The present invention relates to a sawing de¬ vice as defined in the preamble of claim 1.

Traditionally, long timber is sawn to a fixed size by moving the timber against a stopper adjusted to a suitable position with respect to the saw blade used, so that when the timber is in position the saw blade cuts a piece of desired fixed length off the timber. The fixed-length piece is then removed and the timber to be sawn is further advanced longitudinally against the stopper. In this manner, sawing is contin¬ ued in stages by moving the timber and then sawing it . The main problem with present sawing equip¬ ment and methods used to cut timber to a fixed size is that they are slow, which is due to the intermittent nature of the sawing. As the cutting operation itself is a relatively fast action, most of the time is con¬ sumed while the saw blade is waiting for the timber to be moved into the sawing position against the stopper. The slowness of sawing is a particularly bad problem in industries where there is a need for large quanti¬ ties of relatively short fixed-length timber pieces, for example in furniture industry, prefabricated buil¬ ding industry and parquet industry. The object of the invention is to eliminate the drawbacks referred to above. A specific object of the invention is to produce a new type of sawing devi¬ ce that enables long timber to be accurately cut into fixed-length pieces in a continuous process as fast as possible.

As for the features characteristic of the sa¬ wing device of the invention, reference is made to the claims .

The sawing device of the invention comprises a conveyor for conveying the timber to be sawn and blades for cutting the timber at desired points, said

blades being rotated by a first power unit and dis¬ posed in a transverse position relative to the lengthways direction of the timber to be sawn. Accor¬ ding to the invention, the sawing device comprises a rotatable frame rotated by a second power unit and supporting the blades, of which there are preferably at least two. Moreover, the sawing device comprises a third power unit and, in the rotatable frame, guide rails along which the blades can be moved back and forth by means of the third power unit in the directi¬ on of the axles of the blades, i.e. in the longitudi¬ nal direction of the timber to be sawn.

Thus, as the axes of rotation of the blades and the axis of rotation of the rotatable frame are parallel to each other and parallel to the direction of motion of the timber to be sawn, it is possible, by rotating the blades and the rotatable frame supporting them, to cut the timber to a fixed size while the tim¬ ber is in continuous and steady motion, by only moving the blades back and forth in the direction of their axles at the velocity of motion of the timber.

The rotatable frame preferably comprises bla¬ de axles disposed at the same distance from the axle of the rotatable frame and parallel to it. The blades are preferably supported by sepa¬ rate blade holders movable along guide bars parallel to the axles of the blades.

The back-and-forth movement of the blades in the direction of their axles is preferably implemented using a motion chain, which is connected to the blade holders and can be moved back and forth.

In a preferred embodiment, none of the power units is mounted on the rotatable frame, but the first, second and third power units are mounted outsi- de the rotatable frame and coupled via concentric ax¬ les to the rotatable frame.

The third power unit, which moves the blades back and forth in the direction of the axles, is pre¬ ferably arranged to work in synchronism with the con¬ veyor that moves the timber to be sawn, in such manner that the velocity of motion of the sawing blade in the direction of its axle is always the same as the velo¬ city of the timber moving on the conveyor.

The sawing device of the invention preferably has two sawing blades mounted in the rotatable frame, but the number of blades can also be considerably lar¬ ger, in which a lower speed of rotation of the rota¬ table frame will result in the same sawing efficiency.

The sawing device of the invention has signi¬ ficant advantages as compared with prior art. The pro- duction of a large number of fixed-size pieces of wood is not an intermittent but a continuous and smooth process in which the timber to be processed is moving at a constant speed throughout the sawing process . Thus, for example, from a normal board the sawing de- vice can cut three fixed-size pieces of 60 cm per se¬ cond, and even more.

In the following, the invention will be de¬ scribed in detail by referring to the attached draw¬ ing, which presents an axonometric diagram of a sawing device according to the invention.

The sawing device of the invention presented in the drawing comprises a suitable conveyor 1 to¬ gether with its power units 18 for moving an object to be sawn 19 in its lengthways direction. The sawing de- vice comprises a rotatable frame 6, which is supported by its axle 12, which in turn is supported on the frame 20 of the sawing device. Supported on the frame 20, a second power unit 5 is arranged to rotate the rotatable frame 6 about its axle 12. Mounted between the two end pieces of the ro¬ tatable frame 6 and parallel to the axle 12 are a first pair of guide bars 8 and a second pair of guide

bars 9 as well as a first blade axle 10 and a second blade axle 11. Supported on the first guide bars 8 and the first blade axle 10 is a first blade holder 13, which carries a first blade 3. In the same way, a sec- ond blade holder 14 carrying a second blade 4 is sup¬ ported on the second blade axle 11 and the second guide bars 9. The blade axles 10 and 11 are coupled via power transmission belts 21 to an axle 16 concen¬ tric with the axle 12 of the rotatable frame 6 and mounted inside it and coupled to a first power unit 2, which is mounted on the frame 20, to rotate the blades 3 and 4.

The blade holders 13 and 14 supported on the guide bars 8 and 9 are attached to a motion chain 15, which moves back and forth on chain wheels 15. The chain wheels are rotated back and forth by means of a third power unit 7, which is coupled to the chain wheels via an axle 17 concentric with the axle of the rotatable frame and mounted inside it . The sawing device presented in the drawings works as follows. The first power unit 2 rotates the saw blades 3 and 4 while the second power unit 5 ro¬ tates the rotatable frame 6 at a suitable speed. The third power unit 7 moves the blade holders 13 and 14 and the sawing blades 3 and 4 rotating with these back and forth in the direction of motion of the object to be sawn so that when one of the blade holders is mov¬ ing forward, the other one is moving backward. Thus, when the device is in operation, as the conveyor 1 is moving the object at the same speed as the third power unit 7 is moving the blades in the longitudinal direc¬ tion of the object, when the sawing blade engages the object, it will be moving at the speed of the object, cut it through and leave the object area before stop- ping and returning to the first end of the rotatable frame.

Thus, in the sawing device the sawing blade touches the moving object to be sawn while itself mov¬ ing at the speed of the object in the same direction and, after cutting the object, moves aside and returns back to the starting position of a new sawing opera¬ tion. At the same time, the other saw blade performs corresponding sawing and returning actions on the op¬ posite side of the common rotation axis of the saw blades. The synchronisation of the motors in the saw¬ ing device and of their movements can be implemented using electronic or mechanical means known in them¬ selves. The blades 3 and 4 are preferably rotated con¬ tinuously by means of the first power unit 2, but the rotation of the rotatable frame 6 by the second power unit 5 and the back-and-forth motion of the blades produced by the third power unit 7 may be either con¬ tinuous or intermittent according to need, depending e.g. on the quality of the object to be sawn, on the blades being used, the length of the pieces to be cut, and so on.

The invention has been described above as an example by the aid of the attached drawing, but dif¬ ferent embodiments of the invention are possible within the framework of the inventive idea defined by the claims.