Patent Publication Number: US-4731957-A

Title: Knife sharpener

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Use 
     This invention relates generally to a knife sharpener hand held or held in position by clamping or the like to a fixed object and, particularly to a knife sharpening device that can be used by persons of varying degrees of skill in sharpening knives and the like to produce a precision edge to the blade sharpened thereby. 
     2. Description of the Prior Art 
     The prior art discloses many examples of hand-held sharpeners for kitchen knives or the like (see U.S. Pat. Nos. 62,472; 605,289; and 4,494,340 for examples) an many examples of sharpening devices for other items (see U.S. Pat. Nos. 1,963,442; 2,398,560 and 2,800,040, for examples). 
     U.S. Pat. Nos. 605,289 and 1,963,422 teach the use of circular cutting blades and U.S. Pat. Nos. 62,472; 2,398,560 and 2,800,040 teach linear cutting blades. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention there is provided an improved knife sharpener for sharpening knives which is hand-held and requires little or no skill for its use to produce an expertly sharpened edge to a knife. 
     The knife sharpener generally comprises two handle or body portions, a cutter blade of equilateral triangular configuration securely locked between the handle or body portions and extending from the interior of the body portion through an opening on one end of the handle or body portion. The extended or apex portion of the cutter blade is positioned within the opening whereby a blade of a knife or the like can be drawn between the edge of the opening and one side of the cutter blade for sharpening the blade edge. The cutter blade is chamfered or angled along its edges to provide the proper slope to the blade edge being sharpened. The cutter blade can be rotated to expose new cutting surfaces. The handle or body portion may be hollow for containing additional or extra cutter blades. 
     A knife sharpener in accordance with the present invention offers several advantages over the prior art. For example, the cutter blade is self-positioning to the correct cutting angle and may be rotated to expose new cutting edges. This is made possible by cutouts within the handle or body portions that properly positions and locks the cutter blade in place. The apex of the cutter blade is centered between two extending arms formed on one end of the body of the device. These arms provide a proper reference angle between their inner surfaces and cutter blade cutting surface for the knife blade edge to be sharpened at a proper angle and prevents undesired physical contact with the cutter blade edges thus preventing injury to the user and/or damage to the cutter blade. A guard is provided in one embodiment to prevent inadvertent injury to the thumb of the user by the blade being pulled through the sharpener. Other objects and advantages of the invention will hereinafter appear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective elevated view of the sharpening device of the invention; 
     FIG. 2 is an exploded view of the device of FIG. 1; 
     FIG. 3 is a bottom plan view of one of the handle or body portion of the devices of FIGS. 1 and 2; 
     FIG. 4 is a section of the handle or body portion of FIG. 4 taken along line 4--4 thereof; and 
     FIG. 5 is a section of the device of FIG. 1 with the addition of a thumb guard. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now to the various drawing Figures. FIG. 1 depicts the blade sharpening device 10 of the invention. The device comprises mating body portions 12 and 14. The body portions may be constructed from any material suitable for the purpose intended. Aluminum or other light weight metal or plastic of various types may be used. The body portion may be machined, cast or formed by any other known method for forming materials. 
     End 16 of the blade sharpening device includes a cutout 18 within which an equilateral triangular shaped cutter blade 20 extends from between the body portions. The edges 22 of the cutter blade 20 are chamfered or angled toward one side of the blade. 
     The body portions 12 and 14 are secured together by means of a pair of countersunk type screws 24. 
     As can be clearly seen in FIG. 2, the threaded screws 24 extend through an angled aperture 27 in portion 12 and thread into engaging thread 26 in portion 14. A mating cutout 28 is formed in both body portions 12 and 14 for receiving the cutter blade 20 in a locking engagement with the body portions along side 30 and corners 32 and 34. When the cutter blade is installed as shown in FIG. 1 and in phantom in FIGS. 3 and 4 and the body portions 12 and 14 are assembled, the side 30 and corners 32 and 34 lock the cutter blade 20 into operating position and prevent any movement of the cutter blade 20 when a knife blade (not shown) or the like is drawn through the cutout 18 between either wall 36 or 38 and edges 22 of the cutter blade 20 for sharpening thereof. 
     As blade edges 22 wear, the body portions can be separated as shown in FIG. 2 and the blade 20 can be rotated in position to expose one new surface 22 to the opening 18 plus an unused portion of the other surface. The cutter blade 20 can be periodically rotated in this manner until all surfaces 22 are no longer suitable for the purpose intended at which time a new cutter blade 20 can be inserted into the opening 28. 
     Depending on the materials of construction the inner surfaces of the body portions may be hollow to conserve materials of construction. When constructed in this manner strengthening walls 40 are employed. The space between the various walls 40 and outside walls are suitable for the storing of extra cutter blades 20. 
     To provide a good grip on the body portion when sharpening knife blade and the like, a roughened portion 42 may be provided on the outer surface of each body portion. The roughening portion 42 may be machined or cast into the body portions during fabrication or coated thereon after fabrication as desired. 
     The cutter blade 20 is preferrably constructed of carbide or is carbide coated. Blades of this type are available from Enco Company as model TPG-322. Suitable blades from other manufactures or distributors can be used equally as well to practice the invention. 
     FIG. 5 depicts an end section of the device 16 of FIG. 1 with the addition of a thumb guard 42 which is secured to at least one portion 16 by means of fastening means 44. The fastening means typically will be screws passing through the thumb guard 42 and engaging threads on portion 36, or by casting the guard integrally with one portion of 16. The guard 42 extends from the adjacent portion 36 on the side adjacent the chamfered surface of the blade 20 providing a guard for the thumb of the user when the blade is pulled toward the hand of the user. 
     Other variations, applications and ramifications of this invention will occur to those skilled in the art upon reading this disclosure. Those are intended to be included within the scope of this invention, as defined in the appended claims.