FI114297B - Increasing shearing resistance in disk chipper knife by surface hardening knife edge zone bordering chip exit side opening - Google Patents

Abstract

The edge zone (18) of the knife base surface bordering the knife side opening of the chip exit is surface hardened. The hardening is carried out as induction hardening to a depth of 2-3 mm. The hardening zone is to a width of 20 mm. The hardening is at least to hardness of 50 HRC. The knife base (2') is tempered and annealed to a hardness of about 300 HB and then machined to its nominal dimensions prior to surface hardening. Independent claims are also included for (a) a disk chipper.

Description

114297

METHOD TO INCREASE Abrasive Durability of a Blade Chipper and a Hedge Chopper

This invention relates to a method of increasing the abrasion resistance of a disc chuck blade base member, and to a corresponding disc chisel.

Disc chippers are commonly used in the forest industry to chop wood before further processing. The rotating disc of the chop is fitted with evenly spaced blades which chop against a solid counter blade from the logs. The chips are discharged through the chip opening through the disc which is located in the direction of rotation in front of the blade. The blade is generally secured to the disc by means of separate attachment pieces. The fasteners are fastened to the disc by screw connections, and the blade is locked between the fasteners by the clamping forces provided by the screw connections. The attachment piece between the blade and the disk, i.e., the base of the blade, partially defines the chip opening through the disk.

In the chipping process, the chips that are detached by the blade collide with the blade base in the chip opening, where they bounce and continue along the chip opening through the blade disc. Side of blade base exposed to chips / · '; heavy consumption. The material of the blade base must be of medium strength steel (hardness about 300HB) and sufficiently tough to prevent it from breaking into pieces in case of damage. However, such material does not have · *. · *: Sufficient abrasion resistance against the impact of chips.

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An attempt has been made to provide a solution to the abrasion problem, which comprises providing the tip of the blade base with a replaceable sharpened material made of wear-resistant material. This structure is described, for example, in U.S. Patent No. 5,765,452.

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As is evident from the said patent, the tip of the blade base is impaired: the ability to receive compressive forces when the actual blade base is made of a material with a relatively low yield point. As a result, it has now been sought to make the blade base as a single piece, as disclosed, for example, in U.S. Patent No. 5,765,452 to 114297. The abrasion resistance of the one-piece blade base on the surface adjacent to the chipping opening has been improved by the use of surface-worn parts. However, there have been problems with these. Weldability limits the hardness of the material used in the wear part, and compromises have to be made between attachment and wear resistance. Consumable parts fastened by other means have also encountered mounting problems.

In this connection, it should be noted that the problem area or part of the blade base is a very small area adjacent to the tip. Otherwise, the blade base must be of medium strength steel with the above-mentioned properties. This important particle or part that faces the chip stream must be very hard and well bonded to the actual blade substrate. The local hardness of the part may even exceed the hardness of the blade.

According to the invention, this object is achieved by the measures given in the appended claims 1.

In carrying out the invention, it is advantageous to use a steel with suitable properties in the blade base. The carbon content must be appropriate, ie 0.3 - 0.5 • ·: V%. The steel in question is quenched and passed to a hardness level of 300 HB. Then '. * ·· The blank has sufficient strength and toughness and is easy to machine.

After machining, a limited portion is surface hardened, preferably i 'as induction hardening. The hardened area is approximately 20 mm wide on the wear surface.

* <· * · '* The hardening depth is suitably 2-3 mm. In this case, the hard part of the blade base • · has a metal bond to the massive base. A hardness of at least 50HCR, even above 60HRC, is easily achieved. The above figures are for guidance only and, for example, good hardening can also be achieved with low carbon content and other alloying agents. The toughness of the induction hardened tip i can be improved by conducting a discharge at a temperature of, for example, 200-250 '·; * ° C.

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The invention and its details will be described in more detail below with reference to the accompanying drawings in which

Figure 1 illustrates a conventional blade chuck assembly and blade base,

Figure 2 shows the blade base with a sharp stop,

Figure 3 shows a cutting tool assembly with a modern disc chopper blade,

Figure 4a shows a blade base according to the invention and Figure 4b shows an alternative blade base.

Figure 1 shows a commonly used cutter assembly. The blade 1 is secured in place by pressing the blade with the blade base 2 against the wear plate 3. The blade base 2 is pressed against the blade 1 by means of a screw 5 supporting the blade disc 4. The concave surface 6 of the blade base against the blade 1 is made so that the blade base rests against the blade at positions 7 v; and 8, whereby the blade 1 receives the best possible support despite small manufacturing inaccuracies. In Figures 1 and 2, the arrows represent the forces exerted on the blade base by the other parts of the blade disc. In the figures, the concavity of the blade base against the blade of * »· · ·: ··: * inna 6 is emphasized to illustrate this. In the figure: **: repair of the surface 9 worn by the chips of the blade base is performed by the technique; by hard welding, or worn blade base is replaced.

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Hard welds need to be machined and due to their limited hardness, wear is relatively fast, which requires frequent replacement of the blade base * · «.

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The blade base 14 of Figure 2 is provided with a blade stop 10 which is secured to I · ·: ·. with screws 11 to the blade base. The> i »I t * t worn from the surface 12 encountered by the chips is replaced with a new one. However, the secure attachment of the blade stop to the blade base is difficult to accomplish and the problem is often the sufficient support of the blade 1 and the blade stop 10 114297 4 at the surface 13. Figure 2 also illustrates the forces exerted on the other parts of the blade disc by the arrows. On the surface 13 tends to tyssääntyä use of the blade 1 and the further steel terävasteeseen 10 and 14 against the direction of the arrow F of the blade base parallel to the chipping effect. If the surface 13 is inclined, the blade 1 is movable, whereby sticks and chips are allowed between the blade and the wear plate 3 and / or the blade stop 10. As a result, the wear of the sharpening blade is accelerated and the positioning of new blades becomes more difficult. In the blade base of Fig. 1, the stabilization occurs on the surface 8.

Fig. 3 shows a new type of cutter assembly with a tip angle α of less than 40 °. The blade T is fixed to the blade base 15 by means of a blade press 16 and screws 17. The small tip angle a improves the quality of the chips and reduces the chip and chip counts. Getting a blade base with a smaller tip angle to be sufficiently sturdy to support the blade is even more difficult. Thus, in the blade assembly of Fig. 3, it is particularly important that the blade base is formed by a uniform piece providing sufficient support and that undesirable strain on the surface 19 is avoided.

The blade base according to the invention is shown in Figures 3, 4a and 4b.

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Carbon content of about 0.3 to 0.5% is used to make a blade; a substrate blank which is quenched and released to a hardness level of 300 HB. Blank • i · *: Machined into blade substrate 2 '(Fig. 4a) and subjected to chipping wear: "i. Induction hardening 18. In Fig. 4a, Induction hardened region 18 has a width L of about 20 mm and a depth T of 2 to 3 mm. chassis 2 'solid body with sufficient toughness but still good abrasion resistance on the chipping side surface after the blade I * * .This hard chassis surface has a metal bond »to the massive base. Surface hardness over 50 HRC (= 500HB) is easily achieved At the same time, the yield strength of parts locally increases by about 70%.

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The above numerical values are only indicative and, for example, good hardening of the blade substrate material can also be achieved with low carbon content and other alloying materials. The toughness of the induction hardened tip can be improved by discharging at temperatures of, for example, 200 to 250 ° C.

The induction hardened tread 18 makes the blade base 2 'more abrasion resistant and more robust in supporting the blade against chipping forces. The tendency of the blade base to adjust is eliminated by the invention. If it is still desired to use a smaller replaceable wear member, i.e. a sharp stop 10, as shown in Fig. 4b, the induction hardening 18 'in the blade base 14' after the blade stop 10 will better support the blade stop 10. Also, the abrasion resistance of the blade base 14 'after the blade stop is improved.

The induction hardening 18 'is also shown in the turntable assembly in Fig. 3, whereby the surface 19 is well prevented and the support of the blade 1' is improved.

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Claims (7)

114297 6 A method for increasing the abrasion resistance and strength of the cutting aperture surface of a disc chopper blade (1 ') substrate body (2', 14 ', 15), characterized in that the surface aperture (18,18', 18 ") of the cutting aperture surface is hardened. ?. Method according to Claim 1, characterized in that the quenching is carried out by induction quenching. Method according to claim 1 or 2, characterized in that the hardening is carried out to a depth of about 2-3 mm. Method according to one of claims 1 to 3, characterized in that the tip strip is tempered to a width of about 20 mm. Method according to one of the preceding claims 1 to 4, characterized in that the surface hardening is carried out to a value of at least 50HRC. Method according to one of the preceding claims 1 to 5, characterized in that the material of the support body is steel having a carbon content in the range of 0.3 to 0.5% and that the support body is quenched and brought to a hardness level of about 300 HB and machined to its final dimensions. 7. A disc chopper, characterized in that it has a blade base (2, 14 ', 15) having a surface hardened tip strip (18,18', 18 "). • • • • • * • • • • • • • • • • • • • • • • • • • f42 · 114297 7