An electric toothbrush comprising:
- a handle having an upper portion and a lower portion;
- a replaceable brush head comprising a head body, a plurality of bristles fixed to the head body, and a detachable fastener;
- a reciprocating bar provided inside the handle;
- a head unit base having a head receptacle portion, an actuator receiving recess, and a bar guiding portion, wherein the reciprocating bar is protruded from the handle and received in the actuator receiving recess, wherein the actuator receiving recess is configured to engage the reciprocating bar in either penetration mode or polishing mode;
- an engaging device disposed at an end of the reciprocating bar and engaging the head unit base with the reciprocating bar so that the brush head and the head unit base move relative to the reciprocating bar in either penetration mode or polishing mode;
- a selection device that places the engaging device either in the penetration mode or the polishing mode;
- and
- an actuator that disposed inside the handle and moves the reciprocating bar back and forth,
- wherein the brush head moves together with the reciprocating bar in the polishing mode, wherein the brush head is free to move relative to the reciprocating bar within a predetermined distance in the penetration mode, wherein the longitudinal axis of the brush head is inclined from the longitudinal axis of the handle with a predetermined angle,
- wherein the handle comprises a connecting sleeve that is provided on the end of the handle that is adjacent to the selection device,
- wherein the selection device comprises:
- a selection sleeve provided between the handle and the head unit base and surrounding the connecting sleeve of the handle;
- a selection groove provided inside the selection sleeve;
- and
- a selection protrusion that is provided on the connecting sleeve and receives the selection groove,
- wherein the selection protrusion comprises four angularly spaced mode recesses that keep the selection groove either in the polishing mode or the penetration mode,
- wherein the bar guiding portion is provided at a lower portion of the head unit base,
- wherein the bar guiding portion of the head unit base comprises a plurality of engaging protrusions on outside, wherein the plurality of engaging protrusions are enclosed by the selection sleeve and engage therewith, and
- wherein the engaging device comprises an arrow-shaped protrusion and the actuator receiving recess comprises an arrow-shaped groove for receiving and locking the arrow-shaped protrusion, wherein the arrow-shaped protrusion includes a first two surfaces meeting each other with an angle smaller than 90 degrees and a second two surfaces meeting each other with an angle larger than 90 degrees so as to form a wedge-shaped point, wherein a gap is formed in a remaining space of the receiving recess when the arrow-shaped protrusion is unlocked in the arrow-shaped groove, such that the gap works as a gap through which the reciprocating bar can move when the arrow-shaped protrusion is not locked in the arrow-shaped groove,
- wherein the selection sleeve of the selection device further comprises locking recesses in an upper portion of the selection groove, wherein the selection device further comprise a locking protrusion that is received by one of the locking recesses in each mode, by which the locking is achieved, wherein the locking recesses are apart from each other by about 90 degrees,
- wherein the engaging device comprises a step portion under the engaging device for preventing the engaging device and the end of the reciprocating bar out of the actuator receiving recess.