Abstract:
A method of manufacturing razor blades from a strip material includes reducing the thickness of a lengthwise-extending blade edge region of the strip material.

Description:
TECHNICAL FIELD 
     This invention relates to manufacturing razor blades. 
     BACKGROUND 
     Razor blades are typically made from a continuous strip of stock material that is hardened and sharpened while the strip travels along a processing line. The strip is then divided in blade length sections used in the manufacture of individual razor cartridges. 
     In some applications, blades are supported on bent supports that are slidably mounted in the cartridge housing to move up and down during shaving. For example,  FIG. 1  shows cartridge  10  with blades  12  slidably mounted in housing  14 , and  FIG. 2  shows a blade  12  on a support  16 . In these applications, the blades cannot overlap and thus have a small dimension “a” from the cutting edge  18  to the back edge  20 . The strip material and blade sections, however, must have a sufficient distance from the front edge to the back edge in order to properly secure and hold the material and sections during processing and attaching to blade supports. It thus is necessary to remove a portion of the blade material after processing and attaching so that the blade will have the desired small dimension from the cutting edge to the back edge. In some applications, the rear section  22 , shown in  FIG. 3 , is removed by bending the rear section  22  between 60° and 90° with respect to the front section  24  after the front section has been attached to the blade support.  FIG. 3  also shows spot weld  26 , used to attach blade  12  to support  16 . There typically is an upturned portion at the rear edge  20  of the attached blade section where the rear section has been removed. In some cases the rear section  22  is not easily removed. 
     In U.S. Pat. No. 6,629,475, a method of manufacturing razor blades is described in which the strip material is offset to provide a portion  22  that is easier to remove. 
     SUMMARY 
     The invention generally relates to methods of manufacturing razor blades that include reducing the thickness of a strip material in all or part of the lengthwise-extending region that later becomes the blade edges of the razor blades. 
     In one aspect of the invention, the method includes (a) pressing a portion of the lengthwise-extending blade edge region to provide the portion with a thickness that is less than the strip material adjoining the region; and (b) converting the strip material into razor blades. The portion may be, for example, at least 15%, at least 30%, at least 50%, at least 70%, at least 90%, or about 100% of the strip material that ultimately becomes the blade edges of the razor blades. “Blade edge”, as used herein, includes the wedge-shaped portion of the blade from the sharpened tip to the interception with the flat portion of the blade. 
     In some embodiments, pressing includes passing the strip material between rollers that contact and reduce the thickness of the strip material. 
     In some embodiments, pressing provides the lengthwise-extending blade edge region with one or more beveled surfaces. For example, after pressing, the lengthwise-extending blade edge region can have an upper beveled surface and a corresponding lower beveled surface. The beveled surface(s) can be, for example, generally straight, generally concave, or generally convex. 
     In some embodiments, the lengthwise-extending blade edge portion is generally centrally located on the strip material. In other embodiments, a lengthwise-extending blade edge portion can be located at one or both side edges of the strip material. 
     In some embodiments, the method further includes offsetting a first lengthwise-extending portion of the strip material from a second lengthwise-extending portion of the strip material and, optionally, subsequently flattening the offset strip material to remove some or all of the offset. 
     In another aspect of the invention, the method includes contacting a surface of the lengthwise-extending blade edge region with a roller to provide a beveled surface. The beveled surface may extend, for example, at least 15%, at least 30%, at least 50%, at least 70%, at least 90%, or about 100% across the region. 
     In another aspect of the invention, the method includes converting a strip material including a lengthwise-extending blade edge region that subsequently becomes blade edges on the razor blades and has a thickness that is less than the thickness of the strip material adjoining the lengthwise-extending blade edge region into razor blades including the blade edges. 
     Reducing the thickness of all or part of the strip material in the region that becomes the blade edges through the above methods can provide, for example, one or more of the following benefits: (1) a reduction in wasted strip material; (2) a reduction in sharpening time and/or an increase in sharpening line speed; (3) an increase in the life of sharpening equipment; (4) a variety of options regarding the shape of the strip material in the blade region of the strip material prior to sharpening; and (5) a variety of options for converting a strip material into multiple strands, which potentially increases the throughput of downstream processes. 
     In preferred embodiments, the strip material is a metal, for example, stainless steel. 
     Other aspects of the invention include the strip materials processed using any of the above methods, and razor blades and razor blade precursors made using any of the above methods. 
     Strip material” means an elongated, flat strip of material, for example, stainless steel or another metal that is at least 500 feet, at least 1,000 feet, or even at least 5,000 feet long. 
     Length, width, thickness, upper, and lower as applied to the strip material is explained during the discussion of  FIGS. 5 and 6 . 
     Other aspects, features, and advantages of the method will be apparent from the Figures, the Detailed Description, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a shaving razor cartridge; 
         FIG. 2  is a section showing a prior art razor blade used in the  FIG. 1  cartridge; 
         FIG. 3  is a section showing the  FIG. 2  blade prior to removal of a rear section used to engage the blade during processing and attaching; 
         FIG. 4  is a flow chart of a method for making razor blades that also provides section views of the strip material and razor blades; 
         FIG. 5  is a diagrammatic plan view of a process line for performing some of the steps in  FIG. 4 ; 
         FIG. 6  is a flow chart of a method for making razor blades that also provides section views of the strip material and razor blades; 
         FIG. 7  is a flow chart of a method for making razor blade precursors that also provides section views of the strip material and razor blade precursors; 
         FIG. 8  is a flow chart of a method for making razor blade precursors that also provides section views of the strip material and razor blade precursors; 
         FIG. 9  is a flow chart of a method of processing a strip material that also provides section view of the strip material; and 
         FIG. 10  is a diagrammatic plan view of a process line for performing some of the steps in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 4 , a stainless steel strip material  30  is converted into razor blades  32  having blade edges  34 . Strip material  30  has a thickness (t) between about 0.002 inch and about 0.006 inch (for example, about 0.003 inch or about 0.004 inch) and a width (w) sufficient to provide razor blades  32 . 
     Initially, strip material  30  is passed between rollers that press (in this case through rolling down) the strip material along its length at region  31 . This reduces the thickness (t) of the strip material in region  31  in a predetermined manner to provide generally straight beveled surfaces  36 . Beveled surfaces  36  subsequently are converted to blade edges  34  in razor blades  32 . 
     Strip material  30  optionally then is heat treated to harden the stainless steel (step not shown) and the strip material separated at the middle of region  31 . Beveled surfaces  36  are sharpened to provide blade edges  34 . After sharpening, the separated portions of the strip material  30  are chopped into blade length sections, and each section further processed to provide razor blades  32  (chopping and further processing not shown). Razor blades  32  can be mounted on a razor blade support, such as support  16  in  FIG. 2 , for example, by welding. 
     Referring to  FIG. 5 , a process line for performing the rolling down process in  FIG. 4  includes an unwind station  42  for providing a strip material  30 . Strip material  30  moves lengthwise in direction L and has upper (u) and lower (l) surfaces. Strip material  30  passes through weld station  44  and tension leveling station  46 . Weld station  44  is used when the end of one roll of strip material  30  needs to be attached to the end of a subsequent roll; tension leveling station  46  works with tension leveling station  50  to maintain the appropriate tension on strip material  30  during processing. 
     Strip material  30  next passes through roll down station  48 , which includes the rollers that roll down the strip material in region  36  shown in  FIG. 4 . Strip material  30  subsequently passes through tension leveling station  50  and is wound onto a spool at winding station  52 . The strip material then can be heat treated, separated, sharpened, and made into razor blades. A heat treating station optionally can be provided prior to winding station  52 . 
     Referring to  FIG. 6 , a stainless steel strip material  56  is converted into razor blades  60 . Strip material  56  is rolled down at both sides to provides generally straight beveled surfaces  58 . Strip material  56  then is slit lengthwise and further processed to provide razor blades  60  (left side of  FIG. 6 ). The further processing includes heat treating and the sharpening of beveled surfaces  58  to provide blade edges; the separated portions of strip material  56  are chopped into blade length sections after sharpening. Optionally, strip material  56  with beveled surfaces  58  can be heat treated, and beveled surfaces  58  sharpened, prior to lengthwise chopping. 
     Referring to  FIG. 6  (right side), alternatively the rolled down strip material is offset along its length at region  62  and then flattened to provide weakened region  64 . Offsetting and flattening are described in U.S. Ser. No.  —————— , which is owned by the same owner as the present application and was filed on the same day as the present application. This application is hereby incorporated by reference. The offset can be, for example, between about 10% and about 50%, and preferably between about 20% and 40%, of the thickness (t) of sheet material  30 . Flattening removes, for example, at least 75% of the offset. After flattening, strip material  56  can be separated lengthwise and further processed to provide blade edges; the separated portions of strip material  56  are heat treated and chopped into blade length sections after sharpening. Optionally, strip material  30  can be heat treated, and beveled surfaces  58  sharpened, prior to the lengthwise separation. 
     Referring to  FIG. 7 , a stainless steel strip material  66  is rolled down along its length at region  68 . After roll down, region  68  of strip material  66  includes generally convex beveled surfaces  70 . Strip material  66  can be heat treated to harden the stainless steel (step not shown) and the strip material then separated at approximately the middle of region  68  to provide separated portion  72 , each including a generally convex beveled surface  74 . Surface  74  is sharpened and separated portion  72  is chopped into razor blade length sections, which are further processed to provide razor blades (steps not shown). 
     Referring to  FIG. 8 , a stainless steel strip material  76  is rolled down along its length to provide generally concave beveled surfaces  78 . The rolled down strip material optionally can be heat treated to harden the stainless steel (step not shown) and the strip material separated to provide portions  80 , each including a generally concave beveled surface  82 . Surface  82  is sharpened and separated portion  80  is chopped into razor blade length sections, which are further processed to provide razor blades (steps not shown). 
     Referring to  FIG. 9 , a stainless steel strip material  84  is rolled down centrally to provide beveled surfaces  86 . The rolled down strip material is then offset along its length at regions  88  and flattened to provide weakened regions  90 . Offsetting and flattening are described in U.S. Ser. No. 11/259,553, which was incorporated by reference previously. After flattening, the strip material includes blade portions  94  and blade precursor removable portions  92 . The strip material is separated centrally lengthwise either before or after heat treatment and, after further processing including sharpening of separated beveled surfaces  86 , converted into razor blade precursors including razor blade portions and removable portions. Razor blade precursors including blade and removable portions is described in U.S. Pat. No. 6,629,475, which also is hereby incorporated herein. 
     Referring to  FIG. 10 , a process line for performing the roll down, offset, and flattening steps in  FIG. 9  includes an unwind station  96 , a weld station  98 , tensioning stations  100  and  108 , a roll down station  102 , and a winding station  110 ; these stations were discussed previously in connection with  FIG. 5 . The process line further includes an offset station  104  and a flattening station  106  subsequent to roll down station  102 . Offset and flattening stations are described in U.S. Ser. No. 11/259,553. 
     Other embodiments are within the claims For example, other pressing techniques can be used to reduce the thickness of a portion of the blade edge region of the strip material. Moreover, although strip materials are rolled down on two surfaces in the processes shown in  FIGS. 4-10 , optionally the strip material can be rolled down on only one surface. Alternatively, when both the upper surface and lower surface are rolled down (or otherwise pressed) one side can be rolled down (or otherwise pressed) more than the other. Thus, in this alternative embodiment one rolled down (or otherwise pressed) surface will vary less in thickness from the adjoining strip material than the other rolled down (or otherwise pressed) surface of the strip material. 
     In other embodiments, any of the above procedures can be combined with the procedures for thinning, and optionally for controlling the tension, described in U.S. Ser. No. 11/259,552; this application was filed on the same day as the present application, is owned by the same owner, and is hereby incorporated by reference. For example, one optional procedure includes (1) rolling down (or otherwise pressing) the strip material (optionally in combination with offsetting and/or flattening) while also thinning the strip material, (2) adjusting the tension on the strip material to compensate for the added length of the strip material resulting from thinning, and (3) rolling down the strip material a second time (again optionally combined with offsetting and/or flattening). The tension in the strip material optionally also may be adjusted after step (3), if this step also significantly thins the strip material. 
     Although in the embodiments shown in  FIG. 4  and  FIGS. 6-9  rolling down decreases the thickness of approximately the entire blade edge region of the strip material, rolling down (or other form of pressing) can be used to reduce the thickness of only a portion of the blade edge region.