Abstract:
The invention relates to saucer-type handle components ( 5, 6 ) that pertain to a hollow handle and are produced in several steps. Said handle is used for a toothbrush. Said components are joined together and are inserted into an injection mould ( 25 ). A synthetic material, preferably a thermoplastic elastomer, is injection-moulded around the mould-parting line between the handle components ( 5, 6 ) in said injection mould ( 25 ). The connection seam ( 22 ) thus produced holds the two handle components ( 5, 6 ) together in a nondetachable manner and seals the hollow space ( 13 ) which is formed by the handle components ( 5, 6 ).

Description:
BACKGROUND 
   The present invention relates to a method for producing a hollow handle for a teeth cleaning device and to a handle produced by this method. 
   DE-U-298 17 994.6 discloses a toothbrush in which the hollow handle comprises two handle parts produced in separate steps, of which at least one handle part is formed in a shell-shaped manner. The two handle parts are welded to each other along the common parting join and are consequently connected to each other in a nondetachable manner. Adhesive bonding of the handle parts is also proposed. 
   A prerequisite for allowing handle parts consisting of plastic to be correctly welded to each other is that the handle parts consist of weldable plastics, i.e. plastics of the same family, which restricts the selection options for the plastics to be used. 
   SUMMARY 
   The present invention is consequently based on the object of providing a method of the type stated at the beginning that allows handle parts of a wide variety of materials to be joined together to form a hollow handle and connected to each other in an nondetachable and sealed manner. 
   The fact that, when the handle parts are joined together, they are coated or encapsulated with a plastics material along the common parting joint by the injection-molding process has the effect that a high-quality sealed connection, which can no longer be manually broken, is obtained between the handle parts. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter of the invention is explained in more detail below on the basis of the drawings, in which purely schematically: 
       FIG. 1  shows in side view a toothbrush without the brush head, with the handle parts separate from each other, 
       FIG. 2  shows in side view and partly in section the toothbrush put together from the two handle parts according to  FIG. 1 , 
       FIG. 3  shows a section along the line III—III in  FIG. 2 , 
       FIGS. 4 and 5  show the injection mold for producing the connection seam between the handle parts, 
       FIG. 6  shows a cross section through the handle comprising the two joined-together and interconnected handle parts, 
       FIG. 7  shows in a representation corresponding to  FIG. 6  but on an enlarged scale another form of the connection between the handle parts, 
       FIG. 8  shows in a representation corresponding to  FIG. 7  a further form of the connection between the handle parts, 
       FIG. 9  shows in side view and in a representation corresponding to  FIG. 1  another embodiment of a toothbrush before the handle parts are joined together, 
       FIG. 10  shows in side view the toothbrush according to  FIG. 8  in the assembled state, and 
       FIG. 11  shows the injection mold for producing the handle parts and the connection seam. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   A teeth cleaning device produced according to the invention, such as an electrically operated toothbrush  1 , will be described on the basis of  FIGS. 1–3 . 
   The toothbrush  1  has a handle  2 , which merges with a neck  3 , to which a brush head  4  is attached. The handle  2  comprises two handle parts  5  and  6 , of which at least the handle part  5  and preferably also the handle part  6  is formed in a shell-shaped manner. The neck  3  is formed by two neck parts  7 ,  8 , which are formed in one piece with the assigned handle parts  5  and  6 , respectively. The two neck parts  7   a ,  8   a  are likewise formed in a shell-shaped manner. The brush head  4  ( FIG. 2 ) has a bristle carrier  9 , from which clusters of bristles  10  protrude in a known way. The bristle carrier  9  is detachably mounted on a continuation  11  of the neck part  8 . In the case of the present exemplary embodiment, the brush head  4  is consequently exchangeable. It goes without saying that it is also possible to form the bristle carrier  9  in one piece with the neck part  8 , which in this case means that the brush head  4  is not exchangeable. Provided at the rear end of the handle  2  is a closure cap  12 , which closes off a cavity  13  defined by the two shell-shaped handle parts  5  and  6 . The closure cap  12  in the present exemplary embodiment is secured by means of a bayonet fastener. However, it is also possible, for example, for the closure cap  12  to be designed in such a way that it can be screwed on. 
   The hollow space  13  defined by the handle and neck parts  5 ,  6 ,  7 ,  8  is divided by a transverse wall  14 , molded onto the handle part  5 , into a rear hollow space  13   a  and a front hollow space  13   b . In  FIGS. 2 ,  15  denotes a detent groove which is provided on the inner side of the handle parts  5 ,  6  and belongs to the mentioned bayonet connection, by means of which the closure  12  is detachably secured to the handle  2 . The rear hollow space  13   a  serves for receiving a battery (not represented), which is supported at one end on the closure cap  12  and at the other end on a contact spring  16 , which is attached to the transverse wall  14 . Accommodated in the neck  3  is a micro-motor  17 , which is connected to a vibration element  18 , for example an oscillating armature, which serves the purpose of making the brush head  4  vibrate. The micro-motor is connected to one terminal of the battery in the rear hollow space  13   a  by means of an electrical connecting line  19  via the closure cap  12 . A further connecting line  20  connects the micro-motor  17  to a manually actuable switch  21 , which is provided in the handle part  5  and is connected via a connecting line  20 ′ to the contact spring  16 , which is in contact with the other terminal of the battery. By actuating the switch  21 , the micro-motor  17  is switched on and off. For securing or positioning the various electrical and mechanical parts of the drive for the brush head  4 , positioning or holding parts, such as for example the transverse wall  14 , are provided on at least one handle or neck part  5 ,  7  or  6 ,  8 . 
   The handle  2  and the neck  3  preferably consist of the same material and either of the same plastic as the bristle carrier  9  or of a different kind of plastic. The handle and neck parts  5 ,  7  and  6 ,  8  are preferably produced by a one-component or multi-component injection-molding process. 
   As  FIGS. 1 and 2  reveal, the handle and neck parts  5 ,  7  and  6 ,  8  are produced in separate steps and then joined together. In this case, the end faces  5   a ,  7   a  and  6   a ,  8   a  of the parts  5 ,  7  and  6 ,  8  lying against one another form a parting joint therebetween, which is closed by means of a connection seam  22  ( FIG. 3 ) in a way still to be described. 
   The method for producing a toothbrush of the type shown in  FIGS. 1–3  is now described on the basis of  FIGS. 4–6 . 
   The handle parts  5 ,  6  produced as mentioned in separate steps and for example at spatially separate locations, with molded-on neck parts  7  and  8 , respectively, are joined together to form the finished handle  2  with neck  3 . The handle parts  5 ,  6  joined together and possibly held together by additional mechanical means are then placed into an injection mold  25 , such as that represented in  FIG. 4 . Of this injection mold  25 , the two mold halves  26  and  27  are represented purely schematically.  28  denotes an injection opening provided in the upper mold half  26 . The mutually facing end faces  5   a  and  6   a  and also the end faces  7   a ,  8   a  of the neck parts  7  and  8  define a parting joint  30 . After the closing of the injection mold  25 , i.e. the bringing together of the two mold halves  26 ,  27 , a plastics material is injected by means of an only schematically represented injection unit  29  into the mold cavity of the injection mold  25  ( FIG. 5 ). The injected plastics composition closes the parting joint  30  between the handle and neck parts  5 ,  6 ,  7  and  8  over its entire length or only over part of its length and then forms the connection seam  22 . In  FIG. 6 , the finished handle  2 , removed from the injection mold  25 , is represented in cross section. 
   In the exemplary embodiment described, affinitive plastics are used for the handle and neck parts  5 ,  6 ,  7  and  8  and the connection seam  22 , i.e. plastics which enter into a material bond with one another during the injection-molding operation. This is the case, for example, whenever polypropylene (PP) is used for the handle and neck parts  5 ,  6 ,  7 ,  8  and a corresponding thermoplastic material, preferably a thermoplastic elastomer, is used for the connection seam  22 . Such a material bond is also obtained if the handle and neck parts  5 ,  6 ,  7 ,  8  consist of SAN (styrene acrylonitrile) and a corresponding thermoplastic material, for example a suitable thermoplastic elastomer, is used for forming the connection seam  22 . 
   The method according to the invention, i.e. the closing of the parting joint  30  between the handle and neck parts  5 ,  6 ,  7 ,  8  by the injection-molding process has the advantage that even handle and neck parts which consist of plastics which are not affinitive with the plastic which is used for the connection seam  22  can be connected to one another in this way. This is the case, for example, if one handle or neck part  5 ,  7  consists of polypropylene (PP) and the other handle part  6 ,  8  consists of SAN and a thermoplastic elastomer that enters into a material bond either with PP or SAN and not with the other plastic is used for forming the connection seam  22 . In such cases, no material bond is produced between the parts, requiring a different configuration of the connection seam and/or of the handle and neck parts. Such embodiments are now described on the basis of  FIGS. 7 and 8 , in which a handle  2 ′ is shown in cross section. 
   In the case of the embodiment shown in  FIG. 7 , in the mutually facing end faces  5   a ′,  6   a ′, defining the parting joint  30 ′, there are preferably cleat-shaped projections  31 ,  32 , which are surrounded by the plastics material of the connection seam  22 ′. The projections  31 ,  32  lying opposite one another form a hollow space  33 , into which the injected plastics composition can penetrate. In  FIG. 7 , the part of the connection seam  22 ′ lying in this space  33  is denoted by  34 . 
   This formation provides a mechanical, i.e. positive and nonpositive, connection between the handle parts  5 ′ and  6 ′ and the connection seam  22 ′. It goes without saying that the positive or nonpositive connection between the handle parts  5 ′,  6 ′ and the connection seam  22 ′ can also be produced in some other way, for example by providing depressions in the end faces  5   a ′ and  6   a ′ of the handle parts  5 ′,  6 ′, which are then filled with the plastics material of the connection seam  22 ′. 
   In the case of the exemplary embodiment according to  FIG. 8 , alongside the parting joint  30 ′ in the two handle parts  5 ′,  6 ′ there are recesses  35  and  36 , which are filled with the plastics material of the connection seam  22 ′. In this case, the parts  22   a ′,  22   b ′ of the connection seam  22 ′ lying in these recesses  35 ,  36  grip behind cleat-like projections  37  and  38 , respectively, of the handle parts  5 ′,  6 ′. The recesses  35 ,  36  lying respectively opposite one another in the handle parts  5 ′,  6 ′ are respectively connected to one another over part of the length of the parting joint  30 ′ by means of apertures  39 , which are filled with the plastics material of the connection seam  22 ′. For holding together the joined-together handle parts  5 ′,  6 ′ before coating along the parting joint  30 ′, in the region of the mutually facing end faces  5   a ′,  6   a ′ of the handle parts  5 ′,  6 ′ there are mechanical centering or holding arrangements  40 , which in the exemplary embodiment according to  FIG. 8  are formed in the manner of tongue-and-groove connections. Preferably associated with these tongue-and-groove connections are cleat-like projections in one handle part  5 ′, which engage in equally and oppositely formed grooves in the other handle part  6 ′. 
   A mechanical connection of this type between the handle parts  5 ′,  6 ′ also makes it possible to produce one handle part or both handle parts from a material other than plastic, for example from a metal, such as for example nonferrous metal or aluminum, or even from wood. 
   The method explained on the basis of  FIGS. 4–7  also allows toothbrushes designed differently than the toothbrush according to  FIGS. 1–3  to be produced, as now explained by way of example with reference to  FIGS. 9 and 10 . 
   The toothbrush  41  shown in these  FIGS. 9 and 10  comprises a handle  42 , a neck  43  and a brush head  44 . The latter has a bristle carrier  44   a , which is in one piece with the neck  43  and is provided with clusters of bristles  44   b . The handle  42  comprises an upper handle part  45 , formed in a shell-shaped manner, and a lower handle part  46 , which is in one piece with the neck  43  and may also be formed in a shell-shaped manner. The two handle parts  45 ,  46  define a hollow space  47 . After the joining together of the two handle parts  45 ,  48 , the parting joint is closed as already described by means of a plastics material in the injection-molding process. The connection seam formed thereby is denoted by  48  ( FIG. 9 ). 
   The two handle parts  45 ,  46  are positioned with respect to each other and held together by mechanical means before the coating of the parting join with the plastics material. For this purpose, the upper handle part  45  is provided with downwardly protruding, pin-like lugs  49 , which engage in openings  50  provided in the lower handle part  46  when the handle parts  45 ,  46  are joined together. 
   The two handle parts  45 ,  46  are produced in separate steps. If the handle parts  45 ,  46  consist of plastic, they are preferably produced by the one-component or multi-component injection-molding process. 
   After the joining together of the handle parts  45 ,  46 , the handle  42  is coated by a plastics material in an injection mold in the region of the parting joint between the handle parts  45 ,  46 , as has been explained on the basis of  FIGS. 4–6 . 
   In the case of the exemplary embodiments described above, the handle parts  5 ,  6 ,  45 ,  46  are produced in separate locations from one another, preferably by the injection-molding process, are subsequently joined together and are then encapsulated along the parting joint  30  with the plastics material of the connection seam  22 ,  48  in a further injection-molding operation. 
   It is also conceivable, however, to perform certain steps among these at the same location. For example, firstly a first handle part may be produced. A second handle part is produced in a two-component injection mold and remains in this injection mold. The first handle part is joined together with the second handle part in the injection mold, for example with the aid of a robot. Then the forming of the connection seam takes place in this two-component injection mold, possibly after the joined-together handle parts have been transferred into a further cavity of the injection mold, for example by means of a robot, by injecting the corresponding plastics material. It is also possible to bring the second handle part into the further cavity, then join the first handle part together with the second handle part, and after that form the connection seam by injecting the corresponding plastics material into this further cavity. 
   The production of the two handle parts and of the connection seam may also take place at the same location, i.e. in a multi-component injection-molding installation, which is explained on the basis of  FIG. 11 . 
     FIG. 11  shows in the same representation as  FIGS. 4 and 5  the two mold halves  26 ′ and  27 ′ of a three-component injection mold  25 ′. In a first cavity  52 , the first handle part  5  is produced—with the injection mold  25 ′ closed—by injecting the corresponding plastics material by means of the assigned injection unit  29 . At the same time, in a second cavity  52 ′ of the injection mold  25 ′, the second handle part  6  is produced by injecting another plastics material by means of the assigned injection unit  29 . Finally, likewise at the same time, in a third cavity  52 ″ of the injection mold  25 ′, the connection seam  22  is formed between the handle parts  5  and  6 , produced in a preceding injection cycle and then joined together, by injecting a further different plastics material by means of the assigned injection unit  29 . 
     54  denotes a robot arm, having suction heads  56  for the handle parts  5 ,  6  and the toothbrush  1 . With the mold halves  26 ′,  27 ′ separated from each other after an injection operation, the suction heads  56 , which can be connected to a vacuum source, simultaneously grasp the two handle parts  5 ,  6  and the toothbrush  1  and lift them out of the corresponding cavities  52 ,  52 ′,  52 ″. 
   The first handle part  5  is then inserted by means of the robot arm  54  into the third cavity  52 ″ of the mold half  26 ′ and released by deactivating the corresponding suction head  56 . Subsequently, the handle parts  5 ,  6  are joined together, in that the robot arm  54  places the second handle part  6  onto the first handle part  5 . By deactivating the assigned suction head  56 , the second handle part  6  is released. Once the robot arm  54  has been moved out of the region of the injection mold  25 ′—also for discharging the toothbrush  1 —, the two mold halves  26 ′,  27 ′ are moved toward each other, in order to close the injection mold  25 ′ for the next injection operation. 
   It is also possible to join the two handle parts  5 ,  6  together outside the injection mold  25 ′—for example during an injection operation—and then place them in the third cavity  52 ″. This procedure is advantageous in particular when further parts are to be introduced into the cavity  13  or one of the handle parts  5 ,  6  is to be provided with a surface finish or be printed on. 
   It should be mentioned for the sake of completeness that it is of course also possible to feed more than one of the cavities  52 ,  52 ′,  52 ″ by means of a common injection unit  29 . This is so if the handle parts  5 ,  6  consist of the same plastics material, or the plastics material for the connection seam  22  is also used for producing a membrane on one or both handle parts  5 ,  6 . 
   It goes without saying that the injection mold  25 ′ may have a number of rows of first, second and third cavities  52 ,  52 ′,  52 ″ for the simultaneous production of a number of toothbrushes  1 . 
   As described, preferably a soft plastic, i.e. a plastic that remains elastomeric, with a Shore hardness of preferably 10–70, is used for the forming of the connection seam  22 ,  48 . However, it is also possible to use a hard plastic in the same way as for the handle and neck parts. 
   At least the upper handle part  5  or  44  may be opaque entirely or in certain regions or transparent entirely or in certain parts. 
   The hollow space  13 ,  47  in the handle  2 ,  42  may be filled with a liquid and/or items. In the case of toothbrushes, as they are shown in  FIGS. 8 and 9 , the filling of the hollow space takes place before the injection-molding of the connection seam. 
   The fact that the connection seam  22 ,  48  consists of plastic allows the connection seam also to be used as an element in the visual design, by choosing the color of the plastic. 
   In the same injection-molding operation in which the plastics material for the connection seam is injected, other regions of the handle, of the neck or of the brush head, for example the finger resting region or sealing elements, may also be formed from this plastics material.