NZ717727B2 - Curve cutting with a circular saw blade - Google Patents

Abstract

Sawmilling curved timber presents a number of problems that result in unnecessary timber loss and undesired stress on the saw blades. A method (500) and calculating unit (620) for curve sawing of a block (100) in a cutting direction (S) with a first circular saw blade (110) is disclosed. The method (500) comprises determining (501) a radius (R) of curvature of a first portion of the block by measuring the curvature of the block (100) in the direction of cutting (S); calculating (502) a vertical inclination angle (?) of the first circular saw blade (110) in a vertical plane (V) relative to the cutting direction (S) in the block (100), based on the determined radius (R) of the curve sawing; inclining (503) the first circular saw blade (110) with the calculated (502) vertical inclination angle (?); and sawing (508) the block (100) in the cutting direction (S) with the inclined (503) first circular saw blade (110) along the determined (501) radius (R) of the curve sawing. (500) comprises determining (501) a radius (R) of curvature of a first portion of the block by measuring the curvature of the block (100) in the direction of cutting (S); calculating (502) a vertical inclination angle (?) of the first circular saw blade (110) in a vertical plane (V) relative to the cutting direction (S) in the block (100), based on the determined radius (R) of the curve sawing; inclining (503) the first circular saw blade (110) with the calculated (502) vertical inclination angle (?); and sawing (508) the block (100) in the cutting direction (S) with the inclined (503) first circular saw blade (110) along the determined (501) radius (R) of the curve sawing.

Description

CURVE CUTTING WITH A CIRCULAR SAW BLADE TECNICAL FIELD The invention relates to a method and a calculation unit. More specifically, the invention relates to curve sawing of a block utilising at least one circular saw blade.

BACKGROUND A common way to decompose logs into boards and planks is that in a first stage in a so- called stock-taking saw, cut a rectangular block by cutting off the sides, called back sides of the log. The block that remains to divide in a second step in a second-coming so—called division saw has a rectangular cross section, but is usually more or less curved in the longi- tudinal ion, depending on the log curve. Curve sawing is ore a usual manner by sawing recut to decompose the curved block and thus gain advantages as to quality and increased yield, as a result of following the grain of the wood to a greater extent compared to straight sawing. It may be added that curve sawed boards later straightens out when drying.

Curve sawing comprises g the curved block past the division saw in a curved path that follows the log's curvature. In some cases, a different curve radii when curve sawing along a log. This is due to a rootstock often is crooked in the root end, but may be ht- ened in the top end. The division saw may be a single circular saw blade (single blade) or double circular saw blades e blades or twin blades).

When sawing recut with double blades, or twin blades, these often are conflicting and dis- placed in the feed direction to permit vertical overlap between the circular saws and a cer- tain safety margin to prevent the saw blades from coming into contact with each other. In some cases the overlying and the underlying saw blade may be parallel to each other in a vertical plane, i.e. lack displacement in the feeding direction in relation to each other. In such case, the rotation of the saw blades may be synchronised with each other so that the saw teeth on each respective the saw blade engage in the gap n the serrations on the opposite saw blade, much like the teethes of a pair of inter acting gears, but without touching each other.

A problem occurring at such tight curve sawing is that the saw cuts into the log becomes oblique and curved due to undesirable geometry. The ude of this so-called decom- position error may be O.2—O.6 mm for the relatively large radius curves that are used today, imately 40-60 meters. For double blades the situation becomes even worse by saw cuts are broadened and rear-sawing is done. Rear-sawing means that the blade of the cir- cular saw blade’s rear part (in the log feed direction) will engage as a result of unwanted side forces that push on the blade, resulting in a wider kerf, or saw cut, in the block than othen/vise. This increases chip loss, resulting in a d yield.

Furthermore, due to the undesirable side forces that occur on the saw blade, it must be ioned to withstand this stress laterally, i.e. to be thicker than ise would be necessary. This however increases kerf loss further. In addition, there is also an increased risk of blade ation or breakage and /or that the saw blade must be replaced more frequently than ise which can be costly, not least as the production has to be stopped when the saw is at a standstill due to maintenance.

It may also emerge an increased need to insert a wiper slot in the saw blade, which gener- ates further sawdust and thus lowers the yield r.

A further problem with curve sawing is that the timber often has a stronger curvature than the minimum bending radius possible to comply with a ar saw, resulting in that the grain cannot be followed. Another problem is that the wood may be bent in different direc- tions. In such case, it may not be possible to curve saw the wood so that the grain fol- lowed.

It may be concluded that there is a need for improvement to se yield and reduce kerf loss associated with curve sawing of timber, as well as to increase the quality of sawn tim- ber, especially as economical margins may be strained in the sawmill industry.

SUMMARY It is therefore an object of this invention to avoid at least some of the above listed disad- vantages and allow an improved procedure for curve sawing of wood.

According to a first aspect of the invention, this objective is achieved by a method for curve sawing of a block in a cutting direction with at least one first circular saw blade. The method comprises ining the radius of the curve sawing, by measuring the curvature of the block in the direction of cutting. The method also comprises calculating a al inclination angle of the first circular saw blade in a vertical plane relative to the direction of cutting in the block, based on the determined radius of the curve sawing. Furthermore, the method also comprises inclining or scewing the first circular saw blade with the calculated vertical inclination angle. The method also comprises sawing of the block in the direction of WO 20593 3 cutting of the inclined first circular saw blade along the determined radius of the curve sawing.

According to a second aspect of the invention, this objective is achieved by a calculating unit for enabling the inclination of at least one first circular saw blade when curve sawing a block in a cutting direction. The calculation unit comprises a receiver configured to receive a ement signal from a measurement unit, relating to the block curvature in the di- n of cutting. r, the ating unit also comprises a processor, configured to determine a radius of the curve sawing, based on the ement of the curvature of the block in the cutting direction, and to calculate a vertical inclination angle of the first circular saw blade in a vertical plane relative to the cutting direction in the block, based on the de- termined radius of the curve sawing. The calculation unit also comprises a transmitter con- figured to transmit a control signal to a control unit, for inclining the first circular saw blade with the calculated vertical inclination angle.

By inclining, tilting or skewing the saw blade in the vertical plane when cutting with single blade, inclined saw-track is avoided. By correspondingly inclining the saw blades against each other when g with dual blades, so that both blades are tilted toward each other, it is avoided that the saw cuts s inclined both at the top and the bottom of the saw- track, or kerf. This increases the yield as crude measurements may be d when the cut boards become more rectangular than they othenNise would be. Thereby, the radius of curvature may be reduced, which further increases the yield.

Furthermore, according to some embodiments when cutting with dual blades, the blade shafts when cutting with double blades may be angled toward each other in a horizontal plane so that the intersection of the ions of the respective blade shafts is located in the centre of curvature of the block. Thereby, back sawing and the broadening of the saw track created by back sawing is eliminated, or at least reduced, resulting in a higher yield and decreased logging waste.

Other advantages and additional novel features will become apparent from the following ed description of the invention.

LIST OF FIGURES The invention will now be bed in further detail with reference to the accompanying figures, which illustrate embodiments of the invention: Figure 1A is a tic illustration showing curve sawing with a single blade saw according to an embodiment of the invention.

Figure 1B is a schematic illustration showing curve sawing with a double blade saw according to an ment of the invention.

Figure 2A is a schematic illustration showing curve sawing with a single blade saw in a side perspective, according to an embodiment of the invention.

Figure ZB is a schematic illustration g curve sawing with a double blade saw in a side perspective, according to an embodiment of the invention.

Figure 3A is a schematic illustration showing curve sawing with a single blade saw according to an embodiment of the invention.

Figure SB is a schematic illustration g curve sawing with a double blade saw according to an embodiment of the invention.

Figure 4 is a schematic illustration g curve sawing with a double blade saw according to an embodiment of the invention as seen from above.

Figure 5 is a flow diagram illustrating an embodiment of a method for curve sawing.

Figure 6A is a schematic illustration showing curve sawing with a single blade saw according to an embodiment of the invention.

Figure GB is a schematic illustration showing curve sawing with a double blade saw according to an embodiment of the invention.

Figure 7 is an illustration of a calculating unit according to an embodiment of the in- vention.

DETAILED DESCRIPTION The invention is defined as a method and a calculation unit, which may be realised in any of the below described embodiments. This invention may be implemented in many different forms and should not be seen as limited by the herein described embodiments. These de- scribed embodiments are rather ed to illustrate s aspects of the invention.

Further aspects and features of the invention may become apparent from the ing detailed description, taken in conjunction with the accompanying gs. Figures are however rather to be consider as examples of various embodiments of the invention and should not be viewed as ng the invention, which is limited only by the accompanying patent claims. Furthermore, the figures are not necessarily drawn to scale and are, unless otherwise , intended to conceptually illustrate various aspects of the invention.

Figure 1A shows curve sawing with single blade according to an embodiment of the inven- tion. A block 100 of a certain ure with a radius of curvature R is fed passing a first circular saw blade 110 in a curved path, wherein the first circular saw blade 110 herein will cut up a kerf, or saw cut d line in the Figure) in a cutting direction S through the block 100. This first ar saw blade 110 may also be denominated single blade and is in the illustrated example performing as a division saw, as referenced in the background sec- tion.

In some embodiments, such division saw may also comprise a plurality of single blades which operate in parallel with each other to thereby partition the block 100 in boards and planks in one single fed of the block 100 through the division saw.

Figure 1B illustrates curve sawing with double blade according to an embodiment of the invention. The block 100, which has a certain curvature with a radius of curvature R, is fed in a curved path passing the first circular saw blade 110 and a second circular saw blade 120, which thereby are cutting a kerf, or saw cut (dashed line) in the block 100, in the cut- ting direction 8. This first ar saw blade 110, er with the second circular saw blade 120, which also may be termed double blade or dual blade, are in the illustrated ex- ample, performing as the division saw referenced in the background section.

In some embodiments, such division saw may also comprise a plurality of double blades which may operate in parallel with each other to thereby ion the block 100 in boards and planks in one single fed of the block 100 through the division saw.

Figure 2A shows curve sawing in a single blade embodiment of the invention, illustrated in a side view. The block 100, which has a certain curvature with a radius of curvature R is fed in a curved path passing the first circular saw blade 110, whereby the first circular saw blade 110 herein will sawing up a kerf, or saw cut, in the cutting direction 8 through the block 100. The block 100 may for example be fed to the first circular saw blade 110 on a treadmill according to some embodiments. The first circular saw blade 110, which has a diameter d, rotates about a shaft 130 in a horizontal plane H. The rotation of the first circu- lar blade 110 may be made either counter-clockwise, which is most common, or ise.

Regardless of the direction of rotation of the circular saw blade 110, the desired sawing zone is situated in front of a vertical plane V passing through the first saw blade shaft 130, while an red back sawing zone is situated behind this vertical plane V, relative to the ion of cutting 8.

Figure 2B shows curve sawing with double blade of embodiment of the invention, viewed in side view. The block 100, which has a certain curvature with a radius of curvature R, is fed into a curved path passing the first circular saw blade 110 and the second circular saw blade 120 in a curved path, wherein the first circular saw blade 110 along with the other circular saw blade 120 herein will cut up a joint kerf in the direction of cutting 8 through the block 100. The block 100 may for example be fed to the first circular saw blade 110 and second circular saw blade 120 on a treadmill with a saw base 200 in which the block 100 is ed, in some embodiments. The first circular saw blade 110 rotates about a shaft 130 in the horizontal plane H. The second circular saw blade 120 rotates about a shaft 140 in the horizontal plane H.

The rotation of the first and second ar saw blades 110, 120 may be made either coun- terclockwise, which is most common, or clockwise in different embodiments. less of the direction of rotation of the cutting circular saw blades 110, 120, the desired sawing zone is situated forward of a vertical plane V passing through the respective shafts 130, 140 of the respective cutting circular saw blades 110, 120; while an undesired back sawing zone is located behind the al plane V, in relation to the ion of cutting 8.

Figure 3A is a schematic illustration showing curve sawing according to a single blade embodiment of the invention, n the first circular saw blade 110 is inclined at a verti- cal angle of inclination B in relation to the al plane V.

By inclining the circular saw blade 110 in the vertical plane V, with the vertical angle of in- clination B slanted kerfs may be avoided when curve sawing the block 100. The size of such vertical inclination angle [3 may for example be ined as a function of the curva- ture radius R in some embodiments.

In this way, when the slanted kerfs are eliminated or at least reduced, the yield is increased as crude measures may be reduced. This in turn may also enable the curve radius R to be reduced, which r increases the yield and y of the sawn timber when the curve sawing better follows the log curvature and thus the fibre direction of the wood. The wood has better strength properties in the fibre direction than in other directions. Back sawing may further be d, which reduces the width of the kerf and thereby also ses the yield further. Further reduced lateral load on the circular saw blade 110 thus enable further reduction of the curve radius R and in some embodiments also the blade thickness, further increasing the yield and quality of the sawn timber. By controlling the circular saw blade 110 according to an algorithm, or by a look-up table, a correction of the kerf created in the block 100 from curve sawing by the circular saw blade 110 is accomplished.

The vertical angle of inclination B may e.g. be set to 0.23 degrees in tight curves with a radius of curvature R of 50 meters. This represents a slope of 0.6 mm over a height of 150 mm. This is merely mentioned as an illustrative example of le angle of inclination B.

A typical size of the vertical angle of inclination B may in practice be less than 1 .

Further, the vertical angle of inclination B may depend not only by the curvature radius R, but also by further parameters according to some embodiments, such as the block height, blade diameter d and/ or by a vertical ce from the centre of the circle saw blade to the saw base 200 on which the block 100 is situated, according to some embodiments.

Further, the vertical angle of inclination B may be calculated based on the following algo- rithm in some embodiments: l3 = arctan (Xaverage — Xtop)/((d/ 2) - U), wherein: ge = (Xstart + Xend)/2§ Xtop = R(1-cos otoP)/cos atop; Xena = R(1-cos Gem/cos Gena; Xstan = R(1-cos ostan)/cos dstan; atop = arctan (-e/2);’R; (lend = arctan (d/2 sin yend - (e/2))/R; ostan = arctan (d/2 sin ystan - (e/2))IR; Ystan = arccos (u/(d/2)); Yend = 'Ystan; Ytop = 0; u = the vertical distance from the centre of the circular saw blade to the saw base 200 on which the block 100 is placed during the sawing; and d = er of the circular saw blade.

Figure 3B is a schematic illustration depicting curve sawing with double blade according to an embodiment of the invention, wherein the second circular saw blade 120 is inclined with a vertical angle of ation B, and the first circular saw blade 110 is inclined at a vertical angle of inclination -B, relative to the vertical plane V. , by ng the circular saw blades 110, 120 to lean against each other, such that tilting of both upper and lower part of the kerf may be avoided during curve sawing of the block 100. The magnitude of this verti- cal angle of ation B and -B respectively, may for example be determined as a function of the radius of curvature R in some embodiments.

In this way, as the saw cut slope, or tilting kerf as it also may be ed to as, may be eliminated or at least reduced, the yield may be increased as crude es may be re- duced. This in turn may also lead to that the curve radius R may be reduced, which further may increase the yield and quality of the sawn timber as the made curve sawing better follows the log curvature and thus the fibre direction of the wood. The timber has better strength properties in the fibre direction than in other directions. Further, back sawing may be avoided, which reduces the width of the saw cut and thereby further increase the yield.

In on, the lateral load on the circular saw blades 110, 120 is reduced, which makes it possible to r reduce the curve radius R and in some embodiments even saw blade thickness, further increasing the yield and quality of the sawn timber. By controlling the circular saw blades 110, 120 according to an algorithm, or by a look-up table, a correction of the saw cut when curve sawing with the circular saw blades 110, 120 through the block 100 may be achieved.

The vertical angle of ation B and - [3 tively, may e.g. be set to 0.23/ -0.23 de- grees in tight curves with a radius of curvature R of 50 meters. This represents a slope of 0.6 mm over a height of 150 mm. This is merely ned as an illustrative example of possible angle of inclination B. A typical size of the vertical angle of inclination [3/ - B may in practice be less than 1 degree.

Further, the al angle of inclination [3f 43 may depend not only on the curvature radius R, but also on further parameters according to some embodiments, such as on the block height, blade diameter d and/ or by a vertical distance from the centre of the circular saw blade to the saw base 200 on which the block 100 is placed, according to some embodi- ments.

Further, the al angle of inclination [3/ -B may be calculated based on the following al- gorithm in some embodiments: l3 = arctan (Xaverage - Xtop)/((d/2) - U).

- B = - arctan age - Xtop)/((d/2) - U), wherein: Xaverage = (Xstart + Xend)/2; Xtop = R(1-cos atop)/cos atop; Xena = R(1-cos dend)/cos dend; Xstart = R(1-cos Gstan)/C0$ astart; 9 2014/050870 Gimp = arctan (-e/2)/R; (lend = arctan (d/2 sin yend - (e/2))/R; Gstan = arctan (d/2 sin vstan - (e/2))!R; Ystart = arccos 2)); Yend = 'Ystan; Ytop = 0; u = the al distance n the centre of the circular saw blade and the saw base 200 on which the block 100 is placed during the sawing; and d = diameter of the circular saw blade.

Figure 4 is a schematic illustration showing the curve sawing with double blade according to the embodiment of the invention, seen in a top view.

The blade axes of the first circular saw blade 110 and second circular saw blade 120 are here angled toward each other in the horizontal plane H with a horizontal angle a, for point- ing to a common centre of curvature. This angling with a respective horizontal inclination angle a may in some ments be made variable as a function of the position of the centre of curvature and thus be a function of the radius of curvature R.

Hereby, the saw cut slope, or tilting kerf, or inclination of the saw cut may be eliminated or at least reduced. This increases the yield as crude measurements may be reduced. This in turn may also lead to that the curve radius R may be reduced, which further increases the yield and y of the sawn timber when the curve sawing may better follow the log curva- ture and thus the fibre ion of the wood. The wood has better strength properties in the fibre direction than in other directions. Back sawing may be further avoided, thus reducing width of the saw cut and thereby further increase the yield. In addition, the lateral load on the ar saw blades 110, 120 is reduced, which makes it possible to further reduce the curve radius R and in some embodiments even saw blade thickness, further increasing the yield and quality of the sawn timber. By controlling the horizontal angle of inclination s of the circular saw blades 110, 120 according to an algorithm, or by a look-up table, a correc- tion of the saw cut when curve sawing with the circular saw blades 110, 120 through the block 100 may be achieved.

The horizontal angle of inclination s of the first ar saw blade 110 and the second circu- lar saw blade 120 may in some embodiments be based, in addition to being based on the determined radius R of the curve sawing, on a distance el 2 in the cutting direction 8 be- tween the centre of circle saw blade and a centre plane for the radius R of the curve saw- ing of the block 100 according to some embodiments.

The horizontal inclination angle a of the first circular saw blade 110 and/ or the second cir- cular saw blade 120 may for example be based on the following algorithm according to some ments: a = arctan((e/2)/R), wherein e/2 = a distance in the direction of cutting 8 between the centre of the circle saw blade and a centre plane of the radius R of the curve sawing of the block 100.

Figure 5 is a flow diagram illustrating an embodiment of a curve cutting methodology. The flow chart of Figure 5 illustrates a method 500 for curve sawing in a g direction 8 of a block 100 with at least one first circular saw blade 110. The block 100 may comprise a log of wood on which the sides have been previously cut. The log of wood may comprise any arbitrary kind of wood, such as e.g. pine, , oak, beech, birch or similar. The block 100 has a curvature in the cutting direction 8 with a radius of ure R. This radius of curvature R may vary along the block length, or be constant in different embodiments.

To perform curve sawing correctly, the method 500 comprises a number of actions 501- 508. It should be noted that some of the described actions may be comprised only in some alternative embodiments of the ion, such as s 504-507. Further, it is noted that the described actions may be med in a somewhat different chronological order than the order number indicates, and/ or that some of them may be performed in parallel. The procedure 500 comprises the following actions: Action 501 A radius R of the curve sawing is determined by measuring the curvature of the block 100 in the cutting direction 8. The cutting direction 8 is ed in the horizontal plane H and is opposite to the feed ion of the block 100.

This measurement may be performed before the log arrives to the stock-taking saw, or while the block 100 is located between the stock-taking saw and ng saw according to various embodiments. Further, measurements of the curvature of the block 100 may be repeated continuously according to some embodiments, while the block 100 is processed.

Further, the determined radius R of the curve sawing may vary along the cutting direction 8 of the block 100, e.g., when the block 100 has an S—shape or the like. Thus, according to some embodiments, a plurality of radii R of the block 100 may be determined, which varies along the direction of cutting 8.

Action 502 A al angle of inclination [3 of the first circular saw blade 110 is calculated in a vertical plane V in relation to the direction of cutting S in the block 100, based on the determined radius R of the curve sawing.

The calculation of the al angle of inclination [3 of the first circular saw blade 110 and / or second circular saw blade 120 may in some embodiments be based on, in addition to the determined radius R of the curve sawing, on the diameter d of the circular saw blade and/ or the al distance u from the centre of the circular saw blade to a saw base 200, on which the block 100 is situated.

According to some ments, the calculation of the vertical angle of inclination B of the first circular saw blade 110 and/ or the second circular saw blade 120 may be based for example on the following thm: l3 = arctan (Xaverage - xlop>/((d/2) - u). wherein: Xaverage = (Xstart + Xend)/2; Xtop = R(1-cos grog/cos atop; Xend = R(1-cos Gend)/COS dend; Xstan = R(1-cos ostan)/cos 013m; atop = arctan (-e/2)/R; orend = arctan (d/2 sin yend - (e/2))/R; orsm = arctan (d/2 sin vstan - (e/2))/R; Ystan = arccos (u/(d!2)); Yend = 'Ystart; Ytop = 0; u = the vertical ce between the centre of the circular saw blade and the saw base 200 on which the block 100 is placed during the ; and d = diameter of the circular saw blade.

Action 503 The first circular saw blade 110 is inclined by the estimated 502 vertical angle of inclination By inclining the first circular saw blade 110 in the vertical plane V with the vertical angle of inclination B when cutting with single blade, a sloped kerf may be avoided, or at least may problems associated with such sloped kerf be reduced. This increases the yield as crude measurements may be reduced when the cut boards become more rectangular than they otherwise would be.

Another effect of inclining the circular saw blade 110 with the calculated 502 vertical angle of ation B in the vertical plane V is that the curve radius R may be reduced. Hereby is it enabled to make curved cuts with a smaller radius of curvature R than usly possi- ble because of the resulting slope of the kerf in the prior art. By enabling curve sawing with tighter radius R, it is possible to further increase the yield and quality of the cut boards when the logs frequently are more curved than the minimum radius of curvature R that ac- g to prior art solutions may be possible to follow during curve sawing.

Action 504 This action may be performed in some alternative embodiments of the method 500, wherein the curve sawing is performed by the first circular saw blade 110 and a second circular saw blade 120, which is positioned offset in the vertical plane V in relation to the first circular saw blade 110. The circular saw blades 110, 120 may saw a single joint saw cut through the block 100 along the determined 501 radius R of the curve sawing.

The second circular saw blade 120 may be inclined with the ated 502 vertical angle of inclination B in the opposite direction in the vertical plane V in relation to the first ar saw blade 110, so that the second circular saw blade 120 is inclined towards the first circu- lar saw blade 110 in the vertical plane V. An example of such inclination of first and second circular saw blades 110, 120 is illustrated in Figure 38.

By inclining the circular saw blades 110, 120 in the vertical plane V, with the vertical angle of inclination B, it may be avoided that the kerf is tilted at both the top and bottom of the kerf. Thereby slanted kerfs may be avoided or at least may the ms associated with such d kerfs be reduced. Thus, the yield increased by crude measurements may be d when they sawed boards become more rectangular than they othenNise would be.

Action 505 This action may be med in some alternative embodiments of the method 500, in which action 504 has been performed.

WO 20593 13 A horizontal inclination angle a may be calculated for the first circular saw blade 110 and the second circular saw blade 120 in a horizontal plane H in relation to the ion of cut- ting S in the block 100, based on the determined radius R of the curve sawing.

The calculation of the horizontal angle of inclination s of the first circular saw blade 110 and the second circular saw blade 120 may in some embodiments be based on, in addition to the determined radius R of the curve sawing, on a distance 9/ 2 in the direction of cutting 8 between the circular saw blade centre and a centre plane of radius R of the curve sawing of the block 100.

The horizontal angle of inclination e of the first circular saw blade 110 and/ or the second circular saw blade 120 may ing to some embodiments be based on the following algorithm: a = ((e/2)/R), wherein: e/2 = a distance in the direction of cutting 8 between the centre of the circle saw blade and a centre plane of the radius R of the curve sawing of the block 100.

Action 506 This action may be med in some ative embodiments of the method 500, in which action 504 and action 505 have been performed.

The first circular saw blade 110 may be inclined by the estimated 505 horizontal angle of inclination a.

Thereby back sawing may be avoided when sawing with double blades, as the lateral load on the circular saw blades 110, 120 decreases. This leads to reduced kerf width and thus also increased yield as less wood is lost in sawdust. In addition, by the decreased lateral load on the circular saw blades 110, 120, blade thickness of the circular saw blades 110, 120 may be reduced, further reducing chip wastage and leading to furthermore increased yield.

Action 507 This action may be performed in some alternative embodiments of the method 500, in which action 504, action 505 and action 506 have been med.

The second circular saw blade 120 may be inclined with the calculated 505 horizontal an- gle of inclination s but in the opposite direction in the horizontal plane H with respect to the first circular saw blade 110 so that the second circular saw blade 120 is inclined towards the first circular saw blade 110 in the horizontal plane H.

Action 508 The block 100 is cut into the direction of cutting S with the inclined 503 first circular saw blade 110 along the ined 501 radius R of the curve sawing.

According to some ments, the method 500 may be performed continuously during the sawing of the block 100. on, the radius of curvature R may be uously measured and remeasured at the block 100 and the vertical inclination angle [3, respec- tively, the horizontal angle of inclination s recalculated based on such uous meas- urement. It is thereby enabled sawing along a varying radius R of the curve sawing of the block 100, as well as a varying slope in the al plane V and possibly the horizontal plane H, depending on the varying radius R.

Thereby curved cuts are enabled that better follows the block curvature, cutting the boards better following the grain of the wood. This increases the quality of the cut boards further.

Figure 6A shows a system 600 configured to incline at least one first circular saw blade 110 during curve sawing in a cutting direction 8 of a block 100, when curved cutting is made with a single blade. As previously mentioned, a plurality of circular saw blades may be mounted in parallel in a horizontal plane, for example on the same shaft 130, whereby the final cutting of a plurality of boards of the block 100 may be made in one single feed ing to some ments.

The system 600 comprises a measuring unit 610, configured to measure the curvature in the direction of cutting S of the block 100. This ement device 610 may for example measure the distance to some measurement points on the block 100 by means such as light, e.g. laser, or other electromagnetic radiation. Hereupon, laser triangulation may be used for performing the measurement in accordance with certain embodiments. In some embodiments, the measuring device 610 may comprise e.g. a 3D camera, a Time of Flight (TOF) camera, a stereo camera, a light-field camera, or the like. The measurement device 610 may further for example comprise a 3D log scanner in certain embodiments. Such 3D measurement frame may comprise laser light measures of the distance to the surface of the block 100 as it passes h the measurement frame. Thereby, the whole surface of the log to be seen and each measuring beam has in turn a plurality of laser measuring de- vices.

The measurement unit 610 may for example determine the distance of a measurement point on the block 100 by emitting a modulated light wave, detecting the corresponding reflected light wave from the measuring point at block 100 and measuring the reflected light wave offset relative to the emitted light wave. The distance to the respective measuring points may then be calculated as the wavelength of light and the speed is known - ters.

A Time-of-Flight camera is a camera that takes a sequence of images and measuring a distance to an object based on the known speed of light by measuring the time required for a light signal between the camera and subject/ object.

The measurement unit 610 may then transmit the measured distances to measuring points on the block 100 to a calculation unit 620, which is also sed in the system 600. The calculation unit 620, which will be bed in conjunction with the description of Figure 7, is configured to perform calculations based on measurements received from the measure- ment device 610, which calculations may establish such block curvature radius R to be ed when curve sawing the block 100. Further, the calculation unit 620 may be config- ured to calculate a vertical angle of inclination B of the first circular saw blade 110 in a ver- tical plane V in relation to the cutting direction 8 of the block 100, based on the ined radius R of the curve sawing. The calculation unit 620 may se for example a com- puter or similar device with the ed computing capacity.

The measurement unit 610 may also be configured to generate and transmit a l sig- nal to a control unit 630, which is also comprised in the system 600. The control unit 630, which for example may be situated in at least one end of the first shaft 130 of the first circu- lar saw blade 110, may cause inclination of the first circular saw blade 110 with the calcu- lated vertical angle of inclination B, for example, by inclining the first circular saw-blade shaft 130, in either or both of the mounting points of the shaft 130.

The measurement unit 610, the ation unit 620 and the control unit 630, which are comprised in the system 600 may se distinct logical entities, or may alternatively in some embodiments be housed in the same or partly the same physical device. For exam- ple, the calculation unit 620 may be comprised within the measurement device 610 or the 16 2014/050870 control unit 630 in some embodiments. Further, the listed devices 610, 620, 630 are ar- ranged to communicate with each other over a wired or wireless interface.

Such wireless interface may se communication via radio waves, for example, based on, or inspired by, any of the following technologies: GSM, EDGE, UMTS, CDMA, CDMA2000, TD-SCDMA, LTE, LTE-Advanced; Wi-Fi, according to one of the IEEE stan- dards 802.11 a, b, g and/ or n, IP, Bluetooth and/ or NFC (Near Field Communication).

Said wired interface may comprise e.g. a cable connection, an Internet-connected network or a communication system sing one or more communication buses to interconnect the enumerated units 610, 620, 630 with each other and alternatively also with other de- vices such as a controller and/ or sensor. The communication bus may for example com- prise one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Oriented Systems Transport), or any other bus configuration; or alternatively a ss connection, based on e.g. any of the above listed technologies for wireless communication.

Figure GB illustrates an embodiment of the system 600, configured for inclination, or mis- ent, of a first circular saw blade 110 and a second circular saw blade 120 when per- forming curve sawing in a saw direction S of a block 100, Le, performing curve sawing with dual blade. As previously mentioned, a plurality of circular saw blades 110, 120 may be mounted parallel to the horizontal, for example at the same respective shaft 130, 140, whereby the simultaneous g of a plurality of boards in the block 100 is made possible according to some embodiments.

In this illustrative scenario, the curve sawing of the first circular saw blade 110 and the second circular saw blade 120, which second circular saw blade 120 is oned offset in the vertical plane V in relation to the first circular saw blade 110 (and in some alternative embodiments displaced also in the horizontal plane H), saw a single joint saw cut through the block 100 along with the determined radius R of the curve sawing. The control unit 630 is thereby further configured to e also the second circular saw blade 120 with the cal- culated vertical inclination angle [3 in the opposite direction in the vertical plane V in relation to the first circular saw blade 110 so that the second circular saw blade 120 is inclined to- wards the first circular saw blade 110 in the vertical plane V. This feature has previously been illustrated in Figure 3B and as further explained in conjunction with the description of Figure SB.

Further, the calculating unit 620 according to some embodiments may be configured to calculate a horizontal angle of inclination e of the first circular saw blade 110 and the sec- ond circular saw blade 120 in a horizontal plane H in relation to the direction of cutting S in the block 100, based on the determined radius R of the curve . Hereupon, although the control unit 630 may be configured to incline the first circular saw blade 110 with the calculated horizontal ation angle a, and to e the second circular saw blade 120 with the calculated horizontal inclination angle a but in the opposite direction in the horizon- tal plane H with respect to the first circular saw blade 110, such that the second circular saw blade 120 is inclined s the first circular saw blade 110 in the horizontal plane H.

This relationship is illustrated in Figure 4 and discussed in detail in the ponding text of the description.

The control unit 630 may, according to some embodiments comprise a plurality of physical devices, arranged to operate on the shaft 130 of the first ar saw blade 110, and/ or the shaft 140 of the second circular saw blade 120, in the horizontal plane and/ or the verti- cal plane respectively, such that the desired r relationship of the circular saw blades 110, 120 is obtained.

Figure 7 is also illustrating a schematic overview of the system 600, configured to incline at least one first circular saw blade 110 when performing curve sawing of a block 100 in a saw direction 8, but with a particular focus on calculating unit 620.

The calculation unit 620 is configured to m at least some of the previously-described actions 501-508, comprised in the description of the method 500 for curve sawing of a block 100 in a direction of sawing S with at least one first circular saw blade 110.

The calculation unit 620 s inclination or misalignment, i.e. skew or bias, of at least a first circular saw blade 110, when performing curve sawing of the block 100 in the direction of sawing S. The calculation unit 620 may for example comprise a computer or the like in some embodiments. Such computer may be e.g., a desktop er, a server, a mobile computer, a PDA, a tablet, a phone, a netbook or similar.

In order to correctly calculate and thereby enable inclination of the circular saw blade 110, or circular saw blades 110, 120, the calculating unit 620 comprise a number of compo- nents, which are detailed in the following detailed description. It may be noted that some of the described components may be t in some embodiments only. Furthermore, it is noted that some additional electronics of the ation unit 620, not entirely required in order to understand the function of the calculation unit 620 according to the invention, has not been depicted in Figure 7, to not impede or unnecessarily complicate the understand- ing of the ion.

The calculation unit 620 comprises a er 710. The receiver 710 is configured to re- ceive a measurement signal from a measurement unit 610, comprising information related to the curvature of the block 100 in the cutting ion 8.

The receiver 710 is configured to receive the measurement signal from the measurement unit 610 over a wired or wireless interface according to different embodiments.

Furthermore, the calculation unit 620 comprises a sor 720. The processor 720 is configured to determine a radius R of the curve sawing, based on the ed result of the measurement of the curvature of the block 100 in the cutting ion 8. The processor 720 is also configured to calculate a vertical inclination angle [3 of the first circular saw blade 110 in a vertical plane V, in relation to the cutting direction 8 in the block 100, based on the determined radius R of the curve sawing.

The processor 720 may comprise, for example, one or more Central Processing Unit(s) (CPU), microprocessor(s) or other logic designed to interpret and execute instructions and/ or to read and write data. The processor 720 may handle data for input, outflow or comput- ing of data, also comprising data buffering, control and the like.

In some embodiments, the processor 720 may be further ured to calculate a n- tal inclination angle a of the first circular saw blade 110 and the second circular saw blade 120, in a ntal plane H in relation to the g direction 8 in the block 100, based on the determined radius R of the curve sawing, in some embodiments.

The ation unit 620 also comprises a transmitter 730. Transmitter 730 is configured to send a l signal to a control unit 630, comprising an instruction for inclining the first circular saw blade 110 with the calculated vertical inclination angle [3.

According to certain embodiments the curve sawing may be performed by means of the first circular saw blade 110 and a second circular saw blade 120, which is positioned in offset in the vertical plane V in relation to the first circular saw blade 110. Said saw blades 110, 120 may create a single joint saw cut through the block 100 along the determined radius R of the curve sawing.

The transmitter 730 may then be further configured to send a control signal to the control unit 630, for ing the second circular saw blade 120 with the calculated vertical inclina- tion angle [3, but in the opposite direction in the vertical plane V in relation to the first circu- lar saw blade 110 so that the second circular saw blade 120 is inclined toward the first cir- cular saw blade 110 in the vertical plane V.

The transmitter 730 may also be configured to send a control signal to the control unit 630, for inclining the first circular saw blade 110 with the calculated ntal angle of inclina- tion a, and inclining the second circular saw blade 120 with the calculated horizontal incli- nation angle 2 but in the opposite direction in the ntal plane H, relative to the first circular saw blade 110 so that the second circular saw blade 120 is inclined s the first circular saw blade 110 in the horizontal plane H, which is illustrated in Figure 4.

The transmitter 730 is configured to transmit the control signal to the control unit 630 over a wired or wireless interface, such as e.g. any of the aforementioned wired or wireless inter- faces.

Further, the calculation unit 620 may comprise, or be connectable to, a volatile or non- le data memory 725 i.e., a storage means for data such as e.g., a memory card, a flash drive, a USB memory stick, a hard drive or other similar data storage device. On the data memory 725 may for example information related to certain curve radii R be stored in a look-up table or the like, associated with various respective corresponding values of the vertical inclination angle B, and/ or the ntal inclination angle a.

In some embodiments, the calculation unit 620 may comprise or be table to a moni- tor (not shown). The monitor may be configured to show and/ or illustrate information re- lated to the curve sawing, such as text or image illustrating aspects of the curve sawing to a human or of the saw.

Furthermore some embodiments of the invention may comprise a computer program for controlling the curve sawing of the block 100 in the cutting direction 8 with at least one first circular saw blade 110. Such a computer program may be configured to perform the method 500, according to at least one of the actions 501-508 when the computer m is ed in the sor 720 in the calculation unit 620.

The actions 501-508 previously described may be implemented by one or more processors 720 of the calculation unit 620, along with computer m code for performing any, some or all of the actions 501-508. y, a er program comprising instructions for performing the actions 501-508, may calculate a vertical inclination angle [5 of the first ar saw blade 110 in a vertical plane V in relation to the direction of cutting S in a block 100 with a particular measured radius R of the curve sawing, thereby enabling inclination of the first circular saw blade 110 with the calculated vertical inclination angle B, then the computer program is loaded into the processor 720.

PATENT

Claims (21)

1. A method for curve sawing of a block in a cutting direction with a cutting device that es at least a first ar saw blade, wherein the cutting device has a reference position in which the first circular saw blade lies within a first plane that extends along the cutting direction, a rotational axis of the first circular saw blade is normal to the first plane, a first axis that extends through the first circular saw blade is el to the cutting direction, and a second axis that extends through the first circular saw blade is perpendicular to the cutting direction, the first axis, and the rotational axis, the method comprising: determining a radius of curvature of a first portion of the block based at least on a measurement of the curvature of the block in the cutting direction; determining a first ation angle for the first circular saw blade about the first axis based at least on the ined radius of curvature; inclining the first circular saw blade to the first inclination angle by rotating the first circular saw blade a first rotational distance about the first axis in a first rotational direction; and causing the first circular saw blade to saw the first portion of the block in the cutting direction along the curvature with the inclined first circular saw blade.

2. The method according to claim 1, wherein the first inclination angle is determined based at least in part on a height of the block, a diameter of the first circular saw blade, and/or a vertical ce between the centre of the first circular saw blade and a saw base on which the block is placed.

3. The method according to claim 2, wherein determining the first inclination angle of the first circular saw blade includes calculating the first inclination angle according to the following thm: β = arctan (Xaverage - Xtop)/((d/2) - u), wherein: Xaverage = (Xstart + Xend)/2; Xtop = R(1-cos αtop)/cos αtop; Xend = R(1-cos αend)/cos αend; Xstart = R(1-cos )/cos αstart; αtop = arctan (-e/2)/R; αend = arctan (d/2 sin γend - (e/2))/R; αstart = arctan (d/2 sin γstart - /R; γstart = arccos (u/(d/2)); γend = -γstart; γtop = 0; R = the radius of curvature; e/2 = a distance in the direction of g between the centre of the first circular saw blade and a centre plane of the radius of curvature; u = the vertical distance between the centre of the first circular saw blade and the saw base on which the block (100) is placed during the sawing; and d = diameter of the first circular saw blade.

4. The method according to claim 1, wherein determining the first inclination angle includes accessing a look-up table, n the p table includes a plurality of curve radii and corresponding inclination angles associated with the curve radii, and fying the first inclination angle based on the determined radius of curvature.

5. The method according to any one of claims 1-4, wherein the cutting device further includes a second circular saw blade, and wherein, when the cutting device is in the reference position, the second circular saw blade lies within the first plane, a third axis that extends through the second circular saw blade is parallel to the first axis and the cutting direction, and a fourth axis that extends through the second circular saw blade is parallel to the second axis, and wherein the curve sawing is performed by means of the first ar saw blade and the second circular saw blade, which are arranged to jointly create a common saw cut through the block , the method further comprising: inclining the second circular saw blade by rotating the second circular saw blade said first onal distance about the third axis, but in a second rotational direction that is opposite to the first rotational direction, such that the first circular saw blade and the second circular saw blade are inclined in opposite ions relative to the first plane.

6. The method according to claim 5, further comprising: determining a second inclination angle for the first circular saw blade about the second axis based at least on the determined radius of curvature; inclining the first circular saw blade to the second inclination angle by rotating the first circular saw blade a second rotational distance about the second axis in a third rotational direction, and inclining the second circular saw blade by rotating the second ar saw blade said second rotational distance about the fourth axis in a fourth onal direction that is opposite to the third rotational direction, such that the rotational axes of the first circular saw blade and the second circular saw blade intersect at a centre of curvature of the first n of the block.

7. The method ing to claim 6, wherein the second inclination angle is ined based at least in part on a distance in the cutting direction between the centre of one of the circular saw blades and a centre plane of the radius of curvature.

8. The method according to claim 7, wherein the second inclination angle is determined according to the ing algorithm: ε = arctan ((e/2)/R), wherein: e/2 = the distance in the cutting direction between the centre of said one of the circular saw blades and the centre plane of the radius of curvature.

9. The method according to any one of claims 1-8, wherein, when the cutting device is in the reference position, the first axis is substantially horizontal and the second axis is substantially vertical.

10. A computer program product comprising instructions to cause a er to perform the method according to any one of the claims 1-9 when the computer program is ed by a processor of the computer.

11. A calculation unit for use with a cutting device having at least a first circular saw blade to m curved sawing of a block in a cutting direction, wherein the cutting device has a reference on in which the first circular saw blade lies within a first plane that extends along the cutting direction, a onal axis of the first circular saw blade is normal to the first plane, a first axis that extends through the first circular saw blade is parallel to the cutting direction, and a second axis that extends through the first circular saw blade is perpendicular to the cutting direction, the first axis, and the rotational axis, which calculation unit comprises: a receiver configured to receive, from a measurement unit, a measurement signal relating to the curvature of the block in the cutting direction; a processor configured to determine a radius of curvature of a first portion of the block based at least on the received measurement signal and to determine a first inclination angle for the first circular saw blade about the first axis based at least on the determined radius of curvature; and a transmitter configured to send a control signal to a l unit to cause the control unit to rotate the first circular saw blade a first rotational distance about the first axis, in a first rotational direction, to the first inclination angle.

12. The calculation unit of claim 11, wherein the processor is configured to ate the first ation angle based at least in part on a height of the block, a er of the first circular saw blade, and/or a vertical distance between the centre of the first circular saw blade and a saw base on which the block is placed.

13. The calculation unit of claim 12, wherein the processor is configured to calculate the first inclination angle according to the following algorithm: β = arctan (Xaverage - Xtop)/((d/2) - u), wherein: Xaverage = t + Xend)/2; Xtop = s αtop)/cos αtop; Xend = R(1-cos αend)/cos αend; Xstart = R(1-cos αstart)/cos αstart; αtop = arctan (-e/2)/R; αend = arctan (d/2 sin γend - (e/2))/R; αstart = arctan (d/2 sin γstart - (e/2))/R; γstart = arccos (u/(d/2)); γend = -γstart; γtop = 0; R = the radius of curvature; e/2 = a distance in the direction of cutting between the centre of the ar saw blade and a centre plane of the radius of curvature; u = the vertical distance between the centre of the first circular saw blade and the saw base on which the block (100) is placed during the sawing; and d = diameter of the first circular saw blade.

14. The calculation unit according to claim 11, further including a memory in communication with the processor, wherein the memory includes a plurality of curve radii stored in association with a corresponding plurality of inclination angles, and wherein the processor is configured to ine the first inclination angle by identifying the first inclination angle from among the ity of inclination angles based on the determined radius of curvature.

15. The calculation unit according to any one of claims 11-14, wherein the cutting device further includes a second circular saw blade, and wherein when the cutting device is in the nce position the second circular saw blade lies within the first plane, a third axis that extends h the second circular saw blade is parallel to the cutting direction and the first axis, and a fourth axis that extends through the second ar saw blade is parallel to the second axis, wherein the curve sawing is performed by the first circular saw blade and the second circular saw blade, which are arranged to jointly create a single saw cut through the block, and wherein the transmitter is further ured to send a control signal to the control unit to cause the control unit to rotate the second circular saw blade said first rotational distance about the third axis, in a second rotational direction that is opposite to the first rotational direction, such that the first circular saw blade and the second circular saw blade are inclined in opposite directions relative to the first plane.

16. The calculation unit of claim 15, wherein the processor is further configured to determine a second inclination angle for the first circular saw blade about the second axis, relative to the first plane, based at least on the determined radius of curvature; and wherein the transmitter is r configured to send a control signal to the control unit to cause the control unit to rotate the first circular saw blade a second rotational ce about the second axis in a third rotational direction to the second inclination angle, and to rotate the second ar saw blade said second rotational distance about the fourth axis, in a fourth rotational direction that is opposite to the third rotational direction, such that the rotational axes of the first circular saw blade and the second circular saw blade intersect at a centre of curvature of the first portion of the block.

17. The calculation unit according to claim 16, wherein the processor is configured to determine the second inclination angle based at least in part on a distance in the cutting direction between the centre of one of the circular saw blades and a centre plane of the radius of curvature.

18. The calculation unit according to claim 17, wherein the processor is configured to determine the second inclination angle according to the following algorithm: ε = arctan ((e/2)/R), wherein: e/2 = the distance in the cutting ion between the centre of said one of the circular saw blades and the centre plane of the radius of curvature.

19. A system for inclining at least a first ar saw blade of a cutting device to perform curve sawing of a block in a cutting direction, wherein the cutting device has a reference on in which the first circular saw blade lies within a first plane that extends along the cutting direction, a rotational axis of the first circular saw blade is normal to the first plane, a first axis that extends through the first ar saw blade is parallel to the cutting ion, and a second axis that s through the first circular saw blade is perpendicular to the cutting direction, the first axis, and the rotational axis, the system comprising: a measurement unit configured to measure the curvature of the block in the cutting direction; a calculation unit according to any one of claims 11-18; and a control unit operatively coupled with the ation unit and the measurement unit, n the control unit is operable to incline at least the first circular saw blade about the first axis in response to one or more control signals from the calculation unit.

20. The system according to claim 19, wherein the calculation unit includes a computer and the measurement unit is configured to measure distances to a plurality of measurement points along the block by means of light or other electromagnetic radiation.

21. The system according to claim 20, wherein the measurement unit includes a 3D , a Time of Flight , a 3D scanner, a stereo camera, or a light-field camera. WO 20593