Patent Publication Number: US-6988438-B2

Title: Active sawguide assembly and method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Divisional Patent Application of U.S. patent application Ser. No. 10/621,938 filed Jul. 17, 2003, now U.S. Pat. No. 6,877,411, which is a Division of U.S. patent application Ser. No. 09/792,891 filed Feb. 23, 2001, now U.S. Pat. No. 6,612,216, which claims priority from U.S. Provisional Patent Application No. 60/184,422 filed Feb. 23, 2000. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a method and an apparatus for straight or curve sawing workpieces such as cants or timbers or lumber, and in particular relates to an active sawguide package system which is constantly adjusted to a target line during sawing, for curve sawing workpieces according to an optimized profile. 
     BACKGROUND OF THE INVENTION 
     It is known that in today&#39;s competitive sawmill environment, it is desirable to quickly process straight or non-straight cants so as to recover the maximum volume of cut lumber possible from the cant. For non-straight cants, volume optimization means that, with reference to a fixed frame of reference, either the non-straight cant is moved relative to a gangsaw of circular saws, or the gangsaw is moved relative to the cant, or a combination of both, so that the saws in the gangsaw may cut an optimized non-straight path along the cant, so-called curve-sawing. 
     A canted log, or “cant”, by definition has first and second opposed cut planar faces. In the prior art, cants were fed linearly through a profiler or gang saw so as to produce at least a third planar face either approximately parallel to the center line of the cant, so called pith sawing, or split taper sawing, or approximately parallel to one side of the cant, so called full taper sawing; or at a slope somewhere between split and full taper sawing. For straight cants, using these methods for volume recovery of the lumber can be close to optimal. However, logs often have a curvature and usually a curved log will be cut to a shorter length to minimize the loss of recovery due to this curvature. Consequently, in the prior art, various curve sawing techniques have been used to overcome this problem so that longer length lumber with higher recovery may be achieved. 
     Curve sawing typically uses a mechanical centering system that guides a cant into a secondary break-down machine with chipping heads or saws. This centering action results in the cant following a path very closely parallel to the center line of the cant. Cants that are curve sawn by this technique generally produce longer, wider and stronger boards than is typically possible with a straight only sawing technique where the cant being sawn has significant curvature. Boards that are cut using curve sawing techniques straighten out once they are stacked and dried. 
     Curve sawing techniques have also been applied to cut parallel to a curved face of a cant; the above mentioned full taper sawing. See for example Kenyan, U.S. Pat. No. 4,373,563 and Lundstrom, Canadian Patent No. 2,022,857. Both the Kenyan and Lundstrom devices use mechanical means to center the cant during curve sawing and thus disparities on the surface of the cant such as scars, knots, branch stubs and the like tend to disturb the machining operation and produce a “wave” in the cant. Also, cants subjected to these curve sawing techniques tend to have straight sections on each end of the cant. This results from the need to center the cant on more than one location through the machine. That is, when starting the cut the cant is centered by two or more centering assemblies until the cant engages anvils behind the chipping heads. When the cant has progressed to the point that the centering assemblies in front of the machine are no longer in contact, the cant is pulled through the remainder of the cut in a straight line. It has also been found that full taper curve sawing techniques, because the cut follows a line approximately parallel to the convex or concave surface of the cant, can only produce lumber that mimics these surfaces, and the shape produced may be unacceptably bowed. 
     Thus in the prior art, so called arc-sawing was developed. See for example U.S. Pat. Nos. 5,148,847 and 5,320,153. Arc sawing was developed to saw irregular swept cants in a radial arc. The technique employs an electronic evaluation and control unit to determine the best semi-circular arc solution to machine the cant, based, in part, on the cant profile information. Arc sawing techniques solve the mechanical centering problems encountered with curve sawing but limit the recovery possible from a cant by constraining the cut solution to a radial form. 
     Applicant is also aware of U.S. Pat. No. 4,572,256, U.S. Pat. No. 4,690,188, U.S. Pat. No. 4,881,584, U.S. Pat. No. 5,320,153, U.S. Pat. No. 5,400,842 and U.S. Pat. No. 5,469,904; all of which relate to the curve sawing of two-sided cants. Eklund, U.S. Pat. No. 4,548,247, teaches laterally translating chipping heads ahead of the gangsaws. The U.S. Pat. Nos. 4,690,188 and 4,881,584 references teach a vertical arbor with an arching infeed having corresponding non-active tilting saws and, in 4,881,584, non-active preset chip heads mounted to the sawbox. 
     U.S. Pat. No. 4,599,929 to Dutina teaches actively translating and skewing of gangsaws for curve sawing, where a saw guide package is adjusted. The saw axle may also be adjusted in view of the average inclination over the sawing line of the entire longitudinal profile of the workpiece or of parts of the longitudinal profile. 
     U.S. Pat. No. 4,144,782 to Lindstrom teaches that when curve sawing a log, the log is positioned so as to feed the front end of the log into the saw with the center of the log exactly at the saw blade. In this manner the tangent of the curve line for the desired cut profile of the log extends, starting at the front end, parallel with the direction of the saw blade producing two blocks which are later dried to straighten and then re-sawn in a straight cutting gang. 
     U.S. Pat. No. 5,884,682 to Kennedy et. al, discloses that optimized lumber recovery is best obtained for most if not all cants if a unique cutting solution is determined for every cant. Thus for each cant a “best” curve is determined, which in some instances is merely a straight line parallel to the center line of the cant, and in other instances a complex curve that is only vaguely related to the physical surfaces of the cant. 
     U.S. Pat. No. 5,722,474 to Raybon, et al. teaches using scanned data to saw a cant, by moving the cant through the gang sawbox while pivoting and translating the gang sawbox. The gang sawbox contains a fixed sawguide package to curve saw the curvature in the log. 
     U.S. Pat. Nos. 5,761,979 and 5,870,936 to McGehee disclose using a saw guide or saw guides where sawguides and saws are actively translated along a fixed driven arbor. The sawguides and saws may be skewed a few degrees on either side of the perpendicular to the arbor axis, so that the saws either actively traverse a non-symmetrical board fed into the saws lineally for optimum board edging, or actively follow a curved path for sawing boards from a cant fed into the saws lineally, from optimized data of the scanned profile. This system permits curve sawing without requiring the movement of the entire saw box. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an active sawguide assembly, used to position saws along an arbor to permit curve sawing without the need to move the entire saw box. 
     The sawguide assembly includes a set of sawguides positioned adjacent to one another to create an array of laterally-abutting sawguides. A sawguide biasing means, which may include a biasing assembly such as a sawguide clamping cylinder, biases the sawguides against one another. An array support, such as one including a shaft or other elongate member such as a bar, supports the array for movement along a lateral path generally parallel to the axis of the arbor. A means for actively laterally translating the array which may include a lateral driver, which may itself comprise a translation cylinder, is used to move the entire array in unison along the lateral path. A means for actively simultaneously pivoting each sawguide includes a sawguide array skewing assembly which by, in one embodiment, the use of a steering block, rotatably couples the sawguides to one another so that the sawguides can be pivoted in unison about their respective pivot axes by a means for actively selectively pivoting a cooperating steering structure (which may include the steering block), and which may include a skewing driver. 
     Another aspect of the invention is directed to a method for a laterally translating saws along and pivoting saws relative to a drive arbor. The method includes simultaneously laterally positioning an array of adjacent, laterally-contacting sawguides along a drive arbor. The sawguides are also simultaneously pivoted about their pivot axes causing the contacting lateral sides of the sawguides to slide over one another. 
     Other features and advantages of the invention will appear from the following description in which the disclosed embodiment is described in detail in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood by reference to drawings, wherein: 
         FIG. 1  is a plan view showing the sawing system of the present invention. 
         FIG. 2  is an isometric view showing the active sawguide assembly of the present invention 
         FIG. 3   a  is an enlarged view taken from  FIG. 1  showing the active sawguide package having been skewed right and translated left. 
         FIG. 3   b  is an enlarged view taken from  FIG. 1  showing the active sawguide package having been skewed right and translated to the center of the sawbox. 
         FIG. 3   c  is an enlarged view taken from  FIG. 1  showing the active sawguide package having been skewed left and translated to the center of the sawbox. 
         FIG. 4  is an enlarged isometric view of the active sawguide package of the present invention. 
         FIG. 4   a  is the view of  FIG. 4  showing the sawguide package skewed. 
         FIG. 5  is an isometric view of a sawguide containment plate and one sawguide of the active sawguide package of the present invention. 
         FIG. 6  is a cross-sectional view section line  6 — 6  in  FIG. 9 . 
         FIG. 7   a  is an enlarged partially cut-away view taken from  FIG. 9 . 
         FIG. 7   b  is the view of  FIG. 7   a  showing the sawguide containment plate in a lowered position. 
         FIG. 8  is an enlarged side elevation view of a sawguide showing the side lubrication path. 
         FIG. 9  is an enlarged view, along section line  9 — 9  in  FIG. 1 , of the active sawguide system of the present invention within the sawbox. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawing figures wherein similar characters of reference represent corresponding parts in each view, the active sawguide assembly of the present invention is generally indicated by the reference numeral  10 . 
     A workpiece  12  is fed transversely from the mill in direction A and is directed onto a lineal transfer  14  and positioned against a fixed fence  16  or other positioning means, for roughly or approximately centering the workpiece on the lineal transfer. Once workpiece  12  is roughly centered on lineal transfer  14  it is translated lineally in direction B through a lineal scanner  18  towards sawbox  20 . Scanner  18  scans workpiece  12 . Once through the scanner workpiece  12  is translated onto an infeed sharpchain transfer  22  positioned within the infeed area of sawbox  20 . As best seen in  FIG. 9  a plurality of overhead driven press rolls  24  are located above infeed sharpchain transfer  22 . Press rolls  24  press down on workpiece  12  to feed workpiece  12  straight into sawbox  20  in direction B. 
     The outfeed area of sawbox  20  also has a circulating sharpchain transfer  60  cooperating with a plurality of outfeed overhead pressrolls  62 . Pressrolls  24  press workpiece  12  onto lower infeed sharpchain  24 . Pressrolls  24  and  62  provide for continued straight feeding of workpiece  12  through sawbox  20 . Note, however, workpiece  12  could be fed through sawbox  20  along a curved or partially curved path. 
     As best seen in  FIGS. 2 and 4 , active sawguide assembly  26  is mounted within sawbox  20 . Active sawguide assembly  26  guides a plurality of circular saws  28  mounted in parallel array on splined arbor  30 . Arbor  30  is supported by sawbox  20  through bearings  31  for rotation about a saw axis  33 . Saws  28  are held snugly between pairs of sawguides and are spline mounted onto the arbor so as to be free to translate, i.e. slide, laterally on the arbor. Other cross-sectional shapes, such as scalloped, may also be feasible for arbor  30 . Active movement, as better described below, of sawguide assembly  26  actively moves the saws so that an optimized sawing path through workpiece  12  may be followed, thereby producing improved lumber recovery. The optimized sawing path is determined by an optimizing processor (not shown) processing data from the scanned image of workpiece  12 . 
     As best seen in  FIGS. 3   a ,  3   b  and  3   c , in operation sawguide assembly  26  simultaneously skews to a desired skew angle α and laterally translates to a cut starting position as workpiece  12  begins to enter into sawbox  20 . Once sawing commences, sawguide assembly  26  and saws  28  actively skew and translate in unison. Arbor  30  is driven to turn saws  28  in direction C for sawing of workpiece  12 . Otherwise it remains fixed relative to the sawbox. Thus by a combination of skewing and lateral translation relative to the sawbox, boards  12   a  are sawn from workpiece  12  by the saws following an optimized curve as workpiece  12  passes straight through sawbox  20 , sawbox  20  remaining fixed. Thus, curve sawing of workpiece  12  can be accomplished with only the movement of sawguide package and the associated hardware shown in figures  2 – 3   c . This eliminates the need to move the entire sawbox  20 , which may weigh as much as 20,000 to 40,000 pounds, as is necessary with many prior curve-sawing systems. This increases the speed, efficiency and throughput of the system while simplifying the design and operation. 
     As best seen in  FIGS. 2 and 4 , active sawguide assembly  26  includes a set of adjacent sawguides  26 ′ cooperating in pairs. Each sawguide pair includes sawguides  26   a  and  26   b  mounted on and supported by a sawguide bar  32 . Sawguide  26   a  and  26   b  in each sawguide pair are sandwiched together between sawguide steering block  34  and a sawguide clamping block  36 . Steering block  34  is fixed to bar  32  by a pivot pin  34   a  as is discussed below. Sawguide clamping block  36  presses the sawguides together against steering block  34  with a constant pressure which may be between 6,000 to 10,000 lbs. per square inch. Sawguide clamping cylinder  38  is mounted to end  32   a  of sawguide bar  32  by cylinder rod  38   a . Cylinder  38  tensions rod  38   a  so as to drive parallel push rods  38   b  and  38   c  against clamping block  36 . Clamping block  36  is thus actuated by sawguide clamping cylinder  38  via push rods  38   b  and  38   c . Clamping push rods  38   b  and  38   c  are parallel to, and disposed on opposite sides of, sawguide bar  32 . They are journelled through parallel apertures in mounting block  40 . Rods  38   b  and  38   c  are rotatably mounted to clamping block  36  by spherical rod ends  38   d  &amp;  38   e , so that when cylinder rod  38   a  pulls on sawguide bar  32 , clamping rods  38   b  and  38   c  apply pressure to clamping block  36  as clamping block  36  is articulated as set out below. Accordingly, sawguides  26 ′ are biased against one another by a sawguide biasing assembly comprising sawguide clamping cylinder  38  acting on sawguide clamping block  36  with the sawguides captured between blocks  34  and  36 , and as such is one example of a means for biasing the array of sawguides against a steering structure such as including steerina block  34 . 
     Sawguide bar  32  is slidably journalled in collars  33   a and  33   b  mounted on corresponding sawbox walls  20   a  and  20   b  and so may be translated back and forth in direction D by actuation of translation cylinder  42 . Translation cylinder  42  is rigidly mounted to mounting block  40 . Mounting block  40  is rigidly mounted to end  32   a  of sawguide bar  32 . Translation cylinder  42  actuates translation cylinder rod  42   a . The distal end  42   b  of translation cylinder rod  42   a  is mounted to wall  20   a  of sawbox  20 , so that translation cylinder  42  when actuated actively translates sawguide bar  32  (and cylinder  42 , block  40 , cylinder  38  and rods  38   a – 38   c  therewith) in direction D relative to sawbox  20 . Therefore, translation cylinder  42  acts as one example of a means for actively laterally translating the array of sawguides in unison along a lateral path defined by sawguide bar  32 . Simultaneously, articulating steering cylinder  44  actively skews sawguide assembly  26  in direction E about pivot axis F, so as to follow an optimized sawing path such as illustrated by way of example in  FIGS. 3   a – 3   c . Steering cylinder  44  is pivotally mounted to block  41 , between anus  41   a , by means of pin  41   b . Block  41  is rigidly mounted to end  32   b  of sawguide bar  32 . Accordingly, the distance between block  41  and block  34  remains fixed. 
     Sawguide steering block  34 , which is one example of a steering structure included in a means for actively simultaneously pivoting each sawguide, is rotatably mounted to sawguide bar  32  by steering pin  34   a . Pin  34   a  lies along axis F. Steering pin  34   a  is mounted through steering block  34  and sawguide bar  32 , so that steering block  34  may be pivoted about pivot axis F relative to sawguide bar  32  by actuation of cylinder  44  driving rod  44   a  and so that steering block  34  translates with sawguide bar  32  when sawguide bar  32  translates back and forth in direction D. Steering cylinder  44  and block  41  both translate with sawguide bar  32 . Steering cylinder  44  is one example of a means for actively selectively pivoting the steering structure. 
     Cylinder rod  44   a  is connected to steering block  34  by a zero clearance spherical rod end  44   b  seated in cup  34   b . Spherical rod end  44   b  allows steering block  34  to be pivoted in direction E the optimized skew angle α, that is, skewed from the orthogonal to the axis of rotation of driven arbor  30 . Sawguide clamping block  36  will give resiliently under pressure, just enough to allow the sawguide  26   a  to slide over and relative to adjacent sawguide  26   b  as the sawguide assembly  26  is actively skewed by pivoting of steering block  34  in direction G. The sliding of adjacent sawguides one over the other while maintaining the sawguides pressed together allows for the active skewing of the sawguide package and hence the active steering of the saws. 
     As best seen in  FIG. 4 , steering block  34  has an elliptical aperture  34   c  to allow steering block  34  to skew the required angle while restraining sawguide assembly  26  from vertical translation. 
     As best seen in  FIG. 5 , a sawguide containment plate  50  is rotatably supported by a containment plate shaft  50   a . When elevated to the horizontal as seen in  FIG. 7   a , a track  51 , mounted on plate  50  parallel to shaft  50   a , engages the underside of sawguide assembly  26 . Track  51  has a trough or channel  51   a  along its length for engaging correspondingly positioned sawguide pivot containment pins  52  mounted to the underside of each sawguide  26 ′. Pins  52  form a laterally spaced array lying in a plane containing steering pin  34   a  Each sawguide  26 ′ has its corresponding pin  52 . Pins  52  hold sawguides  26 ′ in position during skewing, providing for pivoting of each sawguide  26 ′ about its corresponding pivot axis F. Channel  51  a has a length as required for the desired capacity of sawbox  20 . That is, when sawguide assembly  26  is translated in direction D, pivot pins  52  slide along channel  51  a while simultaneously allowing sawguides  26  to actively skew. 
     Sawguides  26 ′ each have an elongated “C”-shaped relief  56 , which allows the sawguides to slide onto sawguide bar  32 . Relief  56  when mounted over sawguide bar  32  holds sawguides  26  in relative position while allowing the changing of sawguides  26 ′ when required without the need to disassemble the entire sawguide assembly  10 . When the sawguide clamping cylinder  38  is released, sawguide containment plate  50  can, as best seen in  FIGS. 7   a  and  7   b , be lowered in direction G by actuation of sawguide containment plate cylinder  54 . This then allows sawguides  26 ′ to rotate upwardly in direction H to change either saws  28  or sawguides  26 ′. Sawguides  26 ′ are removed, for example, to change the sawguide pads  26   c.    
     Sawguides  26 ′, steering block  34  and pressure block  36  include internal lubrication galleries. The lubrication galleries feed lubrication fluid to zigzag lubrication channels  58  located externally on one side of each sawguide  26 ′ as better seen in  FIG. 8 . The lubrication fluid flows from the galleries, via ports  58   a , into and along channels  58 . The lubrication fluid distributes itself between the side surfaces of adjacent sawguides  26 ′ so as to reduce friction and allow the side surfaces of sawguides  26 ′ to scuff and slide over one another when sawguide package is skewed under pressure. Sawguides  26 ′ and  26   b  may also include dissimilar metals or other materials or coatings to further reduce scuffing friction or gauling when sawguides  26 ′ are actively skewed during optimized sawing. 
     In use, workpieces  12  is directed to sawbox  20  and driven past saws  28 . Sawguides  26 ′ laterally position saws  28  along the axis of arbor  30  and also change the skew angle of the saws  28  according to the desired path to be cut. The set of sawguides  26 ′ is captured between sawguide steering block  34  and sawguide clamping block  36 , with steering block  34  pivotally secured to bar  32 . Shaft  32  and the sawguides  26 ′ therewith are moved laterally, that is in the direction of arrow D, in unison thus sliding saws  28  along arbor  30  by the activation of translator cylinder  42 . The skew angles of circular saws  28  are changed in unison by actuating articulating cylinder  44 . 
     Modification and variation can be made to the disclosed embodiment without departing from the subject of the invention as defined in the following claims. For example, instead of using clamping cylinder  38 , a spring-type clamping device could be used. Also, rods could be used to secure blocks  34 ,  36  to one another so long as relative sliding movement between the sawguides is permitted; in such case sawguide assembly  26  could be slidably mounted to bar  32 . It may be desired to use lateral position devices, such as piston and cylinder arrangements, extending from both sides of sawguide assembly  26 . While the surfaces of sawguides  26 ′ are preferably flat and smooth, it may be possible to replace the disclosed flat surface to flat surface engagement between the sawguides with, for example, a series of rollers. It may be possible for the end-most sawguide  26 ′ to perform the functions of steering and clamping blocks  34 ,  36  so to eliminate the need for separate blocks  34 ,  36 . The invention has described with reference to a horizontally-oriented saw axis  33 . The invention is also applicable for saw axes at other orientations, such as vertical and generally vertical; appropriate modifications to the various components of the system, such as the use of appropriate workpiece infeed components, may be made, when the necessary or desirable, when saw axis  33  is not horizontal. 
     Any and all patents, patent applications and printed publications referred to above are hereby incorporated by reference.