Abstract:
An attachment for an electric toothbrush, including a working head and coupling member mountable on a toothbrush handpiece. The coupling member includes a sleeve-shaped coupling insert with an engagement section for locking with the handpiece. The coupling insert is displaceable relative to the coupling member or an actuating member such that an axial movement of the coupling insert relative to the coupling member or actuating member produces an unlocking/locking movement of the engagement section in a direction transverse to the attachment longitudinal direction. The attachment or actuating member is first moved axially relative to a locked coupling insert until the axial relative movement releases the lock for the coupling insert and the attachment to be separated from the toothbrush handpiece. This two-stage attaching or connecting mechanism permits use of non-self-locking connecting or faying contours because the locking movement takes place in a direction transverse to the attachment longitudinal direction.

Description:
TECHNICAL FIELD 
     This invention relates to an electric toothbrush having a handpiece and an attachment mountable thereon, and more particularly to the attachment for such a toothbrush. 
     BACKGROUND 
     EP 0 500 537 B1 discloses an electric toothbrush on which the attachment brush is connected on the one hand to a front-end shank part of the toothbrush handpiece and on the other hand to a drive shaft projecting therefrom. For this purpose, the brush has radially resilient detent hooks which can be locked in place in corresponding detent notches on the handpiece. 
     DE 103 52 993 A1 discloses in addition an electric toothbrush on which the attachment brush is fixed only directly to the drive shaft which projects at the front end out of the toothbrush handpiece. For this purpose the attachment brush has a coupling member with an inner recess of the blind-hole type into which an on the whole sleeve-shaped mount is inserted. Said mount, into which the drive shaft can be inserted with a snug fit, includes several spring elements which are radially resilient and intended to ensure a zero-play connection between the attachment brush and the drive shaft. 
     Excess play in attachment couplings and drive mechanisms can adversely affect handpiece and attachment life and performance. For example, that attachment can become separated due to the vibrations of the electric toothbrush drive and the forces applied by brushing. Accordingly, improvements are sought in electric toothbrushes and attachment tools for treating the oral cavity. 
     SUMMARY 
     One aspect of the invention features an easy-to-couple connection between the attachment and the toothbrush handpiece, which accommodates production tolerances, holds the attachment brush on the toothbrush handpiece with zero play, and yet can be readily released and re-established. 
     One aspect of the invention features an attachment mountable to a handpiece of an electric toothbrush. The attachment includes a working head and a coupling member joined to the working head. The coupling member is configured to be coupled to the handpiece and includes a sleeve-shaped coupling insert disposed within the coupling member. The coupling insert includes an engagement section configured to lockingly engage the handpiece. Additionally, the coupling insert is configured to be axially displaceable within the coupling member substantially along a longitudinal attachment axis to produce one of an unlocking and a locking movement of the engagement section in a direction transverse to the longitudinal attachment axis. 
     In some implementations, the coupling member features an actuating member including an unlocking section configured such that an axial movement of the coupling insert causes the unlocking section to engage the coupling insert and move the engagement section into an unlocked position. 
     In some implementations, the engagement section defines a detent contour configured to be radially movable by the actuating member. 
     In some implementations, the engagement section features a radially expandable detent ring axially moveable against a tapered surface on the actuating member substantially along an attachment longitudinal axis. 
     In some implementations, the engagement section defines a resilient catch configured to slide over the handpiece into snap-fit engagement with the handpiece. 
     In some cases, the catch is unseatable from snap-fitted engagement with the handpiece by an axial relative movement between the actuating member and the coupling insert. 
     In some implementations, the coupling insert is biased towards disengagement from the actuating member. 
     In some implementations, the actuating member is configured as a ring disposed in the coupling member and features actuating fingers protruding axially substantially in the attachment longitudinal direction. 
     In some implementations, the actuating member features a slide axially displaceable along the attachment longitudinal axis. 
     In some implementations, the actuating member features a ring bearing an individual attachment identifier. 
     In some implementations, the engagement section and an actuating member define cooperative beveled surfaces configured to cause the engagement section to move between locked and unlocked positions as the engagement section rides over the actuating member. 
     In some implementations, the engagement section defines a detent hook joined to a pivot arm configured such that detent hook is radially movable towards an unlocked position during axial movement of the detent contour away from the working head. 
     In some implementations, the coupling insert features a plurality of shell segments forming a conical mount diametrically variable through axial movement of the attachment to connect to or release the handpiece. 
     In some cases, the attachment features a spring biasing the shell segments towards an outwardly expanded position. 
     In some implementations, the coupling insert features a sleeve having an engagement section on a circumferential wall of the sleeve. 
     In some cases, the coupling insert features a conical mount configured to receive a complementary conical connecting member of the toothbrush handpiece push-fitted thereon. 
     In some cases, the conical mount of the coupling insert features a bevel of more than 7 degrees. 
     In some implementations, the coupling member features an insert mount configured to receive the coupling insert in an enclosed fit. 
     In some cases, the engagement section is radially extensible and the insert mount is substantially conical such that the coupling insert is loosely seated in the insert mount, in a position moved away from the working head. 
     In some cases, at least a portion of the insert mount features a cylindrical configuration. 
     In some implementations, the coupling insert features a spring section configured to moveably secure the coupling insert in the coupling member 
     In some cases, the spring section features a helical spring connected to a retaining ring which is movable into engagement with an inner wall of the coupling member. 
     In some cases, the spring biases the coupling insert axially along an attachment longitudinal axis. 
     In some implementations, the at least one engagement section in an initial condition is fixed in place by means of a predetermined breaking piece in a predetermined initial position relative to the remaining body of the coupling insert. The engagement section, together with the remaining body of the coupling insert, defines a mount into which one of a cylindrical connecting member and a conical connecting member of a first toothbrush handpiece is insertable, and into which a conical connecting member of a second toothbrush handpiece is configured to be insertable by breaking the predetermined breaking piece to widen the engagement section. 
     In some implementations, a plug-on shaft disposed in the coupling member defines a coupling contour configured to engage a drive shaft of the toothbrush handpiece. The coupling contour further defines a conical faying surface with a bevel of more than 7 degrees. 
     In some cases, the coupling contour of the plug-on shaft is substantially free of undercuts or axially effective snap-action connections. 
     Another aspect of the invention features, an electric toothbrush with a handpiece and an attachment. The handpiece features a powered drive shaft and the attachment is configured to be driven by the drive shaft. The attachment features a working head, a coupling member joined to the working head, and a sleeve shaped coupling insert. The coupling insert is disposed within the coupling member and includes at least one engagement section configured to lock with the handpiece. Additionally, the coupling insert sleeve is configured to be axially displaceable within the coupling member substantially along a longitudinal attachment axis to produce one of an unlocking and a locking movement of the engagement section in a direction transverse to the longitudinal attachment axis. 
     Another aspect of the invention features an electric toothbrush including a connecting member which is insertable with a snug fit into the coupling member of an attachment brush. The coupling member is conical and has a bevel of more than 7°. The attachment includes a working head and a coupling member joined to the working head and mountable on a toothbrush handpiece. The coupling member includes a sleeve-shaped coupling insert having at least one engagement section for locking with the toothbrush handpiece by positive and/or frictional engagement therewith. The coupling insert is displaceable relative to the coupling member and/or an actuating member connected thereto axially in the attachment longitudinal direction and is connected to the engagement section, such that an axial movement of the coupling insert relative to the coupling member and/or the actuating member produces an unlocking and/or locking movement of the engagement section in a direction transverse to the attachment longitudinal direction. 
     Features of the device permit, between at least a part of the coupling insert and the tubular coupling member of the attachment or an engagement section joined thereto, an axial relative movement in the direction of the attachment longitudinal axis and to translate this axial relative movement into an unlocking or locking movement of the coupling insert in a direction transverse to the attachment longitudinal direction. This enables, on the one hand, a firm and also vibration-resistant connection to be obtained between the attachment and the toothbrush handpiece, while, on the other hand, enabling the connection to be released and re-established by the axial push-on and pull-off movement known in the art. The coupling insert of the attachment is displaceable relative to its coupling member and/or an actuating member connected thereto axially in the attachment longitudinal direction, and it is connected to the engagement section, which is lockable onto the handbrush handpiece by positive or frictional engagement therewith, such that an axial movement of the coupling insert relative to the coupling member and/or the actuating member produces an unlocking and/or locking movement of the engagement section in a direction transverse to the attachment longitudinal direction. 
     If the coupling insert or the engagement section is locked onto the toothbrush handpiece, the attachment or an actuating member connected thereto is first moved axially substantially in the attachment longitudinal direction relative to the locked coupling insert, whereby the coupling insert initially does not move relative to the toothbrush handpiece on account of its being locked thereto. After the axial relative movement has released the lock the coupling insert can be pulled together with the attachment off the toothbrush handpiece. This two-stage attaching or connecting mechanism permits even non-self-locking connecting or faying contours to be provided at the interface between the toothbrush handpiece and the coupling insert because fixedly securing is assured nevertheless by the locking movement which takes place in a direction transverse to the attachment longitudinal direction. 
     In particular the interface between the toothbrush handpiece and the coupling insert of the attachment can thus be rendered insensitive to tolerances, e.g., accommodating of production tolerances. On the other hand it is possible to control the axial relative movability between the coupling insert and the attachment or the actuating member fastened thereto by means of a suitable adaptation of the contour at the interface between the coupling insert and the coupling member or actuating member, in particular an unwanted axial displacement of the coupling member relative to the coupling insert can be prevented by a self-locking configuration of the contours of the coupling insert and the coupling member which are in seating engagement with each other. 
     In a particular implementation, the coupling insert defines a conical mount which widens away from the working head of the attachment, defining a bevel of more than 7°. The conical mount need not be configured to be self-locking, and the stub-shaped connecting member of the toothbrush handpiece, which conventionally projects at the front end, may be configured with a complementary bevel of more than 7°. These relatively pronounced tapers of the connecting member of the toothbrush handpiece and of the mount defined by the coupling insert render the connection insensitive to tolerances because differences in diameter can be compensated for by a suitable axial movement. 
     To avoid transferring the problem of an unwanted disengagement to the interface between the coupling insert and the coupling member of the attachment (i.e., to avoid an unwanted axial displacement of the tubular coupling member of the attachment relative to the coupling insert), which would result in unlocking of the coupling insert, it is possible to use various mechanisms. For example, other implementations provide a catch mechanism between the coupling insert and the coupling member of the attachment, which can be released by overcoming a predetermined detent force. 
     Alternatively or in addition, the coupling member may have an insert mount into which the coupling insert is insertable by frictional engagement with a snug and self-locking fit. For example, the insert mount may be of a conical configuration with a bevel of less than 7° so that the coupling insert firmly clamps itself in place in self-locking manner in the insert mount of the tubular coupling member when the attachment is plugged onto the toothbrush handpiece. Again, alternatively or in addition, a spring device may be provided which acts between the coupling insert and the coupling member and holds the coupling insert in the desired axial position. 
     To achieve simple operation of the attachment and to be able to easily pull the attachment off the toothbrush handpiece, a further aspect of the invention provides for the actuating member to have an unlocking section which is arranged and configured such that during an axial movement of the coupling insert away from the working head the unlocking section is movable into engagement with the coupling insert and forces its engagement section into an unlocked position. In other words, the actuating member is arranged and configured such that the actuating member automatically unlocks the coupling insert when the attachment is being pulled off the toothbrush handpiece. 
     In a particular implementation, a wedge-shaped surface is provided on the engagement section of the coupling insert and/or the actuating member, which surface produces an unlocking movement while the engagement section rides over the actuating member. A pair of wedge-shaped surfaces can be provided, but other implementations use a pair of beveled surfaces arched in a spherical or concave configuration which, while the engagement section rides over the actuating member as the result of the axial relative movement translates said axial movement into an unlocking movement in a direction transverse to the axial direction. 
     In reversal of the kinematics, other implementations of the invention provide for the actuating member to effect not the unlocking but the locking of the coupling insert or the engagement section connected thereto. In this case the engagement section in its initial position may adopt, or be biased into, a non-locking position. When the attachment is plugged onto the toothbrush handpiece, the engagement section of the coupling insert is forced into the locking position by way of the actuating member. Additionally, as previously described, the coupling insert may be configured to be self-locking and the locking, which occurs on its own while the attachment is being seated onto the toothbrush handpiece, is then released by means of the actuating member while the attachment is being removed again. 
     In a particular implementation, the engagement section forms a spring catch and/or a detent clip which, while the coupling member is being plugged onto the toothbrush handpiece, slides over its connecting member, rebounds elastically in the process and, upon reaching the fully plugged-on position, snaps into place by positive engagement. When the attachment is to be removed again from the toothbrush handpiece, the spring catch or detent clip is unseated from its snapped-in position by an axial relative movement between the actuating member and the coupling insert. 
     Generally, the engagement section may be configured in a variety of ways. According to particular implementation, the engagement section includes a detent contour in the form of a detent hook, which is provided on the protruding end of an engagement finger which is resilient and/or pivotal about a transverse axis and radially movable by the actuating member. Additionally, the at least one engagement finger may be integrally made of one piece with the body of the coupling insert and be separated from the rest of the body for example by longitudinal slits in order to be resilient in relation to the remaining body. 
     Alternatively or in addition, an engagement section may also be provided in the form of a rocker which at its one end has a detent contour in the form of a detent hook for locking engagement with the toothbrush handpiece, and at its other end forms an actuating section which is movable into engagement with the aforementioned actuating member. In this case, too, the engagement section may be integrally made of one piece with the body of the coupling insert, in particular by way of a flexible connecting bar in the middle section of the aforementioned rocker. 
     Alternatively or in addition, the engagement section may have a detent contour the form of a detent hook which is pivotally mounted by way of a pivot arm such that during an axial movement of the detent hook by way of the pivot arm there is produced simultaneously a radial movement component causing the detent hook to be locked or unlocked. To produce the necessary axial movement, the detent hook may have a follower element which catches the connecting member of the toothbrush handpiece while plugging on the attachment and/or the actuating member while pulling off the attachment. 
     According to a particular implementation, the sleeve-shaped coupling insert is provided in the form of a slotted sleeve and/or comprised of a plurality of shell segments, with the sleeve sections or the plurality of shell segments being radially extensible and compressible so that the mount defined by the sleeve sections or shell segments may adopt different diameters for accommodating the connecting member of the toothbrush handpiece. The sleeve sections or the shell segments may sit in a conical insert mount in the coupling member of the attachment so that the mount defined by the sleeve sections or shell segments is expandable or able to grow narrower or wider during axial displacement of the coupling insert in the coupling member. 
     A particular implementation utilizes a slotted detent ring on the whole sleeve-shaped coupling insert, which ring is diametrically variable or radially compressible and extensible. Compression may be forced by a conical seat in the coupling member or, where applicable, also by biasing the detent ring. Conversely, an extension or widening of the detent ring may be effected, for example, by way of a pair of beveled surfaces on the detent ring and the actuating member. 
     In a particular implementation of the invention, the coupling insert, which is axially movable in the coupling member, is fixed in place on the coupling member and secured from falling out and/or is biased into a defined initial position by means of a spring. This spring may be configured in a variety of ways. In a particular implementation, an elastic spring section is formed on the coupling insert and secured to the tubular coupling member. The elastic spring section may be formed from at least two helical and/or spiral-shaped spring arms which extend approximately on an enveloping surface, which is coaxial with the coupling insert longitudinal axis, and are connected to a retaining ring which is movable into engagement with the inner wall of the tubular coupling member, in particular by locking engagement therewith. In this arrangement, the spring may be provided on the side of the coupling insert close to the working head. 
     Alternatively or in addition to the axially displaceable mounting of the coupling insert in the tubular coupling member, other implementations provide an axially displaceable actuating member in the form of a slide, in order to effect the axial relative movement between the coupling insert and the actuating member. The slide may be guided, for example, in a longitudinal groove in the tubular coupling member. 
     In an additional implementation of the invention, the actuating member is immovably fixed in place on the tubular coupling member of the attachment. In this arrangement, the actuating member may be generally formed by an integrally formed section of the coupling member itself. In a particular implementation the actuating member is formed as a ring which is inserted in the coupling member. The actuating member may include at least one actuating finger which protrudes axially substantially in the attachment longitudinal direction and through which the coupling insert or its engagement section is actuatable in a direction transverse to the attachment longitudinal direction. 
     In a particular implementation of the invention, the actuating member is used in a dual function. The actuating member may have a section which is visible from the outside of the attachment and has a user-specific marking which individualizes the attachment and allows a respective user of the attachment to identify “his” or “her” attachment. The actuating member may be in the form of a colored ring of which at least portions are visible on the outside of the coupling member of the attachment, forming its front end. 
     In an additional implementation, the coupling insert is configured such as to enable it to be coupled with different toothbrush handpieces, to be more precise with different connecting members of such toothbrush handpieces. In particular the coupling insert is configured such as to be suitable for coupling engagement with a cylindrical connecting member of a toothbrush handpiece on the one hand and with a conical connecting member of a toothbrush handpiece on the other hand or also, where applicable, with connecting members formed with variously pronounced tapers. In an additional implementation, the at least one engagement section of the coupling insert in an initial condition is fixed in place by means of a predetermined breaking piece in a predetermined initial position relative to the remaining body of the coupling insert, such that said section defines together with said remaining body of the coupling insert a mount into which a cylindrical and/or slightly conical connecting member of a first toothbrush handpiece can be inserted with a snug fit and firmly clamped. When the at least one predetermined breaking piece is broken, the engagement section can be moved radially so that a more pronounced conical connecting member of a second toothbrush handpiece can be inserted with a snug fit with widening of the engagement section. In a particular implementation, the remaining body of the coupling insert apart from the engagement section defines a mount which is shaped to conform to the more pronounced conical connecting member of the second toothbrush handpiece. 
     Alternatively or in addition to providing the coupling insert with such a predetermined breaking point, the usability of the attachment on different toothbrush handpieces may be assured by the use of an adapter. In this case the coupling insert and the mount defined by it are shaped to conform to the more pronounced conical contour of the connecting member of the aforementioned second toothbrush handpiece so that such a more pronounced conical connecting member, in particular with a bevel of more than 7°, can be inserted with a snug fit. By contrast, if the attachment is to be used for an aforementioned first toothbrush handpiece having a cylindrical or only slightly conical connecting member, then a sleeve-shaped adapter whose outer contour has a more pronounced taper and is adapted in particular for a snug fit in the mount defined by the coupling insert is push-fitted onto the connecting member of said toothbrush handpiece. Such an adapter sleeve is locked by positive and/or frictional engagement on the toothbrush handpiece. The adapter sleeve may also serve to enable an attachment with a coupling insert of the aforementioned type, which includes a predetermined breaking section, to be used for a toothbrush handpiece having a cylindrical or only slightly conical connecting member even after the predetermined breaking point has been broken. 
     Tapers of various degrees can be used to effect self-locking of the clamp mechanism. For example, it can be advantageous in some cases to provide more pronounced complementary tapers on the stub or neck of the toothbrush handpiece and on the attachment to obtain a connection permitting more lenient tolerances. 
     In various cases, the attachment can be an attachment brush for dental cleansing, interproximal cleaning devices, gum massage heads or other oral care instrument. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a fragmentary view, in longitudinal section, of an electric toothbrush, showing the front-end connecting member of the toothbrush handpiece and the attachment brush seated thereon, with the coupling insert seated in the tubular coupling member of the attachment brush in a locked position; 
         FIG. 2  is a longitudinal sectional view of the toothbrush of  FIG. 1 , which is turned through 90° compared to the illustration in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the toothbrush of  FIGS. 1 and 2  in the region of the catch mechanism between the coupling insert in the attachment brush and the neck of the toothbrush handpiece; 
         FIG. 4  is a fragmentary view, in longitudinal section, of an electric toothbrush showing the connection of the attachment brush to the handpiece of the toothbrush, with the coupling insert in the coupling member of the attachment brush including a locking rocker; 
         FIG. 5  is a fragmentary view, in section, of the coupling insert in the coupling member of an attachment brush, on which the coupling insert has a locking arm in the form of a bistably mounted spring finger; 
         FIG. 6  is a top plan view of the bistably mounted spring finger of the coupling insert of  FIG. 5 ; 
         FIG. 7  is a fragmentary view, in section, of the coupling insert in the coupling member of an attachment brush in which a detent hook mounted on a pivot arm is provided; 
         FIG. 8  is a longitudinal sectional view of the coupling insert in the coupling member of an attachment brush in which the coupling insert is in the form of a split sleeve having two shell segments; 
         FIG. 9  is a top plan view of the coupling insert of  FIG. 8 , showing the two shell segments of the sleeve-shaped coupling insert; 
         FIG. 10  is a longitudinal sectional view of the coupling insert in the coupling member of an attachment brush in which the coupling insert includes an expandable detent ring; 
         FIG. 11  is a fragmentary view, in longitudinal section, of an electric toothbrush in which the coupling insert in the coupling member of the attachment brush has a predetermined breaking point and without breakage of the predetermined breaking point is suitable for a toothbrush handpiece having a cylindrical connecting member, as shown in  FIG. 11 , and after breakage of the predetermined breaking point is suitable for a toothbrush handpiece having a conical connecting member, with  FIG. 11  showing the still unbroken condition of the predetermined breaking points; 
         FIG. 12  is a fragmentary view, in longitudinal section, of the toothbrush of  FIG. 11  in a plane turned through 90° compared to  FIG. 11 ; 
         FIG. 13  is a cross-sectional view of the connection between the attachment brush and the handpiece of the toothbrush of  FIGS. 11 and 12  in the region of the detent hooks of the coupling insert; and 
         FIG. 14  is a perspective view of the coupling insert of the attachment brush of  FIGS. 11 to 13 . 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The toothbrush  1  shown in  FIGS. 1 to 3  comprises a handpiece  4  and, connected thereto, an attachment in the form of an attachment brush  33 . The handpiece  4  comprises a housing in which a drive motor and a power supply device are accommodated and on which an actuating switch for switching the drive on and off is provided. On the front end of the handpiece  4  shown in  FIG. 1  the housing of the handpiece  4  forms a forward-protruding stub-shaped connecting member  34  which in the embodiment shown is conically shaped and tapers towards its free end, with the conical contour of the connecting member  34  advantageously having a bevel  35  of more than 7° and therefore cannot be clamped in self-locking manner. Extending from the frontal end of said connecting member  34  is a drive shaft  31  which is adapted to be driven in an oscillatory rotational motion. 
     The attachment brush  33  comprises a working head  2  with a set of bristles, not shown in greater detail, which, in the embodiment shown, is adapted to be driven in an oscillatory rotational motion about a bristle zone axis pointing approximately in the bristle longitudinal direction. Said working head  2  is carried by an on the whole tubular coupling member  3  which can be plugged onto the neck or the connecting member  34  of the toothbrush handpiece  4 . In the interior of said tubular coupling member  3  the attachment brush  33  comprises a plug-on shaft  29  adapted to be coupled to the drive shaft  31  of the handpiece in a manner preventing relative rotation. 
     To fasten the attachment brush  33  to the handpiece  4  the tubular coupling member  3  includes a coupling insert  5  in the form of a coupling sleeve which is accommodated in the tubular coupling member  3  for axial displacement in the direction of the attachment longitudinal direction  38 . The coupling member  3  forms with its inner wall an insert mount  16  in which the coupling insert  5  is seated with a snug fit at least in its locked condition, which will be described below in more detail. The insert mount  16  may be configured in a variety of ways, for example, it may be of an on the whole cylindrical or on the whole tapered or conical configuration, or also it may include a cylindrical section as well as a conical section. In the embodiment shown, the insert mount  16  is on the whole slightly conical, with a cylindrical section being provided on its region  40  intended for the inner end of the coupling insert  5 . 
     A spring  17  holds the coupling insert  5  axially in the coupling member  3  or biases it into a predetermined initial position. Said spring  17  is provided on the side of the coupling insert  5  close to the working head  2 . On the one hand, the spring  17  is connected to the coupling insert  5 , and, on the other hand, it is fixed to the coupling member  3 . In the embodiment shown, the spring  17  comprises a retaining ring  20  which is in locking engagement with the inner wall of the coupling member  3 . Other implementations are possible for the spring  17 . According to the illustrated implementation, the spring  17  comprises two helical or spiral-shaped spring sections  18  and  19 , which coil around the plug-on shaft  29  and the drive shaft  31 , cf.  FIG. 1  and  FIG. 2 . In this arrangement, the spring sections  18  and  19  are integrally made of one piece with the coupling insert  5  and connected to the retaining ring  20 . The spring  17  allows an axial movement of the coupling insert  5  to the extent required to permit locking and unlocking. 
     The sleeve-shaped coupling insert  5  forms with its inner circumferential surface a mount  13  which is shaped to conform to the outer circumferential contour of the connecting member  34  of the toothbrush handpiece  4  so that said handpiece can be inserted into the mount  13  with a snug fit. The mount  13  is of an on the whole conical configuration, with the bevel of the respective taper—adapted to the connecting member  34 —being greater than 7°. The coupling insert  5  has two mutually opposing engagement sections  6  in the form of resilient coupling or spring fingers  12  which are integrally made of one piece with the remaining body of the coupling insert  5  and are separated from said insert by U-shaped slits so that engagement fingers  12  can spring open and shut radially in a direction transverse to the attachment longitudinal direction  38 . The engagement fingers  12  extend with their longitudinal axis substantially parallel to the attachment longitudinal direction  38 . 
     As  FIG. 1  shows, the engagement fingers  12  carry on their free ends radially inwardly protruding detent hooks  11  adapted to snap into conformably shaped detent notches  41  in the outer circumferential surface of the connecting member  34  of the toothbrush handpiece  4 . Other suitable detent contours may be provided; for example, a geometrical reversal of the illustrated embodiment comprising detent projections on the connecting member  34  and detent notches on the engagement fingers  12 . 
     As  FIG. 3  shows, the connecting member  34  and the mount  13  defined by the coupling insert  5  are not circular in cross section but are both flattened. In particular the connecting member  34  has two mutually opposing flattened surfaces where the detent notches  41  are provided. The engagement fingers  12  have their inner sides complementary to the two flattened surfaces and the detent notches  41  provided therein. 
     To be able to release the lock shown in  FIG. 1  between the coupling insert  5  and the connecting member  34  of the toothbrush handpiece  4 , the coupling member  3  of the attachment brush  33  includes an actuating member  7  in the form of a ring which in the illustrated embodiment is seated on the frontal end of the tubular coupling member  3  on the side remote from the working head  2 . The ring may be provided as a colored ring so that it performs the dual function of individualizing the attachment brush  33  by the user being able to identify “his” or “her” attachment brush from the color of the actuating member  7 . 
     The actuating member  7  comprises two unlocking sections  8 , each in the form of an actuating finger  21  projecting axially in the attachment longitudinal direction into the interior of the coupling member  3 . These actuating fingers  21  engage in the mount  13  formed by the coupling insert  5  in the area of the free ends of the engagement fingers  12 . Provided on the projecting ends of the actuating fingers  21  are beveled surfaces  10  which serve to cooperate with beveled surfaces on the projecting ends of the engagement fingers  12  of the coupling insert  5 . The beveled surfaces  9  and  10  are formed such that during the axial riding motion of the engagement fingers  12  over the actuating fingers  21 , the engagement fingers  12  are spread radially outwardly, whereby they are lifted out of the detent notches  41  in the connecting member  34  of the toothbrush handpiece  4 . 
     In the illustrated embodiment the coupling insert  5  is axially displaceable in the coupling member  3  in order to produce the axial movement. Alternatively or in addition, the annular actuating member  7  could be axially displaceable in the coupling member  3 . In the illustrated embodiment the actuating member  7  is, however, securely seated on the coupling member  3  by a catch mechanism  42  on the inner wall of the coupling member  3 . 
     Consequently, the following mode of operation results: 
     While the attachment brush  33  is being plugged onto the toothbrush handpiece  4 , the connecting member  34  threads into the mount  13  of the coupling insert  5 , whereby the detent hooks  11  slide along the outer circumferential surface of the connecting member  34  as the engagement fingers  12  spread open. Upon the fully plugged-on position being reached, the engagement fingers  12  spring radially inwardly causing the detent hooks  11  to engage the detent notches  41  with a snap action. The coupling insert  5  forms a spring catch which upon being plugged onto the toothbrush handpiece  4  locks automatically to said handpiece. In the locked position the connecting member  34  sits in the conical mount  13  with a snug fit. Similarly, the coupling insert  5  is snugly received in the insert mount  16  of the coupling member  3 . 
     To release the positive-engagement lock the user simply needs to pull the attachment brush  33  in the attachment longitudinal direction  38  off the toothbrush handpiece  4 . This results first in an axial relative movement between the coupling member  3  and the coupling insert  5  because the latter is held by the detent hooks  11  axially securely on the toothbrush handpiece  4 . As the result of such axial relative movement the actuating fingers  21  of the actuating member  7  move under the engagement fingers  12  or the detent hooks  11  so that the engagement fingers  12  are lifted by way of the pair of beveled surfaces  9  and  10  radially out of the detent notches  41 . During the axial relative movement between the coupling insert  5  and the coupling member  3 , a corresponding deformation of the spring sections  18  and  19  of the spring  17  occurs. 
     When the engagement fingers  12  with their detent hooks  11  are unlocked from the toothbrush handpiece  4 , the coupling insert  5  is pulled together with the coupling member  3  off the handpiece  4 . The spring  17  operates to return the coupling insert  5  to its initial position. This spring return function is advantageous but not absolutely necessary. Due to the conical configuration of the mount  13  and/or a possibly provided follower element, the coupling insert  5  would be pushed back into its locking position when plugged again onto the toothbrush handpiece  4  even in the absence of the spring  17 . 
     As is shown in  FIG. 2 , in a particular embodiment, the plug-on shaft  29  of the attachment brush  33  is coupled to the drive shaft  31  in the handpiece by conical faying surfaces, and the drive shaft  31  is conically shaped on its end protruding from the housing of the handpiece  4 , a bevel being equally allowed to be greater than 7°. The plug-on shaft  29  has a conformably shaped, frontally open, advantageously blind-hole type mount  43  which comprises a faying surface  32  which is adapted to the taper of the drive shaft  31  and likewise has a bevel of more than 7°. By firmly plugging on the attachment brush  33  it is possible to obtain a connection by positive and/or frictional engagement between the plug-on shaft  29  and the drive shaft  31 . This connection may be free of axially effective snap-action connections or other axial holding means. 
     In a particular embodiment of the invention shown in  FIG. 4 , the unlocking of the coupling insert  5  relative to the toothbrush handpiece  4  does not have to be effected at the free ends of the engagement fingers  12  nor by an actuating member in the form of a ring inserted at the front end. As  FIG. 4  shows, the engagement sections  6  of the coupling insert  5  may be configured advantageously in the form of a rocker  44 . In a manner similar to that previously described in  FIGS. 1 to 3 , the sleeve-shaped coupling insert  5  is provided with engagement fingers  12  which extend in the longitudinal direction, are able to spring radially outwardly and inwardly and mount detent hooks  11  on their free ends in corresponding manner. However, the engagement fingers  12  are mounted in a middle section by way of a joint  45  for pivotal movement relative to the remaining body of the sleeve-shaped coupling insert  5 , whereby the joint  45  can be configured in the form of a flexible connecting section which connects said engagement fingers  12  to the remaining body of the coupling insert  5 . In this arrangement, the engagement fingers  12  project axially beyond the joints  45  and have on their ends remote from the detent hooks  11  beveled surfaces  9  which cooperate with beveled surfaces  10  on the inner wall of the coupling member  3 . At the same time the beveled surfaces  9  and  10  form detent means  46  by means of which the coupling insert  5  is able to make snap-action engagement with the coupling member  3 . As  FIG. 4  shows, the beveled surfaces  9  on the rockers  44  are part of a radial projection adapted to snap into a circumferential groove in the inner wall of the coupling member  3 . 
     Consequently, the following mode of operation results: When it is desired to unlock the brush attachment  33  from the locked position in the toothbrush handpiece  4  shown in  FIG. 4 , then the attachment brush  33  is simply pulled in the attachment longitudinal direction  38  off the handpiece  4 . This results first in an axial relative movement between the coupling member  3  and the coupling insert  5  because the latter is held by the detent hooks  11  securely on the toothbrush handpiece  4 . As a result, the detent means  46  slide out of their engaged position, with the rockers  44  being actuated by way of the beveled surfaces  9  and  10  so that the engagement fingers  12  pivot about the joints  45  and the detent hooks  11  are levered out of the detent notches  41 . After the unlocking of the detent hooks  11  the coupling insert  5  can then be pulled off together with the coupling member  3 . The colored ring  47  inserted into the coupling member  3  at the frontal end prevents the coupling insert  5  from slipping completely out of the coupling member  3 . 
     When the attachment brush  33  is plugged onto the toothbrush handpiece  4  again, first the connecting member  34  threads into the mount  13  formed by the coupling insert  5 , with the detent hooks  11  sliding over the connecting member  34 . As  FIG. 4  shows, provision is made in the region of the joints  45  for radially inwardly protruding shoulders which form a follower element. During the plugging on, the corresponding frontal surfaces of the connecting member  34  of the handpiece  4  abut against this follower element, thus ensuring that when the plugging on is completed the coupling insert  5  is pressed fully into the coupling member  3  until the detent means  46  snap in place again on the rockers  44  and the engagement fingers  12  spring back again correspondingly in order to cause snapping engagement of the detent hooks  11  with the detent notches  41 . 
       FIGS. 5 and 6  show another implementation of the invention in which the coupling insert  5  includes a bistably mounted, resilient engagement finger  12  which in accordance with the previous embodiments carries on its free end a detent hook  11  which snaps into a corresponding detent notch on the toothbrush handpiece  4 . Where the embodiment shown in  FIGS. 5 and 6  corresponds to the previous embodiments, reference will be made to their description. 
     As  FIGS. 5 and 6  show, the engagement finger  12  is joined to two sections  48  and  49  spaced apart from each other in axial direction on a tension rod  50  in the form of two tension strips  51  and  52  arranged to the right and left of the engagement finger  12 , such that the distance between the two attachment points on the sections  48  and  49  is shorter than the arc length of the engagement finger  12  between said two attachment points. This compels the engagement finger  12  to adopt an arcuately curved position, namely either the locked position illustrated in  FIG. 5  by solid lines or the unlocked position illustrated by broken lines. The section of the engagement finger  12  between the aforementioned sections  48  and  49  forms a pressure strip. The entire arrangement corresponds, so to speak, to a “clicker” which can be pressed bistably back and forth between two positions. 
     To actuate the engagement finger  12  the region of the inner wall of the coupling member  3  provides an actuating member  7  with a protruding actuating lug  53  which during a corresponding axial movement is able to urge the outwardly projecting bulge of the engagement finger  12 , which is in the locking position, radially inwardly in order to force the engagement finger  12  into the unlocked position. In the illustrated embodiment, the actuating member  7  is configured in the form of a slide which is axially displaceable relative to the coupling member  3 . However, other implementations may provide an axially fixed actuating member  7  if required. The return to the re-locked position can be effected by a second actuating lug  54  on the inside of the coupling member  3 , which acts for example on the free end section of the engagement finger  12 , which faces outwards in the unlocked position, cf.  FIG. 5 . In this embodiment, too, the coupling insert  5 , which is of a sleeve-shaped configuration and sits in the coupling member  3 , may be mounted for axial displacement relative to the coupling member  3 . 
     Another implementation is shown in  FIG. 7 , in which the coupling insert  5  is of a sleeve-shaped configuration sitting in the coupling member  3 . The insert mount  16  of the coupling member  3 , in which the coupling insert  5  is seated, and/or the mount  13  of the coupling insert  5  for the toothbrush handpiece  4  may be conically formed in the previously described manner. 
     In the embodiment illustrated in  FIG. 7 , an engagement finger  12  having a radially inwardly protruding detent hook  11  is joined by way of a pivot arm  24  to the body of the coupling insert  5 , such that during swinging back the engagement finger  12  is moved radially outwardly away from the working head  2 , while conversely, during swinging in it is moved radially inwardly towards the working head  2 . The engagement finger  12  runs in a longitudinal groove in the body of the coupling insert  5 . As  FIG. 7  shows, the engagement finger  12  has on its end close to the working head  2  a follower element  55  which cooperates with the frontal end of the connecting member  34  of the toothbrush handpiece  4  while the attachment brush  33  is being plugged onto the handpiece  4 . When said connecting member  34  is inserted into the mount  13  of the coupling insert  5 , the follower element  55  compels the engagement finger  12  to follow it and moves it axially into the recess of the coupling member  3  towards the working head  2 . This forces the engagement finger  12  into its locked position, which is illustrated in  FIG. 7  by solid lines. The detent hook  11  is engaged in the corresponding detent notch  41  on the toothbrush handpiece  4 . 
     To unlock the attachment brush  33 , the user simply needs to pull it in the attachment longitudinal direction  38  off the toothbrush handpiece  4 . This causes the beveled surface  10  of the actuating member  7  to slide off along the beveled surface  9  of the engagement finger  12 , as a result of which the engagement finger  12  is urged radially outwardly and the detent hook  11  is unlocked so that the engagement finger  12  can also be pulled off the toothbrush handpiece  4 . As  FIG. 7  shows, the engagement finger  12  is received in a pocket  56  between the coupling insert  5  and the coupling member  3  to enable it to travel radially outwardly a sufficient distance for disengagement from the detent notch on the toothbrush handpiece. 
     Another embodiment of the invention is shown in  FIGS. 8 and 9 . In this embodiment, the coupling insert  5  has the form of a slotted sleeve so that two approximately half-shell shaped shell segments  26  and  27  define with their inner walls the mount  13  into which the connecting member  34  of the toothbrush handpiece  4  is insertable with a snug fit.  FIG. 9  shows the splitting of the two shell segments  26  and  27 . The two shell segments  26  and  27  are of a conical configuration on both their inner side and their outer side. The mount  13  is accordingly conical and shaped to conform to the likewise conical connecting member  34 ; similarly, the insert mount  16  of the coupling member  3  of the attachment brush  33  is conical. 
     On their inner circumferential surfaces the shell segments  26  and  27  include respective hooks  11  with which they engage the detent notches  41  on the handpiece  4  in a positive-engagement relationship. 
     To enable the locking and unlocking, the coupling insert  5  is mounted for axial displacement in the coupling member  3 . In a particular implementation, as  FIG. 8  shows, this is effected by way of a catch mechanism  57  which is movable back and forth between two axially spaced notched positions. Other mounting options may be utilized in other implementations of the invention; for example, a spring, a stick-slip seat or the like. In the embodiment shown in  FIG. 8 , the two shell segments  26  and  27  are fixed to a detent element  58  in the form of a detent ring which is held circumferentially in detent notches  59  on the coupling member  3 . From this results the following mode of operation: 
     When the brush attachment  33  is to be unlocked from the locked position in the toothbrush handpiece  5  shown in  FIG. 8 , then the attachment brush  33  must be pulled in the attachment longitudinal direction  38  off the handpiece  4 . The coupling insert  5  initially remains axially secured to the toothbrush handpiece  4  because the detent hooks  11  continue to be engaged, as the result of which an axial relative movement occurs between the coupling insert  5  and the coupling member  3 . As this occurs, the detent element  58  is moved into the detent notch  59  which is a greater distance from the working head  2 . Owing to this axial relative movement the coupling insert  5  obtains at the same time more radial clearance on account of the taper of the insert mount  16  so that the shell segments  26  and  27  are able to move apart in a direction transverse to the attachment longitudinal direction  38 . To ensure this moving apart, for the illustrated embodiment features a spring device  28  which biases the shell segments  26  and  27  into their expanded position. In the illustrated embodiment the spring device  28  comprises spring elements which are arranged on the inner circumference of the shell segments  26  and  27  and take support upon the toothbrush handpiece  4 . 
     When the attachment brush  33  is plugged on again, the connecting member  34  of the toothbrush handpiece  4  threads into the mount  13  until follower elements  55  on the shell segments  26  and  27  enter into engagement with the connecting member  34 , as a result of which the coupling insert  5  is pressed deeper into the coupling member  3  during further insertion of the toothbrush handpiece  4 . In the process, the detent element  58  is moved again into the detent notch near the coupling member  3 . At the same time the shell segments  26  and  27  are caused to converge so that the hooks  11  engage again into the detent notches  41 . 
       FIG. 10  shows a particular implementation in which the coupling insert  5  comprises a sleeve-shaped, conical body which forms with its inner side a conical mount  13  for the connecting member  34  of the toothbrush handpiece  4  and is seated with its outer side in the likewise conical insert mount  16  in the coupling member  3 . In another embodiment, the body, the mount and the insert mount may be of a cylindrical rather than conical configuration. Furthermore, the coupling insert  5  includes a detent ring  25  which, on the one hand, can be radially widened and narrowed and can project relative to the inner contour of the sleeve-shaped body of the coupling insert  5 . Alternatively, the detent ring  25  can be axially movable relative to the coupling member  3 . In addition, it includes a beveled surface  9  which cooperates with a corresponding beveled surface  10  on the actuating member  7  which in turn is seated in the form of a ring at the frontal end of the tubular coupling member  3  where it is axially secured in place. Through axial riding of the detent ring  25  over the actuating member  7 , the detent ring  25  is radially expanded by way of the pair of beveled surfaces  9  and  10 , as a result of which the lock can be released. From this results the following mode of operation: When the attachment brush  33  is to be unlocked from the handpiece  4 , the user needs only to pull the attachment brush  33  in the attachment longitudinal direction  38  off the toothbrush handpiece  4 , whereby initially the detent ring  25  remains axially secured to the handpiece  4  as long as the detent ring  25  is in engagement with the detent notch  41 . However, said ring is expanded by way of the pair of beveled surfaces  9  and  10  the further the coupling member  3  is pulled off axially until it is eventually disengaged from the detent notch  41  and can be pulled together with the coupling member  3  off the toothbrush handpiece  4 . The detent ring  25  is elastically biased into its narrowed locking position; for example, in the manner of a snap ring, so that it returns on its own to its locking position. When the attachment brush  33  is plugged on again, the detent ring  25 , in expanding elastically, slides over the connecting member  34  of the toothbrush handpiece  4  until it can snap into its detent notches  41 . 
       FIGS. 11 to 14  show a particular implementation of the invention. In this implementation the coupling insert  5  is configured such that it can be plugged onto a toothbrush handpiece  4  having a more pronounced taper as well as onto a cylindrical connecting member  34  of a corresponding toothbrush handpiece  4 . For this purpose the engagement fingers  12  of the coupling insert  5  are fixed in their initial condition in a position in which they protrude relative to the remaining body of the coupling insert, namely by means of predetermined breaking points or predetermined breaking pieces  23 . As  FIG. 13  shows, material lands  60  which bridge the U-shaped slits around the engagement fingers  12  are left standing between the sleeve-shaped body and the engagement fingers  12 . The detent hooks  11  on the engagement fingers  12  are formed and arranged such that they form with their inner circumferential surface a clamping surface which can be pushed with a snug fit onto the cylindrical circumferential surface of the connecting member  34  of the toothbrush handpiece  4 . Starting from the detent hooks  11 , the inner circumferential contour of the engagement fingers  12  is of a slightly conical configuration so that the circumferential surface section of the connecting member  34  of the toothbrush handpiece  4 , which is provided at the frontal end, can also be firmly clamped in place, cf.  FIG. 11 . 
     As  FIGS. 13 and 14  show, another two engagement fingers  112  are provided on the coupling insert  5 , which are each offset by 90° in relation to the engagement fingers  12  and separated from said coupling insert likewise by U-shaped slits in the sleeve-shaped body of the coupling insert  5 . Predetermined breaking pieces  23  are also provided in the form of material lands  60  which are left standing and force the engagement fingers  112  likewise into an inwardly protruding position, which is shown in  FIG. 13 . In corresponding manner these additional engagement fingers  112  define with their inner circumferential surface faying surfaces which can be pushed with a snug fit, in particular by frictional and/or clamping engagement, onto the outer cylindrical surface of the connecting member  34  of the toothbrush handpiece  4 . 
     This particular implementation also enables the coupling insert  5  to be fixed with a snug fit on a cylindrical connecting member  14 . In contrast, if the coupling insert  5  is to be pushed onto a conical connecting member  34  of a corresponding toothbrush handpiece  4 , as is shown in  FIGS. 1 and 2 , then the predetermined breaking pieces  23  will break open, thereby enabling the engagement fingers  12  and  112  to spring outwardly, as a result of which the entire inner circumferential surface of the sleeve-shaped body of the coupling insert  5  can act as a mount  13  into which the conical connecting member of the toothbrush handpiece  4  can be inserted with a snug fit. The engagement fingers  12  then provide the catch mechanism as was described in connection with  FIGS. 1 to 3 .