Measuring device for process measurement technology, in particular for capacitive level detection, as well as an arrangement comprising such a measuring device and a container

Abstract

The invention relates to a measuring device (1) for process measurement technology, in particular for capacitive point level detection, comprising an at least partially rotationally symmetrical metallic housing (2) and a sensor tip (3) which is directly adjacent to the housing (2) in the axial direction and which comprises a measuring element (4) and a ceramic casing (5) surrounding the measuring element (4). The casing (5) extends into the housing (2) and has a circumferential projection (6) which increases the diameter of the sensor tip (3). A temperature-resistant, dimensionally stable damping ring (10) is arranged in the axial direction between the housing (2) and the projection (6) of the casing (5), which damping ring is suitable for at least dampening impacts or shocks acting on the sensor tip (3) in the direction of the housing (2). Furthermore, the invention relates to an arrangement comprising such a measuring device (1) and a container.

Description

[0001] The invention relates to a measuring device for process measurement technology according to the preamble of claim 1 and to an arrangement comprising such a measuring device and a container according to the preamble of claim 6.

[0002] Process measurement technology instruments are used in automation technology to monitor the properties of a fluid, for example, with regard to pressure, temperature, flow, and fill level. Furthermore, there are instruments for measuring pH in process measurement technology and analytical measurement technology. They are used in a wide variety of applications, from water treatment and pharmaceutical production to heavy industry.

[0003] Capacitive measuring devices for point level detection, for example, which determine the presence or absence of a certain fill level of a medium, are known, for example from DE 10 2007 059 709 A1. They essentially consist of a housing and a sensor tip which is axially connected directly to the housing. The sensor tip often only contains one electrode of the measuring capacitor, and the other electrode of the measuring capacitor is formed by the environment of the capacitive sensor or measuring device. The measuring capacitor is therefore not generally a capacitor in the sense of a complete electrical component, but rather an arrangement equipped with a capacitance, the active electrode of which is assigned to the capacitive sensor, with a stray electric field extending from the active electrode into the environment. In order to use the measuring electrode as a sensor orTo protect the measuring element from external influences, it is enclosed in a plastic sheath. pH meters may also require a sheath for the measuring tip.

[0004] However, the plastic casing limits the medium temperature to a maximum of approximately 150°C. It is known from the applicant's DE 10 2022 108 591 A1 that for high-temperature applications above 150°C, the casing is made of a ceramic material, while the actual housing of the measuring device is typically made of stainless steel.

[0005] The transition from the ceramic coating to the metallic housing poses a challenge, particularly under certain process conditions where impacts and shocks act on the sensor tip, as both are very hard materials and ceramic is also comparatively brittle.

[0006] The object of the invention is to protect the casing and housing of the measuring device in question from excessive stress using simple means.

[0007] The object is achieved according to the invention by a measuring device having the features of claim 1 and an arrangement having the features of claim 6. Advantageous embodiments of the invention are specified in the subclaims.

[0008] The starting point of the invention is the realization that due to certain process conditions in which blows and impacts act on the sensor tip, direct contact between the sheath and the housing must be avoided.

[0009] According to a first aspect of the invention, a temperature-resistant, dimensionally stable damping ring is arranged axially between the housing and the projection of the casing. This damping ring is advantageously suitable for dampening impacts or shocks acting on the sensor tip in the direction of the housing at least to such an extent that no notch effect or the like occurs, particularly on the ceramic surface of the casing. In such cases, the damping ring absorbs the impact energy and thus acts, in a sense, like an intervertebral disc. This increases the overall robustness of the measuring device.

[0010] According to a further development of the invention, the damping ring has an S-shaped cross-section and is preferably arranged at least partially as an extension of the housing, thereby forming at least a partial part of the outer surface of the measuring device. As a result, it is fixed in position between the housing and the projection and can thus permanently fulfill its function.

[0011] A further advantageous development of the invention provides for the damping ring to be made of an elastomer or thermoplastic, such as PEEK or PTFE. These materials have proven themselves to be durable and reliable.

[0012] Preferably, the measuring device is suitable for capacitive level detection, and the measuring element is thus designed as a measuring electrode. However, a measuring device for measuring the pH value of a medium is also conceivable.

[0013] According to a second aspect, the invention relates to an arrangement comprising a measuring device and a container, which, for receiving the measuring device, has a connecting piece with an axially extending through-opening and a sealing rib projecting into the through-opening. According to the invention, the measuring device is designed as described above, and a sealing element is arranged between the projection of the casing and the connecting piece. In addition to its "intervertebral disc" function, the damping ring also performs the task of supporting the sealing element at the rear so that the sealing element is enclosed between the casing, sealing rib, and damping ring, and permanently and reliably seals the area between the casing and the sealing rib, even under influences such as pressure surges or temperature-related expansion, particularly with regard to hygienic sealing.

[0014] The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

[0015] They show schematically: Fig. 1 shows a measuring device according to the invention using the example of a measuring device for capacitive level detection; Fig. 2 a section of the measuring device according to the invention Fig. 1 as a cross-sectional image; Fig. 3 an enlarged section of a sub-area from Fig. 2.

[0016] In the following description of the preferred embodiments, like reference numerals designate like or comparable components.

[0017] Fig. 1 shows a measuring device 1 according to the invention, which in the present case is designed, by way of example, as a measuring device for capacitive level detection. The measuring device 1 is preferably screwed into an adapter or connecting piece 20 (not shown in detail here) and therefore has an at least partially rotationally symmetrical housing 2. At the front end of the measuring device 1, axially directly connected to the housing 2, is the sensor tip 3, which essentially consists of a measuring element 4, which in the present case is designed as a measuring electrode 4, and a sheath 5 surrounding the measuring electrode 4. With the help of the measuring electrode 4, a capacitance can be measured against a reference potential, which can ultimately be evaluated to determine a limit value for a fill level. The sheath 5 has a projection 6 that increases the diameter of the sensor tip 3. For high-temperature use, the sheath 5 is made of a ceramic material.However, at lower process temperatures, other materials are also conceivable, especially thermoplastics, especially polyetheretherketone (PEEK) or modified polytetrafluoroethylene (PTFE).

[0018] In Fig. 2, which shows a section of the measuring device 1 from Fig. 1 shows the interior of the measuring device 1 as a sectional view. The sheath 5 surrounds the measuring electrode 4 and extends deep into the housing 2. The circumferential projection 6 can also be seen.

[0019] Between the housing 2 and the projection 6 of the casing 5 is a temperature-resistant, dimensionally stable damping ring 10, which has an S-shaped cross-section and is made of an elastomer or thermoplastic, e.g., PEEK or PTFE. Of course, other shapes are also conceivable, and the invention is not limited to this S-shape. The damping ring 10 prevents direct contact between the ceramic casing 5 in the area of ​​the projection 6 and the housing 6, which can occur particularly when impacts or shocks are applied to the sensor tip 3. The damping ring 10 thus acts, in a sense, like an intervertebral disc.

[0020] The measuring device 1 is inserted into a connecting piece 20, which is part of a container, e.g., a tank or the like, and has an axially extending through-opening for this purpose. Typically, the measuring device 1 is screwed into the connecting piece 20. To seal the measuring device 1, the connecting piece 20 has a sealing ridge 21 extending into the through-opening. A sealing element 30, e.g., made of an elastomer or a thermoplastic, is positioned between this sealing ridge 21 and the underside of the projection 6. To prevent the sealing element 30 from shifting backward when the measuring device 1 is inserted, it is supported at the rear by the damping ring 10. The sealing element 30 is thus enclosed between the casing 5, the sealing web 21 and the damping ring 10 and, particularly with regard to hygienic sealing, permanently and reliably seals the area between the casing 5 and the sealing web 21.

[0021] Fig. 3 shows an enlarged view of Fig. 2 circled area. It can be clearly seen how the damping ring 10 is arranged between the housing 2 and the projection 6 of the casing 5 and, in an extension of the housing 2, supports the sealing element 30 at the rear, so that it is pressed downwards towards the medium and closes the area between the casing 5 and the sealing web 21. List of reference symbols 1 measuring device 2 Housing of the measuring device 3 Sensor tip 4 measuring element, measuring electrode 5 Sheathing 6 lead 10 Damping ring 20 connecting pieces 21 Sealing bar 30 sealing element QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2007 059 709 A1

[0003] DE 10 2022 108 591 A1

[0004]

Claims

[1] Measuring instrument (1) for process measurement technology, consisting of - an at least partially rotationally symmetrical metallic housing (2) and - a sensor tip (3) which is directly connected to the housing (2) in the axial direction and which comprises a measuring element (4) and a ceramic casing (5) surrounding the measuring element (4), the casing (5) extending into the housing (2) and having a circumferential projection (6) which increases the diameter of the sensor tip (3), characterized by that a temperature-resistant, dimensionally stable damping ring (10) is arranged in the axial direction between the housing (2) and the projection (6) of the casing (5), which is suitable for at least dampening blows or impacts acting on the sensor tip (3) in the direction of the housing (2). [2] Measuring device (1) according to claim 1, characterized by that the damping ring (10) has an S-shaped contour in cross section. [3] Measuring device (1) according to one of the preceding claims, characterized by that the damping ring (10) is arranged at least partially in extension of the housing (2) and is thus at least partially part of the outer surface of the measuring device (1). [4] Measuring device (1) according to one of the preceding claims, characterized by that the damping ring (10) consists of an elastomer or thermoplastic. [5] Measuring device (1) according to one of the preceding claims, characterized by that the measuring device (1) is suitable for capacitive limit level detection and the measuring element (4) is designed as a measuring electrode. [6] Arrangement comprising a measuring device (1) and a container, wherein the measuring device (1) is suitable for insertion into the container containing the medium to be measured, and wherein the container for receiving the measuring device (1) has a connecting piece (20) with a through-opening extending in the axial direction and a sealing web (21) projecting into the through-opening, characterized by , that the measuring device is designed according to one of the preceding claims, wherein a sealing element (30) is arranged between the projection (6) of the casing (5) and the connecting piece (20) and the damping ring (10) is designed such that it supports the sealing element (30) at the rear.

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