Abstract:
An electric toothbrush includes a brush head to which there is pivotally mounted a main bristle holder. Extending from the brush head is an auxiliary bristle holder which can oscillate in unison with the main bristle holder or in contra-rotational unison with the main bristle holder to increase efficiency of the toothbrush in operation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to electric toothbrushes.  
           [0003]    2. Description of Prior Art  
           [0004]    An electric toothbrush has been described in U.S. Pat. No. 5,784,743. That US Patent discloses an electric toothbrush having a brush head to which there is mounted a bristle holder that pivots back and forth about a pivot axis. The specification describes a drive shaft having a finger which rotates about an axis to effect movement of a plate which interacts with a gear which is attached to a bristle holder. Movement of the plate by the finger results in oscillatory pivotal movement of the bristle holder.  
           [0005]    Irrespective of any specific mechanism by which the bristle holder of such toothbrushes is driven, operational efficiency is limited by the simple oscillatory movement of bristle holder with respect to the brush head.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to overcome or substantially ameliorate the above disadvantage.  
           [0007]    It is a further object of the present invention to provide an electric toothbrush having a pivotally oscillating head as well as an auxiliary head extending from the toothbrush.  
           [0008]    It is further object of the invention to provide an electric toothbrush having a main bristle holder that oscillates pivotally and an auxiliary bristle holder that oscillates pivotally alongside the main bristle holder.  
           [0009]    According to the invention there is provided an electric toothbrush having a handle, a brush head, a main bristle holder mounted to the brush head and driven to oscillate pivotally with respect to the brush head, and an auxiliary bristle holder positioned radially outwardly of the main bristle holder and driven to oscillate pivotally with respect to the brush head.  
           [0010]    Preferably the auxiliary bristle holder is attached to the brush head and is driven to move in a clockwise direction when the main bristle holder moves in a clockwise direction.  
           [0011]    Preferably the auxiliary bristle holder is attached to the brush head and is driven to move in a counter-clockwise direction when the main bristle holder moves in a clockwise direction.  
           [0012]    Preferably the auxiliary bristle holder is attached to the main bristle holder.  
           [0013]    Preferably the auxiliary bristle holder is formed integrally with the main bristle holder.  
           [0014]    Preferably the auxiliary bristle holder is attached to the main bristle holder by a spring plate.  
           [0015]    Preferably, the electric toothbrush has a central longitudinal axis extending between the handle and the brush head, a drive shaft extending along the longitudinal axis from a motor in the handle to a remote and thereof and said drive shaft having a finger of f-set from the central axis at the remote end, a plate pivotably mounted on the central axis having a first end and a second end, a fork at the first end of the plate that embraces the finger and an arcuate contact drive surface at the second end, the main bristle holder being pivotably mounted by a shaft on the central axis to the brush head, and a circular contact surface rotatable with the shaft that engages the arcuate contact surface such that when the drive shaft is rotated by the motor continuously in one direction the main bristle holder is rotated backwards and forwards.  
           [0016]    Preferably the auxiliary bristle holder is mounted to the plate.  
           [0017]    Preferably, the toothbrush further includes a yolk on the brush head against which the auxiliary bristle holder moves so as to cause movement of the auxiliary bristle holder in a direction substantially normal to said clockwise and anticlockwise directions.  
           [0018]    Preferably, the toothbrush further includes a yolk on the brush head against which the auxiliary bristle holder moves so as to cause movement of the auxiliary bristle holder in a direction substantially normal to said clockwise and anticlockwise directions.  
           [0019]    Preferably the auxiliary bristle holder is attached to the main bristle holder by a spring plate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings wherein:  
         [0021]    [0021]FIG. 1 is a part-sectional underplan view of a toothbrush;  
         [0022]    [0022]FIG. 2 is a bottom plan sectional views of part of the toothbrush of FIG. 1;  
         [0023]    [0023]FIG. 3 is a side sectional elevation of part of the toothbrush of FIG. 1;  
         [0024]    [0024]FIG. 4 is an enlarged plan view of a plate for the toothbrush of FIG. 1;  
         [0025]    [0025]FIG. 5 is a part-sectional underplan view of another toothbrush;  
         [0026]    [0026]FIG. 6 is a bottom plan sectional view of part of the toothbrush of FIG. 5;  
         [0027]    [0027]FIG. 7 is a side sectional elevation of part of the toothbrush of FIG. 5;  
         [0028]    [0028]FIG. 8 is an enlarged plan view of a plate for the toothbrush of FIG. 5;  
         [0029]    [0029]FIG. 9 is an enlarged elevational view of brush head portion of either of the toothbrushes of FIG. 1 or FIG. 5;  
         [0030]    [0030]FIG. 10 is an end elevational view of the brush head of FIG. 9; and  
         [0031]    [0031]FIG. 11 is a cross-sectional elevational view of the brush head portion of the toothbrush as illustrated in FIG. 9. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]    As shown in FIG. 1 of the drawings a first form of the toothbrush comprises a handle  10  a brush head  11  and shank  12  having a central longitudinal axis  13 .  
         [0033]    In FIGS. 2, 3 and  4 , a drive shaft  14  is mounted to rotate about the central axis  13  and is held in position at a remote end by a bearing  15 . A boss  16  mounted on the remote end of the shaft  14  is provided with a finger  17  that is off-set from the central axis  13 . A wobble plate  18  is integrally mounted on a short shaft  19  on the axis  13  fixed to the brush head  11 . The wobble plate  18  has a first end integrally formed as a fork  20  that embraces the finger  17  and a second end which carries an arcuate gear  21 . A main bristle holder  22  is integrally mounted on a pivot shaft  23  also on the central axis  13  fixed to the brush head  11 . The shaft  23  is provided with a gear  24  rotatably fixed to the shaft, that meshes with the arcuate gear  21 .  
         [0034]    When the drive shaft  14  is rotated continuously in one direction the main bristle holder  22  is caused to rotate backwards and forwards or oscillate about its central pivot axis. In general terms, the relative positoin of the shaft  19  and the shaft  23  can be varied significantly and the gearing between the gears  21  and  24  altered to produce various arcs of oscillation that may be desired. The arcs of oscillation can range well above 120° for example  
         [0035]    The plate  18  (seen best in FIG. 4) is an integrally formed molded plastic part. The drive shaft  14  may also be integrally formed in plastic material or formed of steel wire where the finger  17  is formed by cranking the remote end of the wire.  
         [0036]    As shown in FIGS. 2, 3 and  4 , the plate  18  has an extension portion  25  which extends radially beyond brush head  11 . At the distal end of the extension  25  there is integrally provided an auxiliary bristle holder  26 . Bristles of the auxiliary bristle holder  26  reside alongside the bristle of the main bristle holder  22 . When plate  18  oscillates pivotally by action of finger  17 , the auxiliary bristle holder  26  also oscillates. The pivot axis of bristle head  26  is that of the shank  19  to which the plate  18  is mounted. When the plate  18  moves in a clockwise direction about this axis, the main bristle holder  22  also rotates in a clockwise direction due to the interaction of arcuate gear  21  with gear  24 .  
         [0037]    A second form of the toothbrush is depicted in FIGS.  5  to  8 . In this embodiment, all features of the toothbrush are the same as those of the embodiment of FIG. 1, however, the auxiliary bristle holder  26  pivotably rotates in a direction opposite to that at which the mean bristle holder rotates at any given time. This is due to a relocation of arcuate gear  21  to the inner side of shaft  23 . The gear  24  has been reposition upon shaft  23  so as to face backwardly such that its teeth inter-mash with the teeth of arcuate gear  21 . As a result, when shaft  23  rotates in a clockwise direction the plate  18  rotates in a counter-clockwise direction. As a result, the main bristle holder  22  rotates counter-clockwise as the auxiliary bristle holder  26  rotates clockwise with the plate  18 .  
         [0038]    It might be desirable to provide a “3-dimensional” movement of auxiliary bristle holder  26 . To this end a further embodiment of the invention is depicted in FIGS.  9  to  11 .  
         [0039]    As best illustrated in FIG. 11, the auxiliary bristle holder  26  is mounted to the main bristle holder  22  by a spring plate  29 . Spring plate  29  can be soldered, riveted, spot-malted, plastic-melted or otherwise attached to main bristle holder  22  and auxiliary bristle holder  26 . For the purpose of illustration, attachment lugs  30  and  31  are shown these may be plastic pins extending from the bristle holders through holes in the spring plate with melted-flat tops.  
         [0040]    The auxiliary bristle holder  26  has a curved serface  27  that engages with a yolk  28  on the brush head  11 . As the auxiliary bristle holder  26  moves across yolk  28 , it is caused to follow a locus  31  by interaction of the curved serface  27  with the yolk  28 .  
         [0041]    In the embodiment depicted in FIGS.  9  to  11 , the auxiliary bristles attached to the auxiliary bristle holder  26  have in combination, a tapered tip  32  as shown FIG. 9. This tip will have components of movement in the direction indicated by arrow A as well as components of movement about the axis of the main bristle holder  22 . In this embodiment, the rotary component of movement of auxiliary bristle holder  26  is fixed by and therefore co-rotational with main bristle holder  22 . However, where a contra-rotational auxiliary bristle holder  26  is desired, the embodiment of FIGS.  5  to  8  could be modified simply by the incorporation of a spring plate between plate  18  and auxiliary bristle holder  26  and the provision of a yolk on brush head  11  with which the auxiliary bristle holder can interact as described. As an alternative to the use of a separate spring plate, the plate  18  could be made from a thin sheet of resilient material such as stainless steel, or could be formed of a more rigid material having a thin portion at extension  25  formed integrally therewith to provide the necessary resiliency.