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Title:
ROTARY MACHINING UNIT
Document Type and Number:
WIPO Patent Application WO/2020/035120
Kind Code:
A1
Abstract:
Rotary machining unit (1) with abrasive strips (3) for grinding or polishing tools. The machining unit comprises a two-part tool holder with a first and a second plate portion that are releasably interconnected. Furthermore, the machining unit comprises a locking mechanism (21) connecting the first and the second plate portion (5,7), wherein the locking mechanism is rotatably mounted on the first plate portion (5). The locking mechanism comprises a central part (23) formed by a circular plate (25) and an annular wall (27) connected therewith, and at least two locking pins (55) connected to the annular wall. The first plate portion (5) and the second plate portion (7) have openings (47,49) which, during assembly, are aligned and arranged to receive a distal end portion (57) of the locking pins (55). The distal end portion (57) of the locking pins is displaced radially between a first locked position, wherein the distal end portion engages the aligned openings (47,49) and a second unlocked position outside the aligned openings, so that the first and second plate portion (5,7) are interlocked or non-interlocked, respectively.

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Inventors:
LARSEN KARSTEN (DK)
Application Number:
PCT/DK2019/050237
Publication Date:
February 20, 2020
Filing Date:
July 30, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
FLEX TRIM AS (DK)
International Classes:
B24D13/14; B24D13/20
Domestic Patent References:
WO2017207008A12017-12-07
WO2001096067A12001-12-20
Foreign References:
US20150209938A12015-07-30
US20110258795A12011-10-27
Attorney, Agent or Firm:
PATRADE A/S (DK)
Download PDF:
Claims:
CLAIMS

1. Rotary machining unit (1) with abrasive strips (3) wherein an abrasive canvas is supported by abrasive brushes for grinding or polishing tools and with an axis of rota- tion (9); the machining unit comprises

- a first connector (11), intended for connecting the machining unit (1) to a motor,

- a two-part tool holder (19) with a first (5) and a second plate portion (7) that are re- leasably connected to each other, wherein the first plate portion (5) is connected to the first connector (11), and the second plate portion (7) is connected to the abrasive strips (3), and

- a locking mechanism (21) connecting the first (5) and the second plate portion (7), characterised in that

the locking mechanism (21) is rotatably mounted on the first plate portion (5) with rotation about the axis of rotation (9), wherein the locking mechanism (21) comprises a central part (23) formed by a circular plate (25) and an annular wall (27) connected therewith, and at least two locking pins (55), which annular wall (27) is connected to the at least two locking pins (55),

- that the first plate portion (5) and the second plate portion (7) have radially-directed openings (47,49) which, during assembly, are aligned and arranged to receive a distal end portion (57) of the locking pins (55),

- that the distal end portion (57) of the locking pins, when rotating the annular wall

(27), is displaced radially between a first locked position, wherein the distal end por tion (57) engages the aligned openings (47,49) and a second unlocked position outside the aligned openings, so that the first (5) and second plate portion (7) are interlocked or non-interlocked, respectively,

- that the annular wall (27) extends through an annular opening (51) in the second plate portion (7), and

- that the central part (23) is provided with a handle (29) for use in rotating the locking mechanism (21). 2. The machining unit according to claim 1, characterised in that the distal end por tion (57) of the locking pin (55) is connected to a proximal end portion (59) via a first hinge joint (61), and the proximal end portion (59) is connected to the annular wall (27) via a second hinge joint (63).

3. The machining unit according to claim 2, characterised in that the hinge joints are formed by narrowed sections (65) in the locking pin (55), which narrowed sections enable a mutual pivoting of the locking pin parts and the annular wall (27). 4. The machining unit according to claim 3, characterised in that the annular wall

(27) and the locking pins (55) are formed as one continuous element.

5. The machining unit according to any of the preceding claims, characterised in that the locking mechanism (21) comprises six locking pins (55).

6. The machining unit according to any of the preceding claims, characterised in that the machining unit (1) comprises a second connection part (13), which is releasably connecting the first connector (11) and the first plate portion (5). 7. The machining unit according to any of the preceding claims, characterised in that an abrasive canvas (75) of the abrasive strip (3) is slotted.

8. The machining unit according to claim 7, characterised in that the abrasive canvas is provided with a diamond material (79).

9. The ability of the machining unit to be used by a robot, according to any of the pre- ceding claims.

10. The ability to use at least one machining unit, according to any of the preceding claims, as a hand tool for machining wind turbines, especially wind turbine blades.

Description:
Rotary machining unit

Field of the Invention

The present invention relates to a rotary machining unit with abrasive strips, wherein an abrasive canvas is supported by abrasive brushes for grinding or polishing tools and with an axis of rotation, wherein the machining unit comprises

- a first connector, intended for connecting the machining unit to a motor,

- a two-part tool holder with a first and a second plate portion that are releasably con nected to each other, wherein the first plate portion is connected to the first connector and the second plate portion is connected to the abrasive strips, and

- a locking mechanism connecting the first and second plate portions.

Background of the invention

Rotary machining units with abrasive strips for abrasive tools comprising a two-part tool holder made of two plate portions are known. The plate portions hold replaceable abrasive strips. The machining unit comprises a first connector to connect the machin ing unit with a motor, a two-part tool holder with a first and a second plate portions that are releasably connected to each other, wherein the first plate portion is connected to the first connector, and wherein the second plate portion is connected to the abra sive strips.

In WO2017 / 207008 Al, rotary machining units are described as explained above.

These machining units have a number of disadvantages, which are explained below:

Replacement of abrasive strips requires manual intervention. Most often, tools are required to separate the individual parts of the machining unit. Thus, replacing the abrasive strips is both time-consuming and requires the use of both hands. Generally, the abrasive strips will be firmly mounted in a plate-shaped holder and in these cases it is the plate-shaped holder that requires the use of both hands for replacement.

Furthermore, the abrasive strips cannot be replaced using a robot. For example, in an automated manufacturing process or a machining line in a factory. Here, the abrasive strips will usually be firmly mounted in a plate-shaped holder. In such situation it is the plate-shaped holder that cannot be replaced using a robot.

Another disadvantage of the known machining units is that it is too complicated to change the abrasive strips when working on wind turbines or wind turbine blades at large height. For such situation, an easy and quick one-handed operation is a neces- sary condition that is not met by the known machining units.

Purpose of the invention

The purpose of the present invention is to provide a machining unit which overcomes these disadvantages.

Furthermore it is the purpose of the invention is to provide a machining unit wherein the abrasive strips and/or the second plate portion can be easily and quickly replaced.

Furthermore it is the purpose of the invention is to provide a machining unit for one- handed operation.

Furthermore it is the purpose of the invention is to provide a machining unit that can be used in the wind turbine industry.

Furthermore it is the purpose of the invention is to provide a machining unit that can be used in the composite- metal- and wood industries.

Furthermore it is the purpose of the invention is to provide a machining unit which, in addition of being able to be used by hands tools, also can be used by robots and other automated machines.

Description of the invention

This is achieved, according to the present invention, with a machining unit of the type specified above, which is characterised in that the locking mechanism is rotatably mounted on the first plate portion with rotation about the axis of rotation, wherein the locking mechanism comprises a central part made of a circular plate and an annular wall connected therewith, and at least two locking pins, which annular wall is con nected with the at least two locking pins, - that the first plate portion and the second plate portion have radially-directed open ings which, during assembly, are aligned and arranged to receive a distal end portion of the locking pins,

- that the distal end portion of the locking pins which, when rotating the annular wall, is displaced radially between a first locked position, wherein the distal end portion engages the aligned openings and a second unlocked position outside the aligned openings, so that the first and second plate portion are interlocked or non-interlocked, respectively,

- that the annular wall extends through an annular opening in the second plate portion, and

- that the central part is provided with a handle for use in rotating the locking mecha- nism.

The abrasive strips are the tools and/or the tool elements that the tool holder is intend- ed to hold.

The abrasive strips may be suitable for use in any grinding or polishing tool.

The abrasive strips may be fixed to the first plate portion.

Alternatively, the abrasive strips may be releasably connected to the first plate portion.

Alternatively, the abrasive strips may be releasably retained between the first and sec- ond plate portion.

Any mechanism may be used to hold the abrasive strips.

The second plate portion may include undercut slots. The slots may extend substan tially in a radial direction.

The abrasive strips may comprise an edge element. The edge element engages the undercut slot.

The first plate portion may comprise an annular outer wall. The first connector may have any configuration depending on the tool or actuator to which it is connected. Thus, for example, the first connector may be an axle or a metal pin.

The locking mechanism may comprise two to twelve locking pins, preferably four to eight locking pins, specifically 6 locking pins.

The machining unit may be made of any material. Preferably, the machining unit is manufactured as a plastic unit.

The locking mechanism may be moulded in one piece.

A further embodiment of the machining unit, according to the invention, is peculiar in that the distal end portion of the locking pin is connected to a proximal end portion via a first hinge joint and that the proximal end portion is connected to the annular wall via a second hinge joint.

A further embodiment of the machining unit, according to the invention, is peculiar in that the hinge joints are formed by narrowed sections in the locking pin, which nar rowed sections allow for a mutual pivoting of the locking pin parts and the annular wall.

Hereby, a rotational movement of the annular wall can be transformed into a radial movement of the distal end portion.

The narrowed sections are flexible due to the material properties of the pins. Examples of suitable materials are plastics materials such as polyamide (PA6 nylon), polyvinyl chloride, acrylonitrile butadiene styrene (ABS) or the like.

A further embodiment of the machining unit, according to the invention, is peculiar in that the openings in the first plate portion are connected to a first guide for controlling the distal end portion of the locking pins. A further embodiment of the machining unit, according to the invention, is peculiar in that the annular wall and the locking pins are formed as one continuous element.

This has the advantage that the entire locking mechanism is formed as a continuous element so that no loose parts can fall out of the machining unit when the abrasive strips or other plate portions are replaced. This is advantageous in challenging work ing conditions, such as when working on mounted wind turbine blades.

A further r embodiment of the machining unit, according to the invention, is peculiar in that the locking mechanism comprises six locking pins.

A further embodiment of the machining unit, according to the invention, is peculiar in that the machining unit comprises a second connector which is releasably connecting the first connector and the first plate portion.

The second connector can, for example, be a bayonet coupling. Thus, the first con nector may consist of a first connection part and a second connection part, where the first connection part is placed on the first plate portion and the second connection part is placed on the first connector.

A further r embodiment of the machining unit, according to the invention, is peculiar in that an abrasive canvas of the abrasive strip is slotted.

A further r embodiment of the machining unit, according to the invention, is peculiar in that the abrasive canvas is provided with a diamond material.

This is an advantage for machining composite materials.

This is an advantage for machining wind turbines, especially wind turbine blades.

The diamond material provides effective grinding for composite materials. Further more, the wear of the abrasive strips is reduced so that the abrasive strips can be used for a longer time. A further embodiment of the machining unit, according to the invention, is peculiar in that the abrasive strips are designed for use in polishing tools.

A further r embodiment of the machining unit, according to the invention, is peculiar in that the first plate portion comprises ribs in a region where the abrasive strips are located.

The ribs support the abrasive strips and hold them in place. The ribs can be positioned in radial direction. The ribs may advantageously be higher in the proximal end portion than in the distal end portion near the outer edge of the first plate portion. Hereby it is obtained that the height of the abrasive strips in the direction of the axis of rotation is lower in an outer region than in a central region of the machining unit. The outer re- gion and central region are shown here in the radial direction. That is, the outer region is near the radial outer edge, while the central region is near the centre in the radial direction.

A further embodiment of the machining unit, according to the invention, is peculiar in that a first pin on the inner side of the annular wall engages an L-shaped groove in an annular support wall on the first plate portion.

The first pin and the L-shaped groove connect the first plate portion and the locking mechanism. The first pin and the L-shaped groove define a first outer position for the locking mechanism relative to the first plate portion. Thus, the first outer position is either in an unlocked position or a locked position.

A further r embodiment of the machining unit, according to the invention, is peculiar in that the locking mechanism comprises a resilient tab which engages a second groove on the first plate portion. The resilient tab and the second groove define a second outer position for the locking mechanism relative to the first plate portion. Thus, the second outer position is either in a locked position or an unlocked position. A further embodiment of the machining unit, according to the invention, is peculiar in that the abrasive strips at an end edge comprises an edge element with a thickening, wherein the second plate portion comprises undercut slots to receive the edge element of the abrasive strips,

wherein the first plate portion and the second plate portion engage each other so that the abrasive strips are retained between the first plate portion and the second plate portion.

A further r embodiment of the machining unit, according to the invention, is peculiar d in that the first plate portion and the second plate portion comprises a second guide for controlling the first and the second plate portions during mutual rotation when assem bling the machining unit.

The first and second plate portions are arranged so that they engage only when the openings in both plate portions are aligned.

Thus, the second plate portion can be rotated on the first plate portion while exerting a slight pressure along the axis of rotation during assembling the machining unit.

When the openings of the first and second plate portions are aligned, the plates engage and cannot be rotated further relative to each other. Subsequently, the locking mecha- nism can be locked by rotating the handle. This increases rapid and easy operation.

A further aspect of the invention is the use of a machining unit described in any claim in a robot.

The machining unit is particularly suitable for use in robots.

The locking mechanism can be operated easily by a robot. There are well-defined out- er positions for the handle in the unlocked and locked position.

The locking mechanism may be designed as a single unit. Thus, there are no individu- al parts that can become detached during use. Since a robot would not be able to de- tect loose parts, this is a significant advantage. Furthermore, the second plate portion and the first plate portion are designed to en gage only when the openings of the first and second plate portions are aligned. Thus, the replacement of the second plate portion or the abrasive strips can be made with a simple and fault-tolerant programming of the robot.

A further aspect of the invention is the use of a machining unit described in any claim in a hand tool for machining wind turbines, especially wind turbine blades.

The machining unit is particularly suitable for use in demanding work situations such as machining a wind turbine blade. The other plate portion and/or the abrasive strips can be replaced with a single one-handed operation without tools. This saves time and increases safety.

The handle is easily accessible in the central part of the machining unit.

The first and second plate portions are arranged so that they engage only when the openings of the both plate portions are aligned. Thus, the second plate portion can be rotated on the first plate portion while exerting a slight pressure along the axis of rota- tion during assembling the machining unit. When the openings of the first and second plate portions are aligned, the plates engage and cannot be rotated further relative to each other. Subsequently, the locking mechanism can be locked by rotating the han dle. This increases rapid and easy operation.

Drawing description

The invention will be explained in more detail with reference to the attached drawing, wherein

Fig. 1 shows the machining unit according to the invention, viewed in perspective,

Fig. 2 shows the machining unit according to the invention, viewed in perspective,

Fig. 3 shows the machining unit according to the invention, viewed parallel to the axis of rotation,

Fig. 4 shows the machining unit according to the invention, viewed perpendicular to the axis of rotation,

Fig. 5 shows the first plate portion, viewed parallel to the axis of rotation, Fig. 6 shows the first plate portion, viewed perpendicular to the axis of rotation,

Fig. 7 shows the first plate portion, viewed in perspective,

Fig. 8 shows the second plate portion, viewed parallel to the axis of rotation,

Fig. 9 shows the second plate portion, viewed parallel to the axis of rotation,

Fig. 10 shows the second plate portion, viewed perpendicular to the axis of rotation,

Fig. 11 shows the locking mechanism according to the invention, viewed in perspec- tive,

Fig. 12 shows the first connector and part of a second connector, viewed in perspec- tive,

Fig. 13 shows the first connector and part of the second connector, viewed parallel to the axis of rotation,

Fig. 14 shows the first connector and part of the second connector, viewed perpen dicular to the axis of rotation,

Fig. 15 shows the locking mechanism in the first plate portion in an unlocked posi- tion,

Fig. 16 shows the locking mechanism of the first plate portion in a locked position, Fig. 17 shows the locking mechanism, viewed parallel to the axis of rotation,

Fig. 18 shows an abrasive strip in perspective, and

Fig. 19 shows an abrasive strip, viewed from one side.

In the description of the figures, identical or similar elements will be denoted by the same reference signs in different figures. Thus, not all the details of each fig ure/embodiment will be explained.

Reference signs

I Machining unit

3 Abrasive strip

5 First plate portion

7 Second plate portion

9 Axis of rotation

I I First connector

13 Second connector

15 First connection part, second connector

17 Second connection part, second connector 19 Tool holder

21 Locking mechanism

23 Central part, locking mechanism 25 Circular plate, locking mechanism 27 Ring-shaped wall, locking mechanism

29 Handle, locking mechanism

31 First pin, locking mechanism

33 Inner side, locking mechanism

35 Resilient tab, locking mechanism 37 Annular outer wall, first plate portion

38 Hole, first plate portion

39 Annular support wall, first plate portion

41 L-shaped groove, first plate portion

42 Second groove, first plate portion 43 First guide, first plate portion

45 Ribs, first plate portion

47 Openings, first plate portion

49 Openings, second plate portion 51 Annular opening, second plate portion 53 Slot, second plate portion

55 Locking pin

57 Distal end portion, locking pin

59 Proximal end portion, locking pin 61 First hinge joint, locking pin

63 Second hinge joint, locking pin

65 Narrowed section, locking pin

67 Edge element, abrasive strip

69 End edge, abrasive strip

71 Thickening, abrasive strip

73 Abrasive element

75 Slotted abrasive canvas

77 Support brushes

79 Diamond materials

81 Axle 83 Second guide

Detailed description of the Invention

Fig. 1-4 show the embodiment of the rotary machining unit 1 according to the inven tion.

Fig. 1 shows a rotary machining unit 1, viewed in perspective. It shows a tool holder 19 with a first plate portion 5 and an annular outer wall 37. In the first plate portion a second plate portion 7 is arranged. Abrasive strips 3 are shown in slots in the second plate portion 7. The abrasive strips 3 are fixed between the first 5 and the second plate portion 7. The second plate portion has an annular opening 51 in the centre. In the annular opening, a central part 23 of a locking mechanism 21 is shown with a handle 29.

Fig. 2 shows the rotary machining unit 1, viewed in a different perspective. The back of the first plate portion 5 is shown. The first plate portion has an annular outer wall 37. A first connector 11 is shown along with an axle 81, which is preferably a metal axle. A second connector 13 is shown. A first connection part 15 of the second con nector 13 is at the centre of the first plate portion. A second connection part 17 of the second connector 13 is connected to the first connector 11. The second connector is a bayonet coupling.

Fig. 3 shows the rotary machining unit parallel to the axis of rotation. A side, which in use faces the workpiece, i.e. the side where the abrasive strips 3 are located, is shown. The abrasive strips 3 are shown, which are radially oriented abrasive strips. The abra- sive strips are in slots 53 in the second plate portion 7. In the centre, the second plate portion has an annular opening 51. In the annular opening of the second plate portion the central part 23 of the locking mechanism 21 with the handle 29 is shown.

Fig. 4 shows the machining unit, viewed perpendicular to the axis of rotation 9. The axle 81 is shown, mainly a metal axle. Further, the annular outer wall 37 of the first plate portion 5 is shown. The abrasive strips 3 are shown, which are fixed between the first and second plate portion. Fig. 5 shows the first plate portion 5, viewed parallel to the axis of rotation, The plate portion includes openings 47 which cooperate with the locking mechanism (not shown) to lock the first plate portion 5 and the second plate portion (not shown) to one another. At the openings 47, there are the radial first guides 43 for guiding the distal end portion (not shown) of the pins (not shown) of the locking mechanism (not shown).

The first plate portion 5 and the second plate portion (not shown) comprise a second guide 83 for controlling the first and the second plate portion during the mutual rota- tion when assembling the machining unit.

The first plate portion 4 comprises a continuous hole 38 at the centre. In the hole, the first connection part 15 of the second connector 13 is shown. The first plate portion comprises a annular support wall 39. The annular support wall 39 comprises an L- shaped groove 41. Further, the annular support wall 39 comprises a second groove 42 which, during use, can accommodate the resilient tab (not shown) located on the lock ing mechanism (not shown).

Ribs 45 are also shown which extend in the radial direction. These ribs 45 support the abrasive strips (not shown). The ribs are higher near the centre and flatten out in the radial direction. This results in the abrasive strips being inclined in a radial direction.

Fig. 6 shows the first plate portion 5, shown in Fig. 5, viewed perpendicular to the axis of rotation 9, An annular outer wall 37 of the first plate portion 5 is shown.

Fig. 7 shows the first plate portion 5, shown in Fig. 5 and 6, viewed in perspective. The annular support wall 39 is shown with the L-shaped groove 41.

Fig. 8-10 show an embodiment of the second plate portion 7, viewed in different ori entations.

Fig. 8 shows the second plate portion 7, viewed parallel to the axis of rotation 9. A front side is shown, which will be facing the workpiece during use. The plate portion comprises an annular opening 51 at the centre. During assembly, the handle (not shown) of the locking mechanism will be available in the annular opening. Slots 53 for receiving the abrasive strips (not shown) are shown.

Fig. 9 shows the second plate portion, viewed parallel to the axis of rotation, A back side is shown, which does not face the workpiece during use. Openings 49 are shown which, during use, will be aligned with the openings in the first plate portion (not shown).

The first plate portion (not shown) and the second plate portion 7 comprise a second guide 83 for controlling the first and the second plate portions during the mutual rota- tion when assembling the machining unit.

Fig. 10 shows the second plate portion 7, viewed perpendicular to the axis of rotation 9. Openings 49 are shown, which cooperate with the locking mechanism during use and which are aligned with the openings in the first plate portion. Slots 53 are shown, which act as undercut holes.

Fig. 11 shows the locking mechanism 21 according to the invention, viewed in per spective. During use, the locking mechanism 21 will be rotatably mounted on the first plate portion (not shown). The locking mechanism 21 comprise a central part 23 formed by a circular plate 25 and an annular wall 27 connected therewith. A handle 29 is placed on the circular plate. Six locking pins 55 are connected to the annular wall 27. The locking pins comprise two hinge joints; a first hinge joint 61 connecting a distal end portion 57 of the locking pin with a proximal end portion 59 of the lock ing pin. The proximal end portion 59 of the pin is connected to the annular wall 27 with a second hinge joint 63. The hinge joints are made as narrowed sections 65. The narrowed sections allow for the mutual pivoting of the locking pin parts and the annu lar wall. Thus, during the assembly on the first plate portion, a rotational movement of the annular wall can be transformed into a radial movement of the distal end portion 57 of the locking pins. A resilient tab 35 is arranged on the circular plate. The resilient tab 35 interacts with a second groove on the first plate portion (not shown).

Fig. 12-14 show the first connector 11 and the second connection part 17 of the sec ond connector 13, viewed in different orientations. Fig. 12 shows the first connector 11 and the second connection part 17 of the second connector 13, viewed in perspective.

Fig. 13 shows the first connector 11 and the second connection part 17 of the second connector 13, viewed parallel to the axis of rotation.

Fig. 14 shows the first connector 11 and the second connection part 17 of the second connector 13, viewed perpendicular to the axis of rotation 9.

The first connector is a metal axle. The second connector is a bayonet coupling.

Fig. 15 shows the locking mechanism 21 mounted in the first plate portion 5. The locking mechanism is in an open position. Thus, the distal end portion 57 of the lock ing pins 55 engages the openings 47 on the first plate portion 5, but does not engage with the openings on the second plate portion (not shown).

Fig. 16 shows the locking mechanism 21 mounted in the first plate portion 5 in a locked position. Thus, the distal end portion 57 of the pins engages the openings 47 of the first plate portion and engages the openings of the second plate portion (not shown).

During the actuation of the locking mechanism 21, a rotational movement of the annu- lar wall is transformed to a radial movement of the distal end portion 57 of the pins. The locking mechanism is designed as a single unit, i.e. the central part 23 of the lock ing mechanism and the annular wall 27 and the locking pins 55 are a continuous unit. Thus, during use, there will be no risk that individual parts becoming detached. This is advantageous in challenging working conditions, such as when working on mounted wind turbine blades.

Fig. 17 shows the locking mechanism, viewed parallel to the axis of rotation, The back side of the locking mechanism is shown. The first pin 31 is shown, which is placed on the inner side 33 of the annular wall 27. The first tap interacts with the L- shaped groove on the first plate portion (not shown). The resilient tab 35 is also shown, which interacts with the second groove on the first plate portion (not shown). Fig. 18 and 19 show the abrasive strip 3. In Fig. 18, the abrasive strip is shown in per spective, and in Fig. 19 the abrasive strip is shown from one side.

The abrasive strip comprises an edge element 67 at an end edge 69. The edge element 67 can engage an undercut slot in the second plate portion (not shown).

The edge element 67 comprises a thickening 71. The second plate portion (not shown) comprises undercut slots for receiving the edge element of the abrasive strips. The first plate portion and the second plate portion engage each other so that the abrasive strips are fixed between the first plate portion and the second plate portion.

The abrasive strip is an abrasive element 73. The abrasive element 73 comprises a slotted abrasive canvas 75 which is supported by support brushes 77 during use. The abrasive canvas is provided with a diamond material 79.