Temporary fastener with clutch

Abstract

A fastener 10 comprises: an elongate hollow body 20 having a first axial aperture 22 in a first end 24 and a second axial aperture 26 in a second end 28. A spindle 40 is located through the elongate h

Description

TEMPORARY FASTENER WITH CLUTCH TECHNICAL FIELD The present disclosure relates to a fastener for temporarily holding a plurality of objects together. Particularly, but not exclusively, the present disclosure relates to a temporary fastener with a clutch arrangement. Aspects of the invention relate to a fastener and method of use of a fastener. BACKGROUND In various industries such as the aerospace and automotive industries, it is known to use temporary fasteners to securely hold or clamp objects or components, often called workpieces, together in a temporary manner. For example, in the aerospace industry it is known to use temporary fasteners, often known as clecos, to temporarily attach sheets of material, such as aluminium, forming the skin of an aircraft, to each other and / or to the airframe of the aircraft prior to application of a more permanent fixing means, such as rivets or bolts. Similar examples can be found in the automotive industry, where sections of a vehicle body may be temporarily held in place whilst other manufacturing operations are carried out. Often the temporary fasteners may be used to hold the workpieces together whilst other manufacturing operations such as cutting, bending, drilling, deburring, welding, riveting or bolting of the workpieces are carried out. Issues can arise in the use of tools used to attach and detach the temporary fasteners to the workpieces, as it can be difficult to provide a desired amount of torque, especially at very low loads, for example below 0.5 Nm. There is therefore a risk in damaging the workpieces when attaching the temporary fasteners. Itis an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a fastener and a method of using a fastener as claimed in the appended claims. According to an aspect of the present invention there is provided a fastener comprising: an elongate hollow body having a first axial aperture in a first end and a second axial aperture in a second end; a spindle located through the elongate hollow body, the spindle comprising a driving portion extending through the first axial aperture of the elongate hollow body, a clamp portion extending through the second axial aperture of the elongate hollow body, and a threaded portion connecting the driving portion to the clamp portion within the elongate hollow body; and a clamp shaft extending over the clamp portion of the spindle, through the second axial aperture of the elongate hollow body, and into the elongate hollow body, the clamp shaft comprising a threaded end engaged with the threaded portion of the spindle for relative axial movement of the clamp shaft along the clamp portion of the spindle, and the clamp shaft further comprising a plurality of clamping legs at an opposite end of the clamp shaft to the threaded end, the plurality of clamping legs configured to move radially as the clamp shaft is moved axially along the clamp portion of the spindle; wherein the driving portion comprises an inner casing and an outer casing, the inner casing engaging with the outer casing via a clutch mechanism. An advantage of the invention is that a fastener can be provided that can be operated using a standard torque wrench, for example an electric torque wrench or a pneumatic torque wrench, also known as a nut runner, whilst providing an accurate clamp load for the fastener. The fastener can therefore be operated using standard torque wrenches or other tools without causing damage to workpieces that may otherwise be damaged by the application of torque to the fastener. The outer casing may comprise a recess and the inner casing may comprise a flange, the flange being located within the recess of the outer casing to prevent relative axial movement between the outer casing and the inner casing. The outer casing may be free to move rotationally relative to the inner casing when the clutch mechanism is disengaged and the outer casing may be prevented from moving rotationally relative to the inner casing when the clutch mechanism is engaged. The clutch mechanism may comprise one or more radially displaceable ball bearings, each of the one or more radially displaceable ball bearings having a portion located within the outer casing and a portion located within the inner casing when the clutch mechanism is engaged, thereby preventing relative rotational movement between the outer casing and the inner casing. The clutch mechanism may comprise three radially displaceable ball bearings. The outer casing may comprise a slot for each radially displaceable ball bearing. The slot for each radially displaceable ball bearing may be dimensioned to receive a respective radially displaceable ball bearing. The slot for each radially displaceable ball bearing may comprise a curved surface with a first portion having a curvature which is equal to or less than the curvature of the radially displaceable ball bearing to be received in the slot. The first portion may be located at a first edge of the slot onto which the radially displaceable ball bearing is engaged during engagement of the fastener to a workpiece. The slot for each radially displaceable ball bearing may comprise a second portion having a larger curvature than that of the first portion of the slot. The second portion may be located at a second edge of the slot onto which the radially displaceable ball bearing is engaged during disengagement of the fastener from the workpiece. An advantage of this feature is that the larger curvature at the second portion of the slot, which provides an clutch engagement surface during disengagement of the fastener from the workpiece, allows a greater torque to be applied to the outer casing during disengagement of the fastener than the first portion of the slot, which provides an engagement surface during engagement of the fastener to the workpiece, allows to be applied to the outer casing during engagement of the fastener, thereby ensuring that the fastener can be disengaged from the workpiece. The clutch mechanism may comprise an axially displaceable ball bearing located within a central aperture of the inner casing, the axially displaceable ball bearing being positioned to be engaged with the one or more radially displaceable ball bearings. Axial displacement of the axially displaceable ball bearing along the central aperture of the inner casing may cause radial displacement of the one or more radially displaceable ball bearings. The clutch mechanism may comprise a compression spring located within the central aperture of the inner casing. The compression spring may be configured to provide a force acting upon the axially displaceable ball bearing to bias the axially displaceable ball bearing towards the one or more radially displaceable ball bearings. The central aperture of the inner casing may be threaded. The clutch mechanism may comprise a headless threaded bolt configured to engage with the compression spring such that the compression spring is compressed between the headless threaded bolt and the axially displaceable ball bearing. The headless threaded bolt may be accessible from a distal end of the driving portion to enable the headless threaded bolt to be rotated to facilitate axial movement of the headless threaded bolt. An advantage of this feature is that by axially moving the headless threaded bolt towards the axially displaceable ball bearing an increased force is exerted upon the axially displaceable ball bearing and therefore an increased force is exerted on the one or more radially displaceable ball bearings, such that a higher torque is required to force the radially displaceable ball bearings out of engagement with the outer casing to allow the outer casing to rotate relative to the inner casing. Thus, by adjusting the position of the headless threaded bolt the clamping force of the fastener on one or more workpiece can be adjusted. According to an aspect of the present invention there is provided a method of use of a fastener according to any preceding claim, comprising: arranging the clamp shaft to be fully extended over the clamp portion of the spindle with the clamping legs having a minimum separation; inserting the clamp shaft through an aperture in a workpiece; applying torque to the driving portion such that the driving portion rotates in a first direction causing the threaded portion of the spindle to rotate relative to the threaded end of the clamp shaft thereby effecting axial movement of the clamp shaft into the elongate hollow body of the fastener over the clamp portion of the spindle to deflect the clamping legs away from each other to provide a maximum separation of the clamping legs; and continuing to apply torque to the driving portion until the clamping legs engage with the workpiece and the clutch mechanism disengages the outer casing from the inner casing. Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a side view of a fastener according to an embodiment of the invention; Figure 2 illustrates a cross sectional view of a fastener according to an embodiment of the invention with a clamp shaft in an extended position; Figure 3 illustrates a cross sectional view of a fastener according to an embodiment of the invention with a clamp shaft in a retracted position; Figure 4 illustrates a cross sectional view of a driving portion of a fastener according to an embodiment of the invention with a spring under a first compressive load; Figure 5 illustrates a cross sectional view of a driving portion of a fastener according to an embodiment of the invention with a spring under a second compressive load greater than the first compressive load; Figure 6 illustrates an outer casing of a driving portion of a fastener according to an embodiment of the invention; Figure 7 illustrates a cross sectional view of the fastener according to an embodiment of the invention, through section A-A of figure 5; Figure 8 illustrates a magnified view of part of the arrangement illustrated in figure; and Figure 9 illustrates blocks of a method of use of a fastener according to an embodiment of the invention. In the drawings, like parts are denoted by like reference numerals. DETAILED DESCRIPTION Examples of the present disclosure relate to a fastener. In particular, examples of the present invention relate to a temporary fastener, though it will be understood that such fasteners may be used in a permanent or semi-permanent manner. Non-limiting examples will now be described with reference to accompanying Figures 1 to 8, where the figures illustrate a fastener 10 and Figure 9, which illustrates a method of use of a fastener 10. The fastener 10 of the present invention may be used as a temporary fastener where workpieces, in the form of various objects or components, for example sheet metal components used in aerospace or automotive construction, are intended to be held together securely in a temporary manner, which may allow further manufacturing operations to be carried out on the workpieces whilst being temporarily held. The fastener 10 comprises a clutch mechanism 100 which is adjustable to limit the torque that can be transmitted to a workpiece via the fastener 10 in a clamping operation. The adjustment of the clutch mechanism 100 allows for workpieces to be held by the fastener 10 with a pre-set force, as will be further explained below in relation to the operation of the fastener 10. With reference to Figure 1, there is shown a fastener 10 having an elongate hollow body 20, which may be in the form of a cylindrical body, but could be of any other shape, which has an inner chamber 30 in which components of the fastener 10 can be located and through which components of the fastener 10 can be translated in a first axis. The first axis is a central axis through the elongate hollow body, in particular the centre of rotation in a cylindrical body. The fastener 10 has, at a first end 24, a fastener driving portion 50, or actuation portion, by which the fastener 10 may be driven or actuated by a tool such as a nut runner. The fastener 10 has, at a second end 28 axially opposite the first end 24, a clamp shaft 80. The clamp shaft 80 extends in the first axis and comprises a plurality of clamping legs 90 at a terminal end 94 of the clamp shaft 80. The clamping legs 90 may be configured to have a closed condition and an open condition. In the closed condition, the clamping legs 90 of the fastener 10 can be inserted through an aperture of a workpiece. In the open condition, the clamping legs 90 of the fastener 10 would not be able to be inserted through that same aperture of the workpiece. In the open condition, the clamping legs 90 of the fastener can be arranged to clamp a workpiece between the clamping legs 90 and an outer surface 32 of the second end 28 of the elongate hollow body 20. Each of the clamping legs 90 may comprise a projecting surface 92, which may be a radially projecting or substantially radially projecting surface 92, that is a surface which is in a plane perpendicular, or substantially perpendicular, to the first axis. The clamping legs 90 are configured to hold a workpiece between the projecting surfaces 92 of the clamping legs 90 and an outer surface 32 of the second end 28 of the elongate hollow body 20 when the driving portion 50 is driven such that the projecting surfaces 92 of the clamping legs 90 move axially to engage with the workpiece. In some embodiments, the outer surface 32 of the second end 28 of the elongate hollow body 20 may be flat. In other embodiments, in particular where the elongate hollow body 20 is cylindrical, the outer surface 32 of the second end 28 of the elongate hollow body 20 may be tapered or have a tapered outer rim, where such tapered end is configured to engage with a countersunk aperture in a workpiece, thereby holding the workpiece in a more stable condition. Further detail of the fastener 10 can be seen in the cross section illustrated in Figure 2, which shows the fastener 10 in a first condition where the clamping legs 90 are in a closed condition, that is a condition where the clamping legs 90 are not separated, or have a minimum separation, in a plane perpendicular to the first axis. In this first condition, where the clamping legs 90 are in a closed condition, the projecting surface 92 may not lie in a plane perpendicular to the first axis but be canted from this plane such that when the clamping legs move to the open condition, they then lie in a plane perpendicular to the first axis. Therefore, in the open condition, the clamping legs 90 have a projecting surface 92 which is parallel to the outer surface 32 of the second end 28 of the elongate hollow body 20, thereby providing a more uniform connection between the clamping legs 90, the elongate hollow body 20 and the workpiece located therebetween. Figure 3 shows the fastener 10 in a second condition where the clamping legs 90 are in an open condition, that is a condition where the clamping legs 90 are separated, or define a maximum separation, in a plane perpendicular to the first axis. In this second condition of the fastener 10, the clamping legs 90 lie in a plane perpendicular to the first axis. The projecting surfaces 92 of the clamping legs 90 may be formed as part of respective enlarged ends of the clamping legs 90 at the terminal end 94 of the clamp shaft 80. In some embodiments, the clamping legs 90 may comprise a tapered portion, the tapered portion tapering towards the enlarged ends of the clamping legs 90 at the terminal end 94 of the clamp shaft 80, such that, when the clamping legs 90 are in the closed condition, the enlarged ends of the clamping legs 90 have, or define, a width, in a plane perpendicular to the first axis, which is less than, the same, or substantially the same as the width or diameter of the clamp shaft 80 portion which does not define the clamping legs 90, in a plane perpendicular to the first axis. That is, when the clamping legs 90 are in the closed condition, the maximum width defined by the arrangement of clamping legs 90 in a plane perpendicular to the first axis is less than or equal to the width or diameter of the non-tapered clamp shaft 80 portion in a plane perpendicular to the first axis. In this way, the clamp shaft 80 including the clamping legs 90 can be inserted through an aperture in a workpiece, where the aperture has a diameter matched to the width or diameter of the clamp shaft 80. Alternatively, or additionally, the clamping legs 90 may be configured to be biased towards each other without any external force being applied to them such that the maximum width of the clamping legs 90, in a plane perpendicular to the first axis, is less than or equal to the width or diameter of the clamp shaft 80 portion which does not define the clamping legs 90, in a plane perpendicular to the first axis. In this way, the clamp shaft 80 including the clamping legs 90 can be inserted through an aperture in a workpiece with a diameter matched to the width or diameter of the clamp shaft 80. The internal separation of the clamping legs 90 reduces towards the terminal end 94 of the clamp shaft 80, this may be through biasing of the clamping legs 90 towards each other, or, in an arrangement without such biased clamping legs 90, by the clamp shaft 80 having an inner diameter which reduces towards the terminal end 94 of the clamp shaft 80. As shown in Figure 2, the elongate hollow body 20 comprises a first axial aperture 22 in the first end 24 and a second axial aperture 26 in the second end 28. A spindle 40 is located through the elongate hollow body 20. The driving portion 50 is formed at, or attached to, one end of the spindle 40. The driving portion 50 extends through the first axial aperture 22 of the elongate hollow body 20. The spindle 40 also comprises a clamp portion 60 formed at, or attached to, a second end of the spindle 40. The clamp portion 60 extends through the second axial aperture 26 of the elongate hollow body 20. The clamp portion 60 of the spindle 40 may be a bar, pin, shaft, or similar extension, extending from the second axial aperture 26 of the elongate hollow body 20 away from and outside of the elongate hollow body 20. The clamp portion 60 extends inside of the clamp shaft 80 towards the plurality of clamping legs 90 at the terminal end 94 of the clamp shaft 80. The spindle 40 also comprises a threaded portion 70 connecting the driving portion 50 to the clamp portion 60 within the elongate hollow body 20. The threaded portion 70, the driving portion 50, and the clamp portion 60 may be integrally formed, or separately formed and subsequently joined together to form the spindle 40. In Figure 2 the clamp shaft 80 extends over the clamp portion 60 of the spindle 40, through the second axial aperture 26 of the elongate hollow body 20, and into the elongate hollow body 20. The clamp shaft 80 comprises a threaded end 82 at the opposite end of the clamp shaft 80 to the plurality of clamping legs 90. The threaded end 82 of the clamp shaft 80 is engaged with the threaded portion 70 of the spindle 40 to allow or facilitate controlled relative axial movement of the clamp shaft 80 along the clamp portion 60 of the spindle 40. When arranged as in Figure 2, the clamp portion 60 of the spindle 40 does not project beyond the terminal end 94 of the clamp shaft 80. In this way, the clamping legs 90, which may be biased towards each other and / or have a tapering inner diameter, are in a closed condition, and are located at a minimum distance from each other. When the fastener 10 is in this first condition, where the clamping legs 90 are in a closed condition, the width of the clamp shaft 80 defined at the position of the clamping legs 90 is less than or equal to the width of the clamp shaft 80 along the remainder of its length to the second axial aperture 26 of the elongate hollow body 20. Figure 3 illustrates the second condition where the clamping legs 90 are in an open condition. The plurality of clamping legs 90 are configured to move radially as the clamp shaft 80 is moved axially along the clamp portion 60 of the spindle 40, in particular to move radially outwards as the clamp shaft 80 is moved axially along the clamp portion 60 of the spindle 40 towards and into the elongate hollow body 20. In particular, the clamp portion 60 of the spindle engages with the internal surface of the clamping legs 90, which may be biased towards each other and / or have a tapering inner diameter, such that as the clamp shaft 80 is moved axially along the clamp portion 60 of the spindle 40 the plurality of clamping legs 90 are increasingly separated until the clamp portion projects beyond a distal end 94 of the clamp shaft 80. The driving portion 50 of the spindle 40 of the fastener 10 comprises an inner casing 52 and an outer casing 56. The driving portion 50 is configured to engage with a torque provider, such as a torque wrench, which may be electric or pneumatic, or even manual, via the outer casing 56. That is, the torque provider provides torque to the outer casing 56 in order to rotate the outer casing 56. The inner casing 52 engages with the outer casing 56 via a clutch mechanism 100, such that when the clutch mechanism 100 is in an engaged condition, the inner casing 52 will rotate with the outer casing 56 as torque is applied to the outer casing 56 by the torque provider. The clutch mechanism 100 is more clearly illustrated in Figure 4 and Figure 5. In order to provide engagement and disengagement of the inner casing 52 with the outer casing 56, without axial separation of the outer casing 56 from the inner casing 52, the outer casing 56 may comprise a recess 58 and the inner casing 52 may comprise a flange 54. The recess 58 may be an annular recess around the circumference of the inner surface of the outer casing 56. The flange 54 may be an annular projection around the circumference of the outer surface of the inner casing 52. The recess 58 and flange 54 engage to provide a connection between the inner casing 52 and the outer casing 56. In particular, the flange 54 of the inner casing 52 is located within the recess 58 of the outer casing 56 to limit or prevent relative axial movement between the outer casing 56 and the inner casing 52. However, the outer casing 56 is still free to move rotationally relative to the inner casing 52 when the clutch mechanism 100 is in a disengaged condition. When the clutch mechanism 100 is engaged, the outer casing 56 may be restricted or prevented from moving rotationally relative to the inner casing 52. In the arrangements shown in Figure 4 and Figure 5, the outer casing 56 may be further restricted or prevented from axial movement relative to the inner casing 52 by the use of an end cap 34 which is positioned radially outward of the outer casing 56 between the outer casing 56 and the elongate hollow body 20. The end cap 34 comprises an annular section 36 which engages with a step 38 in the outer surface of the outer casing 56, the step 38 retaining the outer casing 58 in an axial position relative to the elongate hollow body 20 and therefore retaining the outer casing 58 in an axial position relative to the inner casing 52. In the arrangement shown in Figure 4 and Figure 5, the clutch mechanism 100 comprises three radially displaceable ball bearings 110, that is ball bearings that move at, or substantially at, ninety degrees relative to the first axis. This arrangement is further illustrated in Figure 7, which illustrates a section through A — A of Figure 5. In other examples, a different number of radially displaceable ball bearings 110 can be provided. In some examples one or more radially displaceable ball bearings 110 can be provided. Whilst in some embodiments the radially displaceable ball bearings 110 move at ninety degrees relative to the first axis, in other embodiments the radially displaceable ball bearings may move with a component in the radial direction and a component in the axial direction. Each of the radially displaceable ball bearings 110 will have a portion located within the outer casing 56 and a portion located within the inner casing 52 when the clutch mechanism 100 is engaged. By having portions of the radially displaceable ball bearings 110 spanning both the inner casing 52 and the outer casing 56, relative rotational movement between the outer casing 56 and the inner casing 52 is prevented. When the radially displaceable ball bearings 110 are wholly located within the inner casing 52, relative rotational movement between the outer casing 56 and the inner casing 52 is not prevented, that is, the outer casing 56 is free to move independently of the inner casing 52. In order to accommodate a portion of a radially displaceable ball bearing 110, the outer casing 56 comprises a slot 122 as more clearly illustrated in Figure 6. Where there is more than one radially displaceable ball bearing 110 there will be a separate slot 122 for each radially displaceable ball bearing 110. The slot 122 for each radially displaceable ball bearing 110 may be dimensioned to receive a respective radially displaceable ball bearing 110. That is, the slot 122 in the outer casing 56 into which a radially displaceable ball bearing 110 can be moved is of a size to receive only a portion of the radially displaceable ball bearing 110, such that a portion of the radially displaceable ball bearing 110 will remain in the inner casing 52 at all times. As illustrated in Figure 8, the slot 122 for each radially displaceable ball bearing 110 comprises a curved surface 130. In some embodiments, the curved surface 130 comprises a first portion 132 having a curvature which, in some embodiments, is equal to or less than the curvature of the radially displaceable ball bearing 110 to be received in the slot 122. In such an arrangement, the first portion 132 is located at a first edge 134, or length of the first edge 134, of the slot 122 onto which the radially displaceable ball bearing 110 is engaged during engagement of the fastener 10 to a workpiece, that is, the first portion 132 is located at a first edge 134, or length of the first edge 134, of the slot 122 during application of torque to the outer casing 56 to drive the clamping legs 90 towards the outer surface 32 of the second end 28 of the elongate hollow body 20. In some embodiments, the slot 122 for each radially displaceable ball bearing 110 comprises a second portion 136, where the second portion 136 of the slot 122 has a larger curvature than the curvature of the first portion 132 of the slot 122. In such an arrangement, the second portion 136 is located at a second edge 138, or length of the second edge 138, of the slot 122 onto which the radially displaceable ball bearing 110 is engaged during disengagement of the fastener 10 from the workpiece, that is, the second portion 136 is located at a second edge 138, or length of the second edge 138, of the slot 122 during application of torque to the outer casing 56 to drive the clamping legs 90 away from the outer surface 32 of the second end 28 of the elongate hollow body 20. The larger curvature at the second portion 136 of the slot 122 ensures that the fastener 10 can be disengaged from the workpiece, since the larger curvature allows a greater torque force to be applied to the outer casing 56 before the clutch mechanism 100 disengages than is allowed to be applied to the outer casing 56 during engagement of the fastener 10 with the workpiece before the clutch mechanism 100 disengages. In order to radially displace the radially displaceable ball bearings 110 to engage the clutch mechanism 100, it is necessary to apply force to the radially displaceable ball bearings 110. In order to provide such a force, a spring loaded axially moveable ball bearing 140 may be provided. Alternatively, a pin with a hemispherical tip may be used, where the hemispherical tip engages with the radially displaceable ball bearings 110. The axially displaceable ball bearing 140 is located within a central aperture 142 of the inner casing 52. The axially displaceable ball bearing 140 is positioned in engagement with the radially displaceable ball bearings 110. When contact is made between the radially displaceable ball bearings 110 and the axially displaceable ball bearing 140, axial displacement of the axially displaceable ball bearing 140 along the central aperture 142 of the inner casing 52 causes radial displacement of the one or more radially displaceable ball bearings 110. When the clutch mechanism 100 moves from an engaged condition to a disengaged condition, the radially displaceable ball bearings 110 move into the inner casing 52 effecting movement of the axially displaceable ball bearing 140 in a first axial direction, towards the distal end 152 of the driving portion 50 and when the clutch mechanism 100 is moved from a disengaged condition to an engaged condition, the radially displaceable ball bearings 110 partially move into the outer casing 56 thereby moving the axially displaceable ball bearing 140 in a second axial direction, opposite the first axial direction. The distal end 152 of the driving portion 50 is the end of the driving portion 50 furthest away from the elongate hollow body 20. In order to ensure engagement between the radially displaceable ball bearings 110 and the axially displaceable ball bearing 140, the clutch mechanism 100 may comprise a biasing mechanism 144, for example a compression spring 144 located within the central aperture 142 of the inner casing 52. Such a compression spring 144 provides a force acting upon the axially displaceable ball bearing 140 to bias the axially displaceable ball bearing 140 towards the radially displaceable ball bearings 110. Whilst the biasing mechanism 144 is described with regards to a compression spring 144, other biasing methods may be used, such as hydraulic or pneumatic cylinders. The above-described compression spring 144 may be fixed in position and provide a constant bias force onto the axially displaceable ball bearing 140 meaning that operation of the fastener 10 may be consistent. This may be appropriate for some repeatable manufacturing operations, however, in other circumstances, it may be desirable to be able to adjust the bias force acting on the axially displaceable ball bearing 140 such that the fastener 10 can be used in a variety of manufacturing operations, for example when holding or clamping different materials or materials of different thicknesses. In some embodiments, in order to provide for an adjustment of the bias force, the compression of the compression spring 144 can be adjusted. In order to be able to adjust the compression of the compression spring 144, the fastener 10 is provided with a threaded central aperture 142 in the inner casing 52. A headless threaded bolt 150, for example in the form of a grub screw 150, is configured to engage with the compression spring 144 such that the compression spring 144 is compressed between the headless threaded bolt 150 and the axially displaceable ball bearing 140. The headless threaded bolt 150 can be rotated clockwise or anti-clockwise / counterclockwise to facilitate axial movement of the headless threaded bolt 150 towards or away from the axially displaceable ball bearing 140, thereby shortening or lengthening the compression spring 144. By shortening the compression spring 144 the torque required to be applied to the outer casing 56 in order to disengage the clutch mechanism 100 is increased and by lengthening the compression spring 144 the torque required to be applied to the outer casing 56 in order to disengage the clutch mechanism 100 is decreased. Thus, a greater clamping force on a workpiece can be provided by the fastener 10 by shortening the compression spring 144 prior to applying torque to the outer casing 56 of the driving portion 50 of the fastener 10. The headless threaded bolt 150 may be accessible from the distal end 152 of the driving portion 50 to enable or facilitate the adjustment of the compression spring 144, where the distal end 152 of the driving portion 50 is the end of the driving portion 50 furthest away from the elongate hollow body 20. Figure 9 illustrates a method 900 of use of a fastener 10 of the form described above. Optionally, where the torque setting of the fastener 10 is adjustable, in block 905 the torque required to disengage the outer casing 56 from the inner casing 52 is set by rotating a headless threaded bolt 150 in a central aperture 142 of the inner casing 52 to cause compression or decompression of a compression spring 144 in the inner casing 52. The compression or decompression of the compression spring 144 causes a force applied to one or more radially displaceable ball bearings 110, via an axially displaceable ball bearing 140 onto which the compression spring 144 acts within the central aperture 142 of the inner casing 52, to vary. In block 910 the clamp shaft 80 is arranged to be fully extended over the clamp portion 60 of the spindle 40 with the clamping legs 90 having a minimum separation. In block 915 the clamp shaft 80 is inserted through an aperture in a workpiece. In block 920 torque is applied to the driving portion 50 such that the driving portion 50 rotates in a first direction causing the threaded portion 70 of the spindle 40 to rotate relative to the threaded end 82 of the clamp shaft 80 thereby effecting axial movement of the clamp shaft 80 into the elongate hollow body 20 of the fastener 10 over the clamp portion 60 of the spindle 40 to deflect the clamping legs 90 away from each other to provide a maximum separation of the clamping legs 90. In block 925 torque is continued to be applied to the driving portion 50 until the clamping legs 90 engage with the workpiece. At this point, the clamping legs 90 will be clamped to the workpiece until a clamping force is applied that overcomes the force provided by the compression spring 144 and so the radially displaceable ball bearings will then disengage from the slot 122 in the outer casing 56. Therefore, when the clamping legs 90 have fully engaged with the workpiece under the action of a defined torque, the clutch mechanism 100 disengages the outer casing 56 from the inner casing 52. The outer casing 56 then rotates with the torque provider, such as a nut runner used as a torque provider, and the inner casing 52 remains stationary. Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it will be appreciated that various changes and modifications to the examples can be made without departing from the scope of the invention as claimed. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS o A fastener comprising: an elongate hollow body having a first axial aperture in a first end and a second axial aperture in a second end; a spindle located through the elongate hollow body, the spindle comprising a driving portion extending through the first axial aperture of the elongate hollow body, a clamp portion extending through the second axial aperture of the elongate hollow body, and a threaded portion connecting the driving portion to the clamp portion within the elongate hollow body; and a clamp shaft extending over the clamp portion of the spindle, through the second axial aperture of the elongate hollow body, and into the elongate hollow body, the clamp shaft comprising a threaded end engaged with the threaded portion of the spindle for relative axial movement of the clamp shaft along the clamp portion of the spindle, and the clamp shaft further comprising a plurality of clamping legs at an opposite end of the clamp shaft to the threaded end, the plurality of clamping legs configured to move radially as the clamp shaft is moved axially along the clamp portion of the spindle; wherein the driving portion comprises an inner casing and an outer casing, the inner casing engaging with the outer casing via a clutch mechanism.

2. A fastener according to claim 1, wherein the outer casing comprises a recess and the inner casing comprises a flange, the flange being located within the recess of the outer casing to prevent relative axial movement between the outer casing and the inner casing.

3. A fastener according to claim 1 or claim 2, wherein the outer casing is free to move rotationally relative to the inner casing when the clutch mechanism is disengaged and the outer casing is prevented from moving rotationally relative to the inner casing when the clutch mechanism is engaged.

4. A fastener according to any preceding claim, wherein the clutch mechanism comprises one or more radially displaceable ball bearings, each of the one or more radially displaceable ball bearings having a portion located within the outer casing and a portion located within the inner casing when the clutch mechanism is engaged, thereby preventing relative rotational movement between the outer casing and the inner casing. dS. A fastener according to claim 4, wherein the clutch mechanism comprises three radially displaceable ball bearings.

6. A fastener according to claim 4 or claim 5, wherein the outer casing comprises a slot for each radially displaceable ball bearing, the slot for each radially displaceable ball bearing being dimensioned to receive a respective radially displaceable ball bearing. Tv A fastener according to claim 6, wherein the slot for each radially displaceable ball bearing comprises a curved surface with a first portion having a curvature which is equal to or less than the curvature of the radially displaceable ball bearing to be received in the slot, the first portion being located at a first edge of the slot onto which the radially displaceable ball bearing is engaged during engagement of the fastener to a workpiece.

8. A fastener according to claim 7, wherein the slot for each radially displaceable ball bearing comprises a second portion having a larger curvature than that of the first portion of the slot, the second portion being located at a second edge of the slot onto which the radially displaceable ball bearing is engaged during disengagement of the fastener from the workpiece.

9. A fastener according to any of claims 4 to 8, wherein the clutch mechanism comprises an axially displaceable ball bearing located within a central aperture of the inner casing, the axially displaceable ball bearing being positioned to be engaged with the one or more radially displaceable ball bearings, wherein axial displacement of the axially displaceable ball bearing along the central aperture of the inner casing causes radial displacement of the one or more radially displaceable ball bearings.

10. A fastener according to claim 9, wherein the clutch mechanism comprises a compression spring located within the central aperture of the inner casing and configured to provide a force acting upon the axially displaceable ball bearing to bias the axially displaceable ball bearing towards the one or more radially displaceable ball bearings.

11. A fastener according to claim 10, wherein the central aperture of the inner casing is threaded and the clutch mechanism comprises a headless threaded bolt configured to engage with the compression spring such that the compression spring is compressed between the headless threaded bolt and the axially displaceable ball bearing.

12. A fastener according to claim 11, wherein the headless threaded bolt is accessible from a distal end of the driving portion to enable the headless threaded bolt to be rotated to facilitate axial movement of the headless threaded bolt.

13. A method of use of a fastener according to any preceding claim, comprising: arranging the clamp shaft to be fully extended over the clamp portion of the spindle with the clamping legs having a minimum separation; inserting the clamp shaft through an aperture in a workpiece; applying torque to the driving portion such that the driving portion rotates in a first direction causing the threaded portion of the spindle to rotate relative to the threaded end of the clamp shaft thereby effecting axial movement of the clamp shaft into the elongate hollow body of the fastener over the clamp portion of the spindle to deflect the clamping legs away from each other to provide a maximum separation of the clamping legs; and continuing to apply torque to the driving portion until the clamping legs engage with the workpiece and the clutch mechanism disengages the outer casing from the inner casing.

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