The invention can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.
A fire-resistant shroud (“Fire Shroud”) is provided for an electromagnetic device that is mountable with a portion of the electromagnetic device in a barrier surface of an interior space. As an example, the electromagnetic device may be a barrier surface-mountable loudspeaker. In a further example, the barrier surface-mountable loudspeaker may be a ceiling-mountable loudspeaker. The Fire Shroud includes a synthetic vitreous fiber body having a cavity configured to the shape of the portion of the electromagnetic device. As an example, the cavity may be configured to the shape of a barrier surface-mountable loudspeaker back-can. The synthetic vitreous fiber body may, as an example, include a first synthetic vitreous fiber sheet in the form of a cylinder. In an example, the cylinder may have first and second cylinder edges respectively defining first and second cylinder ends. A second synthetic vitreous fiber sheet may, as an example, be joined with the first cylinder edge and may close the first cylinder end.
Much of the ensuing discussion is directed to Fire Shrouds for barrier surface-mountable loudspeakers. However, in a further example, a Fire Shroud may be configured for utilization with another electromagnetic device that may be mountable with a portion of the electromagnetic device in a barrier surface of an interior space. As an example, such an electromagnetic device may be an in-barrier lighting fixture. In an additional example, such an in-barrier lighting fixture may include a cylindrical back-can typically mounted with a cylinder axis oriented at an angle to the barrier surface, such as a right angle. Such an in-barrier lighting fixture may, as another example, include an elongated back-can mounted coplanar to and with a shallow penetration of the barrier surface.
The term “synthetic vitreous fiber” as used throughout this specification broadly means and includes wools and continuous glass filaments, as they are defined by the International Agency for Research on Cancer (“IARC”). Synthetic vitreous fibers are generally formed from inorganic materials derived from one or more sources including rock, slag, glass precursors such as sand, and clay. The compositions of synthetic vitreous fibers primarily include ingredients selected from silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and iron oxide, and may as examples include other alkaline metal oxides, alkaline earth metal oxides, and other metal oxides. The term “wool” as used throughout this specification broadly means and includes mineral wool, glass wool, refractory ceramic fibers, and engineered bio-soluble fibers. The term “continuous glass filaments” as used throughout this specification broadly means and includes glass filaments formed from a molten composition derived from one or more sources including rock, slag, glass precursors such as sand, and clay that is extruded from a nozzle and continuously spun or drawn. As an example, continuous glass filaments may be made from a composition primarily including silicon dioxide, aluminum oxide, boron oxide, and calcium oxide. In an example, such a composition may be commercially referred to as “electrical glass” or “E-glass,” such as a borosilicate glass.
The term “mineral wool” as used throughout this specification includes slag wool and rock wool, the latter also referred to as stone wool. Rock wool is generally made from compositions including igneous rock such as basalt, diabase, olivine, or their mixtures. Slag wool is generally made from compositions including blast furnace slag. Glass wool is generally made from compositions including more than about 50% by weight silicon dioxide, and may as an example include silicon dioxide at a concentration within a range of between about 55% and about 70% by weight. Refractory ceramic fibers are generally made from compositions including kaolin, having high concentrations of both silicon dioxide and aluminum oxide.
The wools are generally formed from a molten composition by rotary or centrifugal spinning processes without extruding the molten composition through a nozzle. In an example, a wool may be made by melting a composition including inorganic materials derived from one or more sources including rock, slag, glass precursors such as sand, and clay, and blowing a stream of a gas such as air through the molten composition. The gas may include water, in the form of steam as an example. As a further example, the molten composition for forming the wool may then be centrifugally or radially spun onto a spinning wheel.
The absence of extrusion of a molten composition through a nozzle in methods for forming molten compositions into wools typically results in production of discontinuous fibers rather than continuous filaments. The resulting fibers typically have variable diameters. As an example, the diameters of rock wool fibers may vary within a range of between about 3 microns and about 7 microns. In another example, the diameters of glass wool fibers may vary within a range of between about 3 microns and about 15 microns. As a further example, the diameters of refractory ceramic fibers may vary within a range of between about 1 micron and about 5 microns. In contrast, the diameters of continuous glass filaments may, as an example, be controlled to a selected portion of a range, such as a selected portion of a range of between about 3 microns and about 25 microns.
The potential for fibers that are formed from any type of composition to be respirable and to then potentially cause diseases such as cancer is a general concern in fiber manufacture and utilization. Toxicity of fibers, including synthetic vitreous fibers, is partially dependent on their physical dimensions. In general, the greater the diameter and length of fibers, the lower is their typical airborne concentration and resultant potential toxicity. As an example, fibers having diameters of less than about 3 microns are considered by the IARC to be respirable. In general, wools accordingly may be more likely to contain respirable fibers than continuous glass filaments, as filaments tend to have substantially greater lengths and because the diameters of such filaments may be better controlled during manufacture than may be the diameters of discontinuous wool fibers. Since the diameters of some typical rock wool fibers and glass wool fibers may be as small as about 3 microns, some of such fibers may be respirable. In addition, since the lower end of a typical fiber diameter size range for refractory ceramic fibers may be about 1 micron, more of the fibers in refractory ceramic fiber wools may be respirable. In an example where a wool is selected as the source of synthetic vitreous fibers for making synthetic vitreous fiber sheets or a synthetic vitreous fiber body in fabricating a Fire Shroud 100, the type of wool that is selected may be a mineral wool or a glass wool. Utilization of refractory ceramic wools as the source of synthetic vitreous fibers for making synthetic vitreous fiber sheets or a body in fabricating a Fire Shroud 100 may, as an example, thus be avoided. As another example, continuous glass filaments may be selected as the source of synthetic vitreous fibers for making synthetic vitreous fiber sheets or a body for making a Fire Shroud 100. In an additional example, a diameter size range for the continuous glass filaments, including a controlled minimum diameter in excess of about 3 microns, may be selected. As a further example, synthetic vitreous fiber sheets or a body including continuous glass filaments or wool fibers having sampled diameters within a range of between about 6 microns and about 10 microns may be selected for making a Fire Shroud 100. Synthetic vitreous fiber diameter sampling for this purpose may include, as an example, determining the diameters of at least about one hundred selected fibers or filament sections.
Natural mineral fiber sources such as asbestos have uncontrolled, variable, fiber diameters and lengths. Accordingly, natural mineral fiber sources may include more respirable fibers having diameters of less than about 3 microns than may be included in synthetic vitreous fibers. In an example, the utilization of natural mineral fiber sources in fabrication of a Fire Shroud 100 may accordingly be avoided. However, it is understood by those skilled in the art that natural mineral fiber sources may be substituted for or combined with synthetic vitreous fibers in making a synthetic vitreous fiber body or in making synthetic vitreous fiber sheets selected for forming the cylindrical first synthetic vitreous fiber sheet 104 and the second synthetic vitreous fiber sheet 114 in fabrication of the Fire Shroud 100.
The rock, slag, glass precursors such as sand, and clay from which synthetic vitreous fibers are formed all are non-combustible. In addition, rock, slag, glass precursors such as sand, and clay all include metal elements. Such metal elements generally have significant molecular weights. Synthetic vitreous fibers accordingly have substantial mass densities and may function as non-combustible heat insulators. In addition, fabrication of synthetic vitreous fibers into a woven or non-woven sheet or body may trap air in interstices between the fibers. The trapped air itself adds to the non-combustibility and heat insulating capability of the woven or non-woven sheet or body. As an example, graphite fibers may be avoided as an alternative to synthetic vitreous fibers for making the Fire Shroud 100. Graphite fibers themselves are formed of elemental carbon, having a low molecular weight of only 6 grams per mole. Hence, graphite fibers alone may not provide sufficient mass density to insulate the barrier surface-mountable electromagnetic device from the heat of a fire, potentially leading to combustion within or passing through the barrier surface-mountable electromagnetic device.
In an example, synthetic vitreous fibers may be selected and formed into an intertwined mass such as a synthetic vitreous fiber sheet or body, as an integral part of the process for making the fibers themselves from molten materials. In this manner, the intertwined mass of synthetic vitreous fibers may be self-bonded without a need to add other materials or to undertake additional steps for bonding the intertwined fibers together. As a further example, the intertwined mass of synthetic vitreous fibers may include a combustible or non-combustible binder composition. A urea-extended phenol-formaldehyde binder having a Chemical Abstract Service designation of 25104-55-6 may, in an example, be utilized. In another example, an inorganic binder including kyanite, sodium silicate, calcined clay, crystalline silica, and water may be utilized.
The intertwined mass may, as an example, take the form of a flexible sheet. As examples, selected synthetic vitreous fibers may be formed into a woven or non-woven sheet having suitable dimensions for forming, or being cut down to size for forming, the cylindrical first synthetic vitreous fiber sheet 104 and the second synthetic vitreous fiber sheet 114 in fabrication of the Fire Shroud 100. Such woven or non-woven sheets for forming the cylindrical first synthetic vitreous fiber sheet 104 and the second synthetic vitreous fiber sheet 114 may, in an example, have thicknesses of at least about one inch. As another example, the woven or non-woven sheets for forming the cylindrical first synthetic vitreous fiber sheet 104 and the second synthetic vitreous fiber sheet 114 may have thicknesses within a range of between about one inch and about three inches. Synthetic vitreous fiber bodies may as an example have analogous thicknesses. An increased thickness of the sheets generally increases the fire protection provided by the Fire Shroud 100.
The intertwined mass may further, as an example (not shown), take the form of a rigid board. As another example (not shown), the cylindrical first synthetic vitreous fiber sheet 104 may be integrally formed as a seamless cylinder having a defined length, without a first sheet edge 116 or a second sheet edge 118. The defined length may, as an example, be sufficiently large so that a portion of the seamless cylinder may be cut to form a cylindrical first synthetic vitreous fiber sheet 104 sized to the shape of and to contain a portion of the back-can 126 of a selected barrier surface-mountable electromagnetic device. In another example (not shown), the cylindrical first synthetic vitreous fiber sheet 104 may be formed by assembly together of two half-cylinder synthetic vitreous fiber sheets each shaped as a half-cylinder having first and second sheet edges and a defined length. The two half-cylinder vitreous fiber sheets may, as an example, then be assembled together around the back-can 126 of a selected barrier surface-mountable electromagnetic device and joined together using an adhesive composition or a single- or double-sided adhesive tape in a manner analogous to the above discussion of techniques for joining synthetic vitreous fiber sheet edges together. In a further example (not shown), a cylindrical first synthetic vitreous fiber sheet 104 and a second synthetic vitreous fiber sheet 114 may be integrally formed as a cylindrical tube having an integral end-cap substituting for a second synthetic vitreous fiber sheet, collectively constituting a Fire Shroud 100 for assembly onto the back-can 126 of a barrier surface-mountable electromagnetic device. These examples of synthetic vitreous fiber sheets may, as an example, be selected to have a rigid structure.
It is understood by those skilled in the art that the examples of Fire Shrouds 100 discussed throughout this specification both in connection with and as shown in the drawings may be fabricated to include a synthetic vitreous fiber body utilizing first and second synthetic vitreous fiber sheets 104 and 114, or utilizing an integrally-formed cylindrical first synthetic vitreous fiber sheet or two half-cylinder synthetic vitreous fiber sheets instead of the cylindrical first synthetic vitreous fiber sheet, or by integrally forming a body including a cylindrical tube having an integrally-formed cap. It is further understood by those skilled in the art that Fire Shrouds 100 may further be fabricated by forming other synthetic vitreous fiber sheets or bodies that may be integrated to form a cylindrical tube having an integrally-formed cap.
In an example, synthetic vitreous fiber bodies, or sheets for forming the cylindrical first synthetic vitreous fiber sheet 104 and the second synthetic vitreous fiber sheet 114, may be selected that comply with Underwriters Laboratories (“UL”) 723 “Standard for Test for Surface Burning Characteristics of Building Materials”, which itself references UL 263 “Standard for Fire Tests of Building Construction and Materials”. UL 723 is also published as ASTM International (“ASTM”) E84 “Standard Test Method for Surface Burning Characteristics of Building Materials.” As a further example, synthetic vitreous fiber bodies, or sheets for forming the first and second synthetic vitreous fiber sheets 104 and 114, may be selected that comply with UL 2043 “Standard for Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces”. In another example, synthetic vitreous fiber bodies, or sheets for forming the first and second synthetic vitreous fiber sheets 104 and 114, may be selected that comply with National Fire Protection Association (“FPA”) Standard 255 “Standard Method of Test of Surface Burning Characteristics of Building Materials.” In an additional example, synthetic vitreous fiber bodies, or sheets for forming the first and second synthetic vitreous fiber sheets 104 and 114, may be selected that comply with Underwriters Laboratories of Canada (“ULC”) S102-03 “Surface Burning Characteristics of Building Materials and Assemblies” superseding ULC Standard S102-88.
As another example, an FBX COREPLUS 1200® industrial flexible batt insulation having a grade designation of 1210, 1212, 1240, 1260, or 1280 and manufactured from a composition including basalt mineral fibers may be utilized for forming a synthetic vitreous fiber body or the cylindrical first synthetic vitreous fiber sheet 104 and the second synthetic vitreous fiber sheet 114. FBX COREPLUS 1200® industrial flexible batt insulation is commercially available from Fibrex Insulations Inc., P.O. Box 2079, 561 Scott Rd., Samia, Ontario, Canada N7T 7L4; www.fibrex.org. FBX COREPLUS 1200® industrial flexible batt insulation may comply with UL 723, UL 263, and ULC S102-03. As another example, an FBX COREPLUS 1200® pipe insulation having a grade designation of 1210, 1212, 1240, 1260, or 1280, and manufactured from a composition including basalt mineral fibers may be utilized for forming a cylindrical synthetic vitreous fiber body or a cylindrical first synthetic vitreous fiber sheet 104.
Commercially-available synthetic vitreous fiber bodies and sheets may include additional ingredients such as an oil added to prevent fibers from falling off or “dusting off” of the bodies or sheets. In an example, commercially available materials for forming the bodies or first and second synthetic vitreous fiber sheets that do not include dust-controlling oils or other additives may be selected, to avoid non-compliance with applicable standards by UL, ULC, ASTM, NFPA, building codes, or other fire-resistance and smoke-reduction standards. It is understood by those skilled in the art that a binder may nevertheless be needed to maintain the integrity of a synthetic vitreous fiber body or sheet.
As an example, an adhesive composition to be utilized for making the Fire Shroud 100 as discussed above may be selected based on factors including resistance of the adhesive composition to combustion, retention of joint integrity at high temperatures, production of minimal smoke, release of minimal toxic materials upon decomposition, and initial bonding effectiveness of the adhesive to the selected synthetic vitreous fiber bodies or sheets. The adhesive composition may, as an example, include a flame retardant. In an example, the adhesive composition may include a thermosetting polymeric resin so that the adhesive may not melt even upon exposure to extreme heat. Examples of thermosetting adhesive compositions include urea-formaldehyde, resorcinol-formaldehyde, melamine-formaldehyde, and one-component epoxides. As another example, a refractory cement may be utilized. A refractory cement may include ceramic fibers and an inorganic binder. In an example, Fiberstick™ refractory cement, including kyanite, sodium silicate, calcined clay, crystalline silica, and water may be utilized. Fiberstick™ refractory cement is commercially available from Unifax Corporation, 2351 Whirlpool St., Niagara Falls, N.Y. 14305; www.unifrax.com.
In another example, a tape web including a single-sided or double-sided adhesive coating may be selected based on the same factors as discussed above with regard to adhesive compositions. Since the tape web may provide structural strength to a joint but not itself bond to a synthetic vitreous fiber body or sheet, the tape web may be made of a selected material that is more fire-resistant than the adhesive may be. As examples, the tape web itself may be formed from a composition selected from the materials utilized for forming the synthetic vitreous fiber body or sheets, as discussed above. The adhesive composition coating included on either or both surfaces of the tape web may be selected as discussed in the preceding paragraph. In an example, Silicaflex™ Tape AB, including a silicon dioxide fiber web coated on one side with a pressure sensitive adhesive, may be utilized. Silicaflex™ Tape AB is commercially available from ADL Insulflex, Inc., 8783 Dale Rd., Cobourg, Ontario, Canada K9A 4J9; www.adlinsulflex.com.
Following completion of assembly, the Fire Shroud 100 may as an example be slid onto a portion of the back-can 126 of a selected barrier surface-mountable loudspeaker 102 in the direction of the arrow 144, as shown in
The Fire Shroud 100 may be attached to the barrier surface-mountable loudspeaker 102, as examples, by an adhesive composition or an adhesive tape applied to the Fire Shroud 100 and the barrier surface-mountable loudspeaker 102. As a further example, the barrier surface-mountable loudspeaker 102 may include mounting tabs 710 configured to swing laterally away from the back-can 126 and to support weight of the barrier surface-mountable loudspeaker 102 on the c-bracket 602. The Fire Shroud 100 may, as an example (not shown), be secured in place on the barrier surface-mountable loudspeaker 102 by pinching the second cylinder edge 108 of the Fire Shroud 100 between the c-bracket 602 and the mounting tabs 710. In an additional example (not shown), the Fire Shroud 100 may be secured in place on the barrier surface-mountable loudspeaker 102 by pinching the second cylinder edge 108 of the Fire Shroud 100 between the downwardly directed tabs 604 and 606 of the c-bracket 602 and the upwardly directed tabs 608 and 610 of the ceiling rails 612 and 614. As another example (not shown), a plurality of clips may be attached to the second cylinder edge 108 of the Fire Shroud 100 and to one or more of the following: mounting tabs 710, c-bracket 602, and ceiling rails 612 and 614.
The Fire Shroud 100 may, as an example, be utilized to provide fire resistance to an electromagnetic device such as a barrier surface-mountable loudspeaker 102 installed in a ceiling formed by sheet rock or a substitute for sheet rock, or installed in a suspended ceiling including a tile grid frame. The Fire Shroud 100 may further, as examples, be utilized to provide fire resistance to an electromagnetic device such as a barrier surface-mountable loudspeaker 102 installed in another building interior surface such as a wall or floor.
Although the invention has been described with reference to a particular example of an embodiment, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Such changes and modification are intended to be covered by the appended claims.