Abstract:
A log carriage employs a fixed knee and a second, movable knee adapted to move along at least a portion of the length of a log, to enable optimal positioning and minimizing knee interference with scanning of the log.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to sawmill operation. In such operations, raw logs (which might be rather large and heavy) are placed on a moving carriage, which moves the log back and forth in a straight line through the saw for the purpose of sawing off successive slices from the log. Typically the carriage travels along rails. 
     Conventional carriages employ 3 or 4 “knee” assemblies on the carriage, the knees being in spaced apart positions along the length of the carriage and against which the back side of the log (relative to the saw blade) rest. These knee assemblies also include devices to grip and hold the log in position. So, it may be understood that the knees operate as the back rests and grips to secure the log in position to the carriage. The multiple knees spaced along the carriage enable the carriage to grip and process logs of different lengths. As portions of the logs are sawed off, the knees move the log so that at the next pass of the carriage past the log will again be positioned to saw off yet another board. This back and forth motion of the carriage relative to the saw and the incremental moving of the log face into the plane of the saw blade will continue until the log is completely processed, whereupon the carriage will be loaded with the next log and scanning and sawing of that next log will proceed. 
     A typical operation is that the log is placed on the carriage and rotated to an optimal position for beginning cutting based on a pre-scan of the log to determine its shape. Further scanning is typically made while the log is on the carriage to further employ in software determining how best to cut the log. With such conventional carriages, each knee obscures a portion of the log from the scanner, so interpolation or smoothing is done to “remove” the knee from the scan and fill in what is presumed to be the configuration of the log in the obscured portion. Such smoothing can result in inaccurate information, if the portion of the log hidden by the knees does not conform to the assumptions of the smoothing algorithms. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, an improved two knee carriage is provided with one knee position being adjustable along the length of a log. The carriage employs a fixed and a movable knee, whereby the movable knee can be positioned to an optimal position along the log (that position is typically determined from the pre-scan data). 
     Accordingly, it is an object of the present invention to provide an improved carriage adapted for optimum scanning of logs. 
     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 an end view of the carriage with a log thereon; 
         FIG. 2  is a top view thereof without the log; and. 
         FIG. 3  is a side view thereof. 
     
    
    
     DETAILED DESCRIPTION 
     The system according to a preferred embodiment of the present invention comprises a saw carriage having a fixed and movable knee. 
     Referring to  FIG. 1 , an end view of a carriage  10  with a log  12  thereon. A movable knee  14  is translatable in the directions of arrow  16 , moving in and out to position the log relative to the plane of the saw that cuts the log. The carriage is provided with front wheels  18  that ride on rail  22  and rear wheels  20  that ride on rails  24  whereby the carriage moves the log through the saw blade for sawing operations thereon by translation of the carriage along the rails by operation of the wheels riding on the rails. In the illustrated embodiment four sets of front and rear wheels  18 ,  20  are provided. 
       FIG. 2  is a top view of the carriage  10  with the log removed, wherein the carriage comprises a carriage body  11  having a fixed knee  14 ′ near one end of the carriage body (the right most end in this view) and a movable knee  14 ″ which is translatable in the directions of arrow  26  to move the knee  14 ″ left and right in the view of  FIG. 2 , to position the knee differently for accommodation of different configurations of logs  12 . 
     The translation mechanism to move the knee  14 ″ comprises an actuator  28 , which is a hydraulic actuator in a particular embodiment, which attaches to the movable knee  14 ″ and extension and retraction of the actuator causes the knee to translate along the carriage body in the directions of arrow  26 . In  FIG. 2 , a view in phantom is show of the movable knee  14 ″ in a more rightward position, to illustrate an example of a different position thereof, with the actuator  28 ′ showing a more retracted position of the actuator, while actuator  28  shows a more extended position . . . ; and. 
       FIG. 3  is a side view of the carriage with log removed, from the front thereof, for further illustration of the system. 
     Typical operation is that the moveable knee  14 ″ is positioned to a desired location along the length of the carriage, based on the dimensions of next log that is to be loaded (this information is known from a pre-scan of the log, which might typically be done as the log is being conveyed to the carriage). The log is then loaded onto the carriage by a conveying apparatus  30 , which in the illustration comprises a cradle that moves the log onto the carriage in the direction of arrow  34  and then pulls away after the log is received by the carriage. This may be accomplished by, for example, front portion  32  of the cradle being moved down or away from the log to enable the cradle to be retracted in the opposite direction of arrow  34 , and/or by the cradle moving downwardly below the bottom plane of the log to enable retraction. The log may be rotated by the carriage system or other means to be in the optimal rotational position for performing the first cut of the log, the log is clamped to the knees by means not shown, and the carriage then moves the log through the saw, back and forth in the directions of arrow  34 , along the rails  22 ,  24 , typically multiple times, the knees translating the log as each saw pass is made, for example in the direction of arrow  40  of  FIG. 2 , to have the log in position to engage the saw  42  (illustrated schematically) with next pass of the log by the saw. 
     By using such a system, advantages include:
         the scanner is able to obtain more data from the scan of the log, to more accurately process the log, since the third or fourth knees are not blocking the view of the scanner, or more easily process the log since less interpolation or smoothing is required.   since the carriage has fewer knees, the weight of the carriage may be reduced by approximately 2 tons, for a typical installation, so less energy is expended in moving the carriage, saving operation costs.   also, since in the view of  FIG. 3 , the saw is to the right of the view, and the length of the log has been determined to move the left knee to the left end of the log, the carriage need not move through its entire range of left to right motion in the case of logs that are shorter, reducing overall carriage movement and increasing production throughput. Conventional systems, for example, might have the carriage travel its entire rightward motion path before shifting to move leftward.       

     Accordingly, an improved carriage is provided that is adapted for optimal scanning to provide more accurate log analysis, lower operation cost and higher throughput. 
     While a preferred embodiment of the present invention has 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.