Studs for sports footwear

Abstract

A stud 10 for sports footwear (50, fig.2), comprising a ball 14 rotatable within a ball-receiving space 18 in a stud body 12, wherein a portion of the ball protrudes through an aperture 24 in the dist

Description

The present invention relates to a stud for sports footwear and sports footwear comprising at least one such stud. Background Art It is known to have studs protruding from and spaced apart across the sole of sports footwear to provide for improved grip between the footwear and the sports field or like surface. The number and location of studs on the sole of sports footwear depends on the sports game played, the size of the sports footwear, and to lesser extent the preference or requirements of the wearer of the sports footwear. Improvements to studs for sports footwear have tended to focus on improving grip between the footwear and the sports field, or on longevity in use of the studs. Modern sports are increasingly characterised by quickness on the field of play, with rapid changes in speed and direction involved in many different sports. Higher speed is accompanied with greater risk of injury. Sports footwear designers therefore attempt to balance optimal performance with injury risk mitigation. Around 60% of football injuries are non-contact with the foot and ankle the most commonly injured parts of the anatomy. Most ankle related injuries occur on artificial turf compared to grass, and usually during sharp changes of direction. The present inventor has become appreciative that risk of injury during sharp changes of direction may be related to resistance against foot rotation and, more specifically, against forefoot rotation. Football boots with high grip permit fast acceleration but high rotational resistance increases risk of ankle injury. The present invention has been devised in the light of this appreciation. It is therefore an object for the present invention to provide an improved stud for sports footwear, the stud comprising a stud body and having a proximal end which, in use, is disposed towards a sole of the sports footwear, and a distal end which, in use, faces away from the sole. It is a further object for the present invention to provide sports footwear, such as a football boot, comprising plural studs protruding from and spaced apart across a sole of the sports footwear, and of which at least one is an improved stud of a form in accordance with the previous object for the present invention. Statement of Invention According to a first aspect of the present invention there is provided a stud for sports footwear, the stud comprising: a stud body defining a ball receiving space and having a proximal end and a distal end, the proximal end, in use, disposed towards a sole of the sports footwear, the distal end, in use, facing away from the sole, and an aperture defined in the distal end; and a ball supported in the ball receiving space for rotation relative to the stud body, the ball supported such that a portion thereof protrudes through the aperture to define a ground engaging surface. The stud for sports footwear comprises a stud body. The stud body defines a ball receiving space and has proximal and distal ends. When the stud is comprised in sports footwear, such as a football boot, the proximal end is disposed towards a sole of the sports footwear and the distal end faces away from the sole. An aperture is defined in the distal end of the stud body. The stud for sports footwear comprises a ball. The ball is supported in the ball receiving space for rotation relative to the stud body. Furthermore, the ball is supported such that a portion thereof protrudes through the aperture defined in the distal end of the stud body. The portion of the ball protruding through the aperture defines a ground engaging surface. In view of the ball being supported in the ball receiving space for rotation relative to the stud body and hence relative to sports footwear comprising the stud, the protruding portion of the ball may be impelled to rotate when in contact with the ground. Such rotation of the ball reduces traction between the ground and the sports footwear comprising the stud. Such reduction in traction may reduce rotational resistance and thereby reduce risk of injury. As discussed above, good grip permits fast acceleration but high rotational resistance increases risk of ankle injury. Cutting (or change of direction) movements tend to involve application of high pressure to the ground by the sole of the sports footwear. Sprinting tends to involve application of high pressure to the ground by the sole of the sports footwear. In contrast with such linear movements, rotational movement, such as rotation of the forefoot, tends to involve application of lighter pressure to the ground by the sole of the sports footwear. As described above, the portion of the ball protruding through the aperture defines a ground engaging surface. The surface of the portion of the ball protruding through the aperture engages with the ground, such as a sports field. The ball may therefore be impelled to rotate during movement of the sports footwear over the ground. When lighter pressure is applied during rotational movement, the ball may rotate relatively freely to thereby reduce traction during the rotational movement. When higher pressure is applied during linear movements, such as during cutting movements or during sprinting, the ball may be seated more firmly in the stud body to thereby inhibit or even prevent rotation of the ball. This may result in less reduction in traction or even no reduction in traction during such linear movements. The distal end of the stud body surrounding the aperture may define a ground engaging surface. The distal end of the stud body surrounding the aperture may not engage with the ground or may engage with the ground to lesser extent than the surface of the portion of the ball protruding through the aperture when lighter pressure is applied during rotational movement. This may allow for lower traction during rotational movements. On the other hand, the distal end of the stud body surrounding the aperture may engage with the ground or may engage with the ground to greater extent when higher pressure is applied during linear movements. This may allow for greater traction during linear movements. Where the ground is yielding, the ground may deform to receive the portion of the ball protruding through the aperture whereby the distal end of the stud body surrounding the aperture may engage more readily with the ground. A contact part of the stud body may be in contact with a contact surface of the ball during rotation of the ball relative to the stud body. Furthermore, the contact part and the contact surface may be formed of different materials to reduce friction between the contact part and the contact surface. More specifically, one of the contact part and the contact surface may be formed of a plastics material, and the other of the contact part and the contact surface may be formed of a metal. Where the stud body is integrally formed, the stud body may be formed of the plastics material or the metal. Where the ball is integrally formed, the ball may be formed of the plastics material or the metal. The ball may be substantially spherical. Although a substantially spherical ball may provide for freedom of rotation round 360 degrees, the reduced freedom of rotation of a non-spherical ball may be preferred in certain applications. For example, a ball which is oval may be supported in the ball receiving space such that the ball is rotatable relative to the stud body in one direction only. Such unidirectional rotation may be advantageous in certain applications. The stud body may have an external profile which is at least one of the same shape and size as an external profile of a known stud. The stud body may therefore be of generally cylindrical form. Furthermore, the stud body may comprise a flange at the proximal end. The stud body may therefore be of great diameter at the flange with a step reduction in diameter beyond the flange in the direction of the distal end of the stud body. As mentioned above, the stud body may be integrally formed whereby the flange is integral with the rest of the stud body. The ball receiving space may be of generally cylindrical form. The ball may be sized such that it is snugly received in the ball receiving space. Snug reception of the ball in the ball receiving space may, on the one hand, allow for little movement of the ball in the ball receiving space in a direction transverse to the direction of separation of the proximal and distal ends, and, on the other hand, allow for rotation of the ball within the ball receiving space. The aperture defined at the distal end of the stud body may be of less diameter than the ball receiving space. The ball may therefore be held within the ball receiving space at the distal end of the stud body. The diameter of the aperture relative to the diameter of the ball may determine the extent to which the ball protrudes through the aperture. The stud may further comprise a sole attachment member. The sole attachment member may attach the stud body to the sole of the sports footwear. The sole attachment member and the stud body may be configured to releasably attach to each other. The stud body may be so configured towards its proximal end. More specifically, the sole attachment member and the stud body may define interengaging screw threads which cooperate to attach the sole attachment member and the stud body to each other upon their relative rotation. The stud body may define a stud body screw thread on an inside surface of the stud body. More specifically, the stud body screw thread may be defined on an inside surface of the stud body adjacent the ball receiving space defined by the stud body. The stud body screw thread may therefore extend from the ball receiving space towards the proximal end of the stud body. The diameter of the stud body screw thread may be substantially the same as the diameter of the ball receiving space. The sole attachment member may define a sole attachment member screw thread. The sole attachment member screw thread may interengage with the stud body screw thread to attach the sole attachment member and the stud body to each other, as described above. The sole attachment member screw thread may be defined on an exterior surface of the sole attachment member. The stud may be configured, such as in respect of shape and / or size, such that the sole attachment member, and more specifically a distal end of the sole attachment member, bears against the ball supported in the ball receiving space. Resistance to movement of the ball within the ball receiving space away from the aperture may thus be presented whereby a portion of the ball remains protruding from the aperture despite pressure being applied to the protruding portion of the ball. The distal end of the sole attachment member may define a recess which is shaped and / or sized to receive a portion of the ball. A radius of curvature of the ball may be substantially the same as a radius of curvature of the recess. The ball may therefore rotate readily within the recess. Where the ball is substantially spherical, the recess may define a segment of a sphere and more specifically a minor segment of a sphere. The sole attachment member may define a sole attachment member flange at a proximal end of the sole attachment member screw thread (i.e. an end of the sole attachment member screw thread which, in use, is closer to the sole of the sports footwear than the other, distal end of the sole attachment member screw thread). The sole attachment member flange may be sized and / or shaped to abut against the stud body upon inter-engagement of the sole attachment member screw thread and the stud body screw thread to thereby limit an extent to which the sole attachment member screw thread moves towards a distal end of the stud body. The proximal end of the stud body may define a flange recess which extends laterally from the inside surface of the stud body and longitudinally away from the proximal end of the stud body. The flange recess may be sized and / or shaped to receive the sole attachment member flange whereby a sole facing surface of the sole attachment member flange (i.e. the surface of the sole attachment member flange facing the sole of the sports footwear) is substantially aligned with a sole facing surface of the proximal end of the stud body beyond the flange recess (i.e. the surface of the stud body facing the sole of the sports footwear). The sole attachment member may comprise a sole attachment component. The sole attachment component may be configured to releasably attach the sole attachment member to the sole of sports footwear. More specifically, the sole attachment member may define a sole attachment screw thread which cooperates with a sole screw thread defined in the sole. The sole attachment screw thread may be coaxial with the sole attachment member screw thread. Alternatively or in addition, and where the sole attachment member comprises a sole attachment member flange, the sole attachment screw thread and the sole attachment member screw thread may be on opposite sides of the sole attachment member flange. The sole attachment screw thread may be defined on an external surface of the sole attachment member. The sole thread may be defined on the surface of a bore in the sole of the sports footwear. In another form, the sole attachment member may not be comprised in the stud and may be comprised instead in the sports footwear. Sports footwear according to a second aspect of the invention is described further below. In this form, the sole attachment member may be as described above in respect of releasability of sole attachment member from the sports footwear, such as by way of the sole attachment screw thread and the sole screw thread. In a variation of this form, the sole attachment member may be non-releasably attached to the sports footwear. The sole attachment member may therefore not be configured for releasable attachment to the sports footwear such that the sole attachment member, for example, lacks the sole attachment screw thread and the sports footwear lacks the sole screw thread. Instead, the sole attachment member may be non-releasably attached to the sports footwear by bonding of the sole attachment member to the sole of the sports footwear or by forming the sole attachment member integrally with the sole of the sports footwear. In this form, there may be no need for the sole attachment screw thread and perhaps also the sole attachment member flange. The sole attachment member may therefore be constituted by the sole attachment member screw thread. In a further form, the stud body may be non-releasably attached to the sports footwear. More specifically, the stud body may be attached at its proximal end to the sports footwear. The stud body may be non-releasably attached to the sports footwear by bonding of the stud body to the sole of the sports footwear. In this form, the stud may lack the sole attachment member. This form of stud may further comprise a retaining member which is disposed in the ball receiving space to limit movement of the ball away from the aperture defined by the stud body. The retaining member may be immovably supported in the stud body. Alternatively or in addition, the retaining member may be disposed in the ball receiving space such that the ball abuts against the retaining member to thereby limit movement of the ball away from the aperture defined by the stud body. The retaining member may thus have the same function as the sole attachment member in respect of limiting movement of the ball away from the aperture. The retaining member may extend across the ball receiving space at a location spaced apart from the aperture. The ball may be supported in the ball receiving space between the aperture and the retaining member. The retaining member may be relatively thin. Alternatively or in addition, the retaining member may be annular. For example, the retaining member may have the form of a washer. The washer may be formed from metal or plastics material. Where the ball is formed from plastics material, the washer may be formed from metal. Where the ball is formed from metal, the washer may be formed from plastics material. Forming the washer and the ball from different materials in this way may be advantageous in respect of providing for ease of rotation of the ball relative to the washer when the ball abuts against the washer. A portion of the ball may protrude through the retaining member aperture defined by the annular retaining member. The portion of the ball protruding through the retaining member aperture may be at an opposite end of the ball to the portion of the ball protruding through the aperture defined by the stud body. The stud may further comprise a lubricant which is in or is to be received in the ball receiving space of the stud body. The lubricant may provide for ease of rotation of the ball relative to the stud body. According to a second aspect of the present invention there is provided sports footwear, such as a football boot, comprising at least one improved stud according to the first aspect of the present invention. As discussed above, rotational movement may carry greater risk of injury than linear movement. Selection of location on the sole of the sports footwear of one or more improved studs may contribute towards reduction in traction during rotational movement and maintenance of traction during linear movement. The sports footwear may comprise an improved stud attached to the sole of the sports footwear at at least one of: under the first metatarsal head (i.e. under the ball of the foot); the medial heel; and the lateral heel. The sports footwear may comprise plural further studs of known form and function which are located on the sole in accordance with known practice. Locating at least one improved stud at one or more of these locations on the sole may provide for balance between reduction in traction during rotational movement and providing for traction during linear movement. Locating an improved stud at each of these three locations may provide for superior performance in certain circumstances. Furthermore, locating improved studs at these locations on the sole may provide for ease of forefoot rotation to thereby reduce risk of ankle injury. Further embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention. Brief Description of Drawings Further features and advantages of the present invention will become apparent from the following specific description, which is given by way of example only and with reference to the accompanying drawings, in which: Figure 1A is an exploded perspective view of a stud according to a first embodiment of the invention; Figure 1B is a view in cross section of the stud according to the first embodiment; Figure 1C is a side view of the stud according to the first embodiment; Figure 1D is a perspective view of the sole attachment member of the first embodiment; Figure 2 is a perspective view of a football boot comprising studs according to the invention; and Figure 3 is a view in cross section of a stud according to a third embodiment. Description of Embodiments A first embodiment of a stud 10 according to the invention is shown in Figures 1A to 1D. Figure 1A is an exploded perspective view of the stud 10, Figure 1C is a side view of the stud 10, and Figure 1B is a view of the stud 10 in cross section through A-A shown in Figure 1C. Figure 1D is a perspective view of the sole attachment member 16 of the stud 10 of Figures 1Ato 1C. The first embodiment of stud 10 comprises a stud body 12, a substantially spherical ball 14, and a sole attachment member 16. Each of the stud body 12, the ball 14 and the sole attachment member 16 is integrally formed. The stud body 12 is formed from metal, such as aluminium, the ball 14 is formed from a plastics material such as nylon or polyurethane, and the sole attachment member 16 is formed from metal, such as aluminium. The stud body 12 defines a ball receiving space 18 and has a proximal end 20 and a distal end 22. When the stud 10 is comprised in sports footwear, such as a football boot, the proximal end 20 is disposed towards a sole of the sports footwear and the distal end 22 faces away from the sole. An aperture 24 is defined in the distal end 22 of the stud body 12. The distal end 22 of the stud body surrounding the aperture 24 defines a ground engaging surface. The stud body 12 has an external profile of the same shape and size as an external profile of a known stud whereby the stud body is of generally cylindrical form with a flange 26 at the proximal end 20. The stud body 12 is therefore of great diameter at the flange 26 with a step reduction in diameter beyond the flange in the direction of the distal end 22 of the stud body. The ball 14 is supported in the ball receiving space 18 of the stud body 12 for rotation relative to the stud body. Furthermore, the ball is supported such that a portion thereof protrudes through the aperture 24 defined in the distal end 22 of the stud body 12. The portion of the ball protruding through the aperture defines a ground engaging surface. The ball receiving space 18 of the stud body 12 is of generally cylindrical form. The ball 14 and the ball receiving space 18 are relatively sized such that the ball is snugly received in the ball receiving space. Snug reception of the ball 14 in the ball receiving space 18, on the one hand, allows for little movement of the ball in the ball receiving space in a direction transverse to the direction of separation of the proximal and distal ends 20, 22, and, on the other hand, allows for rotation of the ball within the ball receiving space. The aperture 24 defined at the distal end 22 of the stud body 12 is of less diameter than the ball receiving space 18, whereby the ball 14 is held within the ball receiving space 18 at the distal end of the stud body. The diameter of the aperture 24 relative to the diameter of the ball 14 determines the extent to which the ball protrudes through the aperture. The stud body 12 defines a stud body screw thread 28 on an inside surface of the stud body. The stud body screw thread 28 is defined on an inside surface of the stud body 12 adjacent and coaxially with the ball receiving space 18 defined by the stud body. The stud body screw thread 28 extends from the ball receiving space 18 towards the proximal end 20 of the stud body 12. The diameter of the stud body screw thread 28 is substantially the same as the diameter of the ball receiving space 18. The sole attachment member 16 defines a sole attachment member screw thread 30 on an exterior surface of the sole attachment member. The sole attachment member screw thread 30 interengages with the stud body screw thread 28 to releasably attach the sole attachment member 18 and the stud body 12 to each other. As can be seen from Figure 1B, a distal end of the sole attachment member 16 bears against the ball 14 supported in the ball receiving space 18. The distal end of the sole attachment member 16 presents resistance to movement of the ball 14 within the ball receiving space 18 away from the aperture 24 whereby a portion of the ball remains protruding from the aperture despite pressure being applied to the protruding portion of the ball. Referring now to Figure 1D, the distal end of the sole attachment member 16 defines a recess 32. The recess 32 defines a minor segment of a sphere whereby the recess is sized and shaped to receive in abutment a portion of the ball 14 and to allow ready rotation of the ball within the recess 32. It should be noted that Figure 1D is of schematic form whereby Figure 1D does not show the thread of the stud body screw thread 28 or the thread of the sole attachment screw thread 38 described below. The sole attachment member 16 defines a sole attachment member flange 34 at a proximal end of the sole attachment member screw thread 30. The proximal end 20 of the stud body 12 defines a flange recess 36 which extends laterally from the inside surface of the stud body and longitudinally away from the proximal end of the stud body. The flange recess 36 is sized and shaped to receive the sole attachment member flange 34 whereby the surface of the attachment member flange facing the sole of the sports footwear is substantially aligned with the surface of the stud body around the flange recess 36 which faces the sole of the sports footwear. Abutment of the sole attachment member flange 34 against the stud body 12 in this way and upon inter-engagement of the sole attachment member screw thread 30 and the stud body screw thread 28 limits the extent to which the sole attachment member screw thread moves towards the distal end 22 of the stud body. The sole attachment member 16 further defines a sole attachment screw thread 38 (which constitutes a sole attachment component) which is defined on an external surface of the sole attachment member. In use, and as described further below with reference to Figure 2, the sole attachment screw thread 38 cooperates with a sole screw thread defined in the sole of sports footwear. The sole attachment screw thread 38 is coaxial with the sole attachment member screw thread 30. Furthermore, the sole attachment screw thread 38 and the sole attachment member screw thread 30 are on opposite sides of the sole attachment member flange 34. During assembly of the stud 10, a lubricant, such as mineral oil, is introduced into the ball receiving space 18 after the ball 14 is seated in the ball receiving space and before the sole attachment member 16 is attached to the stud body 12. A perspective view of a football boot 50 (which constitutes sports footwear) for a right foot and comprising studs according to the invention is shown in Figure 2. The football boot 50 is of conventional form and function with the exception of some of the studs, as will now be described. The sole 52 of the football boot 50 has a plurality of threaded blind bores defined therein for threaded attachment of studs in accordance with conventional practice. There are eight such threaded blind bores in the forefoot part of the sole 52, two such threaded blind bores in the mid-foot part of the sole, and two such threaded blind bores in the heel of the sole. Seven 54 of the eight threaded blind bores in the forefoot part of the sole 52 receive a stud of conventional form and function. The eighth threaded blind bore 56 in the forefoot part, which is under the first metatarsal head, receives a stud 10 according to the first embodiment. The two threaded blind bores 56 in the heel of the sole 52 receive a stud 10 according to the first embodiment. Each of the two blind bores 54 in the mid-foot part of the sole 52 receives a stud of conventional form and function. Replacing conventional studs with studs 10 according to the first embodiment at these locations tends to reduce traction during forefoot rotation while maintaining traction during linear movements, such as sprinting and cutting movements. Risk of injury, and in particular risk of ankle injury, may thereby be reduced. In a second unillustrated embodiment, the stud is as described above for the first embodiment with reference to Figures 1A to 1D, with the exception of the stud according to the second embodiment lacking the sole attachment member 16. Instead, the sole attachment member 16 is comprised in the football boot 50. In one form, the sole attachment member 16 is of the same form and function as described above with reference to Figures 1A to 1D whereby the sole attachment member is releasably attached to the sole 52. In another form, the sole attachment member is immovably attached to the sole, such as by bonding to the sole or by integral formation with the sole. In this latter form, the sole attachment member lacks the sole attachment screw thread 38. Furthermore, and where the sole attachment member is integrally formed with the sole, the sole attachment member is formed from the same plastics material as the sole. In both forms, a lubricant, such as mineral oil, is introduced into the ball receiving space 18 after the ball 14 is seated in the ball receiving space and before the sole attachment member is attached to the stud body 12. A view in cross section of a stud 70 according to a third embodiment is shown in Figure 3. The stud 70 of Figure 3 comprises a stud body 72, a substantially spherical ball 74, and a washer 76. The ball 74 is formed from stainless steel. The washer 76 is formed from nylon or polyurethane. The stud body 72 is integrally formed with the sole 52 of the football boot 50. The stud body 72 is therefore formed from the same plastics material as the sole 52. The stud body 72 defines a ball receiving space 78. The stud body 72 has an external profile of the same shape and size as an external profile of a known stud whereby the stud body is of generally cylindrical form with a flange 80 at a proximal end of the stud body. The stud body 72 is therefore of great diameter at the flange 80 with a step reduction in diameter beyond the flange in the direction of a distal end 82 of the stud body. An aperture is defined in the distal end 82 of the stud body 72. The distal end 82 of the stud body surrounding the aperture defines a ground engaging surface. The ball 74 is supported in the ball receiving space 78 of the stud body 72 for rotation relative to the stud body. Furthermore, the ball is supported such that a portion thereof protrudes through the aperture defined in the distal end 82 of the stud body 72. The portion of the ball protruding through the aperture defines a ground engaging surface. The ball receiving space 78 of the stud body 72 is of generally cylindrical form. The ball 74 and the ball receiving space 78 are relatively sized such that the ball is snugly received in the ball receiving space. Snug reception of the ball 74 in the ball receiving space 78, on the one hand, allows for little movement of the ball in the ball receiving space in a direction transverse to the direction of separation of the proximal and distal ends of the stud body 72, and, on the other hand, allows for rotation of the ball within the ball receiving space. The aperture defined at the distal end 82 of the stud body 72 is of less diameter than the ball receiving space 78, whereby the ball 74 is held within the ball receiving space 78 at the distal end of the stud body. The diameter of the aperture relative to the diameter of the ball 74 determines the extent to which the ball protrudes through the aperture. The washer 76 is immovably attached to the stud body 72 such that it extends across the ball receiving space 78 and at a location spaced apart from the distal end 82 of the stud body 72. The aperture defined by the washer 76 is of smaller diameter than the diameter of the ball 74. The ball 74 is supported in the ball receiving space 78 between the washer 76 and the distal end 82 of the stud body 72 and such that one end of the ball abuts against the washer with a portion of the ball protruding through the aperture of the washer. The washer 76 limits movement of the ball 74 away from the aperture defined at the distal end 82 of the stud body 72 and such that a portion of the ball remains protruding through the aperture defined at the distal end of the stud body. The ball 74 is thus held between the washer 76 and the distal end 82 of the stud body 72. As described above, the stud 70 of the third embodiment is integrally formed with the sole 52 of the football boot 50. Where the manufacturing process allows, a lubricant, such as mineral oil, is introduced into the ball receiving space 78. A stud 70 of the third embodiment is provided at the same locations on the sole as described above. The remaining studs 54 are of conventional form and function. A football boot 50 having studs 70 according to the third embodiment may offer the same advantages and benefits as a football boot 50 having studs 10 according to the first embodiment.

Claims

1. A stud for sports footwear, the stud comprising:a stud body defining a ball receiving space and having a proximal end and a distal end, the proximal end, in use, disposed towards a sole of the sports footwear, the distal end, in use, facing away from the sole, and an aperture defined in the distal end; anda ball supported in the ball receiving space for rotation relative to the stud body, the ball supported such that a portion thereof protrudes through the aperture to define a ground engaging surface.

2. The stud according to claim 1, wherein a contact part of the stud body is in contact with a contact surface of the ball during rotation of the ball relative to the stud body, one of the contact part and the contact surface formed of a plastics material, and the other of the contact part and the contact surface formed of metal.

3. The stud according to claim 1 or 2, wherein the ball is substantially spherical.

4. The stud according to claim 3, wherein the ball receiving space is of generallycylindrical form and the ball is sized such that it is snugly received in the ball receiving space.

5. The stud according to any one of the preceding claims, wherein the aperture defined at the distal end of the stud body is of less diameter than the ball receiving space and wherein the diameter of the aperture is smaller than a greatest dimension of the ball.

6. The stud according to any one of the preceding claims further comprising a sole attachment member which is configured to releasably attach to the stud body and for releasable attachment to the sole of the sports footwear.

7. The stud according to claim 6, wherein the stud body defines a stud body screw thread on an inside surface of the stud body and the sole attachment memberdefines a sole attachment member screw thread on an exterior surface of the sole attachment member, the stud body screw thread and the sole attachment member screw thread threadedly engaging with each other to releasably attach the stud body and the sole attachment member to each other.

8. The stud according to claim 7, wherein the stud body screw thread is defined on the inside surface of the stud body adjacent the ball receiving space whereby the stud body screw thread extends from the ball receiving space towards the proximal end of the stud body.

9. The stud according to any one of claims 6 to 8, wherein a distal end of the sole attachment member defines a recess which is shaped and / or sized to receive a portion of the ball.

10. The stud according to claim 9 when depending from claim 3, wherein the recess defines a minor segment of a sphere.

11. The stud according to any one of claims 7 and 8, and claims 9 and 10 when depending from claim 7, wherein the sole attachment member defines a sole attachment member flange at a proximal end of the sole attachment member screw thread, the sole attachment member flange sized and / or shaped to abut against the stud body upon inter-engagement of the sole attachment member screw thread and the stud body screw thread to thereby limit an extent to which the sole attachment member screw thread moves towards a distal end of the stud body.

12. The stud according to claim 11, wherein the proximal end of the stud body defines a flange recess sized and / or shaped to receive the sole attachment member flange.

13. The stud according to any one of the preceding claims, wherein the sole attachment member defines a sole attachment screw thread which, in use, cooperates with a sole screw thread in the sole.

14. The stud according to claim 13, wherein the sole attachment screw thread is defined on an external surface of the sole attachment member and is coaxial with the sole attachment member screw thread.

15. Sports footwear comprising plural studs protruding from and spaced apart across a sole of the sports footwear, at least one of the plural studs being an improved stud, the improved stud comprising:a stud body defining a ball receiving space and having a proximal end and a distal end, the proximal end, in use, disposed towards a sole of the sports footwear, the distal end, in use, facing away from the sole, and an aperture defined in the distal end; anda ball supported in the ball receiving space for rotation relative to the stud body, the ball supported such that a portion thereof protrudes through the aperture to define a ground engaging surface.

16. The sports footwear according to claim 15, wherein the at least one improved stud is integrally formed with the sole of the sports footwear.

17. The sports footwear according to claim 16, wherein the stud body is formed of the same plastics material as the sole, and the ball is formed of metal material.

18. The sports footwear according to claim 16 or 17, wherein the improved stud further comprises a retaining member which is disposed in the ball receiving space to limit movement of the ball away from the aperture defined by the stud body.

19. The sports footwear according to claim 18, wherein the retaining member extends across the ball receiving space at a location spaced apart from the aperture, the ball supported in the ball receiving space between the aperture and the retaining member.

20. The sports footwear according to claim 19, wherein the retaining member is relatively thin and annular,a portion of the ball protruding through a retaining member aperture defined by the annular retaining member.

21. The sports footwear according to any one of claims 15 to 20, wherein the sports footwear comprises an improved stud attached to the sole of the sports footwear: under the first metatarsal head; at the medial heel; and at the lateral heel.

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