Fire barrier structure for fire damper

The present invention relates to an annular fire barrier structure which is mountable close to the pass-through point of a fire damper on a wall or ceiling structure, where it is adapted about the duct sleeve element of the fire barrier to receive heat conducted along the duct element and further conduct the heat, e.g., to the wall structure wherein or whereon it is mounted, and which fire barrier structure has placed thereon a tightening band structure.

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 flange 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 ventilation 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.

In all prior-art fire dampers, the fire barrier structure comprises one or possibly a greater number of fire barrier flanges. Depending on longitudinal width (thickness) of the fire barrier, this typically gives sufficient leak-proofness and thermal insulation under a fire situation. However, a risk arises from, e.g., a crack of the flange, whereby the level of leak-proofness falls substantially. A similar problem may also come from the seal joints when the flange is made from two or more parts as described in Fl Pat. Appl. 20051278.

It is an object of the present invention to provide for a fire damper a novel type of fire barrier structure that is free from the above-described problem. The invention is characterized in that the fire barrier structure is comprised of two or a greater number of fire barrier flanges that are adjacently joined with each other in the longitudinal direction of the ventilation duct center axis.

A preferred embodiment of the fire barrier structure according to the invention is characterized in that the number of the fire barrier flanges is two and that the tightening band structure surrounding the flanges comprises a single, contiguous tightening band enclosing both two of the fire barrier flanges.

Another preferred embodiment of the fire barrier structure according to the invention is characterized in that either one of the fire barrier flanges comprises two or a greater number of parts in a conventional fashion and that the end joints of the adjacent fire barrier flanges are mutually displaced circumferentially.

One of the benefits of the invention is that the first flange receives the heat load thus protecting the inner flange. Hence, a possible crack appearing in

the first flange does not cause an immediate risk of leak in the entire fire barrier structure as the next flange remains intact. If the flanges are comprised of multiple parts, they have circumferential joints. Accordingly, the invention allows the joints to be displaced circumferentially in the adjacent flanges so that the structure is free from discontinuities thus reducing the risk of leaks.

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. This kind of mounting is illustrated in more detail in FIG. 1. The fire damper typically comprises a ventilation duct 2 extending through the thickness of wall 1 and a fire barrier structure 3, 3' mounted about the duct sleeve element so as to face the wall. About the fire barrier flange is adapted a tightening band 4 having a width substantially covering the thickness of the flange 3, 3' and a length substantially extending over the entire perimeter 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.

The cross-sectional view of FIG. 2 shows the fire barrier structure comprising two fire barrier flanges 3 and 3', of which the flange denoted by reference numeral 3 is the one located closer to the wall 1. In a conventional fashion, the flange is located at a perforation made about the ventilation duct 2. Additionally, a second fire barrier flange 3' is mounted adjacent to the first fire barrier flange 3. Resultingly, the flanges are situated adjacent to each other and closely abutting in the longitudinal direction of the center axis of

ventilation duct 2. Resultingly, under a fire the flange closest facing the heat receives the heat load thus protecting the next flange. The flanges may have an equal width or, alternatively, the outer flange may be thinner as depicted in the embodiment of FIG. 2. However, the applications of the invention are not limited by such dimensional details.

Having the fire barrier flanges implemented as multipart structures of more than one part as disclosed in Fl Pat. Appl. 20051278, the circumferential joints of each flange are advantageously adjusted in the adjacent flanges into different positions to further enhance the leak integrity of the fire barrier structure.

To a person skilled in the art it is obvious that the invention is not limited by the above-described exemplary embodiment, but rather may be varied within the inventive spirit and scope of the appended claims. Accordingly, while the fire barrier flanges are advantageously made of calcium silicate, also other suitable materials may be considered in the spirit of the invention. While the inner fire barrier flange 3 is most advantageously against a wall, this is no limiting condition for the use of the invention.

It is further possible to provide the inner periphery of both or only one fire barrier flange with a groove suited to be filled with an intumescent seal material capable of sealing under fire the seam between the ventilation duct 2 and the fire barrier structure.

The above text relates to an exemplifying embodiment having two fire barrier flanges. However, the invention is not limited thereto, but instead, the number of fire barrier flanges may be greater as required.

SUBSTITUTE SHEET βRuto 26)

ventilation duct 2. Resultingly, under a fire the flange closest facing the heat receives the heat load thus protecting the next flange. The flanges may have an equal width or, alternatively, the outer flange may be thinner as depicted in the embodiment of FIG. 2. However, the applications of the invention are not limited by such dimensional details.

Having the fire barrier flanges implemented as multipart structures of more than one part as disclosed in Fl Pat. Appl. 20051278, the circumferential joints of each flange are advantageously adjusted in the adjacent flanges in different positions to further enhance the leak integrity of the fire barrier structure.

To a person skilled in the art it is obvious that the invention is not limited by the above-described exemplary embodiment, but rather may be varied within the inventive spirit and scope of the appended claims. Accordingly, while the fire barrier flanges are advantageously made of calcium silicate, also other suitable materials may be considered in the spirit of the invention. While the inner fire barrier flange 3 is most advantageously against a wall, this is no limiting condition for the use of the invention.

It is further possible to provide the inner periphery of both or only one fire barrier flange with a groove suited to be filled with an intumescent seal material capable of sealing under fire the seam between the ventilation duct 2 and the fire barrier structure.