Patent Application
20070062047
This invention relates to razor blades, and more particularly, polymer coated razor blades.
Users of wet shaving razors are susceptible to excessive nicking and cutting. There are many possible explanations for this, but one of them is how the razor blade glides over the skin and how the skin bulge in front of the blade edge is managed. Moreover, as the number of razor blades per cartridge increases, the blade drag against the skin can also increase.
It is common for blades for wet shaving to include a thin polymer coating on the blade edge, which can reduce the frictional resistance between the blade edge and the skin and thereby reduce the cutting force of the hair, greatly improving shaving comfort. Such coatings are described, for example, in U.S. Pat. Nos. 5,645,894 and 5,263,256, the entire disclosures of which are incorporated by reference herein. In general, this polymer coating is applied only to the tip of the razor blade (e.g., the last 25-50 μm) as it is sprayed onto an edge of a stack of blades. Accordingly, a significant portion of the razor blade is not covered with the lubricious coating but instead maintains some contact with the skin.
In some embodiments, the invention can improve shaving comfort and safety by improving the way the blade and cartridge glides over the skin and providing better management of the skin bulge, thus minimizing number of nicks and cuts experienced by a user.
In one aspect, the invention features a razor blade including a first surface comprising a body and a blade edge, and a second surface, wherein the first surface and second surface meet at a tip, and wherein at least a portion of both the body and the blade edge of the first surface are coated by a polymer film.
The polymer film may be discontinuous, and may be disposed on the first surface in a plurality of elongated strips, wherein the elongated strips extend from the tip to a distal portion of the body. The elongated strips may extend across the width of the body, or across only a portion of the body. The polymer film may be provided in the form of an array of bumps, circles, polygons, or ellipses. The elongated strips may be spaced apart from between about 20 μm to about 500 μm, e.g., from between about 100 μm to about 400 μm, and may have a width from about 100 μm to about 500 μm, e.g., about 20 μm to about 400 μm. At least about 20%, e.g., at least about 40%, of the first surface may be coated with the polymer film. The discontinuous polymer film may have a thickness from about 1 μm to about 1 mm, e.g., from about 5 μm to about 30 μm, preferably about 10 μm to about 20 μm.
The razor blade may further include a coating between the razor blade and the discontinuous polymer film, e.g., of diamond like carbon, chromium or a plurality of different coatings. A plurality of raised features may underlie at least a portion of the polymer film. These raised features may be formed of a material selected from the group consisting of metals, ceramics and glass.
In another aspect, the invention features a razor including a safety razor blade unit including a guard, a cap, and a blade located between the guard and the cap. The blade includes a first surface defining a body and a blade edge; and a second surface, wherein the first surface and second surface meet at a tip, and wherein at least a portion of the blade edge of the first surface is coated by a polymer film.
The invention also features methods of shaving and methods of manufacturing razor blades.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
Referring to
The parallel stripes of polymer coating 12 provide a height differential between the surface of the polymer coating 12 and the uncoated upper surfaces of the blade, which creates a space that can be used to manage the skin bulge as the blade passes over the skin of a user. This space can help to improve the way the blade, and ultimately a shaving cartridge that includes the blade, glides over the skin of the user, which in turn can reduce the number of nicks and cuts incurred while shaving.
Although the polymer coating on the blade depicted in
Moreover, the patterns for the polymer coating need not be a repeating geometric shape. The polymer coating can be uniform and continuous or it can be spaced at irregular intervals. In some embodiments, the polymer coating can be discontinuous over the flat, skin-contacting surface of the blade.
In some cases, the polymer pattern can be decorative as well as functional, e.g., shaped as a logo or indicia, e.g., the trademark or tradename of the razor distributor. Alternatively, the polymer pattern can be shaped as a flower, a piece of sporting equipment, or any other configuration that provides for spaces in which the skin bulge can be managed between the height of the polymer coating and the upper surface of the blade. If the pattern is intended to be decorative, the decorative elements of the pattern will typically appear on a portion of the upper surface that will be visible to the user when the blade is positioned in a blade unit. The polymer may also be of an aesthetically pleasing color, and the stripes may be of different colors if desired.
In some preferred embodiments, the polymer coating covers from about 20% to about 75% of the upper surface of the blade (e.g., about 30%, about 40%, about 50%, about 60%, or about 70%.) Generally, a sufficient amount of the surface should be covered so as to provide the desired performance characteristics, without increasing the cost of the product to an undesirable extent.
In general, the blade is coated with a polymer coating such as a polyfluorocarbon, e.g., polytetrafluoroethylene (commercially available under the tradename TEFLON). Suitable polyfluorocarbons are discussed, for example, in U.S. Pat. No. 6,228,428, the disclosure of which is incorporated herein by reference.
The chemical nature of the polymer coating can be altered to change the degree of friction desired for passing the razor blade over the skin of a user. For example, a more lubricious polymer coating can decrease the amount of frictional resistance more than a less lubricious polymer. In some instances, the amount of frictional resistance can be altered by selectively changing the thickness of the polymer coating on the tip of the blade, e.g., by using a solvent to remove a portion of the polymer for example as described in U.S. Pat. No. 5,985,459, the full disclosure of which is incorporated herein by reference.
In some instances, the degree of friction of the blade can be altered by the amount of polymer on the upper surface of the blade. For example, if the polymer is configured as depicted in
In general, the blade 10 is positioned in a shaving cartridge, for example a blade cartridge that includes a plurality of blades. Referring to
Although the cartridge 30, depicted in
The positioning of a blade having a polymer coating can be dependent on a number of factors, including the number of blades in the cartridge, the nature of the polymer coating, the degree of polymer coating, and/or the intended use of the razor (e.g., whether the blade will be in a cartridge for a woman's razor or a man's razor). Any number of configurations is possible, provided that at least one blade includes a polymer coating on the cutting portion of the blade. Often, it will desirable to provide a polymer coating on the blade(s) having the highest degree of exposure, to enhance safety and reduce the likelihood of nicks and cuts.
The polymer can be coated onto the blade in a patterned fashion using a mask. The mask is positioned over the entire upper surface of the blade and once positioned a suspension that includes the polymer coating is sprayed over the mask to cover the exposed portions of the blade. The polymer is then sintered to bond it onto the upper surface of the blade. The pattern of open areas of the mask can be selected to obtain a desired pattern of polymer on the blade, and the thickness of the mask can be varied to modify the thickness of the polymer coating.
Other techniques can also be used to apply the polymer coating to the surface of the blade, for example photo or electron lithography using a photoresist, micro-contact or pad printing, or spraying of a dry powder followed by sintering.
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
