Abstract:
An apparatus useful for sharpening blades includes a blade support, a sharpener guide mounted to the blade support, and a sharpener mount. The sharpener guide includes an elongated guide member defining a sharpening axis extending substantially parallel to a blade axis defined by the blade support. The sharpener mount includes a pivot connector coupled to and complementally configured with the elongated guide member for enabling pivotal movement of the sharpener mount about the sharpening axis and translational movement along the elongated guide member. The sharpener mount may be coupled to a rotary grinder having a grinding wheel, such that the sharpener mount and the grinder may pivot to provide a desired sharpening angle on the blade and move the grinder along the blade while the blade remains in place on the blade support.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention broadly concerns a blade sharpener useful for sharpening the blades of cutting implements, for example, lawn mower blades. More particularly, it is concerned with a blade sharpener which serves as a support for a blade and a guide for a blade sharpening device to move along a cutting edge of a blade. 
     2. Description of the Prior Art 
     A variety of different devices are known for sharpening the blades of cutting implements. For example, sharpening stones and files are well known tools which are drawn across a cutting edge of a blade for sharpening. Other sharpening devices include grinding wheels which rotate and used by placing the edge of a cutting implement in engagement with the rotating wheel, and sharpeners typically used with knives or scissors wherein a body acts as a guide and whereby the cutting edge is drawn along a sharpening stone while generally held in a desired angular relationship by the guide. 
     However, some cutting blades are more robust and more difficult to sharpen. For example, the blades of rotary lawn mowers are designed to be larger and for heavy duty use. While these can be sharpened with conventional grinding wheels, these are often large and expensive machines not practical for use by those performing intermittent sharpening tasks. Moreover, typical grinding wheel sharpening apparatus do not appropriately support the blade and guide the relative movement of the sharpening apparatus along the blade. Thus, an improved blade sharpening apparatus, especially for larger blades such as those of rotary lawn mowers, is needed. 
     SUMMARY OF THE INVENTION 
     The blade sharpener of the present invention provides a mechanism which is not only designed for accurate blade sharpening, but is especially suited for use both by those which frequently sharpen blades as well as those whose sharpening activities are less frequent. The blade sharpener of the present invention not only provides adjustment in the sharpening angle, but provides excellent support for even large blades and further promotes proper sharpening techniques which enhance blade life. 
     Broadly speaking, the blade sharpener of the present invention includes a blade support including a receiving surface defining a blade axis, a sharpener guide mounted to said blade support, and a sharpener mount. The blade support is configured for supporting a blade to be sharpened on the blade receiving surface. The sharpener guide includes an elongated guide member defining a sharpening axis extending substantially parallel to the blade axis. The sharpener mount includes a pivot connector coupled to and complementally configured with the elongated guide member for enabling pivotal movement of the sharpener mount about the sharpening axis and also enables translational movement of the sharpener mount along the elongated guide member. In this way, a sharpening tool such as, for example, a grinder having a rotatable abrasive wheel, may be positioned to engage a cutting edge of a blade supported on the blade receiving surface and move along the cutting edge and engage the cutting edge to sharpen the blade at a desired cutting angle. 
     In preferred embodiments, the sharpener guide includes an adjuster which is pivotally mounted by a coupler to the blade support. The elongated guide may be mounted to the adjuster and by pivoting the adjuster about the coupler, which defines a pivot axis, the angle at which a sharpening tool mounted on the sharpener mount may be adjusted. The pivot axis which is parallel to the elongated guide member and also preferably parallel to the blade axis. 
     Furthermore, the coupler may be spaced from the elongated guide member, and the coupler may include a clamping member for retaining the adjuster in a selected, desired angular relationship to said blade support, which helps to keep the relative position of the sharpening tool even as the sharpener mount translates back and forth along the elongated guide member. This clamping member may include a bolt extending through aligned openings in the adjuster and blade support and a nut threadably received on the bolt, whereby the nut can be tightened to easily hold the adjuster at the desired angle relative to the blade support. 
     While the receiving surface can be variously configured to most readily accommodate different configurations of blades, the receiving surface may be substantially planar. This configuration of receiving surface may be advantageous for use in sharpening rotary lawn mower blades. The blade support may be configured to include a beam which extends substantially perpendicular to the blade-receiving surface, and the sharpener guide may be mounted to the beam. The beam may extend both above and below the sharpening surface. When so configured, the beam can be readily clamped between the jaws of a vise for holding the blade sharpening apparatus stable. Also, the blade support can be mounted directly to a table, bench or the like using clamps or alternatively threaded fasteners such as bolts or screws. When the beam extends downwardly relative to the supporting surface, it may be received in a slot in the table or bench, and this may further help to stabilize the blade sharpening apparatus. The beam may be configured to include a tongue which extends above the blade receiving surface and a blade-receiving gap can be provided between the tongue and the blade receiving surface so that elongated blades can be received on the blade receiving surface and the apparatus can be rugged and balanced. Also, a blade holding member can be provided and mounted to the beam or other part of the blade support. The blade holding member can be used to hold the blade on the blade-receiving surface and clamp the blade to fix it in position during sharpening. The blade holding member can include a bar which extends in a spaced, parallel plane to the blade-receiving surface and include one or a plurality of retaining members which are coupled to the bar for shiftable movement to hold and release the blade from the blade support. 
     The sharpener mount may include a bearing received on the elongated guide member for simultaneous pivotal movement about said elongated guide and translational movement along said guide. A sharpening tool may be mounted on the sharpener mount. The sharpener tool may be a file, abrasive stone, or more preferably, a grinder, such as a motorized grinder. The grinder may include a shaft carrying a rotatable abrasive wheel, the shaft being offset from said sharpening axis and having an axis of rotation which remains oriented substantially 90° relative to the sharpening axis during translation of the sharpener mount along the elongated guide member and during pivotal movement about the sharpening axis. 
     These and other features of the present invention will be appreciated by those skilled in the art with reference to the drawings and the detailed description of the preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an upper front isometric view of a blade sharpener in accordance with the present invention, showing a rotary lawn mower blade located on the blade support, a sharpener guide pivotally coupled to the blade support, and a rotary grinder mounted to a sharpener mount; 
         FIG. 2  is an upper rear front isometric view of the blade sharpener, showing the coupler as a bolt with a nut tightened thereon for holding the position of the sharpener guide relative to the blade support, and the blade sharpener clamped by a vise; 
         FIG. 3  is a left side elevational view of the blade sharpener, showing a grinding wheel of the grinder engaging a lawn mower blade for sharpening; 
         FIG. 4  is an exploded view showing the sharpener guide hereof positioned for mounting directly to a supporting surface having a slot therein; and 
         FIG. 5  is a front view of the blade sharpener hereof mounted to a supporting surface, with a portion of the blade support shown in vertical cross-section to illustrate the positioning of a lower part of a beam of the blade support received in a slot in the support surface. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, an apparatus for use as a blade sharpener  10  broadly includes a blade support  12 , a sharpener guide  14 , and a sharpener mount  16 . The blade sharpener  10  is configured to be held by a vise  18  coupled to a supporting surface  20  as shown in  FIGS. 1-3 , or alternatively mounted directly to the supporting surface  22  as shown in  FIGS. 4 and 5 . While the blade sharpener  10  is particularly adapted for sharpening the blade  22  of a rotary lawn mower, it may be appreciated that the blades of other tools having a cutting edge such as, for example, a machete, may also be sharpened by the blade sharpener  10  hereof. 
     In greater detail, the blade support  12  is preferably formed of metal such as mild steel and includes a base  24  including a blade receiving surface  26 , and a beam  28 . The base  24  may be drilled with holes  30  and  32  which may be countersunk. The blade receiving surface  26  is preferably elongated such that its width and depth as seen in  FIG. 3  is smaller than its length as seen in  FIG. 5 . The blade receiving surface  26  presents a blade axis B which is generally parallel to the orientation of the elongated blade  22  positioned thereon in a sharpening position. While the blade receiving surface may be contoured, intermittent or otherwise configured, as shown in the drawings the blade receiving surface  26  is most preferably substantially flat and in normal use extends generally horizontally. The beam  28  is preferably positioned intermediate and most preferably substantially midway between the longitudinal ends of the base  24 , and oriented substantially perpendicular to the blade receiving surface  26  as seen in  FIG. 5 . The beam  28  extends rearwardly from the base  24  and also includes a forwardly extending tongue  34 . The tongue  34  is spaced upwardly from the blade receiving surface  26  to present a blade receiving gap  36  between the tongue and the receiving surface. The beam  28  also preferably includes a mounting or locating flange  38  which extends generally downwardly below the base  24  during normal orientation and use. While the flange  38  could be provided separate from the beam  28  and oriented generally parallel to blade axis B or at another angle, for economy of manufacture the flange  38  is most preferably generally aligned with the beam and perpendicular to the blade axis B. The flange  38  may then be conveniently clamped between the jaws of vise  18  as shown in  FIGS. 1-3  or positioned in a slot  40  in the supporting surface  20  as shown in  FIGS. 4 and 5 . 
     The sharpener guide  14  includes an elongated guide member  42  and may, in particularly preferred embodiments, include an adjuster  44 . The elongated guide member  42  may be configured as an elongated rod  46  of steel or the like defining a sharpener axis S. The rod  46  and the sharpener axis S is preferably substantially parallel to the blade axis B. The rod  46  may be mounted directly to the blade support  12 , or more preferably to the adjuster  44  by a coupling  48 . The rod  46  may be attached to the coupling  48  by set screw  50 , and a guard  52  may be welded or otherwise attached to the adjuster  44 . The adjuster  44  may be provided as an elongated element  54  having a rearwardly extending handle  56  and pivotally mounted to the blade support  12  by a coupler  58 . The coupler  58  defines a pivot axis P which is generally parallel to the sharpener axis S and spaced generally rearwardly therefrom as shown in  FIG. 3 . The coupler  58  as illustrated includes a bolt  60  which extends through aligned holes in the adjuster  44  and the beam  28  of the blade support  12 , a nut  62  which is threaded onto the bolt  58  which provides a clamping force to tighten the adjuster  44  against the beam  28  (or loosening to permit pivoting of the sharpener guide  14 ) and associated washers  64 . 
     The sharpener mount  16  is configured to support a sharpening tool  66 . The particular configuration of the sharpener mount  16  will thus vary according to the particular sharpening tool  66 , for example a sharpening stone, file, or, as illustrated in the drawings, a rotary, motor-driven grinder  68  having a shaft  70  rotatably mounting an abrasive wheel  72  thereon. The sharpener mount  16  is configured for translation back and forth along the elongated guide member  42  and preferably pivoting thereon. In this regard, when the elongated guide member  42  is configured as rod  48 , the sharpener mount  16  may be provided with a bearing  74  which is complementally configured with the rod  48  to retain the sharpener mount  16 , and therefor the sharpening tool  66 , in alignment and to shift along the rod  48  as well as pivot about it. The bearing  74  thus permits translational movement of the sharpener mount  16  toward and away from the blade support  12  and pivoting movement about axis S. The sharpener mount  16  may be provided with a pair of arms  76  and  78 , with the bearing  74  coupled proximate one end of the arms, and attachments  80  extending through holes proximate the other end of the arms  76  and  78 . As shown in  FIGS. 1 and 2 , for example, these attachments  80  serve to mount the sharpening tool  66  to the arms  76  and  78 , preferably fixedly so as to prevent pivoting of the sharpening tool  66  relative to the sharpener mount  16 . When the sharpening tool  16  is a grinder  68  as illustrated, the attachments  80  are relatively simple, such as a bolt  82  and the grinder handle  84 , because the grinder  68  is provided with threaded holes which threadably receive the bolt  82  and the grinder handle  84 . Thus, simply by inserting the bolt  82  and grinder handle  84  into the threaded holes in the grinder  68  and tightening, the sharpening tool is fixably coupled to the sharpener mount  16 . 
     A blade holding member  86  is also preferably provided, and this may be provided as a part of the blade support  12  as shown in  FIGS. 1 through 5 . The blade holding member  86  may include a bar  88  positioned above the blade receiving surface  26  and coupled to the beam  28 . The bar  88  may be provided with one or a pair of securement members  90 , which may be threaded rods  92  provided with handles  94  for holding the blade  22  in fixed position against the blade receiving surface  26  with the blade extending generally through the gap  36  and oriented to have its cutting edge  96  extend along or generally parallel to the blade axis B. 
     The blade sharpening apparatus  10  of the present invention greatly simplifies the task of sharpening large, rugged blades of cutting tools. The provision of the flange  38  permits the blade support  12  to be held by a vise  18 . By simply inserting the mounting flange  38  between the jaws of the vise  18  and tightening the jaws against the mounting flange  38 , the blade support  12  is held in position ready to receive a blade  22  of a cutting tool. Alternatively, as shown in  FIGS. 4 and 5 , the blade sharpening apparatus  10  can be mounted directly to a supporting surface  20  such as a table or bench top. The mounting flange  38  need not be included for mounting directly to a supporting surface  20 , as threaded fasteners  98  such as bolts and nuts, lag screws or the like can be inserted through the holes  30  and  32  in the base  24  and held by nuts or threading into the material of the supporting surface  20 . However, when the flange  38  is a part of the blade support  12 , the provision of slot  40  in the supporting surface  20  gives additional lateral support and removes some of the stress on the threaded fasteners  86 . 
     After the sharpening tool  66  is mounted to the sharpener mount  16  as shown in the drawings and described above, the sharpener mount  16  is coupled to the sharpener guide  14  by sliding the bearing  74  over the rod  48 . The coupler  58  may be loosened to permit pivoting of the adjuster  44  to the desired position. Because the sharpening tool  66  may be free to pivot about the rod  48 , the pivoting of the adjuster  44  largely provides for comfort and a natural position for the sharpening tool  66  as shown in  FIG. 3 , so that the sharpening tool  66  assumes an orientation consistent with the existing angle to which the blade  22  was previously sharpened. However, in some applications it may be desired to have the angle between the sharpening tool and the orientation of the blade (i.e., the sharpening angle) controlled to a greater degree. If this is desired, then the rod  48  could be, for example, a square rod and the bearing  78  could be provided with a complementally sized and configured inner configuration so that the bearing  78  could translate along the rod  48  but not pivot. In this way, the user would pivot and then tighten the adjuster to determine the desired sharpening angle. The blade  22  is then placed atop the blade receiving surface  26  with the cutting edge  96  oriented toward the sharpening tool  66 . The blade  22  is positioned in the gap  36  between the tongue  34  and the blade receiving surface  26 . Then, the threaded rods  92  of the blade holding member are rotated to hold the blade  22  in position. In operation, it is believed that improved sharpening without unintentional rounding of the cutting edge  96  of the blade  22  can be accomplished by starting the grinder  68  so that the shaft  70  and the abrasive wheel  72  rotate, and then moving the grinder  68  in a generally inward direction toward the beam. In this way, there is a lesser tendency to have the abrasive wheel excessively grind the tip of the cutting edge  96 , thereby causing rounding. Typical rotary mower blades  22  have two cutting edges, and in this way once one cutting edge  96  is sufficiently sharpened, the blade  22  is released from the blade receiving surface  26 , rotated 180°, and then the other cutting edge  96  of the blade  22  can be sharpened. 
     Although preferred forms of the invention have been described above, it is to be recognized that such disclosure is by way of illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventor hereby states his intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.