FIRE DAMPER FOR VENTILATION SYSTEM

Abstract

 A fire damper for a ventilation system has expandable sealing means (11, 12) configured to seal the interface between outer edge portions of a damper blade (310) and inner wall portions of a fire damper frame (110). The expandable sealing means (11, 12) extends along the inner frame wall portions, which define an air flow opening of the fire damper, and it is covered by a flexible sealing fabric (13).

Description

TECHNICAL FIELD

[0001] The present invention relates to a fire damper for a ventilation system, as well as a ventilation system comprising such a fire damper.

BACKGROUND

[0002] Fire dampers are frequently used in ventilation systems. They come in different sizes and shapes and have the purpose of preventing the spread of fire and/or smoke through the building. Typically, when a rise in temperature is detected the fire damper closes its damper blades to stop the flow of for instance poisonous gases in the ventilation ducts. A sealing mechanism is typically present on either the damper blade or the fire damper frame, or both. This enables the blades of the fire damper to keep shut during a fire.

[0003] There are certain drawbacks with the sealing mechanism of prior-art structures. For instance, the structure may be difficult to mount. In some cases, the sealing mechanism may also adversely affect the air flow through the fire damper. This is because it takes up much space in the interface between the edge portions of the damper blade and the inner surface of the fire damper frame.

[0004] For fire dampers with several damper blades, the prior-art structures at hand are difficult to mount and/or do not provide a sufficient sealing between the damper blades and the fire damper frame. Hence, there are improvements to be made.

[0005] A known fire damper called 'RABR' marketed by Bevent Rasch is disclosed in a pamphlet dated 21/08/2020. In certain situations, fire dampers of this kind suffer from some of the drawbacks mentioned above. For instance, various seals are oftentimes provided on the blades of the fire damper which adds to the overall costs. Furthermore, a frame made up of sheet metal and relying solely on seals between the blades may lead to insufficient sealing effect in the closed position.

[0006] Further background art is disclosed for instance in WO2007/068786A1 and EP2062617A1.

SUMMARY

[0007] An object of the present invention is to solve or at least mitigate the problems related to prior-art. This object is achieved by means of the technique set forth in the appended independent claims; preferred embodiments being defined in the dependent claims.

[0008] In one aspect, there is provided a fire damper for a ventilation system, which comprises a frame defining an air flow opening, and at least one damper blade which is configured to close and open the opening and which is rotatably mounted to the frame. Furthermore, there is provided expandable sealing means configured to seal the interface between edge portions of the damper blade and inner wall portions of the frame in the closed position, and to extend along the inner frame wall portions, which define the air flow opening. A flexible sealing element covers the expandable sealing means.

[0009] An advantage of the flexible sealing element is that it provides a smooth and adaptive sealing. Moreover, the flexible sealing element does not disturb the air flow when the damper blades are in open position. Another advantage of the flexible sealing element is that it provides a reduced heat transfer between an inner and outer side of the fire damper. It hence creates a heat barrier between the two sides (openings) of the fire damper. One side is facing the presumed heat area, and the other is facing the cold area in the ventilation system.

[0010] In conventional fire dampers, it is common to provide sealing arrangements on both the frame and the damper blades. Hence, an advantage of providing sealing means on the frame - as in the fire damper of this disclosure - is that the damper blades may have a simpler structure and/or shape. With the sealing concept of the fire damper according to the teachings herein, which will be further described below, there is no need for additional sealing means between each blade. For fire dampers with more than one blade, this also reduces the time for manufacturing the damper blades and/or mounting them onto the frame. The simplicity of the frame structure facilitates the production of the fire damper.

[0011] In an embodiment, the expandable sealing means comprises a strip of intumescent material configured to - upon activation - press against edge portions of the at least one damper blade in the closed position.

[0012] In a further embodiment, the expandable sealing means comprises a strip of resilient material, such as rubber.

[0013] Preferably, the intumescent strip and resilient strip are arranged in conjunction with each other and extend in parallel to each other along the inner circumference of the frame which defines the opening of the fire damper.

[0014] In an embodiment, the expandable sealing means comprises a strip of intumescent material and a strip of resilient material, such as rubber, disposed on top of the intumescent strip. This strip assembly covered by the flexible element provides an efficient sealing effect in the interface between the frame and the blades. Preferably, the expandable sealing means covered by the flexible element extends around an inner circumference of the frame, thereby forming a continuous resilient pad. This design further enhances the sealing effect.

[0015] The flexible sealing element is preferably made from a fire retardant web of fabric material having a low-friction outer surface for engagement with an edge portion of the damper blade. Furthermore, the flexible sealing element may have a silicone coating. Additionally, the flexible sealing element may be impermeable to the material of the expandable sealing means. The flexible sealing element may also be interpreted as giving rise to a tension or resistance between the frame and the blades of the fire damper.

[0016] In an embodiment, the flexible sealing element has an inner surface configured to face an associated frame wall portion, and an outer surface configured to engage with an edge portion of the damper blade, such as end edge portions of each damper blade and longitudinal edge portions of the damper blades configured to abut two opposing wall portions of the fire damper frame. Preferably, the outer surface of the flexible element is a low-friction surface. Put differently, the flexible sealing element has an inner surface and an outer surface, wherein the inner surface is configured to face an adjacent frame wall portion and the outer surface is configured to abut an edge portion of a damper blade.

[0017] In another embodiment, an elongated space extends along the length of each frame wall portion and is defined by the adjacent frame wall portion and the inner surface of the flexible sealing element opposite the frame wall portion. Moreover, the elongated space is configured to accommodate the expandable sealing means arranged on the inner frame wall portion. Thanks to this limited space, less expandable or swelling material is needed for the sealing means, which in turn reduces the cost of manufacture.

[0018] In yet another embodiment, the flexible sealing element has longitudinal lateral portions which are fastened to the frame wall portion. The flexible sealing element also has a mid section at a distance from the frame wall portion. When the lateral portions of the flexible sealing element are fastened to the associated frame wall portion, the distance between the flexible sealing element and the frame wall portion, related to the position of the mid section, provides the elongated space described above. This elongated space may have a substantially parabolic shape when seen in cross section.

[0019] The expandable sealing means is configured to be accommodated in the elongated space opposite the mid section of the flexible sealing element.

[0020] In an embodiment, the frame comprises four frame wall portions which - when assembled - form a substantially rectangular frame. Preferably, each one of the four frame wall portions comprises an elongated groove which extends along a length of the frame wall portion and which receives the expandable sealing means. An advantage with such a groove in the frame wall portions is that the mounting of the expandable sealing means is facilitated since it fits directly in place. This reduces the time and cost of assembling the frame. Furthermore, the protrusion of the sealing means in the air flow channel can be reduced. Another advantage of having a groove in the frame wall portions is that the thickness of the interface between the frame wall portions and the edge portions of the damper blades is reduced. This way, the pressure drop is reduced in comparison with bulky prior-art sealing structures. A further advantage of having a groove in the frame wall portions is that the amount of expandable sealing means may be reduced. This reduces the overall cost of producing the fire damper.

[0021] The fire damper may further comprise means for operating the at least one damper blade and for locking the same in the closed position.

[0022] In a further aspect, there is provided a ventilation system comprising at least one fire damper designed in line with the structures described above.

[0023] An idea behind the improved fire damper concept of the teachings herein is that the emergency arrangement configured to engage the damper blades in the closed position is based on a seal assembly which extends around the inner circumference of the fire damper frame. This seal assembly is smoothly covered by a flexible sealing element, preferably a fire-retardant fabric, which extends around the inner circumference of the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By way of example, embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a perspective partial view of a fire damper with four damper blades in an open position,

Fig. 2 is a perspective view of four frame wall portions of a fire damper frame,

Fig. 3 is a perspective view of a fire damper frame with four damper blades in a closed position,

Fig. 4 is a schematic representation of an inner wall portion of a fire damper,

Fig. 5 is a perspective view of an inside of a fire damper with two damper blades shown,

Fig. 6 is a close up view of an end portion of a frame wall portion shown in Fig. 2,

Fig. 7 shows the assembly of Fig. 6 with a sealing element arranged on top,

Fig. 8 is a cross-sectional view of a damper blade rotated with respect to a frame wall portion from an open position to a closed position,

Fig. 9 is a cross-sectional view of the damper blade of Fig. 8 in a closed sealing position with respect to the frame wall portion,

Fig. 10 is a cross-sectional view of the damper blade of Figs 8-9 in the closed position during and after fire, and

Fig. 11 is a perspective view of a multi-blade fire damper shown in an open position.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] With reference to Fig. 1, a fire damper FD according to an embodiment is shown. The fire damper FD has a frame 100 built up by four frame wall portions 110, 111, 112, 113 (see Fig. 2). Each wall portion has an inner side facing an air flow opening AFO of the fire damper FD and an outer side facing outwards from the fire damper FD. The multi-blade fire damper FD is configured to be installed in a duct of a ventilation system but may also be installed in a wall of a building. The frame wall portions 110-113 are preferably made from a fire retardant material, such as calcium silicate. They may also be made of other suitable materials.

[0026] The fire damper FD and its frame 100 have a substantially rectangular shape. For instance, the dimensions of the fire damper may be 200x200 mm up to 800x800 mm or more. Mounted to the first and second side wall portions 110, 111 at the inner circumference of the frame 100 are four substantially rectangular damper blades 310, 320, 330, 340. Each damper blade 310, 320, 330, 340 has respective end edge portions 311, 311', 321, 321', 331, 331', 341, 341' configured to be rotatably mounted to the fire damper frame 100 at distinct positions such that each damper blade 310, 320, 330, 340 is arranged in parallel with a neighboring damper blade. Each damper blade is mounted to the frame 100 at pivot points by means of which each damper blade 310, 320, 330, 340 is rotatable between an open and closed position. The open position is shown in Figs 1 and 11, and the closed position is shown schematically in Fig. 3.

[0027] Blade operating means 510, 520, 530, 540 are arranged at the pivot points on an external side of the fire damper FD at the same side as the second side wall portion 111. Corresponding blade operating means are arranged at corresponding pivot points on an opposite outer side of the fire damper FD at the same side as the first side wall portion 110 (not shown in Fig. 1). The frame 100 and its components will be further described below.

[0028] In the following, the emergency operation of the fire damper FD shown in Fig. 1 is described. In case of fire, hot fire gases at a temperature in the excess of about 72 °C spread in the building and in the ventilation system in which the fire damper FD is installed. Once such fire gases are detected by sensor means (not shown), the blade operating means 510-540 of the fire damper FD are activated by an actuator (not shown) so that the damper blades 310, 320, 330, 340 close the air flow opening AFO of the fire damper FD and are locked in closed position. Typically, the actuator is linked to the blade operating means via a linkage system (not shown).

[0029] For instance, the linkage system may be coupled to a temperature sensor and/or smoke detector (not shown). The linkage system, which is preferably covered by a casing 550, may be controlled by a control unit 500 (see Fig. 11). The movement of the blade operating means may be effected by means of an electric motor (which may have a temperature sensor and/or smoke detector) and/or the linkage system. When the sensor or detector is activated, the electric motor is deactivated and the air flow opening AFO of the fire damper FD is closed. For instance, the sensor and/or detector may be located in the ventilation duct, in the vicinity of the fire damper.

[0030] The sensor means operatively coupled to the fire damper may be sensitive to temperature, gases and/or smoke. For instance, the sensor means may be located in the vicinity of the fire damper FD or somewhere else in the building. The sensor means may be a fire and/or smoke detector or the like. The emergency operation of the fire damper FD will be further described below, in particular with reference to Figs 8-10.

[0031] The frame 100 of the fire damper FD is illustrated in Figs 2 and 3 with its four frame wall portions or frame members 110-113. In Fig. 2 the inner wall portions are shown, i.e. the sides of the frame wall portions facing the air flow opening AFO of the fire damper FD. Each frame wall portion 110-113 is elongated and has a substantially rectangular shape. The four wall portions can be divided into a first side wall portion 110, a second side wall portion 111, a top wall portion 112 and a bottom wall portion 113. In Fig. 2, the side wall portions 110, 111 are somewhat shorter than the top wall portion 112 and the bottom wall portion 113. However, it may be that the side wall portions 110, 111 are longer instead.

[0032] The first side wall portion 110 has a first sheet metal strip 120 and the second wall side portion 111 has a second sheet metal strip 120' attached to their surface. Put differently, the first sheet metal strip 120 is provided on the first side wall portion 110 and the second sheet metal strip 120' is provided on the second side wall portion 111. Each sheet metal strip 120, 120' is elongated and arranged along the length of the first and second side wall portions 110, 111, respectively. The first sheet metal strip is provided with first pivot shaft holes 121, 122, 123, 124 and the second sheet metal strip is provided with corresponding second pivot shaft holes 121', 122', 123', 124'. The pivot shaft holes are arranged at a distance from one another along the length of the respective sheet metal strip 120, 120'. In turn, the pivot shaft holes are configured to receive a type of rotatable shaft (not shown) which is in turn configured to hold each one of the rotatable damper blades in position. The length of each sheet metal strip 120, 120' corresponds to the end positions of the pivot shaft holes 121, 124 and 121', 124', respectively.

[0033] Furthermore, each frame member 110-113 has a groove 130 (not shown in Figs 2-3) extending along the length of the same. This will be further discussed below in relation to Figs 6-7.

[0034] In Fig. 3, the frame 100 is shown as assembled. As can be seen, the first side wall portion 110 is arranged opposite the second side wall portion 111. The top wall portion 112 is in turn arranged opposite the bottom wall portion 113. Together, they define a substantially rectangular frame 100. The damper blades 310, 320, 330, 340 are rotatably mounted to the inner first side wall portion 110 at their respective end edge portions 311, 321, 331, 341 and on the inner second side wall portion 111 at their corresponding opposite end edge portions 311', 321', 331', 341'. Here, the damper blades 310, 320, 330, 340 are in their closed position. In other words, the air flow opening AFO as previously shown in Fig. 1 (and 11) is shut in Fig. 3.

[0035] By the improved fire damper FD in accordance with the teachings herein, one can slow down the spread of heat through a fire damper. Moving on to Figs 4-5, a part of the frame is shown schematically.

[0036] In Fig. 4, a frame structure according to an embodiment is shown. Here, a sealing arrangement 10 is arranged to separate an inner sheet metal piece 210, 212, 213 and an outer sheet metal piece 220, 222, 223. The inner and outer sheet metal pieces clamp the sealing arrangement 10 to the frame 100. The clamping of the sealing arrangement 10 to the frame by means of the inner and outer sheet metal pieces is further illustrated schematically in Figs 8-10. The sealing arrangement 10 is preferably made from materials with a coefficient of thermal conductivity which is substantially lower than steel. In case of emergency, the blade operating means will move the damper blades 310, 320, 330, 340 into closed position. This way, high temperature gases heading towards the fire damper FD from either side of the fire damper will be hindered from spreading both by the physical blocking of the damper blades 310, 320, 330, 340 in closed position, and by the sealing arrangement 10 which has a substantially lower thermal conductivity than steel. The sealing arrangement 10 will be further described below. The dots provided on the sealing arrangement 10 correspond to the first pivot shaft holes 121-124 of the first sheet metal strip 120 referred to with respect to Fig. 2 above. These holes 121-124 are configured to receive mountings of the damper blades 310, 320, 330, 340.

[0037] Fig. 5 illustrates a part of the frame from another perspective. Here, two damper blades 310 and 320 are shown rotatably mounted to an inner side wall portion of the frame 100. As can be seen, the damper blades 310, 320 are in an open position and the sealing arrangement 10 is provided along an inner circumference of the frame 100. In fact, the sealing arrangement 10 is attached to an inner frame wall portion. The inner frame wall portion is not shown in Fig. 5 since it is covered by the sealing arrangement 10. Inner sheet metal pieces and outer sheet metal pieces of the fire damper are then arranged on an inner side of the respective inner frame wall portions 110-113, on opposite sides of the sealing arrangement 10. It is clear from Fig. 5 that the damper blades 310, 320 are in close contact with and abutting the sealing arrangement 10 at their end edge portions 311' and 321'.

[0038] Only one corner of the inside of the fire damper is shown in Fig. 5. It should be noted that the sealing arrangement 10 is provided along the entire circumference of the inside of the fire damper frame. Also shown in Fig. 5 is the longitudinal side edge portions of the damper blades 310, 320. Each damper blade is provided with a corresponding elongated recess 350, 351, also called a blade engaging portion, which extends along the entire length of each damper blade. In short, the blade engaging portion 350 of the damper blade 310 is configured to, in a closed position, engage with an adjacent blade engaging portion 351 of its neighboring damper blade 320. This way, the air flow opening AFO will be shut in the closed position. This function applies equally to the damper blades which are not shown in Fig. 5. It follows that the blades having their longitudinal side edge portions in contact with the top wall portions and bottom wall portions, respectively, only have one blade engaging portion each.

[0039] Thanks to the matching blade engaging portions 350, 351 of the damper blades 310, 320 shown in Fig. 5, a tight and secure engagement is achieved between adjacent damper blades in the closed position. This efficient abutment and engagement makes it possible to use a blade design without extra seals on the blade edge surfaces which engage each other when the fire damper blades are closed. Owing to this "seal-free" design, extra costs can be avoided which reduces the overall cost of the fire damper.

[0040] The arrows in Fig. 5 indicate the rotational movement of the blades 310, 320 when they are to be turned into the closed position. The damper blades 310, 320 are movably controlled by the control unit 500 shown in Fig. 11, which for instance can be an electric motor.

[0041] In Fig. 6, a part of the frame wall portion 113 of Fig. 2 is shown. Here, one can clearly see the groove 130 as briefly mentioned above. In the groove 130, an expandable sealing element or strip 11 is provided. This expandable strip 11 may for instance be made from an intumescent sealing material which swells at elevated temperatures, for instance caused by hot fire gases. A different wording for this is a heat expanding graphite material. Furthermore, the expandable strip 11 has an elongated shape and extends along the length L1, L2, L3, L4 of the groove 130 (see Fig. 2). For instance, L1-L4 are substantially of the same length. The expandable strip 11 can be seen as a strip of intumescent material which is configured to - upon activation, i.e. at elevated temperatures ― press against edge portionsof each damper blade 310, 320, 330, 340 in the closed position (see Fig. 10). The strip 11 may for instance be about 1,5 mm thick. The activation of the expandable strip 11 is referred to as the point in time at which the expandable strip 11 is affected by a temperature rise over a predetermined temperature of about 130-180 °C such that it starts swelling.

[0042] On top of the expandable strip 11, a sealing element or strip 12 of resilient material is arranged. Together, the expandable strip 11 and the resilient strip 12 may be referred to as an assembly. The resilient strip 12 also has an elongated shape which, when seen in cross-section, is substantially half-moon-shaped. See also Figs 8-10. The resilient strip 12 is typically a strip of resilient material, such as rubber. More specifically, the resilient strip 12 may be made of EPDM (Ethylene Propylene Diene Monomer) rubber. However, other shapes are possible for both the expandable strip 11 and the resilient strip 12 as long as they fulfil their purpose of providing a pressure against a flexible cover or sealing element 13 to substantially provide a parabolic shape. This shape will be further described below in relation to Figs 8-10.

[0043] Just as for the expandable strip 11, the resilient strip 12 extends along the length L1-L4 of the groove 130. The resilient strip 12 is not necessarily arranged on top of the expandable strip 11. Rather, the resilient strip 12 is arranged in conjunction with the expandable strip 11. For instance, the resilient strip 12 may be arranged substantially adjacent to the expandable strip 11 within the groove 130. Moreover, the resilient strip 12 may be attached to the expandable strip 11 by an adhesive (not shown). The expandable strip 11 and the resilient strip 12 work together to provide a tight seal against the damper blades in a cold mode, i.e. when the temperature is at or below 72 °C, since the resilient strip 12 presses against the flexible sealing element 13 which in turn creates a seal between the frame and the respective damper blades.

[0044] The reason why the groove 130 does not extend along the entire length of the top wall portion 112 and the bottom wall portion 113 as shown in Fig. 2 lies in the mounting or assembly of the frame 100 from the four frame wall portions 110, 111, 112, 113. As shown in Figs 2 and 6-7, each frame wall portion 110-113 has a groove 130 extending along the length of the respective wall portion. These should be regarded as non-limiting examples. Hence, optionally, no groove 130 is present in the frame wall portions 110-113 and the sealing arrangement 10 is provided on substantially flat inner surfaces of the wall portions 110-113 of the frame 100. This is shown for instance in Figs 8-10.

[0045] In Fig. 7, the part of the frame wall portion 113 of Fig. 6 is shown, now with the flexible sealing element 13 on top. The flexible sealing element 13 covers the assembly formed by the expandable strip 11 and the resilient strip 12. The following description applies to the other frame wall portions 110, 111, 112 as well. Together, the expandable strip 11, the resilient strip 12 and the flexible sealing element 13 define a sealing arrangement 10 of the type described above. Just as for the expandable strip 11 and the resilient strip 12, the flexible sealing element 13 extends substantially along the length L1-L4 of the groove 130.

[0046] When the fire damper is in a closed position, the sealing arrangement 10 is in contact with the end edge portions of the damper blades at the interface between the damper blades and an inner side wall portions 110 and 111 of the frame 100, as well as with longitudinal edge portions of two damper blades at the interface between the two damper blades and an inner top and bottom wall portion 112, 113, respectively. This is shown explicitly in Fig. 3 and implicitly in Fig. 5. The flexible sealing element 13 has a substantially rectangular strip-like shape, and it is preferably made from a fire retarding web of fabric material which may be provided with a coating, for instance silicone. The coating may be provided on both sides of the flexible sealing element 13. Preferably, the flexible sealing element 13 has a low friction surface to engage the edge portions of the damper blades. Moreover, it is configured not to disturb the air flow when the damper blade is in an open position. Contrarily, together with the expandable strip 11 and the resilient strip 12, it is configured to engage the damper blade in a closed position to block the air flow. The flexible sealing element 13 may be fixedly attached to the frame wall portions 110-113 by stapling with staples 601, 602, 603, 604. Optionally, the flexible sealing element 13 is attached to the frame wall portions 110-113 by an adhesive (not shown).

[0047] Moreover, on all frame wall portions 110-113, holes 400 for mounting the inner and outer sheet metal pieces on either side of the flexible sealing element 13 of the sealing arrangement 10 are present.

[0048] In the following, the sealing arrangement 10 contributing to the effective sealing of the fire damper is described. Applicable to all frame wall portions 110-113 described herein, the flexible sealing element 13 may be seen as a barrier between a damper blade 310, 320, 330, 340 and an associated frame wall portion. An outer surface OS of the flexible sealing element 13 is configured to be in engagement with an edge portion of the fire damper blade. Furthermore, the outer surface OS is of low-friction material so that the damper blades can rotate smoothly against the outer surface OS of the flexible sealing element 13.

[0049] Between the frame wall portion and an edge portion of the associated damper blade, the flexible sealing element 13 which preferably is impermeable to the material of the expandable sealing strip 11, defines a limited expansion zone, or elongated space ES, for the expandable sealing strip 11. In particular, this elongated space ES, slows down the expansion process of the expandable sealing strip 11 at high temperatures, such as during fire. The resilient strip 12 is also present under the flexible sealing element cover 13 and fulfils its sealing purpose up until it has been burnt away, which is when the fire damper is activated. Notably, in case of fire and/or smoke, the resilient strip 12, which typically is of rubber material, burns away at higher temperatures.

[0050] The flexible sealing element 13 has an inner surface IS facing an associated frame wall portion. Furthermore, the flexible sealing element 13 has lateral portions 13A, 13B fastened to the frame wall portion, for instance by means of fasteners 601-604 (see Fig. 7) or by an adhesive. A mid or intermediate section 13C of the flexible sealing element 13 between the lateral portions 13A, 13B is arranged at a distance from the frame wall portion. The elongated space ES, which extends along the length of the frame wall portion, is defined by the adjacent frame wall portion and the inner surface IS of the flexible sealing element 13 opposite the frame wall portion. As mentioned, the elongated space ES accommodates the expandable sealing means 11, 12 provided on the inner frame wall portion opposite the mid section 13C of the flexible sealing element 13. As a result of this sealing arrangement 11-13, only a limited amount of swellable sealing strip 11 is needed to ensure a proper sealing between the inner frame wall portion and the associated damper blade since it will not be consumed as fast as if there were no flexible sealing element present. Thanks to this sealing arrangement 10, the fire damper can stay in a closed position for up to 60 minutes using only a relatively small amount of expandable sealing strip 11.

[0051] Now turning to Figs 8-10, the emergency operation of the fire damper FD is further illustrated schematically. It is to be noted that Figs 8-10 apply to all end edge portions 311, 321, 331, 341, 311', 321', 331', 341' of the damper blades 310, 320, 330, 340 described herein. Furthermore, Figs 8-10 also apply to the longitudinal edge portions of the dampers blades which are in contact with the top and bottom wall portions 112, 113 of the frame 100 as shown in the drawings. No groove 130 is shown in Figs 8-10. Thus, as already mentioned, the presence of the groove 130 in previously illustrated embodiments should be regarded as non-limiting examples.

[0052] Fig. 8 shows a first side wall portion 110 of the fire damper FD when a damper blade 310 is in an open position. The arrow illustrates the rotational movement of the damper blade 310. In the normal open position, i.e. at ambient temperature or at temperatures below about 72 °C, the expandable strip 11 is not activated. On top of the expandable strip 11, the resilient strip 12 is arranged. The resilient strip 12 provides a sealing function in the closed position of the fire damper. Together, the expandable strip 11 and the resilient strip 12 form an assembly. On top of this assembly, the flexible sealing element 13 is arranged to provide a smooth and flexible surface with respect to the end edge portion 311 of the damper blade 310. One can say that the resilient strip 12 is sandwiched between the expandable strip 11 and the flexible sealing element 13. Here, the resilient strip 12 abuts against the flexible sealing element 13 such that the flexible sealing element 13 is arc-shaped or forms the shape of a parabola. On either side of the flexible sealing element 13, the inner and outer sheet metal pieces 210, 220 are provided to form the inside of the fire damper FD. In an alternative embodiment, the expandable strip 11 is placed substantially within a groove 130 of the associated frame wall portion 110 as shown in Figs 2 and 6-7.

[0053] In Fig. 9, the fire damper FD is in a closed position right after the blade operating means have rotated the damper blade 310 into the closed position, i.e. right upon/after activation by an actuator (not shown). This situation arises when for instance fire and/or smoke has been detected somewhere in the building. The detection may be performed by a sensor as described previously. At this point, the air flow opening AFO is closed. As can be seen, the end edge portion 311 of the damper blade 310 comes into abutment against the flexible sealing element 13 which is now smoothly bent. The resilient strip 12 is pressed between the expandable strip 11 and the flexible sealing element 13. As shown in Fig. 9, the resilient strip 12 contributes to the sealing of the damper blade 310 against the inner frame wall portion 110 in the closed position of the fire damper. Until now, the expandable strip 11 is still not activated since the temperature rise has not yet affected the intumescent material properties of the same.

[0054] Furthermore, as shown in Figs 8-9, the resilient strip 12 applies pressure against the mid section 13C of the flexible sealing element 13 such that the end edge portion 311 of the blade 310 can rotate smoothly at the flexible sealing element 13 and so as not to create undesired air bubbles between the outer surface OS of the flexible sealing element 13, constituting the outermost part of the sealing arrangement 10, and the end edge portions of the associated blade.

[0055] Fig. 10 illustrates the situation during or after fire. Here, the temperature is high enough for the expandable strip 11 to swell. This typically occurs at temperatures of about 130-180 °C. Thus, Fig. 10 shows the situation in which the expandable strip 11 is activated by an increase in temperature. At this point, the resilient strip 12 has melted and burned away. The expandable strip 11 swells due to its intumescent material properties and thereby presses against the end edge portion 311 of the damper blade 310 which is still in a locked/closed position. The swelling of the expandable strip 11 improves the seal at the interface between the first side wall portion 110 and the end edge portion 311 of the damper blade 310. The flexible sealing element 13, which is still present, presses against the end edge portion 311 of the damper blade 310 to securely lock the same. This way, only a limited amount of expandable sealing strip 11 is needed to ensure a proper sealing between the inner frame wall portions and the damper blades. Moreover, thanks to the sealing arrangement 10, the fire damper can stay in a closed position for up to 60 minutes. In the absence of a flexible sealing element 13, the expandable strip 11 would for instance have the dimensions 30x4 mm instead of 15x1,8 mm, where the latter is more favorable since less material can be used. In other words, during or after fire, the expandable strip 11 helps, together with the flexible sealing element 13, in creating a tight seal between the frame and blades.

[0056] Moreover, as already mentioned, the groove 130 described with respect to Figs 2 and 6-7 may be arranged in the frame side wall portion 110 of Figs 8-10. The groove 130 would then be configured to receive at least one of the expandable strip 11 and the resilient strip 12. In that case, the interface between the side wall portion 110 and the end edge portion 311 of the damper blade 310 would be smaller (thinner) as compared to the situation shown in Figs 8 and 9 since the assembly of the expandable strip 11 and the resilient strip would be "hidden" in the side wall portion 110. In other words, the parabola shape of the flexible sealing element 13 would be shifted towards the side wall portion 110, thereby reducing the distance between the sealing arrangement 10 and the end edge portion 311 of the damper blade 310. Hence, the pressure drop between the inner and outer sides of the fire damper FD would also be reduced.

[0057] It should be noted that Figs 8-10 only show the interface between the first side wall portion 110 and the damper blade 310. It is to be understood that the situation of Figs 8-10 applies alto to the rest of the described damper blades 320, 330, 340 and the respective wall portions 111, 112, 113 as well. There is a circumferential sealing arrangement surrounding the edge portions of the damper blades in the closed position.

[0058] Put differently, the expandable strip 11 may be arranged in the groove 130 of each frame wall portion 110-113 in order to reduce the size or thickness of the interface between the damper blades 310, 320, 330, 340 and the inner circumference of the frame 100. At temperatures below the predetermined temperature about 72 °C (Fig. 8), the sealing arrangement 10 is intact. In other words, the expandable strip 11, the resilient strip 12 and the flexible sealing element 13 exhibit their original shape. At temperatures just above about 72 °C (Fig. 9), such as in the initial moments of a fire and/or smoke detection, the blade operating means has closed the damper blades and the sealing arrangement 10 as a whole starts to react to the rise in temperature. At this point, the flexible sealing element 13 is in engagement with the edge portion of the associated damper blade.

[0059] At temperatures well above about 72 °C (Fig. 10), the resilient strip 12 has decomposed (burnt) and the expandable strip 11 is in its expanding mode. Here, the expandable strip 11 presses against the edge portions of each corresponding damper blade. In other words, the expandable sealing strip 11 presses against the flexible sealing element 13 which is in abutment with the associated blade and limits the further expansion of the expandable sealing strip 11 which would otherwise leak out on both sides of the fire damper. Hence, a tight seal is achieved and the fire/gas and the heat are prevented from spreading through the fire damper FD.

[0060] The sealing mechanism can also be described in the following manner. When in a cold mode, i.e. when the temperature is below 72 °C, the resilient strip 12 presses against the flexible sealing element 13 which in turn creates a seal between the frame 100 and the respective damper blades. The flexible sealing element 13 does not disturb the air flow in an open position. In hot mode, i.e. when the temperature is well above about 72 °C, the flexible sealing element 13 is heated, the resilient strip 12 decomposes, and the expandable strip 11 takes over and presses against the damper blade which is in closed position. The expandable strip 11 preferably creates a foam which is impermeable to air. Moreover, when in hot mode the expandable strip 11 diffuses into crevices and possible cracks, thereby contributing to a reliable sealing between the frame and the damper blades.

[0061] It should be noted, that the damper blades are typically in an open position at ambient temperature and when no particular poisonous or hazardous gases are detected. At temperatures below about 72 °C, the damper blades are normally in an open position to allow air flow through the fire damper. At temperatures above about 72 °C, the damper blades are shut by the mechanical blade operating means into a closed position. In the open position, air can flow through the air flow opening. In the closed position, air cannot flow through the opening.

[0062] The activation of the expandable strip 11 occurs when a sensor/detector (not shown) has sensed something upon which the blade operating means 510, 520, 530, 540 are actuated. One can say that the blade operating means are actuated by an actuator. The actuator may be an electric motor. When the blade operating means 510, 520, 530, 540, are actuated by for instance an electrical signal coming from a smoke detector, each damper blade 310, 320, 330, 340 is rotated from the open position to the closed position. It may be that the blade operating means have been actuated by an increase in temperature over a predetermined value.

[0063] Moreover, when mounted to the frame 100, the flexible sealing element 13 covers the expandable sealing means 11, 12. In the open position of the fire damper FD, i.e. when the air flow opening AFO is open, the flexible sealing element cover 13 assumes an essentially parabolic shape when seen in cross-section. Moreover, the elongated space ES between the inner surface IS of the flexible sealing element 13 and the adjacent inner frame wall portion 110-113 may be regarded as a space-limited expansion zone for the expandable sealing means 11, 12, in a sense that the expansion of the expandable sealing means 11, 12 is restricted in the elongated space ES. This implies that in case of fire and/or smoke, the air flow opening AFO is closed upon activation, and the expandable sealing means 11, 12 is allowed to expand in the space-limited expansion zone under the sealing element cover 13 only to a certain extent.

[0064] Put differently, when the fire damper FD is activated to be in a closed position due to a rise in temperature, the expansion of the expandable sealing means 11, 12 is limited by the flexible sealing element 13. This way, in contrast to existing prior-art structures, only a limited amount of expandable sealing means 11, 12 is required to hold back the spread of fire and/or smoke through the fire damper FD for a given time period. This is advantageous in that a smaller amount of expandable sealing material, or strip 11 is used in comparison with prior-art structures.

[0065] Hence, the flexible sealing element 13 may limit the expansion of the expandable sealing strip 11 of the expandable sealing means 11, 12 due to its material characteristics. This way, the time period during which the expandable sealing strip 11 is consumed may be prolonged. Another advantage of the sealing setup discussed above is that a reduced amount of expandable sealing strip 11, as compared to similar prior-art setups, may be used.

[0066] In an aspect, there is provided a sealing arrangement 11-13 for a fire damper FD to be included in a ventilation system. The sealing arrangement comprises expandable sealing means 11, 12 configured to - upon activation - seal the interface between edge portions of a damper blade 310 and inner wall portions of a fire damper frame. The expandable sealing means 11, 12 extend along the inner frame wall portions, which define an air flow opening AFO of the fire damper FD, and are covered by a flexible sealing element 13 which preferably is of a fire retardant material

[0067] Finally, it should be mentioned that the invention is by no means limited to the embodiments described herein and modifications are feasible without departing from the spirit of the invention. For instance, the number of damping blades may vary as well as the means for operating the same. The frame carrying the blades may have different shapes than the one described herein. Although rectangular fire dampers are described herein, other shapes are possible. The same goes for the cross section of the ventilation duct in which the fire damper is installed. Even though the resilient strip has been shown on top of the expandable strip, other arrangements are feasible.

Claims

1. A fire damper for a ventilation system, comprising:

a frame (100) defining an air flow opening;

at least one damper blade (310, 320, 330, 340) configured to close and open said opening, said damper blade being rotatably mounted to the frame (100); and

expandable sealing means (11, 12) configured to seal the interface between edge portions of the damper blade (310, 320, 330, 340) and inner wall portions of the frame (100) in said closed position; said expandable sealing means (11, 12) extending along said inner wall portions, which define said opening, and being covered by a flexible sealing element (13).

2. The fire damper as claimed in claim 1, wherein said expandable sealing means comprises a strip (11) of intumescent material configured to - upon activation - press against edge portions of said at least one damper blade (310, 320, 330, 340) in the closed position.

3. The fire damper as claimed in claim 2, wherein said expandable sealing means comprises a strip (12) of resilient material, such as rubber.

4. The fire damper as claimed in claim 3, wherein said intumescent strip (11) and said resilient strip (12) are arranged in conjunction with each other and preferably extend in parallel to each other along the inner circumference of the frame (100) which defines said opening.

5. The fire damper as claimed in claim 4, wherein said resilient strip (12) is disposed on top of the intumescent strip (11).

6. The fire damper as claimed in any one of the preceding claims, wherein said flexible sealing element (13) is made from fire retardant material.

7. The fire damper as claimed in any one of the preceding claims, wherein the flexible sealing element (13) has an inner surface (IS) configured to face an associated frame wall portion (110-113), and an outer surface (OS) configured to engage with an edge portion of the damper blade (310, 320, 330, 340), wherein the outer surface (OS) preferably is a low-friction surface.

8. The fire damper as claimed in claim 7, wherein an elongated space (ES) extending along the length of each frame wall portion (110, 113) is defined by the adjacent frame wall portion (110-113) and the inner surface (IS) of the flexible sealing element (13) opposite said frame wall portion (110-113), and wherein said elongated space (ES) accommodates the expandable sealing means (11, 12) arranged on the inner frame wall portion (110-113).

9. The fire damper as claimed in any one of the preceding claims, wherein the flexible sealing element (13) has longitudinal lateral portions (13A, 13B) fastened to the frame wall portion (110-113), and a mid section (13C) at a distance from said frame wall portion (110-113).

10. The fire damper as claimed in claim 9, wherein the expandable sealing means (11, 12) is accommodated in said elongated space (ES) opposite said mid section (13C) of the flexible sealing element (13).

11. The fire damper as claimed in any one of the preceding claims, wherein said expandable sealing means (11, 12) covered by the flexible sealing element (13) extends around an inner circumference of the frame (100), thereby forming a continuous resilient pad.

12. The fire damper as claimed in any one of the preceding claims, wherein the frame (100) comprises four frame wall portions (110-113) which - when assembled - form a substantially rectangular frame.

13. The fire damper as claimed in claim 12, wherein each one of the four frame wall portions (110-113) comprises an elongated groove (130) extending along a length of said frame wall portion, wherein the groove (130) receives said expandable sealing means (11, 12).

14. The fire damper as claimed in any one of the preceding claims, further comprising means for operating said at least one damper blade (310, 320, 330, 340) and for locking said at least one damper blade in said closed position.

15. A ventilation system comprising at least one fire damper as claimed in any one of the preceding claims.

Drawing