BRIEF DESCRIPTION OF THE DRAWINGS
The objects and features of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which:
FIG. 1 is an exemplary block circuit diagram of an embodiment of the present invention;
FIG. 2 sets forth a cross sectional view of an exemplary mouth cleaning device in accordance with the embodiment of the present invention;
FIGS. 3A and 3B describe an exemplary operation of the mouth cleaning device in accordance with the embodiment of the present invention, FIG. 3A shows a current waveform chart and FIG. 3B shows a voltage waveform ;
FIG. 4 presents an equivalent circuit of the human body; and
FIG. 5 depicts a current waveform showing a surge current.
DETAILED DESCRIPTION OF EMBODIMENTS
The embodiments of the present invention will be described with reference to the accompanying drawings which form a part hereof. Referring to FIG. 2, there are illustrated a head portion 1 formed by arranging bristles 10 on one end side of a shaft 11 and a handle portion 2 accommodating therein a power source (e.g., battery or the like) 20. The handle portion 2 includes therein a driving shaft 21 having one end connected with the head portion 1, an actuator 22 for moving the driving shaft 21 in an axial reciprocating motion or the like, and a circuit board 24. Moreover, the handle portion 2 has an electrode 23 on an outer surface thereof, and the head portion 1 has an electrode 13 near roots of the bristles 10.
As illustrated in FIG. 1, the electrode 23 is connected with the positive pole of the battery 20 via an output resistor Rol and a boosting circuit 3 mounted on the circuit board 24. Further, the electrode 13 of the head portion 1 is connected with the grounded negative pole of the battery 20 via a conduction plate 12 installed inside the shaft 11, the driving shaft 21, and the circuit board 24 (i.e., an output resistor RO2, a current limit transistor TRa and limit resistor Rlim2 mounted thereon).
The circuit board 24 has a current limit circuit 4 shown in FIG. 1, in addition to the boosting circuit 3. The current limit circuit 4, which is formed of the control resistor Rlim1, the current limit transistor TRa and a limit resistor Rlim2, generates a constant base current from a reference DC voltage VR (current limit control DC voltage) via the control resistor Rlim1, and limits a collector current that can flow through the current limit transistor TRa. The control resistor Rlim1 serves to adjust the reference DC voltage VR, and can variably adjust a current limit when it is configured as a variable resistor, according to individual differences in a resistance of a human body, individual differences in reaction to a current and the like. It is preferable that the maximum value of the limited current which can flow through the human body is lower than or equal to about 300 μA.
The boosting circuit 3 boosts a battery voltage VB and generates a voltage Vh (Vh>VB) under the control of a boost control circuit 30. This voltage Vh is preferably a voltage which allows the supply of a current of a magnitude that enables required effects to be obtained even if a resistance of a conduction path including a human body is not uniform. For example, when a current of about 100 μA needs to flow on the assumption that a maximum resistance (including a contact resistance or the like) of the path including the human body is about 150 kΩ, the voltage Vh is about 15 V (=150 kΩ×100 μA).
If the handle portion 2 is held and the head portion 1 is inserted into the mouth in a state where the voltage Vh generated by the boosting circuit 3 is applied to the electrodes 13 and 23, the current flows from an output resistor Rol to the current limit transistor TRa via the electrode 23, the human body, the electrode 13, the conduction plate 12, the driving shaft 21 and an output resistor Ro2. However, the current is limited to, e.g., about 100 μA, by the aforementioned base current. Therefore, even when the resistance of the human body is low, the current greater than or equal to about 100 μA does not flow and, also, an surge current can be suppressed. Therefore, the current flowing in the human body is allowed to have a waveform drawn by a solid line in FIG. 3, thus inflicting no safety problem as caused in a conventional case indicated by a dashed line in FIG. 3.
The circuit configuration illustrated in FIG. 1 is just an example and can be varied in various ways. For example, the output resistors Ro1 and Ro2 can be omitted, and the configuration of the current limit circuit is not limited to the shown example, either.
Moreover, as depicted in FIG. 1, there is provided a transistor TRb which temporarily blocking a current by reducing a base potential of the pulsed current limit transistor TRa to zero at regular intervals so that the current can flow through the human body. In particular, if the current flowing in the human body has a pulse shape of a frequency ranging from about 400 Hz to 15000 Hz, the effect of massaging the gums is enhanced.
The electrode 13 is a negative electrode to which a unipolar pulsed current is supplied to prevent elution of an electrode metal. When an electrode inserted into a mouth serves as an anode, teeth or gums serve as a cathode. In that case, a metal of the anode is eluted, and the eluted metal is deposited on the teeth or the gums serving as the anode.
In the above embodiment, though the mouth cleaning device is described to have the actuator 22 for moving the head portion 1, it is also possible to omit the actuator 22 (or any other substitute driving units for it).
While the invention has been shown and described with respect to the embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.
Patent Application
20080086189
