Housing for a process automation field device, and field device

Abstract

The invention relates to a housing for a process automation field device. A support ring (3) is connected to an inner wall (10) of a cover (1), and a maximum outer dimension of the viewing pane (2) is less than or equal to an inner diameter of an inner opening (39) in the support ring (3). A securing ring (4) is arranged in a circumferential opening (30) in the support ring (3). A spring element (5) is arranged between the securing ring (4) and a viewing pane (2) and exerts a spring force between the viewing pane (2) and the securing ring (4). The viewing pane (2) lies on a base (11) of the cover (1). In a state in which the support ring is detached from the inner wall (10), the outer radial extent of the support ring (3) can be changed. The invention further relates to a field device.

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 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 covers, are made partially or entirely of sheet metal. Covers that allow a view of, for example, a display unit 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. Several components are therefore required to secure the viewing window and provide the necessary seal. These different components necessitate different processing methods, such as welding or electropolishing. Furthermore, the potential replacement of components, such as the viewing window, should be considered—especially from an environmental perspective—and the fastenings should therefore be reversible. All of this can increase the assembly effort.

[0006] The invention is based on the objective of proposing a housing with a removable viewing cover, which is characterized by the easiest possible assembly.

[0007] The invention solves the problem by providing a housing for a field device for process automation, comprising a lid, a viewing window, a support ring, a retaining ring, and a spring element, wherein the support ring is connected to an inner wall of the lid, wherein the support ring and the viewing window are designed and coordinated such that a maximum outer dimension of the viewing window is less than or equal to an inner diameter of an inner recess of the support ring, wherein the retaining ring is partially arranged in a circumferential recess of the support ring, wherein the spring element is arranged between the retaining ring and the viewing window and exerts a spring force between the viewing window and the retaining ring, wherein the viewing window rests at least partially on a base of the lid, and wherein the support ring is designed in such a way thatand that the support ring, in a state detached from the inner wall, is variable with respect to its outer radial extension.

[0008] The lid is essentially cup-shaped and preferably made of sheet metal or any other metal. It preferably has the form of a hollow cylinder with a circular base. The inner wall encloses the interior. The base closes the lid on one side, with an opening in the base, for example, in the form of a circular hole. Below the hole is a viewing window, which thus closes the lid with respect to the opening and primarily allows a view of components located beneath the lid when the housing is installed, i.e., in the finished field device. This could be, for example, a display unit. The viewing window is held axially by a spring element that presses it against the base of the lid. The spring element rests on a retaining ring, which itself is held within a recess of a support ring.The support ring is firmly attached to the inner wall of the lid and therefore forms a secure fixing point, at least for the aforementioned components: retaining ring, spring element, and viewing window. The support ring is characterized by two features: Firstly, its outer circumference can be adjusted before it is attached to the inner wall. This allows the support ring to be made smaller to fit the lid. This simplifies assembly and, more importantly, prevents the support ring from rubbing against the inner wall and damaging the surface. Secondly, the support ring is designed so that the inner recess it encloses is larger than or equal to the outer circumference of the viewing window. This allows the support ring to be inserted and secured first, and then the viewing window to be inserted into the lid. Therefore, for example...It is possible, after fixing the support ring, to perform work on the lid and support ring combination that is not suitable for the viewing window and could even damage it. This includes, for example, electropolishing the lid. Furthermore, it is possible to modify the support ring's outer circumference or adapt it to the lid's dimensions so that the outer circumference matches the lid's inner circumference in the mounting area. This allows for a gap-free connection between the support ring and the lid. As a result, gap-free assembly is possible, for example, using laser welding without filler material.

[0009] Therefore, the following procedure applies to the assembly of the lid, for example:

[0010] Reducing the outer circumference of the support ring, inserting the support ring into the lid, fixing the support ring to the inner wall, optionally performing additional steps such as electropolishing, inserting the viewing window, inserting the spring element, and inserting the retaining ring into the circumferential recess of the support ring, while simultaneously pre-tensioning the spring element. As already mentioned, the support ring can be fixed to the inner wall, for example, by welding, and in particular by laser welding, or by bonding.

[0011] In one embodiment, the retaining ring has a smaller inner diameter than the support ring. The retaining ring thus narrows the interior space enclosed by the support ring, thereby providing a correspondingly large counter surface for the spring element.

[0012] One embodiment involves the support ring being at least partially elastically deformable and having a continuous slot. This embodiment allows the support ring to change its outer diameter. The slot allows the two sides that define it to move relative to each other, creating a smaller outer diameter. Due to its elasticity, the support ring then returns to its original shape when, after being positioned correctly, the force that previously compressed it is released. This allows, for example, the support ring to be easily inserted into the lid. It also makes it possible to increase the outer diameter of the support ring by stretching it.

[0013] In one embodiment, the support ring is essentially realized as a type of hollow cylinder. Further functions of the support ring can be implemented through a suitable internal or external structure.

[0014] One embodiment involves a retaining ring designed in the form of a snap ring. The advantage of a snap ring is that it can be compressed for assembly to create a smaller outer circumference. Subsequently, once the force is released, the snap ring relaxes and moves, in particular, into the circumferential recess of the bearing ring. When the snap ring has fully relaxed within the circumferential recess, its outer diameter is preferably larger than the inner diameter of the recess's rim.

[0015] One design involves the lid having an opening in its base. Depending on the design, the part of the base that surrounds the opening is either flat or sloped inwards.

[0016] The following two embodiments relate to sealing the transition between the base of the lid and the viewing window. Each uses at least one sealing element for this purpose. One embodiment involves the viewing window having a recess, and an internal sealing element located in this recess between the viewing window and the base of the lid. In this embodiment, the viewing window is designed to at least partially accommodate a sealing element, which is then wedged between the viewing window and the base of the lid, thus creating the seal.

[0017] One embodiment involves the placement of an external sealing element between an edge region of the viewing window and the base of the lid. In this embodiment, a seal is achieved by positioning a sealing element between the outer edge of the viewing window and the base.

[0018] The following details relate to the further geometry of the support ring.

[0019] One embodiment includes a support ring with an axially extending stop surface above the circumferential recess, extending towards the base of the lid. The support ring is characterized by being attached to the inner wall of the lid, at least with a portion of its outer wall. It also features a circumferential recess that projects into the interior of the lid. In this embodiment, the support ring has a section extending towards the base of the lid from the circumferential recess. This section contains an axially extending stop surface, i.e., along a longitudinal axis of the lid. This stop surface at least partially surrounds the viewing window and thus provides radial fixation.

[0020] One embodiment involves a compensating ring positioned radially between the contact surface of the support ring and the viewing window. In this additional embodiment, the compensating ring serves to radially adapt the viewing window to the inner diameter of the contact surface. Therefore, it is possible, for example, to use viewing windows of different sizes with a compensating ring. A suitable compensating ring is used in each case.

[0021] One embodiment involves the support ring having a circumferential outer surface that tapers conically towards the base of the lid. In this embodiment, the outer surface of the section adjoining the circumferential recess is modified by being conically tapered. This simplifies the insertion of the support ring into the lid. Furthermore, the radial fixation of the viewing window is improved. The conical taper also results in less material and weight. Finally, it is also possible to use the support ring with lids that deviate from the shape of a pure hollow cylinder. One embodiment involves connecting the support ring to the inner wall of the lid via a welding process.

[0022] One design involves the spring element being designed as a wave spring.

[0023] In an alternative embodiment, the spring element is a profiled sealing element. The sealing element is designed to adequately secure the viewing window. The sealing element consists, for example, of a plastic with the necessary properties. Preferably, the sealing element is designed to encompass only the lateral edge of the viewing window.

[0024] One design consists of the viewing window being made at least partially of glass or plastic.

[0025] One embodiment provides that the housing further comprises a housing neck, that the inner wall of the lid has a groove for reversible attachment of the lid to the housing neck, that the support ring has at least one recess, and that the groove and the at least one recess are designed and coordinated in such a way that the at least one recess allows movement of the support ring and lid relative to each other that is essentially unimpeded by the groove. This embodiment takes into account that the lid is attached to a housing neck and that, for this purpose, the lid has a contour or groove. In particular, if the groove on the inside projects into the interior of the lid, this embodiment provides that the support ring can be moved more easily past the groove by means of at least one recess.In one embodiment, the recess, or possibly the recesses, correspond to an enlarged negative form of the embossing. The embossing on the lid is, for example, part of a bayonet fitting.

[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:

[0028] Fig. 1: a spatial representation of the housing of a field device, Fig. 2: a section through a part of the housing cover according to a first embodiment,

[0029] Fig. 3: a section through part of a lid according to a second embodiment and

[0030] Fig. 4: a view into the spatial representation of the lid of Fig. 3.

[0031] 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 12 through which a display unit (not shown) located under the viewing window 2 can be viewed. The cover 1 and its components are preferably rotationally symmetrical about the longitudinal axis.

[0032] Fig. 2 shows part of a section through a lid 1 according to a first embodiment.

[0033] The cup-shaped lid 1 has an inner wall 10 and an opening 12 in its base 11. The opening 12 is closed by the viewing window 2. On its end face facing the base 11, the viewing window 2, in this configuration, has a recess 20 containing an internal sealing element 6. The term "internal sealing element" refers to the fact that the sealing element 6 is located radially within the area of ​​the viewing window 2. The viewing window 2 presses the internal sealing element 6 against the base 11 of the lid 1, thereby sealing this area.

[0034] The viewing window 2 is laterally encompassed by the stop surface 32 of the support ring 3 and thus radially fixed. The axial fixation of the viewing window 2 is achieved by the combination of the support ring 3, the retaining ring 4, and the spring element 5. The support ring 3 has an inner recess 39, to which the circumferential recess 30 extends axially towards the base 11 of the cover 1. The retaining ring 4 projects into the recess 30 and has a smaller inner recess than the support ring 3. Therefore, the retaining ring 4 also projects radially further inwards than the support ring 3. The spring element 5 rests on the retaining ring 4, and its spring force thus acts between the retaining ring 4 (and ultimately the support ring 3) and the viewing window 2. This provides the overall axial fixation.

[0035] Of particular relevance for assembly is the fact that both the support ring 3 and the retaining ring 4 have variable outer diameters. The support ring 3 has a slot 31, and the retaining ring 4 is designed as a snap ring, also with a slot. Furthermore, the support ring 3 and the retaining ring 4 are made of a material that allows them to be elastically deformed. The assembly of the cover 1 is therefore as follows:

[0036] The support ring 3 is drawn together so that it can be inserted into the cover 1 without contacting the inner wall 10. The height of the support ring 3 is designed such that it is in the correct axial position precisely when it abuts the base 11 of the cover 1. In the case shown, the support ring 3 is welded to the inner wall 10.

[0037] The next step involves, for example, processing the outside of lid 1. This is easily possible because, in particular, no further welding is required that could cause the outside of lid 1 to discolor. Therefore, the rough welding takes place first, before the surface can be finely finished.

[0038] In the next step, the viewing window 2 (in the example shown additionally in conjunction with the inner sealing element 6) is inserted into the lid 1 until the viewing window 2 rests on the base 11.

[0039] The spring element 5 and the retaining ring 4 are then inserted. The retaining ring 4 – in this example a snap ring – has a significantly smaller outer diameter during insertion than the maximum diameter of the inner recess 39 of the support ring 3. When the retaining ring 4 is located within the area of ​​the circumferential recess 30 of the support ring 3, the force compressing the retaining ring 4 is released, and the elastically designed retaining ring 4 springs into the area of ​​the recess 30 of the support ring 3. Therefore, the combination of the retaining ring 4 and the support ring 3 provides a sufficiently large bearing area for the spring element 5. The spring element 5 rests on the retaining ring 4 and is thus pre-tensioned by the insertion of the retaining ring 4 to axially secure the viewing window 2.

[0040] It can also be seen that the cover 1 is attached to the housing via a bayonet fitting. A corresponding indentation 13 can be seen on the inner wall 10 for this purpose.

[0041] Fig. 3 shows a variant of the lid 1, in which the viewing window 2 is taller and radially smaller than the viewing window 2 of the embodiment shown in Fig. 2. For example, the viewing window 2 in the embodiment shown in Fig. 2 is made of plastic, while in the embodiment shown in Fig. 3 it is made of glass.

[0042] In both versions, the dimensions of the cover 1 and the support ring 3 are the same. To compensate for the difference in the viewing window 2, a compensating ring 8 is provided, on which the viewing window 2 rests. This ensures radial fixation. A suitable tool (not shown here) is used, for example, to determine the axial position of the compensating ring 3 during assembly. It can be seen that the tapered outer surface 33 of the support ring 3 serves for radial fixation and the appropriate force transmission.

[0043] A further difference from the design shown in Fig. 2 is evident with regard to the base 11 of the cover 1 and the type of seal between the viewing window 2 and the outside world. In the design shown in Fig. 3, the base 11 around the opening 12 has a radially and axially inwardly inclined profile, in contrast to the purely flat profile in Fig. 2. An external sealing element 7 is provided, located between the base 11 and the viewing window 2, and encompassing the outer surface of the viewing window 2 facing the base 11. The curved profile of the base 11 serves two purposes: firstly, to protect the sealing element 7 from media or external influences during operation, thus creating a chambered seal for the sealing element 7; and secondly, to achieve a defined compression of the sealing element 7 by utilizing the spring action of the base 11.Therefore, if the viewing window 2 is pressed against the stop towards the bottom 11 during assembly, the sealing element 7 cannot be compressed too tightly.

[0044] Fig. 3 also clearly shows the wave structure of the spring element 5, which rests on the support ring 3 and presses circumferentially against the viewing window 2.

[0045] In an alternative embodiment – ​​not shown – the spring element 5 is a profile sealing element which, like the sealing element 7, encompasses the outer edge of the viewing window 2 and presses the viewing window 2 against the base 11 of the cover 1.

[0046] The view in Fig. 4 of the interior of the cover 1 shows how the retaining ring 4 rests on the support ring 3. The retaining ring 4 is a known snap ring that can be compressed for assembly. The support ring 3 has the continuous slot 31 through which the support ring 3 can be compressed. In this embodiment, there is also a recess 34 below the slot 31, which geometrically corresponds to the shape of the embossing 13. The recess 34 is thus essentially a slightly larger negative form of the embossing 13. In this example, the recess 34 and the embossing 13 allow the support ring 3 to be moved along the longitudinal axis of the cover 1 during insertion. Alternatively, the recess 34 allows movement around the embossing 13, which includes a rotation. Reference numerals

[0047] Lid

[0048] Viewing window

[0049] Support ring

[0050] retaining ring

[0051] Spring element, inner sealing element, outer sealing element

[0052] Compensating ring

[0053] inner wall of the lid

[0054] bottom of the lid

[0055] Opening at the bottom of the lid

[0056] Embossing of the inner wall of the lid

[0057] Recess of the viewing window, circumferential recess of the support ring

[0058] Slot of the support ring

[0059] Contact surface of the support ring

[0060] Outdoor area

[0061] Recess of the support ring

[0062] inner recess

[0063] case neck

Claims

Patent claims 1. Housing for a field device for process automation, comprising a cover (1), a viewing window (2), a support ring (3), a retaining ring (4), and a spring element (5), wherein the support ring (3) is connected to an inner wall (10) of the cover (1), wherein the support ring (3) and the viewing window (2) are designed and aligned such that a maximum outer dimension of the viewing window (2) is less than or equal to an inner diameter of an inner recess (39) of the support ring (3), wherein the retaining ring (4) is in a circumferential recess (30) of the support ring (3) is partially arranged, wherein the spring element (5) is arranged between the retaining ring (4) and the viewing window (2) and exerts a spring force between the viewing window (2) and the retaining ring (4), wherein the viewing window (2) rests at least partially on a base (11) of the cover (1), and wherein the support ring (3) is designed such that the support ring (3) is variable with respect to its outer radial extension in a state detached from the inner wall (10).

2. Housing according to claim 1, wherein the support ring (3) is at least partially elastically deformable, and wherein the support ring (3) has a continuous slot (31).

3. Housing according to claim 1 or 2, wherein the retaining ring (4) is designed in the manner of a snap ring.

4. Housing according to one of claims 1 to 3, wherein the lid (1) has an opening (12) in its base (11).

5. Housing according to one of claims 1 to 4, wherein the viewing window (2) has a recess (20), and wherein an inner sealing element (6) is located in the recess (20) between the viewing window (2) and the bottom (11) of the cover (1).

6. Housing according to one of claims 1 to 5, wherein an outer sealing element (7) is located between an edge region of the viewing window (2) and the bottom (11) of the cover (1).

7. Housing according to one of claims 1 to 6, wherein the support ring (3) has an axially extending stop surface (32) in the direction of the bottom (11) of the cover (1) above the circumferential recess (30).

8. Housing according to one of claims 1 to 7, wherein a compensating ring (8) is located radially between the stop surface (32) of the support ring (3) and the viewing window (2).

9. Housing according to any one of claims 1 to 8, wherein the support ring (3) has a circumferential outer surface (33) which tapers conically towards the bottom (11) of the cover (1).

10. Housing according to one of claims 1 to 9, wherein the support ring (3) is connected to the inner wall (10) of the cover (1) by a welding process. 1 1 . Housing according to one of claims 1 to 10, wherein the spring element (5) is designed as a wave spring.

12. Housing according to any one of claims 1 to 11, wherein the housing further comprises a housing neck (100), wherein the inner wall (10) of the lid (1) has an embossing (13) for reversibly attaching the lid (1) to the housing neck (100), wherein the support ring (3) has at least one recess (34), and wherein the embossing (13) and the at least one recess (34) are designed and coordinated such that the at least one recess (34) allows movement of the support ring (3) and the lid (1) relative to each other that is substantially unhindered by the embossing (13).

13. Field device for determining and / or monitoring at least one process variable with a housing according to one of claims 1 to 12.

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