Patent Publication Number: US-2021162623-A1

Title: Apparatus and method for heat treating wood

Description:
RELATED APPLICATION 
     This application claims the benefit of Provisional Application Ser. No. 62/942,845, filed Dec. 3, 2019, which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This disclosure relates generally to an apparatus and method for heating treating wood. 
     BACKGROUND 
     The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art. 
     A traditional Japanese process for treating wood comprises intensely burning and brushing the wood as a preservative heat treatment. It may be known as Shou Sugi Ban or Yakisugi. It is commonly applied to cypress. The heat treatment is alleged to improve siding longevity by preventing decay and insect infestation, to make wood planks more dimensionally stable, and to improve fire retardancy. 
     Such treatment many also create grain patterns in the wood, that are considered attractive. The process may only require heat treatment and brushing, so there are no potential allergens added, which may be desirable for some commercial and office applications. 
     Traditionally, the Shou Sugi Ban process was done over an open fire, banding three boards together into a triangular chimney, and standing it over the fire. The fire would burn up the inside of the boards, then be knocked apart. Then any fire on the boards would be extinguished and the boards brushed. More recent techniques have been developed, but these are largely unsuitable for production quantities, 
     INTRODUCTION 
     The following paragraphs are intended to introduce the reader to the more detailed description that follows and not to define or limit the claimed subject matter. This summary is intended to introduce the reader to the more detailed description that follows and not to limit or define any claimed or as yet unclaimed invention. One or more inventions may reside in any combination or sub-combination of the elements or process steps disclosed in any part of this document including its claims and figures. 
    
    
     
       DESCRIPTION OF THE DRAWING FIGURES 
       For better understanding of the present invention and to show more clearly how it may be carried out in effect, reference will now be made, by way of example, to the drawings which show an example of an apparatus of the present disclosure and in which: 
         FIG. 1  is a perspective view of the discharge end of an apparatus of the present disclosure; 
         FIG. 2  is a perspective view of part of the apparatus of the present disclosure, showing boards being treated; 
         FIG. 3  is perspective enlarged view of part of the apparatus of the present disclosure, showing details of the radiant heaters and burners; 
         FIG. 4  is an enlarged view along the length of the apparatus of the present disclosure; 
         FIG. 5  is a side view of one end of the apparatus of the present disclosure; 
         FIG. 6  is perspective view of the radiant heaters and burners of the apparatus of the present disclosure; 
         FIG. 7  is an end view of the apparatus of the present disclosure; 
         FIG. 8  is a side view of the apparatus of the present disclosure, showing brushes; and 
         FIG. 9  is a side view of the other end of the apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Various apparatuses or methods will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover apparatuses and methods that differ from those described below. The claimed inventions are not limited to apparatuses and methods having all of the features of any one apparatus or method described below, or to features common to multiple or all of the apparatuses or methods described below. It is possible that an apparatus or method described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or method described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicant(s), inventor(s) and/or owner(s) do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document. 
     For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements or steps. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments generally described herein. Furthermore, this description is not to be considered as limiting the scope of the embodiments described herein in any way, but rather as merely describing the implementation of various embodiments as described. 
     The apparatus of the present disclosure has a main frame  10 , which has longitudinal frame members  12 . Supporting legs  14  support the longitudinal frame members  12 , and diagonal bracing members  16  connect to the supporting legs  14  to the frame members  12 . The longitudinal frame members  12  may be I section members, and both the supporting legs  14  and bracing members  16  may be square section channels, welded to the longitudinal frame members  12 . 
     Cross or tie members  18  extending between and beneath the longitudinal frame members  12 . The tie members  18  may also be square section channels, welded to the frame members  12 . Optionally, to enable ready movement of the apparatus, wheels  20 , which include, but are not limited to, caster wheels, are mounted on the supporting legs  14 . 
     Upper L section channel members  30  are mounted on the longitudinal frame members  12 , with horizontal flanges  36  extending inwardly towards one another. Lower L channel members  32  are secured, e.g. by welding, to the supporting legs  14 , below the longitudinal frame members  12 . Additionally, vertical support members  38  may be provided to support these lower L channel members  32 . As for the upper channel members  30 , the lower channel members  32  have horizontal flanges  36  extending inwardly and towards one another. At a discharge end, as shown in  FIG. 1 , the lower channel members  32  include flange extensions that curve downwardly, which may be formed by cutting away the vertical leg of the L section channels. 
     A steel chain conveyor belt  50  is provided for supporting and transporting wood boards  95 . The conveyor belt  50  may be formed from any suitable material and in any suitable manner that is capable of supporting the wood boards or planks  95 . The conveyor belt provides a generally planar surface that supports and conveys the wood boards or planks  95 . It may not require any elements to engage the wood boards or planks  95 . Where a particularly vigorous brushing action is provided, the belt  50  may include projecting elements to engage wood boards or planks  95  to prevent them slipping on the conveyor  50 . It will be understood that, in use, the conveyor generally not be completely covered by wood boards or planks  95 , so that parts of the conveyor will be subject to the full radiant heat from a burner assembly  90  detailed below. Thus, the conveyor  50  will be formed from steel or other material capable of withstanding the heat from the burner assembly  90 . 
     Along the length of the apparatus, the L channel members  30  serve to support the steel chain conveyor belt  50  in a first direction, and the L channel members  32  serve to support the steel chain conveyor belt  50  in a second, return direction. At a discharge end of the apparatus, there is a drive shaft  52  on, mounted in a pair of bearings, which in turn are mounted on the ends of the longitudinal frame members  12 . On the drive shaft  52 , between the bearings  54 , there are 3 toothed sprocket wheels  56  (not shown in detail), with two sprocket wheels mounted to engage outer edges of the conveyor belt  50 , and a third sprocket mounted to engage the centre line of the conveyor belt  50 . The drive shaft  52  and sprocket wheels may be in the form of a cylinder with teeth providing the sprocket drive. 
     As shown in  FIG. 7 , the drive shaft  52  extends outside the bearings  54 . On one side, an electric drive motor  58  is connected through a transmission  60  to the drive shaft  52 . In known manner, the transmission  60  can provide required reduction gearing, which may be a worm drive. 
     On the other end of the drive shaft  52 , on the discharge end of the apparatus, there is mounted a drive sprocket  62 , for driving brushes, as shown in  FIG. 5 . 
     As shown in  FIG. 9 , at the other end of the main frame  10 , there is an end, idler shaft or cylinder  170  provided with sprockets or teeth  172  and mounted in bearings  174 . 
     Above the longitudinal frame members  12 , there are a number of additional frame elements. Two inverted U frames  70  and  72  have side legs, which may be square section channels, welded or otherwise secured to the longitudinal frame members  12 . The U frames  70  and  72  have top members, which may be inverted U section channels, connected to the side legs and providing respective threaded mounts  74  and  76  for respective screw mounting shafts  78  and  80 . 
     As best shown in  FIG. 3 , an infrared radiant heater or burner assembly generally indicated at  90 , includes a longitudinal tube  92 , connected to individual infrared radiant heaters or burners  94  by a short connecting tubes. At one end, and igniter  96  is provided. At the other end, a control unit  98  is provided connected to a gas supply line  100 , for supplying combustible gas to the infrared radiant heaters or burners  94 . While gas fired infrared radiant heaters are shown, it will be understood that any suitable heater could be used, for example electric radiant heaters. 
     The screw shafts  78 ,  80 , at their lower ends are mounted for rotation in flanges secured to the longitudinal tube  92 . For example and as shown, knots can be secured to the shafts  78 ,  80  both above and below each of the flanges, so that the screw shafts simply rotate within apertures in the flanges. As shown, handles,  82 ,  84  are provided at the upper end of the screw shafts  78 ,  80 , for rotating the shafts stop rotation of the shaft  78 ,  80 , in their screw mounts  74 ,  76  can be used to raise and lower the infrared radiant heater or burner assembly  90  as required. 
     To provide additional guidance or alignment to the radiant heater or burner assembly  90 , brackets  102  can be provided. 
     To further inverted frames  110 ,  112 , which are generally similar, are also mounted to the longitudinal frame members  12 . Each inverted frame  110 ,  112  comprises an inverted U-shape channel  114 , and a pair of legs  116  on one side and a pair of legs  118  on the other side. As shown in  FIG. 5 , the inverted U-shaped channels  114  one inverted frame  110  may extend out beyond the side of the frame  12 , on one side. 
     First and second cylindrical brushes  120 ,  122  are mounted on the shaft, with the shafts mounted in pairs of respective bearings  124 , 126 . On one side, for each of the cylindrical brushes  120 ,  122 , a mounting shaft  142 ,  144 , extends through the respective bearing  124 ,  126 , for mounting of a respective drive sprocket  128 ,  130 . An idler sprocket  132  is mounted to a support bracket  134 . A further idler and tension sprocket  136  is rotatably mounted on the end of an arm  138  that is pivotally mounted to a flange attached to one of the bracing members  16 . The tension spring  140  is connected between the arm  138  and the bracing member  16 . 
     A drive chain  150  engages all of the sprockets  62 ,  128 ,  130 ,  132  and  136 . The tension and idler sprocket  136  ensures that the chain is maintained in tension. The idler sprocket  132  ensures that the chain  150  fully engages both of the drive sprockets  128 ,  130 . As detailed below, the bearings  124  and  126  are mounted for vertical sliding movement in the side legs  116 ,  118 , to permit vertical adjustment of the position of the cylindrical brushes  120 ,  122 . The provision of the idler and tension sprocket  136 , and its range of motion ensures that a suitable tension can be maintained in the chain  150 , irrespective of the vertical position of the brushes  120 ,  122 . 
     As explained below, to accommodate different thicknesses of boards, and to enable the intensity of the brushing to be varied, the vertical position of the brushes  120 ,  122  is adjustable. To this end, the bearings  124 ,  126  are slidably mounted in the side legs  116 ,  118 . In a similar manner to the adjustment for the radiant heater or burner assembly  90 , pairs of respective threaded shafts are provided for the brushes  120 ,  122 . Each threaded shaft  142 ,  144 , at its lower end, may have a pair of nuts secure thereto, and on either side of the flanges of the bearings  124 ,  126 , so as to provide a simple, rotating support for the respective brush  120 ,  122 . At its upper end, each mounting shaft  142 ,  144  may be provided with further nuts, as shown, on either side of the inverted U-shaped channel  114 . By adjusting the position of these nuts along the shafts  142 ,  144 , the vertical position of the shafts  142 ,  144 , and hence the vertical location of the brushes  120 ,  122  can be adjusted. 
     A further and final inverted frame  160  is attached to the longitudinal frame members  12 . A damping cloth  161  is mounted to this frame  160 . For this purpose, the cloth  161  could be formed to provide an elongate channel into which a rod  162  is inserted. In known manner, the rod  162  can be supported, at either end, in brackets  164  and secured with clips  166 . 
     The frame  160  is also provided with spray nozzles  168  that would be connected to a water source. 
     In use, the electric drive motor  58  is used to drive the sprockets  56 , to pull the chain conveyor belt along a top run in the upper channel members  30 , from the end shaft  65  towards the damping cloth  162 . The chain conveyor belt, returns, in a lower run supported by the lower channel members  32 , below the top run. As shown, the length of the chain is such as to leave a substantial loop of the chain conveyor belt hanging between the ends of the lower channel members  32  and the end shaft  65 . This loop is dimensioned to have sufficient weight, to provide sufficient attention to pull the chain conveyor belt  50  along the channel members  32  and to maintain that lower run of the conveyor belt generally in tension, as shown. 
     Simultaneously, as the motor drives the conveyor belt  50 , the drive sprocket  62 , on the end of the drive shaft  52 , drives the chain  150 . Consequently, the chain  150  drives the cylindrical brushes  120 ,  122  causing the brushes to rotate clockwise, as viewed in  FIG. 8 , effectively causing the bottom surfaces of the brushes  120 ,  122  to be moving in the opposite direction to the motion of the chain conveyor belt  50 . 
     It will therefore be understood that this basic configuration provides for the chain conveyor belt to transport wood boards or planks  95  from one end, under the infrared radiant heater or burner assembly  90 , under the brushes  120 ,  122  and under the damping cloth  162 , to be discharged from the apparatus. 
     To achieve a desired charring and heat treatment of the wood boards or planks  95 , a number of parameters can be varied. Firstly, the speed of the chain conveyor belt  50  can be varied as desired. In this configuration, this will inherently vary the rotational speed of the rotating brushes  120 ,  122 . It will be understood that, in alternate configurations, a separate drive can be provided to the brushes  120 ,  122 , so that their speed can be independent of the speed of the chain conveyor belt  50 . 
     A number of parameters of the infrared radiant heater or burner assembly  90  can be varied. Firstly, using the mounting shafts  78 ,  80 , the height of the radiant heater or burner assembly  90  can be adjusted as desired. The height can be adjusted, for example, in accordance with the thickness of the wood boards or planks  95  being treated and/or in accordance with the desired height or spacing between the radiant heaters or burners  94  and the wood boards or planks  95 , which in turn may depend upon the type of wood  95  being treated. 
     The level of radiant heat provided by the radiant heater or burner assembly  90  can also be adjusted. Thus, the number of radiant heaters or burners  94  that are actually activated for anyone treatment session can be adjusted, and it is not necessary for all of the banners to be lit. In addition, the heat provided by each radiant heater or burner  94  can be adjusted, by adjusting the amount of gas supplied to it. 
     The height of the brushes  120 ,  122  can be adjusted. As for the radiant heater or burner assembly  90 , the thickness of the wood boards or planks  95  being treated may be a parameter used to determine the height of the brushes. Additionally, the height of the brushes  120 , and  22  may be varied depending upon, for example, the level of brushing required, the hardness or other qualities of the wood  95  being treated. 
     Examples of variations in parameters for different elements of the apparatus for different types of wood are given in the following table: 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 Burner 
                   
                   
               
               
                 Wood 
                 Burner 
                 assembly 
                 Conveyor 
                 Brush 
               
               
                 Type 
                 Temperature 
                 Height 
                 Speed 
                 Height 
               
               
                   
               
             
            
               
                 Cedar 
                  750° F.-1800° F. 
                 2½″-5″  
                 35 fpm-60 fpm 
                 ½″-1½″ 
               
               
                   
                 (400° C.-980° C.) 
               
               
                 Pine 
                 1000° F.-1800° F. 
                 2″-6″ 
                 32 fpm-45 fpm 
                 ¾″-3½″ 
               
               
                   
                 (540° C.-980° C.) 
               
               
                 Fir 
                 1200° F.-1800° F. 
                 2½″-5½″ 
                 32 fpm-40 fpm 
                 ¾″-3″  
               
               
                   
                 (650° C.-980° C.) 
               
               
                 Tamarak/ 
                 1000° F.-1800° F. 
                 2″-6″ 
                 32 fpm-45 fpm 
                  ¾-2½″ 
               
               
                 Larch 
                 (540° C.-980° C.) 
               
               
                   
               
            
           
         
       
     
     As indicated in the above table, the various parameters can be adjusted for different types of wood  95 . The conveyor speed is expressed in feet per minute (fpm). The heights for the burner assembly  90  and the brushes  120 ,  122  are expressed in inches above the level of the conveyor  50 . For the burner assembly  90 , this measurement is the distance between the bottom of the individual burners  94  and the top of the conveyor  50 . For the brushes, the measurement again is in inches and is measured between the lowermost point of the brushes  120 ,  122  when not in contact with the wood and the conveyor  50 . It will be understood that, to achieve the necessary brushing action, the lowermost point of the brushes needs to be below the top of the wood board. 
     For this purpose allowance has to be made for the fact that the actual thickness of wood boards or planks  95  (at least in N. America) is less than a nominal dimension or thickness of the lumber, before it&#39;s dressed/planed. For example, for a ¾″ thick cedar board, the actual thickness may only be about ⅝″ thick. Accordingly, the brushes  122 ,  124  may be set at ½″ above the conveyor  50 , which will put the extended bristles of the brush at ⅛″ below the surface of the board. The bristles will bend when they come in contact with the board, which will provide the necessary pressure and brushing action. 
     The heat treatment of the wood boards or planks  95  is intended to affect significant charring of the wood  95 , to provide an attractive appearance and/or to enhance the appearance of the wood  95 . In many cases, the level of heat will be such that the wood  95  catches fire, to some extent, as shown in  FIG. 6 . For this reason, the damping cloth  162  is provided at the end of the conveyor belt  50 . As the word passes under the brushes  120 ,  122 , it then passes under the damping cloth  162 , which is sprayed with water, to extinguish any flames or burning on the wood boards or planks  95 . Additionally, the brushes  120 ,  122  would be formed from bristles that are resistant to heat or flames, e.g. the brushes may be formed with steel bristles. 
     While the apparatus and method have been described as including rotating brushes. The present disclosure envisages that any suitable motion can be applied to the brushes that will effect the required brushing action. For example, the brushes can have a planar brushing surface and be provided with oscillating movements along a line, which be aligned with the direction of motion of the wood board or at an angle to the wood board. It is also possible that a brush or brushes can be mounted for rotation about an axis perpendicular to the surface of the wood board, the rotation being either continuous or oscillating. 
     A number of embodiments have been described herein. However, it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the embodiments as defined in the claims appended hereto. A person skilled in the art will also recognize that the embodiments described above should be read as representative of a plethora of permutations and combinations not explicitly described, the permutations and combinations incorporating elements from various embodiments. More particularly, other variants may comprise any possible, practical combinations of features disclosed in the claims, beyond those defined by the claims and their dependencies.