METHOD FOR FIRE BLOCKING IN A VENTILATION DEVICE AND A FIREBLOCKING VENTILATION DEVICE

Abstract

A flame and fire resistant ventilation device includes a mesh element having a plurality of vent openings dimensioned to quench transient flames, a swelling element formed of or coated with an intumescent material, to permanently seal the ventilation device during sustained fire exposure, at least one heat sink body providing a surface for absorbing and dissipating heat, at least one heat storing capacity element associated with the heat sink body to prevent fire spread by sustained direct exposure to flames, and a heat insulating structure to prevent fire spread through the ventilation device by heat conduction, at least for the initial period of swelling of the swelling element.

Description

BACKGROUND OF THE INVENTION

The invention relates to a flame resistive ventilation device intended as a fire blocking device, in particular for blocking flames, which can be transferred through ventilation grates and similar apertures with air transfer (“ventilation devices”). The term “fireblocking ventilation device” is directed to a passive element, open for air transfer, which prevents the spreading of fire by penetration of flames, heat conduction, convection or radiation. The invention also relates to a method for fire blocking in a ventilation device.

Open flame arresters are known which function as heat sink for explosive combustion or short-lived fireballs. They are arranged open, so that air transfers, but not flames. They are often made of steel, either as perforated plates or mesh or as steel strip bodies pressed together, and similar. The function of arresting deflagration combustion first became known as Davy's net in 1815, used by Sir Humphrey Davy, and such elements have been used for different industrial purposes, such as for engine block ventilation and in gas production facilities, as explosion flame shields for personal safety offshore and similar.

Building fires are in some instances transferred by flames spreading through openings and channels containing or being adjacent to combustible elements or materials. An example of such a risk in buildings are the inlets to ventilated, non-heated roofs (voids) or attics, where flames on the outside of a wall or from a window, can spread through ventilators in eaves and into combustible structures in attics. Such areas are not easy accessible, and fires that take hold in such areas often result in dramatic consequences.

Such fire spreading is hard to stop, and thus far one has not considered it possible to combine the demand for venting and fire resistance. Activateable dampers are considered to be too unsafe because flames can pass for minutes before closing, because of the weathering, because of mechanical and movable parts and because of dry materials, which can ignite before closing.

From U.S. Pat. No. 5,565,274 (Perrone et al.) is known, for instance, an attic hatch, which comprises intumescent material and which is closed with a heat-triggered activator.

From U.S. Pat. No. 5,811,731 (Jacques et al.), it is known to line an intumescent material around a cable channel. There are vents for conducting excess heat from cables and a steel grille, which will be disintegrated in case of a fire.

From U.S. Pat. No. 5,750,927 (Baltazar), an air tight fire resistant cover is known, which has the ability to dissipate heat from the solid material being protected.

From U.S. Pat. No. 3,976,825 (Anderberg) a tight cable penetration is known, which is provided for blocking air in normal operation, and smoke and fire in the event of fire.

Previously known patents and solutions for preventing fire spreading in openings for air passages have a weakness in that, during a period before they are activated, they allow flames to pass through and ignite combustible gas and/or easily ignitable solid materials on the side that is to be protected. Some certified products allow gaps or insufficient sealing, which make pilot flames and smoke spreading possible, even when they are closed.

In U.S. patent application Ser. No. 10/518,378, parent of this application, a fire blocking device is described which comprises a grille body with a plurality of openings permitting an air flow therethrough, said body being formed of, or coated with an intumescent material and a thermally conductive metal mesh also permitting an air flow, wherein the metal mesh has a capacity for heat storage and the intumescent material swells when exposed to sufficient heat to seal the openings.

Being suitable for some areas of use, this previous fire blocking device had limitations in more respects, e.g. for making a cavity fire barrier and for providing a two way ventilation device.

SUMMARY OF THE INVENTION

The main object of the present invention is to create passive and instantly acting fireblocking devices, being an improvement to the prior art, including the ventilation device of the parent application.

It is a further object to provide a fire stop air ventilation device for air passages, which instantly, i.e. even during the first millisecond and until the openings are sealed prevent fire from spreading via the air passage from one area with a fire, to a room, duct or other building or machine voids, where fire can cause damage and/or spread further to other and vulnerable areas with combustible materials that can spread a fire.

It is a still further object to provide a versatile flame resistive ventilation device, which can have different embodiments for various purposes, both one-way and two-way. As an example, the ventilation device should be adaptable for use as a cavity flame barrier device.

Further objects will be discussed in the description of embodiments of the invention.

To achieve the above objects, the invention is directed to a novel method for blocking fire in a ventilation device arranged in building or similar structure, comprising:

• • providing at least one mesh element for quenching flames to which the device is exposed;
  • providing at least one element which can absorb heat from the flames to which it is exposed;
  • providing at least one element which accumulates the heat absorbed by the heat absorbing element for an initial period exceeding the swelling period of the swelling element;
  • providing an intumescent swelling element which swells upon exposure to heat, converting the device from open to closed state; and
  • retarding transfer of heat by providing a thermal break to the heat absorbed during the period of fire resistance.

The invention also comprises a flame and fire resistant ventilation device, comprising:

• • a mesh element having a plurality of vent openings dimensioned to quench transient flames,
  • a swelling element formed of or coated with an intumescent material, to permanently seal the ventilation device during sustained fire exposure;
  • at least one heat sink body providing a surface for absorbing and dissipating heat;
  • at least one heat storing capacity element associated with the heat sink body to prevent fire spread by sustained direct exposure to flames; and
  • heat insulating means to prevent fire spread through the ventilation device by heat conduction, at least for the initial period of swelling of the swelling element. When used for instance in vented roofs or vulnerable eaves, the fireblocking devices according to the invention will instantly prevent flame spreading while not blocking air passage in the normal state. At the same time, birds, insects, leaves and embers are kept out. The air velocity may be reduced in regard to fully open venting gaps between soffit boards, but this may be an advantage, as new research indicates that former regulations were exaggerated and less energy efficient.

The fireblocking devices according to the invention can be produced at low cost with inexpensive materials. Installation of the fireblocking device or post-installation with replacement of existing ventilating grilles, respectively, can take place without any particular training and in an easy manner. Furthermore, it is possible to make the fireblocking device according to the invention maintenance-free.

The invention will be described further in connection with examples of embodiments, which discloses further details of the invention.

Examples of applications of the invention are vents in walls, bulkheads, tanks, ducts, air duct terminals, openings for natural ventilation, in processing plants, vented facade exteriors, vented fire blankets, open fire protective curtains or open protective screens against explosions.

The advantages of a fireblocking device according to the invention can be summarized as follows:

• • No mechanical movable parts.
  • It can be installed into fire barriers, protective hoods, pipes, ducts, vented dressings, vented roofs and attics.
  • It prevents fire spreading by heat convection, instantaneously and during the entire fire resistance period.
  • It prevents fire spreading by heat radiation, instantaneously and during the entire fire resistance period.
  • It prevents fire spreading by heat conduction, instantaneously and during the entire fire resistance period.
  • It is non-combustible.
  • It prevents fire spreading by explosion combustion, diffuse flame combustion and fire ball.
  • It becomes gas tight from impact of heat from fire.
  • It can be cleaned by flushing.
  • It can be post-installed into existing constructions.

A fireblocking device according to the invention can be used in various applications. It is suitable for buildings, especially in connection with vented attics and as ventilating grilles for ducts and voids that contains combustible material, or which can transfer flames to other combustible structures. Additional fireblocking devices according to the invention can be arranged after one another in a duct or in a transition area. Smoke blocking can easily be obtained by integrating a smoke blocking device or adding one in series as prescribed for smoke and fire dampers by current regulation (ICC in USA).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described below with reference to the drawings, in which:

FIGS. 1 and 2 are a front view and a schematic cross section, respectively, of an embodiment of the invention with a two-way structure;

FIG. 3 is a cross sectional view of a second embodiment of the invention, with a one-way vent,

FIG. 4 is a cross sectional view of a further embodiment of the invention, being arranged in a cavity, and

FIG. 5 is a cross sectional view through sample vent openings in board with multiple vent openings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. Basic Two Way Flame and Fire Resistant Ventilation Device

In FIG. 1. a front view and in FIG. 2, a cross section through a first embodiment of a flame resistive ventilation device 11 according to the invention are shown schematically.

The flame resistive ventilation device 11 is arranged in an opening 12 in a wall 13 of a building. The ventilation device 11 is arranged in a rectangular or alternatively round or oblong frame 14.

The flame resistive ventilation device 11 of FIG. 1 has five main elements:

• • on each side of the ventilation device a heat sink element 15, 16 comprising a mesh which may also have a quenching effect,
  • an open mesh intumescent element 17, 18 adjoining each of the heat sink elements, and
  • a centrally arranged quenching gap element 19 comprising a metal mesh.

This embodiment may be arranged to have a relatively low temperature in the central area of the quenching gap element 19, allowing the use of a non-heat resistant material.

The embodiment of the ventilation device 10 shown in FIG. 1 is related to a wall 11 by being arranged with a frame 12 in a hole 13 in this wall. The frame will then act as a thermal insulator. The hole 13 may be rectangular, circular or with another suitable form.

A pair of grilles 17 and 18 are arranged in a series in the frame 12. The grilles 17 and 18 are made of intumescent material or of a metal grid or slats coated with an intumescent material.

In this embodiment mainly different elements are used to provide the different functions of the invention.

A vent according to this embodiment may typically have a size of 500×500×30 millimeters. The mesh elements may be of stainless steel and typically have a mesh size of about 1 to 8 millimeters, e.g. 2 millimeters.

The mesh in practical embodiments of the invention may serve multiple purposes, such as reinforcing intumescent expansion, providing effective venting area and providing flame quenching.

The invention does not require any specific intumescent material. Designs that require large expansion may require 5-15 times expansion of normal state, while even 2 times expansion may be sufficient in other designs. Typical intumescent materials are basically hydrants or endothermic materials containing water that transforms to steam upon heat exposure, or they may be sodium silicate or graphite used for providing high pressure expansion which compacts the resulting char.

2. One-Way Flame and Fire Resistant Ventilation Device

FIG. 3 shows the cross section of a second embodiment of a flame resistive ventilation device 21 according to the invention. The embodiment of FIG. 3 is intended for one-way use, which may be sufficient for many purposes, for example for venting non-heated roofs or attics.

The ventilation device of FIG. 3 comprises a frame 22, e.g. of hard wood, for providing a thermal break. Any material of low thermal conductivity and heat resistance may be used. The exposed face is covered with a shield 23 which may be of any reactive intumescent material of endothermic, heat sink properties.

The frame 22 is intended for a one way ventilation device, but an optional symmetrical part 22A for a corresponding two way device is also shown.

Centrally in the frame 22, an intumescent grid or grille 24 is shown. Any common intumescent ventilation grid can be applied.

On each side of the intumescent grille 24, a metal mesh with a quenching effect is arranged, on the upstream side a first quenching element 25 and on the downstream side a second quenching element 26. The main purpose of the quenching elements 25 and 26 is to provide an instant blocking of flames through the ventilation device. Both quenching elements 25, 26 may also have a heat sink effect.

Upstream of the first quenching element 25, a heat sink 27 provided by a metal sheet or dish with multiple perforations is arranged, the perforations each having a maximum size corresponding to a quenching gap size of fire gases.

Downstream of the second quenching element 26, a further metal mesh 28 of wire is arranged. This metal mesh provides a further third quenching element 29.

In an alternative embodiment, the quenching elements 25, 26 may be deleted, the element 29 then being the main quenching element. In either case, the inumescent grille 24 and the heat sink 27 may have a quenching effect. All said elements will contribute to the heat absorbing and the heat sink effect.

3. Cavity Flame and Fire Resistant Ventilation Device

FIG. 4 shows a cross section through a cavity ventilation device 31 according to an embodiment of the invention. The cavity ventilation device 31 is arranged in a cavity 32 defined by e.g. the core wall 33 and the sheathing 34 of a building. The cavity 32 can extend over the height of the core wall 33 and along the complete perimeter of the building. Thus the cavity ventilation device 31 can have the general shape of a rod manufactured in suitable lengths, to be inserted in the cavity 32 before arrangement of the sheathing.

The cavity ventilation device 31 of this embodiment comprises two generally tubular rolls 35, 36 of wire mesh or grid, which are formed of one sheet, with an intermediate web 37 connecting the rolls 35, 36. The web 37 is tangentially to the rolls, providing a plain side for resting against the core wall 33.

In each of the tubular rolls 35, 36 an intumescent element 38, 39 is inserted. The intumescent elements 38, 39 are ribbon shaped and arranged parallel to the core wall 33, leaving a space 40, 41 on each side for venting. The intumescent elements may be carbon based, with a thickness of 4 millimeters and a width of 45 millimeters.

The tubular rolls 35, 36 and the intermediate web 37 may be of a 2 millimeter wire mesh. Thus the rolls 35 of metal mesh will act as a quenching gap element for instant flame blocking. Typical dimensions for the rolls 35, 36 when oblong are 28×36 millimeters.

The tubular rolls 35, 36 will have the double function of providing a heath sink on the inlet side and a quench gap on the outlet side. Thus the cavity vent 31 will be two-sided, sustaining flames from both sides.

Used at the lower part of a wall of a building, the cavity vent according to the invention will also provide a bar for small rodents, small birds and similar animals.

By making the intumescent elements 38, 39 of a mesh, allowing venting, said elements may be arranged horizontally, which may provide a more efficient closing when exposed to flames. This arrangement is however more likely to be clogged by deposits of dust over time.

In an alternative embodiment, the cavity vent according to the invention may have an intumescent element in only one of the tubular rolls 35, 36, preferably the lower. It may also comprise a single roll, with one or more intumescent element.

4. Perforated Board Vent

FIG. 5 shows a section through a board 50 provided for construction purposes. The board 50 may be of any common construction material, e.g. of fiberboard, gypsum, composite material, high density mineral wool or any substrate that by itself will resist fire exposure. The basic requirement is the ability to act as a heat barrier for a certain period of time, normally defined by building and fire protection regulations.

The board 50 has multiple stepped holes 42, 43, 44. Each stepped hole has a narrow part 45 with quenching abilities to stop the flames, and a wider part 46 accommodating an annular cartridge 47 of an intumescent material to act as a swelling element when heated. The walls 48 of the narrow part 45 function as a heat sink and a heat accumulator. The walls of the wider part are designated as element 49.

In an alternative embodiment, the holes are uniform, the quenching gaps will be the restrictions achieved by the annular or doughnut shaped cartridges 47 of intumescent material. The heat absorber will be the exposed mass of the board 50, the heat sink will be the mss of the same board, which will also function as an insulator, together with the air of the holes 42-44.

The mass of the board 50 functions as a thermal shield or heat insulation.

A typical size of the board 50 may be 2400×1200×30 millimeters. The smaller opening may have a diameter of 2 millimeters, the wider opening may be typically up to 10 millimeters. The intumescent ring may have an inner diameter of 2-5 millimeters or more, designed to close the smaller opening.

In an alternative embodiment, for two way use, the hole design may be symmetrical, with a larger bore on each side.

As a material for a heat sink element or heat accumulator, it is possible to utilize a range of materials and structures for heat absorption, e.g. one or more of the following endothermic materials or heat sink structures: mesh grids, water-filled tubes and pellets, gypsum pellets, chemical endothermic ampoules, powder pellets, sand, gravel, and other endothermic devices and porous materials that permit cold air transfer.

Claims

1. Method for blocking fire in a ventilation device arranged in building or similar structure, comprising: providing at least one mesh element for quenching flames to which the device is exposed;providing at least one element which can absorb heat from the flames to which it is exposed;providing at least one element which accumulates the heat absorbed by the heat absorbing element for an initial period exceeding the swelling period of the swelling element;providing an intumescent swelling element which swells upon exposure to heat, converting the device from open to closed state; andretarding transfer of heat by providing a thermal break to the heat absorbed during the period of fire resistance.

2. Method according to claim 1, additionally comprising passing air trough an open space between the swelling element and the mesh element, and the heat absorbing element.

3. Method according to claim 1, wherein a plurality of mesh elements are provided.

4. Method according to claim 1, wherein a centrally located mesh element is provided.

5. A flame and fire resistant ventilation device, comprising: a mesh element having a plurality of vent openings dimensioned to quench transient flames,a swelling element formed of or coated with an intumescent material, to permanently seal the ventilation device during sustained fire exposure;at least one heat sink body providing a surface for absorbing and dissipating heat;at least one heat storing capacity element associated with the heat sink body to prevent fire spread by sustained direct exposure to flames; andheat insulating means to prevent fire spread through the ventilation device by heat conduction, at least for the initial period of swelling of the swelling element.

6. A ventilation device according to claim 5, wherein at least one said mesh element with a plurality of openings with quenching abilities for the fire gas introduced at a fire, is arranged downstream to the swelling element.

7. A ventilation device according to claim 6, wherein the integrated mesh element is arranged in a distance downstream to the swelling element to leave a heat absorbing airspace.

8. A ventilation device according to claim 6, comprising a further mesh with at least a plurality of openings with quenching ability, said further mesh being arranged downstream to the first mesh, at a distance therefrom.

9. A ventilation device according to claim 5, wherein the swelling element has a plurality of evenly distributed openings permitting an air flow therethrough.

10. A ventilation device according to claim 9, comprising two said swelling elements to provide bidirectional function, arranged symmetrically to a said mesh element with a plurality of openings provided to quench flames.

11. A ventilation device according to claim 5, comprising a supportive metal mesh upstream of the swelling element.

12. A ventilation device according to claim 11, wherein the supportive metal mesh is integrated with the swelling element.

13. A ventilation device according to claim 5, for blocking fire in a cavity in a building through which air flows, which cavity may extend over at least a substantial part of a wall or a floor, comprising: an elongated swelling element, anda longitudinal channel element of mesh which is arranged to surround at least a part of the swelling element, to provide a quenching element and a heat sink and a heat absorber at least at the upstream side of the device,said swelling element being arranged coplanar to a direction in which the air flows through the cavity.

14. A ventilation device according to claim 13, wherein the longitudinal channel element is tubular and arranged to fill the cavity in cross section.

15. Device according to claim 14, comprising two said longitudinal channel elements, at least one of said longitudinal channel elements being provided with an intumescent element and wherein said two tubular elements are joined by a web of the mesh material.

16. Device according to claim 13, wherein the mesh is a perforated metal sheet.

17. A ventilation device according to claim 5, wherein the mesh element comprises a dish with multiple perforations each having a maximum size corresponding to a quenching gap size of fire gases.

18. A ventilation device according to claim 5, wherein the heat storing capacity element comprises at least one material or structure selected from the group consisting of a mesh grid, water-filled tubes, water-filled pellets, gypsum pellets, chemical endothermic ampoules, powder pellets, sand and gravel.

19. A flame blocking ventilation device, comprising at least one mesh element comprising a board with heat insulating properties, with a plurality of openings with quenching abilities for the fire gas introduced at a fire, each of the plurality of opening being stepped in size, from a larger portion to a smaller portion; anda swelling element arranged within an opening of the at least one mesh element in the larger portion thereof, comprising an intumescent material with the ability to swell during a swelling period when exposed to the heat of a fire, to close the passage for an air flow,wherein the mesh element has heat absorbing and heat accumulating capacities for the swelling period, and providing a thermal break.