U.S. patent application number 10/600032 was filed with the patent office on 2004-01-15 for toothbrush with elastomer filled flexible head.
Invention is credited to Cann, David Victor.
Application Number | 20040006837 10/600032 |
Document ID | / |
Family ID | 26308483 |
Filed Date | 2004-01-15 |
United States Patent
Application |
20040006837 |
Kind Code |
A1 |
Cann, David Victor |
January 15, 2004 |
Toothbrush with elastomer filled flexible head
Abstract
The invention relates to a toothbush comprising: i) an elongated
handle having distal and proximal ends and one or more elastomeric
handle regions therein; and ii) a resiliently flexible head
attached to the proximal end of the handle, the head including a
pair of opposing faces, one of the pair being a bristle-bearing
face with bristles attached to and extending from the face, wherein
at least one of the pair has one or more elastomer-containing,
transverse grooves therein; and iii) one or more elastomer supply
channels extending between the elastomeric handle regions and the
transverse grooves, whereby at least one of the elastomeric handle
regions and the transverse grooves can be filled with elastomer
from a single injection point. The elastomeric regions in the head
can be used to make the head flexible and the whole brush can
conveniently be made on conventional machines.
Inventors: |
Cann, David Victor; (Surrey,
GB) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Family ID: |
26308483 |
Appl. No.: |
10/600032 |
Filed: |
June 20, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10600032 |
Jun 20, 2003 |
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10132976 |
Apr 24, 2002 |
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10132976 |
Apr 24, 2002 |
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09101918 |
Aug 20, 1998 |
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6408476 |
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09101918 |
Aug 20, 1998 |
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PCT/US97/00968 |
Jan 17, 1997 |
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Current U.S.
Class: |
15/167.1 ;
300/21 |
Current CPC
Class: |
A46B 5/002 20130101;
A46B 5/0025 20130101; A46B 5/02 20130101; A46B 9/04 20130101; B29L
2031/425 20130101; A46B 2200/1066 20130101; A46B 7/06 20130101;
A46B 9/025 20130101 |
Class at
Publication: |
15/167.1 ;
300/21 |
International
Class: |
A46B 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 1996 |
GB |
9601012.9 |
Claims
What is claimed is:
1. A toothbrush, comprising: i) an elongated handle having distal
and proximal ends and one or more elastomeric handle regions
therein; and ii) a resiliently flexible head attached to the
proximal end of the handle, the head including a pair of opposing
faces, one of the pair being a bristle-bearing face with bristles
attached to and extending from the face, wherein at least one of
the pair has one or more elastomer-containing, transverse grooves
therein; and iii) one or more elastomer supply channels extending
between the elastomeric handle regions and the transverse grooves,
whereby at least one of the elastomeric handle regions and the
transverse grooves can be filled with elastomer from a single
injection point.
2. A toothbrush according to claim 1 wherein all of the elastomeric
handle regions and the transverse grooves can be filled with
elastomer from a single injection point.
3. A toothbrush according to claim 2 wherein at least one supply
channel extends to the distal end of the handle.
4. A toothbrush according to claim 3 wherein the elastomer
injection point is located at the distal end of the handle.
5. A toothbrush according to claim 4 wherein both the
bristle-bearing face and the opposing face include transverse
grooves therein.
6. A toothbrush according to claim 5 wherein the transverse grooves
divide the head into segments which are flexibly connected by
hinges, wherein each hinge is located between the opposing faces
and at a distance of at least about 10% of the depth of the head
from each of the faces, the hinges being less than the full width
of the head.
7. A toothbrush according to claim 6 wherein handle is made from an
opaque material and the supply channel passes from one face of the
handle to its opposite face so that when filled with elastomer, the
supply channel appears to be discontinuous.
8. A method for making the toothbrush according to claim 1
comprising the step of injecting molten elastomer, under pressure,
into the injection point and causing it to flow along the supply
channel and into the grooves.
9. A toothbrush comprising a handle and an articulated head, said
head having at least two sections to thereby define a composite
head having an upper surface and a lower surface, said at least two
sections having respective longitudinally spaced ends facing each
other, each of said head sections having a plurality of tufts of
bristles extending from the lower surface thereof, said facing ends
having an elastomeric material therebetween, said handle area
having a molded-in channel that may be used to introduce
elastomeric material into said head.
10. The toothbrush of claim 9, wherein the handle includes a grip,
and wherein elastomeric material may be introduced into said
molded-in channel though said grip.
11. The toothbrush of claim 9, wherein at least some of the tufts
extending from the bottom surface of one of said head sections are
of uniformly different lengths.
12. The toothbrush of claim 9, wherein the free ends of at least
some of the tufts extending from one of said head sections form a
slant with respect to the lower surface of said head section.
13. The toothbrush of claim 12, wherein the elastomer between the
facing ends forms at least one wing portion along the longitudinal
axis of the upper surface of the head.
14. The toothbrush of claim 9, wherein the elastomer between the
facing ends is generally T shaped.
15. The toothbrush of claim 12, wherein the elastomer between the
facing ends is generally T shaped.
16. A toothbrush comprising a handle and an articulated head, said
head having at least two sections to thereby define a composite
head having an upper surface and a lower surface, said at least two
sections having respective longitudinally spaced ends facing each
other, each of said head sections having a plurality of tufts of
bristles extending from the lower surface thereof, said facing ends
having an elastomeric material therebetween, wherein at least some
of the tufts extending from the bottom surface of one of said head
sections are of uniformly different lengths, wherein at least some
of the free ends of the tufts extending from one of said head
sections form a slant with respect to the lower surface of said
head section, wherein the length of the elastomer between the
facing ends of said two head sections varies, said length being
measured along the toothbrush longitudinal axis.
17. The toothbrush of claim 16, wherein the elastomer between the
facing ends forms at least one wing portion along the longitudinal
axis of the upper surface of the head.
18. The toothbrush of claim 17, wherein the elastomer between the
facing ends is generally T shaped.
19. A toothbrush comprising a handle and an articulated head, said
head having at least two sections to thereby define a composite
head having an upper surface and a lower surface, said at least two
sections having respective longitudinally spaced ends facing each
other, each of said head sections having a plurality of tufts of
bristles extending from the lower surface thereof, said facing ends
having an elastomeric material therebetween, wherein the length of
the elastomer between the facing ends of said two head sections
varies, said length being measured along the toothbrush
longitudinal axis.
20. The toothbrush of claim 19, wherein the elastomer between the
facing ends forms at least one wing portion along the longitudinal
axis of the upper surface of the head.
21. The toothbrush of claim 19, wherein the elastomer between the
facing ends is generally T shaped.
22. A method of producing a toothbrush comprising: molding, of one
material, a toothbrush handle aligned with and integrally joined to
a composite head, the composite head including at least a first and
a second section, the composite head having an upper and lower
surface, the first section and the second section having respective
longitudinally spaced ends facing each other, the handle having a
molded in channel that may be used to introduce elastomeric
material into said head; injecting an elastomer into the molded in
channel; and tufting both the first section and the second section
each with a plurality of tufts.
23. The method of claim 22, wherein the tufts extending from one of
said head sections are of uniformly different lengths.
24. The method of claim 22, wherein the length of the elastomer
between the facing ends of said two head sections varies, said
length being measured along the toothbrush longitudinal axis.
25. The method of claim 22, wherein the step of tufting both the
first section and the second section is performed after the step of
injecting an elastomer into the molded in channel.
26. A method of producing a toothbrush comprising: molding, of one
material, a toothbrush handle aligned with and integrally joined to
a composite head, the composite head including at least a first and
a second section, the composite head having an upper and lower
surface, the first section and the second section having respective
longitudinally spaced ends facing each other, the handle having a
molded in channel that may be used to introduce elastomeric
material into said head; injecting an elastomer between said facing
ends of said first and second sections; and tufting both the first
section and the second section each with a plurality of tufts,
wherein the length of the elastomer between the facing ends of said
two head sections varies, said length being measured along the
toothbrush longitudinal axis.
27. A method of producing a toothbrush comprising: molding, of one
material, a toothbrush handle aligned with and integrally joined to
a composite head, the composite head including at least a first and
a second section, the composite head having an upper and lower
surface, the first section and the second section having respective
longitudinally spaced ends facing each other, the handle having a
molded in channel that may be used to introduce elastomeric
material into said head; injecting an elastomer between said facing
ends of said first and second sections; and tufting both the first
section and the second section each with a plurality of tufts.
28. The method of claim 27, wherein the tufts are organized as rows
substantially transverse to the longitudinal axis of the toothbrush
handle, and wherein the rows of tufts extending from one of said
head sections are of uniformly different lengths.
29. The method of claim 27, wherein the step of tufting both the
first section and the second section is performed after the step of
injecting an elastomer between said facing ends of said first and
second sections.
30. A toothbrush comprising a handle and an articulated head, said
head having at least two sections to thereby define a composite
head having an upper surface and a lower surface, said at least two
sections having respective longitudinally spaced ends facing each
other, each of said head sections having a plurality of tufts of
bristles extending from the lower surface thereof, said facing ends
having an elastomeric material therebetween, said handle area
having a molded-in channel that may be used to introduce
elastomeric material into said head, wherein the length of the
elastomer between facing ends of said head sections varies, said
length being measured along the toothbrush longitudinal axis.
Description
CROSS REFERENCE TO CO-PENDING APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No, 09/101,918 filed Aug. 20, 1998, which was the National Stage of
International Application No. PCT/US97/00968, filed Jan. 17, 1997,
the substances of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a toothbrush, more
particularly to a toothbrush with a comprising regions of elastomer
in both the head and the handle wherein one or more elastomer
supply channels connect the regions so that they can all be filled
with elastomer from a single injection point.
BACKGROUND OF THE INVENTION
[0003] The configuration of human teeth requires that the ideal
bristle contour for toothbrushes for brushing the buccal or outside
surfaces of teeth 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 is relatively rigid and of a fixed
curvature or configuration.
[0004] 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.
[0005] 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.
[0006] WO 92/17093 discloses a toothbrush having a handle and at
ore 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 be the use of
transverse, and optionally longitudinal, grooves on the opposite
face of the head to the bristles. The grooves can be wholly or
partially filled with an elastomer.
[0007] Co-filed, application WO 92/17092 further discloses a
toothbrush having a handle and at one and thereof a bristle-bearing
head which is flexibly and resiliently linked to an extended
portion of the handle. The space between the head and the handle
may be filled with an elastomer. The applicant markets a brush
called the `Schwingkopf under the name `Dr. Best` which contains
same of the features disclosed in WO 92/17092. The brush has an
elastomeric handle grip and an elastomer filled groove connecting
the grip to an elastomer filled region in the neck of the brush.
However, the brush does not contain transverse grooves in the
head.
[0008] It is well-known to provide elastomeric grips in the handles
of toothbrushes. It is also know from the above-mentioned PCT
applications to provide transverse grooves containing elastomer
into a brush head. To the present applicant's knowledge however, it
has not been disclosed how both these objects can be achieved using
a conventional single-point, injection moulding process.
[0009] It has now been found that all of the elastomer filled areas
of the brush can be filled by a single-point injection moulding
process by providing one or more elastome supply channels which
connect the grooves in the head to the grips in the handle.
[0010] It is accordingly an object of this invention to provide a
toothbrush with a flexible head and handle grips which can be made
by a simple injection moulding process.
[0011] It is yet a further object of this invention to provide a
toothbrush which has good long-term durability.
SUMMARY OF THE INVENTION
[0012] According to one aspect of the present invention there is
provided a toothbrush, comprising:
[0013] i) an elongated handle having distal and proximal ends and
one or more elastomeric handle regions therein; and
[0014] ii) a resiliently flexible head attached to the proximal end
of the handle, the head including a pair of opposing faces, one of
the pair being a bristle-bearing face with bristles attached to and
extending from the face, wherein at least one of the pair has one
or more elastomer-containing transverse grooves therein; and
[0015] iii) one or more elastomer supply channels extending between
the elastomeric handle regions and the transverse grooves.
[0016] whereby at least one of the elastomeric handle regions and
the transverse grooves can be filled with elastomer from a single
injection point.
[0017] According to a second aspect of the invention there is
provided a toothbrush, comprising:
[0018] i) an elongated handle having distal and proximal ends and
one or more elastomeric handle regions therein; and
[0019] ii) a resiliently flexible head attached to the proximal end
of the handle, the head including a pair of opposing faces, one of
the pair being a bristle-bearing face with bristles attached to and
extending from the face, wherein each of the pair has one or more
elastomer-containing, transverse grooves therein, the grooves
dividing the head into segments which are flexibly connected by
hinges, wherein each hinge is located between the opposing faces
and at a distance of at least about 10% of the depth of the head
from each of the faces, the hinges being less than the full width
of the head; and
[0020] iii) one or more elastomer supply channels extending between
the elastomeric handle regions and the transverse grooves,
[0021] whereby at least one of the elastomeric handle regions and
the transverse grooves can be filled with elastomer from a single
injection point.
[0022] The toothbrush of this invention comprises a handle
including elastomeric regions, which can be used to improve the
user's grip on the handle, and a head which has transverse grooves
that allow the head to flex under the action of brushing and
accommodate itself to, for example, the differing profiles of
individual users' teeth. The head further includes elastomer
contained within the grooves on at least one face. The elastomer
improves the resilience of the head by acting like a spring, so
that when a force applied to bend the head is removed, the head
returns within a short period of time to its original
configuration. The toothbrush further comprises one or more supply
channels which connect the elastomeric regions in the handle to the
transverse grooves in the head enabling the elastomer in both the
head grooves and handle regions to be supplied from a single
elastomer injection point. The grooves divide the head into
segments and define hinges which connect the segments. Preferably,
there are transverse grooves on both of the opposing faces and the
hinges are located between the faces so that they are subject to
the minimum amount of tension or compression. In this case the
hinges are preferably less than the full width of the head so that
elastomer can flow, from one face of the had to the opposing face.
The interconnectivity of the elastomer containing parts enables all
of them to be filled with elastomer using a single-point injection
moulding process on conventional equipment.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Handle
[0024] The toothbrush of this invention comprises an elongated
handle having distal and proximal ends and one or more elastomeric
handle regions therein. The handle can be of shape and external
dimension suitable for toothbrushes. The elastomeric regions in the
handle are generally designed to act as hand or finger grips but
they can be provided for solely aesthetic purposes, for example to
give the brush a distinctive appearance. The elastomeric regions
can be flush with the surface of the handle or raised or recessed
from the handle surface. Preferably at least a part of one
elastomeric region is raised for providing better grip. In general
the elastomeric regions are provided by initially moulding the
handle the handle to comprise voids which are then filled by the
elastomer in a separate injection moulding step. The voids provide
some physical entrapment of the elastomer, but preferably the
elastomer is chosen so that it becomes bonded to the handle
material through the injection moulding process. The voids can be
arranged so that when filled with elastomer the various elastomer
regions, at least when handle material is opaque, give the
appearance of being completely discrete. At least one, preferably
all, of the elastomeric regions in the handle is connected by the
elastomer supply channel(s) described below to the, transverse
grooves in the head. Typically, the elastomer in the grips of the
handle is a substantial part of the total volume of elastomer to be
injected. For this reason the elastomer injection point is
preferably located at the distal end of the handle. In this
context, `at the distal end of the handle` means that the injection
point is located closer to the distal end than to the proximal end
of the handle.
[0025] The handle, and also the toothbrush head, are generally made
of relatively non-compressible materials, preferably with a modulus
of elasticity of at least about 500 MPa, more preferably at least
about 1000 MPa, which are conventional in the manufacture of
toothbrushes, especially plastics materials. Suitable plastics
materials include, for example, polyamides and polypropylenes.
Polypropylene is preferred. Suitable polypropylenes include the
material `Polypropylene PM 1600` (marketed by Shell), having a
modulus of elasticity (ISO 178) of 1500 MPa and Apryl 3400 MA1 from
Elf Atochem. Preferably, a foaming agent such as Hydrocerol HP20DP
from Boehringer-Mannheim is mixed with the polypropylene at a level
of from about 1% to about 3%, preferably from about 1.5% to about
2.5%. by weight of the polypropylene.
[0026] The foaming agent assists the flow of the polypropylene
during mouldng and, in particular, helps to ensure uniform
formation of the hinges in the head.
[0027] Suitable elastomers for use herein include thermoplastic
elastomers with a Shore hardness of 30-80 and a modulus of
elasticity of less than about 500 MPa preferably less than about
300 MPa, such as Santoprene and Thermoflex. An exemplary elastomer
is `PTS Thermoflex 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. Elastomers PL12291, PL12292, and
PL12293 (marketed by Multibase, Saint Laurent Du Pont, France) are
also suitable for use herein. In general, choosing the elastomer so
that is based upon the same chemical class of polymers as material
of the head segments assists in bonding the elastomer to the head
segments. For example, when the head segment are made from
polypropylene, the elastomer is preferably based upon
polypropylene. The elastomers can optionally be mixed with a
suitable plasticiser or foaming agent to make them more
compressible. The colour of the elastomer material can be the same
as that of the head segments, or it may be different thereby
achieving a distinctive striped or otherwise patterned
appearance.
[0028] The handle itself is generally rigid. 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 brushing the teeth, the head still flexes in the manner and to
the extent described below.
[0029] Head
[0030] The toothbrush of this invention further comprises a
resiliently flexible head attached to the proximal end of the
handle, the head including a pair of opposing faces, one of the
pair being a bristle-bearing face with bristles attached to and
extending from the face, wherein at least one of the pair has one
or more elastomer-containing transverse grooves therein.
[0031] Suitable materials for the head are the same as those for
the handle. Preferably the head and handle are co-moulded in a
single injection moulding step, so that the head and handle form
one continuous piece. In any case the long axis of the handle
defines a longitudinal axis of the head. The head also has a
transverse axis lying orthogonal to the longitudinal axis and
generally parallel to the opposed faces. References to transverse
or longitudinal herein refer to directions which are respectively
parallel to these transverse and longitudinal axes unless indicated
otherwise. The head itself is also generally elongated with its
elongated axis also being a longitudinal axis.
[0032] The head includes transverse grooves on at least one of the
bristle-bearing face and the opposing face, the grooves dividing
the head into segments. The grooves allow the head to flex or bend
along its longitudinal axis. This allows the brush head to flex so
that it acquires a convex profile along the longitudinal axis when
pressed against the teeth. This makes it particularly suitable for
brushing the lingual or inside surfaces of the teeth. The grooves
can be linear or non-linear, such as curved or zigzag. Non-linear
grooves help to offset compression stress in the elastomeric
material filling the grooves as the head bends. The term
`transverse grooves` as used herein can also encompass grooves
whose main axis, as defined by the straight line joining the start
and endpoints of the grooves is offset from the transverse axis of
the head by an angle of up to and including 45.degree.. In
preferred embodiments both the bristle-bearing face and the
opposing face include one or more transverse grooves therein.
[0033] The head also includes one or more longitudinal grooves on
al least one of the bristle-bearing face and the opposing face. The
term `longitudinal grooves` as used herein can also encompass
grooves whose main axis, as defined by the straight line joining
the start and endpoints of the grooves is offset from the
`longitudinal axis of the head by an angle of up to 45.degree..
Longitudinal grooves can allow for example, the outer longitudinal
rows of bristles to flex away from the inner ones. They also act as
elastomer supply channel(s) to the transverse grooves as described
below.
[0034] Where there are grooves on both of the opposing faces,
grooves on one face can be directly opposed to grooves on the other
face or partially or wholly offset. Preferably, the grooves are
directly opposed or only partially offset.
[0035] The grooves, which separate the segments of the head, also
define hinges, which are thinned regions of the bead at the base of
the grooves.
[0036] 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 transverse grooves are
varied in this way. Changing the depth of the grooves controls the
location and thickness of the hinges which connect the segments.
For a toothbrush head of between about 4 to about 6 mm thickness,
typically about 5 mm, suitable groove depths are in the range from
about 1.4 to about 3 mm, preferably from about 1.5 to about 2.8 mm.
Suitable hinge thicknesses are in the range from about 0.4 to about
2.0 mm, preferably from about 0.5 to about 1.5 mm. Where transverse
grooves are used then, desirably, the hinges which are or will be
nearer to the handle are less flexible than those which are or will
be more remote from it. In this way more uniform bending of the
head can be achieved. The variation in flexibility can be achieved
by varying the hinge thicknesses. In a preferred embodiment the
hinge nearest the handle is up to about 3 times, preferably up to
about 2 times as thick as the hinge most remote from the handle. An
exemplary set of hinge thicknesses for a toothbrush with 3
transverse grooves are respectively about 1.2, 0.6 and 0.6 mm
reading from the handle end. If identical hinges are used along the
brush head then there is a tendency for flexing of the head to
occur predominantly at the hinge nearest the handle. The depth of
grooves on the bristle bearing face can be different to those on
the opposing face. Preferably the grooves on the bristle-bearing
face are less deep than those on the opposing face. In embodiments
where there is elastomer in the grooves on both faces, this allows
more elastomer to be put under compression than under tension. The
elastomer to segment bonds are stronger under compression than
under tension.
[0037] Increasing the width of the grooves increase the gap between
the segments and therefore the length of the hinges, which
increases their flexibility. However, since it is preferred to
insert bristles into the segments rather than into the elastomer,
increased groove length also leaves less space for the bristles,
within a given head size. Suitable groove widths are in the range
from about 0.3 to about. 3.0 mm, preferably from about 1.2 to about
2.0 mm. The grooves are preferably tapered slightly inwards towards
the bottom of the groove, suitably converging at an angle of from
about 3 to about 10.degree., to facilitate moulding. As the brush
is flexed the width of the groove changes, more rapidly at the top
of the groove than at the bottom of the groove, the relative change
being a function of the groove width and depth. Since this change
in groove width results in compression or tension of elastomer
contained within the groove, it can be seen that, for a given
elastomer, the groove geometry can be used to control the flex
angle.
[0038] The hinges can be the full length of the grooves or,
preferably, there can be one or more gaps in or to the side of the
hinges the grooves in these regions being the full depth of the
head. The gap allows elastomer to flow from one face to the other
during the moulding process so that elastomer can be used on both
sides of the head and vet still supplied from a single injection
point. In a preferred embodiment, the hinges are discontinuous,
with two or more hinges, preferably just two, connecting each
segment to its neighbour or to the handle. In this embodiment there
are gaps between the hinges and to each side. In linear grooves,
the hinge widths are not generally critical, provided that they are
such that gaps are still created, however, wide hinges can be
subject to distortion if they are used within a non-linear groove.
Suitable hinge widths are in the range from about 0.5 to about 4.0
mm, preferably from about 1.0 to about 3.0 mm.
[0039] It is preferred that each hinge is located between the two
faces and at a distance of at least about 10%, preferably at least
about 20%, more preferably at least about 30% of the depth of the
head from each of the faces. The distance of the hinge from the
face is measured by the perpendicular line drawn from the top of
the face to the nearest boundary surface of the centre of the
hinge. Locating the hinges away from the faces of the brush means
that they are subject to less stretching or compression as the head
is flexed and improves their durability. In a particularly
preferred embodiment, the brush head has transverse grooves which
are arranged in pairs such that one member of each pair is on each
face and directly opposes the other member of the pair, with one or
more hinges therebetween connecting the segments so that each hinge
is located between the two faces and at a distance of at least
about 10%, preferably at least about 20%, more preferably at least
about 30% of the depth of the head from each of the faces.
[0040] The grooves on at least one face of the brush contain
elastomer, preferably bonded to the segments of the head. The term
`elastomer` herein refers to a material which is both elastically
compressible and elastically extensible. Thus when the head is
flexed in a direction orthogonal to the opposed faces, the
elastomer is put either under tension or under compression. The
elastomer has the effect of limiting the head flexibility thereby
reducing the stretching or compression of the hinges and of
limiting the stress at the bond between the elastomer and the head
segments. A more durable head is thus obtained. Preferably, grooves
on both the bristle-bearing face and the opposing face contain
elastomer so that elastomer is put under compression whichever
direction is chosen. The elastomer on the opposed face is of course
put under tension but the tensile stress on the elastomer to
segment bonds is limited and is shared with the hinge material.
[0041] Preferably all of the grooves are wholly filled with the
elastomer. Complete filling of the grooves has an advantage of, for
example, avoiding contamination of the grooves by toothpaste
deposits. The grooves can be partially filled though, provided that
sufficient elastomer is used to give effective moderation of the
flexibility of the head.
[0042] The whole head has a conventional, generally flattened shape
but remains flexible when compared to that of a conventional brush.
By `flexible` is meant herein that when a 3 Newton force 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 2.degree..
[0043] The end of the head which is to be held fixed is defined by
the line which is perpendicular to the axis along which bending
takes place and which touches the first row of bristles. In the
preferred embodiments hating transverse grooves, where the head
bends along the longitudinal axis, the end should be that which
connects to the handle. The end of the head where the force is to
be applied is the opposite end of the head at the furthest point
away along the bending axis. By `resiliently flexible` is meant
that, when the 3 Newton force is removed, the head will return to
its original position without the application of external force.
The angle through which the head bends when a 3 Newton force is
applied as above is referred to herein as the flex angle. The flex
angle can conveniently be measured by measuring the vertical
displacement (y) of the free end of the head under a 3 Newton force
and the distance y and the distance between the clamping point and
the application of the force (x), the flex angle being derived by
the relationship tan(flex angle)=y/x. In preferred embodiments the
flex angle is at least 3.degree., more preferably at least
5.degree. and it can be as high as 15.degree. or more. The
construction of the head, in particular the dimensions of the
grooves and hinges, the extent of elastomer filling of the grooves
and hardness of the elastomer is, however, such that the flex angle
is limited to less than about 40.degree., preferably less than
30.degree., more preferably less than 20.degree.. This has been
found to give an acceptable degree of flexibility for users without
exposing the hinges and elastomer-segment bonds to undue
stress.
[0044] In highly preferred embodiments, only one of the opposed
faces is bristle-bearing and when the head is in its normal
unstressed state, the free ends of bristles lying along a
longitudinal axis of the brush form a generally concave profile. In
highly preferred embodiments the bristle-bearing face is concavely
shaped. In these embodiments the head preferably has a flex angle
such that the bristle-bearing face of the head is able to bend to
the extent that the free ends of bristles lying along a
longitudinal axis of the brush form a generally convex profile. The
face of the head can be concave along either or both of the
orthogonal axes of the head lying within the general plane of the
bristle-bearing face. 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 500 mm, more preferably from 15 to 250 mm, especially from 25 to
150 mm
[0045] The brush head has bristles extending from one of the pair
of opposing faces. The bristles can he made of any of the materials
well 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
cross-sections including, but not limited to, rectangular,
hexagonal and trilocular. Furthermore, the diameter and length of
the bristles can vary within the usual dimensions known by a person
skilled in the art. The bristles are generally conventionally
grouped into tufts and can be attached to the brush head by a
variety of processes. Preferred processes herein are stapling and
fusion. The bristles can be inserted into the segments or the
elastomer, preferably into the harder material of the segments.
Cutting and end-rounding of the bristles can be done using any of
the methods commonly known in the art.
[0046] Supply Channels
[0047] A further essential feature of the toothbrush of this
invention is one or more elastomer supply channels extending
between the elastomeric handle regions and the transverse grooves,
whereby at least one, preferably all, of the elastomeric handle
regions and the transverse grooves can be filled with elastomer
from a single injection point. In the head these are conveniently
provided by one or more longitudinal grooves intersecting the
transverse grooves.
[0048] In especially preferred embodiments the brush head comprises
both transverse grooves on each of the opposed faces so that the
head can bend along the longitudinal axis and at least one
longitudinal groove which connects the transverse grooves and
extending along the handle to connect further with the voids that
are used to form the handle grips. The longitudinal groove permits
molten elastomer to flow from an injection point to the elastomeric
handle regions and then further to the transverse grooves in the
head.
[0049] This is generally achieved by a separate injection moulding
step after the moulding of the handle and the segments of the head
has been completed. Preferably, all of the elastomer is injected
from a single injection point. A preferred method of making the
toothbrush of the invention comprises the step of injecting molten
elastomer, preferably at a temperature in the range from about
220.degree. C. to about 260.degree. C., more preferably from about
230.degree. C. to about 250.degree. C., under pressure, into the
injection point and causing it to flow along the supply channel and
into the grooves. Suitable injection pressures are in the range
from about 35 MNm.sup.-2 (350 bar) to about 50 MNm.sup.-2 (500
bar), preferably from about 42 MNm.sup.-2 (420 bar) to about 48
MNm.sup.-2 (480 bar).
[0050] In use, toothbrushes comprising the brush head of this
invention can be used for cleaning the teeth by an entirely
conventional tooth brushing hand action preferably in a manner
recommended by dental health authorities. The brush head of the
invention can also be used in electrically driven toothbrushes or
children's toothbrushes.
[0051] The invention will now be described by way of example only,
with reference to the accompanying drawings in which:
[0052] FIG. 1 is a partial side view of a first embodiment of the
invention, depicting the 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.
[0053] FIG. 2 is a plan view of a toothbrush head showing
transverse grooves, a longitudinal groove acting as a supply
channel, and discontinuous hinges. The bristles are omitted for the
sake of clarity.
[0054] FIG. 3 is a perspective view of a toothbrush according to
the invention. The bristles are omitted for the sake of
clarity.
[0055] FIG. 4 is a perspective view of the toothbrush shown in FIG.
3 with the elastomer not shown in order to show the hinges, grooves
and supply channel more clearly.
[0056] FIG. 5 is a schematic showing the measurement of the flex
angle.
[0057] Referring to FIG. 1, the brush head (1) has substantially
parallel top and bottom-faces, comprising segments (2) flexibly
connected by hinges of head material (3). The top and bottom faces
carry equal numbers of generally parallel transverse grooves (4)
filled with elastomer (5). A longitudinal groove (not shown)
connects the transverse grooves and extends into the handle (8),
acting as a supply channel. Tufts of bristles (6), extending from
the top face, form a concave surface (7) at their free ends.
[0058] Referring to FIG. 2. a toothbrush head (1) is formed
integrally at one end of a handle (8). The head includes three
pairs of transverse grooves (4). one of each pair being on each of
the top and bottom surfaces. The transverse grooves are in the form
of waves and a single longitudinal groove (9) connects the
transverse grooves and extends into the handle, acting as a supply
channel. The grooves are entirely filled with elastomer (5). The
transverse grooves define segments of the head (2) which are
connected to each other by hinges (3). There are gaps (10) between
and to each side of the hinges so that in the gaps, the elastomer
extends from top to bottom surfaces.
[0059] In FIGS. 3 and 4 the head (1) is co-moulded with the handle
(8) and is concave along its longitudinal axis on the
bristle-bearing (upper) surface. Voids (11) in the handle are
filled with elastomer to provide hand grips (16). The voids are
connected to each other by a longitudinal groove (12) on the
reverse side of the handle which extends into the head and connects
the transverse grooves (4) as shown in the view in FIG. 2. The
elastomer in the voids and the grooves is injected from a single
injection point (13) and is of a different colour to the head
material to give a distinctive appearance. The head has holes (14)
disposed on the top surface thereof to accommodate tufts of
bristles.
[0060] FIG. 5 illustrates the measurement of the flex angle. The
head (1) is clamped (15) against the first row of bristles (6) at
the end which is attached to the handle (8) and a 3 Newton force
(F) is applied to the opposite end. The dashed lines show the
original position of the brush head before the force is applied.
The vertical displacement (y) of the free end of the head under the
force F is measured and the flex angle is derived from the distance
y and the distance between the clamping point and the application
of the force (x) by the relationship tan (flex angle)=y/x.
* * * * *