Abstract:
The plywood composed by carbon fabrics and veneers and method of manufacturing thereof are disclosed. Several layers of carbon fabrics and veneers are symmetrically placed within the plywood, where a hot-melt adhesive is used to adhere the adjacent layers. Further, a suitably high temperature and high pressure are provided at the same time to melt the hot-melt adhesive and make the carbon fabrics and veneers adhere tightly. This plywood composed by carbon fabrics and veneers has a higher toughness and thinner thickness compared with conventional plywood.

Description:
RELATED APPLICATIONS  
       [0001]     The present application is based on, and claims priority from, Taiwan Application Serial Number 94102052, filed Jan. 24, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The invention generally relates to plywood and the manufacturing method thereof, in particular, to plywood with carbon fabric and manufacturing method thereof.  
         [0004]     2. Related Art  
         [0005]     Traditionally, plywood is composed by several layers of veneers disposed in parallel and adhered together using a hot-melt adhesive (such as urea resin). This type of plywood provides the feeling close to natural wood because it is made of solid veneers. It is widely used in daily life. For example, using this kind of plywood on furniture can provide a natural wood outlook. However, the toughness of a single piece of veneer is insufficient. The number of veneers usually is increased to increase the strength of the plywood. For example, plywood may contain three to five layers of veneers. This method inevitably increases the thickness of the plywood. That is, the conventional plywood cannot achieve the advantages of small thickness and high toughness simultaneously. This fact restricts the applications of its products.  
       SUMMARY OF THE INVENTION  
       [0006]     To achieve a higher strength and smaller thickness and to maintain the feeling of natural wood, the invention provides plywood whose structure contains several layers of light and thin carbon fabrics that have better mechanical properties than veneers.  
         [0007]     An embodiment of the invention provides plywood composed by carbon fabrics and veneers. In particular, the plywood includes carbon fabric to make it lighter, thinner, and stronger than a conventional plywood. Moreover, the upper and lower outer layers of the plywood are still made of the veneer to maintain the feeling of natural wood.  
         [0008]     The embodiment of the invention provides a manufacturing method of the plywood composed by carbon fabrics and veneers. In accordance with the method, several layers of carbon fabrics and several layers of veneers are stacked inside the plywood. A hot-melt adhesive is used to adhere the layers together. The adhered layers of carbon fabrics and veneers are then disposed in a molding apparatus. Appropriate heat and pressure are imposed on the adhered layers to form the desired plywood.  
         [0009]     In a preferred embodiment, an odd number of veneer layers and an even number of carbon fabric layers are stacked in parallel into a compound stack of materials. The upper, lower, and middle layers of the compound stack of materials are veneers symmetrically placed within the plywood. Carbon fabric layers are also placed symmetrically in the compound stack of materials. Adhesive layers are applied to both surfaces of the stacked layers, which layers are then sent into a molding apparatus for imposing appropriate heat and pressure simultaneously. Afterwards, the temperature of the molding apparatus is lowered. Once the adhesive between the layers cures, the pressure is removed. The plywood composed by carbon fabrics and veneers is formed.  
         [0010]     The outlook of the disclosed plywood still maintains the features and texture alike natural wood. The carbon fabrics inside the stacked layers can increase the toughness and reduce the thickness and weight of the plywood. Therefore, the disclosed plywood is lighter, thinner, and yet stronger than the prior art. It has a wider range of applications than the conventional plywood. For example, it can be used in products for vehicles, electronics, furniture, and indoor decorations. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     These and other features, aspects and advantages of the invention will become apparent by reference to the following description and accompanying drawings which are given by way of illustration only, and thus are not limitative of the invention, and wherein:  
         [0012]      FIG. 1  is a flowchart showing how to make the disclosed plywood according to an embodiment of the invention;  
         [0013]      FIG. 2A  shows three-layer plywood made in accordance with a preferred embodiment of the invention and its cross-sectional view;  
         [0014]      FIG. 2B  shows a seven-layer plywood made in accordance with a preferred embodiment of the invention and its cross-sectional view; and  
         [0015]      FIG. 3  is a cross-sectional view of another plywood manufactured according to a preferred embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.  
         [0017]     We use preferred embodiments to disclose plywood composed by carbon fabrics and veneers and the manufacturing method thereof. Any person skilled in the art can readily understand and implement the invention from the following description.  
         [0018]     A flowchart of manufacturing the plywood is given in  FIG. 1 . In step  101 , an odd number of veneer layers and an even number of carbon fabric layers are disposed in parallel to form a compound stack of materials. In particular, the upper, lower, and middle layers are the veneer layers placed symmetrically. Likewise, the carbon fabrics are placed symmetrically in the plywood. In step  103 , an adhesive is applied on both surfaces of each stacking layer. In step  105 , the compound stack of materials is sent into a molding apparatus, where appropriate heat and pressure are imposed simultaneously so that the adhered layers do not fall apart. In step  107 , the temperature of the molding apparatus is lowered. After the adhesive between the layers is cured, the pressure is removed. The plywood composed by carbon fabrics and veneers is formed.  
         [0000]     Structure of Plywood with Carbon Fabrics  
         [0019]      FIG. 2A  is an exploded view of the three-layer plywood  201  made in accordance with a preferred embodiment of the invention.  FIG. 2B  is a cross-sectional view of the three-layer plywood  201 . The outer layers of the three-layer plywood  201  are an upper veneer  203   a  and a lower veneer  203   b . A carbon fabric  205  is between the upper veneer  203   a  and the lower veneer  203   b . In particular, the textures of the upper veneer  203   a  and the lower veneer  203   b  are horizontal for one and vertical for the other. For example, if the upper veneer  203   a  has a horizontal texture, then the lower veneer  203   b  has to have a vertical texture. One advantage of this configuration is that they have complimentary effect to avoid cracks occurred in one particular direction. Moreover, an adhesive  207  is used to combine the three-layer plywood  201 . In particular, the adhesive  207  preferably may be a hot-melt adhesive, such as urea resin.  
         [0020]     The number of layers in the disclosed plywood may be any odd number such as five and seven or more.  FIG. 3  shows the cross-sectional view of another plywood  309  whose number of layers is seven. In this structure, the upper, lower and middle layers are an upper veneer  303   a , a lower veneer  303   b , and a middle veneer  303   c . The other four layers  311   a ,  311   b ,  313   a , and  311   b  may be veneers and/or carbon fabrics. It should be noted that these four layers have to be carbon fabrics and/or veneers placed symmetrically with respect to the middle veneer layer  303   c . For example, if the layer  311   a  is a carbon fabric, then the layer  311   b  has to be a carbon fabric too. If the layer  313   a  is a veneer, then the layer  313   b  has to be a veneer too. Moreover, the veneers are disposed in such a way that their textures have to be perpendicular to each other to produce a complimentary effect. That is, if the layer  313   a  is a veneer and the layer  311   a  is a carbon fabric, then the textures of the upper veneer  303   a , the layer  313   a  and the middle veneer  303   c  have to be vertical-horizontal-vertical or horizontal-vertical-horizontal. Besides, the number of carbon fabrics in the plywood  309  can vary according to different requires of the final product. For example, the plywood  309  may contain two or four layers of carbon fabrics. Moreover, the plywood  309  uses an adhesive  307  to combine the layers. In particular, the adhesive  307  preferably may be a hot-melt adhesive, such as the urea resin.  
         [0021]     It should be mentioned that the disclosed plywood uses carbon fabrics in place of conventional veneers as the inner layers. Since the thickness of a single piece of carbon fabric (about 0.5 mm) is smaller than that of a single piece of veneer (about 1˜1.5 mm), the thickness of the disclosed products can be significantly reduced.  
         [0022]     Another advantage of the disclosed plywood is that its toughness is far better than the conventional veneer plywood of the same thickness. In the case of same layers, the disclosed plywood is stronger than the conventional veneer plywood at least by a factor of three.  
         [0023]     It is thus seen that the disclosed plywood with carbon fabrics is thinner, lighter, and yet stronger than the conventional plywood.  
         [0000]     Manufacturing Method of the Plywood with Carbon Fabrics  
         [0024]     In a preferred embodiment, an odd number of veneer layers and an even number of carbon fabric layers are disposed in parallel according to the above-mentioned method to form a compound stack of materials (see  FIGS. 2B and 3 ). In particular, the number of layers in the compound stack of materials has to be odd. The inner layers are symmetric in structure. An adhesive coating machine is used to apply an adhesive on both surfaces of the layers for adhering adjacent layers together. The adhesive preferably may be a hot-melt adhesive, such as urea resin. Using a hot-melt adhesive has the advantages of fast curing, stable properties, and suitable for combining many different materials. Therefore, the adhesive can provide the required adhesive ability at the veneer/veneer, veneer/carbon fabric, and carbon fabric/carbon fabric junctions. The compound stack of materials is sent into a molding apparatus where appropriate heat and pressure are imposed. If a steel mold is used to impose a pressure, the thickness of the pressure-imposing material is about 12 mm and the heating temperature is between 90° C. and 110° C. The imposed pressure is between 95 lb. and 105 lb. The molding time is between 10 min. and 15 min. The temperature is lowered for the adhesive between the layers to cure, after which the pressure is then removed. The plywood has the upper and lower layers of veneers and carbon fabrics disposed in between.  
         [0025]     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.  
         [0026]     While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.