This invention relates to a saw mill for sawing logs, comprising a base on which there is arranged a stationary means for reception of a log, a saw device provided with an endless band saw blade, which device is carried by a means that is arranged on the base and is movable in relation to this one in a direction which is essentially parallel with the longitudinal direction of the imaginary log, the band saw blade having two essentially horisontal portions which during sawing have a motion direction that is essentially perpen¬ dicular to the intended motion direction of the means carrying the saw device.

Such devices are previously known. An essential problem when sawing logs, when the log is stationary and the saw moves, is to receive a fine and straight saw cut. According to known technique attempts have been made to solve this problem by carrying up the band saw by at least two girders or the like which are placed on each side of the log. This means that the frame of the band saw, the main part of which is placed above the log that shall be sawn, according to the known technique has frame parts, which extend down to the girders on each side of the log and move on these ones essentially in the longitudinal direction of the log. An essential drawback with this solution where frame parts of the band saw are positioned on each side of the log is that the accessibility is bad when handling logs and boards. This invention intends to solve this problem. This has been made possible by a device of the kind mentioned by way of introduction which is characterized by that the means carrying the band saw device comprises a sledge or the like, positioned in the saw mill on one side of the stationary means for reception of the log, and that the sledge is slidable on at least two elongated, essentially parallel prisms which

function as a control and dolly means for the sledge with the band saw device and which has a longitudinal direction that is essentially parallel with the longitudinal direction of the imaginary log. Due to that fact a very good accessibility is received when laying logs into the saw mill and when taking out sawn boards from the same. Moreover, the service and the repair of the band saw device like, for instance, band exchanges are facilitated. Furthermore, a very good control of the sledge with its band saw device is received, which gives an extremely fine and straight saw cut.

The remaining features of the device according to the invention will appear more closely in the following description of a preferred embodiment of the invention. In this connection is referred to the drawings, where Fig. 1 shows a plane view of the device according to the invention, Fig. 2 shows a view of the device seen in the direction of the arrows II-II, and Fig. 3 shows a view of the device, seen in the direction of the arrows III-III.

Referring to the drawing is shown there in Fig. 1 a view from above of the saw mill according to the invention. The saw mill comprises a saw device 1 which is applied onto a sledge 2, which is displaceable there and back on an elongated base 3. The sledge is driven by a gear motor via a chain. The base comprises two elongated girders 4,5, which are positioned essentially parallel with and at a distance from each other. At even spaces along these ones are arranged pairs of pillars 6,7 (see Fig. 3), the two pillars of each pair being positioned just opposite each other, which pillars are intended to carry prism-like means 8,9, i.e. elongated, cylindrical bodies, the basic surfaces of which are polygons. In this case the cross section of the prisms is essentially square. On these prisms 8,9 the sledge 2 with saw device 1 is intended to slide

there and back. As appears from Fig. 3 the outermost prism 8 is so arranged that one of its four plane side portions faces the bottom plate 10 of the sledge 2, whereas the inner prism 9 is so arranged that one of its corner portions, i.e. one of the pointed portions of the prism, faces the bottom plate 10. Furthermore, at the area of this prism 9 the bottom plate 10 at its underside is provided with two small plates 11,12, which are arranged in V-form with the V directed downwards and are intended to cooperate with the prism 9 standing on edge. By this arrangement a very effective, lateral control of the sledge is received. According to a preferred embodiment a plastic piece 15,16 or the like, preferably made of rubalone, is arranged between respective plate 11,12 and respective side portion 13,14 of the prism 9. The primary purpose of these plastic pieces 15,16 is to give the sledge a good slide and to bring away saw dust.

The outer prism 8 is intended to cooperate with the outer part 17 of the bottom plate 10 of the sledge 2. This part 17, as appears from Fig. 3, is folded around the prism and has a portion 18 extending in under the outer, lower edge portion 19 of the prism 8. At the inside of the bottom plate portion 18 is fastened an angle iron 20 which via a plastic piece 21, preferably made of rubalone, is intended to be in contact with the lower edge portion 19 of the prism 8. Also between the upper side portion 22 of the prism 8 and the bottom portion 10 of the sledge a plastic piece 23 is intended to be positioned. The plastic pieces 21,23 have the same function as the plastic pieces 15,16 and in similarity with these ones are preferably intended to be fastened in the bottom plate 10 or parts 11,12,17,18 belonging to it. Due to the arrangement with a folded portion 17,18 of the bottom plate 10 around the outer side portion of the prism 8, whereby a dolly means is created, the

sledge 2 and the saw device 1 become very stably and securely arranged on the prisms 8,9. This is of great importance, since the saw device is free-lying according this invention. As appears from all three figures an elongated, stationary saw table 1124 or the like is arranged on a side portion 25 of the base 3. This saw table has a longitudinal direction which is essentially parallel with the longitudinal direction of the girders 4,5, the saw table being close to the inner girder 5. On this saw table the log that shall be sawn is intended to be placed, the log being placed in the longitudinal direction of the table.

As appears from Fig. 1 the saw device 1 has an extension over the saw table, which is essentially perpendicular to the longitudinal direction of the saw table 24, the outer portion 26 of the saw device coming radially outside the saw table. The saw table 24 with the log put on it can be raised or lowered in order to come in right position in relation to the saw device being above the saw table. This is made possible by means of a hydraulic lifting device 27 as is indicated in Fig. 2.

In Fig. 3 the saw device 1 is shown more closely. This device comprises a band saw having two wheel-like means 28,29, which are connected by an endless band saw blade 30. The band saw blade is so arranged that it has two essentially horisontal portions, an upper band portion 31 and a lower band portion 32. Thus, when sawing it is the lower band portion 32 that goes into engagement with the log. The operation of the band saw is made by means of an electric motor 33 which transmits the force to the wheel means 28 via a chain 34 or the like. An essential part of this invention is that the saw head, i.e. the band saw itself with the frame portion is free-lying, i.e. the outer portion of the

saw head projecting out over the saw table 24 is hanging feely over the saw table. Due to that fact the accessibility for service of the band saw and for handling of logs and boards is improved. Moreover, due to that fact opportunities are created for tightening the band saw blade 30 effectively. According to the invention this is made by means of a hydraulic plunger 35 which is intended to act between the wheel means 28,29 and which has a pressing pressure up to 15 tons. This means that the band saw blade can be powerfully tightened in an effective way. This fact plus the fact as has been mentioned previously, namely the effective control of the sledge 2 and the effective suspension of the sledge and the saw device in the base, which suspension counteracts the forces from the free-lying saw head, has the consequence that the saw cut becomes extremely even and fine, which contributes to a good saw result.

In the frame portion of the band saw itself is made a recess 36 in the area above the lower band portion 32 and between the lower halves of the wheel means 28,29. This recess creates space for the log during the sawing procedure.

The device according to the invention is primarily intended to be used for sawing thick logs, logs having a diameter as large as 1,5 m can be sawn. Furthermore, the saw device is so designed that the different moments of the sawing procedure can be controlled by means of a computer. In this connection it is of importance that the computer operator can survey the different moments. This surveyance and control is facilitated by the fact that the saw head is free- lying.

The invention is, of course, not limited to the described embodiment but can be modified within the scope of the following claims.