Patent Publication Number: US-2016237699-A1

Title: Access floor-panel and core

Description:
TECHNICAL FIELD 
     The invention relates generally to flooring systems for buildings, and to access floors for enclosing under-floor air delivery plenums within buildings. 
     BACKGROUND OF THE INVENTION 
     Under-floor air delivery plenums are an energy-efficient means of air distribution, popularly used in heating and cooling schemes for large spaces, particularly in office buildings. The system typically employs a raised access floor having a plurality of floor panels supported by a plurality of support posts above a structural floor in abutting end to end fashion. The space between the floor panels and the structural floor forms a plenum, through which conditioned (e.g. heated or cooled) air can be forced to circulate from a centrally located source. Apertures and vents in the floor panels permit the conditioned air to enter the room above the floor panels. Under-floor air delivery plenums are desirable because they permit widespread distribution of conditioned air throughout large spaces without extensive and complex ductwork. 
     The floor panels used in access floors must have sufficient bending strength, shear strength, and rigidity to support the loads of the room above (furniture, equipment, personnel, activities etc.). The floor panels must have sufficiently precise dimensions to permit forming an airtight seal between their abutting edges. The floor panels must be sufficiently light as to not impose undue structural loads on the support posts and structural floor. For widespread adoption, the access floor system must have sufficiently low cost of manufacture and installation to be commercially competitive with other air distribution systems. 
     Designers of access floors are typically faced with several problems. For example, lightweight strong materials are often too costly for particular applications, while inexpensive materials such as reinforced concrete are too heavy for particular applications. Furthermore, it is often necessary to install a carpet above the access floor in order to form a substantially airtight seal. 
     It would therefore be advantageous to provide a lightweight concrete access-floor panel that has desired strength and weight characteristics and a method of manufacture thereof that mitigates or eliminates at least one disadvantage of the prior art. 
     SUMMARY 
     In accordance with one aspect of the invention, there is disclosed a structural floor panel for use in a raised access floor arrangement that forms an under-floor plenum air distribution plenum. The floor panel may include a lightweight concrete core bonded to a concave pan by means of an adhesive. The concrete core has substantially flat and parallel top and bottom surfaces that oppose each other. At least one edge may be positioned contiguous with the respective peripheries of the top and bottom surfaces. The concrete core includes a monolithic casting of constituent ingredients that may include cement, coarse lightweight aggregate, water, fly ash, and sand. The resulting casting (i.e. concrete core) may have a mass density in the range of 1650 to 1850 kilograms per cubic meter. 
     In an aspect, the concrete core may have a compressive strength in the range of 40 to 50 megapascals and/or a flexural strength in the range of 5 to 7 megapascals. 
     In another aspect, a volume of reinforcing fibers may be added during the casting process to provide additional properties to the concrete core. The reinforcing fibers may be made from steel, iron, carbon/graphite, a polymer, or a combination thereof, or from other materials. 
     In yet another aspect, the concrete core is adapted for use in the concrete access floor panel by having bevelled edges and a 120-150 Grit finish on the bonded surfaces. 
     In an aspect, the concrete core is manufactured by mixing its prepared ingredients in a dry-casting apparatus. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  depicts a general perspective view of the lower aspect of the concrete core of the invention, indicated generally by reference number  100 , illustrating the general form thereof, according to an embodiment of the invention; 
         FIG. 2  depicts a partial cross-sectional profile view of the structural floor panel of the invention, indicated generally by reference number  200 , illustrating the general configuration and the components thereof, according to an embodiment of the invention; and 
         FIG. 3  depicts a process (i.e. method of manufacture) for making a concrete structural floor panel, according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates an embodiment of a concrete core  100  for use in structural access floor panel. In a typical access floor system, a number of structural floor panels are placed in an adjacent arrangement to create an access floor with an air distribution plenum formed below the access floor. 
     The concrete core  100  may have a flat rectangular bottom surface  115  positioned substantially parallel to a flat top surface (not shown). The concrete core  100  may have a bevelled edge  117  that is positioned contiguous with the respective peripheries of the bottom surface  115  and the top surface. The concrete core  100  may be a monolithic casting of constituent ingredients selected from an ingredient set that may include cement, coarse lightweight aggregate, water, fly ash, and sand. 
     The proportion of the ingredients may vary depending on a particular application and the desired characteristics of the structural concrete core  100 ; however, in some embodiments the concrete core  100  comprises the following ingredients and respective proportions by mass, 18% ±1% cement, 45% ±1% coarse lightweight aggregate, 7% ±1% water, 6% ±1% fly ash, 24% ±1% sand. 
     In various embodiments, the structural concrete core  100  ( 210  in  FIG. 2 ) has a mass density in the range of 1650-1850 kg/m3, a compressive strength of in the range of 40-50 MP, and a flexural strength in the range of 5-7 MP. 
     In some embodiments, reinforcing fibers may be added as an ingredient during the casting process to give the concrete core desired characteristics such as additional compressive and flexural strength. The reinforcing fibers may be oriented so as to provide specific strength characteristics. 
     The reinforcing fibers may be made from a variety of materials such as steel, iron, carbon/graphite, polymers, and/or particular combinations thereof. 
     Referring to  FIG. 2 , in an embodiment of the invention an access floor panel  200  includes a pan  220 , a structural concrete core  210 , a bond layer  230 , and an adhesive sealant tape  240 . The bottom panel  225  of the pan  220  may have a form substantially identical to the bottom surface  215  of the concrete core  210 . The side  227  of the pan  220  may conform substantially to the edge  217  of the concrete core  210 . A bond layer  230 , of an adhesive filler material, spans and substantially fills the interface between the pan  220  and the concrete core  210 . 
     A sealant tape  240  may be affixed to the edge  217  of the concrete core  210  near the perimeter  242  of the top surface  212  of the concrete core  210 , and encircles the periphery of the structural panel  200 . In some embodiments, a fluid sealant such as calking may be applied in the place of sealant tape. 
     In some embodiments, the concrete core  100 ,  210  has a 5° bevelled edge  117 ,  217  to facilitate assembly with the pan  220 . The bevelled edge may vary from 5° in certain applications. In another aspect, the concrete core  100 ,  210  has a surface finish of 120-150 Grit on its bottom surface  115 ,  215  and edge  117 ,  217 , to facilitate adhesion of the filler layer. 
     In another aspect, an adhesive sealant tape encircles the edge of the panel  200  to seal the structural gap between the panel  200  and adjacent panel(s). 
     In some embodiments, the core  210  is casted in a predetermined manner to be thinner than the desired thickness of the panel (by more than the thickness of the pan) so that a face surface may be applied to the top surface of the core. By applying the face surface, the desired thickness of the panel is achieved. A particular face surface may be applied for one or more aesthetic and/or functional reasons, such as slip/wear resistance, weight/cost, or to create a pattern or effect desired by the user. 
     In another aspect, the panel  200  has a square shape and a thickness of approximately 25.4 mm. It will be appreciated that the surface shape and thickness of a panel (or core) of the invention may vary according to a particular application. For example, a panel may have a surface shape that is triangular, rectangular, polygonal, etc. 
     In another aspect, a hole proximate to each corner of the panel permits mounting and alignment of the panel as part of an access floor. The holes may be aligned with support posts that support the access floor. The holes typically penetrate the panel (through the core and pan) such that a securing device such as a bolt or pin can securely join the panel to the support posts. In some embodiments, a plurality of structural panels  200  may be placed in adjacent fashion and secured to a plurality of support posts to create an under-floor air delivery plenum. A variety of panels  200  may be chosen based on their respective face surface to create a desired floor pattern or aesthetic appearance. The panels may be selected from a variety of surface shapes as described above (such as square, rectangular, polygonal, etc.) to provide a desired look and effect for a particular floor application. 
     In some embodiments, each panel may be supported by one or more support posts with each support post having a pedestal head at its top for supporting the load of one or more panels. The pedestal head may include a self-leveling acoustic gasket. The gasket operates to restrict sound from travelling between the respective panels and other parts of the floor assembly to adjacent rooms and areas, as well as to restrict air from leaking from the plenum below the panels. 
     In some embodiments, one or more stringers (i.e. rails) may be connected between various support posts. A panel may sit on the stringers in addition to the pedestal heads. The stringers may include a gasket to facilitate self-leveling of the panels, and to restrict acoustic communication and air leakage from the plenum. The stringer gaskets and pedestal head gaskets may be formed from felt, foam and/or other suitable materials. 
     In some embodiments, a given pedestal head is adapted to support a plurality of panels. Typically, four panels are supported by a single pedestal head (when the panels are in the middle of the floor and not adjacent to the perimeter of the building). A given pedestal head may include four locating tabs which protrude upwards from the pedestal head. The locating tabs facilitate the locating/guiding of each panel on the pedestal head during installation and also operate to keep each panel in place during use. When each of the four panels is located on the pedestal head, a panel/head connection may be installed at the interface of all four panels with a single hold down location fastener and tension washer. The hold down location fastener may be a bolt. When the tension washer is installed, it places a downwards force on each panel thus securing each panel and adding additional strength and stability to each panel. It will be appreciated that panels in the middle area of the floor will be installed with four tension washers, one each at the interface of each corner of the panels with the adjacent panels. 
     In some embodiments, a calibration process may be implemented to ensure that the metal pan is formed with precision during formation (i.e. stamping and forming) and after the pan is formed together with the concrete core. An edge coating may be painted on each side of the panel (i.e. on the pan) which operates to restrict air leakage and acoustic communication between adjacent panels and other parts of the floor system. The edge coating operates as a gasket integrated into the panel. In some embodiments, the concrete core is not integrated with a metal pan and an edge coating is applied direction to the concrete surface. The coating (whether applied to the pan or directly to the concrete core) also provides structural edge protection during installation and while in use. 
     The resulting panel may be constructed with specific characteristics within known tolerances. In one embodiment, the panel has a precise size with a tolerance of maximum +/−0.010″ which allows low bare panel air leakage value and precise ability for each panel to stay on a 24.000″ grid layout throughout the flooring system. The concrete core may have a relatively high internal particle bond which reduces pull out of concrete particles and performs well in dynamic and static loading situations. The concrete core may be ground with diamond abrasion under water to a fine approximation of 100 grit roughness. 
     In some embodiments, a panel is made by adhering a steel pan to the concrete core with a reactive (moisture cure) polyurethane adhesive. The adhesive may be applied at a rate of 10 grams/sf. Given that the grinding in one embodiment is performed under water, the unique composition and process of creating the concrete core allows an amount of water to be retained within the concrete core. The combination of the reactive moisture cure adhesive facilitates curing (bond strength) between the pan and the core and within the core itself for a period of time after the adhesive is applied. This essentially allows the internal bond of the concrete core itself and between the core and the pan to strengthen over time. 
     In some embodiments, the resulting panel assembly has superior acoustic value due to its higher density and low air leakage value which affects flanking acoustic sound. 
     In some embodiments, the concrete core is ground to precise dimensional tolerance of maximum +/−0.010″ on thickness and flat and parallel with +/−0.015″. 
     In some embodiments, the panel assembly is 0.875″ thick +/−0.010″ and has structural capacity on 24″ centers sufficient to meet all structural building codes in North America. The panel assembly may be non-combustible according to building code definitions CAN/ULC 5135 in Canada ASTM E 136 in the United States. 
     In some embodiments, a process for manufacturing (i.e. a method of manufacture for) a concrete core (such as cores  100 ,  210 ) includes providing a constituent ingredient set to give the resulting core particular strength, weight, tolerance, and other desired characteristics. The ingredient set may include a variety of materials in predetermined proportions such as 18% ±1% cement by mass, 45% ±1% coarse lightweight aggregate by mass, 7% ±1% water by mass, 6% ±1% fly ash by mass and 24% ±1% sand by mass. An apparatus for measuring the moisture content of some or all the ingredients (such as a moisture meter) may be provided. In some embodiments, an apparatus for drying some of all of the ingredients may also be provided. In other embodiments, certain ingredients may be dried in the environment using evaporation. 
     To mix the ingredients, a concrete dry-casting apparatus (such as a mixer and/or consolidation equipment) is provided as well as a mold (i.e. form) for forming the concrete core. 
     The lightweight aggregate and/or sand may be dried using the drying apparatus to a predetermined moisture value. The desired moisture value may be determined in advance according to a particular access-flooring application to give the resulting concrete core desired characteristics. In some embodiments, the proportion of ingredients may be adjusted depending on the measured moisture content and the desired moisture content. For example, it may be found that the sand has a higher moisture content than is desired. The relative proportion of sand relative to lightweight aggregate may be adjusted (in this example, by providing more lightweight aggregate) so that the desired moisture content may be achieved. In other embodiments, constituent ingredients may be dried as described above using the drying apparatus (such as a fan or by applying heat) and/or relying on evaporation. 
     The process of manufacture includes mixing and forming the ingredients using a dry-casting apparatus and forming the mixed materials into a monolithic concrete casting by employing a mold. 
     The resulting concrete cast formed may have a mass density selected from the range 1650-1850 kilograms per cubic meter, a compressive strength selected from the range 40-50 megapascals, and/or a flexural strength selected from the range 5-7 megapascals. 
     The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art. 
     Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.