Abstract:
A process for making a composite profile may take advantage of the properties of two different materials, such as their strength, holding properties, ability to be readily coated or processed, and cost. In a preferred embodiment, the process makes use of a crush rib to ensure that the parts are flush with each other. In another preferred embodiment, the process makes use of a gap between the insert and the core, filling the gap with a coating.

Description:
[0001]    This application claims priority from U.S. Provisional Application S/No. 60/434,891 filed Dec. 20, 2002. 
     
    
     
       BACKGROUND  
         [0002]    The present invention involves forming a profile from two or more different materials to make a composite profile with an outside appearance of a single piece, while sharing the desirable characteristics of the individual materials in the composite profile. The materials in the composite may be dissimilar materials, such as Medium Density Fiberboard (MDF) and wood.  
         SUMMARY  
         [0003]    The purpose of the present invention is to fabricate a profile, such as a stile for a window shutter, which is made substantially from one core material, such as MDF, while also including one or more insert components, such as wooden inserts. The core material may have its own desirable characteristics, such as being easy to coat with a thermoplastic resin, being inexpensive, or being able to be processed easily. Similarly, the insert may have other desirable characteristics, such as providing good beam strength and/or providing better holding power than the core material for hinge screws or for assembly screws.  
           [0004]    The fabricating process may further include the coating of the composite profile with a skin, such as a thermoplastic extrusion, which covers the outside surfaces of the profile, to give the visual impression of a single piece of homogeneous construction. The profile is visually attractive due to the coating; it is relatively inexpensive, since a substantial portion of the profile is made from inexpensive material, and it has good beam strength, good column strength, good screw holding characteristics, or other desired characteristics, because of the strategically placed insert(s). In some embodiments, the coating also serves to enhance the bond between the core and the insert(s).  
           [0005]    The manufacturing process may be designed such that the process of inserting the composite profile through the extrusion die assists in bringing the dissimilar materials together to an exact position, relative to each other, to enhance the impression of a single, homogeneous piece. In a preferred embodiment, this is accomplished by incorporating crush ribs between the core and the insert. The crush ribs literally crush or deform to provide the needed room for the insert to go into the core just the right distance to provide a flush exterior finish of the insert and the core.  
           [0006]    One or more of the materials in the profile may be hygroscopic materials, which may expel gases and vapors as they are heated during the production process. In a preferred embodiment, these profiles are coated with a hot thermoplastic extruded skin, such as a polypropylene coating, which covers the outside surfaces of the profile. Coating hygroscopic materials has been a problem in the past, with the escaping gases causing poor adhesion of the coating.  
           [0007]    By using a composite profile, a large portion of the surface area to be coated may be made of a material that is less hygroscopic and less likely to encounter problems when it is coated by a hot thermoplastic material.  
           [0008]    In addition, U.S. utility patent application Ser. No. 10/232,452, filed Aug. 30, 2002, and titled Process for Applying Coatings, which is hereby incorporated by reference, describes a continuous process for forming an envelope or coating over a core that may expel gases and vapors as it is heated during the production process. This process may be used in the present invention to treat any remaining surfaces of the profile that would benefit from such treatment. As disclosed in the patent application referenced above, heat and/or a high speed, high volume air stream is applied across the surface of the material to be coated in order to drive off the gases that would have been formed during the coating process and that would have interfered with adhesion of the coating.  
           [0009]    The air stream also cools down the substrate, so that the internal portions of the substrate will not reach high enough temperatures during the coating process to cause further expulsion of gases. A preferred embodiment of the present invention takes advantage of this method for applying coatings to manufacture a composite profile which is inexpensive and less labor intensive than composite profiles manufactured in the prior art.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a section view through a core used in a prior art process;  
         [0011]    [0011]FIG. 2 is a section view through the core of FIG. 1, with end pieces added to the core;  
         [0012]    [0012]FIG. 3 is an end view of the core and end pieces of FIG. 2 after machining;  
         [0013]    [0013]FIG. 4 is an end view of the core and end pieces of FIG. 3 after side pieces have been added;  
         [0014]    [0014]FIG. 5 is an end view of the product of FIG. 4 after it has been machined;  
         [0015]    [0015]FIG. 6 is an exploded end view of the product of FIG. 5;  
         [0016]    [0016]FIG. 7 is a sectional view of a composite profile made in accordance with the present invention;  
         [0017]    [0017]FIG. 8 is an end view of the core of the composite profile of FIG. 7;  
         [0018]    [0018]FIG. 9 is an end view of the insert of the composite profile of FIG. 7;  
         [0019]    [0019]FIG. 10 is an enlarged view of detail  10  in FIG. 8;  
         [0020]    [0020]FIG. 11 is an enlarged view of detail  11  in FIG. 7;  
         [0021]    [0021]FIG. 12 is an enlarged view of detail  12  in FIG. 7;  
         [0022]    [0022]FIG. 13 is a sectional view of a second embodiment of a composite profile made in accordance with the present invention;  
         [0023]    [0023]FIG. 14 is an enlarged view of detail  14  in FIG. 13;  
         [0024]    [0024]FIG. 15 is a sectional view of another embodiment of a composite profile made in accordance with the present invention; and  
         [0025]    [0025]FIG. 16 is a sectional view of the core of the composite profile of FIG. 15.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    [0026]FIGS. 1 through 6 depict a typical prior art manufacturing process for a composite profile  9  (shown in FIGS. 5 and 6), wherein the core  10  is likely a wooden core or some other hygroscopic material which may expel gases and vapors as it is heated during the production process. If the profile  9  will ultimately be coated with a skin coating such as a thermoplastic polypropylene extrusion, the core  10  first is wrapped with a non-hygroscopic material to avoid the problems of poor adhesion or blistering of the coating. This process of wrapping the core  10  is depicted in FIGS. 1 through 5.  
         [0027]    In FIG. 1, the core  10  is cut to the desired size. In FIG. 2, two end pieces  12  are glued onto the ends of the core  10 . This sub-assembly, including the end pieces  12  and the core  10 , is then cut or machined to size to obtain smooth top and bottom surfaces  14  and  16 , respectively, as shown in FIG. 3. Two side pieces  18  are then glued to the smooth top and bottom surfaces  14 ,  16 , as shown in FIG. 4. Finally, the assembly is machined again to the finished dimensions, obtaining the desired profile  9  as shown in FIG. 5. FIG. 6 shows an exploded view of the profile  9 . This wrapped profile  9  may then be coated with a thermoplastic material without encountering adhesion problems due to escaping vapors, since the pieces  12 ,  18  are not made of hygroscopic materials. As may be appreciated, this process is very labor intensive and very time consuming, as it requires multiple gluing steps, time waiting for the glue to dry, and multiple machining steps.  
         [0028]    [0028]FIG. 7 shows a composite profile  20  made in accordance with the present invention. The profile  20  includes a core  22 , shown in more detail in FIGS. 8 and 10, and an insert  24 , shown in more detail in FIG. 9. In this embodiment, the core  22  is made from medium density fiberboard (MDF), and the insert  24  is made from wood. Since the medium density fiberboard is easily coated with the thermoplastic material, only the exposed surface of the wooden insert will be treated by the process described in the referenced patent application prior to coating.  
         [0029]    The size and shape of the core  22  and of the insert  24  may vary as required to obtain the desired physical characteristics of the profile  20 , such as beam strength, column strength, cost, hygroscopic properties, and screw holding capabilities. Although this embodiment only shows a single insert, there may be more than one insert  24 . The material for the core  22  is likely to be a less expensive material, such as MDF, while the material for the insert  24  is more likely to be a more expensive material, such as wood. However, these material choices may be reversed if it makes sense to do so (that is, the core  22  may be wood and the insert  24  may be MDF), or other materials may be used for obtaining other desired traits of the profile  20 , such as lighter weight, for instance.  
         [0030]    [0030]FIG. 8 shows the core  22 , which, in this embodiment, is made from a piece of MDF machined to the desired finished dimensions and including a U-shaped channel  26  open to one end of the core  22 . The U-shaped channel has two legs  36 , a bottom  29 , and an open top  31 . It is understood that the core  22  has the same profile along its entire length. Two V-shaped crush ribs  28 , shown in more detail in FIG. 10, project from the bottom of the channel  26  toward the open end  31  of the core  22 . The height of the V-shaped crush ribs  28 , from the base  29  to the point of the V, usually is in the range of 0.01 to 0.05 inches.  
         [0031]    [0031]FIG. 9 is a sectional view or an end view of the insert  24  of FIG. 7 prior to its insertion into the core  22 . Again, the insert  24  has the same profile along its entire length. This insert  24  is made out of wood and is approximately rectangular in cross section except for two shoulders  30  along the sides of the insert  24 , which make the base  32  of the insert  24  slightly wider than the top  34  of the insert  24 . The dimensions of the insert are such that the base  32  fits snugly between the legs  36  of the channel  26 , and the height of the insert  24 , as measured from the base  32  to the top  34 , is slightly less than the depth of the U-shaped channel  26  from the base  29  to the open end  31  and slightly greater than the distance between the tops of the crush ribs  28  and the open top  31  of the channel  26 .  
         [0032]    [0032]FIG. 7 shows the assembly of the profile  20  with the insert  24  lodged inside the channel  26 , such that the base  32  of the insert  24  is adjacent the bottom  29  of the channel  26 , and the top  34  of the insert  24  is flush with the top  31  of the core  22 . FIG. 12 shows that the upper tip of the V-shaped crush rib  28  has been crushed by the bottom  32  of the insert  24 . The insert  24  preferably is inserted into the channel  26  by inserting the base  32  of the insert into the open top of the channel  26 , moving it toward the crush ribs  28  and crushing the crush ribs  28  sufficiently to make the upper edges  31 ,  34  flush with each other.  
         [0033]    In the preferred manufacturing process, the elongated core  20  and insert  24  are placed adjacent and parallel to each other, with the base  32  of the insert  24  directed toward the open channel  26  of the core  20 . Then, a set of guiding rollers (not shown), which aligns and directs the profile toward the entry plate of the extrusion die (for applying the skin coating), applies pressure to the bottom  21  of the core  20  and to the top  34  of the insert  24  so as to push the insert  24  into the channel  26  of the core  22  until the top  34  of the insert  24  is flush with the top edge  31  of the core  22 . In the process, the crush ribs  28  are crushed or deformed to allow the insert  24  to move into the channel  26  the desired distance until the outer surfaces of the insert  24  and of the core  22  are flush.  
         [0034]    Finally, the profile  20  passes through the extrusion die (not shown), where it is coated with a skin  38 , such as a thermoplastic polypropylene coating  38 , as shown best in FIG. 11. Since the base  32  of the insert  24  is wider than the top  34 , a gap  40  is formed between the sides of the insert  24  and the legs  36  of the core  20  down to the shoulders  30 . This gap  40  is seen in FIGS. 7 and 11. When the profile  20  is being coated, some of the coating  38  enters into the gap  40 , where it solidifies and cures.  
         [0035]    The thermoplastic polypropylene coating  38  in this embodiment has a higher bonding affinity for the MDF than for the wood. This is especially true for any surfaces of the wood which have not been pre-treated just prior to the coating process with the heat and/or air knife procedure outlined in the referenced patent application, such as the sides and the bottom of the insert  24 . The sides and bottom of the insert  24  are not treated immediately prior to coating, because these surfaces are already inside the channel  26  of the core  22 .  
         [0036]    As the coating  38  enters the gap  40  and fills the void between the insert  24  and the core  22 , it forms a plug  41 , having a strong bond with the MDF. This plug  41  traps the insert  24  by preventing the wider shoulders  30  of the insert  24  below the plug from moving outwardly to separate the insert from the core. Thereafter, in order for the insert  24  to be pulled out from the core  22 , the plug of coating  38  would have to be sheared, or it would have to separate from the MDF, with which it has a strong bond. Thus, despite potentially poor adhesion between the coating  38  and any surfaces of the insert  24  that are not pretreated with heat and/or an air knife just prior to coating, the insert  24  is secured to the core  22  with all the adhesive strength that the coating  38  has for the MDF core.  
         [0037]    [0037]FIGS. 13 and 14 show another embodiment of a composite profile  120 , including a core  122  and an insert  124 . In this embodiment, the insert  124  has a substantially rectangular cross-section, without the shoulders  30  of the previous embodiment. This has the advantage of not having to do the extra machining of these shoulders on the insert  124 . Instead, the U-shaped channel  126  of the core  122  is widened slightly at the outer ends to form the gap  140 , shown best in FIG. 14. As with the previous embodiment, there is a wider gap between the core and the insert  124  near the outer surface of the insert  124  than farther into the core  122 . The profile  120  is assembled in the same manner as the previously described profile  20 , with guide rollers pressing the insert  124  against crush ribs  128  at the bottom of the channel  126  of the core  122  and the profile  120  then entering the extrusion die for applying the coating  138 . The coating  138  again flows into the gap  140 , where it solidifies and cures to provide additional coating thickness which must be sheared in order to remove the insert  124 , and this additional thickness is adjacent the top portion of the insert  124 , which has benefited from the heat and/or air knife pretreatment to enhance the bonding characteristics of the coating  138  to the insert  124 .  
         [0038]    The profile  120  of this embodiment is less expensive to manufacture than the profile  20  of the first embodiment, because it requires less handling and machining of the insert  124 . However, the integrity of the bond between the insert  124  and the core  122  is not as good. FIGS. 15 and 16 show another embodiment that improves the bond.  
         [0039]    In FIGS. 15 and 16, the composite profile  220  includes a core  222  and inserts  224 ,  246 . To improve the bond, small amounts of glue are applied to the inside of the legs  236  of the core  222  prior to inserting the insert  224  into the channel  226 , such that, when the insert  224  is assembled into the channel  226 , the glue is smeared and spread over the contact surfaces between the core  222  and the insert  224 . Shallow pockets  242  extend lengthwise along the bottom of the channel  226  adjacent the legs  236 , and these pockets  242  are a repository for any extra glue which may have been applied.  
         [0040]    However, certain materials, such as MDF, are hydrophilic, and they will absorb moisture from the glue. As a result, they may expand unevenly, resulting in a bowing of the profile  220 . To counter this uneven expansion, glue may be applied to the opposite end of the core  222 , so that it also absorbs a similar amount of moisture and thus cancels out any residual stresses which may cause the piece to bow.  
         [0041]    However, the glue preferably should not be applied to a surface which will be extrusion coated, because the glue may then cause poor adhesion and blistering of the coating. The solution disclosed in this embodiment of the profile  222  is to machine a second channel  244  opposite the first channel  226 , and to provide a second insert  246  to go inside this second channel  244 . The purpose of this second channel  246  is to provide a surface for the application of the glue to counter the glue applied in the first channel  226 . The purpose of the second insert  246  is to cover the second channel  246  so that the glue is not exposed to the coating. The second insert  246  may be of the same material as the core  222 , such as MDF, or it may be of the same material as the first insert  224 , such as wood, or it may of a third distinct material. The second insert  246  may also be designed so that it contributes to the desired attributes of the composite profile  220 , such as improved beam strength, improved column strength, improved screw holding power, and/or lighter weight.  
         [0042]    It should be noted that, as long as the core is being machined anyway, it makes sense to make the crush ribs integral to the core. However, the crush ribs  28 ,  128 ,  228  need not be an integral part of the core  22 ,  122 ,  222 . They may instead be an integral part of the inserts  24 ,  124 ,  224 ,  246 , or they may even be separate pieces.  
         [0043]    It should also be noted that, where the composite profiles use a hygroscopic material for either the core or the insert(s), and at least one surface of said hygroscopic material is in direct contact with the extruded coating, that surface preferably should be pretreated with the heat and/or air knife process disclosed in the Process for Applying Coatings patent application prior to the coating process.  
         [0044]    While several embodiments of the present invention have been shown and described, it is not practical to describe all the possible variations and combinations that could be made within the scope of the present invention. It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the invention as claimed.