Patent Publication Number: US-6216756-B1

Title: Log processing apparatus

Description:
TECHNICAL FIELD 
     This invention generally relates to processing logs, and more specifically to a log processing apparatus for centering and processing a log tapered sides. 
     BACKGROUND OF THE INVENTION 
     Multiple processes turn logs into finished wood products for consumers. One important process involves using a log saw to cut a large log into smaller sections of predetermined lengths for ease of handling and further processing. Log saws may be stationed at a variety of locations in a mill. When used in a veneer mill, log saws typically are stationed after a debarking machine, which takes the bark off of a log, and before a veneer lathe, which peels a long veneer strip from the log. 
     To minimize waste, is important that the log saw cut the log in a cutting plane perpendicular to a central longitudinal axis of the log. If the log saw cuts the log in a cutting plane that is askew relative to the central longitudinal axis of the log, the log typically will is have to be squared off by a separate machine before further processing, thereby consuming unneeded time and energy and wasting valuable wood product material. 
     In a veneer mill, typically the veneer lathe will square the log off with a pair of facing tools positioned near each end of the log. These facing tools typically cause pitting in the ends of the log as they cut across softer and harder regions of the end g of the log. As the veneer lathe peels a sheet of veneer from the log section, the pitted ends of the log will translate into pitted sides on the veneer sheet. 
     Often, logs fed to a log saw for sectioning will be tapered in shape, with a wide base, a narrow top, and tapered sides extending therebetween One problem with cent log saws is that they typically are unable to center a tapered log such that the log saw may be cut in a cutting plane perpendicular to the central longitudinal axis of the log. Log saws equipped with horizontal planes of su t normally will hold a tapered log such that the central longitudinal axis of the tapered log extends at a slight incline relative to the plane. In this case, a saw blade that is perpendicular to the plane of support Will cut the log in a cutting plane that is inclined to the central longitudinal axis of the log, thereby necessitating that the tapered log be squared off by a separate machine, as described above. 
     Certain log saws have been designed with an inclined conveyor for moving a tapered log into a cutting station such that the central longitudinal axis of the tapered log is normal to the plane of cutting. However, these devices generally are cumbersome, slow in operation, and designed to handle logs of similar size that are oriented with their tapers extending in the same direction. 
     In addition, a log saw is most efficient when it is capable of analyzing a log, and applying a predetermined formula to determine the optimum number and length of sections to cut from the log Current log sawing systems utilize a three dimensional scanner and associated computer software to determine optimum section lengths. A saw operator reads the section lengths, adjusts a mechanical stopper to the specified distance, then feeds the log through the saw until an end of the log rams the stopper. The operator cuts the log and readjusts the stopper to repeat the cycle. 
     This process is arduous on the operator and the machinery. Great impact forces are produced as the logs ram against the stop, necessitating the use of ear protection by the operator, and causing wear on the machine. In addition, operator error may cause the stopper to be placed out of position, and the log to be miscut. 
     In addition, a log saw is most efficient when the cycle time of the saw blade during each cut is minimized. Cycle time for a cut primary is affected by movement of the log and movement of the saw blade. Current log saws typically accelerate a log from a full stop, move the log into the machine, and bring the log back to a full stop in position for cutting. When attempting to operate a log saw at high speeds, bringing the heavy log to a complete stop takes valuable time and energy. In addition, time typically also is wasted on each cut cycle while waiting for the log to bounce repeatedly against the stop before coming to a rest. 
     Current saw blades often require the saw blade to travel the same distance on each cut regardless of the diameter of the log being cut, wasting time and energy when cutting logs of smaller diameter. This is because current log saws typically position both small and large logs such that the bottom of the log rests near the bottom of the circular saw blade when the log is being cut. In such a configuration, moving the saw blade from a retracted position to an extended position where the bottom of the saw blade cuts completely through the bottom of the log requires the saw blade to travel a distance significantly greater than the diameter of smaller logs. 
     SUMMARY OF THE INVENTION 
     A log processing apparatus is provided for processing a tapered log, where the tapered log has a central axis, and a region of larger diameter and region of smaller diameter. Typically the log processing apparatus includes a frame assembly and a roller assembly. The roller assembly typically includes a pair of upstream rollers coupled to the frame assembly by a pair of upstream roller mounts, and a pair of downstream rollers coupled to the frame assembly by a pair of downstream roller mounts. Each of the upstream and downstream rollers typically are positioned on opposing sides of a travel path of the tapered log, each roller including a contact region and an axis of rotation, the contact region of each roller being configured to clamp against an opposing side of the tapered log and guide the tapered log along the travel path. Each of the pair of upstream and downstream roller mounts typically are configured to support and adjust the axes of rotation of a pair of respective rollers toward and away from the travel path in tandem such that the contact region of each roller remains substantially equidistant from the travel path of the log. Typically, the pair of upstream rollers and the pair of downstream rollers are configured to adjust independently of each other and clamp the tapered log in respective regions of larger and smaller diameter, thereby supporting the tapered log such that the central axis of the tapered log remains substantially aligned with the travel path. The log processing apparatus may also include a saw assembly positioned adjacent the roller assembly, the saw assembly including a saw blade configured to cut the tapered log along a cutting plane substantially perpendicular to the central axis of the tapered log. 
     The advantages of the present invention will be understood more readily after a consideration of the drawings and the Detailed Description of the Preferred Embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view showing a log processing apparatus constructed in accordance with the present invention. 
     FIG. 2 is a top view of the log processing apparatus. 
     FIG. 3 is a side view of another embodiment of the log processing apparatus. 
     FIG. 4 is a cutaway side view showing a saw assembly of the log processing apparatus in a retracted position. 
     FIG. 5 is a cutaway side view of the saw assembly of FIG. 3 in an extended position. 
     FIG. 6 is a detail side view of a pair of rollers of the log processing apparatus, in a pressed-together configuration holding a small diameter log. 
     FIG. 7 is a detail side view of a pair of rollers of the log processing ape in a spaced-apart configuration holding a large diameter log. 
     FIG. 8 is a cross-sectional view of the roller shown in FIG. 7, showing in detail a right-hand sheave of the roller. 
     FIG. 9 is a cross-sectional view of the roller shown in FIG. 7, showing in detail a left-hand sheave of the roller. 
     FIG. 10A is a view of a horizontal centering device in a closed configuration, guiding a small log. 
     FIG. 10B is a view of the horizontal centering device of FIG. 10A in an open configuration, guiding a large log. 
     FIG. 11 is a schematic view of electronic components of the present invention 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, log processing apparatus  10  typically is configured to operate between an infeed conveyor  12  equipped with a horizontal centering device  14 , and an outfeed conveyor  16 . The log processing apparatus is configured to receive a log  18  from the infeed conveyor through the horizontal centering device, process the log with a tool, such as saw assembly  20 , and pass the log to outfeed conveyor  16 . The tool, it will be appreciated, may be virtually any kind of tool, including a drill, sander, lathe, debarker, stainer, etc., but herein is described as a saw assembly. Where a saw is used, log processing apparatus  10  alternatively may be referred to as log saw  10 . 
     Log processing apparatus  10  includes a frame assembly  22  configured to support an infeed guide or roller assembly  24 . Infeed guide assembly  24  is configured to guide log  18  from infeed conveyor  12  through horizontal centering device  14  and into the log processing apparatus. 
     As shown in FIGS. 10A and 10B, log  18  is centered horizontally by arms  136   a    136   b  which are biased against the log by piston  138  and linkage  137  as the log passes through the horizontal centering device. Rollers  140  include sloped sections  142  that are configured to lift the log from wheel  144  and vertically center the log before it passes into the infeed guide assembly. 
     Typically, log processing apparatus  10  also includes an outfeed guide or roller assembly  26  mounted to the frame assembly in spaced-apart relation to infeed guide assembly  24 . Outfeed guide assembly  26  is configured to guide the tapered log from the log processing apparatus to outfeed conveyor  16 . 
     Infeed guide assembly  24  typically includes a pair of upstream guides or rollers  28   a ,  30   a  positioned on opposing sides of a travel path  32 . Upstream guides  28   a ,  30   a  are biased toward travel path  32  by an upstream clamping mechanism  34   a . Typically, clamping mechanism  34   a  includes a pair of upstream guide or roller mounts  36   a ,  38   a  pivotably mounted to a respective one of main shafts  40   a  and  42   a , and being configured to rotate about a respective axis  44   a  and  46   a . Upstream guide mounts  36   a ,  38   a  include respective intermeshing gear regions  48   a ,  50   a  which enable mounts  36   a .  38   a  to pivot in tandem an equal distance from travel path  32  and in opposite directions from each other about respective main shafts  40   a  and  42   a . Intermeshing gear regions  48   a  and  50   a  are configured to pivot guides  28   a  and  30   a  such that the distances  52   a  and  54   a  between respective contact regions  56   a  and  58   a  of guides  28   a  and  30   a  and travel path  32  remain substantially equal in magnitude, thereby centering a central longitudinal axis  60  of log  18  between the contact regions and along travel path  32 . 
     A distal end of each of upstream guide mounts  36   a  and  38   a  is configured to support a respective axle  62   a  or  64   a . Each of guides  28   a  and  30   a  is mounted rotatably to a respective one of axles  62  or  64   a  and configured to rotate about a respective axis of rotation  66   a  or  68   a . As upstream guide mounts  36   a  and  38   a  pivot in tandem toward and away from travel path  32 , axles  62   a  and  64   a  and axes of rotation  66   a  and  68   a  are moved along clamping paths  70   a  and  72   a.    
     Typically, air cylinder  74   a  is pivotably attached to frame assembly  22  at a lower end by air cylinder support  76   a . Air cylinder  74   a  includes a piston  78   a  pivotably mounted to a lower one of the upstream guide mounts. The piston is configured to selectively extend from and retract into air cylinder  74   a  thereby causing the lower upstream guide mount  38   a  to rotate about lower main shaft  42   a.    
     As lower upstream guide mount  38   a  is rotated, intermeshing of gear regions  48   a  and  50   a  in turn causes the upper upstream guide mount  36   a  to pivot in tandem with the lower upstream guide mount  38   a  about main shafts  40   a  and  42   a . By applying pressure to air cylinder  74   a  and extending piston  781  clamping mechanism  34   a  is able to clamp log  18  such that the central longitudinal axis  60  of log  18  is centered along travel path  32  between guides  28   a  and  30   a.    
     Infeed guide assembly  24  also may include a pair of downstream guides or rollers  28   b  and  30   b  positioned on opposing sides of the travel path  32 . Downstream guides  28   b  and  30   b  are biased toward travel path  32  by a downstream clamping mechanism  34   b . Typically, clamping mechanism  34   b  includes a pair of downstream guide or roller mounts  36   b  and  38   b  pivotably mounted to a respective one of main shafts  40   a  and  42 , and being configured to rotate about a respective axis  44   a  or  46   a . Downstream guide mounts  36   b  and  38   b  include respective intermeshing gear regions  48   b  and  50   b , which enable mounts  36   b  and  38   b  to pivot in tandem an equal distance from travel path  32  and in opposite directions from each other about respective main shafts  40   a ,  42   a . Intermeshing gear regions  48   b  and  50   b  are configured to pivot guides  28   b  and  30   b  such that the distances  52   b  and  54   b  between respective contact regions  56   b  and  58   b  of guides  28   b  and  30   b  remain substantially equal in magnitude, thereby substantially centering a central longitudinal axis  60  of log  18  between the contact regions along travel path  32 . 
     A distal end of each of downstream guide mounts  36   b  and  38   b  is configured to support a respective axle  62   b  or  64   b . Each of guides  28   b  and  32   b  is rotatably mounted to a respective one of axles  62   b  or  64   b  and configured to rotate about a respective axis of rotation  66   b  and  68   b . As upstream guide mounts  36   b  and  38   b  pivot in tandem toward and away from travel path  32 , axles  62   b  and  64   b  and axes of rotation  66   b  and  68   b  are moved along clamping paths  70   b  and  72   b.    
     Typically, air cylinder  74   b  is rotatably attached to frame assembly  22  at a lower end by air cylinder support  76   b . Air cylinder  74   b  includes a piston  78   b  pivotably mounted to a lower one of the downstream guide mounts. The piston is configured to selectively extend from and retract into air cylinder  74   b , thereby causing the lower downstream guide mount  38   b  to rotate about lower main shaft  42 . 
     As lower downstream guide mount  38   b  is rotated, intermeshing of gear regions  48   b  and  50   b  in turn causes the upper downstream guide mount  36   b  to pivot in tandem with the lower downstream guide mount  38   b  about main shafts  40   b  and  42   b . By applying pressure to air cylinder  74   b  and extending piston  78   b , clamping mechanism  34   b  is able to clamp log  18  such that the central longitudinal axis  60  of log  18  is centered along travel path  32  between guides  28   b  and  30   b.    
     The pair of upstream guides  28   a  and  30   a  and the pair of downstream guides  28   b  and  30   b  are configured cooperatively to clamp tapered log  18  in respective regions of larger and smaller diameter when each of the air cylinders  74   a  and  74   b  are pressurized and biasing clamping mechanisms  34   a  and  34   b  inward, thereby aligning the central axis  60  of the tapered log substantially along the travel path  32 . Where the central axis  60  is irregularly shaped, central axis  60  may diverge from travel path  32  in certain regions, however clamping mechanisms  34   a  and  34   b  act to substantially center log  18  between contact regions  56   a  and  58   a , and  56   b  and  58   b  of guides  28   a  and  30   a  and  28   b  and  30   b , respectively. 
     As shown in FIG. 2, infeed guide assembly  24  also may include a motor  80   a  drivingly coupled to upper main shaft  40   a . As shown in FIG. 4, upper main gear  82   a  is mounted to upper main shaft  40   a  and lower main gear  84   a  is mounted to lower main shaft  42   a . Main gears  82   a ,  84   a  are configured to mesh and transfer power from upper main shaft  40   a  to lower main shaft  42   a.    
     An upper center drive gear  86   a  is coupled to upper main shaft  40   a  and a lower center drive gear (not shown) is coupled to lower main shaft  46   a . As shown in FIGS. 2,  4 , and  5 , the center drive gears are configured to intermesh with and transfer power to a respective pair of peripheral drive gears, such as  90   a  and  90   b , or  92   a  and a counterpart drive gear (not shown). Drive gears  90   a  and  90   b  are mounted to axles  62   a  and  62   b , respectively, and are configured to cause guides  28   a  and  28   b , respectively, to rotate. Drive gear  92   a  and a counterpart (not shown) are mounted to axles  64   a  and  64   b , respectively, and are configured to cause guides  30   a  and  30   b , respectively, to rotate. As clamping mechanisms  34   a  and  34   b  move axles  62   a ,  62   b , and  64   a ,  64   b  along clamping paths  70   a    70   b ,  72   a ,  72   b , respectively, center drive gears  86   a ,  88   a  are configured to remain in constant driving contact with the peripheral drive gears  90   a  and  90   b , and  92   a  a counterpart (not shown), respectively. 
     Log processing apparatus  10  also may include outfeed guide assembly  26 . Typically, outfeed guide assembly  26  is substantially similar in componentry and construction to infeed guide assembly  24 . Like parts in the infeed and outfeed guide assemblies are labeled with identical numerals, but with different letter indicators. For example,  28   a  and  28   b  respectively indicate the upper upstream and downstream guides on the infeed guide assembly, whereas  28   c  and  28   d  respectively indicate the upper upstream and downstream guides on the outfeed guide assembly. Outfeed guide assembly  26 , in conjunction with infeed guide assembly  24 , enables the log processing apparatus  10  to grip independently each of an upstream section  18   a  and a downstream section  18   b  of log  18 , after log  18  is cut. 
     Referring now to FIGS. 4 and 5, a saw assembly is shown generally at  100 , including a saw support structure  102  pivotably attached to frame assembly  22 . Saw support structure  102  is configured to support saw blade  104  and saw motor  106 . Saw motor  106  is configured to drive saw blade  104  via belt  108 . Piston  110  is attached at one end to frame assembly  22  and at a second end to saw support structure  102 , and is configured to extend and cause saw support structure  102  to pivot about pivot axis  112 . As saw support structure  102  pivots relative to frame assembly  22  about pivot axis  112 , so do saw blade  104  and saw motor  106 , and belt  108 . 
     Saw blade  104  is configured to rotate about an axis of rotation  114  and cut tapered log  18  as saw support structure  102  is pivoted toward the tapered log. Axis of rotation  114  typically moves along cutting path  116  as saw support structure  102  rotates the saw blade into the tapered log, such that the saw blade cuts the tapered log along a cutting plane substantially perpendicular to the central axis of the tapered log. Because the infeed and outfeed guide assemblies substantially center the log vertically with respect to the saw blade, the blade is able to cut completely through the log upon traveling less than half the diameter of the saw blade in the horizontal direction. In addition, where horizontal centering device  14  is configured to sense the width of the log, the saw blade support structure may be configured to rotate the saw blade only a minimum distance necessary to saw through the log, thereby minimizing motion of the saw blade and shortening the cut cycle time for logs of smaller diameter. 
     FIG. 3 shows another embodiment  11  of the log processing apparatus, where saw support structure  102  is mounted to track  150  and piston  152 . Piston  152  is configured to move saw support structure  102  and saw blade  104  along track  150  at a rate of speed substantially equal to the rate of speed of the log moving along the travel path. In this embodiment, saw assembly  20  is configured to cut log  18  while the log is moving. Because the log does not have to be slowed to a complete stop to be cut, cycle time per cut is reduced. 
     Referring now to FIGS. 6,  7 ,  8 , and  9 , guides or rollers  28   a ,  30   a  include a pair of inwardly sloping disks or sheaves  122  configured to center laterally a log within the roller or guide. A toothed wheel  124  is positioned adjacent an inward side of each inwardly sloping disk  122 . Toothed wheel  124  includes teeth  124   a , and is configured to rollingly engage tapered log  18 . Inwardly sloping disks  122  may further include fins  125 . Preferably, fins  125  do not touch log  18  as it is clamped by the rollers. Alternatively, fins  125  are configured to center and/or rollingly engage the log as it is clamped. Fins  125  preferably extend radially outward from a respective axis of rotation of the roller and connect toothed wheel  124  to outer disk  126 . Fins  125  typically are positioned behind every other tooth  124   a  on wheel  124 . As can be seen in FIGS. 8 and 9, fins on opposing disks typically are offset such that the fins are positioned behind alternating teeth. 
     Each roller is configured to rotate about an axis of rotation, and move vertically under the power of a respective clamping mechanism Typically, the roller is driven under power transferred through a respective axle. By varying the vertical distance between an opposed pair of rollers, a variety of sizes of logs may be clamped and conveyed by the rollers, as illustrated in FIGS. 6 and 7. Typically, only the toothed wheel  124  touches the log as it is being held by the rollers. 
     As shown in FIG. 1, after saw blade  104  cuts tapered log  18 , infeed guide assembly  24  remains in gripping contact with an infeed section  18   a  of the tapered log and outfeed guide assembly  26  remains in gripping contact with an outfeed section  18   b  of the tapered log. The outfeed section of tapered log then typically is fed to outfeed conveyor  16  for further processing by other machines. 
     As shown in FIG. 2, log processing apparatus  10  may also include position sensors  130   a - 130   d  configured to sense the position of the log along the travel path. Typically, sensors  130   a - 130   d  are optoelectric sensors attached at intervals along frame assembly  22 . Alternatively, virtually any other type of sensor may be used. In addition log processing apparatus  10  may also include a width sensor  132  configured to sense the width of the log. Typically, width sensor  132  is a sensor mounted to piston  138  that is configured to measure the degree to which the log causes arms  136  to separate and piston  138  to extend. Alternatively, virtually any other sensor may be used to sense the width of the log. In addition, a length sensor  134 , such as a digital scanner or other device, may be positioned, for example, on infeed conveyor  16 . 
     As shown in FIG. 11, controller  142  is coupled to position sensors  130   a - 130   d , width sensor  132 , and length sensor  134  such that it may receive information about the width, length, and current position of the log. The controller may also be linked to a rotation sensor  135  on a roller, such that the controller may compute the position of the log based on the rotation of the roller. In addition, controller  142  may be coupled to motors  80   a  and  80   b , saw motor  106 , piston  110 , and air cylinders  74   a - 74   d . Controller  142  typically is configured to receive information about the position, width, and length of the log from sensors  130   a - 130   b ,  132 , and  134 , apply a predetermined formula to derive an optimum cutting plan for the log, and instruct motors  80   a  and  80   b  to cause the rollers to rotate and move the log until data from rotation sensor  135  and position sensors  130   a - 130   d  confirm that the log is in a predetermined position for cutting according to the optimum cutting plan. After positioning the log at the predetermined position, controller  142  is configured to instruct the saw motor  106  and piston  110  to rotate saw blade  104  and cut the log. 
     By advancing and stopping the log with the rollers, the present invention avoids the wear and tear on operators and machinery associated with traditional mechanical stops on log saws. By centering the log between the rollers and cutting the log in a cutting plane perpendicular to the central axis of the log, the present invention avoids wasted time and material and pitting associated with squaring off a log following a nonperpendicular cut. Log saws according to the present invention also decrease the cycle time associated with each cut by moving the saw blade a minimum distance calculated based on the measured width of the log. In addition, cut cycle time is reduced with certain embodiments of the present invention that cut the log while it is in motion, thereby obviating the need for stopping and starting the log at each cut. 
     While the invention has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the invention includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. No single feature, function, element or property of the disclosed embodiments is essential. The following claims define certain combinations and subcombinations which are regarded as novel and non-obvious. Other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such claims are also regarded as included within the subject matter of applicant&#39;s invention irrespective of whether they are broader, narrower, or equal in scope to the original claims.