EP2099591B1 - Shearing foil for an electric razor - Google Patents

Abstract

A shaving foil for an electric shaving apparatus. The shaving foil includes a perforated region with a plurality of holes which are separated from each other by bars. The perforated region is divided at least into two zones, preferably a central zone, a first edge zone, and a second edge zone. The central zone is arranged between the first edge zone and the second edge zone. The holes in the central zone have (i) an average size which is smaller than the average size of the holes in the first edge zone and in the second edge zone, (ii) a floating mean value of the size of the openings in the central zone smaller than a floating mean value of the size of the openings in the first edge zone and the second edge zone, or both (i) and (ii).

Description

The invention relates to a shaving foil for an electric shaver.

Electric shavers usually have at least one perforated shaving foil and at least one lower blade which is designed to be movable relative to the shaving foil. The shaving foil has a multiplicity of holes into which hair is inserted during the shaving process. The undercutter is disposed in the immediate vicinity of the shaving foil and is continuously moved past the holes of the shaving foil during the shaving process. This has the consequence that the threaded into the holes of the foil sheared hair are cut by the lower blade. The formation of the foil, in particular the size and shape of the holes, has a not inconsiderable influence on the razor result achievable with the razor.

In this context, it is from the DE 24 55 723 C2 It is known to make the mean diameter of the holes in a peripheral region of the shaving foil, which serves at least partially for holding the shaving foil on a shaving head frame, smaller than in a central region of the shaving foil. In this case, the ratio of the measured over the thickness of the shear foil cross-sectional area of the hollow webs, which separate the holes from each other and the holes over the entire shear foil to achieve a nearly constant bending stiffness coordinated. In this way, the shear foil should be designed so that it has a nearly constant bending stiffness while maintaining stable edge regions and a thin central region over all hole areas.

From the DE 23 21 028 A is an adjustable in the shaving head of a dry shaver arranged screen with sieve holes of different dimensions known. The screen film has a single undivided perforated field in which the dimensions of the screen holes in the adjustment direction of the screen film continuously change. This is to be an optimal adaptation of the screen to the different nature of the facial skin of the user or different users are possible.

From the CH 424 528 A is known a foil whose perforation is composed of spiky recesses in the central region and rectangular slots in the outer edge regions. Such a compiled hole geometry inevitably leads to extreme differences and variations in the width of the individual holes limiting Stege. This is extremely disadvantageous in terms of a homogeneous mechanical property of the film as well as in terms of their area utilization.

The invention has for its object to form a shaving foil of an electric shaver so that the best possible shaving result can be achieved.

This object is achieved by the combination of features of claim 1.

The shaving foil for an electric shaver according to the invention has a perforated area with a plurality of holes separated by webs. The perforated region is subdivided into at least one central zone, a first edge zone and a second edge zone, the central zone being arranged between the first edge zone and the second edge zone. The shear foil according to the invention is characterized in that the holes in the central zone have an average size which is smaller than the average size of the holes in the first edge zone and in the second edge zone and / or in that a sliding average for the size of the holes in the central zone is smaller than in the first edge zone and in the second edge zone, wherein the webs have a width which is the same throughout the perforated area.

The shaving foil according to the invention has the advantage that it allows a very thorough and at the same time skin-friendly shave. This is achieved by the invention variation of the hole size in the individual zones of the perforated portion of the shaving foil, created by the shaving in the entire contact area between the shaving foil and the skin of the user of the shaver favorable conditions regarding the concavity of the skin in the holes of the shaving foil and changes in the mechanical property of the foil are kept small. As a result, for example, an exact compliance with a desired shape in the curvature of the foil is facilitated.

The said zones of the shaving foil need not be in the form of clearly defined or sharply demarcated areas; according to the present invention, a corresponding variation of the mean hole size of the perforation along at least one direction is sufficient. The variation itself forms the corresponding zones. The variation of the hole sizes is preferably continuous, since this - as explained later - favorable mechanical properties result, for example, optimal adaptation of the foil to the / the associated (n) lower blade.

The central zone is preferably arranged in a first direction between the first edge zone and the second edge zone.

It is particularly advantageous if the subdivision of the perforated region is designed such that during a shaving of a skin area in the central zone of the perforated area a higher contact pressure of the shaving foil against the skin area is to be expected than in the first edge zone and in the second edge zone. This means that in the areas in which a high contact pressure is expected, small holes are formed and in the areas where a low contact pressure is expected, large holes are formed. Since the skin bulges the more strongly in the holes, the higher the contact pressure and the larger the holes, a high contact pressure can be compensated by small hole sizes and thus counteract a different degree of indentation of the skin in the holes of the foil. Accordingly, an optimum value for the concavity of the skin into the holes can be realized in the entire contact area between the shaving foil and the skin, thereby achieving a thorough and skin-friendly shave.

In a preferred embodiment of the shaving foil, a curvature is formed within the perforated area, which assumes its zenith in the central zone. Depending on whether the razor is equipped with one or more shear films of this type, the highest contact pressure occurs in the shave at the zenith or near the zenith of the curvature, so that small holes in the vicinity of the zenith are advantageous. In particular, when the shaver is equipped with a plurality of shear foils, it may be advantageous if the central zone is asymmetrical to the zenith of the curvature and / or the moving average for the size of the holes has a minimum outside the zenith.

The shaving foil is preferably firmly clamped in a foil frame which can be fixed on the razor. This allows easy handling of the foil and ensures a defined geometry of the individual zones of the foil after the fixation of the foil frame on the shaver. At least one further foil may be clamped in the foil frame.

In a preferred embodiment of the shaving foil, at least some of the holes have different shapes. This has a positive effect on the threading behavior of the foil and opens up a variety of possibilities in the arrangement of the holes and the Realization of a desired size distribution of the holes. In particular, compliance with a constant web width is possible even with a variation of the hole size. Preferably, at least some of the holes are formed as irregular polygons. Furthermore, it is advantageous if the size of at least some of the holes varies according to a statistical distribution. As a result, good surface utilization in the perforated region of the shaving foil can be achieved.

The moving average for the size of the holes may vary along the first direction within the perforated area according to a predetermined function. The predetermined function can in particular have a continuous course. As a result, a good adaptation to the continuous course of the contact pressure of the shaving foil against the skin area can be achieved. The moving average for the size of the holes may be constant along a second direction within the perforated area. The shear foil is preferably formed so that the first direction and the second direction are perpendicular to each other. Furthermore, the shearing foil is preferably designed such that the second direction extends parallel to a provided direction of movement of a shearing blade cooperating with the shaving foil. The first direction preferably extends perpendicular to an intended direction of movement of a shear blade cooperating with the shaving foil. This means that the size of the holes preferably varies perpendicular to the direction of movement of the doctor blade.

At least some of the holes may be statistically distributed over at least a portion of the perforated area and / or formed as polygons having shapes varying according to a statistical distribution. Furthermore, the shearing foil can be designed so that the holes in the central zone, in the first edge zone and / or in the second edge zone each have at least a predetermined minimum distance from each other with respect to their centers. This can avoid that the foil has holes that provide no significant contribution to the shaving result due to lack of size.

The holes of the shear foil are preferably formed as polygons whose internal angles are each smaller than 180 °. At least some of the holes may be formed as Voronoi polygons. The formation of the holes as Voronoi polygons allows a simple construction of the shear foil with good cutting properties.

The mean values for the size of the holes can each be formed as arithmetic mean values. The moving averages for the size of the holes at varying locations of the perforated Areas may each be formed as an averaging over the holes in a given subarea or as an averaging over a predetermined number of holes with a given neighborhood relationship.

Within the perforated area, at least one central zone, a first edge zone and a second edge zone are formed, thereby locating the central zone between the first edge zone and the second edge zone, the holes being formed in the central zone with an average size that is smaller as the average size of the holes in the first edge zone and in the second edge zone and / or that the holes are formed so that a moving average for the size of the holes in the central zone is smaller than in the first edge zone and in the second edge zone , Furthermore, a distribution of surfaces is determined, which adjoin each other gaplessly and the holes in the central zone, the first edge zone and / or the second edge zone of the shaving foil are formed in accordance with the determined distribution.

As a result, optimum utilization of the perforated region of the shaving foil can be achieved. When determining the distribution of the areas for a zone, the distribution of the areas in an adjacent zone can be taken into account at least in certain areas. This allows, for example, a seamless transition between the zones. The surfaces can be formed as polygons, in particular as Voronoi polygons.

To construct the surfaces, a distribution of generator points can be generated. In particular, the generator points can be generated at statistically determined positions. When generating the generator points, at least one boundary condition can be met. In particular, when generating the generator points of a zone, at least one boundary condition with respect to the generator points of an adjacent zone can be maintained. This allows adaptation of the areas of adjacent zones to each other. For example, when generating a new generator point, in each case a minimum distance to all previously generated generator points can be maintained. The sides of the surfaces can be determined as sections of mid-perpendicular between generator points.

It is particularly advantageous if the regularity of the distribution of the areas is increased iteratively. As a result, distributions with different degrees of regularity can be constructed based on the same methodology. In particular, it is possible to proceed in such a way that with each iteration the center of gravity of the surfaces is determined and used as new generator points. In each case, the center of gravity determination can be based on an inhomogeneous mass density. In this way, a desired distribution of the size of the surfaces can be generated by specifying the course of the mass density.

In the area of the sides of the surfaces, the webs can be formed with a predetermined width.

ermittelt werden, wobei r der Radius eines Kreises ist, dessen Flächeninhalt dem Flächeninhalt des Lochs beim Winkel γ entspricht, r_min der Radius eines Kreises ist, dessen Flächeninhalt dem Flächeninhalt eines Lochs beim Winkel γ_max entspricht, γ ein Azimutwinkel relativ zu einem Zenit einer Krümmung der Scherfolie ist und a₂ sowie γ_max Fitparameter darstellen.Preferably, the size of the holes, the webs of which act on the skin during shaving of a skin area during shaving of a skin area depending on the position of the holes in the perforated portion of the shaving foil are each chosen so that the skin equally deep into the holes einwölbt. As a result, the same thoroughness is achieved in the area of all the holes involved in the shave. In particular, the size of the holes (16) according to the formula $$r=\frac{r_{\min }}{\sqrt{1-\frac{{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\left(\gamma -{\gamma }_{\mathrm{Max}}\right)}{a_2^2}}}$$

where r is the radius of a circle whose area corresponds to the area of the hole at the angle γ, r _{min is} the radius of a circle whose area corresponds to the area of a hole at the angle γ _max , γ an azimuth angle relative to a zenith of one Curvature of the shear foil is and represent a ₂ and γ _max fit parameters.

The invention is explained below with reference to the embodiments illustrated in the drawings.

Fig. 1

ein Ausführungsbeispiel eines elektrischen Rasierapparats in einer perspektivischen Darstellung,

Fig. 2

eine der in Fig. 1 dargestellten Scherfolien in Schnittdarstellung,

Fig. 3 bis 6

verschiedene Ausführungsbeispiele der Scherfolie in einer ausschnittsweise dargestellten Abwicklung,

Fig. 7 bis 10

je eine Momentaufnahme während der Erzeugung eines Voronoi-Diagramms,

Fig. 11 bis 13

weitere Ausführungsbeispiele der Scherfolie in einer ausschnittsweise dargestellten Abwicklung,

Fig. 14

ein Diagramm für den Verlauf der Größe der Löcher für das in Fig. 13 dargestellte Ausführungsbeispiel der Scherfolie,

Fig. 15

ein Diagramm für einen möglichen Verlauf der Tiefe der Hauteinwölbung in Abhängigkeit vom Azimutwinkel und

Fig. 16

ein weiteres Ausführungsbeispiel der Scherfolie in einer ausschnittsweise dargestellten Abwicklung.

Show it:

Fig. 1

an embodiment of an electric shaver in a perspective view,

Fig. 2

one of the in Fig. 1 Scherfolien shown in section,

Fig. 3 to 6

Various embodiments of the foil in a fragmentary processing shown,

Fig. 7 to 10

one snapshot each while generating a Voronoi diagram,

Fig. 11 to 13

Further embodiments of the shaving foil in a fragmentary illustrated settlement,

Fig. 14

a diagram for the course of the size of the holes for the in Fig. 13 illustrated embodiment of the shaving foil,

Fig. 15

a diagram for a possible course of the depth of Hauteinwölbung depending on the azimuth angle and

Fig. 16

a further embodiment of the foil in a fragmentary processing shown.

Fig. 1 shows an embodiment of an electric shaver 1 in a perspective view. The razor 1 has a housing 2 durable in the hand and a shaving head 3 attached thereto. On the housing 2, a switch 4 for switching on and off of the shaver 1 is arranged. The shaving head 3 has two lower blades 5, each having a plurality of individual blades.

Furthermore, in Fig. 1 two shear sheets 6 shown, which are attached to a film frame 7. The film frame 7 forces the shear films 6 in a curved shape, which is matched to the contour of the lower blade 5. The film frame 7 is constructed so that it can be fixed together with the two shaving foils 6 on the shaving head 3 and easily removed again. In Fig. 1 the film frame 7 is removed from the shaving head 3 with the two shaving foils 6.

In the operating state of the razor 1, the lower blade 5 are offset by a not shown electric motor, which is disposed within the housing 2, in a linear oscillating movement relative to the shear foil 6. The lower blades 5 move parallel to its main extension in a direction of movement 8 which is represented by a double arrow. Furthermore, a double arrow for illustrating a cutting direction 9 of the shear films 6 is shown. At the in Fig. 1 shown curved configuration of the shear sheets 6 whose cutting direction 9 is parallel to the axis of curvature. When the shaving foils 6 are attached to the shaving head 3 of the razor 1, the cutting direction 9 of the shaving foils 6 coincides with the direction of movement 8 of the lower knives 5.

The movement of the lower blade 5 relative to the shear foil 6 causes hair that penetrate through one of the perforated shear sheets 6 to the associated lower blade 5, detected by the lower blade 5 and severed in cooperation with the shear foil 6.

The in Fig. 1 Shaver 1 shown can be modified or further developed in many ways. For example, the razor 1 may have only a lower blade 5 and a shear foil 6. Furthermore, the razor 1 may have additional shearing means such as a central cutter, a long-hair trimmer, etc. In addition, the shaving head 3 may comprise, for example, at least one rotating lower blade 5 and at least one circular shaving foil 6 having an annular area surrounding and being raised or recessed to a circular area.

Fig. 2 shows one of the in Fig. 1 Scherfolien shown in section 6. The cut is guided transversely through the shaving foil 6, so that the cutting direction 9 of the shaving foil 6 runs perpendicular to the plane of the drawing. The shaving foil 6 has a curvature 10 with a zenith 11. In the presentation of the Fig. 2 For example, in a razor 1 having a plurality of shear sheets 6, the zenith 11 of each shear sheet 6 is defined by the line of contact between a plane tangent to all the shear sheets 6 and the respective shear sheet 6.

With proper handling of the shaver 1, the shaving foil 6 rests against the skin during shaving in the area of the zenith 11. Due to the elasticity of the skin, the regions of the shaving foil 6 adjacent to the zenith 11 also have skin contact. For the following considerations, the shaving foil 6 is divided into several zones. A central zone 12 includes the zenith 11 and an adjacent area on both sides. An edge zone 13 adjoins the central zone 12 on one side and an edge zone 14 on the other side. The central zone 12, the two edge zones 13 and 14 and possibly further zones Together form a perforated portion 15 of the shaving foil 6. The formation of the shaving foil 6 within the perforated region 15 will be explained in more detail below.

Fig. 3 shows an embodiment of the shaving foil 6 in a detail shown settlement. The shearing foil 6 has a plurality of holes 16 which are separated from one another by webs 17. The holes 16 in the illustrated embodiment each have the shape of a hexagon. In the region of the central zone 12 holes 16 are present with a smaller area than in the region of the edge zone 14. The conditions in the edge zone 13, not shown, correspond to those in the illustrated edge zone 14. The difference in size at the holes 16 results from the fact that the Hexagons each have different extensions parallel to a transverse direction 18 of the shaving foil 6, which is illustrated by a double arrow and perpendicular to the cutting direction 9. The webs 17 each have the same width in the central zone 12 and in the edge zone 14.

The curved trained shear foil 6 can be considered simplified as a rigid cylinder, which is pressed against the skin during shaving in the region of the zenith 11 of the curvature 10. In this case, the skin is an elastic medium. This has the consequence that the skin gives way elastically and conforms to the curvature 10 of the shaving foil 6. In addition, the skin bulges in the holes 16 of the shaving foil 6. The thickness of the indentation of the skin into the holes 16 of the foil 6 depends on the local pressure with which the foil 6 is pressed against the skin and on the geometry of the holes 16. This means, for example, that the skin remains at a constant size Holes 16 bulge more in the holes 16, the stronger the local pressure.

A strong indentation of the skin in the holes 16 of the shaving foil 6 results in a particularly thorough shaving, since the hairs are severed close to the skin. However, the risk of skin irritation also increases, especially when skin contact with the lower blade 5 occurs. According to the invention, it is therefore provided to arrange holes 16 of small dimensions at the locations of the shaving foil 6 at which a large local pressure occurs during shaving. At the locations of the shaving foil 6, where a small local pressure occurs during shaving, holes 16 of large dimensions are placed. The holes 16 are usually chosen so large that the skin does not touch the lower blade 5.

According to the theory of hertzian pressure, the pressure in the middle of the contact surface of the cylinder, i. H. in the region of the zenith 11 of the curvature 10 of the foil 6, the largest and decreases from the outside. Accordingly, the holes 16 in the central zone 12, at the center of which the zenith 11 of the curve 10 is located, are made smaller than in the peripheral zones 13 and 14. That is, the increased local pressure in the central zone 12 is reduced in size the holes 16 is compensated. In the peripheral zones 13 and 14, in which the local pressure is smaller than in the central zone 12, larger holes 16 are provided for compensation than in the central zone 12. Overall, with such a distribution of the sizes of the holes 16, there are less differences in the concavity of the skin into the holes 16 of the sheeting 6 than would be the case for a uniform size of the holes 16 in the central zone 12 and in the peripheral zones 13 and 14 , This, in turn, results in similar results in terms of thoroughness of shaving and skin care in all zones. Compared to a constant size of the holes 16 can thus achieve a better skin care or the same skin care better thoroughness of the shave with the same thoroughness of shaving. The larger holes 16 in the peripheral areas also result in the threading of hair into the shaving foil 6 being easier and thus improving the efficiency of shaving.

The foregoing is based on the fact that the razor 1 is handled during shaving so that, in a razor 1 having a single shaving foil 6, the zenith 11 of the curve 10 is laterally approximately centered in the contact area formed between the shaving foil 6 and the skin surface , Compliance with this geometry can be facilitated by the user of the razor 1, characterized in that a further shear system and a pivot mechanism is provided which brings the shaving foil 6 respectively in said orientation. The pivoting mechanism can be realized, for example, by a pivotable mounting of the shaving foil 6 or of the entire shaving head 3 on the housing 2 of the shaver 1.

As will be explained in more detail below, applies to a razor 1 with a plurality of shaving foils 6 similar, which due to the action of several shear films 6 on the skin, the zenith 11 of the curvature 10 is no longer exactly in the middle of the respective contact surface. In a razor 1 with multiple sheeting 6 handling during shaving is done so that each shear foil 6 have skin contact. By this constraint, the proper handling of the razor 1 is relatively easy for the user. For further simplification, in turn, the previously described pivoting mechanisms can be provided.

Fig. 4 shows a further embodiment of the shaving foil 6 in a perspective view of a development shown in fragmentary form. Also in this embodiment, smaller holes 16 are formed in the central zone 12 of the shaving foil 6 than in the marginal zones 13 and 14, the width of the webs 17 in the central zone 12 and in the peripheral zones 13 and 14 being equal. Deviating from Fig. 3 However, not all holes 16 are formed as hexagons. Hexagons are provided only in the central zone 12. In addition, the central zone 12 also has other polygons. The margins 13 and 14 have other polygons. Through differently formed polygons, the thoroughness of the shave can be further increased.

Fig. 5 shows an embodiment of the shaving foil 6 according to the prior art in a detail shown settlement. In this embodiment, the holes 16 in the central zone 12 and in the edge zones 13 and 14 of the shaving foil 6 have a hexagonal shape, wherein the holes 16 are each formed smaller in the central zone 12 than in the edge zones 13 and 14. In the area Transitions between the peripheral zones 13 and 14 and the central zone 12 vary both in size and shape of the holes 16. The transition zones thus each represent a suture line between two ordered zones within which the holes 16 are each formed identically. In the ordered regions on both sides of the seam line, however, the holes 16 are formed differently. In the area of the seam lines, the shearing foil 6 has increased rigidity. This results in the curvature 10 to a deviation from a desired shape and accordingly to increased wear.

Fig. 6 shows an embodiment of a shaving foil 6 according to the invention in a development shown in fragmentary form. This embodiment is characterized in that the holes 16 in the central zone 12 and in the edge zones 13 and 14 are each arranged irregularly and have different shapes and different sizes. The sizes of the holes 16 vary so that the arithmetic mean of the areas of the holes 16 in the central zone 12 is smaller than in the two edge zones 13 and 14. By such a shaping can be achieved that between the edge zones 13 and 14 and the central zone 12 each no seam line is formed. This achieves a more even curvature 10 and accordingly an improvement in the wear behavior.

The averaging, for example, the calculation of the arithmetic mean, allows for varying hole sizes a systematic description of the hole size distribution and can be done over the entire area of the central zone 12 and the edge zones 13 and 14 respectively. For a detailed examination, a moving average for the hole size can also be used in each case. The moving average may be determined as the arithmetic mean of the hole sizes within a given sub-area. In this case, all holes 16 are considered, which are arranged completely or with a predetermined fraction within the sub-area. The partial surface may be formed, for example, as a square or a circle. Likewise, the partial surface may for example also be formed as an elongated rectangle which extends parallel to the cutting direction 9 over the entire perforated portion 15 of the shaving foil 6 and parallel to the transverse direction 18 has dimensions in the range of the size of a hole 16 or a few holes 16. As a result, a good averaging and at the same time a high resolution for the description of the size variation of the holes 16 parallel to the transverse direction 18 can be achieved. A similar effect can also be achieved by including in the averaging, in each case, all holes 16 which are cut by a line running parallel to the cutting direction 9. Instead of specifying a subarea, the averaging can in each case also be based on a fixed number of holes 16 which are in a predefined neighborhood ratio to the point for which the mean value is to be calculated. For example, in each case a predetermined number of holes 16 are used whose centers have the smallest distances to the point. Unless otherwise stated, these variants of averaging can also be used in the exemplary embodiments of the shaving foil 6 described below and also apply to other exemplary embodiments of the shaving foil 6, which are not explicitly described.

An array of holes 16 may be generated, for example, by a method derived from the Russian mathematician Georgi F. Voronoi. The relevant theory is in G. Voronoi: "Recherches sur les Paralléloèdres Primitives", Journal for Pure and Applied Mathematics, Volume 134, pages 198-287 (1908 ). In addition, other approaches are possible that provide a suitable irregular or aperiodic arrangement of holes 16.

In the following the Voronoi decomposition of the plane is described, with which the in Fig. 6 illustrated arrangement of holes 16 has been generated. Details of this procedure can be found in A. Okabe, B. Boots and K. Sugihara: "Spatial Tesselations - Concepts and Applications of Voronoi Diagroms ", published by John Wiley & Sons (1992), ISBN 0 471 93430 5 be read.

Fig. 7 to 10 each show a snapshot while creating a Voronoi diagram.

As in Fig. 7 For example, initially statistically distributed generator points 19 are generated in one level. Then, for each generator point 19, an environment is determined in which each surface element is closer to the respective generator point 19 than to any other generator point 19. This environment has the form of a polygon, which is also referred to as a Voronoi polygon. The Voronoi polygons cover the entire level without gaps, so that there is a tiling of the plane. When the generator points 19 are arranged periodically, the Voronoi polygons cover the plane with a periodic pattern. In the case of aperiodic arrangement of the generator points 19, the pattern of the Voronoi polygons is also aperiodic. An area-filling arrangement of Voronoi polygons is also referred to below as a Voronoi diagram.

One way of generating the Voronoi polygons is to construct connecting lines 20 between each generator point 19 to all adjacent generator points 19. This is in Fig. 8 shown.

Thereafter, for each connecting line 20, a perpendicular bisector 21 is determined which is orthogonal to the respective connecting line 20 and intersects the connecting line 20 in the middle between the connected generator points 19. This is in Fig. 9 , shown.

The mid-perpendiculars 21 in turn intersect each other. The intersections of the mid-perpendiculars 21 form the vertices of the Voronoi polygons. The Voronoi polygons constructed in this way are in Fig. 10 shown. The Voronoi polygons each have a convex shape, ie the inner angles of their corners are each smaller than 180 °.

To produce shear films 6 based on Voronoi polygons, the sides of the Voronoi polygons are each formed as webs 17 having a predetermined width. The remaining between the webs 17 surfaces of the Voronoi polygons are each executed as holes 16.

The formation of Voronoi diagrams depends on the arrangement of the generator points 19. Distributing the generator points 19 statistically in the plane gives Voronoi diagrams containing a large variation of Voronoi polygons with very small to very large surface areas. Such Voronoi diagrams are too irregular as a basis for the formation of shear films 6. In the context of the invention is therefore intended to use Voronoi diagrams, which have a greater regularity. Such Voronoi diagrams can be generated, for example, by means of a method called "simple sequential inhibition process" (see HX Zhu, SM Thorpe and AH Windle: "The geometric properties of irregular two-dimensional Voronoi tesselations", Philosophical Magazine A, Volume 81, Number 12, pages 2765 - 2783 (2001 )). According to this method, first a first generator point 19 is randomly arranged in the plane. Thereafter, the position of another generator point 19 is determined at random. If the further generator point 19 is too close to the first generator point 19, the further generator point 19 is discarded and its position is redetermined. This is repeated until the further generator point 19 has at least one fixed minimum distance d from the first generator point 19.

In this way, the other generator points 19 are determined, in each case it is checked whether the minimum distance d is complied with all existing generator points 19. Only if this is the case, the respectively newly determined generator point 19 is accepted. This means that it is checked in the determination of the n-th generator point 19, whether the minimum distance d to all n-1 previously determined generator points 19 is met. Geometrically, this approach corresponds to the generation of a random distribution of circular disks whose center is in each case a generator point 19 and which have the predetermined minimum distance d as the diameter 5, the circular disks not being allowed to overlap. In this case, the largest possible minimum distance d can be realized by generating a hexagonal arrangement of circular disks. This would correspond to a periodic array of Voronoi polygons, each formed as an identical regular hexagon, where the key _width d _{hexagon of} each hexagon, ie twice the distance of the sides from the center of the hexagon, respectively corresponds to the minimum distance d.

For a given total area A and a predetermined number n of generator points 19, the area F per Voronoi polygon is: $$F=\frac{A}{n}\mathrm{,}$$

The area F _{hexagon of} a hexagon with a key width d _hexagon is: $$F_{\mathit{hexagon}}=\frac{\sqrt{3}}{2}{\mathrm{<figure-callout\; id="2"\; label="d\; hexagon"\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">d\; </figure-callout>}}_{\mathit{hexagon}}^{\mathit{}}\mathrm{,}$$

Thus, the maximum possible minimum distance d in this case is: $$d=d_{\mathit{hexagon}}=\sqrt{\frac{A}{n}\cdot \frac{2}{\sqrt{3}}}\mathrm{,}$$

Consequently, values for the minimum distance d in the range 0 <d <d _{hexagon can be} specified. In this case, the greater the value for the minimum distance d, the more regular the Voronoi diagram is. As a measure of the regularity of a Voronoi diagram, a regularity parameter α can be defined as the ratio between the minimum distance d and the _hexagon key _{width hexagon of} the hexagon, which represents the maximum possible minimum distance d: $$\alpha =\frac{d}{d_{\mathit{hexagon}}}\mathrm{,}$$

If the Voronoi polygons are completely statically formed, the minimum distance d is equal to zero. Thus, the regularity parameter α also has the value 0 in this case. With perfectly regular formation of the Voronoi polygons, the minimum distance d corresponds to the key _width d _hexagon . Thus, the regularity parameter α then has the value 1.

Shear films 6, which are based on Voronoi diagrams with different regularity parameters α are in the FIGS. 11 and 12 shown.

FIGS. 11 and 12 show further embodiments of the shaving foil 6 in a detail shown settlement. In both embodiments, the holes 16 of the shear foil 6 are formed as Voronoi polygons, which within the central zone 12 a have smaller mean surface area than within the edge zones 13 and 14. In addition, the edge zones 13 and 14 each seamlessly into the central zone 12 via.

In the embodiment of Fig. 11 the regularity parameter α has a value of 0.7 in each segment. In the embodiment of Fig. 12 the regularity parameter α has a value of 0.8 in each segment. Accordingly, the shaving foil 6 in the embodiment of the Fig. 12 in the individual zones a more regular pattern than in the embodiment of Fig. 11 , This applies both in terms of surface area and in terms of the shape of the Voronoi polygons.

To generate a pattern for a shear foil 6 with several zones, first the generator points 19 within one of the zones, for example within the central zone 12, are determined. Thereafter, the generator points 19 of an adjacent zone, for example, the edge zone 13 are determined. In each case, it is checked whether the minimum distance d to the generator points 19 of the currently and the previously processed zone is complied with. For processing further zones, the procedure is analogous. In each case care is taken to ensure that for each newly determined generator point 19, the minimum distance to all previous generator points 19 of the present and all previously processed zones is met. For each zone, a separate regularity parameter α can be specified. Likewise, it is also possible to specify the same regularity parameter α for all zones. In the first zone, the generator points 19 can also be arranged periodically or quasi-periodically. If a seamless transition is to be made to the other zones, then the generator points 19 in the other zones are not arranged periodically or quasi-periodically.

In a modification of the procedure according to the invention, in the production of Voronoi diagrams for a shaving foil 6, the above-described specification of the minimum distance d between the generator points 19 can be dispensed with, thereby initially producing a statistical distribution of Voronoi polygons. The resulting pattern is referred to in the following as Poisson Voronoi pattern. Then the center of gravity is calculated for each Voronoi polygon. The calculated focal points are the generator points 19 of a new Voronoi diagram. The Voronoi polygons of the new Voronoi diagram are more uniform than the Voronoi polygons of the underlying Poisson Voronoi pattern. Again, for the new Voronoi polygons, the centroids can be calculated and used as new generator points 19. This procedure can be continued iteratively until the Voronoi diagram is sufficient is homogeneous. In the limiting case of very many iterations, a Voronoi diagram is approximated, which is referred to below as the centroid Voronoi diagram. The iterative change of a Voronoi diagram over continued centroid formations is based on the so-called Lloyd algorithm of Stuart P. Loyd. Details are in S. Loyd: "Least Squares Quantization in PCM", IEEE Transactions on Information Theory, Volume 28, Number 2, pages 129-137 (1982 ).

The center of gravity calculation does not necessarily have to be based on a spatially constant mass density. It is also possible to use a spatially varying mass density (see Q. Du, V. Faber and M. Gunzburger: "Centroidal Voronoi Tessellations: Applications and Algorithms", SIAM Review, Volume 41, Number 4, pages 637-676 (1999 )). In this case, the iterative method converges to a centroid Voronoi diagram that has Voronoi polygons with a small surface area at low density sites and Voronoi polygons with a large surface area at low mass density sites. The following relation exists between the mass density p (x, y) and the surface area F (x, y) of the Voronoi polygons: $$F\left(x,y\right)~\frac{1}{\sqrt{\rho \left(x,y\right)}}\mathrm{,}$$

By means of a corresponding specification of the mass density, a desired distribution of the surface area of the Voronoi polygons and thus the size of the holes 16 of the shaving foil 6 can be produced. The size of the holes 16 can vary both steadily and discontinuously. An embodiment of a shaving foil 6 with a continuously varying size of the holes 16 is shown in FIG Fig. 13 shown.

Fig. 13 shows a further embodiment of the shaving foil 6 in a detail shown settlement. In this embodiment, the size of the holes 16 varies continuously and has a minimum value in the region of the zenith 11 of the curve 10. As the distance from the zenith 11 increases, the size of the holes 16 increases. The curve according to which the size of the holes 16 varies is in FIG Fig. 14 shown.

Fig. 14 shows a diagram for the course of the size of the holes 16 for the in Fig. 13 illustrated embodiment of the shear foil 6. On the abscissa, the distance y of the holes 16 from the zenith 11 is applied. On the ordinate, the size of the hole area F is plotted. As a thin line, a desired course of the size of the hole area F is shown, which is based on a sine function which has a minimum in the region of the zenith 11 (y = 0). As a thick line, the actual course of the size of the average hole area F is further shown. Again Fig. 14 can be seen, the actual course is in good approximation with the desired sine function match.

In the following it will be explained with which course of the size of the holes 16 of the shaving foil 6 a particularly good shaving result can be achieved:

If the skin is considered approximately as a homogeneous, isotropic, linear-elastic medium with a semi-infinite extent, the result for a razor 1 with a single foil 6 within the contact surface of the foil 6 on the skin is a pressure q (y): $$q\left(y\right)=\frac{e}{2R}\sqrt{b^2-{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}\mathrm{,}$$

In this case, y represent the respective distance from the zenith 11 of the curvature 10 of the shear foil 6, E is the modulus of elasticity of the skin, R is the radius of curvature 10 of the shear foil 6 and b is half the width of the contact surface in the y direction, ie the shearing foil 6 lies in the Area -b <y <+ b on the skin. For the width 2b of the contact surface, the following applies: $$2b=4\sqrt{\frac{R\cdot P}{\pi \cdot e}}\mathrm{,}$$

Where P is the force per unit length with which the razor 1 is pressed against the skin during shaving.

Outside the contact surface of the shaving foil 6 on the skin, the pressure q (y) has the value 0.

By approximating a circular formation of the holes 16 of the shaving foil 6 with a radius a, the indentation of the skin in one of the holes 16 can be estimated by integrating the Boussinesq solution for the impression of a punctiform indentor over the hole. The underlying theory in this respect is in J. Boussinesq: "Application of the Potentiels a l'Equilibre et du Mouvment des Solides Elastiques, Gauthier-Villars (1885). The depth D of the skin bulge with respect to the plane of the hole 16 in the center of the hole 16 results in: $$D\left(q\right)=\frac{q\cdot \left(1-{\mathrm{<figure-callout\; id="2"\; label="\nu "\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">\nu </figure-callout>}}^2\right)}{\mathit{\pi E}}\cdot 2\sqrt{\pi }\cdot \sqrt{F}\mathrm{,}$$

ein Geometriefaktor für ein Quadrat bzw. des Rechtecks zu ergänzen ist. Dieser zusätzliche Faktor weist bei einem kreisförmigen Loch 16 exakt den Wert 1 auf. Für ein quadratisches oder ein rechteckiges Loch 16 weist der zusätzliche Faktor nicht exakt den Wert 1 auf, liegt aber nahe beim Wert 1.Here, v is the transverse contraction number of the skin. The factor F is a measure of the area of the hole 16. For square or rectangular holes 16, similar formulas result, in addition to the factor $2\sqrt{\pi }$

a geometry factor for a square or the rectangle is to be added. This additional factor has exactly the value 1 for a circular hole 16. For a square or rectangular hole 16, the additional factor does not exactly equal 1, but is close to 1.

In general, the depth D of the skin bulge at a small aspect ratio convex hole 16, i. H. with sides of approximately equal length, depending primarily on the area and not on the shape of the hole 16. The above formula for the depth D of skin bulge is thus also approximately applicable to hexagons and Voronoi polygons.

In a razor 1 with two shear films 6, for example according to Fig. 1 , Distributes the force with which the razor 1 is pressed against the skin, on the two shear films 6. Consequently, acts on each of the two shear films 6, only half the force. In addition, the impressions in the skin caused by the shear foils 6 influence each other. This results in that the maximum local pressure q is not formed in each case in the region of the zenith 11 of the shear foils 6, but in each case offset by an azimuth angle γ _max . For a razor 1 with two shaving foils 6, the following azimuth dependence for the depth D of the skin bulge results in the holes 16 of the shear foils 6: $$D\left(\gamma \right)=r\cdot \left(1-{\mathrm{<figure-callout\; id="2"\; label="\nu "\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">\nu </figure-callout>}}^2\right)\cdot \sqrt{{a_2}^2-{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\left(\gamma -{\gamma }_{\mathrm{Max}}\right)}\mathrm{,}$$

und γ_max stellen Fitparameter dar. Ein Beispiel für einen Verlauf der Tiefe D der Hauteinwölbung ist in Fig. 15 dargestellt.In this case, γ are the azimuth angle relative to the zenith 11 of the respective foil 6, r is the radius of a circle whose surface area corresponds to the area of the hole 16 of the foil 6, ie $r=\sqrt{F/\pi }\mathrm{,}{\mathrm{a}}_2$

and γ _max represent fit parameters. An example of a course of the depth D of skin bulge is in FIG Fig. 15 shown.

Fig. 15 shows a diagram for a possible course of the depth D of Hauteinwölbung as a function of the azimuth angle γ. The abscissa shows the azimuth angle y, the ordinate shows the depth D of the skin bulge. The diagram refers to a razor 1 with two shear films 6. The representation is chosen so that it reproduces the conditions in the region of one of the two shear films 6, wherein on the left side of the diagram, the other foil 6 with a mirror image of the Depth D of skin invagination would connect. The plotted points represent measured values that are suitable for a test subject with the in Fig. 1 shaver 1 were determined. The solid line was determined by the above formula (I) using as a fit parameter a ₂ = 0.59 and γ _max = 5 °.

$$r_{\min }=\frac{\mathit{sf}}{\left(1-{\nu }^2\right)\cdot a_2}\mathrm{l}\ddot{\mathrm{a}}\mathrm{ßt\; sich}\left(\mathrm{J}\right)\mathrm{schreiben\; als}r=\frac{r_{\min }}{\sqrt{1-\frac{{\sin }^2\left(\gamma -{\gamma }_{\max }\right)}{a_2^2}}}$$

Despite the idealizations on which the formula (I) is based and according to which the skin is regarded as a homogeneous, isotropic, linear-elastic medium with a semi-infinite extent, the curve agrees relatively well with the measured values. The formula (I) can therefore be used to determine the size of the holes 16 of the shaving foil 6 for a desired depth D of the skin bulge. For this purpose, the formula (I) is resolved according to the radius r. It is particularly advantageous if the depth D of the skin bulge corresponds to a thickness sf of the shaving foil 6. In this case, the hair from the lower blade 5 is severed directly on the skin surface, i the lower blade 5 but the skin just barely touched. Thus, for r: $$r=\frac{\mathit{sf}}{\left(1-{\mathrm{<figure-callout\; id="2"\; label="\nu "\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">\nu </figure-callout>}}^2\right)\cdot \sqrt{{a_2}^2-{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\left(\gamma -{\gamma }_{\mathrm{Max}}\right)}}\mathrm{,}$$

$$r_{\min }=\frac{\mathit{sf}}{\left(1-{\mathrm{<figure-callout\; id="2"\; label="\nu "\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">\nu </figure-callout>}}^2\right)\cdot a_2}\mathrm{l}\ddot{\mathrm{a}}\mathrm{eats\; himself}\left(\mathrm{J}\right)\mathrm{Write\; as}r=\frac{r_{\min }}{\sqrt{1-\frac{{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0006.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\left(\gamma -{\gamma }_{\mathrm{Max}}\right)}{a_2^2}}}$$

By varying the surface area of the holes 16 of the shaving foil 6 as a function of the azimuth angle γ according to the formula (K), there is approximately a constant depth D for skin concavity in the entire contact area between the shaving foil 6 and the skin. Since the formula (K) diverges, the holes 16 of the shaving film 6 become very large for large azimuth angles γ, that is, at a great distance from the zenith 11. This can lead to problems if the shaver 1 is not placed perpendicular to the skin, since then in the area of large holes 16 a high local pressure q prevails and the skin consequently bulges very deeply into the holes 16. This problem can be solved by the size of the Holes 16 in each case only in the vicinity of the zenith 11 or in the vicinity of the azimuth angle γ _max according to the formula (K) varies and outside this environment is limited to a maximum value. An embodiment of a thus formed shaving foil 6 is in Fig. 16 shown.

Fig. 16 shows a further embodiment of the shaving foil 6 in a detail shown settlement. This embodiment is provided for a razor 1 with two shaving foils 6. In this case, the azimuth angle γ _max , for which the local pressure q is at a maximum, is approximately 10 ° and approximately corresponds to the mean extent of a hole 16. In the central zone 12, which in this exemplary embodiment is symmetrical about the azimuth angle γ _max The holes 16 are formed as regular hexagons on both sides of the central zone 12 are followed by an edge zone 13 or 14, in which the holes 16 are formed as Voronoi polygons and are on average larger than in the central zone 12. The Voronoi polygons were constructed according to the Lloyd method and do not exceed a given maximum size In the transition areas between the central zone 12 and the edge zones 13 and 14, respectively, the size of the holes 16 varies according to the formula (K) On one side of the central zone 12 there are two further zones 13 'and 13 ", in which the holes 16 are larger than in zone 13, but do not grow according to the formula K. n. In 13 'they grow weaker and in 13 "their size is limited to a maximum value.

Claims (6)

1. A shaving foil for an electric shaving apparatus (1), with a perforated region (15) which has a plurality of holes (16) that are separated from one another by webs (17), wherein the perforated region (15) is subdivided into at least a central zone (12), a first edge zone (13) and a second edge zone (14), and the central zone (12) is arranged between the first edge zone (13) and the second edge zone (14), characterized in that the holes (16) in the central zone (12) have an average size that is smaller than the average size of the holes (16) in the first edge zone (13) and in the second edge zone (14), and/or in that a floating mean value for the size of the holes (16) is smaller in the central zone (12) than in the first edge zone (13) and the second edge zone (14), and wherein the webs (17) have a width that is the same over the entire perforated region (15).
2. The shaving foil according to any one of the preceding claims, characterized in that at least some of the holes (16) are in the form of irregular polygons.
3. The shaving foil according to any one of the preceding claims, characterized in that the floating mean value for the size of the holes (16) varies in accordance with a predefined function along the first direction (18) within the perforated region (15).
4. The shaving foil according to claim 3, characterized in that the predefined function has a continuous characteristic.
5. The shaving foil according to any one of the preceding claims, characterized in that the holes (16) are formed as polygons whose internal angles are respectively less than 180°.
6. The shaving foil according to any one of the preceding claims,
   characterized in that at least some of the holes (16) are formed as Voronoi polygons.

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