Personal hygiene device

A personal hygiene device, extending in a 3-dimensional space that is spanned by an x-y-z coordinate system, the device comprising:

• a drive unit having a support and a stator fixedly mounted at the support;
• an armature that is spring-mounted at the support for driven linear oscillating motion along a first longitudinal direction that is parallel to or coincides with the x-axis of the x-y-z coordinate system, the armature having a center of gravity located in rest at a coordinate [xa, ya, za] and a drive shaft fixedly coupled with the armature, the drive shaft having a center of gravity located in rest at a coordinate [xd, yd, zd];
• a first treatment head assembly detachably connected to the drive shaft, the first treatment assembly having a center of gravity located in rest at a coordinate [xt1, yt1, zt1] and a secondary mass element spring-mounted at the support for essentially linear oscillating motion along the first longitudinal direction, the secondary mass element having a center of gravity located in rest at a coordinate [xm, ym, zm];
• wherein at least the coordinate [xa, ya, za] of the center of gravity of the armature has an offset in at least one of the y-direction and z-direction with respect to the coordinate [xd, yd, zd] of the center of gravity of the drive-shaft or with respect to the coordinate [xt1, yt1, zt1] of the center of gravity of the first treatment head assembly, wherein ya≠yd and/or ya≠yt1 and/or za≠zd and/or za≠zt1, and the secondary mass element is configured such that the coordinate [xm, ym, zm] of the center of gravity of the secondary mass element is aligned with coordinate [xj, yj, zj] of a joint center of gravity of a combination of the drive shaft, the first treatment head assembly, and the armature in the at least one offset direction, wherein ym=yj and zm=zj, so that a line connecting the coordinate [xm, ym, zm] of the center of gravity of the secondary mass element and the coordinate [xj, yj, zj] of the joint center of gravity is parallel to or coincides with the x-axis,
• wherein an alignment of the coordinates in the offset direction has a residual offset of from 5 μm to 100 μm.