Patent Application
20160073581
This invention generally relates to a laser clad knife guard for a sickle bar assembly.
Knife guards are used in sickle style cutting systems. They act as the stationary surface for moving sickle blades to cut against or at least to protect or cover the sickle blades. Examples are shown in U.S. Pat. Nos. 6,962,040, 4,660,361, 7,478,522, and 8,464,506 the disclosures of which are incorporated by reference as the present invention may be applied and/or incorporated into these examples in various embodiments.
Knife guards are primarily constructed of steel and manufactured in a variety of ways including forging, casting, welded fabrication of stamped components, and machining. In some instances, a hardened plate is assembled into the guard to create a surface known as a ledger plate that the sickle runs on and the edge. Past efforts to improve the hardness of the shearing surfaces of the ledger plate have not met with the desired cutting efficiency or wear characteristics which in turn have resulted in increased costs in both harvesting and equipment repair and or replacement. Past efforts to improve the hardness of the ledger plate and in turn the ledger bars and shearing edges have included hardening via quench and temper or austemper, carbonizing or carbonitriding, induction hardening, flame hardening, or boronizing. In some cases, more than one of these treatments is performed on the part in order to impart varying properties within the knife guard.
With the exception of induction hardening, the remaining treatments are high heat processes of over 1500° F. and require the entire part to be raised into these temperature ranges. The knife guard in its original state contains internal stresses. Accordingly, distortion of the part is a factor with these processes. Distortion is not desirable where the knife guard provides a bearing surface supporting sliding movement and reciprocation of a sickle bar. The result is often additional machining or straightening processes to bring the part back within specification. These additional steps increase cost.
In the case of induction hardening, typically very elaborate induction coils and quenching processes are required to perform the process in a repeatable and predictable manner. Induction heat is a resistance type of heating. The result of this process along with flame hardening a heat affected zone which is driven deep into the part. In order to achieve the desired microstructure in knife guard material, a quench process must be used to reduce the internal temperature of the knife guard quickly enough to create the proper metallurgical transformation. In addition, the induction process focuses the energy in the thinner section of the knife guard edge resulting in the risk of melting the material at the edge. The depth of the heat affected zone also creates a similar situation to the previously mentioned treatments in that it causes stresses in the part to be relieved often resulting in distortion of the part.
The present invention is generally directed towards cladding the knife guard in one or more select regions. Cladding may be deposited on an entire top surface of a ledger bar to improve the wear characteristics of the ledger bar. Additionally or alternatively, the cladding may be deposited along flank surfaces of each tine so as to laterally extend the flank surfaces, provide a top flank surface that extends the ledger surface and provides a hardened shearing edge so as to maintain the sharpness of the shearing edges of the knife guard.
In one aspect, the invention provides for a knife guard that comprises a guard body that further comprises a base material. The base material includes a mounting bar that defines at least one bolt hole and at least one tine projecting forward from the mounting bar. The base material has a first hardness. A clad material is deposited on the base material. The clad material is of a second hardness greater than the first hardness.
In an embodiment the knife guard may include a ledger surface that is adapted to bear against or at least face a sickle bar assembly. The ledger surface may include a region of the clad material formed integrally with an outer surface of the base material.
In another embodiment, the base material base material may be steel. The clad material may be at least 0.1 millimeter in maximum depth thickness along the base material and less than 3 millimeters. The depth measured in the direction of deposition.
Each of the tines may include a central protrusion and a pair of flank surfaces on either side of the central protrusion that extend toward a bearing surface. The flank surfaces may intersect the bearing surface at a shearing edge. The region of clad material may include at least one portion formed along and extending the flanks laterally so as to extend the ledger surface and form part of the shearing edge. The clad material may project horizontally outward from the base material to extend the flanks horizontally outward relative to the central protrusion.
The knife guard may further include a free region of base material that is not of the clad material. The free region being disposed above the central protrusion along the ledger surface and between first and second portions of clad material, the first and second portions being formed along the flanks so as along ledger surface and forming part of the shearing edge.
The knife guard may further include a trash bar that extends perpendicularly to an extension direction of the at least one tine and connects adjacent tines of the at least one tine. The free region may extend along the ledger surface and extending along a trash bar portion of the ledger surface defined by the trash bar. The trash bar is free of the clad material.
The knife guard may include a ledger bar that extends perpendicularly to an extension direction of the at least one tine, the ledger bar may define a ledger bar portion of the ledger surface. The ledger bar portion may form part of the region of clad material along a length and an entire top surface thereof.
Preferably, more than 30% of the ledger surface is free of the region of clad material.
The clad material on the flank surfaces of the knife guard may extend from the ledger surface at the shearing edge toward the central protrusion a width between 0.5 millimeter and 10 millimeter and may be between at least 0.1 millimeter and 3 millimeter in depth thickness on the flank surface. The depth may be perpendicular to the width.
The knife guard may further include a dilution zone wherein the clad material forms the dilution zone with the base material at a junction therebetween.
In an embodiment, over 85% of an outer surface of the knife guard may form an untreated region of base material. The clad material may be limited to less than 15% of the outer surface.
In another embodiment, the base material may have a hardness of less than 50 HRC and the clad material may have a hardness greater than 50 HRC.
In another embodiment, the at least one tine may comprise a plurality of tines with valleys between the tines. The at least one bolt hole may include a plurality of bolt holes that have respective bolt mounting centers aligned along a mounting axis that extends perpendicularly relative to a forward extending axis direction of the tines. The bolt holes may be formed in mounting bosses formed along the mounting bar. A connecting trashbar may extend perpendicularly relative to the forward extending axis direction and connect adjacent tines. The mounting bar may include a ledger bar. The ledger bar and the tines may define a ledger surface that extends in a plane. A sickle clearance channel may be formed between the ledger bar and the trash bar. Ribs at a bottom of the sickle clearance channel may connect the ledger bar and the trash bar.
The ledger bar may project from a mounting plate portion of the mounting bar and the mounting bosses may be formed into the mounting plate.
In an embodiment, each one of the pair of flank surfaces comprise a base flank surface and an extended flank surface. The extended flank surface extends laterally outward from the base flank surface relative to the central protrusion. The extended flank surface is comprised of the clad material.
Each extended flank surface includes a top extended flank surface that is coplanar with and forms part of the ledger surface.
Each of the top extended flank surfaces intersects with the extended flank surfaces at the ledger surface to form part of the shearing edge.
In an embodiment, the extended flank surface may extend from the ledger surface of each tine toward the central protrusion a depth between 0.5 and 10 millimeters. The extended flank surfaces may extend outwardly away from the base flank material and laterally away from the central protrusion to provide and extended flank surface depth between 0.1 and 3 millimeters but typically less than a millimeter.
In an embodiment, greater than 50% of each of the flank surface may be free of clad material.
In an embodiment, greater than 50% of each ledger surface may be free of clad material.
In another aspect, the invention provides a cutter bar assembly that includes a linear array of a plurality of the knife guards. The cutter bar assembly may include a cutter bar support that may have a mounting flange that extends in parallel relation to the linear array. The sickle bar assembly may extend in a longitudinal direction in parallel relation with the cutter bar support in order to reciprocate back and forth in the longitudinal direction for cutting. T sickle bar assembly may include a sickle bar and a plurality of sickle knives mounted to the sickle bar. The knife guards may be arranged in side by side relation and the sickle knives may be arranged in side by side relation. The knife guards and the sickle knives may be in vertically overlapping relation.
The sickle bar may slide along the knife guards along a region of clad material formed on an outer surface of the base material.
In yet another aspect, the invention provides a method of forming a knife guard. The knife guard comprises a guard body. The guard body may be comprised of a base material and may include a mounting bar that defines at least one bolt hole and at least one tine projecting forward from the mounting bar.
The method may include cladding with a laser a region of a second material on to the base material to provide a second hardness greater than the first hardness.
The cladding with the laser may include using at least one of the following lasers CO2, YAG, Diode and Fiber.
The cladding may include targeting and confining the application of the laser to the region being of an outer surface of the guard body. The region may be less than 15% of an area of the outer surface.
The region is deposited along a perimeter of the ledger surface at the shearing edges to form a sliding interface with a sickle bar assembly that reciprocates relative the knife guard in use.
At least 30% of the ledger surface may include an untreated region free of cladding and wherein distortion may be eliminated or reduced such that subsequent machining or straightening operations are not conducted on the ledger surface after the cladding.
In an embodiment the region is deposited horizontally along opposing sides of the base material of the at least one tine, thereby forming a shearing edge with the second material.
Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.
As shown in
The knife guard 10 includes a ledger surface 28 that is adapted to bear against or at least face a sickle bar assembly 30. Typically the ledger surface 28 will come into contact with the sickle bar assembly 30 to guide or maintain linear reciprocating movement of the sickle bar assembly 30.
Turning to
In an embodiment, the extend flank surface 31 may be of a width between 0.5 and 10 millimeters. In a preferred embodiment the depth may be between 2.5 and 6 millimeters, and in a more preferred embodiment between 4 and 5 millimeters.
Further, the cladding 24 deposited along the base flank surfaces 29 provides a top extended flank surface 35 on each side of the tine 20. The top extended flank surfaces 35 are coplanar with the ledger surface 28 and thus extend not only the flanks 34 but also the bearing surface 28 of the tines 20. In an embodiment a thickness 46 of cladding 24 provides for a maximum cladding depth 46 that extends outwardly from the base flank 29 to the extended flank surface 31 between 0.1 millimeters to 3 millimeters. In a more preferred embodiment the cladding width along the extended top surface may be between 0.1 and 1 millimeters.
Further, where the top extended flank surface 35 meets the extended flank surface 31 a shearing edge 38 is formed. Thus, the shearing edge 38 is comprised of the cladding 24. Accordingly, the cladding 24 provides the material of the second hardness that comprises the shearing edge 38. The hard shearing edge 38 provides the advantage of decreased wear when cutting crop and thus increased efficiency and lower overall costs with improved life of the tine 20. Further, because the cladding 24 also extends the ledger surface 28 of the tine 20 the shearing edges 38 of the ledger surface 28 wear more slowly when the sickle knives 78 (
Turning briefly to
Laser cladding technology is utilized to deposit the cladding along the flanks 34 and the ledger bar 80 as schematically illustrated in
Thus, dilution zones 57 are present at the base flank surface 29 as shown in
The hard/wear resistant laser clad material 24 referred to in various embodiments of the invention is material composed of a medium to high percentage of hard particles. These hard particles can be: Tungsten Carbide, Titanium Carbide, Chrome Carbide, Iron Carbide, Diamond, Ceramics, or any other high hardness particles in the range of HV 1200-2500 (Vickers scale hardness). The high hardness particles are then bonded and held in place to the base material through the metallurgical bond. In the alternative to carbides, powders of various metal alloys or other amorphous materials may be laser clad according to the present invention. Carbide alternatives as envisioned or discloses in U.S. Pat. No. 6,887,586 or U.S. RE 29,989 (see also U.S. Pat. No. 3,871,836), the entire teachings and disclosures of which are incorporated herein by reference.
The knife guard 10 may further comprise a free region 42 of base material 14 that is not a cladding. As illustrated in
The mounting bar 16 includes a ledger bar 80 that extends perpendicularly to an extension direction 56 of the at least one tine 20. The ledger bar 80 defines a ledger bar portion 80a of the ledger surface 28 wherein the ledger bar portion 80a forms part of the region of cladding 24 along the length thereof. More than 30% of the overall ledger surface 28 may be free of the region of cladding 24. Not every embodiment of a cladded guard 10 has a ledger bar 80 and thus would not have a ledger bar portion 80a that would be part of the cladding 24 or form part of ledger surface 28.
Over 85% of the outer surface of the knife guard 10 may form an uncladded region of base material 14. The clad material 24 may be limited to less than 15% of the outer surface of the knife guard 10, and often substantially less.
In an embodiment, the base material 14 may have a hardness of less than 50 HRC and the clad material 24 may have a hardness greater than 50 HRC. In a more preferred embodiment the clad material 24 may have a hardeness greater than 60 HRC. Some embodiments may be even greater than 70 HRC. The clad material has a hardness at least 5 HRC points higher than the base material and typically 10 HRC points or more, higher than the same base material.
The at least one tine 20 may comprise plurality of tines 20 with, as shown for example in
An embodiment of the present invention showing two portions of tines 20 is shown in
The laser used to harden the base material 14 may include using at least one of the following lasers; CO2, YAG, Diode and fiber. The laser beam consists of a column of light energy of similar wave length. These different types of lasers produce different wave lengths of light. These lasers each have their own unique characteristics, but all work well in heat treating applications.
The method of using the laser to laser harden the knife guard 10 has the advantage over other processes currently in use of involving a smaller heat effected zone that is created with the laser. The smaller heat affected zone results in less distortion of the part and minimal disruption to the microstructure of the base part, which allows better material properties in the base part after laser hardening.
The lower distortion eliminates subsequent machining and/or straightening operations, thus reducing processing time and costs. The process of heat treating the base material 14 for strength and toughness, then machining the surface (if necessary) for the section to ride on, then laser hardening can be performed easily. This process of hardening the edge after heat treat is difficult to perform without distortion or the risk of melting the edge material.
A laser tool 94 may make an angular approach to clad along the flank surfaces 34 and the ledger bar 80.
All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
This patent application is a continuation of co-pending PCT Application No. PCT/US2015/018059, filed Feb. 27, 2015, which claims the benefit of U.S. Provisional Patent Application No. 62/050,687, filed Sep. 15, 2014, and U.S. Provisional Patent Application No. 62/050,880, filed Sep. 16, 2014, the entire teachings and disclosure of which are incorporated herein by reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 62050687 | Sep 2014 | US | |
| 62050880 | Sep 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2015/018059 | Feb 2015 | US |
| Child | 14854851 | US |
