FIELD OF THE DISCLOSURE

The present disclosure relates to sharpening knives, and more particularly to a grinding element for a knife sharpener. The present disclosure further concerns a knife sharpener having such a grinding element.

BACKGROUND OF THE DISCLOSURE

A conventional way of sharpening a knife is to grind the cutting edge thereof against a grinding stone at a desired angle, so as to obtain a desired blade geometry, i.e., bevel angle(s). Typically, the grinding is done in multiple steps moving from coarse grinding stones to finer ones so that a sufficient sharpness is achieved. However, this conventional way of sharpening is often perceived as relatively challenging task to be carried out correctly.

To this end, dedicated knife sharpeners have been developed, where a knife is sharpened by moving it along the longitudinal direction of the blade, such that a cutting edge of the knife acts upon the grinding element causing it to rotate. Such knife sharpeners are very easy to use but leave room for improvement. Particularly, obtaining sufficient material removal from the blade so as to achieve a desired blade geometry requires numerous passes of the knife over the grinding element. On the other hand, if the coarseness of the grinding element is increased so as to obtain more efficient grinding action, the obtainable sharpness decreases.

For example, publications US 2469797 A, US3691700 A and US 2011244767 A1 disclose knife sharpeners according to the prior art.

BRIEF DESCRIPTION OF THE DISCLOSURE

An object of the present disclosure is to provide a grinding element for a knife sharpener which allows easy sharpening of a knife, while obtaining improved sharpness quicker than with conventional sharpeners. It is a further object of the present disclosure to provide a knife sharpener with such a grinding element.

The objects of this disclosure are achieved by a grinding element and a knife sharpener which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

According to a first aspect of the present disclosure, a grinding element for a knife sharpener is provided. Particularly, the grinding element of the first aspect of the present disclosure is intended for use in a knife sharpener of the type, where a knife is sharpened by moving it along a feed axis of the sharpener, such that the cutting edge of the knife acts upon the grinding element, causing it to rotate.

The grinding element comprises a body defining a central axis, and having a radially outwardly opening annular groove extending about said central axis around the whole circumference of the body.

Preferably, but not necessarily, the annular groove is arranged concentric with the central axis.

Moreover, the annular groove defines a trough as a radially innermost part of the groove and a pair of annular side surfaces co-axial with the central axis. Suitably, the trough is radially offset from the central axis. The side surfaces are arranged on opposing sides of the trough facing each other, and inclined with respect the central axis. Suitably, the side surfaces are arranged symmetric with respect to each other about the trough.

Particularly, the inclinations of the side surfaces with respect to a normal of the central axis are less at a radially outer portion of the side surfaces than at a radially inner portion of the side surfaces.

This provides improved sharpening characteristics for the grinding element, as the radially inner portion of the side surfaces will grind a secondary bevel on the cutting edge of the knife, while the radially outer portion of the side surfaces will grind a primary bevel for a distance from the secondary bevel towards the spine of the blade, such that the bevel angle of the secondary bevel is greater than that of the primary bevel. Such a blade geometry has been found to be beneficial for the cutting properties of the associated knife, and to allow expediting of the sharpening process.

Preferably, but not necessarily, at least a part of the side surfaces intended to be in contact with a cutting edge of a knife when in use, are arranged to be abrasive so as to constitute abrasive surfaces. This can be done, for example, by providing the side surfaces with an abrasive material (such as an abrasive coating), an abrasive surface texture, or by providing the side surfaces themselves of an abrasive material. Naturally, any combination of these may be provided in order to achieve desired grinding characteristics.

According to an embodiment of the first aspect of the present disclosure, the side surfaces constitute abrasive surfaces, such that the abrasive surfaces are less coarse (i.e. , finer) at a radially inner portion of the side surfaces than at a radially outer portion of the side surfaces. Consequently, the primary bevel of a blade is sharpened more aggressively with the coarser portion of the side surfaces, while the secondary bevel of the cutting edge will be sharpened with the finer portion of the side surfaces. As a result, a desired geometry of the blade and a sharp cutting edge is obtained simultaneously.

According to an embodiment of the first aspect of the present disclosure, the radially outer portion of the inner surfaces constitutes abrasive surfaces of a first coarseness corresponding to a grit size of between 150-400, suitably 300, whereas the inner portion of the side surfaces constitutes abrasive surfaces of a second coarseness corresponding to a grit size of between 600-1500, suitably 800.

Such respective coarseness of the radially inner and outer portions has been found to provide a suitable combination of both sharpening efficiency and obtained sharpness.

According to an embodiment of the first aspect of the present disclosure, the annular side surfaces define, at a radially inner portion thereof, a first pair of opposing frustoconical surfaces having a first angle of inclination with respect to the normal of the central axis. Moreover, the annular side surfaces define, at a radially outer portion of the annular side surfaces, a second pair of opposing frustoconical surfaces having a second angle of inclination with respect to the normal of the central axis, Particularly, the first angle of inclination differs from the second angle of inclination.

Preferably, but not necessarily, the first angle of inclination is 1 -3 degrees, suitably 2 degrees greater than second angle of inclination.

Preferably but not necessarily, the first angle of inclination is 20-24 deg, suitably 22 deg, whereas the second angle of inclination is 18-22 deg, suitably 20 deg.

Preferably but not necessarily, the first frustoconical surfaces extend in a direction radially away from the central axis for a first radial distance, and the second frustoconical surfaces extend in a direction radially away from the central axis for a second radial distance, wherein the first radial distance most suitably corresponds to the second radial distance. That is, the respective radial dimensions of the first frustoconical surfaces and the second frustoconical surfaces are suitably equal.

Preferably but not necessarily, the radially innermost point of first frustoconical surface is offset from the central axis by a first radial offset, suitably corresponding to the first radial distance. That is, the respective radial dimensions of the trough of the groove and the first frustoconical surfaces are suitably equal. Naturally other types of relative dimensions and/or geometries of the side surface may be used. For example, the side surfaces may be provided with additional opposing frustoconical surfaces. Alternatively, the side surfaces may be provided as curved surfaces, such as a hyperboloid surface

According to an embodiment of the first aspect of the present disclosure, the grinding element may comprise projections at the opposing ends of the body along and concentric with the central axis. Particularly, the projections are suitably arranged such that the grinding element may be supported form the projections in a translationally fixed manner, while allowing rotation of the grinding element about its respective central axis.

The first aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

According to a second aspect of the present disclosure, a knife sharpener is provided. The knife sharpener comprises a base section for supporting the knife sharpener on a planar surface, a handle section for a user to hold the knife sharpener in place, and an operating section for holding a grinding element.

The knife sharpener further comprises a grinding element supported at the operating section in a translationally fixed manner, while allowing rotation of the grinding element about its respective central axis.

The knife sharpener is further configured such that, upon movement along a feed axis, at least a cutting edge of a knife acts upon the grinding element, thereby grinding the cutting edge.

Particularly, the grinding element is provided according to the first aspect of the present disclosure, as described above, and is supported at the operating section in a translationally fixed manner, while allowing rotation of the grinding element about its respective central axis.

Preferably, but not necessarily, the feed axis is inclined with respect to the normal of the central axis of the grinding element at a feed angle of between 14-18 deg, suitably 16 deg.

This has been found to provide good operating characteristics for the knife sharpener, and results in suitable bevel angles for a sharpened blade, when a grinding element having a first angle of inclination and a second angle of inclination in the numerical ranges specified above in connection with the first aspect of the present disclosure is used. Preferably, but not necessarily, the knife sharpener has a longitudinal axis defined perpendicular to the intended feed axis, wherein the handle section and the operating section being arranged adjacent to each other along the longitudinal axis.

Preferably, but not necessarily, the knife sharpener comprises a guide for guiding a knife along the feed axis.

Preferably, but not necessarily, the knife sharpener comprises a magnet arranged at the operating section below the grinding element, when in use.

The second aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which:

Fig. 1 schematically illustrates a grinding element according to an embodiment of the present disclosure, as seen from a direction transverse to a central axis thereof;

Fig. 2 schematically illustrates a knife in operating configuration with respect to the grinding element of Fig. 1 ;

Fig. 3 and Fig. 4 schematically illustrate perspective views of a knife being sharpened with the grinding element according to an embodiment of the present disclosure;

Fig. 5a and Fig. 5b illustrates a knife sharpener according to an embodiment of the present disclosure in different configurations;

Fig. 6a illustrates a microscopic image of a knife sharpened with a conventional knife sharpener, and

Fig. 6b illustrates a microscopic image of a knife sharpened with a knife sharpener according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Fig. 1 is a schematic representation of a grinding element 1 according to an embodiment of the present disclosure. Particularly, the grinding element 1 has a body 2, on which an annular groove 3 is arranged to run around the whole body 2 about a central axis AC of the body 2. The groove 3 defines a trough 4 as a radially innermost portion thereof and side surfaces 5 on opposing sides of the trough 4.

The annular side surfaces 5 define a radially inner portion 5a and a radially outer portion 5b thereof. Particularly, the radially inner portion 5a of the opposing side surfaces 5 have an inclination A with respect to a normal N of the central axis AC. Correspondingly, the radially outer portion 5b of the opposing side surfaces 5 have an inclination B with respect to a normal N of the central axis AC. Particularly, the radially inner portion 5a has a greater inclination A than the inclination B of the radially outer portion 5b.

Although not illustrated, the first angle of inclination A is preferably between 20 - 24 deg, more preferably 22 deg, while the second angle of inclination is preferably between 18 - 22 deg, more preferably 20 deg.

The trough 4, i.e. the bottom of the groove 3 is radially offset from the central axis AC by a radial offset RO. Moreover, the radially inner portion 5a of the opposing side surfaces 5 extends for a first radial distance RD1 from the trough 4, whereas the radially outer portion 5b of the opposing side surfaces 5 extends for a second radial distance RD2 from the radially inner portion 5a. In the embodiments illustrates in Fig. 1 and Fig. 2, the first radial distance, second radial distance and the radial offset are substantially equal with each other, although other dimensioning may readily be used.

Moreover, in the illustrated embodiments, the side surfaces 5 are provided as a first pair of frustoconical surfaces 5a’ forming the radially inner portion 5a of the side surfaces 5, and a second pair of frustoconical surfaces 5b’ forming the radially outer portion 5b of the side surfaces 5.

The grinding element 1 also comprises projections 6 at the opposing ends of the body 2 along and concentric with the central axis AC. Particularly, the grinding element 1 may be supported form the projections 6 in a translationally fixed manner, while allowing rotation of the grinding 1 element about its respective central axis AC.

Fig. 2 illustrates a knife 11 in operating configuration with respect to the grinding element 1 of Fig. 1 , as seen from a spine side of the knife. Particularly, the knife 1 is fed along a feed axis AF, which is inclined at and feed angle C with respect to the normal N of the central axis AC. Although not illustrated, the feed angle is preferably 14 - 18 deg, more preferably 16 deg.

Particularly, the feed axis AF and the inclinations A, B of the radially inner and radially outer portions 5a, 5b are arranged such that the cutting edge 11 of the knife contacts the opposing side surfaces 5 of the annular groove 3, thereby grinding the cutting edge and sharpening the knife. Most suitably, the feed axis AF and the inclinations A, B of the radially inner and radially outer portions 5a, 5b are arranged such that a cutting edge point of contact PA, corresponding to a secondary bevel of the cutting edge 11 a, engages with the radially inner portion 5a of the grinding element 1 , while a cutting edge point of contact PB, corresponding to a primary bevel of the cutting edge 11 a, engages with the radially outer portion 5b of the grinding element 1 .

Fig. 3 illustrates a view from a perspective showing a cutting edge point of contact PA corresponding to a secondary bevel of the cutting edge 11 a, which engages with the radially inner portion 5a of the grinding element 1 . Correspondingly, Fig. 4 illustrates a view from a perspective showing a cutting edge point of contact PB corresponding to a primary bevel of the cutting edge 11 a, which engages with the radially outer portion 5b of the grinding element 1. Particularly, Figs. 3 and 4 illustrate different views of the same situation. That is, a secondary bevel and a primary bevel of the knife contact the grinding element simultaneously.

As a secondary bevel is suitably ground to a finer finish (i.e. sharper) than the primary bevel (more coarse), the radially inner portion 5a of the opposing side surfaces 5 is suitably provided with an abrasive surface corresponding to a finer grit size. Correspondingly, the radially outer portion 5b of the side surfaces 5 is suitably provided with an abrasive surface corresponding to a more coarse grit size.

Fig. 5a and Fig. 5b illustrate a knife sharpener 7 according to an embodiment of the present disclosure. The knife sharpener 7 comprises a base section 8, on which the knife sharpener is intended to be supported on a planar surface. The knife sharpener 7 further comprises a handle section 9 for a user to securely hold the sharpener 7 in place.

Moreover, the knife sharpener 7 comprises an operating section 10 in which the grinding element 1 is supported in translationally fixed manner, while allowing rotation thereof about its central axis AC. Suitably, the operating section 10 is arranged adjacent to the handle section 9 along a longitudinal axis AL of the knife sharpener 7.

Although not illustrated, the knife sharpener has an intended feed axis AF perpendicular to the longitudinal axis AL thereof, while the grinding element 1 being support such that the feed axis AF is inclined with respect to the normal of the grinding element’s central axis AC.

Moreover, in order to facilitate feeding of a knife along a feed axis AF, the knife sharpener 7 is provided with a guide 12. The guide 12 has a slot in which a blade of a knife 11 is receivable in such that the cutting edge 11 a thereof engages with the grinding element 1 as described above.

For the purport of clarity, Fig. 5a illustrates a knife sharpener 7 with the guide 12 separated, whereas Fig. 5b illustrates the same with the guide 12 in place. Fig. 6a illustrates a microscopic image of a knife 11 ’ sharpened with a conventional knife sharpener. As clearly shown, a cutting edge 11 a’ with single bevel is achieved. Furthermore, in order to achieve a sufficiently quick sharpening procedure, a comparatively coarse abrasive surface is used, resulting respectively in a comparatively coarser sharpening result.

Fig. 6b illustrates a microscopic image of a knife sharpened with a knife sharpener 7 according to the present disclosure. Particularly, a cutting edge 11 a with a primary bevel (coarser) is achieved, ground by a radially outer portion 5b of the grinding element 1 . The coarseness of the primary bevel corresponds substantially to that of cutting edge 11 a’ of the comparative knife illustrated in Fig. 6a. The knife 11 a of Fig. 6b, however also exhibits a secondary bevel with a finer finish, ground by the radially inner portion 5a of the grinding element 1.

LIST OF REFERENCE NUMERALS

AC central axis

N normal to central axis

AF feed axis

AL longitudinal axis

PA cutting edge point of contact with radially inner portion

PB cutting edge point of contact with radially outer

A first angle of inclination

B second angle of inclination

C feed angle

RD1 first radial distance

RD2 second radial distance

RO radial offset

1 grinding element

2 body of grinding element 3 annular groove

4 trough of groove

5 annular side surfaces

5a radially inner portion of side surfaces 5a’ first pair of frustoconical side surfaces

5b radially outer portion of side surfaces

5b’ second pair of frustoconical side surfaces projections knife sharpener base section

9 handle section

10 operating section

11 knife

11 ’ comparative knife 11 a cutting edge of knife

11 a’ cutting edge of comparative knife

12 guide