AU749354B2 - Toothbrush with an exchangeable part - Google Patents

Abstract

The invention relates to a toothbrush comprising a handle, a head in the form of an elongated housing which is open on one side, a brush part removably inserted in said housing and having a support with bristles mounted thereon. On the rear side of the support, the inventive toothbrush has a projection penetrating in an opening located in the rear part of the housing. The support with said projection is composed of an elastic rubber material which enables elastic sealing against said housing and with its projection sealing against the opening. The brush part can be ejected from the housing by applying pressure on the projection through elastic deformation of said support. The bristles are fixed to the support by welding or injection.

Description

The invention concerns of a tooth brush having the features of the precharacterizing 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.

The handle of a conventional tooth brush (FR 2544497A) has a through 20 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 overdimensioned relative to the cross section of the hole to effect clamping. There is a relatively large risk that the support becomes prematurely detached.

o 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 Al 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 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.

e .e 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 Al) 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 2 e w r tn 20 unreliable with respect to function.

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According to another suggestion (DE 2 311 043 Al) 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 S•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 S 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 cthickness of the housing back. Consequently, the 7 consA uctional height in the area of the head increases which 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.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of each claim of this application.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

It is a preferred feature of the invention to produce a tooth brush with S 20 removable brush part which avoids the abovementioned disadvantages.

In one aspect, the present invention is a tooth brush comprising a 'handle, a head formed as elongated housing which is open on one side, a replaceable brush part inserted into the housing comprising a support and bristles mounted thereto via welding or injection moulding, wherein the support comprises a shoulder at its rear side penetrating into an opening at the back of the housing, wherein the housing has projections on the surfaces facing the support which engage with positive fit into the support and the brush part can be ejected through application of pressure onto the shoulder, characterised in S°that the support comprising the shoulder consists of rubber-elastic material and elastically seals against the housing and, with its shoulder, against the opening, wherein, under the application of pressure to the shoulder, the shoulder buckles inwardly and the rubber-elastic deformation of the support which propagates through the support leads to release of the support from the projections.

The shoulder can consist of a rubber-elastic material and elastically seal 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 the detachment thereof from the projections.

In accordance with the invention, the support can consist of a rubberelastic 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 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 utilised to release the positive .engagement.

The deforming capability of the support and of the projection can, however, be directly utilised 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 the 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 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 utilised 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 a..

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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 ro eo positive engagement is achieved, i.e. the user notices precise fixation of the brush part.

e e 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.

1 shows part of a back of a tooth brush in plan view; 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 i, 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 S. 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 The continuous jaw 8 and the wall 9 define a dimensionally stable frame which constitutes, together with 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 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 plateshaped 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 h one finger onto the pressure surface 15 in the direction 11 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 edge 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 at the transition between shoulder 14 and plateshaped part 13 of the support 4.

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Claims (9)

1. Tooth brush comprising a handle, a head formed as elongated housing which is open on one side, a replaceable brush part inserted into the housing comprising a support and bristles mounted thereto via welding or injection moulding, wherein the support comprises a shoulder at its rear side penetrating into an opening at the back of the housing, wherein the housing has projections on the surfaces facing the support which engage with positive fit into the support and the brush part can be ejected through application of pressure onto the shoulder, characterised in that the support comprising the shoulder consists of rubber-elastic material and elastically seals against the housing and, with its shoulder, against the opening, wherein, under the application of pressure to the shoulder, the shoulder buckles inwardly and the rubber-elastic deformation of the support which propagates through the support leads to release of the support from the projections.

2. Tooth brush according to claim 1, characterised in that the support comprises, on its side carrying the bristles, a continuous edge strip tightly sealing the housing at its open lower side.

3. Tooth brush according to claim 2, characterised in that the edge strip overlaps the housing up to its side surfaces.

4. Tooth brush according to any one of the claims 1 through 3, characterised in that bristles are also mounted to the edge strip.

Tooth brush according to any one of the claims 1 through 4, characterised in that the bristle ends to be mounted are provided with a molten enlargement via which they are embedded in the support through extrusion- 25 coating with the rubber-elastic support material.

6. Tooth brush according to claim 5, characterised in that the enlargement projects past the outer surface of the bristles on all sides, by 0.1 to 0.2mm.

7. Tooth brush according to any one of the claims 1 through 6, characterised in that the opening has the projections.

8. Tooth brush according to claim 7, characterised in that the support comprises depressions which correspond to the projections on the housing and/or the opening. 13

9. Tooth brush according to any one of the claims 1 through 8, characterized in that the opening is covered at the back of the housing by a flexible disc accommodating the ejection pressure, against which the shoulder of the support seats. Dated this third day of May 2002 Coronet-Werke GmbH Patent Attorneys for the Applicant: F B RICE CO *o*