Automation field device

Abstract

Automation field device for determining and / or monitoring a process variable, comprising: - a housing body (1.4) which has, at least in sections, a substantially cylindrical region (1.5) which forms at least part of an interior space (1.3), the housing body being formed from a first plastic, in particular a plastic comprising a polyvinylidene fluoride; - field device electronics which are arranged in the interior space; - a hollow-cylindrical stiffening body which is designed in such a way that an outer lateral surface of the stiffening body bears with an accurate fit against an inner lateral surface of the interior space, the stiffening body being formed from a second plastic, which has a higher impact strength than the first plastic.

Description

[0001] Field device of automation technology

[0002] The invention relates to a field device for automation technology for determining and / or monitoring a process variable.

[0003] In automation technology, particularly in process automation technology, field devices are frequently used to determine, optimize, and / or influence process variables. Sensors, such as level gauges, flow meters, pressure and temperature gauges, conductivity meters, etc., are used to detect process variables, measuring levels, flow rates, pressure, temperature, and conductivity, respectively. Actuators, such as valves or pumps, are used to influence process variables, changing the flow rate of a liquid in a pipe section or the fill level in a container. In principle, field devices are defined as all devices used close to the process that provide or process process-relevant information. In the context of the invention, remote I / Os are also considered field devices.Generally speaking, field devices are those located at the field level. A large number of such field devices are manufactured and distributed by the company Endress+Hauser.

[0004] Such field devices always have a housing, which, depending on the application, may be made of one or more plastics, particularly polyvinylidene fluoride (PVDF). A disadvantage of such plastic housings is that they often fail impact resistance tests according to the specifications in the international standard IEC 60079-0 (edition of December 13, 2017).

[0005] To remedy this and pass the impact resistance test, individual components located inside the field device housing are potted with a potting compound. An example of such a component is the antenna in a level gauge, which is encased in the potting compound. The potting compound dampens the impact energy, allowing the device to pass the impact resistance test. The disadvantages of this method are that such potting compounds are expensive, and the pouring and curing process is time-consuming. Furthermore, the potting compound is heavy, making the finished field device heavy as well.

[0006] The invention is based on the objective of providing a remedy for this problem.

[0007] The problem is solved according to the invention by the field device of automation technology according to claim 1.

[0008] The field device according to the invention for automation technology for determining and / or monitoring a process variable comprises:

[0009] - a housing body which has at least partially a substantially cylindrical area which forms at least part of an interior space, wherein the housing body is made of a first plastic, in particular a plastic comprising a polyvinylidene fluoride;

[0010] - field device electronics located in the interior;

[0011] - a wooden cylindrical stiffening body, which is designed such that an outer surface of the stiffening body fits precisely against an inner surface of the interior, wherein the stiffening body is made of a second plastic which has a higher impact resistance than the first plastic.

[0012] According to the invention, the use of a hollow cylindrical stiffening body is proposed instead of a potting compound. The stiffening body exhibits higher impact resistance than the actual housing body. This offers the advantage of significantly reducing both material and manufacturing costs.

[0013] An advantageous embodiment of the field device for automation technology according to the invention provides that the wooden cylindrical stiffening body has a fiber-reinforced, in particular glass-, kevlar- or carbon fiber-reinforced plastic, which is preferably reinforced with fibers, in particular glass-, kevlar- or carbon fibers, by at least 15 wt.%, particularly preferably at least 20 wt.%, and most preferably at least 30 wt.%.

[0014] Another advantageous embodiment of the field device according to the invention for automation technology provides that several locking elements, in particular locking hooks, are formed around a continuous end of the wooden cylindrical stiffening body, by means of which the stiffening body is fixed to the housing body.

[0015] A further advantageous embodiment of the field device according to the invention for automation technology provides that the field device is a level measuring device for determining and monitoring the level of a fill level of a substance located in a container by means of a microwave time-of-flight measurement method, and wherein the field device further comprises an antenna for transmitting and / or receiving microwaves, which is at least partially arranged in the interior, wherein several spring elements are formed circumferentially at an end face of the wooden cylindrical stiffening body, preferably the end face on which the locking elements are formed, which serve to receive and / or position the antenna for transmitting and / or receiving microwaves.

[0016] The invention is explained in more detail with reference to the following drawings. They show:

[0017] Fig. 1: a schematic arrangement of a level gauge on a container, and

[0018] Fig. 2: a sectional view of the level gauge without the antenna attachment.

[0019] Figure 1 shows a schematic arrangement of a field device 1 for automation technology in the form of a level gauge on a container 2. The container 2 holds a substance 3, the level L of which is to be determined by the level gauge 1. For this purpose, the level gauge 1 is mounted on the container 2 at a known installation height above the substance 3. It is oriented such that it emits microwaves towards the surface of the substance 3. The field device shown in Figure 1 has an optional antenna attachment through which the microwaves are emitted towards the surface of the substance 3. The antenna attachment 6 is attached to a fluid-tight housing 4 of the level gauge 1. After reflection from the surface of the substance, the level gauge 1 receives the reflected microwaves depending on the distance from the surface of the substance.

[0020] Typically, the level sensor 1 is connected to a higher-level process control system via a bus system, such as "PROFIBUS", "HART" or "Wireless HART". This allows for the communication of information about the operating status of the level sensor 1. Furthermore, information about the fill level L can be transmitted to control, for example, the inflows and outflows at the tank 2.

[0021] Fig. 2 shows a sectional view of the level gauge 1 without the antenna attachment 6. This view reveals that the housing body 4 has, at least in sections, a substantially cylindrical area 4.1, which forms at least part of an interior space 4.2. Field device electronics 7 and an antenna 5 for transmitting and receiving microwaves are arranged in the interior space 4.2. In the illustrated embodiment, this is a horn antenna. The housing body 4 is made of a first plastic, in particular a plastic containing polyvinylidene fluoride (PVDF).

[0022] Furthermore, the level gauge 1 has a wooden cylindrical stiffening element 8. The stiffening element 8 is designed such that an outer surface 8.1 of the stiffening element fits precisely against an inner surface of the interior 4.3, allowing the stiffening element 8 to be slid or pressed into the housing 4 during assembly. The stiffening element 8 is made of a second plastic. This plastic has a higher impact resistance than the plastic of the housing 4. The wooden cylindrical stiffening element 8 can be made of a fiber-reinforced plastic, such as a glass fiber, Kevlar, or carbon fiber-reinforced plastic. The fiber-reinforced plastic can be reinforced with fibers by at least 15 wt.%, preferably at least 20 wt.%, and particularly preferably at least 30 wt.%.

[0023] Several locking elements 8.2 are formed around a continuous circumference at one end face of the cylindrical wooden stiffening body 8. In the illustrated embodiment, the locking elements 8.2 are designed in the form of locking hooks. The locking elements 8.2 serve to fix the stiffening body to the housing body. Accordingly, the housing body 4 has locking means. The locking means in the housing body can, for example, be implemented as notches into which the locking hooks of the stiffening sleeve engage.

[0024] Additionally or alternatively, several spring elements 8.3 can optionally be formed around the end face of the wooden cylindrical stiffening body 8. The spring elements 8.3, which are, for example, finger-shaped, serve to receive and / or position the antenna 5 for transmitting and / or receiving microwaves.

[0025] Reference symbol list for field devices in automation technology, in particular.

[0026] Level gauge, container, contents, housing body, cylindrical area of ​​the housing body, interior, inner surface of the interior, antenna for transmitting and / or receiving microwaves, antenna attachment, field device electronics, stiffening body, outer surface of the stiffening body, locking elements, spring elements

Claims

Patent claims 1. Field device of automation technology for determining and / or monitoring a process variable, comprising: - a housing body (4) which has at least a section having a substantially cylindrical area (4.1) which forms at least part of an interior space (4.2), wherein the housing body (4) is made of a first plastic, in particular a plastic comprising a polyvinylidene fluoride; - a field device electronics (7) which is arranged in the interior (4.2); - a wooden cylindrical stiffening body (8) which is designed such that an outer surface of the stiffening body (8.1) fits precisely against an inner surface of the interior (4.3), wherein the stiffening body (8) is made of a second plastic which has a higher impact resistance than the first plastic.

2. Field device of automation technology according to claim 1, wherein the wooden cylindrical stiffening body (8) comprises a fiber-reinforced, in particular glass-, kevlar- or carbon fiber-reinforced plastic, which is preferably reinforced with fibers, in particular glass-, kevlar- or carbon fibers, by at least 15 wt.%, particularly preferably at least 20 wt.%, and most preferably at least 30 wt.%.

3. Field device of automation technology according to claim 1 or 2, wherein several locking elements (8.2), in particular locking hooks, are formed around a front end of the wooden cylindrical stiffening body (8), by means of which the stiffening body (8) is fixed to the housing body (4).

4. Field device of automation technology according to one or more of the preceding claims, wherein the field device is a level measuring device for determining and monitoring a fill level of a substance (3) located in a container (2) by means of a microwave time-of-flight measurement method, and wherein the field device further comprises an antenna (5) for transmitting and / or Receiving the microwaves, which is at least partially arranged in the interior (4.2), comprising several spring elements (8.3) being formed circumferentially at an end face of the wooden cylindrical stiffening body (8), preferably the end face on which the locking elements (8.2) are formed, which serve to receive and / or position the antenna (5) for transmitting and / or receiving the microwaves.

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