Patent Publication Number: US-2007101826-A1

Title: Knife sharpener

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to knife sharpeners, and more particularly, to a knife sharpener that utilizes a pair of curved sharpening rods that engage and interact with an impact-absorbing flexible bumper arm assembly which controls and guides the sharpening rods to optimal angles and pressures that enhance obtaining even and consistent edge alignment of a knife regardless of what sharpening techniques are used.  
      Various blade or knife sharpening devices are known in the prior art that utilize a pair of sharpening rods that are pivotally mounted and cross one another over a slot which receives and guides the blade to be sharpened. Representative of this prior art are U.S. Pat. Nos. Cozzini 5,478,272, Bloomington 5,040,435 and Juranitch 5,655,959, Inman 4,550,632, Gangelhoff 5,440,953, Juranitch 4,934,110 the contents of which are incorporated by reference herein.  
      As described in the 5,478,272 and 5,655,959 patents, the sharpening rods define a V-shaped intersection there between that overlies a knife guiding slot, with the V-shaped intersection point moving along the slot as the knife is pressed against the sharpening rods.  
      One drawback of the prior art is that at the point that the rods reach an end-of-motion stopper, continued pressing of the knife against the V-shaped intersection results in some loss of control over the precise angles at which the knife meets that sharpening rods. Present art uses a resilient device and stop member located adjacent the bottom end of the slot on the back and positioned to be engaged by free ends of the rods when the cross-over point of the rods reaches toward a bottom end of the slot, the resilient device exerting a force on the rods which resists the force applied to the rods by a knife blade being sharpened.  
      Another drawback of prior art 5,478,272 and 5,655,959 patent is the use a fixed stop member on the front of the housing plate. Present invention uses a tip enhancer mounted on the front of the housing plate which sharpens the tip of the knife blade as it is withdrawn from the slot. Present invention differs in that the tip enhancer not only acts as a stop member, but is position at correct angles to sharpen the tip of the knife and prevents the knife blade from cutting the surface of the housing plate.  
      Another drawback of all prior art is the use of a housing plate having all components attached to the front of their unit. Present invention has a housing plate having all components attached to the front of their unit. Present art uses a pivoting mechanism for the rods, biasing the cross-over point toward the top end of the housing plate mounted on the rear. Unlike other, prior art knife sharpeners that have been made for food processing plants, this new design concept protects all the fragile, sensitive hardware, as well as their critical adjustments. It is for this reason that all critical adjustments and hardware have been placed on the reverse side of the housing unit, away from the operator, and is further stabilized and protected by being mounted on a solid piece of UHMW and/or high-density polyethylene material. Prior art do not have the protective positioning of the hardware being placed on the reverse side of the housing unit, away from the operator. All prior art units have working components on the front of their unit.  
      There is no leverage, protection, or strength when all the hardware and adjustments are facing the operator. The rods bend toward the operator, adding more stress and fatigue. The adjustments facing the operator are knocked out of place more easily. This new unit, with the hardware on the backside, brings the rods in towards the housing for support, strength and durability.  
      Another drawback of all prior art is that no recessed slot is used to guide the knife. Present invention uses a recessed slot allowing deeper insertion of the knife blade since all components are mounted on the rear (back) of unit.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide an improved knife sharpener.  
      It is another object of the present invention to provide a knife sharpener that is more durable, and easier to use.  
      It is another object of the present invention to place all moving parts on the rear of unit away from operator.  
      It is yet a further object of the present invention to provide a knife sharpener that utilizes a pair of curved sharpening rods that are controlled to provide optimal angles and pressures and which obtain even and consistent edge realignment and/or edge retrieval, regardless of the sharpening technique being employed by the particular person who sharpens the knife.  
      The foregoing and other objects of the invention are realized with a knife sharpening unit that supports on a housing plate a pair of sharpening rods that are curved to specific dimensions for maximizing the knife sharpener&#39;s ability to utilize and engage an impact-absorbing flexible bumper arm assembly. The flexible bumper arm assembly controls and guides the sharpening rods at their end-of-travel point, in a manner that alters the angle of intersection between the sharpening rods and the pressures applied to the blade of the knife to obtain even and consistent edge realignment.  
      Preferably, the sharpener is provided with markings on the housing plate that permit adjustment of the initial intersection point between the sharpening rods. Preferably, additional markings are provided to indicate to a user a “sweet spot” of the knife sharpening unit.  
      The pair of sharpening rods are resiliently biased to an initial position, defining an initial intersection, by a spring mechanism. In one embodiment, that mechanism is in the form of first and second leaf or plate springs, the free ends of which are fixed between pairs of cams that enable adjusting the location of the initial intersection point of the sharpening rods across the knife slot. Preferably, the mechanism comprises coiled springs. Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a back view of the knife sharpener of the present invention.  
       FIG. 2  is a side view of the knife sharpener of the present invention, as seen along lines  2 - 2  in  FIG. 1 .  
       FIG. 3  is a front view (partially in perspective) of the knife sharpener of the present invention.  
       FIG. 4  is a top view of the knife sharpener of the present invention, as seen along lines  4 - 4  of  FIG. 3 .  
       FIG. 5  shows a modified, front view of the knife sharpener of the present invention, including a tip enhancer device.  
       FIG. 6  shows a modified back view of the knife sharpener of the present invention, including an alternate spring mechanism for the sharpening rods.  
       FIG. 7  is perspective of the front of the knife sharpener of the present invention, illustrating the manner of its utilization.  
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION  
      With reference to the drawings and primarily  FIG. 1 , the knife sharpener  10  of the present invention is comprised in the main of a housing plate  53  with two main sections  54  and  56  that are separated by a knife slot  60 . The housing plate supports a pair of pivotally movable sharpening rods  12 ,  14  that are resiliently biased toward an initial position by spring arms  24 ,  30 , the sharpening rods crossing one another at a movable V-shaped intersection point  13 , the location of which moves along the slot  60 , as a knife is pressed down the slot  60 .  
      The housing plate  53  is preferably made of a solid, ½ inch thick UHMW and/or high-density polyethylene, durable, one-piece construction material. It has been designed so that the knife blade  77  ( FIG. 8 ) will avoid cutting into the housing plate  53  during normal use. The blind high wall  55  ( FIG. 8 ) on the right side of the housing plate  53  helps guide the blade  77  down into the sharpening slot  60 .  
      Four adjustable upper and lower offset cams  26 ,  28  and  32 ,  34  elevate and lower the stainless steel spring arms  24 ,  30  to easily position the sharpening rods  12 ,  14  to the proper height and into the center of the sharpening slot. Proper cam adjustments also create the correct positive and negative force within the spring arms  24 ,  30  as to precisely generate the even, consistent flex tension necessary to keep the blade angles symmetrical for maximizing edge retrieval.  
      Each sharpening rod spring assembly is made of a combination of the following materials: a round, stainless steel sharpening rod  12 ,  14  and a flat stainless steel spring  24 ,  30 . These two pieces are mounted onto a block of UHMW  16 ,  18 , or stainless steel material.  
      The four adjustable upper and lower cams can easily position the sharpening rods  12 ,  14  into the center of the sharpening slot  60  by elevating or lowering the flat, stainless spring arm. Unlike other sharpeners, this new use of cams allows for adjustments to compensate for material fatigue, as well as proper angle setup adjustment specifications.  
      The rods  24 ,  30  are supported at their non-free ends in first and second respective blocks  16 ,  18  that are pivotally mounted by pivots  20 ,  22 . Note further the alignment windows  36  and  38 , which help an operator align the initial V-shaped intersection (crossing point) of the rods  12 ,  14  by adjusting the cams  26 ,  28  and  32 ,  34  by operating their center screws using an appropriate tool, for example, a screwdriver (not shown).  
      As will be explained, the windows  60  and  66  indicate the position of the “sweet spot” of the knife sharpener  10 . Reference numeral  58  identified an angled, cut away from the section  56  of the housing  53  at the point of entry into the slot  60 , while  62  indicates the sidewall that is also referenced as  55  in  FIG. 8 , which provides improved guidance for the knife being sharpened.  
      The newly designed adjustable, flexible bumper arms  46 ,  48  and positive stop  40  provide the best angles and the necessary pressure for obtaining an even, consistent edge realignment, no matter what sharpening technique is used. These flexible bumper arms  46 ,  48  add a considerable, additional amount of pressure, over and above what pressure is generated through the flat, stainless steel spring arms  24 ,  30  above. This is called the “sweet spot” for edge retrieval. This is the area that enables a damaged edge to be reconstructed through the addition of a concentrated force that is generated where the greatest point of leverage is being exerted. The extra force being exerted by these flexible bumper arms  46 ,  48  spans over an additional ¼ inch on the path downward, toward the “sweet spot” area. The ¼ inch “sweet spot” area most effectively accommodates and captures the greatest variation of knife blade angles which exist on all knife blades within the processing industry. The additional, graduated pressure within the flexible bumper arms traveling within the ¼ inch distance, absorbs any undo shock; and it guarantees that the edge angles will not be damaged, but rather be finessed to capture the greatest variety of edge angles for perfect realignment.  
      A square corner stop design, for the flexible bumper arms, has also been incorporated as a feature of this unit. It has been put into a centered position between the flexible bumper arms with a ¼ inch travel distance on each side. It is also nearly perfectly centered with the knife-sharpening slot  60 , so that the knife blade angles will be maintained in straight alignment, no matter what sharpening technique is used.  
      The flexible bumper arms  46 ,  48  and the square stop  40  have an additional ¼ inch high-low vertical adjustment specifically suited to a customer&#39;s needs. See the groove  42  and fixing bolt  44 . These new design elements have been incorporated on the unit to keep all elements of the sharpener in harmony with one another.  
      The square bumper stop  40 , within the center of the flexible bumper arms, has been positioned to align itself exactly in the center of the sharpening slot, so that when the sharpening rods hit the flexible bumper arms at the same time, both arms will further increase the pressure necessary for a heavy duty edge realignment, and will stop at the same time, at the same point, assuring edge alignment and symmetry. The adjustable, flexible bumper arm unit is preferably made of Teflon, HD poly or UHMW material. This unit is on the backside of the housing unit  53 , facing away from the operator, thereby protecting it from operator abuse. Prior art units have their hardware facing toward the operator.  
      Other knife sharpening units do not have these capacities. They either stop on a solid rod, as in U.S. Pat. No. 5,478,272, or rely on the pressure of stop points positioned high above on the sharpening rods, to create the necessary force below for edge retrieval. These units produce higher stress levels on the sharpening rods, eventually leading to breakage within the stress points of the rods and damaging the knife blade and the sharpener itself Both of these sharpeners cannot keep the sharpening rods in consistent alignment at the bottom of the sharpening slot, or cannot be adjusted to the proper angles necessary for reaching a variety of edge angles, or cannot be effectively readjusted to compensate for material fatigue.  
      Other knife sharpeners do not have the proper adjustments or design features to keep the knife blade from cutting into the components of their housing units. As a result, it is common for the edges to become further damaged at the bottom point of the sharpening process.  
      Referring to  FIG. 5 , the newly designed tip enhancer  79 ,  82 ,  84  comprises a circular stainless steel cover plate  79  on the front side of the housing unit  53  that supports two specially treated and tempered stainless steel rods  82 ,  84  which are tack welded to it, forming an “X” pattern, at the best angles for realigning a knife blade&#39;s edge. The tip enhancer  79 ,  82 ,  84  has been placed at the bottom of the sharpening slot  60  as a deflecting device to keep the knife blade tip from cutting into the body of the sharpening unit while maintaining the proper angles on the knife blade. The tip enhancer serves as an additional sharpening feature. The tip enhancer specifically sharpens the tip of the knife. It is located at the bottom of the sharpening slot  60 , at the end of the sharpening process where the other knife sharpening units cut into the body of the sharpener, damaging the knife blade&#39;s edge and the unit itself, and dulling the edge&#39;s tip that has just been sharpened. It is for this reason that this unit is called the tip enhancer.  
      The tip enhancer  79 ,  82 ,  84  mounted on the front side of the housing plate will be precisely linked by two bolts that enter through the pre-slotted holes of the tip enhancer, passing through the pre-slotted holes of the housing unit  53  and through the pre-slotted holes of the flexible bumper arm unit  40  mounted on the backside, affixed with two stainless steel nylon inserted cap nuts. The square corner stop  40  of the flexible bumper arm, the center point of the tip enhancer and the sharpening slot  60 , are always in direct correlation with each other.  
      Stainless steel flathead socket cap screws and locknuts are used for all adjustment points on the knife sharpener. These threaded screws and locknuts are inserted through the solid UHMW and/or high-density polyethylene housing unit and are locked into position with a stainless steel locknut that covers over the drilled holes. As a result, no pathogens are able to form within these suspect areas. Quick adjustments on the processing line are more easily achieved using the components within this sharpening unit. The screw lengths are slightly extended by ¼ inch to protect the precise adjustment of the locknut for each component. On competitive units, the locknuts are easily being hit, throwing the components out of adjustment.  
      An ½ inch long×¼ inch wide viewfinder window slot  64 ,  66  is strategically placed horizontally on the housing unit for the operator&#39;s viewing of the “sweet spot”, which can be identified as being the slots at the bottom of the sharpening unit horizontally positioned on both the right hand and the left hand side of the slot  60 . The sharpening rods  12 ,  14  cross over into an imaginary line between the two slot windows. When the sharpening rods first make contact with the flexible bumper arm adjustment below, this is the top of the viewfinder slot window. As the sharpening rods&#39; cross over points continue down ¼ inch into the “sweet spot” area, they eventually stop at the flexible bumper arms  46 ,  48 . It is at this point that the rods are at the bottom of the viewfinder window, visually indicating that the coordinating adjustments are in synch with the “sweet spot”, providing the best edge retrieval. This window is a visual indicator to the operator that the flexible bumper arm unit  40  is in proper coordination with the adjustments of the sharpening rod and spring assembly above. No other sharpening units have this adjustment.  
      The horizontal ½ inch long×¼ inch wide sight alignment setup windows  36 ,  38  are strategically placed on the right and left hand sides of the sharpening slot&#39;s top or initial position. These windows provide an imaginary line crossover point for the rods to be set at their starting position. When the sharpening rods are centered within the sharpening slot, somewhere within the ¼ inch adjustment position of these two windows, this indicates that the proper adjustments have been made on the sharpening rod and spring assembly cams. As the sharpening rods&#39; spring assembly material fatigue, adjustments will have to be made in accordance with the existing fatigue factors. The horizontal slot windows are always a constant guide for bringing adjustments back to their best settings.  
      The over-sized, 2 inches high, blind guide wall  54  for knife blade placement is on the right side of the housing unit. It is 2 inches higher than the left wall  56 . The 2 inches high blind guide wall offers a liberal amount of surface area  54  for blade placement. This is the starting point for the knife blade to be guided down into the sharpening slot, without cutting into the housing unit.  
      The universal mounting holes  50 ,  52  are placed at the bottom of the housing unit to secure the knife sharpening housing unit to its position on the processing line. The reason we use the words “universal mounting holes” is because these holes can accommodate other manufacturers&#39; or end users&#39; mounting hole positions. This will give the end user the potential for easy adoption.  
      A knife-sharpening channel  70  ( FIG. 3 ) runs along the total distance of the sharpening slot  60  on the front, side facing the operator. This is a recessed area that is ½ inch equidistant from each side of the sharpening slot  60  and is ¼ inch deep into the depth of the housing unit&#39;s thickness. The purpose of this slot is threefold: it allows for a visible path for the operator to follow; it allows for a deeper insertion of the knife blade edge into the knife sharpening rod area to achieve complete coverage of the knife blade; and/or the depth of the slot keeps the knife handle from hitting the sharpening rod hardware and protects it from undo pressure and physical abuse.  
      Unlike other, prior art knife sharpeners that have been made for food processing plants, this new design concept protects all the fragile, sensitive hardware, as well as their critical adjustments. It is for this reason that all critical adjustments and hardware have been placed on the reverse side of the housing unit, away from the operator, and is further stabilized and protected by being mounted on a solid piece of UHMW and/or high-density polyethylene material. Prior art do not have the protective positioning of the hardware being placed on the reverse side of the housing unit, away from the operator. All prior art units have working components on the front of their unit.  
      There is no leverage, protection, or strength when all the hardware and adjustments are facing the operator. The rods bend toward the operator, adding more stress and fatigue. The adjustments facing the operator are knocked out of place more easily. This new unit, with the hardware on the backside, brings the rods in towards the housing for support, strength and durability.  
      With reference to  FIG. 6 , a modified pivoting mechanism for the rods  12  and  14  is in a form that substitutes for the spring plates  24 ,  30  of  FIG. 1 , respective first and second coil springs  90 ,  92 , the free ends of which are supported in fixing pins  17   b,    19   b,  at one end, and in the pivoting blocks  16 ,  18  by the fixing pins  17   a,    19   a  at the other end, as shown. This embodiment does not require the adjusting cams  26 ,  28  and  32 ,  34  of  FIG. 1 , but provides instead, respective cams  13 ,  15  which pivot around pins  13   a,    15   a,  and which can be adjusted to fix the initial crossing position of the rods  12 ,  14 . Items  17 ,  17   a,    90 ,  17   b,    18 ,  19   a,    92 ,  19   a  are covered and protected by using plate  86 , indicated by dotted lines. Further, the bumper arms  46  and  48  of the stop  40  pivot about the undercutting in the material at  46   a,    48   a  to create living hinges that provide the appropriate pivoting action, as well as prevention of breakage of the material of the stopper  40  at the point of bending.  
      Although the present invention has been described in relation to particular embodiments, thereof, many other variations and modifications and other uses will become apparent to those skilled in the art, or to those who work with these units on a daily basis. It is preferred, therefore, that the present invention be limited, not by specific disclosure herein, but only be appended claims.