Abstract:
A rotary electric shaver including an outer cutter frame mounted on a shaver main body housing a motor therein, outer cutters held in an outer cutter mounting hole formed in this outer cutter frame the upper surfaces thereof providing skin contacting surfaces, and inner cutters that rotate while being pressed against the inner surfaces of the outer cutters and have cutter bodies for cutting hair entering hair introduction openings formed in the outer cutters; wherein the outer cutters are provided tiltable relative to the outer cutter frame, and the outer cutter frame is tiltable relative to the shaver main body.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an electric shaver and more particularly to a rotary electric shaver. 
         [0003]    2. Description of the Related Art 
         [0004]    Generally, in an electric rotary shaver, the outer surface of a ring-shaped top face (shaving portion), which is a thin layer portion, of an outer cutter(s) makes a skin contacting surface, and the inner cutter(s) that rotates while sliding against the inner surface of this shaving portion from below cut(s) whiskers (hair) advancing into hair introduction openings formed in the shaving portion of the outer cutter(s). In this type of electric shaver, hair introduction openings are formed in the thin shaving portion of the outer cutter so that they cross in substantially the radial direction, thus being substantially in the shape of slits of a certain width. In this structure, it is possible to make the outer cutter closely contact the curved surface of the skin being shaved by way of providing the outer cutter in a tiltable manner, thus enhancing the shaving feel. In such a rotary type shaver as this, two or three outer cutters are typically mounted in a holder (outer cutter frame). 
         [0005]    In such an electric shaver having two or three outer cutters, in order to enhance the tightness of the contact between the outer cutters and the skin, it is necessary to make the angle by which the outer cutters are allowed to tilt larger. If, however, the range of tilting of the outer cutters only is made larger, when the outer cutters tilt at the maximum, the circumferential edges of the outer cutters will strike the skin sharply, allowing the pressure of contact on the skin to become larger. As a result, problems arise that the skin is pressed into the hair introduction openings, causing deep shaving and skin damage, and further causing a burning sensation in the skin after the shaving. 
         [0006]    In Japanese Patent Application National Publication (Kohyo) No. H09-503424, in order to eliminate such problems, it is proposed that a skin support rim that surrounds the outer circumferences of the outer cutters be interposed between the outer cutters and the holder, and this skin support rim be divided for each outer cutter or coupled so as to be bendable, so that the respective portions of the skin support rim be made tiltable relative to the outer cutters and holder, either independently or linked together. One example thereof is a structure in which a pair of projections (support members) that protrude outward in the outer radial direction are provided in the skin support rim surrounding each outer cutter, and these projections are engaged in the inner circumferential surfaces of the outer cutter mounting holes of the holder. 
         [0007]    However, this structure has problems. Since tiltable skin support rims are provided between the holder and the outer cutters, a large number of precision parts are required for the shaver head, and thus it is inevitable that the structure becomes complex. 
         [0008]    On the other hand, there is a shaver that includes outer cutters provided directly in a holder (outer cutter frame) without using skin support rims.  FIGS. 8(   a ) through  8 ( d ) show the shaver head of such a conventional shaver.  FIG. 8(   a ) is a top view thereof, and  FIGS. 8(   b ) to  8 ( d ) are views seen from point a in  FIG. 8(   a ).  FIG. 8(   b ) illustrates the normal condition of the outer cutters, and the tilted conditions of the outer cutters are shown in  FIGS. 8(   c ) and  8 ( d ).  FIGS. 9(   a ) and  9 ( b ) show the skin pressed in the vicinity of the center of the outer surface of the shaver head, and  FIGS. 10(   a ) and  10 ( b ) show the skin pressed in the vicinity of the periphery of the outer surface of the shaver head. 
         [0009]    In  FIGS. 8(   a ) through  8 ( d ), the reference numeral  1  refers to a shaver head,  2  an outer cutter frame (outer cutter holder), and  3  outer cutters. The outer cutter frame  2  is secured to the upper surface of a shaver main body (not shown) that has a motor therein. In the outer cutter frame  2 , three outer cutter mounting holes  4  are formed at, respectively, the positions of the apexes of an equilateral triangle, and outer cutters  3  are respectively installed in the outer cutter mounting holes  4  from below. More specifically, each one of the outer cutter  3  is shaped substantially as a shallow cylinder with the top closed, having radially formed hair introduction openings (slits)  5  formed in the circular top face (shaving portion) thereof (see  FIG. 8(   a )), while the open end thereof is formed with a flange bent in the outer circumferential direction, so that the flange engages the outer cutter mounting hole  4  of the outer cutter frame  2  from below. 
         [0010]    Against the inner surfaces (lower surfaces) of the circular shaving (top) portions of the outer cutters  3 , inner cutters (not shown) are pressed from below by springs and are rotated by the motor. In other words, a drive shaft, which is rotationally driven by the motor installed inside the shaver main body and to which an upward oriented return propensity is imparted, is engaged with each one of the inner cutters. The inner cutters are thus pressed against the inner surfaces of shaving portions of the outer cutters  3  by the upward oriented return force (upward pushing force) of the drive shaft; and thus, the outer cutters  3  can be pushed down inside the outer cutter mounting hole  4 , and they also can tilt. 
         [0011]    When a convex portion of the skin  6  comes into contact with the outer cutter frame  2  as seen from  FIG. 8(   c ), the outer cutters  3  tilt toward the inside to a maximum angle β 1 . When, on the other hand, a concave portion of the skin  6  comes in to contact with the outer cutter frame  2  as shown in  FIG. 8(   d ), the outer cutters  3  tilt toward the outside to a maximum angle β 2 . 
         [0012]    When a convex portion and a concave portion of the skin  6  come into contact with the outer cutter frame  2  substantially evenly, the skin  6  contacts the area X indicated by diagonal hatching lines in  FIG. 8(   a ). In other words, the skin  6  comes into contact with the area X on the upper surface of the outer cutter frame  2  excluding the outer cutter mounting holes  4 . For this reason, the contact pressure with which the skin  6  contacts the outer cutters  3  will not become excessive, and deep shaving can be prevented. 
         [0013]    When the curvature of the convex portion of the skin  6  is small, the skin  6  contacts only in the vicinity of the center of the outer cutter frame  2  as seen from  FIGS. 9(   a ) and  9 ( b ). The diagonally hatched portion Y in  FIG. 9(   b ) indicates the area of the skin  6  to which the shaver comes into contact during shaving. Conversely, when the curvature (in the opposite direction) of a concave portion of the skin  6  is small, the skin contacts only on the outer circumferential side of the outer cutter frame  2  as illustrated by diagonally hatched lines in  FIG. 10(   b ). In other words, the diagonally hatched portions Z in  FIG. 11(   b ) indicate areas of the skin  6  to which the shaver comes into contact in this situation. 
         [0014]    As seen from the above, when the curvature of the convex portion or concave portion of the skin  6  is small, the contact areas Y and Z become small, as shown in  FIG. 9(   b ) and FIG.  10 ( b ), the use efficiency of the outer cutters  3  lowers, the shaving efficiency declines, and the shaving feel deteriorates. 
       BRIEF SUMMARY OF THE INVENTION 
       [0015]    Accordingly, the object of the present invention, which is devised in view of such circumstances as described above, is to provide a rotary electric shaver which is suitable for implementing small shaver head size without involving complex structure, and with which it is possible to enhance the outer cutter utilization efficiency, and enhance the shaving feel when, in particular, the curvature of concave or convex portions of the skin is small. 
         [0016]    The above object is accomplished by a unique structure of the present invention for a rotary electric shaver that includes:
       a shaver main body housing therein a motor,   an outer cutter frame mounted on the shaver main body,   an outer cutter(s) provided in an outer cutter mounting hole(s) formed in the outer cutter frame, an outer surface of the outer cutter providing a skin contacting surface, and   an inner cutter(s) that rotates while being pressed against an inner surface of the outer cutter(s) and has cutter bodies for cutting hair entering hair introduction openings formed in the outer cutter; and       
 
         [0021]    in the present invention, the outer cutter(s) is provided so as to be tiltable relative to the outer cutter frame, and the outer cutter frame is provided so as to be tiltable relative to the shaver main body. 
         [0022]    In the present invention, as seen from the above, the outer cutter(s) can tilt relative to the outer cutter frame, and this outer cutter frame can also tilt relative to the shaver main body. Accordingly, the shaver has an even greater maximum angle to which the outer cutter(s) tilts relative to the shaver main body. As a result, the outer cutter(s) have expanded contact surface areas relative to the skin; and thus the outer cutter utilization efficiency is high, and enhanced shaving feel is provided. It is also possible to prevent deep shaving, since the angle of tilt of the outer cutter(s) relative to the outer cutter frame is prevented from becoming excessive. Furthermore, because the outer cutter frame itself tilts relative to the shaver main body, complex structure can be avoided, and the shaver head is well suited to being made smaller. 
         [0023]    In the present invention, when a plurality of outer cutters are provided in the outer cutter frame, a corresponding number of outer cuter mounting holes are formed in the outer cutter frame, and bend-allowing portions or means are provided between the adjacent outer cutter mounting holes, so that the bend-allowing means allow portions of the outer cutter frame surrounding the outer cutters tilt either independently or together with other portions. The bend-allowing means can be slits that are cut from the outer circumference of the outer cutter frame toward the center of the outer cutter frame. 
         [0024]    Three outer cutters can be provided at equal intervals in the circumferential direction in the outer cutter frame; and in this structure, the outer cutter frame is provided with three slits provided at equal angles of 120° apart, and the outer cutter frame is attached to said shaver main body at three circumferential portions of the outer cutter frame that are between adjacent two slits. In addition, in this structure, the center part of the outer cutter frame is formed so as to be depressible. 
         [0025]    In the present invention, for instance, such a structure can be employed that
       outer circumferential lower portions of the outer cutter frame which are between adjacent slits are made in contact with the shaver main body so as to make support points, and   projections arising from the shaver main body side and near the support points are engaged with the outer circumferential inner surface of the outer cutter frame. In the outer cutter frame of the present invention, three outer cutters are typically provided at equal intervals in the circumferential direction; however, one or two outer cutters can be provided, and more than three outer cutters can also be provided.       
 
         [0028]    In the present invention, the outer cutter(s) is tiltable relative to the outer cutter frame. However, the outer cutter(s) can also be provided so as to be both tiltable and depressible. With the tiltable and depressible outer cutter(s), the movable range of the outer cutter(s) increases even further, and the advantages of the present invention increases even further. 
         [0029]    Moreover, in the present invention, an outer cutter upward pushing spring load can be set to be smaller than an outer cutter frame upward pushing spring load. In this structure, when the skin is pressed against the shaver, the outer cutter(s) will first either tilt or depressed, and then the outer cutter frame will tilt. Thus, setting the spring force is made easy. The outer cutter upward pushing spring load can be set by a drive shaft return spring; and the outer cutter frame upward pushing force can be set by the springiness which the outer cutter frame itself has and by an upward pushing spring that elastically supports the inner cutter holder. An upwardly oriented return propensity is constantly imparted to the outer cutter(s) by the outer cutter upward pushing force, and, in conjunction therewith, an upwardly oriented spring load is applied to the outer cutter frame as well. 
         [0030]    In the present invention, the outer cutter frame bends every time the tilt angle changes; as a result, when a bending force is repeatedly applied to the outer cutter frame, there is a danger that damages develop in the bending portion(s) due to fatigue, deteriorating the durability. Accordingly, in the present invention, a flat spring having a plurality of erected portions that respectively erect on the horizontally outer sides of the outer cutter mounting holes of the outer cutter frame is provided in the outer cutter frame. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0031]      FIG. 1  is front view of the rotary electric shaver according to one embodiment of the present invention; 
           [0032]      FIG. 2  is a vertical cross-sectional view of the shaver head of the shaver of the present invention; 
           [0033]      FIG. 3  is a vertical cross-sectional view of one cutter unit of the shaver of the present invention, comprising an outer cutter and an inner cutter, combined; 
           [0034]      FIG. 4(   a ) is a top view of the outer cutter frame used in the shaver of the present invention,  FIGS. 4(   b ) through  4 ( d ) being side elevation views thereof; 
           [0035]      FIG. 5(   a ) is a top view of the outer cutter frame combined with outer cutters,  FIGS. 5(   b ) through  5 ( g ) being side elevation views thereof; 
           [0036]      FIG. 6(   a ) is a top view of the outer cutter frame of another embodiment of the present invention,  FIG. 6(   b ) being a side elevation view thereof,  FIG. 6(   c ) being a bottom view thereof,  FIG. 6(   d ) being a top view of the spring used in the outer cutter frame of  FIG. 6(   a ), and  FIG. 6(   e ) being a side elevation view of the spring; 
           [0037]      FIG. 7(   a ) is a top view of the outer cutter frame of still another embodiment of the present invention,  FIG. 7(   b ) being a side elevation view thereof,  FIG. 7(   c ) being a bottom view thereof,  FIG. 7(   d ) being a top view of the spring used in the outer cutter frame of  FIG. 7(   a ), and  FIG. 7(   e ) being a side elevation view of the spring; 
           [0038]      FIG. 8(   a ) is a top view of a shaver head of a conventional rotary shaver,  FIGS. 8(   b ) through  8 ( d ) being side views thereof; 
           [0039]      FIGS. 9(   a ) and  9 ( b ) illustrate the shaver head of a conventional rotary shaver in use; and 
           [0040]      FIGS. 10(   a ) and  10 ( b ) illustrate the shaver head of a conventional rotary shaver in use. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]      FIG. 1  shows a shaver according to one embodiment of the present invention,  FIG. 2  shows a vertical cross-section of the shaver head of the shaver of  FIG. 1 ,  FIG. 3  shows a vertical cross-section of one cutter unit that comprises an outer cutter and an inner cutter,  FIG. 4(   a ) is a top view of the outer cutter frame of the shaver of  FIG. 1 , and  FIGS. 4(   b )- 4 ( d ) are side views thereof.  FIG. 5(   a ) is a top view of the outer cutter frame in which outer cutters are installed, and  FIGS. 5(   b )- 5 ( g ) are side views thereof.  FIG. 2  is a cross-section taken along the lines II-II in  FIG. 5(   a ). 
         [0042]    In  FIG. 1 , the reference numeral  10  refers to a shaver main body, and  12  is a shaver head. The shaver head  12  is detachably attached to the upper part of the shaver main body  10  or is attached to the upper part of the shaver main body  10  so that it is opened and closed. To this shaver head  12 , three sets of cutter units  18  each comprising, among others, an outer cutter  14  and an inner cutter  16  (described subsequently), are attached. The centers of three outer cutters  14  that correspond to the three cutter units  18  are located at the apexes of an equilateral triangle. 
         [0043]    The shaver head  12  has an outer cutter frame  20  ( FIG. 1 ) that can open and close (openable) upward relative to the shaver main body  10  or that can be attached and detached (detachable) with respect to the shaver main body  10 . The outer cutters  14  are installed in three outer cutter mounting holes  22  formed in the outer cutter frame  20 . The cutter units  18  that respectively include the outer cutters  14  are urged upward; in other words, the outer cutters are urged in a direction that the outer cutters  14  protrude upward. 
         [0044]    Each outer cutter  14  is made of metal sheet formed into a substantially shallow topped bowl or cylinder that is upwardly convex (see  FIGS. 2 and 3 ). The top portion of the outer cutter  14  is circular, and a substantially circular opening is formed in the center of this circular top portion so that an outer cutter cover  24  is secured in this opening from above. An engagement recess  26  is formed in the bottom of the outer cutter cover  24 ; and in to this engagement recess  26 , the tip of the inner cutter  16  is engaged so that axial wobble of the inner cutter  16  is prevented. 
         [0045]    In the circular top portion of the outer cutter  14  shown in  FIG. 3 , a single ring-shaped groove  28  is formed so that it is centered on the center axis x that is, when seen from above, a center of rotation of the inner cutter  16 ; and as a result, a pair of internal and external ring-shaped outer cutter thin layer portions are formed so that the internal and external thin layer portions sandwich the ring-shaped groove  28  in between. The outer surfaces of these outer cutter thin layer portions make skin contacting surfaces, while the inner surfaces thereof form inner cutter tracks  30   a  and  30   b  in which the cutter blades of the inner cutter slide. 
         [0046]    In the outer cutter  14 , numerous long slit-shaped hair introduction openings  32  (see  FIGS. 1 and 5(   a ) are formed, in substantially the radial direction, so that the hair introduction openings  32  cross the thin layer portions from the center axis x thereof (see  FIGS. 2 and 3) . The lower surfaces of ribs  34  that remain between adjacent hair introduction openings  32  in the outer cutter thin layer portions constitute outer cutter blades that work together with the inner cutter  16  to cut the hair. Thus, the top portion of each outer cutter forms a shaving portion 
         [0047]    The outer surface of the top portion of each outer cutter  14 , that is, the outer surfaces of the ribs  34 , are positioned on a plane which is perpendicular to the center axis x (the center axis x being a perpendicular line), as seen from  FIGS. 2 and 3 . In other words, the outer surfaces of the ribs  34  are flat. 
         [0048]    The inner surface of the top portion (or thin layer portion) of each outer cutter  14  (that is, the bottom surfaces of the ribs  34 ) respectively constitute inner cutter tracks (ring-shaped tracks)  30   a  and  30   b . The inner surfaces (bottom surfaces) of these inner cutter tracks  30   a  and  30   b  ride on a plane y shown in  FIG. 3  that is perpendicular to the center axis x, as seen from below (from the inside). This plane y coincides with the bottom surfaces of the ribs  34  of the outer cutter. These inner surfaces of the outer cutter are polished by a grindstone, thus cutting edges are formed along the lower edges of the ribs  34 . 
         [0049]    The inner cutter  16  has a hub unit  36 , made of a resin, opening downward in substantially conical shape, and numerous cutter bodies  38  are secured at equal intervals in the circumferential direction of the hub unit  36  to surround the hub unit  36 . The cutter bodies  38  can be connected in a ring shape to form a single piece. Each of the cutter bodies  38  has an upper part that is divided in a two-pronged shape; and two cutter blades  40   a  and  40   b , which are the divided parts, slide in and against the inner cutter tracks  30   a  and  30   b , respectively, from below. The upper edges of these cutter blades  40   a  and  40   b  from cutting edges or blade edges, which are polished horizontally along the above-described plane y. 
         [0050]    As seen from  FIG. 3 , the hub unit  36  has an engagement hole  42  of a square shape, when seen from below (or in horizontal cross-section), so that it opens downward; and into this engagement hole  42 , a drive shaft  44 , which protrudes out from the shaver main body  10 , engages. In the upper end of this drive shaft  44 , a plate-shaped engagement head  46  is formed, and this engagement head  46  is engaged with the engagement hole  42  of the hub unit  36  of the inner cutter  16  from below. The drive shaft  44  is rotationally driven by a motor (not shown), which is housed inside the shaver main body  10 , and rotates the inner cutter  16 . 
         [0051]    The drive shaft  44  has a return propensity in an upwardly protruding direction due to a return spring  44 A (see  FIG. 2 ) that pushes the inner cutter  16  upward. As a consequence, the cutter blades  40   a  and  40   b  of the inner cutter  16  are elastically pushed in and against the inner cutter tracks  30   a  and  30   b  of the outer cutter  14  from below. The outer cutter  14 , moreover, is formed with a flange  48  that protrudes outwardly from the bottom outer circumference, and this flange  48  engages the interior of the outer cutter mounting hole  22  of the outer cutter frame  20  from below. As a consequence, the cutter unit  18  that is comprised of the outer cutter  14  and the inner cutter  16  can sink downward (or is depressed), exhibiting elasticity, relative to the outer cutter frame  20 . In other words, the upward return force from the return spring  44 A of the drive shaft  44  generates an outer cutter upward pushing spring load that pushes the outer cutter  14  upward. 
         [0052]    Next, the outer cutter frame  20  will be described with reference to  FIGS. 1 ,  4 , and  5 . 
         [0053]    The outer cutter frame  20  is a substantially triangular shape when seen from above. The portions of the vicinity of the three apexes of the substantially triangle outer cutter frame  20  are formed into a circular arc shape so as to surround the cutter units  18 , and the outer circumferences are bent downward. In this outer cutter frame  20 , three outer cutter mounting holes  22  into which the three outer cutters  14  are inserted are formed at positions constituting the apexes of an equilateral triangle, and three slits  50  are respectively formed between adjacent two outer cutter mounting holes  22  so that, as best seen from  FIG. 5(   a ), each of the slits  50  advances inwardly from the outer circumference between two outer cutter mounting holes  22 . In other words, in the shown embodiment, each of three slits  50  is formed from the side wall to the top surface of the outer cutter frame  20 , starting from the lower edge of the side wall of the outer cutter frame  20  to substantially the middle point between the upper edge of the side wall to the center of the outer cutter frame  20 , so that the slits  50  constitute a tilt-allowing portion or means (or bend-allowing portion or means) that allows the portions surrounding the outer cutters  14  to tilt (or bend). 
         [0054]    With this outer cutter frame  20 , as will be described subsequently, three areas of the lower surfaces A in the circular arc shaped corners of the triangle outer cutter frame  20  (see  FIG. 4(   a )) are brought into contact with the shaver main body  10  so as to make support points. When the central area of the outer cutter frame  20  is pressed downward, the outer cutter frame  20  bends so that the central area is depressed. The outer cutter frame  20 , then, can return to the condition shown in  FIG. 2  by the elasticity of the outer cutter frame  20  itself, by the return springs  44 A installed in the drive shafts  44 , and by an outer cutter upward pushing spring  56  described subsequently, when the pressing force is removed. In other words, by  FIG. 4(   b ) it is shown that the outer cutter frame  20  is in a free condition in which no external force applied thereto; and in this situation, the outer cutter mounting holes  22  (or a plane defined by each cutter mounting holes  22 ) tilt toward the outer circumference so that they incline outwardly at an angle B 0  from the center of the outer cutter frame  20 . The tilt plane of the outer cutter mounting holes  22  in this situation is indicated by the reference symbol B 3 . 
         [0055]    When, as shown in  FIG. 4(   c ), a downward external force F 1  is applied on near the center of the outer cutter frame  20 , the outer cutter frame  20  tilts or bends with a help of the slit(s)  50 , and such central area descends with the vicinities of the circumferential edge lower surfaces A as support points or center of tilting or bending, and the outer cutter mounting holes  22  are positioned substantially horizontal as indicated by angle B 1 . 
         [0056]    When the downward external force intensifies and becomes F 2 , then as shown in  FIG. 4(   d ), the outer cutter frame  20  further tilts or bends with a further help of the slit(s)  50 , the central area of the outer cutter frame  20  descends and is depressed, so that the angle of the outer cutter mounting holes  22  is inverted to take the angle B 2 . 
         [0057]    The above-described outer cutter frame  20  is installed in the shaver main body  10  in such a manner as illustrated in  FIG. 2 . In other words, a frame member  10 A is fitted on the upper end of the shaver main body  10 , and an inner bottom plate  10 B is provided on this frame member  10 A to cover it. The frame member  10 A is in contact with the outer cutter frame  20  at support points A which are located at three locations (see  FIG. 4(   a )) on the outer cutter frame  20  as described above and is separated from the circumferential edge of the outer cutter frame  20  except at these support points A. In other words, three outer cutter frame clearances  20   a  are respectively provided between the frame member  10 A and the inner bottom plate  10  and below the above-described three slits  50 , so that portions of the outer cutter frame near the respective slits  50  can be lowered into the clearances  20   a ; and the central area of the outer cutter frame  20  is able to move up and down by the elasticity of the outer cutter frame  20  itself and to the elasticity of the return spring  44 A and outer cutter upward pushing spring  56 , etc. 
         [0058]    Three of the above-described drive shafts  44  pass through the inner bottom plate  10 B. The inner bottom plate  10 B has, as seen from  FIG. 2 , raised portions that are positioned with gaps with respect to the outer cutter frame  20  in the vicinity of positions facing the support points A of the outer cutter frame  20 . Inside these gaps, three erected portions  10 C′ of a flat spring  10 C, which is secured to the lower surface of the inner bottom plate  10 B, are located. The upper ends  10 C″ of the erected portions  10 C′ of the flat spring  10 C, which are positioned on the horizontally outer sides of the outer cutter mounting holes  22  of the outer cutter frame  20 , are bent in a U-shape (lateral U-shape) and engaged with concavities  20 A formed in the inner surface of the outer cutter frame  20 . In other words, the upper ends  10 C″ of the erected portions  10 C′ of the flat spring  10 C are respectively engaged with the concavities  20 A which are formed in the inner circumferential surface of the outer cutter frame  20  and near the three support points A. The outer cutter frame  20  is thus held on the shaver main body  10  by the three erected portions  10 C′ of the flat spring  10 C and three support points A. Instead of the above described flat spring  10 C, three flat springs ( 10 C) respectively having erected portions ( 10 C′) with the upper ends ( 10 C″) engaged with the concavities ( 20 A) can be employed. 
         [0059]    As seen from  FIG. 2 , the outer cutter frame  20  is supported from below by an outer cutter frame holder  52 , and this outer cutter frame holder  52  is in turn supported by an inner cutter holder  54 . The outer cutter frame holder  52  has projections  52   a  formed so as to erect for supporting the outer cutter frame  20  at a plurality of locations in the circumferential direction. The inner cutter holder  54  is held by a knob  58 , which is connected to the center part  20 B of the outer cutter frame  20 , with the outer cutter upward pushing spring  56  in between. 
         [0060]    More specifically, the knob  58  passes through the center of the inner cutter holder  54  and is prevented from being separated from the inner cutter holder  54  by a C-ring  58   a . Externally-threaded screw is formed on the tip portion of the knob  58  so that it engages an internally-threaded screw  20 C that is securely inserted in the outer cutter frame  20 . 
         [0061]    Accordingly, when the knob  58  is screwed into the internally-threaded screw  20 C, the outer cutter frame holder  52  and the inner cutter holder  54  are pressed by the spring pressure of the outer cutter upward pushing spring  56  and held in the outer cutter frame  20 . 
         [0062]    The outer cutter frame holder  52  is provided such that the inside of the center part  52   d  thereof is movable downward with a certain play relative to the center part  20 B of the outer cutter frame  20 , and the circumferential edge part  52   c  of outer cutter frame holder  52  is supported by the upper surface of the inner cutter holder  54 . 
         [0063]    Three inner cutters  16  are commonly mounted, so as to be movable with a certain play, on the inner cutter holder  54 . More specifically, openings  54   a  into which the hub units  36  of the inner cutters  16  are inserted are formed in the inner cutter holder  54 ; and the inner cutters  16  are held in the inner cutter holder  54  by engagement between pawls  54   b  of the inner cutter holder  54  and expanded-diameter portions  36   a  of the hub units  36  of the inner cutters  16 . In this structure, the pawls  54   b  protrude in the inner radial direction (or protrude inwardly) from the inner circumferential edge of the openings  54   a  of the inner cutter holder  54 , and the expanded-diameter portions  36   a  are formed outwardly at the lower edges of the hub units  36  of the inner cutters  16 . The outer cutter frame holder  52  is, as described above, elastically supported in the center part of the outer cutter frame  20  by the inner cutter holder  54 , knob  58 , and outer cutter upward pushing spring  56 . 
         [0064]    The action of the outer cutter frame  20  in the shaver described above of the shown embodiment will be described below with reference to  FIGS. 5(   a ) through  5 ( g ). 
         [0065]    In the assembled condition of the shaver head  12  or when the shaver is not in use, the upper surface of the outer cutter frame  20  is, as seen from  FIG. 4(   b ), tilted so that the center part  20 B (see  FIG. 2)  thereof is higher than the outer circumference portion thereof. In this situation, the tilt angle of the upper surface of the outer cutter frame  20  relative to a horizontal plane is, as shown in  FIG. 4(   b ), B 0 ; and the outer surface of the top faces of the outer cutters  14  are parallel to the thus tilted upper surface of the outer cutter frame  20  as shown in  FIG. 5(   c ); and thus, the angle K 0  subtended by the tilt angle B 0  of the outer cutter frame  20  and the outer cutters  14  is 0°. R 2  in  FIG. 5(   c ) shows the concave curved surface of the skin to be shaved. 
         [0066]      FIG. 5(   b ) shows a situation in which the concave curved surface of the skin is smaller than at the time represented in  FIG. 5(   c ) (when the curvature is greater). In this case, the tilt or angle of the outer cutter frame  20  is unchanged, and only the outer cutters  14  tilt outwardly, along the skin curved surface R 1 , so that the tilt angle of the outer cutters  14  relative to the outer cutter frame  20  becomes K 1 . 
         [0067]    In the situation of  FIG. 5(   d ) in which the curvature of the concave curved surface R 3  of the skin is smaller than in  FIG. 5(   c ), the tilt or angle of the outer cutter frame  20  is unchanged, and only the outer cutters  14  tilt (inwardly) at a tilt angle K 2 . 
         [0068]    In the situation of  FIG. 5(   e ), the shaver is brought up against a comparatively flat skin surface R 4  (a cheek, for instance). The center area of the outer cuter frame  20  is pressed by the skin surface R 4 ; and as a result, the outer cutter frame  20  tilts or bends with a help of the slit(s)  50 , and the upper surface of the outer cutter frame  20  becomes substantially parallel with the top faces of the outer cutters  14 . 
         [0069]      FIG. 5(   f ) shows a situation that shaving is performed on the skin (the chin, for instance) in which the curvature of the convex curved surface R 5  is relatively large and opposite from the situation of  FIG. 5(   b ). In this situation, the outer cutter frame  20  further tilts or bends with a further help of the slit(s)  50 , so that the tilt angle of the outer cutters  14  relative to the outer cutter frame  20  becomes K 1 ′. 
         [0070]      FIG. 5(   g ) illustrates a case that the shaving is performed on the curved surface R 6  that is of greater convex compared to  FIG. 5(   f ) with the curvature even smaller. In this situation, the outer cutter frame  20  even further tilts or bends with an even further help of the slit(s)  50 , so that the tilt angle of the outer cutters  14  relative to the outer cutter frame  20  is K 2 ′ that is greater than the tilt angle K 1 ′ in  FIG. 5(   f ). 
         [0071]    In the structure of the above-described embodiment, the range of the tilt angle of the outer cutters  14  relative to the outer cutter frame  20  is K 1  to K 2  as shown in  FIGS. 5(   b ) to  5 ( g ), and the outer cutter frame  20  can tilt with an angle of B 0  to B 2  as diagrammed in  FIGS. 4(   b ) to  4 ( d ). As a result, tilting of the outer cutters  14  becomes possible for a total range of (K 1 +B 0 ) to (K 2 ′+B 2 ). Accordingly, the shaver has broadened contact surface areas of the outer cutters relative to skin irregularities, thus, the shaver has an enhanced outer cutter utilization efficiency and provides an improved shaving feel. Furthermore, the circumferential edges of the outer cutters  14  are prevented from biting into the skin by the surface B 3  (see  FIG. 4(   b )) of the outer cutter frame  20 , and thus deep shaving is prevented. 
         [0072]      FIGS. 6(   a ) through  6 ( e ) show another example of the outer cutter frame of the present invention.  FIG. 6  ( a ) is a top view of the outer cutter frame,  6 ( b ) a side view thereof, and  6 ( c ) a bottom view thereof.  FIG. 6(   d ) is a top view of a flat spring used in this embodiment, and  6 ( e ) is a side view of this flat spring. In the outer cutter frame  120  of this example, the durability of the outer cutter frame  120  is higher than that of the previously described outer cutter frame, and the freedom of elastic force setting is made larger. 
         [0073]    More specifically, in this example of  FIGS. 6(   a ) through  6 ( e ), a substantially three-pronged shape flat spring  150 , which extends from the center of the outer cutter frame  120  to three areas that are respectively between adjacent outer cutter mounting holes  122 , is secured in the inner central surface of the outer cutter frame  120 . This flat spring  150  is secured to the inner surface of the outer cutter frame  120  by thermal bonding or by an adhesive or the like, so that damages resulting from fatigue when the center part of the outer cutter frame  120  is repeatedly pushed down is prevented, thus increasing the durability, and increasing the range of up and down movement of the center part of the outer cutter frame  120 . 
         [0074]    The flat spring  150  preferably is made of, for instance, a thin stainless steel sheet that has outstanding springiness. A thin sheet having a thickness of 0.2 mm, for instance, is very suitable. In  FIGS. 6(   a ) through  6 ( c ), those parts of the shaver that are the same as in the above-described embodiment are designated with the same reference symbols, and no description thereof is provided. The diagonally hatched areas in  FIG. 6(   c ) are portions that constitute the support points A. 
         [0075]      FIGS. 7(   a ) through  7 ( e ) show still another example of the outer cutter frame of the present invention.  FIG. 7(   a ) is a top view of the outer cutter frame,  7 ( b ) a side view thereof, and  7 ( c ) a bottom view thereof.  FIG. 7(   d ) is a top view of a flat spring used in this example, and  FIG. 7(   e ) is a side view of this flat spring. In this example, the flat spring  250  has a different shape from that of the flat spring  150  in the example shown in  FIGS. 6(   c ) through  6 ( e ). 
         [0076]    More specifically, in the flat spring  250  used in the outer cutter frame  220 , the three tip ends are bifurcated; in other words, the tip ends of the flat spring  150  described above are each divided into a two-pronged shape, so that the tip ends extend along the outer circumferences of the outer cutter mounting holes  22  formed in the outer cutter frame  220 . With this flat spring  250  having bifurcated tip ends, the area of contact between the flat spring  250  and the inner surface of the outer cutter frame  220  is enlarged, and the effectiveness achieved by securing the flat spring  250  is enhanced. In  FIGS. 7(   a ) through  7 ( e ), those parts that are the same as those of  FIGS. 6(   a ) through  6 ( e ) are designated with the same reference symbols, and no further description thereof is provided.