The invention relates to the cutter guide of a sawing machine, especially a bandsaw, as defined in the preamble of claim 1.

The cutter guide of a sawing machine is used to control the cutter such that the timber passing through the sawing machine will be cut by the cutter exactly at the desired point. A bandsaw is a sawing machine that comprises an endless cutter passing over saw discs and controlled by means of a cutter guide disposed above and underneath the cutting point.

The task of the cutter guide of a sawing machine, especially of a bandsaw, is to steer the cutter and to maintain it in the correct sawing position. To achieve this, the tool bits of the cutter guide require service, such as cleaning and lubrication. The tool bits are lubricated by spraying a mixture of water and emulsifier, especially oil, such as rapeseed oil, through a nozzle. One to two nozzles are provided for each tool bit and in addition, one to two nozzles are provided on the outer surfaces of the endless cutter for cooling of the cutter.

In current cutter guides the lubrication arrangement involves a problem. The lubricant tank is usually located far from the sawing machine, often requiring a piping tens of metres long. A lubricant containing water and the emulsifier above tends to become rancid, i.e. to grow bacteries which precipitate the lubricant. Precipitated lubricant interferes with the lubricant supply. Usually each nozzle is equipped with a screen to prevent the lubricant from proceeding, because solid matter will readily clog the small nozzle outlet, thus preventing the lubricant from reaching the object. Clogging is particularly frequent after shutdowns of the sawing machine. Under these circumstances, pipes, nozzles and particularly screens require relatively frequent cleaning; otherwise there is a risk of a costly shutdown of the sawing machine during its operation.

A further problem of current cutter guides is that they accumulate sawdust. Sawdust accumulates especially on top of the cutter guide, thus preventing the lubricant jet from the nozzle from reaching the cutter and the cutter guide. Short of lubricant, both the cutter and the cutter guide will be heated and wear rapidly in use, also requiring frequent service and replacements.

The purpose of the present invention is to provide a new cutter guide allowing the drawbacks above to be substantially eliminated. The invention is characterised by the features set out in the characterising clause of the independent claim.

The cutter guide of a sawing machine, especially a bandsaw, in accordance with the invention includes a tool bit, with associated fasteners and positioning means. In accordance with the invention, the tool bits contain a duct system, through which lubricant is supplied to the moving cutter.

In the preferred embodiment of the invention, the duct system includes a connecting duct and a set of nozzle ducts disposed to open to the guide surface of the cutter.

The invention has the advantage of reducing service required for the cutter guide. This cutter guide no longer requires the use of actual nozzles, and hence not of screens with a clogging tendency. The amount of actual lubricant used with water may be reduced; water as such will be sufficient lubricant during the sawing operation. A particularly advantageous feature is that a thin layer of lubricant, especially water, will form during sawing between the moving cutter and the cutter guide, particularly its guide surface, and this thin layer will remain on the cutter even when it rotates over the saw discs until the following sawing cycle.

The invention has the further advantage of efficiently preventing sawdust from accumulating on the cutter guide, owing to the fact that the nozzle ducts open to the guide surface of the cutter guide. The reason why sawings accumulate is that they absorb lubricant and subsequently adhere to the cutter guide and to other sawing machine components in the vicinity of the cutter and the cutter guide.

A still further advantage of the invention is that the cutter and the cutter guide are easy to clean by introducing water under high pressure into the duct system of the tool bit and further to the moving cutter.

The invention also has the advantage of improving the sawing result of frozen timber with the use of the cutter guides in accordance with the invention. The amount of water supplied through the duct system of the tool bit is adjustable, allowing sawdust to be more efficiently removed from the saw notch. This results in a good saw cut and a product of better quality than those obtained with sawing machines provided with conventional cutter guides.

Still one advantage of the invention is that the actual feeding of lubricant and/or emulsifier can be performed locally. This implies that a separate lubricant supply, such as an emulsion cartridge or the like, can be provided for each cutter guide in accordance with the invention, from where lubricant is periodically supplied to the cutter guide and the saw cutter whenever necessary. It should be noted that, in this way, the lubricant will admix with water only in the cutter guide or in the immediate vicinity of this. This arrangement completely avoids the previously frequent serious inconvenience of bactery deposits in the mixture of water and emulsifier.

The invention has the further advantage of the tool bit not being subjected to strong wear to the same extent as the tool bits in conventional cutter guides. This is primarily due to the fact that a thin film of water and/or lubricant, which provides efficient protection against wear for the tool bit, is formed between the tool bit and the moving cutter.

The invention also has the advantage of the effective lubricant supply subjecting the cutter to intense cooling, so that the temperature of the cutter does not rise much. The result of this is that pitch from the timber does not stick to the cutter in the same amount as with conventional cutter guides.

The invention and its other advantages are described in greater detail below with reference to the accompanying drawings, in which

figure 1 illustrates a bandsaw viewed in the direction of movement of the log;

figure 2 illustrates the bandsaw of figure 1 laterally viewed;

figure 3 is a cross-section of the cutter guide in accordance with the invention;

figure 4 illustrates the cutter guide of figure 3 viewed from above;

figure 5 is a longitudinal section A-A (figure 3) of a tool bit of a cutter guide in accordance witii the invention;

figures 6a to 6e are various possible cross-sectional views B-B (figure 4) of the tool bit of the cutter guide in accordance with the invention; and

figure 7 is a front view of the tool bit of a cutter guide in accordance with the invention.

Bandsaw 1 is schematically shown in figures 1 and 2. Bandsaw 1 includes two saw discs 2, 3, about which cutter 4, i.e. an endless cutter belt, is arranged to rotate. Saw discs 2, 3 are rotatably fixed to frame 5. Driving equipment 6a is provided in connection with the lower saw disc 3. Clamping equipment 6b for cutter 4 is arranged in connection with the upper saw disc 2. Log T or a similar piece of timber to be sawn is brought in an appropriate position perpendicularly to cutter 4 moved by means of saw discs 2, 3, and an appropriate longitudinal piece is sawn from log T by means of the cutter. Above and under the cutting point, near the upper saw disc 2 and the lower saw disc 3, respectively, cutter guides 7, 8, i.e. upper cutter guide 7 and lower cutter guide 8, are disposed. With the aid of cutter guides 7, 8, cutter 4 is fitted to pass exactly along the desired sawing line at the sawing point, in the correct position.

Cutter guides 7, 8 are identical in principle. Such a cutter guide 7, 8 is illustrated in figures 3 and 4. Cutter guide 7, ^includes a tool bit 9, its fasteners 10 and positioning means 11. Fasteners 10 include a support 12 and fastening means 10a, 10b, 10c, lOd. Positioning means 1 1, including adjusting nuts 1 la, 1 lc, are used to position tool bit 9 such that the guide surface 14 of the tool bit adopts an adequate position to steer the cutter 4 passing in front of it. Adjustment nuts 1 la, 1 lc are connected to two pin-like guide and stopper means 10a, 10b of fasteners 10. The first fastening means 10c of fastener 10, such as screws, are used to lock tool bit 9 in position on support 12. The second fastening means lOd, such as a nut, is used to attach support 12 and tool bit 9 removably to frame 5 of bandsaw 1.

Tool bit 9 is provided with a duct system 15, through which lubricant is supplied on the moving cutter 4. The duct system 15 includes a connecting duct 16 and a set of nozzle ducts 17, disposed to open to the guide surface 14 of tool bit 9, as shown for instance in figure 5.

Connecting duct 16 in duct system 15 is most preferably a cylindrical bore, disposed to extend from the lateral suface 18 of the tool bit 9 inside the tool bit. Nozzle ducts 17, in turn, extend from the guide surface 14 of the tool bit 9 inside the tool bit, joining connecting duct 16. The cross area of connecting duct 16 is larger than the cross area of each individual nozzle duct 17 in order to ensure efficient lubricant supply from connecting duct 16 to nozzle ducts 17.

Connecting duct 16 of duct system 15 is preferably substantially parallel with the guide surface 14 of tool bit 9, in a plane perpendicular to the direction of movement C of cutter 4. Nozzle ducts 17 connect connecting duct 16 through outlets 19 with the guide surface 14 of tool bit 9. Outlets 19 of nozzle ducts 17 are placed at regular intervals a on guide surface 14 of tool bit 9 over the entire width t of the cutter. They are preferably in a plane substantially perpendicular to the direction of movement C of cutter 4, as shown in figures 5 and 7 for instance.

In a preferred embodiment of the invention, a groove 20 is provided on guide surface 14 of tool bit 9, as illustrated in figures 6b-6e. Outlets 19 of nozzle ducts 17 open up in this groove 20. Groove 20 is most preferably perpendicular to the direction of movement C of cutter 4. The length p of groove 20 equals at least nearly the width t of cutter 4.

The first end 20a of groove 20 is preferably disposed near the toothed edge 4a of cutter 4; in this way, lubrication and cooling will be directed to the critical zone of cutter 4. Most often, toothed edge 4a extends 2 to 3 mm outwards from edge 9a of tool bit 9, in the lateral direction of this. The first end 20a of groove 20 extends to the vicinity of this edge 9a of the tool bit. Most preferably, the length p of groove 20 and the position of its second end 20b are adapted to the width t of cutter 4 such that the back 4b of cutter 4 barely covers the second end 20b of groove 20, and the straight line assumingly connecting the bottoms of the grooves between the teeth in the toothed edge 4a of cutter 4 and the second end 20b of the groove most preferably face each other. In this case, the length p of groove 20 equals the width t of cutter 4, subtracted by some millimetres, e.g. 5 mm.

The pressure of the lubricant discharged from nozzle ducts 17 through groove 20 against cutter 4 will remain essentially constant with the arrangements above, and no lubricant will be lost by discharge from the ends 20a, 20b of groove 20 past cutter 4. This arrangement also has the advantage that, should any of nozzle ducts 17 clog, lubricant will still spread from the remaining nozzle ducts 17 through groove 20 advantageously over the entire width t of cutter 4.

In one preferred embodiment of the invention, groove 20 of the guide surface 14 of tool bit 9 is bevelled 21, as illustrated in figures 6c, 6d and 6e. This bevelling 21 is disposed at the output edge of groove 20 with regard to the movement of direction C of cutter 4. Bevelling 21 has the advantage that no impurities, such as sawdust, will

gather in groove 20 during the sawing operation, but will be rinsed away along with the lubricant.

In a preferred embodiment example of the invention, illustrated e.g. in figures 6c and 6e, nozzle ducts 17 of duct system 15 are disposed to form a small sharp angle α downwards from connecting duct 16 towards the guide surface 14 of the tool bit. With this proceeding, the lubricant fed through duct system 15 will adopt the direction of movement C of cutter 4, and no impurities or other foreign substances will penetrate in the ducts, should the lubricant supply be interrupted for some reason.

Lubricant feed duct 22 is arranged to be connected with an appropriate connecting pipe 27 to connecting pipe 16 in duct system 15 projecting from tool bit 9, such as lateral surface 18 of the tool bit. This duct 22 is further most preferably connected to a water source, such as a water distribution system or a water tank 23, as illustrated schematically in figure 4. Feed duct 23 preferably comprises a lateral branch 24, which is most preferably located near tool bit 9. Optionally lateral branch 24 is connected directly to connecting duct 16 of tool bit 9. Lateral branch 24 of the feed duct is connected to a lubricant supply source, such as lubricant container 25 or a lubricant network (which several sawing machines may use in common). Lubricant container 25 is most preferably a replaceable, relatively small-sized lubricant cartridge. Lateral branch 24 is also provided with a controllable valve 26. As before, oil, such as vegetal rapeseed oil, is used as a lubricant.

The use of the cutter guide in accordance with the invention involves the following advantages, among others. When the cutter 4 of the bandsaw has been fitted into position around saw discs 2, 3 and clamped with the adequate tension force by means of driving and clamping equipment 6, bandsaw 1 is ready for operation. Water supply is then started from tank 23 through feed duct 22 to duct system 15 of tool bit 9, from where it is discharged through nozzle ducts 17 and groove 20, if provided, inbetween tool-bit 4 and guide surface 14. The pressure prevailing between tool bit 4 and guide surface 14 of the guide piece remains essentially constant during operation, and in this manner a thin water film forms between guide surface 14 and cutter 4, the water film keeping cutter 4 constantly apart from tool bit 9 and its guide surface in practical operation. Thus, tool bit 9 will wear only to a small extent in use. On the surface of cutter 4, a water film forms, which rotates along with saw discs 2, 3 back to cutter guides 7, 8 (cf. figures 1 and 2). This water

film cools cutter 4, it prevents pitch from returning to the surface of cutter 4, and it protects the saw notch against impurities in timber piece T to be sawn.

As stated above, the actual lubrication of cutter 4 can take place by means of pure water. However, any suitable lubricant may be used periodically by opening valve 26 and introducing lubricant from container 25 into the supply water for cutter guide 7, 8. Lubricant is used when the operation of bandsaw 1 is about to end and/or when saw discs 2, 3 of cutter 4 are to be protected against corrosion. However, it should be noted that, instead of oil, any suitable lubricating substances which protect cutter 4 and saw discs 2, 3 may be used.

The invention has been described above with reference to a number of preferred embodiments, however, it can, of course, be applied in various ways within the scope of the inventive idea defined in the accompanying claims.