SPECIFICATION
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`SHAVING HEAD FOR A DRY SHAVER
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`Field of the Invention
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`The present invention is directed to a shaving head for a dry shaver, and
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`more particularly to a shaving head including a slit cutter unit.
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`Background of the Invention
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`In order to entrap and cut relatively long hairs, there have been proposed
`so-called slit cutter unit composed of a straight outer cutter with a plurality of hair
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`introducing slits and an inner cutter with a plurality of blades reciprocating relative
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`to the outer cutter along a lengthwise axis of the outer cutter.
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`Japanese Patent
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`Publication No. 10-323463 discloses a shaving head having the slit cutter unit, in
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`which the outer cutter is configured to provide two arrays of slits respectively on
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`opposite width ends of the outer cutter. The arrays of slits are staggered with
`each other along the lengthwise axis in order to cover substantially the full length
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`of the outer cutter, aiming to entrap the hairs over a wide skin area by moving the
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`shaving head back and forth in a direction perpendicular to the lengthwise axis.
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`For this purpose, the outer cutter is configured to have a parallel pair of raised
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`platforms which are spaced in a width direction of the outer cutter for contact with
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`the skin, and are provided respectively with the arrays of the slits. The-raised
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`platforms are connected by a trough within which a comb is disposed for
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`smoothing the hairs. Due to the intervention of the trough, top surfaces of the
`raised platforms on opposite widthwise sides of the outer cutter are interrupted,
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`i.e., bridges defined between the adjacent ones of the slits on the one raised
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`platforms become discontinuous from the corresponding bridges on the other
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`raised platform. Thus, it is likely that the hair entrapped between the slit in the
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`SHAVING HEAD FOR A DRY SHAVER
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`Field of the Invention
`
`The present invention is directed to a shaving head for a dry shaver, and
`
`more particularly to a shaving head including a slit cutter unit.
`
`Background of the Invention
`
`In order to entrap and cut relatively long hairs, there have been proposed
`so-called slit cutter unit composed of a straight outer cutter with a plurality of hair
`
`introducing slits and an inner cutter with a plurality of blades reciprocating relative
`
`to the outer cutter along a lengthwise axis of the outer cutter.
`
`Japanese Patent
`
`Publication No. 10-323463 discloses a shaving head having the slit cutter unit, in
`
`which the outer cutter is configured to provide two arrays of slits respectively on
`
`opposite width ends of the outer cutter. The arrays of slits are staggered with
`each other along the lengthwise axis in order to cover substantially the full length
`
`of the outer cutter, aiming to entrap the hairs over a wide skin area by moving the
`
`shaving head back and forth in a direction perpendicular to the lengthwise axis.
`
`For this purpose, the outer cutter is configured to have a parallel pair of raised
`
`platforms which are spaced in a width direction of the outer cutter for contact with
`
`the skin, and are provided respectively with the arrays of the slits. The-raised
`
`platforms are connected by a trough within which a comb is disposed for
`
`smoothing the hairs. Due to the intervention of the trough, top surfaces of the
`raised platforms on opposite widthwise sides of the outer cutter are interrupted,
`
`i.e., bridges defined between the adjacent ones of the slits on the one raised
`
`platforms become discontinuous from the corresponding bridges on the other
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`raised platform. Thus, it is likely that the hair entrapped between the slit in the
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`one raised platform is not successfully guided to the staggered slit in the other
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`platform, while the outer cutter is moved across the skin. This means that the
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`hair may have a chance of being out only within the slit in one of the platforms,
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`reducing the hair cutting efficiency. Moreover, since the bottom surfaces of the
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`platforms are discontinuous, the inner cutter has to be shaped in a rather
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`complex configuration, which eventually leads to the increase in fabrication cost
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`and even reduces the effective shearing contact area between the outer cutter
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`and the inner cutter to lower the cutting efficiency.
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`DISCLOSURE OF THE INVENTION
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`In view of the above problems, the present invention has been achieved to
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`provide an improved shaving head for a dry shaver which is capable of
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`increasing the cutting efficiency, yet allowing the use of the inner cutter of simple
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`structure. The shaving head in accordance with the present invention has a slit
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`cutter unit which comprises an outer cutter shaped to have a top surface for
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`contact with a user’s skin, and an inner cutter driven to reciprocate in
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`engagement with a bottom surface of the outer cutter. The outer cutter is
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`elongated to have a lengthwise axis and a width axis. The outer cutter is
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`configured to have a U-shaped structure with a pair of legs connected by a
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`crossbar, and to have a plurality of slits which are spaced in the lengthwise axis
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`to leave a plurality of bridges each between the adjacent ones ofthe slits. The
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`slits extend continuously over a full width of the crossbar and into upper ends of
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`the legs in a direction generally perpendicular to the lengthwise axis, giving two
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`straight slit paths respectively on opposite width ends of the outer cutter. The
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`straight slit paths on the opposite width ends are staggered With respect to each
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`other along the lengthwise axis.
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`The feature of the-present invention resides in
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`that each of the bridges extends along the width axis of the outer cutter to make
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`the bottom surface of the outer cutter smoothly continuous over the full length of
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`the bridge, and that each bridge is formed at its longitudinal center with a
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`deflection which is angled with respect to the width axis so as to leave, between
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`the adjacent ones of the deflections, an angled path through which the straight
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`slit paths of each slit extends continuously. With this feature, it is possible to
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`smoothly guide the hair once entrapped in one of the straight slit paths into the
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`other straight-slit path, increasing a chance of cutting the hair. Moreover, the
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`smooth bottom surface of the outer cutter allows the use of the inner cutter of a
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`simple structure, as well as enlarges the effective shearing contact area between
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`the outer cutter and the inner cutter, thereby increasing the cutting efficiency.
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`It is preferred that the outer cutter is preferred to be shaped from a single
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`metal sheet. Also, it is preferred that each bridge is shaped to have, along the .
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`lengthwise axis, a trapezoidal cross-sectionwith a longer base side defined by
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`the bottom surface and with a shorter top side defined by the top surface of the
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`outer cutter, in order to successfully introduce the hairs into the straight slit paths.
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`Further, each bridge may be formed in its top surface with a notch which
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`acts to raise the flattened hairs while the outer cutter is moving in contact with the
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`skin, improving the cutting efficiency in combination of the staggered slit
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`arrangement. The notch is preferably formed in the top surface of the
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`deflection.
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`The outer cutter is preferred to have its top surface curved along the
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`lengthWise axis to have its lengthwise center projecting than the opposite
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`lengthwise ends in order to fit the outer cutter intimately successfully on a curved
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`skin portion for cutting the hairs at such portion.
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`Each bridge may be tapered towards its longitudinal ends to have a
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`thickness which is smaller at the longitudinal ends thereof to have a width which
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`is smaller at the longitudinal ends than at the deflection, thereby introducing the
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`hairs into the slits successfully.
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`The shaving head of the present invention may include a perforated cutter
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`unit comprising an outer cutter foil having a plurality of perforations for
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`introducing the hairs, and an inner cutter driven to move relative to the outer
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`cutter foil.
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`In a dry shaver including the above-mentioned shaving head and a motor
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`having a driving element which is connected to drive the inner cutters, it is
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`preferred that the inner cutter of the slit cutter unit is made of a metal into a
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`unitary structure having a hook fro engagement with a coupler made of a plastic
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`material for connection with the driving element. The coupler is formed with
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`studs which are mechanically engaged and heat-welded to the hook for
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`establishing secure connection between the inner cutter and the coupler made Of
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`different materials.
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`These and still other advantageous features of the present invention will
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`become more apparent from the following detailed explanation of the preferred
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`embodiments when taken in conjunction with the attached drawings.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a perspective view of a dry shaver with a shaving head in accordance
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`with a preferred embodiment of the present invention;
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`FIG. 2 is an exploded perspective view of the shaving head with associated parts
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`' of the shaver;
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`FIG. 3 is a cross-section of the shaving head with associated parts of the shaver;
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`FIG. 4 is an exploded perspective view of the shaving head;
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`FIG. 5 is an exploded perspective view of a portion of the shaving head;
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`FIG. 6 is a perspective view of a slit cutter unit included in the shaving head;
`FIGS. 7 to 9 are respectively top, front, and bottom views of the slit cutter unit;
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`FIG. 10 is an exploded perspective view of the slit cutter unit;
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`FIG. 11 is a perspective view of an outer cutter of the slit cutter unit;
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`FIG. 12 is a top view of the outer cutter of the slit cutter unit;
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`FIG. 13 is a cross-section taken along line X-X of FIG. 12;
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`FIG. 14 is a cross-section taken along line Y-Y of FIG. 12;
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`FIG. 15 is a sectional view of the slit cutter unit;
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`FIG. 16 a perspective view illustrating a modification of the outer cutter of the slit
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`cutter unit; and
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`FIG. 17 is a sectional view of the slit cutter unit of the above modification.
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`BEST MODE FOR CARRYING. OUT THE INVENTION
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`Referring now to FIGS. 1 to 3, there is shown a dry shaver equipped with a
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`shaving head in accordance with a preferred embodiment of the present
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`invention. The shaver is basically composed of an elongated grip 10 and the
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`shaving head 20 mounted on top of the grip 10. The grip 1O accommodates
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`therein a motor 12 for operating the shaving head 20.
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`The shaving head 20 includes two perforated cutter units 30 and a slit
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`cutter unit 40 interposed between the perforated cutter units 30. Each
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`perforated cutter unit 30 is designed for shaving relatively short hairs, and
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`includes an outer arcuate foil 31 with a plurality of perforations and an associated
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`inner cutter 32 composed of a plurality of arcuate blades 33. The slit cutter unit
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`40 is designed for shaving relatively long hairs, and includes an elongated outer
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`straight cutter 140 with a plurality of slits 42 and an inner cutter 240, the details of
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`which will be explained later. Also included in the shaving head 20 is a cradle
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`case 22 which mounts a detachable cutter holder 50 carrying the two outer
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`arcuate foils 31 and the slit cutter unit 40, as best shown in FIG. 2. The inner
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`cutters 32 and 240 are driven by the motor 12 to reciprocate relative to the outer
`arcuate foils 31 and outer straight cutter 41. Release buttons 29 are provided
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`on opposite ends of the cradle case 22 for releasably holding the cutter holder 50.
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`The cradle case 22 is also configured to accommodate therein the motor 12 with
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`two output elements 13 which project on top of the cradle case 22 for connection
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`with the inner cutters 32. A pin 15 is secured to one of the output elements 14
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`and is detachably connected to the inner cutter 240 of the slit cutter unit 40 for
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`reciprocating the same. The output elements 13 and the pin 14 are collectively
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`referred to as a driving element for reciprocating the inner cutters 32 and 240.
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`The cradle case 22 is formed separately from the hand grip 10 and is
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`mOvably supported thereby by a support mechanism so as to be capable of
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`effecting a combination of swiveling and depressing movements relative to the
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`hand grip 10 in order to bring the cutter units 30 and 40 into smooth and effective
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`shaving contact with various areas of the user’s skin. The hand grip 10
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`accommodates therein rechargeable batteries as well as a circuit board mounting
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`electronic components realizing a driving circuit for driving the motor and a
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`charging circuit for the batteries. A switch button 19 is disposed in a curved
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`recess on front of the hand grip 10 to activate the driving circuit for energizing the
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`motor 12 to reciprocate the inner cutters.
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`As shown in FIGS. 4 and 5, the cutter holder 50 includes a rectangular
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`frame 51 which supports a pair of cassettes 61 each carrying the foils 31 of the
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`perforated cutter unit 30, in addition to the slit cutter unit 40. Each cassette 61 is
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`formed at its longitudinal. ends respectively with studs 63 which are slidably
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`received in vertical slots 53 in the longitudinal ends of the frame 51 so that the
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`cassette 61 or the outer cutter 31 carried thereon is movable at either longitudinal
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`ends relative to the frame 51 and is therefore capable of being depressed and
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`even inclined with respect to the width axis of the cradle case 22. A cover 54 is
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`fixed to each cassette 61 to be movable therewith and conceal a major portion of
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`the cradle case 22 therebehind.
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`As shown in FIGS. 6 to 10, the slit cutter unit 40 includes a chassis which
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`carries the outer cutter 140 and retains the inner cutter 240 in such a manner as
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`to allow the reciprocating movement of the inner cutter 240 relative to the outer
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`cutter 140. The chassis is composed of two end supports 71 which are secured
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`to the opposite lengthwise ends of the outer cutter 41, respectively, and which
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`support a coupler 80 carrying the inner cutter 240 by means of springs 84 such
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`that the inner cutter 240 is movable relative to the outer cutter 140 with a suitable
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`contact pressure therebetween. The coupler 80 is made of a plastic material
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`and is formed at its center with a joint 85 for connection with the driving element,
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`i.e., the pin 14 projecting on top of the cradle case 22. The coupler 80 is also
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`formed with studs 86 which are mechanically engaged and heat-sealed to
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`associated C—shaped hooks 246 on the side of the inner cutter 240 shaped from
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`a metal sheet. Each of the end supports 71 is slidably received in center vertical
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`slots 54 of the frame 51 and is secured to one of the cassettes 61 to be movable
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`together therewith relative to the frame 51 or the cradle case 22, and is therefore
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`allowed to be depressed or inclined with respect to a width axis of the cradle
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`case 22. When the cutter holder 50 is attached to the cradle case 22, each
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`outer foils 31 can be allowed to be independently depressed against a spring
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`force acting on the inner cutter 32 by a spring provided in each of the drive
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`elements 13 on the side of the cradle case 22. Further, the inner cutter 32 is
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`swingably connected to the drive element 14 such that each perforated cutter unit
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`30 can be inclined in opposite directions, in addition to being depressed relative
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`to the cradle case 22 in the like manner as the cradle case does relative to the
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`hand grip.
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`The end supports 71 are mounted to the frame 51 and are biased upwardly
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`therefrom by longitudinally spaced springs 74. The bias of the springs 74 is
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`additive to the spring bias acting on the inner cutter 240 to give a strong resisting
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`force to the combination of the slit cutter unit 40 and the outer cutter 72 of the
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`one perforated cutter unit 30 movable together with the slit cutter unit 40. Thus,
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`the combination is made more resistive to the depressing and inclining
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`movements than the other perforated cutter unit 30, whereby the cutter units 30
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`on opposite sides of the slit cutter unit 40 can be depressed or inclined
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`independently from each other against different resistances.
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`Referring to FIGS. 7 to 13, the outer cutter 140 of the slit cutter unit40 is
`shaped from a single metal sheet into a generally U-shaped configuration having
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`a crossbar 141 and a pair of legs 142 depending from opposite width ends of the
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`crossbar 141. As best shown in FIG. 13, the upper end of each leg 142 is bent
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`at an angle (a) of about 60° with respect to the crossbar 141 to define an angled
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`shoulder 144 thereat. The crossbar 141 is finished to have a flat top surface
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`and a flat bottom surface, except at the width ends where the top surface
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`declines towards the angled shoulder 144 at an angle ((3) of about 12°.
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`The slits 42 are arranged along a lengthwise axis of the outer cutter 140 to
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`leave a plurality of parallel bridges 44 each between the adjacent ones of the slits.
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`Each slit 42 extends over the full width of the crossbar 141 into the upper ends of
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`the legs 142, i.e., the angled shoulders 144, as best shown in FIGS. 11 and 13.
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`A dent 146 is formed immediately below the tip of the shoulder 144 which acts to
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`raise the flattened hairs.
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`Each of the bridges 44 is formed at its longitudinal center with a deflection
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`46 which is angled with respect to the width axis of the outer cutter 140 so as to
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`give a deflection path 47 in each slit 42 at the width center of the outer cutter 140.
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`Thus, each slit is formed on opposite width ends of the outer cutter 140 with
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`straight slit paths 48 which are staggered with respect to eaCh other along the
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`lengthwise axis of the outer cutter 140, and communicate with each other through
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`the deflection path 47, as shown in FIG. 9. The straight slit paths 48 run
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`generally in a direction perpendicular to the lengthwise axis of the outer cutter,
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`and are staggered with respect to each other by a distance (D) of about 1/4 to 1/2
`
`of a pitch (P) at which the bridges 44 are arranged along the lengthwise axis.
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`The deflection 46 is bent within a horizontal plane to make the bottom
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`surface of the whole bridge 44 smoothly continuous through the deflection, as
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`shown in FIG. 13. With this result, the inner cutter 240 can be made into a
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`simple structure having a plurality of flat blades 244 each capable of being kept in
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`contact with the bottom surface of the bridges 44 over a wide area including the
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`deflections 46, thereby enhancing cutting efficiency of the outer cutter 140.
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`Further, since the straight slit paths 48 are continuous through the deflection path
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`47 as being confined between the side faces of the deflection 46, the hairs
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`entrapped in one of the straight slit paths can be smoothly guided through the
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`deflection path 47 to the other straight path 48 while'the shaving head 20 is
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`moving across the user’s skin in the direction perpendicular to the lengthwise
`axis of the outer cutter, as shown in dotted lines L1, thereby being given an
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`increased chance of being cut, by making the best use of the inner cutter 240
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`designed to be kept in contact with the bottom surfaceof the bridges including
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`the deflections. Thus, the hair can be out even in the deflection path 47 or
`- immediately before or after advancing to and from the deflection path. While the
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`shaving head 20 is moving across the skin, the hair that has been flattened as
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`being pressed by one end of the bridge 44 is permitted to rise up into the
`deflection path 47 and subsequently into one of the straight slit paths 48, as
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`indicated by dotted lines L2 in FIG. 12.
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`Further, the outer cutter 140 is formed in its top sUrface of each deflection
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`47 with a notch 49. The notch 49 has parallel straight edges running in the
`lengthwise axis on top of the bridge 44 for raising the flattened hair and guiding it
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`into one of the straight slit paths 48 behind the notch 49 with respect to the
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`moving direction of the shaving head for increasing the cutting efficiency in
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`. combination of the staggered slit arrangement. That is, the initially flattened hair
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`can be raised by the edges of the notch 49 so as to be successfully out
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`immediately after it enters into the deflection path 47 or the straight slit paths 48.
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`As best shown in FIG. 12, each of the bridges 44 is shaped to have a
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`tapered section 45 at an intermediate portion between the deflection 46 and each
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`longitudinal end, in order to have a width smaller at the each longitudinal end
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`than at the a portion adjacent to the deflection 46, thereby enlarging a width of
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`the straight slit path 48 at its open end for introducing the hairs into the slit with
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`enhanced efficiency. Further, as shown in FIG. 14, each of the bridges 44 has a
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`trapezoidal cross section along the length wise axis with the bottom surface
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`defining a longer base side and the top surface defining a shorter top side of the
`trapezoid, in order to give sharp cutting edges 43 at the opposite lower ends of
`
`the bridge for enhancing the cutting efficiency, in addition to that the hair can be
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`readily introduced into the slits. The opposite top ends of the bridge are
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`rounded to give a soft contact with the skin.
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`The inner cutter 240 is also made from a single metal sheet into a generally
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`U-shaped configuration having a crossbar 241 and a pair of legs 242 depending
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`from opposite width ends of the crossbar 241 through beveled edges 243. The
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`inner cutter is cut at a portion extending from the crossbar 241 to the upper end
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`of the legs through the beveled edges 243 to give a plurality of the flat blades 244
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`each having a smooth straight top surface in shearing contact with the bottom
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`surface of the bridges 44, as shown in FIG. 15. The hooks 246 extend from the
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`center of the individual legs 242 for secure connection with the coupler 80
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`through the mechanical engagement and the heat-welding with the studs 86 on
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`both sides of the coupler 80. The inner cutter 240 is also formed on each of the
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`legs 242 with spacer projections 248 which are kept in sliding contact with the
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`inner surfaces of the legs of the outer cutter for an exact widthwise positioning of
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`the inner cutter in relation to the outer cutter 140.
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`The perforated cutter unit 30 and the slit cutter unit 40 are each shaped to
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`have an arcuate contour along the lengthwise axis with a longitudinal center
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`projecting than the opposite lengthwise ends in order to make a smooth fit on
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`curved skin surface areas, particularly a concave skin area, for example, the
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`lower jaw.
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`As shown in FIGS. 16 and 17, the outer cutter 140 of the slit cutter unit 40
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`may be shaped to be devoid of the notch in the top surface of each deflection 46.
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`The notch may be alternately formed in the top surface of each bridge other than
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`the deflection.
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`Like parts are designated by like reference numerals for easy
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`comprehension.
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