U.S. patent application number 12/768988 was filed with the patent office on 2010-12-09 for toothbrush bristle and method for manufacturing such a bristle.
This patent application is currently assigned to Braun GmbH. Invention is credited to Karl Herzog.
Application Number | 20100306944 12/768988 |
Document ID | / |
Family ID | 41198572 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100306944 |
Kind Code |
A1 |
Herzog; Karl |
December 9, 2010 |
TOOTHBRUSH BRISTLE AND METHOD FOR MANUFACTURING SUCH A BRISTLE
Abstract
A method for manufacturing filaments for personal hygiene
articles is described. The filaments are provided with a surface
structure with at least one surface recess such as dimples and/or
pittings. The filament includes at least a portion made of a
material soluble by a corrosive agent and is covered in part with a
cover layer stable to the corrosive agent such that a surface
portion of the filament body substantially corresponding to the at
least one surface recess is uncovered. The filament body is
contacted with the corrosive agent for a limited time to create the
surface recess in the uncovered surface portion.
Inventors: |
Herzog; Karl;
(Frankfurt/Main, DE) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;Global Legal Department - IP
Sycamore Building - 4th Floor, 299 East Sixth Street
CINCINNATI
OH
45202
US
|
Assignee: |
Braun GmbH
Cincinnati
OH
|
Family ID: |
41198572 |
Appl. No.: |
12/768988 |
Filed: |
April 28, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/IB2010/050928 |
Mar 3, 2010 |
|
|
|
12768988 |
|
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Current U.S.
Class: |
15/207.2 ;
216/56 |
Current CPC
Class: |
A46D 1/00 20130101; D01F
8/00 20130101; D01F 11/00 20130101; A46D 1/0276 20130101; A46D
1/0292 20130101; D01D 5/34 20130101; A46D 1/0284 20130101; A46D
1/023 20130101; A46D 1/006 20130101; D01D 10/00 20130101; A46D 1/05
20130101; A46D 1/0238 20130101 |
Class at
Publication: |
15/207.2 ;
216/56 |
International
Class: |
A46D 1/00 20060101
A46D001/00; A46D 1/04 20060101 A46D001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2009 |
EP |
09 003 095.8 |
Claims
1. A filament for use in a personal hygiene implement, the filament
comprising: a filament body made, in part, by a material soluble by
a corrosive agent; a cover layer made, in part, by a material
stable to the corrosive agent, the filament body being within the
cover layer, the cover layer having surface features thereon.
2. The filament of claim 1, wherein the surface features comprise
dimples in the cover layer.
3. The filament of claim 2, wherein the dimples extend through the
thickness of the cover layer such that the filament body is
exposed.
4. The filament of claim 1, wherein the cover layer and the
filament body comprise holes therethrough, wherein the holes of the
filament body and the holes of the cover layer are aligned.
5. The filament of claim 4, wherein an oral care agent is disposed
within the holes of the filament body and/or the holes of the cover
layer.
6. The filament of claim 4, wherein the holes of the filament body
are connected to a longitudinal cavity in the filament body.
7. The filament of claim 1, wherein the cover layer comprises a
first material and a second material, wherein the first material is
soluble by a corrosive agent and wherein the second material is
stable to the corrosive agent.
8. The filament of claim 1, wherein the cover layer comprises a
photo active material.
9. A method for manufacturing a filament for a toothbrush wherein
the filament is given a surface structure, the method comprising
the steps of: obtaining a filament body; providing a cover layer
over the filament body; creating uncovered portions of the filament
body; and contacting the filament body with a corrosive agent for a
limited time to create a surface recess in the uncovered portions
of the filament body.
10. The method according to claim 9, covering the filament body
completely with a continuous cover layer and removing a portion of
the cover layer to provide at least one void.
11. The method according to claim 10, further comprising the steps
of providing a photosensitive material for the continuous cover
layer; irradiating a first portion of the cover layer with light or
radiation; exposing a second portion of the cover layer to no
radiation; and removing the first portion or the second portion of
the cover layer.
12. The method of claim 11, further comprising the step of
contacting the first portion or the second portion of the cover
layer with a photographic developer.
13. The method of claim 9, further comprising the steps of
inhomogeneously co-extruding the cover layer onto the filament
body, and removing a portion of the cover layer to expose the
filament body.
14. The method of claim 11, further comprising the step of cutting
the filament body into a plurality of filaments.
15. The method of claim 9, further comprising the step of providing
a void in the cover layer using at least one tool.
16. The method according to claim 9, further comprising the steps
of shielding a first section of the filament body; shielding a
second section of the filament body, wherein the first section and
the second section are spaced from each other; irradiating an
unshielded section of the filament between the first section and
the second section to remove the cover layer in the unshielded
section; and contacting the filament body with the corrosive agent
for a limited time in the unshielded section to create a reduced
diameter section.
17. The method of claim 9, further comprising the step of providing
a tapered tip to the filament body.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of prior
copending International Application No. PCT/IB2010/050928, filed
Mar. 3, 2010, designating the United States.
FIELD OF THE INVENTION
[0002] The present invention relates generally to filaments, in
particular bristles and more particularly tooth-cleaning bristles
comprising a surface structure with at least one surface recess
such as dimples and pittings, and to a method for manufacturing
such a filament. Moreover, the present invention also relates to a
toothbrush head including a plurality of tufts of such
bristles.
BACKGROUND OF THE INVENTION
[0003] In brushes, particularly toothbrushes, which may be used for
cleaning and/or the application of liquids or powders, usually a
plurality of bristles forming a bristle field with a plurality of
bristle tufts, are provided for effecting the desired function. The
bristles are often filaments, in particular monofilaments made of
plastic and comprise a smooth, cylindrical circumferential surface.
However, such filaments also may have non-circular cross-sections
e.g. with a polygonal shape, a star shape, an oval shape etc.
[0004] For some applications, it is desired to give the
circumferential surface a specific surface structure having a
desired roughness and/or a relief-like structure having projections
and recesses like dimples and pittings. Such a surface structure
may have different functions. Basically, such a surface structure
increases the surface area of the filament in comparison to a
filament with a smooth, cylindrical surface. Such a surface area
increase provides larger adhesive forces, so in cleaning
applications, debris and dust particles are better held on the
filament or, in other applications, liquids or powder may be better
held on the filament. Furthermore, the surface structure may
improve the cleaning efficiency in particular for plaque and other
particles strongly bonded to the teeth. Particularly, by means of
an appropriate surface structure the filament provides an abrasive
effect. For some applications it is desired that the cross-section
of the filament varies along the longitudinal extension of the
filament.
[0005] Document DE 19818345 A1 describes bristles for a toothbrush
which bristles include a plastic core which is covered by a
rubber-elastic cover layer. So as to achieve a high cleaning
efficiency and an abrasive effect despite the soft surface, the
said rubber-elastic cover layer is provided with a surface
structure including dimples and pittings which are created in a hot
pressing process.
[0006] Such a hot pressed surface structure has, however, some
disadvantages. In particular, there are certain restrictions with
regard to the achievable shapes of the surface structure. Usually,
only shallow dimples and pittings with a smooth, rounded edge may
be provided, what is also due to the rubber-elastic material of the
cover layer which shows a certain resilience and tends to regain
its original shape after a hot pressing treatment. Due to the shape
limitations, such a surface structure may achieve limited abrasive
effects and thus a limited cleaning efficiency only. Moreover, such
a hot pressing process is rather complicated for filaments having a
tiny diameter and thus rather expensive.
SUMMARY OF THE INVENTION
[0007] It is therefore an objective of the present invention to
provide an improved filament with a surface structure of the
aforementioned type and an improved method for manufacturing such a
filament which avoid the disadvantages of the prior art and further
develop the latter in an advantageous way. More particularly, the
present invention aims to provide an improved surface structure on
a bristle achieving high cleaning efficiency without sacrificing
easy and cost-efficient manufacturing.
[0008] According to the present invention, this objective is
achieved by a method as defined in claim 1, a filament as defined
in claim 9 and a toothbrush head as defined in claim 16. Preferred
embodiments of the present invention are laid down in the dependent
claims.
[0009] To achieve the aforementioned objective, it is suggested to
produce the desired surface structure in an etching process and to
provide the filament with at least one etch recess or etch pitting.
To allow an easy control of the shape of such etch recesses or etch
pittings, the filament body basically consists of a material which
is soluble by a corrosive agent, wherein certain portions of the
filament body's surface are shielded against contact by the
corrosive agent whereas other portions are not shielded so that the
corrosive agent may act on the soluble material of the filament
body only in selected surface portions. According to the present
invention, the method for manufacturing the filament is
characterized in that a filament body with at least a portion made
of a material soluble by a corrosive agent is covered in part with
a cover layer stable to said corrosive agent such that a surface
portion of said filament body substantially corresponding to said
at least one surface recess is uncovered, and said filament body is
contacted with said corrosive agent for a limited time to create
the surface recess in said uncovered surface portion.
Correspondingly, a filament according to the present invention is
characterized in that its surface structure includes at least one
etch pitting or etch recess in a filament body made at least in
part of a material soluble by a corrosive agent. Advantageously,
such etch recesses or etch pittings differ from mechanically
produced recesses or pittings in their shape and contour.
Mechanically produced recesses and pittings such as drilled bores,
hot pressed depressions or milled slots or cut slots usually have
an absolutely regular and even shape exactly corresponding to a
basic geometrical structure with straight or at least evenly bowing
contour lines, whereas etch recesses or etch pittings according to
the present invention may show some surface roughness and fuzzy
contour lines with deviations from precisely geometrical shapes
with straight or absolutely evenly curved lines what may even
further increase adhesive forces to dust particles and the desired
abrasive effect for cleaning surfaces with strongly bonded
pollution such as plaque.
[0010] According to preferred embodiments of the present invention,
the said etch recesses and etch pittings, respectively, may have
different shapes and arrangements on the filament. According to a
first preferred embodiment of the invention, a plurality of
basically circular dimples may be provided in the circumferential
surface of the filament, wherein such dimples may have a random
distribution over the circumferential surface area or, in the
alternative, may be positioned in a matrix-like distribution. In
addition to such dimples or in the alternative thereto, the surface
structure may include at least one etch recess with an elongate
shape that extends over at least 1/3, preferably at least 1/2 of
the filament's longitudinal extension. Such an elongate etch recess
basically may have a slot-like shape. However, according to a
preferred embodiment of the present invention, the at least one
elongate etch recess may have a shape such that the filament's
cross section varies in shape over the longitudinal extension of
the filament. More particularly, cross-sections taken at different
longitudinal positions may differ from each other. Such varying
cross-sections may be achieved by an elongate recess that varies in
width and/or which has a curved longitudinal shape preferably with
a curved longitudinal shape. According to a particularly preferred
embodiment of the invention, an elongate etch recess having a
helical contour may be provided in the circumferential surface of
the filament. More particularly, at least two such elongate,
helically configured etch recesses may be provided on different
sides of the circumferential surface of the filament.
[0011] In addition or in the alternative to the aforementioned
embodiment, the filament may have etch recesses or etch pittings of
other shapes. For example, according to another preferred
embodiment of the invention, certain portions of the
circumferential surface of the filament corresponding to a desired
pattern may be recessed by etching so that a pattern of preferably
bar-shaped and/or rib-shaped and/or pin-shaped projections formed
by the non-recessed portions project in radial direction from the
circumferential surface of the filament.
[0012] In addition or in the alternative to at least one of the
aforementioned surface structures, the filament may have etch
recesses which form preferably bore-like channels inside the
filament body. Such bore-like channels may perforate the filament
completely and/or may have a limited depth and/or may be
interconnected with each other so a channel system is provided
inside the filament body.
[0013] So as to achieve easy, but nevertheless precise control of
the shape of the etch recesses, a corrosive agent resistant cover
layer is provided on the filament body which basically consists of
a material soluble by said corrosive agent, so certain portions of
the surface of the filament body made of such a soluble material
are protected against contact with the corrosive agent.
Consequently, the said cover layer made of a material stable to the
corrosive agent, covers only certain portions of the surface area
of the filament body to be contacted with the corrosive agent. In
other words, the cover layer includes at least one void that gives
the corrosive agent access to a respective portion of the soluble
material of the filament body as said filament body is exposed to
the surrounding and thus the corrosive agent in the region of said
void in the cover layer.
[0014] The said cover layer covering certain portions of the
filament body and not covering certain other portions thereof, may
be applied to the filament body in different ways. According to an
advantageous embodiment, the said cover layer may be applied in a
multiple-step process, wherein particularly in a first step the
entire portion of the filament to be contacted with the corrosive
agent is covered with a continuous cover layer and wherein in a
further step certain portions of said initially continuous cover
layer are removed to provide voids in said cover layer through
which the corrosive agent gets access to the filament body's
material under the cover layer. Completely covering the filament
portion to be contacted with the corrosive agent first and removing
certain cover layer portions then in a second step provides for
easy manufacturing with still reliable covering of the portions to
be protected against etching. However, in the alternative it also
would be possible to provide the cover layer in a one-step process,
wherein the cover layer material is deposited on the filament body
only in the portions to be covered, whereas no material is
deposited on the surface portions which are not to be covered.
Nevertheless, the aforementioned application of the cover layer in
a multiple-step process is preferred in terms of process handling,
cost efficiency and reliable covering of the surface portions to be
protected against etching.
[0015] According to a preferred embodiment, a photosensitive
material may be used for the cover layer so certain portions of the
cover layer may be removed or fixed by irradiating the respective
portions with light or any other appropriate radiation. More
particularly, it is a preferred embodiment of the invention to
completely cover the filament's surface, or at least the portion of
the filament's surface to be contacted with the corrosive agent,
with a photosensitive cover layer material in a first step and
then, in another step, to subject only portions of said
photosensitive cover layer material to light so the respective
irradiated portions are changed in their material properties
compared to the non-irradiated portions, whereas the other portions
not irradiated do not change their properties. If a positively
photosensitive material is used, the irradiated portions may be
removed by a photographic developer. In the alternative, it is also
possible to use a negatively photosensitive material which is fixed
by light irradiation. In this case, the portions of the initially
continuous cover layer which are to be removed are not irradiated,
whereas the remaining portions which are subjected to light
irradiation are fixed on the filament surface.
[0016] The removal of the unstable portions may be achieved in
different ways. According to an advantageous embodiment of the
invention, the photosensitive cover layer material including so to
say stable portions and unstable portions may be contacted with an
appropriate liquid such as a photographic developer which removes
the unstable portions of the cover layer. Preferably, the filament
provided with the respective continuous cover layer including
stable and unstable portions may be dipped and drained into a
respective bath of liquid.
[0017] Use of such a photosensitive material for the cover layer
allows precisely shaping the voids in the cover layer. According to
a preferred embodiment, light is irradiated onto the filament
surface covered with the cover layer of photosensitive material via
a mask facing the filament's surface covered with the cover layer.
For example, such a mask may have a tubular configuration
surrounding the respective filament from all sides and having
openings allowing the access of light to certain portions of the
filament only. In a preferred embodiment of the invention, lenses
may be used to direct the light exactly to the portions to be
subjected to irradiation. Such lenses are preferably positioned
between the respective mask and the filament surface.
[0018] In addition or in the alternative to such masking of the
photosensitive cover layer, a light irradiation system providing a
precisely focused light beam also may be used to achieve selected
irradiation. For example, a laser beam could be used to effect
curing of certain portions of the photosensitive cover layer
material only. However, the aforementioned embodiment with masking
of the cover layer material is more preferred in terms of cost
efficiency and safety measures, since no specific safety measures
necessary for laser applications are necessary.
[0019] In another embodiment of the present invention, the cover
layer stable to the corrosive agent may be applied to the filament
body made of the material soluble by the corrosive agent in a
co-extrusion process. In particular, in such a co-extrusion
process, the main filament body made of the material soluble by the
corrosive agent, may be co-extruded with a circumferential cover
layer made at least in part of a material stable to said corrosive
agent. So as to provide the desired voids in the cover layer in a
subsequent step, the co-extruded cover layer may be subjected to
mechanical treatment. For example, bores may be drilled into the
cover layer or desired recesses may be cut into the cover layer by
other mechanical tools.
[0020] According to another preferred embodiment of the invention,
the cover layer is co-extruded from a mixture of at least two
materials including a first material stable to the corrosive agent
and a second material soluble by the corrosive agent, wherein the
co-extrusion process is controlled such that in the co-extruded
cover layer there is an inhomogeneous distribution of the said two
materials. In particular, the second material soluble by the
corrosive agent is distributed in the co-extruded cover layer in a
desired pattern which may include a random distribution of
basically circular spots or a distribution in longitudinal stripes
etc. To produce the desired voids in the co-extruded cover layer,
the filament covered with the initially continuous cover layer is
contacted with an appropriate corrosive agent for removing the
material portions of the cover layer not stable to this corrosive
agent. The corrosive agent for producing the voids in the cover
layer may be the same corrosive agent used for etching the recesses
into the filament body's core made of a respective soluble
material. However, in an alternative embodiment the materials may
be selected such that different corrosive agents are necessary for
and subsequently applied to the filament so as to remove first, by
means of a first corrosive agent, only the respective portions of
the cover layer to produce the desired voids therein and then, in a
second step, by means of a second corrosive agent, to produce the
desired recesses in the filament body through the previously
produced voids in the cover layer. Such selective etching allows
precise control of the depth and shape of the etch recesses in the
filament body under the cover layer.
[0021] In order to achieve high efficiency and high manufacturing
capacities, the aforementioned steps of covering the filament body
with the cover layer, providing the desired voids in the cover
layer and/or contacting the partly covered filament body with the
corrosive agent are effected in a continuous process in which a
long filament roving is continuously moved through a plurality of
respective stations in a subsequent way. For example, a continuous
fiber or filament may be taken from a spool and then moved, e.g. by
means of respective deflection wheels, through different treating
stations so as to produce the desired surface structure on the
continuous filament roving which is then, after having created the
surface structure, cut or otherwise separated into a plurality of
separate bristles. More particularly, the long filament roving is
continuously moved first through a cover layer application station
in which preferably liquid photosensitive cover layer material is
applied to the filament roving. For example, the filament roving
may be moved through a dipping station. After having been covered
with the photosensitive cover layer material, the filament roving
may then be moved through an irradiation station in which certain
portions of the cover layer are subjected to light irradiation.
Preferably, light flashes can be applied through a mask and the
openings thereof, so that only certain portions of the cover layer
material are irradiated even when the filament roving is
continuously moving.
[0022] In order to remove the unstable portions of the cover layer
material, the continuously moving filament roving can be directed
through a photographic developer dipping which forms part of a
respective cover layer removal station. Thereafter, the long
filament roving may be continuously moved through an etching
station which may include a corrosive agent dipping station so as
to dip and drain the filament roving with the corrosive agent.
Finally, the filament roving can be moved through a cutting station
to cut the filament roving into a plurality of bristles.
[0023] According to another preferred embodiment of the invention,
the etched recesses or etched pittings may be filled with a medical
treatment medium such as, e.g., an antibacterial liquid or gel that
is dispensed and applied to the teeth and the gingiva during
cleaning the teeth.
[0024] These and other features which may define the invention for
themselves or in combination with each other and also in
sub-combination different from the definition in the claims, will
become apparent in greater detail from the following description
and from the figures which illustrate preferred embodiments of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The figures show:
[0026] FIG. 1: a schematic functional diagram of an installation
for manufacturing toothbrush bristles with a surface structure in a
continuous process, said installation including a plurality of
treating stations through which a bristle roving is continuously
moved to apply different treatments to the bristle roving,
[0027] FIG. 2: a schematical side view of a bristle, wherein a part
of the bristle is shown in a longitudinal-sectional view to
illustrate the cover layer for protecting the bristle body's
material against application of the corrosive agent, wherein the
cover layer is shown with different portions of different curing
conditions before producing voids in the cover layer,
[0028] FIG. 3: a schematical side view of the bristle portion
similar to FIG. 2 wherein in the longitudinal-sectional window the
cover layer is shown with the voids giving the corrosive agent
access to the bristle body material under the cover layer and with
etch pittings in the circumferential surface of the bristle,
[0029] FIG. 4: a functional diagram of an installation for
producing bristles with a surface structure in a continuous process
according to an alternative embodiment of the invention according
to which the filament is coming from a nozzle,
[0030] FIG. 5: an enlarged, schematical front view of an
irradiation station, wherein said irradiation station includes
masks for masking the photosensitive cover layer, a light source
for directing flashes of light through said masks and lenses
between the masks and the continuously moving bristle roving,
[0031] FIG. 6: a schematical side view of the bristle roving coming
from a co-extrusion apparatus, wherein in a partly
longitudinal-sectional view the co-extruded cover layer including
an inhomogeneous mixture of different materials is shown,
[0032] FIG. 7: a schematical side view of a bristle roving coming
from a co-extrusion apparatus similar to FIG. 6, wherein specific
tools are used for creating voids in the cover layer shown in the
partly longitudinal-sectional view of the bristle roving,
[0033] FIG. 8: a longitudinal-sectional view of a bristle
illustrating the arrangement of etch recesses providing for a
reduced stiffness of the bristle,
[0034] FIG. 9: a cross-section of a bristle along line A-A in FIG.
10,
[0035] FIG. 10: a schematical side view of a bristle having a
pattern of rib-like projections created by etching the neighboring
portions between the rib-like projections,
[0036] FIG. 11: a cross-section of the bristle of FIG. 10 along
line B-B in FIG. 10,
[0037] FIG. 12: a schematical side view and partly
longitudinal-sectional view of a bristle with a surface structure
according to another embodiment of the invention, said surface
structure including pin-shaped projections,
[0038] FIG. 13: a schematical side view and partly
longitudinal-sectional view of a bristle with a surface structure
according to another embodiment of the invention, said surface
structure including recesses in the shape of through-holes,
[0039] FIG. 14: a schematical side view and partly
longitudinal-sectional view of a bristle according to another
embodiment of the invention, said bristle having a surface
structure with through-holes interconnected by a longitudinal
hole,
[0040] FIG. 15: a schematic longitudinal-sectional view of a
masking arrangement for creating an etch recess in the form of a
reduced diameter section,
[0041] FIG. 16: a schematic side view of a bristle having a reduced
diameter section as produced by the masking arrangement of FIG.
15,
[0042] FIG. 17: a schematic side view of a bristle with a surface
structure of another preferred embodiment of the invention, said
surface structure including a reduced diameter section which, by a
further treatment step, has been turned into a needle-like tip,
[0043] FIG. 18: a cross-sectional view of a bristle according to
another preferred embodiment of the invention taken along line A-A
in FIG. 19,
[0044] FIG. 19: a schematic side view of a bristle according to
another embodiment of the invention, said side view showing the
position of a plurality of cross-sectional planes in which
cross-sections of FIG. 21-27 have been taken, as well as the
helical configuration of a longitudinal recess in the
circumferential surface of the bristle,
[0045] FIG. 20: a schematic side view of the bristle of FIG. 19
showing the helical configuration of a longitudinal recess in the
circumferential surface of the bristle,
[0046] FIG. 21-27: cross-sectional views of the bristle of FIG.
18-20 taken in different planes in FIG. 19, and
[0047] FIG. 28: a schematical side view of an electric toothbrush
having a bristle field with bristles of one of the preceding
figures.
DETAILED DESCRIPTION OF THE INVENTION
[0048] According to the preferred embodiment of the invention shown
in FIG. 1, a filament or bristle roving 7 much longer than the
finished bristle is taken from a spool 11, continuously moved
through a plurality of treatment stations and wound around a second
storage spool 12. Between the two spools 11 and 12, the said
bristle roving 7 runs through a plurality of treatment stations,
wherein the bristle roving 7 is deflected by means of a plurality
of rollers 13 to direct the bristle or filament roving 7 through
the treatment sites.
[0049] The filament roving 7 coming from the first storage spool 11
is preferably a filament or monofilament made of plastic with an
e.g. cylindrical shape and/or circular cross section. Particularly,
the roving coming from the first spool 11 is a filament made of a
material soluble by a corrosive agent. For example, the bristle can
be made of a plastic such as polyamide or polybutylene
terephthalate.
[0050] Coming from the first storage spool 11, the filament or
bristle roving 7 runs through a coating bath 14 of a coating
station 15. Said coating bath 14 contains a photosensitive liquid
which changes its condition when subjected to light. The liquid
adhering to the bristle roving 7 leaving said coating bath 14 is
dried by means of a drier 16 preferably including a heat source
such as a heater. Thus, the bristle roving 7 is covered with a
cover layer 5 completely covering the circumferential surface of
the filament as shown in FIG. 2.
[0051] After having dried said cover layer 5, the continuously
moving bristle roving 7 runs through a cover layer removing station
17 in which voids are produced in said cover layer 5. Said cover
layer removing station 17 includes an irradiation station 18 and a
photographic developer station 19.
[0052] In said irradiation station 18, only portions of the
circumferential surface of the filament are irradiated with light
so that the cover layer 5 includes irradiated portions and
non-irradiated portions. To control the shape of the irradiated
portions, said irradiation station 18 includes a preferably tubular
mask 20 through which the bristle roving 7 runs. Said mask 20 is
provided with at least one through-hole through which radiation
from a light source 50 can be applied to the cover layer 5. As
shown in FIG. 5, the mask 20 does not need to have a tubular shape,
but may comprise a plurality of masking elements 21 facing
different sides of the bristle 1, each of said masking elements
preferably comprising at least one through-hole through which
radiation of a predetermined cross-sectional shape is applied to
the circumferential surface of the bristle 1.
[0053] Preferably, optical means 52 such as lenses 51, reflectors
etc. may be further used to direct light in a predetermined pattern
onto the bristle. As FIG. 5 shows, lenses 52 may be positioned
between the masking elements 21 and the bristle 1 to focus the
light beams or light flashes.
[0054] Depending on the type of photosensitive coating material,
the irradiation may make the photosensitive material stable to
developer liquid or unstable to developer liquid. Such
photosensitive reaction is known as such as positive photosensitive
reaction or negative photosensitive reaction. In case positive
photosensitive material is used for the coating layer 5, then the
irradiated portions are removed by contacting the cover layer 5
with photographic developer liquid in a developer bath of developer
station 19. In contrast, if a negative photographic reaction is
utilized, the portions of the cover layer 5 that should remain on
the bristle 1 are irradiated and thus so to say cured to make such
portions resistant against the photographic developer.
[0055] Consequently, when the bristle roving 7 leaves the removing
station 17, the cover layer 5 includes a pattern of voids
corresponding to the pattern of the surface structure to be
produced in the bristle's circumferential surface. In a further
cleaning station not explicitly shown and possibly positioned after
said developer station 19 and upstream of an etching station 22,
remaining developer liquid may be removed from the bristle roving
7.
[0056] As shown in FIG. 1, the filament then runs through the
etching station 22 including a corrosive agent bath 23. As shown in
FIG. 1, the path of the bristle roving 7 through said corrosive
agent bath 23 is adjusted to have a defined length in response to
the speed of the filament so that a desired contact time is
achieved. For example, the depth 24 and/or the horizontal length 25
of the path in the liquid bath 23 may be adjusted to achieve the
desired time period over which the bristle is contacted by the
corrosive agent. In addition or in the alternative to such
adjustment of the bristle roving path through the bath, also the
conveying speed of the bristle roving may be adjusted, wherein,
however, the aforementioned adjustment of the length of the dipping
path is preferred since adjustment of the speed also affects the
other treatment stations.
[0057] By means of contacting the bristle roving 7 in the etching
station 22 with a corrosive agent, the said corrosive agent gets
access to the filament 1 under the cover layer 5 through the voids
therein and consequently, material of said bristle body 4 is
removed in the region of the voids in the cover layer 5. This is
basically illustrated by FIG. 3 showing dimples or pittings created
in the bristle body 4 at positions where the cover layer 5 has
voids 3. In neighboring portions where the cover layer 5 has no
voids 3, the bristle body 4 is prevented from contacting the
corrosive agent so the bristle body 4 can maintain its initial
configuration.
[0058] As shown by FIG. 4, the manufacturing method does not
necessarily include use of a spool from which the initial bristle
roving is taken. The filament 1 may directly come from the
extrusion process, wherein preferably the filament coming from a
nozzle 26 of an extruder is preferably cooled in a cooling station
27 which may include a cooling bath into which the filament is
extruded. The cooled filament is then preferably lengthened and/or
stretched in a tensioning station 28 which may include a plurality
of biased rollers about which the filament runs, cf. FIG. 4.
Thereafter, the process may continue with coating station 15 as
shown in FIG. 1.
[0059] According to an alternative embodiment of the present
invention, the cover layer 5 may be provided to the bristle body 4
in a co-extrusion process that is illustrated by FIG. 6. The
filament 1 is extruded by means of a suitable nozzle 26 which is
known as such and adapted to co-extrude a thin circumferential
cover layer 5 onto the core body of the extruded filament.
Preferably, the co-extruded cover layer 5 is made of at least two
different materials including a material stable to at least one
corrosive agent and another material not stable to said corrosive
agent. The co-extrusion process is controlled in such a way that
the said two materials are distributed inhomogeneously in the cover
layer 5. Particularly, the material not stable to the corrosive
agent may be concentrated in randomly distributed spots 29. When
the cover layer 5 is contacted with a suitable corrosive agent, the
said spots of material not stable to the corrosive agent are
removed so respective voids are created in the cover layer.
[0060] As shown in FIG. 7, the desired voids in the cover layer 5
also can be produced by means of tools 30 such as laser beams,
water jets, sand jets, milling tools, drilling tools or other
mechanical or non-mechanical tools etc. Via the drilled or cut
voids in the cover layer 5, the corrosive agent gets access to the
bristle body 4 under the said cover layer 5 so pittings or other
recesses 3 can be etched.
[0061] As shown in FIG. 8, the etch recesses 3 may be distributed
in a specific pattern that reduces the column strength or buckling
resistance of the bristle 1. For example, on at least two opposite
sides, preferably on at least four opposite sides of the
circumferential surface, the bristle may have etch recesses or etch
pittings spaced from each other in longitudinal direction of the
bristle, wherein preferably the recesses on one side are offset in
the longitudinal direction relative to the recesses on the opposite
side, as is shown in FIG. 8.
[0062] Such a reduced buckling resistance of the bristles provides
advantages in some tooth cleaning applications, e.g. in electric
toothbrushes with an oscillating movement of the bristle tufts in
the longitudinal direction thereof
[0063] FIGS. 9 to 11 show another embodiment of a bristle with a
surface structure 2 that includes a plurality of bar-shaped
projections 31 wherein said bar-shaped projections are arranged in
a plurality of rings spaced in the longitudinal direction of the
bristle. In the shown embodiment, each ring of projections includes
bar-shaped projections extending parallel to the longitudinal
direction of the bristle and bar-shaped projections extending
parallel to the circumferential direction of the bristle, wherein
longitudinally oriented projections alternate with
circumferentially oriented projections. Other configurations are
possible.
[0064] The said projections 31 are surrounded by etched recesses.
More particularly, the entire circumferential surface of the
bristle 1 with the exception of the aforementioned bar-shaped
projections 31 has been subjected to an etching treatment.
Advantageously, the said bar-shaped projections 31 are provided
with sharp edges 32 at the boundary of their top surfaces. On the
other hand, the transition between the recessed circumferential
portions and said projections is rounded, cf. FIG. 10.
[0065] According to FIG. 12, the projections 31 also may have the
shape of pins. According to FIG. 12, the said pins are randomly
distributed over the entire circumferential surface. The pin-shaped
projections 31 project from the basic circumferential surface in
radial direction. The material of the bristle body 4 between the
said pin-shaped projections 31 has been removed by etching.
Advantageously, the top surface of said pin-shaped projection is
surrounded by a sharp edge 32 substantially having a 90.degree.
contour or angle. The bottom of the projections is rounded into the
basic circumferential surface, cf. FIG. 12.
[0066] As shown by FIG. 13, through-holes 45 may be provided in the
bristle body 4, which through-holes 45 may be created by an etching
process as described above. As shown by FIG. 14, the said
through-holes 45 extending through the bristle body 4 substantially
perpendicular to the longitudinal axis thereof may be connected to
a longitudinal cavity 33 e.g. formed by a cylindrical bore in the
center of the bristle body 4.
[0067] The etch recesses 3 including the aforementioned
through-holes 45 as well as the central cavity 33 may be filled
with an application medium such as medical liquids and/or gels,
cleaning substances or flavors and aromatics. Through said
through-holes 45, the substance stored in said central cavity 33
may be dispensed.
[0068] According to the embodiment of FIGS. 15 and 16, two sections
of the filament or bristle 1 spaced from each other are shielded by
means of two shields 34 having no voids. Between the said two
shields 34, a portion of the bristle 1 is unshielded so light
sources 35 can irradiate the uncovered section of the bristle 1 and
consequently the cover layer 5 can be removed completely from said
section of predetermined length of the bristle 1.
[0069] The bristle is then contacted with the corrosive agent so
that in said uncovered bristle section the diameter of the bristle
is reduced, i.e. the bristle is given a reduced diameter section.
As shown in FIG. 16, a section 37 with a reduced diameter
alternates with sections 38 of greater or original diameter. As
indicated by reference numeral 36, the bristle roving can be cut
into pieces at the reduced diameter section. This allows, in a
subsequent treatment step as illustrated by FIG. 17 to create
tapered bristles with a sharpened or needle-like tip.
[0070] As can be seen from FIGS. 18 to 27, the aforementioned
etching process also may be used so as to manufacture bristles with
a cross-section that varies along the longitudinal extension of the
bristle. As shown by FIGS. 19 and 20, the filament 1, after having
been etched in the aforementioned way, has an unchanged diameter D
in cross-sectional plane 76, whereas in cross-sectional plane 84,
cf. FIG. 19, the said filament has a reduced diameter d, cf. FIG.
20. Moreover, between said two cross-sectional planes 76 and 84,
the filament is provided with an etched surface structure including
helical recesses which extend from cross-sectional plane 77 to
cross-sectional plane 83, cf. FIG. 19. More precisely, the said
helical recesses 3 are formed by etched regions having an elongate
shape and a reduced diameter, wherein the borders of said elongate
recesses have a helical shape as shown in the figures.
[0071] In each of two opposite quadrants 39, there is a step
extending between the said planes 77 and 83, wherein said step
follows a helical line 40 with a thread pitch in clockwise
direction corresponding to a right hand thread. On the other hand,
in each of two opposite quadrants 41, there is a step between the
said planes 77 and 83, wherein said step follows a helical line 42
with a thread pitch in counterclockwise direction corresponding to
a left hand thread.
[0072] As can be seen by a comparison of FIGS. 19 and 20, the said
helical lines 40 and 42 meet each other in points 43 and 44 which
are positioned in plane 77 and plane 83, respectively, cf. FIGS. 19
and 20. Consequently, at the said meeting points 43 and 44 a sort
of tip or needle-like contour is defined by the helical lines 40
and 42.
[0073] As can be seen from FIGS. 21 to 27, the width of the etched
recess 3 between the respective helical lines 40 and 42 varies
along the longitudinal extension of the bristle, more precisely
increases from plane 78 to plane 82. Consequently, the bristle
varies in its cross-section continuosly from cross-sectional plane
to cross-sectional plane along the longitudinal extension of the
bristle.
[0074] The bottom edge of the step defined by the helical lines 40
and 42 and limiting the recesses there between is somewhat rounded,
whereas preferably the upper edge 32, cf. e.g. FIG. 24, bordering
the non-etched diameter section is preferably a sharp edge with an
angle of about 90.degree..
[0075] Taking into account the reduced diameter d in the sectors
defined by the etched recesses between the helical lines 40 and 42
and, on the other hand, taking into account the large diameter D in
the non-etched sectors, a mean diameter can be determined or
calculated. In view of the varying width of the etched recess
between the helical lines 40 and 42, the said mean diameter and
thus the stiffness and/or the column or buckling resistance of the
bristle 1 varies continuously from the maximum value in the
cross-sectional planes 76 or 77 to the minimum value in the planes
83 and 84.
[0076] Similar to the illustration given in FIG. 17, the bristle
having the helical recess as shown in FIGS. 18 to 27 also may be
further processed in a subsequent treatment step so as to create a
tapered bristle with a sharpened or needle-like tip. The
aforementioned etching step producing the reduced diameter section
and the helical recesses reduces the necessary amount of work for
the said tapering step and thus the manufacturing costs.
[0077] The described method may be applied to filaments having a
circular cross-section, but also to filaments having a
cross-section deviating from a circle. The respective filaments or
bristles may be used for brushes and brooms, but also for dental
floss, textiles, mattings, pads, nets, sponges, thermal
insulations, yarns and threads and other applications. However, a
particularly preferred application for the described bristle 1 is
use of such bristles in bristle tufts 53 of a toothbrush head 54
and even more particularly use thereof in an electric toothbrush 55
(FIG. 28).
[0078] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0079] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extent that any meaning or definition of
a term in this document conflicts with any meaning or definition of
the same term in a document incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
[0080] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *