Abstract:
Discloses a bristle head oscillation mechanism for an electrically driven toothbrush. A toothbrush bristle head is rotatably disposed at an end of an elongate housing. A drive shaft is rotatably disposed in the elongate housing and has an offset end coupled to one end of a pivot arm. The other end of the pivot arm is coupled to the toothbrush bristle head. Rotation of the drive shaft pivots the pivot arm to effect oscillation of the bristle head with respect to the elongate housing.

Description:
FIELD OF THE INVENTION 
     This invention relates to electrically operated toothbrushes and more particularly to an oscillating head mechanism for an electrically operated toothbrush. 
     BACKGROUND OF THE INVENTION 
     Electrically operated toothbrushes provide a device for cleaning teeth that has a mechanized bristle head which is operable to effect motion between the bristle head and the handle of the toothbrush to provide a scrubbing action to the teeth to which the bristle head is applied. Electrically operated toothbrushes provide a range of motions between the bristle head and the toothbrush handle to augment the scrubbing action the bristle heads apply to the teeth which are to be cleaned by the toothbrush. 
     Electric toothbrushes provide an oscillating motion to the bristle head have been described in the prior art including, for example, in U.S. Pat. No. 5,625,916 to McDougall. The disclosure of McDougall describes an electrically driven toothbrush having an oscillating head that is operable by rotation of a rotating shaft coupled to the head which is driven by an electric motor. The mechanism of McDougall provides a limited range of oscillation to the bristle head. Because the bristles extending from the bristle head of a toothbrush are flexible, the motion or movement of the portion of the other end of the bristles in contact with the teeth of a user is reduced from the motion imparted to the bristles by the bristle head. To promote cleaning of the teeth of a user, it is desirable to have an efficacious relative motion or scrubbing contact of the toothbrush bristles to the teeth and gum tissues of the user. Because of bristle flexibility, a limited range of motion of a bristle head can result in bristle end immobilisation when the toothbrush bristles are applied to the teeth or gums of a user. Bristle end immobilisation in has the undesirable result of an inefficacious rocking motion of the toothbrush bristle ends relative to the tooth and oral surfaces that are sought to be cleaned. 
     It is desirable to provide a range of motion of a toothbrush bristle head of an electric toother brush that facilitates a brushing action to be applied by the toothbrush bristles when engaged with the teeth and oral surfaces to be cleaned. 
     It is an object of the present invention to provide an electrically operable toothbrush with an oscillating bristle head driven through an efficacious range of motion relative to the toothbrush handle. 
     In one of its aspects, the invention provides a bristle head oscillation mechanism for an electrically driven toothbrush comprising an elongate housing having a drive shaft rotatably mounted therein. A bristle head is rotatably disposed at an end of the elongate housing and coupled to a pivot arm pivotable about a pivot axis depending from the housing. Opposing ends of the pivot arm are coupled to the drive shaft and to the bristle head respectively. Rotation of the drive shaft pivots the pivot arm to effect oscillation of the bristle head with respect to the elongate housing. 
     The preferred embodiments of the invention will now be described with reference to the accompanying drawings in which the same reference numerals are used to describe like features of the invention throughout the various figures of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation view of an electric toothbrush incorporating features of the invention. 
     FIG. 2 is a front elevation view of a bristle head assembly portion of an electric toothbrush incorporating features of the invention. 
     FIG. 3 is a side elevation of the bristle head assembly of FIG.  2 . 
     FIGS. 4 a ,  4   b  and  4   c  are cross-sectional views of a preferred embodiment of the bristle head assembly taken along cutting line  4 — 4  of FIG.  3 . 
     FIGS. 5 a  and  5   b  are side elevation views exemplifying rotation orientations of the drive elements of a preferred embodiment of the present invention. 
     FIG. 6 is a cross-sectional view of a preferred embodiment of the bristle head assembly of the present invention taken along cutting line  6 — 6  of FIG.  2 . 
     FIG. 7 is an enlarged view of a preferred embodiment of a preferred embodiment of a pivot lever; and 
     FIG. 8 is an elevation view of a bristle head. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an elevation view of an electric toothbrush generally referenced by reference numeral  10 . The electric toothbrush has a handle portion  12 , which houses the toothbrush prime mover elements including an electric motor, shown in ghost outline form  13 , and a power source, typically, a battery, shown in ghost outline form  15 . The toothbrush  10  has a power switch  14  conveniently located on the device to control activation of the electric motor. The electric toothbrush includes a bristle head assembly  16  extending from an end of a handle portion  12  of the electric toothbrush. Generally, the bristle head assembly  16  is removably mountable on handle portion  12  of the electric toothbrush to facilitate replacement. The end of bristle assembly  16  remote from the handle portion  12  has a bristle head  18 , which provides a mount for a plurality of bristle clusters  20  that the user applies to the teeth and oral surfaces to be cleaned. 
     FIG. 2 is a front elevation view of the bristle head assembly  16  which has a mount coupling  22  adapted to releasably engage the handle portion  12  of the electric toothbrush providing mechanical coupling between the bristle head assembly and the handle. When needed, for example, when bristles  20  become worn, a new bristle head assembly  16  can be mounted on the handle portion  12  to maintain optimal operation of the electric toothbrush. FIG. 3 is a side elevation view of the bristle head assembly  16  of FIG.  2 . 
     FIGS. 4 a ,  4   b  and  4   c  are cross-section views of the backside of the bristle head assembly  16 . Each respective FIG. 4 a ,  4   b  and  4   c  shows a different rotational position of drive shaft  24  and related drive apparatus to depict the rotating effect and consequent oscillating rotational displacement of the bristle head  18  in relation to the bristle head assembly  16 . An end of drive shaft  24  includes an engagement coupling  26  that is adapted to mate with a rotating drive output of the prime mover in the handle  12  of the electric toothbrush  10  when the bristle head apparatus  16  is mounted thereon. In operation, drive shaft  24  is driven in rotation by the prime mover drive motor assembly and during the course of the rotation of drive shaft  24 , it will rotate through the three orientations or positions shown in FIGS. 4 a ,  4   b  and  4   c  of the drawings. The end of drive shaft  24  remote from engagement coupling  26  is coupled to pivot arm  30 . In the preferred embodiment, drive shaft  24  has an off set end  28  adapted to couple to a mating pivot drive slot  40  formed in an end of pivot arm  30 . In operation, rotation of drive shaft  24 , causes pivot arm  30  to rotate in an oscillatory motion about a pivot axis  32 , depicted in the drawings of the preferred embodiment as an axle extending from pivot arm  30 . In the position shown in FIG. 4 a , the offset end  28  is rotated to a position corresponding to maximum clockwise rotation of pivot arm  30  about pivot axis  32 . The end of pivot arm  30  remote from the offset  28  is coupled to the bristle head  1   8 . In the preferred embodiment, coupling of the pivot arm  30  to bristle head  18  is effected by a drive pin  34  that engages a head drive slot  36  of bristle head  18  resulting in an oscillatory rotating motion imparted to bristle head  18  by coupling engagement with pivot arm  30 . 
     FIG. 4 b  shows respective orientations of the apparatus of the bristle head assembly in another rotation orientation of drive shaft  24 . Further rotation of drive shaft  24  from the orientation of FIG. 4 a  to the orientation of FIG. 4 b  causes the drive shaft offset end  28  to rotate pivot arm  30  into an axially parallel relationship between pivot arm  30  and drive shaft  24 . From the drive shaft rotation orientation of FIG. 4 b , further rotation of drive shaft  24  will result in the respective orientations of the apparatus of the bristle head assembly to be arranged as depicted in FIG. 4 c . In the orientation of FIG. 4 c , the drive shaft offset end  28  rotates pivot arm  30  in the counter-clockwise direction from the position of FIG. 4 b  to the most counter-clockwise point of rotation as depicted in FIG. 4 c . Continued rotation of drive shaft  24  will cause the drive shaft offset end  28  to return to the substantially parallel relationship of FIG. 4 b . In this manner, rotation of drive shaft  24  causes bristle head  18  to rotate about head pin  38  in an oscillatory fashion. The direction of rotation of the drive shaft  24  is immaterial to the manner of operation of the invention. While the foregoing description with reference to the rotation of the drive shaft  24  has been in sequence from FIGS. 4 a ,  4   b  and  4   c , it will be understood that the opposite rotational direction is equally applicable. That is, a reverse rotational direction of drive shaft  24  to sequence the bristle head assembly apparatus through FIGS. 4 c ,  4   b  and  4   a  will also effect oscillatory rotation of bristle head  18  with respect to bristle head assembly  16 . 
     To facilitate oscillation of bristle head  18  consequent on pivoting movement of pivot arm  30 , head drive slot  36  is dimensioned to correspond substantially to the width of drive pin  34  in one cross sectional dimension, namely, in the dimension circumferential to said bristle head. In the orthogonal cross sectional dimension, namely the dimension radial to said bristle head, head drive slot  36  has a length sufficient to accommodate radial displacement of drive pin  34  consequent on the movement of bristle head  18  through the operating range of oscillation. The operating range of oscillation is depicted in FIGS. 4 a ,  4   b  and  4   c.    
     FIGS. 5 a  and  5   b  show the moving elements of the preferred embodiment of the invention and FIG. 6 shows a side cross-section view of the bristle head assembly taken along cutting line  6 — 6  of FIG.  2 . 
     FIG. 7 is a side elevation view of the pivot arm shown generally by reference numeral  30 . Drive shaft  24  is coupled to an end of pivot arm  30 . Coupling of drive shaft  24  to pivot arm  30  is preferably effected by providing a pivot drive slot  40  in pivot arm  30  dimensioned to receive a drive shaft engagement element  44  extending from the offset end  28 . Pivot drive slot  40  has a width substantially corresponding to the width of drive shaft engagement element  44  and has an upper and lower extremity  42  defining a length to accommodate the vertical travel of the engagement element  44  during rotation of drive shaft  24 . The engaging element  44  may extend parallel to the axis of drive shaft  24  or may be angled. If engagement element  44  is angled, it is preferably angled to correspond with the angular displacement of pivot arm  30  at the outermost clockwise or counter-clockwise angular displacement of the pivot arm about pivot axis  32 . The angular displacement of the arm  30  about pivot axis  32  is shown in FIGS. 4 a  and  4   c . If the engagement element  44  is angled, upper and lower extremities  42  of slot  40  may also be provided with a correspondingly angled inclination to that of the engagement element  44 . 
     As shown most clearly in FIG. 7, the relative lengths A and B, of the drive end  46  and driven end  48  respectively of the pivot arm  30  may be varied. The relative lengths of the drive end and driven end of pivot arm  30  control the oscillation range of angular displacement of bristle head  18 . In the preferred configuration, length B is greater than length A. In the configuration of the preferred embodiment, the lever action of pivot arm  30  enables the limited range of angular displacement that offset  28  is capable of imparting to drive end  46  of pivot arm  30  to be translated into a larger range of angular displacement that driven end  48  is capable of imparting to bristle head  18 . In this arrangement, oscillating angular displacement of bristle head  18  to include rotations efficacious for cleaning teeth or oral surfaces with pliable bristles, including various pliabilities such as soft, medium or hard bristles, can be readily obtained. 
     FIG. 8 shows a side elevational view of a preferred embodiment of the bristle head  18 . The bristle head  18  has a head pin  38  for rotating engagement with a corresponding mating hole  39  (see FIG. 6) of the bristle head assembly  16 . Securing means, preferably in the form of a groove  50  and corresponding mating engaging seat  52  provided in the mating hole  39  of the bristle head assembly  16 , retaining the bristle head  18  on the bristle head assembly. Head slot  48  is provided at a radial distance C from the head pin  38  as required to obtain optimal rotational displacement of bristle head  18  about head pin  38  during operation of the tooth brush. The radial distance C is located to facilitate an optimal torque to be applied to the bristle head  18  by the prime mover of the electric toothbrush to effect efficacious cleaning in the oscillation of the bristle head  18 . Increasing the radial distance C that head slot  40  is from head pin  38  will increase the torque that can be applied to bristle head  18  for a given power output of the toothbrush prime mover but with consequent decrease in rotational displacement of bristle head  18 . Conversely, decreasing the radial displacement distance C that head slot  40  is from head pin  38  will decrease the torque applied to bristle head  18  for a given power output of the toothbrush prime mover but with a consequent increase in the angular displacement of the bristle head  18 . 
     Now that the invention has been described with reference to the preferred embodiments disclosed here and in the drawings, numerous substitutions and mechanical equivalents will occur to those skilled in the art. The invention is not limited to the exact structure and embodiments depicted herein, but rather is defined in the claims appended hereto.