CHOPPING BLADE OF HARDENED STEEL, CHOPPING DRUM AND CHOPPING DRUM ASSEMBLY

Abstract

A chopping blade for cutting against a shear bar has a main body made of hardened steel. The blade body is formed with at least one cutting-edge region, a fastening region for fastening the blade to a carrier and in each case a transition region between the cutting-edge region and the fastening region. The main body bears a hard material coating in the cutting-edge region. The hardness of the main body is uniform throughout over all regions. A chopping drum carries a multiplicity of these chopping blades on its periphery and, upon rotation of the chopping drum, the chopping blades cut material upon running up against a stationary shear bar.

Claims

1. A chopping blade for cutting against a shear bar, the chopping blade comprising: a main body of hardened steel having at least one cutting edge bounding a cutting edge region, a fastening region, and a transition region between said cutting-edge region and said fastening region; a hard material coating in said cutting-edge region of said main body; and said main body having a uniform hardness of between 44 and 52 HRC throughout the entire said main body with said cutting edge region, said transition region, and said fastening region, and said main body having the characteristics of having been heat treated for a time period of less than 5 minutes and at a temperature of above 900 C.

2. The chopping blade according to claim 1, wherein said main body has been heat treated for less than 2 minutes.

3. The chopping blade according to claim 1, wherein said main body has a microstructure formed by heat treatment and said microstructure of said main body is uniform over all said regions.

4. The chopping blade according to claim 4, wherein said microstructure of said main body is a martensitic or a bainitic heat treatment microstructure.

5. The chopping blade according to claim 1, wherein the hardness of said main body is uniform and has a uniform value between 46 and 50 HRC.

6. The chopping blade according to claim 5, wherein the hardness of said main body has a uniform value of substantially 48 HRC.

7. The chopping blade according to claim 1, wherein a thickness of said hard material layer varies over a length of said main body.

8. The chopping blade according to claim 7, wherein the thickness of said hard material layer varies within a range between a minimum thickness of 0.1 mm and a maximum thickness of 1 mm.

9. The chopping blade according to claim 8, wherein the thickness of said hard material layer varies within a range between a minimum thickness of 0.2 mm and a maximum thickness of 0.4 mm.

10. A chopping drum, comprising: a rotationally symmetrical carrier body mounted to a rotary shaft and having a periphery; and a plurality of chopping blades, each according to claim 1, mounted on said periphery of said carrier body and each being disposed to have a respective said cutting edge pointed in a common tangential direction.

11. A chopping drum assembly, comprising: a stationary shear bar; a rotationally symmetrical carrier body mounted to a rotary shaft and having a periphery; and a plurality of chopping blades, each according to claim 1, mounted on said periphery of said carrier body and each being disposed to have a respective said cutting edge pointed in a common tangential direction and aligned so that, upon rotation of the chopping drum about said rotary shaft, said chopping blades run past said shear bar at a cutting gap and, in cooperation with said shear bar, cut material moving into said cutting gap.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0030] FIG. 1 is an elevation view of an exemplary chopping drum with several chopping blades fastened thereto;

[0031] FIG. 2 is a sectional and schematic view illustrating a blade and its corresponding hardness profile along its width, including that of a prior art blade and or a blade according to the invention; and

[0032] FIG. 3 is a partial diagrammatic view showing a chopping blade as it passes by a stationary shear bar in a chopping drum assembly.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a chopping drum 1 with a rotary shaft 2. A plurality of chopping blades 3 are attached to the peripheral wall about the circumference of the drum 1. The blades have cutting edges that are all pointing in the same forward direction, here referred to as a common tangential direction. A variety of different blade forms are possible, such as flat blades, blades bent about their longitudinal axis or coiled blades. Also, they may be provided in an extremely wide variety of lengths and they may be arranged parallel or inclined with respect to the axis of rotation of the drum in an extremely wide variety of patterns, such as oriented or offset in relation to one another. In the exemplary drum, provision is made of two rows of blades alongside one another, the blades 3 each being inclined with respect to the axis of rotation and each row of blades being inclined in a different direction with respect to the axis of rotation. The blades 3 are fastened to the drum by way of screws 4, as is indicated on a respective blade 3 of each row of blades.

[0034] FIG. 2 is a sectional view of a flat chopping blade 3. The chopping blade has a main body with three regions along its width, namely, a cutting-edge region 5, a transition region 6 and a fastening region 7. In the cutting-edge region 5, that side of the main body of the blade 3 which lies opposite the oblique side bears a hard material layer 8 extending along the cutting edge 9. In use, the main body becomes worn more quickly by the cut material in the cutting-edge region 5 than the hard material layer 8, giving rise to a self-sharpening effect, as indicated by a dashed line. In the fastening region 7, the main body of the blade 3 has an opening serving for the passage of one of the fastening screws (shown in FIG. 1). The latter may screwed, for example, directly into a thread in a blade carrier of the chopping drum. On the side of the screw head, provision can be made of a pressure plate for distributing the clamping forces which act here, in addition to impact loads, on the main body. The transition region 6 lies between the cutting-edge region 5 and the fastening region 7 of the main body, belongs to the blade projection and can be exposed to high bending and impact loads.

[0035] The graph shows the hardness profile over the width of a chopping blade of the prior art (curve X=prior art) and over the width of a chopping blade according to the invention (curve Y). In the cutting-edge region, the main body of the blade of the prior art (curve X) has a hardness A, for example, 55 HRC, which drops in the transition region and, after a drop in hardness to approximately a natural hardness D of the main body, such as, for example 30 HRC, changes into a hardness C, for example 40 HRC, in the fastening region.

[0036] The different hardnesses are achieved by conventional heat treatment processes and are reflected in different heat treatment microstructures, as a result of which different coefficients of volume expansion also arise in the various regions, leading to residual stresses.

[0037] In the case of the main body of the blade of the present invention, by contrast, the hardness and preferably also the heat treatment microstructure is uniformly at value B, such as, for example, 48 HRC, over the entire width. That is, the hardness is constant from the cutting edge 9 as far as the end of the fastening region 7 remote from the cutting edge 9, and therefore no residual stresses can arise and also the production is facilitated. Given a suitable choice of the uniform hardness B, excessive wear cannot be observed in the cutting-edge region and also damage caused by bending, impact or clamping forces does not occur in the transition region and in the fastening region.

[0038] FIG. 3 is a schematic showing the interaction between a chopping blade 3, which is mounted on a chopping drum 1, and a stationary shear bar 10 during a cutting process. The material 11 to be cut, for example harvest material such a straw, corn stalk, maize, sugar cane, and the like, is pushed in the direction of the arrow 12 towards a cutting edge 14 of the shear bar 10. As the cutting edge of the blade 3 moves in the direction of the arrow 13 past the cutting edge 14, the material 11 is cut by the interaction between the blade 3 and the shear bar 10. This process results in very high forces that act on the chopping blade 3 (and also the shear bar or counter-blade 10), requiring the blade 3 to have superior hardness.