Patent Publication Number: US-2010112921-A1

Title: Sharpening device for knife blades

Description:
The invention relates to a sharpening device for knife blades, comprising a base plate, a guiding slot in the form of a recess in the base plate for a knife blade to be sharpened, and main sharpening rods mounted on both sides of the guiding slot in pivotable fashion against an elastic spring-activated resetting force, with the main sharpening rods crossing each other in a crossing point in the area of the guiding slot. 
     With the aid of such a sharpening device as it has become known e.g. from U.S. Pat. No. 6,866,569 B2, knife blades dulled through use can be sharpened and brought back to form. In order to avoid any damages to the base plate which is usually made of a plastic material and any contamination of the knife blade and of any material cut by the knife blade, for example meat, with severed plastic parts, blade protection elements made of metal may be provided in the entry area of the guiding slot. The sharpening process takes place by abutting the knife blade against the main sharpening rods and dragging the knife blade along the main sharpening rods that follow the movement of the knife blade along the guiding slot. In order to obtain the desired quality of the cutting edge and contouring accuracy during the sharpening of a knife blade, the knife blade needs to be guided through the sharpening device repeatedly. 
     The invention is based on the objective of increasing during the treatment of a knife blade the sharpening effect of the sharpening device on the knife blade guided through it and to obtain a desired sharpening result with fewer treatment consequences. 
     This task is solved in accordance with the invention by providing pre-sharpening elements in at least one segment of the guiding slot that follow the course of the guiding slot on both sides. 
     During a movement carried out along the guiding slot, a knife blade passes the pre-sharpening elements and is sharpened by being swiped along the latter. The additional sharpening effect is achieved in the case of the sharpening device in accordance with the invention through the fact that a knife blade to be sharpened abuts against the movable main sharpening rods and the stationary, fixed pre-sharpening elements along the guiding slot while following the course of its guided path. The efficiency of the sharpening process is increased in the case of the sharpening device in accordance with the invention due to the fact that the desired result is achieved by means of fewer guided movements of the knife blade through the sharpening device as compared to conventional sharpening devices. The pre-sharpening elements lie opposite each other on both sides of the guiding slot and are designed as grinding, whetting and/or polishing elements. As a rule, the material of the pre-sharpening elements is a hardened material such as a metal or a ceramic. In addition, the pre-sharpening elements serve as protection for the base plates in which the guiding slot is provided. The base plate is made of a plastic material or a light metal and is typically manufactured as a die cast component. 
     In a preferred embodiment of the sharpening device in accordance with the invention, the pre-sharpening elements are provided in the entry area of the guiding slot. In the entry area, the frequency of the knife blades abutting or, respectively, striking the lateral sides of the guiding slots is high in comparison with the further course of the guiding slot. In addition, the blade protection function of the pre-sharpening elements is particularly advantageous in the entry area. 
     In an additional embodiment of the sharpening device in accordance with the invention, the pre-sharpening elements extend from the entry opening of the guiding slot to the crossing point of the main sharpening elements. In this embodiment, the guiding path from the insertion of the knife blade into the guiding slot to the abutment of the knife blade on the main sharpening rods is put to the greatest possible use in order to achieve an additional sharpening effect through the pre-sharpening elements. 
     In an additional preferred embodiment of the invention, the pre-sharpening elements extend across the entire length of the guiding slot. The advantage of this embodiment lies in the fact that the entire guiding path of the knife blade is utilized for the sharpening of the knife blade at the time of its insertion as well as at the time of its extraction. 
     Moreover, the guiding slot preferably has a widening in the entry area. The widening facilitates the insertion of a knife blade, making it possible to design the guiding slot as narrow as possible and thereby further improving the guiding of the knife blade and the sharpening result. 
     Preferably, the pre-sharpening elements protrude into the guiding slot. The selected distance between the pre-sharpening elements lying opposite each other is less than the width of the guiding slot, thereby assuring a good sharpening effect of the pre-sharpening elements on the knife blade. 
     In an additional preferred embodiment of the sharpening device in accordance with the invention, the pre-sharpening elements are designed as rods, preferably as round rods. However, the pre-sharpening elements may also have an angular, in particular a triangular profile with a sharpening edge directed towards the center of the guiding slot. The rods preferably run along the lateral edges of the guiding slot and are appropriately formed on the frontal as well as on the rear lateral edges. 
     In a preferred further embodiment of the invention the pre-sharpening elements protrude into the guiding slot with half of their diameter, preferably with their entire diameter. This enables the knife blade to be positively abutted against the pre-sharpening elements and a good sharpening effect. 
     In a preferred embodiment of the invention, the pre-sharpening elements and/or the main sharpening elements have on their surface a coating, such as a wolfram carbide coating or a diamond coating, in particular where the pre-sharpening elements have a coarser surface structure than the main sharpening elements. The choice of the sharpening material determines the sharpening effect, such as grinding, whetting or polishing. If a very hard material is selected, no abrasion of the blade material will take place but rather a deformation of the same. The actual sharpening process takes place at the pre-sharpening elements with the coarser surface structure while during the final traction, the knife blade is subjected to a finishing treatment, for example polishing, by the main sharpening elements with a finer surface structure. 
     An additional preferred embodiment of the sharpening device in accordance with the invention is characterized by the fact that the pre-sharpening elements are arranged in replaceable fashion on the base plate. Removable or, respectively, replaceable pre-sharpening elements not only facilitate the cleaning of the sharpening device in accordance with the invention, but the sharpening device can also be optimally accessorized with corresponding pre-sharpening elements depending on the intended use. The sharpening device in accordance with the invention can fulfill its sharpening function, at least partially, after the removal of the fixed pre-sharpening elements, i.e. exclusively with the main sharpening rods, as well as after the removal of the movable main sharpening rods, i.e. only with the pre-sharpening elements. 
     Moreover, a protective plate is preferably provided on the base plate below the guiding slot crosswise to the course of the guiding slot. During the intended use of the sharpening device in accordance with the invention, the knife blade is not slowed down at the lower end of the guiding slot and strikes it. The protective plate prevents any damages to a retaining fixture in which the sharpening device is accommodated and fixed as well as any injury to a user holding the sharpening device. 
     Advantageously, the sharpening device has a handle preferably provided with an anti-slipping coating. The handle permits a user to hold the sharpening device in one hand while being able to guide the knife with the knife blade to be sharpened into the sharpening device. The anti-slipping coating prevents the hand from sliding or, respectively, from slipping off the handle. 
    
    
     
       Additional advantages and characteristics of the invention can be found in the description and in the figures of the drawing. The sharpening device in accordance with the invention is shown in the figures in one embodiment. The characteristics shown in the figures are purely schematic and are not to be understood as being to scale. Shown are: 
       in  FIG. 1  a frontal view of a sharpening device in accordance with the invention; and 
       in  FIG. 2  a top view of the sharpening device shown in  FIG. 1 . 
     
    
    
       FIG. 1  represents a sharpening device  1  with an essentially oval-shaped base plate and a handle  3  designed as a hand grip with a recess  4 . The dimensions and the material, in this case a plastic material, of the sharpening device  1  are selected in such a way that that the sharpening device  1  can be held by a user in one hand. The handle  3  allows a user to hold the sharpening device  1  in one hand while being able to guide a knife with a knife blade to be sharpened into the sharpening device  1 . A protective plate  5  is provided between the base plate  2  and the handle  3  to protect a hand holding the sharpening device  1 . The handle  3  is preferably provided with an anti-slipping coating. The anti-slipping coating prevents the hand from sliding or, respectively, from slipping off the handle  3 . 
     A slit-like guiding slot  6  is cut into the base plate  2  almost over its entire longitudinal extension. Pre-sharpening elements  7   a  and  7   b  designed as round rods frame the guiding slot  6  on both sides. In an entry area  8 , the guidance slot  6  is widened or, respectively, broadened. On both sides of the guidance slot  6 , mounting agents  9   a  and  9   b  are arranged on which main sharpening rods  10   a  and  10   b  are mounted in pivotal fashion. The main sharpening rods  10   a  and  10   b  are arranged minor-inverted relative to the guiding slot  6  and cross each other in a crossing point  11 . 
     In the initial position as shown, the curved main sharpening rods  10   a  and  10   b  abut against upper stoppers  12   a  and  12   b . In the case of an insertion movement  13  of a knife blade guided along the guiding slot  6 , the blade meets the main sharpening rods  10   a  and  10   b  at the crossing point  11  and guides them into a final position not shown. To this end, the main sharpening rods  10   a  and  10   b  execute pivotal movements  14   a  and  14   b  against a resetting force that is generated by a spring element in the mounting agents  9   a  and  9   b . In their final position, the main sharpening rods  10   a  and  10   b  abut a lower stopper  15 , and the processed or, respectively, treated knife blade is at the lower end  16  of the guiding slot  6 . During its course through the entire guiding slot  6 , from the entry area  8  to the lower end  16 , the knife blade is swiped along the pre-sharpening elements  7   a  and  7   b  and along the main sharpening rods  10   a  and  10   b.    
     In the entry area  8  of the guiding slot  6 , the pre-sharpening elements  7   a  and  7   e  are slanted vis-à-vis the alignment of the guiding slot  6  (shown vertical in the figure). The angle between the intake slant and a transversal axis standing vertical to the median axis of the guiding slot  6  (shown horizontal in the figure) is selected larger than 45° in accordance with the invention. The pre-sharpening elements  7   a  and  72  follow an ever differentiable curve across their entire longitudinal extension; in other words, the course of the curve shows neither any steps nor any edges. In the figure, the pre-sharpening elements  7   a  and  7   b  are largely bow-shaped, with a convex alignment. In addition, it is advantageous that the pre-sharpening elements  7   a  and  7   b  narrow from the entry area  8  to the lower end  16  of the guiding slot  6 . In this way, the sharpening effect of the sharpening device  1  in accordance with the invention is further increased. 
     In its adjustment to the opening width of the guiding slot  6 , the widened entry area  8  is always selected in such a way that the pre-sharpening elements  7   a ,  7   b  may contribute to the sharpening of a knife blade. 
       FIG. 2  shows a view of the sharpening device from above. The guiding slot  6  is formed on the base plate  2  delineated by the protective plate  5  on the lower side. The pre-sharpening elements  7   a  and  7   b  protrude into the guiding slot  6  and narrow it, resulting in an easier guiding of a knife blade to be sharpened and a better sharpening result. The single main sharpening rod  10   a  is mounted rotatably in the mounting agent  9   a ; two parallel main sharpening rods  10   b  and  10   b ′ are rotatably mounted in mounting agent  9   b . The main sharpening rods  10   a ,  10   b ,  10   b ′ mesh with each other and cross each other in the initial position in the area of the guiding slot  6  as shown. 
     A sharpening device  1  with a guiding slot  6  for a knife blade to be sharpened and main sharpening rods  10   a ,  10   b  arranged on both sides of the guiding slot  6  which cross each other in the area of the guiding slot  6  and which execute pivoting movements  14   a ,  14   b  when a knife blade abuts against an elastic spring activated resetting force is additionally provided with pre-sharpening elements  7   a ,  7   b  in at least one longitudinal segment of the guiding slot. A knife blade to be sharpened presses against the fixed pre-sharpening elements  7   a ,  7   b  and against the movable main sharpening elements  10   a ,  10   b  when following its guided path along the guiding slot  6 , thereby improving the sharpening effect of the sharpening device  1  on the knife blade.