Abstract:
A blade sharpener comprises a work surface consisting of a single support line. A grinding wheel defines a plane that contains the support line. The grinding wheel is swingable in the grinding wheel plane to a selected position relative to the support line. A blade is supported on the support line in a manner that produces a first cutting surface on the blade cutting edge. The single support line enables mulching blades to be sharpened without having to impart angular motions in space to them as they are fed past the grinding wheel. The grinding wheel is swingable to different positions relative to the support line, thereby enabling the grinding wheel to produce different cutting surfaces on the blades. Swinging of the grinding wheel is achieved by mounting it to a plate that pivots about an axis perpendicular to the grinding wheel plane. A mobile work table having a top plate of finite area is selectively retainable over and removable from the single line support.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to sharpening equipment, and more particularly to apparatus that sharpens a wide variety of cutting blades. 
     2. Description of the Prior Art 
     Rotary power mowers of various types are well known and are in widespread use. They vary greatly in size, complexity, and operating characteristics. However, all rotary power mowers utilize the common component of a rotary cutting blade. The blades are relatively long, narrow, and thin. A cutting edge is sharpened into each end of the blade. As the blade rotates under power from the mowing machine, the cutting edges shear vegetation. 
     The cutting edges of some rotary blades lie along substantially straight lines for their full lengths. A typical example of such a blade is shown at reference numeral  3  in FIGS. 1-3. The blade  3  has a longitudinal centerline  4  and a flat bottom surface  6 . There are a pair of cutting edges  8 , both of which lie along straight lines  10  that are substantially parallel to the longitudinal centerline  4 . The cutting edges  8  and the straight lines  10  coincide. 
     Each cutting edge  8  is defined by the junction of the blade bottom surface  6  and a cutting surface  12 . The bottom surface  6  and cutting surface  12  subtend a cutting angle L. Each cutting edge  8  intersects an end  34  of the blade  3  at a tip  38 . The tips  38  are especially important, because they are the portions of the blade  3  that first come into contact with the vegetation being cut by a power mower. The blade has back edges  2  opposite the cutting edges  8 . There are an infinite number of imaginary lines  14  along the blade bottom surface  6  between the cutting edge  8  and the back edge  2 . Flat blades such as the blade  3  are used to shear vegetation and expel it tangentially away from a mowing machine. 
     Other cutting blades have cutting edges that are not straight but instead lie along curved lines. The curved cutting edges are particularly useful for mulching the vegetation in addition to shearing it and expelling it. FIGS. 4-7 show a typical mulching blade  16  having five sections: a relatively long center section  26 , a pair of angled sections  28  that slope downwardly and away from the ends of the center section  26 , and a pair of end sections  30  on the ends of the angled sections  28 . The end sections  30  lie in a plane that is substantially parallel to the plane of the center section  26 . The center section has a bottom surface  22 , the angled sections have respective bottom surfaces  48 , and the end sections  30  have respective bottom surfaces  49 . 
     The mulching blade  16  further has curved cutting edges  18 . Each cutting edge  18  lies along a respective curved line  20 . The cutting edges  18  and lines  20  are defined by the junctions of the bottom surfaces  22 ,  48 ,  49  of the blade sections with associated cutting surfaces  24 . The cutting edges  18  intersect the ends  40  of the mulching blade at tips  42 . There are an infinite number of imaginary lines  32  on the mulching blade bottom surfaces between the cutting edges  18  and the back edges of the blade opposite the cutting edges. 
     A routine task associated with rotary power mowers is sharpening the blades. For that purpose, a variety of mechanized equipment has been developed. For example, a division of Wall Enterprises, Inc. of New Whiteland, Ind., markets rotary blade grinding machines. Magna-Matic Corporation of Waldo, Wis., is a manufacturer of blade grinding and balancing machines. 
     Prior blade sharpening machines have not been entirely satisfactory. As one reason, they generally have been limited to sharpening blades with straight cutting edges, i.e., flat blades such as blade  3  depicted in FIGS. 1-3. That is because the prior machines had flat work surfaces of substantial area and lying in a single plane. The blades were supported on the work surfaces and manually fed lengthwise, i.e., parallel to the longitudinal centerline  4  of the blade  3 , while in contact with a grinding wheel. The flat area of the work surface was satisfactory for straight edge blades, because no angular movements of the blade in space were required to grind the cutting edge. 
     On the other hand, the flat area work surfaces of prior blade sharpeners presented considerable difficulty with mulching blades, such as mulching blade  16  of FIGS. 4-7. That is because the mulching blade curved edges  18  required that the blades be fed crosswise in addition to lengthwise in order to properly grind the curved cutting edges. Simultaneous crosswise and lengthwise feeding of the blades was difficult to do, especially at the transitions between the various sections, such as the transitions between the center section  22  and the angled sections  28 , and the transitions between the angled sections and the end sections  30 . The prior sharpeners used relatively wide grinding wheels, such as one inch, which exacerbated the problem. Moreover, with a flat work surface of substantial area, the curved cutting edges of the different sections contacted the grinding wheel at different angular locations on the grinding wheel periphery. As a result, the cutting angles of the cutting edges at the different blade sections varied considerably. A uniform cutting angle was possible only by carefully imparting angular motions to the blade while lengthwise and crosswise feeding it. 
     An associated problem with the large flat work surface of a prior machine is that the work surface is cut out to make room for the grinding wheel. The work surface is therefore rather limber and prone to vibrate and create excessive noise during operation. A related problem with the cutout in the work surface is that the blade cutting edge is not supported directly under the grinding wheel. It is very difficult to properly grind the tips of a blade using such a machine, because the cutting force of the grinding wheel is not resisted by any force except that produced by the operator. Even if the operator does not yield to the cutting force, the blade itself can bend because it is only cantilever supported by the work surface. Since the tips of the cutting edges are the most important part of the blade, any error in grinding the tips is quickly reflected in substandard mowing machine performance. 
     U.S. Pat. No. 5,329,731 shows an attachment for a grinding machine that facilitates sharpening mulching blades. The attachment has two flat work surfaces, each of substantial area, along which a blade is fed. However, the flat large area work surfaces limit the attachment&#39;s usefulness when sharpening mulching blades having certain contours. In fact, some style mulching blades can not be sharpened at all when using the attachment of the U.S Pat. No. 5,329,731 patent. For some other mulching blades, even using the attachment of the U.S. Pat. No. 5,329,731 patent produces varying cutting angles on the blade cutting edges along different sections of the blade. 
     Yet another deficiency of prior sharpening machines concerns the grinding wheels and their mountings. In prior machines, the grinding wheels were mounted directly to the armature shafts of electric motors. Accordingly, the grinding speed was limited to the motor speed. However, many grinding wheels are capable of cutting at higher speeds than conventional motor speeds. Hence, the full cutting capabilities of the grinding wheels were not used. A related problem concerns the composition of the grinding wheels used with prior blade sharpeners. To compensate for the lower production obtained by slower than usable grinding wheel speeds, prior sharpeners used harder than necessary grinding wheels. Such grinding wheels tended to burn rather than cut the metal from the blades. Further, the excessively hard grinding wheels easily loaded up with steel particles from the blades. Consequently, the grinding wheels had to be dressed periodically, which resulted in unproductive time. 
     Perhaps the biggest problem with prior blade grinding machinery is the lack of ability to grind blades of any length and configuration. For example, the grinding machine shown in U.S. Pat. No. 5,329,731 has upstanding posts that restrict lengthwise and even crosswise feeding of a blade past the grinding wheel. Consequently, the size and type of blades that are sharpenable are limited. 
     Thus, a need exists for improvements in blade grinding machines. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a blade sharpener is provided that is capable of properly and efficiently grinding both curved and straight edge blades without restriction. This is accomplished by apparatus that includes a work surface that supports a blade only along a single straight line, but that support line is directly opposite the surface of the blade being sharpened. 
     According to one aspect of the invention, the support line is a longitudinal line along a cylindrical surface on the top of a pedestal. The pedestal is mounted to a base. A pivot plate is connected to the base for pivoting about a horizontal axis. An electric motor and a grinding wheel are secured to the pivot plate. The grinding wheel is relatively narrow, and it is driven by a belt from the motor. The grinding wheel defines a plane that is parallel to and that contains the support line of the work surface. An adjustment mechanism pivots the pivot plate to adjust the position of the grinding wheel relative to the work surface. 
     To use the blade sharpener, the pivot plate is adjusted to bring the grinding wheel periphery close to the work surface. A blade to be sharpened is oriented such that its longitudinal centerline is generally horizontal and perpendicular to the work surface. The blade cutting edge is also usually perpendicular to the work surface. The end of the blade is placed on the work surface. The blade is fed crosswise into contact with the grinding wheel periphery such that the cutting edge at the blade tip is sharpened. The support by the work surface directly under or very close to the cutting edge at the blade tip minimizes any problems associated with sharpening the tip. The blade is then fed lengthwise along the grinding wheel periphery, all the while being supported only by the single support line of the work surface. When an angled section of the blade, and the corresponding curve in the cutting edge, reaches the work surface, the single support line enables the blade to rise and fall relative to the grinding wheel while keeping the blade cutting edge always in contact with the grinding wheel and always supported directly under or close to the blade surface being cut by the grinding wheel. In that manner, blades of a wide variety of contours and cutting edges can be efficiently sharpened. 
     Further in accordance with the present invention, blades having cutting edges of unlimited length are sharpenable. The blade sharpener has no posts or other members that restrict the length of the blade cutting edge. Similarly, there is no crosswise restriction in the access of the blade to the grinding wheel. 
     It is a further feature of the invention that it takes full advantage of modern grinding wheel technology. As one example, the production rates available from high grinding wheel speeds now available are utilized by means of an updrive of the belt drive between the motor and the grinding wheel. Consequently, rather than being limited to the speed of the motor, the grinding wheel is rotated approximately 20 percent faster than in prior blade sharpening machines. At the same time, the grinding wheel has a hardness only slightly greater than that of steel blades. The combination of the relatively soft grinding wheel and higher grinding wheel speed results in rapid and clean cutting of the blade during the sharpening process. The tendency of burning metal, rather than cutting it, from the blade that results from using the prior hard grinding wheels at slower speeds, is eliminated. In addition to having higher production, the blade sharpener of the invention eliminates the need for a grinding wheel dresser. 
     According to another aspect of the invention, a flat work surface of substantial area is interchangeable with the single support line work surface. For that purpose, a mobile work table has a top plate from which depend a pair of parallel lugs. The lugs are spaced apart a distance slightly greater than the width of the pedestal that includes the single line work surface. A clamp is joined to the lugs. By placing the mobile work table over the pedestal and actuating the clamp, the large area flat work surface is retained on the blade sharpener. The mobile work table finds use when sharpening flat workpieces such as straight rotary mower blades. 
     The method and apparatus of the invention, using a single line work support surface, thus sharpens mulching blades in an efficient manner. The single support line enables blades of practically any size and contour to be sharpened, even though the blades are supported directly opposite the blade surface being sharpened by the grinding wheel. 
     Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a typical straight cutting blade that is advantageously sharpened by the blade sharpener of the present invention. 
     FIG. 2 is a top view of FIG.  1 . 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG.  2  and rotated 90 degrees clockwise. 
     FIG. 4 is a perspective view of a typical mulching blade that is efficiently sharpened on the blade sharpener of the invention. 
     FIG. 5 is a front view of the mulching blade of FIG.  4 . 
     FIG. 6 is a top view of FIG.  5 . 
     FIG. 7 is a cross-sectional view taken along line  7 — 7  of FIG.  6  and rotated 90 degrees clockwise. 
     FIG. 8 is a perspective view of the front side of the blade sharpener of the invention. 
     FIG. 9 is a perspective view of the back side of the blade sharpener. 
     FIG. 10 is an end view of the single line work support and pedestal of the blade sharpener. 
     FIG. 11 is a schematic view showing the relation between the grinding wheel and the work surface according to the present invention. 
     FIG. 12 is a view similar to FIG. 8, but showing a mulching blade being sharpened by the blade sharpener of the invention. 
     FIG. 13 is a perspective view of a mobile work table for the blade sharpener. 
     FIG. 14 is an end view showing the mobile work table retained to the blade sharpener. 
     FIG. 15 is a perspective view showing a straight blade being sharpened using the mobile work table of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto. 
     Referring to FIGS. 8 and 9, a blade sharpener  1  is illustrated that includes the present invention. The blade sharpener  1  is particularly useful for sharpening blades, such as those typically represented at reference numeral  3  of FIGS. 1-3 and reference numeral  16  of FIGS. 4-7, of rotary lawn mowers. However, it will be understood that the invention is not limited to use with rotary cutting implements. 
     The blade sharpener  1  is comprised of a sturdy C-shaped frame  5  having a base  7 , a back wall  9 , and a top wall  11 . A post  13  between the base  7  and the top wall  11  adds rigidity to the frame  5 . The blade sharpener is easily portable by means of a handle  15  on the top wall and several rubber feet  17  on the underside of the base. 
     Upstanding from the top surface of the base  7  are a pair of brackets  19 . As illustrated, each bracket  19  is L-shaped, having a short leg  21  that is fastened to the base and a vertical leg  23 . A shaft  25  extends between the legs  23  of the brackets. The shaft  25  defines an axis  26  and pivotally supports a pivot plate  27 . 
     Pivoting of the pivot plate  27  about the shaft  25  is achieved by an adjustment mechanism  29 . In the preferred embodiment, the adjustment mechanism  29  is in the form of a crank  31  with a handle  33 . The crank  31  receives a stud  35  that passes through a slot  72  in the frame top wall  11 . The stud  35  has right-hand threads at one end  37  and left-hand threads at the other end  39 . The threads at end  37  engage mating threads of a trunion  41 . The trunion  41  is supported on the frame top wall by a pair of bearings  43 . The stud end  39  engages a clevis  45 . The clevis  45  is attached to the pivot plate by a swivel pin  47 . It is thus seen that oppositely turning the crank  31  causes the pivot plate to pivot in the directions of arrows  44  and  46  about the shaft  25 . 
     Secured to the pivot plate  27  close to the adjustment mechanism  29  is an electric motor  47 . For example, a flange of the motor  47  may be secured to the pivot plate by fasteners, not shown. The motor armature shaft  51  extends through the pivot plate. A timing pulley  53  is connected to the motor shaft  51 . 
     On the opposite end  54  of the pivot plate  27  as the adjustment mechanism  29  is a narrow grinding wheel  55 . The grinding wheel  55  has a periphery  52  and two flat sides  50 . The grinding wheel  55  is on the same side of the pivot plate as the motor  47 . The grinding wheel is rotatably mounted to the pivot plate for rotation about an axis  56 . The grinding wheel defines a plane  60  that is perpendicular to the grinding wheel axis of rotation  56 . Also see FIG.  10 . The plane  60  is approximately midway between the grinding wheel side surfaces  50 . 
     Mounting of the grinding wheel  55  is preferably by a shaft  59  that rotates in a pair of flange bearings  57 , one of which is secured to each side of the pivot plate  27 . A threaded arbor  74  with a driving flange fits over and rotates with the shaft  59 . The grinding wheel is clamped on the arbor  74  against the driving flange by an arbor nut  76  and spacer  78 . The arbor driving flange conforms to American National Standards Institute specification B7.1-1988. A pulley  58  is connected to the shaft  59  on the opposite side of the pivot plate as the grinding wheel. The pulley  58  has a diameter that is preferably approximately 20 percent smaller than the motor pulley  53 . A timing belt  61  is trained over the two pulleys  53  and  58 . Accordingly, energizing the motor  47  causes the grinding wheel to rotate approximately 20 percent faster than the motor shaft  51 . Rotation of the grinding wheel is unidirectional in the direction of arrow  62 . It will be recognized that turning the adjustment mechanism crank  31  turns the stud  35  and causes the grinding wheel axis of rotation to swing in the directions of the arrows  44  and  46  along an arcuate line  64 . 
     According to an important aspect of the invention, the grinding wheel  55  is made of relatively soft materials. Specifically, the grinding wheel ceramic and binder are only slightly harder than the hardness of the steel of commercially important cutting blades. A preferred grinding wheel is one marketed by the Norton Company of Worchester, Mass., under model number  32 A. Further, the width of the grinding wheel is relatively narrow compared to prior grinding wheels. For example, in a preferred embodiment of the blade sharpener  1 , the grinding wheel width is approximately 0.50 inches. 
     The blade sharpener  1  further comprises a work surface  63 . It is a feature of the invention that the work surface  63  is a single straight support line  65  that lies in the plane  60  the grinding wheel  55 . The straight line is thus perpendicular to the shaft axis  26 . Preferably, the straight support line  65  is a longitudinal line along a cylindrical surface. As illustrated, the support line lies along a semi-cylinder  66 . The semi-cylinder  66  is part of a pedestal  67  that is mounted to the base  7  by fasteners  69 . 
     As mentioned, turning the crank  31  of the adjustment mechanism  29  causes the axis of rotation  56  of the grinding wheel  55  to swing along the arcuate line  64 . Turning to FIG. 11, it is seen that the periphery  52  of the grinding wheel changes its spatial relation with the pedestal  67  as the pivot plate  27  pivots about the shaft  25  and the grinding wheel axis of rotation swings along the line  64 . The blade sharpener  1  is designed such that the tangent  68 A of a radius  70 A of the grinding wheel makes a desired angle A with the work surface line  65  when the grinding wheel periphery just contacts the inner end  71  of the work surface  63 . In that situation, the grinding wheel axis of rotation is represented at reference numeral  56 A. 
     To produce an angle B greater than angle A, the adjustment mechanism  29  is adjusted to pivot the pivot plate  27 , and thus the grinding wheel axis of rotation  56 , in the direction of arrow  46 . Doing so swings the grinding wheel axis of rotation to a position  56 B and also brings the grinding wheel periphery  52  into grinding contact with the semi-cylinder  66 . The grinding wheel  55  cuts the semi-cylinder along line  73  back a desired amount X from the end  71 . The tangent  68 B of the grinding wheel radius  70 B then makes the desired angle B with the work surface  63 . 
     To produce an angle C less than angle A, the adjustment mechanism  29  is adjusted to pivot the pivot plate  27  in the direction of arrow  44  to a position  56 C for the grinding wheel axis of rotation. That action moves the grinding wheel periphery  52  away from the work surface  63  by a distance Y. The tangent  68 C of the grinding wheel radius  70 C makes an angle C with an extension of the work surface straight line  65 . 
     In the illustrated construction, the blade sharpener  1  includes a grit guard  75 . The grit guard  75  has a top section  77  that is attached to the frame top wall  11 . The top section  77  joins to an angled section  79  that terminates above the level of the frame base  7 . A duct  81  opens into the angled section  79 . The duct  81  is connectable via a hose or the like, not illustrated in the drawings, to an exhaust system. 
     Shields  82  of clear material, such as Lexan plastic, fit between the frame base  7  and the walls  9  and  11  on both sides of the blade sharpener  1 . The shields  82  provide full access to the work surface  63  while preventing direct access to the grinding wheel  55 , pulleys  53  and  58 , and timing belt  61 . 
     To use the blade sharpener  1  to sharpen a straight edge blade  3 , the adjustment mechanism  29  is adjusted to produce the desired cutting angle L, such as angles A, B, or C, on the blade cutting edges  8 , FIG.  3 . For example, the adjustment mechanism may be adjusted to pivot the pivot plate  27  to produce an angle between angles B and C, FIG. 11, equal to the desired angle L. The bottom surface  6  of the blade close to the tip  38  is laid on the work surface  63  with the cutting edge out of contact with the grinding wheel  55 . The blade is held such that its longitudinal centerline  4  is generally parallel to the grinding wheel axis of rotation  56 . The blade is supported on the work surface along only one of the imaginary lines  14  on the blade bottom surface. However, the blade is supported for its full width between the cutting edge and the associated back edge  2 . The blade is slowly fed crosswise in the direction of arrow  83  until the cutting edge contacts the grinding wheel  55  such that the grinding wheel removes the desired amount of material from the blade to produce the cutting surface  12  close to the tip. Then the blade is fed lengthwise in the direction of arrow  85  to produce the desired cutting surface  12  for the full length of the blade cutting edge. Feeding the blade in the direction of arrow  85  results in supporting the blade on constantly changing imaginary lines  14  on the blade bottom surface  6 . 
     The blade sharpener  1  is particularly effective for sharpening mulching blades such as blade  16 , FIGS. 4-7. Looking also at FIG. 12, the bottom surface  49  of the mulching blade end section  30  adjacent a tip  42  is laid on the work surface  63  out of contact with the grinding wheel  55 . The mulching blade is supported only along one imaginary line  32 . The blade is cross fed in the direction of arrow  83  to produce the proper cutting surface  24  adjacent the tip  42 . The mulching blade is then fed lengthwise in the direction of arrow  85  to sharpen the cutting edge  18  of the section  30 . When the blade angled section  28  reaches the work surface, the blade becomes supported by only one imaginary line  32  along the angled section bottom surface  48 . Consequently, little, if any, angular movement of the mulching blade in space is required to maintain proper contact between the grinding wheel and the blade. The narrow width of the grinding wheel further contributes to the efficient and proper grinding of the cutting edge at the transition between the blade end and angled sections. When the blade center section  21  reaches the work surface, the bottom surface  26  smoothly slides onto the work surface without requiring any angular movement of the blade in space. The cutting edge at the transition between the angled section and the center section  22  is therefore properly sharpened with ease. In general, the blade rises and falls in space during lengthwise feeding, but the single line support of the blade on the work surface eliminates most, if not all, angular movements of the blade during the sharpening process. Further, the same cutting angle is produced on the cutting edges of all the blade sections. 
     An outstanding advantage of the blade sharpener  1  is that the blade being sharpened is supported on the work surface  63  very close to the grinding wheel periphery  52 . In fact, for cutting angles greater than angle A (FIG.  11 ), the blade is supported fully up to the cutting edge itself. For blade  3 , for example, the blade is supported along the imaginary lines  14  up to the cutting edge  8 . For cutting angles less than angle A, there is a short distance Y from the cutting edge that is not supported. A typical unsupported distance Y is quite small, being in the range of approximately 0.30 inches to 0.40 inches. Compared with the proportion of the total blade width between the cutting edge and the back edge that is supported on the work surface, the unsupported length Y is not detrimental to sharpening performance. 
     During the sharpening process, grit and metallic particles travel tangentially from the grinding wheel periphery  52  toward the grit guard  75 . A source of vacuum connected to the duct  81  draws the grit and particles through the duct and to a collection location. Because of the relatively high speed of the grinding wheel  55  and its relatively soft composition, the grinding wheel removes metal from the blade in a true cutting fashion. The grinding wheel thus very rapidly removes material from the blade but does not load up with burned particles of metal. Consequently, dressing the grinding wheel is rarely, if ever, required. 
     Further in accordance with the present invention, the work surface  63  with the single support line  65  can be replaced by a work surface having a finite flat area. Turning to FIG. 13, a mobile work table  87  has a flat top plate  89  and two depending lugs  91 . The height of the lugs  91  is slightly greater than the height of the pedestal  67 . The space between the lugs  91  is slightly greater than the width of the pedestal. Jaws  93  of a manually actuated clamp  95  are welded or otherwise permanently joined to the opposite facing sides  97  of the lugs  91 . The amount of gripping force producible by the clamp  95  is adjustable by a screw  99 . A nut  101  on the screw  99  is lockable against a fixed member  103  of the clamp. The nut  101  is set to produce a repeatable force by the jaws  93  on the lugs. 
     FIGS. 14 and 15 shows the mobile work table  87  in place over the pedestal  67  on the blade sharpener  1 . The mobile work table lugs  91  are placed alongside the pedestal. Actuating the clamp  95  causes the lugs to tightly squeeze the pedestal  67  and thereby retain the mobile work table to the pedestal. The mobile work table top plate  89  is used for sharpening flat workpieces, such as blade  3 , that remain in a single plane as they are fed past the grinding wheel  55 . The mobile work table is easily removable from the pedestal by releasing the clamp  95  when it is desired to sharpen a mulching blade  16  (FIGS.  4 - 7 ). 
     In summary, the results and advantages of cutting blades for rotary power mowers and the like can now be more fully realized. The blade sharpener  1  provides both rapid sharpening of the blades as well as convenient adjusting of the blade cutting angle. This desirable result comes from using the combined functions of the work surface  63  and the adjustment mechanism  29 . The work surface is in the form of a straight support line  65  that supports a blade only along one line of the blade at a time. A mulching blade rises and falls relative to the grinding wheel with minimum if any angular motions in space as different sections of the mulching blade are fed past the grinding wheel. Depending on the cutting angle produced on the blade as set by the adjustment mechanism, the blade may be supported for its full width along the bottom surface. A mobile work table  87  having a flat top surface area is removeably retainable over the pedestal  67  that contains the work surface support line. The combination of the relatively fast speed of the grinding wheel  55  and its relatively soft composition enables rapid blade sharpening without burning the blade or loading the grinding wheel. 
     It will also be recognized that in addition to the superior performance of the blade sharpener  1 , its construction is such as to significantly reduce the cost of manufacture as compared to traditional blade sharpening machines. Also, since the blade sharpener is made of a simple design and with rugged components, the need for maintenance is minimal. 
     Thus, it is apparent that there has been provided, in accordance with the invention, a blade sharpener for curved and straight edge blades that fully satisfies the aims and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.