GB2429944A

GB2429944A - Knife sharpener

Info

Publication number: GB2429944A
Application number: GB0601783A
Authority: GB
Inventors: Arthur Mason
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-01-28
Filing date: 2006-01-28
Publication date: 2007-03-14
Anticipated expiration: 2026-01-28
Also published as: GB2429944B; GB0601783D0

Abstract

A knife sharpener 10 for sharpening the blade 32,33 of a knife or other implement such as scissors comprises a base unit 11 and a closure member 12. The base unit comprises a body portion 24 which rotatably supports a rotatable honing stone 20 and further comprises a location formation which secures said closure member to the base unit. The base unit and the closure member co-operate to define a sharpening chamber into which a blade may be received for sharpening by the honing stone. The base unit and closure member comprise guide 30,31 means to provide support for a blade in a pre-determined orientation relative to the honing stone for sharpening of the blade by the honing stone. The sharpener may be a stand alone device or may be attached to a food mixer.

Description

1 2429944

KNIFE SHARPENER

This invention relates to a knife sharpener and in particular, though not exclusively, to an electrically powered knife sharpener.

The knife sharpener may be a self-contained unit which incorporates means such as an electric motor for rotating a sharpening device, or it may be in the form of an attachment which, in common with other attachments, may be selectively securable to the power unit of a food mixer.

Many different proposals have been put forward for the design of a knife sharpener, including versions which are suitable for use as attachments to the base power unit of a food mixer. Examples of known knife sharpener attachments are to be found, for example, in US-A-2949709, US-A-2694275 and JP2758431.

Although known knife sharpener devices do perform with varying degrees of success, they each are found to possess one or more disadvantages such as high manufacturing costs, poor sharpening performance, poor reliability or inconvenience in use.

The present invention seeks to provide a knife sharpener which is an improvement over known devices.

In accordance with the present invention there is provided a knife sharpener for sharpening the blade of a knife or other implement such as scissors, said knife sharpener comprising a base unit and a closure member, said base unit having a body portion which rotatably supports a honing member and said body portion further comprising at least a first location formation whereby said closure member may be secured to the base unit, said base unit and closure member co-operating to define a sharpening chamber into which a blade may be received for sharpening by the honing member, at least one of the base unit and closure member comprising guide means to provide support for a blade in a pre-determined orientation relative to the honing member for sharpening of the blade under action of the honing member during rotation of the honing member.

The closure member may be substantially permanently secured to the base unit or may be selectively removable therefrom, for example to facilitate removal of particulate matter accumulated in the chamber in consequence of sharpening action or for periodic replacement or redressing of the honing member.

The guide means may be constructed as an integral part of the closure member or as an integral part of the base unit body portion. In a further alternative it may be a separate component which, typically, may be positioned between and secured to each of the base unit and closure member.

The guide means, whether an independent component or an integral part of one of the base unit and closure member may be defined at least in part by a substantially cylindrical or frusto-conically shaped wall portion which defines a part of the aforementioned sharpening chamber. The guide means preferably comprises two guide supports at different orientations relative to the honing member whereby, for example, one support may be used for sharpening a blade at one particular angle whilst the other may be used to sharpen a blade at a different angle. Preferably one of the guides supports a blade for sharpening at an angle of 45 , that being appropriate for sharpening of scissors, and the other for sharpening at an angle of 320, that being appropriate for the sharpening of knife blades. Said angle may be an included angle (i.e. the angle between two surfaces either side of the blade edge) in which case, for a knife blade having a symmetrical form each face may be honed at an angle of 160 relative to a notional plane which intersects the knife edge and is parallel with the body of the blade.

It is to be understood that although two specific angles of sharpening have been referred to, the guide supports may be selected for sharpening at other angles. Optionally one or both of the guide supports may be adjustable for different angles of sharpening.

Preferably the honing member is substantially in the form of a rotatable disc having a substantially planar surface against which a blade may be brought to bear for sharpening during rotation of the honing member. Alternatively, the honing member may be non-planar, and may, for example, comprise a grinding surface which is of a frusto-conical shape, the apex angle of that frusto-conical shape typically lying within the range 1200 to 1800. The material of the surface of the honing member for sharpening a blade may be of any suitable known material such as stone, or a composition comprising fine metal particles as used in the disc of an angle grinder.

The honing member may be rotatably supported by a bearing secured relative to the body portion of the base unit. Said body portion may provide support for two bearings which lie axially spaced apart relative to the length of the axis about which the honing member is rotatably supported. A particularly suitable type of bearing is one of the bush type, for example comprising bronze bushes. Alternatively, however, other types of bearings such as ball or roller bearings may be employed, in which case it is particularly preferred that they are of the sealed type to resist ingress of, and damage by, dust material generated in use by the sharpening process.

An aperture provided in the guide means for allowing the edge of a blade to be inserted into the sharpening chamber into contact with the honing member may comprise a guide surface which defines the minimum angle between the blade and a grinding surface of the honing member. That minimum angle may for example be related to either of the aforementioned sharpening angles of 32 (or half angle of 16 ) or 45 . Optionally said aperture may have associated therewith an auxiliary guide surface which controls the maximum angle between a blade edge and the honing member. Thus even if a user fails to firmly hold the blade against the main guide surface, for example to achieve a sharpened edge having either of the intended angles of 32 or 45 , it is ensured that the grinding angle is not so great as to inhibit formation of a useful sharpened edge.

The base unit body portion, closure member (and guide means if not an integral part of the base unit or closure member), may be formed for example from moulded material such as a plastics material. A suitable plastics material is polycarbonate.

If the closure member is selectively removable from the base unit, interlock means, such as mechanical interlock means, may be provided to prevent removal of the closure member if, in the case of a knife sharpener device which is in the form of an attachment for a food mixer, the knife sharpener device is in situ on the food mixer. In the case of a self contained knife sharpener device of the present invention, interlock means may be provided to ensure that a selectively removable closure member cannot be removed unless a power unit within the base unit is immobilised.

One embodiment of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which:- Figure 1 is a perspective view of a knife sharpener attachment device is accordance with the present invention, and Figure 2 is a longitudinal sectional view of the knife sharpener of Figure 1.

The knife sharpener 10 shown in Figures 1 and 2 is in the form of an attachment which can be secured to and driven by the power unit of a food mixer.

The knife sharpener device 10 comprises a base portion 11 and a closure cap 12.

The base portion 11 comprises a body 24 having a lower peripheral formation 13, for example a bayonet or screw threaded type formation whereby it may be selectively secured to the power unit of a food mixer.

In a substantially similar manner, the base unit 11 additionally comprises an upper formation 14, again which may be of a bayonet or screw threaded type, for selectively securing the closure cap 12 to the base unit 11.

The base unit 11 comprises a lower annular wall 15 and, towards the upper end near the formation 14, a three-arm spider arrangement 16, the wall 15 and spider 16 each supporting one of a pair of bronze bush type bearings in which a shaft 17 is rotatably mounted.

The lower end 18 of the shaft comprises a prong formation 19 for engaging with and being rotated by the output drive a food mixer power unit. The upper end of the shaft 17 has secured thereto a disc shaped honing stone 20 having an upper planar grinding surface 21.

The closure cap 12 comprises a substantially planar upper surface 25 formed integrally with a frusto-conically shaped side wall 26 which also defines the guide means. The inner sides of the surfaces 25 and 26 serve in part to define a substantially enclosed grinding chamber 27 over the upper surface 21 of the honing stone 20. Although the upper surface of the closure cap is planar in this embodiment of the invention, it is to be understood that other shapes, such as a dome shape may be utilised.

The waIl 26 is formed with a pair of substantially diametrically opposite apertures 28, 29 in the form of slots through which a knife blade may be inserted for contact with the honing stone 20. Each slot in this embodiment of the invention subtends an angle in the order of 1200 about the rotational axis of the shaft 17.

Each slot 28, 29 has associated therewith a guide surface 30, 31 against which the face of a blade may be held whilst the blade is brought into contact with the grinding surface 21. One guide surface 30 supports a blade 32 for sharpening at an angle of 32 relative to the surface 21 whilst the other guide surface 31 supports a blade (typically the blade of a pair of scissors), for sharpening at an angle substantially equal to 45 relative to the surface 21.

Interlock means, not shown, is provided to ensure that the closure cap 12 cannot be removed from the base unit 11, e.g. for purpose of cleaning and removal of grinding dust from the chamber 27, unless the lower edge formation 13 of the base unit 11 has been disengaged from the power unit of a food mixer.

In use of the aforedescribed knife sharpener, with the honing stone 20 rotated via the shaft 17, a knife blade 32, 33 is drawn lengthwise (i.e. perpendicular to the plane of Figure 2) through a guide slot 28, 29 with the blade being held down firmly against the associated guide surface 30, 31 thereby to result in sharpening of the blade edge to the required angle. AMDE2

Claims

1. A knife sharpener for sharpening the blade of a knife or other implement such as scissors, said knife sharpener comprising a base unit and a closure member, said base unit having a body portion which rotatably supports a honing member and said body portion further comprising at least a first location formation whereby said closure member may be secured to the base unit, said base unit and closure member co-operating to define a sharpening chamber into which a blade may be received for sharpening by the honing member, at least one of the base unit and closure member comprising guide means to provide support for a blade in a pre-determined orientation relative to the honing member for sharpening of the blade under action of the honing member during rotation of the honing member.

2. A knife sharpener according to claim 1, wherein the closure member is selectively removable from the base unit to facilitate removal of particu'ate matter accumulated in the chamber in consequence of sharpening action or for periodic replacement or redressing of the honing member.

3. A knife sharpener according to claim 1, wherein the closure member is substantially permanently secured to the base unit.

4. A knife sharpener according to any one of claims 1 to 3, wherein the guide means is an integral part of the closure member.

5. A knife sharpener according to any one of claims I to 3, wherein the guide means is an integral part of the base unit body portion.

6. A knife sharpener according to any one of claims I to 3, wherein the guide means is a separate component which, in use, is positioned between and secured to each of the base unit and closure member.

7. A knife sharpener according to any one of the preceding claims, wherein the guide means is defined at least in part by a substantially cylindrical or frusto-conically shaped wall portion which defines a part of the said sharpening chamber.

8. A knife sharpener according to any one of the preceding claims, wherein the guide means comprises two guide supports at different orientations relative to the honing member.

9. A knife sharpener according to claim 8, wherein one guide support supports a blade for sharpening at an angle of 450

10. A knife sharpener according to claim 8, wherein one guide support supports a blade for sharpening at an angle of 32 .

11. A knife sharpener according to any one of the preceding claims, wherein the honing member is substantially in the form of a rotatable disc having a substantially planar surface against which a blade may be brought to bear for sharpening during rotation of the honing member.

12. A knife sharpener according to any one of the preceding claims, wherein the honing member is rotatably supported by a bearing secured relative to the body portion of the base unit.

I 3. A knife sharpener according to claim 12, wherein the body portion of the base unit provides support for two bearings which lie axially spaced apart relative to the length of the axis about which the honing member is rotatably supported.

14. A knife sharpener according to claim 12 or claim 13, wherein a said bearing is one of the bush type.

15. A knife sharpener according to claim 12 or claim 13, wherein a said bearing is a ball or roller bearing of the sealed type.

16. A knife sharpener according to any one of the preceding claims, wherein an aperture provided in the guide means for allowing the edge of a blade to be inserted into the sharpening chamber into contact with the honing member comprises a guide surface which defines the minimum angle between the blade and a grinding surface of the honing member.

17. A knife sharpener according to claim 16, wherein said minimum angle is related to that for sharpening at one of 32 and 45 .

18. A knife sharpener according to claim 16 or claim 17, wherein a said aperture has associated therewith an auxiliary guide surface which, in use, controls the maximum angle between a blade edge and the honing member.

1 9. A knife sharpener according to claim 1 and substantially as herein before described with reference to the accompanying drawings. AMCL2

19. A knife sharpener according to any one of the preceding claims, wherein the closure member is selectively removable from the base unit and interlock means is provided to prevent removal of the closure member if, in the case of a knife sharpener device which is selectively attachable to a power unit such as that of a food mixer, the knife sharpener device is in situ on the power unit.

20. A knife sharpener according to any one of claims Ito 18, wherein the knife sharpener is a self contained unit comprising a power unit and interlock means is provided to inhibit removal of a selectively removable closure member unless a power unit within the base unit is immobilised.

21. A knife sharpener according to claim I and substantially as herein before descnbed with reference to the accompanying drawings. AmcIl I0 Amendments to the claims have been filed as follows

1. A knife sharpener for sharpening the blade of a knife or other implement such as scissors, said knife sharpener comprising a base unit and a closure member, said base unit having a body portion which rotatably supports a honing member and said base unit and dosure member cooperating to define a sharpening chamber into which a blade may be received for sharpening by the honing member, said body portion further comprising at least a first location formation whereby said closure member may be secured to the base unit in a manner in which it is selectively removable from the base unit to facilitate removal of particulate matter accumulated in the chamber in consequence of sharpening action or for periodic replacement or redressing of the honing member, at least one of the base unit and closure member comprising guide means to provide support for a blade in a pre-determined orientation relative to the honing member for sharpening of the blade under action of the honing member during rotation of the honing member, and said knife sharpener further comprising interlock means to prevent or inhibit removal of the closure member if either the knife sharpener is in situ on a power unit to which it is selectively attachable or unless a power unit within the base unit is immobilised 2 A knife sharpener according to claim 1, wherein the knife sharpener is selectively attachable to a power unit such as that of a food mixer.

3. A knife sharpener according to claim 1, wherein the knife sharpener is a self-contained unit comprising a power unit.

5. A knife sharpener according to any one of claims 1 to 3, wherein the guide means is an integral part of the base unit body portion.

6 A knife sharpener according to any one of claims 1 to 3, wherein the guide means is a separate component which, in use, is positioned between and secured to each of the base unit and closure member.

7 A kn!fe sharpener accordig to any one of the preceding cms, wherein the guide means is defined at least in part by a substantially cylindrical or frusto-conically shaped wall portion which defines a part of the said sharpening chamber.

9. A knife sharpener according to claim 8, wherein one guide support supports a blade for sharpening at an angle of 45 .

10. A knife sharpener according to claim 8, wherein one guide support supports a blade for sharpening at an angle of 320 11. A knife sharpener according to any one of the preceding claims, wherein the honing member is substantially in the form of a rotatable disc having a substantially planar surface against which a blade may be brought to bear for sharpening during rotation of the honing member.

12 A knife sharpener according to any one of the preceding claims, wherein the honing member is rotatably supported by a bearing secured relative to the body portion of the base unit.

13. A knife sharpener according to claim 12, wherein the body portion of the base unit provides support for two bearings which lie axially spaced apart relative to the length of the axis about which the honing member is rotatably supported.

14 A knife sharpener according to claim 12 or claim 13, wherein a said bearing is one of the bush type.

1 5 A knife sharpener according to claim 12 or claim 13, wherein a said bearing is a ball or roller bearing of the sealed type.