Abstract:
An electrical toothbrush having a longitudinally reciprocating brush head which automatically rotates about the longitudinal axis while undergoing longitudinal brushing movements in order to align the brush head with the curvature of the gum for better dental care. An example of a drive mechanism together with appropriate motion transformation means to gradually turn the plane of the brush head about the longitudinal axis during a reciprocating longitudinal teeth brushing motion is described.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to electric toothbrushes and, more particularly, to electric toothbrushes having a brush head which is reciprocally movable along a longitudinal axis as well as about the same longitudinal axis.  
         BACKGROUND OF THE INVENTION  
         [0002]    Electric toothbrushes are well known and have been very popular because of the superior teeth and gum cleaning compared to cleaning by conventional manual toothbrushes.  
           [0003]    Electric toothbrushes generally include a main housing with a handle portion inside which a motor is mounted. A brush head with bristles is usually connected to the motor shaft in order to generate the appropriate vibrations or other reciprocating motions. A transmission link is generally provided between the motor and the brush head to convert the uni-directional rotation of the motor shaft to the appropriate reciprocating teeth brushing motions. Examples of such appropriate teeth brushing motions include reciprocating motion along a longitudinal axis which is generally parallel to the axis of the motor shaft. Another type of such appropriate motions is by rotating the bristle holder about an axis which is generally perpendicular to the motor shaft axis or perpendicular to the plane of the brush head. U.S. Pat. No. 5,383,242 to Bigler Michael discloses a toothbrush having a reciprocating motion which combines a longitudinal reciprocating motion along a longitudinal axis which is parallel to the motor shaft as well as a rotational motion perpendicular to that longitudinal axis. Another type of brushing action is generated by the vibration of the brush head as a result of the vibrational movement of an eccentric weight attached to the motor shaft or gears attached to the motor shaft. In this latter design, the eccentric weight is usually located proximal to the motor in the housing and the vibrations generated is unpleasant for the user. Therefore, this eccentric weight generated vibration is less preferable in modern day electric toothbrush designs.  
           [0004]    Dentist research reports have suggested that it is preferable to brush the teeth by following the veins of the teeth with the bristles of the toothbrush engaging the teeth along a direction which is generally normal to the plane of the teeth. While conventional electric toothbrushes provide a variety of reciprocating motions to enhance teeth brushing, there has been no specific and effective design of toothbrushes having a longitudinally reciprocating brush head which simultaneously provides automatic alignment of the brush head inclination so that the plane of the brush head can follow the general curvature of the teeth arrangements for optimal brushing.  
         OBJECT OF THE INVENTION  
         [0005]    It is therefore an object of the present invention to provide electric toothbrushes having a toothbrush head which is reciprocally movable along a longitudinal axis and, at the same time, providing automatic alignment of the brush head plane about the longitudinal axis in order to follow the curvature of the teeth arrangement for optimal tooth brushing. It is also an object of the present invention to provide specific embodiments of such a design of toothbrushes which are simple enough for practical utilization. At a minimum, it is an object of the present invention to provide an electric toothbrush with an improved brushing mechanism and/or brushing mode.  
         SUMMARY OF THE INVENTION  
         [0006]    According to the present invention, there is provided an electric toothbrush including an electric toothbrush including a brush head with bristles, an elongated main housing, a motion transmission link, motion generating means and motion transformation means, wherein:  
           [0007]    said brush head includes an elongated stem for connecting said brush head to said motion generating means via said motion transmission link,  
           [0008]    said motion generating means include means for generating reciprocating motions along a longitudinal axis,  
           [0009]    said motion transmission link transmits the reciprocating motions generated by said motion generating means along said longitudinal axis to said elongated stem of said brush head,  
           [0010]    said elongated stem is rotatable about said longitudinal axis while undergoing said reciprocating motions said longitudinal axis, and  
           [0011]    said motion transformation means include means to rotate said brush head about said longitudinal axis while said elongated stem is undergoing reciprocating longitudinal motions along said longitudinal axis.  
           [0012]    Preferably, the combination of said tracking means and said guiding means results in oscillatory movements of said bristle holder about said longitudinal axis as and when said elongated stem reciprocally moves along said longitudinal axis.  
           [0013]    Preferably, further including a collar member which is provided with guiding means, said collar being received within said main housing and including a peripheral wall which generally extends along said longitudinal axis and surrounds at least a portion of said elongated stem of said bristle holder, said guiding means include at least a guiding track which is formed on said peripheral wall, said guiding track generally extends along said longitudinal axis longitudinally as well as transversally, said elongated stem of said bristle being provided with tracking means which follow the shape of said guiding track in response to the reciprocating longitudinal motion generated by said motion generating means, said transversal extension of said guiding track causes turning of said bristle holder about said longitudinal axis.  
           [0014]    Preferably, said turning of said bristle holder about said longitudinal axis is reversed when said axial longitudinal motion of said elongated stem reverses.  
           [0015]    Preferably, a spring member interconnects said collar member and said motion generating means, said spring member is disposed so that it is compressed by said motion generating means when said motion generating means moves said elongated stem along a first axial direction, said compressed spring member decompresses and moves said elongated stem along an axial direction opposite to that first axial direction when said motion generating means moves along that opposite axial direction.  
           [0016]    Preferably, said spring member includes a helical spring disposed between said bristle holder and said motion generating means and surrounding at least a portion of said elongated stem.  
           [0017]    Preferably, said motional generating means includes a motor having a motor shaft rotatable about a first axis parallel to said longitudinal axis, said rotational motion of said motor about said first axis being transformed into reciprocating motion along said longitudinal motion by gear arrangements, said gear arrangements include an eccentric crank arm arrangement, said eccentric crank arm arrangement transforms said rotational motion of said motor shaft into reciprocating motion of said crank arm along said longitudinal axis. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    Preferred embodiments of the present invention of an electric toothbrush will be described in further detail below by way of example and with reference to the accompanying drawings, in which:  
         [0019]    [0019]FIG. 1 is an exploded view of a first preferred embodiment of the toothbrush showing the major components,  
         [0020]    [0020]FIG. 2 is a perspective view of the toothbrush of FIG. 1 assembled but with the main housing  22  removed to expose the moving parts,  
         [0021]    [0021]FIG. 3 is a cross-sectional view taken longitudinally along the base of the bristle holder  11  of the toothbrush of FIG. 1 and viewed perpendicularly from the plane of the bristle holder towards the direction of extension of the bristles.  
         [0022]    [0022]FIG. 4 is a longitudinal cross-sectional view of the assembled toothbrush of FIG. 1 showing an enlarged view of the connection between the motion generating means and the bristle holder,  
         [0023]    [0023]FIG. 5 is a longitudinal view of the toothbrush of the present invention with the main housing removed and the tracking means disposed near the middle portion of the guiding track. The plane of the bristle holder  11  in this Figure has been turned by 90 degrees for convenient description,  
         [0024]    [0024]FIG. 6 is a longitudinal view of the toothbrush of FIG. 5 with the tracking means located near the bottom and of the guiding track, and  
         [0025]    [0025]FIG. 7 is a longitudinal view of the toothbrush of FIG. 5 with the tracking means located at the top and of the guiding track. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    Referring to FIGS.  1 - 7  showing a first preferred embodiment of the present invention, the electric toothbrush  1  includes a brush head  10 , a main housing  20  including a neck portion  21  and a handle portion  22 , reciprocating motion generating means and motion transforming means. The main housing is preferably made of hard plastics and the handle portion  22  generally includes compartments for accommodating batteries and the motion generating means.  
         [0027]    The brush head  10  includes a bristle holder  11  and an elongated stem  12  extending longitudinally from the lower side of the bristle holder towards the longitudinal end of the main housing  20 . The bristle holder  11  includes a base surface from which bristles  13  extend generally in a perpendicular manner.  
         [0028]    The reciprocating motion generating means include a motor  30  and a motion transmission link. The motor  30  is received within the handle portion  22  of the housing with the motor shaft  32  aligned generally parallel to the longitudinal axis of the elongated main housing  20  of the toothbrush  1 . The motion transmission link includes a teethed wheel  31  mounted at the upper-most end of the motor shaft  32  with its plane of rotation generally perpendicular to the motor shaft  32 . The teethed wheel  31  meshes with a crown or face gear  33  which is mounted on an axis which is generally perpendicular to the motor shaft  32  so that the main plane of the face gear  33  is generally parallel to the motor shaft  32 . A crank arm  34  which is slidably movable along and within the neck portion  21  of the main housing  20  in a closely fitted manner is connected eccentrically to the face gear  33  via an off-centred pivotal driving pin  35  on the main plane of face gear  33 . More precisely, the lower end of the crank arm  34  is connected to the off-centred pivotal driving pin  35  via a connecting piece  36 , as is more particularly shown in FIG. 3.  
         [0029]    The connecting piece  36  is a generally T-shaped member with a generally transversal slot along its wider portion for receiving the off-centred connecting pivotal driving pin  35 . This transversal slot allows movement of the connecting pin  35  along the slot while the connecting pin  35  is undergoing circular motion due to the rotation of the face gear  33 . Hence, the driving arrangement between the pivotal connecting pin  35  on the face gear  33  and the generally transversal slot on the connecting piece  36  facilitates the conversion of a rotational motion of the pivotal connecting pin  35  into a longitudinal reciprocating motion, since the crank arm  34  is restricted to be movable along the longitudinal axis. In other words, the rotational motion of the eccentric pivotal connecting pin  35  when driving the connecting piece  36  having the transversally extending slot will result in a reciprocating motion of the crank arm  34  along the longitudinal axis of the main housing  20  which is generally parallel to the axis of the motor shaft  32  in the present embodiment for driving the brush head  10 .  
         [0030]    The longitudinal movement of the crank arm  34  can of course be aligned with a different longitudinal axis by adjusting the inclination of the neck portion  21  with respect to the motor shaft  32  and with appropriate gear arrangements. Thus, with the combination of the motor  30  and the transmission link, and with the movement of the connecting crank arm  34  being restricted along the longitudinal axis of the main housing  20 , rotational motions of the motor  30  about the axis of the motor shaft  32  will be transformed into longitudinal reciprocating motions of the crank arm  34  generally along the longitudinal axis of the housing  20  of the toothbrush  1 .  
         [0031]    In the present embodiment, the reciprocating motion generating means including the motor  30 , the teethed wheel  31 , the face gear  33 , the crank arm  34 , the pivotal driving pin  35 , and the connecting piece  36  are formed as a subassembly inside the handle portion  22 .  
         [0032]    Referring to FIGS.  3  to  7 , it will be noted that the elongated stem  12  of the toothbrush  1  is received inside the tubular housing of the neck portion  21  of the main housing  22  for connection to the crank arm  34 . In the present embodiment, the crank arm  34  is connected to the elongated stem  12  via a connection member  37 . More specifically, the connection member  37  includes a first collar portion for engaging with one end, the near end, of the crank arm  34  and a second collar portion for engaging with the distal end (i.e., the end not connected to the bristle holder  11 ) of the elongated stem  12 . The first and second collar portions are generally co-axial hollow cylindrical members extending in the opposite directions along the longitudinal axis of the main housing  22 , which is parallel to the motor shaft  32 . Engagement means are formed on the second collar portion so that the elongated stem  12  is “locked-in” with the second collar portion. The engagement means in the present embodiment are a pair of apertures dimensionally corresponding to that of a pair of radial stud engaging members formed near the distal end of the elongated stem  12 . Naturally, the hollow part of the second collar portion is dimensioned to receive that portion of the elongated stem  12  bearing the stud engaging members.  
         [0033]    The near end of the crank arm  34  is connected to the first collar portion of the connection member  37  by corresponding fastening means. In this example, the near end of the crank arm  34  is shaped so that it has a head portion and a narrowed neck portion. The connection is done by trapping the head portion of the coupling end of the crank member  34  within the hollow body of the first collar portion of the connection member  37  by a radially and inwardly extending circumferential flange.  
         [0034]    With this arrangement, it will be noted that the sub-assembly comprising the elongated stem  12 , the connection member  37  and the crank arm  34  has a substantially constant length. In addition, the elongated stem  12  is rotatable relative to the crank arm  34  and the main housing  22  or the motor. Thus, it will be observed from the above arrangements that when the crank arm  34  advances towards the brush head  10 , it will push the connection member  37  and therefore the elongated stem  12  to advance in the direction of the brush head  10 . When the crank arm  34  retreats towards the motor end, the elongated stem will be withdrawn by the crank arm  34 . It will also be noted that the elongated stem  12  can be rotatable about its longitudinal axis during such reciprocating motions.  
         [0035]    In order to generate a combined longitudinal reciprocating motion along the axial direction as well as a reciprocating rotational motion of the brush head  10  about the longitudinal axis of its elongated stem  12  so that the plane of the brush head can be turned automatically to follow the curvature of the gum while performing the longitudinal reciprocating motions, a motion transforming means is provided between the brush head  11  and the motion generating means. The motion transformation means in the present embodiment includes a generally hollow collar member  41  which is received within the neck portion  21  of the main housing  20  at a location intermediate between the brush head and the connection member  37 .  
         [0036]    Referring to the Figures, it will be noted that the collar member  41  includes a hollow cylindrical body having a peripheral wall extending generally in the longitudinal or axial direction. A pair of longitudinally extending radial flanges are provided on the collar member  41  to prevent rotation of the collar member  41  inside the neck portion.  
         [0037]    The elongated stem  12  of the brush head  10  is slidably received within the hollow portion of the collar member  41  so that the collar member  41  surrounds different portions of the elongated stem  12  during the longitudinal motions of the elongated stem  12 . In general, the collar member  41  is disposed intermediate between the distal end of the elongated stem and the lower side of the brush head  10 . In order to provide a gradual and automatic alignment or turning of the plane of the bristle holder  11  about the longitudinal axis of the elongated stem  12  while the elongated stem  12  is undergoing reciprocating motions along the longitudinal axis, guiding means are formed on the collar member  41 . In the present specific embodiment, the guiding means include at least a guiding track  45  which extends along the longitudinal direction as well as transversally so that the resulting guiding track  45  is non-parallel to the longitudinal axis of the motor shaft  32  or the axis of the main housing  20 .  
         [0038]    Tracking means are provided on the elongated stem  12  so that the elongated stem  12  can follow the shape of the guiding path formed by the guiding means to cause turning of the brush head  10  about the longitudinal axis. The tracking means in the present specific embodiment includes a pair of studs extending radially from the elongated stem  12 . The studs are preferably closely fitted within the guiding tracks  45  to permit close and accurate tracking of the gradual longitudinal and transversal variation of the path during longitudinal movements. A helical spring  46  is disposed on the elongated stem  12  between the lower end of the collar member  41  and the upper end of the connection member  37 . The compression in this spring  46  helps to maintain the longitudinal disposition of the collar member  41  relative to the neck portion  21 . Also it may provide additional assistance for the elongated stem  12  to return towards the handle portion when the crank arm  34  retreats towards the motor end.  
         [0039]    The operation of the toothbrush of the present invention will be further explained by reference to FIGS.  5 - 7  below. In these drawings, the plane of the brush head  10  relative to the elongated arm  12  has been twisted by 90° for convenient explanation by reference to the moving parts as shown in the Figures. In the following description, reference to the front section of the housing  22  means the part of the housing that has been removed to expose the moving parts. The phrases “left” and “right” sides of the handle refer to the respective sides of the handle when viewing from the front portion of the housing and out of the drawing page.  
         [0040]    Referring to FIG. 5, it will be noted that the tracking means formed on the elongated stem is disposed at about the middle portion of the guiding track  45  formed on the collar member. This corresponds to a position at which the bristles are generally perpendicular to the front portion of the main housing. When the motor shaft  32  rotates so that the crank arm  34  is moved downwards towards the motor, as shown in FIG. 6, the tracking means formed on the elongated stem  12  will be moved downwards towards the lower end of the guiding track  45 . When this movement is complete, the skewness or the transversal component of the tracking slot has caused the plane of the brush head  10  to move towards the right side of the handle.  
         [0041]    When the motor shaft  32  continues to rotate, the crank arm  34  will reverse direction and push the elongated stem  12  to move upwards. At the same time, the angular direction of rotation of the brush head reverses and the brush head  10  will be restored to the previous position of FIG. 5 when the tracking means returns to the middle portion of the tracking slot. At this instant, the plane of the brush head  10  is substantially parallel to the front portion of the main housing  22 . Further rotation of the motor shaft will drive the elongated stem  12  further upwards and, at the same time, the co-operative movement between the tracking means along the guiding tracks  45  will result in simultaneous and gradual rotation of the plane of the bristle holder towards the left side of the front portion of main housing  22 , as shown in FIG. 7.  
         [0042]    Of course, the plane of the brush head can be aligned in a different manner so that the correlation between the angle of the plane of the brush head and the main housing can be varied or even reversed. Thus, by utilizing a collar member having tracking means disposed between the brush head and the connection member, a purely longitudinal reciprocating motion can be transformed into a combined longitudinal and rotational motion respectively along and about the axis to enhance performance of the toothbrush by providing automatic alignment of the plane of the bristle so that the plane of the bristles can be substantially perpendicular to the plane of the teeth to be brushed. It will be noted that when the connection member is moved upwards, the helical spring will be compressed.  
         [0043]    When the connection member is moved upwards to the bristle holder as a result of further rotational movement of the motor shaft, the stored compression of the compressed spring  46  will help to return the elongated stem downwards to prepare for the next upward movement.  
         [0044]    In the present specific embodiment, the tracking slot is generally inclined to the longitudinal axis at a substantially constant inclination. It will of course be appreciated that the slot or guiding tracks can be made into different curvatures, for example, concavely or convexly, to suit the appropriate turning rate of the plane of the bristle head. It will be appreciated that although the guiding means of the present specific embodiment define a path which gradually diverges from the longitudinal axis of the elongated stem  12  as the path extends towards the bristle holder, the guiding means can be designed to form a convergent path towards the brush head instead.  
         [0045]    While the present invention has been explained by reference to the preferred embodiments described above, it will be appreciated that the embodiments are only examples provided to illustrate the present invention and are not meant to be restrictive on the scope and spirit of the present invention. The scope of this invention should be determined from the general principles and spirit of the invention as described above. In particular, variations or modifications which are obvious or trivial to persons skilled in the art, as well as improvements made on the basis of the present invention, should be considered as falling within the scope and boundary of the present invention. Furthermore, although the present invention has been explained by reference to a specific embodiment of utilizing a collar member formed with guiding tracks for motion transformation, it should be appreciated that the invention can apply, whether with or without modification, to other forms of electric toothbrushes with different forms of motion transformation means to achieve the desirable combined longitudinal and rotational motion along and about the same longitudinal axis without loss of generality.