DE102022130669A1 - Screw-in connection element for Ex-i and Ex-d compliant transmission of electrical signals - Google Patents

Abstract

Screw-in connecting element (1) for Ex-i and Ex-d compliant conduction of electrical signals in a field device housing of a field device, comprising:
- at least one metal pin (1.1),
- a fixing material (1.2) into which the at least one metal pin is inserted over part of its length in such a way that the fixing material completely surrounds the metal pin in this part and the metal pin protrudes from the fixing material on both sides beyond its end faces,
- a substantially rotationally symmetrical metal bushing (1.3) enclosing the fixing material with an external thread (1.4), wherein the metal pin, the fixing material and the metal bushing are designed such that a distance (d) between the metal pin and the metal bushing is not less than a value specified in the standard DIN EN 60079-11 (2011 edition) for an air gap and/or creepage distance in air and wherein the external thread of the metal bushing is further designed such that it corresponds to a value specified in the standard DIN EN 60079-1 (2011 edition) for the engaged threads.

Description

The invention relates to a screw-in connecting element for the Ex-i and Ex-d compliant transmission of electrical signals between a connection compartment and a separate electronics compartment in a field device housing of a field device, as well as to a field device housing of a field device in automation technology.

In automation technology, field devices are used to determine and/or monitor process variables. In the context of this application, field devices are basically all measuring devices that are used close to the process and that provide or process process-relevant information. These include, for example, level measuring devices, flow measuring devices, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity measuring devices, etc., which record the corresponding process variables of level, flow, pressure, temperature, pH value or conductivity. In this case, field devices should also be understood to mean actuators that can be used to control a process. Such field devices are manufactured and sold in various designs by the E+H Group.

The field devices have a transmitter unit arranged in a housing of the field device. The transmitter unit generally has an evaluation and/or control unit comprising a first electrical assembly and a connection unit comprising a second assembly. The evaluation and/or control unit is used to generate an electrical signal representing the process variable and/or to generate an electrical signal used to control the process variable, such as a voltage and/or a current. The connection unit is used to connect external supply lines, for example to supply power to the field device and/or to forward the electrical signals generated by the evaluation unit.

Particularly in the process industry but also in automation technology, physical or technical quantities often have to be measured or determined by field devices in areas where there is a potential risk of explosion, so-called potentially explosive areas. By taking suitable measures in the field devices and evaluation systems (such as voltage and current limitation), the electrical energy in the signal to be transmitted can be limited so that this signal cannot trigger an explosion under any circumstances (short circuit, interruptions, thermal effects, etc.). Appropriate protection principles have been defined for this in IEC EN DIN 60079-ff.

According to this standard, design and circuitry measures for field devices for use in potentially explosive atmospheres are defined based on the applicable ignition protection types. One of these ignition protection types is the ignition protection type “intrinsic safety” (marking Ex-i, IEC EN 60079-11 , June 2011 edition).

The “intrinsic safety” type of protection is based on the principle of current and voltage limitation in an electrical circuit. The energy of the electrical circuit that could ignite an explosive atmosphere is limited in such a way that neither sparks nor excessive heating of the electrical components can ignite the surrounding explosive atmosphere.

The type of protection "intrinsic safety" defines three protection levels: Ex-ia, Ex-ib and Ex-ic. Level a is the highest level at which two countable errors in combination must not lead to a malfunction and thus cause an ignition (2-fault safety). Level b defines that one countable error must not lead to a malfunction and thus cause an ignition (1-fault safety). At level c, no error safety is defined, so that an ignition can be caused even in the event of a malfunction (0-fault safety).

In addition, there is the type of protection flameproof enclosure (marking Ex-d, IEC DIN 60079-1 , edition 2011), which is based on the principle that any explosion that may occur inside the housing is contained. This is achieved by an explosion-pressure-resistant design of the housing together with flameproof gaps at all housing openings.

In many cases it is desirable to arrange the first and second modules spatially separated from each other in the field device housing. This is required, for example, by the above-mentioned protection classes for explosion protection. On the other hand, with spatial separation, for example, the electronics unit can be housed in an electronics compartment and the connection unit in a connection compartment separated from it by a partition wall. This protects the first module housed in the electronics compartment against deliberate or unintentional manipulation, in particular contact, if the second module housed in the connection compartment group a line or a cable is connected. Due to the spatial separation, the connection compartment can also be opened under environmental conditions that are critical for the first assembly arranged in the electronics compartment (for example in the case of high humidity or precipitation) without the first assembly being damaged.

In order to electrically connect the two spatially separated electrical or electronic components, bushings are used today that are designed to meet the requirements of either the intrinsic safety Ex-i ignition protection type or the flameproof enclosure Ex-d ignition protection type. Additional measures must be implemented to implement both types of ignition protection. For example, the bushing must be at least partially cast with a casting compound in order to meet the required requirements.

However, such measures are accompanied by higher manufacturing costs for the corresponding field device.

The invention is therefore based on the object of providing a solution that is as simple and cost-effective as possible in order to electrically connect two spatially separated assemblies to one another while complying with the requirements of the ignition protection types Ex-i and Ex-d.

The object is achieved according to the invention by the screw-in connecting element according to patent claim 1 and the field device housing according to patent claim 10.

• - wenigstens einen Metallstift,
• - ein Fixiermaterial, in das der wenigstens eine Metallstift auf einen Teil seiner Länge derartig eingebracht ist, dass das Fixiermaterial den Metallstift in diesem Teil vollständig umgibt und der Metallstift beidseitig aus dem Fixiermaterial über dessen Stirnseiten hinausragt,
• - eine das Fixiermaterial umschließende im Wesentliche rotationssymmetrische Metallbuchse mit einem Außengewinde, wobei der Metallstift, das Fixiermaterial und die Metallbuchse derartig ausgebildet sind, dass ein Abstand d zwischen dem Metallstift und der Metallbuchse nicht kleiner als ein in der Norm DIN EN 60079-11 (Ausgabe 2011) vorgegebener Wert für eine Luft- und/oder Kriechstrecke in Luft ist und wobei ferner das Außengewinde der Metallbuchse derartig ausgeführt ist, dass es einem in der Norm DIN EN 60079-1 (Ausgabe 2011) vorgegebenen Wert für die im Eingriff befindlichen Gewindegänge entspricht.

The screw-in connecting element according to the invention for the Ex-i and Ex-d compliant transmission of electrical signals between a connection compartment and a separate electronics compartment in a field device housing of a field device comprises:

• - at least one metal pin,
• - a fixing material into which the at least one metal pin is inserted over part of its length in such a way that the fixing material completely surrounds the metal pin in this part and the metal pin protrudes from the fixing material on both sides beyond its end faces,
• - a substantially rotationally symmetrical metal bushing with an external thread enclosing the fixing material, wherein the metal pin, the fixing material and the metal bushing are designed in such a way that a distance d between the metal pin and the metal bushing is not less than a distance specified in the standard EN 60079-11 (Edition 2011) is a specified value for a clearance and/or creepage distance in air and wherein the external thread of the metal bushing is designed in such a way that it corresponds to a value specified in the standard EN 60079-1 (Edition 2011) specified value for the engaged threads.

According to the invention, a connecting element that can be screwed into a partition wall of a two-chamber field device housing is proposed, which is designed such that a length and a quality of an external thread of the connecting element corresponds to the specifications of the Ex-d regulations and, in addition, a distance between the metal pin and the metal bushing corresponds to the specifications of the Ex-i regulations.

An advantageous embodiment of the connecting element according to the invention can provide that the distance d between the metal pin and the metal bushing is not smaller than a value specified for a voltage of 30 V and a protection level ia, ib for the clearance and/or creepage distance in air according to Table 5 of the standard DIN EN 60079-11.

A further advantageous embodiment of the connecting element according to the invention can provide that the fixing material and the metal bushing are designed such that the distance d between the metal pin and the metal bushing is not less than 1.5 mm, preferably not less than 1.75 mm, particularly preferably not less than 2 mm.

A further advantageous embodiment of the connecting element according to the invention can provide that the external thread of the metal bushing is designed in such a way that it Standard DIN EN 60079-1 (Edition 2011) for a gas group B and/or for a tolerance class of 7H/8g or 6H/6g for the engaged threads.

A further advantageous embodiment of the connecting element according to the invention can provide that the external thread of the metal bushing is designed in such a way that it comprises not less than 5, preferably not less than 6, very particularly preferably not less than 7 fully cut threads.

A further advantageous embodiment of the connecting element according to the invention can provide that the external thread of the metal bushing is designed in such a way that it comprises no more than 11, preferably no more than 10, very particularly preferably no more than 9 fully cut threads.

A further advantageous embodiment of the connecting element according to the invention can provide that the external thread is designed such that it has a thread pitch of at least 0.79 mm per revolution.

A further advantageous embodiment of the connecting element according to the invention can provide that the fixing element comprises a glass, preferably melted into the metal bushing, or a ceramic, preferably soldered into the metal bushing.

A further advantageous embodiment of the connecting element according to the invention can provide that the metal bushing is an M7 metal bushing.

The invention further relates to a field device housing of a field device of automation technology, wherein a first electrical assembly is arranged in an electronics compartment of the field device housing and a second electrical assembly is arranged in a connection compartment of the field device housing, wherein the electronics compartment and the connection compartment are separated from one another by an intermediate wall of the field device housing, wherein in the intermediate wall at least one receptacle for the connecting element according to one or more of the preceding claims is formed with an internal thread corresponding to the external thread of the connecting element, wherein the connecting element is screwed into the at least one receptacle, so that an Ex-i and Ex-d separation is provided between the connection compartment and the electronics compartment.

A further advantageous embodiment of the field device housing according to the invention can provide that several, in particular two or three receptacles for a connecting element according to one or more of the preceding claims are formed in the intermediate wall, each with an internal thread corresponding to the external thread of the connecting element, wherein a connecting element is screwed into each receptacle, so that an Ex-i and Ex-d separation is provided between the connection compartment and the electronics compartment.

• 1: eine schematische Darstellung eines Feldgeräts der Automatisierungstechnik, und
• 2: einen Längsschnitt durch ein erfindungsgemäß ausgebildetes einschraubbares Verbindungselement.

The invention is explained in more detail with reference to the following drawings. It shows:

• 1 : a schematic representation of a field device in automation technology, and
• 2 : a longitudinal section through a screw-in connecting element designed according to the invention.

In 1 is a schematic representation of a field device 1 of automation technology. The field device 1 of process and automation technology is used to determine and/or monitor at least one chemical and/or physical process variable of a medium 2 and is arranged, for example, outside of a container containing the medium 2. The field device 1 can, as in 1 shown, flush with the container wall 20. The field device 1 has a field device housing 3 in which a first chamber 14 and a second chamber 15 are arranged, which are separated from one another by a partition or intermediate wall 16, which is connected to the housing 12 in a particularly pressure-tight manner. The partition or intermediate wall 16 has a receptacle 19 into which a feedthrough or connecting element 1 according to the invention, which will be described in more detail below, is screwed. The receptacle 19 is designed in the partition or intermediate wall 16 in such a way that it has an internal thread which fits an external thread of the connecting element 1, which will also be described in more detail below.

The connecting element 1 is designed to establish an Ex-i, in particular Ex-ia and Ex-ib as well as Ex-d compliant electrical connection between a first electrical assembly 17 arranged in the first chamber 14 and a second electrical assembly 18 arranged in the second chamber 15.

The first electrical assembly 17 can, for example, represent a sensor and/or field device electronics unit which is designed to determine at least one measured variable of the medium. The at least second electrical assembly 18 can, for example, represent a connection electronics unit for connecting the field device to a two-wire line.

In the 1 In the exemplary embodiment shown, only one connecting element 1 is shown, but several connecting elements can also be provided in order to connect the first electrical assembly to the second electrical assembly.

2 shows a screw-in connection element 1 for the Ex-i, in particular Ex-ia and Ex-ib as well as Ex-d compliant transmission of electrical signals between a connection compartment and a separate electronics compartment in a field device housing of a field device in detail.

The connecting element 1 comprises a substantially rotationally symmetrical metal bushing 1.3 with an external thread 1.4. In the metal The bushing 1.3 can be, for example, an M7 metal bushing. The metal bushing 1.3 has a collar 1.31 at one end and a cylindrical part 1.32 adjoining the collar 1.31, the length L2 of which is significantly greater than its radius. The length of the collar L1 can be, for example, approx. 1 mm, preferably approx. 1.25 mm, particularly preferably approx. 1.5 mm. The length of the cylindrical part L2 can be at least 7 mm, preferably at least 7.5 mm, particularly preferably at least 8 mm.

The cylindrical part 1.32 has the external thread 1.4 on its outside. The external thread 1.4 of the metal bushing 1.3 is designed in such a way that it corresponds to a standard EN 60079-1 (April 2015 edition) specified value for the engaged threads. This means that the external thread 1.4 meets the Ex-d requirements in terms of quality and length. In particular, the external thread 1.4 can be designed in such a way that it corresponds to a value for the engaged threads specified in the standard DIN EN 60079-1 (2011 edition) for a gas group B and/or for a tolerance class of 7H/8g or 6H/6g. For example, the external thread 1.4 of the metal bushing 1.3 can be designed in such a way that it comprises no fewer than 5, preferably no fewer than 6, very particularly preferably no fewer than 7 fully cut threads. In addition or alternatively, the external thread 1.4 of the metal bushing 1.3 can be designed in such a way that it comprises no more than 11, preferably no more than 10, very particularly preferably no more than 9 fully cut threads. Additionally or alternatively, the external thread 1.4 can be designed such that it has a thread pitch of at least 0.79 mm per revolution.

A fixing material 1.2 is inserted into the metal bushing 1.3, in particular in the cylindrical part 1.32 of the metal bushing 1.3, into which a metal pin 1.1 is inserted. The metal pin 1.1 is inserted in such a way that it protrudes from the fixing material 1.2 on both sides beyond its front sides and thus also the front sides of the metal bushing 1.3 and the fixing material 1.2 completely surrounds the metal pin in the inserted part.

The fixing material 1.2 can, for example, comprise glass and be fused into the metal bushing. Alternatively, the fixing material 1.2 can comprise a ceramic inlay which is soldered into the metal bushing.

The metal pin 1.1, the fixing material 1.2 and the metal bushing 1.3 are arranged and designed in such a way that a distance d between the metal pin 1.1 and the metal bushing 1.3 is not less than a value specified in the standard EN 60079-11 (June 2012 edition) is a specified value for an air gap and/or creepage distance in air. In particular, they are arranged and designed in such a way that the distance d between the metal pin 1.1 and the metal bushing 1.3 is not less than a value specified for a voltage of 30 V and a protection level ia, ib for the air gap and/or creepage distance in air in accordance with Table 5 of the standard DIN EN 60079-11. For example, the fixing material 1.2 and the metal bushing 1.3 can be designed in such a way that the distance d between the metal pin 1.1 and the metal bushing 1.3 is not less than 1.5 mm, preferably not less than 1.75 mm, particularly preferably not less than 2 mm.

List of reference symbols

1

Screw-in connecting element

1.1

Metal pin

1.2

Fixing material

1.3

Metal bushing

1.31

Collar of the metal bushing

1.32

Cylindrical part of the metal bushing

1.4

External thread

d

Distance between metal pin and metal bushing

10

Field device in automation technology

12

medium

13

Field device housing

14

First Chamber

15

Second Chamber

16

Partition or intermediate wall

17

First electrical assembly, especially electronic unit

18

Second electrical assembly, especially sensor unit

19

Recording

20

Container wall

L1

Length of the collar of the metal bushing

L2

Length of the cylindrical part of the metal bushing

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited non-patent literature

• EN 60079-11 [0005]
• EN 60079-1 [0008]
• EN 60079-11 [0014, 0036]
• EN 60079-1 [0014, 0033]
• Standard DIN EN 60079-1 [0018]

Claims (11)

Screw-in connecting element (1) for the Ex-i and Ex-d compliant conduction of electrical signals between a connection compartment and an electronics compartment separated therefrom in a field device housing of a field device, comprising: - at least one metal pin (1.1), - a fixing material (1.2) into which the at least one metal pin is inserted over part of its length in such a way that the fixing material completely surrounds the metal pin in this part and the metal pin protrudes from the fixing material on both sides beyond its end faces, - an essentially rotationally symmetrical metal bushing (1.3) enclosing the fixing material with an external thread (1.4), wherein the metal pin, the fixing material and the metal bushing are designed in such a way that a distance (d) between the metal pin and the metal bushing is not smaller than a value specified in the standard DIN EN 60079-11 (2011 edition) for an air and/or creepage distance in air and wherein the external thread of the metal bushing is also designed in such a way that it corresponds to a corresponds to the value specified in DIN EN 60079-1 (2011 edition) for the engaged threads. Connecting element according to Claim 1 , where the distance (d) between the metal pin and the metal bushing is not less than a value specified for the clearance and/or creepage distance in air for a voltage of 30 V and a protection level ia, ib in accordance with Table 5 of the standard DIN EN 60079-11. Connecting element according to one or more of the preceding claims, wherein the fixing material (1.2) and the metal bushing (1.3) are designed such that the distance (d) between the metal pin and the metal bushing is not less than 1.5 mm, preferably not less than 1.75 mm, particularly preferably not less than 2 mm. Connecting element according to one or more of the preceding claims, wherein the external thread (1.4) of the metal bushing (1.3) is designed such that it corresponds to a value for the engaged threads specified in the standard DIN EN 60079-1 (2011 edition) for a gas group B and/or for a tolerance class of 7H/8g or 6H/6g. Connecting element according to one or more of the preceding claims, wherein the external thread (1.4) of the metal bushing (1.3) is designed such that it comprises not less than 5, preferably not less than 6, most preferably not less than 7 fully cut threads. Connecting element according to one or more of the preceding claims, wherein the external thread (1.4) of the metal bushing (1.3) is designed such that it comprises no more than 11, preferably no more than 10, most preferably no more than 9 fully cut threads. Connecting element according to one or more of the preceding claims, wherein the external thread (1.4) is designed such that it has a thread pitch of at least 0.79 mm per revolution. Connecting element according to one or more of the preceding claims, wherein the fixing element (1.2) comprises a glass, preferably melted into the metal bushing (1.3), or a ceramic, preferably soldered into the metal bushing. Connecting element according to one or more of the preceding claims, wherein the metal bushing (1.3) is an M7 metal bushing. Field device housing of a field device of automation technology, wherein a first electrical assembly (17) is arranged in an electronics compartment (14) of the field device housing and a second electrical assembly (18) is arranged in a connection compartment (15) of the field device housing, wherein the electronics compartment (14) and the connection compartment (15) are separated from one another by an intermediate wall (16) of the field device housing, wherein in the intermediate wall (16) at least one receptacle (19) for the connecting element (1) according to one or more of the preceding claims is formed with an internal thread corresponding to the external thread (1.4) of the connecting element (1), wherein the connecting element (1) is screwed into the at least one receptacle (19) so that an Ex-i and Ex-d separation is provided between the connection compartment (15) and the electronics compartment (14). Field device housing of a field device of automation technology according to the preceding claim, wherein in the intermediate wall (16) several, in particular two or three receptacles for a connecting element according to one or more of the preceding claims are formed, each with an internal thread corresponding to the external thread (1.4) of the connecting element (1), wherein a connecting element is screwed into each receptacle (19), so that an Ex-i and Ex-d separation between the connection compartment and the electronics compartment.

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