Abstract:
An ink pen assembly of a continuous ink jet printer includes a printhead nest and an ink pen cartridge removably received within the nest. The cartridge includes a pen body in electrical communication with the printhead nest, and a nozzle body in fluid communication with the printhead nest. A charge electrode charges ink drops breaking off from ink jetted from an outlet of the nozzle body. A deflection electrode deflects the charged ink drops along an axis substantially transverse to a direction of travel of a substrate being printed. An ink block mount includes an ink blocking element for diverting deflected ink drops. An ink block actuator pivots with respect to the pen body to adjust the position of the ink blocking element. The printhead nest defines at least four ink outlets for delivering different colored inks, and at least four ink pen cartridges are removably received by the printhead nest.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an ink pen assembly of a continuous ink jet printer. 
     As described in Jochimsen, U.S. Pat. No. 4,639,736, titled INK JET RECORDER, incorporated by reference herein, continuous ink jet printers produce a continuous stream of ink drops directed at a substrate. The ink drops include printing and non-printing drops. The ink drops are selectively charged such that the non-printing drops are deflected to prevent the non-printing drops from reaching the substrate. 
     A removable nozzle unit including a charging tunnel for producing a continuous stream of ink drops and charging the non-printing drops is described in Fargo et al., U.S. Pat. No. 5,160,938, titled METHOD AND MEANS FOR CALIBRATING AN INK JET PRINTER, incorporated by reference herein. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, an ink pen cartridge is removably received within a printhead nest of a continuous ink jet printer. The ink pen cartridge includes a pen body configured to be placed in electrical communication with the printhead nest, and a nozzle body which defines an inlet configured to be placed in fluid communication with the printhead nest to receive ink from the printhead nest. The nozzle body also has an outlet through which ink is jetted. 
     A charge electrode charges ink drops breaking off from the ink jetted from the nozzle body outlet. A deflection electrode deflects the charged ink drops. The deflection electrode is configured and arranged such that charged ink drops are deflected along an axis substantially transverse to a direction of travel of a substrate to be printed. 
     Embodiments of this aspect of the invention may includes one or more of the following features. 
     An ink block mount is connected to the pen body and includes an ink blocking element for diverting deflected ink drops. An ink block actuator configured to be placed in mechanical communication with the printhead nest is used to adjust the position of the ink blocking element. The ink block actuator is mounted to the pen body to pivot with respect to the pen body. 
     The nozzle body houses a tube through which ink flows. A transducer is mounted to the tube for synchronizing breakup of ink jetted from the nozzle body outlet into ink drops. 
     The pen body defines an ink drain for draining ink from the pen body to the printhead nest. A mist bib formed from, e.g, acid-etched stainless steel, is mounted to the pen body for collecting spray produced when ink droplets contact a substrate. 
     An electrical connection board is mounted to the pen body for providing the electrical communication with the printhead nest. 
     In certain embodiments, the pen body includes a barrier plate defining a drop charging chamber. The charge tunnel and deflection electrodes are located within the drop charging chamber and spaced from the barrier plate. The barrier plate is inclined with respect to a side wall of the drop charging chamber. 
     According to another aspect of the invention, an ink pen cartridge removably received within a printhead nest of a continuous ink jet printer includes a pen body, a nozzle body, a deflection electrode, and an ink block actuator configured to be placed in mechanical communication with the printhead nest. Movement of the ink block actuator relative to the pen body adjusts the position of an ink blocking element. 
     Embodiments of this aspect of the invention may includes one or more of the following features. 
     A charge electrode charges ink drops breaking off from the ink jetted from the nozzle body outlet. An ink block mount includes the ink blocking element for diverting the deflected ink drops. 
     According to another aspect of the invention, an ink jet nozzle includes a nozzle body defining an ink passage and a vacuum passage. A jet housing is located within the ink passage. A tube is located within a through bore of the jet housing. An outlet of the vacuum passage is in fluid communication with an outlet end of the tube. An ink passage inlet and a vacuum passage inlet are defined in a single sealing face of the nozzle body. 
     Embodiments of this aspect of the invention may includes one or more of the following features. 
     An ink passage seal is located at the inlet of the ink passage, and a vacuum passage seal is located at the inlet of the vacuum passage. 
     A transducer is mounted to the tube for synchronizing breakup of a jet of ink from the tube outlet into ink drops. A first spring abuts the transducer on an upstream side of the transducer, and a second spring abuts the transducer on a downstream side of the transducer. The first and second springs locate the transducer with respect to the tube prior to fixing the transducer to the tube. The second spring is connected to a ground plane of the transducer to act as a shield. 
     The tube comprises a capillary tube having an inner diameter of about 100 microns. The inner diameter is reduced to about 10 microns at the outlet end of the tube. A filter is located at the inlet end of the tube. 
     According to another aspect of the invention, a printhead nest for receiving an ink pen cartridge includes a housing defining an ink outlet for providing ink to the ink pen cartridge, a mechanical link for interfacing with the ink pen cartridge to adjust the position of an ink blocking element of the ink pen cartridge, and an electrical connection for interfacing with the ink pen cartridge to control a deflection electrode of the ink pen cartridge. 
     Embodiments of this aspect of the invention may includes one or more of the following features. 
     A fluid catcher receives ink that drains from the ink pen cartridge. The housing defines four ink outlets, four mechanical links, and four electrical connections. The ink outlets provide ink to four ink pen cartridge. The mechanical links and electrical connections each interface with one of the four ink pen cartridges. 
     According to another aspect of the invention, an ink pen assembly includes an ink pen cartridge and a printhead nest. The ink pen cartridge includes a pen body, a nozzle body, a charge electrode, and a deflection electrode. The printhead nest includes a housing defining an ink outlet for providing ink to an inlet of the nozzle body, and an electrical connection for interfacing with the pen body to control the charge tunnel and deflection electrodes. The ink pen is configured for placement in the printhead nest and removal from the printhead nest as a single unit. 
     According to another aspect of the invention a continuous ink jet printer includes a printhead nest defining at least four ink outlets. The printhead nest is configured to deliver a different colored ink through each of four ink outlets. At least four ink pen cartridges are removably received by the printhead nest. Each ink pen cartridge defines an ink inlet aligned with one of the ink outlets for receiving ink from the printhead nest when the ink pen cartridges are received by the printhead nest. Each ink pen cartridge also includes a charge electrode for charging ink drops breaking off from the received ink, and a deflection electrode for deflecting charged ink drops. Each deflection electrode is configured and arranged such that charged ink drops are deflected along an axis substantially transverse to a direction of travel of a substrate to be printed. The charge electrode is adjustable to impart varying levels of charge to the ink drops such that different ink drops are deflected by different amounts by the deflection electrode to facilitate registration of the ink drops from the at least four ink pen cartridges on a substrate. 
     Advantages of the invention includes a disposable ink pen cartridge which includes all of the components of a continuous ink jet printhead, e.g., the drop producing, drop charging, and drop deflecting elements, which are likely to fail. The ink pen cartridge can be quickly removed and disposed of and replaced with a new cartridge. The failed cartridge can be replaced even while the continuous ink jet printer remains turned on. 
     Other features and advantages of the invention will be apparent from the following detailed description, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of an ink pen assembly of the invention; 
     FIG. 2 is a perspective view of an ink pen cartridge of the assembly of FIG. 1; 
     FIG. 3A is an exploded view of the ink pen cartridge of FIG. 2; 
     FIG. 3B is a side view of a knife edge of the ink pen cartridge of FIG. 2; 
     FIG. 4A shows a pen body of the ink pen cartridge of FIG. 2 with a side of the pen body removed; 
     FIG. 4B is a partial bottom view of the pen body of FIG. 4A; 
     FIG. 5A is a top view of a nozzle body of the ink pen cartridge of FIG. 2; 
     FIG. 5B is a cross-sectional side view of the nozzle body of FIG. 5A; 
     FIG. 6A is a top view of the assembly of FIG. 1 shown during printing on a substrate; 
     FIG. 6B is a side view of the assembly of FIG. 1 shown during printing on the substrate; 
     FIG. 7 is an illustration of a pen electronics board assembly of the ink pen assembly of FIG. 1, shown mounted to a continuous ink jet printer; 
     FIG. 8 is a cross-sectional side view showing the interface of the ink pen cartridge of FIG. 2 with a printhead nest of the pen electronics board assembly of FIG. 7; and 
     FIG. 9 illustrates a priming pen being mounted to the printhead nest. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, an ink pen assembly  10  of a continuous ink jet printer includes a printhead nest  16  and up to four disposable ink pen cartridges  14 , one cartridge being shown in FIG. 1, received by nest  16 . Nest  16  is a component of a pen electronics board assembly  20  mounted to move along a lead screw  22  (FIGS. 6B and 7) of the printer. Each ink pen preferably deliveries a different color ink to a substrate to produce a multi-color image on the substrate, as described, e.g., in Ingraham et al., U.S. Pat. No. 5,416,612, incorporated by reference herein. When an ink pen becomes clogged or otherwise reaches the end of its useful service life, the ink pen can be removed from the nest and replaced with a new ink pen. 
     Referring to FIGS. 2 and 3A, ink pen cartridge  14  includes a pen body  30  and a nozzle body  40 . Nozzle body  40  is mounted to pen body  30  with pins  62 ,  64  which pass through mounting holes  32 ,  34  in pen body  30  and corresponding mounting holes  42 ,  44  in nozzle body  40 . An ink block actuator, e.g., knife edge arm  50 , is mounted to pen body  30  to pivot about a pivot pin  66  received in mounting holes  36  of pen body  30 . A finger grip  54  of arm  50  provides an easy means for the user to grasp ink pen  14  for insertion and removal from nest  16 . 
     Referring to FIGS. 3A,  4 A and  4 B, housed within an electrode mounting section  70  of pen body  30  is a charge tunnel  72 , a ground deflection electrode  74 , a high voltage deflection electrode  76 , and an ink blocking element, e.g., knife edge  94 . A barrier plate  71  defines a drop charging chamber  93  in which the charge tunnel, electrodes, and knife edge are located. Extending from either side of barrier plate  71  are a knife edge mount  84 , a charge tunnel mount  73 , a ground electrode mount  75 , and a deflection electrode mount  77 . Each of the mounts  84 ,  73 ,  75 ,  77  defines a through bore  83 ,  73   a ,  75   a ,  77   a , respectively. 
     A knife edge housing  80  includes a shaft  82  which extends through bore  83  of knife edge mount  84 . Bore  83  has a slot  85  which permits flow of air into charging chamber  93 . When positioned within mount  84 , end  86  of shaft  82  is received within arm  50  such that a hole  88  in shaft  82  is aligned with a pair of holes  56  (only one hole is shown in FIG. 3A) in arm  50 . When assembled, holes  56  and  88  are aligned with a pair of slots  38  in pen body  30 . A pin  68  passes through slots  38  and holes  56  and  88  such that movement of arm  50  about its pivot point causes pin  68  to slide vertically within slots  38  thus changing the vertical position of knife edge  94 . A spring  90  captured between guide  84  and arm  50  biases arm  50  to pivot about pivot pin  66  in the direction of arrow  90   a.    
     Shafts  72   a ,  74   a ,  76   a  of the charge tunnel, ground electrode, and deflection electrode, respectively, are mounted within through bores  73   a ,  75   a ,  77   a , respectively. The charge tunnel, electrodes and knife edge are spaced from barrier plate  71 , e.g., by about ⅜ inch, and barrier plate  71  is inclined, e.g., by about 45 degrees, with respect to a side wall  95  of drop charging chamber  93 . This spacing tends to limit spray of ink onto barrier plate  71 , and the inclined position of the barrier plate facilitates dripping of any ink that does reach the barrier plate off of the barrier plate. 
     Referring again to FIG. 3A, in use, printing ink is received at a first end  46  of nozzle body  40  and is delivered as discrete ink droplets from a second end  48  of the nozzle body. Non-printing ink drops exiting from nozzle body  40  are charged when passing through a hole  92  in charge tunnel  72 . The charged non-printing ink drops are deflected by electrodes  74 ,  76  in a direction transverse to a direction of travel of the substrate (see arrow A, FIG. 6B) such that the non-printing drops impact knife edge  94  preventing the non-printing ink drops from reaching the substrate. 
     Referring to FIG. 3B, knife edge  94  has a curved ink contacting surface  94   a  along an edge  94   b . The knife edge is preferably formed from, e.g., zirconia ceramic, that is injected molded and then ground on one side to produce a sharp edge. Non-printing ink drops hit surface  94   a  and roll down the knife edge. A bottom cap  100  (FIGS. 3A and 4A) mounted to pen body  30  includes a drain port  102  through which non-printing ink drops falling from knife edge  94  pass to a collection tray  104  of nest  16  (FIG.  1 ). Bottom cap  100  also defines a drip-inducing post  103  positioned below ground electrode  74  to induce any ink which may fall on electrode  74  to drip off of electrode  74 . A nest mounting guide  79  extends from a bottom surface  101  of cap  100 . 
     Printing ink drops passing through charge tunnel  72  are charged to a lesser degree than the non-printing ink drops such that the printing ink drops are not deflected by the electrodes into the knife edge. The printing ink drops pass by the knife edge and through an outlet  98  to contact the substrate. 
     A mist bib  110  is positioned over lower section  111  of mounting section  70 . Lower section  111  includes four protrusions  113  (two protrusions are shown in FIG. 3A) over which holes  115  in mist bib  110  are positioned to mount mist bib  110  to lower section  111 . Mist bib  110  defines an outlet  98   a  through which the printing ink drops pass to contact the substrate. Mist bib  110  acts to collect spray formed when the ink drops contact the substrate. Mist bib  110  is formed, e.g., by photo-mask engraving stainless steel having a photoresist coating, and acid-etching the exposed areas of the stainless steel. 
     Referring to FIGS. 5A and 5B, the ink jet nozzle body  40  defines an ink passage  120  having an inlet  130  and an outlet  132 . An o-ring cavity  134  located at inlet  130  in a face  135  of nozzle body  40  houses an o-ring  136 . O-ring  136  provides a seal with nest  16 , described further below. A jet housing  122  is received in passage  120  with an o-ring  123  providing a seal between jet housing  122  and a wall  121  of passage  120 . 
     Jet housing  122  includes a body  124  defining a channel  126 . A capillary tube  128 , e.g., a 100 micron inner diameter tube, located within channel  126  has an inlet end  128   a  and an outlet end  128   b  extending to outlet  132 . Tube  128  has a 10 micron restriction at outlet end  128   b . A piezoelectric transducer  140  is received over capillary tube  128 . The restriction in tube  128  and transducer  140  cause ink flowing through tube  128  to be broken into discrete ink drops, as described in West et al., U.S. Pat. No. 5,407,136, titled INK-JET NOZZLE, incorporated by reference herein. Transducer  140  acts to synchronize the breakup of the ink into drops. Ink flowing in inlet  130  passes through filter  129  before entering tube  128 . Filter  129  is glued in place, e.g., by a preformed epoxy ring which melts at a given temperature. 
     A pair of springs  142 ,  144  are positioned over tube  128  on either side of transducer  140 . The springs locate transducer  140  with respect to tube  128  prior to fixing the transducer to the tube. Spring  142  is connected to a ground plane of the transducer to act as a shield. 
     A nozzle  146  supports tube  128 . An end cap  148  provides a seal around tube  128  at outlet end  132  of ink passage  120 . An o-ring  150  provides a seal between pen body  30  and nozzle body  40 . To secure transducer  140  to tube  128 , solid potting is applied through an opening  151  in nozzle body  40 . 
     Nozzle body  40  also defines a vacuum passage  170 . A second o-ring cavity  172  located at a vacuum inlet  130   a  in end face  135  of the nozzle body houses an o-ring  174 . O-ring  174  provides a seal with nest  16 , described further below. An outlet  176  of vacuum passage  170  communicates with the distal end of the tube through region  178  surrounding nozzle  146  and channel  180  defined between end cap  148  and nozzle  146 . Cleaning fluid can be pumped into chamber  93  through vacuum passage  170 . 
     An o-ring cover  188  (FIG. 2) is provided to retain o-rings  136 ,  174  in o-ring cavities  134 ,  172 , respectively, prior to positioning of the ink pen in the printhead nest. o-ring cover  188  includes a t-slot  189  which fits over a nozzle body lip  121 . 
     Beside having ink and vacuum communication with nest  16 , ink pen  14  is also in electrical and mechanical connection with nest  16 . Referring to FIG. 3A, mounted to an underside  200  of ink pen body  30  is an electrical connection board  202 . Board  202  includes electrical contacts  204  which interface with nest  16  to provide signals to transducer  140 , charge tunnel  72 , and electrodes  74 ,  76 , as described further below. 
     To register ink drops in print processing of color images, as described, e.g., in Ingraham et al., supra, the charge applied to the printing ink drops by the charge tunnel is varied to adjust the deflection of the printing ink drops in a direction transverse to the direction of travel of the substrate. Referring to FIGS. 6A and 6B, electrodes  74 ,  76  are oriented with respect to the direction of travel of the substrate (along arrow A) such that the electrodes deflect the ink drops along arrow B, oriented in a direction transverse to substrate travel and in the direction of travel of ink pen assembly  10 . This results in a trajectory of the ink drop along arrow C. To accommodate changes in the charge of the printing drops, the knife edge is moved by adjusting the position of the knife edge arm, as described below, to insure that non-printing drops hit the knife edge while the printing drops pass by the knife edge. 
     Registration of four ink colors delivered by the four ink pens is performed by adjusting the charge applied to the printing ink drops by the charge tunnel (by varying the voltage applied to the charge tunnel), and by adjusting the pixel locations in the direction of substrate travel, as described in Ingraham et al., supra. 
     Referring to FIGS. 7 and 8, nest  16  includes five partitions  220  defining four ink pen receiving t-slots  222 . Lip  221  (FIG. 3A) of nozzle body  40  slides into t-slot  222  to connect nozzle body  40  to nest  16 . Nest  16  also includes four pins  240 . Guide  79  of ink pen cap  100  is received over a respective pin  240  to help align the ink pen with the nest. In a back wall  224  of each slot  222  is an ink outlet  230  and a vacuum outlet  232 . With an ink-pen  14  positioned in t-slot  222 , ink outlet  230  is in fluid communication with ink passage  120  of nozzle body  40 , and vacuum outlet  232  is in fluid communication with vacuum passage  170  of nozzle body  40 . O-rings  136 ,  174  provide seals between wall  224  of nest  16  and end face  135  of nozzle body  40 . 
     To provide an electrical connection between nest  16  and the ink pens, nest  16  includes four electrical contact regions  250 . With ink pen  14  positioned in nest  16 , contacts  204  of board  202  interface with contact region  250 . Each contact region  250  includes six contact points: a 2000 volt power supply; a charge tunnel charge level signal for adjusting the charge imparted to the ink drops by the charge tunnel; a 1 MHz stimulation voltage to the transducer; an ink pen ground; an ink pen sensor; and a primer fixture (described below) sensor. The ink pen sensor and primer fixture sensor sense when an ink pen or the primer fixture are in place in the nest. LEDs  252  (FIG. 1) signal when an ink pen or the primer fixture is in position in the nest. 
     Nest  16  also includes motor actuated, knife edge positioning pins  260 . Each pin  260  contacts an undersurface  210  of arm  50 . Raising and lowering of pin  260  causes arm  50  to pivot about its pivot point, thus adjusting the vertical position of knife edge  94 . 
     An ink pen is inserted into nest  16  simply by grasping finger grip  54  and sliding lip  221  of nozzle body  14  into slot  222 . When an ink pen needs to be replaced, the individual ink pen is removed from nest  16  simply by pulling up on finger grip  54 . The ink pen is hot swapable, i.e., the power to the ink jet printer can be left on when an ink pen is removed from the nest and a new ink pen inserted into the nest. The ink pen sensing contact of the nest detects when the ink pen has been removed and shuts down dangerous voltages until the new ink pen is inserted. 
     Referring to FIG. 9, to prime the system, a priming pen  300  is provided. Pen  300  includes four slots  302  which are received within t-slots  222 . Pen  300  includes four electrical contacts  304  which interface with contact region  250  to provide a signal indicating that the priming pen is in position in nest  16 . 
     Other embodiments are within the scope of the following claims. 
     For example, the nest can be configured to accept more than four ink pens. Eight ink pens would permit color printing twice as fast as with four ink pens, would allow the use of high and low density colors to expand the color range, and would also permit additional colors to be used while printing.