Patent Publication Number: US-2005139097-A1

Title: Method for applying ink activator to an ink image in dip transfer printing

Description:
FIELD OF THE INVENTION  
      This invention generally relates to coating with liquid spraying. More particularly, this invention relates to printing with ink that requires an activator, and even more particularly, relates to transfer printing systems.  
     BACKGROUND OF THE INVENTION  
      Printing with ink sometimes requires application of a liquid spray to an ink image to complete the printing or finishing process. For example, in dip transfer printing, a pattern is printed in solvent based ink on a water soluble film such as polyvinyl acetate. The printed film is then placed on the surface of water in a dipping tank with the printed side up and the soluble film side down. The water dissolves the water soluble film while a solvent activator, such as xylene, is sprayed from the sprayer over the printed solvent based ink image. The printed image then becomes fluid and the object to be printed is dipped into the water in the dipping tank through the floating printed ink image. The ink adheres to the object immediately and the object is removed from the tank and dried. The result is a seamless print on the object.  
      Applying the liquid solvent activator uniformly to the ink image at an appropriate rate produces a high quality transfer printing. Too much activator blurs the ink images and, without enough activator, the ink image will not adhere to the surface of the object being printed.  
      Liquid solvent activator has been applied to ink images in dip transfer printing with hand held sprayers and with spray nozzles carried on a bar which extends across the top of a dipping tank. The bar carrying the spray nozzles travels back and forth along the length of the bath. The bar is carried on wheels at each end of the bar. The wheels ride along both sides of the bath on tracks. The wheels of such an applicator sometimes bind and slow or even stop the applicator. As a result, the applicator applies liquid activator nonuniformly and the resulting coating is nonuniform. Hand held sprayers apply liquid activator only if the operator is very skilled. There are similar problems with applying other liquid coatings such as varnish or lacquer top coatings.  
      Accordingly, there is a need for a liquid coating applicator that applies liquid uniformly and there is a particular need for a printing system for an activator applicator that applies activator uniformly to an ink image.  
     SUMMARY OF THE INVENTION  
      This invention solves the above-described problem in the art by providing a liquid coating applicator for applying a liquid coating to an object, the applicator comprising a cantilever comprising a mounting member and a projecting member extending from the mounting member to a distal end, a liquid sprayer mounted to the projecting member, and a reciprocator for shifting the sprayer back and forth over the object so that the liquid can be sprayed on the object with the liquid sprayer. This applicator is suitable for applying a variety of liquid coatings such as printing ink activators and top coats such as varnish or lacquer.  
      More particularly, this invention encompasses a printing system for printing an image with ink activated with liquid activator comprising a support for holding a sheet printed with ink image and an activator applicator including a cantilever, an activator sprayer, and a reciprocator for shifting the sprayer back and forth over the support. The cantilever comprises a mounting member and a projecting member extending from the mounting member to a distal end. The activator sprayer is mounted to the projecting member and the reciprocator shifts the sprayer back and forth over the support so that the activator can be sprayed on the ink image with the activator sprayer while the support holds the ink image. The cantilever allows the sprayer to shift smoothly back and forth over the support without binding so that the sprayer applies the activator uniformly.  
      According to one embodiment, the reciprocator shifts the cantilever back and forth. More specifically, the reciprocator comprises a track and a carriage engaged with the track. The carriage is connected to the mounting member of the cantilever such that the carriage can travel back and forth on the track while carrying the cantilever. Desirably, the reciprocator comprises a driver, such as a rodless pneumatic cylinder, for moving the carriage back and forth on the track.  
      According to another embodiment, the projecting member of the cantilever is a telescoping rod and the reciprocator comprises an actuator for selectively expanding and alternatively contracting the telescoping rod and thereby shifting the sprayer back and forth over the support.  
      According to still another embodiment, the projecting member of the cantilever has a track extending along the length of the projecting member and the reciprocator comprises a carriage connected to the sprayer and engaged with the track such that the carriage can travel back and forth on the track while carrying the sprayer.  
      The printing system of this invention desirably comprises a tank for holding a dipping liquid such that the printed sheet can float on a surface of the dipping liquid while the sprayer sprays activator on the ink image. Alternatively, the support may comprise a table having a hard surface for holding a printed sheet and printing systems other than dip transfer printing systems.  
      Other features, objects, and advantages of this invention will be appreciated from the following detailed description of embodiments, drawings and claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a perspective view of dip transfer printing system made in accordance with an embodiment of this invention.  
       FIG. 2  is a side elevation view of the printing system illustrated in  FIG. 1 .  
       FIG. 3  is an end elevation view of the printing system illustrated in  FIG. 1 .  
       FIG. 4  is a partial sectional view of an activator sprayer transport which is a component of the printing system illustrated in  FIG. 1 .  
       FIG. 5  is an elevation view of an alternative printing system made in accordance with an embodiment of this invention and including a telescoping sprayer actuator.  
       FIG. 6  is a side elevation view of the alternative printing system illustrated in  FIG. 5 .  
       FIG. 7  is a plan view of another alternative printing system made in accordance with another embodiment of this invention.  
       FIG. 8  is a side elevation view of the alternative embodiment illustrated in  FIG. 7 . 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
      As summarized above, this invention encompasses a system for printing with ink which requires an activator, such as a liquid solvent, for final transfer of the ink to an object. This invention is particularly suited for use in dip transfer printing, but is also useful in other types of printing processes wherein an activator is applied to an ink image. Several embodiments of this invention are described below. As will be appreciated by those skilled in the art, these embodiments are adaptable for applying other types of liquid coatings including top coats such as varnish or lacquer.  
       FIG. 1  illustrates a dip transfer printing system  10  made in accordance with an embodiment of this invention and generally includes a dip tank  12  for holding water  14  and an activator applicator  16 . The water  14  in the dip tank supports a sheet printed with an ink image and the activator applicator  16  applies activator to the ink image before final transfer of the ink image to an object.  
      The dip tank  12  has a rectangular cross-section and rests on feet  18  extending from a bottom panel  20 . Side panels  22  and  24  and end panels  26  and  28  extend upwardly from the bottom panel  20  and define a rectangular open top  30  surrounded by rim  32 . The tank  12  is deep enough to allow an object to be dipped into the tank and printed via dip transfer printing without the object impacting the bottom or sides of the tank. Dividing bars  34  and  36  are positionable across the top  30  of the tank for dividing the surface of the water  14  of the tank into different sections for isolating printed sheets floating on the water in the tank.  
      As shown in  FIGS. 2-4 , the activator applicator  16  generally comprises a track  38  extending along one side panel  24  of the dip tank  12 , a cantilever transport  40  engaged with the track, a sprayer  42  mounted to the cantilever for applying activator, and a rodless pneumatic cylinder  44  for driving the cantilever transport along the track. As will be explained in more detail below, the cantilever arrangement of the activator applicator  16  provides a smooth, controllable transport for the activator sprayer  42 . This arrangement provides superior control for activator application because it travels smoothly without binding and is easily controlled for providing appropriate amounts of activator to the ink image and applying the activator more uniformly. The result is more consistently high quality printing.  
      The track  38  of the activator applicator  16  comprises a pair of parallel, spaced bars  46  and  48  extending along the one side panel  24  of the dip tank  12  between mounting blocks  50  and  52 . The mounting blocks  50  and  52  are secured to the rim  32  of the dip tank  12  with a bracket  54  which extends downwardly from the rim along the exterior of the dip tank. The parallel bars  46  and  48  of the track  38  desirably have at least one flat surface  56  and  58  and, in  FIG. 4 , the parallel bars have a square cross-section with the four flat sides angled with respect to the adjacent side panel  24  of the dipping tank  12 .  
      The cantilever transport  40  comprises a mounting member  60  engaged with the track  38  for reciprocating movement along the track and a projecting member  62  extending from the mounting member above the track and over the open top  30  of the dip tank  12  to a free distal end  64 .  
      The mounting member  60  of the cantilever transport  40  includes an S-shaped portion  66  for engaging the track  38 . The S-shaped portion  66  comprises a lower panel  68  extending diagonally and upwardly toward the dip tank, a middle panel  70  extending diagonally and outwardly from the lower panel, and an upper panel  72  extending diagonally and inwardly toward the dip tank from the middle panel. A vertical portion  74  extends vertically upwardly from the upper panel  72  to the projecting member  62 . The mounting member  60  also includes a first wheel  76  rotably mounted to the lower panel  68  with a hub  78  and a second wheel  80  rotably mounted to the middle panel  70  of the mounting member with another hub  82 . The first wheel  76  is arranged to travel along the flat surface  56  of the first parallel bar  46  of the track  38  and the second wheel  80  is arranged so as to travel along the flat surface  58  of the second parallel bar  48  of the track. The wheels  76  and  80  are arranged so that they carry the weight of the cantilever transport  40  as the cantilever transport travels back and forth along the track  38 .  
      A support rod  84  extends from the vertical portion  74  of the mounting member  60  to the projecting member  62  for stabilizing the projecting member.  
      The sprayer  42  of the activator applicator  16  includes a plurality of spray heads  86  mounted to and spaced along the projecting member  62  of the cantilever transport  40 . The spray heads  86  are arranged so that nozzles  87  are directed downwardly for spraying activator onto the ink image floating on water in the dip tank  12 . Liquid activator is fed under a hydraulic pressure through tubing (not shown) to a manifold  88  mounted to the mounting member  60  of the cantilever transport  40  and then through additional tubing to the spray heads  86 . Pressurized air for pneumatic control of the spray heads is fed through another manifold  90  mounted to the mounting member  60  and then to the spray heads  86  through flexible tubing. The spray heads  86  could also be electrically activated. The spray heads and nozzles  87  are sized and arranged so as to uniformly apply an appropriate amount of activtaor to the ink image to the dip tank  12  at an appropriate rate.  
      As best shown in  FIG. 4 , the rodless pneumatic cylinder  44  includes a connector  92  which engages the middle panel  70  of the cantilever transport mounting member  60  and connects to a Teflon slide block  96  which fits between the middle panel of the mounting member and the second bar  48  of the track  38 . Pressurized air is supplied to each end of the rodless pneumatic cylinder  44  and drives the connector  92  and the cantilever transport  40  back and forth along the track  38 .  
      A position sensor  98  extends from the mounting member  60  below the projecting member  62  for sensing the position of the cantilever transport  40  relative to the dip tank  12 . The position sensor  98  sends a signal to a controller for controlling the movement and position of the cantilever transport. The design of the control system for the printing system  10  is well within ordinary skill and is not described herein in detail. Generally described, the control system is set to control the speed and position of the cantilever transport  40  and the rate of delivery of liquid activator through the nozzles  87  of the spray heads  86 .  
      The operation of the printing system  10  is as follows. First, the dip tank  12  is filled with water and the speed of the cantilever transport  40  and the rate of liquid activator delivery through the spray heads  86  are set. A sheet of water soluble film, such as polyvinyl acetate, is printed with an organic solvent ink and then placed ink side up and water soluble film side down onto the surface of water in the dipping tank  12 . The cantilever transport  40  then travels along the track  38  over the dipping tank  12  and sprays activator on the organic solvent ink image. The activator, which is an organic solvent such as xylene, dissolves and liquefies the ink image. An object to be printed is then dipped through the liquefied ink image into the water in the dipping tank and removed. The ink in the dipping tank wraps around and adheres to the object as the object is dipped into the tank through the ink image. Any remaining water soluble film is washed off of the object and the printed object is then allowed to dry. The object may then be coated with a protective top coat such as a lacquer, if desired.  
      The track  38  and the cantilever transport  40  arrangement provides for a smoother and steady movement of the sprayer  42  back and forth along the dip tank  12 . Because there is only a single track  38  and the weight of the cantilever transport  40  and sprayer  42  rests on the wheels of the cantilever transport, the activator applicator  16  travels smoothly and uniformly and does not bind.  
      Although the printing system  10  described above is a dip printing system, this invention encompasses other transfer printing processes including the use of water-based inks and activators.  
       FIGS. 5 and 6  illustrate a printing system  100  made according to another embodiment of this invention. This embodiment  100  comprises a support  101 , which is a dipping tank for holding water  102  for supporting a sheet printed with an ink image. The tank  101  has substantially the same structure as the dipping tank  12  described in the previous embodiment. As such, the dipping tank  101  comprises side panels  104  and  106  and end panels  108  and  110 . It should be understood, however, that the support surface for the printed ink image can also be a hard surface for printing methods other than transfer dip printing.  
      The embodiment illustrated in  FIGS. 5 and 6  also includes a cantilever structure  111  mounted to one end  108  of the dipping tank  101 . The cantilever comprises an actuator  112  mounted to a bracket  114  connected to the one end panel  106  of the dipping tank  101 . The actuator  112  drives a telescoping rod  116  which is extendable by the actuator from one end  108  of dipping tank to the opposite end  110  of the dipping tank. A sprayer mounting member  118  is mounted to the telescoping rod  116  and carries spray heads  120 . The telescoping rod  116  carries the spray heads back and forth over the dipping tank  101  for depositing activator on an ink image floating on water in the dipping tank. The operation of this alternative embodiment is the same as for the printing system  10  illustrated in  FIG. 1  except for the mechanism for reciprocating the spray heads.  
      A printing system  128  made in accordance still another embodiment of this invention is illustrated in  FIGS. 7 and 8 . This printing system  128  has the same structure and operation as the system  10  illustrated in  FIG. 1  with some exceptions as described below.  
      The printing system  128  illustrated in  FIGS. 7 and 8  comprises a dipping tank  130  for holding water  132  for supporting sheets of water soluble film printed with organic solvent based ink. The dipping tank  130  is rectangular in cross-section and comprises side panels  134  and  136  and end panels  138  and  140 . A cantilever  142  comprises a mounting member  144  mounted to one end panel  138  of the dipping tank  130  and a projecting member  146  extending from the mounting member over the dipping tank  130 . The projecting member  146  comprises a rodless pneumatic cylinder  148  which extends along the length of the dipping tank  138  between the side panels  134  and  136  of the dipping tank. A sprayer mounting member  150  is mounted on the rodless cylinder  148  and a plurality of spray heads  152  are mounted on the sprayer mounting member. The rodless pneumatic cylinder  148  drives the sprayer mounting member  150  and the spray heads back and forth along the projecting member  146  while the spray heads deliver liquid activator to the ink images floating on the water in the dipping tank  130 .  
      It should be understood that the foregoing relates to the particular embodiments of the present invention, and that numerous changes may be made therein without departing from the scope of the invention as defined by the following claims.