DE102016218658B3 - check valve - Google Patents

Abstract

The invention relates to a check valve (1). In order to provide a check valve with integrated flow sensor which can be produced simply and inexpensively, the check valve has the following: a base body (2) with a plurality of through-openings (4, 4a, 4b), and - an electrically conductive membrane (3) comprising an inner portion (3.1) fixed to the base body (2) with a first electrical contact (7) and a surrounding, movable outer portion (3.2), the base body (2) at least one in the region of the passage openings (4, 4a, 4b ) arranged electrode (5, 5a, 5b) which is in communication with a second electrical contact (8), and wherein in a closed position, the membrane (3) covers the through holes (4, 4a, 4b) and the outer portion (3.2 ) is arranged adjacent to the at least one electrode (5, 5a, 5b).

Description

The invention relates to a check valve.

The EP 3 144 507 A1 discloses an integrated bypass valve with pressure, position and flow feedback. The bypass valve includes a housing for directing fluid flow through the bypass valve. A disk is disposed within the flow path having an inner periphery and an outer periphery. The bypass valve also has at least one strain gauge arranged on the disc. One of the inner and outer peripheries of the disc is secured to the bypass valve housing, and one of the inner and outer edges of the disc is free to flex from the bypass valve housing in response to fluid flow through the bypass valve, so that measurement of the deflection of the disc Load of the strain gauge induced.

In the JPH06-341 571 A a diaphragm valve is disclosed which can detect damage to the diaphragm.

In the prior art, various methods are known for measuring the flow of a fluid, ie a gas or a liquid, through a conduit or the like. As a flow in this context, the volume flow (volume per unit time) or the mass flow (mass per unit time) are considered. Measuring devices used for this purpose are sometimes referred to as flow meters or flow meters. Apart from mechanical solutions, such as the oval gear meter or the turbine wheel meter, various other measuring methods (optical, electromagnetic, ultrasonic-based and others) enable the detection of the current flow of a fluid. The majority of available methods provide high quality results, but are usually very costly to implement. This means, in particular, a relevant limitation for the automotive industry, where the cost plays a major role.

There have also been proposed solutions in which a flow sensor is integrated into a check valve. Such a check valve, which prevents the flow of a fluid in one direction and allows in the other direction, can be used in a variety of areas. If a measurement of the flow is desired, the integration of a corresponding sensor in the check valve is advantageous because this can usually be saved in space. However, here is a structurally simple as possible, cost-effective solution desirable.

In the field of motor vehicle construction, such a check valve could be used with a flow sensor, for example. Within a system for brake booster, which would make it possible not only to control the direction of flow of air from a brake booster to a vacuum source (eg., A vacuum pump), but also to measure the flow.

The US 2008/0053537 A1 discloses a check valve having a valve body having an opening and a flap which is pivotally mounted on the valve body and can release or close the opening. On the valve body first and second conductor elements are arranged, which are spaced from each other. A third conductor element is disposed on the flap and dimensioned to close the gap between the first and second conductor elements. Depending on the arrangement, it is possible to determine so by closing a circuit the open or closed state of the flap.

The US 2012/0080621 A1 discloses a check valve having a valve body in which a spring-loaded closure element is arranged. On one side of the closing element a wireless interrogatable sensor is arranged and on opposite sides of the sensor two antenna elements are provided. By irradiating an interrogation signal and receiving a response signal modified by the sensor, the pressure under which the sensor stands can be determined.

The US 3,587,326 A discloses a device for measuring acceleration. Here, a sample mass is connected to an elastic membrane which closes a fluid-filled chamber. The chamber communicates via a check valve with a tube in which a drop of liquid metal is arranged. On the opposite side of the drop, the tube passes into a closed chamber and is filled with a pressurized gas. Opposite conversion sections of the tube are covered with a conductor element or a resistance element, which each extend in the axial direction. The elements mentioned form together with the metal droplets parts of a circuit. The resistance of the same can determine the position of the metal drop, which in turn depends on the position of the sample mass under the influence of an acceleration.

The US 8,800,473 B1 describes a flow sensor with a base part, which can be used, for example. In a pipe system, and a pivotally arranged thereon, spring-loaded baffle element, which at least partially fill a pipe cross-section in a rest position can. Arranged on the baffle element is an arcuate display section, which moves from the rest position into a display chamber of the base part during the deflection of the baffle element. The display chamber may, for example, be designed to be transparent, so that the position of the damming element, which corresponds to a flow rate, can be read visually. Alternatively or additionally, the position can be registered electrically, for example via a Hall sensor on the display chamber and a magnetic element on the display section.

The WO 2013 / 018011A2 discloses a micropump having a layered structure in which a silicon plate is disposed between two glass plates. Each of the plates is provided with microstructures through which parts of the pump itself as well as inlet and outlet channels are formed. In this case, sensors are also provided which each comprise a thin silicon membrane which deforms when pressure changes. Due to the piezoresistive properties of the membrane this is accompanied by a change in the resistance, which can be detected electrically.

The US 4,213,021 A discloses a check valve with a valve body, is arranged in the spring-loaded closing element, with which the valve body can be closed. The closing element has a magnet and in the wall of the valve body, a reed switch is arranged, which is closed depending on the position of the closing element by the magnet or opens. This can be used to close the condition of the reed switch on the flow rate within the valve. In order to avoid that hysteresis effects lead to opening or closing at significantly different flow rates, the closing element has a special geometric configuration with a nose section. This results in that the flow rate remains approximately the same over a certain displacement path of the closing element.

In view of the state of the art, the provision of a check valve which can be produced simply and inexpensively and which permits the most accurate flow measurement still offers room for improvement.

The invention has for its object to provide a simple and inexpensive to produce check valve with integrated flow sensor.

According to the invention the object is achieved by a check valve having the features of claim 1, wherein the dependent claims relate to advantageous embodiments of the invention.

It should be noted that the features listed in the following description as well as measures in any technically meaningful way can be combined with each other and show other embodiments of the invention. The description additionally characterizes and specifies the invention, in particular in connection with the figures.

The invention provides a check valve. As a check valve in this case each type of valve is considered, which allows in dependence on a pressure difference on the two sides of the valve, the passage of a fluid, ie a gas or a liquid in one direction and prevents in the opposite direction. In particular, the check valve according to the invention can be used to regulate the flow of a gas, for example air. The check valve has a base body with a plurality of through holes. The base body may also be referred to as a valve body and corresponds to the stationary part of the check valve, which is installed, for example, on or in a fluid line. For this purpose, it may comprise connecting means such as threads or holes for receiving screws. The passage openings serve in the operating state to allow passage of the fluid through the check valve. With regard to the geometry of the through holes exist in the context of the invention, no restrictions. For example. For example, each passage opening may be elongated or short in the intended passage direction of the fluid.

Furthermore, the check valve has an electrically conductive membrane, which has an inner portion fixed to the base body with a first electrical contact, and a portion surrounding, movable outer portion. The term "membrane" in this case implies that it is a flexible, at least partially planar body formed. In this case, two sections can be distinguished, of which the inner section is fastened to the base body, while the outer section is movable relative to the base body (and the inner section). The mobility is of course accompanied by a deformation of the flexible membrane. The outer portion can be lifted in particular from the base body, so move perpendicular to the surface. The inner portion may be attached to the base body, for example by gluing or ultrasonic welding, but possibly also mechanically, for example by clamping. In the described arrangement, the inner portion forms, so to speak, the center of the membrane, while the outer portion forms its edge, so to speak.

The membrane is electrically conductive, which includes both the possibility that it altogether consists of an electrically conductive material (for example a polymer matrix in which electrically conductive particles are embedded) or else that it is only partially electrically conductive, for example a conductive one Coating has. In this case, a first electrical contact is arranged on the inner portion, which allows, for example, the connection to a current or voltage source. The electrical contact can be made very simple, for example. As a metallic pin to which a cable can be soldered, or as a connector. It is also possible for an electrical line fixedly connected to the non-return valve to be connected directly to the electrical contact. Such a line can for example also be formed as a conductor on a circuit board, which forms at least a part of the base body. On such a circuit board further interconnects may be applied, whereby a layered arrangement of a plurality of mutually insulated interconnects is possible. It is understood that the first electrical contact with the membrane or with its electrically conductive part is conductively connected.

Furthermore, the base body has at least one electrode arranged in the region of the through openings, which electrode is in connection with a second electrical contact. The at least one electrode can be formed flat on or below the surface of the base body. It is connected to the second electrical contact, so that, for example, via the second electrical contact, a voltage can be applied to the at least one electrode. The connection between an electrode and the second electrical contact can be given indirectly via at least one intermediate element. Apart from the connection to the second electrical contact, the at least one electrode can be electrically insulated toward the outside (for example, by a dielectric) or else it can be at least partially electrically contactable. The at least one electrode is electrically conductive in itself, so that at least within the same charges or currents can flow. The statements made above regarding the design of the first electrical contact also apply with respect to the second electrical contact. The second electrical contact allows connection to a source of current or voltage. The second electrical contact may be arranged on the base body.

In a closed position, the membrane covers the passage openings and the outer portion is arranged adjacent to the at least one electrode. Of course, this is the closed position of the check valve, in which this prevents passage of a fluid against the intended direction. Here, the membrane acts as a closing element, which covers the passage openings. It can also be said that the membrane closes the passage openings or closes covering. In order to be able to act as a movable closing element, the membrane at least partially covers the passage openings with the movable outer section. Preferably, the through openings are predominantly covered by the outer portion. Furthermore, the outer portion is disposed adjacent to the at least one electrode, which includes the possibility that the outer portion contacts the at least one electrode. Due to the proximity of the electrically conductive membrane to the at least one electrode, the closed position can be detected by measuring at least one electrical variable. For example. For example, the at least one electrode may be insulated by a dielectric, wherein the electrically conductive membrane acts as a counterelectrode. Depending on the position of the outer portion relative to the at least one electrode, the capacitance of the arrangement changes, wherein the closed position, a certain, often characteristic, capacity can be assigned. In this case, therefore, the first and the second electrical contact would be connected to those of a voltage source, resulting in a capacitance-dependent charging of the arrangement.

In a passage position, the outer portion, however, at least partially lifted from the base body, which means on the one hand, that the through holes are at least partially released, on the other hand, that the outer portion This leads in any case to a change in electrical properties, eg Change in the capacity, wherein there is a relationship between a changing electrical quantity and the number of shared through holes or the released area. In the check valve according to the invention, it is thus possible to determine the opening state of the valve or the flow through the same via a measurement of an electrical variable. Depending on the geometric and material configuration of the various elements, the relationship between the measurand and the flow may be complicated, but may be e.g. be determined in tests by calibration.

The invention thus provides a check valve which can be used simultaneously as a flow sensor. The check valve can be relatively simple and thus constructed inexpensively. Also, a very space-saving design is possible. It should also be noted that normally the outer portion of the diaphragm is the only moving part of the valve, resulting in virtually no wear and a blocking of the valve is hardly possible. Normally, the only movement is the lifting of the outer portion of the base body, ie there is no friction between moving parts against each other.

As electrodes, a plurality of contact elements are preferably arranged on the base body, which are connected to the second electrical contact via resistance elements, wherein in the closed position the outer section bears electrically conductively against the contact elements. The term "contact element" implies that an electrical connection can be produced via each of these elements, which means that the contact elements are electrically conductive per se, and / or at least part of their surface is electrically conductive. The contact elements can be formed flat on the surface of the base body. The term "resistance element" implies of course an electrical resistance, which refers in the broadest sense to an AC resistance, so an impedance. Instead of a "resistance element" one could therefore speak of an "impedance element". Embodiments are conceivable in which at least one resistance element has a predominantly capacitive or inductive effect, so that the alternating current resistance is dominated by the reactance. However, the resistor elements preferably act as ohmic resistors, so that the effective resistance represents the dominant component. The term "resistive element" is not to be construed restrictively in terms of resistance value or resistivity. Thus, the resistance or resistivity of each of the resistive elements may be less than that of the electrically conductive membrane. Each resistance element may, for example, be formed as a sheet resistance or otherwise. The contact elements are connected via the resistance elements to the second electrical contact, so that in an electrical connection with a contact element, those resistance elements which are connected between this contact element and the second electrical contact, are included in the circuit. The resistance elements can be arranged on or in the base body.

In the closed position, the outer portion is electrically conductive to the contact elements. As a result, an electrical connection is made, which is why the membrane must be electrically conductive at least on the side facing the contact elements. In the closed position, therefore, an electrical connection results overall from the first electrical contact via the electrically conductive diaphragm, the contact elements and the resistance elements to the second electrical contact. Thus, an electric current can flow and from the ratio of voltage and current, a total resistance can be determined, which is characteristic of the closed position. If the resistance elements act at least partially capacitive and / or inductive, an alternating voltage can of course be applied.

In the passage position, however, the outer portion is at least partially lifted from the base body, which means on the one hand, that the through holes are at least partially released, on the other hand, that the outer portion may only be applied to a part of the contact elements or no contact element. As a result of the connection via the resistance elements, this changes the total resistance that can be measured between the first and second electrical contacts, whereby there is a relationship between the measured resistance and the number of released through openings or the released area. Thus, it is possible to determine via a resistance measurement, the opening state of the valve or the flow through the same. Depending on the geometric and material configuration of the various elements, the relationship between the resistance and the flow may be complicated, but it may be e.g. be determined in tests by calibration.

During the transition from the closed position into the passage position, preferably only a part of the outer portion first releases from the base body, thereby releasing a passage opening or a part of the passage openings, successively releasing further parts of the outer portion as the pressure difference increases, and gradually the further passage openings release. This is accompanied by the fact that the outer portion gradually releases from an increasing number of contact elements, which is accompanied by a successive change in the total resistance. In this regard, the check valve acts similarly to a potentiometer (as far as the resistance elements have a resistance), but with discrete resistance values, the membrane or the outer portion of which acts as an actuator.

There are different interconnections of the contact elements and the resistance elements conceivable, which includes, for example, also series circuits. Preferably, the contact elements are connected in parallel with respect to the second electrical contact. A series connection of contact elements could technically lead to problems in the evaluation, since the loss of contact of one of these contact elements would in no way differentiate metrologically from the contact loss of all contact elements. In a parallel connection, the one or the associated with a contact element Resistance elements connected via the diaphragm with the first electrical contact, if the membrane touches the corresponding contact element.

In one embodiment, at least a part of the contact elements with respect to the inner portion is arranged on the outside of the passage openings. Such an arrangement favors the detachment of the outer portion from the contact elements, whereby the position of the membrane can be reliably detected. If the membrane only partially releases the through-openings with a low flow rate, it would be possible, if the contact elements were arranged next to or inside the through-openings, to continue to make contact between the membrane and all the contact elements. In particular, it is possible in this case for a first subgroup of outer contact elements to be arranged on the outside of the through openings and for a second subgroup of inner contact elements to be arranged next to or even inside the through openings. Such a staggered arrangement may favor the resolution of the measurement. During the successive detachment of the outer portion, the contact with the outer contact elements may first break off, and the contact with the inner contact elements may be interrupted only after a larger flow rate.

Normally, it is hardly possible via the measurement of the resistance to identify which contact elements the membrane is in contact with and which are not, and thus also not, which passage openings are released and which are not. Although it would be theoretically possible to identify by the choice of suitable different resistance values for the individual resistance elements based on the total resistance, which resistance elements are connected to the circuit. In practice, however, this would be expensive and hardly feasible for precision reasons. As a rule, therefore, only statements about the number of shared through-openings are impossible. In this respect, it is advantageous if elements of the check valve are designed as similar as possible and / or are arranged symmetrically. From the aspect of similarity or symmetry, various embodiments are preferred, some of which will be discussed below. In addition, however, a different embodiment of elements or an asymmetric arrangement is conceivable.

According to one embodiment, the passage openings and / or the contact elements are arranged symmetrically with respect to a central axis. This may mean, for example, that passage openings or contact elements are each offset by 30 °, 45 °, 60 °, 90 ° (ie in general 360 ° / N, where N is an integer), etc. with respect to one another. This may, for example, also mean that there are two or more subgroups of passage openings or contact elements, wherein the elements of a subgroup are mutually offset as described, but the elements of different subgroups could be offset by an arbitrary angle to one another. Alternatively, an asymmetrical arrangement of the passage openings or the contact elements is possible. This can be combined with other asymmetric designs, which will be mentioned below. An asymmetric arrangement of the through openings generally leads to an asymmetric detachment of the membrane.

In particular, all passage openings may have the same cross section. This refers on the one hand to the cross-sectional area, on the other hand to the shape of the cross section. This can be circular in particular. Likewise, all passage openings may be arranged at the same distance from the central axis. As a variant, there could also be two or more subgroups of passage openings which each have the same cross section and / or are arranged at the same distance from the central axis. Alternatively, it is conceivable that at least two passage openings have a different cross-section, which may contribute, for example, to the fact that the membrane preferably separates from the passage openings with a larger cross-section. Also, the relationship between the resistance and the flow rate can be varied.

Advantageously, the membrane may be formed symmetrically with respect to the central axis. This includes in particular the possibility of a circularly symmetrical configuration. Overall, it can not necessarily be expected in a symmetrical design that the deformation of the outer portion is also symmetrical with respect to the central axis. However, if the pressure difference of the inflowing fluid is distributed approximately symmetrically, a deformation in all parts of the outer portion is approximately equally likely. In the long run, this can mean that all areas are loaded equally, which can have an advantageous effect on the service life of the check valve. Alternatively, an asymmetric design of the membrane is possible, which generally leads to an asymmetric detachment from the through holes. This, too, can possibly be used to advantage.

In the event that the outer portion of the membrane is completely lifted off all the contact elements, the circuit between the first and second electrical contact could be completely interrupted. Basically, such is one Design possible. According to an alternative embodiment, the first and the second electrical contact are permanently connected to one another via a reference resistor. "Permanent" here means that during normal operation of the check valve, so when solving the outer portion of the base body, the connection is not released. The resistance of such a reference resistor can basically be chosen differently. However, it should not be significantly smaller than the resistance values of the resistive elements, since in this case the total resistance of the system would be dominated by the reference resistance, which could complicate the measurements.

Also, it may be metrologically unfavorable if the reference resistance is significantly greater than the resistance values of the resistance elements. The permanent connection of the first and second electrical contact may, for example, be provided via the inner portion of the membrane or via a separate connection, which may be arranged on the base body.

Advantageously, each contact element is connected to the second electrical contact via a resistance element, wherein all resistance elements have the same electrical resistance. As a result, irrespective of which of the contact elements the membrane comes into contact with or to which it loses contact, there is always the same change in the total resistance. Alternatively, however, resistive elements with different electrical resistances are possible.

The precision of the measurement can be significantly improved if each through hole is assigned at least one contact element. This means that at least one contact element, possibly also a group of contact elements, is provided for each passage opening. The thus assigned contact element or the contact elements are spatially arranged in the vicinity of the respective passage opening. Thus, there is a close relationship between the loss of contact on a contact element and the release of the corresponding through hole.

Basically, it is sufficient for the function of the check valve that the membrane is flexible, where they can possibly be easily guided by the flowing fluid or the pressure difference in the closed position or can be held in this. In order to enable a reliable closure of the passage opening, however, it is preferred that the outer portion is elastically deflectable from the closed position. That is, due to a pressure difference through a fluid, the outer portion can be deflected so that it releases the through hole, but this deflection is elastic, which means that a restoring force occurs by which the outer portion is returned to the closed position, as soon as no external pressure difference or external force acts more. The closed position may in this case correspond to a relaxed position of the outer portion or the outer portion may be biased in the closed position against the base body. In order to realize the elastic deflectability, in particular the membrane itself may be formed elastically. Alternatively, an additional return element could be provided that acts on the membrane.

The check valve according to the invention can be integrated in a variety of systems in which the actual valve function is to be combined in a space-saving and cost-effective manner with a measurement of the flow. For example. For example, in a brake booster system, the check valve may be inserted in a communication line between a brake booster and a vacuum source (a mechanically or electrically operated vacuum pump or the intake manifold of the engine). This makes it possible to determine the flow in a simple manner. This opens up various possibilities, for example a detection of leaks in the system, without making an immediate pressure measurement within the brake booster. Thus, the expected pressure in the brake booster can be indirectly determined or estimated. From the expected pressure in the brake booster and the pressure in the vacuum source, an expected flow can be derived. If this expected flow does not match the measured flow, it can be concluded that there is a leak. This is advantageous over systems in the prior art, which rely on an immediate pressure measurement in the brake booster for such a fault diagnosis, which is complicated and costly due to the pressure sensor to be integrated there. In contrast, the check valve according to the invention is inexpensive and can be easily integrated.

Further advantageous details and effects of the invention are explained in more detail below with reference to an embodiment shown in the figures. Show it

1 a perspective view of a check valve according to the invention in a closed position;

2 a representation of the check valve 1 without membrane;

3 a perspective view of the check valve 1 in a passage position; such as

4 a plan view of the check valve 3 without membrane.

In the different figures, the same parts are always provided with the same reference numerals, which is why these are usually described only once.

1 schematically shows a perspective view of a check valve according to the invention 1 , The check valve 1 has a base body 2 on top of which an electrically conductive membrane 3 is attached. Here is an interior section 3.1 the membrane 3 For example by gluing or clamping on the base body 2 attached, while in the present example areally much larger outer section 3.2 opposite the base body 2 is mobile. In this case, the outer section 3.2 be bent and so on a surface 2.1 be lifted off the base body. The interior section 3.1 has a first electrical contact 7 on that with a circuit 11 connected is. The electrical contact 7 may possibly also for the positive or non-positive connection of the membrane 3 with the base body 2 serve. The base body 2 here has a circular cross-section and is just like the membrane 3 symmetrical to a central axis A. But there are also other shapes conceivable, for example. Oval or rectangular. The base body 2 may be provided, for example, with threaded elements or holes for screws, by means of which it can be fastened within a fluid line.

The further structure of the check valve 1 is related to the partial view in 2 explains in which the membrane 3 was omitted. The base body 2 has a total of six through holes 4 each with the same, circular cross-section, which are arranged at the same distance from the central axis A offset by 60 ° to each other. The passage openings 4 serve to a fluid, eg. Air, through the base body 2 let through. However, the fluid is on the side of the membrane 3 a higher pressure on, the through holes 4 through the membrane 3 closed, ie the check valve 1 located in an in 1 illustrated closed position.

Outwardly offset from the passage openings 4 is a series of contact elements 5 on the surface 2.1 formed, which are shown here in a circle, which is to understand, however, purely by way of example. One can have two subgroups of six contact elements each 5 differ, which have a slightly different distance from the central axis A. Overall, the contact elements 5 however, arranged symmetrically with respect to the central axis A, wherein each passage opening 4 two contact elements 5 could assign. Each of the contact elements 5 is about a resistance element 6 with a second electrical contact 8th on the base body 2 connected. The second electrical contact 8th is also connected to the circuit 11 connected. The resistance elements 6 are presently identical and may, for example, be formed as metal oxide layer resistors which are on the surface 2.1 are applied. The resistivity of each resistive element 6 may in this case, for example, at least by a factor of 10 be greater than the specific resistance of the membrane 3 ,

Furthermore, the first electrical contact 7 via a reference resistor 9 with the second electrical contact 8th connected. The resistance of the reference resistor 9 is normally at least of the order of magnitude of that of the resistive elements 6 ie he should not be much smaller. By the reference resistance 9 is the circuit 11 constantly closed, in which also a measuring device 10 is switched on, for example. Includes a voltage source and to determine the total resistance of the current in the circuit 11 measures.

In addition, the circuit can 11 between the first electrical contact 7 and the second electrical contact 8th through the conductive membrane 3 and one contact element each 5 and a resistive element 6 be closed, provided the membrane 3 with the outer section 3.2 on the contact element 5 is applied. Here is the resistance element 6 between the electrical contacts 7 . 8th parallel to the reference resistor 9 and possibly other resistance elements 6 connected.

The between the electrical contacts 7 . 8th measurable total resistance thus decreases as the number of contact elements increases 5 coming from the membrane 3 be touched. In the in 1 shown closed position is the membrane 3 with the outer section 3.2 on all contact elements 5 on, whereby the total resistance is minimal.

The membrane 3 consists of an elastic material, the outer section 3.2 in the in 1 shown closed position is relaxed. He is, however, through one of the passageways 4 acting fluid pressure elastically deflected from the closed position, so that it is completely or partially from the surface 2.1 of the base body 2 takes off. Such a condition is in 3 and 4 shown the the check valve 1 show in a passage position. Here is the outer section 3.2 partially elastically bent, leaving it from the surface 2.1 is lifted off. 4 is a plan view in which the membrane 3 not shown, but a hatched area F the part of the surface 2.1 designated, on which the membrane 3 is applied. By partially lifting the outer section 3.2 are some passages 4b at least partially released, which can lead to a flow of the fluid, while other through holes 4a continue through the membrane 3 are closed. Because of that the outer section 3.2 from the surface 2.1 Lifting takes place, a detachment of some contact elements 5b while other contact elements 5a continue with the membrane 3 stay in contact. The resistance elements 6 that with the contact elements 5b are electrically connected, of which the membrane 3 solved, are no longer part of the circuit 11 , A corresponding increase in resistance may be provided by the measuring device 10 be registered.

Thus, increasing the flow is accompanied by an increase in resistance. A corresponding relationship, which is generally complicated and theoretically difficult to deduce, can be determined by calibration in a series of experiments.

LIST OF REFERENCE NUMBERS

1

 check valve

2

 base body

2.1

surface

3

 membrane

3.1

first section

3.2

second part

4, 4a, 4b

 Through opening

5, 5a, 5b

 contact element

6

 resistive element

7, 8

 electric contact

9

 reference resistor

10

 measuring device

11

 circuit

A

 central axis

F

 area

Claims (10)

Check valve ( 1 ) with - a base body ( 2 ) having a plurality of passage openings ( 4 . 4a . 4b ), and - an electrically conductive membrane ( 3 ), comprising one on the base body ( 2 ) fixed inside section ( 3.1 ) with a first electrical contact ( 7 ) and a surrounding, movable outer portion ( 3.2 ), the base body ( 2 ) at least one in the region of the passage openings ( 4 . 4a . 4b ) arranged electrode ( 5 . 5a . 5b ) which is connected to a second electrical contact ( 8th ), and wherein in a closed position the membrane ( 3 ) the passage openings ( 4 . 4a . 4b ) and the outer section ( 3.2 ) adjacent to the at least one electrode ( 5 . 5a . 5b ) is arranged. Check valve according to claim 1, characterized in that as electrodes a plurality of contact elements ( 5 . 5a . 5b ) on the base body ( 2 ) and resistance elements ( 6 ) with the second electrical contact ( 8th ), wherein in the closed position the outer portion ( 3.2 ) electrically conductive at the contact elements ( 5 . 5a . 5b ) is present. Check valve according to claim 2, characterized in that the contact elements ( 5 . 5a . 5b ) with respect to the second electrical contact ( 8th ) are connected in parallel. Check valve according to one of claims 2 or 3, characterized in that at least a part of the contact elements ( 5 . 5a . 5b ) with respect to the inner section ( 3.1 ) on the outside of the passage openings ( 4 . 4a . 4b ) is arranged. Check valve according to one of claims 2, 3 or 4, characterized in that the passage openings ( 4 . 4a . 4b ) and / or the contact elements ( 5 . 5a . 5b ) are arranged symmetrically with respect to a central axis (A). Check valve according to claim 5, characterized in that all passage openings ( 4 . 4a . 4b ) are arranged at the same distance from the central axis (A). Check valve according to one of claims 5 or 6, characterized in that the membrane ( 3 ) is formed symmetrically with respect to the central axis (A). Check valve according to one of the preceding claims, characterized in that the first ( 7 ) and the second electrical contact ( 8th ) via a reference resistor ( 9 ) are permanently connected. Check valve according to one of claims 2, 3, 4 or 5, characterized in that each contact element ( 5 . 5a . 5b ) via a resistance element ( 6 ) with the second electrical contact ( 8th ), all resistance elements ( 6 ) have the same electrical resistance. Check valve according to one of the preceding claims, characterized in that the outer section ( 3.2 ) is elastically deflectable from the closed position.

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