Abstract:
A guide arm for a gang sawmill is provided adjacent to an inlet of a gang saw and is movable about a pivot pin depending on the actual curvature of a cant to adjust (continuously or fixed) the position of an incoming cant to maximize the yield of usable boards produced by the gang saw by moving the cant relative to the saw as a conveyor feeds the cant through the gang saw.

Description:
This invention relates to a device for improving the recovery of curved logs or cants by getting more marketable lumber from them. 
     BACKGROUND OF THE INVENTION 
     In preparing lumber for the construction market, it has been the object to provide boards of substantially uniform thickness along the length of each board. In the past, it has been the practice to sell unevenly cut boards at below high quality boards due to the variations in the sawn boards, However, with the increasing price of raw logs and the decreasing value of finished lumber, attempts have been made to improve the sawing apparatus to enable improved handling of curved cants to increase the amount of merchandisable lumber obtained. Further, the devices installed in mills to saw curved cants have generally been complicated in structure and expensive to maintain to allow accurate sawing of curved cants. 
     DESCRIPTION OF THE PRIOR ART 
     A number of employed devices, such as that shown in U.S. Pat. No. 5,722,474, commonly referred to as the “Wiggle Box Gang”, use a pivoting gang saw arrangement where the arbor on which the saws are mounted is pivotable about a vertical axis as the cant is fed to the gang. While such systems have generally been effective in salvaging curved cants, that is, the mill operator was able to produce more usable boards than straight sawing technologies, initial cost and installation of such systems has been expensive and the maintenance has been relatively high. Where a pivoting gang apparatus such as this is utilized, there is a significant gap in the flow of cants through the system to allow the pivoting mechanism to set properly for the on-coming piece. This, coupled with a maximum speed limitation imposed by the saw&#39;s ability to saw properly, limited the volume of material processed to sometime necessitate multiple lines to reach the production goals desired. 
     Another employed device is often referred to as a “Curved Canting” system. In a conventional curved canting operation, a chipping station precedes the gang saw station where chipping heads are physically separated from the gang saw chamber. In such an operation, the chipping heads are moved and controlled in a manner to follow the path of curvature of a cant to chip two parallel faces on the sides of the cant. The cant is then fed to the gang saw. The conventional curved canting system provides a fixed control guide arm mounted on the conveyor apparatus immediately upstream of the bank of saws in the gang so that the saws themselves need not be pivotally mounted but only rotatably mounted on a conventional driven arbor. The cutting of a curved cant often, however, results in what is called a snipe end board, that is, one the thickness of which varies from one dimension to a smaller dimension in thickness. Such produced boards frequently require cutting off the non-uniform end piece which is then discarded thereby reducing the yield. 
     Thus, there is a need for a more controllable system and device to handle curved cants that will not require major modification of an already installed fixed apparatus and one which can be easily maintained by mill employees. 
     SUMMARY OF THE INVENTION 
     The present invention of the variable guide system provides a control guide arm mounted on the conveyor apparatus immediately upstream of the bank of saws in the gang so that the saws themselves need not be pivotally mounted but only rotatably mounted on a conventional driven arbor. An inspection station is provided upstream of the guide arm and upstream of the chipping station and will provide output to the guide arm in a timed manner so that the guide arm will be pivoted about a mounting axis to engage the cant in cooperation with a press arm as the front end of the cant is entering the gang saw. The inspection station is provided with a plurality of light sources, such as lasers and light detectors and may be one of those that are commercially available. The actuation device for the guide arm may be one of a number of types including an electrically actuated solenoid, a fluid piston and cylinder. 
     The advantages of the present invention are believed to be apparent from the following description taken in conjunction with the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic view from the top of a gang saw apparatus and associated conveyors showing the location of the guide arm of the present invention upstream of the gang saw with the cant, guide and push bars positioning the end of a cant just prior to engaging the gang saw; 
         FIG. 1B  is an alternative schematic view showing a transverse inspection station.  FIG. 1C  is an alternative schematic view showing a transverse inspection and an out-of-line sawing section. 
         FIG. 2  is a perspective view of the mounting and the variable guide actuation mechanism used in the present invention. 
         FIG. 3  is a top view of the guide arm of the present invention; and 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, there is shown in  FIG. 1  a schematic illustration of an apparatus for cutting a cant  10  into boards by passing the cant between a gang saw set. In a typical arrangement, a cant  10  will be fed on a conveyor  14  after having been chipped on both sides at a pivoting chipping station  11  which will follow an inspection station  12 . At the inspection station  12 , the curvature, if any, of the cant is determined by a series of photo detectors, lasers, cameras and light sources mounted above, below and alongside the conveyor path  14  and preferably on either side of the cant  10 . In the event that no curvature of any significance is detected at the inspection station  12 , a guide arm  16  will be set to its home “zero” position and a press arm  21  ( FIG. 1C ) will be operated, such as by a piston and cylinder  32  ( FIG. 1A ) that is activated when a sensor detects the presence of a cant  10 , to push the leading end  19  of the cant  10  against the guide arm  16 . However, any curvature detected at the inspection station  12  will be analyzed by a computer at the inspection station  12  which will calculate any required pivoting of the chipping station  11  as cant  10  travels along the path  14  in order to maximize the amount of useful board lumber that will be obtained as the cant is fed through the gang saw  18 . For this purpose, the output of the inspection station will be communicated to an actuator  32  as described below. As noted above, the press arm  21  is operated upon detection of cant  10  and simply presses the cant  10  against the facing surface of the guide arm  16  while the guide arm  16  will be pivoted about axis  22  to adjust the position of the end  19  relative to the gang saw  18  in order to position the cant to minimize the effect of the curvature at the point of contact with the gang saw  18 . An auxiliary guide arm  36  may be positioned to pivot about axis  22  by a piston and cylinder  38  ( FIG. 1B ) independently of guide arm  16 . 
     Referring to  FIG. 2 , there is shown a perspective view of the guide arm  16  mounted adjacent to a fixed side bar  20  of the conveyor apparatus typically used in a saw mill. The guide arm  16  is connected to the actuating cylinder  32 . The opposite end  24  of the guide arm  16  has an inner edge  26  from which a leaf or tongue  28  extends and which has an aperture receiving a pin to which is attached one end of an operating arm  30 , the opposite end of which is attached to a piston head located in a cylinder  32  which may be fluid actuated. The cylinder  32  will, of course, be rigidly attached to the conveyor frame or other fixed support. It will be understood by those skilled in this art that various actuators may be employed in this environment. Control of the cylinder  32  will be effected by actuation of the supply or bleed valves in the fluid lines connected to the cylinder  32  as is well understood in this technology. For example, the valves may be solenoid actuated by a current supplied by the output of a computer associated with the inspection station  12 , the details of which are also well understood in this technology and which is commercially available from a number of sources in the market. Typically, the inspection station  12  will determine the curvature of portions of the cant  10  in relation to the speed of the conveyor  15  moving the cant along the path  14 . The analysis by the computer in the inspection station  12  will be effective to impart a pivot motion to the chipping station  11  on the conveyor  15  so that the lengths of board formed by the gang saw will be the maximum possible for a cant having the detected curvature. This will increase the yield of the mill virtually independently of curvature of the logs provided to form the cants  10 . 
     Referring to  FIGS. 2 and 3 , a yoke  34  is pivotably mounted to the side bar  20  by pivot pin  102  and yoke  34  is connected to the auxiliary guide arm  36  which extends in a direction opposite to the direction of guide arm  16 . The guide arm  16  is pivotably mounted to the side bar  20  by the pivot pin  100 . Preferably, the guide arm is made of hardened steel and may be L-shaped in cross-section as shown in  FIG. 2  to ensure that it is more easily moved by the piston and cylinder arrangement shown without causing undue wear on the cylinder actuator. It will be understood that the arm  36  may also be independently actuated by a separate piston and cylinder arrangement controlled by the output of the inspection station  12 . This will effectively extend the range of curved cants that can be handled with the apparatus of this invention. 
     It will be appreciated that the operation of the guide bar  16  for many curved cants will be set once by the inspection station readings for each cant depending on the detected curvature. It is contemplated that more than one adjustment of the guide bar  16  for an individual cant may be required such as where there is more than one curvature present in the cant. Also, continuous movement of the guide bar can be effected such as for severely irregular cants. 
     Having described the invention, it will be apparent to those skilled in this art that various modifications may be made thereto without departing from the spirit of the invention as defined in the appended claims.