PROCESS CONNECTION, SENSOR ASSEMBLY AND PROCESS SYSTEM

Description

[0001] The present invention relates to a process connection, in particular for a sensor unit in a process plant, a sensor assembly with such a process connection, and a process plant with at least one corresponding sensor assembly and / or at least one corresponding process connection. Comparable embodiments can be found, for example, in EP 3 783 248 A1, US 2021 / 190620 A1, DE 10 2016 008419 A1, DE 199 41 188 A1, and WO 2018 / 099666 A1.

[0002] Such process connections generally serve to connect specific units, such as sensor units and / or control units, to process plants. In particular, these process connections are designed to introduce measuring probes of corresponding sensor units through openings in pipes into the largely closed system of the process plant.

[0003] It is always necessary to design the process connection in such a way that no leakage occurs at the corresponding process connection when installed, and especially between the measuring probe and the process connection. Particularly in the food industry, the so-called bacterial tightness must be achieved. A system with a leakage rate on the order of 10⁻⁴ < mbar*l / s is considered "bacterial tight".

[0004] The object underlying the invention is therefore to provide a process connection with which the bacteria-tight insertion of a measuring probe of a sensor unit into a corresponding process plant is possible in a robust and reliable manner.

[0005] This problem is solved by a process connection according to claim 1. Advantageous embodiments of such a connection are described in the dependent claims. Furthermore, according to the two dependent claims, the present invention also relates to a sensor assembly with such a process connection and to a process plant with at least one such sensor assembly and / or at least one such process connection.

[0006] According to the present invention, a process connection, particularly for a sensor unit in a process plant, comprises an outer threaded adapter with a screw-in channel provided with an internal thread, an inner threaded adapter with a cylindrical through-channel and an external thread, and an annular molded seal. The outer threaded adapter has a radially circumferential, inwardly projecting, hollow cylindrical projection at one end of the screw-in channel. The annular molded seal rests against said hollow cylindrical projection in the axial and radial directions within the screw-in channel of the outer threaded adapter. The external thread of the inner threaded adapter engages with the internal thread of the outer threaded adapter.The inner threaded adapter is designed to press the molded seal axially onto a cover surface of the hollow cylindrical projection of the outer threaded adapter, the cover surface being oriented substantially perpendicular to the axial direction. According to the invention, the process connection includes a spacer ring which radially surrounds the molded seal inside the outer threaded adapter and also rests on the hollow cylindrical projection. According to the invention, the spacer ring is designed to limit radial deformation of the molded seal during compression by the inner threaded adapter and / or to limit the degree of maximum axial compression of the molded seal by the inner threaded adapter.

[0007] The term "hollow cylindrical" should not preclude the possibility that the projection between one of its end faces and its inner circumference has a rounded edge, chamfer, or step. Nor should it necessarily preclude the possibility that the inner circumference has smaller recesses and / or projections. Designs are also possible in which the axial length of the hollow cylindrical projection is greater than or equal to its inner diameter. However, a hollow cylindrical projection with an axial length smaller than its inner diameter is preferred, and disc-shaped designs for the hollow cylindrical projection are particularly desirable. It is important that the hollow cylindrical projection runs essentially perpendicular or straight along the longitudinal axis of the screw-in channel and the through-channel, which are concentrically aligned with each other.In particular, the opening of the hollow cylindrical projection has a cross-section that essentially corresponds to the cross-section of the measuring probe to be inserted. For example, both cross-sections are circular, but other configurations are also possible, such as oval, square, or other polygonal cross-sections. The term "annular" is preferably understood to mean circular, but also includes other configurations such as oval or polygonal shapes. The axial and radial directions refer here to the longitudinal axis of the process connection, which also corresponds to the longitudinal axis of the through-channel and the screw-in channel. The entire process connection, or at least individual components thereof, can be designed to be largely rotationally symmetrical about the aforementioned longitudinal axis.

[0008] The designed annular seal, when the process connection is assembled with the sensor unit inserted, is pressed axially and essentially without stress against the hollow cylindrical projection by the inner threaded adapter. The inserted measuring probe then presses the seal radially against the inner circumference of the hollow cylindrical projection. The respective contact surfaces on the hollow cylindrical projection, onto which the seal is pressed, are clearly separated from one another (in particular by an upper edge of the hollow cylindrical projection). This ensures a particularly robust and tight seal between the outer threaded adapter and the measuring probe in the area of ​​the hollow cylindrical projection.

[0009] To optimize the centering of the inner threaded adapter, and thus the measuring probe, within the process connection and consequently the sealing effect of the molded seal, the inner threaded adapter preferably includes an axially projecting cylindrical extension or extension below its external thread (i.e., axially in the direction of the molded seal). This extension is received by a precisely fitting bore in the outer threaded adapter. The cylindrical extension preferably rests completely against the bore in the outer threaded adapter. In particular, the cylindrical extension and the outer threaded adapter can have a maximum radial distance (i.e., a fit accuracy) of less than 0.1 mm or less than 0.05 mm. The bore is preferably machined concentrically with the central longitudinal axis of the process connection. The through-channel in the inner threaded adapter is, in turn, concentric with the cylindrical extension or extension.

[0010] Thus, the measuring probe is concentrically centered on the molded seal. The precise fit of the measuring probe to the flow channel in the inner threaded adapter prevents the measuring probe from being displaced eccentrically relative to the molded seal by acting forces (e.g., back pressure during flow measurements). The consequence of such displacement would be uneven compression of the molded seal, which must be avoided.

[0011] According to the invention, as already explained above, the process connection has a spacer ring which radially surrounds the molded seal inside the outer threaded adapter and also rests on the hollow cylindrical projection. The spacer ring is designed to limit radial deformation of the molded seal during compression by the inner threaded adapter and / or the degree of maximum axial compression of the molded seal by the inner threaded adapter.

[0012] This design limits the maximum deformation of the molded seal, which on the one hand allows for better sealing and on the other hand leads to increased durability and reliability of the molded seal.

[0013] The spacer ring in question can be designed as an axially protruding projection of the inner thread adapter.

[0014] This type of design requires few individual components and is therefore more user-friendly during assembly and maintenance.

[0015] Alternatively, the spacer ring in question can be designed as a component separate from the inner thread adapter, in particular in the form of a circular ring which surrounds the molded seal in the radial direction.

[0016] This allows the spacer ring to be used as a retrofit component and adapted even more flexibly to the specific application. In particular, the spacer ring can be made of a material that differs from the material of the inner thread adapter.

[0017] Preferably, the process connection has a pressure plate which is provided between the inner threaded adapter and the molded seal.

[0018] The pressure plate in question acts as a separate force transmitter between the inner threaded adapter and the molded seal and can, in particular, be made of a material that is chemically more compatible with the molded seal than the material of the inner threaded adapter. Specifically, a previously described spacer ring is formed integrally with the pressure plate.

[0019] Furthermore, the inner threaded adapter, the molded seal, and the pressure plate are preferably designed such that the friction between the molded seal and the pressure plate is greater than the friction between the inner threaded adapter and the pressure plate. In particular, the contact surface between the inner threaded adapter and the pressure plate is designed as a sliding bearing. The one-piece design of the spacer ring and pressure plate results in a design with fewer individual components (compared to separate designs of these two components) and thus enables more user-friendly assembly and maintenance.

[0020] This design prevents the molded seal from being radially clamped when it is pressed onto the hollow cylindrical projection by the inner threaded adapter via a screwing motion. In other words, this design serves to minimize friction between the inner threaded adapter and the molded seal, so that the inner threaded adapter exerts essentially only axial forces on the molded seal. This increases the service life of the clamped molded seal and the tightness of the process connection in the assembled state.

[0021] Preferably, the inner threaded adapter, or if provided, the pressure plate, has an axially projecting fixing collar along its inner circumference, which engages in the molded seal.

[0022] This design allows for a further increase in the tightness of the process connection in the assembled state by further restricting the space for the mold seal, while the fixing collar simultaneously ensures a centered or central positioning of the mold seal.

[0023] Preferably, the difference between the height of the spacer ring and the collar height of said fixing collar is less than or equal to 0.1 mm. In particular, the collar height of the fixing collar is equal to the height of the spacer ring or up to 5%, up to 10%, or up to 15% (e.g., 0.1 mm) greater than the height of the spacer ring.

[0024] In tests, this size ratio of collar height of the fixing collar and height of the spacer ring has proven to be particularly advantageous for obtaining especially robust and tight process connections.

[0025] Preferably, the molded seal has an annular main body with an inner diameter that is smaller than the inner diameter of the hollow cylindrical projection and an outer diameter that is larger than the inner diameter of the hollow cylindrical projection. In the relaxed state of the molded seal, the main body has, in particular, a rectangular, square, oval, or round cross-section.

[0026] The main body in question is designed, by virtue of the aforementioned features, to rest easily on the hollow cylindrical projection inside the outer threaded adapter. Furthermore, a rectangular or square main body, in particular, can be pressed together very effectively between the hollow cylindrical projection of the outer threaded adapter and the inner threaded adapter.

[0027] Furthermore, the fixing collar preferably has an outer diameter which is less than or equal to the inner diameter of the main body of the molded seal.

[0028] This prevents the fixing collar from exerting pressure on the main body of the mold seal in an axial direction, thus preventing undesirable tension on the mold seal.

[0029] Furthermore, preferably the main body of the molded seal and the spacer ring are dimensioned such that the maximum axial deformation of the main body of the molded seal (i.e. its clamping dimension) during compression by the inner threaded adapter is limited to 0.2mm to 0.9mm.

[0030] This size range for the clamping dimension has proven to be particularly suitable for reliable and especially bacteria-proof sealing (leakage rate on the order of 10 -4< mbar*I / s).

[0031] Furthermore, the molded seal preferably also has a sealing collar, in particular radially circumferential and preferably dovetail-shaped, which projects into the opening inside the hollow cylindrical projection. In the relaxed state of the molded seal, this sealing collar has a width, at least in sections, that is greater than the difference between the inner diameter of the hollow cylindrical projection and the outer diameter of a measuring probe of a corresponding sensor unit to be guided through the process connection.

[0032] This allows for a structurally simple, robust, and highly reliable sealing design of a section of the molded seal, which is pressed radially against an inner wall of the hollow cylindrical projection of the outer threaded adapter by the measuring probe. Specifically, the main body of the molded seal has a rectangular cross-section with rounded corners. The inner lower corner of the main body transitions into the sealing collar. The sealing collar itself widens axially downwards, but then terminates straight and parallel to the axial normal. This design has proven to be particularly robust and yet leak-proof in tests.

[0033] Preferably, the diameter of the through-channel of the inner threaded adapter, and if provided, the inner diameter of the pressure plate and / or the fixing collar, is equal to an outer diameter of a measuring probe of a corresponding sensor unit to be guided through the process connection.

[0034] This largely reduces play between the individual components of the process connection and the measuring probe, resulting in a robust and reliable overall design.

[0035] Preferably, the diameter of the external thread of the inner thread adapter or the diameter of the internal thread of the outer thread adapter is equal to the diameter of the external thread of the screw-in section of a screw-in connection of a sensor unit to be coupled to the process connection. In particular, the outer diameter of the spacer ring and / or the outer diameter of the pressure washer, if present, is less than or equal to the aforementioned diameter.

[0036] In other words, when assembled, a single internal thread of the outer thread adapter engages with both the external thread of the inner thread adapter and the external thread of the screw-in section of the sensor unit's screw-in connection. Specifically, the spacer ring and the pressure washer are each movable along the screw-in channel into their installation position within the hollow cylindrical projection. This design enables a particularly simple and robust overall assembly.

[0037] Preferably, the inner threaded adapter has a circumferential groove in its interior, in which a centering ring, particularly in the form of an O-ring, is provided. The centering ring has an inner diameter that is smaller than the outer diameter of a corresponding measuring probe and an outer diameter that is larger than the diameter of the through-channel of the inner threaded adapter.

[0038] This centering ring enables even better centered guidance of the measuring probe through the through-channel of the inner threaded adapter, resulting in further leakage protection between the measuring probe and the process connection.

[0039] Preferably, the screw-in channel of the outer threaded adapter has a radially circumferential collecting groove, which is provided axially between the internal thread of the outer threaded adapter and the hollow cylindrical projection and extends radially beyond the internal thread of the outer threaded adapter. The outer threaded adapter further particularly has a radially extending drain channel, which is connected to the collecting groove.

[0040] The collection groove serves as a catchment area for any fluid that has leaked past the mold seal, thus acting as a buffer to, for example, capture an "initialization leak" that only occurs during the initial commissioning of the process plant. The preferably also provided drain channel allows the fluid to be discharged from the collection groove and, if necessary, fed to a leakage sensor to empty the groove after a leak and monitor the leakage.

[0041] According to the invention, a sensor assembly for a process plant comprises a sensor unit with a screw-in connection and a measuring probe with a measuring head guided through the screw-in connection. Furthermore, the sensor assembly according to the invention comprises one of the process connections described above. The screw-in connection has a screw-in section with an external thread. The screw-in connection is screwed into the screw-in channel of the process connection from the end opposite the hollow cylindrical projection of the outer thread adapter, such that the measuring head of the measuring probe protrudes from the process connection through the hollow cylindrical projection or is at least flush with it.

[0042] Such a sensor assembly is particularly efficient and can be integrated into a suitable process plant in a tightly sealed manner.

[0043] According to the invention, a process plant comprises at least one previously described sensor unit and / or at least one previously described process connection.

[0044] Such a process plant benefits from the advantages of the sensor assembly and / or process connections according to the invention as described above.

[0045] The invention is described below by way of example with reference to the accompanying drawings. These show: FIG. 1 A sensor assembly with a process connection according to a first embodiment of the present invention, shown once in a side view (left) and once in cross-section (right); FIG. 2 A sensor assembly with a process connection according to a second embodiment of the present invention, shown once in a side view (left) and once in cross-section (right); FIG. 3 A sensor assembly according to one of the Figure 1 and 2with an additional control and / or evaluation unit on the measuring probe; FIG. 4 a detailed view of the cross-section of the sensor assembly made of FIG. 1 in the area of ​​the inner thread adapter; and FIG. 5 a detailed view of a cross-section of a corresponding sensor assembly with an alternative embodiment of the process connection according to the invention.

[0046] Fig. 1 Figure 1 shows a first embodiment of a sensor assembly 1 with a sensor unit 2 and an exemplary process connection 3 according to the present invention, both in side view (left) and in cross-section (right).

[0047] As can be seen here, the sensor unit 2 comprises a screw connection 5 and a measuring probe 7 guided through it. The measuring probe 7 is fixed in the screw connection 5 by suitable fixing means 9. The measuring probe 7 includes a measuring head 8, which, in the embodiment shown, protrudes from the process connection 3 at the bottom. Alternatively, the measuring head 8 can also simply be flush with the process connection 3.

[0048] The process connection 3 comprises an external threaded adapter 11, an internal threaded adapter 13, and a molded seal 15. The external threaded adapter 11 surrounds a screw-in channel which is provided with an internal thread. The screw-in connection 5 comprises a screw-in section 17 with an external thread which engages with the internal thread of the external threaded adapter. The internal threaded adapter 13 also has an external thread which engages with the internal thread of the external threaded adapter 11. Both the screw-in connection 5 and the internal threaded adapter 11 are provided with a through-channel through which the measuring probe 7 passes when installed.

[0049] To optimize the centering of the inner threaded adapter 13, and thus the measuring probe 7, in the process port 3, and consequently the sealing effect of the molded seal 15, the inner threaded adapter 13 includes an axially projecting cylindrical extension 14 below its external thread. This extension is received by a precisely fitting bore in the outer threaded adapter 11. This bore is machined concentrically with the central longitudinal axis of the process port 3. The through-channel in the inner threaded adapter 13 is, in turn, concentric with the cylindrical extension 14. Thus, the measuring probe 7 is concentrically centered with respect to the molded seal 15. The precise fit of the measuring probe 7 to the through-channel in the inner threaded adapter 13 prevents the measuring probe 7 from being displaced eccentrically relative to the molded seal 15 by acting forces (e.g., back pressure during flow measurements).The consequence of such a shift would be an uneven compression of the molded seal 15, which should be avoided.

[0050] As seen in the cross-sectional view (i.e., on the right in FIG. 1 As can be seen in the figure, the outer threaded adapter 11 includes a radially circumferential collecting groove 19 between the area in which the molded seal 15 is provided and its internal thread. This groove serves to collect and at least temporarily store any fluid that leaks from the process plant through the molded seal 15. As shown in Fig. 2 As shown, this collection groove 19 can be connected to a drain channel 21. This serves to drain the medium from the collection groove 19 and, if necessary, to supply it to a separate leakage sensor (not shown).

[0051] As in the Figure 1 and 2 As shown, a contact ring 23, in particular in the form of a further sealing ring, can be provided between the screw connection 5 and the outer thread adapter 11.

[0052] In addition to the provision of drainage channel 21 in the design made of FIG. 2 The only other significant difference between the designs is... Figure 1 and 2 in that the inner thread adapter 13 in FIG. 1 shorter than the inner thread adapter 13 in FIG. 2 This leads to the following in the design: FIG. 1 A further collection area 24 is formed for the medium that leaks through the molded seal 15. This makes particular sense here because of the missing drain channel 21, in order to increase the capacity for receiving the medium that leaks through the molded seal 15.

[0053] As further explained in FIG. 3 As shown, the sensor unit 1 can also include a control and / or evaluation unit 25 at the respective measuring probe 7. Suitable means for this are well known and are therefore not discussed in detail here.

[0054] The following refers to FIG. 4 the in FIG. 1 The sensor assembly 1 shown in the area of ​​the inner thread adapter 13 is described in detail.

[0055] The outer threaded adapter 11 comprises at its lower end an inwardly directed, radially circumferential, hollow cylindrical projection 27. A main body 29 of the molded seal 15, which has a square cross-section, sits on this projection. The molded seal 15 itself is annular, in particular circular. In addition to the main body 29, the molded seal 15 comprises a radially circumferential, dovetail-shaped sealing collar 31, which engages in the hollow cylindrical projection 27.

[0056] The molded seal 15 is centered with respect to the hollow cylindrical projection 27, and thus with respect to the longitudinal axis of the process connection 3, by a fixing collar 33, which is formed here as part of the inner threaded adapter 13. In addition to the fixing collar 33, the inner threaded adapter 13 is also designed with a spacer ring 35 in the form of an axially projecting projection in order to spatially limit the deformability of the molded seal 15.

[0057] Furthermore, the inner thread adapter 13 has a radially circumferential groove 37 in which a centering ring 39, in particular in the form of an O-ring, is provided.

[0058] The following section will discuss in more detail the respective size relationships in the illustrated example.

[0059] The internal thread of the outer thread adapter 11, the external thread of the inner thread adapter 13, and the external thread of the screw-in section 17 of the screw-in connection 5 all have the same thread diameter DG. Therefore, only an internal thread with the constant thread diameter DG needs to be formed in the outer thread adapter 11 to secure both the inner thread adapter 13 and the screw-in connection 5 within it.

[0060] In FIG. 4 The molded seal 15 is shown in its relaxed form, while the inner threaded adapter 13 is shown in its position pressing the molded seal 15, in order to clearly illustrate the actual design of the molded seal 15 and at the same time the compression dimension.

[0061] As explained above, the molded seal 15 comprises the main body 29 and the sealing collar 31. The main body 29 rests axially against the hollow cylindrical projection 27. For this purpose, the main body 29 has an inner diameter DHI, which is smaller than the inner diameter DVI of the hollow cylindrical projection 27, and an outer diameter DHA, which is larger than the inner diameter DVI of the hollow cylindrical projection 27. To retain the molded seal 15, the fixing collar 33 has an outer diameter DKA, which is less than or equal to the inner diameter DHI of the main body 29 of the molded seal 15. To optimize the seal, the main body 29 of the molded seal 15 and the spacer ring 35 are dimensioned such that the maximum axial deformation, i.e., the clamping dimension, of the main body 29 of the molded seal 15 is limited to 0.2 mm to 0.9 mm.This can be achieved, for example, by having the spacer ring 35 have a height HD that is 0.2 mm to 0.9 mm smaller than the height HH of the main body 29 of the molded seal 15. Furthermore, the difference between the height HD of the spacer ring 35 and the collar height HK of the provided fixing collar 33 is preferably less than or equal to 0.1 mm. In particular, the collar height HK of the fixing collar 33 is equal to the height HD of the spacer ring 35 or up to 0.1 mm greater than the height HD of the spacer ring 35.

[0062] The outer diameter DHA of the main body 29 of the molded seal 15 is smaller than the inner diameter DDI of the spacer ring 35 in order to give the main body 29 of the molded seal 15 sufficient room to deform during the pressing process through the inner threaded adapter 13.

[0063] How further the FIG. 4As can be seen, the sealing collar 31 of the molded seal 15 has a width BK which is greater than the difference between the inner diameter DVI of the hollow cylindrical projection 27 and the outer diameter DMA of the measuring probe 7. This ensures that the sealing collar 31 of the molded seal 15 is reliably and firmly pressed radially against the inner circumference DVI of the hollow cylindrical projection 27 by the measuring probe 7.

[0064] In order to guide the measuring probe 7 through the process connection 3 with the smallest possible gap, the through-channel through the inner threaded adapter 13, the through-channel through the screw connection 5 and the fixing collar 33 have a through-channel diameter DD which corresponds to the outer diameter DMA of the measuring probe 7.

[0065] In order to be reliably clamped between the measuring probe 7 and the inner threaded adapter 13 in the assembled state of the sensor assembly 1, the centering ring 39 has, in the relaxed state, an inner diameter which is smaller than the outer diameter DMA of the measuring probe 7, and an outer diameter which is larger than the through-channel diameter DD.

[0066] The following describes an example of how to assemble such a sensor assembly.

[0067] First, a decision is made as to which sensor unit 2 is to be mounted at a designated opening of a process plant. Then, a suitable process connection 3, and in particular a suitable external threaded adapter 11, is selected and mounted to a suitable opening of the process plant (not shown) in a known manner, ensuring the tightest possible seal against leakage, in particular by means of bolts and / or screws and, if necessary, a gasket or a weld. Next, the molded seal 15 is inserted into the external threaded adapter 11 and into the hollow cylindrical projection 27. The inner threaded adapter 13, with the pre-assembled centering ring 39, is then screwed into the external threaded adapter 11 until the spacer ring 35 rests on the hollow cylindrical projection 27. This results in an initial axial compression of the molded seal 15.Alternatively, the process connection 2 can be pre-assembled and, in particular, pre-tensioned before installation on the process plant.

[0068] Finally, the measuring probe 7 of the sensor unit 2 is inserted into the process port 3 through the through-channel of the inner threaded adapter 13 and tightened in place by means of the screw connection 5. The measuring probe 7 then presses the sealing collar 31 of the molded seal 15 radially against the hollow cylindrical projection 27. This results in a particularly tight seal between the measuring probe 7 and the process port 3. The through-channels of the molded seal 15 and the inner threaded adapter 13 are dimensionally and geometrically matched to the respective measuring probe 7 to optimize the sealing of the connection.

[0069] By pressing the molded seal 15 in several stages, first axially and then radially, a bacteria-tight seal is possible, for example, at process pressures of up to 16 bar and process temperatures between 10°C and 110°C. At process pressures below 1 bar, a bacteria-tight seal is even possible at process temperatures of up to 150°C. For example, at a process pressure of 0.3 bar and a process temperature of 25°C, a gasoline- and oil-tight seal (leakage rate in the range of 10⁻⁵ < mbar*l / s) was even demonstrated for a period of at least 15 minutes. The process pressures mentioned here are not to be understood as actual pressures but as gauge pressures relative to normal atmospheric pressure.

[0070] The following refers to FIG. 5 Another embodiment for a process connection 3 according to the invention with a correspondingly inserted sensor unit 2 is described.

[0071] Since the embodiment shown here largely corresponds to the one from

[0072] FIG. 4 Since this corresponds to the previous section, not every single feature will be explicitly described again here, but rather reference will be made to the relevant explanations in the previous section. Only the structural and functional differences compared to the one in FIG. 4 The embodiment shown is described in more detail.

[0073] The main difference lies in the fact that in the FIG. 5 In the embodiment shown, the fixing collar 33 and the spacer ring 35 are not formed as components of the inner thread adapter 13.

[0074] Specifically, the spacer ring 35 is designed here as an independent component separate from the inner thread adapter 13 in the form of a radially circumferential ring.

[0075] The fixing collar 33 is formed as part of a separate pressure plate 41, distinct from the inner threaded adapter 13, which is positioned between the inner threaded adapter 13 and the molded seal 15. The spacer ring 35 is, for example, positioned between the separate pressure plate 41 and the hollow cylindrical projection 27, as shown. Alternatively, the spacer ring 35 can also be arranged radially surrounding the pressure plate 41 in contact with the inner threaded adapter 13 and the hollow cylindrical projection 27.

[0076] To prevent radially circumferential stress on the mold seal 15 during axial compression by the inner threaded adapter 13, the friction between the inner threaded adapter 13 and the pressure plate 41 is set lower than that between the pressure plate 41 and the mold seal 15. Specifically, the contact surface between the pressure plate 41 and the inner threaded adapter 13 acts as a sliding bearing. Alternatively, if required, the contact surface between the pressure plate 41 and the mold seal 15 could also have the lower friction and act as a sliding bearing, although this design is more difficult to implement from a material perspective.

[0077] To simplify assembly and create a robust overall system, the outer diameter DA of the pressure plate and especially of the spacer ring 35 is less than or equal to the thread diameter DG.

[0078] In addition to the two embodiments shown from the Figures 4 and 5 Hybrid forms of these are also conceivable. Specifically, for example, only the spacer ring 35 could be formed as a separate component from the inner threaded adapter 13, while the fixing collar 33 and, if applicable, the pressure washer 41 are integrated into the inner threaded adapter.

[0079] Finally, it should be noted that the described embodiments are merely examples and in no way limit the scope of the pending claims. Many variations and modifications are available to a person skilled in the art, which are covered by the scope of protection of the accompanying claims but are not explicitly described here. Reference symbol list

[0080] 1 Sensor assembly 2 Sensor unit 3 Process connection 5 Screw-in connection 7 Measuring probe 9 Fixing means 11 Outer thread adapter 13 Inner thread adapter 14 Cylindrical extension 15 Molded seal 17 Screw-in section 19 Collection groove 21 Drain channel 23 Contact ring 24 Further collection area 25 Control and / or evaluation unit 27 Hollow cylindrical projection 29 Main body 31 Sealing collar 33 Fixing collar 35 Spacer ring 37 Groove 39 Centering ring 41 Pressure washer BK Sealing collar width DA Outer diameter DD Through diameter DG Thread diameter DDI Inner diameter of the molded seal DHA Main body outer diameter DHI Main body inner diameter DKA Outer diameter of the fixing collar DMA Measuring probe outer diameter DVI Projection inner diameter HDD Spacer ring height HH Main body height

Claims

1. A process connection (3), in particular for a sensor unit (2) in a process plant, wherein the process connection (3) comprises: an external threaded adapter (11) which has a screw-in passage and which is provided with an internal thread; an internal threaded adapter (13) having a cylindrical through passage and an external thread; and an annular molded seal (15), wherein the external threaded adapter (11) has a radially peripheral inwardly projecting hollow cylindrical projection (27) at one end of the screw-in passage, wherein the external thread of the internal threaded adapter (13) is in screw engagement with the internal thread of the external threaded adapter (11), wherein the annular molded seal (15) contacts said hollow cylindrical projection (27) in the axial and radial direction within the screw-in passage of the external threaded adapter (11), wherein the internal threaded adapter (13) is configured to press the molded seal (15) in the axial direction onto a cover surface of the hollow cylindrical projection (27) of the external threaded adapter (11), said cover surface being substantially oriented to the axial direction, characterized in that the process connection (3) has a spacer ring (35) which radially surrounds the molded seal (15) in the interior of the external threaded adapter (11) and rests on the hollow cylindrical projection (27), wherein the spacer ring (35) is configured to limit a radial deformation of the molded seal (15) during the pressing by the internal threaded adapter (13) and / or the degree of the maximum axial pressing of the molded seal (15) by the internal threaded adapter (13).

2. A process connection (3) according to claim 1, wherein the internal threaded adapter (13) has an axially projecting cylindrical lug or prolongation (14) below its external thread and a precisely fitting bore is provided in the external threaded adapter (11) and receives said lug or prolongation (14), wherein the bore in the external threaded adapter (11) extends concentrically with the central longitudinal axis of the process connection (3) and the through passage in the internal threaded adapter (13) extends concentrically with the cylindrical lug or prolongation (14).

3. A process connection (3) according to claim 1 or 2, wherein said spacer ring (35) is configured as an axially projecting projection of the internal threaded adapter (13) or as a separate component from the internal threaded adapter (13), in particular in the form of a circular ring which surrounds the molded seal in the radial direction.

4. A process connection (3) according to any one of the preceding claims, wherein the process connection (3) has a thrust washer (41) which is provided between the internal threaded adapter (13) and the molded seal (15), wherein in particular the spacer ring (35) is formed in one piece with the thrust washer (41).

5. A process connection (3) according to claim 4, wherein the internal threaded adapter (13), the molded seal (15) and the thrust washer (41) are formed such that the friction between the molded seal (15) and the thrust washer (41) is greater than the friction between the internal threaded adapter (13) and the thrust washer (41), wherein in particular the contact surface between the internal threaded adapter (13) and the thrust washer (41) is configured as a sliding bearing.

6. A process connection (3) according to any one of the preceding claims, wherein the internal threaded adapter (13), or - if provided - the thrust washer (41), has an axially projecting fixing collar (33), which engages into the molded seal (15), along its inner periphery.

7. A process connection (3) according to claim 6, wherein the difference in the height (HD) of the spacer ring (35) from the collar height (HK) of said fixing collar (33) is less than or equal to 0.1 mm, wherein in particular the collar height (HK) of the fixing collar (33) is equal to the height (HD) of the spacer ring (35) or is up to 5% or up to 10% or up to 15%, preferably 0.1 mm, greater than the height (HD) of the spacer ring (35).

8. A process connection (3) according to any one of the preceding claims, wherein the molded seal (15) has an annular main body (29) having an inner diameter (DHI) which is smaller than the inner diameter (DVI) of the hollow cylindrical projection (27) and having an outer diameter (DHA) which is larger than the inner diameter (DVI) of the hollow cylindrical projection (27), wherein the main body (29) in particular has a rectangular, square, oval or round cross-section in the relaxed state of the molded seal (15), wherein the fixing collar (33) in particular has an outer diameter (DA) which is less than or equal to the inner diameter (DHI) of the main body (29) of the molded seal (15).

9. A process connection (3) according to claim 7 or 8 having the features of claim 3, wherein the main body (29) of the molded seal (15) and the spacer ring (35) are dimensioned such that a maximum axial deformation (i.e. a clamping dimension) of the main body (29) of the molded seal (15) is limited to 0.2mm to 0.9mm during the pressing by the internal threaded adapter (13).

10. A process connection (3) according to any one of the claims 7 to 9, wherein the molded seal (15) further has a sealing collar (31), in particular a radially peripheral and preferably dovetail-shaped sealing collar, which projects into the opening in the interior of the hollow cylindrical projection (27), wherein, in the relaxed state of the molded seal (15), this sealing collar (31) at least sectionally has a width (BK) which is greater than the difference between the inner diameter (DVI) of the hollow cylindrical projection (27) and the outer diameter (DMA) of a measurement probe (7) to be guided through the process connection (3).

11. A process connection (3) according to any one of the preceding claims, wherein the diameter (DD) of the through passage of the internal threaded adapter (13), and - if provided - the inner diameter (DD) of the thrust washer (41) and / or the fixing collar (33), is equal to an outer diameter (DMA) of a measurement probe (7) to be guided through the process connection (3), and / or wherein the diameter (DG) of the external thread of the internal threaded adapter (13) or the diameter (DG) of the internal thread of the external threaded adapter (11) is equal to the diameter (DG) of the external thread of the screw-in section (17) of a screw-in connection (5) of a sensor unit (2) to be coupled to the process connection (3), wherein in particular the outer diameter (DA) of the spacer ring (35) and / or the outer diameter (DA) of the thrust washer (41), if present, is less than or equal to said thread diameter (DG).

12. A process connection (3) according to any one of the preceding claims, wherein the internal threaded adapter (13) has a peripheral groove (37) in its interior, in which peripheral groove (37) a centering ring (39), in particular in the form of an O-ring, is provided, wherein said centering ring (39) has an inner diameter which is smaller than the outer diameter (DMA) of a corresponding measurement probe (7) and has an outer diameter which is larger than the diameter (DD) of the through passage of the internal threaded adapter (13).

13. A process connection (3) according to any one of the preceding claims, wherein the screw-in passage of the external threaded adapter (11) has a radially peripheral collection groove (19) which is provided axially between the internal thread of the external threaded adapter (11) and the hollow cylindrical projection (27) and which projects radially beyond the internal thread of the external threaded adapter (11), wherein the external threaded adapter (11) further in particular has a radially extending drain passage (21) which is connected to the collection groove (19).

14. A sensor assembly (1) for a process system, comprising: a sensor unit (2) having a screw-in connection (5) and a measurement probe (7) which is guided through the screw-in connection (5) and which has a measurement head (8); and a process connection (3) according to any one of the preceding claims, wherein the screw-in connection (5) has a screw-in section (17) having an external thread, wherein the screw-in connection (5) is screwed into the screw-in passage of the process connection (3) with the external thread of the screw-in section (5) from that end which is disposed opposite the hollow cylindrical projection (27) of the external threaded adapter (11) such that the measurement head (8) of the measurement probe (7) projects through the hollow cylindrical projection (27) out of the process connection (3) or at least terminates with it.

15. A process plant comprising at least one sensor assembly (1) according to claim 14 and / or at least one process connection (3) according to any one of the preceding claims 1 to 13.