Patent Publication Number: US-2010108438-A1

Title: Panel for acoustic damping and fire protection applications

Description:
FIELD OF THE INVENTION 
     The present application relates to panels or barrier walls, and more particularly, to a panel with acoustic or damping properties, and suitable for fire resistant applications. 
     BACKGROUND OF THE INVENTION 
     Residential, commercial, industrial workplaces and other facilities (such as hospitals, schools, government buildings) are all susceptible to a fire outbreak. For example, there are fire hazards associated with machinery. For example, there are fire hazards associated with equipment or facilities which house, use, or make flammable materials or fuels or other types of chemicals or hazardous materials. 
     Fire rated barriers are typically used to protect facilities and/or equipment against fire or the spread of fire. Fire rated barriers are designed to provide containment should a fire start, for example, as a result of equipment failure. In an electrical power grid, for example, transformers are a common piece of equipment in the distribution and transmission stations. Transformers are also prone to overheating resulting in fire and/or explosions, often without a prior warning. As a result, containment or isolation of fire hazardous equipment, such as transformers in a distribution and transmission station, is a critical safety and operational concern. Typically, this involves providing a fire barrier between two or more oil-filled transformers. 
     Industrial workplaces and facilities also have operating machinery which tends to generate noise levels which can be very loud at peak operating times. Similarly, commercial buildings, offices, facilities such as hospitals and clients, will have spaces or rooms that need to be isolated from noise. In order to reduce the noise levels, acoustic or sound damping structures can be put into place or the machines can be isolated in a separate area or room in the facility. It will be appreciated that while such known approaches can be effective in reducing noise levels, they require infrastructure for the facility. 
     Accordingly, there remains a need for improvements to address these shortcomings in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention comprises a panel or barrier wall that is tunable or configurable for acoustic damping. According to another embodiment, the present invention comprises a fire resistant panel that is configurable for absorbing sound waves. 
     According to an embodiment, the present invention provides an acoustic panel comprising: an inner core formed from a cementicious material; a first outer layer and a second outer layer; the inner core being positioned between the first outer layer and the second outer layer and being affixed to respective surfaces of the first and second outer layers; and at least one of the first outer layer and the second outer layer includes a plurality of perforations configured for allowing at least a portion of acoustic energy to pass into the inner core. 
     According to another embodiment, the present invention provides a method for making an acoustic panel, the method comprising the steps of: providing an inner core formed from a cementicious material which is partially cured; positioning an outer sheet on said partially cured inner core; the outer sheet including a plurality of holes and the plurality of holes including projections that are pushed into the partially cured inner core to form a mechanical bond between the outer sheet and the inner core. 
     According to another embodiment, the present invention provides a fire resistant acoustic panel assembly comprising: an inner core formed from a cementicious material; a first metallic layer and a second metallic layer; the inner core being positioned between the first metallic layer and the second metallic layer and being affixed to respective surfaces of the first and second metallic layers; and at least one of the first metallic layer and the second metallic layer including a plurality of perforations configured for allowing at least a portion of acoustic energy to pass into the inner core. 
     According to another embodiment, the present invention provides an acoustic panel assembly comprising: an acoustic panel; a support member configured for supporting the acoustic panel; the acoustic panel including, an inner core formed from a cementicious material; a first metallic layer and a second metallic layer; the inner core being positioned between the first metallic layer and the second metallic layer, and being affixed to respective surfaces of the first and the second metallic layers; at least one of the first metallic layer and the second metallic layer including a plurality of perforations configured for allowing at least a portion of acoustic energy to pass into the inner core; an acoustic absorptive material positioned in the support member and adjacent to the acoustic panel, and configured to provide additional absorption of acoustical energy. 
     According to another embodiment, the present invention comprises an acoustic panel comprising: an inner core formed from a fire resistant material; a first outer layer and a second outer layer; the inner core being positioned between the first outer layer and the second outer layer and being affixed to respective surfaces of the first and second outer layers; and at least one of the first outer layer and second outer layer including a plurality of perforations configured for allowing at least a portion of acoustic energy to pass into the inner core. 
     Other aspects and features according to the present application will become apparent to those ordinarily skilled in the art upon review of the following description of embodiments of the invention in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the accompanying drawings which show, by way of example, embodiments according to the present application, and in which: 
         FIG. 1(   a ) is a front view of an acoustic panel according to an embodiment of the present invention; 
         FIG. 1(   b ) is a side view of the acoustic panel of  FIG. 1  according to an embodiment of the present invention; 
         FIG. 2  is an exploded view of the acoustic panel of  FIG. 1  according to an embodiment of the present invention; 
         FIG. 3(   a ) is a side sectional view of a mounting configuration for the acoustic panel; 
         FIG. 3(   b ) is a side sectional view of another mounting configuration for the acoustic panel; 
         FIG. 3(   c ) is a side sectional view of another mounting configuration for the acoustic panel; and 
         FIG. 4  is a side sectional view of an acoustic panel configurable for additional acoustic damping according to an embodiment of the invention. 
     
    
    
     Like reference numerals indicate like or corresponding elements in the drawings. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference is first made to  FIGS. 1(   a ) and  1 ( b ), which shows an acoustic panel according to an embodiment of the invention. The acoustic panel is indicated generally by reference  100  and comprises an outer panel, sheet or skin  110  and an inner core  120 . A pair of outer panels,  110   a  and  110   b , are affixed to each side of the inner core  120  and form a “sandwich” type structure. According to an embodiment, the acoustic panel  100  is configured to provide sound attenuation (i.e. absorption of sound waves) and also capable of functioning as a fire resistant barrier and/or providing impact or blast protection. 
     According to an embodiment, the inner core  120  a sound absorbing composite material. According to an embodiment, the outer panels  110  comprise metallic sheets that are mechanically bonded to both sides of the inner core  120 . According to an embodiment, holes or openings  130  are pierced or punched in the metallic sheets  110 . According to an embodiment, the pierced holes  130  are made in a grid pattern indicated generally by reference  140 . The holes or openings  130  are pierced so as to include projection or tines  132  that remain attached to the metal sheet  110  as shown in  FIG. 2 . The metal tines or projections  132  form a structural element that is mechanically pressed into the material forming the inner core  120 . The pierced holes or apertures  130  function to allow passage of sound waves into the inner core  120  where they are absorbed to provide sound dampening. The pierced holes or apertures  130  on the face of the outer panels  110  also provide a discontinuous surface which serves to break-up or interfere with the reflection of sound waves from the outer panels  110 . According to an embodiment, by varying the diameter and/or number and/or spacing of the holes or apertures  130 , the acoustic panel  100  can be tuned or configured for various sound damping characteristics or applications. 
     According to an embodiment, the acoustic panel  100  is made or assembled by placing one metallic sheet  110   a  against the inner core  120 . The metallic sheet  110   a  includes the holes  130 , which according to an embodiment, have been formed by piercing the metallic sheet  110   a  in known manner (for example, with punches and a press), and according to another aspect, the holes  130  are punched in a manner to form the tines  132  on one surface, i.e. the surface of the metallic sheet  110   a  that contacts the inner core  120 . The metallic sheet  110   a  is positioned on the inner core  120  and pressure is applied to push the tines  132  into the inner core  120  before the composite material for the core has cured. This process is repeated for the other metallic sheet  110   b . According to another aspect, the inner core  120  is placed between both of the metallic sheets  110   a ,  110   b , e.g. to form a “sandwich” configuration and pressed together to drive the tines  132  into the inner core  130  before the composite core material has cured. 
     As will be described in more detail below, it has been discovered that the inner core  120  can be formed from certain materials that can comprise fire resistant compounds and can also be configured to provide acoustic dampening or sound absorption. 
     According to an embodiment, the inner core  120  comprises a composite material manufactured using the Hatschek process as will be understood by one skilled in the art. The composite core comprises a cement-limestone matrix  122  that is reinforced with cellulose and/or man-made fibers indicated generally by reference  124  as depicted in  FIG. 2 . The Hatschek process allows different types of reinforcing fibers to be blended and oriented within the cement-limestone matrix while also permitting the composite core to be manufactured in a variety of thicknesses. 
     According to one aspect, the thickness of the inner core  120  is varied to provide different degrees of acoustic dampening or sound absorption. According to another aspect, the acoustic dampening or sound absorption characteristics of the inner core  120  can be varied or “tuned” (e.g. maximum sound reduction in the desired octave bands) by adjusting the percentages of the individual components forming the composite material. 
     According to an exemplary implementation, the outer panels  110  are formed from metal sheets having a thickness of 24 gauge or 26 gauge. The pierced holes  130  have a nominal diameter of 7/32″ and the grid  140  comprises a nominal 25/32″× 25/32″ square grid arranged over substantially the entire surface of the metal sheet. With the 25/32″ centers on the grid  140 , the diameter of the holes  130  can be increased (or decreased) and the diameter of the holes  130  can be used as another parameter for tuning the acoustic panel  100 . 
     According to another aspect, the thickness of the metallic sheets for the outer panels  110  can be varied. For example, metallic sheets less than 24 ga or 26 ga can be used where the panel  100  is limited to acoustic loads, and thicker metallic sheets can be used where the panel  100  is subject to external loads, such as wind and/or blast forces or blast over pressures. According to another aspect, the outer panels  110  are fabricated from materials that are better able to withstand the intended environmental conditions. In a typical application, the metallic sheets would be formed of galvanized steel for cost considerations. In other applications, the metallic sheets are formed from more expensive materials, such as stainless steel, monel or other types of specialized metals, that are capable of withstanding the environmental conditions and/or application requirements, for example, chemical industry, or commercial building applications. 
     According to an embodiment, the inner core  120  is formed from a composite material comprising a primarily cement-limestone matrix (approximately &gt;80%) indicated by reference  122  in  FIG. 2 . The primarily cement-limestone matrix  122  is reinforced with cellulose and/or man-made fibers indicated by reference  124  in  FIG. 2 . the fibers  124  are distributed throughout core  120 . According to another embodiment, other or additional cementicious admixtures, for example, silica fume and/or fly ash, can be included in composite core material to enhance the mechanical and/or acoustic properties of the inner core  120 . According to another aspect, the type, size and/or density of the fibers  124  can be varied to create, for example, a more flexible or lighter panel, or a more rigid or denser panel. According to another aspect, the thickness of the inner core  120  can be varied to increase or decrease the sound absorption properties of the panel  110  or for specific bandwidths. 
     Reference is next made to  FIG. 3(   a ), which shows different configurations for mounting or installing the acoustic panels  100  according to embodiments of the present invention. In a first configuration indicated generally by reference  310 , the acoustic panel  100  is affixed or attached using suitable fasteners to a support framework comprising one or more C-channel members indicated by reference  312 . As shown in  FIG. 3 , the acoustic panel  100  is attached to the C-channel member  312  with self-drilling screws  314 . The type and size of fasteners used will depend on the size/weight of the acoustic panels  100  and/or the expected external loads exerted on the panel(s)  100 . Similarly, the external design loads will affect or vary the spacing of the fasteners. For support members that have open or accessible sections, such as the C-channel member  312 , nut and bolt fasteners can be used. 
     Reference is next made to  FIG. 3(   b ) and a second configuration indicated generally by reference  320 . The acoustic panel  100  is affixed or attached using suitable fasteners to a support framework comprising a hollow member (e.g. square or rectangular) indicated generally by reference  322 . As depicted in  FIG. 3(   b ), the fasteners comprise self-drilling screws  314 . The size and number of self-drilling screws  314  used will depend on the factors as described above. 
     Reference is next made to  FIG. 3(   c ), and a third configuration indicated by reference  330 . The acoustic panel  100  is affixed or attached to an angle iron support member indicated by reference  332  using a bolt  316  and nut  317  for the fastener. As described above, the number and spacing of the bolts  316  (and nuts  317 ) will depend on the external design loads that the panel  100  is designed to withstand. In addition, if the panel  100  is configured with a thicker inner core  120  and/or thicker or heavier gauge outer sheets  110 , then additional fasteners and/or structural support will be required to support the additional weight of the panel. 
     Reference is next made to  FIG. 4 , which shows an acoustic panel assembly according to another embodiment of the present invention and indicated generally by reference  200 . The acoustic panel assembly  200  provides a configuration for use in applications where a larger acoustic assembly or acoustic performance is required, for example, a thicker inner core will provide increased sound dampening characteristics, but the weight considerations associated with a cementicious inner core  120  may be unsuitable for the application or installation. As shown, the acoustic panel assembly  200  comprises an acoustic panel  100 , a support frame or member  210  and an absorptive material core  220 . The acoustic panel  100  is configured in a manner as described above. The absorptive material core  220  comprises one or more layers of an acoustic absorptive mat indicated generally by reference  220 , and individually by references  220   a ,  220   b , . . .  220   n . As shown, the absorptive mats or layers  220  are arranged to fill the cavity formed by the support frame  210 . 
     According to another aspect, the acoustic panel assembly  200  can include a protective sheet or film indicated generally by reference  230  in  FIG. 4 . The protective film  230  covers the acoustic absorptive mats  220  and provides protection from dust, dirt, moisture and other environmental elements. According to another embodiment, the acoustic panel assembly  200  can include another metal sheet or panel indicated by reference  240 . According to an embodiment, the metal sheet  240  comprises a metal sheet perforated with holes or apertures. According to one aspect, the metal sheet  240  serves to protect the protective film  230  and acoustic mats  220 . In a manner similar to that described for the outer panels  110 , the holes or apertures can have various opening sizes and/or hole centers for different acoustic configurations. The thickness of the metal sheet  240  can also be varied for different applications. 
     According to another embodiment, the acoustic panel assembly in accordance with the embodiments of the present invention is suitable to also function as a fire resistant panel. The fire resistance of the panel is derived from the fire resistive properties of the cementicious inner core  120 . The fire resistance of the panel is further augmented by the metallic sheets utilized for the outer panels  110 . By using different fire rated metals for the outer panels  110 , the fire resistance of the panel assembly  100  can be increased or decreased as needed for the particular application or installation. Similarly, by varying the composition and/or thickness of the inner core  120 , the fire resistance of the panel assembly  100  or  200  can be configured for the particular application or installation. 
     In summary and according to one aspect, the acoustic panel according to an embodiment of the present invention provides an acoustic panel that can be configured for sound dampening applications. According to another aspect, the acoustic panel can be tuned for specific sound dampening applications. 
     In summary and according to another embodiment of the present invention, the fire resistant acoustic panel provides a fire resistant panel that also functions as an acoustic barrier. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Certain adaptations and modifications of the invention will be obvious to those skilled in the art. Therefore, the presently discussed embodiments are considered to be illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.