EP0663272B1 - Method for subdividing logs in pieces that are machined on all sides - Google Patents

Abstract

The trunk cutting process involves cutting a conical tree trunk with axial grain (37) into wooden items machined on all sides. The wooden items run mainly with the grain and towards the border lines (34) of the tree trunk. The tree trunk is curved in a plane. The items (55, 56) are directed towards the border lines (34, 35) of max. convexity or concavity. The tree trunk may first be planed on two sides to a base plane and then shaped. This base plane may be parallel to the plane of the curvature.

Description

The invention relates to a method for breaking down a conically shaped tree trunk provided with axial fibers into all-round processed wood products, in which the wood products are produced on two opposite sides of the tree trunk essentially in the same direction as the fibers and in the same direction as generatrices on the sides of the tree trunk.

A method of the type mentioned above is known from DE-OS 42 09 407.

In a method known from DE-PS 31 14 843, the conically shaped tree trunk is placed on a conveyor running in a horizontal plane. The log is first flattened on both sides using chipper tools. In a subsequent step, corner milling cutters are used to attach longitudinal corners to the tree trunk. The height of the corner milling cutters can be adjusted and adjusted so that they run along the tree trunk in a direction parallel to the central longitudinal axis. The model created in this way is then dismantled by means of circular saws, by first making saw cuts along the inside of the corners in order to separate side boards from the main goods.

A disadvantage of this and other known profiling methods is that the model is generated along the central longitudinal axis of the tree trunk. Because of the taper of the tree trunk, it must therefore be chipped around its circumference, with increasing depth of engagement in the direction of the thicker trunk end. It is also known to first make axial saw cuts in the area of the tree circumference in the area of the thick trunk end in the case of very long and strongly conical tree trunks, so that not all of the wood to be removed is machined, but at least shorter boards are produced.

These known methods have the disadvantage in common that the remaining wood of the model lies in the center of the tree trunk. On the other hand, it is known that the wood in the center of a tree trunk is the poorest quality wood, while the higher quality wood is in the range located. When using the known methods, it is therefore sometimes necessary to cut out an area in the center of the model when it is being dismantled, which is only useful for uses with low quality requirements for the wood or is even disposed of in some other way.

The above-mentioned disadvantages become even more serious when tree trunks are broken down that are bent in addition to their taper. The bend or curvature usually runs in a preferred plane. With tree trunks of this type, it is known to saw off the tree trunk on one or both sides on one side, so that the tree trunk can then be processed in a sawmill system with a vertical plane of curvature. It takes advantage of the fact that a curved tree trunk can be dismantled at least in planes parallel to the plane of curvature with conventional, vertically running saws, ie it can be processed in conventional sawmill systems.

However, if this is done, the model lies in the tree trunk in such a way that the axially extending fibers run through the model in an arc. The surface of the model therefore cuts the curved fibers in large areas, so that wood products of reduced strength are created.

From the aforementioned DE-OS 42 09 407 a method for sawing long timber is known. In the known method, two band saws are used to disassemble the long wood, which are guided symmetrically to the center line of the long wood in the axial direction through the long wood. The special feature is that the band saws can be adjusted in a direction transverse to the center line by means of a computer-controlled device.

In this way, cuts can be made that are not parallel to the center line. With the known method it is e.g. possible to disassemble a cylindrical but crooked tree trunk so that the cutting line follows the curved center line of the tree trunk in its direction. The boards produced in this way are then also somewhat curved, but this curved shape can be straightened by simultaneous pressing during later drying. Furthermore, the known method can also be used with conically grown tree trunks. After that, several parallel boards should be sawn on two opposite sides of the tree trunk and in the center of the tree trunk, the boards on the surface lines of the tree trunk being inclined by half the cone angle to the boards that are sawn out of the center of the tree trunk. Between the boards sawn out in the center of the tree trunk and the boards sawn out at the surface lines, tapered, i.e. wedge-shaped woods left. According to the known method, with their inclined surfaces facing the surface lines, these are to be placed on top of one another in reverse and glued together, so that overall a straight wood product is produced.

The method known from DE-OS 42 09 407, however, has a major disadvantage insofar as the dismantling of conical tree trunks is addressed. Since boards are also sawn out of the center of the tree trunk using the known method, namely boards of the greatest width, the part of the tree trunk which has the poorest wood quality is used there. In contrast, the tapered sections, which are close to the surface lines of the tree trunk, are inevitably processed into thick wood products by gluing, although wood of higher quality is available there and one could also produce relatively thin wood products there.

Another method for cutting tree trunks is known from WO 92/22402. This known method addresses the problem of curved tree trunks. According to this known method, the curved tree trunks are to be dismantled by first flattening them laterally in planes parallel to the plane of curvature. In the transition area on both sides of the flattened corners are then to be milled in the axial direction in a manner known per se, in order to subsequently cut off side boards either parallel to the plane of curvature or perpendicularly thereto. The routing of the corner milling cutters must follow the natural curvature of the tree trunk. If the side boards are cut parallel to the plane of curvature, i.e. parallel to the flattened surfaces, a straight saw cut is required. If, on the other hand, the side boards are sawn off perpendicular to the plane of curvature, the saws used for this must also follow the natural curvature of the tree trunk and slightly curved boards are created which require post-treatment.

In contrast, the invention is based on the object of developing a method of the type mentioned at the outset such that wood products with the best wood quality are produced in the tree trunk, the fibers further being intended to run as parallel as possible to the longitudinal direction of the finished wood product.

This object is achieved in a method of the type mentioned above in that the wood products are produced at the thinner end of the tree trunk up to the center line of the tree trunk, in such a way that a wedge-shaped residue remains around the center line after the production of the wood products.

The object underlying the invention is completely achieved in this way.

The method on which the invention is based is basically detached from conventional dismantling methods, in particular profiling methods for tree trunks. With conventional methods, it was taken for granted that the model, i.e. the whole of the wood products to be produced is in one piece and lies in the center of the tree trunk. The method according to the invention is fundamentally detached from this idea because, according to the method according to the invention, all of the wood products produced are produced oriented to the surface lines of the tree trunk. In this way, as is known per se from DE-OS 42 09 407, the wood area of optimal quality on the tree trunk is used, namely the wood area on the circumference of the tree trunk. As a result of the fact that the wood products are produced at the thinner end of the tree trunk from the circumference of the tree trunk to the center line of the tree trunk, the residual wood resulting from the conicity of the tree trunk lies in the center of the tree trunk, i.e. precisely where the wood is of the lowest quality . The residual wood obtained in this way can then either be processed into wood products of inferior quality or machined or otherwise disposed of.

In a preferred embodiment of the method according to the invention, the tree trunk is curved in one plane, and the wood products are produced in the same direction as the surface lines of maximum convexity or concavity.

This measure has the advantage that even with curved tree trunks of the usual type, wood products with an essentially fiber-parallel structure are produced. Since the wood products are produced in the same direction as the surface lines of maximum curvature, and the curvature of such tree trunks is generally restricted to a single level, the tree trunks can also be largely processed in conventional plants.

For this purpose, according to a preferred development of the exemplary embodiment, the tree trunk is first flattened on two sides parallel to a reference plane and then profiled.

This measure has the advantage that known profiling methods can be used to maximize the wood yield.

It is further preferred in the invention if the reference plane is parallel to the plane of the curvature.

This measure also has the advantage that largely conventional systems can be used to dismantle the tree trunk.

In a further preferred development of the invention, before the wood products are produced, a side product is first produced when it is flattened, which lies in the same direction as the line of highest elevation above the flat side produced in the tree trunk when flattened.

This measure has the advantage that, for example, a board of the highest quality is produced as side goods, these boards lying at an acute angle to one another in the tree trunk due to the conicity of the tree trunk.

Fig. 1A - 1B

in Seitenansicht und in Draufsicht (nicht maßstäblich) einen konischen und gekrümmten Baumstamm sowie ein aus dem Baumstamm erzeugtes Model mit angedeuteter Zerlegung in Hauptware und Seitenware, jeweils nach dem Stand der Technik;

Fig. 2A - 2D

eine Darstellung, ähnlich Fig. 1A - 1B, zur Erläuterung von ersten Schritten eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens;

Fig. 3A - 3D

eine Darstellung, ähnlich Fig. 2A - 2D, jedoch für darauffolgende Schritte des Verfahrens;

Fig. 4A - 4D

eine weitere Darstellung, ähnlich Fig. 2A - 2D, jedoch für noch weitere Schritte des Verfahrens;

Fig. 5A - 5D

eine weitere Darstellung, ähnlich Fig. 2A - 2D, für weitere darauffolgende Schritte des Verfahrens.

An embodiment of the invention is shown in the drawing and is explained in more detail in the following description. Show it:

1A-1B

a side view and a top view (not to scale) of a conical and curved tree trunk and a model produced from the tree trunk with indicated dismantling into main goods and side goods, in each case according to the prior art;

2A-2D

a representation, similar to Figures 1A - 1B, to explain first steps of an embodiment of a method according to the invention;

3A-3D

a representation, similar to Figures 2A - 2D, but for subsequent steps of the method;

Figures 4A-4D

another representation, similar to Figures 2A - 2D, but for still further steps of the method;

5A-5D

another representation, similar to FIGS. 2A-2D, for further subsequent steps of the method.

In the prior art illustrated in FIGS. 1A and 1B, 10 denotes a tree trunk, the conicity and curvature of which are exaggerated for better illustration. The tree trunk 10 has a thin end 11 and a thick end 12. The intermediate surface 13 is conical.

The conicity of the tree trunk 10 can be seen in the top view according to FIG. 1B. 14 there is a convex surface line and 15 a concave surface line, the surface lines 14, 15 each representing the location of the maximum convexity or concavity. The center line 16 of the tree trunk 10 is also curved in the illustration in FIG. 1B.

With 17 fibers of the tree trunk 10 are designated. These fibers 17 run essentially in the same direction as the center line 16, but have a smaller radius of curvature in the region of the concave surface line 15 than in the region of the convex surface line 14. With d ₁ and d ₂ in FIG. 1B it is also indicated that the fiber spacings or fiber thicknesses increase from thin end 11 to thick end 12.

1A in FIG. 1A finally denotes that plane in which the tree trunk 10 is curved. Since the tree trunk 10 is only curved in this one plane 18, the center line 16 appears in FIG. 1A as a straight line.

In FIG. 1A, a model is also drawn or a dismantling instruction for the tree trunk 10. With 20, a so-called main item is designated, namely in the example shown two solid squared timbers, while 21 denotes the so-called side product, that is four side boards in the embodiment shown.

The remaining area 22, the thickness of which naturally increases towards the thick end 12 of the tree trunk 10, is machined in conventional methods or into so-called short goods, i.e. short boards processed.

Since, as described at the outset, in conventional methods the model consisting of main goods 20 and side goods 21 is placed in the center of the tree trunk 10, its position in the tree trunk results as shown in dash-dot lines in FIG. 1B. There it can be clearly seen that the outer contour of the main goods 20 shown in dash-dotted lines intersects the fibers 17 in large areas, so that in particular the corners of the main goods 20 are of little stability at the axial ends because both in the area of the end face and in the area the fibers 17 emerge from the flat side of the main goods 20 there.

1B clearly shows that the main goods 20 consist predominantly of wood in the center of the tree trunk 10, while the wood, which is more valuable per se, remains unused in the area of the outer surface 13 and is cut, for example.

In this regard, the method according to the invention is intended to remedy the situation.

2A-2D show first steps of the method according to the invention. In this way, a tree trunk 30 with a thin end 31 and a thick end 32 can again be seen, the outer surface of the tree trunk 30 again being designated by 33. A convex surface line 34 and a concave surface line 35 again characterize the areas of greatest convexity or concavity on both sides of the curved center line 36. The fibers 37 also run here in the same direction as the center line 36. The tree trunk 30 is also only curved in a single plane 38.

In this respect, the relationships are identical to those shown in FIGS. 1A and 1B.

According to the method according to the invention, boards 41 are first cut off, which lie above or below plane 38 and run parallel to surface lines of the surface 33. For this purpose, it is necessary to make an oblique saw cut, since the boards 41 are inclined to the center line 36 by half the cone angle of the tree trunk 30. In a first variant of the invention, the boards 41 can be sawed off directly from the tree trunk 30 by making a correspondingly oblique saw cut. Alternatively, one can first saw out a model 40a through two parallel saw cuts, as indicated in FIG. 2A with two flat sides 42. The flat sides 42 lie parallel to the plane of curvature 38. The separated sides of the tree trunk 30 can then be processed further in a separate sawing device in order to now saw off the boards 41.

As can be clearly seen from FIG. 2B, the boards 41 do not yet lie optimally with respect to the direction of the fibers 37. However, the boards 41 are made of high quality wood because they are cut out of the area of the lateral surface 33.

In the representation of FIGS. 3A-3D, the model 40b is not only flattened on two sides at 42, as already explained, but it can also be seen that a forest edge 43 is only present in the region of the concave surface line 35, because that on the opposite convex Surface line 34 located forest edge was already machined, as indicated by a second flat side 45. The second flat side 45 was produced by guiding a suitable cutting tool along a curved first surface 44 along the tree trunk 30.

With corner milling machines known per se, corners 50 are now aligned in the same direction as the surface lines 34 and 35 over the entire axial length of the model 40b.

4A-4D it can be seen that the model 40c is now disassembled in a first work step by first sawing off a first side board 55 along the second surface 51 on the convex surface line 34, and then one along a third surface 52 first main item 56 is separated from the model 40c. The saw cuts are not straight.

The curved surfaces 51 and 52 are at a constant distance from one another, as indicated by a constant thickness D for the first main article 56 in FIG. 4B.

It can also be seen from FIG. 4B that the fibers 37 run in the same direction as the first side board 55 or the first main article 56.

5A-5D, the remaining model 40d is further broken down by producing a second main article 60 and a second side board 61 along a fourth surface 58 and a fifth surface 59 in the area of the concave surface line 35 will. It is also the case here that the surfaces 58, 59 are at a constant distance from one another and run in the same direction as the concave surface line 35.

The side boards 55 and 61 and the main goods 56 and 60 preferably, but not necessarily, have the same cross-sectional shape, they only have a slightly different radius of curvature and a slightly different length.

These curved wooden products 55, 56, 60, 61 are then brought into a straight shape and dried or subsequently.

FIG. 5B also clearly shows that a wedge-shaped remnant 65 of the model 40d remains, which can be attributed to the conical shape of the tree trunk 30. The rest 65 lies in the tree trunk 30 around the center line 36, that is in the region of the lowest wood quality.

Overall, it can therefore be clearly seen that wood products 55, 56, 60, 61 are produced by the method according to the invention, which on the one hand are structured practically completely parallel to the fibers and on the other hand are removed from the edge region of the tree trunk 30, where the highest wood quality is present. The wood products produced according to the method according to the invention are therefore systematically of higher quality than wood products which were produced according to the prior art described at the outset in two respects.

Claims (5)

1. A method for dividing up a conically shaped log (10; 30) having axial fibers (17; 37) into wood products (20, 21; 55, 56, 60, 61) being machined on all sides thereof, the wood products (20, 21; 55, 56, 60, 61) being generated on two opposite sides of the log (10; 30) and essentially parallel to the fibers (17; 37) and parallel to surface lines on the conical sides of the log (10; 30), characterized in that at the thinner end of the log (30) the wood products (55, 56, 60, 61) are generated to the center line (36) of the log (30) such that a wedge-shaped residual piece (65) remains around the center line (36) after the generation of the wood products (55, 56, 60, 61) is completed.
2. The method of claim 1, characterized in that the log (30) is curved in a plane (38), and that the wood products (55, 56, 60, 61) are generated parallel to the surface lines of maximum convexity and concaveity, respectively.
3. The method of claim 1 or 2, characterized in that the log (30) is first flattened (42) on two sides parallel to a reference plane, and is then profiled.
4. The method of claim 2 or 3, characterized in that the reference plane extends parallel to the plane (38) of curvature.
5. The method of claim 3 or 4, characterized in that prior to the generation of the wood products ( 55, 56, 60, 61) a lateral piece (41) is generated during flattening, the lateral piece (41) extending parallel to the line of maximum elevation above the flat side of the log (30) generated during flattening.

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