Abstract:
A knife blade sharpener including two generally circular sharpening members pivotally mounted about a pivot axis and having opposed grinding edges. The grinding edges are located along one side of a notch formed in each of the generally circular sharpening members and can be brought to face one another, adjustably subtending an obtuse angle therebetween. The pivot axis may be established by a screw and a knurled nut enabling the user to tighten the two generally circular sharpening members together at a selected subtended angle for sharpening. A knife blade may be drawn through a wedge shaped gap between the two mutually facing grinding edges, and thereby sharpened. The knife blade sharpener has resilient gripping pads and a holster which facilitates gripping as well as for stowage.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to sharpening tools, and more particularly, to a hand held knife sharpener. 
       BACKGROUND OF THE INVENTION 
       [0002]    Knives will become dulled with use and therefore periodically require sharpening. It is possible to maintain a grindstone for this purpose. However, a single grindstone can result in uneven grinding along the length of the knife blade edge. Also, a grindstone may be cumbersome to carry and use if large, and may be easily lost if small. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention addresses the above stated need by providing a compact knife blade sharpener having opposed grinding edges. The grinding edges are each formed on a generally circular sharpening member both mounted about a pivot axis for mutual pivot or rotation about the pivot axis. The generally circular sharpening members are pivotally adjusted such that a wedge shaped gap separating the opposed grinding edges corresponds to a cross sectional profile of a knife blade being sharpened. The two generally circular sharpening members are locked in the selected adjustment. The knife blade is drawn through the gap and contacted with both of the grinding edges. 
         [0004]    The knife blade sharpener may have resilient pads on the generally circular sharpening members to facilitate grip while sharpening. A holster may be provided to further facilitate grip and also for storage. 
         [0005]    It is an object of the invention to provide improved elements and arrangements thereof by apparatus for the purposes described which is inexpensive, dependable, and fully effective in accomplishing its intended purposes. 
         [0006]    These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Various objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
           [0008]      FIG. 1  is a perspective view of a knife blade sharpener, according to at least one aspect of the invention; 
           [0009]      FIG. 2  is a diagrammatic plan view of a major component of a knife blade sharpener, according to at least one aspect of the invention; 
           [0010]      FIG. 3  is an exploded side view of a knife blade sharpener, according to at least one aspect of the invention; 
           [0011]      FIG. 4  is a perspective view of a knife blade sharpener, according to at least one aspect of the invention; 
           [0012]      FIG. 5  is an environmental plan view of a knife blade sharpener, according to at least one aspect of the invention, with a knife blade shown in cross section; 
           [0013]      FIG. 6  is a plan view of a knife blade sharpener and a holster therefor, according to at least one aspect of the invention; 
           [0014]      FIG. 7  is a plan view of a knife blade sharpener explaining a geometric feature of a grinding edge; and 
           [0015]      FIG. 8  is a block diagram summarizing steps of a method of sharpening a knife, according to at least one aspect of the invention 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring first to  FIG. 1 , according to at least one aspect of the invention, a knife blade sharpener  100  includes a first sharpening member  102  having a first grinding edge  104  and a second sharpening member  106  having a second grinding edge  108 . Referring also to  FIG. 2 , which generically and diagrammatically illustrates overall configuration of each of the first and second sharpening members  102 ,  106 , the first and second sharpening members  102 ,  106  each have a generally circular circumferential surface  105 A or  105 B with a wedge shaped notch  112 . In  FIG. 2 , the wedge shaped notch  112  is indicated by an arrow  110  indicating magnitude of an angle subtended by the sides  114 ,  116  of the notch  112 . The notch  112  may subtend an angle of about ninety degrees of the generally circular circumferential surface  105  which generically represents the generally circular circumferential surfaces  105 A and  105 B. The notches of the first and second sharpening members  102 ,  106  represented by the wedge shaped notch  112  in  FIG. 2  may be equal in subtended angular magnitude. 
         [0017]    The first grinding edge  104  of the first sharpening member  102  is along one side of the notch (such as the notch represented as  112  in  FIG. 2 ). Similarly, the second grinding  108  edge of the second sharpening member  106  is along one side of the notch, such that the first and grinding edges  104 ,  108  face one another after the first and second generally circular sharpening members are locked together by the screw  118  and nut  120 . 
         [0018]    The first and second grinding edges  104 ,  108  may be part of a strip formed from a carbide material, such as for example silicon carbide or tungsten carbide. Each strip may be adhered to its associated first or second generally circular sharpening member  102  or  106 , which may be formed from a metal such as aluminum or steel, or alloys thereof. 
         [0019]    Also referring to  FIGS. 3 and 4 , the first and second sharpening members  102 ,  106  are pivotally secured to a pivot member. An illustrative pivot member may comprise a screw  118  and a threadably compatible nut  120  having an enlarged head bearing a knurled surface  122 . The pivot member establishes a pivot axis  124 . The first and second sharpening members  102 ,  106  are pivotally secured to the pivot member to pivot about the pivot axis  124  such that the first grinding edge  104  and the second grinding edge  108  have a common point of intersection  126  ( FIG. 4 ), and are infinitely angularly adjustable such that the first and second grinding edges  104 ,  108  subtend an angle (e.g., the angle  128  in  FIG. 4 ) of variable angular magnitude. The angle (e.g., the angle  128 ) is of variable angular magnitude in that it is adjustable. Once set to a selected magnitude, which preferably corresponds to the angle of a profile of a knife blade  10  (as seen in  FIG. 5 , the first and second sharpening members  102 ,  106  are locked together such that the angle is set until the next adjustment. Obviously, only that portion of the knife blade  10  near the point is of the critical angle to which the knife blade sharpener  100  is set. 
         [0020]    The pivot member and a lock locking the first and second sharpening members  102 ,  106  together may be unitary, thereby serving both to establish the pivot axis  124  and also as a lock which is configured to releasably secure the first and second grinding edges  104 ,  108  at a selected subtended angular relation to accommodate the knife blade  10 . 
         [0021]    The subtended angular relation may be set if the angle of the critical part of the knife blade  10  is known. If not known, this angle may be measured. Once the angle of the knife blade  10  is known, the knife blade sharpener  100  may be adjusted by using an indicating feature. One of the first and second sharpening members  102 ,  106  (or, if desired, both) includes indicia  130  indicative of the angle (e.g., the angle  128 ) subtended by the first and second grinding edges  104 ,  108 . The notch (corresponding to the notch  112  seen in  FIG. 2 ) of the first sharpening member  102  or the second sharpening member  106  includes a first side (such as the first side  114  in  FIG. 2 ) including the grinding edge  104  or  108  and a second side (such as the side  116  in  FIG. 2 ), the second side having a beveled portion  132  ( FIGS. 1 and 4 ) resulting in an edge  134  immediately proximate the indicia  130 . Because each of the first and second sharpening members  102 ,  106  has more than nominal thickness, errors of parallax could interfere with accurate setting of the angle (e.g., the angle  128 ). The beveled portion  132  causes the edge  134  to be so close to the indicia  130  that errors of parallax will not occur. 
         [0022]    If the cutting angle of the knife (e.g., the knife  12  in  FIG. 5 ) is not known, it may be measured by applying a coloring agent such as magic marker to the knife blade near the cutting edge, and drawing it through the knife blade sharpener  100 . When the first and second grinding edges  104 ,  108  are spaced apart such that a slight removal of the coloring agent occurs on each side of the blade of the knife, the knife blade sharpener  100  is adjusted to the cutting angle of the knife. At this point, the indicia  130  indicates the cutting angle, and the indicia may be read, and the value remembered or recorded. 
         [0023]    Best seen in  FIGS. 1 and 4 , the knife blade sharpener  100  may include at least one and if desired, two gripping pads  136 ,  138  on one or both of the first and second sharpening members  102 ,  106 . The gripping pad  136  or  138  may be fabricated from a synthetic substance such as neoprene. 
         [0024]    Turning now to  FIG. 6 , the knife blade sharpener  100  may include a separate holster  140  configured to receive the knife blade sharpener  100  in close cooperation therein. The holster  140  forms a pocket having a first side  142  and an opposed second slide  144 , each side  142  or  144  including a slot  146  configured to avoid contact with the pivot member when the knife blade sharpener  100  is slid into the pocket. An arrow  148  indicates the direction of insertion of the knife blade sharpener  100  into the holster  140  and withdrawal from the holster  140 . The holster  140  not only protects the knife blade sharpener  100  from damage as well as protecting people from potential injurious contact with the grinding edges  104 ,  108 , but also facilitates grip of the knife blade sharpener  100  when being used. Grip may be by hand, or alternatively, within a holder such as a vise (not shown). The holster  140  may be fabricated from leather, among other materials. 
         [0025]      FIG. 7  shows a geometric characteristic of the knife blade sharpener  100 , wherein the first grinding edge  104  of the first sharpening member  102  is offset from a radius  150  radiating from the pivot axis  124 . The first grinding edge  104  is displaced or projects into the notch (such as the notch  112  of  FIG. 2 . The first grinding edge  104  aligns with a projection line  152  which is displaced to the right of the radius  150  in  FIG. 7 , by a distance of about three thirty-seconds of an inch, with the overall diameter  154  of the first sharpening member  102  being about two and seven-eighths inches. Alternatively stated, the degree of offset of the first grinding edge  104  is about one thirtieth of the overall diameter  154  of the first sharpening member  102 . The first grinding edge  104  is parallel to the radius  150 . 
         [0026]    The second sharpening member  106  (see  FIG. 4 ) may have the same characteristics relating to offset as the first sharpening member  102 . 
         [0027]    As a method of sharpening a knife blade (e.g., the knife blade  12 ) as shown in  FIG. 8 , the method includes providing two generally circular sharpening members (e.g., the generally circular sharpening members  102 ,  106 ) pivotally mounted about a pivot axis (e.g., the pivot axis  124 ) and having opposed grinding edges (e.g., the grinding edges  104 ,  108 ), the grinding edges each located along one side of a notch (e.g., the notch  112  in  FIG. 5 ) formed in each of the generally circular sharpening members (step  160 ). The method includes adjusting the two generally circular sharpening members to a selected subtended angular relationship between the two generally circular sharpening members such that a wedge shaped gap (e.g., the gap  128  in  FIG. 4 ) exists between the opposed grinding edges, the selected subtended angular relationship corresponding to an angular configuration of the knife blade (step  162 ). The method includes securing the two generally circular sharpening members in the adjusted subtended angular relationship (step  164 ), and drawing the knife blade through a gap between the two grinding edges in contact with the two grinding edges (as seen for example in  FIG. 5 ) (step  166 ). 
         [0028]    While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is to be understood that the present invention is not to be limited to the disclosed arrangements, but is intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible.