CUTTER BLADE ASSEMBLY AND DRY SHAVER FOR VARIABLE HEIGHT OF CUT

Abstract

A dry shaver unit includes a housing and a cutter blade assembly mounted in the housing. The cutter blade assembly includes a cutter blade and cooperating shear blade arrangement. The thickness of the shear blade varies over its surface, such that the spacing between a portion of the skin engaging surface of the shear blade and the opposite face thereof is increased as compared with the spacing required to achieve a close shave. The cutter blade assembly is mounted in the housing such that a plurality of portions of the shear blade having different thicknesses are simultaneously available for application to a surface to be shaved.

Claims

1. A dry shaver unit comprising: a housing having an opening formed in a wall thereof; and at least one cutter blade assembly mounted in the housing and disposed proximate to the opening, the cutter blade assembly comprised of: a cutter blade having a cutter blade surface oriented toward the opening in the housing for shaving hair extending from a skin of a user; and an elongated flexible foil having a skin-engaging surface on one side thereof and an inner cutter blade surface on the other side thereof, the foil overlaying the cutter blade such that the skin-engaging surface is spaced from the cutter blade surface, the foil including: a plurality of uniformly narrow diameter hair entry openings extending through the foil for holding hairs at the surface of the skin and for aligning the hairs relative to the cutter blade surface such that the hairs are generally held perpendicular to the cutter blade surface, the thickness of the foil defining a spacing between the cutter blade surface of the cutter blade and the skin-engaging surface of the foil, wherein the spacing increases continuously and uniformly from a minimum spacing at a first portion of the cutter blade assembly to a maximum spacing at a second portion of the cutter blade assembly, wherein the first and second portions are arranged at substantially opposite ends of the foil and a plurality of portions of said foil, each having a different thickness, are simultaneously available for application to a surface to be shaved and wherein all of the hair entry openings over the entire field of said foil have the same narrow diameter and wherein the foil is movable within the housing relative to the cutter blade surface such that the spacing between the cutter blade surface and the skin-engaging surface may be selectively varied.

2. A dry shaver as claimed in claim 1, wherein the spacing between the portion of the skin-engaging surface of the foil and the opposite face thereof is between about 100 microns (m) and about 500 microns (m).

3. A dry shaver as claimed in claim 1, wherein the foil is fixedly mounted in the housing.

4. A dry shaver as claimed in claim 1, wherein the foil is arcuate in shape.

5. A dry shaver as claimed in claim 4, wherein the foil is formed in an inverted U-shape.

6. A dry shaver as claimed in claim 1, wherein said housing has side grooves formed therein and said elongated flexible foil has side edges dimensioned to slidingly move within said side grooves, said side edges each of a uniform thickness.

7. A method for shaving hairs of a user progressively closer to hinder the occurrence of pseudofolliculitis barbae, the method including the steps of: a) providing a dry shaver unit comprising: a cutter blade having a cutter blade surface for shaving hair extending from a skin of a user; and an elongated flexible foil having a skin-engaging surface on one side thereof and an inner cutter blade surface on the other side thereof, the foil overlaying the cutter blade such that the skin-engaging surface is spaced from the cutter blade surface of the cutter blade, the foil including: a plurality of uniformly narrow diameter hair entry openings extending through the foil for holding hairs at the surface of the skin and for aligning the hairs relative to the cutter blade surface such that the hairs are held generally perpendicular to the cutter blade surface, the thickness of the foil defining a spacing between the cutter blade surface of the cutter blade and the skin-engaging surface of the foil, wherein the spacing increases continuously and uniformly from a minimum spacing at a first portion of the foil to a maximum spacing at a second portion of the foil, wherein the first and second portions are arranged at substantially opposite ends of the foil and a plurality of portions of the foil, each having a different thickness, are simultaneously available for application to a surface to be shaved and wherein all of the hair entry openings over the entire field of the foil have the same narrow diameter and wherein the foil is movable relative to the cutter blade surface; b) positioning the foil relative to the cutter blade such that the second portion of the foil is disposed over the cutter blade surface of the cutter blade; c) shaving the hairs of the user; d) re-positioning the foil relative to the cutter blade such that a portion of the foil of greater or lesser thickness is disposed over the cutter blade surface of the cutter blade; e) shaving the hairs of the user; and f) repeating steps d)-e) until a desired length of the hair is obtained, the length being selected to reduce the occurrence of pseudofolliculitis barbae.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will now be described with reference to certain preferred embodiments thereof and the accompanying drawings, wherein:

[0036] FIG. 1 is a diagrammatic representation of a portion of human skin, in the region of the surface of the skin, in section, showing inner and outer skin layers and hair growth, and representing also a particular condition in which an individual's body hair is subject to growth in a manner more horizontal than vertical;

[0037] FIG. 2 is a pictorial view of a rotary shaver of known construction, to which the present invention may be applied;

[0038] FIG. 3 is a side sectional view of a shear blade of conventional construction for use in the shaver of FIG. 2;

[0039] FIG. 4 is an isometric view of a shear blade of the cutter blade assembly according to a first embodiment of the present invention;

[0040] FIG. 5 is a side cross-sectional view of the shear blade of FIG. 4;

[0041] FIG. 6 is an isometric view of a shear blade of a rotary cutter blade assembly according to a second embodiment of the present invention;

[0042] FIG. 7 is an isometric view of a shear blade of a rotary cutter blade assembly according to a third embodiment of the present invention;

[0043] FIG. 8 is a front elevation view of a rotary shaver head in which three cutter blade assemblies according to the present invention are mounted to provide a central raised shaving platform;

[0044] FIG. 9 is a diagrammatic view in section of the rotary shaver head of FIG. 8 in which the central raised shaving platform is in its raised condition;

[0045] FIG. 10 is a side cross-sectional view of the rotary shaver head of FIG. 9, in which the central raised shaving platform has been depressed;

[0046] FIG. 11 is a perspective view of a shear foil of a dry shaver unit according to an embodiment of the invention;

[0047] FIG. 12 is a side sectional view of an adjustable foil blade in a dry shaver in accordance with the present invention; and

[0048] FIG. 13 is a pictorial representation of an embodiment of foil blade suitable for a dry shaver according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

[0049] FIG. 1 is a representation in sectional view of a portion of the surface of the skin of an individual. As shown in FIG. 1, the outer layer 1 of the skin is underlaid by an inner layer 2. Hairs 3 and 3a grow outwardly through the skin from respective root regions 4 and 4a and emerge through the outer layer 1 of the skin. In the normal way, as indicated by hair 3, a hair should emerge from the skin outer layer 1 and extend outwardly above the skin surface substantially at right angles to the skin surface. Depending on the region of the skin surface in question, certain hairs such as that designated by reference 3a in FIG. 1 may have a hair follicle which is oriented horizontally and almost parallel with the skin surface. When a hair emerges from such a follicle onto the skin surface, as indicated at reference 3b, it does so obliquely and in a highly tangential manner.

[0050] If an individual suffering from such tangential hair growth wishes to effect a close shave and cuts the hair relatively close to the skin outer surface, a condition known as pseudofolliculitis barbae may develop. This occurs when the hairs are cut too short such that the sharp, cut edge of the hair becomes engaged by the horny outer layer 1 of the skin and is re-directed downwards into the dermis. The hair thus burrows back beneath the surface of the skin, as indicated at reference 3c, rather than emerging from the skin and growing externally in the normal manner. If growth then continues with the hair 3 running into and under the skin, the inevitable result is ingrowth of the hair accompanied by inflammation of the skin.

[0051] It is therefore preferable to prevent the development of any such inflammation and the present invention addresses this problem. The concept underlying the avoidance of such skin conditions is to cut the hair slightly above the surface of the skin in areas of the body surface where the possibility of such in growing conditions arising is likely to be greatest. The advantages of its being possible to cut hair in accordance with the principles of the present invention are not however limited only to skin conditions such as that illustrated with reference to FIG. 1, but the invention is also applicable to all skin circumstances where shaving bumps or other skin eruptions or imperfections militate against an excessively close shave, such as in the bikini area. The invention provides the user of a dry shaver with the ability to selectively cut body hair either tightly or to a greater length, depending on the region of the skin in question, i.e. the area currently being shaved.

[0052] Referring now to FIG. 2 of the drawings, there is shown a rotary dry shaver of generally conventional construction. The shaver 41 has a number of cutter blade assemblies 42, typically three as shown in the drawing, or alternatively two assemblies 42, in each case located at the cutting end face 43 of the shaver body 44. In such constructions, each cutter blade assembly 42 has an external or shear blade, which has hair entry apertures or slits and is underlaid, in the assembled condition, by a rotating cutter blade, which severs hairs extending into the cutting region of the cutter blade through the slits or perforations (apertures) of the shear blade. Each of the shear blades has a particular thickness or depth dimension of the hair entry slits or perforations, so as to provide for a corresponding depth of cut. In conventional dry shavers, the thickness of the shear blade is as small as possible so as to achieve the closest possible shave.

[0053] Referring now to FIG. 3, there is shown an external cutting member or shear blade 51 of generally conventional configuration. A cutter blade assembly 42 equipped with this type of shear blade 51 may be regarded as providing a minimum depth of cut, for a tight shave. As shown in this drawing, the shear blade 51, which is in the general shape of a top-hat, or an inverted cup, has a series of generally radially-oriented, optionally skewed, hair entry slits or apertures 52, in an outwardly-directed generally disc-shaped region 55 of the blade 51, which is upwardly-oriented when incorporated in a cutter blade assembly 42 mounted on a rotary dry shaver 41 as shown in FIG. 2. The outer surface of this disc-shaped region 55 of cutting member 51 comes into contact with the skin during a shaving operation. At the periphery of the disc, a generally annular peripheral wall portion 56 extends (downwardly in the mounted condition on shaver 41) to terminate in an externally-directed holding flange 53, by which the shear blade is secured in position on the shaver 41. Centrally of the generally disc-shaped region 55, radially inward of the slits 52, there is a provided a central dished portion 54, which is set back from the skin-engaging surface defined by the outer face of region 55 at the slots 52.

[0054] Referring now to FIGS. 4 and 5, shear blade 61 is generally similar in construction to blade 51, so that blades 51 and 61 are interchangeable on the dry shaver 41 of FIG. 2. Shear blade 61 has a series of generally radially-oriented, optionally skewed, hair entry slits or apertures 62, provided on a skin-engaging region 65 thereof. As shown in FIG. 4, the skin-engaging region 65 of shear blade 61 comprises a plurality of substantially radially-oriented tines or struts 603. A hair entry opening 62 is provided between each pair of adjacent tines. The skin-engaging region 65 is substantially annular in shape and is upwardly-oriented when incorporated in a cutter blade assembly and mounted on the rotary shaver 41. The outer surface of this skin-engaging region 65 of cutting member 61 thus comes into contact with the skin during a shaving operation. Similarly to shear blade 51, shear blade 61 is provided with an annular peripheral wall portion 66 which extends (downwardly in the mounted condition on shaver 41) to terminate in an externally-directed holding flange 63, by which the shear blade may be mounted on the shaver 41. Centrally of the skin-engaging region 65, radially inward of the slits 62, there is a provided a central portion 64, which is substantially saucer-shaped and is recessed from the skin-engaging surface defined by the outer face of region 65 at the slots 62.

[0055] In order to selectively provide for a more generous shave, in other words a less tight or close shave leaving a longer beard length, shear blade 61 varies in thickness about its circumference, as shown in FIGS. 4 and 5. The thickness of a portion of the skin-engaging region 65 of the shear blade 61 is increased relative to the remainder of the skin-engaging region of the shear blade, to create a raised portion 69. In the embodiment shown in FIGS. 4 and 5, the spacing between the skin-engaging surface of the shear blade and the opposite face thereof is increased over about one third of the circumference of the shear blade. This allows a longer or more generous shave to be achieved when the thicker or raised portion 69 of the shear blade is applied to the face and a closer shave to be achieved when the thinner portion 67 of the skin-engaging region is applied to the face.

[0056] The shear blade 61 has two transition regions 601 and 602 wherein the spacing between the skin-engaging surface of the shear blade and the opposite face 68 thereof varies or tapers. If one were to trace an imaginary path around the circumference of shear blade 61 in a clockwise direction, the spacing between the skin-engaging surface of the shear blade and the opposite face 68 thereof would increase at transition region 601 and decrease at transition region 602. In the embodiment shown, each transition region comprises three tines or struts 603.

[0057] The only dimensional difference between the shear blades 51 and 61 is in the thickness of the blade in the thicker or raised portion 69. The thickness of each of the tines or struts 603 in this portion of the shear blade 61 is thus increased relative to the remainder of the tines of the shear blade. In the embodiment shown in FIGS. 4 and 5, the thickness of the blade in the thicker or raised portion is about 250 microns. The thickness of blade 61 over the reminder of its circumference is less than 100 microns. Slits 62, flange 63 and central region 64 correspond to portions 52, 53 and 54 of the standard cutter 51 of FIG. 3. However, at portion 69 of shear blade 61, the slits 62 are substantially greater in depth than the slits at portion 67 of shear blade 61, since each slit 62 runs from the skin-engaging surface of the thickened portion through to the opposite face thereof. The slits in portion 69 are thus also greater in depth than the slits 52 of blade 51.

[0058] In an alternative embodiment of the shear blade, the peripheral wall may be greater in height at said portion of the shear blade where the spacing between the skin engaging surface and the opposite face thereof is increased, so as to further raise that portion of the skin engaging surface of the shear blade. Accordingly, when the raised portion 69 of shear blade 61 is applied to the face, the hairs are cut at a longer length than in the case of the blade 51. In use of this embodiment of the invention, the raised portion 69 of shear blade 61 is to be applied to skin areas where the cut is not to be too tight, so as to avoid the dermatological and other skin problems previously identified, while the thinner portion 67 of shear blade 61 may be used in a similar manner to shear blade 51 to achieve a tight shave and good appearance where this does not create any skin hazard or potential damage.

[0059] Referring now to FIG. 6, there is illustrated a shear blade 91 according to a second embodiment of the present invention. Shear blade 91 is generally similar in construction to blade 61 and comprises a series of generally radially-oriented, optionally skewed, hair entry slits or apertures 92, provided on a skin-engaging region 95 thereof. In order to selectively provide for a more generous shave, in other words a less tight or close shave leaving a longer beard length, shear blade 91 varies in thickness about its circumference, as shown in FIG. 6.

[0060] The thickness of a portion of the skin-engaging region 95 of the shear blade 91 is increased relative to the remainder of the skin-engaging region of the shear blade, to create a raised portion 99. In the embodiment shown in FIG. 6, the spacing between the skin-engaging surface of the shear blade and the opposite face thereof is increased over about one eighth of the circumference of the shear blade.

[0061] In the embodiment shown in FIG. 6, the thickness of the blade 91 at the raised portion 99 is about 250 microns. The thickness of the blade over the remainder of its circumference is less than 100 microns.

[0062] Referring now to FIG. 7, there is illustrated a shear blade 101 according to a third embodiment of the present invention. Shear blade 101 is generally similar in construction to blade 61 and comprises a series of generally radially-oriented, optionally skewed, hair entry slits or apertures 102, provided on a skin-engaging region 105 thereof. In order to selectively provide for a more generous shave, in other words a less tight or close shave leaving a longer beard length, shear blade 101 varies in thickness about its circumference, as shown in FIG. 7.

[0063] In the embodiment shown in FIG. 7, the shear blade 101 is tapered about its entire circumference, such that the transition regions 111, 112 extend over substantially the whole of the circumference of the shear blade. The spacing between the skin-engaging surface 105 of the shear blade 101 and the opposite face thereof increases continuously and uniformly from a minimum spacing to a maximum spacing, and decreases continuously and uniformly from the maximum spacing to the minimum spacing.

[0064] FIGS. 8, 9 and 10 illustrate a shaver head 71 of a rotary dry shaver according to an embodiment of the invention in a second aspect. The cutting drive and mounting arrangements of the rotary shaver of the invention are generally in accordance with substantially conventional arrangements well-known in the industry and only the particular deviations from such constructions required by the present invention are now described in detail. The rotary shaver comprises three cutter blade assemblies 72 mounted in a trefoil arrangement within an outer housing 77, which together form a shaver head 71. Each cutter blade assembly includes a shear blade 73 as described above with reference to FIGS. 4 and 5, and an associated rotary cutter blade. As shown in FIGS. 9 and 10, each shear blade 73 is moveably mounted within a frame 76, which in turn is moveably mounted within the shaver head housing 77. As shown in FIG. 8, the cutter blade assemblies 72 are arranged such that the portion 74 of each assembly which has an increased spacing between the skin-engaging surface of the shear blade and the opposite face thereof (that is, the thicker portion) is oriented centrally of the shaver such that said portions are arranged adjacent one another to provide a central raised shaving plane or platform 75.

[0065] The shear blades 73 are resiliency biased upwards, that is, towards the skin-engaging region of the shaver head, the biasing means being substantially conventional and not illustrated. Each shear blade is therefore resiliently downwardly displaceable within the shaver. The frames 76 are also resiliently biased upwards in a similar manner to the shear blades 73. The frames 76 are thus also resiliently downwardly displaceable within the shaver. The biasing means is such that the shear blade 73 and the frames 76 are effectively floatingly mounted within the housing 77.

[0066] As illustrated in FIG. 9, each frame 76 is greater in height at its centrally oriented portion 78 than at the outwardly oriented portions 80 thereof. Since the shear blades are biased upwards and are retained in the shaver by the frames 76 within the outer housing 77, each of the cutter blade assemblies 72 is mounted in the shaver head 71 at an angle to the horizontal, such that the central (thicker) portion 74 of each assembly is tilted upwards relative to the outwardly oriented (thinner) portions 79 of each assembly. Thus, each shear blade 73 is thicker at its central portion 74 than at its outwardly oriented portions 79, and is also tilted upwards at the central portions 74 relative to the outwardly oriented portions 79. When the shaver is first applied to the skin surface to be shaved, the increased height of the shear blades and the upward tilt ensures that only the central raised shaving platform 75 engages the skin, providing for a longer or more generous shave.

[0067] In an alternative embodiment, in addition to each shear blade 73 being thicker at its central portion 74 than at its outwardly oriented portions 79, and being tilted upwards at its the central portions 74 relative to the outwardly oriented portions 79, the peripheral wall portion of each shear blade 73 is also increased in height at the central portion 74 relative to the outwardly oriented portions 79 to further raise the central shaving platform 75. When the shaver is first applied to the skin surface to be shaved, the increased thickness of the shear blades, the upward tilt and the increased wall height ensure that only the central raised shaving platform 75 engages the skin, providing for a longer or more generous shave.

[0068] In order to achieve a close shave, it is necessary to bring the outwardly oriented (thinner) portions 79 of the shear blades into contact with the skin surface. This may be done by exerting pressure on the central raised shaving plane 75, that is, by pressing the shaver head 71 more firmly against the skin surface to be shaved. Pressure exerted on the central raised shaving plane 75 causes each moveably mounted shear blade and associated moveable frame to be displaced downwardly into the shaver at a central portion thereof thereby allowing the outwardly oriented portions of the shear blades to engage the skin as shown in FIG. 10. Since the shear blades are thinner at their outwardly oriented portions, the spacing between the skin-engaging surface of each of the shear blades and the opposite face thereof for co-operation with the associated cutter blade is relatively small, and a close shave may be effected.

[0069] In use, when the shaver is first applied to the skin surface to be shaved, the central raised platform 75 contacts the skin and may be used to carry out a long or generous shave of the skin surface. Skin irritation and inflammation due to pseudofolliculitis barbae may thus be avoided in areas where hair growth is tangential to the skin. In order to effect a tight shave in areas of the skin where hair growth is perpendicular to the skin, and which are thus not prone to pseudofolliculitis barbae, the user presses the shaver slightly more firmly against the skin. This causes the central raised portions 74 of the shear blades 73 and/or the frames 76 to pivot against their biasing means so that they are tilted downwards, that is, into the shaver body. The thicker raised portions 74 of the shear blades 73 (and the central portions 78 of the frames 76) are thus depressed into the shaver body, such that their skin-engaging surfaces are lowered to substantially the same level as the skin-engaging surfaces of the outer portions 79. Each shear blade is thus brought to a horizontal or near horizontal position as shown in FIG. 10 of the drawings. The thinner outwardly oriented portions 79 of the shear blades 73 are thereby allowed to engage the skin. The spacings between the skin-engaging surfaces of the shear blades and the opposite faces thereof in these regions of the shaver are small and a tight shave may therefore be achieved as with a conventional rotary shaver.

[0070] Referring now to FIG. 11, there is illustrated a shear foil 121 of a dry shaver unit according to an embodiment of the first aspect of the invention. The thickness of the foil 121 varies along the elongate extent thereof, such that a plurality of portions 129,127 having different thicknesses are provided. The shear foil 121 maybe mounted in a shaver housing such that the plurality of portions of the foil 129, 127 having different thicknesses are simultaneously available for application to the skin. In the embodiment shown in FIG. 11, the thickness of the foil 121 at the thicker portion 129 is about 250 microns. The thickness of the foil at the thinner portion 127 is less than 100 microns.

[0071] When mounted in the shaver housing, each portion 129, 127 may be selectively applied to the surface to be shaved by rotating the shaver about its longitudinal axis. Alternatively, each portion 129, 127 may be selectively applied to the surface to be shaved by inverting the shaver. Thus, the thicker portion of the foil may be applied to problem areas of the skin which are prone to pseudofolliculitis barbae, and the thinner portion may be applied to areas of the skin which are not prone to pseudofolliculitis barbae.

[0072] In the embodiment shown in FIG. 11, the shear foil is tapered over its length, such that its thickness varies continuously and uniformly from one end to the other. A portion of intermediate thickness 123, is thus available for application to the skin, for example, by holding the shaver unit perpendicular to the surface. In alternative embodiments, the thickness of the foil may change abruptly at a point along the length of the foil, to give a relatively short transition region.

[0073] An embodiment of the invention applicable to a foil type dry shaver is shown in FIG. 12. A removable shaver head portion 11 is mounted on a shaver body portion 12. The head 11 is seated on the body portion 12 to enclose the upper or drive portion 13 of the shaver body portion 12 in conventional manner. A generally conventional drive arrangement is applied such as by drive member 14 to an outwardly curved or convex cutter blade 15 to provide either reciprocating movement in the axial direction of the curved cutter blade 15, or alternatively oscillatory or circumferential motion about this axis. A spring arrangement such as a helical spring 16 urges the curved displaceable cutter blade 15 against the inner surface of a cooperating perforated foil blade 17, which serves as a substantially stationary shear member for the movable blade cutter 15 under shaving conditions, i.e. foil blade 17 remains substantially static with respect to cutter blade 15 during an actual shaving operation.

[0074] The perforated foil blade 17 is received in a bent-over configuration within an open top region of the shaver head 11. The foil blade 17 is received and accommodated in curved guide grooves extending along opposite inner walls of the shaver head 11. One such guide groove is indicated by reference 27. It is a particular feature of the invention that this perforated foil which serves as the shearing blade 17 has a thickness which varies along the length of the foil, as shown in FIGS. 12 and 13.

[0075] Referring now also to FIG. 13 in particular, there is shown a favoured embodiment of the perforated foil blade or shear cutter 17, formed as an integral unit, in which the perforated central region of the blade 17, designated by cross-hatching, is surrounded by side 18 and end 19 members or blade regions, which are unperforated and define therefore lateral members and end or cross-members of the blade structure. The blade 17 has a thinner region 21 towards one axial end in its generally longitudinal direction and a thicker region 22 towards its other axial end. In the region of the thicker end 22, an aperture 23 is provided through which a fastener 24, FIG. 12, enables the blade 17 according to the invention to be coupled to an operating or control button 25, which is displaceable on the exterior of the shaver head 11 in the longitudinal direction of the blade 17 and is guided by a guide slot 26 provided in the housing of the shaver head 11.

[0076] By this arrangement a foil portion of the desired thickness is selectively brought into a cutting disposition with respect to the cutter blade 15 by controlled sliding movement of the foil blade 17 in its longitudinal direction This is facilitated by the external button arrangement 25 which runs in the guide slot 26 along the surface of the shaver unit head 11. In this manner, a required depth of cut may be readily chosen and speedily varied in controlled manner as required by the user. Retention of a particular selected position of the foil 17 may be achieved by cooperating frictional interaction between button 25 and slot 26, e.g. by button 25 and connection or fastener portion 24 defining a nip or light gripping engagement between inner and outer face regions of head 11 bordering slot 26.

[0077] In order to provide guidance for the side edges 1a of the variable thickness shear blade 17, the guide grooves 27 in the shaver head have a dimension between the opposite side surfaces of the guiding groove 27 which may vary but is always appropriate for the thickness dimension of the blade 17 in the relevant region. In order to ensure that the thinner regions of the foil 17 are appropriately guided, the guide grooves 27 then may be provided, if necessary, with appropriate resilient means, such as leaf springs or the like, to urge the foil 17 towards an appropriate side face of the groove 27, and thereby take up as it were any possible intervening redundant space between a thinner portion of the foil 17 and the opposite side wall of the guiding groove 27. Alternatively, in either embodiment of the foil, the side edges 18 or the corresponding side frame members may be arranged to have a uniform thickness throughout the longitudinal extent of the shear blade or foil 17, so that the provision of resilient means in the guide grooves is not then required.

[0078] The installed foil blade 17 is stretched as it were over the curved surface of cutter blade 15 at the cutting end of the shaver head unit 11. The foil blade 17 is tensioned in the outward direction by the spring-loading (16), underlying cutter blade 15, which also serves for holding it in place.

[0079] In the embodiment as shown in FIGS. 12 and 13 of a foil 17 suitable for use with the invention, variation in thickness is substantially continuous from one end of the foil 17 to the other, from a minimum thickness portion 21 at a first end, to a maximum thickness region 22 at the other end. In this way, a substantially infinite variation of thickness can be selected between the two extremes. The side edges of the foil 18 may however be of constant or uniform thickness over the entire longitudinal extent of the blade 17, depending on the properties of the material selected for the foil 17.

[0080] The words comprises/comprising and the words having/including when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0081] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.