Abstract:
A head for a toothbrush has a motion directing assembly structured for rotating a first set of bristles in an oscillating motion through an arc of rotation about a central rotational axis while simultaneously moving the first set of bristles in a linear reciprocating motion generally parallel to the central rotational axis. In further embodiments, a second set of bristles is moved as well, and in an oscillating motion through an arc of rotation about the same central rotational axis as the first set of bristles, in the opposite rotational direction, while simultaneously moving in a linear reciprocating motion in the opposite linear direction relative to the first set of bristles, such that as one set of bristles is moving inwardly, the other set of bristles is moving outwardly relative to the brush head. In further embodiments, multiple first and second sets of bristles are arranged in pairs, wherein the first and second sets of bristles in each pair are driven in both the oscillating motion and linear reciprocating motion, in opposite directions relative to one another.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to electric toothbrushes and, more particularly, to an electric toothbrush providing dual action bristle motion and, more specifically, oscillating motion of bristles about an arc of rotation and simultaneous reciprocating motion of the bristles away from and back towards the toothbrush head to create a pumping-type action for effectively cleaning tooth surfaces and inter-proximal crevices between teeth.  
         [0003]     2. Discussion of the Related Art  
         [0004]     The benefits of brushing one&#39;s teeth using motorized toothbrushes are well known, and motorized movement in toothbrushes has been the subject of much recent innovation and design activity. Also, the commercial market has seen the introduction, over the last several years, of many different types of motorized toothbrushes. However, an examination of the available technology shows a tendency toward increasingly complex, expensive, and non-commercially feasible methods of achieving motorized motions in the bristles and heads of toothbrushes to aid in more effectively cleaning one&#39;s teeth.  
         [0005]     The commercial marketplace has become divided into two price markets. On the higher priced end are some of these more complex motorized toothbrushes that provide various motions to the bristles and brush head. The lower end of the market has become the province of very simple motorized toothbrushes that only vibrate through the use of an offset weight attached to the motor shafts and which provide very little true additional cleaning benefit with their use, since no vigorous motion is transmitted to the cleaning surface of the brush. The vibrations are also very uncomfortable to the hand and act to discourage brushing one&#39;s teeth for an adequate period of time.  
         [0006]     Numerous electric toothbrushes have been developed over the years. Some known devices are shown in U.S. Pat. Nos. 5,070,567; 5,186,627; 5,274,870; 5,341,534; 5,378,153; 5,732,433; and 6,360,395. The disadvantage of these devices is that bristles lack an up and down movement relative to the brush head and therefore perform less than optimal in cleaning tooth surfaces. Another disadvantage is that these devices lack bristle arrangement to clean hard-to-access crevices between teeth. The device shown in U.S. Pat. No. 6,574,820 discloses an embodiment in which an inter-dental probe moves up and down relative to a second set of bristles. This embodiment provides enhanced cleaning of the crevices between tooth surfaces. However, the disadvantage is that the inter-dental probe does not rotate (thereby does not provide the benefits of bristle twisting motion). Another disadvantage is that the second set of bristles does not move up and down (thereby does not provide the additional cleaning benefits resulting from a pumping up-and-down oscillating motion of bristles on tooth surfaces). Accordingly, it has been considered desirable to develop a new and improved electric toothbrush which would overcome the foregoing difficulties and others while providing better and more advantages.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention is directed to a toothbrush head which provides a dual action bristle motion, including an oscillating motion and a simultaneous linear reciprocating motion of at least one set of bristles. In several preferred embodiments, the brush head is adapted for use with an electric toothbrush having an elongated body with a hollow interior defining a housing. The elongated body includes a handle portion, a head and a neck extending between the handle portion and the head. A motor contained and supported within the handle portion is disposed in driving engagement with a drive assembly. The drive assembly includes a swivel arm arrangement having a distal end disposed within the head portion of the elongated body. The swivel arm arrangement is operatively driven by the motor to move the distal end in a reciprocating motion. A bristle member is fitted to the head portion of the elongated body and is movable about a central rotational axis.  
         [0008]     The bristle member includes a first portion movably captivated within the interior of the head portion of the housing, and a second portion disposed on an exterior of the bottom face of the head. The second portion of the bristle member includes a bristle support structure with a first set of bristles extending outwardly therefrom and arranged in a generally circular pattern about the central rotational axis. A motion directing assembly is structured and disposed for moving the bristle support structure and the attached first set of bristles in an oscillating motion through an arc of rotation about the central rotational axis. The motion directing assembly is further structured for simultaneously directing the bristle support structure and the attached first set of bristles in a linear reciprocating motion away from and back towards the bottom face of the head portion and generally parallel to the central rotational axis.  
         [0009]     In several further embodiments of the invention, a second set of bristles is movably supported on the head portion and the motion directing assembly is structured and disposed for simultaneously moving both the first set of bristles and the second set of bristles, wherein both sets of bristles oscillate in opposite directions about the central rotational axis, while simultaneously moving in the linear reciprocating motion. When moving in the linear reciprocating motion, the first set of bristles moves in the opposite direction to the second set of bristles so that when the first set of bristles is raised towards the head, the second set of bristles is lowered away from the head, and when the first set of bristles is lowered away from the head, the second set of bristles is raised towards the head.  
         [0010]     In still further embodiments of the invention, multiple first and second sets of bristles are provided and arranged in corresponding pairs, with each pair consisting of a first set of bristles and a second set of bristles. The first and second sets of bristles in each pair are driven by the motion directing assembly in both the oscillating motion and linear reciprocating motion, in opposite directions, in a manner similar to the previously described embodiments.  
         [0000]     Objects and Advantages of the Invention  
         [0011]     It is a primary object of the present invention to provide a controlled and predetermined oscillating up-and-down motion of bristles in a motorized toothbrush, thereby creating a pumping-type action to effectively clean tooth surfaces and access difficult-to-reach crevices between the teeth.  
         [0012]     It is a further object of the present invention to provide a motorized toothbrush with two sets of bristles moving in an up-and-down manner (in opposite directions from one another) while oscillating/rotating (in opposite directions from one another) and wherein the first set of bristles extends to its maximum length to effectively penetrate crevices between the teeth while the second set of bristles withdraws to its minimum length to allow the first set of bristles to achieve maximum penetration and further where the first set of bristles withdraws to its minimum length while the second set of bristles extends to its maximum length to effectively clean tooth surfaces.  
         [0013]     It is still a further object of the present invention to provide a motorized toothbrush with two sets of bristles and wherein the bristle sets are moved in an alternating up-and-down action while each oscillating set of bristles rotates, thereby providing a unique and superior cleaning action that targets both tooth surfaces and inter-proximal crevices between teeth.  
         [0014]     Other objects, features, and advantages of the invention will become apparent upon reading the following detailed description in conjunction with the accompanying drawings. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0015]     For a fuller understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which:  
         [0016]      FIG. 1  is a perspective view in accordance with the first preferred embodiment of the present invention;  
         [0017]      FIG. 1B  is an exploded view illustrating relation of disk with brush head floor;  
         [0018]      FIG. 1C  is a front view illustrating the bristles in an up position;  
         [0019]      FIG. 1D  is a front view illustrating the bristles in a down position;  
         [0020]      FIG. 2A  is an exploded view illustrating relation of disk with top of brush head;  
         [0021]      FIG. 2B  is an exploded view of alternate embodiment illustrating relation of disk with top of brush head;  
         [0022]      FIG. 3  is a side view illustrating relationship of disk with wall of brush head;  
         [0023]      FIG. 4A  is an exploded view illustrating relation of disk with brush head floor;  
         [0024]      FIG. 4B  is a side view of disk illustrating position of protruding feet;  
         [0025]      FIG. 4C  is a bottom plan view of brush head floor;  
         [0026]      FIG. 4D  is a front view with bristle in an up position;  
         [0027]      FIG. 4E  is a front view with bristle in a down position;  
         [0028]      FIG. 6C  is a front view illustrating first set of bristles in an up position and second set of bristles in a down position;  
         [0029]      FIG. 6D  is a top plan view;  
         [0030]      FIG. 6E  is a bottom plan view;  
         [0031]      FIG. 6F  is an exploded view;  
         [0032]      FIG. 7  is an exploded view;  
         [0033]      FIG. 8A  is an exploded view;  
         [0034]      FIG. 8B  is a top plan view;  
         [0035]      FIG. 8C  is a front sectional view taken along line  8 C- 8 C in  FIG. 8B ;  
         [0036]      FIG. 8D  is a side view;  
         [0037]      FIG. 9A  is a top plan view;  
         [0038]      FIG. 9B  is a front view;  
         [0039]      FIG. 9C  is a side view illustrating relation of rack with drive gears;  
         [0040]      FIG. 10A  is a perspective view;  
         [0041]      FIG. 10B  is a top plan view;  
         [0042]      FIG. 10C  is a front view;  
         [0043]      FIG. 10D  is a side view. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0044]      FIG. 1  illustrates an electric toothbrush  100  which has an elongated body  30 . A first end  27  of the elongated body  30  has a head  23  and the opposite second end  32  defines a handle  33 . The elongated body portion  30  further includes an angled neck  29  which is located between the head  23  and the handle  33 . Angled shaft  29  is parallel with the longitudinal axis  39  of the elongated body portion  30 . The elongated body portion  30  also includes a hollow portion  31  which houses a motor  1 . The motor  1  provides power to the bristle supporting structure  24  to rotate in an oscillating action. Power is provided to the motor by a battery (not shown).  
         [0045]     A first gear  2  is operatively connected to and powered by the motor  1 . The first gear  2  rotates about the longitudinal axis  39 . A second gear  4  is operatively connected to the first gear  2 . The second gear  4  is approximately normal to the first gear  2 . The second gear  4  is preferably a bevel gear and rotates about an axis approximately perpendicular to the longitudinal axis  39 . Teeth  3  of the first gear  2  mesh with teeth  5  of the second gear  4  causing second gear  4  to rotate when first gear  2  rotates.  
         [0046]     A swivel arm arrangement is linked between the second gear  4  and the bristle supporting structure  24 . In a preferred embodiment, the swivel arm arrangement includes a first swivel arm  7 , a second swivel arm  9  and a third swivel arm  16 . The first swivel arm  7  is pivotally connected to the second gear  4  via a pin  6 . The second swivel arm  9  is pivotally connected to the first swivel arm  7  via a pin  8 . A shaft  12  is fixedly secured at a shaft first end  10  to the second swivel arm  9 . The shaft  12  is pivotally attached at a shaft second end  28  to the third swivel arm  16 . The shaft  12  is housed within the angled neck  29  and is generally parallel with the longitudinal axis  39 .  
         [0047]     A guide spacer  11  is located within the angled shaft  29  and surrounds the shaft  12  adjacent the first end  10  of the shaft  12  to minimize lateral movement of the shaft  12 . A second guide spacer  13  is located adjacent the second end  28  of the shaft  12  to also minimize lateral movement of the shaft  12 . Guide spacers  11 ,  13  align the shaft  12  within the angled shaft  29  and minimize its movement from side to side within the angled shaft  29 .  
         [0048]     The third swivel arm  16  has a first end  15  and a second end  18 . The third swivel arm  16  is pivotally connected to the second guide spacer  13  at the first end  15  via a pin  14 . The third swivel arm  16  is connected at the second end  18  to the bristle supporting structure  24  via a pin  19 . The pin  19  is connected to a disk  21  of the bristle supporting structure  24  which is housed within the head  23 .  
         [0049]     As the first gear  2  rotates, the second gear  4  is rotated, thus moving the lower end of first swivel arm  7  in a circular fashion about the circular path of movement of pin  6  as the opposite upper end of the first swivel arm  7  moves in a linear reciprocating motion generally along the longitudinal axis  39 . The first swivel arm  7  retains its orientation of approximately parallel to the longitudinal axis  39  of the elongated body portion  30  during movement. The second swivel arm  9  pivots with respect to its pin connection  8  with the first swivel arm  7  thus allowing the shaft  12  to reciprocate in a back and forth manner toward and away from the brush head with minimal lateral motion.  
         [0050]     During operation, the third swivel arm  16  moves back and forth along the longitudinal axis  39  of the elongated body portion  30  along with the shaft  12 . The third swivel arm  16  has an offset arm  17  which is offset from the longitudinal axis  39  and moves the disk  21  of the bristle supporting structure  24  in a partially rotating or oscillating motion. As the third swivel arm  16  moves back and forth, the offset arm  17  moves along an outside edge  20  of the disk  21  in a partially rotating or oscillating fashion about an axis which is approximately normal to the longitudinal axis  39 . This causes the bristles  25  to also move in a partially rotating or oscillating manner about a central rotational axis  102  approximately normal to the longitudinal axis  39 . When the third swivel arm  16  moves back and forth, the disk  21  rotates about the central rotational axis  102 . The third swivel arm  16  also retains its orientation of approximately parallel to the elongated body portion longitudinal axis  39  during movement.  
         [0051]     The head  23  has a first end  26 , a second end  22  and a bottom plate  34 . The bristle supporting structure  24  is movably fitted to the head  23  and extends through the bottom plate  34 . The bristle supporting structure  24  oscillates about the central rotational axis  102  and has bristles  25  which extend outwardly and generally parallel to the central rotational axis  102 . Referring to  FIGS. 1B, 1C  and  1 D the swivel arm  16  is pivotally attached to a rotatable disk  21  by a pin  19 . When the swivel arm  16  moves back and forth, bristle member  101  is rotated and counter-rotated. A solid threaded cylinder  38  is attached to disk  21  at one end and to a circular bristle supporting structure  24  at the opposite end. Tufts of bristles  25  are arranged in a circular pattern on bristle supporting member  24 . A hollow cylinder  35  (having threads  36  on its internal walls) is attached to bottom plate  34  of brush head  23 . Central axis of disk  21 , cylinder  38  bristle supporting structure  24  and cylinder  35  is the same. When the disk  21  rotates, threads  37  on solid cylinder communicate with internal threads  36  in hollow cylinder  35  and cause bristles  25  to move up and down (relative to the bottom plate  34  brush head  23 ) while oscillating through an arc of partial rotation.  FIG. 1C  illustrates the bristles  25  in an “up” position with the swivel arm  16  pulled back.  FIG. 1D  illustrates the bristles  25  in a “down” position with the swivel arm  16  extended and end of swivel arm  18  pivotted down while disk  21  is in a rotated position.  
         [0052]     A second preferred embodiment is illustrated in  FIG. 2A . A threaded solid cylinder  41  is attached to the top plate  40  of the brush head  23 . A hollow cylinder  42  (having threads  36  on its internal walls) is attached to the disk  21 . When swivel arm  16  (not shown) moves back and forth, disk  21  rotates and counter-rotates. When the disk  21  rotates threads  37  on the solid cylinder  41  communicate with threads  36  in the hollow cylinder  42  to cause the bristles  25  to move up and down while oscillating through an arc of rotation about central rotational axis  102 .  FIG. 2B  illustrates an alternative arrangement in which a hollow cylinder  44  is attached to top plate  40  of brush head  23  and has threads  38  in its internal walls. A solid cylinder  45  is attached to disk  21  and has threads  37  on its external walls. When disk  21  is rotated, bristles  25  move up and down (while oscillating/rotating) when the threads  37  communicate with threads  38 .  
         [0053]     A third preferred embodiment is illustrated in  FIG. 3 . The outer edge of rotatable disk  21  has threads  46 . The inside wall of brush head  23  also has threads  47  adapted to communicate with the threads  46  of the rotatable disk  21 . When swivel arm  16  (not shown) moves back and forth disk  21  rotates and counter-rotates. When the disk  21  rotates and counter-rotates, bristles  25  move up and down while oscillating through an arc of rotation about the central rotational axis  102 .  
         [0054]     A forth preferred embodiment is illustrated in  FIGS. 4A, 4B ,  4 C,  4 D, and  4 E. Referring to  FIGS. 4A and 4C  protruding ramps  49 , located on the top surface of the bristle supporting structure  24 , slide in and out of grooves  50  located on bottom surface of floor  34  of brush head  23 . When the disk  21  is rotated and counter-rotated, protruding ramps  49  slide in and out of grooves  50  and force the bristle supporting structure  24  to move up and down in a linear reciprocating motion. A spring  48  lifts bristle supporting structure  24  toward bottom surface  34 .  FIG. 4D  illustrates the bristles  25  in an “up” position where the ramps  49  are entirely fitted into grooves  50  and the spring  48  is in its relaxed state.  FIG. 4E  illustrates the bristles  25  in a “down” position where disk  21  is rotated, the ramps  49  have moved out of grooves  50 , and the spring  48  is in its compressed state. Accordingly, as the disk  21  is rotated and counter-rotated by movement of the swivel arm assembly, the bristle supporting structure and bristles  25  are moved in the oscillating motion through an arc of rotation about the rotational axis  102 , while simultaneously moving in the linear reciprocating motion parallel to the central rotational axis  102 .  
         [0055]     A fifth preferred embodiment is illustrated in  FIG. 5A . Swivel arm  16  is attached to a toothed rack  53 . Rack  53 , generally parallel to swivel arm  16 , moves back and forth when the swivel arm  16  moves back and forth. Teeth  54  on rack  53  communicate with teeth  52  on spur gear  51  to cause gear  51  to rotate and counter-rotate when the rack  53  moves back and forth. The gear  51  is attached to a hollow cylinder  38  having threads  36  on its internal walls. Hollow cylinder  38  is attached to bristle-supporting structure  24  at one end and couples with threaded solid cylinder  41  at opposite end. When the gear  51  is rotated and counter-rotated, threads  37  of solid cylinder  41  communicate with threads  36  on hollow cylinder  38  to move the bristles  25  up and down while simultaneously oscillating about an arc of rotation on the central rotational axis  102 . An alternative arrangement is illustrated in  FIG. 5B . A hollow cylinder  35  has threads  36  on its internal walls and is attached to floor  34 . A solid cylinder  38  having threads  37  on its walls is attached to gear  51  at one end and bristle supporting structure  24  at the opposite end. When rack  53  moves back and forth, threads  37  communicate with threads  36  and cause bristles  25  to move up and down while simultaneously oscillating through the arc of rotation about the central rotational axis  102 .  
         [0056]     A sixth preferred embodiment is illustrated in  FIGS. 6A-6F . In this embodiment, swivel arm  16  is attached to a structure having two parallel toothed rack arms (first rack arm  58  and second rack arm  60 ). First rack arm  58  is laterally offset from the second rack arm  60 . Teeth  59  of first rack arm  58  are adapted to communicate with teeth  63  of an upper spur gear  62  and to engage the upper gear  62  in order to rotate and counter-rotate the gear  62  about the central rotational axis  102  when the rack arm  53  moves back and forth. Teeth  61  of second rack arm  60  are adapted to communicate with teeth  52  of the lower spur gear  51  to engage the lower gear  51  to rotate and counter-rotate on the same central rotational axis  102  when the rack arm  60  moves back and forth. A first hollow cylinder  55  having threads  37  on its external surface is attached to upper gear  62 . One end  79  of first set of tuft of bristles  56  is adapted to be permanently fitted into hole  80  of first hollow cylinder  55 . A second hollow cylinder  38  having threads  36  on its internal walls is attached to lower gear  51 . Circular bristle supporting structure  24  accommodating second set of bristles  25  is attached to second hollow cylinder  38 . When the swivel arm assembly moves back and forth, first and second rack arms ( 58  and  60  respectively) move back and forth and engage gears  51  and  62 , respectively, to rotate and counter-rotate (in opposite directions from one another), thereby causing first and second set of bristles  56  and  25 , respectively, to rotate and counter-rotate (in opposite directions from one another). Threads  36  and  37  on the cylinders ( 38  and  55  respectively) communicate to move up and down the first sets of bristles  56  while simultaneously moving up and down the second set of bristles  25  (in an opposite direction from the first set  56 ).  FIG. 6B  illustrates the first set of bristles  56  in a “down” position while the second set of bristles is in an “up” position. In this state, the first set of bristles  56  extends to its maximum length to penetrate interproximal crevices, while the second set of bristles  25  withdraws to its minimum length to allow the first set of bristles  56  to achieve its maximum penetration.  FIG. 6C  illustrates the first set of bristles  56  in an “up” position, while the second set of bristles is in a “down” position. In this state the second set of bristles  25  is projected to its maximum length to clean tooth surfaces, while first set of bristles  56  is withdrawn to its minimum length.  FIG. 6D  is a top plan view of the rack arms  58  and  60 .  FIG. 6E  is a bottom plan view illustrating the relationship between the first set of bristles  56  with cylinder  55 , bristle supporting structure  24 , and the second set  25 .  FIG. 6F  illustrates an alternative in which hollow cylinder  55  telescopically slides into hollow cylinder  38 . The threads  37  of solid cylinder  41  communicate with threads  36  of cylinder  55  to move the first set of bristles  56  in an up and down direction while rotating. Threads  96  of a hollow cylinder  35  communicate with threads  97  on external wall of cylinder  38  to move the second set of bristles  25  in an up and down motion while rotating.  
         [0057]     A seventh preferred embodiment is illustrated in  FIG. 7 . The swivel arm  16  has two side arms (first side arm  65  and second side arm  66 ) that are pivotally attached to swivel arm  16  thereby allowing end (that end which is attached to disks  64  and  21  respectively) of side arms  65  and  66  to move laterally up and down. First side arm  65  is pivotally attached to top disk  64  and is adapted to rotate and counter-rotate top disk  64  when it ( 65 ) moves back and forth. Second side arm  66  is pivotally attached to bottom disk  21  and rotates bottom disk  21  when it ( 66 ) moves back and forth. A hollow cylinder  38 , attached to lower disk  21 , has threads  36  on its internal walls. Solid cylinder  55 , attached to upper disk  64 , has threads  37  on its external walls. When swivel arm  16  moves back and forth, movement of side arms  65  and  66  causes upper and lower disks ( 64  and  21  respectively) to rotate (in opposite directions from one another). Threads  37  on solid cylinder  55  communicate with threads  36  on hollow cylinder  38  to move first and second set of bristles ( 56  and  25  respectively) up and down (in opposite directions from each other), while rotating about the central rotational axis  102  (in opposite directions from each other). An O-ring  99  is fitted within hole  43  to provide a seal between the hole  43  and cylinder  38 , thereby preventing entry of water and foreign material into the interior of the brush head  23  during operation.  
         [0058]     An eighth preferred embodiment is illustrated in  FIGS. 8A, 8B ,  8 C, and  8 D. Sets of bristles  56  are arranged in parallel rows on bottom plate  34  of brush head  23 . Swivel arm  16  moves back and forth to rotate a disk  70  which is attached to a drive gear  67 . The proximity and arrangement of adjacent spur gears  68  in relation to the drive gear  67  causes the adjacent gears  68  to rotate when the drive gear  67  rotates. A first hollow cylinder  55  attached to adjacent gears  68  has threads  37  on its external walls. A tuft of bristles  56  is permanently fitted into bottom of hollow cylinder  55 . A second hollow cylinder  36  having threads  35  on its internal walls is attached to floor  34  of the brush head  23 . Referring to  FIG. 8C  shaft end  87  of shaft  73  protruding from center of disk  70  fits into hole on top plate  40  to minimize sideway movement of drive gear  67  when the disk  70  rotates. Opposite end  74  of shaft  73  fits in hole  88  on bottom plate  34 . Refering to  FIG. 8A , a middle plate  69  has holes  72  positioned to allow shafts  71  extending from center of gear  68  to move up and down and provide alignment to the gears during rotation. Plate  69  has a large hole  90  to allow the drive gear to be inserted and positioned with adjacent gears  68  during assembly. When the adjacent gears  68  are rotated and counter-rotated threads  37  on the solid cylinder  55  communicate with threads  35  of the hollow cylinder  36  to move the tuft of bristles  56  up and down while rotating. Adjacent tuft of bristles  56  are in opposite (up or down) position.  FIG. 8B  is a top plan view with the top plate removed illustrating the relationship of the drive gear  67  with adjacent gears  68 .  FIG. 8C  is a sectional view taken along line  8 C- 8 C in  FIG. 8B  illustrating the disk  70 , drive gear  67 , adjacent gear  68  and plate  69 .  FIG. 8D  is a side view illustrating the drive gear  67  in relation to the adjacent gears  68  and the up or down positions of bristles  56 .  
         [0059]     A ninth preferred embodiment is illustrated in  FIGS. 9A, 9B , and  9 C. Swivel arm  16  is attached to a rack member  75  having teeth  91  on both sides. Teeth  91  on rack member  75  engage drive gears  92  to rotate when the rack member  75  moves back and forth. The proximity and arrangement of adjacent gears  68  cause adjacent gears  68  to counter-rotate when the drive gear  92  rotates. Referring to  FIGS. 9B and 9C  a hollow cylinder  93  attached to top plate  40  of the brush head  23  has threads  36  on its internal walls. A solid cylinder  95  having threads  37  on external walls is attached to gears  92  and  68 . Tuft of bristles  56  are permanently fitted into hollow cylinder  98 . When the rack  75  moves back and forth, drive gears  92  and adjacent gears  68  are rotated and counter-rotated. Threads  36  in the hollow cylinder  93  communicate with threads  37  on the solid cylinder  95  to move the bristles  56  up and down while rotating.  FIG. 9C  is a side view illustrating the rack  75  in relation to drive gears  92  and adjacent gears  68  and up and down positions of tuft of bristles  56 .  
         [0060]     A tenth preferred embodiment is illustrated in  FIGS. 10A, 10B ,  10 C, and  10 D. Pairs of tufts of bristles ( 56  and  25 ) are arranged in parallel rows on bottom plate  34  of brush head  23 . Referring to  FIGS. 10B and 10C  swivel arm  16  is attached to a rack-supporting structure having three parallel rack arms ( 81 ,  83 , and  82 ). The middle rack arm  83 , laterally offset from the two side rack arms ( 81  and  82 ), is adapted to engage the upper gears  62  to rotate when the rack arm  83  moves back and forth. The two side rack arms ( 81  and  82 ) are adapted to engage lower gears  52  to rotate when the rack arms ( 81  and  82 ) move back and forth. Referring to  FIGS. 10C and 10D  a first hollow cylinder  55 , attached to upper gear  62 , has threads  37  on its external walls, and is adapted to permanently fit first set of bristles  56  (designed to access interproximal crevices between teeth). A second hollow cylinder  38 , attached to lower gear  52 , has threads (not shown) on its internal walls. Bristle supporting structure  24  is attached to second hollow cylinder  38 . Second set of bristles  25  (designed to clean tooth surfaces) is attached to bristle supporting structure  24 . A shaft  71  protrudes from center of gear  62  and fits in hole in upper plate  40  to prevent sideway movements of gear  62  during rotation. When swivel arm  16  moves back and forth, middle rack arm  83  engages upper gears  62  to rotate and counter-rotate while both side rack arms  81  and  82  engage lower gears  52  to rotate and counter-rotate (in opposite direction of upper gear  62 ). Threads on the two cylinders ( 38  and  55 ) communicate to move the first set of bristles  56  up and down (in opposite direction of movement of second set of bristles  25 ) while rotating.  
         [0061]     While the present invention has been shown and described in accordance with various preferred and practical embodiments, it is recognized that departures from the instant disclosure are fully contemplated within the spirit and scope of the invention without limitation, except as set forth in the following claims as interpreted under the doctrine of equivalents.