Boards and planks are sawed out of logs on sitigle-blade circular sawmills or band saws, such that a traveling table and the log attached to it are moved against the blade, and afler one saw-cul has been sawed, they are moved back lor the lollowing work phase and to saw the saw-cut. One saw-cut is sawed with one to-and-fi-o movement.

In sawing, the log has lo be turned to different positions, and depending on the thickness of the log and the width and thickness of the sawed lumber, the log has to be moved several limes back and forlh. For example, when sawing a log from which two planks and six thin boards can be obtained, the log or part of the log is hastened to move on the circular sawmill or band saw to and fro 23 times.

Moving the log to and fi-o is a slow and time-consuming job. The capacily of circular sawmills and band saws is small when used in this way, so that sawing is often unprofitable.

There are currently secondary circular saws or corresponding saws, which have been mounted onto circular sawmills or band saws, by which two or more saw-cuts can be sawed. The problem in sawing a log is, how to get the optimal benefit from all of the wood, because the top end of the log is thinner than the trunk end.

The object of the invention is to provide a log sawing method, whereby the disadvantages associated with current methods will be eliminated. Furthermore, the object of the invention is to provide a method whereby sawing is expedited and

whereby sawing can be made profitable by taking into account the difference in diameter between the top end and trunk end of the log. Additionally, the object of the invention is to provide a circular sawmill or band saw accessory, which is easy to use, simple in its structure and advantageous in use. Furthermore, the object of the invention is to provide an accessory, whereby the job of the operator of the circular sawmill or band saw will be made easier.

The object of the invention is accomplished with a method and an accessory, the characteristics of which are set forth in the claims.

In a method applied in accordance with the invention, a lifting device, on top of which is placed the top end of the log, is mounted onto the log's traveling table to adjust the elevation of the log. The top end of the log and its elevation in relation lo the blades can be adjusted with the lifting device. Thus, the log can be positioned such that the resulting unit of sawed lumber will be the broadesl, longesl, most uniform and square- edged unit possible. The lifting device is located at the front end or at the back end of the traveling table because of the device and its use. The log can be position either with the trunk end in the front, or with the top end in the front, depending on which end of the traveling table the lifting device has been mounted.

In a method applied in accordance with the invention, two or more cross-wise saw-cuts are simultaneously sawed by two or more secondary circular saws, which have been mounted perpendicularly in relation lo the primary blade, whereby one or more sawed lumber unit (s) is (are) obtained with one to-and-fro movement of the log.

Using the secondary blades, cross-wise saw-cuts are sawed in the same to-and-fro movement as the primary blade is sawing the primary saw-cut. Thus, the sawing is carried out quickly and simply. In the previously described method of sawing, using a normal single-bladed circular sawmill, 23 to-and-fro movements of the log were needed, however when using this method, only nine to-and-fro movements of the log are necessary. Thus, sawing this way becomes 2.56 limes faster.

In one advantageous application of the invention, the secondary circular saws are fixed to the front of the blade of the circular sawmill or band saw and the blades of the secondary circular saw saw the cross-wise saw-cuts bel'ore the sawed lumber unit is cut off of the log. It is also possible to fix the secondary circular saws to the back of the

blade. Such structures are simple. In bolh cases, the secondary circular saws are mounted such that the tip of the secondary circular saw blade extends to the saw-cut which is made by the primary saw blade.

In the following advantageous application of the invention, secondary circular saws are adjusted in relation to one another with an adjuster to regulate the width of the unit of sawed lumber. Thus, the width of the unit of sawed lumber can be regulated easily and simply in the most appropriate way for the purpose by taking the measurements of the log into account.

In the following application of the invention, the secondary circular saws are adjusted with a lifting mechanism along the vertical width of the log to control the vertical position of the unit of sawed lumber. Thus, the secondary circular saws can be moved to the desired level along the vertical width of the log, so that a sawed piece of wood can be cut in the desired width from the desired place on the log.

In the following application of the invention, indicating devices located on the secondary circular saws indicate the position of the blades of the secondary circular saws on the surface of the log. This kind of an indicating device can be an indicating device, known as such, for example, different indicating devices based on the use of lights, such as a laser light indicator. With indicating devices the secondary circular saws and log can be guided such that a unit of sawed lumber, cut in the desired width and from the desired place on the log, can be sawed with the secondary circular saws.

A circular sawmill or band saw accessory formed in accordance with the invention comprises a lifting device which is fixed to the log's traveling table and which is for adjusting the elevation of the top end of the log. The top end of the log can be adjusted to the desired elevation with the lifting device.

In a certain advantageous application of the invention, the accessory comprises an ajuster for adjusting the secondary circular saws in relation lo one another in order to regulate the width of the unit of sawed lumber. Additionally, the accessory comprises a lifting mechanism for regulating the secondary circular saws to control the vertical positioning on the log of the unit of sawed lumber.

The invention shall now be described in mure cietail with reference to the accompanying drawing, Figure 1 illustrates a certain application of a circular sawmill, as viewed from the side, in which a method applied in accordance with the invention is being used, and which includes an accessory formed in accordance with the invention, Figure 2 illustrates a circular sawmill formed in accordance with Figure 1, as viewed lìom above, Figure 3 illustrates a circular sawmill formed in accordance with Figure 1, as viewed from the end, Figure 4 illustrates a circular sawmill formed in accordance with Figure 1, as viewed Irom the end, to which is fixed a third secondary circular saw blade, and Figures 5 and 6 illustrate the position of a log on the traveling table and a log being sawed using a certain specialized sawing method applied in accordance with the invention.

The figures illustrate a single-blade circular sawmill which comprises a. frame 5, a blade 1, a blade gear 6, a moving traveling table 4, an ajustable control 2 and an impression roller 3 which are attached to and/or supported on the frame. The log to be sawed 1 is placed on the moving traveling table 4 during sawing and the log and the table are moved in relation to the circular saw blade and frame in a way known as such.

The control 2 is attached adjustably in a conventional way to the frame 5. The ajustable control 2 defines the thickness of the sawed lumber. The impression roller 3 is designed in a way known as such to press the log against the ajustable control 2.

When the log is sawed, it is between the ajustable control and the impression roller.

A circular sawmill formed according to the invention, additionally comprises two secondary circular saws 9,10, which are, in this application, located in front of the primary blade next to the control 2 and attached to the frame 5. Additionally, the device comprises a lifting plate 11, which functions as a lifting device, and which, in this application, is located in the front of the traveling table, a turning axle 12, which is attached to the lifting plate, and an arm 13, which is attached to the axle, and by which the lifting plate 11 is controlled. Additionally, the device comprises a self-closing camping device 14 which is attached to the axle, and which clamps the lifting plate in the position to which it has been adjusted. The lifting plate adjusts the position of elevation of the top end of the log to the desired height. lt is also possible to move the

lifting plate and the log during the sawing, whereby the mechanism can saw curved pieces from the log.

Figure 3 illustrates a transfer gear 15, by which the lower secondary circular saw 10 is moved into the sawing position. Additionally, the figure illustrates the gear 16 of the lower circular saw and the power transmission 17 from the gear to the blade of the circular saw. The upper circular saw 9 has a corresponding device, but they are not numbered. The blade gear is a conventional device, such as a hydraulic motor, electric motor, pneumatic motor, etc. Furthermore, this figure illustrates an ajuster 20, by which the distance between the upper and lower secondary circular blades is adjusted, hereby cletenrniring or deiWiing the sawed width. Secondary blades can be tumed into and out of the sawing position in a way appropriate for the purpose, for example, by mechanically lifting, pneumatically, hydraulically, or electrically.

The figure also illustrates a lifting mechanism 21, by which both secondary circular saws are simultaneously lifted. This mechanism controls the elevation of the sawed wood in respect to the log being sawed, and with it, curves can be sawed by moving the secondary circular saws during the sawing. The lifting mechanism can be, for example, servo cylinders, servo engines, mechanically operated lifts or other mechanism appropriate for the purpose.

The device additionally comprises indicating devices (not illustrated in the figures) which are laser lighls, or corresponding lighls, which indicate the positionings of the sawing blades on the surface of the log.

Secondary circular saws formed in accordance with Figure 4 have a third blade 28, whereby the sawed lumber can be more effectively sawed with the secondary circular saws.

When using a method carried out in accordance with the invention and a circular sawmill in accordance with the figures, the log 8 is placed on the moving traveling table 4 with the top end towards the blades, and the desired elevation of the top end of the log is adjusted according to Figures 5 and 6 using the lifting plate 11. The lifting plate and the parts attached to it also move with the traveling table when sawing is taking place. The spaces between the blades of the secondary circular saws 9,10, are adjusted as desired, as is their elevation from the level of the traveling table.

The secondary circular saws are mounted such that the tip of the blade of the secondary circular saws extends to the saw-cut being made by the primary saw blade. While the sawing is being done, the traveling table is moved with the log attached to it against the blades. In the way shown in Figures 5 and 6, saw-cuts 23 and 24 can first be sawed, and then saw-cuts 25,26,27, whereby two separate units of prepared sawed lumber are obtained. Figures 5 and 6 illustrate special sawing options, for example, when sawing with the log surface and a rotlen core should be leI't unsawed. The sapwood of a butt log is the best raw material and the core is bad, so a method and a device formed in accordance with the invention also enable this kind of option. Naturally, the ways lo saw are numerous and they can vary considerably in different cases.

Secondary circular saws, or circular saws can also be moved under the safety guard of the circular sawmilt centre ! if one chooses net to use the secondary circular saw.

The invention is not limited to the advantageous applications presented herein. Ils Iorrn can vary within the frames of the idea of the invention put forth in the claims.