Note: Descriptions are shown in the official language in which they were submitted.
CA 02424739 2006-09-07
SAFETY RAZOR BLADE UNIT
This invention relates to safety razors of the kind in which a blade unit
assembly is carried by a handle and includes at least one blade member with a
cutting
edge which is moved across the surface of the skin being shaved by means of
the
handle. A blade unit may be mounted detachably on a razor 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 fixedly attached to the handle with the
intention that
the entire razor be discarded when the blade or blades have become dulled.
Detachable and replaceable blade units are commonly referred to as shaving
cartridges.
There have been various proposals for mounting a blade unit on a
handle to enable movement of the blade unit during shaving with the aim of
maintaining conformity of the skin contacting parts with the skin surface
during
shaving. For example, many razors currently marketed have blade units which
are
pivotable about longitudinal axes extending parallel to the cutting edges of
the
elongate blades incorporated in the blade units. In WO 97/26119 and WO
99/04938,
there are described safety razors with blade unit support structures which
permit
further freedom of movement of the rigid blade units relative to the razor
handles. It
has also been proposed to make the blade unit flexible between supporting
points at its
ends so that the cartridge can bow under shaving forces. WO 88/04980 describes
another construction in which flexible blade elements are carried by a
deformable
foam block, but there is no separate handle as the razor is held by means of
the foam
block. In spite of these previous attempts, there remains a need for a safety
razor with
a blade unit which is able to conform closely to the skin contours during
shaving.
The present invention has for its object to fulfill the foregoing need
and, in accordance with the invention, there is provided a safety razor blade
unit
comprising at least one blade with a sharp cutting edge extending lengthwise
of the
blade unit, and a support structure supporting the at least one blade, the
support
structure being resiliently compliant along the length of the blade unit under
shaving
forces imposed on the blade unit during shaving, the support structure
including spring
elements disposed along the blade unit to oppose local deformation of the
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blade unit under the shaving forces encountered in the regions where the
spring
elements act.
In a preferred embodiment several spring elements are distributed
along the blade unit, and each spring element is deformable in such a manner
so
that it exerts a substantially constant restoring force irrespective of the
degree of
deformation.
With such an assembly the deformation of the blade unit under
shaving forces can vary along the length of the blades unit enabling the blade
unit
to conform to skin undulations along the blade unit, with the forces exerted
by the
blade unit against the skin being substantially uniform along the blade unit.
As a
result, close conformity between the blade unit and the skin contours can be
achieved without causing discomfort due to the blade unit being pressed
against the
slcin under higher forces in certain confined areas.
Conveniently the spring elements are so formed that they deform by
buckling, and they may consist of webs of resiliently flexible material.
Alternatively, the spring elements may comprise leaf springs, or other spring
devices, which are capable of exerting a substantially constant force over the
normal
range of the blade unit deformation.
One form of safety razor blade unit according to the invention
comprises at least one blade with a sharp cutting edge and a support structure
supporting the at least one blade, the support structure having a blade
platform
structure carrying the at least one blade and having a front located forward
of the at
least one blade and a rear located behind the at least one blade, an
intermediate
structure, a base, a hinged connection between the intermediate structure and
the
front of the blade platform structure, the intermediate structure being
movably
mounted to the base to permit movement of the front of the blade platform
structure
towards and away from the base, and spring elements acting to urge the front
of the
blade platform structure away from the base and to urge the rear of the blade
platform structure to rotate away from the base about the hinged connection,
there
being several spring elements disposed along the blade unit to act on
respective
portions of the blade platform structure being capable of displacement against
the
action of the spring elements unaccompanied by corresponding displacement of
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other portions of the blade platform structure.
According to a further aspect of the invention provides a safety razor
blade unit comprising at least one blade with a sharp cutting edge, and a
support
structure supporting the at least one blade, the support structure having a
blade
platform structure carrying the at one blade, a sub-frame, a base, the sub-
frame
having a forward edge hingedly connected to the blade platform forwardly of
the at
least one blade, and a rear edge hingedly connected to the base, and spring
elements
acting between the sub-frame and the blade platform structure and acting
between
the sub-frame and the base to urge the blade platform structure away from the
base.
Several spring elements can be distributed along the blade unit and
act between the sub-frame and respective portions of the blade platform
structure.
Also, several spring elements can be distributed along the blade unit and act
between the base and respective portions of the sub-frame.
In a currently preferred embodiment the support structure includes an
upper frame on which the blade or blades are carried, and a sub-frame, with
spring
elements being interposed between the upper frame and the sub-frame.
Conveniently the support structure is formed by a unitary moulding of a
resiliently
flexible material, such as rubber or rubber-like material, the spring elements
then
being integral with the upper frame and also being integral with the sub-frame
of
the blade unit. With the support structure formed as a unitary moulding,
manufacture of the blade unit is facilitated as assembly of components is
minimized.
The upper frame is preferably hinged to the sub-frame at the front of the
support
structure, and with a moulded construction the comlection between them can be
conveniently provided by a living hinge. The hinged connection between the
upper
frame and the sub-frame is preferably displaceable downwardly, generally
towards
the handle, under load forces exerted on the upper frame near the front
thereof.
The sub-frame can be supported with respect to an underlying base in a manner
permitting movement of the sub-frame towards the base against the action of
suspension springs which can also be formed by webs of resiliently flexible
material
which deform by buckling so that a substantially constant return force is
exerted on
the sub-frame.
The upper frame can form a guard surface for contacting the skin
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_Q._
ahead of the blades during a shaving strolce, and a cap surface for contact
with the
skin behind the blades. Alternatively, a separate guard element and/or a
separate
cap element could be mounted on the upper frame, although any such separate
element would itself need to exhibit substantial flexibility along its length,
or
perhaps be divided up into short segments so as not to inhibit the flexing of
upper
frame to conform to the shin contours. One type of element which could with
advantage be provided is a lubricating strip, wluch could be located adjacent
the
front or rear edges of the blade unit, such strips being adapted to deliver
lubricant to
the shin surface during shaving in a manner well l~nown per se.
In another embodiment of the invention the blade or blades are
carried by an upper frame consisting of a series of independent upper frame
members spaced apart along the blade unit and extending substantially
perpendicular
to the length of the blade unit, these upper frame members being acted upon by
respective spring elements. The forward end of each upper frame member is
mounted for movement against the action of the respective spring element about
an
axis extending lengthwise of the blade unit. The spring can act on an arm
which is
attached to and extends rearwardly from the forward end of the upper frame
member so that this member is biased to an upper pivotal position.
Conveniently
the spring urges a pin upwardly against the arm, the pin being guided for up
and
down movement with respect to a base frame, and the upper frame member can be
pivotally mounted on a support post guided for up and down movement
substantially parallel to the direction of pin movement, whereby the forward
end of
the upper frame member can move downwardly under shaving forces imposed on
the blade unit against a restoring force exerted by the spring element.
Although the blade units of the invention may have a single blade, a
plurality of blades e.g. 2, 3, 4 or more blades, are preferably included and
extend
continuously along the blade unit with their sharpened edges substantially
parallel.
These blades are flexible for conforming to the slcin contours. Another
possibility is
for several blade segments to be disposed along the blade unit so that they
are able
to move relative to each other as the upper frame flexes. To facilitate
assembly of
the blade unit the blades are preferably interconnected by transverse strips
attached
to the undersides of the blades, these strips and the blades together forming
a
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flexible blade assembly in which in an undeformed condition, the blades and
strips are
substantially coplanar to enhance the flexibility of the blade assembly. The
blades are
preferably as described in our Canadian Patent Application No. 2,421,150 of
October 11,
2001.
The foregoing and other preferred features of the invention are
described in more detail below reference to some specific embodiments that are
also
illustrated in the accompanying drawings, in which:
Figure 1 shows in perspective a safety razor equipped with a blade
unit in accordance with the invention in a front perspective mew;
Figure 2 is a front elevation of the blade unit of the razor shown in
Figure 1;
Figure 3 is an end elevation of the blade unit;
Figure 4 is a cross section taken along the line IV-IV in Figure 2;
Figure S is an isometric view of the blade unit;
1 S Figure 6 is a view showing the blade unit as seen in the direction of
the avow VI in Figure 3;
Figure 7 is an exploded isometric view of the blade unit;
Figures 8 and 9 show the blade unit from the front and rear
respectively, in a deformed condition as may arise during shaving;
~ Figures 10 and 11 show the blade unit from the front and rear,
respectively, in another deformed condition as may arise during shaving;
Figure 12A is an isometric view from the front showing a blade unit
as illustrated in Figures 1 to 11 but with a modified support structure;
Figure 12B is an isometric view of the support structure of the blade
unit shown in Figure 12A;
12A;
Figure 13 is a rear isometric view of the blade unit shown in Figure
Figure 14 is an isometric view showing from the front another safety
razor with the blade unit embodying the invention;
Figure 15 is an isometric view showing the blade unit of the safety
razor of Figure 14 ~ from the rear;
Figure 16 is a rear elevation of the blade unit of the razor of Figures
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14 and 1 S;
Figure 17 is a cross-section taken along the line XVII-XVII in
Figure 16;
Figure 18 is an end elevation of the blade unit of Figures l4 and J 5
Figure 19 illustrates in perspective another embodiment of a safety
razor having a blade unit in accordance with the invention;
Figure 20A and 20B show on an enlarged scale a leaf spring included
in the blade unit of the razor shown in Figure 19;
Figure 21 is an isometric view illustrating a further embodiment of a
safety razor with a blade unit according to the invention;
Figure 22 is a rear isometric view of the razor of Figure 21;
Figure 23 is an end view of the razor shown in Figure 21;
Figure 24 is a front elevation of the razor shown in Figures 21-23;
and
Figure 25 is a cross-section taken along the line X~V-XXV in Figure
24.
The razor illustrated in Figures 1 to 11 has a handle 1 on which a
blade unit 2 is mounted. As shown the hurdle 1 has a fixed support platform 3
to
which the blade unit 2 is securely fastened, but the blade unit could equally
well be
releasably connected to the handle I to allow replacement of the blade unit 2.
The
blade unit 2 comprises a support structure 4 on which a blade assembly 5 is
carried.
In the illustrated embodiment the support structure 4 consists of a unitary
moulding
of rubber or a material having similar resiliently flexible properties to
materials having
appropriate characteristics include (i) Kraton~ 62705 having a hardness of 55
on the
Shore A scale manufactured by the Shell Corporation, (ii) Evoprene~ #966
having a
Shore A hardness value of 27 and distribution by Gary Chemical Corporation of
Leominister, Mass., (iii) Santoprene~ 271-55 having a Shore A hardness value
of 55 and
manufactured by Advanced Elastomerics Corporation and (iv) Santoprene 271-73
having
a Shore A hardness value of 73 and also manufactured by Advanced Elastomerics
Corporation.
The support structure 4 includes a blade platform structure formed by
an upper frame 6 on the upper face of which the blade assembly 5 is
positioned, a
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sub-frame 7 which has the form of a substantially planar sheet, and a base 8
which
can also have the formed of a substantially planar sheet. The upper frame 6 is
hingedly connected to the sub-frame 7 at the front of the support structure 4,
and in
particular the upper frame 6 and sub-frame 7 are integral and are connected by
a
living hinge 9 at their forward edges. The upper frame 6 and the sub-frame 7
lie in
first and second planes respectively, and axe relatively positioned normally
to
diverge from each other rearwardly away from the hinge 9. The sub-frame 7 and
the base 8 are hingedly connected at the rear of the support structure 4, and
more
especially the sub-frame 7 and base 8 are integrally connected by a living
lunge 10
at their rear edges. The sub-frame 7 and base 8 are disposed normally to
diverge
from each other in the direction forwardly away from the hinge 10. With this
configuration the upper frame 6, sub-frame 7 and base 8 as viewed in end
elevation
(Figure 3), or transverse cross-section (Figure 4) define a Z shape, but with
the
angle a subtended between the upper frame 6 and the sub-frame 7 being greater
than the angle ~3 subtended between the sub-frame 7 and the base 8 so that the
upper frame 6 is normally set at an appropriate angle with respect to the stem
of the
handle 1 and to ensure the desired deformation characteristics of the support
structure as explained below. Several spring elements in the form of flexible
webs
of the handle 1 and to ensure the desired deformation characteristics of the
support
structure as explained below. Several spring elements in the form of flexible
webs
12 are distributed along the blade unit 2. The flexible webs 12 extend between
and
are integrally interconnected with the upper frame 6 and the sub-frame 7, the
flexible webs 12 being uniformly spaced apart along the support structure 4.
As
shown there are six spring webs 12 although more or less than this number may
be
employed. The spring webs 12 normally lie in respective parallel planes
perpendicular to the planes of the upper frame 6 and the sub-frame 7. The
spring
webs 12 constitute respective spring elements and each web 12 is capable of
deforming by buckling, to allow the portion of the upper frame 6 in the region
of
that web 12 to be displaced towards the sub-frame 7 with the deformed or
buckled
web 12 exerting a substantially constant restoring force independent of the
degree of
buckling and hence the downward displacement of the upper frame 6. Since the
spring webs 12 act independently of each other, different portions of the
upper
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_g-
frame 6 along the length thereof may be readily displaced by different amounts
towards the
sub-frame 7.
The sub-frame 7 is similarly supported with respect to the base 8 by several
suspension springs 14 distributed along the blade unit 2 between the sub-frame
7 and the base
8. These suspension springs are also formed by resiliently flexible webs
integral with the sub-
frame 7 and the base, there being six suspension spring webs 14 uniformly
spaced apart along
the blade unit 2 in the illustrated embodiment. The spring webs 14 lie in
respective planes
perpendicular to the length of the blade unit 2 and conveniently the webs 14
are aligned and
coplanar with the spring webs 12. The spring webs 14 which can also deform by
buckling
serve as independent spring elements acting between the sub-frame 7 and the
base 8, and they
allow local displacement of the sub-frame 7 towards the base 8 and hence the
handle 1, while
exerting a substantially constant restoring force resisting such displacement.
The resiliently
flexible nature of the support structure with the spring webs 12, 14, is such
that localized
portions of the upper frame 6 and the blade assembly 5 carried thereon can be
deflected
towards the razor handle 1 in order to adapt to the skin contours without
necessarily
influencing the dispositions of other portions thereof, and the upper frame 6
and the blade
assembly 5 can as a consequence contort to comply with the undulations of the
skin area over
which they are moving. Thus, the blade unit 2 is resiliently compliant to
ensure close contact
with the skin over the full area spanned by the blades.
Thus, Figures 8 and 9 illustrate the blade unit 2 with the upper frame 6 and
blade assembly 5 deformed into a concave form, their medial portions M being
displaced
towards the handle 1 by a greater amount than their end portions E with the
spring webs 12,14
towards the centre M of the blade unit 2 being buckled to a greater extent
than those webs
12,14 located nearer the ends of the blade unit 2. Figures 10 and 11 on the
other hand show
the blade unit 2 deformed into a convex configuration, the blade assembly 5
and upper frame
6 being displaced downwardly towards the handle 1 by a greater amount at the
ends E of the
blade unit 2 than at the central portion M of the blade unit 2, and in this
case the spring webs
12,14 towards the ends of the blade unit being buckled more than those webs
closer to the
centre of the blade unit. Although both sets of webs 12,14 are shown buckled
in
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Figures 8 to 11 this is not inevitable or essential. It is possible, for
example as a
result of downward shaving force applied towards the rear R of the blade unit
for
the spring webs 12 to buckle so that the upper frame 6 and blade assembly 5
are
displaced downwardly adjacent the rear edge R without the suspension spring
webs
14 buckling and without any displacement of the upper frame 6 and the blade
assembly 5 at their front edge F. Also a force applied near the front edge F
can
cause downward displacement of the upper frame 6 and blade assembly 5 at their
front edge due to the suspension spring webs 14 buclcling without the spring
webs
12 becoming buckled. As a consequence, the upper frame 6 and blade assembly 5
are compliant both in the direction longitudinally of the blade unit 2 and in
the
direction perpendicular thereto in order to adapt to conform closely the
contours of
a skin area being shaved. Because the a~igle a, subtended between the upper
frame
6 and the sub-frame 7 is greater than the angle [3 subtended between the sub
frame
7 and the base 8, the spring webs 12 are somewhat longer and correspondingly
weaker than the spring webs 14, whereby the spring webs 14 exert a greater ,
resistance to downward displacement of the upper frame 6 and the blade
assembly 5
at their front edge F than the resistance to downward displacement exerted by
the
spring webs 12 at the rear edge R of the upper frame 6 and blade assembly 5,
which characteristic is considered desirable as during shaving greater forces
are
generally imparted to a blade unit in the region of the guard than those
exerted in
the region of the cap.
In the embodiment illustrated in Figures 1 to 11, the blade assembly
5 comprises a guard member 15 and a plurality of elongate blades 16, the guard
member 15 and the blades 16 being formed by flexible strips of metal. The
blades
16 have parallel forwardly facing sharpened edges 17. The guard member 15 and
the blades 16 are interconnected by transverse strips 18 such as steel as used
for the
manufacture of blade in conventional blade units, which may be made of the
same
material as the blades 16, e.g. steel, and which attached to the undersides of
the
blades and guard member. Maximum flexibility of the blade unit is ensured by
the
blades 16 and transverse connecting strips 18 being coplanar in the normal,
undeformed condition of the blade assembly and the blade unit. The guard
member
15 is also substantially coplanar with the blades 16 and connecting strips 18
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although as shown in Figures 6 and 7 the guard member has an upwardly inclined
rear portion, and slits 19 are spaced along the length of this portion of the
guard
member 15 for enhanced flexibility of this member 15. Including the guard'
member 15 in the blade assembly 5 can be advantageous in reliably defining the
shaving geometry of the blades, and the first blade in particular. The strips
18 have
turned-down T-shaped ends which are engaged with notches 20,21 moulded in the
front and rear edges of the upper frame 6 in order to secure the blade
assembly 5 to
the support structure 4. The upper frame 6 includes longitudinal front and
rear
frame members 22 and a series of transverse frame members 23 spaced along the
blade unit 2 and substantially perpendicular to the length of the blade unit
2. The
transverse frame members 23 are acted upon by respective spring elements and
the
upper edges of the spring webs 12 are attached to the respective frame members
23.
In the assembled blade unit 2 the strips 18 of the blade assembly 5 extend
above
respective frame members 23. The cap 24 of the blade unit 2 includes a
flexible
lubricating strip 25 which sits in a groove extending along the rear
longitudinal
member 22 of the upper frame 6 and is held in place by the transverse strips
18 of
the blade assembly 5. The support structure 4, at the front of the upper frame
6 in
the region of its hinged connection to the sub-frame 7, forms a guard 26 which
has
longitudinal ribs 27 moulded thereon although protrusions of other
configurations
could be provided. Also, if preferred, a separate flexible guard element could
be
mounted on the support structure 4 and have a desired guard surface
configuration.
The modified safety razor blade unit shown in Figures 12A, 12B and
13 is for the most part the same as that described above with reference to
Figures 1
to 11. However, in this embodiment the sub-frame 7A has the form of a
corrugated
sheet rather than a substantially planar sheet. The corrugations which are
only
shallow and have their ridges 7b and valleys 7c directed paxallel to the
planes of the
spring webs 12,14, serve to increase the flexibility of the sub-frame in the
longitudinal direction of the blade unit 2. Another difference is that in
place of the
notches 21 for securing the trailing ends of the blade carrying strips 18,
through
holes 21A are provided in the rear longitudinal frame member 22, the ends of
the
strips 18 being inserted through the respective holes 21A to ensure a secure
connection between the blade assembly S and the unitary support structure 4.
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In Figures 14 to 18 there is illustrated an embodiment in which the
safety razor has a blade unit 102 mounted on a handle 101, the blade unit 102
including a flexible blade assembly 105 carried by a compliant support
structure
104. The blade assembly 105 includes flexible strip blades 116 interconnected
by
transverse strips 118 attached to the undersides of the blades 116, as well as
a
flexible guard bar 126 and a flexible cap bar 125 respectively carried on the
transverse strips 18 in front of and behind the blades 116. The support
structure
104 has a base frame 108 shown U-shaped in cross-section with upper and lower
platforms 130,132. A series of upwardly extending support members in the form
of
posts 134 are spaced apart along the base frame 108 and are slidably guided
for up
and down movement in holes formed in the upper and lower platforms. The posts
134 project above the upper platform 130 and have enlargements or abutments
135
which engage the underside of the upper platform 130 to limit their upward
displacement. Mounted pivotally on the upper ends of the support posts 134,
for
pivotal movement about an axis A directed longitudinally of the blade unit
102, are
respective upper frame members 123, these frame members 123 being arra~zged
normally to extend upwardly and rearwardly from their forward ends 123a which
are connected to the support posts 134. The down-turned ends of the transverse
strips 118 of the blade assembly are engaged with the respective upper frame
members 123. The forward 123a end of each upper frame member 123 is bent
through nearly 180° and extended to form a rearwardly directed arm 136,
and a pin
138, which lilce the posts 134 is guided in holes in the upper and lower
platforms
130, 132 of the base frame 108, bears against the arm 136 to urge the upper
frame
member 123 to an upper pivotal position. Each of the pins 138 is pushed
upwardly
by a coil spring 112 which surrounds the pin 138 between the lower platform
132
and an abutment flange 139 on the pin 138. The abutment flange 139 also serves
to
limit the upward movement of the pin 138 by engaging the underside of the
upper
platform 130. The springs 112 also act to bias the support posts 134 to their
uppermost positions so that the normal position of the support structure 104
and
blade assembly 105 is as illustrated in the drawings. However, the upper frame
members 123 are moveable independently of each other, as are their respective
support posts 134, and this, in conjunction with the flexibility of the blade
assembly
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105, means that the blade unit 102 is resiliently compliant to enable close
conformity with the skin contours during shaving. To further enhance the
compliant
characteristic of the blade unit 102 the upper frame members 123 can
themselves be
resiliently flexible. The arrangement of the restoring springs 112 to resist
the
deformation of blade unit under shaving forces is such that there is a
substantially
uniform force exerted by the blade unit against the shin irrespective of the
degree of
blade unit deformation over the area of contact with the shin.
The embodiment of the razor illustrated in Figures 19 and 20 is
basically similar to that of Figures 12 to 16. The blade unit 202 which is
mounted
on the razor handle 201 includes a blade assembly 205 carried on a support
structure 204 including a base frame 208 and an upwardly projecting support
posts
234 guided for up and down sliding movement relative to the base frame 208.
Upper frame members 223 are in this case shown as constituted by the
transverse
strips 218 which interconnect the blades 216 and support the flexible guard
and cap
bars 226, 225, although separate frame members could be provided. The upper
frame members 223 have their forward ends pivoted on the upper ends of the
posts
234. Respective spring elements in the form of leaf springs 212 are mounted on
the
base frame 208 adjacent the rear edge and extend forwardly and upwardly for
the
free ends of the springs 212 to act on the upper frame members 223. As
demonstrated by Figures 20A and 20B which depict one of the springs 212 in an
unstressed and a stressed condition, respectively, the springs 212 are arcuate
in
cross-section. The effect of this spring configuration is that the spring
tends 212 to
flatten as it is deformed due to downward pivotal movement and/or displacement
of
the associated upper frame member 223, and in this way the spring 212 exerts a
substantially constant return force irrespective of the deformation of the
blade unit
202 during shaving.
The razor illustrated in Figures 21 to 25 is generally similar to that of
Figures 19 and 20, but differs in that in place of the support posts 234,
pivotal
support arms 334 with lower rear ends pivotally connected to the base frame
308,
are provided to mount the upper frame members 323 on which is carried the
blade
assembly 305 including the parallel blades 316, the flexible guard bar 326 and
the
flexible cap bars 325. First spring elements consisting of leaf springs 312
are
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mounted on the support arms 334 and act on extension fingers 336 of the upper
frame members 323 to bias the upper frame members 323 to an uppermost pivotal
position, and second spring elements 314 which are formed by respective leaf
spring
arms 314 of a common comb-shaped leaf spring 315 mounted on the base frame
308, act with their free ends against the undersides of the support arms 334.
The
leaf spring elements 314 are strongly pre-tensioned so that the forces exerted
on the
respective support anus 334 do not increase significantly as the support arms
are
pivoted downwardly by shaving forces imparted against the upper face of the
blade
unit in use of the razor, the upward pivotal movement of the arms 323 being
limited
by fingers 324 thereon abutting against the base structure 308 as may be seen
in
Figure 25. The upward pivotal movement of the arms 323 is similarly limited by
the fingers 336 abutting the arms 334. As in the previous embodiments, the
blades
316 and the blade assembly 305 as a whole is flexible, so that, with
independently
supported upper frame members 323 the blade unit 302 is resiliently compliant
over
the full area of its contact with the skin during shaving.
Other support structure arrangements and modifications to the
specifically described embodiments are possible without departing from the
principles of the invention and will occur to those skilled in the art. Merely
by way
of example it is mentioned that the pivotal mountings and associated leaf
springs
312, 314 between the pivotal support arms 334 and the base frame 308 andlor
between the pivotal support arms 334 an the upper frame members 323 in the
embodiment shown in Figures 21 to 25 could be replaced by living hinges. It is
to
be understood, therefore, that the embodiments specifically described above
are
given by way of non-limiting example only and it is the intention that the
scope of
the invention should be limited only by the claims which follow.
