Abstract:
A rotary electric shaver provided with a plurality of cutter units, each of which has an outer cutter ( 72 ) and an inner cutter ( 84 ), which rotates while elastically contacting the outer cutter from below. The shaver comprising: a plurality of outer cutter assemblies ( 70 ), each of which is made integral with a cutter circumferential rim ( 74 ) having the outer cutter of each cutter unit secured thereto and which is movably retained in a mounting port formed in the cutter frame ( 66 ), a pushup plate ( 92 ) which contacts the outer cutter assembly from below to push up the outer cutter assembly, a cutter retaining plate ( 90 ) which is retained by the cutter frame and which is positioned below the pushup plate, and an outer cutter float spring ( 94 ) which is compressively interposed between the cutter retaining plate and the pushup plate to impart an upward return tendency to the pushup plate. Each outer cutter can independently move, thus ensuring smooth vertical movement or rocking of the outer cutter and also permitting an increased shaving area.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a rotary electric shaver in which a cutter frame held by a shaver main body is provided with a plurality of cutter units, each of which includes an outer cutter and an inner cutter to be rotated while bringing the inner cutter into resilient contact with the outer cutter from below. 
         [0003]    2. Description of the Related Art 
         [0004]    In this type of electric shaver, when a substantially discoid outer cutter is pressed against skin with a high pressing force, the outer cutter tends to deeply dig into the skin, undesirably causing excessively deep shaving or an excessive pressure of contact between the outer rim of the outer cutter and the skin, possibly resulting in discomfort of the user of the shaver. As a solution thereto, it has conventionally been proposed to surround the outer periphery of the outer cutter by a cutter circumferential rim (skin supporting rim) so as to prevent the contact pressure between the outer cutter and skin from becoming excessive (refer to JP 09-503424(T). 
         [0005]    In the rotary electric shaver disclosed in the aforesaid JP 09-503424(T) (corresponding to WO 96/02368, U.S. Pat. No. 5,625,950 and EP 0719203A), the cutter circumferential rim (skin supporting rim) is movably retained relative to a cutter frame, and the outer cutter is movably retained relative to the cutter circumferential rim. When the outer cutter is brought into firm contact with skin, the skin around the outer cutter depresses the cutter circumferential rim, so that the contact pressure is distributed between the outer cutter and the cutter circumferential rim, thus reducing the contact pressure applied to the outer cutter. 
         [0006]    The aforesaid patent also discloses adjoining cutter circumferential rims connected with a hinge to prevent the heights of the adjoining cutter circumferential rims from becoming significantly uneven thereby to ensure that the shaving surface of a head unit smoothly slides along a curved skin surface. 
         [0007]    The rotary electric shaver disclosed in the aforesaid JP 09-503424(T) poses a problem in that, since the outer cutter is movable relative to the cutter circumferential rim, increasing the travel amount (the amount of depression or the amount of rocking) of the outer cutter causes the edge of the outer cutter to be easily caught by the opening rim of an outer cutter mounting port of the cutter circumferential rim. More specifically, the outer cutter is inserted from below into the outer cutter mounting port of the cutter circumferential rim, and the flange of the outer cutter engages the inner edge of the outer cutter mounting port of the cutter circumferential rim. Therefore, firmly pressing the outer cutter against skin causes the outer cutter to deeply dig into the cutter circumferential rim. 
         [0008]    Further, since adjoining cutter circumferential rims are connected with a hinge, a vertical movement, a rocking or a circular movement of one cutter circumferential rim causes an adjacent cutter circumferential rim to move up and down or rock, preventing each cutter circumferential rim from independently moving. In other words, when one outer cutter moves down or rocks along an uneven skin surface, the adjacent cutter circumferential rim and the outer cutter also moves down or rocks together, adversely affecting the performance of the adjacent outer cutter. 
         [0009]    Further, more members interlock with the vertical movement or rocking movement of a single outer cutter, resulting in higher resistance applied to a vertical travel of the subject outer cutter. In addition, the presence of the hinged structure between cutter circumferential rims inevitably leads to a smaller outside diameter of the outer cutter or a smaller shaving area of the head unit, i.e., the total area of the shaving surfaces of the individual outer cutters. On the other hand, increasing the outside diameter of the outer cutter would increase the size of the cutter frame. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has been accomplished under the circumstances as aforementioned, and an object thereof is to provide a rotary electric shaver which restrains an outer cutter from being caught by the inner edge of a mounting port of a cutter circumferential rim when the outer cutter moves down, enables each outer cutter to move independently without affecting the movements (e.g., downward movement or rocking) of adjoining cutter circumferential rims, ensures smooth movement of a head unit even when adjacent cutter circumferential rims come to differ in height or tilt, ensures smooth vertical movement or rocking of the outer cutter with low resistance, and permits a larger shaving area. 
         [0011]    According to the present invention, the aforesaid object is achieved by a rotary electric shaver in which a plurality of cutter units having an outer cutter and an inner cutter is installed to a cutter frame retained on a shaver main body, the inner cutter being rotated while bringing the inner cutter into resilient contact with the inner surface of the outer cutter, the rotary electric shaver comprising: 
         [0012]    a plurality of outer cutter assemblies, each of which is made integral with a cutter circumferential rim having the outer cutter of each cutter unit secured thereto, the respective outer cutter assembly being movably retained in a mounting port formed in the cutter frame; 
         [0013]    a pushup plate which contacts said outer cutter assembly from below to push up the outer cutter assembly; 
         [0014]    a cutter retaining plate which is retained by the cutter frame and which is positioned below the pushup plate; and 
         [0015]    an outer cutter float spring which is compressively interposed between the cutter retaining plate and the pushup plate to impart an upward restoring tendency to the pushup plate. 
         [0016]    According to the present invention, the outer cutter and the cutter circumferential rim are integrally secured, so that the outer cutter will not move down or tilt or rock in relation to the cutter circumferential rim and will not be caught by the cutter circumferential rim. Moreover, each of the plurality of outer cutter assemblies having the outer cutter and the cutter circumferential rim combined into one piece is movably retained in the mounting port provided in the cutter frame. This arrangement restrains adjacent outer cutter assemblies from interfering with each other when they move, thus preventing the performance of adjacent outer cutters from being adversely affected. 
         [0017]    Furthermore, each outer cutter assembly is independent from other assemblies, so that the movement of an outer cutter assembly does not cause the remaining outer cutter assemblies to vertically move or rock and does not lead to an increased resistance applied to a vertical movement of the subject outer cutter assembly. In addition, even if the difference in height or tilt between adjoining outer cutters increases, the cutter frame provided between the adjoining cutter circumferential rims accommodate such difference, thus allowing the head unit to smoothly move or slide on the shaving surface of skin. 
         [0018]    Thus, the need for the hinge structure among the cutter circumferential rims is obviated, making it possible to increase the diameters of the outer cutters so as to increase the shaving area. In other words, increasing the diameters of the outer cutters will not result in a larger cutter frame. 
         [0019]    Each of the plurality of outer cutter assemblies may be attached to the mounting port of the cutter frame such that the outer cutter assembly can be rocked on a rocking axis which is orthogonal to a straight line extending from the center of the cutter frame in a radial direction (in the direction from the center of the cutter frame to the shaving surface of the outer cutter) and which passes the center of the outer cutter. In this case, a pair of engaging hooks may be protrusively provided in the vicinity of the rocking axis of the outer cutter assembly and positioned symmetrically with respect to the center of the outer cutter, and the engaging hooks may be locked on the mounting port of the cutter frame from below. 
         [0020]    In the case where three outer cutter assemblies are retained by the cutter frame, the outer cutter assemblies may be arranged such that the centers of the three outer cutters are positioned at the apexes of an equilateral triangle in relation to the center of the cutter frame. In the case where two outer cutter assemblies are retained, the outer cutter assemblies may be arranged such that the centers of the outer cutters are positioned symmetrically with respect to the center of the cutter frame. The rotary electric shaver in accordance with the present invention is most desirably provided with three outer cutter assemblies. Alternatively, however, the rotary electric shaver may include two or three or more outer cutter assemblies. 
         [0021]    The outer cutter assembly may simply rock such that the edge of the assembly adjacent to the center of the cutter frame moves down. Alternatively, however, the whole outer cutter assembly may move or slide down. For example, each outer cutter assembly may be constructed so as to lock, from below, the engaging hooks, which is provided on the cutter circumferential rim to install the assembly to the mounting port of the cutter frame, onto the edge of the mounting port of the cutter frame such that the assembly is free to move down or sink. 
         [0022]    The pushup plate, which pushes up each of the outer cutter assemblies, is elastically supported upward by an outer cutter float spring compressively interposed between the pushup plate and the cutter retaining plate retained by the cutter frame. A removable plate, which is free to rotate about the central axis of the cutter frame (the axis which is perpendicular to the upper surface of the cutter frame or the shaving surface and which passes the center of the cutter frame), is retained by the cutter retaining plate, so that the removable plate can be engaged with or disengaged from the inner surface of the cutter frame. For example, a projection provided on the peripheral edge of the removable plate may be disengageably locked onto to a fixing rib secured to (or integrally formed with) the cutter frame such that the projection is engaged or disengaged in the circumferential direction. 
         [0023]    The cutter retaining plate held against the inner surface of the cutter frame may be formed integrally with an inner cutter fall proof ring for preventing the inner cutter of each cutter unit from falling off. More specifically, the ring prevents the inner cutter from falling off the cutter unit when the head unit in which the cutter unit has been installed to the cutter frame is attached to or detached from the main body, thus ensuring easy installation and removal of the head unit. 
         [0024]    The pushup plate preferably abuts against the bottom surface of the cutter circumferential rim of each outer cutter assembly at an edge thereof adjacent to the center of the cutter frame and resiliently pushes up each cutter circumferential rim at an edge thereof adjacent to the center of the cutter frame. In this case, the cutter circumferential rim may be made rockable, and the reset rocking position of the cutter circumferential rim may be restricted by engaging or disengaging the edge of the cutter circumferential rim adjacent to the outer periphery of the cutter frame with or from the cutter frame. 
         [0025]    In the case where a rotary electric shaver has three cutter unit, there is a void among three inner cutter fall proof rings formed integrally with the cutter retaining plates. The void efficiently accommodates the pushup plate, the outer cutter float spring and the like coaxially on the central axis of the cutter frame. This arrangement is ideally suited to reduce the size of the head unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a perspective exterior view of a rotary electric shaver according to an embodiment of the present invention; 
           [0027]      FIG. 2  is a sectional view taken at line II-II in  FIG. 1 ; 
           [0028]      FIG. 3  is an enlarged sectional view of a part of  FIG. 2 ; 
           [0029]      FIG. 4  is an exploded perspective view of a head unit of the electric shaver in  FIG. 1 ; 
           [0030]      FIG. 5  is a top plan view of the appearance of the head unit of the electric shaver in  FIG. 1 ; 
           [0031]      FIG. 6  is a sectional view taken at line VI-VI in  FIG. 5 ; 
           [0032]      FIG. 7  is a bottom view illustrating the interior of the head unit of the electric shaver in  FIG. 1 ; 
           [0033]      FIG. 8  is a perspective view of the interior of the head unit of the electric shaver in  FIG. 1  observed obliquely from below; 
           [0034]      FIG. 9  is an exploded perspective view of the interior of the head unit of the electric shaver in  FIG. 1  observed obliquely from below; and 
           [0035]      FIG. 10  is a perspective view of a removable assembly including a cutter retaining plate. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    Referring to  FIG. 1  to  FIG. 4 , a shaver main body  10  includes a case  14 , in which a substantially columnar grip  12  has its upper portion bent obliquely upward toward the front. The case  14 , the front and back of which can be separated, houses therein a chargeable battery  16 , an electric motor  18 , a control circuit board  20 , and the like, as illustrated in  FIG. 2 . A power switch  22  is mounted on the front surface of the case  14 . Below the switch  22 , displays  24  composed of LED lamps indicating the remaining battery power level of the battery  16 , an operation mode and the like are provided such that the displays  24  can be visually seen through a translucent portion  14 A of the case  14 . 
         [0037]    A head unit  26  is detachably mounted on the top of the case  14  such that the head unit  26  can be opened and closed. The head unit  26  is tilted relative to the grip  12  of the case  14  such that the shaving surface thereof (the upper surface of a cutter frame  66 , which will be described hereinafter) is oriented obliquely upward to the front. The rotation output shaft of the electric motor  18  is oriented toward the head unit  26 . 
         [0038]    A reduction gear assembly  32  is placed between an inner top cover plate  28  covering the top of the main body  10  and an inner bottom cover plate  30  securing the electric motor  18 , as illustrated in  FIG. 3 . The reduction gear assembly  32  reduces the rotational speed of a rotation output shaft  18 A of the motor  18  by a small gear  32 A and an inner cutter large gear  32 B and transmits the reduced speed to three inner cutter drive shafts  34  through a large spur gear  36 . The bottom end of each of the inner cutter drive shafts  34  is rotatably supported by the inner bottom cover plate  30 , and the middle portion thereof penetrates the inner top cover plate  28  into the head unit  26 . 
         [0039]    The respective large spur gears  36  secured to the three inner cutter drive shafts  34  meshes a gear formed on the top surface of the inner cutter large gear  32 B. An eccentric cylindrical cam  38  is formed integrally with the top surface of the inner cutter large gear  32 B, and drives an edge-trimming cutter  40 . More specifically, a cam follower  42  which engages the cam  38  to rock is integral with a supporting point portion  46  of a trimmer drive lever  44  which penetrates an inner top cover plate  28  and rocks, and causes the trimmer drive lever  44  to laterally swing. When the edge-trimming cutter  40  is raised, the trimmer drive lever  44  is engaged in the edge-trimming cutter  40  to cause the edge-trimming cutter  40  to reciprocate. 
         [0040]    A waterproof plate  48  is secured to the top surface of the inner top cover plate  28  of the main body  10 , and a substantially bowl-shaped head holder  50  is retained above the waterproof plate  48  such that the head holder  50  is slightly rockable. The aforesaid three inner cutter drive shafts  34  are positioned at the apexes of the equilateral triangle, the center of which is the central axis  52  of the head unit  26  (refer to  FIGS. 3 to 7 ). As described above, the bottom portions of the inner cutter drive shafts  34  are rotatably supported by the inner bottom cover plate  30 , and the middle portions thereof extend upward, penetrating the inner top cover plate  28 , the waterproof plate  48  and the head holder  50 . Universal joints  54  are mounted on the upper ends of the inner cutter drive shafts  34 . 
         [0041]    Substantially conical flexible sealants  56  and  58  are installed between the inner cutter drive shafts  34  and the waterproof plate  48  and the head holder  50 , as illustrated in  FIG. 3 . The universal joint  54  has a connecting drive shaft  60  secured to the upper end of the inner cutter drive shaft  34 , a connecting driven shaft  62  slidably retained in an axial direction relative to the connecting drive shaft  60 , and a coil spring  64  compressively installed between the drive shaft  60  and the driven shaft  62 . The upper end of the connecting driven shaft  62  is provided with a spherical portion, the top plan view of which is substantially quadrangular. The spherical portion is inserted from below into a substantially quadrangular concavity  88  and movably engages the concavity  88 . The concavity  88  is formed in a boss  86  of an inner cutter  84 , which will be discussed later, and opens downward. 
         [0042]    The head unit  26  will now be described. In the head unit  26 , three cutter units are attached to the cutter frame  66 , which can be opened upward and which is mounted on the head holder  50 . The cutter frame  66  is substantially triangular as observed in the front view thereof, and the periphery thereof is gently curved downward. The cutter frame  66  has three circular mounting ports  68 , as illustrated in  FIGS. 3 and 4 , in which the outer cutter assemblies  70  are movably retained. 
         [0043]    More specifically, each of the outer cutter assemblies  70  includes an outer cutter  72  which is substantially discoid and the rim of which is folded downward, a cutter circumferential rim  74  in which the outer periphery of the outer cutter  72  is fitted, and a stopper ring  76  which is fitted in the inner periphery of the cutter circumferential rim  74  to fix the outer cutter  72  to the cutter circumferential rim  74  (refer to  FIGS. 3 ,  6  and  9 ). The top surface of the outer cutter  72  has many hair introduction openings arranged in the radial direction, the top surface jutting out slightly beyond the cutter circumferential rim  74 . 
         [0044]    As illustrated in  FIG. 3 , the inner circumferential surface of each of the mounting ports  68  of the cutter frame  66  is formed of a spherical surface, the diameter of which increases upward, and the outer circumferential surface of the cutter circumferential rim  74  is formed of a spherical surface matching the spherical surface of the inner circumferential surface of the mounting port  68 . The cutter circumferential rim  74  has a pair of engaging hooks  82  and  82 , which are positioned symmetrically to each other and which are protrusively provided downward in the vicinity of the straight line, i.e., the rocking axis  80 , which is orthogonal to a straight line  78  passing the center of the cutter frame  66 , i.e., the central axis  52  of the head unit  26  (only one of the straight lines  78  is shown in  FIG. 5 ) and which passes the center of the outer cutter  72  (refer to  FIGS. 4 ,  5  and  7 ). 
         [0045]    The engaging hooks  82  and  82  engage the bottom rim of the mounting port  68  when the outer cutter assembly  70  is pushed into the mounting port  68  of the cutter frame  66  from above. Thus, the outer cutter assembly  70  is allowed to rock about the rocking axis  80 , using a point in the vicinity of the engaging hooks  82  and  82  as the supporting an pivot point. The outer periphery of the cutter circumferential rim  74  relative to the rocking axis  80  juts out to the upper edge of the mounting port  68 . This arrangement restricts a portion of the outer cutter assembly  70  adjacent to the center (the central axis  52 ) of the cutter frame  66  from rising while allows the portion of the outer cutter assembly  70  to move down. Here, a portion of the cutter circumferential rim  74  that is adjacent to the center (the central axis  52 ) of the cutter frame  66  is resiliently elastically pushed up by a pushup plate  92 , which will be discussed later, thus allowing the portion of the outer cutter assembly  70  adjacent to the center (the central axis  52 ) to be elastically pushed down. 
         [0046]    The inner cutter  84  rotates in slidable contact with the inner surface of the outer cutter  72 , thereby cutting hair introduced into the hair introduction openings of the outer cutter  72 . The outer cutter  72  and the inner cutter  84  constitute the cutter unit. The boss  86  is secured to the bottom surface of the inner cutter  84 , and the boss  86  has the concavity  88 , which opens downward and into which the connecting driven shaft  62  of the universal joint  54  is locked (refer to  FIGS. 6 to 9 ). 
         [0047]    A cutter retaining plate  90  is detachably installed to the inner surface of the cutter frame  66 . As illustrated in  FIGS. 3 ,  4 ,  9  and  10 , the cutter retaining plate  90  retains the pushup plate  92 , which elastically pushes up the cutter circumferential rim  74  of the outer cutter assembly  70 . More specifically, the annular pushup plate  92  is mounted on a cylindrical guide  90 C formed at the center of the cutter retaining plate  90  with an outer cutter float spring  94  made of a coil spring interposed therebetween, thus abutting three ribs  92 A, which are protrusively provided at regular intervals on the top surface of the pushup plate  92 , against the bottom surface of the cutter circumferential rim  74  (refer to  FIG. 6 ). 
         [0048]    Thus, the three ribs  92   a  abut against the cutter circumferential rim  74  at the side adjacent to the center (the central axis  52 ) of the cutter frame  66 . This causes a portion of each of the three outer cutter assemblies  70  adjacent to the center of the cutter frame  66  to be resiliently pushed up about each of the rocking axes  80 . When the outer cutters  72  are pushed down against skin, the portions of the outer cutter assemblies  70  adjacent to the center of the cutter frame  66  move down about the rocking axes  80 . At this time, the pushup plate  92  compresses the spring  94 . 
         [0049]    The cutter retaining plate  90  is detachably installed to the inner side of the cutter frame  66  by a Y-shaped removable plate  96 . More specifically, a cylinder (collet)  96 A with slits, which rotatably penetrates the guide  90 C of the cutter retaining plate  90  ( FIG. 3 ), is formed at the center of the removable plate  96 . A hook provided at the distal end of the cylinder  96 A is locked to the upper end of the guide  90 C. The distal ends of legs  96 B of the removable plate  96  ( FIG. 10 ), which radially extend, can be engaged with or disengaged from three fixed ribs  66 A, which are protrusively provided on the inner surface of the cutter frame  66 , in the circumferential direction. 
         [0050]    Further, the cylinder  96 A of the removable plate  96  engages with a central projection  66 B ( FIGS. 6 and 9 ) protrusively provided at the center of the bottom surface of the cutter frame  66  (on the central axis  52 ) so as to position the removable plate  96 . Three troughs  90 A formed in the cutter retaining plate  90  ( FIG. 10 ) engage with the upper edges of the ribs  66 A thereby to position the cutter retaining plate  90 . 
         [0051]    As illustrated in  FIG. 3 , the head holder  50  has an opening  50 A opposing the boss  48 A positioned at the center of the waterproof plate  48 , and a capping member  98  comes in slidable contact with the top surface surrounding the opening  50 A. The capping member  98  is secured to the boss  48 A by screwing a screw  98 A penetrating the capping member  98  from above into the boss  48 A. The central bottom surface of the head holder  50  is pressed upward by a coil spring  98 B, which surrounds the boss  48 A of the waterproof plate  48  and which is compressively installed between the waterproof plate  48  and the boss  48 A. As a result, the central portion of the head holder  50  is vertically sandwiched between the capping member  98  and the coil spring  98 B, allowing the head holder  50  to rock in a direction in which the central axis  52  tilts. 
         [0052]    Three inner cutter fall proof rings  90 B surrounding the bosses  86  of the inner cutters  84  of the cutter unit are integrally formed with the cutter retaining plate  90  ( FIG. 10 ). These rings  90 B prevent the inner cutters  84  from falling off when the head unit  26  is attached or detached or opened or closed in a state where the three cutter units have been attached to the head unit  26  and the cutter retaining plate  90  has been secured to the cutter frame  66 . 
         [0053]    The head unit  26  constructed as described above is attached to the head holder  50  by a hinge  100 , so that the head unit  26  can be opened and closed. More specifically, the hinge  100  formed of a substantially U-shaped member swingably retained on the edge of the cutter frame  66  is retained by inserting the hinge  100  into a groove formed in the head holder  50 . A portion of the edge of the head holder  50  on the opposite side from the hinge  100  can be locked by a locking device  102  provided on the head holder  50 . 
         [0054]    In the present embodiment, the cutter circumferential rim  74  of the outer cutter assembly  70  can be rocked about the rocking axis  80  ( FIG. 5 ), and the side of the cutter circumferential rim  74  adjacent to the center of the head (adjacent to the central axis  52 ) is resiliently pushed up by the rib  92 A of the pushup plate  92  ( FIGS. 3 ,  4 ,  6  and  10 ). When, therefore, the top surface (the shaving surface) of the head unit  26  is pressed against skin, the cutter circumferential rim  74  rocks while pressing the pushup plate  92  down. At this time, if only one outer cutter assembly  70  out of three assemblies is pressed down, then the pushup plate  92  merely tilts, exerting no influences on the forces for depressing the remaining outer cutter assemblies  70 . Thus, the three outer cutter assemblies  70  independently rock without influencing each other, so that the three outer cutter assemblies  70  do not interfere with each other in shaving performance. 
         [0055]    Further, the top surface of the cutter frame  66  is exposed among the mounting ports  68  of the three cutter circumferential rims  74  ( FIGS. 1 ,  4  and  5 ). Hence, when the head unit  26  slides on skin while one cutter circumferential rim  74  is deeply down, a bulging portion of the skin is temporarily supported by the top surface of the cutter frame  66  between the adjacent cutter circumferential rims  74 . In other words, the difference in height between the adjacent cutter circumferential rims  74  is accommodated by the top surface of the cutter frame  66 , thus allowing the head unit  26  to smoothly move.