Tapping toothbrush

Abstract

The present disclosure relates to a low-cost toothbrush with an easy-to-manufacture design that provides a tapping motion of the brush head. In one embodiment, a dental cleaning device includes an eccentric rotating mass motor and a drive shaft mechanically coupled to the motor. A spring element is attached to the drive shaft in a configuration that acts in a direction perpendicular to the axis of the drive shaft. The spring element and the drive shaft form an assembly having a resonant frequency. A power source supplies sufficient power to the motor to cause the motor to operate near the resonant frequency of the assembly.

Description

[Technical Field]

[0001] The present invention relates to the field of oral care devices, and more particularly to power toothbrushes. [Background technology]

[0002] Electric toothbrushes typically provide either a sweeping brush head motion, in which the brush head rotates about its longitudinal axis, or a rotary motion, in which bristle tufts arranged in a circular pattern rotate about an axis perpendicular to the longitudinal axis of the toothbrush. Low-cost electric toothbrushes with sweeping brush head motion typically use an eccentric rotating mass (ERM) motor to achieve the sweeping brush head motion. Summary of the Invention [Problem to be solved by the invention]

[0003] Low-cost electric toothbrushes often exhibit an uncontrolled orbital sweeping motion, which is generally ineffective. They also produce significant vibrations in the handle and brush, which can be uncomfortable for the user. More efficient toothbrushes exist that produce good results using a mechanical resonator and a magnetic coil to drive the brush movement. Such systems are complex, requiring tuning and electronics such as a processor and MOSFET to create an optimal AC signal to drive the coil. This results in higher manufacturing costs.

[0004] No. 8,418,300, incorporated herein by reference, describes an electric toothbrush system with a resonance-seeking characteristic that can be manufactured at low cost using an electric motor. In the embodiment described herein, as the motor RPM increases from zero after start-up, the frequency of the drive signal increases to near resonance, and energy from the drive signal is transferred to the rotational motion of the driven assembly, creating a useful amplitude of brush head sweeping motion. [Means for solving the problem]

[0005] A toothbrush that moves the brush head exclusively in a direction parallel to the bristles' direction can provide good cleaning results. This motion (referred to as "tapping" in the following discussion) has not previously been available in low-cost electric toothbrushes. In accordance with aspects and embodiments described herein that address such needs, the present disclosure relates to a low-cost toothbrush with an easy-to-manufacture design that provides a tapping motion of the brush head.

[0006] In one embodiment, a dental cleaning device includes a rotary motor with an eccentric mass and a driven member mechanically coupled to the motor. In an embodiment, the motor is an eccentric rotary mass motor. A spring element is attached to the driven member in a configuration that acts in a direction perpendicular to the axis of the driven member. The spring element and the driven member form an assembly having a resonant frequency. A power source supplies sufficient power to the motor to cause the motor to operate near the resonant frequency of the assembly.

[0007] In an embodiment, the apparatus also includes a frame from which the driven member extends, the driven member being a drive shaft coupled to the motor, and the spring element being a torsion spring mounted between the drive shaft and the frame and oriented to apply a force to the drive shaft in a direction perpendicular to the axis of the motor.

[0008] In one embodiment, the driven member includes a drive shaft and a brush head coupled to the drive shaft, the brush head having bristles oriented in a direction parallel to the direction of the force exerted by the spring element.

[0009] In embodiments, when the motor is operating, the brush head moves primarily in a tapping motion. While the motor is operating near the resonant frequency of the assembly, the brush head moves primarily in a tapping motion.

[0010] In an embodiment, the power source may be a DC power source, which may be a battery, which may be rechargeable or replaceable.

[0011] In an embodiment, the spring element may include a pair of torsion springs disposed on opposite sides of the driven member.

[0012] In an embodiment, the spring element may comprise a plastic element. The spring element may be a helical spring, a torsion bar, or a leaf spring.

[0013] In one embodiment, the electric toothbrush includes a frame, an eccentric mass rotary motor mounted to the frame, and a drive shaft mechanically coupled to the motor. A torsion spring is attached to the drive shaft and the frame in a configuration that applies a force to the drive shaft in a direction perpendicular to the axis of the drive shaft. The torsion spring, drive shaft, and frame form an assembly having a resonant frequency. The brush head is attached to the drive shaft with the bristles of the brush head oriented parallel to the direction of the force exerted by the torsion spring. A battery provides the motor with sufficient DC power to operate the motor near the resonant frequency of the assembly. In this embodiment, while the motor is operating near the resonant frequency, the brush head moves in a substantially tapping motion. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an illustration of a side view of an electric toothbrush according to one embodiment of the present invention. [Figure 2] FIG. 1 is an end view of a brush head of an electric toothbrush, with arrows indicating the direction of movement. [Figure 3] FIG. 1 is an end view of a brush head of an electric toothbrush with arrows indicating direction of movement according to one embodiment of the present invention. [Figure 4] 1 is a schematic illustration of a top view of an electric toothbrush according to embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the drawings, like reference numerals generally refer to like elements throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0016] The disclosed subject matter will be better understood from a consideration of the following detailed description in conjunction with the drawings. The detailed description and drawings provide exemplary embodiments of the invention described herein. Those skilled in the art will understand that variations, modifications, and variations can be made to the disclosed embodiments without departing from the scope of the invention described herein.

[0017] With reference to FIGS. 1, 2, and 3, an electric toothbrush 10 has a brush head 11 attached to a drive shaft 12 that extends outward from a housing 14. The housing 14 is sized and shaped to serve as a handle for the user. The brush head 11 may be replaceable. The toothbrush 10 has a longitudinal axis 16 that passes through the drive shaft 12 and a neck 18 of the brush head 11. In a conventional electric toothbrush, the drive shaft 12 rotates about the longitudinal axis 16. This, in turn, rotates the brush head 11 through an arc generally indicated by the arrow in FIG. 2. This arc is perpendicular to the longitudinal axis 16. Rotational motion through an arc perpendicular to the longitudinal axis of the electric toothbrush is referred to herein as a sweeping motion. With reference to FIG. 3, the embodiment described herein provides for movement of the brush head in a generally up-and-down direction, indicated by the double-headed arrow in FIG. 3. This direction is generally perpendicular to the longitudinal axis 16 of the drive shaft 12 and parallel to the length of the bristles 20 (see double-headed arrow 21 in FIG. 1). Movement of the brush head in a direction generally perpendicular to the longitudinal axis and parallel to the length of the bristles is referred to herein as a tapping motion.

[0018] While conventional power toothbrushes primarily provide a sweeping motion, it is recognized that a predominant tapping motion is effective for cleaning teeth. An power toothbrush providing this motion would be an effective alternative to the sweeping motion of commonly available power toothbrushes, and in some cases, could be more effective than conventional sweeping motions. The embodiments described herein provide an effective alternative cleaning mechanism, namely, a power toothbrush with a brush head that primarily moves in a tapping motion, that can be easily manufactured at relatively low cost.

[0019] Referring to FIG. 4, in the illustrated embodiment, an eccentric rotating mass motor (ERM) 22 is mounted inside the housing 14. ERM motors are commercially available that are sized and shaped to fit within the housing 14 used as a toothbrush handle. A DC power supply 24 is connected to the ERM motor 22, providing a constant voltage to the motor 22. The power supply 24 may be a replaceable or rechargeable battery. The battery 24 need only provide a battery voltage of approximately 1 to 3 volts, matching the specified operating voltage of the ERM motor 22. The effective voltage can be varied by pulse width modulation if it is desired to vary the performance of the toothbrush to provide different performance levels to the user or to address voltage degradation as the battery discharges.

[0020] The drive shaft 12 is mechanically coupled to a motor 22 and extends outward from the housing 14 to engage the brush head 11. The ERM motor 22 provides reciprocating power that is transmitted to the brush head 11 via the drive shaft 12. An example of a coupling mechanism between the drive shaft and the brush head that can transmit such power is described in U.S. Pat. No. 8,782,841, which is incorporated herein by reference. A seal 26, which may be, for example, a rubber seal, is provided at the end of the housing 14 to seal the opening where the drive shaft 12 exits the housing 14, preventing water or other fluids from entering the housing 14.

[0021] The torsion spring 30 is mounted inside the housing 14 and on the drive shaft 12 in a configuration in which the torsion spring 30 acts on the drive shaft 12 in a direction perpendicular to the drive shaft axis 16 and parallel to the length of the bristles 20 on the brush head 11. In the illustrated embodiment, the housing 14 functions as a frame that is substantially stationary relative to the drive shaft axis 16. In other embodiments, a separate frame that is stationary relative to the drive shaft 12 can be housed within the housing 14, and in such alternative embodiments, the torsion spring 30 is attached to the frame and the drive shaft 12. A pair of torsion springs mounted on opposite sides of the drive shaft can be used.

[0022] The torsion spring 30 may be made of a metal or plastic material. Inexpensive plastics such as polyoxymethylene (POM) or polyamide can be used, which can be formed as a torsion bar, helical spring, leaf spring, or a combination of leaf spring, V-shaped leaf spring, or spiral spring.

[0023] In an embodiment, the drive shaft 12, torsion spring 30 and housing / frame 14 may be fabricated as a single piece from a plastic material (such as POM or PA), or may be separate pieces of metal or plastic assembled together.

[0024] In operation, the ERM motor 22 imparts a reciprocating motion to the drive shaft 12, which is transferred to the brush head. The spring element 30 acts in a direction perpendicular to the drive shaft axis 16 and parallel to the extension of the bristles 20, providing the necessary stiffness to encourage translational movement of the drive shaft 12 and brush head 11 and inhibit orbital movement. With the brush head 11 and spring element 30 oriented such that the direction of the bristles 20 is parallel to the force exerted by the spring 30, this results in a predominantly tapping motion of the brush head 11. To minimize movement at the seal 26, the torsion spring 30 in the illustrated embodiment is positioned close to the seal 26.

[0025] The motor, drive shaft 12, brush head 11, and spring 30 combine to form a mechanical resonant system. After the motor 22 is powered on, its frequency increases. As it approaches the resonant frequency of the resonant system, the motor frequency stabilizes and the system establishes a balance between the energy output of the motor 22 and the energy absorbed by the resonant system. At this point, the brush head 11 moves with a tapping motion with substantial amplitude because the resonant system is absorbing most of the energy from the motor 22 and the torsion spring 30 is exerting a force that results in the dominant tapping motion of the brush head 11. The voltage of the DC signal from the power supply 24 is controlled to that stable point, where the higher the voltage, the closer it is to (or exceed) the resonant frequency. Reference is made to U.S. Pat. No. 8,418,300, owned by the assignee of the present invention, which describes an electric toothbrush with a resonance-seeking characteristic. In the embodiment described in this patent, as the motor RPM increases from zero after start-up, the frequency of the drive signal increases to near resonance, and energy from the drive signal is transferred to the rotational motion of the driven assembly, creating an effective amplitude of brush head sweeping motion.

[0026] Changes to the resonant system change the resonance characteristics and, therefore, the amount of energy it can absorb. For a given toothbrush, its resonance characteristics may change over time, for example, due to the spring element gradually losing its stiffness over time or due to wear effects on other parts of the system. Resonance characteristics vary from toothbrush to toothbrush due to manufacturing tolerances. Also, aspects of how the user interacts with the toothbrush (e.g., how tightly the toothbrush is gripped or applied to the teeth) may affect the resonant system. Because the output of the motor 22 in this embodiment increases near the resonant frequency of the resonant system rather than to a preset frequency, it does not require manufacturing tuning or adjustment to operate at optimal performance. This also allows the use of relatively inexpensive materials and relatively large manufacturing tolerances. The spring element 30 can be formed from low-cost plastics such as POM or PA because the system self-adjusts to gradual stiffness changes over time. The drive shaft, housing, and spring can be fabricated as a single plastic part made from common plastics such as POM or PA, and the resonance-seeking characteristics of this embodiment accommodate any stiffness changes over the life of the product. In such an embodiment, the plastic structure can also provide the motor mounting (clamp or adhesive) and housing interface.

[0027] In the illustrated embodiment, overshoot can be avoided. If the system cannot absorb the energy output of the motor 22 as a result of a change or dispersion in resonance characteristics, the motor frequency will rise above the resonant frequency of the resonant system. This is called "overshoot." When overshoot occurs, the motor frequency continues to rise and never decreases to the resonant frequency. This can lead to undesirable consequences, such as unpleasant vibration of the toothbrush in the user's hand, increased wear on the toothbrush elements, and inefficient movement of the brush head.

[0028] In an embodiment, the drive shaft 12 has properties that act as a compliance element between the motor 22 and the brush head 11, absorbing some of the motor power. This keeps the operating frequency of the motor 22 below the system resonant frequency, avoiding overshoot. The compliance element can alternatively be an add-on component.

[0029] While the present invention has been illustrated and described in detail in the drawings and description, such drawings and description are illustrative or exemplary only and are not restrictive. The present invention is not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Thus, the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the invention.

[0030] All definitions and definitions used herein shall be understood to apply over and above any dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meaning of the defined terms.

[0031] While several inventive embodiments have been described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions and / or obtaining the results and / or obtaining one or more of the advantages described herein, and each such variation and / or modification is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on the particular use or application for which the teachings of the present invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. Accordingly, it is to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and their equivalents, the inventive embodiments may be practiced otherwise than as specifically described and claimed.

Claims

1. 1. A dental cleaning device comprising: a rotary motor having an eccentric mass; a driven member mechanically coupled to the motor and coupled to a brush head having bristles; a spring element attached to the driven member and acting in a direction perpendicular to the axis of the driven member and parallel to the direction of the bristles, a spring element, wherein the motor, the spring element, and the driven member form an assembly having a resonant frequency; and a power supply that supplies sufficient power to the motor to cause the motor to operate near a resonant frequency of the assembly, wherein while operating near the resonant frequency, the driven member moves in a primarily tapping motion.

2. a frame from which the driven member extends; the driven member includes a drive shaft coupled to the motor; The apparatus of claim 1 , wherein the spring element comprises a torsion spring mounted between the drive shaft and the frame in a direction that applies a force to the drive shaft in a direction perpendicular to the axis of the motor.

3. The apparatus of claim 2 , wherein the motor comprises an eccentric rotating mass motor.

4. the driven member further comprising the brush head coupled to the drive shaft; 4. The device of claim 2 or 3, wherein the brush head has bristles oriented in a direction parallel to the direction of the force exerted by the spring element.

5. 5. The device of claim 4, wherein the brush head moves primarily in a tapping motion when the motor is operating.

6. 5. The device of claim 4, wherein the brush head moves in a primarily tapping motion while the motor is operating near a resonant frequency of the assembly.

7. 7. The apparatus of claim 1, wherein the power supply is a DC power supply.

8. The apparatus of claim 7 , wherein the DC power source comprises a battery.

9. The device of claim 8 , wherein the battery is a rechargeable battery.

10. The device of claim 8 , wherein the battery is a replaceable battery.

11. 7. The apparatus of claim 2, wherein the spring element comprises a pair of torsion springs disposed on opposite sides of the drive shaft.

12. 12. The device of any preceding claim, wherein the spring element comprises a plastic element.

13. 12. The device of claim 2, wherein the spring element comprises a helical spring.

14. 12. The device of claim 2, wherein the spring element comprises a leaf spring.

15. 15. An apparatus according to any one of claims 4 to 14, wherein the driven member comprises a drive shaft that acts as a compliance element between the motor and the brush head, keeping the operating frequency of the motor below the system resonant frequency.

16. An electric toothbrush, The frame and an eccentric mass rotary motor attached to the frame; a drive shaft mechanically coupled to the motor; a torsion spring attached to the drive shaft and the frame and configured to apply a force to the drive shaft in a direction perpendicular to the axis of the drive shaft, a torsion spring, the torsion spring, the motor, the drive shaft, and the frame forming an assembly having a resonant frequency; a brush head attached to the drive shaft with the bristles of the brush head parallel to the direction of the force exerted by the torsion spring; a battery supplying DC power to the motor sufficient to cause the motor to operate near the resonant frequency of the assembly; The electric toothbrush, wherein the brush head moves in a substantially tapping motion while the motor is operating near the resonant frequency.

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