Patent Publication Number: US-2010122464-A1

Title: Razor Cartridge with Skin Engaging Member

Description:
FIELD OF THE INVENTION 
     The present invention relates to a razor cartridge and more particularly to a razor cartridge with a skin engaging member or shaving aid strip. 
     BACKGROUND OF THE INVENTION 
     In shaving systems of the wet shave type, factors such as the frictional drag of the razor across the skin, the force needed to sever hairs, and irritation of pre-existing skin damage can create a degree of shaving discomfort. Discomfort, and other problems accompanying wet shaving systems, can be alleviated by the application of shaving aids to the skin. Shaving aids may be applied prior to, during, or after shaving. A number of problems accompany the use of pre- and post-applied shaving aids. Pre-applied-shaving aids can evaporate or can be carried away from the site of application by repeated strokes of the razor. Post-applied-shaving aids are not present on the skin during shaving and thus their application may be too late to prevent an unwanted affect. Both pre-applied and post-applied shaving aids add additional steps to the shaving process. 
     Proposals have been made to incorporate a shaving aid e.g., lubricant, whisker softener, razor cleanser, medicinal agent, cosmetic agent or combination thereof, into a razor, e.g., by depositing a shaving aid in a recess on the razor, by incorporating a shaving aid directly into one or more molded polymeric components of the razor, by adhesively securing a shaving aid composite to the razor, and by use of a mechanical connection between a shaving aid composite and the razor. A water-soluble shaving aid, e.g., polyethylene oxide, has been mixed with a water-insoluble material, e.g., a polystyrene polymer, to form an insoluble polymer/soluble skin engaging member also known as a shaving aid strip, a shaving aid composite, a lubricating strip. The skin engaging member has been mounted on razor and shaving cartridge structures, adjacent the shaving edge or edges, of single or multiple blade shaving systems. Upon exposure to water, the water-soluble shaving aid leaches from the skin engaging member onto the skin. 
     One problem associated with razor cartridges is that a user has no indication as to when the razor cartridge is nearing the end of its&#39; optimal shave performance and should be replaced. One solution to this problem has been to utilize the skin engaging member or lubricating strip to provide an indication or signal to the user that the cartridge has reached the end of its&#39; optimal shave performance and should be replaced. Such solutions include the use of a two colored lubrication strip. As the user shaves the lubrication member wears away. Typically, in two color systems one of the layers, e.g., the first layer which may be colored blue, is positioned to wear away first thus exposing the second layer which has a different color, e.g., white, than the first layer. This provides an indication to the user that the razor cartridge should be replaced. 
     One problem associated with the two color lube strip indicators is that they do not provide an exacting correlation between the indication and or signal to the user and the change from an optimal shave performance to a sub-optimal shave performance. For example, the indication changes even though the optimal shave performance may have passed long ago or has yet to pass. There is a need to provide the user with an indication that correlates with the change between an optimal shave performance and a sub-optimal shave performance. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a razor cartridge comprising a guard, a cap and a plurality of blades each with sharpened edges located between the guard and the cap. The cap comprises a cap edge positioned nearest the blades and an erodible skin engaging member. The plurality of blades comprise a cap blade defining a blade edge nearest the cap and an adjacent blade defining a blade edge positioned immediately adjacent to the cap blade and between the cap blade and the guard. The skin engaging member comprises at least one upper layer comprising an erodible skin engaging layer of a first color. The upper layer has an upper surface, a lower surface and a first thickness dimension. The skin engaging member comprises a base layer positioned below the upper layer comprising an erodible skin engaging layer of a second color different from the first color. The base layer has an upper surface, a lower surface and a thickness dimension. During shaving the upper layer eroding exposing the upper surface of the base layer, the upper surface of the base layer being positioned relative to the cap edge such that when the upper layer has eroded the cap blade edge has a final exposure defined by the adjacent blade edge, the cap edge and the upper surface of the base layer. 
     Preferably, the first color is green. Preferably, the second color is red. The second color may be white. 
     The upper layer and the base layer preferably each comprise a solid polymeric material. Preferably, the upper layer and the base layer each comprise a water soluble shaving aid and a water insoluble polymer. 
     The upper surface of the upper layer is positioned relative to the cap edge such that prior to use the cap blade edge has a first exposure defined by the adjacent blade edge and the upper surface of the upper layer. 
     The final exposure is greater than first exposure. 
     The upper layer may comprise two layers, three layers or more. 
     During shaving the upper layer erodes exposing said upper surface of said base layer to provide a color change that signals to a user that the cartridge should be replaced 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following description taken in conjunction with the accompanying drawings. 
         FIG. 1  is a perspective view of a razor cartridge which includes a skin engaging member of the present invention. 
         FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a perspective view of the skin engaging member included in the razor cartridge depicted in  FIG. 1 . 
         FIG. 4  is a side elevation view of the skin engaging member of  FIG. 3 . 
         FIG. 5  is a sectional view of a razor cartridge identical to that of  FIG. 2 , depicting the razor cartridge prior to use. 
         FIG. 6  is a sectional view of a razor cartridge identical to that of  FIG. 2 , depicting the razor cartridge after several shaves. 
         FIG. 7  is a sectional view of a razor cartridge identical to that of  FIG. 2 , depicting the razor cartridge after numerous shaves. 
         FIG. 8  is a side elevation view of an alternative skin engaging member of the present invention. 
         FIG. 9  is a side elevation view of an alternative skin engaging member of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 , and  2  the razor cartridge  14  includes housing  16 , which carries three blades  17 ,  18  and  19 , a finned elastomeric guard  20 , and a skin engaging member or shaving aid strip  22  located on a skin-engaging portion (in this case the cap  23 ) of the cartridge  14 . The blades  17 ,  18  and  19  are positioned between the guard  20  and the cap  23 . The blades  17 ,  18  and  19 , each have a sharpened edge,  17 ′,  18 ′ and  19 ′, respectively. 
     Blade  19  is referred to as the cap blade as it is positioned nearest the cap  23 . Blade  18  is referred to as an adjacent blade given its&#39; proximity to the cap blade  19 . Adjacent blade  18  is positioned adjacent to the cap blade  19  and between the cap blade  19  and the guard  20 . While the razor cartridge is shown with three blades, the cartridge may include two, three, four, five, six blades, etc. 
     The skin engaging member  22  is in the form of a narrow elongated strip of dimensions suitable for placement on a razor cartridge. The skin engaging member  22  may be about 2.5 cm to about 3.7 cm in length, and about 0.15 cm to about 0.35 cm in width. The skin engaging member  22  is locked in an opening in the rear of the cartridge  14 . The skin engaging member may be secured to cartridge  14  by other known methods such as ultrasonic welding or gluing. While shown at the rear portion of this particular razor cartridge, the skin engaging member may be located at any skin-engaging portion of the cartridge and may be fabricated in any size or shape deemed appropriate. For example, the skin engaging member can be incorporated into razor cartridges such as the Fusion®, Venus®, Mach 3®, Sensor Excel®, Atra Plus® and Custom Plus® razors sold by The Gillette Company, as well as in other commercial razor cartridges. 
     Referring to  FIGS. 3 and 4 , skin engaging member  22  includes an exposed lengthwise-extending erodible skin engaging upper layer or portion  24  and a lengthwise-extending erodible skin engaging base layer or portion  26  positioned below the upper layer  24 . The base layer  26  preferably extends under the upper layer  24  and provides support for upper layer  24 . The boundary between respective layers may approximate a plane as shown. However, the boundary between respective layers may approximate other shapes such as curvilinear, arcuate either convex or concave. Base layer  26  also includes connecting portion  30  which serves to lock the skin engaging member into a mating receiving portion of the cartridge. 
     The upper layer  24  has an upper surface  31  and a lower surface  32 . The base layer  26  has an upper surface  33  and a lower surface  34 . Upper surface  31  is the exposed surface of skin engaging member  22  facing the user prior to use. Lower surface  32  faces and directly contacts upper surface  33 . 
     Each layer or portion of the skin engaging member or shaving aid strip  22  preferably comprises a solid polymeric material. Each layer of the skin engaging member  22  preferably comprises a lubricious water-soluble polymer as the main shaving aid and a water-insoluble polymer to serve as a matrix in which the water-soluble polymer is dispersed. A layer having a greater amount of water-soluble polymer will wear at a faster rate or more quickly than a layer with a lower amount of water-soluble polymer, all other things being equal. Preferably, the upper layer will comprise a greater amount of water-soluble polymer in percent by weight than the base layer. The base layer which acts to hold the skin engaging member in place within the cartridge and provides support for the upper layer preferably comprises a lesser amount of water-soluble polymer by weight than the upper layer. 
     Preferably, the upper layer or portion  24  will comprise about 0% to about 30%, more preferably about 10% to about 25%, by weight water-insoluble polymer, and about 65% to about 95%, more preferably about 65% to about 95%, by weight lubricious water-soluble polymer. Preferably, the base layer or portion  26  will comprise about 20% to about 60%, more preferably about 25% to about 40%, by weight water-insoluble polymer, and about 50% to about 85%, more preferably about 55% to about 75%, by weight lubricious water-soluble polymer. 
     Typical lubricious water-soluble polymers include polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, modified hydroxyalkyl cellulose, polyvinyl imidazoline, polyvinyl alcohol, polysulfone and polyhydroxyethylmethacrylate. The preferred lubricious water-soluble polymer is polyethylene oxide. The more preferred polyethylene oxides generally are known as POLYOX (available from Union Carbide Corporation) or ALKOX (available from Meisei Chemical Works, Kyoto, Japan). These polyethylene oxides will preferably have molecular weights of about 100,000 to 8 million daltons, most preferably about 300,000 to 5 million daltons. It is preferred to use a blend of polyethylene oxides, typically a blend having at least one polyethylene oxide having a molecular weight in the range of 100,000 to 500,000 and at least one polyethylene oxide having a molecular weight in the range of 3 million to 8 million. The most preferred polyethylene oxide comprises a blend of about 40% to 80% by weight of polyethylene oxide having an average molecular weight of about 5 million (e.g. POLYOX COAGULANT) and about 60% to 20% of polyethylene oxide having an average molecular weight of about 300,000 (e.g. POLYOX WSR-N-750). A 60:40 blend of these two polyethylene oxides (5 million: 300,000) is especially preferred. 
     Suitable water-insoluble polymers which can be used include polyethylene, polypropylene, polystyrene, butadiene-styrene copolymer (e.g. medium and high impact polystyrene), polyacetal, acrylonitrile-butadiene-styrene copolymer, ethylene vinyl acetate copolymer, polyurethane and blends thereof such as polypropylene/polystyrene blend or polystyrene/impact polystyrene blend. The more preferred water-insoluble polymer is polystyrene, preferably a general purpose polystyrene, such as NOVA C2345A, or a high impact polystyrene (i.e. polystyrene-butadiene), such as NOVA 5410 or Total 975E. The strip or any portion should contain a sufficient quantity of water-insoluble polymer to provide adequate mechanical strength, both during production and use. 
     The upper layer or portion  24  of the shaving aid strip  22  may also include a material which allows it to wear more quickly and/or which facilitates the inclusion of relatively high levels of water-soluble polymer. One such material is polycaprolactone, as described in copending application U.S. Ser. No. 09/506,628 (Docket No. 8070) filed on Feb. 18, 2000. Preferably, the polycaprolactone will be included in an amount of about 1% to about 10% by weight. Polycaprolactones are available from PERSTOP/SOLVAY under the name CAPA® polymers (e.g., 6100, 6505, 65065 and 6800). Preferably, the polycaprolactone will have a molecular weight between about 1000 and about 80,000 daltons, more preferably between about 30,000 and 60,000 daltons, and most preferably about 50,000 daltons. 
     The shaving aid strip, or any portion, also may contain other conventional shaving aid ingredients, such as low molecular weight water-soluble release enhancing agents such as polyethylene glycol (MW&lt;10,000, e.g., 1-10% by weight PEG-100), water-swellable release enhancing agents such as cross-linked polyacrylics (e.g., 2-7% by weight), antioxidants, preservatives, botanical oils, vitamin E, aloe, cooling agents, essential oils, beard softeners, astringents, medicinal agents, mineral oil, etc. 
     The upper layer  24  comprises a first color. The first color is preferably green. The upper layer  24  is preferably colored green with a green dye or pigment such as phthalocyanine pigment green  7 . The base layer  26  comprises a second color which is different from the first color. The second color is preferably white. The base layer  26  is preferably colored white with a dye or pigment such as titanium dioxide. The base layer  26  may be colored red with a dye or pigment such as DPP pigment red 254 
     A wear indicating effect is produced when the upper and base layers are made of disparately colored materials (e.g. green colored upper layer and white or red colored base layer). Upon use, the upper layer  24  at the skin engaging surface is typically worn off (or eroded) through use. With sufficient use, the base layer  26  is exposed, thus providing the user with an indication via the color change from the first color to the second color that the razor cartridge and/or skin engaging surface have reached the end of their optimal effective life or optimal performance and should be replaced. 
     The colorants may be released by leaching or abrasion. A layer may contain, for example, between about 0.1% and about 5.0% (preferably between about 0.5% and 3%) colorant by weight. 
     The first layer  24  has a first thickness dimension  25 . Preferably the first thickness dimension  25  is from about 0.2 to about 1.0 mm. The base layer  26  has a second thickness dimension  27 . Preferably, the first thickness dimension  25  is less than the second thickness dimension  27 . Preferably, the second thickness dimension  27  is from about 1.0 to about 3.0 mm. 
     Skin engaging members of the present invention may be fabricated by any appropriate method, including injection molding and extrusion, the latter being preferred. All of the components of the strip are blended prior to molding or extrusion. For best results, it is preferred that the components are dry. 
     The skin engaging member may be formed by combining extruders via an input transition die assembly. The upper layer may be delivered through a ¾ inch diameter Brabender PL2200 Plasti-corder, with a pressure of about 2500-8000 psi, a rotor speed of about 12 to 25 rpm, and a temperature of about 2450-380° F. The extruder may be ½ to 1 inch in diameter. The base layer may be delivered through a 1.5 inch diameter Davis Standard with a pressure of about 2500-3500 psi, a rotor speed of about 10 to 20 rpm, and a temperature of about 290°-385° F. The extruder may be ¾ to 1.5 inch in diameter. The die assembly may be between about 350°-420° F. The feed throat sections for the extruders may be cooled to about 62° F. The output speed may be between about 30 to 70 feet per minute. 
     Referring now to  FIGS. 5-7 , the blade exposure is defined to be the perpendicular distance or height of the blade edge measured with respect to a plane tangential to the skin contacting surfaces of the blade unit elements next in front of and next behind the blade edge. Therefore, for the razor cartridge  14  of the present invention, the exposure of the cap blade  19  is measured with reference to a plane  50  tangential to the edge  18 ′ of the adjacent blade  18  and either the exposed surface of the skin engaging member  22  or the cap edge  48 . 
     In  FIG. 5  the razor cartridge  14  is shown prior to use. The exposure  52  of the cap blade  19  prior to use in this embodiment is about +0.2 mm. The exposure of the cap blade  19  prior to use is measured with reference to plane  50  tangential to the edge  18 ′ of the adjacent blade  18  and the upper surface  31  of the upper layer  24 . Prior to use the upper surface  31  of the upper layer  24  is the exposed surface of the skin engaging member  22 . 
     In  FIG. 6  the razor cartridge  14  is shown after several shaves. The exposure  52  of the cap blade  19  after several shaves is about +0.25 mm. The exposure of the cap blade  19  after several shaves is measured with reference to plane  50  tangential to the edge  18 ′ of the adjacent blade  18  and the exposed surface of the upper layer  24 . After several shaves the exposed surface is located between the upper surface (no longer present) and the lower surface  32  of the upper layer  24 . After several shaves a portion of the upper layer  24  has eroded away and thus the original upper surface  31  is no longer present. 
     In  FIG. 7  the razor cartridge  14  is shown after numerous shaves. The exposure  52  of the cap blade  19  after numerous shaves is about +0.3 mm. The exposure of the cap blade  19  after numerous shaves is measured with reference to plane  50  tangential to the edge  18 ′ of the adjacent blade  18  and the cap edge  48  and the upper surface  33  of base layer  26 . After the numerous shaves the entire upper layer has eroded away and thus the upper surface and lower surface of the upper layer  24  are no longer present. The location of the upper surface  33  of the base layer  26  is positioned substantially equivalent to or aligned with the cap edge  48 . 
     The end of optimal shave performance is reached when the entire upper layer  24  has eroded away. At this point in time the edge  18 ′ of the adjacent blade  18 , the cap edge  48  and the upper surface  33  of the base layer  26  define the exposure of the cap blade  19 . This situation is a very short period of time as any additional shaves will start to erode the base layer  26 . Once erosion of the base layer  26  has started the exposure of the cap blade  19  will be defined by the edge  18 ′ of the adjacent blade  18  and the cap edge  48  as the position of these two elements is forever fixed. 
     Thus, having the dividing line between the upper layer  24  and the base layer  26  positioned substantially equivalent to or aligned with the cap edge  48  provides an indication that directly correlates with the change between an optimal shave performance and a sub-optimal shave performance. The dividing line between the upper layer  24  and the base layer  26  may be defined by the upper surface  33  of the base layer  28 . 
     Referring to  FIG. 8  skin engaging member  22  includes an exposed lengthwise-extending erodible skin engaging upper layer or portion  24  and a lengthwise-extending erodible skin engaging base layer or portion  26  positioned below the upper layer  24 . The base layer  26  preferably extends under the upper layer  24  and provides support for upper layer  24 . Base layer  26  also includes connecting portion  30  which serves to lock the skin engaging member into a mating receiving portion of the cartridge. Base layer  26  has an upper surface  33 . 
     The upper layer  24  includes two upper layers  60  and  61 . Upper layer  60  is preferably colored green and upper layer  61  is preferably colored yellow. 
     Referring to  FIG. 9  skin engaging member  22  includes an exposed lengthwise-extending erodible skin engaging upper layer or portion  24  and a lengthwise-extending erodible skin engaging base layer or portion  26  positioned below the upper layer  24 . The base layer  26  preferably extends under the upper layer  24  and provides support for upper layer  24 . Base layer  26  also includes connecting portion  30  which serves to lock the skin engaging member into a mating receiving portion of the cartridge. Base layer  26  has an upper surface  33 . 
     The upper layer  24  includes three upper layers  60 ,  61  and  62 . Upper layer  60  is preferably colored green, upper layer  61  is preferably colored yellow and upper layer  62  is preferably colored white. 
     The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.” 
     All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern. 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.