Fire barrier for fire damper

The present invention relates to an annular fire barrier flange which is mountable close to the pass-through point of a fire damper on a wall or ceiling structure, where the barrier is adapted about the duct sleeve element of the fire damper to receive heat conducted along the duct element and further conduct the heat therefrom forward to the basic structure wherein or whereon it is mounted, and which barrier has placed thereon a tightening band with a width substantially equal to the thickness of the barrier and a length extending substantially about the perimeter of the barrier.

Accordingly, the invention more particularly relates to a fire damper for a ventilation duct of a circular cross section, wherein the damper blade obviously also is circularly shaped. Broadly, the function of a fire damper is such that under normal conditions the blade is either in an open or a closed position as desired. Under fire, the fusible link of the fire damper melts thus allowing the blade to close if it has previously been in its open position. The rotation of the fire damper blade may be implemented, e.g., with the help of a spring or a separate actuator motor.

The fire damper is mounted, e.g., in a wall or ceiling structure or on the surface thereof. Onto the duct sleeve of the fire damper is generally mounted an annular fire barrier serving to receive the heat conducted along the duct sleeve and forward the heat to the wall structure (when the fire barrier is mounted against the wall). Additionally, the fire barrier may be employed for sealing the duct sleeve element's perforation that serves to retard thermal conduction in the fire damper duct. Still further, a fire barrier flange can be utilized in mounting a fire damper on a wall surface.

The fire barrier flange is conventionally fabricated into a single element either by casting or cutting from a prefabricated material such as a calcium silicate

plate. A problem handicapping the use of a single-part fire barrier flange is its slightly complicated installation. Moreover, casting such an object is a clumsy and time-consuming operation due to the lengthy drying period.

Alternatively, the fire barrier may have a multipart structure of more than one flange part for easier installation as is disclosed in Fl Pat. Appl. 20051278.

Wall and ceiling structures are designed for different fire resistance ratings, commonly known in the art as, e.g., 30 min, 60 min and 120 min fire rating. Herein, also the fire barrier must be compatible with the higher fire ratings. To this end, the seal has to be improved to make the fire barrier meet the sealing and fire rating requirements of the longer time and higher temperature. It is an object of the invention to achieve a fire barrier structure capable of fulfilling such extended fire rating and leak-proofness requirements. The fire barrier according to the invention is characterized in that between the fire barrier flange and the ventilation duct, substantially surrounding the entire perimeter of the duct, is adapted an intumescent seal. This arrangement makes the structure energy-absorbing and capable of receiving the deformations of the duct's metallic structure.

A preferred embodiment according to the invention is characterized in that to the inside surface of the fire barrier flange, substantially about the entire inner periphery thereof, is made a groove wherein the intumescent seal material is placed. By virtue of the groove, the intumescent seal during its intumescence remains firmly fixed in place thus assuring a prolonged leak-proofness under stress.

Another preferred embodiment according to the invention is characterized in that the cross section of the virgin intumescent seal is made smaller than the size of the groove. Then, the intumescent seal has a swelling freeboard, whereby the intumescent swelling of the seal cannot break the edge of the fire barrier flange.

The invention is next described in more detail with the help of a preferred exemplifying embodiment by making reference to the appended drawings in which

FIG. 1 shows an axonometric view of a wall portion having a fire damper of circular cross section mounted thereon; and

FIG. 2 shows a cross-sectional view of the assembly of FIG. 1.

Accordingly, the invention relates to fire damper of a circular cross section mounted in a hole made through a wall 1. The fire damper typically comprises a ventilation duct sleeve element 2 extending through the thickness of wall 1 and a fire barrier flange 3 surrounding the duct sleeve element so as to face the wall. About the fire barrier flange is adapted a tightening band 4 hav- ing a width substantially covering the thickness of the flange 3 and a length substantially extending over the entire periphery of the flange. The tightening band is tensioned in place by means of screws, for instance, as illustrated in the diagrams at the tightening point denoted by reference numeral 5.

FIG. 2 shows a cross section of a metallic duct sleeve element 2 with the fire barrier flange 3 adapted thereabout. Additionally shown in FIG. 2 is perforation 6 serving to retard thermal conduction in the ventilation duct. The fire barrier flange 3 is mounted at perforation 6.

The essential feature of the invention is that the seam between the fire barrier flange and the ventilation duct sleeve is secured by an intumescent seal material. One method of implementing this arrangement is to provide the inside surface of the fire barrier flange in the fashion indicated by reference numeral 7 in FIG. 2 with a groove that encircles with a substantially constant cross section about the entire inner periphery ("inside surface") of the fire barrier flange 3. Into this groove 7 is placed an intumescent seal 8 having a cross section smaller than that of groove 7. In the illustrated embodiment, the

intumescent seal is particularly selected to be narrower than the groove 7, whereby the intumescence of the seal cannot break the flange edge at the groove.

To a person skilled in the art it is obvious that the invention is not limited by the above-described exemplary embodiments, but rather may be varied within the inventive spirit and scope of the appended claims. Accordingly, the seal groove depth and shape can be modified to suit a particular application and optimized dimensioning. Respectively, the invention is by no means limited to a certain material of fire barrier flange or whether the flange is made as a single-part or multipart element.

It is further possible to adapt plural fire barrier flanges adjacent to each other, whereby at least one, possibly all of the flanges has/have an intumescent seal arrangement of the type according to the invention. Hereby, the intumescent seal of one additional flange can also protect the adjacent flange next to it. The intumescent seal of the first flange begins to function at the temperature of approx. 200 ⁰ C, while the flange more remote from the fire begins to swell later. The intumescent seal also retards axial conduction of heat and seals any cracks.