TOOTHBRUSH

Abstract: A toothbrush having a head (2) which is made flexible by virtue of being made in the form of a number of segments (2A-E), each linked by thin integral links (7) of defined thickness and length, and the link may also incorporate an elastomeric material (9) to modify flexibility. The invention provides optimised flexibility characteristics of the head.

Description: Toothbrush This invention relates to toothbrushes, in particular to toothbrushes having a flexibly linked region in their head. Generally toothbrushes comprise a plastics material handle with a plastics material head adjoining the handle at a base end of the head, generally via a neck region, the head and handle being disposed along a longitudinal toothbrush axis, the head having bristles extending from a bristle face of me head which is an opposite head surface to a back face of the head. The direction between the bristle face and the back face being is defined as the thickness of the head. Bristles are generally distributed in bristle tufts mounted in socket holes in the bristle face, or may be fused into d e head material. Toothbrushes having a flexibly linked region in their head are known. For example WO 92/17093 discloses a toothbrush in which the head is divided into two or more segments which are flexibly and resiliently linked to each other and/or to the handle of the toothbrush. A particular form of the toothbrush of WO 92/17093 has a head which has grooves in the back face of the head, these grooves being filled with an elastomer material to modulate the flexibility of the head. The embodiments disclosed in WO 92/17093 have their grooves distributed in a generally uniform distribution over the reverse face of the head, or around the longitudinal mid point of the head, so as to enable the whole head to accommodate itself to the curved shape of the teeth. WO 96/02165 discloses toothbrushes with flexible heads similar in construction to those of WO 92/17093, and having a generally concave profile of bristle ends. DE-G 87 05 474.4 discloses a toothbrush in which the tip region of the head is hinged to a base region of die head and an operating button on the handle allows the tip region to fold relative to the base region. WO 97/24048 discloses a toothbrush in which d e head is divided into two portions, having a flexible link about half way along the head. It is an object of this invention to provide a toothbrush with a flexible head in which the flexibility of the head is improved and ideally optimised. According to a first aspect of this invention a toothbrush comprises a plastics material handle with a plastics material head adjoining me handle at a base end of the head, d e head and handle being disposed along a longitudinal toothbrush axis, the head having bristles extending from a bristle face of the head and having an opposite back face, the head comprising at least two adjacent segments integrally linked by a flexible link of the plastics material of the head, a first surface of the link being in the same surface as either the bristle face or the back face of the head, characterised in that the minimum thickness of the link is between 0.2 and 2.0 mm. The term "thickness" as used herein refers to the dimension measured in the direction between me bristle face and the opposite back face. Preferably the minimum thickness of the link is between 0.5 and 1.0 mm, most suitably between 0.2 and 0.5 mm. Preferably the minimum length of the link between adjacent linked segments is at most 0.4 mm. Preferably the minimum thickness of the link is 0.2 to 0.3 mm, and the minimum length of die link between adjacent linked segments is at most 0.3 mm, desirably 0.2 mm. In one embodiment of this first aspect of the invention the link is in the form of a strip of the plastics material having a second surface opposite to and substantially parallel to me said first surface. The link is preferably linear between the linked segments, and may suitably also be linear oriented across the longitudinal axis of the head, or parallel to the longitudinal axis of the head. By "linear" is meant mat the link is constructed to flex along a fold axis, and in a "linear" link the fold axis follows a substantially straight line. Alternatively the link may follow a curved, chevron or zig-zag linear path as seen in plan view onto the bristle face or back face of the head. According to a second aspect of this invention a toothbrush comprises a plastics material handle with a plastics material head adjoining the handle at a base end of the head, die head and handle being disposed along a longitudinal toothbrush axis, the head having bristles extending from a bristle face of the head, and an opposite back face, the head comprising at least two adjacent segments integrally linked by a flexible link of the plastics material of the head, a first surface of the link being in the same surface as either the bristle face or the back face of the head, characterised in that the minimum thickness of the link is between 0.2 and 0.5 mm, and the link has a second surface opposite to the first surface, the second surface being a cylindrically or conoidally concave surface having a radius of curvature of between 0.1 and 2.0 mm, the radius being aligned in the direction generally perpendicular to the linked direction. Preferably the minimum thickness of the link is 0.2 to 0.3 mm, and die radius of curvature is 0.3 - 1.4 mm. The concave surface is preferably a cylindrically concave surface. The link is preferably linear between the linked segments, and may suitably be linear oriented across the longitudinal axis of d e head, or parallel to die longitudinal axis of die head. Alternatively the link may follow a curved, chevron or zig-zag linear path as seen in plan view onto me bristle face or back face of the head. In these two aspects of the invention, if the first surface is the same surface as the bristle face and the toothbrush head has bristle tufts mounted in socket holes in the bristle face, the minimum distance between die edges of adjacent socket holes is preferably no less than 0.45mm, particularly no less than 0.55 mm. According to a third aspect of this invention a toothbrush comprises a plastics material handle with a plastics material head adjoining die handle at a base end of the head, die head and handle being disposed along a longitudinal toothbrush axis, the head having bristles extending from a bristle face of the head, and an opposite back face of die head, the head comprising at least two adjacent segments integrally linked by a flexible link of the plastics material of the head, the link being situated intermediate between the bristle face and the back face of the head, characterised in that the maximum thickness of the link is between 0.2 and 3.0 mm. Preferably the length of the link between adjacent linked segments is 1.0 to 2.5 mm, suitably 1.0 to 1.5 mm. Preferably the maximum thickness of the link is between 0.2 and 0.4 mm, and the lengdi of the link between adjacent linked segments is 1.0 to 2.0 mm. In one embodiment of mis third aspect of the invention die link is in the form of a strip of the plastics material having a first surface facing in the direction of the bristle face, and an opposite second surface facing in the direction of the back face, both the said first and second surfaces being substantially parallel to me bristle face of the head. The link is preferably linear between the linked segments, and may suitably be linear oriented across the longitudinal axis of the head, or parallel to d e longitudinal axis of the head. Alternatively ie link may follow a curved, chevron or zig-zag linear path as seen in plan view onto die bristle face or back face of the head. The link of this third aspect may be nearer to either die bristle face or the opposite face of the toothbrush, for example nearer to the bristle face. In all of the above aspects of the invention the link may link segments which are sequentially longitudinally arranged along die longitudinal direction of d e toothbrush head. In such a construction the link will preferably extend substantially widdiways across d e head, i.e with a fold axis across die head. Such a link may extend across die whole widtii of the head or partly across d e width of the head, e.g there may be apertures in the head material between links. For example die link may be a link which links longitudinally adjacent plastics material segments of me toothbrush head, and being in the form of a diin integral strip of plastics material extending across the head of the toothbrush between the linked segments, hence having a fold axis across me said head. In all of the above first second and third aspects of the invention the linked segments comprising the head will be thicker man the link, toothbrush heads being typically 3 to 6 mm thick. The provision of the above-described links will consequently result in chasms in the plastics material of the bristle face and / or the back face of the head, i.e as the said plastics material thins to form the integral link between the linked segments, widi the link at the bottom of the chasm, and me chasm may be wholly or partly filled with an elastomeric material. Preferably the said link lies at the bottom of a chasm in the plastics material of the toothbrush head, and the said chasm contains an elastomeric material, e.g. to make up the depth of the chasm. In the first, second and tiiird aspects of the invention the dimensions of the plastics material parts of links described are such that the links are both flexible and resilient. The use of an elastomer material as described above to fill a chasm in the toothbrush head in these aspects may be additionally used to modify the flexibility and resilience of the link, in forming a composite link region comprised of both the plastics material link and the infilling of elastomer. According to a fourth aspect of this invention a toothbrush comprises a plastics material handle with a plastics material head adjoining the handle at a base end of die head, the head and handle being disposed along a longitudinal toodibrush axis, die head having bristles extending from a bristle face of the head, and having an opposite back face, the head comprising at least two adjacent segments integrally linked by a flexible link of the plastics material of die head, characterised in diat the maximum thickness of the link is at most 0.2 mm, the said link lying at me bottom of a chasm in the plastics material of the toothbrush head, the chasm containing an elastomeric material bonded to the said link to form a composite plastics material / elastomer material link between the segments. Suitably the length of the link, between adjacent linked segments in this fourth aspect of die invention is between 0.5 and 3.0 mm, e.g 0.8-1.6 mm, e.g around 1.2 mm. In this fourth aspect of die invention one surface of d e link may be in die same surface as die bristle face or the back face of the head, or alternatively the link may be formed at an intermediate position in the thickness of the head between die bristle face and die back face of the head. In one embodiment of mis fourth aspect of die invention the link is in the form of a strip of the plastics material having a first surface and an opposite second surface, bodi the said first and second surfaces being substantially parallel to die bristle face, or die back face, of the head. The link is preferably linear between the linked segments, and may suitably be linear oriented across the longitudinal axis of the head, or parallel to the longitudinal axis of the head. Alternatively the link may follow a curved, chevron or zig-zag linear path as seen in plan view onto the bristle face or back face of the head. In diis fourth aspect of the invention the link may link segments which are sequentially longitudinally arranged along the longitudinal direction of die toothbrush head. In such a construction the link will extend widthways across the head, i.e widi a fold axis across die head. Such a link may extend across the whole widdi of the head or partly across the width of the head, e.g mere may be apertures in the head material between links. In the fourth aspect of the invention the dimensions of the plastics material parts of links described are such that the link is flexible but has little or no effective resilience. The use of an elastomer material as described above to fill one or more chasms in the toothbrush head in this fourth aspect is to modify the flexibility and resilience of the link, in forming a composite link region comprised of both the plastics material link and the infilling of elastomer. In all of the above described embodiments the nature, dimensions and orientation of the segments, the Iink(s) and/or the chasms between segments may differ at different parts of the head, e.g to provide different degrees of flexibility at different places on die head, e.g to make me parts of the head toward the tip of the head remote from the handle more, or less, flexible than parts of the head toward the base of die head. For example greater flexibility may be achieved by diinner links. For example the links may be thicker or longer as between linked segments at some regions of the toothbrush head than at odier regions. For example when the link lies at the bottom of two chasms respectively in the bristle face and the opposite back face, i.e by virtue of the link being at an intermediate position in me toothbrush head between the bristle face and the opposite back face, the relative width, depth, shape or taper of die two chasms may be the same or different, for example to encourage the toothbrush head to fold more preferably in one direction than another. Typically die toothbrush heads of the invention will have a thickness, i.e the dimension between die bristle face and the opposite back face of die head, of 3-6 mm, generally around 4-5 mm, e.g 4.2 ±, 0.3 mm. The toothbrush of the invention can be made by known one- (i.e plastics material only) or two- (plastics material and elastomer material) component injection moulding techniques. In all of die above aspects of the invention when there are two or more composite links comprising plastic material and elastomeric material, and / or if mere are other regions of elastomer in the toothbrush structure, e.g additional flexible regions or an elastomeric grip pad, die elastomer in the links and / or in the other regions of elastomer may be linked by moulding channels in the plastics material of the toothbrush head and if appropriate the neck and handle. Such elastomer is normally introduced into die toothbrush strucmre by an injection moulding operation, of a known nature, in which hot fluid elastomer is injected into d e toothbrush structure under conditions which cause bonding between die elastomer and the plastics material. Such moulding channels minimise the number of injection moulding points needed for the injection of fluid elastomer. Such channels may run longitudinally along die toothbrush and may, in consequently creating thinned areas of the plastics material wholly or partly filled with an elastomer, e.g grooves or surface channels in the plastics material parts, contribute to the flexibility of the toothbrush head or die entire too brush strucmre. In particular if the link(s) link segments which are sequentially longitudinally arranged along the longitudinal direction of die toothbrush head, longimdinally oriented moulding channels of this type may be employed to join diem. Other features of the construction of the toothbrush of this invention, e.g die handle, bristles, neck region or other flexible regions widiin the toothbrush structure may be generally conventional. Suitable plastics materials for the plastics material parts of the toodibrush of this invention include the plastics materials widely used for manufacture of toothbrushes, e.g polyesters, PBT, polypropylene and polyamides, for example the plastics materials disclosed in GB 2216785 A. An example of a suitable polypropylene is the material "Polypropylene PM 1600" marketed by Shell. Suitable elastomer materials include the elastomer materials widely used for manufacture of the elastomeric grip pads and flexible link parts of toothbrushes, e.g TPE, SBS (styrene-butadiene-styrene block copolymer) and SEBS (styrene-ethylene- butylene-styrene block copolymer), for example available from Gummiwerk I raiburh GmbH & Co., Waldkraiburg (DE), and "PTS Thermoflex 75" having a modulus of elasticity (ISO 178) of 100 Mpa and a hardness (ISO 868) of 80 Shore A, marketed by Plastic Technologie Service, Germany. Such elastomers may be chemically or physically treated, e.g by foaming or plasticising to modify d eir compressibility. The invention will now be described by way of example only with reference to the accompanying figures which show: Fig. 1 an overall view of a toombrush of the first, second and diird aspects of this invention. Fig. 2 an enlarged section of a link according to the first aspect of this invention. Fig. 3 an enlarged section of a link according to the second aspect of this invention. Fig. 4 an enlarged section of a link according to the third aspect of this invention. Fig. 5 an enlarged section of a link according to die fourth aspect of this invention. Fig. 6 an enlarged detail of die bristle face of a toothbrush head of the invention. Fig. 7 an enlarged section of another link according to this invention. Referring to Fig. 1, Fig 1A shows a generalised overall back view of a toothbrush of mis invention, and Fig. IB shows a generalised side view of a toombrush of this invention. The toothbrush consists of a plastics material handle (1) with a plastics material head (2) adjoining die handle at the base end of the head, via a neck region (3), the head and handle being disposed along a longitudinal toodibrush axis A--A. The head (2) has bristles (4) extending from a bristle face (5) of the head, which is an opposite head surface to a back face (6) of the head (2). The direction between the bristle face and die back face "t" is defined as d e thickness of the head (2) and is ca. 5 mm. Bristles (4) are distributed in bristle tufts mounted in socket holes in the bristle face (5), but may be fused into the head material. The head (2) comprises a number (six are shown) of adjacent segments (2A, 2B, 2C, 2D, 2E) integrally linked by a flexible link (7) of the plastics material of the head, a first surface of die link (7) being in the same surface as die bristle face (5) of the head (2). Each link (7) comprises a thin strip of plastics material at the bottom of a chasm (8) in the plastics material of the head (2), me chasm being filled widi an elastomeric material (9), diereby forming a composite link. In Fig 1 these links (7) are shown in a generalised manner and are shown in Figs 2 to 5, and described below, in more detail with discussion of alternative constructions. The toothbrush head may comprise any number of such segments (2 A etc.) two being a convenient number. The handle (1) incorporates an elastomeric grip pad (10) which is integrally linked by elastomeric material in a moulding channel (11) witih me chasms (8) in the head. The moulding channel (11) comprises a surface groove in the neck (3) and head (2), Figs. 1C and ID showing cross sections at C--C and D-D respectively. Referring to Fig 2 an enlarged longitudinal section of the region of the head around a link (7) is shown in more detail. The link (7) comprises a flexible link of the plastics material of the head, a first surface (7A) of the link being in the same surface as bristle face (5) of the head. The minimum thickness of the link, "t 1 ", is between 0.2 to 0.3 mm, and the minimum length of the link "l 1 ", between adjacent linked segments (2F, 2G) is at most 0.2 mm. The link (7) is in the form of a strip of the plastics material having a second surface (7B) opposite to and substantially parallel to the first surface (7A). The link (7) shown is linear between the linked segments (2F, 2G), and is oriented across die longitudinal axis A-A of the head. It will be apparent that Fig. 2 equally well represents a link (7) having its first surface in the same surface as back face (6) of the head (2). In Fig 2 the elastomer filling (9) is shown, and the chasm (8) is shown as being parallel sided near the surface and tapering toward the link (7) at its bottom. Referring to Fig. 3 an enlarged longitudinal section of the region of the head around a link (7) is shown in more detail. The link (7) comprises a flexible link of the plastics material of the head, a first surface (7C) of the link being in the same surface as bristle face (5) of die head. The minimum thickness of the link, "t 2 " , is between 0.2 to 0.3 mm. The link has a second surface (7D) opposite to the first surface (7C), the second surface (7D) being a cylindrically or conoidally concave surface having a radius of curvature "r" of between 0.1 and 2.0 mm, the radius being aligned in the direction generally perpendicular to the linked direction, i.e generally perpendicular to d e axis A— A. The link (7) shown is linear between the linked segments (2H, 21), and is oriented across the longimdinal axis A— A of d e head. It will be apparent that Fig. 3 equally well represents a link (7) having its first surface in the same surface as back face (6) of the head (2). In Fig 3 die elastomer filling (9) is shown, and die chasm (8) is shown tapering toward the link (7) at its bottom. Referring to Fig 4 an enlarged longitudinal section of die region of the head around a link (7) is shown in more detail. The link (7) comprises a flexible link of the plastics material of the head, die link (7) being situated intermediate between die bristle face (5) and the back face (6) of die head. The maximum thickness "t 3 ", of the link (7) is between 0.9 and 1.2 mm, and the length "l 2 ", of die link between adjacent linked segments (2J, 2K) is 1.5 mm. The link (7) is in the form of a strip of the plastics material having a second surface (7E) opposite to and substantially parallel to its first surface (7F). The link (7) shown is linear between the linked segments (2J, 2K), and is oriented across the longimdinal axis A--A of the head. In Fig 4 the elastomer filling (9) is shown, and me two chasms (8) in the bristle face (5) and back face (6) are shown as tapering toward the link (7) at their bottom. In Figs 2, 3 and 4 the plastics material link (7) has dimensions such that it has flexibility and resilience. Referring to Fig. 5 an enlarged longitudinal section of die region of the head around a link (7) is shown in more detail. The link (7) comprises a flexible link of the plastics material of the head, d e link (7) being simated intermediate between the bristle face (5) and die back face (6) of the head. The maximum thickness "t 4 ", of the link (7) is less than 0.2 mm. The link (7) is in the form of a strip of die plastics material having a second surface (7G) opposite to and substantially parallel to its first surface (7H). The link (7) shown is linear between the linked segments (2L, 2M), and is oriented across the longimdinal axis A— A of the head. In Fig 5 the elastomer filling (9) is shown, and the two chasms (8A, 8B) in the bristle face (5) and back face (6) respectively are shown as tapering toward the link (7) at their bottom, being wider toward respectively the bristle face (5) and the opposite back face (6). The taper of the two chasms (8A, 8B) may be the same or different, for example to encourage the toothbrush head to fold more preferably in one direction man another. In Fig. 5 the plastics material link (7) has dimensions such that it has flexibility but virtually no resilience, and serves principally as a link holding the linked segments (2L, 2M) together, the strength, flexibility and resilience being determined primarily by the properties of the elastomer infilling (9). Referring to Fig. 6, the region of the bristle face (5) is shown in more detail. The head (2) of the toodibrush of Fig. 6 may include any of the types of link (7) discussed above, so the detail of the link is not shown. The bristles (4, not shown in Fig. 6) are arranged in discrete tufts which are mounted in bristle socket holes (12) in the bristle face (5). The socket holes (12) are generally circular. The distance "d" between the edges of adjacent socket holes (12) is greater dian 0.55 mm. Referring to Fig. 7 an enlarged longimdinal section of the region of the head around a link (7) is shown in more detail. The link (7) comprises a flexible link of the plastics material of the head, die link (7) being simated intermediate between the bristle face (5) and the back face (6) of the head, die thickness T of the head (2) being 4-5 mm, e.g 4.2 +_ 0.3 mm. The maximum thickness "t 5 ", of the link (7) is 0.2 mm ± 0.1 mm. The link (7) is in the form of a strip of the plastics material having a second surface (71) opposite to and substantially parallel to its first surface (7J). The length l 3 of link (7) between the linked segments (2N, 2O) is 1.2mm ± 0.3 mm. The link (7) shown is linear between the linked segments (2N, 2O), and is oriented across me longimdinal axis A-A of the head. In Fig 7 the elastomer filling (9) is present but for clarity is not shown, and me two chasms (8A, 8B) in the bristle face (5) and back face (6) respectively are shown as tapering toward the link (7) at their bottom, being wider toward respectively me bristle face (5) and the opposite back face (6) than at their bottom surface i.e the link (7). At their widest, in the surfaces (5, 6) of the toothbrush head the width W of the chasms (8A, 8B) is 2.4mm ± 0.3 mm. The depth d 1 of the chasm (8A) in the bristle face is 0.9 ± 0.4mm, and the depth d 2 of the chasm (8A) in the bristle face is 3.1 ±_ 0.4mm. The taper of the two chasms (8A, 8B) may be the same or different, for example to encourage die toothbrush head to fold more preferably in one direction than another. In Fig. 7 d e slopes of the sides of the chasms (8A, 8B) are such that their respective depths d 1 and d 2 are attained in slopes s 1 and s 2 of 0.5 - 0.7 mm. Each of the bottom corners of the chasms (8A, 8B) has a radius of 0.2-0.4 mm, e.g. 0.3 mm. The link (7) in Figs 1 to 7 also serves to allow all of the various linked segments (2A-2O) of the head to be integrally linked by plastics material, enabling formation by injection of fluid plastics material at a single injection point.

Claims: Claims: 1. A toothbrush which comprises a plastics material handle wim a plastics material head adjoining die handle at a base end of the head, die head and handle being disposed along a longimdinal toodibrush axis, the head having bristles extending from a bristle face of the head, the head having an opposite back face, the head comprising at least two adjacent segments integrally linked by a flexible link of me plastics material of the head, a first surface of die link being in the same surface as either the bristle face or die back face of me head, characterised in that the minimum thickness of the link is between 0.2 and 2.0 mm. 2. A toombrush according to claim 1 characterised in that die the minimum thickness of the link is between 0.5 and 1.0 mm. 3. A toothbrush according to claim 1 characterised in that d e minimum thickness of die link is between 0.2 and 0.5 mm. 4. A toodibrush according to any one of claims 1 to 3 characterised in that the minimum length of the link between adjacent linked segments is at most 0.4 mm. 5. A toothbrush which comprises a plastics material handle wim a plastics material head adjoining die handle at a base end of the head, d e head and handle being disposed along a longimdinal toodibrush axis, die head having bristles extending from a bristle face of the head, die head having an opposite back face, the head comprising at least two adjacent segments integrally linked by a flexible link of die plastics material of the head, a first surface of the link being in the same surface as either the bristle face or the back face of the head, characterised in that the minimum thickness of the link is between 0.2 and 0.5 mm, and the link has a second surface opposite to die first surface, d e second surface being a cylindrically or conoidally concave surface having a radius of curvamre of between 0.1 and 2.0 mm, the radius being aligned in the direction generally perpendicular to die linked direction. 6. A toothbrush which comprises a plastics material handle with a plastics material head adjoining die handle at a base end of the head, die head and handle being disposed along a longimdinal toothbrush axis, d e head having bristles extending from a bristle face of the head, me head having an opposite back face, die head comprising at least two adjacent segments integrally linked by a flexible link - 11 - RECTIFIED SHEET (RULE 91) of the plastics material of the head, me link being simated intermediate between the bristle face and die back face of the head, characterised in that die maximum thickness of the link is between 0.2 and 3.0 mm. 7. A toothbrush according to claim 6 characterised in that die maximum thickness of the link is between 0.2 and 0.4 mm. 8. A toothbrush according to claim 6 or 7 characterised in that die length of die link between adjacent linked segments is between 1.0 to 2.5 mm. 9. A too brush according to claim 8 characterised in that die lengdi of the link between adjacent linked segments is 1.0 to 2.0 mm. 10. A toothbrush according to any one of preceding claims 1 to 9, characterised in diat die said link lies at the bottom of a chasm in the plastics material of the toombrush head, and die said chasm contains an elastomeric material. 11. A toothbrush which comprises a plastics material handle wim a plastics material head adjoining die handle at a base end of die head, die head and handle being disposed along a longimdinal toodibrush axis, the head having bristles extending from a bristle face of the head, die head having an opposite back face, the head comprising at least two adjacent segments integrally linked by a flexible link of the plastics material of the head, characterised in that die maximum thickness of the link is at most 0.2 mm, the said link lying at the bottom of a chasm in the plastics material of the toodibrush head, the chasm containing an elastomeric material bonded to die said link to form a composite plastics material / elastomer material link between the segments. 12. A toothbrush according to claim 11 characterised in diat die length of the link, between adjacent linked segments is between 0.5 and 3.0 mm. 13. A toothbrush according to any one of die preceding claims characterised in mat die link links segments which are sequentially longitudinally arranged along die longimdinal direction of the toodibrush head. 14. A toothbrush according to any one of die preceding claims 4 to 13 characterised in that die link lies at the bottom of two chasms respectively in the bristle face and the opposite back face, by virtue of die link being at an intermediate - 12 - RECTiFIED SHEET (RULE 91) position in the toothbrush head between die bristle face and die opposite back face, characterised in that the relative widdi, depth, shape or taper of the two chasms is the same or different. 15. A toothbrush according to any one of the preceding chaims characterised in that the link comprises a flexible link of the plastics material of the head, being situated intermediate between die bristle face and the back face of the head, die diickness of the head being 4 - 5 mm, the maximum thickness of the link being 0.2 mm ±_ 0.1 mm, the lengdi of the link between the linked segments being 1.2mm ±. 0.3 mm. 16. A toothbrush according to claim 15 characterised in that there are two chasms, in the bristle face and back face respectively, tapering toward die link at dieir bottom, being wider toward respectively me bristle face and the opposite back face, at their widest, in die surfaces of the toothbrush head d e widdi of die chasms being 2.4mm ±. 0.3 mm. 17. A toothbrush according to any one of the preceding claims 4 to 16 in which the link lies at die bottom of two chasms respectively in the bristle face and die opposite back face, by virtue of the link being at an intermediate position in the toothbrush head between die bristle face and the opposite back face, characterised in diat the relative width, depdi, shape or taper of die two chasms is different. 18. A toothbrush according to any one of the preceding claims, characterised in that die namre, dimensions or orientation of the segments, the link(s) and/or die chasms between segments differs at different parts of die head to provide different degrees of flexibility at different places on d e head. - 13 - RECTIFIED SHEET (RULE 91)

Inventors: KRAMER HANS, KRAMER, HANS
Applicants: KRAMER HANS, SMITHKLINE BEECHAM CONSUMER, KRAMER, HANS, SMITHKLINE BEECHAM CONSUMER HEALTHCARE GMBH
Application year: 1997
Main classification: A46B7
IPC codes: A46B7