Diaphragm valve

Abstract

The invention concerns a diaphragm valve (1) comprising: - a valve housing (2), having a first housing part (3) and a second housing part (4), defining a membrane space (17) therebetween, the first housing part comprising one or more fluid inlets (5) and one or more fluid outlets (6), and a fluid passage (7) in the membrane space, - a membrane (8), arranged in the membrane space, - membrane position regulation means (23) for regulating the position of the membrane in the membrane space, wherein - the membrane (8) is made of a material (9) having a Poisson ratio of 0.5, and - the first housing part (3) comprises a bulge accommodation cavity (13) for accommodating the bulge (12), and - the second housing part (4) comprises a forcing zone (14) for forcing the membrane towards the bulge accommodation cavity.

Description

[0001] Title: Diaphragm valve

[0002] FIELD

[0003] The present invention relates to a diaphragm valve, comprising: a valve housing, having a first housing part and a second housing part connected to the first housing part, defining a membrane space therebetween, the first housing part comprising one or more fluid inlets and one or more fluid outlets, and a fluid passage in the membrane space between the one or more fluid inlets and the one or more fluid outlets, a membrane, arranged in the membrane space, fixed between the first housing part and the second housing part, for regulating a fluid flow in the fluid passage, wherein the membrane is compressed between the first housing part and the second housing part in a membrane compression zone by compression means, such that a bulge is created in the membrane, and membrane position regulation means for regulating the position of the membrane in the membrane space, and thereby the degree of fluid flow in the fluid passage.

[0004] BACKGROUND

[0005] US 6886591 B2 discloses a relief valve comprising a diaphragm for control of process pressure. The diaphragm has a fluid pressure on a first side and a process pressure on a second side. The second side is engagable with a process void and at least one vent void, such that when the process pressure is below the fluid pressure the diaphragm is engaged with the vent void. When the process pressure is above the fluid pressure the diaphragm is not engaged with the vent void. The diaphragm according to US 6886591 B2, however, is intended to regulate pressure and is thus not suitable for controlling mass flow accurately.

[0006] US 7673650 B2 discloses another pressure regulating valve comprising a diaphragm for control of process pressure. The diaphragm has a reference pressure on a first side and a process pressure on a second side. The second side is engagable with a process void and at least one vent void such that when the process pressure is below the reference pressure the diaphragm is engaged with the vent void. When the process pressure is above the reference pressure the diaphragm is not engaged with the vent void.

[0007] A problem with the prior art diaphragm valves is, however, that a relatively large force / pressure is needed to press the diaphragm membrane against the one or more inlets or outlets to regulate the fluid flow in the fluid passage. The skilled person understands that what is a relatively large force or pressure depends on a.o. the size of the valve and the pressure differential. This is especially relevant in normally closed (NC) valves, but can be a problem in normally open (NO) valves too.

[0008] The applicant has discovered a problem related to prior art diaphragm valves with respect to fixing the membrane in place and minimizing leakage. The membrane is fixed between the first housing part and the second housing part in a membrane compression zone by compression means, such that a bulge is created in the membrane. This bulge, however, can cause the membrane to flex in undesirable directions. Due to the specific construction of the prior art valves, which are designed for easy construction and cleanability / hygiene of the first housing part containing one or more inlets and outlets, the bulge is created at the “wrong side” of the membrane, causing the membrane to bulge away from the one or more inlets and outlets, therefore leading to valve leakage. This problem of membrane bulging was previously unrecognized in the field of diaphragm valves.

[0009] An object of the present invention is thus to provide a diaphragm valve, wherein the bulge is induced in the direction of the one or more inlets or outlets.

[0010] Another object of the invention is to provide a diaphragm valve, wherein a relatively lower force / pressure is needed to press the bulge against the one or more inlets or outlets in order to regulate the fluid flow in the fluid passage.

[0011] Yet another object of the invention is to provide a diaphragm valve, wherein the valve housing is shaped so that the bulge is always created in the right direction, at the “right side” of the membrane, to prevent valve leakage.

[0012] A further object of the invention is to provide a diaphragm valve, wherein the valve regulates the flow over a small pressure differential (Ap).

[0013] SUMMARY

[0014] Thereto, the diaphragm valve according to the present invention is characterized in that: the membrane is made of a membrane material having a Poisson ratio of about 0.5, in that the first housing part comprises a bulge accommodation cavity for accommodating the bulge, comprising the one or more fluid inlets and the one or more fluid outlets, and in that the second housing part comprises a forcing zone configured for forcing the membrane to bulge towards the bulge accommodation cavity when the membrane is compressed.

[0015] Due to the fact that the first housing part comprises a bulge accommodation cavity for accommodating the bulge, comprising the one or more fluid inlets and the one or more fluid outlets, and due to the fact that the second housing part comprises a forcing zone configured for forcing the membrane to bulge towards the bulge accommodation cavity when the membrane is compressed, a relatively lower force / pressure is required by the membrane position regulation means, e.g. pressure regulation means, to press the bulge against the one or more inlets or outlets in order to regulate the fluid flow in the fluid passage, because essentially a degree of “pretension” is provided on the membrane by the compression means. The forcing zone furthermore ensures that the membrane bulges “in the right direction” when such a pretension / compression is applied. Thus, it is no longer necessary to provide a relatively large pressure on the non-fluid side / backside of the membrane (i.e. the side turned away from the one or more inlets or outlets - the frontside being the membrane side turned towards the one or more inlets or outlets, contacting the fluid) to provide the force needed to press the membrane against the one or more inlets or outlets. A full seal can be achieved by merely providing a relatively small pressure increase on the backside of the membrane. This advantage also makes it possible to very easily use pilot valves in a pilot circuit reliant on the pressure of the medium upstream of the valve to regulate the valve.

[0016] The valve can be opened by reducing the pressure on the backside. To fully open the valve, the pressure on the backside is typically reduced to the outlet pressure. In addition, it is possible to partially open the valve by fine-tuning the pressure on the backside of the membrane between the pressure of the valve inlet and outlet by e.g. using the aforementioned pressure regulation means.

[0017] As mentioned in the foregoing, due to the fact that the second housing part comprises a forcing zone for forcing the membrane to bulge towards the bulge accommodation cavity when the membrane is compressed by the compression means, the bulge is automatically pushed “in the right direction” towards the one or more inlets or outlets, decreasing chances of leaking.

[0018] In essence, the Poisson ratio of about 0.5 of the membrane material is advantageously used to contribute to a proper seal of the fluid passage. Thicker membranes bulge more strongly, but it is also desirable to use limited amounts of material. In addition, thinner membranes are more suitable for fine-tuning the opening of the valve. Obviously, the membrane should be low- or non-permeable to the fluid used. It is furthermore desirable that the membrane has relatively broad chemical compatibility with fluids.

[0019] It is noted that EP 3555506 B1 , in fact, discloses an example of a diaphragm valve with a membrane that can flex in the wrong direction. EP 3555506 B1 in essence does not disclose that the membrane is compressed between the first housing part and the second housing part in a membrane compression zone by compression means, such that a bulge is created in the membrane. Fig. 2A of EP 3555506 B1 , for example, shows that the membrane is to be loosely arranged in a recess at the circumference of the membrane. However, the membrane is not arranged in the recess in such a way that a compressive force can be exerted on the membrane, so that a bulge forms in the membrane. The screws 29 as disclosed e.g. in Fig. 2B of EP 3555506 B1 are only suitable for connecting the housing parts together, not for compressing the membrane between the housing parts. The construction of the diaphragm as shown in Fig. 2A of EP 3555506 B1 shows that it is not even possible to use the housing parts for compressing the membrane, because the rigid housing parts abut each other and therefore can not even be moved towards each other to facilitate compression of the membrane.

[0020] Related to the foregoing, the valve of EP 3555506 B1 also does not disclose a forcing zone configured for forcing the membrane to bulge towards the bulge accommodation cavity when the membrane is compressed. EP 3555506 B1 merely discloses an "inversion inhibitor" that (nevertheless) allows the membrane to fully “flip” in the wrong direction (see Fig. 2A of EP 3555506 B1), in contrast with the present disclosure.

[0021] According to the present disclosure, pretension may therefore be provided on the membrane by the compression means. Thus, a relatively lower force / pressure is required by the membrane position regulation means, e.g. pressure regulation means, to press the bulge against the one or more inlets or outlets in order to regulate the fluid flow in the fluid passage, because of the pretension provided on the membrane by the compression means. Thus, it is no longer necessary to provide a relatively large pressure on the non-fluid side / backside of the membrane (i.e. the side turned away from the one or more inlets or outlets).

[0022] The forcing zone therein is preferably to be configured to ensure that the membrane bulges towards the bulge accommodation cavity when the pretension is applied, i.e. to ensure that the membrane does not “flip” in the wrong direction.

[0023] The membrane compression zone preferably surrounds the bulge, more preferably fully surrounds the bulge to prevent leakage.

[0024] The compression means may comprise one or more compression elements, such as one or more pens or screws or clamps, compressing the first housing part and the second housing part against the membrane in the membrane compression zone. The membrane is thus squeezed in between the first and second housing parts by the compression elements. Thereto, the compression elements may extend through the first and second housing parts (as well as the membrane itself). The degree of compression can be controlled by controlling the tightening of the compression elements, for example by controlling torque.

[0025] The bulge accommodation cavity in the first housing part preferably is quite shallow. The ideal depth of the cavity is dependent on the precise membrane material and the precise Poisson ratio, which can vary around 0.5, such as ranging from 0.45 - 0.55. The ideal depth for any application also depends on the membrane thickness. Typical bulge accommodation cavity depths can be 1 - 50 times the membrane thickness, preferably 10 - 20 times the membrane thickness.

[0026] The bulge accommodation cavity may be shaped so its center snugly accommodates the bulge in the bulge accommodation cavity. A snug fit on the sides of the cavity is not necessary. This allows for wider material tolerances, including (sub)-type of membrane material, (small) variations or flaws in membrane thickness or (small) variations or flaws in the geometry of the membrane edging, the housing, the clamping or any rings. , strict fit may lead to buckling of the membrane in undesired directions.

[0027] The bulge accommodation cavity preferably has a rounded profile to prevent sharp edges damaging the membrane. In a preferred embodiment the bulge accommodation cavity has a concave shape, preferably a shallow concave shape, having a diameter to depth ratio of e.g. 5:1 - 20:1 , such as 10: 1 - 20: 1 , but more conelike configurations are possible too.

[0028] Preferably, the membrane material comprises rubber.

[0029] In a preferred embodiment, the membrane is reinforced, for example with a mesh.

[0030] Preferably, the membrane material comprises rubber and the rubber is reinforced with a mesh.

[0031] The membrane may have a thickness of 0.5 - 2.0 mm, preferably 0.6 - 1.5 mm, more preferably 0.6 - 0.9 mm, when the membrane is not compressed. It is desirable to have membranes with highly constant thickness, but small flaws are acceptable, especially on the edges of the membrane.

[0032] At least one of the one or more fluid inlets or at least one of the one or more fluid outlets may be arranged in a center of the bulge accommodation cavity for optimal flow (control) properties.

[0033] The membrane therein may be arranged with respect to the center of the bulge accommodation cavity in such a way, that the bulge blocks the at least one fluid inlet or the at least one fluid outlet in the center of the bulge accommodation cavity.

[0034] The forcing zone may comprise a substantially flat surface adjacent to the membrane compression zone for forcing the membrane to bulge towards the bulge accommodation cavity. The substantially flat part / surface may be situated just inside the compression zone and the flat part then constitutes the forcing zone. It may also comprise a slight incline towards the first housing part. For hygienic applications, a very flat or highly polished part is preferred, especially for the parts in contact with the fluids. The width of the forcing zone may be 3 - 30 times, preferably 5 - 10 times, the membrane thickness, and thus preferably only comprises part of the diameter of the second housing part. If the diaphragm valve is circular, the forcing zone is preferably annular. The forcing zone thus always extends further in the direction of the center of the diaphragm valve than the compression zone.

[0035] The second housing part may comprise a further cavity for accommodating the membrane when the membrane position regulation means cause the membrane to move towards the second housing part in order to fully open the fluid passage. The further cavity may further comprise a pressure regulation recess as part of the membrane position regulation means. This further cavity / pressure regulation recess may be needed to fully open the membrane at higher flows. It also prevents the membrane sticking to the second housing part.

[0036] The one or more fluid inlets may comprise multiple fluid inlets and / or the at least one or more fluid outlets comprise multiple fluid outlets, such as groups of fluid inlets and / or fluid outlets, for instance concentrically arranged groups of inlets / outlets. In certain applications, the inlets and outlets can be switched.

[0037] The one or more fluid inlets and / or the one or more fluid outlets are preferably axisymmetrically arranged with respect to a center of the bulge accommodation cavity.

[0038] The inlets and outlets are constructed of non-porous material, and so are the outer housing parts, and any tubing connected to the inlet and outlet. Steel especially SST (stainless steel), is a preferred material for any tubing or parts containing inlets and outlets.

[0039] Diaphragm valves are typically arranged in a circular configuration. Thus the first and second housing parts are preferably both circular. In niche applications, oval, elliptic or ovoid configurations are conceivable, but the skilled person understands that sharp corners should be avoided, especially near the membrane.

[0040] Both housing parts are preferably made of an inflexible material. Steel and aluminium are preferred in hygienic applications, especially SST. In other fields, plastic is preferred. 3D-printing the housing parts is also conceivable.

[0041] The second housing part may also comprise an additional slit. The slit may be combined with the pressure regulation recess. This prevents the membrane position regulation means for controlling / regulating membrane position / bulging from being blocked by the membrane if it gets temporarily “stuck” in a fully open position, as most membrane materials with the desired Poisson ration are somewhat sticky.

[0042] Another aspect of the invention concerns a flow control device comprising an aforementioned valve.

[0043] The control of membrane position and regulation of flow can be usefully achieved by a pressure regulator regulating pre-pressure. A pilot valve is particularly preferred pressure regulator.

[0044] The skilled person will understand that the aforementioned diaphragm valve / flow control device is particularly suitable for low flows of 1 - 500 l / min, preferably 1 - 300 l / min, more preferably 10 - 200 l / min, even more preferably 20 - 50 l / min.

[0045] US 2020 / 282966 A1 discloses a diaphragm valve, wherein the membrane is used as an actuator, not as a regulator.

[0046] WO 2006 / 046942 A1 discloses a pinch-type valve. The pinch-type valve can be regarded as a rolled-up dome valve. However, the rubber of the pinchtype valve needs to be extensively modified in order to obtain a functional valve.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention will be explained in more detail below, with reference to illustrative embodiments shown in the drawings. Therein:

[0049] Figure 1 shows an example embodiment of a prior art diaphragm valve, in cross-section, wherein the diaphragm valve is in an uncompressed state;

[0050] Figure 2 shows the diaphragm valve according to Figure 1 , wherein the diaphragm valve is in a compressed state with the membrane bulging in the “wrong” direction;

[0051] Figure 3 shows an example embodiment of a diaphragm valve according to the invention, in cross-section, in a first compressed position;

[0052] Figure 4 shows an example embodiment of a diaphragm valve according to the invention, in cross-section, in several closed / compressed positions, as well as a fully open position with part of the housing removed for clarity; and

[0053] Figure 5 shows a perspective, exploded view of an example embodiment of a diaphragm valve according to the invention.

[0054] DETAILED DESCRIPTION

[0055] Figures 1 - 5 will be discussed in conjunction. Figure 1 shows an example embodiment of a prior art diaphragm valve 1 , in cross-section, wherein the diaphragm valve 1 is in an uncompressed state. The diaphragm valve 1 comprises a valve housing 2, having a first housing part 3 and a second housing part 4 connected to the first housing part 3. The housing parts 3, 4 define a membrane space 17 therebetween in which the membrane 8 is arranged. The first housing part 3 comprises one or more fluid inlets 5 and one or more fluid outlets 6, and a fluid passage 7 in the membrane space 17 between the one or more fluid inlets 5 and the one or more fluid outlets 6. Preferably, more fluid outlets 6 than fluid inlets 5 are provided. The membrane 8 is fixed between the first housing part 3 and the second housing part 4, for regulating a fluid flow in the (closable) fluid passage 7. The membrane 8 is shown in a relaxed state, because the membrane 8 is not compressed by the first housing part 3 and the second housing part 4. The diaphragm valve 1 , more in particular the second housing part 4, comprises membrane position regulation means 23 for regulating the position of the membrane 8 in the membrane space 17, and thereby the degree of fluid flow in the fluid passage 7. The membrane position regulation means 23 may be pressure-based, i.e. the membrane position regulation means 23 comprise / may be connected to pressure regulation means 23, as shown in Figure 1.

[0056] As shown in Figure 2, the membrane 8 as shown in Figure 1 may be compressed between the first housing part 3 and the second housing part 4 in a membrane compression zone 11 by compression means 10, such that a bulge 12 is created in the membrane 8.

[0057] As mentioned in the foregoing, a problem with the prior art diaphragm valves as shown in Figures 1 and 2 is that a relatively large force / pressure is needed to press the diaphragm membrane 8 against the one or more inlets 5 or outlets 6 in order to regulate the fluid flow in the fluid passage 7.

[0058] The applicant has discovered that a problem occurs related to the prior art diaphragm valves as shown in Figures 1 and 2, with respect to fixing the membrane 8 in place and minimizing leakage. The membrane 8 is fixed between the first housing part 3 and the second housing part 4 in a membrane compression zone 11 by compression means 10, such that a bulge 12 is created in the membrane 8. The diaphragm valve 1 as shown in Figures 1 and 2 causes the membrane 8 to flex / bulge in undesirable directions. Due to the specific construction of the prior art valves, which are designed for easy construction and optionally cleanability / hygiene of the first housing part 3 containing one or more inlets 5 and outlets 6, the bulge 12 is created at the “wrong side” of the membrane 8 (i.e. the side indicated with reference numeral 20), causing the membrane 8 to bulge away from the one or more inlets 5 and outlets 6, therefore leading to valve leakage. This problem of membrane bulging was previously unrecognized in the field of diaphragm valves.

[0059] Figure 3 shows an example embodiment of a diaphragm valve 1 according to the invention, in cross-section, in a first compressed position. The membrane 8 is made of a membrane material 9 having a Poisson ratio of about 0.5. The first housing part 3 comprises a bulge accommodation cavity 13 for accommodating the bulge 12, comprising the one or more fluid inlets 5 and the one or more fluid outlets 6. The second housing part 4 furthermore comprises a forcing zone 14 configured for forcing the membrane 8 to bulge towards the bulge accommodation cavity 13 when the membrane 8 is compressed.

[0060] Due to the fact that the first housing part 3 comprises a bulge accommodation cavity 13 for accommodating the bulge 12, comprising the one or more fluid inlets 5 and the one or more fluid outlets 6, and due to the fact that the second housing part 4 comprises a forcing zone 14 configured for forcing the membrane 8 to bulge 12 towards the bulge accommodation cavity 13 when the membrane 8 is compressed, a relatively lower force / pressure is required by the membrane position regulation means 23, such as pressure regulation means 23, to press the bulge 12 against the one or more inlets 5 or outlets 6 in order to regulate the fluid flow in the fluid passage 7, because essentially a degree of “pretension” is provided on the membrane 8 by the compression means 10.

[0061] Diaphragm valves are typically arranged in a circular configuration. Thus the first 3 and second 4 housing parts are preferably both circular. In niche applications, oval, elliptic or ovoid configurations are conceivable, but the skilled person understands that sharp corners should be avoided.

[0062] Both housing parts 3, 4 are preferably made of an inflexible material. Steel and aluminium are preferred in hygienic applications, especially SST (stainless steel). In other fields, plastic is preferred. 3D-printing the housing parts 3, 4 is also conceivable.

[0063] The forcing zone 14 furthermore ensures that the membrane 8 bulges “in the right direction” when such a pretension / compression is applied. Thus, it is no longer necessary to provide a relatively large pressure on the non-fluid side / backside 20 of the membrane 8 (i.e. the side turned away from the one or more inlets 5 or outlets 6 - the frontside 26 being the membrane side turned towards the one or more inlets 5 or outlets 6, contacting the fluid) to provide the force needed to press the membrane 8 against the one or more inlets 5 or outlets 6. A full seal can be achieved by merely providing a relatively small pressure increase on the backside 20 of the membrane 8.

[0064] The valve 1 can be opened by reducing the pressure on the backside 20. To fully open the valve 1 , the pressure on the backside 20 is typically reduced to the outlet pressure. In addition, it is possible to partially open the valve 1 by fine-tuning the pressure on the backside 20 of the membrane 8 between the pressure of the valve inlet and outlet.

[0065] The Poisson ratio of about 0.5 of the membrane material 9 is advantageously used to contribute to a proper seal of the fluid passage 7. Thicker membranes 8 bulge more strongly, but it is also desirable to use limited amounts of material 9. In addition, thinner membranes 8 are more suitable for fine-tuning the opening of the valve 1. Thus the skilled person can fine-tune valve properties by adjusting the membrane thickness to the expected range of inlet- and outlet pressure.

[0066] The membrane compression zone 11 preferably surrounds the bulge 12, more preferably fully surrounds the bulge 12, to prevent leakage. Please also refer to Figure 5, wherein the compression zone 11 is more clearly indicated. These figures show an uninterrupted membrane compression zone 11 , but variations with interruptions are conceivable for niche valves.

[0067] The compression means 10 may comprise one or more compression elements 18, such as one or more pens or screws, compressing the first housing part 3 and the second housing part 4 against the membrane 8 in the membrane compression zone 11.

[0068] The bulge accommodation cavity 13 may be shaped so that the center 19 snugly accommodates the bulge 12 in the bulge accommodation cavity 13. A snug fit on the sides of the cavity is optional, not required. The bulge accommodation cavity 13 may for instance have a concave shape.

[0069] As mentioned in the foregoing, the compression means 10 may comprise one or more compression elements 18, such as one or more pens or screws or clamps, compressing the first housing part 3 and the second housing part 4 against the membrane 8 in the membrane compression zone 11. The membrane 8 is thus squeezed in between the first 3 and second 4 housing parts by the compression elements 18. Thereto, the compression elements 18 may extend through the first and second housing parts 3, 4, as well as the membrane 8, e.g. via a through-hole. The compression elements 18 are preferably arranged at regular intervals with respect to the compression zone 11 , such that even compression of the membrane 8 is provided.

[0070] The bulge accommodation cavity 13 in the first housing part 3 preferably may be relatively shallow. The ideal depth of the cavity 13 is dependent on the membrane material 9 and the precise Poisson ratio, which can vary around 0.5, such as ranging from 0.45 - 0.55. The ideal range also depends on the membrane 8 thickness, and optional presence of reinforcement. Typical bulge accommodation cavity 13 depths can be 1 - 50 times the membrane 8 thickness, preferably 10 - 20 times the membrane 8 thickness. The depth is typically not constant over the whole diameter of the bulge accommodation cavity 13.

[0071] The membrane 8 may have a thickness of e.g. 0.5 - 4.0 mm, preferably 1.0 - 3.5 mm, more preferably 2.0 - 3.0 mm, when the membrane 8 is not compressed by the compression means 10.

[0072] The bulge accommodation cavity 13 may be shaped so that the center 19 snugly accommodates the bulge in the bulge accommodation cavity 13. The bulge accommodation cavity 13 preferably has a rounded profile to prevent sharp edges damaging the membrane 8. In a preferred embodiment, e.g. the embodiments shown in Figures 3, 4 and 6, the bulge accommodation cavity 13 has a concave shape, preferably a shallow concave shape, having a diameter to depth ratio of e.g. 5: 1 - 20: 1 , such as 10:1 - 20:1 , but more cone-like configurations are possible too.

[0073] The membrane material 9 preferably comprises rubber.

[0074] The membrane material 9 may also be reinforced.

[0075] When the membrane material 9 comprises rubber, the rubber may e.g. be reinforced with a mesh (not shown).

[0076] The membrane 8 preferably has a thickness of 0.5 - 2.0 mm, preferably 0.6 - 1.5 mm, more preferably 0.6 - 0.9 mm, when the membrane 8 is not compressed by the compression means 10.

[0077] At least one of the one or more fluid inlets 5 or at least one of the one or more fluid outlets 6 may be arranged in a center 19 of the bulge accommodation cavity 13.

[0078] The membrane 8 may be arranged with respect to the center 19 of the bulge accommodation cavity 13 in such a way, that the bulge 12 blocks the at least one fluid inlet 5 or the at least one fluid outlet 6 in the center 19 of the bulge accommodation cavity 13.

[0079] The forcing zone 14 may comprise a substantially flat surface 27 adjacent to the membrane compression zone 11 for forcing the membrane 8 to bulge towards the bulge accommodation cavity 13. The substantially flat surface 27 may be situated just inside the compression zone 11 and the flat surface 27 then constitutes the forcing zone 14. It may also comprise a slight incline towards the first housing part 3. For hygienic applications, a very flat part 27 is preferred, which may be polished. The width of the forcing zone 13 may be 3 - 30 times, preferably 5 - 10 times, the membrane 8 thickness, and thus preferably only comprises part of the diameter of the second housing part 4. If the diaphragm valve 1 / membrane 8 is circular, the forcing zone 14 is preferably annular. The forcing zone 14 thus always extends further in the direction of the center of the diaphragm valve than the compression zone 11. It may, for example, extend about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, or about 10 mm further towards the center of the diaphragm valve 19 than the compression zone 11 .

[0080] The second housing part 4 may comprise a further cavity for accommodating the bulge 12 when the membrane position regulation means 23 cause the membrane 8 to move towards the second housing part 4 in order to fully open the fluid passage 7. The further cavity may further comprise a pressure regulation recess 15 as part of the membrane position regulation means 23. This further bulge accommodation cavity / pressure regulation recess 15 may be needed to fully open the membrane 8 at higher flows. It also prevents the membrane 8 sticking to the second housing part 4. The second housing part 4 may also comprise an additional slit. The slit may be combined with the pressure regulation recess 15. This prevents the membrane position regulation means 23 for controlling / regulating membrane 8 position / bulging from being blocked by the membrane 8 if it gets temporarily “stuck” in a fully open position, as most membrane materials 9 with the desired Poisson ration are somewhat sticky.

[0081] Figure 4 shows an example embodiment of a diaphragm valve 1 according to the invention, in cross-section, in several closed / compressed positions of the bulge 12, 12’, as well as a fully open position of the bulge 12”. In the first closed position of the bulge 12, a first force / pressure is provided by the membrane position regulation means 23 in combination with the compression means 10 to close the fluid passage 7. In the second closed position of the bulge 12’, a second force / pressure, being larger than the first force / pressure, is provided by the membrane position regulation means 23 in combination with the compression means 10 to close the fluid passage 7, e.g. to withstand larger fluid pressures. The bulge 12’ in the second closed position is therefore “wider” than the bulge 12 in the first closed position, due to the larger pressure acting on the backside 20 of the bulge 12’. The dashed line indicates the bulge 12” in the fully open position of the valve 1. Figure 5 shows a perspective, exploded view of an example embodiment of a diaphragm valve 1 according to the invention (for instance the embodiments of the diaphragm valve 1 as shown in Figures 3 and 4). The one or more fluid inlets 5 may comprise multiple fluid inlets and / or the at least one or more fluid outlets 6 comprise multiple fluid outlets, e.g. arranged in groups. The one or more fluid inlets 5 and / or the one or more fluid outlets 6 may be axisymmetrically arranged with respect to a center 19 of the bulge accommodation cavity 13. The membrane 8 therein may be arranged with respect to the center 19 of the bulge accommodation cavity 13 in such a way, that the bulge 12 blocks the at least one fluid inlet 5 or the at least one fluid outlet 6 in the center 19 of the bulge accommodation cavity 13. Compression means 10 comprising compression elements 18, such as screws or pens - e.g. 3, 4, 6 or more compression elements 18 - are schematically indicated, for creating the compression zone 11 in / on the membrane 8 (by squeezing the first housing part 3 and the second housing part 4 towards each other). The compression means 10 are preferably configured to provide even pressure on the membrane 8 to ensure leak-free operation of the valve 1 , e.g. by spacing the compression means 10 at regular intervals with respect to the membrane 8 and housing parts 3, 4.

[0082] In an example embodiment a flow controller device in the form of a mass flow controller (MFC) is combined with a diaphragm valve 1 according to the invention. The fluid of the main fluid flow to be measured / controlled enters via a main fluid inlet and leaves the mass flow meter via a main fluid outlet. A thermal sensor flow path / bypass may be placed before the diaphragm valve 1. The MFC may further comprise laminar flow element (LFE). The LFE is a critical component of the thermal mass flow meter and is based on the so-called bypass principle. The LFE basically creates a shunt. The diaphragm valve 1 is arranged at a downstream end of the LFE. The mass flow is measured in the bypass of the main flow channel. Due to the specific dimensions of the LFE similar linear pressure / flow characteristics as in the capillary sensor tube of the bypass can be created. The diaphragm valve 1 should be optimized to the LFE. The MFC has main flow path (MFP) through the mass flow meter and the diaphragm valve 1. A regulation flow path (RFP) through the mass flow meter and the diaphragm valve 1 may be present. The RFP is regulated by means of a pilot valve. A major advantage of the mass flow meter design as shown in Figure 5 is that the flow pre-pressure presses the various mass flow meter components together, thereby minimizing leakage in case of fluid leakage. A pilot valve is a particularly preferred means for controlling / regulating membrane 8 position / bulging and works by regulating pre-pressure. The skilled person will understand that the aforementioned diaphragm valve / flow control device is particularly suitable for low flows of 1 - 500 l / min, preferably 1 - 300 l / min, more preferably 10 - 200 l / min, even more preferably 20 - 50 l / min.

[0083] Although the invention has been described above with reference to example embodiments, variants within the scope of the present invention will readily occur to those skilled in the art after reading the above description. Such variants are within the scope of the independent claims and the dependent claims. In addition, it is to be understood that express rights are requested for variants as described in the dependent claims. It should also be noted that the example embodiments shown in the Figures, or features thereof, may be combined to yield embodiments not explicitly shown in the Figures.

[0084] LIST OF REFERENCE NUMERALS

[0085] 1. Diaphragm valve

[0086] 2. Valve housing

[0087] 3. First housing part

[0088] 4. Second housing part

[0089] 5. Fluid inlet

[0090] 6. Fluid outlet

[0091] 7. Closable fluid passage

[0092] 8. Membrane

[0093] 9. Membrane material

[0094] 10. Compression means

[0095] 11. Membrane compression zone

[0096] 12. Bulge (12: first compression state, 12’: second compression state, 12”: open state)

[0097] 13. Bulge accommodation cavity

[0098] 14. Forcing zone

[0099] 15. Pressure regulation recess

[0100] 16. -

[0101] 17. Membrane space

[0102] 18. Compression element

[0103] 19. Center

[0104] 20. Backside of membrane

[0105] 21. Main fluid inlet

[0106] 22. Main fluid outlet

[0107] 23. Membrane position regulation means

[0108] 24. -

[0109] 25. -

[0110] 26. Frontside of membrane

[0111] 27. Flat surface of forcing zone

Claims

CLAIMS1. Diaphragm valve (1) comprising: a valve housing (2), having a first housing part (3) and a second housing part (4) connected to the first housing part, defining a membrane space (17) therebetween, the first housing part comprising one or more fluid inlets (5) and one or more fluid outlets (6), and a fluid passage (7) in the membrane space between the one or more fluid inlets and the one or more fluid outlets, a membrane (8), arranged in the membrane space, fixed between the first housing part and the second housing part, for regulating a fluid flow in the fluid passage, wherein the membrane is compressed between the first housing part and the second housing part in a membrane compression zone (11) by compression means (10), such that a bulge (12) is created in the membrane, membrane position regulation means (23) for regulating the position of the membrane in the membrane space, and thereby the degree of fluid flow in the fluid passage, characterized in that the membrane (8) is made of a membrane material (9) having a Poisson ratio of about 0.5, in that the first housing part (3) comprises a bulge accommodation cavity (13) for accommodating the bulge (12), comprising the one or more fluid inlets (5) and the one or more fluid outlets (6), and in that the second housing part (4) comprises a forcing zone (14) configured for forcing the membrane to bulge towards the bulge accommodation cavity when the membrane is compressed.

2. Valve (1) according to claim 1 , wherein pretension is provided on the membrane (8) by the compression means (10).

3. Valve (1) according to claim 2, wherein the forcing zone (14) is configured to ensure that the membrane (8) bulges towards the bulge accommodation cavity (13) when the pretension is applied.

4. Valve (1) according to any one of the preceding claims, wherein the membrane compression zone (11) surrounds the bulge (12), preferably fully surrounds the bulge.

5. Valve (1) according to any one of the preceding claims, wherein the compression means (10) comprise one or more compression elements (18), such as one or more pens or screws, compressing the first housing part (3) and the second housing part (4) against the membrane (8) in the membrane compression zone (11).

6. Valve (1) according to any one of the preceding claims, wherein the bulge accommodation cavity (13) is shaped so that a center (19) snugly accommodates the bulge (12) in the bulge accommodation cavity.

7. Valve (1) according to any one of the preceding claims, wherein the bulge accommodation cavity (13) has a concave shape.

8. Valve (1) according to any one of the preceding claims, wherein the membrane material (9) comprises rubber.

9. Valve (1) according to any one of the preceding claims, wherein the membrane material (9) is reinforced.

10. Valve (1) according to any one of the preceding claims, wherein the membrane (8) has a thickness of 0.5 - 2.0 mm, preferably 0.6 - 1.5 mm, more preferably 0.6 - 0.9 mm, when the membrane is not compressed by the compression means (10).

11. Valve (1) according to any one of the preceding claims, wherein at least one of the one or more fluid inlets (5) or at least one of the one or more fluid outlets (6) is arranged in a center (19) of the bulge accommodation cavity (13).

12. Valve (1) according to claim 11 , wherein the membrane (8) is arranged with respect to the center (19) of the bulge accommodation cavity (13) insuch a way, that the bulge (12) blocks the at least one fluid inlet (5) or the at least one fluid outlet (6) in the center (19) of the bulge accommodation cavity (13).

13. Valve (1) according to any one of the preceding claims, wherein the forcing zone (14) comprises a substantially flat surface adjacent to the membrane compression zone (11) for forcing the membrane (8) to bulge towards the bulge accommodation cavity (13).

14. Valve (1) according to any one of the preceding claims, wherein the second housing part (4) comprises a further cavity (15) for accommodating the bulge (12) when the membrane position regulation means (23) cause the membrane (8) to move towards the second housing part (4) in order to fully open the fluid passage (7).

15. Valve (1) according to any one of the preceding claims, wherein the one or more fluid inlets (5) comprise multiple fluid inlets and / or the at least one or more fluid outlets (6) comprise multiple fluid outlets.

16. Valve (1) according to any one of the preceding claims, wherein a width of the forcing zone (14) is 3 - 30 times, preferably 5 - 10 times, the membrane (8) thickness.

17. Flow control device, comprising a valve (1) according to any one or the preceding claims.

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