Acoustics – Sound-modifying means – Sound absorbing panels
Reexamination Certificate
2000-08-25
2002-09-03
Dang, Khanh (Department: 2837)
Acoustics
Sound-modifying means
Sound absorbing panels
C181S286000, C181S294000, C181S295000
Reexamination Certificate
active
06443257
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to building materials, and more particularly it relates to acoustical panels having fire retardant properties for use in ceiling and wall structures.
BACKGROUND OF THE INVENTION
Acoustical ceiling or wall panels generally include an acoustically absorbent inner core, a backing material for enhancing panel strength, and front facing for enhancing the aesthetic appearance of the panel.
Typically, the inner core may comprise fiberglass bats formed from resin impregnated fiberglass. Other inner core materials may comprise wet-laid mineral, slag mineral, or cellulosic fibers. Rock, slag mineral and cellulosic fibers may also utilize a variety of inorganic fillers such as perlite, clays and gypsum. Panels designed for high acoustical absorption necessarily contain highly porous cores achieved by using low-density bats or cores. These cores, by themselves, lack the necessary characteristics to finction as ceiling or wall panels.
Additionally, gravity may cause the inner core to deform. When starch is used as a binder for slag mineral fibers, high humidity may also weaken the panel strength. Those structural deficiencies may require the use of a backing material attached to one side of the core.
In addition to poor structural integrity, the inner cores of acoustical panels often lack sufficient light reflecting and uniformity in shade or color to render their natural appearance aesthetically pleasing. For that reason, the inner core usually requires a decorative facing applied to the opposite side of the core that receives the backing material.
Although known inner cores are acoustically permeable and can absorb acoustical energy, some acoustical energy will inevitably be transmitted through the core and into adjacent spaces, unless the core includes a sufficient thickness and surface area to dissipate the sound as heat energy. Since sufficient surface area to completely dissipate the acoustic energy is often difficult to achieve in an economically feasible fashion, most manufacturers employ a barrier comprised of a thin layer of aluminum foil. The aluminum foil is impermeable to air and highly dense with respect to other materials within the panel and, therefore, increases the overall sound absorption. The aluminum foil is also incombustible, which makes the foil desirable for a Class A rating in building material applications.
For example, U.S. Pat. No. 3,183,996 to Capaul discloses an acoustical structural panel which includes an inner metal slag core having a paper facing with a coating of aluminum flake for the purpose of heat reflection. Similarly, U.S. Pat. No. 4,627,199 to Capaul discloses a tackable acoustical structure comprising a tack pin retaining layer, a sound absorptive layer and a metal foil septum separating the tack pin retaining layer and the sound absorptive layer to enhance the sound absorbent and flame-retardant properties of the structure. Additionally, U.S. Pat. No. 4,428,545 to Capaul utilizes a metallic backing which imparts enhanced sound transmission and insulation properties to a finished acoustical panel construction.
The use of a metallic foil as a backing within acoustical panels presents several problems. The first problem relates to impurities left on a finished panel product as a result of the production process. More specifically, the production process requires the use of oil in the converting process of aluminum foil prior to installation on the acoustical panel. As a result, the oil creates a black residue on the acoustical panel, which makes handling the panel quite difficult upon installation into a grid within a dropped ceiling pre-assembly. If not carefully installed, the black residue may mar the highly light reflective white face surface of the acoustical panel with smudges and stains.
Another problem associated with the use of a thin aluminum film as a backing material is the tendency of the aluminum foil to buckle and tear. Since the relative cost of aluminum is high with respect to other materials within a typical acoustical panel, it is necessary to apply only a thin foil having a thickness, for example, of approximately 0.0015 inches. The foil may buckle or tear during the application of the foil to the core and trimming of the foil from the panel during the panel manufacturing process. Furthermore, the foil is liable to tear or become perforated during remaining production steps and even during installation by the customer. A third issue arises from the increased utilization of devices that propagate or receive transmission signals such as radios, cellular telephones and infrared control devices for lighting and heating. Aluminum and other metallic foils tend to block or interfere with signals in the electromagnetic spectrum. Thus, ceilings having panels with aluminum foil backing present a broad metal surface in a room, over an entire floor, and often on every floor throughout an office building, which virtually renders all wireless communication devises useless.
Some have attempted to utilize paper backings within acoustical panels. For example, U.S. Pat. No. 4010,817 to Warren et al. forms the acoustical panel on top of the paper by screeding the panel material onto the paper and then drying the cast pre-assembly. U.S. Pat. No. 5,753,871 to Kahara uses a nearly identical process to form an inner core of mineral wool and starch binder gel to a paper backing within a molding tray to form an acoustical panel.
There are several problems associated with wet forming a material to a paper backing. First, Warren and Kahara must re-wet the paper backing when applying a latex finish facing to the acoustical panel to avoid warping of the panel. Additionally, the manufacturing methods of Kahara and Warren also require the additional step of removing the partially finished panel from the mold for final processing. Those steps add additional cost to the manufacturing process, thus making such methods undesirable.
With the foregoing problems associated with the prior art use of metallic foils and paper backings within acoustical panels in mind, it is a general object to create an acoustical panel with a paper backing having desirable acoustical sound absorption properties, while being simple and inexpensive to manufacture.
SUMMARY OF THE INVENTION
The present invention provides a multi-layered, substantially rigid and self-supporting acoustical panel. The panel comprises a core which has a first face with a second face that is disposed opposite the first face. There is applied to the first face an acoustically permeable facing layer. Additionally, a calendered paper backing adapted to be applied to the core is provided. The paper backing is substantially free of metallic material and includes a flame-retardant material.
Furthermore, a method of manufacturing a multi-layered, substantially rigid acoustical panel is provided. The method includes providing an acoustically absorbent core having a first face, and a second face disposed opposite the first face. A finishing layer is applied to the first face of the core, and a calendered, flame-retardant, and substantially metallic material free cellulosic sheet is adhered to the second face of the core.
In one embodiment, the core may comprise an acoustical fiberglass bat, which is bound into a semi-rigid state with a resin material. The core may also include slag mineral fiber, cellulosic fiber or polymeric fiber materials having a filler of clay, perlite, gypsum or any other material suitable for filling purposes. Additionally, any number of binders would be suitable for the aforementioned fillers, including starches or polymeric resins. In addition to the above-referenced materials, the acoustically absorbent core may comprise a cemetitious or polymeric foam having any number of filler materials. The core material may also comprise bound aggregate particles.
In a further embodiment, the face layer may comprise an air permeable scrim material adhered to the panel core with poly (vinyl acetate) glue. In other embodiments, the facing may include th
Kulas Laurel
Wiker Anthony L.
AWI Licensing Company
Dang Khanh
Womble Carlyle Sandridge & Rice PLLC
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