Personal Care Devices

Abstract

To provide a personal care device configured to determine a stroke length from the distance between pairs of adjacent start and end points.SOLUTION: A personal care device 2, in particular a hair removal device such as an electric shaver, according to the present invention comprises: an elongated handle 40 for manually moving the personal care device in a short stroke and / or a long stroke along a body surface 5; a work head 41 attached to the handle for effecting a personal care treatment to the body surface; and a determination unit 42 including at least one sensor for determining a stroke length to differentiate between the short stroke and the long stroke. The determination unit determines a velocity of the work head and / or the handle, and determines a beginning point and an end point of a stroke when the determined velocity reaches zero and / or changes signs.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a personal care device, in particular a hair removal device such as an electric shaver, comprising an elongated handle for manually moving the personal care device in short and / or long strokes along a body surface, a working head attached to the handle for performing a personal care treatment on the body surface, and a determination unit including at least one sensor for determining a stroke length to distinguish between short and long strokes. [Background technology]

[0002] Personal care devices are widely used to apply different kinds of personal care treatments to users, such personal care devices may include hair removal devices such as epilators, shavers, or razors, which may be powered or manual and / or wet or dry, or beard trimmers. Furthermore, other personal care devices include powered or manual toothbrushes, interdental cleaning devices or gum massaging devices, or skin treatment devices such as massage devices or vibrating devices. All such personal care devices suffer from the problem that different users use the personal care device in different ways, the same user may behave differently from one stroke or shave to the next, and different users have different preferences for the mechanical settings of the personal care device.

[0003] In a more general situation, some users tend to press the working head quite hard against the body surface to be treated, while others apply rather only slight pressure. Some users tend to move the working head over the body surface in rather short strokes, while others apply longer strokes. Depending on the habits and preferences of the user, the working head should give the user a softer or more controllable working head, which can be addressed by different movement characteristics of the suspension that allows the movement of the working head relative to the handle and / or the movement of the working head elements relative to the working head reference. Preferences also change during a single shave, for example, depending on the stage of shaving, or for other reasons that are entirely user-dependent.

[0004] When using a personal care device in different treatment modes or on different body parts, it may also be desirable for the same user to change the movement characteristics of the movable hair or body treatment part of the device relative to the non-moving part (e.g., as a handle). For example, when shaving the upper lip area under the nose, short strokes are often made and more control is desired, so the stiffness of the working head may need to be increased, whereas when shaving the cheek or area around the Adam's apple with longer strokes, less stiffness and / or rotation / pivot range may be needed to achieve a better contour fit.

[0005] More generally, there are two main cases where the detection of short strokes is particularly relevant for detecting behavioral changes and can adjust at least one operating parameter of the personal care device. First, in situations or areas where the user is unable to achieve the desired goal of a precise and thorough personal care treatment, such as a clean shave without leaving hair behind, a very common human behavior is to shorten the specific stroke length from the standard value to a significantly shorter operation, i.e. to the handle, so that the working head is moved back and forth or up and down with a stroke of shortened length. Second, in areas such as the upper lip, consumers usually do not want to touch anatomical boundaries such as the lips or nose with the personal care device, so that the anatomical boundaries only allow short strokes. In such situations, users often prefer a more rigid configuration of the movable treatment part of the personal care device, which gives them more or less control over the treatment characteristics of the device.

[0006] Various adaptations can be made to the personal care device to match the configuration of the device to the stroke pattern and thus to the user's behavior. For example, the suspension of the working head relative to the handle and / or the suspension of the working head elements relative to the working head datum can allow various types of movement of the working head and the working head elements, such as rotational and / or linear movements thereof, respectively. More specifically, the working head can tilt and / or pivot relative to the elongated handle, and the tilt and pivot axes can extend substantially parallel to the skin contact surface of the working head and transversely to each other. Additionally or alternatively, the working head can pop or float relative to the handle along a pop axis substantially perpendicular to the skin contact surface and / or substantially parallel to the longitudinal axis of the handle. Similarly, the working head elements, such as the shear foil cartridge of a shaver, can tilt and / or pivot and / or pop relative to the working head frame or working head datum to allow adaptation to the contours of the skin.

[0007] To satisfy different user habits and preferences, the suspension of the working head and / or the suspension of the working head elements relative to the working head reference can be adjusted to change the characteristics of the adaptation movement of the working head and / or the working head elements to the skin contours. For example, the tilt and / or pivot and / or pop-out stiffness can be increased or decreased to provide a more accurate or softer characteristic of the adaptation movement. Furthermore, the tilt and / or pivot and / or pop-out range with respect to the maximum rotational and / or linear displacement can also be changed.

[0008] For example, EP 3 546 153 (B1) shows an electric shaver that changes its configuration depending on the stroke length. More specifically, the stroke length is detected by an optical system including an accelerometer or a camera, and the pivot stiffness of the working head is adjusted in response to the detected stroke length. More specifically, the shaver has a pivotable suspension of its working head to enable the pivoting of the working head relative to the handle, and a pop-out suspension of the shear foil cartridge to enable the pop-out of the shear foil cartridge relative to the working head frame. The pivot stiffness of the working head and the pop-out stiffness of the shear foil cartridge are controlled by mechanical springs that can be adjusted by an actuator to increase or decrease the pivot stiffness and the pop-out stiffness in terms of the torque and force required to achieve a specific pivot angle and a specific pop-out displacement. Furthermore, the adjustment mechanism is configured to adjust the angular pivot range of the working head to enable a larger or smaller maximum angular displacement.

[0009] A similar adjustability of the working head of an electric shaver is shown in EP 35 46 152 (B1), where it is proposed to detect stroke characteristics such as speed and length by means of an accelerometer, and direction and pattern related to the rotational movement of the shaver by means of a gyroscope.

[0010] Another option for adjusting the treatment characteristics is adjusting the cutting length of the hair trimmer, for example WO 2018 / 069265(A1) discloses a hair trimmer including an adjustment actuator for adjusting the cutting length of the trimmer.

[0011] WO 2009 / 006011 A1 discloses a grooming tool that includes an acceleration sensor for triggering movement of the device. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] European Patent No. 3 546 153(B1) [Patent Document 2] European Patent No. 35 46 152(B1) [Patent Document 3] International Publication No. 2018 / 069265(A1) [Patent Document 4] International Publication No. 2009 / 006011(A1) Summary of the Invention [Means for solving the problem]

[0013] The object underlying the present invention is to provide an improved personal care device which avoids at least one of the drawbacks of the prior art and / or further develops existing solutions.

[0014] A more specific objective underlying the present invention is to achieve accurate and reliable discrimination between long and short strokes without complex sensor devices.

[0015] Another objective underlying the present invention is to achieve a robust determination of stroke length despite different specific behaviors of different users, such as gripping the handle in different ways, and different preferred directions for moving the working head along the body surface.

[0016] In order to achieve at least one of the above-mentioned objects, it is proposed to determine the stroke length based on a speed or physical characteristic related to the speed or physical characteristic of the working head and / or the handle of the personal care device, in order to enable the use of reduced sensor equipment, and to determine the stroke length by analyzing the speed. More specifically, the determination unit provided for determining the stroke length in order to distinguish between short strokes and long strokes can be configured to determine the start and end points of a stroke when the speed of the working head and / or the handle becomes zero or close to zero, and / or when its sign changes from positive to negative and / or vice versa, from negative to positive, or based on another detected change in the characteristic value, and to determine the stroke length from the distance and / or path length between a pair of adjacent start and end points.

[0017] Analysis of the speed of the working head and / or handle allows the determination of the stroke length, and more specifically the differentiation between long and short strokes, without the need for complex sensor equipment such as cameras or image sensors, and allows the control of the adaptation of relevant configuration parameters such as the working head stiffness, not only for use in difficult areas such as the upper lip area, but also when the user encounters other problems such as difficult hair and therefore changes the behavior with regard to the change from a long stroke to a short stroke or vice versa.

[0018] It is to be understood that the term "stroke" can encompass not only straight or linear paths, but also curved movement paths or a combination of both shavers. Since the sensor contributing to the detection of stroke length can detect changes along at least one axis (or multiple), the derived sensor signal can also detect changes independently as to whether the movement path is curved or straight, in other words, in the case of a curved path, changes (e.g., directional changes or multiple changes in sign from positive to negative) along at least one measurement principal axis. Furthermore, it is understood that the shaver is in no way limited to the way it can be moved on the skin to be treated or the body part to be shaved. The determination unit can distinguish between short strokes and long strokes based on any shaver movement on the skin, as will be further described below.

[0019] The speed of the personal care device can be determined, for example, by a speed sensor. However, advantageously, the speed may be derived from the acceleration signal of an acceleration sensor measuring the acceleration of the working head and / or the handle. Such an acceleration sensor may be placed on the working head or at least in close proximity to the working head to determine the acceleration of the working head. For example, the acceleration sensor may be placed near the skin contact surface of the working head to determine the acceleration at a position close to the interface of the working head with the skin or body surface to be treated. As a result, the speed that can be calculated or otherwise derived from the acceleration signal is close to the speed at which the working head moves on the body surface. However, alternatively, the acceleration sensor may also be housed in the handle for practical reasons, in which case a correction of the acceleration signal may be performed to account for the acceleration of the working head and its skin contact surface. Such a correction can be achieved, for example, by determining the rotation of the handle and taking into account the known distance of the acceleration sensor in the handle from the skin contact surface.

[0020] To improve the accuracy of the calculation of the velocity from the acceleration, disturbances that distort the acceleration signal and / or represent effects that do not correspond to the relevant movement of the personal care device can be eliminated. More specifically, a filter can be used to remove vibrations and / or effects on the acceleration signal that are due to vibrations of the shaver. For example, a low pass filter, such as a second order low pass filter, may be used. Regardless of the particular type of filter, the filter can have a cutoff frequency set between the frequency of the relevant vibrations and the highest possible frequency of manual movement or user's hand movement. For example, a cutoff frequency in the range of 25-35 Hz or substantially 30 Hz can be used.

[0021] In addition to or as an alternative to filtering the effects resulting from vibration, the effects of gravity on the acceleration signal can be removed. More specifically, a filter such as a high-pass filter can be used to remove the proportion of the measurement signal due to gravity. Such filtering is based on the assumption that the effects of gravity change fairly slowly, while the stroke movement of the handle is fairly fast. It should be understood that the low-pass and high-pass filter characteristics can be combined into a so-called band-pass filter, and a reference to one of a low-pass filter or a high-pass filter can also include a reference to a band-pass filter.

[0022] For example, the filter can have a cutoff frequency in the range of 1 Hz to 2 Hz, with a cutoff frequency of about 1.3 Hz working well. Shorter time values ​​may suppress actual motion, while larger time values ​​may contaminate the calculation with changes in the orientation of the personal care device that are not due to the shaver stroke.

[0023] Determining the velocity from the acceleration signal may include integration over time. More specifically, the filtered acceleration signal may be integrated over time to obtain the velocity of the work head and / or handle of the personal care device.

[0024] Advantageously, a low-pass filter can be used to obtain the velocity, the properties of which are such that it is possible to carry out a mathematical integration of frequencies above a cut-off frequency, in other words, the properties of a region called the stop band, rather than the pass band, of the filter used for the integration, are used to obtain the velocity from the acceleration signal.

[0025] For example, the cutoff frequency may be set to a value sufficiently lower than the frequency of the stroke movement to ensure integration of the stroke acceleration without significant loss. For example, a cutoff frequency in the range of 0.2-0.35 Hz or 0.25-0.30 Hz can be used. For example, a cutoff frequency of about 0.27 Hz can work well.

[0026] The acceleration sensor can measure acceleration in at least one direction of interest, for example, up and down acceleration, or acceleration in a direction that is substantially parallel to the skin contact surface of the working head and substantially perpendicular to the front of the handle where the thumb is usually located and / or where the on / off switch is often located. If the working head has a substantially rectangular cross section and / or an elongated working element such as an elongated shear foil cartridge, the direction in which acceleration is measured can be substantially parallel to the skin contact surface, substantially perpendicular to the long axis of the rectangular cross section and / or perpendicular to the longitudinal axis of the elongated working element. Advantageously, the acceleration sensor is configured to measure acceleration along at least one of a first axis extending in the longitudinal handle direction, a second axis perpendicular to the first axis and extending through the front and rear of the handle, and / or a third axis perpendicular to the first and second axes.

[0027] Nevertheless, the acceleration sensor may be a multi-axis sensor for measuring acceleration in at least two or three axes, for example along a pair of axes that are perpendicular to each other and parallel to the skin-contacting surface of the working head.

[0028] Advantageously, at least one measurement axis of the acceleration sensor is an axis having a fixed orientation relative to the personal care device, in other words, the acceleration is not measured along an axis fixed in space, but rather along an axis fixed to the working head and / or the handle of the personal care device.

[0029] When the personal care device rotates, an acceleration signal is caused by such rotation and therefore the velocity values ​​determined from the acceleration signal change and are affected by such rotation. To eliminate or at least reduce such effects of device rotation, a rotation sensor may be provided or, more generally, the rotation of the working head and / or handle of the personal care device may be measured or determined.

[0030] Advantageously, the inaccuracy of the velocity calculated from the acceleration signal can be corrected by using the rotational velocity that can be measured by the rotational sensor and by the distance between the acceleration sensor and the skin contact surface of the working head. Depending on the direction of rotation, a rotation ratio can be added or subtracted to the velocity calculated from the acceleration signal of the acceleration sensor.

[0031] In order to accurately recognize the transition from a long stroke pattern to a short stroke pattern or vice versa, the determined stroke length can be compared with a reference value or threshold value, which can be determined from an average value of the lengths of a sufficient number of previous strokes. More specifically, the determination unit may be configured to determine a sliding average of the lengths of a predetermined number of previous strokes, whereby at least the last two strokes are taken into account for the determination of the sliding average. For example, the last three or the last five or the last ten strokes can be taken into account and / or a sliding average specified over a predetermined period of time considered for determining the sliding average of the stroke length can be taken into account.

[0032] Essentially, the sliding average can be considered as a threshold against which the currently determined stroke length can be compared to determine whether it is a short or long stroke. However, the determination unit may also be configured to apply a scaling factor or multiple scaling factors to the stroke lengths of the preceding strokes taken into account for the calculation of the sliding average. More specifically, such a sliding factor can be selected to give a greater weight to the latest stroke or the two latest strokes. Such a scaling factor helps to achieve a sufficiently fast reaction and at the same time provides for a continuous adaptation of the system.

[0033] According to one aspect, a determination unit is provided for determining the stroke length during the body treatment operation, in particular in real time, so that the advantage of this distinction of stroke length can be used within the same or a single shaving procedure.

[0034] The personal care device comprises two separate parts, a first part is provided for providing a body treatment and a second part at least partially comprises a decision unit, thus the decision unit can be part of the personal care device but can also be separate from the personal care device.

[0035] The second part is carried out in a smart device, for example a smartphone or a wearable device, whereby at least the microprocessor power of the smartphone is used to perform all calculations and to provide a minimal additional visualization of the shaving procedure within a software application designated for that purpose.

[0036] A personal care device, in particular a hair removal device such as an electric shaver, comprises an elongated handle (40) for manually moving the personal care device (2) in short and / or long strokes (30, 31) along a body surface (5), a working head (41) attached to said handle (40) for performing a personal care treatment on said body surface (5), and a determination unit (42) including at least one sensor for determining a stroke length to distinguish between short and long strokes, wherein a second sensor is provided configured to measure a correction signal for correcting the stroke length determination signal, such second sensor can for example be a rotation sensor as mentioned above, in order to eliminate handle rotations that do not affect the shaving stroke.

[0037] Additionally or alternatively, the determination unit may be configured to ignore stroke lengths that exceed a predefined maximum value. Ignoring strokes that are too long and therefore somewhat unreasonable helps the system to rationally distinguish between normal long strokes and short strokes that are commonly used by a particular user. [Brief description of the drawings]

[0038] [Figure 1] A side view of a personal care device including an elongated handle that rotatably supports an working head with a skin-contacting surface in contact with a user's body surface, the personal care device may be an electric shaver, and includes a determination unit including an acceleration sensor housed within the handle for determining stroke length and distinguishing between long and short strokes. [Diagram 2] 1 is a flow chart showing the measurement and evaluation steps performed by a determination unit of a personal care device to determine a long stroke and a short stroke. [Diagram 3] FIG. 2 is a functional diagram of speed versus stroke length for a personal care device, with regions of short stroke detected being indicated on the functional diagram. [Figure 4]FIG. 2 is a perspective front view of a user's face showing the areas where short and long strokes are typically applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] As can be seen, in order to enable the use of reduced sensor equipment, it is proposed to determine the stroke length based on the speed of the working head and / or handle of the personal care device and to analyze the speed to determine the stroke length. More specifically, the determination unit provided for determining the stroke length for distinguishing between short strokes and long strokes can be configured to determine the start and end points of the stroke when the speed of the working head and / or handle becomes zero and / or when its sign changes from positive to negative and vice versa, and to determine the stroke length from the distance and / or path between pairs of consecutive start and end points adjacent to each other. The analysis of the speed allows the distinction between long strokes and short strokes without the need for complex sensor equipment such as cameras or image sensors, and allows adaptive control not only for use in difficult areas such as the upper lip area, but also when the user encounters other problems such as difficult hair and therefore changes his behavior with respect to the change from long strokes to short strokes or vice versa.

[0040] The velocity of the personal care device can be determined, for example, by a velocity sensor. However, advantageously, the velocity may be derived from an acceleration signal of an acceleration sensor measuring the acceleration of the working head and / or handle. Such an acceleration sensor may be located at or at least in close proximity to the working head to determine the acceleration of the working head. For example, the acceleration sensor may be located near the skin contacting surface of the working head to determine the acceleration at a location close to the interface of the working head with the skin or body surface to be treated.

[0041] As a result, the velocity that can be calculated or otherwise derived from the acceleration signal is close to the velocity at which the working head moves over the body surface. However, alternatively, the acceleration sensor may also be housed in the handle for practical reasons, in which case a correction of the acceleration signal may be performed to account for the acceleration of the working head and its skin-contacting surface. Such a correction may be achieved, for example, by determining the rotation of the handle and taking into account the known distance of the acceleration sensor in the handle from the skin-contacting surface.

[0042] To improve the accuracy of the calculation of the velocity from the acceleration, disturbances that distort the acceleration signal and / or represent effects that do not correspond to the relevant movement of the personal care device can be eliminated. More specifically, a filter can be used to remove vibrations and / or effects on the acceleration signal that are due to vibrations of the shaver. For example, a low pass filter, such as a second order low pass filter, may be used. Regardless of the particular type of filter, the filter can have a cutoff frequency set between the frequency of the relevant vibrations and the highest possible frequency of manual movement or user's hand movement. For example, a cutoff frequency in the range of 25-35 Hz or substantially 30 Hz can be used.

[0043] In addition to or as an alternative to filtering the effects resulting from vibration, the effects of gravity on the acceleration signal can be removed. More specifically, a filter such as a high-pass filter can be used to remove the proportion of the measurement signal due to gravity. Such filtering is based on the assumption that the effects of gravity change fairly slowly, while the stroke movement of the handle is fairly fast.

[0044] For example, the filter can have a cutoff frequency in the range of 1 Hz to 2 Hz, with a cutoff frequency of about 1.3 Hz working well. Shorter time values ​​may suppress actual motion, while larger time values ​​may contaminate the calculation with changes in the orientation of the personal care device that are not attributable to the stroke.

[0045] Determining the velocity from the acceleration signal may include integration over time. More specifically, the filtered acceleration signal may be integrated over time to obtain the velocity of the work head and / or handle of the personal care device.

[0046] Advantageously, a low-pass filter can be used to obtain the velocity, the properties of which are such that it is possible to carry out a mathematical integration of frequencies above a cut-off frequency, in other words, the properties of a region called the stop band, rather than the pass band, of the filter used for the integration, are used to obtain the velocity from the acceleration signal.

[0047] For example, the cutoff frequency may be set to a value sufficiently lower than the frequency of the stroke movement to ensure integration of the stroke acceleration without significant loss. For example, a cutoff frequency in the range of 0.2-0.35 Hz or 0.25-0.30 Hz can be used. For example, a cutoff frequency of about 0.27 Hz can work well.

[0048] The acceleration sensor may measure acceleration in at least one direction of interest, for example, up and down acceleration, or acceleration in a direction that is substantially parallel to the skin-contacting surface of the working head and substantially perpendicular to the front surface of the handle where the thumb is typically located and / or where the on / off switch is often located. Where the working head has a substantially rectangular cross-section and / or an elongated working element such as an elongated shear foil cartridge, the direction in which acceleration is measured may be parallel to the skin-contacting surface, perpendicular to the major axis of the rectangular cross-section, and / or perpendicular to the longitudinal axis of the elongated working element.

[0049] Nevertheless, the acceleration sensor may be a multi-axis sensor for measuring acceleration in at least two or three axes, for example along a pair of axes that are perpendicular to each other and parallel to the skin-contacting surface of the working head.

[0050] Advantageously, at least one measurement axis of the acceleration sensor is an axis having a fixed orientation relative to the personal care device, in other words, the acceleration is not measured along an axis fixed in space, but along an axis fixed to the working head and / or the handle of the personal care device.

[0051] When the personal care device rotates, an acceleration signal is caused by such rotation and therefore the velocity values ​​determined from the acceleration signal change and are affected by such rotation. To eliminate or at least reduce such effects of device rotation, a rotation sensor may be provided or, more generally, the rotation of the working head and / or handle of the personal care device may be measured or determined.

[0052] Advantageously, the inaccuracy of the velocity calculated from the acceleration signal can be corrected by using the rotational velocity that can be measured by the rotational sensor and by the distance between the acceleration sensor and the skin contact surface of the working head. Depending on the direction of rotation, a rotation ratio can be added or subtracted to the velocity calculated from the acceleration signal of the acceleration sensor.

[0053] In order to accurately recognize the transition from a long stroke pattern to a short stroke pattern or vice versa, the determined stroke length can be compared with a reference value or threshold value, which can be determined from an average value of the lengths of a sufficient number of previous strokes. More specifically, the determination unit may be configured to determine a sliding average of the lengths of a predetermined number of previous strokes, where at least the last two strokes are taken into account for the determination of the sliding average. For example, the last three or the last five or the last ten strokes can be taken into account, or a predetermined period of time observed can be taken into account for determining the sliding average of the stroke length.

[0054] Basically, the sliding average can be considered as a threshold against which the currently determined stroke length can be compared to determine whether it is a short or long stroke. However, the determination unit can include a scaling factor application device 47 (see FIG. 1 ) for applying a scaling factor or factors to the stroke length of the preceding strokes taken into account for the calculation of the sliding average. More specifically, such a sliding factor can be selected to give a greater weight to the latest stroke or the two latest strokes. Such a scaling factor helps to achieve a sufficiently fast reaction and at the same time provides a continuous adaptation of the system.

[0055] To avoid disturbing the distinction between long and short strokes, a counter of the number of short strokes may be incremented each time a short stroke is detected in the previous step. Such a counter may be reset to zero each time a stroke exceeds the maximum accepted length. Such a reset may be performed before the stroke is terminated. A reset may also be performed as soon as the current stroke becomes too long.

[0056] Such a reset can achieve fast response to user behavior and avoid the adverse effects on discrimination that can occur when a slow long stroke follows a fast short stroke.

[0057] Furthermore, the determined speed may be checked for validity. More specifically, the average of the absolute values ​​of the speeds of the past short time intervals may be calculated, and if said average value is lower than a predefined threshold, said stroke counter may be reset. Such a step may serve, for example, to recognize a stop or interruption of the treatment. For example, a stop or interruption of the shaver movement may be recognized as a significant short stroke, which may be prevented by said check of the speed.

[0058] In order to more reliably identify a true change in stroke pattern, the number of short strokes identified by the above-mentioned counter can be compared with a minimum number of short strokes required, or vice versa, the number of long strokes that can be counted by the long stroke counter can be compared with a minimum number of long strokes required. As soon as the minimum required number is reached or exceeded, a positive output signal can be generated indicating that a change in stroke pattern has occurred. For example, said threshold or minimum required number can be two or three or five. A value of only one brings the risk of a false output signal, while a number greater than five, or greater than three, or greater than two can increase the reaction time of the system. Thus, a decision unit can be considered to be very sensitive if it is already able to react after one or two or less than six strokes.

[0059] According to a further advantageous aspect, the control unit can constantly keep track of the average stroke length and speed during the calculations and adapt the thresholds according to these values ​​to improve the accuracy of the individual user's behavior detection so as to achieve a kind of self-learning and personalization of the device. For example, a shift of the stroke length threshold, which is used to ignore strokes that are too long, and / or a shift of the speed threshold, which is used to identify interruptions, can be performed in this way.

[0060] As becomes clear from the figures, a specific method is proposed to determine short and long strokes and to reliably distinguish between short and long stroke patterns, in order to allow a rapid adaptation of the configuration of the personal care device. The length of the stroke movement during a treatment session, such as shaving, is determined and a signal is given as soon as the stroke becomes short, i.e. as soon as the geometric length of the stroke falls below a certain predefined value. This signal can be used for various purposes within the device, such as to adjust something. The present invention concerns determining the length of the stroke. The use of the obtained signal is the subject of other inventions.

[0061] A stroke can be understood as a typically repeated movement of a personal care device 2, such as a shaver, on the user's skin during shaving. Figure 4 illustrates such a movement. Measurement of their length may be performed based on data from an acceleration sensor and, optionally, from a gyro sensor measuring rotation. In addition to the measurement, a calculation is also performed. As shown in Figure 4, long strokes 31 can typically be performed when shaving the cheek area, while short strokes 30 are typically performed in "difficult" areas with boundaries, such as the area between the nose and the upper lip (see Figure 4). As mentioned before, other reasons may cause the user to perform short strokes.

[0062] As shown in FIG. 1 , the personal care device 2 may be an electric shaver having an elongated handle 40 pivotably supporting a working head 41 which may pivot about a pivot axis and / or tilt about a tilt axis relative to the handle 40, the tilt axis and / or the pivot axis may extend substantially parallel to the skin-contacting surface 4 or, if both the tilt axis and the pivot axis are present, may be perpendicular to each other.

[0063] The working head 41 may carry one or more working tools such as a cutting implement, for example for a long hair trimmer having a shear foil cartridge and / or finger-like cutting blades.

[0064] In addition to, or as an alternative to, such rotational adjustability, the working head 41 may also be linearly displaceable relative to the handle 40, for example along an axis substantially perpendicular to the skin contacting surface 4, to enable popping of the working head 41 relative to the handle 40. Additionally, or as an alternative, the working tool may be displaceable relative to the working head reference, for example to enable popping of a shear foil cartridge relative to the working head reference.

[0065] The mobility of the working head 41 relative to the handle 2 and / or the working tool relative to the working head reference can be adjusted by an adjustment actuator depending on the stroke length, as will be described in detail. More specifically, the pivoting and / or tilting and / or popping stiffness can be adjusted from hard to soft depending on whether the user performs a short or long stroke.

[0066] A determining unit 42 is provided for determining the stroke length and distinguishing between short and long strokes, such determining unit 42 may include at least one sensor 1, such as an acceleration sensor, and an electronic evaluation unit 42a, which may be part of and / or connected to an electronic control unit for controlling the personal care device 2. Such an electronic control unit may include a microprocessor and a memory device for storing program applications and / or data, such electronic control unit may also control the operation of the personal care device 2, including controlling the aforementioned adjustment actuators to make the suspension of the working head 41 firmer or softer.

[0067] As can be seen from FIG. 2 , the decision unit 42 can execute the following steps, all or only some of which may be executed, and the order of the steps may be changed without regard to their numbering (numbering starting with 10 depends on other reference signs used in other figures):

[0068] Step 10 - Measure the device acceleration: The acceleration of the device in at least one direction of interest, for example the upward or downward direction, can be measured (see FIG. 2). This can be done via an acceleration sensor 1 of the device 2 shown in FIG. 1. It is also possible to measure the undesirable but unavoidable force of gravity. A sensor 1 with an analog output can be chosen.

[0069] Step 11 - Eliminate vibrations: A filter 43 may be used to remove effects due to vibrations of the personal care device 2. This filter 43 may be a second order low pass filter, see figure 1. Its cut-off frequency may be set between the frequency of the vibrations and the highest possible frequency of the hand movements. For example, around 30Hz is a good value.

[0070] The filter 43 can be constructed in hardware, or a combination of hardware and software filtering, or optionally software filtering only, may be possible.

[0071] The analog signal of the acceleration sensor may be digitized and the next steps may be performed based on the digital data.

[0072] Step 11 - Removing Gravity: A high pass filter 44 may be used to remove the proportion of the measurement signal due to gravity. This step may work on the assumption that the effect of gravity is slowly changing and the stroke motion is faster.

[0073] A good value for the cutoff frequency of this filter 44 is, for example, about 1.3 Hz. A shorter time value will suppress real movements, a larger time value will mix in orientation changes of the personal care device 2 that are not due to stroke into the calculation.

[0074] Step 12 - Calculate the speed: The remaining part of the acceleration signal may be integrated over time to obtain the velocity of the personal care device. This may be done with the help of a low pass filter 3. The properties of the low pass filter may be used, which performs a mathematical integration of the frequencies above the cut-off frequency. Usually it is expected that the pass band of the filter is used. However, here the properties of the region called the stop band are used.

[0075] The cut-off frequency may be set to a value sufficiently lower than the frequency of the stroke movement, in this way ensuring that the stroke acceleration can be integrated without significant losses. A good value for the cut-off frequency is, for example, about 0.27 Hz.

[0076] Rotational measurements can be used to improve the determination of velocity from the measured acceleration, thus increasing the accuracy of measurements and calculations. For rotational measurements, the correct axis should be selected. If an up-down movement of the skin-contacting surface 4 of the personal care device is determined, the corresponding rotational axis is the left-right axis of the personal care device. In other words, the rotational axis monitored by the rotational sensor is the axis about which rotation causes a movement in and / or against the direction of the measured acceleration.

[0077] To refine the calculation of the velocity value, the movement due to the rotation can be added / subtracted to the movement determined from the acceleration sensor 1. For example, the velocity of the object may be the velocity of the skin contact surface 4 of the working head 41, for example at the interface between the shaving foil and the skin 5 (see FIG. 1). For practical reasons, the acceleration sensor 1 may be arranged at different positions in the device, for example in the handle (see FIG. 1). As soon as the device rotates, the velocity values ​​determined from the acceleration at the acceleration sensor 1 and the true velocity at the skin contact surface 4 can be different.

[0078] This inaccuracy can be corrected by a correction unit 49 using the value of the rotation speed measured by the rotation sensor 48 and the known distance between the acceleration sensor 1 and the area of ​​the device of interest, e.g. the skin contact surface 4.

[0079] Step 13 - Calculate position: The position of the device 2, and more specifically the position of the working head 41, can be calculated from the velocity in the same way that the velocity can be calculated from the acceleration. Such position calculations can be absolute or can be relative to other position values. A filter 3 with the same characteristics as described above may be used.

[0080] Step 14 - Detecting the start and end of the stroke: Whenever the velocity of the personal care device changes sign, the current position of the personal care device can be considered as the end of a stroke and the start of the next stroke. The sign of the velocity can be obtained from the previously calculated velocity value.

[0081] Step 14 - Calculate the stroke length: The current stroke length may be calculated continuously from the position at the start of the stroke and the current device position. The (preferably relative) position value of the start of the stroke can be obtained from the previous step from the position calculation above and the current device position.

[0082] Step 16 - Short stroke detection: Whenever the end of a stroke is detected, a comparison of its length with a defined maximum acceptable length of a short stroke 30 can be made by a comparator 45. If the stroke is shorter than this maximum length, it is accepted as a short stroke 30.

[0083] Figure 3 shows a 2D plot where the horizontal axis represents stroke length. Region 21 in Figure 3 represents strokes that are too long and are therefore excluded in this step of the algorithm. Stroke 31 in FIG. 4 is an example of such a stroke, which is too long. Stroke 30 in FIG. 4 is an example of a short stroke that is accepted in this step.

[0084] Step 17 - Counting Short Strokes A counter 50 of the number of short strokes may be incremented whenever a short stroke 30 is detected in the previous step. This counter may be reset to zero every time a stroke exceeds the maximum accepted length. Such a reset may occur before the stroke is finished. A reset occurs as soon as the current stroke becomes too long. This approach helps to provide a fast reaction to the user's behavior. A slow long stroke after a short stroke would otherwise confuse the algorithm in a very troublesome way.

[0085] Step 15 - Checking the speed: The average of the absolute value of the speed over the past short time intervals can be calculated and if this value is lower than some defined threshold, the stroke counter 50 can be reset. This is important to recognize the stop or interruption of a treatment session, e.g. shaving. Otherwise, a stop in the movement of the personal care device would be recognized as a rather short stroke.

[0086] Region 22 in FIG. 2 represents a region that may be excluded from short stroking due to such insufficient velocity.

[0087] Area 20 represents shaving strokes that are considered valid short strokes.

[0088] Step 18 - Check the short stroke counter: The number of short strokes 30 counted in step 17 can be compared to a minimum required number of short strokes 30. As soon as this minimum required number is reached or exceeded, a positive output signal can be generated. A minimum required number that has been found to be useful may be two.

[0089] A value of only one may pose the risk of an erroneous output signal, while numbers greater than 2 or 3 or 5 may increase the reaction time of the algorithm to disturbing levels.

[0090] Device self-learning / personalization: The control unit can constantly track the average stroke length and velocity during calculations and adapt the thresholds according to these values ​​to improve the accuracy of individual user behavior detection.

[0091] The shift in the stroke length threshold used in block 16 is indicated by arrow 23 in FIG.

[0092] The shift in the velocity threshold used in block 15 is indicated by arrow 24 in FIG.

[0093] Additionally or alternatively, the determination unit may be configured to ignore stroke lengths that exceed a predefined maximum value. Ignoring strokes that are too long and therefore somewhat unreasonable helps the system to rationally distinguish between normal long strokes and short strokes that are commonly used by a particular user. <<Other embodiments>> The present disclosure includes the following representative configurations. (Configuration 1) 1. A personal care device, in particular a hair removal device such as an electric shaver, comprising an elongated handle (40) for manually moving said personal care device (2) in short and / or long strokes (30, 31) along a body surface (5), a working head (41) attached to said handle (40) for performing a personal care treatment on said body surface (5), and a determination unit (42) comprising at least one sensor (1) for determining a stroke length to distinguish between said short and long strokes (30, 31), wherein said determination unit (42) is configured to determine a velocity of said working head (41) and / or said handle (40), to determine start and end points of said strokes (30, 31) when the determined velocity becomes zero and / or changes sign, and to determine the stroke length from the distance between a pair of adjacent start and end points. (Configuration 2) 2. The personal care device of configuration 1, wherein the determination unit (42) comprises an acceleration sensor housed in the handle (40) for determining its acceleration, the determination unit (42) further comprises an evaluation unit (42) for evaluating the acceleration signal of the acceleration sensor (1) and determining a velocity from the acceleration signal, and / or the working head is arranged to pivot relative to the handle. (Configuration 3) 3. The personal care device of configuration 2, wherein the evaluation unit (42) is configured to integrate the acceleration signal over time to determine a velocity. (Configuration 4) 4. The personal care device of configuration 2 or 3, wherein the determination unit comprises, in addition to the acceleration sensor, also a rotation sensor for detecting rotational movement of the handle. (Configuration 5) 5. The personal care device of configuration 4, wherein the rotational sensor is configured to provide a correction signal to the determined speed. (Configuration 6) 6. The personal care device of configuration 5, wherein the evaluation unit (42) comprises a low pass filter (3) for performing a mathematical integration to determine the velocity based on the acceleration signal and / or the low pass filter (3) has a cut-off frequency set to a value below the expected frequency of the short and long strokes (30, 31) and performs the mathematical integration for frequencies above the cut-off frequency. (Configuration 7) 7. The personal care device of configuration 6, wherein the cut-off frequency of the low pass filter (3) is in the range of 0.20 Hz to 0.40 Hz, or 0.25 Hz to 0.35 Hz, or 0.25 Hz to 0.30 Hz. (Configuration 8) A personal care device according to any one of claims 2 to 7, wherein the determination unit (42) comprises a filter (43) for removing influences resulting from vibrations of the personal care device on the acceleration signal of the acceleration sensor (1), in particular a second order low pass filter with a cut-off frequency set between the frequency of expected vibrations of the personal care device (2) and the highest expected frequency of the short and long strokes (30, 31), said cut-off frequency being more particularly in the range of 10 Hz to 100 Hz, or 20 Hz to 40 Hz or 25 Hz to 35 Hz. (Configuration 9) 9. The personal care device of any one of configurations 2 to 8, wherein the determination unit (42) comprises a filter (44) for removing the effect of gravity on the acceleration signal of the acceleration sensor (1). (Configuration 10) 10. The personal care device of configuration 9, wherein the filter (44) for removing the effects of gravity is a high pass filter having a cutoff frequency in the range of 0.8 Hz to 2.0 Hz or 1.0 Hz to 1.5 Hz. (Configuration 11) 11. The personal care device of any one of configurations 1 to 10, wherein the determination unit (42) comprises a comparator (45) for comparing the determined stroke length with a reference value forming a boundary between a long stroke (31) and a short stroke (30), and further comprising a dynamic reference value determiner (46) for dynamically determining the reference value from the stroke lengths of a number of preceding strokes. (Configuration 12) 12. The personal care device of claim 11, wherein the dynamic baseline determiner (46) is configured to determine a sliding average of the stroke length of two or more preceding strokes or a specified sliding average over a predetermined period of time. (Configuration 13) 13. The personal care device of configuration 11 or 12, wherein the dynamic reference value determiner (46) includes a scaling factor applicator (47) for applying a scaling factor to the stroke lengths of the preceding strokes used to determine the reference value, the scaling factor applicator (47) being configured to give more weight to stroke lengths of more recent strokes than to stroke lengths of less recent strokes. (Configuration 14) 14. A personal care device according to any one of the preceding configurations, wherein the determination unit (42) is configured to ignore stroke lengths exceeding a predetermined maximum value. (Configuration 15) 15. The personal care device of any one of configurations 2 to 14, wherein the acceleration sensor (1) of the determination unit (42) is configured to measure acceleration along at least one axis extending substantially parallel to the skin-contacting surface of the working head, substantially parallel to a longitudinal cross-sectional plane parallel to the longitudinal axis of the handle (40) and substantially perpendicular to the skin-contacting surface of the working head (41), or to measure acceleration along two axes perpendicular to each other and parallel to the skin-contacting surface of the working head (41). (Configuration 16) 16. The personal care device of any one of configurations 2 to 15, wherein the acceleration sensor is configured to measure acceleration along at least one of a first axis extending in a longitudinal handle direction, a second axis extending perpendicular to the first axis and passing through the front and back of the handle, and / or a third axis perpendicular to the first and second axes. (Configuration 17) 17. The personal care device of configuration 15 or 16, wherein the determination unit (42) comprises a rotation sensor (48) for measuring a rotation speed and / or a rotation acceleration, and a correction unit (49) for correcting the acceleration signal of the acceleration sensor (1) based on the measured rotation speed and / or rotation acceleration and the distance between the acceleration sensor (1) and the skin contact surface of the working head (41). (Configuration 18) 18. A personal care device according to any one of configurations 1 to 17, wherein the determination unit (42) comprises a counter (50) for counting the number of short strokes and / or long strokes, the counter (50) being configured to be reset to zero whenever a stroke exceeds a maximum accepted length and / or the average value of the determined speed is lower than a predefined threshold. (Configuration 19) 19. A personal care device according to any one of configurations 1 to 18, wherein the determination unit (42) is configured to issue a stroke pattern change signal indicative of a change from a long stroke pattern to a short stroke pattern and / or from a short stroke pattern to a long stroke pattern when a predetermined number of short strokes and / or a predetermined number of long strokes have been counted, the predetermined number being greater than 1 and less than 6. (Configuration 20) 20. A personal care device according to any one of the preceding configurations, further comprising an adjustment device including at least one adjustment actuator for adjusting at least one treatment characteristic in response to a signal from the determining unit (42) indicative of a change in the stroke length pattern or indicative of the determined stroke length pattern. (Configuration 21) The personal care device of configuration 20, wherein the adjustment device includes at least one adjustment actuator for adjusting the tilt stiffness and / or the pivot stiffness and / or the pop-out stiffness of the working head (41), and / or the pivot stiffness and / or the tilt stiffness and / or the pop-out stiffness of the working tool relative to a working head reference, in response to the signal from the determination unit (42) indicating a change in the stroke length pattern. (Configuration 22) 22. A personal care device according to any one of configurations 1 to 21, wherein the determination unit is provided for determining the stroke length during the body treatment action, in particular in real time. (Configuration 23) 23. The personal care device of any one of configurations 1 to 22, wherein the personal care device comprises two separate parts, a first part being provided for providing the body treatment and a second part at least partially comprising the decision unit. (Configuration 24) 24. The personal care apparatus of configuration 23, wherein the second part is implemented in a smart device, for example a smartphone or a wearable device. (Configuration 25) A personal care device, in particular a hair removal device such as an electric shaver, as required according to any one of claims 1 to 24, comprising an elongated handle (40) for manually moving the personal care device (2) in short and / or long strokes (30, 31) along a body surface (5), a working head (41) attached to the handle (40) for performing a personal care treatment on the body surface (5), and a determination unit (42) comprising at least one sensor (1) for determining a stroke length for distinguishing between the short and long strokes (30, 31), characterized by a second sensor configured to measure a correction signal for correcting the stroke length determination signal.

Claims

1. A personal care device, in particular a hair removal device such as an electric shaver, comprising an elongated handle (40) for manually moving said personal care device (2) in short and / or long strokes (30, 31) along a body surface (5), a working head (41) attached to said handle (40) for performing a personal care treatment on said body surface (5), and a determination unit (42) including at least one sensor (1) for determining a stroke length for distinguishing between said short and long strokes (30, 31) by comparing it with a reference value, said determination unit (42) being adapted to determine a speed of said working head (41) and / or said handle (40), to determine start and end points of said strokes (30, 31) when the determined speed becomes zero and / or changes sign, and to determine the start and end points of said strokes (30, 31) adjacent to each other.

1. A personal care device configured to determine a stroke length from a distance between a pair of start and end points of a stroke, the determination unit (42) comprising a speed sensor (1) housed in the handle (40) and determining its speed, or the determination unit (42) comprising an acceleration sensor (1) housed in the handle (40) and determining its acceleration, and an evaluation unit (42) for evaluating an acceleration signal of the acceleration sensor (1) and determining the speed from the acceleration signal, the determination unit (42) comprising a comparator (45) for comparing the determined stroke length with the reference value forming a boundary between a long stroke (31) and a short stroke (30), and further comprising a dynamic reference value determiner (46) for dynamically determining the reference value from the stroke lengths of a number of preceding strokes.

2. The personal care device of claim 1 , wherein the working head is mounted to pivot relative to the handle.

3. 3. The personal care device of claim 2, wherein the evaluation unit (42) is configured to integrate the acceleration signal over time to determine a velocity.

4. 4. A personal care device according to claim 2 or 3, wherein the decision unit comprises, in addition to the acceleration sensor, also a rotation sensor for detecting a rotational movement of the handle.

5. The personal care device of claim 4 , wherein the rotational sensor is configured to provide a correction signal to the determined speed.

6. 6. Personal care device according to claim 5, wherein the evaluation unit (42) comprises a low pass filter (3) for performing a mathematical integration for determining the velocity based on an acceleration signal.

7. 7. A personal care device as claimed in claim 6, wherein the low pass filter (3) has a cut-off frequency set to a value below the expected frequencies of the short and long strokes (30, 31) and performs the mathematical integration for frequencies above said cut-off frequency.

8. 8. A personal care device according to claim 7, wherein the cut-off frequency of the low pass filter (3) is in the range of 0.20 Hz to 0.40 Hz, or 0.25 Hz to 0.35 Hz, or 0.25 Hz to 0.30 Hz.

9. 2. The personal care device of claim 1, wherein the determination unit (42) comprises a filter (43) for removing influences resulting from vibrations of the personal care device on the acceleration signal of the acceleration sensor (1), in particular a second-order low-pass filter with a cut-off frequency set between the frequency of expected vibrations of the personal care device (2) and the highest expected frequency of the short and long strokes (30, 31), said cut-off frequency being more particularly in the range of 10 Hz to 100 Hz, or 20 Hz to 40 Hz or 25 Hz to 35 Hz.

10. 2. The personal care device of claim 1, wherein the determination unit (42) comprises a filter (44) for removing the effect of gravity on the acceleration signal of the acceleration sensor (1).

11. 11. The personal care device of claim 10, wherein the filter (44) for removing the effects of gravity is a high pass filter having a cutoff frequency in the range of 0.8 Hz to 2.0 Hz or 1.0 Hz to 1.5 Hz.

12. 2. The personal care device of claim 1, wherein the dynamic baseline determiner (46) is configured to determine a sliding average of the stroke length of two or more preceding strokes or a specified sliding average over a predetermined period of time.

13. 13. A personal care device according to claim 1 or 12, wherein the dynamic reference value determiner (46) comprises a scaling factor applicator (47) for applying a scaling factor to the stroke lengths of the preceding strokes used to determine the reference value, the scaling factor applicator (47) being configured to give more weight to stroke lengths of more recent strokes than to stroke lengths of less recent strokes.

14. 2. The personal care device of claim 1, wherein the determination unit (42) is configured to ignore stroke lengths that exceed a predetermined maximum value.

15. 2. The personal care device of claim 1, wherein the acceleration sensor (1) of the determination unit (42) is configured to measure acceleration along at least one axis extending substantially parallel to the skin contact surface of the working head, substantially parallel to a longitudinal cross-sectional plane parallel to the longitudinal axis of the handle (40) and substantially perpendicular to the skin contact surface of the working head (41), or to measure acceleration along two axes perpendicular to each other and parallel to the skin contact surface of the working head (41).

16. 2. The personal care device of claim 1, wherein the acceleration sensor is configured to measure acceleration along at least one of a first axis extending in a longitudinal handle direction, a second axis extending perpendicular to the first axis and passing through the front and back sides of the handle, and / or a third axis perpendicular to the first and second axes.

17. 16. The personal care device of claim 15, wherein the determination unit (42) comprises a rotation sensor (48) for measuring a rotation speed and / or a rotation acceleration, and a correction unit (49) for correcting the acceleration signal of the acceleration sensor (1) based on the measured rotation speed and / or rotation acceleration and on the distance between the acceleration sensor (1) and the skin contact surface of the working head (41).

18. 2. The personal care device of claim 1, wherein the determining unit (42) comprises a counter (50) for counting the number of short and / or long strokes, the counter (50) being configured to be reset to zero whenever a stroke exceeds a maximum accepted length and / or the average value of the determined speed is lower than a predefined threshold value.

19. 2. The personal care device of claim 1, wherein the determination unit (42) is configured to issue a stroke pattern change signal indicative of a change from a long stroke pattern to a short stroke pattern and / or from a short stroke pattern to a long stroke pattern when a predetermined number of short strokes and / or a predetermined number of long strokes are counted, the predetermined number being greater than 1 and less than 6.

20. 20. The personal care device of claim 19, further comprising an adjustment device including at least one adjustment actuator for adjusting at least one operating parameter in response to a signal from the determination unit (42) indicative of a change in the stroke pattern or indicative of the determined stroke pattern.

21. 21. The personal care device of claim 20, wherein the adjusting device comprises at least one adjusting actuator for adjusting the tilt stiffness and / or the pivot stiffness and / or the pop-out stiffness of the working head (41) and / or the pivot stiffness and / or the tilt stiffness and / or the pop-out stiffness of the working tool relative to a working head reference in response to the signal from the determination unit (42) indicating a change in the stroke pattern.

22. 2. A personal care device according to claim 1, wherein said determination unit is provided for determining said stroke length during said personal care treatment action, in particular in real time.

23. 10. The personal care device of claim 1, wherein the personal care device comprises two separate parts, a first part provided for providing the personal care treatment and a second part at least partially comprising the decision unit.

24. 24. The personal care apparatus of claim 23, wherein the second part is implemented in a smart device, for example a smartphone or a wearable device.

25. 2. A personal care device, in particular a hair removal device such as an electric shaver, according to claim 1, comprising an elongated handle (40) for manually moving the personal care device (2) in short and / or long strokes (30, 31) along a body surface (5), a working head (41) attached to the handle (40) for performing a personal care treatment on the body surface (5), and a determination unit (42) including at least one sensor (1) for determining a stroke length to distinguish between the short and long strokes (30, 31), characterized in that the personal care device further comprises a second sensor configured to measure a correction signal for correcting the stroke length determination signal.

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