Patent Publication Number: US-11638927-B2

Title: Selective wetting of a roller

Description:
BACKGROUND 
     In press printing, a liquid agent such as an ink, a coating or a primer is applied to a wettable surface of a roller, for example an anilox or gravure roller. An auxiliary roller may be provided to selectively wet portions of the roller. For example, the auxiliary roller may have radially-extending rubber portions that engage and wet selected portions of the roller. 
    
    
     
       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 cross-sectional view of an example selective wetting apparatus; 
         FIG.  2    is simplified schematic plan view of the wetting apparatus of  FIG.  1   ; 
         FIG.  3    is a simplified schematic cross-sectional view of an example selective wetting apparatus; 
         FIG.  4    is simplified schematic plan view of the wetting apparatus of  FIG.  4   ; 
         FIG.  5    is a simplified schematic cross-sectional view of an example selective wetting apparatus; 
         FIG.  6    is simplified schematic plan view of the wetting apparatus of  FIG.  5   ; 
         FIG.  7    is a simplified schematic plan view of an example flow unit; 
         FIG.  8    is a flowchart of an example of a method of operating selective wetting apparatus; 
         FIG.  9    is a flowchart of a further example of a method of operating selective wetting apparatus; 
         FIG.  10    is a flowchart of a further example of a method operating selective wetting apparatus; and 
         FIG.  11    is a simplified schematic of an example machine readable medium and a processor including instructions for operating wetting apparatus for selective wetting. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows an example selective wetting apparatus  2  for use in press printing, comprising a roller  20 , an applicator unit  10  to convey a liquid agent to the wet a wettable roller surface  22  of the roller, and a flow guide  50  to locally prevent wetting along an axial portion of the roller surface  22 . 
     The roller  20  is rotatable about a roller axis  24 . In this example it is substantially cylindrical. 
     The applicator unit  10  is to receive and convey a liquid agent  14  to an applicator lip  12  which extends parallel to the roller axis  24  and is radially spaced apart from the roller surface  22  (i.e. with respect to the roller axis  24 ) to define a gap  30  between the lip  12  and the roller surface  22 . The gap  30  therefore has an axial extent corresponding to the overlapping axial extents of the lip  12  and the roller surface  22 . 
     The gap  30  is sized so that liquid agent  14  conveyed to the lip  12  forms a liquid bridge  32  (shown in dashed lines in  FIG.  1   ) over the gap  30  to wet the wettable roller surface  22 . A suitable size for the gap may depend on the operating conditions (e.g. temperature), the type of liquid agent  14 , and the materials and surface conditions of the lip  12  and the roller  20 . 
     In this particular example, the roller axis  24  is substantially horizontal, and the applicator unit  10  is disposed to one lateral side of the roller  20  so that the radial gap between the lip  12  and the roller surface is substantially horizontal. In other words, the lip  12  is positioned so that the closest point on the roller surface as a tangent direction which is substantially vertical. In other examples, the applicator unit  10  may be at a different angular position with respect to the roller surface, for example, the lip  12  may be on a radial line that is inclined to the horizontal by ±30°. 
     The flow guide  50  is to direct a gas flow  56  into a regulated axial portion of the gap  30  to locally prevent formation of a liquid bridge in the regulated axial portion, and thereby prevent wetting of a corresponding axial portion of the roller surface  22 . As shown in  FIG.  1   , the flow guide  50  may comprise an elongate member extending from a flow reception portion  52  away from the gap  30  to a flow guide edge  54  adjacent the gap  30 . For example, a gas flow  56  may be received on the flow guide  50  at the flow reception portion  52  and flow along the flow guide  50  to be discharged into the gap  30  at the flow guide edge  54  to locally prevent formation of a liquid bridge. 
     The axial portion of the gap  30  corresponding to the guide edge  54  is referred to as a regulated axial portion of the gap, since the presence of a liquid bridge  32  over the gap  30  in that axial portion can be regulated by the presence or absence of the gas flow  56  being directed along the flow guide  50  into the gap  30 . 
     In this example, the flow guide  30  is generally disposed above the gap  30  so that the gas flow  56  is directed into the gap  30  along a direction having a downward component. This may aid diverting the liquid agent  14  to prevent formation of a liquid bridge. The gas flow  56  may be directed along a direction which is inclined with respect to the vertical, and may be inclined with respect to the local tangent of the roller surface  22  at the gap  30 . 
       FIG.  1    is a cross-sectional view of the wetting apparatus at the regulated axial portion.  FIG.  1    shows the flows of liquid agent  14  and gas  56  in the wetting apparatus  2  according to two modes of use corresponding to the presence and absence of a gas flow  56  along the flow guide  50 . In both modes of use, it may be assumed that the roller  20  rotates about the roller axis  24  so that the roller surface  22  moves downwardly at the gap  30  (i.e. anticlockwise in  FIG.  1   ). 
     In the first mode of use, there is no gas flow along the flow guide  50  so that a liquid bridge  32  forms from the lip  12  to the roller surface  22  (as shown in dashed lines) over the regulated axial portion of the gap  30 , and liquid agent  14  is thereby conveyed over the liquid bridge to the roller surface  22 . In the second mode of use, the gas flow  56  along the flow guide  50  is present and is directed into the regulated axial portion of the gap  30  to divert a path of liquid agent  14  delivered along the applicator unit  10  so that it is diverted away from the roller surface  22 . In  FIG.  1   , the liquid agent  14  is shown in solid lines, as diverted by a gas flow  56  directed into the regulated axial portion of the gap. 
     In this example, the flow guide  50  has an open guide surface to direct the gas flow to the gap. The term “open guide surface” relates to the gas flow  56  along the flow guide  50  being unbounded except by the guide surface of the flow guide. In other words, the guide surface of the flow guide  50  is not opposed by an opposing guide surface which bounds the flow. The gas flow may follow the guide surface by virtue of the Coanda effect (i.e. a boundary layer effect that causes it to follow the guide surface) This is in contrast to a ducted flow which is bound by opposing walls enclosing the flow. However, in other examples, a flow guide may be to direct a ducted gas flow. 
       FIG.  2    shows the example wetting apparatus  2  in plan view. As shown, in this example the roller  20  has a greater extent along the roller axis  24  than the lip  12  of the applicator unit  10 , such that the roller  20  protrudes beyond the lip  12  at both axial ends. Accordingly, in this particular example the gap  30  has an axial extent along the roller axis  24  equal to that of the lip  12 . 
     As shown, in this example the flow guide  50  has an axial extent along the roller axis  24  which is less than the axial extent of the gap  30 , and is spaced apart from both axial ends of the gap  30 . Accordingly, the flow guide  50  defines a regulated axial portion  34  of the gap corresponding to where the guide edge  54  of the flow guide  50  is to direct the flow into the gap  30  to locally prevent formation of a liquid bridge. In this example, all other axial portions  36  of the gap  30  (i.e. on both sides of the regulated axial portion  34 ) are to convey the liquid agent across the gap  30  uninterrupted, such that the corresponding axial portions  36  of the roller surface are wetted in use. Such axial portions of the roller surface may therefore be referred to as “wetted axial portions”, and the respective axial portions of the gap  30  may be referred to as “unregulated axial portions”. 
       FIG.  3    shows a further example of a selective wetting apparatus  4  which differs from that described above with respect to  FIGS.  1  and  2    in the configuration of the applicator unit  10 ′; a flow unit  40  comprising two flow guides  50 ; a controllers; and a doctor blade  38 . In this example, the selective wetting apparatus  4  is for controlling selective wetting of a liquid agent which is a print agent such as a primer or coating for use in press printing. 
     In this example, the applicator unit  10 ′ comprises a supply chamber  16  which is to store and supply liquid agent  14  at a regulated pressure and flow rate to an applicator arm  17  extending from the supply chamber  16  to the applicator lip  12 , which is positioned opposite the gap  30  as described above with respect to the selective wetting apparatus  2  of  FIGS.  1  and  2   . 
     In this example, the applicator arm  17  comprises an upper member  18  and a lower member  19  defining a substantially planar slot flow pathway therebetween for conveying liquid agent  14  from the supply chamber  16  to the lip  12 . As shown, in this example, the lower member  19  terminates proximally of the upper member  18  (i.e. closer to the supply chamber  16 ), such that the upper member  18  projects beyond the lower member  17  towards the roller  20  to terminate at the lip  12 . As shown schematically in  FIG.  3   , the liquid agent is retained on an underside surface of the upper member  18 , for example by surface tension forces. By projecting beyond the lower member  19 , the lip  12  may reliably define the closest point to the roller surface, so that the behaviour of the liquid agent  14  at the lip  12  and over the gap  30  may be accurately predicted and controlled. 
     In this example, the applicator unit  10  and roller  20  are coupled to a controller  62 . For example, the controller  62  may control rotation of the roller  20  and a rate of supply of liquid agent through the applicator unit  10 , as will be described below. 
     In this example, there are two flow guides  50 , each substantially as described above with respect to the wetting apparatus  2  of  FIGS.  1  and  2   . In this example, the two flow guides  50  form part of a flow unit  40  comprising a flow guide support  42 , a blower (or gas mover)  44  and the two flow guides  50 . 
     In this example, the flow guide support  42  is an elongate member extending parallel with the roller axis  24  to support each of the flow guides  50 . Each of the flow guides  50  are independently detachably attached to the flow guide support  42 . The flow guides  50  may be detachably attached in any suitable way, for example by way of cooperating attachment portions (e.g. a latching or snap-fit arrangement, or a slot), or by a mechanical fastener such as a bolt, screw, rivet or clamp. In this particular example, each of the flow guides  50  are moveable along the flow guide support  42  by virtue of being detachably attachable at a plurality of different positions along the flow guide support  42 . The two flow guides  50  are located at different axial positions along the gap  30 , as will be described below. 
     In this example, the flow unit  40  comprises a plurality of blowers  44  corresponding to the plurality of flow guides  50 . In other examples, there may be one blower  44  for multiple flow guides  50 , or a plurality of blowers  44  each associated with one or more flow guides  50 . 
     In this particular example, each blower  44  has a nozzle to direct a gas flow  56  over a corresponding one of the flow guides  50 . In this example, each blower is independently controllable by the controller  60  of the flow unit  40 , so that gas flows can be independently selectively caused to flow along each respective flow guide  50  to result in a plurality of different combinations of unwetted and wetted axial portions on the roller surface  22  of the roller, as will be described below. 
     In this example, the selective wetting apparatus  4  further comprises a doctor blade  38  to meter liquid agent received on the wettable roller surface  22 . The doctor blade  38  has a tip which is to engage the roller surface  22  at a position rotationally downstream of the gap  30 , such that in use an angular portion of the roller surface  22  rotates first past the gap  30  before second reaching the doctor blade. In the particular example of  FIG.  3   , the doctor blade  38  has a tip which engages the roller surface  22  below the gap  30 . As shown in  FIG.  3   , the doctor blade  38  has a gap-facing side which is to receive the gas flow  56  passing through the regulated axial portion of the gap  30 , and the diverted liquid agent  14 . In some examples, the doctor blade  38  may be to direct the diverted liquid agent  14  to a drain or collection arrangement, such as a liquid agent reservoir for resupply to the applicator unit  10 ′. 
       FIG.  4    schematically shows the selective wetting apparatus  4  in plan view. As shown, in this example there are two flow guides  50  at different axial positions along the gap  30 . In this example, a first one of the flow guides  50  is disposed towards but spaced apart from a first axial end of the gap  30 , such that the corresponding regulated axial portion  34  of the gap is spaced apart from the respective (closest) axial end of the gap  30 . A second one of the flow guides  50  is disposed adjacent the opposing axial end of the gap  30 , such that the respective regulated axial portion  34  of the gap extends to the respective axial end of the gap. Accordingly, in this particular example, the first one of the flow guides  50  is to selectively cause an unwetted lane on the roller surface  22 —i.e. an unwetted portion surrounded by wetted portions. In contrast, the second one of the flow guides  50  is to selectively narrow the axial extent of a wetted portion of the roller, by effectively forming a lane at one axial end of the gap  30 . In press printing, the pattern of wetted and unwetted portions is transferred to a substrate. 
       FIG.  4    also shows the blowers  44  provided in opposing relationship to each of the respective flow guides  50  to direct a gas flow  56  onto the respective flow guides  50 . As shown, each blower  44  is coupled to a controller  60  for independently selectively activating and stopping the blowers  44 , as will be described below. 
       FIG.  5    shows a further example selective wetting apparatus  6  which differs from the selective wetting apparatus  4  described above with respect to  FIGS.  3  and  4    in the configuration of the flow unit  40 ′. In this example, there are two flow guides  50  detachably attached to a flow guide support  42  by way of a slider arrangement. In this particular example, each of the flow guides  50  has a protrusion which cooperates with a corresponding groove in the flow guide support  42  to permit axial sliding of each of the flow guides  50  along the flow guide support to vary their axial position. The flow guides may be clamped in place, for example by a clamp, locking bolt or grub screw. The sliding arrangement may provide a particularly simple and efficient way of adjusting the axial positions of the flow guides  50 . Flow guides  50  may be detachable by sliding them out of the groove, which may be open at one or both axial ends of the flow guide support  42 . 
     In this example, the flow unit  40 ′ comprises an elongate blower  46  which is to direct a planar gas jet  48  along a direction perpendicular to the roller axis  24 . In this particular example, the elongate blower  46  is elongate along a direction parallel with the roller axis  24 , and has an axial extent substantially equal and coextensive with the axial extent of the gap  30 . In this example, the elongate blower  46  has an elongate nozzle  47  in the form of an axial slot along its axial extent, so as to direct the planar gas jet from the blower  46 . As shown in  FIG.  5   , in this example the blower  46  is disposed on a side of the flow reception end  52  of each of the flow guides which is closer to the roller  20 , and is to direct the planar gas jet  48  along a direction substantially tangential to the closest point on the roller surface  22  towards the respective flow guides. Where the planar gas jet  48  intersects the respective flow guides  50 , it is caused to turn to form the gas flow  56  as described above. By providing a blower  46  having an elongate nozzle, flow guides  50  in a plurality of different positions may be used to direct respective gas flows  56  into respective regulated axial portions of the gap  30  using the gas flow source—i.e. the elongate blower  46 . 
       FIG.  6    schematically shows the selective wetting apparatus  6  in plan view. As shown, the flow guides  50  are disposed in similar axial positions along the gap  30  as described above with respect to the selective wetting apparatus  4  of  FIGS.  3  and  4   . However, in this example, the flow guides  50  have differing axial widths. By providing flow guides  50  of differing axial widths, a pattern of wetted and unwetted axial portions on the roller surface  22  (and thereby, any substrate to which the pattern is applied) can be adjusted by interchanging different flow guides  50 , adjusting their axial positions, or both. Flow guides  50  may be selected from a set of flow guides of assorted widths. 
       FIGS.  3 - 6    show flow units  40 ,  40 ′ as installed in respective selective wetting apparatus  2 ,  4 . Such flow units  40 ,  40 ′ may be provided separately and retroactively installed in a wetting apparatus to provide a selective wetting apparatus as described above.  FIG.  7    shows a flow unit  140  for installation in a wetting apparatus to locally disrupt supply of liquid agent from a lip of an applicator unit over a gap to a wettable roller surface of a roller. Components of the flow unit  140  are shown in solid lines in relation to components of an apparatus in which the flow unit  140  is to be installed, shown in dashed lines respectively. The flow unit  140  comprises a blower  46  comprising an elongate nozzle to direct a planar gas jet  48  along a jet direction normal to a first axis  142 . In this example, the nozzle is elongate along the first axis  142 . 
     The flow unit  140  further comprises a flow guide  50  having an axial extent along the first axis  142  which is less than the axial extent of the nozzle along the first axis  142 . Accordingly, the flow guide  50  is to direct a sub-portion of the planar gas jet  48  (in use) into a corresponding regulated axial portion of the gap between the wettable surface of the roller and the lip of the applicator unit. 
     In this example, the flow unit  140  is to be installed in a wetting apparatus so that the first axis  142  is parallel with a roller axis  24  of a roller  20 , such that the planar gas jet  48  is directed from the elongate nozzle along a direction normal to the roller axis. 
     In other examples, the flow unit  140  may comprise an elongate nozzle  47  which is to fit to a blower, or re-direct a gas flow from a blower, which is separate from the flow unit  140 , for example a blower provided in the apparatus in which the flow unit  140  is to be installed, or a separate blower. 
     The flow unit  140  may have any of the features of the example flow units  40 ,  40 ′ described above with respect to  FIGS.  3 - 6   . For example, the flow unit  140  may further comprise a flow guide support, and the flow guide  50  may be moveable along the flow guide support to vary an axial position of the regulated axial portion of the gap in use. Further, there may be a plurality of flow guides  50  axially spaced apart from each other, each having an axial extent along the first axis  142  which is less than the axial extent of the nozzle along the first axis  142 . Each flow guide  50  may be to direct a respective axial portion of the gas jet into a respective regulated axial portion of the gap to locally disrupt supply of liquid agent to the roller surface, thereby preventing wetting of a corresponding axial portion of the roller surface. 
     The example flow units  40 ,  40 ′,  140  described above with respect to  FIGS.  3 - 7    may be provided as a kit—i.e. a flow unit kit. Examples of such a kit are shown in each of  FIGS.  3 - 7   , as installed. The kit may comprise an elongate nozzle to direct a planar gas jet along a direction normal to a first axis, a flow guide support, and a plurality of flow guides each mountable to the flow guide support to direct an axial portion of the gas jet into a corresponding regulated axial portion of a gap to locally disrupt supply of liquid agent to a roller surface, thereby preventing wetting of a corresponding axial portion of the roller surface. 
     The flow unit kit may comprise at least two flow guides having different axial extents along the first axis when mounted to the flow guide. By providing a kit having flow guides of different axial extents, an operator may assemble a flow unit by selecting one or more of the flow guides to prevent wetting of a portion of the roller surface having a corresponding axial extent. In other words, an operator may select a flow guide having a width corresponding to an intended width of an unwetted portion on a roller. 
     A flow unit may be assembled from the kit having a plurality of flow guides, as described above. For example, a flow unit kit may comprise ten flow guides of assorted widths, permitting assembly of a flow unit with flow guides in a large number of permutations of flow guide widths and axial positions. 
     In the examples described above, wetting of the roller is prevented by directing a gas flow into the gap between the applicator unit and the roller. The apparatus for directing the gas flow can be provided separately to the applicator unit and roller equipment, and may be retroactively installed. Accordingly, wetting of a roller can be selectively controlled without modification of the applicator unit and the roller, or introduction of a bespoke auxiliary roller having raised portions or grooves to control selective wetting. 
       FIG.  8    is a flowchart of an example method  80  of selectively wetting a roller of a selective wetting apparatus, which will be described, by way of example, with respect to the selective wetting apparatus  4  of  FIGS.  3 - 4   . 
     In this example, the method is conducted by a controller  60  of the flow unit and a separate controller  62  coupled to the applicator unit  10  and roller  20 . Each controller  60 ,  62  may comprise a processor and a non-transitory machine readable medium (such as a memory) encoded with instructions executable by the processor to conduct respective parts of the method  80  as described below. In other examples, there may be a controller which is coupled to the applicator unit  10  and roller  20 , together with the flow unit  40 . 
     In block  82 , the controller  62  controls the applicator unit  10  to cause a liquid agent  14  to be conveyed along the applicator unit  10  to the lip  12  so that the liquid agent forms a liquid bridge over an unregulated axial portion  36  of the gap  30  to wet a corresponding axial portion of the roller surface  22 . In this example, the roller  20  is rotating whilst the liquid agent is conveyed to the lip, such that the roller surface  22  is wetted by the liquid agent as the roller  20  rotates. 
     In block  84 , the controller  60  of the flow unit  40  controls a blower  44  of the flow unit  40  to direct a gas flow  56  along a respective flow guide  50  into a regulated axial portion  34  of the gap  30  to locally prevent formation of a liquid bridge, thereby preventing wetting of a corresponding axial portion of the roller surface  22 , which may be referred to as an unwetted portion. 
     In some examples, the blower may be inactive for a period before it is controlled to cause the gas flow  56  to flow into the regulated axial portion  34  of the gap. Accordingly, when the blower is inactive a liquid bridge may form over the respective regulated axial portion  34 . In the example selective wetting apparatus  4  there are two blowers  44  associated with respective flow guides  50 . Either one may be controlled to direct the gas flow  56  as described above with respect to block  84 , or each blower  44  may be controlled together. When each of the blowers are inactive, an axial extent of the roller surface  22  corresponding to the axial extent of the gap  30  may be wetted. 
       FIG.  8    shows blocks executed by the controller  62  coupled to the applicator unit  10  in solid lines, and blocks executed by the controller  60  of the flow unit  40  in dashed lines. Each block may be instructed independently by respective instructions encoded on respective non-transitory machine readable media. 
       FIG.  9    is a flowchart of a further example method  90  of selectively wetting a roller of a selective wetting apparatus, which will be described, by way of example, with respect to the selective wetting apparatus  4  of  FIGS.  3 - 4   . 
       FIG.  9    includes blocks  82 ,  84  of causing liquid agent to flow towards the roller and causing gas to flow into the air gap as described above with respect to  FIG.  8   . 
     In block  96 , the controller  60  of the flow unit  40  controls the blower to stop directing the gas flow  56  along the flow guide  50  into the respective regulated axial portion  34  of the gap whilst the roller  20  is rotating. Accordingly, formation of a liquid bridge at the regulated axial portion  34  is no longer prevented, and an axial portion of the roller surface  22  corresponding to the regulated axial portion  34 , where wetting was prevented whilst the blower  44  was directing the gas flow  56 , becomes wetted. It will be appreciated that this may be an angularly-separated portion of the roller surface  22 . By activating and deactivating the blower, the formation of a lane on the roller surface  22  where wetting is prevented may be selectively controlled. 
       FIG.  10    is a flowchart of a method  100  of selective wetting a roller of a selective wetting apparatus, which will be described, by way of example, with respect to the selective wetting apparatus  4  of  FIGS.  3 - 4   . 
       FIG.  10    includes block  82  of causing liquid agent to flow towards the roller as described above with respect to the methods  80 ,  90  of  FIGS.  8 ,  9   . 
     In block  104 , the controller  60  of the flow unit  40  controls the blowers  44  to operate in a first combination in which a first blower  44  directs a respective gas flow  56  into a respective first regulated axial portion  34  of the gap  30 , and a second blower  44  is stopped so that it does not direct a respective gas flow into a respective second regulated axial portion  34  of the gap  30 . For example, the first blower  44  may be disposed towards one axial end of the gap  30 , and the second blower  44  may be disposed towards an opposing axial end of the gap  30 . 
     In block  106 , the controller  60  of the flow unit  40  controls the blowers to operate in a second combination in which the second blower  44  directs a respective second gas flow  56  into the respective second regulated axial portion  34  of the gap. Accordingly, the second combination results in a different pattern of wetted and unwetted axial portions on the roller surface  20 , since the second blower  44  is activated in the second combination but not in the first. In this particular example, the first blower is stopped in block  106 , but in other examples the first blower may be active (i.e. it may direct the respective gas flow along the flow guide  50  and into the respective first regulated axial portion  34 ). 
     By controlling the blowers in at least first and second combinations such as those described above, wetted and unwetted portions of the roller surface may be varied in use. 
     By way of example, such combinations may be interchanged during press printing to selectively control the formation of lanes on a substrate (i.e. axial portions of the substrate where a liquid agent is selectively omitted in printing), or to control narrowing of an axial extent of a liquid agent by preventing wetting at an axial edge of the gap. 
     In each of the example methods  80 ,  90 ,  100  described above, the method is conducted by a controller  60  of the flow unit and a separate controller  62  coupled to the applicator unit  10  and roller  20 . Each controller  60 ,  62  may comprise a processor and a non-transitory machine readable medium (such as a memory) encoded with instructions executable by the processor to conduct respective parts of the method  80  as described below. In other examples, there may be a controller which is coupled to the applicator unit  10  and roller  20 , together with the flow unit  40 . 
     Examples in the present disclosure can be provided as methods, systems or machine readable instructions, such as any combination of software, hardware, firmware or the like. Such machine readable instructions may be included on a machine (or 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.  FIG.  11    schematically shows a non-transitory machine readable medium  110  comprising instructions  112  and a processor  114 . The instructions  112  may be to cause, when executed by the processor  114 , execution of one or more blocks of the methods  80 ,  90 ,  100  as described above with respect to  FIGS.  8 ,  9 ,  10   , for example blocks described above as controlled by the controller  60  of the flow unit  40 , or by the controller  62  coupled to the applicator unit  10  and the roller  20 . 
     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 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. Features described in relation to one example may be combined with features of another example. 
     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.