BACKGROUND [0001] Fluid ejection devices may be used for the controlled ejection of a fluid, such as printing fluid, in a print operation.

BRIEF DESCRIPTION OF DRAWINGS

[0002] Examples will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

[0003] Figure 1 is a simplified schematic of an example fluid delivery device;

[0004] Figures 2A-C are simplified schematics of an example fluid delivery device at different stages of operation;

[0005] Figure 3 is a flowchart of an example method; [0006] Figure 4 is a flowchart of an example method; and

[0007] Figure 5 is a simplified schematic of an example machine-readable medium in association with a processor.

DETAILED DESCRIPTION [0008] Some examples herein relate to a fluid ejection device for the controlled delivery of a fluid, such as a printing fluid, towards a substrate, for example during a print operation to print an image to the substrate. The printing fluid may comprise an ink. According to some examples herein, the fluid ejection device comprises a chamber for retaining a volume of printing fluid (for example, to be ejected from the fluid ejection device, e.g. towards a substrate, during a print operation) and a regulator to control the level (or the amount or volume etc.) of printing fluid in the chamber. In these examples, the regulator may comprise an expandable element that is fluidly connected to the atmosphere (e.g. an area outside the chamber of the fluid ejection device) and the chamber is held at a negative, or suction pressure, such that when the level (or amount or volume) of printing fluid in the chamber decreases (as may be the case, for example, during a print operation) the regulator is caused to expand (or inflate with air). The regulator may be connected to a valve which controls the influx of (new) printing fluid (e.g. from a reservoir). When the regulator expands this may cause the valve to open so that printing fluid is permitted to enter the chamber, for example from a printing fluid reservoir. Via this mechanism, as the amount of printing fluid decreases in the chamber, the regulator controls new printing fluid to enter the chamber to fill the chamber. This interaction between the regulator and the valve may maintain the level of printing fluid in the chamber to within an acceptable range during a print operation. As the regulator expands, to cause the valve to open and new printing fluid to enter the chamber, the printing fluid will exert a pressure on the regulator, with the collapsing of the regulator causing the valve to close. This pressure, which increases as the printing fluid in the chamber increases, can bias the regulator to contract (or collapse or deflate) which may close the valve to stop new printing fluid from entering the chamber. In this way, the mechanism may be considered to be self-regulating as fluid entering the chamber will stop the expansion of the regulator when the fluid reaches an acceptable level. A standpipe may fluidly connect the chamber to a fluidic die of the fluid ejection device. The fluidic die may comprise a nozzle for the ejection of fluid from the chamber and fluid may be urged from the chamber to the nozzle via the standpipe so that the fluid can exit the device through the nozzle.

[0009] Occasionally, air may enter a fluid ejection device. For example, air may be ingested into the device where it may remain in the standpipe and/or the fluid chamber. Some factors that may cause air ingestion into the fluid ejection device are the permeability of the fluidic die (which may vary) and the ink delivery system, in addition to ink outgassing or being ingested through the nozzles of the fluidic die. If air is ingested into the device, then it may accumulate in the fluid chamber, for example it may rise to a top, or upper area, of the chamber and may accumulate there. If air enters the chamber, then it may affect the proper expansion of the regulator due to the volume taken up by the air and therefore the effect that this additional volume may have on the pressure differential across the regulator, and the pressure experience by the regulator. As the regulator is pressure-controlled (e.g. the expansion and/or contraction thereof), this may affect the flow of printing fluid during a printing process. This may, in turn, cause defects in the print quality of images printed by a user. In addition, a loss of back pressure may cause the ink flow outside the device which may lead to a failure in the device.

[0010] Some examples herein are directed to the reduction and/or prevention of air accumulation in the fluid chamber of a fluid ejection device for a long period of time. Some examples herein are directed to forcing (e.g. automatically or manually) any air that has migrated to the chamber out of the chamber. For this purpose, according to some examples herein (to be described in more detail below) there is provided a fluid ejection device comprising a non-return valve disposed at an upper end of the fluid chamber. The non-return valve is to permit any air in the chamber to exit the chamber and to prevent air outside the chamber from entering the chamber. According to another example (to be described in more detail below) the regulator in the chamber is caused to expand (or inflate etc.) in response to the level (or volume) of printing fluid in the chamber being detected at below a predetermined threshold. In this way, when the printing fluid in the chamber falls below the threshold, printing fluid is caused to enter the chamber (e.g. from a printing fluid reservoir) via the expansion of the regulator. In this way, the air is forced towards an upper end of the fluid chamber where it is permitted to exit the chamber via the non-return valve. The predetermined threshold may be adjustable and/or settable and may be set at a level where, if the printing fluid drops below this level, it may be reliably inferred that air has migrated into the chamber. In this way, when the printing fluid drops to below a level indicating the presence of air in the chamber, printing fluid may be forced into the chamber which will force air in the chamber towards an upper portion of the chamber at which is located a one-way valve to vent the air. In this way, according to some examples, air may be extracted from a fluid ejection device through a one-way air valve (e.g. a check valve or a non-return valve) that will allow air to escape the fluid chamber as new fluid enters the fluid ejection device. As the fluid level in the chamber increases, air is pushed outside of the chamber, and outside of the device, via the one-way valve.

[0011] Figure 1 schematically shows an example fluid ejection device 100. The fluid ejection device 100 comprises a printing fluid chamber 102 for retaining a volume of printing fluid and an expandable pressure regulator 104 disposed in the chamber 102 for controlling the influx of printing fluid into the chamber (as will be described later). The device 100 also comprises an upper end 107 and a non-return valve 106 disposed at the upper end 107 of the chamber 102. The non-return valve 106 is to permit any air in the chamber 102 to exit the chamber and to prevent air outside the chamber 102 from entering the chamber 102. In other words, the non-return valve 106 comprises a one-way valve or a check valve that permits air to move through the valve in one direction. Therefore, as the expandable pressure regulator 104 controls printing fluid to enter the chamber 102, the regulator 104 may cause printing fluid to enter the chamber which will force any air present in the chamber 102 upwards and toward the upper end 107 of the chamber 102 where it will be forced out of the chamber 102 via the non-return valve 106. For example, expansion of the expandable pressure regulator 104 may cause printing fluid to enter the chamber. In this way, any air that has accumulated in the chamber 102 may be forced out of the chamber by controlling the regulator 104 to meter fluid flow into the chamber. In the device 100, the regulator 104 is shown connected to the atmosphere at point 103 (although, in other examples, the regulator 104 may not be connected to the atmosphere). The chamber 102 may be held at a negative pressure such that the device 100 is able to maintain the level of fluid in the chamber 102 and the negative pressure regardless of the location of the device 100 (e.g. any variations in outside pressure, altitude, etc.). This means that as the fluid level in the chamber 102 decreases (e.g. during a print job) the pressure differential across the regulator 104 causes air to fill the regulator from the atmosphere (at 103), and expand, which will cause printing fluid to enter the chamber (by opening a valve). The regulator may therefore comprise a flexible element, for example a flexible membrane, the regulator may comprise a balloon, and/or the regulator may comprise an expandable and/or collapsible element. The regulator may comprise an inflatable element (e.g. by the influx of a gas such as air). An outlet is schematically depicted at 101 and the fluid ejection device 100 may be to eject printing fluid out of the device via the outlet 101. The outlet 101 may comprise a fluidic die and/or a nozzle. The fluid ejection device 100 may comprise a printhead cartridge, or printer cartridge. The fluidic die may comprise a printhead die or print die. [0012] The device 100 of Figure 1 allows a user (for example, a user suspecting that air has become trapped in the chamber) to force the expansion of the regulator 104 which will force the trapped air towards the valve 106 and out of the device 100 via the valve 106. The fluid ejection device 100 of Figure 1 may therefore be periodically controlled, e.g. by a user, to “purge” any air that a user suspects has become trapped in the chamber. In this way the device 100 allows a user who has suspected that the chamber contains air to cause expansion of the regulator 104 to force fluid into the chamber 102 and to force the trapped air out of the device 100. However, in other examples the device 100 may be automatically controlled to expel the trapped air, for example by automatically (e.g. under the control of a controller, e.g. at predetermined periods of time) causing the regulator 104 to expand to force any air in the chamber 102 out of the device 100 via the valve 106. In this way the device 100 may be periodically, e.g. at predetermined time intervals, controlled to purge any air that has become trapped in the chamber. Another example of automating the purging process will now be described with reference o Figures 2A-C. [0013] Figures 2A-C show an example device 200. The device 200 may comprise the device 100 and like features will be denoted by like reference numerals. Accordingly, the fluid ejection device 200 comprises a printing fluid chamber 202 for retaining a volume of printing fluid, shown at 209, the printing fluid chamber comprising an expandable pressure regulator 204 for controlling the influx of printing fluid into the chamber, and a non-return valve 206 disposed at an upper end 207 of the chamber 202, the non-return valve 206 being to permit any air in the chamber 202 to exit the chamber and to prevent air outside the chamber from entering the chamber 202. As shown in Figure 2, the non-return valve 206 is located in an upper surface, or roof, of the printing fluid chamber 202. In this way, in use, air is forced upwards through the chamber 202.

[0014] The regulator 204 is expandable (and/or inflatable) and is connected to the atmosphere at 203. In this way, the pressure in the chamber 202 may be set at a negative, or suction, pressure, such that when the fluid level decreases the pressure differential causes the regulator 204 to expand. Figure 2a shows the device 200 in a state at which the printing fluid 209 is at a level where the regulator 204 is not caused to expand (as shown in Figure 1). This may be regarded as an equilibrium state of the device 200. Figure 2b shows the device 200 where the level of printing fluid 209 is low such that the pressure differential between the inside of the chamber 202 and the outside of the device 200 causes the regulator to expand (as described above with reference to Figure 1). The regulator may comprise an inflatable balloon and expansion of the regulator may comprise allowing air to enter the regulator 204 from the outside via the connection 203 to the atmosphere (which may be regarded as an air inlet for the regulator). Figure 2c shows the device 200 where the regulator 204 has been caused to expand to force air inside the chamber 202 towards the valve 206 and out of the chamber 202 via the valve 206. This will be described in more detail below.

[0015] The device 200 comprises a fluidic die 213 comprising a number of nozzles 214 (although four are shown in Figure 1 this is for illustrative purposes) for the expulsion of printing fluid from the device 200 (e.g. for the controlled evacuation of printing fluid during a print job). The nozzles 214 may comprise a nozzle array. A standpipe 212 connects the fluidic die 213 and the chamber 202. A fluid valve 220 connects a reservoir 249 of printing fluid to the chamber 202 via fluid line 248. When the fluid valve 220 is open, fluid flows from the reservoir 249 into the chamber 202, via line 248, to fill the chamber 202. The regulator 204 is such that when the regulator 204 is in an unexpanded, or un-filled, configuration (shown in Figure 2A), then the valve 220 is shut and fluid cannot flow into the chamber 202. The regulator is connected to a bias 230 such that, when the regulator 204 expands it moves the bias 230. The bias 230 is connected to the valve 220 such that when the regulator 204 expands it causes the valve 220 to open. The bias 230 may be to bias the regulator 204 such that expansion of the regulator acts against the bias 230, and this forces the valve 220 open (this is schematically shown in Figures 2B and 2C to be described below). When the regulator

204 expands, this causes the valve 220 to open so that printing fluid enters the chamber

202 to fill the chamber. When the regulator 204 expands (e.g. via the pressure differential when the level of fluid in the chamber is low) the regulator 204 may overcome the force exerted by the bias 230. This configuration is shown in Figure 2b. Figure 2b shows the device 200 during a print job in which fluid is expelled from the nozzles 214 from the chamber 202 and, accordingly, the level of fluid in the chamber 202 is low. The pressure differential between the interior of the chamber 202 and the outside of the device 200 causes air to fill the regulator 204 and the regulator 204 to expand, which opens the valve 220 as described above. When the regulator 204 contracts, or un- expands, or collapses, or deflates etc. the valve 220 is caused to close which shuts off the supply of fluid from the reservoir 249.

[0016] With reference to Figure 2C, the device 200 may comprise air bubbles (schematically indicated at 260) trapped in the chamber 202. The device 200 of the Figure 2 example comprises a controller 250 that is to cause (e.g. force) the regulator 204 to expand as will now be described. The controlling of the regulator 204 to expand via the controller 250 to now be described is a separate process from the “automatic” expansion of the regulator 204 when the printing fluid level in the chamber drops, which is caused by the pressure differential across the regulator 204 and the chamber 202. The controller 250 is therefore to cause a forced expansion of the regulator 204. The device 200 comprises a printing fluid sensor 210 to detect a level of printing fluid 209 in the chamber 202. The sensor 210 may therefore be to measure, or detect, a volume of printing fluid 209 in the chamber 202. The device 200 comprises a cap 240 for the nozzles 214, e.g. a cap for a nozzle array. The cap 240 is to seal the nozzles (or nozzle array) so that printing fluid is prevented from exiting the device 200 via the nozzles 214 when the nozzles are capped. As stated above, the controller 250 is to cause the regulator 204 to expand, for example, the controller 250 may be to force air into the regulator 204 (e.g. into an interior chamber thereof) so that the regulator 204 expands. This is shown in Figure 2C. In order to force the trapped air 260 out of the device via the valve 206 the controller is connected (e.g. communicably connected, for example by an electrical or wireless connection) to the sensor 210. The controller 250 can therefore determine, via the sensor 210, the level (or volume) of printing fluid in the chamber 202. The controller 250 is to monitor the level of printing fluid in the chamber 202 and, when the controller detects the level of printing fluid in the chamber 202 to be below a target level (which may be a pre-set or pre-determined threshold), the controller 250 is to cause expansion of the regulator 204 as shown in Figure 2C. The controller 250 may therefore be to cause expansion of the regulator 204 to allow fluid to enter the chamber 202 when the printing fluid sensor 210 detects the level of printing fluid in the chamber 202 to be below a target level. The target level may be user-settable and/or user-adjustable. The controller 250 monitoring the fluid level from the sensor 210 and acting to expand the regulator 204 when the level drops below the target level means that the process depicted in Figure 2C may be performed automatically, for example whenever the controller 250 detects (from the sensor 210) that the fluid level is low. The controller 250 may be to cause the cap 240 to be placed in sealing engagement with the nozzles 214 to seal the nozzles. For example, the controller 250 may be to, in response to determining that the fluid level is below the target level, cause the nozzle cap 240 to seal the nozzles

214, cause the regulator 204 to expand to thereby open the valve 220 to force printing fluid to enter the chamber 202 from the reservoir 249 via the line 248 which will, in turn, force any air 260 present in the chamber 202 toward the upper end 207 of the chamber and out of the chamber 202 via the valve 206. The controller 250 may be further to continually (e.g. automatically), e.g. in real-time, monitor the level of printing fluid in the chamber 202. In other words, the controller 250 may be to detect when the printing fluid in the chamber 202 falls below the target level and also when the printing fluid in the chamber rises above the target level (e.g. due to the controller 250 forcing the regulator to expand as described above). The controller 250 may be to, when it is detected that the level of printing fluid in the chamber 202 rises to above the target level, cease (or stop) the expansion of the regulator. In this way the controller 250 may be to maintain (e.g. automatically) the level of printing fluid in the chamber 202 to within a target range. The controller 250 may also be to cause the cap 240 to disengage from the nozzles 214. In this way, the controller 250 may be to monitor to level of printing fluid in the chamber 202 and, if the level falls below the target level, the controller 250 may be to: cause the cap 240 to seal the 214, cause the regulator 204 to expand to cause printing fluid to enter the chamber 202, continue to monitor the fluid level in the chamber 202, and, if the fluid level rises above the target level, the controller 250 may be to stop the expansion of the regulator 204 which may cause the regulator 204 to collapse back to an equilibrium configuration (e.g. as shown in Figure 2A) and cause the cap 240 to disengage from the nozzles 214. Therefore, as the fluid level in the chamber 202 is increasing, any gas (e.g. air) in the chamber is forced out of the camber via the valve 206 and the cap 240 avoids fluid exiting the device 200 via the nozzles 214. In this way, the nozzle cap 240 may be to seal the nozzles 214 such that when the nozzle cap 240 engages the nozzles 214 the cap 240 fluidly seals the nozzles 214. In this way when the nozzles 214 are capped (e.g. during the process of filling the chamber 202 with fluid) the increased fluid pressure in the chamber 202 cannot cause fluid to exit the device 200 through the nozzles 214. In some examples, the controller 250 may comprise an actuator which may be user- manipulatable and the user, via actuation of the actuator, may control the controller 250 to cause the regulator 204 to expand, as described above. In this way, the expansion of the regulator 204 may be performed manually or automatically. In the example of manual actuation, the process described above to fill the chamber 202 with fluid to cause air 260 to migrate towards the valve 206 may be triggered by a user, for example when the user suspects an air gain. In the example of automatic actuation, the controller 250 may cause fluid to fill the chamber 202 when the controller 250 detects a lowering of the printing fluid level in the chamber 202 (e.g. via the sensor). The controller may be to cause the expansion of the regulator 204 to stop. Put another way, the controller 205 may be to cause the regulator 204 to collapse. This may comprise stopping gas to be forced inside the regulator 204. In this example, when gas no longer causes expansion of the regulator 204 the regulator 204 returns to atmospheric pressure (due to its connection 203 with the atmosphere) and so the regulator returns back to an equilibrium position. Collapse of the regulator 204 causes the valve 220 to close. The controller 250 may therefore be to simultaneously cause the regulator 204 to expand and detect the level of fluid in the chamber 202. The controller 250 may therefore be able to trigger the regulator 204 to expand when it detects that the level of fluid inside the chamber 202 is lowering. The controller 250 may be to perform the method 300 and/or 400 and may comprise a processor 504 which will now be described with reference to Figures 3-5 respectively.

[0017] Figure 3 shows an example method 300 which may comprise a computer- implemented method. The method may comprise a method of regulating the amount of printing fluid in a fluid ejection device, such as the device 100 or 200. At block 302 the method comprises monitoring, by a sensor, the level of printing fluid in a printing fluid chamber of a fluid ejection device. For example, block 302 may comprise monitoring by the ink level sensor 210 the level of printing fluid 209 in the chamber 202 of the device 200. At block 304 the method comprises determining whether the level of printing fluid in the chamber drops below a predetermined threshold. If yes, and the level of printing fluid is below the predetermined threshold then, at block 306, the method comprises causing, by a processor, a regulator of the fluid ejection device to expand to thereby cause printing fluid to enter into the printing fluid chamber and cause any gas in the printing fluid chamber to migrate towards a one-way valve of the fluid ejection device. For example, block 306 may comprise causing, by the controller 250, the regulator 204 to expand to cause fluid to enter the chamber 202 from the reservoir 249 to cause the air 260 to migrate towards the one-way valve 206. Block 304 may comprise determining whether the level of fluid in the device is lowering. As above, the regulator may comprise an expandable and/or collapsible and/or inflatable element and may comprise a flexible element such as a flexible membrane. The one-way valve may comprise a check valve or a non-return valve.

[0018] In this way, the method 300 may be to automatically monitor the fluid level in a fluid chamber of a fluid ejection device and to automatically cause the fluid level to raise when the fluid level is detected to be too low. The low level of fluid may indicate the presence of air in the chamber and therefore the regulator may be automatically expanded when it is inferred that the air is present in the chamber (based on the detected fluid level).

[0019] The method 300 may comprise, prior to causing, by the processor, at block 306, the regulator of the fluid ejection device to expand, moving a cap into engagement with a nozzle of the fluid ejection device to seal the nozzle while the regulator expands. For example, this may comprise causing the cap 240 to seal the nozzles 214 while the regulator 204 expands. This may comprise causing the cap 240 to seal a nozzle array. In these examples, prior to the expansion of the regulator the nozzles are capped (and sealed) so that there is no “bleed-through” of printing fluid through the nozzles. The method 300 may comprise, following expansion of the regulator, if the level of printing fluid in the chamber is above the predetermined threshold, causing the regulator of the fluid ejection device to stop expanding. In this example, the method may additionally comprise moving the cap out of engagement with the nozzle to uncap the nozzle. In these examples, although the regulator has been caused to expand as a result of the printing fluid level being detected to be too low, the printing fluid level is monitored and, if the level returns to an acceptable level (which may be at or above the predetermined threshold), then the expansion of the regulator may be stopped. In this way, the fluid level returning to the acceptable level may be taken as an indication that any gas in the chamber has been expelled (via the one-way valve). In these examples the nozzles may be uncapped as fluid will no longer be forced into the chamber. The method may further comprise automatically monitoring, in real-time, by the printing fluid level sensor, the level of printing fluid in a printing fluid chamber of a fluid ejection device; and, if the level of printing fluid in the chamber drops remains below the predetermined threshold, then the method comprises causing, by a processor, the regulator of the fluid ejection device to continue to expand; and, if the level of printing fluid in the chamber rises above the predetermined threshold, then the method comprises causing the regulator of the fluid ejection device to stop expanding. In this way the method described above may be continued automatically so that the level of printing fluid is continually monitored, and the regulator is expanded or caused to collapse (e.g. by stopping expansion) according to the fluid level.

[0020] In this regard, Figure 4 shows another method 400 which may comprise a computer-implemented method and which may comprise the method 300 as described above with reference to Figure 3. The method may comprise a method of regulating the amount of printing fluid in a fluid ejection device, such as the device 100 or 200. At blocks 402 and 404 the method comprises monitoring the printing fluid level and determining whether the level is above the predetermined threshold, for example as described above with respect to blocks 302 and 304 of the method 300. If it is determined that the level of fluid is below the threshold then at block 406 the method comprises causing a nozzle cap to seal a nozzle (or nozzle array) of the fluid ejection device (for example seal a nozzle of a fluidic die of the fluid ejection device, e.g. nozzle

214 of the die 213). At block 408 the method comprises causing the regulator to expand, for example as described above with respect to block 306 of the method 300. At block 410 the method comprises, following expansion of the regulator at block 410, determining whether the level of printing fluid remains below the threshold. As indicated by the looping arrow, if yes and the printing fluid remains below the threshold then the method continues. Put another way, the regulator continues to be expanded to allow printing fluid into the chamber. If no and the printing fluid is above the predetermined threshold, then the method comprises blocks 412 and 414 at which expansion of the regulator is ceased and the nozzles are uncapped, respectively. [0021] Figure 5 shows an example non-transitory machine-readable, or computer-readable, medium 502 comprising a set of machine-readable, or computer- readable, instructions 506 stored thereon. The medium 502 is shown in Figure 5 in associated with a processor 504. The instructions 506, when executed by the processor 504, may be to cause the processor to perform the method 300 and/or the method 400 as described above (e.g. any of the blocks thereof). The instructions 506, when executed by the processor 504 are to cause the processor to monitor the level of printing fluid in a chamber of a fluid ejection device (such as the device 100 or 200) and, if the level (or amount or volume etc.) of printing fluid falls below a predetermined threshold, the instructions are to cause the processor to control an expandable element (e.g. the regulator 104 or 204) of the fluid ejection device to cause the chamber to fill with printing fluid and to urge any gas in the chamber to exit the chamber via check valve (such as the valve 106 or 206). The instructions may be to cause the processor to cap (and/or seal) a nozzle of the fluid ejection device (e.g. a nozzle array) prior to controlling the expandable element to expand (e.g. as described above to prevent any bleed through of fluid while the fluid chamber is filled). The instructions may be to cause the processor to uncap the nozzle of the fluid ejection device if the level of printing fluid in the chamber is above the predetermined threshold. To cause the regulator to expand the instructions may be to cause the processor to cause gas (e.g. air, such as air from the atmosphere) to be directed into the expandable element to cause the expandable element to inflate. This may be applicable in examples where the expandable element comprises a flexible and/or inflatable membrane. The instructions may be to cause the processor to continually monitor the level of printing fluid in the chamber and, if the level of printing fluid falls below the predetermined threshold, control an expandable element of the fluid ejection device to expand, and, if the level of printing fluid rises above the predetermined threshold, cause the expandable element to stop expanding. The check valve may comprise a one-way valve or a non-return valve.

[0022] Some examples herein may therefore increase the life of a fluid ejection device by providing a means by which any trapped air in the device may be expelled. In turn, this may save costs in warranty claims if the fluid ejection device is damaged (e.g. due to trapped air) during the life of its warranty. Some of the examples described above that automatically monitor the fluid level and can automatically cause expansion of the regulator (e.g. via a controller or processor) may reduce the number of instances of user interventions. Some of the examples herein may also reduce the frequency of replacing the fluid ejection device and reduce or eliminate any troubleshooting time resulting from the air ingestion. This may, in turn, improve customer satisfaction and the user experience by providing a more reliable image quality for the life of the fluid ejection device.

[0023] Examples in the present disclosure can be provided as methods, systems or machine-readable instructions, such as any combination of software, hardware, firmware or the like. Such machine-readable instructions may be included on a machine (e.g. a computer) readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having machine (e.g. computer) readable program codes therein or thereon.

[0024] The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart. It shall be understood that each flow and/or block in the flow charts and/or block diagrams, as well as combinations of the flows and/or diagrams in the flow charts and/or block diagrams can be realized by machine readable instructions.

[0025] The machine-readable instructions may, for example, be executed by a general-purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine-readable instructions. Thus, functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit, ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors.

[0026] Such machine-readable instructions may also be stored in a machine- readable (e.g. computer-readable) storage that can guide the computer or other programmable data processing devices to operate in a specific mode.

[0027] Such machine readable instructions may also be loaded onto a computer or other programmable data processing devices, so that the computer or other programmable data processing devices perform a series of operations to produce computer-implemented processing, thus the instructions executed on the computer or other programmable devices realize functions specified by flow(s) in the flow charts and/or block(s) in the block diagrams.

[0028] Further, the teachings herein may be implemented in the form of a computer software product, the computer software product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure.

[0029] While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above-mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims.

[0030] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims.

[0031] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.