Patent Application
20050198837
The invention relates to shaving razors with multiple blades.
In recent years shaving razors with various numbers of blades and geometries have been proposed in the patent literature and commercialized, as described, e.g., in U.S. Pat. No. 6,212,777 and U.S. Published patent applications Nos. 2002/0144404 A1 and 2002/0157259 A1.
Increasing the number of blades on a shaving razor generally tends to increase the shaving efficiency of the razor and provide better distribution of compressive forces on the skin but it can also tend to increase drag forces, reduce maneuverability, and reduce the ability to trim. Increasing the number of blades also requires increasing the area occupied by blades or reducing the spacing between the cutting edges of the blades. Increasing the area occupied by blades can affect shaving performance. Reducing the spacing between blades results in a change on the skin bulge between cutting edges and the effectiveness of the shave, potentially requiring changes in other parameters in blade geometry such as blade tangent angle and exposure. Increasing the number of blades can also affect the rinsability of the razor, which affects the ability to remove shaving debris from the blade area.
The invention features, in general, a shaving razor blade unit including a housing, and a shaving surface defined by a group of at least five parallel blades supported by the housing, the distance from the cutting edge of a first blade of the group to a last blade of the group being between 3.8 mm and 4.6 mm, preferably between 4.0 mm and 4.4 mm, and most preferably between 4.1 mm and 4.3 mm.
Particular embodiments of the invention may include one or more of the following features. In particular embodiments, the span between cutting edges is between 0.95 mm and 1.15 mm, preferably between 1.0 mm and 1.1 mm, most preferably about 1.05 mm. The exposure of blades between the first blade and said the blade is approximately 0.0. The blades have a blade tangent angle between 18° and 25°, preferably between 20° and 23°, most preferably about 21.5°. The first blade has a negative exposure. The last blade has a positive exposure. The blades are movably mounted with respect to the housing, e.g., on support members that are movably mounted on the housing.
Embodiments of the invention may include one or more of the following advantages. Shaving razor blade units provide good force distribution over many blades and improved shaving performance without increasing the area taken up by the blade units to too large an extent while retaining rinse-through capability.
Other advantages and features of the invention will be apparent from the following description of particular embodiments and from the claims.
Referring to
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The increased number of blades tends to desirably distribute compressive forces of the blades against the skin, but will increase the area taken up by the blades if the spans remain the same, with potential difficulties in maneuverability and trimming. Reducing spans for an increased number of blades tends to desirably reduce the overall area taken up by blades and to reduce the bulge of skin between cutting edges with a potential improvement in comfort. Reducing the span, however, can reduce the rinsability and ability to clear shaving debris from the blade area. In a five-bladed razor, the lower end of the span range of 0.95 mm provides good comfort but increased potential for problems associated with clearing shaving debris, and the upper end of the span range of 1.15 mm provides good clearing of shaving debris but potential for skin bulge and decreased comfort, such that span values within the range, and in particular, values closer to the most preferred 1.05 mm span, provide a good balance of reduced size and good comfort while maintaining sufficient rinsability to avoid shaving debris problems. The distance ST from the first cutting edge 408 to the last cutting edge 408 is four times the inter-blade span and thus is between 3.8 mm and 4.6 mm, preferably between 4.0 mm and 4.4 mm and most preferably about 4.2 mm, i.e., between 4.1 mm and 4.3 mm.
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Elongated bent metal support 400 is made of metal that is between 0.004″ and 0.009″ thick (dimension T), preferably metal between 0.005″ and 0.007″ thick, and most preferably metal about 0.006″ thick. Platform portion 406 has a length LP length from its front end 452 to the bent portion 404 less than 0.7 mm, preferably less than 0.6 mm, and most preferably about 0.55 mm. The bent portion 404 has an inner radius of curvature R that is less than 0.1 mm, preferably less than 0.09 mm and most preferably less than 0.08 mm. The angle α between base portion 402 and platform portion 406 is between 108° and 115°, preferably between 110° and 113°, most preferably about 111.5°.
Other embodiments of the invention are within the scope of the appended claims.
