Abstract:
An electrical dentifrice dispensing toothbrush using a replaceable bristle unit with a permanent drive head and handle is described. The replaceable bristle unit consists of a rotary bristle element and a stationary bristle element that has an opening for the flow of dentifrice material through the drive head. The bristle unit is snap-on latched to the side walls of the drive head. Opposing tabs which also function as pressure sensors on the bristle unit are pressed toward each other to release the bristle unit. A linkage is used to convert the rotation of the drive shaft to a planar oscillation that enables a compact drive head configuration. The dentifrice dispensing is accomplished by using a rotary solenoid for actuating an internal button that applies pumping pressure to the dentifrice material. As a benefit to arthritis suffers, no external squeezing action is involved.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    It has been recognized that an electrical toothbrush is more effective in removing plaque and preventing gum disease than a conventional manual toothbrush. It is also well known that the manual squeezing action of dentifrice dispensing presents a significant challenge to severe arthritis suffers who lack finger dexterity and strength. Thus a total-electrical toothbrush is desirable for everyday dental care and a necessity for the physically challenged. Oral hygiene requires that toothbrush bristles should be replaced on a regular basis for maintaining bristle effectiveness and minimizing bacteria buildup. While the entire toothbrush can be replaced, it is desirable to discard only the part having bristles and retain the drive mechanism and the brush handle as permanent parts for minimizing the replacement costs. For long service life of the permanent parts, all wearable parts need to be included in one replacement unit. For the ease of replacement, it is desirable to have a replaceable snap-on bristle unit for fastening on a permanent drive head containing driving components. For the convenience of portability, it is desirable to have a self-contained, dentifrice dispensing electrical toothbrush for brushing anywhere at anytime. For the ease of operation especially for the physically challenged, it is desirable simply to press on an electrical switch for the automatic dispensing of dentifrice material to the top of the bristles. The objects of this invention are to achieve all of the above desirable features in one electrical toothbrush.  
           [0002]    (1)Field of the Invention  
           [0003]    The present invention relates to electrical dentifrice dispensing toothbrushes with a replaceable bristle unit.  
           [0004]    (2)Prior Art  
           [0005]    It is recognized in the prior art that electrical toothbrushes which have oscillatory brush elements are more effective than toothbrushes with rotating brush heads. The reciprocating movement and wiping action of the bristles provides an effective means for plaque removal. U.S. Pat. No. 4,326,314 by Moret and Jousson describes a means for oscillating a brush head through an oscillating shaft which is connected to a cam riding on a biased wheel mounted on the shaft of a motor. Since the source of vibration is at the cam and the motor which is usually located in the handle, a strong vibration may cause discomfort during brushing.  
           [0006]    To minimize the vibration at the handle, U.S. Pat. No. 5,625,916 by McDougall provides a means for converting rotary motion to oscillatory motion near the brush head area which is remote to the motor. It uses a bent remote-most end of a shaft having rotary motion to engage with a slot formed on the side of a bristle holder to force it to oscillate back and forth as the bent remote-most end is driven in a circular annular path. While it achieves relocation of the vibration source to the brush head, the central axis of the bent remote-most end is required to intersect with the central axis of the brush head. This requirement precludes its application from simultaneously driving two brush heads since the same central axis of the remote-most end of a shaft cannot intersect two separate central axes in its circling positions. Also, its use of a closed ended slot on the side of the brush head for engagement also prevents the remote-most end from reaching more than one brush head.  
           [0007]    Owing to its complex assembly, the entire neck including the brush head, the mounting base and the drive shaft assembly are replaced when the brush head is changed.  
           [0008]    U.S. Pat. No. 5,784743 by Shek uses an off-set finger mounted at the end of a rotating shaft for engaging the fork of a pivotally supported wobble plate which is meshed with a gear for oscillating a brush head. The use of the closed end fork and the blocking of the extension of the finger by the pivoting and gear-meshing mechanism prohibit its application to oscillate two brush heads. Similarly, the replacement of the whole neck including the drive shaft is required when the brush head is replaced.  
           [0009]    The prior art has also recognized that the brushing area is broadened and the brushing time reduced when two brush heads are used instead of one. For oscillating two brush heads, U.S. Pat. No. 5,353,460 by Bauman uses an oscillating shaft to drive one brush head and utilizes a linkage between the two brush heads to drive the other brush head. The linkage requires a pivoting post on each brush head which adds an increased friction load to the drive mechanism for oscillation of the brush heads. U.S. Pat. No. 5,099,536 by Hirabayashi uses two shafts aligned at different angles. The gearing mechanism allows for driving more than one brush head but its drive mechanism does not cause oscillatory motion. In order to change the brush head, each of the above two patents also requires replacing the neck connected to the brush head which includes part of a drive shaft assembly.  
           [0010]    A description of an electrical toothbrush which dispenses liquid is provided in U.S. Pat. No. 5,321,866 by Klupt. The patent discloses a delivery means for a cleaning liquid through oscillating brush heads. A motor is connected to a series of gear mechanisms causing a drive shaft to oscillate and a piston to pump the liquid through a flow conduit to openings in the brush head. Because it is connected to the same motor, the motorized piston pumps the liquid continuously while the brush heads are oscillating. This common drive mechanism is not desirable for dispensing material that only needs to be dispensed prior to the brushing action.  
           [0011]    A dentifrice dispensing electric toothbrush of U.S. patent application Ser. No. 09/649074 by Kuo mounts a pair of rotary bristle elements on a pair of posts attached to a brush head and uses a retention cradle for keeping the two rotary bristle elements in free-to-rotate positions. The neck of the toothbrush includes a channel which is part of the flow path for dentifrice material that is pumped from the cartridge to the brush head. The pumping is achieved by using an elastic compressible button positioned on the external surface of the brush handle for manually supplying a pumping force to pump dentifrice and for simultaneously activating a switch positioned inside the brush handle to energize the motor. Although only the bristle elements and the retention cradle are replaced, the posts which are subject to wear from the oscillation motion remain on the brush head. A worn post can cause wobbling of oscillating bristle element and noise that results in reduced service life of the toothbrush. Also, catch arms used in the retention cradle are only for keeping the bristle elements in place in packaging, not required in the operation of the toothbrush. Furthermore, the elevated position of the cradle platform from the bristle base is a barrier for the free brushing motion and running of cleaning water. As for dentifrice dispensing, the requirement of manual squeezing on the compressible button on the handle is a major hindrance for a severe arthritis suffers who lack of finger dexterity and strength.  
           [0012]    In view of the deficiencies as exemplified in above patents in the prior art, there is a pressing need for an electrical dentifrice dispensing toothbrush that can provide permanent drive head and handle with minimal replacement of bristle parts, and a pumping means that does not require manual squeezing action for dispensing the dentifrice material.  
         SUMMARY OF THE INVENTION  
         [0013]    This invention provides an electrical toothbrush that satisfies the needs for less throw-away, easy replacement of bristle elements and high cleaning efficiency. It also provides an electrical means of dispensing dentifrice material from a cartridge attached to the brush head for the convenience of users in general and especially for severe arthritis sufferers who have difficulty in the manual squeezing action of dispensing toothpaste. The replaceable bristle unit which is mounted on a permanent drive head consists of a rotary bristle element, a staionary bristle element, and a detachable snap-on platform which has a post for supporting the free-rotation of the rotary bristle element. The mounting of the rotary bristle element on the post is un-detachable as detachment is prevented by the engagement of the annular groove in the bushing of the bristle element and the protruding rim of the post with 90 degree detent angle. All the wearable parts are included in the replaceable bristle unit and the driver components, including the drive shaft, remain in the permanent drive head and the body of the electrical toothbrush. The replaceable bristle unit is locked to the drive head through the engagement of its latch arms with the latch recesses on the side walls of the drive head. The latch arms are released for replacing the bristle unit by applying an opposing force on the tabs that are on the opposite ends of the latch arms which are hinged on the edges of the detachable platform. The tabs are optionally layered with rubber material and positioned below the bristle surface and for protecting gums from excessive brushing pressure. The replaceable bristle unit of present invention may have two rotary bristle elements or a combination of a rotary and a stationary bristle element. For achieving the use of the minimal disposal bristle unit with a compact drive head, the present invention optionally employs an oscillation conversion linkage for converting the rotational motion of a drive shaft at the input end to a planar oscillation in the output end for driving the rotary bristle element. The planar oscillation motion reduces the height requirement (in the bristle direction) for the drive head.  
           [0014]    The present invention also includes an electrical dentifrice dispensing toothbrush which uses a replaceable bristle unit and an electrical means of delivering dentifrice material from a cartridge in the handle to the top of bristles. To achieve these functions, the detachable platform of the replaceable bristle unit has an opening for slidably mounted on the wall of a spout opening extending from the top of the drive head. The delivery of the dentifrice material is achieved by using a toothbrush neck having two separated channels. One channel houses the drive shaft and the other channel functions as part of the flow path for the dentifrice material as it is pumped from the handle to the brush head. The electrical pumping mechanism includes a switch, a rotary solenoid, and a plunger in contact with a resilient compressible button. The activation of the switch causes the rotary solenoid to move the plunger to press on the resilient compressible button for applying pressure to force dentifrice material to flow to the top of the bristles. Through a control mechanism, release of the switch causes the rotary solenoid, the plunger, and the elastic button back to their original home positions and accordingly the follower inside the cartridge advances to keep the dentifrice material inside the cartridge at a packed condition for next pumping action.  
           [0015]    The replaceable bristle unit of present invention is applicable to dual rotary bristle elements, a combination of rotary and stationary bristle elements, or a combination of rotary and dentifrice dispensing bristle elements.  
           [0016]    The essential components of the electrical toothbrush include 1) a handle which serves as a housing for a motor, batteries and a cartridge containing dentifrice material; 2) a replaceable bristle unit having a rotary bristle element with a drive notch and a detachable platform having latch arms; 3) a drive head having a driver component that engages with the drive notch of the bristle element and latch recesses on its side walls for locking with the latch arms of the detachable platform; 4) a neck which connects the handle and the drive head; 5) a drive mechanism that is driven by a motor and imparts an oscillatory motion to the driver component in the drive head. The electrical dentifrice dispensing. toothbrush also includes; 6) a series of flow path components including a spout in the drive head, a flow channel in the neck, a pump chamber, a one-way valve and an internal resilient compressible button; 7) an electrical actuation mechanism including a switch, a rotary solenoid, and a plunger which presses on the resilient compressible button for dispensing the dentifrice material when the switch is actuated; 8) a refillable dentifrice cartridge. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 a  is a cross section view of a drive mechanism for an electrical toothbrush having a replaceable bristle unit.  
         [0018]    [0018]FIG. 1 b  is an enlarged cross section side view of the drive mechanism; and the replaceable bristle unit shown in FIG. 1 a.    
         [0019]    [0019]FIG. 2 a  is a cross section side view of an oscillatory bristle element.  
         [0020]    [0020]FIG. 2 b  is a cross section side view of a snap-on bristle platform.  
         [0021]    [0021]FIG. 2 c  is a cross section side view of a drive head.  
         [0022]    [0022]FIG. 3 a  is a perspective view of a drive head.  
         [0023]    [0023]FIG. 3 b  is a cross section view along  3   b - 3   b  of the drive head shown in FIG. 3 a.    
         [0024]    [0024]FIG. 4 a  is a perspective view of an oscillatory bristle element.  
         [0025]    [0025]FIG. 4 b  is a perspective view of a snap-on bristle platform having two posts.  
         [0026]    [0026]FIG. 4 c  is a perspective view of a replaceable bristle unit with two oscillatory bristle elements.  
         [0027]    [0027]FIG. 4 d  is a perspective view of a post.  
         [0028]    [0028]FIG. 5 a .is a perspective view of a snap-on bristle platform having a post and an area having an array of bristle planting holes (not illustrated).  
         [0029]    [0029]FIG. 5 b  is a perspective view of a replaceable bristle unit having an oscillatory bristle element and an array of stationary bristles.  
         [0030]    [0030]FIG. 6 a  is a side view of a drive head showing a latch recess on a side wall.  
         [0031]    [0031]FIG. 6 b  is a side view of the mounting of a replaceable bristle unit having latch arms locked on the drive head.  
         [0032]    [0032]FIG. 6 c  is a top view of the replaceable bristle unit having notches and openings on the opposing edges of the detachable platform.  
         [0033]    [0033]FIG. 7 a  is a cross-section view of a replaceable bristle unit.  
         [0034]    [0034]FIG. 7 b  is a cross section view of a drive head having an oscillation linkage with an elbow-shaped lever.  
         [0035]    [0035]FIG. 7 c  is a cross section view of the mounting of a replaceable bristle unit on a drive head.  
         [0036]    [0036]FIG. 8 a  is an illustration of the engagement between a drive shaft, bristle elements and an oscillation linkage shown in FIG. 7 c.    
         [0037]    [0037]FIG. 8 b  is a perspective view of the oscillation linkage shown in FIG. 8 a.    
         [0038]    [0038]FIG. 9 a  is a cross section view of the mounting of a replaceable bristle unit on a drive head having an oscillation linkage with a straight lever.  
         [0039]    [0039]FIG. 9 b  is an illustration of the engagement between a drive shaft and the oscillation linkage shown in FIG. 9 a.    
         [0040]    [0040]FIG. 10 a  is a cross section view of a dentifrice dispensing electrical toothbrush with the pumping actuator in the non-dispensing position.  
         [0041]    [0041]FIG. 10 b  is a cross section view of a dentifrice dispensing electrical toothbrush with the pumping actuator in the dispensing position.  
         [0042]    [0042]FIG. 11 a  is a perspective view of a snap-on bristle platform having a post and a through hole located in an array of bristle planting holes.  
         [0043]    [0043]FIG. 11 b  is a perspective view of a replaceable bristle unit having an oscillatory bristle element and an array of stationary bristles with a dentifrice conduit therein.  
         [0044]    [0044]FIG. 11 c  is an enlarged cross-section view of the mounting of the replaceable bristle unit as shown in FIG. 11 b  on a drive head having a flow conduit as shown in FIGS. 10 a  and  10   b.   
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0045]    [0045]FIG. 1 a  shows an electrical toothbrush  2  having a handle  4  and a drive head  10  connected by neck  6 . Replaceable bristle unit  13  having bristle elements  8  and  9  detachably mounted on drivehead  10 . Motor  12  and batteries  50  are positioned within handle  4 . Leaf spring contact  54  is situated at the end of battery  50  and switch  52  extends through an opening in the base of the handle. Batteries  50  are connected to motor  12  by contact  46 . Drive shaft  16 , having a central longitudinal axis with first end and second end, is positioned in neck  6 . Drive shaft  16  and motor  12  are connected by an U-Shaped cam assembly  22 , which imparts an oscillating motion to the drive shaft through the engagement of its first end  18  with bias wheel  14  mounted on motor  12 . Mounted on second end  20  of the drive shaft is an oscillation driver which is drive tab  34  on the base of cap  26  having a recess for the mounting. Drive tab  34  extends radially outward from the central longitudinal axis of drive shaft  16  and oscillates within a limited angle in concert with drive shaft  16 . As explained below, drive tab  34  in turn imparts its oscillating motion to bristle elements  8  and  9  which increases brushing efficiency. The principle operation of an oscillatory electrical toothbrush is known in the prior art and a detailed description of the drive mechanism as shown in FIG. 1 a is given in the Patent Application Series No. 09/649074 by Kuo.  
         [0046]    As shown in FIG. 1 b,  FIG. 2 a  and FIG. 4 a , a plurality of bristles  76  are attached to the top surface of base  84  of first bristle element  8 . Notch wall  92  with drive notch  90  is appended to side wall  88  of bristle base  84 . The underside of bristle base  84  has split bushing walls  85  which are shaped to mate with first post  86  of platform  72 . When mounted, notch walls  92  are positioned and extended beyond first slot  63 . First slot  63  is of segmented circular annular shape with inner edge  97 , shown in FIG. 2 b , having equal radial distance from the central axis of first post  86 . Drive notches  90  of first and second bristle elements  8  and  9  accommodates drive tab  34  such that when drive tab  34  is positioned in drive notch  90 , the oscillating motion of drive tab  34  causes first and second bristle elements  8  and  9  to freely oscillate on first and second posts  86  and  87  respectively. Advantages of having a pair, of matching bushing and post in, one replaceable bristle unit are that both bushing and post are wearable and undergoing the same dimensional variation under the same usage environment and duration. Replacing the bristle element and the detachable platform with the post at the same time avoids possible dimensional mismatch which may occur when replacing with a new rotary bristle element on a used post. The following provides more detailed descriptions of the structures and functions of an electrical toothbrush of the present invention.  
         [0047]    A replaceable bristle unit  13  is comprising first and second bristle elements  8  and  9  and platform  72 . Platform  72  is attachable to and detachable from drive head  10  (shown in FIGS. 3 a  and  3   b ), which permits the removal and replacement of bristle elements  8  and  9 . A, pair of opposing tabs  58  extend from the top surface of platform  72 . Portions of tab  58  overlap portions of arms  60  and are configured in a manner such that inward deflection of tabs  58  toward each other causes outward deflection of opposing arms  60  and their disengagement from drive head  10 .  
         [0048]    [0048]FIG. 2 a ,  2   b  and FIG. 4 d  show the mounting of first and second rotary bristle elements  8  and  9  on first and second posts  86  and  89  respectively. The one-way engagement of bristle base  84  of bristle element  8  on post  86  is enabled by the mounting of two half-circle-shaped split bushing walls  85  on the underside of bristle base  84  on two half-circle-shaped split shaft walls  91  (FIG. 4 d ) of post  86 . Gap  95  between the split walls  85  allows wall deflection apart from each other while gap  97  of post  86  allows for deflection of its split walls  91  toward each other. Each bushing-wall  85  is of cantilever configuration extending from the underside of bristle base that provides flexibility for outward deflection for accommodating the insertion of the post. On the other hand, each split shaft-wall  91  of post  86  is also of cantilever configuration extending from the platform  72  that enable further ease of insertion inside the bushing walls  85 . For preventing disengagement, first post  86  has retention rim  100  on each split shaft wall and the flexible bushing has annular groove  101  (FIG. 2 a ) on each split bushing wall at corresponding mating positions. The diameter of retention rim  100  of post  86  is smaller than the diameter of annular groove  101  engaged therein but is larger than the inner diameter of bushing walls  85 . Also, the nominal inside diameter of bushing walls  85  is slightly larger than the diameter of post  86  for establishing a clearance between the post and the bushing for the free rotation of the bristle element. Besides, both the underside lower edge  103  (FIG. 2 b ) of retention rim and the corresponding edge  105  (FIG. 2 a ) of the annular groove are right-angle (90 degree) with respect to their rotational axis. This configuration prevents bristle base dislodged from the post. The beveled surfaces at the free end of flexible busing wall is for facilitating the insertion of the beveled top surface of the post. The engagement dimensions including lengths, diameters and wall gaps of the mating pair of a bushing and a post are designed for enabling free rotation, ease of mounting and preventing dislodgment of the bristle element. The orientation of the gap  95  (FIG. 2 a ) between the two split walls of the bushing is at right-angle (90 degree) with respect to the symmetry plane (crossing the axis of the bushing) of notch walls  92 , while the orientation of gap  97  between two split walls of the post is aligned with the symmetric plane (crossing the post) of the drive head. As the maximum oscillation angle of notch walls is less than 90 degree from the symmetric plane of the snap-on platform, the oscillation motion of the bushing walls  85  does not cause its split gap  95  to overlap with the split gap  97  of post  86 . The smoothness of oscillation motion of bristle base  84 , therefore, is not affected by the presence of two gaps  95  and  97 . Furthermore, for enhancing the retention of the bristle element when oscillating, rib  93  is added to a notch wall&#39;s inner surface facing the central axis of the bushing. The radial distance of outer surface of a notch wall  92  from the central axis of bushing is smaller than the radial distance of outer edge  99  of first slot  63  from first post  86 . But the radial distance of inner edge  89  of rib  93  is smaller than that of inner edge  97  of first slot  63  such that rib  93  has an interference with inner edge  97  of slot  63  when first bristle element  8  is fully mounted on post  86 . However, in the mounting of first bristle element, the flexibility of the bushing walls  85  allows deflections of the bushing walls against first post  86  and slight tilting of the bristle element for inserting notch walls  92  in a slanted orientation to slide into slot  63  and then upright itself in mounting on the post with the central axis of bushing walls  85  coincide with that of first post  86 . The height of rib  93  with respect to bottom surface  73  of platform  72  when rib  93  is at the mounted position is determined in a manner that the clearance between rib  93  and bottom surface  73  of platform  72  enables free oscillation of bristle element  9 . The two interference features as described, e.g. between rib edge  89  and slot edge  97 , and between post rim  100  and bushing groove  101 , provides an effective retention means to ensure sufficient retention force for preventing the detachment of a bristle element from the post being mounted at high speed oscillation. During brushing, the brushing pressure pushes the bristle element against the post, therefore, the bristle element cannot detach from the post under the brushing condition. Alternatively, a retention means can be the engagement between ribs attached at the end of bushing walls and annular grooves created on shaft walls of a post.  
         [0049]    Moreover, when bristle element  9  is latched in position, a clearance between the top surface of the platform  72  and the bottom surface of the bristle element allows for the free oscillation of the bristle element on post  87 . In manufacturing, because of the small protrusions of retention rims  100  from the post walls and the shallow annular recess  101  of the bushing walls as well as the flexibility of cantilever structures, these undercut features can be injection molded. The detachable platform and the two mounted bristle elements forms a replaceable bristle unit for locking on the drive head. Further referring to FIG. 4 b  and  4   c , for integrating the locking feature to the detachable platform, two notches  59  are provided on each side of two opposing latch arms  60  which are positioned at the middle of each opposing edge  71  of platform  72  for enabling the deflection of the latch arms  60 . In addition to adding flexibility of the latch arms  60 , through hole  57  positioned next to the inner edge of each latch arm is for the creation of the inward retention rib  64  at the end of latch arm  60  by the injection molding process.  
         [0050]    For mounting of a replaceable bristle unit, the, drive head of the present invention as shown in FIG. 3 a ,  3   b  consists of the drive head base having side walls including latch recesses  65 , a top  69  having periphery edge  67  and oscillation first and second slots  63  and  63 ′ which are for accommodating notch walls  92  of rotary bristle elements  8  and  9  respectively. Drive tab  34  situated in recess  35  is in communication with the drive motor contained in the handle of the electrical toothbrush. Referring to FIGS. 2 b ,  2   c , peripheral inner rim surface  68  on the underside (bottom) of snap-on platform  72  matches with the corresponding peripheral edge surface  67  of the top  69 .  
         [0051]    The platform features as described for the mounting of two rotary bristle elements in FIGS. 4 a ,  4   b ,  4   c  and  4   d  are applicable to a replaceable bristle unit having a rotary bristle element and a stationary bristle element. FIG. 5 a  shows a detachable platform having split post  86  and oscillation slot  63  for the mounting of bristle element  8 , bristle area  117  having an array of molded-in tuft holes (not shown) for implanting bristles :of stationary bristle element  119  and latch arms  60  for latching to the drive head of an electrical toothbrush. The detachable platform also has a rim wall as a locating feature for snug fitting on the peripheral edge of the drive head, which is similar to the detachable platform of the dual rotary bristle elements as described previously.  
         [0052]    [0052]FIG. 6 a ,  6   b  and  6   c  show external views of the mounting of replaceable bristle unit  13  on a drive head  10 . Latch recess  65  on side wall of drive head  10  as shown in FIG. 6 a  is mated with rib  64  (shown in FIG. 4 b ) at bottom end of latch arm  60  of detachable platform  72  of replaceable bristle unit  13  which has dual rotary bristle elements  8  and  9  as shown in FIG. 6 b . The width, thickness, depth, and position of inward extending ribs  64  are designed for mating with the corresponding dimensions of latch recesses  65  on each side of drive head  10  with tight tolerances for secure engagement. Furthermore, the height of each opposing tabs  58  is designed for making tabs  58  as pressure sensors by which a user reduces the brushing pressure when a tab touches teeth or gum during brushing and that the tabs are coated with rubber layers for cushioning and protecting gums. FIG. 6 c  shows the top view of the mounting of replaceable bristle unit  13  on drive head  10 .  
         [0053]    [0053]FIGS. 7 a ,  7   b  and  7   c  show a low-profile compact drive head of present invention for mounting replaceable bristle unit  13  having two rotary bristle elements  8  and  9 . The oscillation driver of low-profile drive head  219  is an oscillatory conversion linkage  233  for converting circular cam-motion at input end of the linkage to a planar oscillating motion at the output end. As shown in FIGS. 8 a  and  8   b  oscillation conversion linkage  233  consists of a pair of notch walls  230  at the input end, a swing arm  238  at the output end, and a stud shaft  234  extending from linkage lever  232  that connects the input end and the output end. Stud shaft  234 , which is supported by bushing  236  as shown in FIG. 7 c  attached to drive head base  240 , functions as a pivot point for the oscillation of linkage  233 . Drive notch  290  formed between two parallel notch walls  230  at input end  230  is engaged with offset rod  234  of cam  226  mounted on the second end of the drive shaft  216 , which is directly coupled to motor  212  in a manner such that the central longitudinal axis of offset rod  234  is parallel to and offset from the central longitudinal axis of drive shaft  216 .  
         [0054]    Rotation of drive shaft  216  and cam  226  cause movement of offset rod  234  in drive notch  290  in a manner that it imparts an oscillating motion to lever  232  against stud shaft  234 , which is inserted in bushing  236  on the inner surface of bottom wall  240  of drive head base  219 . Lever  232  and stud shaft  234  transmits the rotational motion of the drive shaft  216  into planar oscillating motion of swing arm  238  in a plane parallel to that of platform  72 . Through the engagement with the notches of the two bristle elements  8  and  9  which face each other, swing arm  238  transmits the oscillation motion to bristle elements. The use of the planar oscillating motion as input for driving the oscillation of the bristle elements reduces the functional height (in the axial direction of stud shaft) required for the drive head as compared to the non-planar oscillation of drive tab  34  used in FIG. 1 a.  It also enables the use of parallel contact surfaces for the swing arm in the areas engaging with the notch walls of the bristle element for reducing the contact pressure, therefore, prolongs the service life of the linkage lever. Besides, the planar oscillation does not exert lifting force on the notch walls that tends to separate a rotary bristle element from a post.  
         [0055]    Furthermore, structurally the length of notch walls  230  is sufficient to enable the inner surface of the notch wall to remain in contact with the offset rod  234  during a full 360 degree rotation of drive shaft  216 . The width of notches  290  is the same as the diameter of offset rod  234 . The inner surfaces of the notches are rounded to reduce friction and minimize the clearance between the offset rod and the drive notches. In addition, linkage lever  232  on the input end is of elbow shape configuration  244  enabling the creation of rim wall  246  on the top  248  of drive head  219  for snug fitting with the inner surface of rim wall  68  of platform  72  which supports two rotary bristle element  8  and  9 . In manufacturing, the oscillation conversion linkage may be injection molded either of high strength and wear-resistant plastic material or of metal, in which all corners are rounded. Besides, rim wall  246  provides peripheral structure support and sealing surface similar to the function of edge surface  67  as illustrated in FIG. 3 a . When the bristle unit is detached, the recess area of the drive head is exposed for cleaning if needed.  
         [0056]    For a replaceable bristle unit using combined rotary and stationary bristle elements as shown in FIG. 5 a  and  5   b , the elbow-shaped configuration  244  of linkage lever  232  as shown in FIG. 8 is replaced by a straight configuration. FIG. 9 a  shows the mounting of the replaceable unit of rotary and stationary bristle elements  8  and  119 ′ on drive head  219 ′ having oscillation linkage  233 ′ with straight lever  232 ′ as shown in FIG. 9 b . Oscillation linkage  233 ′ having straight lever  232 ′ consists of swing arm  238 ′ at the output end, notch walls  230 ′ at the input end, bushing through hole  235  positioned between the two ends for accommodating stud shaft  234 ′ which extends from the underside of top wall  249  of drive head  219 ′. Referring to FIG. 9 b , the input end has parallel notch walls  230 ′ forming notch  290 ′, which is engaged with offset rod  234  of cam  226  of drive shaft  216 . The width of notch  290 ′ is the same as the diameter of offset rod  234 . The length of notch walls  230  is sufficient to enable the inner surface of the notch wall to remain in contact with offset rod  234  during a full 360 degree rotation of drive shaft  216 . With bushing hole  235  engaged with stud shaft  234 ′ which extends from the inner surface of top  249 , straight lever  232 ′ converts the rotation motion of drive shaft  216  to planar oscillation of swing arm  238 ′. Since stationary bristle element  119 ′ is used, output swing arm  238 ′ of the linkage engages only with the drive notch of the rotary bristle element  8  and causes it to have angular oscillation. Because of the straight arm configuration of the linkage, drive head  219 ′ has lower profile than that using an elbow-shaped oscillation linkage.  
         [0057]    The replaceable bristle unit structure of the present invention is also applicable to a dentifrice-dispensing toothbrush such as that shown and described in U.S. Pat. No. 5,909,977 by Kuo. A dentifrice-dispensing electrical toothbrush of the present invention integrates a replaceable bristle unit having a spout opening with an electrical means to dispense the dentifrice material stored in the reservoir of the handle to the top of bristles through the spout opening. As shown in FIGS. 10 a  and  10   b,  dentifrice-dispensing electrical toothbrush  402  has handle  404 , neck  406  and replaceable bristle unit having bristle elements  408  and  409  mounted on drive head  410 . Neck  98  has two chambers that are separated by partition  110 . Channel  100  contains the drive shaft  416  while flow channel  102  provides the flow path for dentifrice material from the pump chamber  94  to bristle element  409 . Similar to FIG. 1 a,  U-shaped cam  22  is positioned between one end of drive shaft  416  and motor  412 . Cap  426  with drive tab  434  is attached to the second end of drive shaft  416 . Motor  412  is powered by battery  450  which is stored in handle  404 . Dentifrice containing cartridge  124  having follower  126  is detachably mounted in handle  404 . Dentifrice material is pumped from pump chamber  94 , through channel  102  and spout opening  114 , to bristle element  409 . The delivery of dentifrice material is achieved using an electrical-mechanical actuator that consists of rotary solenoid  456 , cam  454 , and plunger  452  for contacting on resilient compressible button  96  as shown in FIG. 10 a,  which shows these components at the non-dispensing home positions. Upon activating rotary solenoid  456  by pushing on button switch  460  positioned on the external surface  468  of handle  404 , cam  454  which is mounted on the shaft of the rotary solenoid  456  rotates 180 degree from the non-dispensing home position to move plunger  452  forward to depress on compressible button  96  to the fully compressed dispensing position. The compression of the resilient compressible button provides the pumping force to push the dentifrice material to the bristle areas through the spout opening. FIG. 10 b  shows cam  454 , plunger  452  and resilient compressible button  96  at the dispensing positions. Then upon the release of button switch  460 , through a control circuitry (not shown) rotary solenoid  456  is energized to cause cam  454  to return to the home position, at which point the resiliency of the compressible button  96  not only restores the compressible button to its original position but also causes the plunger to move backward to the home position. During the recovery of the resilient compressible button to its original shape, the vacuum created in chamber causes dentifrice material to flow from cartridge  124  through one way check valve  122  and into chamber  94  to replace the quantity of dentifrice material removed from the pumping force. The flow of dentifrice material from cartridge  124  causes advancement of follower  126  at the base of the cartridge. Repeated actuation of switch button  460  can pump additional dentifrice material to the top of bristle element  409 . Although the use of a rotary solenoid is preferred, the actuation of the plunger for compressing on the elastic button can be achieved by linear solenoid or a clutch connected to motor  412 .  
         [0058]    Also shown in FIG. 10 a , while post  106  of rotary bristle element  410  has split walls as described previously, post  108  is hollow and in communication with flow channel  100  and terminates at opening  114  forming spout  115 . The outer wall of spout  115  is part of post  108 . Platform  121  mounted with bristle elements  8  and  120  as shown in FIG. 11 b  is detachably secured to drive head  410  as shown in FIG. 11 c,  which is an enlarged view of the drive head as shown in FIGS. 10 a  and  10   b,  by latch arm  60  and rib  64 . Referring to FIG. 11 a,  in addition to an array of tuft holes for stationary bristle element  120 , platform  121  has opening  112  which is shaped to mate with hollow post  108 . When replaceable bristle unit  401  is mounted on drive head  410 , opening  112 , spout  115 , and channel  102  are aligned to provide a continuous path for dentifrice material to flow from chamber  94  to the bristles of bristle element  120 .  
         [0059]    When all of the dentifrice material is depleted from cartridge  124 , the cartridge is removed from the handle and replaced by a full cartridge. Cartridge  124  is fastened by threads to one way check valve  122  and retained in position by holding arms (not shown) which are part of the outside wall of the handle. The partial exposure of the cartridge facilitates cleaning of the handle wall when the cartridge is replaced. Sealing of spout opening  114  of the dentifrice dispensing electrical toothbrush is similar to that described in U.S. Pat. No. 5,909,977 by Kuo.  
         [0060]    The invention has been described in detail with reference to preferred embodiments thereof. However, it is understood that variations and modifications can be effected within the spirit and scope of the invention.