Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BLIND-END HOLES CONFIGURATION FOR A TOOTHBRUSH
This invention relates to a toothbrush having a handle portion and a neck
portion
connecting the handle portion with a head, said head having a brushing side
and a rear side
opposite thereto, said brushing side including a plurality of bristle tufts
for cleaning the teeth, said
tufts being attachable in the head through tufting apertures using an anchor,
with each tufting
aperture being assigned a blind-end hole having sidewalls and a bottom. The
present invention
relates furthermore to a method of manufacturing such a toothbrush.
From WO 2006/050039 A1 there is known a toothbrush head in which the blind-end
holes
extend at different depths into the head from the brushing side of the head.
Given bristle tufts of
equal length for the respective blind-end holes, ft is suggested in this
manner to produce a
topography of the bristle ends on the brushing side.
From DE 102 21 786 A1 it is also known to insert bristle tufts of equal length
into blind-
end tufting holes in the head, likewise with the aim to obtain a different
topography of the bristle
ends by providing the brushing side of the head with an inclination.
From WO 2008/059435 there is known a toothbrush having in the toothbrush
bristle zone
an LED, partly in the head and partly protruding therefrom.
The aim is to keep the thickness of the toothbrush head as small as possible
in order to
enable a comfortable use in the mouth. This stands, however, in contrast to
the increasing
functional demands placed on a toothbrush head, making it necessary to provide
head
geometries which, owing to their complex inner structure, make it difficult to
produce a visually
faultless hard plastic injection molding. During the injection molding process
the plastic material
flowing into the die for molding the head is exposed to turbulence between the
various blind-end
tufting holes and other recesses or cavities of the molding and therefore
flows very unevenly,
particularly to undercuts or more complex structures lying farther away from
the injection point.
This problem is aggravated as soon as plastic materials are used for the head
which exhibit
greater shrinkage on cooling subsequent to the injection molding process.
Depending on the inner
structure of the head, visual faults or sunk spots, in particular also on the
rear side of the head,
are the undesired consequence.
It is therefore an aspect of the present invention to provide a toothbrush
which has a
complex inner structure within the head while yet affording a visually
flawless manufacture, in
particular also with regard to the rear side of the head. It is another aspect
of the present
invention to provide a suitable method.
In one aspect, provided is a toothbrush having a handle portion and a neck
portion
connecting the handle portion with a head, said head having a brushing side
and a rear
side opposite thereto, said brushing side including a plurality of bristle
tufts for cleaning
the teeth, said tufts being attachable in the head through tufting apertures
using an
anchor, with each tufting aperture being assigned a blind-end hole having
sidewalls and
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a bottom, wherein provision is made for a chamfer or radius in the transition
area
between the bottom and the sidewalls, with a cross-sectional area of the head
between a
first bottom and the rear side differing from a cross-sectional area of the
head between a
second bottom and the rear side, and said first bottom and said second bottom
being
arranged in the head in such a way that the minimum distance y between the
first bottom
and the rear side as well as the minimum distance x between the second bottom
and the
rear side as well as the minimum distance x between the second bottom and the
rear
side are each in the range of between 0.5 and 2.5 mm.
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An advantageous aspect of the invention has revealed that a minimum distance x
or
y of between 0.5 and 2.5 mm between a bottom of a blind-end hole provided for
the insertion
of bristle tufts and the rear side of the head enables a thinner toothbrush
head to be
provided which affords more comfortable handling in the mouth. lf, in
addition, the cross-
sectional areas within the head between the bottoms and the rear side differ
significantly
from blind-end hole to blind-end hole, thus resulting in a more complex
structure, it is of
importance that in the transition area between the bottom of the blind-end
hole and the
sidewalls of the blind-end hole a chamfer or radius is provided, because this
enables the
injection molding to reach a higher level of perfection. In this arrangement,
there are no
restrictions to the small size of the bottom provided that the chamfered or
radiused area
rendering the blind-end hole smaller becomes correspondingly larger to form
nearly a
bottom. Considered as cross-sectional area between bottom and rear side of the
head is in
particular a section through the head which cuts across the blind-end hole and
forms a plane
arranged at right angles to the toothbrush longitudinal axis. Conventionally,
the toothbrush
longitudinal axis extends from the head end to the handle end of the
toothbrush or,
depending on the overall geometry, at least from the beginning of the head
adjacent to the
neck portion to the end of the head. Differences in the cross-sectional area
or in the wall
thicknesses of the injection molding may be attributable to recesses and
cavities in the
injection molding, undercuts or different configurations of the blind-end
holes relative to each
other. Of course, similar problems for the sides of the head or the brushing
side or other
portions of the toothbrush should be remedied in a similar way.
In a further advantageous aspect, the minimum distance x and y between the
bottom
and the rear side of the head is fixed to between 0.8 and 2 mm. Particularly
when the length
of the blind-end holes and thus the depth of the bottom or the distance to the
rear side are
fitted to suit each other in such a way that in a complex head structure wall
thicknesses of
approximately uniform magnitude result, uniform cooling in the molding after
the injection-
molding process and with it uniform shrinkage are ensured. Sunk spots at
locations where
major amounts of material have accumulated can thus be avoided. In particular
when this
minimum distance x and y is in the range of between 0.5 and 2.5 mm or 0.8 and
2 mm
between the bottom and the rear side for all or the majority of the blind-end
holes of the
head, it is ensured that, depending on how the inner structure of the head is
otherwise
designed, the material thicknesses in the head are still sufficiently uniform,
in spite of an
inhomogeneous inner structure, in order to be able to obtain a flawless
injection-molded
product.
In a further advantageous aspect, provision is made for third and fourth blind-
end
holes which can be tufted with bristles to the same depth, with the third and
fourth blind-end
holes being constructed such that their bottoms extend to different depths.
This makes it
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possible for the tufting depth of the tufts to be alike in the third and
fourth blind-end holes
while yet providing, due to different levels of depth, compensating chambers
to compensate
for material accumulations and the attendant material shrinkage problems.
In another advantageous aspect, the chamfer or radius in the fourth blind-end
hole is
followed by a constriction (opposite the sidewall lying above) and an
adjoining further radius
or chamfer and only then by the closing bottom. This enables the constriction
to remain
devoid of bristle tufts which affords, as set forth in the foregoing, a
largely uniform tufting
depth and hence a simplified manufacturing process.
In another advantageous aspect, the head has a first interior region and a
second
interior region, with the first interior region being made of hard plastic and
the second interior
region including an electrically operable function element or part thereof.
The head is thus
characterized by an inhomogeneous, rugged inner structure, with the second
interior region
requiring the provision of cavities in the molding of the first interior
region. These cavities to
be provided in the head in addition to the blind-end hole geometries result in
added
complexity, causing the flow areas of the liquid plastic to be severely
narrowed, with many
angles and boundaries and undercuts during the injection-molding operation in
the die.
Furthermore, the second interior region defines maximum material thicknesses
which
prescribe a certain cooling period for the plastic molding.
In another advantageous aspect, an injection point for the hard plastic of the
head is
provided on the neck or on the handle portion, and the blind-end holes are
spaced at
different relative axial distances to the injection point on the head, with
provision being made
in the hard plastic of the head for a free space for the function element
between these blind-
end holes spaced at different relative distances. Preferably, blind-end holes
are hence
provided both in the injection direction before, and in the injection
direction after, the free
space or cavity for the function element. In addition, blind-end holes may
also be provided
laterally or above the cavity, causing the complexity of the inner structure
to be enhanced
still further and making it necessary to take into account the material
thicknesses or
measures against undesired shrinkage effects closely.
In another advantageous aspect, the head includes at least one fifth blind-end
hole
which is arranged adjacent to and above the function element or above the free
space or
above the second interior region and is shorter than the third and fourth
blind-end holes.
Hence it is proposed shortening the blind-end hole depth at those locations in
the head
where the free space is correspondingly limited by other cavities for the
formation of blind-
end holes. In an alternative embodiment, all the blind-end holes are reduced
to this
dimension at a uniform depth from the brushing side of the head into the head
interior.
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In another advantageous aspect, the rear side of the head is made of the same
hard
plastic as the brushing side. This does not preclude injection molding the
head at other locations
using the two-component or multi-component injection molding technique, for
example, when it is
desired to have elastomer elements molded on in the brushing area. However,
the rear side
remains preferably at least in part devoid of a second plastic component
which, while it may
conceal visual defects on the molding on the one hand, adds to the thickness
of the head on the
other hand.
In another advantageous aspect, the head is formed of a hard plastic material
which
exhibits more than 1% material shrinkage after the actual injection-molding
operation. Rather than
selecting a different hard plastic, which is likewise conventional for the
injection molding of
toothbrush bodies but entails other disadvantages, for solving the material
shrinkage problems
which may produce visual defects already from 1% material shrinkage, it is
accordingly preferred
to match the inner structure of the head to the demands of material shrinkage.
In another advantageous aspect, the head is formed of polypropylene (PP hard
plastic).
Polypropylene usually has 2% material shrinkage after the injection-molding
process.
In another advantageous aspect, the head is formed of polyethylene,
polyoxymethylene
(POM), styrene-acrylonitrile (SAN) or copolyester hard plastic.
In another advantageous aspect, the head includes first and second bristle
tufts of
different lengths from the bottom of the blind-end hole to the bristle end
spaced from the brushing
area of the head, with the first and second bristle tufts being of
approximately equal length from
the brushing side to the bristle end. Alternatively, the first and second
bristle tufts are of different
lengths from the brushing side to the bristle end.
In another advantageous aspect, provision is made in the head for at least one
blind-end
hole having its central axis arranged at an angle to the perpendicular on the
brushing side. Hence
the head includes blind-end holes or tufting holes which extend at an
inclination therein and are
thus able to receive bristle tufts emerging from the head angularly. Angled
bristle tufts enhance
the cleaning performance of the bristles on the tooth, in which case however
the angled blind-end
holes may lead to increased turbulence of the liquid plastic in the die of the
molding to be
produced, in particular on staggered angled arrangements.
The present invention relates also to a method of manufacturing a toothbrush
exhibiting
the features as described herein.
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Further objects, advantages and application possibilities of the present
invention will
become apparent from the subsequent description of embodiments with reference
to the
accompanying drawing. It will be appreciated that any feature described and/or
represented
by illustration, when used singularly or in any meaningful combination, forms
the subject
matter of the present invention, irrespective of their summary in the claims
or their back-
reference.
In the drawing,
FIG. 1 is a perspective view of a bristled head of a toothbrush according to
the
invention;
FIG. 2 is a top plan view of the head of FIG. 1, shown devoid of bristles;
FIG. 3 is a longitudinal sectional view taken along the line A-A of FIG. 2;
and
FIG. 4 is a cross-sectional view taken along the line B-B of FIG. 2, but with
the
bristles shown attached to the head.
FIG. 1 shows in a perspective representation the head of a manual or electric
toothbrush. The neck portion of the toothbrush adjoins the breakaway line 2
and is not
shown in the Figures. Arranged in longitudinal continuation of the neck
portion along the
longitudinal axis 3 is a handle portion of the toothbrush in which electrical
components are
received according to the present embodiment in order to supply an
electrically operable
function element in the head with energy and the corresponding electrical
components. For
this purpose, the handle portion and the neck portion are provided preferably
with cavities in
the interior. In the present case, the electrically operable function element
is preferably an
LED arranged in protruding fashion on the brushing side 5 of the head within
the bristle tufts
6. According to the present embodiment, the brushing side 5 is preferably of
planar
construction. Arranged on the brushing side are front cleaning bristles 6a
positioned
adjacent to the distal end of the head 1. The front cleaning bristles 6a are
aligned forwardly
at an angle to the longitudinal axis 3 so that the posterior wisdom teeth can
be reached
particularly well. The bristle zone includes furthermore two outer rows of
bristle tufts 6b
which according to the present embodiment are arranged at an inclination to
the handle
portion. Provided between these outer rows of bristle tufts 6b are two center
bristle rows
having bristle tufts 6c arranged at an inclination towards the distal end of
the head 1. It will
be understood that the toothbrush may include any other bristle configurations
or oral care
elements in combination with bristle tufts 6.
FIG. 2 shows a top plan view of the head and hence the brushing side 5 of the
toothbrush. FIG. 3 shows a longitudinal section along the line A-A of FIG. 2,
and FIG. 4
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shows a cross-section along the line B-B of FIG. 2. The bristle tufts 6 are
not shown in
FIGS. 3 and 2. In FIG. 4 the bristle tufts have been added. Provided in the
front half of the
head 1 is a ramp 7 or, alternatively, for example, an elastomer element (not
shown) which
surrounds the LED 4. The associated cable connections are not shown in FIGS.
2, 3 and 4.
The LED is inserted into the mounting hole 8 within the ramp 7 or the
elastomer element.
Adjoining in the interior of the head is a free space 9 or cavity 9 for the
electrical leads to be
provided for the electrically operable function element (here LED). The
molding of the head
1 includes corresponding recesses for this free space.
As becomes apparent in particular from FIG. 3, blind-end holes 11, 12, 13 and
14 are
provided for receiving the bristle tufts 6a through tufting apertures 10. The
blind-end holes
are tufted with bristle tufts, which in turn are comprised of a multiplicity
of bristles or
filaments, using the method referred to as anchor tufting (also called
stapling technique). In
this process, an anchor 15 (see FIG. 4) is driven centrally into a bristle
tuft in a manner
known in the art, said anchor seating itself in the hard plastic of the head
to thereby ensure a
secure fastening of the bristle tufts 6 in the head. The blind-end holes 11,
12, 13 and 14
have respective sidewalls 16 which form the lateral boundary surfaces for the
bristle tufts in
the blind-end holes. In combination with the sidewalls 16, the blind-end holes
thus define as
a rule a cylindrical body. Bottoms 17 and 18 are provided to limit the blind-
end holes in
downward direction in the interior of the head 1. The sidewalls 16 are
connected with the
bottoms 17 through chamfers or radiuses which ultimately form a conically
tapering or
frusto-conical section in the blind-end hole. According to this embodiment,
the head 1 has
blind-end holes 11, 13 and 14 which have their sides bounded exclusively by
the sidewalls
16, the adjoining chamfers or radiuses 19 and the bottoms 17. The tufting
depth of the
bristle tufts within the blind-end holes 11, 13 and 14 extends to roughly the
bottoms 17.
Unlike the other blind-end holes, the blind-end holes 12 are provided with
constrictions 20,
so that the following structure results for these blind-end holes. Adjoining
the tufting
apertures 10 of the blind-end holes 12, sidewalls 16 begin to extend into the
depth of the
head 1, which sidewalls continue downwardly in a chamfer or radius 19 which,
similar to the
other blind-end holes, is of a conically or frusto-conically tapering
configuration. Adjoining
the chamfer or radius 19 further into the depth is a constricted portion 20
which in this case
is likewise hollow, cylindrical, but of a smaller diameter than that defined
by the sidewall 16.
This constricted portion continues in a further chamfer or radius which
connects the
constriction with the bottom 18 of the blind-end holes 12. The constriction
may also be
formed by other geometries, as, for example, the frustum of a cone, a cone, a
taper or
curved surfaces. Unlike the other blind-end holes, the blind-end holes 12
are not tufted
down to the bottom but only as far as the first chamfer or radius 19 which is
located at
approximately the same level of depth as the chamfer or radius 19 of the
adjacent blind-end
holes 11. In consequence, the front group of bristle tufts 6a of the head 1
extends to a
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uniform tufting depth in the head 1, which simplifies the manufacturing
process. The
purpose of the constriction 20 is to prevent sunk spots from developing due to
material
shrinkage which would occur in the absence of such a constriction on material
accumulation
in the area of cross-section of the head on the rear side, because shrinkage
is reduced
owing to the lower amount of material accumulation and a shortened cooling
period of the
plastic material subsequent to the injection-molding operation. The vertical
extension of the
lowermost point of the bottom of the blind-end holes to the outer surface of
the rear side 21
of the head defines the minimum distances x and y, respectively (see FIG. 3).
According to
the present embodiment, the minimum distance x between the lowermost point of
the blind-
end hole 12 and the rear side 21 is 1 mm, approximately. A minimum distance of
between
1.2 and 1.6 mm, approximately, is predetermined at y between the lowermost
point of the
blind-end hole 11 and the rear side 21 directly thereunder. Advantageously,
this distance
varies for all the blind-end holes of the head between 0.5 and 2.5 mm or
preferably between
0.8 and 2 mm. Because these areas can be at different distances from the
injection point, it
may be appropriate to provide different distances between the lowermost
bottoms of the
blind-end holes and the rear side of the head.
The blind-end holes 14 have likewise the same tufting depth for the bristle
tufts as
the blind-end holes 11 and 12. The blind-end holes 14 are arranged laterally
next to the
cavity or free space 9. The blind-end holes 13 extend into the head less
deeply than the
other blind-end holes. Extending further deeply adjacent to the blind-end
holes 13 is the
cavity 9 (see in particular FIGS. 3 and 4).
As becomes apparent particularly from FIG. 1, the length of the bristle tufts
from the
bottom of the blind-end holes to the bristle ends in the cleaning area is not
predetermined by
the depth of the blind-end holes. The topography nevertheless identifiable
from FIG. 1 with
height differences in the bristle tuft ends is determined after insertion of
the bristle tufts in the
blind-end holes by cutting the bristle ends to length and endrounding them
subsequently.
Thus, as illustrated in FIG. 4, bristle tufts 6b and 6c are provided in the
head which are of
equal length between the brushing side 5 and the bristle ends but extend to
different depths
in the blind-end holes of the head, so that the overall lengths of the bristle
tufts differ in spite
of like end height.
As becomes apparent in particular from FIG. 4, the cavity 9 is closed tight by
an end
cover 22. The end cover 22 is not shown in FIG. 3. The subject-matter of this
application
can be used to advantage regardless of the construction of an end cover 22 or
cavities 9 in
the head. The provision of a cavity 9 in addition to the blind-end holes
increases however
the inner complexity of the head 1 so that material shrinkage and visual
flawlessness in the
injection-molding process are not achievable with the known approaches. As
becomes
additionally apparent from FIGS. 3 and 4, sections are provided in vertical
extension below
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the bristle tufts on the rear side 21 of the head 1 which are not in alignment
with the cavity 9
or the cover 22, so that particularly at these locations sunk spots due to
material shrinkage
could develop in the absence of the measures herein described.
According to this embodiment, the head is injection-molded from a plastic
component
made of hard plastic, namely polypropylene. The injection point for the
molding in the die is
preferably located in the neck or handle portion of the toothbrush.
Alternatively, the injection
point is provided in the head. In the absence of a further plastic component
or in particular
soft plastic component on the rear side 21 of the head 1, this embodiment
provides likewise
no possibility of concealing visual flaws in the injection-molding process by
a soft plastic.
Depending on the type of visual flaw, concealing it by over-coating the
visually objectionable
areas is not always possible either.
The method of manufacturing the toothbrush is composed of the following
process
steps: Injection-molding of at least the plastic head, where applicable,
together with the
neck or handle portions, using in particular polypropylene or other materials.
Then bristle
tufts 6 are inserted in the head and anchors are driven into the head to
secure the bristle
tufts. Finally, the end sections of the bristle tufts 6 are finished by
cutting the bristle tufts 6 to
the proper length or topography, by endrounding them and applying further
finishing steps,
where appropriate. In cases where the electrically operable function element
(here LED) is
not cast integrally with the head in the prior injection-molding process,
mounting of this
element in the head takes place subsequent to the above tufting steps.
