Patent Publication Number: US-2006010696-A1

Title: Hand tool with cutting blade having cutting surfaces with wear-enhancing coating thereon

Description:
BACKGROUND OF THE INVENTION  
      The present invention is directed generally to hand tools, and more particularly to a hand tool with a cutting blade having cutting surfaces with a wear-enhancing coating thereon.  
      Hand tool cutting devices, such as utility knives and hacksaws, typically use metallic cutting blades with sharp cutting surfaces. During use, these cutting surfaces engage the material to be cut as the tool is manually moved with respect to the material to be cut. Over time, these cutting edges become dull and the user must replace the blade in what is typically a time consuming process. An increase in blade life therefore would increase the hand tool&#39;s efficiency by reducing the frequency of blade replacement.  
     SUMMARY  
      The present invention is directed to a manually operated cutting tool, comprising: a frame having a handle portion adapted to engage a user&#39;s hand for manual movement of the frame relative to a material to be cut; a blade removably affixed to the frame and moveable along therewith during a cutting operation; the blade having a plurality of cutting surfaces and formed of a base material of a first material having a first toughness and a rigid wear-enhancing outer coating of a second material, different from the first material, external of the cutting surfaces of the base material; the second material having a second toughness more than the first toughness. The frame may be a hacksaw frame or a utility knife frame. The coating second material of the coating may comprises tungsten. Alternatively, the second material of the coating may comprise zirconium or boron carbide. Further still, the second material of the coating may comprise titanium, such as for example comprising at least one alloy material selected from the group consisting of titanium nitride, titanium cabronitride, aluminum titanium nitride, titanium aluminum nitride, titanium carbide, and titanium nickel. The coating may comprises a vapor deposition applied material, such as a physical vapor deposition applied material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a hand operated cutting tool constructed in accordance with one embodiment of the present invention.  
       FIG. 2  shows the cutting blade of  FIG. 1 .  
       FIG. 3  shows a cross-section of the blade of  FIG. 2  along line  3 - 3 .  
       FIG. 4  shows a hand operated cutting tool constructed in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As illustrated in  FIG. 1 , a hand operated cutting tool, generally designated  10 , is shown constructed according to the present invention. As is customary, the tool  10  includes a frame  12  and a cutting blade  20  removably attached thereto. The frame  12  includes a handle  14  for gripping by a user. For the hacksaw type tool shown in  FIG. 1 , the frame  12  advantageously also includes two blade mounts  16 , one toward each end of the frame. For further details of the frame  12 , attention is directed to co-pending U.S. patent application Ser. No. 10/845,047, filed May 13, 2004, the disclosure of which is incorporated herein by reference.  
      The blade  20  of  FIG. 1  is generally elongate, as shown in  FIG. 2 . The blade includes two spaced mounting holes  22  for engaging with the blade mounts  16  as described in the above-reference application. The blade  20  includes a metallic base  24  or substrate that includes a plurality of cutting surfaces  26 , as is known in the art. For the present invention, the cutting surfaces  26  are coated with a tough, rigid coating  30  of a material different from the material of the base  24  so as to increase the wear resistance of the blade  20 . For example, the base material may be a conventional hardened steel material, while the coating  30  is a titanium nitride material applied by a physical vapor deposition process. As indicated above, the purpose of the coating is to increase the wear resistance of the cutting surfaces  26 . Thus, the material of the coating  30  has a material toughness that is greater than the material toughness of the material of the base  24 . Therefore, as used herein, the term “wear-enhancing coating” does not include paint as paint is not considered to have high toughness. By adding the rigid coating  30 , the useful life of the blade  20  is significantly increased, such as by two to seven times as much or more.  
      The wear-enhancing coating  30  may advantageously comprise titanium. Further, the titanium containing wear-enhancing coating  30  may advantageously comprise at least one alloy material selected from the group consisting of titanium nitride, titanium cabronitride, aluminum titanium nitride, titanium aluminum nitride, titanium carbide, and titanium nickel. The coating may be a single layer, or may comprise multiple layers. The wear-enhancing coating  30  may alternatively comprise zirconium nitride, boron carbide, chromium nitride, tungsten, tungsten disulfide.  
      The coating  30  may advantageously be applied to the cutting surfaces by a vapor deposition process, such as the processes known as physical vapor deposition, plasma deposition, chemical vapor deposition. Just by way of example, suitable coatings may be applied to the cutting surfaces of the blades by a physical vapor deposition process by a company known as Bodycote Metallurgical Coatings, having an office in Greensboro, N.C. Alternatively, but believed to be less advantageous, the coating  30  may be applied by a dipping, sputtering, or other known coating process. It is believed advantageous if the coating  30  is applied after the formation of the cutting surfaces on the base material.  
      In another embodiment, the hand operated cutting tool may take the form of a tool  10   a  commonly referred to as a utility knife. See  FIG. 3 . Such tools  10   a  typically utilize a trapezoidal shaped cutting blade  40  with the razor type cutting surfaces  44  disposed along the long edge of the trapezoid. The cutting surfaces  44  of the blade&#39;s substrate  42  are coated with wear-enhancing coating  46  as described above. Such blades  40  typically also include one or more notches (not shown) in the opposing edge for engaging with retaining means for removably mating the blade to the frame  12   a.  Advantageously, the retaining means is associated with a moveable blade carriage (not shown) within the tool  10   a.  Additional details concerning such tools, but with uncoated blades, are shown in U.S. Pat. Nos. 6,553,674; 6,446,340; 6,357,120; and U.S. patent application Publication US 2004/0107580, which are all incorporated herein by reference.  
      The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.