DE-102024132954-A1 - Housing for a field device for process automation and field device

Abstract

The invention relates to a housing. A cover (1) has a base (10) with a recess (11). A viewing window (2) rests on the base (10). A preloading element (3) is partially arranged in a circumferential groove (13) in an inner wall (11) of the cover (1) and partially projects out of it. The viewing window (2) is in direct contact with the preloading element (3) and is under axial preload. The invention further relates to a field device.

Inventors

• Armin Gerland
• Rouven Kummle
• Stefan Rauch

Assignees

• Endress+Hauser SE+Co. KG

Dates

Publication Date

20260513

Application Date

20241112

Claims (9)

1. Housing for a field device for process automation, with a cover (1), with a viewing window (2), and with a preloading element (3), whereby 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), whereby an outer diameter of the groove (13) is larger than an inner diameter of the inner wall (12), whereby the preloading element (3) and the groove (13) are designed and aligned such that the preloading element (3) is partially arranged in the groove (13) of the cover (1) and partially protrudes from the groove (13), and whereby the groove (13), the viewing window (2), and the preloading element (3) are designed and aligned such that the viewing window (2) is aligned with the preloading element (3). is in direct contact and is under axial preload.
2. Housing after Claim 1 , wherein the prestressing element (3) is essentially ring-shaped, and wherein the prestressing element (3) consists of an elastomer.
3. Housing after Claim 1 or 2 , wherein the height of the groove (13) is greater than the height of the prestressing element (3).
4. Housing after one of the Claims 1 until 3 , wherein the inner wall (12) of the lid (1) has a narrowing section (14), wherein the narrowing section (14) has a decreasing inner radius towards the bottom (10), and wherein the groove (13) is located downstream of the narrowing section (14) towards the bottom (10).
5. Housing after one of the Claims 1 until 4 , wherein the bottom (10) of the lid (1) has a recess (15) running around the recess (11), wherein the lid (1) further comprises a sealing element (4), and wherein the sealing element (4) is arranged in the recess (15).
6. Housing after Claim 5 , wherein the sealing element (4) is an O-ring.
7. Housing after one of the Claims 1 until 6 , wherein the lid (1) is at least partially made of metal, and/or wherein the viewing window (2) is made of glass.
8. Housing after one of the Claims 1 until 7 , wherein the prestressing element (3) consists at least partially of a material with a low to very low compression set - preferably with a compression set of less than 35%.
9. Field device for determining and/or monitoring at least one process variable with a housing according to one of the Claims 1 until 8 .

Description

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. 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. Such housings, or at least their covers, are made, for example, partially or entirely of sheet metal. 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 under 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. The invention is based on the objective of proposing a housing with a viewing window that is characterized by reduced costs and the easiest possible assembly. The invention solves the problem by providing a housing for a field device for process automation, comprising a cover, a viewing window, and a preloading element, wherein the cover has a base with a recess, the viewing window rests on the base of the cover, the cover has a circumferential groove in an inner wall, the outer diameter of the groove being larger than the inner diameter of the inner wall, the preloading element and the groove being designed and aligned such that the preloading element is partially arranged in the groove of the cover and partially protrudes from the groove, and the groove, the viewing window, and the preloading element being designed and aligned such that the viewing window is in direct contact with the preloading element and is under axial preload. The lid of the housing according to the invention is a so-called viewing lid, insofar as it has a recess and a viewing window located beneath it. The inner diameter of the lid is dimensioned such that the viewing window can be inserted. Thus, the outer diameter of the viewing window is preferably smaller than or equal to the inner dimensions of the lid. The viewing window is axially fixed to the base of the lid by a preload element, which is partially located in a groove in the inner wall and partially protrudes from it. The protrusion of the preload element provides the support surface for the viewing window in the axial direction. By matching the dimensions of the preload element and the viewing window, and by the position of the groove relative to the base, in conjunction with the design of the preload element, it is ensured that the viewing window and the preload element are in direct contact with each other and that the viewing window is under axial preload. Because the viewing window and the preload element are in direct contact with each other, a spring element as required in the prior art is therefore unnecessary. The preload element thus combines the functions of the spring element and the snap ring in a single component. This not only simplifies manufacturing but also contributes to cost reduction. One embodiment provides that the prestressing element is essentially ring-shaped and made of an elastomer. Elastomers are elastically deformable plastics. They can be elastically deformed under tensile or compressive stress and subsequently return to their original shape. Such an elastomer-based prestressing element is therefore suitable for assembly. The prestressing element is first deformed, particularly in terms of its external dimensions, which is also simplified by its ring shape. The deformed prestressing element is then inserted into the groove, where it relaxes and returns to its original shape. According to one embodiment, the groove and the prestressing element are designed and aligned such that an outer surface of the prestressing element is adapted to an inner surface of the groove. In this embodiment, the prestressing element rests fully against the inner surface of the groove with its outer surface. In one embodiment, the prestressing element has a substantially rectangular cross-section. In one embodiment, the elastomer has a hardness between 60 Shore and 80 Shore, preferably 70 Shore. In one embodiment, the material, and preferably the elastomer, from which the prestressing element is made belongs to the group of materials that exhibit a low to very low compression set. Compression set describes h