Abstract:
A hand-operated blade sharpener providing engagements of a blade by an abrasive stone at pre-selected angles to the blade is disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 60/793,412, filed on Apr. 20, 2006, which is herein incorporated by reference. 
     This application incorporates by reference commonly assigned U.S. patent application Ser. No. 11/392,445. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of hand tools and, more specifically, to blade sharpeners. 
     BACKGROUND OF THE INVENTION 
     It is recognized that there is a difficulty in sharpening or re-sharpening blades, such as for example, knife blades, using hand tools and other means generally known to those skilled in the art. In particular, retention of the correct angular position of a blade relative to an abrasive medium (for example, an abrasive stone) or facilitation of repetitive smooth passes of the blade or the abrasive medium represent challenging tasks for a user of average skills. 
     Various devices have been suggested to overcome problems associated with sharpening of blades using hand-operated tools; however, despite the considerable effort in the art, further improvements would be desirable. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is a blade sharpener providing, in operation, repetitive engagements of a blade by an abrasive stone at pre-selected angles to the blade. The blade sharpener includes a clamping mechanism adapted for receiving, gripping, and releasing the blade, a sharpening assembly including an abrasive stone unit and a guiding rod coupled to the abrasive stone unit, a bearing module adapted to pivotally support and provide a clearance fit to the guiding rod, and a base. The base is adapted to rotationally secure the clamping mechanism in pre-selected positions and to support the bearing module at a controlled distance from an axis of rotation of the clamping mechanism. 
     Various aspects and embodiments of the invention are described in further detail below. 
     The Summary is neither intended nor should it be construed as being representative of the full extent and scope of the present invention, which these and other additional aspects will become more readily apparent from the detailed description, particularly when taken together with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a front view of a blade sharpener in accordance with one embodiment of the present invention. 
         FIG. 2  shows a perspective view of a portion of the blade sharpener of  FIG. 1  in an intermediate position of a clamping mechanism of the blade sharpener. 
         FIG. 3  shows an exploded perspective of a portion of the blade sharpener of  FIG. 1 . 
         FIG. 4  shows a perspective view of a portion of the blade sharpener of  FIG. 1  in an intermediate position of a clamping mechanism of the blade sharpener. 
         FIG. 5  shows a perspective view of a portion of the blade sharpener of  FIG. 1  in a clamped position of a clamping mechanism of the blade sharpener depicting a clamped blade in an operable horizontal position. 
         FIG. 6  shows a side view of a portion of the blade sharpener of  FIG. 1 , the sharpener assembly. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The images in the drawings are simplified for illustrative purposes and are not depicted to scale. 
     The appended drawings illustrate exemplary embodiments of the invention and, as such, should not be considered as limiting the scope of the invention that may admit to other equally effective embodiments. It is contemplated that features or steps of one embodiment may beneficially be incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the figures,  FIG. 1  depicts a front view of a blade sharpener  100  in accordance with one embodiment of the present invention, and  FIG. 2  depicts a perspective view of a portion of the blade sharpener  100  in an intermediate position of its clamping mechanism. 
     The blade sharpener  100  generally comprises a rotatable clamping mechanism  110 , a sharpening assembly  120 , a bearing module  130 , a J-shaped base  140 , and an optional handle  150 . A blade  101  being sharpened (for example, blade of a knife (as shown in  FIG. 1 ), an arrow broadhead, a blade of a tool, and the like) is depicted gripped by jaws of the clamping mechanism  110 . Illustratively, the base  140  is manufactured as a single structural element comprising vertical short and long sides  142  and  146  and a horizontal side  148 . 
     Components of the blade sharpener  100  may be fabricated from metals, plastics, and other suitable materials using conventional design considerations known to those skilled in the art of hand tools. 
     The clamping mechanism  110  generally includes a jaw assembly  112  disposed external to a short side  142  of the base  140 , a threaded shaft  113 , a cylindrical thrust bushing  114 , a wing nut  116 , and a compression assembly  118  disposed external to a long side  146  of the base  140 . In an alternate embodiment, the wing nut  116  may be substituted by a rotationally controlled threaded member (for example, a combination of a hex nut and a nut driver such as a wrench, and the like). 
     The jaw assembly  112  comprises tapered jaws  102 A and  102 B, a jaw housing  104 , and a rectangular spacer  106  securing, using a screw  169 , the jaw assembly  112  to an end face of the threaded shaft  113 . Operable together with the threaded shaft  113  as a screw drive, the wing nut  116  by engaging the thrust bushing  114  forces the jaws  102 A,  102 B to grip the blade  101 . Accordingly, by retracting the wing nut  116  away from the thrust bushing  114 , the jaws  102 A and  102 B may be opened for receiving or releasing the blade  101 . 
     In one embodiment, the jaws  102 A and  102 B are provided with compressible inserts  103  adapted to form or enhance friction-based contacts between the jaws and the blade  101 . In a further embodiment (not shown), to keep the jaws  102 A and  102 B open during receiving or releasing the blade  101 , the jaw assembly  112  may include a wire or flat spring  170  applying a tensile force to the jaws. 
     The compression assembly  118  is mounted on the threaded shaft  113  and comprises a coil spring  115 , thrust washers  117 , and an adjusting knob  119 . In operation, the coil spring  115  exerts an axial force that pulls the jaw assembly  112  towards an outer surface  141  of the side  142  of the base  140 . 
     The clamping mechanism  110  is rotatably secured in clear coaxial openings formed for the thrust bushing  114  and the threaded shaft  113  in the sides  142  and  146 , respectively. The jaw assembly  112  may be rotated, in the directions illustrated with an arrow  107 , using the jaws  102 A and  102 B as a lever. 
     The side  142  comprised one or more indexers  109  (for example, studs (as shown in  FIG. 2 ), spring-loaded balls, and the like) that protrude through the surface  141  towards the jaw assembly  112 . Together with mating elements  111  (for example, indexer-capturing openings (as shown in  FIG. 2 ) or recesses) formed in the jaw housing  104 , the indexers  109  facilitate releasable rotational indexing of the jaw assembly  112 . Torque required for rotating the jaw assembly  112  is regulated, using the adjusting knob  119 , by a pulling force exerted by the coil spring  115 . 
     In one embodiment, the blade sharpener  100  comprises two pairs of the symmetrically disposed indexers  109  and respective mating elements  111 , which are adapted for releasably capturing and retaining the jaw assembly  112  in opposing horizontal positions suitable for sharpening particular sides of an edge of the blade  101 . In one of such positions, the jaw  102 A is disposed above the jaw  102 B as shown in  FIG. 1 , while in the other position (not shown), the jaw  102 A is similarly disposed below the jaw  102 B. 
     The sharpening assembly  120  includes a guiding rod  122  and an abrasive stone unit  124 . The abrasive stone unit  124  is detachably affixed to the guiding rod  122  (using, for example, a check nut  121 ) and generally includes an abrasive stone  125  (e.g., sharpening or honing stone), an enclosure  126  releasably supporting the abrasive stone  125 , and a handle  128 . The handle  128  is adapted for applying, by hand, the abrasive stone  125  to the blade  101 . In an alternate embodiment, the handle  128  may be a portion (for example, structural member) of the enclosure  126 . In operation, the sharpening assembly  120  may be engaged in movements illustrated using arrows  105 A and  105 B. 
     The bearing module  130  comprises a spherical bearing  132  and a retainer assembly  136  movably securing the spherical bearing  132  to the side  146  of the base  140 . In the depicted embodiment (shown in detail in  FIG. 3 ), the retainer assembly  136  includes a locking bolt  160 , a bracket  162 , holders  133 A and  133 B housing, together, the spherical bearing  132 , a spacer  164 , a thrust washer  166 , and a knob  168 . 
     The spherical bearing  132  has a clear opening  134  (shown in  FIG. 1  with broken lines and in  FIG. 2 ) that is adapted for receiving, pivotally supporting, and providing a clearance fit to the guiding rod  124 . In the depicted embodiment, the spherical bearing  132  and the holders  133 A,  133 B are disposed in an elongated cutout  137  formed in the side  146 . 
     The bearing module  130  comprises a spherical bearing  132 , a holder  133  (shown in  FIG. 2 ) housing the spherical bearing  132 , and a retainer assembly  136  movably securing the holder  133  to the side  146  of the base  140 . The spherical bearing  132  has a clear opening  134  (shown in  FIG. 1  with broken lines and in  FIG. 2 ) that is adapted for receiving, pivotally supporting, and providing a clearance fit to the guiding rod  124 . In the depicted embodiment, the spherical bearing  132  and the holder  133  are disposed in an elongated cutout  137  (shown in  FIG. 2 ) formed in the side  146 . 
     In one embodiment, the side  146  comprises a scale  139  (shown in  FIG. 2 ). The scale  139  (for example, engraved scale) allows disposing the spherical bearing  132  at a controllable (i.e., pre-selected) distance  131  from an axis of rotation of the clamping mechanism  110  (i.e., axis of the threaded shaft  113 ), thus defining an angle  135  (shown in  FIG. 1 ) at which, in operation, the abrasive stone  125  engages the blade  101 . 
     More specifically, when the sharpening assembly  120  is driven by using the handle  128 , the abrasive stone  125  may be engaged, tangentially with respect to the blade  101 , in repetitive translational, lateral, or harmonic movements that are performed, in the directions of the arrows  105 A or  105 B, at the same angle  135  to the blade  101 . Using the retainer assembly  136 , a user may adjust the angle  135  by varying a position of the clamping mechanism  110  in the cutout  137  (i.e., by varying the distance  131  defined by the scale  139 ). 
     In one embodiment, the handle  150  is adapted for holding the blade sharpener  100  by hand (for example, a pistol-grip handle) and may releasably be secured (using, for example, a screw  151 ) to the horizontal side  148  of the base  140 . In a further embodiment, the handle  150  comprises an enforced opening  152  for rotatably mounting the blade sharpener  100  onto an external support  154  (shown in phantom). 
     In operation, using the wing nut  116 , a user secures the blade  101  in the jaw assembly  112  disposed in one of the positions defined by the indexers  109  and elements  111 , for example, in a first horizontal position depicted in  FIG. 1 . Then, the user secures the abrasive stone  125  in the sharpening assembly  120 , protrudes a portion of the guiding rod  122  through the opening  134  in the spherical bearing  132 , and adjusts location of the bearing module  130  on the side  146  of the base  140  to select the angle  135  between contacting surfaces the abrasive stone  125  and the blade  101  (i.e., adjusts the distance  131  and angle  135 ). 
     In operation, the user sharpens the blade  101  by engaging the blade with the abrasive stone  125  and, in case of double-edged blades, rotates the jaw assembly  112 , about the axis of rotation of the clamping mechanism  110 , in a second horizontal position opposing the first horizontal position. 
     Although the invention herein has been described with reference to particular illustrative embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. Therefore numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present invention, which is defined by the appended claims.