Filter housing and ventilation device

Abstract

Filter housing of a ventilation device, comprising: - a housing part (2) which defines a shaft (4) accessible via an opening (3) of the housing part (2), into which a filter component (5) can be inserted in order to cover a flow channel of the ventilation device across its cross-section when the filter component (5) is inserted into the shaft (4), - a seal (6) arranged around the opening (3), and - a cover (7) which, in its installed operating state, rests against the seal (6) and closes the opening (3) of the housing part (2), characterized in that the housing part (2) is designed as a foam molded body (2a) which has two bearing seats (8.1, 8.2) arranged on opposite sides of the opening (3), and The lid (7) has a hinge pin (9.1, 9.2) at each of its opposite ends to form a pivotable flap (7a), each hinge pin (9.1, 9.2) being designed for rotatable mounting in one of the bearing seats (8.1, 8.2) of the foam molded body (2a).

Description

[0001] The invention relates to a filter housing of a ventilation device, comprising a housing part that defines a shaft accessible via an opening in the housing part, into which a filter component can be inserted to cover a flow channel of the ventilation device across its cross-section when the filter component is inserted into the shaft, a seal arranged circumferentially around the opening, and a cover which, in its installed operating state, rests against the seal and closes the opening of the housing part. The invention also relates to a ventilation device with such a filter housing.

[0002] US Patent 2004 / 0172927 A1 describes a filter cover assembly attached to an opening in an air conditioner housing to close the opening, with a filter installed in the housing to remove contaminants from the air flowing into the air conditioner. The filter cover assembly comprises a first filter cover, a second filter cover, and a fastening assembly for attaching the first filter cover to the second filter cover. The first filter cover includes a first cover body to close a predetermined portion of the housing opening, the first cover body having a connecting part for locking to the housing. The second filter cover includes a second cover body to close the remaining portion of the opening, the second cover body having an engagement part for connecting to the fastening assembly.

[0003] The object of the invention is to create a filter housing for a ventilation device that enables particularly quiet and airtight operation. A further object of the invention may be to create a filter housing for a ventilation device that provides easy access to the filter in order to change the filter with minimal effort.

[0004] The task is solved by a filter housing of a ventilation device, comprising: - a housing part which defines a shaft accessible via an opening in the housing part, into which a filter component can be inserted in order to occupy a flow channel of the ventilation device across its cross-section when the filter component is inserted into the shaft, - a seal arranged around the opening, and - a cover which, in its installed operating state, rests against the seal and closes the opening of the housing part, wherein the housing part is designed as a foam molded body which has two bearing seats arranged on opposite sides of the opening, and The lid has a hinge pin at each opposite end to form a pivoting flap, each hinge pin being designed for rotatable mounting in one of the bearing seats of the foam molded body.

[0005] The ventilation device can be, for example, a ventilation system for supplying and extracting air from rooms. Such a ventilation device can be installed, for example, in the interior of buildings, in facades, and / or in wall boxes within a building wall. The ventilation device comprises at least one ventilation duct and at least one fan connected to the ventilation duct for conveying air within the duct. To improve air quality and / or for hygienic reasons, filters are used that can filter out particles contained in the air transported within the ventilation device and / or chemically and / or physically neutralize unwanted gaseous components in the air.

[0006] The filter can be, for example, a hygiene filter or a pollen filter. It can also be any other type of filter. The filter is designed as a filter element or component that can be inserted into the filter housing. The filter element or component can, for example, consist of a filter fleece, in particular a filter fleece made of at least one fiberglass mat. The filter fleece can be integrated into a filter frame. The filter frame and filter fleece can be manufactured as a single plastic composite body. The filter can be designed as a filter cartridge. The filter or filter cartridge can be designed to be replaceable. For example, the filter or filter cartridge can be inserted into the filter housing like a slide-in mechanism and removed again by pulling it out.

[0007] The filter component or filter cartridge is removable, i.e., replaceable, and inserted into the filter housing, allowing for easy filter maintenance. The filter can be easily removed from the filter housing, enabling inspection of its condition, cleaning if necessary, and / or replacement with a new filter.

[0008] In its installed position, the filter component is placed in the airflow path so that the air conveyed in the air duct must pass through the filter component or its filter fleece. For this purpose, the filter component is inserted into a chamber of the filter housing. If the filter housing is integrated into the ventilation system or connected to the airflow duct of the ventilation system, the conveyed air is directed through the chamber of the filter housing in such a way that it must pass through the filter component. The filter chamber can be made, for example, of expanded polypropylene (EPP) or be integrated as a separate component within a foam body made of expanded polypropylene (EPP). The filter housing can therefore be either a single component or, alternatively, it can consist of several components.

[0009] The housing section of the filter housing defines the shaft accessible through an opening in the housing section, into which the filter component can be inserted. When inserted into the shaft, the filter component occupies a flow channel of the ventilation device across its cross-section. The opening in the housing section provides access to the shaft, allowing the filter component to be inserted into or removed from the shaft through the opening.

[0010] During the operation of a ventilation device that includes the filter housing and the filter component, the opening is closed by a cover.

[0011] The filter component has a seal arranged around the opening. The seal is designed and positioned in such a way that, when the lid is attached to the filter housing, the lid seals the shaft airtight. In this respect, the seal closes any gap between the filter housing or the shaft of the filter housing and the lid.

[0012] Accordingly, in its installed operating state, the cover rests against the seal and closes the opening of the housing part or the opening of the shaft, which, when the cover is removed, forms an access opening to the shaft.

[0013] In contrast to previously known designs, the invention provides that the housing part of the filter housing is designed as a molded foam body. Accordingly, the filter housing according to the invention does not require thin-walled housing components, in particular thin-walled housing components made of thermoplastic material or metal sheets. By designing the filter housing as a molded foam body, particularly good noise reduction and thermal insulation are achieved. Therefore, according to the invention, a thin-walled housing made of thermoplastic material or metal sheets can be omitted.

[0014] The foam molding body can be manufactured from materials such as polyethylene (PE) or polypropylene (PP) using a molding process. In this process, foam particles, such as those made from expanded polystyrene (EPS), expanded polyethylene (EPE), or expanded polypropylene (EPP), can be sintered to form the housing part of the filter housing.

[0015] If necessary, the foam molded body can also be produced using an extrusion process, for example.

[0016] The cover, necessary for access to the shaft, is hinged directly onto the foam molding.

[0017] The foam molding body has two bearing seats arranged on opposite sides of the opening. These two bearing seats are designed as pivot bearings, with their axes of rotation lying on a common pivot axis. This pivot axis determines the axis of rotation about which the cover is pivotably mounted on the foam molding body by means of the bearing seats. According to the invention, the cover is thus designed as a pivotable flap.

[0018] The lid has a hinge pin at each opposite end to form a pivotable flap, each hinge pin being designed for rotatable mounting in one of the bearing seats of the foam molded body.

[0019] In a basic design, the hinge pins are formed as circular cylindrical rods that extend outwards along two opposite edges of a rectangular or square flap. The axes of symmetry of the two circular cylindrical rods lie on a common straight line, which forms the axis of rotation or pivot axis of the flap.

[0020] Accordingly, the two bearing seats of the foam molding each have a circular cylindrical inner wall whose radius of curvature is adapted to the radius or diameter of the hinge pins, so that the hinge pins are at least partially positively guided in the bearing seats. The bearing seats are radially open, allowing the hinge pins of the flap to be inserted into the bearing seats in a radial direction to the pivot axis. The bearing seats can be formed by groove-like recesses in the foam molding, which extend to the edge of the shaft of the foam molding.

[0021] The bearing seats can accordingly be formed by radially open pin receptacles, which are molded into the foam body and into which the hinge pins of the pivoting flap can be inserted radially to the pivot axis determined by the hinge pins.

[0022] The pivoting flap can be easily mounted to the foam molded body by inserting the hinge pins of the flap into the pin receptacles of the foam molded body.

[0023] The foam molded body may have a frame projection surrounding the opening, which forms a seat for the seal.

[0024] The frame projection can be formed by a continuous wall section that protrudes from a base plane in the foam molded body. The frame projection thus comprises a continuous wall section that runs around the edge of the opening, i.e., the access opening to the shaft. In the case of a rectangular or square opening, the frame projection also extends around the opening in a correspondingly rectangular or square shape. The frame projection has a continuous cover surface. This cover surface can form a sealing surface against which the pivoting flap rests directly when the flap is pivoted into its closed position, in which it closes the shaft opening. In this closed position, the flap rests directly and airtight against the cover surface of the frame projection.

[0025] Alternatively, a circumferential recess or groove can be incorporated into the cover surface, forming a sealing seat for a separate, circumferential seal. When the separate seal is inserted into the sealing seat, it protrudes slightly beyond the cover surface of the frame projection, allowing the pivoting flap to seal airtight against this protrusion when it is pivoted into its closed position, where the flap closes the shaft opening. The separate seal can, for example, be an elastomer seal.

[0026] The filter housing may have a mounting frame that can be attached to the foam molding body, which, when attached, covers the hinge pins of the pivoting flap mounted in the foam molding body in order to prevent the hinge pins from radially loosening from the pin receptacles of the foam molding body.

[0027] If, as previously described, the bearing seats are formed by radially open pin receptacles molded into the foam body, and the hinge pins of the pivoting flap can be inserted radially into these receptacles relative to the pivot axis defined by the hinge pins, it must be ensured that the hinge pins of the pivoting flap, inserted radially into the pin receptacles, remain in their positions within the receptacles and do not spring back out radially. For this purpose, a mounting frame can be attached to the foam body, designed in such a way that it at least partially covers the radial cutouts of the pin receptacles when the pivoting flap is inserted, so that the hinge pins of the pivoting flap do not spring back out of the pin receptacles in an undesirable manner, for example, when the pivoting flap is swung into its closed position.The mounting frame attached to the foam molded body forms a form-fitting retaining device to hold the hinge pins in the pin receptacles.

[0028] The mounting frame can be detachably attached to the foam molding. This allows the mounting frame to be removed from the foam molding at any time, should the need arise. For example, the mounting frame can include one or more holes through which screws can be inserted, which can then be screwed directly into the foam molding. The screws can be designed, for example, as rigid foam anchors or insulation anchors.

[0029] The mounting frame can have a frame opening adapted to the shape of the pivoting flap, so that the flap can be pivoted from its closed position through the frame opening of the mounting frame into an open position, despite the mounting frame being attached to the foam molded body.

[0030] For this purpose, the mounting frame can, for example, have a window cutout whose shape and size are adapted to the shape and size of the opening in the housing part, in particular being at least the same size or at most slightly larger. The window cutout can also be designed in such a way that a filter component can be inserted into the shaft through the window cutout of the mounting frame or removed from the shaft through the window cutout of the mounting frame.

[0031] The mounting frame can also have a window opening, the shape and size of which may be adapted to the shape and size of the hinged flap itself. For example, the mounting frame can have a rectangular or square window opening that is slightly larger than the rectangular or square flap.

[0032] The mounting frame can have a protruding edge on an inner edge of the frame opening on one side opposite the hinge pins of the pivoting flap and the pin receptacles of the foam molding, which forms a counter-support for locking means of the pivoting flap.

[0033] To form the protruding edge, a recess, channel, or niche is molded into the foam body. This ensures that, when mounted, the mounting frame does not rest fully on the foam body, but rather a portion of the mounting frame remains exposed. The recess, channel, or niche of the foam body extends beneath the mounting frame, specifically in the area of ​​the inner edge of the mounting frame's opening, which is opposite the hinge pins of the pivoting flap or the pin receptacles of the foam body. Behind this protruding edge of the mounting frame, at least one locking element of the pivoting flap can engage positively when the flap is in its closed position. Possible embodiments of the at least one locking element of the pivoting flap are explained in more detail below.

[0034] The mounting frame can be detachably attached to the foam molded body using fasteners.

[0035] The mounting frame can therefore be detachably attached to the foam molding. This allows the mounting frame to be removed from the foam molding at any time, should this be necessary. For example, the mounting frame can include one or more holes through which screws can be inserted, which can then be screwed directly into the foam molding. The screws can be designed, for example, as rigid foam anchors or insulation anchors.

[0036] The pivoting flap may have at least one locking device on its front edge opposite the hinge pin of the pivoting flap, which, in the closed position of the pivoting flap, locks onto a counter-support of the foam molded body or the mounting frame in order to hold the pivoting flap in its closed position.

[0037] The locking device can have at least one locking hook. The locking hook can be connected to the surface section of the pivoting flap via a spring-elastic tongue section. The at least one locking hook and the spring-elastic tongue section can be made of a plastic material. The at least one locking hook and the spring-elastic tongue section can be manufactured together with the pivoting flap or the surface section of the pivoting flap as a single injection-molded plastic part. In this respect, the at least one locking hook and the spring-elastic tongue section can be integrally formed with the pivoting flap. The locking hook can have an inclined surface that is designed and arranged such that, during a closing movement of the pivoting flap, the inclined surface rests against an edge of the filter housing or the surface section of the pivoting flap.The locking tab engages with the housing part or, for example, with the projecting edge of the mounting frame. During the flap's pivoting movement, this pushes the locking hook away, thus pre-tensioning the elastic tongue section. When the pivoting flap is in its closed position, the locking hook engages behind the edge or projecting edge of the mounting frame as the elastic tongue section relaxes. The locking hook then positively locks the pivoting flap in its closed position. The elastic tongue section can be straight, U-shaped, or S-shaped.

[0038] In a simple design, the counter-support can be formed, for example, solely by an undercut in the housing part. This means that the counter-support can be formed by an undercut section of the housing part. Alternatively, the counter-support can be formed on a component separate from the housing part. Specifically, the counter-support can be integrated into the frame attachment. In this embodiment, the counter-support can be formed by an inner edge of a frame opening in the frame attachment. This inner edge does not lie flush with the housing part, but is undercut in the housing part; that is, the inner edge of the frame opening is designed as a projecting edge that can be positively engaged by the at least one locking hook when the pivoting flap is in its closed position.

[0039] The pivoting flap can have at least one retaining tab at its trailing edge in a central section between the two hinge pins. This tab is designed to press the flap against the seal when it is in the closed position. The seal can be formed solely by a circumferential cover surface of a frame projection on the housing part. This cover surface itself forms the sealing surface, i.e., the seal against which the pivoting flap rests when it is pivoted into its closed position, where it closes the opening of the shaft. In this closed position, the flap rests directly on the cover surface of the frame projection, creating an airtight seal.

[0040] Alternatively, a circumferential recess or groove can be incorporated into the cover surface, forming a sealing seat for a separate, circumferential seal. When the separate seal is inserted into the sealing seat, it protrudes slightly beyond the cover surface of the frame projection, allowing the pivoting flap to seal airtight against this protrusion when it is pivoted into its closed position, where the flap closes the shaft opening. The separate seal can, for example, be an elastomer seal.

[0041] The retaining tab ensures that the pivoting flap can be supported against the housing or mounting frame from below on the side of its trailing edge, i.e., along the longitudinal extent of the hinge pins, when the pivoting flap is in its closed position. This is particularly advantageous when the flap is made of a self-elastic material, such as plastic, which (without the retaining tab) would be prone to bulging in its plane, potentially compromising the airtight seal of the flap intended to close the shaft opening. The retaining tab provides support for the flap, especially in a particularly vulnerable central area, thus preventing unwanted bulging.When the flap is in its closed position, the retaining tab presses against the underside of the housing part or the mounting frame, thereby forcing the plane of the flap downwards towards the sealing seat. The retaining tab can be located, in particular, in a central region of the trailing edge between the two hinge pins and extend at least approximately or exactly in the plane of the flap on one side of the pivot axis opposite the flap.

[0042] The problem is also solved by a ventilation device with at least one ventilation duct and at least one fan connected to the ventilation duct in terms of flow technology for conveying air within the ventilation duct, comprising a filter housing coupled into the ventilation duct according to one of the described embodiments.

[0043] The filter housing can accordingly have a flow channel section which, from a fluid dynamics perspective, is connected on the inflow side to a ventilation duct of the ventilation device and on the outflow side to the ventilation duct of the ventilation device. The flow channel section also includes the shaft of the filter housing into which the filter element is inserted. In its installed state, the filter element is thus located in the flow channel section and is subjected to the air flowing through the ventilation duct of the ventilation device. The filter housing can accordingly have a first connection port to which a first ventilation duct section of the ventilation device can be connected, and a second connection port, preferably on the opposite side, to which a second ventilation duct section of the ventilation device can be connected.

[0044] Specific embodiments of the invention are explained in more detail in the following description with reference to the accompanying figures. Specific features of these exemplary embodiments can, regardless of the specific context in which they are mentioned, and optionally considered individually or in further combinations, represent general features of the invention.

[0045] They show: Fig. 1 an exploded view of an exemplary first embodiment of a filter housing according to the invention, Fig. 2 a perspective partial view of a housing part of the filter housing according to Fig. 1 in a unique position, Fig. 3 a perspective partial view of the housing part according to Fig. 2 and a swiveling flap when closed, Fig. 4 a partial sectional view through the pivoting flap in the area of ​​a locking means of the pivoting flap in engagement with a projecting edge of an attachment frame according to Fig. 1 in a rest position, Fig. 5 a partial sectional view through an assembly of filter housing, swiveling flap and mounting frame according to Fig. 1 in a closed position of the flap, Fig. 6 a perspective view of the pivoting flap according to Fig. 1 in a unique position, Fig. 7 a top view of the assembly of filter housing, pivoting flap and mounting frame according to Fig. 5 in the closed position of the flap, Fig. 8 an exploded view of an exemplary second embodiment of a filter housing according to the invention, Fig. 9 a perspective view of a housing part of the filter housing according to the second embodiment in isolation, Fig. 10 a perspective view of the pivoting flap according to the second embodiment in isolation, Fig. 11 a perspective view of a mounting frame according to the second embodiment in isolation, Fig. 12 a perspective view of the assembly of the filter housing and pivoting flap of the second embodiment in a closed position of the flap with the mounting frame removed, and Fig. 13 a sectional view of the assembly of filter housing and pivoting flap according to Fig. 12.

[0046] In the Fig. Figure 1 shows a filter housing 1 of a ventilation device in an exploded view.

[0047] The filter housing 1 has a housing part 2 which defines a shaft 4 accessible via an opening 3 of the housing part 2, into which a filter component 5 can be inserted in order to cover a flow channel of the ventilation device across its cross-section when the filter component 5 is inserted into the shaft 4.

[0048] The filter housing 1 has a seal 6 arranged around the opening 3.

[0049] The filter housing 1 also includes a cover 7 which, in its installed operating state, rests against the seal 6 and closes the opening 3 of the housing part 2.

[0050] The housing part 2 is designed as a foam molded body 2a, which has two bearing seats 8.1, 8.2 arranged on opposite sides of the opening 3.

[0051] The lid 7 has a hinge pin 9.1, 9.2 at each of its opposite ends to form a pivotable flap 7a, each hinge pin 9.1, 9.2 being designed for rotatable mounting in one of the bearing seats 8.1, 8.2 of the foam molded body 2a.

[0052] Since the housing part 2 of the filter housing 1 is designed as a foam molded body 2a, the filter housing 1 does not require thin-walled housing walls, in particular without thin-walled housing walls made of thermoplastic material or metal sheets. By designing the filter housing as a foam molded body 2a, particularly good noise reduction and thermal insulation are achieved. According to the invention, a thin-walled housing made of thermoplastic material or metal sheets can therefore be omitted.

[0053] The foam molded body 2a can be manufactured from polyethylene (PE) or polypropylene (PP) using a molding process. In this process, foam particles, such as expanded polystyrene (EPS), expanded polyethylene (EPE), or expanded polypropylene (EPP), can be sintered to form the housing part 2 of the filter housing 1.

[0054] In the present embodiment, the bearing seats 8.1, 8.2 are formed by radially open pin receptacles which are molded into the foam body 2a and into which the hinge pins 9.1, 9.2 of the pivotable flap 7a can be inserted radially to the pivot axis S determined by the hinge pins 9.1, 9.2.

[0055] In the case of the present embodiment according to Fig. 1 to Fig. 7 a frame projection 10 surrounding the opening 3 is formed on the foam molded body 2a, which forms a seat for the seal 6.

[0056] In the present embodiment, the filter housing 1 also comprises a mounting frame 11 which can be attached to the foam molded body 2a and which, in its attached state, covers the hinge pins 9.1, 9.2 of the pivotable flap 7a mounted in the foam molded body 2a in order to prevent the hinge pins 9.1, 9.2 from radially loosening from the pin receptacles 8.1, 8.2 of the foam molded body 2a.

[0057] The mounting frame 11 has a frame opening 12 adapted to the shape of the pivoting flap 7a ( Fig. 1) so that the flap 7a can be pivoted from its closed position through the frame opening 12 of the mounting frame 11 into an open position, despite the mounting frame 11 being attached to the foam molded body 2a.

[0058] As specifically in Fig. 4 shown in an enlarged partial view, the mounting frame 11 has an inner edge 13 on one of the hinge pins 9.1, 9.2 of the pivoting flap 7a and the pin receptacles 8.1, 8.2 of the foam molded body 2a opposite one of the hinge pins 9.1, 9.2 of the pivoting flap 7a and the pin receptacles 8.1, 8.2 of the foam molded body 2a ( Fig. 1) the frame opening 12 has a projecting edge 14a which forms a counter-support 14 for at least one locking means 15 of the pivotable flap 7a.

[0059] In the case of the illustrated embodiment of the Fig. 1 to Fig. The pivotable flap 7a has exactly two locking devices 15, as is particularly evident in Fig. 1 is recognizable.

[0060] In the present embodiments, the mounting frame 11 is detachably attached to the foam molded body 2a by means of fasteners 16. The fasteners 16 can, for example, be designed as rigid foam anchors or insulation anchors.

[0061] The pivotable flap 7a has locking means 15 on its leading edge opposite the hinge pins 9.1, 9.2 of the pivotable flap 7a. In the closed position of the pivotable flap 7a, these locking means engage with a counter-support 14 of the foam molded body 2a or the mounting frame 11 to hold the pivotable flap 7a in its closed position. In the present embodiments, the counter-support 14 is provided in the form of the projecting edge 14a on the mounting frame 11, as is shown in particular in Fig. 4 is shown.

[0062] The respective locking device 15 has a locking hook 17, which is connected to the surface section of the pivotable flap 7a via a spring-elastic tongue section 18. The locking hook 17 and the spring-elastic tongue section 18 can be made of a plastic material. In the present embodiments, the locking hook 17 and the spring-elastic tongue section 18 are manufactured together with the pivotable flap 7a or the surface section of the pivotable flap 7a as a single injection-molded plastic part. In this respect, the respective locking hook 17 and the associated spring-elastic tongue section 18 are integrally formed with the pivotable flap 7a. The locking hook 17 has an inclined surface 19, which is designed and arranged such that, during a closing movement of the pivotable flap 7a, the inclined surface 19 rests against an edge of the filter housing 1 or the surface section of the pivotable flap 7a.of the housing part 2 or, for example, at the projecting edge 14a of the mounting frame 11, whereby, during the pivoting movement of the flap 7a, the locking hook 17 is pushed away, i.e., the elastic tongue section 18 is pre-tensioned and, in a position where the pivoting flap 7a is in its closed position, the locking hook 17 engages behind the edge or behind the projecting edge 14a of the mounting frame 11 by the elastic tongue section 18 relaxing again. The locking hook 17 then holds the pivoting flap 7a positively in its closed position, as is the case, for example, in . Fig. Figure 4 shows the elastic tongue section 18 can be either straight, rib-shaped, S-shaped, or as shown in Fig. The design shown in section 4 is U-shaped.

[0063] In a simple embodiment, the counter-support 14 can, for example, be formed solely by an undercut in the housing part 2. This means that the counter-support 14 can be formed by an undercut section of the housing part 2. Alternatively, the counter-support 14 can be formed on a component separate from the housing part 2, as is the case in the present embodiments.

[0064] The counter-support 14 can thus be specifically formed on the frame attachment 11. In this embodiment, the counter-support 14 can be formed by an inner edge of the frame opening 12 of the frame attachment 11. This inner edge does not lie flush with the housing part 2, but is undercut in the housing part 2, i.e., the inner edge of the frame opening 12 is designed as a projecting edge 14a, which is positively engaged by the respective locking hook 15 when the pivotable flap 7a is in its closed position, as is the case in particular in Fig. 4 is shown.

[0065] As specifically in Fig. 5 and Fig. As shown in Figure 6, the pivotable flap 7a can have at least one retaining tab 20 at its rear edge in a central section between the two hinge pins 9.1, 9.2, which is formed in the closed position of the pivotable flap 7a ( Fig. 5) Press the flap 7a against the seal 6.

[0066] The retaining tab 20 ensures that the pivoting flap 7a can be supported from below against the mounting frame 11 on the side of its trailing edge, i.e., along the longitudinal extent of the hinge pins 9.1, 9.2, when the pivoting flap 7a is in its closed position. This is particularly advantageous when the flap 7a is made of a self-elastic material, such as plastic, which (without the retaining tab) would create the risk of the flap 7a bulging in its plane, potentially compromising the airtight seal of the flap 7a, which is intended to close the opening 3 of the shaft 4. Due to the retaining tab 20, the flap 7a is supported, particularly in a critical central area, thus preventing unwanted bulging. When the flap 7a is in its closed position ( Fig.5) The retaining tab 20 presses against an underside of the mounting frame 11, which in turn pushes the plane of the flap 7a downwards towards the seal 6. The retaining tab 20 can, as shown, be located in a central region of the trailing edge between the two hinge pins 9.1, 9.2 and extend at least approximately or exactly in the plane of the flap 7a on one side of the pivot axis S opposite the flap 7a.

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