Note: Descriptions are shown in the official language in which they were submitted.
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OVAL FRAME RAZOR
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.
There has been a general tendency over recent
years for razor blade units to have been reduced a.n
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
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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 30mm.
Therefore, a razor blade unit according to the
invention has a length not greater than 60mm,
preferably not greater than 50mm, and a length in the
range of 40 to 45mm 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
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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
Y
blade unit a.s in the range of 12 to 23mm, in particular
to 20mm. 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
10 blades during shaving, and preferably each of the guard
and cap surfaces has a width of not less than 4.Omm, 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 140mm2, and the
15 combined skin contact areas of the cap and guard are
preferably at least 400mm2, and most preferably in the
range of 450 to 500mm2. 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 a.n 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 a.n 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 a.n the range of 10 to 20 degrees, and more
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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 100mm, and preferably of about
50mm 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 450mm2. The most preferred footprint area
is in the range of 600-750mm2, and more specifically
between 650 and 720mm2.
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 3mm. Preferably the curvature at any corner is
at least 5mm. 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 a.n terms of a percentage compared with a
circle which always provides the maximum area for any
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given perimeter length. Thus, the circularity for any shape is
defined by the equation:
Circularity = A x 4 x 100
pz
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 corner; 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 a~;pect ratios below about 2.75 have
a circularity greater than 70%, and more particularly in the
order of 80%. Typical prior art blade units have a circularity
of less than 65%. The comp<~ratively large circularity of a
blade unit according to the invention can be achieved with
rounded corners at the ends of the blade unit with relatively
large radii of curvature of: at least 6mm, or with oval,
elliptical or polygonal shapes which need not necessarily be
symmetrical.
Having regard to the foregoing, the present invention
resides in a razor blade unit: comprising at least one elongate
blade having a rectilinear :>harpened edge and mounted in a
substantially inflexible carrier, a skin contacting surface
surrounding the at least one blade edge and including guard and
cap surfaces on opposite side~:~ of the at least one blade edge,
the aspect ratio of the length to width of the skin contacting
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surface being in the range c>f from 1 to 4, as seen in cross
section in a plane perpendicular to the at least one blade edge
the skin contacting surface being convex, the overall length of
the blade unit at the skin contacting surface being not greater
than 60 mm, the skin contactiru~ surface having a circumscribing
perimeter confining a footprint area of at least 450mm2, and the
circumscribing perimeter being so shaped that the footprint area
confined by said perimeter has 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
footprint area of the skin contacting surface and having corner
radii of 30% of said width.
A razor equipped with a blade unit as described above
has been found in shave tests to achieve a significantly
improved overall performance in shaving the axilla and has also
been found to be very effect::ive in shaving other body areas,
such as the legs.
It should be understood that unless otherwise stated,
all dimensions and areas quoted herein are measured in a
projected plane and as seen :in plan view so the effect of the
convex curvature of the skin. contacting surface of the blade
unit has not been taken into account in determining the relevant
dimensional data.
To further illustrate the invention some forms of
razor blade unit shaped and dimensioned in accordance with the
invention will now be described with reference to the
accompanying drawings, in which:
Figures 1 to 9 are ~crhematic plan views of razor blade
units embodying the invention;
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Figure 10 is a graph showing circularity
plotted against aspect ratio (maximum length/maximum
width) and showing the results for the blade units of
Figures 1 to 9 and for some prior art blade units;
Figure 11 is a schematic cross-section
through the blade unit of Figure l;
Figure 12 illustrates a modified shape of
guard and cap surfaces for the blade unit of
Figure 1;
Figure 13 illustrates in perspective a blade
housing of a blade unit as shown in Figure 1;
Figure 14 illustrates in partial perspective
view a blade unit as shown in Figure 1 and having guard
and cap surfaces similar to those of the Figure 13
embodiment; and
Figures 15 and 16 are views corresponding to
Fig. 14 showing blade units with two and three
forwardly facing blades, respectively.
Each of the blade units shown in Figures 1 to
9 will comprise a blade housing which incorporates a
substantially inflexible blade carrier frame
conveniently moulded from plastics material. The
housing defines a skin contact area surrounding an
elongate rectangular aperture 2 in which a blade (not
shown in Figs. 1-9) with a sharp rectilinear edge is
mounted. A single blade may be provided, but
preferably two or more blades with parallel sharpened
edges are mounted in the aperture 2. In the particular
embodiment shown in Fig. 14, there are three blades,
two facing forwardly and one facing rearwardly so that
the razor blade unit will shave in both directions
although forward movement across the skin will
generally provide a slightly better result. Figure 15
shows an embodiment with two blades in tandem, and
Figure 16 shows another embodiment with three blades
with parallel edges all facing in the forward
direction. Each of the blade units of Figures 1 to 9
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may be regarded as being adapted to receive two blades,
or three blades mounted similarly to the blades in
Figure 14 or all in tandem. The blade housing in each ,
of the embodiments shown a.n Figures 1 to 9 has a guard
area 3, which is located forwardly (below as viewed in
the drawings) of the blade aperture, and a cap area 4
behind (above in the drawings) of the blade aperture 2.
The particular blade unit of Figure 1 a.s oval
and has the shape of a rectangle with semicircular
ends. The dimensions as measured in the projected plan
view as illustrated are as follows:
Overall length = 42.Omm
Overall width _ l8.Omm
End radius - 9.Omm
Guard area = 206mm2
Cap area _ 277mm2
Total skin contact area _ 504mm2
Total footprint area
within perimeter _ 6g6~2
The blade unit of Figure 2 is approximately
rectangular With corners of large radii of curvature.
The particular dimensions for this embodiment are:
Overall length _ 4l.Omm
Overall width _ l8.Omm
Corner radius - 6.Omm
Guard area _ 213mm2
Cap area _ 2 g 6~2
Total skin contact area _ 520mm2
Total footprint area
within perimeter s 7032
Figure 3 illustrates a blade unit of
asymmetric configuration. At the ends of the front
edge of the blade unit housing are rounded corners of
large radius (as in -.Fig. 2), and the corners at the
ends of the rear edge are rounded with a substantially
greater radius of curvature. The specific dimensions
are:
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Overall length - 40.6mm
Overall width - l8.Omm
Front end corner radius _ 6.Omm
Rear end radius - lO.Omm
Guard area _ 1852
r
Cap area _ 2832
Total skin contact area _ 488mm2
Total footprint area
within perimeter _ 66g~2
Figures 4-6 show blade units with housings of
the same overall shape and size of that shown in Figure
1, but the position of the blade aperture is different.
In Figure 4 the aperture is located so that the guard
and cap areas are equal, whereas in Figure 5 it a.s
positioned so that the cap area is substantially
smaller than the guard area (but still at least 140amn2)
and in Figure 6 it is positioned so that the guard area
is substantially smaller than the cap area (but still
at least 140mm2).
Figure 7 illustrates a polygononal blade unit
shaped essentially as a rectangle with chamfered
corners 7 with faces at 135 to the longitudinal front
and rear sides and to the ends. In the case of a blade
unit of overall length 42mm and overall width l8mm, the
chamfers may lie along the diagonals of squares
measuring 5mm x 5mm.
All the embodiments of Figures 1-7 have
rectilinear front and rear edge portions which, at
least over a major part of the blade length are
parallel to the blade edge(s). This can be desirable
to ease orientation of the blade unit and assist the
user in knowing in which direction the blade unit
should be moved over the skin. It is not essential,
however, and the dimensional criteria of a blade unit
embodying the invention can be obtained with other
configurations. Figure 8, for example shows a blade
unit of elliptical outline, and even a circular shape
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as shown a.n Figure 9 is possible although it is not the
most desirable embodiment.
Figure 10 shows a graph showing circularity .
plotted against aspect ratio, i.e. the maximum
length/maximum width of the blade unit. The points ,
representative of the blade units of Figures 1-9 are
indicated (1)....(9), the points representative of
three prior art female razor blade units currently
marketed are indicated A, B and C, and the point
representative of a square is indicated S for
comparison purposes. The line Rye which extends
generally diagonally across the graph is representative
of rectangles with corner radii of 30~ of the rectangle
width. The dotted line RL is representative of
rectangles with corner radii of 10$ of the rectangle
length. The horizontal line is drawn at a circularity
of 65~. It can be seen that all the preferred
embodiments of the invention denoted on the graph have
aspect ratios between 1.5 and 2.8, and for the majority
the aspect ratio is in the range of 2.0 to 2.5.
Furthermore, the embodiments of the invention have
circularity greater than the circularity of a
corresponding rectangle with the same aspect ratio and
having corners rounded at a radius of 10~ of the
rectangle length (RL) or of 30~ of the rectangle width
(RW). In addition, the embodiments of the invention
have greater circularity than the prior art blade units
and those included on the graph all have values above
60~, and more especially above 70~. (It may be noted
that there are two points (8) shown in Figure 10 to
depict two alterative elliptical shapes).
In all of the embodiments of the invention
the skin contacting surfaces are not flat and the views
of Figures 1 to 9 are merely the projected plan areas. -
The surfaces are preferably shaped to make at least
three point, and ideally at least four point contact
with an imaginary circumscribing circle with a radius
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of 25mm. Figure 11 shows this preferred relationship
for a blade which could, for example, be the blade unit
of Figure 1. The imaginary circle a.s drawn in dotted
line, and it can be seen that the cap and guard
surfaces are in substantial conformity with this
circle. In Figure 11 the guard and cap surfaces are
essentially flat, but they could be convexly curved to
provide even closer conformity, e.g. as depicted in the
schematic illustration of Figure 12. The cap and guard
surfaces are inclined to a plane P, which is the
"shaving surface" tangential to the skin contact
surfaces immediately in front of and behind the
blade(s), at an angle which is 15° in the exemplary
embodiment illustrated. In any particular embodiment
the most appropriate inclination angle will depend on
the blade unit width and will be chosen accordingly,
but for most embodiments of the invention at least, an
angle in the range of 10° to 20° will be required to
ensure close conformity with the imaginary circle. In
the case of a convex guard and/or cap surface, as in
Figure 12, it will be appropriate to consider the
inclination of a chord line intersecting the edges of
the surface in question nearest and most remote from
the adjacent blade.
In Figure 13 there a.s illustrated a preferred
form of blade unit housing. It has a frame 10 defining
an aperture 2 to accommodate the blades and the
components which fix them in the frame. Mounted on the
frame are guard and cap components each having an
elastomeric surface element 12 defining a skin contact
area formed with an array of cylindrical pockets 13
evenly distributed over essentially the entire surface
area. For ease of manufacture and assembly the
elastomeric element is moulded onto a support 14 which
is firmly fastened a.n the frame 10. Figures 14, 15 and
16 show a modified construction wherein the elastomeric
elements 12 are carried directly by the frame of the
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blade unit. These figures also shows the tirades 15
fitted within the frames, and one of the securing clips
16 which are provided at each end of the blade unit to _
retain the blades in place.
It is important to note that, as previously
mentioned, all the dimensions quoted in the description
and claims of this specification regarding length,
width and area are based on the profile of the blade
unit skin contacting surface projected onto a plane
which is parallel to the plane of the shaving surface
i.e. the plane denoted P a.n Figure 11. In addition,
when calculating the circularity, any minor
irregularities in the perimeter, e.g. due to small
indentations, such as narrow notches or projections
which can significantly change the perimeter without
substantially changing the area, should be disregarded.
