This invention relates to a wet shaving razor cartridge having at least two blades, where the primary blade is positioned at a greater angle relative to a blade plane than the final blade.
Safety razors used for wet shaving are well known. Over the years, wet shaving razors have evolved to include a multiplicity of blades with the goal of increasing the closeness of the shave that is achieved while also still providing a comfortable shaving experience. Razors currently on the market strive to achieve an optimum balance between efficiency, closeness and comfort of a shave. Achieving this balance is made difficult because of the many different types of hair, different shaving habits and variables of a razor cartridge that influence the shaving characteristics of a safety razor.
One such variable is the angle at which blades are presented to skin to be shaven. Wet shaving razors currently manufactured and sold by The Gillette Company® in the Fusion® range have five blades, positioned at an angle of 21.5° relative to a blade plane. Over the years, a considerable amount of research has been done to arrive at this optimal angle for blades in a cartridge that enables a close, efficient shave, without causing a user an unacceptable level of discomfort. In this respect, increasing the angle of the blades leads to an increase in efficiency and closeness of a shave but a decrease in comfort levels experienced by a user.
The present invention seeks to further improve the balance between closeness and comfort of a shave.
According to a first aspect of the invention, there is provided a wet shaving razor cartridge, comprising a housing, a primary blade located at a front end of the housing and a final blade located at a rear end of the housing, the primary and final blades having blade edges that extend in parallel to a length of the housing, a blade plane tangential to the primary blade edge and the final blade edge, wherein an angle αp between the primary blade and the blade plane is greater than an angle αf between the final blade and the blade plane.
The relative difference between angles αp and of will result in a difference between efficiency and closeness and comfort between the primary blade and the final blade. The angle αp of the primary blade will result in the primary blade providing a more efficient/close shave relative to the final blade, but a user will likely experience more discomfort from the primary blade than the final blade. As the primary blade is exposed to most hair and accordingly typically cuts more hairs than other blades in a multi-blade cartridge, the inventors have found that the decrease in comfort caused by the increase in angle of the primary blade is offset by the efficiency of the shaving stroke. Any discomfort caused by the primary blade is further offset by the relatively smaller angle of the final blade. The greater efficiency of the increase in angle of the primary blade results in an overall closer shave and fewer required strokes. Thus, overall, a user will experience a closer/more efficient shave without a significant decrease in comfort.
Embodiments of the invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which:
The invention is applicable to razor cartridges in general that are used in a wet shaving system.
The primary blade 40 extends away from the blade plane y at an angle αp relative to the blade plane while the final blade 44 extends away from the blade plane y at an angle αf relative to the blade plane. As shown in
A typical blade edge is shown in
As explained above, however, there is a trade-off between the increase in comfort and a decrease in efficiency and closeness of a shave. In this respect, as the angle α is decreased, there is a greater likelihood that contact between a blade edge and a hair will result in a “skive-cut”. A skive-cut occurs when the blade edge cuts into one side of a hair and, rather than cutting straight across the hair, cuts diagonally through the shaft, leaving one side of the hair longer than another side. By not cutting a hair cleanly, a user may need to shave more frequently, or increase the number of shaving strokes. By contrast, as the angle α is increased, there is less chance that contact between a blade edge and hair will result in a skive-cut, and the sharp tip 60 will penetrate hairs closer to the skin, thus resulting in a more efficient/close shave.
The present inventors have found that increasing the blade angle for all blades in a cartridge decreases the level of comfort experienced by a user by an unacceptable amount. However, by varying the angle of blades across a cartridge, it is possible to balance a slight decrease in comfort with increased efficiency across some blades, provided that for other blades, the balance is tipped towards increased comfort with a possible resultant decrease in efficiency.
In the embodiment shown in
In each of these cases, the first blade is expected to cut most efficiently but may cause the greatest amount of discomfort to a user. By contrast, the final blade will cut least efficiently, but will also cause the least amount of discomfort to a user.
In an embodiment shown in
In an alternative embodiment, not shown, the primary blade and one or more of the additional blades are positioned at an angle αp of between about 25°, 27°, 29°, 31° and 33° to 35°, 37°, 39°, 41° and 44° and any remaining additional blades and the final blade are positioned at an angle αf of between about 2°, 3° and 4° to about 5°, 6°, 7° and 8° less than αp.
In a preferred embodiment shown in
In preferred embodiments of the invention, the primary blade has a greater angle relative to the blade plane compared with the other blades in the cartridge and the primary blade has lower exposure compared with other blades in the cartridge. Thus, any decrease in comfort felt by the increase in blade angle is offset by the reduction in load applied to that blade. Where exposure and, accordingly, the load is greatest, the angle of the blade relative to the blade plane is smallest to maximize the feeling of comfort.
The blades of the present invention may be secured to the housing in any known way, for example, the blades may be attached to blade supports, or they may be bent blades that are secured directly to the housing. In embodiments of the present invention, the housing has a blade retaining member having a plurality of slots for receiving either the blade supports or, where bent blades are used, the blades. The angle of the respective blades relative to the blade plane can be determined by an angle in the blade support, where blade supports are used, or by a bend in a blade where bent blades are used. Alternatively, the angle of bend in the respective blade supports or bent blades may be kept the same, and the angle of the respective slots in the blade retaining member may be varied to result in blade edges at varying angles to the blade plane.
In typical cartridges, the blades are usually carried by the housing, which is generally a molded plastic frame, either independently of each other or in unison under forces imparted on the blades by the skin during shaving. In one embodiment of support within the housing, the blades are mounted fixedly within slots in a blade retaining member. In most instances, there will be one or more rigid blade retaining member disposed along a length of the housing to provide adequate and immovable support for the blades disposed therein. In another instance, the blades may be floatably mounted within the housing. Here, the plurality of blades is supported by one or more spring loaded blade retaining member where the blades are permitted to respond to the forces encountered during shaving.
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.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, 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.
Number | Date | Country | Kind |
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10190049.6 | Nov 2010 | EP | regional |