The present invention is for a device to enable a simple way of obtaining relatively constant speed of flow from an air inlet device independent of the volume flow through the device to the room that is served. The device also has the function of a smoke barrier in case of fire.

Air terminal devices for variable flow of air are available in the market as"variable flow terminals"but the devices have a comparatively complicated function that requires automation and high pressure in the connected duct.

In ventilation systems using low temperature air in order to cool a room the air shall be supplied in such a way that the air jet immediately at the terminal is mixed with a large quantity of room air. In order to obtain an efficient mixing the speed of the air which is blown in has to be high but must not generate sounds. The air jet will after a short distance be almost at the ambient temperature and thus cause as little draught as possible.

Traditionally in most cases the flow of air is kept invariable and the temperature of the air that is supplied is varied depending upon the need of cooling of the room. This causes a high consumption of energy as the invariable flow of air during the winter requires heating when the outdoor temperature is lower than what is needed for the cooling of the room.

In order to function well an air terminal with low temperature air and a variable flow of air also have a variable inlet flow area so that the speed of the blown in air is comparatively constant independent of the flow of air through the terminal. If the area is maintained and the flow of air decreases, then at a certain relation the air that is supplied through the terminal will flow downwards adjacent the terminal without being mixed with room air and thus cause an experience of draught at the dwelling zone underneath the terminal.

A pressure difference between the ventilation duct and the room that is served may be obtained either by that the pressure in the duct is obtained by a inlet air fan or by that the room is at underpressure by means of an outlet air fan.

Especially in case of an underpressure in the room it is important that the terminal functions also at very small pressure differences as it is in practice not possible to

have more than 15-25 Pa underpressure without leakage flows of undue air to the room through the surrounding surfaces of room becoming to large, also after sealing measures having been taken.

Variation of the flow of air to the terminal is not obtained by means of the air terminal but by some other means, e. g. a local restriction valve that is controlled due to the temperature in the room or a fan the speed of which is controlled due to the outdoor temperature. The present invention is not for the control of the flow of air in itself but the function is to adjust the area for the blowing in of air according to the existing pressure difference between the duct and the room.

The object of the air terminal device according to the invention is to achieve in a simple way a variation of the inflow area by means of the pressure difference that exists between the room and the ventilation duct that is connected to the air terminal device.

It is also an object of the invention to direct the inflowing air so that it is distributed over the wall surface or roof surface at which the terminal device is mounted. It is a further object to achieve a protection against spreading of smoke gases in case of fire.

The device is so designed that the said function is achieved also when the pressure difference between the room and the duct is very small (<5 Pa). One or more cover discs cover the free area of the terminal device to the room. These discs will below be named shutters. One such shutter with suspension means has a function which may be looked upon as similar to that of a"see-saw", where on one side of the point of balance there is the shutter which opens in a first direction and inwards to the room and at the other side of the point of balance there is a counter weight that moves in a second direction opposite to the first direction and inwards the terminal device and the duct. The expression"movable beam"in the following description may be looked upon as similar to the"see-saw". The expression"fixed beam"in the following description is similar to"the support of the see-saw".

The invention will below be described more in detail with references to the embodiments that are shown in the enclosed drawings.

Figures 1A and 1 B schematically show a vertical cross section of a terminal device according to the invention mounted to a ceiling.

Figure 2 schematically shows a vertical cross section of the invention mounted to a ceiling.

Figure 3 schematically shows a horizontal cross section of the invention mounted to a ceiling.

Figure 4 schematically shows a vertical section of an embodiment according to the same principle but where the air terminal device is mounted to a wall instead of a ceiling as in figures 1,2 and 3.

Figure 4 also shows an additional embodiment wherein an elastic temperature sensor means affects the change of area that is caused by a difference of temperature. Such a function may be important in the case when the terminal device is connected directly to the open outdoor air or to an air duct where a lot of cold air may be transferred to the device.

Figures 5A and 5B show an example of a calculation of force and torque balances by a air terminal device mounted to a ceiling.

Figure 6 shows viewed from the room another embodiment of the invention have four shutters.

Figure 7 is a vertical cross section of the device according to figure 6.

In the figures 1 B, 4,5B and 7 the device is shown with the shutters in an open position and in the figures 1A, 2,3,5A and 6 with the shutters in a closed position.

Reference numeral (1) is for a detail of the air terminal device that connects to a ceiling (2) and the ventilation duct (3). A fixed beam (4) is mounted in the cross section area of the device (1). The fixed beam (4) has notches for hanging points (5) that control the position of hanging of movable beams (6).

The shutter (7) is fixed to two movable beams (6). These movable beams (6) have a notch for a hanging point (5) that controls the position of hanging on the fixed beam (4). The shutter (7) can be one or more shutters depending upon which direction and capacity of blown in air that is desired. The movable beams may be one or more for each shutter, but 2 of them seems to be most useful.

The notches of the fixed beam (4) and the moveable beams (6) are so designed that the contacting surface (5) will be very small and so that movements of the shutter (7) having movable beams (6) takes place with very small friction : This is an important condition in order that the device will function properly at small pressure differences.

There are other ways to obtain a low friction by a small contacting area, such as e. g. points instead of edges, linear contacting surface or bearing.

In order to control the position of the shutter (7) the movable beams (6) have counterweights (8) that cause the shutter (7) to close the free area of the device (1) when the pressure difference between the room and the connected duct (3) is small.

At increasing pressure drop the shutter (7) opens with a turning movement so that the area of blowing in is increased. The counterweight (8) is dimensioned so that the pressure drop and thus the speed of blowing in will be correct for the installation in question thereby that the counterweight (8) create a torque which is opposite to the torque which is caused by the weight of the shutter (7), the beams (6) and pressure difference between the room and the duct by influence of pressure on the shutter (7).

In the example of an embodiment of figures 1,2 and 3 the fixed beam (4) divides the cross section area of the device (1) at the middle. A copy of the shutter (7) with the movable beams (6) is mounted at the opposite side of the fixed beam (4). The direction of blowing in then is in two opposite directions. The shutters (7) are named (A) and (B) in figure 3. In case of single direction blowing in it is arranged so that the free area is partly covered by a fixed cover/shutter (7) which forms a part of the fixed device (1). The shutters redirect the inflowing air so that it mainly follows the surface at which the device is mounted.

In the example of an embodiment shown in figure 4 there is an additional function where an elastic, temperature sensitive means (10) affects the movements of the shutter (7) due to pressure difference so that the movement e. g. is counteracted when the temperature of the inflowing air in the duct is decreased. Such a function might be important in the case when the device is connected directly to the outdoor air or to a ventilation duct wherein very cold air may be distributed to the device. In the example the means (10) is a weak bimetal spring. The reference (FV) indicates torque that is caused by movement of bimetal spring at a warmer temperature of inflowing air and (FK) at a colder temperature of inflowing air.

Figure 5 illustrates the following example of a calculation in order to determine characteristics of the arranging of the counterweight at certain given conditions. A certain increase of the relative torque of the counterweight is necessary to make the movement steady, otherwise the device will open fully and instantaneously at the smallest increase of pressure. In the example it is assumed that the distance of the centre of gravity in the horizontal plane (TPL1 and TPL2) is 100 mm at each side of the centre of balance. The total mass (m1) of the shutter is assumed to be 50 g and the centre point of gravity (TPL1) of the mass has the same position as the centre point of the influence of the air pressure at the surface of the shutter. It is further assumed the initial pressure for opening of the shutter shall be 5 Pa and the pressure to fully open the shutter shall be 25 Pa, meaning the sum of static and dynamic pressure on the

shutter. The shutter shall open so that its angle to the horizontal plane changes from 0 to 30 degrees. In the figure F11, F12 and F21, F22 respectively indicate the torque influencing power at different angle to the horizontal plane at respectively closed and open shutter. M1 and m2 indicate the total mass on either side of the point of balance and the area of the shutter that is affected by the air pressure is 0,01 m2. The angles a1 and a2 are the angles of the counterweight to the horizontal plane seen from its centre of gravity. Under these assumptions at the opening pressure 5 Pa the torque exerted by the air pressure on the shutter in closed position will be 470 gmm and the torque of the mass of the shutter will be 4698 gmm, totally 5168 gmm. At an air pressure of 25 Pa the shutter will be fully open which corresponds to a torque exerted by the air of 1607 gmm and the torque of the mass of the shutter is in this position 3215 gmm, totally 4822 gmm. The torque of the counterweight shall at both angles (a1 and a2) be the same as the total torque of the shutter. It can then be calculated that the angle a2 shall be 7,6 degrees and the angle a1 shall be 22,4 degrees to the horizontal plane. The mass of the counterweight shall be 52,1 g.

In the embodiment of the invention that is shown in the figures 6 and 7 a protective plate (9) is arranged above (in case of mounting at the ceiling) the counterweights.

This protective plate prevents dirt and impurities from building upon the counterweights and the mounting arrangement. The protective plate can also be mounted so that it sets a limit the movements of the counterweights and then also for the largest possible opening of the shutter. In this and other embodiments of the invention it is also possible to connect the shutters so that all of the shutters always are at essentially the same opening angle.

In case of fire in a closed room then the air pressure is increased due to the much increased temperature. When the pressure in room becomes greater than in the air duct the shutters of the device will close. In this way spreading of smoke gases through the duct system to other rooms is prevented or made difficult.