Note: Descriptions are shown in the official language in which they were submitted.
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17932.8
PCT/EP99/04128
Translation of Application as Amended on June 6, 2000
Tooth Brush with an Exchangeable Brush Part
The invention concerns of a tooth brush having the features
of the pre-characterizing part of claim 1. A tooth brush of
this kind is described in DE 196 24 962 A.
The removable brush part of the brush head serves several
purposes. Continuous use of a tooth brush causes wear mainly
of the bristles, in particular of the bristle ends. According
to today's dental findings, the bristle ends should be
rounded in the shape of a dome to avoid damage to the enamel
and injuries of the gingiva. Even though modern manufacturing
techniques enable perfect rounding of the bristle ends, they
wear quickly through use and lose their round shape. There
are also additional signs of wear, e.g. the bristles can no
longer remain erect. For this reason, a tooth brush which is
used three times a day, as recommended by dentists, should be
replaced after a couple of weeks. To avoid large material
loss, or on the other hand, to save resources, tooth brushes
with removable brush parts have become more and more
important. On the one hand, only the worn part has to be
disposed of, and on the other hand, the user is more inclined
to replace it at regular intervals. Finally, the user will
save a considerable amount of money since the main part of
the tooth brush can be reused.
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The handle of a conventional tooth brush (FR 2 544 497 A) has
a through hole in the region of the brush head, the hole
having a large cross section at the side facing the bristles
and a smaller cross section at the back of the tooth brush.
The bristles are embedded in a support having appropriately
adapted cross sectional shapes, the support being inserted in
the hole in the handle and, when desired, can be exchanged
through the application of pressure in the back side region.
The support should be fashioned from a soft, a rigid or a
semi-rigid plastic. It can only be held in the hole if it is
sufficiently over-dimensioned relative to the cross section
of the hole to effect clamping. There is a relatively large
risk that the support becomes prematurely detached.
The removable brush part must be mounted to the tooth brush
head such that it does not detach too easily during use. On
the other hand, the brush part should be removable from the
head with relatively little force, in particular without
requiring any tools. These requirements are met by a number
of models. DE 44 34 617 A1 and DE 37 24 640 C2 disclose
forming the head as a housing which is open on one side and
provided with grooves or projections on the inside and to
provide the support with corresponding projections or grooves
which interlock when the support is pressed into the housing
from the open side. Therein, the support comprises a sealing
edge overlapping the open lower side of the housing. For
ejection of the brush part, the rear side of the support is
provided with a pin-like projection which engages in a
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correspondingly formed opening at the rear of the housing and
onto which pressure can be applied from the rear side of the
head for ejecting the brush part.
These known types comprising a form-fitting connection
between the head and brush parts have the disadvantage that
gaps between the head and the brush part cannot be avoided
into which liquids, tooth care residues etc. penetrate which
can cause hygienic problems since bacteria preferably
accumulate in moist gaps. This disadvantage is further
increased in that the head, which normally consists of a hard
plastic material, is constantly stressed by the retaining
forces which produces creeping and fatigue symptoms in the
plastic materials. This again endangers secure permanent
fixing of the brush part. Moreover, the gaps increase in size
leading to increased hygienic problems.
These hygienic problems are solved in another known type (DE
196 24 962 A1) in that the shoulder is resiliently locked in
the head on the rear side of the support such that the
housing side jaws and the corresponding side surfaces of the
support must not perform a fastening function and thus can
abut one another in a close and tight fashion thereby
avoiding gaps between them. Insertion of several sealing
rings aims to achieve a similar effect (DE 196 00 767 C1)
which is, however, demanding with respect to production and
unreliable with respect to function.
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According to another suggestion (DE 2 311 043 A1) the support
consists of a rubber-elastic material and is inserted into
the head with positive fit. The head has the shape of a
circular frame which is open on the upper and lower sides of
the head. The rubber-elastic support is pressed into the ring
and ejected from the back for replacement. Since the circular
head can only have a relatively small diameter and the
annular housing must have a certain minimum wall thickness
for reasons of stability, the bristle field is relatively
small. In addition, the deformable volume of the support is
small such that sealing of the support with respect to the
housing is possible only to a limited degree. If the support
is correspondingly over-dimensioned to achieve sufficient
tightness, the deformation resistance during insertion and
ejection is correspondingly high, i.e. insertion and ejection
is more difficult. In the known embodiment, the support forms
a depression on its rear side where dirt will accumulate.
All of the known types have the following disadvantages. To
fasten the bristles in the support and provide them with
sufficient pulling-out resistance, they have to be anchored
at a certain depth in the support. In conventional tooth
brushes, the thickness of the head depends essentially on its
mounting length. In the case of a tooth brush with removable
brush part, the thickness of the head will inevitably
increase since the thickness of the support which must be
adapted to the required mounting length, is increased by the
wall thickness of the housing back. Consequently, the
constructional height in the area of the head increases which
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is not desirable for its use. The head should be as slim as
possible to prevent excessive bending of the bristles, even
in case of limited mouth spaces, in particular with children
and mainly in the outer molar area. Sometimes it is also
desirable to have a certain elasticity in the area of the
head which can be achieved only with corresponding small head
strength. The known tooth brushes with replaceable brush part
do not meet these requirements due to their excessive
constructional height.
It is the underlying object of the invention to produce a
tooth brush with removable brush part which avoids the above-
mentioned disadvantages.
This object is achieved in accordance with the invention in
that the support, with shoulder consists of a rubber-elastic
material and elastically seals against the housing and seals
with its shoulder against the opening and that, upon
application of pressure on the shoulder, same buckles
inwardly and the rubber-elastic deformation propagated to the
support leads to detachment thereof from the projections.
In accordance with the invention, the support consists of a
rubber-elastic material which must allow the brush part to be
ejected merely through rubber-elastic deformation of the
support by applying pressure onto the rear side of the
support. This means on the other hand, that fixing of the
brush part in the support is effected primarily by elastic
restoring forces of the support material. The retaining
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forces and the forces during ejection are primarily accepted
by the rubber-elastic material of the support and have much
less effect on the brush head such that same cannot be
permanently deformed.
The rubber-elastic construction of the support also permits
disposition of the necessary means for providing the positive
fit retaining forces at any location along the constructional
height of the support. Towards this end the housing has
projections at surfaces facing the support which positively
engage into the support. The retaining forces do not thereby
lead to a continuous loading of the housing, rather only
during insertion and exchange. During exchange, the rubber-
elasticity of the support is utilized to release the positive
engagement.
The deforming capability of the support and of the projection
can, however, be directly utilized for elastic sealing of the
housing at all open sides. On the other hand, sufficient
anchoring of the bristles must be guaranteed despite the
rubber-elastic construction of the support. This is effected
in accordance with the invention using mounting techniques
which are known per se, i.e. by welding or injection molding
the bristle ends. This type of mounting has the advantage
over conventional pressing techniques, with which the looped
bristle bundles are mounted with anchors in the bristle
support, that the mounting length can be reduced to a minimum
such that the support can be thin and thus the total
constructional height of the head can be reduced. Welding or
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injection molding provides sufficient anchoring of the
bristles despite the elastic deformation of the support, in
particular when the brush part is ejected. A pulling-out
resistance of 25N can be easily achieved, which is not
possible with conventional pressing techniques.
The support advantageously comprises, on its side carrying
the bristles, a continuous edge strip tightly sealing the
lower side of the housing, which tightly abuts like a sealing
lip due to the rubber-elastic properties of the support
material and additionally prevents formation of a gap. This
sealing lip can overlap the head up to its side surfaces
thereby simultaneously forming a cover of the outer side of
the hard brush head to protect the mucous membrane.
The mounting of the bristles to the support in accordance
with the invention offers the possibility of also mounting
bristles on the sealing lip such that, in contrast to all
conventional brushes where the bristle stock is disposed at a
considerable separation from the continuous edge of the head,
the entire width of the head can be utilized or conversely,
the width of the head can be correspondingly reduced.
The bristles may be mounted by welding on or welding in. They
are preferably embedded by injection molding and comprise a
molten enlargement on their mounting ends by means of which
they are embedded in the support by extrusion-coating with
the support material. Advantageously, the enlargement
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projects past the remaining surface of the bristles on all
sides, by 0.1 to 0.2mm.
The above-mentioned measures ensure that, despite the elastic
deformation of the support during insertion or ejection, the
bristles are retained with sufficient pulling-out resistance.
The brush part can also be fixed in the housing if the
opening has projections on the surfaces facing the support
which engage in the support with positive fit.
Preferably, the support comprises depressions corresponding
to the projections on the housing and/or the opening. In
contrast to the above-mentioned, positive-fit connection
only, this embodiment has the advantage that one feels when
positive engagement is achieved, i.e. the user notices
precise fixation of the brush part.
Finally, the opening at the back of the head can be covered
by a flexible disc at which the support or its shoulder
seats.
Hermetic sealing of the rear side of the head is thereby
guaranteed.
The invention is described below with reference to an
embodiment illustrated in the drawing.
Fig. 1 shows part of a back of a tooth brush in plan view;
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Fig. 2 shows a section II-II in accordance with Fig. 1;
Fig. 3 shows a plan view of the bristle set of the tooth
brush;
Fig. 4 shows a section IV-IV in accordance with Fig. 3;
Fig. 5 shows a section in accordance with Fig. 4 during
ejection of the brush part; and
Fig. 6 shows a section in accordance with Fig. 4 of
another embodiment.
The tooth brush shown in figures 1 through 3 consists of a
longitudinal handle 1, broken off in the drawing, a head 2
and a removable brush part 3 which comprises a support 4
including bristle stock 5 of individual bristle bundles 6.
The head 2 of the tooth brush is formed as a housing 7 into
which the brush part 3, including support 4, is removably
inserted. The support consists of a rubber-elastic material,
preferentially an elastomer of high compressibility.
The housing 7 comprises a continuous jaw 8 as lateral border
which is closed by a wall 9 in the direction of the handle 1
(Fig. 2 and 4). The continuous jaw 8 and the wall 9 define a
dimensionally stable frame which constitutes, together with
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the back 10, a receptacle for the support 4 which is open
towards the bottom.
In the embodiment shown, the housing also has an opening 11.
The support 4, which is flat on the side of the bristle stock
5, consists of a plate-shaped part 13 whose contours
correspond to the contours formed by the inner side of the
jaw 8 and the wall 9, and a plug-like shoulder 14 which
penetrates into the opening 11 and is simultaneously
elastically fitted therein. The shoulder 14 has an exposed
end face which slightly projects past the back 10 of the
housing 7 to form a pressure surface 15. This pressure
surface may be optically emphasized, as shown in figure 1,
and possibly have a profiled surface. The opening 11 may also
be closed by a flexible elastomer disc via which the pressure
surface 15 can be acted upon.
The cross-section of the housing 7 may have the shape of a
rectangular box. In this event, elastic deformation of the
support is sufficient for fixing the brush part and for
sealing. In the embodiment shown, the jaws 8 are slightly
inclined towards the inside. Therein, retaining catches 12
are disposed on the inside of the jaws 8 which are associated
with correspondingly formed catch recesses 16 in the plate-
shaped part 13 of the support 4.
The position of use shown in figures 2 and 4 allows easy
replacement of the brush part 3 with a new one by pressing
with one finger onto the pressure surface 15 in the direction
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of the bristle stock 5 as a result of which, the pressure
surface 15 curves inwardly, and the deformation propagated
through the support leads to detachment of the catch recesses
16 from the retaining catches 12 such that the brush part 3
can be pushed out. The bundles 5 thereby spread outwardly
without becoming detached from the support 4.
The bristles 6 of the brush part 3 are welded to the support
4 (bundle 20) or welded into the support (bundle 21) or
provided with enlargements 17 which are extrusion-coated with
the support material (bundle 22).
In the embodiment according to Figs. 1 through 5, the plate-
shaped part 13 of the support 4 is provided with a continuous
edge strip 23 which overlaps the open side of the housing 7
towards the outside and forms a sealing lip which performs
additional sealing functions and also covers the edges of the
housing 7 to thereby provide mucous membrane protection.
In addition to the rubber-elastic deformation of the support,
in the embodiment in accordance with Fig. 6, the opening 11
is provided with a cylindrical wall 18 at the back 10 of the
housing 7 which comprises, on its end face located in the
housing, inwardly facing retaining catches 19 or a continuous
retaining bead which engages into correspondingly shaped
depression/depressions 19 at the transition between shoulder
14 and plate-shaped part 13 of the support 4.
