GB2528935A

GB2528935A - Rotating tool for abrading and other uses

Info

Publication number: GB2528935A
Application number: GB1413879.6A
Authority: GB
Inventors: Ismael Martinez Delgado; Lee Shaun Wagstaff; Andrew Roberts
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2014-08-05
Filing date: 2014-08-05
Publication date: 2016-02-10
Also published as: GB201413879D0

Abstract

A machine tool 2 comprising a shaft 12, for attaching the tool to a rotary drive, and a head, to which a removable abrading disk 10 may be attached, mounted for rotation via a universal joint 20 to the shaft. The universal joint 20 comprises an inner member 22 contained within an outer member 24, the universal joint 20 being so arranged that, in use, the inner member 22 rotates relative to the outer member 24 with two degrees of freedom, whilst rotational movement is transmitted between the inner 22 and outer 24 member. The outer 24 member, and preferably the inner member 22, are of single-piece construction and may be made, preferably from nylon, using 3-D printing. The inner member 22 may further have a spherical body from which extend two pairs of opposing cylindrical portions 34. A flexible seal may also be included between the interior of the outer member 24 and the exterior, and the head may include a spigot 26 for piloting the tool 2 around a hole in which the spigot is received. Methods of preparing the surface of a metal for an aircraft and electrically bonding a metal part to another are also included.

Description

ROTATING TOOL FOR ABRADING AND OTHER USES

BACKGROUND OF 11W INVENTION

100011 The present invention relates to a rotating tool for abrading and other uses.

More particularly, but not exclusively, this invention concerns a machine tool having a shaft and a head mounted thereon, and/or concerns one or more parts of such a tool. The invention also concerns a method of manufhcture of such a tool or part thereof, and the use of such a tool. Such uses may extend to a method of preparing the surface of a metal article for use in an aerospace application, such as when electrically bonding one metal part to another in an aircraft. The invention also concerns an aircraft or a part thereof including at least two metal parts bonded to each other in such a way.

[0002] In an aircraft it is important for metal parts to be electrically bonded to one another to avoid/reduce the risk of the creation of potential differences between separate components / parts of the aircraft, There is therefore a need for metal parts to be reliably electrically bonded to each other so that there is a common potential between such parts (i.e. electrically connected to a common "ground" or "earth"). Certain metal parts for use in an aircraft have coatings which can reduce the electrical conductivity between such a part and a further metal part in contact therewith. For example, when bolting two components together, one or both of the components may have such a coating, which needs to be removed, before securing the bolt in place. It is therefore common practice to remove a coating from a component, by mechanical action such as abrasion, in the local area of contact so as to expose the bare metal and thus permit good electrical contact. More generally, it is common practice in the aircraft industry for non-conducting finishes, coatings, grease or lacquers to be removed from the bonding/earthing areas prior to any installation.

[0003] A conventional method of preparing a surface of a component before bolting it to another part will now be described with reference to Figure 1. A coated metal component 104 has a hole 106 for receiving a bolt (not shown), The front surface 108 of the component 104 in the region of the hole 106 is abraded by an abrading tool 102 so as to expose bare metal for providing an electrical bonding surthce. The abrading tool 102 is a power tool having a rotary drive and an abrading head 110 attached to the power tool via a shaft 112.

[0004] With the use of a conventional abrading tool, as described above for example, it is difficult to provide a good quality finish (i.e. uniformly stripped around the hole). The size ofthe abrading head and tool can contributeto such difficulties, particularly in difficult to access regions, especially when the surface of the abrading head can not reliably be placed flat against the surface to be stripped/abraded. It can also be difficult to abrade the region with high accuracy. The abrading head can easily stray when abrading around the hole, resulting in a risk of uneven abrasion and possibly resulting in unnecessary abrasion beyond the local area immediately around the hole. As a result of such difficulties, it may be relatively time-consuming to perform carefully and accurately the necessary preparation of surfaces, to the required standard/quality, before they are electrically bonded together.

Also, much dust, and other undesirable particulate matter, is created by the abrading which makes the task a dirty one to perform, With such dust and dirt being created during performance of the task, it is desirable that the tools used for the job should be resistant to wear and damage from such foreign matter.

[0005] It is known to provide a universal joint -of a ball and socket type -between a hand-operated power tool and a sanding disc -see US 2,854,829 for example. However, it is believed that such a powered sanding disc would be difficult to maintain, difficult to keep clean and would not be suited to aerospace applications, particularly when seeking to abrade around a hole in a metal surface controlled fashion prior to electrically bonding a further metal part thereto, 10006] The present invention seeks to mitigate the above-mentioned problems.

Alternatively or additionally, the present invention seeks to provide an improved tool.

Alternatively or additionally, the present invention seeks to provide an improved universal joint. Alternatively or additionally, the present invention seeks to provide an improved method of electrically bonding one metal part to another in an aircraft or a part thereof,

SUMMARY OF THE INVENTION

[0007] According to a First aspect of the invention there is provided a machine tool.

The tool comprises a shaft having a first end for attaching to a rotary drive and a second end. The tool comprises a head mounted for rotation via a universal joint to the shaft. The universal joint comprises an inner member contained within an outer member. The universal joint is so arranged that, in use, the inner member rotates relative to the outer member with two degrees of freedom, whilst rotational movement is transmitted between the inner member and the outer member. The outer member is of single-piece construction.

[0008] According to a second aspect of the invention there is provided a method of manufacturing a head for attachment to a shaft so as to make a tool according to any aspect of the invention as described or claimed herein. The method according to this second aspect of the invention includes a step of growing the outer member around the inner member or a partial formed inner member.

[0009] According to a third aspect of the invention there is provided a method of preparing the surface of a metal article for use in an aerospace application in which a part of the surface needs to be treated. The method according to this third aspect of the invention includes a step of rotating a tool (according to, or resulting from, any aspect of the invention as described or claimed herein) so that the head of the tool acts on the part of the surface to be treated.

[0010] According to a fourth aspect of the invention there is provided a method of electrically bonding one metal part to another in an aircraft or a part thereof The method according to this fourth aspect of the invention includes a step of abrading at least a part of the surface of at least one of the metal parts so as to expose an area of bare metal by using the method according to the third aspect of the invention. The method according to this fourth aspect of the invention includes a step of bonding the metal parts to each other so that a path of conduction is provided via the abraded surface.

[0011] According to a fifth aspect of the invention there is provided an aircraft or a part thereof including at least two metal parts bonded to each other by means of the method according to the fourth aspect of the invention.

[0012] According to a sixth aspect of the invention there is provided a universal joint, having the features of the universal joint of the tool according to, or resulting from, any aspect of the invention as described or claimed herein.

[0013] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention as described or claimed herein. For example, the method of the invention may incorporate any ofthe features described with reference to the apparatus ofthe invention and vice versa.

DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: [0015] Figure 1 shows a tool according to the prior art; [0016] Figure 2 shows a cross-sectional side view of a tool according to a first embodiment of the invention; 100171 Figure 3 shows a use of a tool in a method according to a second embodiment of the invention; 100181 Figure 4 shows a perspective view of a tool according to a third embodiment of the invention, the tool comprising a head attached to a shaft via a universal joint; 100191 Figure 5 shows a perspective view of the tool of the third embodiment viewed in a direction showing the region where the shaft attaches to the universal joint; [0020] Figure 6 shows a further perspective view of the tool of the third embodiment; [0021] Figure 7 shows a perspective exploded view of the tool according to the third embodiment of the invention showing separately the head, a part of the universal joint and the shaft; 100221 Figure 8 shows a perspective view of the head (incorporating part of the universal joint) alone of the third embodiment; [0023] Figure 9 shows a further perspective view of the head alone of the third embodiment; [0024] Figure 10 is a cross-sectional side view of the tool according to the third embodiment of the invention; [0025] Figure Ii is a cross-sectional view taken across the plane indicated by line A-A of Figure 10; and [0026] Figure 12 shows an aircraft including a component having two metal parts bonded together in which a surface of one part has been abraded using a tool according to an embodiment of the invention.

DETAILED DESCRIPTION

[0027] A first embodiment is illustrated by Figure 2, which shows an abrading tool attachment 2 for a rotary drive power tool (not shown in Figure 2) comprising an abrading head 10 connected to a steel shaft 12 which facilitates attachment to the power tool. The abrading head 10 is connected to the shaft 12 via a universal joint 20. The abrading head and the universal joint 20 are made from nylon. The abrading head 10 includes a spigot 26. The abrading head 10 comprises an abrading disc 11 which is fixed to an abrading disc holder 13. In this embodiment the annular-shaped abrading disc 11 is stuck (with adhesive on the reverse side, i.e. the non-grinding surface, of the disc) on the nylon holder 13 and thus surrounds the spigot 26 which protrudes beyond the abrading surface 27.

[0028] The universal joint 20 is ofaball and socket type, there being a ball part 22 and a socket part 24. The shaft 12 comprises a threaded end 12b which screws into a threaded recess in the ball part 22. The ball part 22 and socket part 24 are so shaped that rotational motion of the shaft 12 is transmitted by the universal joint 20 to the abrading head 10.

Pivoting motion centred about the ball part 22 about any axis perpendicular to the axis of the shaft is accommodated by the universal joint which allows the shaft to pivot +/-10 degrees from its neutral position (in which the plane of the abrading disc is perpendicular to the axis of the shaft).

[0029] The abrading disc holder 13, including the universal joint formed by the ball part 22 and the socket part 24, is made by "growing" the parts 22, 24 from nylon altogether.

[0030] Figure 3 shows the abrading head of the first embodiment in use in a method, according to a second embodiment, of abrading a circular area surrounding a hole 6 in a coated surface 4 of a metal aircraft part. The universal joint 20 enables the operator to correctly position the abrading disc 1 Ito keep the entire abrading surface in contact with the area to be stripped. Thus, the universal joint 20 accommodates misalignment between the rotation axis of the shaft and the perpendicular direction to the (planar) area to be abraded/stripped. The abrading disc I I may thus be maintained parallel to the surface to be abraded. This is particularly relevant when the bonding point is located in areas with difficult access (e.g. wing tank). An obstacle 28 is schematically illustrated in Figure 3.

The universal joint 20 in the tool 2 allows the axis of rotation 32 of the chuck 3 of the power tool 2a to be angled to the surface to be worked at an angle different from that of the axis of rotation 30 of the abrading head 10. When abrading a surface the shaft of the tool is typically rotated at a speed of about 20,000 rpm (revolutions per minute). A vacuum operated dust extraction unit is used to capture dust caused by the abrading.

100311 Once the abrading disc 11 is worn, it can be replaced by sticking another disc onto the head 10. The spigot 26 acts as a pilot which additionally aids alignment of the abrading head with the hole 6. The method of the second embodiment thus facilitates accurate and even abrading of the region around the hole 6 so as to expose the required amount of bare metal for providing an &ectrical bonding surface. A bolt may then be attached to the coated metal component 4 by bolting through the hole, with adequate bonding reliably being provided by the abraded surface.

[0032] A third embodiment is shown in Figures 4 to Ii, Identical reference numerals are used to refer to similar parts of the first embodiment. Figures 4 to 6 show perspective views of an abrading tool 2 taken from various angles. An exploded view of three parts of the tool is shown in Figure 7. Thus, the tool comprises a shaft 12 having a first end 12a for attaching to a rotary drive of a power tool (not shown) and a second opposite end 12b attached to a universal joint 20. The universal joint comprises an inner member 22 contained within an outer member 24. Figures 8 and 9 show the outer member 24 of the universal joint in perspective looking into the joint from the side into which the shaft is inserted. Figure 10 shows a cross-section of the tool taken across a plane that contains the axis of rotation of the shaft, and Figure 11 shows a cross-section of the tool taken across the plane indicated be line A-A in Figure 10.

1ø] Tt will be seen from Figures 7 and 10 that the inner member 22 has a threaded recess 23 which facilitates the attachment of the second end I 2b of the shaft, which has a complementary thread. The inner member 22 has four substantially cylindrical bearing portions 34 that project from a spherical body 36 in a cruciform pattern. Each bearing portion 34 bears against a first internal spherically curved bearing surface 38 inside the outer member 24. Each of the four bearing portions 34 has a circular profile when viewed end-on. The spherical body 36 of the inner member bears against a second internal spherically curved bearing surface 40 of the outer member 24, formed by four internal bearing segments 42 equiangularly located about the central axis of the outer member 24.

The four internal bearing segments 42 each have side walls 42a against which a corresponding side wall of the bearing portion 34 bears, typically in sliding contact, as the tool rotates. Thus, the rotation of the shaft 12 causes rotation of the inner member 22 to which it is attached. The bearing portions 34 of the inner member 22 engage with the internal bearing segments 42 of the outer member 24 and thus cause rotation of the outer member 24. However, the inner member 22 is permitted to rotate relative to the outer member 24 with two degrees of freedom (for example about a first axis that passes through the centre of the end face of one of the four cylindrica' bearing portions 34 and also the opposite bearing portion 34, and about a second axis that passes through the centres of the end faces of the other two of the four cylindrical bearing portions 34), 10034] The outer member 24 is of single-piece construction. The inner member 22 is of single-piece construction. In this embodiment, the inner member and outer member are both grown by means of a direct metal laser sintering process, which results in the inner and outer members being components that are monolithic items made from tool steel. A polyurethane annular gasket (not shown separately in the Figures) is provided to seal over the gap around the shaft 12 in the region around where the shaft enters the hole defined by the outer member 24. The tool of the third embodiment may be used in a method of abrading as described in relation to the second embodiment. The shaft may pivot by up to degrees from its on-axis (neutral) position.

[0035] Figure 12 shows for the sake of completeness two metal parts 4 joined together by a metal nut and bolt 52 with metal washers 54, the surface immediately surrounding the hole through which the bolt extends having been abraded by means of a tool according to an embodiment of the present invention. The abrading removes surface coating on the metal surface, this exposing bare metal so as to ensure good electrical conductivity between the metal parts. The extent of the abrading is controlled by means of a spigot on the tool piloting the rotation of the abrading head so that the abrasion is constrained to a well-defined circular area around the hole.

100361 Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein.

10037] Tt will be seen that the illustrated embodiments have in common that a machine tool is provided. Generalising, the tool comprises a shaft having a first end for attaching to a rotary drive and a second end, The tool also has a head mounted for rotation via a universal joint to the shaft. The universal joint comprises an inner member contained within an outer member, The universal joint is so arranged that, in use, the inner member rotates relative to the outer member with two degrees of freedom, whilst rotational movement is transmitted between the inner member and the outer member, The outer member, and optionally the inner member, is of single-piece construction. It may be that minimising the number of parts in the universal joint assists with the retention of grease/lubricant within the joint and/or protection against ingress of dust, dirt or other unwanted material in the universal joint. Such grease/lubricant retention may further be assisted by the optional provision of a flexible seal provided around the shaft thus providing at least a partial seal between the interior of the outer member and the exterior. The flexible seal is configured to accommodate relative pivoting motion of the shaft relative to the head.

10038] The inner member may be configured and arranged such that it can not be removed from the outer member without breaking one of the inner member and the outer member. Such a feature may be achievable by manufacturing one or both of the inner member and the outer member by means of a 3-D printing technique. Such a feature may result from a close-fitting desired geometry of the inner member and outer member which reduces play in the universal joint.

[0039] The inner member may have a generally spherical body. There may be two pairs of opposing substantially cylindrical bearing portions each having a generally circular cross-section extending from the generally spherical body of the inner member, The cylindrical bearing portions may each have a central axis that passes through the centre of the spherical body. The cylindrical bearing portions may each have an end face that lies on a notional sphere having its centre at the centre of the spherical body. The end faces may bear against a corresponding spherical surface of the outer member of the universal joint. The side wall of each cylindrical bearing portion may bear against a corresponding formation of the outer member of the universal joint so that rotational movement can be transmitted from the rotating shaft to the rotating head via the universal joint. The inner member may, as a result of the geometry ofthe cylindrical bearing portions and of the outer member of the universal joint, be able to rotate (relative to the outer member) about any of the axes of the cylindrical bearing portions. There may be four such cylindrical bearing portions equiangularly arranged about the generally spherical body so as to define a cruciform shape.

[0040] The head may include an integrally provided abrading disc. Alternatively, the head may be configured to receive a removable abrading disc, for example so that difference abrading discs may be attached for different applications or so that worn discs can readily be replaced. The head may be configured for effecting an action on another object not being in the forni of an abrading action. For example, the head may be arranged to perform polishing or brushing or the like, The head may be one that performs a grinding action, an abrading action, a buffing action, a lapping action and/or a polishing action, or may at least be configured to receive an attachmentflxture that performs at least one of the foregoing actions. For example, instead of using an abrading disc, a brush attachment could be used. The tool could be adapted for use in polishing or cleaning, by means of attaching a suitable polishing / cleaning disc for example in place of the above-described abrading disc.

-10 - [0041] The universal joint may be employed in other applications and may have independent utility.

[0042] The head may optionally include a spigot for piloting rotational motion of the head centrally about a bore, which in use receives the spigot.

[0043] The shaft may be integrally formed with a part of the universal joint. It may alternatively be directly connected to, but detachable from, the universal joint, for example attaching to the inner member. The shaft is preferably metal.

100441 The power tool with which the machine tool may be used will typically be a hand-operated power tool, for example an air-powered tool. The hand-operated power tool may be powered by an electric motor. The tool could be employed in application where rotational speeds of below 2,000 rpm might be common. The tool could be employed on a hand-operated tool (i.e. not a power tool).

10045] The machine tool according to any of the embodiments described above may be made by means of a method of manufacture in which the head for attachment to the shaft is at least partially made by growing it. For example, the outer member may be grown, at least partially, around the inner member or a part thereof The inner and outer members are preferably grown contemporaneously. A part of the inner member may be grown and then a part of the outer member may be grown and so on, until both inner member and outer member are fully formed. The inner and outer members may be grown simultaneously. At least one of the inner member and the outer member may be grown using a 3 -D printing technique. It will be understood that the term "growing" as used herein encompasses any form of 3-D printing (or "additive manufacturing" technique). The 3-D printing technique used may employ stereo lithography. The 3-D printing technique used may employ selective sintering, The 3-D printing technique used may employ selective bonding. The 3 -D printing technique used may employ selective curing. The 3-D printing technique used may employ building up a 3-D structure by means of forming successive layers of solid material.

[0046] The inner and outer members of the universal joint may be made from other materials and / or employing other manufacturing techniques. For example, a selective laser sintering (SLS) technique may be used. A fused deposition moulding (FDM)

-II -

technique could alternatively be used. Direct Metal Laser Sintering (DMLS) may be used.

The inner member and outer member may both be grown using a 3-D printing technique that produces non-metal, for example, nylon articles. The inner member and outer member may both be grown using a 3-D printing technique that produces metal articles, for example tooling steel.

10047] A method of preparing the surface of a metal article for use in an aerospace application in which a part of the surface needs to be treated is described above in which the rotating head of a machine tool acts on the part of the surface to be treated, for example rotating against the surface to perform an action such as abrading. Such an action may have application in a method of electrically bonding one metal part to another in an aircraft or a part thereof, and also in other methods. Such methods may include a step of abrading at least a part of the surface of a metal part so as to expose an area of bare metal. There may be a step of bonding metal parts to each other so that a path of electrical conduction is provided via a surface that has been abraded by the tool. When a rotating head acts on such a surface, dust, debris and other dirt may be created, As such a dust extraction system may be employed, such as provided by a vacuum cleaning apparatus.

100481 In use, the universal joint accommodates misalignment between the rotation axis of the shaft and the perpendicular direction to the (planar) area to be worked on.

Misalignment of up to 20 degrees, and in some cases 25 degrees, can be accommodated by means of the apparatus of the invention, [0049] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. Tt will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

-12 -CLAIMSA machine tool comprising: a shaft having a first end for attaching to a rotary drive and a second end, and a head mounted for rotation via a universal joint to the shaft, wherein the universal joint comprises an inner member contained within an outer member, the universal joint being so arranged that, in use, the inner member rotates relative to the outer member with two degrees of freedom, whilst rotational movement is transmitted between the inner member and the outer member, and the outer member is of single-piece construction.
2. A machine tool according to claim 1, wherein the inner member is of one-piece construction.
3, A machine tool according to claim I or claim 2, wherein the inner member can not be removed from the outer member without breaking one of the inner member and the outer member.
4. A machine tool according to any preceding claim, wherein the inner member has a generally spherical body from which extend two pairs of opposing substantially cylindrical bearing portions each having a generally circular cross-section, and all having central axes that coincide at the centre of the spherical body and end faces that coincide with a notional sphere having its centre at the centre of the spherical body.
5. A machine tool according to any preceding claim, wherein the tool includes a flexible seal provided around the shaft to provide at least a partial seal between the interior of the outer member and the exterior, -13 -
6. A machine tool according to any preceding claim, wherein the head is configured to receive a removable abrading disc.
7. A machine tool according to any preceding claim, wherein the head includes a spigot for piloting the tool, in use, to rotate around a hole in which the spigot is received.
8, A machine tool according to any preceding claim, wherein the shaft is directly connected to but detachable from the universal joint.
9. A method of manufacturing a head for attachment to a shaft so as to make a tool according to any of claims 1 to 8, wherein the method includes a step of growing the outer member around the inner member or a partial formed inner member.
10. A method according to claim 9, wherein the method includes a step of growing both the inner member and the outer member contemporaneously.
11. A method according to claim 9 or 10, wherein the method includes forming at least one of the inner member and the outer member at least partially using a 3-D printing technique.
12. A method of preparing the surthce of a metal article for use in a aerospace application in which a part of the surface needs to be treated, wherein the method comprises the step of rotating a tool according to any of claims 1 to 8 or a tool made in accordance with the method of any of claims 9 to 1 1 so that the rotating head acts on the part of the surface to be treated.
13. A method according to claim 12, wherein the method includes using the rotating head of the tool to abrade the surthee to be treated, -14 -
14. A method of electrically bonding one metal part to another in an aircraft or a part thereof, wherein the method includes a step of abrading at least a part of the surface of at least one of the metal parts so as to expose an area of bare metal by using the method of claim 13, and a step of bonding the metal parts to each other so that a path of conduction is provided via the abraded surface.
15. An aircraft or a part thereof including at least two metal parts bonded to each other by means of the method according to claim 14.
16. A universal joint having the features of the universal joint of the tool of any of any of claims 1 to 8 or of a tool made in accordance with the method of any of claims 9 to 11.