Abstract:
A blade with an easily and economically maintainable cutting edge for cutting vegetation in a rotary cutting machine such as in a lawnmower or brush cutter is described. A blade assembly is comprised of an elongated blade with replaceable inserts that enhance the cutting and mulching functions of the rotary cutting machine. The replaceable inserts are installed at a skew angle and provide an easily maintainable cutting edge that has geometrically shaped fingers that provide both a chopping and a slicing action that enhances the cutting performance of the blade assembly. Mulching blades re-cut the vegetation severed by the shaped fingers into smaller pieces before the vegetation exits the rotary cutting machine to minimize or eliminate the need to pick up the cut vegetation while maintaining an aesthetically pleasing final cut. Each replaceable insert has a safety connector that prevents the dislodging of the replaceable insert from the blade assembly during operation in the event that fasteners fail during operation. An integral blade is also anticipated that has geometrically shaped fingers installed at a skew angle that provide both a chopping and a slicing action.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates, in general, to blades for rotary cutting machines such as those used to maintain lawns and to cut various types of vegetation found in yards and fields. The ease with which the sharpness of the blade can be maintained is determined by the effort required to replace or remove the blade for sharpening. A cutting edge that provides both a chopping and slicing action while cutting the vegetation ensures a cleaner and more accurate cut. A blade that provides quick and economic maintenance of a sharp cutting edge in a rotary cutting machine with superior performance is provided in the present invention.  
         [0003]     2. Description of the Prior Art  
         [0004]     Maintaining sharp cutting edges in a rotary cutting machine is currently a time consuming and inefficient process that usually requires the removal of the entire blade from the mower. In both home and commercial mowing applications, the maintenance of a sharp cutting edge is very important due to the demand for a fast and aesthetically pleasing final cut which can be a major cost of operation. Typically, mowers utilize either a blade with a cutting edge at each end or two or more blades on a blade platform, each with a single cutting edge at one end, with three or more blades being very common. Dull blades cause the vegetation being cut to be broken off as opposed to being cut which effects the efficient operation of the mower and produces an unevenly and ununiformly cut lawn that frequently results in unsightly brown edges. The maintenance of blades with sharp cutting edges is important to achieving the desired result of an evenly cut lawn or field without brown edges.  
         [0005]     In order to maintain blades with a sharp cutting edge, a dull blade, in a prior art rotary cutting machine, must be removed and either sharpened by one of various well known methods or replaced with a new blade. Blade removal and sharpening is the most typical method of maintaining a sharp cutting edge. Problems can be encountered if the cutting edge is incorrectly sharpened. The cutting properties, balance, and hardness of the cutting edge, and safety could be dramatically affected by an improperly sharpened cutting edge. The typical end result of sharpening a case hardened blade is that the hardened surface of the cutting edge is removed, exposing softer metal that dulls more quickly than the original hardened surface, and the balance of the blade is upset. An improperly balanced blade increases the wear on the mower and can cause a greatly increased vibration which could cause failure of the metal in the blade. In a typical commercial mower, blade rpm is generally between 2000 to 4000 rpm. A broken blade could become dislodged due to vibration induced stress and possibly impact the operator or a bystander at a high velocity causing injury or damage.  
         [0006]     The process of removal, sharpening, balancing and installing a set of three blades in a typical commercial rotary cutting machine can take 30 minutes or more. For a commercial operator, with a fleet of mowing machines, a significant amount of human resources can be saved by providing a safe, rugged, inexpensive, replaceable alternative to the method of maintaining blades with sharp cutting edges commonly in use today.  
         [0007]     Complete replacement of the blade is expensive and time consuming. In prior art blades, some have been described with replaceable cutting edges. To date, none have gained market availability or acceptance due to various negative attributes such as lack of operator safety, poor cutting performance, manufacturing complexity, dangerous engineering defects (such as the replaceable cutting edge separating from the main blade due to fastener failure), and a high cost to produce. No prior art replaceable cutting edge blade has addressed the risk of a separation of the replaceable cutting edge element from the main blade in the event of fastener failure or disengagement during operation.  
         [0008]     Accordingly, it is an object of this invention to provide an effective blade for various applications of a rotary cutting machine that is inexpensive and easy to maintain which employs an effective system for easy alignment and secure retention during operation and employs an effective system for cutting vegetation that provides an aesthetically desirable final cut.  
       SUMMARY OF THE INVENTION  
       [0009]     In carrying out this invention, in one form thereof, a blade for cutting vegetation, such as grass in a typical lawn or a varied spectrum of vegetation in a field, by a rotary cutting machine is anticipated. The new features of the blade of the present invention are anticipated in the form of both a blade assembly or an integral blade. The blade assembly for cutting vegetation in a rotary cutting machine has an insert holder that is an elongated blade with two blade ends and has a longitudinal axis that extends beyond the length of the elongated blade. The elongated blade is adapted to rotate about a central axis that passes through the longitudinal axis, usually at a right angle. One or more insert ends are located at one or more of the blade ends, wherein each of the insert ends is configured to receive a replaceable insert. The elongated blade, in one embodiment of the invention, has a replaceable insert at only one of its blade ends. In this case, the elongated blade is attached to a blade platform at the blade end that does not have an insert end. Usually there are multiple elongated blades spaced around the circumference of the blade platform as the blade platform rotates about a central axis passing through the center of the blade platform and intersects each longitudinal axis.  
         [0010]     In the embodiment of the invention where the elongated blade has a replaceable insert attached at each of two insert ends, the central axis of rotation is located at the center of the elongated blade. In all embodiments of the present invention, maintaining balance of the elongated blade assembly or blade platform is anticipated. Each of the one or more insert ends have a top surface facing away from the vegetation, a bottom surface facing toward the vegetation, a leading edge that is formed to receive the replaceable insert; a trailing edge; one or more insert end fasteners for attaching the replaceable insert to the one or more insert ends; and a safety connector. The safety connector is included to ensure that the replaceable insert can not come loose from the elongated blade during operation. The safety connector functions by centrifugal force of the spinning elongated blade during operation to maintain the integrity of the blade assembly. In the event that the insert end fasteners that connect the replaceable insert to the insert end fails during operation, the centrifugal force created by the spinning elongated blade activates the safety connector to prevent the replaceable insert from dislodging from the insert end.  
         [0011]     The replaceable insert is a flattened blade adapted to mate with any one or more of the insert ends on the elongated blade. Each replaceable insert has a bottom side; a top side; a rear facing edge; a front facing edge for cutting vegetation; an insert safety connector that engages the safety connector on the one or more insert ends of the elongated blade; and one or more insert fasteners that matingly engages the one or more insert end fasteners on each of the one or more insert ends in order to connect the replaceable insert to each insert end. The replaceable insert can be configured to be mounted either on the top or on the bottom of each insert end. The bottom mount location is shown as a preferred embodiment in the attached drawings, but either method of installation is anticipated herein.  
         [0012]     The integral blade for cutting vegetation in a rotary cutting machine is an elongated blade with two blade ends and a longitudinal axis extending beyond the length of the elongated blade and is adapted to rotate about a central axis that passes through the longitudinal axis, usually at a right angle. One or more blade ends is formed into a cutting end. Each of the one or more cutting ends has a top surface facing away from the vegetation; a bottom surface facing toward the vegetation; a front facing edge for cutting the vegetation; and a trailing edge. The front facing edge for the integral blade has all of the features of the shaped leading edge for the replaceable insert described below. In an alternate embodiment, the integral blade has a cutting end at only one of its blade ends. In this case, the integral blade is attached to a blade platform at the blade end that does not have a cutting end. Usually there are integral blades spaced around the circumference of the blade platform. The blade platform rotates about a central axis passing through the center of the blade platform and intersects each longitudinal axis. In the case where the integral blade has a cutting end at each of two blade ends, the central axis of rotation is located at the center of the elongated blade. In both embodiments of one or two cutting ends on an integral blade, maintaining balance of the integral blade or blade platform is anticipated to minimize vibration while rotating during operation.  
         [0013]     The front facing edge of the replaceable insert and of the integral blade is a shaped leading edge that is tailored specifically to the vegetation to be cut. The shaped leading edge has a plurality of geometric fingers along the shaped leading edge. Each geometric finger has a spacing distance, S, and each has a depth, D. A shape ratio is defined by dividing the depth, D, by the spacing distance, S. The shape ratio is held to values between zero (0.00) and one (1.00) to maximize cutting efficiency and effectiveness. In selecting a shape ratio for a particular application, spacing distance should be larger than two times the diameter of the largest item of vegetation being cut to ensure optimum performance. A shape ratio of 0.3 is preferred for most applications.  
         [0014]     The most effective shapes of the geometric fingers described herein provide a combination of chopping and slicing of the vegetation in order to provide a cleaner and more uniform cut which is desired with any rotary cutting machine application. There are several geometric shapes anticipated for effective use in the present invention that provide both a chopping and slicing action when cutting vegetation; however, other geometric shapes are contemplated herein that may not have both a chopping and a slicing action. As the vegetation impacts the geometric fingers during operation, a sinusoidal shape chops at its top edge and bottom edge and slices at its side edges between its top edge and its bottom edge. In a similar manner, a trapezoidal shape chops at the top edge and slices along its side edges. A spaced trapezoidal shape chops both at its top edge and at its spaced edge while maintaining a slicing action along its side edges. Triangular shaped geometric fingers maximize the slicing action along its side edges while minimizing the chopping action at its top edge that forms a point but the point creates an improved ability to penetrate more difficult vegetation. A spaced triangular shape improves the chopping function along the space edge while maintaining the slicing action along the side edges and the penetration improvement of the top edge. A circular shaped geometric finger is similar in function to a sinusoidal shaped geometric finger and chops along its top edge and its bottom edge while it slices at its side edges between the top edges and the bottom edges. The geometric fingers are anticipated to have various other shapes such as conic sections, like parabolas or hyperbolas, or any other shape that combines a chopping, penetrating and a slicing action. The geometric finger can be a combination of different shapes or can be constructed with a variable shape factor.  
         [0015]     The front facing edge for the blade assembly and the integral blade, in addition to having geometric fingers, has a cutting angle relative to either the bottom side or the top side of the replaceable insert. The cutting angle is maintained between 20 degrees and 85 degrees for optimum performance. A cutting angle of 35 degrees is preferred for most applications. Angles are measured in a conventional counter clockwise manner, looking from one insert end with an insert installed toward the other end of the elongated blade or looking from one blade end of the integral blade toward the other end of the integral blade.  
         [0016]     One or more stiffening ribs can be added to either the blade assembly or the integral blade to improve performance in heavier duty applications. As either the blade assembly or the integral blade rotates during operation, an imbalance or stress due to impacting vegetation can cause the elongated blade to flex. The addition of a stiffening rib will minimize any flexing that might occur. Too much flexing will generate vibration and cause additional wear on the rotary cutting machine and on the elongated blade.  
         [0017]     One or more mulching blades can be added to either the blade assembly or to the integral blade to re-cut the vegetation that has been cut by the front facing edge. Mulching blades protrude above the top surface of the elongated blade at an angle greater than 20 degrees. The advantage to incorporating the mulching blades on either the blade assembly or the integral blade is that there is no need to collect the cut vegetation to achieve a cleanly cut appearance that is desirable in many applications wherein a rotary cutting machine is used. As the vegetation is re-cut into small pieces, it is evenly dispersed over the area being cut which further enhances vegetation growth as the cut vegetation decays.  
         [0018]     In order to enhance the performance of the blade assembly or the integral blade, the trailing edge of the insert end or of the cutting end, respectively, forms a lift surface with the top surface that causes air flow which lifts the vegetation into the path of the rotating front facing edge. The lift surface acts as a fan blade drawing air from the area of the vegetation which creates a vacuum effect on the vegetation making it stand up to be cut by the rotating blade assembly or integral blade. The result is uniformly cut vegetation such as grass in a lawn where each blade of grass has the appearance of being cut uniformly.  
         [0019]     The leading edge of the insert end on the blade assembly and the cutting edge on the integral blade are formed at a skew angle with the longitudinal axis. The skew angle changes the angle of attack for the front facing edge of the replaceable insert and the integral blade during operation. The skew angle adds a slicing action to any cutting edge and enhances the slicing action of the geometrically shaped fingers described above. The skew angle causes one section along the cutting edge to engage the vegetation prior to a second section engaging the vegetation relative to the direction that the rotary cutting machine advances over the vegetation which creates both a normal and a tangential component to the interaction between the front facing edge and the vegetation. The tangential component adds the slicing action to the path of the front facing edge as it passes through the vegetation being cut. The skew angle for best performance is between +15 degrees and −15 degrees relative to said longitudinal axis. A skew angle of 5 degrees is preferred for most applications. As stated above, angles are measured in a conventional counter clockwise manner, looking down on the top surface of the elongated blade.  
         [0020]     The replaceable insert is attached to the insert end of the elongated blade for the blade assembly by one or more insert end fasteners. There are various means and methods for connecting the replaceable insert to an insert end as contemplated in this invention. Most obvious is a combination of one or more nuts and bolts. Through holes are aligned through both the replaceable insert and the insert end where a bolt is passed through and a nut is connected thereto to join the replaceable insert to the insert end. One or more gripper tabs on the replaceable insert that extend from the replaceable insert over an edge of the insert end can be used to reinforce the union of the replaceable insert and the insert end which minimizes relative movement between the replaceable insert and the insert end, particularly when a hard object is struck during operation.  
         [0021]     In an alternate embodiment of the insert end fasteners, one or more fastener slots in the one or more insert ends is matingly located to receive one or more fastener tabs on the replaceable insert. The fastener tabs are inserted into the fastener slots and locked into place with a retainer spring by sliding the replaceable insert distally away from the central axis. A retention boss prevents the retainer spring from rotating during operation. One or more gripper tabs on the replaceable insert that extend from the replaceable insert over an edge of the insert end can be used to reinforce the union of the replaceable insert and the insert end which minimizes relative movement between the replaceable insert and the insert end, particularly when a hard object is struck during operation.  
         [0022]     One embodiment of a safety connector in a blade assembly in the present invention, is a safety tab on a replaceable insert that engages a safety tab slot on an insert end. There are several embodiments of safety tabs on replaceable inserts that mating engage safety tab slots on insert ends that are contemplated in the present invention. For example, a safety tab on a replaceable insert is a flap perpendicular to the replaceable insert with a hook protruding from the top of the flap and extending distally such that when the safety tab is inserted into a safety tab slot on an insert end and the replaceable insert is shifted distally away from the central axis, the hook on the safety tab engages the safety tab slot on the insert end. The safety tab slot in the insert end has a front wall substantially parallel to the longitudinal axis, a back wall substantially parallel to the longitudinal axis, a proximal wall that is generally perpendicular to the longitudinal axis and extends between the front wall and the back wall and a distal wall formed to create a locking angle relative to the longitudinal axis and extending between the front wall and the back wall. The safety tab is designed to maintain the installation of the replaceable insert under centrifugal loading induced by the rotation of the blade assembly and has been included in the present invention to prevent the dislodging of the replaceable insert in the event that insert fasteners fail during operation and cause damage or injury as a result of the replaceable insert striking a person or thing. In the event that the insert fasteners fail in this example, the safety tab will engage the distal wall of the safety slot at the locking angle. The replaceable insert will be under centrifugal loading during operation which will cause the safety tab to migrate to a more distal position along the locking angle of the safety tab slot thereby creating a force that pulls the front facing edge of the replaceable insert toward the trailing edge of the insert end. As the safety tab pulls the replaceable insert toward the trailing edge, the gripper tabs will more tightly engage the leading edge of the insert end completely securing the replaceable insert to the insert end. The locking angle anticipated in this invention is between 30 degrees and 60 degrees relative to said longitudinal axis measured in a conventional counter clockwise manner, here looking down on the top surface of the elongated blade. A locking angle of 45 degrees is preferred in most applications. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     A more complete understanding of the invention may be had by reference to the accompanying drawings in which:  
         [0024]      FIG. 1  is a perspective view of the bottom of a rotary cutting machine according to this invention, showing blade assembly with an insert holder with a replaceable insert located at each end of an elongated blade.  
         [0025]      FIG. 2  is a bottom view of a blade platform according to this invention, showing multiple blade assemblies with a single replaceable insert located at an insert end of an elongated blade.  
         [0026]      FIG. 3  is a perspective view of an insert holder, for use with a replaceable insert (not shown) located at each end of an elongated blade, to be installed using bolts and having a stiffening rib.  
         [0027]      FIG. 4  is a perspective view of a replaceable insert that uses nut and bolt combination as fasteners in cooperation with gripper tabs, having mulching blades and a safety tab.  
         [0028]      FIG. 5  is a perspective view of a blade assembly with an insert holder, showing a replaceable insert located at each end of an elongated blade showing an added detail of one replaceable insert being completely installed using bolts in cooperation with gripper tabs as fasteners and the other replaceable insert being partially installed prior to bolts being installed.  
         [0029]      FIG. 6  is a perspective view of a blade assembly with an insert holder having one insert end, showing a replaceable insert installed at the insert end of an elongated blade using bolts in cooperation with gripper tabs as fasteners and having mulching blades.  
         [0030]      FIG. 7  is a perspective view of a blade assembly with an insert holder having one insert end, as viewed from below, showing a replaceable insert, indicating assembly order using bolts in cooperation with gripper tabs as fasteners.  
         [0031]      FIG. 8  is a perspective view of a replaceable insert with a safety tab without mulching blades using bolts in cooperation with gripper tabs as fasteners.  
         [0032]      FIG. 9  is a perspective view of an insert holder, for use with a replaceable insert (not shown) located at each end of an elongated blade, to be installed using fastener slots in cooperation with a replaceable insert having fasteners tabs without a stiffening rib.  
         [0033]      FIG. 10  is a perspective view of a replaceable insert that uses fastener tabs in cooperation with gripper tabs and fastener slots in an insert end (not shown) as fasteners, having mulching blades and a safety tab.  
         [0034]      FIG. 11  is a perspective view of a blade assembly with an insert holder, showing a replaceable insert located at each end of an elongated blade with the added detail of one replaceable insert being completely installed using fastener tabs in cooperation with gripper tabs and fastener slots on insert ends as fasteners and the other replaceable insert being partially installed showing the transition of the fastener tabs and the safety tab as they advance from first insertion to final installation.  
         [0035]      FIG. 12  is a perspective view of a blade assembly with an insert holder having one insert end, showing a replaceable insert installed at the insert end of an elongated blade with fastener tabs acting in cooperation with fastener slots and gripper tabs as fasteners and having mulching blades.  
         [0036]      FIG. 13  is a perspective view of a blade assembly with an insert holder having one insert end, as viewed from below, showing a replaceable insert, indicating assembly order using fastener tabs and fastener slots in cooperation with gripper tabs as fasteners.  
         [0037]      FIG. 14  is a perspective view of a replaceable insert with a safety tab without mulching blades using fastener tabs and fastener slots (not shown) in cooperation with gripper tabs as fasteners.  
         [0038]      FIG. 15  is a top view of a section of one embodiment of a shaped leading edge, a spaced trapezoid, on a replaceable insert, indicating the dimensional relation between the spacing distance, S, of each finger and the depth, D, of each finger.  
         [0039]     FIGS.  16 ( a ) through  16  ( h ) are perspective views of several embodiments of the shaped leading edge of the replaceable insert, showing various embodiments that are contemplated to be used as geometric fingers and defining the cutting angle formed, as shown, with the bottom face of the replaceable insert.  
         [0040]      FIG. 17  is a perspective view of a replaceable insert with an alternate embodiment of a safety tab with mulching blades for use with nut and bolt combinations in cooperation with gripper tabs as fasteners.  
         [0041]      FIG. 18  is a perspective view of an alternate embodiment of an insert holder and a replaceable insert with another alternate embodiment of a safety tab with mulching blades for use with nut and bolt combinations in cooperation with gripper tabs as fasteners.  
         [0042]      FIG. 19  is a perspective view of an integral blade with a shaped leading edge installed at a skew angle and with a lift surface without mulching blades. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]     Referring now to the drawings wherein like reference numerals have been used throughout to designate like parts among the several views. Referring to  FIG. 1  which shows a perspective view of the bottom of a rotary cutting machine  10  having a blade assembly  5  with an insert holder  20  located at each blade end  6  of elongated blade  22  each with a replaceable insert  30  that rotates about a central axis  7 . In  FIG. 2 , blade platform  15  is shown with multiple blade assemblies  5 , each having an elongated blade  22  with a single insert holder  20  and a replaceable insert  30  located at only one blade end  6  spaced around the circumference of blade platform  15  configured to rotate about central axis  7 .  
         [0044]      FIG. 3  is a perspective view of insert holder  20  prior to the installation of replaceable inserts  30  (not shown). Insert holder  20  consists of an elongated blade  22  that rotates about central axis  7 . Longitudinal axis  24  extends beyond the length of insert holder  20  to define relative placement of elements of the present invention. Elongated blade  22 , as shown, has two insert ends  25  located distally from central axis  7  at each blade end  6  of insert holder  20 . Each insert end  25  has a top surface  26 , bottom surface  27 , trailing edge  29  and leading edge  28 . Leading edge  28  is shaped to engage replaceable insert  30  (not shown). Blade holes  43  are located on insert end  25  to match up with similar holes in replaceable insert  30  (not shown). Leading edge  28  is formed at skew angle  31  relative to longitudinal axis  24 . Skew angle  31  is maintained between +15 degrees and −15 degrees relative to longitudinal axis  24 . Trailing edge  29  forms lift surface  33  with top surface  26 . Lift surface  33  functions during operation to generate a vacuum on the vegetation being cut (not shown) so that a clean and accurate cut is achieved. In order to provide a stronger elongated blade  22 , stiffening rib  37  is incorporated on insert holder  20 . Additional stiffening ribs  37  can be incorporated if a more ridged blade is desired. Safety tab slot  32  is located to engage a safety tab  42  on replaceable insert  30  (not shown). Safety tab slot  32  has a front wall  51  that is generally parallel to longitudinal axis  24 , a back wall  52  that is generally parallel to longitudinal axis  24 , proximal wall  53  generally perpendicular to longitudinal axis  24  that extends between front wall  51  and back wall  52 . Distal wall  54  extends between front wall  51  and back wall  52  at locking angle  41  relative to the longitudinal axis  24 .  
         [0045]      FIG. 4  is a perspective view of one preferred embodiment of replaceable insert  30 . Replaceable insert  30  is a formed from a flattened blade  35 . Flattened blade  35  has a front facing edge  36 , a topside  39 , a bottom side  38 , a safety tab  42 , mulching blades  45 , gripper tabs  46  and insert holes  55 . Front face edge  36  is comprised of a shaped leading edge  40 . One embodiment of a preferred shaped leading edge is a sinusoidal shape as shown in  FIG. 4 . Mulching blades  45  protrude above top side  39 . As shown a  FIG. 4 , mulching blades  45  are oriented relative to front facing edge  36  at mulching blade angle  47 . Mulching blades  45  in other possible embodiments are arranged such that there is a mulching blade edge  57  oriented toward front facing edge  36  to re-cut vegetation (not shown) after being cut by shaped leading edge  40 .  
         [0046]     A perspective view of blade assembly  5  with two insert holders  20  on elongated blade  22  each with a replaceable insert  30  is shown in  FIG. 5 . Assembled end  11  shows replaceable insert  30  completely installed on insert end  25 . Partially assembled end  12  shows replaceable insert  30  just prior to complete assembly with safety tab  42  inserted in safety tab slot  32 . After inserting safety tab  42  in safety tab slot  32 , replaceable insert  30  is shifted distally from central axis  7  causing safety tab  42  to engage distal wall  54  and causes blade holes  43  to align with insert holes  55  (not shown) in replaceable insert  30 . At assembled end  11 , safety tab  42  has been inserted in safety tab slot  32  and adjusted to engagement position  48 . Nut and bolt combinations  44  securely fasten replaceable insert  30  to insert end  25 . Gripper tabs  46  engage leading edge  28  to further secure replaceable insert  30  to insert end  25 . In the event that nut and bolt combination  44  fails, safety tab  42  will be forced against distal wall  54  through centrifugal force and further cause gripper tabs  46  to be drawn tightly against leading edge  28  as it migrates along locking angle  41 , thereby preventing replaceable insert  30  from becoming dislodged from insert end  25 . Trailing edge  29  forms lift surface  33  with top surface  26 . Lift surface  33  functions during operation to generate a vacuum on the vegetation being cut (not shown) so that a clean and accurate cut is achieved. In order to provide a stronger elongated blade  22 , stiffening rib  37  is incorporated on insert holder  20 . Additional stiffening ribs  37  can be incorporated if a more ridged blade is desired. Mulching blades  45  re-cut the vegetation that has been cut by the front facing edge  36 . Mulching blades  45  protrude above the top surface  26  of elongated blade  22 .  
         [0047]      FIG. 6  shows a perspective view of blade assembly  5  with replaceable insert  30  installed on insert holder  20 , as was described in  FIG. 5 , but only at only one insert end  25 . Insert holder  20  is contemplated to be used with a blade platform  15  as shown in  FIG. 2 . Insert holder  20  is attached to blade platform  15  (not shown) at pin hole  56 .  FIG. 7  is a perspective view of blade assembly  5  with insert holder  20  with a replaceable insert  30  as shown in  FIG. 6  prior to assembly. Nut and bolt combination  44  aligns insert holes  55  with blade holes  43  as safety tab  42  is inserted in safety tab slot  32  and shifted distally from pin hole  56 .  FIG. 8  is a perspective view of an alternate embodiment of replaceable insert  30  without mulching blades  45  as shown in  FIG. 4 . Replaceable insert  30  has insert holes  55  for use with nut and bolt combination  44  (not shown) to attach replaceable insert  30  to insert end  25  (not shown).  
         [0048]     An alternate embodiment of insert holder  20  is shown in perspective view in  FIG. 9 . Insert holder  20  is shown with two insert ends  25  such that during operation it will rotate about central axis  7  that passes through a midpoint of insert holder  20 . In this embodiment, no stiffening rib  37  is shown as was shown in  FIG. 3  but is also contemplated for this embodiment. Leading edge  28  is a simple chamfered edge as shown. In  FIG. 9 , fastener slots  58  replace blade holes  43  and insert holes  55  as shown in  FIG. 3  and  FIG. 4 , respectively. Retainer spring  59  is attached to insert end  25  by retention fastener  61 . Retention boss  62  prevents retainer spring  59  from rotating during operation. All other features of insert holder  20  as described in  FIG. 3  are equally contemplated for insert holder  20  as shown in  FIG. 9 .  FIG. 10  is a alternate embodiment of replaceable insert  30  as was shown in  FIG. 4  with fastener tabs  60  that engage fastener slots  58  on alternate embodiment of insert holder  20  shown in  FIG. 9  and replace nut and bolt combination  44  as shown in  FIG. 5 .  
         [0049]     A perspective view of an alternate embodiment of blade assembly  5  with two insert holders  20  with replaceable inserts  30  with fastener tabs  60  is shown in  FIG. 11 . Assembled end  11  shows replaceable insert  30  completely installed on insert end  25 . Partially assembled end  12  shows replaceable insert  30  just prior to complete assembly with safety tab  42  inserted in safety tab slot  32  and fastener tabs  60  inserted in fastener slots  58 . Retainer spring  59  is moved under spring tension to permit safety tab  42  to be inserted into safety tab slot  32 . After inserting safety tab  42  in safety tab slot  32  and fastener tabs  60  into fastener slots  58 , replaceable insert  30  is shifted distally from central axis  7  causing safety tab  42  to engage distal wall  54  and causes fastener tabs  60  to engage fastener slots  58  in replaceable insert  30 . Referring now to assembled end  11 , safety tab  42  has been inserted in safety tab slot  32  and adjusted to engagement position  48 . Retainer spring  59  closes behind safety tab  42  as safety tab  42  engages distal wall  54 , retainer spring  59  holds safety tab  42  at engagement position  48  during operation. Retainer bosses  62  keeps retainer spring  59  from rotating about retention fastener  61  during operation. Gripper tabs  46  engage leading edge  28  to further secure replaceable insert  30  to insert end  25 . During operation, safety tab  42  and fastener tabs  60  will engage safety tab slot  32  and fastener slots  58 , respectively, through centrifugal force and further cause gripper tabs  46  to be drawn tightly against leading edge  28  as safety tab  42  slides along locking angle  41 , thereby securely connecting replaceable insert  30  to insert end  25 . Fastener tabs  60  and fastener slots  58  are the main means to connect replaceable insert  30  to insert end  25 . Safety tab  42  in cooperation with safety tab slot  32  provide a back up means to ensure that replaceable insert  30  does not become dislodged from insert holder  20  in the event that fastener tabs  60  fail.  
         [0050]      FIG. 12 , is a perspective view of an alternate embodiment of blade assembly  5  with replaceable insert  30  installed on insert holder  20 , as was described in  FIG. 11 , but only at one insert end  25  with fastener tabs slots  58 . Insert holder  20  is contemplated to be used with a blade platform  15  as shown in  FIG. 2 . Insert holder  20  is attached to blade platform  15 , shown in  FIG. 2 , at pin hole  56 .  FIG. 13  is a perspective view of an alternate embodiment of insert holder  20  with replaceable insert  30  from  FIG. 12  prior to assembly. Fastener tabs  60  and safety tabs  42  are shown prior to assembly as safety tab  42  and fastener tabs  60  are inserted in safety tab slot  32  and fastener slots  58 , respectively.  FIG. 14  is a perspective view of an alternate embodiment of replaceable insert  30  with fastener tabs  60  and without mulching blades  45  as shown in  FIG. 10 .  
         [0051]      FIG. 15  (not to scale) is a top view of a section of shaped leading edge  40  of replaceable insert  30  (not shown in its entirety) defining spacing distance  63  and depth  64  of geometric fingers  70 . Shaped leading edge  40  has a plurality of geometric shaped fingers  70 . A spaced trapezoidal shape is shown in  FIG. 15  for illustration purposes; however, other shapes are equally contemplated and will be described herein. Spacing distance (S)  63  is the distance between equivalent points along shaped leading edge  40 . Depth (D)  64  is the distance from top edge  67  of a geometric finger  70  to spaced edge  66 , as shown here, or to an equivalent point at the base of a geometric finger  70  that may not have a spaced edge  66  as will be described below. The ratio of depth  64  divided by spacing distance  63  defines a shape ratio (SR)  71 . The shape ratio  71  is held to values between zero (0.00) and 1.00 for best performance. Optimally the shape ratio is 0.3. During cutting operation, top edge  67  and spaced edge  66  chop the vegetation while side edge  68  slices the vegetation. The combination of chopping and slicing the vegetation provide a more accurate and effective cut which is an object of this invention.  
         [0052]      FIG. 16 ( a ) through  16 ( g ) show a perspective view of various embodiments of shaped leading edge  40 . Each embodiment shown provides a cleaner and more uniform cut for various cutting applications which is desired with any rotary cutting machine. As the vegetation impacts the geometric fingers  70  during operation, a sinusoidal shape shown in  FIG. 16 ( a ) chops at its top edge  67  and bottom edge  69  and slices at its side edges  68 . A circular shaped geometric finger  70  shown in  FIG. 16 ( b ) is similar in function to a sinusoidal shaped geometric finger  70  shown in  FIG. 16 ( a ) since the top edge  67  and bottom edge  69  chop and the side edge  68  slice vegetation. A rectangular shaped geometric finger  70  as shown in  FIG. 16 ( c ) is better suited for tougher cutting applications such as fields where saplings might be cut because there is only a chopping function that is accomplished by top edge  67  and spaced edge  66 . FIGS.  16 ( d ) and  16 ( e ) show two embodiments of triangular shaped geometric fingers  70 . In  FIG. 16 ( d ), top edge  67  is a point that provides improved penetration but no chopping function while still providing a slicing function with its side edges  68 . The chopping function is added in the spaced triangular shape of  FIG. 16 ( e ), where spaced edge  66  provides a chop edge. In a similar manner as shown in FIGS.  16 ( f ) and  FIG. 16 ( g ), both trapezoidal shapes chop at top edge  67  and slice at side edges  68 . Spaced trapezoidal shape shown in  FIG. 16 ( g ) has an additional chop edge at spaced edge  66  that is not present in the trapezoidal shape in  FIG. 16 ( f ). Geometric fingers  70  are anticipated to have various other shapes such as conic sections, like parabolas or hyperbolas or any other shape, in particular any shape that combines a chopping or penetrating and a slicing action. The cross section A-A′ of front facing edge  36  is shown in  FIG. 16  ( h ) and has a cutting angle  65  relative to either the bottom side  38  or the top side  39  of replaceable insert  30  and is common among all embodiments of shaped leading edge  40 . For optimum performance, cutting angle  65  is maintained between 20 degrees and 85 degrees. A cutting angle  65  of 35 degrees is preferred for most applications. Angles are measured in a conventional counter clockwise manner, looking from one end of replaceable insert  30  toward the other end of the replaceable insert  30 .  
         [0053]      FIG. 17  shows a perspective view of an alternate embodiment of replaceable insert  30  shown in  FIG. 4  for use on insert end  25  shown in  FIG. 3 . Safety tab  42  in  FIG. 17  is constructed differently but is installed and functions in the same manner as the safety tab  42  from  FIG. 4  without changing safety tab slot  32  in  FIG. 3 .  
         [0054]      FIG. 18  shows a perspective view of and alternate embodiment of insert end  25  as shown in  FIG. 3  and replaceable insert  30  as shown in  FIG. 4 . Insert end  25  in  FIG. 18  has a different configuration for safety tab slot  32  and is constructed to receive the alternate embodiment of safety tab  42  on replaceable insert  30 . Both embodiments function in a similar manner, safety tab  42  is inserted into safety tab slot  32  on insert end  25  and shifted distally to align insert holes  55  with blade holes  43  for assembly. In the event fastener failure, centrifugal force will act to engage safety tab  42  with safety tab slot  32  to prevent dislodging of replaceable insert  30 .  
         [0055]     Integral blade  72  is shown in perspective view in  FIG. 19  with two blade ends  6  each configured with a cutting end  75 . Each cutting end  75  has an embodiment of a shaped leading edge  40  as shown in FIGS.  16  ( a ) through  16 ( h ). In similar manner to the leading edge  28  of  FIG. 3 , shaped leading edge  40  is formed at a skew angle  31  relative to longitudinal axis  24 . Each cutting end  75  has a top surface  26 , bottom surface  27 , trailing edge  29  and shaped leading edge  40 . Skew angle  31  is maintained between +15 degrees and −15 degrees relative to longitudinal axis  24 . A skew angle  31  of 5 degrees is optimum for most applications. Trailing edge  29  forms lift surface  33  with top surface  26 . Lift surface  33  functions during operation to generate a vacuum on the vegetation being cut (not shown) so that a clean and accurate cut is achieved. In order to provide a stronger integral blade  72 , a stiffening rib  37 , as shown in  FIG. 3 , can be added to integral blade  72  to improve performance for heavier duty applications. Mulching blades  45  (not shown) are also contemplated for an alternate embodiment of the integral blade  72 .  
         [0056]     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.