Abstract:
A lumber sorter using a conveyor system with hooks that pick up, move and drop lumber. The lumber sorter includes limiters attached to the hooks that restrict the rotation of the hooks while the limiters are running in raceways. The limiters restrict the rotation of the hooks between a first and second orientation through the use of opposing contact points that contact with opposing walls of the raceways. The limiters maintain the hooks in a substantially vertical position while they carry lumber, but permit the hooks to be pivoted to drop the lumber at a designated position. The use of limiters having first and second contact points allows for the pivot direction and degree of rotation to be configurable and predetermined by the position and placement of the contact points.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     MICROFICHE APPENDIX 
     Not Applicable. 
     TECHNICAL FIELD 
     This invention relates lumber sorters for use in the lumber industry and more particularly a pivot hook limiter for use in a lumber sorter. 
     BACKGROUND 
     Lumber sorters are used in sawmills to sort lumber as it is produced from timber stock which is introduced into the sawmill to be cut into board lengths. During the course of processing of the timber stock into board lumber, various lengths of board lumber are produced from the timber stock of varying widths, thicknesses and lengths. To facilitate processing of like dimensioned board lumber, one or more of the dimensions of width, thickness or length of the board lumber are used for sorting. For example, certain dimensioned board lumber can be selected for processing into 8 foot 2×4&#39;s and this lumber can be sorted into a common bin or group of bins. The sorting of board lumber after initial cutting is generally carried out on an automated basis by a bin lumber sorting system. A bin lumber sorting system has a plurality of open topped bins to receive board lumber. The lumber to be sorted is provided to the bin lumber sorting system on a feed conveyor where it is transferred to a sorting conveyor. The sorting conveyor delivers the lumber to a target open topped bin to carry out the sorting process. In the bin lumber sorting system, it is the sorting conveyor that moves the lumber across a plurality of upwardly open bins to the open topped bin that is targeted to receive selected boards matching the dimensional parameters assigned to that bin. A typical bin lumber sorting system may include anywhere from tens to several hundreds of bins to receive the board lumber to be sorted. 
     There are existing board and lumber transport devices for transporting lumber to sorting bins that rely on a sorting conveyor system for example, a J-hook sorter, a push lug sorter, or a drag chain sorter. 
       FIG. 1  is a side elevation view of a portion of a lumber sorter known, for example, from Canadian patent application number 2,383,558 published on 2003-10-26, showing a portion of a feed conveyor  10  and a sort conveyor  20 . Feed conveyor  10  delivers pieces of board lumber  12  along an upper surface  14 , which may be, for example, a rail or a chain. Pieces of board lumber  12  are ambulated along upper surface  14  at predetermined intervals determined by the spacing of lugs  16  on upper surface  14 . Upper surface  14  advances dependent on rotation of pulley  18  in a clockwise direction, which results in transport of pieces of board lumber  12  along upper surface  14  toward pulley  18 , which may be a sprocket. Sort conveyor  20  obtains pieces of board lumber  12  from feed conveyor  10 . Sort conveyor  20  has a pulley  22 , which may be a sprocket, which rotates in a counter-clockwise direction to move a belt  34  (which may be a flexible belt or a chain, as desired) around the periphery of pulley  22  and in the direction of arrow  24 . Hooks  26  are pivotally connected to belt  34  and are conveyed along with belt  34 . As successive hooks  26  of sort conveyor  20  move laterally in approach to pulley  22 , hooks  26  are supported in an inverted position by resting on support guide  28 . Support guide  28  ends near pulley  22  permitting each hook  26  passing in the region between the end of support guide  28  and pulley  22  to rotate about pivot  30  to move hook shoulder  31  toward stop  32  of pulley  22 . As the belt  34  conveys each hook  26  around the periphery of pulley  22 , stop  32  restrains the rotation of each hook  26  to orient hook an opening  43  of each hook towards feed conveyor  10  in preparation to transfer pieces of board lumber  12  from supply conveyor  10  to the sort conveyor  20 . 
     The transfer of pieces of board lumber  12  from feed conveyor  10  to sorting conveyor  20  occurs in the transfer region where the two conveyors overlap. To transfer pieces of board lumber  12 , the distal end  36  of hook  26  is positioned below the upper surface  14  of the feed conveyor  10 . When the hook  26  has reached a transfer point, hook  26  rotates about its pivot  30  to permit a support arm of hook  26  to descend below and pass beneath a piece of board lumber  12  on feed conveyor  10  in the direction of arrow  38 . In this manner, lugs  16  and distal ends  36  of each of the hooks  26  define a transfer area for the pieces of board lumber  12  to be transferred from the feed conveyor  10  to the sorting conveyor  20 . 
     Support guide  28  supports hooks  26  and belt  34  while they travel along the top run of sort conveyor  20 . Support guide  29  supports hooks  26  and belt  34  as they travel along the bottom run of sort conveyor  20 . While a hook  26  is travelling along support guide  29 , it is free to rotate about pivot  30  and may rotate an undesirable amount. Undesirable excess rotation may cause improper functioning of the lumber sorter. 
     An apparatus for limiting the rotation of the hook is desired. 
     SUMMARY 
     Aspects of the present invention provide techniques for limiting the rotation of hooks within a lumber sorter through the use of a limiter. 
     One aspect of the present invention provides a lumber sorter having a belt running on a pair of opposed pulleys and a plurality of hooks pivotally connected to the belt, the lumber sorter comprising a raceway defined by a pair of vertically opposed walls separated by a predetermined distance and a respective limiter rigidly coupled to each hook, each limiter comprising first and second contact elements for engaging the walls of the raceway so as to thereby limit rotation of the hook to a range between a first orientation that is substantially orthogonal to the belt and a second orientation that is substantially parallel to the belt. 
     In one embodiment, the limiter is a rectangular block having one pair of diagonally opposed straight edges, and wherein the first contact element is a first one of the pair of diagonally opposed straight edges of the block and the second contact element is a second one of the diagonally opposed pair of straight edges of the block. 
     In another embodiment the lumber sorter has a respective positioning member associated with each pulley for guiding the limiter into the raceway in a select one of the two orientations such that when the positioning member releases the assembly, the assembly will counter-rotate under gravity to the other of the two orientations. 
     The above techniques can be implemented to control the rotation of hooks in a lumber sorter and thereby alleviate shortcomings of known lumber sorters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Representative embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: 
         FIG. 1  is a side elevation diagram of an acquisition end portion of a known lumber sorter; 
         FIG. 2  is a side an elevation diagram of a hook and limiter assembly in a raceway usable in the present invention; 
         FIG. 3A  is another side elevation diagram of six hook and limiter assemblies travelling counter-clockwise around a pulley in a conveyor system usable in the present invention; and 
         FIG. 3B  is a continuation of  FIG. 3A  showing a side elevation diagram of six hook and limiter assemblies travelling counter-clockwise around a pulley in a conveyor system usable in the present invention. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     In general, the present invention extends the techniques of prior lumber sorting systems by employing a limiter connected to a hook to limit the rotation of the hook while the limiter is within a raceway. 
       FIG. 2  is a side elevation view of a portion of a representative embodiment of a sort conveyor  21  of a lumber sorter constructed in accordance with principles of the present invention, showing generally a hook and limiter assembly in a raceway. Sort conveyor  21  has a hook  26  for picking up, moving and dropping pieces of board lumber. Hook  26  has a head portion  27 , a distal end  36  and an opening  43 . Hook  26  has a carrying portion  5  for carrying pieces of board lumber. Hook  26  is pivotally connected to a belt  34  at a pivot  30  such that it can rotate with respect to belt  34 . Also connected to hook  26  is a limiter  80  which is connected to hook  26  about pivot  30 . Hook  26  and limiter  80  form an assembly  81 . Limiter  80  is shown running within a raceway  90  which is comprised of an upper wall  92  and a lower wall  94 . Raceway  90  may be provided as an elongate channel defined by the vertically opposed upper wall  92  and lower wall  94 . The distance between upper wall  92  and lower wall  94  is predetermined according to the shape and/or size of limiter  80 . Limiter  80  will have at least one dimension that is longer than the distance between upper wall  92  and lower wall  94  to impede rotation of limiter  80  within raceway  90 . 
     In the embodiment shown in  FIG. 2 , limiter  80  is a block with a first contact element  82 , a second contact element  84 , a first rounded edge  86  and a second rounded edge  88 . First contact element  82  and second contact element  84  are positioned apart from each other at a distance that is greater than the width of raceway  90  as formed by upper wall  92  and lower wall  94 . In operation, limiter  80  can rotate within raceway  90  upon rounded edges  86 ,  88  until first contact element  82  and second contact element  84  contact raceway walls  92 ,  94 . Continued rotation is arrested because the width formed by first and second contact elements  82 ,  84  is greater than the width of raceway  90  as formed by walls  92 ,  94 . In the embodiment shown in  FIG. 3 , first contact element  82  and second contact element  84  restrain limiter  80  from rotating clockwise, but do permit counter-clockwise rotation if force is applied to counter-act gravity. Because hook  26  is connected to limiter  80  to form assembly  81 , assembly  81 , and therefore hook  26 , are also limited in their rotation accordingly. 
     Alternative embodiments permit different configurations of the degree of rotation of limiter  80  within raceway  90  by, for example, altering the location of contact elements  82 ,  84 . For example, the rotation of limiter  80  within raceway  90  may be reduced below 90 degrees by including a lug (not shown) on limiter  80  between first contact element  82  and second rounded edge  88  and between second contact element  84  and first rounded edge  86 . In this embodiment the lugs become alternate contact elements that meet walls  92 ,  94  of raceway  90  and restrict continued rotation before limiter  80  has rotated 90 degrees. 
     Another alternative embodiment has a limiter that is not comprised of a block. For example, first and second contact elements  82 ,  84  may be pegs (not shown) or ends of a rigid elongate member (not shown). The pegs or ends of the rigid elongate member limit the continued rotation of limiter  80  once they contact walls  92 ,  94  of raceway  90  because they are spaced apart at a distance that is greater than the separation between walls  92 ,  94 . 
       FIG. 3A  is another side elevation diagram of a portion of sort conveyor  21  constructed in accordance with the principles of the present invention showing generally six hook and limiter assemblies  81  travelling counter-clockwise around a pulley  22  in the direction of arrows  24 . The operation of limiters  80  in sorting pieces of board lumber is described with reference to the assemblies  81  shown in the diagram, proceeding counter-clockwise from assembly  81   a  through to  81   f.    
     Assembly  81   a  is travelling within raceway  90   a  in a first orientation. First contact element  82   a  is in contact with upper wall  92   a  and second contact element  84   a  is in contact with lower wall  94   a , preventing the downward rotation of distal end  36   a  under gravity. First contact element  82   a , upper wall  92   a , second contact element  84   a , lower wall  94   a  and gravity maintain assembly  81   a  in the first orientation relative to belt  34 . The application of pivotal force to assembly  81   a  in a counter-clockwise direction rotates  81   a  in a counter-clockwise direction up to about 90 degrees, until first contact element  82   a  meets lower wall  94   a  and second contact element  84   a  meets upper wall  92   a , at which point further counter-clockwise rotation is impeded and a clockwise rotation will be effected by gravity once the applied force ceases. 
     Assembly  81   b  is exiting from raceway  90   a  in the first orientation. As assembly  81   b  exits raceway  90   a  first contact element  82   b  and second contact element  84   b  come out of contact with the walls of raceway  90   a . As assembly  81   b  exits raceway  90   a , lug  100   b , which is connected to pulley  22 , rotates into contact with head portion  27   b . The rotation of assembly  81   b  under gravity is impeded by the contact between lug  100   b  and head portion  27   b  such that assembly  81   b  is maintained in the first orientation relative to belt  34 . 
     Assembly  81   c  is rotating along the periphery of pulley  22  in the first orientation. As assembly  81   c  rotates along the periphery, lug  100   c  rotates with pulley  22  and maintains contact with head portion  27   c . The rotation of assembly  81   c  under gravity is impeded by the contact between lug  100   c  and head portion  27   c  such that assembly  81   c  is maintained in the first orientation relative to belt  34 . 
     Assembly  81   d  is continuing to rotate along the periphery of pulley  22  such that limiter  80   d  is being guided to entry within raceway  90   b  in the first orientation. Lug  100   d  ensures that assembly  81   d  is in the proper orientation as limiter  80   d  enters raceway  90   b . The rotation of assembly  81   d  under gravity is impeded by the contact between lug  100   d  and head portion  27   d  such that assembly  81   d  is maintained in the first orientation relative to belt  34  and is in a suitable orientation for the entry of limiter  80   d  within raceway  90   b . As lug  100   d  guides limiter  80   d  into raceway  90   b , first contact element  82   d  and second contact element  84   d  come into contact with lower wall  94   b  and upper wall  92   b  respectively. 
     Assembly  81   e  is travelling within raceway  90   b  in the first orientation and has just been released from contact between head portion  27   e  and lug  100   e . First contact element  82   e  is in contact with lower wall  94   b  and second contact element  84   e  is in contact with upper wall  92   b . Upon release by lug  100   e , assembly  81   e  rotates clockwise about 90 degrees under gravity on rounded edges  86   e ,  88   e  to the second orientation, as indicated by arrow  110 . 
     Assembly  81   f  is travelling within raceway  90   b  and has just rotated clockwise about 90 degrees under gravity along the direction of arrow  110  to a second orientation. First contact element  82   f  is in contact with upper wall  92   b  and second contact element  84   f  is in contact with lower wall  94   b , preventing the continued clockwise rotation of assembly  81   f  beyond the second orientation. First contact element  82   f , upper wall  92   b , second contact element  84   f , lower wall  94   b  and gravity maintain assembly  81   f  in the second orientation relative to belt  34 . The application of pivotal force to assembly  81   f  in a counter-clockwise direction rotates  81   f  in a counter-clockwise direction up to about 90 degrees, until second contact element  84   f  meets upper wall  92   b  and first contact element  82   f  meets lower wall  94   b , at which point further counter-clockwise rotation is impeded and a clockwise rotation will be effected by gravity once the applied force ceases. 
       FIG. 3B  is a continuation of  FIG. 3A  showing another portion of sort conveyor  21  constructed in accordance with the principles of the present invention showing generally six hook and limiter assemblies  81  travelling counter-clockwise around a pulley  23  in the direction of arrows  24 . The operation of limiters  80  in sorting pieces of board lumber is described with reference to the assemblies  81  shown in the diagram, proceeding counter-clockwise from assembly  81   g  through to  81 L. 
     Assembly  81   g  is travelling within raceway  90   b  in the second orientation. First contact element  82   g  is in contact with upper wall  92   b  and second contact element  84   g  is in contact with lower wall  94   b , preventing continued rotation under gravity. First contact element  82   g , upper wall  92   b , second contact element  84   g , lower wall  94   b  and gravity maintain assembly  81   g  in the second orientation relative to belt  34 . The application of pivotal force to assembly  81   g  in a counter-clockwise direction rotates  81   g  in a counter-clockwise direction up to about 90 degrees, until second contact element  84   g  meets upper wall  92   b  and first contact element  82   g  meets lower wall  94   b , at which point further counter-clockwise rotation is impeded and a clockwise rotation will be effected by gravity once the applied force ceases. 
     Assembly  81   h  is exiting from raceway  90   b  in the second orientation. As assembly  81   h  exits raceway  90   b  first contact element  82   h  and second contact element  84   h  come out of contact with the walls of raceway  90   b . As assembly  81   h  exits raceway  90   b , lug  100   h , which is connected to pulley  23 , rotates into contact with head portion  27   h . The rotation of assembly  81   h  under gravity is impeded by the contact between lug  100   h  and head portion  27   h  such that assembly  81   h  is maintained in the second orientation relative to belt  34 . 
     Assembly  81   i  is rotating along the periphery of pulley  23  in the second orientation. As assembly  81   i  rotates along the periphery, lug  100   i  rotates with pulley  23  and maintains contact with head portion  27   i . The rotation of assembly  81   i  under gravity is impeded by the contact between lug  100   i  and head portion  27   i  such that assembly  81   i  is maintained in the second orientation relative to belt  34 . 
     Assembly  81   j  is continuing to rotate along the periphery of pulley  23  in the second orientation such that limiter  80   j  is being guided to entry within raceway  90   a . Lug  100   j  ensures that assembly  81   j  is in the proper orientation as limiter  80   j  enters raceway  90   a . The rotation of assembly  81   j  under gravity is impeded by the contact between lug  100   j  and head portion  27   j  such that assembly  81   j  is maintained in the second orientation relative to belt  34  and is in a suitable orientation for the entry of limiter  80   j  within raceway  90   a . As lug  100   j  guides limiter  80   j  into raceway  90   a , first contact element  82   j  and second contact element  84   j  come into contact with lower wall  94   a  and upper wall  92   a  respectively. 
     Assembly  81   k  is travelling within raceway  90   a  in the second orientation and has just been released from contact between head portion  27   k  and lug  100   k . First contact element  82   k  is in contact with lower wall  94   a  and second contact element  84   k  is in contact with upper wall  92   a . Upon release by lug  100   k , assembly  81   k  rotates counter-clockwise about 90 degrees under gravity on rounded edges  86   k ,  88   k  to the second orientation, as indicated by arrow  111 . 
     Assembly  81 L is travelling within raceway  90   a  and has just rotated counter-clockwise about 90 degrees under gravity along the direction of arrow  111  to the first orientation. First contact element  82 L is in contact with upper wall  92   a  and second contact element  84 L is in contact with lower wall  94   a , preventing the continued counter-clockwise rotation of assembly  81 L beyond the first orientation. First contact element  82 L, upper wall  92   a , second contact element  84 L, lower wall  94   a  and gravity maintain assembly  81 L in the first orientation relative to belt  34 . 
     As shown in  FIGS. 3A and 3B , gravity is used to transition assembly  81  from one orientation to the other. Between transitions, limiter  80 , raceway walls  92 ,  94  and lug  100  cooperate to maintain the assembly  81  in its current orientation. Before it is transitioned, assembly  81  is moved from one raceway to another while held by a lug to restrain its rotation relative to the belt. Once assembly  81  has been moved to the other raceway, it is released by the lug allowing gravity to transition assembly  81  to the other orientation. The transition from the first orientation to the second orientation allows hook  26  to pick up pieces of board lumber from a feed conveyor. This arrangement allows for assembly  81  to be rotated to a dropping position by diverter lug  42  and counter-rotated by gravity to a resting, or carrying, position and no further. 
     In the foregoing description, assembly  81  rotates from one orientation to the other under the force of gravity. However, this is not essential. If desired, mechanical means may be used to force rotation of the assembly  81 , either acting with or against the force of gravity. 
     Now that the invention has been described, numerous modifications, substitutions and mechanical equivalents will occur to those skilled in the art. The invention is not limited to the preferred embodiments described herein with reference to the described drawings, but is defined in the claims appended hereto.