Not Applicable
1. Field of the Invention
This invention relates to a cutting knife, for example, a cutting knife used for agricultural mixers. Additionally, this invention relates to a method of manufacture of a cutting knife with inserts. In one embodiment, the present invention is directed to a knife used in a vertical-type feed mixer.
2. Discussion of the Background
Agricultural mixers are used for mixing hay and silage together with other nutrients including animal feed supplements and grains. These feed materials are then discharged and fed to various livestock such as cattle and dairy cows. Sometimes the mixing of such feed includes depositing a whole round hay bale into the mixer and processing to the desired consistency before and during the mixing of the other feed ingredients.
In known feed mixers there are many different configurations including horizontal augers, reel type arrangements, and vertical augers. Each of these arrangements utilizes one or more augers with cutting knives or blades to facilitate the processing of long stemmed materials such as hay or other forages.
Known cutting knives typically include a steel plate, which is profiled into various sizes and shapes and sharpened to create a cutting edge, and designed to be attached to the moving auger or other mixing means. In some cases these cutting knives are attached to a stationary surface inside the mixer, and the material is moved across the cutting edges. In the process of mixing the feed materials, long stemmed hay and forages are forced across the sharpened surfaces of the knives, cutting the material into shorter sections which is more desirable for the livestock to eat.
The sharpened cutting surfaces of the knives can wear quickly, and thus many designs and methods have been attempted to attain a knife that maintains a sharp edge for a long period of time without being brittle. One such method is a simple heat-treating of the steel surface to increase the hardness and thus the durability and strength thereof. Another method is to add an abrasion resistant material to the knife. The abrasion resistant material is fused at high temperature to the cutting edge, then heat-treated for strength. The abrasion resistant material is more durable than the base material, so the knife tends to maintain a sharp edge as the base material wears. Another method is to heat-treat the knife, then cement (braze) carbide inserts onto the leading edge. However, this method results in a loss of beneficial properties of the heat-treatment in areas that are re-heated during the cementing process. One disadvantage of conventional heat-treated knives is that the sharpened edges become dull quickly, despite the hardened edge created by the heat-treatment.
One disadvantage of a knife with the abrasion resistant material is that the heat-treating on the base material must be such that the base material wears faster than the abrasion treated edge. This often requires that a backer plate be added directly behind the base plate for added strength.
A conventional type of knife is a knife with stepped teeth, which includes an insert cemented on two edges. One disadvantage of knives with stepped teeth and carbide inserts is that the abrasion resistance of the knife body is compromised when the carbide is cemented into position because the benefit of heat-treatment in the area of the inserts is somewhat nullified by the high temperature required for brazing.
A disadvantage of knives with stepped teeth and carbide inserts is that the carbide, which can be expensive, is normally present in the full length of the steps because the steps are designed as the mounting surface for the carbide and do not have a sharp edge themselves.
Another disadvantage of knives with stepped teeth and carbide inserts is that since the ends of the carbide inserts are normally perpendicular to the cutting edges, they do not fit tightly into the acute or obtuse angle of the steps if the leading edge are curved.
Another disadvantage of typical knives with stepped teeth and carbide inserts is that the carbide can only be cemented on two edges, leaving one end vulnerable to impact and damage.
Accordingly, it is an objective of an exemplary embodiment of the present invention to provide a cutting knife which overcomes some or all of the problems associated with known devices and makes a considerable contribution to the art of mixing materials.
Other objects and advantages of exemplary embodiments of the present invention are one or more of the following:
Accordingly, one aspect of the present invention includes a knife assembly with a knife plate including a leading edge. This aspect of the present invention can further include a cutting element cemented to the leading edge with brazing material via a brazing process. The knife plate can be heat-treated after the addition of the cutting element so as to form a heat-treatment area on the leading edge. Furthermore, the heat-treatment area can be substantially unaffected by the brazing process.
Another aspect of the present invention includes a knife assembly including a knife plate with a leading edge and a cutting element cemented to the leading edge via a brazing process.
Another aspect of the present invention includes a method of manufacturing a knife assembly including; forming a leading edge on a side of a knife plate comprising a first material, forming a slot in the leading edge, inserting, into the slot, an insert comprising a second material different from the first material, brazing the insert to the knife plate with a brazing material after the insert is inserted into the slot, and heat-treating at least a portion of the knife plate after the brazing. A hardness of the portion of the knife plate after heat-treating can be different than a hardness of the portion of the knife plate before the heat-treating.
These and other advantages of the invention will become more apparent and more readily appreciated from the following detailed description of the exemplary embodiments of the invention taken in conjunction with the accompanying drawings, where;
The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. With reference to
In the exemplary embodiment of
The leading edge 22 is sharpened to form sharpened faces 40 which can be scallop-shaped. Each sharpened face 40 typically has a lower edge 42, an upper edge 44, a back edge 46, and a front edge 48. At the intersection of the lower edge 42 and the front edge 48 is a leading corner 50. These leading corners 50 create a repeating pattern 56 of sharpened faces 40, which can be measured by a pattern length 54. It is to be understood that the sharpened faces could also be manufactured using a plurality of straight cuts at various angles, to form the basic curved shape. The sharpened faces could also be made with a series of straight cut steps. It is not necessary that the pattern length be constant over the entire length of the knife 10, changes in the pattern length are possible. For example, it is possible for the size of the sharpened faces 40 to increase or decrease as they progress from the heel edge 28 to the toe edge 30.
In order to increase the life of the leading edge 22, cutting elements 60 may be utilized. The cutting element 60 is generally triangular in cross section, or wedge shaped. However any other shape with a forward cutting edge may be used. The cutting elements of
In order to adequately mount the cutting element 60 into the plate 20, a plurality of slots 80 are created in the leading edge 22. Each slot 80 can have several relatively flat faces, including a slot back face 82, a slot front face 84 which is towards the toe edge 30 of the plate 20, and a slot rear face 86 which is towards the heel edge 28 of the plate 20. If the shape of the cutting elements 60 is different from that shown, the shape of the slots 80 will correspond, match, or approximate the shape of the cutting elements 60. The distance between the slot front face 84 and the slot rear face 86 define a slot length 88. The cutting elements 60 are preferably cemented into place at all three mating surfaces (or at whatever surface of the slot 80 is configured to mate with the cutting element 60), with the rear end surface 66 of the cutting element 60 adjacent to the slot back face 82 of the slot 80, the front end surface 68 of the cutting element 60 adjacent to the slot front face 84 of the slot 80, and the rear end surface 70 of the cutting element 60 adjacent to the slot rear face 86 of the slot 80. The ability to firmly cement all three of the mating surfaces gives the cutting element 60 a firm base for attachment. Moreover, if each of the three mating surfaces of the cutting element 60 are covered (abutted) or partially covered by the surfaces of the slot 80, the slot faces at least partially protect the cutting element 60 from impact and damage. It should be noted that in some cases, it may be desirable to cement only a portion of each of the three faces. Moreover, it may be beneficial, in some cases, to cement part or all of only two of the faces of the cutting element 60.
The slot front face 84 of the slot 80 is generally adjacent to the leading corner 50 of the sharpened face 40. The result is that the cutting elements 60 can be cemented into the slots 80 so that the front corner 74 of the cutting element 60 is coincident with the leading corner 50 of the sharpened face 40. This way, the cutting elements 60 can be positioned where most of the cutting is being performed. Therefore, the cutting elements 60 do not need to occupy the entire length of the sharpened face 40. The remaining portion of the sharpened face 40 (after accounting for the slot 80) is a partial lower edge 52, which continues to cut the materials as the material slides past the cutting element 60. In the embodiment shown in
In other embodiments, the slot 80 can be offset from the front edge 48. To assist the cutting performed by the cutting elements 60, the lower edge 52 can be in substantially the same plane as the cutting edge 72. Slight deviations are possible without degradation of the overall cutting power of the knife 10. Typically, at least the lower edge 52 of the plate 20 is heat-treated. Such heat-treatment hardens the material, especially the surface of the material. Therefore, the lower edge 52 retains its sharpness for a longer period of use. The effect and extent of heat-treatment depends on the temperatures used and the duration of time for which a given object is heat-treated. For example, some heat-treatments affect the entire thickness of the heat-treated object. Other heat-treatments harden only the material near the surface.
The heat-treatment is typically carried out in a temperature-controlled salt bath at a temperature of 1550-1575° F. Further, the heat-treatment is preferably performed as austempering. However, other heat-treatments can be used.
As cutting elements 60 can be made of a more expensive material than the material used in the plate 20, the use of a combination of cutting element 60 and the partial lower edge 52 can result in a significant cost savings over conventional knives, which apply their cutting elements 60 to the entire length of the leading edge 22.
The cutting elements 60 can be composed of a variety of different materials, for example, a combination of tungsten carbide and cobalt can work well in these applications. The cutting elements 60 can be cemented into place using a brazing process. The cement used preferably melts at a temperature higher than that required in any subsequent heat-treatment of the finished part.
In some embodiments, the brazing is so-called “high temperature brazing.” In that case, the temperature of the brazing process occurs at 1615° F. or higher. Other embodiments use so-called “low temperature brazing.” In that case, the temperature is held at 1100° to 1200° F. In either case, the brazing material will typically have a melting point at least 75° higher than the temperature at which heat-treatment occurs. Thus, when high-temperature brazing is used, the melting point of the brazing material is 1690° F. or higher. A preferred brazing material used in the brazing process is LUCAS MILHAUPT HI-TEMP 548, but other brazing materials can be used.
By attaching the cutting elements 60 to the plate prior to heat treating the knife 10, the plate 20 can be fully heat-treated and the cutting elements 60 can be solidly attached. In other words, the area around the cutting elements 60 is heat treated, and the heat-treatment is not later degraded during heating required by the brazing process. Thus, the hardness (and, therefore, the durability) of the lower edge 52 is enhanced compared to edges that are heat-treated only before a brazing process is performed. Said differently, by heat-treating the leading edge 22 after the cutting elements are attached, the efficiency of the knife 10 improves because the sharpness of the leading edge lasts longer. Furthermore, as the present invention allows multiple small inserts to be brazed into the plate 20 without degradation of the heat-treatment effect, the knife 10 can be better shaped to optimize the cutting process.
In order to achieve different cutting performance, the leading edge 22 can be straight (as shown), or manufactured with a convex or concave arc. Because the cutting elements 60 typically do not span the entire length of the sharpened face 40, more options for the shape of the leading edge contour are possible with less machining done to the carbide material itself.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically described herein.