Abstract:
A method and apparatus for making an rigid foam insulating panel is disclosed. The panel includes an rigid foam sheet with a plurality of grooves or recesses in which reinforcing strips are placed. Both sides of the sub-assembly are covered with a reinforcing sheet made of plastic, paper, foil, or a combination thereof. These reinforcing sheets are bonded to the surface of the rigid foam sheet and provide structural support to the sheet, as well as retaining the reinforcing strips in place. They also provide a vapor barrier on both sides of the sheet to prevent the migration of moisture through the sheet toward the wall covering, which will typically be attached to the side of the sheet in which the reinforcing strips are inserted.

Description:
FIELD OF THE INVENTION 
   The invention relates to insulation and construction devices. More particularly, it relates to the design and manufacture of rigid foam insulating panels. 
   BACKGROUND OF THE INVENTION 
   Rigid foam panels have been in wide use since the oil crisis of the early 1970&#39;s. Whether for exterior or interior use, rigid foam panels have provided an additional layer of insulation for houses and commercial buildings that, before the energy crisis, were often uninsulated, or insulated with fiberglass batting. 
   As with any new technology, rigid foam panels have been refined over the years. Originally, the panels were used as a replacement for fiberglass batting, and were cut to fit between studs. Later, sheets of rigid foam were used on the sides of houses being remodeled to add additional insulation to the exterior walls. 
   One continuing problem with the use of rigid foam panels has been their fragility as compared to other building materials, such as wood, steel, fiberglass and the like. The panels have limited tensile strength, and therefore cannot be used by themselves to support a great deal of weight on small connectors, such as nails and screws. Furthermore, the forces needed to attach nails and screws to a wall or ceiling of a house or commercial building when doing original construction or repair can quite easily damage the foam panels during installation. 
   When foam panels are used to form an insulated sheath around a wall that is being constructed, remodeled, or repaired, some of the most difficult issues are how to attach the foam panels. Since they are easily crushed, they cannot be used as an outer  surface covering by themselves, or with a coat of paint, for example. As a result, some environmentally hardened wall covering must be applied over them, such as shingles, shakes, wallboard, and wood or other paneling. 
   When rigid foam insulation is applied it must therefore permit or provide for an additional layer to be attached to it, or at least be in contact with its outer surface. This problem is not a trivial one to solve, especially for interior walls in which another relatively fragile material, gypsum board, is attached. One cannot easily, and in many cases may not wish to attach the layer of wall covering directly to the wall or studs behind the rigid foam paneling. For example, when attaching interior wall covering to a concrete wall, particularly an exterior concrete wall, it is especially bad to have fasteners such as nails or screws penetrating the wall-covering passing through the rigid foam layer, and being embedded in the concrete wall. Such fasteners provide a simple channel for heat loss and for vapor or water penetration to the outer surface of the wall covering. 
   My co-pending application entitled “An Insulated Concrete Wall System And Method For Its Manufacture”, filed contemporaneously with this application, describes a concrete wall system using the rigid foam panel described herein, and is incorporated by reference in this application for methods of using the panel, ways of constructing the panel, the structure and features of the panel, and all other teachings. 
   Another disadvantage to plain rigid foam sheets is their tendency to obscure the location of appropriate hanging points for the wall coverings that are subsequently attached through them to a wall. For example, once a complete sheet of rigid foam is attached to a wall, the trusses, and framing to which they were attached is completely covered up. When the subsequent layer of wall covering, such as siding or wallboard is attached, it is difficult, if not impossible to identify the location of the studs or trusses to which the foam was attached, and to which the wall covering must be attached as well. The only way to identify the location of the studs is with such tools as “stud finders”, special electronic devices that can be waved in front of the wallboard to find the location of a good mounting point for the wall covering, such as the underlying studs or trusses. These devices are notoriously unreliable, sensing as they do, the presence of a stud by capacitive or inductive means. In addition, their use  requires a separate hand to move the stud finder back and forth across the front of the wall covering until a “beep” is heard or a small red light flashes. All of this happens because the rigid foam covers up the mounting locations for mounting the subsequent wall-covering layer. 
   What is needed is a modified rigid foam panel and an efficient method of manufacturing it that avoids some, if not all of these problems (depending upon the embodiment). It is an object of this application to provide such a panel. 
   SUMMARY OF THE INVENTION 
   In accordance with the first embodiment of the invention, an insulated wall panel is provided including a rigid foam sheet with first and second planar sides and having first and second grooves extending substantially the full length of the sheet in a substantially parallel orientation in the first side of the sheet, a first reinforcing strip having a length, a top and a bottom, with the bottom being disposed in the first groove and the top facing outwardly away from the first groove, wherein the first strip extends substantially the full length of the sheet, a second reinforcing strip having a length, a top and a bottom with the bottom being disposed in the second groove and the top facing outwardly away from the second groove, wherein the second strip extends substantially the full length of the sheet, a first thin reinforcing layer bonded to the first planar side of the rigid foam sheet, and extending across the top of the first and second grooves, and a second thin reinforcing layer bonded to the second planar side of the sheet and extending across substantially an entire surface of the second planar side. The bottoms of the first and second strips may have two downwardly extending flanges that are oriented substantially perpendicular to the first planar side. The top of the first and second reinforcing strips may be mechanically textured over the length of the first and second strips to provide an improved gripping surface for drills and self-tapping or fine-threaded wallboard screws. The top of the first and second reinforcing strips may have a plurality of holes spaced apart at predetermined intervals along the length of the first and second reinforcing strips. The top of the first and second reinforcing strips may have a plurality of slots spaced apart at predetermined intervals along the length of the first and second reinforcing strips.  The first reinforcing layer may be bonded to the rigid foam sheet to enclose the first and second reinforcing strips and to define a first vapor barrier across substantially the entire first side of the sheet. The second reinforcing layer may be bonded to the rigid foam sheet to define a second vapor barrier across substantially the entire second side of the rigid foam sheet. The first and second reinforcing layers may have a tensile strength at least 100 times as great as the tensile strength of the rigid foam sheet. A first portion of the first reinforcing layer may extend across the top of the first reinforcing strip and be placed in tension when the panel is bent away from the first reinforcing strip before the foam sheet will fracture at the first groove. A second portion of the first reinforcing layer may extend across the top of the second reinforcing strip and may be placed in tension when the panel is bent away from the second reinforcing strip before the rigid foam sheet will fracture at the second groove. 
   In accordance with a second embodiment of the invention, a method of manufacturing an insulated wall panel is provided that includes the steps of creating a foam block having first and second opposing sides, cutting the foam block to form a plurality of stacked individual foam sheets having first and second sides and a plurality of parallel recesses in the first side, inserting a reinforcing strip having a top and a bottom into each of the plurality of recesses in each of the plurality of sheets, covering the tops of each of the reinforcing strips with a first thin reinforcing layer, and bonding the first reinforcing layer to the first side of each of the rigid foam sheets. The method may also include the step of bonding a second reinforcing layer to the second side of each of the rigid foam sheets. The step of cutting the foam block may include the steps of drawing a hot wire frame of substantially equally spaced parallel hot wires through the block from the first side to the second opposing side of the block, and simultaneously forming each of the plurality of grooves in the block with each of the hot wires in the hot wire frame, and completing a path through the block by substantially simultaneously separating the block into a plurality of sheets. 
   The step of bonding the first reinforcing layer may include at least one of the following steps: (a) applying adhesive to the first side of each of the plurality of sheets and subsequently rolling the first reinforcing layer onto the first side; (b) applying adhesive to the first reinforcing layer and subsequently rolling the first reinforcing layer onto the first sides of each of the foam sheets, and (c) rolling the first  reinforcing layer onto the first sides of the foam sheets and subsequently heating the first reinforcing layer to form a thermal bond between the first sides of the foam sheets and the first layer. The method may include the step of orienting the foam sheet with respect to a means for trimming each sheet such that there is a predetermined distance between the means for trimming and the reinforcing strips, and trimming an edge of the foam sheet. 
   In accordance with a third embodiment of the invention, a method of manufacturing an insulated foam panel is provide that includes the steps of continuous foaming a liquid matrix of expanding foam precursor, channeling the liquid matrix out through a nozzle, capturing the liquid matrix between two parallel and advancing thin sheets of reinforcing material, inserting a plurality of continuous webs of reinforcing strip between the two sheets of reinforcing material, maintaining the sheets in a substantially parallel spaced apart orientation as they advance over a distance sufficient to permit the liquid matrix to expand, fill substantially an entire void between the two sheets, and harden in the form of a continuously moving ribbon of insulated panel, and repeatedly and successively cutting the moving ribbon into a plurality of individual insulating panels having a cut edge substantially perpendicular to the direction of advancement. The method may include the steps of unrolling a plurality of ribbons of reinforcing material at substantially the same linear rate as the first and second sheets advance, and roll forming the plurality of unrolled ribbons into the plurality of continuous webs of reinforcing strip. The method may include the step of continuously trimming lateral opposed edges of the ribbon of insulated paneling as the ribbon advances and prior to the step of spacing the plurality of continuous webs of reinforcing strips a first predetermined distance apart. The steps of maintaining the sheets may include the step of simultaneously maintain the plurality of continuous webs of reinforcing strips at the first predetermined distance apart.  

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a plan view of an insulated panel in accordance with the present invention; 
       FIG. 2  shows an end view of the panel in  FIG. 1 ; 
       FIG. 3  is an end view of the reinforcing strip of the panel in  FIGS. 1 and 2 ; 
       FIG. 4  is an end view of an alternative reinforcing strip for the panel of  FIGS. 1 and 2 ; 
       FIG. 5  is a fragmentary plan view of the reinforcing strips of  FIGS. 1–4  showing an elongated slot construction; 
       FIG. 6  is a fragmentary plan view of the reinforcing strip of  FIGS. 1–4  showing a mounting hole; 
       FIG. 7  is a fragmentary plan view of the reinforcing strip of  FIGS. 1–4 ; 
       FIG. 8  illustrates an alternative arrangement of reinforcing strips for the insulated panel of  FIG. 1 ; 
       FIG. 9  illustrates one method of forming a plurality of insulating foam sheets from a solid foam block; 
       FIG. 10  illustrates the path followed by a hot wire in order to make the individual sheets from the foam block of  FIG. 9 ; 
       FIG. 11  illustrates the step of removing excess material from each of the grooves formed as shown in  FIGS. 9 and 10 ; 
       FIG. 12  illustrates a first process for assembling the insulated foam panel of the foregoing FIGURES; and  
       FIG. 13  illustrates an alternative process for forming the insulated foam panels of the preceding FIGURES. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIGS. 1 and 2 , an insulated foam panel  10  is shown that includes an rigid foam sheet  12  having two grooves  14 ,  16  into which two reinforcing strips  18  are disposed. The panel is preferably four feet wide by eight feet long (4′×8′) and between one and three inches (1″–3″) in thickness. The two reinforcing strips are preferably equidistantly spaced from the center of the panel two feet (2′) apart leaving a one-foot (1′) margin on either side. In this manner, when the panels are placed adjacent to each other by abutting their edges in a checkerboard arrangement, a continuous expanse of equidistantly spaced reinforcing strips on two foot centers will be provided. 
   On the outer surfaces of panel  10  are two thin reinforcing sheets  20  and  22 . The first of these, sheet  20 , extends completely across the side of the rigid foam sheet proximate to the reinforcing strips. The second of these, sheet  22 , extends completely across and covers the entire surface of the opposing side of the sheet. 
   The reinforcing layers or sheets are preferably made of plastic, paper, foil or a combination thereof, preferably in a composite film form, if more than one material is used. The preferred plastic for the sheets is polyolefin or polyester. 
   Rigid foam sheet  12  may be formed of any of a variety of rigid foam materials. These materials may be thermoplastic or thermosetting foams. Preferred foam materials include polystyrene, polyisocyanurate and polyurethane. The sheet, depending on application, has a thickness of between one and three inches with a thermal resistance (“R”) value of between 3 and 8 per inch of thickness. 
   Reinforcing strips  18  extend substantially the entire length of the panel in a parallel side-by-side arrangement. As shown in  FIG. 1 , two strips are preferably provided. Alternatively, three strips (or more) can be provided as shown in  FIG. 8 .  
   The strips preferably have a top surface  19  that is substantially coplanar with the surface of the rigid foam sheet. In this manner, when reinforcing sheets  20  and  22  are bonded to the surface of rigid foam sheet  12 , the top surfaces  19  of the reinforcing strips (i.e., the outwardly facing surface of the reinforcing strips) will be adjacent to the reinforcing sheet and at substantially the same level, applied to the outer surface without lifting it up away from the surface of the sheets. With this arrangement, when subsequent layers of material, such as gypsum board, are attached to the reinforcing strip, the inner panel-facing surface of these wallboards will be flush with both the foam sheet and with the tops of the reinforcing strips. 
   Referring now to  FIGS. 3 and 4 , reinforcing strips  18  may have several different cross-sectional profiles.  FIGS. 3 and 4  represent just two possible cross-sectional profiles of the strips. The embodiments of both  FIGS. 3 and 4  have a central web portion  24  with two outwardly extending fins  26 . As shown in  FIG. 3 , these fins  26  can be rolled at their free ends to provide gripping edges  28  that can be inserted into rigid foam sheet  12  to hold reinforcing strips  18  into position. Central web  24  of the strips preferably has a recessed central portion  30  that extends substantially parallel to and slightly below (as shown in  FIG. 2 ) the surface of the insulated panel  10 . On either side of this recessed central portion are two non-recessed portions  32  and  34  that define the topmost surface of the reinforcing strips. Portions  32  and  34  are preferably disposed coplanar with the surface of rigid foam sheet  12 . By recessing a portion of the web of reinforcing strips  18 , the head of a fastener,  36  used to attach the panel to a wall can be completely recessed below the nominal surface of insulated panel  10 . 
   Referring now to  FIGS. 5–7 , reinforcing strips  18  can be provided with a variety of surface finishes and fastening mounts. As shown in  FIG. 5 , elongate slots  37  extending substantially parallel to the length of the strips can be disposed in a spaced apart arrangement over the length of the strip. As shown in  FIG. 6 , holes  38  can similarly be provided along the length of the strip. As shown in  FIG. 7 , the top surface of reinforcing strips  18  can be textured, such as by knurling, roll-forming, punching or stamping. This textured surface provides surface irregularities that reduce the tendency of drills or self-tapping screws to wander when they are drilled through reinforcing strip  18 .  
   There are several ways of making insulated panels in accordance with this invention.  FIGS. 9–11  and  13  show one method for making insulated panel  10 , and  FIG. 12  shows another preferred method. 
   Referring now to  FIG. 9 , a foam block  40 , typically having outer dimensions on the order of three feet by four feet by eight feet (3′ ×4′ ×8′) is cut into a stack of rigid foam sheets using a hot wire frame. Each of the joints between the stacked foam sheets  12  shown in  FIG. 9  is formed by a hot wire or ribbon following the path shown in  FIG. 10 . These wires, in order to form a plurality of insulated foam sheets having a constant thickness, are about eight feet (8′) long and are spaced equidistantly apart. Their spacing is preferably equal to the desired thickness of the rigid foam sheets. The wires are parallel to each other and lie in a plane. At their ends, they are attached to a frame that holds them in this orientation. The wires are heated and the frame is advanced until all the wires contact side  42  of block  40 . The frame is translated through the block such that all the wires follow the path shown in  FIG. 10 , simultaneously forming the first grooves  14  in the partially separated block then returning to their original path  44  as the frame traverses block  40  until the second groove  16  is formed by the wires following path  44  as shown in  FIG. 10 . Once the second groove is formed, the wires again return to their original path  44  and continue until they all substantially simultaneously exit side  43  of the foam block  40  and each of the rigid foam sheets  12  are substantially simultaneously separated from each other. 
   When this cutting process is complete, a stack of individual foam sheets is produced as shown in  FIG. 9 . Each of the rigid foam sheets includes two long strips of rigid foam  46  that must be removed from each of the sheets as shown in  FIG. 11 . 
   While this is the preferred process, an alternative process could use the same frame of hot wires that travel along a straight line through block  40  to form a stack of sheets each sheet having two smooth opposing surfaces and no recesses  14  and  16 . In this process, once the sheets have been formed, they can be separated and have their grooves  14 ,  16  formed individually and sequentially on each sheet. Preferably, two hot knives, ribbons, wires, rolls, or a milling cutter will be drawn down the length of  each sheet  12  simultaneously forming the two grooves  14  and  16  starting at one end of each rigid foam sheet  12  and traveling the length of that sheet until the two groove-forming tools reach the other opposing end of the sheet in a single pass that forms both recesses simultaneously. The path followed by the tool making the recess is preferably parallel to the longitudinal extent of the recesses in this method. 
     FIG. 13  illustrates a continuation of the panel forming process that started in  FIGS. 9–11 . In  FIG. 13 , a panel is shown in various steps of its assembly and manufacture starting at the left and proceeding in the direction of the arrows to the right side of the FIGURE. In the center of the FIGURE are three alternative processes,  49 A,  49 B,  49 C, each of which are suitable for applying the reinforcing sheets to the rigid foam sheet  12 . In step  48 , two reinforcing strips  18  are inserted into grooves  14 ,  16  in the rigid foam sheet  12 . Once the strips are inserted into the sheet, the reinforcing sheets  20 ,  22  are applied to each side of the rigid foam sheet  12 . 
   In step  49 A, adhesive-dispensing nozzles  50 ,  52  apply adhesive to reinforcing sheet material being drawn off two rolls  54  and  56 . Rigid foam sheet  12  with reinforcing strips  18  inserted is then moved between these rolls and the adhesive-coated reinforcing sheet material is unrolled and applied to the opposing surfaces of the rigid foam sheet  12 . 
   In alternative step  49 B, located in the center of  FIG. 13 , two adhesive dispensing nozzles  58 ,  60  apply an adhesive directly to both sides of the rigid foam sheet  12  itself, and reinforcing sheet material on two rolls  62 ,  64  is subsequently rolled onto the rigid foam sheet  12  as it moves rightward. 
   In step  49 C, located at the bottom of  FIG. 13 , no adhesive is applied and the rigid foam sheet  12  is covered on both sides with the reinforcing sheet material that is held on rolls  66 ,  68 . 
   In step  70 , two heated rollers or sheets  72  and  74  are pressed against both sides of the sheet to either (a) cure the adhesive previously applied in steps  49 A and  49 B, or to (b) thermally bond reinforcing sheets  20 ,  22  to the rigid foam sheet  12  previously assembled in step  49 C. Once this heating is complete, the completely assembled insulated foam panel  10  is removed as shown in step  76 .  
   Nozzles  50 ,  52 ,  58  and  60  that are used to apply adhesives, preferably apply an even layer of adhesive across the entire face of either the reinforcing sheet  20 ,  22  or the rigid foam sheet  12  as shown in steps  49 A and  49 B. In this manner, the bond preferably extends across the entire interface between the reinforcing sheets  20 ,  22  and the rigid foam sheet  12 . 
   In an alternative embodiment, any or all of the nozzles may apply glue to an intermediate roller that is thereby covered with glue. This intermediate roller will then transfer the glue to the rollers shown in the FIGURES by rolling contact. 
   The process shown in  FIG. 13  illustrates the formation of the most complete and preferred embodiment of this invention. As noted above, there may be different numbers of reinforcing strips, not just two as shown in  FIG. 13 , that are inserted into the rigid foam sheet  12 . In addition, one of the reinforcing sheets need not be applied. 
   Finally, although steps  49 A– 49 B show adhesive applied to either both sides of the rigid foam sheet  12  (step  49 B) or to both sheets of reinforcing sheet material ( 49 A). It should be understood that these two processes can be combined, so that one side of the rigid foam sheet  12  is covered with an adhesive coated reinforcing sheet and the other side of the rigid foam sheet  12  has adhesive applied directly to it. 
     FIG. 12  shows a continuous process of forming insulating wall panels  10 . In this embodiment, a nozzle  80  directs a flow of a liquid matrix  81  of expandable foam precursor such that it forms a thin, wide sheet, preferably on the order of four feet wide. The liquid matrix flows between two reinforcing sheets  20 ,  22  unrolled by rollers  82  and  84 . A plurality of metallic reinforcing strips, such as those shown and described above, are roll-formed by rollers  86  from thin, flat sheet stock on roll  88  and are inserted adjacent to the top or the bottom (as shown here) of the liquid matrix. The sheets and the foam in between them as well as the reinforcing strips are advanced through the machine between two sheet supports  90 ,  92 , each of which may be shoes, such as shown here, or an endless belt loop supported by rollers. These sheet supports constrain and support the liquid matrix as it cures to rigid foam. By varying the spacing of the sheet supports, insulated panels of several thicknesses may be made using the same machine.  
   Once the composite structure reaches the end  94  of the supports, the foam has cured and the panel is substantially rigid. This continuous sheet of paneling is then cut to discrete lengths by a flying cutter  96 , disposed after the end  94  of the supports. 
   In an alternative embodiment, nozzles  80  can direct the flow of foam beads or pellets instead of a liquid matrix. In this alternative embodiment, sheets supported  90 ,  92  are preferably heated by steam to cause the beads or pellets to expand and bond to each other to form the foam core of the panel. An example of a machine illustrating this foam bead or pellet process for forming a sheet can be seen in U.S. Pat. Nos. 4,379,107 and 5,786,000. 
   While those skilled in the art may recognize other ways in which the present application may be useful, this application is not to be limited by the descriptions given above, but is to be limited solely by the scope of the claims that follow.