Patent Publication Number: US-11648618-B2

Title: Self-sharpening cutting tooth for a felling apparatus

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to cutting teeth used for a felling apparatus having a circular saw. More particularly, the present disclosure relates to self-sharpening saw teeth for a felling apparatus. 
     BACKGROUND 
     Forestry machinery such as felling apparatuses are used to harvest trees and other vegetation. Felling apparatuses include feller bunchers having cutting implements, often circular saws. 
     In use, the teeth of the circular saw of a felling apparatus wear quickly and are designed most often to be removable from the circular saw of the felling apparatus. This is because each individual tooth becomes dull or rounded at its exposed cutting region from use, which may result in both a decrease in productivity as well as poor cut quality. In some instances, dull cutting teeth can result in the saw blade binding or stalling within the cut, causing a poorly cut surface, damage to the tree fibers, and undesirable bending load on the saw blade. When the saw blade binds within the cut, an operator may have to forcefully remove the saw blade from the tree and then reenergize the saw blade. Subsequently the operator would have to carefully position the saw blade back into the kerf of the previous cut to complete the cut or otherwise waste a portion of the tree with a new cut. 
     Thus, human operators periodically change each individual cutting tooth, or alternatively rotate each cutting tooth if the specific cutting tooth has additional cutting regions not yet dulled. Changing or rotating each cutting tooth of a saw of a felling apparatus requires significant down time, as the felling apparatus must not be in operation for the saw teeth to be changed or rotated. 
     Furthermore, cutting teeth of saw blades occasionally impact hard surfaces such as rock formations. Durable teeth which are not only replaceable, but also exhibit good wear performance and high impact strength are desirable for felling applications. Current carbide insert cutting teeth may provide increased wear performance but may have poor impact strength. Conversely, current hardened steel cutting teeth may provide better impact strength but may have less wear performance. 
     SUMMARY OF THE DISCLOSURE 
     The current disclosure provides improvements in saw teeth for circular saws of felling apparatuses. 
     In one embodiment, a cutting tooth includes a tooth body with a mounting side, a front face spaced from the mounting side, and a plurality of lateral faces extending between the mounting side and the front face. The tooth body also includes an interior hardness as well as a coating applied to at least one of the lateral faces to form a lateral hardface of the cutting tooth. The lateral hardface has a hardness greater than the interior hardness with an edge at the lateral hardface closest to the front face defining a cutting edge region of the cutting tooth with the portion of the front face adjacent to the edge of the lateral hardface. 
     In another embodiment, a cutting tooth includes a hardened tooth body having an interior hardness and having a hardened outer body layer with an outer body layer hardness greater than the interior hardness. The tooth body may also include a mounting side, a front face space from the mounting side, and a plurality of lateral faces extending between the mounting side and the front face with a hardface formed on at least one of the lateral faces. Such cutting tooth may have a hardface hardness greater than the outer body layer hardness. 
     Numerous objects, features and advantages of the embodiments set forth herein will be readily apparent to those skilled in the art upon reading of the following disclosure when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a side perspective view illustration of a cutting tooth having self-sharpening features with a mounting hole. 
         FIG.  1 B  is a side perspective view illustration of a cutting tooth having self-sharpening features with a shank. 
         FIG.  2 A  is a side perspective view illustration of an additional embodiment of a cutting tooth having self-sharpening features with a mounting hole. 
         FIG.  2 B  is a side perspective view illustration of an additional embodiment of a cutting tooth having self-sharpening features with a shank. 
         FIG.  3    is a side view illustration of a cutting tooth having two self-sharpening cutting regions. 
         FIG.  4    is a top view illustration of a coated cutting tooth on a circular saw of a felling apparatus engaging a tree. 
         FIG.  5 A  is a side view illustration of an embodiment of a cutting tooth having a full coating on the lateral face. 
         FIG.  5 B  is a side view illustration of an additional embodiment of a cutting tooth having a partial coating on a lateral face. 
         FIG.  5 C  is a side view illustration of an additional embodiment of a cutting tooth having a partial coating on the lateral face. 
         FIG.  6    is a cross-sectional view illustration of a cutting tooth with a coating on two lateral faces with the cross section illustrating the outer body layer and the interior of the cutting tooth. 
         FIG.  7 A  is a cross-sectional view illustration of the cutting tooth as illustrated in  FIG.  5    but in a partially worn state. 
         FIG.  7 B  is a cross-sectional view illustration of the cutting tooth as illustrated in  FIG.  7 A  but in a further worn state. 
         FIG.  7 C  is a cross-sectional view illustration of the cutting tooth as illustrated in  FIG.  7 B  but in a further worn state. 
         FIG.  8    is a side view illustration of a felling apparatus with felling head which may utilize the cutting teeth disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings and particularly to  FIGS.  1 - 3   , a cutting tooth is shown and generally designated by the numeral  100 .  FIGS.  1 - 3    illustrate a cutting tooth  100  with a tooth body  102  having a mounting side  200 , a front face  106 , and a plurality of lateral faces  108 . The front face  106  is spaced apart from the mounting side  200  with the plurality of lateral faces  108  extending between the mounting side  200  and the front face  106 . The cutting tooth  100  is applicable to feller apparatuses, also understood to be feller buncher machines which are generally used to quickly saw through trees and/or brush. These machines generally include a felling head with a circular saw having a plurality of cutting teeth mounted to the cutting saw. The cutting tooth  100  may also be used on other cutting apparatuses such as, for example, brush mulchers. 
     The front face  106  of the cutting tooth  100  is generally understood to be the face of the cutting tooth  100  that faces the cutting direction when mounted to a circular saw for a felling apparatus. The mounting side  200  is generally understood to be the side of the cutting tooth  100  which mounts against a circular saw of a felling apparatus. As illustrated in  FIGS.  1 A and  2 A , the cutting tooth  100  may include the mounting hole  104  whereby the cutting tooth  100  may be mounted to a circular saw of a felling apparatus via a bolt or similar hardware. As illustrated in  FIGS.  1 B and  2 B , the cutting tooth  100  may include a shank  122  for mounting rather than a mounting hole extending through the front face. 
     The lateral faces  108  of the cutting tooth  100  are generally understood to be on the sides of the cutting tooth  100  and in some embodiments span between mounting side  200  and front face  106 . One or more of the lateral faces  108  may include a coating  112  to form a lateral hardface  114 . The lateral hardface  114  may include an edge  116  which with the adjacent portion of the front face  106  defines the cutting edge region  118  of the cutting tooth  100 . As used herein, the edge  116  of the lateral hardface  114  is generally understood to be the portion of the lateral hardface  114  near the front face  106  and which contacts the material desired to be cut when in use with a circular saw of a felling apparatus. The cutting edge region  118  of one lateral face  108  of cutting tooth  100  extends between tips  120  and as illustrated may have a generally “U” shaped appearance. In further optional embodiments, the cutting edge region may have more of a “V” shaped appearance or alternatively other shapes depending on the specific geometry of the cutting tooth. In other embodiments, the cutting edge region could be a generally straight line. 
     Coating  112  may be applied to one or more of the lateral faces  108  in forming lateral hardfaces  114 . As illustrated in  FIGS.  1 A and  1 B , the coating  112  is on a significant portion of one of the lateral faces  108  to form a lateral hardface  114 .  FIG.  2    illustrates an additional embodiment where the coating  112  is applied to multiple lateral faces  108  to create two lateral hardfaces  114 . As illustrated in  FIGS.  2 A and  2 B , the lateral hardfaces  114  may be adjacent to one another rather than opposite each other. 
       FIG.  3    is an illustration of a side view of a cutting tooth  100  with two lateral hardfaces  114 , the two hardfaces on generally opposite sides of the tooth body  102 . In use, if one of the lateral hardfaces  114  of the cutting tooth  100  in  FIG.  3    becomes too worn, the cutting tooth  100  may be removed and rotated about 180° about central axis  300  of cutting tooth  100  and then remounted on the cutting implement. 
     Additionally, as illustrated in  FIG.  3   , the front face  106  is concave with at least one of the lateral faces  108  extending forward beyond the central portion  110  of the front face  106 . Additionally, where the coating  112  is part of the lateral face  108  to form a lateral hardface  114 , the lateral hardface  114  also extends beyond the central portion  110  of the front face  106 . As used herein, the term “concave” is understood to mean that the front face of the cutting tooth curves or orients inward towards the tooth body  102  of cutting tooth  100 . In some embodiments, the central portion  110  of the front face  106  is understood to be the most inward area of the front face  106 . The central axis  300  is the axis spanning from the mounting side  200  to the front face  106  through the central portion  110  about which cutting tooth  100  may be rotated so that a different cutting edge region  118  may be positioned on the cutting implement to cut when a different cutting edge region  118  on the cutting tooth  100  is worn. In further reference to central axis  300 , in some embodiments the lateral hardface  114  extends in a direction no greater than 30° offset from the central axis  300 . In some embodiments, the lateral hardface extends in a direction no greater than 30° offset from the cutting direction. 
     Referring now to  FIG.  4   , there is a top view illustration of a cutting implement  402  engaging the cutting material  400  with a cutting tooth  100  having a lateral hardface  114 . Additionally illustrated, is a cutting tooth  100  having a lateral hardface  114  out of engagement with the cutting material  400 . In some embodiments, the cutting implement  402  may be a circular saw that rotates in the circular direction indicated by the arrow labeled with the numeral  408 . The cutting material  400  may be a tree and include cut portion  412  whereby the cutting tooth  100  with coating  112  and lateral hardface  114  has already removed cuttings  410 . 
     The edge  116  of the lateral hardface  114  of the cutting tooth  100  at cutting edge region  118  engages the cutting material  400  while the cutting implement  402  rotates in the circular direction  408 . 
     Generally, the cutting teeth  100  are mounted to the cutting implement  402  at mount locations  406  and may be affixed via mounting hardware  404 . When the cutting edge regions  118  of the cutting teeth  100  become too worn from engaging cutting material  400 , the mounting hardware  404  may be removed and the cutting teeth  100  may be remounted so that the opposite lateral hardfaces  114  and the unworn cutting edge region  118  may be positioned to engage the cutting material  400 . 
     Referring now to  FIGS.  5 A- 5 C , there are multiple side view illustrations of different embodiments of cutting tooth  100 .  FIG.  5 A  illustrates cutting tooth  100  having the coating  112  on the entire lateral face  108  to create the lateral hardface  114 .  FIG.  5 B  illustrates coating  112  on a substantial portion of lateral face  108  to create a partial lateral hardface  114 .  FIG.  5 C  illustrates the coating  112  applied to the lateral face  108  to just below the central portion  110  of front face  106  of the cutting tooth  100 . Various coverage by the coating  112  on the lateral faces  108  provide for differing surface areas of lateral hardfaces  114  which may be useful for different applications. As such, optional embodiments of cutting teeth  100  include various arrangements of lateral hardfaces  114  which is generally controlled by the application of coating  112  to the lateral faces  108  of the cutting tooth  100 . 
     Hardness Transition as Illustrated by  FIG.  6     
     The coating  112  as applied to one or more lateral faces  108  to create lateral hardfaces  114  of a cutting tooth  100  advantageously provides an increased hardness at the cutting edge region  118 .  FIG.  6    is a cross-section side view illustration of a cutting tooth  100  through both lateral hardfaces  114 . In addition to the various aspects of the cutting tooth  100  as illustrated in  FIG.  3   ,  FIG.  6    further illustrates hardened outer body layer  600  and tooth interior  602 . Generally, the coating  112  which creates the lateral hardface  114  provides an increased hardness over a cutting tooth not having such coating. In some embodiments, coating  112  provides a Rockwell C hardness of 65 or greater at the surface of the lateral hardface  114 . Otherwise stated, coating  112  can have a Rockwell C hardness of 65 or greater which provides the lateral hardface  114  with a hardface hardness greater than the rest of the tooth body  102 . In some embodiments, coating  112  provides a Rockwell C hardness of 70 or greater at the surface of the lateral hardface  114 . Hardened outer body layer  600  of the tooth body  102  may have a Rockwell C hardness in a range of from about 58 to about 64. 
     Hardened outer body layer  600  of tooth body  102  of cutting tooth  100  may be created in a variety of manners. For example, hardened outer body layer  600  may be the result of tooth body  102  having a carburized surface or case hardened. As a result, hardened outer body layer  600  may have a hardness in a range of from about 58 to about 64 Rockwell C and optionally a hardness in a range of from about 60 to about 62 Rockwell C. 
     Tooth body  102  of cutting tooth  100  also includes interior  602 . Interior  602  is understood to be the interior portion of tooth body  102  of cutting tooth  100  and has an interior hardness in a range of from about 25 to about 35 Rockwell C. In certain embodiments, the hardness of interior  602  may be lessor or greater though the interior hardness is less than that of coating  112  of cutting tooth  100 . Thus, cutting tooth  100  may include interior  602  with an interior hardness in a range of from about 25 to about 35 Rockwell C; a hardened outer body layer  600  with an outer body layer hardness in a range of from about 58 to about 64 Rockwell C, and a lateral hardface  114  with a hardface hardness of at least 65 Rockwell C. In some embodiments of cutting tooth  100 , at least a portion of the outer surface of tooth body  102  is hardened to form hardened outer body layer  600  having an outer body layer hardness greater than the interior hardness and less than the hardface hardness. Furthermore, in some embodiments only a portion of the surface of the tooth body  102  of cutting tooth  100  may be hardened. 
     In use, cutting tooth  100  may be positioned wherein front face  106  includes hardened outer body layer  600  so that in an unworn state of cutting tooth  100  (as illustrated in  FIG.  6   ), cutting edge region  118  of cutting tooth  100  presents in a cutting direction, edge  116  of lateral hardface  114  adjacent the hardened outer body layer  600  of front face  106 . In some embodiments, cutting edge region  118  of cutting tooth  100  includes edge  116  of lateral hardface  114  with a portion of hardened outer body layer  600  of front face  106 . 
     Thus, one can otherwise describe  FIG.  6    as illustrating a cutting tooth  100  that includes tooth body  102  with lateral hardface  114  such that a cross section of cutting tooth  100  through the lateral hardface  114  transitions from the hardness of the hardened outer body layer  600  to the hardness of interior  602 . 
     The Self-Sharpening Feature of the Cutting Tooth 
     The transition of an increased hardness at lateral hardface  114  to the hardened outer body layer  600  to the interior  602  of tooth body  102  provides a cutting tooth  100  with a self-sharpening characteristic. As cutting tooth  100  wears from use, the wear pattern of cutting tooth  100  is such that cutting edge region  118  remains sharp and able to cut through the cutting materials.  FIG.  6    illustrated a cross-sectional view of a cutting tooth  100  with two lateral hardfaces  114  in an unworn state.  FIGS.  7 A-C  illustrate cutting teeth  100  with successively increasing wear patterns. 
     Referring now to  FIG.  7 A  there is a schematic cross-sectional illustration of cutting tooth  100  having initial wear pattern  700 . Thus, after use hardened outer body layer  600  of front face  106  adjacent cutting edge region  118  is worn away as illustrated by wear pattern  700 . Whereas lateral hardface  114  continues to remain and wears at a slower rate due to the increased hardness of lateral hardface  114  in comparison to the hardness of hardened outer body layer  600 . 
     Now referring to  FIG.  7 B , wear pattern  702  of cutting tooth  100  illustrates greater wear than wear pattern  700  of  FIG.  7 A . Thus, wear pattern  702  illustrates further wearing of hardened outer body layer  600  and additionally wearing of interior  602  of cutting tooth  100 . Cutting edge region  118  has experienced slight wear as has lateral hardface  114  but not as significantly as interior  602  and hardened outer body layer  600  of front face  106 . 
     Referring now to  FIG.  7 C , wear pattern  704  illustrates significantly more wear of hardened outer body layer  600  from front face  106  as well as further wear of interior  602  of cutting tooth  100 . Additionally, lateral hardface  114  has been slightly more worn in comparison to  FIG.  7 B  though continues to wear at a lessor rate than interior  602  and hardened outer body layer  600  of front face  106 . 
     In comparing the unworn cross section as illustrated in  FIG.  6    to the increasing wear patterns of  FIGS.  7 A-C , cutting edge region  118  remains relatively sharp rather than dulling or rounding. This is due to the increased hardness of lateral hardface  114  in comparison to the hardened outer body layer  600  and tooth interior  602 . Thus, cutting edge region  118  of cutting tooth  100  is self-sharpening during because of the faster wear of front face  106  and interior  602  than of lateral hardface  114 . In the worn states as illustrated in  FIGS.  7 A-C  hardened outer body layer  600  of front face  106  is worn away so that cutting edge region  118  presents in the cutting direction edge  116  of lateral hardface  114  adjacent the worn regions of front face  106 . 
     Embodiments of the Coating for the Lateral Hardface 
     Referring now to  FIGS.  1 - 7 C , coating  112  may be applied to one or more lateral faces  108  of the tooth body  102  of the cutting tooth  100  in differing thicknesses. Generally, the thickness of coating  112  controls the thickness of cutting edge region  118 . In some embodiments, coating  112  may have a thickness in a range from about 0.25 mm to about 3 mm. In some embodiments, coating  112  may have a thickness in a range from about 1 mm to about 3 mm. 
     In some embodiments, coating  112  may be a fused alloy that is substantially harder and more wear-resistant than the material used for the tooth body  102 . For example, coating  112  may be harder than 1045 grade steel even in a hardened conditioned. In some embodiments, the coating  112  may be metallurgically bonded to the tooth body  102 . In some embodiments, the coating  112  may be applied to a portion of tooth body without the hardened outer body layer  600 . 
     Commonly owned U.S. Pat. No. 5,879,743, the entire contents of which are incorporated herein by reference, discloses an alloy which may be used as the coating  112 . The coating  112  in some embodiments may be at least 60% of a transition metal of Group VIII of the Periodic Table, such as iron, cobalt, or nickel. However, the coating  112  may be based on other metals in other embodiments. Minor components, about 0.1 to about 20 wt. % of the coating  112 , typically are boron, carbon, chromium, iron (in nickel and cobalt-based alloys), manganese, nickel (in iron and cobalt-based alloys), silicon, tungsten, molybdenum, one or more carbide forming elements, or combinations thereof. Elements in trace amounts, less than about 0.1 wt. % of the coating  112 , such as sulfur, may be present as de minimis, contaminants. The coating  112  has a fusion temperature which is lower than the melting point of cutting tooth  100 , in some embodiments, about 1110° C. or less, and optionally between about 900° C. and about 1200° C. Generally, the coating may include an iron-based alloy including at least 60 weight percent of iron, cobalt, or nickel. In some embodiments, the coating  112  may include one or more elements selected from iron, nickel, and cobalt, and two or more elements selected from boron, carbon, chromium, molybdenum, manganese, tungsten, and silicon. 
     Coating  112  may be applied as slurry and can be formed from polyvinyl alcohol (PVA) and a fusible, hard metal alloy in the form of a finely divided powder. Typical particle sizes range from about 90 mesh to about 400 mesh. The average particle size may be finer than about 115 mesh and in some embodiments may be finer than about 200 mesh. The powder can be a mixture of powders of different particle sizes. The slurry for forming coating  112  may be spray coated, spun cast, dipped, poured, or spread on tooth body  102 . 
     In some embodiments, the coating  112  of cutting tooth  100  may be formed from a substantially uniform aqueous slurry of polyvinyl alcohol and a fusible, hard metal alloy in the form of a finely divided powder is formed and coated on the tooth body  102 . The aqueous slurry may then be dried to leave a solid layer of fusible, hard metal alloy in a polyvinyl alcohol matrix on the tooth body  102 . Such steps in some embodiments may be repeated one or more times to build up a thicker coating. Additionally, the thickness of an unfused slurry for the coating  112  can be adjusted by a shrinkage factor to result in a desired thickness of the coating  112  on the tooth body  102  after metallurgical bonding. 
     In some embodiments, the coating  112  of cutting tooth  100  may be formed from an aqueous polyvinyl alcohol solution and a substantially uniform layer of a fusible, hard metal alloy in the form of a finely divided powder is distributed onto the coating of the polyvinyl alcohol solution before the polyvinyl alcohol solution dries. The steps of coating the metal surface, distributing the fusible hard metal alloy, and drying the slurry or the solution coating to leave a solid layer may be repeated one or more times to result the coating  112  being thicker. 
     Dipping, pouring, brushing, paste and tape methods, and repeated spraying are techniques which may be used for creating a thicker coating  112 . In some embodiments, the ratio of hard metal alloy to PVA solution is in the range of about 4:1 to about 8:1 and the concentration of PVA solution is about 1% to about 15% PVA by weight. For example, 0500/0250 and 0600/0250 or similar slurries may be used in some embodiments to create the coating  112 . The representation xxxx/yyyy indicates the slurry parameters, where xxxx=weight ratio of powdered alloy to polyvinyl alcohol and yyyy=weight percent of polyvinyl alcohol present in the aqueous solution as a binder. A decimal point is implicit after the first two digits in the representation. Thus, 0500 represents 5.0. Thick slurry compositions, a high ratio of alloy to PVA solution, may be applied as a squeezable paste, or can be rolled into tapes for bonding to the tooth body  102 . For some embodiments, the ratio of alloy to PVA solution may be in the range of about 8:1 to about 15:1 by weight and the concentration of PVA solution may be about 2% to about 15% PVA by weight. In the above procedures, additives can function as dispersants, suspending agents, and plasticizers. 
     The dried slurry may then be metallurgical bonded to the tooth body  102  to create the coating  112 . In some embodiments, the tooth body  102  with the layer of fusible, hard metal alloy in the polyvinyl alcohol matrix or with the aqueous polyvinyl alcohol solution with the layer of fusible, can be heated to the fusing temperature of the hard metal alloy under a protective atmosphere until the hard metal alloy has fused onto the tooth body  102  in forming coating  112 . Heating may occur in a controlled atmosphere, in some embodiments, in an inert or reducing atmosphere, excluding nitrogen which may nitride the coating  112 . In some embodiments, after metallurgically bonding the coating  112  to the tooth body  102 , remaining carburized metal of the tooth body  102  can be hardened to a desired hardness by quenching. 
     In some embodiments the coating  112  may be applied via thermal spraying to the tooth body  102 . Thermal spraying includes the use of a heat source to melt a powdered or wire-form material into small droplets which may then be sprayed onto the tooth body  102 . In some embodiments, laser cladding may be used for applying the coating  112  to the tooth body  102 . Such process includes the used of powdered material fed into a laser beam as such is moved across tooth body  102 . The powdered material melts onto tooth body  102  and forms the coating  112 . Furthermore, in some embodiments, plasma transferred arc welding may be used for obtaining the coating  112  on the tooth body  102 . For plasma transferred arc welding, a high-density plasma arc is used to metallurgically bond powdered or wire-form material to the tooth body  102  in forming the coating  112 . Referring now to  FIG.  8    there is a felling apparatus indicated by numeral  800 . Felling apparatus  800  is understood to be a feller buncher for harvesting trees and other wood vegetation. Generally, a typical tree feller buncher first cuts the tree and then places the tree in bunches on the ground for further processing with other machines. Felling apparatus  800  includes felling head  802  which includes a cutting device for cutting the trees. Generally, such cutting device of felling head  802  includes cutting implement  402  which may be a circular saw. On cutting implement  402  the various embodiments of cutting teeth  100  of this disclosure may be incorporated to provide both felling head  802  as well as felling apparatus  800  the advantages of the disclosed cutting teeth. 
     Thus it is seen that the apparatus and methods of the present disclosure readily achieve the ends and advantages mentioned as well as those inherent therein. While certain preferred embodiments of the disclosure have been illustrated and described for present purposes, numerous changes in the arrangement and construction of parts and steps may be made by those skilled in the art, which changes are encompassed within the scope and spirit of the present disclosure as defined by the appended claims Each disclosed feature or embodiment may be combined with any of the other disclosed features or embodiments.