Safety razors

Cutlery – Razors – Combined

Patent

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Details

30 50, B26B 2144

Patent

active

054309395

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention is concerned with safety razors of the kind comprising at least one blade and a blade support of moulded polymeric material which together form a shaving unit which is discarded as a whole when the cutting edge of the or each blade becomes dulled. The blade support is designed to form skin-engaging guard and cap surfaces for engaging the skin respectively ahead and rearwardly of the blade edge or edges.
The shaving unit may be of the disposable cartridge type adapted for coupling to and uncoupling from a razor handle or may be integral with the handle so that the complete razor is discarded as a unit when the blade or blades become dulled.
It is known to provide such shaving units with an insert which releases a lubricious water-soluble polymeric material in the presence of water; the use of such inserts significantly improves shaving comfort. A shaving unit having such an insert is described, for example, in British Specification 2024082B and shaving units of this kind have been commercially available for some years.
The preferred lubricious water-soluble polymeric material for such inserts is polyethylene oxide and this is the material which is, as far as is known, used in all commercially available shaving units of this kind. This polymer is subject to the disadvantage that it continues to leach from the insert after the shaving unit has been used because of the water it absorbs. This can cause unsightly and undesirable swelling of the insert and can lead to the insert sticking to surfaces, such as a razor tray, with which it comes into contact making it difficult to remove the razor when it is next wanted for use and, in extreme cases, leading to the insert being damaged when the razor is forcibly removed from the surface to which it is adhered.


Summary of the Invention

We have now found that the benefits of using a shaving unit with such an insert can be obtained, while avoiding or reducing the disadvantages referred to, by forming the cap and/or the guard portion of the blade support, or an insert in the cap and/or the guard portion, of a lubricious polymeric material which is selectively water soluble, that is which is more water-soluble under the conditions present during shaving (e.g. at pH's greater than 8 or a elevated temperatures) than it is under other conditions (e.g. at lower pH's or at ambient temperature).


Detailed Description of the Invention

According to the present invention, there is provided a shaving unit which comprises at least one blade and a blade support of moulded polymeric material which provides skin-engaging guard and cap surfaces, in which the cap portion and/or the guard portion of the blade support, or a moulded insert in the cap portion and/or the guard portion, is formed of at least one lubricious polymeric material which is more water-soluble under the conditions present during shaving than it is under other conditions, or of a mixture of such a lubricious polymeric material with one or more other materials.
Whether the cap and/or guard portions or the moulded insert are formed of the lubricious polymeric material alone or of a mixture containing it depends on whether the mechanical properties of the lubricious polymeric material are such that the moulded polymer has sufficient strength to withstand normal usage. Where the moulded lubricious polymeric material does not have sufficient strength for this purpose, it is used in combination with one or more other mouldable materials which are adapted to provide the required strength. The other material is preferably a hydrophobic polymeric material; suitable hydrophobic polymers are, for example, polystyrene, polyethylene, polypropylene and polyacetal, that is the polymers which are conventionally used to make moulded shaving unit parts.
The lubricious polymer can, of course, be used in admixture with one or more other materials, such as the hydrophobic polymers just mentioned, even when it has sufficient strength to be used on its own. Such a mixture may be desirable in o

REFERENCES:
patent: 4170821 (1979-10-01), Booth
patent: 4381293 (1983-04-01), Michel
patent: 4624051 (1986-11-01), Apprille et al.
patent: 4850106 (1989-07-01), Braun et al.
patent: 4872263 (1989-10-01), Etheredge, III
patent: 4875287 (1989-10-01), Creasy et al.
patent: 5094912 (1992-03-01), Deibig et al.
patent: 5113585 (1992-05-01), Rogers et al.

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