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 the cutting teeth of 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 a first feature of the invention, in the first sharpening step a rotating sharpener is moved to contact the first cutting tooth to be sharpened and the sharpener is pressed against the first cutting tooth in at least one set sharpening angle for removing material from the cutting edge of the cutting body of the first cutting tooth for forming a first end face. In the next sharpening step the rotating sharpener is taken to the opposite side of the cutting body of the cutting tooth in relation to the first end face and it is pressed against the cutting tooth for removing material and forming a second end face to the cutting edge of the cutting body.

[0008] According to a second feature of the invention the first and second end faces are cut so that they form an acute angle on their trailing sides.

[0009] According to a third feature of the invention in the first sharpening step material is removed from the cutting edge of the cutting body for forming a third end face.

[0010] According to a fourth feature of the invention, in the sharpening step subsequent to the first sharpening step material is removed from the side of the cutting flange opposite the third end face for forming a fourth end face so that with the third end face it forms an acute angle on its trailing side.

[0011] According to a fifth feature the second end face is shorter than the first end face, measured from the tip of the cutting edge of the cutting body parallel with the longitudinal axis of the cutting chain.

[0012] According to a sixth feature of the invention at least the first end face is in at least two different angles in relation to the cutting edge.

[0013] According to a seventh feature at least the third end face is in at least two different angles in relation to the cutting edge.

[0014] According to an eighth feature of the invention the cutting edge of the cutting body is curved.

[0015] According to a ninth feature of the invention the cutting chain is moved in the direction of its longitudinal axis for positioning the second cutting tooth for sharpening. In the sharpening step of the second cutting tooth the rotating sharpener is kept rotating in the same direction as in the first step and the rotating sharpener is moved against the second cutting tooth to be sharpened in the set sharpening angle for removing material from the cutting edge of the second cutting tooth.

[0016] According to a tenth feature of the invention the rotating sharpener is a sharpening disc being rotated to the same direction during sharpening of at least two teeth and the cutting chain is moved in the direction of the longitudinal axis of the cutting chain and the sharpening disc is adjusted into the set sharpening angle so that the sharpening disc extends in an angle over the cutting chain and the sharpening disc is turned for sharpening the second cutting tooth so that the edge of the sharpening disc on the on the entry side of the cutting chain is turned over the cutting chain to the other side of the cutting chain on the entry side of the cutting chain.

BRIEF DESCRIPTION OF DRAWINGS

[0017] 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 a perspective view of an apparatus according to at least one embodiment of the cutting chain sharpening apparatus in the first sharpening position on the first side of the cutting chain,

FIGURE 3 shows the apparatus of Figure 2 in the second sharpening position,

FIGURE 4 shows the apparatus and position of Figure 2 from the opposite side of the cutting chain,

FIGURE 5 shows the apparatus and position of Figure 3 from the opposite side of the cutting chain,

FIGURE 6 shows the cutting chain centering apparatus used in an apparatus according to at least one embodiment of the invention,

FIGURE 7 shows the forming of a first and third end face according to at least one embodiment; and FIGURE 8 shows the forming of a second end face according to at least one embodiment.

EMBODIMENTS

[0018] DEFINITIONS

[0019] 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.

[0020] 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 be cut. 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 chain 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.

[0021] 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.

[0022] The following is a disclosure of a grinding apparatus that can be used for carrying out this method. A more detailed description of the apparatus is in international application PCT/FI2018/050521. 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. However, the sharpening method and apparatus described below 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.

[0023] FIGURE 2 illustrates a sharpening apparatus with a cutting chain 4 positioned thereon for sharpening. FIGURES 2 to 5 only show the components of the apparatus relating to the sharpening of the cutting tooth. It will be obvious that an automatic sharpening apparatus or machine also comprises the normal body components, safety devices, cabinets and the like. They are not shown here. For example, one skilled in the art of metal machining devices will understand which auxiliary devices, safety devices and the like are needed for this kind of machine or apparatus.

[0024] In the apparatus of FIGURES 2 to 5 the cutting chain 4 is arranged to run on the sharpening table 9 via idler sprockets. The idler sprockets 10 and the

sharpening table 9 can be provided with grooves for the guide tangs of guide links 3. Thus the cutting chain 4 is supported in the same way as in the groove of the chain bar of a chainsaw. The cutting chain 4, tensioned between the idler sprockets 10, is moved forward one step at a time. The movement direction of the cutting chain 4 is shown by the3 direction arrow 11. Here the sharpener is a sharpening disc 12 which in FIGURES 2 to 5 is shown in sharpening positions against the cutting tooth 7. The sharpening disc 12 is rotated in the direction shown by the rotation direction arrow 17. The sharpening disc 12 must be positioned in correct angle in relation to the tooth to be sharpened of the cutting chain 1 on the sharpening table 9. This angle depends on the type of the cutting chain and the position of the sharpening disc and the resulting sharpening angle is also set by means of adjustments of the position of the sharpening disc 12. The sharpening disc 12 is attached to a transfer arm 13 by means of which the movement of the sharpening disc 12 towards the tooth 7 to be sharpened and the adjustment of the angle of the sharpening disc 12 longitudinally and transversely in relation to the longitudinal axis of the cutting chain can be carried out. Additionally the rotation of the sharpening disc around the axis of the transfer arm 13 for rotating the sharpening disc 12 in order to process the cutting teeth 7 on different sides of the cutting chains is carried out by means of the movement arm. The rotational movement of the sharpening disc 12 is carried out by means of motor unit 14. The motor unit 14 is fastened to the transfer arm 13 and the sharpening disc 12 is fastened on its shaft 15. The motor unit can be any apparatus assembly allowing a sufficient rotation speed, torque and adjustability. Various electric motor drives are an alternative, comprising an electric motor, its control and adjustment units and a transmission, if necessary.

[0025] The cutting chain is sharpened using the apparatus according to

FIGURES 2 - 5 so that the cutting chain 1 is first installed on the idler sprockets 10 and the sharpening table 9 and tensioned. As the cutting chains 1 are endless loops during sharpening, the cutting chain 1 can be locked simply by tensioning with a third, movable idler sprocket, for example. This allows the cutting chain 1 to be securely fastened to the apparatus and to be moved in the direction of its longitudinal axis. The cutting chain 1 can be installed on the sharpening apparatus manually, partly automatized or fully automatized, such as by means of robots. A service robot for installing the chains for sharpening and removing sharpened chains is well suitable for use with the method and apparatus according to this invention. Both of these steps or only one of them can be automatized by means of said robot or robots or other automatic manipulator. The advantage of the robot is the versatility of its operation and the flexibility by changing programming and control. For sharpening the cutting chain is locked in place as described below. The cutting tooth to be sharpened must be positioned so that the grinding edge 16 of the sharpening disc 12 contacts the edge of the cutting tooth during processing movement so that a section of correct length can be ground off the edge of the cutting tooth 7 for sharpening the cutting tooth 7. The movement of the cutting chain 1 in the direction of its longitudinal axis can be carried out by, for example, using one or more idler sprockets as drive sprockets or by catching hold of the cutting chain 1 and moving it forwards or backwards one step at a time. The control data of the control system of the apparatus, mechanical sensors, optical sensors or even machine vision systems can be used for indicating the correct position of the cutting tooth. [0026] When the cutting chain 1 is installed in the sharpening apparatus, the apparatus must be informed about the type of the chain so that the apparatus can correctly position the sharpening disc 12 in sharpening position. The type of the cutting chain can be indicated by means of a code attached to the chain, machine vision, RFID chip or the operator can also manually enter the type of the cutting chain into the apparatus. Next, the apparatus adjusts the longitudinal inclination angle and the transverse angle of the sharpening disc 12 in relation to the longitudinal axis 1 of the chain. The operator can also make the adjustments. The inclination angle defines the sharpness of the angle (inclination angle in relation to the cutting chain) of the cutting edge 8 of the cutting tooth 7 and the transverse angle defines the angle of the slant of the cutting edge 8 in the direction of movement of the chain. When the angles are set and the sharpening apparatus has been adjusted, the sharpening disc 12 is suspended by the transfer arm 13 at a distance from the cutting chain 1 and the tooth to be sharpened. The sharpening disc 12 in is an angled position so that in side of the entry direction of the cutting edge (direction arrow 11 of the cutting chain) of the sharpening disc 12 the processing edge 16 of the sharpening disc 12 points towards the entry direction of the cutting chain 12, forming an acute angle on the entry side of the cutting chain in relation to the longitudinal axis of the cutting chain 12. When the first cutting tooth 18 to be sharpened - in this case one of the right-hand cutting teeth as seen against the entry direction of the cutting chain 12 - is positioned in the sharpening position, the sharpening disc 12, pushed by the transfer arm 13, makes a straight movement in the direction of the inclination angle towards the first cutting tooth 18 to be sharpened. When the grinding edge 16 of the sharpening disc 12 contacts the cutting tooth 18 to be sharpened, the cutting edge 16 cuts material from the cutting edge 8 of the first tooth to be sharpened, thus sharpening the tooth. The movement of the sharpening disc 12 continues until the cutting edge 8 has been processed, subsequent to which the sharpening disc 12 makes a return movement suspended by the transfer arm 13. When the sharpening disc has moved away from in front of the first tooth 18 to be sharpened, the cutting chain 1 can be moved in direction of its longitudinal axis. The movement can be forwards or backwards. When the sharpening disc 12 has returned to its initial position, it is turned in the direction of the plane of the sharpening disc 12 so that the grinding edge 16 of the sharpening disc 12 in the entry direction of the cutting chain 12 moves over the cutting chain 1 in a similar but opposite angle as for the sharpening of the first tooth to be sharpened 18. Thus the cutting angle of the sharpening disc 12 and especially the cutting direction defined by the rotation direction remain the same and there is no need to change the rotation direction of the sharpening disc. The turning axis runs along the center in the direction of depth of the sharpening disc 12 and through the rotation axis and the surface corresponding with the grinding edge 16.

[0027] FIGURE 6 illustrates the sharpening table 9 from above. The idler sprockets 10 are on both sides of the sharpening table 9 and the cutting chain to be sharpened runs via the idler sprockets over the sharpening table 9. There is a groove 20 in the middle of the sharpening table 9 for dividing the sharpening table 9 into two halves 9a and 9b. This groove 20 comprises two clamping jaws 21a and 21b, the ends of which are provided with gripping pads 21a and 21b. The clamping jaws 21a, 21b are arranged to move synchronously so that they move at identical rates when closing. Thus they are pressed together in the longitudinal center of the groove 20, along which the cutting chain 1 to be sharpened runs. The gripping pads 22 of the clamping jaws 21a, 21 b are arranged to catch the tang of the guide tooth 3. Due to the synchronous movement of the jaws 21a, 21 b and the moving compression occurring on both sides, the cutting chain is always positioned on the same place of the sharpening table 9 and the grinding edge 16 of the sharpening disc 12 correctly contacts the tooth. Such a centering locking of the cutting chain 1 compensates the width differences of various types and sizes of cutting chains, as the differences can be large enough to otherwise cause a different sharpening on different sides of the cutting tooth. The thickness of the guide teeth 3 varies from 1.6 mm to 2.00 mm and without centering each chain would require a different mechanical adjustment. Such an adjustment would of course be possible, but it would reduce the degree of automatization and could slow the operation down.

[0028] The cutting tooth 7 of the cutting chain consists of a cutting body 23 extending outwards from the plane of the chain formed by drive links 1 and guide links 3 and a cutting flange 24 connected to opposite side of the chain formed by drive links 1 and guides 3. The cutting body 23 and the cutting flange 24 form the part of the cutting chain that cuts the wood. The cutting chain 23 arcs over the side and upwards over the chain formed by the guide teeth 2 and drive links 1 as seen from the direction opposite the tang 25 of guide links 3 of the cutting chain to form a cutting flange 24. Usually the cutting flange 24 is slightly slanted in relation to the surface of the drive links 1 of the cutting tooth 7 so that the cutting edge of the cutting flange 24 is further in front the upper surface of the drive links than the trailing edge. Because of this the cutting flange and the cutting tooth 7 are lowered during sharpening when material is removed from the front edge of the tooth.

[0029] The cutting edge 8 is in the surface pointing towards the depth gauge 6 and it is divided into the cutting edge of the cutting body 23 and the cutting edge of the cutting flange 24 In a cutting chain sharpened in a known way the cutting edge of the cutting body 23 is trough-like, following the curved form of the cutting body on the side on the side of the cutting chain and the form of the surface of the disc used in sharpening. On the part of the gutting flange 24 the cutting edge is straight and it extends in an angle away from the direction of the cutting tooth. Thus the cutting edge 8 is formed at the intersection of outer surfaces pointing away from the cutting chain and end faces formed during sharpening and extending from cutting edge as seen in relation to the depth gauge.

[0030] The sawdust formed during sawing with a cutting chain sharpened as described above can accumulate between the teeth, affect the movement of the chain and affect the sawing result. To eliminate this phenomenon or at least to alleviate it, the sharpening is made as shown in figures 7 and 8. The actual cutting edge 8 is formed in the usual manner by grinding the cutting tooth 7 with a sharpening disc 12 pressed against it. The sharpening disc 12 forms a first end face 26 on the cutting tooth, at the cutting body of the cutting tooth 7 and extending in an angle away from the direction of the depth gauge 6. Usually the sharpening disc simultaneously forms a third end face 28 on the edge of the cutting flange 24 facing the depth gauge 6. The first 26 and the third end face 28 are at a defined angle in relation to the outer surface of the cutting tooth 7 and they form an acute angle to the trailing side of the outer surface and the end face. This forms a sharp cutting edge. A second end face is also formed on the cutting tooth 7 as shown in figure 8. In this step the outer edge of the cutting body of the cutting tooth 7, i.e. , the edge opposite the first end face seen from the cutting chain is slightly processed for forming a second end face. Thus a cutting edge with two angled sides (V-form) with acute angle on the trailing side is formed on the cutting edge 23. The function of the second end face 27 is to direct the sawdust formed during sawing so that the sawdust is not accumulated behind the cutting tooth 7.

[0031] The outer edge of the cutting flange 24 can be ground similarly so that a V-form is formed on the cutting edge. In this case a fourth end face 29 is ground between the outer surface of the cutting flange, i.e. the surface pointing away from the cutting chain, and the cutting edge. The sharpening of the cutting tooth 7 can be modified in many other ways as well. The edge part of the cutting tooth 7, i.e. the cutting edge 8 of the cutting body 23 and the cutting flange 24 can be contoured, for example, so that the cutting edge surface is provided with an opposite facet/angle so that the cutting part of the cutting tooth has two cutting surfaces at an angle in relation to each other. The cutting surface of the cutting tooth is in V-shape in two directions and the angles of the end faces can be different in relation to the cutting edge. The cutting surface formed by the end faces can also be contoured so that the end face has different angles/degrees in relation to the cutting edge 8 at different points of the cutting surface. The angles of the cutting surfaces can be in the range of 0 to 90 degrees in relation to the cutting edge, depending on the temperature and species of the wood to be sawn. The cutting tooth can be contoured in different degrees of angle both on the sides and the top. The cutting tooth can be contoured by means of a sharpening servo controlling the sharpening disc of a sharpening machine as described above, a separate servo elsewhere or a separate machine,

[0032] The method of sharpening described above allows sharpening the cutting chain according to the species of the wood and the weather of the timber harvesting time. Harder wood species require different edge angles and the hardness of wood varies also according to its temperature. A trunk frozen in winter is harder than wood growing during 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.

[0033]

[0034] The operator of the cutting machine can define how much material is removed from the cutting tooth 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.

[0035] 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.

[0036] 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.

[0037] Instead of an alternating sharpening described above the work sequence can be carried out so that the cutting teeth of one side are sharpened first and the teeth of the opposite side are sharpened subsequently, after turning the sharpening disc. In principle the sharpening disc can be rotated in both directions, but if the grinding direction is inwards from the tip of the cutting edge, burrs are not so easily formed at the tip of the cutting edge. This also applies to other sharpeners. It is preferable to use a stone disc or a ceramic 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.

[0035] Instead of a turnable disc it is also possible to use two discs or round files to grind the cutting chain from different angles or a combination thereof. The round file can also be used in turnable way, similar to the sharpening disc described in the example. If a sharpener grinding the cutting chain from two sides is used, they are used for processing the cutting teeth of the same side without stopping their rotation.

INDUSTRIAL APPLICABILITY

[0039] 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 table, halves 9a, 9b 10. Idler sprocket

1 1. Cutting chain direction arrow

12. Sharpening disc

13. T ransfer arm

14. Motor unit

15. Shaft

16. Processing edge

17. Rotation direction arrow

18. First cutting tooth to be sharpened

19. Second cutting tooth to be sharpened

20. Groove

21. Clamping jaws 21a, 21b

22. Gripping pads

23. Cutting body

24. Cutting flange

25. Guide tang

26. First end face

27. Second end face

28. Third end face

29. Fourth end face