Abstract:
A rotary electric shaver including an outside outer cutter and an inside outer cutter capable of mutually moving up and down independently, a drive shaft to which an upward return tendency is imparted, an outside inner cutter guide that engages the drive shaft and rotates integrally therewith, an outside inner cutter secured to the outside inner cutter guide, an inside inner cutter guide having a plurality of engagement pawls that engage the outside inner cutter guide from above so as to be able to move up and down and that rotates together with the outside inner cutter guide, an inside inner cutter secured to this inside inner cutter guide, and an upward-pushing spring mounted between the upper surface of the outside inner cutter guide and the lower surface of the inside inner cutter guide, for urging the inside inner cutter guide upward.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotary electric shaver wherein an inner cutter rotates while, from below, sliding against a plurality of outer cutters provided coaxially. 
     2. Description of the Related Art 
     For some time, rotary electric shavers of the so-called two-track (double track) type, having two tracks (ring-shaped channels wherein the inner cutter travels) provided coaxially in a ring-shaped outer cutter, have been widely used. Here, the two tracks are provided in one common outer cutter, and the two inner circumferential and outer circumferential tracks are corresponding. The inner cutter that slides against these two tracks is also formed integrally. That is, the inner cutter is such that an outside inner cutter that slides against the outer circumferential track and an inside inner cutter that slides against the inner circumferential track are made integral therein, this inner cutter is made to engage from above with a drive shaft that is urged upward, and the inner cutter presses against the outer cutter due to the upward return force on the drive shaft. 
     With this conventional shaver, there is a problem that because the outer cutter is made integral, the entire surface contacting the skin will move up and down in correspondence with irregularities in the skin surface, but the outer cutter cannot minutely follow the fine irregularities in the skin surface. 
     Thereupon, in Japanese Patent Application Laid-Open Nos. 2001-755 and 55-158084, for example, it is proposed that the outer cutter be divided so as to correspond to inner and outer circumferential tracks, making an inside outer cutter and an outside outer cutter capable of independently moving up and down. 
     In the shavers disclosed in Japanese Patent Application Laid-Open Nos. 2001-755 and 55-158084, the outer cutter is divided between the inner and the outer circumference, but the inner cutter support structure is very complex, the number of parts is extremely large, and the shavers become large and bulky. In the shavers described in Japanese Patent Application Laid-Open Nos. 2001-755 and 55-158084, holder units for the outside inner cutter and the inside inner cutter are formed in tubular shapes on the same axis, and these tubular holder units are driven by a motor. Furthermore, springs for urging the respective tubular holder units upward are accommodated inside these tubular holder units. As a consequence, the size becomes larger, with the up-and-down dimension and the diameter of the support portion of the inner cutter becoming large. Furthermore, because the structure is complex, there are other problems, such as the assembly is difficult and the number of assembly operations is increased, it is very difficult to effect a water-resistant structure, and cleaning out whisker shavings is also difficult. 
     Moreover, because the structure of the drive system for transmitting the rotation of the motor to the inner cutter differs drastically from the conventional structure wherein an upward return force is imparted to the drive shaft, a dedicated design becomes necessary, and it becomes necessary also to introduce new manufacturing equipment. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention, which was devised in view of such circumstances as describes above, is to provide a rotary electric shaver where the inner cutter support structure is simplified, making it possible to reduce the number of parts and make the shaver size smaller, assembly is easy and productivity can be improved, the adoption of a water-resistance structure becomes easy, cleaning whisker shavings is made easy, and introducing new manufacturing equipment can be made unnecessary. 
     The above object is accomplished by a unique structure of the present invention for a rotary electric shaver including a plurality of outer cutters mutually provided coaxially and a plurality of inner cutters that rotate while sliding against these outer cutters from below. The electric shaver further includes an outside outer cutter and an inside outer cutter capable of moving up and down, independently of each other, while being concentric and coaxial, a drive shaft that is rotationally driven by an electric motor and to which an upward return tendency is imparted (an upwardly biasing force), an outside inner cutter guide that engages with this drive shaft and rotates integrally with this drive shaft; an outside inner cutter that is secured to this outside inner cutter guide and slides against the outside outer cutter from below, an inside inner cutter guide that has a plurality of engagement pawls for engaging the outside inner cutter guide from above so as to be able to move up and down and that rotates together with the outside inner cutter guide, an inside inner cutter that is secured to this inside inner cutter guide and slides against the inside outer cutter from below, and an upward-pushing spring that is loaded between the upper surface of the outside inner cutter guide and the lower surface of the inside inner cutter guide, for urging the inside inner cutter guide upward. 
     In other words, the inner- and outside inner cutter guides are mutually displaced in the axial direction, making them multi-level, and an upward-pushing spring is sandwiched between the two. 
     While dividing the outer cutter between an inside outer cutter and an outside outer cutter, and making them capable of moving up and down independently, respectively, the inner cutter that slides against these inner- and outside outer cutters from below is divided between an inside inner cutter and an outside inner cutter, which are made, respectively, so as to slide independently against the inner- and outside outer cutters. With this construction the ability to follow the skin surface is enhanced and it is possible to improve both the quality of the shave and the feel of the shave. 
     To the drive shaft to which an upward return tendency is imparted, an outside inner cutter guide to which the outside inner cutter is secured is engaged, so the outside inner cutter is pressed against the outside outer cutter by the return force on the drive shaft. As a consequence, there is no need for a dedicated spring for upwardly urging the outside inner cutter. 
     Furthermore, the inside inner cutter guide to which the inside inner cutter is secured engages the outside inner cutter guide from above so that it can move up and down, and an upward return force is imparted to the inside inner cutter by a spring that is compressed between these two inner cutter guides. The outside inner cutter guide and the inside inner cutter guide, therefore, will be held so as to be mutually superimposed in the axial direction in what might be called an up-and-down bi-level configuration. As a consequence, there is no need to form the two inner cutter guides concentrically, nor is there any need to load a spring inside this concentric tube. Hence the number of parts is reduced, the structure is simplified, and making the shaver smaller is possible. 
     Furthermore, because the structure is simple, assembly is also easy, and productivity improves. Moreover, adopting a water-resistant structure is also easy, and cleaning the whisker cuttings also becomes easy. Meanwhile, the drive shaft to which the upward return tendency is imparted is of a structure widely adopted in conventional electric shavers. Therefore, since all that need be done is to modify the inner cutter support structure, conventional production equipment may be easily used, and the need to introduce special new manufacturing equipment is eliminated. 
     In the present invention, the outside inner cutter guide can be made one comprised of a tubular unit having an engagement hole into which the drive shaft engages, an outside inner cutter holder unit that extends from the upper part of this tubular unit in the outer circumferential direction, and a plurality of openings that pass through that outside inner cutter holder unit in the up and down direction. In this case, the inside inner cutter guide can be structured so as to comprise an inside inner cutter holder unit positioned above the outside inner cutter guide, and a plurality of engagement pawls, that extend downward from this inside inner cutter holder unit, advance into the outside inner cutter guide openings, and engage the outside inner cutter guide so as to be able to move up and down. 
     Still further the outer cutter can be made so that, causing the outer circumference of the inside outer cutter to engage the inner circumferential edge of the outside outer cutter, it is made to be capable of mutual independent up-and-down movement (sinking in). If this is done, then the outside outer cutter and the inside outer cutter can be brought into close proximity, and the gap in the radial direction there between can be made small. 
     In order to cause the outer circumference of the inside outer cutter to engage with the inner circumference of the outside outer cutter, all that need be done is to form slits that open downward, at a plurality of places in the circumferential direction, in the inner circumference of the outside outer cutter, cause pawls for engaging these slits in the outer circumference of the inside outer cutter to protrude in the outer radial direction; and, when these slits and pawls are engaged, to secure the inner circumferential lower edge of the outside outer cutter in the circumferential direction with an anti-vibration ring. The slits and the pawls may also be reversed. That is, it is also possible to provide pawls which protrude out in the inner radial direction of the outside outer cutter, and provide slits in the inner circumference of the inside outer cutter. 
     If a protruding wall erected in the outside inner cutter guide so as to be oriented upward is made to slide against the inner circumference of this anti-vibration ring, shaft wobble in the outside inner cutter guide can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of an assembled inner cutter support unit according to one embodiment of the present invention with the outer cutter and inner cutter excluded; 
         FIG. 2  is a cross-section taken along the lines  2 - 2  in  FIG. 1 , showing the outer cutter and inner cutter in their combined; 
         FIG. 3 , similarly, is a cross-section taken along the lines  3 - 3  in  FIG. 1 ; and 
         FIG. 4  is a top plan view of an outside inner cutter guide in the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a top plan view diagramming the assembled condition of an inner cutter support unit that is one embodiment of the present invention,  FIG. 2  is a section view taken along the lines  2 - 2  in  FIG. 1 , diagramming the outer cutters and inner cutters in their combined condition,  FIG. 3 , similarly, is a section view taken along the line  3 - 3  in  FIG. 1 , and  FIG. 4  is a top plan view of an outside inner cutter guide.  FIGS. 1 and 4 , moreover, diagram conditions with the outer cutter(s) and inner cutter(s) excluded. 
     In  FIGS. 2 and 3 , symbol  10  designates an outside outer cutter, and  12  an inside outer cutter, which are combined concentrically or coaxially to form an outer cutter  14 . The outside outer cutter  10  has a circular ring shape, the cross-section formed by the plane thereof in the radial direction inclusive of the centerline thereof, being shaped substantially as an inverted U that opens downward. The upper surface of the outside outer cutter  10  is formed of thin material, wherein many slit-shaped whisker induction holes  16  oriented substantially radially are formed in the circumferential direction. The outside outer cutter  10  is fitted from below into an outer cutter insertion hole  20  provided in an outer cutter case  18 . 
     More specifically, the outer circumferential lower edge of the outside outer cutter  10  is bent outward at a plurality of locations in the circumferential direction, which bends  22  engage vertical channels  24  provided in the outer cutter case  18 , from below. Here the vertical channels  24  open downward, the bends  22  engage into these vertical channels  24  from below; and, when they come up against the upper ends of the vertical channels  24 , the upper limit position of the outside outer cutter  10  is established. 
     In the inner circumferential surface of the outside outer cutter  10 , a plurality of slits  26  are formed which open downward. Into these slits  26 , pawls  32  of the inside outer cutter  12  engage so as to be movable up and down, as is described below. In this condition, the inner circumferential lower edge of the outside outer cutter is secured by an anti-vibration ring  28  in the circumference direction. This anti-vibration ring  28  prevents vibration in an outside inner cutter guide  60  when protruding walls  76  provided in this outside inner cutter guide  60 , described subsequently, slide against it. 
     The outer diameter of the inside outer cutter  12  is slightly smaller than the inner diameter of the outside outer cutter  10 , whereupon insertion of the inside outer cutter  12  inside the inner diameter of the outside outer cutter  10  is possible. The center part of the inside outer cutter  12  is slightly sunken in, the outside thereof protrudes in a circular ring shape, and, there, many slit-shaped whisker induction holes  30  oriented substantially radially are formed in the circumferential direction. 
     The outer circumferential lower edge of the inside outer cutter  12  is bent outward at a plurality of locations in the circumferential direction, and pawls  32  comprising these bends are capable of engaging the slits  26  provided in the outside outer cutter  10 . In the sunken part in the center of the inside outer cutter  12 , a cap  34  is adhesively secured. The center of this cap  34  protrudes downward, passing through the inside outer cutter  12 , and there a concavity  36  is formed. Into this concavity  36 , a protrusion  86  on the center axis of rotation of the inside inner cutter guide  78 , described subsequently, engages, whereupon shaft wobble in the inside inner cutter guide  78  is prevented. 
     Next, the inner cutter support unit is described. An inner cutter  50  has an outside inner cutter  52  that slides against the lower surface of the outside outer cutter  10 , and an inside inner cutter  54  that slides against the lower surface of the inside outer cutter  12 . The outside inner cutter  52  and the inside inner cutter  54  have outer circumferential portions of rings  56  and  58  consisting of thin metal sheet cut upward at a certain interval in the circumferential direction, so that the entirety is formed in what is substantially a windmill shape. 
     The outside inner cutter  52  is secured to the outside inner cutter guide  60 . Here, the outside inner cutter guide  60  has a tubular part  62 , a flange-shaped outside inner cutter holder  64  that extends in the outer radial direction from the upper part of this tubular part  62 , and four openings  66  that pass through this outside inner cutter holder  64  in the up-and-down direction. In other words, the outside inner cutter holder  64 , which is a ring-shaped disk, is held by four support arms  68  which extend out in a radial shape from the tubular part  62 . 
     In the tubular part  62 , an engagement hole  72  that is square as seen from above ( FIG. 4 ) is formed, into which a drive shaft  70  ( FIG. 2 ) that is rotationally driven by an electric motor engages from below. Into this engagement hole  72 , an engagement ball  74  that is substantially square as seen from above, formed at the upper end of the drive shaft  70 , engages, whereupon the outside inner cutter guide  60  is rotationally driven by the drive shaft  70 . A circular ring part  56  of the above-described outside inner cutter  52  is bonded to the upper surface of the outside inner cutter holder  64 . 
     On the upper surface of the outside inner cutter holder  64  of this outside inner cutter guide  60 , four protruding walls  76  are formed so as to project upward from the vicinity of the outer circumferential ends of the support arms  68 . The outer circumference of these protruding walls  76  slides against the inner circumferential surface of the anti-vibration ring  28  secured to the above-described outside outer cutter  10 . 
     The inside inner cutter  54  is secured to the inside inner cutter guide  78 . Here, the inside inner cutter guide  78  comprises an inside inner cutter holder  80 , exhibiting what is substantially a crucifix form as seen from above, positioned above the above-described outside inner cutter guide  60 , and four engagement pawls  82  that extend downward from the tip ends of what is substantially the crucifix form of this inside inner cutter holder  80 . The engagement pawls  82  advance from above into the openings  66  of the outside inner cutter guide  60 , and the lower ends of the engagement pawls  82  engage the inner circumferential edges of these openings  66  from below. 
     On the upper surface of the inside inner cutter holder  80 , a protruding wall  84  that is hexagonal as seen from above, and the protrusion  86  that is positioned in the center thereof and protrudes upward, is formed. The circular ring part  58  of the inside inner cutter  54  is secured to the upper surface of this inside inner cutter holder  80 . In the center of the circular ring part  58  a hexagonal opening is formed. This opening is made to fit around the outer circumference of the protruding wall  84  of the inside inner cutter holder  80 , thereby securing together the inside inner cutter  54  and the inside inner cutter guide  78  in a definite manner. 
     Between the upper surface of the outside inner cutter guide  60 , that is, the center of the upper surface of the outside inner cutter holder  64 , and the lower surface of the inside inner cutter guide  78 , a coil spring  88  is compressed and mounted. This coil spring  88 , more specifically, is an upward-pushing spring that continually urges the inside inner cutter guide  78  upward, whereupon the inside inner cutter guide  78  moves up and down within the range of the play between the engagement pawls  82  and the inner circumferential edges of the openings  66  which they engage. Here, the return force of the coil spring  88  is set weaker than the return force on the drive shaft  70 . 
     When the outside inner cutter guide  60  and the inside inner cutter guide  78  are combined in this manner, this assembly (inner cutter assembly) is mounted on the drive shaft  70 . More specifically, the engagement ball  74  of the drive shaft  70  is engaged into the engagement hole  72  of the tubular part  62  of the outside inner cutter guide  60  below. Then the outer cutter case  18  wherein the outer cutter  14  has been mounted is mounted in the main case (not shown in the drawings). Here, the main case houses the motor, battery, and control circuit and the like, and the outer cutter case  18  is mounted on the top part thereof. 
     At this time, the outside inner cutter  52  engages with the lower surface of the outside outer cutter  10  and is pushed down, and pushes the drive shaft  70  down. That is, the outside inner cutter  52  contacts the outside outer cutter  10  due to the upward return force on the drive shaft  70 . The inside inner cutter  54 , moreover, engages with the lower surface of the inside outer cutter  12  and is pushed down. At this time, the inside inner cutter guide  78  to which the inside inner cutter  54  is secured compresses the coil spring (upward-pushing spring)  88 . That is, the inside inner cutter  54  contacts the inside outer cutter  12  due to the return force of the spring  88 . 
     When, in this condition, the motor is started, and the drive shaft  70  rotates, the inner- and outside inner cutters  60  and  78  rotate, and the outside inner cutter  52  and inside inner cutter  54  rotate while sliding against the lower surfaces of the outside outer cutter  10  and inside outer cutter  12 . When only the inside outer cutter  12  comes against the skin surface and is pushed down, the inside inner cutter guide  78 , together with the inside inner cutter  54 , descends while compressing the coil spring  88 . At this time, because the force of the coil spring  88  is set weaker than the return force on the drive shaft  70 , the outside inner cutter guide  60  will not descend. For this reason, the outside inner cutter  52  will not descend so as to be removed from the lower surface of the outside outer cutter  10 . 
     When only the outside outer cutter  10  comes against the skin surface and is pushed down, the outside inner cutter  52  and the outside inner cutter guide  60  descend while pushing down the drive shaft  70 . At this time, the inside outer cutter  12  descends together with the outside outer cutter  10  because the outer circumferential pawls  32  in the inside outer cutter  12  are engaging the upper ends of the slits  26  in the outside outer cutter  10 . 
     In this embodiment, as shown in  FIGS. 2 and 4 , the pawls  32  of the inside outer cutter  12  engage the upper edges of slits  26  in the outside outer cutter  10 , in which condition the engagement pawls  82  of the inside inner cutter guide  78  will be removed from the inner circumferential edges of the openings  66  of the outside inner cutter guide  60 . For this reason, when the outside outer cutter  10  is pushed down, the inside outer cutter  12  will stop with the pawls  32  thereof engaging the upper ends of the slits  26  of the outside outer cutter  10 . As a consequence, when only the outside outer cutter  10  is pushed down, the inside outer cutter  12  also will descend integrally therewith. 
     Moreover, the outer cutters are not limited to combinations of two cutters, that is, of an outer circumferential one and an inner circumferential one, and it is possible instead to provide three or more outer cutters concentrically, and, corresponding thereto, array three or more inner cutters in a ring form. It should be apparent to one of ordinary skill that the present invention comprehends such configurations also.