| JP2003311594 | DROSS REMOVING METHOD AND DROSS REMOVING APPARATUS FOR USE THEREIN |
| JP2003305652 | GRINDING WHEEL |
| JP2005039293 | METHOD OF CLEANING CMP PAD CONDITIONING DISK |
MARKHAM, Kenneth (14 St Marks Crescent, Newport NP20 5HD, GB)
MCFARLANE, Stephen, (14 St Marks Crescent, Newport NP20 5HD, GB)
PETERS, Neil (14 St Marks Crescent, Newport NP20 5HD, GB)
MARKHAM, Kenneth (14 St Marks Crescent, Newport NP20 5HD, GB)
MCFARLANE, Stephen, (14 St Marks Crescent, Newport NP20 5HD, GB)
Claims
1. A rotary tool for a hand held drive comprising a backing disk having a central bore or fitting for fitting to a hand held rotary drive, and comprising a plurality of projections extending from the disk, each projection having an outer part and an inner part, the outer part surrounding substantially the inner part, the inner part being of relatively harder material than the outer part and the inner part being exposed at the end of the projection furthest from the disk to form an exposed tip standing higher than the adjacent surrounding outer part for striking a work surface during rotation, all said tips lying substantially only in one common pitch circle.
2. A rotary tool as claimed in claim 1 wherein each tip is substantially equally spaced around the pitch circle.
3. A rotary tool as claimed in claim 1 or claim 2 wherein the tips are arranged such that they can strike the work surface during rotation, one by one at substantially the same work surface location.
4. A rotary tool as claimed in any one of the preceding claims wherein each projection is cylindrical and the inner part is held approximately centrally in the projection.
5. A rotary tool as claimed in any one of the preceding claims wherein a portion of each projection is received in an aperture formed in the disk.
6. A rotary tool as claimed in claim 5 wherein the portions of the projections are held in the apertures by means of welding or brazing of the portion.
7. A rotary tool as claimed in claim 5 wherein the portions of the projections are held in the apertures by means of deforming the material of the portions and/or the disk.
8. A rotary tool as claimed in any one preceding claim wherein the disk is a generally flat plate, the bore or fitting has an axis for rotation, and the projections lie in a cylindrical plane substantially coaxial with the axis. 9. A rotary tool as claimed in any one of the preceding claims 1 to 7 wherein the disk is dished, the bore or fitting has an axis for rotation, and the projections lie in a conical plane substantially coaxial with the axis.
10. A rotary tool as claimed in any one preceding claim wherein the disk and projections are formed as a moulding, the inner parts being formed from moulding inserts.
11. A rotary tool as claimed in any one preceding claim wherein the disk and projections are formed from steel and the inner part is tungsten carbide.
12. A rotary tool as claimed in any one preceding claim wherein the disk and projections are formed as a pressing or forging, the inner parts being inserted into the pressed or forged dish.
13. A rotary toll as claimed in any one preceding claim wherein the disk includes apertures to form shock absorbing spokes.
14. A rotary tool as claimed in any one preceding claim a rotary tool substantially as described and illustrated herein. 15. A method of removing layers or deposits from a surface, the method comprising the steps, in any suitable order, of: i) providing a rotary tool as claimed in any one of the preceding claims; ii) rotating the tool on a drive at speed of 6000 to 14,000 rpm in a hand held rotary drive; Ni) while the tool is rotating in a first plane, bringing the tips one at a time into contact with a work surface having said surface layers or deposits, said surface having a second plane which is not parallel to the first plane thereby causing hammering or chipping of said surface by said tips; and iv) at least partially removing said layers or deposits by means of said chipping or hammering.
16. A method of removing layers or deposits from a surface as claimed in claim 15 wherein the projections sacrificially wear so that their inner part is exposed above the surface of their adjacent outer part to form or reform said tips because their outer part is softer than their inner part.
17. A method of removing layers or deposits from a surface as claimed in 15 or 16 wherein the hammering or chipping occurs at a rate which exceeds 500 blows per minute. |
Tool for a hand held rotary drive
This invention relates to a tool for a hand held rotary drive, particularly, but not exclusively for removing paint, rust, deposits, encrustations or other surface layers from hard surfaces, such as concrete or metal. Rotating wire brushes and wearable abrasive disks are known, which can remove deposits from a surface, but where thick and/or tough layers are encountered, their useful life is short.
Cutting blades which use tungsten carbide teeth tips have been employed in commercially available products. These blades have many disadvantages. The tungsten carbide is brittle so a tough backing material, usually steel, is used.
The tungsten carbide tips need to joined to the backing is some way. This can be done mechanically but the result is a bulky cutter. Alternatively, the tips can be brazed into position. The tips often break or are lost completely when the tip comes adrift from the backing material. This is extremely dangerous when the tip is being rotated at high speed. These types of cutters are of no use when removing thick surface layers or deposits.
Embodiments of the present invention address the problems mentioned above. Accordingly the invention provides a rotary tool for a hand held drive comprising a backing disk having a central bore hub, boss or fitting for fitting to a rotary hand held drive, and comprising a plurality of projections extending from, e.g. a face of the disk, each projection having an outer part and an inner part, the outer part surrounding substantially the inner part, the inner part being of relatively harder material than the outer part and the inner part being exposed at the end of the projection furthest from the disk to form an exposed tip standing higher
than the adjacent surrounding outer part for striking a work surface during rotation, all said tips lying substantially only in one common pitch circle.
In a preferred embodiment, each tip is substantially equally spaced around the pitch circle. Conveniently, the tips are arranged such that they can strike the work surface during rotation, one by one at substantially the same work surface location.
In an embodiment, each projection is cylindrical and the inner part is held approximately centrally in the projection. It is preferred that a portion of each projection is received in apertures formed in the disk. In that case the portions of the projections may be held in the apertures by means of welding or brazing of the portion or by means of deforming the material of the portions and/or the disk to form a rivet.
In one embodiment, the disk is a generally flat plate, the bore or fitting has an axis for rotation, and the projections lie in a cylindrical plane substantially coaxial with the axis.
In a different embodiment, the disk is dished, the bore or fitting has an axis for rotation, and the projections lie in a conical plane substantially coaxial with the axis. It is possible that the disk and projections are formed: as a moulding, the inner parts being moulding inserts; or a single piece pressing, the inner party being inserted directly into the pressed projections.
The disk and projections may be formed from steel and the harder material may be tungsten carbide.
The disk may include apertures to form shock absorbing spokes.
The invention extends to a rotary tool substantially as described and illustrated herein.
The invention extends also to a method of removing layers or deposits from a surface, the method comprising the steps, in any suitable order, of: i) providing a rotary tool as mentioned above; ii) rotating the tool on a drive at speed of 6000 to 14,000 rpm in a hand held rotary drive; iii) while the tool is rotating in a first plane, bringing the tips one at a time into contact with a work surface having said surface layers or deposits, said surface having a second plane which is not parallel to the first plane, thereby causing, hammering or chipping of said surface by said tips; and iv) removing said layers or deposits by means of said hammering or chipping.
In the method the projections may sacrificially wear so that their inner part is exposed above the surface of their adjacent outer part to form or reform said tips, because their outer part is softer than their inner part.
The invention extends to any novel feature, or combination of novel features disclosed herein, whether or not those features are mentioned in combination herein. Embodiments of the invention will now be described by way of example only, with reference to the drawings wherein:
Figure 1 shows one embodiment of a tool for a hand held rotary drive;
Figures 2a and 2b show, in the alternative, details of the tool shown in Figure 1 ;
Figures 3 and 4 show a second embodiment of a tool for a hand held rotary drive;
Figures 5,6,7 and 8 show further embodiments of a tool for a hand held rotary drive; and Figure 9 illustrates a tool in use.
Figure 1 sows a rotatable tool 10 having a backing disk 12, which includes a central bore 14 for fitting to the arbour of an angle grinder (not shown). The tool includes twelve (in this case) projections 16, only one of which is identified, extending from a front face 15 of disk 12 approximately perpendicular to the face 15. The projections 16 each have a central axis which extends in a cylindrical plane coaxial with the axis of rotation of the tool 10, so that they have a common pitch circle.
Figure 2a shows a section along line M-Il in Figure 1. One of the projections 16 can be seen in more detail in section. The projection includes an outer part in the form of a steel cylindrical body 20 having an inner part in the form of a tungsten carbide core rod 22, the end of which forms a tool tip 23. The rod is compressed by the surrounding steel and held in place by friction. The body 20 provides a tough support for the rod 22 so that large pieces of the tungsten carbide cannot break off in use. The projections have a portion of reduced diameter 24 which is received in a complementary aperture 28 in the disk 12. In this instance the projections are welded to the back of the disk to hold them in place at weld area 26.
Figure 2b illustrates an alternative method of fixing the projections 16 to the disk 12. In this alternative, the reduced diameter portion 24 of each
projection 16 is deformed into a countersunk area 27 on the back of the disk to form a rivet.
Figure 3 shows a sectional side view of second embodiment of a rotatable tool 30 which is similar to the embodiment described above accept that the disk 32 shown is dished to form a concave area 33 and a mounting face 36 for the projections. The mounting face 36 is not perpendicular to the axis of rotation of the tool, so the projections 16 extend not in parallel but in a conical plane having an included angle of about 10 degrees. The tool tips 23 have a common pitch circle also, centred on the bore 14. The dished arrangement improves the tool's ability to reach internal corners around rivet heads, stepped areas, and the like. The disk can be made form thinner material because the dished shape is stiffer, which reduces material and transport costs, and reduces inertia of the tool in use.
Figure 4 shows a view in the direction of arrow A in Figure 3. It can be seen from this drawing that this tool has eight projections 16. Also shown are scallops 34 in the disk, between each projection, which reduce the spinning weight of the tool to reduce inertia further. It is possible to provide apertures (not shown) in the disk 12 between the bore 14 and the projections 16. Such apertures would be unlikely to become clogged because such apertures would be raised above the work area and so would be less likely to catch debris such as marine growth in the form of weed etc. The benefits of such apertures in the disk are mentioned below.
Figure 5a shows a third embodiment of a rotary tool 50 which is similar to the embodiments described above and also could be modified to include some
of those features described such as the concave area 33 around the bore 14. In this embodiment the tool 50 is pressed from a single piece of metal to form, in one operation, a backing disk 58 and eight, in this case, projections 59. The projections 59 extend not in parallel but in a conical plane having an included angle of about 10 degrees. Tungsten carbide core rods 22 forming an inner part of the projections 39 are inserted and secured in the projections 39 before or after pressing to shape. The cores 22 can be held in place by deformation of the projection around the core 22. The exposed cores 22 form tool tips 23.
Figure 5b shows a sectional view of the tool 57 shown in Figure 5a. It is apparent from this Figure that the projections 59 are formed integrally with the backing disk 58 from a single piece of material, with no joins.
Figures 6 a, b and c illustrate a central spigot or boss 69 incorporated with a rotatable tool 60 similar to the tool 10 shown in Figure 1. The tool 60 has a backing disk 12, which is modified to include the boss 69. The boss 69 could be used with the other tools shown.
The central spigot or boss 69 adds additional security of fixing the tool to the hand held rotary drive. This will be desirable when the tool is subjected to high accelerations and vibrations because it is less likely to work loose.
The boss 69 could be threaded or plain bore but will always include a method for clamping the boss 69 to the rotary drive arbour. Figures 6 a, b and c show an example of how this clamping effect could be embodied in a threaded boss. Two screws 61 are fitted into threaded holes 68 in the disk 12. The holes 68 are parallel and equally spaced on a pitch circle co-axial with bore 14. When the screws 61 are threaded through the disk 12 from the front face 15 and out of
the back face, they abut projections 62 on the boss 69. Further tightening of the screws 61 causes the projections 62 and the nearby material of the boss to be deformed. This deformation is concentrated and assisted by two parallel slots 63 that allow the projections 62 and nearby material to flex independently of the main body of the boss. Since the rotary drive arbour will be a threaded shaft running through the boss 69, any distortion of the boss will cause binding of the male and female threads, thereby clamping the boss onto the rotary drive arbour.
Referring to Figures 7 and 8, a further rotary tool 70 is illustrated, with elements which are the same as, or similar to, the embodiments mention above having like reference numerals. In this embodiment the backing disk 12 has apertures 72, only one of which has been identified. These apertures 72 form spokes 74 which extend generally radially from a central bore 14.
The spokes 74 provide flexibility in the disk 12 which absorbs the shocks and vibrations generated by the hammering action of the tool tips 23. This in turn leads to reduced vibration for the user and also reduces the tendency for the tool to creep, i.e. slowly shift its position relative the arbour on which it is mounted, and thereby reduce the clamping force required at the arbour. It will be noted that the spokes 74 could be spirally formed or could be another non-linear shape to increase their length and thereby increase the shock absorbing properties mentioned immediately above.
Apertures 72 have a further advantage in that, when the tool 70 is rotated, the user can observe the work surface under the tool. Further, the risk of tool clogging is reduced because the apertures 72 allow better egress of
material away from the working area. Better extraction of material from the work area can be achieved when the apertures 72 are provided, when compared the plain disk shown in Figure 1. The apertures 72 have a further benefit when used under water. The spinning disk 12 with apertures has hydrodynamic effects which pull the disk toward the work surface, thereby reducing the driver's effort to use the tool. This effect is augmented if the disk is dished as shown in Figure 3.
The disk 12 includes an annular groove 76 adjacent the bore 14 which holds an elastomeric O ring 78. The O ring, in an uncompressed state sits proud of the rear surface of the disk 12, so that it is compressed by the locking element of an arbour when the disk is held in an arbour. The compression of the O ring provides friction between the driving flange of the arbour and the disk, and resiliently forces the disk away from the flange toward a locking element of the arbour. This friction and resilient force reduces creeping of the tool relative to the arbour and maintains the clamping force of the arbour when the tool is subjected to shock and vibration.
Projections 16 in this embodiment are held in an aperture 27 which is the same size as the diameter of the projections 16. A shoulder 71 is provided on the cylindrical body 20. The body 20 is welded to the disk at the periphery 73 of the shoulder 71 .
Figure 9 shows tool 10 in use. However the same technique can be used for the the other tools 30,50,60 & 70 described above. The tool 10 is fitted to an hand held rotary drive, in this instance in the form of an angle grinder 90 having a standard arbour 92. In use the tool 10, is spun at high speed i.e. 6000 rpm to
14,000, on the angle grinder 90, and presented to a bonded coating, paint, rust, scale, marine encrustation or similar surface layer or deposit to be removed. The tool is rotated in a plane A which is not parallel to the work surface B. The action causes the tool tips 23 to strike the surface all at a single point C or short arc and thereby chip-off the surface layer or deposit. The action of the tips 23 has been found to be equivalent to the linear chipping actions of known industrial chipping hammers or needle guns. Such chipping hammers and needle guns produce significant vibration in the hands and arms of the user, however, it has been found that the rotary tool described above produces less vibration. The chipping action of the tools results in wearing of tips 23. As the tungsten carbide of the tips wears it will approach the same level as the surrounding steel body 20 or projections 59. The steel body 20 or projections 59 will wear sacrificially, and leave the tungsten carbide tip 23 exposed slightly above the level of the steel body, so the tips 23 are being reformed constantly in use. Thus, the projection 16 or 59 will have a slightly raised central part or tip which is used for chipping off the layers or deposits, but the tungsten carbide rod 22 will not be exposed to such a degree that it becomes vulnerable to breakage due to a lack of support.
Embodiments of the tool have been described and illustrated but it will be understood that many variants and alternatives will be readily apparent to the skilled addressee. For example the tool could be a single moulding or casting, replacing the separate disk and projections illustrated. In such a modification, the tungsten carbide rods can be inserted in the mould prior to moulding or casting. A forging could be used, in which case the tungsten carbide rods 22 could be inserted after forging.
The materials described could be replaced by other materials. For example the steel disk and projection bodies could be replaced by brass or bronze when working in corrosive conditions such as a marine environment. An aluminium casting, or moulded polymer or composite could be used for light duty work. In practice the overall diameter of the tools 10,30,50,60 or 70 described and illustrated will be about 70mm to about 250mm in diameter. The supporting disks for example disks 12 or ,32, will have a material thickness of about 1.5mm to about 6mm. The number of projections could be from about 4 to about 30 and is dependent on the diameter and intended speed of use. The tools described provide an efficient chipping action in a single point or short arc on a material surface. The action is effective because it has been found that there is a hammer type blow hitting the surface rather than a rubbing or abrasive action. Thus repeated blows to the surface thousands of times a second can be achieved if for example a ten tip tool is used at 10,000 rpm, - 10 X 10,000/60= 1667 blows per second. Blows at a rate of 500 to 1500 times a second have achieved good results, and blows at a rate of about 1000 per second work very well, for example, 8 tips at speed of 7500rpm. Additionally clogging is overcome and the tool has a low inertia when compared with abrasive type tools.
The tools described and illustrated are efficient at removing surface coatings or deposits from hard underlying substrates such as steel or concrete, for example to prepare the substrates for repainting, because they provide a hammering action. The tools have no detachable parts so they are safer than tools with detachable parts which could fly-off in use. The tools are intended to fit a standard arbour of an angle grinder or other standard hand held drive. The use
of tungsten carbide in the embodiments employs that material to good advantage, making use of the material's heat and wear resistance in a hammering or chipping action. The tools shown are not intended to cut, mill, grind or polish the substrate. An advantage of tools described herein is that, unlike conventional grinding tools, they do not clog. The construction of the tools described allows the rods to withstand constant high frequency impacts e.g. up to 7000 blows per second. The large number of blows allows just a little coating or deposit to be removed by each tip and so only a light loading is applied to each tip as it revolves and hits the surface at each revolution. Since each tip is used to chip, by lifting from the substrate surface and repeatedly hitting it once every revolution, less heat is generated when compared with abrasive tools that rub the surface, generally over a significant arc. The tips have, therefore a longer life than say, abrasive particles. The use of the fast spinning tools herein reduces vibrations in the hands and arms of the user when compared with tools which produce linear chipping actions. The rotary action has been found to be particularly effect at removing unwanted surface layers such as bonded coatings or linings, paint scale, rust marine growth or encrustation, from hard materials such as steel or concrete.