Abstract:
A lumber retrieval method renders a lumber handling system readily adaptable to compensate for irregular floors, an irregular overhead track, and variable station locations. In some examples, the method involves laser scanning the top profile of multiple stacks of lumber, each of which contain boards of a unique size. Based on the scanned profiles and the size of the boards, the method determines and displays the number of boards at each station. In some examples, the system provides a calibration mode that automatically determines the discrete locations of multiple stacks of lumber and compensates for a nonparallel relationship between the track and the floor. In some examples, the scanning and calibration process help determine the quantity of boards at each station.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This present application is a continuation-in-part of U.S. patent application Ser. No. 14/577,779 filed on Dec. 19, 2014; which is a division of U.S. patent application Ser. No. 13/136,922 filed on Aug. 15, 2011 now U.S. Pat. No. 8,960,244; which claims priority to provisional patent application No. 61/402,654 filed on Sep. 2, 2010. This present application also claims priority to provisional patent application No. 62/324,151 filed on Apr. 18, 2016. Each of the aforementioned applications and U.S. Pat. No. 8,960,244 are specifically incorporated herein by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    This provisional patent application generally pertains to material handling and more specifically to the retrieval and delivery of lumber. 
       BACKGROUND 
       [0003]    Various machines and methods have been developed for retrieving individual pieces of lumber or boards stacked at one location and feeding the boards individually to a saw. Examples of such systems are disclosed in U.S. Pat. Nos. 6,379,105 and 6,923,614; each of which are specifically incorporated herein by reference. Additional lumber handling systems are disclosed in U.S. Pat. Nos. 2,730,144; 3,873,000 and 3,952,883; each of which are specifically incorporated herein by reference. A lumber processing system for making prefabricated trusses and panels is disclosed in U.S. Pat. No. 7,950,316; which is specifically incorporated herein by reference. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a schematic diagram showing an example system and method for automatically setting up and calibrating lumber stations for an automatic lumber retrieval system in accordance with the teachings disclosed herein. 
           [0005]      FIG. 2  is a top view similar to  FIG. 1  of U.S. Pat. No. 8,960,244. 
           [0006]      FIG. 3  is a series of diagrams showing a side view of various example systems and methods for automatic lumber retrieval systems in accordance with the teachings disclosed herein. 
           [0007]      FIG. 4  is an assortment of views showing various example systems and methods for automatic lumber retrieval systems in accordance with the teachings disclosed herein. 
           [0008]      FIG. 5  is a series of diagrams showing a side view of various example systems and methods for automatic lumber retrieval systems in accordance with the teachings disclosed herein. 
           [0009]      FIG. 6  is a schematic diagram showing an example system and method for automatically setting up and calibrating lumber stations for an automatic lumber retrieval system in accordance with the teachings disclosed herein. 
           [0010]      FIG. 7  is a schematic diagram similar to  FIG. 6  showing the example system and method for automatically setting up and calibrating lumber stations, wherein the stations are stocked with lumber. 
           [0011]      FIG. 8  is a schematic diagram showing an example method of operation of the automatic lumber retrieval system shown in  FIGS. 6 and 7 . 
           [0012]      FIG. 9  is a schematic diagram showing another example method of operation of the automatic lumber retrieval system shown in  FIGS. 6 and 7 . 
       
    
    
     DETAILED DESCRIPTION 
     Floor/Track Compensation, Define Stations and Monitor Inventory (FIG.  1 ) 
       [0013]      FIGS. 1-5  illustrate examples of a lumber retrieval system  10  and related methods that applies to the systems and methods disclosed in U.S. Pat. No. 8,960,244; which is specifically incorporated herein by reference. Items in  FIGS. 1-9  having the same or similar reference numbers as those found in U.S. Pat. No. 8,960,244 generally correspond to similar or identical items of that patent. 
         [0014]    The illustrated lumber retrieval system  10  enables users to rapidly change lumber station numbers and locations during the course of a day. Another feature covered here is calculating the quantity of boards  16  in each station  310  (e.g., first station  310   a,  second station  310   b,  third station  310   c,  etc.). This information can be used at the start of a job to determine if there is enough lumber in the system to complete a job order  330  ( FIGS. 6 and 7 ) without hand-counting individual boards  16 . This information can also be used during a job to alert the operator (user) that a station  310  is getting low on lumber and allows the operator to prepare more lumber for loading. 
         [0015]    In some examples, stations  310  are set by jogging trolley  36  until a laser dot or laser beam  156  of laser unit  284  is a half-inch past the end point of a station  310 . In some examples, the end point of that station is then defined by a back stop  332  (upright part) of a lumber support  44  (e.g., a cart or rack) or magazine station. The position value at that point is recorded and then manually entered into the corresponding station input box of a controller  162 . This is repeated for each station  310  until all stations are calibrated. The process of positioning the laser dot manually by jogging can be time consuming and might require two persons, one to jog trolley  36  and the other to view its position. In such examples, to reconfigure the system, it is necessary to repeat the manual steps and enter the values. In some examples, the lumber supports  44  or stations  310  must have at least a two-inch gap  334  between the end point of one station  310  and the beginning point of the next station  310 . In some examples, this is defined in software in controller  162  to differentiate between the start of the next station versus a single station with a small gap between boards. 
         [0016]    In addition or alternatively, system  10  accomplishes the aforementioned method automatically via a scanning algorithm used in the board pick up process. In this case, the operator places one or more boards  16  in each desired station  310  with one of the boards  16  against the station&#39;s back stop  332 , as shown in  FIG. 6 . The operator pushing a “Station Scan” button  336  on controller  162  (e.g., on the controller&#39;s touchscreen  188  sends trolley  36  and its laser unit  284  down the full length of the system, thereby locating and recording the end point of each station  310 . When this scan is performed, the lumber in each station  310  must not have any horizontal gaps between boards greater than two inches. In some examples, a valid station location is the end point found when scanning identifies at least a two-inch empty space (no lumber) beyond it. The beginning of any station  310  beyond the currently found station is automatically defined to start two inches beyond the end point of the current station, assuming lumber and an end point is found for the next station. 
         [0017]    Once stations  310  are located and defined, a graphical representation (e.g., image  190 ) of each located station  310  and its overall dimensions are displayed on the operator&#39;s control screen  188 . In some examples, the end point for each station  310  is also displayed. Stations  310  are sequentially numbered by the software. A cross sectional view (image  190 ) of the lumber stack is displayed as defined by a height measurement made by laser unit  284  and a horizontal location for each height measurement based on the encoded trolley/laser position along track  32 . 
         [0018]    At this point, system  10  might not be aware of the size of the individual boards  16  in each station  310  because several boards  16  may be positioned tightly against each other, side-by-side. To set the size, in some examples, the operator selects the graphical representation of an individual station (e.g., via touchscreen  188  or mouse), and a selection box  338  appears with lumber size and description choices. After choosing a size (2×4 for example), the software produces a grid work of rectangles based on the cross sectional size of a 2×4 and overlays the grid onto the displayed view of the lumber stack cross section, thus showing the size and stacked location of individual boards  16 . In this manner each station  310  is rapidly defined and set up. Another variation of this would be to place only one board  16  in each station  310  and let the scanning determine and automatically set the lumber size. This might be useful at initial setup of the machine before quantities of lumber are added. 
         [0019]    Knowing the height, width, shape and size of the lumber allows easily calculating the quantity of boards  16  in each station  310 . One possible problem with calculating the exact height of the lumber stack, however, is that individual stations  310  may vary in elevation because of changes in floor height. The truss, framework or track  32  supporting trolley  36  and laser unit  284  may also bow up or down, which would affect the height measurement of the stack as seen by laser unit  284 . In some examples, compensation for this at machine installation and startup is done by “mapping” the height variation over the length of the system. 
         [0020]    One way to accomplish this would be to place one board  16  in each available station  310  and scan the entire length to record the heights of boards  16  and their horizontal location within the system. This would define the height error over the length of the system as it was installed, taking into account any height variation of floor  340  and track  32 . The resulting “map” is then used to automatically adjust the height readings of lumber stacks in stations  310 , thus allowing the system to correctly calculate the number of boards  16  in each station  310 . Another way to map the system height is to physically measure the height of laser unit  284  to floor  340  (e.g., with a tape measure) at various horizontal locations and input the measured values into software of controller  162  to create a calibration map. 
         [0021]    In some examples, a lumber handling method for retrieving a plurality of boards of various sizes from a plurality of stations supported by a floor is defined as comprising: a trolley carrying a laser scanner over the plurality of stations; the laser scanner scanning the plurality of boards; identifying discrete stations of the plurality of stations based on scanning at least a predetermined gap size between two adjacent stations of the plurality of stations; calculating a floor compensation for a potential variation in floor height of the floor; calculating a trolley compensation for a potential error in a linearity of a travel path of the trolley; calculating a number of boards in a chosen station of the plurality of stations based on a size of a board at the chosen station, a laser-scanned map of the chosen station, the floor compensation and/or the trolley compensation; and providing a notification of when the number of boards in the chosen station decreases to a predetermined lower limit. 
       Trolley Speed Function of Board Weight/Length (FIG.  2 ) 
       [0022]    A lumber delivery machine might present hazards to personnel working nearby and are generally protected with a “light curtain” safety device which senses a person entering a dangerous area of the machine&#39;s operating space. The danger might involve being struck by traveling machine parts or the board which is being transported by machine  10 . The light curtain consists of one or more light beams from an emitter that are monitored continuously by a receiver. Light curtains are well known and commonly used for safety protection. A worker entering the protected zone will break one of the beams and initiate a rapid stop of the machine. This is typically done by disconnecting power to the drive motors and applying a brake to rapidly stop the machine when personnel are detected. The light curtain safety device is located beyond the dangerous area and set back an additional distance to allow the machine to come to a complete stop before the personnel can reach the hazardous movement. The amount of setback is determined by using a safety formula which is accepted by the applicable safety agency or authority having safety jurisdiction. The approach speed of a person and the stopping time of the machine are used in the equation to compute setback requirements. Higher machine speeds increase the stopping time of the machine and accordingly require a larger setback of the light curtain. Larger setbacks, while desirable for safety reasons, usually use valuable plant space and are therefore regarded as unproductive. The tradeoffs between safety light curtain setback (unproductive space) and machine speed (more productivity) are reduced with the present invention. 
         [0023]    Lumber retrieval machine  10  includes trolley  36  and is set up to deliver different sizes of boards  16  from a plurality of stations  310  to a saw  14  or other secondary process. Boards  16  can vary in length from as short as 5 ft to as long as 24 ft. Safety light curtains are setback from the hazard, which may be the end of a 24-ft board or may be the moving trolley  36  of machine  10 , depending on whether a board  16  is being retrieved or whether trolley  36  is returning for another board and is not carrying a board. It can be seen from this explanation that the distance to the safety hazard varies depending on the length of a board being carried and whether a board  16  is even present. This fact allows the trolley travel speed (and hence the stopping distance) to also be variable based on the presence or absence of a board and the board&#39;s length. In some examples, a suitable board length detection system accomplishes this. The detection system could take many forms. One method, for example, would be based on sensors to measure the boards (length, width, thickness, and/or weight) and another would require board measurement input (length, width, thickness, and/or weight) from the sawing process being fed by lumber delivery system  10 . Using this information, the maximum speed is easily calculated and implemented by the processor controlling trolley  36  and lumber delivery system  10 . This allows trolley  36  to travel faster when unloaded or when carrying a shorter or lighter board. 
         [0024]    In some examples, the invention is defined as a lumber handling method of using a trolley  36  for retrieving a board  16  from a plurality of boards of various sizes from a plurality of stations  310  and transferring board  16  toward saw  14 , wherein the lumber handling method comprises: the trolley traveling over at least one station of the plurality of stations while the trolley is carrying the board; the trolley traveling over the at least one station while the trolley is not carrying the board; and limiting a travel speed of the trolley based on at least one of the following: (a) a weight of the board, (b) a length of the board, and (c) whether or not the trolley is carrying the board. 
         [0025]    In some examples, a lumber handling method of using a trolley for retrieving a board from a plurality of boards of various sizes from a plurality of stations and transferring the board toward a saw is defined as comprising: the trolley traveling over at least one station of the plurality of stations while the trolley is carrying the board; the trolley traveling over the at least one station while the trolley is not carrying the board, and limiting a travel speed of the trolley based on at least one of a weight of the board and a length of the board. 
       Independent Dual Head (FIG.  3 ) 
       [0026]    Some examples of lumber retrieval system  10  include a single set of board pickers  184  (for picking up one board  16 ), as shown in Diagram-A of  FIG. 3 . Other examples include two sets of board pickers  184  (for picking up two boards  16  of equal or different size), as shown in Diagram-B of  FIG. 3 . Board picker  184  is schematically illustrated to represent any apparatus capable of lifting board  16  up from a lumber support or stack of lumber. Examples of board picker  184  include, but are not limited to, piercing tools, suction cups, hooks, grippers, etc. The single head version can retrieve a single board  16  in one cycle and deliver it to saw  14  or other process. The double board picking head version can pick up two boards  16  at once and deliver them in a single cycle. In some examples, both use a single vertical pickup axis. Some double board versions are equipped with multiple pick up devices (board picker) on a single head making it capable of lifting two boards simultaneously and delivering them to the process. This speeds the delivery of lumber when compared to the single board version especially in the case of a large system where travel time increases due to the length of travel required. 
         [0027]    The single head version has delivery speed limitations based on delivering only one board per cycle. Some two board versions can improve on the delivery speed, but only under certain circumstances. In some versions, two boards being picked up must lie adjacent to each other. In some examples, the pickup devices for each board are a fixed distance apart making it unsuitable for two boards that are not spaced to match the fixed distance. This limits its use to certain sizes of boards. In such examples, any two boards must be picked up simultaneously which means they must come from the same lumber stack. Because boards in stacks are often skewed it is not possible or desirable to pick up a board on one stack and then lower the first picked board again to pick up from a second stack, as the board being lowered may interfere with the second lumber stack. Requiring the two boards to come from the same stack and hence be the same dimensions is a limitation of such systems. Some end processes, such as sawing, may require different sized boards in the cutting sequence making it undesirable to deliver two like-sized boards at once. A further disadvantage lies in the fact that the double board head must retrieve adjacent boards. Sometimes adjacent boards are not available, as when there is a single board left on a layer. 
         [0028]    The new multiple picking head design, as shown in Diagrams C-G does not have these shortcomings. The construction uses two individual picking heads  184   a  and  184   b,  each with its own vertical axis which can be operated independently. They are mounted to a single trolley  36  and move together in the horizontal direction. The spacing on the two heads  184   a  and  184   b  is wide enough to pick up two wide boards (2″×12″ for example) without interference from each other. Boards  16  can easily be picked up from the same stack of lumber (e.g., from a first stack of lumber  146 ) if like sized boards are required or picked up from two different lumber stacks  146  and  152  to deliver different sized boards. The end process, such as sawing, can now receive unlike boards  16  in sequence and delivered in one cycle. Diagram-C shows head  184   a  picking a first board  16  from one stack, Diagram-D shows head  184   b  picking a second board  16  from another stack, Diagram-E shows both boards  16  being delivered to saw  14 , Diagram-F shows heads  184   a  and  184   b  retrieving a second pair of boards  16 , but this time the two boards  16  are identical and taken from the same stack, and Diagram-G shows trolley  36  delivering both boards  16  to saw  14 . 
         [0029]    A further advantage of the design shown in Diagrams C-G is that if one picking head  184   a  or  184   b  malfunctions, the other head can still be used in a single board per cycle delivery mode to keep the end process supplied with lumber. This design shown in Diagrams C-G is not limited to double picking head design, as any number of picking heads  184  could be added to a single trolley  36  to increase production by delivering multiple boards  16  per cycle. This design would be especially advantageous when feeding multiple saws  14  or processes with one lumber retrieval system. 
         [0030]    In some examples, a lumber handling method of using a trolley for transferring a load toward a saw, wherein the load comprises selectively a first board, a second board, and a combination of both the first board and the second board, the lumber handling method is defined as follows: in a first selected operation, the trolley carrying the first board without the second board toward the saw; in a second selected operation, the trolley carrying the second board without the first board toward the saw; and in a third selected operation, the trolley carrying simultaneously the first board and the second board toward the saw. 
       Selective Crown Orientation (FIG.  4 ) 
       [0031]    This is a description of a system for identifying the existence and direction of crowning in dimensional lumber and orient it correctly before sawing. Crown is a warp or curve that occurs along a narrow edge  302  of a board  16  (i.e., curve about an axis that is perpendicular to the widest face  300  of board  16 ). When lumber is used for the construction of roof trusses  126  or wall panels  128  it might be advantageous to identify the crown direction and orient the crown correctly before cutting it into components. In roof trusses, for example, it might be advantageous to assemble the truss with the convex crowned edge  302  facing upward in the truss. With the present invention, the non-symmetrical angles of the roof truss components are cut after the crown is detected and the lumber is oriented accordingly. This invention detects the crown direction and automatically orients board  16  correctly based on the requirements of the sawing operation. The crown can be introduced to the saw either convex or concave side first, depending on the job requirements. 
         [0032]    This crown responsive system can be incorporated into lumber delivery system  10 . Boards  16  are conveyed laterally on a series of conveyor chains or belts (schematically identified by reference number  306  of  FIG. 4 ). The longest length of the board is perpendicular to the movement of the conveyor. A series of photoelectric sensors  304  are actuated when the leading or trailing edges (e.g., edge  302 ) of board  16  passes over or under them. In some examples, sensors  304  are spaced apart 12″ (more or less depending on the accuracy required) and oriented along the length of a board in a straight line. Controller  162  (e.g., a PLC) captures the photoelectric input from each sensor  304  and records the time of each input as the board passes under or over the sensors. Software evaluates the timing of the inputs and plots the times as a line. The deviation from a straight line is calculated mathematically to determine the amount and direction of crown. Note that the board may be skewed on the conveyor and a perfectly straight board would actuate each sensor sequentially from one end to the other. This does not affect the calculation of the deviation from a straight line when crowned boards are scanned, nor does it affect the calculation for a straight board with no crown. 
         [0033]    After the crown has been detected, a board turning device  305  may be used to reorient the board to the preferred crown direction (if required) to prepare it for sawing. Some systems may not require board turning device  305  to orient the board. Sending the crown direction to certain saws may cause the saw to re-orient the cuts in the components to match the identified crown, therefore producing parts with the desired crowning direction. 
         [0034]    In some examples, a feature incorporated into the software of controller  162  is a self-learning mode. It can be difficult to orient all the photoelectric sensors  304  in a perfectly straight line and keep them straight. Because of this, a simple way to compensate for this has been devised. To calibrate, the operator puts controller  162  into a calibration mode and sends a perfectly straight board  16  through the system. Even though photoelectric sensors  304  might not be in a straight line, controller  162  can detect the curve generated by the straight board and the non-linear sensors and quickly compensate by computing a “map” or correction value for each sensor  304 . This will now be applied to all subsequent calculations to correct for the non-aligned photoelectric sensors  304  until the system is calibrated again. 
         [0035]    In some examples, a lumber handling method of using a trolley for transferring a board from a station toward a saw, wherein the board is warped in either a first direction or a second direction, the lumber handling method is defined as comprising: determining in which direction the board is warped; the trolley transferring the board between the station and the saw; the saw cutting the board; and based on which direction the board is warped, selectively inverting (turn board&#39;s upper face down) or not inverting (leave board&#39;s upper face facing up) the board prior to the saw cutting the board. 
       Main Trolley Plus Shuttle Trolley (FIG.  5 ) 
       [0036]    In some examples, a lumber retrieval system&#39;s delivery speed is limited by the horizontal travel time required to deliver a board to the process and return to the position of the next board. Longer systems containing more lumber stacks are desirable from a quantity and variety standpoint but require longer delivery cycle time. Simply speeding up the travel speed can improve this, but maximum speed is limited by several factors. One factor is the required mechanical construction and electric motor power requirements to accelerate and decelerate the trolley and board combination. The most critical factor is one of safety. High speeds can cause machine damage in a runaway condition, but more importantly, can create danger to personnel. Higher speeds almost always increase emergency stopping time and also increase the severity of injury should an accident occur. Therefore, it is advantageous to operate the retrieval system at lower speeds while still maintaining high board delivery rates to the end process. 
         [0037]    One design to take advantage of low speed movement with high delivery rates uses a lumber shuttle (shuttle trolley  36   b ) to deliver lumber  16  to the process (e.g., saw  14 ) while a main trolley  36   a  and board picking head  184  combination are picking up the next board  16 . In some examples, lumber shuttle  36   b  operates on the same track  32  as the trolley  36   a  and picking head. Trolley  36   a  and shuttle  36   b  are equipped with independent motors and can freely move along track  32 . The lumber shuttle  36   b  is equipped with a lumber receiving device  308  that can transport one or more boards. Boards picked up from one station  310  by the trolley and picking head combination  36   a  are transferred (handed off) to shuttle  36   b  at variable locations on track  32 . Lumber shuttle  36   b  then transports a single board  16  or multiple boards  16  to a board receiving area  316  to feed saw o 14   o  or other process. During the lumber shuttle delivery process, the trolley and picking head  36   a  are free to pick up another board  16 . If the lumber shuttle  36   b  has not returned when the next board  16  is ready to be handed off, trolley  36   b  is directed to move towards the trolley&#39;s receiving/hand-off area  316 . Controller  162  controlling the system calculates the optimal hand off point (based on saving the most time) and directs trolley  36   a  and lumber shuttle  36   b  to meet at that point. If controller  162  determines that no time will be saved with a hand off, the hand off is canceled, and lumber shuttle  36   b  will move out of the trolley&#39;s way to allow trolley  36   a  to complete the delivery to receiving area  316  that, for example, feeds saw  14 . It can be seen that working together in this manner is of great benefit especially if the travel distances involved are long. 
         [0038]    The shuttle system described can receive multiple boards  16  in one hand off or multiple boards in multiple hand offs and deliver them to board receiving area  316 . Another variation of this design includes two separate lumber shuttles  36   b  on opposite sides of trolley  36   a.  Each shuttle  36   b  would feed receiving area  316  for an individual process located at each end of the lumber delivery system. 
         [0039]    In some examples, a lumber handling method of using a main trolley and a shuttle trolley for transferring a board from a station toward a saw, the lumber handling method is defined as comprising: the main trolley conveying the board from the station toward the shuttle trolley; and the shuttle trolley conveying the board from the main trolley toward the saw. 
         [0040]      FIGS. 6-9  show various methods for setting up, calibrating and operating lumber handling system  10 . These illustrations show system  10  comprising a track/trolley system  342 , laser unit  284 , a saw system  314 , controller  162 , and plurality of stations  310 . 
         [0041]    Stations  310  are for supporting a stack of lumber (e.g., first stack  146  and second stack  152 ) each comprising a plurality of boards  16 . In the illustrated example, a first station  310   a  has first stack of lumber  146  comprising a first plurality of boards  144 , and second station  310   b  has second stack of lumber  152  comprising a second plurality of boards  150 . In some examples, the first plurality of boards  144  are of a different size than that of the second plurality of boards  150 . Boards  144 , for example, might be 2×4&#39;s while boards  150  are 2×6&#39;s. 
         [0042]    In another example, boards  144  and  150  might both be 2×4&#39;s but be of different lengths. In still other examples, boards  144  and  150  might be identical in size. In any case, stations  310  provide a supply of boards  16  to be processed by saw system  314 . 
         [0043]    Each station of the plurality of stations  310  comprises at least one of a parking spot  343  on floor  340 , a lumber support  44  (e.g., a cart) on parking spot  343 , and a board  16  on the cart or on some other type of lumber support. In some examples, a station  310  is just parking spot  343 . In some examples, a station  310  is parking spot  343  plus a cart on parking spot  343 , wherein no lumber is on the cart. In some examples, a station  310  is parking spot  343 , a cart on parking spot  343 , and at least one board  16  on the cart. Plurality of stations  310  includes at least first station  310   a  and second station  310   b.  The example illustrated in  FIGS. 6-9  shows the plurality of stations  310  also having third station  310   c  and can actually have many more stations as well. 
         [0044]    Track/trolley system  342  is for retrieving chosen boards  16  from stations  310  and delivering them to board-receiving area  316  that feeds saw  14 . Track/trolley system  342  comprises at least one overhead track  32  and at least one trolley apparatus  36 ′ that travels along track  32 . Trolley apparatus  36 ′ includes one or more trolleys  36 . In some examples trolley apparatus  36 ′ is a single trolley  36  carrying a board picker  184  (e.g., board picker  184   a  and  184   b ) and laser unit  284 . Board picker  184  is schematically illustrated to represent any apparatus capable of lifting board  16  up from a lumber support or stack of lumber. Examples of board picker  184  include, but are not limited to, piercing tools, suction cups, hooks, grippers, etc. In some examples trolley apparatus  36 ′ includes a first trolley for carrying board picker  184  and a separate second trolley for carrying laser unit  284 . In some examples, drive system  272  ( FIG. 2 ) moves trolley apparatus  36 ′ along track  32  in response to an output signal  282  from controller  162 . Controller  162  receives a feedback signal  267  from laser unit  284 . 
         [0045]    Laser unit  284  is primarily for finding the right board from the right station. Laser unit  284  is schematically illustrated to present any device that emits laser beam  156  for sensing a distance between a surface and the laser emitting device. An example of laser unit  284  includes, but is not limited to, a model RF603-260/1250-232-I-IN-AL-CC-3 laser triangulation position sensor provided by Riftek of Minsk, Russia. Input  267  and output  288  schematically represent control communication between controller  162  and laser unit  284 . Upon scanning the upper surface profile of stacks of lumber, laser unit  284  identifies the location of each stack of lumber relative to each other and in relation to board receiving area  316  because controller  162  being in communication with laser unit  284  and a drive system  272  that moves trolley  36  can correlate laser scan readings with the position of the trolley&#39;s board picker  184 . 
         [0046]    Saw system  314  comprises board receiving area  316  and at least one saw  314  for cutting boards to size. Board receiving area  316  is schematically illustrated to represent any structure for receiving boards  16  from trolley apparatus  36 ′ and transferring those boards to saw  14 . Examples of board receiving area  316  include, but are not limited to, a conveyor, a ramp, a chute, a part transfer mechanism, board turning device  305 , and various combinations thereof. Saw  14  cuts the boards received from area  316  to create a kit of cut boards  344  (e.g., pieces  112 ,  114 ,  116 ,  118  and  120 ) that are assembled to create a structural board assembly  127  (e.g., roof truss  126  or wall panel  128 ). In some examples, a plurality of structural board assemblies  127  are grouped as specified in a job order  330  that is entered into controller  162 . Job order  330 , for example, might specify a certain group of structural board assemblies  127  that are intended to be shipped to a particular customer or job site. 
         [0047]    Controller  162  is schematically illustrated to present any electrical device able to provide various outputs in response to various inputs. In response to the inputs, controller  162  controls various components of system  10  including, but not limited to, controlling drive system  272  of trolley system  342 , controlling board picker  184  and various actuators thereof, controlling laser unit  284 , and controlling digital display  188  (e.g., a touchscreen). Examples of controller  162  include, but are not limited to, a single computer, a system of multiple computers, a single PLC (programmable logic controller), a system of multiple PLCs, various combinations of one or more computers and PLCs, and various combinations of computers, PLCs, sensors, laser units, switches, touchscreens, relays, etc. A specific example of controller  162  is a model CP6201-0001-0200 industrial computer by Beckhoff of Verl, Germany. 
         [0048]    The lower portions of  FIGS. 6 and 7  show a basic flow chart or algorithm that illustrates some example data processing functions of controller  162 . In many cases, these data processing functions are part of some example lumber handling methods that pertain to lumber handling system  10 . At least one such lumber handling method and system will now be further described with reference to the drawing figures. 
         [0049]      FIGS. 2 and 6-9  illustrate carrying laser unit  284  above and over the plurality of stations  310  via trolley apparatus  34 ′ of track/trolley system  342 , wherein track/trolley system  342  comprises trolley apparatus  36 ′ and track  32  along which trolley apparatus  36 ′ travels. Arrow  346  of  FIG. 6  represents trolley apparatus  36 ′ moving laser beam  156  over stations  310 , which illustrates determining a plurality of floor-to-track error values  348  (e.g., plurality of laser calibration readings  348   a  or a plurality of vertical distance readings  348   b ) that vary based on floor  340  and track  32  deviating from being parallel to each other. Example means for measuring the track-to-floor deviations or error values  348  include, but are not limited to, laser scanning the height of a certain lower target point  350  on each cart, laser scanning a single board  16  on each cart, and manually measuring  355  a vertical distance  352  from some upper reference point  354  on trolley apparatus  36 ′ to lower target point  350  of each cart (or to lower target point  350 ′ on a single board  16  or to lower target point  350 ″ on floor  340 ). Arrow  360  illustrates recording the plurality of floor-to-track error values  348  on controller  162 . 
         [0050]    In some examples, a laser calibration reading is a substantially vertical distance of the laser beam between the laser unit and a laser beam obstruction. In some examples, the laser calibration reading is measured directly by the laser unit. A vertical distance reading is a manually measured, substantially vertical distance from an upper reference point (e.g., face of the laser unit, fixed point on the frame of the trolley apparatus, etc.) to a lower target point (e.g., floor itself, frame of the cart, a board resting on the cart, etc.), wherein the upper reference point is substantially fixed vertically relative to the laser unit, and the lower target point is directly below the upper reference point 
         [0051]    Arrow  362  of  FIG. 7  represents scanning the plurality of stations  310  with laser unit  284  as trolley apparatus  36 ′ carries laser unit  284  over the plurality of stations  310  during a normal operating period. The normal operating period is when laser unit  284  repeatedly scans stations  310  for the purpose of finding a board  16  to be retrieved from the right station  310  and for monitoring the number of boards at each station  310 . Arrow  364  represents recording a plurality of lumber scanned readings  366  via controller  162  as a result of scanning the plurality of stations  310  during the normal operating period. Block  368  represents calculating a plurality of error-compensated readings  370  via controller  162  based on a comparison or difference of lumber scanned readings  366  and the plurality of floor-to-track error values  348 . 
         [0052]    The top portion of  FIG. 7  shows storing first stack of lumber  146  at first station  310   a,  wherein first stack of lumber  146  comprises the first plurality of boards  144  each of a first board size  371  (e.g., 2×4). Arrow  372  represents entering first board size  371  into controller  162 . The top portion of  FIG. 7  also shows storing second stack of lumber  152  at second station  310   b,  wherein second stack of lumber  152  comprises the second plurality of boards  150  each of a second board size  374  (e.g., 2×6) that is distinguishable from first board size  371 . Arrow  376  represents entering second board size  374  into controller  162 . 
         [0053]    Block  378  represents controller  162  calculating a first quantity of boards  380  of first plurality of boards  146  based on the plurality of error-compensated readings  370  and first board size  371 . Readings  370  identify a fairly accurate cross-sectional area of each stack of lumber, and dividing that by the cross-sectional area of a single board provides the number of boards in that stack. Block  382  represents controller  162  calculating a second quantity of boards  384  of second plurality of boards  150  based on the plurality of error-compensated readings  370  and second board size  374 . 
         [0054]    In  FIG. 8 , arrows  386  illustrate track/trolley system  36 ′ carrying a first board  16  along a trolley travel direction  388  from first station  310   a  to board-receiving area  316 , wherein first station  310   a  is between second station  310   b  and board-receiving area  316 . Trolley travel direction  388  is substantially parallel to track  32 . Arrows  390  of  FIG. 9  represents track/trolley system  36 ′ carrying a second board  16  along trolley travel direction  388  from second station  310   b,  over first station  310   a,  and to board-receiving area  316 . Arrow  392  of  FIGS. 2, 8 and 9  represents transferring boards  16  from board-receiving area  316  to saw  14 . 
         [0055]      FIG. 6  illustrates an example laser-scanning method for automatically calibrating system  10  to compensate for floor  340  and track  32  deviating from parallel alignment with each other. The trolley&#39;s travel movement, as indicated by arrow  362 , and laser beam  156  detecting lower target point  350  (e.g., point  350  on the cart or point  350 ′ on a single board  16  or point  350 ″ on floor  340 ) at each station  310  represents scanning the plurality of stations  310  with laser unit  284  as trolley apparatus  36 ′ carries laser unit  284  in the trolley travel direction  388  over stations  310  during a calibration period ( FIG. 6 ) that occurs before the normal operating period ( FIG. 7 ). Upon scanning  362  the plurality of stations  310  during the calibration period, controller  162  records a plurality of laser calibration readings  348   a  that vary as a result of floor  340  and track  32  deviating from being parallel to each other. 
         [0056]    Alternatively,  FIG. 6  illustrates an example manual means for calibrating system  10  to compensate for floor  340  and track  32  deviating from parallel alignment with each other. The trolley&#39;s travel movement, as indicated by arrows  362  and  388  and dimension  350  or  352 ′ extending from an upper point  354  on trolley apparatus  36 ′ to lower target point  350 ,  350 ′ or  350 ″ represents selectively positioning trolley apparatus  36 ′ to a plurality of locations along trolley travel direction  388 . Tape measure  355  and dimension  352  (alternatively dimension  352 ′) represents manually measuring a plurality of vertical distance readings from upper reference point  354  to lower target point  350  (or point  350 ′ or point  350 ″) at each station  310 , and doing so during a calibration period ( FIG. 6 ) that occurs before the normal operating period ( FIG. 7 ), wherein upper reference point  354  is substantially fixed vertically and horizontally relative to laser unit  284 , and lower target point  350  (or point  350 ′ or point  350 ″) is substantially directly underneath upper reference point  354  when vertical distance  352  is measured. Lower target point  350  (or point  350 ′ or point  350 ″) is substantially fixed horizontally with reference to upper reference point  350  (at the time of manual measurement), and lower target point  350  is at a substantially fixed vertical distance from floor  340  at a localized area  394  directly beneath lower target point  350 . Arrow  396  represents manually entering the plurality of vertical distance readings  352  into controller  162 , wherein readings  352  vary as a result of floor  340  and track  32  deviating from being parallel to each other, and the plurality of floor-to-track error values  348   b  are determined based on the plurality of vertical distance readings  350 . 
         [0057]    Arrow  362  and the various positions of trolley apparatus  36 ′, as shown in  FIG. 7 , represents scanning the plurality of stations  310  at least once with laser unit  284  as trolley apparatus  36 ′ carries laser unit  284  over the plurality of stations  310 .  FIG. 2  shows controller  162  creating an elevation profile map  164  of the plurality of stations  310  in response to laser unit  284  scanning the plurality of stations  310 . Laser beam  156 ′ shown in  FIG. 6  and/or  FIG. 7  represents detecting a gap  334  exceeding a predetermined width between first station  310   a  and second station  310   b  by scanning the plurality of stations  310  with laser unit  284 . Section  398  of digital image  164  represents controller  162  noting the location of gap  334  and defining a relative location of first station  310   a  and/or second station  310   b  relative to each other based on the location of gap  334 . Controller  162  noting a location of gap  334  means that controller  162  at least temporarily records, stores or pays particular attention to the location of gap  334 . 
         [0058]    In some examples, gap  334  is detected automatically by laser unit  284  and controller  162 . In other examples, gap  334  is detected with the assistance of a worker observing when laser beam  156  enters gap  334 . For instance, in some examples, detecting gap  334  exceeding a predetermined width is achieved through a manual visual observation  400  of laser unit  284 , trolley system  36 ′, and/or laser beam  156 ′ as laser unit  284  scans the plurality of stations  310 . Arrow  402  of  FIG. 6  and  FIG. 7  represents manually entering the location of the gap into controller  162 . 
         [0059]    Arrow  404  of  FIGS. 6 and 7  represents defining a job order  330  that specifies making a certain set of structural board assemblies  127  of a predetermined quantity. For example, a job order  330  might specify making ten roof trusses  26  and four wall panels  128 . Arrow  404  also represents entering job order  330  into controller  162 . Block  406  represents controller  162  determining whether the first plurality of boards  144  and the second plurality of boards  150  are of sufficient quantities to satisfy the requirements of job order  330 . Lights  408  (e.g., lights  408   a,    408   b  and  408   c ) serve as an alert that identifies which if any stations  310  have an insufficient quantity of boards for job order  330 . In the example illustrated in  FIG. 7 , lights  408   b  and  408   c  indicate that stations  330   b  and  330   c  need more boards. In some examples, lights  410  (e.g., lights  410   a,    410   b  and  410   c ) serve as a notice that identifies which of the plurality of stations  310  will most likely need to be replenished first based on the current and upcoming job orders and the quantity of boards in the various stacks of lumber. In the illustrated example, light  410   b  indicates second station  310   b  will be the first needing to be replenished, even though third station  310   c  has fewer boards. 
         [0060]    In some examples, when the actual board size of a stack of lumber is known, digital profile  164  can be enhanced to create a digital image showing not only the outline or elevation profile map of the stack but also showing individual boards within the stack. The lower portion of  FIG. 7  shows screen  188  of controller  162  displaying a first image  190   a  depicting first stack of lumber  146  based on the elevation profile map  164  and the first board size, wherein first image  190   a  shows a first plurality of individual boards within the first stack of lumber  146 . Likewise, controller  162  displays a second image  190   b  depicting the second stack of lumber  152  based on elevation profile map  164  and the second board size, wherein second image  190   b  shows a second plurality of individual boards within the second stack of lumber  152 . 
         [0061]    In  FIG. 2 , arrows  412  and  414  are examples illustrating saw  14  cutting at least a first board  112  and a second board  114  to create a kit of cut boards  314 . Arrows  122  represent assembling the kit of cut board  314  to create a structural board assembly  127 . 
         [0062]    The laser scanning process shown in  FIG. 6  illustrates determining the first board size (board width) by scanning a first individual board  16  of the first plurality of boards  144 , and determining the second board size (board width) by scanning a second individual board  16  of the second plurality of boards  150 . The board size is determined based on how far trolley apparatus  36 ′ travels from a front edge of the board to the back edge of the board. In some examples, the board&#39;s vertical thickness is assumed to be a nominal two inches (e.g., about 1.5 inches). 
         [0063]    Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of the coverage of this patent application is not limited thereto. On the contrary, this patent application covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.