The present disclosure relates to a magnetic sharpening jig, in particular for holding, by magnetic force, a cutting tool with a magnetizable blade to be sharpened or polished and for positioning the same with respect to a sharpening and/or polishing tool such as a rolling sharpener.
A generic magnetic sharpening jig is known from DE 20 2020 001 180 U1. A rolling sharpener is known, for example, from EP 3 278 928 A.
The magnetic sharpening jig known from the prior art is adapted to specific blade dimensions and comprises two contact sides. Blades with a greater blade height are intended to contact one contact side of the magnetic sharpening jig and are supported backwards on the planar base so that the cutting edge of the cutting tool to be sharpened or polished projects beyond the upper side of the magnetic sharpening jig and is accessible for processing with the rolling sharpener. For blades with a lower blade height, a step is provided on the other contact side of the magnetic sharpening jig, on which the blade back can rest so that the cutting edge projects beyond the top of the magnetic sharpening jig and is accessible for processing with the rolling sharpener. The step for supporting the blade on the rear side is necessary with this magnetic sharpening jig to ensure a secure hold on the magnetic sharpening jig even when high forces are applied to the blade during the sharpening or polishing process.
Embodiments discussed herein provide a magnetic sharpening jig which can be used in a more versatile manner and with which blades of different sizes and geometries can be positioned reliably on the magnetic sharpening jig.
The magnetic sharpening jig according to embodiments discussed herein serves in particular for holding a cutting tool to be sharpened or polished with a magnetizable blade by means of magnetic force and for positioning the same relative to a sharpening and/or polishing tool such as a rolling sharpener. In some embodiments, the magnetic sharpening jig has at least one flexible contact element with which the magnetically attracted blade of the cutting tool comes into contact as intended.
An advantage of embodiments discussed herein compared to the prior art is essentially that the flexible contact element significantly increases the static friction of the blade on the magnetic sharpening jig. The static friction of the blade on the magnetic sharpening jig is largely defined by the magnetic holding force and the static friction coefficient of the contact element. The flexible contact element has a very high static friction coefficient with respect to the magnetizable blade, in particular made of metal. The static friction coefficient of the flexible contact element compared to the magnetizable blade is usually significantly higher than that of the body of the magnetic sharpening jig, which is made of wood, plastic or metal, for example. Due to its flexibility, the contact element adapts ideally to the surface of the blade and, if necessary, ensures extensive contact with the blade while compensating for unevenness. This further improves the static friction between the contact element and the blade. Due to the flexible contact element, the blade of the cutting tool can be held on the magnetic sharpening jig by magnetic force alone, even without a rear side support or step. Even when force is applied to the blade with the sharpening and/or polishing tool in the course of the sharpening or polishing process, the blade remains fixed in the intended holding position on the magnetic sharpening jig. The flexible contact element thus considerably improves the static friction and holding properties of the magnetic sharpening jig. Relative movement between the magnetic sharpening jig and the blade of the cutting tool is prevented by the flexible contact element. This prevents damage to the blade, such as scratches. In addition, the flexible contact element ensures damping of the impact when the blade of the cutting tool is magnetically attracted to a body of the magnetic sharpening jig. In this case, the flexible contact element ensures a better contact noise and a better contact response to the body of the magnetic sharpening jig.
It can be advantageous if the contact element is made of plastic, preferably an elastomer, preferably a vulcanizate of natural rubber or silicone rubber (silicone). Silicone is an inexpensively available material with excellent static friction and damping properties. For the present application, a contact element made of silicone proves to be optimal. However, the flexible contact element can also be, for example, a metal plate with rubber coating or vulcanized surface or a sprayed-on coating.
It may prove useful if the contact element has a Shore A hardness in the range 1 to 90, preferably in the range 20 to 40. In principle, the static friction coefficient of the contact element increases with decreasing Shore A hardness. On the other hand, the load-bearing capacity and dimensional stability of the contact element increase with increasing Shore A hardness. A contact element with low Shore A hardness, for example in the range of 20 to 40, in particular in the range of 20 to 30, proves to be optimal. The Shore A hardness is preferably measured according to DIN EN ISO 868, DIN ISO 7619-1 and ASTM D2240-00.
It may prove helpful if the magnetic sharpening jig has a body on which the contact element is arranged, wherein preferably the body of the magnetic sharpening jig is partly or entirely made of wood and/or plastic and/or metal.
It can be useful if the contact element has a higher flexibility than the body and/or a magnet of the magnetic sharpening jig. In this way, the contact element dampens a contact impact between the blade and the body and/or magnet of the magnetic sharpening jig.
It can be useful for the magnetic sharpening jig to have at least one contact side on which the contact element is arranged, wherein the contact element covers the contact side in sections or covers the entire surface. In this way, unintentional contact of the blade with the body of the magnetic sharpening jig can be prevented. In addition, the contact element can be colored and used as a decorative element on the body of the magnetic sharpening jig.
It may prove practical if the magnetic sharpening jig has at least one magnet for generating the magnetic force, wherein the contact element covers one, several or all magnet(s) of the magnetic sharpening jig in sections or covers the entire surface (preferably such that the magnet is not visible). In this way, unintentional contact of the blade with the magnet can be prevented.
It may be helpful if the contact element is configured to elastically deform under the action of the magnetically attracted cutting tool, preferably to form a negative shape for a portion of the blade of the cutting tool in contact with the contact element. In particular, this allows the magnetically attracted blade of the cutting tool to be pressed into the contact element under elastic deformation of the latter and thus to be held not only frictionally but also positively on the contact element if necessary. In particular, if the back of the magnetically sharpened blade runs across the contact element, the back of the blade can “dig” into the contact element. A step supporting the rear side of the blade can form below the back of the blade. In this way, the blade can be held securely with the magnetic sharpening jig even when considerable force is applied by a sharpening or polishing tool. For this purpose, it is useful if the contact element projects from a planar contact side of a body of the magnetic sharpening jig so that the body of the magnetic sharpening jig does not interfere with elastic deformation of the contact element by the magnetically attracted blade.
It may be preferred if the contact element is configured such that contact between the magnetically attracted cutting tool and a body of the magnetic sharpening jig and/or at least one magnet of the magnetic sharpening jig is partially or completely prevented. This prevents the magnetically attracted blade of the cutting tool from being scratched or otherwise damaged.
It can be useful if the contact element has a planar contact surface for the blade of the cutting tool. This allows the blade to be positioned freely relative to the contact surface.
It may prove useful if the contact element has at least one marking which preferably indicates the amount of a sharpening angle, wherein the marking is preferably formed as a recess in the contact surface of the contact element, wherein the marking is particularly preferably arranged centrally in the contact surface. The marking facilitates the operation of the magnetic sharpening jig for a user. Particularly in the case of a magnetic sharpening jig with several different contact sides, the marking makes it easier for the user to find a contact side with a suitable sharpening angle.
It may be useful if the magnetic sharpening jig comprises a plurality of contact elements, preferably arranged on different, preferably on contact sides of a body of the magnetic sharpening jig facing away from or opposite to each other, wherein the contact elements preferably include different acute angles with an installation plane of the magnetic sharpening jig. The sharpening angle, which is preferably measured between the surface of the contact element (or contact surface) and a plane aligned perpendicular to the base, is preferably in the range between 15° and 20°. The sharpening surface of a rolling sharpener is usually aligned in a plane perpendicular to the base. The angle between the contact surface of the contact element and the base is preferably in the range between 70° and 75°.
Another aspect relates to a set comprising a magnetic sharpening jig according to one of the preceding embodiments and a rolling sharpener, preferably a rolling sharpener according to EP 3 278 928 A. Such a rolling sharpener is movable in a rolling manner over a base and has at least one end-face sharpening or polishing surface.
Still another aspect relates to a method of sharpening or polishing a cutting tool using the magnetic sharpening jig according to one of the preceding embodiments, comprising the steps of:
Step A preferably involves a horizontally aligned, planar base, e.g. a tabletop or kitchen countertop. A cutting tool with magnetizable blade in the sense of step B is, for example, a conventional kitchen knife with stainless steel blade. In step C, the blade of the magnetizable blade is preferably aligned parallel to the contact surface, as shown in
It can be advantageous if the blade is arranged in step C such that the blade is spaced apart from the base and/or the cutting edge is facing away from the base. This makes the blade easily accessible for machining.
The contact element of the magnetic sharpening jig preferably has at least one of the following features:
The contact element is molded onto a body and/or a magnet of the magnetic sharpening jig. A body of the magnetic sharpening jig preferably has at least one of the following features:
A magnet of the magnetic sharpening jig preferably has at least one of the following features:
An installation section of the magnetic sharpening jig preferably has at least one of the following features:
Further preferred embodiments result from combinations of the features disclosed, the description, and the drawings.
The magnetic sharpening jig 1 serves for holding, by magnetic force, a cutting tool 2 to be sharpened or polished with a magnetizable blade 2a and for positioning the same relative to a sharpening and/or polishing tool such as a rolling sharpener 3. The magnetic sharpening jig 1 comprises at least one flexible contact element 4 with which the magnetically attracted blade 2a of the cutting tool 2 comes into contact as intended. The magnetic sharpening jig 1 is independent of the cutting tool 2 and its blade 2a. Therefore, the description focuses on the magnetic sharpening jig 1, in which the blade of the cutting tool 2 contacts the contact element 4 in a planar manner, as is clearly shown in
The magnetic sharpening jig 1 is adapted in particular for positioning cutting tools 2 in the form of kitchen knives. Kitchen knives often have a stainless steel blade 2a with an approximately planar blade and a slightly curved, one-sided cutting edge 2b. However, it is possible in principle that, apart from kitchen knives, other cutting tools 2 can also be positioned with the magnetic sharpening jig 1.
The shape of the cutting tool 2 and the blade 2a are therefore not decisive. The advantage of the magnetic sharpening jig 1 lies precisely in the fact that it can be used universally for different blade sizes and geometries.
Preferred embodiments are explained below with reference to the Figures.
The magnetic sharpening jig 1 according to the first embodiment is described below with reference to
The magnetic sharpening jig 1 comprises an approximately cuboidal body 5, which has a trapezoidal cross-section in a cross-sectional plane intersecting the contact element 4 perpendicularly (parallel to the blade plane or drawing surface) as shown in
On the lower side of the body 5, flexible installation sections 7 are located in the corner regions in each case and are inserted in a frictional manner into corresponding openings on the lower side of the body 5. Each installation section 7 is configured as a plastic plug and comprises a head and a shaft projecting from the head with a fir-tree structure, wherein the individual holding ribs have a saw-tooth structure in cross-section. The holding ribs are wedge-shaped and taper towards the end of the shaft projecting from the head. The flanks of the shaft and the holding ribs attached to it are inclined in the insertion direction, i.e. towards the end of the shaft facing away from the head, at a smaller angle to the shaft axis than in the opposite direction. Accordingly, a force to insert the shaft into the corresponding opening of the body 5 is less than a force required to withdraw it again from this opening. The plastic plug is preferably made of silicone and preferably has a Shore A hardness in the range of 40 to 60.
In a state in which the installation sections 7 are inserted into the cylindrical recesses on the lower side of the body 5 and are positioned there in a frictional manner, the slightly rounded heads of these installation sections 7 project beyond the lower side of the body 5 of the magnetic sharpening jig 1 and define an installation plane E for setting up the magnetic sharpening jig 1 on a flat base U (see
The body 5 of the magnetic sharpening jig 1 is preferably made of untreated or varnished wood (e.g. oak, walnut, beech or spruce) and preferably has exclusively planar sides. The edges on the lower side of the body 5 are preferably more weakly chamfered or rounded than the other edges of the body 5.
In the first embodiment, the body 5 of the magnetic sharpening jig 1 has a length L of approx. 82 mm (measured at the top), a height H of approx. 22 mm and a width B of approx. 56 mm. Including the installation sections 7, the height H1 of the magnetic sharpening jig 1 is approximately 25 mm.
The side of the body 5 that faces the positioning plane E of the magnetic sharpening jig 1 and forms an acute angle (90°—α1) of, for example, 70° with it, forms the contact side 8 of the magnetic sharpening jig 1. The sharpening angle α1 formed on this side of the magnetic sharpening jig 1 is 20° and corresponds to the angle between the contact side 8 and a vertical sharpening plane S aligned perpendicular to the positioning plane E, in which the sharpening or polishing surface of a rolling sharpener 3 is located and moves. In this embodiment, the side of the body 5 opposite the contact side 8 is aligned parallel to the sharpening plane S.
Two, preferably cylindrical, bores are made in the contact side 8 of the body 5, into which correspondingly shaped, cylindrical magnets 6 are inserted with a precise fit in order to be flush with the contact side 8 of the body 5 at the end face.
The contact side 8 of the body 5 and the outward-facing end faces of the magnets 6 inserted in the bores are covered and bonded over their entire surface by an flexible silicone contact element 4 with a rectangular outline. The contact element 4 has a thickness in the range of, for example, 0.5 mm and a Shore A hardness of, for example, 30. On its side facing away from the body 5, the contact element 4 forms a planar contact surface for the blade 2a of the cutting tool 2, against which the blade can ideally abut over the entire surface without the cutting tool 2 coming into contact with the body 5 of the magnetic sharpening jig 1. Optionally, a marking for indicating the amount (“20°”) of the respective contact angle α1 is provided on the contact surface of the contact element 4, e.g. it is worked into the center of the contact element 8 as a recess. Marking in the form of an imprint is also possible.
To sharpen or polish a cutting tool 2 with the magnetic sharpening jig 1, the magnetic sharpening jig 1 is placed with the installation sections 7 on a planar base U (step A). A provided cutting tool 2 with magnetizable blade 2a and cutting edge 2b, such as a kitchen knife with stainless steel blade (step B), is arranged with its magnetizable blade 2a in the magnetic field of the magnetic sharpening jig 1 as intended in such a way that the blade is aligned parallel to the contact surface of the contact element 4 and only the magnetically attracted blade 2a comes into (full) surface contact with the contact element 4. The cutting edge 2b faces away from the base U and the blade 2a is spaced apart from the base U. The blade 2a is thus held in contact with the contact element 4 solely by the magnet force of the magnetic sharpening jig 1. The flexible contact element 4 is elastically deformed by the blade 2a under the influence of the magnetic force until a force equilibrium is reached between the flexible restoring force of the contact element 4 and the magnetic force of the magnetic sharpening jig 1 exerted on the blade 2a. With a correspondingly soft and flexible contact element 4, the magnetically attracted blade 2a presses into the contact element 4. If the back of the blade runs across the contact element 4, a step is formed on the rear side of the blade 2a due to the elastic deformation of the contact element 4, which makes it even more difficult for the blade 2a held in contact with the contact element 4 to move. In this state, the blade 2a of the cutting tool 2 is machined with the rolling sharpener 3 with at least one end-face sharpening or polishing surface. The rolling sharpener 3 rolls horizontally over the flat base U and is held in contact with the cutting edge 2b of the blade 2a of the cutting tool 2 with the grinding or polishing surface aligned in a vertical plane. The direction of movement of the rolling sharpener 3 is approximately parallel to the extension direction of the blade. The sharpening angle α is defined by the plane of extension of the blade held in contact with the contact element 4 as intended and the vertical plane of the sharpening or polishing surface of the rolling sharpener 3.
In the second embodiment, described below with reference to
In the second embodiment, the body 5 of the magnetic sharpening jig 1 has a length L of approx. 112 mm (measured at the top), a height H of approx. 22 mm and a width B of approx. 56 mm. Including the installation sections 7, the height H1 of the magnetic sharpening jig 1 is approximately 25 mm.
Number | Date | Country | Kind |
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10 2020 123 500.3 | Sep 2020 | DE | national |
The present application is a U.S. National Phase of International Application No. PCT/EP2021/074644, filed Sep. 8, 2021, which claims priority to German Application No. 10 2020 123 500.3, filed Sep. 9, 2020.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2021/074644 | 9/8/2021 | WO |