Housing for a process automation field device, and field device

Abstract

The invention relates to a housing (100) for a process automation field device. A fastening neck (1) has a fastening structure (11), and a cover has a corresponding fastening structure (21). A cover (2), which comprises a base (22) and a wall (23) that carries the fastening structure (21), has an insert part (3) and a sealing element (4). When the fastening neck (1) and the cover (2) are connected to one another, the fastening neck (1) presses, via the sealing element (4), against the insert part (3), which rests on the base (22) of the cover (2).

Description

[0001] Housing for a field device for process automation and field device

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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).

[0006] 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.

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

[0008] The invention is based on the objective of proposing a housing with a removable lid 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 – preferably on an outer surface – has a mounting structure, wherein the cover – preferably on an inner surface – has a mounting structure which 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 wall of the cover carries the mounting structure, wherein the cover has an insert and a sealing element, and wherein, in the case that the mounting neck and the cover are connected to each other, the mounting neck presses against the insert via the sealing element and the insert rests on the base of the cover.

[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] For sealing, the lid features an insert and a sealing element. The lid, the mounting collar, the insert, and the sealing element are designed and coordinated so that when the lid is placed on the mounting collar—that is, when the housing is assembled—the mounting collar presses against the insert via the sealing element, causing the insert to rest on the bottom of the lid. The mounting collar thus indirectly presses—via the sealing element—on the insert, which rests on the bottom of the lid. This creates a seal between the mounting collar and the insert, provided by the sealing element, and between the lid and the insert.

[0012] Provided the sealing element is elastically deformable, when the lid and mounting neck are screwed together, only a frictional force acts between the insert and the lid. Therefore, suitable materials can be used and combined that are characterized by the lowest possible frictional force.

[0013] 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, the insert, the base of the lid, and the extent by which the mounting collar protrudes into the lid when fixed.

[0014] By separating axial and radial movement according to the invention for the sealing function or fixing, the respective components involved can be appropriately designed and coordinated to obtain the desired housing.

[0015] 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.

[0016] 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.

[0017] In one embodiment, the sealing element consists at least partially of an elastomer.

[0018] In one design, the insert consists at least partially of a metal.

[0019] The materials of the insert and the lid – especially the lid 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.

[0020] One design of the housing provides that the mounting structure of the lid and the mounting structure of the mounting neck implement a bayonet closure.

[0021] In an alternative design, the fastening structures consist of an internal thread and a corresponding external thread.

[0022] One embodiment of the housing includes an insert with a bottom and a top surface. The bottom surface is designed to have a locally limited contact area, and the top surface is designed to have a receptacle for the sealing element. This embodiment reduces the area responsible for friction between the insert and the base of the lid. Contact across the entire underside, which faces the base of the lid when assembled, is preferably avoided. The contact surface and the base of the lid are preferably designed to correspond with each other in order to further reduce friction. The top surface 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.

[0023] In one embodiment, the contact surface is a circular ring around the longitudinal axis of the insert.

[0024] One design of the housing provides that the insert is configured so that the contact surface and the receptacle are opposite each other. In this configuration, the contact surface is located below the receptacle when the insert is mounted. Therefore, when mounted, the mounting collar presses vertically against the insert and thus onto the contact surface, ensuring optimal force transmission.

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

[0026] One embodiment of the housing includes a cover with a friction surface on its base, and the insert and cover are designed and aligned such that, during the connection of the mounting collar and cover, essentially only the friction surface and the bearing surface are in contact with each other, both with respect to the base and the underside. In this embodiment, the base of the cover has a friction surface over which, and only over which, the bearing surface of the insert is guided by friction during the assembly of the cover and mounting collar.

[0027] One embodiment of the housing provides that the receptacle is formed by at least one circumferential rim. In this embodiment, the receptacle for the sealing element is formed by at least one circumferential rim. Depending on the specific design, the rim surrounds the top of the insert either radially outwards or radially inwards. This prevents the sealing element from being displaced, for example, outwards or inwards. As a result, the sealing element remains in the required position.

[0028] One embodiment of the housing involves the sealing element and the rim being designed and aligned such that the sealing element lies radially outside the rim. In this embodiment, the sealing element surrounds the rim of the receptacle, thus encompassing the rim.

[0029] One embodiment of the housing provides that the receptacle is formed by an inner circumferential rim and an outer circumferential rim, and that the sealing element is located between the inner and outer circumferential rims. In this embodiment, the sealing element is situated between two rims and is laterally confined by them. During compression, the lateral movement of the sealing element is thus limited.

[0030] One embodiment of the housing involves the outer circumferential rim and the sealing element being designed and aligned such that the outer circumferential rim at least partially overlaps the sealing element. In this embodiment, the sealing element is partially located between an upper end of the outer rim and the section of the insert on which it rests. This serves to integrate the insert and the sealing element into a single component, which simplifies both the manufacturing and handling of the housing.

[0031] One design of the housing includes the sealing element being an O-ring, an X-ring, or a molded seal.

[0032] One embodiment of the housing provides that the wall and / or the mounting neck have a pre-chamber, that, at least in the case where the mounting neck and the cover are connected, the pre-chamber is located on a side of the wall facing away from the bottom, that the housing further has a sealing lip, and that, in the case where the mounting neck and the cover are connected, the sealing lip is located at least partially within the pre-chamber. Since the sealing only occurs at the end face of the mounting neck, this embodiment provides a kind of upstream seal or at least protection for the area between the end face of the cover and the end face of the mounting neck, i.e., the area of ​​the mounting neck that is enclosed by the wall of the cover.For this purpose, a sealing lip, preferably made of an elastomer or any other sealing material, is located in a chamber upstream of the following area. The sealing lip can thus also be understood as a dust trap.

[0033] 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.

[0034] The invention is explained in more detail with reference to the following figures. They show:

[0035] Fig. 1: a section through a field device,

[0036] Fig. 2: an enlarged section of Fig. 1 and

[0037] Fig. 3: an enlarged section through an alternative design of a field device.

[0038] Figure 1 shows a section through a field device, and Figure 2 shows a detail thereof. Both figures are described together below. The depicted design is essentially rotationally symmetrical about the longitudinal axis 101.

[0039] The field device of Fig. 1 comprises a housing 100 with a body containing electronics or measuring components (not shown) and a cover 2, which is screwed onto a mounting neck 1. The connection is achieved via a bayonet fitting. For this purpose, the mounting neck 1 has a suitable mounting structure 11 on its outer surface 10, and the cover 2 has a corresponding mounting structure 21 on its inner surface 20, into which the mounting structure 11 of the mounting neck 1 engages.

[0040] The actual sealing of the transition between the cover 2 and the mounting neck 1 or the interior of the housing 100 takes place at the upper end face of the mounting neck 1. To protect the area with which the wall 23 of the cover 2 surrounds the mounting neck 1, a front sealing lip 5 is located in a pre-chamber 12, which here is formed only by the mounting neck 1 (see Fig. 2).

[0041] The sealing function is performed by the insert 3 and the sealing element 4 located on it, which in this case is, for example, an O-ring. In the assembled state shown here, the upper end of the mounting neck 1 presses into the sealing element 4, thereby pressing the insert 3 against the base 22 of the cover 2. The contact between the cover 2 and the insert 3 is reduced to the annular contact area shown here between the friction surface 24 of the cover 2 and the bearing surface 31 of the insert 3. This significantly reduces the friction between the two components 2 and 3, which then only occurs in these well-defined areas.

[0042] The bearing surface 31 of the insert 3 is located on the underside 30 of the insert 3, which, in the assembled state shown here, faces the top of the field device and the base 22 of the cover 2. The top surface 32 of the insert 3 has a receptacle 33 for the sealing element 4 on its radial outer surface. The receptacle 33 is formed by a radially inner circumferential rim 34 and a radially outer circumferential rim 34'. The sealing element 4 can thus be placed on the top surface 32 of the insert 3 and is then laterally encompassed by the two circumferential rims 34 and 34'. As already mentioned, it is fixed perpendicular to the top surface 32 by the upper end of the mounting collar 1. Fig. 3 shows an alternative embodiment of the cover 2 and mounting collar 1. Only the differences from the embodiment shown in Fig. 2 are described below.In this embodiment, it is very clearly visible how the bearing surface 31 of the insert 3 rests on the friction surface 24 of the cover 2. Furthermore, the receptacle 33 of the insert 3 is formed here only by a circumferential rim 34, which is located radially inside relative to the sealing element 4.

[0043] Reference symbol list

[0044] Mounting neck

[0045] Lid

[0046] insert

[0047] Sealing element

[0048] Sealing lip

[0049] Outside of the mounting neck

[0050] Mounting structure of the mounting neck

[0051] Atchamber

[0052] Inside of the lid

[0053] Lid mounting structure

[0054] bottom of the lid

[0055] Wall of the lid

[0056] friction surface of the lid

[0057] Underside of the insert

[0058] Support surface of the insert

[0059] Top side of the insert

[0060] Insert recess, 34' circumferential edge of the insert 0 housing 1 longitudinal axis

Claims

Patent claims 1. Housing (100) for a field device for process automation, comprising a mounting neck (1) and a cover (2), wherein the mounting neck (1) has a mounting structure (11) preferably on an outer surface (10), wherein the cover (2) has a mounting structure (21) preferably on an inner surface (20) which corresponds to the mounting structure (11) of the mounting neck (1) and allows a reversible connection between the mounting neck (1) and the cover (2), wherein the cover (2) has a base (22) and a wall (23), wherein the wall (23) of the cover (2) supports the mounting structure (21), wherein the cover (2) has an insert (3) and a sealing element (4), and wherein, in the case that the mounting neck (1) and the cover (2) are connected to each other, the mounting neck (1) presses against the insert (3) via the sealing element (4), and the insert (3) rests on the bottom (22) of the lid (2).

2. Housing (100) according to claim 1, wherein the fastening structure (21) of the cover (2) and the fastening structure (11) of the fastening neck (1) implement a bayonet closure.

3. Housing (100) according to claim 1 or 2, wherein the insert (3) has a bottom (30) and a top (32), wherein the bottom (30) is designed to have a locally limited support surface (31), and wherein the top (32) is designed to have a receptacle (33) for the sealing element (4).

4. Housing (100) according to claim 3, wherein the insert (3) is designed such that the support surface (31) and the receptacle (33) are opposite each other.

5. Housing (100) according to claim 3 or 4, wherein the lid (2) has a friction surface (24) on the base (22), and wherein the insert (3) and the lid (2) are designed and aligned such that, during connection of the fastening neck (1) and the lid (2) to each other, with respect to the base (22) and the underside (30), substantially only the friction surface (24) and the bearing surface (31) are in contact with each other.

6. Housing (100) according to one of claims 3 to 5, wherein the receptacle (33) is formed by at least one circumferential rim (34, 34').

7. Housing (100) according to claim 6, wherein the sealing element (4) and the rim (34) are designed and aligned such that the sealing element (4) is located radially outside to the rim (34).

8. Housing (100) according to claim 6, wherein the receptacle (33) is formed by an inner circumferential rim (34) and by an outer circumferential rim (34'), and wherein the sealing element (4) is located between the inner circumferential rim (34) and the outer circumferential rim (34').

9. Housing (100) according to claim 8, wherein the outer circumferential rim (34') and the sealing element (4) are designed and aligned such that the outer circumferential rim (34') overlaps the sealing element (4) at least partially.

10. Housing (100) according to any one of claims 1 to 9, wherein the sealing element (4) is an O-ring, an X-ring or a molded seal.

11. Housing (100) according to any one of claims 1 to 10, wherein the wall (23) and / or the mounting neck (1) has / has a pre-chamber (12), wherein, at least in the case where the mounting neck (1 ) and the cover (2) are connected to each other, the pre-chamber (12) is located on a side of the wall (23) facing away from the bottom (22), wherein the housing (100) further comprises a sealing lip (5), and wherein, in the case where the mounting neck (1 ) and the cover (2) are connected to each other, the sealing lip (5) is located at least partially in the pre-chamber (12).

12. Field device for determining and / or monitoring at least one Process size with a housing (100) according to one of claims 1 to 11.

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