Patent Publication Number: US-11396201-B2

Title: Apparatus and method for applying a liquid to a printing surface

Description:
BACKGROUND 
     The process of printing sometimes involves applying coating of a primer to the surface of a member which is to be printed before the application of ink or other substances. Primer can be applied to the surface as a continuous coating, for example by applying the primer to an anilox roller and subsequently transferring the primer from the roller to the surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples are further described hereinafter with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a section of an apparatus for applying liquid to a printing surface according to some examples; 
         FIG. 2  and  FIG. 3  illustrate a housing and liquid guide members which form a part of the apparatus for applying liquid according to an example; 
         FIG. 4  illustrates the liquid guide member according to an example; and 
         FIG. 5  is a flow chart of a method according to an example. 
     
    
    
     DETAILED DESCRIPTION 
     It can be advantageous, when providing a coating of a liquid such as a primer across a surface, to provide spaces where the primer is not applied. These spaces may then be used for purposes which might be impeded by the presence of the liquid, such as the application of an adhesive. 
       FIG. 1  is a diagram showing a section of an apparatus  100  for applying a liquid to a printing surface. The apparatus  100  comprises a housing  110 , a liquid guide member  120 , a first doctor blade  140 , a second doctor blade  141  and an anilox roller  150 . 
       FIGS. 2 and 3  shows the housing  110  and the liquid guide members  120  from different perspectives. In  FIG. 2 , it can be seen how the liquid guide member  120  fits into an aperture  111  in the housing  110 . In use, the housing receives liquid from a pump so that the liquid fills the housing at a predetermined pressure. As the liquid continues to be pumped into the housing  110 , the liquid will also flow out of the aperture  111  and across a liquid conduction surface  112  to the anilox roller  150 . The anilox roller  150  turns in the direction indicated by the arrow  151 , so that the liquid flowing across the liquid conduction surface  112  is spread across the surface of the anilox roller  150 . 
     The aperture  111  shown in  FIG. 2  is a slit, in that it is longer on a first axis than it is on a second orthogonal axis, and has a substantially regular width along the length of the longer axis. 
       FIG. 4  shows a liquid guide member  120 . The guide member  120  comprises an upper plate  121  and a forward plate  122 . The upper plate  121  comprises a first inlet  123  and a second inlet  124 , the first inlet being connected to a first channel  125  and the second inlet  124  being connected to a second channel  126 . The first inlet  123 , the second inlet  124 , the first channel  125  and the second channel  126  all comprise holes set into the upper plate  121 , so that when the guide member  120  is inserted into the aperture  111  of the housing  120 , the liquid conduction surface  112  forms a floor of the channels  125 ,  126 . 
     The upper plate  121  is of a size such that when inserted into the aperture  111  it will obstruct the flow of liquid through the aperture. In particular, the aperture  111  comprises a first side defined by the housing and a second side defined by the housing which is opposite to the first side, and the upper plate  121  extends from the first side to the second side when it is inserted into the aperture  111 . As such, the liquid will flow on either side of the liquid guide member  120  but be obstructed in the region of the liquid guide member  120 , except where liquid can flow into the inlets  123 ,  124  and so pass through the aperture  111  and along the channels  125 ,  126 . 
     As such, liquid in the housing  110  can pass into the first inlet  123 , and then into the first channel  125 , passing through the aperture  111  and then flowing along the first channel  125  over the liquid conduction surface  112 . Similarly, liquid in the housing  110  can pass into the second inlet  124 , and then into the second channel  126 , passing through the aperture  111  and then flowing along the second channel  126  over the liquid conduction surface  112 . 
     Since the flow of liquid in the vicinity of the liquid guide member  120  is partially obstructed, the total amount of liquid which flows through the aperture  111  in this region is less than the total amount of liquid which flows through the aperture  111  in a similarly sized region which does not contain a liquid guide member  120 . 
     The forward plate  122  of the liquid guide member  120  comprises a first transfer surface  127 , a second transfer surface  128  and a support member  129 . The support member  129  extends from the upper plate  121  and connects to the parts of the forward plate  122  which provide the first transfer surface  127  and the second transfer surface  128 . As such, the support member  129  helps to provide rigidity in the forward plate  122  in use, by resisting deformation of the first transfer surface  127  and the second transfer surface  128 . The support member  129  also helps to locate the liquid guide member in the apparatus  100 . In particular, the support member  129  comprises a lip  130  which engages with the housing  110  and therefore helps to position the liquid guide member  120  with respect to the housing  110  as shown in  FIG. 1  and 
       FIG. 3 . 
     As the liquid in the first channel  125  arrives at the forward plate  122 , it flows onto the first transfer surface  127  and spreads out across the first transfer surface  127 . Similarly, as the liquid in the second channel  125  arrives at the forward plate  122 , it flows onto the second transfer surface  128  and spreads out across the second transfer surface  128 . 
     The first channel  125  and the second channel  126  are provided with a first wider end section  131  and a second wider end section  132  respectively. The first wider end section  131  and the second wider end section  132  are both wider than the average width of their respective channel  125 ,  126 , when measured in a direction which is orthogonal to the direction of movement of the liquid through the respective channel  125 ,  126  and orthogonal to the direction of movement of the anilox roller  150 . The liquid spreads into the first wider end section  131  and the second wider end section  132  before passing onto the first transfer surface  127  and the second transfer surface  128 . This helps to establish an even spread of the liquid across the transfer surfaces  127 ,  128 . 
     The first transfer surface  127  is wider than the first channel  125 , when measured in a direction which is orthogonal to the direction of movement of the liquid through the first channel  125  and to the direction of movement of the anilox roller  150 . As such, the liquid will spread out and establish a thinner layer as it flows from the first channel  125  to the first transfer surface  127 , such that the rate of flow of liquid across the first transfer surface  127  is less than the rate of flow of liquid across the liquid conduction surface  112 . 
     Similarly, the second transfer surface  128  is wider than the second channel  126 , when measured in a direction which is orthogonal to the direction of movement of the liquid through the second channel  126  and to the direction of movement of the anilox roller  150 . As such, the liquid will spread out and establish a thinner layer as it flows from the second channel  126  to the second transfer surface  128 , such that the rate of flow of liquid across the second transfer surface  128  is less than the rate of flow of liquid across the liquid conduction surface  112 . 
     As can be seen in  FIG. 1 , the transfer surfaces  127 ,  128  are proximate to the anilox roller  150 . As such, the liquid forms a stable bead between the transfer surfaces  127 ,  128  and the anilox roller  150 , and is transferred from the transfer surfaces  127 ,  128  to the anilox roller  150 . 
     The first transfer surface  127  and the second transfer surface  128  define a void of width L. The support member  129  is set back from the first transfer surface and the second transfer surface, so that it does not transfer liquid to the anilox roller. Liquid which flows along the channels  125 ,  126  remains confined to the transfer surfaces  127 ,  128 , and liquid which flows on either side of the liquid guide member  120  is obstructed from reaching the void by the liquid guide member. As such, no liquid reaches the part of the anilox roller which is proximate to the void. The liquid guide member therefore provides a strip on the surface of the anilox roller  150  of width L in which no liquid is applied. 
     In this way, a coating of liquid is applied across a surface such as the surface of the Anilox roller  150 , except in a lane which corresponds to the void defined by the liquid guide member or members  120 . The lane may then be used for purposes which would be prevented by the presence of the liquid. 
     The liquid can be transferred from the anilox roller to a further surface, the further surface being coated in the liquid except in strips whose width and location is defined by the size and location of the liquid guide members  120 . In a particular example an adhesive may be applied in these strips, for example to attach a laminate covering to the further surface. 
     If there is an excess of liquid reaching the forward plate  122 , the excess will tend to flow down the side of the forward plate  122  which is opposite to the anilox roller, and as such it will not reach the anilox roller. 
     The first doctor blade  140  is located adjacent to the housing  110  and the first guide member  120  as shown in  FIG. 1 , so that the first doctor blade  140  passes over the surface of the anilox roller  150  after the liquid is applied. The first doctor blade  140  scrapes away any excess liquid on the surface of the anilox roller  150 . 
     The second doctor blade  141  is also located adjacent to the housing  110  and the liquid guide member  120 , but it is arranged so that the second doctor blade passes over the surface of the anilox roller  150  before the liquid is applied. 
     As such, the first doctor blade  140 , the second doctor blade  141 , the housing  110  and the anilox roller  150  define an enclosed space in which the liquid is contained, except where the liquid is moved out of the enclosed space on the anilox roller. 
     The second doctor blade  141  helps to restrain any flow of liquid which might otherwise pass over the exposed surface of the upper plate  121  of the liquid guide member, and so helps to prevent the transfer surfaces  127 ,  128  receiving too much liquid. As such, the second doctor blade  141  helps to maintain a stable bead between the transfer surfaces  127 ,  128  and the anilox roller  150 , and therefore helps to prevent liquid flowing into the void defined by the transfer surfaces  127 ,  128 . 
     The liquid guide member  120  can be inserted at any position in the aperture  111 , in order to provide a strip on the surface of the anilox roller  150  in which no liquid is applied at any desired position along the longitudinal axis of the anilox roller  150 . As can be seen in  FIG. 2 , a plurality of liquid guide members can be inserted into the aperture  111  in order to provide a plurality of strips on the surface of the anilox roller  150  in which no liquid is applied. Although three liquid guide members are shown, it is possible to use one, two, four or any other number of liquid guide members  120  in order to provide the desired number of strips. 
     In an alternative example of a liquid guide member, the inlets and/or channels of the liquid guide member may be provided as grooves in an upper plate, so that floors of the inlets and the channels are provided by the material of the liquid guide member. 
       FIG. 5  shows a method for applying liquid to a printing surface  200 . The method comprises providing an apparatus in section  210 . The apparatus comprises a housing arranged to receive the liquid, and the housing comprises an aperture. The aperture comprises at least a first side defined by the housing and a second side defined by the housing which is opposite to the first side, such that the liquid can flow out of the housing by passing through the aperture between the first side and the second side. 
     The method  200  further comprises inserting a liquid guide member into the aperture in section  220 . The liquid guide member is inserted into the aperture so that it extends from the first side to the second side. The liquid guide member comprises a first transfer surface, a second transfer surface which is separated from the first transfer surface by a gap, a first channel which extends from a first inlet adjacent to the aperture to the first transfer surface, and a second channel which extends from a second inlet adjacent to the aperture to the second transfer surface. 
     The method  200  further comprises operating the apparatus in section  230 . When the apparatus is operated, liquid will flow along the first channel from the aperture to the first transfer surface and then transfer from the first transfer surface onto the printing surface, and the liquid will flow along the second channel from the aperture to the second transfer surface and then transfer from the second transfer surface onto the printing surface as the printing surface moves relative to the apparatus. 
     The liquid may be one which is intended as a preparatory coat for a surface to which other substances, such as inks, may be subsequently applied. The liquid may be a primer. 
     Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components, integers or operations. Throughout the description and claims of this specification, the singular encompasses the plural unless the context demands otherwise. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context demands otherwise. 
     Features, integers or characteristics described in conjunction with a particular aspect or example are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the elements of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or operations are mutually exclusive. Implementations are not restricted to the details of any foregoing examples.