FI56896C - LUFTRIDAOANORDNING - Google Patents

Description

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^ (11) UTLÄGGNINGSSKRIFT 30030 C (45) Fnt'fiUi \ ij 10 :: 4 W: 0 'Sw ^ v' (51) Kv.lk. * / Lnt.CI. 'F 24 P 9/00 E 06 B 3/92 SUOMI - FINLAND (21) t · "« Ι * »Ι <· ™.-Pit *« »ttn» eicnlng 1082/73 (22) Htkemltpilvi - AnsBknlngidig 06.0U.73 (23) Alkupilvi — Glltlghettdtg 06.0U .73 (41) Became Public - Bllvlt offmtllg 08.10.7 3

National Board of Patents and Registration .... ..- .. ..., ......., _ M 9 (44] Date of publication and date of publication -

Patents and registrars '' Anaöktn utiagd och utUkrKtm pubiicmd 31 * 12 * 79 (32) (33) (31) Privilege requested —Begird priorittt 07.0U. 72

1U.03.73 USA (US) 2U1925, 33977U

(71) (? 2) Erling Berner, Box 9, Allison Park, Pennsylvania 15101, USA (7U) Berggren Oy Ab (5U) Air curtain unit - LuftridAanordning

The present invention relates to an air curtain device in which air is supplied transversely over a door opening from an air chamber through an outlet. Such devices are already known, for example, from U.S. Patents 3,231,006, 3,430,676 and 3,698,465.

Of these, it is known to provide a unitary closing element which can be moved up and down in the door opening and in which an air fan is mounted on the upper part of the closing element and communicates via an outlet with an air chamber inside the element. Known structure

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however, it is heavy and it is an object of the present invention to provide and develop an air curtain device which is lighter in construction and with which the door opening can be closed more or less. In addition, according to the invention, it is possible to adjust the intensity of the air curtain.

2 568S6

The invention is characterized in that one wall part of the air chamber is formed as a collapsible hollow door, the interior of which constantly forms an open connection between the air chamber and the outlet, the outlet being arranged at the free end of the door and preferably adjustable to change air direction.

The collapsible hollow door actually represents the possibility of expanding the air chamber and at the same time allows the outlet to be placed at the desired location, whereby the force of the air curtain can be further adjusted.

According to the invention, it is advantageous to form a door from parallel door elements, the individual door elements on the front and rear side of the door being offset from each other in a direction perpendicular to the plane of the door so that they can slide against each other during extraction and compression. Opposite door elements can be connected to each other, for example by transverse strips.

In addition, it is preferred that the opposing door elements are assembled into closed-open, U-shaped cross-sectional elements, each element having at least one tubular channel extending from the bottom of the U to telescopically cooperating with the tubular channel of the adjacent element in the closed direction.

3 56896

The invention will now be described in more detail with reference to the accompanying drawings, in which:

Figure 1 shows a front view of some of the panels attached to each other at their edges with the door closed.

Figure 2 shows a cross-section of a closed door showing the joining of the door panels to each other.

Figure 3 shows a partial cross-section of the door as before with the door closed; in this construction a different way of connecting the door panels has been used.

Figure 4 shows a cross-section of the door when it is open with the panels nested; in addition, the picture shows details of the door lifting and lowering device.

Figure 5 shows a cross-section of the air chamber along line 4-4 of Figure 4.

Figure 6 is a similar cross-section of the air chamber partially open and using a tangential fan.

Figure 7 shows another cross-section of the door with it open and using a tangential fan mounted on the door.

Fig. 8 shows a section along the lines 8-8 of Fig. 7, showing the opposite panels of the inner and outer door elements of the door connected to each other by handles.

Figure 9 shows a detail drawing of the edge joint between the panels.

Fig. 10 shows a detail drawing of an edge joint between two panels, in which the lower edge of the panel has a roller which bears against the outer surface of the lower panel.

Figure 11 shows a modification of the previous edge joint with a roller at the top of the panel against the inner surface of the panel above.

Fig. 12 is a detail drawing of another method of edge joining using a resilient sealant inside the bends of the opposing panel edges.

Figure 13 shows a longitudinal section of a tangential fan.

Fig. 14 shows a cross-section of a tangential fan in which the air intake takes place from the side.

Fig. 15 is an end sectional view of a panel structure comprising U-shaped interlocking portions with downwardly directed legs in panels and interlocking circular air ducts.

568S6 4

Fig. 16 shows a cross-section of doors such as Figs. 4, 6 and 7, the panels of which are further insulated.

Figure 1 shows a row of overlapping panels 10, 12, 14 and 16 arranged so that their ends run in sealing guides 18 arranged at opposite ends of the door opening 20 so that they can move vertically, thus forming the outer element A of the door.

As can be seen from Figure 2, there are a group of corresponding panels 11, 13, 15 and 17 which form the inner element B of the door. The door may have more or fewer panels than shown in the figure depending on the height of the door opening and the size of the individual panels.

The panels may be wider or narrower at the top and bottom of the door for economical fabrication of the door, or to reinforce the door by using narrow or wide panels at those points as needed. However, as can be seen from Figure 5, the panels are preferably all of the same width, so that they can be made of long standard webs by cutting pieces of the required length. Thus, all panels 11-17 with U-bend are interchangeable and can thus be easily replaced with new ones if they are damaged or broken.

Both door elements A and B are spaced apart and can be raised and lowered either separately or together so that the space between them remains the same width at all times, but they are best suited for use as a whole, as will be seen later. At the upper edge of the door opening 20 (Fig. 6) a fan 21 is fixedly mounted, which is preferably a tangential fan, e.g. as disclosed in U.S. Patent 3,362,469. As shown in several figures, an air chamber 19 is mounted at the top of the door opening, to which the air flow from the fan 21 is directed. The air chamber 19 has two fixed side walls 24 and 25, the lower edges 26 and 27 of which are connected to the uppermost respective panels of each door element (A and B) so that the air coming from the fan enters the space C between the door elements.

As can be seen in Figures 2, 3, 4, 5 and 6, each Door Element consists of a plurality of overlapping panels, the panels going upwards being outside the panel below so that when the door is completely up, all panels of the door elements are nested inside the panels 28 and 29. As the space between the elements expands when the door is closed, the air space 19 increases correspondingly in the closing direction of the door, its size depending on whether the door is fully open, half-closed or fully closed.

As can be seen from Figure 9, both the top and bottom edges of each panel, except the top and bottom, are bent so that the top edge is bent first to the side and then down and the bottom edge again first outwards and then upwards to stiffen these edges. This bend will be hereinafter referred to as the U-or-peek. The lower panels 10 and 11 have U-bends only at the upper edges, while the upper side walls 2b and 25 of the air chamber 19 have similar U-bends only at the lower edges 26 and 27. · The upper sliding panels 28 and 29 have U-bends to engage the walls of the air chamber 19. 2b and 25 to the U-bends at the lower edges 26 and 27.

As shown in Figs. 9 and 12, the upper edge 30 of the panel 14 is first bent horizontally and the edge 31 of the bend is bent downward to form a downwardly turned U-shaped bend to which a first horizontal bend 32 at the lower edge of the upper panel and an upward U-bend at its edge 33 fit. . As can be seen, the U-bend of the lower edge 32 of the upper panel 16 fits into the U-bend 30 and 31> of the upper edge 30 of the lower panel 14, but is preferably slightly smaller than this. These edges are shown as U-folds, but can also be shaped differently, as shown in Figures 10 and 11.

However, they are meant to fit together in sufficiently tight, detachable joints to stiffen the edge of both panels. The bend joints thus reinforce and stiffen the panels, whereby the adhesive bends also form a seam that is tight enough to prevent air leaks. Adhesive bends lock the panels together so that they cannot rattle or move due to wind pressure. Although these folding joints are tight, they easily detach vertically when the panels are lifted and again hit their position when the door is lowered. Just keeping in mind that U-bends can be shaped differently, the term "U-bend" will be used in the following as a kind of generic term.

When said wall opening is closed, e.g. by a sliding door, which is common practice in garages, warehouses and industrial premises, and the door opening is protected by an air curtain which prevents heat transfer between indoor and outdoor space, the structures mentioned herein can be used to protect any wall opening, such as a window in which the sanction "state" is used 568se here as well as a kind of generic term.

As can be seen in Figure 12, a resilient seal 34 can be fitted to the joint between the panels to improve the tightness of the joint. The upwardly bent edge of the panel 16 bears against the inner surface of the panel 14 as it slides upward. Correspondingly, the downwardly bent edge 31 of the lower panel bears against the inner surface of the panel 16, these surfaces guiding the passage of the edges as the doors open and close so that the U-bends of each panel lock to each other.

Correspondingly, the lower connecting bend 35 and the lower connecting bend 36 below engage and detach as the lower panel slides along the upper panel inside the door as it is driven and closed (Figures 2-6). A respective pair of folds 37 and 38 at the respective panel edges of the door inner element B functions in the same way as the bends in the outer element A by gripping or guiding the inner panels as the inner door element B closes at the same time as the outer element A.

As can be seen from Figures 4, 5, 6 and 7, a lifting roller 40 is mounted at each end of the door on a shaft 39 »which is rotated by a motor 4l. The other end of the wires 42 is wound on rollers 40 and their lower ends are attached to lugs 43 between the lower panels. Usually two wires 42 are used at opposite ends of the door, whereby as the rollers 40 rotate the panel group in each door element rises vertically upwards from the lowest panels 10 and 11. A horizontal protruding shoulder 84 (Fig. 7) can be mounted at the top of each pair of panels. the next panel with it facing up until all the panels are up and nested (Figures 4, 6 and 7).

In the solution presented here, it has been preferred to always tie opposite panels at the same height from their top edge with buckles 45. For example, the bottom bracket 46a is welded or bolted at 50 to the top surface 36 at each end of the handle as it passes over the top edge of the bottom panels 10 and 11. together. Similarly, the bracket 46b above the previous one binds the panels 12 and 13 together and the next bracket 46c binds the panels 14 and 15, respectively, until the top bracket 46 binds the two top panels together. Thus, the entire panel set of door elements A and B consists of paired panels, each pair rising as a unit each time the wires 42 rotate on rollers 40, with the lowest panels 10 and 11 attached to the lower ends of the wires rising first, then lifting a pair of panels at a time.

7 56896

Said lowest pair of panels, consisting of interconnected panels 10 and 11 and usually also a nozzle 44, fits inside the next pair of panels, where it rises when the door is opened. The panels 10 and 11 and the handles 46a between them abut the frames 46b of the panels 12 and 13 above them, the latter panels rising upwards inside the next pair of panels 14 and 15, which in turn rise inside the pair of panels 16 and 17, and so on. , until all panels are nested and the door is fully open (Figures 4, 6 and 7).

The sides of the door opening are sealed with a trough 18 (Figures 2 and 8), at least one of the flanges 54 of which runs obliquely downwards so that the distance between the flanges corresponds to the respective thickness of the lowered door, the lower edges of each pair of panels resting against the flanges 54 the entire set of panels with the weight of the panels against the flanges. However, in a preferred embodiment, a different method is used, in which part of the flange 54 is bent inwards at the lower edge of each pair of panels, these bends forming bearing surfaces for the pairs of elements with the door lowered (points 56, Fig. 2). together support pairs of panels on either side of the door.

According to another embodiment (Fig. 3), shoulders 57 are attached to the flange 54 on the inner surface of the chute, forming successive steps on which the lower edges of the door panels rest.

It is advantageous to clad or coat the webs of the trough 18 with a sealing material, such as plastic, foam rubber or, above all, polyfluoroethylene to prevent air leaks at the edges of the door and to reduce friction between the ends of the door panels and the trough.

The lower panels 10 and 11 (Fig. 4) are parallel to each other and the space between their lower edges is open, allowing an air flow to form between them, which forms an air curtain of equal strength. As shown in Figures 2, 6 and 7, the lower panels 10 and 11 are attached to the two sides of the nozzle. The nozzle comprises a grille formed by slats 58, the slats of which are pivotable in the transverse direction to control the air flow. In addition, in order to direct the air flow in the direction of travel of the door, i.e. towards the elements A and B, the supercharger plate 60 can be mounted on the edge of the nozzle opening to direct the air flow towards the inner door element B. The charge plate 60 can also be mounted on the opposite side of the nozzle, whereby the air flow is directed towards the outer door element A.

8 56896

In yet another embodiment (Figure 2), in front of the nozzle opening, there is a curved slit plate 62 which is pivotable in front of the nozzle so that the air flow between the slits 64 is directed either inwards in the direction of arrows 67 or outwards in the direction of arrows 65.

The centrifugal or tangential fan 21 is firmly attached to the inner wall 69 at the wall opening 20 and draws air from the wall-confined space 13 by pushing it into the air chamber 19. from its outlet 23 · From the air chamber 19, the airflow is directed downwards along the space between the door elements A and B to the nozzle at the bottom of the door, from where it is discharged as an air curtain.

With the lifting rollers in the chamber 19, driven by the motor 4l, the door can be partially or completely raised or to the desired intermediate height. In this case, the fan 21 presses air along a variable length duct C between the door elements, the length of the duct depending on the current position of the door, into a nozzle 44, from which the air is discharged as an air curtain across the still open part of the door opening. In this way, air can be taken from inside the building at a certain point and led down through the door into a flat and evenly warmed air curtain.

The door can be easily raised and lowered without interfering with the flow of air in the space between the door elements.

As shown in Figure 6, the fan 21 (preferably a tangential fan) is mounted next to the air chamber 19 so that the air flow 23 enters the air chamber 19 at a constant pressure. Although this fan could be a conventional centrifugal fan, the tangential fan has several advantages over the previous one, primarily that the air flow 23 to the chamber 19 is homogeneous and has very little vortex. Figure 6 shows a fan mounted next to an air chamber 19 blowing air into it in a horizontal direction. In this case, the entire air curtain device can be installed inside the door opening 20. In addition, when the fan is thus mounted at one end of the door opening, it could be made to operate horizontally, whereby several air chambers 19 would be moved transversely by means of servo devices (not shown); then the air curtain could run either vertically or horizontally across the wall opening 20.

In the variation shown in Figures 7 and 14, the fan is mounted on the door device, the entire door device being mounted on either the inner or outer surface of the wall opening 56896 9 20; i.e., either the outer or inner element A or B of the door comes into contact with the wall surfaces 69 or 71. The advantage of this embodiment is that the installation of the fan on the door device is easy and that the door can be installed against the inner or outer walls 69 or 71 of the building.

It is, of course, possible to mount a fan in the longitudinal direction of the door at one end of the air chamber 19, blowing air into the chamber in its longitudinal direction (Fig. 5) · For this purpose, a fan 75 driven by the motor 75 is mounted at one end of the air chamber 19 blowing air in the direction of arrows 73. However, it is more preferable to mount the fan either on the air chamber as shown in Fig. 7, or if the door is inside the seat opening, inside or outside it near the top of the wall opening, whereby the air flow 23 enters the air chamber 19 horizontally (Fig. 6).

As shown in Fig. 6, air flows from the chamber 19 in the closing direction of the door while maintaining the space between the door elements. Thus, when the door is partially open (Fig. 6), the intermediate space is considerably longer than when the door is fully open and the panels are all nested as in Fig. 7 · In the intermediate space there is a constant air pressure from the fan 21 and air is released from the nozzle 44 or the gap between the lower panels 10 and 11 at constant pressure either. straight down or downhill. Thus, a laminar air flow is discharged from the nozzle at a relatively constant pressure, the pressure being the same as in the air chamber 19, regardless of the position of the door, i.e. regardless of the length of the space between the door elements.

Experience has shown that if the ratio of the cross-sectional area A (which changes when the door opens) to the cross-sectional area Za of the nozzle outlet can be kept at 1: 3 or higher (A / Za = 3/1), the air velocity in the nozzle remains within 10% of its nominal value. This can be calculated from the equation uo = Va-f — SF-'w · j ° o o 2 2bQ = nozzle width UQ = air velocity in the nozzle W = wind speed X = distance of some point in the air curtain from the nozzle The relationship between these factors can be shown in the following example: 56896 10

The air velocity in the nozzle is 30.5 m / s, the width of the nozzle is 7.62 cm, the height of the door opening is 4.27 m. In this case, the air curtain can prevent a horizontal air flow (wind) with speed W from penetrating through: Tt _ ta ir \ / 0 , 07β2 X 1.68 '„/ T _ e- nö„ / „W - 30.5 y —J —— \ 27 - = 50» 5 x Τϋ 5.28 m / s

Aperture height Air speed mouth- Maximum wind speed, from the floor, m at the foot m / s which the air curtain can retain m / s 4.27 30.5 5.28 3.96 "5.48 3.66" 5.69 3.35 " 5.97 3.05 "6.25 2.75" 6.60 2.44 "6.96 2.13" 7.50

As can be seen from the table above, the wind speed can increase from 5.28 m / s to 2.50 m / s without the wind being able to penetrate through the air curtain if the door is lowered from 4.27 m to 2.13 m on the intermediate highway.

As shown in Figures 2, 3, 6, 7 and 9, each pair of panels finally slides vertically between the end panels 18 so that each pair of panels slides between the pair above it when the door is opened. The panels 12, 14 and 16 (Fig. 10) may be provided with rollers 68 mounted on the inner flange 33 which support the lower panel 14 against the outer surface, reducing friction between the panels while preventing the surface of the panels from being scratched. The rollers 68 may be separate rollers in a long row along the edge of the panel, or there may be only one long roll at the edge.

As seen in Figure 11, it may be advantageous to mount the roller on the top flange 31 of the panel, with the roller 68 rotating against the inner surface of the upper panel 16 as the panel 14 moves relative to the panel 16, leaving any scratches inside the panel pair. It will be appreciated that the rollers 68 may be mounted on both the top and bottom of the panel.

As shown in Figure 12, it may be advantageous to provide a padding, insulating or sealing strip 34 between the aligned panel webs in the U-bend of the flange against the edge of the flange 33 to soften the contact between them or to seal the gap between the flanges. Seals 34 of the same type may be mounted in the same manner on the inner bend to which the flange edge 32 abuts.

In the variation of Figure 15, the panel assemblies may be U-shaped portions consisting of a flat top 66 and downwardly bent sides 78, as disclosed in U.S. Patent 2,057,850. Each of these U-shaped portions is sized to fit together , lower to upper, with a group of such parts forming a collapsible door. The top portion 66 of the panel assembly may have similar, mating, and sealing flanges horizontally outwardly, while the flange 80 bent at the bottom pivots horizontally inwardly hitting the top end 84 of the adjacent U-shaped panel assembly 66. to which the tubular elements 86 are attached. These elements are arranged to always slide vertically into the corresponding tube of the lower part, the inner part of the door being formed by a series of separate, collapsible channels connecting the upper chamber 88 to a lower chamber 90 with a nozzle 44 as previously described. The U-shaped panel elements rise into each other as well as the pipe sections inside them, forming collapsible air ducts. The channels terminate in a lower chamber 90 with a nozzle at the bottom; 44, from which air is discharged as an air curtain while a group of nested tubes 86 directs air from chamber 88 to chamber 90 in all positions of the door. Although round tubes are most preferred, rectangular or other tubes may be used.

According to another embodiment, the outer element A and the inner element B of the door can be raised and lowered separately; in this case, the handles connecting the opposite panels are omitted. The top edge of the panels of each door element has inwardly directed shoulders 84 which the top edge of the inner panel strikes when the door is lifted, thereby next lifting the upper panel until all the panels of the door half are up and nested (Figure 7). In such a solution, two separate lifting wires must be used, each of which wraps around rotating lifting rollers 40 (not shown) on their own shaft 39.

Instead of using the flange formed by the cover bracket according to Figures 10, 11 and 12, this flange may, as shown in Figure 9, extend along the entire length of the panel and may have sealing elements as required. The flanges may be in addition to the transverse straps 46.

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In the modified embodiment shown in Figures 2 and 6, or in all the panels of the inner door element B, there may be grille-like openings or manually adjustable flaps in a row extending from end to end of the panel of the inner door element. These air openings 92 can either always be open or they can be closed manually or opened, e.g. in the form of slatted curtains, whereby part of the air flowing in the intermediate space leaves horizontally from said openings. The air vents are best placed in the bottom panel, but of course they can also be placed at some other desired height.

The air vents 92 can also be located on the side 81 of the air chamber 19, whereby air is discharged from them horizontally to the extent adjusted by the respective opening angle of the flaps. In this way, when the door is partially open, air flows from the nozzle 44, forming a protective air curtain in the door opening and at the same time air is discharged from the air openings in the wall of the air chamber, if desired.

Alternatively, when the door is closed, the air vents in the bottom panel in particular can be opened to provide a horizontal air flow, as the actual air curtain breaks against the floor or the lower edge of the door opening when the door is closed. In any case, a horizontal air flow from the air vents on the side can be achieved at any height.

According to another embodiment shown in Fig. 16, the panels can be insulated with sheets of insulating material 96, which may be some insulating fabric, foam, etc. Thus, the panels 15, 17, etc. are thermally insulated. Said insulation is precisely an advantage in preventing the condensation of the moisture flowing in the intermediate space C on the cold metal surfaces of the panels. Although both elements A and B of the door are most often insulated symmetrically, it may sometimes be sufficient to insulate only the element whose temperature differs most from the temperature of the air flowing in the intermediate space C.

As described above, two door elements consisting of separable panels form an inner and outer door of the door, each of which can be raised and folded separately in different ways, such as, for example, a garage or storage door. However, these door halves work best together, with their opposite panels at the same height being connected to each other by handles so that the distance between the panels increases in the opening direction of the door, so that the pairs of panels protrude when the door opens. Although said detachable pairs of panels are usually and preferably horizontal moving up and down guided by sealing troughs mounted on their ends, usually U-steels, they can also be mounted on the side of the wall opening as a combination of vertical pairs of panels and between the lower guides, acting in the same way as a door formed by horizontal panels, but moving across a wall opening from the edge of the opening to the edge.

The panels of the nested pairs of panels are best connected to each other by handles so that they remain vertically parallel, the panels forming a door panel unit with the handles connecting them, said base having said transverse handles and said panels facing downwards. The top and bottom edges of the adjacent panels have U-shaped bends and also have rollers that prevent the panels from scratching each other as they slide interleaved vertically.

The open space between the panels forms a channel through which air can flow unimpeded from the fan in connection with the upper end of the door between the lower panels at the lower end of the door, acting as nozzles, or to a nozzle mounted on said lower panels, from which it exits as an air curtain.

Thus, the door structure described above may, if necessary, act as a mere door consisting of the most interlocking units forming an easily strong door to be raised and lowered, in which the panels of each unit lock tightly to adjacent panels, stiffening the door surface; but nevertheless forming an air duct of varying length from the interior of the door, along which air can flow in the direction of movement of the door, the door was then fully open or completely closed or in some position between these extreme positions in the wall opening. Thanks to such a structure, the fan can be easily and simply mounted fixedly on the wall at the wall opening inside the space delimited by said wall, whereby the fan draws warm or cold air from said interior by blowing it into the air chamber installed in the wall opening above the door. From this air chamber, the air flows evenly downwards to the nozzle at the bottom, from where it exits as an air curtain to the desired height. Transverse airflow towards the room can easily be achieved by providing the inner half of the door with air vents to the desired height.

The foregoing description is intended only to illustrate embodiments and not to limit the invention other than on the basis of the following claims.

Claims (9)

An air curtain device, in which air from an air chamber (19) is measured across a doorway via an outlet (44) from the air chamber, characterized in that a wall portion of the air chamber (19) is designed as a compressible hollow door (10-17), the inner space of which always forms an open connection between the air chamber and the outlet (44), the outlet being arranged at the free end of the door and is preferably adjustable in and for changing the air direction. An air curtain device according to claim 1, characterized in that the door is formed by parallel door elements (10-17) in that the individual door elements at the front and back of the door, seen in a direction perpendicular to the door plane, are mutually displaced, so that during the pull-out and compression glide at each other. 3 · Air curtain device according to claim 2, characterized in that the opposing door elements (10, 11-12, 13-14, 15-16, 17) are connected to each other, for example by means of transverse straps (46). Air curtain device according to claim 1 or 2, wherein the door at the sides is guided in U-shaped guides (18), characterized in that the guides (18) have abutments (56, 57) for supporting the individual door elements (12 - 17). ) in the extended position. 5 · Air curtain device according to claim 4, characterized in that the stops are inwardly facing portions (56) of the legs (54) of the U-shaped guides (18). 6. An air curtain device according to claim 4, characterized in that the stops consist of step-like inserts (57) arranged on the legs (54) of the guides (18). 7 · Air curtain device according to any of the preceding claims, characterized in that the air chamber (19) and / or one or more door elements (11) have adjustable (92) openings for expelling air to the room. An air curtain device according to any one of claims 2-7, characterized in that the individual door elements (10-17) are slidably supported by rollers (68) in a manner known per se. An air curtain device according to claim 2, characterized in that the opposing door elements are closed together in the closing direction, open to the cross section U-shaped element (78), each element having at least one tubular channel (86) extending from the U : the bottom (66) of the telescopic interaction with the tubular channel (86) of the closing element (78).