Patent Publication Number: US-6668416-B1

Title: Toothbrush

Description:
FIELD OF THE INVENTION 
     This invention relates to toothbrushes, in particular to toothbrushes having a feature in their structure to modify flexibility. 
     BACKGROUND OF THE INVENTION 
     Toothbrushes are known which have a feature in their structure to modify their flexibility during use. For example EP 0 033 641A discloses a toothbrush having a series of ‘S’ bends in its handle, and DE 39 234 95A discloses a toothbrush having cut-outs in its handle which contain a flexible elastomer. Such features are included in a toothbrush to absorb excessive brushing forces. 
     It is an object of this invention to provide an alternative structure of toothbrush having a flexibility-modifying feature in its structure. 
     SUMMARY OF THE INVENTION 
     According to this invention a toothbrush is provided having a head and a handle being made of a hard plastic material and being disposed along a longitudinal axis, the head having bristles extending therefrom in a bristle direction which is generally perpendicular to the longitudinal direction, the toothbrush having a width direction generally perpendicular to both the longitudinal axis direction and the bristle direction, the toothbrush having a resiliently flexible composite region between its head and handle characterised in that the composite region comprises one or more members which are generally triangular shape in section when cut in a plane parallel to the longitudinal direction and perpendicular to the width direction, each of the triangular shapes having an apex which points in a direction either generally in the bristle direction or generally at a direction 180° to the bristle direction, the at least one triangular sectioned member comprising either at least one triangular sectioned member made of a resilient elastomeric material different to the hard plastic material of the toothbrush head and handle situated longitudinally between two adjacent regions of a hard plastic material, or at least one triangular sectioned member made of a hard plastic material situated longitudinally between two adjacent regions of elastomeric material different to the hard plastic material of the toothbrush head and handle. 
     DETAILED DESCRIPTION, OF THE INVENTION 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a toothbrush of the first embodiment of this invention 
     FIG. 1A shows a side view of a first embodiment of a toothbrush of this invention. 
     FIG. 1B shows a plan view of the toothbrush of FIG. 1A looking down onto the face of the head from which the bristles extend. 
     FIG. 1C shows a plan view of the toothbrush of FIG. 1A looking down onto the opposite face of the head to that from which the bristles extend. 
     FIG. 2 shows the “skeleton” of a toothbrush of FIG. 1 
     FIG. 2A shows a side view of the plastic material skeleton of the toothbrush of FIGS. 1A-1C. 
     FIG. 2B shows a plan view of the plastic material skeleton of the toothbrush of FIGS. 1A-1C looking down onto the face of the head from which the bristles extend. 
     FIG. 2C shows a plan view of the plastic material skeleton of the toothbrush of FIGS. 1A-1C looking down onto the opposite face of the head to that from which the bristles extend. 
     FIG. 3 shows an alternative construction of the toothbrush of the first embodiment of this invention. 
     FIG. 3A shows a side view of an alternative construction of a toothbrush of the first embodiment of this invention. 
     FIG. 3B shows a plan view of the toothbrush of FIG. 3A looking down onto the face of the head from which the bristles extend. 
     FIG. 3C shows a plan view of the toothbrush of FIG. 3A looking down onto the opposite face of the head to that from which the bristles extend. 
     FIG. 3D shows a side view of the folded region of the hard plastic skeleton without the elastomer material in place. 
     FIG. 4 shows a toothbrush of the second embodiment of this invention. 
     FIG. 4A shows a side view of a toothbrush of the second embodiment of this invention. 
     FIG. 4B shows a plan view of the toothbrush of FIG. 4A looking down onto the face of the head from which the bristles extend. 
     FIG. 4C shows a plan view of the toothbrush of FIG. 4A looking down onto the opposite face of the head to that from which the bristles extend. 
     FIG. 4D shows an enlarged cross section about line D—D of FIG.  4 B. 
     FIG. 5 shows the skeleton of the toothbrush of FIG.  4 . 
     FIG. 5A shows a side view of the plastic material skeleton of the toothbrush of FIGS. 4A-4C. 
     FIG. 5B shows a plan view of the plastic material skeleton of the toothbrush of FIGS. 4A-4C looking down onto the face of the head from which the bristles extend. 
     FIG. 5C shows a plan view of the plastic material skeleton of the toothbrush of FIGS. 4A-4C looking down onto the opposite face of the head to that from which the bristles extend. 
    
    
     In a first embodiment the one or more member is/are made of elastomeric material and is constructed such that as a bending force is applied to the toothbrush head the adjacent hard plastic material bears upon an elastomeric member to apply compressive pressure to the member. 
     In a second embodiment the one or more member is/are made of hard plastic material and is constructed such that as a bending force is applied to the toothbrush head the hard plastic material bears upon an adjacent region of elastomeric material to apply compressive pressure to the region of elastomeric material. 
     Preferably there is more than one triangular sectioned member, for example two or three such triangular sectioned members, being sequentially longitudinally disposed in the toothbrush, and the respective directions in which the apexes of longitudinally adjacent members point are 180° apart, i.e. so that with any two longitudinally adjacent members the apex of one will point generally in the bristle direction and the apex of the adjacent neighbouring member will point generally in the opposite direction. 
     For example if there are three such longitudinally adjacent members the apex of two of the members may point in the bristle direction and the apex of the member in between the two may point in the 180° opposite direction, or the apex of the central member may point in the bristle direction and the apex of the members on longitudinally either side may point in the 180° opposite direction. 
     The term “generally triangular” includes triangles of all types, e.g. isosceles triangles, equilateral triangles. The term also includes triangles with one or more rounded apexes or curved sides. The term also includes three-sided shapes with concave or convex curved sides, ogival shapes or pointed arch shapes. The term also includes semi-circular or semi-elliptical shapes. The term also includes polygonal shapes with more than three sides but which are generally triangular, for example hexagons having alternating relatively long and relatively short sides, and quadrilaterals having a relatively long base and a relatively short side opposite the base, with the other two sides tapering toward the short side to thereby define an apex angle, e.g. an acute apex angle between them. 
     Preferably the generally triangular sectioned member(s) is/are generally prismatic in shape, having generally parallel edges which extend generally in the width direction of the toothbrush. 
     Preferably the generally triangular sectioned member(s) extend(s) substantially or entirely through the entire thickness dimension of the toothbrush, i.e. the dimension through the toothbrush which is generally perpendicular to both the longitudinal axis and the width direction, so that the apex of the triangular shape is exposed on a first surface of the toothbrush and/or the opposite base of the triangular shape is exposed on the opposite surface of the toothbrush distanced from the first surface by the thickness dimension. 
     Preferably at least one generally triangular sectioned member extends across the whole width of the toothbrush, so that for example a generally triangular shaped end surface of a prismatic member is exposed on each widthways separated side of the toothbrush. 
     Preferably in the first embodiment (i.e. with one or more elastomeric triangular sectioned member) there are at least two, particularly three, of the elastomeric members with a region of the hard plastic material longitudinally between each pair of them. 
     In the first embodiment preferably at least one, preferably both of the adjacent regions of a hard plastic material have a surface which is inclined at a non-perpendicular angle to the longitudinal direction, so that the surfaces of the adjacent regions of plastic material define an acute angle between them, being the apex angle of the triangular sectioned member. In such a construction as a bending force is applied to the toothbrush head the plastic material of the inclined surfaces bears upon an elastomeric member to apply compressive pressure to the member. Preferably there is such a surface at each longitudinal end of the composite region. If there are two or more triangular sectioned members then between longitudinally adjacent pairs of the members such plastic parts are preferably substantially planar, each longitudinally opposed surface of such a planar part comprising such an inclined surface. Longitudinally adjacent pairs of the hard plastic material parts may be integrally linked by one or more thin integral bridge of the plastic material, being thin enough to be flexible. For example the plastic parts may comprise two or more such planar parts inclined toward each other to define an apex angle, e.g. an acute angle between them, and linked together adjacent to an apex of the triangular member to form a “V” shaped fold with the fold axis aligned transverse to the longitudinal direction. A plurality of such parts may be integrally formed linked together to form a zig-zag, or “Z”, folded region. 
     Preferably in the second embodiment (i.e. with one or more hard plastic triangular sectioned member) there are at least two, particularly three, of the hard plastic material members with a region of the elastomeric material longitudinally between each pair of them. 
     In the second embodiment preferably at least one, preferably both of the adjacent regions of elastomeric material have a surface which is inclined at a non-perpendicular angle to the longitudinal direction, so that the surfaces of the adjacent regions of elastomeric material define an acute angle between them, being the apex angle of the triangular sectioned member. In such a construction as a bending force is applied to the toothbrush head the plastic material of the triangular sectioned hard plastic members bears upon an elastomeric member between them to apply compressive pressure to the member. Preferably there is such a surface at each longitudinal end of the composite region. If there are two or more triangular sectioned members then between longitudinally adjacent pairs of the members such elastomeric parts are preferably substantially planar, each longitudinally opposed surface of such a planar part comprising such an inclined surface. 
     Longitudinally adjacent pairs of the hard plastic triangular sectioned members of this second embodiment, and adjacent hard plastic material parts of the toothbrush, may also be linked by one or more thin flexible structure of the hard plastic material, for example one or more of said structure(s) being in the form of a thin integrally moulded bridge bridging longitudinally adjacent pairs of the members. 
     One or more of the hard plastic triangular sectioned members of this second embodiment members may also be longitudinally penetrated by a longitudinally extending “core” of an elastomeric material which may itself integrally link the elastomeric pads. The parts of the core between the members and/or between the member(s) and a longitudinally adjacent part of the toothbrush structure may comprise the pads. 
     Preferably the toothbrush of the invention comprises a hard plastic “skeleton” having one or more cavity in its structure which correspond to the position of the elastomer parts of the toothbrush, and the elastomer part(s) occupies the one or more cavity. Such a “skeleton” may be integrally made of the hard plastic material, in which the one or more cavity is/are integrally bridged by one or more thin flexible structure(s) of the hard plastic material to which the elastomer material is moulded. The general idea of making two component toothbrushes using a first component hard plastic skeleton having one or more cavity therein about which are subsequently moulded one or more second component elastomer parts is well known in the art, for example from WO 94/05183 and others. 
     The hard plastic parts of the toothbrush may be made of any hard plastic material as is presently used in the manufacture of toothbrushes, e.g. as disclosed in EP 0 033 641A or WO 99/17915. Polypropylene materials are often used. The elastomer material may be any elastomer material or any elastomer material which is presently used in the manufacture of toothbrushes e.g. as disclosed in WO 99/17915, WO 92/17092 or WO 92/17093. Many such two component toothbrushes are known and there is a prolific choice of suitable hard plastics and elastomeric materials. 
     The composite region may be located in any desired location in the toothbrush. For example the member(s) may be located in the grip handle part of the toothbrush; and/or between the grip handle part and the head of the toothbrush for example between the grip handle and the thinner “neck” that usually lies between the handle and the head of a toothbrush, or in such a neck, and/or between the part of the head immediately adjacent to such a neck and the neck itself. When located between the part of the head immediately adjacent to the neck and the neck itself the apex of the triangular shape may point in the bristle direction or in the opposite direction. 
     When there is more than one triangular sectioned member each may have the same or different dimensions or be made of the same or a different material, particularly in the first embodiment, with elastomeric members so that each member may have the same or different flexibility e.g. compressibility or stretchability, characteristics. 
     The toothbrush of the invention may also include other known features of toothbrushes, for example the elastomer grip pads disclosed in EP 0 033 641A or the flexible head construction disclosed in WO 97/07707, WO 98/37788 or WO 92/17093, or the flexible link between the head and handle disclosed in WO 92/17092 or WO 97/24949 or EP 0 613 636A. The contents of these disclosures are included herein in their entirety by way of reference. 
     The bristles of the toothbrush of this invention may be entirely conventional, for example made of known materials and may be fixed into the head by known techniques such as the widely used small metal “anchors”, or fused and welded into the plastic material of the head via known “anchorless” bristling processes. 
     The toothbrush of the invention is preferably made using an injection moulding process in which a hard plastic “skeleton” having one or more cavity corresponding to the position of the elastomer part(s) of the toothbrush, is first made in a first moulding operation using a first mould cavity, and the elastomeric part(s) is/are then made in this second moulding operation by positioning the skeleton in a second mould having one or more cavities corresponding to the elastomer member(s) and a fluid elastomer is then injected into the aperture(s) in the skeleton to thereby form the elastomeric part(s) of the toothbrush. 
     Such a process comprises a further aspect of this invention. 
     The invention also provides injection moulds suitable for use in the above-described process having a first cavity in which the hard plastic parts of the toothbrush are made and/or a second cavity in which the elastomer part(s) of the toothbrush are made. 
     The invention will now be described, by way of example only, with reference to the accompanying drawings. 
     Referring to FIG. 1, a toothbrush (overall  11 ) is shown in a side view in FIG. 1A, in plan view in FIG. 1B, and in underside view in Fig.  1 C. 
     The toothbrush  11  comprises a head  12 , and a handle  13  disposed along the longitudinal axis A—A, with a neck region  14  between the head  12  and handle  13 , and being integrally made of hard plastic material. Bristles  15  (shown schematically) extend from the head  12  in a general bristle direction B—B. The toothbrush  11  has a width direction W—W generally perpendicular to both A—A and B—B. 
     The toothbrush  11  includes three members  16 ,  17 ,  18  made of an elastomer material, being sequentially longitudinally disposed along the toothbrush  11 , and located between the handle  13  and neck  14 . 
     Each of the members  16 ,  17 ,  18  is of a generally triangular prism shape, with generally triangular shape ends  19 , exposed on opposite widthways separated sides of the toothbrush  11 . The triangular shape of the sections of the members  16 ,  17 ,  18  have slightly curved sides and rounded apexes. Each of the members  16 ,  17 ,  18  extends entirely across the width of toothbrush  11 , and entirely through the thickness of toothbrush  11 , so that in each member  16 ,  17 ,  18  an apex e.g.  16 A is exposed on one surface of the toothbrush  11  and an opposite base e.g.  16 B is exposed on the opposite surface of the toothbrush  11  separated by the thickness dimension i.e. in the direction B—B. 
     It is seen that with each of the members  16 ,  17 ,  18  an apex  16 A,  17 A,  18 A points either in the bristle direction B—B or in the 180° opposite direction relative to the bristle direction B—B. 
     It is also seen that longitudinally between each pair of the longitudinally adjacent members  16 ,  17 ,  18  is a thin, substantially planar, region  110 ,  111  of the hard plastic material of the head  12  and handle  13  inclined at a non-perpendicular angle to the longitudinal direction, so that the surfaces of the adjacent regions of plastic material  110 ,  111  define an acute angle between them. 
     The section of each of the members  16 ,  17 ,  18  is substantially an equilateral triangle, but the exposed base  16 B,  17 B,  18 B is slightly convex curved. Longitudinally adjacent sides of the triangles  16 ,  17 ,  18  are substantially parallel with the hard plastic region  110 ,  111  between. 
     Located between the base of the head  12 , i.e. the part of the head  12  immediately adjacent to neck  14  is another elastomer member  112 , again in the form of a generally triangular sectioned prism, this time being an isosceles triangle with its apex  112 A facing in the bristle direction B—B and its short, slightly curved base  112 B facing in the 180° direction, and its triangular ends  113  exposed on either side of the toothbrush  11 . 
     The handle  13  of the toothbrush.  11  is also provided with elastomer grip pads  114 . 
     Referring to FIG. 2, features corresponding to those of the toothbrush of FIG. 1 are numbered to correspond. FIG. 2 shows a toothbrush “skeleton”  21  overall being only the hard plastic parts of the toothbrush of FIG.  1 . 
     In the skeleton  21 , the places to be occupied by the elastomer members  16 ,  17 ,  18  and  112  are represented by cavities  22 ,  23 ,  24 ,  25  into which a fluid elastomeric material (not shown) can be injected. The cavities  22 ,  23 ,  24 ,  25  are longitudinally bounded by adjacent regions of a hard plastic material which have a surface which is inclined at a non-perpendicular angle to the longitudinal direction, so that the surfaces of the adjacent regions of plastic material define an acute angle between them, being the apex angle of the triangular sectioned member  16 ,  17 ,  18 ,  112  located between pairs of such surfaces. The cavities  22 ,  23 ,  24 ,  25  are bridged by thin plastic bridge structures  26  integrally of the hard plastic material, around which the elastomeric material  16 ,  17 ,  18  and  112  is moulded and bonds under the conditions of the injection moulding of the elastomer (suitable moulding conditions to achieve such a bond are known in the art). The structures  26  therefore penetrate longitudinally right through the members  16 ,  17 ,  18 . The structures  26  may or may not contribute resilience or stiffness to the composite of elastomer and hard plastic so formed. The skeleton also has cavities  27  corresponding to the position of the grip pads  114 . Although shown as small cylindrical rods the structures  26  may have any desired cross section e.g. being elongate in a particular direction so as to modify the flexibility about a particular bend axis. 
     The head part  28  of the skeleton  21  also includes holes (not shown) for the subsequent insertion of bristles  15 . 
     Typically the skeleton  21  is made integrally by providing a cavity of a corresponding shape in a steel mould (not shown) and injecting fluid plastic material into the cavity. The skeleton  21  is then removed from the dis-assembled mould and inserted into a second mould (not shown) which has cavities corresponding to the shape and position of the members  16 ,  17 ,  18 ,  112  and the pads  114 . Fluid elastomer material is then injected into the cavities of the second mould so as to form the elastomer parts  16 ,  17 ,  18 ,  112  and  114 . Such a process is known in the art, e.g. in WO 94/05183. 
     Referring to FIG. 3, features corresponding to those of FIGS. 1 and 2 are numbered correspondingly. FIG. 3 shows a toothbrush  31  similar in concept to that of FIG. 1, having three elastomer members  32 ,  33 ,  34  with their apexes  32 A,  33 A and  34 A pointing in a corresponding direction to those of members  16 ,  17 ,  18  of FIG.  1 . 
     However in the toothbrush  31  of FIG. 3 the skeleton  35  of the toothbrush includes an integral region of zigzag folded thin leaves  36  shown in more detail in FIG.  3 D. Each of the leaves  36  is substantially planar with its plane at an angle ax less than 90° to the longitudinal axis, so as to form an acute angle between longitudinally adjacent leaves  36 . The leaves  36  are sufficiently thin that they are resiliently flexible. This construction is shown more clearly in FIG. 3D, where the folded region of the hard plastic skeleton is shown without the elastomer material in place. A “V” shaped fold is shown, with its fold axis aligned parallel to the width direction W—W, i.e. perpendicular to the plane of the paper of FIG. 3D, and its apex  37  adjacent to and defining an apex of a triangular sectioned member ( 33  not shown in FIG.  3 D). In the construction shown in FIGS. 1 to  3  each elastomeric member  32 ,  33 ,  34  is located between longitudinally adjacent regions of hard plastic material having a surface which is inclined at a non-perpendicular angle to the longitudinal direction, so that the surfaces of the adjacent regions of plastic material define an acute angle between them, being the apex angle of the triangular sectioned member. The surfaces  38  of the skeleton  35  are at the longitudinal ends of the composite region are also inclined at a non-perpendicular angle to the longitudinal direction. Spaces  39  are thereby defined for the subsequent formation therein of the elastomeric members  32 ,  33 ,  34  in an injection moulding stage. 
     Elastomeric members  32 ,  33 ,  34  are formed in the angles between adjacent leaves  36 , being consequently substantially triangular in section when cut by the plane parallel to the longitudinal axis A—A and the bristle direction B—B. The shapes of the sections of the members  32 ,  33 ,  34  are quadrilaterals, having opposite facing substantially parallel relatively short and relatively long sides comprising the apex  32 A,  33 A,  34 A and the base  32 B,  33 B,  34 B respectively of a generally triangular shape, and sloping sides which converge from the base toward the apex. Apexes  32 A,  33 A,  34 A is defined by the junction between adjacent leaves  36 , and an opposite base  32 B,  33 B,  34 B is exposed at the surface of the toothbrush  31 . 
     The toothbrush  31  is made by a process similar to that of toothbrush  11  above, i.e. a “skeleton”  35  made of the hard plastic material of the head  12  and handle  13  is made by injection moulding, and including integrally the region of leaves  36 . The skeleton  35  is then placed in a second injection mould having cavities corresponding to the position and dimensions of the members  32 ,  33 ,  34  to be formed. These members  32 ,  33 ,  34  are then made by injecting fluid elastomer material into these cavities of the mould. 
     In use each of the toothbrushes  11 ,  31  works in the same way. Pressure applied to the head  12  by using it to brush the teeth transmits a bending force to the region of the toothbrush  11 ,  31  where the members  16 ,  17 ,  18 ,  32 ,  33 ,  34  are. The thin leaves  26 ,  36  easily bend, causing compressive force to be applied to the members  16 ,  17 ,  18 ,  32 ,  33 ,  34 . These elastomeric members  16 ,  17 ,  18 ,  32 ,  33 ,  34  consequently absorb excessive brushing pressure. 
     Referring to FIG. 4, a toothbrush (overall  41 ) is shown in a side view in FIG. 4A, in plan view in FIG. 4B, in underside view in FIG. 4C, and inna cross section at D—D in FIG.  4 D. 
     The toothbrush  41  comprises a head  42 , and a handle  43  disposed along the longitudinal axis A—A, with a neck region  44  between the head  42  and handle  43 , and being integrally made of hard plastic material. Bristles  45  (shown schematically) extend from the head  42  in a general bristle direction B—B. The toothbrush  41  has a width direction W—W generally perpendicular to both A—A and B—B. 
     The toothbrush  41  includes three members  46 ,  47 ,  48  made of the same hard plastic material as the head  42  and handle  43 , being sequentially longitudinally disposed along the toothbrush  41 , and located between the handle  43  and neck  44 . 
     Each of the members  46 ,  47 ,  48  is of a generally triangular prism shape, with generally triangular shape ends  49 , exposed on opposite widthways separated sides of the toothbrush  41 . The triangular shape of the sections of the members  46 ,  47 ,  48  have slightly curved sides and rounded apexes. Each of the members  46 ,  47 ,  48  extends entirely across the width of toothbrush  41 , and entirely through the thickness of toothbrush  41 , so that in each member  46 ,  47 ,  48  an apex e.g.  46 A is exposed on one surface of the toothbrush  41  and an opposite base e.g.  46 B is exposed on the opposite surface of the toothbrush  41  separated by the thickness dimension i.e. in the direction B—B. 
     It is seen that with each of the members  46 ,  47 ,  48  an apex  46 A,  47 A,  48 A points either in the bristle direction B—B or in the 180° opposite direction relative to the bristle direction B—B. 
     Longitudinally between each pair of the longitudinally adjacent members  46 ,  47 ,  48  is a thin pad, e.g. a layer  410  made of an elastomeric material. Longitudinally between each members  46 ,  48  and the longitudinally adjacent part of the toothbrush handle  43  and neck  44  is also a thin pad, e.g. a layer  411  made of an elastomeric material. 
     It is also seen that the section of each of the members  46 ,  47 ,  48  is substantially an equilateral triangle, but the exposed base  46 B,  47 B,  48 B is slightly convex curved. Longitudinally adjacent sides of the triangles  46 ,  47 ,  48  are substantially parallel with the elastomeric pads  410  between. 
     Located between the base of the head  42 , i.e. the part of the head  42  immediately adjacent to neck  44  is another hard plastic member  412 , again in the form of a generally triangular sectioned prism, this time being an isosceles triangle with its apex  412 A facing in the bristle direction B—B and its short, slightly curved base  412 B facing in the 480° direction, and its triangular ends  413  exposed on either side of the toothbrush  41 . Longitudinally between the member  412  and the longitudinally adjacent part of the toothbrush handle  43  and neck  44  is also a thin pad, e.g. a layer  414  made of an elastomeric material. 
     The handle  43  of the toothbrush  41  is also provided with elastomer grip pads  415 . 
     Extending longitudinally through each of the members  46 ,  47 ,  48  is a longitudinally extending “core”  416  of an elastomeric material (shown dotted in FIG. 4 because internal and obscured). FIG. 4D shows an enlarged cross section about line D—D of FIG.  4  through exemplary member  48 , showing the internal construction with the elastomer core  416 . Although shown of circular cross section the core  416  may be of any convenient cross section, e.g. oval, rectangular etc. 
     Referring to FIG. 5, this shows a toothbrush “skeleton”  51  overall being only the hard plastic parts of a toothbrush. This is shown in a side view in FIG. 5A, in plan view in FIG. 5B, and in underside view in FIG.  5 C. 
     In the skeleton  51 , the places to be occupied by elastomer pads (not shown) are represented by cavities  52 ,  53 ,  54 ,  55 ,  56 ,  57  into which a fluid elastomeric material (not shown) can be injected. The cavities  52 ,  53 ,  54 ,  55 ,  56 ,  57  are bridged by thin plastic bridge structures  58  integrally of the hard plastic material, around which elastomeric material of pads to be formed is moulded and bonds under the conditions of the injection moulding of the elastomer (suitable moulding conditions to achieve such a bond are known in the art). The structures  58  are embedded in the elastomeric material during the moulding operation and penetrate longitudinally right through the elastomeric pads (not shown). The structures  58  may or may not contribute resilience or stiffness to the composite of elastomer and hard plastic so formed. Between longitudinally adjacent pairs of the cavities  52 ,  53 ,  54 ,  55 ,  56 ,  57  are located triangular sectioned members  59  of hard plastic material. The skeleton  51  also has spaces  510 ,  511  corresponding to the position of the grip pads (not shown). Although shown as small cylindrical rods the structures  58  may have any desired cross section e.g. being elongate in a particular direction so as to modify the flexibility about a particular bend axis. 
     The head part  512  of the skeleton  51  also includes holes  513  for the subsequent insertion of bristles (not shown). 
     Typically the skeleton  51  is made integrally by providing a cavity of a corresponding shape in a steel mould (not shown) and injecting fluid plastic material into the cavity. The skeleton  51  is then removed from the dis-assembled mould and inserted into a second mould (not shown) which has cavities corresponding to the shape and position of the elastomer pads. Fluid elastomer material is then injected into the cavities of the second mould so as to form the elastomer pads in the cavities  52 ,  53 ,  54 ,  55 ,  56 ,  57 . Such a process is known in the art, e.g. in WO 94/05183.