Title: Ventilation unit

Field

The invention relates to a ventilation unit.

Background

The invention relates to a ventilation unit, comprising an elongated casing having two long sides and two short sides, and comprising an elongated air inlet and an elongated air outlet. Such ventilation units are commonly known and may be applied e.g. in the upper parts of windows etc. aiming to provide a room with fresh air from the outside.

A problem of the commonly known ventilation units is that, especially at higher and/or fluctuating wind and thermal pressures to the ventilation unit's inlet, especially at high wind, excess energy loss will occur and draught may be experienced inside the room to be ventilated.

British patent application GB 2320563 discloses a ventilator canopy for mounting adjacent a slot in a window sash. The canopy comprises a rigid wing with an edge flexibly hinged to the canopy. A spring normally forces the wing to an open position, permitting airflow through the slot in the window sash. Thus ventilation is possible. When there is an excessive pressure differential between the inside and the outside of the window, the pressure differential forces the wing to close the opening. This prevents drafts.

French patent No. 2 086 925 describes a ventilation with a blade spring which deforms under the force of air current. The deformation changes the position of the blade in a diverging ventilation opening, thus regulating air flow.

Summary

The present invention aims to provide ventilation by a unit having a simple but effective self-regulating throughput mechanism, meeting the drawback of the prior art ventilation units.

Preferably, the self-regulating throughput mechanism comprises an elongated, flexible foil, extending between both short sides of the casing and being fixed, at those both short sides, to the outlet side, said foil, moreover, between its fixed ends being supported by a resilient support member, exerting a spring force to the foil into the direction of the inlet.

It may be preferred that said support member is arranged such that said spring force acts on about the middle of the length of the foil. Besides, it may be preferred that at least the outlet is provided with a grid or mesh, serving, besides as a filter for insects etc., as a stop layer for the foil.

Brief description of the drawing The invention will be elucidated now by a description of an exemplary embodiment of the ventilation unit, with reference to

Figure 1 showing a longitudinal section of the exemplary embodiment;

Figure 2 showing a transverse section of the exemplary embodiment.

Detailed description of an exemplary embodiment

In figure 1, showing a longitudinal section of the exemplary embodiment of the ventilation unit, comprises an elongated casing having two long sides with an elongated inlet 1 for fresh air and an elongated air outlet 2 respectively. Furthermore, the casing may have two connection walls connecting walls that form the long sides. The outlet 2 is provided with a grid or mesh 7. The outlet forms a passage for air, for transferring fresh air from the outside to a room within e.g. a house and/or air from that room to the outside.

A flexible foil 3 is provided, capable of at least partly covering the passage. The flexible foil 3 has an elongated shape, extending between both short sides 4 of the casing and being fixed, at those both short sides 4, to the outlet side 2, e.g. by means of clamping plates 5. Thus, mutually opposite ends of the foil may be fixed. Moreover, between its fixed ends 4, the foil 3 is supported by a resilient support member 6, which exerts a spring force to the foil into the direction of the inlet 1 (see arrow a), i.e. acting away from the air passage. Preferably the air passage does not extend beyond clamping plates. In another embodiment the air passage may extends further to allow for a residual air flow.

As shown in the embodiment of figure 1, the fact that a flexible foil 3 is used enables the cross-section of foil 3 to assume the shape of a pair of straight limbs, from the point of support by support member 6 to clamping plates 5 respectively, under influence of the force from support member 6 and the forces at clamping plates 5. Furthermore, the fact that a flexible foil 3 is used allows wind pressure to press foil 3 against grid or mesh 7 in the areas in the vicinity of the short sides 4 and close (or reduce) the open area of the passage. With increasing wind pressure the areas will grow from clamping plates 5 toward the central part of the ventilation unit. In a preferred embodiment flexible foil 3 is a flexible foil in the sense that is has no own rigidity, i.e. that the cross-section of foil 3 can be bent at any position in the cross- section without resulting in elastic forces produced by foil 3 that meaningfully resist bending of foil 3 under influence of the forces at clamping plates 5, the spring force from resilient support member 6 and the pressure force from inlet air pressure.

In the exemplary embodiment of figure 1 the support member is arranged such that the spring force (arrow a) acts on about the middle of the length of the foil 3. Here the support member 6 is configured as an elongated, about U-shaped metal spring, which supports the foil 3 with the movable middle portion of its U- shape at the location of arrow a, and which is fixed, at

the ends of the U-shape at the outlet plate. Instead of a U-shape an L shape may be used. The spring may extend from the short side of the elongated opening in the casing. Instead of an elongated spring, a spring may be used that extends from another part of the casing. The ventilation unit may e.g. be installed into a window frame, a window or a door. The casing of the ventilation unit may be at least partly formed by the window or door. Fresh air, indicated by arrows b, can flow from the outside to the inside room. The advantage of the ventilation unit is that when the inlet air (wind) pressure exceeds a certain level, the foil 3 will be forced (arrow b) against the force (arrow a) of the spring 3. Due to the flexibility of the foil 3, the foil 3 will, at rather low wind pressure in first instance be pressed to the grid or mesh 7 in the areas in the vicinity of the short sides 4 and close (or reduce) the opening areas between the air inlet and outlet. If the wind pressure increases, those areas will extend toward the central part of the ventilation unit. At high wind pressure, the ventilation unit may be closed entirely, until the wind subsides again.

In this way the room can be ventilated (with minimal draught risk) without causing wind flows in the room which may be experienced as draught. If the e.g. fixing clamps 8 are configured as adjusting screws the spring tension of element 6 (and thus force a), and thus the admissible wind flow, can be made adjustable.

Foil 3 provides for an anti-progressive relation between the area of the air passage and the pressure difference across the ventilation unit. At small pressure difference, where foil 3 presses against little or no part of grid or mesh 7, a small increase in pressure difference already leads to a large increase of the restriction of air passage. This is because in this case a relatively small movement of support member 6 at the point of contact between foil 3 and support member 6 suffices to allow flexible foil 3 to be pressed against a relatively large area of grid or mesh 7 near clamping plates 5. At higher pressure differences, when foil 3 already presses against a

relatively large area of grid or mesh 7, a much larger increase in pressure is needed to achieve the same or a smaller increase of the restriction of air passage, because a larger movement of support member 6 at the point of contact is required for this. The length of the foil is the length in the direction between clamping plates 5. Preferably the force acts in the foil in the middle of this length, or no more from middle than the part of the length over which the support member 6 supports foil 3, or at least no more than ten percent of the length away from the middle. This provides for the strongest anti-progressive effect. The length of the air passage also extends between clamping plates 5. The width of the air passage extends transverse to this length. Preferably foil 3 has a width that is at least equal to the width of the air passage.

Preferably, the construction never allows foil 3 to close off grid or mesh 7 entirely. In practice a small open area of grid or mesh 7 will always be left adjacent the point of support of foil by support member 6. This prevents resonance, which can be a cause of irritating noise from the ventilation unit and a cause of quickened wear.

The inlet may be provided with a further grid or mesh. In other words first and second walls that contain the elongated openings for the inlet and the outlet may both be provided with a grid or mesh. As used herein a grid or mesh is any structure capable of retaining flexible foil 3 when it is pressed against the structure, with openings in the structure that allow air to pass, if not covered, and are small enough to allow flexible foil 3 to be retained by the structure. The first and second wall may be mutually opposite walls of the casing. Preferably the casing comprises two connecting walls connecting the first and second wall. The connecting walls may connect the first and second wall in a part of the casing between the ends of flexible foil 3. In this case the width of the flexible foil 3 is preferably smaller than the distance between said

two connecting walls, leaving a passageway for the air between the flexible foil 3 and the connecting walls.

In an embodiment the further grid or mesh at the inlet may be used in cooperation with the flexible foil 3 to provide an air passage with variable area under circumstances wherein air flows from the outlet to the inlet. In an embodiment resilient support member 6 is configured to exert resilient forces on flexible foil towards the inlet or towards the outlet, dependent on whether its point of contact with flexible foil is moved towards the outlet or the inlet respectively. Resilient support member 6 may be fixed to flexible foil for example and/or it may have parts on mutually opposite sides of the surface of foil 3 at the point of contact, e.g. comprising a clamp attached to a U-shaped or L- shaped metal spring, flexible foil 3 running between the U or L- shaped metal spring and the clamp.

A ventilation unit is provided comprising an elongated wall with an elongated passage (2) for air, wherein the passage (2) can at least partly be covered by a flexible foil (3) that is fixed at both ends (5), said foil (3) being supported at an intermediate location between said fixed ends (3) by a resilient support member (6), exerting a spring force (a) to the foil (3) into a direction acting away from said passage (2). Preferably, the direction of action of the spring force (a) is opposite to the direction of the air flow to be expected.

In many cases the unit will act as an inlet provision of outside air into the room. However, under all circumstances the provision is able to act as an outlet provision too, in the case an overpressure is created inside the room.