Patent Publication Number: US-2023145873-A1

Title: Apparatus and method for treating a relief plate precursor with improved liquid evacuation

Description:
FIELD OF INVENTION 
     The field of the invention relates to an apparatus and a method for treating a relief plate precursor, in particular a printing plate precursor, with a liquid. 
     BACKGROUND 
     Washer apparatus for printing plate precursors are known. Typically, a transport bar is used to move a printing plate precursor through such washer apparatus using a transport system. The washer further uses a liquid to partially remove material from the precursor and in most cases brushes are used to increase the efficiency. Due to splashing and liquid running over the transport bar this transport system may get wetted. Depending on the nature of the liquid this may lead to degradation of the transport system e.g. by corrosion. Another drawback is that during the washing the liquid gets loaded with material of the precursor which may stick to the transport system upon drying and may lead to malfunction. 
     SUMMARY 
     The object of embodiments of the invention is to provide an apparatus and method which avoids wetting to the transport system. 
     According to a first aspect of the invention there is provided an apparatus for treating a relief plate precursor, such as a printing plate precursor, with a liquid. The apparatus comprises a treatment compartment, a transport system with one or more transport bars, and a protection system. The treatment compartment is configured for treating the relief plate precursor with a liquid. A transport bar of the one or more transport bars is configured to be coupled to a relief plate precursor. The transport system is configured to move the transport bar with the coupled relief plate precursor through the treatment compartment. To that end the transport bar is provided with a coupling portion configured to couple the transport bar to the transport system. The protection system is configured to guide and evacuate the liquid such that the transport system is protected against wetting with the liquid of the treatment compartment. 
     By providing a protection system which is such that it keeps liquid away from the transport system, wetting of the transport system is avoided. Thus, problems related to the wetting of the transport system, such as corrosion or malfunctioning, are avoided or reduced. 
     Preferably, the protection system comprises a liquid evacuation part extending lengthwise next to the transport system and below an outer end of the transport bar. The liquid evacuation part is provided with an upwardly extending portion at a side facing the transport system. In that manner, the upwardly extending portion will stop liquid flowing over the liquid evacuation part towards the transport system. The other side of the liquid evacuation part which is furthest away from the transport system may extend horizontally or downwardly so that the liquid can be evacuated into a reservoir below the liquid evacuation part. However, it is also possible that the liquid evacuation part consists of the upwardly extending portion only, e.g. an upwardly sloping portion and that this portion alone guides the liquid to a reservoir. 
     Preferably, the transport bar is provided at the outer end with an upwardly extending portion. In such an embodiment, the upwardly extending portion of the liquid evacuation part extends between the transport system and the upwardly extending portion of the transport bar. In that manner, liquid present on the transport bar will be stopped by the upwardly extending portion of the transport bar, and can flow sideways off the transport bar on the liquid evacuation part where liquid is evacuated to a reservoir as described above. 
     Preferably, the treatment compartment comprises a wall portion having a lower edge right above the outer end of the transport bar, when the transport bar moves through the treatment compartment. More preferably, the wall portion extends next to the upwardly extending portion of the transport bar such that an upper edge of the upwardly extending portion of the transport bar is higher than the lower edge of wall portion. Also preferably, the liquid evacuation part extends below the lower edge of the wall portion. In that manner, any liquid splashes or drops on the wall portion of the treatment compartment may glide along the wall portion onto the evacuation part or on the transport bar, such that those splashes or drops are evacuated, and are prevented form wetting the transport system. The wall portion may comprise openings configured to allow components of the liquid application means, such as a shaft, to penetrate through the wall portion. The wall portion is typically an upright wall portion, preferably a vertical wall portion. 
     In a preferred embodiment, the transport bar comprises a bridge portion extending from the upwardly extending portion of the transport bar over the upwardly extending portion of the liquid evacuation part to join the coupling portion. Such bridge portion provides an appropriate connection with the coupling portion. 
     In an exemplary embodiment, the transport bar is provided at the outer end with an inverse-U-shaped portion having an outer leg forming the coupling portion and an inner leg forming the upwardly extending portion, wherein the upwardly extending portion of the liquid evacuation part extends between the outer and inner leg of the inverse-U-shaped portion. In that manner, the coupling portion can be located at more or less the same height of the main part of the transport bar, such that the force exerted by the transport system on the coupling portion is more or less in the same plane as the plane of the relief plate precursor and the transport bar, thus avoiding that the transport bar starts to turn. 
     In an exemplary embodiment, the transport bar is provided at the outer end with a substantially Uor V-shaped portion having a downwardly extending inner leg and an outer leg forming the upwardly extending portion, wherein the upwardly extending portion of the liquid evacuation part extends between the outer leg of the substantially U- or V-shaped portion and the coupling portion. In such an embodiment, liquid on the transport bar may flow in the U- or V-shaped portion, and be evacuated sideways from there onto the evacuation part. Also in such an embodiment, the coupling portion can be located at more or less the same height of the main part of the transport bar, such that the force exerted by the transport system on the coupling portion is more or less in the same plane as the plane of the relief plate precursor and the transport bar. 
     Preferably, the outer end of the transport bar is supported on the liquid evacuation part. The outer end may be supported on a horizontal or inclined portion of the liquid evacuation part or on the upper edge of the upwardly extending portion of the liquid evacuation part. 
     Preferably, a height of the upwardly extending portion of the transport bar is more than 5 mm, more preferably between 5 mm and 100 mm. Preferably, a height of the upwardly extending portion of the liquid evacuation part is more than 5 mm, more preferably between 5 mm and 100 mm. Preferably, a distance between a lower edge of the upwardly extending wall portion and the liquid evacuation part is smaller than 10 mm, more preferably between 0 mm and 5 mm. 
     In a preferred embodiment, the transport system is substantially symmetric with respect to a central axis of the apparatus, with a first and second transport mechanism for being coupled to a first and second outer end of the transport bar, respectively. In such an embodiment, the transport bar is provided at the first and a second outer end with a first and second upwardly extending portion, respectively, and the protection system comprises a first and a second liquid evacuation part below the first and the second outer end, respectively, and extending lengthwise next to the first and second transport mechanism of the transport system, respectively. Preferably, the first liquid evacuation part is provided with a first upwardly extending portion extending between the first transport mechanism and the first upwardly extending portion of the transport bar and the second liquid evacuation part is provided with a second upwardly extending portion extending between the second transport mechanism and the second upwardly extending portion of the transport bar. Although such symmetric set-up is generally preferred, it is noted that there may be provided a driven transport mechanism at the first outer end of the transport bar and a simple guide mechanism at the second outer end of the transport bar. Depending on whether such guide mechanism requires protection against wetting, it me be arranged either in a similar manner as the driven transport mechanism with protection system, or without protection system. 
     Preferably, the transport system comprises a lead screw, preferably a pair of lead screws, or a chain or belt, preferably a pair of chains or belts. Such lead screw or chain or belt extends in the movement direction, one side of the treatment compartment or on either side of the treatment compartment. 
     Preferably, the treatment compartment comprises a plurality of liquid application means having an axis arranged parallel to the transport bar. Preferably, the transport system comprises a first and a second transport mechanism extending perpendicular on the axis of the liquid application means, at a first and second side of the liquid application means, respectively. Preferably, a coupling location between the transport bar and the first and second transport mechanism is located lower than an upper side of the liquid application means, preferably lower than the axis of the liquid application means. In that manner, the apparatus can be compact, and the transport system can be arranged at a relatively low location in the apparatus. 
     The liquid application means may comprise rollers, brushes, spraying nozzles, pipes, a table arranged below a roller or brush, and combinations thereof. Preferably the liquid application means are rollers or cylindrical brushes. The brush may be e.g. a movable (rotating or oscillating) brush (flat or cylindrical). A table below a brush or roller may extend with an outer end thereof over the liquid evacuation part, and in particular over a substantially horizontal part thereof. Preferably, the table is positioned at a lower level than an upper edge of the upwardly extending portion of the liquid evacuation part, such that any liquid flowing from the table on the liquid evacuation part is stopped by the upwardly extending portion of the liquid evacuation part. 
     Preferably, the liquid application means comprises a shaft and a liquid application tool intended to contact the relief plate precursor, such as bristles, arranged on the shaft, and the liquid evacuation part extends below the transport bar and below the shaft of the liquid application means, at a distance of the liquid application tool. In that manner the liquid evacuation part will not hinder the treatment by the liquid application tool, whilst allowing a good evacuation of any liquid on the transport bar. 
     In an exemplary embodiment, the transport bar is provided with one or more holes for evacuating liquid through said one or more holes. This will further help in evacuating the liquid away from the transport system. The one or more holes are preferably located at least at the lowest part of the transport bar e.g. at the bottom of the U- or V-shaped portion having a downwardly extending inner leg. 
     Preferably, the liquid evacuation part is made of a metal, an alloy, a plastic resistant to the liquid, or combinations thereof. 
     Preferably, the transport bar is provided with at least one penetration element, more preferably a plurality of penetration elements. The shape of the at least one penetration element may be selected from a group comprising: a rod with e.g. a round, elliptical, triangular, rectangular or multi-angular cross section, a blade, a needle, or combinations thereof. The at least one penetration element may be made of metal or an alloy. 
     Preferably, the length of the transport bar is from 100 mm to 10000 mm, more preferably from 200 mm to 5000 mm, most preferably from 500 mm to 3000 mm. 
     According to a preferred embodiment, the apparatus comprises a plate coupling station and/or decoupling station configured for coupling and/or decoupling the relief plate precursor to or from the transport bar. The plate coupling station may be configured to engage the at least one penetration element in an area near an edge of a relief plate precursor. More preferably, each penetration element has a sharp tip or edge capable of causing a penetrating action in the material of the relief plate precursor, and the plate coupling station is configured to cause a penetration by the at least one penetration element at least partially into or through an unperforated area near an edge of a relief plate precursor. In that manner the penetration elements are pushed in the material of the printing plate without generating waste. However, it is noted that the invention also covers the use of pre-perforated relief plate precursors which are coupled to the transport bar in the plate coupling station. 
     Preferably, the transport system is configured to move the at least two transport bars in a closed loop through the apparatus. Two, three or more transport bars may be transported simultaneously in the apparatus. For example, one of the at least two transport bars may be transported through the treatment compartment whilst another one is being transported back to the plate coupling station. 
     The apparatus may further comprise additional components selected form the group comprising: a pump, a filter, a sensor (temperature, solid content, density, pressure, etc.), a gear, a motor, a spraying system, a control unit configured to control one or more components thereof, and combinations thereof. 
     According to another aspect of the invention there is provided a method for treating a relief plate precursor with a liquid. The method comprises:
     providing a transport bar with a coupling portion configured to couple the transport bar to a transport system, and with at least one penetration element, preferably a plurality of penetration elements, configured to couple the transport bar to a relief plate precursor;   coupling the relief plate precursor to the at least one penetration element of the transport bar;   coupling the coupling portion of the transport bar to the transport system;   controlling the transport system such that the transport bar with the coupled relief plate precursor is moved through a treatment compartment where the relief plate precursor is treated with a liquid;   evacuating liquid over the transport bar towards a liquid evacuation part whilst the transport bar is moving through the treatment compartment, such that the liquid is evacuated before it can reach the transport system.   

     Preferably, the liquid evacuation part extends lengthwise next to the transport system and below an outer end of the transport bar, said liquid evacuation part being provided with an upwardly extending portion at a side facing the transport system, such that liquid is stopped at said upwardly extending portion of the liquid evacuation part. More preferably, the transport bar is provided at the outer end with an upwardly extending portion, and the upwardly extending portion of the liquid evacuation part extends between the transport system and the upwardly extending portion of the transport bar, such that liquid is stopped at said upwardly extending portion of the transport bar, and evacuated to a lower reservoir via the liquid evacuation part. 
     Preferably, the method further comprises decoupling the transport bar from the treated relief plate precursor in a plate decoupling station of the treatment apparatus. Preferably, the transport bar is moved in a closed loop from a plate coupling station through the treatment compartment to the plate decoupling station and back to the plate coupling station. Preferably, at least two transport bars are being transported simultaneously in the treatment compartment. In other words, the transport bar or bars can circulate automatically in the apparatus. An operator may bring the relief plate precursor to be treated to the plate coupling station, and next the coupling, treating and decoupling is performed automatically whereupon the transport bar is automatically returned to the plate coupling station. In that way an operator does not have to decouple or return the transport bar. This reduces the number of required manual interactions. 
     Preferably, the treatment in the treatment compartment is selected from the group comprising washing, brushing, rinsing, spraying, optionally in combination with any one of the following: developing, heating, cooling, removing of material, treating with gases or liquids, with electromagnetic waves, and combinations thereof. 
     The method may further comprise the step of performing a post-treatment on the relief plate precursor, said post-treatment being selected from the group comprising washing, brushing, rinsing, spraying, drying, irradiating, developing, heating, cooling, removing of material, treating with gases or liquids, sanding, cutting, treating with electromagnetic waves and combinations thereof. Also, the method may further comprise the step of performing a pre-treatment on the relief plate precursor, said pre-treatment being selected from the group comprising: cutting, ablation, exposure to electromagnetic radiation, and combinations thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings are used to illustrate presently preferred non limiting exemplary embodiments of the apparatus and method of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a schematic perspective view of an exemplary embodiment of an apparatus for treating a relief plate precursor; 
         FIG.  2    is a perspective view of an exemplary embodiment of an apparatus for treating a relief plate precursor, wherein a wall portion has been omitted for clarity purposes; 
         FIG.  3 A  is a detailed perspective view illustrating in detail a portion of  FIG.  2   , with the wall portion included; 
         FIG.  3 B  is a detailed perspective view illustrating in detail a portion of  FIG.  2   ; 
         FIG.  4    is a side view of the exemplary embodiment of  FIG.  2   ; 
         FIG.  5    is a schematic perspective view of an exemplary embodiment of a transport bar; 
         FIG.  6    is a detailed perspective view illustrating a portion of an exemplary embodiment of a plate coupling station; and 
         FIGS.  7 A- 7 D  illustrate side view of four further exemplary embodiments of an apparatus for treating a relief plate precursor. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG.  1    illustrates schematically an apparatus  1000  for treating a relief plate precursor, such as a printing plate precursor P. The apparatus is for instance a washing apparatus for washing a relief plate precursor with a liquid. However, also other treatments are possible such as brushing, rinsing, spraying, drying, irradiating, developing, heating, cooling, removing of material of the relief plate precursor, treating the relief plate precursor with gases or liquids, sanding the relief plate precursor, cutting the relief plate precursor, treating it with electromagnetic waves, or combinations thereof. 
     The apparatus  1000  comprises a transport system  210 ,  220 ,  230  with at least one, preferably at least two, and even more preferably at least three transport bars  100  intended to be coupled to a relief plate precursor. For example, four transport bars  100  may be provided to the transport system  210 ,  220 ,  230  as illustrated in  FIG.  1   . The transport bar  100  is coupled to a leading edge  3  of the relief plate precursor P and preferably extends over more than the entire length of the leading edge  3 , such that end parts of the transport bar  100  can be coupled to a transport mechanism of the transport system  210 ,  220 , see further. It is noted that it is also possible to couple a plurality of relief plate precursors to the transport bar  100 . Preferably, the length of the transport bar  100  is between 100 mm and 1000 mm, more preferably between 1000 mm and 4000 mm. 
     The apparatus  1000  comprises a plate coupling station  300  configured for coupling a relief plate precursor P to a transport bar  100 , a treatment compartment  400  configured for treating the relief plate precursor whilst the transport bar  100  to which the relief plate precursor P is coupled, is moved through the treatment compartment  400 , and a plate decoupling station  500  configured for decoupling the treated relief plate precursor P from the transport bar  100 . Preferably, the transport system  210 ,  220 ,  230  is configured to automatically move each transport bar  100 , after being coupled to a relief plate precursor P in the plate coupling station  300 , from the plate coupling station  300  through the treatment station  400  to the plate decoupling station  500 , and, after being decoupled from a treated relief plate precursor P, from the plate decoupling station  500  back to the plate coupling station  300 , such that the transport bar  100  moves in a closed loop through the apparatus  1000 . In the illustrated example of  FIG.  1   , four transport bars  100  circulate in the apparatus  1000 . However, the invention also cover embodiments where the transport bars are brought back manually from the plate decoupling station  500  t0 the plate coupling station  300 . 
     In a preferred embodiment, each transport bar  100  is provided with a plurality of penetration elements  110  (here in the form of pins or rods), and the plate coupling station  300  is configured to engage the plurality of penetration elements  110  in an area near the leading edge  3  of the relief plate precursor P. In  FIG.  1   , the relief plate precursor P has a leading edge  3 , a trailing edge  4 , both perpendicular to a forward transport direction Tf of the relief plate precursor P through the apparatus  1000 , and two side edges  1 ,  2  parallel to the forward transport direction Tf. An area near the leading edge  3  of the relief plate precursor P is coupled to the plurality of penetration elements  110  of the transport bar  100 .  FIG.  5    illustrates a more detailed exemplary embodiment of a transport bar  100 . The plurality of penetration elements  110  preferably have sharp tips, and the plate coupling station  300  is preferably configured to cause a penetration of the plurality of penetration elements  110  at least partially into or through an unperforated area near the leading edge  3  of the relief plate precursor P. However, it is noted that according to another exemplary embodiment, the apparatus  1000  of  FIG.  1    may also be used with transport bars  100  which are provided with a plurality of penetration elements  110  which do not have a sharp tip. For example, the area near the leading edge  3  of the relief plate precursor P may be pre-perforated before bringing the relief plate precursor P to the plate coupling station  300 , such that the plurality of penetration elements  110  can be arranged through pre-perforated holes in the area near the leading edge  3 . 
     The treatment compartment  400  has an inlet side  410  and an outlet side  420 . A transport bar  100  with a coupled relief plate precursor P is moved through the treatment compartment  400  from the inlet side  410  to the outlet side  420 , wherein the transport bar  100  moves in the forward transport direction Tf. Between the outlet side  420  of the treatment compartment  400  and the plate decoupling station  500 , there is provided a plate discharge zone  600 . A relief plate precursor P is pulled by the transport system fully out of the treatment compartment  400  in the plate discharge zone  600  before being decoupled from the transport bar  100  in the decoupling station  500 . In that way, when the relief plate precursor P is decoupled from the transport bar  100 , the relief plate precursor P can be discharged in the plate discharge zone  600 . At the bottom of the plate discharge zone  600  there may be provided a removal means configured to remove a treated relief plate precursor P after being decoupled from the transport bar  100  in the plate decoupling station  500 . In the illustrated embodiment, the removal means  700  is a trolley configured for receiving the treated relief plate precursor P in the plate discharge zone  600 , and for being moved out of the plate discharge zone  600 , such that it can be easily transported away of the plate discharge zone. For example, if the apparatus  1000  is a washer, an operator may transport the washed relief plate precursor P to a dryer in order to dry the washed relief plate precursor. In other non illustrated embodiments, the removal means  700  may be a carrier, a robot, a moving belt, at least one rotating drum, etc. Also such devices can be configured to move a treated relief plate precursor P out of the plate discharge zone  600  after being decoupled in the plate decoupling station  500 . 
     In the embodiment of  FIG.  1   , the transport system comprises a forward transport mechanism which comprises first transport mechanism  210  on one side of the apparatus  1000 , and a second transport mechanism  220  on the other side of the apparatus  1000 . The transport mechanism  210 ,  220  is configured to transport the transport bar  100  with a coupled relief plate precursor P at least from the inlet side  410  to the outlet side  420  of the treatment compartment  400 , and optionally from the outlet side  420  to the plate decoupling station  500 , in the forward transport direction Tf. To that end, a first outer end  101  of the transport bar  100  is coupled with the first forward transport mechanism  210 , and a second outer end  102  of the transport bar  100  is coupled with the second forward transport mechanism  220 . As illustrated in  FIG.  6   , the transport system  210  may comprise a bar coupling means  215  configured to couple the transport bar  100 , and more in particular the first outer end  101  and the second outer end  102  of the transport bar to the first and second forward transport mechanism  210 ,  220 . Only the first outer end  101  and the first transport mechanism is shown in  FIG.  6   , but it is understood that the second outer end  102  and the second transport mechanism  220  may be embodied in a similar manner. The bar coupling means  215  may be configured e.g. for pushing or moving the transport bar  100  in the direction of the first and second forward transport mechanism, in order to cause a coupling of the outer ends  101  and  102  of the transport bar  100  to the forward transport mechanism  210 ,  220 . In the embodiment of  FIG.  1   , the treatment compartment  400  has a first and second opposite lateral side  430 ,  440  extending in the forward transport direction Tf, and the first and second forward transport mechanism  210 ,  220  extend at the first and second opposite lateral side  430 ,  440  of the treatment compartment  400 , respectively. 
     The transport system further comprises a backward transport mechanism  230  configured to transport the transport bar  100  from the plate decoupling station  500  back to the plate coupling station  300 . In the illustrated embodiment of  FIG.  1   , the backward transport mechanism  230  is located at an upper side of the apparatus  1000 . However, in other embodiments, the backward transport mechanism  230  could be arranged in a lower portion of the apparatus  1000 , below the forward transport mechanism  210 ,  220 . A backward transport mechanism  230  may comprise any one of the following: one or more belts, one or more chains, one or more lead screws, a linear motor, or combinations thereof. In  FIG.  1   , the backward transport mechanism  230  is arranged centrally above the treatment compartment  400 . However, the backward transport mechanism  230  could also be realized with a first and second backward transport mechanism located at opposite lateral sides of the treatment compartment  400  above or below the first and second forward transport mechanism  210 ,  220 . Alternatively, the backward transport mechanism may be located at a lateral side of the treatment compartment, and optionally the transport bar may be rotated and transported backward in a vertical position. However, in order to reduce the footprint of the apparatus the backward transport mechanism is preferably located above or below the first and second forward transport mechanism  210 ,  220 . As illustrated in  FIG.  1   , the backward transport mechanism  230  is located partly above the treatment compartment  400 , and the transport system further comprises an upward transport mechanism  250  configured to move a decoupled transport bar  100  in the plate decoupling station  500  upward towards the backward transport mechanism  230 . For example, the upward transport mechanism  250  may move the transport bar  100  in an upward direction Tu, typically a vertical direction, towards the backward transport mechanism  230  which moves the transport bar  100  in a backward transport direction Tb opposite to the forward transport direction Tf, back to the plate coupling station  300 . The upward transport mechanism  250  may comprise any one or more of the following: magnetic means, electromagnetic means, clamping means, vacuum means, linear motors, chains, belts, lead screws, piston or combinations thereof. In other embodiments where the backward transport mechanism  230  is located below the forward transport mechanism, there may be provided a downward transport mechanism. The downward transport mechanism may comprise any one or more of the following: magnetic means, electromagnetic means, clamping means, vacuum means, linear motors, chains, belts, lead screws, piston or combinations thereof, or occur simply by gravity. 
       FIG.  5    illustrates a more detailed exemplary embodiment of a transport bar  100 . The transport bar  100  is provided with a first coupling portion  121  and a second coupling portion  122  at the first outer end  101  and the second outer end  102 . In this case the coupling portions  121 ,  122  are configured with coupling means to be used in combination with a lead screw. The transport bar  100  is provided with penetration elements  110 . The transport bar  100  is equipped with channels  120  allowing alignment pins to pass through the transport bar  100  from below the transport bar. 
     As illustrated in  FIG.  6   , in an exemplary embodiment, the first forward transport mechanism  210  comprises a first lead screw, and the first coupling portion  121  is configured to be coupled to the first lead screw  210 . In a similar manner, the second forward transport mechanism  220  may be provided with a second lead screw which can be coupled to the second coupling portion  122 . In other embodiments, the first and/or second forward transport mechanism  210 ,  220  may comprise other transport means such as a chain or belt, and the first and second coupling portions  121 ,  122  may be adapted accordingly. 
       FIGS.  2 ,  3 A,  3 B and  4    illustrate in detail an exemplary embodiment of an apparatus  1000  for treating a relief plate precursor with a liquid. The apparatus  100  comprises a treatment compartment  400  with a plurality of liquid application rollers  450  and a transport system  210 . The treatment compartment  400  is configured for treating the relief plate precursor with a liquid. The transport system  210  is for use with one or more transport bars  100 , e.g. a transport bar as described above in connection with  FIG.  5   . The transport system  210  is configured to move the transport bar  100  with the coupled relief plate precursor through the treatment compartment  400 . The transport bar is provided with a coupling portion  121  configured to couple the transport bar  100  to the transport system  210 , for example as described above in connection with  FIG.  6   . Further, the apparatus comprises a protection system  900  configured to guide and evacuate liquid on the transport bar such that the transport system is protected against wetting with the liquid of the treatment compartment. In that manner the relief plate precursor can be coupled to the penetration elements  110  of the transport bar  100 , and the coupling portion  121  of the transport bar  100  can be coupled to the transport system  210 . The transport system  210  is controlled, e.g. using a controller  800  as illustrated in  FIG.  1   , such that the transport bar  100  with the coupled relief plate precursor is moved through the treatment compartment  400  where the relief plate precursor is treated with a liquid. During this treatment, liquid is evacuated over the transport bar  100  towards a liquid evacuation part  900  whilst the transport bar  100  is moving through the treatment compartment  400 , such that the liquid is evacuated before it can reach the transport system  210 . 
     As is best visible in  FIG.  3 B  and  FIG.  4   , the protection system  900  comprises a liquid evacuation part  910  extending lengthwise next to the transport system  210  and below the first outer end  101  of the transport bar  100 . The liquid evacuation part  910  is provided with an upwardly extending portion  911  at a side facing the transport system  210  and with a substantially horizontal portion  913  on the side of the transport bar  100 . This substantially horizontal portion  913  supports the transport bar  100  during its movement through the treatment compartment  400 . In other embodiments the substantially horizontal portion  913  may be omitted and the transport bar  100  could be supported on the upwardly extending portion  911 . The liquid evacuation part  910  may be made of a metal, an alloy, a plastic resistant to the liquid, or combinations thereof. 
     The transport bar  100  is provided at the first outer end  101  with an upwardly extending portion  131 . The upwardly extending portion  911  of the liquid evacuation part  910  extends between the transport system  210  and the upwardly extending portion  131  of the transport bar  100 . More in particular, in the embodiment of  FIGS.  2 - 4   , the transport bar  100  is provided at the first outer end  101  with an inverse-U-shaped portion having an outer leg forming the coupling portion  121  and an inner leg forming the upwardly extending portion  131 . The outer leg  121  and the inner leg  131  are interconnected by a bridge portion  141  extending from the upwardly extending portion  131  of the transport bar  100  over the upwardly extending portion  911  of the liquid evacuation part to join the coupling portion  121 . The upwardly extending portion  911  of the liquid evacuation part  910  extends between the outer and inner leg  121 ,  131  of the inverse-U-shaped portion. 
     As illustrated in  FIG.  3 B , liquid dropping from the liquid application rollers  450  on the transport bar  100  will be stopped at the upwardly extending portion  131  of the transport bar  100  and flow sideways onto the liquid evacuation part  910  where the liquid is stopped at the upwardly extending portion  911  of the liquid evacuation part  910 . From there the liquid is evacuated to a lower reservoir (not shown). Also liquid falling directly on the liquid evacuation part  910  will not reach the transport mechanism  210  because of the upwardly extending portion  911  of the liquid evacuation part  910 . 
     As illustrated in  FIG.  3 A , the treatment compartment  400  comprises a wall portion  410  having a lower edge  411  right above the first outer end  101  of the transport bar  100 , when the transport bar  100  moves through the treatment compartment  400 . The lower edge  411  is shown to be located at a small distance d of the horizontal portion  913  of the liquid evacuation part  900 , e.g. d &lt; 5 mm. This wall portion  410  has been omitted in  FIGS.  2 ,  3 B and  4    for clarity purposes. The wall portion  410  extends next to the upwardly extending portion  131  of the transport bar  100  such that an upper edge of the upwardly extending portion  131 , located at the level of the bridge portion  141 , is higher than the lower edge  411  of wall portion  410 . The liquid evacuation part  910  extends below the lower edge  411  of the wall portion  410 . 
     Although  FIGS.  2 - 4    only illustrate the arrangement at the first outer end  101  of the transport bar  100 , it will be understood that the arrangement at the second outer end  102  of the transport bar  100  may be similar. More in particular, as shown in  FIG.  5   , the second outer end  102  may be provided with an upwardly extending portion  132 . The protection system  900  may comprises a second liquid evacuation part (not shown) below the second outer end  102 , and extending lengthwise next to the second transport mechanism  220  of the transport system. Preferably, the second liquid evacuation part is provided with a second upwardly extending portion extending between the second transport mechanism  220  and the second upwardly extending portion  132  of the transport bar  100 . In a preferred embodiment, the first and second transport mechanism  210 ,  200  may be a first and second lead screw. 
     The treatment compartment  400  comprises a plurality of liquid application rollers  450  having an axis A arranged parallel to the transport bar  100 , see in particular  FIG.  4   . The first and second transport mechanism  210 ,  220  extend perpendicular on the axis A of the liquid application rollers  450 , at a first and second side of the liquid application rollers  450 , respectively. A coupling location between the transport bar  100  and the first and second transport mechanism  210 ,  220  is located lower than an upper side of the liquid application rollers  450 , and in the illustrated embodiment lower than the axis A of the liquid application rollers  450 . In that manner a very compact arrangement is achieved. 
     A liquid application roller  450  comprises a shaft  451  and a liquid application tool  452 , such as bristles, arranged on the shaft  451 , and the liquid evacuation part  910  extends below the transport bar  100  and below the shafts  451  of the liquid application rollers  450 . Preferably, tables  460  are arranged below the liquid application rollers  450 . The tables  460  may extend with an outer end thereof over the substantially horizontal portion  913  of the liquid evacuation part  910 , as shown in  FIGS.  3 A and  3 B . Optionally, the height of the tables  460  may be adjustable. By adjusting the height different operating modes may be set. For example, a smaller distance between the shaft  451  and the table  460  may be used in combination with a fast process leading to a lower quality compared to a higher distance in combination with a slower process. The table  460  is positioned at a lower level than an upper edge of the upwardly extending portion  911  of the liquid evacuation part  910 , such that any liquid flowing from the table  460  on the liquid evacuation part  910  is stopped by the upwardly extending portion  911  of the liquid evacuation part  910 .. 
     Optionally, the transport bar  100  may be provided with one or more holes (not shown) for evacuating liquid through said one or more holes. For example, there may be arranged one or more holes between the upwardly extending portion  131  and a central portion of the transport bar  100 , in an area located above the liquid evacuation part  910  or above the reservoir (not shown). 
       FIGS.  7 A- 7 D  illustrate four other exemplary embodiments of an apparatus for treating a relief plate precursor with a liquid, wherein similar components have been indicated with the same reference numerals as above. 
     In the embodiment of  FIG.  7 A , the liquid evacuation part  910  is similar to the one described above in connection with  FIGS.  2 - 4   . The transport bar  100  is provided at the first outer end  101  with an upwardly extending portion  131 , a bridge portion  141  extending over the upwardly extending portion  911  of the liquid evacuation part  910 , and a coupling portion  121  extending upwardly from the bridge portion  141 . As in the embodiment of  FIGS.  2 - 4   , a wall portion  410  extends next to the upwardly extending portion  131 , with a lower edge  411  thereof being below the level of the bridge portion  141 . 
     In the embodiment of  FIG.  7 B , the liquid evacuation part  910  is similar to the one described above in connection with  FIGS.  2 - 4   . The transport bar  100  is provided at the first outer end  101  with an upwardly extending portion  131 , here sloping upwardly and not oriented vertically, a bridge portion  141  extending over the upwardly extending portion  911  of the liquid evacuation part  910 , and a coupling portion  121  extending downwardly from the bridge portion  141 . As in the embodiment of  FIGS.  2 - 4   , a wall portion  410  extends next to the upwardly extending portion  131 , with a lower edge  411  thereof being below the level of the bridge portion  141 . 
     In the embodiment of  FIG.  7 C , the liquid evacuation part  910  comprises an upwardly extending portion  911   a ,  911   b  with a vertical portion  911   b  at the side of the transport mechanism  210  and an inclined portion  911   b  protruding inwardly. The transport bar  100  is provided at the first outer end  101  with a V-shaped portion having a downwardly extending inner leg  136  and an outer leg forming the upwardly extending portion  131 . The upwardly extending portion  911   b  of the liquid evacuation part  910  extends between the outer leg  131  of the V-shaped portion and the coupling portion  121 . Further, a bridge portion  141  extends over the upwardly extending portion  911   b  of the liquid evacuation part  910 . As in the embodiment of  FIGS.  2 - 4   , a wall portion  410  extends next to the upwardly extending portion  131 , with a lower edge  411  thereof being below the level of the bridge portion  141 . In this embodiment, the transport bar  100  is supported on the upwardly extending portion  911   b  of the liquid evacuation part  910 . It is noted that portion  911   a  may also be omitted in the embodiment of  FIG.  7 C . 
     In the embodiment of  FIG.  7 D , the liquid evacuation part  910  comprises an upwardly extending portion  911   a ,  911   b  with a vertical portion  911   b  at the side of the transport mechanism  210  and an inclined portion  911   b  protruding inwardly. The transport bar  100  is provided at the first outer end  101  with a U-shaped portion having a downwardly extending inner leg  136  and an outer leg forming the upwardly extending portion  131 . The upwardly extending portion  911   b  of the liquid evacuation part  910  extends between the outer leg  131  of the U-shaped portion and the coupling portion  121 . Further, a bridge portion  141  extends over the upwardly extending portion  911   b  of the liquid evacuation part  910 . As in the embodiment of  FIGS.  2 - 4   , wall portion  410  extends next to the upwardly extending portion  131 , with a lower edge  411  thereof being below the level of the bridge portion  141 . In this embodiment, the transport bar  100  is supported on the upwardly extending portion  911   a  of the liquid evacuation part  910 . 
     Optionally, holes may be provided in the transport bars  100  illustrated in  FIGS.  7 A- 7 D . For example, in the embodiments of  FIGS.  7 C and  7 D , holes may be provided in the V- or U-shaped portions. 
     A relief plate precursor generally comprises a support layer made of a first material and an additional layer made of a second material which is different from said first material. The support layer may be a flexible metal, a natural or artificial polymer, paper or combinations thereof. Preferably the support layer is a flexible metal or polymer film or sheet. In case of a flexible metal, the support layer could comprise a thin film, a sieve like structure, a mesh like structure, a woven or non-woven structure or a combination thereof. Steel, copper, nickel or aluminium sheets are preferred and may be about 50 to 1000 µm thick. In case of a polymer film, the film is dimensionally stable but bendable and may be made for example from polyalkylenes, polyesters, polyethylene terephthalate, polybutylene terephthalate, polyamides und polycarbonates, polymers reinforced with woven, nonwoven or layered fibres (e.g. glass fibres, Carbon fibres, polymer fibres) or combinations thereof. Preferably polyethylene and polyester foils are used and their thickness may be in the range of about 100 to 300 µm, preferably in the range of 100 to 200 µm. 
     A relief precursor may carry an additional layer. For example, the additional layer may be any one of the following: a direct engravable layer (e.g. by laser), a solvent or water developable layer, a thermally developable layer, a photosensitive layer, a combination of a photosensitive layer and a mask layer. Optionally there may be provided one or more further additional layers on top of additional layer. Such one or more further additional layers may comprise a cover layer at the top of all other layers which is removed before the imageable layer is imaged. The one or more additional layers may comprise a relief layer, and an anti-halation layer between the support layer and the relief layer or at a side of the support layer which is opposite of the relief layer. The one or more additional layers may comprise a relief layer, an imageable layer, and one or more barrier layers between the relief layer and the imageable layer which prevent diffusion of oxygen. Between the different layers described above one or more adhesion layers may be located which ensure proper adhesion of the different layers. 
     In a preferred embodiment the relief plate precursor comprises a support layer made of a polyester of polymer material, and an additional layer made of a directly engravable material such as a resin material. The optional layer may then be a laser ablative layer. In an exemplary embodiment the relief plate precursor may contain at least a dimensionally stable support layer, a relief layer and an imageable mask layer. Optionally, further layers may be present. There may be a cover layer at the top of all other layers which is removed before the imageable mask layer is imaged. There may be an anti-halation layer between the support layer and the relief layer or it may be located at the side of the support layer which is opposite of the relief layer. There may be one or more barrier layers between the relief layer and the imageable mask layer which prevent diffusion of oxygen. Between the different layers described above one or more adhesion layers may be located which ensure proper adhesion of the different layers. One or more layers may be removable by treatment with a liquid. The liquids used may be the same or different for different layers. Preferably the liquids used are different. 
     In a preferred embodiment the relief plate precursor comprises a photosensitive layer and a mask layer. The mask layer may be ablated or changed in transparency during the treatment and forms a mask with transparent and non-transparent areas. Underneath of transparent areas of the mask the photosensitive layer undergoes a change in solubility and/or fluidity upon irradiation. The change is used to generate the relief by removing parts of the photosensitive layer in one or more subsequent steps. The change in solubility and/or fluidity may be achieved by photo-induced polymerization and/or crosslinking, rendering the irradiated areas less soluble. In other cases the electromagnetic radiation may cause breaking of bonds or cleavage of protective groups rendering the irradiated areas more soluble. Preferably a process using photo-induced crosslinking and/or polymerization is used. 
     Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.