Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a rotary electric shaver which rotatively drives inner cutters, which are in resilient contact with inner bottom surfaces of circular outer cutters. 
         [0003]    2. Description of the Related Art 
         [0004]    There has been known a so-called rotary electric shaver which has circular or disk-shaped outer cutters and inner cutter rotating on the inner side of the outer cutters so that beard hair entering the hair introduction slits formed in the outer cutters is cut by the rotating inner cutters. As this type of electric shaver, there has been known in which outer cutter installing holes are formed in an outer cutter frame secured to a shaver main body and circular outer cutters are supported in the outer cutter installing holes such that the outer cutters are slightly movable in a vertical direction and slightly inclinable with respect to the outer cutter frame. 
         [0005]    However, the aforesaid construction provides the outer cutters with a limited movable range relative to the outer cutter frame, thus presenting a problem in that the close contact between the outer cutters and skin is restricted with resultant unsatisfactory shaving feeling or inadequate user-friendliness. It has been proposed, therefore, to provide a rim which is movable relative to the main body (the rim being also referred to as an outer cutter rim, an cutter circumferential rim, a skin supporting rim or a skin protecting rim) between the outer cutters and the main body (the outer cutter frame) so as to expand the movable range and the inclinable range of the outer cutters. 
         [0006]    JP 9-503424(T) (corresponding to WO 96/02368, U.S. Pat. No. 5,625,950 and EP 0719203) discloses a shaving apparatus which has a skin supporting rim ( 6 ) provided between an outer cutter and a main body (an outer cutter frame and a holder  2 ). The outer cutter is held by the rim such that it is slightly movable in a vertical direction and also slightly inclinable, and the outer periphery of the rim is pivotally supported by the outer cutter frame of the main body. More specifically, the rim enters a circular opening of the outer cutter frame, and a pair of projections provided on the outer periphery of the rim is engaged with the inner peripheral surface of the opening provided in the outer cutter frame. In other words, a pivotal supporting section is disposed between the outer periphery of the rim and the opening of the outer cutter frame. Further, adjoining rims are hinge-connected (e.g., by a tongue-and-groove joint). It has been required, therefore, to form the linear joint of the adjoining rims. In addition, the restoring force of an inclined rim has been imparted by an upward force of an inner cutter drive shaft or the force of restoration (the force for restoring from an inclination) of an inner cutter drive shaft to the upright position thereof. 
         [0007]    JP 2007-151925(A) (corresponding to US 2007-124936 (A1)) discloses a shaving apparatus in which the upper surface of a shaver main body (a head bottom plate) is provided with an upright wall (a supporting section  54 ) surrounding a cutter circumferential rim (cutter frame  18 ) holding an outer cutter, and each cutter circumferential rim is independently and pivotally retained to the upright wall. In other words, the upper surface of the shaver main body (the head bottom plate) is exposed between the cutter circumferential rims. 
         [0008]    JP 2007-117190(A) (corresponding to US 2007-089298(A1) and EP 1779983A1) discloses a shaving apparatuses in which a cutter unit ( 16 ) consisting of an assembly of an outer cutter and an inner cutter is pivotally retained in an outer cutter mounting aperture ( 20 ) formed in an outer cutter frame ( 18 ), which is openable/closable or detachable relative to a shaver main body. 
         [0009]    JP 2007-319339(A) (corresponding to US 2007-277379(A1) and EP 1862271A1) discloses a shaving apparatus in which an outer cutter frame ( 20 ) fixed to a shaver main body is provided with an outer cutter mounting hole ( 22 ) for mounting each cutter unit ( 18 ), a slit ( 50 ) extending toward the center of the shaver main body from an outer periphery is formed between adjoining outer cutter mounting hole ( 22 ), and a portion surrounding each of outer cutters ( 14 ) partitioned by the slit ( 50 ) is inclinable or bendable. 
         [0010]    According to the shaving apparatus disclosed in JP 9-503424(T) (corresponding to WO 96/02368, U.S. Pat. No. 5,625,950, and EP 0719203), the adjoining cutter circumferential rims (the skin supporting rims) are hinge-connected, so that the joint portion is linear, thus restricting the shapes or placements of the cutter circumferential rims. 
         [0011]    Further, pressing or depressing one cutter circumferential rim against the skin and inclining the cutter circumferential rim on the skin causes all cutter circumferential rims to be interlockingly pressed and tilted, resulting in an increase in a pressing force (depressing start pressure or an inclination start pressure) of each cutter circumferential rim. The pressing force or the inclining start pressure is set by an upward force or a force of an inner cutter drive shaft to restore from an inclination. The contact pressure applied by the inner cutter to the outer cutter cannot be set excessively low; otherwise, the performance for shaving beard or shaving feeling would be deteriorated. For this reason, it is difficult to set the pressing force of the cutter circumferential rims to an adequately small value. 
         [0012]    Further, according to the shaving apparatus disclosed in JP 9-503424(T) (corresponding to WO 96/02368, U.S. Pat. No. 5,625,950, and EP 0719203), the outer cutter and the rim are reset to their stationary positions by the force of the inner cutter drive shaft to restore to an upright position. Since the inner cutter drive shaft is normally vertical, the outer cutter will normally restore to a horizontal position. This presents a problem in that the inclination of the outer cutter at the stationary position cannot be arbitrarily set. There is another problem in that the inclinable range of the cutter circumferential rim is restricted. 
         [0013]    According to the shaving apparatus disclosed in JP 2007-151925(A) (corresponding to US 2007-124936(A1)), the upright wall of the upper surface of the shaver main body is exposed between adjoining cutter circumferential rims. This causes a problem such that the head assembly becomes inevitably larger, and shaving debris or beard trimmings easily adhere to the upper surface of the shaver main body, making it difficult to remove the debris. 
         [0014]    The shaving apparatus disclosed in JP 2007-117190(A) (corresponding to US 2007-089298(A1) and EP 1779983A1) presents a problem in that the outer cutter frame surrounding a plurality of cutter units inevitably becomes large, resulting in a large head unit. The one disclosed in JP 2007-319339(A) (corresponding to US 2007-277379(A1) and EP 1862271A1) has a drawback in that the cutter unit tilts (or bends) together with the portion partitioned by the slit of the outer cutter frame, thus restricting the movement of the outer cutter and also preventing easy cleaning. 
       SUMMARY OF THE INVENTION 
       [0015]    The present invention has been accomplished under the circumstances as aforementioned, and an object thereof is to provide a rotary electric shaver which is capable of enhancing the design freedom of the shape and placement of a cutter circumferential rim, accomplishing a reduced depressing force or an inclination start pressure of an outer cutter so as to allow the outer cutter to easily trace skin irregularities thereby to improve shaving feeling, permitting arbitrary setting of the tilt of the outer cutter in its stationary position according to user preference, expanding the inclinable range of the cutter circumferential rim, permitting a reduced size of a head unit, allowing the head unit to be easily cleaned, and enhancing the design freedom of a shaver surface. 
         [0016]    According to the present invention, the aforesaid object is achieved by a rotary electric shaver which pivotably retains a plurality of outer cutters on a head bottom plate at the top of a shaver main body and rotatively drives inner cutters while bringing the inner cutters into resilient contact with inner surfaces of the outer cutters, the rotary electric shaver comprising: 
         [0017]    a plurality of cutter circumferential rims, each which is detachable from the shaver main body, and separately surrounds and holds each of the outer cutters; 
         [0018]    a pivotal supporting section which pivotably retains the respective cutter circumferential rims on a pivotal axis passing the center of the respective outer cutters; and 
         [0019]    a detachable blind cover which fills a gap between the cutter circumferential rims and which is in resilient contact, from below, with a bottom edge of the cutter circumferential rim, the bottom edge being adjacent to the center of the shaver main body. 
         [0020]    The individual cutter circumferential rims are not joined to each other and pivotally move independently from each other, thus leading to less restriction on the shape and placement of the cutter circumferential rims. This allows the shape and placement of the cutter circumferential rims to be determined relatively freely. Hence, the shape and placement of the cutter circumferential rims or the like can be determined according to, for example, design requirements. 
         [0021]    Depressing or tilting one cutter circumferential rim requires the application of a depressing force which is larger than the resultant force of the upward force and the force of restoration from an inclination of a single inner cutter drive shaft associated with the cutter circumferential rim and an upward restoring force of the blind cover. The restoring force of the blind cover can be set to a sufficiently small value, and therefore the depressing start pressure or an inclination start pressure can be set to a sufficiently small value, thus making it possible to improve the traceability of the outer cutters relative to the skin with resultant better shaving feeling. At this time, the blind cover has already started to descend, so that the remaining cutter circumferential rims will be subjected to the upward force of one inner cutter which is in sliding contact with the outer cutter, thus requiring a relatively small depressing force for the remaining cutter circumferential rims to descend and tilt. With this arrangement, adjoining cutter circumferential rims will be easily depressed when a head unit is slid on the skin, and smooth movement can be achieved, leading to improved shaving feeling. 
         [0022]    Here, each of the cutter circumferential rims has a blind cover upwardly engaged therewith, so that the cutter circumferential rim restores to its stationary position by the force of restoration to an upright position of the inner cutter drive shaft and an upward force of the blind cover. Therefore, the inclination of the outer cutter can be arbitrarily set by appropriately setting the upward force of the blind cover. For example, the upper surface of the outer cutter can be inclined outward in its stationary mode. Moreover, the inclinable range of the cutter circumferential rims can be expanded. 
         [0023]    Furthermore, there is no need to provide the upper surface of the shaver main body (the head bottom plate) with a wall, namely, an upright wall, which surrounds the cutter circumferential rim, thus permitting a reduced size of the head unit. Further, since the upright wall is unnecessary and gaps among the cutter circumferential rims are covered by the blind cover, the chances of entry of shaving debris from thereunder are minimized and the detachable designs of the cutter circumferential rims and the blind cover permit easy removal of shaving debris. 
         [0024]    Preferably, the outer cutters are disposed at equal intervals in a circumferential direction around the center of the shaver main body (head), as observed in a top plan view, and each of the cutter circumferential rims is held on a straight line (pivotal axis) which is orthogonal to a straight line in a radial direction passing the center of the shaver main body and the center of the outer cutter and which also passes the center of the outer cutter, as observed in a top plan view, while the blind cover is held at the center of the shaver main body (head). In this case, the upward forces applied to the plurality of outer cutters will be equal and every outer cutter will share the same condition of use, thus providing excellent shaving feeling. 
         [0025]    Preferably, the blind cover is retained at the center of the main body such that the blind cover is movable in the vertical direction within a predetermined range and also free to move in an inclining direction, while being provided with an upward restoring tendency by a spring or the like. In this case, for example, a depressing force applied to one cutter circumferential rim causes the blind cover to descend while tilting, leading to improved traceability of the blind cover relative to the cutter circumferential rim. 
         [0026]    Preferably, the blind cover comprises a cylindrical pillar locked by a clicking mechanism or a snapping mechanism onto a cover mounting shaft rising from the center of the head bottom plate, a coil spring is accommodated in the pillar, and a coil spring is abutted against the upper end of the cover mounting shaft thereby to impart the upward restoring force to the blind cover. By setting the coil spring to a sufficiently low tension, the depressing force (descending start pressure) or the inclination start pressure of the cutter circumferential rims can be controlled to a sufficiently small value, permitting further improved shaving feeling. 
         [0027]    The blind cover preferably has a shape which extends out from the center of the main body in the radial direction via the gap between adjoining cutter circumferential rims. This makes it possible to minimize the size of the blind cover with a consequent reduced weight, permitting further improved traceability relative to the vertical movements of the cutter circumferential rims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a view of a rotary electric shaver, which is an embodiment of the present invention; 
           [0029]      FIGS. 2A and 2B  are exploded perspective views of a head unit of the rotary electric shaver in  FIG. 1 ,  FIG. 2A  illustrating the head unit with one cutter assembly removed, and  FIG. 2B  illustrating the head unit with all cutter assemblies removed; 
           [0030]      FIG. 3  is an exploded perspective view of one cutter assembly which has been disassembled and observed aslant from above; 
           [0031]      FIG. 4  is an exploded perspective view of one cutter assembly which has been disassembled and observed aslant from below; 
           [0032]      FIGS. 5A and 5B  are bottom views of the cutter assembly,  FIG. 5A  illustrating an outer cutter, an inner cutter, and a cutter retaining plate, which have been assembled, and  FIG. 5B  illustrating the cutter assembly from which the outer cutter, the inner cutter, and the cutter retaining plate have been all removed; 
           [0033]      FIGS. 6A and 6B  are side views of the head unit,  FIG. 6A  illustrating the head unit in a stationary state (a normal standby mode), and  FIG. 6B  illustrating the head unit, which has been tilted inward when a neighborhood of the center of the head unit has been depressed (an in-use mode); 
           [0034]      FIGS. 7A and 7B  are sectional side views of the cutter assembly,  FIG. 7A  illustrating a section which includes a pivotal axis C, and  FIG. 7B  illustrating a section which is orthogonal thereto; 
           [0035]      FIGS. 8A and 8B  are sectional side views of the cutter assembly with the inner cutter removed therefrom,  FIG. 8A  illustrating a section which includes a pivotal axis C, and  FIG. 8B  illustrating a section which is orthogonal thereto; and 
           [0036]      FIG. 9A  is a sectional side view of a blind cover mounting section, and  FIG. 9B  is a sectional top view of the blind cover mounting section taken at line B-B in  FIG. 9A . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0037]    Referring to  FIG. 1 , a rotary electric shaver  10  combines a main body  12  and a head unit  14 , which is mounted on the upper surface of the main body  12 , into one piece. The main body  12  mainly accommodates an electric motor, a battery, and a control circuit (none of them being shown). The head unit  14  has three outer cutters  16  disposed on an equilateral-triangular apexes. Three cutter assemblies  20  are detachably retained on a head bottom plate  18 , which provides the upper surface of the main body  12 , such that the three cutter assemblies  20  are disposed equidistantly (at 120-degree intervals) relative to a center P of the head unit  14 . 
         [0038]    Each of the cutter assemblies  20  is pivotable about a straight line (pivotal axis) C which is orthogonal to a straight line B in a radial direction passing a center P ( FIG. 2 ) of the head unit  14  and which passes a center Q of the outer cutter  16 . In other words, each of the three cutter assemblies  20  is independently supported by pivotal supporting sections  22  (refer to  FIG. 7A ) and pivotally moves about its pivotal axis C. 
         [0039]    As illustrated in  FIGS. 3 and 4 , the cutter assembly  20  comprises the outer cutter  16  shaped approximately like an inverted cup, an cutter circumferential rim (serving as a cutting member frame and also as a skin protection rim)  24  which holds the outer cutter  16 , a cutter retaining plate  26  detachably secured to the cutter circumferential rim  24  from below, an inner cutter  28  accommodated between the outer cutter  16  and the cutter retaining plate  26 , and an inner cutter shaft  30  made integral with the inner cutter  28 . The cutter circumferential rim  24  has a circular opening  32  through which the outer cutter  16  passes from below. Four divided arcuate guide walls  34  and  34   a,  which have a slightly larger diameter than that of the opening  32  and are arranged in the circumferential direction, are protrusively provided on the inner lower surface of the cutter circumferential rim  24 , as illustrated in  FIGS. 4 and 5 . A flange  16   a  ( FIGS. 4 and 7A ) provided on the opening rim of the outer cutter  16  engages a rim  32   a  of the opening  32  ( FIG. 4 ) from below, thus restricting an upward escape of the outer cutter  16  from the cutter circumferential rim  24 . The outer cutter  16  is vertically movable within a range of the heights of the guide walls  34 , which guide the flange  16   a  (the range denoted by “a” in  FIGS. 7A and 7B ). 
         [0040]    The cutter assembly  20  will now be described with reference to  FIGS. 5B and 8A . On the lower surface of the cutter circumferential rim  24 , a pair of upright walls  36 ,  36  is formed at positions where opposing portions of the guide walls  34 ,  34 , which oppose each other with the pivotal axis C therebetween, are expanded in the direction of the pivotal axis C. Each of these upright walls  36  has a small aperture  38  positioned on the pivotal axis C ( FIGS. 5 and 8 ). Projections  40   a  of pivotable axial members  40  penetrate these apertures  38  from the inside of the opening  32 . The projections  40   a  have semispherical distal ends, and only the distal portions jut out to the outside from the apertures  38  of the upright walls  36 . Inside proximal portions  40   b  of the pivotable axial members  40  have a diameter which is larger than that of the apertures  38 . The proximal portions  40   b  abut against the upright walls  36 , thereby defining the protrusion amounts of the projections  40   a  in the outward direction. Both ends of a wire spring  42 , which is substantially arcuate, are secured to the proximal portions  40   b  of the pair of right and left pivotable axial members  40 ,  40  on the inside diameter side, thereby imparting the outward restoring tendency. 
         [0041]    The cutter circumferential rim  24  is provided with another pair of guide walls  34   a,    34   a  on the opposite side from the guide walls  34 ,  34 , sandwiching the pivotal axis C therebetween. A semicircular descent wall  44  is formed on the outer side of the guide walls  34   a,    34   a  to surround the guide walls  34   a,    34   a.  Both ends of the descent wall  44  extend out to cover the outer sides of the upright walls  36 ,  36  (refer to  FIG. 4 ). The wire spring  42  is retained on the inner surface of the descent wall  44  by engaging a central portion thereof with a projecting first stopper  46  provided on the inner surface of the descent wall  44  (refer to  FIG. 7B  and  FIG. 8B ). Thus, both ends of the wire spring  42  are secured by being fitted in the proximal portions  40   b  of the pivotable axial members  40 . The wire spring  42  imparts a restoring force which pushes the projections  40   a,    40   a  of the pivotable axial members  40 ,  40  outward. 
         [0042]    As illustrated in  FIGS. 3 and 4 , the inner cutter  28  and the inner cutter shaft  30  are set in the outer cutter  16  from below the cutter circumferential rim  24  and then the cutter retaining plate  26  is attached to the cutter circumferential rim  24 . The cutter retaining plate  26  has an inner opening  26   a  at the center thereof through which a lower portion of the inner cutter shaft  30  passes, and outer openings  26   b  which surround the inner opening  26   a  and which let beard trimmings or shaving debris fall therethrough. The outer periphery of the cutter retaining plate  26  is provided with a lug  50 , which engages a projecting second stopper  48  formed in the descent wall  44  of the cutter circumferential rim  24 , and an attaching/detaching hook  52  positioned on the opposite side from the lug  50 . 
         [0043]    As illustrated in  FIGS. 7B and 8B , the cutter retaining plate  26  is fixed by first engaging the lug  50  with the second stopper  48  and then engaging the upper end of the hook  52  with an engaging aperture  54  provided in the guide wall  34  in a state the upper surface in the vicinity of the outer periphery of the cutter retaining plate  26  is abutted against an end surface of the guide wall  34  of the cutter circumferential rim  24  from below. The hook  52  has an operating end  58  formed as an integral portion thereof. By pushing the operating end  58  into the inside, the upper end of the hook  52  is disengaged from the engaging aperture  54 , thus allowing the cutter retaining plate  26  to be released from the cutter circumferential rim  24 . 
         [0044]    The cutter assembly  20  constructed as described above is detachably mounted on the head bottom plate  18  of the main body  10  by the pivotal supporting sections  22 . More specifically, three inner cutter drive shafts  56  projected from the head bottom plate  18 , and a pair of pillars  60  is installed in a protruding manner on the pivotal axis C of each of the three cutter assemblies  20 , each of the inner cutter drive shafts  56  being held therebetween (refer to  FIG. 2(B) ). Each of the pillars  60  has an engaging recess  62  with or from which the pivotable axial member  40  of the cutter assembly  20  engages or disengages. The engaging recess  62  may alternatively be a through hole and may have any shape as long as the shape allows the projection  40   a  at the distal end of the pivotable axial member  40  to engage therewith or disengage therefrom. 
         [0045]    A blind cover mounting shaft  64  projects out at the center of the head bottom plate  18  of the shaver main body  10 , and a trifurcate blind cover  66  is detachably installed onto the blind cover mounting shaft  64  ( FIG. 2B ). More specifically, a cylindrical pillar  68 , which is to be snapped onto the blind cover mounting shaft  64 , projects at the center of the bottom surface of the blind cover  66 . Pushing the pillar  68  down to fit it onto the outer periphery of the cover mounting shaft  64  by snapping or clicking secures the trifurcate blind cover  66  in place. The pillar  68  includes a coil spring  64   c  therein ( FIG. 9A ), which imparts an upward restoring tendency to the cover  66  when the blind cover  66  is secured onto the cover mounting shaft  64 . Each extended arm end of the blind cover  66  in the direction of the outer periphery is locked between the adjacent pillars  60 ,  60  of the head bottom plate  18  (refer to  FIG. 7B ). 
         [0046]    Here, the mounting section of the blind cover  66  will be described in detail. As illustrated in  FIG. 9A , the blind cover mounting shaft  64  has a smaller-diameter portion  64   b  beneath an upper end portion  64   a.  The inside diameter of the cylindrical pillar  68  is set such that the upper end portion  64   a  of the mounting shaft  64  is free to be slidable therein. A pair of slits  68   a,    68   a,  which extends in the circumferential direction, is formed, with the central axis of the pillar  68  sandwiched therebetween, in the lower outer periphery of the pillar  68 . A clip  68   b  made of an approximately U-shaped wire spring is installed in the slits  68   a,    68   a.    
         [0047]    The pillar  68  is joined to the mounting shaft  64 , the coil spring  64   c  being installed between the inner bottom of the pillar  68  and the upper end portion  64   a  of the mounting shaft  64 . More specifically, aligning the bottom end of the pillar  68  to the upper end portion  64   a  of the mounting shaft  64  and then pushing the bottom end of the pillar  68  downward causes the clip  68   b  to be pushed open once by the upper end portion  64   a  of the mounting shaft  64 , thus engaging the clip  68   b  with the smaller-diameter portion  64   b.  As a result, the blind cover  66  is free to move (vertically movable and also inclinable) within the range of the vertical dimension of the smaller-diameter portion  64   b  and is provided with an upward restoring tendency by the coil spring  64   c.  Further, the clip  68   b  abuts against the bottom edge of the upper end portion  64   a  from the side of the smaller-diameter portion  64   b,  thereby restricting the upward movable range of the blind cover  66 . This state is illustrated in  FIG. 9A . 
         [0048]    After attaching the cover  66  to the head bottom plate  18 , the cutter assembly  20  is detachably installed onto the pillars  60  with a click. More specifically, the lower end of the inner cutter shaft  30  is aligned with the inner cutter drive shaft  56  while setting the descent wall  44  of the cutter circumferential rim  24  of the cutter assembly  20  along the outer periphery of the head bottom plate  18 . An upward restoring tendency is imparted to the polygonal (rectangular) engaging head of the inner cutter drive shaft  56  by a coil spring (not shown) built in the inner cutter drive shaft  56 . The lower end of the inner cutter shaft  30  has an engaging recess in which the engaging head of the drive shaft  56  is locked. With such arrangement, by pushing the cutter assembly  20  downward, the inner cutter  28  comes in an upward resilient contact with the outer cutter  16  by the restoring force of the inner cutter drive shaft  56 . 
         [0049]    When the cutter assembly  20  is further pushed downward against the restoring force, the distal projection  40   a  of the pivotable axial member  40  attached to the cutter circumferential rim  24  comes in contact with the upper edge of the pillar  60  of the head bottom plate  18  and to be pushed in against the wire spring  42  until the projection  40   a  engages with the engaging recess  62  of the pillar  60  with a snap or a click. In this state, the cutter assembly  20  pivotally moves about the pivotable axial member  40 , i.e., the pivotal axis C. 
         [0050]    The restoring force of the coil spring built in the inner cutter drive shaft  56  is applied to the outer cutter  16  and the cutter circumferential rim  24  upward through the intermediary of the inner cutter  28 . The upward restoring force of the inner cutter drive shaft  56  acts on the pivotal axis C of the cutter circumferential rim  24  ( FIGS. 5 and 7 ), so that the upward restoring force is considered hardly effective for the cutter circumferential rim  24  to restore from an inclination. Meanwhile, the blind cover  66  is urged upward by the coil spring  64   c  in the pillar  68 , and the bottom surface of the cutter circumferential rim  24 , which bottom surface is adjacent to the center P of the head unit  14 , abuts against the blind cover  66  ( FIG. 9A ). Thus, the cutter assembly  20  becomes still and stable in the state illustrated in  FIG. 6A . At this time, a stepped portion  44   a  provided on the outer peripheral surface of the descent wall  44  of the cutter circumferential rim  24  (refer to  FIGS. 6 ,  7 B, and  8 B) abuts against a peripheral upper edge  18   a  of the head bottom plate  18  to position the cutter assembly  20 . 
         [0051]    With the three cutter assemblies  20  installed, pressing the central area of the head unit  14  against the skin to be shaved causes the cutter assemblies  20  to go down at the center of the head unit  14 . In other words, the central portion of the head unit  14  goes down about the pivotal axis C (the state illustrated in  FIG. 6B ). The upper surface of the cutter circumferential rim  24  is long (wide) in the direction of the pivotal axis C and short (narrow) in the direction orthogonal thereto. The cutter circumferential rim  24  pivotally and vertically moves in the direction orthogonal to the pivotal axis C, so that the pivotal movement of the cutter circumferential rim  24  and the descent of the outer cutter  16  prevent the contact pressure applied by the upper surface of the cutter circumferential rim  24  and the outer cutter  16  to skin from becoming excessive. This secures protection of skin. 
         [0052]    On the other hand, the cutter circumferential rim  24  does not pivotally move in the direction orthogonal to the pivotal axis C, so that the contact pressure on the skin on the pivotal axis will be absorbed only by the vertical movement of the outer cutter  16  relative to the cutter circumferential rim  24 , leading to a possibility of inadequate absorption of the contact pressure. However, the upper surface of the cutter circumferential rim  24  expands out over the pivotal supporting sections  22 , that is, expands in the direction of the pivotal axis C; therefore, the area of contact with the skin in the direction of the pivotal axis C is increased. This leads to a lower pressure of contact (the contact pressure per unit area) between the skin and the outer cutters, thus enhancing the protective effect for skin. 
         [0053]    The pivotal supporting sections  22  supporting the cutter circumferential rim  24  is not located between the cutter circumferential rim  24  and the head bottom plate  18 , which provides the outer cutter frame. Rather, the pivotal supporting section  21  is located under the cutter circumferential rim. This arrangement makes it possible to reduce the size of the head bottom plate  18  and minimize the chances of shaving debris adhering to the pivotal supporting sections  22 . Furthermore, each of the cutter assemblies  20  is detachably installed to the main body  10 , permitting easy cleaning of the head unit  14 . 
         [0054]    The cutter circumferential rims  24  of the three cutter assemblies  20  are in the state illustrated in  FIG. 6A , the portions thereof adjacent to the center of the main body (head unit) being pushed up by the blind cover  66 . Pushing down only one cutter circumferential rim  24  causes the blind cover  66  to descend also. Accordingly, when the head unit  14  is moved along a skin surface to be shaved, the adjacent cutter circumferential rims  24  can be depressed and inclined with an extremely small depressing force, since the blind cover  66  have already been down. This arrangement permits smooth movement of the head unit  14  and leads to improved shaving feeling. 
         [0055]    In addition, since the blind cover  66  pushes up the cutter circumferential rims  24 , the angles of the upper surfaces of the outer cutters  16  in the stationary (normal standby) mode can be set such that the outer cutters  16  are inclined outward, as illustrated in  FIG. 6A , rather than being restricted only to the setting by a restoring force for the inner cutter drive shaft to its upright position. This arrangement allows the movable and inclinable range of the outer cutters to be expanded.

Technology Category: 7