Note: Descriptions are shown in the official language in which they were submitted.
W0 96/02165 PCT/US95/08740
~ 2194054
RESILIENTLY FLEXIBLE BRISTLE BEARING HEAD TOOTHBRUSH
Field of the Invention
The present invention relates to toothbrushes, more particularly to
toothbrushes which
comprise a flexible brush head with a generally concave bristle surface (i.e.
the surface
defined by the free ends of the bristles) in order to conform the toothbrush
to the
curvature of human teeth.
Background of the :Invention
The configuration of human teeth requires that the; ideal bristle contour for
toothbrushes
for brushing the buccal or outside surfaces of teetlh be concave and that the
ideal bristle
contour for brushing the lingual or inside surfaces of teeth be convex. Most
brushes
have a single piece head which is of comparable thickness to the handle and
which,
consequently, is relatively rigid and of a fixed curvature or configuration.
Some brushes
may, however, incorporate a means for allowing the head to flex relative to
the handle,
as described for example in EP-A-371,293. Even so, such brushes have limited
effectiveness. Other brushes are known which arE: adjustable into several
different but
fixed configurations. Adjustable toothbrushes are often difficult to
manipulate and may
be unreliable.
A further drawback of conventional brushes is that pressing the brush
sufficiently hard
against the teeth to get good cleaning risks damaging or discomforting the
softer, adjacent
gums. To a certain extent this can be solved by modifying the configuration of
the brush, or
by varying bristle hardness or length, though again, a single configuration
cannot be
optimum for all circumstances.
US-A-4,712,267, issued to ChenQ, discloses a convertible toothbrush comprising
an S-
shaped elongated handle of shape-retaining material having curved end regions
of
opposite curvature, a flexible brush block containing bristles, and a means
for mounting
the flexible brush block on the handle for longitudinal movement along the
length of the
handle. The curved portions of the handle bend tlhe flexible block and
bristles into a
concave or convex configuration which corresponds to the curved configuration
of the
handle.
-- 2194054
EP-A-454,625, assigned to Warner-Lamben: om an , describes an adjustable
curvature
toothbrush whose head is in the form of a loop. A cam or slide mechanism
changes the
curvature of the head between concave and convex configurations. In an
alternative
embodiment, the head is an integral part of the handle which is in the form of
a compressible
closed loop, the bristle surface being in a concave configuration when the
handle is in its
uncompressed state, becoming convex when the handle is compressed.
EP-A-577,656, to Linener & Fischer bH, discloses a toothbrush having a handle
and at
one end thereof a bristle-bearing head, wherein the head is in the form of two
or more
segments flexibly and resiliently linked to each other and/or to the handle,
one or more of
the segments being bristle bearing. In one embodiment this is achieved by the
use of
transverse, and optionally longitudinal, groovc;s on the opposite face of the
head to the
bristles. Under application of pressure in use the brush head may adopt a
convex
configuration. In another embodiment the handle extends into a frame into
whose interior
the head is resiliently linked. When pressure is applied to the centre of the
brush head it
adopts a concave configuration.
While the above toothbrushes provide brush beads with some degree of
flexibility, none
of them is entirely satisfactory, in particular, they either fail to provide
both convex and
concave configurations within the one embodiment or they require undue
manipulation or
skill on behalf of the user.
It is accordingly an object of this invention to provide a toothbrush with a
head which
can flexibly conform to either the convex or concave surfaces of the teeth and
which
provides good cleaning and is easy to manufacture and use.
It is a further object of the invention to provide a toothbrush which can
clean the teeth
efficiently with minimal damage to adjacent l;um tissue.
Summary of the Invention
According to one aspect of the present invention there is provided a
toothbrush, having a
handle and a resiliently flexible bristle-bearing head wherein, when the
toothbrush is in its
normal stress-free configuration, the free ends of bristles lying along a
longitudinal and/or
transverse axis of the brush form a generally concave profile; and wherein the
head has a
pair of opposing faces with bristles mounted on one of said pair and the same
and the
opposite face having one or more linear or non-linear grooves therein; and
wherein one or
more of the grooves is wholly or partly filled with an elastomeric material.
The toothbrush head of this invention, being flexible, can flex under the
action of
toothbrushing so as to accommodate itself to the differing profiles of
individual users'
.... ~rp 96/02165 219 ~ ~ ~ ~ p~~S95/08740
teeth. In particular, the flexible head of the toothbrush of the present
invention has, in
its normal stress-free configuration, a bristle profile adapted to suit the
buccal surface of
the teeth but, at least in preferred embodiments, can bend continuously
through a flat
position to a convex configuration to accommodate the lingual surface of the
teeth
generally better than would be the case with a conventional rigid-headed
toothbrush.
'The head may be adapted in such a way that the outer rows of bristles can
flex away
from the centre to limit the pressure applied to gums when the brush head is
pressed
against the teeth. In all cases the head is resilient, so that when an applied
force is
removed, the brush head returns to its original configuration.
Detailed Description of the Invention
The toothbrushes of the invention take the form of an elongated handle with,
as an
essential component, a resiliently flexible bristle-bearing head. At least a
first part of the
head is formed as an integral extension to the handle. At least one area of
this part of
the head is sufficiently thin that the head will bend under normal brushing
forces.
Preferably, the head further comprises one or more areas of a second,
elastomeric~
material formed in or around the first part of the head, so that the whole
head has a
conventional, generally flattened shape but remair.~s flexible when compared
to that of a
conventional brush. By flexible is meant herein that when a normal bnishing
force (2 - 4
Newtons) is applied to one end of the head, the other end being held fixed,
the end to
which the force is applied will deflect through an angle of at least 1 degree
(the flex
angle). In preferred embodiments the flex angle is at least 5 degrees, more
preferably at
least 10 degrees and it can b~e as high as 45 degrec;s or more. In highly
preferred
embodiments the flex angle is such that the head is able to bend through into
a convex
configuration. At least one face of the head has bristles attached thereto.
The handle of the toothbrush of the invention, and that part of the head which
is an
extension of the handle may be made of materials which are conventional in the
manufacture of toothbrushes, especially plastics materials. Suitable plastics
materials
include, for example, polyamides and polypropylenes. An example of a suitable
polypropylene is the material 'Polypropylene PM 1600' (marketed by Shell),
having a
modulus of elasticity (ISO 178) of 1500 MPa and a hardness (ISO 868) of 75
Shore A.
The handle itself is generally rigid and may be of a shape which is
conventional in the
manufacture of toothbrushes. Optionally, the handle may comprise a neck
portion which
is more flexible than the rest of the handle, as known in the art, provided
that it is
sufficiently rigid that, in use, when force is applied to the head,
particularly when
WO 96/02165
PCT/US95/08740
4
brushing the teeth, the head may still flex in the manner and to the extent
described
above.
In a preferred aspect of the invention, the head has one or more bristle-
bearing faces and
at least one bristle-bearing face of the head forms a generally concave
configuration
when the brush is in its normal unstressed state. The face of the head may be
concave
along either or both of the transverse and longitudinal axes of the head.
Where the face
is concave along the longitudinal axis, the radius of curvature may vary along
the length
of the head. The radius of curvature is preferably from 10 to SOOmm, more
preferably
from 15 to 250mm, especially from 25 to 150mm.
In one embodiment the first part of the head comprises one or more extensions
which are
integral with the handle, and of such thickness that the desired flexibility
is achieved
whilst maintaining structural integrity of the head under expected conditions
of use. The
extensions are generally substantially thinner than the handle. Preferably
there is only
one such extension. The head may vary in thickness along its length in order
to control
the profile obtained as the head is flexed under e~,;ternal bending forces. In
this
embodiment the head extensions are preferably at least partially, and more
preferably
wholly, surrounded by an elastomeric material, siiid material also filling any
gaps
between multiple extensions. The extensions) may carry some surface ribbing or
detailing to assist the adhesion of the elastomer to them.
In yet further embodiments the head has a pair of opposing faces with bristles
mounted
on one of said pair and the same and / or the opposite face having one or more
linear or
non-linear grooves therein. The grooves create tt;~in hinges which make the
head
flexible, the portions of the head between the grooves preferably being of
comparable
thickness to a conventional non-flexible head.
The grooves can be oriented generally transverse or parallel to the
longitudinal axis of
the handle and can follow generally curved or zig-zag paths. In particular the
grooves
may run longitudinally along the head to allow thc; outer longitudinal rows of
bristles to
flex away from the inner ones. Preferably there vvill instead or in addition
be transverse
grooves so that the head can bend along the longitudinal axis.
The grooves can be of variable width and depth and the distances between
grooves can
also be varied. In this manner the flexibility of the head along the length
and / or across
the breadth of the head can be modified. Preferably only the transverse
grooves are
varied in this way.
2194054
S
One or more of the grooves, preferably all, can be wholly or partially filled
with an
elastomeric material. In this way too the flexibility and / or resilience of
the head may
be varied and contamination of the grooves by, for example, toothpaste
deposits may be
reduced or avoided completely. The colour of the elastomeric material may be
the same
as that of the material of the head, or it may be different thereby achieving
a distinctive
striped or otherwise patterned appearance.
The grooves may be generally straight or they may follow curved or zig-zag
paths.
Non-linear grooves help to offset compression stress in the elastomeric
material filling
the grooves as the head bends.
Suitable elastomeric materials herein are therrnoplastic elastomers with a
Shore hardness
of 30 - 80 such as Santoprene and Thermoflex. A particularly suitable
elastomer is '1?TS
ThermoflexT"' 75' (marketed by Plastic Technologie Service, Germany), having a
modulus
of elasticity (ISO 178) of 100 MPa and a hardness (ISO 868) of 80 Shore A. The
elastomers may optionally be mixed with a suitable plasticiser or foaming
agent to make
them more compressible.
The bristles can be made of any of the materials weU known in the art.
Suitable bristle
materials herein are polyester and nylon, such as Dupont Nylon 612~'~"''. The
bristles are
preferably of circular cross-section but can also be of other crass-sections
including, but
not limited to, rectangular, hexagonal and trilobular. Furthermore, the
diameter and
length of the bristles can vary within the usual dimensions known by a person
skilled in
the art, provided that, when the brash is in the unstressed state, the overall
objective of
having a generally concave bristle surface is sxill met. The bristles are
generally
conventionally gmuped into tufts and can be attached to the brush head by a
variety of
processes. Preferred processes herein are stalpling and fusion. The bristles
can be
inserted into either or both of the head extension and the elastomeric
material. Cutting
and end-rounding of the bristles can be done using any of the methods commonly
known
in the art.
In use, the toothbnrsh of this invention can be; used for cleaning the teeth
by an entirely
conventional toothbrushing hand action, prefe;rably in a manner.~ecommended by
dental
health authorities. The toothbrush of the inva;ntion can also be used in
electrically driven
toothbrushes or children's toothbrushes.
WO 96/02165 ~ ~ PCT/US95/08740 --
6
The invention will now be described by way of example only, with reference to
the
accompanying drawings in which:
Fig 1 is a partial side view of a first embodiment of the invention, depicting
a toothbrush
head with transverse grooves. Although the head is flat in its unstressed
state, the
bristles are cut to different lengths so that the bristle surface is concave
along the
longitudinal direction.
Fig 2 is a similar view of a second embodiment illustrating a toothbrush head
where the
first part is formed by a single extension integral with the handle and is
further
surrounded by elastomer. The head is pre-formed so that it is naturally
concave in its
unstressed state.
Fig 3 is a partial side view of a third embodiment showing a grooved
toothbrush head,
the face of which is concave in its unstressed configuration and illustrating
how the
toothbrush head can bend from a concave configiration to a convex one to suit
both
buccal and labial surfaces of the teeth (shown in plan).
Fig 4 is a plan view of a toothbrush head, constituting a fourth embodiment of
the
invention and which comprises three thin longitudinal extensions surrounded by
elastomer. The head is able to bend around both longitudinal and transverse
axes.
Fig 5 is a transverse section through the head of Fig. 4 along the line AA' .
The bristles
are cut so that the bristle surface is naturally concave along the transverse
axis.
Fig 6 is a plan view of a fifth embodiment wherein the head has both
transverse and
longitudinal grooves. The grooves are filled with elastomer.
Fig 7 is a transverse section through a toothbrush head constituting a sixth
embodiment
with two longitudinal grooves on each face. The; head is pre-formed so that
its face is
naturally concave along the transverse axis. The; grooves are filled with
elastomer.
Fig 8 shows how the longitudinal outer rows of the brush head of Fig. 7 can
flex away
from the gums as force is applied when brushing;.
Figs 9 and 10 are plan views of heads constituting further embodiments with
chevron-
like and waved transverse, elastomer-filled grooves.
PCT/US95/08740
WO 96102165
7
Fig 11 is a partial plan view of a still further embodiment whose head has
transverse
grooves wherein, along the centre line of the head, the grooves are the full
depth of the
head so that two rows of approximately parallel hunges are created.
Fig 12 is a partial side view of yet another embodiment showing a side view of
a head
with variable depth grooves, giving greater flexib~lility nearer the neck of
the brush.
Referring to Fig 1, a toothbrush head (1) is formE;d integrally at one end of
a handle (2).
The head ( 1 ) has two substantially parallel faces, and in a top face are
mounted bristles
distributed in a plurality of tufts (3). The upper ~~nd lower faces carry a
number of
generally parallel transverse grooves (4), leaving a thin, flexible hinge of
head material
(5). The bristles are cut so that the bristle surfacE: (6) is concave when the
brush is in its
natural unstressed state.
In Fig 2 a first part of the brush head is formed by a single thinned
extension (7) of the
handle (2). The extension is surrounded by an ehastomer (8) so that the whole
head is of
comparable thickness to a conventional brash. Tlhe head is pre-formed into a
naturally
concave configuration but is sufficiently flexible l:hat, under normal
brushing forces the
head can be made to bend back into a convex configuration. The bristle tufts
(3) in this
example are of approximately equal length and are fused into the elastomeric
material.
In Fig 3 the head is pre-formed into a naturally concave configuration (9)
ideally suited
to clean the buccal surface of teeth (10). Transverse grooves (4) confer
flexibility on the
brush head so that under normal brushing forces l:he head can be made to bend
back into
a convex configuration (11) more suited to the labial surface (12) of the
teeth. The
grooves may additionally be filled with an elastorneric material, optionally
of a different
colour to the head material to give a distinctive appearance.
In Figs 4 and 5 the head (1) comprises multiple extensions (13) of the handle,
surrounded by elastomer (8) so that the overall shape of the head is
conventional, whilst
being flexible in both longitudinal and transverse directions. The bristle
tufts (3) are
shown fused into the elastomer and are cut so that the bristle surface (6) is
generally
concave.
In Fig 6, the head (1) carries both transverse (4) .and longitudinal (14)
grooves. The
grooves are filled with elastomer. Holes (15) are drilled into one face of the
head in the
regions of normal thickness between the grooves (16) to accommodate bristle
tufts by a
conventional stapling process.
WO 96102165 ' PCT/US95/08740
8
In Figs 7 and 8 the head (1) is pre-formed so that it is naturally concave
along the
transverse axis. Longitudinal grooves (14) on both upper and lower faces of
the head
confer flexibility. In this way the outer rows of bristles (17) can flex away
from the
gums (18) as the teeth (19) are brushed, thus avoiding gum damage.
Figs 9 and 10 show heads with non-linear, transverse, elastomer-filled
grooves. The
grooves are in the form of chevrons (20) or waves (21). In both cases, the
grooves give
the brush a distinctive appearance and, further, help to offset compression
stress in the
elastomeric material within the grooves as the brush bends. The figures show
the back
of the head, which becomes compressed as the brush head bends towards a convex
configuration.
In Fig 11 the head has transverse elastomer-fillet3 grooves (4). For clarity
the elastomer
is not shown. Around the centre axis of the brush BB' the grooves pass right
through the
brush head (22) leaving a row of hinges (5) on each side of the head. The
bristle tufts
(3) are conventionally stapled into the thicker parts of the head.
In Fig 12 the depth of the grooves (4) is shown to increase in the direction
towards the
handle (2), the deepest grooves being closest to the end of the head nearest
to the handle.
This results in the part of the head closest to the handle (2) being more
flexible by virtue
of having thinner hinges than the part of the head furthest from the handle.
The grooves
are filled with elastomer.
