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:
[0001]    This application is a continuation-in-part of U.S. application Ser. No. 10/518,378 filed Feb. 8, 2005, which is a filing under 35 USC 371 of PCT/NO2003/000238 filed Jul. 4, 2003, and a continuation-in-part of U.S. application Ser. No. 12/476,223 filed Jun. 1, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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&#39;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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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 
       [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    Further objects will be discussed in the description of embodiments of the invention. 
         [0017]    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.       
 
         [0023]    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.       
 
         [0029]    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. 
         [0030]    The invention will be described further in connection with examples of embodiments, which discloses further details of the invention. 
         [0031]    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. 
         [0032]    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.       
 
         [0043]    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 
         [0044]    The invention will be further described below with reference to the drawings, in which: 
           [0045]      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; 
           [0046]      FIG. 3  is a cross sectional view of a second embodiment of the invention, with a one-way vent, 
           [0047]      FIG. 4  is a cross sectional view of a further embodiment of the invention, being arranged in a cavity, and 
           [0048]      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 
       [0049]    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. 
         [0050]    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 . 
         [0051]    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.       
 
         [0055]    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. 
         [0056]    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. 
         [0057]    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. 
         [0058]    In this embodiment mainly different elements are used to provide the different functions of the invention. 
         [0059]    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. 
         [0060]    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. 
         [0061]    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 
       [0062]      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. 
         [0063]    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. 
         [0064]    The frame  22  is intended for a one way ventilation device, but an optional symmetrical part  22 A for a corresponding two way device is also shown. 
         [0065]    Centrally in the frame  22 , an intumescent grid or grille  24  is shown. Any common intumescent ventilation grid can be applied. 
         [0066]    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. 
         [0067]    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. 
         [0068]    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 . 
         [0069]    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 
       [0070]      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. 
         [0071]    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 . 
         [0072]    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. 
         [0073]    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. 
         [0074]    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. 
         [0075]    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. 
         [0076]    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. 
         [0077]    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 
       [0078]      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. 
         [0079]    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 . 
         [0080]    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 . 
         [0081]    The mass of the board  50  functions as a thermal shield or heat insulation. 
         [0082]    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. 
         [0083]    In an alternative embodiment, for two way use, the hole design may be symmetrical, with a larger bore on each side. 
         [0084]    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.