Patent Publication Number: US-2007113716-A1

Title: Sawdust-free wood cutting method and apparatus

Description:
RELATED APPLICATION  
      This application is a continuation of U.S. patent application Ser. No. 10/998,677 filed on Nov. 30, 2004 which is a continuation of U.S. patent application Ser. No. 10/634,873 filed on Aug. 6, 2003, which is a continuation of a PCT/CA03/00222 filed on Feb. 14, 2003 and claiming priority on Canadian Patent Application No. 2,374,201 filed on Mar. 1, 2002. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to wood industries and, more particularly, to a sawdust-free cutting method and apparatus.  
      2. Description of the Prior Art  
      In conventional sawmill installations, wood pieces are typically sawn by bringing the wood pieces in contact with a rotating circular saw having a toothed outer circumference. There is normally an important speed differential between the advancing speed of the wood pieces and the tangential speed at the periphery of the rotating circular saw. This results in the generation of sawdust, which constitutes an important source of waste.  
      U.S. Pat. No. 4,009,741 issued on Mar. 1, 1997 to Zimmerman discloses a woodworking machine comprising a number of power driven feed rollers for feeding wood products into and through a cutting zone. The cutting zone includes a pair of coplanar toothed saw blades. An overhead dust collector is provided above the cutting zone to carry away virtually all sawdust generated while the machine is being operated.  
      U.S. Pat. No. 4,614,138 issued on Sep. 30, 1986 to Altman discloses a cutter apparatus for sheet materials, such as plaster board, wherein a pair of axially spaced, coplanar blades are driven in opposite directions and in a way such as to create a speed differential between respective cutting edges of the blades. During cutting, the sheet material is self-propelled by the action of the blades.  
      Although the cutting apparatuses described in the above patents are effective for cutting wood products and sheet materials, it has been found that there is a need for a new cutting method and apparatus for cutting a variety of wood products without virtually producing any sawdust.  
     SUMMARY OF THE INVENTION  
      It is therefore an aim of the present invention to provide a sawdust-free wood cutting apparatus adapted to reduce wood waste resulting from the generation of sawdust.  
      It is also an aim of the present invention to provide a new wood cutting method adapted to minimize waste while cutting a piece of wood.  
      Therefore, in accordance with the present invention, there is provided a sawdust-free wood cutting apparatus comprising:  
      a frame,  
      a guide mounted to said frame for guiding a piece of wood along a feed path having a cutting zone,  
      at least one circular blade mounted in said cutting zone and driven in rotation about an axis transversal to said feed path, said circular blade having a toothless circumferential cutting edge,  
      a source of power driving said circular blade about said axis, and  
      a feeder advancing the piece of wood to be cut through said cutting zone at a linear speed substantially equal to a tangential speed at said toothless circumferential cutting edge of said circular blade.  
      In accordance with a further general aspect of the present invention, there is provided a method of cutting a piece of wood, comprising the steps of: driving in rotation a blade having a smooth outer cutting circumference, bringing a piece of wood in contact with said blade at a speed substantially equal to a tangential speed at said smooth outer cutting circumference. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which:  
       FIG. 1  is a front right perspective view of a sawdust-free wood cutting apparatus in accordance with a first embodiment of the present invention;  
       FIG. 2  is a back left perspective view of the sawdust-free wood cutting apparatus of  FIG. 1 ;  
       FIG. 3  is a top plan view of the sawdust-free wood cutting apparatus;  
       FIG. 4  is a back elevation view of the sawdust-free wood cutting apparatus;  
       FIG. 5  is a front elevation view of the sawdust-free wood cutting apparatus;  
       FIG. 6  is an end view of an inlet end of the sawdust-free wood cutting apparatus;  
       FIG. 7  is an enlarged front view of a discharge end of the sawdust-free wood cutting apparatus; and  
       FIG. 8  is an enlarged end view, partly broken away, of the sawdust-free wood cutting apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Now referring to the drawings, and in particular to  FIGS. 1 and 2 , a sawdust-free wood cutting apparatus embodying the elements of the present invention and generally designated by the numeral  10  will be described. As will be seen hereinafter, by cutting with at least one blade, as opposed to sawing, it is possible to use virtually 100% of the volume of wood to be processed. That is to say that very little waste or no waste at all occurs in the wood cutting apparatus  10 . This represents significant savings over conventional sawing devices wherein about 12% of the processed wood is transformed in sawdust.  
      The sawdust-free wood cutting apparatus  10  is intended to cut wood pieces, such as a wooden board, wood planks and lumbers. More specifically, the sawdust-free wood cutting apparatus  10  generally comprises a table  12 , a pair of vertically spaced-apart feed rollers  14   a  and  14   b  at an upstream end  15  of the table  12 , a pair of discharge rollers  16   a  and  16   b  at a downstream end  17  of the table  12 , and a pair of coplanar circular cutting blades  18   a  and  18   b  between the pairs of feed and discharge rollers  14   a ,  14   b ,  16   a  and  16   b.    
      The table  12  includes a horizontal planar support surface  20  supported above a ground surface by four legs  22  depending from the corners of the support surface  20 . First and second axially spaced-apart rectangular slots are defined in the support surface  20  for respectively receiving the feed roller  14   a  and the discharge roller  16   a  with the peripheral side surface of the rollers  14   a  and  16   a  substantially flush with the top surface of the support surface  20 . According to the illustrated embodiment, the feed roller  14   a  and the discharge roller  16   a  are identical and journaled to the table  12  for free rotation about respective rotating axes. The rollers  14   a  and  16   a  are not power driven and are caused to be rotated only by the piece of wood W ( FIGS. 7 and 8 ) traveling thereon from the upstream end  15  of the table  12  to the downstream end  17  thereof.  
      The feed roller  14   b  and the discharge roller  16   b  are adapted to frictionally engage a top surface of the piece of wood W ( FIGS. 7 and 8 ) to be cut and are supported by respective overhead mounting structures  28 . As shown in  FIGS. 1, 2 ,  4 ,  5  and  7 , each mounting structure  28  includes a roller mounting plate  30  provided with downwardly depending cylindrical bushings  32  at the corners thereof for sliding movement along four vertical cylindrical rods  33  extending upwardly from the support surface  20 . Each roller mounting plate  30  carries a pair of laterally spaced-apart pillow blocks  34  ( FIG. 8 ) on an undersurface thereof for rotatably supporting one of the feed roller  14   b  and discharge roller  16   b . A top plate  36  is secured to the upper distal end of the rods  33 . An adjustable biasing structure  38 , such as a spring or a piston and cylinder arrangement, is provided between the top plate  36  and the underlying roller mounting plate  30  to provide adjustability for vertical translating and positioning of the rollers  14   b  and  16   b  against the top surface of the piece of wood W to be processed.  
      The upper feed and discharge rollers  14   b  and  16   b  are preferably ribbed and made of a material having a high coefficient of friction to prevent any slippage between the piece of wood W and the rollers  14   b  and  16   b  while the piece of wood W is being advanced by the rollers  14   b  and  16   b  through the apparatus  10 .  
      As shown in  FIG. 5 , the feed roller  14   b  and the discharge roller  16   b  are both power driven by a motor  40  via an endless drive chain  42  engaged on a sprocket wheel  44  mounted on a first output shaft  46  of a gear box  48  operatively connected to the motor  40 . The drive chain  42  extends over a sprocket wheel  50  ( FIG. 6 ) connected to the feed roller  14   b  and then over two intermediate sprockets  52  and  54  mounted to the table  12 . The drive chain  42  extends from the sprocket  54  to another sprocket  56  ( FIG. 4 ) connected to the discharge roller  16   b . The chain  42  then engages a second pair of intermediate sprockets  58  and  60 , which are mounted to the table  12 , before returning to the sprocket  44 . The sprockets  50  and  56  are identical to ensure that the tangential speed at the periphery of the rollers  14   b  and  16   b  is equal. This speed corresponds to the advancing speed of the wood piece W through the apparatus  10 .  
      The piece of wood W is guided along a rectilinear feed path through the apparatus  10  in order to ensure straight cuts C ( FIG. 3 ). As best shown in  FIG. 3 , this is achieved by urging one lateral edge of the piece of wood W in sliding contact with a vertical guiding surface  62  of an axially extending angle iron  64  or the like adjustably mounted on one side of the feed path. The angle iron  64  has a horizontal foot  68  in which a given number of slots  66  are defined for receiving fasteners. A plurality of fastener receiving holes  70  are defined in the support surface  20  of the table  12  for allowing the angle iron  64  to be secured in a variety of lateral positions on the support surface  20 .  
      The piece of wood W, while traveling on the table  12 , is urged against the vertical guiding surface  62  by a pushing mechanism  72  mounted on the support surface  20  on a side of the feed path opposite to the angle iron  64 . As shown in  FIGS. 1 and 3 , the pushing mechanism  72  includes a base plate  74  defining a pair of slots  76  ( FIG. 3 ) adapted to receive fasteners  78  ( FIG. 3 ) for adjustably mounting the base plate  74  on the support surface  20  of the table  12 . A pivot plate  80  having a boomerang-like shape is pivotally mounted at  82  to the base plate  74  for pivotal movement about a vertical axis. The pivot plate  80  carries at an apex thereof a roller  84  having a vertical pivot axis  86 . A pneumatic cylinder  88  or the like is pivotally mounted at  90  to a bracket  92  fixed to the base plate  74 . The pneumatic cylinder  88  has a piston  94  having a distal end pivotally connected to one end of the pivot plate  80  opposite the pivot  82 . The pneumatic cylinder  88  is adjusted to bias the roller  84  in rolling contact with one side of the piece of wood W and, thus, maintain the other side of the piece of wood W in sliding contact the guiding surface  62 .  
      The piece of wood W is cut longitudinally into two parts by the combined action of the axially spaced coplanar circular cutting blades  18   a  and  18   b . As best shown in  FIG. 7 , the lower and upper coplanar blades  18   a  and  18   b  are placed slantwise behind each other so that their combined penetration depth equals at least the thickness of the piece of wood W to ensure a complete cut therethrough. The blades  18   a  and  18   b  are provided in the form of smooth edged circular blades. According to the illustrated embodiment, both blades have the same diameter and a same sharpened circumferential edge. As shown in  FIG. 8 , each blade  18   a / 18   b  tapers on each blade side around its sharpened circumferential edge regions. Satisfactory results have been obtained with 8 inches diameter blades having a 0.110 inch thick peripheral edge region. Spruce pieces of 2 inches thick have been cut in the wood fiber direction using such blades. Spruce pieces having a thickness of ⅝ inch have also been cut in a direction transversal to the wood fiber.  
      As shown in  FIG. 8 , the circular blades  18   a  and  18   b  are fixedly mounted to respective shafts  106  and  108  journaled to a box-like structure  110  mounted on the table  12 .  
      The upper circular blade  18   b  is vertically adjustable by a screw adjustment mechanism generally depicted at  112 .  
      The blades  18   a  and  18   b  are driven at the same speed but in opposite directions by the motor  40 . As shown in  FIG. 2 , the gear box  48  is provided with a second output shaft  96  having a sprocket wheel  98  mounted thereon. An endless drive chain  100  extends over the sprocket wheel  98  for transmitting power to two other sprocket wheels  102  and  104  respectively mounted to the shafts  108  and  106  of the upper and lower circular cutting blades  18   b  and  18   a . A tensor equipped with a sprocket wheel  114  is engaged with the drive chain  100  to maintain an appropriate tension therein.  
      In operation, the blades  18   a  and  18   b  are driven at the same speed but in opposite directions (see  FIG. 7 ) so that the tangential speed at the outer circumference thereof be equal to the advancing speed of the piece of wood W advanced from the upstream end  15  of the table  12  to the downstream end thereof  17  by the feed and discharge rollers  14   b  and  16   b . By so passing the wood piece W between a pair of lower and upper toothless blades  18   a  and  18   b  driven at a speed corresponding to advancing speed of the piece of wood W, the piece of wood W is cut, as opposed to being sawn, and virtually no sawdust is generated. By having no differential of speed between the tangential speed at the circumference of the blades  18   a  and  18   b  and the piece of wood W, the friction between the blades  18   a  and  18   b  and the piece of wood W is almost reduced to zero.  
      The above-described driving arrangement of sprocket wheels and chains driving the feed roller  14   b , the discharge roller  16   b  and the blades  18   a  and  18   b  guarantee the equality of the advancing speed of the wood piece W and the tangential speed of the blades  18   a  and  18   b . The advancing speed of the piece of wood W through the apparatus  10  may be about 365 feet/minutes.  
      Although the preferred embodiment of the present invention has been described as including a pair of coplanar circular blades, it is also contemplated to use a single cutting blade.