WO2000003619A1

WO2000003619A1 - A grooming implement

Info

Publication number: WO2000003619A1
Application number: PCT/US1999/016098
Authority: WO
Inventors: David Victor Cann; Kilian John O'neill
Original assignee: The Procter & Gamble Company
Priority date: 1998-07-17
Filing date: 1999-07-16
Publication date: 2000-01-27
Also published as: EP1098579A1; CA2337166A1; JP2002520107A; AU5106199A; GB9815643D0

Abstract

The invention relates to a personal grooming implement (1), such as a toothbrush, comprising a segmented, articulating head attached at one end to a handle, the segments being disposed longitudinally along the head and jointed to each other by an elastomer which is preferably fused to each segment. The joint nearest the free end of the head has a groove (11) on its upper surface to improve its flexibility relative to the other joints, thus providing for more uniform bending of the head.

Description

A GROOMING IMPLEMENT

Field of the Invention

The present invention relates to a personal grooming implement, such as a toothbrush, comprising a segmented, articulating head attached at one end to a handle, the segments being disposed longitudinally along the head and jointed to each other by an elastomer which is preferably fused to each segment. The joint nearest the free end of the head has a groove on its upper surface to improve its flexibility relative to the other joints, thus providing for more uniform bending of the head.

Background of the Invention

The configuration of human teeth requires that the ideal bristle contour for toothbrushes for brushing the buccal or outside surfaces of teeth be concave and that the ideal bristle contour for brushing the lingual or inside surfaces of teeth be convex. Most commercial brushes have a single piece head which is of comparable thickness to the handle and which is relatively rigid and of a fixed curvature or configuration.

A further drawback of conventional brushes is that pressing the brush sufficiently hard against the teeth to get good cleaning risks damaging or discomforting the softer, adjacent gums. To a certain extent this can be solved by modifying the configuration of the brush, or by varying bristle hardness or length, though again, a single configuration cannot be optimum for all circumstances.

Recently, there has been considerable interest in providing brushes with a degree of flexibility in the head. The means for achieving this has generally been to provide for one or more articulating joints, often partially or wholly filled with elastomer in order to modify the flexibility of the joint or to prevent the ingress of toothpaste. Illustrative of the art are WO 92/17092, WO 92/17093, WO 96/02165, WO 97/07707, WO 97/20484, WO 97/24048, WO 97/25899, WO 97/25900, WO 98/07349, WO 98/12948, WO 98/27846 and WO 98/27847.

One of the difficulties encountered in making an articulated, multi-segment head in which the joints between segments are longitudinally disposed along the head, is in controlling the relative flexibility of the joints between segments such that the head bends in a uniform curve. In practice, unless special steps are taken, there is a tendency for most bending to occur at the joint nearest the handle. WO 97/25900, referenced above, recognises this problem and discloses as a solution that integral hinges between the segments nearer to the handle are desirably less flexible than those which are more remote from it. This approach cannot be adopted however for brushes such as those described in WO 98/27846, also referenced above, where there are no hinges between segments and the elastomer is relied upon for bonding segments together. Decreasing the amount of elastomer used can put at risk the overall integrity of the brush head. Furthermore, unless the head thickness is also reduced, which may make it impractical to insert bristle tufts, the removal of elastomer creates voids which may fill up with toothpaste and make the brush unsightly or unhygienic. WO 98/27847 discloses the use of elastomers of different hardness as a means of controlling individual joint flexibility, in particular the use of a softer elastomer at the tip joint. The use of multiple elastomer types has the disadvantage however of complicating the manufacturing procedure.

It has now been found that removal of elastomer from the head surface which carries the bristles or other personal grooming means, is surprisingly efficient at improving the flexibility of the brush in the direction of bending of the head away from the face bearing the grooming means. Consequently, the flexibility of the tip joint can be improved relative to other joints whilst keeping to a minimum the amount of elastomer removed.

It is accordingly an object of this invention to provide a multi-segmented head for a personal grooming implement, such as a toothbrush, which provides uniform bending of the head way from the bristles or the like whilst retaining high strength and minimising dirt build-up.

Summary of the Invention

According to the present invention there is provided a personal grooming implement, the implement comprising a handle having two ends, and an articulated head connected to one end of the handle, the head having handle and tip ends, upper and lower faces and comprising three or more segments, the handle end being connected to the handle, the segments being spaced along a longitudinal axis defined by the handle and tip ends of the head and being joined to adjacent segments by joints made of an elastomer which extend transversely across the head, whereby each segment can articulate relative to neighbouring segments, at least one of the segments comprising a grooming means on an upper face thereof, the elastomer in each joint extending to the lower face of the head, characterised in that, in the joint nearest the tip end of the head, the elastomer only partially fills the joint such that there remains a groove in the upper face of the head, the remaining joints being completely filled with elastomer or partially filled such that grooves on the upper surface are of lesser depth than that of the tip joint, the flexibility of the tip joint being thereby increased relative to remaining joints. The head of the implement can bend uniformly away from the grooming means, yet at the same time employing sufficient elastomer to maintain head integrity and resilience over a long period and avoiding deep voids which might accumulate dirt.

Detailed Description of the Invention

The personal grooming implement of this invention can be any implement of the type that has a sufficiently elongated handle for the user to grip and, disposed at one end of the handle, a segmented head comprising a grooming means. The implement can, for example be a toothbrush, hairbrush or a massaging implement. More especially, it is a toothbrush.

At least one of the head segments comprises a grooming means. Preferably, each segment comprises a grooming means. The grooming means can take the form of bristles, combing teeth, polishing materials, rubber massage pads and the like. In preferred embodiments herein the implement is a toothbrush wherein the grooming means comprises a plurality of bristles extending from the segments of the head.

The head can be detachably connected to the handle, for example to permit replacement of the head when bristles become worn, in which case the head has a point of attachment for the handle. Alternatively, a first head segment can be continuous with the handle. In a preferred embodiment the handle and a first head segment are a single piece formed by injection moulding. Preferably the handle and all of the head segments are formed within a single mould by injection moulding. The head is of generally flattened construction having opposed upper and lower faces and the head also has a transverse axis lying orthogonal to the longitudinal axis and generally parallel to the opposed upper and lower faces. References to transverse or longitudinal herein refer to directions which are respectively parallel to these transverse and longitudinal axes, unless indicated otherwise.

The head and handle are generally made of relatively non-compressible materials, preferably with a modulus of elasticity of at least about 500 MPa, more preferably at least about 1000 MPa, which are conventional in the manufacture of toothbrushes, especially plastics materials. Suitable plastics materials include, for example, polyamides and polypropylenes. Polypropylene is preferred. Suitable polypropylenes include the material 'Polypropylene PM 1600' (marketed by Shell), having a modulus of elasticity (ISO 178) of 1500 MPa and Apryl 3400 MAI from Elf Atochem. Preferably, a foaming agent such as Hydrocerol HP20DP from Boehringer-Mannheim is mixed with the polypropylene at a level of from about 1% to about 3%, preferably from about 1.5% to about 2.5%, by weight of the polypropylene. The foaming agent assists the flow of the polypropylene during moulding. The handle itself is generally rigid and may be of a shape which is conventional in the manufacture of toothbrushes. Optionally, the handle may comprise a neck portion which is more flexible than the rest of the handle.

The head comprises three or more segments, one of which may be coextensive with the handle. Preferably there are three or four segments, more preferably four. Many more than this increases the manufacturing complexity and, in a toothbrush where bristle tufts are inserted only into the head segments, makes it difficult to achieve a sufficiently high tuft density on the brush head. The head segments are disposed in longitudinal sequence along the head so that a longitudinal line drawn from the handle to the tip end of the head passes through the first head segment then the second head segment and so on. More especially, there is a first head segment which is connected to or continuous with the handle and two or more additional head segments arranged in longitudinal sequence towards the tip or free end of the head. In general, each head segment will be made of the same material which will preferably be the same material as the handle so that they can all be made in a single injection moulding step.

In the finished implement, all the head segments are connected by joints comprising an elastomer. Elastomers are well known in the art of injection moulding. The term "elastomer" herein refers to a material which is both elastically compressible and elastically extensible. For the purposes of this invention, suitable elastomers have a modulus of elasticity of less than 500 MPa. Preferred elastomers for use herein have a modulus of elasticity of less than about 300 MPa, especially preferred are thermoplastic elastomers with a hardness of about 30 Shore A to 74 Shore D, polyolefin types such as styrene-ethylene-butylene-styrene (SEBS) are preferred, for example those based on Kraton® G, but other classes of elastomer, such as polyurethanes and polyamides, can also be used. An exemplary elastomer is 'PTS Thermoflex 75' (marketed by Plastic Technologie Service, Germany), having a modulus of elasticity (ISO 178) of 100 MPa and a hardness (ISO 868) of 80 Shore A. Elastomers PL 12291, PL 12292, and PL 12293 (marketed by Multibase, Saint Laurent Du Pont, France) are also suitable for use herein. In general, choosing the elastomer so that is based upon the same chemical class of polymers as material of the head segments assists in fusing the elastomer to the head segments. For example, when the head segments are made from polypropylene, the elastomer is preferably based upon a polyolefin. The elastomers can optionally be mixed with a suitable plasticiser or foaming agent to make them more compressible. The colour of the elastomer material can be the same as that of the head segments, or it may be different thereby achieving a distinctive striped or otherwise patterned appearance.

The elastomer can be connected to the head segments and/or handle by any suitable means, such as by adhesive or by thermal fusion. The elastomer is preferably incorporated into the implement of the present invention by injection moulding, such that the elastomer becomes fused to the head segments and/or handle. Preferred injection moulding conditions and bonding strengths are described in WO 98/27846 and WO 98/27847.

In highly preferred embodiments herein the head comprises at least one longitudinal groove which connects the transverse elastomer joints and permits the elastomer to flow from one band to the other during an injection moulding process. In an implement with a co-moulded handle, this longitudinal groove can extend along the handle so that the same elastomer injection point in the mould that is customarily used for supplying elastomer to form handle grips can also be used to inject the elastomer for the segment connecting means of the head. Normally the groove will not extend through the full depth of the handle or head at all points, though it can do so where desired, for instance to provide opposed grip points on top and bottom surfaces of the handle.

The joints between segments can be strengthened by integral hinges, preferably as described in WO 97/25900, it is preferred however that the elastomer is essentially the only means connecting the segments, by which is meant that the elastomer is the sole mechanical link between one segment and the next. By sole mechanical link, what is meant is that there are no continuous, non-elastomeric links such as bridges or springs connecting the segments. The elastomer may, however, have other materials dispersed within it, such as flecks of metal or pigments which might be used, for example, to provide a distinctive appearance or modify the properties of the elastomer. These additional materials will generally make a negligible contribution to the mechanical connection between the segments and/or handle such that their removal would not materially alter the strength of connection.

The head has upper and lower faces and the elastomer joints extend transversely across the head and between the faces. The elastomer jointing extends essentially all the way to the lower face of the head so that preferably it is flush with the head segments. It is to be recognised however that a small, functionally inconsequential degree of shrinkage may occur. In the transverse direction, though partial elastomer filling of the joints can be effected, the elastomer preferably extends the full width of the head in order to avoid exposed edges of the segments.

It is an essential feature of the invention that in the joint nearest the tip end of the head (the tip joint), the elastomer only partially fills the joint such that there remains a groove in the upper face of the head. This can of course be arranged by suitable construction of the mould for the preferred injection moulding process. The remaining joints can be completely filled with elastomer or partially filled, provided that other grooves on the upper surface are of lesser depth than that of the tip joint, the flexibility of the tip joint being thereby increased relative to remaining joints, especially for bending of the head away from the upper face.

The depth of groove in the tip joint is suitably from about 5 to about 20%, preferably from about 7 to about 18%, more preferably from about 10 to about 15% of the depth of the head, which is the distance between the upper and lower faces. For a typical toothbrush head the absolute depth of the groove is generally in the range from about 0.3 to about 1.5 mm, preferably from about 0.5 to about 1 mm, more especially about 0.7 mm.

In one embodiment according to the invention the head comprises three segments, of which one is integrally connected to the handle, there being two joints, the joint nearest the handle being wholly filled with elastomer. In a preferred embodiment the head comprises four segments, of which one is integrally connected to the handle. There are three joints, a first joint nearest the handle, a second joint and a tip joint. The elastomer can wholly fill the first and second joints, preferably there are grooves in the upper surface of the head at the second and tip joints, the groove of the tip joint being deeper than that of the second joint. A suitable groove depth for the second joint is from about 3 to about 12%, preferably from about 5 to about 10%, more preferably from about 6 to about 9% of the depth of the head. The absolute depth of the groove in the second joint is generally in the range from about 0.2 to about 1 mm, preferably from about 0.3 to about 0.6 mm, more especially about 0.4 mm, for a typical toothbrush head.

The elastomer joints can vary in thickness, either from one band to the next or even across the width or along the depth of the band. Suitably, their thickness, measured along the longitudinal axis, is in the range from about 0.1 mm to about 10 mm, preferably from about 0.3 mm to about 5 mm, more preferably from about 0.5 mm to about 3 mm. The bands of elastomer can be linear or non-linear. Preferably they are non-linear and take the form of chevrons or waves whose apices point towards the free end of the head.

In preferred embodiments herein, the upper face of the head has a concave profile along the longitudinal axis of the head, though the radius of curvature may vary along the length of the head. The radius of curvature is preferably from 10 to 500 mm, more preferably from 15 to 250 mm, especially from 25 to 150 mm.

The invention will now be described by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a longitudinal, vertical cross-section through the centre of the head of a toothbrush according to the invention; bristles are omitted for the sake of clarity.

Fig. 2 is a plan view of the lower face of the head of a toothbrush according to the invention.

Referring to the figures, a toothbrush head 1 has an upper face 2 and lower face 3 which are substantially parallel to each other and about 5 mm apart. The head has a handle end 4 and tip end 5, the handle end being integrally formed with an elongated polypropylene handle 6. The head comprises four longitudinally spaced, polypropylene segments 7, the first of which is continuous with handle 6. The segments are connected only by bands of a SEBS elastomer 8, having a hardness of 60 Shore A, which extend transversely across the head and between the upper face 2 and lower face 3. A longitudinal groove 9 extends along the bottom face of the head and the handle, connecting the bands of elastomer so that they can all be formed from a single elastomer injection point. The bands of elastomer are of generally uniform thickness along the longitudinal direction but broaden forwards and outwards at the lower face to provide improved keying of the elastomer to the polypropylene segments. The upper face of the head includes tuft holes 10 which for tufting with bristles. In preferred embodiments, the brush head has bristles extending from each of the four segments. Upper face 2 is slightly concave along the longitudinal axis, having a radius of curvature of about 145 mm. The bands of elastomer 8 form the joints between segments 7 allowing them to articulate relative to each other, affording sufficient flexibility to the brush head that it can bend along the longitudinal axis until the top face becomes convex. In doing so the elastomer is stretched along the top face. The elastomer on this face can stretch to more than 200% of its unstressed length without any observable loss of attachment of the elastomer to the segments. The head is able to repeatedly flex to this extent and back to the rest state through 75,000 cycles, without any detachment of the elastomer from the head segments. In order to improve the uniformity of bending, the joint between the third and tip segments is not completely filled with elastomer, such that there is a groove 11 which has a depth of about 0.7 mm, in order to improve the flexibility of the joint. There is also a shallower groove 12, about 0.4 mm deep between the second and third segments, the joint between the first and second segments being wholly filled with elastomer.

The toothbrush is made by sequential injection moulding of first the polypropylene to form the handle 6 and segments 7 and then in a second step the elastomer is injected at a temperature of 255°C, thereby becoming fused to the polypropylene. After the brush has cooled the bristle tufts are inserted by the stapling technique into pre-formed tuft holes 10.

Claims

I. A personal grooming implement, the implement comprising a handle having two ends, and an articulated head connected to one end of the handle,

A. the head having handle and tip ends, upper and lower faces and comprising three or more segments, the handle end being connected to the handle,

B. the segments being spaced along a longitudinal axis defined by the handle and tip ends of the head and being joined to adjacent segments by joints made of an elastomer which extend transversely across the head, whereby each segment can articulate relative to neighbouring segments, at least one of the segments comprising a grooming means on an upper face thereof, the elastomer extending to the lower face of the head

C. characterised in that

D. in the joint nearest the tip end of the head, the elastomer only partially fills the joint such that there remains a groove in the upper face of the head, the remaining joints being completely filled with elastomer or partially filled such that grooves on the upper surface are of lesser depth than that of the tip joint, the flexibility of the tip joint being thereby increased relative to remaining joints.

II. An implement according to Claim 1 wherein the head comprises three segments, of which one is integrally connected to the handle, there being two joints, the joint nearest the handle being wholly filled with elastomer.

III. An implement according to Claim 1 wherein the head comprises four segments, of which one is integrally connected to the handle, a first joint nearest the handle, a second joint and a tip joint.

IV. An implement according to Claim 3 wherein the elastomer wholly fills the first joint and there are grooves in the upper surface of the head at the second and tip joints, the groove of the tip joint being deeper than that of the second joint.

V. An implement according to Claim 3 wherein the elastomer wholly fills the first and second joints.

VI. An implement according to any preceding claim wherein the elastomer is essentially the only means connecting the segments. VII. An implement according to any preceding claim wherein the implement is a toothbrush, the grooming means comprising a plurality of bristles extending from one or more, preferably all, segments of the head.