Note: Descriptions are shown in the official language in which they were submitted.
CA 02247821 1998-08-28
i~VO 97/33729 ' PCT/US97/03862
- 1 -
SAFETY RAZORS
This invention relates to shaving devices and
concerns a safety razor blade unit having at least one
blade with a cutting edge which is moved across the
surface of the skin beiag shaved by means of a handle
to which the blade unit a.s attached. The blade unit
may be mounted detachably on the handle to enable the
blade unit to be replaced by a fresh blade unit when
the blade sharpness has diminished to an unsatisfactory
level, or it may be attached permanently to the handle
with the intention that the entire razor be discarded
when the blade or blades have become dulled. Razor
blade units generally include a guard which defines a
surface for contacting the skin in front of the
blades) and a cap for contacting the skin behind the
blade(s), the cap and guard serving important roles in
establishing the so-called "shaving geometry", i.e. the
parameters which determine the blade orientation and
position relative to the skin during shaving. The
present invention is especially concerned with the
guard and/or cap of a razor blade unit.
It is known to provide a skin engaging guard
or cap with surface configurations intended to produce
pleasant tactile sensations during shaving, for
example, as described in US-A-5191712.
The present invention aims to provide an
improved surface structure on a cap or guard and in
CA 02247821 2002-09-27
_2_
accordance with this object the invention resides in a safety razor blade unit
having at least one
elongate blade and a skin engaging member that is generally parallel to the
blade and extends
along the length thereof and defines a surface of contact with the skin during
shaving. The
surface is defined by spaced projections extending upwardly from a base and
formed of
resiliently flexible material. The projections are present on the member along
substantially the
entire length of the skin engaging member, whereby the upper ends of the
projections can
deflect under forces encountered during shaving. All of the projections have
cross-sections
with concave sides so oriented that the recess formed by the concave side is
open in a direction
generally facing in a direction of movement of the skin engaging member during
shaving over
at least a major part of the width of the recess. The concave sides of the
projections act to
funnel hairs into their respective recesses in order to encourage interaction
with the projections
and scoop and trap moisture from the skin and release that moisture from the
skin when
subsequently encountering and interacting with a hair.
Conveniently, the concave faces of the projections face the direction in which
the blade
unit is moved across the skin surface although they can be inclined to this
direction at an angle
of up to around 45°.
Various cross-sectional shapes for the projections are possible, but a concavo-
convex
shape, in particular a circular arc with a circumferential extent Pram 1/4 to
3/4 of a complete
circle, preferable a semicircular arc, is expedient. An alternative cross-
sectional form has an
arcuate medial portion extended by straight portions, such as in the shape of
a letter U.
Conveniently, the projections are arranged in one or more rows e.g., 3 or 4
rows,
extending along the base generally parallel to the blade, with at least ten
projections in each
row, and possibly up to about 40 projections in each row for a blade unit of
usual length, such
as on a base around 30 mm in length. Suitably, the height ofthe projections
above the base is
in the range of 0.38 mm to 1.5 mm, preferably about 0.75 mm, the thickness
(measured
between the concave and convex faces) is in the range of 0.10 mm to 0.50
CA 02247821 1998-08-28
WO 97/33729 PCT/US97/03862
- 3 -
mm, preferable about 0.17 mm, and the base thickness
fthe thickness where the projections join the base) to
height ratio of the projections is in the range of from
1:1 to 1:15, preferably about 1:4.4.
' 5 In the case of concavo-convex projections
Which in cross-sections are shaped as circular arcs or
include portions of such shape, the outside diameter
may be in the range of 0.3 mm to 3.0 mm, preferably
around 0.75 mm, and the inside diameter may be in the
20 range of 0.1 mm to 2.5 mm, preferably about 0.4 mm.
The inside and outside diameters may increase away from
the base so that the projections are flared upwardly,
or they can reduce away from the base so that the
projections taper towards their free ends, in either
15 case the thickness remaining constant over the height
of the projection. The thickness can also vary over
the height of the projections, such as due to the
internal diameter gradually increasing away from the
base and/or the outside diameter gradually reducing
20 away from the base.
The spacing between the projections in the
direction perpendicular to that in which the blade unit
is moved over the skin during shaving, is preferably at
least 0.1 mm and not greater than the width of one
25 projection in said direction, a most preferred spacing
being around 0.25 mm. If desired, adjacent projections
can be interconnected by membranes moulded integrally
with the projections.
With a razor blade unit according to the
30 invention, the skin contacting surface of the skin
engaging member is highly responsive to local forces,
e.g. due to a projection being encountered by a hair.
The concave faces of the projections can act to funnel
hairs into their recesses in order to encourage
35 interaction with the projections. In, addition these
faces may serve to scoop and trap moisture from the
skin and release that moisture when subsequently
CA 02247821 1998-08-28
WO 97/33729 PCT/US97/03862
- g _
encountering and interacting with a hair. Furthermore,
the non-linear force-deflection characteristic of the
concavo-convex projections can be of advantage in their '
interaction with hairs.
Some embodiments of the invention are '
described in more detail below with reference to the
accompanying drawings in which:-
Figure 1 is a perspective view of a skin
engaging member for a blade unit according to the
invention;
Figure 2 is a plan view of the skin engaging
member;
Figure 3 is a cross-section taken along a
line A-A of Figure 1;
Figures 4 and 5 are front and end elevational
views of the skin engaging member;
Figure 6 shows in perspective a blade unit
equipped with the skin engaging member to form the
guard surface;
Figures 7 (a) to 7 (f) are plan views showing
alternative shapes for the projections of the skin
engaging member; and
Figures 8 (a) to 8 (f) are sectional views
showing alternative forms for the projections.
The skin engaging member 1 illustrated in
Figures 1 to 5 is intended to form either a cap, or
more appropriately a guard surface in a safety razor
blade unit having one or more elongate blades. Figure
6 shows such a blade unit equipped with the skin
engaging member to define the guard surface. Although
the blades of the unit have been omitted it will be
understood that they will be positioned within the
frame 2 of the unit so that their cutting edges are
parallel to the front edge of the skin engaging member
1. The member 1 is moulded a.n one piece of an
elastomeric material. It includes a rectangular base 3
from which extend upwardly projections 4 of semi-
CA 02247821 1998-08-28
WO 97/33729 PCT/US97/03862
- 5 -
circular arcuate cross-section, the concave faces of
these projections facing in the direction in which the
skin engaging member is moved over the skin during
shaving. The projections are arranged in four
longitudinal rows in which the projections are equally
spaced at a distance not greater than the width of the
projections in the direction of the rows, and the
projections of alternate longitudinal rows are
longitudinally staggered by a distance which is half
the centre-to-centre pitch P of adjacent projections in
the same row, consequence projections of successive
rows overlap in the longitudinal direction.
The dimensions are as follows:
Base length . 30mm
Base width: 2.5 mm
Projection height 0.38 mm-1.5 mm, preferably 0.75 mm
Projection outer diameter: 0.3 mm-3.0 mm preferably
0.75 mm
Projection inner diameter: 0.1 mm-2.5 mm, preferably
0.4 mm
Projection thickness: 0.1 mm-0.5 mm, preferably 0.17 mm
Projection spacing (in each row): 0.1 mm-outside
diameter, preferably 0.25 mm
Projections per row: at least 10 and 29 as shown.
In the particular embodiment shown in
Figures 1-5, and more clearly illustrated in Figure
8(a) the projections 4 are upright with a constant
thickness over their height. However, they could be
angled or tilted, especially forwardly and/or
laterally, if preferred, and the thickness may vary
over the height of the projections. It is not
essential for the projections to have the described
orientation and semicircular arcuate form, and some
other acceptable shapes and orientations are shown in
Figures 7 (a) to 7 (f) . According to Figure 7 (a) , the
projection has the shape of a circular arc with a
circumferential extend to 3/4 of a full circle, the
CA 02247821 1998-08-28
-'WO 97/33729 PCT/US97/03862
- 6 -
edges of the projection lying on respective radial
planes. The shape of the projection of Figure 7(b) is
a circular arc, the circumferential extent of the
convex face being 1/4 of the complete circle and the
edges lying in a common plane perpendicular to the
direction of movement during shaving. A projection of
U-shape is shown in Figure 7(c), there being a
semi-circular medial portion extended by straight
portions. The projection depicted in Figure 7(d) has
the same shape as the projections 4 in Figures 1-5, but
the projection is oriented on the base so that its
concave face is inclined at an angle of about 45° to
the forward direction. However, as in all the
embodiments, the recess defined by the concave face is
still open in the forward direction over the major part
of the recess width. Figure 7(e) shows a modified form
of the projection of Figure 7(d) the edges of the
projection each being arranged to lie in a plane
perpendicular to the forward direction. Figure 7(f)
shows a variation of the projection of 7(c), this
projection having an arcuate medial portion defining a
90° bend and extended by straight portions. The
dimensions mentioned above, including the inner and
outer diameters and projection height and thickness,
are also applicable to the skin engaging members with
projections as shown in Figures 7(a) to 7(f).
As indicated above, the thickness of the
projections 4 can vary over their height. Figures
8(b), (c) and (d) illustrate examples of projections
which reduce in thickness towards their upper ends.
According to Figures 8(b) this is achieved by the inner
diameter gradually increasing away from the base
whereas in Figure 8(c) the outer diameter gradually ,
reduces away from the base, and is Figure 8(d) the
inner diameter increases and the outer diameter
decreases away from the base. It is also possible for
the thickness to remain constant over the height of the
CA 02247821 1998-08-28
WO 97/33729 PCT/US97/03862
- 7 -
projections while the diameters of the concave and
convex surfaces change. Thus, Figure 8(e) shows a
' projection which tapers towards its free end due to the
inner and outer diameters decreasing, and Figure 8(f)
shows a projection which flares towards its free end
due to the inner and outer~diameters increasing. The
embodiments of Figures 8(b) to 8(f) are all preferably
made within the dimensional ranges specified above.
Where the thickness varies it is preferably about
0.17 mm at the free upper edge of the projection, and
where the outer diameter varies the maximum is
preferably about 0.75 mm.
In some embodiments of the invention it may
be beneficial to arrange the projections with their
concave faces directed opposite to the direction in
which the blade unit is moved across the skin during
shaving, for example by rotating the described skin
contacting members through 180° in their own planes
before being mounted on the blade unit frames.
In any particular embodiment all the
projections can conveniently be made with the same
shape, size and orientation, but this a.s not strictly
necessary and projections of different form and/or
orientation can be combined in the same embodiment.
Thus, it would be possible to have some projections
oriented as in the above described embodiments with
their concave faces directed forwardly in the direction
of blade unit movement during shaving, and other
projections reversed to face 3.11 the opposite
direction. Other modifications are also possible. For
example it is not essential for projections to be
separated by spaces and they can be interconnected by
webs moulded integrally with the projections and base.
One possibility is to have a row of projections with
interconnecting webs which serve to define a continuous
thin longitudinal fin which is interrupted by the
projections.
CA 02247821 1998-08-28
WO 97/33729 PCTl~TS97/03862
_ g _
The material of the skin engaging member will
have a degree of flexibility appropriate for the shape
and size of projections provided, but a hardness of '
less than 90 Shore A will normally be appropriate.
While it is apparent that modifications and
changes can be made within the spirit and scope of the
present invention, it is our intention, however, only
to be lima.ted by the appended claims.
