WOOD CHIPPER KNIFE

Abstract

A wood chipper knife includes a knife body and, in relation to a vertical axis of the wood chipper knife, at least one cutter side, which comprises a top cutting edge portion and a bottom cutting edge portion that intersect to form a cutting edge. The bottom cutting edge portion includes a planar wood attacking portion, which begins at the cutting edge and towards the knife body is followed by a recess. The recess is a pressure release recess, which, from the wood attacking portion, abruptly falls to a bottom of the pressure release recess, and which stretches from the wood attacking portion to the knife body. The knife body comprises a chip guiding portion, which, from the pressure release recess, rises towards the knife body.

Claims

1.-13. (canceled)

14. A wood chipper knife, comprising: a knife body having a chip guiding portion; and at least one cutter side, which comprises a top cutting edge portion and a bottom cutting edge portion that intersect at an acute angle (a) to form a cutting edge, wherein the bottom cutting edge portion comprises a planar wood attacking portion, which begins at the cutting edge and towards the knife body is followed by a recess, the recess is contoured to abruptly turn from the wood attacking portion to a bottom of the recess, and the chip guiding portion is contoured so as to turn from the pressure release recess towards the knife body.

15. The wood chipper knife according to claim 14, wherein the bottom of the recess is at a depth of at least 0.3 mm from the wood attacking portion.

16. The wood chipper knife according to claim 14, wherein the bottom of the recess is at a depth of 0.5-2 mm.

17. The wood chipper knife according to claim 14, wherein a dimension of the recess from the wood attacking portion to the knife body is 2.8-8 mm.

18. The wood chipper knife according to claim 14, wherein the recess comprises a first transition portion, which from the wood attacking portion, turns towards the bottom of the recess along a concave curve with a radius of curvature of 0.1-1.5 mm.

19. The wood chipper knife according to claim 18, wherein the radius of curvature is 0.5-1.2 mm.

20. The wood chipper knife according to claim 18, wherein the radius of curvature is 0.6-1.0 mm.

21. The wood chipper knife according to claim 18, wherein the radius of curvature is 0.7-1.1 mm.

22. The wood chipper knife according to claim 18, wherein the radius of curvature is about 0.8 mm.

23. The wood chipper knife according to claim 18, wherein the first transition portion includes a straight portion that is adjacent the wood attacking portion and that tangentially transforms into the concave curve.

24. The wood chipper knife according to claim 18, wherein the recess comprises a second transition portion, which from the bottom of the recess turns towards the knife body along a concave curve with a radius of 0.4-7 mm.

25. The wood chipper knife according to claim 24, wherein the second transition portion tangentially transforms into the chip guiding portion of the knife body.

26. The wood chipper knife according to claim 14, wherein the chip guiding portion is inclined towards the knife body at an angle (β) of 10° to 50° in relation to a vertical axis of the knife body.

27. The wood chipper knife according to claim 14, wherein the planar wood attacking portion from the cutting edge to the recess has a width of 5-10 mm.

28. The wood chipper knife according to claim 14, wherein the planar wood attacking portion in relation to a vertical axis of the knife body forms an angle (γ) of 83° to 89°.

29. The wood chipper knife according to claim 14, wherein the bottom of the recess is planar and in relation to a vertical axis of the knife body forms an angle (δ) of 70° to 93°.

30. The wood chipper knife according to claim 14, wherein the acute angle (α) of the cutting edge is 30° to 40°.

31. A wood chipper knife, comprising: a knife body having a chip guiding portion; and at least one cutter side, which comprises a top cutting edge portion and a bottom cutting edge portion that intersect at an acute angle (a) to form a cutting edge, wherein the bottom cutting edge portion comprises a planar wood attacking portion, which begins at the cutting edge and towards the knife body is followed by a recess, and the recess includes a straight portion adjacent to the wood attacking portion and a concave curve portion between the straight portion and a bottom of the recess.

32. The wood chipper knife according to claim 31, wherein a radius of curvature of the concave curve portion is 0.1-1.5 mm.

33. A wood chipper knife, comprising: a knife body having a chip guiding portion; and at least one cutter side, which comprises a top cutting edge portion and a bottom cutting edge portion that intersect at an acute angle (α) to form a cutting edge, wherein the bottom cutting edge portion comprises a planar wood attacking portion, which begins at the cutting edge and towards the knife body is followed by a recess, and the recess includes a concave curve portion between the wood attacking portion and a bottom of the recess, a radius of curvature of the concave curve portion being 0.1-1.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings preferred embodiments of the present invention are shown schematically, wherein:

[0023] FIG. 1 is a cross-sectional view of a wood chipper knife according to a first embodiment of the invention mounted in a knife holder;

[0024] FIG. 2 is a cross-sectional view of the wood chipper knife of FIG. 1;

[0025] FIG. 3 is a cross-sectional view of a wood chipper knife according to a second embodiment of the invention; and

[0026] FIG. 4 is a cross-sectional view of a wood chipper knife according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In the drawings and the description, the same references are used for all three embodiments of the wood chipper knife 1, as the embodiments differ only in certain dimensional aspects. Further, as far as directional indications are used in the description and the claims, such as top and bottom, these refer to the drawings and can therefore differ from reality. Finally, as machinery for wood chipping is well-known, only the wood chipper knife embodiments and a knife holder 20 for these are described and shown.

[0028] A wood chipper knife 1 according to the first embodiment is shown in FIG. 1 mounted in a knife holder 20. The knife holder 20 is, just like the wood chipper knife 1 itself, shown in a cross-sectional view. It extends into the drawing plane along the whole length of the wood chipper knife 1, which in reality means for at least some tenth of a meter.

[0029] The knife holder 20 comprises a base 21 on top and a clamp 22 underneath. Both are held together by means of a bolt 26, which renders it possible to securely clamp a wood chipper knife 1 in between. In order to fit in the knife holder 20, the wood chipper knife 1 comprises a central knife body 2, from which cutters 3 extend mirror symmetrically on both sides of a vertical axis a (or axis or plane of symmetry) illustrated in FIGS. 2 and 3. While in use, the wood chipper knife 1 can be positioned in multiple orientations depending on the orientation of the knife holder 20. For purposes of this discussion, the axis or plane of symmetry will coincide with the direction of gravity and be referred to as the vertical direction. On top the knife body 2 is a central, all flat portion 13, which fits a corresponding flat portion 23 of the knife holder base 21, and to the sides of it, concave grooves 14, which fit corresponding convex crests 24 of the knife holder base 21. Below the knife body 2 is a centered, downwardly protruding apex 15, having inclined sides 16, of which one at a time, depending on how the wood chipper knife 1 is rotated, fits a corresponding flat support 25 of the knife holder clamp 22.

[0030] So far, the wood chipper knife 1 described above corresponds to previous wood chipper knives provided by the applicant. However, in order to cope especially with wood that has a tendency to resist proper chipping due to wood fibers, which are difficult to break apart, the wood chipper knife 1 according to the present invention comprises cutters 3 shaped differently than before, wherein the three embodiments shown in detail in FIGS. 2 to 4 comprise the same main features and differ only dimensionally. Hence, below the three embodiments are described in common and differences pointed out only when necessary.

[0031] According to the invention, each cutter 3 (there is one on each side of the wood chipper knife 1) comprises a top cutting edge portion 4 and a bottom cutting edge portion 5. These intersect at an acute angle α of about 35° to form a cutting edge 6. The bottom cutting edge portion 5 comprises a planar wood attacking portion 7, which begins at the cutting edge 6 and towards the knife body 2 is followed by a recess 8. The wood attacking portion 7 is preferably inclined in relation to said vertical axis a at an angle γ of preferably about 86° or at least within a range of 83° to 89°. From the cutting edge 6 to the recess 8, the planar wood attacking portion 7 has a width of about 7.5 mm according to the first and third embodiments and of about 8.5 mm according to the second embodiment. However, widths within a range of 5-10 mm have proven to fulfil the needs at hand, that is, to put cut wood chips under pressure and to guide them towards the knife body 2.

[0032] The recess that follows the planar wood attacking portion 7 is a pressure release recess 8, which, from the planar wood attacking portion 7, abruptly falls (or, as shown in the drawing, rises) to a bottom 10 of the pressure release recess 8. In this context, pressure release means that cut wood chips, which propagate along the planar wood attacking portion 7 and are under pressure therefrom, due to a sudden hollow when the pressure release recess 8 is reached, are subjected to a sudden substantial release of pressure, which helps to separate wood chips from each other and thus to free them from each other.

[0033] In the first and second embodiments shown, the pressure release recess 8 has a depth of about 1 mm and in the third embodiment a depth of about 0.55 mm. However, depths within a range of 0.3-2 mm are within the scope of the present invention. The bottom 10 of the pressure release recess 8 is planar and does, in relation to said vertical axis a form an angle δ of between 72° (third embodiment) to 90° (first embodiment). The width of the pressure release recess 8 from the wood attacking portion 7 to the knife body 2 amounts for the first embodiment to about 5.0 mm, for the second embodiment to about 4.1 mm, and for the third embodiment to about 3 mm. However, widths within a range of 2.8-8 mm are possible within the scope of the present invention.

[0034] Further, in all three embodiments the pressure release recess 8 comprises a first transition portion 9, which, from the bottom 10 of the pressure release recess 8, rises towards the wood attacking portion 7 along a concave curve. This curve helps to pick up and guide wood chips along the bottom 10 of the pressure release recess 8, which is done best with a curvature radius of about 0.8 mm (first and second embodiments) or 0.5 mm (third embodiment). However, radii within a range of 0.1-1.5 mm have proven to be possible. As discussed above, the curve of the first transition portion 9 defines an abrupt turn from the wood attacking portion 7. A curvature radius within the range of 0.1-1.5 mm would be considered to define an abrupt turn. As also discussed above, the first transition portion 9 can, towards the wood attacking portion 7, tangentially transform into a straight portion. That is, the first transition portion 9 can include a straight portion adjacent the wood attacking portion 7, and that straight portion transitions into a tangent of the concave curve. A first transition portion 9 that includes a straight portion that is adjacent the wood attacking portion 7 and that transitions into a tangent of the concave curve would be considered to define an abrupt turn.

[0035] At the opposite end of the pressure release recess 8, in all three embodiments, there is a second transition portion 11, which from the bottom 10 of the pressure release recess 8 rises towards the knife body 2 along a concave curve. This curve guides wood chips from the bottom 10 of the pressure release recess 8 onto an inclined chip guiding portion 12 described in greater detail below. The radius of the curvature of the second transition portion 11 is preferably of about 0.8 mm (first and second embodiments) or 4 mm (third embodiment), but can, within the scope of the present invention, range from 0.5 to 5 mm.

[0036] The chip guiding portion 12 forms part of the knife body 2. It follows a straight line, which is inclined from the pressure release recess 8 towards the knife body 2 at an angle β in relation to said vertical axis a of preferably about 35° (first and second embodiments) or 47° (third embodiment). However, angles within a range of 25° to 50° are possible, especially if they make it possible for the second transition portion 11 to tangentially transform into the chip guiding portion 12 of the knife body 2, as this is advantageous for guiding chips in an orderly way without a tendency to tumble.

[0037] The inclined chip guiding portion 12 is finally followed by an inclined side 16 of the downwardly protruding apex 15 of the knife body 2. The inclination of the inclined side 16 is, as shown, preferably less steep than the corresponding chip guiding portion 12. The knife holder clamp 22 does preferably, as shown in FIG. 1, also comprise an inclined side 27 with an inclination corresponding to the corresponding inclined side 16 of the knife body 2. By this, it is rendered possible to keep the knife holder clamp 22 of the knife holder 20 out of the way from wood chips guided by inclined side 16 of the knife body 2 and thus to prolong the life of the knife holder 20.

[0038] A skilled person realizes that the above embodiments can be altered in various ways within the scope of the appendant claims as long as the most vital features of the invention, namely the wood attacking portion 7, the pressure release recess 8 and the chip guiding portion 12, are shaped and sized as indicated.