EP4296580A1

EP4296580A1 - Ventilation unit

Info

Publication number: EP4296580A1
Application number: EP23180793.4A
Authority: EP
Inventors: Håvard Augensen
Original assignee: Roros Metall AS
Current assignee: Roros Metall AS
Priority date: 2022-06-22
Filing date: 2023-06-22
Publication date: 2023-12-27
Also published as: NO347620B1; NO20220714A1

Abstract

The present invention is related to a ventilation unit comprising a fume hood and a suction pipe. A flow-regulator plate is arranged in the ventilation unit to be regulate an opening between the fume hood and the suction pipe, wherein the flow-regulator plate is eccentrically rotatably, having an axial rotation axis outside of the opening of the suction pipe, parallel with the suction pipe.

Description

The present invention is related to a ventilation unit, for instance a fume extractor hood to be used in the kitchen, according to the independent claims.

Background

Loss of energy, and energy savings are increasingly important in building, and disbursements to heating and/or cooling are often considerable. Thus, it is important to avoid uncontrolled airflows, uncontrolled inlets and outlets of air. While avoiding loss of temperature, the indoor climate must be ensured, and the air should be replaced regularly. This often involves a balanced ventilation system, whereby a given amount of air are let in and out of the building, often through a heat exchanger.
Further, there is a need for replacement of air and ventilation during cooking, wherein it is desirable to work under a suction fan, such that the smell from cooking is removed from the building, rather than being spread throughout the building. This is especially important in buildings having several residences, such as a block. This is solved by using a ventilation unit such as a kitchen hood, arranged at the site of cooking, in such a way that smell from food and smoke/fume are removed before it is spread into the room.
There are several types of ventilation units, for instance free-hanging which filters and circulates the air back to the room, free-hanging ventilation units which draw the air out of the building and integrated ventilation units being connected to a ventilation system for the building. Free-standing ventilation units are often provided with a separate motor creating negative pressure and drawing air out of the room. Integrated ventilation units rarely has a separate motor, but are often connected to a centralized motor, wherein the ventilation unit is provided with a flow-regulator plate which may be regulated in such a way that balanced airflow is achieved, and in such a way that all residences of the building are provided with approximately the same ventilation.
A ventilation unit further comprises a fume hood and/or grating/filter at the inlet, and a pipe connected to the outlet or the pipe may be a part of the ventilation system. In the following this pipe will be referred to as a suction-pipe.
When the ventilation unit is connected to a centralized ventilation system, it may also be used to exchange of air when there is no cooking, hereinafter referred to as base ventilation. The among of air to be drawn out must be adjusted carefully according to the ventilation system in general, to avoid overpressure or underpressure in the building. Further, if there are several residences in the building, the ventilation system and the ventilation unit must be adjusted to achieve sufficient ventilation in all residences, independent of distance to the centralized motor. This requires that the flow-regulator plate must be adjustable to give correct counter pressure to the ventilation system, and the residences closest to the the motor must have less opening than the residences furthest away when the flow-regulator plate is adjusted to base ventilation. In addition, the flow-regulator plate must be adjustable in such a way that the ventilation unit may be used upon cooking in regular way. This is also known as forced ventilation.
When the ventilation unit is a part of a the ventilation system and used for base ventilation, it will always be an opening in the ventilation unit wherein air is drawn out, and this may cause sound or hum which may be experienced as troublesome.
Several flow-regulator plates for such use are known, such as sliding flow-regulator plates wherein a flow-regulator plate is slid into the suction pipe, as the flow-regulator plate covers the whole or parts of the cross section of the pipe. However, such a solution requires that the whole flow-regulator plate may be arranged on the side of the suction pipe, and further, it is a problem that the distal end of the flow-regulator plate may be vibrating when air flows through the pipe. This will create noise.
Another type of flow-regulator plate is a single leaf damper, wherein a flow-regulator plate shaped as the cross-section of the pipe, is rotated around a radial axis, and limits thus the cross section of the pipe. It is also known flow-regulator plates being rotational connected radially in the centre, and which may be folded such that they only partly limits the cross section. These are all limiting the cross section of the pipe even when fully opened, and therefore noise is often created when air passes by.
Thus, it is an object of the invention to provide a flow-regulator plate which may offer a completely closed or complete open passage into the suction pipe, as well as it may limit a given part of the cross section of the pipe. Further, it is an object to provide a flow-regulator plate and a ventilation system which does not make sound when air passes through, in such a way that the room wherein the ventilation unit is arranged, is quiet.

The invention

The object of the invention is fulfilled with a ventilation unit as stated in the independent claims. Further advantageous features are stated in the dependent claims.
The invention is related to a ventilation unit comprising a fume hood and a suction pipe. A flow-regulator plate is arranged to regulate an opening between the fume hood and the suction pipe, as the flow-regulator plate is eccentrically rotatably having an axial rotation axis outside of the opening of the suction pipe, wherein the rotation axis is parallel to the suction pipe.
By the expression "axial rotation axis" it should be understood that the rotation axis is parallel to axial direction of the suction pipe, i.e. the flow-regulator plate, being fastened perpendicular in relation to the rotation axis, rotates parallel to a radial cross section of the suction pipe. Further, the flow-regulator plate is eccentrically rotatably, which means that the rotation point is not in the centre of the flow-regulator plate. When the plate rotates, the distance in a given direction from the fastening/centre of rotation to the edge of the plate, will vary.
The rotation axis is outside of the opening of the suction pipe, and thus the degree of rotation of the plate will be decisive for how much of the plate will be moved over the opening of the suction pipe, optionally the plate may be connected and rotated in such a way that the opening is not limited. In this way the rotation of the plate may regulate the opening of the suction pipe, and thus regulate the flow of air.
The flow-regulator plate regulates the air flow through the suction pipe, by rotating the plate over the opening and thereby limiting the cross section which may be used for air flow. The means for generating pressure in the system will thus not be regulated, and other suctions or other ventilation means will not be considerably affected.
The ventilation unit may further comprise a device to generate an air flow through the fume hood and into the suction pipe. The device may be a motor being arranged in the ventilation unit, or a motor or pump being a part of the ventilation system, such as in a house or larger tenement house having several residences.
By "fume hood" it is in the context of this application meant to be an arrangement above a fireplace or a kitchen stove, wherein smoke, damp and other gases passes before it is guided into the smoke or suction pipe. The fume hood often has a tapered cross section wherein the smaller cross section is facing the suction pipe, and may for instance be a ventilator hood or a ventilator grid being installed above the fire place / kitchen stove. The fume hood may be extractable in order to occupy less space when the ventilation unit is not in use. The ventilation unit may be installed free-hanging in the ceiling or on a wall, or it may be integrated in a cupboard.
A ventilation unit according to the invention may further comprise a housing wherein the fume hood and the suction pipe is fastened, wherein the fume hood is fastened on one side of the housing, and the suction pipe is fastened on the opposite side, in such a way that the flow of air passes through the housing. The housing, the fume hood and/or the suction pipe may constitute the outer part of the ventilation unit, or they may be fully or partly surrounded by an outer chassis.
"Fastened to", in the context of this application, should include both fastened directly to and fastened by means of further elements.
The suction pipe may be arranged to a pipe socket being fastened or integrated in the housing, or alternatively the suction pipe itself may be provided with a flange at the opening, wherein the flange is fastened on the inside of the housing. In the following we will refer to "supporting surface" to refer to the flange or the area on the inside of the housing, around the opening of the suction pipe. The flow-regulator plate is arranged to be bearing against the supporting surface, at least when the flow-regulator plate is rotated to cover parts or the whole of the opening.
By "bearing against" it should, in the context of this application, be understood that the flow-regulator plate may be arranged up to the supporting surface, and/or in direct contact with the supporting surface, but it should not be exerted any pressure between the flow-regulator plate and the supporting surface, and thus the flow-regulator plate may be rotated unhindered. However, when the device generates a flow of air through the suction pipe, reduced pressure will be created on the upstream side of the flow-regulator plate, and the flow-regulator plate will be drawn towards the supporting surface in such a way that a tight connection is created.
The flow-regulator plate may have the same cross section as the suction pipe, however, it may be advantageous if the flow-regulator plate is larger and may cover the opening of the suction pipe completely, and further that some margin for correct positioning of the flow-regulator plate in completely closed position is given. Further, it may be an advantage that the flow-regulator plate bear against the supporting surface around the whole opening, and thus prevents air from being drawn through the ventilation unit. The flow-regulator plate may also be smaller than the opening of the suction pipe, but then the suction through the ventilation unit may not be completely closed by rotating the flow-regulator plate over the opening. This may for instance be an alternative in base ventilation.
A motor may be arranged to the flow-regulator plate to generate rotation of the flow-regulator plate. The motor may be arranged in direct engagement with the flow-regulator plate, or by several rotation means. By "direct engagement" it should in this context be understood that the motor shaft is directly fastened to the flow-regulator plate without any cogwheels/gears/transmission belts or the similar. By "by several rotation means " it should in this context be understood that the motor shaft is connected to the flow-regulator plate via cogwheels/gear/transmission belts or the similar.
When the motor is in direct engagement with the flow-regulator plate, the motor shaft will be equal to the rotation axis for the flow-regulator plate, and the motor will be fastened to a pivot point of the flow-regulator plate. This will be space saving and may be a good solution when the space is limited. When the motor is arranged to the the flow-regulator plate by rotation means, the motor shaft may be in an angle to the flow-regulator plate and the rotation axis, and this makes several physical arrangements of the motor possible. The motor may for instance be placed at the outer edge of the flow-regulator plate in relation to the rotation point, which will require less power from the motor to achieve the same movement. As the motor is engaged with the outer edge of the flow-regulator plate, and as the outer edge has larger circumference than the rotation point, the positioning of the flow-regulator plate will be more easy to adjust.
The flow-regulator plate has a first end which is arranged to be moved over the opening of the suction pipe, when the plate rotates. The first end is bent in a direction away from the opening of the suction pipe, meaning in a direction towards the fume hood, and may protrude further backwards towards the flow-regulator plate. The angle between the first end and the remaining part of the flow-regulator plate may be 90 degrees, meaning that the first end is perpendicular to the remaining part of the flow-regulator plate, but is preferably more than 90 degrees and thus the first end will protrude backwards toward the flow-regulator plate. The end should be bent or curved away from the suction pipe in such a way that it does not prevent the movement of the flow-regulator plate over the opening of the suction pipe even if it bears against the the supporting surface of the suction pipe/the housing.
The first end of the flow-regulator plate may be bent about 180 degrees, in such a way that it is folded backwards until it is parallel with the remaining part of the flow-regulator plate. In one embodiment, the end is bent in 170 degrees. The distance between the flow-regulator plate and the first end of the flow-regulator plate, may be about 20-25 mm, that is a diameter of the of the first end is about 20-25 mm. At a standard suction pipe having a diameter of about 12,5 cm, an optimal diameter of the curvature of the first end would be 22 mm.
The end is preferably curved in an even curve, and by having such a curved embodiment of the first end, the flow of air will not pass a sharp/straight edge, and thus less vibration in the flow-regulator plate will be created. Since the end is curved in a direction away from the opening of the suction pipe, turbulent flow will not be created inside the suction pipe, and this results in less noise and sound.
The flow-regulator plate may have many shapes, and circle, square and triangle shapes will work when it is eccentrically rotatably. However, it is an advantage if the flow-regulator plate is shaped as a sector of a circle, wherein the rotation point is in a corner opposite to the circular arc. A sector of a circle is a flat shape being defined by two catheti or legs arranged in an angle to each other, and a circular arc connecting the catheti opposite the corner. The length of the catheti are preferably equal, and corresponds to the radius of the sector of the circle.
In the present invention, the radius of the circle sector is preferably equal or larger than the diameter of the suction pipe. When the flow-regulator plate is rotatably connected in the corner opposite the circle arc, at the side of the opening of the suction pipe, the plate may be rotated in such a way that a quarter of a circle having a radius corresponding to the diameter of the opening of the suction pipe, may be sufficient to cover the whole opening. This is an advantage when the ventilation unit should be installed in areas with limited space.
A ventilation unit according to the invention may further comprise electronic components, control boxes, electric converters etc. being arranged to the housing. Lights, control switches / user panel etc. may be fastened to the housing or the chassis for easy operation by an end-user. Further, a ventilation unit preferably comprises a number of filters for filtering the air drawn through the ventilation unit, as the filters may be removed from the ventilation unit for cleaning or to be exchanged. In some embodiments, a ventilation unit according to the present invention may further comprise rails for extraction of the filter and/or the the fume hood when the ventilation unit is used. The filter and/or rails may preferably be fastened to the housing.
The housing may comprise a carrier plate in addition to a top-, bottom- and side cover being fastened to the carrier plate. The suction pipe may then be fastened to the top cover and the fume hood may be fastened to the carrier plate and/or bottom cover.
The flow-regulator plate may be arranged between the carrier plate and the top cover, as the carrier plate has a hole being at the least as big as the opening of the suction pipe. The flow-regulator plate is arranged rotatably in such a way that it may cover both the opening of the suction pipe and the hole in the carrier plate. When the flow-regulator plate is arranged between the carrier plate and the top cover, it will be kept in place even if it is only connected in the rotation centre. By such an embodiment vibrations of the flow-regulator plate are avoided and thus created sound is minimized, and additionally the risk for bending the flow-regulator plate in such a way that it does not cover the opening and thereby allows air to enter the system, is minimized. When the first end of the flow-regulator plate is bent as described above, the first end of the plate will protrude out of the hole in the carrier plate, regardless of the position of the flow-regulator plate.
By having such an embodiment, there may be provided knobs on the flow-regulator plate, which will abut the edge of the hole in the carrier plate and thus stop the rotation. As an alternative, knobs may be arranged on the outer edge of the hole in the carrier plate, in such a way that the edge of the flow-regulator plate is stopped, or optionally the flow-regulator plate is provided with notches, protrusions, indents or the similar which will mechanically prevent the rotation towards similar notches, protrusions, indents or the similar on the carrier plate. By such knobs the maximum and minimum rotation may easily be limited, in such a way that the amount of air to be drawn through the ventilation unit may be regulated. This is particularly advantageous when the ventilation unit is installed in a larger system having several residences.
The motor used to rotate the flow-regulator plate, may alternatively or in addition, be adjusted in such a way that it stops at different positions, such as a stepper motor. This makes it easy to fine-tune the positions, and this may be performed remotely without the need of an operator having access to the ventilation unit. This will also make it possible for an operator to adjust all the ventilation units in a system having several residences from a PC, without access to the residences. This will be very advantageous at the least at start-up of a new system, or after development/ renovation of the system.
In embodiments wherein the ventilation unit has a housing having an upper cover and a carrier plate, a distance plate may be arranged between the carrier plate and the upper cover, on the side of the flow-regulator plate, as the distance plate has a thickness corresponding the flow-regulator plate. With such a distance plate, the top cover may be fastened directly to the carrier plate without risking that the flow-regulator plate will be forced towards the top cover and that the rotation of the flow-regulator plate may be prevented. A distance plate will further prevent vibration of both the flow-regulator plate and other parts of the housing.
The distance plate may have a hole or cut corresponding to the size and movement path of the flow-regulator plate, and be arranged in such a way that it surrounds the flow-regulator plate, preferably on all sides. It may be advantageous as the different parts may be fastened directly to each other and appear as compact, in order to avoid vibration and sound. Further, the hole in the distance plate will limit any movement of the flow-regulator plate beyond the intended path, and the thickness will limit the movement between the carrier plate and the top cover. Such a solution will therefore create less sound.
When installing a ventilation unit according to the present invention, an operator will adjust maximum and minimum opening in relation to other units in the system. This may be performed manually by knobs and mechanical limitations, or by use of an adjustable motor such as a stepper motor, as mentioned above. The suction pipe is coupled to a suction system or a suction pipe in the residence, in such a way that he air is transported out of the residence. After installation, a user may use the ventilation unit as usually, by operating the user panel placed on the outside of the ventilation unit. When the user adjusts to maximum suction the flow-regulator plate will be rotated to the position giving maximum opening of the suction pipe, but the suction will not exceed the maximum allowable in regard to the installation. Correspondingly, when the user turns the ventilation unit off, it will not be closed completely, but the flow-regulator plate will be moved to the position giving minimum opening of the suction pipe.

Example

The invention will in the following be described with reference to a preferred embodiment shown in the Figures. The example is not limiting the invention as defined in the accompanying claims, but is given to illustrate details.
A preferred embodiment is shown in the following figures, where

Figure 1 shows a ventilation unit according to the invention, in perspective from below,
Figure 2 shows parts of the ventilation unit in perspective from below,
Figure 3 shows a section of a ventilation unit according to the invention, wherein a flow-regulator plate is partly moved over a supporting surface for the suction pipe, Figure 4 shows the flow-regulator plate in perspective from below,
Figure 5 shows the flow-regulator plate from the side, and
Figure 6 shows some of the parts of the ventilation unit according to the invention in exploded view.

The different parts are not necessarily to scale in relation with respect to one another. The same or similar parts are given the same reference number in different embodiments. "From below" refers to positions when a ventilation unit is installed, meaning the side where the fume hood will be fastened.
Figure 1 shows a ventilation unit i according to the present invention, comprising an extractable fume hood 1, shown extracted ,a pipe socket 2 being a part of a suction pipe and a flow-regulator plate 3. The flow-regulator plate is rotatably connected to an axial rotation axis A outside of the opening 4 of the suction pipe, and the rotation is performed by a motor 5.
The ventilation unit of Figure 1 is shown without a device to generate airflow through the fume hood and the suction pipe, such as a motor, but an appropriate motor may be connected to the ventilation unit if desirable. If the ventilation unit is a part of a bigger system, the motor/pump of the system will work as a device to generate flow of air and a separate motor may be unnecessary. The ventilation unit shown in Figure 1 is also shown with light 16 and user panel 17 to be operated by a user.
The flow-regulator plate, shown in further details in Figure 3-5 is designed as a er sector of a circle, having two equally long catheti B and a circle arc C connecting them. The length of catheti B corresponds to the diameter of the opening 4 to the suction pipe plus the distance from the edge of the opening 4 to the rotation point, and ca 2-3 cm for extra support. The flow-regulator plate is eccentrically rotatably having rotation point in the corner opposite the sector of a circle, in such a way that when the flow-regulator plate is rotated over the opening 4, it will cover an increasingly larger part of the opening. In the shown embodiment, the motor 5 is located right above the rotation axis and in direct engagement with the flow-regulator plate.
In the Figures, the flow-regulator plate 3 is shown in a position only covering a part of the opening of the suction pipe. When the ventilation unit is arranged in a bigger ventilation system, this may for instance be the maximum allowable opening for this ventilation unit.
The ventilation unit shown in Figures 1 and 2 comprises a housing wherein the fume hood 1 and the pipe socket 2 are connected to opposite sides. The housing comprises a carrier plate 7 and a top cover 8, wherein the flow-regulator plate 3 is arranged between the carrier plate and the top cover. The pipe socket 2 is provided with a flange 10, and connected to the top cover. In the shown embodiment, the flange 10 is fastened to the inside of the housing, i.e. the flange is between the top cover 8 and the carrier plate 7, while the rest of the pipe socket protrudes out through a hole 18 in the top cover. The flange 10 constitutes a supporting surface for the flow-regulator plate 3. When a device to generate airflow through the ventilation unit is running, it will generate a suction in the suction pipe and the pipe socket, and this will draw the flow-regulator plate against the flange 10.
The carrier plate 7 has a hole 9 corresponding to the size of the flow-regulator plate 3, and which is larger than the opening 4 of the suction pipe 2, as the carrier plate 7 and the top cover 8 is arranged in such a way that the hole 9 is above the opening 4, and the pipe socket 2 protrudes through the opening 18 of the top cover. The flow-regulator plate being arranged between the carrier plate and the top cover is rotatably connected in such a way that it may be rotated over the opening 4, and thereby limit a flow of air through it and into the suction pipe 2. A distance plate 19 is arranged between the carrier plate 7 and the top cover 8, as the distance place has a hole or cut 20 corresponding to the size and movement path of the flow-regulator plate, and the distance plate 19 is arranged in such a way that the flow-regulator plate is moved in the hole/cut 20. The distance plate 19 has a thickness corresponding to the thickness of the flow-regulator plate 3, and thus the top cover 8 may be fastened to the carrier plate 7 without preventing rotation of the flow-regulator plate 3. An exploded view of the parts are shown in Figure 6.
The flow-regulator plate 3 has a first end 11 being the first end to be moved over the opening 4 of the suction pipe when the flow-regulator plate 3 is rotated. The first end 11 is curved in an even curvature away from the opening of the suction pipe and protrudes out through the hole 9 in the carrier plate. In the shown embodiment, the curve is 170 degrees, and thus the first end 11 is nearly parallel with the remaining parts of the flow-regulator plate, but in opposite direction. The distance L between the first end 11 and the remaining part of the flow-regulator plate, meaning the diameter of the curvature is preferably 20 mm. This is shown in detail in Figure 4 and 5, respectively.
The flow-regulator plate 3 shown in Figures 1 and 2 is provided with a knob 6 bearing against an edge of the hole 9 of the carrier plate. When the flow-regulator plate rotates to the left of Figure 2, to enlarge the opening of the suction pipe, the rotation of the flow-regulator plate will be stopped when the knob 6 bears against the edge of the hole. This will provide a limitation to maximum opening and thus to maximum air flow through the ventilation unit, independent of the device which generates the flow of air.
Figures 1 and 2 further show an alternative system for limiting rotation of the flow-regulator plate, as a rail 12 with stoppers 13 are arranged on the carrier plate, at the outer edge of the path for the flow-regulator plate. The carrier plate is further provided with a slit 14 close to the rail, and the flow-regulator plate is provided with a protrusion 15. The protrusion protrudes out through the slit 14, and will abut the stoppers 13 an the rail and thus limit the rotation of the flow-regulator plate. In Figure 1 and 2 the stoppers are shown at the end of the rails, but these may be moved in order to achieve desired positions.
When a ventilation unit according to the shown embodiment is installed, an installer will adjust maximum and minimum position of the flow-regulator plate, either by moving the knob 6, or by removing the knob 6 and arrange the stoppers 13 at convenient positions of the rail 12. Maximum and minimum position of the flow-regulator plate may be depending on the ventilation system as a whole in the residence, as the ventilation unit may also be a part of the base ventilation. The pipe socket 2 are connected to the suction pipe or suction system in general in the residence, and the ventilation unit is installed as usual. After installation a user will use the ventilation unit in regular way, by operating the user panel 17 and regulate the lights 16.
The example is given for a specific embodiment, and the invention is not limited to this but includes modifications and variations within the scope of the claims stated below.

Claims

Ventilation unit comprising a fume hood (1) and a suction pipe (2), wherein a flow-regulator plate (3) is arranged inside the ventilation unit to regulate an opening (4) between the fume hood and the suction pipe, characterized in that the flow-regulator plate (3) is eccentrically rotatably, having an axial rotation axis (A) outside of the opening of the suction pipe, in parallel to the suction pipe.
Ventilation unit according to claim 1, characterized in that the flow-regulator plate (3) is arranged to bear against a supporting surface (10) around the opening of the suction pipe.
Ventilation unit according to claim 1 or 2, characterized in that a motor (5) is arranged to the flow-regulator plate (3) to generate rotation.
Ventilation unit according to any one of the preceding claims, characterized in that the the flow-regulator plate (3) has a first end (11) being bent away from the supporting surface (11), and backwards towards the remaining part of the flow-regulator plate.
Ventilation unit according to any one of the preceding claims, characterized in that the first end (11) of the flow-regulator plate is curved about 189 degrees, to be parallel with the flow-regulator plate.
Ventilation unit according to any one of the preceding claims, characterized in that the distance between the flow-regulator plate and the first end of the flow-regulator plate, is minimum 20 mm.
Ventilation unit according to any one of the preceding claims, characterized in that the flow-regulator plate is designed as a sector of a circle, wherein the axis of rotation (A) is in a corner opposite to a circle arc (C)
Ventilation unit according to any one of the preceding claims, characterized by further comprising a housing, wherein the fume hood (1) is fastened on one side of the housing, and the suction pipe is fastened to the opposite side, in such a way that the air flow flows through the housing, wherein the flow-regulator plate (3) is arranged inside the housing, bearing against a supporting surface (10) at the opening (4) of the suction pipe.
Ventilation unit according to claim 8, characterized in that the housing comprises a carrier plate (7) and a top cover (8), wherein the carrier plate (7) has a hole (9) which is at the least as large as the opening (4) of the suction pipe, and wherein the flow-regulator plate (3) is rotatably arranged between the carrier plate (7) and the top cover (8).
Ventilation unit according to claim 9, characterized in that a distance plate (19) is arranged between the carrier plate (7) and the top cover (8), as the distance plate (19) has a thickness corresponding to the thickness of the flow-regulator plate (3).
Ventilation unit according to any one of the claims 8-10, characterized in that at least one knot (6; 12) is arranged on the flow-regulator plate (3) and/or housing, in such a way that the flow-regulator plate is stopped at different positions.
Ventilation unit according to any one of the preceding claims, characterized by comprising means for generating a flow of air through the fume hood and into the suction pipe.