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Title:
PERSONAL CARE DEVICE WITH IMPROVED MEASUREMENT OF PERFORMANCE CHARACTERISTICS
Document Type and Number:
WIPO Patent Application WO/2021/078595
Kind Code:
A1
Abstract:
The present disclosure is directed to personal care devices having improved measurement of performance characteristics including external loads and motion. The personal care device comprises: a drive assembly arranged on or within a handle assembly of a body of the personal care device and a strain gauge sensor deposited on a deformable component of the body. The strain gauge sensor arranged to measure a force or a motion on the body. The strain gauge sensor comprises multiple layers comprising a first insulator layer, a first resistive strain gauge layer, and a first protective layer. The strain gauge sensor is arranged to measure deformation of one or more components of the body on which the strain gauge sensor is deposited.

Inventors:
BEVIS TAYLOR (NL)
SUNGSOO LEE (NL)
Application Number:
PCT/EP2020/078827
Publication Date:
April 29, 2021
Filing Date:
October 14, 2020
Export Citation:
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Assignee:
KONINKLIJKE PHILIPS NV (NL)
International Classes:
A61C17/22; A45D24/10; A46B15/00; B26B19/38; G01L1/22; G01L5/161; G01L5/22
Attorney, Agent or Firm:
PHILIPS INTELLECTUAL PROPERTY & STANDARDS (NL)
Download PDF:
Claims:
CLAIMS:

1. A personal care device (10) comprising: a drive assembly (14) arranged on or within a handle assembly (12) of a body (42) of the personal care device; and a strain gauge sensor (50) deposited on a deformable component (52) of the body, the strain gauge sensor arranged to measure a force or a motion on the body, wherein the strain gauge sensor comprises multiple layers (54) comprising a first insulator layer (60), a first resistive strain gauge layer (62), and a first protective layer (76); and wherein the strain gauge sensor is arranged to measure deformation of one or more components of the body on which the strain gauge sensor is deposited.

2. The device of claim 1, wherein the first insulator layer (60) is deposited on the deformable component (52), wherein the first resistive strain gauge layer (62) is deposited on the first insulator layer, and wherein the protective layer (76) is deposited on the resistive strain gauge layer.

3. The device of claim 1, wherein the multiple layers are connected to one or more contact pads (58) for making electrical connections; and wherein the multiple layers are deposited in a serpentine pattern.

4. The device of claim 1, wherein the strain gauge sensor (50) is deposited on the deformable component using thin-film deposition, chemical deposition, vapor deposition, sputtering, or screen printing.

5. The device of claim 1 , wherein the multiple layers of the strain gauge sensor further comprise a second insulating layer (64) disposed on the first resistive strain gauge layer and a second resistive strain gauge layer (66) disposed on the second insulating layer.

6. The device of claim 5, wherein the strain gauge sensor is arranged to create an unbalanced Wheatstone bridge (46). 7. The device of claim 5, wherein the multiple layers of the strain gauge sensor further comprise a third insulator layer (68) disposed on the second resistive strain gauge layer and a third resistive strain gauge layer (70) disposed on the third insulator layer, and wherein the strain gauge sensor further comprises a fourth insulator layer (72) disposed on the third resistive strain gauge layer and a fourth resistive strain gauge layer (74) disposed on the fourth insulating layer.

8. The device of claim 7, wherein the strain gauge sensor is arranged to create a Wheatstone bridge (48).

9. The device of claim 1, wherein the strain gauge sensor is disposed on an end assembly (40) of the drive assembly.

10. The device of claim 1, wherein the strain gauge sensor is disposed on a torsion spring (18) of the drive assembly.

11. The device of claim 1, wherein the strain gauge sensor is disposed on a node spring (30) of the drive assembly.

12. A power toothbrush (10) comprising: a drive assembly (14) arranged on or within a handle assembly (12) of a body (40) of the power toothbrush; and a strain gauge sensor (50) deposited on a deformable component (52) of the body, the strain gauge sensor arranged to measure a force or a motion on the body, wherein the strain gauge sensor comprises multiple layers (54) comprising one or more insulator layers (60, 64, 68, 72), one or more resistive strain gauge layers (62, 66, 70, 74), and a protective layer (76); and wherein the strain gauge sensor is arranged to measure deformation of one or more components (52) of the body on which the strain gauge sensor is deposited.

13. The device of claim 12, wherein the strain gauge sensor (50) is deposited on an end assembly (40) of the drive assembly (14), a torsion spring (18) of the drive assembly, or a node spring (30) of the drive assembly.

14. The device of claim 12, wherein the strain gauge sensor (50) is deposited on the deformable component using thin-film deposition, chemical deposition, sputtering, vapor deposition, or screen printing.

15. The device of claim 12, wherein the strain gauge sensor is arranged to create a Wheatstone bridge (48).

Description:
PERSONAL CARE DEVICE WITH IMPROVED MEASUREMENT OF PERFORMANCE CHARACTERISTICS

Field of the Invention

[0001] The present disclosure is generally directed to personal care devices, and in particular, personal care devices with improved measurement of performance characteristics including external loads and motion.

Background

[0002] In some small power appliances, the primary motion to perform work is derived from a dynamic system. An example is the oscillating rotational motion in power toothbrushes. When this system experiences external loading from a user, the system reacts in a predictable manner. By sensing these changes of the external loading and the reacting dynamic behavior, the device performance can be optimized in real-time, guidance could be provided to the user, and/or device behavior could be monitored.

[0003] Existing pressure sensors for measuring external loading and the reacting dynamic behavior have shortcomings. For example, a disadvantage with Hall Effect sensors is that there is substantial hysteresis and inaccuracy in the motion converter which reduces theoretical accuracy of any magnetic, optic, or other method of quantifying user loading. This limits the ability to provide higher resolution feedback.

[0004] Placing conventional resistive strain gauges on the shaft of the drive train is possible, however the displacement of these components are quite small per user loading. Moreover, the resulting voltage is typically quite small and this poses challenges for measuring them accurately and inexpensively with an embedded system. Conventional resistive strain gauges are also too large to physically be placed onto small surfaces of many small dynamic systems. Wires emanating from strain gauges have a negative effect on performance as they add effective mass, spring and damping. Physical size constraints of relatively thick components require systems to be designed with this component from the start and retro-fit is difficult.

[0005] Accordingly, there is a need for personal care devices with improved measurement of external loads and performance characteristics. Su miliary of the Invention

[0006] The present disclosure is generally directed to personal care devices, and in particular, personal care devices with improved measurement of external loads or motions. For example, the use of strain gauge sensors can be used to measure external loads, motion, and performance characteristics of a personal care device. The personal care device may be an electric toothbrush, and the strain gauge sensor may be used to estimate user load in the normal direction and rotation by depositing the strain gauge sensor on an internal component of the toothbrush.

[0007] Generally, in one aspect, a personal care device is provided. The personal care device comprises: a drive assembly arranged on or within a handle assembly of a body of the personal care device; and a strain gauge sensor deposited on a deformable component of the body. The strain gauge sensor is arranged to measure a force or a motion on the body. The strain gauge sensor comprises multiple layers comprising a first insulator layer, a first resistive strain gauge layer, and a first protective layer. The strain gauge sensor is arranged to measure deformation of one or more components of the body on which the strain gauge sensor is deposited.

[0008] In an aspect, the first insulator layer is deposited on the deformable component, the first resistive strain gauge layer is deposited on the first insulator layer, and the protective layer is deposited on the resistive strain gauge layer.

[0009] In an aspect, the multiple layers are connected to one or more contact pads for making electrical connections, and the multiple layers are deposited in a serpentine pattern.

[0010] In an aspect, the strain gauge sensor is deposited on the deformable component using thin-film deposition, chemical deposition, vapor deposition, sputtering, or screen printing.

[0011] In an aspect, multiple layers of the strain gauge sensor further comprise a second insulating layer disposed on the first resistive strain gauge layer and a second resistive strain gauge layer disposed on the second insulating layer.

[0012] In an aspect, the strain gauge sensor is arranged to create an unbalanced Wheatstone bridge.

[0013] In an aspect, the multiple layers of the strain gauge sensor further comprise a third insulating layer disposed on the second resistive strain gauge layer and a third resistive strain gauge layer disposed on the third insulating layer. The strain gauge sensor further comprises a fourth insulator layer disposed on the third resistive strain gauge layer and a fourth resistive strain gauge layer disposed on the fourth insulating layer. [0014] In an aspect, strain gauge sensor is arranged to create a Wheatstone bridge.

[0015] In an aspect, the strain gauge sensor is disposed on an end assembly of the drive assembly.

[0016] In an aspect, the strain gauge sensor is disposed on a torsion spring of the drive assembly.

[0017] In an aspect, the strain gauge sensor is disposed on a node spring of the drive assembly. [0018] Generally, in one aspect, a power toothbrush is provided. The power toothbrush comprises: a drive assembly arranged on or within a handle assembly of a body of the power toothbrush; and a strain gauge sensor deposited on a deformable component of the body. The strain gauge sensor is arranged to measure a force or a motion on the body. The strain gauge sensor comprises multiple layers comprising one or more insulator layer, one or more resistive strain gauge layers, and a protective layer. The strain gauge sensor is arranged to measure deformation of one or more components of the body on which the strain gauge sensor is deposited.

[0019] In an aspect, the strain gauge sensor is deposited on an end assembly of the drive assembly, a torsion spring of the drive assembly, or a node spring of the drive assembly.

[0020] In an aspect, the strain gauge sensor is deposited on the deformable component using thin-film deposition, chemical deposition, vapor deposition, sputtering, or screen printing.

[0021] In an aspect, the strain gauge sensor is arranged to create a Wheatstone bridge.

[0022] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0023] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Brief Description of the Drawings

[0024] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. [0025] FIGS. 1A, IB, and 1C are schematic representation of strain gauge sensors according to aspects of the present disclosure.

[0026] FIGS. 2 A and 2B are schematic representation of strain gauge sensors according to aspects of the present disclosure.

[0027] FIG. 3 is a schematic representation of strain gauge sensors on a deformable component according to aspects of the present disclosure.

[0028] FIGS. 4 A and. 4B are illustrations of Wheatstone bridge configurations of strain gauge sensors according to aspects of the present disclosure.

[0029] FIGS. 5 A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 51, 5J, 5K, 5L, 5M, 5N, and 5P illustrate configurations of strain gauge sensors according to aspects of the present disclosure.

[0030] FIG. 6 shows a personal care device according to aspects of the present disclosure.

[0031] FIG. 7 shows components of a drive assembly according to aspects of the present disclosure.

[0032] FIG. 8 shows components of a drive assembly according to aspects of the present disclosure.

[0033] FIGS. 9A, 9B, and 9C show components of a drive assembly according to aspects of the present disclosure.

[0034] FIG. 10 shows methods to determine motion and force from strain gauge sensor readings according to aspects of the present disclosure.

Detailed Description

[0035] The present disclosure is generally directed to personal care devices, and in particular, personal care devices with improved measurement of external loads. For example, the use of strain gauge sensors may be sued to measure external loads and performance characteristics of a personal care device. The personal care device may be an electric toothbrush, and the strain gauge sensor may be used to estimate user load in the normal direction and rotation by depositing the strain gauge sensor on an internal component of the toothbrush. [0036] The embodiments and implementations disclosed or otherwise envisioned herein can be utilized with any personal care device, including but not limited to a toothbrush, a flossing device, an oral irrigator, and many other oral devices. For example, one application of the embodiments and implementations herein is to improve oral cleaning efficacy using an oral care device such as, e.g., a power toothbrush such as a Philips Sonicare ® toothbrush (manufactured by Koninklijke Philips N. V.). However, the disclosure is not limited to a power toothbrush and thus the disclosure and embodiments disclosed herein can encompass any personal care device.

[0037] Generally, thin-film deposition may be used to apply a very thin resistive strain gauge directly to delicate dynamic system components under deformation, which can be used to measure displacements or forces in the system components. When relevant degrees of freedom in the system are measured, performance characteristics can be extracted and external loads applied to the system can be measured. Applicant has recognized and appreciated that thin strain gauges applied directly to active components within a dynamic system enable performance characterization while minimally impacting system properties. This approach enables multiple sensors to be deposited in parallel, on a single device, which enables efficient manufacturing. Further, this approach allows for the stacking of multiple resistive strain gauges in multiple layers, oriented in different directions, upon the same surface area of the host component.

[0038] As an example, the internal, deformable component on which the strain gauge sensor is disposed may be a component of the drive train of the toothbrush or personal care device or the end effector which is moved or rotated by drive train. Various drive train arrangements exist for personal care devices. The drive train portion of the personal care device is responsive to a motor action, including mechanical, electro mechanical, magnetic or other action, to drive, for example, a brush head of an electric toothbrush in a reciprocating manner. One type of drive train arrangement uses a torsion spring which is fixedly mounted at both ends as well as at a node point, where the node point is between the two ends of the torsion spring, typically mid-length. When the drive action excites the torsion spring in its desired out-of-phase torsion mode, it produces a desired reciprocating brush head action through a selected angle. In one example, a node spring is arranged on the v-shaped torsion spring. The arranged of the node spring on the v-spring may, for example, achieve a desired dynamic response of the torsion spring and reduce stress and potential for wear in the area of contact between the v-shaped torsion spring and the node spring. [0039] FIGS. 1A-1C show strain gauge sensors 50 which are deposited on a deformable component 52 internal to the body 42 of a personal care device 10. The strain gauge sensors 50 have multiple layers 54 (shown in FIG. 2) which are deposited on the deformable component 52 in a serpentine pattern 56 which is strain sensitive. The strain gauge sensors 50 are arranged to measure deformation of the deformable components 52 on which the strain gauge sensors 50 are deposited. As the deformable component 52 experiences tension and expands, shown in FIG. IB, the area of the strain sensitive pattern 56 narrows and resistance on the strain sensitive material 56 increases. This results in higher resistance detected on the contact pads 58. As the deformable component 52 compresses, the area of the strain sensitive serpentine pattern 56 thickens and resistance decreases, as shown in FIG. 1 C. The resulting lower resistance can then be detected on the contact pads 58 which make an electrical connection with the multiple layers 54.

[0040] The serpentine pattern 56 of strain sensitive material is obtained by depositing multiple layers 54 of materials in the desired pattern. The layers of the strain gauge 50 may be deposited using thin fdm deposition, for example, by sputtering or vacuum deposition. The layers of the strain gauge may also be deposited by chemical deposition, vapor deposition, screen printing, sputtering, any other known deposition techniques, or any combination of these or other known techniques.

[0041] The individual layers of a multilayer deposited strain gauge sensors 50 are shown in FIGS. 2 A and 2B. As shown in FIG. 2 A, a first insulator layer 60 is deposited on the deformable component 52, a first resistive strain gauge layer 62 is deposited on the first insulator layer 60, and a protective layer 76 is deposited on the first resistive strain gauge layer 62. Multiple strain gauge sensors 50 can be layered on top of each other by adding an additional insulator layer on top of an existing resistive strain gauge layer and an additional resistive strain gauge layer on top of the additional insulator layer. FIG. 2B is a schematic illustration of multiple layer 54 comprising four strain gauge sensors 50 formed by depositing the following layers on the deformable component: a first insulator layer 60, a first resistive strain gauge layer 62, a second insulator layer 64, a second resistive strain gauge layer 66, a third insulator layer 68, a third resistive strain gauge layer 70, a fourth insulator layer 72, a fourth resistive strain gauge layer 74, and a protective layer 76. The protective layer 76, or coating layer or film, can be made of materials such as NiCoCrAlY, AI2O3 or S1O2 and can be an electrical insulator and provide protective coating. The insulator layers 60, 64, 68, 72 provide electrical isolation and can be made of a ceramic material such as, for example, AI2O3. The sensing layers of the strain gauge, the resistive strain gauge layers 62, 66, 70, 74 can be made of metals such as, for example, Pt, NiCr, or PdCr. An intermediate splicing layer to separate the terminals 58 of the strain gauges which are connected to each other to create Wheatstone bridges can also be made of metal such as Pt.

[0042] The use of thin film deposited strain gauges has many benefits. For example, the strain gauges can be placed on smaller spaces. A complete sensor unit may be only 20 pm thick compared to 200 pm of the conventional foil or wire strain gauge system. This may allow minimally intrusive surface strain measurement with minimal load effect. The strain gauges are highly stable and allow for repeated use. The repeatability (between thermal cycles) of the sensors is within 200 microstrain (pe) (25 to 1100 °C) compared to 1000 pe (25 to 600 °C) of conventional gauges. Sensors may be designed for either dynamic or static strain measurements, can have various patterns and gauge resistance, and can be fabricated directly on the test parts. Sensors may be mass produced using microelectromechanical systems (MEMS) based device fabrication technology, such as micro-photolithography. The use of glue can, in some instances, limits both the degree of strain transmission from member to gauge and the temperature at which the device may be used. Since the thin-film gauge is molecularly bonded to the specimen, installation is very stable and the resistance values experience less drift.

[0043] FIG. 3 shows strain gauges 50 which are deposited on a node spring 30 of a drive assembly (shown in FIG. 8). As shown in FIG. 3, one or more strain gauge sensors 50 may be deposited parallel to the direction of motion of the deformable component 52 or one or more strain gauge sensors 50 may be deposited at substantially 45 degrees to the direction of motion to measure torsion. When a single strain gauge 50 is deposited on one surface, for example in the 3 -layer stack shown in FIG. 2A, a single degree of freedom is expected to provide the dominant source of resistance change. When additional strain gauges 50 occupy the same 2D projected area, for example, in a five layer or more stack, the strain gauges can be oriented in multiple directions. In one exemplary configuration, when multiple strain gauge sensors 50 are deposited on top of each other, they may be deposited all in the same direction, or they may be deposited with half of the resistive strain gauge layers 62, 66, 70, 74 perpendicular to the other half of the resistive strain gauge layers 62, 66, 70, 74. [0044] One exemplary architecture for multiple layers 54 of the strain gauges 50 is use of two strain gauges to create an unbalanced Wheatstone bridge 46 (shown in FIG. 4A), where each of the strain gauges acts like a resister in the unbalanced Wheatstone bridge. Another exemplary architecture for multiple layers of the strain gauges is use of four strain gauges to create a Wheatstone bridge 48 (shown in FIG. 4B), where each of the strain gauges acts like a resister in the Wheatstone bridge. The strain gauges which are used to create the Wheatstone bridge may be layered on top of each other or may be arranged adjacent to each other to create the Wheatstone bridge or unbalanced Wheatstone bridge structures.

[0045] Numerous configurations of the strain gauges 50 are also possible. FIG. 5A shows use of one strain gauge, for example to take a strain measurement on a tension or compression bar or to take a strain measurement on a bending beam, in a simple quarter bridge circuit. In this configuration normal and bending strain are superimposed, and temperature effects are not automatically compensated. FIG. 5B shows use of one strain gauge, for example to take a strain measurement on a tension or compression bar or to take a strain measurement on a bending beam, in a quarter bridge with an external dummy strain gauge. This arrangement has two quarter bridges circuits, where one actively measures strain. The other is mounted on a passive component made of the same material, which is not strained. In this configuration temperature effects are well compensated, and normal and bending strain are superimposed and cannot be separated. FIG. 5C shows use of two active strain gauges configured as a Poisson half-bridge. Two active strain gauges are connected as a half bridge, where one of them is positioned at 90 degrees to the other. In this configuration temperature effects are well compensated when material is isotropic.

[0046] FIG. 5D shows use of two strain gauges on a bending beam. The two strain gauges are in a half bridge configuration and are installed on opposite sides of the structure. In this configuration temperature effects are well compensated and a separation of normal and bending strain is permitted (only the bending effect is measured). FIG. 5E shows use of two strain gauges on a bending beam to make a measurement on a tension or compression bar. The two strain gauges are installed on opposite sides of the structure to create a diagonal bridge. In this configuration normal strain is measured independently of bending strain (bending is excluded). FIG. 5F shows use of four strain gauges, for example to take a strain measurement on a tension or compression bar or to take a strain measurement on a bending beam, in a full bridge configuration. Four strain gauges are installed on one side of the structure as a full bridge. This configuration allows for temperature effects to be well compensated. In this configuration, there is a high output signal and excellent common mode rejection. Normal and bending strain cannot be separated, and there is superimposed bending. FIG. 5G shows use of four strain gauges, for example, to take a strain measurement on a tension or compression bar, in a diagonal bridge with dummy gauges configuration. In this configuration normal strain is measured independently of bending strain and bending is excluded. Temperature effects are well compensated.

[0047] FIG. 5H shows use of four strain gauges, for example, to take a strain measurement on a bending beam. Four active strain gauges are connected as a full bridge. This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. This configuration allows separation of normal and bending strain as only the bending effect is measured. FIG. 51 shows use of four strain gauges, for example, to take a strain measurement on a tension or compression bar. Four active strain gauges are used, with two of them rotated by 90 degrees, in a full bridge configuration. This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. In this configuration, normal strain is measured independently of bending strain and bending is excluded. FIG. 5 J shows use of four strain gauges, for example, to take a strain measurement on a bending beam. Four active strain gauges are used, with two of them rotated by 90 degrees, in a full bridge configuration. This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. In this configuration, there is separation of normal and bending strain as only the bending effect is measured.

[0048] FIG. 5K shows use of four strain gauges, for example, to take a strain measurement on a bending beam. Four active strain gauges are used, with two of them rotated by 90 degrees, in a full bridge configuration. This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. In this configuration, there is separation of normal and bending strain as only the bending effect is measured. FIG. 5L shows use of four strain gauges, for example, to take a strain measurement on a bending beam. Four active strain gauges are used in a full bridge configuration. This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. In this configuration, there is separation of normal and bending strain as only the bending effect is measured. FIG. 5M shows use of four strain gauges to measure torsion strain. Four strain gauges are installed, each at an angle of 45 degrees to the main axis as shown, in a full bridge configuration. This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. FIG. 5N shows use of four strain gauges to measure torsion strain, for example, when there is limited space for installation. Four strain gauges are installed in a full bridge, each at an angle of 45 degrees and superimposed (stacked rosettes). This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated. FIG. 5P shows use of four strain gauges to measure torsion strain, for example, when there is limited space for installation. Four strain gauges are installed in a full bridge, each at an angle of 45 degrees and superimposed (stacked rosettes). This configuration has a high output signal and excellent common mode rejection, and temperature effects are well compensated.

[0049] FIG. 6 shows a personal care device 10 and its components. Strain gauge sensors 50 can be used to measure motion by the device and user load. For example, for toothbrushes where the main brushing motion is rotational motion around the Y axis at the brush head 28, torque and torsion strain of the drive assembly 14 can be measured. A translational displacement along the Z axis at the brush head 28 can result in bending moment and bending strain around the X axis in the drive assembly 14. A translational displacement along the X axis at the brush head 28 can result in bending moment and bending strain around the Z axis in the drive assembly 14. A translational displacement along the Y axis at the brush head 28 can result in tension or compression force and normal strain in the Y axis in the drive assembly 14. User load can be measured in multiple directions. For example, a force along the Z axis at the brush head 28 can result in bending moment and bending strain around the X direction of the drive assembly 14. A force along the X axis at the brush head 28 can result in bending moment and bending strain around the Z axis in the drive assembly 14. Torque applied by users at the brush head 28 around the Y axis can be measured by torque and torsion strain around the Y axis in the drive assembly 14. The force along the Y direction at the brush head can be measured by tension or compression force and normal strain along the Y axis in the drive assembly 14.

[0050] Strain gauge sensors 50 can be disposed on internal components of the personal care device to measure motion by the device and user load. For example, strain gauge sensors 50 can be disposed on deformable components of the drive train assembly 14, including the V-spring (or torsion spring) 18 (shown in FIG. 7 and 8), the node spring 30 (shown in FIG. 8 & FIG. 3), or the end assembly 40 (shown in FIG. 7 and 8). Possible placement locations are indicated by circles. [0051] FIG. 7 shows the internal components of a personal care device 10, in particular, a power toothbrush 10, on which the strain gauge sensor 50 may be deposited. Although described herein in conjunction with a power toothbrush, the disclosure and embodiments disclosed herein can encompass any personal care device. Power toothbrush 10 includes a handle assembly 12 in which is positioned an illustrative drive assembly 14. The drive assembly 14 may have various configurations and arrangements, including a motor with drive shaft, an electromagnetic arrangement, or other similar electrical/mechanical arrangements. In FIG. 7, drive assembly 14 drives a drive hub assembly 16 through an oscillating back-and forth action. This oscillating action may have various configurations/paths of travel. One example is a partial rotational action through an angle of 16° (+8). Other actions include a vibrating back-and-forth action, as well as more complex actions.

[0052] Connected to and extending from drive hub assembly 16 is a proximal end 17 of a torsion or V-spring 18. The V-spring 18 may be nodally mounted, i.e. center point 20 along the V- spring will function as a node point and thus will not move while the opposing end portions of the V-spring counter-rotate. The distal end 22 of the torsion or V-spring 18 is mounted in a workpiece hub assembly 24; in this case, a brush hub assembly, connected to an end assembly 40 on which is mounted a toothbrush brush element 28. The angle between the two longitudinal walls of the V- spring is approximately 90° in the example illustrated, although this can be varied, e.g. within a range of 45°-170°. The drive assembly 14 utilizing a torsion or V-spring 18 may be used in other personal care devices 10.

[0053] The drive assembly 14 also includes a nodal spring component which is illustrated in FIG. 8. FIG. 8 shows components of a drive assembly 14 which includes a torsion or V-spring 18 which is fixedly mounted at the respective ends thereof to drive hub assembly 16 and workpiece hub assembly 24, and extending from workpiece hub assembly is an end assembly 40 for a brush head assembly 28 (shown in FIG. 7). The entire drive train can be made replaceable relative to a handle portion of a toothbrush, or the structure can be arranged so that the brush head assembly 28 alone is replaceable.

[0054] Extending between support members 16a, 24a, which are mounted in drive hub assembly 16 and work piece hub assembly 24, is a V-shaped torsion spring 18, which functions as a spring. Mounted to the center point (node point) 20 of torsion spring 18 is a separate node spring 30, in the form of a mounting plate. The mounting plate (node spring) 30 is fixedly attached to the housing of the toothbrush at its outer edges thereof. In this arrangement, mounting plate 30 is secured to the V-shaped torsion spring 18 (V-spring) by a mounting assembly, which includes generally a base insert member 32 which fits within the trough portion of the V-shaped torsion spring 18, a shim member 34 which is positioned between the torsion spring 18 and the node spring 30, configured to provide a stable connection there between, and an attachment member combination 36, 38 which secures the entire assembly firmly together. The mounting plate 30 is also connected fixedly to the housing of the toothbrush. This arrangement reduces the vibration of the handle.

[0055] During operation of the drive train, the drive motor action excites the torsion bar spring 18 in its out-of-phase mode, such that rotation of the proximal half, closer to the drive hub assembly 16, of the torsion spring 18 in one direction results in a rotation of the distal half in the opposite direction. The frequency of the out-of-phase mode is approximately 270 Hz in the embodiment shown. There can be several structural variations of the exemplary general arrangement shown in FIG. 8 which may include the following characteristics. First, the axis of rotation of the node spring (i.e. mounting plate) 30 should be as close as possible to the axis of rotation of the torsion or V-spring 18, in order to achieve the desired dynamic response. Second, the mounting assembly, specifically the insert, shim and the attachment member combination, must provide a stable, strong connection between the V-shaped torsion spring and the node spring (mounting plate) at the node point, in such a manner as to withstand the particular stress at the node point connection for an extended period of time, while also reducing the stresses at that point. Third, the joint must be strong and fixed, so that the out-of-phase response of the V-shaped torsion spring is as linear as possible.

[0056] Strain gauge sensors 50 on the V-spring 18 and node spring 30 can be used to measure motion by the personal care device 10 and user load. Torque input on the drive hub assembly 16 end of the drive assembly 14 (shown in FIG. 9A and FIG. 9B) can be detected on workpiece hub assembly 24 of the drive assembly 14, through a first component 18a of the V spring 18 and through a second component 18b of the V spring separated by the center point 20. The node spring (shown in FIG. 9 A and 9C) is connected to the housing 44 of the personal care device 10 and motion can be detected along that path. [0057] As shown in FIG. 10, the dynamic system of the personal care device 10 can be characterized by the changing resistances of the strain gauges 50. The change in resistance in the normal direction can be utilized to determine the user normal force applied to the end assembly 40 via the use of a calibration function. Similarly, the nodal amplitude can be determined by amplitude of oscillating change in torsional resistance. Finally, the brush amplitude can be determined via user pressure (P user ), and node amplitude (d node ). Since user pressure is most strongly correlated with effective spring load, additional accuracy may be gained by also including actuator current (iactuator) to capture the changing in-mouth damping effects.

[0058] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0059] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0060] The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified.

[0061] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” [0062] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified.

[0063] It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

[0064] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively.

[0065] While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications 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 meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/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. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.