Abstract:
Ink jet cartridge for an ink jet printer including an orifice plate having a plurality of orifices for ink ejection; a cartridge for receiving a reservoir having ink which is adapted to be ejected through the orifices, the cartridge including a cleaning manifold having a plurality of inlet and outlet passages through which cleaning fluid can be applied so that such fluid is directed across the surface of the orifice plate; and a plurality of actuable ultrasonic transducers disposed in operative relationship with respect to the orifice plate and which when actuated produce ultrasonic sound waves which impinge upon the orifice plate to loosen debris whereby the cleaning fluid directed across the surface of the orifice plate carries away such loosened debris.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly assigned U.S. patent applications Ser. No. 09/127,546 filed Jul. 31, 1998, by Ghosh et al, entitled “Non-Contact Ultrasonic Cleaning of Ink Jet Printhead Cartridges”; U.S. patent application Ser. No. 09/159,725 filed Sep. 24, 1998, by Ghosh et al, entitled “Ultrasonic Cleaning of Ink Jet Printhead Cartridges”; U.S. patent application Ser. No. 09/132,628 filed Aug. 11, 1998, by Ghosh et al, entitled “Vacuum Assisted Ultrasonic Cleaning of Ink Jet Printhead Cartridges”; and U.S. patent application Ser. No. 09/179,498 filed Oct. 27, 1998, by Ghosh et al, entitled “High Frequency Ultrasonic Cleaning of Ink Jet Printhead Cartridges”, the teachings of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     This invention relates to an ink jet printer and more particularly to improved cleaning system for self cleaning ink jet printhead cartridges. 
     BACKGROUND OF THE INVENTION 
     Typically, an ink jet printer has at least one printing cartridge from which droplets of ink are directed towards a receiver. Within the cartridge, the ink may be contained in a plurality of channels and energy pulses are used to cause the droplets of ink to be ejected on demand or continuously, from nozzles or orifices in a plate in an orifice structure. 
     In a thermal ink jet printer, the energy pulses are generally provided by a set of electrical resistors, each located in a respective one of the channels, each one of them is individually addressable by current pulses to instantaneously heat and form a droplet or bubble in the channels which contact the resistors. Operation of thermal ink jet printer is described in details in U.S. Pat. Nos. 4,849,774; 4,500,895; and 4,794,409. 
     On the other hand, a piezoelectric ink jet printing system includes a body of piezoelectric material defining a plurality of parallel open topped channels separated by walls. The walls have metal electrodes on opposite sides thereof to form shear mode actuators for causing droplets to expel from the channels. An orifice structure comprising at least one orifice plate defining the holes through which the ink droplets are ejected is bonded to the open end of the channels. The electrical energy pulses are applied to the parallel electrodes causing the channels to shear actuating the expulsion of droplets from the orifice plate. Operation of piezoelectric ink jet print heads is described in details in U.S. Pat. Nos. 5,598,196; 5,311,218; and 5,248,998. 
     Ink jet printing cartridges, whether it is of thermal or piezoelectric kind, use a variety of functional components, all of which must cooperate in a precise manner to achieve maximum efficiency. One of the most important components is an orifice plate having a plurality of orifices or nozzles therein. The nozzles are usually circular in cross section and the diameter of the nozzles may vary from 10 to 100 μm as required by the specification of the printer. Higher the resolution of the printed output, smaller is the ink droplet thereby requiring smaller diameter nozzles or orifices. Ink is ejected through these openings during printing operation. To obtain defect-free printing output, the orifice plates and all the nozzles must be kept clean and free of debris and any kind of obstructions to ink flow at all times. If the orifice plate and nozzles are not clean, many problems can occur thereby undermining the performance of the printer. As for example, paper fibers and other debris accumulated on the orifice plate surface and inside the nozzles can affect the quality of the printed images. Similarly, debris can be dried ink crust and paper dust on the orifice plate as well as in the ink channels and the nozzles can cause the printer to perform poorly. 
     The foregoing problems are overcome, as described in U.S. Pat. No. 5,300,958 to Burke et al, by providing “maintenance or service stations” within the main printer unit. The maintenance stations are designed such that when the printhead ink cartridge is not operating and is in a “parked” position, the cartridge is situated in the maintenance station outside the printing zone for the purpose of routine cleaning of the cartridges. The maintenance station has many components, which are designed to serve many functions. These functions include: (a) priming the printhead cartridge, (b) capping the orifice plate and nozzles (orifices) therein when the printhead is not in operation, (c) wiping contaminants from the orifice plate, (d) preventing ink from drying out in the openings of the orifice plate, and (e) providing a receptacle for discarding the cleaned debris. 
     To accomplish this cleaning, the U.S. Pat. No. 5,103,244 discloses a structure in which a multi-blade wiper is used. The desired cleaning is performed by dragging a printhead (cartridge) across the selected wiper blade. The wiper mechanism also includes a plurality of resilient blades each having an octagonal shape and rotatable about an axis. 
     Another cleaning structure disclosed in U.S. Pat. No. 5,300,958, includes a printhead wiper unit consisting of a single or dual members positioned against each other to form a capillary pathway therebetween. The cartridge includes a compartment having an opening therethrough and an absorbent member impregnated with cleaning solution. 
     Still another cleaning structure is disclosed in U.S. Pat. No. 5,574,485 which includes use of a high frequency ultrasonic liquid wiper wherein a cleaning nozzle is confrontingly aligned but spaced from printhead nozzles. A cleaning solution is held within the cleaning nozzle by surface tension to form a meniscus and is caused to bulge toward into contact with the printhead nozzle face and form a bridge of cleaning solution therewith. In addition to dissolving ink the cleaning solution is ultrasonically excited by a piezoelectric material immediately upstream of the cleaning nozzle to provide a high frequency energized liquid wiper to facilitate cleaning of clogged nozzles without having physical contact with the printhead nozzle face. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide improved cleaning of ink jet printhead cartridges. 
     It is another object of the present invention to provide a more efficient printhead cartridge cleaning system which permits a controlled dislodging of debris accumulated in the orifices of the orifice structure, discarding the debris without contaminating and damaging the cartridges and thereby cleaning the printhead cartridges efficiently. 
     It is another object of the present invention to provide an apparatus for cleaning an ink jet printhead cartridge, which is compact, robust and efficient. 
     It is yet another object of the present invention to provide a cleaning apparatus, which does not abrade or damage the ink jet cartridges. 
     These objects are achieved in an ink jet cartridge for an ink jet printer comprising: 
     (a) an orifice plate having a plurality of orifices for ink ejection; 
     (b) a cartridge for receiving a reservoir having ink which is adapted to be ejected through the orifices, the cartridge including a cleaning manifold having a plurality of inlet and outlet passages through which cleaning fluid can be applied so that such fluid is directed across the surface of the orifice plate; and 
     (c) a plurality of actuable ultrasonic transducers disposed in operative relationship with respect to the orifice plate and which when actuated produce ultrasonic sound waves which impinge upon the orifice plate to loosen debris whereby the cleaning fluid directed across the surface of the orifice plate carries away such loosened debris. 
     Advantages of the invention include: 
     Overcoming many of the disadvantages of the existing technology, such as damage of the orifice plates due to wear, abrasion and distortion; 
     Providing a manifold structure in the cartridge itself which permits an effective way of providing cleaning fluid to clean the orifice plate; 
     Embedding actuable ultrasonic transducers in the orifice plate to provide an effective way of cleaning the orifice plate; 
     Cost-effective electronic integration of the high frequency actuable high frequency ultrasonic transducer to clean ink jet printhead cartridge; and 
     Use of solvents and other undesirable chemicals can be avoided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an end view of the maintenance station comprising the self cleaning cartridges of the invention; 
     FIG. 2 is an exploded view of a self cleaning printhead cartridge of the invention; 
     FIG. 3 is a partial isometric view of the assembled self cleaning printhead cartridge of the FIG. 2 showing the cap; and 
     FIG. 4 is a cross sectional view taken along line  4 — 4  of FIG. 3 showing the details of the orifice structure. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides an apparatus for cleaning an ink jet printhead cartridge which uses at least one actuable ultrasonic transducer embedded in an orifice plate of an ink jet cartridge. A cap is brought in contact with the orifice plate rendering an air tight seal with orifice plate, and a stream of cleaning fluid is pumped over the orifice plate while energizing the embedded actuable ultrasonic transducers. 
     The construction and the use of a typical ultrasonic cleaner has been described in details in a commonly assigned U.S. patent application Ser. No. 09/179,498 filed Oct. 27, 1998 by Ghosh et al, entitled “High Frequency Ultrasonic Cleaning of Ink Jet Printhead Cartridges”. 
     Referring to FIG. 1, a detailed description of the maintenance station  100  of the present invention will now be provided. The maintenance station  100  incorporates self cleaning ink jet printhead cartridges  42 ,  44 ,  46 , and  48  which are attached to a printhead carriage  10  which travels back and forth on a carriage rod  32  through the printing zone as shown by a directional arrow  20 . Printhead carriage  10  is moved bi-directionally typically by means of a drive belt (not shown) which is connected to a carriage motor (not shown). Caps  52 ,  54 ,  56 , and  58  are mounted rigidly on a movable platform  50 . The platform  50  can be made of metals like aluminum or steel or heavy duty plastics. The platform  50  moves up or down as shown by a directional arrow  60 . Four ink jet printhead cartridges  42 ,  44 ,  46 , and  48  are shown here to describe fully the embodiment of the present invention. For purposes of the illustrative embodiment described in this invention, cartridge  42  utilizes black ink while cartridges  44 ,  46 , and  48  can use only cyan, yellow, and magenta ink, respectively. The cartridges  42 ,  44 ,  46 , and  48  are each provided with an orifice structure that can define ink channels (see FIG. 2) but will necessarily include orifice structures  62 ,  64 ,  66 , and  68  through which ink droplets are ejected to a receiver. Furthermore, any number of different colored ink cartridges  42 ,  44 ,  46  and  48  could be used, as warranted by the application of the printer. Typically, ink jet cartridges  42 ,  44 ,  46 , and  48  are preferably piezoelectric ink jet printheads, but other kinds of cartridges, as for example, thermal cartridges may also be acceptable and useful in this invention. 
     Referring again to FIG. 1, ink jet cartridges  42 ,  44 ,  46 , and  48  are provided with ink inlets  42   a ,  44   a ,  46   a , and  48   a  for delivering the black, cyan, magenta and yellow ink to the ink jet cartridges  42 ,  44 ,  46 , and  48 , respectively. Cleaning manifolds  61 ,  63 ,  65 , and  67  corresponding to the ink jet cartridges  42 ,  44 ,  46 , and  48 , respectively are provided with cleaning fluid inlets  42   b ,  44   b ,  46   b , and  48   b , respectively and outlets (not shown) are also provided for circulating cleaning fluid through the orifice plate  40  by means of a pump  70 . Cleaning fluid conveyed through inlet tubes  41 ,  43 ,  45 , and  47 , is circulated back to the pump  70  through a filter  69  and by means of outlet tubes  51 ,  53 ,  55 , and  57  as shown by arrows. 
     The maintenance station  100  of FIG. 1 will be understood by those skilled in the art to be located in a region outside the printing zone at one end of the bi-directional movement, shown by the arrow  20 , of carriage  10 . Cleaning is accomplished when the ink jet cartridges  42 ,  44 ,  46 ,  48  as they are moved by the carriage rod  32  until they enter the maintenance station  100  where they engage the caps  52 ,  54 ,  56 , and  58  and are covered by such caps. Cleaning fluid is then introduced and actuable ultrasonic transducers  71 ,  73 , and  75  are energized, as will be described later. 
     Referring to FIG. 2, an exploded view of the printhead cartridge  42  showing the details of the orifice structure  62  and cleaning manifold  61  along with actuable transducers  71 ,  73  and  75  which are embedded in the printhead base  80 . The printhead cartridge  42  includes several components, which are built individually and assembled together. The orifice structure  62  includes a plastic or rubber gasket  30  which fits around the orifice plate  40 , and is bonded to a printhead base  80 . The gasket  30  helps sealing the cap  120  (see FIG. 3) against the cartridge  42  so that the cartridge  42  remains water tight during the cleaning process. The orifice plate  40  has several openings including at least one row of closely spaced orifices  79  for ejecting ink drops. The diameter of the orifices  79  may vary from 10 to 100 μm. The orifice plate  40  may be formed either by electroforming nickel or chemical etching or laser cutting metal sheets, such as aluminum, copper or stainless steel, and the exterior surface is coated with gold to reduce corrosion caused by chemically active species in ink. The openings  72 ,  74 , and  76  in the orifice plate  40  are provided to accommodate the embedded actuable transducers  71 ,  73 , and  75  (see FIG.  3 ). Similarly, the openings, in the orifice plate  40 , designated as inlet channel  77  and outlet channel  78 , are provided for channeling the cleaning fluid into and out of the printhead base  80 . The printhead base  80  includes ink channels  82  and  84  made from piezoelectric ceramic such as lead-zirconate-titanate, and the actuable ultrasonic transducers  71 ,  73 , and  75  (see FIG.  3 ). The printhead base  80  is preferably made from alumina ceramic or alternatively from metals like aluminum or stainless steel. A series of inlet tubes  85  are provided for the incoming cleaning fluid to be delivered across the orifice plate  40  for ultrasonic cleaning by energizing the actuable ultrasonic transducers  71 ,  73 , and  75 , and an outlet  88  is provide for the cleaning fluid to exit the cleaning manifold  61  through the cleaning fluid outlet  42   c . A series of tubes  85  for delivering a stream of cleaning fluid across the orifice plate  40  are aligned with holes  94  arranged in the cleaning fluid inlet manifold  90  which lead to cleaning fluid inlet  42   b . The cleaning fluid exits through first an outlet channel  78  arranged in the orifice plate  40 , next through another outlet channel  88  arranged in the printhead base  80 , and then finally through an outlet  42   c  which is provided in an outlet gutter  92  being located in the cleaning manifold  61 . The tubes  85  protrude through an inlet channel  77  located in the orifice plate  40  and are kept flushed with the top surface of the orifice plate  40 . The orifice structure  62  is mounted on the cleaning manifold  61 , and those assembled are next bonded on to the ink reservoir  95 . 
     Referring to FIG. 3, a partial view of the ink cartridge  42  in operative relationship with the cap  52  is shown. The cap  52  engages the ink cartridge  42  and makes a watertight seal around the gasket  30 . The cleaning fluid is pumped through the inlet tube  41  to the orifice structure  62  and the actuable ultrasonic transducers  71 ,  73 , and  75  are energized for 10 to 30 seconds to effectively clean the clogged orifices  79  and the ink channels  82  and  84  (see FIG.  2 ). 
     Referring to FIG. 4, a partial cross-sectional view of the ink cartridge  42  along the line  4 — 4  in FIG. 3 is shown. The actuable ultrasonic transducers  71 ,  73 , and  75  are embedded in the printer base  80  so that their top active surfaces are in the same plane as the top surface of the orifice plate  40 . The orifices  79  in the orifice plate  40  are aligned with the open ends of the ink channels  82  and  84  so that ink droplets are ejected from those ink channels as and when each channel is electronically addressed. 
     In view of the above description, it is understood that modifications and improvements will take place to those skilled in the art which are well within the scope of this invention. The above description is intended to be exemplary only wherein the scope of this invention is defined by the following claims and their equivalents. 
     PARTS LIST 
       10  printhead carriage 
       20  directional arrow 
       30  gasket 
       32  carriage rod 
       40  orifice plate 
       41  inlet tube 
       42  black ink cartridge/printhead cartridge 
       42   a  black ink inlet 
       42   b  cleaning fluid inlet 
       42   c  cleaning fluid outlet 
       43  inlet tube 
       44  cyan ink cartridge/printhead cartridge 
       44   a  cyan ink inlet 
       44   b  cleaning fluid inlet 
       45  inlet tube 
       46  magenta ink cartridge/printhead cartridge 
       46   a  magenta ink inlet 
       46   b  cleaning fluid inlet 
       47  inlet tube 
       48  yellow ink cartridge/printhead cartridge 
       48   a  yellow ink inlet 
       48   b  cleaning fluid inlet 
       50  movable platform 
       51  outlet tube 
       52  cap 
       53  outlet tube 
       54  cap 
       55  outlet tube 
       56  cap 
       57  outlet tube 
       58  cap 
       60  directional arrow 
       61  cleaning manifold 
       62  orifice structure 
       63  cleaning manifold 
       64  orifice structure 
       65  cleaning manifold 
       66  orifice structure 
       67  cleaning manifold 
       68  orifice structure 
       69  filter 
       70  pump 
       71  ultrasonic transducer 
       72  opening for transducer 
       73  ultrasonic transducer 
       74  opening for transducer 
       75  ultrasonic transducer 
       76  opening for transducer 
       77  cleaning fluid inlet channel 
       78  cleaning fluid outlet channel 
       79  orifice 
       80  printhead base 
       81  ink channels 
       82  ink channels 
       84  ink channels 
       85  inlet tubes 
       88  outlet channel 
       90  inlet manifold 
       91  outlet manifold 
       92  outlet gutter 
       94  holes 
       95  ink reservoir 
       100  maintenance station