Abstract:
A rotary electric shaver including a disc-shaped outer cutter  10,  which is mounted in the upper part of a shaver main body housing therein a motor and has ring-shaped tracks  18  on the under (inner) surface thereof, and an inner cutter  12 A, which has cutter blades  120  that elastically contact the ring-shaped tracks  18  of the outer cutter  10  from below and is rotated by the motor; and in this shaver, the inner cutter  12 A has vibration elements  132  that travel in the ring-shaped tracks  18  and have a smaller spring constant, compared to the cutter blade  120,  in the direction same as and opposite from the direction in which the cutter blades travel, and the vibration elements  132  vibrate and produce sound when, during shaving, they strike stoppers  134  provided near the vibration elements  132.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a rotary electric shaver in which a rotating inner cutter with its cutter blades elastically in contact with a ring-shaped track of a substantially disc-shaped outer cutter cuts whiskers (hair) entering into the hair introduction openings formed in the outer cutter.  
         [0003]     2. Description of the Related Art  
         [0004]     When an electric shaver is used, vibration and noise are produced by the motor and drive system built installed in the shaver body, and, together therewith, noise (cutting noise, shaving noise, frictional noise, and the like) is produced by the vibration accompanying the friction between the outer cutter and the inner cutter and the vibration of the blades when the hair (whiskers, etc.) advanced between the outer cutter and the inner cutter is cut. In particular, the hair cutting noise and vibration noise caused by the outer cutter and the inner cutter are sensitively felt by the user because the outer cutter is in direct contact with the skin, and directly affect the quality of shaving comfort.  
         [0005]     In reciprocating electric shavers, a plurality of arch-shaped cutter blades held in an inner cutter are caused to reciprocate and slide against the lower surface of an arch-shaped outer cutter; for such reciprocating shavers, it has been proposed, as in Japanese Patent Application Laid-Open (Kokai) No. No. 10-323461, that suitable channels be formed in the inner circumferential edges of the circular arcs of the arch-shaped cutter blades, so that the cutter blades can readily vibrate. It is also commonly known, as disclosed in Japanese Patent Application Laid-Open (Kokai) No. 2005-230237 that, so as to adjust the vibration characteristics of the cutter blades, a vibration control unit comprised of, for instance, cut-ins is provided in the tip ends in the length-wise direction of the cutter blades (so as to be near the linking portions connecting the two ends of the cutter blades to the side edges thereof).  
         [0006]      FIG. 8  shows a cutter unit used in a conventional rotary electric shaver,  FIG. 9  is a side view thereof, and  FIG. 10  shows the cross-section at lines  10 - 10  in  FIG. 8 .  
         [0007]     In this conventional rotary electric shaver, the reference numeral  10  designates an outer cutter, and  12  an inner cutter. The outer cutter  10  is made of metal and is made substantially in a disc shape. The outer circumferential edge thereof is bent so as to be substantially either in a saucer-shape or inverted bowl shape.  
         [0008]     In the upper surface of this round outer cutter  10 , a multiplicity of slits  14  are formed in the radial direction. The slits  14  constitute hair introduction openings. In the upper surface of the outer cutter  10 , a ring-shaped channel  16  is formed; and thus, in the lower surface (inner surface) of the outer cutter  10 , two tracks  18  (only one whereof is shown in  FIG. 10 ) comprising concentric circles are formed on both sides of the ring-shaped channel  16 .  
         [0009]     The inner cutter  12  is comprised of an inner cutter main unit  20  made of a resin and a plurality of cutter blades  22  provided on the inner cutter main unit  20 . The cutter blades  22  contact the lower surface (inner surface) of the tracks  18  of the outer cutter  10  and travel while sliding on the inner surface (lower surface) of the tracks  18  when the inner cutter main unit  20  is rotated by the motor. The cutter blades  22 , as shown in  FIG. 10 , are raised up diagonally from the attachment surface  24  which is set on, so to be attached, to the inner cutter main unit  20 . More specifically, in  FIG. 10 , the angle a by which the cutter blades  22  are bent upward is an acute angle, and it is ordinarily 60 to 80°.  
         [0010]     In the inner cutter main unit  20  of the inner cutter  12 , as seen from  FIG. 9 , an engagement hole  26  is formed, and a rotary shaft (not shown), parallel to the center axis x of the inner cutter  12 , is engaged with this engagement hole  26 . The inner cutter  12  is rotationally driven by the rotary shaft in a direction in which the cutter blades  22  travel toward the left (in the direction of the arrow B) in  FIG. 10 . This rotary shaft has a tendency to return in a direction in which the inner cutter  12  is pushed against the outer cutter  10 , and thus this return force is a pushing-up load for pressing the cutter blades  22  in the tracks  18  of the outer cutter  10 .  
         [0011]     In a reciprocating electric shaver, since the inner cutter moves reciprocally, the cutter blades of the inner cutter are held at right angles with respect to the direction of reciprocation motion. For this reason, it has been possible to configure the shaver so that the inner cutter itself can vibrate.  
         [0012]     In a rotary electric shaver, on the other hand, as seen from  FIGS. 8, 9 , and  10 , the cutter blades  22  of the inner cutter  12  are inclined so that the tip ends (cutting edge) are made to precede in the direction of travel of the cutter blades  22  (or in the direction of rotation of the inner cutter  12 ), thus enhancing the quality of shaving. In such a rotary electric shaver, each cutter blade  22  must have sufficient strength so as not to be bent when cutting hair, and it is also preferred that no irritating noise (buzzing sound) be produced during shaving. For these reasons, the cutter blades are made as rigid as possible to enhance the cutting quality; and more specifically, the thickness β of the cutter blade  22 , in  FIG. 10 , is made large. As a result, since the cutter blades  22  are rigid and do not readily vibrate, it is very difficult to control the sound quality by adjusting the vibration characteristics of the cutter blades  22  by forming channels or the like in the cutter blades  22 .  
       BRIEF SUMMARY OF THE INVENTION  
       [0013]     Accordingly, the object of the present invention, devised in view of such circumstances as described above, is to provide an electric shaver of a rotary type in which it is made to be able to control the sound quality without causing the cutter blades of the inner cutter to vibrate.  
         [0014]     The above object is accomplished by a unique structure of the present invention for a rotary electric shaver that includes: a substantially disc-shaped outer cutter, which is provided in the upper part of the shaver main body housing therein a motor and is formed with a ring-shaped track(s) on its lower surface, and an inner cutter, which is provided with a cutter blade(s) that elastically contacts the ring-shaped track(s) of the outer cutter from below and is rotationally driven by the motor; and in this electric shaver: 
        the inner cutter is provided with a vibration element(s) that is in contact at the upper end with the ring-shaped track(s) of the outer cutter and has a smaller spring constant, in a direction which is the same as and opposite from the direction in which the cutter blade(s) travels, than the spring constant of the cutter blade.        
 
         [0016]     As seen from the above, in the shaver of the present invention, a vibration element(s) is provided on the inner cutter(s), and this vibration element(s) has a smaller spring constant in the direction in which the cutter blade(s) travels and in the opposite direction therefrom than that of the cutter blade(s) of the inner cutter(s), and this vibration element(s) is made so as to vibrate while sliding in the ring-shaped track(s) of the outer cutter. Accordingly, by suitably setting the vibration characteristics of the vibration element, the sound quality is enhanced. It is thus also possible to use cutter blades that have sufficiently high rigidity so as to be able to cut the hair efficiently and provide good cutting quality.  
         [0017]     The vibration element(s) is formed of a metal sheet, thinner than the cutter blade(s), so that the tip end of the vibration element(s) slides against the ring-shaped track(s); and a straight line joining the flexible bending point of the vibration element and the cutting edge formed on the front edge of the vibration element is set to be substantially parallel to the rotational axis of the inner cutter. In this structure, when the vibration element(s) vibrates forwards and backwards along the ring-shaped track(s), the cutting edge(s) of the vibration element(s) is separated from the ring-shaped track(s); accordingly, there is no danger that the vibration element(s) damages the outer cutter blades (which are the lower edges of ribs located between the hair introduction openings of the outer cutter).  
         [0018]     It is preferable that a stopper(s) for limiting the bending extent (or the range of flexibility) of the vibration element(s) be provided on the inner cutter. When the vibration element(s) contact the stopper(s), they produce a pleasant sound, further enhancing the sound quality of the shaver.  
         [0019]     In the present invention, the inner cutter can be made of a cup-shaped central base portion, a supporting portion(s) extending in the radial direction from the central base portion, and a cutter blade linking member which is comprised of a plurality of cutter blades linked in a ring shape and is secured to the upper surface(s) of the tip portion(s) of the supporting portion(s); and the vibration element(s) is secured together with the cutter blade linking member to the supporting portion(s) of the inner cutter.  
         [0020]     In other words, the cutter blade linking member is comprised of a plurality of cutter blades aligned and integrated in a ring shape. In the present invention, further, a plurality of vibration elements can be linked together in a ring shape to form a vibration element linking member, and this vibration element linking member is superimposed on the cutter blade linking member, so that both linking members are secured to the supporting portion(s) of the inner. The vibration element(s) are preferably provided between the cutter blades, respectively, in the circumferential direction; and the stopper(s) are preferably formed integrally in the vibration element linking member.  
         [0021]     It is preferable that the vibration element(s) be curved so that the part below the cutting edge thereof is curved in a direction opposite to the direction in which the vibration element travels. With this structure, when the hair strikes the vibration element(s), the entire vibration element(s) is inclined; and since the curved portion(s) deforms, the hair is caused to smoothly escape. Also, when a vibration element(s) falls over relative to the hair, the hair enters into the concave surface(s) formed by such a curved portion(s); as a result, the vibration element(s) can be inclined smoothly.  
         [0022]     The vibration element(s) and the stopper(s) can be formed by bend-machining a common metal sheet, and both the vibration element(s) and the stopper(s) can be formed as a single part, making the shave structure simple. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0023]      FIG. 1  shows in vertical cross-section a cutter unit according to one embodiment of the present invention;  
         [0024]      FIG. 2  is an exploded perspective view thereof with vibration element omitted;  
         [0025]      FIG. 3  is a perspective view of a part of a vibration element linking member;  
         [0026]      FIG. 4  is a diagram illustrating the action of the vibration element;  
         [0027]      FIG. 5  is a diagram illustrating the action of the vibration element;  
         [0028]      FIG. 6  is a diagram illustrating the action of the vibration element;  
         [0029]      FIG. 7  shows another embodiment of the present invention;  
         [0030]      FIG. 8  is a top view of a conventional cutter unit;  
         [0031]      FIG. 9  is a side elevation thereof; and  
         [0032]      FIG. 10  is a cross-sectional view taken along the lines  8 - 8  in  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]      FIG. 1  shows, in vertical cross-section, the cutter unit according to one embodiment of the present invention,  FIG. 2  is a perspective view of the inner cutter with the vibration element(s) removed,  FIG. 3  is a perspective view of a part of the vibration element linking member, and FIGS.  4  to  6  illustrate, in vertical cross-section, the action of the vibration element, seen correspondingly along the line  10 - 10  line in  FIG. 8 .  
         [0034]     In  FIG. 1 , the same reference numerals are applied to parts that are the same as in  FIG. 8  to  10 , and descriptions of such same parts are not repeated below. The main difference of the structure of the present invention from the structure of  FIGS. 8 and 9  is that vibrating plates  132  are provided between the cutter blades  120  of the inner cutter  12 A.  
         [0035]     More specifically, the inner cutter main unit  20  of the inner cutter  12 A is comprised of, as seen from  FIG. 1 , a substantially cup-shaped hub (central base unit)  100  and, as seen from  FIG. 2 , eight supporting portions  102  formed by arms that extend radially outward from the central base unit  100 . The central base unit (cup-shaped hub)  100  and the supporting portions  102  are integrally molded of a synthetic resin. The tip portions of all the supporting portions  102  are raised upward, and the upper surfaces thereof are positioned on a plane that lies at right angles to the rotational axis x of the inner cutter  12 A.  
         [0036]     Projections  104  and  106  protrude from the upper surface of the supporting portions  102  of the inner cutter  12 A. The projections (holding projections)  104  are for securing a vibration element linking member  110  and a cutter blade linking plate  108 , both will be described below, by hot crimping, while the projections (positioning projections)  106  are for positioning the linking plates  108  and  110 . In the center of the upper surface of the inner cutter main unit  20 , furthermore, a columnar projecting part  112  is provided as seen from  FIG. 1 . This projecting part  112  engaging a concavity  116  of a cutter cover  114  secured to the opening made in the center of the outer cutter  10  when the inner cutter  12 A is combined with the outer cutter  10 , and it prevents the inner cutter  12 A from becoming eccentric relative to the outer cutter  10 . In other words, the projecting part  112  prevents rotational wobbling in the inner cutter  12 A.  
         [0037]     The cutter blade linking member  108 , as shown in  FIG. 2 , is comprised of eight substantially Y-shaped cutter units  118  which are linked in a ring shape. More specifically, each one of the substantially Y-shaped cutter units  118  has two cutter blades  120  that are engaged or fitted in two concentric tracks  18 A and  18 B that are formed in the inner surface of the above-described outer cutter  10  so as to be located on both sides of ring-shaped channel  16 , and the plurality of (eight in the shown embodiment) cutter units  118  are linked in a ring shape by linking portions  122  that pass between the cutter blades  120  that are bifurcated in substantially a Y shape. The cutter blades  120 , as seen from  FIG. 2 , are inclined forward toward the rotating direction y (same as direction of arrow B in  FIG. 10 ) of the inner cutter  12 A. In each of the surfaces of the cutter blades  120 , which is facing the reverse rotating direction (opposite from the rotating direction y), is formed a concavity (recess)  124 .  
         [0038]     The cutter blade linking member  108  can be obtained by press die-cutting a material such as a metal sheet into substantially a ring shape, and, either thereafter or simultaneously therewith, bending the portions for the cutter blades  120 . Cutter unit securing holes  126  are formed in the cutter units  118 , and concavities  124  are formed in the cutter blades  120 ; and these cutter unit securing holes  126  and concavities  124  are formed either simultaneously with the press die-cutting or in a separate process.  
         [0039]     Thus, the cutter blade linking member  108  can be formed with a few press machine-pressing process. Also, because the bend machining angle for bending up the cutter blades  120  is small, the stress applied to the metal material will also be small, making it possible to use a metal material with degraded (low) metal material properties (especially the press-machinability).  
         [0040]     Next, the vibration element linking member  110  will be described.  
         [0041]     This vibration element linking member  110  is formed by pressing or bend-machining a metal sheet that is sufficiently thinner than the cutter blade linking member  108 , and it includes eight sound generators  128 , as shown in  FIG. 3 , linked in a ring shape at linking portions  130 . The vibration element linking member  110  is stacked on the cutter blade linking member  108  and secured, together with the cutter blade linking member  108 , to the inner cutter main unit  20 . The sound generators  128  are positioned between the cutter units  118 .  
         [0042]     Each of the sound generators  128  is comprised of a pair of vibrating plates (vibration elements)  132  and a pair of stoppers  134  which are provided in the vicinity of the vibrating plates (vibration elements)  132 . The vibrating plates  132  are formed by bending up metal sheet so that the tips (upper ends) thereof contact the inner surfaces of the tracks  18  ( 18 A and  18 B) of the outer cutter  10 , and the stoppers  134  are for limiting the range of vibration of the vibrating plates  132 . The vibrating plates  132  and the stoppers  134  are formed integrally.  
         [0043]     The vibrating plates  132  are capable of vibrating in the circumferential direction of the tracks  18  (in the direction y and in the direction opposite therefrom or in the left and right directions in  FIG. 4 ), and the stoppers  134  are formed, as best seen from  FIG. 3 , so as to be bifurcated thus sandwiching the vibrating plates  132  from both (front and back) sides of the vibrating plates  132  with gaps on the both sides of each vibrating plate  132 .  
         [0044]     This vibration element linking member  110  is provided with securing holes  136  in the linking portions  130 . The vibration element linking member  110  is set on the cutter blade linking member  108  with the securing holes  136  of the vibration element linking member  110  and the securing holes  126  of the cutter blade linking member  108  aligned, and the vibration element linking member  110  and the cutter blade linking member  108  are mounted on the supporting portions  102  of the inner cutter main unit  20  so that the securing holes  136  of the vibration element linking member  110  and the securing holes  126  of the cutter blade linking member  108  pass through the holding projections  104  of the supporting portions  102 .  
         [0045]     Then, by hot crimping the tips of the holding projections  104 , the linking members  108  and  110  are secured to the inner cutter main unit  20 . At this point, the positioning projections  106  formed on the supporting portions  102  are in contact with the side edges of the linking portions  122  and  130 , thus positioning the linking members  108  and  110  on the supporting portions  102 .  
         [0046]     The thus made inner cutter  12 A is connected to a rotary shaft (not shown) at its engagement hole  26  ( FIG. 1 ) formed in the central base unit  100  and rotationally driven by a motor (not shown), housed in the shaver body, with respect to the outer cutter  10  ( FIG. 1 ) fitted thereon.  
         [0047]     As shown in  FIG. 4 , each vibrating plate  132  rises substantially vertically relative to the lower surface of the vibration element linking member  110 . In other words, the vibrating plate  132  are raised substantially vertically from the attachment surface  138  of the vibration element linking member  110 , the attachment surface  138  being the lower surface of the vibration element linking member  110  set on the cutter blade linking member  108 . The lower end of each vibrating plate  132  is bent at right angles with a small curvature, and the bent part constitutes a flexible bending point P of the vibrating plate  132 . The vibrating plates  132  and the cutter blades  120  travel toward the left in FIGS.  4  to  6 .  
         [0048]     As seen from  FIG. 4 , the front (leading) edge of each one of the tips of the vibrating plates  132 , on the side toward the direction of travel, makes a cutting edge  140 , and a perpendicular straight line z joining the cutting edge  140  and the flexible bending point P is set to be substantially parallel to the rotational axis x of the inner cutter  12 A. In other words, the vibrating plates  132  are substantially vertical with respect to the upper surfaces of the supporting portions  102  of the inner cutter main unit  20 .  
         [0049]     Below the upper end of each one of the vibrating plates  132 , that is, below the cutting edge  140 , a curved portion  142  is formed. The curved portion  142  is curved so as to be distended from the upper end surface of the vibrating plate  132  in the direction opposite from the direction of travel of the vibrating plate  132 .  
         [0050]     The vibrating plate linking member  110 , after being press and/or bend-machined, is subjected to a suitable heat treatment, so that appropriate flat spring characteristics are imparted. In other words, the spring constant of the vibrating plates  132  in the direction in which the cutter blades travel and in the direction opposite from travel of the cutter blades is sufficiently smaller than the spring constant of the cutter blades  120 .  
         [0051]     The action of the shaver described above will be explained next below.  
         [0052]     When the inner cutter  12 A is rotated (in the direction of arrow y in  FIG. 2 ), the cutter blades  120  and the vibrating plates  132  (which are in contact with the lower (inner) surface of the tracks  18  of the outer cutter) are rotated to travel toward the left side in  FIG. 4 . Before hair  144  enter the slits (hair introduction opening)  14 , the vibrating plates  132 , due to the spring return force of the vibrating plates  132  themselves, are in contact with the stoppers  134 A which are located on the side toward the direction of travel (front side).  
         [0053]     When the hair  144  enters the slits  14  immediately before the cutter blades  120  pass by, the hair is cut by the front edges (cutting edges) of the traveling (rotating) cutter blades  120  and the ribs formed between the slits  14  of the outer cutter.  
         [0054]     When the hair  144  enters the slits  14  after the cutter blades  120  has passed the slits  14  and before the vibrating plates  132  pass the slits  14 , the hair  144  strikes the cutting edges  140  of the vibrating plates  132 .  FIG. 5  shows this situation.  
         [0055]     When the hair  144  strikes the cutting edges  140  of the vibrating plates  132 , as seen from  FIG. 5 , a force F acting in the reverse travel direction (toward the back) is applied to the upper ends of the vibrating plates  132  by the shear resistance of the hair  144 . As a result, the vibrating plates  132  begin to incline in the reverse travel direction (toward the back side) about the flexible bending points P of the vibrating plates  132 . Then, when this force F increases as the inner cutter  12 A rotates, the vibrating plates  132  incline further, strike the stoppers (rear stoppers)  134 B which are located on the rearward side with respect to the direction of travel (back side) of the vibrating plates  132  and cutter blades  120  (or located on the reverse traveling direction), and produce sound. The fall-over angle at this moment is shown by γ.  FIG. 6  illustrates this situation.  
         [0056]     When the vibrating plates  132  attain the fall-over angle γ, they are in contact with the rear stoppers  134 B and are supported thereby; and after the hair  144  is sheared (cut) by the cutting edges  140  of the vibrating plates  132 , the force F is released. The vibrating plates  132 , released from the hair  144 , return to the vertical position shown in  FIG. 4  due to the spring characteristics of the vibrating plates  132  themselves. As a result, the vibrating plates  132  strike the front stoppers  134 A, which are located on the forward side with respect to the direction of travel (front side) of the vibrating plates  132  and cutter blades  120 , and again produce sound.  
         [0057]     As seen from the above, the vibrating plates  132  incline every time hair  144  which enters the slits  14  strikes them, and they strike the front and rear stoppers  134  and produce sound. Accordingly, the sound quality can be changed or improved by setting the vibration characteristics of the vibrating plates  132  and/or the stoppers  134 . In other words, different sounds can be produced by shavers with the use of vibrating plates and/or stoppers of, for instance, different sizes, thicknesses and materials; and the number of vibrating plates and/or stoppers installed can be varied.  
         [0058]     In the above structure, the cutting edge  140  at the upper end of each one of the vibrating plates  132  is positioned near the perpendicular straight line z that passes through the flexible bending point P. Accordingly, when the vibrating plate vibrates, the angle at which the cutting edge  140  contacts the lower surface of the track  18  becomes close to parallel to the lower surface of the track  18 ; and as a result, there is no danger that the cutting edges of the outer cutter  10  formed at the edges of the slits  14  will be damaged.  
         [0059]      FIG. 7  shows, in vertical cross-section, another embodiment of the present invention, seen correspondingly along the line  10 - 10  line in  FIG. 8 . In this embodiment of  FIG. 7 , the vibrating plates  132  have different shape from that of FIGS.  4  to  6 .  
         [0060]     More specifically, each one of the vibrating plates  132 A is curved with a radius of curvature that is larger toward the back (reverse travel direction) from the flexible bending point P; and in a condition that the vibrating plate  132 A is in contact with the front stopper  134 A, the position of the cutting edge  140 A, which is the front edge of the upper end (tip) of the vibrating plate  132 A, is displaced toward the back side by a distance δ from the perpendicular line y that passes through the flexible bending point P.  
         [0061]     In the structure of  FIG. 7 , after the vibrating plate  132 A has fallen over toward the back, when it returns to the (original) position of  FIG. 7 , it strikes the front stopper  134 A and thus its return position is limited. At that time, the cutting edge  140 A is displaced by δ toward the back from the flexible bending point P; as a result, the cutting edge  140 A of the vibrating plate  132 A can be even more definitely prevented from damaging the blades in the tracks  18  of the outer cutter.