Magnetically centred thumbstick

Abstract

The invention provides a magnetically centred thumbstick for use with a handheld device 101 having a touch sensitive interface 102. The thumbstick comprises first and second parts (103,301 fig. 2b) fo

Description

The present invention relates to a magnetically centred thumbstick, particularly for use with a touch screen or other touch sensitive interface. Background A control stick, such as a joystick or thumbstick, is a controlling device comprising a stick which is movable by a user, wherein the movement is translated into electrical signals transmitted to the device being controlled. Control sticks are often used to control video games, with mechanical joysticks or thumbsticks being those most used. Mechanical joysticks are typically centred, meaning when the stick is displaced away from the centre by a user, there is a force exerted on the stick back towards the centre. This force provides feedback to a user and returns the stick to a neutral position once the user releases the control stick. In a mechanical joystick, the centring force is provided by a spring which provides a resilient bias. Feedback to a user affects how smoothly the movements of a joystick can be controlled and increases speed and accuracy of the input. Most control sticks, including the thumbsticks found on most gamepad controllers, are analogue input devices allowing both the magnitude and direction of movement of the thumbstick to be tracked. The feedback also helps with the precision of movement and the maintenance of a desired input. Gaming on mobile devices with a touch screen has become increasingly popular. Many mobile games are developed to take full advantage of the touch screen interfaces, requiring the player to tap on and / or swipe across several different areas of a game area displayed on the screen. However, as the processing power of mobile devices has increased, more traditional game types have also become popular. These games typically include a virtual thumbstick to control the action, provided as part of the onscreen display. The virtual thumbstick allows a player to make inputs in a more traditional manner. Typically, the virtual thumbstick will be coded so that it returns to a centre point on screen when any touch is removed. However, this does not provide any physical feedback to the user. In addition, the position of a virtual thumbstick can be easily lost during play, because the user is not able to locate the virtual thumbstick through touch alone. Use of a virtual thumbstick does not provide the user with the same feedback as a physical joystick or thumbstick, reducing the overall gaming experience. Plug in control sticks or other user interfaces can be used, but may not be compatible with all games and / or devices, and can be bulky proving undesirable or impractical to carry and use with a mobile device. It is an aim of the invention to mitigate one or more of the above-mentioned problems. According to a first aspect of the present invention, there is provided a magnetically centring thumbstick as defined in the appended claim 1. Further optional features are recited in the associated dependent claims. The magnetically centring thumbstick is designed for use with a handheld device with a touch sensitive interface, and comprises an interface component configured to slide across an input surface of the touch sensitive interface and having a conductive input part to contact said input surface in use, and a second part positioned, in use, on an opposite side of the touch sensitive interface from the interface component; wherein at least one of the interface component and the second part comprises a magnet such that the interface component is magnetically attracted to the second part. The handheld device may be a mobile phone handset, tablet or similar. The touch sensitive interface may be a touchscreen. The input part may be a removable / replaceable component. The magnetic attraction / force urges the interface component towards the second part and urges it back into axial alignment when it is moved away from an aligned / neutral position. Feedback is provided to a user though the magnetic force pulling the first part towards the neutral position, which is defined / dictated by the position of the second part. The second part may be configured to be releasably mounted on an opposite side of the handheld device from the interface component. Free positioning of the second part, and thus of the neutral position, can therefore be provided. This allows selection of a specific neutral position, for example aligned with a virtual input provided on a touchscreen display. The second part may comprise a high friction surface, for example of a soft silicone material, for engagement with the handheld device. Providing a high friction surface, for example as provided by a high gloss, low hardness, high friction silicone material, at the interface between the second part and the handheld device helps to ensure that the second part remains in a selected neutral position during use. The interface component and the second part may be magnetically attracted to the handheld device by a common anchor component secured to the handheld device. The anchor component comprises a ferromagnetic material or a permanent magnet. The anchor component may be built into the handheld device or may be provided in a case for the handheld device. For example, the anchor component may be provided within a protective outer case for a mobile phone handset. The case may be provided with a raised section to provide an abutment surface for the second part, to help resist movement of the second part in use. The second part may comprise an ergonomic grip for the hand of a user and / or may comprise a physical clip to engage with the handheld device and / or a cover for the handheld device and provide extra security for the second part. The second component may comprise at least one magnet and means for adjusting the magnitude of magnetic field experienced by the interface component during use. For example, the number of magnets in the second part may be adjustable so that magnets can be added or removed to adjust the strength of the overall magnetic field. Alternatively, or additionally, the position of the or each magnet in the second part may be adjustable, for example by spacers and / or a threaded connection, to increase or reduce the distance between the magnet(s) in the second part and the interface component in use. The second part may comprise a rubberised and / or textured outer surface to increase grip and / or provide aesthetic appeal. The interface component and the second part may be removable from the handheld device and designed to fit together for storage. The thumbstick may further comprise a lid for covering the interface component during storage, wherein the lid is magnetically attracted to the interface component and / or the second part. The lid may have a similar outer shape to the second part so that, when secured together for storage, the components provide a harmonious outer shape, which is preferably smooth and / or curved to avoid sharp edges. Alternatively, the second part may be permanently housed within a casing of the handheld device. For example, the second part could be housed within the body on a mobile phone handset or similar, or behind a touch sensitive interface on a games controller. The interface component may further comprise a non-conductive low friction ring, surrounding the conductive input part, configured to be in contact with the input surface. The ring may include discontinuities and helps to ensure that the interface component sits flat on a flat on a touch sensitive interface such as a touchscreen. The interface component may comprise a soft / rubberised and / or textured outer surface to increase grip and / or provide aesthetic appeal. Additionally, or alternatively the interface component may comprise a raised lip at an outer edge thereof. The interface component may comprise a permanent magnet and / or a selflubricating polymer to reduce friction with the input surface. Another embodiment provides a thumbstick for use with a touch sensitive interface, the thumbstick comprising first and second parts for positioning on opposite sides of the touch sensitive interface, wherein the first part is configured to slide, in use, across an input surface of the touch sensitive interface, and comprises a stylus or similar input part for contacting said input surface, and the second part is securable in a set position, and wherein the first part is magnetically coupled to the second part such that the first part is urged towards the second part. The second part may be configured to be releasably mounted in said set position such that the neutral position can be repositioned as required on the input surface. The second part may comprise at least one suction cup. Th second part may be configured to be housed in a casing for the touch sensitive interface. The stylus provides a precise input to the touch sensitive interface, and may comprise electronic components such that it is an active stylus. An active stylus is configured to be electrically connected to the touch sensitive interface and is more accurate than a passive stylus. A low friction ring may be provided on the first part. The low friction ring helps to prevent damage on the input surface, for example a touchscreen, and minimises resistance from friction which could otherwise interfere with the centring force. The stylus may be located within the low friction ring. The low friction ring may be located on the periphery of a lower section of the first part. The low friction ring may be incomplete. The first part may comprise a thumb grip. The thumb grip helps the user maintain thumb positioning during use. The thumb grip may be textured. The thumb grip may comprise silicone. The stylus may be electrically connected to the thumb grip, such that in use the user is electrically connected to the input screen when an active stylus is used. The first part may comprise a raised edge around the thumb grip. If the user’s thumb does slip on the thumb grip the raised edge provides additional resistance to prevent accidental loss of contact with the thumbstick. The raised edge may comprise the same material as the thumb grip. The thumb grip may be raised. Both the first and second parts may comprise a permanent magnet. The first and second parts may comprise a disk magnet, such that they are substantially flat for storage. Alternatively, either the first or second part may comprise a ferromagnetic material and the other of the first or second part may comprise a permanent magnet. The first and second parts can be kept on the device and stored or stored separately from the device. When stored separately, the first and second parts are held together by the magnetic force to form a single compact package with the magnet(s) fully enclosed. A lid or cover may additionally be provided to cover the first part and protect it from dust and other contaminants. The first part may further comprise a housing located between the upper and lower sections and housing the magnetic material. The thumbstick may comprise a self-lubricating polymer. The second part may comprise a substantially smooth outer surface to avoid it being knocked / dislodged / moved inadvertently. Al further embodiment provides a thumbstick for use with a touch sensitive interface, the thumbstick comprising a first part for positioning on a side of the touch sensitive interface and a second part permanently located on an opposite side of the touch sensitive interface wherein the first part is configured to slide, in use, across an input surface of the touch sensitive interface, and comprises a stylus or similar input part for contacting said input surface, and the second part is secured in a set position, and wherein the first part is magnetically coupled to the second part such that the first part is urged towards the second part. The touch sensitive interface may comprise a games controller and the second part may be secured within the games controller. Also described is a games controller comprising a thumbstick as previously described. For example, a games controller may comprise a touch sensitive interface and a magnetically centring thumbstick, the thumbstick comprising: first and second parts positioned on opposite sides of the touch sensitive interface; wherein the first part is configured to slide, in use, across an input surface of the touch sensitive interface and comprises a stylus for contacting said input surface, and the second part is secured in a set position within the games controller; and wherein the first part is magnetically coupled to the second part such that the first part is urged towards the second part. The input surface may be curved or domed. Optional features described above for one embodiment may also be provided in an alternative embodiment. Detailed description Practicable embodiments are described in further detail below with reference to the accompanying drawings, of which: Figure 1 shows a front view a magnetically centred thumbstick in situ on a touchscreen device; Figure 2a shows a side cutaway view of the first part of the magnetically centred thumbstick of Figure 1; Figure 2b shows a side cutaway view of the second part of the magnetically centred thumbstick of Figure 1; Figure 3 shows a side view of the magnetically centred thumbstick of Figure 1 in situ on a touchscreen device; Figure 4a shows a side view of the magnetically centred thumbstick of Figure 3 in a first position; Figure 4b shows a side view of the magnetically centred thumbstick in a second position Figure 5 shows an alternative magnetically centred thumbstick in situ on a games controller; Figure 6 shows an exploded view of a further alternative magnetically centred thumbstick arrangement, additionally comprising hand grips, for use with a touchscreen device; Figure 7 shows an example aperture for receiving a magnet in the arrangement of Figure 6; Figure 8 shows a magnet cartridge from the arrangement of Figure 6; Figure 9 shows a handgrip from the arrangement of Figure 6; Figure 10 shows a rear view of the assembled arrangement of Figure 6; Figure 11 shows a cross-section of the view of Figure 10, taken at the line marked 11; Figure 12a shows an assembly of components of a thumbstick and a cover provided for storage of the components; and Figure 12b shows a cross section of the cover of Figure 12a. In the first example shown in the figures described below, the thumbstick is shown on a touch screen of a mobile device. However, the general concept is suitable for use on any touch sensitive interface. Figure 1 shows a magnetically centred control stick 100 on a device 101 with a touch screen 102. The control stick 100 comprises a first part 103 placed on the touch screen 102 and a second part located at the back of the device 101 (and not visible in Figure 1)- The first part 103 is movable across the touch screen 102. The first part 103 has free 360° movement across the touch screen 102. The first part 103 is placed on the touch screen 102 with a lower section in contact with the touch screen 102 and an upper section facing away from the touch screen 102. A user interacts with the upper section of the first part 103 and the lower section of the first part 103 interacts with the touch screen 102. The first part 103 provides an input to the touch screen 102 based on the input provided by the user. The input is used to control the touch screen 102. The first part 103 comprises a thumb grip 104. The thumb grip 104 is located substantially centrally on the upper first part 103. The thumb grip is raised. The thumb grip may be textured. The thumb grip may comprise silicone. The upper section of the first part 103 comprises a raised edge 105. The raised edge 105 may comprise the same material as the thumb grip 104. The entire upper section may comprise the same material as the thumb grip 104. The first part 103 is substantially cylindrical. The first part 103 is disk shaped. The first part 103 is circular in cross-section. In this example, the control stick is a thumbstick and is configured to be operated by the thumb of the user. Figure 2a shows a side cutaway view of the first part 103 of the magnetically centred thumbstick. The first part 103 comprises a thumb grip 104, a raised edge 105, a stylus 201 and a low friction ring 202. The stylus or pointer 201 is provided on the lower section of the first part 103. The stylus 201 is configured to be in contact with the touch screen in use. The stylus 201 is what provides an input to the touch screen 102 based on the input provided by the user. The stylus 201 advantageously provides a smaller contact point than the thumb or other digit of a user, and is less deformable, so the contact with the touchscreen interface is more precise and more reliable. If desired, the stylus 201 could comprise internal electronic components to provide an active stylus, being electrically connected to the touch screen. The stylus 201 is electrically connected to skin of the user through the thumb grip 104, such that the user is electrically connected to touch screen when the thumbstick is in use. The low friction ring 202 is located around the stylus 201 on the lower section of the first part 103. The low friction ring 202 is substantially circular and located at the periphery of the lower section of the first part 103. Alternatively, the low friction ring 202 may be any suitable size and shape, located anywhere on the lower section of the first part 103 such that it performs the function of reducing friction between the first part 103 and the touch screen 102 to allow ease of movement of the first part 103 across the touch screen 102 and prevent damage to the touch screen 102. The low friction ring 202 may comprise felt or any other suitable material, such as a self-lubricating polymer. Figure 2b shows a side cutaway view of the second part of the magnetically centred thumbstick. The second part is substantially hemispherical and comprises a substantially flat lower surface 302 and a dimple or indent 303 located in the upper section. Both the first part 103 and the second part 301 may comprise permanent magnets. Alternatively, one of the first part 103 and the second part 301 may comprise a ferromagnetic material and the other of the first part 103 and the second part 301 comprises a permanent magnet. The first part 103 and second part 301 fit neatly together when not in use. This helps to reduce collection of debris on the parts, for example if they are carried in a bag or pocket. Figure 12a shows an example of a first part, or interface component 103, and a second part 301 together with a cover or lid 700 which together form a contained package for storage / transportation. It will be understood that magnets and / or ferromagnetic elements in the first and second parts 103,301 hold these parts together, providing protection for the stylus 201 and preventing the accumulation of dust or other debris on low friction ring 202 and / or any other surface of the first part 103 which moves across the input surface in use. Debris accumulating on this surface increases friction and can cause damage to a touchscreen or similar. The lid 700 surrounds the outside of the first part 103, providing protection to the outer surface of the interface. Particularly where a soft or rubberised outer surface is provides, dust or lint from a bag or pocket could easily adhere to the outer surface of the first part, reducing grip for a user and detracting from the aesthetic appeal. The lid 700 has a size and curvature to correspond to the outer dimensions of the second part, so that when assembled with the first and second parts a sleek outer shape is created with no sharp edges to catch on material of clothes or bags. A small magnet or ferromagnetic element 702 is provided within the lid 700 (see Figure 12b) so that the lid is magnetically secured to the assembly. The magnetic attraction to the lid 700 is preferably tuned to be lower in magnitude than that between the first and second parts 103,301 to ensure that the first and second parts 103,301 remain together when the lid 700 is removed. The magnet or magnetic material of the first part 103 is housed between the upper and lower sections of the first part 103. Alternatively, the first part 103 may comprise a magnet, with the thumb grip 104, raised edge 105, stylus 201, and low friction ring 202, attached to the magnet. The magnet or magnetic material of the second part 301 is housed between the flat lower surface 301 and indent 303 within the second part 301. Alternatively, the entirety of the second part 301 may comprise a permanent magnet shaped accordingly. Figure 3 shows a schematic side view of the magnetically centred thumbstick 100 in situ on a touch screen device 101. The first part 103 is shown at the front of the device which comprises a touch screen 102. The second part 301 is shown at the back of the device 101. The first part 103 and the second part 301 are in close proximity, located either side of the device 101 with the first part in contact with the touch screen 102 of the device 101. The second part 301 is releasably mounted to the back of the device 101, on the opposite side to the touch screen 102. When in use the second part 301 is fixed in position. The second part 301 may be repositioned in relation to the touch screen 102 between uses. The second part 301 may comprise one or a plurality of suction cups to movably mount the second part 301 to the back of the device 101. However, the second part 301 can alternatively simply rely on friction and the magnetic attraction from the first part 104 to maintain a set position in use. In one embodiment, the second part 301 comprises a high gloss, low hardness, high friction silicone material. Alternatively, the second part 301 may be provided within a protective or decorative casing or cover for the device 101, such that when the casing is placed on the device 101 the second part 301 is situated at the back of the touch screen device. Other known means for releasably mounting the second part 301 at the back of the touch screen device 101 may be used. The second part 301 is disk shaped in the illustrated example. Alternatively, the second part 301 may be any suitable shape. The second part 301 comprise a substantially smooth outer surface to avoid it being knocked / dislodged / moved. The first part 103 and second part 301 are substantially the same size. The first part 103 and the second part 301 are substantially the same overall shape. In the example where the first part 103 comprises a permanent magnet, the second part 301 may comprise ferromagnetic material. The ferromagnetic material may comprise filings or a powder contained within a cross sectional area smaller than that of the permanent magnet. Preferably, the ferromagnetic material is contained in a cross-sectional area at least a third of that of the permanent magnet. Operation Operation of the example thumbstick 100 is as follows: The second part 301 is fixed into position at the back of the touch screen device (the front of the device comprising the touch screen). The second part 301 is positioned so as to align with a virtual thumbstick shown on screen. The first part 103 is then placed on to the touch screen 102 of the device 101 on top of the virtual thumbstick shown on screen. The first part 103 may cover the on screen thumbstick. The first part 103 and the second part 301 are magnetically coupled. The first part 103 automatically centres into alignment with the second part 301 due to the force created by the magnetic field. The first part 103 and second part 301 are shown in alignment in figure 3. The position in relation to the touch screen and the neutral position of the first part and stylus 201 can be altered by relocating the second part 301 on the rear of the device 101. The thumbstick as shown in figure 3 is in a neutral position. The neutral position is where the centres of the first part and the second part are aligned. No movement of the first part is being induced by the second part when in this position. There is no sideways force is exerted on the first part in this position. The stylus 201 of the first part 103 is in contact with the virtual thumbstick on screen. The thumb grip 104 of the first part 103 is in direct alignment with the virtual thumbstick. The thumb grip is in electrical connection with the virtual thumbstick through the stylus 201. As a result, the skin of a user is in electrical connection with the virtual thumbstick when in use. The user places a thumb on the first part 103 of the thumbstick, providing an electrical connection between the user and the virtual thumbstick via the thumb grip 104 and stylus 201. When the user moves the first part 103 of the thumbstick across the touch screen, this provides an input to the touch screen 102 which subsequently moves the virtual thumbstick. Figure 4a shows a side view of the magnetically centred thumbstick 100 in situ on a touch screen device 101 in a first position. When the user moves the first part 103 of the thumbstick across the touch screen 102 this displacement creates misalignment of the centres of the first part 103 and second part 301. In figure 4a, the first part 103 has been moved downwardly across the touch screen 102 by the user. Due to the magnetic field, the first part 103 is pulled back towards the second part 301. A resultant upwards force 401, opposite to the force created by the user, now acts on the first part 103, urging it back towards the neutral position shown in figure 3. When the user is in contact with the first part 103 this resultant force will be felt by the user. The resultant force provides feedback to user. When the user releases contact with the first part, the first part will return to neutral position as a result of the resultant force created by the magnetic field. Once in the neutral position, no resultant force is acting on present on the first part 103. The first part 103 is magnetically centred by the second part 201. Figure 4b shows a side view of the magnetically centred thumbstick 100 in situ on a touch screen device 101 in a second position. In figure 4b, the first part 103 has been moved upwardly across the touch screen 102 by the user. Similarly to the case as shown in figure 4a, a resultant force 402, opposite to the force applied by the user, acts on the first part 103. The first part 301 is again urged back towards the neutral position shown in figure 3 by the resultant force and feedback is provided to the user. The strength / size of the magnet or magnets used can be increased or decreased. The larger the magnetic force, the larger the resultant force and the more feedback provided to the user. The type of magnets can determine strength of magnetic force and therefore alter feedback. Two permanent magnets provide the strongest attractive force and, therefore, the strongest feedback. A larger magnetic force provides a stronger reset increasing the speed of play, and also allows a greater spacing between the first and second parts, allowing use of the thumbstick on thicker devices. The magnetic field created by the first part and the second part is not affected by any magnets used for screen closure on mobile device. The magnetic field created by the first part and the second part is of a sufficient size and shape that any magnets present on the touch sensitive interface do not interfere with the operation of the thumbstick. Other examples The thumbstick can be used on a mobile device with a touch screen in conjunction with any known application for drone control. The thumbstick can be used as / with a controller for a drone. The second part 302 may be permanently fixed within a device with a touch sensitive interface. The second part 302 may be permanently fixed in a set position on the opposite side of the input surface of a touch sensitive interface. The second part 302 may be permanently secured in a set position on the opposite side of the input surface of a touch sensitive interface. In another example the touch sensitive interface may be a trackpad, particularly a mouse track pad with a circular boundary. The thumbstick is placed into position as described above, with the first part 103 on one side of the trackpad and the second part 301 on the opposite side of the trackpad. The first part 103 moves across the trackpad within the boundary created by the circumference providing an input to the device connected to the trackpad. The thumbstick may be suitable for use with any interface with a boundary. The touch sensitive interface may also comprise a pressure sensor. In this example, the first part 103 of the thumbstick may also provide an input to the touch screen in the z direction, providing a click or select function. Figure 5 shows a perspective view of the magnetically centred thumbstick 500 in situ on a games controller case, In this example, the thumbstick 500 is provided on a games controller 501 with a touch sensitive interface 502. The touch sensitive interface 502 has a boundary 507. The magnetically centred thumbstick 500 can replace mechanical joysticks / thumbsticks traditionally used in games controllers such as the one shown in Figure 5. The touch sensitive input surface 502 of the games controller 502 may be curved such that it follows the arc of the user’s thumb movement. The input surface 502 may be in the form of a dome. The first part 503 of the thumbstick 500 is configured to slide, in use, across the input surface of the touch sensitive interface 502 and comprises a stylus (not shown) for contacting said input surface to provide an input signal. Other features described in the first part 103 of the earlier example may also be provided. In this example, the second part (not shown) is permanently located on an opposite side of the touch sensitive interface 502 and is not repositionable by the user. The second part is thus permanently located within the games controller, but is otherwise similar to the second part 302 described in the earlier example. The first part 503 is magnetically coupled to the second part as before, such that the first part is urged towards the second part to centre the first part 503 back into a neutral position. The first part 503 of the thumbstick is the only part of the thumbstick which is visible in use. It is easily exchanged to allow the device to be customised and cleaned easily. Mechanical control sticks can suffer from stick drift, where the mechanical parts of the control stick, particularly the spring, wear overtime causing a permanent pitch in one direction off centre. The joystick or thumbstick being magnetically centred would help prevent stick drift. Figure 6 provides an exploded view of an embodiment of the invention. As in the first example described above, the embodiment of Figure 6 is for use with a touchscreen device, illustrated as a mobile phone handset 601. Two interface components, or ‘pucks’ 603, are shown above the screen 602 of the handset 601. Each puck 603 is fundamentally similar to the first part 103 of the control stick 100 described in the first example, and serves the same purpose. In particular, each puck 603 has a raised edge 605, similar to raised edge 105 from the first example, and has a stylus or pointer (not shown) on the underside to provide a precise and reliable interaction with, and thus input to, the screen 602 of the handset 601. A permanent magnet or small piece of ferromagnetic material is provided within each puck to centre and align the puck 603 with another magnet in use. The exploded view of Figure 6 also shows a protective case 607, of the type typically used to avoid scratching or other damage to the handset 601. The case 607 includes a cut-out section 608 to receive the camera ‘bump’ present on many smartphones. It will be understood that different case designs, with different cutouts 608 may be provided for different handset designs. Within the case 607 are two recesses 609A,609B (generally referred to as 609), located towards the left and right sides of the handset 601 when it is held in a landscape orientation. Each of the recesses 609 is designed to receive a magnet 611 A,611B (generally 611). The case 607 can be formed of a plastics and / or rubberised material, and should have a relatively thin wall so that the overall size of the handset 601 is not significantly increased when the case 607 is attached. The magnets 611 in the illustrated example are 0.5 mm thick N42 Neodymium magnets, which provide a relatively high field strength while ensuring that the walls of the case 607 can remain thin. Each magnet 611 within the case 607 provides the attractive force and centring effect for one of the pucks 603, in the same way as already explained for the earlier examples, but also provides additional benefits as described below. Figure 6 additionally shows exploded views of left and right grips 613,633 for connection to the case 607 in use. The grips 613,633 are ergonomically shaped and are provided with a soft and / or textured outer surface, for example formed from silicone, to improve grip and comfort for a user. The left grip 613 comprises a rear housing 615 and front housing 617 which are secured together to form the grip 613. The rear housing 615 comprises a first aperture 619 for receiving a magnet cartridge 621 with a bayonet fitting allowing the cartridge 621 to be releasably secured within the first aperture 619. The magnet cartridge 621 contains a stack of magnets which are attracted to the magnet 611A within the case 607 to locate and hold the left grip 613 in position against an outer surface of the case 607. A second aperture 623 is provided in the front housing 617 for (optionally) receiving a 3mm thick magnet 625 which can similarly provide an attractive force to secure the left grip 613 in position. A silicone / rubber pad 627 is secured over the second aperture 623. The rear housing 615 additionally comprises a resilient clip 629, at an outer edge thereof, designed to engage with an edge of the case 607 and / or handset 601. A raised portion 631 on the outer surface of the case 607, at the centre of a rear wall, provides an abutment surface for an inner edge of the left grip 613 when in position. The clip 629 and raised portion 631 of the case 607, together with the abovementioned magnetic attraction, serve to hold the left grip 613 securely in position during use. The right grip 633 shown in Figure 6 is similar in many respects to the left grip 613, but is simpler in overall design and construction. A rear housing 635 and front housing 637 are again provided, and a resilient clip 639 is provided on the rear housing 635 as before. The right grip 633 however lacks the first and second apertures for a removable magnet cartridge and optional additional magnet. Instead, a ferromagnetic plate 641 is provided on the front housing 637 so that the magnet 611B within the case 607 can attract the right grip 633 and help secure the grip 633 to the case 607. The raised portion 631 of the case 607 and the resilient clip 639 also help to secure the right grip 633 in place as described for the left grip 613 above. The magnets 611 in the case 607 therefore serve to secure the ergonomic grips 613,633 in place, therefore providing anchor points associated with the handset, as well as providing the centring force for the pucks / thumbsticks 603 as in earlier embodiments. Providing one or more magnets 611 in a case 607 removes some of the freedom to position a puck 603 freely in use, to match the location of a virtual thumbstick on screen, but provides other benefits as will be described below. Many games allow an adjustment of the position of user inputs in in the game settings, mitigating any impact from a restricted / fixed magnet position. The lack of free positioning could be further mitigated, if necessary, by providing additional magnets at different locations within the case and / or by providing one or more apertures designed to hold a magnet 611 or other anchor component at more than one set position. For example, Figure 7 schematically shows one possible design, where three overlapping circular cut-outs provide three distinct positions 641,643,645 for a magnet 611. The magnet 611, one positioned, would be held in place between the case 607 and the rear surface of the handset 601. Particularly where the grip 633 includes a simple ferromagnetic plate 639, the attraction between a magnet in the case 607 and the grip 633 will still retain the grip 633 in place during use regardless of which position 641,643,645 is selected for the magnet 611. The more complex design of the left grip 613 advantageously allows for the adjustment of a magnetic force, through the optional inclusion or omission of the 3mm magnet 625 and via the magnet cartridge 621. Increasing the magnetic force can help to provide a more secure connection between the grip 613 and the case 607 (and ultimately the handset 601). Stronger magnetic attraction also increases the restorative force felt by a user through the puck / thumbstick 603 in use. Conversely, a weaker magnetic attraction will reduce the restorative force, giving a ‘lighter’ feel during use. Different users can have a general preference for a lighter or stronger ‘feel’ during gameplay, and / or different situations may benefit from different controller feel. the Figure 8 shows the magnet cartridge 621 described above with the bayonet fitting 647 shown. An indicative stack 649 of magnets 651 is also shown within the cartridge 621. A light spring (not shown) provides a biasing force between the cartridge 621 and the remainder of the grip 613, so that the cartridge 621 can be pushed against the biasing force and rotated to allow removal in the conventional manner. As illustrated, the magnet stack 649 is not secured in place within the cartridge 621 (in use the stack 649 will be attracted and held in place by the magnet 611A in the case), so once a cartridge 621 is separated from a grip the stack 649 can be easily removed and individual magnets 651 can be slid off to reduce the overall magnetic force provided. Additional magnets 651 could be added to a removed stack 649 in a similar manner to increase the magnetic force, but the illustrated embodiment also provides for the addition of magnets 651 to the stack 649 without removing the cartridge. A near complete left grip 613, with only the rubber pad 627 omitted, is shown in Figure 9. The view of Figure 9 clearly shows a stepped profile on the front surface of the grip 613. As shown, a first end section 653, adjacent the resilient clip 629, is lower than a middle section 655 where the second aperture 623 is provided. A slot (not shown) is provided in the step between the first end section 653 and the middle section 655, so that individual magnets 651 can be slid into / onto the stack 649 as indicated by arrow 657. A non-magnetic spacer may also be provided for insertion into the magnet stack 649 to fill empty space and / or to increase the distance between the magnets 651 and the handset 601, and therefore the puck 603. Increasing this distance will reduce the strength of magnetic field experienced by the puck / thumbstick 603, and thus provide a lighter feel as discussed above. With such an arrangement, the lightest feel would be provided by a single magnet 651 behind a spacer, and the strongest field by a full stack 649 of magnets 651 with no spacer included. Although described above as an open cartridge 621, an enclosed cartridge, restraining the magnet stack 649 at both ends, could instead be provided. Such a cartridge could be inserted and removed from an aperture provided on the opposite side of the grip 613 if desired. The bayonet fitting for the cartridge 621 could additionally, or alternatively, be replaced with a threaded / screw fitting or similar. Figure 10 shows a rear view of the left and right grips 613,633 assembled with the cover 607, within which is a handset 601. The location of the removable magnet cartridge 621 in the left grip 613 is also shown. A camera bump 659 can be seen through the cut-out 608 in the case 607. It should be understood that the stepped profile of the grip 613, provides space for the camera bump even where the thickness of the case material is not sufficient to provide a substantially flat rear surface for the grip 613 to sit against. It will also be understood that it is beneficial if the grips 613,633 can be made as universal as possible, so that a single grip design can be used with a wide range of different phones, tablets or other handheld devices, even if different cases 607 are required to account for different device sizes and configurations. Bespoke case designs are able to create a largely universal overall thickness, so the grips 613,633 need only accommodate a relatively small range of thicknesses. The grips are also designed to locate at corners of a touchscreen device, meaning that different overall sizes of device can be accommodated. The size and position of the raised portion 631 on the rear of the case 607 can be adapted to ensure that engagement with the grips 613,633 is maintained. A cross section of the assembly, indicated at 11 in Figure 10, is shown in Figure 11. The cross section shows the engagement of the resilient clips 629,639 of the left and right grips 613,633 with the case 607, and the alignment and positioning of the pucks 603 on the handset 601 within the case 607. It can be seen that the magnet stack 649 and additional magnet 625 in the left grip 613 are aligned with magnet 611A within the case 607 along an axis 661 so that the magnetic forces hold the left grip in place. A puck 603, positioned on the screen 602 of the handset 601 is also held aligned with the axis 661, and the magnetic attraction will cause a restoring force towards this position when the puck 603 is slid across the screen 602 away from this position. Another puck 603 is similarly aligned and held in position by a second magnet 611B at the other side of the case 607, and this second magnet 611B also serves to hold the right grip 633 in place. The arrangement shown in Figures 10 and 11 show the increased size of the grips 613,633 to give a more secure and more comfortable user experience when holding the device for a prolonged period, for example while gaming, but can be easily removed so as not to permanently increase the overall size of the handset 601. The case 607 can remain in place and continue to provide protection to the handset even if the grips are removed. The pucks 603, as previously described, provide improved feel and give feedback to a user, but again are easily removable from the handset when this is not required. The above description is provided to illustrate benefits of the claimed invention and should not limit the scope of protection sought. Alterations are possible, within the scope of the claims. For example, an adjustable magnetic force, as shown in the left grip 613, could be provided in both grips if desired. The method of adjusting the magnetic force may also be realised by different means, for example if using a threaded cartridge the spacing of a set number of magnets from the handset could be adjusted simply by screwing the cartridge in or out of a longer thread. Although shown with two pucks 603 and two grips 613,633, it is conceivable that just a single puck and / or grip could be provided. As an alternative to locating one or more magnets 611 in a case 607, as in the described embodiment, one or more magnets could instead be incorporated directly into the body of a mobile phone handset, a tablet, or a similar touchscreen device. The need for a separate case would thus be obviated. In some instances, particularly when installed within a handheld device, care must be taken with the location of permanent magnets. For example, mobile phone handsets and various other handheld devices typically include compasses and / or other components that can be influenced by local magnetic fields. An alternative arrangement of the invention therefore replaces the magnets 611 within the case 607, or within the handset 601, with ferromagnetic elements to provide common anchor points for magnetic pucks 603 and for the grips 613,633. It will be appreciated that some form of magnet would be needed in the right grip 633, perhaps in place of the ferromagnetic plate 641 described above (an arrangement more like the second aperture 623 and magnet 625 in the left grip 631). The magnets within the grips 613,633 continue to provide the centring / restorative force to the pucks 603 in such embodiments

Claims

1. A magnetically centring thumbstick for use with a handheld device with a touch sensitive interface, the magnetically centring thumbstick comprising: an interface component configured to slide across an input surface of the touch sensitive interface and having a conductive input part to contact said input surface in use, anda second part positioned, in use, on an opposite side of the touch sensitive interface from the interface component;wherein at least one of the interface component and the second part comprises a magnet such that the interface component is magnetically attracted to the second part.

2. The thumbstick of claim 1, wherein the second part is configured to be releasably mounted on an opposite side of the handheld device from the interface component.

3. The thumbstick of claim 2, wherein the second part comprises a high friction surface, for example of a soft silicone material, for engagement with the handheld device.

4. The thumbstick of any preceding claim, wherein the interface component and the second part are magnetically attracted to the handheld device by a common anchor component secured to the handheld device.

5. The thumbstick of claim 4, wherein the anchor component comprises a ferromagnetic material.

6. The thumbstick of claim 4 or 5, wherein the anchor component is built into the handheld device.

7. The thumbstick of claim 4 or 5, wherein the anchor component is provided in a case for the handheld device.

8. The thumbstick of claim 7, wherein the case is provided with a raised section to provide an abutment surface for the second part.

9. The thumbstick of any preceding claim, wherein the second part comprises an ergonomic grip.10.The thumbstick of claim 9, wherein the second part comprises a physical clip.11 .The thumbstick of any preceding claim, wherein the second component comprises at least one magnet and means for adjusting the magnitude of magnetic field experienced by the interface component during use.12.The thumbstick of claim 11, wherein the number of magnets in the second part is adjustable.13.The thumbstick of claim 11 or 12, wherein the position of the or each magnet in the second part is adjustable.14.The thumbstick of any preceding claim, wherein the second part comprises a textured outer surface.15.The thumbstick of any preceding claim, wherein the interface component and the second part are removable from the handheld device and are designed to fit together for storage.16.The thumbstick of claim 15, further comprising a lid for covering the interface component during storage, wherein the lid is magnetically attracted to the interface component and / or the second part.17.The thumbstick of claim 16, wherein the lid has a similar outer shape to the second part.18.The thumbstick of claim 1, wherein the second part is permanently housed within a casing of the handheld device.19.The thumbstick of any preceding claim, wherein the interface component 5 further comprises a non-conductive low friction ring, surrounding theconductive input part, configured to be in contact with the input surface.20.The thumbstick of any preceding claim, wherein the interface component comprises a textured outer surface.io21 .The thumbstick of any preceding claim, wherein the interface component comprises a raised lip at an outer edge thereof.22.The thumbstick of any preceding claim, wherein the interface component 15 comprises a permanent magnet.23.The thumbstick of any preceding claim, wherein the interface component comprises a self-lubricating polymer.

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