Knife sharpener

Abstract

A knife sharpener comprising a base (1 ), a main arm (2), a sharpening arm (3), a carrier (4) for a sharpening element and a connecting element (5) for movable arms connection. The base (1) is equipped with a clamp (6) for removable attachment of the knife, the main arm (2) is attached to the base (1 ), and the carrier (4) is attached by the sharpening arm (3) slidingly in the axis (8) of the sharpening arm (3) in relation to the main arm (2). The sharpening arm (3) is connected to the main arm (2) by the connecting element (5) rotatably around the axis (9) of the arm connection, and the sharpening arm (3) is connected to the base (1 ) by the main arm (2) and the connecting element (5) rotatably around the axis (7) of the main arm (2). The sharpening arm (3) is further connected to the base (1) slidingly by the main arm (2) and the connecting element (5). The sharpening plane of the sharpener is perpendicular to the axis (9) of the arm connection, intersecting in relation to the axis (7) of the main arm (2) and parallel to the axis (8) of the sharpening arm (3).

Description

[0001] Knife Sharpener

[0002] Technical Field

[0003] The proposed solution concerns knife sharpening. Specifically, it applies to sharpeners with a base for holding a knife and with a movable arm with a sharpening element.

[0004] Background of the Invention

[0005] In the current state of technology, there are well-known knife sharpening devices in which the knife is mounted in a jaw on a stand designed to be placed on a table, wherein a sharpening stone is on a movable arm connected to a base rotatably. The blade is usually held horizontally and the sharpening stone slides on the arm, wherein the user manually ensures the actual sharpening by this sliding. An example of such a device is described in document CN214817110U.

[0006] A disadvantage of these well-known solutions is that the sharpening angle is adjusted by the vertical movement of the sharpening arm, wherein this angle is defined by resting the sharpening element against the knife itself. This results in several disadvantages - the angle gradually changes during the sharpening process as the material of the knife or sharpening stone wears down; for a sharpening stone of different thickness, the device needs to be re-adjusted to maintain the same sharpening angle; the sharpening angle may vary at different points along the blade; the sharpening angle may be influenced by how the knife is mounted in the stand's jaw, etc.

[0007] It would therefore be advisable to come up with a knife sharpener that would eliminate at least some of the disadvantages mentioned above, to allow more uniform sharpening of knives during sharpening and / or along the entire blade and to make sharpening easily repeatable, i.e. so that the same or different blade is sharpened in the same way the next time it is mounted.

[0008] Summary of the Invention

[0009] The shortcomings of the solutions known from the prior art are to some extent eliminated by a knife sharpener, which comprises a base, a main arm, a sharpening arm, a carrier for a sharpening element and a connecting element for movable connection of the arms. The base is equipped with a clamp for removable knife attachment. The base can be designed to be placed on a table or other surface, but it can also, alternatively or in addition, be designed to be held in hand during sharpening. The clamp can be a separate part of the base, separated, for example, from the stand or the grip, and the clamp can also be rotatable or sliding in relation to the rest of the base. However, it can also be a fixed and indistinguishable part of the base, or the entire base can be made up by the clamp.

[0010] The main arm is attached to the base. This rotational connection can be implemented, for example, by providing the base with a hole with a bearing and placing a round part of the main arm in this hole. The main arm and the form of the base or its clamp determines the plane of the base, which is perpendicular to the axis of the main arm and at least part of the cutting edge of the sharpened knife lies therein, or the axis of rotation of the jaw lies therein. The inclination between the sharpening plane, i.e. the plane in which the sharpening element moves and in which the ground part of the blade lies after sharpening, and the plane of the base is the sharpening angle a. Usually, this angle is around 20°, for example it can be within the interval of 10-30°. However, this invention can be implemented with any sharpening angle.

[0011] The carrier is attached by the sharpening arm slidingly in the axis of the sharpening arm in relation to the main arm. The carrier can be sliding along the main arm, but also the whole sharpening arm or a part thereof can be sliding in relation to the main arm - this sliding can then be defined by a connecting element. This sliding is then the main movement during sharpening - due this sliding, the sharpening element slides along the blade across the length of the blade. Preferably, the carrier is equipped with a mechanism for removable attachment of the sharpening element.

[0012] The sharpening arm is connected to the main arm by the connecting element rotatably around the axis of the arm connection. This axis is intersecting or skew and at the same time not perpendicular to the axis of the main arm and the axis of the sharpening arm. Its inclination determines the sharpening angle a. The connecting element can be implemented in a number of ways - it can be a piece of solid profile firmly connected at an angle to the main arm, wherein the sharpening arm is then rotatable at the other end of this piece of profile, but it can also be, for example, a relatively complex mechanism that allows to adjust the angle a by small increments, e.g. even by tenths of a degree. In addition to the rotary movement, the connecting element can also define sliding - in different variants, it can be, for example, the sliding of the carrier in the axis of the sharpening arm, the sliding between the main arm and the sharpening arm in the axis of the arm connection, the sliding in the axis of the main arm, etc.

[0013] The sharpening arm is connected to the base rotatably around the axis of the main arm - this is through the main arm and the connecting element. This means that the main arm can rotate relative to the base and / or the connecting element against the main arm, or the sharpening arm against the connecting element. The rotation of the connecting element in relation to the main arm may be more advantageous with regard to the bearings used, e.g. when using rolling sliding bearings between the main arm and the base, the rotation of the main arm in the base may be less advantageous and it is therefore advisable to set this rotation at the connecting element.

[0014] The sharpening arm is slidingly connected to the base through the main arm and the connecting element. Preferably, this sliding is non-perpendicular to the axis of the arm connection, i.e. the direction of this sliding of the sharpening arm relative to the base lies outside the sharpening plane (in each position of rotation of the sharpening plane around the axis of the main arm), so that by sliding the sharpening arm relative to the base, it is possible to move the sharpening plane relative to the blade. This sliding allows, among other things, to adjust the distance between the carrier and the clamp, e.g. to offset the carrier from the blade when a thicker sharpening element is used. This sliding is also involved in the sharpening itself. This may be sliding of the sharpening arm relative to the main arm and / or sliding of the main arm relative to the base - at least one sliding is required, and both may be allowed on the sharpener. The direction of this sliding can therefore be given by the axis of the main arm, the axis of the arm connection and in some variants it can be a sliding in different or another direction. The sliding between the main arm and the base (wherein the sharpening arm can then move along with the main arm) is more preferable.

[0015] The sharpening plane of the sharpener is perpendicular to the axis of the arm connection, intersecting in relation to the axis of the main arm and parallel to the axis of the sharpening arm. The parallelism of the sharpening plane to the axis of the sharpening arm basically means that the sharpening element moves along this plane, or that the functional surface thereof moves directly within it. The perpendicularity of the sharpening plane to the axis of the arm connection ensures that the direction of this axis also sets the direction of the sharpening plane, and thus the direction of sharpening and the inclination of the cutting edge. The intersecting of the sharpening plane relative to the axis of the main arm then allows for the sharpening itself - if this plane was perpendicular to the main arm, it would not be possible to create a uniform cutting edge on the blade independent of the blade attachment. The inclination of this intersecting firmly determines the sharpening angle.

[0016] The sharpening plane is therefore inclined by a set angle to the axis of the main arm during sharpening. At the same time, the sharpening plane can rotate (relative to the base, or the attached blade, around the axis of the main arm), so the intersection of the base plane with the sharpening plane also rotates (for blades with a planar cutting edge if they are attached straight, which is the most standard case in sharpening, the cutting edge is created at this intersection) - this rotation allows to maintain a constant sharpening angle along the entire blade and eliminates the dependence of the form of the ground blade on the attachment of the knife - the blade can be attached at different inclinations, in particular, it can be rotated differently in the plane of the base, and the present invention always allows the cutting edge to be sharpened in the same way at the set angle a. The said rotation of the sharpening plane around the axis of the main arm is variable during the sharpening and it is given by the resting of the sharpening element on the blade - i.e. the position and shape of the blade determines how the sharpening plane is rotated around the axis of the main arm (but not its angle to the axis of the main arm I to the plane of the base). Even a curved blade is sharpened uniformly by this sharpener at the given angle a along its entire length and regardless of how the user has attached the blade in the clamp.

[0017] In other words, the kinematics of sharpening can also be described in such a way that for a constant position of the sharpening arm slide relative to the base in the direction not perpendicular to the axis of the arm connection, the axis of the sharpening arm at all possible positions of rotation around the axis of the main arm defines a conical area with a top on the axis of the main arm, which has a circular intersection with the plane of the base. If the sharpening arm is prevented from sliding relative to the base in the direction outside the sharpening plane, this cone would also determine the shape of the blade - the cutting edge would be a part of the circle. The sliding of the sharpening arm then basically moves this cone along the axis of the main arm, so that by combining movements it is possible to create a cutting edge of any shape, and the ground blade has the desired shape. At any moment during sharpening, the rotation of the sharpening plane around the axis of the main arm and the sliding of the sharpening plane along the axis of the main arm is given by resting of the sharpening element on the blade. However, the inclination of the sharpening plane and thus the sharpening angle is not dependent on the resting on the blade. The sharpening element is therefore guided by the blade during sharpening, wherein the mutual mobility of the mentioned parts of the sharpener provides it with all the required clearance for this movement, but its inclination relative to the axis of the main arm (and thus the sharpening angle a) is secured and the blade does not affect it.

[0018] The advantage of this invention compared to sharpeners of the prior art is that the sharpening angle a is fixed during the sharpening (although it can be adjustable - but it does not change spontaneously during the sharpening, rather it can only be adjusted by the user's intervention before sharpening with regard to the desired angle on the blade). For known sharpeners, for example, the sharpening arm sliding along the main arm is adjusted (or analogous sliding given by a differently implemented parts), but the sharpening angle is not maintained. In the state of the art, this angle is determined by the resting of the sharpening element on the blade, so it is influenced by the thickness of the sharpening element and is influenced by the placement of the knife / blade in the clamp. Because of this, precision sharpening requires a significant level of knowledge and skill to attach the blade correctly. If the blade is removed from the clamp during sharpening, in the state of the art it must be returned in exactly the same position and orientation so that the sharpening can resume. Even so, the sharpening angle along the entire blade will not be the same (at least not for the general blade shape in the general attachment position; it is possible to find a blade shape which, in a certain exact attachment position in the sharpener, would be ground constantly and uniformly even in known sharpeners).

[0019] Sharpening according to the presented sharpener is therefore more precise and easier - the sharpening angle is constant along the entire blade and is not affected by the thickness of the sharpening stone or the rotation of the blade in the clamp.

[0020] The connecting element therefore preferably fixes the sharpening arm at a preset angle to the main arm, wherein the sharpening plane is fixed at a preset angle to the axis of the main arm. This angle determines the sharpening angle (in particular, it can be a preset angle of (90° - a) between the axis of the sharpening arm and the axis of the main arm). This fixation occurs during sharpening, but by user intervention, especially when switching to sharpening a different blade with a different angle on the blade, the angle can be readjusted so that the connecting element then fixes a different angle. Thus, fixing the angle here means that this angle does not change during sharpening and is not dependent on the sharpening element resting against the blade, and on the contrary, this fixed angle forces the blade to be ground along its entire length at the sharpening angle a without significant deviation.

[0021] This preset angle is therefore preferably adjustable. This allows the same sharpener to sharpen different blades with different desired sharpening angles. The adjustability can be given by several preset angles (for example, 2-8 options can be given, e.g. using the head described below), but it can also be continuous adjustment from a certain interval or adjustment with small increments. For example, the connecting element comprises a head comprising at least two holes with differently inclined axes, and comprises further a protrusion that can be removably attached in each of these at least two holes, wherein the head is attached to one arm of the main arm and the sharpening arm and the protrusion is attached to the other one of these arms. The protrusion can be additionally rotatable in the holes, but the given arm may also be rotatable against the protrusion.

[0022] As mentioned above, the sliding connection between the sharpening arm and the base can be defined by sliding attachment of the main arm to the base. The base can comprise enough free space to define this sliding. If this sliding occurs at the connecting element, its range may be limited due to space requirements.

[0023] Alternatively or additionally, however, this sliding connection between the sharpening arm and the base can be defined by the sliding attachment of the sharpening arm to the main arm through the connecting element. The sharpening arm may slide along the connecting element, or the connecting element with the sharpening arm may slide relative to the main arm, or a part of the connecting element with the sharpening arm may slide relative to another part of the connecting element with the main arm.

[0024] The carrier for the sharpening element can be attached to the sharpening arm non- rotatably. Preferably, it is attached to it non-rotatably, for at least a part of its sliding interval so that the sharpening element does not rotate during sharpening. It is also possible to prevent the rotation of the carrier by means of a safety lock mechanism, the release of which by the user then allows rotation, for example to change the sharpening element.

[0025] The sliding axis between the carrier for the sharpening element and the sharpening arm can be perpendicular to the axis of the arm connection. These axes can intersect or be perpendicular and skew. It is also possible to implement the sharpening arm in such a way that the carrier is not slidable in relation to the arm, but the arm slides in relation to the connecting element in the direction of the axis of the sharpening arm. Alternatively, a part of the sharpening arm can slide relative to another part of the sharpening arm, so that the carrier is attached non-movably to one of them and then sliding to the other. More generally, the perpendicular axis can be the connection of the arms with the axis of the sharpening arm.

[0026] The clamp may include a jaw to hold the knife blade perpendicular to the axis of the main arm. If the blade is symmetrical, then the plane of this symmetry can merge with the plane of the base when the blade is attached. It is also possible to use a jaw where the blade is not held perpendicular to this axis, but such a solution may be less suitable for symmetrical blade sharpening. Jaws are a practical means for firmly holding the blade during sharpening, while still being easily releasable. They can be secured, for example, with a screw.

[0027] To ensure the specified sliding between the parts of this sharpener, rolling bearings may be more preferable, with regard to the required sharpening accuracy and compactness of the sharpener. With regard to this, it may also be appropriate that the bearings defining the sliding are different from the bearings defining the rotation, i.e. so that the same bearing does not provide rotation and sliding.

[0028] An additional mechanism for lifting / lightening of the sharpening stone, especially for pushing it away from the base, can be preferably placed between the sharpening arm and the base, especially into the mechanism ensuring their sliding connection. The sharpening stone can be lifted directly or indirectly, e.g., the whole main arm can be lifted.

[0029] This additional mechanism can especially be a flexible element. For example, a coil spring mounted on the main arm. This spring exerts a force between the base and the main arm (especially preferably pushes them away from each other), i.e. it indirectly exerts a force between the base (static during sharpening) and the sharpening stone. This flexible element can make sharpening more comfortable and make it easier to control the pressure of the sharpening stone against the blade.

[0030] This mechanism can further be, e.g., magnetic, hydraulic or pneumatic, or the sharpening stone can be lifted via a pulley with a weight, etc.

[0031] Description of Drawings

[0032] The essence of the invention is further clarified by means of exemplary embodiments thereof, which are described using the accompanying drawings, in which:

[0033] Fig. 1 schematically shows a perspective view of the first exemplary embodiment of a sharpener according to the invention, wherein the individual parts of the sharpener are visible in the figure and the axes in which the individual parts are mutually movable are indicated, and the sharpening angle a is indicated;

[0034] Fig. 2 schematically shows a side view of the sharpener of Fig. 1 , wherein the inclination of the sharpening arm given by its attachment in the head of the connecting element being is shown in particular; Fig. 3 schematically shows a view from above of the sharpener of Fig. 1 and 2;

[0035] Fig. 4 schematically shows a top view of the connecting element head with four holes, which allow the sharpening arm to be attached rotatably at four different angles;

[0036] Fig. 5 schematically shows the section A-A shown in Fig. 4, wherein the plane of the section intersects the axes of the two opposite holes of the head and the inclination of the axes of these holes is visible in this section;

[0037] Fig. 6 schematically shows the section B-B shown in Fig. 4, wherein the plane of the section intersects the axes of the other two opposite holes of the head and the inclination of the axes of these holes is visible in this section;

[0038] Fig. 7 schematically shows a simplified side view of the sharpener according to the invention, wherein the axes of rotation and sliding between the individual components of the sharpener are shown;

[0039] Fig. 8 schematically shows a simplified side view of the sharpener according to the invention in an alternative embodiment, where the sharpening angle is not adjustable, but is fixed by the angle of connection of the connecting element to the main arm;

[0040] Fig. 9 schematically shows a perspective view from above of another (fourth) exemplary embodiment, in which the sharpener is designed for the base to be held in hand, the connecting element comprises a toothed mechanism for adjusting the sharpening angle and shafts defining the sharpening arm slide in relation to the connecting element;

[0041] Fig. 10 schematically shows a perspective view from below of the sharpener in the embodiment of Fig. 9;

[0042] Fig. 1 1 schematically shows a side view of the sharpener embodiment of Figs. 9 and 10. Exemplary Embodiments of the Invention

[0043] The invention will be further explained by means of the exemplary embodiments with reference to the relevant drawings. The first exemplary embodiment of a knife sharpener is shown in Fig. 1 to 3, with details of a head 10 for adjusting the sharpening angle indicated in Fig. 4 to 6. The kinematics of this sharpener, i.e. what parts can move during sharpening and how, is then indicated in the schematic drawing in Fig. 7.

[0044] The knife sharpener in the first exemplary embodiment comprises a base 1, which is used to be placed on a table or other surface, to hold a knife and to carry the other components of the sharpener. The sharpener also comprises a main arm 2 movably attached to the base 1, a sharpening arm 3 with a sliding carrier 4 for a sharpening element, and a connecting element 5, which ensures a movable connection of both arms at a fixed angle, i.e. an angle that is given directly by this connecting element 5 and is thus independent of the movement of the sharpening arm 3 or the main arm 2 and is independent of the resting of the sharpening element in the carrier 4 on the blade 14 of the sharpened knife. In the embodiment shown, the components of the sharpener are metal.

[0045] The base 1 comprises a body of the base 1 with an area to be put on a flat surface, that is round in the embodiment shown. Furthermore, the base 1 comprises a post and a clamp 6 with jaws 13 for fixing the knife. The post is fixed in the body of the base 1 and the clamp 6 is rotationally mounted at its upper end. The clamp 6 with the knife and the arms with the sharpening element can be rotated to a convenient position without having to manipulate the heavy body of the base T The clamp 6 is at the rear end equipped with a hole for sliding and rotating mounting of the main arm 2. There are jaws 13 on the front end.

[0046] The jaws 13 have a cross-section that is evident from the side view in Fig. 2. Both the upper and lower jaws 13 have opposite surfaces at their free ends for contact with the blade 14 of the knife. The middle part of the jaws 13 has increased thickness and comprises screw holes through which the jaws 13 are clamped. Again, the rear part of the jaws 13 has a smaller thickness, which allows the jaws 13 to move in the necessary interval for clamping thereof. As can be seen from Fig. 1 and 3, the upper and lower jaws 13 are divided into two parts for the knife attachment in two places along the blade 14. The holes for the tightening screws for clamping the jaws 13 are also visible in these drawings. The jaws 13 are arranged horizontally, so that the blade 14 held by them is also horizontal.

[0047] In the embodiment shown, the jaw 13 rotation while clamping the blade 14 is realized by the flexibility of the jaw 13 material. As a result, the jaws 13 clamp at one point when tightened before they touch the blade 14 and then bend with further tightening so that they touch the blade 14 flat. To prevent the jaw 13 tightening screw from being also bent by this bend, which could damage it or at least make tightening more difficult, the screw head and nut are equipped with a spherical surface. By these spherical surfaces they fit the hemispherical holes for the bolt and nut (see fig. 1 ). This allows the bolt and nut to tilt with respect to the jaw 13 to a certain extent, and thus to tilt the axis of this bolted connection with respect to the jaw 13. Even when bending the jaws 13, the screw is permanently stressed in the axis only.

[0048] In the embodiment shown, the main arm 2 is implemented as a shaft with one end free and the other rotatably connected to the head 10 of the connecting element 5. Here, this arm has a round cross-section constant over most of the length of the arm. A hole with a bearing is made in the clamp 6 of the base 1 and the main arm 2 is sliding up and down in this hole. The axis 7 of the main arm 2 is the axis of rotation of the head 10 relative to the base 1 and is also the axis for sliding movement between the main arm 2 and the base 1_. In the embodiment shown, the axis 7 of the main arm 2 is vertical.

[0049] The connecting element 5 that connects the sharpening arm 3 to the main arm 2 comprises two components in the embodiment shown - the head 10 attached to the upper end of the main arm 2, and a protrusion 12 rotatably connected to the sharpening arm 3. The head 10 is shown in detail in Fig. 4 to 6. The head 10 has an approximately cylindrical shape, where the lower base comprises a hole for rotational attachment to the main arm 2, and the upper base is divided into four differently inclined surfaces. In each of these surfaces, there is a hole 1 1 with an axis perpendicular to this surface and thus intersecting with respect to the axes of the other holes 1J.. The angle between the axis of the specific hole 1 1 and the axis 7 of the main arm 2 (which coincides with the axis of the cylindrical shape of the head 10) corresponds to the sharpening angle a, i.e. the angle at which the cutting edge surface tilts relative to the blade 14 surface fixed in the jaws 13. In the embodiment shown, the angles for these four holes 1 1 are 15°, 17.5°, 20° and 22.5°. These angles correspond to the most commonly used sharpening angles for different knives.

[0050] In the embodiment shown, these holes 1 1 of the head 10 comprise an internal thread. The protrusion 12 has a shape complementary to all these holes H, i.e. the holes

[0051] 1 1 have different inclinations but the same diameter, depth and thread. The protrusion 12 has an external thread, so it can be fixed in each hole 11 . At the same time, the protrusion

[0052] 12 is rotationally fixed to the rear end of the sharpening arm 3. Thus, the connecting element 5 firmly sets the angle between the arms, or their axes, thanks to the inclination of the holes 1 1 in the head 10 and the protrusion 12 attachment in the selected hole 1 1 , and at the same time the connecting element 5 allows rotation between the arms around the inclined axis 9 of the arm connection (axis of the selected hole 1J.) thanks to the rotary mounting of the protrusion 12 (not shown in Fig. 1 to 3, but has a cylindrical shape in the embodiment shown) to the sharpening arm 3.

[0053] In the embodiment shown, the sharpening arm 3 is designed as a pair of parallel shafts on which the carrier 4 for the sharpening element is slidingly mounted (see e.g. Fig. 1 ). The axis 8 of the sharpening arm 3 then passes between these shafts in the embodiment shown. At the rear end, the sharpening arm 3 is equipped with a material block that connects both shafts and realizes the connection of the sharpening arm 3 with the connecting element 5. This block in the embodiment shown comprises a hole for the protrusion 12 in the direction of the axis 9 of the arm connection. The protrusion 12 can have an enlarged head and a threaded body, i.e. it can be a screw. The body will go through the entire hole in the block, so it can be screwed into the holes 1 1 of the head 10, while the head will not go through the block, so that the protrusion 12 is locked in place when screwed into the head 10 and the sharpening arm 3 cannot be removed from it. The head and the non-threaded part of the protrusion 12 then define the rotational connection between the protrusion 12 and the sharpening arm 3 in the hole of the block that is equipped with a bearing.

[0054] The carrier 4 for the sharpening element contains a bed for the sharpening stone, which is attached here by a shape bond that allows the sharpening stone to be replaced. The dovetail groove of this shape bond is visible in Fig. 1 and 2 at the rear end of the bed at the bottom of the sharpening arm 3. The carrier 4 further comprises a body of the carrier 4 with a pair of holes attached to the sharpening arm 3. These holes of the carrier 4 have bearings and define sliding movement on the sharpening arm 3 shafts in the axis 8 of the sharpening arm 3. The carrier 4 further comprises a handle at the front end of the carrier 4 equipped with a cylindrical widened gripping part.

[0055] In the embodiment shown, there is no sharpening stone housed in the carrier 4, but this stone can also be a part of the sharpener. In the embodiment shown, the carrier 4 is equipped with a pair of dovetail grooves (the upper one is visible in Fig. 1 , the lower one is visible between the jaws 13 in Fig. 2) for attaching standard sharpening stones available on the market with shaped grips for such grooves. The lower groove of the carrier 4 is sliding in the axis 8 of the sharpening arm 3 towards the widened part of the handle and is pushed towards the upper groove by a spring (not shown). The sliding of the lower groove against the spring thus allows the sharpening stone to be inserted or removed, which is then clamped between the grooves, whereby it is attached to the carrier 4 for sharpening.

[0056] Thanks to the used connecting element 5, the sharpening angle a is fixed - the angle between the sharpening plane (which in Figs. 7 and 8 coincides with the axis 8 of the sharpening arm 3) and the plane of the base 1, which is perpendicular to the axis 7 of the main arm 2 (this plane (not shown) is horizontal and passes through the cutting edge in Figs. 7 and 8). The sharpening plane is determined by the inclination of the axis

[0057] 9 of the arm connection. It is further determined by the surface of the sharpening element movable along the axis 8 of the sharpening arm 3. When changing the thickness of the sharpening element, the sharpening plane only slides, it does not rotate - it rotates only at the preset angle of rotation around the axis 7 of the main arm 2 in relation to the plane of the base T In the embodiment shown, the plane of the base 1, i.e. the plane perpendicular to the axis 7 of the main arm 2, is also the plane of the cutting edge - the curve of the blade 14 cutting edge lies in this plane, and this plane is further horizontal.

[0058] In the embodiment shown, this sharpening angle is the inclination of the sharpening arm 3 and thus of the sharpening element in relation to the horizontal plane in which the blade 14 is held by the jaws 13. The sharpening angle is thus ensured by the inclination of the axis 9 of the arm connection in relation to the axis 7 of the main arm 2. When sharpening, the sharpening element slides along the sharpening arm 3 and at the same time along the blade 14. This sliding along the blade 14 is made possible by the rotational connection of the sharpening arm 3 with the base 1_via the connecting element 5 around the axis 7 of the main arm 2_and the rotational connection of the sharpening arm 3 with the connecting element 5 in combination with the sliding against the base 1. The blade 14 itself does not affect the sharpening angle in any way and the sharpening angle is thus constant throughout the whole sharpening process. The sharpening angle can be changed by adjusting the connecting element 5. All these sharpening movements are indicated in Fig. 7. It is also clear from this drawing that the sharpening stone is inclined at the sharpening angle and this angle is fixed by the inclination in the connecting element 5. At the same time, it is clearly visible that a different thickness of the sharpening element would be easily compensated by sliding of the main arm 2 up or down without impacting the sharpening angle a.

[0059] The second exemplary embodiment is realized as the first exemplary embodiment, except that the sharpening angle cannot be adjusted, it is fixed. This embodiment is shown in Fig. 8. Here, the connecting element 5 is implemented as a shaft piece. This connecting element 5 is firmly connected to the main arm 2 (it is of one piece of it) and is inclined to it, which defines the sharpening angle. In principle, the sharpening angle is given by the bend of the main arm 2, wherein the upper bent part then forms the connecting element 5. The sharpening arm 3 is then placed on the connecting element 5 through the hole to define the rotational movement around the axis 9 of the arm connection. In the embodiment shown, the sharpening arm 3 in the axis 9 of the arm connection is also sliding. To ensure kinematics in other embodiments, it is sufficient to slide the main arm 2 in the axis 7 of the main arm 2 or to slide the sharpening arm 3 in the axis 9 of the arm connection, both these slides are not strictly necessary. The purpose of these slides is, simply put, to allow the adjustment of the distance between the sharpening plane and the jaws.

[0060] The third exemplary embodiment is realized as the first embodiment, except for the differently implemented connecting element 5. Instead of the head 10 with several holes 1 1 defining angles a to be preset by the user, in this embodiment the connecting element 5 includes three parts. The first part is attached to the main arm 2, wherein it is rotatable around the axis 7 of the main arm 2 thanks to the main arm 2. The second part is connected to the first part rotatably around the axis perpendicular to axis 7 of the main arm 2. The third part is firmly connected to the sharpening arm 3 and is connected to the second part rotatably around the axis 9 of the arm connection. The inclination a of the axis 9 of the arm connection (and thus the inclination of the sharpening plane) relative to the axis 7 of the main arm 2 is thus adjusted by tilting the second part relative to the first part. This rotational connection is equipped with a series of teeth, defining the rotation a in full degrees between 10° and 40°, as an example, and a spring-pressed safety lock against the teeth. To tilt the second part relative to the first, it is necessary to overcome the force from the spring, which prevents spontaneous tilting during sharpening.

[0061] To allow finer adjustment of the sharpening angle, the connecting element 5 is further equipped with a mechanism for moving the safety lock, or for moving its effector, e.g. a ball pressed against the teeth. This sliding is possible in a relatively small interval and allows to adjust tilting of the second part between whole degrees, e.g. by tenths of a degree, by sliding the effector relative to the teeth.

[0062] The fourth exemplary embodiment is shown in Figs. 9 to 1 1 . In this embodiment, the carrier 4 is not sliding in relation to the shafts of the sharpening arm 3 but is fixed in relation thereto and these shafts slide in the holes on the element attached to the connecting element 5. The sharpening kinematics therefore remains the same as in the embodiments above, only the shafts also move during sharpening. In this embodiment, the bearings for the shafts are placed on the connecting element 5, which reduces the weight that the user has to move during sharpening, because the shafts can be made lighter than these bearings.

[0063] In this embodiment, the base 1 is created as a handgrip, so that the sharpener is held in hand when sharpening. The handgrip has a curved body with a widened end. On the rear side, it comprises a protrusion that provides rotational attachment of the main arm 2. At the upper end, it comprises another protrusion that implements the rotational attachment of the clamp 6. The connecting element 5 in this embodiment is the same as in the third embodiment above, i.e. it is a part with an adjustment wheel, which allows almost any adjustment of the sharpening angle within the interval defined by the design.

[0064] The other features of this embodiment can be realized as in any of the embodiments above, especially as in the first embodiment. In particular, the kinematics during sharpening are the same as in the first embodiment, only there are more options to adjust the sharpening angle. The base 1 in this embodiment is shown in a simplified way in the drawings, its body has a more complex shape for a comfortable and ergonomic grip, which is not evident in the drawings. The form of the connecting element 5 is independent of the form of the sharpening arm 3, the clamp 6 or the base 1, so these elements from any embodiment can be combined with elements from other embodiments as needed, at the discretion of a person skilled in the art or according to the required use of the sharpener.

[0065] Other alternative embodiments:

[0066] In some alternative embodiments, the head 10 can be attached to the sharpening arm 3 and the protrusion 12 to the main arm 2. In alternative embodiments, the number of holes 1 1 in the head 10 can be arbitrary - there can be only one, but there can be eight of them, etc. Instead of the holes 1 1 in the head 10 and the protrusion 12, the connecting element 5 can be equipped with several rotary protrusions 12 on the head 10 for adjusting the inclination between the arms, which have different axes, wherein the other one of the arms, which is not connected directly to the head 10, is provided with a hole 1 1 or a housing for the insertion of one of the protrusions 12.

[0067] In another, preferred embodiment, the jaw 13 is connected to the base 1 or to the clamp 6 rotatably. The axis of rotation of the jaws is preferably perpendicular to the axis 7 of the main arm 2, i.e. it is horizontal according to the embodiment shown. This rotational connection is then equipped with a safety lock to ensure rotation in two main positions differing by 180°. This makes it possible to rotate the jaw 13 and the attached knife by 180° and thus direct the other side of the cutting edge upwards. The entire blade 14 can thus be ground without having to remove the blade 14 from the jaws 13 during sharpening and to fix it therein again rotated. Other features of this embodiment can then be realized, for example, as in the first exemplary embodiment.

[0068] Alternatively, the sharpening arm 3 can be designed with only one guide element, e.g. with a non-circular cross-section, so that this element also secures the carrier 4 against rotation. The hole for placement of the main arm 2 can be created directly in the body of the base 1 instead of in the clamp 6. In some alternative embodiments, in addition to rotation, a sliding movement is defined between the connecting element 5 and the sharpening arm 3, especially sliding in the direction of the axis of rotation, i.e. the axis 9 of the arm connection.

[0069] It is also possible to fix the main arm 2 in relation to the base 1 in a different way than through the hole in the base 1, in which the arm is sliding and rotational. For example, the base 1 can comprise a guide element, e.g., a shaft, and the arm might have a hole located on this guide element. The main arm 2 can then be sliding and rotatable on this guide element, wherein the sliding length is given by the length of the guide element, not of the arm as in the embodiment shown.

[0070] In the next embodiment, the main arm 2 is not sliding in relation to the base 1, but only rotatable. The sharpening arm 3 is then sliding in relation to the connecting element 5, which ensures sufficient sliding between the sharpening arm 3 and the base 1 to enable sharpening with a sufficient range of movements. In principle, the main arm 2 can also be realized, as described in the previous paragraph, with the hole on the guide element, which therefore realizes only the rotary movement here. The main arm 2 can then be designed as the head 10 of the connecting element 5, e.g. as shown in Fig. 5.

[0071] In some embodiments, the sharpening element may be firmly connected to the carrier 4. To replace the sharpening element, it may be necessary to remove the entire carrier 4 from the sharpening arm 3. In some embodiments, the angles given by the holes 1 1 in the head 10 may be different from those shown in the first exemplary embodiment.

[0072] In some embodiments, one of the shafts (whether sliding relative to the carrier 4 or to the connecting element 5) can be shorter, so that the carrier 4 can be removed from it (or it can be pulled out of the connecting element 5) if there is sufficient sliding, and the carrier 4 can then be rotated around the other shaft in relation to the connecting element 5. This can make it easier to replace the sharpening element or to visually inspect it. Even for the sharpening arm 3 realized differently than by means of two shafts, the sliding between the carrier 4 and the connecting element 5 can be defined in such a way that only sliding is allowed in a certain interval (covering the positions of the sharpening element during sharpening) and beyond this interval (in the position where the carrier 4 does not slide during normal sharpening) it is also possible to rotate the carrier 4 in relation to the sharpening arm 3. In other alternative embodiments, the axis 9 of the arm connection is not intersecting in relation to the axis 7 of the main arm 2, but is skew in relation thereto. However, it is still true that the axis 9 of the arm connection is normal to the sharpening plane, which is intersecting in relation to the axis 7 of the main arm 2 at the sharpening angle a. The base 1 can be shaped in some other embodiments to be held in hand, i.e. it includes the grip, and does not have to be shaped for placement on a flat surface, as is the case in the embodiment shown.

[0073] The plane of the base 1 is also the plane of the cutting edge in the embodiment shown and it is horizontal. In other embodiments, however, the cutting edge may partially lie outside this plane - especially if the jaw 13 is attached inclined. When sharpening the blade 14 with the same set angle a on both sides of the blade 14, i.e. when the blade 14 is rotated by 180° around the axis perpendicular to the axis 7 of the main arm 2 after sharpening one side, then the plane of the base 1 is the plane of symmetry of the ground blade 1.4. The individual alternative embodiments listed here describe mainly different features in which these embodiments differ from the others. The other features of these embodiments may be common or taken from another embodiment, in particular all alternative embodiments may have other features implemented as in the first exemplary embodiment, or as in the second, third or fourth embodiment.

[0074] List of Reference Signs

[0075] 1 - base

[0076] 2 - main arm

[0077] 3 - sharpening arm

[0078] 4 - carrier

[0079] 5 - connecting element

[0080] 6 - clamp

[0081] 7 - axis of the main arm

[0082] 8 - axis of the sharpening arm

[0083] 9 - axis of the arm connection

[0084] 10 - head

[0085] 11 - hole

[0086] 12 - protrusion

[0087] 13 - jaw

[0088] 14 - blade

Claims

CLAIMS1. A knife sharpener comprising a base (1 ), a main arm (2), a sharpening arm (3), a carrier (4) for a sharpening element and a connecting element (5) for movable connection of the arms, wherein• the base (1 ) is equipped with a clamp (6) for removable knife attachment,• the main arm (2) is attached to the base (1 ), and• the carrier (4) is attached by the sharpening arm (3) slidingly in an axis (8) of the sharpening arm (3) relative to the main arm (2), characterized in that• the sharpening arm (3) is connected to the main arm (2) by the connecting element (5) rotatably around an axis (9) of the arm connection,• and further, the sharpening arm (3) is connected to the base (1 ) through the main arm (2) and the connecting element (5) rotatably around an axis (7) of the main arm (2),• and further, the sharpening arm (3) is slidingly connected to the base (1 ) via the main arm (2) and the connecting element (5), wherein• a sharpening plane of the sharpener is perpendicular to the axis (9) of the arm connection, non-parallel to the axis (7) of the main arm (2) and parallel to the axis (8) of the sharpening arm (3).

2. The sharpener according to claim 1 characterized in that the connecting element (5) fixes the sharpening arm (3) at a preset angle to the main arm (2), wherein the sharpening plane is fixed at this preset angle in relation to the axis (7) of the main arm (2).

3. The sharpener according to claim 2 characterized in that this angle is adjustable.

4. The sharpener according to claim 3 characterized in that the connecting element (5) comprises a head (10) comprising at least two holes (11 ) with differently inclined axes and further comprises a protrusion (12) removably attachable in each of these at least two holes (1 1 ), wherein the head (10) is attached to one arm fromthe main arm (2) and the sharpening arm (3) and the protrusion (12) is attached to the other one of these arms.

5. The sharpener according to any one of the previous claims characterized in that the sliding connection between the sharpening arm (3) and the base (1 ) is defined by a sliding attachment of the main arm (2) to the base (1 ).

6. The sharpener according to any one of the previous claims characterized in that the sliding connection between the sharpening arm (3) and the base (1 ) is defined by a sliding attachment of the sharpening arm (3) to the main arm (2) through the connecting element (5).

7. The sharpener according to any one of the previous claims characterized in that the carrier (4) for the sharpening element is attached to the sharpening arm (3) non-rotatably.

8. The sharpener according to any one of the previous claims characterized in that a sliding axis between the carrier (4) for the sharpening element and the sharpening arm (3) is perpendicular to the axis (9) of the arm connection.

9. The sharpener according to any one of the previous claims characterized in that the clamp (6) comprises a jaw (13) for holding a blade (14) of the knife perpendicularly to the axis (7) of the main arm (2).

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