Patent Publication Number: US-2007107346-A1

Title: Insulation sheet structure and concrete sandwich wall panel assembly constructed therewith

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
      The present application is a continuation-in-part application of application Ser. No. 10/965,049, filed Oct. 14, 2004 for INSULATION SHEET STRUCTURE AND CONCRETE SANDWICH WALL PANEL ASSEMBLY CONSTRUCTED THEREWITH in the name of Peter Fleischhacker. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable  
     REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to building construction, more particularly, to pre-cast, insulated, concrete panels.  
      2. Description of the Related Art  
      Concrete sandwich wall panels are well known in the building construction art. They typically consist of an insulation layer sandwiched between two concrete layers with ties extending through the insulation layer and into the concrete layers to secure the three layers together. In one method of manufacturing, the first concrete layer is poured in a horizontal form and the insulation is placed on the concrete. Before the concrete sets, the ties are pushed through pre-drilled holes in the insulation and into the concrete. The ties have surface irregularities so that, after the concrete flows around the ties and cures, a secure attachment is provided between the concrete and ties. Finally, the second concrete layer is poured on the insulation. The concrete flows around the surface irregularities of the ties to secure the layers together after the concrete cures.  
      The above-described method has a number of shortcomings. First, it is very labor intensive because a large number of ties must be individually installed before the bottom concrete layer cures. Second, the purpose of the insulation is to minimize thermal transfer between the concrete layers. In order to minimize thermal transfer, the ties need to be poor heat conductors. However, because the ties support the weight of the concrete, the embedded portions of the ties are steel or other metal alloy, which are very good heat conductors. Consequently, the portion of the ties that reside in the insulation layer needs to be poor conductors. This means that the ties cannot be of a single material, which adds complexity and cost to the manufacturing process. Third, the insulation is composed of extruded polystyrene (XPS), which can only be extruded with a rectangular, board-like cross section, profiled cross sections are not possible. Although XPS is a very good insulator, it does not “breath”, that is, its vapor impermeability is too high, and water vapor can be trapped within the building.  
     BRIEF SUMMARY OF THE INVENTION  
      An object of the present invention is to provide an insulation sheet for insulated concrete panel assemblies that minimizes construction labor.  
      Another object is to provide an insulation sheet for insulated concrete panel assemblies that is vapor permeable.  
      A further object is to provide an insulation sheet for insulated concrete panel assemblies that can be manufactured at or close to the job site.  
      The present invention is an insulation sheet for concrete sandwich wall panels and comprises a sheet base composed substantially of expanded cellular foam and having opposed base surfaces, and a plurality of protrusions extending from each of the base surfaces to a distal surface away from said base surface, each of the protrusions having a cross-sectional shape such that a width of the distal surface is greater than a width of the footprint.  
      A concrete panel employing the insulation sheet of the present invention is made by pouring a first concrete layer into a horizontal form, pushing the insulation sheet into the concrete layer before the concrete sets, and then pouring the second concrete layer onto the insulation sheet.  
      The insulation sheet of the present invention is composed of an expanded cellular foam (ECF), which can be molded with surface features and is generally vapor permeable. The insulation sheet has a base and protrusions extending from both base surfaces. The protrusions have two embodiments. In one embodiment, the protrusions are integral with the sheet base and are generally mushroom-shaped so that the concrete flows around and surrounds the protrusions so as to be anchored in the concrete after it sets. The protrusions can be any shape, such as circular and ring-shaped, although any shape or combinations thereof may be employed. In the second embodiment, the protrusion are on inserts that are embedded in the sheet base during molding. The protrusion has a waist into which the concrete flows, anchoring the concrete to the sheet.  
      In the first embodiment, so that stacked insulation sheets can slide easily on one another, the surface area of the smallest protrusions is greater than any area of the same shape between protrusions. This means that the protrusions of adjacent stacked sheets will slide on each other rather than falling in between the protrusions. Optionally, in order to facilitate sheets sliding on each other and pushing the sheet into the first concrete layer, the surface of the protrusions are rounded.  
      In the second embodiment, the protrusions are two parts of separately produced inserts that are embedded in the sheet base. Each protrusion has opposed notches that form a waist for concrete to flow into. The inserts can be anchored into the sheet base in one of two ways. In the first, the sheet base material extends through holes in the insert when the sheet is being produced. In the second, anchor facings sandwich the sheet base therebetween.  
      Narrow ducts extend through the insulation sheet to allow air between the first concrete layer and the insulation sheet to escape while pushing the sheet into the concrete and to facilitate vapor permeability of the panel.  
      Other objects of the present invention will become apparent in light of the following drawings and detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a fuller understanding of the nature and object of the present invention, reference is made to the accompanying drawings, wherein:  
       FIG. 1  is a prospective view of a concrete sandwich of the present invention;  
       FIG. 2  is a perspective view of a section of the insulation sheet of the present invention;  
       FIG. 3  is a top view of a section of the sheet of  FIG. 2 ;  
       FIG. 4  is a cross-sectional view of the sheet of  FIG. 3  along the line  4 - 4 ;  
       FIG. 5  is a cross-sectional view of the concrete sandwich of  FIG. 1 ;  
       FIG. 6  is an enlarged view of a portion of a protrusion;  
       FIG. 7  is a perspective view of an insert of the present invention;  
       FIG. 8  is a cross-sectional view of an insulation sheet of the present invention with the insert of  FIG. 7 ;  
       FIG. 9  is a cross-sectional view of the concrete sandwich using the insulation sheet of  FIG. 8 ;  
       FIG. 10  is a perspective view of another insert of the present invention; and  
       FIG. 11  is a cross-sectional view of an insulation sheet of the present invention with the insert of  FIG. 10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention is an insulation sheet for use in concrete sandwich wall panels and a concrete sandwich wall panel assembly that employs the insulation sheet.  
      A concrete sandwich wall panel  10  of the present invention is shown in  FIG. 1 . The basic method of making the panel  10  is similar to that of the prior art. The first concrete layer  14  is poured to the desired thickness in a horizontal form. This layer  14  is typically a structural component, that is, it bears the weight of other components. The parameters of the first layer  14  are dependent upon the use to which the panel  10  is being put and the strength needed. As a structural component, the thickness of the first layer  14  will typically be in the range of six to twelve inches. The layer  14  may also include re-enforcement bars as needed according to architectural specifications.  
      Before the concrete set, the insulation sheet  12  is pushed into the concrete layer  14 , as explained below. Then the second concrete layer  16  is poured onto the insulation panel  12  in the desired thickness. The second layer  16  is typically of a lighter weight aggregate about one to six inches thick, again depending upon the use to which the panel  10  is put. Re-enforcement bars and/or wire mesh may be included according to architectural specifications. The concrete layers  14 ,  16  may be symmetrical, that is, both have the same thickness and composition, or asymmetrical, that is, different thicknesses and/or compositions. The surface finishes of the concrete layers  14 ,  16  depend on the use to which the panel  10  is put.  
      The insulation sheet  12  of the present invention is composed of expanded cellular foam (ECF), rather than the extruded polystyrene (XPS) of the prior art. Examples of ECFs are expanded polystyrene (EPS), expanded polypropylene (EPP), expanded polyethylene (EPE), and expanded copolymers such as polystyrene/polyphenylene oxide and modified polyphenylene oxide and polyphenylene ether. The density of the ECF will vary depending upon the application and will typically be in the range of from one to twelve pounds per cubic foot.  
      ECF is not restricted to a flat shape, as is XPS. ECF can be molded to include surface features. ECF has some vapor permeability so that water vapor is not trapped within the building. In other words, a panel  10  made with the insulation sheet  12  of the present invention “breathes”. Additionally, a “shape-molding” installation is more easily available to a concrete pre-caster, either by in-house investment and in-house production, or by tapping into one of hundreds of local ECF converters that already have ECF manufacturing know-how and an existing ECF infrastructure. Long-term savings would be in either greatly reduced or eliminated costs associated with transporting XPS sheets from one of the relatively few number of supplier&#39; plants around the country.  
      The insulation sheet of the present invention has two embodiments  12 ,  112 . Both embodiments have a sheet base  18 ,  118  and a plurality of protrusions  20   a ,  20   b (collectively,  20 ),  120  extending from the base surfaces  22 ,  24 ,  122 ,  124  of the sheet base  18 ,  118 . The thickness of the base sheet  18 ,  118  will depend upon how much insulation is desired and can typically be in the range of from one to twelve inches.  
      The difference between the two embodiments lies in the protrusions. In the first embodiment  12  of  FIGS. 2-6 , the protrusions  20  are integrally molded as elements of the sheet  12 . In other words, the sheet  12  is produced in one step as a unitary construct. In the second embodiment  112  of  FIGS. 7-11 , the protrusions  120  are two parts of separately produced inserts  128  that are added to the sheet base  118  during the molding process. In other words, the sheet  112  is produced in two steps, where the inserts  128  are produced in the first step and the sheet base  118  is molded around the inserts  128  in the second step.  
      In the first embodiment of the protrusions  20 , the width of the distal surface  26  of the protrusion  20  is generally larger than the width of the protrusion footprint  28 , the area of the protrusion  20  at the base surface  22 , as shown in the cross-section of  FIG. 4 . In other words, the protrusion cross-section is generally mushroom-shaped. The idea is that, when the sheet  12  is pushed into unset concrete, the concrete flows around and surrounds the protrusions  20 , as at  30  in  FIG. 5 . When the concrete sets, the protrusions  20  are anchored in the concrete. With protrusions extending from both base surfaces  22 ,  24 , the concrete layers  14 ,  16  are interlocked via the insulation sheet  12 , thereby creating an insulated concrete sandwich. The height of the protrusion  20  and the angle  42  of the protrusion side wall  40  are dependent on the density of the ECF used for the insulation sheet  12  and to the weight and density of the concrete layers  14 ,  16 . Consequently, these parameters will vary according to the application. The protrusions  20  can typically range in height from 1/2  inch to two inches and the side wall angle  42  can typically range from one to ten degrees.  
      Because of the integral protrusions, there is no need to manually insert individual ties, like the panels of the prior art. Consequently, manufacturing labor cost is greatly reduced.  
       FIGS. 2-5  show two different shapes for the protrusions  20 : a ring protrusion  20   a  and a circular protrusion  20   b . These are merely illustrative shapes and the present invention contemplates that any protrusion shape or combinations of protrusion shapes that have the characteristics described herein may be employed. For example, all the protrusions can be circular or the protrusions can be other shapes, such as squares and rectangles. The size of the protrusions can vary greatly depending upon the application. The ring protrusions  20   a can be, for example, three to ten inches in diameter and the circular protrusions  20   b  can be, for example, one to five inches in diameter.  
      Typically, the insulation sheets  12  are stacked for delivery to where the panels are manufactured. It is desirable that, as an insulation sheet  12  is needed for a panel  10 , the sheet  12  be easily slid from the top of the stacked sheets  12 . Because the XPS insulation sheets of the prior art are flat, they can be slid off quite easily. The insulation sheet of the present invention solves this issue by using protrusions  20  with a smallest distal surface area that is greater than any area of the same shape between distal surfaces  26 . For example, in  FIG. 3 , the smallest protrusion  20  is circular and the distal surface diameter  34  is greater than the largest circular space  36  between distal surfaces  26 . This means that the distal surfaces  26  of protrusions  20  of adjacent sheets  12  will slide on each other rather than falling in between the protrusions  20 .  
      If the distal surfaces  26  are flat, slight irregularities in the protrusions  20  may cause the protrusions  20  of adjacent sheets  12  to catch each other when trying to slide one sheet  12  off a stack. To solve this issue, the distal surface  26  of the protrusions  20  are optionally rounded, as in  FIG. 4 . In the case of the ring protrusions  20   a , the protrusion  20   a  has a raised ridge in the center of the distal surface  26  that is rounded to the two edges  36 . In the case of the circular protrusions  20   b , the protrusion  20   b  is domed. The rounded distal surface  26  facilitates sliding the sheets  12  along each other because the edges  38  of the protrusions  20  will not catch on each other.  
      Another advantage of the rounded distal surface  26  is that it is easier to push into the first concrete layer  14 . The present invention contemplates other shapes for the distal surface, for example, pointed, that facilitate pushing the insulation sheet  12  into the concrete layer  14 .  
      In the second embodiment, the protrusions  120  are two parts of separately produced inserts  128 . Two examples of inserts  128  of the present invention are shown in  FIGS. 7-11 . The insert  128  has an embedded section  134  and two protrusions  120 . The embedded section  134  is that part of the insert  128  that is embedded within the sheet base  118 . Consequently, the length of the embedded section  134  is the same as the thickness of the sheet base  118 .  
      The protrusions  120  extend from both ends of the embedded section  134 . Each protrusion  120  has a distal surface  126  away from the embedded section  134  and a pair of opposed notches  142  that form a waist  140  that is narrower than the distal surface  126 . The idea is that, when the sheet  12  is pushed into unset concrete, the concrete flows into the waist  140  and surrounds the protrusions  120 , as at  130  in  FIG. 9 . When the concrete sets, the protrusions  120  are anchored in the concrete. With protrusions  120  extending from both base surfaces  122 ,  124 , the concrete layers  14 ,  16  are interlocked via the insulation sheet  112 , thereby creating an insulated concrete sandwich.  
      Because of the protrusions  120  are integral parts of the sheet  112  at the construction site, there is no need to manually insert individual ties, like the panels of the prior art. Consequently, manufacturing labor cost is greatly reduced.  
      The parameters of the insert  128  (height, thickness, diameter, waist size, etc.) depend upon the application, for example, the weight and density of the concrete layers  14 ,  16 , and the material from which the insert  128  is constructed. Obviously, the stronger the material is, the thinner the insert  128  can be while maintaining the same strength. In addition, because the sheet  112  is insulating, the insert material is expected to have a low heat conductivity. Contemplated materials for the inserts  128  include materials that are of similar a similar chemical composition as the sheet base  118 , for example, polystyrene. Using a similar chemical composition facilitates recycling. Other rigid, low-conducting materials are contemplated, such as other plastics and carbon composites.  
       FIGS. 7 and 10  show two different shapes for the inserts  128 : a basic two-dimensional shape in  FIG. 7  and the basic three-dimensional shape in  FIG. 10 . These are merely illustrative shapes and the present invention contemplates that any insert shape or combinations of insert shapes that have the characteristics described herein may be employed. For example, all the inserts can be two-dimensional or the inserts can be other shapes.  
      The protrusion  20  the first embodiment optionally have rounded distal surfaces  26  so that the sheet  12  can be more easily pushed into the first concrete layer  14 . The protrusions  120  of the second embodiment are generally thin enough that there is no need to shape the distal surface  126  to make it easier to push the sheet  112  into the first concrete layer  14 , although for especially large protrusions  120  or heavy concrete it may be desirable to do so.  
      The present invention contemplates two basic ways of anchoring the insert  128  in the sheet base  118 , either of which can be used with any insert configuration. In the first anchor configuration, shown in  FIGS. 7-9 , the embedded section  134  includes one or more holes  136  through which the sheet base material extends, anchoring the insert  128  in the sheet base  118 . The number and size of the holes  136  can depend on the size of the inserts  128  and the thickness of the sheet base  118 .  
      The second anchor configuration, shown in  FIGS. 10 and 11 , has an anchor face  138  at the base of each protrusion  120 . The anchor faces  138  extend outwardly from the embedded section  134  over the sheet base outer surfaces  122 ,  124  to sandwich the sheet base  118  therebetween.  
      The present invention contemplates that a sheet  12  may include both protrusions of the first embodiment and protrusions of the second embodiment.  
      Narrow ducts  32 ,  132  extend through the sheet  12 ,  112  at various locations, providing two functions. First, they allow air between the first concrete layer  14  and the insulation sheet  12 ,  112  to escape while pushing the sheet  12 ,  112  into the concrete, thereby reducing the possibility of air bubble formation. Second, the ducts  32 ,  132  facilitate vapor permeability of the final product. The ducts  32 ,  132  are small enough so that concrete will not fill them. Because a thinner concrete mix would more easily fill larger ducts, the diameter of the ducts  32 ,  132  is dependent on the viscosity and aggregate mix of the concrete.  
      Thus it has been shown and described an insulation sheet and a concrete sandwich assembly constructed therewith that satisfies the objects set forth above.  
      Since certain changes may be made in the present disclosure without departing from the scope of the present invention, it is intended that all matter described in the foregoing specification and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.