Abstract:
A system for determining at least one characteristic of wood furnish from an upstream source. The system includes: an inclined panel comprising a transparent window having a top surface for the wood furnish to slide down; a lighting means adjacent the transparent window for lighting the wood furnish visible through a bottom surface of the window; an image capturing means adjacent the transparent window for capturing an image of the wood furnish visible through the bottom surface of the window; and a processing means in communication with the image capturing means for deriving from the captured images the at least one characteristic of the wood furnish.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to systems and methods for characterizing wood furnish. 
       BACKGROUND 
       [0002]    Characterizing wood furnish is important in the manufacture of engineered wood products including oriented strand board (OSB) and fibreboard. 
         [0003]    For example, measuring the level of fines in wood furnish is important for optimizing OSB production. Fines are small wood particles that are generated as a byproduct during stranding. Fines are too small to be useful in OSB production. In drier woods, such as mountain pine beetle infested wood, fines can account for 5% to 40% of furnish after stranding. High fine levels greatly affect the volume and value recovery from raw wood. The percentage of fines generation is therefore a key indicator used by mills for gauging the production of quality of furnish in OSB production. It is estimated that for an average-sized mill, a 1% improvement in wood recovery by reducing fines would result in wood cost savings on the order of hundreds of thousands of dollars per year. 
         [0004]    A number of variables affect fines generation including characteristics of the wood (e.g. species, moisture content, temperature, pest damage) and operating conditions of the strander (e.g. wood alignment, rotation speed, cutting angle, sharpness of cutting and scoring knives). 
         [0005]    At present, the level of fines in furnish is typically measured by manual sampling and screening. This method is very slow and does not provide “real time” measurements. Fines generation is highly variable and significant changes can occur over very short time spans. Mill operators limited to manual sampling and screening are unable to make timely and effective adjustments in response to changes to the level of fines in wood furnish. 
         [0006]    It is desirable to provide systems and methods that provide operators with real time, accurate measurements of wood furnish characteristics such as the level of fines. 
       SUMMARY OF THE INVENTION 
       [0007]    One aspect of the invention provides a system for determining at least one characteristic of wood furnish from an upstream source. The system includes: an inclined panel comprising a transparent window having a top surface for the wood furnish to slide down; a lighting means adjacent the transparent window for lighting the wood furnish visible through a bottom surface of the window; an image capturing means adjacent the transparent window for capturing an image of the wood furnish visible through the bottom surface of the window; and a processing means in communication with the image capturing means for deriving from the captured images the at least one characteristic of the wood furnish. 
         [0008]    Another aspect of the invention provides a method for determining at least one characteristic of wood furnish from an upstream source. The method includes the steps of: (a) providing an inclined panel comprising a transparent window; (b) receiving the wood furnish from the upstream source onto the inclined panel; (c) allowing the wood furnish to slide down a top surface of the transparent window; (d) directing light onto the wood furnish sliding down the top surface of the window through a bottom surface of the transparent window; (e) capturing images of the wood furnish sliding down the top surface of the window through a bottom surface of the transparent window; and (f) processing the captured images to derive the at least one characteristic of the wood furnish. 
         [0009]    A further aspect of the invention provides a system for determining at least one characteristic of wood furnish from an upstream source. The system includes means for capturing images of the wood furnish; means for lighting the wood furnish; and a processing means in communication with the image capturing means for rendering an edge pixelated image of the captured image of the wood furnish and determining from the edge pixelated image and a calibration factor the at least one characteristic of wood furnish. 
         [0010]    Yet another aspect of the invention provides a method for determining at least one characteristic of wood furnish. The method includes the steps of: (a) directing light onto the wood furnish; (b) capturing images of the wood furnish; (c) processing the captured images to render an edge pixelated image of the captured image of the wood furnish; and (d) determining from the edge pixelated image and a calibration factor the at least one characteristic of wood furnish. 
         [0011]    Further applications of the invention and features of specific embodiments of the invention are described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    In drawings which depict non-limiting embodiments of the invention: 
           [0013]      FIG. 1  shows a schematic view of a system according to an embodiment of the invention; 
           [0014]      FIG. 2  shows a schematic view of a system according to another embodiment of the invention; 
           [0015]      FIG. 3  shows computer-generated pixelated images of wood furnish with fine levels of (a) 100% and (b) 0%; 
           [0016]      FIG. 4  is a graph plotting the percentage of fines in dry aspen furnish measured according to the embodiment shown in  FIG. 2  against the percentage of actual fines in the furnish; 
           [0017]      FIG. 5  is a graph plotting the percentage of fines in mountain pine beetle-infested pine furnish measured according to the embodiment of  FIG. 2  against the percentage of actual fines in the furnish; 
           [0018]      FIG. 6  is a graph comparing the plot of the percentage of fines in furnish measured according to the embodiment of  FIG. 2  against the percentage of actual fines in the furnish, to the plot of the percentage of fines in furnish measured manually against the percentage of actual fines in the furnish; 
           [0019]      FIG. 7  shows a schematic view of a system according to a further embodiment of the invention; 
           [0020]      FIG. 8  shows a partial cutaway view of the embodiment shown in  FIG. 7 ; 
           [0021]      FIG. 9  shows the embodiment shown in  FIG. 7  positioned below a strander; 
           [0022]      FIG. 10  is an image captured through the window of a system according to the embodiment shown in  FIG. 7 ; 
           [0023]      FIG. 11  is a close-up image captured through the window of a system according to the embodiment shown in  FIG. 7 ; 
           [0024]      FIG. 12  is a graph plotting the percentage of fines in dry aspen furnish as measured by the embodiment shown in  FIG. 7  against the actual percentage of fines in the furnish; 
           [0025]      FIG. 13  shows the embodiment shown in  FIG. 7  positioned below a drop chute; 
           [0026]      FIG. 14  shows a system according to a further embodiment of the invention; and 
           [0027]      FIG. 15  shows a schematic side view of the embodiment shown in  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
         [0029]    The invention relates generally to systems and methods for characterizing wood furnish. A camera scans wood furnish passing across a predetermined area lit by a light source. The scanned images are processed by image analysis techniques to determine edge pixel counts. A calibration factor is applied to the edge pixel count to render characteristics of the wood furnish. 
         [0030]    The following description, by way of example, describes the invention in the context of measuring and controlling the level of fines in furnish for OSB production. However, the invention can be applied in the context of other engineered wood processing (e.g. production of fibreboards such as particle board, medium density fibreboard and high density fibreboard) where characterizing wood furnish may be useful. 
         [0031]      FIG. 1  shows one embodiment of the invention. System  110  includes one or more light sources  118 , a camera  120 , and a processor  122 . Processor  122  is in communication with camera  20  and may be built in to the camera. 
         [0032]    System  110  is positioned adjacent a free-falling stream of furnish  130 . Furnish  130  consists of fines  133  and larger wood particles  131 . Light sources  118  and camera  120  focus on a predetermined area through which furnish  130  falls. Furnish  130  free-falls from an overhead source, such as a strander or a downstream end of a belt conveyor. 
         [0033]    Light sources  118  may be any high intensity low heat output light source such as a light emitting diode (LED), laser and fluorescent light. 
         [0034]    Camera  120  may be any high speed, high sensitivity digital camera. For example, camera  120  may be a high speed black and white charge-coupled device (CCD) camera with a shutter speed of 1/10,000 s and capable of capturing more than five images per second. An example of suitable camera with a built-in processor is the Sony™ XCI-V3 smart camera. 
         [0035]    Processor  122  analyzes the images captured by camera  120 . Processor  122  may include a computer loaded with software that correlates the level of fines with the number of edge pixels detected in a captured image. Correlation may be achieved using a calibration factor specific, for example, to the species of wood. For mixed species of wood, a weighted calibration factor based on the ratio of the species can be applied. Processor  122  thereby provides “real time” information about the level of fines in wood furnish  130  to the mill operator who can then make any remedial adjustments. In some embodiments, processor  122  may be provided with a warning limit function, wherein a visual and/or aural warning is communicated to the mill operator if the level of fines being detected in furnish  130  exceeds a maximum threshold. 
         [0036]    Edge pixel detection obviates the need to separate the wood particles and to rely on any particular shape of particles during image processing.  FIG. 3  shows computer-processed images of wood furnish with edge pixels shown by the stippled boundary lines within the darkened rectangular region of interest.  FIG. 3(   a ) is an image of wood furnish with 100% fines, and  FIG. 3(   b ) is an image of wood furnish with 0% fines. 
         [0037]      FIG. 2  shows another embodiment of the invention. System  210  includes light sources  218 , a camera  220  and a processor  222  analogous to light sources  118 , camera  120  and processor  122  respectively. Light sources  218  and camera  220  focus on a fixed focal area through which furnish  230  carried on a conveyor  232  passes. 
         [0038]      FIGS. 4 and 5  are graphs plotting the percentage of fines in furnish samples determined by system  210  against the actual percentage of fines in the samples, in an experimental example. The furnish samples used in  FIG. 4  are dry aspen, and the furnish samples used in  FIG. 5  are mountain pine beetle-infested pine. The measured percentages of fines correlate closely to the actual percentage of fines. The high R 2  values indicate a very good linear trend between the individual measurements of fine percentages. 
         [0039]      FIG. 6  graphs two plots. The first plot is the percentage of fines in furnish measured by system  210  in an experimental example against the actual percentage of fines in the furnish. The second plot is the percentage of fines in furnish measured manually against the actual percentage of fines in the furnish. Compared to manual measurements, measurements by system  210  were found to correlate much better with the actual percentage of fines. The higher R 2  value (R 2 =0.9893) with the measurements by system  210  show that the measurements determined by the present invention provide a more linear trend than that obtained with manual measurements. 
         [0040]      FIGS. 7 and 8  show a further embodiment of the invention. System  310  includes light sources  318 , a camera  320  and a processor  322  analogous to light sources  118 , camera  120  and processor  122  respectively. Light sources  318 , camera  320  and processor  322  are housed in a wedge-shaped enclosure  312 . A top side of enclosure  312  includes an inclined panel  314  ( FIG. 8 ) with a transparent window  316 . 
         [0041]      FIGS. 8 and 9  show projection  324  fixed to and positioning system  310  directly below a source  328  of wood furnish  330 . Wood furnish  330  falls freely onto and slides over window  316 , or falls freely onto a part of panel  314  higher than window  316  and then slides over window  316 . The source  328  of wood furnish  330  in  FIG. 9  may, for example, be a strander, waferizer or flaker. The other end of projection  324  is fixed to a support plate  326  which in turn is fixed to a suitable structure in the mill. Conveyors  332  carries wood furnish  330  that slides off system  310 , as well as wood furnish  330  that does not contact system  310 , downstream for further processing. 
         [0042]    Enclosure  312  is sealed to prevent dust, dirt and other matter from interfering with the function of light sources  318 , camera  320  and processor  322 . The walls of enclosure  312  are opaque except for transparent window  316 . The opacity of enclosure  312  helps to shield camera  320  from unwanted lighting from the mill environment and provides consistent lighting to wood furnish  330  from light sources  318 . Enclosure  312  may be formed in any shape that includes an inclined panel  314  and window  316 . In some embodiments, panel  314  may consist entirely of window  316 . 
         [0043]    Panel  314  and window  316  are inclined at an angle sufficiently above horizontal for wood furnish  330  to slide off by gravitational force and/or displacement by the continual stream of wood furnish  330  from source  328 . The angle of the incline may range from 45 to 75 degrees above the horizontal, for example. Window  316  is transparent and may be formed of a low friction, abrasion resistant material such as hardened glass or sapphire. Window  316  may be flat or any other profile that allows unobstructed sliding of wood furnish  330  along its top surface. Window  316  “self-cleans” from the continual impact of wood furnish  330  falling and sliding on its top surface. 
         [0044]    Both light source  318  and camera  320  are focused on wood furnish  330  in contact with or in close proximity to the top surface of a predetermined area of window  316 . The focal length of light source  318  and camera  320  can therefore be preset, obviating the need for manual or automatic adjustment during operation. Obtaining clear images is also assisted by the fact that wood furnish  330  tends to fall and slide flat against window  316 . Obtaining clear images ensures more accurate image analysis by processor  322 . 
         [0045]      FIGS. 10 and 11  are sample images of wood furnish  330  taken by a camera  320  through window  316  in an experimental example. 
         [0046]      FIG. 12  is a graph plotting the percentage of fines in dry aspen samples determined according to system  310  in an experimental example against the actual percentage of fines in the samples. The measured levels of fines were found to correlate very closely to the actual levels of fines. The high R 2  value (&gt;0.99) indicates a very good linear trend between the individual measurements of fine levels according to the invention. 
         [0047]      FIG. 13  shows system  310  positioned directly below a drop chute  329  at a transfer point between an upstream conveyor (not shown) and a downstream conveyor  332 . Wood furnish  330  from drop chute  329  slides down across inclined panel  314 . As wood furnish  330  slides down across window  316 , images of wood furnish  330  are captured by a camera (not shown) housed in enclosure  312  and the images are processed as described above to provide an operator with the level of fines in wood furnish  330 . Wood furnish  330  slides off panel  314  and is carried downstream by conveyor  332  for further processing. 
         [0048]      FIGS. 14 and 15  show a further embodiment of the invention, similar to system  310 . System  410  has an inclined panel  414 . Rails  434  along each side of panel  414  guide wood furnish  430  down across panel  413  and window  416 . Window  416  is rectangular and may, for example, be approximately 1″ in height and 3″ in width. Camera  420  (with built-in processor  422 ) and light source  418  are housed in hollow projection  424 . Panel  414  and window  416  form a distal side of supporting arm  424 . Camera  420 , processor  422  and light source  418  are connected to a power supply  436 . Camera  420  and processor  422  are connected to an output  438 . Projection  424  is supported by an additional support arm  424 ′. Both projection  224  and support arm  424 ′ are fixed to support plate  426 , which in turn is fixed to a suitable structure in the mill. Projection  424 , support arm  424 ′ and support plate  426  may be formed of a strong, lightweight material such as aluminum. 
         [0049]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.