Abstract:
A conveyor between a log debarker and a flaker has three flat bottom plates which extend the length of the conveyor line, and two vertical side plates. Each of the five plates is driven to oscillate by a hydraulic piston. All five plates together move forward approximately 30 inches at a constant velocity, after the completion of the forward motion, each plate is retracted separately at approximately three times the velocity of the forward motion, to advance logs retained within a trough defined between the side plates in a stepwise forward motion.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
         [0001]    Not applicable.  
         STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUOFTHEND OF THE INVENTION  
         [0003]    The present invention relates to conveyors in general and to conveyors for moving logs in particular.  
           [0004]    Oriented chips or wafers of wood are used to construct oriented strandboard which has several structural and cost advantages over plywood. The strandboard is a truly modem composite material where the orientation of wood fibers in the wafers making up the board can be engineered to give the board desired properties of stiffness and strength. As compared to plywood, strandboard is more efficient at utilizing all the wood fiber present in relatively small diameter logs, and thus is lower cost them plywood. Moreover, strandboard is without the voids typically present in lower grades of plywood. Strandboard is manufactured from wood wafers cut by a flaker from debarked logs. The debarked logs are advanced along the long axes of the logs approximately 30 inches into the flaker. The logs are held fixed while the blades of the flaker, which extend parallel to the axes of the logs, are caused to rotate about a line parallel to the axis of the logs but displaced from the logs, to thereby reduce a 30-inch portion of the logs to wafers. The wafers are thin veneer-like wood chips or flakes which are used to fonn the oriented strandboard. Existing feed mechanisms between a debarker, in which the bark is removed from the logs, and the flaker typically employ two separate chain conveyors which operate by indexing the logs forward than pausing while the flaker makes its cutting stroke and then retracts.  
           [0005]    Chain drives, while widely used for conveying logs, have several disadvantages, particularly where used to feed a flaker. Maintenance costs are higher than is desirable, as the weight and force with which logs can impact the drive systems results in the expenses of down time for repairs. Further, the cycle of advancing, pausing while the flaker makes its cutting stroke, and advancing again is less than ideally suited to the chain drive with the result that energy costs are higher than necessary.  
           [0006]    What is needed is a conveying system of greater reliability, lower cost, and greater efficiency for feeding logs between a debarker and a flaker  
         SUMMARY OF THE INVENTION  
         [0007]    The conveyor system of this invention extends between a log debarker and a flaker. The conveyor has five plates that are arranged within a conveying trough. The plates are continuous and extend the length of the conveyor. Three plates line the bottom of the conveyor trough and are supported on rollers, and two plates are positioned vertically on either side of the trough bottom to form approximately the lower half of the trough sides. The vertical plates forming the sides rest within Cchannels lined with ultra high molecular weight plastic. Each of the five plates is driven with a hydraulic piston. In operation, all five plates together move forward approximately 30 inches at a constant velocity, and then each plate is retracted separately. The motion of the plates is such that the static coefficient of friction holds the logs against the plates during the forward stroke, but the dynamic coefficient of friction, which is lower than the static coefficient of friction, allows the plates to slide with respect to the logs resting thereon. The effect is a stepwise advance of the logs from the inlet to the outlet of the conveyor. Also, because the logs typically are held in contact with other logs when a single plate is retracted, the logs resting on or against the plate are held from reverse motion by the other logs which are engaged with the non moving plates. Because the plates are moved by simple hydraulic pistons which are ideally suited for discontinuous motion, energy usage as compared to a chain drive conveyor is reduced and the required drive power is substantially reduced to approximately 40 percent, of the installed horsepower of a comparable chain drive conveyor. The stroke and timing of the piston movements are easily controlled by a hydraulic control system which, for optimum reconfiguration, may be controlled by a programmable logic controller, or may use simple cam driven timing mechanisms.  
           [0008]    It is an feature of the present invention to provide a conveying system between a log debarker and a flaker which is more reliable and of lower cost.  
           [0009]    It is a further feature of the present invention to provide a conveying system between a log debarker and a flaker which has lower operating costs, and lower energy usage.  
           [0010]    It is another feature of the present invention to provide a conveying system optimized for moving logs between a debarker and a flaker.  
           [0011]    Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic side elevational view of a debarker and flaker connected by the conveyor of this invention.  
         [0013]    [0013]FIG. 2 is an isometric view of the inlet of the conveyor of FIG. 1 where logs are received from the debarker.  
         [0014]    [0014]FIG. 3 is a fragmentary isometric view, partially broken away in section, of the discharge end of the conveyor which leads into the flaker of FIG. 1.  
         [0015]    [0015]FIG. 4 is a cross-sectional view taken along section line  4 - 4  of FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Referring more particularly to FIGS.  1 - 4 , wherein like numbers refer to similar parts, a log conveyor  20  is shown in FIG. 1. The conveyor  20  extends between a debarker  22  and a flaker  24 . Logs  26  are fed into the debarker  22  where the outer bark is removed from the logs. The logs  26  travel along the conveyor  20  advancing approximately 30 inches toward the flaker  24 . The logs  26  are clamped in the flaker  24 , and blades within the flaker  24  reduce a thirty-inch section of the logs to wood wafers or chips which are used to make strandboard or other wood products. Typically, this takes approximately seventeen seconds, after which the clamp within the flaker  24  is released and the logs are again indexed forward thirty inches and the process is repeated.  
         [0017]    The conveyor  20  has a log receiving section  28  which receives logs  26  from the debarker  22 . The log receiving section  28  is as wide as the debarker and has a more narrow rectangular trough  30  which has two vertical sides  32  and a horizontal bottom  34 . The conveyor  20  is of the reciprocating floor or walking floor type. The bottom or floor  34  of the conveyor trough  30  is composed of three plate members  36  having flat upper surfaces  37 . The plate members  36  extend the length of the conveyor  20 , which may be over one hundred feet long and are each about 20 inches wide. Each plate member  36  has a pair of downwardly extending flanges  38  which are about six and one-half inches deep. Between the flanges  38 , roller bearings  40  support the plate members  36 . The roller bearings  40  are mounted to transverse frames  41  which are spaced approximately nine-and-one-half feet on center along the length of the conveyor  20 . Staggered longitudinally on either side of the roller bearings  40  are centering rolls  42  which have internal bearings (not shown) which support the rolls  42  on bearing posts  44 . The rolls  42  position the plate members  36  laterally. The plate members  36  are constructed of heavy gauge steel, for example three-quarters of an inch, and are spaced apart approximately one-quarter of an inch. As shown in FIG. 3, each plate member  36  forms a beam which is driven by a hydraulic actuator  46 . The hydraulic actuator extends between a bracket  48  mounted to the underside of each plate  36  and a support frame  50  which leads into the flaker  24 . The hydraulic actuators  46  cause the plate members  36  to reciprocate. The ends  52  of the plates  36  overlap a horizontal fixed plate  54  adjacent to the in-feed  56  of the flaker  24 .  
         [0018]    The vertical sides  32  of the conveyor trough  30  have vertical plate members  58  which are mounted between lower C-channels  60  and upper C-channels  62 . The lower and upper C-channels are lined with Ultra High Molecular Weight (UHMW) plastic  63  or other low friction material. The vertical plate members  58  have flat inwardly facing surfaces  57  and are constructed of heavy gauge steel, for example three-quarter inch plate steel, and are continuous from one end of the conveyor  20  to the other. The vertical side plate members  58  are caused to move by hydraulic actuators  59  which are mounted between support frames  72 , and brackets  74  on the side plate members  58 .  
         [0019]    Above the moving vertical plate members  58  are fixed side wall sections  64 , and at the inlet  66  of the conveyor  20 , the receiving section  28  extends upwardly and outwardly from the fixed wall sections  64  as shown in FIG. 2. As shown in FIG. 1 and  2 , the receiving section  28  directs the logs  26  into the narrow trough  30 , with first one side  68  and then the other side  70  of the receiving section  28  directing the logs  26  into the trough, in the manner known to those skilled in the art to prevent the jamming of logs.  
         [0020]    The conveyor  20  is particularly well adapted to fulfill the requirements of transporting logs  26  between the debarker  22  and the flaker  24 . The flaker  24  has a rather narrow region of optimal cutting and so the logs which are fed to the flaker  24  should have a compact cross-section as shown in FIG. 4. The narrow trough  30  of the conveyor  20  is adapted to be filled to form a compact mass  71  of logs  26 . Gates  73 , as shown in FIG. 4, are positioned along the trough  30  as shown in FIG. 1 to control the height of the stack of logs. The gates  73  may be arranged and various heights to progressively bring the log stack to the desired height. The hydraulic actuators  46 ,  59  move together at a first velocity to draw the plates  36 ,  58  toward the in-feed  56  of the flaker  24 , thus drawing a compact mass of logs into the flaker  24  an amount proportional to the stroke of the hydraulic actuators  46 ,  59 , for example about 30 inches. A hydraulic clamp or the like (not shown) which typically forms part of the flaker  24  clamps the logs in place while the flaker  24  makes the cutting stroke which reduces the portion of the logs which extends into the flaker  24 , into wafers or chips  76 . The cutting stroke of the flaker, depending on the design of the flaker, may take approximately seventeen seconds.  
         [0021]    During the cutting stroke while the logs are clamped in the flaker, individual plate members  36 ,  58  are moved away from the flaker inlet one at a time. The frictional engagement between the logs and the nonmoving plate members serves to hold the logs in place while single plate members are moved away from the flaker inlet. In addition, more rapid movement away from the flaker inlet could be used, however if the logs are clamped rapid movement to produce a lower coefficient of friction is not necessary.  
         [0022]    There is a synergism between the design of the conveyor  20  and the need to present the flaker  24  with a compact mass  71  of logs. In typical prior art walking floor type conveyors the moving floor members are arranged in upwardly opening convex configuration with the object of transporting material without binding of the logs or other material. The conveyor  20 , in order to position the logs  26  for reduction to wafers in the flaker, places the logs in a compact rectangular shape. As shown in FIG. 4, the gate  73  restricts the height of the log stack to about two feet, where the trough  30  has a width of four and one-half feet to form a compact arrangement of the logs  26 . The compact arrangement necessarily results in fictional engagement of the trough walls, which are also moving components  58  in the conveyor  20 .  
         [0023]    It should be understood that the vertical plate members  58  could be mounted on roller bearings instead of the illustrated low friction bearings or that the low friction plastic inserts  63  at the bottoms of the C-channels  60  as shown could be C-shaped themselves so as to completely line the C-channels  60 .  
         [0024]    It should be understood that the vertical plate members  58  could be stiffened by flanges on the side of the plate opposite the trough  30 . It should further be understood that the dimensions described are by way of example, and that the conveyor may be variously configured depending on the output of the debarker  22  and the capabilities of the flaker  24 . It should further be understood that the gates  73  may have various configurations such as is conventionally used with prior art chain conveyors.  
         [0025]    It should also be understood that depending upon the number of plate members  34 ,  58  two or more plate members could be retracted simultaneously particularly if the logs are held clamped within the flaker  24 .  
         [0026]    It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.