Improved valve for use in flow path

Abstract

The present invention relates to an improved umbrella valve and a system for controlling flow in a flow path comprising the improved umbrella valve. The improved umbrella valve has a solid shaft, a first end and a second end. A flexible umbrella is provided at a first end of the shaft and a stop element is provided at a second end of the shaft, the diameter of the stop element being larger than the diameter of the shaft.

Description

Technical Field

[0001] The present invention relates to a valve for a breath-controlled inhaler for pulmonary inhalation. Background Art

[0002] Inhalers that enable patients to inhale aerosols are needed for many medical applications, such as inhaled treatments for asthma, cystic fibrosis (CF), and other respiratory diseases. Aerosols are small solid particles or liquid droplets dispersed in a continuous gas phase. Typically, medical inhalation therapies require aerosols of fine droplets of liquid formulations of bioactive ingredients or drugs, ideally able to reach the smallest branches of the peripheral lung, such as the bronchioles and alveoli.

[0003] To achieve the desired uniform distribution of droplets in the gas phase, the liquid formulation is atomized in the inhaler by means of a nebulizer, such as an ultrasonic nebulizer, a nozzle nebulizer or a thin film nebulizer.

[0004] The parts of current available atomizer are for example the air path between reservoir, aerosol generator, mixing chamber, mouthpiece and the air inlet and the mouthpiece for liquid or solid particles. According to the design of inhaler, other parts may also be arranged, for example, for controlling the parts of air flow.

[0005] Various inhalers are known in the prior art:

[0006] WO2006 / 083014A1; US11,534,559; US11,458,264B2; US2021 / 0252236; US2022 / 0126036A1; WO2013 / 132056.

[0007] In these breath-controlled inhalers, an air flow is generated within the inhaler when the patient inhales through the mouthpiece. This air flow mixes with the aerosol generated by the aerosol generator, and the air-aerosol mixture is transported to the mouthpiece via an air passage. With some inhalers, the patient is supposed to remove the inhaler's mouthpiece during exhalation and reuse it for inhalation. However, patients often exhale into the mouthpiece, thereby entering the inhaler's air passage. Consequently, breathed air can reach the interior of the inhaler, potentially damaging it over time through moisture or, in the case of powder inhalers, wetting or disturbing the powder.

[0008] Therefore, many existing inhalers have an exhalation valve that prevents exhaled air from reaching the interior of the inhaler (especially the reservoir for liquids or powders and the control electronics) through the mouthpiece, while allowing the user to exhale into the mouthpiece. The exhalation valve used includes a duckbill valve or a flapper valve (for example, in US2022 / 0126036A1, US2021 / 0252236A1, and US11,458,264 B2). During inspiration, when air flow is generated from the air inlet to the mouthpiece, these valves open, and during exhalation, when air flow is generated from the mouthpiece to the interior of the inhaler, the exhalation valve closes. The exhalation valve can also be used to divert air flow into the surrounding environment during exhalation.

[0009] US Pat. No. 11,534,559 B2 discloses an umbrella valve as a breath-controlled air inlet valve, which opens when negative pressure occurs in the air inlet chamber of the inhaler.

[0010] Valves in the air passages affect the air flow during inspiration because they act as an obstruction in the air passage. Therefore, the valve design should minimize the effect on air flow during inspiration and provide optimal air passage obstruction during exhalation. Summary of the Invention

[0011] The improved umbrella valve according to the present invention particularly satisfies the above requirements. In addition, the present invention also relates to a system for controlling the flow in the flow path, which system comprises the improved umbrella valve. As an example, a breath-controlled inhaler comprising the improved umbrella valve and the use of the improved umbrella valve in the air passage of the inhaler are described in the specification. Should be understood that the improved umbrella valve and the system for controlling the flow in the flow path are not necessarily used together with air and used in the air passage, but can be used together with other gases and usually used in the air flow passage. Therefore, "air passage" or "air passage" or "air flow" should also be understood as the broader meaning of "gas passage" or "gas passage" or "gas flow", as the case may be, unless specifically used in relation to the breath-controlled inhaler as described below.

[0012] The improved umbrella valve is a check valve. It includes a solid shaft having a first end and a second end. A flexible umbrella is provided at the first end of the shaft. A stop element is provided at the second end of the shaft, the stop element having a diameter larger than the diameter of the shaft.

[0013] In use, the improved umbrella valve is installed in the central hole of a perforated plate located in the air channel. The perforated plate can have different thicknesses, porosities and diameters. The diameter of the flexible umbrella essentially corresponds to the diameter of the air channel, or it can be slightly oversized to provide a radial seal. The diameter of the stop element should be larger than the diameter of the central hole of the perforated plate into which it is inserted. The stop element can be angled to facilitate insertion. This is the only way for the stop element to hold the second end of the shaft on the upstream side of the perforated plate. At the same time, the stop element should not be so large as to affect the air flow through the air channel, for example, it should cover as few perforations of the perforated plate as possible.

[0014] If the air flow in the air channel strikes the outer side of the umbrella valve (positive pressure), the umbrella is pressed against the perforated plate, thereby axially sealing the perforated plate's holes. Furthermore, an additional seal can be achieved by slightly oversizing the outer diameter of the umbrella valve relative to the inner diameter of the air channel. In contrast, if negative pressure develops outside the umbrella, the umbrella is lifted from the perforated plate and folded downward, away from the plate. Simultaneously, the effective diameter of the umbrella decreases, freeing up a portion of the air channel's diameter for air to circulate through the perforated plate. Depending on the length of the shaft, the first end of the shaft moves away from the perforated plate until further movement is stopped by a stop element.

[0015] The length of the shaft should be chosen so that the folded umbrella is as far away from the porous plate as possible, so as to reduce the air flow through the porous plate as little as possible. The shaft and the stop feature hold the umbrella portion of the valve in place on the porous plate. On the other hand, if the folded umbrella is too far away from the porous plate, there is a risk that the umbrella will tilt and not return to its proper position on the porous plate when the negative pressure decreases. Therefore, the shaft length should preferably be in the range of 20% to 50% of the umbrella diameter, particularly preferably in the range of 30% to 40% of the umbrella diameter. This allows linear movement of the umbrella valve to improve air flow during inhalation. At larger diameters, the ratio of the umbrella's shaft to diameter can be further increased or decreased, depending on the application and the inhalation and expiratory forces to which the umbrella valve is subjected.

[0016] In one embodiment, the diameter of the umbrella is in the range of 9.5 mm to 10.5 mm, and the shaft is at least 2 mm, preferably at least 2.5 mm, and particularly preferably at least 3 mm long. In this embodiment, the shaft is at most 5 mm long, preferably at most 4 mm long. Particularly preferably, the length of the shaft in this embodiment is in the range of 3 mm to 4 mm.

[0017] The umbrella of the umbrella valve is preferably made of silicone or a similar flexible material with sealing properties, such as thermoplastic elastomer (TPE) or thermoplastic polyurethane (TPU). The shaft can be made of the same material or a rigid plastic such as PEEK (polyetheretherketone) or PC (polycarbonate) or metal. The stop element can be formed integrally with the shaft and made of the same material as the umbrella, or it can be attached to the second end of the shaft and made of a different material. The stop element is an element that prevents the second end of the shaft from sliding through the holes of the porous plate. The umbrella can also be formed integrally with the shaft, for example by multi-component injection molding, with a form-fitting connection or material-material bonding, or as a separate component, for example attached to the shaft after the shaft has been installed in the guide of the porous plate. The number of individual parts included in the improved umbrella valve depends on its installation method.

[0018] A system for controlling a flow in a flow path according to the present invention comprises:

[0019] - air passages;

[0020] - a perforated plate located in the air channel and having a central hole;

[0021] - An improved umbrella valve as described above mounted in the central hole of the perforated plate.

[0022] In one embodiment, the diameter of the flexible umbrella of the improved umbrella valve corresponds to the diameter of the air passage.

[0023] In one embodiment, the diameter of the stop element is larger than the diameter of the central hole of the multiwell plate into which it is inserted.

[0024] In one embodiment, the length of the shaft is 1.2 to 5 times the thickness of the porous plate, preferably 2 to 4 times the thickness of the porous plate, most preferably 2 to 3 times the thickness of the porous plate.

[0025] Exemplary breath-controlled inhalers include:

[0026] - air intake,

[0027] - a suction nozzle having a suction nozzle opening,

[0028] - an air passage between the air inlet and the mouthpiece opening, wherein the air passage comprises a mixing chamber,

[0029] - reservoirs for liquids or solid particles,

[0030] an aerosol generator, which is connected to the reservoir and converts the liquid or solid particles from the reservoir into an aerosol and introduces it into the mixing chamber,

[0031] - Improved umbrella valve between the air inlet and the mixing chamber.

[0032] In one embodiment, the improved umbrella valve is mounted in the central hole of a porous plate. The porous plate is located in the air passage between the air inlet and the mixing chamber. The porous plate can also function as an air filter for retaining particles or moisture and can include an appropriate mesh. The thickness of the plate is typically between 0.3 mm and 3 mm.

[0033] The breath-controlled inhaler preferably comprises an air inlet valve between the modified umbrella valve and the air inlet. The air inlet valve is controlled by a pressure sensor which releases the air inlet when a certain negative pressure appears in the mouthpiece.

[0034] The aerosol generator is preferably an electromechanical aerosol generator, which comprises a vibrating membrane that seals the reservoir towards a mixing chamber. Due to the vibration, an aerosol is produced (thin film atomizer) that mixes with the air flow in the air channel.

[0035] In one embodiment, breath-controlled inhaler according to the present invention is made up of head, base and suction nozzle.Head comprises reservoir and aerosol generator, and base comprises the first section of air inlet and air channel.In addition, base can comprise air inlet valve, the electronic equipment and pressure sensor that are used for aerosol generator operation.Suction nozzle comprises suction nozzle opening, the second section of air channel with mixing chamber and the improved umbrella valve at the beginning of the second section of air channel.

[0036] The improved position of the umbrella valve at the entrance to the second section of the air channel prevents exhaled air from entering the first section of the air channel in the base directly from the mouthpiece opening, thereby protecting the electronics there from moisture damage. This can occur due to the user accidentally exhaling into the device. Even with a gasket, leaks can occur. This is due to the complexity of the sealing interface between the components and the tolerance differences between them. This hinders the proper alignment and force of the elastomeric gasket, which is necessary to ensure a tight seal. Moisture can also originate from the surrounding environment, such as when the inhaler is used in a warm room with high humidity after being shipped at low temperatures. Damage to the electronics in the base is particularly serious because the base is used multiple times and is intended to remain suitable for use for a relatively long time, while the mouthpiece and tip are regularly replaced. Furthermore, the improved position of the umbrella valve between the air inlet and the mixing chamber prevents the aerosol-laden air flow from being affected on its way to the mouthpiece opening.

[0037] At the mouthpiece, the patient generates an air flow into which the aerosol generated by the vibrating membrane is admitted. Through the mouthpiece opening, the aerosol-air mixture is inhaled by the patient. The necessary air is drawn into the air channel of the base via the air inlet opening, and from there, reaches the air channel of the mouthpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Exemplary embodiments of the present invention are shown in the accompanying drawings and will be described in more detail below. In the drawings:

[0039] Figure 1a A prior art umbrella valve is shown in a closed position;

[0040] Figure 1b A prior art umbrella valve is shown in an open position;

[0041] Figure 2 An umbrella valve with a short axis and with a long axis is shown;

[0042] Figure 3a The improved umbrella valve is shown in an idle state in a first variant of the air passage of the inhaler;

[0043] Figure 3b shows the improved umbrella valve during inhalation in a first variant of the air channel of the inhaler;

[0044] Figure 3c shows the improved umbrella valve during exhalation in a first variant of the air channel of the inhaler;

[0045] Figure 4a shows the improved umbrella valve in an idle state in a second variant of the air passage of the inhaler;

[0046] Figure 4b shows the improved umbrella valve during inhalation in a second variant of the air channel of the inhaler;

[0047] Figure 4c shows the improved umbrella valve during exhalation in a second variant of the air channel of the inhaler;

[0048] Figure 5 An exploded view of a prior art inhaler is shown;

[0049] Figure 6 shows a longitudinal section of a prior art inhaler;

[0050] Figure 7 shows measurement results related to moisture in a prior art inhaler without an exhalation valve;

[0051] Figure 8 Shown are measurement results related to moisture in a prior art inhaler with an improved umbrella valve.

[0052] Description of Reference Numerals

[0053] 10-Umbrella valve in the prior art

[0054] 12-Axis end, umbrella valve in the prior art

[0055] 14-axis, umbrella valve in the prior art

[0056] 15-Hook, umbrella valve in the prior art

[0057] 16-Umbrella, umbrella valve in the prior art

[0058] 18 – Perforated Plate

[0059] 19 – Piercing

[0060] 20 – Improved umbrella valve

[0061] 23 – Stop element

[0062] 24–Axis

[0063] 26-Umbrella

[0064] 28 – Center hole

[0065] 29 – Perforated plate or filter plate

[0066] 100-base unit

[0067] 101 – Air intake opening

[0068] 102 – air outlet opening

[0069] 103 – Groove

[0070] 104 – Key lock element

[0071] 110 – Air channel

[0072] 118-Intake valve

[0073] 119 – Pressure Sensor

[0074] 200–Nozzle

[0075] 200a – the first section of the nozzle

[0076] 200b – the second section of the nozzle

[0077] 201 – Inhalation port

[0078] 202 – side opening

[0079] 203–Nozzle opening

[0080] 206-Step

[0081] 207 – Air channel

[0082] 208 – Mixing Chamber

[0083] 300–Aerosol head

[0084] 301 – Aerosol Generator

[0085] 302–Storage

[0086] 303 – Key lock element

[0087] 304–lid

[0088] 309–net DETAILED DESCRIPTION

[0089] Figure 1a The umbrella valve 10 of the prior art is shown in a closed position. The shaft 14 is located in the central hole of the porous plate 18, where the shaft 14 is fixed to one side of the porous plate 18 by an umbrella 16 and to the other side of the porous plate 18 by a hook 15. The hook 15 is a widened part of the shaft 14. The shaft end 12 is spaced apart from the umbrella 16 so that the shaft 14 of the umbrella valve 10 can be pulled through the central hole of the porous plate 18 during assembly. In the closed position, the umbrella 16 of the umbrella valve 10 closes the perforation 19 in the porous plate 18. The umbrella valve 10 is in the closed position when a medium (gas or liquid) exerts pressure on the outside of the umbrella 16 (arrow A). From a certain pressure of the medium to the opposite direction (arrow B) through the perforation 19 of the porous plate 18 to the bottom side of the umbrella 16, the umbrella 16 folds downward. The outer area of ​​the umbrella 16 is lifted from the perforation 19 so that the medium (air or liquid) can flow through the perforation 19 ( Figure 1b , arrow C).

[0090] Figure 2 Umbrella valves with both long and short shafts are shown. During installation, they are not pulled through the central hole of the perforated plate, but rather pressed in from one side until the hook engages. The shaft serves as an assembly aid and is supported by an undercut. For purely assembly purposes, it has little axial mobility. Unlike the prior art, it does not perform the axial sliding function under negative or positive pressure in the air channel to better clear the flow cross section.

[0091] Figure 3a and 4a The modified umbrella valve 20 is shown in an idle state as part of a system for controlling flow in a flow path, such as may be found in an inhaler 400 ( Figure 5 and 6 ). Figure 3a The difference between the two variants of the air channel 207 in 4a-c and 4a-c is that Figure 3a -c has a constant diameter of the air passage 207, while Figure 4a The air passage in -c has a step so that the air passage widens between the porous plate or filter plate 29 and the mixing chamber 208.

[0092] The improved umbrella valve 20 comprises a shaft 24 and an umbrella 26 at a first end thereof. The improved umbrella valve 20 differs from the known umbrella valve 10 in that a stop element 23 is located at the second end of the shaft 24. Furthermore, there is no hook 15, as in the case of the umbrella valve 10 of the prior art, which hook fixes the shaft 24 in a fixed position to the perforated plate or filter plate 29. In the idle state, the umbrella 26 is arched towards the shaft 24 due to its natural tension and is located in an indefinite position in the air channel 207 at a maximum distance from the perforated plate or filter plate 29 limited by the stop element 23. Figure 3a and Figure 4a In the embodiment shown, the umbrella of the improved umbrella valve in the idle state is located directly on the perforated plate or filter plate 29. The shaft 24 is mounted in the central hole 28 of the perforated plate or filter plate.

[0093] Figure 3b and 4b Shown is the situation when air stream passes porous plate or filter plate 29 along the direction of arrow D.Air stream passes through porous plate or filter plate 29, and when doing so, lifts the umbrella 26 of umbrella valve 20.Because air stream, umbrella 26 moves away from porous plate or filter plate 29, up to the degree that the stop element at the second end of axle 24 allows.After this, the umbrella 26 of umbrella valve 20 folds downwards away from axle 24 on the direction of air stream D.Now, air further flows downwards along flow path relatively unhindered, for example enters mixing chamber 208, in mixing chamber 208, air stream mixes with the aerosol from the lateral opening 202 that is connected to aerosol generator 301.Air-aerosol mixture flows (arrow E) on the further direction of the mouthpiece opening 203 of inhaler then.

[0094] If an air flow is generated in the opposite direction ( Figure 3c / Figure 4c , arrow F), the umbrella 26 is pressed onto the porous plate or filter plate 29. At the same time, the umbrella 26 closes the perforations in the porous plate or filter plate 29 in the axial direction, and the air flow stops. By slightly oversizing the umbrella valve relative to the inner diameter of the air channel, an additional sealing effect can be produced in the radial direction.

[0095] Figure 5 An exploded view is shown, and Figure 6 There is shown a longitudinal section of an inhaler 400 from the prior art (EP2724741B1) which has been improved by installing an improved umbrella valve 20 in place. The inhaler 400 comprises a base unit 100, a mouthpiece 200 and an aerosol head 300.

[0096] The base unit 100 includes one or more air inlet openings 101, an air outlet opening 102, a recess 103 for accommodating the mouthpiece 200, and one or more key lock elements 104. The air inlet opening 101 and the air outlet opening 102 are connected inside the base unit 100 to form an air channel 110. Under operating conditions and during the user's inhalation phase, air flows from the upstream end to the downstream end of the air channel 110, that is, from the air inlet opening 101 to the air outlet opening 102.

[0097] The pressure sensor 119 measures the negative pressure of the inhalation and starts the aerosol generator 301 from a certain minimum pressure and opens / closes the air inlet valve 118 to control the air flow. The pressure sensor 119 contacts the air passage as an orthogonal bypass relative to the main air flow in the air channel 110.

[0098] The mouthpiece 200 comprises a first section 200a comprising an inhalation port 201 attachable to the air outlet opening 102 of the base unit 100, and a lateral opening 202 for connecting to an aerosol generator 301. Following the inhalation port 201 is an air passage 207 extending in the region of the lateral opening leading to a mixing chamber 208. During use, in the mixing chamber 208, air is mixed with the aerosol mixture from the aerosol head 300. The first section 200a is insertable into the recess 103 of the base unit 100. The second section 200b is located downstream of the first section 200a and comprises an air passage 207 extending from the first section 200a and the mouthpiece opening 203.

[0099] The aerosol head 300 comprises an aerosol generator 301, a liquid reservoir 302 and one or more male or female keying elements 303 that are complementary to the keying elements 104 on the base unit 100. The base unit 100, the mouthpiece 200 and the aerosol head 300 are interconnectable.

[0100] The base unit 100 is assembled with the mouthpiece 200 and the aerosol head 300 by inserting the first section 200a of the mouthpiece 200 into the recess 103 of the base unit 100, subsequently placing the aerosol head 300 on the first section 200a of the mouthpiece 200, and engaging the keying element(s) 303 of the aerosol head 300 with the complementary element(s) 104 of the base unit 100 by applying slight pressure on the aerosol head and the base unit. These assembly steps are intended to create an airtight connection between the air outlet opening 102 of the base unit 100 and the air inhalation opening 201 of the first section 200a of the mouthpiece, as well as between the aerosol generator 301 and the lateral opening 202 in the first section 200a of the mouthpiece 200. Furthermore, the aerosol generator 301 is positioned in the aerosol head 300 such that it is at least partially inserted into the lateral opening 202 of the first section 200a of the mouthpiece 200 when the keying element(s) engage with the complementary element(s).

[0101] Through the air outlet opening 102 of the base unit 100, air flows into the air channel 207 of the nozzle 200 via the air inlet 201 of the first section 200a of the nozzle 200. The air outlet opening 102 is circular and can be located, for example, in the central area of ​​the base unit (e.g., as shown in FIG. Figure 5 The air outlet opening 102 may comprise a sealing element, for example in the form of a gasket, a sealing lip or a bellows, for establishing an airtight connection with the air intake 201 of the suction nozzle 200 .

[0102] The air inlet comprises a perforated plate or filter plate 29 with a central hole 28, which accommodates the shaft 24 of the modified umbrella valve 20. At the same time, the umbrella 26 is located in the air channel 207 of the suction nozzle 200, and the stop element 23 is located in the area of ​​the air outlet opening 102 of the base unit 100 (see also Figures 3a-3c / Figure 4a -c) The improved umbrella valve 20 prevents in particular the air flow entering the mouthpiece opening during exhalation from passing through the possibly incomplete seal, through the inhalation port 201 and the outlet port 102 , and into the base unit 100 .

[0103] The base unit 100 may comprise one or more electrical connectors for electrically connecting, in the assembled state, to complementary connectors of the aerosol head 300. This is particularly important if the aerosol head 300 comprises an ultrasonic or piezoelectric aerosol generator 301, for example an aerosol generator 301 comprising a vibrating membrane 309 (membrane nebulizer).

[0104] The power supplied to the aerosol generator may be provided, for example, by internal batteries or rechargeable batteries housed in the base unit 100 , or by an external energy source connected to the base unit 100 via a cable.

[0105] Figure 7 The results of measurements related to moisture in an inhaler without the prior art improved umbrella valve 20 are shown. Located in the base 100 is a moisture sensor close to the pressure sensor 119. The user inhales through the mouthpiece 200 and then exhales immediately. Figure 6 As can be seen in the graph, the moisture sensor measures an increase in relative humidity during the exhalation phase (time units 320 to 610 on the x-axis). 0 The relative humidity at the sensor increased by about 10% during exhalation, with a rise from 35% at 40°C to 57% at the peak.

[0106] Figure 8 The results of measurements related to moisture in an inhaler with an improved umbrella valve 20 from the prior art are shown. As in the test without the improved umbrella valve, the user inhales through the mouthpiece and then exhales immediately. Figure 7 As can be seen in the graph, the moisture sensor measures a slightly higher relative humidity during the exhalation phase (time units 169 to 553 on the x-axis). The increase in relative humidity is significantly lower than in the case without the modified umbrella valve 20. 0 The relative humidity at the sensor increases from 45% at 5°C to 54% at the peak. On average, the increase in relative humidity at the sensor is about 1.4%.

Claims

1. An improved umbrella valve (20) comprising a solid shaft (24) having a first end and a second end, wherein: A flexible umbrella (26) is provided at the first end of the shaft (24), and is characterized in that a stop element (23) is provided at the second end of the shaft (24), and the diameter of the stop element (23) is larger than the diameter of the shaft (24).

2. The improved umbrella valve (20) according to claim 1, characterized in that The length of the shaft (24) is 20% to 50%, preferably 30% to 40%, of the diameter of the umbrella (26).

3. The improved umbrella valve (20) according to claim 1, characterized in that The umbrella (26) has a diameter of 9.5 mm to 10.5 mm, and the length of the shaft is at least 2 mm, preferably at least 2.5 mm, more preferably at least 3 mm.

4. The improved umbrella valve (20) according to claim 1, characterized in that The umbrella (26) has a diameter of 9.5 mm to 10.5 mm, and the shaft has a length of at least 3 mm to 4 mm.

5. The improved umbrella valve (20) according to any one of claims 1 to 4, characterized in that The umbrella (26) is made of a flexible material, such as silicone, thermoplastic elastomer (TPE) or thermoplastic polyurethane (TPU).

6. The improved umbrella valve (20) according to any one of claims 1 to 5, characterized in that The shaft (24) is made of metal or hard plastic, preferably polyetheretherketone (PEEK) or polycarbonate (PC).

7. The improved umbrella valve (20) according to any one of claims 1 to 6, characterized in that The umbrella (26) and the shaft are integrally formed.

8. A system for controlling flow in a flow path, comprising: Gas channel (207); a perforated plate (29) located in the gas channel (207) and having a central hole (28); an improved umbrella valve (20) mounted in the central hole (28) of the perforated plate (29); The improved umbrella valve (20) includes a solid shaft (24) having a first end and a second end, wherein a flexible umbrella (26) is provided at the first end of the shaft (24), and a stop element (23) is provided at the second end of the shaft (24), wherein the diameter of the stop element (23) is larger than the diameter of the shaft (24).

9. The system according to claim 8, wherein: The diameter of the flexible umbrella (26) corresponds to the diameter of the gas channel (207).

10. The system according to claim 8, wherein: The diameter of the stop element (23) is larger than the diameter of the central hole (28) of the perforated plate (29) into which it is inserted.

11. The system according to claim 8, wherein The length of the shaft (24) is between 1.2 and 5 times the thickness of the perforated plate (29), preferably between 2 and 4 times the thickness of the perforated plate (29), and most preferably between 2 and 3 times the thickness of the perforated plate (29).

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