A ribbon transfer apparatus

Abstract

A ribbon transfer apparatus including at least one roller 30 comprising a plurality of roller electrodes 32a-32e configured to generate an electric field, such that if a first ribbon 19 is positioned

Description

Transfer printing is well known in the art of commercial printing. Typically, a thermal printing apparatus includes a pair of spools onto which tape (also known as ribbon) is wound. The ribbon is a long strip of material carrying ink, typically on one side. The ribbon extends between the spools (and usually passes around one or more guide members). The ribbon is transferred along a ribbon path from a supply spool, to a take up spool, past a printhead which is operable to transfer ink from the ribbon to a substrate. The printhead may include thermally energisable printing elements or pixels, which are operable to warm the ink on the ribbon such that it can be removed from the ribbon and transferred to the substrate to form an image, for example data, a pattern, a bar code, QR code, etc. One or both of the supply spool and the take up spool are typically driven in order to transfer the ribbon between the spools. The ribbon can typically be moved in two directions between the spools, i.e., in a forward direction and reverse direction. When the ribbon on the supply spool reaches its end, it may be necessary to replace the ribbon with a new ribbon, in order to continue printing operations. Changeover of ribbons on existing thermal printing apparatuses requires an interruption in the printing operation. This downtime associated with ribbon changeover reduces throughput and increases costs. A system that allows the printer to continue operation while the ink supplies are replenished is therefore desirable. Prior systems have typically used ribbon re-inking. For example, US 2020 / 039265 A1 describes a system in which hot melt ink is transferred onto a band, in order to re-ink the band. However, such systems are technically challenging to implement and may require a significant redesign to both the printer and the consumables. An alternative method is ribbon splicing, in which an incoming new ribbon is temporarily or permanently joined to an already-installed, nearly-spent ribbon, within the printer itself. However, splicing machines may require adhesive material dispensers, which are themselves a consumable item, to perform the splicing. It is therefore an objective of the present invention to provide systems and methods that reduce or eliminate the downtime required for ribbon changeover. It is also an object of the present invention to provide systems and methods that allow ribbon changeover, without requiring the use of additional consumable items. While the above description relates to adhering a ribbon to another ribbon, it can also be useful to provide temporary adhesion between the ribbon and another object. For example, it can be useful to provide temporary adhesion between the ribbon and a roller, such as the supply spool and / or the take up spool. For example, the ribbon can be temporarily adhered to the supply spool and / or the take up spool, in order to assist with ribbon pickup or ribbon rewinding. It is therefore another objective of the present invention to provide systems and methods to provide temporary adhesion between a ribbon and a roller. Embodiments of the present invention aim to provide an improved printing apparatus and / or method of operating a printing apparatus. BRIEF DESCRIPTION OF THE INVENTION There is provided a ribbon transfer apparatus including at least one roller comprising a plurality of roller electrodes configured to generate an electric field, such that if a first ribbon is positioned in the electric field then an electroadhesive force is generated between the first ribbon and an article. At least two of the roller electrodes may be embedded in the roller, and the article may be the roller. The at least two roller electrodes may form a roller electrode array. The roller electrode array may be interdigitated. At least two of the roller electrodes may be on a surface of the roller, wherein the ribbon transfer apparatus is configured to be used with a first ribbon that comprises a plurality of ribbon electrodes, wherein the roller electrodes on the surface of the roller are configured to be in electrical contact with the ribbon electrodes to supply a voltage to the ribbon electrodes to generate the electric field, and wherein the article is a second ribbon. The ribbon transfer apparatus may further comprise the first ribbon. The ribbon electrodes may form a ribbon electrode array. The ribbon electrode array may be interdigitated. The ribbon transfer apparatus may include a cutting device configured to cut the ribbon. There is also provided a printing apparatus, including a ribbon transfer apparatus as described herein, and a printhead configured to transfer marking medium from a ribbon to a substrate. The printing apparatus may include a storage roller positioned between a supply spool support and the printhead of the printing apparatus. The printing apparatus may include a waste roller positioned between the printhead and a take up spool support of the printing apparatus. There is also provided a ribbon for use in a ribbon transfer apparatus or printing apparatus as described herein, the ribbon comprising a plurality of electrodes configured to generate an electric field when in electrical contact with the roller electrodes. The ribbon electrodes may form a ribbon electrode array. The ribbon electrode array may be interdigitated. There is also provided a method of transferring ribbon in a ribbon transfer apparatus, the ribbon transfer apparatus comprising at least one roller comprising a plurality of roller electrodes configured to generate an electric field, wherein the method comprises: supplying voltage to the plurality of roller electrodes such that an electric field is generated; and positioning a first ribbon in the electric field such that an electroadhesive force is generated between the first ribbon and an article. At least two of the roller electrodes may be embedded in the roller, and the article may be the roller. The at least two roller electrodes may form a roller electrode array. The roller electrode array may be interdigitated. At least two of the roller electrodes may be on a surface of the roller, wherein the first ribbon comprises a plurality of ribbon electrodes, wherein, when the voltage is supplied to the roller electrodes, the roller electrodes on the surface of the roller are in electrical contact with the ribbon electrodes to supply a voltage to the ribbon electrodes to generate the electric field, and wherein the article is a second ribbon. The ribbon electrodes may form a ribbon electrode array. The ribbon electrode array may be interdigitated. The method may include transferring marking medium carried by the first ribbon from the first ribbon to a substrate using a printhead. The method may include providing a storage roller positioned between a supply spool support and a printhead of the printing apparatus. The method may include providing a waste roller positioned between a printhead and a take up spool support of the printing apparatus. The method may include cutting the ribbon using a cutting device. BRIEF DESCRIPTION OF THE FIGURES In orderthatthe present disclosure maybe more readily understood, preferable embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in 5 which: FIGURE 1 is a perspective view of a roller and a ribbon; FIGURE 2 is a perspective view of two rollers and two ribbons; FIGURE 3 is an illustrative cut away view of a printing apparatus, including one or more of the rollers 10 and ribbons of FIGURE 1 or FIGURE 2, and including a storage roller that is not in contact with the ribbon; FIGURE 4 is an illustrative cut away view of the printing apparatus of FIGURE 3, wherein the ribbon is wrapped around the storage roller. 15 DETAILED DESCRIPTION OF THE DISCLOSURE Referring to Figure 1, there is shown a roller 30 and a ribbon 19. The roller 30 may contain one or more electrode arrays 32. The roller 30 may include an electrode array 32 that is embedded in the roller 30, as shown, for example, in Figure 1. In this way, the embedded roller electrode array 32 may be insulated from the ribbon 19 and from any other components. Voltage may be selectively supplied to the roller electrode array 32. When a suitable voltage is supplied to the roller electrode array 32, an electric field is produced in an area surrounding the roller electrode array 32. If a ribbon 19 is positioned within the electric field, then the electric field may cause an electroadhesive effect between the roller 30 and the ribbon 19. For example, the electric field may cause the ribbon 19 and the roller 30 to be attracted to one another. Therefore, the electric field may cause the ribbon 19 to electroadhere to the roller 30. As shown in Figure 1, the electric field developed by supplying a voltage to the roller electrode array 32 may cause the ribbon 19 to move from a first position, where the ribbon 19 is shown with a dotted outline, to a second position, where the ribbon 19 is shown with a solid outline. In the first position, the ribbon 19 may be spaced from the roller 30. In the second position, the ribbon 19 may contact the roller 30. In other words, the application of a suitable voltage to the roller electrode array 32 may cause charges to be generated on the surface of the roller 30. This may cause opposing charges to be generated on the surface of the ribbon 19. These opposing charges may be attracted to one another, thereby causing the ribbon 19 to electroadhere to the surface of the roller 30. The electroadhesive effect between the ribbon 19 and the roller 30 may be temporary, as discussed further below. The roller electrode array 32 may comprise a plurality of electrodes 32a, 32b, 32c, 32d, 32e, which may be closely spaced. In the illustrated example, the roller electrode array 32 includes five closely spaced electrodes 32a - 32e. However, it will be appreciated that any suitable number and arrangement of electrodes 32a - 32e may be included, depending on the strength of the desired adhesive force. The electrodes 32a - 32e may be supplied with alternating positive and negative voltages. The electrodes 32a - 32e may have an interdigitated layout. It will be appreciated that the suitable voltage to be applied to the electrodes 32a - 32e depends on a number of factors, such as the spacing of the electrodes 32a - 32e, the depth of the electrodes in the roller 30 and the weight of the ribbon 19. Therefore, any suitable voltage may be applied to the electrodes 32a - 32e, depending on the properties of the ribbon 19 and the roller 30. For example, a voltage between the electrodes 32a - 32e of 100 V with electrode spacing of 0.1 mm would be expected to develop an electric field of the order of approximately 1 kV / mm. This, in turn, would be expected to achieve an electroadhesive effect in the order of approximately 1 N / cm2. The magnitude of the electroadhesive effect may be increased by increasing the voltage, reducing the electrode spacing, or making the area of the electrodes 32a - 32e adjacent the ribbon 19 larger. Likewise, the magnitude of the electroadhesive effect may be decreased by decreasing the voltage, increasing the electrode spacing, or making the area of the electrodes 32a - 32e adjacent the ribbon 19 smaller. Therefore, it will be appreciated that any of these factors can be adjusted, based on the voltage that is to be supplied and based on the desired strength of the electroadhesive force. It is envisaged that including a roller electrode array 32 that is embedded in a roller 30 may be desirable in many different settings. For example, an electrode array 32 that is embedded in a roller 30 could be used to electroadhere a ribbon 19 to the roller 30, as explained above. This may be useful in a variety of fields. For example, a roller 30 that causes a ribbon 19 to temporarily adhere to the roller 30 may be desirable in a printing apparatus, for example for ribbon pick-up and ribbon re-winding, as explained further below. In addition to, or as an alternative to, the above-described roller electrode array 32, which is embedded in the roller 30, the roller 30 may include electrodes 36 that are not embedded in the roller 30. For example, Figure 2 illustrates a roller 30 including a pair of surface electrodes 36a, 36b. The roller 30 may include two surface electrodes 36: a positive surface electrode 36a and a negative surface electrode 36b. Figure 2 also illustrates a first ribbon 19a, which may include a ribbon electrode array 29. The first ribbon 19a may include a ribbon electrode array 29 only at one or both ends of the first ribbon 19a. For example, the first ribbon 19a may include a ribbon electrode array 29 at a leading end of the ribbon 19a and / or a ribbon electrode array 29 at a trailing end of the ribbon 19a. This may be beneficial to reduce the costs associated with providing electrode arrays 29 along the whole length of the ribbon 19a. Additionally or alternatively, the first ribbon 19a may include one or more electrode arrays 29 in the middle of the ribbon 19a, or electrode arrays 29 along the length of the ribbon 19a. This may be beneficial depending on the portion of the first ribbon 19a that is to be electroadhered. In use, the surface electrodes 36 in the roller 30 may make temporary electrical contact with the ribbon electrode array 29. When the surface electrodes 36 are in electrical contact with the ribbon electrode array 29 and voltage is supplied to the surface electrodes 36, voltage may consequently be applied to ribbon electrode array 29. When a suitable voltage is supplied to the ribbon electrode array 29, via the surface electrodes 36 in the roller 30, an electric field is produced in an area surrounding the ribbon electrode array 29. If a second ribbon 19b is positioned within the electric field, then the electric field may cause an electroadhesive effect between the first ribbon 19a and the second ribbon 19b. For example, the electric field may cause the first ribbon 19a and the second ribbon 19b to be attracted to one another. Therefore, the electric field may cause the first ribbon 19a and the second ribbon 19b to electroadhere to one another. In other words, the application of a suitable voltage to the ribbon electrode array 29 via the surface electrodes 36 may cause charges to be generated on the surface of the first ribbon 19a, This may cause opposing charges to be generated on the surface of the second ribbon 19b. These opposing charges may be attracted to one another, thereby causing the first ribbon 19a and the second ribbon 19b to electroadhere to one another. The electroadhesive effect between the first ribbon 19a and the second ribbon 19b may be temporary, as discussed further below. The second ribbon 19b may also include a ribbon electrode array, which may increase the strength of the electroadhesive force between the ribbons 19a, 19b. However, it will be appreciated that the second ribbon 19b does not need to include a ribbon electrode array, since the electric field provided by the ribbon electrode array 29 in the first ribbon 19a may be sufficient to provide the electroadhesive effect. It is envisaged that including an electrode array 29 that is embedded in a ribbon 19a and surface electrodes 36 on a roller 30 may be desirable in many different settings. For example, including an electrode array 29 that is embedded in a ribbon 19a and surface electrodes 36 on a roller 30 may be used to provide temporary adhesion between two ribbons 19a, 19b, or between two pieces of the same ribbon. This may be useful in a variety of settings. For example, providing temporary electroadhesion between two ribbons 19a, 19b can be useful in a printing apparatus, such as for ribbon splicing, as explained further below. Referring to Figure 3, there is shown a printing apparatus 10. The printing apparatus 10 may include one or more of the above-described rollers and ribbons, as explained in more detail below. For example, the printing apparatus 10 may include one or more rollers 30 having an embedded roller electrode array 32. Additionally or alternatively, the printing apparatus 10 may include one or more rollers 30 having surface electrodes 36. The printing apparatus 10 may include one or more rollers 30 having both an embedded roller electrode array 32 and surface electrodes 36. Additionally or alternatively, the printing apparatus 10 may include one or more ribbons 19a, 19b including a ribbon electrode array 29. The printing apparatus 10 may include a printhead 12 and a pair of spool supports 14,16, upon which a spool 18a, 20 of ribbon 19a may be mounted. The spool supports 14,16 may be rotatable to transfer ribbon 19a from one spool 18a, 20 to the other, past the printhead 12 in a ribbon path. The ribbon path may include one or more guide rollers 26, 28, which may guide the ribbon 19a along its path. It will be appreciated that, depending on the desired shape of the ribbon path and the relative arrangement of the spool supports 14, 16 and printhead 12, the printing apparatus 10 may contain no guide rollers. A substrate 24 is transported past the printhead 12 in a substrate path. The substrate 24 may be any material to be printed, for example a packaging material. The printhead 12 may be moveable substantially linearly and / or angularly relative to the substrate 24 between a non-printing position (optionally a plurality of non-printing positions) and a printing position. The printhead 12 may include thermally energisable printing elements, which are operable to warm the ink on the ribbon 19a when the printhead 12 is in the printing position, such that the ink can be removed from the ribbon 19a and transferred to the substrate 24 to form an image. The printing apparatus 10 may be provided with one or more rollers 30a, 30b. In the illustrated example, the printing apparatus 10 includes a storage roller 30a and a waste roller 30b. The storage roller 30a and / or the waste roller 30b may be configured to temporarily store a portion of the ribbon 19a. Each of the storage roller 30a and the waste roller 30b may be driven to rotate, for example by a respective motor. The storage roller 30a and / or the waste roller 30b may be provided with embedded roller electrodes, as shown in Figure 1, to provide electroadhesion between one or both of the rollers 30a, 30b and the ribbon 19a. For example, the storage roller 30a may comprise an embedded roller electrode array 32. Voltage may be selectively applied to the storage roller 30a. The printing apparatus 10 may be configured to calculate or sense that the supply of ribbon 19a from the supply spool 18a is running low. If the supply of ribbon 19a from the supply spool 18a is running low, then the printing apparatus 10 may be configured to begin a changeover procedure. During the changeover procedure, the printing apparatus 10 may be configured to selectively apply voltage to the embedded roller electrode array 32 in the storage roller 30a. When a suitable voltage is supplied to the roller electrode array 32, an electric field is produced in an area surrounding the roller electrode array 32. The electric field may be produced in an area adjacent the storage roller 30a. If a ribbon 19a is positioned within the electric field, then the electric field may cause an electroadhesive effect between the storage roller 30a and the ribbon 19a. An attractive electroadhesive force may be developed between the storage roller 30 and the ribbon 19a, which may cause the ribbon 19a to adhere to the storage roller 30a. Once a portion of the ribbon 19a has electroadhered to the storage roller 30a, the storage roller 30a may be driven in reverse, in order to wrap several turns of ribbon 19a around the storage roller 30a. The printing operation may be temporarily paused, to prevent problems with tension in the ribbon 19a during this stage. The ribbon 19a may wrap around the storage roller 30a once through electroadhesion, and then the storage roller 30a may be driven in reverse to cause several turns of ribbon 19a to wrap around the storage roller 30a. It will be appreciated that in some cases the storage roller 30a may not need to be driven in reverse, and / or the printing operation may not need to be temporarily paused, depending on the length of ribbon 19a left on the supply spool 18a, the strength of the electroadhesive force and the diameter of the storage roller 30a. The ribbon 19a may be wrapped around the storage roller 30a until the storage roller 30a has sufficient ribbon 19a to continue printing operations during the changeover of the supply spool 18a. The ribbon 19a may be wrapped around the storage roller 30a until the supply spool 18a is empty of ribbon 19a. In this way, the storage roller 30a may ensure that no ribbon 19a from the supply spool 18a is wasted. The voltage may continue to be supplied to the roller electrode array 32 in the storage roller 30a during the period in which the storage roller 30a is retaining the ribbon 19a. Alternatively, the voltage supply to the roller electrode array 32 may be stopped once the ribbon 19a has electroadhered to the storage roller 30a, particularly in cases where the storage roller 30a is driven to wrap several turns of ribbon 19a around the storage roller 30. In this way, the end of the ribbon 19a may be held in place adjacent the storage roller 30a by the outer turns of ribbon 19a. As mentioned above, the electroadhesive effect provided by supplying voltage to the roller electrode array 32 may be temporary. Once the voltage is no longer being supplied to the roller electrode array 32 in the storage roller 30a, the electroadhesive effect may typically endure for up to 30 seconds. It will be appreciated that the duration of the endurance of the electroadhesive force may depend on the properties of the ribbon 19a and / or the storage roller 30a, and on the amount of voltage supplied to the roller electrode array 32 in the storage roller 30a. After a portion of the ribbon 19a has been wound around the storage roller 30a, the supply spool 18a may be replaced by a new supply spool 18b. The supply spool 18a may be replaced once it is empty of ribbon 19a. This may prevent wastage of any ribbon 19a. The supply spool 18a may be replaced manually by a user, or by the printing machine 10 itself. During the printing operation, once ribbon 19a has been transferred to the storage roller 30a, the printing apparatus 10 may use the ribbon 19a from the storage roller 30a for printing. When the first ribbon, or old ribbon, 19a on the storage roller 30a is almost depleted, the leading end of a second ribbon, or new ribbon, 19b from a new supply spool 18b may be brought into close proximity with the storage roller 30a, as shown in Figure 4. For example, the end of the new ribbon 19b may be placed adjacent the storage roller 30a. The new ribbon 19b may be fed in the direction of the storage roller 30a, using any known ribbon handling method, such as a simple gravity feed. The leading end of the new ribbon 19b may be brought close to the trailing end of the old ribbon 19a, as the final turn of the old ribbon 19a is unwound from the storage roller 30a. When the leading end of the new ribbon 19b is brought close to the trailing end of the old ribbon 19a, the ends of the ribbons 19a, 19b may be spliced. In otherwords, the end of the old ribbon 19a and the end of the new ribbon 19b may be temporarily or permanently adhered to one another. For example, the trailing end of the old ribbon 19a and the leading end of the new ribbon 19b may be permanently adhered to one another using known splicing methods, such as by applying an adhesive to the ends of the ribbons 19a, 19b. Alternatively, the leading end of the new ribbon 19b and the trailing end of the old ribbon 19a may be electroadhesively spliced to one another. In addition to, or as an alternative to, the above-described roller electrode array 32, which is embedded in the storage roller 30a, the storage roller 30a may include electrodes that are not embedded in the storage roller 30a. For example, the storage roller 30a may be provided with surface electrodes 36, which are not embedded in the storage roller 30a. For example, and as shown in Figure 2, the storage roller 30 may include two surface electrodes 36: a positive surface electrode 36a and a negative surface electrode 36b. The ribbon 19a on the storage roller 30a, i.e. the old ribbon 19a, may include a ribbon electrode array 29. The ribbon electrode array 29 may be provided only at the trailing end of the ribbon 19a. For example, the ribbon 19a may include a ribbon electrode array 29 at a leading end of the ribbon 19a and a ribbon electrode array 29 at a trailing end of the ribbon 19a. This may be beneficial to reduce the costs associated with providing electrode arrays 29 along the whole length of the ribbon 19a. Alternatively, the ribbon 19a may include one or more electrode arrays 29 in the middle of the ribbon 19a, or electrode arrays 29 along the length of the ribbon 19a. The surface electrodes 36 in the roller 30 may make temporary electrical contact with the ribbon electrode array 29, thereby applying a voltage to the ribbon electrode array 29. The printing apparatus 10 may be configured to supply a voltage to the surface electrodes 36 in the storage roller 30a when the ribbon 19a on the storage roller 19a is almost depleted. The printing apparatus 10 may be configured to supply a voltage to the surface electrode 36 in the storage roller 30a when the surface electrodes 36 in the storage roller 30a are in electrical contact with the ribbon electrode array 29. In this way, the voltage may be supplied to the ribbon 19a via the surface electrodes 36 in the storage roller 30. When a suitable voltage is supplied to the electrode array 29 in the old ribbon 19a, via the surface electrodes 36 in the storage roller 30a, an electric field is produced in an area surrounding the ribbon electrode array 29. If a second ribbon 19b, i.e., the new ribbon 19b, is positioned within the electric field, then the electric field may cause an electroadhesive effect between the old ribbon 19a and the new ribbon 19b. For example, and as described above, the leading end of the new ribbon 19b may be positioned adjacent the trailing end of the old ribbon 19a on the storage roller 30a. When the leading end of the new ribbon 19b is adjacent the trailing end of the old ribbon 19a, the voltage may be supplied to the surface electrodes 36 in the storage roller 30a. If the surface electrodes 36 are in electrical contact with the ribbon electrode array 29 then an electric field may be produced in an area surrounding the ribbon electrode array 29. If the leading end of the new ribbon 19b is in this electric field, then the leading end of the new ribbon 19b and the trailing end of the old ribbon 19a may be attracted to one another, such that the ribbons 19a, 19b are electroadhered to one another. The new ribbon 19b may also include a ribbon electrode array 29. For example, the leading end of the new ribbon 19b may be provided with a ribbon electrode array 29, which may increase the strength of the electroadhesive force between the ribbons 19a, 19b. However, it will be appreciated that the second ribbon 19b does not need to include an electrode array 29 at its leading end, since the charges in the old ribbon 19a may induce opposing charges in the new ribbon 19b that are sufficient to provide the electroadhesive force. Additionally or alternatively, the new ribbon 19b may include a ribbon electrode array 29 in the trailing end of the new ribbon 19b. This may be beneficial, as it can allow another ribbon to be electroadhesively spliced to the new ribbon 19b, once the new ribbon 19b is almost depleted. Although a stronger adherence may be achieved when one or both of the ribbons 19a, 19b are provided with a ribbon electrode array 29, it is envisaged that the ribbons may still be spliced, even if the storage roller 30a does not contain any surface electrodes 36 and / or neither of the ribbons 19a, 19b contains a ribbon electrode array 29. In particular, it is envisaged that the old ribbon 19a and the new ribbon 19b could be spliced using the embedded electrode array 32, if present. For example, a suitable voltage may be supplied to the embedded electrode array 32, when the trailing end of the old ribbon 19a is on the storage roller 30a, and the leading end of the new ribbon 19b is adjacent the storage roller 30a. This may cause an electric field to develop in an area that covers both the trailing end of the old ribbon 19a and the leading end of the new ribbon 19b. This may cause both the old ribbon 19a and the new ribbon 19b to be attracted to the storage roller 30a simultaneously. Although the electroadhesive force provided on the new ribbon 19b may be lower than if either of the ribbons 19a, 19b contain a ribbon electrode array 29, the embedded electrode array 32 in the storage roller 30a may provide a sufficient electroadhesive force to temporarily adhere the old ribbon 19a and the new ribbon 19b to one another, thereby providing splicing of the ribbons 19a, 19b. Similar considerations may be taken into account when considering the suitable voltage that should be applied to the surface electrodes 36 in the storage roller 30a as the roller electrode array 32 described above. As with the roller electrode array 32, it will be appreciated that the suitable voltage to be applied to the electrodes depends on a number of factors, such as the spacing of the surface electrodes 36 and the ribbon electrode array 29, whether the new ribbon 19b includes an electrode array 29, and the weight of the ribbons 19a, 19b. Therefore, any suitable voltage may be applied to the surface electrodes 36, depending on the properties of the ribbons 19a, 19b and the storage roller 30a. As explained above, the leading end of the new ribbon 19b may be temporarily adhered to the trailing end of the old ribbon 19a by electroadherence. In this way, the old ribbon 19a and the new ribbon 19b may be spliced. After the ribbons 19a, 19b have been spliced or electroadhered to one another, the spliced ribbon 19a, 19b may continue on the original ribbon path. In particular, the spliced ribbon 19a, 19b may be unwound from the storage roller 30a, and the new ribbon 19b may travel from the supply spool 18b directly to the printhead 12, optionally passing around one or more guide rollers 26. At this stage, the ribbon 19a, 19b may no longer be in contact with the storage roller 30a and therefore the ribbon path will be the same as that shown in Figure 3. The printing apparatus 10 may be configured to stop the supply of voltage to the storage roller 30a once the ribbons 19a, 19b have been spliced. This may allow the ribbons 19a, 19b to continue on the original ribbon path. There may be a time period required for the switch-off of voltage to lead to a sufficient decrease in electroadhesive force between the ribbon 19a and the storage roller 30a to allow the ribbon 19a to be dropped. For example, the time period may be of the order of a few seconds to 10 seconds. If there is a time period required for the switch-off of voltage to lead to the ribbon 19a being dropped, then the printing apparatus 10 may be configured to switch off the voltage supplied to the embedded electrode array 32 a short time before the storage roller 30a needs to drop the ribbon 19a. The duration of this time period will depend on a number of factors, such as the materials of the ribbon 19a and the storage roller 30a. The printing apparatus 10 may be configured to perform a calibration step with a given ribbon 19a and storage roller 30a, to determine suitable time periods for the supply of voltage to the electrodes 32, 36. These suitable time periods may be stored in a memory in the printing apparatus 10. After the spliced ribbon 19a, 19b leaves the storage roller 30, the ribbon electrodes 29, if present, will lose their electrical contact to the surface electrodes 36 in the storage roller 30a. Therefore, the voltage applied to the ribbon 19a will be lost. Consequently, the electroadhesive effect at the spliced area will begin to diminish. After a certain time period, the electroadhesive effect between the two ribbons 19a, 19b may be diminished until there is no longer an electroadhesive effect between the two ribbons 19a, 19b. This time period may be approximately ten seconds, or a few tens of seconds. It will be appreciated that this time period will depend on a number of factors, such as the material of the ribbons 19a, 19b and the magnitude of the applied voltage to the storage roller 30a. The time period may be increased by adjusting these factors appropriately, or by minimising static discharges from the ribbon 19a, 19b. The time period before the electroadhesive force is lost may be long enough for the ribbons 19a, 19b to remain spliced while it passes the printhead 12, be used in a printing operation, and continue to the waste side of the printing apparatus 10 to be taken up by the take up spool 20. The take up spool 20 may wrap one or more turns of ribbon 19b over the top of the spliced section, while taking up additional waste ribbon 19b, before the electroadhesive effect is diminished to zero. In this way, the spliced section may be held in place on the take up spool 20 by friction between the spliced section of ribbon 19a, 19b and subsequent turns of ribbon 19b. The time taken for an electroadhesive force to diminish has been thought of as a disadvantage in prior art uses (unrelated to the present invention), as the turn-off time prevents instantaneous breaking of the electroadhesive force. However, in the uses described in the present application, the turn-off time is a useful feature, since it lengthens the allowable ‘run’ of the spliced section. Configuring the printing apparatus 10 such that the spliced section remains electroadhered until the spliced section is held in place on the take up spool 20 may be beneficial, as this may allow the printing apparatus 10 to operate without the need for any additional adhesive. In this way, the printing apparatus 10 may be able to operate without requiring an adhesive material dispenser, which removes the need for an additional adhesive, which is a consumable item. Alternatively, the printing apparatus 10 may be configured to make the temporary adhesion caused by the electroadhesive splicing permanent. For example, the printing apparatus 10 may be configured to apply an adhesive to the spliced section. For example, the printing apparatus 10 may comprise a dispenser positioned between the storage roller 30a and the take up spool, which is configured to apply an adhesive such as glue or adhesive tape to the spliced section. The printing apparatus 10 may therefore be configured to permanently adhere the old ribbon 19a and the new ribbon 19b to one another. Alternatively, one or more of the ribbons 19a, 19b may include a meltable layer. For example, one or more of the ribbons 19a, 19b may comprise a dielectric infill. The printing apparatus 10 may be configured to apply a high temperature to the ribbon 19a, 19b in the spliced area. This high temperature may melt the meltable layer, which may act as an adhesive, to adhere the old ribbon 19a and the new ribbon 19b to one another. The printhead 12 may be configured to apply the high temperature to the ribbon 19a, 19b. Alternatively, the printing apparatus 10 may include a separate heating component, that is configured to apply a high temperature to the spliced section. The meltable layer may be adjacent the ribbon electrode array 29. After the ribbon 19a, 19b has been spliced, the ribbon 19a, 19b may continue along the ribbon path past the printhead 12 and towards the waste section of the printing apparatus 10. The ribbon 19a, 19b may run onto the take up spool 20, which may collect the used ribbon 19a, 19b, i.e. the ribbon 19a, 19b that has already passed the printhead 12, as waste. The take up spool 20 may be configured to store the amount of ribbon 19a, 19b from multiple supply spools 18a, 18b. When the take up spool 20 is full or almost full, the waste ribbon 19a, 19b may be emptied from the take up spool 20. The printing operation may be paused while the waste ribbon 19a, 19b is emptied from the take up spool 20. By providing a take up spool 20 that is able to store the quantity of ribbon 19a, 19b from multiple supply spools, the printing apparatus 10 may reduce the amount of downtime associated with ribbon changeover. This may increase the throughput of the printing apparatus 10. In addition to, or as an alternative to, the electrodes 32, 36 in the storage roller 30a, the printing apparatus may include electrodes 32, 36 in a waste roller 30b. For example, the printing apparatus 10 may include a waste roller 30b having an embedded roller electrode array 32. The waste roller 30b may be configured to carry out a similar operation to the storage roller 30a, to further reduce or even eliminate the downtime associated with ribbon changeover. In particular, as shown in Figures 3 and 4, the ribbon path may pass adjacent the waste roller 30b after passing the printhead 12. Voltage may be selectively supplied to a roller electrode array 32 in the waste roller 30b, while the ribbon 19b is passing the waste roller 30b. The printing apparatus 10 may be configured to selectively supply voltage to the waste roller 30b. The printing apparatus 10 may be configured to periodically supply voltage to the waste roller 30b, so that the take up spool 20 can be emptied at regular intervals. Alternatively, the printing apparatus 10 may be configured to detect when the take up spool 20 is becoming full. When the take up spool 20 becomes full, or is close to becoming full, then the printing apparatus 10 may be configured to supply the voltage to the waste roller 30b. When voltage is supplied to the roller electrode array 32 in the waste roller 30b, an electric field may be formed adjacent the waste roller 30b. If the ribbon 19b is within the electric field, then the ribbon 19b may be attracted to the waste roller 30b and may electroadhere to the waste roller 30b, in a similar manner to that described above with reference to Figure 1. The printing apparatus 10 may be configured to cut the waste ribbon 19b between the waste roller 30b and the take up spool 20. For example, the printing apparatus 10 may comprise a blade that may be configured to cut the waste ribbon 19b between the waste roller 30b and the take up spool 20. The ribbon 19b may therefore begin to be wrapped around the waste roller 30b, rather than the take up spool 20. While the waste ribbon 19b is being wrapped around the waste roller 30b, the user may replace the take up spool 20 with an empty take up spool. Since the waste roller 30b can continue collecting the waste ribbon 19b, the printing apparatus 10 may be able to continue the printing operation while the take up spool 20 is replaced. This reduces, or even eliminates, the downtime needed to remove the waste ribbon 19a, 19b from the printing apparatus 10. After a new take up spool 20 has been inserted, the voltage supply to the waste roller 30b may be stopped. This may allow the end of the ribbon 19b on the waste roller 30b to be dropped from the waste roller 30b. This ribbon 19b may be taken up by the new take up spool 20, which may continue to collect the waste ribbon 19b. The amount of printing that can be carried out while using the waste roller 30b may be limited. For example, the amount of printing that can be carried out while using the waste roller 30b may be limited to one turn of ribbon 19a, 19b around the waste roller 30b. This may avoid the ribbon 19a, 19b becoming tangled, when the waste roller 30b releases the ribbon 19a, 19b. The printing apparatus 10 may comprise a controller that is configured to limit the amount of printing that can be carried out while using the waste roller 30b. The printing apparatus 10 may be used with any suitable form of ribbon supply. For example, the printing apparatus 10 may be used with a split cartridge. The split cartridge may comprise a supply side and a waste side. The supply side and the waste side of the split cartridge may be changed asynchronously. It will be appreciated that an embedded roller electrode array 32 and / or surface electrodes 36 can be included in various different components of the printing apparatus 10, depending on the design of the printing apparatus 10. For example, including a roller electrode array 32 in a storage roller 30a may be useful so that the storage roller 30a can take up a portion of ribbon 19a, so that the supply spool 18a can be changed with reduced or eliminated downtime. This may allow the printing apparatus 10 to continue operation for longer, or possibly for the printing apparatus 10 to continuously operate. This may be beneficial, as it may increase the throughput of the printing apparatus 10 and decrease the cost of printing. Including a roller electrode array 32 in a storage roller 30a may additionally or alternatively be used to provide splicing of the old ribbon 19a and the new ribbon 19b. Additionally or alternatively, surface electrodes 36 may be included in a storage roller 30a, to enable an electric field to develop around the ribbon 19a, if the ribbon 19a is provided with a ribbon electrode array 29. This may allow splicing of the old ribbon 19a and the new ribbon 19b. Additionally or alternatively, it may be beneficial for the printing apparatus 10 to include a waste roller 30b. The waste roller 30b may include an embedded roller electrode array 32 and / or surface electrodes 36. Including an embedded roller array 32 in a waste roller 30b may be beneficial, to enable the waste ribbon 19a, 19b to be emptied from the take up roller 20 with reduced or eliminated downtime. This may be beneficial, as it may increase the throughput of the printing apparatus 10 and decrease the cost of printing. Including a roller electrode array 32 in a waste roller 30b may additionally or alternatively be used to provide splicing of the old ribbon 19a and the new ribbon 19b. Additionally or alternatively, surface electrodes 36 may be included in a waste roller 30b, to enable an electric field to develop around the ribbon 19a, if the ribbon 19a is provided with a ribbon electrode array 29. This may allow splicing of the old ribbon 19a and the new ribbon 19b. The printing apparatus 10 may include a controller, which may be operable to control functions of the printing apparatus 10, for example to control movement of the spool supports 14, 16, by controlling operation of drive motors, for example, so as to transfer tape between spools 18a, 20. The controller may be operable to control movement of the storage roller 30a and / or the waste roller 30b. The controller may be operable to control the voltage to be supplied to the or each electrode array 29, 32, and / or the or each surface electrode 36. The controller may be operable to determine when the supply of ribbon on the supply spool is running low, or is likely to be running low, for example by receiving and responding to a signal from a sensor, and / or by monitoring operations of the printing apparatus 10, for example movements of the spools 18a, 20 to estimate the amount of ribbon remaining on the supply spool. The controller may be operable to carry out printing operations, for example by controlling the movement and / or position of the printhead 12 relative to the substrate 24, and / or the energisation of thermal printing elements in the printhead 12. Splicing, whether provided by an embedded roller electrode array 32 and / or by surface electrodes 36, and whether provided in a storage roller 30a and / or a waste roller 30b may be useful to facilitate an easy transition between the old ribbon 19a and the new ribbon 19b. This may reduce or eliminate the downtime associated with ribbon changeover. This may be beneficial, as it may increase the throughput of the printing apparatus 10 and decrease the cost of printing. The use of the electroadhesive effect for splicing may also be beneficial as it may allow a simpler construction of the printing apparatus 10. Prior art techniques such as ribbon re-inking typically require a major redesign of the printing apparatus and consumables. Using the electroadhesive effect for splicing may remove the need for a major redesign of the printing apparatus, and may also remove the need for an adhesive material dispenser or adhesive materials. The printing apparatus 10 may also provide environmental benefits, by removing the need for any additional adhesive materials, which are typically a consumable item. It is also envisaged that an embedded electrode array 32 and / or surface electrodes 36 could be useful in other components of the printing apparatus 10. For example, the supply spool 18a and / or the take up spool 20 could be provided with an embedded electrode array 32 and / or surface electrodes 36. This may be beneficial, to assist with ribbon pick-up or ribbon put-down. The printing apparatus 10 described herein is advantageous, since it provides ribbon pick-up, put down and / or splicing, without the need for any additional consumables, while improving throughput of the printing apparatus 10 and reducing costs. Whilst the apparatus described in detail above includes a printhead and inked ribbon, it will be appreciated that the principles and features described herein may be applied to other ribbon transfer apparatus, in which a ribbon or tape is transferred from one spool to another. A ribbon transfer apparatus may include any combination of the features described above, but need not include a printhead, and / or the ribbon or tape to be transferred need not carry ink or other marking medium. Where the ribbon transfer apparatus is a printing apparatus, the printing apparatus may be a thermal transfer printing apparatus. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The invention may also broadly consist in the parts, elements, steps, examples and / or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples and / or features. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein. Protection may be sought for any features disclosed in any one or more published documents referenced herein in combination with the present disclosure. Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and / or to encompass equivalents.

Claims

1. A ribbon transfer apparatus including at least one roller comprising a plurality of roller electrodes configured to generate an electric field, such that if a first ribbon is positioned in the electric field then an electroadhesive force is generated between the first ribbon and an article.

2. A ribbon transfer apparatus according to claim 1, wherein at least two of the roller electrodes are embedded in the roller, and wherein the article is the roller.

3. A ribbon transfer apparatus according to claim 2, wherein the at least two roller electrodes form a roller electrode array.

4. A ribbon transfer apparatus according to claim 3, wherein the roller electrode array is interdigitated.

5. A ribbon transfer apparatus according to any of the preceding claims, wherein at least two of the roller electrodes are on a surface of the roller, wherein the ribbon transfer apparatus is configured to be used with a first ribbon that comprises a plurality of ribbon electrodes, wherein the roller electrodes on the surface of the roller are configured to be in electrical contact with the ribbon electrodes to supply a voltage to the ribbon electrodes to generate the electric field, and wherein the article is a second ribbon.

6. A ribbon transfer apparatus according to claim 5, further comprising the first ribbon.

7. A ribbon transfer apparatus according to claim 6, wherein the ribbon electrodes form a ribbon electrode array.

8. A ribbon transfer apparatus according to claim 7, wherein the ribbon electrode array is interdigitated.

9. A ribbon transfer apparatus according to any of the preceding claims, including a cutting device configured to cut the ribbon.

10. A printing apparatus, including a ribbon transfer apparatus according to any of the preceding claims, and a printhead configured to transfer marking medium from a ribbon to a substrate.

11. A printing apparatus according to claim 10, including a storage roller positioned between a supply spool support and the printhead of the printing apparatus.

12. A printing apparatus according to claim 10 or 11, including a waste roller positioned between the printhead and a take up spool support of the printing apparatus.

13. A ribbon for use in a ribbon transfer apparatus or printing apparatus according to any of the preceding claims, the ribbon comprising a plurality of electrodes configured to generate an electric field when in electrical contact with the roller electrodes.

14. A ribbon according to claim 13, wherein the ribbon electrodes form a ribbon electrode array.

15. A ribbon according to claim 14, wherein the ribbon electrode array is interdigitated.

16. A method of transferring ribbon in a ribbon transfer apparatus, the ribbon transfer apparatus comprising at least one roller comprising a plurality of roller electrodes configured to generate an electric field, wherein the method comprises:supplying voltage to the plurality of roller electrodes such that an electric field is generated; andpositioning a first ribbon in the electric field such that an electroadhesive force is generated between the first ribbon and an article.

17. A method according to claim 16, wherein at least two of the roller electrodes are embedded in the roller, and wherein the article is the roller.

18. A method according to claim 17, wherein the at least two roller electrodes form a roller electrode array.

19. A method according to claim 18, wherein the roller electrode array is interdigitated.

20. A method according to any of claims 16 to 19, wherein at least two of the roller electrodes are on a surface of the roller, wherein the first ribbon comprises a plurality of ribbon electrodes, wherein, when the voltage is supplied to the roller electrodes, the roller electrodes on the surface of the roller are in electrical contact with the ribbon electrodes to supply a voltage to the ribbon electrodes to generate the electric field, and wherein the article is a second ribbon.

21. A method according to claim 20, wherein the ribbon electrodes form a ribbon electrode array.

22. A method according to claim 21, wherein the ribbon electrode array is interdigitated.

23. A method according to any of claims 16 to 22 including transferring marking medium carried by the first ribbon from the first ribbon to a substrate using a printhead.

24. A method according to claim 23, including providing a storage roller positioned between a supply spool support and a printhead of the printing apparatus.5 25. A method according to claim 23 or 24, including providing a waste roller positioned betweena printhead and a take up spool support of the printing apparatus.

26. A method according to any of claims 16 to 25, including cutting the ribbon using a cutting device.

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