Electric shaver

Abstract

According to one aspect, there are skin contact areas 200, 910, 1110, 1410, 1610 for contacting the user's skin during use of electric shavers 100, 900, 1000, 1100, 1400, 1600, and at least two hair cutting units 150, 160, 170, 1480, 1680 disposed within the skin contact areas, each hair cutting unit having an external cutting member 152, 162, 172, 1482, 1682 having a plurality of hair entry openings, and an internal cutting member covered by the external cutting member 152, 162, 172, 1482, 1682 and movable relative to the external cutting member; N electrodes 180a - d disposed within the skin contact areas 200, 910, 1110, 1410, 1610 so as to contact the skin during use, where N is at least 3; the fundamental frequency f RF and the fundamental period T RF = 1 / f RF A radio frequency (RF) generator 320 configured to generate RF energy having; and an RF energy modulator 310 configured to convert the RF energy generated by the RF generator into N periodically amplitude - modulated RF energy signals and provide each of the N periodically amplitude - modulated RF energy signals S1, S2, S3 to a corresponding one of the N electrodes. In an electric shaver comprising, when viewed in a direction perpendicular to the skin contact area, the external cutting member of each hair cutting unit has a geometric center point 156, 166, 176, 1486, 1686, a first pitch distance 202 which is the distance between the geometric center points of a pair of hair cutting units, and a first minimum pitch distance which is the minimum value of the first pitch distances of all pairs of hair cutting units; when viewed in a direction perpendicular to the skin contact area, each of the N electrodes has a geometric center point 182a - c, a second pitch distance 204 which is the distance between the geometric center points of a pair of the N electrodes, and a second minimum pitch distance which is the minimum value of the second pitch distances 204 of all pairs of the N electrodes, the ratio between the second minimum pitch distance and the first minimum pitch distance being at least 0.8; the fundamental period T MOD of the N periodically amplitude - modulated RF energy signals S1, S2, S3 is the fundamental period T RFgreater than, and the n-th of the N periodically amplitude-modulated RF energy signals S1, S2, S3 has a phase difference of T * (n - 1) / N with respect to the first of the N periodically amplitude-modulated RF energy signals S1, S2, S3, where 2 ≦ n ≦ N, an electric shaver is provided. MOD *(n - 1) / N, where 2 ≦ n ≦ N, an electric shaver is provided.

Description

Technical Field

[0001] The present application relates to an electric shaver, and more particularly to an electric shaver comprising a radio frequency (RF) generator unit for heating the skin during use.

Background Art

[0002] It is generally recognized that applying heat to the skin in the vicinity of a specific temperature range, for example, about 38°C to 40°C, can evoke a comfortable warm feeling. Methods of warming the skin include applying a hot towel, steam, infrared light, etc. to the skin. Incorporating a skin warming unit into a personal care device generally improves the sensory experience of the user during the execution of the personal care routine.

[0003] One such personal care device that employs a skin warming unit is an electric shaver. Electric shavers including mechanical elements to be heated are known, and these mechanical elements can provide warmth to the skin by heat transfer during shaving. The warmth creates a pleasant tactile sensation, thereby improving the user experience.

[0004] Another method of heating the skin is the use of deep dermal heating using radio frequency (RF) energy. The use of RF energy is different from mechanical elements that utilize heat transfer for heating. In RF heating applications, two electrodes are applied to the skin, each applying oppositely charged RF energy to the skin. This creates an electric field in the skin between the two electrodes. RF energy can penetrate deeper into the skin than heat transfer caused by heated mechanical elements, and thus can heat a relatively large area of the skin. Heating can be performed throughout the depth of penetration without relying on the thermal conductivity of both the heat application means and the skin as required by the use of heated mechanical elements.

[0005] Skin heating using RF was first used for skin care applications and tissue resection. For example, tumors within organs are resected by applying RF energy to heat the tumor. This technology was suitable for these applications because RF energy can penetrate deeply into skin tissue and because the control of RF energy is easy.

[0006] In general, RF energy supply parameters, such as electrical and physical characteristics, for example the geometry of the contact electrodes, can be adjusted according to a specific application. Typically, large RF electrodes that receive a low RF voltage are used for skin care applications, and small RF electrodes that receive a high RF voltage are used for surgical applications.

[0007] For example, for superficial RF heating applications used in home skin care devices, the use of bipolar RF energy is included, where two contact electrodes are in fairly close proximity to each other and the flow of current is localized in an area with a small current flow. In contrast, in clinical RF heating applications, a technique called monopolar RF is used, in which one of the contact electrodes is placed far from the other electrode so that current flows through the human body.

[0008] Another RF skin heating technique used in clinical applications is to apply RF energy to the skin using a plurality of, for example, three or more electrodes, and to phase shift or steer the RF energy applied to each electrode. For example, U.S. Patent No. 5,383,917 discloses a multiphase RF resection technique that employs a two-dimensional or three-dimensional electrode array that generates a plurality of current paths on the surface of the resection area and produces a uniform lesion having a size determined by the span of the electrode array. U.S. Patent Application Publication No. 2013 / 0231611 discloses an electrosurgical method and device provided for applying phase-controlled RF energy to a treatment site, comprising a multi-electrode electrosurgical probe electrically coupled to a plurality of RF generators. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] One of the challenges of using bipolar RF energy for heating skin tissue is controlling the uniformity of heating within the tissue volume. When applying RF heating to the skin using an electric shaver, uniform heating of the skin with minimal hot spots is desired for a comfortable thermal experience and to avoid discomfort. To minimize hot spots, it is common practice to use multiple large electrodes. However, this effect is limited by the fact that most of the heating occurs between the two closest electrodes. As described in U.S. Patent No. 5,383,917 and U.S. Patent Application Publication No. 2013 / 0231611, by phase shifting or steering RF energy between multiple electrodes, the RF field can be better dispersed within the tissue, resulting in more uniform tissue heating. However, these solutions use expensive and bulky RF phase steering devices that are required to generate a multi-phase RF signal. Electric shavers have limited space, and it is generally not practical to use such relatively large phase steering devices within them. It has also been observed that the thermal effects of phase shift or steering solutions can be sensitive to the accuracy of the phase difference between RF signals.

[0010] Accordingly, there is a need for improved systems and methods for using an electric shaver for improved uniform heating of the skin using RF.

Means for Solving the Problem

[0011] According to a first specific aspect, a skin contact area for contacting a user's skin during use of an electric shaver, and at least two hair cutting units disposed within the skin contact area, each hair cutting unit having an external cutting member having a plurality of hair entry openings, and an internal cutting member covered by the external cutting member and movable relative to the external cutting member, N electrodes disposed within the skin contact area so as to contact the skin during use, where N is at least 3, the N electrodes, a fundamental frequency fRF and a fundamental period T RF = 1 / fRF A high-frequency (RF) generator configured to generate RF energy having RF , and an RF energy modulator configured to convert the RF energy generated by the RF generator into N periodically amplitude-modulated RF energy signals and to provide each of the N periodically amplitude-modulated RF energy signals to a corresponding one of N electrodes. When viewed in a direction perpendicular to the skin contact area, the outer cutting member of each hair cutting unit has a geometric center point, a first pitch distance that is the distance between the geometric center points of a pair of hair cutting units, and a first minimum pitch distance that is the minimum value of the first pitch distances of all pairs of hair cutting units. When viewed in a direction perpendicular to the skin contact area, each of the N electrodes has a geometric center point, a second pitch distance that is the distance between the geometric center points of a pair of the N electrodes, and a second minimum pitch distance that is the minimum value of the second pitch distances of all pairs of the N electrodes. The ratio between the second minimum pitch distance and the first minimum pitch distance is at least 0.8. The basic period T of the N periodically amplitude-modulated RF energy signals MOD is the basic period T RF is greater than T, and the nth of the N periodically amplitude-modulated RF energy signals has a phase difference of T MOD *(n - 1) / N with respect to the first of the N periodically amplitude-modulated RF energy signals, where 2 ≤ n ≤ N. An electric shaver is provided.

[0012] In some examples, the ratio between T MOD and T RF is at least 10, preferably at least 25.

[0013] In some examples, each of the N periodically amplitude-modulated RF energy signals has the same basic RF energy signal during the basic period T MOD of each respective periodically amplitude-modulated RF energy signal.

[0014] In some examples, the basic RF energy signal comprises a first state and a second state. The first state has a basic frequency f RFand a first RF energy signal having a first RF voltage, and the second state is constituted by a zero signal.

[0015] In some examples, the basic RF energy signal further includes a third state constituted by a second RF energy signal obtained by inverting the first RF energy signal.

[0016] In some examples, the first states of the N periodically amplitude-modulated RF energy signals do not occur simultaneously.

[0017] In some examples, the second states of the N periodically amplitude-modulated RF energy signals do not occur simultaneously.

[0018] In some examples, the N electrodes are arranged adjacent to the hair cutting unit.

[0019] In some examples, the electric shaver includes three electrodes and three hair cutting units arranged in a triangular configuration with respect to each other. The internal cutting member of each hair cutting unit is rotatable with respect to the external cutting member, and each of the three electrodes is arranged on a side portion of the skin contact area between two of the hair cutting units of one pair of the hair cutting units.

[0020] In some examples, the electric shaver includes N hair cutting units. The external cutting member of each of the N hair cutting units is annular, and the N electrodes each include N covering elements respectively arranged at central positions with respect to the external cutting members of each of the N hair cutting units.

[0021] In some examples, the electric shaver includes N hair cutting units, and each of the N electrodes is constituted by at least the skin contact portion of the external cutting member of each of the N hair cutting units.

[0022] In some examples, the electric shaver includes three hair cutting units, and the internal cutting member of each hair cutting unit is configured to linearly reciprocate parallel to the longitudinal direction with respect to the external cutting member, and the external cutting member of each hair cutting unit has a longitudinal extension parallel to the longitudinal direction.

[0023] In some examples, the electric shaver includes four electrodes and four hair cutting units, and the internal cutting member of each hair cutting unit is configured to linearly reciprocate parallel to the longitudinal direction with respect to the external cutting member, and the external cutting member of each hair cutting unit has a longitudinal extension parallel to the longitudinal direction. Each of the four electrodes is constituted by at least the skin contact portion of each of the external cutting members of the four hair cutting units, and the basic RF energy signal continuously includes a first state, a second state, a third state, and a fourth state. The first state is a first RF energy signal having a basic frequency f RF and a first RF voltage, and the second state is a basic frequency f RF and a second RF energy signal having a second RF voltage lower than the first RF voltage. The third state is constituted by a third RF energy signal obtained by inverting the second RF energy signal, and the fourth state is constituted by a fourth RF energy signal obtained by inverting the first RF energy signal.

[0024] In some examples, the ratio between the second RF voltage and the first RF voltage is between 0.25 and 0.5, preferably between 0.3 and 0.35.

[0025] In some examples, the RF energy modulator includes N switch units, and each of the N switch units is configured to apply each of the N periodic amplitude modulated RF energy signals to each of the N electrodes.

[0026] These and other aspects will become apparent from and will be described with reference to the embodiments described below.

[0027] Here, exemplary embodiments will be described merely as examples with reference to the following drawings.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

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Mode for Carrying Out the Invention

[0029] Examples according to the present disclosure provide an electric shaver having a skin contact area for contacting a user's skin during use of the electric shaver. At least two hair cutting units are arranged in the skin contact area, and N electrodes for transmitting RF energy are also arranged in the skin contact area so as to contact the skin during use, where N is at least 3. When viewed in a direction perpendicular to the skin contact area, the outer cutting member of each hair cutting unit has a geometric center point and a first pitch distance that is the distance between the geometric center points of a pair of hair cutting units. The first minimum pitch distance is the minimum value of the first pitch distances of all pairs of hair cutting units. Further, when viewed in a direction perpendicular to the skin contact area, each of the N electrodes has a geometric center point and a second pitch distance that is the distance between the geometric center points of a pair of the N electrodes. The second minimum pitch distance is the minimum value of the second pitch distances of all pairs of the N electrodes. The ratio between the second minimum pitch distance and the first minimum pitch distance is at least 0.8. By arranging the hair cutting units and the N electrodes in this way, the N electrodes will be spread over a substantial area of the skin contact area. Thus, when the skin contact area is applied to the user's skin for use, RF energy flows between the N electrodes, causing most of the skin in contact with the skin contact area to be warmed, leading to an improvement in the uniform warming of the skin.

[0030] An electric shaver according to an example of the present disclosure has a fundamental frequency f RF and a fundamental period T RF = 1 / f RF and is configured to generate RF energy, an RF generator, and an RF energy modulator configured to convert the RF energy generated by the RF generator into N periodically amplitude-modulated RF energy signals and to provide each of the N periodically amplitude-modulated RF energy signals to each of the N electrodes. The fundamental period T MOD of the N periodically amplitude-modulated RF energy signals is the fundamental period T RFgreater than, and the nth of the N periodically amplitude - modulated RF energy signals has a phase difference of T * (n - 1) / N with respect to the first of the N periodically amplitude - modulated RF energy signals, where 2 ≤ n ≤ N. By modulating the RF energy into N periodically amplitude - modulated RF energy signals that are phase - shifted with respect to each other, the use of expensive and bulky RF phase - steering devices, which are used in prior - art solutions, is avoided. As will be explained in more detail below, with the N phase - shifted periodically amplitude - modulated RF energy signals, the RF energy will successively be generated in various amounts between various ones of the N electrodes over various periods, which further leads to a more uniform heating of the skin in contact with the skin - contact area and enables the avoidance of the accumulation of hot spots. MOD *(n - 1) / N with respect to the first of the N periodically amplitude - modulated RF energy signals, where 2 ≤ n ≤ N. By modulating the RF energy into N periodically amplitude - modulated RF energy signals that are phase - shifted with respect to each other, the use of expensive and bulky RF phase - steering devices, which are used in prior - art solutions, is avoided. As will be explained in more detail below, with the N phase - shifted periodically amplitude - modulated RF energy signals, the RF energy will successively be generated in various amounts between various ones of the N electrodes over various periods, which further leads to a more uniform heating of the skin in contact with the skin - contact area and enables the avoidance of the accumulation of hot spots.

[0031] FIG. 1 is a diagram of an exemplary electric shaver 100 to which the technology described herein can be applied. In FIG. 1, the electric shaver 100 is in the form of a rotary shaver, but it will be understood that the technology described herein can be applied to any type of electric shaver 100, such as a foil shaver, as described below. The electric shaver 100 includes a body 110 that is to be gripped in a user's hand and a cutting head 140 in the form of a skin - contact area that includes a plurality of hair - cutting units 150, 160, 170 for cutting / shaving hair. The cutting head of the electric shaver includes a skin - contact area that is arranged to contact a user's skin during use of the shaver. In the example shown in FIG. 1, the skin - contact area includes a first hair - cutting unit 150, a second hair - cutting unit 160, and a third hair - cutting unit 170. However, in other examples, the skin - contact area may include two hair - contact units or may include four or more hair - cutting units.

[0032] The first hair cutting unit 150 includes a first external cutting member 152, the second hair cutting unit 160 includes a second external cutting member 162, and the third hair cutting unit 170 includes a third external cutting member 172. The first, second, and third hair cutting units 150, 160, 170 are mounted on the cutting head 140 at appropriate mounting positions. In this illustrated embodiment, the hair cutting units 150, 160, 170 have a triangular arrangement, but it will be understood that the hair cutting units can be arranged in another arrangement. The external cutting members 152, 162, 172 of the hair cutting units each include a plurality of hair entry openings, which are arranged to contact the skin during use. The corresponding skin contact areas of the first, second, and third hair external cutting members 152, 162, 172 are annular (i.e., ring-shaped). Each of the first, second, and third hair cutting units 150, 160, 170 further includes a corresponding internal cutting member, such as a blade, which is rotatable relative to the external cutting members 152, 162, 172, respectively. The external cutting members 152, 162, 172 are arranged to cover their respective internal cutting members. The hair entry openings include holes and / or thin plates. During use, the hair in this case protrudes from the hair entry openings, and the rotation of the blade relative to the external cutting members 152, 162, 172 cuts the hair protruding through the openings. The electric shaver 100 further includes a motor 130 configured to move the internal cutting member relative to the corresponding external cutting members 152, 162, 172 so that a cutting action occurs.

[0033] The first hair cutting unit 150, the second hair cutting unit 160, and the third hair cutting unit 170 each further include a first covering element 154, a second covering element 164, and a third covering element 174. The first, second, and third covering elements 154, 164, 174 are respectively disposed on the first, second, and third external cutting members 152, 162, 172. The first, second, and third covering elements 154, 164, 174 each include a skin contact area arranged to contact the skin during use. Each of the first, second, and third covering elements 154, 164, 174 is further centrally disposed with respect to the corresponding annular skin contact areas of the first, second, and third external cutting members 152, 162, 172, such that the skin contact areas of the external cutting members 152, 162, 172 surround the corresponding covering elements 154, 164, 174. As shown in FIG. 1, each covering element 154, 164, 174 is disc-shaped, and for this reason, is a covering element also referred to as a cap, shaving cap, or deco cap. Those skilled in the art will envision other suitable shapes and / or forms of the covering member.

[0034] As will be described in more detail below, the electric shaver 100 further includes N electrodes (not shown in FIG. 1) disposed within the skin contact area so as to contact the skin during use. In an example according to the present disclosure, the N electrodes include at least three electrodes. The N electrodes are configured to transmit RF energy such that RF energy is applied to the skin in contact with the skin contact area of the electric shaver during use to warm the skin. Accordingly, the electric shaver 100 further includes an RF energy generator unit 120, which is configured to generate RF energy that is applied to each of the N electrodes in the form of N periodically amplitude-modulated RF energy signals, as will be described in more detail below.

[0035] Figure 2 shows the skin contact area 200 of the electric shaver. In this case, the skin contact area is included in the cutting head of the electric shaver. Figure 2 shows the skin contact area 200 viewed in a direction perpendicular to the surface of the skin contact area. The skin contact area includes a first hair cutting unit 150, a second hair cutting unit 160, and a third hair cutting unit 170, which operate in a corresponding manner as described above with respect to Figure 1.

[0036] The skin contact area 200 further includes a first electrode 180a, a second electrode 180b, and a third electrode 180c, which together constitute N electrodes 180a - c. As shown in Figure 2, the N electrodes 180a - c are arranged adjacent to the hair cutting units 150, 160, 170. The N electrodes 180a - c and the three hair cutting units 150, 160, 170 are arranged in a triangular configuration in this case, and at this time, each of the N electrodes 180a - c is arranged in the lateral portion of the skin contact area 200 between each pair of the hair cutting units 150, 160, 170. For example, the first electrode 180a is arranged in the lateral portion of the skin contact area 200 between the pair of hair cutting units consisting of the first hair cutting unit 150 and the third hair cutting unit 170.

[0037] In use, the electrodes 180a - c are configured to apply N periodic amplitude - modulated RF energy signals to the user's skin to warm the skin. In this case, the electrodes 180a - c are formed of a conductive material that can transmit the N periodic amplitude - modulated RF energy signals and is biocompatible with the skin. For example, the electrodes 180a - c are formed of a metal such as stainless steel, silver, or silver chloride. In this case, the electrodes 180a - c are additionally electrically isolated from each other so that a "circuit" is formed between these electrodes when the electrodes are in contact with the user's skin.

[0038] As shown in FIG. 2, each of the hair cutting units 150, 160, 170 includes corresponding geometric center points 156, 166, 176. Each of the N electrodes 180a - c also includes respective geometric center points 182a - c. The first pitch distance 202 is the distance between the pairs of geometric center points 156, 166, 176 of the hair cutting units 150, 160, 170. As shown in FIG. 2, each of the hair cutting units 150, 160, 170 is arranged such that the first pitch distance 202 between each pair of the hair cutting units 150, 160, 170 is substantially the same. However, in other examples, the first pitch distances 202 between pairs of the hair cutting units 150, 160, 170 may be different. Similarly, the second pitch distance 204 is the distance between the pairs of geometric center points 182a - c of the N electrodes 180a - c. As shown in FIG. 2, each of the N electrodes 180a - c is arranged such that the second pitch distance 204 between each pair of the N electrodes 180a - c is substantially the same. However, in other examples, the distances between pairs of the hair cutting units 150, 160, 170 may be different. Regardless of the arrangement, the first minimum pitch distance 202 is the minimum value of the first pitch distances of all pairs of the hair cutting units 150, 160, 170, and the second minimum pitch distance 204 is the minimum value of the second pitch distances of all pairs of the N electrodes 180a - c. To provide skin warming over a majority of the skin contact area 200, the ratio between the second minimum pitch distance 204 and the first minimum pitch distance 202 is at least 0.8. At this ratio, the N electrodes 180a - c are evenly distributed along with the hair cutting units 150, 160, 170 over a majority of the skin contact area 200, which in that case leads to a more uniform warming of the skin in contact with the skin contact area 200 during use. For example, due to the arrangement of the N electrodes 180a - c, RF energy flows between each of the N electrodes 180a - c, and as a result, most of the skin in contact with the skin contact area 200 will be warmed by the application of the RF energy.

[0039] As described above, the electric shaver according to an example of the present disclosure includes an RF energy generator unit configured to provide each of the N electrodes 180a to 180c with a corresponding one of the N periodically amplitude-modulated RF energy signals. Each of the N periodically amplitude-modulated RF energy signals is phase-shifted from each other over N phases, and as a result, RF energy flows between different ones of the N electrodes in various amounts over the N phases, which leads to an increase in the uniform heating of the skin in contact with the skin contact area of the electric shaver according to an example of the present disclosure.

[0040] FIG. 3 shows an example of a circuit configuration 300. The circuit configuration 300 includes an RF energy generator unit 120 included in the electric shaver according to an example of the present disclosure. The RF energy generator unit 120 includes an RF energy generator unit 120 configured to generate RF energy having a fundamental frequency f RF and a fundamental period T RF . The RF energy generator unit 120 further includes an RF energy modulator 310 configured to convert the RF energy generated by the RF generator into N periodically amplitude-modulated RF energy signals and to provide each of the N periodically amplitude-modulated RF energy signals to each of the N electrodes. As described in more detail below, the RF energy modulator 310 includes a converter unit 312 configured to receive RF energy from the RF generator 320 and output at least one RF voltage signal V RF . The RF voltage signal V RF is output to a switch module 314, and the switch module 314 outputs the N periodically amplitude-modulated RF energy signals to the N electrodes 180. As described in more detail below, the RF energy modulator 310 is configured to convert the RF energy generated by the RF generator 320 into N periodically amplitude-modulated RF energy signals under the control of a microcontroller unit (MCU) 330.

[0041] For example, the MCU 330 controls the RF voltage signal V output from the converter unit 312RF controls the RF energy modulator 310 so that it is modulated according to the RF modulation waveform by the switch module 314. The RF modulation waveform has a basic RF energy signal. The basic period T of the RF modulation waveform MOD is the RF period T of the RF energy output from the RF energy generator 320 RF is greater than. In some examples, the period T of the RF modulation waveform MOD is the RF period T RF is substantially greater than, for example at least 10 times, preferably at least 25 times greater. By modulating the RF energy output from the RF energy generator 320 with an RF modulation waveform having a period greater than the period of the RF energy, the phases of the N periodic amplitude-modulated RF energy signals are shifted relative to each other without using expensive RF phase steering components. Instead, by appropriate control of the switch module 314, N periodic amplitude-modulated RF energy signals are applied to the N electrodes 180, where each of the N periodic amplitude-modulated RF energy signals is phase-shifted from the others. For example, the nth of the N periodic amplitude-modulated RF energy signals is phase-shifted from the first of the N periodic amplitude-modulated RF energy signals by a difference of T MOD *(n - 1) / N, where 2 ≦ n ≦ N. Thus, when N = 3, the N periodic amplitude-modulated RF energy signals are shifted from each other over three phases for application to the electrodes 180.

[0042] Figures 4a to 4c show examples of RF signals applied to the N electrodes. In the examples of Figures 4a to 4c shown, N = 3.

[0043] Figure 4a shows three modulation signals M1, M2, M3 for modulating the RF voltage signal V RF The first modulation signal M1 is for modulating the RF voltage signal V applied to the first electrode RF and the second modulation signal M2 is for modulating the RF voltage signal V applied to the second electrode RFfor modulating, and the third modulation signal M3 is an RF voltage signal V applied to the third electrode RF for modulating. The three modulation signals M1, M2, and M3 have the same RF modulation waveform. In the example of FIG. 4a shown, the Rf modulation waveform has a two-state modulation waveform, and thus, the modulation signals M1 to M3 are two-state modulation signals. The two-state modulation signals M1 to M3 have a first state of +1 and a second state of 0.

[0044] Each of the N modulation signals M1, M2, and M3 has a modulation period T MOD and this period is divided into three phases Φ 1~3 Each of the N modulation signals M1, M2, and M3 is phase-shifted from each other over the three phases Φ 1~3 As shown, during the first phase Q 1 the first modulation signal M1 is in the second state 0, during the second phase Q 2 the first modulation signal M1 is in the first state +1, and during the third phase Q 3 the first modulation signal M1 is in the second state 0. The second modulation signal M2 is in this case phase-shifted from the first modulation signal M1 by one phase unit, and the third modulation signal is phase-shifted from the first modulation signal M1 by two phase units. In this case the modulation signals are such that the nth one of the N modulation signals M1 to M3 signals has a phase difference of T MOD *(n - 1) / N with respect to the first one of the N modulation signals M1 to M3, where 2 ≤ n ≤ N.

[0045] Figure 4b shows N periodically amplitude-modulated RF voltage signals S1 to S3 applied to N electrodes, which may in some instances be referred to as N periodically amplitude-modulated RF energy signals S1 to S3. The first periodically amplitude-modulated RF energy signal S1 is applied to the first electrode, the second periodically amplitude-modulated RF energy signal S2 is applied to the second electrode, and the third periodically amplitude-modulated RF energy signal S3 is applied to the third electrode. The first, second, and third periodically amplitude-modulated RF energy signals S1 to S3 are formed by modulating the RF voltage signal according to the first, second, and third modulation signals M1 to M3 respectively. In this case, in a similar manner to the N modulation signals M1 to M3, the N periodically amplitude-modulated RF energy signals are also phase-shifted from each other according to the condition that the nth one of the N periodically amplitude-modulated RF energy signals S1 to S3 has a phase difference of T MOD *(n - 1) / N with respect to the first one of the N periodically amplitude-modulated RF energy signals S1 to S3, where 2 ≤ n ≤ N. In some instances, the switching modulation of the RF voltage signal V RF is performed by appropriate control of the switch module 314 shown in FIG. 3, as described in more detail below.

[0046] As shown in FIG. 4b, the RF voltage signal constitutes a modulated RF voltage signal, for example, a pulse-width modulation (PWM) signal having a fundamental RF frequency f RF . In this case, referring to FIGS. 4a and 4b, during the phase Φ 1~3 when the modulation signals M1 to M3 are in the first state +1, the N periodically amplitude-modulated RF energy signals S1 to S3 constitute a PWM RF voltage signal, and during the phase Φ 1~3 when the modulation signals M1 to M3 are in the first state +1, the N periodically amplitude-modulated RF energy signals S1 to S3 constitute a zero voltage signal. For example, referring to FIG. 4a, at the first phase Φ 1 , the first modulation signal M1 and the second modulation signal M2 are in the second state 0, and the second modulation signal M2 is in the first state +1. In this case, referring to FIG. 4b, at the first phase Φ 1In this case, the first periodically amplitude-modulated RF energy signal S1 and the third periodically amplitude-modulated RF energy signal S3 are at the zero voltage level, and the second periodically amplitude-modulated RF energy signal S2 is modulated according to the PWM RF voltage signal. The second and third phases Φ 2~3 Among them, the N periodically amplitude-modulated RF energy signals S1 to S3 are thus output in the same manner according to whether the corresponding modulation signals M1 to M3 are in the first state +1 or the second state 0. In some examples, the modulation signals M1 to M3 thus represent the envelopes of the N periodically amplitude-modulated RF energy signals S1 to S3.

[0047] As shown in FIG. 4b, in some examples, the first states of the N periodically amplitude-modulated RF energy signals S1 to S2 do not occur simultaneously. For example, the fact that the N periodically amplitude-modulated RF energy signals S1 to S3 consist of an RF voltage signal V RF may in some examples be referred to as the "first state" of the N periodically amplitude-modulated RF energy signals S1 to S3, but this state does not occur simultaneously in a plurality of the N periodically amplitude-modulated RF energy signals S1 to S3 within any one phase over the three phases Φ 1~3 FIG. 4c shows an RF electrode pair signal indicating the flow of RF current between the electrodes E1 to E3. In some examples, the RF electrode pair signal indicates the flow of RF energy between the electrodes E1 to E3. For example, the first RF electrode pair signal E1-E2 indicates the flow of RF energy between the first electrode E1 and the second electrode E2, the second RF electrode pair signal E2-E3 indicates the flow of RF energy between the second electrode E2 and the third electrode E3, and the third RF electrode pair signal E3-E1 indicates the flow of RF energy between the third electrode E3 and the first electrode E1.

[0048] RF energy flows between different ones of the electrodes E1 to E3 according to the N periodically amplitude-modulated RF energy signals S1 to S3 applied to the electrodes E1 to E3 during any one phase over the three phases Φ

[0049] For example, during the first phase Φ 1~3 Among them, the N periodically amplitude-modulated RF energy signals S1 to S3 are thus output in the same manner according to whether the corresponding modulation signals M1 to M3 are in the first state +1 or the second state 0. In some examples, the modulation signals M1 to M3 thus represent the envelopes of the N periodically amplitude-modulated RF energy signals S1 to S3.1 During this period, RF energy signals exist between the first electrode E1 and the second electrode E2, and between the second electrode E2 and the third electrode E3, which are respectively represented by the first RF electrode pair signal E1-E2 and the second RF electrode pair signal E2-E3. However, for the first phase Φ 1 During this period, there is no RF energy flow between the third electrode E3 and the first electrode E1, which is represented by the zero signal level of the third RF electrode pair signal E3-E1. This is due to the N periodic amplitude-modulated RF energy signals S1-S3 applied to the electrodes E1-E3 during the first phase Φ 1 During this period, there is no RF energy flow between the third electrode E3 and the first electrode E1, which is represented by the zero signal level of the third RF electrode pair signal E3-E1. This is due to the N periodic amplitude-modulated RF energy signals S1-S3 applied to the electrodes E1-E3 during the first phase Φ 1 At the first phase Φ, the modulated RF voltage signal is applied to the second electrode E2, which is indicated by the second periodic amplitude-modulated RF energy signal S2. However, zero voltage signals are applied to the first electrode E1 and the third electrode E3, which are indicated by the first periodic amplitude-modulated RF energy signal S1 and the third periodic amplitude-modulated RF energy signal S3. In this case, referring to Figure 4c again, during the first phase Φ 1 During this period, there is a voltage difference between the second electrode E2 and both the first electrode E1 and the third electrode E3. Therefore, an RF energy flow occurs between these electrodes, which is indicated by the first RF electrode pair signal E1-E2 and the second RF electrode pair signal E2-E3. In some examples, this flow of RF energy corresponds to the magnitude of the RF voltage signal V RF During this period, there is a voltage difference between the second electrode E2 and both the first electrode E1 and the third electrode E3. Therefore, an RF energy flow occurs between these electrodes, which is indicated by the first RF electrode pair signal E1-E2 and the second RF electrode pair signal E2-E3. In some examples, this flow of RF energy corresponds to the magnitude of the RF voltage signal V 1 During this period, there is no voltage difference between the first electrode E1 and the third electrode E3, and the voltages applied to both electrodes are zero. Therefore, during the first phase Φ 1 During this period, there is no RF energy flow between these electrodes, which is shown in the third RF electrode pair signal E3-E1.

[0050] The second and third phases Φ 2~3During this time, the N periodic amplitude-modulated RF energy signals S1 to S3 change, and accordingly, the RF electrode pair signals E1 - E2, E2 - E3, and E3 - E1 also change accordingly. Thus, over the first, second, and third phases Φ 1~3 an RF energy flow occurs between different ones of the electrodes E1 to E3, which results in a more uniform heating of the skin in contact with the three electrodes E1 to E3.

[0051] Figures 4a to 4c show how an RF voltage signal can be amplitude-modulated according to a two-state modulation waveform to apply N phase-shifted periodic amplitude-modulated RF energy signals to N electrodes. However, in other examples, alternative modulation waveforms can be used to modulate the amplitude of the RF voltage signal or even the amplitude of a bipolar RF voltage signal.

[0052] Figures 5a to 5c show examples of RF signals applied to N electrodes. In the examples of Figures 5a to 5c shown, N = 3.

[0053] Figure 5a shows three modulation signals M1, M2, M3 for modulating the bipolar RF voltage signals V RF+ , V RF- . The modulation signals M1 to 3 also here follow the condition that the nth one of the N modulation signals M1 to M3 signals has a phase difference of T MOD *(n - 1) / N with respect to the first one of the N modulation signals M1 to M3, and are phase-shifted from each other over three phases Φ MOD during the modulation period T 1~3 . In the example of Figure 5a shown, the modulation signals M1 to M3 each have an asymmetric three-state modulation waveform. The asymmetric three-state modulation waveform has a first state +1, a second state 0, and a third state -1.

[0054] In a manner similar to that described above with respect to FIGS. 4a - 4c, N modulation signals M1 - M3 that constitute the asymmetric three - state modulation waveform signal of FIG. 5a are applied to an RF voltage signal, and N periodic amplitude - modulated RF energy signals S1 - S3 are generated. However, the additional third state - 1 of the asymmetric three - state modulation waveform means that the N periodic amplitude - modulated RF energy signals S1 - S3 can adopt an additional signal state. In such an example, the third state - 1 corresponds to the N periodic amplitude - modulated RF energy signals S1 - S3 adopting a negative RF voltage signal V RF+ which is the inversion of RF- a positive RF voltage signal V. The second state 0 also corresponds here to a zero - voltage signal. In a plurality of examples, according to the present disclosure, references to "positive voltage signal" and "negative voltage signal" may refer not to the polarity of the voltage signal, but rather to one being the inversion of the other.

[0055] FIG. 5b shows the first, second, and third periodic amplitude - modulated RF voltage signals S1 - S3, which in some examples may be referred to as the N periodic amplitude - modulated RF energy signals S1 - S3. According to the modulation signals M1 - M3 of FIG. 5a, the N periodic amplitude - modulated RF energy signals S1 - S3 are respectively applied to the first, second, and third electrodes E1 - E3. The first, second, and third periodic amplitude - modulated RF energy signals S1 - S3 also, in this case, are phase - shifted from each other over three phases Φ MOD over a modulation period T 1~3 in a manner corresponding to the modulation signals M1 - M3 of FIG. 5a.

[0056] As described above, the first modulation state +1 corresponds to a positive RF voltage signal V RF+ and the third modulation state - 1 corresponds to a negative RF voltage V RF- . These two RF voltage signals have the same basic RF frequency f RFIt may be provided, or may be the inverted versions of each other. The second state 0 corresponds to a 0 voltage signal. In this case, the periodic amplitude-modulated RF energy signals S1 to S3 are positive RF voltage signals V RF+ , negative RF voltage V RF- , or any value of a 0 voltage signal.

[0057] For example, referring to FIG. 5a, during the first phase Φ 1 , the first modulation signal M1 is in the third state -1, the second modulation signal M2 is in the first state +1, and the third modulation signal M3 is in the second state 0. Referring to FIG. 5b in response to this, during the first phase Φ 1 , the first amplitude-modulated RF energy signal S1 has a negative RF voltage V RF- , the second amplitude-modulated RF energy signal S2 has a positive RF voltage V RF+ , and the third amplitude-modulated RF energy signal S2 has a 0 voltage signal. During the second and third phases Φ 2~3 , the N periodic amplitude-modulated RF energy signals S1 to S3 are thus output similarly according to whether the respective modulation signals M1 to M3 are in the first state +1, the second state 0, or the third state -1. In some examples, the modulation signals M1 to M3 thus represent the envelopes of the N periodic amplitude-modulated RF energy signals S1 to S3.

[0058] As shown in FIG. 5b, in some examples, the second states of the N periodic amplitude-modulated RF energy signals S1 to S2 do not occur simultaneously. For example, the fact that the N periodic amplitude-modulated RF energy signals S1 to S3 consist of 0 voltage signals may, in some examples, be referred to as the "first state" of the N periodic amplitude-modulated RF energy signals S1 to S3, but this state does not occur simultaneously in a plurality of the N periodic amplitude-modulated RF energy signals S1 to S3 within any one phase over the three phases Φ 1~3 .

[0059] FIG. 5c shows the RF electrode pair signals E1-E2, E2-E3, E3-E1, and shows the flow of RF energy between electrodes E1 to E3 in the same manner as FIG. 4c described above. In the same manner as described above, RF energy flows between different ones of electrodes E1 to E3 in different amounts over three phases Φ 1~3 and flows according to the N periodic amplitude modulated RF energy signals S1 to S3 applied to electrodes E1 to E3 between any one of the phases. For example, during the first phase Φ 1 , a larger amount of RF energy flows between the first electrode E1 and the second electrode E2 as compared to the flow of RF energy between the second electrode E2 and the third electrode E3 and between the third electrode E3 and the first electrode E1. This is shown in FIG. 5c, which means that the magnitude of the first RF electrode pair signal E1-E2 is larger than those of the second and third RF electrode pair signals E2-E3, E3-E1. The reason is that during the first phase Φ 1 , a negative RF voltage signal V RF- is applied to the first electrode E1, a positive RF voltage signal V RF+ is applied to the second electrode E2, while a zero voltage signal is applied to the third electrode E3. In this case, during the first phase Φ 1 , there is a voltage difference of 2V RF between the first electrode E1 and the second electrode E2. On the other hand, there is a voltage difference of V RF between the second electrode E2 and the third electrode E3 and between the third electrode E3 and the first electrode E1. Therefore, during the first phase Φ 1 , the flow of RF energy between the first electrode E1 and the second electrode E2 is twice that between the second electrode E2 and the third electrode E3 and between the third electrode E3 and the first electrode E1.

[0060] During the second and third phases Φ 2~3 , the N periodic amplitude modulated RF energy signals S1 to S3 change, and thus the RF electrode pair signals E1-E2, E2-E3, E3-E1 also change accordingly. Thus, the first, second, and third phases Φ 1~3Over time, different amounts of RF energy flow between different ones of electrodes E1 to E3, which results in more uniform heating of the skin in contact with the three electrodes E1 to E3.

[0061] Figures 6a through 6c show examples of RF signals applied to N electrodes. In the examples of Figures 6a through 6c shown, N = 3.

[0062] Figure 6a shows three modulation signals M1, M2, M3 for modulating bipolar RF voltage signals V RF+ , V RF- in a manner similar to the modulation signal described in Figure 5a. The modulation signals M1 to 3 also here, the nth one of the N modulation signals M1 to M3 signals has a phase difference of T MOD *(n - 1) / N with respect to the first one of the N modulation signals M1 to M3, and over the modulation period T MOD are phase shifted from each other over three phases Φ 1~3 where 2 ≤ n ≤ N.

[0063] In the example of Figure 6a, the modulation signals M1 to M3 each have a symmetric three - state modulation waveform. The symmetric three - state modulation waveform has a first state +1, a second state 0, and a third state -1, which, as described above with respect to Figures 5a to 5c, also here, can correspond to the positive RF voltage signal V RF+ , the 0 - voltage signal, and the negative RF voltage V RF- . In this case, in a manner similar to that described above with respect to Figures 5a to 5c, the three modulation signals M1, M2, M3 are used to modulate the bipolar RF voltage signal so as to generate three periodically amplitude - modulated RF signals S1 to S3 applied to the three corresponding electrodes E1 to E3. The periodically amplitude - modulated RF signals S1 to S3 that vary over the three phases Φ 1~3 in this case cause a change in the flow of RF energy between the three electrodes E1 to E3, as shown by the RF electrode pair signals E1 - E2, E2 - E3, E3 - E1 in Figure 6c. Thus, the first, second, and third phases Φ 1~3Across different ones of the electrodes E1 to E3, a flow of RF energy occurs, which results in more uniform heating of the skin in contact with the three electrodes E1 to E3.

[0064] Figures 4a to 4c, Figures 5a to 5c, and Figures 6a to 6c show how an RF voltage signal having a basic RF frequency f RF and an RF period T RF is amplitude - modulated with a modulation waveform to generate N periodically amplitude - modulated RF signals having a modulation period substantially smaller than the RF period T RF . Thus, these N periodically amplitude - modulated RF signals can be phase - shifted from each other without using a bulky and expensive RF phase - steering device. Figures 4a to 4c, Figures 5a to 5c, and Figures 6a to 6c show how the above - mentioned RF voltage signal can be modulated according to 2 - state, asymmetric 3 - state, and symmetric 3 - state modulation waveforms. However, those skilled in the art will understand that other suitable modulation waveforms can be used to perform amplitude modulation of the RF voltage signal according to the examples of the present disclosure.

[0065] Figure 7 shows an example of a circuit configuration 700. The circuit configuration 700 includes elements common to the above - described circuit configuration 300, which are assigned corresponding reference numerals and operate in substantially the same manner as described above with respect to Figure 3.

[0066] The circuit configuration 700 includes an RF generator 320 configured to output an RF frequency signal f RF . In some examples, the frequency f of the RF frequency signal RF is in the range of 500 kHz to 10 MHz. The RF generator 320 includes an oscillator for generating the RF frequency signal f RF . The oscillator may be implemented with or without a counter or a frequency divider. The frequency generator 320 receives a PWM control signal PWM C from a microcontroller unit (MCU) 330 to control the frequency generator 320. For example, by varying the duty cycle of the PWM control signal PWM, the RF frequency signal fRF The frequency may vary. In some examples, the duty cycle of the PWM control signal PWM C is from 0% to 100% and has a period from 1 ms to 10 ms. In other examples, a part of the MCU330 is formed by the functionality of the frequency generator 320, in which case the MCU330 directly outputs the RF frequency signal f RF .

[0067] The circuit configuration 700 further includes an RF modulator 310, and the RF modulator 310 further includes a converter unit 312 and a switch module 314. The converter unit 312 is configured to receive the RF frequency signal f RF and convert the RF frequency signal f RF into bipolar RF voltage signals V RF+ , V RF- . The converter unit 312 includes a positive converter unit 710 and a negative converter unit 720. In some examples, the positive converter unit 710 and the negative converter unit 720 each include a switch-mode power supply such as a boost converter. In this case, the battery voltage V BATT may be additionally supplied to the positive converter unit 710 and the negative converter unit 720 respectively. In this case, the positive converter unit 710 is configured to convert the RF frequency signal f RF into a positive RF voltage signal V RF+ , and the negative converter unit 720 is configured to convert the RF frequency signal f RF into a negative RF voltage signal V RF- . In the examples according to the present disclosure, the terms positive RF voltage signal V RF+ and negative RF voltage signal V RF- do not indicate the polarity of the signal, but may indicate that each signal is the inverse of the other. For example, the positive RF voltage signal V RF+ and the negative RF voltage signal V RF- each include a PWM RF voltage signal oscillating at the frequency RF frequency signal f RF , but one is phase-shifted by 180° from the other. In some examples, the positive RF voltage signal V RF+ and the negative RF voltage signal V RF-Each has a peak-to-peak voltage of 10V to 100V. In one example, the positive converter unit 710 and the negative converter unit 720 each include a switch-mode power supply, and the output of each of the positive converter unit 710 and the negative converter unit 720 is modulated by an RF frequency signal f RF to generate a PWM positive RF voltage signal V RF+ and a PWM negative RF voltage signal V RF- respectively.

[0068] The circuit configuration 700 further includes a switch module 314 including a plurality of switch units 730, 740, 750. Each of the plurality of switch units 730, 740, 750 includes a corresponding pair of switches. The first switch unit 730 includes a first switch 732 and a second switch 734. The second switch unit 740 includes a third switch 742 and a fourth switch 744. The third switch unit 750 includes a fifth switch 752 and a sixth switch 754.

[0069] The switch module 314 is configured to receive a positive RF voltage signal V RF+ and a negative RF voltage signal V RF- and output N periodic amplitude-modulated RF signals S1, S2, S3 to N electrodes 180a - c. In the example of FIG. 7 shown, N = 3.

[0070] In this case, the MCU 330 is configured to output a control signal En RF+ to control the switches 732 - 754 of the switch units 730, 740, 750 in order to modulate the amplitudes of the positive RF voltage signal V RF and the negative RF voltage signal V to generate N periodic amplitude-modulated RF signals S1 - S3. 1~6

[0071] As described above with respect to FIGS. 5a - 5c and FIGS. 6a - 6c, a plurality of phases Φ 1~3Over time, the N periodic amplitude - modulated RF signals S1 to S3 transition among three values according to the modulation waveforms used to generate the N periodic amplitude - modulated RF signals S1 to S3. In some examples, the three values are a positive RF voltage signal V RF+ and a zero - voltage signal and a negative RF voltage signal V RF- . In this case, the MCU330 configures the operation of the switches 732 to 754 of the switch units 730, 740, 750 such that the N periodic amplitude - modulated RF signals S1 to S3 are output to the electrodes 180a - c with one of the three values of the positive RF voltage signal V RF+ , the zero - voltage signal, and the negative RF voltage signal V RF- .

[0072] For example, referring briefly to FIG. 5b, during the first phase Φ 1 , the first amplitude - modulated RF energy signal S1 has a negative RF voltage V RF- , the second amplitude - modulated RF energy signal S2 has a positive RF voltage V RF+ , and the third amplitude - modulated RF energy signal S2 has a zero - voltage signal. In this case, referring again to FIG. 7, the MCU330 outputs a control signal En 1 to control the switches 732 to 754 of the switch units 730, 740, 750 in order to output N periodic amplitude - modulated RF signals S1 to S3 having values as outlined for the first phase Φ 1~6 of FIG. 5b.

[0073] For example, to output the first periodic amplitude - modulated RF signal S1 with the negative RF voltage signal V RF- , the MCU330 in this case outputs a first control signal En 1 to activate the first switch 732 to connect the first electrode 180a to the output of the negative conversion unit 720. The MCU330 additionally outputs a second control signal En 2 to deactivate the second switch 734 so that the first electrode 180a is not connected to the output of the positive converter unit 710.

[0074] The positive RF voltage signal VRF+ To output the second periodic amplitude-modulated RF signal S2 in this case, the MCU 330 outputs a fourth control signal En for operating the fourth switch 744 to connect the second electrode 180b to the output of the positive conversion unit 710. 4 In this case, the MCU 330 outputs a third control signal En to disable the third switch 742 so that the second electrode 180b is not connected to the output of the negative converter unit 720. 3 is additionally output.

[0075] To output the third periodic amplitude-modulated RF signal S3 with a 0 voltage signal in this case, the MCU 330 outputs a fifth control signal En and a sixth control signal En for disabling the fifth switch 752 and the sixth switch 754, respectively. 5 and the sixth control signal En 6 The node between the third switch unit 750 and the third electrode 180c is floating in this case so that no voltage signal or 0 voltage signal is applied to the third electrode 180c between the first phases Φ of FIG. 5b. 1 is floating so that no voltage signal or 0 voltage signal is applied to the third electrode 180c.

[0076] Thus, according to the example of the present disclosure, the MCU 330 is configured to change the N periodic amplitude-modulated RF signals S1 to S3 over each of the plurality of phases Φ by appropriate control of the switches 732 to 754 of the switch units 730, 740, 750. The electrodes 180a to c are configured to receive the N periodic amplitude-modulated RF signals S1 to S3, and in that case, RF energy may flow between the electrodes 180a to c through the user's skin over the plurality of phases Φ, causing heating of the skin. 1~3 of the plurality of phases Φ, causing heating of the skin. 1~3 flows between the electrodes 180a to c through the user's skin over the plurality of phases Φ, causing heating of the skin.

[0077] The circuit configuration 700 further includes a low dropout regulator (LDO) 760. The LDO 760 is configured to adjust the battery voltage V when the battery voltage V drops to a low level. BATT when the battery voltage V drops to a low level. BATT is configured to adjust the battery voltage V.

[0078] The circuit configuration 700 further includes a plurality of sense resistors 770a - c including a first sense resistor 770a, a second sense resistor 770b, and a third sense resistor 770c. The first, second, and third sense resistors 770a - c are each disposed in proximity to the first, second, and third electrodes 180a - c, respectively. The plurality of sense resistors 770a - c are in this case configured to measure the temperature of the surface of the corresponding electrodes 180a - c and the skin in contact with the electrode surface. In the example of FIG. 7 shown, each of the plurality of sense resistors 770a - c includes a negative temperature coefficient (NTC) resistor. In one example, each of the plurality of sense resistors 770a - c forms part of a voltage divider. The plurality of sense resistors 770a - c are in this case connected to the MCU 330, and in that case the value of the voltage of each of the sense resistors 770a - c is used as a safety control element. In one example, the MCU responds to the temperature of any one of the plurality of sense resistors 770a - c rising above a threshold by changing the PWM control signal PWM C to reduce the RF frequency signal f RF and is configured to lower the temperature applied to the user's skin.

[0079] FIGS. 8a and 8b show the results of a simulation of RF heating of the skin surface in contact with the electrodes 180a - c disposed in the cutting head of an electric shaver.

[0080] FIG. 8a shows the results obtained using an electric shaver according to an example of the present disclosure, where N periodic amplitude - modulated RF energy signals are applied to the electrodes 180a - c. The user's skin surface was heated to 41.7 °C over 5 seconds. As shown, a flow of RF energy occurs between each of the electrodes 180a - c. Further, as shown, the skin deep penetration is approximately 0.9 mm between each of the electrodes 180a - c. Since the skin heating penetration is the same between each of the electrodes, as a result, the skin in contact with the electrodes 180a - c in the cutting head of the electric shaver is heated more uniformly.

[0081] Figure 8b shows the results obtained using an electric shaver, with single-phase RF energy applied to electrodes 180a - c. The first electrode 180a receives a zero voltage signal, the second electrode 180b receives a positive RF voltage signal V RF+ and the third electrode 180c receives a negative RF voltage signal V RF- . The user's skin was heated to 45.3 °C over 5 seconds. The temperature heating is higher than that provided by the electric shaver according to the example of the present disclosure shown in Figure 8a, but the flow of RF energy by the shaver shown in Figure 8b is less uniform. As shown, a large flow of RF energy occurs between the second electrode 180b and the third electrode 180c. However, the flow of RF energy between the first electrode 180a and both the second electrode 180b and the third electrode 180c is reduced. Penetration of 1.4 mm occurs between the second electrode 180b and the third electrode 180c, and the skin heating penetration between these electrodes is also high, while on the other hand, the penetration that occurs between the first electrode 180a and both the second electrode 180b and the third electrode 180c is approximately 0.5. When the flow of RF energy and skin penetration are non-uniform, a "hotspot" sensation occurs on the user's skin, which is unpleasant. The electric shaver according to the example of the present disclosure shown in Figure 8a heated a skin area 13% wider but did not generate hotspots.

[0082] Examples according to the present disclosure have been described where the electrodes are arranged within the skin contact area of the electric shaver and these electrodes are adjacent to the hair cutting unit of the electric shaver between corresponding pairs of the hair cutting units in the lateral portions of the skin contact area. However, as described below, other arrangements of the hair cutting unit and the electrodes are possible.

[0083] Figure 9 shows another example of the skin contact area 910 of an electric shaver 900. The electric shaver 900 comprises elements common to the skin contact area 200 of the electric shaver described above with respect to Figure 2, and these are assigned corresponding reference numerals and are substantially the same as described above.

[0084] In this case, the electric shaver 900 includes first, second, and third cutting units 150, 160, 170. The first, second, and third cutting units 150, 160, 170 each include corresponding covering elements in the form of first, second, and third electrodes 180a - c. In such an example, the first, second, and third electrodes 180a - c are respectively arranged on the first, second, and third external cutting members 152, 162, 172 in a manner substantially corresponding to the first, second, and third covering elements 154, 164, 174 described above with respect to FIG. 1. The first, second, and third covering elements are in this case formed of a conductive material for transmitting an RF voltage signal. The RF generator unit configured to output N periodic amplitude - modulated RF signals as described above is in this case electrically connected to each of the electrodes 180a - c. In use, the N periodic amplitude - modulated RF signals are in this case applied to the electrodes 180a - c in a manner corresponding to the above - described one. Thus, in use, RF energy flows between the electrodes 180a - c within the user's skin to warm the skin.

[0085] The first, second, and third electrodes 180a - c are in this case electrically isolated from the other elements of the skin contact area 910 such that the "circuit" of the RF voltage is completed only when the electrodes 180a - c are applied to the user's skin. For example, each of the electrodes 180a - c is electrically isolated from its corresponding external cutting member 152, 162, 172 by separating the two elements with an insulating material such as non - conductive plastic.

[0086] Due to the arrangement of the electrodes 180a - c in the electric shaver 900, the geometric centers of each of the hair cutting units 150, 160, 170 are, in this case, aligned with the geometric centers of each of the electrodes 180a - c. The first pitch distance 202 between the geometric centers 156, 166, 176 of each pair of the hair cutting units 150, 160, 170 is, in this case, the same as the second pitch distance 204 between the geometric centers of each pair of the electrodes 180a - c. In the example of the electric shaver 900, the ratio between the second minimum pitch distance 204 and the first minimum pitch distance 202 is, in this case, 1. Thus, the electrodes 180a - c are also, here, distributed over the major area of the skin contact area 910, and thus, as a result of this arrangement, during use, more uniform heating is provided in a large area of the skin in contact with the skin contact area 910. For example, due to the arrangement of the N electrodes 180a - c, RF energy flows between each of the N electrodes 180a - c, and as a result, most of the skin in contact with the skin contact area 200 will be warmed by the application of the RF energy.

[0087] In the examples presented so far, the teachings of the present disclosure have been described in relation to rotary shavers. However, the teachings of the present disclosure can additionally be applied to other forms of electric shavers, such as foil shavers.

[0088] FIG. 10 shows an example of an electric shaver 1000. The electric shaver comprises elements common to the above - described electric shaver 100, which are given corresponding reference numerals and operate in substantially the same manner as described above.

[0089] The electric shaver 1000 is in the form of a foil shaver. Accordingly, the cutting head 140 includes first, second, and third hair cutting units 150, 160, 170. Each hair cutting unit 150, 160, 170 includes a corresponding internal cutting member, such as a blade, and a corresponding external cutting member 152, 162, 172 having a plurality of hair entry openings. The hair entry openings include holes and / or thin plates. Each external cutting member 152, 162, 172 has a corresponding skin contact area that contacts the user's skin during use of the shaver 1000. The hair entry openings are part of the skin contact area. In the embodiment of FIG. 10, each external cutting member 152, 162, 172 is a shaving foil that extends parallel to the longitudinal direction. The external cutting members 152, 162, 172 are arranged to cover the corresponding internal cutting members, and the corresponding internal cutting members are movable relative to the external cutting members. For example, the blade linearly reciprocates parallel to the longitudinal direction relative to the foil. The hairs project through the openings of the foils 152, 162, 172, and the hairs are cut by the reciprocating movement of the blade, and the cut ends are collected in the hair collection area of the shaver 1000. For this reason, the electric shaver 1000 further includes a motor 130 configured to move the internal cutting member relative to the corresponding external cutting members 152, 162, 172 so that a cutting action occurs.

[0090] The RF generator energy unit 120 is configured to apply N periodically amplitude-modulated RF signals to the skin via the skin contact areas provided by the respective external cutting members 152, 162, 172 of the hair cutting units 150, 160, 170. For example, each of the external cutting members 152, 162, 172 of the hair cutting units 150, 160, 170 can transmit N periodically amplitude-modulated RF signals and is formed of a biocompatible conductive material with the skin, such as a metal like stainless steel, silver, or silver chloride. In this way, the entirety of the external cutting members 152, 162, 172 is configured to transmit N periodically amplitude-modulated RF signals. In other words, the external cutting members 152, 162, 172 function as N electrodes for applying N periodically amplitude-modulated RF signals to the user's skin to warm the skin. Each of the N electrodes is in this case constituted by at least the skin contact portion of the corresponding one of the four external cutting members 152, 162, 172 of the hair cutting units 150, 160, 170. Each of the external cutting members 152, 162, 172 is in this case additionally electrically isolated from each other in the electric shaver 1100. For example, there is a gap between each of the external cutting members 152, 162, 172 that electrically isolates the external cutting members 152, 162, 172 from each other. In this way, when the external cutting members 152, 162, 172 are brought into contact with the user's skin, a "circuit" is formed between them.

[0091] FIG. 11 shows another example of the electric shaver 1100. The electric shaver 1100 includes elements common to the above-described electric shaver 1000, which are assigned corresponding reference numerals and operate in substantially the same manner as described above.

[0092] The electric shaver 1100 includes a skin contact area 1110 and first and second hair cutting units 150, 160, 170. As described above, the external cutting members 152, 162, 172 function as N electrodes for applying N periodically amplitude-modulated RF signals to the user's skin to warm the skin. In the arrangement of the electric shaver 1100, the geometric center points 156, 166, 176 of each of the hair cutting units 150, 160, 170 are in this case aligned with the geometric center points of each of the electrodes. The first pitch distance 202 between each pair of geometric center points 156, 166, 176 of the hair cutting units 150, 160, 170 is in this case the same as the second pitch distance 204 between each pair of geometric center points of the electrodes. In the example of the electric shaver 1100, the ratio between the second minimum pitch distance 204 and the first minimum pitch distance 202 is in this case 1. Thus, the electrodes 180a - c are also here distributed over the major area of the skin contact area 1110, and thus, as a result of this arrangement, during use, more uniform heating is provided in a large area of the skin in contact with the skin contact area 1110. For example, due to the arrangement of the external cutting members 152, 162, 172 that function as N electrodes, RF energy flows between each of the N electrodes, and as a result, most of the skin in contact with the skin contact area 1110 will be warmed by the application of RF energy.

[0093] Figures 12a and 12b show an example of how an RF signal can be applied to the external cutting members 152, 162, 172 of the foil shaver type hair cutting units 150, 160, 170.

[0094] Figure 12a shows N modulated signals M1 - M3, where N = 3. The N modulated waveforms M1 - M3 are in this case the first modulation signal M1 for modulating the RF voltage signal V RF applied to the first electrode, the second modulation signal M2 for modulating the RF voltage signal V RF applied to the second electrode, and the RF voltage signal V RFIt consists of a third modulation signal M3 for modulation. As shown in FIG. 12b, the first, second, and third electrodes include the first, second, and third external cutting members 152, 162, 172 of the electric shaver.

[0095] The N modulation signals M1 to M3 each have a two-state modulation waveform consisting of a first state +1 and a second state 0. As described above with respect to FIGS. 4a to 4c, for the N two-state modulation signals M1 to 3, the nth one of the N modulation signals M1 to M3 has a phase difference of T MOD *(n - 1) / N with respect to the first one of the N modulation signals M1 to M3. According to this condition, during the modulation period T MOD the three phases Φ 1~3 are phase-shifted from each other over the range, where 2 ≤ n ≤ N. Thus, in a manner similar to that described above with respect to FIGS. 4a to 4c, the N modulation signals M1 to M3 are used to modulate the amplitude of the RF voltage signal V RF in order to generate N periodic amplitude-modulated RF energy signals.

[0096] FIG. 12b shows how N periodic amplitude-modulated RF voltage signals, which in some examples may be called N periodic amplitude-modulated RF energy signals, can be applied to the external cutting members 152, 162, 172 of the electric shaver over three phases Φ 1~3 . In a manner similar to that described above with respect to FIGS. 4a to 4c, the N periodic amplitude-modulated RF energy signals have a first value +V of the RF voltage signal or a second value 0V of the zero voltage signal according to the states of the corresponding N modulation signals M1 to M3 during a given phase. For example, referring to FIG. 12a, during the first phase Φ 1 , the first modulation signal M1 is in the first state +1, and the second modulation signal M2 and the third modulation signal M3 are in the second state 0. In this case, referring to FIG. 12b, during the first phase Φ 1During this period, the first external cutting member 152 receives a first periodic amplitude modulation signal that is an RF voltage signal +V, and both the second external cutting 162 and the second external cutting member 172 receive second and third periodic amplitude modulation signals that are zero voltage signals 0V, respectively. In this case, a flow of RF energy occurs between the first external cutting member 152 and both the second external cutting 162 and the second external cutting member 172, warming the user's skin.

[0097] In a manner similar to that described above with respect to FIGS. 4a to 4c, the second and third phases Φ 2~3 During this period, N periodic amplitude modulation RF energy signals change according to N modulation signals M1 to M3, and as a result, the flow of RF energy between the external cutting members 152, 162, 172 changes accordingly. In some examples, the modulation signals M1 to M3 thus represent the envelopes of the N periodic amplitude modulation RF energy signals. Thus, over the first, second, and third phases Φ 1~3 the flow of RF energy occurs between different ones of the external cutting members 152, 162, 172, which leads to more uniform heating of the skin in contact with the external cutting members 152, 162, 172.

[0098] A simulation was performed to measure skin heating using an electric shaver that uses modulation signals M1 to M3 according to FIGS. 12a to 12b. These heating results were compared with a simulation of skin heating using an electric shaver having three shaver foil electrodes to which an unmodulated RF signal is applied. In the electric shaver that uses modulation signals M1 to M3 according to FIGS. 12a to 12b, a 25% larger volume of skin was heated compared to the electric shaver that uses an unmodulated RF signal. In the above example, for both shavers, two foil electrodes located on the side of the configuration, for example, the first external cutting member 152 and the third external cutting member 172, have a skin contact area of 4×25 mm, and the central foil electrode, for example, the second external cutting member 162, has a skin contact area of 5×25 mm, and each foil electrode is separated by a 4 mm gap for electrical isolation. The electric shaver that uses modulation signals M1 to M3 used a peak-to-peak voltage of 11 V, while the electric shaver that uses an unmodulated RF signal used a voltage of 19 V.

[0099] FIGS. 13a and 13b show another example of how an RF signal can be applied to the external cutting members 152, 162, 172 of the hair cutting units 150, 160, 170 of the foil shaver.

[0100] FIG. 13a shows N modulation signals M1 to M3, where N = 3. In a manner similar to that described above with respect to FIGS. 12a to 12b, the N modulation signals M1 to M3 are used to modulate the amplitude of the RF voltage signal V RF in order to generate N periodic amplitude-modulated RF energy signals applied to N electrodes. As shown in FIG. 13b, the N electrodes include the first, second, and third external cutting members 152, 162, 172 of the electric shaver.

[0101] Referring back to FIG. 13a, the N modulation signals M1 to M3 each have an asymmetric three-state modulation waveform. In a manner similar to that described above with respect to FIGS. 5a to 5c, for the N modulation signals M1 to M3 in FIG. 13a, the nth one of the N modulation signals M1 to M3 has a phase difference of T MOD *(n - 1) / N with respect to the first one of the N modulation signals M1 to M3. According to this condition, during the modulation period T MOD the three phases Φ 1~3 are phase-shifted from each other over the range, where 2 ≤ n ≤ N. Thus, in a manner similar to that described above with respect to FIGS. 5a to 5c, the N modulation signals M1 to M3 are used to modulate the amplitudes of the positive RF voltage signal +V and the negative RF voltage signal -V in order to generate N periodic amplitude-modulated RF energy signals applied to N electrodes.

[0102] Referring to FIG. 13b, in some cases called the N periodic amplitude-modulated RF energy signals S1 to S3, the N periodic amplitude-modulated RF voltage signals are in this case applied to the first, second, and third external cutting members 152, 162, 172 of the electric shaver over three phases Φ 1~3 . Thus, as described above with respect to FIGS. 5a to 5c, over the first, second, and third phases Φ 1~3 a different amount of RF energy flow occurs between different ones of the external cutting members 152, 162, 172E1 to E3, which results in more uniform heating of the skin in contact with the three electrodes E1 to E3.

[0103] An example according to the present disclosure with N = 3 for the N electrodes and the N periodic amplitude-modulated RF energy signals has thus been presented. However, in other examples, N may be greater than 3, for example N = 4.

[0104] FIG. 14 shows an example of an electric shaver 1400. The electric shaver 1400 includes elements common to the electric shaver 1100 described above, which are given corresponding reference numerals and operate in substantially the same manner as described above.

[0105] The electric shaver 1400 includes a skin contact area 1410 that includes first, second, and third hair cutting units 150, 160, 170, and additionally a fourth hair cutting unit 1480. The fourth hair cutting unit 1480 additionally includes a fourth external cutting member 1480 of the shaver foil type. The fourth hair cutting unit 1480 and the fourth external cutting member 1480 in this case operate so as to substantially correspond to the hair cutting units 150, 160, 170 and the external cutting members 152, 162, 172 described above with respect to FIG. 11. The fourth external cutting member 1480 in this case is formed of a conductive material that can convey the fourth of the N periodically amplitude-modulated RF signals. In this way, the entire external cutting member 1482 is configured to convey the fourth of the N periodically amplitude-modulated RF signals. In other words, the fourth external cutting member 1480 functions as a fourth electrode for applying the N periodically amplitude-modulated RF signals to the user's skin to warm the skin.

[0106] As described above, the external cutting members 152, 162, 172, 1482 function as N electrodes for applying the N periodically amplitude-modulated RF signals to the user's skin to warm the skin. Due to the arrangement of the electric shaver 1400, the geometric centers 156, 166, 176, 1486 of each of the hair cutting units 150, 160, 170, 1480 are in this case aligned with the geometric centers of each of the electrodes. The first pitch distance 202 between the geometric centers 156, 166, 176 of each pair of the hair cutting units 150, 160, 170 is in this case the same as the second pitch distance 204 between the geometric centers of each pair of the electrodes 180a-c. In the example of the electric shaver 1400, the ratio between the second minimum pitch distance 204 and the first minimum pitch distance 202 is in this case 1. In this way, the electrodes are also here distributed over the main area of the skin contact area 1110, and thus, as a result of this arrangement, more uniform heating is provided in a large area of the skin in contact with the skin contact area 1110 during use.

[0107] Figures 15a and 15b show an example of how an RF signal can be applied to the external cutting members 152, 162, 172, 1482 of the foil shavers' hair cutting units 150, 160, 170, 1480.

[0108] Figure 15a shows N modulated signals M1 to M4, where N = 4. The N modulated waveforms M1 to M4 are the first modulation signal M1 for modulating the RF voltage signal V applied to the first electrode, the RF voltage signal V RF applied to the second electrode, the second modulation signal M2 for modulating the RF voltage signal V RF applied to the third electrode, the third modulation signal M3 for modulating the RF voltage signal V RF applied to the fourth electrode, and the fourth modulation signal M4 for modulating the RF voltage signal V RF applied to the fourth electrode. As shown in Figure 15b, the first, second, third, and fourth electrodes comprise the first, second, third, and fourth external cutting members 152, 162, 172, 1482 of the electric shaver.

[0109] The N modulated signals M1 to M4 each consist of an asymmetric 4 - state modulation signal consisting of a first state +1, a second state +1 / 3, a third state -1 / 3, and a fourth state -1. Each of the N modulated signals M1, M2, M3, M4 has a modulation period T MOD which is divided into four phases of Φ 1~4 . In this case, in a manner similar to that described with respect to Figures 4a - 4c, Figures 5a - 5c, Figures 6a - 6c, Figures 12a - 12c, and Figures 13a - 13c, the N modulated signals M1 to M4 are such that the nth of the N modulated signals M1 to M4 has a phase difference of T MOD *(n - 1) / N with respect to the first of the N modulated signals M1 to M4. According to this condition, over the modulation period T MOD , the four phases Φ 1~4 are phase - shifted from each other, where 2 ≤ n ≤ N.

[0110] FIG. 15b shows, in some examples, how N periodically amplitude-modulated RF voltage signals, sometimes referred to as N periodically amplitude-modulated RF energy signals S1 to S3, are applied to the external cutting members 152, 162, 172, 1482 of the electric shaver over four phases Φ 1~4 As in the manner described above, the N periodically amplitude-modulated RF energy signals have a plurality of values consisting of a first value +V of the RF voltage signal, a second value +V / 3 of the RF voltage signal, a third voltage signal -V / 3 of the RF voltage signal, and a fourth value -V of the RF voltage signal, depending on the states of the corresponding N modulation signals M1 to M4 between given phases. In some examples, the modulation signals M1 to M3 thus represent the envelopes of the N periodically amplitude-modulated RF energy signals S1 to S3.

[0111] In some examples, to generate the second voltage value of +V / 3 and the third voltage value of -V / 3, the above-described RF generator unit 312 comprises an additional converter unit for generating +V RF / 3 and -V RF / 3. In such an example, the switch unit 314 in this case further comprises an additional switch for applying to the N electrodes a second voltage value of +V / 3 and a third voltage value of -V / 3.

[0112] In the examples of FIGS. 15a to 15c, the ratio between the magnitudes of the first and fourth voltage values +V, -V and the second and third voltage values +V / 3, -V / 3 is 0.33. However, in other examples, the ratio between the magnitudes of these voltages may be between 0.25 and 0.5, preferably between 0.3 and 0.35.

[0113] Referring to FIG. 15a, during the first phase Φ 1 , the first modulation signal M1 is in the first state +1, the second modulation signal M2 is in the second state +1 / 3, the third modulation signal M3 is in the third state -1 / 3, and the fourth modulation signal M4 is in the fourth state -1. In this case, referring to FIG. 15b, during the first phase Φ 1During this period, the first external cutting member 152 receives a first periodically amplitude-modulated signal having a first value +V, the second external cutting member 162 receives a second periodically amplitude-modulated signal having a second value +V / 3, the third external cutting member 172 receives a third periodically amplitude-modulated signal having a third value -V / 3, and the fourth external cutting member 1482 receives a fourth periodically amplitude-modulated signal having a fourth value -V. In this case, in a manner similar to that described above, the first phase Φ 1 During the period between 1 , due to the voltage differences existing between the external cutting members 152, 162, 172, 1482 of the electric shaver, a flow of RF energy occurs between the external cutting members 152, 162, 172, 1482, warming the user's skin.

[0114] In a manner similar to that described above, for the second, third, and fourth phases Φ 2~4 During the period between 2~4 , N periodically amplitude-modulated RF energy signals change based on N modulation signals M1 to M4, and as a result, the flow of RF energy between the external cutting members 152, 162, 172, 1482 changes accordingly. Therefore, over the first, second, third, and fourth phases Φ 1~4 the flow of RF energy occurs in different amounts between different ones of the external cutting members 152, 162, 172, 1482, which leads to a more uniform heating of the skin in contact with the external cutting members 152, 162, 172, 1482.

[0115] Using an electric shaver that uses modulation signals M1 to M4 according to FIGS. 15a to 15b, a simulation was performed to measure skin heating. The results of these heatings were compared with a simulation of skin heating using an electric shaver having four shaver foil electrodes to which an unmodulated RF signal is applied. In the electric shaver using the modulation signals M1 to M4 according to FIGS. 15a to 15b, a skin volume 60% larger was heated compared to the electric shaver using an unmodulated RF signal. In the above example, for both shavers, the foil electrodes of the first external cutting member 152, the second external cutting member 162, the third external cutting member 172, and the fourth external cutting member 1482 have a 4×25 mm skin contact area, and each foil electrode is separated by a 4 mm gap for electrical isolation. The electric shaver using the modulation signals M1 to M3 used a peak-to-peak voltage of 11 V, while the electric shaver using an unmodulated RF signal used a voltage of 19 V.

[0116] FIG. 16 shows another example of an electric shaver 1600. The electric shaver 1600 includes elements common to the electric shaver 900 described above with respect to FIG. 9. Corresponding reference numerals are assigned to the corresponding elements described above, and they operate corresponding to those described above.

[0117] The electric shaver 1600 includes first, second, and third hair cutting units 150, 160, 170 each having corresponding covering elements in the form of the first, second, and third electrodes 180a - c, respectively, and a skin contact area 1610 in the same manner as the above-described electric shaver 900. The electric shaver 1600 additionally includes a fourth hair cutting unit 1680 having a covering element in the form of a fourth electrode 180d. The fourth covering element is in this case additionally formed of a conductive material for transmitting an RF voltage signal. The RF generator unit configured to generate N periodic amplitude-modulated RF signals as described above is in this case electrically connected to each of the electrodes 180a - d. In use, the N periodic amplitude-modulated RF signals are in this case applied to the electrodes 180a - d in a manner corresponding to the above-described one. Thus, in use, RF energy flows between the electrodes 180a - d within the user's skin to warm the skin.

[0118] Due to the arrangement of the electrodes 180a - d in the electric shaver 1600, the geometric centers of each of the hair cutting units 150, 160, 170, 1680 are in this case aligned with the geometric centers of each of the electrodes 180a - d. The first pitch distance 202 between the geometric centers 156, 166, 176, 1686 of each pair of the hair cutting units 150, 160, 170, 1680 is in this case the same as the second pitch distance between the geometric centers of each pair of the electrodes 180a - d. In the example of the electric shaver 1600, the ratio between the second minimum pitch distance 204 and the first minimum pitch distance 202 is in this case 1. Thus, the electrodes 180a - d are also here dispersed over the main area of the skin contact area 910, and thus as a result of this arrangement, more uniform heating is provided in a large area of the skin in contact with the skin contact area 1610 during use. For example, due to the arrangement of the N electrodes 180a - d, RF energy flows between each of the N electrodes 180a - c, and as a result, most of the skin in contact with the skin contact area 200 will be warmed by the application of RF energy.

[0119] Figures 17a and 17b show another example of how an RF signal is applied to the electrodes of an electric shaver.

[0120] Figure 17a shows N modulated signals M1 to M4, where N = 4. The N modulated waveforms M1 to M4 are the first modulation signal M1 for modulating the RF voltage signal V applied to the first electrode, the RF voltage signal V applied to the second electrode RF the second modulation signal M2 for modulating, the RF voltage signal V applied to the third electrode RF the third modulation signal M3 for modulating, and the RF voltage signal V applied to the fourth electrode RF the fourth modulation signal M4 for modulating. As shown in Figure 17b, the first, second, third, and fourth electrodes 180a to d include the covering elements of the hair cutting units 150, 160, 170, 1680. RF

[0121] The N modulated signals M1 to M4 each comprise a two-state modulation signal consisting of a first state +1 and a second state 0. In a manner similar to that described with respect to Figures 15a to 15b, each of the N modulated signals M1 to M4 is divided into four phases Φ 1~4 over a modulation period T MOD MOD which has. In this case, in a manner similar to that described above, the N modulated signals M1 to M4 are such that the nth of the N modulated signals M1 to M4 signals has a phase difference of T MOD *(n - 1) / N with respect to the first of the N modulated signals M1 to M4, and according to this condition, over the modulation period T MOD the four phases Φ 1~4 are phase-shifted from each other over, where 2 ≤ n ≤ N.

[0122] In a manner similar to that described above, in some examples, N periodically amplitude-modulated RF voltage signals, sometimes called N periodically amplitude-modulated RF energy signals, are generated by applying the N modulated signals M1 to M4 to the RF voltage signal. In a manner similar to that described above, the N periodically amplitude-modulated RF energy signals comprise a plurality of values consisting of a first value +V of the RF voltage signal and a second value 0V of the zero voltage signal, depending on the states of the corresponding N modulated signals M1 to M4 during a given phase.

[0123] For example, referring to FIG. 17a, during the first phase Φ 1 the first modulation signal M1 is in the second state 0, the second modulation signal M2 is in the second state 0, the third modulation signal M3 is in the first state +1, and the fourth modulation signal M4 is in the first state +1. In this case, referring to FIG. 17b, during the first phase Φ 1 the first electrode 180a receives a first periodic amplitude modulation signal that is at a second value of 0V, the second electrode 180b receives a second periodic amplitude modulation signal that is at a second value of 0V, the third electrode 180d receives a third periodic amplitude modulation signal that is at a first value of +V, and the fourth electrode 180d receives a fourth periodic amplitude modulation signal that is at a first value of +V. In this case, in a manner similar to that described above, during the first phase Φ 1 due to the voltage differences existing between the electrodes 180a - d of the electric shaver during the first phase Φ, in this case an RF energy flow occurs between the electrodes 180a - d to warm the user's skin.

[0124] In a manner similar to that described above, during the second, third, and fourth phases Φ 2~4 N periodic amplitude modulation RF energy signals vary based on the N modulation signals M1 - M4, and as a result, the RF energy flow between the electrodes 180a - d changes accordingly. In some examples, the modulation signals M1 - M3 thus represent the envelopes of the N periodic amplitude modulation RF energy signals S1 - S3. In this way, across the first, second, third, and fourth phases Φ 1~4 an RF energy flow occurs between different ones of the electrodes 180a - d, which results in a more uniform heating of the skin in contact with the electrodes 180a - d.

[0125] In practicing the principles and techniques described herein, those skilled in the art will be able to understand and realize variations of the disclosed embodiments by considering the drawings, the present disclosure, and the appended claims. In the claims, the words "comprising," "including," "having" do not exclude other elements or steps, and the singular elements do not exclude a plurality. A single processor or other unit may perform the functions of several matters recited in the claims. The mere fact that certain methods are recited in mutually different dependent claims does not indicate that combinations of these methods cannot be used advantageously. A computer program may be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, for example via the Internet or other wired or wireless electrical communication systems. Any reference signs in the claims should not be construed as limiting their scope.

Claims

1. A skin contact area for contacting the user's skin during use of the electric shaver, and at least two hair cutting units disposed within the skin contact area, each hair cutting unit having an external cutting member having a plurality of hair entry openings, and an internal cutting member covered by the external cutting member and movable relative to the external cutting member, and N electrodes disposed within the skin contact area so as to contact the skin during use, where N is at least 3, and Fundamental frequency f ＲＦ and fundamental period T ＲＦ = 1 / f ＲＦ A high-frequency generator that generates high-frequency energy having the above, a high-frequency energy modulator that converts the high-frequency energy generated by the high-frequency generator into N periodically amplitude-modulated high-frequency energy signals, and supplies each of the N periodically amplitude-modulated high-frequency energy signals to a corresponding one of the N electrodes, and An electric shaver comprising: When viewed in a direction perpendicular to the skin contact area, the external cutting member of each hair cutting unit has a geometric center point, a first pitch distance that is the distance between the geometric center points of a pair of the hair cutting units, and a first minimum pitch distance that is the minimum value of the first pitch distances of all pairs of the hair cutting units, and When viewed in a direction perpendicular to the skin contact area, each of the N electrodes has a geometric center point, a second pitch distance that is the distance between the geometric center points of a pair of the N electrodes, and a second minimum pitch distance that is the minimum value of the second pitch distances of all pairs of the N electrodes, and The ratio between the second minimum pitch distance and the first minimum pitch distance is at least 0.8, and The fundamental period T of the N periodic amplitude-modulated high-frequency energy signals ＭＯＤ is the fundamental period T ＲＦ is greater than, The n-th one of the N periodic amplitude-modulated high-frequency energy signals has a phase difference of T * (n - 1) / N with respect to the first one of the N periodic amplitude-modulated RF energy signals, where 2 ≤ n ≤ N, an electric shaver. ＭＯＤ ​

2. T ＭＯＤ and T ＲＦ The electric shaver according to claim 1, wherein the ratio between and is at least 10, preferably at least 25.

3. Each of the N periodic amplitude-modulated high-frequency energy signals has the same basic high-frequency energy signal during the basic period T of each of the periodic amplitude-modulated high-frequency energy signals. ＭＯＤ The electric shaver according to claim 1 or 2, having the same basic high-frequency energy signal during the basic period T of each of the N periodic amplitude-modulated high-frequency energy signals.

4. The basic high-frequency energy signal has a first state and a second state, and the first state is the basic frequency f ＲＦ and a first high-frequency voltage (V ＲＦ＋ , V ＲＦ－ ), and the second state is constituted by a zero signal (0 V). The electric shaver according to claim 3.

5. The electric shaver according to claim 4, further comprising a third state in which the basic high-frequency energy signal is constituted by a second high-frequency energy signal obtained by inverting the first high-frequency energy signal.

6. The electric shaver according to claim 3, wherein the first states of the N periodically amplitude-modulated high-frequency energy signals do not occur simultaneously.

7. The electric shaver according to claim 4, wherein the second states of the N periodically amplitude-modulated high-frequency energy signals do not occur simultaneously.

8. The electric shaver according to any one of claims 1 to 7, wherein the N electrodes are disposed adjacent to the hair cutting units.

9. An electric shaver comprising three electrodes and three hair cutting units arranged in a triangular configuration with respect to each other, wherein the internal cutting member of each hair cutting unit is rotatable with respect to the external cutting member, and each of the three electrodes is arranged at a lateral portion of the skin contact area between two hair cutting units of one pair of the hair cutting units. The electric shaver according to claim 8.

10. An electric shaver according to any one of claims 1 to 7, comprising N hair cutting units, wherein the external cutting member of each of the N hair cutting units is annular, and the N electrodes each comprise N covering elements respectively arranged at central positions with respect to the respective external cutting members of the N hair cutting units.

11. An electric shaver according to any one of claims 1 to 7, comprising N hair cutting units, wherein each of the N electrodes is constituted by at least the skin contact portion of the respective external cutting member of the N hair cutting units.

12. An electric shaver according to claim 11, comprising three hair cutting units, wherein the internal cutting member of each hair cutting unit linearly reciprocates parallel to the longitudinal direction with respect to the external cutting member, and the external cutting member of each hair cutting unit has a longitudinal extension parallel to the longitudinal direction.

13. Comprising four electrodes and four hair cutting units, the internal cutting member of each hair cutting unit linearly reciprocates parallel to the longitudinal direction with respect to the external cutting member, and the external cutting member of each hair cutting unit has a longitudinal extension parallel to the longitudinal direction, each of the four electrodes is constituted by at least the skin contact portion of the respective external cutting member of the four hair cutting units, The basic high-frequency energy signal continuously includes a first state, a second state, a third state, and a fourth state, and the first state is the basic frequency f ＲＦ and a first high-frequency energy signal having a first high-frequency voltage. The second state is the basic frequency f ＲＦ and a second high-frequency energy signal having a second high-frequency voltage lower than the first high-frequency voltage. The third state is constituted by a third high-frequency energy signal obtained by inverting the second high-frequency energy signal, and the fourth state is constituted by a fourth high-frequency energy signal obtained by inverting the first high-frequency energy signal. The electric shaver according to claim 3.

14. The electric shaver according to claim 13, wherein the ratio between the second high-frequency voltage and the first high-frequency voltage is between 0.25 and 0.5, preferably between 0.3 and 0.

35.

15. The electric shaver according to any one of claims 1 to 14, wherein the high-frequency energy modulator comprises N switch units, and each of the N switch units applies each of the periodic amplitude-modulated high-frequency energy signals of the N periodic amplitude-modulated high-frequency energy signals to each of the N electrodes.

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