Personal hygiene device

Abstract

The present disclosure relates to a personal hygiene device extending in three-dimensional space spanned by an xyz coordinate system, comprising a drive unit, a support, a stator fixedly mounted to the support, and an armature spring-mounted to the support for linear oscillatory motion driven along a first longitudinal direction parallel to or coincident with the x-axis of the xyz coordinate system, the armature rotating along coordinates [x a ;y a ;z a ], and a drive shaft fixedly connected to the armature, wherein the drive shaft is arranged to move along coordinates [x d ;y d ;z d a drive unit having a drive shaft with a center of gravity located at a coordinate [x t1 ;y t1 ;z t1 a first treatment head assembly having a center of gravity located at a coordinate [x ]; and a secondary mass element spring-mounted to the support for essentially linear oscillatory movement along a first longitudinal direction, the secondary mass element having a coordinate [x ] at rest. m ;y m ;z m ], and a secondary mass element having a center of gravity located at the coordinates of the center of gravity of at least the armature [x a ;y a ;z a ] is the coordinate of the center of gravity of the drive shaft [x d ;y d ;z d ], or the coordinates of the center of gravity of the first processing head assembly [x t1 ;y t1 ;z t1 ], has an offset in at least one of the y direction or the z direction, i.e., y a ≠y d and / or y a ≠y t1 and / or z a ≠z d and / or z a ≠z t1 The coordinates of the center of gravity of the secondary mass element are [xm ;y m ;z m ] is a coordinate [x j ;y j ;z j ], i.e., y m =y j and z m =z j As a result, the coordinates of the center of gravity of the secondary mass element [x m ;y m ;z m ] and the coordinate of the composite center of gravity [x j ;y j ;z j ] is designed so that the line connecting them is parallel to or coincides with the x-axis.

Description

Technical Field

[0001] The present disclosure relates to a personal hygiene device comprising a drive unit having a stator armature assembly in which an armature is spring-mounted to a support, and a secondary mass element spring-mounted to the support.

Background Art

[0002] Personal hygiene devices such as electric toothbrushes can be driven by a resonant motor comprising a stator and an armature which is driven in a reciprocating motion and pushed back to its rest position by a restoring force (the restoring force can typically be provided by at least one elastic element such as a leaf spring). Various designs of such resonant motors are known to those skilled in the art. The resonant motor can drive a drive shaft in a linear reciprocating motion. The personal hygiene device may be equipped with a secondary spring mass resonator arranged to cancel out the vibrations generated by the reciprocating armature of the resonant motor by generating an anti-periodic motion and generating vibrations having substantially the same amplitude but a 180-degree shifted phase. International Publication No. WO 2014 / 009916 (A2) discloses one possible design of such a resonant motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is generally a need to optimize the vibration behavior of a personal hygiene device comprising a drive unit having a moving armature and a secondary mass element for canceling out the vibrations generated by the moving armature.

Means for Solving the Problems

[0005] According to at least one embodiment, a personal hygiene device extending in a three-dimensional space spanned by an xyz coordinate system, comprising a drive unit comprising a support, a stator fixedly attached to the support, and an armature spring-mounted to the support for a linear oscillatory motion driven along a first longitudinal direction parallel to or coinciding with an x-axis of the xyz coordinate system, the armature rotating along a coordinate [x a ;y a ;z a ], and a drive shaft fixedly connected to the armature, the drive shaft being moved along coordinates [x d ;y d ;z d and a first treatment head assembly removably connected to the drive shaft, the first treatment assembly being adapted to rotate about coordinates [x t1 ;y t1 ;z t1 a first treatment head assembly having a center of gravity located at a first longitudinal direction; and a secondary mass element spring-mounted to the support for essentially linear oscillatory motion along a first longitudinal direction, the secondary mass element moving at rest along coordinates [x m ;y m ;z m ], and a secondary mass element having a center of gravity located at least at the coordinates of the center of gravity of the armature [x a ;y a ;z a ] is the coordinate of the center of gravity of the drive shaft [x d ;y d ;z d ], or the coordinates of the center of gravity of the first processing head assembly [x t1 ;y t1 ;z t1 ], i.e., y a ≠y d and / or y a ≠y t1 and / or z a ≠z d and / or z a ≠z t1 The secondary mass element has the coordinates of the center of gravity of the secondary mass element [xm ; y m ; z m is aligned with the coordinates [x j ; y j ; z j of the combined center of gravity of the drive shaft, the first processing head assembly, and the armature in at least one offset direction, i.e., y m = y j and z m = z j and as a result, the line connecting the coordinates [x m ; y m ; z m of the center of gravity of the secondary mass element and the coordinates [x j ; y j ; z j of the combined center of gravity is designed to be parallel to or coincide with the x-axis. Personal hygiene device.

Brief Description of the Drawings

[0006] This disclosure will become clearer by a detailed description of exemplary embodiments and also by referring to the drawings.

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Modes for Carrying Out the Invention

[0007] In the context of this specification, "personal hygiene" means the cultivation (or care) of the skin and its appendages (i.e., hair and nails), as well as the teeth and oral cavity (including the tongue, gums, etc.), aiming on the one hand at disease prevention and health maintenance and enhancement ("hygiene"), and on the other hand at aesthetic treatment of the skin and its appendages and improvement of appearance. This includes the maintenance and enhancement of well-being. This includes skin care, hair care, oral care, and nail care. This further includes other grooming operations such as beard care, shaving, and hair removal. Thus, a "personal hygiene device" means any device for performing such cultivation or grooming operations, for example, (cosmetic) skin treatment devices such as skin massage devices or skin brushes; wet shavers; electric shavers or trimmers; electric hair removal devices; and oral care devices such as manual or electric toothbrushes, (electric) flossers, (electric) cleaners, (electric) tongue cleaners, or (electric) gum massagers. This does not exclude the possibility that the proposed personal hygiene device may have more significant advantages in one or more of these cultivation or device areas than in one or more of the other of these device areas.

[0008] The proposed personal hygiene device comprises a treatment head for providing a hygiene treatment. An electric toothbrush is an example of an electric personal hygiene device, specifically an example of a group of electric oral care devices.

[0009] According to the present disclosure, a personal hygiene device has a drive unit comprising a support, a stator fixedly attached to the support, and an armature spring-mounted to the support for a linear oscillatory motion driven along a first longitudinal direction parallel to or coinciding with the x-axis of the xyz coordinate system. The armature has a center of gravity located at the coordinates of the xyz coordinate system indicated by [x a ;y a ;z a , where x a is the x-component, y a is the y-component, z ais the z component, and these notations are used as follows. The armature may be attached to the support by at least one plate-shaped leaf spring, in particular by at least two plate-shaped leaf springs, and these plate-shaped leaf springs extend in a plane parallel to the yz plane of the xyz coordinate system at rest.

[0010] According to the present disclosure, a personal hygiene device has a drive shaft fixedly coupled to an armature, and the drive shaft has a center of gravity located at coordinates [x d ;y d ;z d at rest. The personal hygiene device further has a first treatment head assembly removably connected to the drive shaft. The first treatment assembly has a center of gravity located at coordinates [x t1 ;y t1 ;z t1 at rest. The personal hygiene device also includes a secondary mass element spring-mounted to the support for linear oscillatory motion along a first longitudinal direction, and the secondary mass element has a center of gravity located at coordinates [x m ;y m ;z m at rest. The secondary mass element may be attached to the support by at least one plate-shaped leaf spring, in particular by at least two plate-shaped leaf springs, and these plate-shaped leaf springs extend in a plane parallel to the yz plane of the xyz coordinate system in a stationary state.

[0011] According to the present disclosure, the coordinates [x a ;y a ;z a of at least the center of gravity of the armature have an offset in at least one of the y and z directions with respect to the coordinates [x d ;y d ;z d of the center of gravity of the drive shaft, or with respect to the coordinates [x t1 ;y t1 ;z t1 of the center of gravity of the first treatment head assembly, that is, y a ≠y d and / or y a ≠y t1 and / or z a ≠zd and / or z a ≠z t1 is. The secondary mass element has the coordinates [x m ; y m ; z m of the center of gravity of the secondary mass element, which is aligned with the coordinates [x j ; y j ; z j of the combined center of gravity of the drive shaft, the first processing head assembly and the armature in at least one offset direction, that is, y m = y j and z m = z j is, and as a result, the line connecting the coordinates [x m ; y m ; z m of the center of gravity of the secondary mass element and the coordinates [x j ; y j ; z j of the combined center of gravity is designed to be parallel to or coincide with the x-axis.

[0012] The system described is known to provide low vibration on the outer surface of a handle gripped by a user when the forces transmitted by the mounting spring or springs of the moving armature (along with the mass attached to the armature) and the forces transmitted to the support by the mounting spring or springs of the counter-vibration secondary mass element cancel each other out. This is achieved, inter alia, by bringing their masses closer to each other or making these masses identical, and in particular by adapting the mounting springs so that the resonance frequency of the spring-type secondary mass element is as close as possible to the driving frequency. WO 2014 / 009916 (A2) generally considers this. However, it has been found that a design as shown and considered in WO 2014 / 009916 (A2) still results in residual vibrations that a user may feel when holding the handle. Such residual vibrations may be related to the offset between the center of gravity of the armature, the drive shaft, and the first processing head assembly in the yz plane and the center of gravity of the secondary mass element in the yz plane, i.e., at least one offset in the y or z direction. In a design according to the general description of WO 2014 / 009916 (A2), a z-direction offset is induced by the specific shape of the armature. It is proposed herein to align the center of gravity so that their y-components and their z-components have the same value, reducing the residual vibrations. This means reducing the vibrations felt at the handle by aligning the center of gravity so that the line connecting the two centers of gravity is parallel (or coincident) with the x-axis of the xyz coordinate system defined above, and the simulation results are further considered below in conjunction with FIGS. 4A and 4B.

[0013] The proposed personal hygiene device may comprise a handle part having a handle housing that can be gripped by the user's hand. The support of the drive unit itself may be mounted so as to pivot relative to the handle housing. An elastic element, such as a spring element, may provide a restoring force against any force that pivots the support around the pivot axis. The support may be coupled to a force sensor that enables measuring the force acting on the support and pivoting the support. The personal hygiene device may comprise an exchangeable brush head that itself forms a treatment head or has a treatment head housing to which the treatment head is attached for the movement to be driven. The treatment head housing may then be fixedly coupled to the support. The treatment head may be mechanically coupled to a motion transmission part to form a treatment head assembly.

[0014] The drive unit may comprise a periodic drive signal (e.g., alternating current) used to drive the armature in a reciprocating motion. The drive frequency of the periodic drive signal may be selected to be in the range of 100 Hz to 200 Hz, particularly in the range of 120 Hz to 170 Hz, and even more particularly in the range of 140 Hz to 150 Hz.

[0015] The armature may integrally include a drive shaft, or the drive shaft may be removably coupled to the armature. The drive shaft is used to transmit the motion provided by the armature to a processing head that is driven. The drive shaft may be magnetically coupled to a treatment head assembly that includes a treatment head. The armature (along with any other mass connected to the armature) forms a resonant spring mass system by means of a spring or a plurality of springs by which the armature is attached to a support. The armature may include at least one permanent magnet, and the stator may include a coil that receives an alternating current at a drive frequency, and the drive frequency is selected to be at or near the resonant frequency of the armature spring system. A secondary mass spring system that is a spring attached to the support may form a further resonant spring mass system that may be considered independent of the armature spring system when the support is assumed to be spatially fixed. The drive frequency may be selected to be at or as close as possible to the resonant frequency of the secondary mass element spring system. The secondary mass element spring system is arranged to be excited into linear reciprocating motion by the vibration of the support generated by the armature spring system. The linear motion of the secondary mass element is phase-shifted by 180 degrees with respect to the armature motion. The secondary mass element may be made of a laminated metal sheet.

[0016] The personal hygiene device and the drive unit extend in a three-dimensional space, and the 3D space can be spanned by a Cartesian coordinate system, so that each point in the space can be defined by coordinates [x; y; z]. In a stationary state, various elements of the drive unit, in particular, the armature, the secondary mass element, the drive shaft, and the treatment head assembly, each have a center of gravity that can be determined by their respective coordinates as already discussed. For example, the coordinates [x a ; y a ; z a indicate the center of gravity of the armature, the coordinates [x m ; y m ; z m indicate the center of gravity of the secondary mass element, [x d ; y d ; z d indicate the center of gravity of the drive shaft, and the coordinates [x t1; y t1 ; z t1 indicates the center of gravity of the first treatment head assembly. Here, "first" is used to distinguish the first treatment head assembly, which is part of the personal hygiene device, from a potential further (second) treatment head assembly. The personal hygiene kit may then comprise the personal hygiene device and at least one further replacement head comprising a second treatment head assembly. The mass and the coordinates of the center of gravity of the second treatment head assembly [x t1 ; y t1 ; z t1 may be selected such that two different replacement heads generate different vibration characteristics of the personal hygiene device.

[0017] Figure 1 is a view of an exemplary personal hygiene device 1 implemented as an electric toothbrush. The personal hygiene device 1 comprises a handle part 20 and a first replacement head 10 removably attached to the handle part 20. The first replacement head 10 may comprise a first treatment head 11 attached to a first treatment head housing 12 for movement driven relative to the first treatment head housing 12. The first motion transmission part may be coupled to the first treatment head 11 or may be disposed within the hollow of the first treatment head housing 12. The first treatment head 11 and the first motion transmission part may then together form a first treatment head assembly, as will be considered in more detail below. The first replacement head 10 can be removed and replaced by a new, essentially identical replacement head when the first replacement head 10 is worn out, or the first replacement head 10 can be complemented by at least a second replacement head that provides a different treatment or is intended for use by a different user. In this case, an electric toothbrush is shown and the first replacement head 10 is realized as a brush head that provides a first cleaning treatment of the teeth. Different from the first brush head, a second brush head (i.e., a second replacement head) that provides a different treatment effect may be provided. For example, the second brush head may be structured for a better toothbrushing effect or for a better gum massage effect than the first brush head.

[0018] Figure 2 is a cross-sectional view of an exemplary personal hygiene device 1A according to the present disclosure, which extends within a Euclidean 3D space spanned by a Cartesian xyz coordinate system, enabling the definition of absolute positions of space and relative distances. As an example of all possible coordinate systems that can be used to span the Euclidean 3D space, the Cartesian coordinate system is used. The personal hygiene device 1A is realized as an electric toothbrush and is considered as a non-limiting example, and includes a handle portion 20A and a first replaceable head 10A. The first replaceable head 10A includes a first treatment head 110A and a first motion transmission portion 111A, which together form a first treatment head assembly 120A. Here, the first treatment head 110A includes a carrier element 1102A to which at least one treatment element 1101A is attached. In the illustrated embodiment, a plurality of filament tufts are attached onto the carrier element 1102A. The first treatment head 110A is here attached to a first treatment housing 112A for oscillatory rotation M2 driven about a rotation axis R defined by an axis 1103A. The first motion transmission portion 111A includes a coupling portion 113A pivotally connected to the remainder of the first motion transmission portion 111A. The first treatment head 110A is attached to the first treatment head housing 112A. The first treatment head housing 112A is removably connected to a treatment head adapter 235A of the handle portion 20A.

[0019] The handle portion 20A includes a handle housing 220A and a support 210A pivotally attached to the handle housing 220A, so that the support 210A can pivot around a pivot axis P defined by a shaft 211A. The support 210A carries a drive unit 230A that includes a stator 231A fixedly attached to the support 210A, and an armature 232A and a secondary mass element 233A each spring-mounted to the support 210A. The stator 231A may include a coil, and the armature 232A may include at least one permanent magnet as commonly known in the art, so that the armature 232A can be driven in a linear reciprocating motion M1 when an alternating current is provided to the coil. The driving frequency of the alternating current may be selected to be in the range of 100 Hz to 200 Hz. The drive shaft 234A is fixedly connected to the armature 232A here, and the drive shaft extends along a longitudinal axis L that coincides with or is parallel to the x-axis of the Cartesian xyz coordinate system (in the illustrated example, the longitudinal axis L is parallel to the x-axis of the illustrated Euclidean coordinate system). The front end portion of the drive shaft 234A may include a permanent magnet for coupling with another permanent magnet or a magnetizable metal element provided at a coupling portion 113A of the first motion transmission portion 111A. The processing head adapter 235A forms the front end portion of the support 210A, so that an external force F having a positive z-direction component applied to the first processing head 110A causes a pivoting motion of the support 210A around the pivot axis P. The support 210A may be spring-mounted to the handle housing 220A so that a restoring spring force acts to return the support 210A to its rest position.

[0020] The personal hygiene device 1A may comprise a chassis element 240A that can carry an energy source 241A such as a battery or a rechargeable battery, control electronics, and a PCB 242A that potentially includes at least one sensor for measuring the deflection of a support 210A relative to a handle housing 220A. The support 210A may be pivotally attached to the chassis element 240A, among other things, and the chassis element 240A may be fixedly attached to the handle housing 220A such that the chassis element 240A can be regarded as a part of the handle housing 220A.

[0021] The armature 232A has a center of gravity with coordinates [x a ; y a ; z a (for the center of gravity, also refer to FIG. 3). As can be seen in the illustrated embodiment, the armature 232A is offset from the longitudinal axis L. Thus, the z - coordinate z a is offset from the longitudinal axis L in the illustrated embodiment, and the z - coordinate of the longitudinal axis is shown as z L . The secondary mass element 233A has a center of gravity with coordinates [x m ; y m ; z m . One skilled in the art may, among other things, select the positioning of the secondary mass element such that the z - coordinate of the center of gravity of the secondary mass element coincides with the longitudinal axis, i.e., z m = z L for reasons related to the use that conforms to the available structural volume. Further, the drive shaft 234A has a center of gravity with coordinates [x d ; y d ; z d . When the drive shaft 234A extends along the longitudinal axis L, the z - coordinate of the drive shaft 234A coincides with the z - coordinate of the longitudinal axis L in the illustrated example, i.e., z d = z L . The first treatment head assembly 120A, when stationary, has coordinates [x t1 ; y t1 ; z t1Due to the particular design of the illustrated exemplary first treatment head assembly 120A, the z and y coordinates of the center of gravity of the first treatment head assembly 120A are offset from the longitudinal axis L.

[0022] In operation, the armature 233A is driven into a reciprocating longitudinal motion M1, which moves with the drive shaft 234A and the first process head assembly 120A. By the general principle of conservation of impulse, the impulse of the driven moving parts is in the opposite direction to that transmitted to the support 210A. The spring-mounted secondary mass element 233A is then excited into a reciprocating linear motion M1' that is shifted in phase by 180 degrees by the force acting on the support. The mass M of the armature 233A is a and the mass M of the drive shaft 234A. d and the mass M of the first processing head assembly 120A. t1 Adding these together, we get the combined mass of the driven parts M j , M j =M a +M d +M t1 The combined mass of the driven moving parts M j The mass M of the secondary mass element 233A is essentially the same as m It may be desirable to select a spring constant for the spring or springs attaching the secondary mass element 233A to the support, which may be selected so that the secondary mass element 233A moves essentially in resonance with the drive frequency at which the armature 232A is driven into motion. With such a design, the forces transmitted by the moving parts to the support 210A and from the support 210A to the handle housing 220A essentially cancel each other out. However, as already discussed in the previous paragraph, it has been found that some perceptible vibrations still occur in the handle housing 220B.

[0023] Figure 3 shows a multi-body block diagram used in a simulation program to understand vibration (i.e., amplitude), showing various combined masses and their motion constraints, synthesis, and applied forces. m1 is the mass representing the support 210B and the stator 231B, m2 is the mass of the secondary mass element 233B, which is spring-mounted to the support 210B and is a constraint on linear motion due to the spring stiffness in a direction perpendicular to the longitudinal motion direction, m3 is the mass of the armature 233B and the drive shaft 234B, which are spring-mounted to the support 210B and are similarly constrained in linear motion. Further, in order to drive the armature 233B in motion, a periodically alternating force acts between the stator 231B and the armature 233b. m13 is the mass of the coupling portion 113B of the first processing head assembly 120B, assuming that the coupling portion 113B is fixedly connected to the drive shaft 234B. m11 is the remaining mass of the motion transmission portion 111B pivotally hinged to the coupling portion 113B. m12 is the mass of the first treatment head 110B pivotally mounted to the first treatment head housing 112B. The motion transmission portion 111B is pivotally mounted to the first treatment head 110B. Finally, m10 is the mass of the first treatment head housing 112B assumed to be fixedly connected to the support 210B. MP1, MP2, and MP3 are the measurement points where the obtained vibrations of the simplified model of the interacting components shown are investigated. As schematically shown in Figure 3, in the stationary state, the coordinates of the center of gravity of the armature 232B are [x a ;y a ;z a , the coordinates of the center of gravity of the drive shaft 234B are [x d ;y d ;z d , the coordinates of the center of gravity of the first processing head assembly 120B are [x t1 ;y t1 ;z t1 , and the coordinates of the center of gravity of the secondary mass element 233B are [x m ;y m ;z mThat is. Simscape (trademark) Multibody (trademark) software available from MathWorks, Natick, MA, USA can be used for such simulations.

[0024] Figures 4A and 4B show the simulation results of the effects of shifting the z - coordinate and y - coordinate of the center of gravity of the secondary mass element 233B of the considered arrangement for the vibration amplitude A v respectively. In Figure 4A, the vibration amplitude in the z - direction is shown, and in Figure 4B, the vibration amplitude in the y - direction is shown. In Figures 4A and 4B, z = 0 and y = 0 represent positions on the longitudinal central axis of the drive shaft 234B. In the simulation shown in Figure 4A, the y - coordinate of the secondary mass element 233B was fixed at y m = 0. In the simulation shown in Figure 4B, the z - coordinate of the secondary mass element 233B was fixed at z m = 0. The vibration amplitude indicates the minimum value of the position of the center of gravity of the secondary mass element offset from the longitudinal axis. This effect is more significant for the z - direction offset and also for the measurement point MP3 at the distal end tip of the first treatment head housing. In the simulation, the vibration amplitude A v can be reduced to a level of less than 0.005 mm.

[0025] Therefore, the counter - vibration masses M m and M j already coincide as in the example considered in WO 2014 / 009916 (A2). While the movements of the secondary mass element 233B, the armature 232B, and the drive shaft 234B are essentially restricted to linear motion, the vibrations generated by the moving masses in the support and the first treatment head housing can be further reduced by optimizing the center - of - gravity position of the secondary mass element 233B. If the combined center of gravity of the armature 232B, the drive shaft 234B, and the first treatment head assembly 120B has coordinates [x j ; y j ; Zj] in the stationary state, then in the stationary state, the coordinates of the center of gravity of the secondary mass element 233B are [x m ; y m ; zm is optimally selected to coincide with the coordinates of the center of gravity in the y and z directions, i.e., y m = y j and z m = z j is.

[0026] The user of the personal hygiene device may be stimulated when the personal hygiene device has only a very low perceptible vibration amplitude during operation. Thus, in some embodiments, at least one of the z - coordinate or y - coordinate of the center of gravity of the secondary mass element is offset by a distance in the range of 1 μm to 200 μm, particularly in the range of 5 μm to 100 μm, with respect to the z - coordinate or y - coordinate of the combined center of gravity. Such measurements may cause the user to experience a low vibration amplitude, which is still perceptible in a reassuring way.

[0027] In some embodiments, the personal hygiene device comprises a second replaceable head. Once attached, the coordinates of the center of gravity of the second replacement head [x t2 ; y t2 ; z t2 are different from the corresponding center of gravity of the first replacement head [x t1 ; y t1 ; z t1 in at least one of the y - coordinate and z - coordinate. This makes it possible to control the vibration amplitude felt by the user. For example, if the first replacement head has a normal cleaning function and the second replacement head has a function related to higher power for the user, e.g., a polishing function, a higher vibration amplitude can convey the impression of higher power by the higher vibration amplitude. A similar effect can be achieved by different masses of the first and second treatment head assemblies. At least one of the two discussed measured values can be used.

[0028] The dimensions and values disclosed in this specification are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise indicated, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.

Claims

1. A personal hygiene device extending within a three-dimensional space spanned by an xyz coordinate system, a drive unit, a support, a stator fixedly attached to the support, An armature spring-mounted to the support for linear oscillatory motion driven along a first longitudinal direction parallel to or coinciding with the x-axis of the xyz coordinate system, the armature having a center of gravity located at coordinates [x ａ ; y ａ ; z ａ in a stationary state, the armature, and a drive shaft fixedly coupled to the armature, the drive shaft having a center of gravity located at coordinates [x ｄ ; y ｄ ; z ｄ in a stationary state, the drive shaft, and a drive unit having the drive shaft. A first treatment head assembly removably connected to the drive shaft, wherein the first treatment head assembly has a center of gravity located at coordinates [x ｔ１ ; y ｔ１ ; z ｔ１ when at rest, the first treatment head assembly; A secondary mass element spring-mounted to the support for the essentially linear oscillatory movement along the first longitudinal direction, the secondary mass element having a center of gravity located at coordinates [x ｍ ; y ｍ ; z ｍ in a stationary state, and comprising a secondary mass element. At least the coordinates [x ａ ; y ａ ; z ａ of the center of gravity of the armature are offset in at least one of the y or z directions with respect to the coordinates [x ｄ ; y ｄ ; z ｄ of the center of gravity of the drive shaft, or with respect to the coordinates [x ｔ１ ; y ｔ１ ; z ｔ１ of the center of gravity of the first treatment head assembly, i.e., y ａ ≠ y ｄ and / or y ａ ≠ y ｔ１ and / or z ａ ≠ z ｄ and / or z ａ ≠ z ｔ１ and the secondary mass element has the coordinates [x ｍ ; y ｍ ; z ｍ of the center of gravity of the secondary mass element aligned in the at least one offset direction with the coordinates [x ｊ ; y ｊ ; z ｊ of the combined center of gravity of the drive shaft, the first treatment head assembly, and the armature, i.e., y ｍ = y ｊ and z ｍ = z ｊ and as a result, the line connecting the coordinates [x ｍ ; y ｍ ; z ｍ of the center of gravity of the secondary mass element and the coordinates [x ｊ ; y ｊ ; z ｊ of the combined center of gravity is designed to be parallel to or coincide with the x-axis, The personal hygiene device, wherein the alignment of the coordinates in the offset direction has a residual offset in the range of 5 μm to 100 μm.

2. The coordinates [x ａ ; y ａ ; z ａ of the center of gravity of the armature have an offset in the y - direction and the z - direction with respect to the coordinates [x ｄ ; y ｄ ; z ｄ of the center of gravity of the drive shaft, that is, y ａ ≠y ｄ and z ａ ≠z ｄ ; or the coordinates [x ｔ１ ; y ｔ１ ; z ｔ１ of the center of gravity of the first treatment head assembly have an offset in the y - direction and the z - direction, that is, y ａ ≠y ｔ１ and z ａ ≠z ｔ１ ; and the coordinates [x ｍ ; y ｍ ; z ｍ of the center of gravity of the secondary mass element are aligned in the y - direction and the z - direction with the coordinates [x ｊ ; y ｊ ; z ｊ of the combined center of gravity of the drive shaft, the first treatment head assembly, and the armature, that is, y ｍ = y ｊ and z ｍ = z ｊ ; and as a result, the line connecting the coordinates [x ｍ ; y ｍ ; z ｍ of the center of gravity of the secondary mass element and the coordinates [x ｊ ; y ｊ ; z ｊ of the combined center of gravity is designed to be parallel to or coincide with the x - axis. The personal hygiene device according to claim 1.

3. The personal hygiene device according to claim 1 or 2, comprising a handle housing that can be gripped by a user's hand and a first treatment head housing removably attached to the attachment portion of the support.

4. The personal hygiene device according to claim 3, wherein the first treatment head assembly is movably attached to the first treatment head housing, and the first treatment head assembly and the first treatment head housing together form a first replacement head.

5. The personal hygiene device according to claim 4, wherein the first treatment head assembly includes a first treatment head movably attached to the first treatment head housing for vibratory rotation driven about a rotation axis parallel to the z direction, and a first motion transmission unit removably coupled to the drive shaft and the first treatment head.

6. The personal hygiene device according to claim 5, wherein the first motion transmission unit and the drive shaft are coupled by magnetic coupling.

7. The personal hygiene device according to any one of claims 4 to 6, wherein the drive unit is provided to drive the first treatment head assembly at a frequency in the range of 100 Hz to 200 Hz.

8. The personal hygiene device according to any one of claims 1 to 7, wherein the secondary mass element is made of a laminated metal sheet.

9. The personal hygiene device according to any one of claims 1 to 7, wherein the armature and the secondary mass element are attached to the support by leaf springs each extending in a plane parallel to the yz plane of the xyz coordinate system in a stationary state.

10. The personal hygiene device according to any one of claims 4 to 9, and at least one second replacement head comprising a second treatment head housing and a second treatment head assembly, wherein the center of gravity of the second treatment head assembly, in the mounted state, has coordinates [x ｔ１ ; y ｔ１ ; z ｔ１ with an offset relative to the coordinates [x ｔ２ ; y ｔ２ ; z ｔ２ of the center of gravity of the first treatment head assembly, or the second treatment head assembly has a weight different from the weight of the first treatment head assembly, a personal hygiene device kit.

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