Patent Publication Number: US-2023142039-A1

Title: Cleaning a print apparatus

Description:
BACKGROUND 
     In some print apparatuses, a rotatable transfer member is to transfer an image to a substrate. A rotatable member may transfer the image to the rotatable member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Examples will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: 
         FIG.  1    is a simplified schematic of an example printing apparatus; 
         FIG.  2    is a simplified schematic of an example photoconductor and cleaning station of a print apparatus; 
         FIGS.  3 A- 3 C  is a simplified schematic of a photoconductor in three positions; 
         FIG.  4    is a simplified schematic of an example print apparatus; 
         FIG.  5    is a simplified schematic diagram of example modes of operation of a print apparatus; 
         FIG.  6    is a flowchart of an example of a method; 
         FIG.  7    is a flowchart of an example method; and 
         FIG.  8    is a simplified schematic of an example machine-readable medium in association with a processor. 
         FIG.  9    is a diagram schematically indicating advection times for example cleaning element pairs when an example photoconductor is in a disengaged and semi-engaged position. 
     
    
    
     DETAILED DESCRIPTION 
     In an example print apparatus, which may comprise a liquid electro-photography (LEP) printing device, a fluid image (for example an inked image, for example an image formed by fluid as will be described below) may be formed on a substrate by uniformly charging a photoconductive element and then selectively discharging areas to form a latent image on the photoconductive element that is then coated with a printing fluid (such as an ink, for example electro-ink).  FIG.  1    schematically shows an example print apparatus  100 , which may comprise a LEP printing device. The print apparatus  100  comprises a photoconductor  102 , which may also be referred to as a photoreceptor, and which comprises a photoreceptive, or photoconductive, element on which a latent image is to be formed. In some examples, the photoconductor  102  may comprise a photoreceptive, or photoconductive, drum, such as a rotatable drum and may comprise the photoreceptive, or photoconductive, surface on the outside of the drum, e.g. a cylindrical exterior surface. In some examples the photoconductor  102  may comprise a photoreceptive foil, for example a photoreceptive foil mounted on a drum. In some examples, the photoconductor  102  may comprise a photoreceptive, or photoconductive, belt (for example a movable belt). In some examples the photoconductor  102  may comprise a heatable element. The photoconductor  102  is rotatable (as indicated by the arrow) and therefore a given area of the exterior surface of the photoconductor  102  may pass by a number of stations of the print apparatus  100  to now be described. The print apparatus  100  comprises a latent image forming unit  104  which comprises a charging station  105  and a laser writing system  106  (system  106  may, in some examples, comprise an LED). At the latent image forming unit  104  the charging station  105  may be to apply a uniform charge (e.g. a static charge) to a surface (e.g. an exterior surface) of the rotating photoconductor  102  as the photoconductor  102  rotates about the charging station  105 . The charging station  105  may comprise a charging roller or a corona device (such as a corona wire) to apply the uniform charge to the photoconductor  102  which may, in some examples, be in contact with the charging station  105  but in other examples may not be in contact with the charging station  105 . The laser writing system  106  is to selectively discharge areas of the photoconductor  102  to form a latent image, these discharged areas forming the latent image correspond to an image to be printed by the print apparatus  100 . The print apparatus  100  also comprises a printing fluid developer unit (such as an ink developer unit)  108 . The developer unit  108  is to engage, for example to form a nip, with the photoconductor  102  and is to apply a fluid, for example a printing fluid such as an ink, to the photoconductor  102  to develop a fluid image on the surface of the photoconductor  102 . For example, the developer unit  108  may be to apply a dielectric fluid such as oil to the photoconductor  102 , the dielectric fluid comprising printing fluid (e.g. ink) particles suspended, e.g. charged immersed, in a liquid carrier. The fluid applied to the photoconductor  102  by the developer unit  108  may therefore comprise charged particles (e.g. charged and coloured particles). When the fluid is applied to the photoconductor  102 , charged fluid particles (e.g. ink particles) are attracted to the discharged portion(s) of the photoconductor  102 . In other words, the charged fluid particles are attracted to the latent image and in this way, an image of printing fluid is formed on the surface of the photoconductor  102  (at those portions corresponding to the latent image). In this way, a fluid image (e.g. an inked image) is developed on the surface of the photoconductor  102 . The print apparatus  100  comprises a movable component  110  that is to transfer an image to a substrate  114 . The movable component  110  may comprise a rotatable component (as shown in  FIG.  1   ). The movable component  110  may comprise a transfer member, or an intermediate transfer member. The component  110  may comprise a drum or belt or movable component (e.g. photoreceptive or photoconductive) around which may be wrapped a heatable element such as a blanket, or the component  110  may comprise other than a blanket, for example a different type of heatable component. In these examples, rotatable engagement between the photoconductor  102  and the component  110  transfers the fluid image from the photoconductor  102  to the component  110  and the component  110  rotates to transfer the image to the substrate  114  (for example, via a nip-like impression created between the component  110  and an impression cylinder  112 ). The blanket on the component  110  may be to heat the image prior to the transfer to the substrate  114 . In some examples an image may be directly transferred from the photoconductor  102  to the substrate  114  (e.g. in a dry toner device). The print apparatus  100  may comprise other elements that are omitted from  FIG.  1    for brevity such as a discharging station to remove the uniform charge applied to the photoconductor  102  at  104 . The print apparatus  100  comprises a cleaning station  116  (or a cleaning module or a cleaning system) which will be described in more detail with reference to  FIG.  2   . 
     As will be discussed in more detail with reference to the figures below, the photoconductor  102  is movable between a fully engaged position (not shown in  FIG.  1   ) in which the photoconductor  102  is to engage the movable component  110  to transfer an image formed on a surface of the photoconductor  102  to the movable component  110  and a fully disengaged position, which is shown by the solid lines in  FIG.  2   , in which the photoconductor  102  is remote from the movable component  110 . The photoconductor  102  is therefore movable to an in-between position (or a semi-engaged) position, which is a position in between the fully engaged and fully disengaged positions and is shown by the dotted line in  FIG.  1   . The cleaning station  116  is movable between a disengaged position (in which the cleaning station  116  is remote from the photoconductor  102 ) shown in solid lines in  FIG.  1    and an engaged position (in which the cleaning station  116  is to engage the photoconductor  102 , e.g. to cool and/or clean the photoconductor, as will be described below) shown in dotted lines in  FIG.  1   . As shown in  FIG.  1    by the dotted line configuration of the cleaning station  116  and the photoconductor  102 , and as will be described in more detailed below, some examples herein relate to the cleaning station  116  engaging (shown in dotted lines) the photoconductor  102  when the photoconductor  102  is in a position in between the engaged and fully disengaged positions (the position of the photoconductor  102  shown in dotted lines). The print apparatus comprises a controller  150 . The controller  150  is to control the function of a number of elements of the print apparatus  100 , for example any number of the components  102 - 112  as described above. As will be described below, the controller  150  is to cause the cleaning station  116  to engage the photoconductor  102  when the photoconductor  102  is in a position between the engaged and fully disengaged positions (as indicated by the dotted line positions of  116  and  102  in  FIG.  1   ). 
       FIG.  2    shows the cleaning station  116 . The cleaning station  116  may be to clean and/or cool a surface of the photoconductor  102 . The cleaning station  116  comprises a first cleaning element  120 , a second cleaning element  121 , and a wiper  122 . The first and second cleaning elements  120 ,  121  are depicted schematically as a roller for illustrative purposes. The first and second rollers  120  may each, or both, comprise a sponge roller and/or a wetting roller and/or a squeegee roller). However, in other examples the cleaning elements  120 ,  121  may comprise other than a roller. In these examples, one or both of the cleaning elements  120 ,  121  may comprise a squeegee (for example a resiliently deformable element) that is to indent a sponge to cause fluid to flow from the sponge. The wiper  122  may comprise a wiper blade. The cleaning station  116  is movable about a point  123 . Point  123  may comprise a pivot point and the cleaning station  116  may be pivotally movable (or movable in a hinged fashion about the pivot point). The cleaning station  116  is movable about the point  123  between an engaged position (shown in solid lines in  FIG.  2   ) in which the cleaning station  116  engages the photoconductor  102  and a disengaged position (shown in dotted lines in  FIG.  2   ) in which the cleaning station is remote from the photoconductor  102 . The cleaning station  116  may be to prepare the photoconductor  102  (e.g. the chargeable external surface thereof) for a subsequent print operation following the transfer of the image to the movable component  110  by cleaning off any residual printing fluid and contamination before a new print cycle is commenced. One, or both, of the rollers  120 ,  121  may be to clean residual ink from the surface of the photoconductor  102 . The cleaning station may be provided for the effective cleaning and/or cooling of the photoreceptor  102 . The cleaning station  116  may be to clean any remnant contaminants from the surface of the photoreceptor  102 . The sponges may be to apply a layer of cleaning fluid onto the surface of the photoconductor  102 . For this purpose, the or each roller  120 ,  121  may be connected to a supply of cleaning fluid (for example, cold cleaning fluid) and may be to contact the surface of the photoconductor to form a nip. The cleaning fluid may comprise a dielectric fluid such as oil. As fluid is applied to the photoconductor  102  by one of the elements  120 ,  121  it is metered by the wiper blade  122 . Put another way, the wiper blade  122  may be to ensure that the layer of cleaning fluid on the photoconductor  102  downstream of the wiper  122  is at a constant, or uniform, thickness. For this purpose the wiper  122  may comprise an angle, contact force, and deflection coefficient (or stiffness) in addition to material properties which may affect the thickness of the cleaning fluid after the photoconductor  102  has advanced under the wiper  122 , and which are therefore properties that affect the thickness at which cleaning fluid is applied to the photoconductive surface of the photoconductor  102  after the wiper blade  122 . The cleaning station  116 , by virtue of the rollers  120 ,  121  and wiper  122 , may therefore be to supply a constant flow of cleaning fluid at a constant thickness to the photoconductive surface of the photoconductor  102 . As  FIG.  2    shows, roller  120  may be referred to as a lower roller and roller  121  may be referred to as an upper roller. 
       FIGS.  3 A- 3 C  show the photoconductor  102  and movable component  110  (which, as above may comprise a rotatable drum). The movable component  110  (which will be hereinafter referred to as the transfer member  110 ) may be movable in the sense that it is rotatable but the position of the transfer member  110  in the print apparatus (e.g. relative to another component thereof) may be fixed. In other words, the location and/or position of the transfer member  110  in the print apparatus  100  may not be movable. By contrast, the photoconductor  102  is movable, and is movable both into, and out of, engagement with the transfer member  110 .  FIG.  3 A  shows the photoconductor in an “engaged” or “fully engaged” position,  FIG.  3 B  shows the photoconductor in a “disengaged position” or “fully disengaged position”, and  FIG.  3 C  shows the photoconductor in a “semi-engaged” or “semi-disengaged” position. In the engaged position of  FIG.  3 A , the photoconductor  102  is moved into contact with the transfer member  100  to adopt the position that it is to adopt during printing. In other words, in the fully engaged position, the photoconductor  102  is to perform a print operation. In some examples, in the fully engaged position, the photoconductor  102  may be to form a nip to transfer the fluid image to the transfer member  110 . Herein, by forming a nip between two rollers it may be understood to be the two rollers coming together to provide a finite contact area between the rollers. In other examples, in the fully engaged position the photoconductor  102  may not form a nip and a fluid image may be transferred without contact between the photoconductor  102  and the transfer member  110 . In other words, the photoreceptor  102  in the fully engaged position may be in sufficient proximity to transfer a fluid image formed thereon to the transfer member  110  during a print operation (for example in a print operation utilising a dry toner where toner particles may be electrostatically transferred through the air. In some examples the transfer member  110  may comprise a blanket, for example a heated blanket formed thereon such as wound around a drum of the member, to receive the flluid image from the photoreceptor  102 . In these examples, in the fully engaged position the photoreceptor  102  may be to compress the blanket, for example to compress the blanket by a target, e.g. pre-determined, value, for example calibrated during manufacturing, for the print apparatus to perform a successful print operation. For example, the photoreceptor  102  in the fully engaged position may be to compress the blanket to form a nip between the photoreceptor  102  and the blanket. For example, when in the fully engaged position the transfer member  110  may have a compressed diameter. 
     In the disengaged position of  FIG.  3 B  the photoconductor  102  is remote from the transfer member  110 . In some examples, the disengaged position of  FIG.  3 B  may be the “home” or “parked” position of the photoconductor  102 . In these examples, an actuator may control the position of the photoconductor  102 . For example, the actuator may comprise a displacement actuator. In these examples, the disengaged position of  FIG.  3 B  may correspond to the home position of the actuator that controls movement of the photoconductor. Therefore, the disengaged position of the photoconductor  102  may correspond to the home position of a displacement actuator. In these examples (where an actuator controls the movement and/or position of the photoconductor) the actuator&#39;s position may be calibrated. The photoconductor  102  may therefore be movable along a trajectory between two extreme positions, an extreme engaged position and an extreme disengaged position. The engaged positon and disengaged position, shown in  FIGS.  3 A and  3 B , respectively, may each be one of the extreme positions of the photoconductor  102 . 
     The semi-engaged position shown in  FIG.  3 C  may be a position that is not the fully engaged position shown in  FIG.  3 A  and not the fully disengaged position shown in  FIG.  3 B . The semi-engaged position may therefore be an in-between position, or intermediate position, between two positions that are each at a different extreme of the range of motion of the photoconductor  102 . In other words, the semi-engaged position may comprise any position of the photoconductor  102  that is not the fully engaged or fully disengaged positions, or any position of the photoconductor  102  between the fully engaged or fully disengaged position. In some examples, the semi-engaged position of the photoconductor may be a position in which the photoconductor  102  is as close as possible to the fully engaged position without being in the fully engaged position. For example, the fully engaged position of the photoconductor (indicated at  301  in  FIG.  3   ) may correspond to a distance ‘x 2 ’ that the photoconductor  102  has to move from its home position, (the disengaged position of  FIG.  3 B ) to its fully engaged position. In this example, the distance the photoconductor moves to the semi-engaged positon (position  302  in  FIG.  3   ) may be x 2 −ω with ω being small. In other words, in these examples, w may be approximately 0 but not equal to 0 so that the semi-engage position is as close as possible to the fully engaged position. In some examples, ω may be such that x 2 /ω&lt;0.5. As stated above, in some examples the photoconductor  102  in the fully engaged positon may be to form a nip with the transfer member  110 . In these examples the photoconductor  102  in the semi-engaged position may not form a nip. In other examples the photoconductor  102  in the semi-engaged position may form a nip (but in these examples the nip force would be less than the nip force in the fully engaged position). For example, in the fully engaged position the photoconductor  102  may be to form a nip with the transfer member  110  of nip force y Newtons and, in the semi-engaged position the photoconductor  102  may be to form a nip with the transfer member  110  having a nip force of less than y. Therefore, in some examples the contact area between the photoconductor  102  and the transfer member  110  when the photoconductor  102  is in its semi-engaged position is less than the contact area between the photoconductor  102  and the transfer member  110  when the photoconductor  102  is in its fully engaged position. As stated above, in some examples in the fully engaged position the photoconductor  102  is to compress the transfer member  110  (e.g. a blanket thereon). In these examples in the semi-engaged position the photoconductor  102  may be to compress the transfer member  110  by an amount less than the amount that the transfer member  110  is compressed by the photoconductor  102  when in the fully engaged position. For example, in the fully engaged positon the photoconductor  102  may be to compress the transfer member  110  (e.g. a blanket thereon) by z and in the semi-engaged position the photoconductor  102  may be to compress the transfer member  110  by less than z. In other words, in the semi-engaged position there may be a minor compressive force. For example, in the semi-engaged position the photoconductor  102  may be to compress the transfer member  110  such that its compressed diameter is as close as possible to the compressed diameter when the photoconductor  102  is in the fully engaged position without being equal. For example, the compressed diameter of the transfer member  110  when the photoconductor  102  is in the semi-engaged position may be larger than the compressed diameter of the transfer member  110  when the photoconductor  102  is in the fully engaged position. Of course, in some examples, in the semi-engaged position, the photoconductor  102  may contact the transfer member  110 . In other examples, in the semi-engaged position, the photoconductor  102  may not contact the transfer member  110 . 
     The possible positions that the photoconductor  102  can adopt are shown in  FIGS.  3 A- 3 C  by the dotted line  300  having endpoints  301 ,  302 , the dotted line representing a trajectory, or possible positions, of the photoconductor  102  and each endpoint  301 ,  302  representing an extreme position of the photoconductor  102 . The trajectory  300  of the photoconductor  102  may be confined to a two-dimensional plane and therefore each endpoint  301 ,  302  may be an opposite end of the trajectory of the photoconductor  102 . In  FIG.  3 A , in the engaged position, a centrepoint  303  of the photoconductor  102  is at the first end point  301  (leftmost in the figures) being the (extreme) location at which the photoconductor  102  is in the engaged position. In  FIG.  3 B , in the engaged position, a centrepoint  303  of the photoconductor  102  is at the second end point  302  (rightmost in the figures) being the (extreme) location at which the photoconductor  102  is in the disengaged position. In  FIG.  3 C , the centrepoint  303  of the photoconductor is in an intermediate position  305  in-between the two endpoints  301  and  302  as the photoconductor  102  is in the in-between, or intermediate, semi-engaged position. 
     As stated above, in the fully engaged position ( FIG.  3 A ) the photoconductor  102  may be in position to perform a print operation, for example in a position to transfer a fluid image formed thereon to the transfer member  110 , and/or in the engaged position, the photoconductor  102  may form a nip with the transfer member  110  (e.g. to transfer the image thereto). As stated above, in the semi-engaged position ( FIG.  3 C ), the photoconductor  102  may contact, e.g. touch, the transfer member  110 . For example, as stated above, there may be a small contact area between the photoconductor  102  and the transfer member  110  in the semi-engaged position than in the fully engaged position. In other examples the photoconductor  102  may not contact the transfer member  110 . The photoconductor  102  in the semi-engaged position may be proximate the transfer member  110 . In other words, in the semi-engaged position, the photoconductor  102  may be proximate to the transfer member  110  (but, for example, not proximate enough to perform a print operation, for example as close as possible to the transfer member  110  without being in its fully engaged position) and may in some examples engage (e.g. touch) the transfer member  110 . Therefore, although the photoconductor  102  is depicted in  FIG.  3 C  as not touching the transfer member  110  this is for illustrative purposes to schematically distinguish the depiction of the semi-engaged position from the fully engaged position. In the semi-engage position the photoconductor  102  may touch, e.g. be in contact with, the transfer member  110  (but, for example, without enough force to form a nip as in the engaged position). 
     Although not shown in  FIG.  3    the cleaning station  116  is movable between its engaged position (where it engages the photoconductor  102 ) and its disengaged position (where it is remote from the photoconductor  102 ), as depicted in  FIG.  2   , irrespective of the position of the photoconductor  102 . Put another way, the photoconductor  102  and cleaning station  116  are both movable independent of one another. The cleaning station  116  is therefore movable into engagement with the photoconductor  102  (where the rollers  120 ,  121  and wiper  122  come into contact with the surface of the photoconductor  102  to coat the surface with cleaning fluid and to meter the cleaning fluid) when the photoconductor  102  is in its fully engaged position, its semi-engaged position, and/or its fully disengaged position. This leads to various configurations that the photoconductor  102 , transfer member  110 , and the cleaning station  116 , can adopt as the photoconductor  102  may be in any one of its engaged, semi-engaged, or disengaged positions with the cleaning station engaged or disengaged. As shown in  FIGS.  3 A-C , the photoconductor  102  is movable into engagement with the transfer member  110 , for example, the photoconductor  102  may be pivotable about a pivot point and may therefore be pivotably movable into engagement with the photoconductor  102 , with the cleaning station  116  either engaged or disengaged. These configurations may be used during a “READY-TO-PRINT” state, a “PRE-PRINT” state, and/or a “PRINT” state of the print apparatus  100  to be described below. 
       FIG.  4    shows an example print apparatus  400 , which may comprise the print apparatus  100  as described above and therefore like features will be denoted with like reference numerals. The print apparatus  100  as described above may comprise the print apparatus  400  as shown in  FIG.  4   . The print apparatus  400  comprises a photoconductor  402  (which may comprise the photoconductor  102  as described above), a cleaning station  416  (which may comprise the cleaning station  116  described above) and a controller  450  (which may comprise the controller  150  as described above) for the print apparatus  400 . The photoconductor  402  is movable between a fully engaged position (as described above with reference to  FIG.  3 A ) in which the photoconductor  402  is to engage a movable component  410  (e.g. an intermediate member such as a transfer member, for example a rotatable drum, for example comprising a heated blanket thereon) to transfer an image formed on a surface of the photoconductor  402  to the movable component  410  (hereafter, transfer member  410 ) and a fully disengaged position (as described above with reference to  FIG.  3 B ) in which the photoconductor  402  is remote from the transfer member  410 . The cleaning station  416  is to clean and/or cool a surface of the photoconductor  402  and is movable between an engaged position in which the cleaning station  416  is to engage the photoconductor  402  to clean and/or cool a surface of the photoconductor and a disengaged position in which the cleaning station  416  is remote from the photoconductor  402  (as shown in  FIG.  2   ). In the engaged position, a first element  120  and/or a second element  121  and/or a wiper blade  122  is engaged with the surface of the photoconductor  402  to coat and meter a layer of cleaning fluid to the surface to clean and/or cool the surface of the photoconductor  402 , e.g. as described above. 
     The controller  450  of the print apparatus  400  is to control the position of the cleaning station  416  and may be to control the position of the photoconductor  402 . The controller  450  may be to place the print apparatus  400  in a “READY-TO-PRINT” state, a “PRE-PRINT” state, and/or a “PRINT” state. In each of these three states the cleaning station  416  and the photoconductor  402  may be placed in one of their possible positions (as described above) and the controller  450  may be to control the position of the cleaning station  416  and the photoconductor  402  to place the print apparatus  400  in one of its states. A PRINT state of the print apparatus  400  may be a state in which the apparatus  400  is to perform a print operation. In the PRINT state, each of the components (e.g. as described above including the developer unit and latent image forming unit etc.) may be in the positions that they are to adopt during a print operation. The READY TO PRINT (or “READY) state may be a state of the print apparatus  400  where the print apparatus is not in a PRINT state but is nevertheless switched ON. In the READY state the print apparatus may be on standby to print. The PRE-PRINT state may comprise a state in which the print apparatus  400  is transitioning to the PRINT state (e.g. from the READY state). 
     As for the cleaning station  116  described above, the cleaning station  416  comprises a first cleaning element  420 , a second cleaning element  421 , and a wiper  422 . The first and second cleaning elements  420 ,  421  are depicted schematically as a roller for illustrative purposes. The first and second rollers  420  may each, or both, comprise a sponge roller and/or a wetting roller and/or a squeegee roller). However, in other examples the cleaning elements  420 ,  421  may comprise other than a roller. In these examples, one or both of the cleaning elements  420 ,  421  may comprise a squeegee (for example a resiliently deformable element) that is to indent a sponge to cause fluid to flow from the sponge. In some examples the cleaning station  416  comprises one cleaning element and one wiper. Occasionally, a wiper of the cleaning station  416  may come into contact with a surface (e.g. a photoconductive surface on which the fluid image is to be formed) of the photoconductor  402  when the surface of the photoconductor  402  and/or the wiper is dry. This phenomenon will be referred to as “dry contact”. The photoconductive surface may be dry prior to receiving fluid (e.g. printing fluid from a developer unit or cleaning fluid from the cleaning station  416 ). Dry contact may therefore occur when the photoconductor and/or the wiper is newly-installed (for example due to a parts replacement or maintenance). In other words, in some instances, the wiper and/or the photoconductive surface of the photoconductor  402  may be dry prior to printing. This may lead to damaging in the photoconductor  402  and/or the wiper  422 . For example, the dry contact could lead to a stick-slip contact that could cause the cleaning station  416  to bounce, since the dry wiper may stick to the photoconductive surface rather than wetly gliding over the surface. This type of bouncing may damage the wiper or the photoconductive surface, or if an unusual perturbation is detected by the controller  450  (e.g. movement of the cleaning station) then the controller  450  may force the print operation to stop. Any damage may be subtle but even minor damage may contribute to a decrease in the print quality by introducing print quality defects. Dry contact may arise due to the following. With additional reference to  FIG.  2   , when the cleaning station  116  is rotated into engagement with the photoconductor  102  (e.g. when it is placed in its engaged position), the first roller  120  contacts the exterior surface of the photoconductor before the second roller  121 , and the second roller  121  contacts the surface of the photoconductor  102  before the wiper  122 . The rollers  120 ,  122 , which cause the surface of the photoconductor  102  to be coated with cleaning fluid (e.g. a dielectric fluid such as oil) therefore contact the surface of the photoconductor  102  before the wiper  122 . The time delay between cleaning fluid being applied to the surface of the (rotating) photoconductor by one of the cleaning elements  120 ,  121  (e.g. the first of the two elements to contact the photoconductor) and the cleaning fluid reaching the wiper blade may be referred to as the “advection time delay” or “advection time window”. The length of time under which a dry (e.g. new or replaced following maintenance) wiper and/or photoconductor are in contact are therefore dependent on the advection time delay. Some examples herein relate to increasing the advection time delay. In this way, if the advection time delay is increased then the cleaning fluid has more time to reach the wiper blade  122 , thereby decreasing the time in which the wiper and photoconductor are in dry contact, with no cleaning fluid flowing between them. 
     Referring again to  FIG.  4   , the controller  450  is to cause the cleaning station  416  to engage the photoconductor  402 , e.g. to clean and/or cool the photoconductor, when the photoconductor  402  is in a position between the engaged and fully disengaged position. In other words, the controller  450  is to cause the cleaning station  416  to engage the photoconductor  402  when the photoconductor  402  is in a position between the fully engaged and fully disengaged position. The controller  450  may be to cause the cleaning station  416  to engage the photoconductor  402  when the photoconductor  402  is in the semi-engaged position as described above. For example, the controller  450  may be to cause the cleaning station  416  to engage the photoconductor  402  when the photoconductor  402  is in an intermediate position. For example, the controller  450  may be to cause the cleaning station  416  to engage the photoconductor  402  when the photoconductor  402  is in any position between its two extreme positions. The controller  450  may therefore be to cause the cleaning station  416  to engage the photoconductor  402  when the photoconductor  402  is in the position depicted in  FIG.  3 C  as described above. This is shown in  FIG.  4    by the solid and dotted lines. The solid lines indicate the cleaning station  416  engaged with the photoconductor  402  when the photoconductor  402  is in the semi-engage (or in-between or intermediate etc.) position. The dotted lines show the cleaning station  416  engaged with the photoconductor when in the (fully) disengaged position (e.g. the position shown in  FIG.  3 B ). As shown in  FIG.  4   , when the cleaning station  416  is rotated (or pivoted) into engagement with the photoconductor  402 , the cleaning station  416  engages the photoconductor in a different position when the photoconductor  416  is in the semi-engaged (as shown in solid lines) vs when in the disengaged (as shown in dotted lines). As also shown in  FIG.  4   , this effectively changes the angle at which the cleaning station  416  engages the surface of the photoconductor  402 , meaning that the one of the sponge rollers of the cleaning station  416  engages the photoconductor sooner and the wiper engages the photoconductor  416  later (as compared to when the cleaning station  416  engages the photoconductor in its disengaged position), thereby increasing the advection time when the photoconductor  402  is in its semi-engaged position. For example, for one set of upper and lower rollers, the advection time for the lower roller when the photoconductor  402  is in the disengaged position may be approximately 1.2×10 −1  ms whereas the advection time when the photoconductor  402  is in the semi-engaged position is approximately 3×10 −1  ms—an increase of over 50%. 
     Therefore, engaging the cleaning station  416  to clean and/or cool the photoconductor  402  when the photoconductor  402  is in the semi-engaged position (depicted in  FIG.  4    by solid lines) increases the advection time window. For example, as and stated above, for one given wiper position, dimensions, and angle etc. and two sponges of a set diameter, engaging the cleaning station  416  with the photoconductor  402  when the photoconductor  402  is in the semi-engaged position may increase the advection window by approximately 20 ms A wettability margin, for either sponge, may be defined as follows: 
     
       
         
           
             
               wettability 
               ⁢ 
                   
               margin 
             
             = 
             
               
                 advection 
                 ⁢ 
                     
                 time 
                 ⁢ 
                     
                 for 
                 ⁢ 
                     
                 sponge 
               
               
                 time 
                 ⁢ 
                     
                 taken 
               
             
           
         
       
     
     with time taken being the time in between the sponge contacting the photoreceptor and the wiper contacting the photoreceptor. The wettability margin is therefore different for each sponge however an increased wettability margin is in correspondence with a decrease in the conditions under which there may be dry contact between the wiper and the photoconductor. Therefore, by increasing the advection time for the sponges when the cleaning station  416  engages the photoconductor  402  when the photoconductor  402  is in the semi-engage position, the wettability margin may, in turn, be increased. The length of time in which dry contact between the wiper  422  and the photoconductor  402  may occur may therefore be decreased. This is shown schematically in  FIG.  9   . 
       FIG.  9    schematically shows how the advection times on the lower axis for various pairs of cleaning elements are increased when these cleaning elements engage the photoconductor when it is in the semi-engaged position (vs the fully disengaged position). The elements may comprise rollers, as stated above. A first pair of cleaning elements is denoted by a triangle and a second pair of cleaning elements is denotes by a star (with the upper, darker, star or triangle in each pair denoting the upper, or top, cleaning roller in the pair and the lower, lighter, star or triangle in each pair denoting the lower, or bottom, cleaning roller). The top and bottom rollers in the pair may have a different diameter, and the each pair of rollers may have a different diameter to the rollers in the other pair. The dotted vertical line in  FIG.  9    illustrates the minimum advection time, being the minimum time for fluid having been applied by one of the rollers to pass to the location of the wiper. As  FIG.  9    shows, for the first pair of rollers there is insufficient time between the rollers contacting the photoconductor and the wiper contacting the photoconductor when the cleaning station engages the photoconductor when it is in the disengaged position, however when the same (first) pair of rollers engages the photoconductor when in its semi-engaged position the advection time exceeds the minimum advection time (as these are to the right of the dotted vertical line).  FIG.  9    also shows that, for the second set of rollers, while the rollers exceeds the minimum advection time when the cleaning station engages the photoconductor when in its disengaged position, the advection time is improved when the cleaning station engages the photoconductor when in its semi-engaged position. In either example therefore the advection time may be increased when the cleaning station engages the photoconductor when in its semi-engaged position. 
     As stated above with reference to  FIGS.  3 A- 3 C , when the photoconductor  402  is in its fully engaged position ( FIG.  3 A ), the photoconductor  402  may form a nip with the movable component  410  of the print apparatus. Therefore, when the cleaning station  416  engages the photoconductor  402  in the semi-engage position, the photoconductor  402  may not form a nip with the movable component  410  (e.g. a rotatable component) of the print apparatus  400 . In other examples however, the photoconductor  402  may engage (e.g. touch) the component  410  in this position, although in other examples there may be no contact between the photoconductor  402  and component  410 . The controller  450  may therefore be to move the cleaning station  416  into engagement with the photoconductor  402  when the photoconductor  402  is engaged with (e.g. touches) the transfer member  410 , for example is as close as possible to the transfer member  410  without being in the fully engaged position, for example as described above with reference to  FIG.  3 C . For example, this “as close as possible” minimal contact may enable an efficient heat transfer between the transfer member  410  and photoconductor  402  and may minimise any damage due to the contact between the member  410  and the photoconductor  402 . As stated above, the controller  450  may be to cause the print apparatus  400  to operate in different modes of operation. For example, the controller  450  may be to cause the print apparatus  400  to operate in a READY state, a PRE-PRINT state and a PRINT state. In the READY state the transfer member  410  may be rotating (for example at a slow speed relative to their speed of rotation during the PRINT state), photoconductor  420  may be in its semi-engaged position, and the cleaning station  416  may be disengaged from the photoconductor  402 . Therefore, to place the print apparatus  400  in its READY state the controller may be to cause the transfer member  410  to rotate, place the photoconductor  402  in its semi-engaged position and disengage the cleaning station  416  from the photoconductor  402 . In the PRINT state the transfer member  410  may be rotating at full speed, the photoconductor  402  may be in its fully engaged position, and the cleaning station  416  may be engaged to the photoconductor  402 . Therefore, to place the print apparatus  400  in its PRINT state the controller may be to cause the transfer member  410  to rotate at full, printing, speed, place the photoconductor  402  in its fully engaged position and to engage the cleaning station  416  with the photoconductor  402 . Although the blocks mentioned herebefore have been mentioned in a particular order this is for illustrative purposes and does not imply that this is the order in which the sequence may be performed. 
     The PRE-PRINT state may be regarded as a transition to print state. From the above, the cleaning station  416  does not engage the photoconductor  402  during the READY state and therefore there is no engagement (dry or wet) between the wiper of the cleaning station  416  and the photoconductor  402 . However, in the PRINT state the cleaning station  416  engages the photoconductor  402 . During the PRE-PRINT state the cleaning station  416  is brought into engagement with the photoconductor  402  with the photoconductor  402  in the semi-engaged position. Therefore, in the PRE-PRINT state the photoconductor  402  is in its semi-engaged positon and the cleaning station  416  engages the photoconductor  402  so as to increase the advection time window and wetting margin. As stated above, this may decrease the time under which there may be dry contact between the wiper and the photoreceptor surface and, in turn, decrease the risk of damage to the photoreceptor surface and/or the cleaning station and decrease the risk of having defects in the print quality. Therefore, the controller  450  may be to cause the cleaning station  416  to engage the photoconductor  402  to clean and/or cool the photoconductor  402  when the photoconductor  402  is in a position between the fully engaged and fully disengaged positions during the transition from the READY state to the PRINT state (e.g. during the PRE-PRINT state). According to some examples herein, the photoconductor  402  is therefore in its semi-engage position during the READY state and the PRE-PRINT state of the print apparatus  400 . The controller  450  may therefore to cause the photoconductor  402  to maintain its position during the READY and PRE-PRINT, e.g. to maintain its position during the transition from the READY to the PRE-PRINT state. In other words, the controller  450  may not cause the photoconductor  402  to change its position during the transition from the READY state to the PRINT state (e.g. in the PRE-PRINT state). In another example, the photoconductor  402  may be in its disengaged position during the READY state. In this example, the PRE-PRINT state may comprise moving the photoconductor  402  to its semi-engaged position and, thereafter, the cleaning station may be engaged. 
     The controller  450  may be to cause the following sequence to occur during the PRE-PRINT state, or during the transition to the PRINT state from the READY state: accelerate the rotational speed of the rotating transfer member  410  (which was rotating slowly in the READY state), place the photoconductor  402  in its semi-engaged position, and move the cleaning station  416  into engagement with the semi-engaged photoconductor  402 . The sequence may further comprising moving the photoconductor  402 , with the cleaning station  416  engaged, into the fully engaged position with the transfer member  410 . There may then be a delay to ensure the components are ready for printing. As above, during PRINT, the controller  450  may be to engage the photoconductor  402 , with the engaged cleaning station  416 , with the transfer member  410  (e.g. place the photoconductor  402 , with the cleaning station  416  engaged, into its fully engaged position). This sequence of operation, with the state (e.g. position) of the photoconductor  402  and cleaning station  416  is summarised in  FIG.  5   . As shown in  FIG.  5   , the photoconductor  402  is not to be placed in its engaged or disengaged positon during the READY or PRE-PRINT states, but rather is in its semi-engaged position in both states and therefore the photoconductor&#39;s position may not change between the READY and PRE-PRINT state, but is the same (semi-engage) in both states. As also shown in  FIG.  5   , the cleaning station is engaged during the PRE-PRINT and PRINT states but disengaged in the READY state. 
     As stated above with reference to  FIGS.  3 A- 3 C , when the photoconductor  402  is in the fully engaged position, the photoconductor  402 , may form a first contact area with the transfer member  410  and, when in the disengaged position, the photoconductor  402  may form a second contact area with the transfer member  410 , the second contact area being less than the first contact area. When in the engaged position and the semi-engaged, the photoconductor  402  may be to compress the transfer member  410  such that the compressed diameter of the transfer member  410  is larger when the photoconductor  402  is in the semi-engaged position than when the photoconductor  402  is in the engaged position. 
     The controller  450  may therefore be to control the print apparatus  400  and may be to control the positions of any number of components of the print apparatus  400  that are movable (e.g. the photoconductor  402 , cleaning station  416  which may both be movable, e.g. pivotable, about a fixed point, e.g. a pivot). The controller  450  may therefore be to cause the photoconductor  402  to pivot into engagement with the transfer member  410  (e.g. into the engaged position or semi engaged position) or out of engagement (e.g. to the disengaged position), e.g. with reference to  FIGS.  3 A- 3 C . The controller  450  may be to cause the cleaning station  416  to pivot into engagement with the photoconductor  402  and out of engagement to disengage the photoconductor  402 , e.g. with reference to  FIG.  2   . The controller  450  sets the conditions under which cleaning fluid is applied to the photoconductive surface of the photoconductor  402  which, as stated above, can increase the wetting margin which decreases the time during which dry conditions may exits. This reduces the instances of damage (e.g. to a wiper of the cleaning station  416  and/or to the photoconductive surface of the photoconductor  402 ) but also may provide additional design degrees of freedom to the apparatus  400 . For example, engaging the cleaning station  416  to the photoconductor  402  when the photoconductor  402  is in its engaged position may mean that sponges of varying diameter may be used in the cleaning station  416 . For example, if a sponge roller were used in the cleaning station that was more abrasive to provide an improved cleaning then this may increase the torque to drive the sponge roller (e.g. to rotate the sponge roller) at a target speed. To overcome the torque increase the sponge diameter may be decreased, however a decrease in the sponge diameter may increase the time during which dry contact may occur between the photoconductive surface and a wiper of the cleaning station. However, by engaging the cleaning station  416  with the photoconductor  402  when the photoconductor  402  is in the semi-engage position the time window within which dry contact may occur can be decreased as discussed above to accommodate differing sponge diameters. In turn, this increases the degrees of freedom that are available to optimise the wiper of the cleaning station. As mentioned above, increasing the wetting margin may extend the lifespan of the photoconductive surface of the photoconductor and/or a wiper of the cleaning station in addition to keeping the photoconductor and/or wiper cleaner. As the controller  450  may be to control the positions of the photoconductor  402  and the cleaning station  416 , and may be to control the position of the photoconductor  402  when the cleaning station  416  engages the photoconductor  402  (e.g. to be in the semi-engage position), the controller  450  is able to be programmed to cause a given print apparatus  400  (having a photoconductor and cleaning station) to operate in the manner discussed above. For example a print apparatus  400  whose controls are to cause a cleaning station to engage a photoconductor in the fully disengaged position may be programmed (e.g. re-programmed) to cause the photoconductor to be in the semi-engaged position for the cleaning station to engage, and thus may be programmed to operate in the manner discussed above to increase the wetting margin. The controller  450  may be to perform the methods  600  and/or  700  as will now be described with reference to  FIGS.  6  and  7   , respectively, and may comprise the processor  804  and/or machine-readable medium  800  as will be described with reference to  FIG.  8   . 
       FIG.  6    shows an example method  600  which may comprise a computer-implemented method. The method  600  may comprise a method of cleaning a photoconductor (or photoconductor surface) or a photoreceptor (or photoreceptive surface) of a print apparatus. The method  600  may comprise a method of controlling the position of a photoconductor (or photoreceptor or photoconductive or photoreceptive surface etc.) during a cleaning operation. 
     The method comprises, at block  602 , moving, by a processor, a photoreceptor of a print apparatus. The photoreceptor is movable between a fully engaged position in which the photoreceptor is to engage a transfer member of the print apparatus to transfer a fluid image from the photoreceptor to the transfer member and a fully disengaged position in which the photoreceptor is remote from the transfer member. Block  602  comprises moving the photoreceptor to an intermediate position between the fully engaged and fully disengaged positions. The print apparatus may comprise the print apparatus  100  or print apparatus  400  as described above and the photoreceptor may comprise the photoconductors  102 ,  402  as described above, and the transfer member may comprise the transfer member, or movable component,  110 ,  410  as described above. Therefore, the “intermediate position” of the photoreceptor, to which the photoreceptor is moved at block  602 , may comprise the semi-engaged position as described above and with reference to  FIG.  3 C . 
     At block  604  the method comprises engaging, by a processor, a cleaning system of the print apparatus with the photoreceptor to clean and/or cool the photoreceptor when the photoreceptor is in the intermediate position. Block  602  may comprise causing, by a processor, the cleaning system to engage the photoreceptor. The cleaning system may comprise the cleaning system  116  or  416  as described above and therefore may comprise a first cleaning element, a second cleaning element and/or a wiper (e.g. a wiper blade). As stated above, the first and second cleaning elements may each, or both, comprise a sponge roller and/or a wetting roller and/or a squeegee roller) or other than a roller, for example a squeegee (for example a resiliently deformable element) that is to indent a sponge to cause fluid to flow from the spongeTherefore, block  604  may cause the cleaning system to engage the photoreceptor when the photoreceptor is at a position so as to increase the advection time window and wetting margin and therefore to reduce the conditions, or timed interval, during which dry-contact can occur. The method  600  may therefore reduce the instances of damage to the photoreceptor surface and/or a wiper of the cleaning system, accommodate for sponge rollers of varying diameter, and increase the lifespan of the photoreceptor and/or wiper as described above. The controller  450  described above may be to perform block  602  and/or block  604  of the method  600 . 
       FIG.  7    shows an example method  700  which may comprise a computer-implemented method. The method  700  may comprise a method of cleaning a photoconductor (or photoconductor surface) or a photoreceptor (or photoreceptive surface) of a print apparatus. The method  700  may comprise a method of controlling the position of a photoconductor (or photoreceptor or photoconductive or photoreceptive surface etc.) during a cleaning operation. The method comprises block  702  at which the print apparatus is placed in a READY-TO-PRINT state, block  704  at which the print apparatus is placed in a PRE-PRINT state, and block  706  at which the print apparatus is placed in a PRINT state, for example as described above and with reference to  FIG.  5   . 
     At block  708  the method comprises causing, by a processor, the transfer member to rotate. For example block  708  may comprise causing the transfer member to rotate at a slow speed, for example a speed that is slower than the speed the transfer member is to rotate during a print operation. At block  710  the method comprises causing, by a processor, the photoreceptor to move to the intermediate position (e.g. the semi-engage position). Block  710  may comprise moving, by a processor, the photoreceptor to the intermediate position. At block  712  the method comprises causing, by a processor, the cleaning system to disengage the photoreceptor. For example, block  712  may comprise moving the cleaning system, or causing the cleaning system to move to, its disengaged position. A READY-TO-PRINT (or READY) state, or sequence, of the print apparatus may comprise blocks  708 - 712 . 
     At block  714  the method comprises causing, by a processor, the transfer member to accelerate, for example to a full speed, for example to a speed at which the transfer member is to rotate during a print operation. Block  714  may comprise rotating, by a processor, the transfer member, e.g. at the full speed described. At block  716  the method comprises causing, by a processor, the photoreceptor to be in its semi-engage position. For example, block  716  may be to cause the photoreceptor to remain in its semi-engage position. The photoreceptor may therefore remain in the intermediate position in both the READY and PRE-PRINT states. At block  718  the method comprises causing, by a processor, the cleaning system to engage the photoreceptor. For example, block  718  may comprise moving the cleaning system, or causing the cleaning system to move to, its engaged position. At block  720  the method comprises causing, by a processor, the photoreceptor (with the cleaning station engaged) to move to the fully engaged position. Block  720  may comprise moving, by a processor, the photoreceptor (with the cleaning station engaged) to the fully engaged position. Therefore, at block  720  the photoreceptor may be moved into a nip-engagement with the transfer member, or may be engaged with the transfer member to form a nip, or contact, or near-contact, whichever position in which the photoreceptor is to perform a print operation (e.g. pre-defined or pre-programmed position). At block  722  the method may comprise maintaining the current state of the print apparatus, for example delaying any subsequent operations. Block  722  may comprise a check to determine if all components of the print apparatus are ready for a print operation. Block  722  may comprise performing any number of checks (e.g. quality control checks) before the method advances to the PRINT sequence, comprising block  726 . Any such checks may be performed manually or automatically. The delay is optional and, in some examples, there may be a delay between any of the blocks of the method  700 , this delay being to ensure the correct state of the print apparatus. A PRE-PRINT state, or sequence, of the print apparatus may comprise blocks  714 - 722 . 
     At block  726  the method comprises causing, by a processor, the photoreceptor (with the cleaning station engaged) to move to the fully engaged position. Block  726  may comprise moving, by a processor, the photoreceptor (with the cleaning station engaged) to the fully engaged position. Therefore, at block  726  the photoreceptor may be moved into a nip-engagement with the transfer member, or may be engaged with the transfer member to form a nip. A PRINT state, or sequence, of the print apparatus may comprise block  726 . At block  726  the transfer member may be rotating, for example at the same rotational speed as per block  714  in the PRE-PRINT sequence. In other words, the rotational speed to the transfer member may be the same in the PRE-PRINT and PRINT sequences, and therefore the speed may be maintained in the transition from the PRE-PRINT to the PRINT state. 
     As stated above, then controller  450  of the print apparatus  400  as described above may be to perform the method  600  and/or  700  and therefore any one of the blocks as described above. 
       FIG.  8    shows an example non-transitory machine-readable, or computer-readable, medium  802  comprising a set of machine-readable instructions  806  stored thereon. The medium  802  is shown in  FIG.  8    in association with a processor  804 . The controller  450  described above may comprise the medium  802  and/or the processor  804 . The instructions  806  when executed by the processor  804  are to cause the processor to perform a task. For example, the instructions  806 , when executed by the processor  804 , may be to cause the processor  804  to perform the method  600  or  700  as described above, e.g. any of the blocks thereof. The instructions  806 , when executed by the processor  804  are to cause the processor to cause a cleaning module (such as the cleaning station  116  or  416  as described above with reference to  FIGS.  1 - 5    or the cleaning system as described above with reference to  FIGS.  6 - 7   ) to engage a photoconductive surface of a print apparatus (e.g. a photoconductive surface of a photoreceptor or photoreceptive surface of a photoreceptor as described above) to clean and/or cool the photoconductive surface when the photoconductive surface is in an intermediate position between a fully engaged position where the photoconductive surface is to transfer an image to a blanket (for example a heated blanket, e.g. a thermal blanket, for example a blanket of a movable element such as a transfer member, e.g.  110  or  410 , as described above) and a fully disengaged position where the photoconductive surface is remote from the blanket. The fully engaged position of the surface may be as described above and as shown in  FIG.  3 A , the fully disengaged position may be as described above and as shown in  FIG.  3 B , and the intermediate position may comprise the semi-engaged position as described above and as shown in  FIG.  3 C . The cleaning module may comprise a sponge roller and/or a wiper as described above with reference to the cleaning station  116 . The instructions  806  may therefore be to cause the processor  804  to cause the photoconductive surface to be in the intermediate position, and the cleaning module to engage the surface in the intermediate position, so as to increase the advection time window and wetting margin as described above. The instructions  806  may be to cause the processor  804  to move the photoconductive surface to the intermediate position and engage the cleaning module with the photoconductive surface (e.g. during a READY state or a PRE-PRINT state of the printer), and to move the photoconductive surface, with the cleaning module engaged, into engagement with the blanket (e.g. during a PRINT state of the printer). The instructions  806  may therefore be to cause the processor  804  to cause the printer to operate in a PRE-PRINT state and to cause the photoconductive surface to be in the intermediate position when the printer is operating in the pre-print state (for example as described above with reference to blocks  714 - 722  of the method  700 ). The instructions  806  may therefore be to cause the processor  804  to cause the printer to operate in a READY state, cause the photoconductive surface to be in the intermediate position during the READY state (e.g. as described above with reference to blocks  708 - 712  of the method  700 ), to cause the printer to transition to a PRE-PRINT state, and to cause the photoconductive surface to be in the intermediate position during the PRE-PRINT state. The instructions  806  may be to cause the printer to operate in a READY state and/or a PRE-PRINT state and/or a PRINT state. 
     Some examples herein are therefore directed to engaging a cleaning station (e.g. a sponge roller and wiper thereof) to a photoconductive surface of a photoconductor (e.g. a photoconductive drum) to clean and/or cool the surface when the photoconductor is in a semi-engaged position, which as described above may be any “intermediate” position between two extreme positions of the range of movement of the photoconductor. For example, the photoconductor may be movable between an extreme left and an extreme right position (for example) or fully engaged or fully disengaged position, the photoconductor being engaged to the transfer member to form a nip in the fully engaged position, and the intermediate position being any position between these two positions. For example, the intermediate position may be a semi-engaged position where the photoconductor engages the transfer member but does not form a nip, or is proximate the transfer member without touching the transfer member. As above, engaging the cleaning station with the photoconductor with the photoconductor in this position increases the advection time window and wetting margin, thereby decreasing the time during which a dry wiper (of the cleaning station) may contact a dry photoconductive surface. As also described above this may reduce the risk of damage to the wiper and/or the photoconductor surface, and may therefore increase the lifespan of the p photoconductor and/or the wiper, in addition to decreasing the risk of damaging the print quality of a print operation. 
     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 computer readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon. 
     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. 
     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. 
     Such machine readable instructions may also be stored in a computer readable storage that can guide the computer or other programmable data processing devices to operate in a specific mode. 
     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. 
     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. 
     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. 
     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. 
     The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.