Patent Publication Number: US-8113098-B1

Title: Automated shingle milling system

Description:
BACKGROUND INFORMATION 
     1. Field of the Invention 
     The invention relates to the field of saw mills. More particularly, the invention relates to shingle saw mills. 
     2. Description of the Prior Art 
     Definitions and usage: Shingles and shakes are relatively thin tapered slices of wood, typically cut from cedar logs. Each shingle has a butt, a top, two sides, and two planar faces. The thicker end of the tapered slice is the butt and the thin end the top. The side profile of the shingle is that of an isosceles triangle, with the two planar faces slanting from the butt to the top. The terms “shingle” and “shake” are often used interchangeably in the industry, and the term “shingle” shall be used hereinafter to encompass both the shingle and the shake. 
     The shingle industry has existed in the US for over 200 years. Producing a shingle from a log is a multi-step process, beginning with cutting a length of log that is slightly longer than the length of the finished shingle product, cutting a tapered rough blank or billet from a log, then squaring it up to a shingle by cutting a square butt edge and parallel side edges that are squared to the butt edge. A grading operation is performed manually, in which shingles are given a quality grade. There is no universal industry standard for this grading, so, for purposes of illustration only, an arbitrary grading system that defines quality grades #1 to #3 will be used in this specification. It should be understood, however, that the grading system may change according to order, with #1 identifying the highest quality grade and #3 the lowest acceptable grade. Thus, quality grade #3 may be different for an order that demands the highest quality from that of the standard order. Shingles that do not qualify as #3 are either discarded as waste or possibly cut for shims. The goal of this scanning operation is to maximize certain desirable characteristics or properties, such as size and/or quality, eliminate defective material, and reduce unnecessary waste. 
     As presently done, the sawyer receives a rough blank from the rough-billet saw, which may have live edges, that is, the round of the tree, still on the billet. The sawyer holds the shingle manually over an edging saw, with the butt placed against a flat support, and trims or edges first one side edge so that it is substantially perpendicular to the plane of the butt, flips the shingle, and trims the second side edge so that it is substantially parallel to the first side edge. These edges may not be perfectly square relative to the butt, so the shingles are typically sent through a re-squaring and re-butting machine, which “squares up” the shingle billet, that is, trims the sides so that they are perpendicular to the plane of the butt. 
     The conventional milling process results in significant and unnecessary removal of material from the width of the shingle, which reduces the amount of product or value that can be obtained from each log and increases the amount of waste product. 
     What is needed therefore is an automated process of grading, edging, rebutting, and sorting shingles. What is further needed is such a system that provides a safer work environment by reducing the exposure of the sawyer to saw blades. What is yet further needed is such a system that processes shingles faster and with much less waste production, and maximizes the amount of product that can be recovered from a log. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is an automated shingle milling system that automates several steps in the milling process and eliminates the manual rebutting step. The shingle milling system comprises a billet-cutting saw for cutting rough shingle billets from a log, a butt-trimming saw, a conveyor system, a visual imaging system for detecting properties, characteristics, or defects and optimizing the cutting operation, a gang rip saw for the final side-edging cut, and a sorting system. 
     Logs are first pre-cut into lengths that are slightly longer than the overall desired length of shingles. The billet-cutting saw passes through the pre-cut log, slicing off tapered, billets with live edges. In a side elevational view, the shape of the shingle billets is that of an isosceles triangle. The sides of the billets, at this stage, may be very irregular in shape. The billets are loaded into a magazine and from there pushed onto a conveyor system that feeds the billets through the butt-trimming saw, which square cuts the butt. 
     Upon exiting the butt-trimming saw, the shingle billet is conveyed past the visual imaging system, which scans both faces of the shingle billet. The imaging system confirms quality wood and knots, and also identifies knots and defects that should be removed. It does this by imaging the geometry of the side edges and the characteristics or defects on the face of the billet that have been defined to negatively affect the grade of the finished shingle product. Defects that are detectable by the visual imaging system include, but are not limited to, untrimmed edges, sound knots, unsound knots, holes in the shingle, and other defects. Unsound knots are wood knots that have a tendency to drop out of the shingle with time, whereas sound knots do not. The defect may be such, that the material that includes the defect has to be rejected (rotted material, unsound knots, holes), or it may be such, that the shingle with the defect will be deemed a lower quality product. Depending on the predetermined and selected quality standard, the defect may be allowed or deemed waste material. 
     The billet is then conveyed to the edging station. Based on information from the visual imaging system, a computer processing unit then calculates the best possible cut of the billet, to optimize its value and reduce waste. The shingle billet is fed onto centering apparatus, where it is oriented for a final cutting step by a gang rip saw having a plurality of saw blades. Depending on the location of defects in the billet, two or more saw blades are used to cut one or more shingles. Assuming, for example, that the gang rip saw has four saw blades and that an unsound knot is found in the center portion of the shingle. The two saw blades are positioned along the shaft so as to cut a shingle or a shim on each side of the unsound knot, and two are positioned to trim the edges. The material containing the unsound knot and the trimmed edges is discarded as waste material. The material to each side of the waste material is assigned a quality grade, for example, #1, #2, #3, or shim, and moved along the conveyor toward a sorting station. Ideally, automated sorting apparatus is provided at the outfeed of the rip saw, which drops the finished shingles into bins according to quality grade and shunts the waste material into a waste container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not drawn to scale. 
         FIG. 1  is an illustration of a rough blank. 
         FIG. 2  is an illustration of a conventional finished-product shingle. 
         FIG. 3A  is perspective view of the automated shingle milling system according to the invention. 
         FIG. 3B  is a top plane view of the automated shingle milling system. 
         FIG. 3C  is an elevational view of the automated shingle milling system. 
         FIG. 4  is a perspective view of the visual imaging system and transition station. 
         FIG. 5  is a top plane view of the visual imaging system and transition station, illustrating the alignment belts that move the billet past the imaging cameras and place the billet before the transition pusher. 
         FIG. 6  is a side elevational view of the transition station, showing the upper alignment belts lifted from the billet and the support table raised. 
         FIG. 7  is a plane view of the downstream end of the transition station, showing the pusher and the visual imaging system. 
         FIG. 8  is a block diagram of the visual imaging system. 
         FIG. 9  is a schematic illustration of the auxiliary illumination of the billet. 
         FIG. 10  is an illustration of knot defects on a billet. 
         FIG. 11A  is an illustration of a “shaky wood” defect. 
         FIG. 11B  is an illustration of the visual imaging system mapping of the “shaky wood” defect shown in  FIG. 11A . 
         FIG. 12  is a schematic illustration of the gang rip saw. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art. 
     The invention is an automated shingle milling system  1000 , which receives a shingle blank or billet that has gone through a first edging cut on the sides. The basic steps of the automated shingle milling system  1000  include: automatically precision cutting the butt end of the billet; imaging the billet faces  11  with a camera system to determine the ideal cuts to be made to maximize the quality of the final product and reduce waste; aligning the billet for passage through a gang rip saw, re-imaging the billet to ascertain exact position of the sides of the billet, and then sawing the billet according to instruction from the visual imaging system. 
     A shingle  10  starts off as a rough slice of wood, a rough blank  1 , cut from a round log.  FIG. 1  illustrates a rough blank, with round of tree R attached to the sides.  FIG. 2  illustrates a finished product shingle  10 . The shingle has a butt  12 , a top  14 , two sides  16 , and two planar faces  11 . The butt  12  is thicker than the top  14  and the plane of the butt  12  is cut perpendicular to an imaginary plane  18  that extends between the two faces from the butt to the top  11 A, so as to create a shape that is an isosceles triangle. As used hereinafter, reference designation  10 A shall designate a “blank”,  10 B shall designate a “butt-cut billet” or “butt-trimmed” billet, that is, the butt has been cut square relative to the imaginary plane  18 , and  10 C shall designate a finished-product shingle that has been cut according to pre-defined specifications to optimize the value of the finished product. The reference  12 B shall designate a butt edge that has been squared by a butt saw and  12 A a butt edge that has not yet been squared. The sides  16  are further defined as edged sides  16 A, which still have the round of tree R on them, and trimmed sides  16 B, which have gone through a final side-cut operation. 
       FIGS. 3A-3C  illustrate the automated shingle milling system  1000 ,  FIG. 3A  is a perspective view of the system;  FIG. 3B  is a top plane view, showing particularly the system of conveyor belts used to transport the billets; and  FIG. 3C  is a side elevational view showing particularly the butt saw  200 . The automated shingle milling system  1000  comprises a magazine  100 , a butt-saw  200 , a billet-transport system  300 , a billet-transition-and-aligning station  400 , a visual imaging system  500 , a gang rip saw station  600 , and a sorting station  700 . Blanks  10 A are stored in the magazine  100  and from there forced out individually onto the billet-transport system  300 . In the embodiment shown, the blank  10 A is stored vertically in the magazine  100 , with the butt edge  12 A down. When forced out of the magazine  100  the blank falls onto one of its faces  11  and is moved toward the butt saw  200  along a conveyor belt  330 . Belts  340 , which run continuously and at the same speed as the conveyor belt  330  pick up the blank  10 A and carry it over the butt saw  200 , to square the butt  12 . These belts  340  are similar in construction to the alignment belts  320  described below. In this embodiment, the butt saw  200  includes two saw blades  220  that are mounted vertically, one above the other, the blades offset slightly in the travel direction of the billet and slightly offset also in the direction transverse to the travel direction. The squared blank  10 A is now moved along the billet-transport system  300  as the butt-squared billet  10 B. 
       FIGS. 4-7  show various views of the transition station  400 , along with the visual imaging system  500 . The transition station  400  picks up the billet  10 B after it has been squared, carries the billet  10 B past the visual imaging system  500 , and then aligns and pushes the billet  10 B toward the gang rip saw station  600 . Rather than using the conveyor belts  330 , which are wide belts that transport unconstrained billets  10 A- 10 C, the transition station  400  uses a plurality of alignment belts  320 . It is difficult to transport the billet  10 B with belts, because of its triangular shape and because. in the imaging process, a large portion of the billet has to be cantilevered out from the alignment belts, so that the belts to not interfere with the imaging. The inventor has discovered that POWERTWIST ROLLER DRIVE V-Belt by Fenner Drives is particularly well suited to grab the billet  10 B and move it a horizontal plane. These alignment belts are segmented belts and the particular construction of the segments ensures that there is sufficient friction and compression against the billet to reliably move it forward. In the embodiment shown, two sets of alignment belts are used: a first set of belts  322 , a second set of belts  326 . These belts time the delivery of the billet  10 B into the transition station  400 . Each set of these alignment belts includes an upper belt run  322 A and  326 A, and a corresponding lower belt run  322 B and  326 B, respectively. A plurality of the first set of alignment belts  322  pick up the billet  10 B at the top, i.e., thin, end off of the conveyor belt  330  downstream of the butt saw  200 , and carry it past the visual imaging system  500 , which will be discussed in greater detail below. It is the thicker end of the shingle  10 , i.e., the six or more inches above the butt  12 , that will be visible when shingles are hung as siding on a house wall or roof and so, it is the thicker end of the billet  10 B that is graded by the visual imaging system  500 . Grabbing the billet  10 B across the top end  14  ensures that the graded end is completely visible for imaging. [check one more time for  324 . Get rid of it.] 
     The first set of belts  322  moves the billet  10 B past the visual imaging system  500  into the billet-transition-and-aligning station  400 . Here the billet  10 B is carried by the second set belts  326  onto a support platform  410 . The support platform  410  is pneumatically controlled to rise and fall between a billet-receiving position, shown in  FIG. 7 , and an alignment position, shown in  FIG. 6 . A pusher  420  is mounted on the frame of the transition station  400 . The pusher  420  has a pneumatically actuated cylinder  424  with a push-bar  422  at the end of it. The billet  10 B is moved onto the support platform  410 , which is in the receiving position. The upper run  326 A of the third set of belts is attached to a lift frame  440 . When the billet  10 B is positioned on the support platform  410 , the lift frame  440  is raised up, as shown in  FIG. 6 . This lifts the upper run  326 A of belts from the billet. The support platform  410  is then raised, lifting the billet  10 B off the lower belt run  326 B and bringing the billet  10 B into a position directly in front of the push-bar  422 . The pneumatic cylinder  424  is actuated and the billet  10 B is then pushed by the push-bar  422  out onto a conveyor belt  330  for transport to the gang rip saw station  600 . 
       FIGS. 8 and 9  illustrate elements of the visual imaging system  500 , which comprises a camera  510 , a CPU  520 , vision software  530  that includes “blob tools” for identifying wood quality and determining the side cuts and software analytical tools and algorithms for combining and analyzing data acquired from the blob tools. The CPU  520  and storage means for the vision software  530  may be housed in a support column  501  for the visual imaging system or may be maintained at a remote location. In the preferred embodiment, the camera  510  includes two image-scanning cameras  510 A and  510 B, one for scanning each side of the billet  10 B simultaneously. The camera  510  has a pixel sensor, preferably a high-resolution (1600×1200) sensor, coupled with an advanced digital signal processing (DSP) engine. A suitable lens  514  is used with the camera  510 . The scope of the invention is not limited to the use of particular hardware components for the visual imaging system  500 . Examples of suitable components include the Insight 5403 monochrome vision system, but preferably, a PC-based system that includes at least one high resolution digital camera, such as the IEEE 1394 High Resolution Camera or the Point Grey 2 MP Grasshopper black-and-white camera with Point Grey Development Accessory Kit, Cognex VisionPro Firewire 101. A suitable lens is the Fujinon 12.5 mm lens, although an 8.5 mm lens or other suitable lenses may also be used. Conventional IO modules (PLCs) for communicating between the CPU  520  and machine control devices, which are well known to the person of skill in the art are also included. An auxiliary lighting system  540  may be provided, as illustrated schematically in  FIG. 9 , to illuminate the billet  10 B as it is imaged by the cameras  510 . A suitable example of such a lighting system is the Advanced Illumination LL632-WHIC3D412 LED Line Light Assembly and Advanced Illumination S710 Pulsar High Current Strobe Controller. The strobe lights  540  are triggered just as the cameras  510  image the billet  10 B. 
     The billet  10 B may be presented to the visual imaging system  500 , either in vertical or horizontal orientation, vertical orientation meaning that the billet  10 B is standing on the butt edge  12 B, horizontal orientation meaning that the billet  10 B is carried in a horizontal orientation. In the embodiment shown, the billet  10 B is transported in a horizontal orientation. The cameras  510  are mounted such, that the image-scanning cameras  510 A and  510 B image the billet  10 B from above and from below, respectively. The auxiliary lighting system  540  is mounted to illuminate each face  11  of the billet  10 B as the cameras  510 A/ 510 B scan the billet.  FIG. 6  illustrates two strobe lights  540  set up to illuminate the lower surface  11 B of the billet  10 B. Upper strobe lights  540  may set up similarly on an upper portion of the support column  501  or on an upper portion of the frame of the billet-transition-and-aligning station  400 . The strobe lights  540  are coupled to the camera control system and illuminate the billet  10 B when the cameras fire. The cameras  510  may be controlled so that they fire a brief time apart from each other, to reduce background “noise”, i.e., light pollution. A suitable configuration for the strobe lights  540  is shown in  FIG. 9 . If the billet  10 B is presented in vertical orientation, the cameras would then, of course, be placed in front of and behind the billet. FindEdge software tools are used together with the pixel sensor  512  to locate the butt edge  12 B. Once the butt edge  12 B is located, the FindEdge tools are rotated 90 degrees to locate ideal side edges  16  on the billet  10 B. 
     Defect detection in Northern White Cedar is generally difficult, because of the wide variation in types and sizes of defects, as well as the fact that the highest quality, i.e., clear wood, has a grain pattern. Nevertheless, certain aberrations in the wood grain are reliably recognizable by the visual imaging system  500  of the present invention. Typical wood grain pattern variations are usually subtle, that is, the variations in intensity between adjacent areas of clear wood are small and slow changing. Wood knots are typically darker than the surrounding clear wood and are predominantly round in shape, with a sharp delineation in intensity at the boundary between the knot and the clear wood. Bark rings surrounding knots are typically darker in color than the knot itself and much darker than the surrounding clear wood. 
     The visual imaging system  500  uses the software-based conventional “blob tools” to detect a defect in the billet  10 B. The camera  510  images the faces  11 A and  11 B of the billet  10 B. The blob tool analyzes the images and determines the existence of a blob by analyzing differences in intensity in adjacent pixels, a blob being a group of pixels of similar intensity that are readily distinguishable from the intensity of the pixels in the surrounding material. The blob tool recognizes only dark/light or foreground/background separation. A low-threshold blob tool detects the starkest differences in intensity, such as bark ring or holes, which are typically the darkest occurrences on a shingle. A high-threshold blob tool detects small variations in intensity between adjacent pixels, and a medium threshold blob tool detects dark features, such as whole knots. Thus, multiple applications of the logic with blob tools of varying thresholds are necessary to detect the various types of defects that occur: holes, knots with and without bark rings, colors, etc. The pixel locations of intensity variations that rise to the level of the threshold are used to generate a “defect map”, which maps out the boundary of a defect and projects it onto a map of the billet. Data obtained from the boundary pixel locations allow the visual imaging system  500  to ascertain the perimeter, shape and size of a blob. Algorithms stored in the visual imaging system  500  analyze the data and determine whether the detected blob is, in fact, a defect, such as a knot, or simply “noise”. These algorithms are variable, according to the specifications of the particular batch of shingles being processed. For example, some customers want shingles that contain sound knots, others want only clear wood. These parameters may be entered into the control panel, to adjust the grading definitions for the visual imaging system  500 . 
       FIG. 10  illustrates knot defects in a billet, including a sound knot  60  and an unsound knot  62 . A knot is a blob-like dark area surrounded by light wood and readily discernible by blob tools. The knot may have both dark and light areas within the defined blob area, depending on whether it is a sound or an unsound knot. Whole knots generally are detectable by a blob tool using a medium intensity threshold. If the knot is a sound knot  60 , that is, does not have a bark ring, this type of defect results in a reduction in quality grade from, for example, #1 to #2, but does not necessarily require elimination of the material. On the other hand, the unsound knot  62  has a bark ring surrounding the knot. The bark ring will shrink, weather, or degrade over time, to a greater degree than the surrounding wood as it dries, and consequently, the knot is likely to drop out of the shingle. Unsound knots result in either a degration of quality to the lowest grade, or the area of the billet  10 B containing the unsound knot may be deemed to be waste W. As mentioned above, bark rings tend to be extremely dark features and are detectable by a low-threshold blob tool. Analysis of the combined results of low-threshold and medium-threshold blob tools provides a reliable indication whether the knot is sound or unsound, thereby allowing reliable grading of the shingle  10 B. For example, if the visual imaging system  500  determines a knot using the medium threshold blob tool, but then does not find a bark ring using a low threshold blob tool, the knot is deemed a sound knot requiring quality degradation, for example, from grade #1 to grade #2. These grades are by way of illustration only. The grading system is arbitrary, defined by the individual mill management, and the parameters the correlate to grade #1, #2, etc. may be modified to correspond to the specific customer order. 
     The visual imaging system  500  merges the measurements taken by the blob tools onto the two-dimensional defect map, which corresponds in size and shape to the two-dimensional area of the billet. The visual imaging system  500  then post-processes the data on this two-dimensional map to determine which defects or characteristics affect the quality grade of a finished shingle product  10 C and which result in waste W. Using this information, together with an optimization algorithm, the visual imaging system  500  then determines the best possible saw cuts  20  and  21  on the billet  10 B to optimize the value of the finished shingle product  10 C. As shown in  FIG. 10 , for example, the visual imaging system  500  has determined a first saw cut  20 , to trim the outer edge to remove any live edge or round of tree and create a straight edge, and a second saw cut  21 , to eliminate the unsound knot  62  and, again, to cut a straight second outer edge. The section containing the unsound knot  62  is determined to be waste W. The finished shingle  10 C will be processed further on down the production line according to the quality grade determined by the visual imaging system  500 . 
     Some differences in intensity are detectable only with a high threshold blob tool, that is, the difference in intensity is not as stark or the area is not blob-like, as with a knot defect, are also mapped and identified as possible defects.  FIGS. 11A and 11B  illustrate a “shaky wood” defect  70  detected by the visual imaging system  500 . Shaky wood typically has small depressions and holes in the wood, which are visually detectable as small high-contrast changes in intensity. A shingle  10  containing a shaky wood defect  70  is undesirable and frequently deemed waste. The visual imaging system  500  includes a neighborhood image filter tool, which detects such high-contrast changes and which then produces a black-and-white map of such small, high-contrast changes, with the high-contrast changes shown as bright white areas on black. The areas containing such high-contrast changes are shown as brighter than the background, i.e., the surrounding normal wood grain pattern.  FIG. 11B  is a schematic illustration of the enhanced contrast imaging. The data acquired by the neighborhood image filter tool undergoes post-processing and feature detection/This is a loop processing, in which the edges are defined first, and then in a reiterative process first clear wood is defined, then sound knots, then unsound knots, then holes, shaky wood, etc. After steps, the data from this high-contrast map and the post processing are incorporated into the defect map. The defect map now contains data relating to all types of detected defects or wood characteristics that influence the quality grading. The visual imaging system  500  determines the grade and optimal cut of the billet  10 B, based on this defect map. 
     Once the butt-trimmed billet  10 B has gone through detection by the visual imaging system  500 , it is aligned and moved on toward the billet-transition-and-aligning station  400 , described above. The billet  10 B is aligned and pushed by the push-bar  422  out onto the conveyor  330 , in the direction of the gang rip saw station  600 . A third camera  560  scans the upper surface of the butt-trimmed billet  10 B, to determine precisely where the edges of the billet are. The visual imaging system  500  matches and aligns the image from the third camera  560  with the image previously obtained with the first and second cameras  510 A/ 510 B and sends data to a rip-saw controller  630 , in order to control the positioning of saw blades  612  in relation to defects or undesirable characteristics in the billet. 
       FIG. 12  is an illustration of the gang rip saw  610 , which comprises a set of saw blades  612 A- 612 D mounted on an arbor  620 . A gang rip saw controller  630  receives instructions from the visual imaging system  500  as to what areas on the sides of the butt-trimmed billet  10 B are to be trimmed. The individual saws  612  are then shifted along the arbor  620 , so that they are in a position to cut the billet  10 B according to instructions. Referring again to  FIG. 10 , the visual imaging system  500  has determined that cuts  20  and  21  should be made. Two of the saws  612 B and  612 C are moved into position to effect these two cuts. The outer saws,  612 A and  612 D remain beyond the range of the billet  10 B if they are not needed for a cut. The shingle emerging from the gang rip saw station  60  is now a finished shingle  10 C. An example of a gang rip saw that is suitable for this purpose is a gang rip saw from the company [Mereen-Johnson, Model 4300-DCS/SR-4 “Select-a-Rip”. This saw is a conventional saw that has a modified in-feed so as to accept the triangular shape of the shingle and still grip it. Transport means for carrying the billet under the saw blades is a dip chain, a flat segmented approximately 3″ wide chain or belt, with a rubber surface that grabs the billet. 
     The finished shingle  10 C is pushed onto a last section of the conveyor system  300  toward the sorting station  700 . The sorting station  700  includes a series of actuators  760  and a series of containers  720  for collecting the final product or waste. The actuators  760  shown in  FIG. 3B  are push bars, but other suitable means, such as electrically controlled trap doors that open into containers, or chutes with electrically controlled gates, etc. The containers  720  include a conveyor that carries the product or the waste material into a large container. The controller for the sorting station  700  receives data on the approaching shingle  10 C and actuates the appropriate actuator  760 , which forces the finished product  10 C or waste W into the appropriate container. 
     It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the automated shingle milling system may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.