Abstract:
Discloses apparatus for sorting board lumber at a sawmill. The lumber sorter has a sort conveyor with equidistantly spaced hooks pivotably attached around the length of the conveyor. The hooks have an arcuate support arm and pivot to receive and to release lumber onto and off of the sort conveyor. The support surface of the hook is arranged to increase in distance from the pivot point when the hook is deflected to release the board lumber that it carries, facilitating lumber release with minimal consequential movement or rotation of the lumber caused by the release deflection of the hook.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to the lumber industry and more particularly to lumber sorters used to sort lumber, for example work in process lumber product, or stick placer stick product at a lumber sawmill.  
         BACKGROUND OF THE INVENTION  
         [0002]    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 in post sorting steps, one or more of the dimensions of width, thickness or length of the board lumber are then used for sorting. For example, certain dimensioned board lumber can be selected for processing into 8 foot 2×4&#39;s and that certain dimensioned board 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.  
           [0003]    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. Each of these alternatives has limitations, the most common of which being that the distance between the attachments typically referred to as the lug space must be large. In order to load or unload or divert the material to be sorted in or out of the lug space, an unoccupied space is required which forms a large portion of this lug space. The unoccupied space is required to allow for actuation of mechanical devices such as diverters or gates to impact the transported material to cause it to be redirected into a sorting bin. The unoccupied space between lugs limits the number of lugs in a specified time that can be processed by allowing appropriate time and space for the mechanical steps required to load and unload the material from the sorter conveyor to occur.  
           [0004]    To alleviate the problem caused by hook contact with residual lumber, arrangements for rotation of an L-hook with respect to the sorting chain have been proposed. In one arrangement, the L-hook is interconnected with a chain attachment by means of two arms forming a parallelogram. In the event that the cradle and of the hook comes into contact with residual lumber, the parallelogram is rotated thereby preventing the hook from shearing from the chain.  
           [0005]    In the past, the sort conveyor assemblies of the bin lumber sorting systems that convey the board lumber across the open topped bins provide a flat L-shaped hook to collect the board lumber from the feed conveyor and transport the board lumber by the sort conveyor. When the open topped bin corresponding to the lumber dimension in transport becomes positioned below the sort conveyor, a diverter discharge arm is activated to remove the lumber from the sort conveyor hooks. This manner of dislodging the board lumber from the sorting conveyor has several disadvantages including bruising, shearing or breaking of the board lumber that results in degradation or destruction of the board lumber by the sort conveyor mechanisms hereto for in use. Another shortcoming of the prior art sort conveyor arrangements is that the distance between the hooks of the sorter conveyor must be sufficient to allow the board lumber that is being sorted to be dislodged from the hooks. Consequently, the lug spacing on the sorter conveyor must be sufficiently wide enough to permit the board lumber being sorted to be dislodged from the hooks of the sort conveyor. Accordingly, the hook repetition rate or density on the sorter chain must be sufficiently large to permit the lumber to be sorted to be loaded and unloaded from the sorter conveyor. Thus the hook spacing, and the corresponding unoccupiable space required, on a conventional sorter conveyor is large to permit space to allow to allow the lumber to be dislodged from the hooks for delivery into the targeted receiving bin by actuation of the sorting devices such as diverters or gates that impact the lumber.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention overcomes the shortcomings of the prior art by providing a sorter conveyor having a hook pivotably attached to a sort conveyor that is actuable between a transport position and a transfer position to permit lumber to be acquired by transfer from a feed conveyor and transfer to a target sorting bin.  
           [0007]    The invention comprises a conveyor system for the transport of board lumber to sorting bins, the conveyor system comprising at least a pair of head and tail sprockets with a corresponding chain run extending therebetween. Pivotably attached to the chains in a spaced relation are sort hooks. The sort hooks pivots about a pivot point in relation to the transport chain between a transfer position and a transport position. The hooks are placed at a configured distance along the lengths of the chain. The hooks are used to transport board lumber from a receiving location to a delivery location. Transfer of the board lumber to a selected receiving bin of a receiving location is effected by pivoting the hook into a transfer position, and is effected by contacting the hook with a delivery actuator. The delivery actuator is configurable between a delivery configuration and a pass, or non-delivery configuration using a suitable mechanical device such as a hydraulic, pneumatic or linear actuator to permit the actuator to be selectively operable to deliver lumber to the targeted receiving bin.  
           [0008]    In this manner, lumber is acquired by the sorting conveyor system and dislodged from the conveyor system by interaction between the lugs and the lumber. It is not necessary in accordance with the apparatus of the present invention to have a separate actuator or dislodging mechanism to remove the lumber that is sorted from the sorting conveyor.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The preferred embodiments of the invention will now be described with reference to the accompanying drawings in which like features of the invention are depicted with like reference numerals throughout the various figures.  
         [0010]    [0010]FIG. 1 is an elevation view of an acquisition end portion of a preferred embodiment of a lumber sorting apparatus constructed in accordance with the principles the present invention;  
         [0011]    [0011]FIG. 2 is an elevation view of another portion near open topped sorting bins portion of a preferred embodiment of the lumber sorting apparatus of FIG. 1.  
         [0012]    [0012]FIG. 3 is an elevation view of preferred embodiment of a sort hook.  
         [0013]    [0013]FIGS. 4 a  and  4   b  are cross section views of the sort hook of FIG. 3 taken along cutting line  4 - 4  of FIG. 3.  
         [0014]    [0014]FIG. 5 is a superimposed elevation view of the sort hook of FIG. 3 in a transport orientation and a transfer orientation. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    [0015]FIG. 1 is an elevation view of a portion of a preferred embodiment of a lumber sort apparatus constructed in accordance with the principles of the present invention showing a portion of feed conveyor and a sorter conveyor assembly. A feed conveyor, generally referenced by reference numeral  10 , delivers board lumber pieces  12  along an upper surface  14 , which may be, for example, a rail. The board lumber is ambulated along feed conveyor surface  14  at predetermined intervals determined by the spacing of lugs  16  on feed conveyor  10 . Feed conveyor  10  advances dependent on rotation of sprocket  18  in a clockwise direction, which results in transport of lumber  12  along upper rail  14  toward sprocket  18 . A sorting conveyor  20  obtains transfer of lumber  12  from feed conveyor  10 . The feed conveyor has a sprocket  22 , which rotates in a counter-clockwise direction corresponding to movement of sorting conveyor  20  in the direction of arrow  24 . As successive sort hooks  26  of the sorting conveyor moves laterally in approach to sprocket  22 , the sort hooks are supported in an inverted position by resting on rail  28 . The rail  28  ends near sprocket  22  permitting each sort hook  26  passing in the region between the end of rail  28  and sprocket  22  to rotate about pivot  30  to move hook shoulder  31  toward stop  32  of sprocket  22 . While a single chain and hook arrangement might be used to form sort conveyor  20 , sorting conveyor  20  is preferably constructed from at least a pair of chains  34 . A single chain arrangement is impractical to construct a sort conveyor for use in a typical saw mill which would employ the sort conveyor to transport varying lengths of board lumber ranging from a few feet length to 20 feet. Only the forward chain of the conveyors  10  and  20  are depicted in the drawing, the other chains being located behind and obscured by the forward chain. Naturally, more than two chains and corresponding hooks  26  or lugs  16  could be employed depending on the length of material which is sought to be supported by the respective conveyor.  
         [0016]    A chain  34  transports the sort hooks  26  and the assembly will rotate around sprocket  22  causing each sort hook  26  to orient hook opening  43  toward feed conveyor  10  in preparation to transfer the board lumber material from supply conveyor  10  to the sort conveyor  20 . The lug spacing of the feed conveyor and sorting conveyor may be different, however, the transport speeds of each conveyor must be set such that individual pieces of board lumber on the feed conveyor are transferred to a corresponding hook on the sorting conveyor. When the feed conveyor and the sort conveyor move at the same speed, the spacing of the distal ends  34  of each of the sort hooks  26  along the chain  34  of the sort conveyor has the same pitch as transport lugs  16  of the feed conveyor  10 . The transfer of board lumber material from the feed conveyor to the sorting conveyor occurs in the transfer region where the two conveyors overlap. To transfer a piece of board lumber, the distal end  36  of sort hook  26  is positioned below the rail  14  of the feed conveyor  10 . When the sort hook  26  has reached a transfer point, sort hook  26  rotates about its pivot  30  to permit support arm  52  to descend below and pass beneath board lumber  12  on feed conveyor  10  in the direction of arrow  38 . In this manner, the transport lugs  16  and distal ends  34  of each of the sort hooks  26  define a transfer area for the lumber  12  to be transferred from the feed conveyor  10  to the sorting conveyor  20 . To control the transfer of board lumber pieces from the feed conveyor to the sort conveyor at the transfer point, transfer control apparatus is preferred. For example, transfer control apparatus can be provided by having stop  32  include hook latch means that releasably secures hook shoulder  31  to sprocket  22  until the hook latch means is released at the transfer point.  
         [0017]    [0017]FIG. 2 shows a portion of the sorter conveyor above a series of sort bins  40 . The sort conveyor moves laterally over the series of sort bins, shown in the Figure as being in the direction of flow arrow  24 . Sort hooks  26  carry the board lumber pieces  12  over these sort bins. Above each sort bin  40  is a diverter lug  42  moveable between a discharge position  46  and a pass position  48 . When a piece of lumber in transport on the sorting conveyor passes over its target bin  40 , the diverter lug  42  is positioned to the discharge position. When the diverter lug is moved into the discharge position, the diverter lug acts to deflect sort hook  26  about its pivot  30  causing the sort hook opening  43  to face downward toward sort bin  40 . Deflection of sort hook  26  discharges the board lumber piece  44  from the sort hook  26  transporting it into the selected sort bin  40  under force of gravity. An actuator  50 , for example, a pneumatic or hydraulic cylinder or a linear actuator is used to move diverter lug  42  between the discharge position and the pass position. Control means  60 , for example, a programmable logic controller (PLC) or other automated or computerized means, activates the respective actuators  50  to effect sorting of the board lumber pieces into the appropriate sort bin  40 . The board lumber sort process effected by control means  60  is based on dimension information for each board lumber piece carried on the sort conveyor  20  for sorting. Control means  60  configures and controls whether or not the actuator  50  should function to discharge board lumber  12 ,  44  into an associated sort bin based on measurements taken or observations made of the lumber to be sorted. Based on selection characteristics including length, width, depth or condition of the lumber, a suitable sorting bin  40  is selected for discharge of the lumber to effect sorting of the lumber being carried on the sorting conveyor. The dimension information is input to control means  60  manually by an operator or preferably automatically, by measurement sensors, such as laser or sonar based sensors.  
         [0018]    [0018]FIG. 3 is an elevation schematic view of a sort hook  26  constructed in accordance with the principles of the present invention. Pivot  30  is positioned between the cradle arm  52  and deflection arm  54  of the sort hook  26 . To enable close nesting of sort hooks  26  along the sort conveyor, it is preferable that the lower extremity  56  of the sort hook have an semicircular profile with a radius “R” extending from the pivot point  30 . A semicircular profile of lower extremity  56  permits close nesting or pitch of the sort hooks when the sort hooks rotate relative to the sort chain  34  to acquire board lumber from the feed conveyor  10  as depicted in FIG. 1, and to discharge the board lumber into a sort bin as depicted in FIG. 2. To enable efficacious discharge of board lumber supported by cradle arm  52 , it is preferable that the cradle arm support surface be provided with a, semicircular profile with a radius “RS” which extends from a centre point  60  located near the axis of pivot  30  and toward the sort hook opening  43 . For clarity, a schematic representation of the two circles defined by radius R extending about pivot  30  axis and radius RS extending about centre point  60  with corresponding vertical and horizontal diameters is shown in dashed line form in the figure.  
         [0019]    [0019]FIGS. 4 a  and  4   b  show alternate embodiments of a sort hook pivot. FIGS. 4 a  and  4   b  are cross sections of the sort hook of FIG. 3 taken along cutting line  3 - 3 . The sort hook pivot  30  may be in the form of a hole formed in the body of hook  26  dimensioned to receive a pin  33  as shown in FIG. 4 a.  Or, the sort hook pivot  30  may be in the form of a pair of lugs  30 ′ and  30 ″ as shown in FIG. 4 b.    
         [0020]    [0020]FIG. 5 is a schematic elevation view of the sort hook of FIG. 3 showing two overlapping rotational orientations of the sort hook about pivot  30 . For clarity, a schematic representation of the circle defined by radius R extending about pivot  30  axis is shown in dashed line form in the figure. The rotation of the sort hook  26  from position A to position B is representative of at least a portion of the relative rotation of the sort hook that would occur when the sort hook is deflected to discharge material cradled by the sort hook. When the profile of upper surface  58  of the cradle arm portion of the sort hook is semicircular, as described with reference to FIG. 3, the rotation of the sort hook to effect discharge will cause the upper surface  58  to move downward a distance denoted by arrows  62 . The downward displacement of upper surface  58  relative to pivot  30  assists in discharging board lumber material carried by the sort hook.  
         [0021]    When a pivoting sort hook  26  of the present invention is used, the unoccupied space of a sorting conveyor is decreased. Consequently, the hook density, that is the number of hooks per lineal foot, of the sort chain can be increased thereby resulting in an increased hook rate at a lower chain speed. This provides the ability to sort more pieces of lumber at a given sort chain speed than would be required with a less dense hook count per lineal foot. Also, with a pivoting hook as described herein, removal of the lumber material to be sorted is effected by rotation of the hook. There is no need to contact a deflector or discharge mechanism with the lumber material itself. This reduces the damage to the material that could be caused by discharge mechanisms that strike the material to effect its removal. The activation of the actuator to effect discharge of the material is preferably relatively instantaneous to permit the pivot hook to be rotated from the support position to the discharge position in a brief period of time. This will cause the pivot hook to relatively instantaneously free itself from the transported material, allowing the transported material to be removed by gravity from the sort conveyor without changing the state of the material such as rotating the material. The material can be extracted or transferred from the supply conveyor using the mechanism of the present invention without any requirement to accelerate the material onto the hook. The hook of the present invention simply rotates under the material in a cradling fashion to effect removal of the material from the supply conveyor for transfer to the sorting conveyor.  
         [0022]    With the pivoting hook arrangement of the present invention, sorting hook breakage or shearing of the sort hook from the chain through contact with residual material, for example in an overloaded sort bin, is dramatically reduced as contact of a hook as described herein with residual material merely result in the hook rotating freely about its pivot allowing it to clear the residual material without resulting in breakage or shearing of the hook.  
         [0023]    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 attached drawings, but is defined in the claims appended hereto.