Cross Reference to Related Applications

This application is a continuation-in-part of Application Serial No. 08/588,741 filed January 19, 1996, entitled "METHODS AND APPARATUS FOR ORIENTING POWER SAWS IN A SAWING SYSTEM," which is a continuation-in-part of Application Serial No. 08/408,539, filed March 22, 1995, entitled "METHODS AND APPARATUS FOR ORIENT- ING POWER SAWS IN A SAWING SYSTEM."

Reference to a Microfiche Appendix

A microfiche appendix having one page of microfiche with a total of 48 frames of a computer program constitutes part of this specification.

Technical Field of the Invention

The present invention relates in general to automated sawing systems, and more particularly to techniques for orienting a number of power saws through which wood stock is moved to cut various angles therein.

Background of the Invention

Automated sawing machines and systems are well known and readily available for a host of different applications. For example, there are many types of computer-controlled sawing systems to which lumber is fed so that it is cut in prescribed lengths and at various angles, according to a cut list entered into the computer. In many prefabricated wood structures, various components thereof are cut and pre-assembled, using automated sawing machines to cut the lumber to various lengths and at various angles at the ends of the pieces. As one example, the web and chord components of wooden trusses are often cut and pre- assembled at a factory and then transported to the construction site of rebuilding floors, roof structures, and the like.

Automated sawing systems for cutting the outer chord pieces and the inner web pieces of trusses are highly developed and automated to provide accurate, high speed cutting operations. One such cutting system is known as the "Automaster" saw, model 341, obtain¬ able from Alpine Engineered Products, Inc., Grand Prairie, Texas. In such type of saw, the system is computer controlled to move a number of individual saws and simultaneously cut both ends of a board to desired angles in a single pass through the system. A board is manually loaded on a frontal chain-type material conveyor which transports the board to the cutting area of the system. The board is fed by the material conveyor between a pair of left- hand mounted saws and a pair of right-hand mounted saws, so that the ends of the board can be cut substantially simultaneously. The right-hand set of saws are mounted on a track and can be moved to accommodate different lengths of boards. Further, each of the individual saws can be moved at different angular orientations with respect to the material conveyor so as to saw each end of the board at desired angles as the board moves through the sawing system. In such type of system, each circular saw blade is mounted directly to an electric motor, and the motor is rigidly fixed to the planar face of a large gear-driven sprocket wheel.

The large sprocket wheel is not circular, but is C-shaped with a portion of the middle removed so that the end of a board to be cut can be moved through the saw blade without interference by the sprocket wheel. The inside curved surface of the C-shaped wheel is bearinged so that the wheel and the power saw mounted thereto can be rotated about an axis that passes parallel to the front face of the saw blade. In this manner, the saw can be angled to different positions and be able to cut through a single point on the board without any corrective horizontal movements of the saw. Importantly, the axis of pivotal movement of the saw does not contain a shaft or other apparatus, but rather is in the center of the C-shaped sprocket wheel which is void of apparatus, except for the saw blade, so that a board can be freely carried through the saw path.

The angle of the saw blade can be oriented to different positions by turning the sprocket wheel with a gear-driven mechanism. The large sprocket wheel is mounted for rotation with respect to a complicated bearing arrangement that requires lubrication frequently to prevent galling or wear to the curved bearing surfaces. Any wear in the gear or bearing surfaces leads to inaccuracy in the precise angular positioning of the saw blade, as well as slight play or wobble of the saw blade during actual sawing. Further, the entire C-shaped sprocket wheel and saw motor can be moved vertically by way of an electric screw-driven arrangement. In like manner, the entire set of right-hand mounted saws can be moved horizontally by a gear driven assembly. Only the right-hand set of power saws needs to be moved horizontally, toward or away from the left-hand set of power saws to accommodate different lengths of boards.

With regard to the sprocket wheel arrangement for angling each saw blade, the motor and saw blade are fixed to the sprocket wheel such that when moved through an arc of angles, an axis of pivotal movement is parallel to and extends through the plane of the front face of the saw blade. In this manner, to change the saw cut from a thirty degree angle to a forty-five

degree angle, only the sprocket wheel and attached saw require angular movement, without a corresponding vertical adjustment of the respective electric screw-mechanisms.

As further noted in connection with the Automaster saw system identified above, the in-feed chain conveyor is constructed such that an operator places a board on an upward ly- angled portion of the conveyor where such board is carried to a knee point, at which point the conveyor is oriented horizontally to carry the board laterally into the sawing system. A chain- driven hold-down assembly holds the board to the material conveyor during horizontal movement of the board into the sawing system. With this type of structure, while it is convenient for the operator to load the lumber on the conveyor without having to lift it shoulder high, when the board is carried over the transition knee point to the horizontal part of the conveyor, the board often tumbles or is rolled before it is clamped and thus becomes misaligned with respect to the left-hand set of saws and the right-hand set of saws.

The in-feed chain conveyor of the Automaster saw has two sets of parallel feed chains for carrying the board into the sawing system. One chain conveyor can be horizontally moved along the frame with the one set of power saws, toward or away from the other set of power saws, to accommodate different lengths of boards. In order to accommodate short boards, i.e., about two feet and shorter, the pair of parallel chain conveyors must be moved together, adjacent each other, so as to be able to move the short board between the left-hand set of saws and the right-hand set of saws. In practice, it has been found that because of the drive bearing arrangement at the rear of the conveyors, the chain-tensioning linkage and apparatus required at the frontal part of each chain conveyor, such conveyors cannot be moved a close to each other as would be needed to cut very short pieces of wood.

As noted above, one set of power saws is movable horizontally along the frame, as is the corresponding hold-down mechanism and chain conveyor. The power drive for the hold- down mechanism and the movable chain conveyor is a long square drive shaft that extends

essentially the length of the saw system. Various apparatus is driven by the drive shaft using a square tubular member through which the drive shaft extends to rotate the tubular member. The tubular member transfers the torque to the driven apparatus. Because of the torque required to drive the apparatus via the square drive shaft, the metal-to-metal driving engage- ment between the square shaft and square tubular member causes wear, thus requiring eventual replacement. To replace the worn parts, the procedure is time consuming, as much of the apparatus requires disassembly and then corresponding assembly using new, and often expensive parts.

In view of the foregoing, it can be seen that a need exists for further improvements in automated sawing systems to reduce costs, maintenance, increase the speed of operation, and generally provide an overall improvement with respect to accuracy and efficiency.

Summary of the Invention

The foregoing shortcomings and disadvantages are either eliminated or substantially reduced by the use of one or more of the aspects of the present invention. In accordance with the preferred embodiment of the invention, two of the four power saws are mounted to respective suspension beams by linear bearings for horizontal movement. However, all four saws can be positioned to different angular positions to cut respective angles in the truss boards. The suspension beam is oriented horizontally so that the power saw can be moved in fine increments in a horizontal direction, and maintained in a precise spatial position. The power saw is mounted to the suspension beam via a rotatable shaft, and the shaft is driven by a gear-reduction motor to move the power saw to various desired angles. The axis of angular movement of the saw blade need not be disposed in the plane of the saw blade, but rather can be conveniently offset from the saw blade so that when the power saw is moved in an angular direction, the saw blade is swept through an arc. By utilizing the linear bearings and the beam for mounting the power saws, the cost of the unit is reduced, as is the maintenance thereof compared to the prior art sawing system. The gear-reduction positioning of the power saw assures precision and stable positioning thereof.

A related feature of the invention resides in the positioning of the two horizontally movable power saws, based on the angular position of the associated non-horizontal ly movable power saw to thereby carry out precision cuts in the board at precise locations. Because the power saws are no longer rotated about an axis that passes through the plane of the saw blade, whenever the angle of the blade is changed, the horizontal position is also changed to make a cut through a desired point on the board. Hence, based on the particular angular orientation to which the saw blade is positioned, the computer of the sawing system processes a mathemati¬ cal equation to determine whether, and how much, the power saw must be horizontally moved to achieve the angle cut through a predefined point on the board. Moreover, when a board

end is to be cut with two angles, the processing of the mathematical equation takes into consideration the angular position of one power saw to determine the horizontal displacement of the other power saw to achieve both of the desired angle cuts through the predefined point on the board. In accordance with another feature of the invention, the in-feed chain conveyors are not constructed with a knee between an upward-angled portion and a horizontal portion, but rather are straight along the length thereof, and angled upwardly from a lower in-feed entry end to an upper rear portion thereof which is disposed between the left and right power cutting blades. With this arrangement, the operator can easily load lumber thereon at the in-feed end, a short height above the floor, whereby the conveyor carries the boards upwardly and into the power saws of the cutting system.

In accordance with yet another feature of the preferred embodiment of the invention, the material conveyor is constructed with two chain-feed material conveyors which have cantilevered drive bearings at the back ends thereof, and take-up mechanisms that are generally internal to the body of the conveyor, thus reducing the width of each conveyor. In this manner, the chain conveyors can be moved very close to each other, thereby allowing very short lengths of boards to be carried and cut by the power saws.

In a second embodiment of the invention, the sawing system has five power saws. Two of the power saws are movable linearly in a horizontal direction, two of the power saws are movable linearly in a vertical direction, and one is movable linearly in both a horizontal and a vertical direction. The saws are controllable by a computer having an executable program. The program orients the saws to make cuts at different angular positions and linear distances.

In another aspect of the invention, a lift assembly is secured to the power saw for moving the power saw in a substantially vertical direction. A lift drive is operable connected

to the lift assembly. The lift drive is electrically connected to the computer so that the vertical position of the saw can be adjusted by the computer.

In another aspect of the invention, a method positions the saws such that tips of the saw blades barely extend past an upper edge of a workpiece. The hold-downs are positioned near the tip.

In yet another aspect of the invention, the method parks the power saws not assigned to make a cut. Parking sets the power saw completely above or outside the board to be processed.

Brief Description of the Drawing

Further features and advantages will become more apparent from the following and more particular description of the preferred and other embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters generally refer to the same parts or elements throughout the views, and in which:

FIG. 1 is a generalized view of the apparatus of the cutting system employing the various features of the invention;

FIG. 2 are views of a wooden web for a truss, as the wood stock progresses through the sawing system of the invention; FIGS. 3a and 3b are views of the apparatus for movably mounting a power saw to the sawing system;

FIG. 4 illustrates the various angles at which the power saw can be oriented according to the mounting apparatus shown in FIG. 3;

FIGS. 5 and 6 are respective side and end views of the suspension beam of FIG. 3; FIGS. 7a-7d illustrate the relationship between the angles to be cut in a truss board, and the calculation of a correction factor by which a horizontal movable power saw of the sawing system must be displaced to make an angle cut through a predefined point on the board;

FIGS. 8a and 8b are flow charts showing the basic steps carried out by the sawing system computer to position the four power saws according to the calculation of the correction factors and angular position data;

FIG. 9 is an exploded view of the drive mechanism of an upper portion of the material conveyor of the invention;

FIG. 10 is a cross-sectional view of a material conveyor drive assembly with replace- able plastic inserts between the driven metal parts;

FIG. 11 is a back view of the top portion of the material conveyor of FIG. 9;

FIG. 12 is an exploded view of the chain take-up mechanism of a bottom portion of the material conveyor of the invention; and

FIG. 13 is an isometric view of the assembled portion of the material conveyor of FIG. 12;

FIG. 14 is a generalized view of a second embodiment of the sawing system;

FIG. 15 is a perspective view of a power saw mounted to a lift assembly and a support beam;

FIG. 16 is a top view of the power saw mounted to the lift assembly and the support beam;

FIG. 17 is a partial cross-sectional view of the power saw mounted to the lift assembly and the support beam taken along line 17-17 of FIG. 16;

FIG. 18 is a perspective view of a power saw mounted to a lift assembly;

FIG. 19 is a top view of the power saw mounted to the lift assembly; FIG. 20 is a schematic view of the "home" placement of the power saws in the second embodiment of the sawing system;

FIGS. 21a and 21b are front views of a truss having a truss board having a scissor cut;

FIG. 22 is a flow chart showing the basic steps carried out by the sawing system computer to position the power saws according to the calculation of the linear offsets and angles;

FIGS. 23a and 23b illustrate the relationship of saws 40 and 500 with respect to the angles to be cut in a truss board, the linear offset calculations, and the minimal exposure of the saw blade tip of saw 500;

FIGS. 24a, 24b, and 24c illustrate the relationship of saws 40 and 500 with respect to the angles to be cut in a truss board, the linear offset calculations, and the minimal exposure of the saw blade tip of saw 500; and

FIG. 25 illustrates the distance for carriage length between carriage 20 and movable carriage 22.

Detailed Description of the Invention

A sawing system 10 employing the features and advantages of the present invention is shown in generalized form in FIG. 1. The sawing system 10 of FIG. 1 can be located in an assembly operation where lumber or boards are input on a separate conveyor system (not shown) and carried to the sawing system 10. The operator can then manually move the lumber from the conveyor to the sawing system 10 for cutting to the appropriate lengths and angles. Then, the cut lumber is manually removed, or carried on another conveyor (not shown) to an assembly table where the cut lumber is laid together and fastened by nails or other hardware. The sawing system 10 includes a frame structure 12 to which the other components are fixed so as to maintain the system in a unitary manner so that it can be transported or otherwise shipped or operated as a unit. The frame structure includes an upper back frame member 14, and a lower front frame member 16. The sawing system is computerized, and thus includes a cabinet 13 to house the computer and the associated electrical circuits and control equipment. The cabinet 13 may include a CRT 15, and various manual controls 18, such as knobs or push buttons for allowing the operator to communicate with the computer, in response to prompts and information displayed on the CRT 15. Those skilled in the art can readily devise of the electrical hardware and software for controlling the sawing system 10 in the manner described below. In accordance with the preferred form of the invention, the system frame structure 12 supports a fixed power saw carriage assembly 20 and a movable power saw carriage assembly 22. The fixed power saw assembly 20 includes a framework 24 that supports two power saws 26 and 28 mounted at the right of the system frame structure 12. The right hand set of saws can be independently angularly positioned with a high degree of precision and stability for cutting lumber at various angles. The framework 24 is welded or otherwise fastened to the

system frame structure 12. Further, the right front power saw 26 is movable about twenty-one inches horizontally on a respective suspension beam, which is shown as reference numeral 30. The other associated right back power saw 28 is not longitudinally movable, but is fixed with respect to such movement. The angular movements of both power saws 26 and 28, as well as the longitudinal movement of power saw 26 via the suspension beam 30, can be controlled automatically by a computer control mounted in cabinet 13, or manually by way of the computer and controls 18. Conventional DC drive controls are utilized by the computer to drive the motors that provide angular displacements of all four power saws, as well as to provide horizontal displacements of power saws 26 and 40. With such type of drive controls, the amplitude of the DC voltage determines the speed of the motor, while the duration of the voltage controls the time by which the motor is active.

The fixed power saw carriage assembly 20 also includes a material conveyor 32 angled downwardly to a frontal portion thereof to facilitate loading of boards or lumber thereon. A hold-down mechanism 34 disposed above the material conveyor 32 functions to hold lumber down on the material conveyor 32 to prevent tumbling or unwanted movement of the lumber.

As will be described in more detail below, the material conveyor 32 is driven by a square shaft 36 which is itself driven at one end thereof (not shown).

The movable power saw carriage assembly 22 includes essentially the same compo¬ nents as the fixed power saw assembly 20, but is longitudinally movable up and down the system frame 12. To that end, the movable power saw assembly 22 includes first and second associated power saws 38 and 40, where power saw 40 is suspended from respective movable suspension beam 41. While the left back power saw 40 can be moved both horizontally and angularly, the left front saw 38 can only be moved by angular rotational movements. Both power saws 38 and 40 are controlled so as to be positioned at desired angles for cutting boards at corresponding angles. The power saw suspension assembly of power saw 40 is connected

to a movable carriage framework 42 which, in turn, rests on the system frame 12 via rollers

43. Conventional roller assemblies are utilized for providing movable attachment above and on each side of a rail which is attached to the horizontal frame members 14 and 16. The

movable framework 42 and rollers 43 allow the carriage 22 to be moved longitudinally on the frame 12. Further, the carriage framework 42 is driven by a rack and spur gear arrangement

(not shown) so that the movable power saws 38 and 40 can be positioned very accurately along the system frame 12 with respect to the fixed power saws 26 and 28, thereby enabling the cutting of angles at each end of a board, and leaving the board with a precise overall length. The movable power saw assembly 22 further includes a material conveyor 44 which, together with the associated material conveyor 32, forms an in-feed or entry point of a material conveyor 46. A hold-down mechanism 48 is disposed above the material conveyor

44, and is operable to move downwardly to clamp a workpiece to the material conveyor 44, and thus move the workpiece into the sawing system. An electrical umbilical chord (not shown) having a cable carrying all the electrical power and control signals is connected to the movable power assembly 22 and travels with the assembly as it is caused to move up and down the system frame 12, under control of the computerized control in cabinet 13. It should be noted that the power saws 38 and 40 are independently powered by respective motors, as are the power saws 26 and 28 associated with the fixed carriage 20. However, the material conveyors 32 and 44 are each powered from the common square drive shaft 36. The pair of hold-down mechanisms 34 and 48 are driven by the same source as the square drive shaft 36 to move respective hold-down chains.

It can be appreciated that the long pieces of lumber, the movable power saw assembly 22 is moved to the left in FIG. 1 , carrying with it the movable material conveyor 44 and associated hold-down mechanism 48. In order to cut very short pieces of lumber, the movable power saw assembly 22 is moved to the right, very close to the fixed power saw assembly 20.

The material conveyor 32 and the hold-down mechanism 34 associated with the fixed power saw assembly 20 are movable longitudinally a short distance by a rack and spur gear arrangement (not shown), in coordination with the longitudinal movement of the suspension beam 30. With such a coordinated movement of the apparatus, the power saws 26 and 28 cannot be moved into the associated material conveyor and cut into the metal thereof. The left-hand material conveyor 44 and the associated hold-down mechanism 48 function in the same manner with respect to the movement of power saws 38 and 40.

FIG. 2 illustrates the various stages of a board as it is processed through the cutting system 10. An uncut piece of lumber, such as shown by reference numeral 60, is loaded on the material conveyors 32 and 44 of the in-feed system 46. This is easily accomplished, as the frontal portion of the in-feed system 46 is at an optimal distance above the floor, e.g., about thirty-two inches, thereby eliminating the need for the operator to lift boards to uncomfortable heights. As noted in FIG. 2, the uncut board 60 constitutes raw material with either square or rough ends. Next, the chain (not shown) of each of the material conveyors 32 and 44 have steel dogs that pull the board 60 forward until it is secured under each hold-down mechanism

34 and 48. Each hold-down mechanism has a driven chain which engages the top of the board. The chains of the hold-down mechanism 34 and the associated material conveyor 32 move at the same speed, and thus uniformly move the board into the sawing system.

Assuming the fixed power saws 26 and 28 and the movable power saws 38 and 40 are to be set up to cut two angles at each end of the board so as to achieve the board shown in the top illustration of FIG. 2, the following steps are carried out. First, the sawing set up would be programmed into the computer to move the movable power saw assembly 22 toward the fixed power saw assembly 20 so that the power saws can then be angled and moved on their respective suspension beams to achieve the correct angles and the correct length of the board. It is noted that, although not a necessity, the front right saw 26 cuts the top angle while the

back right saw 28 cuts the bottom angle while the back left cuts the top angle in the board 60. While the system 10 has been described such that the front power saws 26 and 38 perform the respective upper and lower angle cuts, and the back saws 28 and 40 perform the respective lower and upper cuts on the ends of the board, the operations can be reversed or otherwise changed by the appropriate orientations of the power saws in the respective frames. Assuming the angles at both ends of the board are to be forty-five degrees, for example, the front fixed and movable power saws 26 and 38 would be angled so that as the board 60 is moved through such saws, the angles 64 and 62 are cut as the board is moved past the blades of frontal power saws 26 and 38 in the first cutting operation. The back power saws 28 and 40 are angled in the opposite directions so as to achieve the forty-five degree cuts 68 and 66 in the second cutting operation. The entire cutting operation takes only a few seconds or so to complete. The fully cut board is thus carried by the in-feed conveyor 46 through the saws and delivered to an out-feed structure to be carried to an assembly area.

The cut or scrap ends of the board drop onto a disposal system, such as a shaker type system (not shown) that is located in the lower portion of the frame, under the left and right sets of power saws. The disposal system extends the full length of the sawing system 10. The disposal system moves the scrap from the cutting area to a scrap disposal area. Because the disposal system is located under the power saws, more space is required to accommodate such apparatus. In order to circumvent a space problem, the material conveyors 32 and 44 are angled upwardly to provide sufficient space below the power saws.

FIGS. 3a and 3b illustrate the apparatus for linearly moving the power saws 26 and 40, as well as provide angular movements for cutting various angles in the lumber processed by the sawing system 10. The power saw 26 is mounted for precise angular movements with respect to the suspension beam 30, and the suspension beam 30 can be linearly moved back and forth with respect to the board to be cut. The power saw 26 includes an electric motor 80

and an 18-inch saw blade 82, or other appropriate sized saw blade. The saw blade 82 rotates about the axis of the rotating shaft of the motor 80. The electric motor 80 is fixed to a metal base plate 84 that is welded, bolted or otherwise attached to a bearing shaft 86 at one corner of the plate 84. The power saw 26 is angularly moved about the rotational axis of the bearing shaft 86. The pivotal or angular movements of the power saw 26 are shown in FIG. 4 in various positions.

While in the preferred embodiment of the invention, the rotatable shaft 86 is mounted near a corner of the mounting plate 84, the pivotal axis of the plate 84 can be at any other location thereon to achieve different paths of pivotal motion of the saw blade. Indeed, the saws that make the bottom cuts 62 and 68 on the board shown in FIG. 2 are mounted for pivotal movement as shown in FIG. 3a, while the saws that make the top angle cuts 64 and 66 are mounted for pivotal movement near the bottom left corner of the base 84, as viewed in FIG. 3a. Those skilled in the art may prefer to mount the rotatable shaft 86 in the middle of the base plate 84, or at corners of the base plate 84 other than described above. With reference to FIGS. 3-6, the shaft 86 passes through a hole in the suspension beam 30, but is fixed thereto by a pair of bearings 88 and 90. The bearings 88 and 90 are fastened to the suspension beam 30 by bolts or other suitable hardware. The shaft 86 constitutes an output of a first worm gear reduction drive 92. As noted in FIG. 5, the gear reduction unit 92 has an input shaft 94 connected via a coupling 96 to a second helical gear reduction assembly 98 and a reversible drive motor 100. The motor 100 and gear reduction assembly 98 are typically available as a gear motor unit. DC power is supplied to the drive motor 100 by way of the electrical wires 102 to drive the motor in a clockwise or counter¬ clockwise manner. Further, a conventional shaft encoder 104 is connected to the rear shaft end of the motor 100 to provide output signals indicating the angular displacement of the motor 100. The shaft encoder output is shown as the conductors identified by reference

numeral 106. By ascertaining the angular displacement of the motor 100 and knowing the ratio of reductions of the gear box 98 and gear reduction 92, the angular displacement of the saw blade 82 can be accurately determined and maintained. By utilizing an overall gear reduction in excess of 1000:1, very accurate and stable angular positioning of the power saws can be achieved.

With reference again to FIGS. 3, 5, and 6, the suspension beam 30 is suspended by way of a pair of linear bearings 110 and 112. The linear bearings are of a conventional type. This type of bearing includes corresponding v-groove and v-tongue rail with mating surfaces, as better shown in FIG. 6. The v-groove rail is fixed to the top of the suspension beam 30 by screws (not shown) that are threaded into the top edge of the suspension beam 30. The pair of v-tongue members of the bearings 110 and 112 are connected together by a support 114 between a pair of threaded stubs 116 and 118 that are fastened to the support 114, as well as fastened to lateral bracket members 120 and 122. The bracket members 120 and 122 are rigidly fastened to the carriage frame 24 or 42 of the power saws. The linear bearings allow the suspension beam 30 to be accurately suspended without any vertical or lateral play.

Further, two pairs of cam followers, one of which is shown as reference numeral 124, straddle the bottom edge of the suspension beam 30 to limit the sideways movement of the rail, but allow longitudinal movement of the beam 30. Each cam follower 124 is fastened to a bracket which, in turn, is fastened to the power saw carriage frame. Those skilled in the art may prefer to locate the linear bearings at the bottom of the suspension beam 30, and the cam followers at the top.

As can be best seen in FIGS. 5 and 6, the DC drive motor 100 and the two gear reductions 92 and 98 mounted on one side of the suspension beam 30, while the saw motor 80 and mounting plate 84 are mounted to the opposite side. This arrangement of apparatus provides a certain degree of balance to the suspension beam 30, in that the weight of the

apparatus on one side of the suspension beam 30 tends to offset the weight of the apparatus on the other side. This balance reduces wear on the cam followers 124 as well as uneven wear on the linear bearings 110 and 112.

A DC drive motor 126 shown in FIG. 3b provides longitudinal drive to the suspension beam 30, via a rack gear 128 and a mating spur gear 130. The end of the rack gear 128 is bolted to the suspension beam 30. The motor 126 is suitable fastened to the power saw carriage frame in a manner not shown. Further, the drive motor 126 also includes a shaft encoder to provide feedback pulses to the computer system, thereby providing position information as to the longitudinal position of the saw blade 82 of the power saw 26. While not shown, the motor 126 may be provided with internal or external gear reduction assemblies to reduce the speed of the spur gear 130, and thus provide more accurate longitudinal movements of the suspension beam 30. Alternative drive mechanisms, such as screw drives and the like can be utilized for moving the suspension beam 30 by way of the linear bearings 110 and 112. The two power saws 26 and 40 of the sawing system of FIG. 1 are mounted for both longitudinal and angular movements in the same basic manner as shown in FIG. 3. The power saws 28 and 38 are not mounted by way of the suspension beam and linear bearing mecha¬ nisms, but rather are mounted to a fixed frame structure using the bearings 88 and 90 and gear reduction units to provide only angular displacements of the respective saw blades. Those skilled in the art may find it advantageous to equip a sawing system with fewer or more than the four power saws described above, using either the angular rotational and/or the longitudi¬ nal suspension beam movement apparatus.

As noted in FIG. 4, the pivot point of each power saw mounted according to the invention, is coaxial with the axis of the bearing shaft 86, and does not extend through the planar face of the saw blade 82. Because the pivotal axis of the power saw is offset from the

blade 82, the sawing path of the board is not blocked by power saw pivoting apparatus, nor are complicated or maintenance intensive components required. However, because the pivotal axis of the power saw is offset from the plane of the saw blade 82, at least one power saw associated with the fixed power saw assembly 20 and one power saw of the movable power saw assembly 22 requires the capability of horizontal movement. As noted above, the right front power saw 26, as well as the left back power saw 40 are mounted to respective suspension beams 30 and 41, thereby allowing for precise horizontal movements.

FIG. 7a illustrates the reason why one of the power saws in each of the left and right assemblies requires the capability of horizontal movement in order to cut an angle through a board at a precise location. As noted above, the power saw 40 is located at the left back of the sawing system, and is adapted for cutting the top angle in the board 60. Assume, for example, that a 135° angle 133 is to be cut in the board 60, through the predefined point 131. The back left saw 40 is controlled by the computer to rotate the power saw to the correct angular orientation, as well as horizontally move the motor via the suspension beam 41 to make the 135° cut through the predefined point 131. Then, assume next that a 150° angle 135 is to be cut in the top of a subsequent board. If the power saw 40 were simply rotated to the 150° location, then a cut 135 shown in FIG. 7a is made. However, the cut 135 does not pass through the predefined point 131, due primarily to the offset rotational axis of the power saw 40 with respect to the blade. A correction can be made by moving the power saw 40 to the left so that the cut will proceed directly through the predefined point 131. A cut "through" a predefined point is also construed herein to mean that the cut is made just adjacent to the point.

The computation to achieve the correction factor for horizontally locating the saw 40 is complicated by the fact that the associated left front power saw 38 is also pivotal about an offset axis, although not movable in a horizontal direction. The technique according to the

invention for deriving the correction factor and cutting a board with precise angles through a predefined point of the board is set forth below.

With reference to FIG. 7b, assume that the board 60 is to be cut with a top 135° angle 133 through point 131, and a bottom 60° angle 137, again through the predefined point 131. In the example, the predefined point 131 is exactly midway between the top of the board 60 and the bottom of the board shown in FIG. 7b. In order to determine the correction factor, various dimensions between the pivotal axis of the power saws and the board must be known, it be realized that the board is constrained and fixed with respect to the power saws 38 and 40. The material conveyor 44 in conjunction with the hold-down mechanism 48 provide the function of fixing the board laterally with respect to such power saws.

With regard to FIG. 7c, the power saw 40 is shown with respect to the board 60. The vertical distance h, between the top saw pivot point 139 and the predefined point 131 on the board 60 must be known. Another relevant dimension of the power saw 40 is D, which is the distance between the power saw pivot point 139 and a point perpendicular to the front face or kerf of the power saw blade. Further, and with reference to FIG. 7d, the vertical distance h ₂ between the pivot point 141 of the bottom power saw 38 and the predefined point 131 on the board 60 must also be known. Similarly, the distance D ₂ must be determined between the power saw pivot point 141 and a point perpendicular to the front face or kerf of the blade of the power saw 38. Based upon the height of the board 60 and the particular angles to be cut in the board 60, the predefined point can be easily determined as a function of the distances h, and h ₂ between the respective pivot points 139 and 141 of the power saws 40 and 38. Lastly, the required angular orientations of both the power saws 40 and 38 must be known, but the angle data can be easily obtained from the drawings or information relating to the truss chords or webs to be cut. It should be noted that the power saw 40 is programmed to traverse an angular displacement of between 53°-166°, with zero degrees being defined when the blade is

horizontal and 90° when the blade is vertical. On the other hand, the left front power saw 38 is programmed to rotate through an angular range of 14°- 128°. It has been found that these angular displacements are suitable for cutting the various angles normally encountered in wooden trusses. The power saws 40 and 38 are mounted for angular movements about the respective pivot points 139 and 141 as shown in FIGS. 7c and 7d. It is to be understood that the right front power saw 26 is mounted for pivotal movement about the shaft 86 as shown in FIG. 3. The right back power saw 28 has a pivot point below the motor of the power saw and to the lower left corner of the base plate, rather than the upper left corner as shown in FIG. 3 with respect to power saw 26.

It is further noted that the range of horizontal displacements of the power saw 40, due to movement of the suspension beam 30, is about 21 inches. A horizontal reference point from which a correction factor is determined is when the suspension beam 30 can be moved three inches to the right when facing the sawing system 10, and when it can be moved 18 inches to the left. The horizontal reference points are entirely arbitrary and could be estab¬ lished at other positions. In other words, the reference point for determining horizontal displacements or correction factors, is at a point about one-seventh of the total horizontal displacement, as measured from the right-most end position of horizontal travel. Thus, when positioning the horizontally movable power saws 26 and 40, such saws are initially positioned at a respective reference point, and then displaced therefrom based upon the calculation of correction factors, according to the following formula:

As noted above, h, is the vertical distance between the pivot point 139 of power saw 40 and the predefined point 131 on the board, while h ₂ is the distance from the pivot point 141 of power saw 38 to the predefined point 131 of the board. In the equation noted above, θ , is the angle of the blade of power saw 40, while θ ₂ is the angle of the blade of power saw 38, where a zero degree reference is when the saw blade is horizontal. The correction factor resulting from the calculation of this equation is the distance from the reference point of power saw 40 by which such power saw must be horizontally moved in order to cut the angle θ , through the predefined point 131 on the board 60. Positive correction factors refer to displacements toward the left end of the machine, while negative correction factors refer to displacements toward the right of the machine, when viewed from the front of the sawing system 10 of FIG. 1. The portion of the equation is the first set of brackets, before the subtraction sign, represents a dimension contributed by the power saw 38, while the portion of the equation in the last set of brackets represents a dimension contributed by the power saw

40. For sawing systems utilizing only a single horizontally and angularly movable power saw, such as saw 40, then the only portion of the equation needed is the last bracketed portion. By utilizing the correction factor of only a single power saw, it can be horizontally moved so that any angle can abe cut through the same predefined point on the board. A similar equation

noted above can be utilized for determining the correction factor for horizontal displacements of the power saw 26 located on the right hand side of the sawing system 10.

FIGS. 8a and 8b are flow charts depicting the general steps carried out to set up the angular positions of all four power saws, as well as the horizontal position of the horizontally movable power saws. Based upon the drawings of all the dimensions and angles of a truss to be cut with the sawing system, a predefined point associated with one or two angles and at each end of the board can be determined. Further, the linear distance between the predefined points can also be determined, which distance is related to the carriage movement of the movable power saw assembly 22, again with respect to an arbitrary reference position. In other words, the parameters, θ , θ ₂ . h,, h ₂ , D,, D ₂ the predefined points at each end of the board, and the distance between the predefined points is all known either from the truss drawings, tables or other calculations. Such data is entered in a predefined format in the computer so that the computer can decode such information and utilize it in conjunction with the equation. When such data is loaded into the computer and the particular types of trusses associated with a program is selected to be run, the computer proceeds through the generalized steps set forth in FIG. 8. Those skilled in the programming art will readily recognize that the steps of the flow chart can be carried out into many different program languages, utilizing the appropriate instructions to accomplish the result noted.

According to program flow block 300, the computer starts processing the truss and saw cut information to derive the correction factors and the other data necessary to position the apparatus of the sawing system 10. In program flow block 302, the angle data and dimension data are retrieved from the database associated with the particular truss board to be cut. Program flow block 304 includes those instructions for determining which saws can accom¬ plish the desired cuts most efficiently. For example, the front left saw 38 can make cuts at the bottom of a board at angles between 14°-90°, whereas the front right saw 26 can make cuts at

the top of a board at angles between 14°-90°. If a board requires the type of cuts within the ranges noted by the front saws, then the back saws 28 and 40 do not even have to be activated. In carrying out the instructions of program block 304, the computer essentially assesses the type of cuts at each end of the board, and then assigns a particular cut to each power saw, recognizing that one or more of the four power saws may not be required. In program flow block 306, the parameters that include the angle data and dimension data are substituted in the equation to the right of the subtraction sign noted above, and the correction factor for the right hand fixed power saw 28 is calculated. The right hand power saw carriage assembly 20 is fixed with respect to any horizontal carriage movement. In program flow block 308, angle and dimension data corresponding to the left edge of the truss board is substituted into the equation and the correction factor for the left fixed power saw 38 is determined. Then, in program flow block 310, the distance between the predefined point at each end of the truss board is calculated so that it is known where the movable carriage of the left power saw assembly 22 should be positioned. In program flow block 312, the computer calculates the correction factor for the right, front movable power saw 26. The next set of instructions carried out by the computer of the sawing system 10 is shown in program flow block 314. Here, the correction factor for the left, back movable power saw 40 is calculated. The bracketed portion of the foregoing equation to the right of the subtraction sign is processed to determine the horizontal displacement, or correction factor, from the reference position. In program flow block 316, the computer drives the right hand power saws 26 and

28 to the calculated angular positions. As noted in program flow block 318, the power saws 38 and 40 associated with the left assembly 22 are driven to the desired angular positions. The suspension beam 30 to which the right, movable power saw 26 is rotatably attached, is driven horizontally from its reference position according to the calculated correction factor determined in program flow block 312. This is shown in program flow block 320. Then, as

noted in program flow block 322, the suspension beam 41 to which the left power saw 40 is rotatably mounted, is displaced horizontally from the reference position according to the correction factor calculated in program flow block 314. Lastly, the movable carriage of the left power saw assembly 22 is moved according to program flow block 324 either right or left so that the correct spacing will exist between the predefined points on each end of the board after the sawing operation is complete. In other words, the cut board is then of the correct length between the predefined points. The computer then exists the subroutine of FIG. 8b as noted in program flow block 326. It is to be noted that all movements of the saws are processor controlled and occur at substantially the same time. From the foregoing, it can be seen that the horizontal displacement associated with the correction factor is a function of the angular orientations of both of the associated saws. In practice, it has been found that with the apparatus and equipment disclosed above, angles can be cut in truss boards with a precision of +.05°, and various dimensional characteristics of the truss board can be cut with an accuracy of +1/32 inch. FIGS. 9-13 illustrate the details of one material conveyor 32 of the in-feed conveyor system 46. Particularly, FIG. 9 illustrates an upper right-hand view of FIG. 1, while FIG. 13 shows a lower left-hand view of the material conveyor 32, again of FIG. 1. As noted above, the upper portion of the material conveyors 32 and 44 rest on the horizontal frame part 14 while the lower portion of the material conveyors 32 and 44 rest on the lower horizontal frame part 16. Also as noted above, the material conveyors 32 and 44 can be accurately moved laterally by a spur and rack gear arrangement (not shown). Irrespective of their lateral positions on the frame 12, the material conveyors 32 and 44 remain driven by the square drive shaft 36. The material conveyor 32 described in connection with FIGS. 9 and 10 is substan¬ tially identical to the other material conveyor 44.

The material conveyor 32 includes an elongate tubular metal span support 140 that substantially spans the distance between the top back frame member 14 and the top front frame member 16 of the sawing system frame 12 shown in FIG. 1. An upper set of cam rollers 138 and a lower set of cam rollers 141 are mounted for rotation to the bottom of the span support 140. FIGS. 9 and 12 illustrate the upper set of cam rollers 138 fixed to the underside of the span support 140, and the lower set of cam rollers 141 fixed to the span support. Each set of rollers 138 and 141 are spaced apart so as to straddle a square key stock member (not shown) along the top surface of each horizontal frame part 14 and 16 of FIG. 1. With this construction, the material conveyors 32 and 44 are supported for horizontal movement along the frame parts 14 and 16.

A pair of upper protective enclosure plates 142 and 144 are bolted on each side of the span support 140 via the holes, such as shown by reference numerals 146 and 148. A metal chain 150 of the conventional link-type, with dog-ear extensions 151 welded to a link every 16 inches, or so, is routed and over the top surface of the span support 140 and back inside the interior of the span support 140 and back inside the interior of the span support 140, and in between the protective covers 142 and 144. To facilitate travel of the chain 150 on the span support 140, a narrow square key stock 153 is welded to the top surface thereof. The key stock 153 provides a guide on which the chain 150 can move, as well as reduce wear on the span support 140 itself. A sprocket wheel 152 is disposed between the protective covers 142 and 144, and provides a drive for driving the chain 150. It is noted that the chain 150 and dogs 151 engage the lumber or wood and carry the material into the sawing system 10. The return path of the chain 150 is inside the hollow span support 140.

A pair of spaced-apart cantilever bearings 154 and 156 are mounted by bolts (FIG. 11) to a support plate 158. The support plate 158 is welded to the protective cover 142. Both bearings 154 and 156 are mounted in a cantilever manner outside and to the left (when viewed

from the back of the sawing system) of the protective cover 142, as shown in FIGS. 9 and 11. A flanged tubular stub 160 passes through both bearings 154 and 156, and into a QD type bushing 153. Once the tubular stub 160 is situated through the bearings 154 and 156 and snugly inserted into the QD bushing 153, the bushing 153 is tightened to secure the sprocket wheel 152 to the tubular stub 160. Then, the sprocket wheel 152 is laterally adjusted for alignment of the chain 150 with the span support 140. Lastly, the center part of the cantilever bearings 154 and 156 are secured to the tubular stub 160 by set screws (not shown) or other suitable means. With this arrangement, the bearing 154 and 156 support the sprocket wheel 152 in a cantilever manner for rotation and for driving the chain 150. As noted, a flange 162 having a central hole 164 therein is welded or otherwise secured to the end of the tubular stub

160. A square tubular drive member 166 about six inches long is provided, with a flange 168 and 170 fixed at each end thereof. The flange 170 is then bolted to the flange 162 of the tubular stub 160.

Four plastic inserts 172 are provided as a durable cushion between the square drive shaft 36 and the square tubular drive member 166. An end cap 174 having a square hole 176 therein is fabricated for fastening with screws or other suitable means, to the flange 168 of the square tubular drive member 166. With this arrangement, the square drive shaft 36 is passed through the end cap 174, through the square tubular drive member 166, through the round tubular stub 160 and thus exists the protective cover 144, as shown in FIGS. 9 and 1 1. Once the square drive shaft 36 is routed through the square tubular drive member 166, the individual plastic cushions 172 can be manually inserted between the four sides of the square drive shaft 36 and the four corresponding internal surfaces of the tubular drive member 166. Once the plastic cushions 172 are installed, the end cap 174 can be secured to the flange 168 to capture the inserts 172 and maintain them in place. In the preferred embodiment, the drive shaft 36 is

1.25 inches square, and each plastic inserts about one inch wide and about six inches long, with a thickness of about 3/8 inch.

The plastic inserts 172 are fabricated of a UHMW type of plastic that is extremely durable for transferring the rotational drive torque of the square shaft 36 to the square tubular drive member 166. Other types of plastic or cushion material, such as Nylatron, may be equally effective as a durable interface between the metal parts. Each plastic insert is cut from sheet material of 3/8 inch thickness, to pieces about one each by six inches. The plastic members 172 prevent direct metal-to-metal contact between the drive shaft 36 and the tubular drive member 166, thus eliminating wear between the metal parts. Rather, the wear incurred is on the plastic inserts 172, which can be easily replaced by removing the end cap 174, pulling out the old inserts, and inserting new inserts, all without having to remove the drive shaft 36 from the material conveyor 32. Moreover, with the arrangement shown in FIG. 9, the material conveyor can be moved up and down the square drive shaft 36 and yet remain driven at any axial location. It should also be noted that the top portion of the material conveyor 32 is not otherwise fixed to the frame system shown in FIG. 1, but rather rests on the lateral frame member 14 on a set of cam rollers 138 (FIG. 9), as noted above.

Lastly, the upper end of the material conveyor 32 includes an out-feed arm 178 bolted to the protective covers 142 and 148 for catching the cut boards after having been processed through the sawing system 10 of the invention. The arms 178 of each material conveyor 32 and 44 provide a catch mechanism so that the cut boards do not fall on the floor, but rather can be accumulated so that they can be manually unloaded and carried or otherwise conveyed to a truss assembly area. If a conveyor is provided so that the cut boards can be automatically transported to an assembly area, the out-feed arms 178 can be eliminated or removed.

FIG. 10 illustrates a cross-sectional view of the square drive shaft 36 as it passes through and drives the square tubular member 166, with the plastic inserts 172 disposed

therebetween. It can be appreciated that as the square drive shaft 36 is rotationally driven, the side walls thereof exert a torque on the plastic inserts 172 which, in turn, drive the square tubular member 166. As noted above, any wear that wear that is caused by way of this driven relationship is on the plastic inserts 172, which are easily replaceable and inexpensive. The down time of the system due to replacement of the inserts 172 is small, as only the end cap 176 need be loosened and moved away from the flange 168, the worn inserts withdrawn, and new inserts inserted. While the preferred embodiment of the invention utilizes four individual inserts 172, it can be appreciated that all four inserts can be connected at an elongated corner edge thereof by a living hinge, with two of the longitudinal edges of the inserts being disconnected, so that the unit can be wrapped around the drive shaft 36 and slid into the square tubular member 166. It can be appreciated that the down time for removal of the worn inserts and replacement thereof with new inserts is very short and is easily accom¬ plished.

It should be understood that the other in-feed material conveyor 44 is constructed in a mirror image of the material conveyor 32 described above. In other words, the cantilever bearings and drive mechanism of the other material conveyor 44 are mounted on the right (as viewed from the back) of the material conveyor 44 so that the two material conveyors 32 and 44 can be moved very close together to accommodate short pieces of lumber.

With reference now to FIGS. 12 and 13, there is illustrated the in-feed assembly comprising the lower or bottom portion of the material conveyor 32. The bottom portion of the span support 140 is shown, in its relationship to a left side cover 180 and a right side cover 182 that are welded or otherwise secured to the opposing sides of the span support 140. The side covers 180 and 182 enclose a chain take-up mechanism 184 that includes a toothed chain gear sprocket 186 and a yoke 188 having a threaded adjustment rod. The sprocket 186 is secured to the yoke 188 by use of a bearing 194 that is press fit into the bore 196 of the

sprocket 186. A pin 198, welded to a square head 200, passes through the sprocket bearing 194 which is disposed within the yoke 188. The end of the pin 198 is fastened to a square head 202 by using a split pin 203 that is press fit through a bore drilled through the head 202 and the end of the pin 198. The square heads 200 and 202 fit within the square slots 204, 206 of the respective side cover plates 180 and 182. It can be seen that the sprocket 186 is longitudinally constrained by movement of the pin 198, via the square members 200, 202 in the respective slots 204 and 206 of the cover plates 180 and 182. Further, the longitudinal movement or adjustment of the sprocket 186 is obtained by way of the threaded rod 208 which is welded to the yoke 188 at one end, and is threadably adjusted by a lock nut 210 with respect to a bracket 190. The threaded rod 208 passes through a hole in the bracket 190, and the bracket 190 is welded to the internal surface of the side covers 180 and 182 during assembly thereof. An access opening 212 is formed in the right-hand cover plate 182 for making adjustments of the sprocket 186 by way of the lock nut 210. An isometric view of the completely assembled in-feed assembly is shown in FIG. 13, with the access cover 214 removed to show the adjustment mechanism. Further, it can be seen that the square slide member 202 can be moved longitudinally in the slot 206 to provide take-up adjustment of the sprocket 186 and thereby loosen or tighten the conveyor chain 150. It is noted that the top portion of the left and right cover plates 180 and 182 are enclosed only on the top by metal 218 for protection which prevents small objects and the like from falling into the idler chain mechanism. Other spacer pegs can be welded or bolted between the protective cover plates

180 and 182 to maintain the plates securely spaced apart. As further noted in FIG. 13, an opening 220 exists between the span support 140 and the cover plates 180 and 182 for exit of the chain 150 so that it can ride on the top of the key stock 153 welded to the top of the span support 140 and thereby carry boards into the sawing system.

It is noted that the top flat surface 218 of the in-feed assembly provides a rest on which boards can be initially placed, without being moved by the chain 150. When it is desired to feed the board into the sawing system, the operator simply pushes the board from the rest 218 onto the open top of the protective covers 180 and 182, whereby the board is moved forwardly by the protruding dog-ears 151. The board is then captured between the material conveyor 32 and the upper hold-down mechanism 34 and automatically fed to the left and right power saws by a controlled and uniform movement. The upright edge 222 of the in- feed assembly provides an edge to prevent boards from sliding off the assembly, due to its upward incline. While the right-hand in-feed system 32 has been described, it is noted that the left-hand in-feed assembly 44 is identically constructed in a mirror image.

The advantage of the in-feed assembly shown in FIGS. 10 and 11 is that such assemblies are very narrow, whereby the left in-feed assembly 44 can be placed adjacent to the right in-feed assembly 32 to thereby convey very short boards so that both ends thereof can be cut at desired angles by the power saws. Further, no external adjustment apparatus exists for catching of the operator's clothes or that can be covered with sawdust and the like to make adjustment difficult. Boards as short as nine inches can be cut with square angled ends, due to the feature of the in-feed assemblies which can be placed close together to support the short boards as they are carried into the sawing system. This is due also in part to the utilization of the cantilever bearings located on the outside of each material conveyor at the upper ends thereof, thereby allowing the conveyor assemblies to be of a very narrow width and located between opposing saws to cut short lengths of boards.

Description of a Second Embodiment

Referring to FIG. 14, a second embodiment of the invention with five power saws is shown. Movable-power-saw-carriage assembly 22 has a first power saw 500 and a second

power saw 40. First power saw 500 is suspended from movable vertical support and can be moved both vertically and angularly. Second power saw 40, discussed above in detail, is suspended from movable suspension beam 41 and can be moved both horizontally and angularly. Fixed-power-saw-carriage assembly 20 has a third power saw 600, a fourth power saw 26 and a fifth power saw 400. Third power saw 600 is suspended from a movable vertical support and can be moved both vertically and angularly. Fourth power saw 26, discussed above in detail, is suspended from movable suspension beam 30. Fifth power saw 400 is vertically and horizontally positionable.

For the second embodiment, power saws 500 and 600 are movable along vertical supports. For clarity, power saw 500 is discussed in detail with the understanding that power saw 600 substantially mirrors the mechanical structure of saw 500. The mechanical structure and operation of power saws 26 and 40 are already set out above in detail.

Referring to FIG. 18, power saw 500 is movable vertically along a vertical support 516. Saw blade 508 has a diameter of about 55.88 cm (22 inches). It should be noted that different-sized saw-blades can be used depending upon the length of the cut desired. Saw- blade 508 is mounted to electric saw motor 510 such that the saw blade rotates about the motor axis 511. The pivot axis of the saw motor 510, as shown, is perpendicular to and intersects the motor axis 511.

Secured to the motor mount 520 is a reversible electric motor and gear box assembly 522. A shaft encoder 504 is connected to the rear shaft end of motor assembly 522 to provide output signals indicating the vertical displacement of the motor assembly 522. Assembly 522 is secured to the motor mount with bolts or the like. A lift assembly 523 has a sled plate 524 with linear bearings 530 and 532 which are slidably secured to bearing rails 534. Bearing rails 534 are attached to support 516. Linear bearing rails 534 are mounted substantially vertically to the vertical support 516 by welding, bolting or the like.

Sled plate 524 is slideably fastened to support member 516 such that sled plate 524 and the motor assembly 522 are in the same physical frame of reference. Power saw 500 is mounted to the carriage assembly 20 (see FIG. 14) with threaded studs 528 extending from lift support 516 having a longitudinal axis aligned substantially vertical. Referring to FIG. 19, a rack gear 538 is mounted to the side of the lift support 516. A mating spur gear 540 mounted on the gear box axle 542 engages rack gear 538. When motor assembly 522 is activated, torsional force is imparted to spur gear 540, such that the power saw 500 can be selectively raised or lowered along the lift support 526 with respect to the rack gear 538. Conventional direct current ("DC") drive controls are utilized by the computer to drive the motors that provide angular displacements of power saw 500, and to vertically position power saw 500. With such type of drive controls, the amplitude of the DC voltage determines the speed of the motor, while the duration of the voltage controls the time by which the motor is active. The vertical, as with the angular and horizontal, movement can be controlled automatically by the computer control mounted in cabinet 13 or manually by way of the computer and controls 18 shown in Figure 14. An example of a suitable computer control is a model PC-A984-145 Compact Controller available from Modicon, Inc. , North Andover, MA.

Referring to FIG. 15, power saw 400 is shown. Power saw 400 is movable longitudi¬ nally on a horizontal suspension beam 30 with a horizontal range of about twenty-one inches, but can be increased with minor modifications. Saw blade 408 has a diameter of about thirty- two inches. It should be noted that different-sized saw-blades can be used depending upon the length of the cut desired. Saw-blade 408 is mounted to electric saw motor 410 such that the saw blade rotates about the motor axis 411. The horizontal movement mechanism for power saw 400 is the same as for power saw 26, described in detail above. The pivot point of the saw motor 410, as shown, is perpendicular to and intersects with the axis 411 of motor 410.

Lateral bracket members 120 and 122 are rigidly fastened to support member 426 by welding or the like. Extending from a first end 418 is a motor mount 420 with a reinforcement member 421 (shown in FIG. 16). Secured to the motor mount 420 is a reversible electric motor and gear box assembly 422. A shaft encoder 404 is connected to the rear shaft end of motor assembly 422 to provide output signals indicating the vertical displacement of the motor assembly 422. Assembly 422 is secured to the motor mount with bolts or the like. A lift assembly 423 has a sled plate 424, a first lift support member 426 and a second lift support member 427. Referring briefly to FIG. 16, sled plate 424 has linear bearings 430 and 432 which are slidably secured to bearing rails 434. Bearing rails 434 are attached to support 416. Linear bearing rails 434 are mounted substantially vertically to the vertical support 416 by welding, bolting or the like.

Sled plate 424 is slideably fastened to support member 416 such that sled plate 424 and the motor assembly 422 are in the same physical frame of reference. With respect to frame 24 shown in FIG. 14, power saw 400 is mounted to the carriage assembly 20 with threaded studs 428 extending from lift support 416 having a longitudinal axis aligned substan¬ tially vertical. It should be noted that power saws such as fifth power saw 400 can also be mounted to movable carriage frame 22 to achieve the same effects.

A rack gear 438 is mounted to the side of the lift support 416, best shown in Figures 16 and 17. A mating spur gear 440 mounted on the gear box axle 442 engages rack gear 438. When motor assembly 422 is activated, torsional force is imparted to spur gear 440, such that the power saw 400 can be selectively raised or lowered along the lift support 426 with respect to the rack gear 438. Conventional direct current ("DC") drive controls are utilized by the computer to drive the motors that provide angular displacements of power saw 400, and to provide horizontal displacements and vertically position power saw 400. With such type of drive controls, the amplitude of the DC voltage determines the speed of the motor, while the

duration of the voltage controls the time by which the motor is active. The vertical, as well as the angular and horizontal movement can be controlled automatically by the computer control mounted in cabinet 13 or manually by way of the computer and controls 18 shown in Figure 14. Referring to FIG. 20, a positional schematic of saws 26, 40, 400, 500 and 600 in a home position is shown. Power saw 500 is mounted on a pivot point 512 in-line with axis 511 of saw motor 510. Pivot point 512 is located a distance Ph _j from saw blade face 509 and a distance Hi from the Xi -reference. The dHyi -reference line represents the direction of linear motion of power saw 500. The x-references of each saw is designated by the top-of- chain plane of the material conveyor 32, which is also the bottom plane of a board being processed by the assembly. Power saw 40 is mounted on a pivot point 139 distal from axis 41 of saw motor 80. Pivot point 139 is located a distance Pr^ from saw blade face 82, a distance H from the X2-reference, and a distance Hc^ from axis 41. The dHx2-reference line represents the direction of linear motion of power saw 26. Power saw 600 is mounted on a pivot point 612 in-line with axis 611 of saw motor 610. Pivot point 612 is located a distance

Ph- _j from saw blade face 609 and a distance H3 from the x- _j -reference. The dHy 3 -reference line represents the direction of linear motion of power saw 26. Power saw 26 is mounted on a pivot point 27 located distal from axis 41 of saw motor 80. Pivot point 27 is located a distance Ph^ from saw blade face 83, a distance H4 from the x^-reference, and a distance HcL from axis 41. The dHx^-reference line represents the direction of linear motion of power saw 26. Power saw 400 is mounted on a pivot point 412 located in-line with axis 411 of saw motor 410. Pivot point 412 is located a distance Ph _j from saw blade face 409, and a distance He from the x^-reference. The dHx^- and dHyc-reference lines represent the direction of linear motion of power saw 400.

The vertical positioning capability of power saws 400, 500 and 600, respectively, allow processing of larger dimensioned boards. For example, the horizontally-adjustable power saw 26 can readily accommodate two-by-four boards, but cannot provide shallow-deep saw cuts in two-by-twelve boards. The three-saw configuration of power saws 600, 26 and 400 on fixed- power-saw-carriage assembly 20 also enables complex board end processing for trusses implementing "scissor cuts."

Referring to FIG. 21a, a truss 700, assembled with various-sized connector plates 701, implementing a scissor cut is shown. Referring to FIG. 21b, truss board 702 is illustrated in greater detail. The scissor cut has a seat cut 704, a scarf cut 706, and a butt cut 708. Board 702 has a plurality of consecutively numbered points: point-zero 710, point-one 711, point-two

712, point-three 713, point-four 714, point-five 715, and point-six 716. The location of these points are stored within the computer in cabinet 13 and used to process uncut boards. The points are defined in accordance with angle and dimensional data associated with a desired truss board. For convenience, the points are numbered clockwise beginning at the lower-left point.

FIG. 22 is a flow chart depicting the general steps carried out to set the angular positions of the five power saws, the horizontal position of saws 26, 40 and 400, and the vertical position of saws 400, 500 and 600. Based upon the drawings of all the dimensions and angles of a truss to be cut with the sawing system, a predefined point associated with one or two angles at each end of the board can be determined. FIGS. 23a-b and 24a-c serve to illustrate the positioning of the power saws to cut the truss board 702 (shown in FIG. 21b).

The saw blades of power saws 26, 40, 400, 500 and 600 are positioned utilizing variations of a general algorithm. This algorithm takes into account the pivot-point positions of the saws with respect to the x-reference axis and the y-reference axis, as shown in FIG. 20. The general algorithm is:

of the saws with respect to the x-reference axis and the y-reference axis, as shown in FIG. 20. The general algorithm is:

Y-T„

^Λ OFFSET ^J x an(θ_,)

where:

T _x =(Ph)eos(Q _u --) -Hcl(cosQ _M ) +dH _χ -Ph

T _γ = -(Ph)sm(θ _M --) +Hcl(anQ _u ) +dH _r +H

Angle m is the angle between the x-reference and the face of the power saw blades.

In program flow block 802, the angle data and dimension data are retrieved from the database associated with the particular truss board to be cut. Program flow block 804 assigns the saw cuts to the left side saws 500 and 40 for single cuts or double cuts accordingly. In the example shown in FIGS. 21a and 21b, a double cut is made on the left end of the board 702.

In program flow block 806, the position of the assigned left side saws are determined such that a distance from the saw blade edges to the hold-down and to the material conveyor is minimized. In other words, power saw blade 82 is positioned so as not to interfere with material conveyor. Power saw blade 508 has an upper-blade tip 514 that is positioned to extend sufficiently past the board top edge 720 to cut through the board yet avoid interfering with hold-down 34. .An advantage of minimizing the amount upper-blade tips of the saws extend past the top edge 720 is that the hold-downs 34 do not interfere with the processing of shorter truss boards.

As shown in FIG. 23b, hold-down 34 can be placed at about two-inches from the upper-blade tip 514. In the example provided, power saw 500 having a vertical adjustment is making the top cut. The dHy, compensation is determined by the following formula:

max _βφ =c/_ϊy=- +(PA ₁ )-in(θ ₁ -^) -(/tø^si-KΘ. )-..-,

π-in^.=d__ =- +(PA ₁ )sin(θ - π^). -(_fc/ ₁ )sm(θ ₁ )-_f ₁

where:

T =Y+(DIAf2-MINΗPOFFSET)sinθ ₁

For the saw configuration present, minadj parameters for power saw 500 cannot be less than about negative four-inches. Maxadj cannot be more than a positive twelve-inches. The dHyi up-down adjustment is made in ten iterations beginning from the minadj value. Similarly, the dHx, in-out adjustment for saw 40 is determined after blade 82 is oriented to an angle θ ₂ . The dHx value, or X-offset, is the dimension from the y -axis to the object point. In this example, the object point is first-point 711. Knowing this value, saw 40 is aligned to make its cut by the following formula:

Y-Z. dH _n X _0FFSET i_ tan(θ-)

where:

T _χ =(Ph ₂ }cos(d ₂ -^)-Hcl ₂ (cosθ^+dH _χ2 -Ph ₂

___

T _γ = -(PA ₂ )s-n(θ ₂ -^)+-ϊc ₂ (s_αθ ₂ )+_(-f _ϊ -+__ ₂

In program block 808, the saw cuts are assigned to the right side saws 26, 400 and 60 for single cut, double cuts or scissor cuts, accordingly. For the scissor cut shown in FIG. 21b, all the right side saws are assigned for the cut. In program block 810, the positions of the assigned left side saws are determined such that a distance from the saw blade edges to the hold-down and to the material conveyor is ιτιinύτύzed. In this case, saw 400 is of primary concern for interfering with hold-down 34. In other words, power saw blade 408 is posi¬ tioned so as not to interfere with material conveyor 34. Power saw blade 408 has an upper- blade tip 414 that is positioned to extend sufficiently past the board top edge 720 to cut through the board yet avoid interfering with hold-down 34. To position the saws, the seat- butt point elevation, or fifth-point 715 elevation, measured from the x-reference is deter¬ mined. A first dHx, or x-offset, value is the distance from the fifth-point 715 to the y ₄ -axis. Based on this distance, saw 26 is put into place using d e following formula:

£/__j ₄ =r-.+PA ₄ -rHc/ ₄ cosθ ₄ -PA ₄ cos(θ ₄ -— π, )

_£

where:

tanθ ₄

and where:

r _r =-PA ₄ sin(θ ₄ -^ π ,)-rHc/ ₄ sinθ ₄ +_._-> ₄ -rH ₄

With respect to positioning power saw 400, the scarf-butt point elevation, or fourth-point 714 elevation, is determined. Referring to FIG. 24c, the x_int value is determined, which is length A minus length B. Based on this information and the angle 0 ₅ of saw blade 408, the

following formula is used to determine the dHy value and dHx value such that upper-blade tip 414 barely clears the top edge 720:

dHy ₅ = T _y - A _j S-ntθ _j - -) -Hcljsmβ, -H ₅

where:

Ty=Y-(DIA/2-MINΗPOFFSET)smθ ₅

Tκ=X+(DIAp. -MlNΗPOFFSET cosQ,

Program step 612 sets the carriage length between fixed carriage 20 and movable carriage 22. The carriage length is set to position the movable carriage 22 so that the board is cut at the proper length. For example, saws 26 and 40, as shown in FIGS. 23a and 24b, respectively, are assigned to make the bottom cuts for the scissor-truss board 702. The carriage length L is the bottom edge length D plus the left offset F minus the right offset E.

Program step 814 parks the saw heads not used for processing the truss board. Patching a head consists of setting its height adjustment dHy, horizontal adjustment dHx, and angle θ. so that the saw blade is completely above our outside the board to be processed. In the scissor-cut example provided, all the heads are used to process the board 702, so none are parked.

Program step 816 sets the height and horizontal position of hold-downs 34 to avoid the saw blades while still remaining close to the blades. Positioning is accomplished by

determining which saw on the fixed carriage 20 and the saw on the movable carriage 22 extend the furthest along the x-reference axis. It is desirable to place the hold-downs as close as possible to the blade tips such that short truss board members can be processed.

Program step 818 physically positions the saws 26, 40, 400, 500 and 600 through the mechanical apparatus discussed earlier. Movable carriage 22 is driven into place, and hold- downs 34 are positioned according to the determinations made in program step 816.

In program step 820, the truss board 702 is processed through the setup. A plurality of boards can be processed in the configuration. When a new configuration is desired, the program steps shown in FIG. 22 are repeated with the new angle and dimension data. From the foregoing, the various component part of an efficient sawing system are disclosed, with the enhanced capability of moving the power saws, as well as the in-feed material conveyors. With the provisions of the present invention, the various component parts can be manufactured in a more cost efficient manner, and require less maintenance without sacrificing precision or accuracy. Accordingly, various modifications may suggest themselves to those skilled in the art without departing from the spirit and scope of the invention, as defined by the appended claims. Also, those skilled in the art may prefer to utilize some of the features and advantages of the invention, without using all of the features. The invention is not to be restricted to the specific forms shown, or the uses mentioned, except as to the extent required by the claims.