Patent Publication Number: US-2006000521-A1

Title: Board fencing system

Description:
BACKGROUND OF THE INVENTION  
      This invention relates to wood products, and more particularly to a fencing system and method for use in a sawmill for accurately positioning boards.  
      In sawmill operation, boards travel along a conveyor and are trimmed to length (say for example, if 2 by 4 boards are being produced, they will be cut to a specific length). Systems exist for moving the boards from side to side as they travel down the conveyor, to position them relative to trim saws for cutting the boards to the specific length. However, the existing systems tend to lose accuracy at higher speeds. Some such systems employ guide members that flip up to interact with a board, to cause the board to move to one side or another by interaction with the guide member. AS the speed of the board is increased, as the board travels past the guide member, the likelihood of the board to moving farther than was intended will increase. The board&#39;s impact with the guide at higher speed causes the board to bounce or otherwise move beyond the desired amount. This leads to variations in board length or imperfections remaining in a board because of inaccurate positioning relative to a trim saw which was intended to cut away the imperfect portion, which diminishes the value of the product, as it will be less desirable to customers having precise length or quality requirements.  
     SUMMARY OF THE INVENTION  
      In accordance with the invention, a fence system and method is provided to accurately and precisely position a board so that it is oriented to be trimmed to a desired length, while enabling higher throughput than provided by the prior art.  
      Accordingly, it is an object of the present invention to provide an improved board positioning system.  
      It is a further object of the present invention to provide an improved board position system and method for enabling production of precise board lengths.  
      It is yet another object of the present invention to provide an improved system for trimming boards.  
      The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view, partially broken away, of the system according to the invention;  
       FIG. 2  is a top view of the system of  FIG. 1 ;  
       FIG. 3  is a side view taken along line  3 - 3  of  FIG. 2 ; and  
       FIG. 4  is an isometric view of the board positioning mechanism;  
       FIG. 5  is a view of the board positioning mechanism in an extended position;  
       FIG. 6  is a view of the board positioning mechanism in an retracted position;  
       FIG. 7  is another view of the board positioning mechanism in an retracted position;  
       FIG. 8  is a perspective view of a portion of the board positioning system;  
       FIG. 9  is a side view of a portion of the board positioning system;  
       FIG. 10  is an end elevational view of the board positioning system;  
       FIG. 11  is an isometric view of a board position system with plural board positioners installed;  
       FIG. 12  is a top view of the system of  FIG. 11 ;  
       FIG. 13  is a perspective view of the board clamping mechanism as viewed from below; and  
       FIG. 14  is a simplified block diagram of the operation system. 
    
    
     DETAILED DESCRIPTION  
      The system according to a preferred embodiment of the present invention comprises a fence apparatus and method for accurately positioning boards for presentation to a trim saw.  
      In the Figures, a conveyor  12  moves the boards towards trim saws (not shown). The conveyor illustrated includes plural board engagers  15  which interact with the board to move the board in the travel direction indicated by arrow  14 . The boards pass through a scanner  16  which determines the board&#39;s configuration, which may include such information as length and any noted defects which are to be removed by trimming. A low friction surface area  18 , which may comprise an ultra high molecular weight polyethylene, for example, is provided in one region and above that surface, a translation device  22  is employed that has a pneumatically actuated foot member  24  that moves up and down so as to press against the top surface of a board as it passes underneath. The foot member is movable on a translation direction  26 , suitably at 45 degrees to the direction of travel  14  of the conveyor in this embodiment. As a board passes along, the scanner indicates the characteristics of the board, which may include imperfections that are desired to be trimmed off the board. As the board moves under the foot member, the foot is translated downwardly in the direction of arrow  28  and presses against the top of the board  30 . The foot member is simultaneously translated along the translation direction, which causes the board to move along the axis of arrow  20 , side to side, so as to be at the desired position so that the end is trimmed properly. Since the foot translates at an angle to the movement direction of the conveyor (suitably 45 degrees), during the brief period of time that the foot is engaged with the board, the travel speed of the foot in the conveyor direction matches the speed of the board and allows accurate side to side position adjustment of the board (suitably at 90 degrees to the conveying direction in the illustrated embodiment) without disruption of the board&#39;s momentum in the direction of arrow  14 . When the board is at the desired position, the foot is moved upwardly opposite of direction arrow  28 , and the board continues down the conveyor for cutting by the end trim saw.  
      Referring now to  FIG. 3 , a side view showing the board translating mechanism, taken along line  3 - 3  in  FIG. 2 , the mechanism includes a drive motor  32  having a pinion gear  34  that engages with rack  36  attached to a support carrying the pneumatically actuated foot member  24 , whereby operation of the motor causes translation of the foot member along axis  26 .  
      Pneumatic actuator  38  is operative to provide downward and upward motion of the foot member as indicated by arrow  28 .  
      In operation, the conveyor operates and supplies boards, typically one by one, from a board supply not shown. The conveyor passes the board through the scanner  16 , whereupon any defects or other information about the board is determined, and under operation of a computer ( FIG. 14 ), for example, which is programmed with the desired cutting configuration, when the board passes underneath the positioning mechanism, the pneumatic actuator  38  is operated to extend the foot member downwardly in the direction of arrow  28 , so as to engage the top surface of the board. The motor  32  is then actuated to translate the foot member (and consequently, the board) along the axis  26 , which thereby positions the board laterally on the axis  20 . When the board has been moved a desired amount so as to be positioned to be oriented for cutting by trim saws at a desired location, the foot is retracted (by operation of pneumatic actuator  38 ).  
       FIG. 13  is an enlarged perspective view of the pneumatic actuator  38  and foot member  24 . The face of the foot member that interacts with the board face suitably comprises a hardened steel “vee” grooved plate  48 , which may be attached by use of bolts for example, to enable removal and replacement as the plate  48  such as for wear or damage thereto from repeated contact with the boards. The “vee” grooves  50  in the illustrated embodiment suitably run parallel to one another along a direction across the plate. An alternate plate  48  may comprise vulcanized rubber, for example. The actuator in the illustrated embodiment employs two sliding guide member  52  (one being visible in this view) adapted to translate upwardly and downwardly with the extension/retraction of the pneumatic cylinder via bearings  54  mounted in the support frame of the actuator, to provide a more stable foot member.  
       FIG. 14  is a simplified block diagram of the operation/control system employed with the device. A computer or controller  56  communicates with motor actuation block  58  (which drives the motor  32  for directing the operation of the translation mechanism), pneumatic cylinder extend/retract block  60  (which extends and retracts the pneumatic cylinder  38 ) and pressure sensor  62  (which detects and reports the pressure within the pneumatic cylinder/system). Also, either separately or as a portion of the same controller, input from the scanner  16  may be employed in determining how to position the board for trimming.  
      To determine the extent to move the foot member downwardly in order to engage a board, the following method is used. As the foot moves downwardly with the extension of the pneumatic actuator  38 , at some point in time the foot will contact the board. The actuator includes pressure sensor  62  thereon to sense the internal pressure of the pneumatic actuator system. When the foot  24  and plate  48  is contacting the board, the pressure will begin to increase because the pneumatic cylinder is impeded against further extension. This pressure increase feedback is observed by the operating computer or controller  56  running the system, whereupon the extension of the pneumatic cylinders is then halted. Once the board has been moved to the desired location, the pneumatic cylinder is retracted to remove the foot from interaction with the board.  
      The accurate positioning of the board is desirable, as it enables the board to be adjusted prior to cutting, so that any defects which may be present near ends of the board will be in the waste portion of the board that is cut away by the trim saws. This enables a higher quality lower defect board production to be accomplished at high speed.  
      For clarity of illustration in  FIGS. 1-4 , flexible control/power cable system  40  has been removed, but is visible in  FIG. 6 , for example, providing operational power and control to the motor  32  and pneumatic actuator  38 .  
       FIG. 8  is a perspective view which illustrates drive motor  42  powering the conveyor system  12 , via drive chain  44  and its interaction with the conveyor  12 .  
       FIGS. 9-12  illustrate a board fencing system with plural board translating devices  22 ,  22 ′,  22 ″  22 ′″ positioned in spaced arrangement along the direction of movement of the conveyor. In this configuration, the translating devices are arranged alternately in their orientation, wherein devices  22  and  22 ″ are oriented so that extension is in the direction of arrow  44 , while devices  22 ′ and  22 ′″ are oriented so that their extension operation is in the direction of arrow  46 .  
      The use of plural translating devices enables multiple boards to be positioned at the same time, enabling higher throughput.  
      Thus, in accordance with the above described system and method, an improved fence system for accurately positioning boards for feeding to trim saws is provided. The system and method enable high speed yet accurate positioning of the boards to provide a high quality end product.  
      While plural embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.