A METHOD FOR DIVIDING A LOG AND A WOOD UNIT

Abstract: In a method for dividing a log two first cuts (4) are applied in the longitudinal direction of the log for removing surface-near material along two planes extending in the transversal direction of the log substantially in parallel with each other for forming first cut surfaces (4). Furthermore, at least one second cut (5, 6) is applied on the log in the longitudinal direction thereof between said planes and extending in the transversal direction of the log substantially in parallel with the planes. At least a third cut (17, 18) is applied substantially perpendicularly to said planes while intersecting the first cut surfaces (4) so that sub-surfaces (19, 20) thereof results on each side of the third cut, so that at least four first wood pieces (21) having one said sub-surface (19) each are formed.

Description: A method for dividing a log and a wood unit FIELD OF THE INVENTION AND PRIOR ART The present invention relates to a method for dividing a log. Such methods aim at obtaining a wood piece from a log which as such has good wood properties or may be assembled to wood units having such properties, and which by that stipulates a higher price. "Log" also comprises the case of a log already round-reduced before carrying out the method. Methods of this type are already known through many different patents, such as for example the Swedish patent 19 31 5, EP 0 286 701 and EP 0 518 246. However, these methods already known are associated with two substantial disadvantages. Firstly, a complicated and by that costly machine equipment is required for enabling division of the log into wood pieces, and secondly, not all wood pieces obtained in this way have that good wood properties that they may be used as high quality wood with an optimum strength and shape stability. Wood pieces having such properties aimed at may be called "industrial wood" and are primarily characterized by having at least several of the surfaces thereof provided with substantially standing annual rings. SUMMARY OF THE INVENTION The object of the present invention is to provide a method of the type defined in the introduction, in which the disadvantages just mentioned of such methods already known are reduced to a large extent. This object is according to the invention obtained in such a method by applying two first cuts on each side of the centre axis of the log in the longitudinal direction of the log for removing surface-near material along two planes extending substantially in parallel with each other in the transversal direction of the log for forming first cut surfaces, and a) at least one second cut is applied on the log in the longitudinal direction thereof between said planes and extending substantially in parallel with said planes in the transversal direction of the log and b) at least a third cut is applied substantially perpendicularly to said planes while intersecting the first cut surfaces so that sub-surfaces thereof result on each side of the third cut so that at least four first wood pieces having one said sub-surface each are formed, in which a) is carried out before b) or b) is carried out before a). This method may be carried out by means of a conventional simple saw mill equipment, and this means that a main part of the volume of the log may result in so called "cross-sawn industrial wood" by the fact that said third cut is applied substantially perpendicularly to the first and second cuts. Another important advantage of this method is that "cross-sawn industrial wood" is a defined article, which facilitates quality certification of the products produced by this wood article. According to a preferred embodiment of the invention two cuts are applied on each side of the centre axis of the log for forming a centre wood piece resulting from second cuts and restricted by these cuts. Such a wood piece will have substantially standing annual rings of at least the two surfaces resulting from said second cuts, i.e. is to be considered as industrial wood. Additionally, also the first wood pieces receive substantially standing annual rings for the surfaces resulting from the third cut, which is to be compared with a conventional dividing of a log, in which only the very centre deal receives surfaces having substantially standing annual rings. According to another preferred embodiment of the invention also a third second cut is applied along a plane including the centre axis of the log. This is advantageous in the case of larger log dimensions, since an adaptation of the wood output to the log dimension takes place in this way, and it is at large log dimensions well be possible to apply even more than three second cuts for obtaining a higher number of centre wood pieces. According to another preferred embodiment of the invention the centre wood piece or pieces resulting from the application of the second cuts are cut by applying cuts being substantially perpendicular to the second cuts on each side of the centre axis for removing surface-near material and obtaining at least one centre wood piece having a substantially rectangular cross- section. The centre wood piece or the centre wood pieces gets in this way a pleasant appearance. According to another preferred embodiment of the invention two cuts are applied on the centre wood piece substantially perpendicularly to said second cuts on each side of the centre axis and comparatively close thereto for removing the marrow streak of the log while obtaining part centre wood pieces located on each side thereof. Such part centre wood pieces form high quality cross-sawn industrial wood having substantially standing annual rings for at least three surfaces. According to another preferred embodiment of the invention in step b) two third cuts are applied on each side of the centre axis of the log for forming a second wood piece having a substan- tially rectangular cross-section with the sides of the cross- section rectangle formed by the two third cuts, a part of one first cut surface and a part of one second cut. Such a second wood piece is also to be considered as a high quality cross-sawn industrial wood having substantially standing annual rings for at least two sides thereof. Such second wood pieces will of course be obtained on each side of said second cuts, i.e. two for each log. However, at large log dimensions it is well possible to apply more than two third cuts, so that correspondingly more high quality second wood pieces are then obtained. According to another preferred embodiment of the invention said sub-surface and a surface of each said first wood piece emanating from a second cut are used as guide surfaces for material removing machining of the respective first wood piece. It will by this be very easy to machine the first wood piece further for refining it, so that for example this machining is carried out by removing material in the longitudinal direction of the log along a surface extending in the transversal direction substantially perpendicularly to said guide surfaces on the opposite side of the first wood piece with respect to the surface generated by the respective third cut, which constitutes a further preferred embodiment of the invention. Wood pieces having two surfaces suited for glueing to other corresponding such wood pieces for forming a wood unit according to the appended independent claim having a very high shape stability and substantially standing annual rings of all sides may by this be obtained. According to another preferred embodiment of the invention said first cuts are applied substantially in parallel with the extension of the fibres of the log in the longitudinal direction of the log, and according to another preferred embodiment of the invention said first cuts are applied substantially in parallel with the centre axis of the log. The corresponding possibilities are also offered for the other cuts. Thus, sawing or cutting in parallel with the fibres as well as in parallel with the heart may be utilised for the method according to the invention. Further advantages as well as advantageous features of the in- vention will appear from the following description and the other dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a description of methods according to preferred embodiments of the invention. In the drawings: Fig. 1 is a cross-section view of a part of a log , in which cuts intended to be applied on the log according to a division method according to a preferred embodiment of the invention are shown, Fig. 2 is a cross-section view of a wood unit produced from wood pieces obtained by the division method illustrated in Fig. 1 and machined further, and Fig 3 is a view corresponding to Fig. 1 illustrating a division method according to another preferred embodiment of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION How a method for dividing a log according to a preferred embodiment of the invention is composed will now be described with reference to Fig. 1 . First of all, in a first step surface-near material is removed according to two first cuts 2, 3 applied in the longitudinal direction of the log on each side of the centre axis of the log along two planes extending in the transversal direction of the log substantially in parallel with each other for forming first cut surfaces 4. After that two second cuts 5, 6 are applied on the log in the longitudinal direction thereof between the planes defined by said cut surfaces 4 and extending in the transversal direction of the log substantially in parallel with these planes, so that a centre wood piece 7 is obtained. A further cut 8 is then applied on this centre wood piece7 at the ends thereof for removing surface-near material and obtaining at least one centre wood piece having a substantially rectangular cross-section. However, it is also conceivable to apply the cuts 8 before the second cuts 5, 6 are applied. It is later on possible to apply cuts 9, 10 substantially perpendicularly to said second cuts 5, 6 on the centre wood piece on each side of the centre axis 1 1 and comparatively close thereto for removing the marrow streak 12 of the log while obtaining part centre wood pieces 13, 14 in the form of high quality "cross-sawn industrial wood" on each side thereof. Two third cuts 17, 18 are then applied on each of the two outer pieces 15, 16 obtained by applying the second cuts 5, 6 on each side of the centre axis of the log, i.e. when looking at the log not divided yet, substantially perpendicularly to the first cut surface 4 while intersecting them so that sub-surfaces 19, 20 result on each side of the respective third cut, so that four first wood pieces 21 having one said sub-surface 19 are formed in this way. Two second wood pieces 22 in the form of cross-sawn industrial wood having very good properties are in this way ob- tained, which have a substantially rectangular cross-section with the side of the cross-section rectangle formed by the two third cuts 17, 18, a part 20 of the first cut surface as well as a part of a second cut 5 and 6, respectively. The first wood pieces 21 may then be placed in for example a planning machine while utilising the sub-surface 19 and the part of the second cut 5 or 6 extending substantially in parallel therewith as guide surfaces when planning, in which material is removed in the longitudinal direction of the log along a surface extending in the transversal direction substantially perpendicu- larly to said guide surfaces on opposite side of the first wood piece with respect to the surface generated by the respective third cut 17, 18. It is then possible to carry out the machining so that groove or tongue is formed in the surface resulting from the machining. Four wood pieces 21 so machined may then be glued to each other by using said sub-surfaces 19 and the surface resulting from said machining as glue surfaces and while turning the right-angled corners resulting from the respective second and third cut as outer corners for a wood unit 23 having a longitudinal inner hollow space 24 according to Fig. 2. This wood unit has substantially standing annual rings at all surfaces, and the area inscribed by the outer outline thereof is considerably larger than the total cross-section area of the four wood pieces thereof, so that a considerable "wood gain" is made. It is also well possible to machine the circle arc surface of the respective wood piece 21 shown in Fig. 1 and 2 in an optional desired way before the gluing of the pieces together or for using the wood pieces so obtained in another way than by gluing them together with three other such ones, for example by flat planning this surface. It is illustrated in Fig. 3 what a method according to a second preferred embodiment of the invention may look like, in which this method only differs from that shown in Fig. 1 by the application of three second cuts, i.e. a second cut 25 extending sub- stantially through the centre axis of the log is also applied, and the marrow streak is in this case not removed, which however is well possible. This method is suited for larger log dimensions. It would also be possible to apply further second cuts when the dimensions are very large, and it would also be possible to ap- ply more than two third cuts in such cases. The invention is of course not in any way restricted to the preferred embodiments described above, but many possibilities to modifications thereof would be apparent to a man with ordinary skill in the art without departing from the basic idea of the in- vention as defined in the claims. Many such possible modifications have been suggested above, but the list thereof may of course be made considerably longer. It is pointed out that the material removal and the application of the different cuts preferably but not necessarily takes place by sawing. It is underlined that it is within the scope of the invention to ap- ply the different cuts at different points of time and even in different places. Said second cuts may for example be applied in a sawmill and then the first and third cuts be applied on said outer pieces after transport thereof to another sawmill.

Claims: Claims 1 . A method for dividing a log (1 ), characterized in that two first cuts (2, 3) are applied in the longitudinal direction of the log on each side of the centre axis (1 1 ) of the log for removing surface-near material along two planes extending substantially in parallel with each other in the transversal direction of the log for forming first cut surfaces (4), and that a) at least one second cut (5, 6) is applied on the log in the longitudinal direction thereof between said planes and extending substantially in parallel with said planes in the transversal direction of the log and b) at least a third cut (17, 18) is applied substantially perpendicularly to said planes while intersecting the first cut surfaces so that sub- surfaces (19, 20) thereof result on each side of the third cut so that at least four first wood pieces (21 ) having one said sub-surface (19) each are formed, in which a) is carried out before b) or b) is carried out before a). 2. A method according to claim 1 , characterized in that in a) two second cuts (5, 6) are applied on each side of the centre axis of the log for forming a centre wood piece (7) resulting from second cut surfaces and restricted by these cuts. 3. A method according to claim 2, characterized in that also a third second cut (25) is applied along a plane including the centre axis (1 1 ) of the log. 4. A method according to claim 2 or 3, characterized in that the centre wood piece or pieces resulting from the application of the second cuts (5, 6, 25) are cut by applying cuts (8) being substantially perpendicular to the second cuts on each side of the centre axis for removing surface-near ma- terial and obtaining at least one centre wood piece having a substantially rectangular cross-section. 5. A method according to any of claims 2-4, characterized in that two cuts (9, 10) are applied on the centre wood piece substantially perpendicularly to said second cuts (5, 6) on each side of the centre axis (1 1 ) and comparatively close thereto for removing the marrow streak (12) of the log while obtaining part centre wood pieces (13, 14) located on each side thereof. 6. A method according to any of claims 1 -5, characterized in that in step b) two third cuts (17, 18) are applied on each side of the centre axis of the log for forming a second wood piece (22) having a substantially rectangular cross-section with the sides of the cross-section rectangle formed by the two third cuts, a part (20) of one first cut surface and a part of one second cut (5, 6). 7. A method according to any of claims 1 -6, characterized in that said sub-surface (19) and a surface of each said first wood piece (21 ) emanating from a second cut (5, 6) are used as guide surfaces for material removing machining of the respective first wood piece. 8. A method according to claim 7, characterized in that said machining is carried out by removing material in the longitudinal direction of the log along a surface extending in the transversal direction substantially perpendicularly to said guide surfaces on the opposite side of the first wood piece with respect to the surface generated by the respective third cut (17, 18). 9. A method according to claim 7 or 8, characterized in that the machining is constituted by planing. 10. A method according to any of claims 1 -9, characterized in that said first cuts (2, 3) are applied substantially in parallel with the extension of the fibres of the log in the longitudinal direction of the log. 1 1 . A method according to any of claims 1 -4, characterized in that said first cuts (2, 3) are applied substantially in parallel with the centre axis of the log. 12. A method according to claim 2, characterized in that said second cuts are applied substantially in parallel with the extension of the fibres of the log in the longitudinal direction of the log. 13. A method according to claim 2, characterized in that said second cuts (5, 6) are applied substantially in parallel with the centre axis of the log. 14. A wood unit obtained by assembling four first wood pieces (21 ) obtained by carrying out the method according to claim 8 with each of the four corners of the wood unit formed by a right-angled corner of the respective first wood piece emanating from a second cut (5, 6) and a third cut (17, 18), said first wood pieces being glued to adjacent ones along said sub-surfaces and the surfaces resulting from said machining, so that the wood unit has a longitudinal inner hollow space (24).

Inventors: HAMMARSTROEM LARS, HAMMARSTROEM, LARS
Applicants: HAMMARSTROEM LARS, HAMMARSTROEM, LARS
Application year: 1999
Main classification: B27B1
IPC codes: B27B1, B27M3, E04C3