Cutlery – Razors – Multiple blade
Reexamination Certificate
1997-01-13
2001-10-02
Peterson, Kenneth E. (Department: 3724)
Cutlery
Razors
Multiple blade
C070S052000
Reexamination Certificate
active
06295734
ABSTRACT:
This invention relates to safety razors and is particularly concerned with safety razors having blade units with a plurality of blades defining parallel sharpened edges arranged to pass in succession over a skin surface being shaved. The invention is applicable to safety razors having their blade units permanently attached to the razor handle, and to safety razors having their blade units detachably mounted on the handle for replacement when the blade edges have become dulled, and in either case the invention can be incorporated whether the blade unit is immovably mounted to the handle or mounted to move, e.g., to pivot about an axis parallel to the blade edges, relative to the handle under the influence of forces imparted on the blade unit during shaving.
The present invention has specific reference to safety razor blade units incorporating three blades, and the relative positioning of the blade edges. Our prior patent application No. PCT/US94/10717 teaches that with such blade units an improved overall shaving performance can be achieved when the blade edges are set according to a particular geometrical pattern, namely with the first blade, which has its edge nearest the guard, having an exposure not greater than zero, and the third blade, which defines the edge nearest the cap, having an exposure not less than zero. In the most efficacious geometrical arrangement, the first or primary blade has a negative exposure with an absolute value in the range of 0 to 0.2 mm, preferably equal to about −0.04 mm for a primary blade span of around 0.7 mm, the third blade has an exposure with a positive value not greater than about +0.3 mm (preferably less than +0.2 mm), for example around +0.06 mm or +0.09 mm, and the second blade has an exposure of about zero, the second and third blade spans each being 1.0 to 2.0 mm, preferably about 1.5 mm. For convenience the geometrical arrangements described and claimed in the aforementioned prior application are referred to herein as “the target geometry for the blades”. For further information and details of the blade geometry reference may be made to the earlier application the contents of which are incorporated herein by this reference.
The blade exposure is defined to be the perpendicular distance or height of the blade edge measured with respect of a plane tangential to the skin contacting surfaces of the blade unit elements next in front of and next behind the blade edge. This can be a positive number if the blade edge is above this plane i.e., closer to the skin surface to be shaved than the tangential plane, or a negative number if the blade edge is below this tangent plane, i.e., further away from the skin than the tangent plane. The span of a blade is the distance from the blade edge to the skin contacting element immediately in front of that edge as measured along a tangent line extending between said element and the blade edge.
The three-blade geometry specified above is applicable to a blade unit in which the blades are immovably mounted relative to the guard and cap. It also applies to the initial or at rest geometry in the case of a blade unit in which the blades are spring mounted and capable of being deflected under the forces applied to the blades during shaving.
The present invention, recognizes that it may be desirable for some parts of a blade unit to be movable relative to other parts and that this may be accommodated without forfeiting the advantages of the blade geometry discussed above. Thus, according to a preferred embodiment of the present invention there is provided a safety razor blade unit comprising a guard, a cap, and first, second and third blades with parallel sharpened edges located in sequence between the guard and cap, at least one element selected from the blades, guard and cap being movable from a non-shaving position (i.e., at rest position not loaded by shaving forces) to modify a blade exposure dimension of the blade unit and to attain a modified blade geometry (also referred to as the target geometry) wherein the exposure of the first blade is not greater than zero and the exposure of the third blade is not less than zero, at least one of the first and third blades having a different exposure when the at least one movable element is in the non-shaving position.
The at least one element can be lightly biased, such as by means of a spring, to an initial, non-shaving (at rest) position at which the target geometry of the blades does not apply, but when the blade unit is applied to the skin during shaving the at least one element can be displaced to a position in which the target geometry of the blades is attained.
The at least one element can comprise the guard and/or the cap and/or one or more of the blades.
In accordance with another aspect the present invention provides a safety razor blade unit comprising a guard, a cap and a plurality of blades with a parallel sharpened edges located in succession between the guard and cap, at least one of the guard and cap being movable against a spring force from a non-shaving (at rest) position to a predetermined operable position in which a modified blade geometry target geometry is obtained, in the non-shaving position the blade edges being disposed below a plane tangential to the skin contacting surfaces of the guard and cap.
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Gilder Bernard
Terry John Charles
Peterson Kenneth E.
Podszus Edward S.
The Gillette Company
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