Electric shavers
According to an aspect, there is provided an electric shaver ( 100, 900, 1000, 1100, 1400, 1600 ) that comprises: a skin-contacting area ( 200, 910, 1110, 1410, 1610 ) arranged to contact skin of a user during use of the shaver ( 100, 900, 1000, 1100, 1400, 1600 ); at least two hair-cutting units ( 150, 160, 170, 1480, 1680 ) arranged in the skin-contacting area ( 200, 910, 1110, 1410, 1610 ) and each having an external cutting member ( 152, 162, 172, 1482, 1682 ) with a plurality of hair-entry openings and an internal cutting member covered by and moveable relative to the external cutting member ( 152, 162, 172, 1482, 1682 ); N electrodes ( 180 a - d ) arranged in the skin-contacting area ( 200, 910, 1110, 1410, 1610 ) to contact the skin during use, wherein N is at least 3; a radio-frequency (RF) generator ( 320 ) configured to generate RF energy having a basic frequency f RF and a basic period T RF =1/f RF ; an RF energy modulator ( 310 ) configured to transform the RF energy generated by the RF generator into N periodic amplitude-modulated RF energy signals and to provide each of the N periodic amplitude-modulated RF energy signals (SI, S 2 , S 3 ) to a respective one of the N electrodes ( 180 a - d ); wherein: seen perpendicularly to the skin-contacting area ( 200, 910, 1110, 1410, 1610 ), the external cutting member ( 152, 162, 172, 1482, 1682 ) of each hair-cutting unit ( 150, 160, 170, 1480, 1680 ) has a geometric center point ( 156, 166, 176, 1486, 1686 ), a first pitch distance ( 202 ) being a distance between the geometric center points ( 156, 166, 176, 1486, 1686 ) of a pair of the hair-cutting units ( 150, 160, 170, 1480, 1680 ), and a first minimum pitch distance being a minimum of the first pitch distances of all pairs of the hair-cutting units ( 150, 160, 170, 1480, 1680 ); seen perpendicular to the skin-contacting area ( 200, 910, 1110, 1410, 1610 ), each of the N electrodes ( 180 a - d ) has a geometric center point ( 182 a - c ), a second pitch distance ( 204 ) being a distance between the geometric center points ( 182 a - c ) of a pair of the N electrodes ( 180 a - d ), and a second minimum pitch distance being a minimum of the second pitch distances ( 204 ) of all pairs of the N electrodes ( 180 a - d ); a ratio between the second minimum pitch distance and the first minimum pitch distance is at least 0.8; a basic period T MOD of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) is larger than the basic period T RF ; and an n th of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) has a phase difference of T MOD *(U−1)/N relative to a first of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ), wherein 2≤n≤N.
1 . Electric shaver ( 100 , 900 , 1000 , 1100 , 1400 , 1600 ) comprising:
a skin-contacting area ( 200 , 910 , 1110 , 1410 , 1610 ) arranged to contact skin of a user during use of the shaver ( 100 , 900 , 1000 , 1100 , 1400 , 1600 );
at least two hair-cutting units ( 150 , 160 , 170 , 1480 , 1680 ) arranged in the skin-contacting area ( 200 , 910 , 1110 , 1410 , 1610 ) and each having an external cutting member ( 152 , 162 , 172 , 1482 , 1682 ) with a plurality of hair-entry openings and an internal cutting member covered by and moveable relative to the external cutting member ( 152 , 162 , 172 , 1482 , 1682 );
N electrodes ( 180 a - d ) arranged in the skin-contacting area ( 200 , 910 , 1110 , 1410 , 1610 ) to contact the skin during use, wherein N is at least 3;
a radio-frequency (RF) generator ( 320 ) configured to generate RF energy having a basic frequency f RF and a basic period T RF =1/f RF ;
an RF energy modulator ( 310 ) configured to transform the RF energy generated by the RF generator into N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) and to provide each of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) to a respective one of the N electrodes ( 180 a - d );
wherein:
seen perpendicularly to the skin-contacting area ( 200 , 910 , 1110 , 1410 , 1610 ), the external cutting member ( 152 , 162 , 172 , 1482 , 1682 ) of each hair-cutting unit ( 150 , 160 , 170 , 1480 , 1680 ) has a geometric center point ( 156 , 166 , 176 , 1486 , 1686 ), a first pitch distance ( 202 ) being a distance between the geometric center points ( 156 , 166 , 176 , 1486 , 1686 ) of a pair of the hair-cutting units ( 150 , 160 , 170 , 1480 , 1680 ), and a first minimum pitch distance being a minimum of the first pitch distances ( 202 ) of all pairs of the hair-cutting units ( 150 , 160 , 170 , 1480 , 1680 );
seen perpendicular to the skin-contacting area ( 200 , 910 , 1110 , 1410 , 1610 ), each of the N electrodes ( 180 a - d ) has a geometric center point ( 182 a - c ), a second pitch distance ( 204 ) being a distance between the geometric center points ( 182 a - c ) of a pair of the N electrodes ( 180 a - d ), and a second minimum pitch distance being a minimum of the second pitch distances ( 204 ) of all pairs of the N electrodes ( 180 a - d );
a ratio between the second minimum pitch distance and the first minimum pitch distance is at least 0.8;
a basic period T MOD of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) is larger than the basic period T RF ; and
an n th of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) has a phase difference of T MOD *(n−1)/N relative to a first of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ), wherein 2≤n≤N.
2 . Electric shaver as claimed in claim 1 , wherein a ratio between T MOD and T RF is at least 10, preferably at least 25.
3 . Electric shaver as claimed in claim 1 , wherein each of the respective N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) has an identical basic RF energy signal during the basic period T MOD of the respective periodic amplitude-modulated RF energy signal.
4 . Electric shaver as claimed in claim 3 , wherein the basic RF energy signal comprises a first state and a second state, the first state being constituted by a first RF energy signal having the basic frequency f RF and a first RF voltage (V RF+ , V RF− ), and the second state being constituted by a zero signal (0V).
5 . Electric shaver as claimed in claim 4 , wherein the basic RF energy signal further comprises a third state being constituted by a second RF energy signal inverse to the first RF energy signal.
6 . Electric shaver as claimed in claim 4 , wherein the second states of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) do not occur simultaneously.
7 . Electric shaver as claimed in claim 3 , wherein the first states of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) do not occur simultaneously.
8 . Electric shaver as claimed in claim 3 , comprising four electrodes ( 180 a - d ) and four hair-cutting units ( 150 , 160 , 170 , 1480 ), wherein:
the internal cutting member of each hair-cutting unit ( 150 , 160 , 170 , 1480 ) is configured to make a linear reciprocating motion relative to the external cutting member ( 152 , 162 , 172 , 1482 ) parallel to a longitudinal direction, and wherein the external cutting member ( 152 , 162 , 172 , 1482 ) of each hair-cutting unit ( 150 , 160 , 170 , 1480 ) has a longitudinal extension parallel to the longitudinal direction;
each of the four electrodes ( 180 a - d ) is constituted by at least a skin-contacting portion of the external cutting member ( 152 , 162 , 172 , 1482 ) of a respective one of the four hair-cutting units ( 150 , 160 , 170 , 1480 );
the basic RF energy signal comprises, successively, a first state, a second state, a third state, and a fourth state, the first state being constituted by a first RF energy signal having the basic frequency f RF and a first RF voltage, the second state being constituted by a second RF energy signal having the basic frequency f RF and a second RF voltage lower than the first RF voltage, the third state being constituted by a third RF energy signal inverse to the second RF energy signal, and the fourth state being constituted by a fourth RF energy signal inverse to the first RF energy signal.
9 . Electric shaver as claimed in claim 8 , wherein a 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.
10 . Electric shaver as claimed in claim 1 , wherein the N electrodes ( 180 a - d ) are arranged adjacent to the hair-cutting units ( 150 , 160 , 170 ).
11 . Electric shaver as claimed in claim 10 , comprising three electrodes ( 180 a - d ) and three hair-cutting units ( 150 , 160 , 170 ) mutually arranged in a triangular configuration, wherein the internal cutting member of each hair-cutting unit ( 150 , 160 , 170 ) is rotatable relative to the external cutting member ( 152 , 162 , 172 ), and wherein each of the three electrodes ( 180 a - d ) is arranged in a lateral portion of the skin-contacting area ( 200 ) between the two hair-cutting units ( 150 , 160 , 170 ) of a respective one of three pairs of hair-cutting units ( 150 , 160 , 170 ).
12 . Electric shaver as claimed in claim 1 , comprising N hair-cutting units ( 150 , 160 , 170 , 1680 ), wherein the external cutting member ( 152 , 162 , 172 , 1682 ) of each of the N hair-cutting units ( 150 , 160 , 170 , 1680 ) is annular-shaped and wherein the N electrodes ( 180 a - d ) comprise N covering elements each arranged in a central position relative to the external cutting member ( 152 , 162 , 172 , 1682 ) of a respective one of the N hair-cutting units ( 150 , 160 , 170 , 1680 ).
13 . Electric shaver as claimed in claim 1 , comprising N hair-cutting units ( 150 , 160 , 170 , 1480 ), wherein each of the N electrodes ( 180 a - d ) is constituted by at least a skin-contacting portion of the external cutting member ( 152 , 162 , 172 , 1482 ) of a respective one of the N hair-cutting units ( 150 , 160 , 170 , 1480 ).
14 . Electric shaver as claimed in claim 13 , comprising three hair-cutting units ( 150 , 160 , 170 ), wherein the internal cutting member of each hair-cutting unit ( 150 , 160 , 170 ) is configured to make a linear reciprocating motion relative to the external cutting member ( 152 , 162 , 172 ) parallel to a longitudinal direction, and wherein the external cutting member ( 152 , 162 , 172 ) of each hair-cutting unit ( 150 , 160 , 170 ) has a longitudinal extension parallel to the longitudinal direction.
15 . Electric shaver as claimed in claim 1 , wherein the RF energy modulator ( 310 ) comprises N switch units ( 730 , 740 , 750 ) each configured to apply a respective one of the N periodic amplitude-modulated RF energy signals (S 1 , S 2 , S 3 ) to a respective one of the N electrodes ( 180 a - d ).