Abstract:
A cutting apparatus for cants of non-uniform original dimensions includes a pair of band saws at a cutting station through which a cant passes along a path; each band saw is mounted on a carriage that is mounted for movement relative to the path and actuating piston and cylinder devices are used to move each carriage in response to data fed to a control computer from a cant scan.

Description:
FIELD OF THE INVENTION  
         [0001]    The present the invention relates to an improvement in apparatus for cutting a log that has been canted into boards while maximizing the production of the boards from logs with a higher production efficiency than has heretofore been possible with certain prior art equipment. The invention also provides a method of operating the apparatus to optimize production and to provide boards of substantially uniform thickness even where the log exhibits a significant curvature along its longitudinal axis.  
         BACKGROUND OF THE INVENTION  
         [0002]    Due largely to the increasing scarcity of high quality lumber that is available for harvesting, it is becoming increasingly important that the processes employed to cut logs into boards be able to accommodate a greater variety of initial log shapes at efficient production speeds whereby logs that normally would be discarded due to their curvature or other defects will be able to be harvested and efficiently cut into useful wood products. In prior U.S. Pat. No. 5,722, 474 an apparatus and method are disclosed where disk saws are mounted on an axle which in turn is mounted on a pivotable support that is controlled by a computer to permit optimization of the output of the device. A scanning station is employed to record the outer configuration of a canted log which data is fed to the computer to analyze the data obtained and to supply it to the computer operating software for controlling the position of the gang saws relative to a substantially rectilinear path of travel for the log. Ideally, each incoming log is scanned and a unique cutting solution for that log will be derived and utilized to control for each selected increment of length of the log the cutting position of the gang saws in correlation with the throughput speed of the transport conveyor for the log.  
           [0003]    The chief advantage of the arrangement of the aforesaid U.S. patent is that logs that previously were discarded were able to be used to provide marketable wood products. In addition, the production capacity of the mill was increased significantly. However, in the lumber mill industry, there are a large number of installations that have already installed equipment including band type saws. Since the structures of these mill installations does not lend itself to economical adaptation to the curved log cutting techniques disclosed in U.S. Pat. No. 5,722, 474, it has become necessary for other solutions to the efficiency problem to be found.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an apparatus and method of operation for a computer controlled the saw mill cutting operation where the cutting devices employed are band saws mounted on movable carriages and preferably located downstream of chipping devices which in one embodiment are mounted on pivotable carriages to allow the device to accommodate even severe curvature in the log product.  
           [0005]    In a preferred form, each band saw is in the form of a continuous loop having an upper and lower guide pulley mounted on a carriage which in turn is mounted for reciprocation along a rectilinear path. To enhance the production capacity, chipping devices are mounted upstream of the band saws and are themselves preferably mounted on pivoting or shiftable carriages with the chipping devices movable along rectilinear paths on the pivoting carriages to allow the apparatus to accommodate different cant widths. With such an arrangement, a virtually finished cant can be delivered from the device.  
           [0006]    The foregoing and other advantages of the present invention will become apparent as consideration is given to the following detailed description taken in conjunction with the attached drawings, in which:  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a top, plan view of a portion of the band saw mill apparatus showing an infeed conveyor and a portion of the outfeed assembly;  
         [0008]    [0008]FIG. 2 is a side view in elevation of the device of FIG. 1;  
         [0009]    [0009]FIG. 3 is a top, plan view of another embodiment of the band saw mill apparatus of this invention;  
         [0010]    [0010]FIG. 4 is a top plan view of another embodiment of the present invention;  
         [0011]    [0011]FIG. 5 is a top plan view in schematic form of a further modification of the invention of FIG. 1; and  
         [0012]    [0012]FIG. 6 is a top plan view of another modification of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    Referring to the drawings, wherein like numerals designate corresponding parts throughout the several views, there is shown in FIG. 1 a top plan schematic view of a band saw set up  10  which includes an infeed conveyor  12 , an outfeed conveyor  14  and a band saw assembly  16 . Other parts helpful to the understanding of the invention are not illustrated but are disclosed in U.S. Pat. No. 5,722, 474, the disclosure of which is incorporated herein by reference. The feed conveyor  12  will typically carry a cant  18  which, as shown, is severely curved along its longitudinal axis. The cant  18  is fed along with the conveyor  12  to a gap between two band saw assemblies  20  and  22  which are of substantially identical construction so that the following description of band saw assembly  20  will be understood to apply to assembly  22  as well.  
         [0014]    The band saw assembly  20  includes a band saw blade  26  which is in the form of a continuous loop extending about a support  24  which is carried at its center on plates  25 . As is apparent from FIG. 2, the inner plate  25  is attached at its outer periphery to four slide brackets  30  and  32  which, in turn, are slidably mounted on a pair of vertically spaced apart rods  28 ,  29 . In one embodiment, the brackets  30  and  32  may be fixed on rods  28  and  29  and the rods may be shifted by a piston rod  38  carried by a piston  33  so as to move the assembly  20  relative to the path of travel of the curved cant  18  as the curved cant  18  moves from the left to the right in FIG. 1 past the saw blades  26  of each saw assembly  20  and  22 .  
         [0015]    As will be apparent from the following discussion and to those skilled in this technology, a number of techniques are available for shifting the band saw assemblies  20  and  22  relative to the path of travel of the cant  18  from the conveyor  12  to the conveyor  14 . For example, information from an optical scan of the cant  18  may be passed to a control system where computer  31  will analyze the scan information and perform the calculations as noted in U.S. Pat. No. 5,722,474 to determine the optimum cutting operation for the saws. The computer will then send electrical signals along a cable  35  to a linear positioning cylinder  36  to control the actuation of each of these cylinder pistons  33  of each assembly  20  and  22 . A unique cutting solution will be derived by the software running in the computer  31  to optimize the positioning of the band saw assembly&#39;s  20  and  22  relative to the position of the cant  18  between the assemblies  20  and  22  and will take into consideration the velocity of travel of the cant  18  on the conveyor  12 . As described more fully in the aforementioned U.S. patent, an efficient cutting operation will result with the movement of the band saw assemblies  20  and  22  determined by the incremental curvature of the cant  18 . As a result, the expense of mounting a heavy gang saw arrangement for rapid pivoting movement during the travel of that of a cant is eliminated. As shown in FIG. 2, the rod  28  extends parallel to a lower support rod  29  which is provided with its slide brackets  30  parallel to the arrangement as shown in the top plan view of FIG. 1. The cylinders  32  and their actuation mechanisms  36  may be mounted on a post  39  at each outside periphery of the assembly  10 .  
         [0016]    As shown in FIG. 3, another arrangement of the positioning cylinders  32  is shown where a single cylinder  32 ′ extends between two rigid legs  42  and  44  extending outwardly from the plates  25  of the respective band saw assemblies  20  and  22 . The piston rod of the cylinder  32 ′ is connected to rigid arm  42 , through an extension such as at  43 , if needed, and will control the positioning of the two band saw assemblies  20  and  22  relative to each other. Another cylinder  37  with one end rigidly fixed to a support and also attached to arm  44  of one of the cylinders  32  permits positioning of the assembly  16  either with or without varying the position between the band saw assemblies  20  and  22 .  
         [0017]    As shown in FIG. 4, to achieve greater flexibility in the cutting operation two pairs of the band saw assemblies are provided at  20 ,  20 ′,  22  and  22 ′. Each assembly will be provided with its own linear positioning piston and cylinder such as at  48  and these preferably are individually controlled in the same manner as the cylinders in the previous embodiments.  
         [0018]    In handling almost all cants, it is preferable to provide complete finishing treatment of the log separate from the sawing operation alone and this involves separate equipment such as is illustrated in schematic form in FIGS. 5 and 6. In the arrangement of FIG. 5, a chipping platform  50  is located between the in feed conveyor  12  and the band saw assembly  16  and outfeed conveyor  14 . To remove knots, bark or other imperfections from the side edges of the cant  18  stripping bands  52  and  54  are each mounted on separate platforms  55  and  56  each of which is movable by means of separate cylinders  58 ,  60 ,  62  and  64  to permit motion in the direction of arrows  66  as well as rotational motion as shown by the arrows  68 . The cylinders  58 - 64  will typically be fluid actuated so that the  5  control is through the valves supplied from a source of fluid under pressure and the valving may be subjected to control by the same computer  33  that controls the positioning of the band saw assembly  16  since the basic information relative to that already obtained from the scanned cant  18  will be the source for the control signals to be fed to the cylinders  58 - 64 .  
         [0019]    As shown in FIG. 6, a somewhat more limited motion is achieved for the chipping apparatus mounted on a frame  70 , the position of which is controlled by a pair of a piston and cylinders  72  and  74  upstream of the band saw assembly  16 . The chipping devices  76  will be of conventional construction and will therefore not be further described.