Patent ID: 12246460

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS.1-6show a first example of a razor1according to the invention. The razor1has a support2and skin engagement surfaces3-6. For severing hairs7projecting from a user's skin close to the level of the skin surface8, a hair-severing member9having a hair-severing edge10is provided. The razor1further has a stem-shaped handle11for holding the razor1by hand. The hair-severing member9is mounted to the support2in a position relative to the skin engagement surfaces3-6such that the hair-severing edge10is exposed to the user's skin surface8for sawing through hairs7present on the skin when the skin engagement surfaces3-6are in contact with the skin. The hair-severing member9is suspended relative to the support2for allowing movement of the hair-severing member9in a direction of extension12of the hair-severing edge10. In operation, the hair-severing edge10moves along the skin surface8while only slightly contacting the skin as in conventional blade shaving. In this example, the hair-severing edge10is straight, so the hair-severing edge10has a local direction of extension which remains constant along the entire length of the hair-severing edge10. As will be illustrated by further examples, the local direction of extension of the hair-severing edge may also vary along the length of the hair-severing edge. Where, in the discussion of effects, reference is made to the ‘direction of extension of the hair-severing edge’, this has to be read as the ‘local direction of extension of the hair-severing edge at the position of the respective sawing tooth or sawing teeth’ for embodiments in which the direction of extension of the hair-severing edge varies along the length of the hair-severing edge.

The hair-severing edge10has a plurality of sawing teeth14(preferably evenly) arranged along the hair-severing edge10of the hair-severing member9. In the present example, as shown in detail inFIGS.4and5, the sawing teeth14each have two tooth tips16connected by a concavely shaped front tooth edge15. The front tooth edge15of each sawing tooth14is connected to a respective one of two upper side tooth edges29of the sawing tooth14and to a respective one of two lower side tooth edges36of the sawing tooth14via a respective one of the two tooth tips16. Each sawing tooth14is arranged along the hair-severing edge10for sawing through hairs7by movement in the direction of extension12of the hair-severing edge10. InFIG.5, orientations8xand8yof the skin surface8are shown in the direction of extension12of the hair-severing edge10(8x) and in a direction along the skin surface8perpendicular to the direction of extension12of the hair-severing edge (8y). Each lower side tooth edge36connects to a side edge39of a skin contacting surface40of the sawing tooth14which, as shown inFIG.5, extends at a wedge angle41relative to the associated upper side tooth edge29which is smaller than a first tip angle38of the tooth tip16enclosed by the upper side tooth edge29and the lower side tooth edge36. The wedge angle41between the side edge39of the skin contacting surface40and the associated upper side tooth edge29is preferably between 10 and 20°, so that, when the razor1is being used, the skin contacting surface40is approximately in a same plane as the skin surface8(inFIG.5defined by the directions8xand8y).

As shown inFIG.2, the razor1comprises a drive13which is coupled to the hair-severing member9for driving the movement of the hair-severing member9relative to the support2such that the sawing teeth14move in the direction of extension12of the hair-severing edge10with an average velocity larger than or equal to 10 m/s. In this example, the movement of the sawing teeth14is a reciprocal movement in the direction of extension12with said average velocity.

The thicknesses of beard hairs7are typically in a range from about 50 μm, for a thin beard hair, up to about 300 μm for a thick beard hair. Thus, at least the thinnest beard hairs7B would fit in an intermediate space30between two successive sawing teeth14(a sawing tooth and the first next or previous sawing tooth) if a spacing17(seeFIG.5) between two successive sawing teeth14is larger than 50 μm. It has been found that, if beard hairs7are entirely caught in the intermediate space30between the sawing teeth, the beard hairs tend to be just reciprocally moved by the sawing teeth instead of being chipped. To avoid that thin beard hairs are just reciprocally moved and less effectively chipped, a depth18of the intermediate space30between two (preferably each pair of) successive sawing teeth14, in a direction perpendicular to the direction of extension12of the hair-severing edge10, is preferably smaller than or equal to 25 μm when the spacing17between the tooth tips16of two successive sawing teeth14is larger than 50 μm. The depth18between two successive sawing teeth14can be considered up to a straight bottom19of the intermediate space30as shown inFIG.5, but the effective depth can also be determined (limited) by one or more small ridges or other projections between successive sawing teeth14. As is shown inFIG.4, a spacing17between successive sawing teeth14smaller than or equal to 50 μm can also prevent thin hairs7B from fully entering the intermediate space30between successive sawing teeth14, even if the depth18would be large enough to entirely accommodate at least thin hairs7B.

The spacing17between the tooth tips16of two successive sawing teeth14is at most 150 μm, so that, for hairs with an average hair diameter, during movement of the severing edge10along a hair7A or7B, before a sawing tooth14leaves the hair7, a next sawing tooth14already enters a groove in the hair7which the previous sawing tooth14has cut therein. For effective sawing of thin hairs7B, it is advantageous if the spacing17between the tooth tips16of two successive sawing teeth14is very small, but it has also been found that, if the spacing17between the tooth tips16of two successive sawing teeth14is very small, debris obtained during cutting tends to remain stuck in the intermediate spaces30between the sawing teeth14. Therefore, the spacing17is 20 μm or larger. Also, when a large number of sawing teeth14is simultaneously in engagement with a hair7, the advantage of reduced cutting forces may be offset by the large sum of the cutting forces of the individual sawing teeth14in engagement with the hair7. The sum of the cutting forces should preferably not exceed 0.007 N to prevent drag. This is another reason why the spacing17is at least 20 μm.

For avoiding the occurrence of too much drag while allowing to effectively sever hairs7, the average velocity of the sawing teeth14in the direction of extension12of the hair-severing edge10is larger than or equal to 10 m/s. Each saw tooth14can be regarded as a small chisel which, given a certain contact stress at the hair and a lateral motion, will chip away hair tissue from the hair. It has been found that, for effectively sawing through hairs, a ratio between the velocity of the hair-severing edge10in its direction of extension and the velocity at which the depth of the sawing slit in the hair is increased should at least be about 100. Therefore, to be able to shave at acceptable shaving velocities, i.e. velocities in the shaving direction of the razor1of at least 100 mm/s, the minimal velocity of the hair-severing edge10in its direction of extension12should be larger than 100×100 mm/s=10 m/s.

The hair-severing edge10is preferably made of tool grade steel, but the material of the hair-severing edge10is not limited to tool grade steel. There are several ways for manufacturing the sawing blades, such as by chemical etching and laser ablation. However other methods, like growing nickel and a combination of processes like wire spark erosion with mechanical or chemical polishing, are also conceivable.

The front tooth edge15and each of the upper side tooth edges29of each of the sawing teeth14preferably enclose a second tip angle20, as shown inFIG.5, smaller than 80° at the tooth tip16to assure sufficient contact stress at the tooth tip16. Thus, the second tip angles20of the tooth tips16between the front tooth edge15and each of the upper side tooth edges29are preferably each smaller than 80°. The first tip angles38of the tooth tips16between the upper side tooth edge29and the lower side tooth edges36of each sawing tooth14are preferably smaller than 80° and more preferably smaller than 60°. For sufficient sharpness of the tooth tips16, a tip radius RTIP(seeFIG.5) of the tooth tips16is preferably equal to or smaller than 5 μm. The tip radius RTIPof the tooth tips16is schematically shown inFIG.5. For effective sawing, the tooth edges15,29,36preferably have an edge radius REDGEof 5 μm or smaller. Thus, seen in cross-section along a plane perpendicular to the tooth edge15,29, each tooth edge15,29preferably has an edge radius REDGEequal to or smaller than 5 μm. The tooth edges15,29,36preferably have such an edge radius REDGEat least at the position of the tooth tips16and, preferably, up to a distance from the tooth tips16. Said distance may be, for example, 25%, 50% or even 100% of the depth18of the intermediate space30. The edge radius REDGEof the front tooth edge15is shown in detail inFIG.6.

To avoid abrasion of the skin and dragging along of the skin with the movement of the sawing teeth14, the side edges39of the skin contacting surface40, and preferably also portions of the lower side tooth edges36adjacent to the respective side edges39of the skin contacting surface40, are preferably rounded or chamfered, for example to an edge radius larger than 5 μm and preferably larger than 10 μm. Outer ends of the side edges39of the skin contacting surface40may each be curved so as to provide smooth transitions to the lower side tooth edge36and a lower tooth edge42contiguous with that side edge39of the skin contacting surface40.

To further limit movement of the skin induced by movement of the hair-severing member9contacting the skin surface8during use, the razor1according to the present example is equipped with a skin-shielding member5, as show inFIG.3, arranged in a stationary position relative to the support2at a side of the hair-severing member9facing the skin during use. As a result, during use the hair-severing member9is exposed to the skin only in an exposure area32between the hair-severing edge10and an edge33of the skin-shielding member5. The exposure area32has a depth d between 100 and 500 μm, preferably between 250 and 350 μm, in a direction perpendicular to the direction of extension12of the hair-severing edge10. Movement of the skin induced by the movement of the hair-severing member9reduces the effectiveness of the sawing process and is limited as much as possible by exposing the hair-severing member9to the skin only in the relatively small exposure area32that includes the hair-severing edge10. The selected depth d of the exposure area32safeguards sufficient exposure of the hair-severing edge10to the skin and, thereby, sufficient effectivity of the sawing process of the moving hair-severing edge10. The skin-shielding member5also limits skin irritation caused by contact between the moving hair-severing edge10and the skin, because the skin-shielding member5reduces the pressure at which the hair-severing edge10contacts the skin. The skin-facing surface34of the skin-shielding member5may be provided with a friction-reducing coating to reduce skin friction.

As shown inFIG.5, the sawing teeth14each have a width21in the direction of extension12of the hair-severing edge10smaller than 75 μm, so that a large number of tooth tips16can be provided leaving a given minimum spacing17between each pair of successive tooth tips16. For a double-edged (twin tip) sawing tooth14, a width21of 20 μm is preferred for optimizing performance while maintaining sufficient tooth strength.

Instead of a single hair-severing member9, one or more further hair-severing members may be provided in a razor according to the invention, wherein all hair-severing members may be coupled to the same drive arranged for driving the movement of each hair-severing member relative to the support in the direction of extension of its hair-severing edge with the average velocity larger than or equal to 10 m/s.

As mentioned here before, in the razor1according to the present example, the movement of the sawing teeth14in the direction12of extension of the hair-severing edge10is a reciprocal movement.

For high shaving performance, the sawing teeth14each have two tooth tips16, so that the sawing teeth14cut in the two movement directions parallel to the direction12of extension of the hair-severing edge10. Moreover, the second tip angle20of the tooth tips16can be smaller than 80°. Furthermore, in the present example the front tooth edges15, that mutually connect the two tooth tips16of the sawing teeth14, are concavely shaped. As a result of the concave shape of the front tooth edges15, a hair temporarily present between the top of a sawing tooth14and the skin8does not cause the sawing tooth14to be lifted from the skin8so far that shaving performance is significantly compromised. This is the more relevant the thicker the sawing teeth14are.

InFIG.7a hair-severing edge60of a hair-severing member of a second example of a razor according to the invention is shown, which is also configured for shaving with the hair-severing edge60reciprocally moving in its direction of extension12. The sawing teeth64each have a single tooth tip66at the location where the two tooth edges79are mutually connected. The tip angle70of the sawing teeth64is preferably smaller than 60° to keep the negative cutting (rake) angle72as small as possible to achieve a sufficiently high initial contact stress with the hair7to create an initial notch. For obtaining sufficient strength of the sawing teeth64, the sawing teeth64preferably have a base width73of at least 20 μm.

For the sawing teeth14to move in the direction of extension12of the hair-severing edge at an average speed of at least 10 m/s, the reciprocal movement of the sawing teeth14preferably has a stroke length between 1 and 30 mm, and the reciprocal movement preferably has a frequency equal to or larger than 330 Hz. The combination of said stroke length and said frequency results in the required average speed of at least 10 m/s.

The drive13may for instance be a driven resonant system which brings and maintains a mass-spring system in a resonating movement relative to a main body. An example of such a driven resonant system is schematically shown inFIG.2and can be accommodated in a housing portion24of the handle11. The hair-severing member9is movably guided in the direction of extension12relative to the support2by means of a plurality of guiding members35and is attached to a first end of a leaf spring25of which an opposite second end is fixedly connected to the support2. The leaf spring25has a stiffness such that, in combination with the mass of the hair-severing member9connected thereto, it is ‘resonant’ in an Eigen frequency that matches the desired frequency of the reciprocal movement of the hair severing member9in its direction of extension12, for instance 7700 Hz at a stroke length of 1.3 mm. To drive movement at such a high frequency without using a motor revolving at the same rpm or a very high frequency linear electric motor, a rotatable driven drum37carrying multiple alternately polarized magnets26,27and a counter magnet28attached to the leaf spring25can be used. In operation, the counter magnet28is attracted or pushed away by a passing magnet26,27during rotation of the drum37. In this example the excitation frequency of the leaf spring25is six times the number of rotations per unit of time of the drum37. Such a multiplication of the excitation frequency allows use of a standard electric motor for achieving a high excitation frequency. Moreover, the excitation frequency can be an undertone of the Eigen frequency of the mass-spring system formed by the leaf spring25and the hair-severing member9.

InFIG.8a third example of a razor101according to the invention is shown. In this example, the hair-severing edges110of the hair-severing members109have a local direction of extension which varies along the hair-severing edges110. Accordingly, the direction of movement of the sawing teeth of the hair-severing edges110varies along the hair-severing edges110. In particular, each sawing tooth moves in the local direction of extension112of the associated hair-severing edge110at the position of the sawing tooth. In particular, in this example the sawing teeth of the hair-severing edges110move in the respective local directions of extension of the hair-severing edges according to a rotational movement in a single direction. For this purpose, the hair-severing members109are provided in the form of circular saw blades having circular hair-severing edges110. However, other ways to create a continuous motion in a single direction are also conceivable, such as a band saw and a chain saw system. In all such systems, the hair-severing edges can in principle also be driven so as to move in a reciprocating fashion.

To obtain sufficiently long operative sections of the hair-severing edges110in a construction that is sufficiently compact for daily use and can easily be taken along when travelling, the hair-severing edges110of the hair-severing members109preferably have a diameter between 5 and 75 mm.

The drive for rotationally driving the hair-severing members109is preferably arranged for rotating the hair-severing members109about an axis of rotation at speeds of at least 2500 rpm. Such speeds in combination with the diameter of the hair-severing edges110as described here before are suitable to achieve the required average velocity of the sawing teeth of at least 10 m/s.

InFIGS.9and10, a fourth example of a razor151according to the invention is shown, in which the movement of the sawing teeth (not individually visible inFIGS.9and10) of the hair-severing edge160of the hair-severing member159in the local direction of extension162of the hair-severing edge160is a continuous rotational movement in a single direction. The rotational movement can be along any rotational trajectory, for instance as in a chain-saw or a flexible band-saw. In this example, the hair-severing member159is provided in the form of a single circular saw blade to achieve the rotational movement of the hair-severing edge160. For protecting the skin from being damaged or irritated by the rotating hair-severing member159, a skin-shielding member178is provided, which has comb teeth175with a skin engagement surface155contacting the skin during shaving. Between these comb teeth175, open spaces176are present into which the skin can bulge into a position close to or slightly in contact with the hair-severing edge160.

As in the other examples, the hair-severing effect is achieved by sawing through the hairs at or in close proximity to the skin surface. In particular, the sawing teeth of the hair-severing edge160do not interact with the comb teeth175of the skin shielding member178to act as a pair of co-operating hair-cutting teeth as in conventional electrical shaver and trimmers with a moving cutting member moving relative to and co-operating with a stationary cutting member.

While the invention has been described and illustrated in detail in the foregoing description and in the drawing figures, such description and illustration are to be considered exemplary and/or illustrative and not restrictive; the invention is not limited to the disclosed embodiments.

Several features have been described as part of the same or separate embodiments. However, it will be appreciated that the scope of the invention also includes embodiments having combinations of all or some of these features other than the specific combinations of features embodied in the examples.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. For the purpose of clarity and a concise description, features are disclosed herein as part of the same or separate embodiments; however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features disclosed. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.