Blade set for hair cutting appliance and method for its manufacture

Abstract

A stationary blade for a blade set of an electrically operated hair cutting appliance includes first and second walls, where each wall has a first surface, a second surface facing away from the first surface, and a laterally extending leading edge having a plurality of laterally spaced apart longitudinally extending projections. The first surfaces of the first and second walls face each other, at least at their leading edges, while corresponding projections along the leading edges of the first and second walls are mutually connected at their tips to define a plurality of generally U-shaped teeth. The first surfaces of the first and second walls are separated to define a laterally extending guide slot for insertion of a movable blade of the blade set between them. The projections of the first wall have an average thickness that is less than an average thickness of the projections of the second wall.

Claims

1. A method of manufacturing a stationary blade of an electrically operated hair cutting appliance, the method comprising acts of: providing a first metal wall with a first laterally extending leading edge, and having a first surface and a second surface; providing a second metal wall having a second laterally extending leading edge, and having a further first surface and a further second surface; providing a metal strip having a lateral dimension that corresponds to that of the first and second laterally extending leading edges of the first and second metal wall; forming a stacked arrangement by stacking the second metal wall on top of the first metal wall, wherein the first surface and the further first surface face each other, at least at the first and second laterally extending leading edges, and arranging the metal strip in between the first and second laterally extending leading edges, such that a longitudinal cross-section of the stacked arrangement of the stationary blade is generally U-shaped; fixing the stacked arrangement by fixing the metal strip between the first and second laterally extending leading edges to mutually connect the first and second laterally extending leading edges; and creating generally U-shaped teeth by forming a plurality of laterally spaced apart slots into a leading edge of the stacked arrangement, such that said slots extend longitudinally beyond the metal strip, wherein the first surface of the first metal wall and the further first surface of the second metal wall in the stacked arrangement define a guide slot for insertion of a movable blade of said blade set between the first surface and the further first surface, and wherein the first laterally extending leading edge has an average thickness that is less than an average thickness of the second laterally extending leading edge.

2. The method of claim 1, wherein a longitudinal dimension of the metal strip is smaller than that of the first and second metal walls.

3. The method of claim 1, wherein the act of fixing the stacked arrangement by fixing the metal strip between the first and second laterally extending leading edges includes welding the metal strip between the first and second laterally extending leading edges.

4. The method of claim 1, wherein the act of creating generally U-shaped teeth by forming the plurality of laterally spaced apart slots into the leading edge of the stacked arrangement includes machining the plurality of laterally spaced apart slots into the leading edge of the stacked arrangement.

5. The method of claim 1, wherein a longitudinal dimension of the metal strip is smaller than that of the first and second metal walls, wherein the act of fixing the stacked arrangement by fixing the metal strip between the first and second laterally extending leading edges includes welding the metal strip between the first and second laterally extending leading edges, and wherein the act of creating generally U-shaped teeth by forming the plurality of laterally spaced apart slots into the leading edge of the stacked arrangement includes machining the plurality of laterally spaced apart slots into the leading edge of the stacked arrangement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic perspective view of an electric hair cutting appliance fitted with an exemplary embodiment of a blade set according to the present disclosure;

(2) FIG. 2A is a schematic perspective top view of the blade set shown in FIG. 1, comprising a stationary blade and a movable blade;

(3) FIG. 2B is a schematic perspective top view of the blade set shown in FIG. 2A, indicating hidden lines to illustrate the placement of the movable blade within the guide slot of the stationary blade;

(4) FIG. 3 is a schematic perspective top view of the stationary blade of the blade set shown in FIG. 2;

(5) FIG. 4 is a schematic perspective top view of the movable blade, and a connector portion of the stationary blade, of the blade set shown in FIG. 2;

(6) FIG. 5 is top view of the blade set shown in FIG. 2;

(7) FIG. 6 is a cross-sectional side view of the blade set shown in FIG. 2;

(8) FIG. 7 is a schematic perspective bottom view of an alternative exemplary embodiment of a stationary blade, differing from the stationary blade of the blade set of FIGS. 1-7 in that it features longer U-shaped teeth and a convexly curved first, skin-contacting wall;

(9) FIG. 8 is a schematic cross-sectional side view of a blade set including the alternative embodiment of the stationary blade shown in FIG. 7;

(10) FIG. 9 is a schematic perspective bottom view of an embodiment of a stationary blade having a circular geometry; and

(11) FIG. 10 is a schematic cross-sectional perspective view of the stationary blade shown in FIG. 9.

DETAILED DESCRIPTION

(12) FIG. 1 schematically illustrates, in a perspective view, an exemplary embodiment of an electric hair cutting appliance 1 according to the present disclosure. The appliance 1 may include a housing 2, an electric battery, an electric motor, and a blade set 4. The housing 2 may accommodate the electric battery and the electric motor, which may be operably connected so that the motor is powerable from the battery. The blade set 4, which is shown in more detail in FIGS. 2-6, may include a stationary blade 10 that is fixedly connected to the housing 2, and a movable blade 40 that is connected to the motor such that it is movable in a laterally reciprocating motion relative to the stationary blade 10. Apart from the blade set 4, the hair cutting appliance 1 may generally be known in the art.

(13) For ease of reference, a Cartesian coordinate system is indicated in each of the FIGS. 1-6. The x-as of the coordinate system extends in the longitudinal direction associated with length, the y-axis extends in the lateral direction associated with width, and the z-direction extends in the direction associated with height or thickness.

(14) Referring now to in particular FIGS. 2-6, which illustrate the blade set 4 of FIG. 1 in various perspective top, orthogonal top and cross-sectional side views.

(15) The stationary blade 10 of the blade set 4 may include a first wall 20 and a second wall 30. The walls 20, 30 may be generally plate-like, but need not be. Each wall 20, 30 may define a first surface 22a, 32a, a second surface 22b, 32b facing away from the first surface 22a, 32a, and a laterally extending leading edge 23, 33 defining a plurality of laterally spaced apart, generally longitudinally extending projections 24, 34. The first and second walls 20, 30 may be arranged in a spaced apart relationship, such that the first surfaces 22a, 32a face each other. The projections 24, 34 of the leading edges of the first and second walls 20, 30 may preferably be in a one-to-one relationship, wherein each projection 24 of the plurality of projections on the first wall 20 is associated with a facing or opposite projection 34 of the plurality of projections on the second wall 30. The associated projections 24, 34 may be connected at their tips 26, 36, thus forming a plurality of laterally spaced apart, longitudinally extending, generally U-shaped (i.e. double-walled) teeth 12. The first and second walls 20, 30, including the U-shaped teeth 12 they defineor more specifically: the first, inner surfaces 22a, 32a of the first and second walls 20, 30, including first surface portions provided by the projections 24, 34 thereofmay define a laterally extending guide slot 16 for the movable blade 40 of the blade set 4 between them.

(16) The first and second walls 20, 30 of the stationary blade 10 may have different functions. The first wall 20 may serve as a foil that, in operation, may be disposed between the skin of a user and the movable blade 40, so as to prevent the former from direct contact with the latter. To enable body hairs to be cut off at or very close to skin level, the first wall 20, or at least the portion thereof providing for the projections 24, may preferably have the smallest practicable average thickness, which may at least be less than 100 ?m. The second wall's 30 purpose may be to provide the ultra thin first wall 20 with sufficient rigidity against deformations during use. Aside from the structural support provided to the first wall through the plurality of U-shaped tooth 12 connections, two features are proposed to enhance the effective structural strength of the stationary blade: connector portions 18 and a relatively thick second wall 30.

(17) In one embodiment, the first and second walls 20, 30 may be mutually connected by at least one discrete connector portion 18 that extends between their respective first surfaces 22a, 32a. The connector portion 18 may act both as a spacer that prevents the first wall 20 from being pushed against the second wall 30, and as an anchor that prevents the first wall 20 from moving/deforming relative to the second wall 30 in the lateral (y) and/or longitudinal (x) direction. In principle, a connector portion 18 may be disposed anywhere between the first surfaces 22a, 32a of the first and second walls 20, 30; it is, however, preferably not disposed between the projections 24, 34 that define the U-shaped teeth 12. In one embodiment, a connector portion 18 may be disposed at a lateral extremity of the guide slot 16, so as to prevent it from interfering with the movable blade 40 that is to laterally reciprocate within that slot. In another embodiment, such as the one shown in FIGS. 1-6, a connector portion 18 may be disposed at a position between the lateral extremities of the guide slot 16, and correspond to a laterally extending guide or cam slot 46 provided in the movable blade 40, such that the connector portion 18 may also serve as a guide cam for the movable blade 40.

(18) In another embodiment, the first wall 20 may be effectively strengthened by providing the second wall 30, or at least its projections 34, with an average thickness t.sub.2 that is greater than an average thickness t.sub.1 of the first wall 20, or at least of the projections 24 thereof. An average thickness t.sub.2 of the second wall 30 may preferably be greater than 100 ?m, e.g. be in the range of 100 ?m-200 ?m. In a preferred embodiment, the ratio t.sub.2:t.sub.1 between an average wall thickness t.sub.2 of the second wall 30 and an average wall thickness t.sub.1 of the first wall 20 may be at least 3:2, and more preferably 2:1.It is noted explicitly that not all embodiments of the presently disclosed stationary blade need to include a second wall 30, or second wall projections 34, having an average thickness t.sub.2 that is greater than an average thickness t.sub.1 of the first wall 20, or the first wall projections 24, even though such embodiments may not be covered by the presently attached claims. An overall average thickness or height of the stationary blade 10, and in particular the U-teethed leading edge thereof, wherein thickness or height is understood to be the distance between its second surfaces 22b, 32b, may preferably be less than about 1 mm. A small thickness helps to warrant proper hair catching efficiency, in particular when trimming longer hairs. More specifically, it ensures that a small area of contact exists between the leading edge of the stationary blade and the hairs, which assists in bending the hairs into between the laterally spaced U-shaped teeth rather than pushing them flat and away.

(19) The second, outer surface 22b of the first wall 20 may provide for the skin-contacting surface of the stationary blade 10. In one embodiment the first wall 20, or at least (in particular the second surface 22b of) the portion thereof defining its projections 24, may be generally planar. See for example the embodiment of FIGS. 1-6. In another embodiment, such as the embodiment shown in FIGS. 7-8, the first wall 20, or at least (in particular the second surface 22b of) the portion thereof defining its projections 24, may be convexly curved. The convex curvature may be present in longitudinal cross-sections of the first wall 20, i.e. in cross-sectional planes perpendicular to the lateral direction (y), but, alternatively or in addition thereto, also in lateral cross-sections of the first wall 20, i.e. in cross-sectional planes perpendicular to the longitudinal direction (x). During use, when the skin-contacting second surface 22b is pressed against the flexible skin, a convex curvature of the second surface 22b of the first wall 20 provides for a more equal and therefore more comfortable pressure distribution across the skin than a planar second surface. This is in part because the convex curvature prevents high skin strain levels at the circumferential edge of the first wall as it avoids the necessity for the skin to bulge out from under this edge.

(20) As regards the shape and form of the U-shaped teeth 12 of the stationary blade 10, the following may be noted. Facing and tip-connected projections 24, 34 of the first and second walls that define a certain U-shaped tooth 12 may preferably have a same length l and width w; as discussed above, their thicknesses t.sub.1, t.sub.2 may differ. In addition, the plurality of teeth 12 of the stationary blade 10 may preferably be substantially identical, and be arranged such that their tips 14 are linearly aligned. The length l and width w of the teeth 12 may vary between different embodiments. The stationary blade 10 shown in the embodiment of FIGS. 1-6, for instance has relatively short teeth 12, while the alternative embodiment shown in FIGS. 7-8 has relative long teeth 12. In preferred embodiments, the length l of the teeth 12 of the stationary blade may be in the range of 0.5-5 mm. The width w of individual teeth 12 may preferably be constant along their length, but need not be. In preferred embodiments of the stationary blade, an average width w of the teeth 12 may be in the range of 0.1-1 mm. The lateral spacing d between the teeth 12 may preferably be in the range of 0.2-1 mm. The tips 14 of the teeth 12 may preferably be convexly curved/rounded off, as seen in a longitudinal cross-section, so as to avoid cutting the skin during use. The minimum radius of curvature of the tip may preferably be 0.3 mm. Other sharp edges of the teeth 12, e.g. their longitudinally extending lateral edges, may be likewise rounded.

(21) As regards the geometry of the stationary blade 10 as a whole, it is noted that the embodiments of FIGS. 1-8 all have a linear geometry. In another embodiment, however, such as that depicted in FIGS. 9-10, the stationary blade 10 may have a rotational geometry. In such an embodiment the guide slot 16 for the movable blade 40 of the blade set 4 may not extend linearly, as in the embodiments of FIGS. 1-8, but circularly around a central axis L of the blade 10 in a tangential direction t; in accordance therewith, the laterally/tangentially spaced apart U-shaped teeth 12 may all extend longitudinally in a generally radial direction r. It is understood that a matching movable blade 40 may have a circularly curved toothed leading edge, which may be received in the guide slot 16 to be driven in continuous rotational (instead of linearly reciprocating) motion around the central axis L.

(22) As in the embodiment of FIGS. 9-10, the circularly curved leading edges 23, 33 of the first and second walls 20, 30 need not provide for U-shaped teeth 12 along their entire circumferences. Instead, small stubble hair capturing holes 50 may be provided in/along at least one circumferential portion of the leading edge 23 of the first wall; a facing leading edge portion of the second wall may simply be closed. Accordingly, the stationary blade 10 may be configured to both capture relatively long hairs in between the U-shaped teeth 12, and short stubble hairs in the small holes 50.

(23) In different embodiments, the stationary blade 10 may be manufactured from different materials and in different ways.

(24) In a preferred embodiment, the stationary blade 10 may be at least partially made from sheet metal. In some embodiments the metal tips 14 of the U-shaped teeth 12 of the stationary blade 10 may be coated with a layer of plastic, e.g. through plastic micro molding, so as to round them off and provide them with a minimum, skin-comfortable radius that avoids skin cuts.

(25) One method of manufacturing the stationary blade 10 may include (i) providing a metal plate, (ii) stamping a series of identical, longitudinally extending, laterally spaced apart slots into the plate, and (iii) folding/bending the plate into a U-shape along a laterally extending fold-line that extends through said spaced apart slots. It will be clear that, in this embodiment, the metal plate, which may but need not be of uniform thickness, provides for both the first wall 20 and the second wall 30 of the stationary blade 10, while the slots in the plate define the spacings between the teeth 12 of the blade. The fold-line may correspond to the line defined by the leading tips 14 of the U-shaped teeth 12.

(26) Another method of manufacturing the stationary blade 10 may include (i) providing a first metal plate with a first laterally extending leading edge, (ii) providing a second metal plate similar in shape to the first and having a second laterally extending leading edge, and (iii) providing a metal strip having a lateral dimension that corresponds to that of the leading edges of the first and second metal plates and a longitudinal dimension that is significantly smaller than that of the first and second metal plates. The method may further include stacking the second metal plate on top of the first metal plate while arranging the metal strip in between their leading edges, such that a longitudinal cross-section of the stacked arrangement is generally U-shaped. The stacked arrangement may be fixed by welding the strip between the first and second leading edges. Then the welded leading edge of the arrangement may be rounded by means of electrochemical machining Subsequently, U-shaped teeth may be created by machining, e.g. wire-eroding, a plurality of laterally spaced apart slots into the leading edge of the arrangement, which slots may longitudinally extend beyond the strip. It is understood that, in this embodiment, the first metal plate may largely correspond to the first wall 20 of the stationary blade 10, while the second metal plate may largely correspond to the second wall of the stationary blade 10 (or, as in the embodiment of FIGS. 9-10, to a circumferential flange provided on the cylindrical portion of the second wall 30), and the metal strip may define the tips of the projections 26, 36 of both the first and second walls 20, 30.

(27) Either method of manufacturing may further include the insertion of at least one connector portion 18 between opposing first and second walls of the U-shaped stationary blade 10, and welding the connector portion 18 thereto to fix it in place.

(28) In addition to the stationary blade 10, the presently disclosed blade set 4 may further include a movable blade 40. The movable blade 40 may be configured to be laterally slidingly receivable inside the guide slot 16 defined by the stationary blade 10, and include a toothed leading edge 42 for linear reciprocating or continuous rotational motion within, and cutting cooperation with, the U-shaped teeth 12 of the stationary blade 10. In is understood that the toothed leading edge of the movable blade 40 may extend along a generally linear path in case the stationary blade 10 defines a linear guide slot 16 (cf. FIG. 1-8), while it may extend along a curved, in particular circular, path in case the stationary blade 10 defines a circular guide slot 16 (cf FIGS. 9-10). In particular in case the movable blade is configured for reciprocating linear motion, each of the teeth of the movable blade 40 may preferably have two lateral cutting faces, and the number of teeth on the movable blade may typically be smaller than the number of U-shaped teeth 12 on the stationary blade. To facilitate connection of the movable blade 40 to the electric motor within the housing 2 of the hair cutting appliance 1, the movable blade 40 may be connected to a blade stem 44.

(29) In the depicted embodiments of FIGS. 1-8, the movable blade 40 is effectively form-locked between the first, inner surfaces 22a, 32a of the first and second walls 20, 30 of the stationary blade 10; i.e. the inner surfaces 22a, 32a of the walls 20, 30 snugly enclose the movable blade 40 and confine it to lateral sliding movement between them. In an alternative embodiment, the movable blade 40 may be force-locked instead of form-locked. That is, the movable blade 40 may be slidingly received in the guide slot 16 between the inner surfaces 22a, 32a of the stationary blade 10, which guide slot 16 may have a height that well exceeds the height/thickness of the movable blade 40. To ensure that the movable blade is forced into (slidable) contact with the inner surface of 22a of the first wall 20, a mechanical spring may be provided, e.g. a compression spring disposed between the housing 2 of the hair cutting appliance 1 and the blade stem 44.

(30) Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the stationary blade, blade set, etc. according to the present disclosure. Thus, the appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments.

LIST OF ELEMENTS

(31) 1 hair cutting appliance 2 housing 4 blade set 10 stationary blade 12 U-shaped tooth 14 (leading) tip of U-shaped tooth 16 guide slot for movable blade 18 connector portion between first and second walls 20 first, skin-contacting/facing wall 22a,b first, inner surface (a) and second, outer surface (b) of first wall 23 leading edge of first wall 24 projections of first wall 26 tips of projections of first wall 30 second wall 32a,b first surface (a) and second surface (b) of second wall 33 leading edge of second wall 34 projections of second wall 36 tips of projections of second wall 40 movable blade 42 toothed leading edge 44 stem, connecting to motor 46 recess in movable blade for connector portion 18 50 hair capturing hole in leading edge of second wall d spacing between adjacent U-shaped teeth l length of U-shaped tooth L central axis of stationary blade with circular geometry t.sub.1 thickness of first wall t.sub.2 thickness of second wall w width of U-shaped tooth x,r longitudinal, radial direction y,t lateral, tangential direction z height/thickness direction