Cutlery – Razors – Multiple blade
Reexamination Certificate
1998-04-21
2001-02-13
Rada, Rinaldi I. (Department: 3724)
Cutlery
Razors
Multiple blade
C030S084000, C030S077000, C030S076000
Reexamination Certificate
active
06185823
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to safety razors of the kind having a blade unit carried by a handle, the blade unit including an elongate blade with a rectilinear sharpened edge, or a plurality of such blades with parallel edges. The blade unit may be fixedly mounted on the handle with the intention that the entire razor be discarded when the blade edge or edges have become dulled. Alternatively, the blade unit can be detachably connected to the handle to enable replacement of a used blade unit with a fresh blade unit. Replaceable blade units are commonly referred to as cartridges.
SUMMARY OF THE INVENTION
There has been a general tendency over recent years for razor blade units to have been reduced in size, especially regarding the area of the surfaces which contact the skin around the blades during shaving, and the majority of blade units currently available in the marketplace are long and narrow with substantially rectangular configurations as viewed in a direction substantially perpendicular to the skin contacting surfaces. On the whole razor blade units of such shape and size have been found to provide an enhanced shaving performance in comparison with earlier blade units of larger dimensions.
The present invention is aimed specifically at a blade unit for body shaving, primarily in the axillary area. There are already on the market razors intended for use by ladies who do commonly shave their axillae, and like other razors there has been a strong trend towards making the blade units of these female razors with a narrow rectangular configuration as mentioned above. It has become the accepted thinking within the art that such blade units of narrow dimensions are especially beneficial for shaving the axillae since they will more readily fit into the rather deep concave socket of the axilla.
The present invention makes a significant departure from this current thinking in the shaving field and goes directly against all recent developments in this technical area as regards blade unit dimensions. Surprisingly, and contrary to all expectations, shaving tests have shown that not only can a blade unit of relatively large dimensions at least equal the shaving effectiveness of the smaller prior art blade units when shaving the axillae, but large blade units can be shaped to conform to the axilla region of the body so that shaving performance is not diminished, and that in terms of overall comfort large blade units have a superior performance to the prior art blade units and are preferred by users. It appears the added stability given by a large contact area with the skin gives the user greater confidence when shaving the axilla which cannot be viewed very easily during the shaving process, and as a consequence an improved comfort is perceived by the user and this more than counteracts any loss of performance due to the large contact area.
For most adult females, the underarm cavity has a minimum radius of curvature of about 25 to 30 mm. Therefore, a razor blade unit according to the invention has a length not greater than 60 mm, preferably not greater than 50 mm, and a length in the range of 40 to 45 mm is preferred. The width of the blade unit is preferably such that the aspect ratio, namely the ratio of the overall length to the overall width measured perpendicular to the blade, is in the range of 1 to 4, and in most of the preferred embodiments of the invention the aspect ratio is from 1.5 to 2.8, and more precisely in the range of 2.0 to 2.5. In the preferred embodiments the width of the blade unit is in the range of 12 to 23 mm, in particular 15 to 20 mm. Guard and cap surfaces are defined in front of and behind the blade or blades for contact with the skin in front of and behind the blade or blades during shaving, and preferably each of the guard and cap surfaces has a width of not less than 4.0 mm, at least where the width of the blade unit is at a maximum. The guard and cap each has a skin contact area which is preferably not less than 140 mm
2
, and the combined skin contact areas of the cap and guard are preferably at least 400 mm
2
, and most preferably in the range of 450 to 500 mm
2
. As the blade unit of the present invention is rather wide, in order to facilitate contact with the skin in the axilla over at least most of the guard and cap areas, as viewed in cross section in a plane perpendicular to the blade edges, the skin contacting surface is made convex. It is important to understand that the word “convex” as used in the present specification does not necessarily mean that the skin contacting surface is smoothly curved and it implies only that the guard and cap surfaces extend upwardly in the direction from their edges remote from the blade or blades so that the blade edge or edges are at a level above the remote edges of the cap and guard surfaces. More particularly, a straight line joining the outer and inner limits of each of the guard and cap surfaces is inclined at an angle of at least 5°, and possibly up to 25°, to a plane which is tangential to the skin contacting surfaces immediately in front of and behind the blades. In the preferred embodiments the angle of inclination is in the range of 10 to 20 degrees, and more specifically substantially equal to 15°. By virtue of the convexity of the skin contacting surface, the blade unit is preferably shaped to make at least three point contact with an imaginary circumscribing circle having a diameter of from 30 to 100 mm, and preferably of about 50 mm whereby it will be ensured that the blade unit convexity will at least approximately conform to that of the axilla.
An important aspect of the blade unit according to the invention is that it defines a large area over which contact can be made with the skin during shaving, and a circumscribing perimeter extending about the skin contacting surface confines an area, referred to hereinafter as the “footprint area”, of at least 450 mm
2
. The most preferred footprint area is in the range of 600-750 mm
2
, and more specifically between 650 and 720 mm
2
.
Since the invention proposes a blade unit with a long and wide shape, a substantially rectangular configuration with sharp angled corners, at least at the edge adjacent the guard surface, is inappropriate. For the purposes of the present specification a sharp angled corner may be considered to be an angle less than about 120° with a radius of curvature less than around 3 mm. Preferably the curvature at any corner is at least 5 mm. The unacceptability of a substantially rectangular configuration and the objective of providing a large skin contact area means that the blade unit needs to be profiled, as seen in plan generally perpendicular to the skin contacting area, to obtain a relatively large area within the confines of the overall length and width dimensions. The “circularity” of a two dimensional shape is a convenient way of relating the area enclosed by its perimeter to the length of the perimeter, and expressing it in terms of a percentage compared with a circle which always provides the maximum area for any given perimeter length. Thus, the circularity for any shape is defined by the equation:
circularity
=
A
P
2
×
4
π
×
100
where
A
=
the
area
P
=
the
perimeter
Razor blade units according to the present invention have a circularity not less than the lower of (a) 65%, and (b) the circularity of a substantially rectangular area having the same length and width as the skin contacting area and having corner radii of 30% of said width. Preferably the circularity is greater than that of a rectangle with the same overall length and width and rounded corners with radii equal to 10% of the length. For blade units with a low aspect ratio, i.e. less than about 3, the lower limit (a) will apply, although even in the case of these blade units it is preferable that the circularity also exceeds limit (b). Acceptable oval blade units with an aspect ratio above 3.25 may have a circularity of less than 65%. Preferred embodiments with aspect
Brown Frank Edward
Oldroyd Brian
Flores-Saánchez Omar
Podszus Edward S.
Rada Rinaldi I.
The Gillette Company
LandOfFree
Oval frame razor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oval frame razor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oval frame razor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2605066