Abstract:
Bamboo building material and process of manufacture therefor. The material includes a plurality of layers each formed of bamboo segments which have been dried and glue coated. The segments are substantially free of outer nodes and husk and inner membrane material prior to application of glue. The longitudinal axes of the segments in each layer are generally parallel to one another, each layer having segments oriented generally orthogonally with respect to the next adjacent layers thereto. The layers of segments being compressed and bonded together until the glue cures into a single integral structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 11/494,113 filed Jul. 27, 2006. 
     
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    This invention relates generally to structural wood substitutes, and more particularly to a bamboo beam and process for making same from stranded bamboo segments stripped of all epidermis material and formed into multiple cross oriented layers and bonded under high pressure and temperature into a solid bamboo beam product. 
         [0006]    2. Description of Related Art 
         [0007]    Because we have, as a world community, substantially depleted the original tree growth in our forests with which we were blessed, manufacturers of wood products utilized in the construction industry have had to resort to next-generation tree growth which, in many cases, produces substantially less wood product as they are necessarily cut down well short of full maturity in size. 
         [0008]    Composite lumber formed of wood products such as oriented strand board (OSB) as is described in the SBA Structural Board Association U.S. Edition 2005 Manual, has become a popular substitute for solid wood products. By utilizing substantially all of the wood growth of next-generation forests as facilitated by the OSB process, a very substantial composite wood-based product rivaling the strength of solid wood beams is achievable. 
         [0009]    Because of its strength and rapid re-growth cycle, another alternative is to turn to bamboo composite products utilized to form composite wood replacement or alternative beam, plywood and structural products. One particularly interesting bamboo wood replacement product is disclosed in Plaehn, in U.S. Pat. No. 5,543,197. This disclosure teaches a composite bamboo beam which includes segments of bamboo stalk, either split or whole, which are longitudinally aligned and randomly stacked and then compressed and bonded together to form a cohesive bamboo composite structure from which beams of a desired dimension may be cut. Strength consistency is lacking in this bamboo product, however. 
         [0010]    The present invention also utilizes bamboo segments in a unique way to develop an even stronger bamboo beam structure for use in the building industry. The process of compressing and final beam formation is taught by Trautner in U.S. Pat. No. 3,723,230, the teaching of which is incorporated herein by reference. Trautner teaches a continuous press for pressing glue-coated consolidatable press charges into structural composite wood structural components. 
         [0011]    The significant aspect of the present invention is the recognition that bamboo segments may only be securely glued into a cohesive bamboo composite structure after the outer epidermis surface material and nodes have been machined, abraded or otherwise stripped therefrom. Current glue technology is somewhat inadequate in its binding effect with a bamboo surface which still retains any portion of the epidermis husk or inner membrane material prior to the drying and bonding of the bamboo segments as will be more described more completely herebelow. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    This invention is directed to a bamboo building material and process of manufacture therefor. The material includes a plurality of layers each formed of bamboo segments which have been dried and glue coated. The segments are substantially free of outer nodes and husk and inner membrane material prior to application of glue. The longitudinal axes of the segments in each layer are generally parallel to one another, each layer having segments which may be generally parallel or oriented generally orthogonally with respect to the next adjacent layers thereto. The layers of segments being compressed and bonded together until the glue cures into a single integral structure and with improved physical properties. 
         [0013]    It is therefore an object of this invention to provide a composite bamboo structure and beams for use in the building industry as a substitute for solid wood or composite wood products. 
         [0014]    It is another object of this invention to provide a composite bamboo beam structure having higher strength ratios than those previously attained. 
         [0015]    Still another object of this invention is to provide a multi-layer composite bamboo beam incorporating existing OSB manufacturing technology to produce superior bamboo beam products. 
         [0016]    And another object of this invention is to provide composite beam products formed of bamboo segments in multi-layer arrays which clearly exhibits superior glue-to-bamboo segment adhesion by the prior removal of substantially all epidermis materials from the bamboo segments. 
         [0017]    In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with reference to the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0018]      FIG. 1  is a perspective view a portion of the main stalk or culm of bamboo. 
           [0019]      FIG. 2  depicts the longitudinal segmenting of each bamboo stalk. 
           [0020]      FIG. 3  depicts each of the longitudinally segmented portions of the stalk of  FIG. 2 . 
           [0021]      FIG. 4  depicts the step of removing nodes and epidermis material from both inner and outer surfaces, flattening and dewatering of each stalk segment of  FIG. 3  into slats. 
           [0022]      FIG. 5  is a simplified perspective view of one method of stranding process of each of the bamboo slats from  FIG. 4  into bamboo segments. 
           [0023]      FIG. 6  is a perspective view of the bamboo segments being initially treated for insect and parasite removal. 
           [0024]      FIG. 7  is a perspective view of the bamboo segment drying process. 
           [0025]      FIG. 8  is a perspective view of the blending and coating of the dried bamboo segments with a suitable adhesive. 
           [0026]      FIG. 9  shows the orienting and layering of bamboo segments into a composite multi-layer bamboo mat ready for final compressing and bonding into a bamboo structure. 
           [0027]      FIG. 10  is a perspective view of the final step of transforming the bamboo multi-layer mat of  FIG. 9  into the bamboo structure. 
           [0028]      FIG. 11  is a perspective view showing the cutting of the finished bamboo structure into desired sizes. 
           [0029]      FIG. 12  is a perspective view of a preferred process of splitting a length of bamboo stalk into halves. 
           [0030]      FIG. 13  is a perspective view depicting the flattening, dewatering and partial segmenting of each bamboo stalk half produced in  FIG. 12 . 
           [0031]      FIG. 14  depicts the preferred process of stranding each of the bamboo slats produced in  FIG. 13 . 
           [0032]      FIG. 15  is a pictorial view depicting the layering of the bamboo segments into a rigid support frame in preparation for final compressing and bonding of the segments into a bamboo structure. 
           [0033]      FIG. 16  is an end view of a bamboo structure made in accordance with the present invention (with defect) in comparison to a conventional southern pine timber. 
           [0034]      FIG. 17  shows top plan views of the bamboo and conventional timber of  FIG. 16 . 
           [0035]      FIG. 18  is an enlarged end perspective view of the bamboo structure of  FIG. 16  after nailing plate penetration thereinto. 
           [0036]      FIG. 19  is an enlarged end view of  FIG. 18 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    Referring now to the drawings, and particularly to  FIGS. 1 to 4 , a portion of a bamboo stalk is shown at numeral  10  in  FIG. 1  cut into segments at  12  for further processing. In  FIG. 2 , each of the bamboo stalks  10  are shown longitudinally segmented by radial inward cuts at  18  to form bamboo slats  14  and  16  as seen in  FIG. 3 . These longitudinal bamboo slats  14  and  16  have exterior epidermis material on the exterior and interior surfaces  20  and  22 , respectively, including nodes on the inner surface  22  which must be removed in accordance with the present invention for achieving consistent superior bond adhesion for strength as described herebelow. 
         [0038]    In  FIG. 4 , each of the bamboo slats  14  are fed through a pair of abrasion or machining wheels A and C, each of which have radially extending machining tips B and D which rotate in the direction of the arrows to remove all of the green epidermis material from the outer and inner surfaces  20  and  22 , including the nodes. The first modified bamboo slats  14 ′, now having stripped outer and inner surfaces  24  and  26  then move on a continuous basis through rollers E and F which compress and flatten and dewater the bamboo slats at  14 ″ ready for further processing. This equipment, commercially called a veneer slicer, is available from Marunaka and Industrial Machinery Sales of Medford, Oreg. 
         [0039]    With a substantial portion of the moisture having been extracted as shown in  FIG. 4 , the twice-modified bamboo slats  14 ″ are loaded as shown in  FIG. 5  into a stranding machine  40  which includes a stranding drum  44  with blades  42  inwardly disposed and which rotates in the direction of arrow G. The stranded bamboo segments shown generally at  50  preferably having a size range of about 0.015″-0.030″ in thickness, 1″-2″ in width, and 6″-12″ (or longer) in length discharge from the stranding apparatus  40  and are ready for an initial chemical processing as seen in  FIG. 6 . The bamboo segments  50  are fed by conveyor  62  of apparatus  60  onto a sorting conveyor  64  and chemically treated within the interior chamber  66  to remove all insects and parasites for discharge at  68  in the direction of arrow H, the treated segments being shown generally at  50   a . Note that apparatus  60  may accomplish this step by boiling, steam or chemicals. 
         [0040]    In  FIG. 7 , a continuous drying apparatus  70  receives the bamboo segments  50   a  into inlet chute  72 , heated air being forced into the drying apparatus  70  through inlet  74 . Both heated air and bamboo segments  50   a  mix and tumble within the chamber  76  to effect complete moisture drying of the bamboo segments for discharge at  78  in the form of dried bamboo segments  50   b.    
         [0041]    In  FIG. 8 , a glue-applying apparatus  80  receives the dried bamboo segments  50   b  into chute  82 . The inner chamber  84  tumbles the bamboo segments  50   b  while a layer or coating of suitable glue is applied over substantially all of the exterior surfaces of the bamboo segments  50   b . These glue-coated bamboo segments  50   c  are discharged downwardly in the direction of the arrow from discharge chute  86 . The preferred glue coating is available from Black brothers in North Carolina. 
         [0042]    In  FIG. 9 , the bamboo segments  50   c  are dispensed by gravity in the direction of arrows J and K into two different portions of a mat-forming apparatus  90 . The mat, shown generally at numeral  110 , includes multiple layers  100 ,  102 ,  104  and  106  of bamboo segments  50   c  which are cross or orthogonally oriented one to another for added strength in the final product. Rollers  96  and  98  orient the bamboo segments  50   c  in a transverse orientation while those bamboo segments  50   c  being dispensed by gravity through chamber  92  onto longitudinally aligned rollers  94  align the bamboo segments  50   c  in the longitudinal direction of the mat  110 . Each of the layers  100 ,  102 ,  104  and  106  generally have a thickness in the range of about 0.03″-0.06″. This equipment, called a Layup Forming Lines machine is available from Dieffenbacher GmbH &amp; Co. KG of Germany. 
         [0043]    The assembled mat  110  is then fed into a compressing apparatus  120  similar to that described in U.S. Pat. No. 3,723,230 previously incorporated by reference. This compression apparatus  12  applies high pressure in the range of about 200 p.s.i. and optionally heat, depending on the particular adhesive coating utilized, to fully cure the adhesive and convert the mat  110  into a structurally finished product  110   a  which, in  FIG. 11 , is then fed into gang saw cutting wheels  122  for proper sizing prior to shipment. Note that the inclusion of heat facilitates the use of a lesser expensive adhesive to achieve a desired consistent superior strength level. 
         [0044]    By this process, a very homogeneous bamboo structural product or beam is produced, which has exhibited substantially higher strength ratios than previously achieved by other composite bamboo wood substitute products for the construction industry. A key aspect of this invention and enhanced strength consistency is achieved through the removal of all of the epidermis material from the bamboo stalk segments prior to further processing as above described. 
         [0045]    Referring now to  FIG. 12 , an alternate and preferred process for splitting a bamboo stalk  100  into half stalks  106  and  108  is there shown wherein a tapered splitter M is forced lengthwise along the entire stalk  100  as shown. The splitter M is wedge-shaped to facilitate the rapid splitting of the bamboo stalk  100 . Each of the halves  106  (and  108  not shown) in  FIG. 13  is fed through a series of rollers N in the direction of the arrow to produce a flattened slat  106   a . The rollers accomplish the flattening, crosswise partial segmenting and dewatering of each of these bamboo halves in one continuous process. Then, in  FIG. 14 , strander P is forced lengthwise and across the width of each of the slats  106   a  in the direction of the arrow. The first strand removed also removes the exterior epidermis material, including nodes at  102   a . Epidermis on the inner surface may be removed by machining or simply discarded with the last inner layer produced in  FIG. 14 . Note importantly that the flattening process of  FIG. 13  has produced longitudinal breaks at  110  but not full separations therebetween. Thus, the natural fibers hold the slat  106   a  together until the stranding process shown in  FIG. 14  is completed. At that time, the individual strands  112  are produced and ready for further processing and shortening into segments which shown in  FIG. 15  at  12   a , each having a thickness of about 1/16″, a width of about ½″ and a cut length of approximately 6″ to 12″ randomly occurring. Note further that the stranding process of  FIG. 14  splits each segment  112  along natural fiber boundaries, rather than by machine or saw cutting, to avoid robbing material bamboo fiber strength from each segment. 
         [0046]    After the stranding process shown in  FIG. 14 , the segments  112  are then further processed such as that shown in  FIG. 6  as previously described treating the segments  112  for insect and parasite removal. Thereafter, in a process similar to that described in  FIG. 7 , the bamboo segments  112  are dried down to a moisture content of approximately 2% to 4% and then saturation loaded with resin preferably by soaking preferably in the form of phenol-formaldehyde available from Georgia Pacific Company typically used in PARALAM beams for about two hours. A second drying process of the resin-saturated strands is then accomplished to reduce the moisture content down to approximately 8% to 10%. After the consolidation of the resin-saturated and dried strands  112   a  into the frame Q shown in  FIG. 15 , the prepared strands  112   a  are compacted at a pressure of approximately 700 to 1000 psi at an elevated temperature of approximately 180° C. for approximately 60 minutes within the frame Q. 
       Experimental Results 
       [0047]    Test samples were prepared in accordance with the above preferred procedure by Forest Products Laboratories in Madison, Wis. The strands were soaked in pheno-formaldehyde resin for approximately 2 hours in a dilute resin bath. Pre-resin drying, and post-resin soak drying were accomplished as above described. Thereafter, the modulus of elasticity (pounds/in 2 ) (MOE) was experimentally determined and compared to the MOE of Loblolly Pine and Pine Parallel Strandboard, the results of which are shown in Table I below. 
         [0000]                                      TABLE I                   Modulus of Elasticity                Sample Type   MOE (lbs/in 2 )   Density lb/ft 3  (PCF)                       Southern Pine   1.5 million   39           Glu-Lam   1.8 million   37           Paral-Lam   2.0 million   41           Bamboo-Lam   3.4 million   68                        
Note from Table I above that the bamboo specimen prepared in accordance with the teachings of the present invention had a MOE of approximately twice that of the Loblolly pine sample and approximately 50% greater MOE than that of the well-known commercially available STRANDBOARD manufactured by Weyerhaeuser Corporation.
 
       Plate Pressing Embedment Pressure Test 
       [0048]    Referring to  FIG. 16 to 19 , this test, conducted by MITEK® from samples of the invention made by Forest Products Lab in Madison, Wis., involved pressing MT20 connectors into two bamboo test samples of material  114   a  and  114   b , that measured 12⅝″×3½′″×1¼″. The samples resemble LSL type material with the following differences: The texture of wide face was different, one side is rough and the grain could be felt as seen in  FIG. 17 . Fibers of the material, and the opposite face was smooth. The density of the material changed across the width of the member as seen in  FIG. 16 . One edge  116   a  and  116   b  is very dense, and showed no voids or gaps when looking at the end. The opposite edge  118   a  and  118   b  had voids and gaps that existed between the segments of the material, reflective of a sample manufacturing defect. 
         [0049]    The MT20 1″×3″ connector plates U 1  and U 2  one at a time, were pressed into the wide face of the sample, adjacent to the edge of member  114   a  near one end as seen in  FIGS. 18 and 19 . One plate U 2  was pressed into the of the less dense edge  118   a  (the section with the most voids and gaps), and the other plate U 1  was pressed into the more dense edge  116   a . The force required to press the plates into the samples was measured. 
         [0000]    
       
         
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
           
               
                   
                 TABLE II 
               
               
                   
                   
               
               
                   
                 Test Sample 
                 Max Pressure (psi) to Embed 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Plate Pressing Embedment Pressure 
               
             
          
           
               
                   
                 Bamboo beam - denser edge 
                 2966 
               
               
                   
                 Bamboo beam - less dense edge 
                 915 
               
             
          
           
               
                 For Comparison 
               
             
          
           
               
                   
                 SPF 
                 856 
               
               
                   
                 SYP 
                 1327 
               
               
                   
                 TIMBERSTRAND 
                 1549 
               
               
                   
                   
               
             
          
         
       
     
         [0050]    Although the bamboo test specimen appeared to incorporate a defect as above described along one edge of the test sample, nonetheless meaningful results may be drawn with respect to the plate pressed into the properly formed denser edge of the bamboo test specimen when compared to the same test performed on other conventional structural timber, namely SPF (spruce-pine-fir), SYP (spruce-yellow-pine) and TIMBERSTRAND. The data with respect to these conventional wooden structural members was taken from a test by MiTEK® owned by Berkshire &amp; Hathaway, Inc. 
         [0051]    This plate pressing embedment test clearly shows that the bamboo beam, when properly formed as along its denser edge in the test, is substantially denser than that of conventional wooden beams as reflected in nearly twice the pressure required for plate penetration when compared to TIMBERSTRAND, the otherwise highest reported timber test information available. 
         [0052]    While the instant invention has been shown and described herein in what are conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be afforded the full scope of the claims so as to embrace any and all equivalent apparatus and articles.