Patent Publication Number: US-2012026252-A1

Title: Printing method using moving liquid curtain catcher

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly-assigned, U.S. patent application Ser. No. ______ (Docket 95512), entitled “MOVING LIQUID CURTAIN CATCHER” filed concurrently herewith. 
     FIELD OF THE INVENTION 
     This invention relates generally to the field of digitally controlled printing systems, and in particular to continuous printing systems. 
     BACKGROUND OF THE INVENTION 
     Continuous inkjet printing uses a pressurized liquid source that produces a stream of drops some of which are selected to contact a print media (often referred to a “print drops”) while other drops are selected to be collected and either recycled or discarded (often referred to as “non-print drops”). For example, when no print is desired, the drops are deflected into a capturing mechanism (commonly referred to as a catcher, interceptor, or gutter) and either recycled or discarded. When printing is desired, the drops are not deflected and are allowed to strike a print media. Alternatively, deflected drops can be allowed to strike the print media, while non-deflected drops are collected in the capturing mechanism. 
     Drop placement accuracy of print drops is critical in order to maintain image quality. Liquid drop build up on the drop contact face of the catcher can adversely affect drop placement accuracy. For example, print drops can collide with liquid that accumulates on the drop contact face of the catcher. As such, there is an ongoing need to provide an improved catcher for these types of printing systems. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present in invention, a method of printing is includes providing liquid drops travelling along a first path using a jetting module. A moving liquid curtain is provided using a liquid source. Selected liquid drops are caused to deviate from the first path and begin travelling along a second path using a deflection mechanism such that the liquid drops travelling along one of the first path and the second path contact the liquid curtain in a drop interception region of the liquid curtain. The liquid curtain is collected downstream from the drop interception region using a liquid collection device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the detailed description of the example embodiments of the invention presented below, reference is made to the accompanying drawings, in which: 
         FIG. 1  is a simplified schematic block diagram of an example embodiment of a printing system made in accordance with the present invention; 
         FIG. 2  is a schematic view of an example embodiment of a continuous printhead made in accordance with the present invention; 
         FIG. 3  is a schematic view of an example embodiment of a continuous printhead made in accordance with the present invention; 
         FIG. 4  is a schematic cross sectional view of a printhead including an example embodiment of the present invention; 
         FIG. 5  is a schematic cross sectional view of another example embodiment of the present invention; 
         FIG. 6  is a schematic cross sectional view of another example embodiment of the present invention; 
         FIG. 7  is a schematic cross sectional view of another example embodiment of the present invention; 
         FIG. 8  is a schematic cross sectional view of another example embodiment of the present invention; and 
         FIG. 9  is a schematic front view of the example embodiment shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. In the following description and drawings, identical reference numerals have been used, where possible, to designate identical elements. 
     The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of the ordinary skills in the art will be able to readily determine the specific size and interconnections of the elements of the example embodiments of the present invention. 
     As described herein, the example embodiments of the present invention provide a printhead or printhead components typically used in inkjet printing systems. However, many other applications are emerging which use inkjet printheads to emit liquids (other than inks) that need to be finely metered and deposited with high spatial precision. As such, as described herein, the terms “liquid” and “ink” refer to any material that can be ejected by the printhead or printhead components described below. 
     Referring to  FIGS. 1 through 3 , example embodiments of a printing system and a continuous printhead are shown that include the present invention described below. It is contemplated that the present invention also finds application in other types of continuous printheads or jetting modules. 
     Referring to  FIG. 1 , a continuous printing system  20  includes an image source  22  such as a scanner or computer which provides raster image data, outline image data in the form of a page description language, or other forms of digital image data. This image data is converted to half-toned bitmap image data by an image processing unit  24  which also stores the image data in memory. A plurality of drop forming mechanism control circuits  26  read data from the image memory and apply time-varying electrical pulses to a drop forming mechanism(s)  28  that are associated with one or more nozzles of a printhead  30 . These pulses are applied at an appropriate time, and to the appropriate nozzle, so that drops formed from a continuous ink jet stream will form spots on a recording medium  32  in the appropriate position designated by the data in the image memory. 
     Recording medium  32  is moved relative to printhead  30  by a recording medium transfer system  34 , which is electronically controlled by a recording medium transfer control system  36 , and which in turn is controlled by a micro-controller  38 . The recording medium transfer system shown in  FIG. 1  is a schematic only, and many different mechanical configurations are possible. For example, a transfer roller could be used as recording medium transfer system  34  to facilitate transfer of the ink drops to recording medium  32 . Such transfer roller technology is well known in the art. In the case of page width printheads, it is most convenient to move recording medium  32  past a stationary printhead. However, in the case of scanning print systems, it is usually most convenient to move the printhead along one axis (the sub-scanning direction) and the recording medium along an orthogonal axis (the main scanning direction) in a relative raster motion. 
     Ink is contained in an ink reservoir  40  and is supplied under pressure to the manifold  47  of the printhead  30  to cause streams of ink to flow from the nozzles of the printhead. In the non-printing state, continuous inkjet drop streams are unable to reach recording medium  32  due to a catcher  42  that blocks the stream and which may allow a portion of the ink to be recycled by an ink recycling unit  44 . The ink recycling unit reconditions the ink and feeds it back to reservoir  40 . Such ink recycling units are well known in the art. The ink pressure suitable for optimal operation will depend on a number of factors, including geometry and thermal properties of the nozzles and thermal properties of the ink. A constant ink pressure can be achieved by applying pressure to ink reservoir  40  under the control of ink pressure regulator  46 . Alternatively, the ink reservoir can be left unpressurized, or even under a reduced pressure (vacuum), and a pump is employed to deliver ink from the ink reservoir under pressure to the printhead  30 . In such an embodiment, the ink pressure regulator  46  can include an ink pump control system. 
     The ink is distributed to printhead  30  through an ink manifold  47  which is sometimes referred to as a channel. The ink preferably flows through slots or holes etched through a silicon substrate of printhead  30  to its front surface, where a plurality of nozzles and drop forming mechanisms, for example, heaters, are situated. When printhead  30  is fabricated from silicon, drop forming mechanism control circuits  26  can be integrated with the printhead. Printhead  30  also includes a deflection mechanism which is described in more detail below with reference to  FIGS. 2 and 3 . 
     Referring to  FIG. 2 , a schematic view of continuous liquid printhead  30  is shown. A jetting module  48  of printhead  30  includes an array or a plurality of nozzles  50  formed in a nozzle plate  49 . In  FIG. 2 , nozzle plate  49  is affixed to jetting module  48 . However, as shown in  FIG. 3 , nozzle plate  49  can be an integral portion of the jetting module  48 . 
     Liquid, for example, ink, is emitted under pressure through each nozzle  50  of the array to form streams, commonly referred to as jets or filaments, of liquid  52 . In  FIG. 2 , the array or plurality of nozzles extends into and out of the figure. Typically, the orifice size of nozzle  50  is from about 5 μm to about 25 μm. 
     Jetting module  48  is operable to form liquid drops having a first size or volume and liquid drops having a second size or volume through each nozzle. To accomplish this, jetting module  48  includes a drop stimulation or drop forming device  28 , for example, a heater, a piezoelectric actuator, or an electrohydrodynamic stimulator that, when selectively activated, perturbs each jet of liquid  52 , for example, ink, to induce portions of each jet to break-off from the jet and coalesce to form drops  54 ,  56 . 
     In  FIG. 2 , drop forming device  28  is a heater  51 , for example, an asymmetric heater or a ring heater (either segmented or not segmented), located in a nozzle plate  49  on one or both sides of nozzle  50 . This type of drop formation is known with certain aspects having been described in, for example, one or more of U.S. Pat. No. 6,457,807 B1, issued to Hawkins et al., on Oct. 1, 2002; U.S. Pat. No. 6,491,362 B1, issued to Jeanmaire, on Dec. 10, 2002; U.S. Pat. No. 6,505,921 B2, issued to Chwalek et al., on Jan. 14, 2003; U.S. Pat. No. 6,554,410 B2, issued to Jeanmaire et al., on Apr. 29, 2003; U.S. Pat. No. 6,575,566 B1, issued to Jeanmaire et al., on Jun. 10, 2003; U.S. Pat. No. 6,588,888 B2, issued to Jeanmaire et al., on Jul. 8, 2003; U.S. Pat. No. 6,793,328 B2, issued to Jeanmaire, on Sep. 21, 2004; U.S. Pat. No. 6,827,429 B2, issued to Jeanmaire et al., on Dec. 7, 2004; and U.S. Pat. No. 6,851,796 B2, issued to Jeanmaire et al., on Feb. 8, 2005. 
     Typically, one drop forming device  28  is associated with each nozzle  50  of the nozzle array. However, a drop forming device  28  can be associated with groups of nozzles  50  or all of nozzles  50  of the nozzle array. 
     When printhead  30  is in operation, drops  54 ,  56  are typically created in a plurality of sizes or volumes, for example, in the form of large drops  56  having a first size or volume, and small drops  54  having a second size or volume. The ratio of the mass of the large drops  56  to the mass of the small drops  54  is typically approximately an integer between 2 and 10. A drop stream  58  including drops  54 ,  56  follows a drop path, commonly referred to as a trajectory,  57 . Typically, drop sizes are from about 1 pL to about 20 pL. 
     Printhead  30  also includes a gas flow deflection mechanism  60  that directs a flow of gas  62 , for example, air, past a portion of the drop trajectory  57 . This portion of the drop trajectory is called the deflection zone  64 . As the flow of gas  62  interacts with drops  54 ,  56  in deflection zone  64  it alters the drop trajectories. As the drop trajectories pass out of the deflection zone  64  they are travelling at an angle, called a deflection angle, relative to the un-deflected drop trajectory  57 . 
     Small drops  54  are more affected by the flow of gas than are large drops  56  so that the small drop path, commonly referred to as a trajectory,  66  diverges from the large drop path or trajectory  68 . That is, the deflection angle for small drops  54  is larger than for large drops  56 . The flow of gas  62  provides sufficient drop deflection and therefore sufficient divergence of the small and large drop trajectories so that catcher  42  (shown in  FIGS. 1 and 3 ) can be positioned to intercept one of the small drop trajectory  66  and the large drop trajectory  68  so that drops following the trajectory are collected by catcher  42  while drops following the other trajectory bypass the catcher and impinge a recording medium  32  (shown in  FIGS. 1 and 3 ). 
     When catcher  42  is positioned to intercept large drop trajectory  68 , small drops  54  are deflected sufficiently to avoid contact with catcher  42  and strike recording medium  32 . As the small drops are printed, this is called small drop print mode. When catcher  42  is positioned to intercept small drop trajectory  66 , large drops  56  are the drops that print. This is referred to as large drop print mode. 
     Referring to  FIG. 3 , jetting module  48  includes an array or a plurality of nozzles  50 . Liquid, for example, ink, supplied through channel  47  (shown in  FIG. 2 ), is emitted under pressure through each nozzle  50  of the array to form jets of liquid  52 . In  FIG. 3 , the array or plurality of nozzles  50  extends into and out of the figure. 
     Drop stimulation or drop forming device  28  (shown in  FIGS. 1 and 2 ) associated with jetting module  48  is selectively actuated to perturb the jet of liquid  52  to induce portions of the jet to break off from the jet to form drops. In this way, drops are selectively created in the form of large drops and small drops that travel toward a recording medium  32 . 
     Positive pressure gas flow structure  61  of gas flow deflection mechanism  60  is located on a first side of drop trajectory  57 . Positive pressure gas flow structure  61  includes first gas flow duct  72  that includes a lower wall  74  and an upper wall  76 . Gas flow duct  72  directs gas flow  62  supplied from a positive pressure source  92  at downward angle θ of approximately 45° relative to the stream of liquid  52  toward drop deflection zone  64  (also shown in  FIG. 2 ). Optional seal(s)  84  provides an air seal between jetting module  48  and upper wall  76  of gas flow duct  72 . 
     Upper wall  76  of gas flow duct  72  does not need to extend to drop deflection zone  64  (as shown in  FIG. 2 ). In  FIG. 3 , upper wall  76  ends at a wall  96  of jetting module  48 . Wall  96  of jetting module  48  serves as a portion of upper wall  76  ending at drop deflection zone  64 . 
     Negative pressure gas flow structure  63  of gas flow deflection mechanism  60  is located on a second side of drop trajectory  57 . Negative pressure gas flow structure includes a second gas flow duct  78  located between catcher  42  and an upper wall  82  that exhausts gas flow from deflection zone  64 . Second duct  78  is connected to a negative pressure source  94  that is used to help remove gas flowing through second duct  78 . Optional seal(s)  84  provides an air seal between jetting module  48  and upper wall  82 . 
     As shown in  FIG. 3 , gas flow deflection mechanism  60  includes positive pressure source  92  and negative pressure source  94 . However, depending on the specific application contemplated, gas flow deflection mechanism  60  can include only one of positive pressure source  92  and negative pressure source  94 . 
     Gas supplied by first gas flow duct  72  is directed into the drop deflection zone  64 , where it causes large drops  56  to follow large drop trajectory  68  and small drops  54  to follow small drop trajectory  66 . As shown in  FIG. 3 , small drop trajectory  66  is intercepted by a front face  90  of catcher  42 . Small drops  54  contact face  90  and flow down face  90  and into a liquid return duct  106  located or formed between catcher  42  and a plate  88 . Collected liquid is either recycled and returned to ink reservoir  40  (shown in  FIG. 1 ) for reuse or discarded. Large drops  56  bypass catcher  42  and travel on to recording medium  32 . Alternatively, catcher  42  can be positioned to intercept large drop trajectory  68 . Large drops  56  contact catcher  42  and flow into a liquid return duct located or formed in catcher  42 . Collected liquid is either recycled for reuse or discarded. Small drops  54  bypass catcher  42  and travel on to recording medium  32 . 
     Alternatively, deflection can be accomplished by applying heat asymmetrically to a jet of liquid  52  using an asymmetric heater  51 . When used in this capacity, asymmetric heater  51  typically operates as the drop forming mechanism in addition to the deflection mechanism. This type of drop formation and deflection is known having been described in, for example, U.S. Pat. No. 6,079,821, issued to Chwalek et al., on Jun. 27, 2000. Deflection can also be accomplished using an electrostatic deflection mechanism. Typically, the electrostatic deflection mechanism either incorporates drop charging and drop deflection in a single electrode, like the one described in U.S. Pat. No. 4,636,808, or includes separate drop charging and drop deflection electrodes. 
     Referring to  FIGS. 4 through 9 , example embodiments of the present invention are shown. Generally described, a printhead made in accordance with the present invention includes a jetting module that forms liquid drops travelling along a first path. A deflection mechanism causes selected liquid drops ejected by the jetting module to deviate from the first path and begin travelling along a second path. A moving liquid curtain is positioned relative to the first path such that the liquid drops travelling along one of the first path and the second path contact and coalesce into the liquid curtain in a drop interception region of the liquid curtain. A liquid collection device is positioned to collect the liquid curtain downstream from the drop interception region. 
     Referring to  FIG. 4 , a cross-sectional view of printhead  30  including an example embodiment of the present invention is shown in more detail. As described above, jetting module  48  forms drops  54 ,  56  travelling along drop trajectory  57  (shown in  FIGS. 2 and 3 ). Gas flow deflection mechanism  60  deflects drops  54 ,  56  such that drops  54  begin travelling along small drop trajectory  66  and drops  56  begin travelling along large drop trajectory  68  (shown in  FIGS. 2 and 3 ). Catcher  42 , positioned downstream from gas flow deflection mechanism  60  relative to trajectory  57 , includes a liquid manifold  100 , a moving liquid curtain  102 , a liquid deflector structure  104 , and a liquid return  106 . Liquid manifold  100  includes a liquid inlet  108  and a liquid outlet  110 . Liquid outlet  110  is formed by attaching a spacer  116  and a cover  118  to liquid manifold  100 . Cover  118  helps guide liquid toward liquid deflector structure  104  or liquid return  106 . Alternatively, liquid manifold  100  and cover  118  can be an integrally formed one piece structure. Liquid deflector structure  104  and liquid return  106  are included in the liquid collection device described above. 
     Liquid from a liquid source  112  is pressurized using a pump, for example, or another type of liquid pressurization device  134  and provided to liquid manifold  100  through liquid inlet  108 . The pressurized liquid flows toward liquid outlet  110  (indicated in each FIG. by arrow  111 ). As the pressurized liquid exits liquid manifold  100  through liquid outlet  110 , a moving liquid curtain  102  is created. Moving liquid curtain  102  is positioned substantially parallel to trajectory (first path)  57 . Typically, the angle between liquid curtain  102  and trajectory  57  is within ±20° from parallel. Non-printing drops, drops  54  as shown in  FIG. 4 , contact liquid curtain  102  in a drop interception region of liquid curtain  102 . In this sense, liquid curtain  102  functions as the drop contact face  90  (shown in  FIG. 3 ) of catcher  42 . Typically, non-printing drops contact liquid curtain  102  in a region of liquid curtain  102  that is upstream from liquid deflector structure  104 . However, the drop interception region of liquid curtain  102  can be any portion of liquid curtain  102  between liquid outlet  110  and liquid return  106 . 
     Moving liquid curtain  102  continues along its travel path until liquid curtain  102  contacts liquid deflector structure  104 . Liquid deflector structure  104  causes liquid curtain to change direction and move toward liquid return  106 . A vacuum source  114  applies a vacuum to liquid return  106  to assist with liquid removal in liquid return  106  and liquid removal away from liquid deflector structure  104 . Typically, the liquid of liquid curtain  102  is the same liquid as that of the liquid drops  54 ,  56 . However, the liquid used for liquid curtain  102  can be different than that of liquid drops  54 ,  56 . 
     Liquid outlet  110  includes a width  132  dimension that extends in a direction substantially perpendicular to trajectory or first path  57 . Outlet width  132  determines the thickness of liquid film  102 . Outlet width  132  can vary and depends on the width of spacer  116 . Typically, the thickness of moving (flowing) liquid curtain  102  is selected such that variations in the liquid thickness and flow rate resulting from the non-printing drops coalescing with liquid curtain  102  are only small perturbations to liquid curtain  102  that have a minimal effect on the overall characteristics of liquid curtain  102 . 
     Referring to  FIG. 5 , another example embodiment of catcher  42  is shown. In this embodiment, liquid outlet  110  is formed in a discrete component  120  that is attached to liquid manifold  100 . A portion of component  120  is curved so that liquid curtain  102  can be positioned substantially parallel to the first path or trajectory described above. As shown in  FIG. 5 , liquid manifold  100  includes a filter  122  that filters the liquid prior to it exiting liquid outlet  110 . Alternatively, component  120  can include filter  122 , or both component  120  and manifold  100  can include filters. 
     Referring to  FIGS. 6 and 7 , and back to  FIGS. 4 and 5 , liquid curtain  102  is travelling in a direction (indicated in each FIG. by arrow  124 ). The liquid collection device of catcher  42  includes a structure positioned to contact liquid curtain  102  to change the direction of travel of liquid curtain  102  after liquid curtain  102  has collected the non-printing liquid drops (indicated in each FIG. by arrow  136 ). As shown in  FIGS. 4 through 7 , that structure is liquid deflector structure  104 . Liquid deflector structure  104  includes a curved surface  126  around which liquid curtain  102  contacts to change direction. Curved surface  126  can be a stationary surface as shown in  FIGS. 4 and 5  or a moving surface as shown in  FIG. 6 . When curved surface  126  is moving, curved surface  126  typically moves in the same direction as liquid curtain  102  in order to minimize turbulent interaction between curved surface  126  and liquid curtain  102 . Curved surface can be driven using a motor. As shown in  FIG. 6 , curved surface  126  is circular and movement of curved surface  126  is a rotational movement. As shown in  FIG. 7 , liquid deflector structure  104  includes a porous face  128  that contacts liquid curtain  102 . Porous face  128  helps to minimize turbulent liquid curtain  102  curved surface  126  interaction by removing some of the liquid of liquid curtain as it contacts porous face  128 . Porous face  128  is in liquid communication with liquid removal channel  106 . For each of these embodiments, the curvature of the curved surface  126  of liquid deflector structure  104  is application dependent and is typically determined by one of more of several factors including, for example, the properties of the liquid, liquid curtain thickness, liquid curtain velocity, and the amount of liquid curtain—liquid deflector structure overlap. 
     As shown in  FIGS. 4 through 7 , the liquid collection device of catcher  42  also includes liquid return channel  106  that receives liquid curtain  102  after liquid curtain  102  changes direction. When the liquid of the liquid curtain is the same liquid as that of the liquid drops (printed or non-printed), liquid return channel  106  typically returns the liquid to recycling unit  44  so that the liquid can be used again. Alternatively, liquid return channel  106  can deliver the liquid to a storage container so that it can be discarded. 
     Liquid curtain  102  is not supported by structure on the side of liquid curtain  102  that is opposite the drop contact face  90  of liquid curtain  102 . As such, liquid curtain  102  does not flow over or down a structure on the side of liquid curtain  102  that is opposite the drop contact face  90  of liquid curtain  102 . However, in some example embodiments of the present invention, catcher  42  includes structure  130  positioned to maintain the width of liquid curtain  102 . Typically, liquid curtain  102  extends beyond both ends nozzle array  50  of jetting module  48 . Maintaining the width of liquid curtain  102 , using edge guides as shown in  FIGS. 8 and 9 , for example, helps to ensure that liquid curtain  102  has consistent liquid properties, such as thickness and velocity from one end of the liquid curtain to the other end of the liquid curtain across the width of the nozzle array so that non-printing drops encounter the same consistency of liquid regardless of where contact with liquid curtain  102  occurs. 
     Referring back to  FIGS. 4 through 9 , liquid curtain  102  travels from liquid outlet  110  to liquid return channel  106  at a velocity. The specific velocity typically depends on the application contemplated with several factors taken into consideration. These factors can include, for example, print speed, printed liquid, for example, ink characteristics, and desired image quality. Printhead  30  includes a mechanism that regulates the velocity of liquid curtain  102 . This mechanism can be the device, for example, the pump, that pressurizes the liquid that forms liquid curtain  102 . Regulation of the velocity of the liquid curtain can occur throughout the printing operation such that the velocity is changed more then once depending on printing conditions. Alternatively, regulation of the velocity can occur once, typically, at the beginning of a printing operation. Preferably, the velocity of the moving liquid curtain is within ±50% of the velocity of the collected drops and, more preferably, the velocity of the moving liquid curtain is substantially the same as the speed of the collected drops and, more preferably, the velocity of the flowing liquid curtain is the same as the component of the drop velocity in the direction of liquid curtain flow. 
     Referring back to  FIGS. 1-9 , a printing operation of the printing system  20  will be described. Liquid drops are provided, travelling along a first path, using a jetting module. Typically, this is accomplished using one of the techniques described above. A moving liquid curtain is provided using a liquid source. This is accomplished by pressurizing the liquid to create the liquid curtain. Selected liquid drops are caused to deviate from the first path and begin travelling along a second path using a deflection mechanism such that the liquid drops travelling along one of the first path and the second path contact the liquid curtain in a drop interception region of the liquid curtain. Deflection of the selected drops is typically accomplished using one of the techniques described above. The liquid curtain is collected downstream from the drop interception region using a liquid collection device. 
     Collecting the liquid curtain downstream from the drop interception region can include changing the direction of travel of the liquid curtain after the liquid curtain has collected the liquid drops. This can be accomplished by causing the liquid curtain to contact a portion of the liquid collection device. When this is done, the liquid curtain can be caused to contact a curved surface around which the liquid curtain changes direction. The curved surface can be caused to move in the same direction as the liquid curtain. This can include driving the curved surface. After the liquid curtain changes direction, the liquid curtain is caused to flow through a liquid return channel. 
     The velocity of the liquid curtain can be regulated using a regulating mechanism. This mechanism can be the device, for example, the pump, that pressurizes the liquid that forms liquid curtain. Regulation of the velocity of the liquid curtain can occur throughout the printing operation such that the velocity is changed more then once depending on printing conditions. Alternatively, regulation of the velocity can occur once, typically, at the beginning of a printing operation. Preferably, the velocity of the moving liquid curtain is within ±50% of the velocity of the collected drops and, more preferably, the velocity of the moving liquid curtain is substantially the same as the speed of the collected drops and, more preferably, the velocity of the flowing liquid curtain is the same as the component of the drop velocity in the direction of liquid curtain flow. 
     In some example embodiments, providing the moving liquid curtain includes positioning the moving liquid curtain substantially parallel relative to the first path. In the same or other example embodiments, the width of the liquid curtain is maintained using suitably designed structures or devices. Typically, it is preferable that the liquid of the liquid curtain is the same liquid as that of the liquid drops. 
     The moving liquid curtain catcher  42  of the present invention is also suitable for use when high viscosity liquids are being supplied to and ejected by printhead  30 . In applications where a high viscosity liquid is being used for the print and non-print liquid drops, the viscosity of liquid curtain  102  can be lower than the viscosity of the liquid drops. This is done to facilitate movement of the higher viscosity print and non-print liquid drops along the surface of liquid curtain  102  of catcher  42 . A heater can be incorporated into the liquid source  112  to heat the liquid supplied to the liquid manifold  100  and thereby lower the viscosity of the liquid curtain liquid. Alternatively, the catcher  42  or the liquid manifold  100  can include heaters to heat the liquid as it passes through the liquid manifold  100 . In another embodiment, the liquid supplied to the liquid manifold can be distinct from the liquid of the print and non-print drops with the liquid supplied to the liquid manifold having the lower viscosity. Catcher  42  of the present invention finds application, for example, when liquids such as hot melt liquids are used. Typically, these liquids have a rapid increase in viscosity when they contact a relatively cooler catcher face. When used with such liquids, the curtain liquid can be heated to keep the liquid above the gelling or solidifying temperature. 
     The example embodiments of catcher  42  can be made using conventional fabrication techniques. For example, porous surface  104 , spacer  116 , or cover  118  can be made of photo etched stainless steel, electroformed Ni, or laser abated metal, ceramics, or plastics. Alternatively, the components of catcher  42  can be made using conventional MEMS processing techniques in silicon or other suitable materials. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
     PARTS LIST 
     
         
         
           
               20  continuous printing system 
               22  image source 
               24  image processing unit 
               26  mechanism control circuits 
               28  device 
               30  printhead 
               32  recording medium 
               34  recording medium transfer system 
               36  recording medium transfer control system 
               38  micro-controller 
               40  reservoir 
               42  catcher 
               44  recycling unit 
               46  pressure regulator 
               47  manifold 
               48  jetting module 
               49  nozzle plate 
               50  nozzle 
               51  heater 
               52  liquid 
               53  liquid chamber 
               54  drops 
               56  drops 
               57  trajectory 
               58  drop stream 
               60  gas flow deflection mechanism 
               61  positive pressure gas flow structure 
               62  gas 
               63  negative pressure gas flow structure 
               64  deflection zone 
               66  small drop trajectory 
               68  large drop trajectory 
               72  first gas flow duct 
               74  lower wall 
               76  upper wall 
               78  second gas flow duct 
               82  upper wall 
               84  seal 
               88  plate 
               90  catcher face 
               92  positive pressure source 
               94  negative pressure source 
               96  wall 
               100  liquid manifold 
               102  moving liquid curtain 
               104  liquid deflector structure 
               106  liquid return 
               108  liquid inlet 
               110  liquid outlet 
               111  arrow 
               112  liquid source 
               114  vacuum source 
               116  spacer 
               118  cover 
               120  discrete component 
               122  filter 
               124  arrow 
               126  curved surface 
               128  porous face 
               130  structure 
               132  outlet width 
               134  liquid pressurization device 
               136  arrow