GB2376911A - Razor blade - Google Patents

Abstract

A razor blade comprises a layer of silicon carbide, typically rectangular in shape, having an elongate cutting edge, generally greater than 10 mm in length. The silicon carbide can be either polycrystalline or single crystal in structure, and of any polytype with the preferred polytypes being 4H, 6H or 3C. A razor comprising the razor blade is also provided.

Description

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BACKGROUND OF THE INVENTION This invention relates to a silicon carbide (either polycrystalline or monocrystalline) cutting insert and more particularly to a silicon carbide razor blade.

Conventional razor blades are made from steel and go blunt during the hair shaving process. Techniques to improve the longevity of steel blades include the application of hard coatings and the treatment of the steel by, for example, ion implantation. Whilst these enhancement techniques do work, the improvement in longevity (the length of time the blade remains sharp) is only modest.

It has been recognised that harder materials than steel, such as ceramics, would make longer lasting blades. The harder the material and the sharper the edge, the longer the blade will last, provided the edge does not chip. FR 2 536 691 recognises this fact and shows several designs of diamond razor blades made from multiple, single crystals of diamond which had sharpened edges. The provision of such edges onto single crystal diamond is a well developed technique as such blades have been used for surgical instruments such as eye-knives.

WO 93/00204 describes a razor blade which includes a substrate with a wedge-shaped cutting edge and a layer of diamond or diamond-like material coating the substrate and more particularly coating the cutting edge.

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SUMMARY OF THE INVENTION According to the present invention, a razor blade comprises a layer of silicon carbide, typically rectangular In shape, having an elongate cutting edge, generally greater than 10mm in length The silicon carbide can be either polycrystalline or single crystal In structure, and of any polytype with the preferred polytypes being 4H, 6H or 3C.

Further according to the invention, a razor comprises a razor blade as described above so mounted in a holder as to present the elongate cutting edge suitable to carry out a shaving operation- DESCRIPTION OF EMBODIMENTS The layer of silicon carbide will preferably be monolithic providing an elongate cutting edge which itself is monolithic in the sense that it is continuous without any joins or discontinuities. The layer may also be made up of a series of bonded silicon carbide pieces which together define an elongate cutting edge.

The silicon carbide may be single crystal or polycrystalline In nature.

The cutting edge is of a length sufficient to allow the blade to be used for a shaving application The length of the cutting edge will typically be in the range 20 to 50mm.

The silicon carbide razor blade will typically be produced from a layer or sheet of silicon carbide which is cut, for example, by a laser, to the desired shape, e. g. rectangular. In so doing, one elongate edge will be cut at a suitable angle, for example, to provide an elongate cutting edge

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The silicon carbide razor blade of the invention has a sharp cutting edge which will remain sharp, even during extended use, due to the fact that the blade is made of one of the hardest known materials (only diamond and cubic boron nitride are harder). The silicon carbide cutting edge will not rust or oxidise in any way, either during use or during storage, as silicon carbide is chemically inert. The cutting edge will not be scratched and thus impaired by contact with any material other than diamond or boron nitride. Since there are no coatings involved in or at the cutting edge, there is no possibility of coating delamination or erosion during use, as with coated razor blades of the prior art.

An embodiment of the invention will now be described. A sheet of monocrystalline silicon carbide (6H) having flat and parallel surfaces was processed using a lapidary-based technique to a finished thickness of 50 to 250J.. Lm. The surfaces may also be highly polished or be polished to a roughness of less than 100nm Ra.

The silicon carbide sheet was then cut using a laser such as an Nd : Yag laser to produce a product of a razor blade shape, for example a rectangular shape.

The cuts were generally perpendicular to the parallel surfaces, except along one elongate edge where the cut was such as to define an angle, for example an angle of 4 to 30 , with respect to the parallel surfaces. In this manner a cutting edge, typically of 30 to 40mm in length was produced. This cutting edge was single faceted. In an alternative form of the invention, the product was turned over and a second faceted cut, intersecting with the first faceted cut, was produced, again using a laser. The edge can also be applied to the silicon carbide by simple polishing with an abrasive diamond wheel.

The blade was suitable for mounting in a conventional razor holder and was found to be effective in cutting or shaving hair off the skin of a person.

Claims (2)

1. CLAIMS: 1. A razor blade comprising a layer of silicon carbide, said layer having an elongate cutting edge.
2. 2. A razor comprising a holder and a razor blade according to Claim 1, said razor blade being so mounted in said holder as to present said elongate cutting edge for a shaving operation.