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FIELD OF INVENTION  
       [0001]     The present invention relates to fabrication systems and plants for fabricating extended length lumber. In particular, the present invention relates to fabrication systems and plants for continuously fabricating extended length graded lumber of low quality raw lumber.  
       BACKGROUND OF INVENTION  
       [0002]     In the field of architectural construction, lumber is an important structural material needed in variable grades and lengths for trusses, wall frames and the like. Well known fingerjointing techniques are employed in the lumber industry to provide lumber at lengths independently of the length of the available raw lumber. Fingerjointing is also used to provide lumber substantially without lumber strength degrading elements such as wood eyes, wanes and bents. The grading of the lumber on the other hand is accomplished by well known machinery through which the lumber may be continuously feed. The minimal length of individual finger jointed pieces is determined by method and fabrication system by means of which extended length lumber may be economically feasible mass produced. At the time of this invention, the minimal length of individual finger jointed pieces and consequently the spacing between finger joints of common extended length lumber is down to about 1 foot. As may be well appreciated by anyone skilled in the art with reducing lumber piece length a larger percentage of the raw lumber may be utilized. Lumber utilization becomes increasingly important as strength degrading lumber elements increase. Therefore, there exists a need for a fabrication system that provides for economically feasible fabrication of extended length lumber with spacing between finger joints of less than 1 foot. The present invention addresses this need.  
         [0003]     For environmental benefit it is desirable to utilize low quality raw lumber that may be cut from small diameter tree trunks, which may contribute to preserve old growth and may promote lighter and environmentally less invasive timber harvesting machinery and techniques. Unfortunately, low quality raw lumber has a relatively large percentage of wanes, wood rind, wood eyes, bents and other strength degrading elements that degrade the technical and economic feasibility of low quality raw lumber particularly for fabricating graded structural lumber in common fabrication systems and plants. Nevertheless, low quality raw lumber such as for example well known US No. 2 type utility lumber has a theoretical content of at least 75% of well known 1650 grade and higher. Therefore, there exists a need for a fabrication system and method for continuously fabricating graded extended length lumber with maximum grade utilization of input low quality raw lumber. The present invention addresses also this need.  
       SUMMARY  
       [0004]     An extended length graded lumber fabrication system features a number of fabrication stages along a substantially continuous input-to-output fabrication path providing high through put fabrication of graded lumber of extended length in conjunction with the particularities of low quality raw lumber. The fabrication stages include reject recognition stages, a supply lumber grading stage, a lumber sorting stage with additional graded lumber buffer storage paths diverting off the continuous input-to-output fabrication path, a lumber length extension stage and an extended length grading stage.  
         [0005]     The reject recognition stages may include a lumber appearance inspection and out-sorting stage, a moisture measuring stage and a grain inconsistency scanning stage. At a reject cutout and grade separation stage lumber strength degrading elements rejected in the previous scanning stage are cut out. Lumber segments with different grade ratings are also separated. The reject cutout and grade separation stage is computerized controlled in accordance with grade, grain inconsistency information obtained at their respective stages. Grade sorted nominal and shortened length lumber propagates along secondary and tertiary graded lumber buffer storage paths onto a storage paths switching stage at which buffer storage requirements of the continuously processed supply lumber are dynamically adjusted for a continuous buffer storing and grade selective in-feeding into the continuous input-to out fabrication path immediately prior to the lumber length extension stage.  
         [0006]     At the lumber length extension stage well known finger jointing machinery joints the individual graded and reject cleared lumber pieces into a substantially endless single grade lumber string. Part of the lumber length extension stage may also be a well known finger joint proof loader and a travel saw. The finger joint proof loader tests the finger joints according to well known specific finger joint test criteria, which differ from lumber grading criteria. The travel saw cuts computerized controlled the endless lumber coming from the finger jointer into the final extended length and cuts out failed finger joints as well as grade transitions after a dynamic grade fabrication change in the fabrication system. Due to the lumber grading prior to the lumber length extension stage, grade fluctuations of the endless lumber string are brought to a minimum. In the second lumber grading stage the grade of the extended length lumber is verified in accordance with existing grading requirements at the end of the extended lumber fabrication.  
         [0007]     Well known chord(s) and/or well known web strut(s) of a well known wooden truss joist may be made of the single grade extended length lumber fabricated by fabrication system of the present invention.  
         [0008]     The fabrication system may also feature a reject back insertion path diverting off the continuous input-to-output fabrication path following the travel saw and terminating at begin of the continuous input-to-output fabrication path where the raw lumber is in-feed. The raw lumber, the failed finger joint lumber and grade transition lumber may define together with eventual other scrap lumber like from truss fabrication the supply lumber.  
         [0009]     Two separate well known lumber testing machines are preferably employed at the respective first and second lumber grading stage. Nevertheless, the scope of the invention includes an embodiment in which a single lumber grading machine is employed such that the first and second lumber grading stages coincide. Consequently, the continuous input-to-output fabrication path crosses at the coinciding first and second lumber grading stages.  
         [0010]     Dual lumber grading is highly advantageous in minimizing grade fluctuations in the final extended length lumber. Secondary and tertiary graded lumber buffer storage paths in combination with the automated lumber sorting and buffer storage path switching provide for economic mass production of single grade extended length with finger joint spacing of less than 1 foot down to about 4 inches. The tertiary lumber buffer storage path and the reject back insertion path assist also in increasing fabrication economy by reducing lumber waste. The secondary and tertiary lumber buffer storage paths are parallel to the continuous input-to-output fabrication path with computer controlled switching gates that provide together with buffer storage along the individual paths for real time grade switching during extended length lumber fabrication. In summary, minimized grade fluctuations in the final extended length lumber, extended lumber grade bandwidth, reduced lumber waste and real time grade switching contribute to a maximum utilization of input low quality raw lumber. In addition, dynamic grade transitions are accomplished without interrupting the fabrication flow. This is an important aspect in particular in combination with utilized low quality raw lumber and mass fabricated truss components with grade variations tailored to the well known diverse needs in architectural constructions, 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]      FIG. 1   a  is a schematic prior art figure of standard quality raw lumber samples.  
         [0012]      FIG. 1   b  shows a schematic prior art figure of low quality raw lumber samples as preferably utilized in the present invention.  
         [0013]      FIG. 2  depicts a block diagram of a representative first embodiment of the invention.  
         [0014]      FIG. 3  is a block diagram of a representative second embodiment of the invention.  
         [0015]      FIG. 4  shows a schematic floor plan of a fabrication system according to the block diagram of  FIG. 3 .  
         [0016]      FIG. 5  depicts a schematic wooden truss joist. 
     
    
     DETAILED DESCRIPTION  
       [0017]     For the purpose of general understanding of the present invention in combination with the particularities of low quality raw lumber, prior art  FIGS. 1   a  and  1   b  schematically depict a representative assortment of standard quality lumber SQ and low quality lumber LQ. The standard quality lumber SQ of  FIG. 1   a  may be in minimum grade x along sections LGX. Standard quality lumber SQ has limited number of wood eyes WE and other well known lumber strength degrading elements and/or defects. Certain standards for lumber straightness may also apply to the standard quality lumber SQ  
         [0018]     Low quality lumber LQ depicted in prior art  FIG. 1   b  may be of a length between 1-20 feet, with an increased number of lumber strength degrading elements and/or defects such as, wood eyes WE, rinds RD, wanes WN and other well known grain inconsistencies. Standards for straightness may be also lower than in standard quality lumber SQ. The resulting minimum utilizable grade length LG 1 -LG 4  in a low quality lumber LQ may be down to 4 inches. In case of well known United States No. 2 utility lumber, about 75% of the low quality LQ boards with their grade lengths LG 1 -LG 4  of well known 1650 grade and higher.  
         [0019]     For an economically and technically feasible fabrication of single grade extended length lumber from low quality lumber LQ, certain fabrication steps, stages and paths are introduced in the present invention to account for the particularities of low quality raw lumber LQ. Such particularities may include the minimum utilizable grade length LG 1 -LG 2  of down to 4 inches, as well as larger grade fluctuations.  
         [0020]     As shown in  FIG. 2 , a first embodiment of the invention includes the method steps  10  of providing generic lumber, followed by the step  13  of inspecting lumber pieces for defects and/or insufficiencies. The side step  131  of removing rejected pieces takes place in conjunction with step  13 . Step  13  may include but is not limited to well known visual inspection, well known moisture scanning, and/or well known wood eye scanning. The next step  16  includes initial lumber piece grading into grades A-N and the associated step  162  of associating grade information with the graded lumber pieces. Step  16  and  162  may be performed by a well known lumber grading machine such as the METRIGUARD™ Model 7200 lumber tester. In the consecutive step  22 , the lumber pieces are grade sorted in association with the grade information of step  162 . In conjunction with step  22 , grades B-N lumber pieces are buffer stacked in side step  221 . Following both step  22  and step  221  is step  28  in which grade selective in-feeding of grade A-N lumber pieces is performed followed by step  30  of finger jointing the in-fed grade selected lumber pieces into a single grade A-N endless lumber. The endless lumber is then proof loaded in step  32  and in the associated step  322 , a finger joint failure information is associated with the corresponding endless lumber location. After step  32 , the single grade A-N endless lumber is lengthened into extended length single grade lumber and failed finger joints are removed in step  34 . In a final grading step  36 , the extended length lumber pieces are graded.  
         [0021]     Steps  10 ,  13 ,  16 ,  22 ,  28 ,  30 ,  32 ,  34 ,  36  take place along a substantially continuous input-to-output fabrication path CP along which the lumber is substantially continuously propagating as single pieces and/or in stacks. The step  221  takes place along a secondary graded lumber buffer storage path SP. The secondary graded lumber buffer storage path SP diverts off the continuous input-to-output path CP following step  22  and rejoins the continuous input-to-output fabrication path CP at beginning of step  28 .  
         [0022]     In  FIG. 3 , a second preferred embodiment of the invention includes the method steps  10  of providing generic raw lumber, followed by the step  12  of in-feeding supply lumber pieces including the raw lumber and return in-fed lumber from steps  144  and  342 . After scanning lumber moisture in step  18 , lumber appearance is inspected in step  14  and excess moisture boards are removed in step  142  The side step  141  of removing rejected pieces that did not pass the appearance inspection takes also place in conjunction with step  14 . Appearance inspection is preferably performed by trained personnel. The removed moist lumber may be dried as in step  143  and return in-fed as in step  144 . The repeated appearance inspection of dried lumber warrants that well known excess lumber bending or well known lumber cracking that may occur during drying are recognized and removed. Moisture scanning of step  18  may be accomplished by a well known WAGNER™ Apex Moisture Detector.  
         [0023]     The next step  16  includes initial grading of the supply lumber pieces into grades A-N and the associated step  162  of associating grade information with the graded lumber pieces. Steps  16  and  162  may be performed by a well known lumber grading machine such as the METRIGUARD™ Model 7200 lumber tester. The lumber pieces propagate along the continuous input-to-output fabrication path CP from the initial lumber grading towards the following step  20 , in which the lumber pieces are scanned for grain inconsistencies such as wood eyes WE. The grain inconsistency information is associated with the lumber pieces in associated step  202 . Steps  20  and  202  may be performed by a well known NEWNESS™ Advantage Scanner.  
         [0024]     In the consecutive step  22 , the nominal length lumber pieces grain inconsistency testing are grade sorted in association with the grade information of step  162 . In conjunction with step  22 , grades B-N nominal length lumber pieces are secondary buffer stacked in side step  221 . Nominal length in context with the present invention means the length of the raw lumber without scrap lumber and finger joint failure lumber. The nominal length in a preferred embodiment of the invention is between 2-20 feet. Following both step  22  and step  221  is step  24  in which grain inconsistencies and excess moisture portions M are removed from the lumber pieces. In conjunction with step  241 , grades A-N cut lumber pieces are tertiary buffer stacked in side step  241 .  
         [0025]     Next is step  28  in which grade selective in-feeding of grade A-N lumber pieces is performed followed by step  30  of finger jointing the in-fed grade selected lumber pieces into a single grade A-N endless lumber string. The endless lumber string is then proof loaded in step  32  and in the associated step  322 , a finger joint failure information is associated with the corresponding endless lumber location. After step  32 , the single grade A-N endless lumber string is lengthened into extended length single grade lumber in step  34 . Lumber portions including the failed finger joints and/or grade transitions are removed in the corresponding side step  341 . The cut out lumber portions are kept at a predetermined length for return in-feeding them at step  12  as indicated by step  342 . In a final grading step  36 , the extended length lumber pieces are graded.  
         [0026]     Steps  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38  take place along a substantially continuous input-to-output fabrication path CP along which the lumber is substantially continuously propagating as single pieces and/or in stacks. The step  221  takes place along a secondary graded lumber buffer storage path SP. The secondary graded lumber buffer storage path SP diverts off the continuous input-to-output path CP following step  22  and rejoins the continuous input-to-output fabrication path CP at beginning of step  28 . The step  241  takes place along a tertiary graded shortened lumber buffer storage path TP. The tertiary graded shortened lumber buffer storage path TP diverts off the continuous input-to-output path CP following step  24  and rejoins the continuous input-to-output fabrication path CP at beginning of step  28 . Steps  341  and  342  take place along a reject back insertion path RP diverting off the continuous input-to-output fabrication path CP following step  34  and terminating at beginning of step  12 .  
         [0027]     The schematic floor plan of a preferred embodiment of the fabrication system  200  is shown in  FIG. 4 . Along the substantially continuous input-to-output fabrication path CP propagate lumber pieces of predetermined cross section such as 2 by 4 inches on well known conveyor and/or other transport systems commonly utilized for piecewise and/or stack wise continuous lumber transport. At the begin of the continuous input-to-output fabrication path CP is a multiple lengths supply lumber in-feed stage including a hydraulic break down hoist  2122  and small piece conveyor  2124 . The hydraulic break down hoist  2122  breaks down stacked nominal length lumber that is in-fed via a first fork lift access  2101  and an in-feed deck  2121 . Short length lumber pieces, which may be down to 1 foot length are in-fed into the continuous input-to-output fabrication path CP via a second fork lift access  2102  connecting to the small piece conveyor  2124 .  
         [0028]     After the moisture scanner  218 , a lumber appearance inspection and out-sorting stage may include an inspection deck  214  and a third forklift access  2141 . On the inspection deck, the spread lumber pieces gradually move along in lateral direction at a speed suitable for a preferred visual inspection and manual reject removal by trained personnel. The rejected boards are stacked at the third forklift access  2141  for removal.  
         [0029]     Following the inspection deck  214  is a lateral chain feeder  2161  that redirects the remaining boards into longitudinal propagation direction towards the lumber tester  2162  of a first lumber grading stage, the moisture detector  218  of a moisture measuring stage, and the scanner  220  of a grain inconsistency scanning stage. Then the lumber enters an automated lumber sorter  222  in which the lumber pieces are laid out for further processing and/or out-sorting as part of a nominal length lumber grade sorting stage. From the sorter  222 , a nominal length conveyor  2222  receives nominal length boards grade B-N that have passed the grain inconsistency scanning. The sorter  222  may utilize grade information from the first lumber grader  2162  and grain inconsistency information obtained from the scanner  220  to perform the out-sorting in a computerized controlled fashion. Ink marks imprinted on the lumber in the lumber grader  2162  and/or the scanner  220  may be recognized by well known machine vision systems, which may include a camera. Grade marking may be for example via bar code or color code. Additionally, length information may also be coded onto the shortened length boards. In context with the present invention grade A may be preferably a grade most common for the particular quality raw in-fed lumber. In a representative case of No. 2 utility raw lumber, grade A may be the well known 1650 grade. Hence, the highest capacity throughput directly along the continuous input-to-output fabrication path CP is utilized in the most economic fashion. The nominal length conveyor  2222  terminates at a storage path switching stage in the preferred configuration of a pull table  225  and a turn table  2252 . At the pull table  225  the nominal length boards are manually sorted at secondary pull cart accesses  2225  in single grade stacks. The secondary graded lumber buffer storage path SP, which begins at the secondary pull cart accesses  2225  and terminates at the pull-cart in-feed  2287  may include well known temporary buffer storage locations not shown on the schematic plan.  
         [0030]     Behind the automated lumber sorter  222  is a reject cutout and grade separation saw  224 , from which a short piece conveyor  2242  diverts. A waste bin  2243  that automatically captures the out cut rejected lumber portions is placed along the short piece conveyor  2242 . Also part of the storage path switching stage are tertiary cart accesses  2245 , turn table  2252  and tertiary first fork lift accesses  2246 . Lumber pieces having portions that failed the grain inconsistency scanning and/or have more than one grade LG 1 -LG 4  along their length are computerized controlled diverted towards the saw  224  where the rejected lumber portions are cut out in accordance with the grain inconsistency information and grade lengths LG 1 -LG 4  are separated in accordance with grade information from the supply lumber grader  2162 . The remaining grade A-N shortened length lumber pieces end up on the pull table  225  together with the grade B-N sorted nominal length boards. Employing a storage path switching stage for grade selective sorting of nominal and shortened length boards provides necessary flexibility to adjust to varying grade compositions of the supplied and/or raw lumber. On the pull table  225  boards in the length down to about 2 feet are sorted. On the adjacent turn table  2252 , boards of lengths down to about 6 inches are manually grade sorted stacked on pallets on the tertiary first fork lift accesses  2246  for further fork lift manipulation. The tertiary graded lumber buffer storage paths TP, which begin at the tertiary accesses  2245 ,  2246  and terminate at the in-feeds  2287  and  2280  may include well known temporary buffer storage locations not shown on the schematic plan. The manually operated pull table  225  and turn table  2252  may be substituted by an automatic tables and/or well known robotic equipment as may be well appreciated by anyone skilled in the art  
         [0031]     The remaining grade A nominal length lumber passes through a stacker in-feed  2261 , a stacker  2262  and stack jump roll case  2263 , where it is either directly redirected via a stack cross over rollcase  2281  towards a single grade lumber length extension stage or buffer stored in between an stack out-feed deck  2264  and stack in-feed deck  2283 . Stack out-feed deck  2264  has a forth fork lift access  2265  and the stack in-feed deck  2283  has a fifth fork lift access  2282 .  
         [0032]     Buffer storing of the nominal length grade A lumber may be at a well known buffer storage location (not shown) along the continuous input-to-output fabrication path CP. It may be utilized while grade B-N lumber is in-fed at the grade selective in-feeding stage, which further includes a stack jump rollcase  2284  for alternately receiving nominal length grade A lumber from stack crossover rollcase  2281  or from stack in-feed deck  2283 . Pull cart stacked boards may be manually in-fed from stack in-feed  2287  onto a singulation station at which the lumber may be held back temporarily while single grade shortened pieces are in-fed via sixth fork lift access  2280 , pallet dumper  2289  and spreader conveyor  2288 .  
         [0033]     The lumber sorter  222 , stack jump rollcases  2263 ,  2284 , stack cross over roll case, singulation station  2286  and short piece conveyor  2288  with pallet dumper  2289  are computer controlled switching gates that provide together with buffer storage along the individual paths CP, SP, TP in between the switching gates for real time grade switching with substantially uninterrupted extended length lumber fabrication.  
         [0034]     The grade selective in-fed lumber pieces are transported towards a lumber length extension stage including a well known profile machine where the ends of the lumber pieces are machined for finger jointing. The lumber length extension stage further includes well known components such as an assembler conveyor  2304 , crowder  2305 , curing station  2306 , retarder  2307 , a proof loader  232  and a travel saw  234 . An incline chain deck  2302  and a corner feeder  2303  transport the lumber between the profile machine  2301  and the assembler conveyor  2304 .  
         [0035]     The endless lumber string propagating out of the curing station  2306  passes through the proof loader  232 , where finger joint testing is performed in accordance with well known finger joint test criteria. Finger joint failure information is passed onto the travel saw  234  for a computerized controlled out-cutting of failed finger joints in accordance with the finger joint failure information. Failed finger joint portions as well as grade transitions are kept at a minimum length of preferably about 1 foot for out-sorting at sweep table  2344  and reinsertion via seventh fork lift access  2345  and second fork lift access  2102  via reject back insertion path RP. The travel saw  234  also cuts the endless lumber string into extended length lumber of preferably 66 feet length, which is diverted by the sweep table  2344  towards a second lumber grader  236  and a paddle stacker  2381 . There, the extended length lumber is stacked and transported away via eight fork lift access  2382 . The second lumber grader may be similar to the first lumber grader  2162 .  
         [0036]     In a further embodiment of the invention, a single lumber graded is utilized instead of two lumber graders  2162  and  236 . Consequently, the continuous input-to-output fabrication path CP crosses at the first raw lumber grading stage coinciding with the second extended length lumber grading stage.  
         [0037]     In  FIG. 5 , a wooden truss joist  300  has top chords  301 , bottom chords  302  and web struts  303 . Chords  301 ,  302  and/or struts  303  may be fabricated from extended length graded lumber fabricated as above described and/or in accordance with the above described fabrication system  200 .  
         [0038]     Accordingly, the scope of the invention described in the specification and figures is set forth by the following claims and their legal equivalent:

Summary:
An extended length graded lumber fabrication system features a number of fabrication stages along a substantially continuous fabrication path providing high through put fabrication of graded lumber of extended length from low quality raw lumber. The fabrication stages include reject recognition stages, a supply lumber grading stage, a finger jointing stage and a final grading stage for the extended length lumber. The fabrication system is configured in conjunction with the particularities of low quality raw lumber to minimize grade fluctuations, increase grade bandwidth and minimize raw lumber waste during fabrication of extended length graded lumber, which may be used in wooden truss joists. The use of low quality raw lumber cut from small diameter tree trunks is environmentally beneficial. It contributes to preserve old growth and to use lighter and environmentally less invasive timber harvesting machinery and techniques.