Abstract:
A shaving unit that comprises at least one blade and a skin engaging member that has a surface for engaging the user&#39;s skin adjacent the blade edge is described herein. The shaving unit may be of a disposable cartridge type adapted for coupling to and uncoupling from a razor handle or may be integral with a handle so that the complete razor is discarded as a unit when the blade or blades become dulled. The blade edge (or edges) cooperate with skin engaging surfaces to define a shaving geometry. The skin engaging member is comprised of an elongated sheath (or skin engaging layer) made of a mixture of water insoluble matrix and an effective amount of shaving aid and a rigid core (or non-skin engaging layer) extending axially throughout said sheath. The axial position of the core need not be through the central axis.

Description:
This application is a continuation of U.S. application Ser. No. 08/926,819, filed Sep. 10, 1997, now U.S. Pat. No. 6,944,952, which is a continuation of U.S. application Ser. No. 08/461,318, filed Jun. 20, 1995, now U.S. Pat. No. 6,594,904, which is a continuation-in-part of U.S. application Ser. No. 08/269,495, filed Jul. 1, 1994, now abandoned. 

   BACKGROUND 
   1. Field of the Invention 
   This invention relates to an improved skin engaging member for use in razor blade cartridge assemblies and shaving systems of the wet shave type. The present invention resides broadly in providing the skin engaging cap and/or guard surfaces with configurations which reduce frictional drag of the razor across the skin. This invention also relates to a novel method of manufacturing the skin engaging member of the present invention. 
   2. Description of the Prior Art 
   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 non-water-soluble material, e.g., a polystyrene polymer, to form an insoluble polymer/soluble shaving aid composite. The composite 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 composite onto the skin. 
   Extruded composites with relatively large amounts of shaving agent material (up to 80% by weight) and relatively low amounts of water insoluble matrix material (as little as 20%/o by weight) are relatively weak and have a tendency towards mechanical failure, both in assembly and in use. Increase in mechanical strength can be obtained with increased amounts of the matrix material. However, such increase reduces the releasability of the shaving agent material. 
   SUMMARY 
   In accordance with one aspect of the invention, there is provided a shaving unit that comprises at least one blade and a skin engaging member that has a surface for engaging the user&#39;s skin adjacent the blade edge. The shaving unit may be of a disposable cartridge type adapted for coupling to and uncoupling from a razor handle or may be integral with a handle so that the complete razor is discarded as a unit when the blade or blades become dulled. The blade edge (or edges) cooperate with skin engaging surfaces to define a shaving geometry. The skin engaging member is comprised of an elongated sheath (or skin engaging layer) made of a mixture of water insoluble matrix and an effective amount of shaving aid and a rigid core (or non-skin engaging layer) extending axially through out the sheath. The axial position of the core need not be through the central axis. 
   An object of the present invention is to provide a skin engaging member with improved mechanical strength. 
   Another object of the present invention is to provide a skin engaging member with improved shaving aid release characteristics. 
   Yet another object of the present invention is to provide a wear indicating skin engaging member. 
   These and other objects should be evident from the following: 

   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  is a perspective view of a razor unit in accordance with the invention; 
       FIG. 2  is a sectional view taken along the line  2 — 2  of  FIG. 1 ; 
       FIG. 3  is a sectional view of another razor unit in accordance with the invention; 
       FIG. 4  is an enlarged perspective view of a skin engaging member of the present invention; 
       FIG. 5  is a sectional view taken along the line  3 — 3  of  FIG. 4 ; 
       FIGS. 6–7  are sectional views in accordance with  FIG. 5  wherein alternate core geometries are depicted; 
       FIG. 8  is a cross-sectional view of the skin engaging member of  FIG. 1 ; and 
       FIG. 9  is a schematic cross-section diagram of an extrusion die suitable for manufacturing the skin engaging member of  FIG. 4 . 
   

   DETAILED DESCRIPTION 
   The shaving unit (or razor cartridge)  10  shown in  FIGS. 1 and 2  includes base or platform member  12  molded of high impact polystyrene that includes integral coupling groove structure  14  for attachment to a razor handle and guard structure  16  that defines a transversely extending forward skin engaging surface  18 . On the upper surface of platform  12  are disposed steel leading blade  20  having a sharpened edge  22 , steel following blade  24  having sharpened edge  26 , and aluminum spacer member  28  that maintains blades  20  and  24  in spaced relation. Cap member  30  is molded of high impact polystyrene and has body portion  32  that defines skin engaging surface  34  that extends transversely between forwardly projecting end walls  36  and has a front edge  38  that is disposed rearwardly of blade edge  26 . Integral rivet portions  40  extend downwardly from transversely extending body portion  32  and pass through holes in blades  20  and  24 , spacer  28 , and platform  12  to secure cap  30 , blades  20 ,  24  and spacer  28  on platform  12 . Adhesively affixed to skin engaging surface  34  is skin engaging member  42 . 
   The shaving unit (or razor cartridge)  50  shown in  FIG. 3  is of the type shown in Jacobson U.S. Pat. No. 4,586,255 and includes body  52  with front portion  54  and rear portion  56 . Resiliently secured in body  52  are guard member  58 , leading blade unit  60  and trailing blade unit  62 . A shaving aid composite in the form of elongated skin engaging member  64  is frictionally locked in opening  66  of rear portion  56 . 
     FIGS. 4–8  generally depict variations on the present invention. As used herein, the term “core” refers to an internal portion of a skin engaging member as examined at the cross-section. The core typically runs throughout the skin engaging member along an axis. The axis need not be the central axis. The FIGS. designate the core as  70 . Embodiments of the present invention have at least one core element. As used herein, the term “sheath” refers to an outer coating layer(s) over the core. The FIGS. designate the sheath as  72 . 
   Referring now to the drawings, and in particular to  FIG. 4 , there is shown an elongated skin engaging member  64 . The member  64  has a skin engaging surface  74  and an elongated insert member  76 . The insert member  76  is designed to frictionally lock in an opening  66  as shown in  FIG. 3 . The skin engaging member further comprises a rigid core  70  which is surrounded by a sheath  72  made of a mixture of water insoluble matrix and an effective amount of a shaving aid. 
   The sheath includes from about 0% to about 30% by weight, preferably from about 5% to about 15%, of the water insoluble matrix and from about 70% to about 100% by weight of the water soluble shaving aid, preferably from about 85% to about 95% shaving aid. Suitable water insoluble polymers for the matrix include, for example, nylon, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polystyrene, polyacetal and combinations. Suitable shaving aids include, for example, polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxypropyl cellulose, polyvinyl imidazoline, polyethylene glycol, polyvinyl alcohol, methylcellulose, starch, water soluble vinyl polymers (Carbopol® brand sold by B.F. Goodrich), polyhydroxyethylmethacrylate, silicone copolymers, sucrose stearate, vitamin E, panthenol, aloe, essential oils such as menthol and combinations. The examples illustrate sheaths comprising from 65% to 82% polyethylene oxide. 
   The sheath may include additional components such as: plasticizers, such as polyethylene glycol; beard softeners, such as Kraton G 13 A; additional lubricants, such as silicone oil, Teflon® polytetrafluoroethylene powders (manufactured by DuPont), and waxes; shaving aids, such as menthol, eugenol, eucalyptol, safrol and methyl salicylate; fillers, such as calcium carbonate, mica and fibers; tackifiers such as Hercules Regalrez 1094 and 1126; fragrances; antipruritic counterirritant materials such as Frescolat; antimicrobial/keratolytic materials such as Resorcinol; anti-inflammatory agents such as Candilla wax and glycyrrhetinic acid; astringents such as zinc sulfate; surfactants such as pluronic and iconol materials; compatibilizers such as styrene-b-EO copolymers; and, blowing agents such as Uniroyal Celogen Aznp 130. These additives may leach from the surface to provide improved shaving. These components could be dispersed throughout the sheath or alternatively, a second, outer sheath containing the additional element could be extruded or merely coated over the primary sheath. 
   The present skin engaging member is produced by a coextrusion process whereby a rigid core displaces a portion of the sheath. The nature and relative portions of the sheath and core polymeric materials are such that the skin engaging member has adequate mechanical strength, both as initially produced and after a significant amount of water soluble material has been leached out, the quantity of the water-soluble material being sufficient to provide effective shaving assistance, such as lubrication, for the entire expected life of the blade or blades. The function of the core is not only to provide additional rigidity but to displace trapped shaving aid. In conventional skin engaging members, such as those described in U.S. Pat. Nos. 5,063,667; 5,095,619; and 5,113,585, a significant amount of shaving aid is trapped within the insoluble matrix. By displacing it closer to the skin engaging surface  74 , diffusional paths are reduced and more efficient delivery is achieved. Furthermore, the core provides additional mechanical strength for the attaching mechanism, if used. 
   The core must have sufficient mechanical strength and rigidity to provide adequate mechanical strength to the entire skin engaging member, both as initially produced and after a significant amount of water soluble material has been leached out of the sheath. Preferably, the core can be made from a water insoluble polymer or a blend consisting of at least about 50% of water insoluble polymer to prevent the core from disintegrating. Water-soluble polymers for use in such blends include polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxypropyl cellulose, polyvinyl imidazoline, polyethylene glycol, polyvinyl alcohol, methylcellulose, starch, water-soluble vinyl polymers (Carbopol® brand sold by B.F. Goodrich), polyhydroxyethylmethacrylate, and combinations thereof. Suitable water insoluble polymers for use in the core include polystyrene, high impact polystyrene, polypropylene, filled polypropylene, nylon, and blends thereof such as 70% nylon/30% polyethylene oxide, 60% polystyrene/40% polyethylene oxide. 
   Optionally, the core can include additives such as lubricants foaming agents, microspheres, baby powders, fillers such as CaCO 3 , colorants such as TiO 2  silicone copolymers, sucrose stearate, vitamin E, panthenol,  aloe , essential oils, e.g. menthol, and combinations thereof. 
   In an embodiment of the present invention a wear indicating effect is produced using indicating means that may include, for example, a sheath and a core made of disparately colored materials (e.g. white colored sheath and blue colored core). Upon use, the sheath at the skin engaging surface is typically worn off (or eroded) through use. With sufficient use, a second colored region represented by the core is exposed, thus, providing the user with an indication that the shaving unit and/or skin engaging surface have reached their effective life. In a preferred embodiment, the sheath consists of a polyethylene oxide/polystyrene mixture which is white in color and the core consists of nylon and/or styrene which has been colored with a FD&amp;C Blue No. 2 dye. Other suitable dyes or pigments include FD&amp;C Red No. 40, Erythrosine (FD&amp;C Red No. 3), Brilliant Blue FCF (FD&amp;C Blue No. 1), Indigotine (FD&amp;C Blue No. 2), Tartrazine (FD&amp;C Yellow No. 5), Sunset Yellow FCF (FD&amp;C Yellow No. 6) and Fast Green FCF (FD&amp;C Green No. 3) and Titanium Dioxide. The indicating means above is merely illustrative. Any other suitable indicating means, may be used in accordance with the present invention. 
     FIG. 5  depicts a cross section of an alternate skin engaging member. The core  70  follows the general contours of the surface defined by the outside of the sheath.  FIG. 6  depicts a slight variation on that theme where a thicker sheath layer is provided along the skin engaging surface  74 . Still further,  FIG. 7  provides a cross-section wherein a very high degree of sheath material is present along the skin engaging surface. 
   Finally,  FIG. 8  depicts the skin engaging member depicted in  FIGS. 1 and 2 . It is interesting to note that the core in this case provides mechanical strength to the unit yet is not vital to the mechanical locking of the unit. The skin engaging member of  FIGS. 1 and 2  is affixed by adhesive. According to the present invention, the skin engaging members may be affixed by adhesive such as Loctite Super Bonder 499, mechanical locking mechanism, thermal welds. 
     FIG. 9  is a schematic cross section diagram of an extrusion die suitable for manufacturing the skin engaging member of the present invention. Core material  80  is fed into the intrusion die  81  by an extrusion screw, hot melt or other suitable means. In the core inlet port  82  the tight core orifice  83  encounters the sheath material  86 , which has been fed into sheath inlet port  84 , wherein the core becomes encapsulated by the sheath material when viewed in a transverse cross section to the flow of the die material. The encapsulated core then proceeds to the die outlet  85  wherein the continuous skin engaging members can be cured and/or drawn down to provide the appropriate dimensions. Also, it should be noted that the core material could consist of a solid wire or solid plastic material which is fed in through a conventional die to produce an encapsulated skin engaging member. For general discussion of coextrusion technology see Levy, Plastics Extrusion Technology Handbook, Industrial Press Inc., pages 168–188 (1981), incorporated herein by reference. After the continuous skin engaging members are produced, the strand is sent for further processing where it is typically drawn down to the correct size and cut to length suitable for implant into the body of a razor blade cartridge. This cutting can be achieved by knife edge cutting, lasers or water lasers. The skin engaging surfaces of the present invention typically are rectangular in shape with a width of from about 0.05 inches to about 0.1 inches and a length of about 1.2 inches. 
   Applicant considers equivalent embodiments to be part of the present invention. For example, non-rectangular skin engaging surface areas may be utilized (such as ovals) and non-flat surface patterns could be utilized. These and other equivalent embodiments are also contemplated by the present invention. The present invention and the manner of making and using the same should be evident form the following examples: 
   EXAMPLES 
   The following samples were coextruded with a cross-section as in  FIG. 5 . 
   
     
       
             
             
             
           
             
             
             
           
         
             
                 
             
             
               No. 
               Core Composition 
               Sheath Composition 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               1 
               Nylon 70% 
               10% polystyrene 
             
             
                 
               blue pigment 0.5% 
               76% polyethylene oxide 
             
             
                 
               polyethylene oxide 29.5% 
               8% polyvinyl alcohol 
             
             
                 
                 
               5% polyethylene glycol 
             
             
                 
                 
               1% white pigment 
             
             
               2 
               25% polythylene oxide 
               78% polyethylene oxide 
             
             
                 
               75% nylon 
               14% polystyrene 
             
             
                 
                 
               3% polyethylene glycol 
             
             
                 
                 
               5% polyvinyl alcohol 
             
             
               3 
               100% polystyrene 
               82% polyethylene oxide 
             
             
                 
                 
               14% polystyrene 
             
             
                 
                 
               3% polyethylene glycol 
             
             
                 
                 
               1% polyvinyl alcohol 
             
             
               4 
               70% nylon 
               80% polyethylene oxide 
             
             
                 
               29.5% polyethylene oxide 
               16% polystyrene 
             
             
                 
               10.5% blue dye 
               4% polyvinyl alcohol 
             
             
               5 
               98% polystyrene 
               73% polyethylene oxide 
             
             
                 
               2% blue dye 
               5% Salsorb 
             
             
                 
                 
               5% polyvinyl alcohol 
             
             
               6 
               100% polystyrene 
               74% polyethylene oxide 
             
             
                 
                 
               10% polystyrene 
             
             
                 
                 
               10% polyvinyl alcohol 
             
             
                 
                 
               5% polyethylene glycol 
             
             
                 
                 
               1% white TiO2 pigment 
             
             
               7 
               98% polystyrene 
               68% polyethylene oxide 
             
             
                 
               2% blue dye 
               15% polyvinyl alcohol 
             
             
                 
                 
               10% polystyrene 
             
             
                 
                 
               5% polyethylene glycol 
             
             
                 
                 
               2% white TiO2 pigment 
             
             
               8 
               100% polystyrene 
               67% polyethylene oxide 
             
             
                 
                 
               4% Salsorb 
             
             
                 
                 
               14% polyvinyl alcohol 
             
             
                 
                 
               10% polystyrene 
             
             
                 
                 
               4% polyethylene glycol 
             
             
                 
                 
               1% white TiO2 pigment 
             
             
               9 
               99% polystyrene 
               68% polyethylene oxide 
             
             
                 
               1% blue dye 
               20% polyvinyl alcohol 
             
             
                 
                 
               10% polystyrene 
             
             
                 
                 
               2% white TiO2 pigment 
             
             
               10 
               99% polystyrene 
               70% polyethylene oxide 
             
             
                 
               1% blue dye 
               13% polyvinyl alcohol 
             
             
                 
                 
               15% polystyrene 
             
             
                 
                 
               2% white TiO2 pigment 
             
             
               11 
               99% polystyrene 
               65% polyethylene oxide 
             
             
                 
               1% blue dye 
               15% polyvinyl alcohol 
             
             
                 
                 
               15% polystyrene 
             
             
                 
                 
               3% Salsorb 
             
             
                 
                 
               2% white TiO2 pigment 
             
             
               12 
               99% polystyrene 
               65% polyethylene oxide 
             
             
                 
               1% blue dye 
               10% polyvinyl alcohol 
             
             
                 
                 
               15% polystyrene 
             
             
                 
                 
               3% Salsorb 
             
             
                 
                 
               2% white TiO2 pigment 
             
             
                 
             
           
        
       
     
   
   Example 13 
   The following procedure can be used to produce a skin engaging member of the type depicted in  FIG. 4 . 
   The extrusion equipment includes two single-screw extruders, a die cross-head, a cooling channel, and a puller. The strip extruded from the extruders is pulled through a cooling tunnel by a Farris puller (a take-off machine) at a speed of approximately 10 feet per minute with minimum tension on the strip. The strip is air-cooled by blowing dry compressed air into the tunnel at approximately 10 CFM. The extrudate is kept in a cool, dry room. 
   The core blend (70% Zytel 330 brand amorphous nylon/blue pigment, 30% polyethylene oxide blend 60/40 is extruded through the first ¾″ Haake extruder (barrel pressure of 4,343 psi and temperature of 180 EC). The sheath blend (80% polyethylene oxide blend 60/40, 14% polystyrene/white color, 3% PED, and 3% PVA 2025) is extruded through the second ¾″ Haake extruder (barrel pressure of 6,131 psi and temperature of 180 EC). The two materials are then joined and are fed through a cross-head at a temperature of 180 EC, die temperature of 180 EC, and die pressure of 3,600 psi to form a continuous lubricating strip. The line speed is approximately 10 FPM.