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  Method of sharpening cutting edgesUSPTO Application #: 20060084367Title: Method of sharpening cutting edges Abstract: The invention is directed to a method for polishing a cutting edge on a cutting instrument, comprising contacting a cutting edge of a cutting instrument with a polishing pad and a chemical-mechanical polishing composition comprising particles of an abrasive, and a liquid carrier, wherein the abrasive is suspended in the liquid carrier, and abrading at least a portion of the cutting edge to polish the cutting edge. The invention further provides a cutting instrument having a highly uniform edge. (end of abstract) Agent: Steven Weseman Associate General Counsel, I.p. - Aurora, IL, US Inventors: Clifford Spiro, George Steuer, Frank Kaufman USPTO Applicaton #: 20060084367 - Class: 451045000 (USPTO) Related Patent Categories: Abrading, Abrading Process, Razor, Knife, Or Scissors Sharpening The Patent Description & Claims data below is from USPTO Patent Application 20060084367. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention pertains to a cutting instrument and a method for making the same. BACKGROUND OF THE INVENTION [0002] Generally, cutting edges on cutting instruments are manufactured by processing an appropriate feedstock having a thickness that diminishes from the beginning of the cutting edge to the ultimate edge so as to provide a cutting edge. Conventional cutting-edge forming processes typically involve grinding operations that remove material in a gradient beginning at a distance from the ultimate edge to the ultimate edge itself. The process of grinding generally involves contacting the feedstock with hard abrasive particles imbedded in a grinding wheel rotating about an axis, thereby mechanically abrading material from the feedstock. This grinding operation often is carried out with large abrasive particles that tend to leave large gouges in the surface of the cutting edge. Subsequent processes of honing and stropping are then used to reduce the depth of gouges on the cutting edge surface. Honing and stropping are both mechanical processes that remove the softer material of the cutting edge by abrasion by the harder material of the abrasive. [0003] A cutting edge may be characterized in several ways. First, the thickness of the cutting edge at the ultimate edge determines in part the "sharpness" of the cutting edge. A thinner cutting edge will generally encounter less resistance in parting of the material being cut. Another parameter impacting the performance of a cutting instrument is the smoothness and the contour of the cutting edge and of the sides of the cutting edge extending back towards the feedstock comprising the body of the cutting instrument. An irregular contour will lead to small, even microscopic, points that penetrate the material being cut before other parts of the cutting edge encounter the substrate. This leads to some degree of tearing rather than slicing. A cutting edge having a rough surface on the sides of the cutting edge will abrade, or tear, material that passes over the sides of the cutting edge, as the material must be pushed aside to allow for passage of the cutting edge through the material being cut. [0004] In the surgical arts, where the material being cut is living tissue, a sharp and smooth cutting edge in, for example, surgical scalpels, is of paramount interest. The making of an incision in living tissue results in trauma to that tissue, due to the work that must be imparted to the tissue in making the incision. The work required to pass a scalpel through tissue results from many factors, including edge sharpness, force applied to the blade, drag force acting on the sides of the blade, and the like. The trauma caused to tissue from an incision results in increased time required for healing, increased chance for infection, a limitation to the size of physiological structures that can be incised accurately, and unsightly scarring. [0005] In this regard, many efforts have been made to improve the performance of cutting instruments, particularly of surgical instruments such as scalpels. For example, resort has been made to cutting instruments fabricated from diamonds, rubies, and sapphires, which are very hard materials and can be fabricated with edges that are very thin. However, these materials are very expensive and difficult to fabricate. Their hardness is actually a disadvantage in medical operations, as they tend to fracture upon encountering hard structures such as bone, thus potentially leaving fragments in the operative subject. Metals are economically processed into surgical scalpels and the like. However, difficulties with achieving sharp and smooth edges have led to efforts such as coating of cutting edges with friction-reducing materials to reduce trauma resulting from incisions. [0006] The heightened requirements for cutting properties of surgical instruments due to the widespread introduction into clinical practice of new procedures for performing operations on vital organs and the development of microsurgical techniques have led to demands for improved methods of producing cutting instruments and improved cutting instruments themselves. [0007] The invention provides such a method for producing improved cutting instruments and provides improved cutting instruments themselves. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. BRIEF SUMMARY OF THE INVENTION [0008] The invention is directed to a method for polishing a cutting edge on a cutting instrument, comprising (i) providing a cutting instrument having a cutting edge, (ii) contacting the cutting edge with a polishing pad and a chemical-mechanical polishing composition comprising (a) particles of an abrasive, and (b) a liquid carrier, wherein the abrasive is suspended in the liquid carrier, (iii) moving the polishing pad relative to the cutting edge with the chemical-mechanical polishing composition therebetween, and (iv) abrading at least a portion of the cutting edge to polish the cutting edge. [0009] The invention further provides a cutting instrument, comprising a cutting instrument body having two flat faces and a direction of elongation and defining an ultimate edge, and having at least one cutting edge extending parallel to the direction of elongation, wherein a maximum deviation from a line defined by two points on the ultimate edge of the cutting edge separated by 5000 .mu.m of any point on the ultimate edge of the cutting edge between the two points is about 4 .mu.m or less. [0010] The invention also provides a cutting instrument, comprising a cutting instrument body having two flat faces and a direction of elongation and defining an ultimate edge, and having at least one cutting edge extending parallel to the direction of elongation, wherein a maximum deviation from a line defined by two points on the ultimate edge of the cutting edge separated by 750 .mu.m of any point on the ultimate edge of the cutting edge between the two points is about 1 .mu.m or less. BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIG. 1 is a side view of a cutting instrument in accordance with the invention. [0012] FIG. 2 is a schematic drawing illustrating the method used to characterize the contour of a cutting edge. [0013] FIG. 3 is a scanning electron micrograph of a commercially available surgical blade as supplied by the manufacturer. [0014] FIG. 4 is a scanning electron micrograph of the surgical blade illustrated in FIG. 3 after polishing in accordance with the inventive method. DETAILED DESCRIPTION OF THE INVENTION [0015] The invention provides a method for polishing a cutting edge on a cutting instrument. The method involves (i) providing a cutting instrument having a cutting edge, (ii) contacting the cutting edge with a polishing pad and a chemical-mechanical polishing composition comprising (a) particles of an abrasive and (b) a liquid carrier, wherein the abrasive is suspended in the liquid carrier, (iii) moving the polishing pad relative to the cutting edge with the chemical-mechanical polishing composition therebetween, and (iv) abrading at least a portion of the cutting edge to polish the cutting edge. [0016] The cutting instrument can be any cutting instrument and typically comprises a cutting instrument body having two flat faces and a direction of elongation, and having at least one cutting edge extending parallel to the direction of elongation. Examples of cutting instruments suitable for polishing by the inventive method include but are not limited to knives, surgical scalpels, scissors, and razors. The cutting instrument can have any suitable additional features, for example, a separate handle attached to the cutting instrument by suitable means. [0017] Shown in FIG. 1 is a side view of a cutting instrument (10) of the invention. In general any cutting instrument has a body (40) and a cutting edge (30). In such cutting instruments the cutting edge is defined as that portion of the cutting instrument which tapers to a terminating, or ultimate edge (20). The body (40) of the cutting instrument is defined as the structure that transfers an applied load from the cutting instrument driving force to the ultimate edge (20) of the cutting edge (30). In addition, as shown in FIG. 1, a cutting instrument can include an optional handle or grip (50) which serves as a stable interface between the cutting instrument user and the cutting instrument. [0018] The cutting edge can be integral with the cutting instrument body. A cutting edge can be formed directly on a cutting instrument body, thus comprising the same material as the cutting instrument body. The cutting edge can be non-integral with the cutting instrument body and can be formed by layering a second material on the first material of the cutting instrument body. [0019] The cutting instrument and cutting edge can comprise any suitable material. Typically, the cutting instrument and cutting edge comprise a metal. For example, the metal can be a metal alloy, e.g., an alloy of iron with at least one element selected from the group consisting of carbon, chromium, nickel, and cobalt. Preferred alloys of iron include stainless steels and carbon steels. The cutting instrument and cutting edge can comprise any stainless steel or carbon steel. Stainless steels are typically comprised of iron and chromium in various proportions, although other elements, including silicon, nickel, molybdenum, phosphorus, sulfur, copper, and aluminum, are often components of commercially available stainless steels. Carbon steels typically comprise iron and carbon, and can include additional elements, including chromium, nickel molybdenum, vanadium, and silicon. Carbon steels are typically further classified as mild steels, comprising less than about 0.25 wt. % carbon, medium carbon steels, comprising about 0.25 wt. % to about 0.45 wt. % carbon, and high carbon steels, comprising about 0.45 wt. % to about 1.5 wt. % carbon. Continue reading... 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