Abstract:
Replaceable shaving assemblies are disclosed that include a razor cartridge having a blade geometry that is designed to provide a close, comfortable shave. Shaving systems including such shaving assemblies are also disclosed, as are methods of using such shaving systems and methods of manufacturing these cartridges.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a U.S. national phase application of PCT Application Serial No. PCT/US2015/38543, filed Jun. 30, 2015, which claims the benefit of U.S. Provisional Application Ser. No. 62/023,419, filed Jul. 11, 2014, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Shaving systems often consist of a handle and a cartridge in which one or more blades are mounted in a plastic housing. In some cases, the blades are held in place in the housing by a pair of metallic clips, mounted at opposite ends of the length of the blades. 
         [0003]    Most modern razor cartridges include one to five razor blades disposed between a guard and a cap. The cutting edge of each razor blade is positioned adjacent a plane that tangentially intersects the contact surfaces of the guard and the cap. This plane, referred to as the “contact plane,” represents the theoretical position of the surface being shaved. The position of a razor blade&#39;s cutting edge relative to the contact plane is described in terms of the “exposure” of the cutting edge. A cutting edge with “positive exposure” is one that extends through the contact plane and into the area normally occupied by the object being shaved. A cutting edge with “negative exposure” is one that is positioned below the plane and therefore does not intersect the contact plane. A cutting edge with “neutral exposure” is one that is contiguous with the contact plane. Generally, positioning the cutting edge of a blade at a positive exposure has been found to improve closeness, but potentially also increases the chance of skin irritation. On the other hand, neutral or negative blade exposure tends to reduce the likelihood of irritation, but also tends to decrease the closeness of the shave. 
         [0004]    The overall blade geometry of the cartridge, including blade exposure and other factors such as blade span, affects the comfort and closeness of the shave obtained with the razor, as well as the likelihood of nicks and cuts during shaving. As will be discussed further below, comfort and closeness is also impacted by “skin management,” i.e., the way in which the skin bulge contacted by the blade edges is affected by other elements of the razor, including the guard that is provided at the leading edge of most razor cartridges. 
       SUMMARY 
       [0005]    In general, the present disclosure pertains to razor cartridges (also known as blade units), and to shaving assemblies that include such cartridges. 
         [0006]    In one aspect, the invention features a razor cartridge comprising (a) a frame defining a base, said frame having an opening defined in part by a composite guard having a leading guard surface and a cap having a trailing cap surface, said leading guard surface and said trailing cap surface cooperating to define a contact plane tangential thereto and extending across said opening; and (b) at least three razor blades attached to said base, said razor blades being fixedly spaced. The cutting edge of the razor blade closest to the leading guard surface has a cutting edge exposure relative to said contact plane that is positive, and the cutting edge exposures of the other razor blades become less positive from said leading guard surface to said cap. 
         [0007]    By “composite guard,” we mean a guard that includes a flexible elastomeric portion and a rigid or semi-rigid supporting portion that is closer to the blades than the flexible elastomeric portion and that is the last skin-engaging surface prior to the blades. 
         [0008]    Some implementations include one or more of the following features. 
         [0009]    The razor cartridge may include four or more blades, e.g., five blades. 
         [0010]    The composite guard may include an elastomeric guard bar having a skin contacting surface, and a rigid guard bar support defining said leading guard surface, wherein the rigid guard bar support is proximal to the cutting edge of the razor blade closest to the leading guard surface. In some cases, the skin contacting surface of the elastomeric guard bar is higher than an uppermost surface of the rigid guard bar support, e.g., by about 0.05 to 0.5 mm, preferably by about 0.2 to 0.3 mm. 
         [0011]    In some implementations, the cartridge has a pivot point that is closer to the trailing cap surface than to the leading guard surface. The pivot point may be below a lowermost portion of the blades. 
         [0012]    In preferred implementations, the blades are spaced relatively close together. At least two of the blades may have an inter-blade span that is less than about 0.9 mm, e.g., from about 0.75 to 0.85 mm. The primary span, i.e., the distance between a leading edge of the leading guard surface and the cutting edge closest to the leading guard surface may be from about 0.3 to 0.75 mm, e.g., from about 0.35 to 0.45 mm. 
         [0013]    In some implementations, the blades are bent blades, and the blades are fixedly supported within the frame such that the blades are not intended to move relative to the frame during shaving. 
         [0014]    In another aspect, the invention features a razor cartridge comprising (a) a frame defining a base, said frame having an opening defined in part by a guard having a leading guard surface and a cap having a trailing cap surface, said leading guard surface and said trailing cap surface cooperating to define a contact plane tangential thereto and extending across said opening; and (b) at least three razor blades attached to said base, said razor blades being fixedly spaced. The cutting edge of the razor blade closest to the leading guard surface has a cutting edge exposure relative to said contact plane that is positive, the cutting edge exposure of the cutting edges of the other razor blades become less positive from said leading guard surface to said cap, and one or more of the blades has a cutting edge exposure that is negative or neutral. 
         [0015]    In some implementations, razor cartridges according to this aspect of the invention may include any one or more of the features disclosed above. 
         [0016]    In other aspects, the invention features methods of contacting the skin with the razor cartridges described herein, and methods of manufacturing razor cartridges. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a perspective view of a razor cartridge according to one implementation. 
           [0018]      FIG. 2  is a cross sectional view of the razor cartridge shown in  FIG. 1 , taken along line  2 - 2  in  FIG. 4 . 
           [0019]      FIG. 3  is a cut-away perspective view of the razor cartridge shown in  FIG. 1 , cut along line  3 - 3  in  FIG. 1 . 
           [0020]      FIG. 4  is a rear plan view of the razor cartridge. 
           [0021]      FIG. 5  is a diagrammatic cross-sectional view of a portion of the razor cartridge, showing features of the blade geometry of the cartridge. 
           [0022]      FIG. 5A  is an enlarged diagrammatic view showing details of the blade geometry. 
           [0023]      FIG. 6  is a cross-sectional view of the cartridge with the cartridge pivot point indicated. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  shows a razor cartridge  10  that includes a housing  12 , a cap  14 , a composite guard  16 , and a plurality of blades  18  disposed between the cap and guard. In some implementations, the cap  14  may be formed of a rigid plastic. The housing  12  defines a generally rectangular frame surrounding an open area in which the blades are positioned. As shown in  FIGS. 2 and 5 , the housing also defines a rigid guard bar support  21  having a leading guard surface  11  ( FIG. 5 ), and a rigid cap support  23  having a trailing cap surface  13  ( FIG. 5 .) As will be discussed in detail below, the razor cartridge  10  includes a number of features that contribute to enhanced skin management and thus to a close, comfortable shave. 
         [0025]    Referring to  FIGS. 2-3 , the composite guard  16  includes an elastomeric portion having a plurality of fins  17  and an elastomeric guard bar  19 , and a rigid portion provided by the rigid guard bar support  21 . The elastomeric guard bar  19  is supported by the rigid guard bar support  21 , which prevents excessive deflection of the elastomeric guard bar as the elastomeric guard bar stretches the user&#39;s skin during shaving. The elastomeric guard bar uniformly stretches, tensions, straightens and flattens the skin prior to the skin contacting the rigid guard bar support. The rigid guard bar support  21  is the last point of skin contact before the blades. Such composite guards are described in further detail in U.S. application Ser. No. 61/983,790, filed Apr. 24, 2014, the full disclosure of which is incorporated herein by reference. 
         [0026]    The elastomeric guard bar  19  is higher than the guard bar support  21 , and is also higher than the cutting edge of the blade that is closest to the guard bar support (hereafter referred to as the “primary blade.”) In some preferred implementations, the skin contacting surface of the elastomeric guard bar is higher than an uppermost surface of the rigid guard bar support by at least 0.05 mm, e.g., from about 0.05 to 0.5 mm or in some cases from about 0.2 to 0.3 mm higher. This height allows the elastomeric guard bar to stretch the skin prior to the skin contacting the primary blade, thereby managing the skin bulge and reducing the tendency of the primary blade to nick the skin. The rigid guard bar support then supports and manages the skin again prior to contact between the skin and the primary blade, setting the skin up for blade contact. 
         [0027]    Blades  18  are positioned relative to each other and relative to the cutting plane discussed in the Background section above (plane P c  in  FIG. 5A , defined herein between the leading surface  11  of the guard bar support  21  and the trailing surface  13  of the cap support  23 ) by blade positioning elements  22  ( FIG. 2 ). As shown in  FIG. 4 , the blade positioning elements are positioned at intervals along the length of the blades, providing open areas  20  between the blade positioning elements for rinse through of hair and debris. Together, the blade positioning elements provide a base for the blades. 
         [0028]    Referring to  FIG. 2 , each of the blade positioning elements  22  defines a plurality of slots  24  which hold the blades in predefined positions relative to each other, while the curved upper surfaces  26  of the positioning elements  22  support the lower surfaces of the upper portions of the blades to maintain the blades in a predefined shaving geometry. The blades are preferably fixed blades, i.e., they are positioned by the positioning elements  22  in a manner that is intended to substantially prevent deflection of the blades during shaving. 
         [0029]    Referring to  FIG. 1 , a pair of clips  28 , disposed just inboard of the short ends of the housing  12 , retain the blades securely in the housing. The clips may be arranged, for example, as disclosed in U.S. application Ser. No. 61/885,906, filed Oct. 2, 2013, the full disclosure of which is incorporated herein by reference. 
         [0030]    Blades  18  are preferably bent blades, as shown in  FIGS. 2-3 and 5-6 . By “bent blades,” we mean blades that include an elongated blade portion that tapers to a cutting edge, an elongated base portion that is integral with the blade portion, and a bent portion, intermediate the blade portion and the base portion. Such blades are described, for example, in U.S. Pat. No. 5,010,646, the full disclosure of which is incorporated herein by reference. 
         [0031]    It is also preferred that the blades be fixed blades, rather than “sprung” blades (e.g., blades of the type described in U.S. Pat. No. 4,270,268.) Thus, the blades are positioned by their placement in the slots of the blade positioning elements and held in place by the clips such that their position relative to the housing does not change during shaving. 
         [0032]    The distance between the cutting edges of adjacent blades, referred to herein as inter-blade span (S i ,  FIG. 5 ), is selected to enhance skin management, by managing the skin bulge as the cutting surface moves across the user&#39;s skin. The distance between each of the blade edges is preferably less than 0.9 mm, e.g., from about 0.75 to 0.85 mm. 
         [0033]    The primary span (S p ,  FIG. 5 ), i.e., the distance from the leading edge of the guard to the cutting edge of the primary blade, is also important to effective skin management. This distance, along with the relative heights of the elastomeric guard bar, guard bar support, and cutting edge of the primary blade, affects the balance between shaving comfort and closeness. The primary span is preferably from about 0.3 to 0.75 mm, more preferably from about 0.35 to 0.45 mm. Too small a distance tends to impact shaving closeness detrimentally, while too large a distance could cause the skin bulge to be too large, tending to result in nicking or skin irritation. 
         [0034]    The skin management provided by the features discussed above contributes to the ability to have a primary blade with a positive exposure relative to the cutting plane without compromising user comfort. Preferably, the primary blade is positive by at least 0.02 mm, preferably by at least 0.025, e.g., at least 0.035 mm, and in some cases by about 0.04 mm or more. In some implementations, the primary blade could be positive by as much as 0.1 mm. As shown in  FIG. 5A , the remaining blades have a less positive exposure as the blades become closer to the cap, with the blades closest to the cap having a negative exposure. In some cases, the second blade (counting from the primary blade towards the cap) has a neutral or slightly positive exposure, the third blade has a neutral exposure, and the fourth and fifth blades have a negative exposure. 
         [0035]    The cartridge is designed to pivot in a manner that takes advantage of this blade exposure arrangement by causing shaving forces to be relatively evenly distributed over the blades during shaving, with somewhat less force being applied to the primary blade. By applying more force to the negative and neutral blades and less to the primary blade, shaving comfort is enhanced without deleteriously affecting closeness. 
         [0036]    Referring to  FIG. 6 , in preferred implementations the pivot axis P of the cartridge is positioned closer to the cap trailing edge than to the guard leading edge, measured along the x axis, and below the bases of the blades, measured along the y axis. This arrangement, known as “rear pivoting,” reduces the likelihood of nicking due to the positive exposure of the primary blade, especially during clean up strokes, and spreads blade wear relatively evenly between the blades. The rear pivoting arrangement also helps to prevent nicking by the positively exposed primary blade. 
         [0037]    The pivot axis is also positioned below a lowermost portion of the base portions of the blades. This positioning allows the cartridge to have a small footprint. 
         [0038]    The housing  12  can be made of any suitable material including, for example, amorphous blends of polyphenylene ether and polystyrene, e.g., polymers sold under the tradename NORYL resins, acrylonitrile butadiene styrene (ABS), polystyrene, polyethylene terephthalate (PET or PETE), high density (HD) PETE, thermoplastic polymer, polypropylene, oriented polypropylene, polyurethane, polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyester, high-gloss polyester, nylon, or any combination thereof. The cap  14  is preferably formed of the same material as the housing. 
         [0039]    The clips can be made of metals (preferably Aluminum, aluminum alloys) or other malleable material. 
         [0040]    The guard, including the elastomeric portion of the composite guard, may be made of any suitable materials, e.g., as described in U.S. application Ser. No. 61/983,790, filed Apr. 24, 2014. 
         [0041]    A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. 
         [0042]    For example, the cartridge may have more or fewer than five blades. Moreover, the exposure of the blades other than the primary blade may in some implementations be different from the progression described above. 
         [0043]    As another example, while a composite guard bar consisting of an elastomeric guard bar and a rigid guard bar support has been described above, other types of guard bars may be used. 
         [0044]    Moreover, while a generally rectangular cartridge is shown in the Figures, other shapes can be used, e.g., oval. 
         [0045]    Accordingly, other embodiments are within the scope of the following claims.