Abstract:
Cutting members for razors are provided that have been subjected to a localized heat-treating process, e.g., application of laser energy. In some cases, the cutting members include a bent portion, and the localized heat-treating process is used to enhance ductility and thereby facilitate formation of the bent portion.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to cutting members for shaving razors and methods of forming such cutting members. 
       BACKGROUND 
       [0002]    Razor blades are typically formed of a suitable metallic sheet material such as stainless steel, which is slit to a desired width and heat-treated to harden the metal. The hardening operation utilizes a high temperature furnace, where the metal may be exposed to temperatures greater than 1145° C. for up to 18 seconds, followed by quenching. 
         [0003]    After hardening, a cutting edge is formed on the blade. The cutting edge typically has a wedge-shaped configuration with an ultimate tip having a radius less than about 1000 angstroms, e.g., about 200-300 angstroms. 
         [0004]    The razor blades are generally mounted on bent metal supports and attached to a shaving razor (e.g., a cartridge for a shaving razor).  FIG. 1 , for example, illustrates a prior art razor blade assembly that includes a planar blade  10  attached (e.g., welded) to a bent metal support  11 . Blade  10  includes a tapered region  14  that terminates in a cutting edge  16 . This type of assembly is secured to shaving razors (e.g., to cartridges for shaving razors) to enable users to cut hair (e.g., facial hair) with cutting edge  16 . Bent metal support  11  provides the relatively delicate blade  10  with sufficient support to withstand forces applied to blade  10  during the shaving process. Examples of razor cartridges having supported blades are shown in U.S. Pat. No. 4,378,634 and in U.S. patent application Ser. No. 10/798,525, filed Mar. 11, 2004, which are incorporated by reference herein. 
       SUMMARY 
       [0005]    In general, the invention features cutting members that have been subjected to a localized heat-treating process, and methods of forming such cutting members. In some cases, the cutting members include a bent portion, and the localized heat-treating process is used to increase ductility and thereby facilitate formation of the bent portion. 
         [0006]    In one aspect, the invention features a razor blade having an edge portion with a cutting edge and a further portion, the edge portion being bent relative to the further portion in a bending zone spaced from the cutting edge, characterized in that at least the edge portion has a material structure hardened by a first heat treatment and in that the bending zone has a locally re-heated structure. 
         [0007]    In another aspect, the invention features a razor blade comprising a blade body having an edge portion with a cutting edge, wherein the cutting edge has a hardness that is greater than the hardness of a portion of the blade body, the cutting edge having been locally hardened by a selective heat treatment. 
         [0008]    Some implementations of these aspects of the invention include one or more of the following features. The heat treatment used to harden the edge portion may be a laser heat treatment. The locally re-heated structure may be re-heated using laser energy. The locally re-heated structure may have a ductility of about nine percent to about ten percent. The cutting edge may have a hardness of about 540 HV to about 750 HV, e.g., about 620 HV to about 750 HV. 
         [0009]    In a further aspect, the invention features a method including (a) hardening at least a portion of a continuous strip of blade steel; (b) sharpening an edge region of the hardened strip to form a sharpened edge; (c) locally re-heating a portion of the strip spaced from the sharpened edge; (d) deforming the strip to form a bent portion; and then (e) separating the continuous strip into multiple discrete blades, each blade having a first portion, a second portion, with the bent and a bent portion being intermediate the first and second portions. 
         [0010]    Some implementations include one or more of the following features. The locally re-heating step may include applying laser energy to the strip. The hardening step may include applying laser energy to the edge region of the strip. Deforming the continuous strip of material may include pressing the strip of material between a punch and a die. The laser energy may be applied substantially only to a region of the strip that is deformed to form the bent portion of the blades. The ductility of the locally re-heated portion of the continuous strip, after local re-heating, may be about nine percent to about ten percent elongation. The method may further include heat-treating a second edge region of the continuous strip opposite the first edge region to reduce sweep in the blades. 
         [0011]    In yet another aspect, the invention features a method including locally hardening an edge region of a continuous strip of blade steel, without hardening a region of the strip spaced from the edge region, and sharpening the edge region of the hardened strip to form a sharpened edge. 
         [0012]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
     
       DESCRIPTION OF DRAWINGS  
         [0013]      FIG. 1  is a cross-sectional view of a prior art razor blade assembly including a planar cutting member attached to a bent support. 
           [0014]      FIG. 2A  is a cross-sectional view of an embodiment of a bent cutting member for a shaving razor. 
           [0015]      FIG. 2B  is a top view of the cutting member of  FIG. 2A . 
           [0016]      FIG. 2C  is a front view of the cutting member of  FIG. 2A . 
           [0017]      FIG. 3  illustrates a shaving razor that includes the bent cutting member of  FIG. 2A . 
           [0018]      FIG. 4  illustrates a method and apparatus for forming the cutting member of  FIG. 2A . 
           [0019]      FIG. 5  is a partial top view of a strip of blade steel after exiting a cutting device of the apparatus shown in  FIG. 4 . 
           [0020]      FIG. 6  is a partial top view of the strip of blade steel after exiting a bending device of the apparatus shown in  FIG. 4 . 
           [0021]      FIG. 7  is a cross-sectional view of the strip of blade steel taken along line  7 - 7  in  FIG. 4 . 
           [0022]      FIGS. 8A and 8B  illustrate an embodiment of a method of forming a bent region in the strip of blade steel. 
       
    
    
     DETAILED DESCRIPTION  
       [0023]    A preferred cutting member which may be formed by a method that includes a localized heat-treating process, and a razor containing the cutting member, will first be described with reference to  FIGS. 2A-3 . 
         [0024]    Referring to  FIG. 2A , a cutting member  100  includes a blade portion  105 , a base portion  110 , and a bent portion  115  that interconnects blade and base portions  105 ,  110 . Blade portion  105  terminates in a relatively sharp cutting edge  120 , while base portion  110  terminates in a relatively blunt end region. Typically, blade portion  105  of cutting member  100  has a length of about 0.032 inch (0.82 millimeters) to about 0.059 inch (1.49 millimeters). Base portion  110  has a length of about 0.087 inch (2.22 millimeters) to about 0.093 inch (2.36 millimeters). Bent portion  115  has a bend radius R of about 0.020 inch (0.45 millimeter) or less (e.g., about 0.012 inch (0.30 millimeter)). Relative to base portion  110 , blade portion  105  extends at an angle of about 115 degrees or less (e.g., about 108 degrees to about 115 degrees, about 110 to about 113 degrees). Cutting edge  120  of blade portion  105  has a wedge-shaped configuration with an ultimate tip having a radius less than about 1000 angstroms (e.g., from about 200 to about 300 angstroms). 
         [0025]    As shown in  FIG. 3 , cutting member  100  can be used in shaving razor  210 , which includes a handle  212  and a replaceable shaving cartridge  214 . Cartridge  214  includes housing  216 , which carries three cutting members  100 , a guard  220 , and a cap  222 . In other embodiments, the cartridge may include fewer or more blades. Cutting members  100  can be mounted within cartridge  214  without the use of additional supports (e.g., without the use of bent metal supports like the one shown in  FIG. 1 ). Cutting members  100  are captured at their ends and by a spring support under the blade portion  105 . The cutting members are allowed to move, during shaving, in a direction generally perpendicular to the length of blade portion  105 . As shown in  FIGS. 2A and 2B , the lower base portions  110  of cutting members  100  extend to the sides beyond the upper bent and blade portions  115 ,  105 . The lower base portions  110  can be arranged to slide up and down within slots in cartridge housing  216  while the upper portion rests against resilient arms during shaving. The slots of the cartridge housing  216  have back stop portions and front stop portions that define, between them, a region in which cutting members  100  can move forward and backward as they slide up and down in the slots during shaving. The front stop portions are generally positioned beyond the ends of blade portions  105 , so as not to interfere with movement of blade portions  105 . Cutting members  100  are arranged within cartridge  214  such that cutting edges  220  are exposed. Cartridge  214  also includes an interconnect member  224  on which housing  216  is pivotally mounted at two arms  228 . When cartridge  214  is attached to handle  212  (e.g., by connecting interconnect member  224  to handle  212 ), as shown in  FIG. 3 , a user can move the relatively flat face of. cartridge  214  across his/her skin in a manner that permits cutting edges  120  of cutting members  100  to cut hairs extending from the user&#39;s skin. 
         [0026]      FIG. 4  shows a method and apparatus  300  for forming cutting members  100 . A continuous strip of blade steel  350  is conveyed (e.g., pulled by a rotating roll from a roll  305  of blade steel to a heat-treating device  310  (which may comprise multiple heat-treating devices), where strip  350  is heat-treated to increase the hardness and/or increase the ductility of discrete regions of the blade strip. Strip  350  is then re-coiled into a roll  305  of hardened blade steel, and subsequently unwound and conveyed to a sharpening device  315 , where the hardened edge region of the strip is sharpened to form a cutting edge  352 . Strip  350  is again re-coiled into a roll  305  of heat treated and sharpened blade steel, after which it is coated with hard and lubricious coatings using a coating device  325 . Strip  350  is then unwound and conveyed to a cutting/stamping station which includes a cutting device  320 . Cutting device  320  creates transverse slots  355  and adjoining slits  357  ( FIG. 5 ) across longitudinally spaced apart regions of strip  350  (as shown in  FIG. 5 ). Strip  350  is then conveyed to a bending device  330 , within the cutting/stamping station, that creates a longitudinal bend  360  in the regions of strip  350  between transverse slots  355  (shown in  FIGS. 6 and 7 ). After being bent, strip  350  is separated into multiple, discrete cutting members  100  by a separating device  335 , also within the cutting/stamping station. Cutting members  100  may then be arranged in a stack  340  for transport and/or for further processing, or assembled directly into cartridges, and a scrap region  365  of strip  350  is assembled onto roll  345  for recycling or disposal. Scrap region  365 , for example, can be used merely to help convey strip  350  through the blade forming devices described above. Alternatively or additionally, any of various other techniques can be used to convey strip  350  through the blade forming devices. 
         [0027]    In certain embodiments, heat-treating device  310  is a laser device. The laser device can be used to locally harden a discrete region of strip  350  (e.g., the edge region of strip  350 ). For example, laser energy (e.g., laser light) from the laser device can be directed to the strip as the strip is conveyed from the roll to the sharpening device. Strip  350  can be conveyed at a rate of about 5 ft/min (1.5 m/min) to about 200 ft/min (61 m/min) (e.g., about 120 ft/min (36.6 m/min)). Generally, the power of the laser device is directly proportional to the rate at which strip  350  is conveyed. In some embodiments, the laser device is configured to produce energy at about  100  watts to about one kilowatt (e.g., about 200 watts). The light emitted from the laser device can have a wavelength of about 950 nm to about 1440 nm (e.g., about 1064 nm). The discrete region of the strip  350 , which is contacted by the laser light, can reach a temperature of about 1050 degrees Celsius to about 1400 degrees Celsius (e.g., about 1200 degrees Celsius). The time for which the discrete region of strip  350  is heated depends on the power level of the laser device. Typically, the time for which the discrete region of strip  350  is heated decreases as the power level of the laser device increases, and vice versa. The laser energy can, for example, be applied to the discrete region of strip  350  for about 0.010 seconds to about 0.190 seconds. The hardness of the heated region of strip  350  can be increased as a result of the heat-treatment. The heated region of strip  350  can, for example, have a hardness of about 540 HV to about 750 HV (e.g., about 620 HV to about 750 HV). 
         [0028]    While heat-treating device  310  has been described as a laser device, any of various other devices capable of locally treating discrete regions of strip  350  can be used. For example, the heat-treating device can include an induction coil that is arranged about a portion of strip  350  to heat, and thus harden, that portion of strip  350 . 
         [0029]    Moreover, the heat-treating device  310  may include multiple heat-treating devices, for example one or more heat-treating devices configured to heat the entire strip, and one or more heat-treating devices configured for localized heating. For instance, heat-treating device  310  may include a traditional furnace configured to heat the entire strip, followed by a laser configured for localized heating. In this case, the conventional furnace would impart hardness to the entire strip, and then the laser would generally be used to temper or soften a localized area of the strip, e.g., the bend area, to increase ductility. 
         [0030]    Due to its relatively small area, the heated region of strip  350  generally self-quenches after being exposed to the laser energy. Alternatively or additionally, a cooling source (e.g., a cooling fluid) can be applied to the heated region of the strip to aid the quenching process. 
         [0031]    Sharpening device  315  can be any device capable of sharpening the edge of strip  350 . Examples of razor blade cutting edge structures and processes of manufacture are described in U.S. Pat. Nos. 5,295,305; 5,232,568; 4,933,058; 5,032,243; 5,497,550; 5,940,975; 5,669,144; EP 0591334; and PCT 92/03330, which are hereby incorporated by reference. 
         [0032]    Cutting device  320  can be any of various devices capable of providing slots  355  and/or slits  357  in strip  350 . In some embodiments, cutting device is a punch press. In such embodiments, the progression of strip  350  can be periodically paused in order to allow the punch press to stamp slots  355  and/or slits  357  in strip  350 . Cutting device  320  can alternatively or additionally be any of various other devices, such as a high power laser or a scoring operation followed by a bending or fracturing operation. 
         [0033]    Referring again to  FIG. 5 , after strip  350  has been conveyed through cutting device  320 , strip  350  includes multiple, longitudinally spaced apart slots  355  that extend inwardly from the sharpened edge of the strip to a central region of the strip. Slits  357  extend inwardly from slots  355 . Slots  355  are spaced apart by a distance that corresponds to the width of cutting members  100 . In some embodiments, adjacent slots  355  are spaced apart from one another by about 36.20 millimeters to about 36.50 millimeters. In certain embodiments, adjacent slits are spaced apart from one another by about 37.26 millimeters to about 37.36 millimeters. By providing discrete regions that are separated by slots  355 , the bending of strip  350  can be improved. 
         [0034]    Bending device  330  can be any device capable of forming a longitudinal bend in strip  350 . In some embodiments, as shown in  FIGS. 8A and 8B , bending device  330  is an assembly that includes a punch  365  and a die  370 . Punch  365  includes a curved portion  367  that is configured to mate with an associated curved portion  372  of die  370 . Generally, curved portion  367  of punch  365  has a radius that is slightly larger than a radius of curved portion  372  of die  370 . Curved portion  367  of punch  365 , for example can have a radius of about 0.0231″ to about 0.0241″, while curved portion  372  of die  370  can have a radius of about 0.010″ to about 0.014″. Punch  365  also includes a protrusion  369  that is configured to contact a portion of strip  350  that, as discussed below, is offset from sharpened edge  352  of strip  350 . 
         [0035]    To form bent region  360  of strip  350 , the relatively planar strip  350  is positioned between punch  365  and die  370 , as shown in  FIG. 8A . Punch  365  and die  370  are then moved toward one another such that curved portions  367  and  372  generally mate. Punch  365  can, for example, be moved toward die  370  at a rate of about 25 ft/min (10 m/min) to about 500 ft/min (200 m/min). As punch  365  and die  370  are moved toward one another, protrusion  369  of punch  365  contacts a region of strip  350  offset from sharpened edge  352 . As punch  365  and die  370  mate with one another, strip  350  is deformed into a bent position between punch  365  and die  370 . Due to the configuration of punch  365  and die  367 , sharpened edge  352  can remain untouched throughout the bending process. This arrangement can help to prevent damage to the relatively delicate, sharpened edge  352  of strip  350 . 
         [0036]    As a result of the bending process, the thickness of strip  350  in bent region  360  can be reduced, relative to the thickness of strip  350  prior to being bent, by at least about five percent (e.g., about five percent to about  30  percent). Strip  350  in bent region  360 , for example, can have a thickness of about 0.0035 inch (0.089 millimeter) to about 0.0095 inch (0.241 millimeter), while the remainder of strip  350  can have a thickness of about 0.005 inch (0.127 millimeter) to about 0.01 inch (0.254 millimeter). 
         [0037]    Separating device  335  can be any device capable of separating the regions of strip  350  between slots  355  from the remainder of strip  350  to form discrete cutting members  100 . In some embodiments, separating device  335  is a punch press. The progression of strip  350  can be periodically paused to allow the punch press to accurately separate the regions of strip  350  between slots  355  from the remainder of strip  350  to form cutting members  100 . 
         [0038]    Other devices capable of separating the regions of strip  350  between slots  355  from the remainder of strip  350  can alternatively or additionally be used. Examples of such devices include a high power laser or a scoring operation followed by a bending or fracturing operation. 
         [0039]    The cutting member may have certain preferred characteristics, as will now be described. 
         [0040]    In certain embodiments, cutting member  100  is relatively thick, as compared to many conventional razor blades. Cutting member  100 , for example, can have an average thickness of at least about 0.003 inch (0.076 millimeter), e.g., about 0.005 inch (0.127 millimeter) to about 0.01 inch (0.254 millimeter). As a result of its relatively thick structure, cutting member  100  can provide increased rigidity, which can improve the comfort of the user and/or the cutting performance of cutting member  100  during use. In some embodiments, cutting member  100  has a substantially constant thickness. For example, blade portion  105  (except for cutting edge  120 ), base portion  110 , and bent portion  115  can have substantially the same thickness. 
         [0041]    In some embodiments, the thickness of bent portion  115  is less than the thickness of blade portion  105  and/or base portion  110 . For example, the thickness of bent portion  115  can be less than the thickness of blade portion  105  and/or base portion  110  by at least about five percent (e.g., about five percent to about 30 percent, about ten percent to about 20 percent). 
         [0042]    In certain embodiments, cutting member  100  (e.g., base portion  110  of cutting member  100 ) has a hardness of about 540 HV to about 750 HV (e.g., about 540 HV to about 620 HV). In some embodiments, bent portion  115  has a hardness that is less than the hardness of base portion  110 . Bent portion  115  can, for example, have a hardness of about 540 HV to about 620 HV. The hardness of cutting member  100  can be measured by ASTM E92-82—Standard Test Method for Vickers Hardness of Metallic Materials. In certain embodiments, cutting member  100  has a substantially uniform hardness. In other  20  embodiments, cutting edge  120  is harder than the other portions of cutting member  100 . 
         [0043]    In some embodiments, cutting member  100  (e.g., bent portion  115  of cutting member  100 ) has a ductility of about seven percent to about  12  percent (e.g., about nine percent to about ten percent) elongation measured in uniaxial tension at fracture. The ductility of bent portion  115  can be measured, for example, by ASTM E345-93—Standard Test Methods of Tension Testing of Metallic Foil. In some embodiments, bent portion  115  and the remainder of cutting member  100  have substantially the same ductility. In certain embodiments, bent portion  115  has greater ductility than the other portions of cutting member  100 . 
         [0044]    Cutting member  100  can be formed of any of various suitable materials, including GIN 6  and GINB steels and other blade steels. In certain embodiments, cutting member  100  is formed of a material having a composition comprised of about 0.35 to about 0.43 percent carbon, about 0.90 to about 1.35 percent molybdenum, about 0.40 to about 0.90 percent manganese, about 13 to about 14 percent chromium, no more than about 0.030 percent phosphorus, about 0.20 to about 0.55 percent silicon, and no more than about 0.025 percent sulfur. Cutting member  100  can, for example, be formed of a stainless steel having a carbon content of about 0.4 percent by weight, a chromium content of about 13 percent by weight, a molybdenum content of about 1.25 percent by weight, and amounts of manganese, chromium, phosphorus, silicon and sulfur within the above ranges. 
         [0045]    In some embodiments, blade portion  105  and/or base portion  110  have minimal levels of bow and sweep. Bow is a term used to describe an arching normal to the plane in which the portion of the cutting member is intended to lie. Sweep, also commonly referred to as camber, is a term used to describe an arching within the plane in which the portion of the cutting member lies (e.g., an arching of the longitudinal edges of the portion of the cutting member). In some embodiments, blade portion  105  has a bow of about +0.0004 to about −0.002 inch (+0.01 to −0.05 millimeter) or less across the length of the blade portion. In certain embodiments, blade portion  105  has a sweep of about ±0.0027 inch (±0.07 millimeter) or less across the length of the blade portion. Base portion  110  can have a bow of about ±0.0024 inch (±0.060 millimeter) or less across the length of the base portion. By reducing the levels of bow and/or sweep in blade portion  105  and/or base portion  110 , the comfort of the user and/or the cutting performance of cutting member  100  can be improved. 
         [0046]    While certain embodiments have been described, other embodiments are possible. 
         [0047]    For example, the localized heat-treating processes described above can be used to heat treat blades other than the bent blades described above. For instance, a localized heat-treating process can be used to locally harden the edge of a conventional blade such as the prior art razor blades described above with reference to  FIG. 1 . 
         [0048]    Moreover, the order of many of the process steps discussed above can be altered. The process steps can be ordered in any of various different combinations. 
         [0049]    As another example, while heat-treating device  310  has been described as being configured to treat an edge region of strip  350 , heat treating device  310  can alternatively or additionally be arranged to treat additional regions of strip  350  (e.g., regions of strip  350  that are not intended to be sharpened by sharpening device  315 ). In some embodiments, for example the entire strip  350  is hardened by heat-treating device  310 . 
         [0050]    As a further example, while increasing the ductility of a region of strip  350  that is to be bent has been described above, additional or other regions of strip  350  (e.g., regions of strip  350  that are not intended to be bent by bending device  330 ) may be heat-treated to increase ductility. In certain embodiments, for example, substantially the entire strip  350  is heat-treated to increase its ductility. In some embodiments, as noted above, strip  350  is conveyed through a heat treating device to harden substantially the entire strip. After initially hardening substantially the entire strip an edge region of strip  350  is sharpened as described above. Then, strip  350  is subjected to heat treating to increase the ductility of substantially the entire strip, which can help to improve the bending of strip  350 . Strip  350  can then be further processed as discussed above. 
         [0051]    As another example, while the embodiments above describe heat-treating a discrete region of strip  350  to increase the ductility of that region, in certain embodiments, the cutting member forming process can be carried out without this heat-treating step. In such embodiments, strip  350  can be formed of a relatively ductile material. Strip  350  can be conveyed through heat-treating device  310  to locally harden an edge region of strip  350  so that the edge region can be sharpened. After being sharpened, strip  350  can be cut and bent without first heat-treating the bend region. The material from which strip  350  is formed, for example, can be sufficiently ductile so that the second heat-treating step is not required to prevent damage to the strip as a result of the bending process. After bending strip  350 , the remainder of the process can be carried out in accordance with the description herein. 
         [0052]    As an additional example, in some embodiments, a heating device is configured to apply heat to both longitudinal edges of strip  350 . For example, one of the longitudinal edges can be heat-treated, as discussed above, in order to harden the region for sharpening, and the opposing longitudinal edge can be heat treated to reduce (e.g., to prevent) sweep within strip  350 . For example, the opposing longitudinal edge can be heat-treated to substantially the same temperature as edge  352 . In some embodiments, the regions that are heat-treated are symmetrical with respect to a center line of strip  350 . 
         [0053]    Other embodiments are within the scope of the claims.