FAN

Description

[0001] Forward-curved radial fans are known, for which a spiral-shaped housing is essential for pressure build-up. Such fans can be used in a variety of applications. For example, they can be used in electrical household appliances that are air-conducting devices. For example, such fans can be used in kitchen appliances such as extractor hoods, ovens, or refrigerators, or in tumble dryers, for example.

[0002] DE 10 2007 021 318 A1 discloses an extractor housing and an extractor hood. The extractor housing is designed to accommodate at least one fan housing and at least one motor enclosed by the fan housing, including an impeller, in particular a radial fan. The extractor housing also has an extraction opening for collecting vapors from a cooking area. On the top of the fan housing, the fan housing has an air outlet or air nozzle. The fan housing is a spiral housing.

[0003] The arrangement of the spiral casing provides a single discharge direction for the radial fan. However, some applications require a multi-directional discharge direction.

[0004] US 2017 / 002 829 A1 describes a multi-spiral Scirocco fan in which fluid can be discharged in various directions using a fan impeller and motor. The Scirocco fan comprises a drive motor and a fan impeller connected to a drive shaft of the drive motor. The fan has a plurality of blades. At least two spirals are stacked in the center, where the fan impeller is located. The spirals guide the fluid, with the cross-sectional area being linearly increased by the top and bottom surfaces, side surfaces, and the outer peripheral surface. According to one embodiment, the height of each of the spirals can be different from the others.

[0005] EP 2 138 725 A2 discloses a device for dispersing volatile liquids in air. The device comprises a dual centrifugal blower having a first and a second fan, both driven by a motor. Substantially identical components can be used to form the first and second fans.

[0006] GB 542 468 A describes a centrifugal fan having a housing divided into at least two angularly separated spiral chambers, each connected to an external diffuser.

[0007] JP 2010 100108 A shows a blower for a vehicle air conditioning system, which has two fans on a common hub, wherein the outlet openings for both fans are arranged in the same angular position around the hub.

[0008] Finally, DE 10 2007 019 056 A1 describes a fan for an extractor hood with at least one fan wheel and a fan housing surrounding the at least one fan wheel, wherein the inside of the fan housing forms a common fan chamber of the fan for the at least one fan wheel and at least two air outlet openings are provided on the fan chamber offset over the circumference of the fan housing.

[0009] The object of the present invention is therefore to provide a blower that has a multi-directional discharge direction while still achieving minimal performance loss, particularly pressure loss, volume flow loss, efficiency loss, and / or low noise generation. Furthermore, the blower should require as little installation space as possible.

[0010] The invention is based on the finding that this problem can be solved, for example, by cutting the spiral casing in the impeller plane and rotating it around the rotation axis to the required discharge directions.

[0011] According to the invention, the object is achieved by a blower having the features of claim 1.

[0012] Directional specifications such as top and bottom or the derived specifications top and bottom refer to the fan in the orientation in which the axis is vertical.

[0013] According to the invention, the blower comprises a spiral housing and a fan. The fan has an impeller rotatably mounted on an axle. The blower creates a negative pressure, which serves to draw in air from the surrounding area. When the blower is used in a refrigerator or tumble dryer, the air can be clean air. When the blower is used in an extractor hood, the air is contaminated air, which can also be referred to as vapors or fumes, and is cleaned by filter elements before entering the blower.

[0014] According to the invention, a spiral casing is defined as an at least partially closed container for influencing the air flow in the fan. Within the meaning of the present invention, the spiral casing forms at least part of a flow chamber.

[0015] The air can be sucked into the fan via one or more intake openings provided in the spiral casing, and thus enter the interior of the fan. The intake opening or intake openings are located perpendicular to the axis of the fan and in the region of the axis, so that air is sucked into the interior of the fan impeller. In particular, according to the invention, the spiral-shaped air baffles form the radial outer walls of the spiral casing and define the flow space inside. In the region of the spiral-shaped air baffle, the interior, i.e. the flow space, is thus spiral-shaped or helical. The spiral casing is also suitable for accommodating the fan or at least part of the fan, in particular the impeller of the fan. The impeller of the fan is arranged to rotate on an axis, which is a rotational axis, and is used to generate an air flow in the fan.The fan impeller is preferably driven by a motor. The fan motor can also be housed in the spiral casing or be separate from it. The fan is arranged in the spiral casing so that the fan axis passes through the center and the wall or walls of the spiral casing are parallel to the fan axis.

[0016] According to the invention, the spiral housing has at least two exhaust openings which are designed such that the air which is guided from the intake opening or openings through the spiral housing to an exhaust opening can be released back to the outside through them. The at least two exhaust openings preferably point outwards in the radial or tangential direction of the fan. It is also possible within the meaning of the present invention for more than two exhaust openings to be arranged on the fan. Filter elements, for example odor filters, can be arranged at the exhaust openings or downstream of them. The exhaust openings are designed, for example, such that they release the air directly outwards into the environment, whereby the air can first pass through a filter element.Alternatively, the exhaust openings can also be designed to direct the air into a housing, from which the air is then released into the environment. In this alternative, the air can also first pass through a filter element.

[0017] According to the invention, each of the at least two exhaust openings is formed at least partially by one of the spiral-shaped air guide walls of the fan. In particular, one end of the spiral-shaped air guide wall forms at least the radially outer boundary of the exhaust opening. At the other end of the spiral-shaped air guide walls, i.e. the end at which the radius of the air guide wall is smallest, a bevel can be provided which extends outwards from the end of the spiral-shaped air guide wall in a radial or tangential direction. This bevel can also be referred to as a nose. The end of the bevel which faces away from the end of the spiral-shaped air guide wall forms a lateral boundary of the exhaust opening. In the axial directions, the exhaust opening can be delimited by walls which are perpendicular to the axis, for example a cover plate or a partition plate.

[0018] The fact that the blower according to the invention has at least two outlet openings, which are at least partially formed by spiral-shaped air guide walls, results in a number of advantages. Firstly, the blower according to the invention can be used in devices where multi-directional outlet directions are necessary for some applications. Another advantage of the blower according to the invention is that the efficiency of the blower or the volume flow in the blower is not reduced. This is the case with the design according to the invention because the air is guided from the impeller directly through the respective spiral-shaped air guide wall to the respective outlet opening and thus a splitting of the air flow in the flow direction is not necessary, as can be caused when providing a baffle after the outlet of a conventional spiral housing.

[0019] In the blower according to the invention, the at least two spiral-shaped air guide vanes are arranged so as to be rotated relative to one another around the axis of the fan. According to the invention, the axis is the rotational axis of the fan. Accordingly, air guide vanes are referred to as "rotated" if they are rotated relative to one another around the rotational axis such that the exhaust openings formed by them are located at different angular positions around the axis. By rotating them, the exhaust openings of the blower according to the invention can thus point in different directions, for example in opposite directions. In particular, the spiral-shaped air guide vanes can be variably rotated relative to one another. Accordingly, the distance between the at least two exhaust openings can be different and can be variably adjusted depending on the application. The dividing line between the rotated air guide vanes is preferably in the impeller plane, which is perpendicular to the impeller axis.

[0020] An advantage of the embodiment in which the spiral air guide walls are arranged rotated relative to one another is that, for example, no baffle needs to be arranged in the fan or downstream of the outlet opening in order to evenly distribute the volume flow. The use of such a baffle generates a pressure loss and represents an additional source of noise. By rotating the spiral air guide walls relative to one another, the geometry of the spiral housing of the fan according to the invention is changed such that the volume flow is also evenly distributed, just as when using a baffle. An advantage of this embodiment, however, is that the rotation does not impede the air flow in the direction of flow, and therefore no pressure loss occurs and no additional source of noise is created. Furthermore, the efficiency of the fan is not impaired.

[0021] Furthermore, the use of a baffle within a fan, and particularly downstream of the fan in the flow direction, requires a large amount of installation space. An outer housing in which the fan is housed, such as an extractor hood housing, must be designed to accommodate the fan and the baffle. Furthermore, the air flow deflected by the baffle must be guided past the fan, thus resulting in additional airflow around the spiral casing. The present embodiment, in which the air guide walls form the spiral casing and, in particular, guide the air to the outlet openings, avoids the problem of requiring a large amount of installation space, as no additional components are required. According to the present invention, only the spiral-shaped air guide walls are rotated relative to one another.The blower according to the invention can therefore be accommodated in a smaller outer housing than a blower with a downstream baffle.

[0022] In a further preferred embodiment of the blower according to the invention, the at least two outlet openings are arranged at a distance from one another. According to the invention, the at least two outlet openings that are formed separately from one another in the spiral casing are referred to as being arranged at a distance from one another. Accordingly, the two outlet openings are not connected to one another. This embodiment advantageously results in the air discharged to the outside by the blower according to the invention via the at least two outlet openings being able to be discharged in different directions. The orientation of the respective outlet openings can be variably adjusted according to the requirements of the blower according to the invention.

[0023] In the blower according to the invention, the spiral housing is divided in the axial direction of the fan into at least a first region and a second region, each region being delimited by a spiral-shaped air guide wall.

[0024] According to the invention, a region is defined as a part of the spiral housing which has an outlet opening and is delimited by a spiral air baffle, thus forming a spiral segment of the interior of the spiral housing. The delimitation of the region by a spiral air baffle defines the size of the respective region. Thus, a region is defined as the part of the spiral housing into which the air is directed after entering the fan through the intake opening and is guided along the spiral air baffle to the outlet opening. The first region can also be referred to as the upper region and the second region as the lower region of the spiral housing. For the purposes of the present invention, the spiral housing can also be divided into more than two regions. The advantage of this embodiment is that targeted guidance or conduction of the air in the fan is possible.Furthermore, by forming two regions of the spiral casing, the spiral casing can be manufactured from several parts, for example, with each part forming one of the regions. Such a multi-part structure makes it easy to produce cavities, such as in particular the flow space of the respective region, i.e. the spiral space. It is also advantageous that the regions are arranged relative to one another in the axial direction of the fan and, in particular, are adjacent. This allows the first region to be supplied with air via part of the circumference of the impeller, and the second region to be supplied with air via another axially adjacent part of the circumference of the impeller. This ensures that the air flow is reliably distributed between the two regions.

[0025] According to a further embodiment of the fan according to the invention, a separating plate, which is also referred to below as a separating wall, is arranged between the first region and the second region. According to the invention, a flat plate which can be made of metal or plastic is referred to as a separating plate. The separating plate is preferably arranged perpendicular to the axis of the fan. In addition, a passage opening for the fan impeller is provided in the separating plate. The simple design of the separating plate simplifies the manufacture and assembly of the separating plate within the spiral casing and can be carried out with little effort. The separating wall is preferably fixedly positioned within the spiral casing. For example, the separating wall can be connected to the spiral-shaped air guide walls.Another advantage of the embodiment in which a separating plate is provided is that the areas inside the spiral casing are separated from one another and thus turbulence in the air guided in the respective area from the intake opening to the respective exhaust opening cannot occur, which could impair the volume flow or the efficiency of the fan.

[0026] According to the invention, at least one spiral-shaped air baffle is increased in height, starting from the smallest radius. The height of the air baffle is its dimension in the axial direction of the fan. The arrangement of the spiral-shaped air baffle according to the invention forms a spiral or snail. The air baffle can, for example, describe part of a logarithmic spiral, although the air baffle only begins at a distance from the center of the logarithmic spiral. In a logarithmic spiral, the distance from its center changes by the same factor with each rotation around this center. The radius therefore grows proportionally to the spiral length. The air baffle that describes part of a logarithmic spiral has a smaller radius near the center of the spiral than at the end of the air baffle, which forms at least part of the outlet opening.At the end of the spiral air guide wall where the radius is smallest, a bevel in the form of a nose can be provided.

[0027] The height of the spiral air baffle is greatest in the area of ​​the intake opening, which is the end of the spiral air baffle furthest from the smallest radius. The advantage of this design is that the area of ​​the outlet opening is enlarged in the axial direction, thus homogenizing the air flow.

[0028] In a further embodiment of the blower according to the invention, the fan comprises an impeller driven on the axle, with blades arranged on the circumference of the impeller. According to the invention, a rotor driven by a motor can also be referred to as the driven impeller, the axis of which is correspondingly referred to as the rotor hub. The blades can be attached to the rotor hub and extend radially outwards from the rotor hub, in particular curved outwards. The fan is therefore preferably a radial fan. The advantage of this embodiment is that the main flow of the sucked-in contaminated air is deflected by means of the blades and is thus directed in a targeted manner from at least one intake opening within the housing to at least one exhaust opening within the fan. After being sucked in, the air is thus discharged radially outwards, into the interior of the spiral housing, through the blades.By using a radial fan, a higher air flow rate can be achieved than with an axial fan for a given drive power.

[0029] According to one embodiment of the fan according to the invention, the impeller is arranged within the spiral casing near the smallest radius created by the arrangement of the respective spiral air guide vane. The spiral air guide vane is arranged such that it forms part of a logarithmic spiral. Particularly preferably, the spiral air guide vane ends in the immediate vicinity of the impeller.

[0030] In a further embodiment of the blower according to the invention, the spiral housing has at least two cover discs, each of which defines a part of a blow-out opening.

[0031] According to the invention, the cover plates are the walls of the spiral casing which close off the spiral casing in the axial direction. The cover plates can each lie in a plane perpendicular to the axis of the fan. The cover plates are each connected in particular to at least part of the spiral air guide walls. Thus, in this embodiment, the exhaust opening is defined by the end of the spiral air guide wall and the cover wall as well as any provided partition wall. Preferably, the cover plates are each a plate or disk which is impermeable to air. An opening, which is also referred to as an intake opening, is formed in at least one cover plate. In the sense of the present invention, the intake opening is a recess in the cover plate, which is for example a hole.The advantage of this design is that the intake air cannot enter the blower in an uncontrolled manner; instead, the air is directed through the cover plate to the intake opening. Another advantage is that the air flow within the spiral casing is also directed from the intake opening in the cover plate, through which the air enters the blower and the interior of the fan impeller, to the respective exhaust opening and is then discharged to the outside. This prevents the air from escaping uncontrollably from the spiral casing.

[0032] According to one embodiment of the fan according to the invention, an intake grille is provided in at least one cover plate, or an intake grille is provided in each of at least two cover plates, for drawing air into the impeller. The intake grille is the air-permeable cover that covers an intake opening in a cover plate. The intake grille prevents access to the interior of the fan and thus serves to protect the user.

[0033] A fan with an intake opening, preferably with an intake grille, in a single cover plate is also called a single-sided fan. The advantage of this design is that the air enters the impeller in a targeted manner and the air flow is redirected by the impeller blades, directing the air to an outlet opening within the fan.

[0034] A fan that has an intake opening, preferably with an intake grille, in at least two cover plates is also referred to as a two-sided or double-flow fan. In particular, in this embodiment, the intake openings in the cover plates, which are covered by the intake grilles, are arranged opposite one another. The advantage of this embodiment is that a larger amount of air can be drawn into the fan.

[0035] In a further embodiment of the blower according to the invention, the blower is a radial fan with forward-curved blades, also referred to as a forward-curved radial fan. The air is drawn in parallel or axially to the axis (rotor hub) of the impeller and deflected by the rotation of the impeller and expelled radially. Such a deflection can occur, for example, by 90°. The advantage of this embodiment is that the air is guided in a targeted manner from the intake opening to the exhaust opening.

[0036] The fan according to the invention can be incorporated into an air-conducting device, in particular an electrical device. Thus, the present invention also relates to a device with at least one housing according to the invention.

[0037] The device could be a household appliance, for example. In household appliances such as ovens, refrigerators, or tumble dryers, it is advantageous to generate airflows in different directions. In a refrigerator, for example, the air used for cooling can be blown out in different directions from a base of the refrigerator.

[0038] The device can also be an extractor hood, for example.

[0039] The extractor hood can be, for example, a recirculation hood, an exhaust hood, or a downdraft ventilation system. The advantage of using a fan according to the invention in an extractor hood is that the purified air can be blown out in several different directions. This is particularly advantageous, for example, with a ceiling fan, where the air is discharged horizontally in the area of ​​the ceiling. According to the present invention, the air from the extractor hood can be discharged in several directions in recirculation mode.

[0040] Advantages and features described with regard to the blower apply - where applicable - to the device in which it is used and vice versa.

[0041] The present invention is explained in more detail with the accompanying drawings. Fig. 1: a schematic perspective view of the interior of the spiral casing of a first embodiment of a blower; Fig. 2 : a schematic perspective view of the embodiment of the Figure 1 ; Fig. 3 : a schematic perspective view of an embodiment of the blower according to the invention; Fig. 4 : a perspective view of another embodiment of the fan according to the invention; and Fig. 5 : a further schematic perspective view of the further embodiment of the blower according to the invention.

[0042] In Figure 1 A perspective view of the interior of the spiral casing 11 of a first embodiment of a blower 1 is shown. The blower 1 is a radial fan. The blower 1 comprises a spiral casing 11 in which a fan 12, or rotor, is housed. The fan 12 has an impeller 120 driven on the shaft. The impeller 120 is rotatable about the shaft, which is a rotational axis.

[0043] The spiral casing 11 has at least two spiral air guide vanes 110. The air guide vanes 110 are the radial outer walls of the spiral casing 11 and describe the shape of a spiral or snail. In particular, the air guide vanes 110 form part of a logarithmic spiral. In a logarithmic spiral, the distance from its center changes by the same factor with each revolution around this center. The radius therefore grows proportionally to the spiral length. The end of the spiral air guide vane 110, which is arranged closest to the center of the spiral, has a nose 1102. The impeller 120 of the fan 12 is arranged near the nose 1102 of the respective spiral air guide vane 110 within the casing 11.

[0044] In addition, the Figure 1It is shown that the spiral casing 11 has two exhaust openings 111 oriented in different directions, in particular in opposite directions. Within the meaning of the present invention, the spiral casing 11 could also have more than two exhaust openings 111. According to the invention, the two exhaust openings 111 are aligned by arranging the two spiral-shaped air guide walls 110 so that they are rotated relative to one another about the axis.

[0045] Furthermore, the Figure 1that the spiral housing 11 is divided in the axial direction into two regions 1100, 1101, namely a first region 1100, which can also be referred to as the upper region, and a second region 1101, which can also be referred to as the lower region. Accordingly, the spiral housing 11 is constructed in several parts. According to the invention, the part of the spiral housing 11 which has an exhaust opening 111 and is delimited by a spiral air guide wall 110 and thus forms a spiral segment of the interior of the spiral housing 11 is defined as a region 1100, 1101. Thus, a region 1100, 1101 is defined as the part of the spiral housing 11 into which the air, after entering the fan 1 through the intake opening (not shown), is directed and is guided along the spiral air guide wall 110 to the exhaust opening 111.

[0046] In particular, the air is sucked into the fan 1, in particular the impeller 120, through the intake opening (not shown), and the air flow is deflected within the spiral casing 11 by the blades (not shown) arranged on the circumference of the impeller 120, whereby the air is directed in a targeted manner to an exhaust opening 111.

[0047] This embodiment further shows that the first region 1100 and the second region 1101 can be separated from one another by a separating plate 1103. The separating plate 1103 is, in particular, a flat plate that is impermeable to air. The arrangement of a separating plate 1103 within the spiral casing 11 ensures that the air flows of the first region 1101 and the second region 1102 do not swirl together, which could disrupt the volume flow and reduce the overall efficiency of the fan 1.

[0048] Figure 2shows a schematic perspective view of the embodiment of the Figure 1 The spiral casing 11 is formed on the one hand by the spiral air guide walls 110, which are the radial outer walls of the spiral casing 11, and on the other hand by cover plates 112. In contrast to the representation in the Figure 1 , is in the Figure 2 The interior of the spiral casing 11 is not visible, but is covered by a cover plate 112. The cover plates 112 form, for example, the axial boundaries of the spiral casing 11 and represent, for example, the top and bottom of the spiral casing 11. In the present illustration, only one cover plate 112 is shown, which, together with the spiral-shaped air guide wall 110, forms a cavity in the spiral casing 11 and, in particular, defines the exhaust opening 111 of the spiral casing 11.

[0049] In the Figure 2Only one intake opening with an intake grille 113 is shown in the cover plate 112. Accordingly, the fan 1 shown is a single-sided fan 1. However, within the meaning of the present invention, both cover plates 112 can have an intake opening with an intake grille 113; in this case, the fan 1 would be referred to as a two-sided or double-flow fan 1.

[0050] Figure 3 shows a schematic perspective view of an embodiment of the blower 1 according to the invention. The embodiment in Figure 3 of the housing 1 according to the invention basically corresponds to the embodiment of the Figure 2 In contrast to Figure 2 , is in the Figure 3shown that the spiral air guide walls 110 are increased in height starting from the smallest radius. The smallest or smallest radius is located near the center of the spiral of the spiral air guide wall 110. Thus, the height of the spiral air guide wall 110 is greatest in the area of ​​the outlet opening 111. Due to the increased height of the spiral air guide wall 110, the area of ​​the outlet opening 111 is also increased accordingly. Also in the embodiment according to Figure 3 a separating plate 1103 is shown, which is arranged between the areas (not shown).

[0051] In the Figure 4a perspective view of a further embodiment of the blower 1 according to the invention is shown. In this illustration, it can be clearly seen that the spiral housing 11 is divided in the axial direction into a first region 1100 and a second region 1101. Furthermore, it is shown that the two spiral-shaped air guide walls 110 are arranged rotated about the axis with respect to one another, as a result of which the outlet openings 111 point in opposite directions. The impeller 120, which is accommodated in the spiral housing 11, is arranged both within the first region 1100 and in the second region 1101, as a result of which the air flow of the sucked-in air, which enters the impeller via the intake opening in the cover plate (not shown), is deflected by means of the blades (not shown) in the corresponding region 1100, 1101.This ensures targeted air guidance from the intake opening to the corresponding exhaust opening 111 in the corresponding region 1100, 1101 of the spiral casing 11. The impeller 120 is arranged in the respective region 1100, 1101 such that it is located near the smallest radius formed by the arrangement of the respective spiral-shaped air guide wall 110. In this embodiment, in contrast to the first two embodiments, according to the . Figures 1 to 3 , no separating plate is arranged between the areas 1100, 1101.

[0052] In Figure 5 A further schematic perspective view of the further embodiment of the fan according to the invention is shown. In this embodiment, the interior of the spiral casing 11 is shown schematically again. In contrast to Figure 4It can be clearly seen that the impeller 120 is arranged near the nose 1002 of the respective spiral air guide wall 110. The nose 1002 is arranged at the end of the spiral air guide wall 110 that defines the smallest radius of the spiral air guide wall 110. Furthermore, this embodiment also shows that the blower 1 according to the invention has two outlet openings 111 and that the spiral housing 11 has cover plates 112 as a boundary in addition to the spiral air guide walls 110. List of reference symbols

[0053] 1 Blower 11 Spiral casing 110 Spiral air baffle 1100 First section 1101 Second section 1102 Nose 1103 Divider 111 Outlet opening 112 Cover plate 113 Intake grille 12 Fan 120 Impeller

Claims

1. Blower (1) with a spiral housing (11), in which a fan (12) with an impeller (120) arranged in a rotatable manner on an axis is accommodated at least partially, wherein the spiral housing (11) comprises at least two spiral-shaped air conducting walls (110), which at least partially embody at least two blow-out openings (111) on the spiral housing (11) and which extend from a smallest radius up to a radial outer boundary of a blow-out opening and wherein the spiral housing (11) is divided into at least one first region (1100) and a second region (1101) in the axial direction of the fan, wherein each region (1100, 1101) is bound at least partially by a spiral-shaped air conducting wall (110), wherein at least one spiral-shaped air conducting wall (110) is enlarged starting from the smallest radius in terms of height, in other words its dimension in the axial direction of the fan, characterised in that the at least two spiral-shaped air conducting walls (110) are arranged twisted in respect of one another about the axis of the fan and that the blow-out openings formed hereby lie in different angular positions about the axis.

2. Blower (1), according to claim 1, characterised in that the at least two blow-out openings (111) are arranged at a distance from one another.

3. Blower (1) according to one of claims 1 or 2, characterised in that a separating plate (1103) is arranged between the first region (1100) and the second region (1101).

4. Blower (1) according to claim 1, characterised in that the fan (12) comprises an impeller (120) driven on the axis, on the periphery of which blades are arranged.

5. Blower (1), according to one of claims 1 to 4, characterised in that the impeller (120) is arranged within the spiral housing (11) close to the smallest radius, which is produced by the arrangement of the respective spiral-shaped air conducting wall (110).

6. Blower (1), according to one of claims 1 to 5, characterised in that the spiral housing (11) has at least two cover plates (112), which each define part of a blow-out opening (111).

7. Blower (1) according to claim 6, characterised in that a suction grating (113) is present in at least one cover plate (112), or a section grating (113) is present in at least two cover plates (112), for drawing air into the impeller (120).

8. Blower (1), according to one of claims 1 to 7, characterised in that the blower (1) comprises a forward curved radial fan.