BACKGROUND

[001] Some imaging apparatus, such as inkjet printers, perform operations that cause a print fluid such as ink to be discarded into one or more waste containers, sometimes referred to as spittoons.

[002] A waste container to collect the discarded print fluid may be removably installed in a printer, e.g. in a service station of the printer. Once the discarded print fluid reaches a predetermined level in the waste container, the waste container may be removed and an empty waste container may be installed in the printer.

BRIEF DESCRIPTION OF THE DRAWINGS

[003] Some non-limiting examples of the present disclosure will be described in the following with reference to the appended drawings, in which:

[004] Figure 1 is a schematic illustration of an example waste container according to the present disclosure;

[005] Figures 2a and 2b are enlarged views of example wicks as disclosed herein, assembled on example waste containers;

[006] Figure 3 is a schematic illustration of part of an example printing apparatus according to the present disclosure;

[007] Figure 4 is a schematic isometric view showing part of another example printing apparatus according to the present disclosure;

[008] Figure 5 is a schematic isometric view of the example printing apparatus of Figure 4, in another position;

[009] Figure 6 is a schematic illustration of part of an example printing apparatus according to the present disclosure, with an example waste container comprising two wicks;

[0010] Figure 7 is a schematic plan view showing part of another example printing apparatus according to the present disclosure, comprising two wicks; and [0011] Figures 8, 9 and 10 are block diagrams of example methods according to the present disclosure.

DETAILED DESCRIPTION

[0012] Printing devices are generally configured to produce print content (e.g., text, image, etc.) by depositing a print fluid or other image-forming material on a print medium, in response to receiving a print job. For example, an inkjet printing system can include a fluid ejection assembly, such as a printhead assembly, and a fluid supply assembly, such as an ink supply assembly, a print media transport assembly, a service station assembly and an electronic controller.

[0013] Scanning inkjet printers may employ one or more printheads mounted on a carriage which travels repeatedly along a scan axis to deposit ink on a print target, such as a print medium, in a print zone. Printheads may have a plurality of nozzles for firing ink drops on the print target, such that they lay down swaths of ink or other print fluid during each scan travel.

[0014] In an example, print medium may be advanced stepwise, in a direction perpendicular to the scan axis, between swaths. An inkjet printing system may also be an inkjet head of a three-dimensional (3D) printing system, where the inkjet head may deposit a print fluid such as a binding material on a bed of powder build material as a print target, to form a 3D object layer by layer.

[0015] Such printing devices and other image-forming devices may discard as waste some print fluid in connection with one or more procedures or operations.

[0016] For example, a printing device, such as an inkjet printing apparatus, may perform a spitting procedure on a service station to prevent, remove or reduce clogs from a printhead, for example forcing print fluid such as ink through a nozzle of the printhead. The print fluid forced through the nozzle is discarded as waste. In some examples, a wiper mechanism that may be associated to a service station of a printer cleans excess print fluid or debris from the printhead as part of a cleaning procedure. In such examples, the printing apparatus discards the excess print fluid as waste. A printing apparatus may also discard print fluid due to additional or alternative procedures or circumstances. [0017] The discarded print fluid resulting from these procedures is collected in waste receptacles or containers, also known as spittoons. Waste containers may be removably installed in a service station of a printing apparatus, for example on a cassette, and arranged such that components of the printing device or apparatus, such as nozzles associated with a printhead, feed waste print fluid to a corresponding waste container.

[0018] In some scanning inkjet printers, waste containers may be arranged at one end of the print zone and along the scan axis, such that the carriage with the printheads, which is displaceable along the scan axis, can reach a waste container to discharge waste print fluid from the printheads into the waste container.

[0019] As a waste container receives discarded print fluid, the level of the discarded print fluid in the waste container increases. If the capacity of the waste container is exceeded, spills of waste print fluid and other undesirable effects may occur.

[0020] To avoid exceeding the capacity of a waste container and minimize the risk of liquid overflow outside the waste container and consequent printer downtimes, the present disclosure provides an alternative to systems with floaters, or with counters to track an amount of discarded ink collected by each waste container and a controller to estimate the amount of ink stored in a waste container based on the counter readings, by using a reading system that lacks moving parts on the waste container..

[0021] The present disclosure provides for a low-cost container lacking electronics, e.g. controllers and sensors. This architecture makes it less prone to being damaged due to the liquid nature of ink, and easier and cheaper to replace. Figure 1 illustrates an example waste container 100 for receiving waste fluid, such as waste print fluid.

[0022] The example waste container of Figure 1 comprises a top cover 110, which may have an opening 120 to receive waste print fluid. The example waste container 100 also comprises a wick 130 to absorb by capillarity waste print fluid from the waste container 100.

[0023] In examples of waste containers according to the present disclosure, a wick is a porous element, for example made of felt, or of a woven or non- woven fabric of cotton or any other natural or synthetic material, that is suitable for absorbing fluids by capillarity e.g. for drawing up waste print fluid from the waste container. In examples, the wick may be white or of any other color that may change appearance, e.g. change color, when absorbing waste print fluid.

[0024] The wick 130 may comprise a top portion 131 and a stem 132. The top portion 131 of the wick 130 may be attached to the top cover 110 and may be visible from above the top cover 110, i.e. from outside the waste container 100. For example, the wick 130 may project through a hole in the top cover 110 or may be visible through a hole in the top cover 110 or may be visible through a transparent portion of the top cover 110.

[0025] In the present disclosure, spatial references such as top/bottom, upper/lower, horizontal/vertical, upwards/downwards, etc. refer to the position intended for the waste container when in operation, for example mounted in a service station of a printing apparatus.

[0026] In examples of waste containers according to the present disclosure, the wick 130 may be elongate in the direction of insertion of the wick through the top cover 110 of the waste container 100 and of projection into the waste container, i.e. in vertical direction when a waste container is in use. For example, the wick 130 may have an overall length, from the top portion 131 to the distal end of the stem 132, and a maximum width dimension or transverse dimension of the stem 132 (e.g. the diameter in case of a cylindrical stem), with the overall length of the wick 130 being e. g. at least twice, at least three times, or at least five times, the maximum transverse dimension of the stem 132. The overall length of the wick 130 depends on the level of waste print fluid to be detected in the waste container 100; in examples, the overall length may be between 20 mm and 50 mm. In examples, width dimensions of the stem 132 may be between 2 mm and 20 mm.

[0027] In examples, the wick 130 may be formed by a twist or braid of threads, or it may be formed by a piece of a soft or hard porous material configured as a strip, cylinder, block or other shape. In some examples the wick 130 may be a single part, or it may be made up of several parts, of the same material or of different materials: for example, the stem 132 and the top portion 131 may be two parts attached together. The top portion 131 may be shaped like the stem, e.g. it may be formed by the upper portion of the stem itself, or it may be different from the stem 132, in shape and/or materials. For example, the top portion 131 may have a larger width dimension than the stem 132, e.g. the wick may be T-shaped or mushroom- shaped in vertical cross-section. The stem 132 may be e.g. cylindrical, frustoconical, parallelepiped-shaped, strip-shaped or other. In examples, the wick 130 may be made up e.g. by a strip of felt or similar material, e.g. about 3 mm thick, inserted through a slot in the top cover 110 of the waste container 100, folded over the top cover 110, and held in place e.g. with a clip, an adhesive or another fastener.

[0028] In examples, a wick 130 for a waste container 100 according to the present disclosure may have any combination of the above features.

[0029] The stem 132 of the wick 130 may project a length S1 into the waste container and be in contact with the top portion 131 of the wick 130, such that waste print fluid absorbed by the stem 132 may reach by capillarity the top portion 131.

[0030] The length S1 of the stem 132 projecting from the top cover 110 into the waste container 100 defines a level L1 for the waste print fluid in the waste container 100. For example, when in use in a printing apparatus, once waste print fluid received in the waste container 100 reaches level L1 and the stem 132 of the wick 130, the wick 130 starts absorbing waste print fluid by capillarity through the stem 132. The waste print fluid raises by capillarity through the stem 132 to the top portion 131 of the wick 130. This may cause a change in the appearance of the wick 130 and the top portion 131 of the wick 130, e.g. a change in the color from the initial color of the wick material to the color of the waste print fluid or a color related to the color of the waste print fluid.

[0031] The change in appearance of the wick 130 is easily visible and may be inspected from above the top cover 110 of the waste container, visually by an operator and/or automatically using a sensor, such as an optical sensor, and is an indicator that the waste print fluid in the waste container 100 has reached level L1.

[0032] The detection that the waste print fluid has reached a predetermined level in the waste container 100 may be used to trigger an action, for example issuing a warning signal, changing an indicator status, etc.

[0033] Example waste containers disclosed herein enable accurate and timely detection that the waste print fluid has reached a predetermined level in the waste container, with simple and cost-effective elements and without resorting to the calculation of estimates or the use of complex mechanisms. At the same time, a wick 130 may be provided in a waste container 100 in a very simple manner, e.g. through a hole in the top cover 110, with no other alteration of the waste container.

[0034] Example wicks 130 are illustrated in enlarged scale in Figures 2a and 2b, assembled in each case on a top cover 110 of a waste container 100, with the top cover 110 having an opening 1101. In some examples the top portion 131 of the wick 130 may be wider than the stem 132, so the stem 132 may be inserted through the opening 1101 and the top portion 131 may abut on the top cover 110. For example, as illustrated in Figure 2a, the top cover 110 may form the opening 1101, and the stem 132 of the wick 130 may be inserted through the opening 1101, while the top portion 131 of the wick 130 may rest on the upper surface 1102 of the top cover 110. In other examples, such as illustrated in Figure 2b, the top cover 110 may form a seat 1103 in correspondence with the opening 1101 , recessed from the upper surface 1102 e.g. by the top cover 110 having a stepped shape around the opening as shown: the stem 132 of the wick 130 may be inserted through the opening 1101, while the top portion 131 of the wick 130 may rest on the seat 1103.

[0035] In some examples, such as those of Figures 2a or 2b but also including examples of wicks of different shapes and configurations, an upper surface 1311 of the top portion of the wick 130 may be flush with the upper surface 1102 of the top cover 110 of the waste container 100, or may project a distance D1 of less than 5 mm above the top cover 110, e.g. above the upper surface 1102 of the top cover 110, or may be recessed a distance D2 of less than 20 mm below the upper surface 1102 of the top cover 110.

[0036] In other words, the upper surface 1311 of the wick 130 may be in a range of between 5 mm above and 20 mm below the upper surface 1102 of the top cover, to be exposed and easily visible by a user and/or detectable by a sensor, e.g. even by an optical sensor that is displaced above the waste container 100, for example an optical sensor that is displaced horizontally.

[0037] In examples of the present disclosure the wick 130 is removably assembled on the top cover 110 of the waste container 100, e.g. pressure fit through the opening 1101 in the top cover. [0038] Once a waste container 100 has been used in a printing apparatus and filled with waste print fluid, such that the wick 130 has absorbed waste print fluid, the waste container 100 may be removed from the printing apparatus and substituted with an empty waste container 100, with a clean wick 130. The waste container itself may be disposable or may be emptied to be re-used. In examples of re-usable waste containers 100, the wick 130 may be removed after use from the waste container 100 to be disposed of, and a new, clean wick 130 may be fitted to the waste container 100.

[0039] Figure 3 shows a schematic diagram of a portion of an example printing apparatus 200 comprising a waste container for receiving waste print fluid, for example the waste container 100 of Figure 1. The waste container 100 may comprise a top cover 110 and a wick 130, the wick 130 being to change appearance upon contact with a waste print fluid, and projecting a length S1 from the top cover 110 into the waste container 100 and being at least partly visible through the top cover 110.

[0040] A sensor 210, external to the waste container 100 and movable with respect to the waste container 100, may be arranged to detect the visible part of the wick 130. The sensor 210 may be mounted on a carriage 220 which may be displaceable in the printing apparatus 200 as shown by arrows A in Figure 3, e.g. horizontally. The sensor 210 may thus be selectively positioned above the waste container 100, e.g. in particular above the position of the wick 130, to read or detect the visible part of the wick 130 such as the top portion 131 of the wick 130.

[0041] The printing apparatus 200 may comprise a processor 201 for receiving inputs, e.g. readings from sensor 210, and for controlling the operation of the printing apparatus 200, and a non-transitory machine- readable storage medium 202, which may be any electronic, magnetic, optical, or other physical storage device, for storing executable instructions. The non-transitory machine-readable storage medium 202 may be, for example, Random Access Memory (RAM), an Electrically-Erasable Programmable Read-Only Memory (EEPROM), a storage drive, an optical disc, and the like, which may be encoded with instructions executable by a processor such as processor 201 of the printing apparatus 200.

[0042] As a result e.g. of maintenance operations in the printing apparatus, the level of waste print fluid in the waste container 100 may increase with time. [0043] Once the waste print fluid reaches the stem 132 of the wick 130 at predetermined level L1 , the wick 130 draws up waste print fluid from the waste container 100, the waste print fluid reaches by capillarity the top portion 131 of the wick 130, causing the wick to change appearance, for example by changing from an original color of the wick material to a color that depends on the color of the waste print fluid.

[0044] The sensor 210, for example an optical sensor, may read or detect the change in appearance, e.g. in color, of the wick 130, e.g. of the top portion 131 of the wick, between one reading of the wick 130 and a subsequent reading of the wick 130.

[0045] The sensor 210 may be connected to a controller (not shown) of the printing apparatus 200, and a change of appearance of the wick 130 may be determined by the controller of the printing apparatus 200, depending on the output of the sensor 210: for example, if the output of the sensor 210 is above or below a predetermined threshold value.

[0046] For example, the color of the waste print fluid in the waste container 100, and therefore the color of a wick after absorbing the waste print fluid, may depend on the print fluid color or colors used for printing, and their proportion in the waste container 100. Using a clear color for the material of the wick 130, such as white, the readings of an optical sensor such as a spectrophotometer, colorimeter, light sensor, etc. on the clean wick 130 and on the wick 130 after absorbing waste print fluid may present a relatively large difference, regardless of the particular color of the waste print fluid in the waste container 100, and therefore the two conditions of the wick 130 may be distinguished easily and accurately. In some examples the top cover 110 of the waste container 100 may be of a color similar to that of the clean wick 130, for example white or of a clear color, to facilitate the detection of the wick 130 with respect to the surrounding top cover 110 once it has absorbed waste print fluid, e.g. for visual inspection.

[0047] In case of a change in appearance of the wick 130, the controller of the printing apparatus 200 may issue a warning or alarm to signal that the waste container 100 is full and has to be changed or emptied. In some examples, the controller of the printing apparatus 200 may perform other actions, such as disabling further printing until the waste container 100 is replaced, and/or triggering or altering a maintenance routine, and/or others. [0048] Example printing apparatus disclosed herein, with a sensor 210 displaceable on a carriage 220 above the waste container 100, and therefore external to the waste container 100 itself, allow the sensor 210 to be maintained protected from the waste print fluid at all times, reducing the risk of contamination of the sensor surfaces from print fluid mist or splashing. Moreover, since the inspection of the appearance of the wick 130 by the sensor may be performed at regular time intervals, the sensor 210 may be available during the operation of the printing apparatus 200 to perform other detections in neighbouring regions of the printing apparatus, thus providing a versatile and cost-effective solution.

[0049] An example printing apparatus according to the present disclosure, such as printing apparatus 200 of Figure 3, may be any kind of printer using a print fluid, for example an inkjet printer comprising printheads with nozzles for firing print fluid ink drops on a print target: for example the inkjet printer may be a scanning inkjet printer to print an image swath by swath on a print medium such as paper that advances stepwise in-between swaths, or an inkjet head of a three-dimensional (3D) printing system to deposit a print fluid such as a binding material on a bed of powder build material as a print target.

[0050] Figures 4 and 5 illustrates schematically and in isometric view part of an example printing apparatus according to the present disclosure, which may comprise an inkjet printer 250 comprising a print zone 260 and a displaceable carriage 270 reciprocating on a scan axis 280 in a direction A along the print zone 260.

[0051] The carriage 270 may comprise sockets 275 for mounting inkjet printheads (not shown). In a printing operation, the carriage 270 may displace the inkjet printheads over the print zone 260 to deposit swaths of print fluid on a print medium (not shown). A sensor 210, for example an optical sensor, may be mounted on the carriage 270. The sensor 210 may be for example a spectrophotometer or colorimeter, a light sensor, or any other optical sensor able to capture images (e.g. capture lightness and/or color attributes for the pixels of an image, either greyscale or color).

[0052] The sensor 210 may be a sensor employed during the printing operation, e.g. over the print medium or substrate, e.g. over the print zone 260, e.g. to verify the quality of the printed image, align the print medium, to verify the correct advance of the substrate or print medium, etc. [0053] The printing apparatus 250 may also comprise a processor 201 for receiving inputs, e.g. readings from sensor 210, and controlling the operation of the printing apparatus 250, and a non-transitory machine-readable storage medium 202 as disclosed above in relation with Figure 3.

[0054] In some examples, as shown in Figure 4, inkjet printer 250 may comprise a service station 290 at one end of the print zone 260 and along the scan axis 280. A waste container 100, for example as shown and disclosed above in relation with Figures 1 , 2 and 3, may be removably mounted in the service station 290, to be removed and emptied or changed with a new waste container 100 when convenient. The waste container 100 may comprise a wick 130, shown schematically in Figure 4, where the top cover 110 of the waste container 100 is partially cut out to show the stem of the wick 130.

[0055] The wick 130 may be positioned in the top cover 110 of the waste container 100 to be under the path of the sensor 210 as the carriage 270 is displaced along the scan axis 280.

[0056] According to some examples, the top cover 110 of the waste container 100 may be at substantially the same horizontal level as the print zone 260.

[0057] Maintenance operations such as spitting, wiping, etc. may be performed on the printheads of the inkjet printer 250, by displacing the carriage 270 to a position above the service station 290, such as shown in Figure 5. For example, print fluid may be spit into the waste container 100.

As a result of periodic maintenance operations, the level of waste print fluid in the container 100 may increase with time.

[0058] In order to control the level of waste print fluid in the waste container 100 and prevent the capacity from being exceeded, a controller (not shown) of the printing apparatus 250 may cause the carriage 270 to displace the sensor 210 to a position such as that of Figure 5, over the waste container 100, and in particular over the wick 130, at time intervals: for example, when maintenance operations are performed, or at predefined time intervals, for example every hour, once a day, or at any other suitable interval depending on the printing apparatus, usage, waste container capacity, etc.

[0059] A position of the carriage 270 in correspondence with the service station 290 for printhead maintenance operations may be the same as a position in which the sensor 210 may read the wick 130, or it may be a different position of the carriage 270 along the scan axis 280.

[0060] In some examples, the sensor 210 may detect the color of the wick while in movement, for example employing a light sensor or another sensor with a sensing frequency high enough to make a reading of the top portion 131 of the wick 130 during the passage of the sensor 210 above it. In some examples, the carriage 270 may stop for a predetermined period of time when the sensor 210 above the wick 130. The period of time may be e.g. less than 1 second, for example using a spectrophotometer for sensor 210.

[0061] The sensor 210 may be connected to the controller (not shown) of the printing apparatus 250, and a change of appearance of the wick 130 may be determined by the controller depending on the output of the sensor 210, and may trigger a warning signal that the waste container 100 is full and has to be changed or emptied or other actions, such as discussed above.

[0062] In examples of printing apparatus according to the present disclosure, comprising a displaceable carriage such as carriage 270 in Figures 4 and 5, which may displace the sensor 210 horizontally over the waste container 100 installed in the printing apparatus, e.g. in a service station, the distance between the top portion 131 of the wick 130 and the sensor 210, e.g. the vertical distance, when the sensor 210 is vertically above the wick 130, may be of between 2 mm and 100 mm, e.g. between 5 mm and 30 mm.

[0063] In some example printing apparatus according to the disclosure, there may be a sensor 210 on the displaceable carriage 270 for reading the wick 130 and also for reading the print medium during a printing operation. However, in other examples a printing apparatus according to the present disclosure may comprise a sensor 210 for reading the wick 130, different from a sensor employed during printing.

[0064] Figure 6 shows a schematic diagram of a portion of another example printing apparatus 200 according to the disclosure, similar to the printing apparatus of Figure 3. In Figure 3 and Figure 6 the same reference numerals indicate analogous elements.

[0065] The printing apparatus 200 of Figure 6 may comprise an example waste container 100. As shown in Figure 6, example waste containers 100 according to the present disclosure may comprise a first wick 130a and a second wick 130b.

[0066] Each wick 130a, 130b may comprise a top portion 131 a, 131 b as described above, and a stem 132a, 132b projecting downwards into the waste container 100. The stem 132b of the second wick 130b may project from the top cover 110 of the waste container 100 a distance S2, greater than distance S1 of wick 130a, such that the stem 132a of the first wick 130b projects downwards to define a higher level L1 inside the waste container 100 than a level L2 defined by the stem 132b of the second wick 130b. First and second wicks 130a, 130b are both to change appearance, e.g. color, upon contact with the waste print fluid in the waste container 100 and are both at least partly visible through the top cover 110. Apart from the length projecting into the waste container 100, the two wicks 130a and 130b may have the same or different features, such as width dimension, cross section, materials, structure, etc. Each wick 130a, 130b may have features and may be mounted in the top cover 110 as disclosed above in relation with Figures 1 , 2a and 2b.

[0067] The presence of two wicks 130a, 130b projecting downwards to define two different levels L1 and L2 into the container 100 allows detecting two different amounts or volumes of waste print fluid in the waste container 100, and therefore e.g. issuing an early warning to a user when the waste print fluid reaches a lower level L2 in the waste container 100 and issuing a final warning, or perform another action, once the waste print fluid reaches the higher level L1.

[0068] Examples of a printing apparatus 200 as disclosed herein may comprise, as shown in Figure 6, a displaceable carriage 220 carrying a sensor 210, and a waste container 100 with two wicks 130a and 130b as described above. The wicks 130a and 130b mounted on the top cover 110 of the waste container 100 may be positioned near each other or apart from each other, in convenient positions in the waste container 100. In examples, wicks 130a and 130b may be positioned aligned with each other, and with the sensor 210, in the direction of displacement A of the displaceable carriage 220, such that the same sensor 210 may be displaced over wick 130a and over wick 130b, to detect a change in the appearance of each wick 130a, 130b. [0069] In the condition represented in Figure 6, waste print fluid F has reached level L2 and wick 130b has changed color, while wick 130a at level L1 remains its original color, and therefore sensor 210 when placed over wick 130b may detect the change of color of wick 130b, and when placed over wick 130a may detect that there has been no change in the color of wick 130a. A controller (not shown) of the printing apparatus 220, to which the sensor 210 is connected, and provided with the information of the position of each wick 130a, 130b, and corresponding levels L1 and L2, may trigger an early warning or action when the sensor 210 detects a change of color in wick 130b, and a later warning or action, when the sensor 210 detects a change of color in wick 130a.

[0070] Figure 7 illustrates in plan view part of an example printing apparatus 250 according to the present disclosure, similar to that of Figure 4 and in a similar position. In Figures 4 and 7 the same reference numerals indicate analogous elements.

[0071] In Figure 7, an example printing apparatus 250 may comprise a waste container 100 with two wicks 130a and 130b, as discussed in relation with Figure 6. The wicks 130a and 130b may be mounted on the top cover 110 of the waste container 100 aligned with each other and with the sensor 210 that is on the displaceable carriage 220, in a direction A of displacement of the displaceable carriage 220, as shown by the dotted line in Figure 7. The displaceable carriage 220 may therefore be displaced to position the sensor 210 over the wick 130a, or over the wick 130b. In Figure 7, like in Figure 6, the wick 130a is shown as still clean, while the wick 130b is shown as already changed to a darker color, related to that of the waste print fluid.

[0072] Figure 8 illustrates an example method according to the present disclosure, for determining a condition of a waste container of a printing apparatus. The printing apparatus and the waste container used in examples of the method may be as disclosed in any of the examples above, e.g. a waste container 100 as disclosed and printing apparatus 200 or 250 as disclosed.

[0073] In particular, the waste container 100 may include a wick 130 that projects inside the waste container 100 from a top cover 110 of the waste container 100, such that when the level of waste print fluid inside the waste container 100 reaches the wick 130, the wick 130 absorbs waste print fluid by capillarity and changes color to the color of the waste print fluid. [0074] In Figure 8 the method may comprise, in block 500, displacing an optical sensor 210 above the top cover 110 of the waste container 100; in block 510, detecting the color of the wick 130 with the optical sensor 210; and, in block 520, determining a condition of the waste container 100 depending on the detected color.

[0075] For example, if the color of the wick 130 detected in block 510 is the original color of a clean wick, e.g. white, the determined condition of the waste container 100 is that the waste print fluid has not yet reached a predetermined level associated with the wick 130, and there is space available for more waste print fluid; if the color of the wick 130 detected in block 510 is a color different from the original color of a clean wick, the determined condition of the waste container 100 is that the waste print fluid has reached the predetermined level associated with the wick 130.

[0076] Some example methods, as shown in Figure 9, may comprise in block 600 displacing a sensor 210 over the waste container 100; in block 610, detecting with the sensor 210 the color of the wick 130 on the top cover 110 of the waste container 100; in block 620, verifying if the color detected in block 610 indicates that the waste print fluid has reached a predetermined level L1 in the waste container 100: in the affirmative, the process may continue to block 630, in which an action is performed, such as issuing a warning; otherwise, from block 620 the process may return to block 600 after a time delay At in block 640.

[0077] An action performed in block 630 may be selected from: issuing a warning or alarm; changing the status of an indicator in the printing apparatus; triggering a maintenance routine; disabling printing until the waste container is replaced. Several such actions may also be triggered in block 630.

[0078] Figure 10 illustrates an example method according to the present disclosure, for determining a condition of a waste container 100 comprising two wicks, such as wicks 130a and 130b described above in relation to Figure 6.

[0079] The example method may comprise, in block 700, displacing a sensor 210 over the waste container 100; in block 710, detecting with the sensor 210 the color of the wick 130b; in block 720, verifying if the color detected in block 710 indicates that the waste print fluid has reached a predetermined level L2 associated with the wick 130b: in the affirmative, the process may continue to block 730, in which an action is performed, such as issuing a warning; otherwise, from block 720 the process may return to block 700 after a time delay At in block 740.

[0080] After block 730 the process may continue, in block 750, displacing a sensor 210 over the waste container 100; and in block 760, detecting with the sensor 210 the color of the wick 130a; in block 770, verifying if the color detected in block 760 indicates that the waste print fluid has reached a predetermined level L1, associated with wick 130a: in the affirmative, the process may continue to block 780, in which an action is performed, such as issuing a warning; otherwise, from block 770 the process returns to block 750 after a time delay At in block 790.

[0081] An action performed in block 780 may be selected from: issuing a warning or alarm; changing the status of an indicator in the printing apparatus; triggering a maintenance routine; disabling printing until the waste container is replaced. Several actions may also be performed.

[0082] Time delays At referred to above, which may establish the frequency of inspection of the wick or wicks by the sensor, may be set depending on parameters such as usage data of the printing apparatus, spitting and other maintenance operations involving waste print fluid being received in the waste container, historical and statistical data, etc. In some examples, an event instead of a time delay may be used to return the process to the operation of displacing the sensor over the waste container to read the wick: for example, an event related to the maintenance of the printheads.

[0083] In examples of a method according to the present disclosure, the optical sensor 210 may be mounted on a displaceable carriage 220 carrying printheads of the printing apparatus 250. The carriage 220 may selectively displace the printheads over a print zone 260 of the printing apparatus, and over the waste container 100. In some example methods, the sensor 210 may be an optical sensor, such as a colorimeter, spectrophotometer, light sensor, or other optical sensor able to capture images (e.g. capture lightness and/or color attributes for the pixels of an image, either greyscale or color), selectively used to detect images on a print medium in the print zone 260 and to detect the color of a wick on the waste container 100. [0084] The present disclosure also presents examples of a non-transitory machine-readable storage medium encoded with instructions executable by a processor to displace an optical sensor of a printing apparatus above the top cover of a waste container having a wick, and determine a condition of the waste container by detecting the color of the wick with the optical sensor.

[0085] A non-transitory machine-readable storage medium, such as shown by reference 202 above may be encoded with instructions executable by a processor of a printing apparatus, such as processor 201 of example printing apparatus 200 or example printing apparatus 250 disclosed above, and the machine-readable storage medium may comprise instructions to operate the printing apparatus to displace an optical sensor of the printing apparatus above the top cover of a waste container having a wick, and determine a condition of the waste container by detecting the color of the wick with the optical sensor, as in example methods disclosed above.

[0086] The description has been presented to illustrate and describe certain examples, but this patent covers all apparatus, methods, and articles of manufacture fairly falling within the scope of the appended claims. Different sets of examples have been described; these may be applied individually or in combination, sometimes with a synergetic effect. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.