The invention concerns a method as defined in the preamble to Claim 1.

In addition, the invention concerns plant as defined in the preamble to Claim 14.

In state-of-the-art sawing equipment, methods of many kinds have been used. In one state-of-the-art compact sawing equipment, working of the log is carried out as follows. In input equipment preceding the sawing equipment, the log is placed in such a way that the log's warpage is located in a vertical plane. The log is then guided into first working equipment, wherein first parallel planes are formed in the log's opposite round side surfaces. A second piece of working equipment then follows, wherein second parallel planes are formed in the log's remaining opposite round bottom and top surfaces. After the working equipment, the log is guided directly to a division stage, where the cant is divided into timber of the desired size by a circular saw equipped with circular saw blades located in a horizontal direction. Sawing equipment of this kind is very compact when all the pieces of equipment working on the log are located one after the other and the log is not turned over during the sawing. Instead, the low yield constitutes a problem espe- daily with logs having a long diameter. A relatively large part of the log's oppo¬ site round surfaces must be removed by the working equipment as chips, so that the shape of the log is directly suitable for sawing in the division stage.

On the other hand, the yield can be increased, if the first side boards are sawn out of the log immediately after the working equipment. Hereby the side boards are sawn by vertically located circular saw blades off the opposite side surfaces of the log. The side board thus sawn off need not hereby be transported through the sawing of the division stage, but in between the working equipment and the sawing of the division stage at least a clearance as long as the length of the longest log to be sawn must be arranged, wherein the first sawn-off side boards can be dropped away from the line and moved to the side. In addition, space is also required for the input equipment. This again increases considerably the total length of the sawing equipment.

The solution according to the invention constitutes an improvement on the state- of-the-art solutions.

In the solution according to the invention, the sawing equipment is very compact without any harmful effect on the yield.

The principal characteristic features of the method according to the invention emerge from the characterising part of Claim 1.

As to the principal characteristic features of the plant according to the invention, these emerge from the characterising part of Claim 14.

The plant for sawing a log comprises sawing equipment, wherein the log is fed forwards in the input direction. At the beginning of the sawing equipment, a first piece of working equipment is located, which is used to work first parallel planes into the log's opposite round surfaces. A second piece of working equipment is located after the first piece of working equipment in the input direction and it is used to work second parallel planes into the log's remaining opposite round surfaces, which second planes are at an angle of 90 degrees in relation to the first planes. By these two successive pieces of working equipment the log has been formed into a cant of a rectangular shape, where the corner surfaces are round. The second piece of working equipment is followed by a first circular saw, which is used to saw at least one side board couple out of the first or second parallel planes forming a couple. The first circular saw is followed by a second circular saw, which is used to carry out division sawing by sawing the remaining cant into timber of the desired kind. In addition, the plant comprises curved guiding elements, which are placed in between the first circular saw and the second circular saw and which are used to guide the side boards of said at least one side board couple obliquely to the side in relation to the log's input direction, so that the side boards on the first side of said at least one side board couple will move past one side of the second circular saw and the side boards on the other side of said at least one side board couple will move past the opposite side of the second circular saw.

By guiding to the side the side boards sawn off by the first circular saw it is possible to construct compact sawing equipment, where all pieces of equipment working on the log are located one after the other in the log's input direction and at a short distance from each other. The log is not either turned over during the working, but it is guided directly through the sawing equipment. Sawing equip¬ ment of this kind can be constructed to be considerably shorter than such state-of- the-art sawing equipment, wherein the side boards sawn off by the first circular saw are not guided to the side. Thus, with the solution according to the invention considerable saving of space is achieved as well as saving of costs in the construc¬ tion costs.

With the solution according to the invention compact sawing equipment can be constructed, where the yield is also good. In state-of-the-art compact sawing equipment, where the side boards are not released from the log sides before the sawing in the division stage, a larger part must be worked off the log sides as chips by the working equipment, whereby the yield of timber is reduced.

In an advantageous embodiment according to the invention, the log is fed into the sawing equipment in such a way that the log's warpage is located in a horizontal plane. In consequence of this, the division sawing can be carried out in a vertical direction by cutting circular saw blades, whereby the finished pile of timber is in a vertical plane. This again is an advantage in the further handling of the timber pile, where it is easier to separate the individual timber pieces from one another. When the pile of timber is in a vertical plane, the individual pieces of timber will not especially in winter conditions freeze and stick together in the same manner as takes place in a timber pile located in a horizontal plane.

When the timber pile is in a vertical plane, there is not either any need for releas¬ ing knives after the circular saw of the division stage. The timber pieces located in a vertical plane do not remain pressing on the blades in such a way that the blades would overheat. If the pile of timber is in a horizontal plane, then after the circular saw of the division stage releasing knives have to be used, with which the individ- ual pieces of timber are prevented from pressing on the blades of the circular saw.

In the following, the invention will be described by referring to the figures in the appended drawings, which show an advantageous plant embodying the method according to the invention, but the intention is not to limit the invention only to the details of this embodiment.

Figure 1 is a cross-sectional view of a log at various stages of sawing.

Figure 2 is a schematic view of sawing equipment implementing the method according to the invention and seen from one side.

Figure 3 is a view from above of the sawing equipment according to Figure 2.

Figure 4 is a view of how a log 10 is fed into the sawing equipment seen from above.

Figure 1 shows the shape of the wood 10 to be sawn at various stages of treatment A-G in the sawing equipment. In treatment stage A, the wood (log) 10 is placed in a position suitable for sawing and it is fed into the sawing equipment. In the following stage B, the opposite round side surfaces of the wood 10 are worked into parallel planes Ia, Ib. In the following stage C, the remaining opposite round side surfaces of the wood 10 are worked into parallel planes 2a, 2b. In the above- mentioned stages B and C, the log has been formed into a cant of a rectangular shape, which has round un-worked corner surfaces, hi stage D, first cuts 3 of an internal angle shape are worked into the wood's 10 remaining round corner surfaces and bordering on the first parallel planes Ia, Ib of the wood 10. In stage E, a first side board couple 5a, 5b is cut off the top and bottom surfaces of the wood 10. In stage F, second and third cuts 4 of an internal angle shape are worked into the wood's 10 remaining round corner surfaces and bordering on the wood's 10 parallel planes Ia, Ib and 2a, 2b. In stage G, the remaining cant is divided into timber of the desired size, for example, in such a way that from the cant's opposite side surfaces second and third side board couples 6a, 6b, 7a, 7b are cut off and the remaining heartwood is divided into planks 8a, 8b, 9a, 9b.

Figure 2 is a schematic view of sawing equipment according to the invention seen from one side. Figure 3 shows the sawing equipment according to Figure 2 seen from above. The input direction of the log is indicated by an arrow S in the fig¬ ures.

The sawing equipment 900 includes the following pieces of equipment for work- ing on the log 10. At the beginning of the sawing equipment there is a first piece of working equipment working in a horizontal plane, which is a chipping canter 20. The first chipping canter 20 is used to work into the log 10 the parallel planes Ia, Ib of stage B shown in Figure 1 into the log's 10 top and bottom surfaces. The first chipping canter 20 is followed by a second piece of working equipment working in a vertical plane, which is a chipping canter 30. The second chip 30 is used to work the parallel planes 2a, 2b of stage C shown in Figure 1 into the log's 10 side surfaces. Hereby the log 10 has been formed into a cant of a rectangular shape, which has round un-worked corners. The second chipping canter 30 is followed by a first profiling unit 40, which comprises small circular saw blades cutting in a vertical plane and after these milling cutters working in a horizontal plane. The first profiling unit is used to work the cuts 3 of stage D shown in Figure 1. The first profiling unit 40 is followed by a first circular saw 50 cutting in a horizontal plane, which is used to carry out the cutting off of the first side board couple 5a, 5b of stage E shown in Figure 1 from the log's 10 top and bottom surfaces. The first circular saw 50 is followed by successively located second 60 and third 70 profiling units, each of which comprises circular saw blades and milling cutters following after these and used for working the cuts 4 of stage F in Figure 1. The third profiling unit 70 is followed by a second circular saw 80 located in a vertical plane, which is used to carry out a division of the remaining part of the cant into timber 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b of the desired kind. The division is carried out in such a way that second and third side board couples 6a, 6b, 7a, 7b are sawn off the cant edges and the heartwood is divided, for example, into planks 8a, 8b, 9a, 9b. These pieces of equipment working on the log 10 are all conventional pieces of equipment, which are in general use in sawing equipment 900 and which are known to the professional in the art.

In addition to the above-mentioned equipment working on the log 10, the sawing equipment comprises conventional equipment needed for guiding the log 10 and for feeding it onwards, such as guides 100, 110, 120, 130 and input rolls 200, 210, 220, 230, 240 in a vertical direction as well as input rolls 300, 310, 320, 330, 340 in a horizontal direction. These pieces of equipment for guiding the log and for feeding it inwards are also conventional equipment in general use in sawing equipment 900 and known to the professional in the art.

The first circular saw 50 is used to saw off a first side board couple 5a, 5b from the cant. The first side board 5a of the first side board couple 5a, 5b sawn off the bottom surface Ia of the cant is then guided on a first curved guiding element 410 obliquely downwards on to a first guideway 420 and further in between the first guideway 420 and a first belt conveyor 430 located above the first guideway 420. The first belt conveyor 430 then feeds the first lower side board 5a of the first side board couple 5a, 5b along the first guideway 420 obliquely downwards, so that the first lower side board 5a of the first side board couple 5a, 5b moves past the second 60 and third 70 profiling units relating to the division stage as well as the second circular saw 80 below these. The first upper side board 5b of the first side board couple 5a, 5b sawn off the log's 10 top surface Ib is then guided by a second guiding element 510 obliquely upwards on to a second guideway 520 and further in between the second guideway 520 and a second belt conveyor 530 located above the second guideway 520. The second belt conveyor 530 then feeds the first upper side board 5b of the first side board couple 5 a, 5b along the second guideway 520 obliquely upwards so that the first upper side board 5b of the first side board couple 5a, 5b will move past the second 60 and third 70 profiling units relating to the division stage as well as the second circular saw 80 above these. The first lower 5a and upper 5b side boards of the first side board couple 5a, 5b are then guided forward on conveyors in the sawing line.

Figure 4 shows the log's 10 input to the sawing equipment seen from above. Thus, the log 10 is placed in such a way in the input equipment 910 preceding the sawing equipment 900 that the log's 10 curved direction is in a horizontal plane. Conventional input equipment may be used here, such as equipment measuring the log, or equipment rotating the log, etc. By its nature, the log tends to place itself so that its warpage is located in a horizontal plane. When the log is fed into the sawing equipment in such a way that its warpage is located in a horizontal plane, the sawing of the division stage taking place with the second circular saw can be carried out by circular saw blades placed in a vertical direction, which follow the log's curvature. In the sawing at the division stage a timber package hereby results, which is formed by separate adjacent timber pieces located in a vertical plane. After the circular saw blades of the division stage no separating knives will hereby be needed, because the timber pieces are not pressing on the blades.

The total length of the sawing equipment 900 shown in Figures 2 - 4 is approxi- mately 6,7 m. In the embodiment shown in the figures, the first circular saw 50 is used to saw one couple of side boards 5a, 5b off the log, but the first circular saw 50 could also be used to saw two or more side board couples. Hereby the side boards sawn off at each side of the log are guided as one package on the curved guiding elements 410, 510 below and correspondingly above the working equipment 60, 70, 80 relating to the division-sawing stage. Of course, the number of side boards to be released by the first circular saw also determines how many profiling units are needed before the first circular saw. The size of the log to be sawn determines to a far extent how many side boards are sawn off the log by the first circular saw.

In the embodiment shown in the figures, a first profiling unit 40 is used before the first circular saw 50. With this first profiling unit 40 the edges of the side board couple 5a, 5b sawn off by the first circular saw 50 are made straight. In a situation where the edges of the side board couple 5 a, 5b need not be straight, the first profiling unit 40 may be left out.

In the embodiment shown in the figures, the second circular saw 80 is used in the division stage to saw two couples of side boards 6a, 6b, 7a, 7b off the log. It would of course be possible here to saw only one couple of side boards, more than two couples of side boards or no couple of side boards off the log. Of course, the number of side boards to be sawn off by the second circular saw 80 also deter¬ mines how many profiling units are in use before the second circular saw 80. The size of the log to be sawn determines to a far extent how many side boards will be sawn off the log by the second circular saw in the division stage. In a situation where the edges of the side boards need not be straight, there is no need for profiling units before the second circular saw 80.

The division of the heartwood may of course be different from the situation shown in Figure 1, where the heartwood is divided by four circular saw blades. The equipment for working on the log shown in the figures may work with non- adjustable or adjustable settings. The equipment works with non-adjustable settings when adjusting of settings must be done manually during a machine standstill and it works with adjustable settings when adjusting of the settings can be performed automatically.

In the embodiment shown in the figures, the log is placed in such a way in the input equipment preceding the sawing equipment that the log's curved direction is located in a horizontal plane. The log may of course also be placed in such a way in the input equipment preceding the sawing equipment that the log's curved direction is located in a vertical plane. The first couple of side boards is hereby sawn off from the cant's side surfaces by vertically placed circular saw blades of the first circular saw, and sawing in the division stage is carried out by horizon¬ tally placed circular saw blades of the second circular saw, which follow the log's curvature. The sawing in the division stage hereby results in a timber package, which is formed by separate superimposed pieces of timber located in a horizontal plane. Hereby separating knives are needed after the circular saw blades of the division stage, so that the pieces of timber will not press excessively on the circu¬ lar saw blades. If the pieces of timber located in a horizontal plane remain press- ing freely on the blades, the blades will overheat, whereby their useful life will be shorter. Of course, the profiling units must hereby also be adapted in accordance with such a sawing situation.

The log may of course also be fed into the sawing equipment in such a way that the plane in which the log's curved direction is located will form an arbitrary angle with the vertical plane. Hereby the equipment working on the log is placed in a corresponding manner in a position determined by this angle in question.

In the following, claims are presented, which determine the inventive idea, within the scope of which details of the invention can vary from the foregoing presenta¬ tion, which was given by way of example only.