Patent Publication Number: US-2021161069-A1

Title: Crop cutting knives for agricultural combine harvester

Description:
BACKGROUND 
     The present disclosure relates to an agricultural combine harvester, and particularly to crop cutting knives on a head unit of an agricultural combine harvester. 
     SUMMARY 
     In one aspect, a cutting knife configured to be coupled to an agricultural combine harvester to cut crop plants from an agricultural field. The cutting knife includes a base configured to be coupled to a head unit of the agricultural combine harvester. The cutting knife also includes a blade having a blade central axis extending away from the base. The blade includes a plurality of cutting teeth. Each tooth of the plurality of teeth has a tip. The blade includes an edge tangent to each tip on a first side of the blade. The edge is obliquely oriented relative to the blade central axis. The plurality of teeth includes consecutive first, second, and third teeth positioned along the edge with a first distance separating the tips of the first and second teeth. The first distance is measured parallel to the edge. The first distance also separates the tips of the second and third teeth. The plurality of cutting teeth also includes consecutive fourth, fifth, and sixth teeth positioned along the edge with a second distance different than the first distance separating the tips of the fourth and fifth teeth. The second distance measured parallel to the edge. The second distance also separates the tips of the fifth and sixth teeth. 
     In another aspect, a cutting knife is configured to be coupled to an agricultural combine harvester to cut crop plants from an agricultural field. The cutting knife includes a base configured to be coupled to a head unit of the agricultural combine harvester. The cutting knife also includes a blade having a blade central axis extending away from the base. The blade includes a plurality of cutting teeth. Each tooth of the plurality of teeth has a tip. The blade includes an edge tangent to each tip on a first side of the blade. The edge is obliquely oriented relative to the blade central axis. The plurality of cutting teeth includes consecutive first, second, third, and fourth teeth positioned along the edge with a first distance separating the tips of the first and second teeth, a second distance different than the first distance separating the tips of the second and third teeth, and a third distance substantially the same as the first distance separating the tips of the third and fourth teeth. The first, second, and third distances are measured parallel to the edge. 
     In yet another aspect, a cutting knife is configured to be coupled to an agricultural combine harvester to cut crop plants from an agricultural field. The cutting knife includes a base configured to be coupled to a head unit of the agricultural combine harvester. The cutting knife also includes a blade extending away from the base. The blade includes an edge and a plurality of cutting teeth formed from the edge. The plurality of cutting teeth includes a first grouping of teeth positioned along the edge having a first pitch. The plurality of cutting teeth also includes a second grouping of teeth positioned along the edge having a second pitch less than the first pitch. The first grouping of teeth is positioned closer to an end of the blade opposite the base than the second grouping of teeth. 
     In yet another aspect, a crop cutting assembly for a head unit of an agricultural combine harvester. The crop cutting assembly is configured to cut crop plants from an agricultural field. The crop cutting assembly includes a drive linkage configured to reciprocate along an axis and a cutting knife. The cutting knife includes a base configured to be selectively coupled to the drive linkage and a blade extending away from the base. The blade includes an edge and a plurality of cutting teeth formed from the edge. The plurality of cutting teeth includes a first grouping of teeth positioned along the edge having a first pitch. The plurality of cutting teeth also includes a second grouping of teeth positioned along the edge having a second pitch less than the first pitch. The first grouping of teeth is positioned closer to an end of the blade opposite the base than the second grouping of teeth. 
     Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an agricultural combine harvester. 
         FIG. 2  is a perspective view of a portion of a head unit of the agricultural combine harvester of  FIG. 1 . 
         FIG. 3  is a detailed view of a portion of the head unit of  FIG. 2  including a plurality of cutting knives. 
         FIG. 4  is a top view of one embodiment of the plurality of cutting knives of  FIG. 3 . 
         FIG. 5  is a top view of another embodiment of the plurality of cutting knives of  FIG. 3 . 
         FIG. 6  is a top view of another set of the plurality of cutting knives of  FIG. 3 . 
         FIG. 7  is a top view of another set of the plurality of cutting knives of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of supporting other embodiments and of being practiced or of being carried out in various ways. Terms of degree, such as “substantially,” “about,” “approximately,” etc. are understood by those of ordinary skill to refer to reasonable ranges outside of the given value, for example, general tolerances associated with manufacturing, assembly, and use of the described embodiments. 
       FIG. 1  illustrates an agricultural combine harvester  10  that is moveable across an agricultural field to harvest crop plants (e.g., beans, wheat, a combination of corn and wheat, etc.) therefrom. The harvester  10  includes a chassis  15 , wheels  20  coupled to the chassis  15 , a prime mover  25  (e.g., an internal combustion engine) supported by the chassis  15 , and a cab  30  also supported by the chassis  15 . The wheels  20  are driven by the prime mover  25  to move the harvester  10  across the field. The prime mover  25  also provides mechanical, hydraulic, and electrical power to other components and features of the harvester  10 . The cab  30  is configured to support an operator of the harvester  10 . 
     With continued reference to  FIG. 1 , the harvester  10  also includes a grain tank  35 , a threshing unit  40 , and a head unit  45 . The head unit  45  is operable by the prime mover  25  to cut the crop plants from the agricultural field and convey the crop plants to the threshing unit  40  by a conveyor  50 , which is located between the head unit  45  and the threshing unit  40 . The threshing unit  40  is then operable to separate the crop plants into a crop portion, which is collected within the grain tank  35 , and a residue portion, which is discharged from the harvester  10  onto the agricultural field. 
     The illustrated head unit  45  is a draper head unit that includes a frame  55  having a longitudinal axis  60  oriented substantially transverse to a direction of travel of the harvester  10 . The frame  55  supports a reel  65  rotatably extending between opposing sides of the frame  55  and a crop cutting assembly  75  including a drive unit  80  ( FIG. 2 ) located on a side of the frame  55 . In other embodiments, the head unit  45  can be differently configured dependent upon a particular crop plant being harvested. 
     With reference to  FIG. 2 , the drive unit  80  includes a reciprocating mechanism  85  coupled to a drive shaft  90 , which is in operational communication with the prime mover  25 , and a drive linkage  95  (e.g., a drive plate) coupled to a plurality of cutting knives  100  of the crop cutting assembly  75 . In the illustrated embodiment, the reciprocating mechanism  85  is a slider-crank mechanism that receives rotational movement from the drive shaft  90  and converts the rotational movement to a substantially linear reciprocating motion of the drive linkage  95  along an axis substantially parallel to the longitudinal axis  60  of the head unit  45 . In other embodiments, the reciprocating mechanism  85  can be differently configured to linearly reciprocate the drive linkage  95 . 
     As best shown in  FIGS. 2 and 3 , the cutting knives  100  are positioned on a bottom side of the head unit  45  adjacent the agricultural field and are coupled (e.g., selectively fastened) to the drive linkage  95  for movement therewith. The crop cutting assembly  75  also includes a fixed support  105  (e.g., a cross sub frame) that supports the cutting knives  100  during reciprocating movement of the cutting knives  100 . In particular, the fixed support  105  includes protrusions  110  extending in a forward direction (relative to travel of the harvester  10 ) with some of the protrusions  110   a  having a slot  115  sized to receive a cutting knife  100  and configured such that a portion of each of those protrusions  110   a  is located above the cutting knives  100  and another portion of each of those protrusions  110   a  is located below the cutting knives  100 . The protrusions  110   a  are also configured to extend forwardly beyond the cutting knives  100 . In the illustrated embodiment, a distance  118  between adjacent protrusions  110   a  (i.e., a linear distance between tips of adjacent protrusions  110   a  parallel to the longitudinal axis  60 ,  FIG. 2 ) can be between about 3 inches and about 4 inches. The illustrated protrusions  110   b  that do not include the slots  115  are positioned below the cutting knives  100  between adjacent protrusions  110   a . The protrusions  110   b  are configured such that a portion of each knife of the cutting knives  100  extends forwardly beyond the protrusions  110   b.    
     The fixed support  105  also includes hold down members  120  that engage a top surface of the cutting knives  100  to help guide the cutting knives  100  into the slots  115  and inhibit the cutting knives  100  from rotating upwardly away from the agricultural field as the cutting knives  100  reciprocate. In some embodiments, the hold down members  120  can always engage the cutting knives  100  or can be spaced slightly above the cutting knives  100  to selectively engage the cutting knives  100  if the cutting knives  100  begin to move out of alignment with the slots  115 . In other embodiments, the protrusions  110  can be omitted and replaced with another series of cutting knives  100  so that at least one reciprocating mechanism  85  can move two separate series of cutting knives  100  relative to each other. 
     With reference to  FIG. 4 , each cutting knife  100  includes a base  125  having a first central axis  130  oriented substantially parallel to the longitudinal axis  60  of the head unit  45  when the knives  100  are assembled thereto and two blades  135  extending away from the base  125  in the forward direction to each include a second central axis  140  substantially transverse to the first axis  130 . 
     The illustrated base  125  includes a plurality of fastening apertures  142  each sized to receive a fastener (e.g., a bolt, etc.) to couple the cutting knife  100  to the drive linkage  95 . In the illustrated embodiment, the first central axis  130  extends centrally through the fastening apertures  142 . Each illustrated blade  135  includes a first obliquely angled edge  145  and a second obliquely angled edge  150  (relative to the first central axis  130  and the second central axis  140 ) such that each blade  135  is generally triangular in shape. In the illustrated embodiment, the edges  145 ,  150  are positioned on opposing sides  152 ,  154  of the blade  135  and are oriented greater than 45 degrees relative to the first central axis  130  (e.g., between about 50 degrees and about 70 degrees) and are oriented less than 45 degrees relative to the second central axis  140  (e.g., between about 40 degrees and about 20 degrees). The second central axis  140  of the blades  135  is oriented substantially parallel to a central axis of the protrusions  110 . Cutting teeth  155  are positioned along each edge  145 ,  150  between an end  160  of each blade  135  and the base  125 . In particular, each edge  145 ,  150  is a linear edge tangent to all of the tips  170  of the cutting teeth  155  on a particular side  152 ,  154  of the blade  135 . In some embodiments, all of the tips  170  may not align tangent to a corresponding edge  145 ,  150  such that each edge  145 ,  150  is tangent to at least two tips  170  of the cutting teeth  155  (e.g., a linear line between one tip  170  closer to the end  160  and one tip  170  closer to the base  125 ) due to, for example, manufacturing tolerances of forming/shaping the cutting teeth  155 . As shown in  FIG. 4 , each edge  145 ,  150  includes three distinct groupings of teeth  165   a ,  165   b ,  165   c  with each grouping  165   a ,  165   b ,  165   c  having a unique pitch. The pitch of the cutting teeth  155  is defined by a linear distance (parallel to the corresponding edge  145 ,  150 ) separating the tips  170  of adjacent cutting teeth  155 . For example, as the pitch between adjacent cutting teeth  155  increases, the teeth per inch (TPI) of the cutting teeth  155  decreases. Conversely, as the pitch between adjacent cutting teeth  155  decreases, the TPI of the cutting teeth  155  increases. The illustrated first grouping of teeth  165   a  is positioned closer to the end  160  of each blade  135  than the other two groupings  165   b ,  165   c , the second grouping of teeth  165   b  is positioned between the first and third groupings of teeth  165   a ,  165   c , and the third grouping of teeth  165   c  is positioned closer to the base  125  than the other two groupings  165   a ,  165   b . In other embodiments, the groupings of teeth  165   a ,  165   b ,  165   c  can be arranged differently along each edge  145 ,  150  (e.g., the third grouping  165   c  can be positioned the closest to the end  160 , the second grouping  165   b  can be positioned the closest to the end  160 , any of the groupings  165   a ,  165   b ,  165   c  can be positioned between the other two groupings  165   a ,  165   b ,  165   c , etc.), and/or the blade  135  can include more than three groupings of teeth to have more than three groupings of different pitches. 
     The illustrated first grouping of teeth  165   a  includes at least three teeth having a first pitch  175  measured parallel to a corresponding edge  145 ,  150 , the illustrated second grouping of teeth  165   b  includes at least three teeth having a second pitch  180  different than the first pitch  175  measured parallel to a corresponding edge  145 ,  150 , and the third grouping of teeth  165   c  includes at least three teeth having a third pitch  185  different than at least one of the first or second pitches  175 ,  180  measured parallel to a corresponding edge  145 ,  150 . In the illustrated embodiment, the first pitch  175  is greater than the second pitch  180 , and the second pitch  180  is greater than the third pitch  185 . For example, the first pitch  175  is about 7 TPI, the second pitch  180  is about 10 TPI, and the third pitch  185  is about 14 TPI. In other embodiments, the first pitch  175  can be less than or equal to about 8.5 TPI, the second pitch  180  can be greater than or equal to about 8.5 TPI but less than or equal to about 12 TPI, and the third pitch  185  can be greater than or equal to about 12 TPI. In other embodiments, the first grouping of teeth  165   a  can include more than or fewer than three teeth having the first pitch  175 , the second grouping of teeth  165   b  can include more than or fewer than three teeth having the second pitch  180 , and/or the third grouping of teeth  165   c  can include more than or fewer than three teeth having the third pitch  185 . 
     In addition, the first grouping of teeth  165   a  includes a first linear length  190  (along each edge  145 ,  150  from outboard-most tips  170  of the first grouping  165   a ), the second grouping of teeth  165   b  includes a second linear length  195  (along each edge  145 ,  150  from outboard-most tips  170  of the second grouping  165   b ), and the third grouping of teeth  165   c  includes a third linear length  200  (along each edge  145 ,  150  from outboard-most tips  170  of the third grouping  165   c ). In the illustrated embodiment, the third linear length  200  is greater than the first and second linear lengths  190 ,  195 , and the first linear length  190  is greater than the second linear length  195 . For example, the first linear length  190  is between about 30% and about 40% of the total length of each edge  145 ,  150 , the second linear length  195  is between about 15% and about 25% of the total length of each edge  145 ,  150 , and the third linear length  200  is between about 35% and about 45% of the total length of each edge  145 ,  150 . In other embodiments, the first linear length  190  is less than 40% of the total length of each edge  145 ,  150 , the second linear length  195  is less than 30% of the total length of each edge  145 ,  150 , and the third linear length  200  is greater than 30% of the total length of each edge  145 ,  150 . 
     In the illustrated embodiment, the two blades  135  include similar cutting teeth  155 , but in other embodiments, the two blades  135  can include dissimilar cutting teeth  155  (e.g., different groupings and arrangements of the cutting teeth, different pitches, different linear lengths, etc.). 
     As the harvester  10  moves through the agricultural field, stems or stalks of each crop plant are received between adjacent protrusions  110  of the crop cutting assembly  75  so that as the reciprocating mechanism  85  moves the cutting knives  100  back and forth, the cutting knives  100  pinch the stalks of the crop plants against one protrusion  110  to shear the stalks from the crop portions of the crop plants. In the illustrated embodiment, the reciprocating mechanism  85  is configured to move the cutting knives  100  along a cutting length that is generally the same as the distance  118  of the protrusions  110   a . For example, the reciprocating mechanism  85  moves each cutting knife  100  between about 3 inches and about 4 inches in both reciprocating directions. As such, some of the cutting knives  100  move from one slot  115  of a first protrusion  110   a , past a protrusion  110   b , to another slot  115  of an adjacent protrusion  110   a  to shear the stalks from the crop portions of the crop plants. In addition, other cutting knives  100  move from a first protrusion  110   b , through a slot  115 , to an adjacent protrusion  110   b  to shear the stalks from the crop portions of the crop plants. In other embodiments, the cutting length of the cutting knives  100  can be different than the distance  118 . Once the crop portions are sheared from the stalks, the crop portions proceed to the conveyor  50  via the reel  65  and then are conveyed to the threshing unit  40 , as discussed above. 
     The illustrated cutting knives  100  with a variable pitch as disclosed function to efficiently cut different sized crop plants and thereby avoid continual replacement with specific cutting knives to cut specific crop plants, which can be time consuming. In general, the third smaller pitch  185  of the third grouping of cutting teeth  165   c  is efficient in cutting smaller sized/rigidity crop plants (e.g., wheat, barley, rice, oats, etc.) but less efficient in cutting larger sized/rigidity crop plants (e.g., corn, etc.), the first larger pitch  175  of the first grouping of cutting teeth  165   a  is efficient in cutting larger sized crop plants but less efficient in cutting smaller sized crop plants, and the second pitch  180  of the second grouping of cutting teeth  165   b  is efficient in cutting medium sized/rigidity crop plants (e.g., soybeans, canola, oilseed rape, etc.). Also, the smaller sized crop plants are typically planted closer together (e.g., a higher population) than the medium sized crop plants and the larger sized crop plants, which include a lower population. By including the first, second, and third groupings of cutting teeth  165   a ,  165   b ,  165   c  on each edge  145 ,  150  of the blade  135 , the illustrated cutting knives  100  can efficiently cut a wide range of different types of crop plants. 
     For example, when the harvester  10  is harvesting wheat (a relatively smaller sized/rigidity crop plant), the wheat stalks generally move into alignment with the third grouping of cutting teeth  165   c  to be pinched against the protrusions  110  thereby for the wheat stalks to be sheared from the crop portions of the wheat. In other embodiments, the second and first groupings of cutting teeth  165   b ,  165   a  can also shear the wheat stalks, although less efficiently than the third grouping of cutting teeth  165   c . When the harvester  10  is harvesting beans (a relatively medium sized/rigidity crop plant), the cutting knives  100  are configured for the bean stalks to generally move into alignment with the second grouping of cutting teeth  165   b  to be pinched against the protrusions  100  thereby for the bean stalks to be sheared from the crop portions of the beans. In other words, the size of the bean stalks is generally too large to align with the third grouping of cutting teeth  165   c  for the third grouping of cutting teeth  165   c  to cut the bean stalks. In other embodiments, a portion of the bean stalks is initially cut by the third grouping of cutting teeth  165   c  before the second grouping of cutting teeth  165   b  shears the bean stalks. In further embodiments, the first grouping of cutting teeth  165   a  can also shear the bean stalks, although less efficiently than the second grouping of cutting teeth  165   b . When the harvester  10  is harvesting a crop plant (e.g., wheat) with a left over crop plant (e.g., corn or cotton) from a previous harvest dispersed throughout the agricultural field (corn/cotton being a relatively large sized/rigidity crop plant), the cutting knives  100  are configured for the corn/′cotton stalks to generally move into alignment with the first grouping of cutting teeth  165   a  to be pinched against the protrusions  100  thereby for the corn/cotton stalks to be sheared adjacent the agricultural field. In other words, the size of the corn/cotton stalks is generally too large to align with the second and third groupings of cutting teeth  165   b ,  165   c  to be cut by the second and the third groupings of cutting teeth  165   b ,  165   c . In other embodiments, a portion of the corn/cotton stalks is initially cut by the second grouping of cutting teeth  165   b  before the first grouping of cutting teeth  165   a  shears the corn/cotton stalks. 
       FIG. 5  illustrates a cutting knife  400  according to another embodiment. The cutting knife  400  is similar to the cutting knife  100 ; therefore, similar components are designated with similar references numbers plus 300. At least some differences and/or at least some similarities between the cutting knives  100 ,  400  will be discussed in detail below. In addition, the features described with respect to the cutting knife  100  are equally applicable to features described with respect to the cutting knife  400 . 
     The illustrated cutting knife  400  includes a base  425  having fastening apertures  442  and a first central axis  430 . The cutting knife  400  also includes two blades  435  each having a second central axis  440 . Each blade  435  includes a first obliquely angled edge  445  positioned on a first side  452  of the blade  435  and a second obliquely angled edge  450  positioned on a second side  454  of the blade  435  with cutting teeth  455  positioned along each edge  445 ,  450  between an end  460  of each blade  435  and the base  425 . The cutting teeth  455  include two distinct groupings of teeth  465   a ,  465   b  with the first grouping  465   a  having a first pitch  475  between adjacent tips  470  and the second grouping  465   b  having a second pitch  480  between adjacent tips  470 . The second pitch  480  is smaller than the first pitch  475 . For example, the first pitch  475  is about 7 TPI, and the second pitch  480  is about 14 TPI. In other embodiments, the first pitch  475  can be less than or equal to about 10 TPI, and the second pitch  480  can be greater than or equal to about 10 TPI. In further embodiments, the first and second pitches  475 ,  480  can be between about 7 TPI and about 15 TPI. In addition, the first grouping of teeth  465   a  includes a first linear length  490  measured parallel to a corresponding edge  145 ,  150 , and the second grouping of teeth  465   b  includes a second linear length  495  measured parallel to a corresponding edge  145 ,  150 . In the illustrated embodiment, the second linear length  495  is greater than the first linear length  490 . For example, the first linear length  490  is between about 30% and about 40% of the total length of each edge  445 ,  450 , and the second linear length  495  is between about 60% and about 70% of the total length of each edge  445 ,  450 . In another embodiment, the first linear length  490  is less than 45% of the total length of each edge  445 ,  450 , and the second linear length  495  is greater than 45% of the total length of each edge  445 ,  450 . 
     As the harvester  10  moves through the agricultural field to harvest relatively smaller sized crop plants (e.g., wheat), the adjacent pairs of second teeth  465   b  efficiently cut the wheat stalks. Conversely, as the harvester  10  moves through the agricultural field to harvest relatively larger sized crop plants (e.g., corn), the adjacent pairs of first teeth  465   a  efficiently cut the corn stalks. However, as the harvester  10  moves through the agricultural field to harvest relatively medium sized crop plants (e.g., beans), a combination of the first and second teeth  465   a ,  465   b  efficiently cut the bean stalks. In other embodiments, the first teeth  465   a  can help cut the wheat stalks, and the second teeth  465   b  can help cut the corn stalks. 
       FIG. 6  illustrates a cutting knife  700  according to another embodiment. The cutting knife  700  is similar to the cutting knife  100 ; therefore, similar components are designated with similar references numbers plus 600. At least some differences and/or at least some similarities between the cutting knives  100 ,  700  will be discussed in detail below. In addition, the features described with respect to the cutting knife  100  and/or the cutting knife  400  are equally applicable to features described with respect to the cutting knife  700 . 
     The illustrated cutting knife  700  includes a base  725  having fastening apertures  742  and a first central axis  730 . The cutting knife  700  also includes two blades  735  each having a second central axis  740 . Each blade  735  includes a first obliquely angled edge  745  positioned on a first side  752  of the blade  735  and a second obliquely angled edge  750  positioned on a second side  754  of the blade  735  with cutting teeth  755  positioned along each edge  750 ,  755  between an end  760  of each blade  735  and the base  725 . An adjacent pair of first teeth  765   a  includes a first pitch  775  and an adjacent pair of second teeth  765   b  includes a second pitch  780  different than the first pitch  775 . The first pitch  775  is greater than the second pitch  780 . The first teeth  765   a  and the second teeth  765   b  share a tip  770  of a cutting tooth  755 . As such, consecutive adjacent cutting teeth  755  reciprocate between the first pitch  775  and the second pitch  780  such that a series of four adjacent cutting teeth  755  includes the second pitch  780  twice and the first pitch  775  once (e.g., starting with the second pitch  780  adjacent the end  760  and extending toward the base  725 ). 
     As the harvester  10  moves through the agricultural field to harvest relatively smaller sized crop plants (e.g., wheat), the adjacent pairs of second teeth  765   b  efficiently cut the wheat stalks. Conversely, as the harvester  10  moves through the agricultural field to harvest relatively larger sized crop plants (e.g., corn), the adjacent pairs of first teeth  765   a  efficiently cut the corn stalks. However, as the harvester  10  moves through the agricultural field to harvest relatively medium sized crop plants (e.g., beans), a combination of the first and second teeth  765   a ,  765   b  efficiently cut the bean stalks. In other embodiments, the first teeth  765   a  can help cut the wheat stalks, and the second teeth  765   b  can help cut the corn stalks. 
       FIG. 7  illustrates a cutting knife  1000  according to another embodiment. The cutting knife  1000  is similar to the cutting knife  100 ; therefore, similar components are designated with similar references numbers plus 900. At least some differences and/or at least some similarities between the cutting knives  100 ,  1000  will be discussed in detail below. In addition, the features described with respect to the cutting knife  100 , the cutting knife  400 , and/or the cutting knife  700  are equally applicable to features described with respect to the cutting knife  1000 . 
     The illustrated cutting knife  1000  includes a base  1025  having fastening apertures  1042  and a first central axis  1030 . The cutting knife  1000  also includes two blades  1035  each having a second central axis  1040 . Each blade  1035  includes a first obliquely angled edge  1045  positioned on a first side  1052  of the blade  1035  and a second obliquely angled edge  1050  positioned on a second side  1054  of the blade  1035  with cutting teeth  1055  positioned along each edge  1045 ,  1050  between an end  1060  of each blade  1035  and the base  1025 . An adjacent pair of first teeth  1065   a  includes a first pitch  1075  and an adjacent pair of second teeth  1065   b  includes a second pitch  1080  different than the first pitch  1075 . The first pitch  1075  is greater than the second pitch  1080 . The first teeth  1065   a  and the second teeth  1065   b  share a tip  1070  of a cutting tooth  1055 . As such, consecutive adjacent cutting teeth  1055  reciprocate between the first pitch  1075  and the second pitch  1080  such that a series of four adjacent cutting teeth  1055  include the first pitch  1075  twice and the second pitch  1080  once (e.g., starting with the first pitch  1075  adjacent the end  1060  and extending toward the base  1025 ). The cutting knife  1000  also includes a series of five adjacent cutting teeth  1055  that include the first pitch  1075  three times and the second pitch  1080  once. 
     As the harvester  10  moves through the agricultural field to harvest relatively smaller sized crop plants (e.g., wheat), the adjacent pairs of second teeth  1065   b  efficiently cut the wheat stalks. Conversely, as the harvester  10  moves through the agricultural field to harvest relatively larger sized crop plants (e.g., corn), the adjacent pairs of first teeth  1065   a  efficiently cut the corn stalks. However, as the harvester  10  moves through the agricultural field to harvest relatively medium sized crop plants (e.g., beans), a combination of the first and second teeth  1065   a ,  1065   b  efficiently cut the bean stalks. In other embodiments, the first teeth  1065   a  can help cut the wheat stalks, and the second teeth  1065   b  can help cut the corn stalks. 
     In the illustrated embodiments within  FIGS. 4-7 , the base  125 ,  425 ,  725 ,  1025  includes a width (along the first central axis  130 ,  430 ,  730 ,  1030 ) that accommodates two blades  135 ,  435 ,  735 ,  1035  such that the cutting knife  100 ,  400 ,  700 ,  1000  can be easily replaced on the head unit  45  (e.g., the cutting knife  100 ,  400 ,  700 ,  1000  is not too wide as to decease the serviceability of the cutting knife  100 ,  400 ,  700 ,  1000 ) while keeping the cost of manufacturing the cutting knife  100 ,  400 ,  700 ,  1000  relatively low. In other embodiments, each cutting knife  100 ,  400 ,  700 ,  1000  can include one of the blades  135 ,  435 ,  735 ,  1035 , or each cutting knife  100 ,  400 ,  700 ,  1000  can include more than two blades  135 ,  435 ,  735 ,  1035 . In further embodiments, at least one of the blades  135 ,  435 ,  735 ,  1035  can be sized differently (e.g., a smaller triangular shaped blade) than the other blade  135 ,  435 ,  735 ,  735 ,  1035  on the same base  125 ,  425 ,  725 ,  1025 . 
     Although the disclosure has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the disclosure as described. Various features and advantages of the disclosure are set forth in the following claims.