Toothbrush with automatic detection of brushing angle

A toothbrush (10) includes a brushhead (18), a first force sensor (30A) for measuring a first force exerted by the brushhead at a first angle relative to a tooth and a second force sensor (30B) for measuring a second force exerted by the brushhead at a second angle relative to the tooth, the second angle being different than the first angle, and a processing unit (26). The processing unit is structured to: (i) receive first information indicative of the first force as measured by the first force sensor, (ii) receive second information indicative of the second force as measured by the second force sensor, and (iii) determine information regarding a current brushing angle of the brushhead based on the first information and the second information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to toothbrushes, and, in particular, to a toothbrush, such as a power toothbrush, structured to detect brushing angle and provide feedback to the user based on brushing force detected at a plurality of angles.

2. Description of the Related Art

In general, power toothbrushes for cleaning teeth, including removal of plaque, are well known. Typically, power toothbrushes rely on a set of bristles which are attached to a bristle mounting plate, which in turn is moved by a driver mechanism to scrub the surfaces of teeth. Such toothbrushes, which rely on scrubbing action of the bristles for actual cleaning, typically require some amount of force to be exerted by the user against the teeth to accommodate differences in the various shapes and spacing of the teeth and to effectively clean the teeth.

Correct positioning of the bristles of a toothbrush relative to the teeth is essential for efficient plaque removal. To best remove plaque from the teeth, it is often advantageous to brush with the bristles positioned at an angle fairly perpendicular to the tooth. Trials have revealed that users regularly brush their teeth at angle far from the perpendicular. Angles of up to 70 degrees from the perpendicular are common, especially when brushing the inside of the teeth. At such extreme angles, many of the bristles are no longer in contact with the teeth (or are at an inefficient angle) and brushing is extremely inefficient.

SUMMARY OF THE INVENTION

In one embodiment, a toothbrush is provided that includes a brushhead, a first force sensor for measuring a first force exerted by the brushhead at a first angle relative to a tooth and a second force sensor for measuring a second force exerted by the brushhead at a second angle relative to the tooth, the second angle being different than the first angle, and a processing unit. The processing unit is structured to: (i) receive first information indicative of the first force as measured by the first force sensor, (ii) receive second information indicative of the second force as measured by the second force sensor, and (iii) determine information regarding a current brushing angle of the brushhead based on the first information and the second information.

In another embodiment, a method of operating a toothbrush having a brushhead is provided. The method includes generating first information indicative of a first force exerted by the brushhead at a first angle relative to a tooth and second information indicative of a second force exerted by the brushhead at a second angle relative to the tooth, the second angle being different than the first angle, determining information regarding a current brushing angle of the brushhead based on the first information and the second information, and providing user perceptible feedback based on the determined information regarding the current brushing angle.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As used herein, “substantially perpendicular” shall mean at an angle of 90 degrees ±5 degrees.

As used herein, “substantially parallel” shall mean at an angle of 0 degrees ±5 degrees.

FIG. 1is an exploded schematic view of andFIG. 2is a schematic diagram of a power toothbrush10according to an exemplary embodiment of the present invention. As described in detail herein, toothbrush10is structured to detect brushing force at a plurality of angles which, unlike prior art toothbrushes that may have a single force sensor, allows for the brushhead angle, and thus the brushing angle, to be derived. Toothbrush10includes a handle portion12and a DC motor14which is powered by a battery16. Motor14provides the driving action for a brushhead18, which in turn is removably mounted on a motor driveshaft22. It should be understood, however, that various alternative driving action arrangements may be used in a power toothbrush which incorporates the concept disclosed herein. The illustration of a DC motor in the exemplary embodiment is only one of several possible motor systems.

Brushhead18includes a set of bristles24mounted on a bristle back member25which together define the bristle portion of brushhead18. Bristles24accomplish cleaning through an oscillatory action provided to brushhead18by motor14. The operation of motor14is controlled by a processing unit26, which is a common component of power toothbrushes. Processing unit26may be, for example and without limitation, a microprocessor, a microcontroller, or any other suitable processing device and may include a suitable memory for storing routines executed by processing unit26.

As seen inFIGS. 1 and 2, in the exemplary embodiment, handle portion12includes a first force sensor30A for measuring the brushing force exerted by brushhead18against the teeth during use of toothbrush10at a first angle relative to a longitudinal axis32of toothbrush10and a longitudinal axis36of bristles24(as indicated by arrow inFIG. 2), and a second force sensor30B for measuring the brushing force exerted by brushhead18against the teeth during use of toothbrush10at a second angle relative to the longitudinal axis32of toothbrush10and longitudinal axis36of bristles24(different than the first axis). In the exemplary embodiment, first force sensor30A and second source sensor30B are located adjacent to motor14and are structured to measure the force on driveshaft22. Thus, first force sensor30A and second source sensor30B are structured and positioned to measure brushing forces at two different angles. For example, first force sensor30A may be structured and positioned to measure brushing force at an angle that is substantially perpendicular to the longitudinal axis32of toothbrush10and substantially parallel to the longitudinal axis36of bristles24and second force sensor30B may be structured and positioned to measure brushing force at an angle that is substantially parallel to the longitudinal axis32and substantially perpendicular to the longitudinal axis36of bristles24. It will be appreciated, however, that this configuration is meant to be exemplary only, and that alternative angles for each force sensor30A and30B are also possible within the scope of the concept disclosed herein. A number of exemplary alternative configurations for force sensors30A and30B are described in detail elsewhere herein. In addition, as seen inFIGS. 1 and 2, first force sensor30A and second force sensor30B are each operatively coupled to processing unit26and provide a signal to processing unit26indicative of the force measured thereby. In an alternative embodiment, force sensors30A and30B may be located in brushhead18. However, as will be appreciated, the former configuration wherein force sensors30A and30B are located within handle portion12will help to keep the cost of brushhead18down and will avoid interconnection issues across the pluggable interface between brushhead18and handle portion12.

First force sensor30A and second force sensor30B may be any of a number of known or hereafter developed suitable sensing devices for sensing the force exerted by brushhead18. For example, and without limitation, first force sensor30A and second force sensor30B may each be a strain gauge structured to directly measure the brushing force or a sensor, such as a magnetic (Hall) sensor, which indirectly measures the brushing force by measuring the displacement of brushhead18and/or motor driveshaft22.

The measured force values generated by first force sensor30A and second force sensor30B are provided to processing unit26. Furthermore, as seen inFIGS. 1 and 2, handle portion12also includes a feedback device34that is coupled to processing unit26. As described in greater detail herein, during use of toothbrush10, feedback device34is structured to provide user perceptible feedback regarding the brushing angle with respect to the tooth surfaces (i.e., the brushing angle at which bristles24are positioned) that the user is employing at any particular time. The user perceptible feedback generated by feedback device34is designed to encourage the user to brush at a favorable brushing angle. A number of manners in which the brushing angle and or feedback may be determined and/or provided are described in detail herein. Feedback device34may be an audible feedback device, such as a speaker, that is structured to generate an audible feedback signal under the control of processing unit26. Alternatively, feedback device34may be a visual feedback device, such as one or more LEDs, that is/are structured to generate a visual feedback signal under the control of processing unit26. In still another alternative embodiment, the feedback may be implemented by processing unit26modifying the motor drive mode of motor14to give a different sensation in the user's mouth, such as a lowered amplitude, a pulsing of the motor14, or some other alternation of the motor vibration. Such a feedback mechanism may be more easily perceived by the user.

FIG. 5is a flowchart illustrating a method of operation of toothbrush10according to an exemplary embodiment of the disclosed concept wherein a determination of current brushing angle is made/derived based upon brushing forces that are measured at two or more different angles and wherein, in response thereto, feedback is provided to the user of toothbrush10in order to encourage a preferred brushing angle. The method begins at step40, wherein a first brushing force is measured at a first angle by first force sensor30A (referred to herein as F1). Then, at step42, a second brushing force is measured at a second angle different than the first angle by second force sensor30B (referred to herein as F2). The first and second brushing forces measured at step40and42are provided to processing unit26. Next, at step44, processing unit26makes a determination regarding the current brushing angle based on the first and second brushing forces that were measured at step40and42. In the exemplary embodiment, the determination made at step44is a determination as to the degree to which the brushing angle is something other than substantially perpendicular to the surface of the teeth (i.e., the degree of rotation of brushhead18and in particular bristles24and bristle back member25about longitudinal axis32during brushing). For example, and without limitation, step44may involve determining whether, based on the first and second brushing forces, the brushing angle is within an ideal range, a non-ideal yet still acceptable range, or an unacceptable range. As another, simpler example, step44may involve determining whether the brushing angle is above or below a suitable predetermined threshold for acceptable angle. Still other examples are within the scope of the disclosed concept. Finally, at step46, processing unit26causes a user perceptible feedback to be generated through feedback device34based on the determination made in step44. For example, and without limitation, the user perceptible feedback may be causing a particularly colored LED or LEDs forming part of feedback device34to be lit and/or may be causing an audible signal of a particular nature to be generated feedback device34(for instance, a buzzing sound may be generated in the case where the brushing angle is determined to be in an unacceptable range and/or below a suitable predetermined threshold).

A number of non-limiting, exemplary implementations of the method ofFIG. 5will now be described in detail. It will be understood, however, that the implementations described below are meant to be exemplary only and thus are not to be considered limiting.

In a first exemplary implementation, first force sensor30A is structured to measure a force F1at a first angle that is substantially perpendicular to the longitudinal axis32and substantially parallel to the longitudinal axis36of bristles24and second force sensor30B is structured to measure a force F2at a second angle that is substantially parallel to longitudinal axis32and substantially perpendicular to the longitudinal axis36of bristles24. In this exemplary implementation, the determination regarding current brushing angle can be made using the case analysis shown in TABLE 1 below, wherein FTis a typical brushing force of the user of, for example and without limitation, 1-3N

TABLE 1Determination regardingUse CaseF1valueF2valuecurrent brushing angleCase 1FT0Brushing is perpendicularto the tooth surface - IdealbrushingCase 2~FT>0Brushing is not perpendicularto the tooth surface - Nonideal but still acceptablebrushingCase 3<FT>>0Brushing is not perpendicularto the tooth surface - Lessthan acceptable (i.e., ineffi-cient) brushingCase 4<<FTF2 >>> 0Brushing is at a very highangle to the tooth surface -Very inefficient brushing

Based on the case analysis described above, if processing unit26determines that the current brushing of the user falls within Case 3 or Case 4, and thus that the brushing angle is unfavorable and/or unacceptable, then processing unit26will, in the exemplary embodiment, cause feedback device34to provide a corrective signal to the user, such as an alarm sound or a light of a particular color, in order to encourage the user to brush at a better angle.

In the case analysis described above, the proposed figure of merit is the ratio of the measured forces F1/(F1+F2). Thus, the case analysis described above may, in one particular embodiment, be implemented based on the information/formulas provided in TABLE 2 below.

In one particular, non-limiting embodiment, Threshold1=0.8 and Threshold2=0.5. In a simplified example, the case analysis described above may be implemented based upon and using a single feedback formula as follows: if F1/(F1+F2)<Threshold3: bad brushing (red LED lit and/or buzzer sound activated); otherwise brushing angle acceptable. In one particular, non-limiting embodiment, Threshold3=0.65.

In a second exemplary implementation of toothbrush10, shown schematically inFIG. 3, first force sensor30A is structured to measure a force F1at a first angle that is substantially perpendicular to the longitudinal axis32and substantially parallel to the longitudinal axis36of bristles24and second force sensor30B is structured to measure a force F2at a second angle that is substantially perpendicular to the longitudinal axis36of bristles24and that is at an angle α1that is not substantially perpendicular to longitudinal axis32(as demonstrated inFIG. 3). In this second alternative exemplary implementation, a reduction factor of about the cosine of α1is applied and the case analysis described herein may be implemented based on the information/formulas provided in TABLE 3 below.

In a simplified example, the case analysis in this alternative may be implemented based upon and using the single feedback formula as follows: if F1/(F1+F2/cos α1)<Threshold3: bad brushing (red LED lit and/or buzzer sound activated); otherwise brushing angle acceptable.

In a third exemplary implementation of toothbrush10, shown schematically inFIG. 4, first force sensor30A is structured to measure a force F1at a first angle that is substantially perpendicular to the longitudinal axis32and substantially parallel to the longitudinal36axis of bristles24and second force sensor30B is structured to measure a force F2at a second angle that is at an angle α2that is not substantially perpendicular to the longitudinal axis36of bristles24and that is substantially perpendicular to longitudinal axis32(as demonstrated inFIG. 4). In this third alternative exemplary implementation, a reduction factor of about the sine of α2is applied and the case analysis described herein may be implemented based on the information/formulas provided in TABLE 4 below.

In a simplified example, the case analysis in this alternative may be implemented based upon and using the single feedback formula as follows: F1/(F1+F2/sinα2)<Threshold3: bad brushing (red LED lit and/or buzzer sound activated); otherwise brushing angle acceptable.

In a fourth exemplary implementation, first force sensor30A and second force sensor30B are both positioned at angles that are not substantially perpendicular to longitudinal axis36of bristles24. In this case, it may be advantageous if both first and second force sensors30A and30B have the same angle relative to longitudinal axis36of bristles24. The force measured by each of the first and second force sensors30A and30B will be substantially equal (i.e., the normalized signal (F1−F2)/(F1+F2)˜0) if the user is brushing substantially perpendicular to the tooth (ideal case), whilst the brushing angle will increase (i.e. become less ideal) as the absolute value of the normalize force difference (F1−F2)/(F1+F2) between the sensors increases. Thus, in this embodiment, feedback may be generated which indicates a poor brushing angle (e.g., red LED lit and/or buzzer sound activated) when the absolute value of the force difference (F1−F2) exceeds some predetermined threshold value. In an alternate embodiment, a different feedback signal (e.g., green LED lit and/or alternative, positive buzzer sound activated) indicating a good brushing angle may be provided when the absolute value of the force difference (F1−F2)/(F1+F2) is less than or equal to the predetermined threshold value. It is mentioned that in this case also multiple threshold values can be used, such that e.g. green, orange or red feedback can be given.

Furthermore, in the first, second, third and fourth implementations just described, it may be advantageous for the relevant figure of merit to only be judged at absolute force levels above a certain threshold value of, for example and without limitation, 0.25N. Otherwise, feedback may be given when the brushhead18is not really in contact with the teeth.

Moreover, when the brushing action of toothbrush10is primarily on the teeth, the readings of first force sensor30A and second force sensor30B will, as described herein, provide a good indication of the current brushing angle. However, when the brushing action of toothbrush10is on the gum line, readings from first force sensor30A and second force sensor30B may nonetheless falsely indicate ideal brushing angles (e.g., F1/F2>0.8) because the position of toothbrush10on the gums may yield a dominant signal from the first force sensor30A (F1) due to the gum orientation. According to one exemplary, non-limiting particular implementation, this issue may be overcome by employing the concept disclosed herein in combination with the concept described in WO 2014/097242, entitled “Plaque Detection Using A Stream Probe,” owned by the assignee of the present invention, the disclosure of which is incorporated herein by reference. In particular, WO 2014/097242 describes a system wherein signals from a stream probe may be used to obtain information indicating that a brushhead is on the gums. Using this information, more optimized feedback of brushhead orientation according to the concept disclosed herein may be provided. In particular, an indication that brushhead18is positioned on the gums obtained in the manner described in WO 2014/097242 may be used as a check for situations wherein readings from first force sensor30A and second force sensor30B indicate ideal brushing angles, such that if such readings indicate ideal brushing angles yet it is determined that brushhead18is on the gums, feedback indicating ideal brushing angles will not be provided.

Thus, toothbrush10shown inFIGS. 1 and 2and the method of operation shown inFIG. 3provide a system wherein users may be automatically encouraged to employ preferred brushing angles to increase brushing effectiveness and efficiency.