Abstract:
A composite panel includes fibres adhered together by means of an adhesive binder to form a sheet having opposed planar faces and fibre reinforcement ribs imbedded in the sheet.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a composite panel and a method of making the same. 
     BACKGROUND OF THE INVENTION 
     While composite panels are typically made out of wood fibre, they can be made out of other materials such as straw. Composite panels made out of wood fibre are known by a variety of names, including: oriented strandboard, wafer board, and chip board. In the past, structural reinforcement of these composite panels has been achieved by selection of the shape of the panel. For example, some success has been obtained through the use of a sinusoidal form, commonly known as “wave board”. U.S. Pat. No. 3,083,128 and U.S. Pat. No. 4,904,517 disclose structural reinforcement through a plurality of external reinforcing ribs. 
     Unfortunately, the same features of shape or configuration that provide composite panels with their structural reinforcement, have inherent disadvantages that have retarded their commercial acceptance. The panels are difficult to manufacture, as special press platens are required to create the special shapes. The special press platens are difficult to adapt to high speed, high volume production runs. Consequently, the composite panels have tended to be expensive. In use, the special shapes make the composite panels difficult to consistently cut to a desired size and, generally, make them more difficult to work with. 
     SUMMARY OF THE INVENTION 
     What is required is a structurally reinforced composite panel that derives its structural reinforcement from other than its shape. 
     According to one aspect of the present invention there is provided a composite panel which includes fibres adhered together by means of an adhesive binder to form a sheet having opposed planar faces. Fibre reinforcement ribs are imbedded in the sheet. 
     The composite panel constructed in accordance with the teachings of the present invention has planar faces. This enables it to be manufactured with only minor changes to the forming lines of existing plants. The resulting composite panels can be used for virtually any application. The structural reinforcement is embedded in the wood panel in the form of reinforcement ribs. The reinforcement ribs can take a number of forms. For example, the reinforcement ribs can be parallel and spaced at intervals along the sheet or can be serpentine. 
     According to another aspect of the present invention there is provided a method of making a composite panel. A first step involves laying a continuous layer of fibres mixed with an adhesive binder. A second step involves laying onto the layer of fibres, reinforcement ribs of fibres mixed with an adhesive binder. A third step involves pressing the layer of fibres and the reinforcement ribs together to form a panel with planar opposed faces and reinforcement ribs imbedded in the panel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein: 
     FIG. 1 is side elevation view of a conveyor along which the steps in the preferred method of making a composite panel occur. 
     FIG. 2 is a top plan view of the conveyor illustrated in FIG. 1, with parallel spaced reinforcement ribs being formed. 
     FIG. 3 is a side elevation view of a mechanism for forming the parallel spaced reinforcement ribs illustrated in FIG.  2 . 
     FIG. 4 is a side elevation view, in section, of a composite panel fabricated in accordance with the preferred method. 
     FIG. 5 is a top plan view of a mechanism for forming serpentine reinforcement ribs illustrated in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment, a composite panel generally identified by reference numeral  10 , and the method of making the same will now be described with reference to FIGS. 1 through 5. 
     Referring to FIG. 1, the preferred method of making a composite panel includes the following steps. A first step involves laying a first layer  12  of fibres, such as wood particles or straw, mixed with an adhesive binder. In the illustrated embodiment first layer  12  is placed onto a moving conveyor  14  by means of one or more formers  16 . The conveyer is moving in the direction indicated by the arrow  18 . A second step involves laying onto first layer  12  reinforcement ribs  20  of fibres mixed with an adhesive binder. This is accomplished by means of one or more rib formers  22 . Referring to FIG. 2, the reinforcement ribs  20  may be parallel and linear in shape and may be either collinear or transverse with respect to the length of the panel. The structural strength properties of the panel will be determined by the reinforcement rib placement pattern, spacing and density. Referring to FIG. 5, the reinforcement ribs may alternatively be made serpentine  30 . More complex patterns may be achieved by means of a microprocessor controlled forming mechanism that can traverse the production line perpendicular and parallel to the line direction. It will be obvious to one skilled in the art that the selection of the shape and spacing of the ribs will be made based on the requirements imposed by the intended use of the panel. Referring to FIG. 3, parallel linear reinforcement ribs  16  can be formed using, for example, a paddle wheel  32 . Fibres  34  are fed to paddle wheel  32  by, for example, a second conveyer  36 . The spacing of the reinforcement ribs is determined by the speed of rotation of paddle wheel  32  relative to the speed of conveyer  14 . The dimensions of the reinforcement ribs  20  are determined by the speed of second conveyer belt  36  relative to the speed of rotation of paddle wheel  32 . It is possible to form a usable panel using just first layer  12  and reinforcement ribs  20 . It is preferred, however, that a third step be taken of laying onto first layer  12 , a second layer  24  of fibres mixed with an adhesive binder by means of one or more formers  26 . A fourth step involves using a press  28  to press first layer  12  and second layer  24 . 
     Referring to FIG. 4, a composite panel fabricated in accordance with the teachings of the above described method, is generally identified by reference numeral  40 . Panel  40  has planar opposed faces  42  and  44 . Imbedded within panel  40  are reinforcement ribs  20 . 
     In initial tests, it was determined that adding reinforcement ribs  20  increased machine stiffness ratings in both perpendicular and parallel directions. At the present time fines are screened out of the material produced, as the panels are being produced by solid long strands. These fines, representing as much as 30% of material, are viewed as waste material and are disposed of. Where four or more layers are utilized, it is anticipated that all interior layers positioned between the ribs can be made from these waste materials. In contrast, surface layers and reinforcement ribs  20  will be made from higher quality materials with longer strand lengths. Long strand materials are preferred for all surface areas to provide more lengthwise strength to supplement the lateral strength provided by the reinforcement ribs. Reinforcement ribs  20  can be placed in any layer and in any orientation. It is anticipated that the spacing and density of the reinforcement ribs  20  can be selected to suit strength requirements. Similarly, it is anticipated that reinforcement ribs  20  can be placed in the direction of the desired strength increase. This enables the panels to be engineered to suit specific applications. 
     It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims.