Abstract:
A flame retardant panel apparatus, and method, utilize a flame retardant panel, having an exterior and an interior face thereof, with the panel including a panel structure having a primary core encapsulated within a panel frame of reinforced phenolic material, and a layer of flame retardant material attached to the panel structure and extending outwardly therefrom to at least partially define an exterior face of the flame retardant panel. The flame retardant panel is suitable for use in mass transit conveyances, such as subway cars, high speed cars, rail cars, buses, rapid response vehicles, marine vessels, and elevators.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This patent application claims the benefit of U.S. Provisional Patent Application No. 60/703,048, filed Jul. 27, 2005, the disclosure and teachings of which are incorporated herein, by reference, in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to fire retardant panels, and more particularly to fire retardant panels suitable for use in mass transit conveyances, such as subway cars, high speed cars, rail cars, buses, rapid response vehicles, marine vessels, or elevator cars. 
       BACKGROUND OF THE INVENTION 
       [0003]    Public conveyances, such as rail cars, buses, elevators, and the like, are typically subject to government regulations requiring that a passenger compartment of the conveyance be at least partially constructed from fire retardant panels, which provide protection for occupants of the compartment in the event that a fire should occur outside or within the passenger compartment. 
         [0004]    For example, in the past, passenger rail cars and buses have sometimes utilized a flooring system in which floor panels, approximately three-quarters of an inch thick, are mounted to the top side of a floor-supporting underframe. Typically the floor panels have been attached to the underframe by various methods, including adhesive bonding, or fastening with screws or other fasteners. The underframe has typically been deep enough to allow a layer of insulation material (usually glass wool, fiberglass, or rock wool), to be laid upon the top surface of a series of thin steel sheets that are then welded to the bottom side of the underframe, to form an underpan assembly. The underframe is sometimes configured to be deep enough that there is an air gap provided between the underside of the floor panel and the insulation material on the top side of the steel underpan. The air gap serves as an insulation zone for heat transfer, in the event of a fire beneath the transit vehicle. Typically, in North America, such a floor structure is required to pass a fire endurance test for passenger fire safety, in which a completed flooring system is mounted over a pit in which a gas burner is located to simulate a fire beneath the vehicle. During the fire test, weights are placed on the top surface of the floor panels, to simulate a typical live floor loading resulting from carrying passengers. 
         [0005]    In one common form of a floor panel, used in prior flooring systems for mass transit vehicles, a plywood sheet is sandwiched between, and bonded to, the interior surfaces of two stainless steel or aluminum sheets. This construction results in floor panels that are heavier than is desirable. Also, past experience has shown that, during operation of the mass transit vehicle, the plywood core sometimes is exposed to water, which causes the stainless steel or aluminum sheets to delaminate and the plywood panel to rot. 
         [0006]    U.S. Pat. No. 6,824,851, which is assigned to the Assignee of the present invention, and is hereby incorporated in its entirety herein by reference, discloses an approximately three-quarter inch thick phenolic composite flooring system for mass transit vehicles, which provides significant improvement over flooring systems utilizing floor panels having stainless steel or aluminum sheets bonded to the faces of a plywood panel. By virtue of its construction, the phenolic composite flooring system disclosed in U.S. Pat. No. 6,824,851 is considerably lighter in weight than flooring systems utilizing plywood panels clad with stainless steel or aluminum sheets. Also, the flooring system of the &#39;851 patent provides greater ability, than flooring systems using floor panels having a plywood sheet clad with stainless steel skins, to withstand harsh environmental conditions, such as exposure to water or moisture. 
         [0007]    Although use of a phenolic composite flooring system, according to U.S. Pat. No. 6,824,851, in a traditional mass transit vehicle constructions, having an insulation material laid on the top surface of thin steel sheets welded to the bottom of a steel underframe to form an underpan assembly, have been shown to provide significant advantages over similar systems utilizing metal clad plywood floor panels, further improvement is desirable. 
         [0008]    It is desirable to eliminate the insulation and heavy steel underpan, to reduce weight and complexity of the transit vehicle, and to eliminate the cost of the insulation, the steel underpan, and costs incurred in installing the insulation and underpan onto the underframe of the vehicle, while still providing sufficient flame retardant capability to meet governmental regulations. 
         [0009]    Past experience has also shown that use of the air gap and steel underpan in previous mass transit vehicles created a cavity between the underpan and the floor panels which “drummed” during use of the mass transit vehicle. Elimination of the underpan and air gap would also eliminate the cavity, and potentially lead to a quieter passenger cab environment. 
         [0010]    It has also been observed that previous, conventional underpan and underframe assemblies, would, from time-to-time, trap water between the bottom of the floor panel and the top side of the underpan. In some instances, large amounts of standing water would be trapped within the cavity between the underpan and the floor panels. As noted above, this standing water sometimes damage the floor panels, and could amount to significant dead weight which had to be carried by the mass transit vehicle. 
         [0011]    It is desirable, therefore, to provide an improved fire retardant panel apparatus, and a method of making and using such an improved fire retardant panel apparatus, in a form which addresses one or more of the disadvantages of prior flooring systems for mass transit vehicles. It is further desirable to produce a fire retardant panel for use in other conveyances such as elevators and marine vessels. It is further desirable to provide an improved fire retardant panel, and panel apparatus, for use in defining one or more of the floor, ceiling, and/or walls of a conveyance for transporting passengers or other cargo. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    The invention provides an improved flame retardant panel apparatus, and method of making and using such an improved fire retardant panel apparatus, through use of a flame retardant panel, having an exterior and an interior face thereof, with the panel including a panel structure having a primary core encapsulated within a panel frame of reinforced phenolic material, and a layer of flame retardant material attached to the panel structure and extending outwardly therefrom to at least partially define an exterior face of the flame retardant panel. 
         [0013]    Through use of a flame retardant panel, according to the invention, in a mass transit conveyance, such as a rail car or a bus, for example, the underpan and layer of insulation beneath the floor panel, of prior mass transit flooring systems, can be eliminated, while still providing an enhanced flame retardant capability which meets or exceeds applicable government standards. Through use of a flame retardant panel, according to the invention, weight and complexity of a mass transit flooring system are significantly reduced. In addition, a flame retardant panel, according to the invention, provides improved thermal insulation capabilities, and resistance to sound transmission, as compared to prior flame retardant panel constructions. Flame retardant panels, according to the invention, are also inherently more capable of withstanding exposure to water, and provide an improved moisture barrier, as compared to the metal clad plywood floor panels utilized in prior mass transit vehicles. 
         [0014]    In one form of the invention, a flame retardant panel, according to the invention, has an exterior face thereof adapted for attachment to a support frame and an interior face thereof adapted for defining a boundary of a compartment. The flame retardant panel includes a panel structure and a layer of flame retardant material attached to the panel structure. The panel structure includes a primary core encapsulated within a panel frame of reinforced phenolic material. The primary core has first and second faces thereof and a periphery thereof. The panel structure further includes a panel frame including first and second skins, attached to the first and second faces of the primary core, and one or more closeouts disposed between the skins about the periphery of the core, with the one or more closeouts being attached to the periphery of the primary core and to the first and second skins. The layer of flame retardant material is attached to the second skin of the panel frame, and extends outwardly therefrom to at least partially define the exterior face of the flame retardant panel. 
         [0015]    In some forms of the invention, the layer of flame retardant material includes a secondary core of material from the group consisting of balsa wood, phenolic foam, and melamine foam, and an additional skin of reinforced phenolic material. The secondary core is sandwiched between, and attached to, the second skin of the composite support structure and the additional skin. The additional skin is integrally joined to the remainder of the panel frame, to thereby fully encapsulate the secondary core within the reinforced phenolic material from which the panel frame is constructed. 
         [0016]    In some forms of the invention, the layer of flame retardant material includes a layer of intumescent material attached to the second skin. The layer of intumescent material may be bonded onto the second skin. The layer of intumescent material may be a coating containing a intumescent material, which is sprayed, or otherwise applied onto the second skin. The layer of intumescent coating may also take the form of a composite structure, including an intumescent material disposed in a fibrous mat. In some forms of the invention, the layer of intumescent material includes a cured epoxy resin to form a pre-cured layer of intumescent material which is adhesively bonded to the second skin, utilizing an epoxy or other suitable type of adhesive. In some forms of the invention, the layer of intumescent material is impregnated with phenolic resin and placed against the second skin of reinforced phenolic resin, while the second skin is in an uncured state. The impregnated layer of intumescent material and the second skin are then co-cured. Co-curing of the impregnated intumescent material with the second skin, may be carried out contemporaneously with curing of the remainder of the panel frame of reinforced phenolic material. 
         [0017]    In some forms of the invention, the primary core of the panel structure may include a plastic closed cell foam of polyisocyanurate material. The primary core may also be formed from other appropriate materials such as balsa wood. 
         [0018]    In some forms of the invention, the panel structure may include one or more ribs of reinforced phenolic material connecting the first and second skins to one another, and disposed inwardly from the periphery of the primary core. The primary core may be a pre-cured reinforced core, including at least one reinforced phenolic rib and two or more foam strips, with the at least one phenolic rib being positioned between two adjacent ones of the two or more foam strips. Alternatively, the primary core may include a plurality of groupings, each formed from a plurality of plastic foam strips helically wound together in a side-by-side relationship, by rovings of fibrous material. The groupings may be disposed in a side-by-side relationship with one another, and joined together by first and second adhesive scrims applied to first and second faces of the primary core, such that facing and faying portions of the fibrous rovings of adjacent groupings form reinforcements for the reinforced phenolic ribs. 
         [0019]    A fire retardant panel, according to the invention, may define a longitudinal axis thereof, a transverse axis thereof extending substantially perpendicularly to the longitudinal axis, and a thickness thereof extending substantially orthogonally to both the longitudinal and transverse axes of the panel, with both the longitudinal and transverse axes lying substantially within a plane defined by the interior face of the panel. The first and second skins may take the form of a stitched composite reinforcing structure of fibrous material, impregnated with phenolic resin. The reinforcing structure of the skins may have first, second and third layers, with the first layer being disposed adjacent the primary core and comprised of substantially randomly directed fibers, the second layer being disposed against the first layer and comprising substantially longitudinally directed fibers, and the third layer being disposed against the second layer and comprising substantially transversely directed fibers, with the first, second, and third layers being stitched together by stitching extending at least partially orthogonally to the longitudinal and transverse axes. 
         [0020]    In forms of the invention having an additional skin of reinforced phenolic material, the additional skin may also be constructed as described in the preceding paragraph, with the first layer of the reinforcing structure of the additional skin being attached to the secondary core. 
         [0021]    A flame retardant panel, according to the invention, may also include a surfacing veil disposed against the third layer of the reinforcing structure of one of the first, second, or additional skins of reinforced phenolic material. 
         [0022]    One or more of the one or more closeouts, in a flame retardant panel, according to the invention, may be machineable to include at least one mating surface. The mating surface may be a lap joint. 
         [0023]    Where the interior face, of a flame retardant panel, according to the invention, defines a plane of the panel, a closeout, according to the invention, may include at least one bore therethrough extending substantially perpendicularly to the plane of the panel. The primary core, in a flame retardant panel, according to the invention, may include at least one tapping block, with the tapping block including a block of reinforced phenolic material and a metal plate encapsulated within the block. The tapping plate may be adapted to be drilled and tapped, so as to provide the panel with a mounting area. 
         [0024]    A flame retardant panel, according to the invention, may include a heating element adjacent to the interior face of the panel. The heating element may be embedded into the first skin of the panel, and integrally joined thereto by the phenolic material. The heating element may also be adhesively bonded onto the first skin of the panel, using an appropriate adhesive. The heating element may be encapsulated within a sheath of urethane material, and be adhesively bonded to the first skin with an epoxy adhesive, or another appropriate adhesive. 
         [0025]    A flame retardant panel, in accordance with the invention, may include a conduit embedded within the panel and having first and second openings into the conduit through at least one of the interior and/or exterior faces of the panel or the perimeter such that the conduit continues from panel to panel. 
         [0026]    The invention may also take the form of a flame retardant panel apparatus, having multiple interconnected panels, each including an exterior face thereof adapted for attachment to a support frame and an interior face thereof adapted for defining a boundary of a compartment, with at least one of the panels of the flame retardant panel apparatus being a flame retardant panel according to the invention. 
         [0027]    A flame retardant panel apparatus, in accordance with the invention, may take the form of a flooring apparatus for a conveyance. The conveyance may be an elevator, including a floor support structure adapted for attachment thereto of the flooring apparatus according to the invention. The conveyance may be a vehicle or a vessel including a floor support structure adapted for attachment thereto of a flooring apparatus according to the invention. The vehicle or vessel may be a mass transit vehicle or vessel. 
         [0028]    The invention may also take the form of a method for constructing and/or using a flame retardant panel, or a flame retardant panel apparatus, in accordance with the invention. 
         [0029]    In one form of the invention, a method is provided for constructing a flame retardant panel, having an exterior face thereof adapted for attachment to a support frame and an interior face thereof adapted for defining a boundary of a compartment. The method includes forming a panel structure, and attaching a layer of flame retardant material to the panel structure. The panel structure is formed by encapsulating a primary core within a panel frame of reinforced phenolic material, in such a manner that the primary core has first and second faces thereof, and a periphery thereof, and such that the panel frame includes first and second skins attached to the first and second faces of the primary core and one or more closeouts disposed between the skins about the periphery of the primary core, with the one or more closeouts being attached to the periphery of the primary core and to the first and second skins. The layer of flame retardant material is attached to the second skin of the panel frame and extends outwardly therefrom, such that the layer of flame retardant material at least partially defines the exterior face of the panel. 
         [0030]    A method, according to the invention, may include forming the layer of flame retardant material from a secondary core, and an additional skin of reinforced phenolic material, where the secondary core is formed from a material selected from the group consisting of balsa wood, phenolic foam, and melamine foam. The method includes attaching the secondary core between the second skin of the panel structure and the additional skin. A method, according to the invention, may further include integrally joining the additional skin to the remainder of the panel frame, of the panel structure, to thereby fully encapsulate the secondary core within the reinforced phenolic material of the panel frame. 
         [0031]    Alternatively, a method for constructing a flame retardant panel, in accordance with the invention, may include forming the layer of flame retardant material by attaching an intumescent material to the second skin of the panel structure. 
         [0032]    In some forms of the invention, the thickness of a fire retardant panel, according to the invention, may vary and include at least a first and a second thickness thereof, within the periphery of the primary core. The layer of flame retardant material attached to the second skin of the panel frame and extending outwardly therefrom to at least partially define the exterior surface of the panel may extend across the entirety of the exterior face of the panel, throughout both the first and second thicknesses of the panel. Alternatively, the layer of flame retardant material attached to the second skin of the panel frame and extend outwardly therefrom to at least partially define the exterior surface of the panel may extend only partially across the entirety of the exterior face of the panel, throughout one, but not both of the first and second thicknesses of the panel. In some forms of the invention, a first flame retardant structure may be utilized in areas of the panel having the first thickness, and a second flame retardant structure may be utilized in areas of the panel having the second thickness. For example, a flame retardant structure including a secondary core of flame retardant material may be utilized in areas of the panel having the first thickness, and a second flame retardant structure including an intumescent material may be utilized in areas of the panel having the second thickness. 
         [0033]    Similarly, even where the panel has a substantially uniform thickness, the layer of flame retardant material may include first and second sections thereof having different flame retardant structures. For example, the first section of the layer of flame retardant material may be formed from a secondary core and an additional skin, according to the invention, with the second section of the layer of flame retardant material being formed from an intumescent material attached to the second skin of the panel structure in the second section of the flame retardant layer. 
         [0034]    Other aspects, objects and advantages of the invention will be apparent from the following detailed description and accompanying drawings of exemplary embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0036]      FIG. 1  is a perspective illustration of a first exemplary embodiment of a fire retardant panel, in accordance with the invention; 
           [0037]      FIG. 2  is an exploded perspective illustration, showing the internal components and construction of the exemplary embodiment of the fire retardant panel shown in  FIG. 1 ; 
           [0038]      FIG. 3  is a partial cross-sectional illustration of an exemplary embodiment of a fire retardant panel, according to the invention, which includes a fire retardant layer having a secondary core of fire retardant material; 
           [0039]      FIG. 4  is a partial cross-sectional view of an exemplary embodiment of the invention having a layer of intumescent material at least partially defining an exterior face of a flame retardant panel, according to the invention; 
           [0040]      FIG. 5  is a perspective illustration of an alternate embodiment of a primary core of the exemplary embodiment of the fire retardant panel shown in  FIG. 1 ; 
           [0041]      FIGS. 6A-6D  are partial cross-sectional illustrations of an edge of a flame retardant panel, according to the invention, taken along line  6 - 6  in  FIG. 8B , illustrating construction details of several alternate embodiments of the invention; 
           [0042]      FIGS. 7A-7E  are perspective, plan, and elevation views of a fire retardant panel apparatus, according to the invention, in the form of a flooring apparatus for a mass transit rail car; 
           [0043]      FIGS. 8A-8C  are respectively top, bottom, and end views of an exemplary embodiment of a fire retardant floor panel, according to the invention, having sections of greater and lesser thickness to facilitate installation of the floor panel onto a support structure; 
           [0044]      FIGS. 9A-9D  are alternate partial cross-sectional views taken along line  9 - 9  in  FIG. 8B , illustrating construction details of alternate embodiments of fire retardant panels, according to the invention, having areas of greater and lesser thickness located inwardly from the edges of the panel; and 
           [0045]      FIG. 10  illustrates alternate embodiments of the exemplary embodiment of the fire retardant panel shown in  FIG. 1 , wherein the alternate embodiments include a heating element attached to an interior surface of the panel, and a conduit disposed within the panel for passage of wires, or the like through the panel. 
       
    
    
       [0046]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0047]      FIGS. 1 and 2  illustrate a first exemplary embodiment of a flame retardant panel  100 , according to the invention, with  FIG. 1  showing the flame retardant panel in a completed state, ready for attachment to a support frame, and  FIG. 2  illustrating various components of the flame retardant panel  100  in an exploded perspective fashion. 
         [0048]    As shown in  FIGS. 1 and 2 , the first exemplary embodiment of a flame retardant panel  100 , according to the invention, has an exterior face  102  thereof, adapted for attachment to a support frame (not shown), an interior face  104  thereof, adapted for defining a boundary of a compartment and a perimeter  105  thereof extending around the panel  100  between the interior and exterior faces  104 ,  106  of the panel  100 . The flame retardant panel  100  includes a panel structure  106  including a primary core  108  having first and second faces  110 ,  112  thereof and a periphery  114  thereof. In the first exemplary embodiment of the flame retardant panel, as illustrated in  FIG. 2 , the primary core  108  has essentially a planar shape, with the first and second faces  110 ,  112  forming spaced parallel planes, and the periphery  114  being substantially rectangular in shape. In other embodiments of the invention, flame retardant panels, and components thereof may have shapes differing considerably from those illustrated in the exemplary embodiment of the flame retardant panel  100  shown in  FIGS. 1 and 2 . 
         [0049]    In the panel structure  106  of the exemplary embodiment  100 , the primary core  108  is encapsulated within a panel frame of reinforced phenolic material, (illustrated generally by reference numeral  116  in  FIG. 2 ), formed by the combination of first and second skins  118 ,  120 , attached to the first and second faces  110 ,  112  of the primary core  108 , and four closeouts  122 ,  124 ,  126 ,  128 , disposed between the skins  118 ,  120  about the periphery  114  of the primary core  108 . The four closeouts  122 ,  124 ,  126 ,  128  are attached to the periphery  114  of the primary core  108 , and to both the first and second skins  118 ,  120 . 
         [0050]    A layer of flame retardant material  130  is attached to the second skin  120  of the panel frame  116 , and extends outwardly from the second skin  120 , to at least partially define the exterior face  102  of the flame retardant panel  100 . The flame retardant layer  130  is illustrated as a solid slab in  FIG. 2 , but as will be understood from the description below, in various embodiments of the invention the layer of flame retardant material  130  may take a variety of forms and include multiple elements thereof. 
         [0051]    As shown in  FIG. 3 , for example, the layer of flame retardant material  130  may include a secondary core  132  formed from material selected from the group consisting of balsa wood, phenolic foam, and melamine foam. In the embodiment shown in  FIG. 3 , the layer of flame retardant material further includes an additional skin  134  of reinforced phenolic material, with the secondary core  130  being sandwiched between and attached to the second skin  120  of the composite support structure  106  and the additional skin  134 . The additional skin  134  is integrally joined to the remainder of the panel frame  116 , by the closeouts  122 ,  124 ,  126 ,  128 , to thereby fully encapsulate the secondary core  132  within the reinforced phenolic material comprising the panel frame  116 . 
         [0052]    The choice of materials for the secondary core  132  will be dependent upon a variety of factors, unique to a particular embodiment and application of the present invention. Such factors as the thickness of the primary core  108 , and the secondary core  132  are relevant in making the choice of materials for both the primary and secondary cores  108 ,  132 . In general, it is contemplated that the primary core  108  of the present invention will have a substantially greater thickness than the core of the applicant&#39;s &#39;851 floor panel. For example, it is contemplated that, in practicing the present invention, it may be desirable to have the primary core have a thickness in the range of two inches, or more, to enhance thermal resistance, acoustic resistance, and structural strength of the fire retardant panel  100 . It is noted, however, that the invention may be practiced in fire retardant panels  100 , having an overall thickness T of ¾ of an inch, for example. 
         [0053]    Specifically, with regard to factors considered in selecting a material for a secondary core  132 , according to the invention, it is generally contemplated that a preferred thickness for the secondary core would be in the range of ¼ to ¾ inches, with a nominal ½ inch thickness being generally acceptable. The invention may be practiced, however, with secondary cores  132  having substantially greater or lesser thicknesses than these. It is also contemplated, that, in some embodiments of the invention, the secondary core  132  may have a thickness which is substantially greater than the thickness of the primary core  108 . For example, where it is desirable to have a floor panel of a mass transit conveyance have a thickness of ¾ of an inch above a floor support frame, to match the thickness of prior floor panels, the panel structure  106  of a flame retardant floor panel, according to the invention, may have an overall thickness, across the first and second skins and primary core  118 ,  120 ,  108 , of ¾ of an inch, with the secondary core  132  and additional skin  134  extending a larger distance, such as two to three inches, for example, below the second skin  120  of the panel structure  106 . 
         [0054]    In general, balsa wood will have the lowest cost of any of the materials listed above, for use as a secondary core  132 , according to the invention. Phenolic foam will typically cost somewhat more than balsa wood, but provides enhanced thermal insulation, as compared to the same thickness of balsa wood. Melamine foam, also typically costs more than balsa wood, but provides superior acoustic insulation, as compared to balsa wood. Generally therefore, where lowest cost is a primary objective, it is contemplated that a secondary core  132  of balsa wood will be preferred, in practicing the invention. Where enhanced thermal performance is desired, a secondary core of phenolic foam may be preferable. Where enhanced acoustic damping performance is required, a secondary core of melamine foam may be the preferred choice. 
         [0055]    As an alternative to having the additional skin  134  integrally joined to the remainder of the panel frame  116  by the closeouts  122 ,  124 ,  126 ,  128 , secondary closeouts of reinforced phenolic material (not shown) may be positioned about all, or a portion of the periphery of the secondary core  132 , in alternate embodiments of the invention. Alternatively, the additional skin  134  may be configured to wrap around the edges of the secondary core  132 , for attachment to the remainder of the panel frame  116 , in a manner which fully encapsulates the secondary core  132  within the reinforced phenolic material comprising the panel frame  116  and the additional skin  134 . 
         [0056]    As indicated by a dashed line, in  FIG. 3 , in alternate embodiments of the invention, the layer of flame retardant material  130  may further include a layer of intumescent material  136  attached to a second face  138  of the additional skin  134 . The layer of intumescent material  136  may take a variety of forms, bonded onto the second face  138  of the additional skin  134 . For example, the layer of intumescent material  136  may take the form of a coating containing an intumescent material which is sprayed onto, or otherwise applied to the second face  138  of the additional skin  134 . Alternatively, the layer of intumescent material  136  may be a composite structure including an intumescent material disposed in a fibrous mat. Such materials are disclosed in U.S. Pat. No. 5,523,059, for example. One such material, having an unexpanded exfoliating intumescent material disposed in a fiber mat is sold under the trade name, Technofire®, by Technical Fibre Products of Newburgh, N.Y., US. In some forms of the invention, the fibrous mat having the intumescent material disposed therein is impregnated with a resin, such as an epoxy, to form a pre-cured layer of intumescent material, which is then bonded to the second face  138  of the additional skin  136  with an adhesive, such as an epoxy. In other embodiments, the fibrous mat containing the intumescent material is impregnated with phenolic resin and placed against the second face  134  of the additional skin, while the additional skin is in an uncured state, and the layer of intumescent material  136  and the additional skin  134  are co-cured. 
         [0057]    The choice of attaching the fibrous mat containing intumescent material  136  to the additional skin  134  by co-curing, or alternatively by attaching a pre-cured layer  136  of intumescent material to the additional skin  134  may be made as a function of how rapidly it is desired that the intumescent material be activated. Specifically, phenolic resins have higher temperature capabilities then epoxy resins, and will slow the rate at which the intumescent material begins to expand out of the layer of intumescent material  136 . 
         [0058]    Where the layer of intumescent material  136  is provided by applying a coating to the second surface  138  of the additional skin  134 , either ceramic based or non-ceramic based intumescent coatings may be used in practicing the invention. Suitable intumescent coatings, for use in practicing the invention, are available from Micro Phase Coatings, Inc. of Garner, N.C., US. or Avtec Industries of Hudson, Mass., US. 
         [0059]      FIG. 4  illustrates a variation of the first exemplary embodiment of the flame retardant panel  100 , in which the layer of flame retardant material  130  is formed by a layer  136  of intumescent material which is attached directly to the second skin  120  of the panel structure  106 . The layer of intumescent material  136  utilized as shown in  FIG. 4 , may take any of the forms and be attached by any of the methods described above in relation to the embodiment shown in  FIG. 3 . 
         [0060]    As shown in  FIGS. 2-4 , the first exemplary embodiment of the flame retardant panel  100  also includes one or more ribs  140  of reinforced phenolic material connecting the first and second skins  118 ,  120  to one another. The ribs  140  are disposed inwardly from the periphery  114  of the primary core  108 . 
         [0061]    In the exemplary embodiment  100  shown in  FIG. 2 , the primary core  108  is a pre-cured reinforced core, including a plurality of the reinforced phenolic ribs  140  alternated with a plurality of foam strips  142 , with the phenolic ribs  140  being generally positioned between two adjacent ones of the foam strips  142 . The construction of such a pre-cured reinforced core is disclosed in detail in commonly assigned U.S. Pat. No. 6,824,851 B1, which has hereinabove been incorporated into the disclosure of the present invention by reference. 
         [0062]    In manufacturing a fire retardant panel, according to the present invention, utilizing the pre-cured reinforced core  108 , the various components of the fire retardant panel  100  are stacked in a platen press, substantially in the manner indicated in  FIG. 2 , with uncured phenolic resin being applied between the various components where it is desired to have the components adhere to one another, and the stacked uncured structure is subjected to pressure and heat to cure the phenolic material to thereby integrally bond the components of the fire retardant panel  100  to one another. 
         [0063]    In practicing the present invention, it is not required to use a pre-cured core, of the type disclosed in the common assignee&#39;s U.S. Pat. No. 6,824,851 B1. In an alternate embodiment of a primary core  144 , in a fire retardant panel, according to the invention, illustrated in  FIG. 5 , the primary core  144  comprises four groupings  146 , each formed from two plastic foam strips  147  which are bond together in a side-by-side relationship by an overwind of helically directed rovings  148 ,  150  of fibrous material. The rovings  148 ,  150  are more-or-less oppositely directed, and placed in alternating layers, such that the plastic foam strips  147  in each grouping are relatively tightly bound together by the rovings  148 ,  150 . The groupings  146  are disposed in a side-by-side relationship with one another, and joined by first and second scrims  152  adhesively bonded respectively to the first and second faces  110 ,  112  of the primary core  144 , in such a manner that faying portions  153  of the fibrous rovings  148 ,  150  form dry, un-impregnated reinforcements for the reinforced phenolic ribs  140 . 
         [0064]    When constructing the flame retardant panel  100 , utilizing the alternate primary core  144 , the various components of the flame retardant panel  100  are stacked into a platen press, along with the primary core  144  in the same manner as described above for a flame retardant panel  100  utilizing a pre-cured primary core  108 , and additional un-cured phenolic resin is applied to the first and second faces  110 ,  112  of the core  144 . During the curing process, application of pressure and heat causes the uncured phenolic resin to flow into the rovings  148 ,  150  and through the reinforcements  153  formed by adjacent groupings  146 , to thereby form the reinforced phenolic ribs  140 . 
         [0065]    In practicing the invention, where the fire retardant panel  100  defines (see  FIG. 1 ) a longitudinal axis  154  thereof, a transverse axis  156  thereof extending substantially perpendicularly to the longitudinal axis  154 , and a thickness T thereof extending substantially orthogonally to both the longitudinal and transverse axes  154 ,  156  of the panel  100 , with both the longitudinal and transverse axes  154 ,  156  lying substantially within a plane defined by the interior face  104  of the panel  100 , the first and second skins  118 ,  120  may include a stitched composite reinforcing structure (not shown) of fibrous material, impregnated with phenolic resin. As is known in the art, the reinforcing structure of the skins  118 ,  120  may have first, second, and third layers, with the first layer being disposed adjacent the primary core  108  ( 144 ) and including only substantially randomly directed fibers, the second layer being disposed against the first layer and comprising substantially only longitudinally directed fibers, and the third layer being disposed against the second layer and comprising substantially only transversely directed fibers, with the first, second, and third layers being stitched together by stitching extending at least partially orthogonally to the longitudinal and transverse axes  154 ,  156 . In embodiments of the invention utilizing an additional skin  134 , the additional skin  134  may also include a three-layered stitched composite reinforcing structure of fibrous material, impregnated with phenolic resin, of the type described hereinabove with regard to the first and second skins  118 ,  120 , with the first layer of the reinforcing structure of the additional skin  134  being disposed against the secondary core  132 . 
         [0066]    A flame retardant panel, according to the invention, may further include a surfacing veil (not shown), as is known in the art, disposed against at least one of the first, second, or additional skins  118 ,  120 ,  134 , adjacent either the exterior or interior face  102 ,  104  of the flame retardant panel  100 . 
         [0067]    As illustrated in  FIGS. 6A-6D , one or more of the closeouts  122 ,  124 ,  126 ,  128 , of the first exemplary embodiment of the fire retardant panel  100 , may be machineable to include at least one mating surface  158 , such as the lap joint shown in  FIGS. 6A-6D . As shown in  FIG. 1 , and  FIGS. 6A and 6B , the closeout  122 , in the completed panel  100 , includes a pair of bores  159  extending therethrough in a direction substantially perpendicularly to the plane of the panel  100  defined by the longitudinal and transverse axes  154 ,  156 . The closeouts  122 ,  124 ,  126 ,  128 , may also take a variety of forms, as illustrated in  FIGS. 6A-6D .  FIGS. 6A-6D  also illustrate other details of various alternate embodiments of the invention, in which the fire retardant panel  100  includes a beveled surface, either as part of or adjacent to the closeout  122 . 
         [0068]      FIGS. 6A-6D  further illustrate various alternate embodiments, and placements of components in the fire retardant layer. For example, in  FIG. 6C , a layer of intumescent material  136  is utilized on the mating surface  158  and angled side of the panel  100 , in combination with a fire retardant layer having a secondary core and additional skin  134 . In  FIGS. 6A-6D , and also in  FIGS. 9A-9D , as described below, the primary core of the various alternate illustrated embodiments has been designated with reference numeral  408 , to indicate that the primary core  408  may take the form of the exemplary cores  108 , or  144 , as described hereinabove, or any other form within the scope of the invention. 
         [0069]    In similar fashion, the primary core  108  ( 144 ) may also include a variety of materials, additional components, and have configurations other than those specifically illustrated herein. In some embodiments of the invention, the primary core  108  ( 144 ) may include a plastic closed cell foam of polyisocyanurate material. The primary core  108  ( 144 ) may also be fabricated from a variety of other appropriate materials, such as balsa wood. 
         [0070]    As shown in  FIG. 2 , the primary core  108  ( 144 ) may further include at least one tapping block, including a block  162  of reinforced phenolic material, and a metal plate  164  encapsulated within the block  162 . The tapping plate  164  is adapted to be drilled and tapped so as to provide a mounting area, for seating arrangements, for example, in the flame retardant panel  100 . 
         [0071]      FIGS. 7A-7E  illustrate a flame retardant panel apparatus, in the form of a flooring apparatus  200  of a conveyance, illustrated by an under floor support frame  202  of a passenger rail car. The flame retardant floor panel apparatus  200  includes multiple interconnected panels, in the form of a center panel  204  and a pair of identical, reversible, end panels  206 . Each of the multiple interconnected panels  204 ,  206 ,  206  includes an exterior face  208  thereof, adapted for attachment to the support frame  202  and an interior face  210  thereof adapted for defining a boundary, in the form of a floor, of a passenger compartment (not shown). In the panel apparatus  200 , all of the panels  204 ,  206 ,  206  are flame retardant panels, constructed in accordance with the present invention. 
         [0072]    In general, the flame retardant panels  204 ,  206 ,  206  of the flooring apparatus  200  are constructed in the same manner as described hereinabove with regard to the first exemplary embodiment of a flame retardant panel  100 , according to the invention. It will be noted, however, that the panels  204 ,  206  of the flooring apparatus  200  have a first thickness T thereof in sections of the exterior face  208  which are aligned with spaces, as illustrated at  212 , which are defined by the longitudinal rails  214 ,  216 ,  218 , and cross members  220  of the support frame  202 , and a second, thinner, thickness t in sections of the flooring panels  204 ,  206 ,  206  aligned above the various members  214 ,  216 ,  218 ,  220  of the support frame  220 , when the flooring panels  204 ,  206 ,  206  are placed in position on the support frame  202 . This arrangement of two thicknesses T, t is utilized in the exemplary embodiment of the flooring apparatus  200 , so that the smaller thickness t can match the thickness, for example, three-quarters of an inch, of prior and existing floor panels used in conveyances such as rail cars and/or buses. The thickness T of the panels  204 ,  206 ,  206  is increased in areas where the panels  204 ,  206 ,  206  do not rest on the support frame  202 , in order to provide room for the primary core to be made thicker, to thereby provide increased thermal and acoustic insulation, and increased structural stiffness in the floor panels  204 ,  206 ,  206  of the exemplary embodiment of the flooring apparatus  200 , according to the invention. 
         [0073]    In embodiments of the floor apparatus  200 , wherein the floor panels  204 ,  206 ,  206  include ribs of phenolic reinforced material extending between a first and a second skin of the floor panels  204 ,  206 ,  206 , in the manner illustrated by the ribs  140  in  FIGS. 2-4  for the first exemplary embodiment  100 , the ribs will preferably be positioned to extend substantially perpendicularly across the shorter dimension of the spaces  212  within the support frame  202 . In the flooring panels  202 ,  206 ,  206  of the exemplary embodiment of the flooring apparatus  200 , for example, all ribs within the panels  204 ,  206 ,  206  would preferably be oriented in a substantially longitudinal direction parallel to the longitudinal side and middle rails  214 ,  216 ,  218 . 
         [0074]    The floor panels  204 ,  206 ,  206  may be attached to the support frame  202  by any appropriate method, or combination of methods. For example, the floor panels  204 ,  206 ,  206  may be adhesively bonded to the support frame with an adhesive, such as a moisture curing urethane. Alternatively, or in addition to adhesively bonding the floor panels  204 ,  206 ,  206  to the support frame  202 , fasteners, such as screws, bolts, rivets, etc. may also be utilized for attaching the floor panels  204 ,  206 ,  206  to the support frame  202 . 
         [0075]      FIGS. 8A-8C  illustrate another embodiment of a floor panel  300 , for use in a flooring apparatus, according to the invention. The flame retardant floor panel  300  is configured for attachment to a support frame (not shown) of the type illustrated by the support frame  202  in  FIG. 7A  having a series of cross members which would be received in reduced thickness sections  302  of the panel  300 . The panel  300  also includes additional reduced thickness sections  304  configured for resting upon longitudinal rails of a support frame, in the same manner as illustrated in  FIG. 7A  for the flooring apparatus  200 . Through comparison of the drawings illustrating the flooring apparatus  200 , and the flooring panel  300 , it will be appreciated that whereas the flooring panels  204 ,  206 ,  206  of the flooring apparatus  200  had a major axis thereof oriented substantially longitudinally with respect to the support frame  200 , the panels  300  are configured to have a major axis of the panels  300  oriented substantially transversely to the longitudinal axis of the support frame to which the panels  300  are attached. 
         [0076]    As shown in  FIGS. 9A-9D  where a flame retardant panel  100 , according to the invention, includes sections of a first and a second thickness T, t, the layer of flame retardant material  130  may be different in the area of greater thickness T, than in the area of lesser thickness t. For example, as shown in  FIG. 9B , where the flame retardant panel  100  is thicker, the layer of flame retardant material may be constructed in accordance with the embodiment illustrated in  FIG. 2 , while, in the areas of the exterior face in which the panel has a lesser thickness, the layer of flame retardant material  130  may be constructed in accordance with the embodiment illustrated in  FIG. 4 . In other embodiments of the invention, not having sections of differing thickness, the layer of flame retardant material may be constructed differently in various sections of the panel. Also, as indicated in  FIG. 9C , where a panel  100 , according to the invention, includes a reduced thickness section t disposed inwardly from the periphery  105  of the panel  100 , the panel  100  may include a channel-shaped structure  166 , of reinforced phenolic material, or another appropriate material. 
         [0077]    As shown in  FIG. 10 , a flame retardant panel  100 , according to the invention, may include a heating element  170  attached to, or embedded into the first skin  118  of the panel, for providing heating of the interior surface of the panel. 
         [0078]    As also shown in  FIG. 10 , a flame retardant panel  100 , according to the invention, may also include one or more conduits  180  of plastic, metal composite, or pultruded composite, for example, embedded within the panel  100 , and having first and second openings  182 ,  184  into the conduit  180 , through at least one of the interior or exterior faces  102 ,  104  or the perimeter  105  of the panel. 
         [0079]    All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0080]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0081]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.