Patent Publication Number: US-7210229-B2

Title: Razor cartridge

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This is a continuation-in-part of application Ser. No. 10/132,536 filed Apr. 24, 2002, now abandoned the disclosure of which is herein incorporated by reference. 

   FIELD OF THE INVENTION 
   The invention is generally directed to a wet-shave razor cartridge, and more specifically to a wet-shave razor cartridge having multiple razor blades. 
   BACKGROUND OF THE INVENTION 
   The comfort and performance provided by a particular razor is critical to the commercial success of that razor. Modern safety razors used in wet shaving operations to cut hair on hirsute surfaces typically are available in two types—a replaceable having a handle that uses a disposable razor cartridge, or a disposable having a handle combined with a razor cartridge such that the razor cartridge cannot be removed from the handle without destruction of one, the other or both. There are many design similarities between the razor cartridges used in each razor type. 
   Generally, the razor cartridge contains a number of blades with each blade defining a cutting edge; employing a plurality of cutting edges increases the shaving efficiency of the razor by increasing the number of times any one hair is cut in a single pass thereby decreasing the number of strokes necessary to satisfactorily shave a particular hirsute surface. The fewer number of strokes required over any given surface, the less the potential for irritation of that surface. 
   The typical multi-blade razor cartridge includes a frame that supports two or more razor blades. A typical frame can be of a single formed piece of plastic or can be any number of assembled parts. The frame typically provides a leading surface and a trailing surface to which the cutting edges are generally parallel. In use, the hirsute surface being shaved contacts in turn the leading surface, the cutting edges of the blades, and the trailing surface. 
   The leading surface and the trailing surface are generally at opposite sides of an opening defined by the frame in which at least a portion of the cutting edges are exposed. The leading and the trailing surfaces can be used to define a plane that extends over the opening and is approximately tangent to the leading and trailing surfaces. This plane is referred to by those skilled in the art to which the invention pertains, as a “contact plane” and is used as a reference for both qualifying and quantifying the exposure of a cutting edge. 
   With reference to the contact plane, a cutting edge can be qualified as having an exposure that is neutral, positive, or negative. A cutting edge has a neutral exposure if the entire cutting edge is on the contact plane. A cutting edge has a negative exposure if it is neither on nor extends through the contact plane. Similarly, if a cutting edge extends through the contact plane, its exposure is positive. 
   Historically, cutting edge exposure has been neutral, however, this does not necessarily render the closest shave at an acceptable comfort level. Accordingly, it is the general object of the present invention to provide a razor cartridge that improves upon or eliminates the problem associated with the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention is directed in one aspect to a razor cartridge having a frame. The frame has an opening defined in part by a leading surface and a trailing surface, which cooperate to define a contact plane tangential thereto and extending across the opening. At least two razor blades, each having a cutting edge, are coupled to the frame with each cutting edge positioned at least in part in the opening. All of the cutting edges either have a common positive cutting edge exposure or a common negative cutting edge exposure. 
   In accordance with the present invention, the distance from the contact plane with regard to a set of blades all having either a positive or a negative exposure can vary from blade to blade. Alternatively, the distance from the contact plane can be constant for each cutting edge. Moreover, the distance from the contact plane can vary from blade-to-blade in accordance with a linear or non-linear function. 
   In an embodiment of the present invention, at least one blade is angularly offset or skewed relative to another blade. Skewed blades can provide for more effective wash through and thereby debris removal than parallel blades. While one blade has been described as being skewed relative to other blades, the present invention is not limited in their regard as any number, or all of the blades can be skewed without departing from the broader aspects of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a razor. 
       FIG. 2  is a top view of a razor cartridge. 
       FIG. 3  is a diagrammatic front view of a razor cartridge. 
       FIG. 4  is a side elevational cross-sectional view of a four-bladed razor cartridge in accordance with the present invention. 
       FIG. 5  is a side elevational cross-sectional view of a five-bladed razor cartridge in accordance with the present invention. 
       FIGS. 6A–D  schematically illustrate different razor blade orientations relative to the contact plane. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As shown in  FIG. 1 , a wet shaving razor, generally referred to by the reference number  10 , includes a handle  12  coupled to a razor cartridge  14 . The coupling can either be temporary or permanent; the razor  10  is either a replaceable or disposable. In either case, the razor cartridges  14  employed are generally similar. 
   As shown in  FIGS. 2 through 5 , the razor cartridge  14  includes a frame  16  having a number of razor blades  20  (four in  FIG. 4  and five in  FIG. 5 ), coupled thereto. The frame  16  defines an opening  18  wherein a portion of cutting edges  22  defined by each razor blade  20  are exposed. The frame  16  includes a base  24  that defines a plurality of slots  26  that are separated by spacers  28 . Each slot  26  is sized to hold a razor blade  20  at the orientation required and to space the cutting edges  22  one from the other. 
   The frame  16  has a leading surface  30  and a generally opposite trailing surface  32 . During a shaving operation, a hirsute surface contacts in turn the leading surface  30 , the cutting edges  20 , and the trailing surface  32 . The leading surface  30  is defined by a guard  34  and the trailing surface  32  is defined by a guard  36 , where both the cap and the guard are mounted to the base  24 . While the frame  16  has been shown and described as including a cap  36  and a base  24 , the present invention is not limited in this regard. For example, the cap  36  could be replaced by a comfort strip. In addition, the cap  36  and the guard  34  could be molded into the frame  16  and not be separate parts to be attached to a base  24 . 
   The leading surface and the trailing surface,  30  and  32  respectively, cooperate to define a contact plane  38  tangential thereto that extends across the opening  18 . In the illustrated embodiment, the contact plane  38  is defined by a surface created by a series of approximately parallel lines extending between and contacting the leading surface  30  and the trailing surface  32 , over the opening  18 . As shown in  FIGS. 4 and 5 , the lines that define the contact plane  38  tangentially contact the curved leading surface  30  and the curved trailing surface  32  defining a line contact with both the leading and trailing surfaces. While a planar contact plane has been illustrated, the present invention is not limited in this regard as the contact plane  38  could be of almost any contour. For example, if the leading and trailing edges,  30  and  32  respectively, were to undulate, the contact plane  38  would also undulate. 
   The contact plane  38  permits the cutting edge exposure for the cutting edges  22  of each razor blade  20  to be categorized as neutral, positive, or negative. A cutting edge  22  has neutral cutting edge exposure if the entire cutting edge is on the contact plane. A cutting edge  22  has positive cutting edge exposure if any portion of the cutting edge extends through the contact plane  38 . A cutting edge  22  has a negative exposure if the cutting edge neither touches, nor extends through the contact plane  38 . 
   The base  24  includes flow members  40  positioned between successive razor blades  20  and between the razor blades and the frame  16 . There may be any number of flow members  40 , that can be equally or unequally spaced. The flow members  40  engage a hirsute surface at or about the contact plane  38 . The flow members  40  preferably have a small tip radius of about 0.02 to 0.5 mm. However, the present invention is not limited in this regard as other radii can be employed. During a shaving operation, the flow members  40  support the hirsute surface and prevent it from entering the interstitial areas between the razor blades  20  and the razor blades and the frame  16 , thereby reducing razor bum or nicking of the hirsute surface. The number and size of the flow members  40  should be selected to minimize the interference with as much of a cutting edge  22  as possible. 
   Referring to  FIG. 4 , the cutting edges  22  are positioned on a line  42  such that the cutting edges  22  have a common, positive cutting edge exposure wherein each razor blade  20  penetrates the contact plane  38 . Referring to  FIG. 5 , the cutting edges are positioned on a line  44  such that the cutting edges  22  have a common, negative cutting edge exposure. In this case, the razor blade does not penetrate the contact plane  38 . 
   Referring to  FIGS. 6A–D  several patterns of common, negative cutting edge configurations are illustrated. While  FIG. 6  depicts only common, negative cutting edge configurations, it should be readily apparent that similar common, positive cutting edge configurations are possible. 
   In  FIG. 6A , a two-blade all negative configuration is shown wherein the cutting edges  22  are positioned along a line  46  such that each cutting edge is the same distance “u” from the contact plane  38 . It is preferred that the distance from contact surface to contact surface be no greater than about 0.2mm, such as between two adjacent cutting edges  22  or between a cutting edge and an adjacent surface, e.g., leading surface  34  or trailing surface  36 , however, the present invention is not limited in this regard. 
   As shown in  FIG. 6B  a four-blade all negative configuration includes cutting edges  22  located along a line  48  that defines a fair function f( a ). In this embodiment, the razor blades  20  are depicted as being generally parallel giving a constant separation distance x between adjacent razor blades. Separation between adjacent cutting edges  22  is preferably between 0.3, 1.0mm, and more preferably 0.5 mm. However, the invention is not limited in this regard. Separation between adjacent cutting edges  22  does not have to be uniform. Also shown in this embodiment is at least one razor blade  20  having at least one hole  50  therein to allow for the passage of fluid to assist in the removal of shaving debris that accumulates between razor blades and between a razor blade and the frame  16 . 
     FIG. 6C  shows a four-blade all negative configuration wherein two pairs of non-adjacent razor blades  20  all are the same distance u and v from the contact plane  38 . One pair of cutting edges  22  is on one line  52  and the other pair is on another line  54 . The first pair is off the contact plane  38  by a distance denoted by u, and the second pair is off the contact plane by a distance denoted by v. This embodiment further shows that the razor blades  20  do not necessarily have to be parallel one to the other. One of the outer razor blades  20  is skewed by an angle a relative to an adjacent razor blade. Divergence of the razor blades  20  from the cutting edge  22  assists in debris removal from between the razor blades. 
     FIG. 6D  shows a four-blade negative configuration wherein each cutting edge  22  is a different distance (t, u, v, w) from the contact plane  38  and has different spacing (x, y z). In this configuration, one cutting edge  22  is on a first line  56 , a second cutting edge is on a second line  58 , a third cutting edge is on a third line  60 , and a fourth cutting edge is on a fourth line  62 . 
   Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible, particularly versions wherein the contact plane or razor blades are not planar, and the cutting edges have a geometry other than a line. Therefore, the spirit and scope of the invention should not be limited to the description of the preferred versions contained herein.