EP1872918A1 - Sawing of wood boards with a circular saw - Google Patents

Abstract

The method involves providing a small axial thickness for saw teeth (3) at an edge of a circular saw blade (1) than an axial thickness of a radial region of the circular saw blade, where the radial region lies inside the saw teeth. The circular saw blade is operated as a wedge on a sawed wood during the sawing operation due to the thickness difference, where the wood is humidified during the sawing operation. The axial thickness of the saw blade is decreased continuously from the radial region to a radial inner edge of the saw teeth. An independent claim is also included for a saw unit for sawing a wood lamella.

Description

The present invention relates to a method and a saw unit for sawing slats of wood with a circular saw.

Circular saws are common means of sawing wood. In addition to the cutting to length and cutting of slabs into specific formats, it is also important to divide a log, beam or board into a plurality of thinner boards in the axial direction of the circular saw blade, which are referred to below as "slats".

When sawing lamellae, many different aspects are of importance in practice, u. a. Service life and stability of the tools, ie the circular saw blades, dimensional stability of the slats respect. The strength in the direction perpendicular to the cutting plane, ie the axial direction, material loss by the cutting width of the saw blades, throughput of u. U. equipped with several circular saw saw units etc.

Important fields of application for such lamellae are the manufacture of multilayer boards for the construction industry and floor coverings, the invention not being restricted to this area.

Incidentally, the term "lamella" here basically refers to the wood formats resulting from the sawing process according to the invention. These need not necessarily be particularly thin, although preferred thicknesses of the fins will be discussed below. The term initially serves only to distinguish the sawed wood from the unseeded wood. Starting material of the sawing process according to the invention may be boards, beams or whole logs or parent parts, with already pre-sawn boards or beams with a relatively large thickness are preferred.

The invention is based on the technical problem of providing a new method and a new sawing unit for sawing wood slats with a circular saw, which offer practical advantages over the prior art.

This problem is solved by a method for sawing lamellae made of wood with a circular saw having a circular saw blade, characterized in that the circular saw blade has a smaller axial strength of the saw teeth at its edge than the axial thickness of a radially located within the saw teeth portion of the saw blade and the saw blade acts as a wedge during sawing due to this difference in thickness on the sawn wood,
and a correspondingly equipped sawing unit.

Preferred embodiments are specified in the dependent claims and will be explained in addition to the basic ideas of the invention below. The description implicitly always refers to both the sawing process as well as the corresponding circular saw or saw unit, without explicitly distinguishing between the categories.

The basic idea of the invention is the use of a circular saw blade which exerts a wedge effect on the sawn wood and has a special shape for this purpose. Since the circular saw blade is rotationally symmetrical about the axis, this is the cross-sectional profile in the radial direction, in which therefore the axis is in the cutting plane, described. Here is in a region of the circular saw blade, which is "more central" than the saw teeth, a greater axial strength than the axial strength of the saw teeth before. The saw blade is therefore thicker in a central area than outside. This axially stronger region, when immersed in the slot cut by the saw teeth on the outer edge, exerts a force in the axial direction on the sawn wood and thus acts as a wedge.

In contrast, in the prior art circular saw blades are widespread, which have a constant thickness substantially over the largest part of the circular area and in which only the saw teeth are formed outside in the axial direction stronger than this circular area. So here the saw teeth cut a slot in the Wood that does not come into contact with the rest of the saw blade or at most inadvertently and negligibly. It should be just avoided in such circular saw blades that occurs between other areas of the saw blade than the actual saw teeth and the wood a significant friction. The saw teeth must also have a certain minimum axial strength, which leads to a corresponding loss of cut.

In contrast, should not form the "thickest point" of the cross-sectional profile of the saw blade in the invention, the axial strength of the saw teeth. However, even with a saw blade according to the invention, the saw teeth can be axially stronger than the part of the saw blade which adjoins directly inside. Incidentally, the saw blade but in any case further inside stronger than the saw teeth. The saw teeth themselves can be designed with a relatively low axial strength, which allows quite significant reductions in cutting losses. These low sawtooth strengths are not necessarily associated with stability problems due to the better stability of the further thickened saw blade. In the invention, the inner region of the saw blade is also assigned the function of providing the necessary stability of the overall saw blade. A contact between axially thicker areas further inside the saw blade and the already cut by the saw teeth wood is not considered a problem, but rather in the sense of the aforementioned wedge effect sought. This wedge effect then ensures that at least one of the wood sides separated by the cut is pushed away somewhat.

Preferably, a continuous, ie without step-like jumps, decrease in the thickness of the saw blade from the thicker region radially outward. As already mentioned, the saw teeth themselves can be somewhat stronger than the immediately adjacent saw blade area, so that here too a discontinuous and stepwise increase or decrease in the thickness is permitted. However, in this preferred embodiment, this refers only to the transition to the saw teeth themselves and, as it were, to the "shadow" of the saw teeth in the radial direction, that is to discontinuous jumps that do not exceed the thickness of the saw teeth in radial projection. Furthermore, of course, in the innermost region of the saw blade, in which there is no contact with the wood, thickness jumps may be necessary, for technical reasons, for example, to make the saw blade meaningful on the drive axle to mount. Furthermore, discontinuous recesses, which are not perceived by the sawed wood on its way inwardly along the saw blade as a discontinuous increase in strength, are also possible in this embodiment, although not particularly preferred.

Furthermore, it is preferred that the decrease in strength runs monotonically radially from the thicker region to the outside, that is, there is no longer an increase in strength. Preferably, it is even strictly monotone, so it is a continuous uninterrupted strength reduction in the direction radially outward. Of course, this again applies except for the transition to the saw teeth and not necessarily for the areas radially within the strongest area of the saw blade.

However, preferably the radial center of the saw blade is actually also the region of greatest axial strength which, as the embodiment shows, can also continue to the outside by a considerable proportion of the total radius.

With regard to the distribution of the axial thickness on the two sides of the saw blade, so to speak in the two axis-parallel directions, two cases are particularly preferred. In one case, this distribution is the same on both sides, ie the saw blade is (with respect to individual geometrical details of the saw teeth) mirror-symmetrical to a center plane perpendicular to the axis. Such a saw blade unfolds a symmetrical wedging action on both sides separated by the saw cut.

A second preferred variant provides for a "one-sided" increase in strength, that is, the wedge effect is present only on one side and the other side is preferably flat, so that not touched or insignificantly touched by the saw cut wood side. This results in an asymmetric wedge effect.

Preferably, the symmetrical saw blades are used when a central section produces two lamellae, which are bent away on both sides by the wedge effect. Here then can the necessary strength reasons for stability reasons and the tension created by the wedging action is distributed in the wood on both sides.

The asymmetrical "one-sided" variant is preferably used when two saw blades are provided on a common drive axle and lie outward with the side designed in each case as a wedge. Then a core area between the saw blades is left by the parallel and common cuts of the two saw blades, which could not evade in a wedge effect occurring here because of the pairing of the saw blades. The respective outer areas can be pushed away laterally.

In particular, it is preferred in the invention to provide at least one pair of saw blades and a subsequent symmetrical saw blade which divides the core area symmetrically into two lamellae, which is then connected downstream of the two coaxial saw blades, as it were quasi serially. Hereby, a total of four fins are then produced, the first two each outside the coaxial saw blades and the second two separated within the coaxial saw blades and by the symmetrical subsequent saw blade. In the same sense, more "serial stages" than one with two coaxial saw blades are possible, in which case two outer blades are separated per saw blade pair, which are separated from one of the two serially upstream saw blades left between these core area. Depending on whether an odd or even number of lamellae is to be generated in total, a symmetrical central saw blade ultimately or not follows.

Finally, two saw blades can be used for a single sipe cut, which are therefore in a common plane, so are coplanar. These saw blades overlap slightly in the transport direction of the wood, which is why one of them lies slightly in the transport direction in front of the other, so that there is no contact of the saw teeth. This ensures that the individual saw blade does not have to correspond to the entire depth of cut and thus only has to dive into the wood by more than half the depth of cut. The depth of cut is thus divided into two coplanar opposite saw blades, as the embodiment illustrated in more detail. This also applies in particular to individual "sawing stations" in a "serial connection" according to the above explanations.

In a further preferred embodiment, the saw blade or the saw blades, ie the circular saw or saw unit, a planer unit upstream. This plans plane at least one side surface which is perpendicular to the axial direction of the saw blades, and thus creates a defined plane for the Maßeinstellung the subsequent saw cuts.

A particular advantage and at the same time an important preferred feature of the invention is that undried wood or wood with a high residual moisture content can be cut or cut. In particular, essentially unsaved and undried fresh wood can be sawed into lamellae, which can be dried with much less time due to the much larger specific surface area. Furthermore, the use of fresh wood ensures that dimensional errors due to warping of the wood during a drying process prior to the sawing are avoided. The lower distortion also manifests itself in the fact that in the above-mentioned production of a flat reference surface by planing less waste occurs because the present (rough) sawing surface is less uneven. Finally, quality reductions caused by cracks are less of a problem because even smaller stresses build up during the drying of the already cut slats as a result of the significantly lower material thicknesses. The undried wood has in connection with the invention also has the advantage that it can push away a bit better by the mentioned wedge effect, because it reacts more elastic than already dried wood. The term "undried wood" is intended to refer in particular to wood having a residual moisture content of at least 15%, preferably at least 20% and particularly preferably at least 30%.

Further, the area of the plant between the sawed wood sides and the region of the saw blade, which exerts the mentioned wedge effect, preferably applied to a liquid lubricant and coolant. This can be initiated during the sawing process by a hose or the like. Or be sprayed. Preferably, this is a lubricant Water-based, which does not disturb the subsequent drying process, does not affect the sawn lamellae in their quality, low costs and causes no environmental problems. Has proven particularly useful here a solution of soaps, especially soft soap, in water.

The term lamellae has already been introduced as a general term for the products of the process according to the invention. Preferably, however, this refers to boards having a thickness of at most 15 mm, preferably at most 13 mm and particularly preferably at most 11 mm in the axial direction of the saw blade, which applies to hardwood and softwood. Softwood is of special interest.

The resulting lamellae can be used according to the invention for multi-layer building boards, such as so-called. Solid wood panels, which are glued together from a plurality of layers of corresponding fins, but also for core areas, the top or bottom of other multi-layer building boards or a floor covering, as a wear layer same. Especially with more expensive types of wood is the fact that according to the invention by the lower axial strengths of the saw teeth less saw cut and for the already described reasons also lower planing losses occur, of particular interest.

Figur 1

zeigt eine Schnittansicht längs des Radius durch zwei erfindungsgemäße Kreissägeblätter.

Figur 2

zeigt eine Figur 1 entsprechende Darstellung eines symmetrischen erfindungsgemäßen Kreissägeblattes.

Figur 3

zeigt eine schematische Darstellung zur Aufteilung eines Brettes in zwei Lamellen durch eine mit Sägeblättern gemäß Figur 1 ausgestattete Kreissäge.

Figur 4

zeigt eine perspektivische Ansicht einer erfindungsgemäßen Sägeeinheit mit Kreissägen, die Sägeblätter gemäß Figur 1 aufweisen.

In the following, the invention will be explained in more detail with reference to an embodiment, wherein the individual features may be essential to the invention in other combinations and, as already mentioned, implicitly refer to all categories of the invention.

FIG. 1

shows a sectional view along the radius through two circular saw blades according to the invention.

FIG. 2

shows a representation corresponding to Figure 1 of a symmetrical circular saw blade according to the invention.

FIG. 3

shows a schematic representation of the distribution of a board in two lamellae by a circular saw equipped with saw blades according to FIG.

FIG. 4

shows a perspective view of a saw unit according to the invention with circular saws having saw blades according to Figure 1.

FIG. 1 shows a sectional view through an asymmetrical circular saw blade according to the invention. The cut is such that the saw blade radius and the axis of rotation lie horizontally or vertically in the plane of the drawing. In this case, the left-hand illustration is the right half of a section through the radial center from a first saw blade and the right-hand representation is mirror image of it from the radial center of the left half of a section through a second saw blade. Both blades are summarily denoted by 1. The right edge of the left saw blade 1 is shown enlarged in the lower part of FIG. Further, Figure 3 shows a corresponding saw cut by a board 2, which produces two blades 2a and 2b.

The further explanations with reference to FIG. 4 will show that the section through the board 2 ultimately takes place with two opposing saw blades according to the representation in FIG. 1, these actually overlapping somewhat. Thus, FIG. 1 shows a sectional view which contains both saw blade axes, with the actual transport direction of the board being turned out of the vertical on the drawing plane about the vertical in the drawing plane until an actual overlap of the saw blade edges in the projection results.

The individual saw blades 1 have an outer row of teeth 3 with an axial thickness of 1.6 mm. Radially within this row of teeth 3, the axial thickness jumps back to 1 mm, wherein the far greater part of the recess, as the sectional view in Figure 1 shows lower left, on the upper side and the smaller part on the underside. Incidentally, the underside of the saw blade is completely flat, whereas the upper side remains straight and thus at the thickness of 1 mm only for a radial region between the outermost radius of 175 mm and an inner radius of 159 mm in the cross-sectional profile. At this radius of 159 mm, the thickness jumps to 1.2 mm thickness with a production-related small step of 0.2 mm and from there rises linearly, ie at a constant angle, to a final axial thickness of 5 mm, which is achieved at a radius of 90 mm. This results in a very acute angle of rise of about 3 °.

In principle, angles in the range of 1 to 5 °, preferably 2 to 5 ° and particularly preferably 2.5 to 4 ° are advantageous.

Overall, this shows a circular saw blade of radius 175 mm with a comparatively very small sawtooth thickness of 1.6 mm, but a core thickness of 5 mm. In comparison, typical dimensions of a conventional circular saw blade would be a sawtooth thickness of 2.9 mm or 2.5 mm with a homogeneous thickness of the remaining circular saw blade of about 1.8 mm.

FIG. 2 shows a representation corresponding to FIG. 1 of a symmetrical circular saw blade according to the invention. The dimensions are completely analogous with the only difference that the ramp-like rise in this case is distributed symmetrically on both sides of the saw blade, so in each case only half the angle occurs, so that the sum of the two angles is to be set for the mentioned preferred angle ranges here.

Figure 3 shows a section through a board of width 155 mm and any length (perpendicular to the plane) and a thickness of about 15 mm. As a result, a set of two lamellae 2a and 2b of the respective thickness of 6.7 mm (at a cutting width of 1.6 mm) was created by a cut with the two saw blades 1 according to the invention from FIG. 1 or FIG. Instead, with a conventional circular saw blade, the saw cut loss would be 2.5 or 2.9 mm, for example, depending on the lamella thickness, it would be considerably higher on the total wood thickness.

Preferred lamella geometries are in the range of 4 to 10, preferably 5 to 9 mm thick and about 100 to 200 mm wide, and such lamellae may be cut from boards of, for example, 50 mm thick or more. It is readily apparent that either by using thinner starting boards or by producing one or even more than one additional blade of the same starting power, direct economic benefits can be derived from the reduced saw blade losses. The saw blade according to the invention has an outstanding because of the substantially continuous increase in its thickness to 5 mm Stability and pressed by the axial wedge effect the resulting slats slightly apart.

FIG. 4 shows a perspective view of a complete saw unit according to the invention. The timber transport direction runs from right (behind) to left (front). Upstream in the transport direction, a planing unit, not shown, for planing a defined lower reference surface of the board 2, which then rests on the transport plane of the saw unit. In addition to this planing the top surface of the board is planed so far "clean" that it is glued and the total thickness of the board, taking into account the saw cuts losses the desired multiple of the desired lamella thickness. Again, due to the very low distortion of the fresh wood compared to the prior art significantly lower planing losses realized.

The saw unit in this example comprises six individual circular saws 4a to 4f, each with vertical drive axles. The drive axes of the circular saws 4b, 4d, 4f are denoted by 5b, 5d, 5f, the remaining drive axles are concealed by cover hoods, which are folded up in the circular saws 4b, 4d, 4f.

The axes are driven by electric motors 6, of which the motors 6b, 6d, 6f associated with the circular saws 4b, 4d, 4f are shown together with a respective drive toothed belt connected at the top.

The circular saws are each displaced transversely to the transport direction of the wood and adjustable. Corresponding guides are recognizable for the circular saws 4b, 4d, 4f and denoted by 7b, 7d, 7f. The corresponding actuators can be found below and are not specified.

In the figure, not shown in detail are cooling fluid lines, which direct an aqueous solution of greasy soap to the respective circular saw blades and run into the cutting area.

However, FIG. 4 shows, between the circular saws and in the direction of transport, the circular saws 4a and 4b respectively downstream of guides 8 which are in the transport direction Seen substantially represent a rotated by 90 ° and with the legs pointing inward U-profile and thus can prevent breaking away from the wedge effect pushed away slats up and down.

As already explained earlier, the asymmetrical saw blades 1 according to FIG. 1 are particularly suitable for circular saws 4, each with two coaxial saw blades. The oblique planes, which are directed upward in FIG. 1, lie respectively outside, ie at the upper saw blade at the top and at the lower saw blade at the bottom. All circular saws 4a to 4f in Figure 4 are constructed accordingly. It is therefore a total of twelve saw blades 1. Furthermore, the circular saws rotate within a pair (ie, 4a and 4b, 4c and 4d and 4e and 4f) respectively in opposite directions, with the inner areas against the transport direction of the wood, as already the arrows in Figure 1 indicate the axes. Circular saws 4 and saw blades 1 within each pair are, as also already explained, opposite and arranged slightly offset in the transport direction, so that there is an overlap. The two upper saw blades 1 of the circular saws 4e and 4f thus separate in a final common cut a blade from above, while the two lower saw blades cut off a blade down. The remaining core area between the respective saw blades is supplied to the next pair of circular saws 4c and 4d, which in turn, with a smaller axial distance of the saw blades, each separates a blade up and down. The remaining core is reduced by the saw pair 4a and 4b to a single blade remaining between the saw blades. In different embodiments, this remaining core could be separated by a last pair of saws, each with only one symmetrical saw blade according to Figure 2 in two blades, so that a total of a straight blade number is formed. The embodiment of Figure 4, however, generates an odd number, namely seven slats.

After passing through the last pair of circular saws 4a and 4b and the guides 8 behind them, the slats are gripped in total by a roller conveyor station and further transported from the saw unit to be stacked in a conventional manner.

Claims (18)

Method of sawing lamellas (2a, 2b) of wood (2) with a circular saw (4a-4f) comprising a circular saw blade (1)
characterized in that the circular saw blade (1) has a smaller axial strength of the saw teeth (3) at its edge than the axial thickness of a radially located within the saw teeth portion of the saw blade
and the saw blade (1) acts as a wedge during sawing as a result of this difference in thickness on the sawed wood (2). The method of claim 1, wherein the axial thickness of the saw blade (1) decreases continuously from the region towards the radially inner edge of the saw teeth (3). A method according to claim 1 or 2, wherein the axial thickness of the saw blade (1) decreases monotonically from the region towards the radially inner edge of the saw teeth (3). Method according to one of the preceding claims, in which the saw blade (1) has the greatest axial strength in its radial center. Method according to one of the preceding claims, in which the decrease in thickness is present axially on both sides, preferably symmetrically. Method according to one of the preceding claims, in which the circular saw (4a-4f) has two saw blades (1) designed according to claim 1 on a common drive axle (5a-5f). A method according to claim 6, wherein the saw blades (1) on the common drive axle (5a-5f) have an axial unilateral strength decrease on opposite sides. Method according to one of the preceding claims, wherein at least two in the transport direction of the wood (2) serially connected saw blades (1) are used. Method according to one of the preceding claims, in which two coplanar saw blades (1), seen in the direction of transport of the wood (2), are used. Method according to one of the preceding claims, wherein the wood (2) is planed before straightening the blades (2a, 2b) for straightening and thickness adjustment. Method according to one of the preceding claims, in which the wood (2) is undried during sawing of the lamellae (2a, 2b). Method according to one of the preceding claims, in which a coolant is supplied to the wood (2), which cools and lubricates the wood (2) during sawing of the lamellae. The method of claim 12, wherein the coolant contains water as the main component. The method of claim 13, wherein the coolant contains soap, preferably soft soap. Method according to one of the preceding claims, in which the sawn lamellae (2a, 2b) have a thickness of at most 15 mm in the axial direction of the saw blade (1). Method according to one of the preceding claims, wherein from the sawn lamellae (2a, 2b) multilayer construction boards, such as solid wood panels or floor tiles, are produced. Saw unit for sawing slats (2a, 2b) made of wood (2), which has a circular saw (4a-4f) with a circular saw blade (1),
characterized in that the circular saw blade (1) has a smaller axial strength of the saw teeth (3) at its edge than the axial thickness of a region of the saw blade (1) located radially inside the saw teeth (3),
so that the saw blade (1) can act as a wedge during sawing as a result of this difference in thickness on the sawed wood (2). Saw unit according to claim 17 adapted for a method according to one of claims 2 to 16.

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