Cutlery – Razors – Multiple blade
Patent
1992-02-05
1993-07-06
Watts, Douglas D.
Cutlery
Razors
Multiple blade
30 77, 30 87, B26B 2100, B26B 2114, B26B 2116
Patent
active
052242676
DESCRIPTION:
BRIEF SUMMARY
This invention relates to safety razors of the form comprising a frame supporting one or more blade members in a manner permitting movement of the blade members, against resilient restoring forces, in response to forces encountered in use.
A well known example of a safety razor of this general form is disclosed in U.S. Pat. No. 4,492,025 in which the individual blade members of a tandem pair are displaceable against the action of restoring springs in directions perpendicular to a notional plane tangent to fixed guard and cap surfaces before and behind the blade edges so as to reduce the exposure of the blade edges in response to increased forces applied to the edges by the skin in use, whether due to changing skin contours or increased pressures applied by the user's hand or a combination of both.
The present invention is mainly characterized in that the (or each) blade member is movably mounted in the frame in such a manner that the shaving angle of the (or each) blade is reduced when in use the razor encounters increased drag forces, that is to say forces acting substantially parallel with the direction of shaving.
The term "shaving angle" is used herein in its normal sense in the art to indicate the acute angle formed between the median plane of a blade member and a notional plane tangent to the skin engaging members immediately ahead of and behind the blade member. In the case of a single blade razor, these would be the guard and the cap members. In a tandem edged razor, the respective skin engaging members are constituted by the guard and the second blade edge, or the first blade edge and the cap.
In some embodiments of the invention, the razor has a guard member which is displaceable relative to the frame and whose rearward displacement, against the action of resilient restoring forces, is transmitted to the blade members to cause them to pivot or hinge about axes parallel with the blade edges. The guard member may be constrained to move only in directions parallel to the shaving direction or it may be mounted for compound movements in these directions and perpendicular thereto to take account of drag forces and of forces normal thereto.
In another embodiment, it is the increased drag forces sensed by the blade edges which cause the shaving angles of the blades to be reduced.
A principle factor in the magnitude of drag forces is the direction of the grain of the beard, which is different in different regions of the face. For many people, the hair on the cheeks emerges from the skin at an angle thereto, sloping downwardly. Thus, a "downstroke" in these regions is essentially "with the grain". Many men prefer to shave with downstrokes and with "upstrokes" ("against the grain") to obtain a closer shave. Greater drag forces are experienced by the razor in these strokes against the grain. Also, facial skin shows a greater tendency to bulge when a razor is moved up the face, particularly over the cheeks and this also tends to increase the drag forces experienced by the razor.
The shaving angle of blades in modern razors is normally pre-set in manufacture at about 22.degree.-25.degree., which is found to provide an optimum angle of attack between the blade edge and the hairs for efficient cutting, but is necessarily a compromise, bearing in mind that most hairs do not emerge from the skin at right angles thereto. Hence, when shaving with a downstroke so that the blade edges are moving with the grain a relatively high shaving angle is desirable for the blades, but when shaving with an upstroke and the blade edges are moving against the grain a relatively shallower shaving angle is desirable for the blades. In selecting a constant shaving angle for the blades the conflicting requirements of these different shaving conditions must be balanced and a compromise accepted.
With the razors of the present invention, reduction of the shaving angle, in response to increased drag arising from shaving against the grain, tends to bring the blade edge closer to its optimum angle of attack.
A razor according to the inventi
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Oldroyd Brian
Simms Graham J.
Heyrana Sr. Paul M.
The Gillette Company
Watts Douglas D.
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