WO2019138330A1

WO2019138330A1 - Electric toothbrush

Info

Publication number: WO2019138330A1
Application number: PCT/IB2019/050147
Authority: WO
Inventors: Lai Yung LAM
Original assignee: Life Works Products Limited
Priority date: 2018-01-09
Filing date: 2019-01-09
Publication date: 2019-07-18
Also published as: CN111818874B; CN111818874A

Abstract

A toothbrush attachment(100) for detachable attachment to a motor drive unit of an electric toothbrush, wherein the toothbrush attachment(100) comprises a main housing(110) comprising a tubular neck portion(213) having a longitudinal axis(X-X') and a head portion(215) defining a toothbrush receptacle(216), a toothbrush head(200) rotatably mounted on the toothbrush receptacle(216) of the head portion(215) and a rotatable brush axis(Z-Z '), and a drive coupling mechanism(280) mounted inside the neck portion(213) and having a rotation axis(Y-Y '); wherein the driving coupling mechanism(280) comprises a crank shaft(230), a bushing device(240) and a coupling shaft portion; wherein the coupling shaft portion comprises at an axial free end with an engagement means, wherein the crank shaft(230) is for driving the toothbrush head(200) to rotate reciprocally about the brush axis(Z-Z '), and wherein the coupling shaft portion and the crank shaft(230) are integrally molded together as a unitary member and the crank shaft(230) is rotatably mounted on the bushing device(240).

Description

ELECTRIC TOOTHBRUSH

Field

[0001 ] The present disclosure relates to the field of oral care apparatus, and in particular to electric toothbrushes. More specifically, the present disclosure relates to brush heads for electric toothbrushes.

Background

[0002] Electric toothbrushes provide a convenient, useful and effective alternative to manual toothbrushes. Typical modern day electrical toothbrushes comprise a motor drive base unit and a toothbrush attachment which is detachably attached to the base unit. A toothbrush attachment typically comprises a toothbrush head having a forward -facing surface which is to enter into brushing engagement with the teeth of a user and to rotate or vibrate against the teeth to facilitate teeth cleansing. Detachable toothbrush attachments are advantageous and facilitate replacement of brushing heads at regular intervals at reasonably low costs. The motor drive unit, often referred to as a drive unit or a handpiece, typically comprises a motor and a motor driven driving shaft which is to drive the toothbrush head into cleansing rotations. Cleansing rotations are typically reciprocating rotations about a rotation axis between a first rotation angle and a second rotation angle.

Disclosure

[0003] A toothbrush attachment for detachable attachment to a motor drive unit of an electric toothbrush is disclosed. The motor drive unit comprises a motor and a motor driven driving shaft which is to rotate reciprocally about a rotation axis of the driving shaft. The toothbrush attachment comprises a main housing comprising a tubular neck portion having a longitudinal axis and a head portion defining a toothbrush receptacle, a toothbrush head rotatably mounted on the toothbrush receptacle of the head portion and rotatable a brush axis, and a drive coupling mechanism mounted inside the neck portion and having a rotation axis. The drive coupling mechanism comprises a crank shaft, a bushing device and a coupling shaft portion. The coupling shaft portion comprises at an axial free end an engagement means which is adapted for making detachable coupled driving engagement with the driving shaft of the drive unit to receive rotational driving power from the driving shaft and to transmit the received rotational driving power to the crank shaft. The crank shaft is for driving the toothbrush head to rotate reciprocally about the brush axis, and wherein the coupling shaft portion and the crank shaft are integrally molded together as a unitary member and the crank shaft is rotatably mounted on the bushing device.

Figures

[0004] The present disclosure will be described by way of example and with reference to the accompanying figures, in which

Figure 1 is a perspective view of an example toothbrush attachment according to the present disclosure,

Figure 1 A is a perspective view of the example toothbrush attachment of Figure 1 with partial cut away,

Figure 1 B is a perspective view of the example toothbrush attachment of Figure 1 without the tubular housing,

Figure 2 is an exploded view of the example toothbrush attachment of Figure 1 ,

Figure 3 is a perspective view of a brush assembly in the example toothbrush attachment of Figure

1 ,

Figure 4 is a perspective view of semi-assembled toothbrush attachment of Figure 1 ,

Figure 5 is a cross-sectional view of the example toothbrush attachment of Figure 1 in engagement with the drive output end of an example electrical toothbrush drive unit,

Figure 6 is a perspective view of an example toothbrush attachment 200,

Figure 6A is an exploded view of the toothbrush attachment 200,

Figure 6B1 is a perspective view of the drive coupling assembly of the toothbrush attachment 200,

Figure 6B2 is a longitudinal cross-sectional view of the drive coupling assembly of Figure 6B taken along the fin-shaped portion,

Figures 7A and 7B are plan and side elevation views of the toothbrush attachment of Figure 6 with the brush head removed,

Figure 7A1 is a longitudinal cross-sectional view of the toothbrush attachment of Figure 7A viewed in direction A of Figure 7A,

Figures 7A2 and 7A3 are longitudinal cross-sectional views taken along a line E-E’ and viewed in the directions B and C of Figure 7B, respectively, Figures 8A and 8B are perspective and side views of another example drive coupling assembly,

Figure 8C is a cross-sectional view taken along a line F-F’ and viewed in the direction of the arrow of Figure 8B,

Figure 8D is a cross-sectional view taken along a line G-G’ and viewed in the direction of the arrow of Figure 8B, and

Figures 9A and 9B are assembled and semi-assembled views the bushing assembly to the crank member of the drive coupling assembly of Figure 8A.

Description

[0005] An example toothbrush 100 comprises a tubular housing 110 having a first longitudinal end 112 and a second longitudinal end 114, a brush assembly 120 mounted at the second longitudinal end of the tubular housing, and a drive mechanism 180 mounted inside the tubular housing and extending between the first and second longitudinal ends of the tubular housing, as depicted in Figure 1 . The example toothbrush 100 is a toothbrush attachment adapted for use with an electrical toothbrush drive unit (“drive handle”) having a drive output end, as depicted in Figures 1 A and 1 B. To prepare for tooth-brushing use, the toothbrush attachment is to be inserted into an axial end of the electrical toothbrush drive unit so that the drive mechanism is in mechanical coupling with a free axial end of the power output shaft 510 of the drive handle so that rotational or oscillatory motion of the motor output shaft is coupled to the drive mechanism 180 and the brush assembly 120.

[0006] The tubular housing 110 is rigid, elongate and extends along a longitudinal axis X-X’. The tubular housing has optionally a substantially circular cross-section and defines a substantially circular aperture along a substantial portion of its length. The tubular housing 110 has a first longitudinal end 112 (“ handle coupling end’) which is for making coupled engagement with an electrical toothbrush drive and a second longitudinal end 114 (“ bristle carrier end’) on which the brush assembly 120 is attached. The aperture defined by the hollow housing 110 defines a tapered through passageway for through passage of a drive mechanism for driving the bristle carrier. The cross-sectional size of the tubular housing 110 and the through passage defined therein gradually reduces as it extends from the handle coupling end 112 to the bristle carrier end 114.

[0007] A brush holder 116 is integrally formed as an integral extension to the tubular housing 110 and extends axially away from the second longitudinal end 114 of the tubular housing 110. The brush holder 116 comprises a housing which defines a brush receptacle having a receptacle axis. The receptacle axis is substantially orthogonal to the longitudinal axis of the housing in example embodiments such as the present. In example embodiments, the extension of the longitudinal axis X-X’ of the tubular housing projects into the receptacle and intercepts the receptacle axis. The brush holder 116 comprises a main peripheral wall which defines a receptacle compartment and an entry aperture to the receptacle compartment. The peripheral wall comprises an entry portion which extends about the brush receptacle axis to define a substantially circular entry portion. The entry portion is a collar portion having a collar wall defining an entry end. The entry end of the collar portion is a free end defining a top surface of the brush receptacle. The receptacle axis is also the center axis of the brush receptacle which is coaxial with a brush axis Y-Y’. The brush axis Y-Y’ intersects the longitudinal axis X-X’ and is orthogonal thereto in example embodiments such as the present. The brush assembly 120 is mounted on the brush receptacle and is rotatable relative to the brush receptacle about the brush axis Y-Y’.

[0008] The first longitudinal end 112 of the tubular housing 110 is a handle coupling end of the toothbrush attachment 100 and comprises a coupling neck. The coupling neck has an end surface at its longitudinal free end. The end surface defines a coupling plane and a coupling surface which is substantially parallel to the toothbrush axis Y-Y’ or which extends substantially orthogonally to the longitudinal axis X-X’. The coupling surface is to face the drive handle and in abutment contact therewith during use. The coupling neck defines an entry aperture through which a drive shaft 510 of the drive handle is to enter the tubular housing 110 to make mechanical engagement with the drive mechanism.

[0009] Referring to Figures 2 and 3, the brush assembly 120 comprises a bristle carrier 122 and a plurality of cleaning elements 125 mounted on the bristle carrier 122. The bristle carrier 122 comprises a bristle disc 124 and a coupling portion formed on one surface of the bristle disc 124 which is received inside the brush receptacle and not mounted with cleaning elements. The bristle disc is also known as a filament disc where the cleaning elements comprises tufts of bristle filaments. The plurality of cleaning elements 125 is mounted on another free surface of the bristle disc 124 which faces away from the surface on which the drive head 129 is carried. The cleaning elements 125 comprises tufts of brush bristles which extend in a direction substantially parallel to the brush axis Y-Y’ are distributed and mounted. In some embodiments, the tufts extend at different angles and/or inclination and/or orientation with respect to the rotation axis of the brush assembly. The bristle disc 124 is substantially circular and is also known as a filament disc in trade. The coupling portion is a base portion 126 which is integrally formed on one surface of the bristle disc 124 that is opposite facing to the surface carrying the bristles 125. The filament disc comprises a top or first surface on which the cleaning elements are mounted, a bottom or second surface on which the drive head 129 is formed, and a peripheral wall interconnecting the first and second surfaces. The collar portion of the brush holder surrounds the periphery wall of the filament disc. The top surface of the filament disc and the top surface of the receptacle are substantially parallel and/or flush in example embodiments such as the present.

[0010] The brush assembly 120 is rotatably mounted on the toothbrush holder 116 and is rotatable about a brush shaft formed by a connection pin 127. The connection pin 127 has a pin axis which is aligned, i.e. coaxial, with the toothbrush axis Y-Y’ to define an axle of the brush assembly 120. A pin holder having a pin receptacle and pin holder axis is formed in a bottom surface of the brush receptacle to receive the pin 127. The pin receptacle has a pin receptacle axis coaxial with or defining the brush axis Y-Y’. The pin holder axis is substantial coaxial with the receptacle axis in example embodiments such as the presents so that the brush assembly 120 is substantially centrally disposed with respect to the brush receptacle.

[001 1 ] A guide slot 128 extending in a direction parallel to the toothbrush axis Y-Y’ is formed on the base portion 126. The guide slot 128 is formed on one side of the brush assembly 120 which is proximal to a junction formed by intersection of the second longitudinal end 114 and the brush holder 116. The guide slot 128 defines a rearward-facing drive track which faces the entry aperture to the tubular housing 110 and is in driving engagement with the crank member 130.

[0012] A guide slot 129 extending in a direction orthogonal to the toothbrush axis Y-Y’ is formed on the base portion 126. The guide slot 129 is formed on one side of the brush assembly 120 which is distal to and facing away from the junction formed by intersection of the second longitudinal end 114 and the brush holder 116. A guide pin 117 extends from the brush holder 116 and projects into the guide slot 129. The guide slot 129 defines a forward-facing guide track which extends in a direction that is substantially orthogonal to the rotation axis of the brush assembly 120. The guide slot 129 and the guide pin 117 cooperate to form a guide assembly which is to function as a secondary guidance means to mitigate tilting of the brush assembly 120 to maintain the brush assembly 120 to rotate about the toothbrush axis Y-Y’ during operations. The guide track also functions as a limitation device to limit maximum angle or extent of rotation about the toothbrush axis Y-Y’ during operations.

[0013] In example embodiments such as the present, the drive mechanism 180 comprises a crank member 130, a bushing assembly 140, an intermediate shaft 150, and a base support member 160, as depicted in Figures 1 A and 1 B. The crank member 130 comprises a first shaft portion 132, a second shaft portion 134 which is parallel to and offset from the first shaft portion 132, and a third shaft portion 136 interconnecting the first and the second shaft portions. [0014] The crank member 130 has two right angled portions on extending along its length and between its longitudinal ends in example embodiments such as the present. The first shaft portion 132 is a first axially extending shaft portion that is coaxial with the power output shaft of the drive handle and/or coaxial with the longitudinal axis X-X’. The second shaft portion 134 is a second axially extending shaft portion and is an eccentric shaft portion with respect to the motor drive shaft axis. The third shaft portion 136 is a crank arm which is a traversal shaft portion extending orthogonally to both the first and second shaft portions. The first shaft portion 132 proximal the power output shaft and is significantly longer than the eccentric shaft portion 134 which is distal from the power output shaft or proximal to the brush assembly. In example embodiments, the first shaft portion is at least two times the length of the second shaft portion.

[0015] The bushing assembly 140 has an internal bore which is coaxial with the longitudinal axis X-X’ and defines an elongate passageway through which the coaxial shaft portion 132 of the crank member 130 passes and inside which the coaxial shaft portion 132 of the crank member 130 is rotatably held. The internal bore and the elongate passageway are shaped and sized for holding and maintaining the first shaft portion 132 of the crank member 130 coaxially with the longitudinal axis X-X’ so that the first shaft portion 132 is confined and supported to rotate about the longitudinal axis X-X’ as its rotation axis during operations. To provide effective coaxial rotational support to the first shaft portion 132 of the crank member 130, the bushing assembly 140, the bushing assembly 140 is friction fitted inside the tubular housing. To mitigate relative rotational and longitudinal movement between the bushing assembly 140 and the tubular housing 110, cooperating stop means are formed correspondingly on the bushing assembly 140 and the tubular housing 110. To provide more effective coaxial support to the crank member 130, the bushing assembly 140 is mounted on the first shaft portion 132 near the crank arm. The bushing assembly has an external size and shape conforming to the internal dimensions of the elongate housing 210 to prevent relative rotational motion.

[0016] The bushing assembly 140 comprises a first bushing member 142 and a second bushing member 144 which are axially connected. Each of the first bushing member 142 and the second bushing member 144 is made of an engineering thermoplastic, such as po!yoxymethylene (POM), which is suitable to function as a bearing, and comprises a solid body inside which an elongate bore to function as a bearing bore is formed. Matched coupling means are formed at corresponding longitudinal ends of the first bushing member 142 and the second bushing member 144 to facilitate detachable connection in the longitudinal direction parallel to longitudinal axis X- X’. The corresponding coupling means are disposed eccentrically on corresponding end surfaces of the first bushing member 142 and the second bushing member 144. In some embodiments, the first bushing member 142 and the second bushing member 144 are non-detachable, for example, are formed as a unitary member or integral member to mitigate operational noise.

[0017] The intermediate shaft 150 is a coaxial shaft having a first longitudinal end for detachable coupling with the drive shaft 510 of the drive handle and a second longitudinal end for detachable coupling with the crank member 130, and more specifically with the first shaft portion 132 of the crank member 130. The intermediate shaft 150 comprises engagement means at its longitudinal ends to facilitate detachable coupling engagement with the drive handle and the crank member 130. The intermediate shaft 150 has a substantially circular cross section and has its transversal size of the circle defining its cross section gradually reduces as the intermediate shaft 150 extends from the first longitudinal end to the second longitudinal end. The tapering shape of the intermediate shaft 150 facilitates sufficient torque transmission and good robustness and durability while reducing material usage. The intermediate shaft 150 is integrally mold of POM. In some embodiments, the crank member 130 is formed and fixed inside the second longitudinal end of the intermediate shaft 150 by insert molding. In some embodiments, the first longitudinal end of the intermediate shaft 150 has a receptacle having complementary shape of the drive shaft 510 of the electrical toothbrush drive unit, as depicted in Figure 5.

[0018] The base support member 160 is a rigid hollow structure comprising a first longitudinal end which is to be in abutment contact with the drive handle during use and a second longitudinal end which is in coupled engagement with the intermediate shaft 150. The base support member 160 is in the shape of an inverted basket and is integrally formed of ABS. The base support member 160 comprises a peripheral wall which extends between the first longitudinal end and the second longitudinal end and around the longitudinal axis X-X’ to define a receptacle having an internal compartment for closely fitted reception of an end portion 520 of the drive handle. The drive shaft 510 is movable relative to the end portion 520 of the drive handle. The base support member 160, or more specifically, the first longitudinal end the peripheral wall of the base support member 160 defines an entry aperture to the internal compartment of the base support member 160. In some embodiments, the internal surface of the base support member 160 comprises slots or protrusions for receiving coupling means of the end portion 520, such that relative movement between the attachment 100 and the drive handle is restricted.

[0019] The peripheral wall is substantially circular and the diameter of the peripheral wall gradually reduces as the base support member 160 extends from the first longitudinal end to the second longitudinal end. The tapering shape of the base support member 160 facilitates a robust structure to promote good durability while reducing material usage. Two oppositely facing, interference friction reducing windows 162A, 162B are opened on the peripheral wall proximal the second longitudinal end.

[0020] When the brush assembly 120 is duly assembled, the bristle carrying surface of the bristle disc 124 is substantially in flush with the upper free end of the brush holder 116, with the base portion 126 is inside the toothbrush receptacle; the brush assembly 120 is rotatably mounted on the brush holder 116 by the connection pin 127 and with the connection pin 127 functioning as an axle of rotation of the brush assembly 120; the base support member 160 is fixedly mounted on the tubular housing 110 with its first longitudinal end outside of the tubular housing 110 and in abutment contact with the first longitudinal end 112 of the tubular housing 110; the first longitudinal end of the intermediate shaft 150 sits on the second longitudinal end of the base support member 160 such that the intermediate shaft 150 is rotatable relative to the base support member 160 about the longitudinal axis X-X’; the first end of the first shaft portion 132 of the crank member 130 is in coupled engagement with the second longitudinal end of the intermediate shaft 150; and the free end of the eccentric shaft portion of the crank member 130 in driving engagement with the brush assembly 120.

[0021 ] When the brush attachment 100 is attached to the drive handle such that the drive shaft 510 of the drive handle is in driving engagement with the intermediate shaft 150, reciprocating motion of the drive shaft 510 of the drive handle about the longitudinal axis X-X’ will be transmitted to the eccentric shaft portion 134 of the crank member 130 as a reciprocating motion about the longitudinal axis X-X’, but with a rotation radius equal to the orthogonal separation distance between centers of the coaxial shaft portion 132 and the eccentric shaft portion 134. The eccentric reciprocating motion of the eccentric shaft portion 134 about the longitudinal axis X-X’ will be transmitted as reciprocating motion of the brush assembly 120 about the toothbrush axis Y-Y’ due to driving engagement between the eccentric shaft portion 134 and the brush assembly 120, and more specifically, between the eccentric shaft portion 134 and the drive track on the base portion 126 which extends along the toothbrush axis Y-Y’ and in intersection with the longitudinal axis X- X’.

[0022] An example toothbrush head 200 comprises a main housing 210, a brush head 220 having a brush axis Z-Z’ and a drive coupling mechanism 280, as depicted in Figures 6, 6A, 6B1 and 6B2. The main housing 210 comprises a neck portion 213 and a head portion 215, as depicted in Figures 7A and 7B. The neck portion 213 has a first axial end 214 which is for making detachable attachment with a drive unit, a second axial end 212 which is in abutment with the head portion, and a tubular housing portion interconnecting the first axial end 214 and the second axial end 212. The drive unit is, for example, a drive unit of a handheld electrical toothbrush drive unit, which is commonly referred to as a handpiece. The tubular portion extends along a longitudinal axis X-X’ between the first axial end and the second axial end and defines an elongate internal bore having a bore axis. The longitudinal axis is a center axis of the tubular portion about which the tubular portion is substantially laterally symmetrical. The longitudinal axis X-X’ and the brush axis Z-Z’ cooperate to define a plane of lateral symmetry. The elongate internal bore defines a through passageway through which the drive coupling mechanism passes. The tubular portion has an oval-shaped cross section on extending along the longitudinal axis X-X’ and tapers to narrow as it extends from the first axial end to the second axial end. In this example, the width of the tubular portion, measured laterally in a lateral direction, which is orthogonal to the longitudinal axis X-X’ and orthogonal to a plane of lateral symmetry containing the longitudinal axis X-X’ and the brush axis Z-Z’, gradually diminishes as the tubular portion extends from the first axial end towards the second axial end. The depth or thickness of the tubular portion, measured in a direction orthogonal to the longitudinal axis X-X’ and orthogonal to the lateral direction, gradually diminishes as the tubular portion extends from the first axial end towards the second axial end. The rate of diminishing of the depth is faster than the rate of diminishing of the width and the neck portion has a substantially circular cross-section at the second axial end. The neck portion has a forward facing edge which is substantially parallel to the longitudinal axis X-X’ and a rear facing edge which is substantially at a constant acute angle to the longitudinal axis X-X’. The forward-facing edge is an edge on a forward -facing side of the neck portion. The forward-facing side is a side of the neck portion having a same facing orientation as that of the bristles on the brush head. The forward-facing edge is an edge on a plane containing the longitudinal axis X-X’ and the brush axis Z-Z’. The rear-facing edge is on an opposite diametric side of the forward-facing edge and in the rear-facing edge has a facing orientation opposite to that of the forward-facing side.

[0023] The neck portion comprises a support device 260 for supporting the drive coupling mechanism. The support device 260 is a bearing device comprising a first axial end, a second axial end and a peripheral wall extending between the first axial end and the second axial end. The example bearing device is a plug-like device having a substantially cage-like structure. The cage-like bearing device comprises a window portion which is formed on the peripheral wall. The window portion has a first axial end and a second axial end and comprises a plurality of longitudinally extending spacer bars extending between the first axial end and the second axial end. [0024] The first axial end of the bearing device comprises a circumferential flange portion which is outside the neck portion and projects radially away from the peripheral wall and radially away from the center axis of the bearing device. The radial extent of the flange portion is larger than or exceeds the radial extent of the internal bore at the first axial end of the neck portion such that the flange portion is obstructed by the first axial end of the neck portion and cannot move beyond the first axial end of the neck portion into the neck portion. The flange portion comprises a transversally extending flange surface which is in abutment with the first axial end of the neck portion.

[0025] The second axial end of the bearing device comprises a bearing portion and a through aperture extending through the bearing portion. The bearing portion comprises a transversely extending bearing platform on which the coupling end of the coupling shaft portion of the drive coupling mechanism rests. The through aperture is aligned with the drive axle of the handpiece and to permit the drive axle to extend through the bearing platform to enter into coupled engagement with the driving coupling mechanism when the toothbrush head 200 is mounted on the handpiece.

[0026] A latch portion is formed on the bearing device proximal the second axial end. The latch portion protrudes radially from the peripheral wall and is in latched engagement with a corresponding latching aperture or a corresponding latching indentation on the tubular portion.

[0027] The head portion 215 defines a brush-disc holder and has a dome-shaped body inside which a brush receptacle 216 and a receptacle compartment are formed. The dome-shaped body has a substantially hemispherical peripheral wall which extends about a center axis and defines an opened end portion and a closed end portion. The peripheral wall at the opened end portion is substantially circular and is centered about the brush axis Z-Z’ as a center axis and defines an opened end aperture. The outer peripheral wall gradually tapers to narrow on extending axially away from the opened end (i.e., the forward side) along the center axis to define a rounded closed end at the rearward side. A junction aperture is formed on the peripheral wall at a junction where the head portion meets the neck portion. The drive coupling mechanism is to extend through the junction aperture to enter into coupled drive engagement with the head portion. An axle holder 217 is formed on the rounded closed end and extends axially from a base of the closed end towards the open end along the center axis. The axle holder stops below the axial level of the junction aperture.

[0028] The brush head 220 is held on the brush receptacle and is supported on the brush receptacle by a brush axle. The brush axle defines a brush axis which is coaxial with the center axis and about which the brush head is to rotate reciprocally during operations when driven by the drive coupling mechanism. The brush head 220 comprises a disc portion on one side of which a plurality of bristles forming a plurality of bristle groups known as tufts is formed and on another side of which a drive engagement portion is formed. The disc portion, also referred to as a filament disc, has a disc axis which is a center axis of the disc portion and which is coaxial with the center axis of the head portion. The example brush head is to rotate reciprocally during operations about the disc axis and the disc axis is at an angle or is orthogonal to the center axis of the neck portion. The brush head 220 otherwise has the same description and functionality as the brush assembly 120 and the description thereon and in relation thereto is incorporated herein by reference. The bristle filaments may comprise non-elastomeric bristles such as Nylon bristles and/or elastomeric bristles.

[0029] The drive engagement portion is received inside the receptacle compartment and comprises an axle receptacle for receiving the brush axle and a drive slot for engaging with a driving end of the drive coupling mechanism. The drive slot is parallel to and off-set from the brush axle and is adapted to engage with a driving end of the drive coupling mechanism such that rotation of the driving end about a rotation axis of the drive coupling mechanism is to cause rotation of the brush head about the brush axis and rotation of the brush head about the brush axis is to cause upward and downward movements of the driving end along the drive slot. To facilitate driving engagement between the drive engagement portion and the drive coupling mechanism, the drive slot is disposed immediately adjacent to and opposite facing the junction aperture.

[0030] The drive coupling mechanism comprises a coupling portion and a driving portion. The coupling portion is to receive driving motion power from the drive unit and to transmit the received driving motion power onwards to the driving portion. An example driving motion originating from the drive unit is a reciprocating rotational motion about the rotation axis of the driving handpiece. In order to provide a sufficient amplitude of rotation at the brush head to facilitate effective toothbrushing, the coupling portion comprises an off-centered driving member which is radially displaced away from the rotation axis to provide an amplified rotational amplitude. The example driving portion is a crank shaft 230 comprising a first shaft portion 232 having a shaft axis, a second shaft portion 234 which is parallel to and radially displaced from the shaft axis, and an intermediate portion which is orthogonal to the first and second shaft portions and which interconnect longitudinal ends of the first and second shaft portions. The first shaft portion 232 is in abutment with the coupling portion and has a length which is substantially longer than the length of the second shaft portion. The intermediate portion has a length which is comparable to or smaller than the length of the second shaft portion, which is an eccentric shaft portion. A free longitudinal end of the first shaft portion which is distal to the second shaft portion 234 is flapped shaped to facilitate a more reliable driving engagement with the driving portion.

[0031 ] The crank shaft 230 is rotatably held on a bushing device 240 and the first shaft portion 232 extends through the bushing device 240. The bushing device 240 is fixedly fitted inside the neck portion and is prevented from rotating and moving relatively to the main housing. During brushing operations, the first shaft portion 232 of the crank shaft is driven into reciprocating rotations about the shaft axis and is to rotate relative to the bushing device 240. To facilitate through passage of the first shaft portion 232, the bushing device 240 comprises a through bore which extends longitudinally through the bushing device and having a bore axis which is aligned with the rotation axis of the drive unit. The first shaft portion 232, the through bore of the bushing device and the drive axis of the handpiece are axes aligned or coaxial during brushing operations or when in driving engagement.

[0032] The coupling portion 250 extends between a first axial end and a second axial end and comprises a first portion 252 and a second portion 254 which extends radially away from the first portion. The first portion is elongate, has a substantially circular cross section along its length and tapers to gradually narrow as it extends from a first axial end which is in abutment with the support device 260 to the second axial end which is in abutment with the crank shaft 230. The first portion has a substantially bullet shape and has a center axis which is coaxial with the centers of the circles defining the circular cross section of the first portion. The center axis of the first portion aligned with the drive axis of the driving axle of the drive unit and is therefore also a rotational axis of the coupling portion.

[0033] The second portion is a side portion comprising a flange portion which extends radially away from the first portion. The flange portion has a thickness which is substantially smaller than the thickness or diameter of the first portion and protrudes radially from a side of the first portion as a side fin portion or a side wing portion. The first portion and the second portion in combination has a width which is slightly less than the width of the internal bore of the neck portion and the coupling portion 250 is to rotate following rotation of the drive unit. The flange portion tapers to narrow on extending from the first axial end to the second axial end to follow the tapering of the neck portion.

[0034] When assembled, the coupling portion 250 is supported on the support device 260 and is in abutment with the bearing platform surface of the support device. During brushing operations, the coupling portion 250 is driven by the drive unit into reciprocating rotations as a result of driving engagement between the drive unit and the coupling portion. The coupling portion 250 rotates while in abutment with the bearing platform surface of the support device and the bearing platform surface functions as a bearing surface. The reciprocating rotations are coupled onto the driving portion 230 as a result of driving engagement between the coupling portion and the driving portion 230. The amplitude of the reciprocating rotations is amplified by the eccentric second shaft portion 234 and the amplified reciprocating rotations about the rotation axis of the first shaft portion 232 are converted into reciprocating rotations of the brush head about the brush axis. For example, the bristle disc or the brush head is to rotate reciprocally by ±55 degrees about the brush axis corresponding to a rotation of ±25 degrees of the first shaft portion 232.

[0035] The intermediate shaft 250 is elongate and extends between a first axial end 2501 and a second axial end 2502. The first axal end is a first longitudinal end comprising coupling means for receiving a free end of the power drive shaft 510 of the drive handle. The second axal end is a second longitudinal end distal to the first longitudinal end and comprises coupling means for receiving a free end of the crank member 230.

[0036] The intermediate shaft 250 is to function as a power coupling portion to couple drive power of the drive unit to the crank member and comprises a main shaft body which extends between the first axial end and the second axial end. The main shaft body has a generally circular outer periphery and the main shaft body has substantial circular symmetry along its length. The transversal dimensions of the main shaft body diminish on extending from the first axial end to the second axial end so that the main shaft body tapers to narrow on extending towards the brush holder. Tapering of the main shaft body or intermediate shaft 250 facilitates sufficient torque transmission while maintaining good robustness and durability as well as reducing material usage and weight of the intermediate shaft 250. The first axial end comprises a first bore for receiving a free end of the drive shaft of the handle unit and the second axial end comprises a second bore for receiving a free end of the crank member, the first and second bores being coaxial bores and the bores are shaft-end receiving bores. Each of the shaft-end receiving bores has a non-circular internal cross-section which is complementary to a non-circular end of the shaft end being received to mitigate relative rotation between the received shaft and the main shaft body. The main shaft body is hollow for at least a substantial portion of its length.

[0037] The intermediate shaft 250 includes a fin-shaped member which projects radially outwards from a transversal side of the main shaft body. The main shaft body and optionally the intermediate shaft 250 is integrally of high-strength plastics such as POM. The radially protruding fin-shaped member is to rotate or oscillate with the main shaft body during tooth-brushing operations. The fin-shaped member extends substantially or almost along the entire length of the main shaft body to increase torque resistance or torque transmission efficiency of the hollow main shaft body. The fin-shaped member has a radial extent which has additional benefits of helping align and maintain the main shaft body with the drive shaft axis during high-speed operations when the main shaft body oscillates at a high frequency. A fin-shaped member further reduces material usage while providing effective alignment aid, torque resistance or transmissibility and/or other benefits with little materials. The radial extent of the fin-shaped member stops short of the internal periphery of the neck portion so that rotational motion of the fin-shaped member is not obstructed by the neck portion housing.

[0038] A portion of the main shaft body proximal the first axial end has a cutout portion. The cutout portion comprise a longitudinal cutout portion which is transversally off-set from the main shaft body center axis and a transversal cutout portion which extends transversally and radially outwards from a longitudinal end of the longitudinal cutout portion distal from the first axial end to form an L-shaped cutout. The L-shaped cutout increases resilience and flexibility at the base portion of the main shaft body to enhance torque transmission performance, the base portion being proximal to the first axial end. An outer portion of the base portion adjacent and defining the longitudinal cutout forms a resilient clip to resiliently engage with the output shaft of the drive unit. The resilient clip is formed by the residual outer portion of the base portion which defines the longitudinal cutout. The residual portion is an upstanding elongate portion which inclines towards the main shaft body axis on extending away from the first axial end or on extending towards the second axial end due to tapering of the main shaft body to define a resilient clip for engaging with the output shaft end of the drive shaft.

[0039] To facilitate driving engagement between the drive unit and the drive coupling mechanism, a drive shaft receptacle is formed on the first axial end of the coupling portion. The shaft receptacle may be non-axis-symmetrical to facilitate more reliable rotational motion coupling.

[0040] To assemble the drive coupling mechanism, a crank shaft is formed. The crank shaft may be formed from a steel pin of a substantially uniform cross-section. Next, a first shaft portion of the crank shaft is inserted through the bushing device 240. The example bushing device is a singly molded piece made of POM. After the first shaft portion has been inserted through the bushing device 240, the free axial end of the first shaft portion 232 of the crank shaft is flattened or laterally enlarge to form a flapped-shaped end having a larger radial extent than the steel pin or other portions of the crank shaft. The driving portion and the coupling portion are then integrated together, for example, by placing the flap-shaped end into a mold and to perform over-molding to form the coupling portion while the flap-shaped end is in the mold. As a result, the coupling portion and the driving portion are integrally formed as a single piece, as depicted in Figures 6B and 6B1 . When assembled on the main housing, a first bend of the crank shaft 230, which is the bend transitioning from the first shaft portion 232, is proximal the narrowest end of the neck portion, the second shaft portion 234 is forward of the first shaft portion 232 and the center axis of the first portion of the coupling axis is proximal to the rearward facing side of the neck portion.

[0041 ] During operations, the toothbrush attachment is mechanically coupled with the handpiece and the drive shaft of the handpiece is in driving engagement with the driving coupling mechanism . When in the driving engagement, the driving shaft of the handpiece is mechanically coupled with the coupling portion, the center axis of the first portion of the coupling portion is aligned with the shaft axis of the driving shaft and the second portion of the coupling portion, that is, the fin portion, is forward of the driving shaft and forward of the rotation axis of the first portion. When the drive shaft rotates reciprocally about its shaft axis, the coupling portion 250 follows the reciprocal rotation of the drive shaft and rotates reciprocally about the rotation axis Y-Y’, which is parallel to and offset from the longitudinal axis X-X’. The reciprocal rotation of the coupling portion 250 about the rotation axis drives the crank shaft to rotate reciprocally also about the rotation axis, and rotation of the crank shaft causes the second shaft portion to rotate reciprocally at an enlarged radius equal to the transversal or orthogonal separation between the first shaft portion 232 and the second shaft portion 234 to drive the brush head to rotate reciprocally about the brush axis.

[0042] While examples have been described to assist understanding, it should be appreciated that the examples are non-limiting examples. For example, while the brush axis Z-Z’ is orthogonal to the longitudinal axis X-X’ the brush axis may be at a non-right angle to the longitudinal axis. For example, while the crank shaft has a double right-angled portion, the crank or bent portions may have other angles rather than right angles without loss of generality.

[0043] An example drive-coupling assembly 380 comprising a crank shaft 330, a busing assembly 340 and an intermediate shaft 350, as shown in Figures 8A-8D. The bushing assembly 340 comprises a first bushing member 342 and a second busing member 344. The crank shaft 330, the busing assembly 340 and the intermediate shaft 350 have same, similar or equivalent features as those described herein and the relevant descriptions on the crank shaft 130, 230, the bushing assembly 140, 240 and the intermediate shaft 150, 250 are incorporated herein by reference mutatis mutandis for the benefit of succinctness where appropriate and/or where the context allows, with reference numerals increased by 100 where appropriate.

[0044] The bushing assembly 340 has a solid body and an elongate bore extending through the solid body to function as a bearing bore for the crank shaft 330 to pass through. The bushing assembly 340 has external peripheral dimensions conforming to the internal peripheral dimensions of the elongate neck portion of the main housing of the brush attachment to prevent relative rotation between the bushing assembly 340 and the neck portion about the longitudinal axis of the neck portion. The peripheral dimensions herein are dimensions of portions surrounding the longitudinal axis of the neck portion, and are lateral peripheral portions. The bushing assembly 340 has a length comparable to, but slight shorter than, the length of the first shaft portion of the crank shaft to promote stable rotation or oscillation of the crank shaft relative to the neck portion, while permitting the eccentric shaft portion to rotate relative to the solid body. The bushing assembly 340 comprises axially extending grooves formed on the outer peripheral surface of the solid body forming the bushing assembly. Each of the axial grooves is a through slot extending from one axial end to the opposite axial end of the solid body to permit the bushing assembly to slide into the neck portion while guided by an axial rib which protrudes radially from the internal peripheral surface of the neck portion. The axial ribs protruding from the internal surface of the neck portion are to engage with the axial ribs to prevent relative rotation of the bushing assembly 340 relative to the neck portion about the neck portion axis. The bushing assembly 340 has peripheral dimensions comparable to that of the neck portion in example embodiments such as the present.

[0045] In example embodiments, the first bushing member 342 and the second bushing member 344 are connected by having their corresponding inward-facing lateral surfaces in abutment and welded together, for example, by ultrasonic welding to form the bushing assembly 340. The bearing bore of the bushing assembly 340 is formed by cooperation of the first and second bushing members. Referring to Figures 8C, 8D and 9A, the second bushing member 344 comprises a first lateral portion 3441 , a second lateral portion 3442 and an intermediate portion 3443 interconnecting the first and second lateral portions. The intermediate portion is a transversally retracted portion which cooperates with the first and second lateral portions to define an axial indentation openly facing the first bushing member 342. The axial indentation has a lateral clearance which is comparable and slightly larger than the width or lateral dimension of the shaft body to permit rotation relative to the second bushing member 344. The lateral clearance is defined by cooperation of corresponding oppositely-facing side walls of the first and second lateral portions. The first and second lateral portions 3441 , 3442 are distributed on opposite lateral sides of the indentation and the direction of separation defines a lateral direction herein. The axial indentation has a transversal depth which is comparable or slightly larger than the width or lateral dimension of the shaft body to permit rotation relative to the second bushing member 344. The transversal direction is orthogonal to the lateral direction and the axial direction. [0046] The first bushing member 342 comprises a first lateral portion 3421 , a second lateral portion 3422 and an intermediate portion 3423 interconnecting the first and second lateral portions 3421 , 3422. The intermediate portion 3423 is a transversally protruding portion which cooperates with the first and second lateral portions to define an axially extending protrusion facing the second bushing member 344. The transversally protruding intermediate portion 3423 has a forward-facing or transversal-facing surface which cooperates with the intermediate portion 3443 of the second bushing member 344 to define the bearing bore.

[0047] Matched coupling means 346A, 346B, 348A, 348B are formed on corresponding surfaces of the first bushing member 342 and the second bushing member 344 to facilitate connection in a direction orthogonal to the longitudinal axis X-X’. For example, the coupling means comprises transversal protrusions 346A extending from an end surface of the second bushing member 344 and transversal bores 346B disposed inside the first bushing member 342 at positions complementary to the transversal protrusions 346A. The transversal protrusions 346A are secured inside the transversal bores 346B when the first bushing member 342 and the second bushing member 344 are assembled. The corresponding coupling means may also be protrusion 348A disposed on an end surface of the second bushing member 344 and slot 348B disposed at an edge of the first bushing member 342 at positions complementary to the protrusions 348A. While examples have been described to assist understanding, it should be appreciated that the examples are non-limiting examples. For example, both protrusions and bores may be provided on the first bushing member and corresponding bores and protrusions may be provided on the second bushing member. For example, the protrusion may be cylindrical, semi-circular or rectangular. For example, there are only bores or slots provided on the first bushing member or the second bushing member. In cases where only bores are provided, the first bushing member and the second bushing member are assembled along the direction which the protrusions extend. In cases where only slots are provided, the protrusions can enter the slots from more than one direction such that the first bushing member and the second bushing member can be rotatably assembled.

[0048] To assemble the drive coupling assembly, the first shaft portion 332 of the crank shaft 330 is inserted onto the axial indentation of the second bushing member 344. After the first shaft portion 332 has been positioned inside the axial indentation of the second bushing member 344, the first bushing member 342 is coupled onto the second bushing member 344 through matched coupling means 346A, 346B, 348A, 348B. As a result, the axial indentation of the second bushing member 344 is closed by the first bushing member 342. The first shaft portion 332 is forward of the transversally protruding intermediate portion 3423 of the first brushing member 342 and sandwiched between the first bushing member 342 and the second bushing member 344, as depicted in Figure 9A.

[0049] Table of numerals

Claims

1 . A toothbrush attachment for detachable attachment to a motor drive unit of an electric toothbrush, wherein the motor drive unit comprises a motor and a driving shaft which is driven by the motor to rotate reciprocally about a rotation axis of the driving shaft, wherein the toothbrush attachment comprises a main housing comprising a tubular neck portion having a longitudinal axis and a head portion defining a toothbrush receptacle, a toothbrush head rotatably mounted on the toothbrush receptacle of the head portion and a rotatable brush axis, and a drive coupling mechanism mounted inside the neck portion and having a rotation axis; wherein the drive coupling mechanism comprises a crank shaft, a bushing device and a coupling shaft portion; wherein the coupling shaft portion comprises at an axial free end with an engagement means which is adapted for making detachable coupled driving engagement with the driving shaft of the drive unit to receive rotational driving power from the driving shaft and to transmit the received rotational driving power to the crank shaft, wherein the crank shaft is for driving the toothbrush head to rotate reciprocally about the brush axis, and wherein the coupling shaft portion and the crank shaft are integrally molded together as a unitary member and the crank shaft is rotatably mounted on the bushing device.

2. A toothbrush attachment according to Claim 1 , wherein the coupling shaft portion comprises an axis symmetrical first portion and a non-axis symmetrical second portion which is a side portion projecting radially away from the first portion; and wherein the axis symmetrical first portion has a longitudinal center axis which is aligned with the rotation axis.

3. A toothbrush attachment according to Claim 2, wherein the axis symmetrical first portion tapers to narrow on extending towards the head portion.

4. A toothbrush attachment according to Claims 2 or 3, wherein the side portion comprises a fin-shaped flange portion having a radial extent from the first portion, and the flange portion tapers to narrow on extending axially towards the head portion.

5. A toothbrush attachment according to any of Claims 2 to 4, wherein the neck portion comprises a forward-facing edge and a rearward-facing edge, the forward-facing edge and the rearward facing edge are on a plane containing the rotation axis and the brush axis, and the neck portion is laterally symmetrical about the plane; and wherein the fin-shaped flange portion is proximal to the forward-facing edge and the axis symmetrical first portion is proximal the rearward-facing edge.

6. A toothbrush attachment according to any preceding Claims, wherein the crank shaft (230) comprises a first shaft portion (232) which is aligned with the rotation axis and an eccentric shaft portion (234) which is offset from the rotation axis; wherein the neck portion comprises a forward-facing edge and a rearward-facing edge, the forward-facing edge and the rearward facing edge are on a plane containing the rotation axis and the brush axis, and the neck portion is laterally symmetrical about the plane; and wherein the rotation axis is proximal the rearward facing edge and the eccentric portion is proximal the rearward facing edge.

7. A toothbrush attachment according to Claim 6, wherein the neck portion has an oval-shaped cross section with respect to the longitudinal axis of the neck portion, and the rotation axis is parallel to the forward-facing edge and at a small acute angle to the rearward-facing edge.

8. A toothbrush attachment according to Claims 6 or 7, wherein the crank shaft (230) comprises an enlarged flap-shaped portion at a free axial end of the first shaft portion (232), and the enlarged flap-shaped portion is embedded inside the coupling shaft portion by over-molding.

9. A toothbrush attachment according to Claim 8, wherein the bushing device is a unitary device extending between two axial ends and having a longitudinally extending through bore extending between the axial ends, and wherein the flap-shaped portion has a radial extent exceeding clearance of the through bore.

10. A toothbrush attachment according to any preceding Claims, wherein the neck portion comprises a support device (260) having a bearing platform surface on which the drive coupling mechanism is rotatably supported, wherein the support device (260) is a bearing device comprising a first axial end, a second axial end and a peripheral wall extending between the first axial end and the second axial end; and wherein the support device has a cage structure.

1 1 . A toothbrush head for attaching to an output driving shaft of a driving handle of an electric toothbrush, the toothbrush head comprising a tubular housing which extends along a longitudinal axis, a bristle carrier which is mounted on or near a longitudinal end of the tubular housing and rotatable about a carrier axis, and a crank member which extends inside the tubular housing for transmitting driving rotation from a driven end to a driving end; wherein the driving end is offset from the driven end; wherein the crank member is supported to rotate inside the tubular housing by a bushing assembly, the bushing assembly comprises a first bushing member and a second bushing member, wherein the bushing assembly is rotatably fixed on the crank member.

12. The toothbrush head according to Claim 1 1 , wherein the crank member passes through a bore of the first bushing member, the bore has a diameter smaller than the offset distance such that the driven end is prevented from passing through the first bushing member, when the second bushing member is mounted onto the crank member, the bushing assembly is rotatably fixed on the crank member

13. The toothbrush head according to Claim 12, wherein the second bushing member comprises a slot along the longitudinal axis for detachable connection to the crank member.

14. The toothbrush head according to Claim 1 1 , wherein the crank member is a straight metal bar which is bent to form the first shaft portion, the second shaft portion and a crank arm interconnecting the first shaft portion and the second shaft portion.

15. The toothbrush head according to Claim 14, wherein the first shaft portion and the crank arm are at right angle; the crank arm and the second shaft portion are at right angle.

16. The toothbrush head according to Claims 14 or 15, wherein when the second bushing member is detached from the crank member, the first bushing member is movable along the first shaft portion and stops at the crank arm.

17. The toothbrush head according to Claim 1 1 , wherein the toothbrush head comprises an intermediate shaft which is a coaxial shaft having a first longitudinal end for detachable coupling with the output driving shaft of the driving handle and a second longitudinal end secured to the crank member.

18. The toothbrush head according to Claim 17, wherein the intermediate shaft is secured to the crank member by insert molding.

19. The toothbrush head according to Claims 17 or 18, wherein the second bushing member comprises a slot along the longitudinal axis for detachable connection to the crank member at a position between the intermediate shaft and the first bushing member.

20. The toothbrush head according to any preceding Claims, wherein the toothbrush head comprises a base support member fixedly mounted on the tubular housing, the base support member comprises a peripheral wall extending between a first longitudinal end and a second longitudinal end and around the longitudinal axis to define a receptacle having an internal compartment for closely fitted reception of a portion of the output driving shaft of the driving handle; wherein the peripheral wall is opened with at least one window to reduce the area of interference between the base support member and the driving handle.

21 . The toothbrush head according to Claim 20, wherein the peripheral wall is opened with two windows which are oppositely facing.

22. The toothbrush head according to Claim 1 1 , wherein the crank member passes through a groove of the first bushing member, when the second bushing member is mounted to the first bushing member, the crank member is prevented from leaving the groove.

23. The toothbrush head according to Claims 12 or 22, wherein the second bushing member is provided with a coupling mean and the first bushing member is provided with a corresponding coupling mean, such that the second brushing member is fixedly mounted to the first bushing member when the coupling mean engages the corresponding coupling mean.

24. The toothbrush head according to any preceding Claims, wherein the bristle carrier comprises a guide slot extending in a direction parallel to the carrier axis.