Patent Publication Number: US-11045964-B2

Title: Rotary electric shaver with magnet biased blade units

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. P2017-235719, filed on Dec. 8, 2017, and the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a rotary electric shaver. 
     BACKGROUND ART 
     A rotary electric shaver includes a main body in which a motor is built, a head unit having a plurality of blade units each having an outer blade which has a circular shaving surface on an outer side, and an inner blade which is in sliding contact with on an inner surface of the outer blade, and a driving power transmission mechanism transmitting driving power from the motor to rotate the inner blade, and has a structure in which the head unit is connected to a connecting portion disposed in the main body. 
     In the related art, with respect to a connection structure of the head unit in the rotary electric shaver, there is known a configuration in which a compression spring is inserted through a connecting shaft of the connecting portion to cause the head unit to be movable upon pushing (PTL 1: JP-T-2016-514557). In addition, in a reciprocating-type electric shaver having a structure which has one blade unit having an outer blade having an inverted U-shape in cross section and an inner blade which is in sliding contact with a lower surface of the outer blade, there is known a configuration in which magnets which repulsively react with each other are inserted through a connecting shaft of a main body to cause the head unit to be movable upon pushing (PTL 2: JP-UM-A-1-82877). 
     SUMMARY OF INVENTION 
     Technical Problem 
     As in PTL 1, in the configuration in which the compression spring is inserted through the connecting shaft of the connecting portion, in a case where the head unit and the main body close to each other while being coaxial with the connecting shaft, a pressing force is exerted in a direction compressing the compression spring. Therefore, a restoring force of the compression spring acts in a direction in which the head unit and the main body go away from each other while being coaxial with the connecting shaft. 
     However, in a case where the head unit is pressed against a skin surface at a position distant from the connecting shaft, almost no pressing force acts in a direction compressing the compression spring, so that the restoring force of the compression spring also hardly acts. Therefore, if the pressing force by a user is strong, the pressing force is transmitted to the skin surface as it is, and the outer blade strongly presses the skin surface, and if the pressing force by a user is weak, the pressing force is transmitted to the skin surface as it is, and the outer blade weakly presses the skin surface. 
     Normally, when the head unit is pressed against the skin surface, the user is not so conscious of whether or not it is at a position distant from the connecting shaft and pushes the head unit against the skin surface with a substantially constant force. Therefore, in a case of the configuration of PTL 1, for example, when a position close to an outer periphery of the head unit comes into contact with a portion of a jaw or the like where undulation (irregularity) of the skin surface is relatively large, there is a problem that a variation of a force with which the outer blade presses the skin surface increases and as a result, a followability of the outer blade to the skin surface deteriorates. The problem is a factor of hindering a sufficient deep shaving, as well as a factor of leaving some hairs unshaved. In this invention, examples of the hairs include beards, mustache, whisker, and the like. 
     In addition, even if the configuration in which magnets which repulsively react with each other are inserted through a connecting shaft of a main body to cause the head unit to be movable upon pushing as in PTL 2 is applied to PTL 1, the compression spring is merely replaced by the magnet. Therefore, if a position close to the outer periphery of the head unit comes into contact with a place where undulation (irregularity) of the skin surface is relatively large, the problem that the followability of the outer blade to the skin surface deteriorates cannot be solved. 
     Solution to Problem 
     The present invention is made in view of the above circumstances and an object of the invention is to provide a rotary electric shaver having a support structure in which a followability of an outer blade to a skin surface is enhanced as compared to the related art in a rotary electric shaver in which a plurality of blade units are disposed. 
     The present invention has been accomplished under the solutions as disclosed below. 
     A rotary electric shaver according to the present invention includes: a main body in which a motor and a first transmission mechanism that transmits a driving power of the motor are built, and a connecting portion is disposed; a head unit in which a plurality of blade units each having an outer blade having a circular shaving surface on an outer side, an inner blade being in sliding contact with an inner surface of the outer blade, and a driven shaft rotating the inner blade are disposed, and a second transmission mechanism that transmits a driving power of the first transmission mechanism to rotate the driven shaft is built, and which is connected to the connecting portion; and a drive shaft that transmits the driving power of the first transmission mechanism to the second transmission mechanism. The head unit has a first magnet disposed at a position corresponding to each of the blade units. The main body has a second magnet disposed at a position facing and repelling the first magnet. 
     According to the configuration, a support structure that floats the head unit from the main body and flexibly supports the head unit by a repulsive force between the first magnet disposed corresponding to each of the blade units and the second magnet disposed corresponding to the first magnet is provided. Since the repulsive force between the first magnet and the second magnet acts on each of the blade units, the head unit is not limited to a linear operation in an upward and downward direction such as the restoring force of the compression spring inserted through the connecting shaft of the connecting portion in the structure of the related art, and flexibly operates in any of upward, downward, rightward, leftward, frontward and rearward directions. Therefore, the support structure is provided in which a followability of the outer blade to a skin surface is enhanced as compared to the related art. 
     Advantageous Effects of Invention 
     According to the invention, a rotary electric shaver having a support structure can be realized in which a followability of an outer blade to a skin surface is enhanced as compared to the related art in a rotary electric shaver in which a plurality of blade units are disposed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view schematically illustrating an example of a rotary electric shaver according to an embodiment of the invention. 
         FIG. 2  is a sectional view that is taken along line II-II in  FIG. 1  in which an internal structure is omitted. 
         FIG. 3  is a sectional view that is taken along line in  FIG. 2  in which an internal structure is omitted and is a schematic view illustrating a disposition example of a first magnet. 
         FIG. 4  is a view as viewed from C direction in  FIG. 3  and is a schematic view illustrating an example of an engagement structure between a blade setting base and a blade setting base support plate. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings. The embodiment is, for example, a rotary electric shaver  1  in which a plurality of blade units are disposed. Hereinafter, it may be simply referred to as the “electric shaver”. Moreover, in all drawings for explaining the embodiment, the same reference numerals are given to members having the same function and repetitive description thereof may be omitted in some cases. 
     As illustrated in  FIGS. 1 to 3 , the electric shaver  1  includes, for example, a main body  2  gripped by a user and a head unit  4  connected to a connecting portion  3  which is disposed in the main body  2 . Here, in order to make it easy to explain a positional relationship of each portion of the electric shaver  1 , directions are indicated by arrows of X, Y, and Z in the drawings. 
     A front side of the main body  2  is an operation panel and a selection button for selecting an operation is provided. A motor  7 , a power supply unit  91  that supplies electricity to the motor  7 , and a control unit  92  that controls the motor  7  and the power supply unit  91  are built in the main body  2 . 
     The head unit  4  is provided with a plurality of blade units  8  each having a cap-shaped outer blade  81  having a circular shaving surface on an outer side, an inner blade  82  being in sliding contact with an inner surface of the outer blade  81 , and a driven shaft  85  rotating the inner blade  82 . In the embodiment, three blade units  8  are disposed at equal intervals in a circumferential direction with respect to a center of the head unit  4  in a plan view. In addition, the head unit  4  includes an outer blade frame  41  that holds the blade unit  8  such that the blade unit  8  is capable of swing movement, and a blade setting base  42  which holds the outer blade frame  41 . 
     As illustrated in  FIG. 2 , a first transmission mechanism  11  of a gear driving system for transmitting a driving power of the motor  7  is built in the main body  2 . A second transmission mechanism  12  of a gear driving system for transmitting a driving power of the first transmission mechanism  11  via a drive shaft  5  and rotating the driven shaft  85  is built in the head unit  4 . In addition, the main body  2  includes a blade setting base support plate  43  through which the drive shaft  5  penetrated and which supports the blade setting base  42 . In  FIG. 2 , the first transmission mechanism  11  and the second transmission mechanism  12  are indicated respectively by areas surrounded by broken lines. 
     In the example illustrated in  FIG. 2 , the columnar connecting portion  3  is formed in the blade setting base support plate  43  and the connecting portion  3  is inserted into a through-hole  42   a  formed in the blade setting base  42 . A lower projection portion of an inverted dish-like pressing portion  31  is attached to the through-hole  42   a  from an upper side of the blade setting base  42 , and the pressing portion  31  and the connecting portion  3  are connected and fixed by a fixing member  32  such as a screw or a bolt from the upper side. 
     As illustrated in  FIG. 3 , the head unit  4  has a first magnet  51  which is disposed at a position closer to an outer periphery than the drive shaft  5  and the driven shaft  85  with respect to each of the blade units  8 . The first magnet  51  is fixed to the blade setting base  42  by press fitting, bonding, embedding, or other known methods. As illustrated in  FIG. 2 , the main body  2  has a second magnet  52  which is disposed at a position facing and repelling the first magnet  51 . The second magnet  52  is fixed to the blade setting base support plate  43  by press fitting, bonding, embedding, or other known methods. In the embodiment, three first magnets  51  and second magnets  52  are respectively disposed. 
     According to the configuration, a support structure that floats the head unit  4  from the main body  2  and flexibly supports the head unit  4  by a repulsive force between the first magnet  51  and the second magnet  52  is provided. Since the repulsive force between the first magnet  51  and the second magnet  52  acts on each of the blade units  8 , the head unit  4  is not limited to a linear operation in an upward and downward direction as in the structure of the related art, and flexibly operates in any of upward, downward, rightward, leftward, frontward and rearward directions. Therefore, there is provided the support structure in which a followability of the outer blade  81  to a skin surface is enhanced as compared to the related art. 
     As illustrated in  FIGS. 1 to 3 , the first magnets  51  are disposed at equal intervals in the circumferential direction surrounding the connecting portion  3  as the head unit  4  is viewed from an outer blade  81  side. The same applies to the second magnets  52 . According to the configuration, even in a case where a position close to the outer periphery of the head unit  4  comes into contact with a portion of a jaw or the like where undulation (irregularity) of the skin surface is relatively large, a variation of a pressing force with which the outer blade presses the skin surface by the repulsive force between the first magnet  51  and the second magnet  52  can be suppressed. 
     In the embodiment, the first magnet  51  and the second magnet  52  are permanent magnets, and neodymium magnets, ferrite magnets, and other known magnets can be applied. For example, a high repulsive force can be obtained while reducing a space for mounting the magnets by making the first magnet  51  and the second magnet  52  neodymium magnets. 
       FIG. 4  is a view as viewed from C direction in  FIG. 3  and is a schematic view illustrating an example of an engagement structure between the blade setting base  42  and the blade setting base support plate  43 . Line P 1 -P 1  passing through the center of the connecting portion  3  in an axial direction and the outer blade  81  of the head unit  4  in  FIG. 2  and line P 2 -P 2  passing through the center of the first magnet  51  and the center of the second magnet  52  in  FIG. 4  in the front view are in positions where they overlap each other. In the embodiment, a convex portion  45  that protrudes in a radial direction is formed at a position closer to an outer periphery than the first magnet  51  of the blade setting base  42 , and a concave portion  46  that engages with the convex portion  45  in the axial direction is formed at a position closer to the outer periphery than the second magnet  52  of the blade setting base support plate  43 . According to the configuration, for example, even in a case where an external force is applied in the circumferential direction of the head unit  4  by causing the head unit  4  to come into contact with the skin surface, since the convex portion  45  is engaged with the concave portion  46 , it is possible to prevent the head unit  4  from rotating. 
     The invention is not limited to the above-described embodiment, and various modifications are possible without departing from the invention. For example, in the above-described embodiment, the first magnet  51  and the second magnet  52  adopt permanent magnets, but the invention is not limited thereto. It is possible to use an electromagnet for either or both of the first magnet  51  and the second magnet  52 . 
     Further, for example, in the above-described embodiment, the configuration in which the three blade units  8  are disposed is described, but the invention is not limited thereto. There are cases where two blade units  8  are disposed or four or more blade units  8  are disposed.