TECHNICAL FIELD

[0001 ] The present invention relates to maintenance and sharpening of cutting chains used in forestry machinery and corresponding apparatuses. The invention relates especially to a cutting chain produced by means of the method and automatic sharpening of cutting chains of forestry machinery.

BACKGROUND

[0002] Usually the user of hand-held chainsaws sharpens the cutting chains manually on site. The change requirement of harvesters and similar forestry machinery provided with chainsaws is, however, so high that manual sharpening is not practical. Sharpening with machines also allows achieving a more uniform sharpening than manual sharpening. Thus machine contractors reserve a sufficient amount cutting chains to last a month, for example, and the worn cutting chains are periodically transported to a sharpening company for sharpening. The sharpening company checks the chain for damage, sharpens the teeth of the chain and reduces the length and height of the depth gauge as needed. The chain is checked by an employee inspecting the whole length of the cutting chain and transferring the chain to sharpening, repair or reject.

[0003] The sharpening apparatuses currently in use are semi-automatic. The cutting chain to be sharpened is manually placed in the machine and the operator adjusts the correct angle of the grinding disc grinding the cutting teeth and possibly the depth gauge into correct angle and cutting depth, subsequent to which the machine does the sharpening automatically. The depth gauge is often lowered by means of a separate machine designed for the purpose. In this work sequence manual changing of the chains and adjusting the angles and grinding surfaces of the grinding discs is time-consuming and reduces productivity. As the grinding disc is worn in use, the operator must take this into account when setting the adjustments of the machine. Wear can’t be taken into account during sharpening, either.

[0004] The method of sharpening cutting chains has long remained unchanged and usually the teeth of the chain are always ground to the same angle and the depth gauge is lowered to the desired height by evenly grinding material off its top by means of cutting or grinding.

SUMMARY

[0005] The purpose of this invention is to provide a method of sharpening cutting chains, by means of which the procedure of sharpening cutting chains can be improved. The purpose of the invention is also to provide a cutting chain produced by means of the invention or a sharpened, sharp chain provided by means of the invention.

[0006] The invention is characterized by what is disclosed in the

characterizing parts of the independent claims.

[0007] According to the first feature of the invention the depth gauge is shortened at its tip by grinding and material is removed from the depth gauge by at least one other material-removing cutting at a surface different from that of the shortening cutting.

[0008] According to another feature of the invention the front edge of the depth gauge in relation to the direction of the cutting chain is rounded.

[0009] According to a third feature of the invention the rear edge of the depth gauge in relation to the direction of the cutting chain is rounded.

[0010] According to a fourth feature of the invention the front edge of the depth gauge in relation to the direction of the cutting chain is chamfered.

[0011 ] According to a fifth feature of the invention the rear edge of the depth gauge in relation to the direction of the cutting chain is chamfered.

[0012] According to a sixth feature of the invention the grinding of the depth gauge is effected with one controlled cutting movement. [0013] According to a seventh feature of the invention the grinding of the depth gauge is done with the same grinding disc as the grinding of the cutting tooth.

[0014] According to an eighth feature of the invention the depth gauge is ground with a separate grinding apparatus, preferably a grinding disc.

BRIEF DESCRIPTION OF DRAWINGS

[0015] In the following, some embodiments of the invention are disclosed in more detail by means of reference to the appended drawings, in which: FIGURE 1 shows a schematic perspective view of a cutting chain,

FIGURE 2 shows the grinding of the cutting of the depth gauge in one position. FIGURE 3 shows the grinding of the cutting of the depth gauge in another position.

FIGURE 4 shows the grinding of the cutting of the depth gauge in a third position.

EMBODIMENTS

[0016] DEFINITIONS

[0017] In this context the entry direction of the cutting chain refers to a direction parallel with the longitudinal axis of the cutting chain in which the cutting edge of the cutting tooth points, i.e. the direction of the movement of the cutting chain during cutting.

[0018] The first cut means the grinding by means of which the depth gauge is shortened. The second cut means the grinding by means of which the depth gauge is contoured in addition to shortening,

[0019] The purpose of the invention is to enhance the service rotation of cutting chains used in chainsaws. Sharpening of cutting chains is a

considerable part of the service of cutting chains, whereby improving the speed and quality of sharpening and by automatizing the sharpening process a considerable improvement can be made to the various phases of service rotation. The various embodiments of the invention improve the cutting efficiency of the cutting chain and facilitate its movement in the timber to This is of great importance to the service life of the chain and the fuel consumption of the machine powering the chain. Some embodiments facilitate a sharpening method in which the accumulation of wood cutting and shavings behind the cutting tooth is reduced, whereby the chains moves more easily in the timber. This reduces the risk of splitting at the root end of the timber to be cut due to the chain being stuck and bad cutting efficiency. This allows the seller to get a better price for the timber and the work of the machine contractor will also be more profitable.

[0020] FIGURE 1 illustrates an example of a typical cutting chain of a chainsaw. The cutting chain 4 is formed by drive links 1 and guides 3 connected by rivets to form a chain. The longitudinal axis of the cutting chain 4 runs between the drive links 1 along the centerline thereof. Cutting links 5 are provided on both sides of the cutting chain 4. Cutting links 5 are provided at specified intervals on both sides of the cutting chain 4 instead of drive links 1. Cutting links 5 comprise a depth gauge extending upwards from the surface of the cutting chain 4 and at a distance from the depth gauge 6 there is a cutting tooth 7 extending similarly upwards. The leading edge of the cutting tooth 7 is provided with a cutting edge 8, thus defining the direction of travel and cut of the cutting chain. The depth gauge 6 is the first in the direction of travel of the chain and it is meant to travel along the bottom of the gutting groove of the chain saw. The length of the depth gauge 6 defines how much of the cutting edge 8 located at the leading edge of the cutting tooth 7 is exposed behind the depth gauge 6 in the direction of travel of the chain. This defines the cutting depth of the cutting teeth 7 of the cutting chain 4. When a cutting chain is sharpened, the cutting edge 8 of the cutting tooth 7 is ground sufficiently to ensure its sharpness.

Insufficient grinding leaves the tooth dull and excessive grinding reduces the service life of the chain. When the cutting tooth 7 is ground, the depth gauge is also shortened to match. [0021 ] The international application PCT/FI2018/050521 describes a sharpening apparatus that can be used for carrying out the method. The method according to the invention can be carried out by means of other sharpening devices or by using a number or separate devices for carrying out each step of the method, for example. The sharpening method and apparatus described in publication PCT/FI2018/050521 allows flexible and versatile adjustment of sharpening and sharpening angles, whereby the method can be flexibly carried out by means of it and the range of adjustments is good in this method.

[0022] FIGURE 2 shows a sharpening disc 10 positioned against the depth gauge 6 of the cutting chain 4 for contouring the depth gauge. The sharpening disc 10 is arranged suspended from the transfer arm 11 via shaft 13. The sharpening disc can be driven by an electric motor, for example. The sharpening disc 10 is a preferred means for contouring the depth gauge as it allows easily carrying out even small grinding amounts and it is easy to control suspended by the transfer arm by means of servo control or other suitable method. It is conceivable to use a file, strip of sand paper or the like or even a milling tool instead of a sharpening disc.

[0023] The depth gauge 6 of the cutting chain 4 must be ground in connection with sharpening the cutting chain for shortening the depth gauge 6. This is made by lowering the tip of the depth gauge 6. In addition to lowering the tip the depth gauge is also ground by means of at least one other cutting run to contour the depth gauge 6. Thus, in the method one cut is made for shortening the depth gauge and another cut for contouring the depth gauge in other ways than shortening. These cutting movements can be combined to one continuous movement, the difference of the cut being that in one the length of the depth gauge is not changed.

[0024] In principle the depth gauge 6 comprises four surfaces, one in the movement direction of the cutting chain 4 being the front edge 16 facing in the same direction as the cutting edge 8 of the cutting tooth 7, the rear edge 17 on the side of the cutting edge 8 of the cutting tooth 7 and the side surfaces 18 of the depth gauge 6. The front edge 16 is usually convex and the rear edge 17 correspondingly concave. The shape of the depth gauge varies in different cutting chains, but this method of grinding the depth gauge 6 is applicable to all cutting chains.

[0025] The grinding of the depth gauge 6 from various directions is shown in FIGURES 2 to 4. In Figure 2 the grinding is done at the rear edge 17 of the depth gauge, in Figure 3 at the rear edge 17, the corner point of rear edge 17 and the side edge 18 and in Figure 4 in vertical position at the rear edge 17 of the depth gauge. The purpose of working on the depth gauge 6 is to shape the depth gauge into a specific contour. The contouring of the depth gauge reduces friction and sharpness of the corners formed in the shortening of the depth gauge, thus allowing the depth gauge 6 to run lighter along the wood. The depth gauge can be contoured in different degrees of angle both on the sides and the top and/or by rounding. It is possible to use only one contour-correcting grinding in addition to shortening grinding or the depth gauge can be contoured along all of its surfaces. The degrees of the corners formed by grinding are in the range of 1 to 90 degrees in relation to the center axis of the cutting chain, depending on the species and temperature of the wood to be sawn. The depth gauge can be rounded and modified as necessary to achieve an optimal sliding movement in the wood. Thus the method differs from the usually applied method of lowering the depth gauge directly downwards, whereby the depth gauge becomes sharp (straight and sharp edges). The depth gauge 6 can also be contoured by means of a sharpening servo driving the grinding disc used for sharpening the cutting tooth of the cutting chain or a dedicated servo elsewhere and a separate machine.

[0026] The front edge 16 of the depth gauge 6 can be ground to the desired arc or a suitable angle or the front edge 16 can be provided with various angles in order to provide the desired shape. This also applies to the rear edge 17. The corners of the front and rear edges 16, 17 and the side surfaces 18 can be chamfered or rounded. In principle the depth gauge can be contoured as desired as long as tat least one shape-correcting grinding is done in addition to lowering or shortening the depth gauge. It will be obvious that if the method is carried out by means of an automatically controlled apparatus, the grinding disc or other milling means of the apparatus must be able to perform the necessary movements. The simplest way to achieve this is an apparatus with two degrees of freedom, i.e. an apparatus capable of moving the milling device in two directions.

[0027] The surface of the depth gauge 6 can also be contoured so that its surfaces are in different degrees/angles in different points of the surface of the depth gauge 6. The angles of front and rear edges can be in the range of 1 to 90 degrees in relation to the longitudinal axis of the cutting chain, depending on the temperature and species of the wood to be sawn. The depth gauge can be contoured in different degrees of angle both on the sides and the top.

[0028] The method of contouring the depth gauge 6 described above allows contouring the cutting tooth of the cutting chain according to the species of the wood and the weather of the timber harvesting time. Harder species of wood require different edge angles and a different shape of the depth gauge, and the hardness of wood also varies according to its temperature. A frozen trunk in the winter is harder than a growing tree in the summer. The method of sharpening can also be controlled e.g. so that the client ordering the sharpening tells in which conditions they plan to use the cutting chains. The system can be enhanced by combining the sharpening machine to weather forecast service and the wood species data of the harvesting site, for example. When these date are combined with recognizing the cutting chain or the number of ordered chains, it is possible to individually sharpen each chain to suit its purpose, if desired. Alternatively, the customer can order their own preferred sharpening for their cutting chains.

[0029] The operator of the cutting machine can define how much material is removed from the depth gauge and thus optimize the service life of the chain. The optimization can be carried out automatically or by means of machine vision. Machine vision also allows checking the state of the cutting chain, in which the need for sharpening and other possible service are determined and the chain is rejected as unfit for repair, if necessary.

[0030] The sharpening machine can be provided with a machine vision system, by means of which it is possible to achieve many of the functions and advantages mentioned above. It is also possible to use a service robot in the sharpening machine and method for carrying out various functions, especially the positioning of the chain to be sharpened for sharpening and the removal of the sharpened chain.

[0031 ] The above-described different features of the invention can be combined with each other to form various embodiments and apparatuses. The following is a disclosure of additional alternatives that can be used together with the above-mentioned parts or method steps of embodiments or as an alternative thereto.

[0032] It is preferable to use a stone disc or a ceramic disc as the sharpening disc due to the inexpensive price, but on the other hand, while a diamond disc is more expensive to purchase, it will also last longer. Thus it is preferable to optimize the disc choice based on the application.

INDUSTRIAL APPLICABILITY

[0033] The invention is applicable to the servicing of cutting chains of chainsaws.

LIST OF REFERENCE NUMBERS

1 Drive link

2 Rivet

3 Guide link

4. Cutting chain

5. Tooth link

6. Depth gauge

7. Cutting tooth

8. Cutting edge

9. Cutting chain direction arrow

10. Sharpening disc

11. Transfer arm

12. Motor unit

13. Shaft Processing edge

Rotation direction arrow Front edge of the depth gauge Rear edge of the depth gauge Side edge of the depth gauge