INDOOR AIR EXCHANGE ASSEMBLY COMPRISING A PRESSED-FIBRE AIR GUIDE AND METHOD FOR MANUFACTURING PRESSED-FIBRE AIR GUIDE

Abstract

 An indoor air exchange assembly for a reversible-flow ventilation unit comprises a wall mount (28) configured to be attached to an indoor wall face extending in a wall plane, the wall mount (28) comprising an air duct interface (32a); and a cover configured to be held by the wall mount (28), the cover comprising a pressed-fibre air guide (40) having a proximal side configured to face said indoor wall face (30) and a distal side configured to face away from said indoor wall face (30), the proximal side of the pressed-fibre air guide (40) defining an elongate airflow channel (52) extending parallel to the wall plane (P) from the air duct interface (32a) to a ventilation orifice (54).

Description

Field of the invention

[0001] The present invention relates to a reversible-flow ventilation unit, an indoor air exchange assembly for a reversible-flow ventilation unit, a pressed-fibre air guide for an air exchange assembly, and a method of manufacturing such a pressed-fibre air guide.

Background

[0002] In order to save energy in residential buildings, combined exhaust and supply air ventilation systems, with energy recovery between the supply air and the exhaust air in a centralized heat exchanger, have become increasingly popular. Such systems are large and complicated, and may not be well suited for compact installations and/or ventilation upgrades in old buildings.

[0003] EP3943830A1 relates to an alternative, decentralized arrangement, wherein exhaust of air, i.e. moving of air from indoors to outdoors, is time-duplexed with supply of air, i.e. moving air from outdoors to indoors. Each such reversible-flow ventilation unit contains a reversible fan that alternatingly changes direction of the airflow every 70 seconds, thereby periodically alternating between supplying fresh outdoor air and exhausting spent indoor air. An integrated thermal accumulator receives and stores heat from exhaust air during the exhaust cycle, and returns the heat to the supply air during the supply cycle. The ventilation unit comprises an air duct passing straight through the wall, and incorporates all necessary components along a simple, straight flow path.

[0004] There are many design considerations of reversible-flow ventilation units. Preferably, a reversible-flow ventilation unit should be silent and energy-efficient. At the same time, it should be sized and shaped to enable retrofit installation in existing buildings, where space may be limited and no designated position has been reserved for it at construction of the building. Cost also needs to be kept sufficiently low to justify an energy-saving upgrade. Unfortunately, some of those design considerations may conflict with each other.

Summary

[0005] It is an object of the present invention to solve, or at least mitigate, parts or all of the above mentioned problems. To this end, according to a first aspect there is provided an indoor air exchange assembly for a reversible-flow ventilation unit, the indoor air exchange assembly comprising a wall mount configured to be attached to an indoor wall face extending in a wall plane, the wall mount comprising an air duct interface; and a cover configured to be held by the wall mount, the cover comprising a pressed-fibre air guide having a proximal side configured to face said indoor wall face and a distal side configured to face away from said indoor wall face, the proximal side of the pressed-fibre air guide defining an elongate airflow channel extending parallel to the wall plane from the air duct interface to a ventilation orifice. Such a cover transmits very little of any noise emanating from the air duct or generated in the airflow channel. According to embodiments, the airflow channel is shaped as a blind channel extending from the air duct interface to the ventilation orifice. The airflow channel may extend along a single airflow path.

[0006] According to embodiments, the proximal side of the pressed-fibre air guide, adjacent to the air duct interface, may comprise an airflow deflector having the general shape of a half-dome. Such an airflow deflector enables deflecting air from a flow direction substantially perpendicular to the wall plane, determined by a ventilation duct extending through the wall, to a flow direction substantially parallel to the wall plane, and vice versa, with low turbulence and noise.

[0007] According to embodiments, the distal side of the pressed-fibre air guide may have the shape of a developable surface. Such a shape facilitates applying outer functional layers directly onto the pressed-fibre air guide at a low cost and complexity. By way of example, the distal side may have a prismatic shape. The generatrix of the prismatic shape may follow e.g. a gradually curved path, to define e.g. a cylindrical shape having a half-oval cross-section.

[0008] According to embodiments, a length/width ratio, of a length and width of the airflow channel in a plane parallel to the wall plane, is greater than 1.4; even more preferably, the length/width ratio may be between 1.5 and 2.3.

[0009] According to embodiments, the elongate airflow channel may have a maximum width, parallel to the wall plane and perpendicular to the flow direction, of between 140 mm and 190 mm. Alternatively or additionally, it may have a length along its longitudinal direction, parallel to the wall plane, of between 240 mm and 370 mm. It may have a typical maximum width perpendicular to the wall plane of between 30 mm and 70 mm.

[0010] Preferably, the pressed-fibre air guide defines an airflow channel wall with a wall thickness of more than 10 mm. Preferably, at least at some section of the airflow channel wall, the wall thickness exceeds 15 mm, and even more preferred, 20 mm. According to embodiments, the pressed-fibre air guide may have a non-uniform wall thickness. Thereby, the airflow channel may be shaped independently of the distal side of the pressed-fibre air guide, which facilitates obtaining a silent and energy-efficient airflow channel in combination with a simple and attractive exterior, distal, face of the indoor air exchange assembly.

[0011] According to embodiments, the pressed-fibre air guide may have a total width, parallel to the wall plane and perpendicular to the flow direction, of between 160 mm and 230 mm. Alternatively or additionally, it may have a total length, parallel to the wall plane and along the longitudinal direction of the airflow channel, of between 230 mm and 400 mm. It may have a typical total with perpendicular to the wall plane of between 55 mm and 110 mm.

[0012] The shape and dimensions of the entire indoor air exchange assembly may be governed by the outer shape and dimensions of the pressed-fibre air guide. Hence, similarly, the indoor air exchange assembly may have a total width, parallel to the wall plane and perpendicular to the flow direction, of between 170 mm and 240 mm. Alternatively or additionally, it may have a total length, parallel to the wall plane and along the longitudinal direction of the airflow channel, of between 230 mm and 400 mm. It may have a typical total with perpendicular to the wall plane of between 70 mm and 120 mm.

[0013] According to embodiments, the pressed-fibre material of the pressed-fibre air guide may comprise a base fibre impregnated with a binding agent. Preferably, the base fibre of the pressed-fibre material of the pressed-fibre air guide is mineral wool, such as glass wool, rock wool or a combination thereof. Alternatively, the base fibre may be any other suitable refractory fibre, natural fibre such as cellulose or wool, polymer fibre such as polyester fibre or synthetic bicomponent fibre, or a combination thereof. Preferably, the binding agent is organic; for example, it may comprise a thermoplastic and/or a thermosetting polymer. According to embodiments, the pressed-fibre material comprises between 0,75% and 4% of binding agent by weight.

[0014] According to embodiments, the pressed-fibre air guide may comprise, on its proximal side, a liner fabric joined with the pressed fibre material of the pressed-fibre air guide. The liner fabric may serve to stabilize and/or smooth the surface of the proximal side, e.g. to obtain a more laminar airflow with reduced sound emission, and/or facilitate handling. Preferably, the liner fabric is non-woven, e.g. felt. Such a liner fabric may conveniently be cut to shape, and does not require any further treatment prior to joining. An exemplary suitable material of the liner fabric is polyester. According to embodiments, the liner fabric is joined with the pressed fibre material of the pressed-fibre air guide by pressing under the application of heat; this may be done in the same process step as that for shaping the pressed-fibre air guide. According to embodiments, also the distal side may be provided with a layer of liner fabric for grooming the surface, thereby e.g. increasing the adhesion of any outer layer, such as a sound-deadening mass sheet layer. Alternatively, the pressed-fibre material of the pressed-fibre air guide may be exposed on the distal side.

[0015] According to embodiments, the cover may comprise a curved sound-deadening mass sheet layer on a distal side of the pressed-fibre air guide. The sound-deadening mass sheet layer may, for example, be a bitumen sheet. The sound-deadening mass sheet layer may be configured as an adhesive film applied directly to the pressed-fibre air guide.

[0016] According to embodiments, the cover may comprise a trim sheet on a distal side of the pressed-fibre air guide. The trim sheet may also, as the case may be, be positioned on the distal side of any sound-deadening mass sheet layer and/or liner fabric on the distal side of the pressed-fibre air guide. The trim sheet may form the distal-most face of the indoor air exchange assembly, thereby making it possible to obtain any desired character of the surface visible from the interior of the building. The trim sheet may, for example, comprise an outer layer of plastic or wood veneer.

[0017] According to embodiments, the indoor air exchange assembly may further comprise an air filter holder configured to hold a replaceable air filter outside the wall face. Thereby, air drawn from outdoors may be efficiently filtered, and the effective filter area may be maximized.

[0018] The pressed-fibre air guide may be attached directly to the wall mount. Alternatively, according to embodiments, the cover may further comprise a cover frame holding the pressed-fibre air guide. The cover frame may be made of e.g. sheet metal. According to embodiments, the pressed-fibre air guide may be held on a distal side of the cover frame. The cover may further comprise a rim support plate covering the pressed-fibre air guide rim which defines the ventilation orifice. The rim support plate may be an integral part of the cover frame, or separate therefrom. The cover may further comprise an end cover plate covering the end of the pressed-fibre air guide which is opposite to the ventilation orifice. The end cover plate may be an integral part of the cover frame, or separate therefrom.

[0019] According to embodiments, the pressed-fibre air guide may be fixedly confined by the cover frame against movement along at least one direction, for example along the direction of the elongate airflow channel.

[0020] According to embodiments, the cover, along with any cover frame thereof as the case may be, may be movable in relation to the wall mount for access to the air filter holder. Such an arrangement facilitates replacing the air filter. According to further embodiments, the cover frame may be configured to be pivotally connected to the wall mount. Thereby, the cover frame may be conveniently pivoted away from the wall mount to expose the air filter without complicated disassembly. According to embodiments, the pivotal connection may be arranged adjacent to a top edge of the cover frame, and the pivot axis of the cover frame may be substantially horizontal. Thereby, the cover will be biased towards the wall mount by gravity and keep the air filter in place. According to embodiments, the cover frame may be unhingeable from the wall mount without use of tools. By way of example, the pivotal connection may be defined by a set of tabs integrally formed with one of the cover frame and the wall mount, the set of tabs being in register with a set of mating slots formed in the other of the cover frame and the wall mount.

[0021] According to embodiments, the cover frame may be drawn to the wall mount by a magnet. Thereby, the air filter may be easily accessed by pulling the cover away from the wall mount using a force exceeding the attraction force of the magnet.

[0022] According to embodiments, the trim sheet may be attached to the cover frame. The pressed-fibre air guide may be held between the cover frame and the trim sheet. Thereby, the pressed-fibre air guide will be protected from mechanical wear from both the distal side and the proximal side.

[0023] According to embodiments, the trim sheet may be interlocked with the cover frame. An integral mechanical attachment defined by a direct interlock between the trim sheet and the cover frame facilitates producing the indoor air exchange assembly at a low cost. The interlock may be e.g. an elastic interlock, which may facilitate assembly.

[0024] According to embodiments, the cover may comprise a ferromagnetic rim enclosing the ventilation orifice, and the indoor air exchange assembly may further comprise a magnetic lid configured to be magnetically attached to the ferromagnetic rim to cover the ventilation orifice. The ferromagnetic rim may be defined by a rim support plate, which may be an integral part of the cover frame, or separate therefrom.

[0025] According to a second aspect, there is provided a reversible-flow ventilation unit comprising a ventilation duct configured to be installed through a building wall to extend between an indoor wall face and an outdoor wall face; a reversible fan configured to be positioned within the ventilation duct; a heat exchanger configured to be positioned within the ventilation duct; an outdoor air exchange unit configured to be mounted on the outdoor wall face; and an indoor air exchange assembly as defined in any of the appended claims, or in any of the further exemplary embodiments hereinabove. Typically, the ventilation duct may be straight. It may typically have a length of between 15 cm and 50 cm.

[0026] According to a third aspect, there is provided a method of manufacturing a pressed-fibre air guide for an air exchange assembly, the method comprising: providing a mould press comprising a first moulding tool and a second moulding tool; positioning a sheet of fibre material in a moulding cavity of the mould press, the fibre material comprising a base fibre impregnated with a binding agent; positioning a sheet of liner fabric in the moulding cavity of the mould press; pressing the first and second moulding tools together to compress the sheet of fibre material, thereby compressing and shaping the sheet of fibre material to a pressed-fibre air guide defining a blind channel of essentially U-shaped cross-section; and heating the mould press to bind the binding agent, thereby joining the compressed sheet of fibre material with the liner fabric, and stabilizing the shape of the pressed-fibre air guide. Thereby, a highly silencing pressed-fibre air guide of a well-defined and stable shape, which is sufficiently rigid to be self-supporting, which is easy to handle, and which generates a low flow resistance, can be obtained. The mould press can be heated prior to or after positioning the sheet of fibre material in the moulding cavity. Preferably, the base fibre of the pressed-fibre material of the pressed-fibre air guide is mineral wool, such as glass wool, rock wool or a combination thereof. Alternatively, the base fibre may be any other suitable refractory fibre, natural fibre such as cellulose or wool, polymer fibre such as polyester fibre or synthetic bicomponent fibre. Preferably, the binding agent is configured to cure at an elevated temperature. The binding agent may be organic; for example, it may comprise a thermoplastic and/or a thermosetting polymer resin. In the case of a thermoplastic binding agent, it may be preferable to allow the mould to cool prior to removing the pressed-fibre air guide from the mould. According to embodiments, the pressed-fibre material may comprise between 0,75% and 4% of binding agent by weight. Preferably, the liner fabric is non-woven, e.g. felt. Such a liner fabric may conveniently be cut to shape, and does not require any further treatment prior to joining. An exemplary suitable material of the liner fabric is polyester. The mould press may, according to embodiments, be heated to a temperature within the range 150°C to 210°C. According to embodiments, the mould press may be heated by an integrated heating element, which may be controlled based on feedback from an integrated temperature sensor. According to embodiments, the first and second moulding tools may be made of aluminium or an aluminium-based alloy; the high thermal conductivity of aluminium may shorten the cycle time. The moulding face of at least one of the moulding tools may be provided with a layer of fluoropolymer. The pressed-fibre air guide may be adapted for an air exchange assembly of a ventilation unit of, for example, the reversible-flow type defined hereinabove. The pressed-fibre air guide may be shaped to be positioned in an indoor or outdoor air exchange assembly.

[0027] According to a fourth aspect, there is provided a pressed-fibre air guide manufactured with the method defined above. Such a pressed-fibre air guide can be used in an indoor air exchange assembly as defined hereinabove, or alternatively, in an outdoor air exchange unit configured to be mounted on an outdoor wall face, for example in a reversible-flow ventilation unit as described herein.

[0028] According to a more general, fifth, aspect, there is provided an air exchange assembly configured to be attached to a wall face, the air exchange assembly comprising: an air duct interface configured to receive and/or supply an air flow from and/or to an air duct in a wall; a pressed-fibre air guide having a proximal side configured to face the wall and a distal side configured to face away from the wall, the proximal side of the pressed-fibre air guide defining an elongate airflow channel extending along the wall from the air duct interface to a ventilation orifice; and a cover enclosing the distal side of the pressed-fibre air guide. Such an air exchange assembly transmits very little noise between the indoor environment and the outdoor environment, and dampens any noise emanating from the air duct or generated in the airflow channel. The air exchange assembly may be an indoor air exchange assembly or an outdoor air exchange assembly. The fifth aspect, or any embodiment thereof, may form the basis of one or several divisional applications.

[0029] It is noted that embodiments of the invention may be embodied by all possible combinations of features recited in the claims. Further, it will be appreciated that the various optional features described for the pressed-fibre air guide of the indoor air exchange assembly of the first aspect are all combinable with the method of the third aspect, and/or with the pressed-fibre air guide as defined separately in the fourth aspect, and vice versa. Similarly, the various optional features described for the indoor air exchange assembly of the first aspect are all combinable with the fifth, more general aspect described hereinabove.

Brief description of the drawings

[0030] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and nonlimiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

Fig. 1 is an exploded view of a reversible-flow ventilation unit;

Fig. 2 is an exploded view of an indoor air exchange assembly of the reversible-flow ventilation unit of Fig. 1, as seen from a first perspective, to be mounted on an indoor wall face;

Fig. 3 is an exploded view of the indoor air exchange assembly of Fig. 2 as seen from a second perspective;

Fig. 4 is a perspective view of the indoor air exchange assembly of Figs 2 and 3 in a partly open position, illustrating the installation of an air filter;

Fig. 5A is a perspective view of a press mould, a sheet of fibre material and a sheet of liner fabric in a first method step of manufacturing a pressed-fibre air guide of the indoor air exchange assembly of Figs 2-4;

Fig. 5B is a perspective view of the press mould of Fig. 5A during removal of the pressed-fibre air guide after manufacture;

Fig. 6 is a flow chart illustrating the method of manufacturing the pressed-fibre air guide of Fig. 5B;

Fig. 7A is a section, illustrated in perspective, of the pressed-fibre air guide of Fig. 5B, the section taken in a plane perpendicular to the wall face of Fig. 2 and parallel to a longitudinal direction of the pressed-fibre air guide; and

Fig. 7B is a section of the pressed-fibre air guide of Fig. 5B taken in a plane parallel to the wall face of Fig. 2.

[0031] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted.

Detailed description of the exemplary embodiments

[0032] Fig. 1 illustrates a reversible-flow ventilation unit 10 comprising a straight ventilation duct 12 of circular cross-section, configured to be installed through a building wall (not illustrated) to extend in a longitudinal direction L between an indoor wall face and an outdoor wall face. A typical inner diameter of the duct may be e.g. between 140 mm 200 mm, and most typically, between 150 mm and 160 mm. The reversible-flow ventilation unit 10 further comprises a reversible fan 14 and a heat exchanger 16, both of which are configured to be positioned with the ventilation duct 12, an outdoor air exchange unit 18 configured to be mounted on the outdoor wall face, and an indoor air exchange assembly 20 configured to be attached to the indoor wall face. The heat exchanger 16 is of thermal accumulator type, and comprises a mesh 22 of heat exchange channels 24 of metal, extending along the longitudinal direction L, to exchange heat with air passing therethrough. In the illustrated example, the heat exchange channels 24 are of honeycomb shape. A controller 26 controls the fan to alternatingly operate in a supply direction, blowing air from the outdoor air exchange unit 18 to the indoor air exchange assembly 20, and in an exhaust direction, blowing air from the indoor air exchange assembly 20 to the outdoor air exchange unit 18. A typical operation time of the fan 14 between reversals may be e.g. between 30 and 180 seconds. The heat exchanger 16 receives and stores heat from exhaust air during the exhaust cycle, and returns the heat to the supply air during the supply cycle. The indoor air exchange assembly 20 has a proximal end 20a, closest to the wall, and a distal end 20b furthest away from the wall.

[0033] The exploded view of Fig. 2 illustrates the indoor air exchange assembly 20 in greater detail. The indoor air exchange assembly 20 comprises a wall mount 28 configured to be attached to the indoor wall face 30, which extends in a wall plane P. The wall mount may be made of e.g. sheet metal. An inner circular air duct interface 32a of the wall mount 28 is shaped and positioned to be in register with the air duct 12 when the wall mount 28 is attached to the wall face 30. The inner air duct interface 32a may have any other suitable shape, and does not need to have the same size and shape as the air duct 12; however, a shape of the inner air duct interface 32a which mates with the air duct 12 may guide the user to correctly position the wall mount 28 in relation to the air duct 12. The wall mount 28 is cut and folded from a single piece of steel sheet, and may be attached to the wall face 30 by screws (not illustrated) via a set of screw holes 34.

[0034] The indoor air exchange assembly 20 further comprises a cover 36, which is made up of a plurality of parts. The cover 36 comprises a cover frame 38 cut and folded from a single piece of steel sheet, which operates as a support frame holding the other parts of the cover 36. The cover frame 38 comprises an outer air duct interface 38b, which is in register with the inner air duct interface 32a of the wall mount 28, as well as with the air duct 12. Again, however, the outer air duct interface 32b does not need to have the same size and shape as the air duct 12 or the inner air duct interface 32a. The cover further comprises a pressed-fibre air guide 40, which is held in the cover frame 38 on a distal side thereof. For the purpose, the cover frame 38 comprises an end cover plate 38a, which vertically supports the pressed-fibre air guide 40 and, opposite to the end cover plate 38a, a rim support plate 38b, which covers the top face of the pressed-fibre air guide 40. The pressed-fibre air guide is sufficiently rigid to be self-supporting; hence, the cover frame 38, with the end cover plate 38a and the rim support plate 38b, is optional. A distal side of the pressed-fibre air guide 40, i.e. the side facing away from the indoor wall face 30, is covered by a sound-deadening mass sheet 42 of bitumen, which is attached to the pressed-fibre air guide 40 by an adhesive film. A rigid, outer trim sheet 44 is attached to the cover frame 38, and locks the pressed-fibre air guide 40 with its sound-deadening mass sheet 42 within the cover frame 38. The outer trim sheet 44 may be made of e.g. sheet metal, wood or plastic. The distal face of the pressed-fibre air guide 40 is shaped as a developable surface, and more precisely, is shaped as the mantle face of a cylinder having an approximately oval cross-section. Thereby, both the sound-deadening mass sheet 42 and the outer trim sheet 44 can be formed of a respective single sheet of material.

[0035] The wall mount 28 comprises a set of flanges 28a, 28b, 28c folded to define an air filter holder 46 on the distal face of the wall mount 28. An air filter 48 fits in the air filter holder 46, and covers the inner and outer air duct interfaces 32a, 32b. Outdoor air blown from the air duct 12 by the fan 14 will be cleaned by the air filter 46 prior to entering building via the cover 36. Thanks to positioning the filter outside the duct 12, the entire cross-section of the duct 12 is covered by filter material, with no need for a filter frame within the duct cross-section. Thereby, the airflow is maximized, and energy consumption, turbulence and sound are minimized. The air filter 48 is held in place within the air filter holder 46 by the proximal face of the cover frame 38, and is squeezed between the wall mount 28 and the cover frame 38. For the purpose, the top of the cover frame is configured to be mechanically connected to the top of the wall mount 28 in a movable manner. The respective bottom ends of the wall mount 28 and the cover frame 38 are held together by magnet 50.

[0036] Now with reference to Fig. 3, the proximal side of the pressed-fibre air guide 40, i.e. the side facing the wall 30 (Fig. 2), defines an elongate airflow channel 52 extending parallel to the wall plane P (Fig. 2) from the position of the inner and outer air duct interfaces 32a, 32b to a ventilation orifice 54. The indoor air exchange assembly 20 may be installed in a preferred orientation wherein the airflow channel 52 extends vertically upwards from the air duct 12. The airflow channel 52 is shaped as a blind channel extending in a single direction, along a single flow path, from the position of the inner and outer air duct interfaces 32a, 32b to the ventilation orifice 54. Air arriving along the longitudinal direction L of the duct 12 (Fig. 2), via the first and second air duct interfaces 32a, 32b, is deflected by an airflow deflector 52a having the general shape of a half-dome, and is then guided along a straight section 52b of the airflow channel 52 parallel to the wall plane P in an air exchange direction E along which the air is expelled to, or extracted from, the room which is served by the reversible-flow ventilation unit 10 (Fig. 1). Obviously, when the fan 14 (Fig. 1) is operated in the reverse direction, the airflow illustrated by the arrow A is reversed. The pressed-fibre air guide 40 reduces noise leakage from the fan 14 (Fig. 1) in the direction through the cover, while its extent along the distance defined by the elongate airflow channel 52 from the inner and outer air duct interfaces 32a, 32b to the ventilation orifice 54 reduces noise leakage from the fan 14 along the airflow channel 52. The aerodynamic shape of the airflow deflector 52a also minimizes any noise generated by turbulence.

[0037] A magnified portion of the cover frame 38 illustrates, inter alia, a connection interface for connecting the top of the cover frame 38 to the wall mount 28 in a pivotal manner. The cover frame 38 comprises a set of tabs 56a, 56b, which are shaped to fit in mating notches 58 at the top of the flanges 28a, 28c of the wall mount 28. When connected, the mating tabs 56a, 56b and notches 58a, 58b operate as a hinge, enabling the cover 20 to pivot about a hinge axis H. This is illustrated in Fig. 4.

[0038] The magnified portion of the cover frame 38 in Fig. 3 also illustrates the attachment interface for attaching the cover trim 44 to the cover frame 38. The attachment interface is defined by a pair of elongate attachment flanges 60a, 60b extending along the air exchange direction E; in the view of Fig. 3, only a first attachment flange 60a is fully visible, but it will be appreciated that the second attachment flange 60b is arranged in a mirrored configuration along the opposite longitudinal side edge of the cover frame 38. An inner face of the cover trim 44 is provided with a pair of elongate attachment grooves 62a, 62b, which are shaped to receive the attachment flanges 60a, 60b of the cover frame 38 in an interlocking manner. Again, only one of the attachment grooves 62a, 62b, and more precisely the attachment groove 62b configured to interlock with the second attachment flange 60b, is fully visible in the view of Fig. 3, whereas it will be appreciated that the other attachment groove 62a is arranged in a mirrored configuration along the opposite side of the cover trim 44. The cover trim 44 is attached to the cover frame 38 by pressing longitudinal edges 44a, 44b of the cover trim 44 slightly away from each other against an intrinsic bias of the cover frame 44, and allowing the edges to elastically relax back towards their unbiased position with the attachment flanges 60a, 60b in their respective attachment grooves 62a, 62b.

[0039] A flexible sheet of magnetic material defines a magnetic lid 64 configured to be magnetically attached to the rim support plate 38b, which is ferromagnetic due to being made of steel sheet. The magnetic lid 64 can be used for covering the ventilation orifice 54 in case of e.g. chemical or nuclear disasters; when not in used, it can be stored attached to the steel sheet of e.g. the wall mount 28 or the cover frame 38, as schematically illustrated by broken lines in Fig. 2.

[0040] Fig. 4 illustrates how the air filter 48 may conveniently be installed or replaced. The cover 38 is pivoted about hinge axis H in the direction illustrated by the large arrow, away from the wall mount 28, to expose the air filter holder 46. Thereby, the air filter 48 may be inserted into the air filter holder 46 from below. After positioning the air filter 48 in the air filter holder 46, the cover 36 may be pivoted back, against the direction of the arrow, such that the cover frame 38 snaps into magnetic engagement with the magnet 50 held by the wall mount 28.

[0041] Figs 5A and 5B illustrate the manufacture of the pressed-fibre air guide 40 (Fig. 2); the method is also illustrated in the flow chart of Fig. 6.

[0042] Starting with Fig. 5A, in step 601, a mould press 66 comprising a first moulding tool 66a and a second moulding tool 66b is provided. The moulding tools 66a, 66b are made of aluminium, and are provided with integrated heating elements (not illustrated) controlled based on feedback from an integrated temperature sensor (not illustrated). The first and second moulding tools 66a, 66b define a moulding cavity 68 between them, and the moulding faces of the moulding tools 66a, 66b, i.e. the surfaces of the moulding tools 66a, 66b which define the moulding cavity 68, are coated with a layer of non-stick fluoropolymer.

[0043] In step 602, a sheet of airy fibre material 70 is inserted in the moulding cavity 68. The sheet of fibre material 70 comprises a base fibre of mineral wool, which is impregnated with about 2% by weight of a binding agent configured to cure at an elevated temperature, for example a thermosetting polymer resin. A typical thickness t of the sheet of fibre material 70 may be between 50 mm and 150 mm.

[0044] In step 603, a sheet of liner fabric 72 is positioned in the moulding cavity 68. The liner fabric 72 may be e.g. a non-woven polyester fabric.

[0045] In step 604, the first and second moulding tools 66a, 66b are pressed together in the direction of the arrow to compress the sheet of fibre material 70, thereby pressing the sheet of fibre material 70 into the shape of the pressed-fibre air guide 40 of Figs 2-3.

[0046] In step 605, the mould press 66 is heated to about 180°C to cure the binding agent, thereby stabilizing the shape of the sheet of fibre material 70 and joining the fibre material 70 of the pressed-fibre air guide 40 with the liner fabric 72.

[0047] Turning now to Fig. 5B, in step 606, the first and second moulding tools 66a, 66b are drawn apart, and the pressed-fibre air guide 40, formed by the sheet of fibre material 70 (Fig. 5A) and the sheet of liner fabric 72 (Fig. 5A), is removed from the moulding cavity 68 of the press mould 66.

[0048] Fig. 7A illustrates a section of the pressed-fibre air guide 40, the section taken in a plane perpendicular to the wall plane P (Fig. 2), and parallel to the extraction direction E (Fig. 3). The pressed-fibre air guide 40 has a total length L1, parallel to the wall plane and along the longitudinal direction of the airflow channel, i.e. along the extraction direction E, of about 300 mm, and the airflow channel 52 defined therein has a length L2, in the same direction, of about 270 mm. As pointed out hereinabove, the airflow channel 52 comprises an airflow deflector 52a having the general shape of a half-dome, and between the airflow deflector 52a and the ventilation orifice 54, a straight section 52b. The surface of the airflow channel 54 is defined by the liner fabric 72, whereas on most of the remaining surface of the pressed-fibre element, the pressed-fibre material is exposed.

[0049] Fig. 7B illustrates a section of the pressed-fibre air guide 40 taken in a plane parallel to the wall plane P (Fig. 2). As apparent from Fig. 7B, the pressed-fibre air guide 40 has a substantially U-shaped cross-section. The pressed-fibre air guide has a total width W1, parallel to the wall plane and perpendicular to the flow direction along the straight section 52b (Fig. 3) of the airflow channel 52, of about 185 mm, and a total width W2 perpendicular to the wall plane of about 65 mm. Similarly, the airflow channel 52 has, at its widest position, a width W3, parallel to the wall plane and perpendicular to the flow direction, of about 155 mm, and a width W4 perpendicular to the wall plane of about 40 mm. The pressed-fibre air guide 40 defines an airflow channel wall 40a with a minimum wall thickness T of about 15 mm, whereas at most positions, the wall thickness exceeds 20 mm. The length/width ratio L2/W3, of the length L2 and width W3 of the airflow channel in a plane parallel to the wall plane P (Fig. 2), is about 1.8.

[0050] The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. For example, the pressed-fibre air guide 40 need not be configured as a single, integrally formed body; alternatively, it may consist of several separate pressed-fibre elements which are positioned adjacent to each other. The indoor air exchange assembly 20 has been described and illustrated as being mounted to the wall face 30 with the ventilation orifice 54 facing upwards. However, the indoor air exchange assembly 20 may be mounted with the ventilation orifice facing in any other suitable direction, such as sideways or downwards.

[0051] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

1. An indoor air exchange assembly (20) for a reversible-flow ventilation unit (10), comprising

a wall mount (28) configured to be attached to an indoor wall face (30) extending in a wall plane (P), the wall mount (28) comprising an air duct interface (32a); and

a cover (36) configured to be held by the wall mount (28), the cover (36) comprising a pressed-fibre air guide (40) having a proximal side configured to face said indoor wall face (30) and a distal side configured to face away from said indoor wall face (30), the proximal side of the pressed-fibre air guide (40) defining an elongate airflow channel (52) extending parallel to the wall plane (P) from the air duct interface (32a) to a ventilation orifice (54).

2. The indoor air exchange assembly (20) according to claim 1, wherein the proximal side of the pressed-fibre air guide (40), adjacent to the air duct interface (32a), comprises an airflow deflector (52a) having the general shape of a half-dome.

3. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the distal side of the pressed-fibre air guide (40) has the shape of a developable surface.

4. The indoor air exchange assembly (20) according to any of the preceding claims, wherein a length/width ratio (L2/W3), of a length (L2) and width (W3) of the airflow channel (52) in a plane parallel to the wall plane (P), is greater than 1.4.

5. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the pressed-fibre material of the pressed-fibre air guide (40) comprises a base fibre impregnated with a binding agent.

6. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the pressed-fibre air guide (40) comprises, on its proximal side, a liner fabric (72) joined with the pressed fibre material of the pressed-fibre air guide (40).

7. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the cover (36) comprises a curved sound-deadening mass sheet layer (42) on a distal side of the pressed-fibre air guide (40).

8. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the cover (36) comprises a trim sheet (44) on a distal side of the pressed-fibre air guide (40) and, as the case may be, of any sound-deadening mass sheet layer (42) and/or liner fabric (72) on the distal side of the pressed-fibre air guide (40).

9. The indoor air exchange assembly (20) according to any of the preceding claims, further comprising an air filter holder (46) configured to hold a replaceable air filter (48) outside the wall face (30).

10. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the cover (36) further comprises a cover frame (38) holding the pressed-fibre air guide (40).

11. The indoor air exchange assembly (20) according to the combination of claims 9 and 10, wherein the cover frame (38) is movable in relation to the wall mount (28) for access to the air filter holder (46).

12. The indoor air exchange assembly (20) according to any of the claims 10-11, wherein the cover frame (38) is configured to be pivotally connected to the wall mount (28), and/or the cover frame (38) is drawn to the wall mount (28) by a magnet (50).

13. The indoor air exchange assembly (20) according to the combination of claim 8 with any of the claims 10-12, wherein the trim sheet (44) is attached to the cover frame (38), and wherein optionally, the trim sheet (44) is interlocked with the cover frame (38).

14. The indoor air exchange assembly (20) according to any of the preceding claims, wherein the cover (36) comprises a ferromagnetic rim (38b) enclosing the ventilation orifice (54), and the indoor air exchange assembly (20) further comprises a magnetic lid (64) configured to be magnetically attached to the ferromagnetic rim (38b) to cover the ventilation orifice (54).

15. A method of manufacturing a pressed-fibre air guide (40) for an air exchange assembly (20), the method comprising:

providing a mould press (66) comprising a first moulding tool (66a) and a second moulding tool (66b);

positioning a sheet of fibre material (70) in a moulding cavity (68) of the mould press (66), the fibre material (70) comprising a base fibre impregnated with a binding agent;

positioning a sheet of liner fabric (72) in the moulding cavity (68) of the mould press (66);

pressing the first and second moulding tools (66a, 66b) together to compress the sheet of fibre material (70), thereby compressing and shaping the sheet of fibre material (70) to a pressed-fibre air guide (40) defining a blind channel (52) of essentially U-shaped cross-section; and

heating the mould press (66) to bind the binding agent, thereby joining the compressed sheet of fibre material (70) with the liner fabric (72), and stabilizing the shape of the pressed-fibre air guide (40).

Drawing