Housing for a process automation field device, and field device

Abstract

The invention relates to a housing. A viewing pane (2) rests on a base (10) of the cover (1) having a recess (11). A peripheral groove (13) in an inner wall (12) of a cover (1) is delimited by a peripheral edge (14) which has an opening (15). The clamping ring (3) is arranged partially in the groove (13) and projects partially therefrom. The viewing pane (2) is in direct contact with the clamping ring (3) and is under axial preload. The clamping ring (3) comprises a ring structure (30) and, on a radial outer side (31), a tensioning element (32). The tensioning element (32) or the ring structure (30) is elastically resilient, or the tensioning element (32) is elastically resiliently connected to the ring structure (30). The tensioning element (32) projects beyond a plane in which the ring structure (30) is located, specifically towards a side facing away from the base (10).

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 as either sensors or actuators. The sensors typically have a housing containing electronics coupled to a measuring unit. The measuring unit usually detects a process variable or a related measurement variable. The housing is generally multi-part and can be opened multiple times. Access is typically provided via a cover.

[0004] Such housings, or at least their covers, are made partially or entirely of sheet metal, plastic, or a cast material such as die-cast aluminum or precision-cast stainless steel. 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 a viewing window made of glass or translucent plastic is positioned. A spring element and a retaining ring are typically used to secure the viewing window, with the spring element (e.g., a wave spring) bearing against the retaining ring. Thus, several components are required, and manufacturing is correspondingly complex.

[0005] The invention is based on the objective of proposing a housing with a viewing window that is characterized by as few components as possible and by the safest and easiest possible assembly.

[0006] The invention solves the problem by providing a housing for a field device for process automation, comprising a lid, a viewing window, and a clamping ring, wherein the lid has a base with a recess, wherein the viewing window rests on the base of the lid, wherein the lid has a circumferential groove in an inner wall, wherein the groove is bounded on a side facing away from the base by a circumferential rim, wherein the rim has at least one passage that opens onto the groove, wherein the clamping ring and the groove are designed and aligned such that the clamping ring is partially arranged in the groove of the lid and partially protrudes from the groove, wherein the groove, the viewing window, and the clamping ring are designed and aligned such that the viewing window is in direct contact with the clamping ring and is under axial preload.wherein the clamping ring has a ring structure and at least one clamping element on a radial outer side, wherein the clamping element is at least partially elastically resilient and / or the clamping element is elastically resiliently connected to the ring structure and / or the ring structure is at least partially elastically resilient, wherein the clamping element projects beyond a plane in which the ring structure is located, and wherein the clamping ring is arranged in the groove such that the clamping element projects beyond the plane on the side facing away from the ground.

[0007] The lid of the housing according to the invention has a recess in its base that covers a viewing window. This allows viewing inside the housing, for example, to read data from a display unit. To ensure the housing is sealed, a clamping ring presses the viewing window against the base of the lid with axial preload. Since the clamping ring is in direct contact with the viewing window, there is only this one component for axial fixation. This has the advantage of significantly simplifying assembly. The preload is determined by the thickness of the viewing window, the height of the clamping ring, the design of the clamping ring, and the position of the clamping ring's support relative to the base of the lid. The clamping ring is supported in a circumferential groove in the inner wall of the lid and is thus positioned relative to the base and the viewing window. A portion of the clamping ring protrudes from the groove to support and hold the viewing window.The groove is bounded on the side facing away from the bottom of the cover by a continuous rim. This rim is interrupted by at least one passage that opens onto the groove, which therefore extends continuously to the groove. The clamping ring is characterized by a resilient structure. For this purpose, the clamping ring primarily features a ring structure on which the viewing window rests. At least one clamping element is located on the radial outer side of this structure. Depending on the variant, the clamping element is at least partially elastically resilient. Alternatively or additionally, the clamping element is elastically resiliently connected to the ring structure. Furthermore, alternatively or additionally, the ring structure itself is at least partially elastically resilient. In every variant, the clamping ring exhibits elastic resilience in the axial direction. To axially secure the viewing window, the clamping element projects beyond a plane in which the ring structure is located.The height of the clamping ring is thus determined by the height of the ring structure plus the amount by which the clamping element is inclined outwards. The clamping element and the passage work together during housing assembly to ensure that the clamping ring is correctly inserted into the groove and that the spring action is adjusted. For this purpose, the clamping ring is positioned in the groove such that the clamping element projects beyond the plane of the ring structure on the side facing away from the ground. Thus, the base of the ring structure faces the ground, and the raised section formed by the clamping element faces away from the ground. The passage allows a view of the groove from the side facing away from the ground. Therefore, if the clamping element is visible in the passage, it is clear that the clamping ring is not correctly inserted.For correct positioning, the clamping ring must then be rotated in the groove around the longitudinal axis of the lid, so that the clamping element moves out of the passage and can develop the spring effect by resting on the edge.

[0008] The following designs relate in particular to the lid or to the components that are connected to the actual lid.

[0009] One embodiment of the housing provides that the clamping element is essentially designed as a strip inclined away from the plane in which the ring structure is located. In this embodiment, the clamping element has a predominantly elongated structure that is inclined away from the plane. Therefore, in this variant, the clamping element can also be described as a tongue. Such a tongue has the particular advantage that there is only one possible direction of rotation, since in the wrong direction the tongue would collide with one side of the passage. One embodiment of the housing includes the ring structure having at least one receptacle, and the receptacle is arranged radially further inward than the radial end of the groove's edge. In this embodiment, the receptacle is, for example, a recess or a hole into which a tool can be inserted. The clamping ring can then be rotated using the tool.To enable this action, the receptacle is located radially inward on the ring structure to such an extent that it extends beyond the edge of the groove and is therefore accessible.

[0010] One design of the housing provides that the arc length of the clamping element is equal to or less than the arc length of the passage. If the clamping element is equal to or shorter than the passage, it is fully visible even when rotated incorrectly. Furthermore, this ensures that the clamping element will definitely protrude into the passage when it assumes such a rotational position.

[0011] One design of the housing includes a clamping ring with multiple clamping elements and a surrounding rim with multiple passages. The number of clamping elements equals the number of passages. The passages in the rim of the cover serve primarily to allow the clamping elements to move through them, thus enabling the clamping ring to engage in the groove. By ensuring that the number of clamping elements equals the number of passages, it is possible to reliably monitor the presence and protrusion of all clamping elements, and then to securely position them by rotation.

[0012] One design of the housing provides that the tensioning elements are evenly distributed on the outside and that the passages are evenly distributed along the edge. Thus, equal angles are enclosed between adjacent tensioning elements and / or between adjacent passages.

[0013] In an alternative embodiment, the clamping elements are arranged unevenly on the outer surface, and the passages are arranged unevenly on the edge. In this embodiment, adjacent clamping elements and passages each form different angles. Consequently, there can only be one relative position between the clamping elements and passages that allows the clamping ring to be inserted into the groove of the cover via the passages.

[0014] Preferably, in one embodiment, the clamping elements on the outside and the passages on the edge are arranged or distributed correspondingly to each other. Thus, the geometries of the distribution of the clamping elements and the distribution of the passages are coordinated. Therefore, the sequences of the different enclosed angles in the cover or on the clamping ring are identical.

[0015] One embodiment provides that the housing further includes a seal, that the seal is arranged between the viewing window and the base of the lid, and that the clamping ring and the groove are designed and arranged such that the clamping ring presses against the viewing window, resulting in a predetermined preload for the seal. The seal closes the transition between the viewing window and the base of the lid, and therefore, in particular, the transition between the viewing window and the opening in the base of the lid. In the assembled state, the clamping ring presses the viewing window, and thus the seal, against the base of the lid. In this embodiment, the clamping ring is designed and arranged, by its dimensions and the positioning of the groove, such that the predetermined preload of the seal is generated.

[0016] 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.

[0017] The invention is explained in more detail with reference to the following figures. They show:

[0018] Fig. 1: a three-dimensional representation of the housing of a field device, Fig. 2: a section through part of the housing cover during assembly,

[0019] Fig. 3: a spatial representation of the clamping ring,

[0020] Fig. 4: a view into the partially cut-away housing of Fig. 1 ,

[0021] Fig. 5: the view of Fig. 4 with the fully assembled housing of Fig. 1 ,

[0022] Fig. 6: a view of an alternative design of the clamping ring,

[0023] Fig. 7: a view inside a lid according to an alternative embodiment with the clamping ring of Fig. 6 and

[0024] Fig. 8: an enlarged section of the arrangement shown in Fig. 7.

[0025] Fig. 1 shows a housing of a field device with a lower component that supports the housing neck 100 and a cover 1. The cover 1 has an opening 11 through which, for example, a display unit located under the viewing window 2 – not shown here – can be viewed. The cover 1 and its components are preferably rotationally symmetrical about the longitudinal axis.

[0026] Fig. 2 shows the moment of lid assembly, as the clamping ring 3 is rotated about the longitudinal axis of the lid 1. In particular, the initial assembly position is shown.

[0027] The figure shows how the individual clamping elements 32 are located in the passages 15 of the rim 14. The rim 14 defines the side of the groove 13 of the inner wall 12 of the cover 1 that faces away from the bottom 10 of the cover 1.

[0028] As can be seen, the clamping elements 32 have a chamfer which prevents the clamping ring 3 from rotating in one direction. In the other direction, the clamping elements 32 are pushed into the groove 13. In the assembled state, the clamping elements 32 rest on the edge 14 of the groove 13, while the ring structure 30 of the clamping ring 3 rests against the viewing window 2 and secures it. Therefore, the dimensions of the clamping ring 3 determine the force with which the viewing window 2 is pressed against the base 10.

[0029] The number of passages 15 of the edge 14 and the number of tensioning elements 32 are the same.

[0030] Figure 3 shows that the clamping ring 3 consists mainly of a ring structure 30.

[0031] This is, in particular, a closed ring that is essentially circular on the inside and outside. The clamping ring 3 is inserted into the groove 13 of the cover via the passages 15 in the rim 14 (see Fig. 2).

[0032] In the embodiment shown here, four clamping elements 32 are located on the outer surface 31 of the ring structure 30, and these are evenly spaced. There is therefore preferably an angle of 90° between each pair of adjacent clamping elements 32. With more or fewer clamping elements 32, a different angle is provided for each equal distribution.

[0033] The tensioning elements 32 initially abut the ring structure 30 with a plateau whose upper surface is at the same height as the upper surface of the ring structure 30. Following the plateau is an inclined plane over which the tensioning elements 32 project, in particular, out of the plane in which the ring structure 30 is located. Therefore, the overall height of the tensioning ring 3 is determined by the bearing surface of the ring structure 30 and by the tips of the tensioning elements 32.

[0034] Within the angular range of the clamping elements 32, there is a receptacle 33 in the ring structure 30. In the example shown, the receptacles 33 are designed as through holes and allow a tool to be inserted for rotating the clamping ring 3.

[0035] Figure 4 shows that the viewing window 2 rests on the base 10. A seal 4 is provided to seal the transition between the base 10 and the viewing window 2, preventing any media from entering the interior of the housing during operation. The receptacles 33 of the clamping ring 3 are located radially further inward than the rim 14 to allow a tool to engage properly and thus enable rotation of the clamping ring 3. The clamping elements 32 are located in the passages 15 of the rim 14, thereby allowing rotation in only one direction.

[0036] Fig. 5 shows the housing of Fig. 4 in its fully assembled state.

[0037] It can be clearly seen that the clamping ring 3 is now completely in place, and in particular the clamping elements 32 are also arranged in the groove 13.

[0038] The clamping ring 3 of Fig. 6 has five clamping elements 32, which are unevenly distributed around the circular ring structure 30, i.e., they have different arc lengths or different angles between them. Such an uneven distribution has the advantage of preventing incorrect assembly. A Poka-Yoke assembly is thus ensured. For this purpose, the number of clamping elements 32 is equal to the number of passages 15.

[0039] This is shown in Fig. 7, where the clamping ring 3 is located in the cover 1. Corresponding to the five clamping elements 32, there are five passages 15. The distributions and dimensions of the clamping elements 32 and passages 15 are corresponding to each other. Thus, there is only one insertion position.

[0040] In the enlarged section of Fig. 8, it is clearly visible how the clamping elements 32 abut against the sides of the passages 15 and therefore only allow one direction of rotation. Reference numerals

[0041] Lid

[0042] Viewing window

[0043] Tension ring

[0044] seal

[0045] Floor

[0046] recess

[0047] inner wall

[0048] Nut

[0049] edge

[0050] passage

[0051] Ring structure

[0052] Outside

[0053] tensioning element

[0054] Recording

[0055] case neck

Claims

Patent claims 1. Housing for a field device for process automation, comprising a cover (1), a viewing window (2), and a clamping ring (3), wherein the cover (1) has a base (10) with a recess (11), wherein the viewing window (2) rests on the base (10) of the cover (1), wherein the cover (1) has a circumferential groove (13) in an inner wall (12), wherein the groove (13) is bounded on a side facing away from the base (10) by a circumferential rim (14), wherein the rim (14) has at least one passage (15) that opens onto the groove (13), wherein the clamping ring (3) and the groove (13) are designed and aligned such that the clamping ring (3) is partially arranged in the groove (13) of the cover (1) and partially projects out of the groove (13), wherein the groove (13), the viewing window (2), and the clamping ring (3) are designed and coordinated in such a way thatthat the viewing window (2) is in direct contact with the clamping ring (3) and is under axial preload, wherein the clamping ring (3) has a ring structure (30) and at least one clamping element (32) on a radial outer side (31), wherein the clamping element (32) is at least partially elastically resilient and / or the clamping element (32) is elastically resiliently connected to the ring structure (30) and / or the ring structure (30) is at least partially elastically resilient, wherein the clamping element (32) projects beyond a plane in which the ring structure (30) is located, and wherein the clamping ring (3) is arranged in the groove (13) such that the clamping element (32) projects beyond the plane on the side facing away from the base (10).

2. Housing according to claim 1, wherein the clamping element (32) is essentially formed as being out of plane, in in which the ring structure (30) is located, is designed as a forward-leaning strip.

3. Housing according to claim 1 or 2, wherein the ring structure (30) has at least one receptacle (33), and wherein the receptacle (33) is arranged radially further inwards than the edge (14) of the groove (13) ends radially.

4. Housing according to one of claims 1 to 3, wherein an arc length of the clamping element (32) is equal to or less than an arc length of the passage (15).

5. Housing according to one of claims 1 to 4, wherein the clamping ring (3) has several clamping elements (32), wherein the circumferential rim (14) has several passages (15), and wherein a number of clamping elements (32) is equal to a number of passages (15).

6. Housing according to claim 5, wherein the clamping elements (32) are arranged evenly distributed on the outside (31) and the passages (15) are arranged evenly distributed on the edge (14).

7. Housing according to claim 5, wherein the clamping elements (32) are arranged unequally distributed on the outside (31) and the passages (15) are arranged unequally distributed on the edge (14).

8. Housing according to one of claims 1 to 7, wherein the housing further comprises a seal (4), wherein the seal (4) is arranged between the viewing window (2) and the bottom (10) of the cover (1), and wherein the clamping ring (3) is designed and the groove (13) is designed and arranged such that the clamping ring (3) presses against the viewing window (2) in such a way as to provide a predetermined preload for the seal (4).

9. Field device for determining and / or monitoring at least one Process size with a housing according to one of claims 1 to 8.

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