Arrangement consisting of a measuring device and a container

Abstract

Arrangement consisting of a measuring device and a container, wherein the measuring instrument (1) is suitable for insertion into the container which contains the medium to be measured, and wherein the container for receiving the measuring instrument (1) has a connecting nozzle (20) with a through-opening extending in the axial direction and a sealing rib (22) projecting into the through-opening, wherein the measuring instrument (1) comprises a rotationally symmetrical housing part (10) which is flush with the connection nozzle (20) on the medium side and has an outer cone section (11) which forms a chamfered sealing surface pair with an inner cone section (21) provided on the connection nozzle (20), wherein a detachable sealing element (30) is arranged between the housing part (10) of the measuring instrument (1) and the connecting nozzle (20), which is flat and cap-like and extends from the area of ​​the outer cone section (11) to an adjoining cylindrical housing section (12) of the metallic housing part (10), wherein a holding function for fixing the position of the sealing element (30) is realized by a bead (33) arranged on the sealing element (30) in the area of ​​the cylindrical housing section (12) engages in a corresponding groove (13) provided in the cylindrical housing section (12) of the measuring instrument (1) and / or in the connecting nozzle (20), and a sealing function is realized exclusively in the area of ​​the outer and inner cone section (11, 21), so that the sealing function and the holding function of the sealing element (30) take place independently of each other in two spatially separate areas.

Description

[0001] The present invention relates to an arrangement comprising a measuring instrument and a container containing the medium to be measured.

[0002] In automation technology, measuring devices are used to monitor a medium or its properties. This often involves measuring the fill level, pressure, or temperature of the medium in a container. Such measuring devices typically consist of a lower part, referred to as the process connection, and a housing, the upper part, which primarily serves to protect the sensor and its associated electronics. The process connection establishes the link between the measuring device and a container, pipeline, or connection fitting, and usually contains the sensor element itself. In pressure gauges, for example, the sensor element is designed as a piezoresistive or capacitive measuring cell.

[0003] To connect the measuring device to the system or container holding the medium to be measured, nozzle-like adapters, such as those described in German patent DE 196 28 551 B4, have proven advantageous. These adapters have an axially extending through-hole and a circumferential sealing rib located within this through-hole. The measuring device is typically screwed into the adapter, with its lower side, i.e., the process connection, resting against the circumferential sealing rib. By tightening the measuring device with a predetermined torque, the contact pressure between the process connection and the sealing rib of the adapter can be defined.

[0004] Various sealing elements are suitable for sealing the connection between the measuring device or process connection and the adapter, with elastomer seals, i.e., O-rings, being frequently used. However, elastomer seals also have significant disadvantages, particularly regarding their resistance to the three main influencing factors: pressure changes, temperature fluctuations, and chemical resistance. For example, comparatively large volume changes, structural alterations, or surface damage can occur. Therefore, elastomer seals must be replaced regularly, especially due to aging.

[0005] To achieve a long-term stable and easily cleanable connection between the adapter and the measuring device or process connection despite pressure and temperature fluctuations, German patent DE 10 2009 028 662 B4 proposes making the sealing element from a chemically resistant and temperature-resistant thermoplastic, in particular polyetheretherketone (PEEK). PEEK is chemically very stable and exhibits high long-term stability under typical stresses and temperature ranges, for example, in the food and pharmaceutical industries. Furthermore, a PEEK sealing element enables optimal force transmission between the sealing rib and the process connection with a minimal contact area between the outer end of the sealing rib and the sealing element, thus allowing for maximum compression of the sealing element in a virtually linear area. Polytetrafluoroethylene (PTFE) is also a possible option, albeit with some limitations.

[0006] However, the embodiment described in the aforementioned patent specification requires that the wall thickness of the process connection be at least 3.5 mm to ensure the pressure measuring cell is free from stress. Furthermore, the stability of the PEEK sealing element shown in this embodiment is achieved primarily through its ring thickness. To allow for maximum compression between the sealing rib and the process connection, the sealing ring requires an upper stop to prevent the applied force from causing displacement of the sealing ring.

[0007] However, if a small adapter is required for the container due to its small diameter, especially in the case of a pipeline, then the diameter of the measuring device must also be minimized. Due to the internal pressure measuring cell, however, its size cannot be reduced arbitrarily. Further miniaturization of the assembly consisting of the adapter, sealing element, and measuring device would therefore mean reducing the thickness of the PEEK ring, which would compromise its necessary stability.

[0008] The object of the invention is to minimize the diameter of the aforementioned measuring device and thus also of the aforementioned arrangement of measuring device and connecting nozzle, while still ensuring the stability of the sealing element required for maximum compression.

[0009] The problem identified is solved according to the invention by an arrangement as described in claim 1. Advantageous embodiments are specified in the dependent claims.

[0010] According to the invention, a flat, detachable sealing element is provided, extending from the area of ​​the inner cone section into the adjoining cylindrical housing section of the metallic housing part. This gives the sealing element a cap-like shape and fixes it to the measuring device or the connection nozzle in such a way that the position of its front edge remains fixed even after repeated insertion and removal of the measuring device. Even a minimal step between the connection nozzle and the process connection – e.g., a 1 mm step with a 20 mm diameter – is still included in the term "flush transition".

[0011] Crucially, a holding function for positioning the sealing element is achieved by a bead arranged on the sealing element within the cylindrical housing section engaging a corresponding groove provided in the measuring device and / or the connecting stub. A sealing function is implemented exclusively within the outer and inner conical sections. As a result, the sealing function and the holding function of the sealing element are realized independently of each other in two spatially separate areas.

[0012] With this solution, the dimensions of the sealing element can be reduced in the area relevant to the seal, without sacrificing the advantages of maximum compression of the sealing element in a minimal contact area between the outer end of the sealing rib and the sealing element. According to the invention, displacement of the sealing element due to the application of force is now prevented by the inner conical section, so that the sealing element can be designed to be thin and flat and no longer needs to provide the required stability itself.

[0013] The measuring device can be minimized with the solution according to the invention to such an extent that pressure measuring cells for ½ inch process connections can be used and the wall thickness of the measuring device or the process connection is approximately 1.8 mm. This results in an optimal force distribution because the wall thickness of the process connection in the area of ​​the seal does not need to be weakened by indentations, notches, etc., for receiving a sealing ring, given its already minimal thickness.

[0014] The implementation of the retaining function using a bead and groove also has the advantage that the sealing element can be fixed to the measuring instrument or the connection fitting before the instrument is inserted into the fitting, without requiring separate holding or the risk of slippage. Of course, other options are also conceivable, such as retaining it by means of an interference fit, bonding the sealing element to the housing, using a clip connection, or simply using locking tabs instead of the circumferential bead.

[0015] Advantageously, the sealing element can be designed in such a way that it contributes to a flush transition between the housing part of the measuring device and the connection nozzle. This makes it possible to design the transition from the process connection to the adapter or connection nozzle without dead space, so that the arrangement according to the invention can also be used in the pharmaceutical and food industries with special hygiene requirements.

[0016] In an advantageous embodiment of the invention, the sealing element is made of a chemically resistant and temperature-resistant thermoplastic, in particular polyetheretherketone (PEEK). A sealing element made of this material possesses the necessary dimensional stability despite high stress at the sealing edge.

[0017] A further advantageous development provides that the housing part above the inner cone section has a taper corresponding to the thickness of the sealing element. This ensures that the outer diameter of the measuring instrument housing does not increase when the seal is applied and that it has a substantially uniform cylindrical outer contour.

[0018] In a particularly advantageous embodiment, the invention provides that the inner cone section and the outer cone section are positioned at an angle to each other. This causes both sealing surfaces to taper to a point towards the sealing edge, resulting in a quasi-linear surface in which the connecting nozzle contacts the sealing element resting on the process connection. This ensures maximum compression of the sealing element exclusively in this area, thereby fulfilling the requirements of hygiene guidelines.

[0019] The invention is explained in more detail below in connection with figures, using an exemplary embodiment.

[0020] They show: Fig. 1 an arrangement according to the invention comprising a measuring instrument, a connecting nozzle and an intermediate sealing element, Fig. 2 an enlarged representation of the in Fig. 1. Sub-area designated “A”.

[0021] In the following figures, unless otherwise indicated, identical reference symbols denote identical parts with the same meaning.

[0022] In Fig. Figure 1 shows an arrangement according to the invention comprising a measuring device 1, a connection fitting 20, and an intermediate sealing element 30. The measuring device 1 is, by way of example, a pressure gauge with a pressure measuring cell 2. The basic structure of this arrangement, i.e., the measuring device 1 inserted, and in particular screwed, into the connection fitting 20, is known per se. The measuring device 1 has a cylindrical housing section 12 – often also referred to as a process connection – with an external thread that engages an internal thread of the connection fitting 20. The wall thickness of the process connection 12 is approximately 1.8 mm. Above the process connection 12, there is a space for accommodating the sensor electronics and, optionally, evaluation electronics, as well as a connection device for signal and / or power transmission. This area has been omitted from the illustration for the sake of clarity, especially since such a structure is known.

[0023] The connecting nozzle 20 has an inwardly directed sealing rib 22 at its lower end, facing the medium. Due to its conical shape, this sealing rib is referred to as the inner cone section 21. The measuring device 1 or the process connection 12 has an outer cone section 11 as the counterpart to this inner cone 21. The sealing element 20, which is preferably made of PEEK and manufactured by injection molding, is located between the outer cone section 11 and the inner cone section 21.

[0024] The measuring device 1 is screwed flush into the connection nozzle 20 and achieves the dead space-free operation that is particularly necessary for the food and pharmaceutical industries, preventing the accumulation of substances in areas that are difficult or impossible to clean.

[0025] In Fig. 2 is the one in Fig.Figure 1 shows the enlarged section labeled "A". It now becomes clear how the sealing element 30 is arranged between the outer and inner cone sections 11, 21, and that the inner cone section 21 and the outer cone section 11 are at an angle to each other. In this way, maximum compression of the sealing element 30 is achieved exclusively in a quasi-linear sealing area facing the medium.

[0026] To retain the sealing element 30, it has a bead 33 at its rear end 32, facing away from the medium, which engages in a groove 13 provided for this purpose in the process connection 12. In this way, the retaining function and the actual sealing function can be performed independently of each other and in spatially separated areas. The cylindrical section 32 of the sealing element 30 need not be completely circumferential, but can, for example, be formed by longitudinally oriented tabs arranged around the circumference of the sealing element 30 and separated from each other by gaps. In this case, the bead 33 would also no longer be completely circumferential, but only quasi-circumferential, which is also covered by the invention.

[0027] In order to avoid increasing the outer diameter of the process connection by the slid-on seal 30, it is tapered in this area, advantageously by exactly the thickness of the sealing element 30.

Claims

[1] Arrangement consisting of a measuring instrument and a container, wherein the measuring instrument (1) is suitable for insertion into the container which contains the medium to be measured, and wherein the container for receiving the measuring instrument (1) has a connecting nozzle (20) with a through-opening extending in the axial direction and a sealing rib (22) projecting into the through-opening, wherein the measuring instrument (1) comprises a rotationally symmetrical housing part (10) which is flush with the connection nozzle (20) on the medium side and has an outer cone section (11) which forms a chamfered sealing surface pair with an inner cone section (21) provided on the connection nozzle (20), wherein a detachable sealing element (30) is arranged between the housing part (10) of the measuring instrument (1) and the connecting nozzle (20), which is flat and cap-like and extends from the area of ​​the outer cone section (11) to an adjoining cylindrical housing section (12) of the metallic housing part (10), wherein a holding function for fixing the position of the sealing element (30) is realized by a bead (33) arranged on the sealing element (30) in the area of ​​the cylindrical housing section (12) engages in a corresponding groove (13) provided in the cylindrical housing section (12) of the measuring instrument (1) and / or in the connecting nozzle (20), and a sealing function is realized exclusively in the area of ​​the outer and inner cone section (11, 21), so that the sealing function and the holding function of the sealing element (30) take place independently of each other in two spatially separate areas. [2] Arrangement according to claim 1, characterized by , that the sealing element (30) is made of a chemically resistant and temperature-resistant thermoplastic material. [3] Arrangement according to claim 1 or 2, characterized by , that the sealing element (30) consists of polyetheretherketone (PEEK). [4] Arrangement according to any one of the preceding claims, characterized by , that the metallic housing part (10) above the outer cone section (11) has a taper which corresponds to the thickness of the sealing element (30) [5] Arrangement according to any one of the preceding claims, characterized by , that the sealing element is designed in such a way as to contribute to a flush transition between the housing part (10) and the connection nozzle (20). [6] Arrangement according to any one of the preceding claims, characterized by , that the wall thickness of the housing part (10) is approximately 1.8 mm. [7] Arrangement according to any one of the preceding claims, characterized by, that the inner cone section (21) and the outer cone section (11) are at an angle to each other, so that maximum compression of the sealing element (30) takes place exclusively in a quasi-linear sealing area facing the medium.

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