Abstract:
The present invention is a cutting tool having a cutting feature formed along substantially all of a cutting edge formed along a portion of the blade of the edged tool. The cutting feature is characterized by a cutting edge, a first thickness behind the cutting edge, and a second thickness behind the first thickness, with the second thickness being less than the first thickness. The second thickness is preferably established within the first 20% of the depth of the blade adjacent the cutting edge.

Description:
BACKGROUND 
       [0001]    The present invention relates to the field of cutting implements, and more particularly to cutting tools used to slice soft materials and the like. 
         [0002]    Knives having a sharpened cutting edge have been used for many years in the preparation of foods or the cutting of soft materials. Typically, such knives have a blade with a sharpened edge along one or more of the edges of the blade, with the sharpened edge being formed by grinding or honing the edge to form two surfaces joined at an acute angle. Such a blade is easy to manufacture, however it may have limitations with regard to cutting some soft materials, including many foodstuffs. 
         [0003]    As a knife is forced into material to be cut, the cutting edge acts as a wedge, which forces apart the portion of material being cut from the remaining portion of the material. Until the portion being cut off is fully severed from the main portion one or both portions may bear against the sides of the knife being used to cut the material. As the knife is forced further into the material, friction between the material and the sides of the knife both increases the force required to force the knife through the material, and also creates shear forces that are applied to the material being cut. Such shear forces can distort the cut surface of the material, causing ripping or tearing which damages the material being cut, potentially rendering the cut material unusable or simply reducing its aesthetic qualities. 
         [0004]    As shown in  FIG. 1 , in order to minimize the forces generated between the cutting tool  100  and the material, various efforts have been made to reduce the surface contact between the material and the cutting tool  100 . One solution has been to form kullens  102  in one or both sides of the blade  104 . Kullens  102  are concave dimples formed in the surface  106  of the knife, used to reduce contact between the knife surface  106  and the material being cut. As shown in  FIG. 1B , the kullens  102  form thinned sections  108  in the blade  104  above the cutting edge, such that contact between the material and the sides of the blade  104  above the cutting edge  110  are reduced, such that friction forces are reduced. 
         [0005]    The formation of kullens in one or both sides of the blade gives rise to several disadvantages. First, frequent sharpening of the blade wears the cutting edge to the point that the cutting edge becomes formed from the thinned blade sections formed by the kullens (shown as the dashed line  112  in  FIG. 1 ), as well as by the ribs  114  between the individual kullens  102 .  FIG. 2  shows a knife  200  having kullens  102  that has been sharpened to the point that the cutting edge  110  extends through the kullens  102 . Along a first plane  202 , shown in cross-section as  FIG. 2A , the rib  114  between kullens  102  causes the sharpened blade to be thicker adjacent  204  the cutting edge  110 , while along a second plane  206 , shown in cross-section as  FIG. 2B , the kullens themselves cause the thickness  208  of the blade  104  immediately adjacent the cutting edge to be thinner, affecting the performance of the blade  104  when the knife  200  is used for slicing. Such a cutting edge has significant limitations, particularly in that the cutting edge no longer has a substantially constant cross section, and any lateral motion of the knife as material is cut causes the raised portions of the cutting edges formed by the ribs  114  to alternately further force the opening between the main portion and the portion being cut to separate and reclose, creating localized increases in the friction between the material being cut and the knife  200 , as well as localized increases in the shear forces applied to the material being cut. This may result in a ripping, ragged cut that also requires greater effort by the users of the knife. 
         [0006]    A second disadvantage arises from the process used to form the kullens  102  in the blade  104 . The metals used to form knife blades tend to be very hard, but brittle, metals. Where the kullens  102  are machined into a blade  104 , the machining may leave stress concentrations in the structure of the blade  104  that are subject to forming cracks, a propensity which is enhanced by the hard but brittle materials. Where the kullens  102  are formed by a stamping process, stress concentrations again may be formed, giving rise to a similar crack propensity. The more transitions that are formed in the blade geometry, the greater the number of stress concentrations, and accordingly, the more susceptible the blade is to cracking. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention may be embodied in a cutting tool having a blade. The blade may be characterized as having a length, a depth, and a cutting edge extending along at least a portion of the length of the blade. The blade may have a cross sectional shape adjacent the cutting edge that is consistent long the cutting edge. The cross sectional shape may be characterized by the presence of a first thickness above the cutting edge, and a second thickness above the first thickness, where the second thickness is less than the first thickness, such that the reduced thickness in the area of the second thickness reduces surface contact between the cutting tool and material being cut when the cutting tool is used to cut such material. 
         [0008]    Alternately, the present invention may be embodied in a cutting tool having a blade. The blade may be characterized as having a length, a depth, and a cutting edge extending along at least a portion of the length of the blade. The blade may be further characterized as having a cutting feature extending along the cutting edge, wherein the cutting edge is characterized by a sharpened edge, a first thickness above the sharpened edge, and a second thickness above the first edge, wherein the second thickness is less than the first thickness, and the second thickness is achieved close to the sharpened edge. 
         [0009]    Alternately, the present invention may be embodied in a cutting tool having a blade characterized as having a length, a depth, and a cutting edge extending along at least a portion of the length of the blade, with the blade further having a recess formed in a first side of the blade. The recess may extend along at least 50% of the cutting edge, such that a wedge portion is established between the cutting edge and the recess. The wedge portion may have a first thickness at its thickest extent. A second blade thickness may be established by the recess, such that the first blade thickness is greater than the second blade thickness. 
         [0010]    Alternately, the present invention may be embodied in a cutting tool having a blade characterized as having a length, a depth, and a cutting edge extending along at least a portion of the length of the blade, with the blade further having a scab joined to the blade on a first side blade, adjacent to the cutting edge. The scab may be characterized as having a length and a first edge and a second edge and a scab width extending between the first edge and the second edge, with the scab extending along at least 50% of the cutting edge. The first edge of the scab may be disposed adjacent to the cutting edge. The scab may establish a first thickness through the blade and the scab adjacent to the second edge of the scab. The blade may have a second thickness immediately above the first thickness, with the second thickness being less than the first thickness. 
         [0011]    Alternately, the present invention may be embodied in a cutting tool having a blade characterized as having a length, a depth, and a cutting edge extending along at least a portion of the length of the blade. The blade may further include a scab having a v-shaped cross section. The v-shaped cross section may be characterized as having first and second legs. The first leg and the second leg may each have a first end and a second end, with the first leg being joined to the second leg at the first end of each leg to form an acute angle. The first leg and the second leg may each have a length extending from the respective first ends to the respective second ends, as well as a thickness. The length of the first leg and/or the length of the second leg may be less than 10% of the depth of the blade, with the v-shaped scab conforming to the cutting edge of the cutting tool and extending along at least 40% of the cutting edge. The first and second legs may form a first thickness at the outermost extent of the first and second legs. The thickness of the blade adjacent to an uppermost extent of the first and second legs may be less than the first thickness. 
         [0012]    Alternately, the present invention may be embodied in a cutting tool having a blade characterized as having a length, a depth, and a cutting edge extending along at least a portion of the length of the blade, with the blade further having a first scab joined to the blade on a first side adjacent to the cutting edge. The first scab may have a length and a first edge, a second edge, and a first scab width extending between the first edge and the second edge. The first scab may extend along at least 50% of the cutting edge, with the first edge of the first scab being disposed adjacent to the cutting edge. The blade may additionally have a second scab joined to the blade on a second side of the blade, adjacent to the cutting edge. The second scab may also have a length, a first edge, a second edge, and a second scab width extending between the first edge and the second edge, with the second scab extending along at least 50% of the cutting edge, with the first edge of the second scab being disposed adjacent to the cutting edge. The cutting tool may be characterized as having a has a first thickness through the blade and the first and second scabs adjacent to the second edges of the first and second scabs, and a second thickness immediately above the first thickness, with the second thickness being less than the first thickness. 
     
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0013]      FIG. 1  illustrates a prior art knife using a plurality of kullens to reduce the thickness of the blade behind the cutting edge. 
           [0014]      FIG. 1A  illustrates a notional cross section of the prior art knife of  FIG. 1 , with the cross-section taken through a rib between adjacent kullens. 
           [0015]      FIG. 1B  illustrates a notional cross-section of the prior art knife of  FIG. 1 , with the cross-section taken through a kullen. 
           [0016]      FIG. 2  illustrates the prior art knife of  FIG. 1  after repeated sharpenings. 
           [0017]      FIG. 2A  illustrates a notional cross section of the prior art knife of  FIG. 2 , with the cross-section taken through a rib between adjacent kullens. 
           [0018]      FIG. 2B  illustrates a notional cross-section of the prior art knife of  FIG. 1 , with the cross-section taken through a kullen. 
           [0019]      FIG. 3  illustrates a cutting tool with a recess formed adjacent the cutting edge. 
           [0020]      FIG. 3A  illustrates the cutting tool of  FIG. 3  in cross-section. 
           [0021]      FIG. 3B  illustrates the cutting tool of  FIG. 3 , showing a close-up of the cutting edge in cross-section. 
           [0022]      FIG. 4  illustrates a cutting tool such as shown in  FIG. 3  after repeated sharpenings of the cutting edge. 
           [0023]      FIG. 4A  illustrates the cutting tool of  FIG. 3  in cross-section. 
           [0024]      FIG. 5  illustrates a cutting tool utilizing a scab on one side of the blade. 
           [0025]      FIG. 5A  illustrates the cutting tool of  FIG. 5  in cross-section. 
           [0026]      FIG. 6  illustrates the cutting tool of  FIG. 5  in cross section after repeated sharpenings. 
           [0027]      FIG. 7  illustrates a cutting tool utilizing a v-shaped scab on the cutting edge. 
           [0028]      FIG. 7A  illustrates the cutting tool of  FIG. 7  in cross-section. 
           [0029]      FIG. 8  illustrates the cutting tool of  FIG. 7  in cross section after repeated sharpenings. 
           [0030]      FIG. 9  illustrates a cutting tool utilizing multiple recesses. 
           [0031]      FIG. 9A  illustrates a cutting tool as shown in  FIG. 9  in cross-section. 
           [0032]      FIG. 9B  illustrates a cutting tool such as shown in  FIG. 9 , showing a close-up of the cutting edge in cross-section. 
           [0033]      FIG. 10  illustrates a recess formed in a cutting tool, such as the cutting tool shown in  FIGS. 3  and/or  9 , shown in cross section, embodying a cross-sectional shape optimized to rapidly transition the edge of the blade from the wedge portion to the recess. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    In order to provide a more full understanding of the present invention, embodiments of the invention are shown in  FIGS. 3 through 10 , which are described in detail as provided below. 
         [0035]    With respect to the embodiment of  FIG. 3 , in which like numbers represent like elements, there is shown a cutting tool  300  having a thinned section  302  formed immediately behind the cutting edge  304  of a blade  306 . The thinned section  302  may be a recess  308  formed in one side  310  of the blade  306 , such that the area of surface contact between the blade  306  and a material being cut is substantially reduced. The blade  306  may have a length  312  and a depth  314 , as well as a handle  316 , and may come to a point  318  or not. The shape of the blade  306  and the style of the handle  316  may be varied as desired. The thinned section  302  of the blade  306  may typically extend along the majority of the length  312  of the cutting edge  304  of the blade  306 . The blade  306  may have a choil  320  between the cutting edge and the handle  316 . 
         [0036]    The thinned section  302  feature may be formed as a recess  308  on one or both sides of the blade  306  during initial fabrication of the blade  306 , such as during a stamping or forging process by which the blade  306  is formed. Alternately, the thinned section  302  may be formed through a forming process, such as by grinding, machining or milling a recess into the blade. Alternately, as shown in  FIGS. 5 and 7  and discussed further below, the thinned section may be created by the addition of material to one or both sides of the blade adjacent the cutting edge, thus thickening the blade adjacent the edge. 
         [0037]    The purpose of the thinned section  302  is to reduce the surface contact between the material being cut and the side or sides of the blade  306 . Accordingly, when viewed in cross-section such as shown in  FIG. 3A , the blade  306  may include a first portion  322  and a second portion  324 , with the second portion  324  being above the first portion  322  with respect to the cutting edge  304 . The thickness  326  of the first portion is greater than the thickness  328  of the second portion  324 , such that the wedge  330  formed by the cutting edge  304  stops where the first portion  322  transitions to the second portion  324 , such that material that has already been cut, and has passed the first thickness  326 , does not contact the sides of the blade  306  in the area of the second thickness  328 . In order for the blade  306  to have adequate strength, the blade  306  may additionally be provided with a thicker section, such as a spine  332 , to provide strength or stiffness to the blade  306 . In the area of the spine  332 , the thickness of the blade  306  may equal or exceed the first thickness  326 , such that cut material may once again come into contact with the blade  306 . The above is not intended to be construed, however, to infer the requirement of a spine  332 , as the thickness of the knife  300  may remain less than the first thickness  326  for the full extent of the blade  306  above the first portion  322 . Additionally, the cross-section of the blade above the cutting feature  334  formed by the first  322  ad second  324  portion may vary, so long as the cross-section of the blade  306  adjacent the cutting feature  334  retains the relationship between the first and second thicknesses  322 ,  324 . 
         [0038]    Furthermore, it must be noted that the cut portion of material being cut tends to form an angle with respect to the remaining portion of material, such that the transition from the cutting edge  304  to the first thickness  326  tends to separate the material being cut, and thus from being in surface contact with the blade  306 , such that the thickness of the blade  306  above the second thickness  328  can increase the farther above the cutting edge  304  the blade  306  goes, without promoting surface contact between the blade  306  and the material being cut. 
         [0039]    As shown in  FIG. 3 , the cutting feature  334  may be seen as a section of the blade  306  between a recess  308  and the cutting edge  304  including the cutting edge, such that the cutting feature  334  may extend along most of the cutting edge  304 . As shown in  FIG. 3A , the cross section of the cutting feature may include a sharpened edge  336 . The sharpened edge  336  may be formed by grinding, honing, or any other process suitable for generating a sharpened edge  336 . A first thickness  326  may be formed behind the cutting edge  304  to force material being cut apart. A second thickness  328  may be formed above the first thickness  326 . The second thickness  328  is less than the first thickness  326 , such that a gap may be formed between the material being cut, after having been forced apart by the first thickness  326 , and the sides  338 ,  340  of the cutting tool  300  in the area of the second thickness. 
         [0040]    Frequent use may result in the cutting tool being sharpened to the point that sufficient material has been removed such that the first portion  322  has been essentially removed, such as to the dashed line  342  shown in  FIG. 3 .  FIG. 4  illustrates a cutting tool  300  such as shown in  FIG. 3  that has been sharpened to such an extent. As shown in  FIG. 4A , a cutting edge  304  may be formed from the remaining material after the first portion has been sharpened away, allowing the cutting tool  400  to continue to be used after the first portion has been worn away by successive sharpenings. 
         [0041]    As shown more clearly in  FIG. 3B , the first portion  322  may additionally or alternately extend for a distance  344 , such that material is provided to allow some sharpening of the cutting feature  334  before material removal associated with such sharpening begins to reduce the first thickness  326 . The length  344  of the side surfaces  338 ,  340  of the first portion  322  may be chosen to provide for an optimal ability of the cutting tool  300  to be successively sharpened, without the side surfaces  338 ,  340  extending for such a length that surface contact between the material being cut and the side surfaces is adversely increased. The length  344  of the side surfaces  338 ,  340  is therefore dependant upon the speed at which material may be worn away from the blade  306  by sharpening operations, the overall depth  314  of the blade  306 , and the desire to minimize the length of the side surfaces  338 ,  340  to limit friction between the side surfaces  338 ,  340  and material being cut. 
         [0042]    As shown in  FIG. 3 , the thinned section may extend from the cutting edge above the first portion  322  across a substantial portion of the depth  314  of the blade  306  itself. The blade  306  may additionally have a spine  332 . The spine  332  may have a greater thickness than the thinned section  302 , to give strength to the blade  306 . A second edge may be formed on the back edge of the blade  306  if a double sided cutting tool is desired. The second cutting edge may additionally be formed to have a thick portion and a thin portion behind the second cutting edge. 
         [0043]    The proportions of the depth of the first portion  322  to the width of the thinned section  302  to the depth  314  of the blade  306  may be chosen to provide an optimized cutting tool for a particular application. In one presently preferred embodiment, the width  348  of the recess is approximately ⅓ rd  to ⅕ th  of the depth  314  of the blade  306 , when a machined recess is used  346 . Additionally, the depth of the first portion  322  may be between 3 and 6 millimeters, however these dimensions are chosen for the cutting of soft foodstuffs, and the dimensions may be varied as required to accommodate different materials and knife sizes. 
         [0044]    As shown in  FIG. 4 , the cutting tool  400  of the present invention may be sharpened to the point that sufficient material removal has occurred to remove all of the first portion. Such excessive sharpening does not obviate the utility of the cutting tool, however, as the sharpened edge  304  still provides a smooth contour, unlike what may occur with respect to kullens, as discussed above. 
         [0045]    As shown in  FIG. 5 , the first thickness may alternately be formed by bonding or joining a scab  502  or scabs to one or both sides of the blade  306  adjacent the cutting edge  304 . The scab  502  or scabs may preferably extend along most of the cutting edge  304  of the blade  306 . The scab  502  or scabs may preferably be joined to the blade  306  such that the junction of the scab  502  or scabs to the blade  306  adjacent the cutting edge  304  present a smooth transition, such that sharpening of the cutting edge which extends into the scab  502  or scabs allows the sides of the blade  306  to retain a smooth surface adjacent the transition  504  from the cutting edge  304  to the scab  502  or scabs. 
         [0046]    A scab  502  may be joined to only one side of the blade  306 , such as shown in  FIGS. 5 and 5A , without preventing surface contact from being reduced between the side of the blade of the knife and material being cut. Additionally, the use of a scab  502  or scabs in such fashion allows the remaining portion of a hollow ground blade to form a rotational recess, such that the thickness  506  of the blade  306  above where the scab  502  has been attached is thinner that than the thickness  508  of the joined scab  502  and blade  306 , as shown in  FIG. 5A . Additionally, as shown in  FIG. 6 , the cutting tool again does not lose its utility if the scab  502  is completely worn away by sharpening, as the remaining portion of the blade  306  may present a conventional knife cross-section, which while without enjoying the benefit of the present invention, may still be usable for some cutting actions. 
         [0047]    The scab  502  or scabs may be joined to the blade  306  through any method which provides suitable joint strength to prevent the scab  502  from becoming separated from the blade  306  during any cutting or sharpening procedures. Presently, joining the scab  502  to the blade using an epoxy based adhesive has proved suitable, especially when a blade  306  material that is difficult to weld is being used. Where the selected blade material shows ready weldability, ultrasonic welding may be utilized to create a joint of sufficient structural strength between the scab  502  and the blade  306 . 
         [0048]    The blade  306  of the present invention does not need to be formed from a metallic material, although the ready availability of metallic materials may lead to implementation of metallic materials as a cost decision. The blade  306  and/or scab  502  may alternately or additionally be formed from zirconium ceramics, tungsten carbide, or more conventional metals. Where metals are used, various heat treatments or surface hardening treatments may be used to obtain specific properties as desired. Presently, prototypes of the blade  306  of the present invention have been formed used ZDP-189, a proprietary metallurgy produced by Hitachi. ATS-34, another proprietary metallurgy produced by Hitachi, is also believed highly suitable for producing cutting tools implementing the present invention. 
         [0049]    As shown in  FIG. 7A , a scab  702  having a v-shaped cross section  704  may be utilized. The v-shaped cross section  704  may have first  706  and second  708  legs joined at first ends  710 ,  712  of the legs  706 ,  708 , such that a sharpened edge  710  may be formed at the intersection of the legs  706 ,  708 . As the legs  706 ,  708  are angled with respect to each other, the legs  706 ,  708  can form an outermost extent  712 , which establishes a first thickness  714 . Above where the v-shaped scab  702  is joined to the blade  306 , the absence of the material forming the legs creates a thinner section  716  of the blade  306  complex, such that the surface contact reduction of the present invention is accomplished. Although the illustrations show the scab  702  being symmetrical with respect to the centerline  718  of the blade, the cross-section  704  does not need to be symmetrical, and further may vary along the length of the scab, i.e., the length of the legs may decrease or increase as desired as the scab  702  extends along the cutting edge. As shown in  FIG. 8 , the use of a v-shaped scab also provides the benefit of leaving a conventional knife cross-section after the scab has been worn away by sharpening, which although not providing the benefits of the present invention, allows the cutting tool to continue to be used. 
         [0050]    As shown in  FIG. 9 , multiple recesses  902 ,  904  may be formed in the side  906  of a blade  306 , such that when a first thick portion  908  has been worn away through sharpening, a second thick portion  910 , as shown in  FIG. 9A , forms the new cutting edge  912  shown in  FIG. 9B . As shown in  FIG. 9B , where the cutting tool  900  has been sharpened to the point that material has been removed to the dashed line  914  shown in  FIG. 9 , a thick portion  910  still exists above the cutting edge  912 , with a thin portion  916  behind the thick portion  910 . 
         [0051]    As shown in  FIG. 10 , the profile  1002  of a recess  1004  is not limited to arcuate or other forms. Indeed, the use of scabs as shown in  FIGS. 5 and 7  illustrates that the creation of a thin portion of the blade above a thick portion may be accomplished without requiring any material removal from the blade. Notwithstanding, where it is desired to utilize a recess  1004  formed on one or more sides  1006 ,  1008  of a blade, the profile  1002  of the recess  1004  may be formed in two arcuate sections  1010 ,  1012  with the arcuate section joining the thick portion  1014  of the cutting feature  1016  with the thin portion  1018  having a smaller radius  1020  than the radius  1022  Of the remainder of the arc (or other suitable contour) which forms the recess  1004 . The use of a rapid transition from the thick portion  1014  to the thin portion  1018  may assist in minimizing surface contact between material being cut and the sides of the blade of a knife, as well as provide a transition which limits or minimizes stress concentrations from forming in the area of the transition. 
         [0052]    The present invention may be embodied in other specific forms than the embodiments described above without departing from the spirit or essential attributes of the invention. Accordingly, reference should be made to the appended claims, rather than the foregoing specification, as indicating the scope of the invention.