Abstract:
A method for manufacturing a razor blade. In the method, a razor blade blank is coined to produce a razor blade with a cutting edge. It is preferred that the razor blade blank be unhardened for coining. Additional manufacturing steps that may be performed are hardening of the razor blade at least in the vicinity of the cutting edge, and finishing the cutting edge. The method allows for the cost-effective manufacture of razor blades having both linear and non-linear cutting edges.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in Provisional Patent Application No. 60/450,200 filed on Feb. 25, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention generally relates to material processing and, more particularly, to the processing of material to create a cutting edge for a razor blade.  
         BACKGROUND OF THE INVENTION  
         [0003]    In a wet shaving operation, hair is typically removed from a hirsute surface by a razor blade. The razor blade has a sharp edge, generally referred to as the cutting edge, that severs the hair from the surface. The overall comfort of the shave and thus the resulting consumer satisfaction with the razor blade is highly dependent upon the angle of the cutting edge relative to the hirsute surface, and the sharpness, smoothness and uniformity of the cutting edge.  
           [0004]    Since the development of the mass-produced razor blade, grinding one or both generally parallel surfaces of a metal razor blade blank to create intersecting surfaces has been the predominate method used to form cutting edges. Following the grinding operation, the surfaces are finished to deburr, or smooth, the ground surfaces, and sharpen the cutting edge in an operation commonly referred to as stropping. Originally, stropping involved dragging a surface of the cutting edge over a leather strap.  
           [0005]    Grinding followed by stropping has proven to be an efficient and cost effective manufacturing process for mass-producing razor blades having a linear cutting edge. This is due in large part to the configuration of the machinery used to perform the grinding.  
           [0006]    A razor blade with non-linear cutting edges, however, offers potential shaving benefits to consumers. One such non-linear razor blade design incorporates a series of circular apertures, each having a perimeter that is ground and finished to create surfaces that define a cutting edge.  
           [0007]    A problem associated with the use of grinding and stropping to create a non-linear cutting edge, such as in the perimeter of a circular aperture, is that it is costly. In addition, it results in a cutting edge that is not properly angled relative to the hirsute surface to provide the comfortable shave demanded by consumers. As a result, an additional process step of bending the cutting edge to a desired angle is required.  
           [0008]    In an effort to make the manufacturing of non-linear cutting edges more cost efficient, various alternatives to the traditional grinding and stropping method have been proposed. In one method, coining is employed to form round dimples of generally constant cross-section in unhardened steel. After hardening, the top of the dimple is removed by any one of several processes in such a way as to create surfaces that define a cutting edge. The cutting edge is then finished, such as by chemically etching.  
           [0009]    Based on the foregoing, it is the general object of the present invention to overcome the problems and drawbacks with, or improve upon, the prior art.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention resides in one aspect in a method wherein a razor blade blank is first subjected to squeezing in a closed set of dies, an operation referred to by those skilled in the pertinent art to which the present invention pertains as “coining.” The coining operation shapes the razor blade blank into a razor blade having a cutting edge. After coining, at least a portion of the cutting edge may be hardened and then the cutting edge may be finished, creating the finished razor blade.  
           [0011]    Coining the cutting edge permits different shaped cutting edges, such as linear, non-linear, and combinations thereof, to be formed that would otherwise not be economical or even possible employing traditional methods. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a plan view of a razor blade employing a plurality of apertures, each defined by a sharpened peripheral edge.  
         [0013]    [0013]FIG. 2 is a cross- sectional view of the razor blade of FIG. 1 taken along line  2 - 2 .  
         [0014]    [0014]FIG. 3 is an enlarged view of a portion of the peripheral edge of an aperture of FIG. 2 as indicated by the circled area labeled  3 .  
         [0015]    [0015]FIGS. 4A and 4B are a partial cross-sectional side view of a portion of a razor blade bank and a resulting coined portion of a razor blade, respectively.  
         [0016]    [0016]FIG. 5 is a partial cross-sectional side view of a portion of a razor blade coined using the disclosed method.  
         [0017]    [0017]FIG. 6A and 6B are plan views of a razor blade blank and the resulting coined razor blade, respectively.  
         [0018]    [0018]FIG. 7 is a cross-sectional view of the razor blade of FIG. 6 taken along line  7 - 7 .  
         [0019]    [0019]FIG. 8 is an enlarged cross-sectional view of a portion of the razor blade of FIG. 7 as indicated by the circled area labeled  8 .  
         [0020]    [0020]FIG. 9 depicts an alternate cutting edge position for a razor blade of the type depicted in FIG. 6B.  
         [0021]    [0021]FIG. 10 is a plan view of a razor blade manufactured in accordance with the method of the present invention.  
         [0022]    [0022]FIG. 11 is a cross-sectional view of the razor blade of FIG. 10 taken along line  11 - 11 .  
         [0023]    [0023]FIG. 12 is an enlarged top view of the razor blade of FIG. 10 as indicated by the circled area labeled  12 .  
         [0024]    [0024]FIG. 13 is an enlarged side view of the razor blade section of FIG. 11 as indicated by the circled area labeled  13 .  
         [0025]    [0025]FIG. 14 is a plan view of a razor blade manufactured in accordance with the method of the present invention.  
         [0026]    [0026]FIG. 15 is a cross-sectional view of the razor blade of FIG. 14 taken along line  15 - 15 .  
         [0027]    [0027]FIG. 16 is a perspective view of the razor blade of FIG. 14.  
         [0028]    [0028]FIG. 17 is an enlarged perspective top view of the razor blade of FIG. 16 as indicated by the circled area labeled  17 .  
         [0029]    [0029]FIG. 18 is an enlarged side view of the razor blade section of FIG. 15 as indicated by the circled area labeled  18 .  
         [0030]    [0030]FIG. 19 is a plan view of a razor blade manufactured in accordance with the method of the present invention.  
         [0031]    [0031]FIG. 20 is a cross-sectional view of the razor blade of FIG. 19 taken along line  20 - 20 .  
         [0032]    [0032]FIG. 21 is a top perspective view of the razor blade of FIG. 19.  
         [0033]    [0033]FIG. 22 is an enlarged perspective view of the razor blade of FIG. 21 indicated by the circled area labeled  22 .  
         [0034]    [0034]FIG. 23 is an enlarged cross-sectional view of the razor blade of FIG. 20.  
         [0035]    [0035]FIG. 24 is a plan view of a razor blade manufactured in accordance with the method of the present invention.  
         [0036]    [0036]FIG. 25 is a cross-sectional side view of the razor blade of FIG. 24 taken along line  25 - 25 .  
         [0037]    [0037]FIG. 26 is a top perspective view of the razor blade of FIG. 24.  
         [0038]    [0038]FIG. 27 is an enlarged view of the razor blade of FIG. 26 indicated by the circled area labeled  27 .  
         [0039]    [0039]FIG. 28 is an expanded view of the cross-section of FIG. 25.  
         [0040]    [0040]FIG. 29 is an expanded view of the razor blade of FIG. 28 indicated by the circled area labeled  29 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0041]    The method of the present invention is initially explained within the context of manufacturing a razor blade having a plurality of generally circular apertures, each having a perimeter defining a cutting edge. Other razor blades that may be manufactured using the method are then discussed.  
         [0042]    As shown in FIGS. 1 through 3, a razor blade  10  has a plurality of generally circular apertures  12 . Each aperture  12  has a perimeter  14  that defines a cutting edge  16 . As shown in FIGS. 2 and 3, each cutting edge  16  has a leading edge  17 . The leading edge  17  is positioned off but generally parallel to a top surface  18  of the razor blade  10 . The cutting edge  16  is also inclined at an angle ∝relative to the top surface  18 . This angle ∝ establishes an angle of attack for the cutting edge  16  relative to a shaver&#39;s skin (not shown). For shaving comfort, the angle ac is preferably in the range of 10 degrees to 30 degrees and most preferably in the range of 19 degrees to 25 degrees. The cutting edge  16  has a thickness at a root  20  thereof preferably in the range of 0.08 mm to 0.25 mm.  
         [0043]    The method of the present invention will now be described within the context of forming an aperture  12  having a perimeter with a cutting edge  16  as described above. The method, however, is generally applicable to forming all the apertures  12 .  
         [0044]    A razor blade blank  22  into which an aperture  12  with a cutting edge  16  will be formed is depicted in FIG. 4A. As an initial step, a generally round bore  24  having a peripheral surface  26  is created in the razor blade blank  22 , which is a piece of plate stock, i.e., having generally parallel surfaces. At this stage of the process, the material from which the razor blade blank  22  is manufactured is preferably in a workable form, generally referred to by those skilled in the relevant art as “unhardened.” The razor blade blank  22  is coined defining a razor blade  10 , FIG. 4B, having the cutting edge  16 . In the coining operation, the peripheral surface  26  of the razor blade blank  22  is displaced and compressed to create two angled surfaces  28 ,  30  that intersect to define the cutting edge  16 . The cutting edge  16  is coined at an angle ∝ defined relative to the top surface  18  of the razor blade  10 , which in this case is also the top surface of the razor blade blank  22 . While the cutting edge  16  has been shown inclined at an angle ∝ as to the top surface  18 , the invention should not be considered so limited, as it could be generally parallel, or declined, with respect thereto. The coining operation also positions the leading edge  17  generally parallel to the top surface  18 .  
         [0045]    After coining, at least a portion of the cutting edge  16  is hardened preferably in the area proximate the leading edge  17 . The method of hardening is based on the material from which the cutting edge  16  is made. In the case where the material is a metal such as steel, hardening might involve heat treatment. Where the material is a plastic, hardening such as by exposure to infrared light might be appropriate. It is possible that during hardening the entire razor blade may be hardened.  
         [0046]    The cutting edge  16  is then finished thereby finishing the razor blade  10 . Chemical etching may be used to finish the cutting edge  16 . Other methods, however, such as stropping and grinding are considered within the scope of the invention. Finishing may smooth and deburr the surfaces  28 ,  30  as well as provide the final removal of material from the surfaces to obtain the desired sharpness of the cutting edge  16 .  
         [0047]    [0047]FIG. 5 shows a variation on the above-described method. As this method, is similar to the method described above, similar elements of the razor blade  110  will be given the same reference number preceded by a number  1 . Unlike the previous method, the razor blade blank (not shown) is not initially bored. Thus, the coining operation shapes the angled surfaces  128 ,  130  that define the cutting edge  116 , but a slug  28  of material remains, blocking the to be created aperture  112 . The slug  28  can be removed by any one of a number of methods, such as punching or by chemical etching thereby creating the aperture  112 . As with the prior method, at least a portion of the cutting edge  116  is hardened and then the cutting edge is finished to finish the razor blade.  
         [0048]    [0048]FIGS. 6 through 9 show a second razor blade  210  that may be manufactured by the above-described method. As many of the features of this razor blade  210  are similar to the razor blade  10  previously discussed and the razor blade blank  22  from which it was manufactured, similar elements will be given similar reference numbers preceded by the number  2 . FIG. 6A depicts a razor blade blank  222  from which the razor blade  210 , depicted in FIG. 6B, may be coined. The razor blade blank  222  has an array of performed slots  32 , each having a perimeter  34 . As shown in FIG. 6B, after coining a linear perimeter portion  36  of the perimeter  34  of each slot  32  has shaped therein intersecting surfaces  228 ,  230  defining a cutting edge  216 . All the cutting edges  216  are aligned one to the other such that the cutting edges have a common cutting direction indicated by an arrow  38 . As with the previous razor blade  10 , the cutting edge  216  can be planar to (See FIG. 8), or inclined at an angle ∝ relative to (See FIG. 9) the top surface  218 .  
         [0049]    [0049]FIGS. 10 through 13 illustrate a third razor blade  310  that may be manufactured by the above-described method. As many of the features of this razor blade  310  are similar to the previously discussed razor blades  10 , and  210 , similar elements will be given similar reference numbers preceded by the number  3 . The razor blade  310  was coined from a razor blade blank (not shown) having a plurality of performed slots similar to slot  332 , each having cutouts at each end similar to cutouts  40 . Coined into a linear perimeter portion of each slot of the razor blade blank are intersecting surfaces  328 ,  330  that define a cutting edge  316 . The cutting edges  316  are generally parallel one to the other. Like the second razor blade  210 , each cutting edge  316  is generally linear. In this third razor blade  310 , the cutting edge  316  is inclined at an angle a relative to the top surface  318 .  
         [0050]    [0050]FIGS. 14 through 18 illustrate a fourth razor blade  410  that may be manufactured by the above-described method. As many of the features of this razor blade  410  are similar to the previously discussed razor blades  10 ,  210 , and  310 , similar elements will be given similar reference numbers preceded by the number  4 . The razor blade  410  has been coined from a razor blade blank (not shown) having a perimeter portion that is continuously scalloped similar to continuous scalloped cutting edge  416 . The scalloped portion of the perimeter portion of the razor blade blank was coined to shape cutting edge  416 . In the razor blade  410 , each scallop  42  of the cutting edge  416  has a pitch  44  (peak to peak distance). The pitch  44  is preferably between 0.1 and 0.39 mm. Also, each scallop  42  has a depth  45  (from peak to trough of the cutting edge  416 ) of between 0.1 and 6.0 mm. Between any two scallops  42 , the cutting edge  416  adopts an inflection curve  46  having a radii in the range of 0.1 to 1.0 mm. While the scalloped cutting edge  416  has been depicted as regularly formed, this is not a requirement of the invention as it could be irregular; thus the invention should not be considered so limited.  
         [0051]    [0051]FIGS. 19 through 23 illustrate a fifth razor blade  510  that may be manufactured by the above-described method. As many of the features of this razor blade  510  are similar to the previously discussed razor blades  10 ,  210 ,  310  and  410 , similar elements will be given similar reference numbers preceded by the number  5 . This razor blade  510  like the fourth razor blade  410  was manufactured from a razor blade blank (not shown) having a non-linear perimeter portion similar to the non-linear cutting edge  516 , which was coined to create the cutting edge  516 . As a result, the razor blade  510  has a non-linear cutting edge  516 , which in this case is also scalloped. Unlike the fourth razor blade  410  that had an inflection curve  46  between adjacent scallop sections  42 , this razor blade  510  has skin guides  50 . The skin guides  50 , which were also shaped during the coining of the cutting edge  516 , act to control the contract of the skin with the cutting edge  516  during a shaving operation thereby increasing shaving safety and comfort. Each skin guide  50  is preferably 0.08 to 0.5 mm wide (indicated by the letter w) and projects outwardly 0.02 to 1.0 mm beyond the cutting edge  516  (indicated by the letter p).  
         [0052]    [0052]FIGS. 24 through 29 illustrate a sixth razor blade  610  that may be manufactured by the above-described method. As many of the features of this razor blade  610  are similar to the previously discussed razor blades  10 ,  210 ,  310 ,  410  and  510 , similar elements will be given similar reference numbers preceded by the number  6 . The cutting edge  616  of the razor blade  610  was coined in a perimeter of a razor blade blank (not shown) similar to the cutting edge  616 . During coining, not only was the cutting edge  616  shaped but also corrugations  52 . The longitudinal corrugations  52  increase the resistance to bending of the cutting edges  616  during a shaving operation. As a result of the corrugations  52 , the razor blade  610  can be narrower (from the cutting edge  616  to the back of the razor blade denoted by the reference number  54 ). Narrower razor blades  610  are preferred due to the ability to increase rinsability of the razor blade when the razor blade is placed in a cartridge (not shown). Skin guides  56 , which were also formed during the coining operation, project outwardly from and interrupt the cutting edge  616 . These skin guides  56  have similar characteristics to the skin guides  50  discussed above.  
         [0053]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. In particular, the cutting edge has been shown as being created by shaping two surfaces. This, however, is not required as only one surface needs to be shaped to another. Additionally, the cutting edges have been depicted as linear or non-linear for any given razor blade, combination cutting edges are also considered with the scope of the invention. Therefore, the spirit and scope of the invention should not be limited to the description of the preferred versions contained herein.