Disk for farm use, particularly used for field plowing

Translation of description of equivalent WO 2009133293 A2

p0001agricultural use disk, including disk used for making plowing

p0002The present invention relates to a drive for agricultural use, in particular a disc used for preparing the soil.

p0003To prepare the ground by limiting erosion, it is known to use replacement Disk plows. The discs are mounted on a frame for come up to the back of a tractor or the like. The discs may be flat but also have a concavity, are in working position, substantially vertical, inclined optionally ed, and can pivot about a substantially horizontal axis. Several drives can be mounted securely on a pivot shaft relative to the frame or every disc can be pivoted independent from the bearings. CD penetrate the soil at their periphery and thus make it possible to work the upper layer of soil. The shape of the periphery of the disc and the general shape of the disk are adapted to the soil type and the type of work involved. There are thus flat disks, concave, wavy, etc. and the periphery is either circular or toothed or lobed, or .... Such disks then are mainly used for work such eg plowing a stubble plowing or sowing.

p0004The known prior art discs have a central portion which serves for fixing to the chassis and a peripheral portion which is intended to penetrate the ground. The discs are made very often in a steel alloy. This steel is heat treated to harden it so as to limit wear of the disk, in particular at its periphery. The hardness of the disk is limited to not make the brittle disk and avoid ruptures between the central fastening portion and the periphery working the soil. Thus, the known prior art discs generally have a hardness between 49 and 53 HRC (Rockwell hardness degrees), this hardness being homogeneous in the disc. A hardness of 49 ° HRC is approximately 1600 MPa (or 160 kg / mm²) And a hardness of 52 ° HRC corresponding to about 1750 MPa (or 175 kg / mm²) (There is no exact correspondence between the hardness measurements in the international system and the Rockwell hardness). US-4 305.272 discloses a disk for agricultural use which has an outer edge of greater hardness than the central portion of the disc. This difference of hardness is obtained by a differential heat treatment in which a conductive annular part of the heat is disposed at the periphery of the disc. The process embodiment described herein is difficult to implement industrially and knowledge of the Depositor, no disk as described in this document has been marketed. It can only concern of thin steel disks. In addition, the disk made only exhibits increased hardness than at its periphery. The present invention aims to provide a disc which, compared to prior art discs, wears less rapidly without being however more brittle and has enhanced characteristics so as to include extending its lifetime. Preferably, the present invention may be implemented on disk of substantial thickness (beyond 4 mm for example). To this end, the present invention provides a metal disc in particular for agricultural use, comprising a ductile central portion including fixing the disk to a frame and an outer peripheral portion intended especially for the soil-working and having a hardness greater than that of the central portion. According to the present invention, the disk further has a transition region between the central portion and the peripheral portion, which has a hardness gradient in a radial direction and at least in the central part, a hardness gradient will exist in the thickness of the disc.

p0005The peripheral portion of high hardness can increase the wear resistance of the disk. Ductile central portion and the transition zone allow for their part to ensure sufficient flexure to the disc to enable it to undergo significant stress without breaking. In addition, through the hardness gradient in the disc thickness at least in the central part, it is possible to have in the disc thickness varying hardness. For example there may be at mid-thickness disk of a high hardness region and a surface region forming a ductile skin of lesser hardness. It is also conceivable for example that one face of the disc has a hardness greater than the other side of the disc with a hardness gradient extending from one face to the other in the thickness thereof. In a disc according to the invention, the difference in hardness between the central portion and the peripheral portion is preferably at least 20 kg / mm². This difference in hardness between the peripheral part and the central part of the disc increases significantly the performance of the disk according to the invention compared with those of a similar disk uniform hardness.

p0006To promote resistance to wear, the hardness of the peripheral part is preferably at least 1900 MPa (or 190 kg / mm²). The hardness of the central portion is in turn advantageously between 1500 and 1700 MPa (or between 150 and 170 kg / mm²) To allow sufficient bending of the disc the stresses to which it may be subjected and high resistance to fatigue and deformation.

p0007A disc according to the invention may for example be made of a steel alloy doped with boron and containing manganese, chromium and silicon.

p0008Such an alloy allows, by heat treatment, to obtain the hardnesses proposed above. This alloy preferably comprises between 0.35 and 0.42% carbon and / or less than 0.16% chromium.

p0009In a disc according to the invention, the change in hardness in the thickness of the disc in an area with a hardness gradient in the thickness can be between 2 and 15 kg / mm² for example. This hardness gradient in the thickness of the disc is preferably present both in the central part of the disc and in the transition zone.

p0010In one embodiment, a disk according to the invention has a planar central area used for fastening on a frame and surrounded by a concave zone. In this embodiment, the ductile central portion advantageously extends beyond the plane central area. In this way, a ductile zone surrounds the portion of the disc intended to be fastened to a frame and to be fixed thereof.

p0011Disclosed all sizes and all forms of agricultural use discs. However, the present invention is more particularly suited to discs with a diameter of between 400 and 1100 mm and / or disks that are greater than 3 mm, preferably greater than 4 mm.

p0012The present invention also provides a method of manufacturing a disk as described above, the method comprising the steps of: - Production of a blank by cutting a steel sheet,

p0013- Realization of a fixing zone in the center of the blank by punching,

p0014- Eventual drawing of the blank, - heat treatment of the part thus obtained by quenching operation with water or the polymer, and

p0015- Income variable temperature, such income may be achieved using induction heating means.

p0016Income is achieved by heating the room. This income is variable temperature since it is not uniformly heats the room and the temperature reached varies from one zone to another of the room as well as in the thickness of the workpiece. The use of induction heating means possible to control the heating and thus the temperature in the room. It happens in this way to achieve variations in hardness in the disk obtained by the method according to the present invention.

p0017Details and advantages of the present invention become apparent from the following description with reference to the accompanying schematic drawings in which:

p0018Figure 1 is a top view of one embodiment of a disc according to the invention, and

p0019Figure 2 is a sectional view along II-II section line of Figure 1 of the illustrated disc.

p0020The drawings show a disc for use in agriculture with a flat bottom according to the invention. The external shape of this disk is identical to that of a flat-bottomed disc of the prior art. This is a metal disc in the form of a spherical cap with a flat base 2. The latter is at the center of the spherical cap and has a diameter D. There are agricultural use discs having a different form from the form shown in the drawings.

p0021The present invention may also relate these different forms of discs that can be used especially for plowing, seeding and / or stubble operations.

p0022The flat base 2 has at its center a bore 4 for fixing this record on a frame (not shown). The free edge of the disc, corresponding to the periphery of the disc 6 has a bevel used for tillage to chop such as crop residues.

p0023In the embodiment shown in the drawings, the disc has an axis of symmetry which is also here a revolution axis 8. Between the wedge 6 and the flat bottom 2, the disc has a radius of curvature R and a thickness E. purely as a guide, the E value may vary between 3.5 and 8 mm. Disc height is designated F: it is measured along the axis of revolution 8.

p0024According to the present invention, the disc shown has a hardness which varies on the one hand according to the distance to the axis of revolution 8 and on the other hand, as explained below, a hardness gradient will exist in the thickness E of the disk in some areas. then carried out firstly a radial hardness gradient (change in hardness with respect to the axis of revolution 8) and then a transverse hardness gradient -or in the thickness of the disk-.

p0025This disc has radial as well as the hardness gradient two separate parts of hardnesses and a transition zone. This recognizes in Figure 1 a central portion 10 and a peripheral portion 12 separated by the transition zone 14. Mixed lines illustrate in Figure 1 the separations between each of the parts 10 and 12 and the transition region 14. The gradient transverse hardness respect, in the embodiment described, the central portion 10 and the transition zone 14.

p0026The central portion 10 is a ductile zone and the peripheral portion 12 has a greater hardness than the central portion 10. The transition region 14 has in turn a radial hardness gradient and a transverse hardness gradient. The central portion 10 serves in particular for fixing the disk to a frame. Note that in the embodiment of the drawings that the central portion 10 extends beyond the flat base 2. The diameter of the central portion 10 is for example between D + and D + 75 mm 120 mm.

p0027The hardness of the central portion 10 is for example between 1550 and 1650 MPa (or from 155 kg / mm² and 165 kg / mm²) On the surface of the disc. This hardness is substantially constant but may eventually evolve slightly increases from its center to the transition zone 14.

p0028In this central part 10, the hardness varies in the thickness of the disc. for example one can have a greater hardness of heart the thickness of the disc and lower at the surface of the disc. The change in hardness between the heart of the thickness of the disc and the disc surface is for example between 20 and 150 MPa (or between 2 and 15 kg / mm²), Preferably between 30 and 80 MPa (or between 3 and 8 kg / mm²). In this first example, while there are two hardness gradients: one from the heart of the disc thickness to each of the disk surfaces. This first variant is for example adapted to a flat disk (having no concavity contrary to the disk shown in the drawings), the two faces may have to work in flexion. According to another example, the hardness varies from one face to the other of the disc: then we have a single transverse hardness gradient from one surface to the other disc. Variations in hardness from one face to the other are the same as those indicated for the first example, that is to say, they are between 20 and 150 MPa (or between 2 and 15 kg / mm²), Preferably between 30 and 80 MPa (or between 3 and 8 kg / mm²).

p0029Changes in hardness in the thickness of the disc depend on how the drive should work. The face of the disc at the central part which undergoes maximum bending stress is the more ductile with the least élevée- hardness value. Also, this is where the disc works mainly in compression which will be chosen to have the highest hardness.

p0030In the peripheral part 12, the hardness is itself for example between 2000 and 2100 MPa (or 200 kg / mm² and 210 kg / mm²). It is preferably at maximum level bevel 6. The width of the peripheral portion 12, which is annular in shape, is generally between 50 and 300 mm. The hardness does not vary, or very little, in the thickness of the disc at this peripheral portion 12.

p0031In the transition zone 14, the hardness varies, for example substantially linearly, since the hardness value outside of the central portion 10 to the hardness value within the peripheral portion 12. In the example Digital given above by way of example, the hardness increases from about 1600 MPa (or 160 kg / mm²) To 2000 MPa (or 200 kg / mm²). This transition zone has for example a width of the order of several centimeters, depending on the outer diameter of the disc.

p0032Included in this transition region 14 a transverse hardness gradient similar to that described for the central part 10. If the portion Central 10 hardness is greater at the heart of the disc thickness, the hardness in the transition zone 14 is also greater at the heart of the disc thickness. If one side of the central portion 10 is harder than the opposite side, one will find a similar transverse hardness gradient in the transition zone 14.

p0033Most of the known prior art discs have a homogeneous hardness. This is usually in the order of 1600 MPa (or 160 kg / mm²), Which corresponds to approximately 49 ° HRC. With respect to such a disk of the prior art, a disk according to the present invention exhibits a very substantial improvement of both the wear resistance and the mechanical strength (fatigue). Of the tests were used to measure resistance to wear and mechanical stress every time three times greater than the resistance of a disc of the same dimensions of the prior art.

p0034A disc according to the invention is made of steel. The carbon concentration (C) is preferably between 0.35 and 0.42%. This steel is preferably a doped boron steel further comprising manganese, chromium and silicon. The chromium content (Cr) is in turn preferably less than 0.20%, preferably less than 0.16%.

p0035For a variable hardness on the surface of the disk, there are several manufacturing processes. A preferred method is described below. According to this method, the disc is made first of all from a steel (as defined above for example) in the form of a sheet or from a coil. A first cutting operation provides a blank. By punching, the central securing element is formed. This item allows connection to a chassis. By punching, the bore 4 is made, for example. Other embodiments may be envisaged here. Instead of a central bore, several bores may be provided. Next, a bevel blank is produced in the periphery. Here too, the shape of the desired disk, it is possible for example to produce slots and / or other forms at the periphery of the disc. A drawing, for example using heat, allows to give the blank a concave shape.

p0036Finally, a heat treatment is performed. This treatment can give hardness to drive. This is a water quench or to the polymer. The part obtained is then of great hardness. For a central part 10 ductile, a tempering is performed by adopting the tempering temperature according to the disc area. This income then provides a lower hardness at the center and in the transition area 14 between the central portion 10 and the peripheral portion 12 which has a radial hardness gradient and possibly cross. To achieve this there is provided a heating of the workpiece by controlling the temperature in the various zones of the disc. The central part 10 will thus be more heated than the peripheral part 12. The latter may also undergoes income to achieve a stress relieving to remove quenching stresses. A change in hardness may optionally be observed during this operation back to the level of the peripheral zone 12.

p0037By performing this income using induction heating means, it is possible to achieve on the one hand the radial hardness gradient by proper positioning of the heating means and possibly providing cooling means for certain areas and Moreover the transverse hardness gradient described above for example by acting on the frequency of the current used.

p0038A preferred embodiment of the method of the invention provides an income of all the disk but it is not beyond the scope of the invention by not providing a revenue of the central part 10 and possibly also the transition zone 14 . the induction heating means to realize income from variable temperature disc with good control of the heating of the disk as a function of radial position considered only in the thickness of the disc. This control of the heating zones is used to control the variations in hardness in the disk as well as regards the radial hardness gradient that the transverse hardness gradient.

p0039A disk according to the invention thus has on its periphery a portion with a high hardness which is very resistant to wear. This part of the disk is intended to come into contact with the ground work and impinges any type of objects on the ground, and in particular stones.

p0040In the center, the drive is attached to a frame. This attachment is similar to a recess and there is little mechanical stress inside this attachment. The mechanical stresses, including bending, appear in the part of the disc between its fastening and its active part is located in the soil. With the transverse hardness gradient achieved in the central part (and possibly also in the transition zone), a disk according to the invention also has better resistance to flex fatigue and deformation amplitudes, that is, say by fixing the center of the disc by applying repeatedly a bending load to the disc periphery. For discs of a similar size, a disk according to the invention will have a substantially greater resistance (up to three times) that of the prior art disc having a uniform hardness.

p0041The present invention therefore allows to obtain both a greater hardness and better resistance to fatigue and allows a greater deformation of the disc. These characteristics that seemed far antagonists could be obtained on a disc with the present invention.

p0042The present invention also has the advantage of adapting to all types of discs: flat discs, curved, tapered, flat or disc coulters having undulations. The center of the disc may be flat, curved, embossed The periphery of the disk can be circular, toothed, crenellated lobed

p0043The invention can be adapted to all disk size but appear to the skilled person that it is more advantageous for disks large diameter intended to undergo major constraints for small drives. The invention is thus particularly, but not exclusively, adapted to the discs whose diameter is greater than 40 or 50 cm and to discs having a thickness greater than 3.5 or 4mm. The present invention is not limited to the preferred embodiment described above by way of nonlimiting example and the method of embodiment described. It also relates to all variants within the scope of the art in the context of the following claims.