Patent Publication Number: US-7222428-B2

Title: Electric rotary shaver

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electric rotary shaver which causes inner cutters to rotate while contacting substantially disk-form outer cutters, and uses the inner cutters to cut whiskers that are introduced into slits formed in the outer cutters. 
   2. Description of the Related Art 
   In electric shavers of this type, shavers that have a plurality of outer cutters are universally known. For example, such shavers include shavers in which two outer cutters are installed side by side in close proximity to each other, and shavers in which three outer cutters are disposed at the vertices of an equilateral triangle. In this structure, in order to improve the shaving characteristics, it is necessary to arrange the outer cutters so that these cutters are depressable and tiltable, thus causing the outer cutters to incline in conformity to the curvature of the shaving surface. 
   In the shaver disclosed in Japanese Patent No. 2853812, shaving units in which inner cutters are provided in outer cutters are mounted on a retaining plate, and this retaining plate is fastened to the inside wall of a cutter frame (holder). The retaining plate comprises a plurality of bayonet form arms that make an advancing and retracting motion from the center toward the outside. The tip ends of these arms are engaged with and disengaged from the inside wall surface of the cutter frame. Furthermore, the shaving units are mounted on the retaining plate from the side and are elastically held in a mounted state by elastic arms that are integrally formed on the retaining plate, so that the shaving units move slightly upward and downward. 
   Japanese Utility Model Application Publication (Kokoku) No. H2-14748 discloses a shaver in which the outer circumferential edges of outer cutters are pressed by retaining body ( 20 ) that holds inner cutters, and this retaining body ( 20 ) is pressed against a cutter frame via a spring. More specifically, a locking body ( 50 ) is detachably mounted on the cutter frame, and this locking body ( 50 ) has a plurality of anchoring rods that protrude in the radial direction; and these anchoring rods are engaged with or disengaged from the cutter frame by turning the locking body ( 50 ). Furthermore, the retaining body is pressed by a single spring ( 57 ) mounted in the center of the locking body ( 50 ). 
     FIG. 8  is a top view showing the internal structure of another conventional example of a cutter frame, and  FIG. 9  is a sectional view taken along the line  9 — 9  in  FIG. 8 . 
   In this conventional example, three outer cutters  1  are disposed in a common outer cutter holder  2  so that these outer cutters are positioned at the vertices of an equilateral triangle, and the respective outer cutters  1  are anchored to the outer cutter holder  2  so as to be depressable and tiltable. Three inner cutters  4  are held in a holder  3  so that these inner cutters are rotated in a depressable and tiltable manner. Two projections  5  protrude from this inner cutter holder  3  for each outer cutter  1 , with these projections being separated in the circumferential direction of the outer cutters  1  so that the projections do not interfere with the outer cutter holder  2 . 
   The center of the inner cutter holder  3  is elastically supported on the cutter frame  7  by a locking bolt  6 . More specifically, a nut  8  is inserted into the center of the cutter frame  7 , and the inner cutter holder  3  and compression coil spring  11  are disposed between a knob  10  and a retaining ring  9  anchored to the locking bolt  6 . Here, the inner cutter holder  3  is pressed against the retaining ring  9  (i.e., toward the tip end of the locking bolt  6 ) by the coil spring  11 . Accordingly, if the tip end of the locking bolt  6  is screwed into the nut  8 , the inner cutter holder  3  presses against the outer cutters  1  in an elastic manner by means of the coil spring  11 . In other words, the circumferential edges of the outer cutters  1  are pressed by the coil spring  11  via the inner cutter holder  3  that is integrated with the projections  5 . 
   When the cutter frame  7  is mounted on the shaver main body (not shown in  FIGS. 8 and 9 ), the inner cutters  4  engage with the drive shafts (not shown in  8  and  9 ) of the shaver main body and are rotationally driven. These drive shafts advance and retract in the axial direction with a return habit in the direction of protrusion and elastically press the inner cutters  4  against the inside surfaces of the outer cutters  1 . Furthermore, three supporting protrusions  12  (only one is shown in  FIG. 9 ) that support the outer cutter holder  2  in the vicinity of the vertices of the triangular shape are provided to protrude from the shaver main body. 
   In the shaver described in Japanese Patent No. 2853812, the movable range (range of vertical movement and tilting range) of the shaving units comprising outer cutters and inner cutters is limited to the movable range of the elastic arms that are integrated with the retaining plate and is therefore unavoidably extremely small. Accordingly, the outer cutters cannot sufficiently conform to indentations and projections or variations in the inclination of the shaving surface (skin), and the shaving characteristics are therefore poor. Furthermore, when shaving debris is cleaned away, the arms that protrude outward from the center (toward the inside wall of the cutter frame) are pressed toward the center with the fingertips, so that the tip ends of the arms are disengaged from the inside wall of the cutter frame; accordingly, a fine operation using the fingertips is required, and the operating characteristics are poor. 
   In the shaver described in Japanese Utility Model Application Publication (Kokoku) No. H2-14748, the retaining plate ( 20 ) that holds the inner cutters is elastically pressed toward the outer cutters. Accordingly, vertical movement of the outer cutters can be accomplished by vertical displacement of this retaining plate. However, in order to remove the retaining plate for the purpose of cleaning away shaving debris, it is necessary to turn the locking body ( 50 ) with the fingertips, thus making the operating characteristics poor. 
   In the conventional example shown in  FIGS. 8 and 9 , a nut  8  into which the tip end of the locking bolt  6  is screwed is inserted into the cutter frame  7 , and this part is surrounded by the outer cutter holder  2 . Accordingly, it becomes necessary to broaden the spacing of the outer cutters in the vicinity of this nut  8 ; and in cases where three outer cutters are used, it is necessary to broaden the spacing of the respective outer cutters or to increase the diameter of the respective outer cutters. As a result, the size of the cutter frame tends to increase. Likewise, in cases where two outer cutters are used, it is necessary to broaden the spacing of the outer cutters, and this has been a serious problem. Furthermore, when shaving debris is cleaned away, the locking bolt  6  must be rotated with the fingertips. The operating characteristics are thus poor. 
   Furthermore, in the shavers disclosed in  FIGS. 8 and 9  and in Japanese Utility Model Application Publication (Kokoku) No. H2-14748, the retaining body ( 20 ) or inner cutter holder ( 3 ) is pressed by a single coil spring ( 57 ,  11 ) in the center. More specifically, the retaining body ( 20 ) or inner cutter holder ( 3 ) is elastically pressed by a coil spring ( 57 ,  11 ) mounted on the locking body ( 50 ) or locking bolt ( 6 ) fastened to the center of the cutter frame. 
   However, in a shaver in which the retaining body ( 20 ) or inner cutter holder ( 3 ) is thus pressed by a single coil spring ( 57 ,  11 ) in the center, the retaining body ( 20 ) or inner cutter holder ( 3 ) tends to move in the radial direction when the outer cutters are pressed downward. In the case of the shaver described in Japanese Utility Model Application Publication (Kokoku) No. H2-14748, the locking body ( 50 ) is firmly fastened to the cutter frame by means of a plurality of anchoring rods ( 52 ) that protrude in the radial direction. Accordingly, the retaining body ( 20 ) is aligned with the central shaft (protruding pin  15 ) which is fastened at both ends to the cutter frame and the locking body ( 50 ), and the movement of this retaining body ( 20 ) in the radial direction is restricted. 
   Meanwhile, in the shaver shown in  FIGS. 8 and 9 , the tip end of the locking bolt  6  is screwed into a nut  8  that is embedded in the cutter frame, so that a so-called cantilever support is constructed. Accordingly, the locking bolt  6  tends to be unstable, and the inner cutter holder  3  that is held here is also unstable. Accordingly, two pins  13  (see  FIG. 8 ) protrude from the cutter frame  7 , and these pins  13  are passed through the inner cutter holder  3 . 
   In such cases, however, since there is only a single coil spring, it is necessary to use a coil spring with a strong spring force. Consequently, the detachment operating characteristics of the locking body ( 50 ) or locking bolt ( 6 ) when shaving debris is cleaned away are poor. Furthermore, the structure used to position the retaining body ( 20 ) or inner cutter holder ( 3 ) in the radial direction becomes complicated. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention was devised in light of such facts. 
   It is an object of the present invention to provide an electric rotary shaver in which the movable range of the outer cutters can be increased, the spacing of the outer cutters can be narrowed so that the size of the cutter head can be reduced, the operation performed by the fingertips when shaving debris is cleaned away can be simplified, and the retaining plate or inner cutter holder can be stably held without complicating the structure. 
   The above object is accomplished by a unique structure of the present invention for an electric rotary shaver that includes:
         a shaver main body that contains therein a motor,   a cutter frame attached to the shaver main body,   a plurality of circular outer cutters provided in the cutter frame, and   a plurality of inner cutters that are provided insides of the outer cutters so as to be rotationally driven while being elastically pressed against the outer cutters by means of drive shafts that are rotationally driven by the motor; and       

   in the present invention, the electric shaver further includes:
         a cutter retaining plate which is provided inside of the cutter frame and engages with the outer circumferential edges of the outer cutters and rotatably holds the inner cutters;   a locking member which has a plurality of arms that extend outwardly from a center thereof with equal intervals in between in a circumferential direction of the locking member;   a plurality of guide pins which are provided at the tip ends of each one of the arms of the locking member and slidably pass through the cutter retaining plate;   permanent magnets which are provided on the cutter frame and attach the guide pins by magnetic attraction in a detachable manner;   a plurality of compression coil springs which are mounted on the guide pins and compressedly provided between the arms and the cutter retaining plate; and   an anchoring means which prevents the locking member from being separated from the cutter retaining plate by more than a predetermined gap;       

   wherein the locking member and the cutter retaining plate are coupled together into an integral unit by the anchoring means so as to be detachable from the cutter frame. 
   The cutter retaining plate is movable while being guided by the plurality of guide pins and is elastically pressed toward the outer cutters by the compression coil springs mounted on the respective guide pins; accordingly, the movable range of the cutter retaining plate is sufficiently increased and large. Since the guide pins and permanent magnets are not provided in the center of the cutter frame, the adjacent outer cutters can be disposed in a sufficiently close proximity to each other so that the size of the cutter head is reduced. 
   Furthermore, in the present invention, the cutter retaining plate is pressed toward the outer cutters by a plurality of coil springs, and the locking member is fastened by means of permanent magnets; accordingly, when the locking member is to be removed, this locking member can be removed by a force equal to the difference between the spring force of the coil springs and the magnetic attachment force of the permanent magnets. Thus, the removal of the locking member can be accomplished with a light operating force. When the locking member is to be mounted back, since the locking member can be fastened in place merely by aligning the guide pins with the permanent magnets and applying a slight compression so that the coil springs are compressed by a fixed amount by the attachment force of the permanent magnets, the operation required is light and easy. 
   Furthermore, in the present invention, the plurality of guide pins that are used to fasten the locking member to the cutter frame are utilized, and the cutter retaining plate is guided by these guide pins; accordingly, it is not absolutely necessary to make the central shaft protrude from the center of the cutter frame and hold the cutter retaining plate here. The cutter retaining plate can be thus stably held without a complicated structure. 
   In the present invention, the cutter frame is provided with a central shaft that protrudes from the interior center of the cutter frame, and the center of the cutter retaining plate is engaged with this central shaft in a manner that the cutter retaining plate is slidable on the central shaft. With this structure, even when the outer cutters are depressed inward so that the cutter retaining plate sinks inward, the cutter retaining plate has much less tendency to move in the radial direction. Accordingly, the guide pins of the locking member tend not to be moved in relative terms with respect to the permanent magnets, and there is little danger that the guide pins will slip from the permanent magnets. 
   The outer cutters can be comprised of two outer cutters that are installed side by side or can be comprised of three or more outer cutters. In a shaver with three outer cutters, these three outer cutters and inner cutters are disposed at the vertices of an equilateral triangle, and the central shaft is disposed at the center of this triangular shape. In a shaver with two outer cutters that are disposed side by side, the central shaft is provided to be at an intermediate point between the two outer cutters. 
   The permanent magnets can be provided in substantially V-shaped grooves surrounded by the adjacent outer cutters and the inside wall of the cutter frame. With this structure, the spacing of the outer cutters is sufficiently small, and thus this arrangement is much more suitable for reducing the size of the cutter head of the electric shaver. 
   Inclined guide walls that are used to align the tip ends of the guide pins with the permanent magnets can be formed in the vicinity of the portions of the cutter frame to which the permanent magnets are attached. With this structure, strict positioning of the guide pins during the mounting of the locking member becomes unnecessary, thus improving the operating characteristics. It is preferable that these guide walls be formed as inclined surfaces that expand in the form of circular conical surfaces from the end surfaces of the permanent magnets. In these inclined surfaces, the portions on the external diameter side or the internal diameter side with respect to the center of the cutter frame can be left with other portions omitted. The reason for this is that centering of the locking member can be accomplished by the cooperative action of a plurality of guide walls. 
   Furthermore, a projection used to catch the fingers can be provided so as to surround the center of the cutter frame on the locking member. With this projection, attachment and detachment of the locking member are greatly facilitated. This projection used to catch the fingers can be split in the circumferential direction, and it also can be formed as a circumferentially continuous ring. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a perspective view of the cutter head and the driving section of the electric shaver according to one embodiment of the present invention; 
       FIG. 2  is a perspective view of the cutter head showing the inside; 
       FIG. 3  is an exploded perspective view showing the state in which the cutter retaining unit is separated from the cutter head; 
       FIG. 4  is an exploded perspective view in which the outer cutters and inner cutters are separated; 
       FIG. 5  is an exploded perspective view of the cutter retaining unit; 
       FIG. 6  is a longitudinal sectional side view of the cutter head; 
       FIG. 7  is an exploded sectional view of the cutter retaining plate and the locking member; 
       FIG. 8  is a view showing the internal structure of a conventional cutter frame; and 
       FIG. 9  is a sectional view taken along the line  9 — 9  in  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIGS. 1 through 7 , the reference numeral  20  indicates a cutter frame; three outer cutter mounting holes  22  (see  FIGS. 4 and 7 ) are formed in the substantially triangular bottom surface (or top surface) of this cutter frame  20 . 
   The reference numerals  24  indicate outer cutters. These outer cutters have a substantially circular disk form cap shape, and numerous slits  26  are formed in a radial configuration in the circular portions of these outer cutters, which are made of thin metal plates (see  FIGS. 1 and 4 ). Annular outer circumferential rims  28  made of a synthetic resin are integrally fastened to the opening rims of the outer cutters  24 , and three projections  30  are formed to protrude from the edges of these outer circumferential rims  28  at equal intervals in the circumferential direction so that they are in positions that are located slightly to the inside of the outer circumferential surfaces (see  FIG. 4 ). 
   The reference numerals  32  indicate inner cutters. Each inner cutter  32  is comprised of an inner cutter base body  34  (see  FIG. 4 ), which is made of a synthetic resin in which numerous arms extend radially from a cap-form base portion, and a ring-shaped cutter blade connecting body  36 , which is fastened to the tip ends of the arms. In this cutter blade connecting body  36 , numerous cutter blades that make sliding contact with the inside surface of the corresponding outer cutter  24  are integrally formed in an annular configuration. 
   The reference numeral  38  refers to a cutter retaining plate. In this cutter retaining plate  38 , three openings  40  that correspond to the outer cutter mounting holes  22  of the cutter frame  20  are formed. Outer cutter driving rings  41  are inserted into these openings  40  so that these outer cutter driving rings  41  are free to rotate. In the shown embodiment, the shaving characteristics are improved by way of designing so that the outer cutters  24  are rotated at a lower speed than the inner cutters  32  and in the opposite direction from the inner cutters  32 . Accordingly, gears are formed on the outer circumferences of the outer cutter driving rings  41 , and a pinion  46  (described later) is engaged with these gears. 
   In the assembled state shown in  FIG. 6 , the opening rims of the outer cutter driving rings  41  are engaged with the annular outer circumferential rims  28  of the outer cutters  24 . The projections  30  on these outer circumferential rims  28  engage with the end surfaces of the outer cutter driving rings  41 , so that the outer circumferential rims  28  and outer cutters  24  rotate as an integral unit together with the outer cutter driving rings  41 . 
   The inner cutters  32  are provided so that they can be mounted insides of the outer cutter driving rings  41  and so that the inner cutters  32  are rotated in a depressable and tiltable manner inside these outer cutter driving rings  41 . A substantially cloverleaf-shaped protruding walls  42  which surrounds the openings  40  is formed on the surface of the cutter retaining plate  38  that is located on the outer cutters  24  side, and the outer cutter driving rings  41  are mounted inside of this protruding wall  42 . The protruding wall  42  is positioned so as to contact a step portion  20 A (see  FIG. 6 ) formed in the inside wall of the cutter frame  20 . 
   As seen from  FIG. 5 , a small opening  44  is formed in the center of the cutter retaining plate  38 , and a pinion (small gear)  46  is held rotatably in this small hole  44  (see  FIG. 6 ). This pinion  46  is rotationally driven at a low speed by an outer cutter drive shaft  88  (described later) and engages with the outer circumferences of the outer cutter driving rings  41  as described above. A central shaft  48  that is provided to protrude from the center of the inside surface of the cutter frame  20  is inserted in an aperture of this pinion  46 . The pinion  46  and central shaft  48  help positioning the cutter retaining plate  38  when the cutter retaining plate  38  is mounted, and they also have the effect of restricting the movement of the cutter retaining plate  38  in the radial direction when the outer cutters  24  are pressed inward and of preventing the permanent magnets  62  and guide pins  56  (described later) from slipping out of position. 
   A coil spring  46 A is installed in the insertion hole of the pinion  46  into which the central shaft  48  is inserted (see  FIG. 6 ). In the assembled state of the cutter frame  20  and cutter retaining plate  38 , this coil spring  46 A is compressed between the central shaft  48  and the pinion  46 , and thus endows the pinion  46  with a return habit that causes the pinion  46  to return toward the outer cutter drive shaft  88  (described later) in an elastic manner. 
   The reference numeral  50  indicates a locking member. As shown in  FIGS. 1 through 4 , the locking member  50  has three arms  54  that extend radially or outwardly at intervals of 120° in the circumferential direction from a central circular ring portion  52 . Respective guide pins  56  are installed in an upright position with reference to the arms  54  on the tip ends of the three arms  54  so that the pins  56  face the cutter frame  20 . The guide pins  56  are made of a metal that is attached to (or attracted by) the permanent magnets  62  (described later) by magnetic attraction, e.g., a soft magnetic material such as iron, permalloy or the like. 
   In a state in which the center of the circular ring portion  52  is aligned with the center of the cutter retaining plate  38  (the center corresponding to the position of the small opening  44 ), the three arms  54  of the locking member  50  extend radially through the spaces between the adjacent outer cutters  24 . Substantially triangular small plates  58  which fill three V-shaped troughs abutted by the protruding wall  42  that surrounds the adjacent openings  40  are integrally formed on the cutter retaining plate  38 . Guide holes  60 , which have a slightly larger diameter than the guide pins  56  of the locking member  50  and allow sliding movement of these guide pins  56 , are formed in the respective small plates  58 . 
   Circular disk-form permanent magnets  62  are respectively fastened by means of an adhesive agent or the like to the cutter frame  20  in three positions that face the guide holes  60 . In other words, the permanent magnets  62  are respectively provided in three V-shaped gaps surrounded by the adjacent outer cutters  24  and the inside wall of the cutter frame  20 . In a state in which the three guide pins  56  of the locking member  50  are passed through the three guide holes  60  of the cutter retaining plate  38 , these permanent magnets  62  attach or attract the tip ends of the guide pins  56  by magnetic attraction. 
   The reference numerals  64  are coil springs that are mounted on the guide pins  56 . These three compression coil springs  64  are compressed between the arms  54  of the locking member  50  and the triangular small plates  58  of the cutter retaining plate  38 . 
   Engaging holes  66  which pass through parallel to the guide pins  56  are respectively formed in the respective arms  54  of the locking member  50 . Three engaging claws  68  which are engageable with and disengageable from these engaging holes  66  are formed to protrude from the cutter retaining plate  38 . These engaging claws  68  advance into and engage with the engaging holes  66  of the arms  54  when the locking member  50  is assembled with the cutter retaining plate  38 . As a result, these engaging holes  66  and engaging claws  68  form an anchoring means that prevents the locking member  50  from being separated from the cutter retaining plate  38  by more than a predetermined gap and at the same time allows these two parts to approach each other. 
   The predetermined gap, which is formed between the locking member  50  and the cutter retaining plate  38  when the engaging claws  68  are engaged with the engaging holes  66 , has a dimension in which the coil springs  64  mounted on the guide pins  56  are clamped and slightly compressed between the arms  54  and small plates  58 . Furthermore, a flange-form projection  70  used to catch the fingers is integrally formed on the circular ring portion  52  of the locking member  50 . The projection  70  is split into three sections in the circumferential direction. 
   Inclined guide walls  72  (see  FIGS. 2 ,  3  and  6 ) that guide the tip ends of the guide pins  56  to the correct positions when the tip ends of these guide pins  56  are attached by magnetic attraction to the permanent magnets  62  are formed on the portions of the cutter frame  20 , to such portions the permanent magnets  62  being fastened. These guide walls  72  are inclined surfaces that expand outward in a circular conical form from the end surfaces of the permanent magnets  62 . The guide walls  72  need not be complete circular conical surfaces, and they can be surfaces with some portions cut away. For example, the guide walls can be formed as walls in which the internal diameter side is removed and only the external diameter side is left with respect to the center of the cutter frame  20 . In this structure, the three permanent magnets  62  and guide walls  72  act in conjunction to guide the three guide pins  56  and correctly position the locking member  50 . 
   In  FIG. 1 , a driving section  80  is an integral part of the shaver main body (not shown in  FIG. 1 ). This driving section  80  comprises a substantially triangular base plate  82 , a single-driving motor  84  which is attached to the back surface of this base plate  82 , three drive shafts  86  that protrude on the front surface side from positions at the vertices of the triangle of the base plate  82 , and the outer cutter drive shaft  88  that protrudes on the front surface side from the center of the base plate  82 . 
   The three drive shafts  86  are rotationally driven by rotating shaft (not shown) of the driving motor  84 . The drive shafts  86  are endowed with a return habit in the direction of protrusion by coil springs (not shown). The outer cutter drive shaft  88  contains a speed reduction mechanism made of a planetary gear and is rotationally driven at a low speed by the rotating shaft of the motor  84 . 
   A cruciform protruding portion  90  is formed on the end surface of the outer cutter drive shaft  88 . The protruding portion  90  engages with a cruciform recessed portion  46 B (see  FIGS. 2 ,  3  and  6 ) formed in the tip end of the pinion  46  when the cutter head is assembled with this driving section  80 . The pinion  46  is movable toward the cutter frame  20  by the compression of the coil spring  46 A installed in the pinion  46 . Accordingly, when the cutter head and driving section  80  are assembled, the pinion  46  is pressed inward if the engagement of the cruciform protruding portion  90  and recessed portion  46 B is not properly aligned, and the pinion  46  returns when the protruding portion  90  and recessed portion  46 B are engaged as a result of the rotation of the outer cutter drive shaft  88 . 
   Next, the operation of the embodiment described above will be described. 
   First, the outer cutters  24  are mounted in the outer cutter mounting holes  22  of the cutter frame  20 , and the outer circumferential rims  28  of the outer cutters  24  are brought to be engaged with the step portion  22 A of the cutter frame  20 . Then, the inner cutters  32  are mounted in the outer cutters  24 . 
   Meanwhile, the outer cutter driving rings  41  and locking member  50  are assembled with the cutter retaining plate  38  to form a cutter retaining unit. More specifically, the coil springs  64  are first mounted on the guide pins  56 , and the guide pins  56  are next inserted into the guide holes  60  of the cutter retaining plate  38 . Then, when the engaging claws  68  of the cutter retaining plate  38  are engaged with the engaging holes  66  of the locking member  50 , the cutter retaining plate  38  and locking member  50  are integrated to form the cutter retaining unit. The cutter retaining unit is grasped by engaging the fingertips of the thumb and index finger with the projection  70  (used to catch the fingers) of the locking member  50 , and the guide pins  56  are brought to be attached by magnetic attraction to the permanent magnets  62  of the cutter retaining plate  38 . 
   During this mounting process, the guide walls  72  located in close proximity to the end surfaces of these permanent magnets  62  correctly guide the tip ends of the guide pins  56  to the permanent magnets  62 , so that the above-described cutter retaining unit can be set in the correct position. In this state, the cutter retaining plate  38  presses the projections  30  of the outer cutters  24  while compressing the coil springs  64 . Furthermore, a state in which the engaging claws  68  of the cutter retaining plate  38  float slightly upward from the engaging holes  66  of the locking member  50  is produced, so that the cutter retaining plate  38  is allowed to move relative to the locking member  50 . In this case, furthermore, the central shaft  48  advances into the pinion  46 , and the coil spring  46 A is compressed. 
   The cutter head thus assembled is mounted on the shaver main body  80 . When the cutter head is thus mounted, the drive shafts  86  driven by the motor is brought to be engaged with the inner cutters  32  so that the inner cutters  32  are rotated. Furthermore, the protruding portion  90  of the outer cutter drive shaft  88  comes to engage with the recessed portion  46 B of the pinion  46 , so that the outer cutter driving rings  41  can be rotated at a low speed in the opposite direction from the drive shafts  86 . The outer cutters  24  are rotated at a low speed together with the outer cutter driving rings  41 . 
   When, during shaving, the outer cutters  24  contact the skin and are depressed, and the outer cutters  24  press the outer cutter driving rings  41  and cutter retaining plate  38  downward toward the cutter main body. The cutter retaining plate  38  is moved toward the locking member  50  while compressing the coil springs  64  and being guided by the guide pins  56  and center shat  48 . When, on the other hand, the external force that depresses the outer cutters  24  is eliminated, the cutter retaining plate  38  is pushed back (pressed upward) by the coil springs  64  and is pressed by the outer cutter driving rings  41  so that the cutter retaining plate  38  returns to its original position (the position shown in  FIGS. 1 and 6 ). 
   When the shaving debris is to be cleaned away, the projection  70  (used to catch the fingers) of the locking member  50  is grasped with the fingers, and a unit that consists of the locking member  50  and cutter retaining plate  38  (i.e., a cutter retaining unit) is pulled away from the cutter frame  20 . In this case, since the rebound force of the coil springs  64  that contact the small plates  58  of the cutter retaining plate  38  at one end acts on the locking member  50  in a direction that pulls the locking member  50  away, the cutter retaining unit can be removed by a force that is smaller than the magnetic attraction attachment force of the permanent magnets  62 . 
   When the cutter retaining unit is thus removed, the inner cutters  32  and outer cutters  24  remain and are revealed inside the cutter frame  20 ; and these cutters can be cleaned. If necessary, it is possible to remove the inner cutters  32 , so that the inner cutters  32  and the outer cutters  24  that are separated from each other are cleaned. 
   In the above structure, the electric rotary shaver has three outer cutters and inner cutters so that they are positioned at vertices of an equilateral triangle, and the central shaft is positioned at the center of the equilateral triangle. The present invention is also applicable to an electric rotary shaver that has two sets of outer and inner cutters disposed side by side. In this structure, the central shaft of the cutter frame is positioned at an intermediate point between the two outer cutters; and other structures are designed so as to comply with this two outer and inner cutter structure, so that, for instance, the cutter frame  20  is formed with two outer cutter mounting holes  22 , the cutter retaining plate  38  has two openings  40 , the locking member  50  has two arms  54 , and two drive shafts  86  are provided.