Abstract:
A technique for handling residual ink that is from time to time present on the orifice plate of an ink-jet print cartridge. In one preferred embodiment, an ink-jet print cartridge is equipped with an ink-receptive member, such as an absorbent pad. The pad is located so that a service station wiper will move the residual ink from the orifice plate and spread it across the pad. The pad absorbs the ink. In essence, the ink is sequestered on the cartridge, in the pad. The exterior surface of the pad dries quickly so that there is little likelihood of developing a tacky area over the pad to which fibers may stick and degrade print quality.

Description:
TECHNICAL FIELD 
     This invention relates to ink-jet print cartridges, and particularly to handling of residual ink that is present from time to time on the exterior of the cartridge. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     An ink-jet printer includes one or more print cartridges that contain liquid ink in a reservoir. The reservoir is connected to a print head that is mounted to the body of the cartridge. The print head has tiny orifices that enable ejection of minute droplets of ink from the print head to a print medium, such as paper, that is advanced through the printer. 
     Many ink-jet printers include carriages for holding the print cartridge(s). The carriages translate across the width of the paper as the cartridge ejects ink droplets to the paper. Each time the carriage crosses the paper, a swath or effective print zone can be covered with ink as needed to print an image or text. Between carriage translations, the paper is advanced so that the next swath of the image may be printed. 
     Oftentimes, especially for color images, the carriage is translated more than once across the same print zone. With each such translation, a different combination of colors or droplet arrangements may be printed until the complete image is formed. Thus, a carriage and the cartridge it carries often move very close to wet or partially dry ink that was applied during an earlier translation. 
     The ink droplets are expelled through orifices that are formed in an orifice plate that covers most of the print head. Not all of the expelled ink is deposited upon the print medium, however. A small quantity of ink remains on the print head in puddles in the area near the orifices. This residual or waste ink needs to be removed so that it does not collect to an extent that it would interfere with the trajectory of subsequent droplets that are expelled through the orifices. Such interference will degrade the quality of the printed image because subsequent droplets will not be placed on the print medium as intended. 
     Even if residual ink does not interfere with the trajectory of subsequently expelled ink droplets, its presence may create other problems. For instance, partially dry ink on the cartridge body becomes tacky or sticky. In some printing environments, the tacky ink may collect small paper fibers or similar contaminants present in the printer. Even before the residual ink becomes tacky, its surface tension will retain particles such as these fibers. Furthermore, partially dry ink can clog the orifices on the print head, which will cause poor print quality. 
     Fibers that stick to the tacky ink can extend therefrom into contact with the print media. In instances where these extending fibers contact ink on the paper (as is most likely to occur during the multi-scan print mode mentioned above) the carriage movement drags the fiber across the wet ink and produces undesirable streaking of the ink. 
     Irrespective of whether ink streaking occurs, it is desirable to prevent the spread of residual ink to cartridge or printer components that may, over time, be degraded by the corrosive nature of certain ink formulations. 
     Current versions of ink-jet printers often include mechanisms for periodic servicing of the cartridges. These mechanisms are often referred to as service stations. The carriage occasionally moves away from the print media and into engagement with the service station. One of the functions of the service station is to wipe away the residual ink from the orifice plate of the cartridge, to avoid print quality problems, such as orifice clogging. 
     In the past, the residual ink that is wiped from the orifice plate has been deposited in storage trenches formed in the smooth plastic body of the print cartridge near the orifice plate. Even if the ink is properly deposited in the trench, it is stored there in a pool that becomes tacky and susceptible to collecting fibers that cause the ink streaking problem mentioned above. 
     Sometimes, the service station wiper does not properly engage the print cartridge to deposit the residual ink in the trench. Also, the portion of the cartridge that is wiped, including the trench, is usually very close to parts of the carriage (datum features) that secure the cartridge in a precise position relative to the carriage for accurate printing. As a result, some of the ink is inadvertently transferred from the improperly engaged wiper to these carriage parts (or to other parts of the cartridge). The residual ink on these carriage parts builds up over time. Although such buildup is gradual, the residue on the carriage is not removed with each cartridge replacement so, eventually, it can accumulate to an amount sufficient to cause problems, such as ink streaking. Additionally, the residual ink on the carriage may spread to and interfere with other printer components that may contact the carriage. 
     The present invention is directed to handling residual ink in a way that avoids the above noted problems. In one preferred embodiment of the invention, an ink-jet print cartridge is equipped with an ink-receptive member such as an absorbent pad. The pad is located so that a service station wiper will move the residual ink from the orifice plate and to the pad. 
     The pad absorbs the ink. In essence, the ink is sequestered on the cartridge, in the pad. Preferably, the pad is quite porous so that the ink is drawn into the absorbent pad so that the volatile components of the ink quickly evaporate to reduce the likelihood of developing a tacky area over the pad. 
     Moreover, the porosity of the pad means that, as compared to a solid surface, the exposed exterior surface of the pad is greatly reduced, thereby reducing the amount of ink that can be carried on that surface. As a result, the exterior surface of the pad will have a correspondingly reduced tacky area to which fibers may stick. Even if a tacky area does develop, the reduced area of the exposed surface (hence, the reduced amount of ink for holding fibers) means that any fibers that are temporarily held by the tacky area of the pad will more readily wiped away, or be free to fall off (and not cause ink streaking) as soon as the area dries. 
     The ink-receptive material may be mounted to the cartridge body in any of a number of ways. In one preferred embodiment, the material is located so that a service station wiper will immediately engage the material after wiping the orifice plate. Thus, the residual ink is moved onto the ink-receptive material (and off the wiper) before the wiper moves into contact with a carriage part. 
     In another preferred embodiment, the cartridge body is shaped to provide a scraper for scraping the residual ink from the passing wiper. The scraper is configured and located so that the ink scraped from the wiper is deposited on the absorbent pad. 
     Other advantages and features of the present invention will become clear upon study of the following portion of this specification and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a prior art ink-jet print cartridge showing the underside of the cartridge. 
     FIG. 2 is a partial perspective view of one preferred embodiment of a print cartridge adapted to sequester residual ink in accordance with the present invention. 
     FIGS. 3-5 illustrate sequences for sequestering residual ink on an ink-jet print cartridge in accordance one preferred approach to the invention. 
     FIG. 6 is a partial perspective view of another preferred embodiment of a print cartridge adapted to sequester residual ink in accordance with the present invention. 
     FIG. 7 is a partial side view of another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The prior art cartridge  20  shown in FIG. 1 includes a plastic body  22  that comprises a reservoir for containing liquid ink. The cartridge body  22  is shaped to have a downwardly extending snout  24 . A print head is attached to the underside of the snout  24 . The exposed portion of the print head is the exterior surface of an orifice plate  26  that includes minute orifices  28  (in this instance two rows of orifices) from which are ejected ink droplets onto printing medium that is advanced through the printer and very near the orifice plate. 
     At the sides of the cartridge body  22 , near the snout  24 , there are formed features, such as shown by the “L” shaped feature  30  in FIG.  1 . These features provide on the cartridge body datum or reference surfaces  32  that engage corresponding features in a carriage that carries the cartridge in the printer. FIG. 3 shows a portion of one such carriage feature  34  (which can be referred to as a datum hook) that has a surface  36  that engages the datum surface  32  of a cartridge that is carried by the carriage. Empty cartridges are removed from the printer carriage and replaced. 
     The greatest or most reliable printing accuracy occurs where at least some of the engaging registration surfaces cartridge body and carriage are located as closely as practical to the orifices through which the droplets are expelled. In the past, however, the proximity of the carriage components (such as datum hook  34 ) to the orifice plate  26  resulted in undesirable contact between at least some of the residual ink that has migrated from the orifice plate to the carriage components, as mentioned above. 
     The illustration of FIG. 1 also shows a thin circuit  40  that is attached to the body  22  of the cartridge  20 , partly on one side  42  of the cartridge. The circuit, which is flexible before attachment, continuously extends from the side  42  across most of the underside  44  of the snout  24  next to, but not covering, the orifice plate  26 . The circuit  40  may be a thin polyimide material that carries conductive traces. The traces connect at one end to contact pads in the print head that are near the long edges of the orifice plate  26 . The other ends of the traces terminate in contact pads  46  on the circuit, which pads mate with corresponding pads on the carriage. In short, the circuit  40  carries the control signals from the printer microprocessor to the individual components in the print head (such as thin film resistors) that produce the ink droplet ejection through the orifices  28  of the orifice plate. 
     As noted earlier, ink-jet printers often include mechanisms for periodic servicing of the cartridges. These mechanisms are often referred to as service stations that, among other things, periodically wipe residual ink from the outer surface of the orifice plate  26 . FIG. 1 shows in dotted lines a wiper component  50  of a service station. During a servicing operation, the resilient wiper  50  is moved into contact with the underside  44  of the snout and wiped across the orifice plate  26 . Alternatively, the cartridge may be moved relative to a stationary wiper to achieve the same wiping result. 
     FIG. 1 also depicts the above noted approach to storing the residual ink in trenches formed in the pen body. Shown there are two trenches  52 , one trench on each side of the circuit  40  and recessed into the underside  44  of the snout  24 . Ink that is wiped from the orifice plate  26  is deposited in a trench  52  after the resilient wiper  50  is moved from the plate  26 , along the adjacent portion  48  of the circuit  40  and across the opening of the trench  52 . 
     In most instances, the prior approach to residual ink removal works fine. Nonetheless, the above-discussed problems with residual ink movement and ink streaking may arise. The present invention addresses these problems and provides an ink-jet cartridge that is in many respects identical to the just described prior art cartridge. As a result, this description will not repeat the detail relating to preferred embodiment components that substantially match those just described relative to the prior art cartridge  22  (such as the circuit  40 , body  22 , etc.). 
     One preferred embodiment of the present invention is shown in FIG. 2, which depicts a cartridge  120  having a body  122  generally conforming to the body  22  of the FIG. 1 cartridge. A thin circuit  140  (like circuit  40  of the FIG. 1 cartridge) is attached to one side  142  of the body  122  and extends across the underside  144  of the snout  124  of the cartridge. 
     As was the case with the FIG. 1 cartridge, portions of the circuit  140  extend on each long side of the orifice plate  128  that is mounted to the snout underside  144 . In this embodiment, however, such portions of the circuit are covered with ink-receptive material, such as shown as absorbent pads  60 . These pads  60  are fastened to the cartridge to sequester residual ink on the cartridge  120 . In short, the residual ink on the orifice plate  128  is wiped across and held by the pads  60 . 
     More particularly, one embodiment of the pads includes a thin (less than 1 mm) sheet of porous polyethersulfone (PES) that is bonded to the cartridge body  122  (in this case to the circuit  140  that is attached to the body) so that an edge of a pad  60  substantially abuts a long edge of the orifice plate  128 . Other porous material may be used as an alternative to PES. For example, Nylon 6,6 will also suffice. Yet another alternative for the material that is used as a pad is a microporous polyolefin film that is impregnated with desiccants such as silica or calcium carbonate particles that facilitate drying of the residual ink that is wiped onto the pad. 
     This embodiment contemplates use with a service station that wipes the orifice plate in two opposite directions. As a result, the ink-receptive material is in two parts: one pad  60  on opposite sides of the orifice plate  128 . It is also contemplated that a single pad on one side of the orifice plate will suffice in instances where the service station wiper moves in only one direction. 
     As shown in FIG. 2, the pads  60  are sized to fit between the orifice plate  128  and an adjacent trench  152  (generally matching the above-described trench  52 ) formed in the snout  124 . In another embodiment, however, no trenches are provided, and the pads  60  are sized to extend (see dashed lines  62  in FIG. 3) over substantially the entire area of the snout underside  144 , except for the orifice plate  128 . 
     As shown in FIG. 2, the outer surface of the pads  60  are in a plane that is raised somewhat (i.e., raised but extending downwardly in FIG. 2) relative to the plane of the outer surface of the orifice plate  128 . It is also contemplated that the outer, flat surfaces of the pads  60  could be flush with or even recessed relative to that of the orifice plate. 
     The series of FIGS. 3-5 illustrate the removal of residual ink from an orifice plate in accordance with the present invention. FIG. 3 shows in elevation view the cartridge  120  of FIG. 2 facing the front side  142  of the body  122 . The cartridge  120  is mounted to a carriage with the carriage datum hooks  34  engaging the cartridge as described above. The cartridge is shown in the vicinity of a service station that includes a resilient wiper  70 , formed of material such as EPDM rubber. 
     The wiper  70  and cartridge  120  are moved into contact with one another as the cartridge is moved into and/or out of the service station. The wiper may be carried on a sled or other mechanism that is moves the wiper, as by camming action, into the path of the cartridge. The outer tip  72  of the wiper presses against the edge of the orifice plate  128  just inside one of the pads  60  (the left pad in FIG. 3) and is thereafter guided across the orifice plate  128  (left to right in FIG. 3) to wipe from the plate any residual ink, fibers, or other debris that may be there. The wiper  70  is depicted here as a resilient member, but it need not be to carry out this wiping action in accordance with the present invention. 
     After the wiper tip  72  traverses the orifice plate  128 , it encounters the edge of the absorbent pad  60  (here, the right pad in FIG.  4 ). The wiper tip  72  thus wipes across the outer surface of the absorbent pad so that the residual ink moved by the wiper from the orifice plate is wiped or spread across the pad. Thus, if the wiper tip  72  were to continue moving in the same direction (left to right) to contact the proximate carriage datum hook  34  (or any other printer part for that matter), it will have essentially wiped itself clean before such contact, thereby avoiding the undesired spreading of residual ink to, printer parts other than the cartridge  120 . 
     The residual ink that is spread onto the absorbent pad  60  is sequestered there until the cartridge is replaced. Moreover, the absorbent characteristics of the pads  60  draw the ink from the outer surface of the pad, which permits rapid drying of any ink components remaining on the surface. Thus, any fibers that may have been temporarily held to the surface of the pad  60  by the wet ink are, as a result of the absorbence and drying, free to drop off and not cause fiber-tracking problems. 
     FIG. 5 shows that, in the event a trench  152  is employed (instead of the extended pad  62 ) the tip  72  of the wiper will be scraped in the trench opening as the wiper is moved across the trench. As noted, however, at this juncture, the wiper will have already been wiped clean of ink by spreading the ink across the absorbent-material pad  60 . Thus, the trench provides some scraping action, but does not accumulate any significant amounts of liquid ink as occurred with prior art devices. 
     Although only one wiping direction is depicted in FIGS. 3-5, it is contemplated that the wiper  70  could also be wiped in the direction opposite to or perpendicular to the direction shown in the figures. 
     It will be appreciated that the ink-receptive material applied to the body of the cartridge may be embodied in material other than the absorbent pads just described. For instance, in another embodiment of the invention, the area of the cartridge next to the orifice plate  182  is coated with a very thin coating comprising a latex and/or crosslinked water soluble polymeric binder,(10-50 % by weight) and silica and/or alumina of a sol-gel precipitated or fumed absorbent filler that is applied by any of a variety of methods such as, spraying, to form a coating that is then dried and cured. Also, such a coating that includes a silica and/or an alumina filler will suffice. Coatings that use hydrogels are also suitable 
     Moreover, a layer of absorbent material (such as, for example, a fine-mesh nylon loop material) may be attached to the cartridge and covered with another, protective layer (for example, a perforated film of polyimide such as DuPont&#39;s Kapton material) that would, as compared to this type of absorbent material, be more compatible with the wiping operation, to thus protect the absorbent material from damage by the wiper. The absorbent layer and perforated or porous protection layer is attached to the underside  144  of the snout, as appears at  60  in FIG.  2 . This material can be extended as shown at  62  in FIG.  3 . The mechanism for attaching the absorbent and protective layer may be a pressure-sensitive adhesive layer underlying the absorbent layer. 
     FIG. 6 depicts another preferred embodiment of the present invention, which is made part of a cartridge  220  that has a slightly different shape than those described above. The principles of the invention apply, nonetheless. 
     The cartridge  220  of the FIG. 6 embodiment includes a body  222  generally conforming to the body  22  of the FIG. 1 cartridge. A thin circuit  240  (like that  40  of the FIG. 1 cartridge) is attached to one side  242  of the body  222  and extends across the underside  244  of the snout  224  of the cartridge. 
     As was the case in the FIG. 1 cartridge, portions  248  of the circuit  240  extend on each long side of an orifice plate  228  that is mounted to the snout underside  244 . In this embodiment, absorbent pads  260  are fit into correspondingly shaped cavities in the cartridge body on either side of the circuit portions  248 . The pads  260  are thus narrower (in the direction of wiper movement) than the foregoing pads  60 , but the body cavities (hence, pad size) are dimensioned so that the volume of absorbent material available for sequestering the residual ink is adequate to absorb the expected amount of residual ink for a given cartridge size, print head characteristics, etc. 
     As before, the outer surface of the pads  260  may be in the same plane as that of the orifice plate  228 , raised (as is depicted in FIG.  6 ), or slightly recessed relative to the plate. The pads are preferably a sintered ultra-high molecular weight, high-density polyethylene having a 15μ to 40μ pore size and a 25 % to 55 % pore volume. For the pad material discussed above, a pore volume of greater than 35% is preferred. Such material may be pre-molded or cut from stock and press fit into a cavity, or molded (sintered) within the cavity. Alternatively, the pads  260  may be bonded to the cavity walls, heat-staked, or attached by any of a variety of other ways. 
     Other sintered materials that may be suitable for the absorbent pad are polyethersulfone (PES), Nylon 6, and polytetrafluoroethylene (PTFE). Also, composite of polyester and polyethylene fibers may be used. 
     The above noted range of pore sizes provides a sufficient absorption rate for the residual ink. One could, however, select material having pore sizes outside that range and thus accept a different absorption rate while still enjoying the overall benefits of the present invention. Similarly, the pore volume may be selected outside of the preferred range mentioned above and the amount of absorbent material changed to arrive at an adequate capacity for absorbing residual ink in accordance with the present invention. 
     As was the case with the FIG. 2 pads  60 , the residual ink on the orifice plate  228  is wiped across and held by the pads  260  as was described in connection with FIGS. 3-5. 
     The diagram of FIG. 7 depicts another preferred embodiment, which is essentially a modification of the embodiment described with respect to FIG.  6 . In this embodiment, the body  320  of the cartridge is provided with scrapers  321  that protrude from the cartridge body into the path of the wiper  70 . Each scraper extends alongside a cavity in which is carried an absorbent pad  360 . The pad material and location matches the pad  260  described in the embodiment of FIG.  6 . 
     Each scraper  321  is slightly wider than the wiper  70  (as measured in the direction normal to the plane of FIG. 7) and is located so that it will scrape across the tip  72  of the wiper just after the wiper wipes across the surface of the pad  360 . The inside of the scraper (that is, the side facing the center of the orifice plate  328 ) is essentially an extension of a wall of the cavity that holds the pad  360 . As a result, residual ink that is scraped from the wiper  70  by the scraper  321  is deposited at the junction of the scraper and pad  360  so that the ink is absorbed into the pad. 
     It will be appreciated that the just described embodiment ensures complete sequestering of residual ink in the pad  360  even though the pad is relatively narrow (and thus has little surface area exposed to the wiper tip). Also, there is no need to slow the speed with which the wiper  70  moves relative to the print cartridge to ensure the ink is wiped into the narrow pad because the ink scraped from the wiper remains in contact with the pad for complete absorption after the wiper passes. 
     While the present invention has been described in terms of preferred embodiments, it will be appreciated by one of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims. For example, it is also contemplated that absorbent pads could be located on the above described carriage features, thereby to ensure that any residual ink that is brought into contact with the carriage will be absorbed and dried on the carriage-mounted pad.