Abstract:
A cleaning assembly ( 170 ) for removing contaminants from the surface ( 90 ) of an ink jet print head ( 60 ) in a self-cleaning ink jet printer ( 10 ). The print head ( 60 ) defines a plurality of ink channels ( 31 ) terminating in orifices ( 25 ) with a surface ( 90 ) surrounding the orifices ( 25 ). A gutter ( 17 ) is disposed opposite the print head surface ( 90 ) for collecting ink droplets ( 100 ) ejected from the orifices ( 25 ). A cleaning assembly ( 170 ) includes a cup ( 190 ) defining a cavity ( 197 ) with an open end ( 195 ) adapted to make contact with the print head surface ( 90 ). An inflow channel ( 210 ) provides the entry pathway for cleaning liquid to flow into the cavity ( 197 ) via a gap ( 220 ). An outflow channel provides an exit pathway for the flow of cleaning liquid from cavity ( 197 ). The inflow channel ( 210 ) and outflow channel are arranged to direct the flow of cleaning liquid into the cavity ( 197 ), over the print head surface ( 90 ) and orifices ( 25 ) so that contaminants are removed from the print head surface ( 90 ) and orifices ( 25 ).

Description:
FIELD OF THE INVENTION 
     This present invention relates to methods and system for cleaning ink jet print heads utilized in an ink jet printer system. More particularly, the present invention relates to a method and system for hydrodynamically cleaning ink jet print heads. 
     BACKGROUND OF THE INVENTION 
     Modem color printing relies heavily on ink jet printing techniques. The term “ink jet” as utilized herein is intended to include all drop-on-demand or continuous ink jet propulsion systems including, but not limited to, thermal ink jet, piezoelectric, and continuous, which are well known in the printing arts. An ink jet printer produces images on a receiver by ejecting ink droplets onto the receiver medium, typically paper, in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace. 
     In this regard, “continuous” ink jet printers utilize electrostatic charging tunnels that are placed close to the point where ink droplets are ejected in the form of a stream. The electrostatic charging tunnels electrically charge selected ink droplets. The charged ink droplets are then deflected downstream by the presence of deflector plates that have a predetermined electric potential difference between them. A gutter can be utilized to intercept the charged ink droplets, while uncharged ink droplets are free to strike the receiver medium. Ink drops not utilized for printing are transferred to the gutter where they can be recycled. Continuous ink jet systems thus create a continuous stream of ink drops, generated by periodically perturbing an associated print head orifice with, for example, a piezoelectric transducer. 
     In the case of “on demand” ink jet printers, a pressurization actuator is utilized to produce the ink jet droplet at every orifice. One of two types of actuators, either a heat actuator or piezoelectric actuator, may be utilized to produce the ink jet droplet. In the case of a heat actuator, a heater is placed at a convenient location to heat the ink. A quantity of ink will then phase change into a gaseous steam bubble, thereby raising the internal ink pressure sufficiently to permit an ink droplet to be expelled onto the receiver medium. In the case of piezoelectric actuators, a piezoelectric material possessing piezoelectric properties is utilized to produce an electric field when a mechanical stress is applied. The converse is also true. An applied electric field produces a mechanical stress in the material. Naturally occurring materials possessing such characteristics include quartz and tourmaline. The most commonly produced piezoelectric ceramics include lead zirconate titanate, barium titanate, lead titanate, and lead metaniobate. 
     Recently, a new type of continuous ink jet printer was disclosed. U.S. Pat. Nos. 6,079,821 and 6,234,620 to Chwalek et al., which describe a continuous ink jet printer in which on demand asymmetric heating of an ink jet causes selected drops to deflect. In one mode of operation, selected drops are deflected toward an image-receiving medium while the other drops are intercepted in a canopy-type gutter placed in close proximity (e.g., 3 mm) to the ink jet orifice plate. 
     Inks for high-speed ink jet printers, whether of the “continuous” or “piezoelectric” type, must have a number of special characteristics. For example, the ink should incorporate a nondrying characteristic; so that drying of ink in the ink ejection chamber is hindered or slowed to such a state that by the occasional spitting of ink droplets, the cavities and corresponding orifices are kept open. The addition of glycol facilitates free flow of ink through the ink jet chamber. 
     Of course, the ink jet print head is exposed to the environment where printing occurs. Thus, the aforementioned orifices are exposed to many kinds of air born particulates. Particulate debris may accumulate on surfaces formed around the orifices and in the orifices and chambers themselves. The ink may combine with such particulate debris to form an interference that blocks the orifice or alters surface wetting, thereby inhibiting the proper formation of the ink droplet. The particulate debris should be cleaned from the surface and orifice to restore proper droplet formation. In the prior art, cleaning is commonly accomplished by brushing, wiping, spraying, vacuum suction, and/or spitting of ink through the orifice. 
     Thus, inks used in ink jet printers can be said to have the following problems: the inks tend to dry-out in and around the orifices resulting in clogging of the orifices; and the wiping of the orifice plate causes wear on the plate and wiper, the wiper itself producing particles that clog the orifice. 
     Ink jet print head cleaners are known. An ink jet print head cleaner is disclosed in U.S. Pat. No. 4,970,535 titled “Ink Jet Print Head Face Cleaner” issued Nov. 13, 1990, in the name of James C. Oswald (the &#39;535 Patent). The &#39;535 Patent discloses an ink jet print head face cleaner that provides a controlled air passageway through an enclosure formed against the print head face. Air is directed through an inlet into a cavity in the enclosure. The air that enters the cavity is directed past ink jet apertures on the head face and exits via an outlet. A vacuum source is attached to the outlet to create a sub-atmospheric pressure in the cavity. A collection chamber and removable drawer are positioned below the outlet to facilitate disposal of removed ink. The technique uses heated air to remove the ink. Heated air is less effective for cleaning than a liquid solvent and can also damage fragile electronic circuitry that may be present on the print head face. 
     Other print head cleaning systems attempt to incorporate physical elements to clean debris from ink jet print heads. For example, a skip stroke wiping system is disclosed in U.S. Pat. No. 5,774,140 titled “Skip Stroke Wiping System for Ink Jet Print Heads,” issued Jun. 30, 1998, in the name of Kris M. English (the &#39;140 Patent). The &#39;140 Patent discloses a skip stroke wiping method for cleaning an ink jet print head and involves wiping and scraping steps. While the apparatus and method described in the &#39;140 Patent will remove debris, the harsh scraping and wiping steps can wear down the print head over time, thereby requiring a complicated wiping mechanism that is costly to replace if damaged. 
     U.S. Pat. No. 6,183,057 to Sharma et al. describes a cleaning assembly involving a removable gutter (not fixed) and a cup that sealingly engages the print head. Cleaning liquid supplied to the cup flows between a septum and the print head surface, thereby creating a zone of high shear. The cleaning liquid then exits via an outlet provided on the opposite side of the septum. This cup and septum arrangement cannot be utilized to clean the printer when the gutter is fixed. 
     Based on the foregoing, it can be appreciated that what is needed to efficiently clean an ink jet print head is a non-invasive print head cleaning method and system, one that involves the flow of fluids to remove debris and contaminants present on an ink jet print head, without damaging the print head itself. Such a method and system, if implemented, would avoid the aforementioned problems associated with present print head cleaning methods and systems, particularly those that involve heating techniques or complicated wiping mechanisms. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an ink jet printer having a cleaning assembly for cleaning a surface of an ink jet print head. 
     It is another object of the present invention to provide an ink jet printer having a cleaning assembly for cleaning a surface of an ink jet print head having a fixed type gutter. 
     It is another object of the present invention to provide a method and system for pumping a cleaning liquid across the print head surface to achieve cleaning of the surface and print head orifices. 
     It is yet another object of the present invention to remove used cleaning fluid from the print head, thereby cleaning contaminants from the surface of the print head and any associated print head parts, such as an orifice or orifice plate. 
     It is still another object of the present invention to provide a method and system for dislodging and removing contaminants from an ink jet print head and associated print head parts, including the gutter, utilizing a cleaning liquid that is pumped across the print head and simultaneously removed. 
     With the above objects in view, a cleaning assembly for use in an ink jet printer is disclosed. The ink jet printer includes a print head having a print head surface and one or more ink orifices disposed on the surface. The printer also includes a structural member that functions as a gutter for collecting ink, such that the gutter is disposed opposite the print head surface. The cleaning assembly is configured to clean contaminant from the print head surface. 
     According to an exemplary embodiment of the present invention, a self-cleaning printer system comprises a print head defining a plurality of ink channels disposed therein, wherein each ink channel terminates at an orifice. The print head also includes a surface thereon surrounding all the orifices. The print head is capable of jetting ink through the orifices. Ink jets are heated, causing ink drops to form and selectively deviate for printing. A receiver medium or a gutter can intercept the ink drops. In one method of operation, ink is selectively deflected onto a receiver medium (e.g., paper or transparency) supported by a platen disposed adjacent the print head, while the non-deflected ink drops are intercepted by a gutter. 
     Ink intercepted by the gutter can be recycled. Contaminants, such as oily film-like deposits or particulate matter, may reside on the print head surface thereby completely or partially obstructing the orifice. The oily film may, for example, be composed of grease. The particulate matter, on the other hand, may be composed of particles of dirt, dust, metal and/or encrustation of dried ink. The presence of contaminants interferes with the proper ejection of ink droplets from their respective orifices and therefore may give rise to undesirable image artifacts, such as banding. It is thus desirable to clean contaminants from the print head surface and orifices. 
     Therefore, a cleaning assembly is disposed relative to the surface and/or orifices for directing a flow of cleaning liquid along the surface and/or across the orifices, thereby cleaning contaminants therefrom. As described in detail herein, the cleaning assembly has an inflow channel appropriately angled to direct cleaning liquid at the orifices. 
     In another embodiment, cleaning liquid may be forced into the orifices and then out through an outlet provided in the print head. This back-flow enhances cleaning. In yet another embodiment, cleaning liquid may be supplied to the print head surface through a channel provided in the gutter. Thereafter, cleaning liquid can be directed to flow out of a cup via an outlet pipe, a channel in the gutter or through the orifices. In still another embodiment, ink jetting out of the orifices may be collected in a cup and swept away by cleaning liquid flowing into the cup. A pump for supplying cleaning liquid through the cup, print head or gutter is provided and provides suction. In addition, a filter can be used to filter particulate matter from the liquid for later disposal. In yet another embodiment, an ultrasonic transducer is used to enhance cleaning by energizing the cleaning liquid. In still another embodiment, cleaning liquid may carry gas bubbles to aid in cleaning of contaminant. The cleaning liquid may also be surged forward and backward by a piston device, thereby increasing cleaning efficiency. 
     An advantage of the present invention stems from the facts that fluids are non-invasively pumped across the print head in a manner that does not damage the print head. 
     Another advantage of the present invention lies in the ability of the channel to deliver fluids to the print head without damaging the print head surface. 
     A further advantage of the present invention stems from the fact that contaminants and debris can be removed from the print head and associated print head parts without the use of expensive and cumbersome heating techniques typical of many present prior art print head cleaning systems. 
     These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when read in association with the drawings depicted herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, it is believed the invention will be better understood from the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a view in elevation of a self-cleaning ink jet printer with a page-width print head; 
     FIG.  2 ( a ) is a fragmentation view in vertical section of a print head where four ink streams from left hand side are non-deflected (intercepted by gutter), while fifth, sixth, seventh and eighth ink streams are deflected out of the plane of the paper and intercepted by receiver medium; 
     FIG.  2 ( b ) is a side view of print head with a fixed gutter attached showing the pathway for deflected and non-deflected ink drops; 
     FIG.  2 ( c ) is a side view of print head with a fixed gutter attached, the gutter having a slot for allowing cleaning liquid to flow past; 
     FIG. 3 is a fragmentation view in vertical section of the print head showing some of the orifices encrusted with contaminant; 
     FIG. 4 is a view in elevation of a cleaning assembly for removing the contaminant; 
     FIG. 5 is a view in vertical section of the cleaning assembly with a cup and channel disposed to direct cleaning liquid to the print head orifices, surface of orifice plate and fixed gutter; 
     FIG. 6 is a view in vertical section of the cleaning assembly with a cup and channel disposed to direct cleaning liquid to the print head orifices, surface of orifice plate and fixed gutter with a slot; 
     FIG. 7 is an enlarged fragmentation view in vertical section of the cleaning assembly showing the contaminant being removed from the surface of the orifice plate and fixed gutter by flowing cleaning liquid; 
     FIG. 8 is a view in vertical section of the cleaning assembly including a cup with channel disposed to direct cleaning liquid and gas bubbles to the print head orifices, surface of orifice plate and to gutter; 
     FIG. 9 is a view in vertical section of the cleaning assembly, the cleaning assembly including a cup with channel and pressure pulse generator disposed to direct cleaning liquid to the print head orifices, surface of orifice plate and to fixed gutter; 
     FIG. 10 is a view in vertical section of the cleaning assembly including a cup with channel and ultrasonic generator disposed to direct cleaning liquid and pressure waves to the print head orifices, surface of orifice plate and to gutter; 
     FIG. 11 is a view in vertical section of the cleaning assembly including a cup with adjustable channel disposed to direct cleaning liquid to the print head orifices, surface of orifice plate and to fixed gutter; and 
     FIG. 12 is a view in cross-section of a cup with adjustable channel to enable horizontal section of channel to fit beneath fixed gutter and to fully overlap orifices. 
    
    
     References in the detailed description refer to like references in the figures unless otherwise indicated. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present description is directed to elements forming part of, or cooperating more directly with, an apparatus and method in accordance with the present invention. It is to be understood that elements not specifically shown or described herein may take various forms well known to those skilled in the art. Therefore, referring to FIG. 1, there is depicted a self-cleaning printer, generally referred to as  10 , for printing an image  20  on receiver medium  30 . Receiver medium  30  may be configured as a reflective-type receiver (e.g., paper) or a transmissive-type receiver (e.g., transparency). Receiver medium  30  is supported on a platen roller  40 , which is capable of being rotated by a platen roller motor  50  engaging platen roller  40 . Thus, when platen roller motor  50  rotates platen roller  40 , receiver medium  30  advances in a direction illustrated by a first arrow  55 . 
     Referring to FIGS. 1,  2 ( a ),  2 ( b ), and  2 ( c ), printer  10  also comprises a print head  60  disposed adjacent platen roller  40 . Print head  60  includes a plurality of ink channels  70 , a surface  90  and a plurality of print head orifices  25 , and heaters  79  surrounding each orifice  25 . For simplicity, the terms “orifice” and “orifices,” “heater” and “heaters,” and “channel and “channels” shall be used interchangeably throughout with identical reference numerals assigned to the plural and singular form of the element. As shown most clearly in FIGS.  2 ( b ) and  2 ( c ), a fixed gutter  17  is provided for capturing ink drops that are not deflected into the receiver medium  30  and surface  90  faces receiver medium  30 . In order to print image  20  on receiver medium  30 , an ink droplet must be released from orifice  25  in the direction of receiver medium  30  so that receiver medium  30  can intercept the ink droplet. In FIG.  2 ( a ), counting from left to right, the first four orifice heaters  79  have not been energized which causes drops  21  to be intercepted by gutter  17 . The next four heaters  79  are energized, causing drops  23  to deflect and land on receiver medium  30 . Ink drops  24  on receiver medium  30  form the image  20 . Ink drops  23  are deflected out of the plane of the drawing and therefore do not appear to be deflected in FIG.  2 ( a ). Deflected ink drops  23  are more clearly illustrated in FIGS.  2 ( b ) and  2 ( c ). 
     Referring again to FIGS. 1,  2 ( a ),  2 ( b ),  2 ( c ) and FIG. 4, therein is illustrated a self- cleaning printer system which includes an image source  600  (shown in FIG. 1) such as a scanner or a computer that provides raster image data, outline image data in the form of a page description language, or other forms of digital image data. The image source  600  is converted to half-toned bitmap image data by an image processing unit  610 , which stores the image data in memory. A plurality of heater control circuits  620  read data from memory within the image processing unit  610  and apply time-varying electrical pulses to a set of orifice heaters  79  that are part of a print head  60 . These electrical pulses are applied at an appropriate time, and at an appropriate orifice  25 , thereby permitting deflected ink drops  23  from a continuous ink jet stream to form spots on a receiver medium  30 , typically paper. The spots are formed on receiver medium  30  in an appropriate position predetermined by data residing in the memory of image processing unit  610 . Non-deflected ink drops  21  formed at the non-printing area are intercepted by gutter  17 . 
     Still referring to FIGS. 1 and 4, receiver medium  30  is moved relative to page-width print head  60  by rotation of platen roller  40 , which is electronically controlled by paper transport control system  120 . Paper transport control system  120  is in turn controlled by controller  130 . Paper transport control system  120  disclosed herein is, by way of example only, a single configuration and many different configurations are possible based on the teachings herein. In the case of page width print heads, it is most convenient to move receiver medium  30  past a stationary print head. However, in the case of a scanning print system, it is usually more convenient to move the print head along one axis (i.e., the sub-scanning direction) and the receiver medium  30  along an orthogonal axis (i.e., the main scanning direction) in a relative raster motion. Controller  130 , which is connected to platen roller motor  50 , ink pressure regulator  110  and a cleaning assembly, according to the invention described herein, enables printing and print head cleaning operations. Structure and operation of the cleaning assembly is described in detail hereinbelow. In one embodiment, the controller  130  may be a model CompuMotor controller available from Parker Hannifin in Rohrnert Park, Calif. 
     Referring again to FIGS. 1,  2 ,  4 , and FIG. 5, ink is contained in an ink reservoir  109  under pressure. In non-printing state, continuous ink jet drop streams are unable to reach receiver medium  30  due to the position of ink gutter  17 . In such a position, ink gutter  17  blocks the stream, thereby permitting a portion of the ink to be recycled by ink recycling unit  19 . Gutter  17  is a fixed gutter and forms part of print head  60 . Ink recycling unit  19  reconditions the ink and feeds it back to ink reservoir  109 . 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 the geometry and thermal properties of the orifices  25  and thermal properties of the ink. A constant ink pressure can be achieved by applying pressure to ink reservoir  109  under the control of ink pressure regulator  110 . 
     The ink is distributed to the back surface of print head  60  by an ink channel device  35  and through ink channel  31 , as depicted in FIG.  3 . The ink flows preferably through slots or holes etched through a silicon substrate of print head  60  to a front surface  90 , wherein a plurality of orifices  25  and heaters  79  are disposed. By fabricating print head  60  from silicon, it is possible to integrate heater control circuits  620  with the print head  60 . Non-deflected ink drops  21  are intercepted by gutter  17 , while deflected ink drops  23  land on receiver medium  30 . Deflection may be caused by a variety of methods including the asymmetric heating method discussed in U.S. patent application Ser. No. 08/954317 to Chwalek, et al. 
     Referring now to FIG. 3, it has been observed that surface  90  and channels  70  may become fouled by contaminant  140 . Contaminant  140  may be, for example, an oily film or particulate matter residing on surface  90 . Contaminant  140  also may partially or completely obstruct one or more of orifices  25 . The particulate matter may be, for example, particles of dirt, dust, metal and/or encrustations of dried ink. The oily film may be, for example, grease or the like. 
     The presence of contaminant  140  is undesirable because when contaminant  140  completely obstructs an orifice  25 , ink droplets  100  are prevented from being ejected from an effected orifice  25 . Also, when contaminant  140  partially obstructs an orifice  25 , the flight of ink droplets  100  may be diverted from first axis  107  to travel instead along a second axis  117 . If ink droplets  100  travel along second axis  117  or third axis  118 , ink droplet  100  will land on receiver medium  30  in an unintended location. In this manner, such complete or partial obstruction of orifice  25  leads to printing artifacts, such as “banding”, a highly undesirable result. The presence of contaminant  140  may also alter surface wetting and inhibit the proper formation of ink droplets  100 . It is thus desirable to clean (i.e., remove) contaminant  140  to avoid printing artifacts. 
     Therefore, referring to FIGS. 1,  4 ,  5 ,  6  and  7 , a cleaning assembly, generally referred to as  170 , is disposed proximate to surface  90  for directing the flow of cleaning liquid along surface  90  and across orifices  25  to clean contaminant  140  therefrom. Cleaning assembly  170  is movable from a first or “rest” position  172   a  spaced-apart from surface  90  to a second position or “cleaning position”  172   b  engaging surface  90 . This movement can be accomplished, for example, via an elevator  175  coupled to controller  130 . Cleaning assembly  170  may comprise a housing  180  for reasons described presently. Disposed in housing  180  is a generally rectangular cup  190  having an open end  195 . Cup  190  defines a cavity  197  communicating with open end  195 . An elastomeric seal  200  is attached to open end  195  by, for example, a suitable adhesive. The elastomeric seal  200 , which may be composed of rubber or the like, is sized to encircle gutter  17  and one or more orifices  25  thereby sealingly engaging surface  90 . 
     Referring to FIGS.  2 ( b ),  2 ( c ),  5 ,  6 ,  7 ,  8 ,  9 , and  10 , cleaning liquid is pumped into cavity  197  through inflow channel  210 . Inflow channel  210  directs fluid to orifices  25  and surface  90 . Cleaning liquid leaves cavity  197  by one of a number of outflow channels. For example, one possible outflow channel is the gutter channel  18  wherein suction is applied to the gutter channel  18  causing cleaning liquid to leave cavity  197  following arrow  500 . Alternatively, by applying suction to outflow channel  428  provided in print head  60 , cleaning liquid may exit cavity  197  following arrow  510 . Cleaning liquid may also leave cavity  197  through outflow pipe  433  in cup  190 . As described in more detail hereinbelow, a preferred pathway for outflow of cleaning liquid from cavity  197  may be employed to optimize cleaning of contaminant  140  from surface  90  and/or orifices  25 . This method may also be utilized to flush contaminant  145  from gutter  17  and gutter channel  18 . 
     By way of example only, and not by way of limitation, the velocity of the liquid flowing through gap  220  may be about 1 to 20 meters per second. Also by way of example only, and not by way of limitation, the height of gap  220  may be approximately 0.05 to 3 mm. 
     Referring again to FIGS. 5,  6 ,  7 ,  8 ,  9 , and  10 , interconnecting cup  190  and cleaning liquid reservoir  270  form a closed-loop piping circuit  250 . It will be appreciated that piping circuit  250  is in fluid communication with gap  220  for recycling liquid through gap  220 . In this regard, piping circuit  250  comprises a first piping segment  260  extending from cavity  197  to a reservoir  270  containing a supply of cleaning liquid. Piping circuit  250  further comprises a second piping segment  280  extending from reservoir  270  to inflow channel  210 . Disposed in second piping segment  280  is a recirculation pump  290 . Pump  290  pumps cleaning liquid from reservoir  270 , through second piping segment  280 , into cavity  197 , through first piping segment  260  and back to reservoir  270 , as illustrated by a plurality of second arrows  295 . It will be appreciated that for this flow path, valves  330 ,  435 ,  320  are open while valves  425 ,  427 ,  420 ,  430  and  370  are shut. A first filter  300  may be disposed in first piping segment  260 , while a second filter  310  may be disposed in second piping segment  280 . Second filter  310  filters (i.e., separates) contaminant  140  from the cleaning liquid as it circulates through piping circuit  250 . It will be appreciated that portions of piping circuit  250  adjacent to cup  190  are preferably made of flexible tubing in order to facilitate the uninhibited translation of cup  190  toward and away from print head  60 . Translation is accomplished via elevator  175 . It is preferable to remove contaminant  140  from the cleaning liquid as it is re-circulated through piping circuit  250 . This is preferred so that contaminant  140  is not redeposited onto surface  90  and across orifices  25 . Thus, first filter  300  and second filter  310  operate to filter contaminant  140  from the cleaning liquid re-circulating through piping circuit  250 . 
     In the event that there is a desire to squirt ink simultaneously out of one or more of the orifices  25  while cleaning liquid is being pumped into gap  220 , fifth valve  420  can be opened. Furthermore, if cleaning liquid needs to be disposed rather than be recycled, first valve  320  remains closed while third valve  370  opened, thereby permitting cleaning liquid to be collected in sump  350 . At the end of the cleaning cycle, it is preferable to drain cavity  197  before it is detached from surface  90  thereby limiting spillage. 
     Drainage of cavity  197  may be accomplished in the following manner. Valves  330 ,  425 ,  427 ,  420 ,  430  and  320  remain closed while valves  435  and  370  are opened and three-way valve  330  is switched to air vent  335 . Thereafter, suction pump  360  is activated, thereby drawing cleaning liquid from cavity  197 . Suction pump  360  drains cup  190  and associated piping of cleaning liquid before cup  190  is detached and returned to first position  172   a . Liquid flowing into sump  350  may be recycled into reservoir  270  when desired. 
     Referring to FIGS. 5 and 6, cleaning liquid is permitted to flow out of cavity  197  through gutter  17  following arrow  500 . In order to direct fluid from cleaning liquid reservoir  270  to gap  220  and cavity  197 , and thereafter exit gap  220  and cavity  197  through gutter channel  18 , valves  330 ,  427 , and  320  are opened while valves  425 ,  420 ,  430 ,  435 , and  370  are closed. Cleaning liquid exiting seventh valve  427  and travels in fifth piping segment  437  and joins fourth piping segment  415  at location  438 . Cleaning liquid may be collected in sump  350  for further use or as waste by closing valve  320  and opening valve  370 . When cleaning liquid is directed to flow through gutter channel  18  following arrow  500 , contaminant  145  in gutter channel is removed. When desirable, the flow of liquid out of gap  220  and cavity  197  may be directed through a combination of pathways. For example, an additional pathway for cleaning liquid to leave gap  220  and cavity  197  may be employed by opening valve  435 , thereby causing liquid to flow out through outflow pipe  433 . 
     Referring still to FIGS. 5 and 6, cleaning liquid may be directed to gap  220  and cavity  197  from cleaning liquid reservoir  270  and directed to leave gap  220  and cavity  197  through one or more orifices  25 . This is accomplished by pumping cleaning liquid while valves  330 ,  430 , and  320  are open and valves  425 ,  427 ,  420 ,  435  and  370  are shut or closed. When cleaning liquid is directed to flow through orifices  25  following arrow  510 , contaminant  140  present in ink channel  31  leading to orifices  25  is cleaned. Thus, cleaning liquid forced into print head  60  through orifices  25  leaves the ink channel  31  through outflow channel  433 . 
     Referring to FIGS.  2 ( b ),  2 ( c ) and  6  of the present invention, gutter  17  can be designed with a slot  560  cut into first wall  570  and second wall  572  of gutter  17 . Cleaning liquid arriving at gap  220  can continue to flow through slot  560  following arrow  515  of FIG. 6, thereby relieving stress on the frame of gutter  17  caused by the high rate of flow of cleaning liquid arriving through inflow channel  210 . 
     Returning to FIG. 1, elevator  175  may be connected to cleaning cup  190  for elevating cup  190  so that seal  200  sealingly engages surface  90  when print head  60  is at second position  172   b . To accomplish this result, elevator  175  is connected to controller  130 . Controller  130  controls the operation of elevator  175 . Of course, when the cleaning operation is completed, elevator  175  may be lowered so that seal  200  no longer engages surface  90 . 
     As best seen in FIG. 1, in order to clean the page-width print head  60  via cleaning assembly  170 , platen roller  40  must be moved to provide space for cup  190  to engage print head  60 . An electronic signal from controller  130  activates a motorized mechanism (not shown) that moves platen roller  40  in the direction of first double-ended arrow  388 , thereby providing space for the upward movement of cup  190 . Controller  130  also controls elevator  175  for transporting cup  190  from first position  172   a  (i.e., not engaging print head  60 ) to second position  172   b  (i.e., shown in phantom) engaging print head  60 . When cup  190  engages print head cover plate  80 , cleaning assembly  170  circulates liquid through cleaning cup  190  and over print head surface  90 . When print head  60  is required for printing, cup  190  is retracted into housing  180  by elevator  175  to its resting first position  172   a . Cup  190  may be advanced outwardly from and retracted inwardly into housing  180  in the direction of second double-ended arrow  387 . 
     Referring to FIGS. 5,  6 ,  7 ,  8 ,  9  and  10 , the cleaning liquid emerging from cup  190  and piping segment  415  is initially contaminated with contaminant  140  and contaminant  145 . It is desirable to collect this cleaning liquid in sump  350  rather than recirculate the liquid. Therefore, this contaminated liquid is directed to sump  350  by closing first valve  320  and opening third valve  370 , while suction pump  360  operates. The liquid will eventually be free of contaminant  140  and contaminant  145  and may be circulated by closing third valve  370  and opening first valve  320 . A detector  397  disposed in first piping segment  260  determines when the liquid is clean enough to be recirculated. 
     Information from detector  397  can be processed and used to activate the valves thereby directing the exiting of cleaning liquid to sump  350  or into recirculation. In this regard, detector  397  may be configured as a spectrophotometric detector. In any event, at the end of the cleaning procedure, suction pump  360  is activated and third valve  370  is opened so as to suction into sump  350 , any trapped liquid remaining between second valve  330  and first valve  320  (valve  330  is open to air vent  335 ). This process prevents the spillage of liquid when cleaning assembly  170  is detached from surface  90 . This process also causes surface  90  to become substantially dry, thereby permitting print head  60  to function without impedance from cleaning liquid drops disposed about orifices  25 . 
     To resume printing, eighth valve  430  is then closed and fifth valve  420  is opened to prime ink channels  70  with ink. Seventh valve  427  is also opened to recycle ink from gutter  17 . Suction pump  360  is again activated, and third valve  370  is opened to suction away liquid remaining in cup  190 . Alternatively, cup  190  may be detached and a separate spittoon (not shown) may be brought into alignment with print head  60  to collect drops of ink ejected from ink channels  70  and orifices  25  during the priming of print head  60 . 
     Those skilled in the art will appreciate that the mechanical arrangement described above is but one example of an ink jet print head cleaning method and system. Many different configurations are possible. For example, print head  60  may be rotated outwardly about a horizontal axis  389  to a convenient position to provide clearance for cup  190  to engage print head orifice plate  80 . According to the method and system described herein, print head  60  is configured to include a gutter  17 . 
     Referring to FIG. 8, there is shown a second embodiment of the present invention. In this second embodiment of the invention, a pressurized gas supply  390  is in communication with gap  220  thereby permitting a pressurized gas (e.g., pressurized nitrogen or pressurized argon) to be injected into gap  220 . The gas forms a multiplicity of gas bubbles  395  in the liquid to enhance the cleaning of contaminant  140  from surface  90  and/or orifices  25 . Gas bubbles  395  also enhance the cleaning of contaminant  145  in gutter  17 . 
     A third embodiment of the present invention is illustrated in FIG.  9 . In this third embodiment, a pressure pulse generator, such as a piston arrangement, generally referred to as  400 , is in fluid communication with gap  220 . Piston arrangement  400  comprises a reciprocating piston  410  for generating a plurality of pressure pulse waves propagated by the cleaning liquid as it travels through gap  220 . Piston  410  reciprocates between a first position and a second position, thereby causing the cleaning liquid to surge forward and backward through gap  220 , orifices  25  and gutter channel  18 . The second position is shown in phantom in FIG.  9 . Such “to-and-from” motion helps dislodge contaminant  140  and contaminant  145 . The pressure wave effectively enhances the cleaning of contaminant  140  from surface  90  and/or orifice  25  and the cleaning of contaminant  145  in the gutter. 
     The piston arrangement depicted at  400  of FIG. 9 represents one possible technique for generating a pressure pulse. Another technique is illustrated in FIG. 10, wherein a pressure pulse is produced in gap  220 . In FIG. 10, an ultrasonic generator  245  is depicted. Ultrasonic generator  245  is capable of generating a plurality of pressure waves  247  that enhance the cleaning of contaminant  140  from surface  90  and/or orifice  25 . The cleaning of contaminant  145  from gutter  17  is also thereby enhanced. By way of example only, and not by way of limitation, pressure waves  247  may have a frequency of 17 kHz and above. 
     A fourth embodiment of the present invention is illustrated in FIGS. 11 and 12. In this fourth embodiment, a horizontal section  630  is predisposed about channel  210  as shown to extend over orifices  25  so that a narrow passage between horizontal section  630  and the orifice plate  80  is defined. This arrangement provides for more efficient cleaning since a zone of high shear is provided over the orifices  25 . It will be appreciated that the extremity of horizontal section  630  with respect to the channel  210  must not interfere with gutter  17  during docking of cup  190  with orifice plate  80 . Therefore, as shown in FIG. 12 a channel wall  215  is provided and extends within cavity  197  along a surface of cup  190  to form the inflow channel  210 . The position of channel wall  215  is made adjustable to avoid collision with gutter  17  during docking. Once the cup  190  is engaged to surface  90  on orifice plate  80 , the position screw assembly  640  is used to adjust location of horizontal section  630 . Another mechanism (not shown) for adjusting the position of horizontal section  630  is to translate the cup along the surface  90  after the horizontal section  630  has cleared gutter  17  during docking. It will be appreciated that fourth embodiment of the present invention may be combined with ultrasonic generator  245 , pressurized gas supply  390 , and piston arrangement  400 . 
     The cleaning liquid mentioned hereinabove may be composed of any suitable liquid solvent composition, such as water, isopropanol, diethylene glycol, diethylene glycol monobutyl ether, octane, acids and bases, surfactant solutions and any combination thereof. Complex liquid compositions may also be utilized in accordance with the present invention, such as microemulsions, micellar surfactant solutions, vesicles and solid particles dispersed in the cleaning liquid. 
     Based on the foregoing, it can be appreciated that an advantage of the present invention stems from the fact that cleaning assembly  170  is capable of cleaning contaminant  140  from surface  90  and/or orifice  25  without resorting to brushes or wipers. Such brushes or wipers might otherwise damage surface  90  and/or orifices  25 , because inflow channel  210  directs the cleaning liquid at a high velocity to surface  90  and/or orifices  25 . Additionally, cleaning assembly  170  cleans contaminant  140  from surface  90  of orifice plate  80  and/or orifices  25  and contaminant  145  from gutter  17  while the gutter is fixed to print head  60 . 
     Another advantage of the present invention lies in the fact that the cleaning efficiency is increased. Gas bubbles  395 , pressure pulse generator  400 , and ultrasonic generator  245  all work to enhance cleaning. 
     Those skilled in the art can appreciate that the present invention can be modified without departing from the essential teachings of the invention. For example, a heater may be utilized to heat liquids pumped across surface  90 , into orifices  25  and into gutter channel  18  of FIGS. 5,  6 ,  7 ,  8 ,  9 , and  10 , thereby enhancing cleaning of the surface of print head  90 , and/or orifice  25  and gutter channel  18 . This is particularly useful when the cleaning liquid is of a type that increases in cleaning effectiveness as the temperature of the cleaning liquid is increased. In another example, a multiple color printer having a plurality of print heads respectively corresponding to a plurality of colors, one or more dedicated cleaning assemblies per color can be utilized to avoid cross-contamination of print heads by inks of different colors. 
     In yet another example wherein modifications may be made to the present invention without departing from the essential teachings of the invention, a contamination sensor may be utilized to detect when cleaning is necessary. Such a contamination sensor may be configured as a pressure transducer in fluid communication with ink disposed in channels flowing to print head  60 , thereby detecting the rise in ink back pressure when partially or completely blocked channels attempt to eject ink droplets. Such a contamination sensor may also be configured as a flow detector in communication with ink in such channels, thereby detecting low ink flow when partially or completely blocked channels attempt to eject ink droplets. 
     The contamination sensor may also be configured as an optical detector in optical communication with the surface of print head  60  and orifices  25 , thereby optically detecting the presence of contaminants by reflection or emissivity. The contamination sensor may also be implemented as a device that measures the amount of ink released into a spittoon-like container during predetermined periodic purging of associated ink channels. In this case, the amount of ink released into the spittoon-like container is measured by the device and compared against a known amount of ink that should be present in the spittoon-like container if no orifices were blocked by contaminants. Similar modifications may also be made to the configuration depicted in FIGS. 1,  4 ,  5 ,  6 ,  8 , 9  and  10 . 
     While the invention has been described with particular reference to its preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements of the preferred embodiments without departing from the invention. In addition, many modifications may be made to adapt a particular situation and material to a teaching of the present invention without departing from the essential teachings of the invention. 
     PARTS LIST 
       10  . . . printer 
       17  . . . gutter 
       18  . . . gutter channel 
       19  . . . ink recycling unit 
       20  . . . image 
       21  . . . non-deflected ink drops 
       23  . . . deflected ink drops 
       24  . . . ink drops on receiver medium 
       25  . . . print head orifice 
       29  . . . ink 
       30  . . . receiver medium 
       31  . . . ink channel 
       35  . . . ink channel device 
       40  . . . platen roller 
       50  . . . platen roller motor 
       55  . . . first arrow 
       60  . . . print head 
       70  . . . ink channels 
       79  . . . heaters 
       80  . . . orifice plate 
       90  . . . surface 
       100  . . . ink droplets 
       107  . . . first axis 
       109  . . . ink supply reservoir 
       110  . . . ink pressure regulator 
       117  . . . second axis 
       118  . . . third axis 
       120  . . . paper transport control system 
       130  . . . controller 
       140  . . . contaminant 
       145  . . . contaminant in gutter channel 
       170  . . . cleaning assembly 
       172   a  . . . first position (of cleaning assembly) 
       172   b  . . . second position (of cleaning assembly) 
       175  . . . elevator 
       180  . . . housing 
       190  . . . cup 
       195  . . . open end (of cup) 
       197  . . . cavity 
       200  . . . seal 
       210  . . . inflow channel 
       215  . . . channel wall 
       220  . . . gap 
       245  . . . ultrasonic generator 
       247  . . . pressure waves 
       250  . . . piping circuit 
       260  . . . first piping segment 
       270  . . . cleaning liquid reservoir 
       272  . . . air vent for cleaning liquid reservoir 
       280  . . . second piping segment 
       290  . . . recirculation pump 
       295  . . . second arrows 
       300  . . . first filter 
       310  . . . second filter 
       320  . . . first valve 
       330  . . . second valve 
       335  . . . air vent on valve  330  (three-way valve) 
       340  . . . third piping segment 
       350  . . . sump 
       360  . . . suction pump 
       370  . . . third valve 
       388  . . . double ended arrow 
       389  . . . horizontal axis 
       390  . . . pressurized gas supply 
       395  . . . gas bubbles 
       397  . . . detector 
       400  . . . piston arrangement 
       410  . . . piston 
       415  . . . fourth piping segment 
       420  . . . fifth valve 
       425  . . . sixth valve 
       427  . . . seventh valve 
       428  . . . out flow channel from print head 
       430  . . . eighth valve 
       433  . . . out flow pipe from cup 
       435  . . . fourth valve 
       437  . . . fifth piping segment 
       438  . . . location where fifth piping segment joins fourth piping segment 
       500  . . . arrow pointing direction of flow of cleaning liquid in gutter channel 
       510  . . . arrow pointing direction of flow of cleaning liquid through orifice 
       515  . . . arrow pointing direction of flow of cleaning liquid through gutter frame 
       560  . . . slot in gutter frame 
       570  . . . first wall of gutter 
       572  . . . second wall of gutter 
       600  . . . image source 
       610  . . . image processing unit 
       620  . . . heater control circuits 
       630  . . . horizontal section 
       640  . . . positioning screw assembly