The invention concerns a cutting tool comprising a carrier and a plurality of saw teeth which have a tip region and a root region, wherein the saw teeth are directly or indirectly welded to the carrier at the root region.
Cutting tools of the general kind set forth in the form of band saws are known for example from WO 03/059562 A1. Cutting tools of that kind are used for example in processing rocks and stones, wherein the saw teeth of such cutting tools have different cutting properties for example by virtue of coatings on the grinding or cutting segments and can advantageously be adapted to the material to be cut.
To be able to exert a high cutting pressure with conventional, substantially rectangular saw teeth, the application of a high level of force is required on the part of the sawing machine. Attempts to narrow the saw teeth in order to achieve a higher cutting pressure with the same application of force by the sawing machine and thus to increase the advance rate have had the result that saw teeth have individually broken off the carrier.
Therefore the object of the present invention is to develop a cutting tool of the general kind set forth, in which in the cutting operation on the saw tooth a higher cutting pressure and thus a greater advance rate can be achieved without individual cutting teeth breaking off the carrier.
According to the invention that is achieved in that the saw teeth have a tip region and a root region, wherein in a side view the tip region is narrower in a side view than the root region.
The combination of a wide root region with a narrow tip region ensures on the one hand that the saw teeth have a high level of stability in respect of rupture with at the same time an increased cutting pressure. In addition the amount of material involved in each saw tooth is reduced, thus reducing production costs.
In that respect it has proven to be desirable for cutting rocks and stones if the upper edge of the tip region is substantially parallel to the lower edge of the root region. In the simplest case therefore the upper edge of the tip region will also be parallel to the cutting or running direction of the cutting tool, which makes it possible for the cutting tool to be used in both possible running directions.
In a particularly preferred variant it is provided that the tip region and the root region form an L-shape in side view. Such an L-shape ensures a high advance rate and a clean cutting guidance effect with very good stability in respect of the saw tooth. In addition the rise in temperature of such a saw tooth is reduced in comparison with the state of the art with rectangular saw teeth. In the variant in which the tip region and the root region of the saw tooth form an L-shape in side view it has proven to be advantageous if the L-shaped saw teeth face in opposite relationship to the running direction of the cutting tool. In other words, in the preferred situation, the long lateral edge of the saw tooth is to face in the cutting direction.
Another variant provides that the tip region and the root region form an inverted T in side view. With such a configuration for the saw tooth the cutting tool can be used in both cutting directions without the cutting properties changing upon a change in the cutting direction.
Experiments have shown that the cutting tool or the cutting teeth adhere particularly well to the carrier and at the same time have an ideal cutting efficiency when the ratio of the width of the tip region to the width of the root region is 0.8 to 0.4, preferably 0.7 to 0.5, particularly preferably about 0.6. In a preferred variant it has proven advantageous if the ratio of the width of the tip region to the height of the tip region is about 1:1. It is further advantageous if the ratio of the width of the root region to the total height of the saw tooth is between 2:1 and 1:2. The actual width of the tip region in preferred variants is less than 15 mm, particularly preferably between 8 and 12 mm.
So that the wear phenomena at the saw tooth or the cutting tool are comparatively low and so that the rise in temperature of the saw tooth or the cutting tool in operation is also as low as possible it has proven advantageous if the thickness of the saw tooth in the root region is less than the thickness in the tip region.
In that respect investigations have shown that it is particularly desirable if the ratio of the thickness in the tip region to the width of the saw teeth is between 1:4 and 1:2.
In alternative variants it can certainly be provided that the upper edge in the tip region has a curvature. Such a variant is used when the material to be cut requires it.
As a further consequence it is also possible that the upper edge in the tip region is bevelled at least region-wise. Such variants are also adopted in dependence on the material to be cut.
To maximise the durability of the cutting tool it has proven to be advantageous if the carrier has a coating. Such coatings ward off the adverse influences due to a coolant and due to aggressive stone and rock slurries when cutting rock and stone and thus prolong the durability of the cutting tool. In that respect in the simplest case it can be provided that the coating is a galvanisation. It is preferably provided that the coating material has material powder for improving durability and that the coating has SnZnCo, CuSnZn and/or matt nickel.
To still further increase the strength of the teeth and to reduce the probability of a saw tooth breaking off during a cutting operation it has also proven to be advantageous if intermediate portions are introduced between the saw teeth and the carrier, which intermediate portions are so adapted that they permit sintering to the actual saw tooth and at the same time favour welding to the carrier.
Further advantages and details of the invention will be described with reference to the Figures and the specific description by means of advantageous embodiments by way of example. In the drawings:
a shows the portion ‘A’ in
a shows a further variant of an approximately L-shaped saw tooth 3, wherein the height hk of the tip region 4 is approximately equal to the height hf of the root segment 5. It should be noted at this juncture that the same references are used in all Figures, and for that reason each reference will no longer be discussed in detail here. In comparison with the variant in
For securely connecting the intermediate portions 8 to the carrier 2 it is preferably provided that the intermediate portions 8 are welded to the carrier 2 by laser welding. In the case of a variant in the form of a band saw as the cutting tool 1 it is desirable for optimum grinding efficiency if the carrier band 2 has between 25 and 45, preferably about 35 saw teeth 3, per running metre. Optimum flexing and strength properties are achieved by the carrier band 2 being of a thickness of between 0.9 mm and 2.2 mm, preferably about 1.65 mm. In particular 48CrMoV67 has proven its worth as the steel, as the material for the carrier 2. If the intermediate portions 8 comprise a steel with a carbon content of less than 0.35% or a carbon equivalent of less than 0.75%, in particular St52 or 25CrMo4, that ensures good weldability of intermediate portions 8 and carrier 2. In order not to impede the movement of the band saw around rollers of the band saw machine, it is preferably provided that the saw teeth 3 are of a height h of between 8 mm and 15 mm, preferably about 10.5 mm. The necessary hardness of the grinding segments 9, 10 which is required for use in stone or rock is achieved by the use of diamond grain as the cutting means. In that respect a mixture which contains at least two of the elements iron, cobalt, copper, tungsten, tin and nickel has proven its worth as the sintering bond. The band saw shown in
Number | Date | Country | Kind |
---|---|---|---|
06 003 107.7 | Feb 2006 | EP | regional |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/AT2007/000061 | Feb 2007 | US |
Child | 12216605 | US |