Abstract:
A knife assembly includes a knife plate with a leading edge, and a cutting element cemented to the leading edge via a brazing process. The knife plate is heat-treated after the cutting element is cemented to the leading edge so as to form a heat-treatment area on the leading edge. Also disclosed is a method of manufacturing a knife assembly including, forming a leading edge on a side of a knife plate, forming a slot in the leading edge, inserting, into the slot, an insert, brazing the insert to the knife plate after the insert is inserted into the slot, and heat-treating at least a portion of the knife plate after the brazing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     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.  
         [0004]     2. Discussion of the Background  
         [0005]     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.  
         [0006]     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.  
         [0007]     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.  
         [0008]     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.  
         [0009]     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.  
         [0010]     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.  
         [0011]     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.  
         [0012]     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.  
         [0013]     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.  
       SUMMARY OF THE INVENTION  
       [0014]     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.  
         [0000]     Other objects and advantages of exemplary embodiments of the present invention are one or more of the following:  
         [0000]    
       
         
           
              a) to provide a knife with a carbide insert to increase the anticipated life of the sharpened edge;  
              a) to provide a knife in which carbide inserts are brazed into position prior to heat treating;  
              b) to provide a knife in which the base material is heat treated after the carbide inserts are cemented into position;  
              c) to provide a knife in which the cutting elements are not the full length of the repeating pattern of the sharpened leading edge;  
              d) to provide a knife in which the leading edge can be shaped straight, concave, or convex, without affecting the design of the cutting elements;  
              e) to provide a knife in which the cutting elements are cemented on three sides of the knife plate for added strength and durability; and  
              f) to provide a knife which is through-hardened for strength and wear, with enough flexibility to not require a support backing plate.  
           
         
       
     
         [0022]     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.  
         [0023]     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.  
         [0024]     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.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     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;  
         [0026]      FIG. 1  is an isometric view of one exemplary embodiment of a knife with cutting elements.  
         [0027]      FIG. 2  is an isometric view of the knife of  FIG. 1  with the cutting elements removed.  
         [0028]      FIG. 3  is an isometric view from below the knife of  FIG. 1 .  
         [0029]      FIG. 4  is an isometric view of a convex knife according to one non-limiting embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. With reference to  FIGS. 1 through 3 , one exemplary embodiment of the present invention is a knife  10  including a plate  20  having a leading edge  22 , which is sharpened to form a cutting knife such as those used in agricultural feed mixers. By way of example, a feed mixer can be of a variety of configurations, but generally includes a large bin with at least one rotating mixing device or auger on which the knives  10  are typically mounted.  
         [0031]     In the exemplary embodiment of  FIGS. 1 and 2 , plate  20  of the knife  10  also includes a first rear edge  24 , a second rear edge  26 , a heel edge  28 , and a toe edge  30 . When mounted in a working position, the toe edge  30  normally faces toward the outer perimeter of the rotating mixing device, while the heel edge  28  faces toward the centerline of the rotating mixing device. The leading edge  22  faces forward in the direction of rotation of the mixing device. The plate  20  also has a top surface  32  and a bottom surface  34  (see  FIG. 3 ). There are also a plurality of mounting holes  36  which are used to attach the knife  10  to the mixing device of the feed mixer. In addition to, or in place of the mounting holes  36 , other modes of attachment are available such as, by way of non-limiting example: clamping, fixing with keys and keyways, and bonding. Furthermore, other general shapes of the knife  10  are possible. For example, the knife  10  may be substantially half-moon shaped so that the leading edge  22  is concave or convex as shown in  FIG. 4 . Alternatively, the knife  10  may be substantially rectangular. Moreover, the other sections of the plate  20  may be shaped differently to assist attachment of the plate  20  to a mixing device.  
         [0032]     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 .  
         [0033]     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  FIGS. 1-3  have a top surface  62 , a bottom surface  64 , and a rear surface  66 . If, for example, the cutting elements  60  are pie-shaped, triangular, or semi-circular, one or more of the top  62 , bottom  64 , and rear  66  surfaces may be combined or altered. The cutting element  60  typically includes a front end surface  68  and a rear end surface  70 . The intersection of the top surface  62  and the bottom surface  64  forms the cutting edge  72 . The intersection of the top surface  62 , the bottom surface  64  and the front end surface  68  defines a front corner  74 .  
         [0034]     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 .  
         [0035]     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  FIG. 1 , the slot  80  extends into the leading edge  22  so as to at least partially overlap the front edge  48 .  
         [0036]     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.  
         [0037]     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.  
         [0038]     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 .  
         [0039]     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.  
         [0040]     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.  
         [0041]     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.  
         [0042]     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.  
         [0043]     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.