FLUIDIC DEVICE COMBINED A CHECK VALVE AND A DOUBLE-FLOW THROTTLE BODY

Abstract

The invention relates to a fluidic device (1) comprising an inlet (2) and an outlet (3) connected by a housing (4) forming a channel between the inlet (2) and the outlet (3), wherein the device (1) comprises a check valve (5-11) shaped to prevent the flow of fluid from the outlet (3) to the inlet (2), and a throttle element (13-19) shaped to allow the flow of fluid from the inlet (2) to the outlet (3) at a first flow rate when the differential pressure (ΔP) between the outlet (3) and the inlet (2) is below a threshold value (S), and at a second flow rate that is significantly lower than the first flow rate when the differential pressure (ΔP) between the outlet (3) and the inlet (2) is above the threshold value (S).

Description

Technical area

[0001] The invention relates to a fluidic device comprising an inlet and an outlet and combining the functions of a check valve in one direction and a throttle body in the other direction. State of the art

[0002] An over-the-tank valve (OTV) assembly is designed for mounting on top of a fluid tank to allow connection to a line. The tank valve assembly provides filling, dispensing, and safety functions. Advantageously, the consumption / dispensing line includes a check valve to prevent backflow of fluid into the tank. Advantageously, the consumption / dispensing line further includes a restrictor that allows a flow rate corresponding to the rated consumption to flow from the tank when a rated back pressure is present, and drastically limits the outflow when no significant back pressure is present, indicating a critical line rupture situation.

[0003] The invention offers an advantageous concept for combining these three functions in a particularly small volume suitable for a tank valve arrangement. BRIEF SUMMARY OF THE INVENTION

[0004] For this purpose, the invention relates to a fluidic device comprising an inlet and an outlet connected by a housing forming a channel between the inlet and the outlet, the device comprising a check valve shaped to prevent the flow of fluid from the outlet to the inlet, and a throttle body shaped to allow the flow of fluid from the inlet to the outlet at a first flow rate when the differential pressure between the outlet and the inlet is below a threshold value, and at a second flow rate that is significantly lower than the first flow rate when the differential pressure between the outlet and the inlet is above the threshold value.

[0005] The following are special features or embodiments that can be used alone or in combination: - The check valve comprises a check piston and a check seat, wherein the check piston is adapted to be pushed towards the check seat by a fluid flowing from the outlet to the inlet, wherein the check seat has a check bore coinciding with the inlet, and the check piston comprises a check end arranged opposite the check bore, which is shaped complementary to the check bore such that the check end closes the check bore when pressed against it. - the throttle body comprises a throttle piston and a throttle seat, wherein the throttle piston is adapted to be pushed towards the throttle seat by a fluid flowing from the inlet to the outlet, wherein the throttle seat has a throttle bore coinciding with the outlet, and the throttle piston comprises a throttle end arranged opposite the throttle bore, which is shaped complementary to the throttle bore, such that the throttle end closes the throttle bore when pressed against it. - the throttle end is pierced by a leak facing the throttle bore, preferably calibrated, - the check piston and the throttle piston are arranged telescopically, - the check valve further comprises a check preloading means, wherein the check preloading means tends to push the check piston towards the check seat, and the throttle body further comprises a throttle preloading means, wherein the throttle preloading means tends to move the throttle piston away from the throttle seat, - the device further comprises a compensating biasing means which tends to move the check piston away from the throttle piston, - the recoil piston further comprises at least one recoil passage bore, - the throttle piston also includes at least one throttle through-bore, - the check valve seat, which coincides with the inlet, is made of the same material as the housing or with a drilled plug attached to the housing, preferably by means of a thread, and the throttle seat, which coincides with the outlet, is made of the same material as the housing or with a drilled plug attached to the housing, preferably by means of a thread. Short description of the drawings

[0006] The invention is better understood if the following description, which is only exemplary, is read with reference to the accompanying figures, in which: [ Fig. 1] shows a sectional profile view of a device during a pressure drop in the opposite direction, [ Fig. 2] a section profile view of the in the Fig. 1 device shown with a nominal pressure drop in the nominal direction shows, [ Fig. 3] a section profile view of the in Fig. The device shown in 1 exhibits a significant pressure drop, which may indicate a pipe break. [ Fig. 4] A fluidic diagram of a valve arrangement in which a device is housed shows, [ Fig. 5] and [ Fig. 6] a perspective exploded view of the device Fig. 1. Show from two perspectives each, [ Fig. 7] shows a section view of a device according to an embodiment without compensating prestressing means. Description of the embodiments

[0007] Fig. Figure 2 shows a device 1 according to the invention in its rest configuration. This configuration is also essentially identical to the nominal configuration when a slight vacuum fluctuation exists between the right inlet 2 and the left outlet 3 of the device 1. In such a case, the device 1 allows flow from the inlet 2 to the outlet 3 and acts as a throttle element.

[0008] The diagram in Fig. Figure 4 shows the fluid flow diagram of an overhead valve assembly (OTV) 30 on the tank. Such an overhead valve assembly 30 is designed to be mounted on top of a fluid tank 31, such as a hydrogen tank, to allow its connection to a line 32. The tank valve assembly 30 provides filling, dispensing, and safety functions. The line 32 is used either for filling the tank 31 or for draining the fluid contained in the tank 31.

[0009] The valve assembly 30 connects the tank 31 to the line 32 via a main pipe. A device 1 is housed in this main pipe. It further comprises a screen 35, 36 at each end. It also includes a solenoid valve 33 and a shut-off valve 34, which are connected in series with the device 1.

[0010] This main pipe is used for tapping. When valves 33 and 34 are open, the fluid contained in tank 31 can flow from right to left towards pipe 32.

[0011] The valve arrangement 30 further comprises a first branch pipe, in which a check valve 37 is housed and which branches off from the main pipe. This first branch pipe is designed for filling the tank 31. When the valve 34 is open and the solenoid valve 33 is closed, fluid can flow from line 32 from left to right to the tank 31. The check valve 37 ensures that no fluid flows through the first branch pipe during dispensing.

[0012] The valve arrangement 30 further comprises a second branch pipe in which a manual valve 38 is housed and which branches off from the main pipe. This second branch pipe forms a bypass.

[0013] The valve arrangement 30 further includes a vent line comprising a safety valve 39 or a TPRD (thermal pressure relief device) so that fluid can be discharged in the event of overpressure.

[0014] The valve arrangement 30 also includes a temperature sensor 40, which measures the temperature of the tank 31.

[0015] At the location of the valve arrangement 30 where it is situated, a fluidic device 1 according to the invention advantageously performs three functions corresponding to three operating modes: a nominal consumption / tapping mode, a critical mode or a mode for consumption in the event of a break in the line 32 and a filling mode.

[0016] During the filling of tank 31, the fluid pressure at outlet 3 of device 1 is higher than at inlet 2. Solenoid valve 33 is closed. Valve 34 is open. Valve 38 is closed. The fluid flows from left to right in the plane of the diagram. This flow passes through the first auxiliary pipe, allowing flow through check valve 37. In this filling mode, device 1 must act as a check valve to prevent excessive pressure on solenoid valve 33.

[0017] In nominal operation, the fluid from the tank is used by a consumer connected to line 32. Solenoid valve 33 is open. Valve 34 is open. Valve 38 is closed. The fluid flows from right to left. This flow passes through the main line and through device 1 from right to left, i.e., from inlet 2 to outlet 3. In this nominal dispensing mode, device 1 must act as a throttle body with a calibrated opening.

[0018] A break can occur in line 32. If this happens, the line enters a critical mode. In this critical mode, it is desirable to drastically limit the fluid outflow from tank 31. Solenoid valve 33 is still open. Valve 34 is still open. Valve 38 is still closed. The fluid is still flowing from right to left. This flow is still passing through the main line and through device 1 from right to left, i.e., from inlet 2 to outlet 3. In this critical state, device 1 must perform a drastic flow-limiting function, as the discharged fluid is presumably lost.

[0019] For this purpose, the fluidic device 1 is a dipole in that it comprises an inlet 2 and an outlet 3, which are connected by a housing 4. This housing 4 forms a channel between the inlet 2 and the outlet 3.

[0020] The device 1 includes a check valve 5-11. This check valve 5-11 is shaped to prevent the flow of a fluid from the outlet 3 to the inlet 2, i.e. in a direction opposite to the nominal direction of consumption / drainage.

[0021] The device 1 further comprises a throttle body 13-19. This throttle body 13-19 is shaped such that the fluid can flow in the direction of consumption, i.e., from the inlet 2 to the outlet 3. There are two modes: a nominal mode and a critical mode.

[0022] In nominal mode, the fluid circulates at a first flow rate or nominal flow rate. Nominal mode is characterized by a pressure difference ΔP between outlet 3 and inlet 2 that remains low, i.e., below a threshold value S. During nominal discharge, the fluid consumer provides sufficient back pressure so that the pressure drop ΔP does not exceed the threshold value S.

[0023] In critical mode, fluid circulation occurs at a second, or critical, flow rate that is significantly lower than the first flow rate. Critical mode is characterized by the detection of a larger pressure difference ΔP between outlet 3 and inlet 2, i.e., greater than the threshold S. A break in line 32 would result in a very low pressure at outlet 3, approximately equal to atmospheric pressure. The presence of significant pressure at inlet 2 due to the presence of tank 31 would then lead to a significant pressure drop ΔP. Conversely, the detection of a significant pressure drop ΔP greater than the threshold S is interpreted as a break in line 32. The threshold S distinguishes between nominal mode and critical mode.

[0024] To achieve these functions, the invention proposes a device 1. An example of this device 1 is shown in the Fig. 1-3, 5, 6 illustrated. Fig. Figure 1 shows device 1 in filling mode. Fig. Figure 2 shows device 1 in nominal mode. Fig. Figure 3 shows device 1 in critical mode.

[0025] To perform the three functions, the device 1 comprises two components: a check valve 5-11 and a throttle body 13-19. These two components include many similar parts. To distinguish them, the check valve parts 5-11 are marked with the word "check" before their designation, and the throttle parts 13-19 are marked with the word "throttle" before their designation.

[0026] To perform the check valve function, the check valve 5-11 comprises a check piston 5 and a check seat 6. The check piston 5 can slide inside the housing 4. In particular, the check piston 5 is shaped such that it is pushed by a fluid flowing from the left-hand outlet 3 to the right-hand inlet 2 towards the check seat 6, i.e., from left to right in the plane of the figure. The check seat 6 has a check bore 9, which is fluidically connected to the inlet 2 and represents the only fluid flow path. The check piston 5 is shaped at one of its ends, the so-called check end 8, to be complementary to the check bore 9. This check end 8 faces the check bore 9.Thus, when the check piston 5 and its check end 8 are pressed against the check seat 6, the check end 8 closes the check bore 9 and thus prevents any flow of fluid.

[0027] The complementary shape of the backstop 8 and the backstop seat 6 at the edges of the backstop bore 9 is designed to provide a seal. These shapes are, for example, cone / cone or sphere / cone.

[0028] The desired recoil function for device 1 in this application does not require a tight seal. Simple contact between the recoil end 8 and the recoil bore 9 is sufficient. If a tighter seal is required, a seal can be added to the contact ring between the recoil end 8 and the recoil bore 9.

[0029] To perform both flow control functions, the throttle body 13-19 comprises a throttle piston 13 and a throttle seat 14. The throttle piston 13 can slide inside the housing 4. In particular, the throttle piston 13 is shaped such that it is pushed towards the throttle seat 14, i.e., from right to left in the plane of the figure, by a fluid flowing from the right-hand inlet 2 to the left-hand outlet 3. The throttle seat 14 has a throttle bore 17, which fluidically coincides with the outlet 3 and represents the only fluid flow path. The throttle piston 13 is shaped at one of its ends, the so-called throttle end 16, such that it complements the throttle bore 17. The throttle end 16 faces the throttle bore 17. Thus, when the throttle piston 13 and its throttle end 16 are pressed against the throttle seat 14, the throttle end 16 closes the throttle bore 17 and essentially prevents any flow of fluid.

[0030] According to another feature, the throttle end 16 is pierced by a leak 22. This leak 22, or leakage channel, is located opposite the throttle bore 17 and thus connects the outlet 3 to the right part of the throttle piston 13 and therefore to the interior of the device 1. This leak 22 determines the leakage flow rate, i.e., the reduced flow rate, which is the only one permitted in critical mode. This is shown in Fig. Figure 3 illustrates this. The very low pressure at outlet 3 in critical mode, relative to the pressure from tank 31, leads to a significant pressure drop in the device 1. This causes the throttle piston 13 to be pushed by the fluid from right to left, from inlet 2 to outlet 3. This closes the throttle seat 14. The only remaining outlet for the fluid is leak 22, which runs through the throttle piston 13 via its throttle end 16 in line with the throttle bore 17. This leak 22 is preferably calibrated.

[0031] According to a further feature, the check piston 5 and the throttle piston 13 are arranged telescopically. This feature is very advantageous because it makes it possible to design a particularly compact device 1, especially with regard to its length along its axis, and thus facilitates the integration of the device 1 into a valve arrangement 30. For this purpose, each of the two pistons, the check piston 5 and the throttle piston 13, is bell-shaped on the side of its other end 10, 18, which is opposite the end 8, 16 facing the seat 6, 14. Telescopic mounting is then made possible by the bell of one piston 5, 13 enclosing the bell of the other piston 5, 13. Thus, as illustrated in the figures, the check piston 5 surrounds the throttle piston 13 essentially concentrically. The reverse arrangement, i.e., the throttle piston 13 surrounding the check piston 5, would also be possible and equivalent.

[0032] To create a sensor capable of detecting the various pressure drop values ​​that determine the operating mode (nominal mode, critical mode, and filling mode), it is recommended to carefully arrange the prestressing elements 7, 15, and 21, whose respective arrangement and stiffness allow the three in the Fig. To achieve the configurations shown in Figures 1 to 3, corresponding to the operating modes, a person skilled in the art knows how to dimension these prestressing devices according to the modes and threshold values ​​S of the pressure drop value. The threshold value S determines the mode change between nominal mode and critical mode. Another implicit threshold value corresponds to the change in direction of the pressure drop and determines the mode change between nominal mode and filling mode.

[0033] According to a further feature, the check valve 5-11 also includes a check preload device 7. The check preload device 7 is arranged such that it tends to push the check piston 5 towards the check seat 6. This means that the check valve 5-11 is normally closed. An operating pressure from the inlet 2 to the outlet 3 pushes the check piston 5 and acts against the check preload device 7 to open the check valve 5-11. The check preload device 7 acts between the check piston 5 and the housing 4. In a preferred embodiment, the check preload device 7 is a compression spring arranged between the other check end 10 of the check piston 5 and the housing 4 to the left of the check piston 5, i.e., on the outlet 3 side. In the embodiment illustrated in the figures, the retainer is located on the plug 23, which is here considered to be the housing 4.

[0034] According to a further feature, the throttle body 13-19 also includes a throttle preloading device 15. The throttle preloading device 15 is arranged such that it tends to move the throttle piston 13 away from the throttle seat 14. In this way, the throttle body 13-19 is open by default and allows a large initial flow rate to pass through. A small pressure drop below the threshold S is insufficient to force the throttle piston 13 against the throttle seat 14. The throttle preloading device 15 acts between the throttle piston 13 and the housing 4. In a preferred embodiment, the throttle preloading device 15 is a compression spring arranged between the other throttle end 18 of the throttle piston 13 and the housing 4 to the left of the throttle piston 13, i.e., on the side of the outlet 3. In the embodiment illustrated in the figures, the mounting is located on the plug 23, which is here equated with the housing 4.

[0035] A device 1 according to the invention can be operated without the compensating agent 21 described above. Such a device 1 is in Fig. 7 illustrates.

[0036] However, such a device 1 is subject to greater design limitations. This design choice leads to tighter tolerance restrictions in the dimensioning of the check valve preloading devices 7 and the throttle preloading devices 15, as well as in the lengths of the respective telescopic parts of the check valve piston 5 and the throttle piston 13.

[0037] Therefore, according to a further feature, the device 1 advantageously comprises a compensating preload means 21. The compensating preload means 21 is arranged such that it tends to move the check piston 5 away from the throttle seat 13. The compensating preload means 21 acts between the check piston 5 and the throttle piston 13. In a preferred embodiment, the compensating preload means 21 is a compression spring arranged between the check piston 5 and the throttle piston 13.

[0038] According to a further feature, the check piston 5 also includes at least one check passage 11. This at least one check passage 11 is a through-hole that brings the two sides of the check piston 5 into fluid contact. Furthermore, the overall cross-section of the at least one check passage 11 is such that a flow rate through the check piston 5 corresponding to the requirements of the device 1 is enabled, and in particular, a limited flow rate is also enabled in nominal mode. This cross-section must, however, remain small so that the check piston 5 can perform its piston function and move under the influence of a fluid flow coming from the left of the check piston 5. This at least one check passage 11 can be axial, provided it is located on the circumference of the check piston 5. Alternatively or complementarily, if the passage 11 is more central, it is, as shown in the Fig. As shown in Figures 1-3, the rebound end 8 extends partially axially on the side of the other rebound end 10 and terminates radially so as not to alter the rebound piston 5 at the rebound end 8. The rebound end 8 must remain sealed at least where it faces the rebound bore 9 in the rebound seat 6.

[0039] According to another analogous feature, the throttle piston 13 also includes at least one throttle through-bore 19. This at least one bore 19 is a through-bore because it brings the two sides of the throttle piston 13 into fluid communication. Furthermore, the overall cross-section of the at least one throttle through-bore 19 is dimensioned such that a flow rate corresponding to the requirements of the device 1 is possible through the throttle piston 13, in particular a limited flow rate in nominal mode and backflow in critical mode until the check valve 5-11 closes. However, this cross-section must remain small so that the throttle piston 13 can perform its piston function and move under the influence of a fluid flow coming from the right of the throttle piston 13. This at least one bore 19 can be axial, provided it is located on the circumference of the throttle piston 13.Alternatively or complementarily, if the throttle bore 19 is more central, it is, as in the . Fig. 1-3 shown, partially axial on the side of the other throttle end 18 and ends radially so as not to alter the throttle piston 13 at the throttle end 16. The throttle end 16 must remain substantially sealed, at least where it faces the throttle bore 17 in the throttle seat 14. The term "substantially" in the preceding sentence refers to the sealing exception formed by the leak 22.

[0040] In nominal mode, as in Fig. As illustrated in Figure 2, the throttle piston 13 has no contact with the throttle seat 14. The nominal flow rate in nominal mode is then the flow rate determined by the at least one check bore 11 and the at least one throttle bore 19. More precisely, the nominal flow rate is the flow rate determined by the smaller cross-section of the two bores 11 and 19.

[0041] In critical mode, as in Fig. As illustrated in Figure 3, the throttle piston is in contact with the throttle seat 14, so that the throttle 13-19 is locked. The critical flow rate is the flow rate determined by the leak 22.

[0042] The check piston 5 is primarily biased into its closed position by the check preload element 7. Above a pressure threshold S, which is a function of pressure and flow rate, the check piston 5 reaches a stable fully open position. This position is reached either when the windings of the non-preload element 7 are brought together or when the check piston 5 abuts its seat.

[0043] For the nominal conditions: dispensing mode and filling mode, the fluid flow path bores are dimensioned so that the fluidic device 1 has a defined pressure loss coefficient.

[0044] In the critical mode, the differential pressure is significantly above the threshold value S. When the check piston 5 reaches its stable position, the force of the compensating preload device 21 on the throttle piston 13 is no longer dependent on the position of the check piston 5. From a second pressure threshold value S2 onwards, the throttle piston 13 moves towards the seat due to the increase in flow rate. The second threshold value S2 is much larger than the first threshold value S.

[0045] Leak 22 is calibrated according to several system operating parameters.

[0046] The compensating preload element 21 must exert a permanent force to press the throttle piston 13 against the throttle preload element 15. The stiffness of the compensating preload element 21 is very low compared to the stiffness of the check preload element 7, so that movement of the check piston 5 does not cause movement of the throttle piston 13.

[0047] Another feature is that the check valve seat 6 is firmly connected to the housing 4. Alternatively, the check valve seat 6 is made of the same material as a plug 23. The housing 4 or the plug 23 is then drilled through to create the check valve bore 9. The plug 23 is assembled with the housing 4. This can preferably be achieved by means of a thread.

[0048] Another feature is that the throttle seat 14 is firmly connected to the housing 4. Alternatively, the throttle seat 14 is, as in the Fig. Figures 1-3 illustrate a housing 4 made of a material with a plug 23. The housing 4 or the plug 23 is then drilled through to create the throttle bore 17. The plug 23 is assembled with the housing 4, preferably by means of a thread.

[0049] The plug 23 also provides access to the hollow interior of the housing 4, into which all components 5-22 of the device 1 can be inserted during assembly.

[0050] Device 1 is shown with a plug 23 on the left outlet side. It is also possible to implement Device 1 with a plug on the right inlet side. Device 1 can also include two plugs, one on each side.

[0051] The stacking of the components for the assembly of a device 1 is illustrated in more detail in exploded views 5 and 6.

[0052] The invention has been illustrated and described in detail in the drawings and the preceding description. This should be considered illustrative and exemplary, and not as limiting the invention to this description alone. Many alternative embodiments are possible. List of reference symbols 1 device, 2 entrances, 3 outlets, 4 cases, 5 check pistons, 6 Backseat, 7 Backstop devices, 8 Rebounders, 9. Backfire drilling, 10 other rebound effects, 11. Backfire drilling, 13 throttle pistons, 14 Throttle seat, 15 Throttle preload devices, 16 Throttle ends, 17 Throttle bore, 18 other throttle end, 19 Piercing the throttle, 21 compensating preload devices, 22 leaks, 23 plugs, 30 valve arrangement, 31 Tank, 32 lines, 33 Solenoid valve, 34 valve, 35, 36 sieve, 37 Check valve, 38 Bypass valve, 39 Safety valve, 40 temperature sensor, S, S2 threshold.

Claims

[1] Fluidic device (1) comprising an inlet (2) and an outlet (3) connected by a housing (4) forming a channel between the inlet (2) and the outlet (3), characterized by in that the device (1) comprises a check valve (5-11) shaped to prevent the flow of a fluid from the outlet (3) to the inlet (2), and a throttle body (13-19) shaped to allow the flow of a fluid from the inlet (2) to the outlet (3) at a first flow rate when the differential pressure (ΔP) between the outlet (3) and the inlet (2) is below a threshold value (S), and at a second flow rate which is significantly lower than the first flow rate when the differential pressure (ΔP) between the outlet (3) and the inlet (2) is above the threshold value (S). [2] Device (1) according to claim 1, wherein the check valve (5-11) comprises a check piston (5) and a check seat (6), wherein the check piston (5) is adapted to be pushed towards the check seat (6) by a fluid flowing from the outlet (3) to the inlet (2), wherein the check seat (6) has a check bore (9) coinciding with the inlet (2), and wherein the check piston (5) comprises a check end (8) arranged opposite the check bore (9) and shaped complementarily to the check bore (9) such that the check end (8) closes the check bore (9) when pushed against it. [3] Device (1) according to one of claims 1 or 2, wherein the throttle body (13-19) comprises a throttle piston (13) and a throttle seat (14), the throttle piston (13) is adapted to be pressed towards the throttle seat (14) by a fluid flowing from the inlet (2) to the outlet (3), the throttle seat (14) has a throttle bore (17) coinciding with the outlet (3), and the throttle piston (13) comprises a throttle end (16) arranged opposite the throttle bore (17) and shaped complementarily to the throttle bore (17) such that the throttle end (16) closes the throttle bore (17) when pressed against it. [4] Device (1) according to one of claims 1 to 3, wherein the throttle end (16) opposite the throttle bore (17) is pierced by a preferably calibrated leak (22). [5] Device (1) according to one of claims 1 to 4, wherein the check piston (5) and the throttle piston (13) are arranged telescopically. [6] Device (1) according to one of claims 1 to 5, wherein the check valve (5-11) further comprises a check biasing means (7), wherein the check biasing means (7) tends to press the check piston (5) towards the check seat (6), and wherein the throttle body (13-19) further comprises a throttle biasing means (15), wherein the throttle biasing means (15) tends to move the throttle piston (13) away from the throttle seat (14). [7] Device (1) according to one of claims 1 to 6, further comprising a compensating biasing means (21) tending to move the check piston (5) away from the throttle piston (13). [8] Device (1) according to one of claims 1 to 7, wherein the check piston (5) further comprises at least one check through-bore (11). [9] Device (1) according to one of claims 1 to 8, wherein the throttle piston (13) further comprises at least one throttle through-bore (19). [10] Device (1) according to one of claims 1 to 9, wherein the check seat (6) coinciding with the inlet (2) is made of the same material as the housing (4) or with a drilled plug (23) which is preferably attached to the housing (4) by means of a thread, and the throttle seat (14) coinciding with the outlet (3) is made of the same material as the building (4) or with a drilled plug (23) which is preferably attached to the housing (4) by means of a thread.

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