FIELD DEVICE WITH A SENSOR FOR DETECTING A PHYSICAL QUANTITY

Description

[0001] The invention relates to a field device with a sensor for detecting a physical measurement variable.

[0002] Field devices used in industrial plants are already known from the state of the art. Field devices are widely used in automation technology as well as in production automation. Field devices essentially refer to all devices used close to the process and that provide or process-relevant information. Field devices are used to record and / or influence process variables. Sensor systems are used to record process variables. These are used, for example, for pressure and temperature measurement, conductivity measurement, flow measurement, pH measurement, level measurement, etc., and record the corresponding process variables such as pressure, temperature, conductivity, pH value, level, flow, etc. Actuator systems are used to influence process variables.These include, for example, pumps or valves that can influence the flow of a fluid in a pipe or the fill level in a container. In addition to the previously mentioned measuring devices and actuators, field devices also include remote I / Os, wireless adapters, and generally devices located at the field level.

[0003] A large number of such field devices are produced and distributed by the Endress+Hauser Group.

[0004] Field devices typically have a metal or plastic housing into which the field device electronics are installed. A display unit is typically screwed onto the field device housing. Furthermore, the housing of a field device has an opening for connecting a sensor system used to record the process variables.

[0005] For explosion protection reasons, a sensor system is typically housed in a cylindrical insert, which is inserted into the opening of the housing. To prevent axial rotation of the cylindrical insert within the field device housing, or rotation of the field device housing around the cylindrical insert's longitudinal axis, the cylindrical insert is secured to the housing with a snap ring. The cylindrical insert can then only be rotated around its longitudinal axis, which is used to align the sensor system and / or the housing at the measuring point.

[0006] To secure the sensor element against unwanted rotation around the longitudinal axis of the cylindrical insert, a fastener in the form of a screw or wedge is used, for example. This fastener is inserted through the housing perpendicular or parallel to the longitudinal axis of the cylindrical insert to exert a compressive force on the cylindrical insert and thereby secure it. Loosening and re-fastening the cylindrical insert, for example to change the orientation of the field device housing, is only possible with the use of a suitable tool. Often, the field device housing must also be opened for this purpose. For example, the sensor element is permanently installed in a pipeline or container.Although the cylindrical insert cannot be rotated, there may be a need to rotate the housing of the field device, for example to align a display unit of the field device with an operator.

[0007] For manufacturing and cost reasons, it is advantageous to manufacture field device housings from plastic. However, since the use of a fastener to prevent twisting of the cylindrical insert creates stress on the housing, material fatigue can occur in a plastic housing, resulting in cracking or deformation of the plastic and thus leakage of the housing.

[0008] Alternatively, both the opening in the field device's housing and the cylindrical insert are threaded. The cylindrical insert is screwed into the opening until it is firmly in contact with the housing.

[0009] In both variants—the cylindrical insert guided into the housing and the cylindrical insert screwed into the housing—a rubber seal in the form of an O-ring, located between the contact surfaces of the cylindrical insert and the housing, provides the required holding force. However, this method does not provide a defined fixation of the cylindrical insert. The degree of fixation depends on the length of the threaded section of the cylindrical insert. Correct adjustment of the fixation requires precise coordination between the cylindrical insert and the housing.

[0010] DE 10 2017 129 789 A1 discloses a fastening system for a sensor element, which features a fastening ring that provides the mechanical clamping force between the housing and the sensor neck. However, this connection can be broken, for example, by vibrations.

[0011] Based on this problem, the invention is based on the object of presenting an alternative fastening system for a field device, which allows a secure, simple and vibration-stable fastening of a sensor neck of a sensor to the housing of the field device.

[0012] The object is achieved by a field device according to claim 1. With regard to the field device, it is provided that it is equipped with a sensor for detecting a physical measurement value and comprises: a housing with a tubular section, wherein the tubular section has a rotation axis and a first diameter, wherein the housing has a receiving element which is arranged tangentially in a plane normal to the rotation axis on the tubular section; the sensor, which has a substantially tubular sensor neck with a second diameter, wherein the second diameter is smaller than the first diameter, wherein the sensor neck is guided into the tubular section of the housing, a pin-shaped, rotationally symmetrical clamping element with a first end region, a second end region, an elastic region with a mean diameter, and a contact region with a third diameter, wherein the third diameter is larger than the mean diameter, wherein the contact region is between the first end region and the elastic region,between the elastic region and the second end region, or between two partial sections of the elastic region, wherein the second end region has a thread, and wherein the receiving element is designed to receive the clamping element and has a counter thread for receiving the thread of the clamping element, wherein the clamping element is designed to exert a clamping force in the radial direction between the receiving element and the sensor neck by inserting it into the receiving element and screwing the thread into the counter thread to a predetermined first depth by means of the contacting region, so that both a movement of the sensor neck in the tubular section of the housing in the direction of the rotation axis and a rotation of the sensor neck in the tubular section of the housing about the rotation axis is prevented.

[0013] The field device according to the invention thus has a clamping mechanism for attaching the sensor neck to the housing, which is simple and reliable to use. By screwing the thread of the clamping element into the mating thread of the receiving element, the contact area is pushed between the sensor neck and a wall of the receiving element, so that a clamping connection between the sensor neck and the clamping element is achieved. The clamping force resulting from a spring-like bending of the clamping element is so great that both rotation of the sensor neck and axial displacement of the sensor neck in the housing are prevented. By using the threaded connection between the clamping element and the receiving element, the clamping element cannot be spontaneously displaced in a tangential direction, for example due to vibrations, so that the clamping connection is reliably maintained even over an extended period.The elastic range ensures reliable function of the clamping mechanism, regardless of the ambient temperature or any manufacturing tolerances of the components used. Both the expansion and bending of the clamping element counteract vibration.

[0014] The "mean diameter" of the elastic region means that the elastic region does not have to have the same diameter along its entire length, but can also have a thickening / tapering, for example, with a linear progression. The mean diameter is the average of the diameter progression along the length of the elastic region.

[0015] Examples of field devices have already been listed in the introductory part of the description. The invention is suitable for all types of field devices in which the sensor has a sensor neck inserted into the housing of the field device, for example, pressure gauges, ultrasonic measuring devices, etc.

[0016] According to an advantageous embodiment of the field device according to the invention, the clamping element comprises a first guide element arranged between the elastic region and the first end region, wherein the first guide element has a fourth diameter, and wherein the fourth diameter is greater than or equal to a maximum diameter of the elastic region. The first guide element prevents excessive stretching or bending of the clamping element toward the first end region. Because the elastic region is thinner than the first guide element, bending or stretching preferably occurs in the elastic region.

[0017] According to an advantageous embodiment of the field device according to the invention, the clamping element comprises a second guide element arranged between the elastic region and the second end region, wherein the second guide element has a fifth diameter, and wherein the fifth diameter is greater than or equal to a maximum diameter of the elastic region. Because the elastic region is thus substantially thinner than the second guide element, bending or stretching preferably occurs in the elastic region.

[0018] According to an advantageous embodiment of the field device according to the invention, the thread has a sixth diameter, and the fifth diameter is larger than the sixth diameter. This prevents expansion at the level of the second end region, which would place a load on the thread.

[0019] According to an advantageous embodiment of the field device according to the invention, it is provided that the receiving element is designed in sections as a tubular element with a seventh diameter, wherein the seventh diameter is larger than the third diameter, larger than the fourth diameter and larger than the fifth diameter.

[0020] According to an advantageous embodiment of the field device according to the invention, it is provided that the first end region has a stop element with an eighth diameter, wherein the eighth diameter is larger than the seventh diameter.

[0021] These configurations of the seventh and eighth diameters allow the clamping element to be easily inserted into the receiving element, while simultaneously allowing the clamping element to be set to its final position. The length of the clamping element and / or the receiving element is adjusted in such a way that the thread is not overtightened when the clamping element reaches its final position in the receiving element.

[0022] According to an advantageous embodiment of the field device according to the invention, the stop element has a receptacle for torque transmission, in particular by means of a screwdriver or an Allen key, external hexagon key, or Torx key. This facilitates screwing in the clamping element. The use of alternative screw profiles is also conceivable.

[0023] According to an advantageous embodiment of the field device according to the invention, the sensor neck has a circumferential groove on the outward-facing side, wherein regions of the sensor neck above and below the groove are designed to accommodate the contacting region of the clamping element after insertion of the clamping element into the receiving element, so that movement of the sensor neck in the tubular section of the housing in the direction of the rotation axis is prevented, wherein the thread is screwed into the mating thread to a predetermined second depth, wherein the first predetermined depth is deeper than the second predetermined depth. The clamping element is therefore in a setting in which the sensor neck is rotatable or rotatable in the housing.

[0024] According to an advantageous embodiment of the field device according to the invention, it is provided that the tubular section of the housing has at least two support surfaces on the inside, in particular designed as webs or ribs, wherein the support surfaces each rest on a region of the sensor neck above and below the groove, wherein the support surfaces are spaced apart from one another on a circumference of the tubular section at a distance of 120 °.

[0025] According to an advantageous embodiment of the field device according to the invention, it is provided that the support surfaces are designed such that two of the support surfaces each exert a radial clamping force between the tubular section of the housing and the sensor neck when the clamping force is exerted in the radial direction between the receiving element and the sensor neck.

[0026] The contact surfaces therefore serve two functions: First, they prevent the sensor neck from tilting in the housing when the clamping element is in the position where the sensor neck cannot rotate within the housing. Second, the contact surfaces distribute the clamping force across multiple elements, i.e., across two of the contact surfaces and across the contact area of ​​the clamping element. Compared to the variant in which the clamping force acts exclusively on the sensor neck via the contact area of ​​the clamping element, the stability of the mounting is increased, and the load on the individual components is reduced.

[0027] The contact surfaces define the first diameter. It is important to note that the second diameter of the sensor neck is selected so that it is smaller than the first diameter.

[0028] According to an advantageous embodiment of the field device according to the invention, the sensor neck has a diameter smaller than the second diameter below the area on which the support surfaces rest. This prevents the sensor neck from being clamped into the tubular section in this area should a slight temporary tilt occur during the establishment of the clamping force by means of the clamping element.

[0029] According to an advantageous embodiment of the field device according to the invention, it is provided that the clamping element is made of a metallic material or of a plastic, in particular of a fiber- or ball-reinforced plastic.

[0030] According to an advantageous embodiment of the field device according to the invention, it is provided that the housing is made of a metal, in particular aluminum or stainless steel, or of a plastic.

[0031] The invention is explained in more detail with reference to the following figures. Fig. 1 : an embodiment of the field device according to the invention; Fig. 2 : a cross-section through the clamping system in two positions Fig. 3 : a design of the sensor neck; and Fig. 4 : a design of the tubular section of the housing.

[0032] In Fig. 1 An embodiment of the field device according to the invention is shown. This shows a tubular section 100 of the housing 1 of the field device, as well as a section of the sensor neck 200 inserted into the housing. Fig. 1a ) shows an external view, Fig. 1b ) a longitudinal section through the field device.

[0033] The field device is used to record a physical measurand, e.g., relating to a process. For this purpose, the measuring device includes a sensor. For example, the sensor is a pressure or ultrasonic sensor. The housing 1 of the field device contains the field device's electronics, cabling, interfaces, display elements, and / or input elements. The housing is typically made of a metal, particularly aluminum or stainless steel, or of a plastic.

[0034] To attach the sensor to the housing 1 of the field device, the sensor neck 200 of the sensor is inserted into the tubular section 100 of the housing 1. The sensor neck 200 is in Fig. 3 This consists in particular of a metallic material, is cylindrical with a second diameter ⌀ 2, and has a circumferential, circular groove 210. The second diameter ø 2 is above and / or below the groove. The areas above and below the groove can also have different diameters, but not larger than the first diameter ø 1.

[0035] The tubular section 100 of the housing 1 has a first cross section ⌀ 1. A receiving element 110 is mounted in a tangential plane of the tubular section 100. In its basic form, this consists of a small tube with a seventh diameter ⌀ 7 . The receiving element 110 is shaped such that it is open to the inside of the tubular section. This is illustrated in Fig. 4 , which shows the tubular section 100 without the inserted sensor neck.

[0036] To fix the sensor neck 200 in the tubular section 100, a clamping element 300 is inserted into the receiving element 110. The clamping element 110 is pin-shaped and rotationally symmetrical and has a first end region 310 and a second end region 320. A thread with a sixth diameter of ⌀ 6 is attached to the second end region 320, which thread is rotated into a mating thread of the receiving element 110. The first end region 310 has a stop element 370 with an eighth diameter of ⌀ 8, where ⌀ 8 is greater than ⌀ 7, which defines an end position of the clamping element 300 in the receiving element 110.

[0037] The clamping element 340 has a contacting area 340 with a third diameter ⌀ 3. The contacting area 340 protrudes through the opening of the receiving element 110 and the tubular section 100 into the interior of the housing and contacts the groove 210 of the sensor neck.

[0038] If the thread of the clamping element 300 is turned further into the mating thread of the receiving element 110, the clamping element 300 moves in a tangential direction to the sensor neck 200. The stop element 370 has a receptacle for torque transmission 371, which allows, for example, the reception of a screwdriver or an Allen key.

[0039] The clamping element experiences a slight stretching; due to the increasing spring force of the clamping element 300, hereinafter referred to as the clamping force, the contacting region 340 presses successively more strongly on the sensor neck 200. In order to achieve this effect independently of the temperature and any manufacturing tolerances, the clamping element 300 has an elastic region 330 which has a mean diameter which is smaller than the third diameter ⌀ 3. In order to preferably effect the stretching in this elastic region 340, the clamping element has a first guide element 350 with a fourth diameter ⌀ 4 , arranged between the elastic region 330 and the first end region 310, and a second guide element 360 with a diameter ⌀ 5 , arranged between the elastic region 330 and the second end region 320. The fourth and fifth diameters ⌀ 4 , ⌀ 5 must each be larger than the third diameter.Advantageously, the clamping element 300 consists of a metallic material or of a plastic, in particular of a fiber- or ball-reinforced plastic.

[0040] If the clamping force is large enough, a displacement of the sensor neck 200 relative to the tubular section 100, as well as a rotation of the sensor neck 200 about its longitudinal axis is prevented, see Fig. 2b ).

[0041] Since the contacting area 340 is designed in such a way that it can be inserted into the groove 210, a displacement of the sensor neck 200 relative to the tubular section 100 is already prevented in a position of the clamping element 300 in the receiving element 110 if no or only a small clamping force is applied, see Fig. 2a ). In this state, however, the sensor neck 200 is rotatable about its longitudinal axis, which is used, for example, to align the sensor.

[0042] For stability reasons, the tubular section has two, preferably three, receiving surfaces 121, 122 in the form of pins or knobs. These pins or knobs are designed to rest on the sensor neck 200 in the area above and / or below the groove. The support surfaces 121, 122 essentially serve two functions: Firstly, to prevent the sensor neck 200 from tilting in the tubular section 100, and secondly, to distribute the clamping force across the sensor neck 200.

[0043] The fastening method according to the invention allows the sensor neck 200 to be easily and very reliably fixed to the tubular section 100. The fastening is vibration-resistant yet can be released at any time by unscrewing the clamping element 300. Bezugszeichenliste

[0044] 1 Housing 100 Tubular section of the housing 110 Mounting element 121, 122 Mounting surfaces 200 Sensor neck 210 Groove 300 Clamping element 310 First end area 320 Second end area 330 Elastic area 340 Contact area 350 First guide element 360 Second guide element 370 Stop element 371 Mounting for torque transmission ⌀ 1, ..., ⌀ 8 Diameter

Claims

1. Field device with a sensor for recording a physical measured variable, comprising: - a housing (1) with a tubular section (100), wherein the tubular section (100) has a rotary axis (RA) and a first diameter (⌀1), wherein the housing (1) has a supporting element (110), which is arranged tangentially in a plane perpendicular to the rotary axis (RA) on the tubular section (100); - the sensor, which has an essentially tubular sensor neck (200) with a second diameter (⌀2), wherein the second diameter (⌀2) is smaller than the first diameter (ø1), wherein the sensor neck (200) is guided into the tubular section (100) of the housing (1), - a pin-shaped, axially symmetric clamping element (300) with a first end area (310), a second end area (320), an elastic area (330) with an average diameter and a contacting area (340) with a third diameter (⌀3), - wherein the third diameter (⌀3) is larger than the average diameter, wherein the contacting area (340) is located between the first end area (310) and the elastic area (330), between the elastic area (330) and the second end area (320), or between two partial sections of the elastic area (330), - wherein the second end area (320) has a thread, - and wherein the supporting element (110) is designed to support the clamping element (300) and has a mating thread for holding the thread of the clamping element (300), wherein the clamping element (300) is designed to exert a clamping force in the radial direction between the supporting element (110) and sensor neck (200) through insertion into the supporting element (110) and by screwing the thread into the mating thread to a predefined first depth using the contacting area (340), so that both a movement of the sensor neck (200) in the tubular section (100) of the housing (1) toward the rotary axis (RA) and a rotation of the sensor neck (200) in the tubular section (100) of the housing (1) around the rotary axis (RA) is prevented.

2. Field device as claimed in claim 1, wherein the clamping element (300) has a first guide element (350) located between the elastic area (330] and the first end area (310), wherein the first guide element (350) has a fourth diameter (⌀4), and wherein the fourth diameter (⌀4) is larger than or equal to a maximum diameter of the elastic area (330).

3. Field device as claimed in claim 1 or 2, wherein the clamping element (300) has a second guide element (360) located between the elastic area (330) and the second end area (320), wherein the second guide element (360) has a fifth diameter (⌀5), and wherein the fifth diameter (⌀5) is larger than or equal to a maximum diameter of the elastic area (330).

4. Field device as claimed in claim 3, wherein the thread has a sixth diameter (⌀6), and wherein the fifth diameter (⌀5) is larger than the sixth diameter (⌀6).

5. Field device as claimed in at least one of the preceding claims, wherein the supporting element (110) is tubular in sections with a seventh diameter (⌀7), wherein the seventh diameter (⌀7) is larger than the third diameter (⌀3), larger than the fourth diameter (⌀4) and larger than the fifth diameter (⌀5).

6. Field device as claimed in claim 5, wherein the first end area (310) has a stop element (370) with an eighth diameter (⌀8), wherein the eighth diameter (⌀8) is larger than the seventh diameter (⌀7).

7. Field device as claimed in claim 6, wherein the stop element (370) has a support (371) for torque transmission, in particular by means of a screwdriver or an Allen, hexagon or torx wrench.

8. Field device as claimed in at least one of the preceding claims, wherein the sensor neck (200) on the outward-facing side has a circumferential groove (210), wherein the groove (210) is designed to support the contacting area (340) of the clamping element (300) following insertion of the clamping element (300) into the supporting element (110), so that a movement of the sensor neck (200) in the tubular section (100) of the housing (1) toward the rotary axis (RA) is prevented, however a rotation of the sensor neck (200) in the tubular section (100) of the housing (1) around the rotary axis (RA) is enabled, wherein the thread is screwed into the mating thread to a predefined second depth, wherein the first predefined depth is deeper than the second predefined depth.

9. Field device as claimed in claim 8, wherein the tubular section (100) of the housing (1) on the inside has at least two contact surfaces (121,122), in particular designed as bars or ribs, wherein the contact surfaces (121, 122) each touch an area of the sensor neck (200) above and below the groove, wherein the contact surfaces (121,122) are arranged along a circumference of the tubular section (100) at a distance of 120° to one another.

10. Field device as claimed in claim 9, wherein the contact surfaces are designed such that two of the contact surfaces (121,122) each exert a radial clamping force between the tubular section (100) of the housing (1) and the sensor neck (200) upon exertion of the clamping force in the radial direction between the supporting element (110) and the sensor neck (200).

11. Field device as claimed in one of claims 8 to 10, wherein the sensor neck (200) below the area on which the contact surfaces (121, 122) lie has a diameter smaller than the second diameter (⌀2).

12. Field device as claimed in at least one of the preceding claims, wherein the clamping element (300) is made from a metallic material or from a plastic, in particular from a fiber- or bead-reinforced plastic.

13. Field device as claimed in at least one of the preceding claims, wherein the housing (1) is made from a metal, in particular aluminum or a stainless steel, or from a plastic.