Abstract:
A system and method of aligning a charge tunnel of a continuous inkjet printer with a drop generator and a catcher, wherein the charge tunnel passes through an outer wall of a charge tunnel unit, including adjusting a linear position of the charge tunnel unit, and adjusting a rotary position of the charge tunnel unit. The adjusting steps are performed to ensure that the charge tunnel is aligned with the drop generator and the catcher.

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 11/154,290 entitled “System for Aligning a Charge Tunnel of an Ink Jet Printer,” filed Jun. 16, 2005, which relates to and claims priority benefits from U.S. Provisional Patent Application No. 60/580,976 entitled “System for Aligning a Charge Tunnel of an Ink Jet Printer,” filed Jun. 17, 2004, both of which are incorporated by reference herein in its entireties. 

   BACKGROUND OF THE INVENTION 
   Embodiments of the present invention generally relate to a continuous ink jet printer in which a stream of ink is broken into individual droplets which are then charged and deflected as required in order to form indicia on a substrate. In particular, embodiments of the present invention relate to a system for aligning a charge tunnel with other components of an ink jet printer. 
   A continuous inkjet printhead typically incorporates a drop generator having a nozzle that breaks an ink stream into uniformly spaced droplets. The ink drops can typically vary in diameter from 0.003-0.009 inch. The ink drops formed by a nozzle are charged in a charge tunnel which allows them to be deflected in a high voltage field to desired spots on a substrate. For optimum charging of drops, the charge tunnel gap is as narrow as practical considerations allow. In order for the printhead to run clean, it is desirable to align the ink stream well centered in the charge tunnel and into the catcher to gather the non-deflected drops. 
   Typically, the components of a printhead, including the drop generator, the charge tunnel, and the catcher, need to be aligned properly during servicing and normal use, in order to ensure that the printing system operates properly. In order to properly align these components, many printing systems include additional alignment components used in conjunction with a printhead to properly align the ink stream. These components add size and expense to the printhead. 
   Thus, a need exists for an efficient and accurate way to align the printhead components. 
   BRIEF SUMMARY OF THE INVENTION 
   Certain embodiments of the present invention provide a charge tunnel alignment system including a charge tunnel main body, a charge tunnel unit, and first and second fasteners. The charge tunnel main body is defined by lower and upper surfaces, first and second sides, a drop entrance surface and a drop exit surface. A charge tunnel unit channel extends from the upper surface to the lower surface. 
   The charge tunnel unit is positioned within the charge tunnel unit channel. The charge tunnel unit includes an outer wall, a tab extending from the outer wall, and a charge tunnel passing through the outer wall. 
   The first fastener passes through the main body and operatively connects to the tab. The charge tunnel unit may be adjusted in a rotary fashion through an engagement of the first fastener. That is, the first fastener, such as a screw, may be engaged through a screw driver to tighten or loosen the fastener. 
   The second fastener passes through one of the first and second sides of the main body. The second fastener is operatively connected to the charge tunnel unit, such that when the second fastener is engaged, the charge tunnel unit adjusts the charge tunnel unit in either a lateral or radial direction. The second fastener may be a worm screw or camming device, and the charge tunnel unit further includes a reciprocal structure that operatively receives the second fastener. 
   The charge tunnel alignment system may also include a bracket defining a housing slot, wherein the charge tunnel housing is slidably retained within the housing slot. At least one bracket fastener may pass through the bracket and operatively connect to the upper surface of the charge tunnel housing. 
   Certain embodiments of the present invention provide a method of aligning a charge tunnel of a continuous inkjet printer with a drop generator and a catcher. The method includes adjusting a linear position of the charge tunnel unit, and adjusting a rotary position of the charge tunnel unit. The adjusting steps are performed to ensure that the charge tunnel is aligned with the drop generator and the catcher. The linear adjusting steps may occur in horizontal and vertical linear directions. Fasteners are engaged that are either directly or indirectly operatively connected to the charge tunnel unit. 
   The adjusting a linear position includes tightening a fastener that is operatively connected to the charge tunnel unit to move the charge tunnel unit in a first linear direction, and loosening the fastener to move the charge tunnel unit in a second linear direction. The adjusting a rotary position includes tightening a fastener that is operatively connected to the charge tunnel unit to move the charge tunnel unit in a first rotary direction, and loosening the fastener to move the charge tunnel unit in a second rotary direction. 

   
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  illustrates a schematic representation of a continuous ink jet printer. 
       FIG. 2  illustrates an isometric partially exploded view of a charge tunnel alignment system, according to an embodiment of the present invention. 
       FIG. 3  illustrates an isometric exploded view of a charge tunnel housing, according to an embodiment of the present invention. 
       FIG. 4  illustrates a top view of a charge tunnel alignment system, according to an embodiment of the present invention. 
       FIG. 5  illustrates a front view of a charge tunnel alignment system, according to an embodiment of the present invention. 
       FIG. 6  illustrates a top view of a charge tunnel alignment system and drop generator, according to an embodiment of the present invention. 
       FIG. 7  illustrates a side view of a charge tunnel alignment system and drop generator, according to an embodiment of the present invention. 
   

   The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentalities shown in the attached drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a schematic representation of a continuous ink jet printer  10 . The ink jet printer  10  includes a print head with a drop generator  14  connected to receive ink from an ink source  16 . The drop generator  14  incorporates a piezoelectric oscillator that creates perturbations in ink flow at a nozzle  18 . The nozzle  18  emits a stream  17  of uniformly sized and spaced drops  19 . The drops pass through a charging tunnel  22 , where a different charge can be applied to each drop  19 . The drops subsequently pass between a pair of opposed deflection electrodes  24  and  26 . A power source (not shown) is operatively connected to the deflection electrodes  24  and  26  such that a relatively uniform electric field extends between the electrodes  24  and  26 . The charge on a given drop determines the amount it deflects vertically as it passes between the electrodes  24  and  26 . Insulation  28  may be disposed on at least one of the electrodes  24  and  26  to prevent arcing between the deflection electrodes  24  and  26 , and also between the deflection electrodes  24 ,  26  and the charging tunnel  22 . 
   Uncharged or slightly charged drops  30  pass substantially undeflected to a catcher  32 , and are recycled to ink source  16 . Charged drops  34  are projected toward a substrate  36  and are deflected so as to have a trajectory striking the substrate  36  as the substrate  36  moves past the print head. The level of charge applied to the drop controls its vertical displacement/position on the substrate  36 . 
   The charge to be applied to a drop is determined by a controller  38 , which may be implemented by a device such as a general purpose processor, microcontroller, or embedded controller having appropriate input and output circuitry, as is well known in the art. The controller  38  operates under general program control of the instructions stored in an associated memory. The controller is programmed to deliver control signals to the charge tunnel  22  to control the charges applied to the individual drops  19  as they pass therethrough. The operation of such ink jet printers is well known in the art and, hence, will not be explained in greater detail. 
     FIG. 2  illustrates an isometric partially exploded view of a charge tunnel alignment system  40 , according to an embodiment of the present invention. The system  40  includes a bracket  42  and a charge tunnel housing  44 . The bracket  42  includes a main body  46  defined by a lower ledge  48  integrally formed with an upright member  50 , which is in turn integrally formed with an upper ledge  52 . A housing slot  54  is defined between the lower ledge  48 , the upright member  50  and the upper ledge  52 . The charge tunnel housing  44  is configured to be slidably retained within the housing slot  53 . That is, the charge tunnel housing  44  may slide in directions denoted by arrow C. 
     FIG. 3  illustrates an isometric exploded view of the charge tunnel housing  44 . The charge tunnel housing  44  includes a main body  54  having a lower surface  56  integrally formed with sides  58 ,  59 , a drop entrance surface  60 , a drop exit surface  62 , and a top surface  64 . A charge tunnel unit channel  66  extends from the top surface  64  to the lower surface  56 . The charge tunnel unit channel  66  is configured and sized to receive and retain a charge tunnel unit  68 . 
   The charge tunnel unit  68  includes a generally cylindrical main body  70  having an outer wall  77  integrally formed with an outwardly extending tab  72  located at an upper portion  74  of the charge tunnel unit  68 . The tab  72  has a fastener through hole  73  formed therethrough. The through hole  73  may be threaded to receive and retain a fastener, such as a screw. Optionally, the through hole  73  may be configured to receive and retain various other fasteners, such as bolts, clips, pins, and the like. The same holds true for other fastener through holes discussed below. 
   An upper cavity  76  is defined between the outer wall  77  and an intermediate surface  79 . A slot  78  is formed through the outer wall  77  of the main body  70  and defines the charge tunnel. That is, the slot  78  passes linearly through the main body  70 . A cavity  80  may be formed through the outer wall  77  and is perpendicularly oriented with respect to the slot  78 . The cavity  80  extends from the outer wall to a surface within the main body  70  to form a cupped cavity. Optionally, the cavity  80  may be a slightly recessed surface configured to engage a distal end of a fastener. 
   Fastener through holes  82  are formed through the top surface  64  proximate the drop entrance surface  60  and sides  58  and  59 . The through holes  82  are configured to receive and retain fasteners, such as screws, bolts, and the like. Additionally, a channel  84  is formed through the side  58  and is configured to be aligned with, and allow passage to, the cavity  80  formed in the main body  70  of the charge tunnel unit  68 . An additional through hole (not shown) is formed through the side  59 , and is configured to receive a fastener  86 . 
   The drop exit surface  62  includes a charged drop exit opening  87  that is configured to align with, and allow passage to, the slot (charge tunnel)  78  of the charge tunnel unit  68 . A channel  88  is formed through the drop exit surface  62  and extends into the charge tunnel unit channel  66 . Additionally, a fastener through hole  90 , which may extend into the change tunnel adjustment channel  66 , is formed below the channel  88 . A spring  92  is positioned within the channel  88 . A plate  94  having two holes  96  and  98  is positioned on the drop exit surface  62  so that the holes  96  and  98  are aligned with the channel  88  and through hole  90 , respectively. 
   A fastener  100  passes through the hole  96  and into the channel  88 , where the fastener  100  is securably retained (e.g., threadably secured to) by the through hole  73 , thereby exerting pressure on the spring  92 , and vice versa. The fastener  100  may be tightened or loosened, thereby providing a corresponding force on the spring  92 , which abuts the tab  72  around the through hole  73 , thereby exerting a force on the tab  72 . As the fastener  100  is operatively engaged (either by tightening or loosening), the tab  72  moves in response thereto. The spring  92  exerts a constant force against the tab  72  and against the plate  94  in the directions of arrow B. As the fastener  100  is tightened, the spring  92  compresses. As the fastener  100  is loosened, the spring  92  elongates. 
   Engagement of the fastener  100  causes the charge tunnel unit  68  to radially move (e.g., move in a rotary fashion) about a central axis X in the directions denoted by arrow A. As the fastener  100  is tightened, the fastener  100  draws the tab  72  toward the drop exit surface  62  in the direction of A′. Thus, the entire charge tunnel unit  68  moves in response. As the fastener  100  is loosened, the fastener  100  begins to retreat from the through hole  73 , such that the spring  92  (and the movement of the fastener  100  through the through hole  73 ) forces the tab  72  to recede in the direction of A″, thereby causing a corresponding movement in the charge adjustment member  68 . As such, the slot, or charge tunnel  78 , may be radially adjusted through an operative engagement of the fastener  100 . 
   A fastener  101  is positioned through the lower hole  98  and is configured to be received and retained within the through hole  90 . The fastener  101  ensures that the plate  94  remains secured on the drop exit surface  62  at a constant position. As such, the spring  92  exerts a force on the plate  94 , but the plate  94  does not move. Rather, the force exerted by the spring on the plate  94  and the tab  72  causes the tab  72  to move in the direction of A″ when the fastener  100  is loosened. 
   Additionally, the fastener  86  may extend into the charge tunnel unit channel  66  and abut the outer wall  77  of the charge tunnel unit  68 . The fastener  86  may be engaged to move into and away from the charge tunnel unit  68  to provide a linear adjustment of the charge tunnel unit  68  in the directions of arrow C. Optionally, the fastener  86  may be used with the charge tunnel unit  68  so that it may adjust the charge tunnel  78  in a rotary fashion. That is, the fastener may be a worm screw, cam mechanism, or like fastener that engages a reciprocal structure on the charge tunnel unit  68 , thereby adjusting it in a rotary fashion through directions denoted by arrow A. 
   Referring to  FIGS. 2 and 3 , the upper ledge  52  of the bracket  42  includes channels  102  configured to allow fasteners  104  to pass therethrough. The channels  102  are wider than the diameters of the distal ends  106  of the fasteners  106 . As such, the fasteners  104  may move in linear directions as shown by arrows C within the channels  102 . The charge tunnel housing  44  is secured into the housing slot  53  by way of the fasteners  104  engaging the through holes  82 . 
   The fasteners  104  may be used to lock the charge tunnel housing  44  in a lateral direction. Initially, the charge tunnel housing  44  may be adjusted laterally through the engagement of the fastener  110 . Once a desired lateral position is attained, the fasteners  104  may be tightened down to the upper ledge  52  so that the charge tunnel housing  44  is restricted from movement. In order to readjust the central housing in a lateral direction, the fasteners  104  are first loosened in order to allow the charge tunnel housing  44  to move laterally. Optionally, as discussed below, the fasteners  104  may be used to adjust the charge tunnel housing  44  in vertical directions. 
   A channel  108  extends horizontally through the upright member  50  and allows a fastener  110  to pass therethrough. The channel  108  is aligned with the channel  84  of the charge tunnel housing  44  and the cavity  80  of the charge tunnel unit  68 . 
   A spring  112  is disposed within the channel  84  and abuts the charge tunnel unit  68  around the cavity  80 . A distal end of the fastener  110  is disposed through the spring  112  and abuts the charge tunnel unit  68  through the cavity  80 . The cavity  80  may be threaded and a distal end of the fastener  110  may threadably engage the cavity  80 . When the fastener  110  is tightened, the fastener  110  extends further into the cavity  80 . In the process, the fastener  110  draws the charge tunnel housing  44  toward the upright member  50  in the direction of C′. As the fastener  110  is loosened, the fastener  110  recedes from the cavity  80 , the spring  84  elongates, and the charge tunnel housing  44  moves away from the upright member  50  in the direction of arrow C″. The fastener  86  may be engaged to move the charge tunnel housing  44 , as well. 
   Additionally, the fasteners  104  may be engaged to adjust the charge tunnel assembly  66  in vertical directions denoted by arrows D. For example, when the fasteners  104  are tightened, the charge tunnel assembly  66  may be drawn upward in the direction of arrow D′, by way of the fasteners  104  engaging the threaded through holes  82 . As the fasteners  104  are loosened, the charge tunnel unit  68  recedes from the upper ledge  52  in the direction of arrow D″. 
   The fasteners  110  and  86  may be engaged to adjust the charge tunnel unit  68 , and therefore the slot (charge tunnel)  78  in linear directions defined by arrow C. The lateral range of movement of the charge tunnel unit  68  is limited by the range of movement of the fasteners  106  through the channels  102 . 
   As the fastener  110  is tightened, it exerts a force into the charge tunnel unit  68  in the direction of arrow C′, thereby pressing the charge tunnel unit  68  into charge tunnel unit channel  66  and causing the charge tunnel housing  44  to move in the same direction. Optionally, the fastener  110  and spring  112  may abut an outer wall portion (e.g., the side  58 ) of the charge tunnel housing  68 , instead of directly abutting a portion of the charge tunnel unit  68 . In either case, when the fastener  110  is tightened, the charge tunnel housing  44  (and therefore the charge tunnel  78 ) move in the same direction. Also, if the fastener  86  is configured to adjust the charge tunnel housing  44  laterally, the fastener  86  may be loosened, thereby receding away from the charge tunnel unit  68 . As such the charge tunnel  78  moves in the direction of arrow C′. 
     FIG. 4  illustrates a top view of the charge tunnel alignment system  10 . In order to adjust the charge tunnel  78  in a rotary fashion as denoted by arrow A, fastener  100  is engaged, as discussed above. To adjust the charge tunnel  78  in a horizontal linear fashion, the fasteners  110  and  86  are engaged, as discussed above. Optionally, the fastener  86  may be used to adjust the charge tunnel  78  in the directions of arrow A. In order to adjust the charge tunnel housing  44  (as shown and discussed above) through vertical directions, the fasteners  104  may be engaged as discussed above. 
     FIG. 5  illustrates a front view of the charge tunnel alignment system  10 . In order to adjust the charge tunnel  78  in a rotary fashion, the fastener  100  is engaged, as discussed above. Optionally, the fastener  86  may also assist in rotary adjustment of the charge tunnel  78 . The fasteners  104  are engaged to adjust the charge tunnel  78  in directions denoted by arrow D. Further, the fastener  110  is used to adjust the charge tunnel linearly in directions denoted by arrow C. The fastener  110  and spring  92  may abut against the fastener  101 , as shown in  FIG. 5 , instead of abutting against the charge tunnel unit  68 , as discussed above. The charge tunnel alignment system  40  may be positioned on a mount  120 , which may be secured to a printhead deck (not shown). 
     FIG. 6  illustrates a top view of the charge tunnel alignment system  40  and a drop generator  130  having a nozzle  131 .  FIG. 7  illustrates a side view of the charge tunnel alignment system  40  and the drop generator  130 . An alignment cradle  132  is used to secure the system  40  and the drop generator  130 . The drop generator  130  may be adjusted in a vertical plane as shown in side view of  FIG. 2 , which is commonly known. 
   The independent linear and rotary adjustments of the charge tunnel assembly, as discussed above, ensures proper passage of the ink stream from the drop generator  130  through the charge tunnel  78 . Also when the alignment cradle  132  is aligned horizontally to direct the ink stream into the catcher, the charge tunnel assembly  40  follows the alignment cradle and no further adjustment of the charge tunnel assembly  40  is required. 
   In general, the charge tunnel alignment system  40  may be removed from the printer  10  in order for the charge tunnel  78  to be adjusted. Optionally, the charge tunnel alignment system  40  may be adjusted while it is secured within the printer  10 . The charge tunnel  78  may be adjusted manually by an operator engaging the fasteners through a tool, such as a screwdriver. Alternatively, the fasteners may be operatively connected to actuators, servo motors, and the like, which may in turn be in operative communication with a controller. The actuators, and the like, may operate to automatically adjust the charge tunnel  78  by engaging the various fasteners. 
   While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.