WO2013124705A1

WO2013124705A1 - Sharpening method and blade sharpener

Info

Publication number: WO2013124705A1
Application number: PCT/IB2012/001884
Authority: WO
Inventors: Mark James HENRY
Original assignee: De Buyer Industries; Mj Henry Group, Inc.
Priority date: 2012-02-22
Filing date: 2012-08-31
Publication date: 2013-08-29
Also published as: EP2817126A1

Abstract

A method for sharpening a blade comprising the steps consisting in providing a blade (30) - providing a blade sharpener comprising a stationary frame (41 ) a hinged sharpening member (10) wherein the sharpening member is hinged on the stationary frame (41 ) for allowing the pivoting of the sharpening member (10) about a hinge axis (31 ), wherein the hinged sharpening member (10) comprises a single inflexible abrasive element (1 1 ) arranged in an overlapping arrangement relative to a guiding member (21 ) or a plurality of inflexible abrasive elements (1 1, 12, 13), wherein the inflexible abrasive elements (1 1, 12, 13) are arranged in an overlapping arrangement relative either to a guiding member (21 ) or to a second hinged sharpening member (20) provided with inflexible abrasive elements (21, 22, 23), a groove (G) having sharpening faces is formed and is operable to engage a cutting edge on a blade (30) and drawing the blade (30) in the groove (G) between the guiding member (21 ) and the hinged sharpening abrasive member element (10) or between the two opposed and hinged sharpening abrasive members (10, 20), for honing the blade (30), and a sharpener for implementing the above method.

Description

SHARPENING METHOD AND BLADE SHARPENER

FIELD OF THE INVENTION The present invention relates to a sharpening method and to a blade sharpener,

BACKGROUND OF THE INVENTION

The difficulty experienced by most knife users in maintaining sharp edges on their Western -style, or two-sided bevel, blades is well known. Edge sharpening and honing has traditionally been done by hand using Whetstone and Whetsteel. Though the end result can be excellent, the skill and experience required is such that only chefs, butchers and knife enthusiasts reach a good level of competency. However, competencies can range from edges that cut acceptably for the purpose, or are no longer dull, to very sharp and finely honed slicing edges that also have sufficient strength for durability. Hand sharpened edges at this level of refinement are a rarity.

For the majority of the population a simpler and faster solution is required. To reduce the time and skill required to sharpen blades with traditional methods a plethora of sharpening tools or gadgets has been manufactured in recent decades. Very few seek to replicate the time-proven sharpening and honing action of the traditional methods described above, and most focus on removing metal while controlling the edge bevel shape, while improving sharpness with a newly roughened edge.

To replicate the traditional sharpening methods mentioned above, it is necessary to abrade the cutting edge surface with some component of angular motion, as opposed to abrading the edge solely longitudinally. Many tools or gadgets only achieve this longitudinal abrasion, particularly since most of the common inexpensive gadgets use a straight "pull through" motion, with no combined downward motion. The difference is significant in terms of appearance under a microscope and, more importantly, correlating with sharpness and durability of the cutting edge, with the many microscopic "saw teeth" generated by an angular abrading method is known to be more effective, particularly for durability of the cutting edge. It is well known in the blade and knife industries that a chisel-edged blade, or single-bevel blade, having an edge bevel on one side of the blade only and a nominally flat opposing side, in best known in the Japanese blade tradition, generally possesses superior cutting performance when compared with more common two-bevelled, symmetrical cutting edges in the Western European- American blade tradition.

Although primarily used in Japan, chefs and gourmet cooks in the West are well aware of the benefits of chisel-edged blades. However their adoption in practice has been limited to a small number of enthusiasts by the high degree of skill required to maintain or re-sharpen the original very sharp cutting edge. For the majority of home cooks in the West such knives are considered too exotic and too high maintenance, since more familiar two-beveled blades also lend themselves to reasonable maintenance with electric or manual "gadget" sharpeners. In effect, less sharpness and less cutting efficiency is traded for ease of maintenance.

In contrast, for single-bevel blades, usually the only sharpening method acceptable to chefs and those knowledgeable on the subject is the skilled abrasion and polishing of the chisel edge (usually polished into several very accurately angled and aligned lengthwise "facets"), and the flat back face, evenly along the length of the knife, using several grades of whetstone with very precise hand/arm control. Most of the sharpening is performed on the chisel edge itself, with only a very light polish applied to the flat back face. Electric or gadget sharpeners have not been widely accepted among users of single bevel blades because of the very coarse and generally poor results they produce relative to skilled traditional sharpening of these very fine-edged blades on whetstones.

Double bevel or convex edges are well known among skilled knife users for their potential combination of ideal sharpness and durability of the edge. The bulk of the edge is at an acute included angle for minimal resistance to penetration of the blade, while the final extremity of the cutting edge in mechanical contact with the materials being cut, or the surfaces supporting the materials being cut has a less acute angle to strengthen that final extremity, reduce fragility of the edge and improve durability. In practice, the generation of such double bevel or convex edges has been problematic for even skilled knife sharpeners, due to the high levels of accuracy required to generate very small bevels, at very specific angles, uniformly on each side of the blade and along the length of the blade.

It would be highly desirable to combine the benefits of high levels of sharpness and cutting efficiency of single-bevel blades, with the ease of maintenance provided by tool or gadget style sharpeners commonly used for symmetrical two-bevel "Western" blades.

It is the object of the present invention to introduce a high degree of control over cutting edge bevel shapes while simultaneously generating an angular edge abrasion pattern that replicates results of traditional sharpening methods, but with improved accuracy. Both desirable outcomes are achieved with a very simple, convenient and fast innovation described herein.

The present invention eliminates much of the human error inherent in previous manual methods for generating such cutting edges by controlling the angle of the abrasive elements in contact with the cutting edge at each point of downward travel of the blade relative to the abrasive elements.

US 2007/167122 discloses a knife sharpener comprising a set of upwardly extending fingers involving pairs of overlapping, resiliently flexible abrasive fingers or strips between which a knife blade may be drawn for sharpening purposes, said set having a base on which said set is mounted with said fingers in essentially vertical position.

US 2003/075022 discloses a knife sharpener including a pair of overlapping, resiliently flexible, fingers or strips mountable in and/or on a base and abrasive means on at least one portion of inwardly directed, opposed, sharpening faces on the fingers or strips, operable to engage at least one cutting edge on a blade of a knife.

In both documents, abrasive fingers are bent upon honing.

However, since the above knife sharpeners include a pair of resiliently flexible fingers or strips, their interaction with a blade during sharpening is inherently less controllable than with rigid interleaved elements, such as those utilised in the present invention. SUMMARY OF THE INVENTION

Now the applicant has developed a sharpening method and has devised a blade sharpener which significantly improves upon the performance of existing manual knife sharpeners.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A subject of the present application is therefore a method for sharpening a blade comprising the steps consisting in

- providing a blade

- providing a blade sharpener comprising

• a stationary frame

• a hinged sharpening member wherein the sharpening member is hinged on the stationary frame for allowing the pivoting of the sharpening member about a hinge axis, wherein the hinged sharpening member comprises a single inflexible abrasive element arranged in an overlapping arrangement relative to a guiding member or

a plurality of preferably parallel inflexible abrasive elements, wherein the preferably parallel inflexible abrasive elements are arranged in an overlapping arrangement relative either to a guiding member or to a second hinged sharpening member provided with parallel inflexible abrasive elements, or independently pivoting parallel inflexible abrasive elements,

wherein abrasive means are provided on a portion of inwardly directed, opposed, sharpening faces on the inflexible abrasive elements, so that the guiding member and the hinged sharpening abrasive member or the two opposed and hinged sharpening abrasive members form a groove having sharpening faces and are operable to engage a cutting edge on a blade for example of a knife, and wherein preferably the hinge axis of each of the hinged sharpening members is preferably parallel to a cutting edge of the blade, in a vertical plane, during honing.

- drawing the blade in the groove between the guiding member and the hinged sharpening abrasive member or between the two opposed and hinged sharpening abrasive members, for honing the blade. A person skilled in the art can easily understand when the term "a" signifies "at least one". For example when the text provides that the blade sharpener comprises "a sharpening member", "at least one sharpening member" is meant.

The word "parallel" applied to abrasive elements means that the different abrasive elements have a same position in space and are aligned such that they provide a surface as shown in the figures.

The expression "inflexible abrasive elements" means that upon honing, the elements retain their original shape unchanged. For example they are not flexible and resilient ; they do not bend.

According to a particular embodiment, the blade sharpener used in the method of the invention comprises a pair of hinged sharpening members wherein each of the sharpening members is hinged on the stationary frame for allowing the pivoting of the sharpening members about an axis, wherein the hinges axes are preferably parallel and wherein each of the sharpening members has a plurality of parallel inflexible abrasive elements. The inflexible elements are arranged in an overlapping arrangement whereby a groove is created between both sharpening members. The parallel sharpening members are perpendicular to the hinges axes. The abrasive elements are in such a case plates provided in a parallel arrangement as shown on some of the figures.

In another embodiment, instead the blade sharpener comprises a guiding member and a sharpening member hinged on the stationary frame. The guiding member may comprise a plate provided parallel to the hinge axis and may be abrasive or not. The guiding member preferably comprises preferably parallel inflexible elements which may be abrasive or not. The parallel inflexible elements of the guiding member are arranged in an overlapping arrangement relative to the parallel inflexible elements of the hinged sharpening member, whereby a groove is created between the hinged sharpening member and the guiding member.

The edges of the parallel inflexible elements of the guiding member facing the parallel inflexible abrasive elements of the hinged sharpening member define a surface which may be flat or (slightly) concave (relative to a blade). The guiding member is bound to the frame and may be integral with the frame. In the present Application by "slightly concave" is meant for example a radius of concavity of 7.0 m to 0.1 m, preferably of 2.0 m to 0.2 m, most preferably of 1 .5 m to 0.5 m and, most importantly in practise, to ensure the tip of the cutting edge remains in contact with the guiding member. A convex guiding member would contact the side of the blade instead of the very cutting edge, and efficacy of the invention would be reduced, because all of the sharpening and honing action would take place on the main bevel (right side in the drawings), with none on the cutting edge from the flat side of the blade (left side in the drawings).

Hinges or pivots for the abrasive elements may be common pin and hole pivots, attaching the abrasive elements to flexible material or any other method that allows the abrasive elements to pivot around one axis or multiple axes on each element. Multiple axes may be provided by multiple pivot holes, eccentrics, or any other moveable pivot mounting method in order to provide adjustment to abrasive element pivot locations for generating the edge profile at varying angles for given cam profiles.

The stationary frame on which the sharpening members are hinged is preferably incorporated in a knife scabbard or knife block. However, the frame may be freestanding, for example with a handle extending laterally to a sharpening axis of the sharpener, or is mountable on a supporting wall.

The blade is preferably drawn down and backward in the groove between two opposed and hinged sharpening and/or honing abrasive elements, or between a guiding member and hinged sharpening abrasive elements, or between two banks of individually hinged and independent abrasive elements and initially engages a top part of the abrasive elements. A down and forward blade motion may also be used, or a substantially forward or backward motion. The blade is held about vertically (in cross section) in the groove between the abrasive elements during the swiping motion, or constrained in this orientation by common mechanical means such as guides.

The angle of the abrasive elements in contact with the blade edge at each point of downward travel of the blade is pre-determined by the cam profile of each abrasive element. Cam profiles can be designed to generate any desirable edge shape, from traditional symmetrical Western-style cutting edges to traditional Japanese-style single-bevel edges, or asymmetrical edges. Edge profile shapes thus generated may also be uniform in angle such as flat facets of any angle, progressive in angle such as a convex edge of any curvature, or a combination of facets or curvature, one example being a double bevel edge with two facets of different angles on each side of the cutting edge.

The bevel shapes can be widely varied according to the desired cam profiles and include profiles providing as a result single bevel, double bevel, symmetrical, asymmetrical and convex shapes for the honed blade. The preferred desirable shapes are shown in figures 7a (symmetrical single bevel), 7b (symmetrical double bevel) and 7c (symmetrical convex).

Hinges may be provided at a top part of the abrasive elements, or at a bottom part of the abrasive elements, preferably top because mechanical resistance does not increase as the blade travels downward across the abrasive elements, as it does when hinges are at the bottom and the blade approaches the hinges. When hinges are provided at a top part of the abrasive elements, mechanical resistance can be provided by springs and other more controllable means. When hinges are provided at a bottom part of the abrasive elements, the blade encounters rapidly escalating resistance to downward travel as it approaches the hinges and, in practice, this may lead to most of the abrasive action occurring near the hinges, though this may be controlled with spring resistance to more evenly modulate resistance throughout the downward stroke.

Each of the sharpening or guiding members has a plurality, preferably the same number, of inflexible elements. The number of inflexible elements of each of the sharpening or guiding members may be any number from 2 upwards, preferably 2 to 8 elements, more preferably 2 to 5 elements, most preferably 2 to 4 elements.

A sharpener used in a method of the invention has for example 1 , 2 or 3 successive, optionally spaced, pairs of sharpening members, preferably a single pair.

Abrasive means are provided on a portion of inwardly directed, opposed, sharpening faces on the inflexible elements, preferably on the whole sharpening faces.

The hinged abrasive elements may be individually hinged or not.

The abrasive elements may be made from various materials or coatings or mechanical surface finishes achieving the desired aggressiveness or smoothness of sharpening or honing. The abrasive elements may have abrasive properties inherent to the material used for the manufacture or by mechanical surface roughness or provided by a coating on the surface of the material in contact with the blade. The surface may also appear be nominally smooth, to the naked eye, or of harder or softer material than the blades.

Furthermore, the abrasiveness of the surfaces of the faces of the abrasive elements in contact with the blade may be varied along the cam profile. For example, a zone of cam profile designed to generate the final edge bevel may also be provided with a very fine abrasive surface for very fine honing, while a zone of the cam profile designed to generate or abrade the bulk of the edge shape may have a more aggressive abrasive contact surface. Different rates of blade abrasion and resulting bevel surface finishes are thus obtained.

A sharpener used in a method of the invention has for example two spaced pairs of sharpening members with different honing performance.

When the stationary frame is a knife scabbard or knife block or is inserted into a knife scabbard or knife block, the mounting brackets or plates extend into a hole, aperture, slot, or groove of said knife scabbard or knife block.

Under preferred conditions for implementing the invention, a blade sharpener defined above is provided with means for mounting or holding the abrasive elements with sufficient rigidity to constrain motion to rotation around the hinges axes when swiping a blade between the abrasive elements.

To maximize utility, the abrasive elements may be mounted in any manner which constrains them longitudinally against the forces imparted by the blade, for example, but not limited to: attached to handles, in or on knife blocks, benches, walls, in or on scabbards or other storage devices, in or on any other convenient surface or anchor point which constrains the hinges so the abrasive elements to rotate around their hinge axes.

During honing, blades tend to repel the hinged sharpening members. Therefore, a device limiting pivoting amplitude is preferably provided, generally opposite to the hinge of the abrasive elements. For example if a hinge is provided at a top part of the abrasive elements, a device limiting pivoting amplitude is preferably provided at a bottom part of said abrasive elements, but may be mounted anywhere that provides the required resistance.

Means of returning the abrasive elements to their original position after each swipe of a blade through the abrasive elements are preferably provided.

A subject of the present invention is also a blade sharpener which is useful in particular for implementing the above sharpening method, comprising

• a stationary frame

· a hinged sharpening member wherein the sharpening member is hinged on the stationary frame for allowing the pivoting of the sharpening member about a hinge axis, wherein the hinged sharpening member comprises a single inflexible abrasive element arranged in an overlapping arrangement relative to a guiding member or

a plurality of preferably parallel inflexible abrasive elements, wherein the preferably parallel inflexible abrasive elements are arranged in an overlapping arrangement relative either to a guiding member or to a second hinged sharpening member,

wherein abrasive means are provided on a portion of inwardly directed, opposed, sharpening faces on the inflexible abrasive elements, so that the guiding member and the hinged sharpening abrasive member or the two opposed and hinged sharpening abrasive members form a groove having sharpening faces and are operable to engage a cutting edge on a blade for example of a knife, and wherein preferably the hinge axis of each of the hinged sharpening members is parallel to a cutting edge of the blade, in a vertical plane, during honing.

Preferred blade sharpeners according to the invention are provided with a hinged sharpening abrasive member or a plurality of members which oppose a convex or concave or preferably nominally flat plate, allowing a side of the blade with a nominally flat face to slide along the plate, while the opposite side of the blade with angled bevel or bevels is honed or sharpened by the hinged sharpening abrasive member or members.

The blade sharpeners according to the invention have advantageous properties because of their inventive design. While operator skill and time is minimized by the simple down and back blade swiping method, the invention achieves a high degree of edge bevel shape control and accuracy while also generating the angular abrasion pattern similar to that generated by the arcing swiping action across traditional Whetstone and Whetsteel.

The blade sharpeners and the method according to the invention benefit of high levels of sharpness and cutting efficiency of single-bevel blades, with the ease of maintenance provided by tool or gadget style sharpeners commonly used for symmetrical two-bevel "Western" blades.

They introduce a high degree of control over cutting edge bevel shapes while simultaneously generating an angular edge abrasion pattern that replicates results of traditional sharpening methods, but with improved accuracy.

The present invention further eliminates much of the human error inherent in previous manual methods for generating such cutting edges by controlling the angle of the abrasive elements in contact with the cutting edge at each point of downward travel of the blade relative to the abrasive elements.

Preferred conditions for implementing the sharpening method described above also apply to the blade sharpeners of the invention.

The scope of the invention can be understood better by referring to the examples given below, the aim of which is to explain the advantages of the invention.

The invention will now be described by means of the following drawings.

Figures 1 a and 1 b represent a perspective view of two versions of a blade sharpener of the invention with two sharpening members.

Figure 2 shows a perspective view of a blade in honing position between two sharpening members of Figure 1 b.

Figure 3 shows a lateral view of the two versions of a blade sharpener of Figures 1 a and 1 b.

Figure 4 shows a perspective view of a blade sharpener of the invention in the format of individually hinged abrasive elements. Figure 5 shows a perspective view of a blade in honing position between two sharpening members of a blade sharpener of the invention in the format of individually hinged abrasive elements.

Figure 6 shows a lateral view of the two versions of a blade sharpener of Figure 4.

Figure 7 shows a view of three preferred cutting edge shapes for two-sided blade edges (bottom drawings) and shows a lateral view of the type of cam profiles that may generate those edges (top drawings).

Figure 8 shows a view of a traditional Japanese style edge (or chisel edge, or single bevel edge) (left drawing), and shows a lateral view of a blade sharpener of the invention with one guiding member and a sharpening member hinged on the stationary frame (right drawing).

Figure 9 represents a perspective view of a blade of a single bevel knife located in contact with a blade sharpener provided with a single hinged sharpening element

Figure 1 0 is a front view similar to the view of figure 9.

DESCRIPTION OF THE DRAWINGS Figures 1 a and 1 b represent a perspective view of two versions of a blade sharpener of the invention with two hinged sharpening members 10, 20, viewed from the top.

Each hinged sharpening member 10, 20 is provided with a plurality of parallel inflexible abrasive elements. The parallel inflexible abrasive elements 1 1 , 12, 13 of the first hinged sharpening member 1 0 are arranged in an overlapping arrangement relative to second hinged sharpening member 20 provided with parallel inflexible abrasive elements 21 , 22, 23.

The sharpening members 1 0, 20 are rigid plates each comprising three parallel abrasive elements, 1 1 , 1 2, 13 and 21 , 22, 23 respectively. Two elongated parallel holes have been manufactured in each rigid plate and then a small bar 14, 24 has been soldered at the bottom part of the abrasive elements, 1 1 , 12, 1 3 and 21 , 22, 23 after interleaving said abrasive elements, 1 1 , 1 2, 13 and 21 , 22, 23. Rods 15, 25 used as hinges providing hinges axes have been provided at the bottom part of the abrasive elements (Fig 1 a) and at the top part of the abrasive elements (Fig 1 a). A groove G is created between the inwards surfaces of both sharpening members 1 0, 20 by the successive parallel abrasive elements, 1 1 , 12, 13 and 21 , 22, 23.

On Figure 1 a, a small bar 14 has been provided at the bottom part of a single abrasive element.

Figure 2 shows a blade 30 in position for honing. The cutting edge 31 of a blade 30 applies downward pressure in the groove G provided between the top parts of two abrasive members 10, 20. Upon honing, the blade 30 is drawn between the two opposed and sharpening abrasive elements of hinged members 10, 20. Bottom bars 14, 24 get closer upon downwards pressure of the blade 30 and they come into contact if no obstacle interferes.

A stationary frame to which the pivoting abrasive elements are fastened for operation is not represented on this figure but will be schematised in figure 1 0.

Figure 3 shows one potential cam profile for each of top (left drawing) and bottom (right drawing) hinged versions of abrasive members. The shape of the left sharpening members is a question mark whereas the shape of the right sharpening members is a fishhook.

Figure 4 shows the invention in the format of individually hinged parallel abrasive elements, arranged in two opposing banks, hinged at top (left drawing) and bottom (right drawing). The drawings show four abrasive elements in each bank. Interestingly, hinges of both abrasive members of the blade sharpener of the invention represented on Figure 4b are mingled as a single rod.

The hinged abrasive elements of this embodiment are individual rigid parallel abrasive plates 1 1 , 12, 13, 18 and 21 , 22, 23, 28. The main surface of the abrasive plates 1 1 , 1 2, 13, 18 and 21 , 22, 23, 28 is perpendicular to the hinges 1 5, 25 axes and to the length of the groove G, in contrast with the embodiments of Figures 1 -3 where the plate was parallel to the hinges 1 5, 25 axes.

Figures 4a and 4b also illustrate the meaning of the words "parallel" and "interleaved" applied to abrasive elements. The different spaced abrasive elements 1 1 , 1 2, 13 (or 21 , 22, 23) have a same inward shape, a same position in space and are aligned, such that they each provide a surface as shown in the figures. In other terms, the surface defined by the inner edges of abrasive elements 1 1 and 12 and the surface defined by the inner edges of abrasive elements 12 and 13 or 1 1 and 13 are superimposed. Said surfaces of each series of abrasive elements provide there between a groove G where a blade can be drawn for honing.

Figure 5 shows a blade 10 with concave prints in honing position in the groove between two abrasive members 10, 20 of Figure 4a, each comprising four individual abrasive elements, 1 1 , 12, 13, 18 and 21 , 22, 23, 28 respectively. Upon honing and downwards pressure of the blade, blades tend to repel the hinged sharpening members.

Figure 6 shows a lateral view of each of top and bottom hinged individual abrasive elements of Figures 4a and 4b. On this view the shape of an individual abrasive element of Figures 4b is the shape of a finger. Since the different spaced abrasive elements 1 1 , 12, 13 (or 21 , 22, 23) have a same inward shape, a same position in space and are aligned, such that they each provide a surface only each left and right first abrasive plate is seen.

Figure 7 shows detail of three preferred cutting edge shapes for two-sided blade edges. Figure 7 additionally shows the general type of cam profiles of the blade sharpener of Figure 4a with top-hinged abrasive members that may generate those edges. Not shown is the possibility of combining any of these edge styles or other styles asymmetrically, so that one side of the blade has a different shape to the other.

Figure 8 shows a traditional Japanese style edge, also named chisel edge or single bevel edge (left drawing), and a lateral view of a blade sharpener of the invention with one guiding member and one sharpening member hinged on the stationary frame (right drawing).

This type of abrasive members cam profile that may be used to generate an edge such as represented on the left drawing. This type of edge typically has a very small and fine final cutting edge, "A", for durability, a larger main bevel, "B", and bevels may be only one or several. To obtain the nominally flat side of the blade, a nominally flat vertical guide or guides, "C", may be provided on one side, with or without abrasive or low friction properties, while the bevelled side is generated abrasive elements, like "D" shown here or other types described in this document, hinged at top, "E", or bottom. Shown is one possible cam profile with two distinct different angled zones that may generate both a small (A) and large bevel (B) as the blade travels down through these zones (while also being swiped forward or back between the abrasive elements as described in this document).

The structure of this blade sharpener of the invention differs from the structure of this blade sharpener of Figure 4a or Figure 5 in that there is a single hinged abrasive member 10. The structure of this hinged abrasive member 10 is similar to that of figure 4a or 5 and comprises four parallel plates as abrasive elements.

The left elements 21 that have the effect of a guiding member 21 are not hinged but are interleaved with the hinged abrasive elements 1 1 , etc. The left elements 21 etc. are bifunctional because they may be provided with an inwards abrasive surface. They provide an inwards surface (right vertical surface on the drawing) which may be flat as represented, or slightly concave (for example a radius of concavity of 1 m to 0.3 m).

Upon honing and downwards pressure of the blade, blades tend to repel the hinged sharpening member 1 0. Therefore, spring means 40 are provided at a bottom part of the abrasive elements between said abrasive elements and stationary frame 41 for limiting pivoting amplitude. Individual springs may be provided for each abrasive element or preferably a single spring means effective on all the abrasive elements.

Figure 9 represents a perspective view of a blade 30 of a single bevel knife located in contact with a blade sharpener provided with a single hinged sharpening member 1 1 arranged in an overlapping arrangement relative to an abrasive guiding member 21 .

The blade sharpener comprises a guiding member 21 and a sharpening member 1 1 hinged on a stationary frame 41 schematized in figure 10. The guiding member 21 comprises a plate provided parallel to the hinge axis of pin 15 and is abrasive. In this embodiment, the hinged sharpening member 1 1 having a pin 15 providing a hinge axis is fastened to a stationary part of a frame 41 of a sheath facing the front side of the blade 30. The hinged sharpening member 1 1 may pivot about the pin 15. Therefore a honing is provided by the hinged sharpening member 1 1 and by the abrasive guiding member 21 . The cutting edge 32 is therefore provided with two bevels. The hinged sharpening member 1 1 also functions as a de-burring element. The hinged sharpening member 1 1 may comprise several rigid abrasive elements, particularly parallel plates 1 1 , 12, 13, 1 8 as shown on figures 4, 5 or 6. Rather than being provided at an end of the guiding member/abrasive plate 21 , the hinged sharpening member 10 may be partly introduced in a slot of a corresponding size provided in the guiding member 21 . When the hinged sharpening member 1 1 comprises several rigid abrasive elements, said elements are preferably interleaved with a series of corresponding slots similar to the space between two adjacent abrasive elements represented on the left of figures 4a or 4b.

Figure 10 is a perspective view similar to the view of figure 9, further showing a sheath 41 to which sharpening member 1 1 is hinged.

Claims

1 . A method for sharpening a blade comprising the steps consisting in

- providing a blade (30)

- providing a blade sharpener comprising

• a stationary frame (41 )

• a hinged sharpening member (10) wherein the sharpening member is hinged on the stationary frame (41 ) for allowing the pivoting of the sharpening member (10) about a hinge axis (31 ), wherein the hinged sharpening member (10) comprises

a single inflexible abrasive element (1 1 ) arranged in an overlapping arrangement relative to a guiding member (21 ) or

a plurality of inflexible abrasive elements (1 1 , 12, 13), wherein the inflexible abrasive elements (1 1 , 12, 1 3) are arranged in an overlapping arrangement relative either to a guiding member (21 ) or to a second hinged sharpening member (20) provided with parallel inflexible abrasive elements (21 , 22, 23) elements or independently pivoting parallel inflexible abrasive elements, wherein abrasive means are provided on a portion of inwardly directed, opposed, sharpening faces on the inflexible abrasive elements (1 1 , 1 2, 13, 21 , 22, 23), so that the guiding member (21 ) and the hinged sharpening abrasive member element (1 0) or the two opposed and hinged sharpening abrasive members (10, 20) form a groove (G) having sharpening faces and are operable to engage a cutting edge on a blade (30) for example of a knife.

- drawing the blade (30) in the groove (G) between the guiding member

(21 ) and the hinged sharpening abrasive member element (10) or between the two opposed and hinged sharpening abrasive members (10, 20), for honing the blade (30).

2. A method according to claim 1 , wherein the hinged sharpening member (10) comprises a plurality of parallel inflexible abrasive elements (1 1 , 12, 13), wherein the parallel inflexible abrasive elements (1 1 , 12, 13) are arranged in an overlapping arrangement relative to a second hinged sharpening member (20) provided with parallel inflexible abrasive elements (21 , 22, 23), wherein the hinges axis (31 ) of the sharpening members are parallel.

3. A method according to claim 1 , wherein the hinged sharpening member (1 0) comprises a single inflexible abrasive element (1 1 ) arranged in an overlapping arrangement relative to a guiding member (21 ).

4. A method according to claim 1 , wherein the hinged sharpening member (10) comprises a plurality of parallel inflexible abrasive elements (1 1 , 12, 13), wherein the parallel inflexible abrasive elements (1 1 , 12, 13) are arranged in an overlapping arrangement relative to a guiding member (21 )

5. A method according to one of claims 1 to 5, wherein the hinged sharpening member (1 0) comprises parallel inflexible abrasive elements (1 1 , 12, 1 3) arranged in an overlapping arrangement relative to a second hinged sharpening member (20) provided with parallel inflexible abrasive elements (21 , 22, 23), wherein the edges of said parallel inflexible elements facing the parallel inflexible abrasive elements of the hinged sharpening member (10) define a surface which is flat or concave.

6. A method according to one of claims 1 to 5, wherein each of the sharpening or guiding members comprises 2 to 5 elements.

7. A method according to any one of claims 1 to 6, wherein the hinge of the sharpening member or members is provided at a top part of the abrasive elements.

8. A method according to any one of claims 1 to 7, wherein a device limiting pivoting amplitude of the sharpening member or members is provided.

9. A blade sharpener comprising

• a stationary frame (41 )

a plurality of inflexible abrasive elements (1 1 , 1 2, 13, 21 , 22, 23), wherein the inflexible abrasive elements (1 1 , 12, 13, 21 , 22, 23) are arranged in an overlapping arrangement relative either to a guiding member (21 ) or to a second hinged sharpening member (20),

wherein abrasive means are provided on a portion of inwardly directed, opposed, sharpening faces on the inflexible abrasive elements (1 1 , 12, 13, 21 , 22, 23), so that the guiding member (21 ) and the hinged sharpening abrasive member element (1 0) or the two opposed and hinged sharpening abrasive members (10, 20) form a groove (G) having sharpening faces and are operable to engage a cutting edge on a blade (30) for example of a knife.

10. A blade sharpener according to claim 9, wherein the inflexible abrasive elements (1 1 , 12, 13, 21 , 22, 23) are parallel and wherein the hinge axis (31 ) of each of the hinged sharpening abrasive members (1 0, 20) is parallel to a cutting edge of the blade (30), in a vertical plane, during honing

1 1 . A blade sharpener according to claim 9, wherein the hinged sharpening abrasive member or a plurality of members oppose a convex or concave or nominally flat plate, allowing a side of the blade with a nominally flat face to slide along the plate, while the opposite side of the blade with angled bevel or bevels is honed or sharpened by the hinged sharpening abrasive member or members.