Abstract:
A reflective insulative blanket for use in construction applications, such as curing concrete, thawing frozen ground and other insulative purposes. The blanket comprises at least one moisture-impervious layer attached to an insulative layer. The insulative layer includes a plurality of hollow, insulative elements. The moisture-impervious layer may close the insulative elements and/or the space surrounding the insulative elements, thereby entrapping air to provide the insulative properties of the blanket. The blanket preferably includes two moisture-impervious layers, one attached to each side of the insulative layer. The blanket further includes a reflective layer secured to the outside of at least one of the moisture-impervious layers. The reflective layer reflects thermal energy before it has passed through any portion of the blanket, thereby reducing heat retention within the blanket and improving lateral thermal conduction.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    I. Field of the Invention  
           [0002]    The present invention relates to insulative blankets and more particularly, to a reflective insulative lateral heat distributing blanket for use in construction applications.  
           [0003]    II. Description of the Related Art  
           [0004]    Construction projects many times require the maintenance of a set temperature range for curing concrete, and preventing pipes or other materials from freezing. This can often be achieved with a certain degree of success by laying an insulating material over the appropriate area. In some applications, it may be necessary to supply an area with supplementary heat. For example, in some geographical areas it may be necessary to supply supplementary heat to thaw the ground before roads, pipes, foundations or concrete floors may be laid, or repairs can be made to existing infrastructure. During cold weather concreting it may be necessary to supply supplementary heat to protect freshly placed concrete from freezing. To assure timely development of strength, it may be necessary to maintain concrete placements at temperatures well in excess of cold weather ambient air temperatures for a period of several days. This heating is typically accomplished by placing any of a variety of conventional hydronic heating elements on the ground or concrete, usually in a serpentine fashion, beneath the insulating materials.  
           [0005]    Historically, a variety of insulative materials such as sawdust, straw, wool blankets, and bats of foam or fiberglass insulation have been used in construction projects to maintain a desired temperature range and to retain heat from heating elements. These materials are problematic because they can be cumbersome, dirty, time consuming to apply, expensive, hard to remove and difficult to move or reuse. Further, these materials may absorb moisture from the ground, wet, freshly poured concrete, or surrounding elements, thereby reducing the insulative properties of the insulative materials and potentially impairing the concrete curing process. In addition, these materials are often deficient when used in conjunction with heating elements because they do not provide lateral conduction of heat, thereby causing uneven surface temperatures.  
           [0006]    Insulative blankets have become a common alternative to the traditional insulating materials discussed above. One such insulative blanket is shown in FIG. 1 and generally includes a type of “bubble wrap” insulative layer  102  and an aluminum foil layer  100  laminated to the upper surface of the insulative layer  102 . The blanket in FIG. 1 further includes moisture-impervious layers  104   a  and  104   b  disposed on opposite sides of the laminated insulative layer  102  and aluminum foil  100 . In use, emitted radiant energy radiates upwardly from the ground (or heating elements), passing through the moisture-impervious layer  104   a  and the insulative layer  102  before reaching the reflective aluminum foil layer  100 . The emitted radiant energy is then reflected by the aluminum foil layer  100  back through the insulative-layer  102  and the moisture-impervious layer  104   a . As the emitted radiant energy passes through the moisture-impervious layer  104   a  and the insulative layer  102 , some of it is converted into heat and is retained by the blanket, thereby reducing the amount of heat energy that is returned to the ground. In applications where hydronic or other heating elements are used to provide supplementary heat, the inherent heat retention of the blanket may not provide adequate and uniform lateral heat distribution. This can in turn result in uneven temperatures across the concrete or ground. This shortcoming is typically addressed by laying the heating elements in closer proximity, thereby requiring more heating elements over a given area or decreasing the area being heated. Even if the heating elements are laid in closer proximity, the insulative blanket is not conducive to conducting heat, thereby, preventing lateral uniformity of temperature across the concrete or ground.  
         SUMMARY OF THE INVENTION  
         [0007]    The noted problems are overcome by the present invention wherein an insulative blanket is provided with an external reflective layer. In a preferred embodiment, the insulative blanket includes an insulative layer sandwiched between a pair of moisture-impervious layers. The reflective layer is secured to the outside surface of one of the moisture-impervious layers to reflect emitted radiant energy before it has passed through any portion of the blanket. The metal foil being in direct contact with heating elements also allows the foil to conduct heat laterally providing a more uniform distribution of heat to the concrete or ground.  
           [0008]    In a more preferred embodiment, the insulative layer is formed out of a plastic material having a plurality of indentations. The moisture-impervious layers are secured to both sides of the insulative layer, sealing the indentations and entrapping air to provide the insulative blanket with improved insulative qualities.  
           [0009]    In another preferred embodiment, the reflective blanket may be provided with a reflective layer on each side. More specifically, a reflective layer is secured to the outside surface of each moisture-impervious layer. This permits the blanket to reflect radiant energy from the sun with minimal absorption by the blanket.  
           [0010]    The present invention provides a simple, cost-effective, lightweight and moisture-impervious insulative blanket. The external reflective layer allows radiant energy to be reflected without passing through any portion of the blanket, thereby reducing heat retention by the blanket and providing improved lateral heat conduction and more uniform heat distribution. As a result of the moisture-impervious layers, the blanket does not leach or absorb moisture from curing concrete or the surrounding elements. By using the moisture-impervious layers to seal the indentations of the insulative layer, the present invention requires fewer layers than conventional “bubble-wrap” insulative blankets, and may therefore have less weight and be less expensive to manufacture.  
           [0011]    These and other objects, advantages and features of the invention will be more fully understood and appreciated by reference to the detailed description of the preferred embodiments in the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is an exploded, cross sectional view of an insulative blanket manufactured in accordance with the prior art;  
         [0013]    [0013]FIG. 2 is a perspective view of a portion of an insulative blanket manufactured in accordance with a preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 3 is a cross sectional view of a portion of the insulative blanket taken along line III-III of FIG. 2;  
         [0015]    [0015]FIG. 4 is a cross sectional view of a first alternative insulative blanket having reflective layers on both sides; and  
         [0016]    [0016]FIG. 5 is a cross sectional view of a second alternative insulative blanket having a foam insulative layer. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    An insulative blanket constructed in accordance with the present invention is illustrated in FIGS.  2 - 3  and generally designated  10 . As perhaps best shown in FIG. 3, the insulative blanket  10  generally includes an insulative layer  20 , a pair of moisture-barrier layers  40   a  and  40   b  and a reflective layer  30 . The moisture-barrier layers  40   a  and  40   b  are secured to each side of the insulative layer  20 . The reflective layer  30  is laminated or otherwise secured to the outside of one of the moisture-barrier layers  40   a  or  40   b . The present invention is described in connection with an insulative blanket adapted for use in standard construction applications. The present invention is, however, readily adapted for use in specialized applications, for example, by varying the material and or specifications of the moisture-impervious, insulative and reflective layers.  
         [0018]    The insulative layer  20  includes a substantially planar base  23  having a plurality of protruding insulative elements  24 , as perhaps best shown in FIGS. 2 and 3. The insulative elements  24  are preferably hollow, generally cylindrical elements arranged in a regular pattern over the entire extent of the insulative layer  20 . The size, shape and arrangement of the insulative elements  24  can vary from application to application as desired. For example, the insulative elements  24  may take on other shapes, such as triangles, squares, elongate lines, troughs, ovals or essentially any other shape. The apexes  25  of the insulative elements  24  are preferably arranged in a co-planar configuration to provide a uniform surface to intersecure with the moisture-impervious layer  40   a . As described in more detail below, the insulative elements  24  are sealed by the moisture-impervious layer  40   b  to provide the desired insulative properties. The insulative layer  20  is preferably manufactured from a substantially planar sheet of plastic material that is formed to define the insulative elements  24 , as described in more detail below. To increase the efficiency of the insulative blanket  10 , the insulative layer  20  is made out of materials that resist moisture absorption while providing the necessary insulative properties. In the preferred embodiment, the sheet  22  is manufactured out of a plastic material, an example of a suitable plastic is linear low-density polyethylene, with a thickness of 1-10 mils. It should be readily apparent that the sheet  22  may be formed with a variety of thicknesses and other types of plastics. Alternatively, the preferred insulative layer  20  may be replaced by other conventional insulative materials. For example, the insulative layer may be replaced by a layer of conventional “bubble wrap.” Further, the insulative layer may be made out of a variety of other synthetic or plastic materials such as closed cell polypropylene foam, closed cell polyethylene foam, polyester, nylon, or fibrous synthetic materials that maintain their insulative properties when wet, as shown in FIG. 5. If desired, the insulative layer  20  may also include multiple sheets secured together (not shown) or other configurations to provide greater insulation. Multiple blankets may also be laminated together to provide extra insulative properties while maintaining the ease of manufacturing by producing one standard blanket  10 , which only is laminated to give the desired heat retention.  
         [0019]    As noted above, the moisture-impervious layers  40   a  and  40   b  are secured to opposite sides of the insulative layer  20 . The moisture-impervious layers  40   a  and  40   b  are generally planar sheets extending substantially coextensively with the insulative layer  20 . In the preferred embodiment, moisture-impervious layer  40   a  is secured to the upper surfaces of the apexes  25  and moisture-impervious layer  40   b  is secured to the lower surface of the base  23 . Moisture-impervious layer  40   b  seals the insulative elements  24  entrapping air within spaces  14 . Similarly, moisture-impervious layer  40   a  seals the upper surface of the blanket  10  cooperating with the sealed edges of the blanket  10  to entrap air in the space defined around the insulative elements  24 . The sealed air spaces  14  give the blanket  10  improved insulative qualities. The moisture-impervious layers  40   a  and  40   b  are made out of a thin flexible plastic to produce a lightweight insulative blanket  10 . In the preferred embodiment, the moisture-impervious layers  40   a  and  40   b  are manufactured from polyethylene plastic having a thickness of approximately 1-4 mils. The thickness of the moisture-impervious layers  40   a  and  40   b  can vary from application to application with the type of material and the degree of durability required. The moisture-impervious layers  40   a  and  40   b  may also be made out of other materials such as nylon, polyester or other synthetic materials to provide variations in durability, flexibility and weight. If desired, the moisture-impervious layers  40   a  and  40   b  can be manufactured from heavier materials such as canvas, cloth or synthetic materials such as polyester or nylon, to give greater durability and reduce the likelihood of tearing, cutting or burning. Both the insulative layer  20  and moisture-impervious layers  40   a  and  40   b  may be manufactured out of a flame-retardant material and/or out of biodegradable and/or sunlight degradable material.  
         [0020]    As described above, the reflective layer  30  is secured to the outer surface of one of the moisture-impervious layers  40   a  or  40   b . The reflective layer  30  is preferably a thin sheet of metallic foil, such as aluminum foil, which provides a lightweight and inexpensive blanket. Alternatively, other materials may be used, such as tin, copper, nickel, zinc, and any other element or combination of elements so long as it provides a surface that is capable of reflecting radiant energy. The thickness of the reflective layer may vary, but in the preferred embodiment the reflective layer has a thickness of about 0.3 mils or greater. A thicker reflective layer may be used to provide increased lateral heat conduction. The reflective layer in some cases may also be made out of highly reflective non-metallic materials to provide greater flexibility and durability to the reflective layer. As an alternative to the use of a foil material, the reflective layer  30  may alternatively be deposited on the moisture-impervious layer  40   a  or  40   b , such as by spray painting or vacuum deposition.  
         [0021]    II. Method of Manufacture and Assembly  
         [0022]    As noted above, the insulative blanket  10  is preferably manufactured out of plastic materials, although materials such as biodegradable, air degradable or light degradable plastics, foam insulations, synthetic materials or any other material that provides insulative properties while resisting the absorption of moisture may be used. In a preferred embodiment, the insulative layer  20  is formed from a sheet of flexible plastic, preferably linear low density polyethylene having a thickness of 5-15 mils. The plastic is preferably provided in the form of an elongate roll, although individual smaller pieces may be used. The insulative elements  24  are formed in the sheet using conventional techniques and apparatus. One technique is to move the plastic sheet  22  across a heated roller that includes a plurality of spaced indentations corresponding in size, shape and configuration to the desired insulative elements. A vacuum is created in each of the indentations to draw the sheet into the indentations, thereby forming the insulative elements  24 . Alternatively, the insulative layer  20  may be formed by passing the plastic sheet  22  between two heated rollers, the first roller having indentations and the other having protrusions. These rollers form the insulative elements  24  by rolling the sheet  22  between them. The apexes  25  of the insulative elements  24  define an upper planar surface, while the base  23  defines the lower plane.  
         [0023]    One or both of the moisture-impervious layers  40   a  and  40   b  are then applied to the insulative layer  20  using conventional techniques and apparatus. In some embodiments, the formed side of the insulative element  24  could serve as moisture-impervious layer  40   a  or  40   b . The moisture-impervious layers  40   a  and  40   b  are formed in approximately the size of the insulative layer  20 , but other sizes may be used and cut to fit the insulative layer  20 . In the preferred embodiment, the moisture-impervious layers  40   a  and/or  40   b  are laminated to each side of the insulative layer  20  by adhesive, heat or other methods well known in the art. In some applications, the moisture-impervious layers  40   a  and/or  40   b  may be secured to the insulative layer  20  only along the peripheral edges of the blanket  10 .  
         [0024]    In the preferred embodiment, the reflective layer  30  is laminated or otherwise attached to at least one of the moisture-impervious layers  40   a  and  40   b  using conventional techniques and apparatus. The reflective layer  30  is preferably attached to the moisture-impervious layer  40   a  or  40   b  before the moisture-impervious layer  40   a  or  40   b  is attached to the insulative layer  20 . It may, however, be attached to the moisture-impervious layer  40   a  or  40   b  after the moisture-impervious layer  40   a  or  40   b  is attached to the insulative layer  20 . In the preferred embodiment, the reflective layer  30  is a metallic foil that is secured to the moisture-impervious layer  40   a  or  40   b  by heat lamination or adhesive or cement. Another method for manufacturing the reflective layer  30  is to apply a reflective material using conventional deposition techniques and apparatus. For example, the reflective material, such as a metallic paint, can be spray deposited on the outer surface of the moisture-impervious layer  40   b . Alternatively, the reflective material can be applied using a conventional vacuum deposition technique.  
         [0025]    The exterior edges of the insulative blanket  10  are preferably sealed to prevent moisture and other contaminants from entering the space around the insulative elements  24 . The peripheral edge is preferably sealed by heat welding or by adhesively intersecuring the various layers of the blanket  10 . Alternatively, a trim element (not shown) may be applied around the periphery of the blanket  10 . For example, a flexible, plastic strip (not shown) may be folded around the edges and secured to the upper and lower surfaces of the blanket  10  by lamination or an adhesive.  
       ALTERNATIVE EMBODIMENTS  
       [0026]    A first alternative embodiment is shown in FIG. 4. In this embodiment, the blanket  10 ′ includes a second reflective layer  30   b  disposed on moisture-impervious layer  40   a . As a result, the blanket  10 ′ includes reflective layers  30  and  30   b  on both outer sides. The moisture-impervious layers  40   a  and  40   b  and reflective layers  30  and  30   b  may be manufactured by any of the methods above in connection with the preferred embodiment. The second reflective layer  30   b  is particularly useful in applications where it is desirable to reflect away the sun&#39;s radiant energy, such as in certain concrete curing applications.  
         [0027]    In a second alternative embodiment (not shown), the insulative blanket  10  may be formed with only one of the moisture-impervious layers  40   a  and  40   b . For example, the top moisture-impervious layer  40   a  may be omitted. The blanket  10  still retains its insulative qualities because the moisture-impervious layer  40   b  seals the insulative enclosures  14 . Alternatively, the bottom moisture-impervious layer  40   b  may be omitted, so that the insulative layer  20  is bounded by the top moisture-impervious layer  40   a  on one side, and on the other side by the reflective layer  30 , allowing the blanket  10  to retain its insulative qualities as described above in connection with the preferred embodiment.  
         [0028]    In a third alternative embodiment (not shown), at least one of the moisture-impervious layers  40   a  or  40   b  is formed from a darker color, such as black, to absorb thermal energy from the sun during the day. This allows the insulative blanket  10  to absorb heat from the sun lowering the need for supplementary heat.  
         [0029]    The above descriptions are those of preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law and the doctrine of equivalents.