Housing for a field device for process automation and field device

Abstract

The invention relates to a housing (100) for a field device for process automation. A mounting neck (1) has a mounting structure (10), and a cover has a corresponding mounting structure (20). The cover (2) has a base (21), an opening (210) in the base (21), a wall (22) for the mounting structure (20), an insert (3), a sealing element (4), a sliding ring (5), and a viewing window (6). The viewing window (6) is located in a receiving chamber (31) of the insert (3). When the mounting neck (1) and the cover (2) are connected, the mounting neck (1) presses against the insert (3) via the sealing element (4), which in turn presses the sliding ring (5) against the base (21) of the cover (2).

Description

[0001] The invention relates to a housing for a field device for process automation. The invention further relates to a field device. The field device serves, for example, to determine and / or monitor process variables such as fill level, flow rate, mass flow rate, pressure, temperature, or pH value.

[0002] In modern technology, it is common practice to monitor and control processes in process plants using field devices. These field devices are therefore designed either as sensors or actuators.

[0003] Field devices, in the form of sensors, typically have a housing containing electronics coupled to a suitable measuring unit. This measuring unit usually detects the process variable or a related measurement parameter. The housing is generally multi-part and can be opened multiple times. Access is usually provided via a cover.

[0004] Such housings, or at least their lids, are made partially or entirely of sheet metal. Due to the limitations of the manufacturing process inherent in the choice of material, a bayonet fitting or any other type of closure is used, requiring only one type of guide for the necessary insertion and twisting motion when attaching the lid. The seal between the housing and lid is typically achieved with an elastomer material that is compressed when the lid is closed. This compression can be either radial or axial (e.g., similar to a jam jar).

[0005] The rotational movement generates friction due to the contact between the sealing element and the lid. This frictional force must be overcome during the lid's rotation and should therefore be as low as possible. The frictional force and the degree of compression of the sealing element are interdependent. Consequently, such sealing concepts are often characterized either by low compression with low frictional forces or by high compression with high frictional forces. A higher degree of compression results in a stronger seal. However, the desirable combination of high compression and low frictional forces is not currently found in the art.

[0006] Covers that allow a view of, for example, a display unit located inside the housing are also known in the prior art. For this purpose, the so-called viewing cover has a recess beneath which is a viewing window made of glass or translucent plastic. The corresponding electronic component is located beneath this window. Because of the opening in the cover, a seal against the interior of the cover is required.

[0007] The DE 10 2021 110 826 A1 shows a housing for a field device, the two-part cover of which is connected to the housing body via a bayonet fitting. For the sealing function, a sealing ring is pressed by the cover against a stop surface of the housing.

[0008] The invention is based on the objective of proposing a housing with a removable viewing cover that is characterized by both the easiest possible assembly and the highest possible sealing effect.

[0009] The invention solves the problem by providing a housing for a field device for process automation, comprising a mounting neck and a cover, wherein the mounting neck has a mounting structure, wherein the cover has a mounting structure that corresponds to the mounting structure of the mounting neck and allows a reversible connection between the mounting neck and the cover, wherein the cover has a base and a wall, wherein the base has an opening, wherein the wall of the cover supports the mounting structure, wherein the cover has an insert, a sealing element, a sliding ring and a viewing window, wherein the insert has a receiving space, wherein the receiving space and the viewing window are designed and aligned such that the receiving space accommodates the viewing window, and wherein, in the case that the mounting neck and the cover are connected to each other,The fastening neck presses against the insert via the sealing element, and the insert – preferably via the viewing window – presses the sliding ring against the bottom of the lid.

[0010] The housing has a lid that is connected to a mounting neck via corresponding fastening structures. The lid is essentially pot-shaped, comprising a base and a surrounding wall. In one embodiment, the lid has its fastening structures on the inside and the mounting neck on the outside, so that the lid at least partially encompasses the mounting neck when the housing is assembled. In an alternative embodiment, the mounting neck has its fastening structure on its inside, and the lid has its corresponding fastening structure on its outside.

[0011] The lid also features an opening and a viewing window in its base. The viewing window fills the gap in the base and allows a view into the housing. For this purpose, the viewing window is preferably larger than, or at least the same size as, the opening in the base, provided that its outer diameter is greater than or equal to the inner diameter of the opening.

[0012] The sliding ring reduces the frictional forces between the disc and the lid. Because it lies flush against both the disc and the lid, it also prevents, for example, the ingress of foreign objects.

[0013] The viewing window is located in a receiving chamber of the insert, wherein the sliding ring preferably seals a transition between the viewing window and the insert.

[0014] For sealing between the cover and the interior of the field device, the cover features an insert and a sealing element. When the housing is assembled, i.e., when the cover is mounted on the mounting collar, the collar presses against the insert via the sealing element, thus creating a seal. Furthermore, the insert presses the sliding ring against the base of the cover. This movement preferably occurs via the viewing window, so that the insert presses the viewing window against the sliding ring and thus indirectly presses the sliding ring against the base. At least when screwed into place, the insert is preferably free from direct contact with the base of the cover.

[0015] Provided the sealing element is elastically deformable, when the lid and mounting neck are screwed together, only a frictional force acts between the sliding ring and the lid. Therefore, suitable materials can be used and combined that are characterized by the lowest possible frictional force.

[0016] The compression builds up gradually during the fastening of the lid onto the mounting collar, as the distance between the upper end of the mounting collar and the base of the lid is continuously reduced. The maximum compression depends in particular on the dimensions of the sealing element, insert, sliding ring, any viewing window, the base of the lid, and the extent to which the mounting collar protrudes into the lid when fixed.

[0017] One advantage of the invention is therefore the separation of the axial movement, which leads to the compression of the sealing element, from the rotational movement of the cover relative to the mounting neck. Therefore, friction can be reduced in those components that are in mechanical contact with each other by using suitable material pairings.

[0018] In one embodiment, the cover and the mounting neck are connected via a rotational movement. This results in axial movement between the cover and mounting neck relative to each other, thereby compressing the sealing element.

[0019] In one embodiment, the sealing element consists at least partially of an elastomer. One embodiment of the housing includes a sealing element that is an O-ring, an X-ring, or a molded seal.

[0020] In one design, the insert consists at least partially of a metal.

[0021] The materials of the sliding ring and the cover – especially the cover base – are selected and coordinated in such a way that the resulting material pairing produces the lowest possible coefficient of friction. The choice of materials also depends, for example, on the structure or roughness of the contacting surfaces.

[0022] One design of the housing provides for a bayonet-style closure for both the lid and the mounting neck. In an alternative design, the mounting structures consist of an internal and a corresponding external thread.

[0023] One design of the housing includes an insert with a bottom and a top. The bottom provides the receiving space, and the top is designed to accommodate the sealing element. When installed, the bottom, with the receiving space for the viewing window, faces the bottom of the lid. The top of the insert also features a receptacle for the sealing element, ensuring that the sealing element is securely positioned on the insert and thus in the correct location within the lid.

[0024] In one embodiment, the contact surface is a circular ring around the longitudinal axis of the insert.

[0025] The mounting neck is preferably designed as a hollow cylinder with a circular base.

[0026] Furthermore, the invention relates to a field device with a housing according to one of the preceding or following embodiments. The explanations apply accordingly to the field device, so repetition is omitted. The field device serves, for example, to measure or monitor fill level, temperature, pressure, flow rate, or pH value.

[0027] The invention is explained in more detail with reference to the following figures. They show: Fig. 1: a spatial representation of the screwed-together housing and Fig. 2: a section through part of the casing of the Fig. 1.

[0028] The Fig. Figure 1 shows a housing 100 of a field device with a lower component that carries the mounting neck 1 and a cover 2. The cover 2 has an opening 210 through which a display unit (not shown) located inside the housing 100 can be viewed. A viewing window 6 is located in the cover 2 (more precisely, in the base 21, which is oriented upwards here), and this window closes the housing 100. A section of the sliding ring 5 is located between the viewing window 6 and the rim of the opening 210 in the cover 2. The position of a part of the mounting structure 20 can be seen on the outside of the wall 22 of the cover 2.

[0029] The Fig. Figure 2 shows part of a section through the housing 100 of the Fig. 1.

[0030] The cover 2 is shown screwed onto the mounting neck 1. The connection is achieved via a bayonet fitting. For this purpose, the mounting neck 1 has a mounting structure 10 on its outer surface, and the cover 2 has a corresponding mounting structure 20 on the inner surface of its wall 22, into which the mounting structure 10 of the mounting neck 1 engages.

[0031] The lid 2 has an opening 210 in its base 21. The pot- or cup-shaped lid 2 contains the viewing window 6, which is made of glass, for example, and whose outer diameter is larger than the inner diameter of the opening 210.

[0032] The viewing window 6 lies in the receiving space 31 of the insert 3, which is designed here as a radially circumferential support surface around a central recess. A sealing component – ​​not shown here – ensures a seal between the viewing window 6 and the insert 3. The central recess allows a clear view of the display unit of the field device – also not shown here.

[0033] The sealing of a transition between the cover 2 and the mounting neck 1 or the interior of the housing 100 is carried out at the upper end face of the mounting neck 1. The insert 3 has a radially circumferential receptacle 30 in which the sealing element 4 is located.

[0034] In the assembled state shown here, the upper end of the mounting neck 1 presses into the sealing element 4. This, in turn, pushes the insert 3 towards the viewing window 6 and thus the sliding disc 5 against the base 21. As a result, only the base 21 of the cover 2 and the sliding ring 5 have very reduced indirect contact. Friction can be further reduced through an optimized material combination. Reference symbol list 1 Mounting neck 2 lids 3 insert 4 Sealing element 5 sliding ring 6 Viewing window 10 Mounting structure of the mounting neck 20 Lid fastening structure 21 Bottom of the lid 22 Wall of the lid 30 Insertion of the insert 31 Receiving space of the insert 100 cases 210 Opening the bottom of the lid QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 110 826 A1

[0007]

Claims

[1] Housing (100) for a field device for process automation, with a mounting neck (1) and a cover (2), wherein the fastening neck (1) has a fastening structure (10), wherein the lid (2) has a fastening structure (20) which corresponds to the fastening structure (10) of the fastening neck (1) and allows a reversible connection between the fastening neck (1) and the lid (2), wherein the lid (2) has a base (21) and a wall (22), wherein the base (21) has an opening (210), wherein the wall (22) of the lid (2) supports the fastening structure (20), wherein the lid (2) has an insert (3), a sealing element (4), a sliding ring (5) and a viewing window (6), wherein the insert (3) has a receiving space (31), wherein the receiving chamber (30) and the viewing window (6) are designed and coordinated such that the receiving chamber (31) accommodates the viewing window (6), and wherein, in the case that the fastening neck (1) and the lid (2) are connected to each other, the fastening neck (1) presses against the insert (3) via the sealing element (4) and the insert (3) - preferably via the viewing window (6) - presses the sliding ring (5) against the bottom (21) of the lid (2). [2] Housing (100) according to claim 1, wherein in the case that the insert (3) presses the sliding ring (5) against the base (21), the insert (3) is free from direct contact with the base (21) of the cover (2). [3] Housing (100) according to claim 1 or 2, wherein the opening (210) of the base (21) and the viewing window (6) are designed and aligned such that the viewing window (6) has an outer diameter greater than or equal to an inner diameter of the opening (210). [4] Housing (100) according to one of claims 1 to 3, wherein the insert (3), the sliding ring (5) and the viewing window (6) are designed and coordinated such that the sliding ring (5) seals at least one transition between the viewing window (6) and the insert (3). [5] Housing (100) according to any one of claims 1 to 4, wherein the fastening structure (20) of the cover (2) and the fastening structure (10) of the fastening neck (1) implement a bayonet closure. [6] Housing (100) according to any one of claims 1 to 5, wherein the insert (3) has a bottom (30) and a top (32), wherein the underside (30) has the receiving space (31), and wherein the top side (32) is designed to have a receiving space (30) for the sealing element (4). [7] Housing (100) according to any one of claims 1 to 6, wherein the sealing element (4) is an O-ring, an X-ring or a molded seal, and / or wherein the sealing element (4) is made of an elastomer. [8] Field device for determining and / or monitoring at least one process variable with a housing (100) according to any one of claims 1 to 7.

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