Abstract:
A brush head for an electrically driven toothbrush includes a holding part ( 2 ) that provides at least one connecting element for mechanically coupling the brush head to the electric drive of the toothbrush, wherein the holding part ( 2 ) integrally forms a stud ( 4 ) defining a pivot axis (S) about which the brush head is pivotable, and a plate ( 6 ) which at its end facing away from the stud ( 4 ) carries at least one bristle bundle ( 8 ) which at its attachment-side end includes a thickening ( 14 ) formed by surface melting. For improving the brush head, a substantially disc-shaped bristle carrier ( 10 ) is connected to a holding part ( 2 ) and includes a bore that is penetrated by the bristle bundle ( 8 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to European Patent Application No. EP 15193697.8, filed on Nov. 9, 2015, which is hereby incorporated by reference as if set forth in its entirety herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to a brush head for an electrically driven toothbrush. Such a brush head is commonly sold as a component of an attachment part which can be connected to a handpiece of the electrically driven toothbrush that commonly accommodates the drive in itself. The attachment part is an expendable item and made from plastic material. The attachment part usually comprises a sleeve member which is penetrated by a drive shaft that can be connected to a drive shaft of the handpiece. Disposed at the free end of the sleeve member is commonly the brush head according to the present invention. 
         [0004]    Description of Related Art 
         [0005]    Cleaning elements for the oral cavity are generally subject to the demand of having them be designed very compact and in space-saving manner since the space in the oral cavity is limited, where cleaning buccal tooth surfaces is difficult anyway due to the cheek being in the immediate vicinity. 
         [0006]    There are various options for attaching bristle bundles, which are usually used for tooth cleaning, to a bristle carrier. The Inmold Method, in which a thickening is formed on the bristle bundle and sealed with liquid plastic material which forms the bristle carrier or at least a part thereof, allows the production of brushes which are relatively small in height. Height within the meaning of the present invention is there understood to be the extension substantially parallel to the filaments of the bristle bundles. 
         [0007]    Technical plastic materials are generally not suitable for the Inmold Method due to their high viscosity under processing conditions. However, such technical plastic materials are commonly used to form a stud of the brush head which interacts with the shaft of the attachment part in order to impart the rotational or pivotal motion of the brush head during cleaning. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is based on the problem of providing an improved brush head for an electrically driven toothbrush. 
         [0009]    To solve this problem, the present invention proposes a brush head having the features described in detail herein. It is a brush head for an electrically driven toothbrush. This brush head has a holding part that provides at least one connecting element for mechanically coupling the brush head to the electric drive of the toothbrush. The holding part has a stud which defines a pivot axis of the brush head. The holding part is commonly located entirely or in part within the aforementioned sleeve member of the attachment part and is accommodated therein in such a manner that the brush head can perform a rotational or pivotal motion relative to the sleeve member but is captively coupled to the sleeve member. The connecting element for mechanically coupling the brush head to the electric drive is in the simplest case a receptacle provided on the stud in which the drive shaft of the attachment part engages in order to impart, for example, a cyclic pivotal motion relative to the sleeve member onto the brush head. The connecting element is in this case located on the outer circumferential surface of the holding part, i.e. is in its extension perpendicular relative to the pivot axis defined by the holding part recessed in the commonly cylindrical stud. At its free end, the stud usually comprises a centering bore which interacts with a centering pin of the sleeve member to define a bearing for the pivotal motion of the brush head. On the side which is usually opposite the connecting element, the stud regularly has a locking recess into which a locking pin being fixedly connected to the sleeve member engages in order to secure the brush head within the sleeve member in such a manner that the brush head cannot be pulled along the pivot axis out from a receptacle formed on the sleeve member for the stud. The shaft provided in the sleeve member for coupling to the stud preferably comprises a substantially cylindrical locking head, the cylinder axis of which extends approximately parallel to the pivot axis of the locking pin. For accommodating this locking pin, the centrical stud typically comprises a locking pin receptacle provided eccentrically relative to the pivot axis, but in parallel extension thereto. 
         [0010]    The previously discussed elements of the stud are after mounting the latter onto the sleeve member usually disposed within the sleeve member. 
         [0011]    The centrical stud is radially protruded by a plate which according to the invention is provided as a component of the holding part. The holding part is accordingly composed of the centrical stud and the plate. The plate usually has a base surface that substantially corresponds to and/or runs parallel to the base surface of the surface of the brush head penetrated by the cleaning elements of the brush head. This surface can be circular or oval. The base surface of the surface, i.e., the contour thereof, is selected with a convex circumferential edge to protect the tender oral mucosa from damage. 
         [0012]    The brush according to the invention in a manner known per se comprises at least one bristle bundle which is supported by the plate at its end facing away from the stud and in this direction protrudes over the plate. The bristle bundle at its attachment-side end comprises a thickening which is formed by surface melting and by way of which the bristle bundle is attached to the brush head by insert molding. The bristle bundle is then attached using the Inmold technology. In addition to a bristle bundle having at least one, commonly several filaments, other cleaning elements can also be provided on the brush head and connected to the brush head by insert molding, or are subsequently attached to the solidified plastic material by way of other connections, for example, by snapping, soldering or gluing them on. 
         [0013]    The brush head also comprises a substantially disc-shaped bristle carrier. The bristle carrier usually has a base surface which corresponds to the surface penetrated by the bristle bundle. The disc-shaped bristle carrier regularly forms this surface, i.e. forms the upper end of the brush head. The bristle carrier is disc-shaped, i.e. has substantially co-planar main surfaces, where one of which usually forms the surface of the brush head and the other is provided disposed opposite to the plate and regularly in parallel extension thereto. The bristle carrier is designed as a relatively thin disc with a thickness between 0.5 and 3.0 mm. The bristle carrier has a bore to the bristle bundle which is penetrated by the bristle bundle. The thickening formed by surface melting is located on the rear side of the bristle carrier. The thickening protrudes radially over the bore so that the bristle bundle is due to the end-side thickening locked relative to the bristle carrier in a positive-fit manner and secured against being pulled out. The thickening can directly abut the mouth of the bore. The plate can in correspondence to the position of the respective thickening comprise a recess receiving the corresponding thickening, which enhances a compact design of the brush head. 
         [0014]    The bristle carrier is connected to the holding part, for example, in such a manner that no gap extending in the height direction exists between the bristle carrier and the plate. The bristle carrier can abut directly against the plate. The bristle carrier and the holding part are there commonly shaped as two components that are initially produced separately and subsequently joined. This connection can be effected by welding, for example, ultrasound or frictional engagement. 
         [0015]    The bristle carrier can also be connected to the plate with the interposition of an intermediate layer which partially or completely accommodates the thickening. This intermediate layer can be an adhesive layer. It can also be produced by injection molding. 
         [0016]    In this case, the bristle carrier and the holding part are first produced as separate components, where the bristle carrier is provided with the bristle bundle(s). The components thus prepared are inserted into an injection mold and held spaced apart from each other so that the thickening of the bristle bundle is disposed between the upper side of the plate and the underside of the bristle carrier, preferably in sealing abutment against the bore. Plastic material is then injected into the gap remaining between the two parts and completely fills the gap and connects the bristle carrier to the holding part. The intermediate layer formed thereby is in the form of an insert molding preferably not only disposed between the bristle carrier and the plate. It can also entirely or in part circumferentially surround the plate and/or the bristle carrier. For example, an abutment edge can thereby be produced from a different material which encloses the bristle carrier and the holding part circumferentially and defines the outer contour. The injected material is usually a thermoplastic material. This plastic material can be soft elastic material. Alternatively, the injected material can be formed from a hard component, for example, PP, PE, PA, POM, PC or PBT. Generally preferable is easy-flowing plastic material, preferably plastic material with an MFI&gt;15 g/10 min at 2.16 kg and a test temperature corresponding to the plastic material. It is also possible to add to the injected material an additive which has a cleaning or polishing effect so that the teeth or tissue regions within the oral cavity can be gently cleaned by the outer circumference of the brush head. 
         [0017]    According to a further preferred embodiment of the present invention, the plastic material introduced into the intermediate space overlaps or underlaps the bristle carrier or the plate, respectively. A configuration is there usually to be ensured in which the plastic material introduced into the intermediate space also transitions free of discontinuity and continuously to a surface of the bristle carrier or of the holding part, respectively. The bristle carrier can have a radial projection or radially circumferential edge which is provided spaced from the surface of the bristle carrier and is overlapped by the plastic material injected into the intermediate space in order to secure the bristle carrier also in a positive-fit manner relative to the holding part. Similarly, the plastic material injected into the intermediate space can also be provided on the underside of the plate. Also the plate can for this purpose form a radial projection which is underlapped by the solidified plastic material introduced into the intermediate space in order to also connect the plastic material introduced into the intermediate space to the holding part also in positive-fit manner in the direction of the pivot axis. 
         [0018]    It is in view of the strongest possible connection preferable to take the plastic material introduced into the intermediate space up to the stud so that the plastic material introduced into the intermediate space substantially covers the rear side of the plate and forms the underside of the widened part of the brush head which protrudes radially to the pivot axis over the commonly cylindrical stud. The plate and the bristle carrier can there be formed with an identical base surface, where the plastic material introduced into the intermediate space is confined to precisely this intermediate space. If the plastic material inserted into the intermediate space circumferentially surrounds the bristle carrier or the plate, then the outer contour of the widened part is also, inter alia, commonly solely, defined by the plastic material introduced into the intermediate space. The plastic material introduced into the intermediate space, however, can also be disposed only below the bristle carrier so that the latter alone defines the surface penetrated by the bristle bundles and is on the rear side covered by the plate and the plastic material that is injected into the intermediate space and can also surround the plate on the rear side in order to connect the bristle carrier in a positive-fit manner to the holding part also in the direction of the pivot axis. 
         [0019]    In view of the simplest possible production of the brush head according to the invention, it is proposed according to a preferred development of the present invention that the plate and/or the holding part form a spacer which defines the intermediate space. The respective spacer is usually integrally formed on the bristle carrier or the plate, respectively. The spacer protrudes in the direction of the pivot axis from the bristle carrier or the plate, respectively, and with its free end abuts against a counter surface which is formed by the bristle carrier or the plate, respectively. The spacer(s) can be provided on both the bristle carrier as well as on the plate in order to define the intermediate space. In the production of the brush head, the prefabricated parts bristle carrier and holding part are accordingly spaced apart in the injection mold by way of the spacers, but are already pressed against one another, which can lead to a certain deformation of the spacers. However, the intermediate space which always remains is filled with the plastic material introduced into the intermediate space during insert molding, so that a brush head with predetermined dimensions can be produced not least due to the spacers. 
         [0020]    The height of the intermediate space preferably corresponds approximately to the size of the thickening in order to set the height of the brush head as compact as possible. This criterion is already fulfilled where the height corresponds to 80 to 200% of the height extension of the thickening. 
         [0021]    According to a further preferred embodiment of the present invention, nubs are provided on the rear side of the plate, i.e. on the side facing away from the bristle carrier, and are preferably integrally formed on the holding part. The free ends of these nubs are exposed on the undersurface of the brush body. The nubs usually extend parallel to the pivot axis. The aforementioned nubs also serve to position the plate in an injection mold in such a manner that the plastic material introduced into the intermediate space can flow around the underside of the plate and solidify there, so that this underside is substantially entirely formed by the plastic material introduced into the intermediate space and only the nubs with their free ends are exposed on this undersurface. A predetermined layer thickness of the plastic material introduced into the intermediate space on the underside of the brush head is thereby defined in a simple manner. The spacing required for this purpose in the injection molding material is reliably and simply set by the nubs. The nubs are usually disposed in radial direction within an outer edge of the plate so that the latter can at the edge be configured relatively thin and can be enclosed by the plastic material introduced into the intermediate space. 
         [0022]    The abovementioned spacers and/or nubs are usually provided distributed in the circumferential direction on the upper surface or the undersurface of the bristle carrier and/or the plate, respectively. 
         [0023]    The present invention also relates to an attachment part for an electric toothbrush comprising a sleeve member, a drive shaft provided therein, which can be coupled to a drive of the electric toothbrush, and a brush head according to the present invention. The brush head is there coupled to the drive shaft. The sleeve member at its end disposed opposite to the brush head comprises mechanical connection options for holding the attachment part on the handpiece of the electric toothbrush. Furthermore, the drive shaft is at the end side configured such that the drive shaft is coupled to the drive shaft of the handpiece when the sleeve member is attached onto the housing of the handpiece of the electric toothbrush in order to transmit the rotational motion of the drive shaft to the brush head. The brush head is there commonly pivoted, i.e. the drive shaft is not driven in a rotational manner but is only pivoted cyclically by a certain angular range. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Further details and advantages of the present invention shall become apparent from the following description of embodiments in combination with the drawing, in which: 
           [0025]      FIG. 1  is a perspective, partially sectional view of a first embodiment of the present invention; 
           [0026]      FIG. 2  is a cross-sectional view of a second embodiment; 
           [0027]      FIG. 3  is a cross-sectional view of a third embodiment; 
           [0028]      FIG. 4  is a cross-sectional view of a fourth embodiment; 
           [0029]      FIG. 5  is a cross-sectional view of a fifth embodiment; 
           [0030]      FIG. 6  is a perspective side view of a top side of a sixth embodiment of the present invention; 
           [0031]      FIG. 7  is a perspective side view of a bottom side of sixth embodiment of the present invention; 
           [0032]      FIG. 8  is a perspective side view of the bristle carrier of the sixth embodiment; 
           [0033]      FIG. 9  is a top view of the bristle carrier depicted in  FIG. 8 ; 
           [0034]      FIG. 10  is a top view corresponding to  FIG. 9  after tufting and securing bristle bundles against the bristle carrier by melting; and 
           [0035]      FIG. 11  is a perspective side view of the holding part of the sixth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    The figures each schematically illustrated the embodiments. Reference numeral  2  denotes a holding part which forms a stud  4  and a plate  6  protruding radially therefrom and provided integrally on the stud  4 . A bristle bundle  8  penetrates a bore  12  provided in a bristle carrier  10  and with its thickening  14  abuts at the rear side of the bristle carrier  10  against the latter. To simplify the illustration, only one bristle bundle  8  is shown in  FIG. 1 . It goes without saying that the entire surface  16  being formed by the bristle carrier  10  is protruded by bristle bundles or other cleaning elements, for example, TPE cleaning elements, in order to achieve a cleaning effect over the entire surface. The bristle bundles and the cleaning elements can have different diameters, colors, material properties and contours as well as different bristle filaments and a different number of bristle filaments, as is customary in the market. Suitable cleaning elements are, in particular, TPE cleaning elements which extend substantially parallel to the bristle bundle  8 . Such TPE elements can also be attached to the bristle carrier  10  in an articulate manner. 
         [0037]    Reference numeral  18  denotes an intermediate space enclosed between the underside of the bristle carrier  10  and the upper side of the plate  6 . Projecting into this intermediate space  18  is a spacer  20  protruding from the plate and abutting against the underside of the bristle carrier  10  and holding the latter at a predetermined distance from the plate  6 .  FIG. 1  illustrates only one such spacer  20 , although several such spacers  20  protrude from the surface of the plate  6  in order to hold and support the bristle carrier  10  in a punctiform manner but at various locations relative to the plate  6 . 
         [0038]    A nub  22  protrudes from the underside of the plate  6 . Several of these nubs  22  are also provided on the underside of the plate  6  and formed integrally thereonto. 
         [0039]    Reference numeral  24  denotes plastic material that is injected into the intermediate space  18 . It entirely fills the intermediate space  18 . The plastic material  24  also surrounds the bristle carrier  10  circumferentially, but ends on the surface  16  flush with the bristle carrier  10 . The plastic material  24  also surrounds the underside of the plate  6  and extends radially up to the stud  4 . A widened part of the brush head denoted with reference numeral  26  is in this embodiment formed in the manner of a disc which is composed of the bristle carrier  10 , the plate  6 , and the injection molded plastic material  24 . The edges of the disc are each rounded. The plastic material  24  is presently an easily flowing thermoplastic elastomer which not only connects the bristle carrier  10  to the plate  6  but also forms an outer-side boundary of the disc from relatively soft material which is gentler to the tender oral mucosa than harder plastic material. 
         [0040]    The holding part  2  is formed from technical plastic material. Technical plastic material exhibits high wear resistance and a high modulus of elasticity of at least 1500 MPa. The viscosity of such technical plastic material is relatively high. The MFI of a technical plastic material of the present invention is at 20 g/10 min at the test temperature corresponding to the plastic material and a load of 2.16 kg. A technical plastic material is, in particular, POM, PA, PC, or PBT. The holding part  2  is made of such material. The stud  4  commonly comprises the connections, holders and centering devices presented in the general description with which the embodiment shown can be held in a sleeve member (not shown) of an attachment part for an electric toothbrush and can be mechanically coupled to the drive. 
         [0041]    In the embodiment shown, the plastic material  24  can impart adhesion between the bristle carrier  10  and the holding part  2  made of the technical plastic material. The bristle carrier can there be formed from a hard component, for example, PA, PET, PP, PE, POM, PC, or PBT, respectively. 
         [0042]    The embodiment shown in  FIG. 1  assumes that a positive-fit connection is necessary for reliable attachment of the plastic material  24  to the holding part  2 . The plastic material  24  also extends on the underside of the plate and accordingly forms the undersurface of the widened part  26  which is penetrated by the stud  4 . The material nature of the bristle carrier  10 , however, is such that the plastic material  24  can only in a positive substance-fit manner be reliably bonded to the bristle carrier  10 . The plastic material  24 , however, surrounds the bristle carrier  10  merely circumferentially. 
         [0043]    To produce the embodiment shown in  FIG. 1 , the bristle carrier  10  is first produced from plastic material by way of injection molding, where the bore  12  or the bores are formed during injection molding. The bristle carrier  10  is thereafter provided with the bristle bundles  8 , the attachment-side end being initially arranged at a distance from the bristle carrier  10  and being melted to form the thickening  14 . The bristle bundle  8  is then displaced axially in order to abut the thickening  14 , formed during the surface melting process, against the underside of the bristle carrier  10 . 
         [0044]    The holding part  2  is by injection molding prepared from the technical plastic material in the final contour with all functional surfaces on the stud  4 . The two prepared components  2  and  10  are placed into an injection mold. The holding part  2  is there assigned to the one mold half, and the bristle carrier  10  to the other mold half. The bristle carrier  10  is there commonly held by a so-called perforated field plate which is usually outside the injection mold provided with the bristle carrier  10  and thereafter for completion of the injection mold inserted into the latter. When the injection mold is closed, the spacers  20  are abutted against the underside of the bristle carrier  10  and are there slightly compressed. The remaining intermediate space  18  is filled with the plastic material  24  that is then injected. The otherwise flat rear side of the plate  6  is by the nubs  22  held at a distance from the injection mold so that a gap remains there that is filled with the plastic material  24  in order to form the rear-side injection molding of the plate with the plastic material  24 . After sufficient cooling of the plastic material  24 , the mold nest is opened and the completed product shown schematically in  FIG. 1  is taken out. 
         [0045]      FIG. 2  shows a cross-sectional view of a basic form of the present invention. Identical components are marked with the same reference symbols as in the previously described embodiment. This applies to all the figures of the drawing. 
         [0046]    In the basic form according to  FIG. 2 , the intermediate space  18  is filled with the plastic material  24 . The plastic material  24  ends flush with an outer circumferential surface of the widened part  26  which is formed at the top by the edge of the bristle carrier  10 , at the bottom by the edge of the plate  6  and therebetween by the plastic material  24 . 
         [0047]    In the embodiment according to  FIG. 3 , the plate  6  has a smaller radial extension than the bristle carrier  10  as compared to  FIG. 2 . The plastic material  24  circumferentially surrounds both the bristle carrier  10  as well as the plate  6  but does not contribute anything to a higher thickness above the surface  16  or below the underside of the plate  6 , respectively. The plastic material  24  is merely an impact protection which surrounds the bristle carrier  10  and the plate  6  circumferentially. In such a configuration, the holding part  2  and the bristle carrier  10  are usually formed from plastic materials which adhere to the plastic material  24  that is injected into the intermediate space  18 , so that a positive substance-fit connection arises in the direction of the pivot axis S. 
         [0048]    The embodiment shown in  FIG. 4  substantially corresponds to  FIG. 2 , where, however, the spacers  20  formed integrally on the holding part  2  protrude from the plate  6  and abut against the underside of the bristle carrier  10  in order to define the intermediate space  18 . 
         [0049]    The configuration shown in  FIG. 5  substantially corresponds to the example according to  FIG. 1 . However, the bristle carrier  10  there has a locking edge  28  being formed spaced from the surface  16  and radially projecting over the surface  16  formed by the bristle carrier  10  and being protruded by the plastic material  24  in the direction of a pivot axis marked with reference symbol S. As a result, also the bristle carrier  10  is in a positive-fit manner secured against being pulled out in the direction of the pivot axis S. Due to the underside of the plate  6  being underlapped, a correspondingly acting positive-fit connection is established between the plastic material  24  and the holding part  2 . In addition, the plastic material  24  surrounds both the bristle carrier  10  as well as the plate  6  at the outer circumference so that a positive-fit connection is given also in a direction that is radial to the pivot axis S. The embodiment shown in  FIG. 5  is particularly suitable for connecting the various components when the material of the bristle carrier  10  and the material of the holding part  2  are incompatible with the plastic material  24  in terms of adhesion. 
         [0050]    The brush head depicted in  FIGS. 6 and 7  show a specific embodiment with sickle-shaped bristle bundles surrounding a round central bristle bundle  8 . 1 . While the central bristle bundle  8 . 1  is composed of between 320 and 400 filaments, the sickle-shaped bristle bundles are made of between 160 and 200 filaments, each of which have a size of 5 mil i.e 0.127 mm. Eight outer sickle-shaped bristle bundles  8 . 2  are circumferentially spaced apart from each other at the outer circumference with an essentially circumferential extension, while intermediate sickle-shaped bristle bundles  8 . 3  are arranged radially inwardly thereof and between the central bristle bundle  8 . 1  and the outer sickle-shaped bristle bundles  8 . 2 . Those intermediate sickle-shaped bristle bundles  8 . 3  have a rather radial extension. In other words, the longitudinal axis of the longitudinal sickle-shaped bristle bundles  8 . 3  extend essentially in a radial direction. 
         [0051]    The specific geometry of the bristle bundles  8  of this sixth embodiment is derivable from the top view of the bristle carrier  10  depicted in  FIG. 9 . This bristle carrier  10  has multiple bores  12  corresponding in geometry with the size of each bristle bundle  8 . The rear surface of the bristle carrier  10 , i.e. the main surface of the bristle carrier  10  facing towards the holding part  6  shows rims encircling each bore  12 , which rims are identified with reference numeral  30 . The rims each project from an essentially flat surface, which surface defines the rear surface of the bristle carrier  10 . When preparing the bristle bundles  8 , the same are inserted into the bristle carrier  10  and melted such that the melt generated by each bristle bundle  8  contacts the circumferential rim  30  of a respective bore  12  assigned to a respective bristle bundle  8  to contact, preferably join by welding, the bristle bundle  8  against the bristle carrier  10 , namely against the circumferential rim  30  of the assigned bore. The product received is depicted in  FIG. 10 , which shows the rearward surface of the bristle carrier  10  with a thickening  14  clearly visible for each bristle bundle. The thickening for the outer bristle bundles  8 . 2  are identified with reference numeral  14 . 2 . The thickening for the central bristle bundle  8 . 1  is identified with reference numeral  14 . 1 . The intermediate thickenings  14 . 3  are assigned to the respective intermediate bristle bundles  8 . 3 . After melting the bristle bundles  8  against the bristle carrier  10 , the surface thereof is essentially free of gaps, preferable completely sealed. 
         [0052]    The plate  6  of the holding part  2  depicted in  FIG. 11  has multiple through-holes  32  extending parallel to the stud  4 , which projects from the back surface of the plate  6 . Those through-holes  32  are disposed between conical spacers  20 , which project the plate  6 . From a ring-shaped central channel  34  recessed in the upper surface of the plate  6 , radial channels  36  extend in radial direction and generally terminate at the through-hole  32 . A channel identified with reference numeral  38  is not assigned to a respective through-hole. 
         [0053]    When placing the holding part  2  and the tufted bristle carrier  10  in an injection molding tool, an intermediate space is held free by the conical spacers  20  cooperating with the rearward surface of the bristle carrier  10 . As the spacers  20  are conical, a holding force of the injection molding tool may deform the tip portion of the spacer  20  depending on the surface configuration of the thickening  14 , which is not exactly controlled and results from solidification of the melt formed by the bristle bundles  8 . Thereafter and as already described for the previous embodiments, plastic melt is injection-molded into the intermediate space to join the holding part  2  and the bristle carrier  10 . Such melt will be allowed to thoroughly distribute in the intermediate space  18  and at the rearward surface of the plate  6  as the melt can pass through the plate  6  through the through-holes  32 . In the present embodiment, the plastic material is injected from the rear, i.e. lower side of the plate  6  to flow around the outer circumference thereof and through the through-holes  32 . The plastic material will flow in the intermediate space  18  assisted by the radial channels  36 ,  38  and the central channel  34  to equally distribute in the intermediate space and will flow around the bristle carrier  10 . However, as in the previous embodiment, the surface  16  of the bristle carrier  10  will form the surface of the final brush head being projected by the bristle bundles  8 . 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           2  holding part 
           4  Stud 
           6  Plate 
           8  bristle bundle 
           8 . 1  central bristle bundle 
           8 . 2  outer sickle-shaped bristle bundle 
           8 . 3  intermediate bristle bundle 
           10  bristle carrier 
           12  bore 
           14  thickening 
           14 . 1  central thickening 
           14 . 2  outer thickening 
           14 . 3  intermediate thickening 
           16  surface 
           18  intermediate space 
           20  spacer 
           22  nub 
           24  plastic material injected into the intermediate space  18   
           26  widened part 
           28  locking edge, widened part of the brush head 
           30  circumferential rim 
           32  through-hole 
           34  central channel 
           36  radial channel 
           38  radial channel without through-hole 
         S pivot axis