Abstract:
A dry shaver comprising one or more pairs of shear plates having a comb shape and rotary blades in contact with the shear plates which slide on said shear plates while rotating. The rotary blades of each pair of shear plates are supported at only two points within the shaver case and rock or incline with the supporting points acting as fulcra, whereby a close fit to the curved surface of the skin is achieved.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a shaver of the so-called rotary type wherein rotary blades rotate in contact with a shear plate having a comb shape. More particularly, the present invention is directed to an improved rotary shaver so arranged and constructed that the rotary blades achieve a free rocking motion relative to the case during the shaving process. 
     As is commonly known the shear plate is fixed to the case. With this type of shaver, however, the shear plate does not fit the curved skin surface, very well resulting in a poor shaving efficiency, a difficulty in cutting the beards sufficiently short and also a long time required for shaving. 
     Another known type of dry shaver has rotary blades mounted on the drive shaft over a spring so as to be displaceable along its axis, with the shear plate mounted thereon and supported thereby. With this type of shaver, however, the external force to which the shear plate is subjected during shaving is directly transmitted to the rotary blades with a resultant increase in the friction between the shear plate and rotary blades, which, in turn, can cause a decrease of the revolution rate of the blades and, more critically, an adverse effects on the rotary blades-to-drive shaft coupling system. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a dry shaver whose shear plate can rock or incline to fit the skin surface being shaved. 
     Another object of this invention is to provide a shaver of such construction that the outer shear plate is so attached to the case that it can rock freely. 
     A further object of the present invention is to provide a shaver wherein the rotary blade is fixed to the driving shaft with no play therebetween so that the compression force of the compression spring against the rotary blade and thus against the shear plate is parallel to the driving shaft and perpendicular to the shear plate at all times. 
     Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     The construction embodying the present invention with the shear plate movably supported by the case helps protect the rotary inner blades from the action of the external force to which the shear plate is directly subjected, the external force being transmitted to act only on the case. Thus an unnecessary increase of the friction between the shear plate and the rotary blades can be successfully prevented, thereby reducing the wear of both the shear plate and the rotary blades and precluding an adverse effect on the cutter-to-shaft coupling. The present invention is characterized by the shear plate supporting mechanism wherein the case is provided with two supporting points for the shear plate so that the shear plate can rock freely with said supporting points acting as a fulcra. 
     According to the present invention, it is also possible to provide the shear plate supporting mechanism wherein there is provided supporting members with two supporting points for the shear plate, and said supporting members, in turn, are mounted on the case to be supported thereby at two points apart from those on said supporting member so that the shear plate can rock or slant freely relative to the case. 
     A further feature of the present invention is a power transmitting mechanism which enables rotation of the blades sliding in contact with the shear plate. This may be accomplished, for example, by connecting the drive shaft to the power source over a universal joint and having the rotary blades mounted on the drive shaft so powered. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein, 
     FIG. 1 is a diagram showing the external appearance of the dry shaver according to the present invention; 
     FIG. 2 is a sectional view of a portion of the shaver; 
     FIG. 3 is a perspective view of the assembly for supporting the shear plate on the holder of the case, with the assembly disassembled and viewed from the bottom; 
     FIG. 4 is a diagram illustrating the mechanism for supporting the shear plate on the holder; 
     FIG. 5 is a perspective view of the disassembled holder of another embodiment of the present invention showing two shear plates; and 
     FIG. 6 is a sectional view showing the structure of the key parts of the holder in a further embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, the case 2 housing the battery, motor 1 etc., is composed of a body 3 and a holder 4. The holder 4 has three circular openings 5, 5, 5 so arranged as to be positioned at the vertices of an equilateral triangle. Three circular shear plates 6, 6, 6 are movably set in the openings 5, 5, 5 with some play and rotary blades 7, 7, 7 are so mounted as to be freely rotatable in these circular shear plates 6. 
     The holder 4 has a supporting member 9 secured thereto with a screw 8 at the center on the back thereof. The supporting member 9 protruding partially into the openings 5, 5, 5 serves to prevent the rotary blade 7 for dropping out of the shear plate 6. 
     Each of the openings 5 is formed in two stages so that the holder 4 has an inward flange 4a, and, on the back of the flange 4a, a pair of projections 4b, 4b are arranged symmetrically across the center. 
     The flange 6a of the shear plate 6 has on its topside a pair of recesses 6b, 6b arranged symmetrically across the center, the recesses receiving the above-mentioned projections 4b, 4b. Such fitting mechanism serves to prevent rotation of the shear plate 6 along the blade 7 and at this time allows rocking of the shear plate 6. 
     The abovementioned supporting member 9 contains a pair of upward projections or edges 9a, 9a arranged point-symmetrically so as to support the flange 6a of the shear plate 6 or both sides from beneath. The projections 9a, 9a are positioned under the recesses 6b, 6b. Hence, the shear plate 6 can rock with the projections 9a, 9a acting as fulcra. 
     The supporting projections 9a, 9a are so positioned that the vertical amplitude of the rocking motion of the shear plate 6 is maximum at a point nearest to or remotest from the center of the holder 4, i.e., they are so positioned as to support the shear plate 6 where symmetric across the center thereof and equidistant from the center of the holder 4. 
     More particularly, the supporting projections 9a, 9a are located on or close to a line passing the center of the shear plate 6 and perpendicular to the plane containing a line passing the center of the shear plate 6 and the center of the holder 4. 
     Recesses 4c, 4c are formed on the back of the holder 4 for positioning the supporting member 9, and for receiving a part of the projections 9a, 9a of the supporting member. 
     On the shaft of the motor 1 is mounted the driving gear 10 which is in mesh with the driven gear 11. The drive shaft 12 is connected to the driven shaft 11 over a universal joint to be described hereinafter, its rectangular tip 12a fitting in the rectangular hole 7a in the leg of the rotary blade 7. 
     The universal joint disclosed herein is not to be considered of a limiting nature in the light of the present invention, and thus various equivalent alternatives can be used. The flange 12b at the lower end of the drive shaft 12 has two sides parallel along its periphery and two convex sides bordering thereon. The abovementioned driven gear has, in its center, a bore 11a whose wall is similar to and a little larger than the peripheral surface of the flange 12b. Hence the flange 12b is fitted in the bore 11a with some play and thus the flange 12b, being rotatable with the rotation of the driven gear 11 can slant freely relative to the driven gear 11. 
     In the center of the keep plate 13, secured to the topside of the annular projection 11b of the driven gear 11, there is a hole 13a through which the drive shaft 12 is set with some play while between the drive shaft 12 and the driven gear 11 there is provided a compression spring 14. 
     The hole 13a is so dimensioned that the flange 12b cannot slip therethrough. A washer 15 is also provided. In this way the joint between the drive shaft 12 and the driven gear 11 constitutes a universal joint. The spring 14 pushes up the drive shaft 12 so that it is securely fitted to the rotary blade 7, thus ensuring a high shaving efficiency. A cover 16 has a hole 16d for accommodating the drive shaft 12. The cover is secured with screws, not shown, to the body, and serves to cover for the driving gear 10 and the driven gear 11. The cover 16 has on its topside around the center an annular projection 16a, the inside wall thereof forming a bore 16b which provides the space for the holder 8a of the screw 8. The annular projection 16a has in it a hole 16c, in which the retainer 17 is set so as to be freely slidable. 
     Between the retainer 17 and the cover 16 is mounted a compression spring 18. The retainer 17 is provided with a push button 19 connected thereto which partially protrudes through the hole 2a of the body 2. In this case the retainer 17 is made of a head steel. 
     The retainer 17 also has a hole 17a which communicates with the hole 16a when it is displaced against the repulsive force of the spring 18 by pushing the push button 19. 
     As shown in FIG. 2, the rim of the hole 17a is in engagement with the head 8a of the screw 8 when the retainer 17 is in its normal position. At this time the holder 4 is thus secured to the body 3. When the retainer 17 is displaced against the repulsive force of the spring 18 by pushing the push button 19, the holder 4 is disengaged from the body 3. When this shaver is used with the switch 20 turned on, the shear plates 6, 6, 6 are allowed to rock with the supporting projections 9a as fulcra so as to fit the curved skin surface, the rocking amplitude being largest where it is nearest to the center of the head 4. 
     The rotary blades 7, 7, 7 follow this rocking motion of the shear plate 6, 6, 6 and are driven by the drive shaft 12 which is allowed to slant accordingly relative to the driven gear. 
     Referring now to FIG. 5 is another embodiment of the present invention, especially the shear plate supporting mechanism thereof. The shear plate 106 has a pair of recesses 106c, 106c which are adapted to match a pair of projections 109a, 109a of the supporting member 109 so that the supporting projections 109a can fit in the recesses 106c respectively. The fitting junctures, which serve as fulcra for the rocking of the shear plate 106, also prevent rotation of the shear plate 106. The recess 6b of FIG. 3 receiving the projection 4 of the holder 4 on the upper side of the flange 6 can then be dispensed with. 
     The supporting projections 109a, 109a are so positioned that the vertical amplitude of the rocking motion of the shear plate is maximum at a point nearest to or remotest from the center of the holder 104, i.e., they are so positioned as to support the shear plate 106 where symmetric across the center thereof and equidistant from the center of the holder 104. 
     When with either of the two embodiments the supporting member is made of an elastic material, the supporting member can flex according to the external force the shear plate is subjected to, thus allowing the shear plate to slant freely. In such a case it is also possible to dispense with the projection 104b. 
     Described below is still another embodiment with reference to FIG. 6. In this embodiment the supporting member 209 rotatably supports the ring 220 by two supporting projections 221, 221 and the ring 220, in turn, supports the shear plate 206, again rotatably by pins 222, 222 which are positioned apart from the supporting points with an angle of 90°. Thus, the supporting projection is inserted into a hole 206 and the pin is inserted in a hole 220a of the ring. In a similar manner, the supporting projections 221, 221 are so positioned that the vertical amplitude of the rocking motion of the shear plate is maximum at a point nearest to or remotest from the center of the holder 104. 
     The supporting mechanism allows the shear plate 206 to slant in any direction according to the external force to which it is subjected. In any of the embodiments of the present invention described above, the shear plate is supported on the case in such a manner that it can slant freely so as to fit the curved skin surface and thus a high shaving efficiency is ensured. 
     It is to be understood that the embodiments described above are not to be interpreted in a limiting amount and that further variations are possible on the basis of the principle of the present invention set forth herein.