bond is produced, by means of the heating device (5), between the individual housing parts (30, 31) of the plastics housing (4), between the plastics housing (4) and the measuring tube (2), and / or between the plastics housing (4) and a transmitter housing (6).

Description

[0001] Field device for process automation

[0002] The invention relates to a field device for process automation for determining a process variable of a flowable medium.

[0003] In automation technology, particularly in process automation technology, field devices are often used to record and / or influence process variables. Sensors integrated into, for example, level measuring devices, flow meters, pressure and temperature measuring devices, pH-redox potential measuring devices, conductivity measuring devices, etc., are used to record process variables. These sensors record the corresponding process variables: level, flow, pressure, temperature, pH value, or conductivity. Actuators such as valves or pumps are used to influence process variables; they can be used to change the flow of a liquid in a pipe section or the fill level in a container. Field devices are essentially all devices that are used close to the process and that provide or process-relevant information.In the context of the invention, field devices also include remote I / Os, radio adapters or generally electronic measuring components that are arranged at the field level.

[0004] A field device is in particular selected from a group consisting of flow measuring devices, level measuring devices, pressure measuring devices, temperature measuring devices, point level measuring devices and / or analytical measuring devices.

[0005] Flow meters include, in particular, Coriolis, ultrasonic, vortex, thermal and / or magnetic-inductive flow meters.

[0006] Level measuring devices include, in particular, radar-based level measuring devices, microwave level measuring devices, ultrasonic level measuring devices, time-domain reflectometric level measuring devices, radiometric level measuring devices, capacitive level measuring devices, inductive level measuring devices and / or temperature-sensitive level measuring devices.

[0007] Pressure measuring instruments are in particular absolute, relative or differential pressure devices.

[0008] Temperature measuring devices are in particular measuring devices with thermocouples and / or temperature-dependent resistors.

[0009] Point level measuring devices include, in particular, vibronic point level measuring devices, ultrasonic point level measuring devices and / or capacitive point level measuring devices.

[0010] Analytical measuring devices include, in particular, pH sensors, conductivity sensors, oxygen and active oxygen sensors, (spectro)photometric sensors, and / or ion-selective electrodes. EP 1 696 214 A1 discloses a flowmeter for measuring the flow of a flowing medium, comprising a plastic measuring tube for conveying the medium and a connecting device for connecting one end of the measuring tube to one end of a plastic pipeline. The connecting device is a heating device in the form of heating wires integrated into an inner wall of the measuring tube or into a connecting sleeve. When the heating wires are heated, the inner wall partially melts at the connection point between the measuring tube and the connecting body or between the measuring tube and the pipeline, and a fused connection is created.

[0011] DE 10 2013 102 544 A1 also discloses a plastic measuring tube having a magnetic system adapter for attaching a magnetic system. The adapter has heatable heating wires, which enable partial melting of the adapter material. This ensures a material-to-material connection between the adapter and the plastic measuring tube. This type of connection allows for a quickly adaptable and reliable material connection.

[0012] The invention is based on the object of further developing the known solutions.

[0013] The problem is solved by the field device according to claim 1.

[0014] The process automation field device according to the invention comprises:

[0015] - a measuring tube for carrying a flowable medium;

[0016] - a sensor for determining a physical and / or chemical quantity;

[0017] - a plastic housing for protecting the sensor, wherein the plastic housing has individual housing parts, wherein the plastic housing has a housing interior in which the sensor is at least partially arranged;

[0018] - a heating device, characterized in that a material-to-material melt connection between the individual housing parts of the plastic housing, between the plastic housing and the measuring tube and / or between the plastic housing and a transmitter housing is created by means of the heating device.

[0019] Unlike EP 1 696 214 A1 and DE 10 2013 102 544 A1, the subject matter of the invention does not require the measuring tube and the pipeline or the measuring tube and a magnet system adapter to be connected to each other via a heating device, but rather that the individual housing parts of the plastic housing be fused to each other, to the measuring tube, or to a transmitter housing. However, it is not excluded that other components of the field device can also be fixed in place using a heating device.

[0020] Advantageous embodiments of the invention are the subject of the subclaims.

[0021] One embodiment provides that the measuring tube comprises a plastic measuring tube.

[0022] One embodiment provides that the measuring tube comprises a support tube which has at least one partial area in which the support tube is coated with a plastic layer, wherein the cohesive melt connection is located in the coated partial area.

[0023] This has the advantage that the application of the heating device is not limited to purely plastic measuring tubes. The support tube can be, for example, a metal tube, particularly a steel tube, a ceramic tube, or a glass tube. The support tube can be completely coated on its outer surface or, alternatively, only at the points where the plastic housing is in contact with the measuring tube.

[0024] One embodiment provides that the plastic housing has a first and a second half-shell, wherein a material-locking melt connection between the first and second half-shell is created by means of the heating device.

[0025] The first half-shell and the second half-shell can be arranged radially relative to the measuring tube or pushed onto it axially. The first half-shell and the second half-shell form the housing parts, which are joined together via the fusion joint to form the plastic housing.

[0026] One embodiment provides that a triple point is present at which the first half-shell, the second half-shell and the measuring tube meet, wherein the triple point is at least selectively sealed by the material-to-material melt connection.

[0027] A triple point is a point at which three components - in this case the measuring tube, the first half-shell, and the second half-shell - come together. Due to tolerances, a gap can arise at the triple point, which must be subsequently sealed at great expense. This is eliminated if a material-to-material fusion connection created by the heating device is used to connect the individual components. This results in the material of the half-shells and / or the measuring tube melting at the triple point and sealing the triple point. One embodiment provides for the transmitter housing to comprise a plastic transmitter housing in which the measuring and / or communication electronics are arranged, wherein a material-to-material fusion connection between the plastic transmitter housing and the plastic housing is created by means of the heating device.

[0028] One embodiment provides that the transmitter housing comprises a plastic transmitter housing in which the measuring and / or communication electronics are arranged, wherein the plastic housing has a connection piece for the transmitter housing, in particular the plastic transmitter housing, wherein the connection piece is arranged in a connecting manner between the plastic transmitter housing and the plastic housing, wherein a material-to-material melt connection between the connection piece and the plastic housing and / or between the connection piece and the plastic transmitter housing is produced by means of the heating device.

[0029] One embodiment provides that the plastic housing has a first and second collar, wherein the plastic housing has a casing, wherein the first and second collar delimit the housing interior in the axial direction of the measuring tube, wherein the casing delimits the housing interior in the radial direction of the measuring tube, wherein a material-to-material melt connection between the casing and at least the first collar, in particular the first and second collar, is produced by means of the heating device.

[0030] One embodiment provides that the heating device has a heating element which is arranged between the measuring tube and the plastic housing, and / or wherein the heating device has a heating element which is arranged between the plastic housing and the connecting piece, and / or wherein the heating device has a heating element which is arranged between the connecting piece and the plastic transmitter housing, and / or wherein the heating device has a heating element which is arranged between the plastic housing and the plastic transmitter housing.One embodiment provides that the heating device has a heating element which is arranged integrally in a housing body of the plastic housing, and / or wherein the heating device has a heating element which is arranged integrally in a connection piece body of the connection piece, and / or wherein the heating device has a heating element which is arranged integrally in a transmitter housing body of the plastic transmitter housing.

[0031] The heating element can be encapsulated in plastic during the manufacturing process of the plastic housing or the housing parts of the plastic housing, the connection piece body, or the transmitter housing body. This ensures that the heating element is integrally formed within the corresponding component. The heating element can be connected to a power supply via a contacting device on the heating device with electrical connections. When a voltage is applied to the heating element, it is heated. If the temperature of the heating element rises above the melting point of the plastic, the plastic begins to melt. A molten bond forms once the plastic has cooled and hardened. This type of bond is not only extremely strong but also liquid- and gas-tight. This is particularly advantageous in applications where the plastic housing is exposed to the elements.

[0032] One embodiment provides that the heating element comprises a heating foil or a heating welding wire.

[0033] Heating welding wires are offered, for example, by the company Orbi-Tech. A heating welding wire is a resistance wire, e.g., metallic, radially enclosed in a plastic sleeve made of polyethylene or polypropylene. Heating foil is a plastic foil in which a wound or structured resistance wire, e.g., metallic, is integrally arranged.

[0034] One embodiment provides that the material-to-material melt connection is formed by heating the heating device and locally melting the measuring tube and / or the plastic housing and / or the plastic transmitter housing.

[0035] One embodiment provides that the connection is designed to seal the interior of the housing from the outside.

[0036] One embodiment provides that the field device of the process automation is a magnetic inductive flowmeter, wherein the sensor has at least two measuring electrodes and a magnetic field generating device. The invention is explained in more detail with reference to the following figures. It shows:

[0037] Fig. 1: a longitudinal section and a cross section through a first embodiment of the field device according to the invention;

[0038] Fig. 2: a longitudinal section and a cross section through a second embodiment of the field device according to the invention;

[0039] Fig. 3 : a longitudinal section through a third embodiment of the field device according to the invention;

[0040] Fig. 4 : a perspective view of a longitudinal section through a fourth embodiment of the field device according to the invention; and

[0041] Fig. 5 : a perspective view of a longitudinal section through a fifth embodiment of the field device according to the invention.

[0042] Some embodiments of the present disclosure are described in more detail below with reference to the accompanying figures. The figures illustrate some, but not all, embodiments of the disclosure. Indeed, these disclosures may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Different embodiments, each illustrating individual details of the inventive subject matter, may be combined with one another to form new embodiments not shown in the figures. Like numbers refer to like elements throughout.

[0043] The components illustrated in the figures represent components that may or may not be present in various embodiments of the present disclosure described herein, so that the embodiments may include fewer or more components than those illustrated in the figures without departing from the scope of the present disclosure. Some components may be omitted or shown in phantom in one or more figures to reveal underlying components.

[0044] The phrases "in an exemplary embodiment," "some embodiments," "various embodiments," and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure and may be included in more than one embodiment of the present disclosure. Such phrases do not necessarily refer to the same embodiment.

[0045] The word "example" or "exemplary" is used herein to mean "serving as an example or illustration." Any implementation described herein as "exemplary" is not necessarily to be understood as preferred or advantageous over other implementations.

[0046] If the description of the figures states that a component, part, or feature is "preferably," "possibly," "typically," "optionally," or "for example" (or other such wording) included, or that a feature "may" be included, or that a feature "could" or "should" have a property, it is not required that a specific component or feature be included or exhibit the feature. Such components or features may be optionally included in some embodiments, but they may also be excluded. An embodiment not included in the figures may also include all features—provided they do not contradict each other—of the embodiments shown.

[0047] Fig. 1 shows a longitudinal section and a cross-section through a first embodiment of the field device 1 according to the invention. The field device 1 comprises a measuring tube 2 for conveying a flowable medium. The measuring tube 2 can have a round or square cross-section. In the case of a square cross-section, the corners can be rounded. The measuring tube 2 shown is made of a plastic. The measuring tube 2 can be made entirely of a plastic or additionally comprise a fiber composite to increase its load-bearing capacity.

[0048] To determine a physical and / or chemical measured variable, the field device 1 has a sensor 3. The physical and / or chemical measured variable can be, for example, the flow velocity, volume flow, mass flow, pressure, temperature, density, pH value, electrolytic conductivity, fill level, concentration, degree of fermentation, or viscosity of the medium. The sensor 3 itself can be a pH probe, a conductivity probe, a temperature sensor, or a pressure sensor. Alternatively, the sensor 3 can also include components necessary for determining a flow velocity, volume flow, mass flow, and / or viscosity.Thus, the sensor 3 can comprise at least two measuring electrodes and a magnet system in order to determine a flow velocity of the guided medium based on Faraday's law of electromagnetic induction. Alternatively, the sensor 3 can comprise at least two ultrasonic transducers spaced apart from one another in the flow direction, which are configured to determine a flow velocity or a variable of the medium derived therefrom based on a transit time difference measurement. Alternatively, the sensor 3 can comprise a vibration exciter and one or two vibration sensors, which together are configured to determine a mass flow and / or a viscosity based on the vibration behavior of the measuring tube 2. Alternatively, the sensor 3 can comprise a paddle protruding into the measuring channel of the measuring tube, which paddle is used to determine a flow velocity or a variable of the flowing medium derived therefrom.The field device 1 shown comprises a plastic housing 4 for protecting the sensor 3, which is arranged on the outer surface of the measuring tube and at least partially encloses the sensor 3. The plastic housing 4 has individual housing parts 30, 31, which together form the plastic housing 4 and enclose a housing interior 4*. The housing parts 30, 31 can, for example, be at least two half-shells arranged on the outer surface of the measuring tube in the radial direction of the measuring tube. The sensor 3 is at least partially arranged in the housing interior 4*. This means that the sensor 3 can be located entirely within the housing interior 4* or, alternatively, can extend through an opening in the plastic housing 4, so that one part is located within the housing interior 4* and another part is located outside the housing interior 4*.

[0049] According to the invention, the field device 1 has a heating device 5 which is designed to create a materially bonded fused connection between the plastic housing 4 and the measuring tube 2 during the manufacture of the field device 1. The housing body of the plastic housing 4 is heated by means of the heating device 5, which leads to the local melting of the plastic housing body of the plastic housing 4. The molten section of the housing body then bonds to the outer surface of the measuring tube 2. The measuring tube 2 can also be formed from a plastic which is selected such that it is also melted at least in sections by the heating device. If both parts to be joined are melted and not just one part, an even improved fused connection can be achieved.

[0050] The heating device 5 comprises a heating element 17a, which can be arranged between the measuring tube 2 and the plastic housing 4 or which can be arranged integrally in the plastic housing 4.

[0051] The housing parts 30, 31 can be a first and a second half-shell 10a, 10b. Thus, a material-to-material fusion connection created by the heating device 5 would be present between the first and second half-shells 10a, 10b. At a connection point between the first and second half-shells 10a, 10b and the measuring tube 2, a so-called triple point 11 forms. At this point, a gap often forms that requires complex sealing. The triple point 11 can be sealed at least selectively by the material-to-material fusion connection. The heating device 5 can be configured to melt the contact area of ​​the two half-shells 10a, 10b and / or the outer surface of the measuring tube 2 in such a way that the heated material fills and seals the triple point 11.

[0052] Fig. 2 shows a longitudinal section and a cross-section through a second embodiment of the field device 1 according to the invention. The second embodiment differs from the first embodiment in that the measuring tube 2 has a support tube 7 which is made of a metal, a glass, a ceramic or a plastic and which is coated with a plastic layer 8 at least in a partial area 9. The plastic layer 8 can be located on the entire outer surface of the support tube 7 or only cover at least a partial area 9 in which the material-to-material fusion connection is also located.

[0053] Furthermore, the second embodiment differs from the first embodiment in that a material-to-material melt connection is created between the plastic housing 4 and the measuring tube 2 via the plastic layer 8.

[0054] Furthermore, in addition to the heating element 17a, the heating device 5 has a heating element 17b, which can be arranged between the components 30, 31 of the plastic housing 4 or which can be arranged integrally in an edge region of one of the components 30, 31. The heating element 17b is designed to be heated after the components 30, 31 have been mounted or positioned on the measuring tube 2, in order to melt the corresponding edge region of the component 30, 31 or the edge regions of the at least two components 30, 31 and thus create a fused connection between the two components 30, 31.

[0055] Fig. 3 shows a longitudinal section through a third embodiment of the field device 1 according to the invention. The third embodiment differs from the first embodiment in that the plastic housing 4, in addition to a first and second collar 15a, 15b, also has a casing 16, which together form the plastic housing 4 in the finally assembled state. The first and second collars 15a, 15b delimit the housing interior 4* in the axial direction of the measuring tube 2. The casing 16, on the other hand, delimits the housing interior 4* in the radial direction of the measuring tube 2. A heating element 17b can be arranged between the first collar 15a and / or the second collar 15b and the casing 16. Alternatively, the heating element 17b can be integrated into the first collar 15a and / or the second collar 15b. Alternatively, the heating element 17b can also be integrated into the casing 16. The heating element 17b is ora plurality of heating elements 17b are part of the heating device 5. The heating device 5 is designed to produce a material-locking fusion connection between the individual housing parts, ie the first collar 15a, the second collar 15b and / or the casing 16.

[0056] Fig. 4 shows a perspective view of a longitudinal section through a fourth embodiment of the field device 1 according to the invention. The field device 1 shown is a magnetic-inductive flowmeter 20, the sensor of which has at least two measuring electrodes 21, 22 and a magnetic field generating device 23. The magnetic field generating device 23 can comprise at least one coil with a coil core, which is arranged on the outer surface of the measuring tube 2. The at least two measuring electrodes 21, 22 can be designed as capacitive electrodes that are spaced from the medium by the wall of the measuring tube 2 or - as shown - as galvanic electrodes, each of which is arranged in an opening of the measuring tube 2 and is designed to be in contact with the medium when a medium flows through the measuring tube 2 or when a medium is located in the measuring tube 2.The fourth embodiment can have the details of the three previous embodiments. However, the illustrated fourth embodiment differs from the previous embodiments at least in that a materially bonded fused connection is created between the plastic housing 4 and a connecting piece 14 by means of the heating device 5. The connecting piece 14 serves as an intermediate piece or adapter for a transmitter housing (not shown, see Fig. 5), in which the measuring and / or communication electronics (not shown, see Fig. 5) are arranged. The connecting piece 14 can preferably be formed from a plastic and have the heating element 17c and the heating element 17d integrated into the plastic body of the connecting piece 14. Alternatively, the heating element 17c can be arranged between the connecting piece 14 and the plastic housing 4. Alternatively, the heating element 17d can be arranged between the connecting piece 14 and the transmitter housing.During assembly of the field device 1, the heating element 17c is configured to create a material-to-material melt connection between the connection piece 14 and the plastic housing 4. During assembly of the field device 1, the heating element 17d is configured to create a material-to-material melt connection between the connection piece 14 and the transmitter housing.

[0057] Fig. 5 shows a perspective view of a longitudinal section through a fifth embodiment of the field device 1 according to the invention. The fifth embodiment differs from the fourth embodiment in that the transmitter housing 6 is connected directly to the plastic housing 4. A connection piece, as in the fourth embodiment, is not provided. The transmitter housing 6 shown comprises a plastic transmitter housing 12 in which the measuring and / or communication electronics 13 are arranged. Since no connection piece is provided, the connection must be made directly between the plastic transmitter housing 12. Therefore, a material-to-material fusion connection exists between the plastic transmitter housing 12 and the plastic housing 4, which is created by means of the heating device 5.Thus, the heating device 5 has a heating element 17e, which can be arranged between the plastic housing 4 and the plastic transmitter housing 12 or which can be integrated into the transmitter housing body 12' of the plastic transmitter housing 12. Alternatively, the integral melt connection can also be established via a heating element (not shown) integrated into the plastic housing 4, in particular in a contact area in contact with the transmitter housing 6.

[0058] For all configurations, the heating element 17a, 17b, 17c, 17d, 17e can comprise a heating foil 17* or a heating welding wire 17'. Heating welding wires are offered, for example, by the company Orbi-Tech. A heating welding wire is a resistance wire, e.g., a metallic one, radially enclosed in a plastic sleeve made of polyethylene or polypropylene. The heating foil is a plastic foil in which a wound resistance wire, e.g., a metallic one, is arranged integrally or forming a structure.

[0059] For all embodiments, the fusible link can be designed to seal the housing interior 4* from the outside.

Claims

PATENT CLAIMS 1. Field device for process automation (1), comprising: - a measuring tube (2) for carrying a flowable medium; - a sensor (3) for determining a physical and / or chemical measured variable; - a plastic housing (4) for protecting the sensor (3), wherein the plastic housing (4) has individual housing parts (30, 31), wherein the plastic housing (4) has a housing interior (4*) in which the sensor (3) is at least partially arranged; - a heating device (5), characterized in that a material-to-material melt connection between the individual housing parts (30, 31) of the plastic housing (4), between the plastic housing (4) and the measuring tube (2) and / or between the plastic housing (4) and a transmitter housing (6) is produced by means of the heating device (5).

2. Field device of process automation (1) according to claim 1, wherein the measuring tube (2) comprises a plastic measuring tube (2).

3. Field device of process automation (1) according to claim 1 or 2, wherein the measuring tube (2) comprises a support tube (7) which has at least one partial region (9) in which the support tube (7) is coated with a plastic layer (8), wherein the material-to-material melt connection is located in the coated partial region (9).

4. Field device of process automation (1) according to one of the preceding claims, wherein the plastic housing (4) has a first and second half shell (10a, 10b), wherein a material-to-material melt connection between the first and second half-shells (10a, 10b) is produced by means of the heating device (5).

5. Field device of process automation (1) according to claim 4, wherein a triple point (11) is present at which the first half-shell (10a), the second half-shell (10b) and the measuring tube (2) meet, wherein the triple point (11) is at least selectively sealed by the material-to-material melt connection.

6. Field device of process automation (1) according to one of the preceding claims, wherein the transmitter housing (6) comprises a plastic transmitter housing (12) in which the measuring and / or communication electronics (13) are arranged, wherein a material-to-material melt connection between the plastic transmitter housing (12) and the plastic housing (4) is produced by means of the heating device (5).

7. Field device of process automation (1) according to one of claims 1 to 5, wherein the transmitter housing (6) comprises a plastic transmitter housing (12) in which the measuring and / or communication electronics (13) are arranged, wherein the plastic housing (4) has a connection piece (14) for the transmitter housing (6), in particular the plastic transmitter housing (12), wherein the connection piece (14) is arranged in a connecting manner between the plastic transmitter housing (12) and the plastic housing (4), wherein a material-to-material melt connection between the connection piece (14) and the plastic housing (4) and / or between the connection piece (14) and the plastic transmitter housing (12) is produced by means of the heating device (5).

8. Field device of process automation (1) according to one of the preceding claims, wherein the plastic housing (4) has a first and second collar (15a, 15b), wherein the plastic housing (4) has a casing (16), wherein the first and second collars (15a, 15b) delimit the housing interior (4*) in the axial direction of the measuring tube (2), wherein the casing (16) delimits the housing interior (4*) in the radial direction of the measuring tube (2), wherein a material-to-material melt connection between the casing (16) and at least the first collar (15a), in particular the first and second collars (15a, 15b), is produced by means of the heating device (5).

9. Field device of process automation (1) according to one of the preceding claims, wherein the heating device (5) has a heating element (17a) which is arranged between the measuring tube (2) and the plastic housing (4), and / or wherein the heating device (5) has a heating element (17b) which is arranged between the components (30, 31) of the plastic housing (4), and / or wherein the heating device (5) has a heating element (17c) which is arranged between the plastic housing (4) and the connecting piece (14), and / or wherein the heating device (5) has a heating element (17d) which is arranged between the connecting piece (14) and plastic transmitter housing (12), and / or wherein the heating device (5) has a heating element (17e) which is arranged between the plastic housing (4) and the plastic transmitter housing (12).

10. Field device of process automation (1) according to one of claims 1 to 8, wherein the heating device (5) has a heating element (17a, 17b) which is arranged integrally in a housing body (4') of the plastic housing (4), and / or wherein the heating device (5) has a heating element (17c, 17d) which is arranged integrally in a connection piece body (14') of the connection piece (14), and / or wherein the heating device (5) has a heating element (17e) which is arranged integrally in a transmitter housing body (12') of the plastic transmitter housing (12).

11. Field device of process automation (1) according to claim 9 or 10, wherein the heating element (17a, 17b, 17c, 17d, 17e) comprises a heating foil (17*) or a heating welding wire (17').

12. Field device of process automation (1) according to one of the preceding claims, wherein the material-to-material melt connection is formed by heating the heating device (5) and locally melting the measuring tube (2) and / or the plastic housing (4) and / or the plastic transmitter housing (12).

13. Field device of process automation (1) according to one of the preceding claims, wherein the melt connection is designed to seal the housing interior (4*) to the outside.

14. Field device of process automation (1) according to one of the preceding claims, wherein the field device of process automation (1) is a magnetic-inductive flow meter (20), wherein the sensor (3) has at least two measuring electrodes (21, 22) and a magnetic field generating device (23).

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