Patent Publication Number: US-6212776-B1

Title: Electric shaver

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electric shaver and more particularly to an electric rotary shaver. 
     2. Prior Art 
     Generally, in electric shavers, particularly in electric rotary shavers, inner cutters are rotated on the under surface of outer cutters; and the hair is cut by the shearing force generated between these two cutters. In some shavers, only one single shaving unit that consists of an inner cutter and an outer cutter is installed in the shaver head of the shaver; and there are also shavers in which two shaving units or three shaving units are installed in the shaver head, each being called a twin-headed shaver and a triple-headed shaver, respectively. In the twin-headed shaver, the shaving units are arranged side by side; and in the three-headed shavers, the shaving units are generally arranged in an inverse equilateral triangle shape so as to obtain the most efficient shaving results. 
     In any of these shavers currently marketed, only the inner cutters are rotated by a motor installed inside the shaver casing so that the shearing force is obtained between the rotating inner cutter and the non-rotating outer cutter which are designed to be inwardly depressible during shaving. 
     Since the outer cutter which ordinarily has radial slits for introducing facial hair is not rotated as described above, the hair does not enter into the slits easily, resulting in that shaving is occasionally not performed efficiently. So as to execute a smooth and efficient shave, it is common to move the shaving head (and therefore the outer cutters) circularly on, for example, the face, which sometimes causes muscle fatigue in the arm that holds the shaver; and therefore, such a prior art shaver has a problem with the shaving effect and with the use thereof. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of the present invention is to provide an electric shaver that can reduce the necessity of circular movements of the shaver in use, thus ensuring an easy, quick and smooth shave. 
     It is another object of the present invention to provide an electric shaver having high hair raising and take-in efficiency and hair cutting efficiency by way of a rotatable outer cutter(s) and a rotatable inner cutter(s). 
     It is still another object of the present invention to provide an electric shaver which includes a rotatable outer cutter(s) which can function as a “comb” so as to smoothly raise and bring the hair into the slits formed on the outer cutter(s) and further between the outer cutter(s) and inner cutter(s), thus ensuring a smooth and quick shave. 
     The above-described objects of the present invention are accomplished by a unique structure for an electric rotary shaver which includes at least one shaving unit that comprises an outer cutter (outer cutting member) and an inner cutter (inner cutting member) so that not only is the inner cutter rotated but also the outer cutter is rotated via a series of gears provided between a single rotary power source and the shaving unit(s). In other words, according to the electric shaver of the present invention, the outer cutter(s) is provided with a ring gear(s) on, for example, its circumferential surface(s), and this ring gear(s) is meshed with a gear(s) rotated by a transmission gear(s) which is rotated by a drive gear(s) that causes the corresponding inner cutter(s) to rotate. 
     Furthermore, according to the present invention, the outer cutter(s) and the inner cutter(s) are rotatable not only in the same directions but also in the opposite directions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an explanatory illustration showing the inside of the first embodiment of the electric shaver according tithe present invention wherein the shaver includes two pairs of inner and outer cutting members; 
     FIG. 2 is an exploded perspective view showing the essential portion thereof; 
     FIG. 3 is an explanatory illustration showing the inside of the essential portion thereof being viewed from the direction of lines  3 — 3  in FIG. 2; 
     FIG. 4 is a perspective view of an outer cutting member that is employed in the present invention; 
     FIG.  5 ( a ) is a partially sectional explanatory illustration showing one meshing connection between the gear of an outer cutting member and a gear that rotates the outer cutting member, and FIG.  5 ( b ) is a partially sectional explanatory illustration showing another meshing connection between the gear of an outer cutting member and a gear that rotates the outer cutting member; 
     FIG. 6 is a plan view showing the gear arrangement employed in the first embodiment of the present invention; 
     FIG. 7 is a plan view showing the gear arrangement which is different from the one employed in the first embodiment shown in FIG. 6; 
     FIG. 8 is a plan view showing the gear arrangement employed in the second embodiment of the present invention in which the shaver includes three pairs of inner and outer cutting members; 
     FIG. 9 is a sectional explanatory illustration showing the meshing connection between the gear of one of three outer cutting members and a relay gear that rotates the outer cutting member employed in the second embodiment of the present invention; and 
     FIG. 10 is a plan view showing the gear arrangement which is different from the one employed in the second embodiment shown in FIG.  8 . 
     FIG. 11 is a plan view showing the gear arrangement employed in the third embodiment of the present invention in which the shaver includes one pair of inner and outer cutting members; and 
     FIG. 12 is a plan view showing the gear arrangement which is different from the one employed in the third embodiment shown in FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described in detail below based upon the embodiments with reference to the accompanying drawings. 
     FIG. 1 shows the inside of the shaver according to the first embodiment of the present invention, FIG. 2 is an exploded perspective view showing the essential portion thereof, and FIG. 3 shows the cross section thereof. 
     In these Figures, the electric shaver is generally referred to by the reference numeral  10 , and it includes a shaver housing  12  and two shaving units each substantially comprising an outer cutting member  20  and an inner cutting member  30 . The tip end of the inner cutting member  30  is in contact with an inner surface of a circular top end wall of the outer cutting member  20 . 
     The shaver housing  12  is opened at one end and a removable head frame  16  covers this open end; and the shaver housing  12  is provided therein with a mounting plate  12   a  and a drive shaft holder  12   b . A cutting member retaining frame  12   c  is detachably mounted to the undersurface of the head frame  16  by way of a fixing screw  12   c ′. Furthermore, a single electric motor  14  that is actuated by an AC and/or DC power source, a battery  18  which actuates the motor  14 , and an ON-OFF switch  19  which connects the motor  14  and battery  18  are provided in the shaver housing  12 . 
     The head frame  16  is provided so as to be elastically snap-fitted to the shaver housing  12  in a removable fashion; and each of two outer cutting members  20  is fitted in each of two circular apertures  16   a  opened in the head frame  16 . The circular apertures  16   a  are slightly larger in diameter than the outer cutting members  20 . Typically, the outer cutting member  20  is, as best shown in FIG. 4, comprised of a shallow cylinder made of metal having the circular top end portion with hair entry apertures  20 ′ that are slits opened radially. 
     Furthermore, each of the outer cutting members  20  is provided with a ring gear  22 . The ring gear  22  is made of, for example, plastic and securely fixed on the outer circumferential surface of the outer cutting member  20  as shown in FIG.  4 . As best seen in FIG.  5 ( a ), the root area of the outer cutting member  20  is situated on the inner side of the head frame  16  so that the outer cutting member  20  is in a circular aperture  16   a  opened in the head frame  16 , and the ring gear  22  of the outer cutting member  20  is located between the flange  20   a  of the outer cutting member  20  and the head frame  16  so that the outer cutting member  20  is prevented from coming off of the head frame  16 . 
     The inner cutting members  30  and outer cutting members  20  are provided between the head frame  16  and the cutting member retaining frame  12   c ; and each of the inner cutting members  30  is, as seen from FIG. 3, positioned inside each of the outer cutting members  20  so that the inner cutting member  30  is (as described below) rotated inside the outer cutting member  20  by the drive motor  14 . Two inner cutting members  30  are connected to the motor  14  via a motor shaft gear  14   a , two primary gear wheels  50 , two primary drive shafts  60  and rotation transmission blocks  32  which are attached to the inner cutting members  30 . These elements for rotating the inner cutting members  30  are referred to as an inner cutting member drive assembly. 
     More specifically, the motor  14 , secured to the mounting plate  12   a , has a motor shaft gear  14   a  on its output shaft  14 ′, and this motor shaft gear  14   a  is meshed with two primary gear wheels  50  (only one is shown in FIG.  3 ). Each of the primary gear wheels  50  is rotatably journalled on a primary spindle  12   x  (only one shown) which is fixed in the mounting plate  12   a . Each of the primary gear wheels  50  has a hollow hub  52  at the center which has a cavity inside so as to accommodate a flange  62  of each of two primary drive shafts  60  (only one shown) which has a hollow bore inside. The flange  62  formed at one end of the primary drive shaft  60  is coupled to the inside of the hollow hub  52  of the primary gear wheel  50  so that the primary drive shaft  60  is coaxially coupled to the primary gear wheel  50  and rotated thereby. A coil spring  64  is provided inside the hollow bore of each of the primary drive shafts  60  so as to be compressed between the primary drive shafts  60  and the primary gear wheels  50 , thus pressing the primary drive shaft  60  towards the head frame  16 . Accordingly, the outer flange  20   a  of the outer cutting member  20  is urged towards the head frame  16  by the coil spring  64 ; and when the shaver is in use, the outer cutting member  20  can be depressed, against the driving force of the coil spring  64 , toward the inside of the shaver housing  12  together with the inner cutting member  30  and primary drive shaft  60 . 
     In other words, the outer cutting members  20 , the inner cutting members  30  and the primary drive shafts  60  are depressible in the direction toward the mounting plate  12   a  during the use of the shaver; and each of the primary drive shafts  60  is able to make a swivel motion because of the spaces between the outer surface of the primary drive shaft  60  and the inner surfaces of the hollow hub  52  and because of the spaces between a first shaft hole  12   b   1  of the drive shaft holder  12   b  and the surface of the primary drive shaft  60 . Thus, it is facilitated that a coupling tongue  66  formed at other end of each primary drive shafts  60  engages the engagement hole  32   a  of the rotation transmission block  32  attached to each inner cutting member  30 . 
     Furthermore, a single secondary gear wheel  100  is rotatably journalled on a secondary spindle  12   y  which is fixed in the mounting plate  12   a . The secondary gear wheel  100  is, like the primary gear wheels  50 , provided with a hollow hub  102  at the center which has a cavity inside so as to accommodate the flange  112  of the secondary drive shaft  110  which has a hollow bore inside. This flange  112  formed at one end of the secondary drive shaft  110  is coupled to the inside of the hollow hub  102  of the secondary gear wheel  100  so that the secondary drive shaft  110  is coaxially coupled to the secondary gear wheel  100  and rotated by the secondary gear wheel  100 . A secondary coil spring  104  is provided inside the hollow bore of the secondary drive shaft  110  so that the secondary coil spring  104  can be compressed between the secondary drive shaft  110  and the secondary gear wheel  100  and presses the secondary drive shaft  110  in the direction toward the head frame  16 . The secondary drive shaft  110  has a coupling tongue  116  at its other end which is engaged with a tip end gear  120 . 
     The tip end gear  120  comprises a gear portion  120   a  and rotation transmission portion  120   b  and is provided so that the gear portion  120   a  is located between the head frame  16  and the cutting member retaining frame  12   c . The tip end gear  120  has a pin  124  that engages a recess  16   b  (see FIG.  5 ( a )) formed in the inner surface of the head frame  16  so as to allow end the gear  120  to be rotatable; and the gear tooth  120   c  formed on the gear portion  120   a  of the tip end gear  120  is meshed with the ring gears  22  that are attached to the outer cutting members  20 , and the rotation transmission portion  120   b  is engaged with the coupling tongue  116  of the secondary drive shaft  110  via an engagement hole  120   d  formed in the rotation transmission portion  120   b  so that the tip end gear  120  is rotated by the secondary drive shaft  110 . 
     In the above structure, because of the presence of the second coil spring  104 , the secondary drive shaft  110  can make a swivel motion by way of a space between the outer surface of the secondary drive shaft  110  and the inner surface  102   b  of the hollow hub  102  and a space between the outer circumference of the secondary drive shaft  110  and the inner surface of a secondary shaft hole  12   b   2  of the drive shaft holder  12   b . Thus, the coupling tongue  116  of the secondary drive shaft  110  easily can engage the engagement hole  120   d  of the rotation transmission portion  120   b  of the tip end gear  120 . 
     In the embodiment above, as shown in FIG.  5 ( a ), the ring gear  22  is provided on the outer circumferential surface of the outer cutting member  20  and meshed with the gear  120   c  circumferentially formed on the tip end gear  120 . However, as shown in FIG.  5 ( b ), the outer cutting member  20  may have a ring gear  22   a  on the under end surface so that the ring gear  22   a  is meshed with an annular gear tooth  120   e  formed on the upper end surface of the tip end gear  120 . 
     Furthermore, a transmission spindle  12   z  is fixed to the mounting plate  12   a , and a transmission gear  130  is rotatably journalled on this transmission spindle  12   z . The transmission gear  130  is provided between one of two primary gear wheels  50  and the secondary gear wheel  100  and meshed with these gear wheels  50  and  100  so that the rotation of one of the two primary gear wheels  50  rotates the transmission gear  130  and the rotation of the transmission gear  130  rotates the secondary gear wheel  100 . 
     The secondary gear wheel  100 , the secondary drive shaft  110  and the tip end gear  120  provided adjacent to the inner cutting member drive assembly described above are referred to as an outer cutting member drive assembly. 
     FIG. 6 shows the gear arrangement employed in the above embodiment, and it particularly shows the motor gear  14   a ′, two primary gear wheels  50 , transmission gear  130 , secondary gear wheel  100 , tip end gear  120  and two ring gears  22  provided on the outer cutting members  20 . 
     As seen from FIG. 6, the gear G 1  (which corresponds to the motor shaft gear  14   a  in FIGS. 2 and 3) is meshed with two gears G 2   a  and G 2   b  (each corresponding to the two primary gear wheels  50 ) which are installed side by side. The gear G 3  (which corresponds to the transmission gear  130  in FIGS. 2 and 3) is meshed with one (G 2   a ) of the two gears G 2   a  and G 2   b  and also with the gear G 4  (which corresponds to the secondary gear wheel  100  in FIGS.  2  and  3 ). The gear G 4 ′ (which corresponds to the tip end gear  120 ) is provided on the same axis as the gear G 4  (with the secondary drive shaft  110  in between), and the gear G 4 ′ is meshed with two gears G 5   a  and G 5   b  (each corresponding to the ring gears  22  attached to the two outer cutting members  20  in FIGS.  2  and  3 ). 
     With the gear arrangement described above, when the gear G 1  (motor shaft gear  14   a ) is rotated by the motor in one direction P, the gears G 2   a  and G 2   b  (primary gear wheels  50 ) which are meshed with the gear G 1  are rotated in another (or opposite) direction N. In other words, the inner cutting members that are rotated by the primary gear wheels  50  (gears G 2   a  and G 2   b ) are rotated in the direction N. On the other hand, when the gear G 2   a  is thus rotated in the direction N, the gear G 3  (transmission gear  130 ) meshed with the gear G 2   a  is rotated in the direction P; as a result, the gear G 4  (secondary gear wheel  100 ) meshed with the gear G 3  is rotated in the direction N. Since the gear G 4 ′ (tip end gear  120 ) is axially provided on the gear G 4 , the gear G 4 ′ is rotated in the direction N; and when the gear G 4 ′ is thus rotated in the direction N, the two gears G 5   a  and G 5   b  (ring gears  22 ) which are meshed with the gear G 4 ′ are rotated in the direction P. In other words, the two outer cutting members that have the ring gears  22  (gears G 5   a  and G 5   b ) are rotated in the direction P by the end gear  120  (gear G 4 ′). 
     With the structure described above, the two inner cutting members are rotated in one direction N, and the two outer cutting members are rotated in another or opposite direction P. In other words, the inner cutting members and the outer cutting members are rotated in different or opposite directions from each other. 
     FIG. 7 shows a modification of the above embodiment; and in this embodiment of FIG. 7, the inner and outer cutting members are rotated in the same direction. 
     As seen in FIG. 7, an auxiliary transmission gear G 3   a  is interposed between and meshed with gear G 3  (corresponding to the transmission gear  130 ) and the gear G 4  (corresponding to the secondary gear wheel  100 ), so that the rotation of gear G 3  is transmitted to the gear G 4  via the auxiliary transmission gear G 3   a.    
     Accordingly, unlike the embodiment shown in FIGS. 2 and 3, when the gear G 3  (transmission gear  130 ) is rotated in the direction P by the gear G 2   a  (primary drive gear  50 ), the gear G 4  (secondary gear wheel  100 ) is rotated in the direction P by the presence of the auxiliary transmission gear G 3   a  which is rotated in the direction N by the gear G 3 , and the gear G 4 ′ (tip end gear  120 ) provided axially on the gear G 4  is also rotated in the P direction. As a result, the gears G 5   a  and G 5   b  (ring gears  22 ) of the outer cutting members  20 , which are meshed with the gear G 4 ′ rotating in the direction P, are rotated in the direction N. Thus, the two outer cutting members that have ring gears  22  (gears G 5   a  and G 5   b )are rotated in the direction N which is the same rotational direction of the two inner cutting members. 
     As seen from the above, the shaver according to the above embodiment that has two pairs of inner and outer cutting members has a structure that comprises: 
     a shaver housing provided therein with a single motor which has a motor gear attached to an output shaft thereof; 
     a mounting plate provided inside the shaver housing; 
     two primary gear wheels rotatably provided, side by side, on the mounting plate and meshed with the motor gear so as to be rotated in one direction by the motor gear; 
     two primary drive shafts coaxially coupled to the primary gear wheels so as to be rotated in one direction by the primary gear wheels; 
     two inner cutting members coupled to the primary drive shafts so as to be rotated by the primary drive shafts in one direction; 
     a transmission gear rotatably provided on the mounting plate and meshed with one of two primary gear wheels so as to be rotated thereby in another direction which is opposite from one direction; 
     a secondary gear wheel rotatably provided on the mounting plate and meshed with the transmission gear so as to be rotated thereby in one direction; 
     a secondary drive shaft coaxially coupled to the secondary gear wheel so as to be rotated in one direction by the secondary gear wheel; 
     a tip end gear coupled to the secondary drive shaft so as to be rotated thereby in one direction; and 
     two outer cutting members provided so that each one of two inner cutting members is situated in each one of two outer cutting members, each of the outer cutting members being provided thereon with a ring gear which is meshed with the tip end gear so as to be rotated in another direction; 
     and therefore, it is possible to rotate two outer cutting members and two inner cutting members in the opposite direction; and, alternately, with an addition of an auxiliary transmission gear, it is also possible to rotate two outer cutting members and two inner cutting members in the same direction. 
     FIG. 8 shows the gear arrangement employed in the second embodiment of the present invention. 
     In this embodiment, three pairs of outer and inner cutting members are installed in an equilateral triangle (inverse equilateral triangle) configuration; and three inner cutting members are rotated in one direction and three outer cutting members are rotated in another direction which is opposite thereto. The basic structure of the second embodiment is the same as the first embodiment described above, and the second embodiment is an extension of the basic structure of FIGS. 2 and 3 from a two cutter system to three cutter system; accordingly, the second embodiment will be described with reference only to the gear engagement shown in this FIG.  8 . 
     As seen from FIG. 8, the gear G 1  (which represents a motor shaft gear  14   a  in FIGS. 2 and 3) is provided at the center of three gears G 2   a , G 2   b  and G 2   c  (each representing primary gear wheel  50  in FIGS. 2 and 3) which are arranged in an inverse equilateral triangle shape and meshed therewith. The gear G 3  (which represents a transmission gear  130  in FIGS. 2 and 3) is meshed with the gear G 2   a  and also with gear G 4  (which represents a secondary gear wheel  100  in FIGS.  2  and  3 ). Gear G 4 ′ (which represents a tip end gear  120  in FIGS. 2 and 3) is provided on the same axis as the gear G 4  so as to be rotated thereby, and the gear G 4 ′ is meshed with two gears (G 5   a  and G 5   b ) of the three gears G 5   a , G 5   b  and G 5   c  (each representing the ring gears  22  of the three outer cutting members  20  in FIGS. 2 and 3) which are arranged, like the three gears G 2   a , G 2   b  and G 5   c , in an inverse equilateral triangle shape. 
     In this second embodiment, a relay gear G 6  is additionally provided so as to mesh with the gear G 5   b  and a gear G 5   c . In other words, the gear G 6  is rotatably provided on the undersurface of the head frame  16  as shown in FIG. 9 by way of the reference numeral  140  and is meshed with one (G 5   b ) of two gears (G 5   a  and G 5   b ) and the remaining gear G 5   c  (ring gear  22 ). 
     Accordingly, when the gear G 1  (motor gear) is rotated by the motor in one direction P, the gears G 2   a , G 2   b  and G 2   c  (primary wheel gears  50 ) which are meshed with the gear G 1  are all rotated in another (or opposite) direction N. In other words, the three inner cutting members are rotated in the direction N. On the other hand, when the gear G 2   a  is thus rotated in the direction N, the gear G 3  (transmission gear  130 ) meshed therewith is rotated in the direction P; as a result, the gear G 4  (secondary gear wheel  100 ) meshed with the gear G 3  is rotated in the direction N. Since the gear G 4 ′ (tip end gear  120 ) is on the same axis as the gear G 4 , the gear G 4 ′ is rotated in the direction N. When the gear G 4 ′ is thus rotated in the direction N, gears G 5   a  and G 5   b  (ring gears  22 ) which are meshed with the gear G 4 ′ is rotated in the opposite direction P. When the gear G 5   b  is thus rotated in the direction P, the gear G 6  (relay gear  140 ) meshed therewith is rotated in the direction N; as a result, the gear G 5   c  which is meshed with the gear G 6  (ring gear  22 ) is rotated in the direction P. In other words, the gears G 5   a , G 5   b  and G 5   c  are all rotated in the direction P, and the three outer cutting members having the ring gears  22  that correspond to the gears G 5   a , G 5   b  and G 5   c  are all rotated in the direction P. 
     With the structure described above, in this second embodiment, the three inner cutting members are rotated in one direction N, and the three outer cutting members are rotated in another direction P. In other words, the inner cutting members and the outer cutting members are rotated in different or opposite directions from each other. 
     The embodiment shown in FIG. 10 includes, in addition to the structure of FIG. 8, an auxiliary transmission gear G 3   a  is provided between the gear G 3  (transmission gear) and gear G 4  (secondary gear wheel) so that the auxiliary transmission gear G 3   a  is meshed with these gears G 3  and G 4 . 
     Accordingly, when the gear G 3  (transmission gear  130 ) is rotated in the direction P, the auxiliary transmission gear G 3   a  is rotated in the direction N which causes the gear G 4  (secondary gear wheel) to rotate in the direction P so that the gears G 5   a  and G 5   b  (ring gears  22 ), which are provided on the outer cutting members and meshed with the gear G 4 , are rotated in the direction N by the gear G 4 ′ which is rotated by the gear G 4 . Since the gear G 5   b  is thus rotated in the direction N, the relay gear G 6  is rotated in the direction P which causes the remaining gear G 5   c  (ring gear  22 ) provided on the outer cutting member to rotate in the direction N. 
     Thus, three inner cutting members and three outer cutting members are rotated in the same direction N. 
     As seen from the above, the shaver having three inner cutting members and three outer cutting members has a structure that comprises: 
     a shaver housing containing therein a single motor which has a motor gear attached to an output shaft thereof; 
     a head frame provided at one end of the shaving housing; 
     a mounting plate provided inside the shaver housing; 
     three primary gear wheels rotatably provided on the mounting plate and meshed with the motor gear so as to be rotated in one direction by the motor; 
     three primary drive shafts, each being coaxially coupled to each one of the three primary gear wheels so as to be rotated in one direction by the primary gear wheels; 
     three inner cutting members, each being coupled to each one of the three primary drive shafts so as to be rotated in one direction by the primary drive shafts; 
     a transmission gear rotatably provided on the mounting plate and meshed with one of three primary gear wheels so as to be rotated thereby in another direction which is opposite from one direction; 
     a secondary gear wheel rotatably provided on the mounting plate and meshed with the transmission gear so as to be rotated thereby in one direction; 
     a secondary drive shaft coaxially coupled to the second gear wheel so as to be rotated thereby in one direction; 
     an end gear coupled to the second drive shaft so as to be rotated thereby in one direction; 
     a relay gear provided on the head frame; and 
     three outer cutting members provided so that each one of three inner cutting members is situated in each one of three outer cutting, the three cutting members being provided with ring gears, respectively, the ring gears provided on two of the three outer cutting members being meshed with the end gear being rotated in another direction by the end gear; and the ring gear provided on a remaining one of the three outer cutting members being meshed with the relay gear which is meshed with the ring gear provided on either one of the two of the three ring gears, 
     therefore, it is possible to rotate three outer cutting members and three inner cutting members in the opposite direction; and, alternately, with an addition of an auxiliary transmission gear, it is possible to rotate three outer cutting members and three inner cutting members in the same direction. 
     FIG. 11 schematically shows the gear arrangement of the third embodiment of the present invention in which one inner cutting member and one outer cutting member are provided so as to rotated in the same direction. The basic structure of the third embodiment is the same as the first and second embodiments described above and has a simplified structure compared to a two or three cutter system. Accordingly, the third embodiment will be described with reference only to the gear engagement shown in this FIG.  11 . 
     More specifically, when the motor activated, the gear G 1  or motor shaft gear  14   a  is rotated in one direction P; and since the gear G 2  (representing a primary gear wheel  50 ) is meshed with this gear G 1  (motor shaft gear  14   a ), the gear G 2  is rotated in another (or opposite) direction N. Accordingly, the inner cutting member that is connected to a first drive shaft which is coaxially coupled to the gear G 2  is rotated in the direction N by the gear  2  (primary gear wheel  50 ). 
     Meanwhile, when the gear G 2  (the primary gear wheel  50 ) is rotated by the gear G 1  (motor shaft gear  14   a ) in the direction N as described above, the gear G 3  (representing a transmission gear  130 ) meshed with this gear G 2  is rotated in the direction P; and therefore, the gear G 4  (representing a secondary gear wheel  100 ) which is meshed with this gear G 3  is rotated in the direction N, and the gear G 4 ′ (representing a tip end gear  120 ) coupled to the gear G 4  via the secondary drive gear ( 110 ) is rotated in the direction N. As a result, gear G 5  or the ring gear  22  of the outer cutting member which is meshed with the gear G 4 ′ (tip end gear  120 ) is rotated in the direction P, and the outer cutting member to which the gear G 5  or the ring gear  22  is attached is rotated in the direction P. 
     As seen from the above, the inner cutting member is rotated in one direction N, and the outer cutting member is rotated in another or opposite direction P. In other words, the inner cutting member and the outer cutting member are rotated in different or opposite directions from each other. 
     FIG. 12 shows a modification of the third embodiment shown in FIG. 11; and in this modified embodiment, the inner cutting member and the outer cutting member are rotated in the same direction. 
     More specifically, as seen from FIG. 12, an auxiliary transmission gear G 3  ( 130   a ) is additionally provided between the gear G 3  (transmission gear  130 ) and gear G 4  (secondary gear wheel  100 ) so that the rotation of the gear G 3  is transmitted to the gear G 4  via the auxiliary transmission gear G 3   a.    
     Accordingly, unlike the embodiment of FIG. 11, the gear G 4  (secondary gear wheel  100 ) is rotated in the direction P when the gear G 3  (transmission gear  130 ) is rotated in the direction P because of the presence of the auxiliary transmission gear G 3   a  ( 130   a ), and so is the gear G 4 ′ (tip end gear  120 ). Thus, the gear G 5  or the ring gear  22  of the outer cutting member that meshes the gear G 4 ′ (tip end gear  120 ) is rotated in the opposite direction N, and the inner cutting member is, therefore, rotated in the direction N, which is the same rotational direction of the outer cutting member. 
     In any of the above embodiments, it should be noted that the tooth shapes of the gears, the sizes or the diameters of the gears, and the number of teeth of each one of the gears shown in FIGS. 1 through 12 are merely illustrative for explanation purposes and do not represent the gear elements (such as the shapes of the gears and teeth, the sizes or the diameters of the gears, the gear ratio, the number of gear teeth, meshing configurations, etc.) of each one of the gears utilized in actual products. It is contemplated that any gear ratio and number of rotations of the inner and outer cutting members can be employed so as to secure the best shaving result. In addition, though the outer cutting member(s) and the inner cutting member(s) can be rotated by different rotational numbers, it is preferable that the outer cutting member(s) be rotated slower than the inner cutting member(s). For instance, when the inner cutting member(s) is rotated at a speed of 2500±500 (or 2,000-3,000) rpm, it is desirable to set the outer cutting member(s) to be at a speed of less than 100 rpm, preferably at a speed of 40-80 rpm. In other words, a good shaving effect can be obtained when the inner cutting member(s) and the outer cutting member(s) are rotated at a rotational ratio of approximately 42:1. 
     Furthermore, in any of the above embodiments, the transmission gear  130  (or gear G 3 ) is rotated by the primary gear wheel(s)  50  (gear(s) G 2 , G 2   a , G 2   b  G 2   c ) so as to rotate the secondary gear wheel  100  (or gear G 4 ) which rotates the outer cutting member(s)  20  via the secondary drive gear  110 , tip end gear  120  (gear G 4 ′) and ring gear(s)  22  (gear(s) G 5 , G 5   a , G 5   b , G 5   c )). However, it can be designed so that the transmission gear  130  (G 3 ) is directly rotated by the motor  14 . In this case, the transmission gear  130  (G 3 ) is coupled to the output shaft  14 ′ of the motor  14  (instead of being rotatably journalled on the transmission spindle  12   z ) and meshed with the primary gear wheel(s)  50  and the secondary gear wheel  100  so as to rotate the primary and secondary drive shafts  60  and  110 ; in addition, a gear that corresponds to the motor shaft gear  14   a  (G 1 ) is rotatably provided on the mounting. plate  12   a  and meshed with the primary gear wheel(s)  50 . With this structure, the same function and effect as the above embodiments is obtainable. 
     As seen from the above, according to the present invention, not only the inner cutting member(s) but also the outer cutting member(s) are rotated by a single power source, and, in addition, these inner cutting member(s) and outer cutting member(s) are rotated in the same direction or in the opposite directions. Accordingly, the rotating outer cutting member(s) can raise the lying hair to introduce the raised hair into the slits (hair entry apertures) of the outer cutting member(s), so that shaving can be done extremely easily, efficiently and smoothly.