Hair guide element, hair cutting assembly, electric shaver, and manufacturing method

Abstract

A hair guide element for electric shavers is provided. [Solution] The hair guide element (10) has a skin contact surface (12) for contacting the skin and a cutting element facing surface for facing the cutting element, the cutting element facing surface facing in the opposite direction to the direction the skin contact surface faces. The outer circumference of the hair guide element provides the hair guide element with a toothed profile including teeth (20) arranged along the main axis (MA) of the hair guide element, each tooth including part of the skin contact surface and part of the cutting element facing surface. Slots (26, 26', 28, 28') separate adjacent teeth (20) along the main axis (MA). Each pair of slots includes a longer slot (26; 26') and a shorter slot (28; 28'). A hair cutting assembly (10) comprising the hair guide element and the cutting element, and an electric shaver comprising such a hair cutting assembly are further provided.

Description

Technical Field

[0001] The present disclosure relates to a hair guide element for an electric shaver, a hair cutting assembly comprising the hair guide element and a cutting element, an electric shaver comprising the hair guide element or the hair cutting assembly, and a method of manufacturing the hair guide element.

Background Art

[0002] The hair cutting and hair guiding components of an electric shaver, such as an electric dry shaver, can be manufactured in various ways. Generally, the hair cutting assembly of an electric shaver includes two cutting elements, namely a fixed blade such as a comb or foil having a surface for contacting the skin and designed to guide / deliver the incoming hair, and a movable blade, usually located below the fixed blade. The movable blade does not contact the skin, receives the hair sent thereto through the fixed blade, and moves in a reciprocating motion to cut the hair. The blades of the hair cutting assembly can function as a shearing system for cutting hair.

[0003] Both cutting elements can perform their respective functions by having a specific two-dimensional geometric shape when viewed in a plane for each element, and by having a cutting edge whose geometric shape is designed to achieve effective cutting of hair. Such geometric shapes can be manufactured by photochemical machining, also known as etching, which is a wet chemical method that does not use electricity. Another possible procedure is precision (or pulsed) electrochemical machining (PECM), in which case the cutting element usually acts as an anode and the material is removed by an electrochemical process. The cutting element can also be manufactured by mechanical methods such as stamping, welding, bending, etc.

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is desirable to provide hair cutting and / or hair guide components for electric shavers having improved geometric shapes, and methods for manufacturing such improved hair cutting and / or hair guide components. It is also desirable to provide improved etching methods that can be used to manufacture hair cutting and / or hair guide components, and other types of articles. [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, a hair guide element for an electric shaver is provided, the hair guide element comprising a skin contact surface for contacting skin, a cutting element opposing surface for facing a cutting element, the cutting element opposing surface facing in the opposite direction to the direction in which the skin contact surface faces, and a toothed profile including teeth arranged along the principal axis of the hair guide element, each tooth including a portion of the skin contact surface and a portion of the cutting element opposing surface, the teeth comprising a first set of teeth extending in a first direction perpendicular to the principal axis of the hair guide element and a second set of teeth opposite to the first direction The slots include a second set of teeth extending in the direction, and the slots separate adjacent teeth from each other along the principal axis of the hair guide element, the slots include pairs of slots, each pair of slots includes a longer slot and a shorter slot, the longer and shorter slots of each pair extend along a common slot axis which is perpendicular to the principal axis, one of the longer and shorter slots defines between adjacent teeth of the first set of teeth, and the other of the longer and shorter slots defines between adjacent teeth of the second set of teeth.

[0006] The shorter and longer slots of each pair of slots may be arranged back-to-back such that the shorter slot receives the hair in the direction opposite to the direction in which the longer slot receives the hair.

[0007] As the skin-contacting surface of the hair guide element moves across the skin, hairs are received into the slots and can then reach the surface opposite the cutting element. Longer slots can offer more opportunities for hairs, especially longer hairs, to be received into them, thereby helping to increase cutting efficiency. However, arranging two relatively long slots back-to-back risks making the width of the hair guide element excessively large, which could reduce the compactness of the shaver head of an electric shaver containing such a hair guide element, and thus impair the application of the hair guide element to relatively narrow areas of skin, such as between the nose and upper lip.

[0008] Therefore, the pair of back-to-back longer and shorter slots can balance the efficient cutting of longer hairs with the compactness of the hair guide element design.

[0009] The hair is preferably receivable within the slot between adjacent teeth.

[0010] Each tooth may have a tooth axis extending from the principal axis of the hair guide element to the distal end of the tooth (e.g., the tip). Each tooth axis may bisect each tooth. Each tooth may be symmetrical with respect to its tooth axis. Each tooth axis may be oriented parallel to the first and second directions, i.e., transversely with respect to the principal axis of the hair guide element.

[0011] The teeth can be arranged at regular intervals along the main axis of the hair guide element.

[0012] Optionally, the hair guide element includes a hair guide surface capable of receiving hair from the skin so that it is guided on the hair guide surface when the skin contact surface is in contact with the skin.

[0013] Optionally, at least a portion of each tooth includes a portion of the hair guide surface and an apical region positioned to receive hair as the hair guide element moves over the skin, the portion of the hair guide surface extending in a direction perpendicular to the principal axis, away from the apical region toward a portion of the cutting element-facing surface, the portion of the hair guide surface enabling the hair received in the apical region to be guided toward the portion of the cutting element-facing surface.

[0014] Optionally, the tooth thickness in the tip region is less than 250 μm, and this tooth thickness is the diameter of the smallest conceptual circle whose circumference intersects both a portion of the hair guide surface and a portion of the skin contact surface, with the plane of the smallest conceptual circle perpendicular to the principal axis.

[0015] Optionally, the smallest conceptual circle does not extend outside the tooth. Thus, the tooth thickness can be measured less than 125 μm from the end of the apical region in a direction perpendicular to the principal axis (125 μm is the maximum radius of a circle with a diameter of 250 μm).

[0016] When the hair guide element is moved over the skin with the skin contact surface in contact with the skin, the hair can ride up onto the tip region and slide along a portion of the hair guide surface toward a portion of the cutting element's opposing surface.

[0017] Users of conventional electric shavers may notice that even though the electric shaver's comb moves over the skin where hair is present, such hairs may not be cut. This can lead users to move the comb over the same area of ​​skin multiple times, which can cause skin irritation.

[0018] One reason why hair remains uncut is the angle at which it protrudes from the skin surface, particularly the relatively small angle. For example, hair on the neck can protrude from the skin surface at an angle of only about 10°.

[0019] When the tooth thickness in the tip region is less than 250 μm, preferably less than 200 μm, it has been found that more hairs can be successfully cut with less passage of the hair guide element across the skin, and as a result, there is less skin irritation.

[0020] This is because when the hair protrudes from the surface of the skin at an angle of about 10°, and the hair length is about 1.5 mm corresponding to the upper limit of facial hair growth in 3 days (0.5 mm per day), a tooth with a thickness less than 250 μm in the tip region can enter the gap of about 260 μm between the end of the hair and the surface of the skin.

[0021] It should be noted that the skin contact surface may have a single plane, and the circumference of the smallest conceptual circle whose diameter defines the tooth thickness intersects the single plane of the skin contact surface.

[0022] The term "transverse to the spindle" may mean perpendicular or at least substantially perpendicular to the spindle when viewing the hair guide element in a plane such that the skin contact surface or the cutting element facing surface faces the viewer.

[0023] The modifier "substantially" may refer to a deviation of up to 10° from perpendicular.

[0024] In some embodiments, a part of at least some of the hair guide surfaces of the teeth includes an inclined surface, and this inclined surface descends from the tip region towards a part of the cutting element facing surface as the inclined surface extends transversely to the spindle, and the inclined surface moves further away from the skin contact surface as the inclined surface descends towards a part of the cutting element facing surface. Thus, the hair received on the tip can slide down the inclined surface towards the cutting element facing surface.

[0025] Separating the hair from the skin in this way can help properly orient the hair for cutting when the hair slides down the inclined surface towards the cutting element facing surface.

[0026] In some embodiments, a step is defined between the lowermost region of the descending inclined surface and a portion of the cutting element facing surface, and the step provides a height difference of 50 μm or less between the portion of the cutting element facing surface and the lowermost region. In such embodiments, a hair can slide down the inclined surface until it reaches the step, at which point the sliding motion of the hair can end, but the hair can overcome the step, for example, by hitting or rolling over the portion of the cutting element facing surface from the lowermost region of the inclined surface.

[0027] By limiting the height difference to 50 μm or less, an average hair that has slid down the inclined surface and reached the lowermost region can relatively easily overcome the step. This is because the height difference does not exceed half of the average value of the diameter of facial hair, i.e., 50 μm.

[0028] The inclined surface may have a gradient defined by the lateral extent of the inclined surface that is greater than the height of the inclined surface. The lateral extent extends parallel to the skin contact surface from the tip region to a first point aligned with the lowermost region of the inclined surface at the base of the step, and the height extends perpendicular to the skin contact surface from the tip region to a second point aligned with the lowermost region.

[0029] Due to the lateral extent being greater than the height, the inclined surface descends relatively gently from the tip region to the lowermost region of the inclined surface compared to, for example, scenarios where the lateral extent is the same as or smaller than the height.

[0030] Such a relatively gently descending inclined surface can assist the hair in sliding thereon towards the cutting element facing surface.

[0031] In some embodiments, the lateral extent is at least twice as large as the height. Alternatively or additionally, the lateral extent may be at least 200 μm, while the height is 100 μm or less.

[0032] In some embodiments, the lowest region of the inclined surface is where the inclined surface reaches the surface opposite the cutting element in a step-free manner. Thus, hair can slide continuously down the inclined surface to reach the surface opposite the cutting element. This facilitates the guidance of hair to the surface opposite the cutting element, particularly in embodiments where it is required that hair overcome a step defined between a portion of the surface opposite the cutting element and the lowest region of the inclined surface.

[0033] In such embodiments, the inclined surface may have a gradient defined, for example, by a lateral extension of the inclined surface that is greater than the height of the inclined surface, the lateral extension extending parallel to the skin contact surface from the tip region to a first point aligned with the lowest region of the inclined surface, and the height extending perpendicular to the skin contact surface from the tip region to a second point aligned with the lowest region. The lateral extension may be, for example, at least twice as large as the height. Alternatively or additionally, the lateral extension may be at least 200 μm, while the height is 100 μm or less.

[0034] It should be reiterated that, because the lateral spread is greater than the height, the inclined surface slopes relatively gently downward from the tip to the bottom, thereby helping the hair slide along the inclined surface toward the surface opposite the cutting element.

[0035] In some examples, the inclined surface may include an inclined planar region.

[0036] The first and second sets of teeth may allow the hair guide element to guide the hair toward the surface opposite the cutting element when the hair guide element is moved in opposite directions across the skin.

[0037] At least a portion of the teeth (each including a portion of the bristle guide surface and a tip region where the tooth thickness is less than 250 μm) may be included in a first set of teeth and a second set of teeth.

[0038] Therefore, the hair-lifting and hair-guiding attributes of the tip region and the hair-guide surface may be exhibited when the hair-guide element is moved in opposite directions across the skin.

[0039] Note that the length of each slot can be defined along the central slot axis that extends laterally to the spindle and bisects the slot, from the connection area where each slot connects the adjacent teeth between them to a point located between the ends / end faces of the adjacent teeth. If the adjacent teeth (between which the slot is defined) have their ends / end faces at different distances from the spindle, the shorter end / end face of the two adjacent teeth (i.e., the end / end face closer to the spindle) determines the length of the slot.

[0040] Each slot may have an open end distal to the main axis and a closed end opposite to it (at the opposite end of the slot along the central slot axis). The closed end may be defined by the connection region described above.

[0041] Each shorter slot may have a closed end on the same side as the open end of the spindle. Each longer slot may have a closed end on either (i) the same side as the open end of the spindle but closer to the spindle than the closed end of the shorter slot, or (ii) the opposite side from the open end of the spindle. In case (ii), the longer slot extends across the spindle.

[0042] The slots may have various shapes. The opposing sides of each slot (defined by adjacent teeth) may be parallel or have a tapered width. The width of each slot (measured, for example, in a direction parallel to the spindle) may be substantially constant over at least a portion of the length of the slot. In some examples, the width may be tapered such that the open end of the slot is wider than the opposing closed end of the slot. (This shape may be preferred to facilitate the introduction of hair into the open end of the slot.) Alternatively, in some examples, the width may be tapered such that the open end of the slot is narrower than the opposing closed end of the slot.

[0043] The connecting elements can connect the hair guide elements to the side members that support the hair guide elements. Each connecting element may include a portion of the skin contact surface. Alternatively or additionally, each connecting element may include a portion of the surface facing the cutting element.

[0044] The connecting elements may be included within the toothed profile such that a hair can be accommodated within the space defined between one of the connecting elements and one of the teeth.

[0045] The connecting elements and teeth can be arranged alternately along the main axis of the hair guide element. In some examples, 2 to 5 teeth (for example, in each of the first and second sets of teeth) are arranged between consecutive connecting elements.

[0046] The connecting element may be shorter than at least a portion (or all) of the tooth, so that the aforementioned portion of the tooth extends further than the connecting element in a lateral direction relative to the principal axis. These additional extensions in the lateral direction may help the tooth lift hair, especially hair lying relatively flat.

[0047] At least some of the teeth in the first set may be of the same length, and / or at least some of the teeth in the second set may be of the same length. The length of a tooth can be measured from the spindle to the end of the tooth (the end being the point furthest from the spindle).

[0048] In some embodiments, the first set of teeth may include a first pair of adjacent teeth, and the second set of teeth may include a second pair of adjacent teeth. The first and second pairs of teeth may be identical in shape, but may be offset from each other along the principal axis of the hair guide element. In this way, pairs of teeth that are mirror images of each other (e.g., mirror symmetric with respect to the principal axis) can be provided, even though the second pair of teeth is offset from the first pair of teeth. These pairs may be offset by only one tooth such that the proximal teeth of the first pair share a common tooth axis with the distal teeth of the second pair (where “distal” and “proximal” are defined along the principal axis). This arrangement can present piecewise identical profiles on both sides of the hair guide element, which can facilitate the equal and good reception of hairs within the slots defined by the toothed profiles when the hair guide element is moved in either direction over the skin. In particular, the mirror arrangement can provide longer slots (each a shorter slot) on both sides of the hair guide element.

[0049] In some embodiments, the hair guide element comprises a spine portion from which a first set of teeth extends in a first direction perpendicular to the main axis, and a second set of teeth extends in a second direction perpendicular to the main axis from which the spine portion.

[0050] The spine portion may define a first H-shaped configuration together with two adjacent teeth of the first set and two adjacent teeth of the second set, and a portion of the spine portion may form a crossbar of the first H-shaped configuration. The first H-shaped configuration may be repeated along the principal axis of the hair guide element. Optionally, the first H-shaped configuration may be repeated at intervals along the principal axis.

[0051] The spine portion may further define a second H-shaped configuration with the second two adjacent teeth of the first set and the second two adjacent teeth of the second set, and a portion of the spine portion may form a crossbar of the second H-shaped configuration. The first and second H-shaped configurations may differ in that the crossbar of the first H-shaped configuration deviates from the principal axis of the hair guide element in a first direction, while the crossbar of the second H-shaped configuration deviates from the principal axis in a second direction. In this way, the longer slots are provided on both sides of the hair guide element to increase the opportunity to receive longer hairs into the slots when the hair guide element is moved across the skin in either direction.

[0052] In some examples, the first H-shaped configuration is repeated at intervals along the main axis, and the second H-shaped configuration is repeated at intervals. One or more instances of the first H-shaped configuration may be provided between consecutive instances of the second H-shaped configuration.

[0053] The spine portion optionally has a meandering shape such that the shorter and longer slots alternate along the second set of teeth, while the longer and shorter slots alternate along the first set of teeth. In such embodiments, a balance can be struck between efficiently cutting longer hairs and the compactness of the design along the length of the spine portion of the hair guide element. The alternating arrangement may allow the longer slots to be located very close together (along the main axis) on both sides of the hair guide element. This helps ensure that longer hairs can be cut as the hair guide element moves across the skin in either of two opposing directions.

[0054] Teeth may be supported by a spinal portion. In particular, some or all of a tooth may be supported by a spinal portion alone. Each such tooth may have a cantilever configuration, supported at one end (the "root" of the tooth) by the spinal portion and unsupported at the opposite end (the tip of the tooth distal to the spinal portion). Such a cantilever configuration may help the tooth more effectively lift hair, especially relatively flat-lying hair. The spinal portion may extend along a main axis and may form part of a hair guide element that provides a connecting base for the root of each tooth.

[0055] In some embodiments, the skin contact surface is at least partially demarcated by a rounded edge that curves convexly toward the surface opposite the cutting element. The convex curve of the rounded edge can help enhance comfort when the user is moving the hair guide element across the skin. This is because the convex curve helps reduce or eliminate the scratching sensation that the user might otherwise experience in scenarios where such a convexly curved rounded edge is not included in the hair guide element.

[0056] In some embodiments, the rounded edges have a radius of curvature of at least 30 μm, for example, at least 50 μm. Such a minimum radius of curvature can provide the user with particularly improved comfort when moving the hair guide element across the user's skin.

[0057] A second aspect of this disclosure provides a hair cutting assembly comprising a hair guide element according to any embodiment described herein and a cutting element positioned to face a surface opposite to the cutting element.

[0058] For example, the surface facing the cutting element may be in contact with the cutting element, but the hair guide surface may not be in contact with the cutting element.

[0059] The cutting element may include multiple cutting portions, with gaps between each adjacent pair of cutting portions. Hair can be cut between the first edge of a cutting portion and the second edge of a portion of the cutting element-facing surface belonging to the teeth of the hair guide element.

[0060] In some embodiments, the first edge of the cut portion is sharper than the second edge of a portion of the surface facing the cutting element.

[0061] According to a third aspect of the present disclosure, an electric shaver is provided comprising a hair cutting assembly according to any embodiment described herein and a motor drive system for moving the cutting element.

[0062] The motor drive system can move the cutting element on the surface opposite the cutting element so as to reciprocate along an axis parallel to the main axis of the hair guide element.

[0063] This movement can cause hair to be cut between the cutting element and the hair guide element.

[0064] In some embodiments, the hair cutting assembly is positioned within the shaver head of an electric shaver, adjacent to at least one further hair cutting assembly.

[0065] For example, the hair cutting assembly is located within the shaver head of an electric shaver, adjacent to at least one further hair cutting assembly comprising a perforated foil and an undercutter positioned to cut hairs protruding through the openings in the perforated foil.

[0066] Such perforated foil-undercutter configurations of further hair cutting assemblies can help cut shorter hairs, while hair cutting assemblies (equipped with hair guide elements and cutting elements) may be for cutting longer hairs.

[0067] In some embodiments, the hair cutting assembly is positioned between a first further hair cutting assembly and a second further hair cutting assembly.

[0068] In such embodiments, a first further hair cutting assembly may comprise a first perforated foil and a first undercutter positioned to cut hair protruding through a first opening in the first perforated foil, and a second further hair cutting assembly may comprise a second perforated foil and a second undercutter positioned to cut hair protruding through a second opening in the second perforated foil.

[0069] A fourth aspect of this disclosure provides a method for manufacturing a hair guide element according to any embodiment described herein, the method comprising etching a metal substrate to form at least a portion of the hair guide element.

[0070] The hair guide elements may be formed by etching a stainless steel substrate. In other words, the method may include etching such a stainless steel steep substrate to form at least a portion of the hair guide elements.

[0071] In some embodiments, an etching-resistant material is placed on a metal substrate to mask the metal substrate, and openings are defined through this etching-resistant material, the etching-resistant material extending continuously between the openings and including a continuous region surrounding the openings, and etching involves delivering an etching solution to the metal substrate through the openings so that individual recessed regions in the metal substrate are etched below the openings, the etching-resistant material is resistant to the etching solution, and etching continues until at least a portion of the individual recessed regions fuse under the continuous region of the etching-resistant material to form one or more fused etched regions, and a portion of the metal substrate remains below one or more fused etched regions after etching.

[0072] In such embodiments, the formation of one or more fused etching regions may include, for example, the formation of the hair guide surface and tip region of a hair guide element.

[0073] This can provide an advantageous method for realizing a hair guide element using, for example, a method that includes a single etching step.

[0074] The metal substrate may have a first thickness before etching, and etching is continued until the thickness of the metal substrate is reduced such that the metal substrate has one or more second thicknesses below one or more fused etching regions, where one or more second thicknesses are non-zero but smaller than the first thickness.

[0075] In some embodiments, etching continues until a portion below one or more fused etching regions includes a planar region of the etched metal substrate, which is located below at least a portion of the opening and below where a continuous region of etching-resistant material extends between at least a portion of the opening.

[0076] In some embodiments, the opening may include a larger opening and a smaller opening, the larger opening allowing more etching solution to pass through and reach the metal substrate during etching than the smaller opening.

[0077] In such embodiments, the larger and smaller openings may be positioned relative to each other such that, for example, etching provides an inclined profile, e.g., an inclined planar region, that slopes from the lower region of the etched metal substrate, where more of the metal substrate is removed below the larger opening, to the upper region of the etched metal substrate, where less of the metal substrate is removed below the smaller opening.

[0078] Providing such an inclined profile may involve forming an inclined surface of a hair guide element.

[0079] In some embodiments, one or more unmasked areas are provided adjacent to the areas where the etching-resistant material is masking the metal substrate, and etching continues until the metal substrate is completely removed by etching beneath one or more unmasked areas, but a portion of the metal substrate still remains beneath one or more fused etching areas.

[0080] Therefore, a single etching process can be used to etch the metal substrate beneath the unmasked area completely through its thickness, while in the fused etching area, only the metal substrate can be partially etched.

[0081] In some embodiments, the continuous region is connected to a peripheral region of the etching-resistant material, and the continuous region remains connected to the peripheral region after etching of the material when one or more fused etching regions are formed.

[0082] The surrounding area helps to hold the continuity area in place during etching, thereby reducing the risk of the continuity area being removed during etching and consequently causing unintended over-etching of the metal substrate.

[0083] At least a portion of the openings may be arranged in an aligned pattern, and / or at least a portion of the openings may be distributed in an irregular manner.

[0084] In some embodiments, the aligned pattern includes an array of openings. The aligned pattern may include, for example, at least one of a rectangular array of openings and a hexagonal array of openings.

[0085] In a hexagonal array, each aperture is spaced a single distance from its six nearest adjacent apertures. Therefore, a hexagonal array can help provide relatively uniform etching in the fused etching region beneath the hexagonal array of apertures.

[0086] In some embodiments, the opening area of ​​the continuous region is 25% or less, for example, 1% to 25%, or in the range of 0.01% to 25%, and the opening area is determined by (i) obtaining a fraction by dividing the total area of ​​the openings by the total area of ​​the etching-resistant material provided with the continuous region and the openings, and (ii) multiplying that fraction by 100.

[0087] Such an aperture area of ​​up to 25% can help minimize the risk of over-etching the metal substrate.

[0088] This method may include removing an etching-resistant material and leaving an etched metal substrate containing one or more fused etching regions, such that a portion of the metal substrate remains beneath one or more fused etching regions.

[0089] In some embodiments, etching includes spraying an etching solution onto a metal substrate with an etching-resistant material placed on it. Alternatively or additionally, etching may include moving the metal substrate through an etching zone where the etching solution is delivered, with an etching-resistant material placed on it.

[0090] The etching solution may comprise at least one selected from ferric chloride solution, copper sulfate solution, nitric acid solution, and picric acid solution. Such an etching solution may be particularly well suited for etching stainless steel.

[0091] In some embodiments, the etching-resistant material is placed on an unetched surface of a metal substrate. For example, the etching-resistant material may be placed on a surface of a metal substrate that has been surface-treated, e.g., cleaned, but not etched by a previous etching process. [Brief explanation of the drawing]

[0092] [Figure 1A] A perspective view of an example hair cutting assembly is provided. [Figure 1B] Figure 1A provides a cross-sectional view of the hair cutting assembly shown. [Figure 1C] Figure 1A provides an enlarged cross-sectional view of the hair cutting assembly shown. [Figure 1D] Figure 1A provides another enlarged cross-sectional view of the hair cutting assembly shown. [Figure 1E] Figure 1A provides a plan view of the hair guide element of the hair cutting assembly shown, as seen from the front of the skin contact surface of the hair guide element. [Figure 2] Figure 1E provides a first cross-sectional view of the hair guide element shown. [Figure 3A] Figure 1E provides an enlarged plan view of a portion of the hair guide element shown, and the inset provides a perspective view of hair on the hair guide surface of the hair guide element. [Figure 3B] The movement of the hair guide elements across the skin, as shown in Figure 1E, is schematicly illustrated. [Figure 4A] Figure 1E provides a second cross-sectional view of the hair guide element shown. [Figure 4B] An enlarged view showing a portion of the second cross-sectional view provided in Figure 4A is provided. [Figure 5] A reproduction of the second cross-sectional view provided in Figure 4A shows the hair being guided by the hair guide surface of the hair guide element. [Figure 6] A partial example of the hair guide element is shown. [Figure 7A] This shows a part of a hair guide element, illustrating an example where a step is defined between the hair guide surface of the hair guide element and the surface facing the cutting element. [Figure 7B] Figure 7A provides an enlarged view showing a portion of the hair guide element. [Figure 8] A reproduction of the second cross-sectional view provided in Figure 7A shows the hair being guided by the hair guide surface of the hair guide element. [Figure 9] Figure 1E provides an enlarged plan view of a portion of the hair guide element shown, and the inset provides a perspective view of the hair between the teeth of the hair guide element. [Figure 10]An example of an electric shaver foil is shown. [Figure 11A] This diagram schematically illustrates the process of etching a metal substrate. [Figure 11B] This diagram schematically illustrates the process of etching a metal substrate. [Figure 12] A schematic cross-sectional view is provided showing the delivery of the etching solution and the gradual removal of the metal substrate region by the etching solution. [Figure 13] A schematic cross-sectional view is provided showing the delivery of etching solution to one side of a metal substrate. [Figure 14] An example of an etching-resistant material placed on a metal substrate (left) and the resulting etched metal substrate (right) is schematically shown. [Figure 15] Another example schematically shows an etching-resistant material placed on a metal substrate (left) and the resulting etched metal substrate (right). [Figure 16] Further examples schematically show an etching-resistant material placed on a metal substrate (left) and the resulting etched metal substrate (right). [Figure 17] A cross-sectional view of a hair cutting assembly is provided, in which the hair guide element is manufactured using an etching method as an example. [Figure 18] Further examples schematically show an etching-resistant material placed on a metal substrate (left) and the resulting etched metal substrate (right). [Figure 19] Further examples schematically show an etching-resistant material (left) placed on a metal substrate and the resulting etched metal substrate (right). [Figure 20] This provides a cross-sectional view of another hair cutting assembly in which the hair guide element is manufactured using an etching method as an example. [Figure 21] The present invention provides a plan view of an etching-resistant material that divides a rectangular array of openings through which an etching solution can be delivered to a metal substrate. [Figure 22]The present invention provides a plan view of an etching-resistant material that divides a hexagonal array of openings through which an etching solution can be delivered to a metal substrate. [Figure 23] The present invention provides a plan view of an etching-resistant material that divides irregularly distributed openings through which an etching solution can be delivered to a metal substrate. [Figure 24] This provides a plan view of an etching-resistant material that divides large and small openings through which an etching solution can be delivered to a metal substrate. [Modes for carrying out the invention]

[0093] A hair guide element for an electric shaver is provided. The hair guide element has a skin contact surface for contacting the skin and a cutting element facing surface for facing a cutting element, the cutting element facing surface facing in the opposite direction to the direction the skin contact surface faces. The outer circumference of the hair guide element provides the hair guide element with a toothed profile including teeth arranged along the principal axis of the hair guide element, each tooth including part of the skin contact surface and part of the cutting element facing surface.

[0094] A hair cutting assembly comprising a hair guide element and a cutting element is further provided, and an electric shaver comprising such a hair cutting assembly is also provided. Furthermore, a method for manufacturing a hair guide element is provided.

[0095] Figures 1A to 1D provide various diagrams of an example hair cutting assembly 10, 16. The hair cutting assembly 10, 16 is used in an electric shaver and may be included therein, for example. The hair cutting assembly 10, 16 includes a hair guide element 10 for guiding the hair before it is cut by the hair cutting assembly 10, 16.

[0096] The hair guide element 10 may include a skin contact surface 12 for contacting the skin (not visible in Figures 1A to 1D) and a cutting element opposing surface 14 for facing the cutting element 16, which may be included in the cutting assemblies 10, 16 together with the hair guide element 10. The cutting element opposing surface 14 may face in the opposite direction to the direction the skin contact surface 12 faces.

[0097] The cutting element facing surface 14 faces the cutting element 16 and can contact the cutting element 16 when the hair guide element 10 is placed together with the cutting element 16 within the hair cutting assembly 10, 16.

[0098] The motor drive system included in the electric shaver can move the cutting element 16 on the cutting element facing surface 14 so as to reciprocate along an axis parallel to the main axis MA of the hair guide element 10 while the cutting element facing surface 14 is in contact with the cutting element 16.

[0099] This movement can cause hair to be cut between the cutting element 16 and the hair guide element 10.

[0100] Note that the hair guide element 10 can be considered an outer cutter, outer blade, or comb, and the cutting element 16 is an inner cutter or inner blade. Hair can be cut between the first edge of the hair guide element 10 and the second edge of the cutting element 16. The second edge of the cutting element 16 may be sharper than, for example, the first edge of the hair guide element 10, in other words, it may have a smaller radius of curvature. Alternatively, the first edge of the hair guide element 10 may be sharper than the second edge of the cutting element 16, in other words, it may have a smaller radius of curvature.

[0101] As shown in Figure 1C, the skin contact surface 12 can be at least partially separated by a rounded edge 17 that curves convexly toward the cutting element opposing surface 14.

[0102] The convex curve of the rounded edge 17 can help enhance comfort when the user is moving the hair guide element 10 across the skin. This is because the convex curve helps reduce or eliminate the scratching sensation that the user might otherwise experience in scenarios where such a convexly curved rounded edge 17 is not included in the hair guide element 10.

[0103] The hair guide element 10, for example, a comb, can be formed from any suitable material, such as a metal material. Particular reference is given to the hair guide element 10 comprising stainless steel. Alternatively or additionally, the cutting element 16, for example, an inner cutter or inner blade, may comprise a metal material, such as stainless steel. Particular reference is given to embodiments in which the hair guide element 10 comprises stainless steel and the cutting element 16 comprises stainless steel.

[0104] In some embodiments, the hair guide element 10 and / or cutting element 16 are formed by etching a stainless steel substrate. Etching processes that may be used in manufacturing the hair guide element 10 and / or cutting element 16 are described in detail below herein.

[0105] Referring to Figures 1C and 1D, the hair guide element 10 may include a hair guide surface 18 capable of receiving hair from the skin so that the skin contact surface 12 is in contact with the skin. The hair may be guided along the hair guide surface 18 toward the cutting element opposing surface 14, and this hair may be cut between the hair guide element 10 and the cutting element 16.

[0106] It should be noted that the hair guide surface 18 can be distinguished from the cutting element opposing surface 14 in that (at least) the cutting element opposing surface 14 may come into contact with the cutting element 16, while the hair guide surface 18 does not come into contact with the cutting element 16.

[0107] Embodiments relating to the design and manufacture of a hair guide element 10 having such a hair guide surface 18 are described in more detail below in this specification.

[0108] In some embodiments, referring to Figures 1A and 1E, the hair guide element 10 has an outer circumference that provides the hair guide element 10 with a toothed profile including teeth 20 arranged along the principal axis MA of the hair guide element 10. Hair can be caught and cut between the teeth 20 of the hair guide element 10. It should be noted that in embodiments in which the hair guide element 10 includes such a toothed profile, the hair guide element 10 can be considered a comb.

[0109] Each tooth 20 may include a portion of the skin contact surface 12 and a portion of the cutting element facing surface 14. Therefore, referring to Figures 1B and 1C, the upper surface of the tooth 20 may be in contact with the skin, while the lower surface of the tooth 20 faces, for example, the cutting element 16 and makes contact with it.

[0110] It should be noted that the terms “upper” and “lower” as used in this context refer to the orientations shown, for example, in Figures 1B and 1C. This orientation may be appropriate, for example, when the hair guide element 10 is used to cut hair under the chin with the skin contact surface 12 facing upward so as to contact the skin under the chin; however, it will be understood that the hair guide element 10, the hair cutting assemblies 10, 16, and the electric shaver comprising the hair cutting assemblies 10, 16 may be oriented in any suitable manner to allow the skin contact surface 12 to contact the skin at any given location and cut the hair growing from there.

[0111] The cutting element 16 may include multiple cutting portions, with gaps between each adjacent pair of cutting portions. The hair can be cut between a first edge of a portion of the cutting element-facing surface 14 belonging to the teeth 20 of the hair guide element 10 and a second edge of the cutting portion.

[0112] In some embodiments, the second edge of the cut portion is sharper than the first edge of a portion of the cutting element-facing surface 14, in other words, it has a smaller radius of curvature. Alternatively, the first edge of a portion of the cutting element-facing surface 14 may be sharper than the second edge of the cut portion, having a smaller radius of curvature.

[0113] The hair guide element 10 can be mounted on the hair cutting assemblies 10, 16 in any suitable manner. In some embodiments, referring to Figures 1A and 1D, a connecting element 22 of the hair guide element 10 can connect the hair guide element 10 to a side member 24 of the cutting assemblies 10, 16, for example, a side member 24 in the form of a side sheet. The connecting element 22 supports the hair guide element 10 and mounts it within the hair cutting assembly 10.

[0114] The connection between the connecting element 22 and the side member 24 can be achieved using any suitable mounting technique, for example, by welding the connecting element 22 to the side member 24, such as by laser welding.

[0115] Referring to Figure 2, which provides a first cross-sectional view AA of the hair guide element 10 shown in Figure 1E, each connecting element 22 may include a portion of the skin contact surface 12 and / or each may include a portion of the cutting element opposing surface 14. In such embodiments, the rounded edge 17 may be convexly curved from the portion of the skin contact surface 12 toward the portion of the cutting element opposing surface 14.

[0116] In some embodiments (not shown), the connecting element 22 includes a portion of the hair guide surface 18. Alternatively, as shown in Figures 1A to 1E and Figure 2, the teeth 20 include a portion of the hair guide surface 18, while the connecting element 22 does not include any portion of the hair guide surface 18.

[0117] In some embodiments, the connecting element 22 may be included in a toothed profile such that the hair is receivable in the space defined between one of the connecting elements 22 and one of the teeth 20, and / or between adjacent connecting elements 22 and between adjacent teeth 20.

[0118] Several connecting elements 22 may be provided to support the hair guide element 10 at intervals along the main axis. The connecting elements 22 and teeth 20 may be arranged alternately in a regular or irregular pattern. In some embodiments, 2 to 5 teeth of a first set of teeth may be arranged between consecutive connecting elements 22. Similarly, 2 to 5 teeth of a second set of teeth may be arranged between consecutive connecting elements 22. In the specific example shown in Figures 1A and 1E, 3 teeth of the first set and 3 teeth of the second set are arranged between consecutive connecting elements 22.

[0119] Alternatively or additionally, the connecting element 22 can be shorter than at least a portion of the teeth 20, thereby allowing the aforementioned portion of the teeth 20 to extend further than the connecting element 22 in a lateral orientation relative to the spindle MA.

[0120] To determine whether the connecting element 22 is shorter than the tooth 20, the lengths of the connecting element 22 and the tooth 20 can be considered as the distance from the spindle MA to the end of the relevant connecting element 22 or tooth 20 that is furthest from the spindle MA (on the same side of the spindle MA).

[0121] At least some (or all, if optional) of the teeth in the first set may be the same length or substantially the same length. At least some (or all, if optional) of the teeth in the second set may be the same length or substantially the same length. (Here again, length is measured from the principal axis to the end of each tooth.) "Substantially the same length" can be understood as referring to teeth with a length difference of 10% or less.

[0122] Providing a set of teeth of the same length on one or both sides of the spindle MA can help further optimize the use of space within the shaver head. This makes it possible to make the individual teeth as long as possible while minimizing the overall dimensions of the hair guide element 10 in the direction lateral to the spindle MA.

[0123] Nevertheless, in some embodiments, some teeth may have different lengths (i.e., a difference in length of more than 10%). In particular, some teeth of the first set may have different lengths, and / or some teeth of the second set may have different lengths.

[0124] The term “lateral to the principal axis MA” may mean that the hair guide element 10 is perpendicular to the principal axis MA, or at least substantially perpendicular, when viewed in plane such that the skin contact surface 12 or the cutting element opposing surface 14 faces the viewer. Figure 1E shows such a plan view with the skin contact surface 12 facing the viewer. The modifier “substantially” may refer to a deviation of up to 10° from the perpendicular.

[0125] With respect to the hair guide element 10, for example the main shaft MA of a comb, it should be noted that the main shaft MA may extend along the length of the hair guide element 10, in other words, along its longest dimension, from the first end portion 25A to the second end portion 25B of the hair guide element 10.

[0126] The main axis MA can, for example, bisect the hair guide element 10 such that the main axis MA separates the hair guide element 10 into a pair of elongated halves of the hair guide element 10.

[0127] The end portions 25A and 25B of the hair guide element 10 may be toothless, for example, so that the toothed profile of the hair guide element 10 extends between them without being included in the end portions 25A and 25B.

[0128] In at least some embodiments, the teeth 20 include a first set of teeth extending laterally with respect to the spindle MA in a first direction, and a second set of teeth extending laterally with respect to the spindle MA in a second direction opposite to the first direction. The first and second sets of teeth allow the hair guide element 10 to guide the hair toward the cutting element facing surface 14 when the hair guide element 10 is moved in opposite directions across the skin.

[0129] In the toothed profile of the hair guide element 10, slots 26, 26', 28, and 28' are intrinsically shown to separate adjacent teeth 20 along the main axis MA from each other.

[0130] In embodiments in which the teeth 20 include a first set of teeth and a second set of teeth, the slots 26, 26', 28, 28' may include slots 26, 28' that separate adjacent teeth of the first set of teeth from each other, and slots 26', 28 that separate adjacent teeth of the second set of teeth from each other.

[0131] Alternatively or additionally, slots 26, 26', 28, 28' may include first slots 26, 26' and second slots 28, 28' that differ from each other in terms of their lengths (at least) lateral to the spindle MA. Embodiments in which such first and second slots 26, 26', 28, 28' of different lengths are provided in the hair guide element 10 are described in more detail below.

[0132] In some embodiments, referring here to Figures 1B-1D, 3A and 3B, at least a portion of the teeth 20, for example, the portion of the teeth 20 extending further than the connecting element 22 in a transverse direction with respect to the spindle MA, each includes a portion of the hair guide surface 18 and a tip region 30 positioned to receive hair HA as the hair guide element 10 is moved over the skin SK. The portion of the hair guide surface 18 may extend in a transverse direction with respect to the spindle MA, away from the tip region 30 toward a portion of the cutting element facing surface 14, so as to enable the portion of the hair guide surface 18 to guide hair HA received on the tip region 30 toward a portion of the cutting element facing surface 14.

[0133] As shown in Figures 3A and 3B, when the hair guide element 10 is moved over the skin SK in the direction indicated by arrow DR with the skin contact surface 12 in contact with the skin SK, the hair HA can ride up onto the tip region 30 (relative to the surface of the skin SK) and slide along a portion of the hair guide surface 18 toward a portion of the cutting element opposing surface 14.

[0134] Part of the hair guide surface 18 is also visible in Figures 4A and 4B, and it should be noted that Figure 4A provides a second cross-sectional view BB of the hair guide element 10 shown in Figure 1E. Figure 4B provides, in particular, an enlarged schematic view showing the tip region 30.

[0135] Users of conventional electric shavers may notice that even though the electric shaver's comb is moved over the skin SK in areas where hair HA is present, such hair HA may remain uncut. This can lead users to move the comb over the skin SK multiple times in the same area, which can cause skin irritation.

[0136] Referring again to Figure 3B, we can see that one reason why hair HA remains uncut is the angle α of the hair HA relative to the surface of the skin SK, particularly the relatively small angle α relative to the surface of the skin SK. For example, hair HA on the neck can protrude from the skin surface at an angle α of only about 10°.

[0137] Therefore, referring to Figure 4B, the tooth thickness T1 in the tip region can be less than 250 μm, and this tooth thickness T1 is the diameter of the smallest conceptual circle C1 whose circumference intersects both a portion of the hair guide surface 18 and a portion of the skin contact surface 12, with the plane of the smallest conceptual circle C1 perpendicular to the principal axis MA. As is clear from the example in Figure 4B, the use of the “smallest conceptual circle” to measure the tooth thickness T1 does not require the tip region to have a circular geometric shape.

[0138] It was found that when the tooth thickness T1 in the tip region 30 is less than 250 μm, preferably less than 200 μm, more hairs HA can be successfully cut with less passage of the hair guide element 10 across the skin SK, resulting in less skin irritation. This is because, when the hair HA protrudes from the surface of the skin SK at an angle α of about 10° and the length of the hair HA is about 1.5 mm, which corresponds to the upper limit of facial hair growth in 3 days (0.5 mm per day), the tooth 20 with a thickness T1 of less than 250 μm in the tip region 30 can enter a gap of about 260 μm between the end of the hair HA and the surface of the skin SK.

[0139] Generally, at this point, the skin contact surface 12 may have a single plane, and it should be noted that the circumference of the smallest conceptual circle C1 whose diameter defines the tooth thickness T1 intersects with the single plane of the skin contact surface 12.

[0140] At least a portion of the teeth 20 (each including a portion of the bristle guide surface 18 and a tip region 30 having a tooth thickness T1 of less than 250 μm) may be included in a first set of teeth and a second set of teeth.

[0141] Therefore, the hair-lifting and hair-guiding attributes of the tip region 30 and the hair-guiding surface 18 may be exhibited when the hair-guiding element 10 is moved in opposite directions across the skin SK.

[0142] In some embodiments, referring to Figures 3A, 3B, 4A, 4B, 5, and 6, at least a portion of the hair guide surface 18 of the teeth 20 includes an inclined surface, which descends from the tip region 30 toward a portion of the cutting element facing surface 14 as the inclined surface extends laterally with respect to the main axis MA, and the inclined surface moves further away from the skin contact surface 12 as the inclined surface descends toward a portion of the cutting element facing surface 14.

[0143] Therefore, referring to Figure 5, the hair HA received on the tip region 30 can slide down the inclined surface toward the cutting element opposing surface 14 in the direction indicated by arrow 31. Separating the hair HA from the skin SK in this way helps to properly orient the hair HA for cutting as it slides down the inclined surface toward the cutting element opposing surface 14.

[0144] The inclined surface can be considered, for example, a chamfer for carrying the hair HA to the cutting plane defined by the cutting element opposing surface 14. Thus, after being lifted onto the tip region 30, the hair HA can be carried along the inclined surface / chamfer that can be cut between the hair guide element 10 and the cutting element 16 once the hair HA reaches the cutting element opposing surface 14.

[0145] It should be reiterated that the hair guide surface 18 does not need to be in contact with the cutting element 16, and in embodiments where the hair guide surface 18 includes an inclined surface, the inclined surface does not need to be in contact with the cutting element 16.

[0146] Alternatively or additionally, at least a portion of the teeth 20 including the inclined surface may extend further than the connecting element 22 in a lateral direction relative to the spindle MA. For example, at least a portion of the teeth 20 including the inclined surface may protrude from the side member 24 of the hair cutting assemblies 10, 16, while the end of the connecting element 22 may be coplanar with the side member 24, or at least protrude less from the side member 24 compared to at least a portion of the teeth 20 having the inclined surface.

[0147] At least a portion of the teeth 20 that protrude laterally from the main spindle MA and further than the connecting element 22 may include a tip portion 30 and at least a portion of an inclined surface.

[0148] In some embodiments, referring to Figure 4B, the lowest region 32 of the inclined surface is where the inclined surface reaches the cutting element opposing surface 14 in a step-free manner. Thus, the hair HA can slide down the inclined surface continuously to reach the cutting element opposing surface 14.

[0149] This facilitates guiding the hair HA to the cutting element opposing surface 14, particularly in embodiments such as those shown in Figures 7A, 7B, and 8, where the hair HA is required to overcome a step 36 defined between a portion of the cutting element opposing surface 14 and the lowest region 32 of the inclined surface.

[0150] It should be noted that whether such a step 36 is defined between a portion of the cutting element opposing surface 14 and the lowest region 32 of the inclined surface may depend on the technique used to create the inclined surface, e.g., chemical etching, electrochemical etching (ECM), precision (or pulsed) electrolytic machining (PECM), laser removal, and / or wire cutting. Chemical etching methods that may be used to achieve the inclined surface of the hair guide element 10 are described in detail below herein.

[0151] In some embodiments, referring to Figure 4B, the inclined surface has a gradient defined by a lateral extension L1 of the inclined surface that is greater than the height H1 of the inclined surface, the lateral extension L1 extending parallel to the skin contact surface 12 from the tip region 30 to a first point P1 aligned with the lowest region 32 of the inclined surface, and the height H1 extending perpendicular to the skin contact surface 12 from the tip region 30 to a second point P2 aligned with the lowest region 32.

[0152] Because the lateral spread L1 is greater than the height H1, the inclined surface descends relatively gently from the tip region 30 to the bottom region 32, compared to a scenario where the lateral spread L1 is equal to or less than the height H1, as shown in the example in Figure 6.

[0153] Such a relatively gently sloping surface can help the hair HA slide on it toward the cutting element opposing surface 14.

[0154] In some embodiments, the lateral spread L1 is at least twice as large as the height H1. Alternatively or additionally, the lateral spread L1 may be at least 200 μm, while the height H1 is 100 μm or less.

[0155] As shown in Figures 7A, 7B, and 8, in an embodiment where a step 36 is defined between the lowest region 32 of the downward-sloping surface and a portion of the surface 14 facing the cutting element, the step 36 can provide a height difference HD of 50 μm or less, for example, 40 μm or less, between the portion of the surface 14 facing the cutting element and the lowest region 32.

[0156] In such embodiments, the hair HA can slide down the inclined surface until it reaches the step 36, at which point the sliding motion of the hair HA may end. However, the hair HA can overcome the step 36, for example, by hitting or rolling over a portion of the cutting element opposing surface 14 from the lowest region 32 of the inclined surface.

[0157] By limiting this height difference HD to 50 μm or less, the average hair HA that slides down the slope and reaches the lowest region 32 can relatively easily overcome the step 36. This is because the height difference HD does not exceed half the average diameter of facial hair HA, i.e., 50 μm.

[0158] In an embodiment in which a step 36 is defined between the lowest region 32 of the downward-sloping surface and a portion of the surface 14 facing the cutting element, referring to Figure 7B, the inclined surface may have a gradient defined by a lateral extension L1 of the inclined surface that is greater than the height H1 of the inclined surface, the lateral extension L1 in this case extending parallel to the skin contact surface 12 from the tip region 30 to a first point P1 aligned with the lowest region 32 of the inclined surface at the base of the step 36, and the height H1 extending perpendicular to the skin contact surface 12 from the tip region 30 to a second point P2 aligned with the lowest region 32. For example, the lateral extension L1 is at least twice as large as the height H1. Alternatively or additionally, the lateral extension L1 may be at least 200 μm, while the height H1 is 100 μm or less.

[0159] It should be reiterated that, because the lateral spread L1 is greater than the height H1, the inclined surface slopes relatively gently downward from the tip region 30 to the lowest region 32, thereby helping the hair HA slide along the inclined surface toward the cutting element opposing surface 14.

[0160] In an embodiment in which the rounded edge 17 curves convexly from a portion of the skin contact surface 12 toward a portion of the cutting element opposing surface 14, referring here to Figures 4A, 5, 7A, and 8, the rounded edge 17 may have a radius of curvature R1 of at least 30 μm, for example, at least 50 μm. Such a minimum radius of curvature R1 of the rounded edge 17 can provide the user with particularly improved comfort when moving the hair guide element 10 across the user's skin SK.

[0161] A rounded edge 17, for example, having a radius of curvature R1 of at least 30 μm, such as at least 50 μm, may be provided around the entire circumference of the hair guide element 10.

[0162] In some embodiments, rounded edges 17, for example, having a radius of curvature R1 of at least 30 μm, such as at least 50 μm, may be included in the teeth 20 and the connecting element 22.

[0163] The radius of curvature R1 of the rounded edges 17, for example, the rounded edges 17 of the teeth 20 and the rounded edges 17 of the connecting element 22, may be in the range of 30 μm to 70 μm.

[0164] In some embodiments, referring to Figures 4A, 4B, 5, 6, 7A, 7B, and 8, each tooth 20 includes an end face 37, and the rounded edge 17 curves convexly from a portion of the skin contact surface 12 to the end face 37.

[0165] A portion of the end face 37 may intersect, for example, the circumference of the smallest conceptual circle C1 whose diameter defines the tooth thickness T1.

[0166] A further edge 38 may be defined between the end face 37 and a portion of the hair guide surface 18. The further edge 38 may have, for example, a radius of curvature R2 of at least 7 μm.

[0167] Such a minimum radius of curvature R2 of the further edge 38 can help minimize or prevent hair HA from getting caught on the further edge 38 when the hair guide element 10 is moving over the skin SK.

[0168] The radius of curvature R2 of the further edge 38 may be, for example, in the range of 7 μm to 13 μm.

[0169] In some embodiments, the radius of curvature R1 of the rounded edge 17 is at least 30 μm, and the radius of curvature R2 of the further edge 38 is at least 7 μm.

[0170] For example, the radius of curvature R1 of the rounded edge 17 is at least 50 μm, and the radius of curvature R2 of the further edge 38 is at least 7 μm. In a non-limiting example, the radius of curvature R1 of the rounded edge 17 is in the range of 30 μm to 70 μm, and the radius of curvature R2 of the further edge 38 is in the range of 7 μm to 13 μm.

[0171] It should be reiterated that the hair HA can be cut between the first edge of the hair guide element 10 and the second edge of the cutting element 16. In some embodiments, the radius of curvature R3 of the first edge of the hair guide element 10 is at most 3.5 μm, for example, 1 μm to 3.5 μm.

[0172] The maximum radius of curvature R3 of the first edge can help cut the hair HA against it.

[0173] In some embodiments, the radius of curvature R1 of the rounded edge 17 is at least 30 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is at most 3.5 μm. For example, the radius of curvature R1 of the rounded edge 17 is at least 50 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is at most 3.5 μm.

[0174] In some embodiments, the radius of curvature R2 of the further edge 38 is at least 7 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is at most 3.5 μm. For example, the radius of curvature R2 of the further edge 38 is in the range of 7 μm to 13 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is in the range of 1 μm to 3.5 μm.

[0175] In some embodiments, the radius of curvature R1 of the rounded edge 17 is at least 30 μm, the radius of curvature R2 of the further edge 38 is at least 7 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is at most 3.5 μm. For example, the radius of curvature R1 of the rounded edge 17 is at least 50 μm, the radius of curvature R2 of the further edge 38 is at least 7 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is at most 3.5 μm.

[0176] In a non-limiting example, the radius of curvature R1 of the rounded edge 17 is in the range of 30 μm to 70 μm, the radius of curvature R2 of the further edge 38 is in the range of 7 μm to 13 μm, and the radius of curvature R3 of the first edge of the hair guide element 10 is in the range of 1 μm to 3.5 μm.

[0177] In some embodiments, referring here to Figure 9, slots 26, 26', 28, 28' that separate adjacent teeth 20 along the spindle MA include pairs of slots 26, 28;26', 28', each of which includes a longer slot 26;26' and a shorter slot 28;28'. The longer slots 26;26' and shorter slots 28;28' of each pair of slots 26, 28;26', 28' extend along a common slot axis A2;A2' which is perpendicular to the spindle MA, with one of the longer slots 26;26' and the other of the shorter slots 28;28' defining between adjacent teeth of a first set of teeth, and the other of the longer slots 26;26' and the other of the shorter slots 28;28' defining between adjacent teeth of a second set of teeth.

[0178] In other words, the shorter slot 28;28' and the longer slot 26;26' of each pair of slots 26, 28;26' can be arranged back-to-back such that the shorter slot 28;28' receives hair HA in the direction opposite to the direction in which the longer slot 26;26' receives hair HA.

[0179] When the skin contact surface 12 of the hair guide element 10 is moved over the skin SK in the direction indicated by arrow DR in Figure 9, the hair HA can be received into the slots 26, 28' and then reach the cutting element opposing surface 14. The longer slots 26; 26' can provide more opportunities for the hair HA, especially longer hair HA, to be received therein, thereby helping to increase cutting efficiency. However, providing two relatively long slots 26; 26' in a back-to-back arrangement risks making the width of the hair guide element 10 excessively large, which could reduce the compactness of the shaver head of an electric shaver containing such a hair guide element 10, and thus impair the application of the hair guide element 10 to relatively narrow areas of skin SK, such as between the nose and the upper lip.

[0180] Therefore, the pair of longer and shorter slots, 26', 28'; 26', 28', can balance the efficient cutting of longer hairs HA with the compactness of the hair guide element 10 design.

[0181] In some embodiments, continuing with reference to Figure 9, the hair guide element 10 includes a spine portion 39 from which a first set of teeth extends in a first direction perpendicular to the main axis MA, and a second set of teeth extends in a second direction perpendicular to the main axis MA from which the spine portion 39.

[0182] The spine portion 39 may have a meandering shape such that the shorter slots and the longer slots 28, 26' alternate along the second set of teeth, while the longer slots and the shorter slots 26, 28' alternate along the first set of teeth. In other words, the spine portion may include continuous segments that are offset from each other in a direction lateral to the principal axis.

[0183] In such embodiments, a balance can be struck between efficiently cutting longer hairs HA and the compactness of the design along the length of the spine portion 39 of the hair guide element 10. In the example shown in Figure 9, all teeth are supported only by the spine portion. Each tooth has a cantilevered form, supported at one end by the spine portion and unsupported at the other end (distal to the spine portion). Such a cantilevered form may help the tooth more effectively lift hair, especially hairs that lie relatively flat. Any two or more combinations of (i) cantilevered teeth, (ii) hair guide surface 18, and (iii) limited tooth thickness T1 in the tip region 30 are thought to result in particularly effective hair lifting.

[0184] Note that the lengths of each slot 26, 26', 28, and 28' extend laterally with respect to the spindle MA and can be defined along the central slot axis A2;A2' which bisects the slots 26, 26', 28, and 28', from the connection regions 40, 40';42, 42' that connect adjacent teeth 20 defined between them, to points 44, 44';46, 46' located between the end / end faces 37 of adjacent teeth 20.

[0185] The distance D1 from the point where a portion of the cutting element opposing surface 14 terminates and aligns with the connection regions 40, 40'; 42, 42' along the central slot axis A2; A2' of each slot 26, 26', 28, 28' can define the cutting length. Although not bound by theory, the cutting length of the slot is thought to have a significant impact on the efficiency of cutting long hairs. When the skin contact surface 12 of the hair guide element 10 is moved over the skin SK in the direction indicated by arrow DR in Figure 9, the hair HA may be initially caught under the spinal portion 39 and pressed against the skin. As the hair guide element continues to move in the direction indicated by DR, the free end of the hair HA is released from under the spinal portion 39 and the hair springs up from the skin. As shown in Figure 9, at the point when the hair is upright, the base of the hair (where it contacts the skin) is still positioned between the two portions of the cutting element opposing surface 14. This means that the hair is properly positioned (for example, between the cutting element 16 and the hair guide element 10) so that it is cut by the cutting element 16.

[0186] From this, it can be seen that the length of the slot correlates with the maximum length of hair HA that can be cut by this mode. This partially explains why it is desirable to have a long slot. If the hair HA is longer than the cutting length (defined by the range of the cutting element opposing surface 14), the base of the hair may already be beyond the reach of the cutting element 16, for example, beyond the end of the slot 26', when the free end of the hair is released from under the spine portion 39 and stands upright.

[0187] It should be understood that slots can have various shapes. The opposing sides of each slot (defined by adjacent teeth) may be parallel or may define a tapered width. The width of each slot (measured, for example, parallel to the spindle) may be substantially constant over at least a portion of the slot's length. Alternatively, the width may be tapered such that the open end of the slot is wider than the opposing closed end of the slot. (This shape may be preferred to facilitate the introduction of hair into the open end of the slot.) Or, in some examples, the width may be tapered such that the open end of the slot is narrower than the opposing closed end of the slot.

[0188] More generally, this disclosure relates in part to the hair guide element 10 itself, since the hair guide element 10 can, in principle, be supplied separately from any other components such as the cutting element 16.

[0189] The hair guide element 10 is further intended to be provided together with the cutting element 16 within the hair cutting assemblies 10, 16.

[0190] This disclosure further provides an electric shaver comprising a hair cutting assembly 10, 16 according to any embodiment described herein, and a motor drive system for moving the cutting element 16.

[0191] In some embodiments, the hair cutting assemblies 10, 16 are positioned within the shaver head of an electric shaver, adjacent to at least one further hair cutting assembly.

[0192] For example, the hair cutting assemblies 10, 16 are located within the shaver head of an electric shaver, adjacent to at least one further hair cutting assembly comprising, for example, a perforated foil 50 of the type shown in Figure 10, and an undercutter positioned to cut hairs HA protruding through the openings 52 of the perforated foil 50.

[0193] Such perforated foil-undercutter configurations of further hair cutting assemblies can help cut shorter hairs HA, while hair cutting assemblies 10, 16 (equipped with hair guide elements 10 and cutting elements 16) may be for cutting longer hairs HA.

[0194] It should be noted that the perforated foil 50 may be statically mounted within the shaver head so that the perforated foil 50 itself is not driven by the motor drive system. Conversely, the undercutter may be driven by the motor drive system so that it moves relative to the statically mounted perforated foil 50 and cuts the hair HA protruding through the opening 52 of the perforated foil 50.

[0195] In some embodiments, the hair cutting assemblies 10, 16 are positioned within the shaver head between a first further hair cutting assembly and a second further hair cutting assembly.

[0196] In such embodiments, a first further hair cutting assembly may comprise a first perforated foil 50 and a first undercutter positioned to cut hair HA protruding through a first opening 52 of the first perforated foil 50, and a second further hair cutting assembly may comprise a second perforated foil 50 and a second undercutter positioned to cut hair HA protruding through a second opening 52 of the second perforated foil 50.

[0197] The perforated foil 50 can be formed from any suitable material. In some embodiments, the perforated foil includes a metallic material such as stainless steel.

[0198] Components of the hair cutting assemblies 10, 16 and / or further hair cutting assemblies, such as the hair guide element 10, the cutting element 16, and / or the perforated foil 50, can be manufactured through a process that includes etching a metal substrate, such as a stainless steel substrate. Such a process is described in detail below in this specification.

[0199] Figures 11A and 11B schematically show such a metal substrate 100 (see Figure 11A a) and Figure 11B a), for example, a stainless steel substrate, whose surface may be treated, for example, cleaned, before the photoresist layers 102A, 102B are placed thereon (see Figure 11A b) and Figure 11B b). Placing the photoresist layers 102A, 102B on the metal substrate 100 may include, for example, applying a pre-formed photoresist film to the metal substrate 100, which can be considered a dry photoresist film. Alternatively or additionally, placing the photoresist layers 102A, 102B on the metal substrate 100 may include applying a lacquer to the metal substrate 100, which dries to form the photoresist layers 102A, 102B.

[0200] In the case of a pre-formed photoresist film, it can be applied to the metal substrate 100 by rolling the pre-formed photoresist film onto the metal substrate 100, for example, by hot rolling.

[0201] It should be noted that the metal substrate 100 may be a metal sheet, in other words, a sheet of a metal material, such as a sheet of stainless steel.

[0202] In some embodiments, referring to Figure 11B, arranging photoresist layers 102A and 102B on a metal substrate 100 includes arranging the first photoresist layer 102A on a first side of the metal substrate 100 and arranging the second photoresist layer 102B on a second side of the metal substrate 100, the second side facing away from the first side.

[0203] Etching-resistant materials 104A and 104B can be formed by selectively illuminating photoresist layers 102A and 102B placed on a metal substrate 100 (see Figure 11Ac), and Figures 11Bc) and d).

[0204] In some embodiments, referring to Figure 11A, the pattern may be printed onto the photoresist layers 102A and 102B using a direct imaging device, and within the illuminated area, the photoresist layers 102A and 102B are polymerized and thus completely adhered to the surface of the metal substrate 100.

[0205] Figure 11B shows a phototool, such as a photomask, having light-transmitting regions 106A, 106B that allow light 110A, 110B to reach the photoresist layers 102A, 102B and polymerize the photoresist layers 102A, 102B to form an etching-resistant material 104A, 104B, and optically opaque regions 108A, 108B that block light 110A, 110B from reaching the photoresist layers 102A, 102B, leaving the photoresist layers 102A, 102B unpolymerized beneath them.

[0206] If photoresist layers 102A and 102B are not illuminated by etching-resistant materials 104A and 104B (see Figures 11Ad and 11Bd), the photoresist layers 102A and 102B can be removed in a subsequent development step. For example, the photoresist layers 102A and 102B can be removed, or in other words washed away, by applying a solvent in which the photoresist layers are soluble but the etching-resistant materials 104A and 104B are insoluble, by illumination of the photoresist layers 102A and 102B. Thus, after development, masked regions of the metal substrate 100 are provided where the surface of the metal substrate 100 is masked by etching-resistant materials 104A and 104B, and unmasked regions 112A and 112B are provided where the etching-resistant materials 104A and 104B do not mask the metal substrate 100.

[0207] During etching, etching solutions 114A and 114B are delivered to the metal substrate 100 on which the etching-resistant materials 104A and 104B are located (see Figures 11Ae and 11Be). The etching-resistant materials 104A and 104B are resistant to etching solutions 114A and 114B so that they protect the areas beneath the metal substrate 100 from etching by the etching solutions 114A and 114B. Meanwhile, etching regions 116A and 116B, where the metallic material of the metal substrate 100 is etched away by the etching solutions 114A and 114B, are formed beneath the unmasked regions 112A and 112B.

[0208] Etching solutions 114A and 114B can be delivered to the first and / or second side of the metal substrate 100 (on which the etching-resistant materials 104A and 104B are placed).

[0209] Etching may include spraying etching solutions 114A and 114B onto the metal substrate 100 with etching-resistant materials 104A and 104B placed thereon, for example, spraying etching solutions 114A and 114B onto a first side and / or a second side of the metal substrate 100.

[0210] Alternatively or additionally, etching may involve moving the metal substrate 100 through etching zones where etching solutions 114A and 114B are delivered to the metal substrate 100, for example, by spraying them onto it, with etching-resistant materials 104A and 104B placed thereon.

[0211] In such embodiments, etching can be controlled, for example, by controlling the speed at which the metal substrate 100 moves through the etching zone, and / or by adjusting distribution parameters that determine, for example, how much of the etching solution 114A, 114B is distributed per unit time. Such distribution parameters may include, for example, the delivery pressure of the etching solutions 114A, 114B.

[0212] Any suitable etching solutions 114A and 114B can be used, provided that they are capable of etching the metallic material constituting the metal substrate 100, such as stainless steel. In some embodiments, the etching solutions 114A and 114B include at least one selected from ferric chloride solution, copper sulfate solution, nitric acid solution, and picric acid solution. Such etching solutions may be particularly effective, for example, when the metal substrate 100 is a stainless steel substrate.

[0213] After etching, the etching-resistant materials 104A and 104B can be removed, leaving the etched metal substrate 100. For example, the (polymerized) photoresist layers 102A and 102B can be removed, and their residues can be peeled off to provide a clean, all-metal surface of the etched metal substrate 100 (see Figures 11Af and 11Bf).

[0214] In embodiments in which such an etching process is used to manufacture components of hair cutting assemblies 10, 16 and / or further hair cutting assemblies, the etching resulting from the delivery of etching solutions 114A, 114B to a metal substrate 100 (on which etching-resistant materials 104A, 104B are placed) can define at least partially the geometric shape of the components, for example, the cutting edges included in the components.

[0215] Such components manufactured in this manner may have a defined overall geometric shape, including, for example, overall dimensions and edge shape, such as the cut edge shape.

[0216] It should be noted that the edge shape, for example, the cut edge shape, can be generated by a combination of the etching process and the patterns of the etching-resistant materials 104A and 104B, which may result in a defined radius of curvature (or a set of defined radii of curvature) taking into account the defined edge angle and the adhesion quality of the etching-resistant materials 104A and 104B on the surface of the metal substrate 100.

[0217] The above-mentioned radii of curvature R1, R2, and / or R3 can be achieved by controlling the etching process and the patterns of the etching-resistant materials 104A and 104B, including their adhesion to the metal substrate 100.

[0218] For example, one approach could be to use a metal substrate 100 having etching-resistant materials 104A and 104B equally patterned on each of the first and second sides of the metal substrate 100, and then spray etching toward both sides of the metal substrate 100.

[0219] This can result in defined edge angles, such as the cutting edge angle, and defined radii of curvature.

[0220] Figure 12 schematically shows the progression of the profile during a one-sided etching process of a metal substrate 100 in the form of a metal sheet. In this non-limiting example, the defined cut edge shape (see circle 118 in Figure 12) is located on the side of the etched metal substrate 100 opposite to the side to which the etching solution 114A is delivered, for example, sprayed.

[0221] As the metallic material of the metal substrate 100 is etched away by the etching solution 114A, the first etched region 116A is formed beneath the non-masked region 112A, and some under-etching may also exist beneath the portion of the etching-resistant material 114A positioned between the non-masked regions 112A, as indicated by arrow 120 in Figure 12.

[0222] In the scenario shown in Figure 12, the metallic material of the metal substrate 100 is ultimately completely removed by the etching solution 114A under the non-masked area 112A, resulting in a defined cut edge shape 118 adjacent to the area where the metallic material is completely removed.

[0223] More generally, referring to Figures 11A f) and 11B f), it should be noted that etching can remove all of the metallic material from the metal substrate 100 beneath the unmasked areas 112A and 112B (see area 122 in Figures 11A and 11B), and / or partially remove the metallic material from the metal substrate 100 to reduce its thickness without completely removing the metallic material beneath the unmasked areas 112A and 112B (see partially etched area 124 in Figure 11B).

[0224] With respect to a partially etched region 124 in which the thickness of the metal substrate 100 is reduced rather than the metallic material being completely removed, one possibility for achieving such a partially etched region 124 is to place a first etching-resistant material 104A on a first side of the metal substrate 100 and a second etching-resistant material 104B on a second side of the metal substrate 100. As shown in Figure 13, the unmasked region 112A can expose a portion of the first side of the metal substrate 100, while the second etching-resistant material 104B forms a closed resist on the second side of the metal substrate 100. In such an example, removal of less than half of the metallic material can be achieved by delivering the etching solution 114B only in the direction of the second side with the closed resist, and, depending on the atmosphere of the etching solution, partially removing the metallic material through contact with the first side of the metal substrate 100 where the unmasked region 112A is located. However, achieving such a partially etched region 124 in this manner may not allow for the simultaneous and complete removal of the metallic material in adjacent areas of the metal substrate 100.

[0225] Therefore, it is desirable to provide an etching method that enables the creation of a partially etched region 124 in a more controlled manner, for example, by completely removing the metallic material in the area of ​​the metal substrate 100 adjacent to the partially etched region 124.

[0226] Referring here to Figure 14, the etching method according to the present disclosure comprises providing a metal substrate 100 on which etching-resistant materials 104A, 104B are arranged to mask the metal substrate 100, and an opening 126 is defined through the etching-resistant materials 104A, 104B. The etching-resistant materials 104A, 104B extend continuously between the openings 126 and include a continuous region 128 surrounding the openings 126.

[0227] Therefore, the openings 126 are separated from each other by the continuous regions 128 so that the openings 126 are not connected to each other.

[0228] The etching method includes etching the metal substrate 100, which includes delivering etching solutions 114A, 114B to the metal substrate 100 through the opening 126 so that individual recessed regions within the metal substrate 100 are first etched under the opening 126. This is in a similar manner to the initial formation of the etched region 116A shown in Figure 12, but it should be noted that the individual recessed regions are formed under the opening 126 defined within a continuous region 128 of the etching-resistant material 104A, 104B, rather than under a non-masked region 112A. The etching is continued until at least a portion of the individual recessed regions fuse under the continuous region 128 of the etching-resistant material 104A, 104B, thereby extending the continuous region 128 over locations on the metal substrate 100 located between the initially formed individual recessed regions, where the metallic material of the metal substrate 100 is removed as the individual recessed regions fuse to form one or more fused etched regions 130. The etching leaves a portion 132 of the metal substrate 100, which remains beneath one or more fused etching regions 130.

[0229] The opening 126 provides a method for controlling the addition of etching solutions 114A and 114B to the metal substrate 100, thereby leaving a portion 132 of the metal substrate 100 below the fused etching region 130 after etching.

[0230] Creating a portion 132 in this way may, for example, involve forming the hair guide surface 18 of the hair guide element 10.

[0231] Each of the apertures 126 may have a diameter in the range of 5 μm to 500 μm, or, if not circular, a maximum dimension across each aperture 126. Alternatively or additionally, the spacing between the nearest apertures 126 may be in the range of 5 μm to 500 μm.

[0232] It should be noted that the aperture 126 can be considered, for example, a micro-aperture, such as one with a diameter or maximum dimension (if not circular) in the range of 5 μm to 500 μm.

[0233] To avoid any ambiguity, the diameter or maximum dimension refers to the measured value of each opening 126 when the metal substrate 100 is viewed in plane facing the continuous region 128 (as shown on the left side of each of Figures 14 to 16).

[0234] In some embodiments, the opening area of ​​the continuous region 128 is 25% or less, for example, 1% to 25%, or in the range of 0.01% to 25%, and the opening area is determined by (i) obtaining a fraction by dividing the total area of ​​the openings 126 by the total area of ​​the etching-resistant materials 104A and 104B on which the continuous region 128 and the openings 126 are provided, and (ii) multiplying that fraction by 100.

[0235] Such an aperture area of ​​up to 25% can help minimize the risk of over-etching the metal substrate 100.

[0236] For illustrative purposes, the resolution limit of an illuminator for selectively illuminating photoresist layers 102A and 102B may be 20 μm to 25 μm, and 314 μm. 2 ~525μm 2 This gives the area per opening 126 (which is circular in this non-limiting example). A 25% opening area corresponds to a ratio of 3:1 between the area covered by the continuous region 128 and the uncovered area corresponding to the opening. Thus, 314 μm 2~525μm 2 Regarding the area per opening 126, the minimum total area of ​​etching-resistant materials 104A and 104B per opening 126 is 1256 μm². 2 ~2100μm 2 This is the result.

[0237] The area of ​​the continuous region 128 used to determine the opening area may be demarcated by a conceptual boundary corresponding to the shortest line that can be drawn around the outermost opening 126 of the openings 126, and it should be noted that this line intersects with the perimeter of each of the outermost openings 126.

[0238] The aperture 126 can be provided, for example, by selectively irradiating the photoresist layers 102A and 102B using a photomask, so that the photoresist layers 102A and 102B are not irradiated at the points where the aperture 126 should be provided. Therefore, during development, the photoresist layers 102A and 102B are removed at these points, thereby providing the aperture 126.

[0239] Once the opening 126 is defined through the etching-resistant materials 104A and 104B, the delivery of the etching solution 114A and 114B through the opening 126 forms a fused etching region 130, with a portion 132 of the metal substrate 100 still remaining beneath the fused etching region 130 after etching.

[0240] With regard to the delivery of etching solutions 114A and 114B, if it is desirable to keep distribution parameters such as delivery pressure constant, the speed at which the metal substrate 100 moves through the etching zone can be increased if the metal substrate 100 is etched more than desired, for example, if the metal substrate 100 below the opening 126 is unintentionally completely etched. On the other hand, if a greater degree of etching is required to provide a fused etching region 130, the speed at which the metal substrate 100 moves through the etching zone can be decreased.

[0241] If it is desirable to keep the speed at which the metal substrate 100 moves through the etching zone constant, the distribution parameters can be adjusted to provide a fused etching region 130 while a portion 132 of the metal substrate 100 remains below the fused etching region 130. For example, if the metal substrate 100 is etched more than desired, e.g., if the metal substrate 100 is unintentionally completely etched through the opening 126, the delivery pressure of the etching solution can be reduced. On the other hand, if a greater degree of etching is required to provide a fused etching region 130, the delivery pressure can be increased.

[0242] If it is desirable to maintain existing distribution parameters, such as keeping the delivery pressure constant and maintaining the existing speed of the metal substrate 100 passing through the etching zone, the openings 126, for example, their diameter or maximum dimension (e.g., within the range of 5 μm to 500 μm), spacing (e.g., within the range of 5 μm to 500 μm), and / or number can be adjusted to provide a fused etching region 130 while a portion 132 of the metal substrate 100 remains below the fused etching region 130. For example, if the metal substrate 100 is etched more than desired, for example, if the metal substrate 100 is unintentionally etched completely through, the diameter / maximum dimension of the openings 126 can be reduced. On the other hand, if a greater degree of etching is required to provide a fused etching region 130, the diameter / maximum dimension of the openings 126 can be increased.

[0243] This may represent an advantage of the etching method according to the present disclosure, because by adjusting the size, spacing, and / or number of the openings 126, it is possible to provide a method for achieving an etched metal substrate 100 having a three-dimensional shape associated with a portion 132 without having to adjust existing process settings.

[0244] Referring to Figures 14 to 16, the metal substrate 100, for example, a metal sheet, may have a first thickness TH1 before etching. The first thickness TH1 may be, for example, 0.04 mm to 2.5 mm.

[0245] Etching may be continued until the thickness of the metal substrate 100 is reduced such that the metal substrate 100 has one or more second thicknesses TH2;TH2A, TH2B below one or more fused etching regions 130, where one or more second thicknesses TH2;TH2A, TH2B are non-zero but smaller than the first thickness TH1, for example, 0.04 mm to 2.5 mm.

[0246] In some embodiments, etching continues until a portion 132 below one or more fused etching regions 130 includes a planar region of the etched metal substrate 100, which is located below at least a portion of the opening 126 and below where continuous regions 128 of etching-resistant materials 104A, 104B extend between at least a portion of the opening 126.

[0247] Figures 14 and 15 schematically illustrate how the size of the opening 126 may affect how much of the portion 132 remains after etching. In Figure 15, the larger opening 126 causes more removal of the metal substrate 100 to provide a thinner portion 132 compared to the portion 132 provided by the smaller opening 126 shown in Figure 14. This may be due to the fact that more etching solution 114A, 114B is able to reach the area of ​​the metal substrate 100 under the larger opening 126 shown in Figure 15 compared to the amount of etching solution that is able to reach the area of ​​the metal substrate 100 under the smaller opening 126 shown in Figure 14.

[0248] In some embodiments, as shown in Figure 16, an opening 126 penetrating the same continuous region 128 includes a larger opening 126A and a smaller opening 126B, where the larger opening 126A allows more etching solution 114A, 114B to pass through and reach the metal substrate 100 than the smaller opening 126B during etching.

[0249] In such embodiments, the larger opening 126A and the smaller opening 126B may be positioned relative to each other such that, for example, etching provides an inclined profile, e.g., an inclined planar region, that slopes from the lower region of the etched metal substrate 100 where more of the metal substrate 100 is removed under the larger opening 126A to the upper region of the etched metal substrate 100 where less of the metal substrate 100 is removed under the smaller opening 126B.

[0250] Such a sloping profile can be achieved, for example, by progressively changing the size of the opening 126, such that an intermediate-sized opening 126C, which is between the size of the larger opening 126A and the smaller opening 126B, is positioned between the larger opening 126A and the smaller opening 126B.

[0251] It is implied that the etched metal substrate 100 has multiple second thicknesses TH2A and TH2B relative to the inclined profile, and it should be noted that only two of these are indicated by double-headed arrows in Figure 16.

[0252] Referring to Figure 17, providing an inclined profile through the larger opening 126A and the smaller opening 126B may involve forming an inclined surface on the hair guide surface 18 of the hair guide element 10. Furthermore, the size of the openings 126, particularly when forming an inclined surface, the larger opening 126A can help control etching so that a desired tooth thickness T1 is achieved in the tip region 30.

[0253] It should be noted that the etching method according to this disclosure can enable inclined profiles, for example, chamfered shapes in which the length of the inclined profile is longer than half the thickness TH1 of the metal substrate 100. Therefore, an inclined surface whose lateral spread L1 is greater than its height H1, for example, at least twice as large, can be achieved using the etching method, for example. It should be reiterated that the lateral spread L1 may be, for example, at least 200 μm, while the height H1 may be 100 μm or less.

[0254] In some embodiments, referring again to Figures 14 to 16, one or more unmasked areas 112A, 112B are provided adjacent to the areas where etching-resistant materials 104A, 104B are masking the metal substrate 100, and etching continues until the metal substrate 100 is completely removed by etching under one or more unmasked areas 112A, 112B, but a portion 132 of the metal substrate 100 remains under one or more fused etching areas 130.

[0255] Therefore, using a single etching process, the metal substrate 100 beneath the non-masked regions 112A and 112B can be etched completely through its thickness, while the fused etching region 130 can only be partially etched.

[0256] This single etching step could mean, for example, that etching-resistant materials 104A and 104B can be placed on the (yet) unetched surface of a metal substrate 100, such as a metal sheet. For example, etching-resistant materials 104A and 104B can be placed on the surface of a metal substrate 100, such as a metal sheet, that has been surface-treated, for example, cleaned, but has not been etched by a previous etching process.

[0257] Alternatively or additionally, the etching method may further include, after etching, removing the etching-resistant materials 104A, 104B, leaving an etched metal substrate 100 containing one or more fused etching regions 130, with a portion 132 of the metal substrate 100 still remaining beneath one or more fused etching regions 130.

[0258] Furthermore, referring to Figures 14 to 16, the continuous region 128 of the etching-resistant materials 104A and 104B may be connected to the peripheral region 134 of the etching-resistant materials 104A and 104B, and the continuous region 128 remains connected to the peripheral region 134 after etching to form one or more fused etching regions 130. The peripheral region 134 may, for example, lack openings.

[0259] The peripheral region 134 helps to hold the continuous region 128 in place during etching, thereby reducing the risk of the continuous region 128 being removed during etching and consequently causing unintended over-etching of the metal substrate 100.

[0260] When the metal substrate 100 is viewed in a planar view facing the continuous region 128 of the etching-resistant materials 104A and 104B, the continuous region 128 may be in the form of a tongue-shaped projection that protrudes from the peripheral region 134.

[0261] Since the etching solutions 114A and 114B are delivered through the opening 126, the delivery direction in which the etching solutions 114A and 114B are delivered, for example, by spraying, may be toward the side of the metal substrate 100 where the continuous regions 128 of the etching-resistant materials 104A and 104B are located.

[0262] The etching solution 114B may be delivered to only one side of the metal substrate 100, as shown in Figure 18, or the etching solutions 114A and 114B may be delivered to both sides of the metal substrate 100, as shown in Figure 19.

[0263] The ability to spray-etch a metal substrate 100, for example, a metal sheet, equally from both sides, can, for example, yield a desired cut edge shape, but can still form a three-dimensional shape associated with the portion 132 of the metal substrate 100 that remains after etching.

[0264] When the etching solution 114B is delivered toward only one side of the metal substrate 100, the continuous region 128 (which demarcates the opening 126) may be located on the side of the metal substrate 100 toward which the etching solution 114B is being delivered.

[0265] In such embodiments, the etching-resistant materials 104A, 104B may nevertheless include the (first) etching-resistant material 104A, which is positioned on the side of the metal substrate 100 opposite to the single side to which the etching solution 114B is directed.

[0266] The advantage of delivering the etching solutions 114A and 114B to one side of the metal substrate 100 in this manner, for example by spraying, is that it may be possible to obtain different radii of curvature (and cutting angles, if blades are manufactured) compared to when the etching solutions 114A and 114B are delivered to both sides of the metal substrate 100.

[0267] More generally, in embodiments where the etching-resistant materials 104A and 104B include a first etching-resistant material 104A positioned to mask a first side of the metal substrate 100 and a second etching-resistant material 104B positioned to mask a second side of the metal substrate 100, with the second side facing away from the first side, the first etching-resistant material 104A may include a continuous region 128 surrounding and extending between the openings 126, and the second etching-resistant material 104B may include further continuous regions where further openings are defined.

[0268] Further continuous regions may, for example, surround and extend between further openings.

[0269] In an embodiment where a continuous region 128 and a further continuous region as shown in FIG. 19 are employed, a part of the metal substrate 100 where one or more fused etching regions 130 are formed is sandwiched between the continuous region 128 and the further continuous region after etching.

[0270] In some embodiments as shown in FIG. 19, one or more non-mask regions 112A are provided adjacent to a location where the first etching-resistant material 104A is disposed to mask the first side of the metal substrate 100, and / or one or more (further) non-mask regions 112B are provided adjacent to a location where the second etching-resistant material 104B is disposed to mask the second side of the metal substrate 100.

[0271] For example, at least one of the one or more (further) non-mask regions 112B is aligned with one of the one or more non-mask regions 112A.

[0272] This can assist in etching the metal substrate 100 completely through the thickness between the aligned non-mask regions 112A and the (further) non-mask regions 112B.

[0273] Referring now to FIG. 20, the continuous region 128 defining the opening 126 can enable the formation of the hair guide element 10 having the hair guide surface 18 and the tip region 30 as described above, while the further continuous region defining a further opening can enable the formation of the recessed portion 136 of the skin contact surface 12 of the hair guide element 10.

[0274] At least a part of the opening 126 can be arranged in an aligned pattern as in the embodiments shown in FIGS. 14 to 16, FIG. 21, FIG. 22, and FIG. 24. Alternatively or additionally, at least a part of the opening 126 may be distributed in an irregular pattern as in the embodiment shown in FIG. 23.

[0275] In some embodiments, the aligned pattern includes an array of openings 126. The aligned pattern may include, for example, at least one of a rectangular array of openings 126 (see Figure 21) and a hexagonal array of openings (see Figure 22).

[0276] In the hexagonal array, as shown in Figure 22, each opening 126 is spaced a single distance SP1 from its six nearest adjacent openings. Thus, the hexagonal array can help provide relatively uniform etching in the fused etching region 130 beneath the hexagonal array of openings 126.

[0277] In contrast, referring to Figure 21, in the rectangular array, there may be a first nearest neighbor distance SP2 between a given opening 126 and four of the eight openings 126 surrounding the given opening 126 in the rectangular array, and a second distance SP3 greater than the first nearest neighbor distance SP2 between the given opening 126 and the other four of the eight openings 126 surrounding the given opening 126 in the rectangular array.

[0278] Figure 24 shows an aligned array of openings 126 whose size gradually changes, so note that intermediate-sized openings 126C1, 126C2, and 126C3 are positioned between the larger opening 126A and the smaller opening 126B.

[0279] For example, intermediate-sized openings 126C1, 126C2, and 126C3 may include the largest intermediate-sized opening 126C1, the smallest intermediate-sized opening 126C3, and an intermediate-sized opening 126C2 whose size is between the size of the largest intermediate-sized opening 126C1 and the size of the smallest intermediate-sized opening 126C3.

[0280] More generally, the Disclosure provides a method for manufacturing foils 50, combs, or blades 10, 16 for electric shavers, the method comprising performing an etching method according to any embodiment described herein to provide an etched article having one or more fused etching regions 130, such that a portion 132 of a metal substrate 100 remains beneath one or more fused etching regions 130. The etched article may define the foils 50, combs, or blades 10, 16, or the foils 50, combs, or blades 10, 16 may be formed by subjecting the etched article to one or more post-processing steps performed following etching.

[0281] It should be noted that the term "blade" can, in principle, encompass the foil 50 and the hair guide element 10, such as a comb, because the foil 50 and the hair guide element 10 can interact with the undercutter or cutting element 16 so that the hair HA is cut between the foil 50 / hair guide element 10 and the undercutter / cutting element 16. The term "blade" can also encompass the undercutter and the cutting element 16.

[0282] One or more post-processing steps may include, for example, polishing the etched article and / or subjecting the etched article to precision (or pulsed) electrolytic machining (PECM).

[0283] However, an advantage of the etching method described herein is that it may not require additional process steps, such as additional process steps including PECM, to produce a three-dimensional shape in which the metallic material of the metal substrate 100 is removed only partially.

[0284] With respect to the perforated foil 50, the etching method described herein, in particular the portion 132 remaining after etching, can provide the three-dimensional geometric shape of the perforated foil 50 in addition to the openings 52 of the perforated foil 50. The perforated foil 50 may be made of, for example, stainless steel and etched using the etching method described herein.

[0285] The etching method described herein can generate a three-dimensional shape of the etched metal substrate 100 by the portion 132 remaining beneath the fused etched region 130 after etching, for example, thus requiring only one masking, illumination, and etching sequence with photoresist layers 102A and 102B, rather than multiple such sequences.

[0286] The three-dimensional shape can function in components of an electric shaver, such as a hair guide element 10, for example, a comb, a cutting element 16, and / or a perforated foil 50, as a way to generate defined geometric shapes for improvements such as friction reduction, hair feeding, lifting, and gliding.

[0287] The dimensions and values ​​disclosed herein should not be understood as being strictly limited to the exact numerical values ​​listed. Instead, unless otherwise specified, each such dimension is intended to mean both the listed value and the functionally equivalent range encompassing that value. For example, a dimension disclosed as "40 mm" is intended to mean "approximately 40 mm."

[0288] All documents referenced herein, including any patents or patent applications that are cross-referenced or related, and any patent applications or patents on which this application claims priority or benefit thereof, are incorporated herein by reference in their entirety, unless expressly excluded or otherwise limited. No reference to any document shall be deemed prior art to any invention disclosed or claimed herein, nor shall any such invention be taught, suggested, or disclosed, either alone or in combination with any one or more other references. Furthermore, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to that term in this document shall prevail.

[0289] While specific embodiments of this disclosure have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications within the scope of the invention be covered in the appended claims. Any reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A hair guide element (10) for an electric shaver, A skin contact surface (12) for contacting the skin (SK), A cutting element opposing surface (14) that faces the cutting element (16), and which faces in the opposite direction to the direction that the skin contact surface faces, A toothed profile including teeth (20) arranged along the principal axis (MA) of the hair guide element, wherein each tooth includes a portion of the skin contact surface and a portion of the cutting element facing surface, and Equipped with, The teeth (20) include a first set of teeth extending in a first direction perpendicular to the principal axis (MA) of the hair guide element, and a second set of teeth extending in a second direction opposite to the first direction. A hair guide element (10) having slots (26, 26', 28, 28') that separate adjacent teeth (20) along the main axis (MA) of the hair guide element, wherein the slots comprise pairs of slots (26, 28; 26', 28'), each of which comprises a longer slot (26; 26') and a shorter slot (28; 28'), and the longer and shorter slots of each pair extend along a common slot axis (A2; A2') perpendicular to the main axis, with one of the longer and shorter slots defining between adjacent teeth of a first set of teeth, and the other of the longer and shorter slots defining between adjacent teeth of a second set of teeth.

2. The hair guide element (10) according to claim 1, wherein the connecting element connects the hair guide element (10) to a side member (24) for supporting the hair guide element.

3. (i) Each of the connecting elements (22) includes a portion of the skin contact surface (12), and / or (ii) The hair guide element (10) according to claim 2, wherein each of the connecting elements (22) includes a portion of the cutting element facing surface (14).

4. The hair guide element according to claim 2 or 3, wherein the connecting element (22) is included in the toothed profile such that a hair can be received in a space defined between one of the connecting elements (22) and one of the teeth (20).

5. A hair guide element according to any one of claims 2 to 4, wherein two to five teeth are arranged between consecutive connecting elements in each of the first and second sets of teeth.

6. The hair guide element according to any one of claims 2 to 5, wherein the connecting element (22) is shorter than at least a portion of the tooth (20), so that at least a portion of the tooth (20) extends further than the connecting element (22) in a lateral direction with respect to the main shaft (MA).

7. The bristle guide element according to any one of claims 1 to 6, wherein at least a portion of the teeth of the first set are substantially the same length, and / or at least a portion of the teeth of the second set are substantially the same length.

8. At least a portion of the teeth each includes a portion of the hair guide surface and a tip region (30) positioned to receive hair as the hair guide element moves over the skin, wherein the portion of the hair guide surface extends in a direction perpendicular to the principal axis, away from the tip region toward the portion of the cutting element-facing surface, thereby enabling the portion of the hair guide surface to guide the hair received in the tip region toward the portion of the cutting element-facing surface.

9. The hair guide element (10) according to claim 8, wherein at least a portion of the hair guide surface (18) of the tooth (20) includes an inclined surface, the inclined surface descends from the tip region (30) toward a portion of the cutting element opposing surface (14) as the inclined surface extends laterally with respect to the main axis (MA), and the inclined surface moves further away from the skin contact surface (12) as the inclined surface descends toward a portion of the cutting element opposing surface.

10. A hair guide element (10) according to any one of claims 1 to 9, comprising a spine portion (39), wherein a first set of teeth extends from the spine portion in a first direction laterally with respect to the main axis (MA), and a second set of teeth extends from the spine portion in a second direction laterally with respect to the main axis.

11. The hair guide element (10) according to claim 10, wherein the spine portion has a meandering shape such that the shorter slots and the longer slots (28, 26') alternate along the second set of teeth, while the longer slots and the shorter slots (26, 28') alternate along the first set of teeth.

12. The hair guide element (10) according to claim 8 or 9, wherein the teeth (20) are supported by the spine portion (39).

13. A hair guide element (10) according to any one of claims 1 to 12, A cutting element (16) is arranged to face the cutting element opposing surface (14) and A hair cutting assembly (10, 16) comprising:

14. The hair cutting assembly (10, 16) according to claim 13, A motor drive system for moving the cutting element (16) An electric shaver equipped with [features].

15. A method for manufacturing a hair guide element (10) according to any one of claims 1 to 12, comprising etching a metal substrate (100) to form at least a portion of the hair guide element.

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