WO2010023562A2

WO2010023562A2 - Knife sharpener

Info

Publication number: WO2010023562A2
Application number: PCT/IB2009/007211
Authority: WO
Inventors: Chun Ming Cheung
Original assignee: Technical (Hk) Manufacturing Limited
Priority date: 2008-08-28
Filing date: 2009-08-28
Publication date: 2010-03-04
Also published as: WO2010023562A3; GB2463029A; GB2463029B; GB0815646D0

Abstract

A knife sharpener comprises: a grinding block (22) mounted on a vertical axle and having a horizontal grinding surface (26); a motor (21) arranged to rotate the grinding block (22); one or more guides (10,11) pivotally mounted on a support and adapted to receive the blade of a knife so that the cutting edge of the blade contacts the grinding surface (26); and an adjustment mechanism arranged to adjust the angle of the guides (10,11) relative to the grinding surface (26).

Description

KNIFE SHARPENER

This invention relates to a knife sharpener particularly but not exclusively of the kind used in domestic kitchens or restaurants, wherein a rotating grindstone or grinding block is used in conjunction with a guide for maintaining a knife blade at a desired angle in relation to the surface of stone during the sharpening process. This invention also relates to a protractor for checking the angle of a knife or other blade and to a kit of parts comprising a sharpener and protractor.

A sharpener in accordance with this invention may also be used for sharpening other bladed tools, particularly domestic clippers, slicers, shears or razors.

According to a first aspect of the present invention a knife sharpener comprises: a grinding block mounted on a vertical axle, the grinding block having a circumference and an horizontal grinding surface; a motor arranged to rotate the grinding block; a plurality of guides each guide being pivotally mounted on a support for rotation about a pivot axis, the guide being adapted to receive a blade of a knife so that a cutting edge of the blade contacts the grinding surface; wherein the guides are located on opposite sides of the grinding surface; and wherein the axis of each guide is located below the grinding surface; and an adjustment mechanism arranged to adjust an angle of the guides relative to the grinding surface;

Each guide is preferably arranged so that a blade may rest on the surface thereof in use assuring constant alignment at a desired angle in relation to the grinding block.

The guides are inflexible, so that the circular disposition of the blade is constant. Use of articulated linkages in the guide is avoided. Preferably two guides are located on diametrically opposed sides of the grinding surface.

The two guides may have a common pivot axis. Alternatively and more preferably the two guides may be located on adjacent pivot axes. These axes may extend orthogonally relative to axle of grinding block. The pivot axes are preferably located close together. The distance between the axes is preferably less than the diameter of the grinding block. i The axis or axes of the guides are located below the grinding surface. In order to avoid blocking the passage of the blade so that the whole of the upper surface of the grinding block may be used.

The axis of each guide may be located below the plane of the grinding surface either axially below the grinding block or radially outwardly of the grinding block. Location of the axis or axes below the block allows convenient access to the grinding surface using a generally horizontally held knife blade which may be pressed downwardly during the grinding process.

In preferred embodiments the grinding block is biased upwardly by spring means so that it is urged in use against the downwardly facing edge of a knife blade pressed against the grinding surface. Alternatively the grinding block may be rigidly located upon the chassis of the apparatus. A rigid location may be preferred for durability in use.

The adjustment mechanism may comprise a shaft having right handed and left handed threaded portions, sliding blocks having corresponding threaded bores, each block engaging one of the threaded portions and wherein each sliding block is connected to a respective guide.

In this arrangement rotation of the shaft raises or lowers both of the guides simultaneously in opposite directions about their pivot points. In preferred embodiments the guides are each connected to a respective sliding block by a linkage pivotally attached at each end to the guide or sliding block.

An actuation knob or lever is preferably provided at one end of the shaft to facilitate adjustment of the angle of the sliding blocks in use.

Threaded engagement of the shaft and sliding blocks is advantageous since the mechanical advantage of the arrangement prevents movement of the sliding block due to pressure of the blade but allows the guide to be easily raised or lowered by turning the actuation knob or lever.

One of the guides may include a pointer or scale adapted to co-operate with scale or pointer of the housing to indicate the angle at which the guide is positioned. The guide or guides may be inclined to provide a whole angle of the blade of about 15- 30°, preferably 20-25° more preferably about 25°.

In preferred embodiments the casing of the knife sharpener comprises a chassis and a cover. The cover may be removable to facilitate cleaning and removal of debris from the grinding stone.

The support for the guides may be mounted on the chassis of the device.

Alternatively the guides may be mounted on the interior of the casing or cover for the device. The latter arrangement avoids contamination by debris from the grind stone.

The guides may each comprise a guide surface having an inwardly facing edge and an aperture; wherein the grinding block is located in the aperture.

In a preferred embodiment a shoe mounted on an upper part of the chassis or interior of the cover or casing is biased downwardly, for example, by spring biasing means into engagement with a respective guide. The biasing means may comprise two or more springs arranged to urge the shoe downwardly against an upper surface of a knife blade. Use of two or more springs ensures even application of force across the surface of the blade. The arrangement of the guide and shoe defines a slot to receive a knife blade, the knife blade being urged downwardly against the guide by the biased shoe to ensure proper positioning of the blade during the sharpening process. The shoe may carry a cleaning pad to facilitate removal of particles of metal or on the grinding block during removal from the block after sharpening.

In an alternative embodiment, a resilient retainer arrangement is provided to retain a knife blade in engagement with a guide. The retainer arrangement may comprise first and second resilient members; each guide having an inwardly facing edge; a respective retainer being mounted on each edge; each resilient member having a downwardly facing surface co-operating with an upwardly facing surface of the guide to define a blade receiving slot; wherein a knife blade received in the slot may contact the grinding surface. Each resilient member may comprise upper and lower members defining a channel dimensioned to receive the edge of the guide. Preferably the channel is dimensioned to allow limited movement of the upper member to receive the blade of a knife.

Alternatively the channel is dimensioned so that the edge of the guide is securely engaged, the resilient members being flexible to accommodate the blade.

Preferably an aperture provided in the lower retainer member is dimensioned to allow passage of the grinding block into the channel.

The resilient member may be composed of resilient material, for example, spring material or resilient plastic, to exert a downward pressure on the knife blade sufficient to maintain the blade in contact with the guide in use. Alternatively the member may be rigid but having an internal spring keep arranged to bear downwardly on a blade inserted in the slot.

In a preferred embodiment, the upper resilient member is curved upwardly away from the guide. In this embodiment, the blade may be conveniently inserted between the upper member and guide.

The upper resilient member may include a shield arranged to cover the grinding block.

This serves to prevent accidental contact with the grinding block, for example, by a user's fingers.

A knife sharpener in accordance with the present invention confers many advantages. The angle at which the blade is sharpened can be easily adjusted to suit the grade of steel from which the blade is made, the intended use of the knife of the degree to which it is to be sharpened. An embodiment of the invention in which two guides are employed allows both sides of a knife blade to be conveniently sharpened in consecutive strokes through the slots on either side of the grinding block.

The motor may be directly connected to the axle of grinding block. The motor having a operating speed of about 15-30,000 rpm may be employed, preferably 15-20,000 rpm more preferably about 20,000 rpm. 1OW DC motor may be used. A grinding head having a minimum diameter, for example about 20 mm may be preferred in order to minimise the weight of the grinding head yet provide a solid grinding surface for robust use.

A collection tray may be provided for debris from the grinding process. Alternatively or in addition a magnetic collector may serve to collect steel particles from the grinding process.

According to a second aspect of this invention there is provided a kit comprising the knife sharpener and a knife blade angle protractor comprising a body having front and rear casings forming front and rear faces to the body and having a peripheral rim, the rim having a multiplicity of triangular slots extending from front to rear faces of the body, each slot having a different apical angle selected to receive a cutting edge of a knife blade with a respective predetermined angle.

The apical angle of each slot preferably is the angle of a respectively angled blade together with an angular increment to provide compensation to thickness of the blade itself and clearance sufficient to allow the blade to be inserted into and removed from the slot. For example a clearance of 2 degrees of arc may be added to the angle of the blade. Double sided blades or single sided blades, with one flat side may be accommodated. Blade angles of 5, 10, 15, 20, 25 and 30 degrees may be provided.

In a preferred embodiment the front and rear casings may be manufactured separately and clipped or fastened together. Preferably each side of each slot is formed by only one of the casing portions. In this way the sides of the slots may be accurately formed without use of sharpened tooling. In a preferred embodiment each casing comprises a peripheral array of teeth or castellations disposed in alternate arrangement when assembled, the sides of each tooth or castellation comprising right and left sides of adjacent slots.

The casing may be circular or disc shaped. Alternatively a square or rectangular casing may be conveniently used with the sides having differently shaped slots for different kinds of blades.

The device of the present invention is simple and economical in use. Once the angle of the blade has been set using the adjustment knob or lever the knife may be simply drawn through the slot on each side of the grinding head to produce a uniformly sharpened blade. The protractor affords a simple way of checking the angle of a blade before sharpening, during the sharpening process and afterwards.

The kit therefore provides a simple and easily used means for determining the angle of a blade and either sharpening it at the same angle or of changing the angle during sharpening to suit a desired purpose.

The invention is further described by means of example but not in any limitative sense with reference to the accompanying drawings of which:

Figure 1 is a perspective view of a knife sharpener in accordance with this invention with the cover removed;

Figure 2 is a side elevation of the knife sharpener shown in Figure 1;

Figure 3 is a cross section through the knife sharpener shown in Figure 2;

Figure 4 is a cross section from the rear of the sharpener shown in Figure 2;

Figure 5 is a cross sectional end elevation of the sharpener;

Figure 6 is a perspective view illustrating the sharpener;

Figure 7 is a cross sectional view through the sharpener shown in Figure 6 ;

Figure 8 is an end elevation of the sharpener;

Figure 9 is a plan view of a protractor in accordance with this invention,

Figure 10 is a perspective view of casings forming the protractor shown in Figure 9; and

Figures 11 and 12 shows an alternative sharpener in accordance with this invention. The knife sharpener illustrated in Figures 1 to 8 comprises a base (1) defining a chassis upon which a platform (2) is mounted. The upper part of the cover (not shown) fits onto the base (1) to form an enclosed unit having apertures permitting entry of a knife.

A pair of uprights (3) extend from the platform (2) to support a grinding head and guide members as described below.

An actuation knob (4) connected to shaft (5) permits the angle of the guides to be adjusted. Left and right handed screw threads (8 and 9) on the shaft co-operate with threaded bores in the sliding blocks (28, 29). Rotation of the knob (4) causes movement of the sliding blocks in opposite directions inwardly or outwardly along the shaft. A motor (21) located on a forward side of the platform relative to the shaft (5) carries an axle and grinding head (22). In an alternative embodiment the motor may be located rearwardly of the platform relative to the shaft. The grinding head comprises a grinding disc (22) having a horizontal upwardly facing grinding surface (26) and a lower supporting base portion (27) to engage the drive shaft (not shown) of the motor. Two guide members (10, 11) are mounted on pivots (16, 17) extending orthogonally of the drive shaft of a motor so that the guide members may rotate about the pivots(16, 17) to adjust the angle of the guide surfaces (24, 25) with relation to the horizontal surface (26) of the grinding block (22). Linkages (18, 19) pivotally connected to the sliding blocks (28, 29) and guides (10, 11) cause the guides (10, 11) to be raised and lowered as the knob (4) is turned.

In a preferred embodiment the guides (10, 11) are inclined at the same angle relative to the grinding surface (26). However in the illustrated embodiment the guides (10, 11) are shown at different angles for ease of appreciation of the movement of the components of the device. A scale (12) attached to the guide (10) co-operates with a transparent window in the casing (not shown) to provide a visual display of the angle. Alternatively a pointer mounted on the guide (10) may co-operate with a scale (12) mounted on the casing to provide the angular display.

In a first preferred embodiment the grinding block, base portion and horizontal surface (27), (22), (26) are rigidly secured to the drive shaft of the motor (21). In an alternative embodiment a spring loaded attachment may be used to bias the grinding surface (26) upwardly towards a knife blade in use.

The shaft (5) is located at a rearward portion of the platform (2) alongside the motor (21) to provide a compact construction. An upper housing (13) is secured to the platform (2). A pair of shoes (14, 15) are biased downwardly by pairs of spring loaded bushes (23) so that a slot is formed between each guide surface (24, 25) and the respective shoe (14, 15). A knife blade inserted between the guide surface and shoe is retained snugly, wider blades being secured by their cutting edges so that the device may be used for sharpening a wide range of culinary or other knives.

The location of the pivot or pivots (16, 17) below the surface of the grinding block allows a blade to pass across the entire surface of the grinding block without obstruction.

Figures 9 and 10 show a protractor for checking the angle of a blade before, during or after sharpening. The protractor comprises front and rear casings (30, 31) which are clipped together or otherwise fastened to form a disc-shaped laminar member with a peripheral array of differently angled slots (32, 33, 34 etc). The front casing carries markings indicating the apical angle and shape (single or double sided) of each slot. Each casing is formed with an array of teeth (35, 36 etc) the sides of each tooth comprising the right and left sides (37, 38) respectively of adjacent slots, hi this way the slots may be accurately manufactured by injection moulding without a need for the tooling to include acutely angled portions corresponding to the slots.

The grinding tool and protractor may comprise a kit of parts. In use the cutting edge of a knife may be inserted into the slots in the protractor in turn until a close fit is obtained. At that stage the user may decide to maintain that angle, setting the scale on the sharpener accordingly or a different angle may be chosen.

Figures 11 and 12 illustrate an alternative embodiment of the invention wherein the shoes (14,15) are replaced with a pair of resilient members (101,102). In Figures 11 and 12 the same numerals are used to denote like components shown in the preceding figures.

Two opposed guides (24,25) are mounted on pivot axes (16,17), extending parallel to each other and perpendicular to the axis of rotation of the base portion of the grinding block (22). The grinding block (22) has a horizontal circular grinding surface (26). The guides (10,11) have planar guide surfaces (24,25). The guides and support surfaces are inflexible so that a knife blade may be held rigidly against the grinding surface (26) in use. The guides (10,11) have inwardly facing surfaces (104,105) with partially circular apertures (106,107) arranged to receive the grinding block so that the horizontal surface (26) can be contacted by the edge of a knife resting on the surfaces (25,25).

First and second resilient members (101,102) form a retainer arrangement. The first resilient member (101) has upper (108,109) portions defining a channel (110) between the portions. The retainers (101,102) may be formed from resilient metal or plastics material and are dimensioned so that the retainer (101) may be inserted onto the edge (104) of guide (10) so that limited flexural movement of the upper member (108) is permitted as the knife is inserted between the upwardly facing surface (24) and downwardly facing surface of member (108). The second retaining member (102) is constructed similarly.

A cover (103) extending from the upper surface of member (101) covers the head of the grinding block (26) preventing accidental contact with the surface of the block during use.

The end (111) of the upper member (108) is curved upwardly away from surface (24) to facilitate insertion of the knife blade into the slot.

The axes of the pivot (16,17) are located beneath the circumference (22) of the grinding block and are arranged orthogonally to the axis of rotation of the grinding block in the embodiments shown in Figures 1-8 and 11 and 12.

In an alternative embodiment, both guides (10,11) may share a common pivot.

Claims

1. A knife sharpener comprising a grinding block mounted on a vertical axle, the grinding block having a circumference and an horizontal grinding surface; a motor arranged to rotate the grinding block; a plurality of guides each guide being pivotally mounted on a support for rotation about a pivot axis, the guide being adapted to receive a blade of a knife so that a cutting edge of the blade contacts the grinding surface; wherein the guides are located on opposite sides of the grinding surface; and wherein the axis of each guide is located below the grinding surface; and an adjustment mechanism arranged to adjust an angle of the guides relative to the grinding surface;

2. A knife sharpener as claimed in claim 1, wherein the guides are inflexible.

3. A knife sharpener as claimed in claim 1 or 2, wherein the or each axis is located below the circumference of the grinding block.

4. A knife sharpener as claimed in any preceding claim, wherein the two guides have a common pivot axis.

5. A knife sharpener as claimed in any of claims 1 to 3, wherein the two guides are located on adjacent axes extending orthogonally of the axle of the grinding block.

6. A knife sharpener as claimed in claim 5, wherein the axes are parallel.

7. A knife sharpener as claimed in any preceding claim, wherein the grinding block is biased upwardly by spring means.

8. A knife sharpener as claimed in any of claims 1 to 6, wherein the grinding block is rigidly located on the chassis of the apparatus.

9. A knife sharpener as claimed in any preceding claim, wherein the adjustment mechanism comprises a shaft having right-handed and left-handed threaded portions, sliding blocks having correspondingly threaded, bores, each sliding block engaging one of the threaded portions, wherein each sliding block is connected to a respective guide.

10. A knife sharpener as claimed in claim 9, wherein each guide is connected to a respective sliding block by a linkage pivotally attached at each end to the guide or sliding block.

11. A knife sharpener as claimed in any preceding claim, wherein the guides are mounted on the interior of a casing or cover for the device.

12. A knife sharpener as claimed in any preceding claim, comprising a shoe mounted on an upper part of a chassis or interior of a cover, where a casing is biased downwardly into engagement with a respective guide.

13. A knife sharpener as claimed in any of claims 1 to 11 including a resilient retainer arrangement to retain a knife blade in engagement with the guide.

14. A knife sharpener as claimed in claim 13 wherein the retainer arrangement comprises first and second resilient members; each guide having an inwardly facing edge; a respective resilient member being mounted on each edge; each resilient member having a downwardly facing surface cooperating with an upwardly facing surface of the guide to define a blade receiving slot; wherein a knife blade received in the slot may contact the grinding surface in use.

15. A knife sharpener as claimed in claim 13 or 14 wherein each resilient member comprises upper and lower members defining a channel dimensioned to receive the edge of the guide.

16. A knife sharpener as claimed in claim 15 wherein the channel is dimensioned to allow limited movement of the upper member to receive the blade of a knife.

17. A knife sharpener as claimed in any of claims 13 to 15 wherein the channel is dimensioned so that the resilient member may be securely engaged to the guide and wherein the resilient member is flexible to allow insertion of the blade.

18. A knife sharpener as claimed in any preceding claim wherein each guide comprises a guide surface having an inwardly facing edge and an aperture; wherein the grinding block is located in the aperture.

19. A knife sharpener as claimed in claim 18 wherein an aperture provided in the lower resilient member is dimensioned to allow passage of the grinding block into the channel.

20. A knife sharpener as claimed in any of claims 13 to 19 wherein the upper resilient member is curved away from the guide.

21. A knife sharpener as claimed in any of claims 13 to 20 wherein the upper resilient member includes a shield arranged to cover the grinding block.

22. A kit comprising a knife sharpener as claimed in any preceding claim in combination with a protractor comprising a body having front and rear casings forming front and rear faces to the body and having a peripheral rim, the rim having a multiplicity of triangular slots extending from front to rear faces of the body, each slot having a different apical angle selected to receive a cutting edge of a knife blade with a respective predetermined angle.

23. A protractor as claimed in claim 15 wherein each casing is formed with an array of teeth the sides of each tooth comprising the right and left sides respectively of adjacent slots.