DE102020121582A1 - Differential pressure sensor for determining the differential pressure of two pressures - Google Patents

Abstract

The invention relates to a. Differential pressure sensor (1) for determining the differential pressure of two pressures (p1, p2) with a measuring mechanism (2) and a converter chamber (3), a differential pressure measuring cell (12) with a pressure-sensitive element (13) being arranged in the converter chamber (3). and wherein a coplanar double diaphragm system with two double diaphragms (4a, 4b) is provided on or in an end region of the measuring unit (2) facing the process, wherein the two double diaphragms (4a, 4b) each consist of a separating diaphragm (5a, 5b) and an in In the direction of the pressure effect, there are overload diaphragms (6a, 6b) arranged behind the separating diaphragm (5a, 5b), with a first pressure chamber (7a) between the first separating diaphragm (5a) and the first overload diaphragm (6a) and between the first overload diaphragm (6a) and the base body (9) a first additional pressure chamber (8a) is formed, wherein between the second separating membrane (5b) and the second overload membrane (6b) a second pressure chamber (7b) and between the second A second additional pressure chamber (8b) is formed between the overload diaphragm (6b) and the base body (9), with the first pressure chamber (7a) being assigned a first connecting capillary (10a) and the second pressure chamber (8b) being assigned a second connecting capillary (10b). the pressures (p1, p2) are transmitted hydraulically to the pressure-sensitive element (13), wherein the first additional pressure chamber (8a) is assigned a first auxiliary capillary (11a) and the second additional pressure chamber (8b) is assigned a second auxiliary capillary (11b), wherein - to protect against overpressure occurring on one side (PeÜL) - the first connecting capillary (10a) is hydraulically coupled to the second auxiliary capillary (11b) and the second connecting capillary (10b) to the first auxiliary capillary (11a), and the connecting points/crossings between the first connecting capillary (10a) and the second auxiliary capillary (11b) and the second connecting capillary (10b) and the first auxiliary capillary (11a) in a spatial area angeo are arranged, which is located behind the area of the converter chamber (3) facing away from the process.

Description

The invention relates to a differential pressure sensor for determining the differential pressure of two pressures. The differential pressure sensor according to the invention is preferably used in the field of automation technology.

Differential pressure gauges are used in particular for the continuous measurement of pressure differences in measurement media, e.g. in liquids, vapours, gases and dust. For example, the level of a medium in a container or the flow of a medium through a pipe can be determined from the differential pressure.

A silicon chip is usually used as the pressure-sensitive element. In order to achieve good measuring sensitivity, a differential pressure sensor preferably works in a range that is close to a critical limit value for the pressure (nominal pressure). If the critical limit is exceeded, there is a risk that the chip will be destroyed. Since silicon chips, in particular, have a relatively low overload resistance, overload protection is usually assigned to a differential pressure sensor. This is preferably designed in such a way that it affects the measurement sensitivity and the measurement accuracy of the pressure-sensitive element as little as possible.

From the DE 3 222 620 A1 a pressure difference measuring device has become known which has a pressure measuring transducer device protected against overload. The measuring device has a central receiving body which forms an antechamber on two opposite sides between a membrane bed and a separating membrane. In the receiving body, an additional chamber is provided in each case behind the side facing away from the membrane bed, which is delimited by a prestressed additional membrane. Inside the receiving body there is also a measuring chamber, which is divided into two sub-chambers by the pressure sensor device. Each of the two partial chambers of the measuring chamber is connected to one of the two antechambers via a respective connecting channel. Each of the two connecting channels is connected to one of the two additional chambers via an additional channel.

If the device is exposed to a differential pressure below or in the range of the nominal differential pressure value, then this differential pressure is transmitted to the pressure sensor device via the connecting channels. The additional membranes develop a small effect, which is negligible in a first approximation. If the pressure difference exceeds the nominal pressure difference value by a predetermined value as a result of an overload, the pressure transmitter liquid located below it is pressed into the antechamber assigned to it on the high-pressure side of the separating membrane. The liquid that is pushed out reaches the auxiliary diaphragm on the low-pressure side via the connection channel and the auxiliary channel, causing it to lift. Thus, in the event of an overload, the liquid that is pressed out on the high-pressure side under the separating diaphragm is under the lifting additional diaphragm on the low-pressure side. Consequently, an overload of the pressure sensor device is avoided. In the case of the German patent application, the converter chamber is integrated into the measuring mechanism.

From the WO 2018/165122 A1 a coplanar differential pressure sensor has become known, in which the pressure inputs with separating membrane and overload membrane are arranged in one plane - namely in the end area facing the process - and not on opposite, parallel planes as in the aforementioned German patent application. It is a so-called double membrane system. The advantage of double membrane systems lies in the significantly lower oil volume that is required for the hydraulic operation of the differential pressure sensor. In addition, the pressure-loaded center membrane weld can be dispensed with here, so that the measuring mechanism can be made in one piece. As in the previously mentioned patent application, the overload protection is also arranged in the measuring mechanism in this known solution, ie the crossed capillaries are located in the measuring mechanism. The converter chamber is placed directly on the measuring mechanism or integrated into the measuring mechanism.

The known solutions have several disadvantages: Since the crossed hydraulic pressure feedthroughs are arranged in the measuring mechanism, e.g. in the known coplanar design, for the purpose of oil filling, externally exposed bores are required, which are closed after filling. The closure areas are potential corrosion weak points. In addition, the holes are quite long, which has a negative impact on manufacturing costs. Long bores also inevitably require a larger oil volume, which in turn makes it difficult to implement overload protection in the measuring mechanism. Since defined distances between the pressure ducts must be maintained, there are limits to minimizing the dimensions of the measuring unit.

The object of the invention is to propose a pressure sensor with overload protection and reduced oil volume. At this point, the term "oil volume" is chosen because the hydraulic transmission fluid is usually in the specified measuring range almost incompressible oil, for example a silicone oil.

The task is solved by differential pressure sensors for determining the differential pressure of two pressures with a measuring mechanism and a converter chamber. A differential pressure measuring cell with a pressure-sensitive element is arranged in the converter chamber. The pressure-sensitive element is preferably a silicon chip. The differential pressure is determined using a capacitive or resistive measuring method or a resonator.

A coplanar double membrane system with two double membranes is provided on or in an end area of the measuring unit facing the process. Each of the two double diaphragms consists of a separating diaphragm and an overload diaphragm arranged behind the separating diaphragm in the direction of the pressure effect. A first pressure chamber is formed between the first separating diaphragm and the first overload diaphragm, and a first additional pressure chamber is formed between the first overload diaphragm and the base body. A second pressure chamber is formed between the second separating diaphragm and the second overload diaphragm, and a second additional pressure chamber is formed between the second overload diaphragm and the base body. A first connecting capillary is associated with the first pressure chamber and a second connecting capillary is associated with the second pressure chamber. Furthermore, a first auxiliary capillary is associated with the first additional pressure chamber and a second auxiliary capillary is associated with the second additional pressure chamber. The pressure is transmitted to the pressure-sensitive element hydraulically via the capillary system. To protect against overpressure occurring on one side, the first connecting capillary is hydraulically coupled to the second auxiliary capillary and the second connecting capillary to the first auxiliary capillary. The connection points/crossings between the first connection capillary and the second auxiliary capillary and the second connection capillary and the first auxiliary capillary are arranged in a spatial area which is located behind the area of the converter chamber which is remote from the process.

• - Das Messwerk ist einteilig ausgestaltet.
• - Das Messwerk hat einen einfachen und in weiten Teilen symmetrischen Aufbau.
• - Kosteneinsparung beim Messwerk werden insbesondere durch Materialeinsparungen (kleine Dimensionen) und eine vereinfachte Fertigung und Bearbeitung erreicht: Die Anzahl der Bohrungen ist gering, sie können z.B. kostengünstig durch Erodieren hergestellt werden.
• - Aufgrund des Abstands zwischen Messwerk und Wandlerkammer lässt sich eine gute mechanische und thermische Entkopplung zwischen Messwerk und Wandlerkammer erreichen.
• - Ein einseitig auftretender Überdruck auf der Hochdruckseite wird hydraulisch auf die Rückseite der Überlastmembrane/Zusatzmembrane der Niederdruckseite und parallel zur Wandlerkammer geleitet. Wandlerkammer und Überlastmembrane liegen druckdynamisch parallel. Je geringer das zu verschiebende Ölvolumen ist (das Ölvolumen in der Zusatzdruckkammer ist im normalen Messbetrieb bevorzugt vernachlässigbar), desto effektiver arbeitet der Überdruckschutz.
• - Eine schnelle Reaktionszeit des Überlastschutzes wird weiterhin über die Dimensionierung der Hilfs- und Verbindungsleitungen und ggf. über in die Kapillaren eingebrachte Dynamikbremsen erreicht.
• - Aufgrund der günstigen Lage der Befüllungsöffnungen bevorzugt im Messwerk und/oder in der Wandlerkammer lässt sich die Menge der Hydraulikflüssigkeit, insbesondere des Silikonöls, zusätzlich minimieren.

The solution according to the invention has the following advantages:

• - The measuring mechanism is designed in one piece.
• - The measuring mechanism has a simple and largely symmetrical structure.
• - Cost savings in the measuring mechanism are achieved in particular through material savings (small dimensions) and simplified production and processing: the number of bores is small, they can be produced inexpensively, for example, by eroding.
• - Due to the distance between the measuring mechanism and the converter chamber, a good mechanical and thermal decoupling between the measuring mechanism and the converter chamber can be achieved.
• - An overpressure occurring on one side on the high-pressure side is routed hydraulically to the back of the overload diaphragm/additional diaphragm on the low-pressure side and parallel to the converter chamber. In terms of pressure dynamics, the converter chamber and overload diaphragm are parallel. The smaller the oil volume to be displaced (the oil volume in the additional pressure chamber is preferably negligible in normal measuring operation), the more effectively the overpressure protection works.
• - A fast response time of the overload protection is also achieved through the dimensioning of the auxiliary and connecting lines and, if necessary, through the dynamic brakes introduced into the capillaries.
• - Due to the favorable position of the filling openings, preferably in the measuring mechanism and/or in the converter chamber, the quantity of hydraulic fluid, in particular the silicone oil, can also be minimized.

Measuring mechanism and converter chamber, both separate components, can be spatially separated from one another via a further component, an intermediate module, or both components can be separated from one another via an intermediate module. This achieves a mechanical decoupling between the measuring unit and the sensitive differential pressure measuring cell, which is located in the converter chamber. The joints between the components are of course designed to be pressure-resistant and gas-tight.

Because of the reduced oil volume, the measurement error of the differential pressure sensor according to the invention, which is generated by the temperature gradient, is also relatively small. Furthermore, a small oil volume also enables the use of smaller diaphragm diameters, which is very advantageous for realizing a coplanar differential pressure sensor with effective overload protection. The reason for this can be seen in the fact that with a small measuring range, the activation or deflection of the membranes can be kept low, which is reflected in smaller measuring errors.

In general it can be said that, in order to protect the pressure-sensitive element against excess pressure, it is ensured according to the invention that excess pressure occurring on one side on the coplanar double membrane system is limited in such a way that destruction of the pressure-sensitive element is excluded.

According to one embodiment of the differential pressure sensor according to the invention, the additional membranes are prestressed in such a way that they only lift off from the base body when a predetermined critical limit pressure is exceeded. This ensures that the overload protection is only activated when there is a risk of overpressure damaging the pressure-sensitive element. Due to the virtual non-existence of the overload chambers in normal measuring operation, the required oil volume can be reduced again, which brings with it the corresponding advantages already described above. Process membrane / separating membrane that can be used in conjunction with the solution according to the invention is from US 10,656,039 B2 known.

As a result of the full-surface and preferably form-fitting contact of the overload membranes on the housing of the measuring mechanism, the measured pressure reaches the pressure chambers, the correspondingly coupled auxiliary and connecting capillaries to the corresponding overpressure chambers and to the minus or plus side of the pressure-sensitive element. possibly A hydraulic channel is provided in the membrane beds or on the backs of the overload membranes. In terms of pressure dynamics, the overload membranes and the pressure-sensitive element are parallel. The deflection of the overload diaphragms is forcibly prevented up to a predetermined value as a result of their pretension. The preload of the overload diaphragms is designed in such a way that it is larger than the measuring range of the differential pressure sensor.

The pressure-sensitive element receives the pressure information for the plus side via the second pressure chamber, the second connecting capillary and the first auxiliary capillary coupled to it. The pressure-sensitive element receives the pressure information for the minus side via the first pressure chamber, the first connecting capillary and the second auxiliary capillary coupled to it. Due to the parallel connection, the pressures applied to the sides of the pressure-sensitive element also act on the back of the corresponding overload diaphragms. The pressure-sensitive element deflects according to the applied differential pressure. Incidentally, the effect of the parallel paths via the overload pressure chambers is almost negligible due to the prestressed, essentially full-surface and/or positive or non-positive contact of the overload membranes on the housing of the measuring mechanism.

The prestressing of the overload membranes ensures that they are only deflected when a critical overpressure occurs on one of the double membranes, which would entail the risk of destroying the pressure-sensitive element. For example, as soon as a critical overpressure occurs at the second separating diaphragm, the second separating diaphragm is moved against the second overload diaphragm until it is in contact with the overload diaphragm. When the pretension is exceeded, the first overload membrane is deflected and the transmission fluid pushed out of the second pressure chamber is pushed into the first additional pressure chamber via the second connecting capillary and the first auxiliary capillary coupled to it. The pressure in the first additional pressure chamber and in the first pressure chamber that is operatively connected to it increases. This continues until the hydraulic fluid is shifted from the high-pressure side to the low-pressure side. The hydraulic pressure in the measuring unit can then no longer rise and the pressure limitation, i.e. the overpressure protection, takes effect.

Furthermore, the connecting capillaries and the auxiliary capillaries in the measuring unit and in the converter chamber, if necessary in the intermediate module 19, are preferably capillary bores. These run essentially parallel to the longitudinal axis of the differential pressure sensor. The transitions between the connecting capillaries and the auxiliary capillaries between the measuring unit and the converter chamber, as well as in the area behind the converter chamber, are preferably realized via capillary tubes which are fastened pressure-tight, non-positively and gas-tight in the bores.

In addition, it is proposed that the measuring unit be arranged in a process connection, with the process connection having a diameter in the area facing the process that is larger than the diameter in the area facing away from the process, in which it is pressure-, gas- and/or or connected in a liquid-tight manner. Due to the separation of measuring mechanism and converter chamber, it is also possible in a simple manner to implement an electrically insulated separation between the two components—measuring mechanism and converter chamber. More on that later. It goes without saying that the connecting capillaries and the auxiliary capillaries in the area behind the converter chamber can also be implemented as capillary bores.

In order to also ensure that a one-sided overpressure is limited before it reaches the pressure-sensitive element, an advantageous embodiment of the differential pressure sensor according to the invention proposes that the connecting capillaries and/or the auxiliary capillaries be designed and/or dimensioned in such a way that a pressure above the specified critical limit pressure lying overpressure is compensated by the overload protection before it is transmitted to the differential pressure measuring cell. In order to additionally protect the pressure-sensitive element from pressure peaks, dynamic brakes are installed in the connecting lines or in the connecting capillary between the measuring mechanism and the intermediate module or between the intermediate module and the converter chamber, according to one embodiment of the differential pressure sensor. The dynamic brakes are flow resistances, eg sintered metal inserts. The dynamic brakes can also be designed in such a way that they also assume the function of explosion protection.

An advantageous embodiment of the differential pressure sensor according to the invention provides that the measuring unit has two filling bores for filling the hydraulic system of the differential pressure sensor with a hydraulic fluid. The filling bores essentially run parallel to the connecting capillaries and the auxiliary capillaries. Alternatively or additionally, at least one filling hole is provided on the converter chamber. After filling with the hydraulic fluid, the filling bores are closed in a pressure-tight and gas-tight or at least liquid-tight manner with an associated closure element. For example, a closure element is a ball that is pressed into the bore and then caulked. It is also possible to weld the closure element in the bore. The amount of hydraulic fluid required can be reduced by introducing filling elements, e.g. filling rods, into the filling bores.

Due to the arrangement of the outlets of the filling openings in the rear of the sensor and thus in the interior of the differential pressure sensor, the filling holes - behind the closing elements - are protected against corrosion. Furthermore, the corresponding areas of the filling bores can also be cast on the outside; however, this is not absolutely necessary due to the closed position of the filling bores within the housing adapter from the outside.

The connecting and auxiliary capillaries can also be designed in such a way that they electrically insulate the converter chamber from the measuring mechanism. The electrical insulation of the converter chamber from the measuring mechanism is preferably carried out via additional elements. These can be arranged at different points in the connecting or auxiliary capillaries. An additional insulating element can be, in particular, a ceramic insulating body or an insulating glazing. The connection must be gas-tight: either it is a soldered connection or a glazing. As stated, the electrical insulators can be provided in the converter chamber and/or in the measuring unit or in the area between the measuring unit and the converter chamber and/or in the area behind the converter chamber. In particular, the electrical insulators can also be integrated as intermediate pieces in the connecting and auxiliary capillaries designed as capillary tubes.

• - Guarding für besseres EMV (elektromagnetisches Verhalten);
• - Geringerer bzw. kein Fremdspannungseinfluss;
• - Möglichkeit einen kapazitiven Siliziumchip einzusetzen, bei dem das Guarding eine Voraussetzung ist, dass nur geringere Störkapazitäten auftreten;
• - Der bislang erforderliche isolierende Keramiksockel in der Wandlerkammer kann entfallen; Bei einer bevorzugten Ausgestaltung des erfindungsgemäßen Differenzdrucksensor wird das drucksensitive Element, üblicherweise ein Silizium-Chip, bevorzugt auf einen Silizium-Sockel aufgebracht. Nimmt man einen Silizium-Sockel anstelle des sonst üblichen Glassockels, so lässt sich ein günstigeres thermisches Verhalten (T-Hysterese) erreichen, was sich in einem geringeren statischen Druckfehler niederschlägt. Erklärung: Der E-Modul von Glas ist verschieden von dem E-Modul von Silizium. Bei Glas tritt eine größere Verformung und somit ein größerer Fehler infolge eines statischen Drucks auf als bei Silizium. Da Silizium jedoch kein Isolator ist, sondern eine gewisse Leitfähigkeit aufweist, sind für den sicheren elektrischen Betrieb Mindestisolationsstrecken erforderlich. Diese können z.B. durch in die Verbindungsleitungen eingesetzte keramische Isolierkörper und/oder entsprechend ausgestaltete Dynamikbremsen realisiert werden.
• - Der volle oder partielle Ex-Schutzverguss in der Wandlerkammer, der bislang bei Differenzdrucksensoren erforderlich war, kann entfallen. Bislang wurde der Verguss genutzt, um die Mindestabstände der stromführenden Elemente zum Massepotential möglichst gering halten zu können. Diese Abstandsreduzierung kann bei der Ausgestaltung der Erfindung entfallen, wo die Isolationselemente in den Verbindungskapillaren angeordnet sind. Zwecks Erzielung einer sicheren elektrischen Isolierung können die erforderlichen Mindestabstände um einiges kleiner ausfallen als beiden bislang bekannt gewordenen Lösungen. Auch lassen sich diese Mindestabstände ohne großen Aufwand erreichen.

This makes it possible to separate earth and ground (circuit zero point; Ue = reference point of the electrical supply = ground) and to achieve the following advantages for the current feedthrough:

• - Guarding for better EMC (electromagnetic behavior);
• - Lower or no external voltage influence;
• - Possibility to use a capacitive silicon chip, in which the guarding is a prerequisite that only low interference capacitances occur;
• - The previously required insulating ceramic base in the converter chamber can be omitted; In a preferred embodiment of the differential pressure sensor according to the invention, the pressure-sensitive element, usually a silicon chip, is preferably applied to a silicon base. If a silicon base is used instead of the usual glass base, a more favorable thermal behavior (T hysteresis) can be achieved, which is reflected in a lower static pressure error. Explanation: The modulus of elasticity of glass is different from the modulus of elasticity of silicon. Glass suffers from greater deformation and thus greater error due to static pressure than silicon. However, since silicon is not an insulator but has a certain conductivity, minimum insulation distances are required for safe electrical operation. These can be implemented, for example, by using ceramic insulating bodies in the connecting lines and/or correspondingly designed dynamic brakes.
• - The full or partial explosion protection potting in the converter chamber, which was previously required for differential pressure sensors, can be omitted. So far, encapsulation has been used in order to be able to keep the minimum distances between the current-carrying elements and the ground potential as small as possible. This reduction in distance can be omitted in the embodiment of the invention where the insulation elements are arranged in the connecting capillaries. In order to achieve reliable electrical insulation, the required minimum distances can be a lot smaller than both have been aware of up to now which solutions. These minimum distances can also be achieved without great effort.

Furthermore, it is provided that the electrical connecting pins or connecting lines from the electrical converter are routed in a gas-tight manner through one of the end regions of the converter chamber facing away from the process in the direction of an electronic circuit board. The gas-tightness is preferably achieved via glass bushings. Since the transducer chamber is electrically isolated from the measuring mechanism, the wall thickness of the glass bushings can be made thinner. This allows the distance between the pins to be reduced. The aim is in particular to achieve a pressure resistance that is greater than 1280 bar. Smaller glazing elements allow more PINs to be accommodated in the same space. This may also mean that less oil volume is required.

In order to increase the measurement accuracy, the converter chamber is designed in such a way that the same transmission liquid or oil volumes are present on the low-pressure side and the high-pressure side. The oil volumes on the high-pressure and low-pressure side can be equalized, for example, by creating a corresponding additional volume by enlarging or lengthening one of the bores.

• 1a: eine Darstellung, die den Aufbau eines erfindungsgemäßen Differenzdruckaufnehmers schematisch skizziert,
• 1b: der Weg des Drucks/Überdrucks im Kapillarsystem des in 1a gezeigten Differenzdruckaufnehmers,
• 2: eine realistischere Darstellung der in den Figuren 1a und 1b gezeigten Ausgestaltung bei Anliegen eines Überdrucks,
• 3a: eine Variante zu der in 3a gezeigten Ausgestaltung mit zusätzlichen Befüllungsöffnungen in der Wandlerkammer,
• 3b: die in 2 gezeigte Ausgestaltung mit Pfeilen, die die Übertragung des Drucks anzeigen,
• 4: eine Explosionsdarstellung einer bevorzugten Ausgestaltung der Wandlerkammer mit Stromdurchführung,
• 5: unterschiedliche Darstellungen vorteilhafter Varianten, wie die elektrische Isolierung zwischen Messwerk und Wandlerkammer erreicht wird,
• 6: unterschiedliche Ansichten und Schnitte durch eine Wandlerkammer mit einer Einheit zur Kompensation des statischen Drucks,
• 7: die Schaltung der elektrischen Anschlüsse von Differenzdruckmesszelle und statischer Druckmesszelle, und
• 8: einen Längsschnitt durch einen schematisch dargestellten Differenzdruckmesssaufnehmer, und
• 9: eine Draufsicht auf einen Füllkörper, bei dem die Druckmesszelle und die Druckmesszelle für den statischen Druck in einer Ebene angeordnet sind.

In order to record and subsequently compensate for the influence of the static pressure on the measured values of the differential pressure sensor, a corresponding pressure-sensitive element for measuring the static pressure is provided in the converter chamber. In order to keep the oil volume as small as possible, the pressure-sensitive element for measuring the differential pressure and the pressure-sensitive element for measuring the static pressure are stacked one on top of the other. This is where the advantage of the previously mentioned reduction in the size of the bushings for the PINs comes into play: Since these are smaller, the four additional PINs, which provide the measured values of the static pressure element, can be accommodated in the converter chamber without enlarging them would have to be. The arrangement of the PINs is dealt with in more detail below in the description of the figures. However, it is also possible to arrange the pressure-sensitive element for measuring the differential pressure and the pressure-sensitive element for measuring the static pressure next to one another, that is to say virtually in one plane.

• 1a : an illustration that schematically outlines the structure of a differential pressure sensor according to the invention,
• 1b : the path of the pressure/overpressure in the capillary system of the in 1a shown differential pressure sensor,
• 2 : a more realistic representation of those in the figures 1a and 1b configuration shown when an overpressure is present,
• 3a : a variant of the in 3a shown embodiment with additional filling openings in the converter chamber,
• 3b : in the 2 embodiment shown with arrows indicating the transmission of the pressure,
• 4 : an exploded view of a preferred embodiment of the converter chamber with current feedthrough,
• 5 : different representations of advantageous variants of how the electrical insulation between the measuring mechanism and the converter chamber is achieved,
• 6 : different views and sections through a converter chamber with a static pressure compensation unit,
• 7 : the circuit of the electrical connections of the differential pressure measuring cell and static pressure measuring cell, and
• 8th : a longitudinal section through a differential pressure measuring sensor shown schematically, and
• 9 : a plan view of a packing in which the pressure measuring cell and the pressure measuring cell for the static pressure are arranged in one plane.

In 1a the structure of a differential pressure sensor 1 according to the invention is sketched schematically. 2a outlines the path that an overpressure occurring on one side takes in the capillary system of the differential pressure sensor 1. The differential pressure sensor 1 is used to determine the differential pressure of two pressures p1, p2. The measurement of the differential pressure of two pressures p1, p2, for example in a pipe, is used to determine the flow rate. Another application of a differential pressure sensor 1 is, for example, the determination of the fill level of a fluid medium located in a tank.

The coplanar differential pressure sensor 1 consists of the components: measuring unit 2 and converter chamber 3. The measuring unit 2 is arranged in the process connection 21. The process connection 21 has larger dimensions in the area facing the process than in the area facing away from the process. The converter chamber 3 is integrated into the housing adapter 22 . process Connection 21 and housing adapter 22 are connected to one another via joint 20 in a pressure-tight, gas-tight and/or liquid-tight manner. If necessary, an intermediate module 19 is provided between the measuring unit 2 and the converter chamber 3, which is not shown in the figures.

In its end region facing the process, the measuring unit 2 has two double membranes 4a, 4b lying in one plane, which together form a coplanar double membrane system. Each of the two double diaphragms 4a, 4b consists of a separating diaphragm or a process diaphragm 5a, 5b and an overload diaphragm 6a, 6b arranged behind the separating diaphragm 5a, 5b in the direction of the pressure effect. A first pressure chamber 7a is formed between the first separating membrane 5a and the first overload membrane 6a and a first additional pressure chamber 8a is formed between the first overload membrane 6a and the base body 9 . A second pressure chamber 7b is formed between the second separating membrane 5b and the second overload membrane 6b, and a second additional pressure chamber 8b is formed between the second overload membrane 6b and the base body 9. The overload membranes 6a, 6b are preferably prestressed in such a way that they essentially rest against the base body 9 during regular measurement operation and only lift off from the base body 9 when a predetermined critical limit pressure is exceeded on one side - i.e. on one of the two separating membranes 5a, 5b . Destruction of the pressure-sensitive element 13 can only be ruled out if care is taken to ensure that the pressure transmitted to the pressure-sensitive element 13 arranged in the pressure-measuring cell 12 is always below this critical limit pressure.

A first connecting capillary 10a is assigned to the first pressure chamber 7a and a second connecting capillary 10b is assigned to the second pressure chamber 8b. The first additional pressure chamber 8a is assigned a first auxiliary capillary 11a and the second additional pressure chamber 8b is assigned a second auxiliary capillary 11b. To protect against an overpressure PeÜL occurring on one side, the first connecting capillary 10a is hydraulically coupled to the second auxiliary capillary 11b and the second connecting capillary 10b to the first auxiliary capillary 11a. The connection points/crossings between the first connection capillary 10a and the second auxiliary capillary 11b and the second connection capillary 10b and the first auxiliary capillary 11a are arranged in a spatial area which is located behind the area of the converter chamber 3 facing away from the process. The pressures p1, p2 are transmitted hydraulically via the capillaries 10a, 10b, 11a, 11b to the minus side or plus side of the pressure-sensitive element 13.

The hydraulic transmission medium in the capillary system is a liquid 16 that is largely incompressible in the specified measuring range of the differential pressure sensor 1, e.g. a silicone oil.

The connecting and auxiliary capillaries 10a, 10b, 11a, 11b in the measuring unit 2 and in the converter chamber 3 are preferably designed as capillary bores. However, it is also possible to configure the capillary bores at least in part as capillary tubes 17 . In the case shown, capillary tubes 17 are provided between the capillary bores of measuring mechanism 2 and converter chamber 3 and possibly in the area behind converter chamber 3 .

In order to ensure that the overload protection takes effect before an overpressure PeÜL occurring on one side is transmitted to the pressure-sensitive element 13, the capillaries 10a, 10b, 11a, 11b are suitably dimensioned. In addition, dynamic brakes 18 are provided. In the case shown, the dynamic brakes 18 are provided in the capillaries that lead to the minus and plus sides of the pressure-sensitive element 13 . The dynamic brakes 18 can be sintered metal inserts. If the differential pressure sensor 1 is used in a potentially explosive area, the dynamic brakes 18 are made from a non-conductive material. In this case, the dynamic brakes 18 then fulfill a dual function: delayed transmission of the pressure and explosion protection, which is designed according to the required type of explosion protection. It goes without saying that dynamic brakes 18 in the two variants described above can be integrated at all points within the capillary system where their use ensures the correct functioning of the overload protection. As already mentioned, the dimensions (length and diameter) of the connection and auxiliary capillaries are additionally or alternatively designed in such a way that the overload protection can develop its effect.

The capillary system of the differential pressure sensor 1 is filled with a hydraulic transmission fluid 16 via the filling bores 14a, 14b. The arrangement and position of the filling holes 14a, 14b is chosen so that the volume of oil required for filling is as small as possible.

The filling bores and the closure elements 15a, 15b are designed and arranged as far as possible in such a way that the closed filling bores 14a, 14b in the measuring unit ( 1a , 1b , 2 , 3b ) or in the converter chamber 3 and in the measuring mechanism 2 ( 3a ). This arrangement in the interior of the differential pressure measurement saufnehmers 1 are the filling holes 14a, 14b - protected against corrosion - even outside of the closure elements 15a, 15b. Furthermore, the corresponding areas of the filling bores 14a, 14b can be cast to the outside; however, this is not absolutely necessary due to the closed position of the filling bores 14a, 14b from the outside.

A preferably spherical closure element 15a, 15b is provided as a pressure-tight, gas-tight or at least liquid-tight closure, which is pressed from the outside into the filling bore 14a, 14b and then caulked. In principle, other methods for closing the openings are also available. However, welding is regarded as critical insofar as negative repercussions on the defined properties of the transmission liquid 16 can occur as a result of the temperature increase.

The figures 3a and 3b show the activation of the overpressure protection when a one-sided overpressure occurs on the double diaphragm 4b. The overpressure protection works analogously when an overpressure occurs at the double diaphragm 4a. As already mentioned, the two figures differ only in the arrangement of the filling bores 14a, 14b. While at the in 3a shown embodiment, the filling takes place via the measuring unit 2, is in 3b an additional filling is carried out via the converter chamber 3.

The overload diaphragms 5a, 5b are pre-stressed in such a way that in normal operation they are in positive contact with the housing 9 or lie over their entire surface. As a result, there is almost no oil volume in the overload chamber 8b that can be displaced. If an overpressure PeÜL occurs at the process diaphragm 4b, the process diaphragm 5b is moved against the overpressure diaphragm 6b and the overpressure PeÜL is transmitted via the connecting capillary 10b and the auxiliary capillary 10a to the rear of the overload diaphragm 6a. As soon as the overpressure PeÜL is greater than the preload of the overpressure membrane 6a, this is deflected in the same way as the process membrane 5a. The double-diaphragm system 4a on the low-pressure side receives all the transfer fluid that is pushed out of the double-diaphragm system 4b on the high-pressure side.

According to the invention, the transfer liquid 16 is transferred from the high-pressure side of the double-diaphragm system 4b to the low-pressure side of the double-diaphragm system 4a until no more transfer liquid 16 can be displaced on the high-pressure side, since the separating diaphragm 5b rests on the overload diaphragm 6b supported on the base body of the measuring mechanism 2. The maximum pressure applied to the plus side (+) of the pressure-sensitive element 15 can be defined or dimensioned via the restoring force of the overload membrane 6a, 6b (spring in the deflected state). Due to the parallel connection of overload membranes 6a, 6b and pressure-sensitive element 13, the pressure at pressure-sensitive element 13 does not exceed the critical limit value in the event of excess pressure. This effectively counteracts the destruction of the pressure-sensitive element 13, usually a silicon chip.

In order to support the overpressure PeÜL first deflecting the overload membrane 6a before it reaches the membrane of the pressure-sensitive element 13, the capillary geometries may be adjusted accordingly. In addition, dynamic brakes 18 may also be connected upstream of the access capillaries to the pressure-sensitive element 13 ( 3a ). In particular, the connecting capillaries 10a, 10b and the auxiliary capillaries 11a, 11b are suitably dimensioned in terms of length and diameter in such a way that the overload protection function reliably takes effect.

4 shows an exploded view of a cube-shaped configuration of the differential pressure measuring cell 12 and visualizes how the individual components of the differential pressure measuring cell 12 and the current bushing 23 are arranged in the converter chamber 3 . An insulating base (eg, a ceramic base) 31 is bonded to the bottom surface of a recess in the transducer chamber 3 with a suitable adhesive 30 . The differential pressure measuring cell 12 , which preferably has a silicon chip as the pressure-sensitive element 13 , is connected to the ceramic base 31 by means of an adhesive 32 . For the purpose of minimizing the required volume of oil or the volume of the transmission liquid 21, a filling body 33 is provided, which encloses the pressure measuring cell 13 as closely as possible in the side area. The filling body 33 is closed with a cover 34 . The converter chamber 3 is closed to the outside with a sealing cap 34 for the current feedthrough 23 . The silicon chip 13 is insulated via the insulation base, for example a ceramic base 31 or glass base, which has a thickness of d≧0.5 mm for reasons of explosion protection, for example. Furthermore, the filling body 33 with the cover 34, which is made of a suitable plastic, for example, takes over the insulation of the silicon chip 15 and its bond connections. The connecting capillaries 10a, 10b, designed as capillary tubes, and the auxiliary capillaries 11a, 11b are shown below.

5 shows different representations of advantageous variants of how the electrical insulation between measuring unit 2 and converter chamber 3 can be realized via insulation elements 25, preferably insulation tubes 25, adapted in or on the capillary tubes. In these configurations, ubri In general, the previously described bonded ceramic base 31 in the converter chamber 3 can be dispensed with. The electrical insulation between measuring mechanism 2 and converter chamber 3 takes place in the area of the capillary tubes between the corresponding connecting capillaries 10a, 10b or at the transition of the capillary tubes to measuring mechanism 2 or to converter chamber 3.

As in the illustration on the left 5 can be seen, the electrically insulating ceramic tubes 25 in the converter chamber 3 ( 5a ), in the intermediate area between converter chamber 3 and measuring unit 2 ( 5c ) or in measuring element 2 ( 5b ) to be executed. The insulation preferably achieves potential isolation from ground or the internal ground. This is required for Ex ia safety level and electrical safety. The alternative that the Ex isolation can also be achieved by appropriate design of the dynamic brakes 22 has already been mentioned above. The differential pressure measuring sensor 1 according to the invention can also be used in potentially explosive areas. To do this, it must meet the ex d safety requirements, for which additional safety measures are required.

6 shows a converter chamber 3 or its components and different sections through the converter chamber 3. In this embodiment, a measuring cell 27 is also provided for determining the static pressure. In 6a shows the power bushing 23 with an advantageous arrangement of the connection pins 26 for the differential pressure measuring cell 14 with the pressure-sensitive element 15 and the measuring cell 27 arranged above it for determining the static pressure. The PINs 26 are preferably found symmetrically in the edge area of the two pressure measuring cells 14, 27, which are preferably arranged stacked one on top of the other. However, it can also be an advantage to position at least one PIN asymmetrically in order to make subsequent processing, for example soldering on the circuit board, safer later in the process (poka-yoke principle). Either the PINs 26 all end in one plane or in parallel planes. Two pins 1.1, 1.2 of the eight pins 26 ( 7c ) can be used without insulation, e.g. B. soldered, since they are on ground / housing potential.

PINS 2 and 3 could be electrically connected together, i.e. in a common PIN, to potential ( 7b ). The electrical insulation then preferably takes place via a glazing. If the ground PINS 1.1, 1.2, which correspond to PINS 1, 8, and PINS 2, 3 for the power supply are combined, the two bridges are connected in parallel to the power supply. This circuit is shown in 7c .

In order to meet the requirements of electrical safety and for use in hazardous areas, all PINs 26 are arranged or spaced such that there is sufficient dielectric strength both from PIN 26 to PIN 26 and from PIN 26 to the housing/ground of the converter chamber 3 is. Since the oil volume is all the smaller, the smaller the interior space of the converter chamber 3 is dimensioned, the interior space preferably has a diameter of <10 mm, in particular <8 mm.

6b shows a longitudinal section through the pressure measuring cells 14, 27 stacked one on top of the other. The pressure measuring cell 27 is an absolute pressure measuring cell. The PINS 26 are routed through the electrical feedthrough 30 so that they are isolated from one another. The power feedthrough 23 is designed to be pressure-resistant and gas- or liquid-resistant. The PINs 26 are either soldered or glazed. Alternatively they are pressed in or impulse welded. Only the ground PINS are arranged in the housing without insulation, all others must be insulated. This is possible if the housing is isolated and connected to the measuring unit via the capillaries. Otherwise, all PINs (including the ground PINS) must be electrically isolated.

In order to minimize the oil volume required, the differential pressure measuring cell 14 with the bonding wires 24 is embedded as closely as possible in the filling body 33 and the filling body cap 37 . The packing cap 37 has a recess for receiving the chip/static pressure cell 27 . The sealing cap 35 follows an insulating film 29. 6c shows a cross section in the area of the differential pressure measuring cell 14, while 6d shows a section in the area of the chip 27 for measuring the static pressure.

In the figures 7a , 7b and 7c the circuits for the previously mentioned arrangements of the PINs 26 are shown. The differential pressure (1.2) and the static pressure (1.1) are measured via two resistance bridges. The measured values are sent to an electronic circuit board 36 for further processing. 7a shows the basic connection diagram of the two Si chips 15, 27. In order to be able to operate the circuit completely independently, eight PINs 26 are required; minimum are six PINs 26 ( 7b ) necessary. 7c shows a circuit with 7 PINs 26. This interim solution has a separate plus supply, but a common ground. The advantage of using a smaller number of PINs 26 is clearly that space can be saved. The PINs 26 for the ground connection can also be implemented as a direct connection between the corresponding PIN 26 or the corresponding PINs 26 and the conductive housing (metal housing). the Connection can be realized by soldering, pressing or welding.

• (2), (3): PINs 26 für den Anschluss der Versorgungsspannung,
• (4), (5): PINs 26 für das Brückenausgangssignal der statischen Druckmesszelle 27,
• (6), (7): PINs 26 für das Brückenausgangssignal der Differenzdruckmesszelle 14,
• 1 = (1.1): Versorgungsspannungs-Minusanschluss (Masse),
• 8 = (1.2): Versorgungsspannungs-Minusanschluss (Masse).

Below is the function of each in 7 shown PINs 26 listed:

• (2), (3): PINs 26 for connecting the supply voltage,
• (4), (5): PINs 26 for the bridge output signal of the static pressure measuring cell 27,
• (6), (7): PINs 26 for the bridge output signal of the differential pressure measuring cell 14,
• 1 = (1.1): supply voltage minus connection (ground),
• 8 = (1.2): supply voltage minus connection (ground).

As already described above, a common PIN 26 can also be used for the ground connection.

• ① Innenvolumen, das ev. mit einem Verguss ausgefüllt ist
• ② Schweißung zwischen Gehäuseadapter und Messwerk 2
• ③ Druckzuführung Wandlerkammer 3 - Messwerk 2
• ④ Druckzuführung zur Wandlerkammer 3
• ⑤ Stromdurchführung 23 mit PIN/Einglasung
• ⑥ Ölverschluss 20
• ⑧ Trennung zwischen Gehäuse und Sensorrückraum 16
• ⑨ Exd-Gewinde Gehäuse-Sensor, z.B. über ein Second Containment und/oder einen Verguss
• ⑩ Verschlusskappe 35 Stromdurchführung 23 (GDF)

8th shows a longitudinal section through a differential pressure measuring sensor 1 shown schematically 8th lists the different zones AG to which the differential pressure sensor 1 is exposed. Since the zones are listed by name in the figure, they will not be repeated at this point. The encircled numbers schematically document components that characterize the basic structure of the differential pressure sensor 1 according to the invention:

• ① Inner volume that may have been filled with encapsulation
• ② Welding between housing adapter and measuring unit 2
• ③ Pressure supply converter chamber 3 - measuring mechanism 2
• ④ Pressure supply to converter chamber 3
• ⑤ Power feedthrough 23 with PIN/glazing
• ⑥ Oil cap 20
• ⑧ Separation between the housing and the rear of the sensor 16
• ⑨ Exd thread housing sensor, eg via a second containment and/or encapsulation
• ⑩ Closing cap 35 power feedthrough 23 (GDF)

9 shows a plan view of a packing 33 in which the pressure measuring cell 12 and the pressure measuring cell 27 for the static pressure are arranged in one plane. The distances between the pins - can be seen in the 9 only the recesses 38 for the pins from the power feedthrough - are chosen so that a galvanic isolation is ensured.

Reference List

1

differential pressure sensor

2

measuring mechanism

3

converter chamber

4

double membrane system

4a, 4b

first double diaphragm, second double diaphragm

5a, 5b

first separating diaphragm, second separating diaphragm

6a, 6b

first overload diaphragm, second overload diaphragm

7a, 7b

first pressure chamber, second pressure chamber

8a, 8b

first additional pressure chamber, second additional pressure chamber

9

body

10a, 10b

first connection capillary, second connection capillary

11a, 11b

first auxiliary capillary, second auxiliary capillary,

12

differential pressure measuring cell

13

pressure-sensitive differential pressure element

14a, 14b

filling hole

15a, 15b

closure element

16

transmission fluid

17

capillary tubes

18

dynamic brake

19

intermediate module

20

coincidence

21

process connection

22

housing adapter

23

current feedthrough

24

bond connection

25

isolation tube

26

pin code

27

Measuring cell for determining the static pressure

28

Packing cap with recess

29

Insulation film / PTFE film

30

Adhesive for gluing the insulation base (ceramic base)

31

ceramic base

32

Adhesive for gluing the pressure measuring cell

33

random packing

34

packing cover

35

Closing cap for power feedthrough

36

electronics board

37

fill cap

38

Recess for pin

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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 assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 3222620 A1 [0004]
• WO 2018/165122 A1 [0006]
• US 10656039 B2 [0015]

Claims (18)

Differential pressure sensor (1) for determining the differential pressure of two pressures (p1, p2) with a measuring mechanism (2) and a converter chamber (3), a differential pressure measuring cell (12) with a pressure-sensitive element (13) being arranged in the converter chamber (3). and wherein a coplanar double diaphragm system with two double diaphragms (4a, 4b) is provided on or in an end region of the measuring unit (2) facing the process, wherein the two double diaphragms (4a, 4b) each consist of a separating diaphragm (5a, 5b) and an in In the direction of the pressure effect, there are overload diaphragms (6a, 6b) arranged behind the separating diaphragm (5a, 5b), with a first pressure chamber (7a) between the first separating diaphragm (5a) and the first overload diaphragm (6a) and between the first overload diaphragm (6a) and the base body (9) a first additional pressure chamber (8a) is formed, wherein between the second separating membrane (5b) and the second overload membrane (6b) a second pressure chamber (7b) and between the second A second additional pressure chamber (8b) is formed between the overload diaphragm (6b) and the base body (9), a first connecting capillary (10a) being assigned to the first pressure chamber (7a) and a second connecting capillary (10b) being assigned to the second pressure chamber (7b), wherein a first auxiliary capillary (11a) is assigned to the first additional pressure chamber (8a) and a second auxiliary capillary (11b) to the second additional pressure chamber (8b), whereby - to protect against overpressure occurring on one side (PeÜL) - the first connecting capillary (10a) is hydraulically connected to the second auxiliary capillary (11b) and the second connection capillary (10b) is coupled to the first auxiliary capillary (11a), the pressures (p1, p2) being hydraulically transmitted to the pressure-sensitive element (13), the connection points/crossings between the first connection capillary (10a) and the second auxiliary capillary (11b) and the second connection capillary (10b) and the first auxiliary capillary (11a) arranged in a spatial area s ind, which is located behind the area of the converter chamber (3) facing away from the process. differential pressure sensor claim 1 , wherein the overload membranes (6a, 6b) are prestressed in such a way that they rest against the base body during normal operation and only lift off from the base body (9) when a predetermined critical limit pressure is exceeded. Differential pressure sensor according to one or more of the preceding claims, wherein the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b) in the measuring unit (2) and in the converter chamber (3) are capillary bores which are essentially parallel to the Run along the longitudinal axis of the differential pressure sensor (1). Differential pressure sensor according to one or more of the preceding claims, wherein the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b) are designed as capillary bores or as capillary tubes in the region of the converter chamber (3) facing away from the process. Differential pressure sensor according to one or more of the preceding claims, wherein the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b) in the area between the measuring unit (2) and the converter chamber (3) are designed as capillary tubes (17) which are connected to the corresponding capillary bores are connected in a pressure-tight and gas-tight manner in the measuring unit (2) and converter chamber (3). Differential pressure sensor according to one or more of Claims 1 - 5 , wherein the measuring unit (2) is arranged in a process connection (21), the process connection (21) in the area facing the process having a diameter which is larger than the diameter in the area facing away from the process, in which it is connected to the intermediate module ( 19) or the housing adapter (22) is connected in a pressure-tight, gas-tight and/or liquid-tight manner. Differential pressure sensor according to one or more of Claims 1 until 6 , wherein the connecting capillaries (10a, 10b) and/or the auxiliary capillaries (11a, 11b) are designed and/or dimensioned in such a way that an overpressure (PeÜL) above the predetermined critical limit pressure is limited by means of the overload protection before the overpressure is applied to the pressure-sensitive element (13) is transmitted. Differential pressure sensor according to one or more of Claims 1 until 7 At least one dynamic pressure brake (18) is inserted in each of the connecting capillaries (10a, 10b), the dynamic pressure brakes (18) preferably being arranged in front of the pressure-sensitive element and/or designed such that an overpressure (peÜL) above the predetermined critical limit pressure is limited before the excess pressure is hydraulically transmitted to the pressure-sensitive element (13). Differential pressure sensor according to one or more of the preceding claims, wherein the measuring unit (2) has two filling holes (14a, 14b) for filling the hydraulic system of the differential pressure sensor (1) with a hydraulic fluid (16) are provided, wherein the filling bore ments (14a, 14b) run essentially parallel to the connecting capillaries (10a, 10b) and the auxiliary capillaries (11a, 11b), and wherein the filling bores (14a, 14b) each have a closure element (15a, 15b) after filling with the Hydraulic fluid (16) are sealed pressure-tight and gas-tight or at least liquid-tight. Differential pressure sensor according to one or more of the preceding claims, wherein electrical connection pins are guided in a gas-tight manner through one of the end regions of the converter chamber (3) facing away from the process in the direction of an electronic circuit board (36). Differential pressure sensor according to one or more of the preceding claims, wherein electrical insulators (25) are provided in the connecting capillaries (10a, 10b; 17) and the auxiliary capillaries (11a, 11b) which electrically insulate the converter chamber (3) from the measuring mechanism (2). . Differential pressure sensor according to at least one of the preceding Claims 1 - 11 , wherein the connecting capillaries (10a, 10b, 17a, 17b) are provided at least in sections with an electrical insulator (25), in particular a ceramic insulating body or an insulating glazing, and/or via a gas-tight connection in the corresponding capillaries of the measuring mechanism (2) and/or the converter chamber (3) or the capillary tubes (17). Differential pressure sensor according to one or more of the preceding claims, wherein the electrical insulators (25) are provided in the converter chamber (3) and/or in the measuring mechanism (2) and/or in the space between the measuring mechanism (2) and the converter chamber (3). Differential pressure sensor according to one or more of the preceding claims, wherein the electrical insulators (25) are each integrated as intermediate pieces in the connecting capillaries (10a, 10b) designed as capillary tubes (17a, 17b). Differential pressure sensor according to one or more of the preceding claims, wherein the pressure-sensitive element (13) is a silicon chip, and wherein the differential pressure (p2-p1) is determined using a capacitive or resistive measuring method or resonator. Differential pressure sensor according to one or more of the preceding claims, wherein the converter chamber (3) is designed in such a way that the same transmission liquid volumes are present on the low-pressure side (-) and the high-pressure side (+). Differential pressure sensor according to one or more of the preceding claims, wherein a pressure-sensitive element (27) for measuring the static pressure is provided in the converter chamber (3). Differential pressure sensor according to one or more of the preceding claims, wherein the pressure-sensitive element (13) for measuring the differential pressure and the pressure-sensitive element (27) for measuring the static pressure are stacked on top of one another or arranged next to one another in the converter chamber (3).

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