|Publication number||USRE39242 E1|
|Application number||US 09/863,467|
|Publication date||Aug 22, 2006|
|Filing date||May 22, 2001|
|Priority date||Nov 13, 1996|
|Also published as||DE19749670A1, DE19749670B4, US5907335|
|Publication number||09863467, 863467, US RE39242 E1, US RE39242E1, US-E1-RE39242, USRE39242 E1, USRE39242E1|
|Inventors||Eric Joseph Johnson, Eric Mattis, Donald L. Michael|
|Original Assignee||Hewlett-Packard Development Company, L.P.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (34), Referenced by (2), Classifications (9), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is related to three other co-owned applications filed concurrently herewith, namely: U.S. patent application Ser. No. 08/747,855, filed on Nov. 13, 1996 entitled WET-WIPING PRINTHEAD CLEANING SYSTEM USING A TRANSFER ELEMENT, HP Docket No. 10961139; U.S. patent application Ser. No. 08/747,884, filed on Nov. 16, 1998 entitled WET-WIPING PRINTHEAD CLEANING SYSTEM USING A PRINTHEAD TREATMENT FLUID STORED IN A NON-FLOWABLE STATE, HP Docket No. 10961134; and U.S. patent application Ser. No. 08/747,857, filed on Nov. 13, 1996 entitled WET-WIPING PRINTHEAD CLEANING SYSTEM USING A DIRECT CONTACT TECHNIQUE, HP Docket No. 10961133.
1. Field of the Invention
The present invention relates to the cleaning of printheads in computer-driven printers of the type generally known as inkjet printers. More particularly, the invention relates to such cleaning in printers employing a “wiper” which slidingly engages and wipes a nozzle orifice plate surface of a printhead to remove excess ink and accumulated debris to improve printhead performance and print quality.
2. Description of the Related Art
Ink-jet printing systems typically operate by ejecting ink from a plurality of small, closely-spaced nozzles located on the printhead. For proper functioning, an ink-jet printhead must be routinely serviced.
During printing, stray droplets of ink, dust, paper fibers and other debris can accumulate around the nozzles on the orifice plate surface and interfere with the trajectory of subsequently ejected ink droplets, thereby affecting print quality. To minimize this, the ink-jet printhead can be cleaned by intermittently wiping the orifice plate surface to remove the accumulated ink and debris.
During periods of inactivity, ink in the nozzles can dry or harden, plugging the nozzles. Thus, ink-jet printheads may be capped to maintain an appropriate environment around the nozzles and to postpone their clogging. This capping may be done automatically after a short period of inactivity, even during the middle of printing a page, if the printer is waiting for more data.
Inkjet printers generally have a printhead service station to which an inkjet printhead is moved by carriage, and a cap which sealingly contacts the printhead is generally located at the service station. At the service station, the printhead (or multiple heads if such are used) are occasionally cleaned and, if necessary, primed with ink. For use in this cleaning function wipers are located at the service station. The service station can include a “sled” carrying these elements and others required to service the one or more printheads of the printer. This sled itself can be moved transversely to an axis of motion of the printhead carriage, for example in a vertical direction, so as to bring the caps or wipers for example into or out of contact with the printhead. Alternatively, a tumbler can be provided at the service station, and wipers, as well as caps, can be located on the tumbler. Rotation (and in some cases also vertical movement) of the tumbler effects wiping of the printhead, and/or alignment of one or more caps with one or more printheads positioned adjacent the tumbler at the service station.
To improve printing speed and the clarity and contrast of the printed image, recent advancements in the art have focused on improving the ink itself. For example, to provide faster, more waterfast printing with darker blacks and more vivid colors, improved pigment-based inks for inkjet applications have been developed. These pigment-based inks have a higher suspended solids content than earlier dye-based inks. Both types of ink dry quickly, which allows inkjet printing mechanisms to use plain paper. However, the combination of small nozzles and quick-drying ink leaves the printheads susceptible to clogging, in this case not only from the dried ink and minute dust particles or paper fibers, but also from the solids within the inks themselves. Further, this dried ink is more difficult to remove the previously used dry-based inks when dried. These characteristics compound the problems affecting print quality mentioned above.
Another characteristic of these pigment-based inks contributes to the nozzle clogging problem. The pigment-based inks use a dispersant to keep the pigment particles from flocculating. Unfortunately, the dispersant tens to form a tough film on the printhead orifice plate face as the ink “vehicle” or carrier component of the pigment-based ink evaporates. Besides the debris accumulated on the printhead face from ink over-spray, paper crashes and printer printing for example, this dispersant film also attracts and binds paper dust and other contaminants as well as solid from the ink itself. It has been recognized that this film, as well as ink residue and debris surrounding the printhead nozzles, is quite difficult to removed from the printhead.
Known cleaning systems used in printers of this type employ wipers which incorporate a blade formed of an elastomeric material such as a vinyl or EDPM. The wiper blade and a printhead are moved relative to one another so that the blade wipes accumulation from the critical area of the printhead incorporating the nozzle orifices. This system is not always fully effective even with older, dye-based inks. Some systems employ a second wiper formed of a soft absorbent material to further clean or “buff” the printhead. In other printhead servicing systems ink from the pen is ejected or drawn out and used to help lubricate the wiper and dissolve ink residues adhering to the printhead, with the goal of improving cleaning effectiveness. While this later scheme works well with some dye-based ink systems, it involves wasting ink that would otherwise be used for printing. Such a system is disclosed in commonly-owned U.S. Pat. No. 5,103,244 issued Apr. 7, 1992 to Gast, et al. and U.S. patent application Ser. No. 398,709 filed Mar. 6, 1995, the disclosures of which are incorporated herein by reference.
Furthermore, cleaning systems using ink drawn from the printhead do not work as well, generally speaking, with high-solids waterfast ink formulations. Reasons for this include the dried residue from such inks being more resistant to breakup and removably mechanical forces applied by the wiper as mentioned above, and that the kinetics of redissolution are slow in these inks. These factors, for example, limit the effectiveness of this known cleaning process, and that is undesirable. Also, with this system more ink residue collects on the wiper, and some of these accumulations can be pushed back into the nozzles of the printhead which can at least temporarily cause one or more nozzles not to fire properly, degrading print quality.
It has been recognized that application of a fluid solvent or other treatment fluid to the printhead will mitigate the problem of dried ink by showing the drying of ink or redissolving ink residues, rendering the printhead easily cleanable by wiping. However, many problems associated with use of a treatment fluid have been identified.
Storage of the treatment fluid in adequate amounts for the life of the printer without leaking is problematic. For example leaks can occur due to tipping the printer and pressure differentials due to a charge in temperature or altitude during shipment. Another problem recognized is application of treatment fluid to a printhead having undesirable accumulation of ink solids, dispersants, and other debris without contamination of the source of treatment fluid by such accumulations. It is desirable to maintain the means of applying treatment fluid and the treatment fluid itself in an uncontaminated state to provide consisting printhead cleaning over the life of the printer. Also, metering the amount of treatment fluid applied in wiping is recognized as important. Consistent optimally cleaning effectiveness as well as print quality can be compromised by application of too little or too much treatment fluid. Too little treatment fluid results in less effective residue removal allowing undesirable accumulation. Too much treatment fluid can result in one or more nozzles being at least temporarily disabled due to excess treatment fluid being pushed into the nozzle by the wiper, or drawn into the nozzle by negative pressure associated with operation.
In sum there are many problems, including identifying optimal ways of applying treatment fluid to enhance wiping effectiveness, that have been identified but not resolved in known cleaning systems. It is therefore recognized that an improved cleaning system, particularly for printers using pigment-based inks employing high solids content and dispersants, is needed to provide and maintain optimal functioning of thermal inkjet printheads.
The present invention accordingly provides a system for servicing a portion of a printhead of an inkjet printer of the type having a printhead reciprocally moved by a carriage and a wiper positioned and adapted to move relative to the printhead in wiping contact therewith to remove unwanted accumulations from a portion of the printhead to be cleaned when the printhead and the wiper are moved relative to each other by movement of at least one of the two elements consisting of the printhead and the wiper. The system includes a source of printhead wiping treatment fluid. It also includes projecting treatment fluid through the atmosphere in a reproducible quantity from the source of treatment fluid onto at least one of the said two elements (printhead and wiper) so as to be available to assist in wiping. The system provides for wiping the printhead by relatively moving the wiper and the printhead subsequent to placing the treatment fluid on at least one of these elements.
In a further more detailed aspect, the invention further includes providing an applicator adapted to place treatment fluid in a reproducible quantity on the surface of at least one of the printhead and wiper elements by projecting the treatment fluid through the atmosphere onto at least one of the printhead and wiper elements, avoiding direct contact therewith. Additional steps include transporting treatment fluid from the source of printhead treatment fluid to the applicator and projecting treatment fluid onto at least one element. The source of printhead treatment fluid can be permanently located or replaceable.
In more detail the invention further includes the option of providing a source of treatment fluid that acts both as a treatment fluid reservoir and as an applicator. The source of treatment fluid can incorporate a treatment fluid-jetting apparatus employing on demand drop ejection technology, and projecting jettable treatment fluid therefrom towards at least one element of the two elements consisting of the printhead and the wiper. Such a fluid jetting apparatus can be a cartridge having therein a treatment fluid reservoir and an on demand drop ejection means for projecting treatment fluid, and such a cartridge can be replaceable. Accordingly, in another more specific aspect the source of treatment fluid can be either permanently located within the printer or it can be a replaceable component.
In another detailed aspect the apparatus for projecting treatment fluid can comprise a low-volume spray pump. Such a spray pump can be connected by a conduit to a treatment fluid reservoir. The pump can be actuated by an actuator controlled by the printer controller or actuated by movement of structure carrying the element to which treatment fluid is applied, being the carriage, a service station tumbler or sled, or by movement of other structure coordinated with movement of the printhead or wiper.
In a further more detailed aspect, the apparatus for projecting treatment fluid through the atmosphere can include a spring which is elastically deformed and is adapted to impart energy to the treatment fluid or structure coupled to treatment fluid so as to impel treatment fluid toward at least one of the printhead and wiper elements on rebound of the spring.
FIG 24 is a sectional view of source of treatment fluid in another alternate embodiment incorporated in a service station of the printer of FIG. 1.
Certain reference numbers are used to refer to certain like elements in the various embodiments shown in the figures. However, this is purely for convenience. Use of the same or different reference numbers for any element is not to be construed as limiting the invention, or to imply elements are in all ways the same or different.
With reference to
While it is apparent that the printer components may vary from model to model, the typical inkjet printer 10 includes a chassis 12 and a print medium handling system 14 for supplying a print medium 13 to the printer 10. The print medium can be one of numerous types of suitable sheet material, such as paper, card-stock, transparencies, mylar, foils, etc. depending on the application, but for convenience, the illustrated embodiment is described using paper as the print medium. The print medium handling system 14 moves the print media into a print zone 15 from a feed tray 16 to an output tray 18, for instance using a series of conventional motor-driven rollers (not shown). In the print zone 15, the media sheets receive ink from an inkjet pen cartridge, such as a black ink pen cartridge 20 and/or one or more color ink pen cartridges 22, 24, 26. The illustrated embodiment employs a group of 4 discrete monochrome pens, however in other embodiments, for example, a tri-color pen can be used with a monochrome black ink pen, or a single monochrome black pen 20 may be used alone.
The illustrated pen cartridges 20, 22, 24, 26 each include reservoirs for storing a supply of ink therein, although other ink supply storage arrangements, such as those having reservoirs mounted on the chassis 12 and fluidly connected by a flexible conduit for example, may also be used. The cartridges 20, 22, 24, 26 incorporate printheads 30, 32, 34, 36 respectively. With reference also to
The printer chassis 12 defines a chamber 48 that provides a printhead servicing region including a service station 50, supported by the chassis and located at one end limit of the travel path of the carriage 42. The service station 50 includes a vertically moveable platform or frame referred to herein as a sled 52, supported by the service station within the servicing region. The sled is configured to support various service station components, such as wipers, caps, and priming units. A variety of suitable capping and printing designs are known and commercially available. In one embodiment (not shown) one or more wipers may be positioned stationary and only the caps are vertically moveable.
Referring now to
Before a primed pen 20, 22, 24, or 26 is again moved to the print zone 15 to print, these accumulations are removed in this embodiment by moving the sled to the wiper position and passing the printhead 30, 32, 34, or 36 desired to be cleaned past the wiper 70 which is carried by a spring mount 72. As seen in
As mentioned however, often in known devices the wiping action is less effective than desired. This can be due for example to the wiper being worn from numerous previous wiping cycles and/or dried accumulations being too firmly attached to the orifice plate surface to be removed in this way.
Referring now to
The treatment fluid 74 serves one or more of several functions depending upon the particular application. First, it lubricates the wiper 70 in wiping so as to reduce wear of the wiper. As is readily appreciated, wiper function is dependent on maintaining a desired wiper geometry, for example a wiper edge 84. Wear changes this geometry, for example by degradation of this edge over the life of the printer 10 to a rounded or uneven shape. Lubrication of the wiper accordingly provides better wiping function over the life of the printer by reducing wear of the wiper.
A second benefit of the treatment fluid 74 is that it dissolves some of the dried ink residues accumulated on the printhead 30. This allows such deposits to be more easily removed.
Third, the treatment fluid 74 helps the wiper 70 to transport both dissolved ink and other dried residue and accumulations in wiping. This results in a more thorough removal of such debris.
A fourth function of the treatment fluid 74 is that a thin film of fluid, which does not dry, is left on the printhead 30. Ink residue and other debris subsequently deposited on the printhead over this layer of fluid are more easily wiped off as they have less tendency to adhere to the printhead.
The treatment fluid used in the exemplary embodiment, polyethylene glycol (PEG), is relatively non-volatile, and relatively viscous. Again, depending on application, other fluids may be used, for example having properties selected for optimal performance with the particular ink being used. Treatment fluids that have been found to work well with pigment-based inks are generally characterizable in that they are water-soluble, somewhat viscous, and relatively non-volatile. Depending on the application PEG having an molecular weight of between about 200 and 600 is used. It has been found that by mixing PEGs of differing molecular weights treatment fluid properties can be varied to perform optimally in various embodiments of the invention for example.
Variation of the material comprising the treatment fluid 74, and the properties of a given material can be made so as to emphasize any function, such as lubrication, to increase wiper and printhead 30 life. Or alternatively, for example, it could be selected to best help dissolve ink residue and/or prevent residue and contaminants from adhering to the printhead.
An applicator, being in the illustrated embodiment a wick 80, is provided which draws treatment fluid from the fluid chamber 76 by capillary action, and is disposed through an opening 82 in the sled 52 between the cap 66 and wiper 70. Thus positioned it extends upward beyond the sled sufficient distance to contact the printhead 30 when it is in the capped position. A small reproducible amount of treatment fluid is deposited on the orifice plate 40 of the printhead 30 as a result of this contact. This treatment fluid is placed adjacent an edge of the plate nearest the wiper at a location wiped by the wiper so as to be available to the wiper in a subsequent printhead wiping operation. The wiper 70 will first come in contact with the deposited treatment fluid and thereafter wipe across the portion of the orifice plate to be cleaned. This can be made to occur each time the printhead 30 is wiped for example. As will be apparent, if the pen is not otherwise to be capped, the operation of dabbing, or depositing treatment fluid on the printhead orifice plate before wiping in this way is performed in a relatively short time. Also application of treatment fluid to printhead can be combined with priming.
In another embodiment (not shown), the applicator wick can be carried by a spring-mounted gimbal. Freedom of movement about two perpendicular axes for example provides uniform contact between such an applicator wick and a printhead.
The amount of fluid deposited depends on the surface area of the contact, the pore size of the applicator wick used, the properties of the surface of the orifice plate 40, the properties of the treatment fluid, and the relative force (if any) applied at the contact point due to relative positioning for example, or that applied as a result of a spring mounting (not shown) being used. In the illustrated embodiment the fluid supply is intended to be sufficient for the life of the printer, accordingly only a small amount of fluid is transferred to the printhead each time the wick makes contact.
In the illustrated embodiment the wick 80 is positioned to just come in contact with the printhead 30 when the pen 20 is capped. Force great enough to appreciably deform the wick is not applied to the wick by the printhead and vice-versa. The size of a rectangular area at the tip of the wick which comes in contact with the surface 40 of the printhead is approximately 12 millimeters by 0.5 millimeters. The relative porosity of the wick is characterized by a pore size of approximately 60 microns. The treatment fluid used is a PEG of molecular weight 400. This combination has been found to work well with presently-known and commercially-available orifice plates, for example those sold throughout the world by the assignee of the present invention.
In a further alternate embodiment, the applicator wick 80 is positioned so as to not contact the printhead 30 while capped, but rather, wipingly contact the printhead as the printhead it moves past along its path of motion with the carriage and deposits treatment fluid on the printhead. This wiping contact occurs when the sled is in the second, or wiping position. As the printhead 30 moves towards the print zone, the wick applies treatment fluid as said printhead moves past the applicator wick. Subsequently, the wiper wipes the orifice plate, clearing treatment fluid and unwanted accumulations therefrom.
In the illustrated embodiment, the applicator wick 80 is stabilized by the shape of the container 76 and by a second wicking material block 86 which fits snugly within the fluid container 76. This is perhaps best appreciated as shown in FIG. 5. An open-cell foam for example may be used to form the second wicking block. The foam should be selected so as to be compatible with the treatment fluid. Polyurethane foam can be used with PEG treatment fluid for example. The fluid is transported by capillary action through this block to the applicator wick 80, which can be formed of a material having relatively higher capillary attraction force properties. The applicator wick itself can be formed so as to have greater capillary attraction forces acting in and adjacent its upper extract which actually contacts the printhead 30 for example by compressing the applicator wick in this location. The applicator wick in any case is continuously supplied with treatment fluid which is drawn upward for application to the printhead.
With reference to
The closed chamber 78 containing the supply of treatment fluid 74 is scaled but for the opening 82 through the sled 52. The configuration of the container, sled, applicator wick, and second reservoir wicking block 77 formed of a porous media such as rigid or elastomeric open-cell foam which completely fills the chamber, acts by capillary forces to prevent treatment fluid from leaking from the chamber during shipment for example. As can be appreciated, a small vent opening 79 can be provided to allow air to enter as fluid is withdrawn.
Other embodiments of the invention employ any of several types of treatment fluid sources, as discussed below including chambers disposed elsewhere in, on, or adjacent the service station 50, or, alternatively, collapsible flexible enclosures such as accordion folded envelopes or simple bags formed of a flexible material. In any case the treatment fluid source should be designed to prevent leaking of the fluid. In rigid chamber constructions, having an opening for admitting air, this can be accomplished by filling the chamber with a porous media such as foam, as shown, or fibers (oriented or random) to provide pore spaces small enough so that capillary action will prevent fluid from leaking, or providing a one way valve at the air intake opening. With a flexible bag containing only treatment fluid, leaking due to air expanding in the chamber due to a temperature change during shipping, for example, can be prevented as a vent is not required due to collapsibility of the bag. In this latter embodiment the flexible bag is connected by conventional means to a tube, in turn conventionally connected to a housing of a wick holder comprising the wick applicator, the holder being mounted (for example by a spring gimbal mount) at the proper location adjacent a wiper.
In further alternate embodiments (not shown) the treatment fluid is fed by gravity from a reservoir to a wicker holder. The wick holder can enclose all but the tip of the applicator wick, which tip can have a higher capillary force than the rest of the applicator wick (formed for example of another material). Treatment fluid is drawn to the tip by capillary action and subsequently applied to the printhead.
In another embodiment, shown schematically in
Alternatively, the flow of treatment fluid to the applicator wick 80 through the line 90 can be controlled by other means (not shown) so that fluid will never leak. One means for example is to use a switch or mechanical valve that is open only when the printer is upright and in operation.
As can be appreciated, the embodiment of
Among the possible ways to implement this embodiment of the present invention a design found to work well involves incorporating a porous open cell rigid foam block 108 in the treatment fluid reservoir 100 incorporated in the pen 20. This foam block completely fills the reservoir and is impregnated with treatment fluid. In a further embodiment (not shown) the wick 102 is eliminated and an exposed portion of this foam is positioned to intercept the wiper 70 in relative wiping movement.
An example of a device where a treatment fluid is carried with the pen, and a device having a two-piece wiper having two pieces with opposed surfaces and a capillary space therebetween for conveying a treatment fluid to the tip of the wiper is disclosed in commonly-owned U.S. Pat. No. 5,300,958 issued Apr. 5, 1994 to Burke, et al., the disclosure of which is incorporated herein by reference.
As will be apparent, this pen-mounted treatment fluid source allows replacement of the treatment fluid supply with each new pen cartridge 20. This embodiment allows a smaller amount of treatment fluid to be stored and reliably dispensed (one pen life vs. a printer lifetime supply), and allows the lubricant to be more closely matched with the properties of the ink used. This later consideration is particularly noteworthy as it allows improvement of the ink formulations used over the lifetime of the printer without needing to consider the properties of the treatment fluid embodied in existing printers.
Returning now to
The treatment fluid container 76 is then joined to the sled by solvent or sonic welding, or by use of an adhesive for example, passing the applicator wick through the opening 82 to do so. The treatment fluid container 76 is configured to provide a receptacle 98 which receives the printing unit 60 of the sled 52. In another operation a wiper 70 formed of an elastomeric material having desired properties is mounted on a spring mount 72 which is retained against the sled by a portion of a retainer 96 which cooperates with the sled for this purpose.
With reference now to
In operation the carriage 42 moving towards the service station 50 first contacts the applicator housing 116 at the first position 117 and moves the applicator ahead of the carriage across the service station to a second position 119 where it remains while the pens 20, 22, 24, 26 are positioned adjacent their respective caps 66 for servicing or when caped between printing operations for example. As the carriage moves toward the print zone 15 from the service station 50 the applicator housing 116 follows the carriage 42 due to the rebound force of the biasing coil spring 118. As the applicator housing 116 traverses the service station in each direction the wicking tip applicator wipingly contacts the wipers 124 and deposits a small reproducible amount of treatment fluid, for example such as 1-5 microliters of PEG, to each wiper to assist in wiping as before described. As can be appreciated in this embodiment treatment fluid is first applied to the wiper 124, rather than the printhead 30. It will be noticed also that wiping in both directions of carriage travel occurs in this embodiment, and that treatment fluid is similarly applied to the wipers.
This embodiment gives the advantage of dosing the wipers 124 with treatment fluid by an applicator 122 moving with the pens 20, 22, 24, 26 without having to mount it (or a reservoir 120 of treatment fluid to supply it) on the carriage 42. In another embodiment the applicator housing 116 can comprise a separate treatment fluid cartridge which can be replaced periodically.
This embodiment provides an advantage in that the applicator wiper combination 128 acts as an intermediate transfer element to transfer treatment fluid from a source of treatment fluid 73 to the printhead. The result is that the applicator nib 122, and consequently the treatment fluid 74 is kept cleaner as the printhead 30 is wiped by the first wiper just previous to application of treatment fluid by the applicator/wiper combination 128 and the applicator nib 122 does not directly contact the printhead.
With reference now to
This embodiment provides the advantage of a carriage-mounted treatment fluid applicator 132 without having to carry the treatment fluid reservoir 144 on the carriage. Accordingly the doseable applicator 132 acts as a transfer element, transferring treatment fluid from a source 73 of treatment fluid 74 to the wiper 70. Also, by providing a checkvalve 141 located downstream of the pump 140 with sufficiently high cracking pressure, unwanted fluid leakage from the reservoir, such as might occur during shipment for example, is prevented. T he amount of treatment fluid in the hopper 134 is kept small so that leakage from the hopper due to tipping of the printer 10 for example, should it occur, is minimized. Also, the applicator 132 could be replaced by a wicking block formed of a porous media, which is periodically re-saturated with treatment fluid as required, to mitigate spilling from the hopper.
In operation, the printhead 30 wipingly contacts the composite dosing wiper 146, and in doing so deforms a first elastomeric wiper 150 and squeezes somewhat the saturated porous segment 148 causing treatment fluid 74 to be expelled upwardly onto the second wiper 151. The first wiper 150 is provided with a ramp portion 154 to assist in easing the relative wiping movement of the printhead 30 over the porous segment 148 so that no direct contact between the printhead and the porous segment occurs. As a result the foam comprising the porous segment is kept cleaner. The squeezing action of the wiping contact between the dosing wiper and the printhead gives rise to a pumping action which also can assist in drawing treatment fluid upward within the porous layer, as well as into the composite dosing wiper from the source of treatment fluid via the passageway 152.
As can be appreciated with reference to
Turning now to
In the illustrated embodiment pressurization is provided by a spring-loaded piston pump 140 actuated by depression of the sled 52 as the printhead 30 of the pen 20 is capped, the pump being placed between the sled and printer service station structure 50 for example. The duckbill applicator 132 acts as a checkvalve in operation of the pump. A further checkvalve 142 is required for pumping, as is well known, and is placed in a conduit 152 supplying treatment fluid from a collapsible fluid reservoir 144 for example. A low volume spray pump (not shown) of conventional configuration could be substituted, such a pump having its nozzle projecting upward so as to spray the orifice plate 40 upon the pen being capped.
With reference to
Also incorporated in the tumbler 162 are caps 66 which are used to cap the pens as described above. The caps can be pivotally and/or spring-mounted on the tumbler to facilitate capping and a consistent tight seal. Provision for vacuum priming is not made in connection with the tumbler-mounted caps, and in this embodiment the orifice plate 40 nozzles are cleared by “spitting” ink into a “spittoon” 168 provided for catching ejected ink and debris. This spitting operation can be performed less often in a printer according to the invention due to the printhead being kept cleaner by increased wiping effectiveness achieved with use of treatment fluid. In another embodiment (not shown) the tumbler can be made to rise and lower by provision of movable supports for the tumbler and an actuation means, for example a worn gear arrangement, or a solenoid. This may be done for example in connection with capping the printhead 30 or rotating the wipers 70 past the printhead without contacting it.
With reference particularly to
The scrapers are moveable closer to and away from the tumbler 162 to engage the wipers 70 as desired, but not the cap 66 for example. The movement of the scraper is coordinated with rotation of the tumbler by providing a cam surface 174 on the tumbler 162 and a follower 176 coupled to a hinged frame 178 carrying the scrapers. The frame pivots about a hinge 180 having an axis parallel to the axis of rotation of the tumbler. A link 182 connected to the cam follower is attached to the frame and in operation pulls a scraper-carrying first end of the frame opposite a second hinged end 181 of the frame closer to the tumbler as required for scraping the wipers 70 of a dual wiper set 144. In one embodiment the hinged frame is biased to a position away from the wiper for example, and is drawn closer by the cam surface.
The service station also includes a source of treatment fluid 184 disposed at the lower portion of the service station 50. This source of treatment fluid further includes a capillary applicator 109 in fluid contact with the interior of a closed chamber 78, similar to that described above, of a treatment fluid reservoir 100 containing a low volatility solvent 74 such as PEG described above. The capillary applicator 109 illustrated has two elastomeric flap components 190, 191 having chamfered portions 189 adjacent the upper tip 114 and planar opposed surfaces 192, 193 separated by a capillary space 112 therebetween. As described above, fluid rises in the capillary space to a tip portion 114. The applicator is formed of EDPM having a durometer of 70. The elastomeric flaps 190, 191 of the specialize applicator 109 are provided with hinge portions 194, 195 near their bases which allow the two halves of the upper part of the applicator to separate somewhat. This allows more treatment fluid to congruent at the upper portion by spreading the capillary wider in this area. In the illustrated embodiment the two elastomeric flaps are substantially identical. However, in another embodiment they can be given differing geometries, for example to provide a particular desired functional property.
Each of the flaps 190, 191 have identical geometries, simplifying assembly. For example in one embodiment each flap is four millimeters high measured from stabilizing wings 196, 197 disposed at their bases, and are one millimeter thick. The chamber portion 189 is three millimeters in height and has a thickness at the tips 114 of each flap of 0.2 millimeters. The width of the flaps (perpendicular to the plane of the page in
The chamber 78 of the reservoir 100 is formed by a containment 186 formed in the service station 50 and a lid 187. The lid has an opening 188 through which the applicator protrudes. The enclosed interior volume is filled with an open-cell foam material, fibrous or otherwise porous material comprising a porous media wicking block 110 impregnated with treatment fluid. One or more small vents 79 are provided to admit air from near the bottom of the chamber 78 as treatment fluid is depleted from the reservoir. This arrangement is similar to that described above in that the fluid is retained in the reservoir by capillary attraction during shipping, etc. but is available to the wiper as required. In one embodiment the wicking block employs a polyurethane foam or other treatment fluid-compatible material having a pore size, pore volume, and capillary fluid attractive properties compatible with the applicator 109. In this regard the pores must be sufficiently large, even when compressed by the applicator as illustrated, and the foam properties otherwise selected so that a capillary gradient between the reservoir 100 and the applicator 109 tends to draw fluid upwards as discussed above.
As will be appreciated, the foam or other porous media comprising the wicking block 110 within the reservoir 100 is compressed somewhat at a location directly adjacent the applicator 109 as the applicator further comprises stabilizing wings 196 and 197 which protrude into and impinge upon the wicking block 110, reducing pore size at that location. Accordingly localized higher capillary forces within the wicking material will tend to draw treatment fluid toward the compressed area and make it available to the applicator at its base, to be drawn into the capillary space within the applicator and migrate to the upper tip portion 114.
Treatment fluid in a small reproducible quantity is transferred from the tip 114 to each wiper 70 as the wiper wipingly contacts the applicator 109 as it rotates past. After passing each of the wipers by the applicator for example, the wiper set 144 rotated around to the orifice plate 40 of a carriage-mounted pen 20 positioned for servicing and wipes the orifice plate. As mentioned, after wiping each wiper is cleaned by the scraper 170 as it passes by in wiping contact therewith. This process can be controlled according to a preprogrammed sequence by the printer controller, or in response to an operator-initiated cleaning sequence.
The source of treatment fluid 184 can take other forms. Referring to
In a further embodiment a protective layer 204 of a differing material is placed over the exposed surface portion 202 of the foam. The layer serves to protect underlying foam or, alternatively, another porous media, from abrasion occasioned by the wiping contact of the wiper 70. The protective layer also serves a metering function if the porosity of the protective layer material is controlled to allow only a desired amount of treatment fluid through due to pumping action during each pass of the wiper, and also can be made to act to regulate the amount of fluid transferred to the wiper by providing a textured surface wiping or drawing excess fluid from the wiper as it passes. Depending on roughness of the surface 202 the protective layer 204 can also perform a wiper 70 cleaning function, removing dried ink accumulations for example as the wiper wipes the protective layer. The protective layer in one embodiment is made of a woven material such as polymeric filament or stainless steel wire fabric or metals, or a porous layer of another wear-resistant material, for example a more wear-resistant foam layer as described below, or a porous sheet of plastic or metal material which allows migration of treatment fluid therethrough. Such a sheet may be formed for example by a sintering process, or by ablating holes in a non-porous sheet. The relative wetting and pore size characteristics of the compliant foam block 200 comprising the fluid reservoir 100 and those of the protective layer 204 are controlled so that treatment fluid is drawn to the surface 202 to be available to the wiper by capillary action, or by the pumping action of the passage wiper, or some combination thereof.
In one embodiment the protective layer 204 is a nylon mesh, having a pore size small enough to retain the selected treatment fluid by capillary and attractive forces in the mesh. The mesh is disposed over a PEG-impregnated polyurethane foam. In another embodiment the protective layer is a stainless steel mesh. In either embodiment it has been found that the pore size of the mesh can be larger or smaller than that of the foam.
With reference to
In another embodiment, illustrated in
As can be appreciated, in each of the embodiments of
With reference to
In operation, treatment fluid is brought upward from the reservoir 100 to be available to the wiper 70 by rotation of the transfer roller. This rotation can be solely by means of wiping contact of the wiper in one embodiment, which wiping contact rotates the transfer roller a part of one rotation at each pass and makes fresh treatment fluid available on its surface to be transferred to the wiper on the next pass. In another embodiment the roller is rotated by a drive motor (not shown) coupled thereto and rotation is controlled by the printer controller and coordinated with rotation of the wiper to dispense a small reproducible amount of treatment fluid to be transferred to the wiper 70 for wiping.
A cantilevered metering wiper 224 can be employed to further control the amount of treatment fluid on the roller surface to be picked up by the wiper 70, by wiping off excess treatment fluid. As will be appreciated the metering wiper, which is shown bending upward to contact the roller in
With reference to
In the illustrated embodiment of
As mentioned, the embodiments shown in
Advantages obtained by use of a transfer wheel roller element 222 between the treatment fluid reservoir 100 and the wiper 70 include reducing contamination of the treatment fluid reservoir 100, and providing a metering function. For a given treatment fluid the amount transferred to the printhead 30 or wiper 70 can be varied for example by varying the roughness of the surface of the roller contacting the wiper or printhead 30, the wetting properties of materials used, for applied in contact of the wheel with other elements, and the use or not of a metering wiper 224 and the stiffness the metering wiper.
With reference to
In the illustrated embodiment a piston pump 140, such as described above for example is actuated by a cam 248 incorporated in the tumbler 162 and pumps treatment fluid from a collapsible reservoir 220 onto the corrugated surface 240 of the first inclined portion 242. The pumping of fluid is thus controllable by the printer controller (not shown) by way of rotation of the cam of the tumbler 162 in either direction. Pumping is coordinated with wiping so that fluid is present on the corrugated surface of the first inclined portion when the wiper 70 wipingly contacts it.
The pan 246 can have a closed bottom (not shown) so that ink and debris collect and dry there, or could be plumbed to drain into an absorbent media 250 for example. In another embodiment the pan is plumbed for recycling of the treatment fluid, for example by providing a flow-backchecked drain conduit 252 connected to a sludge trap 254 and the reservoir 220. As can be appreciated, the reservoir in this embodiment is located at a lower elevation than the pan. A further checkvalve 253 is provided to prevent retrograde flow of treatment fluid back into the pan 246.
With reference to
With reference to
In another embodiment the treatment fluid 75 can comprise a treatment fluid, such as PEG of lower molecular weight for example, liquid at ambient temperature, micro-encapsulated and dispersed within a wax or wax-like material which is solid at ambient temperature. When melted, such a material release the treatment fluid. Moreover, in another embodiment the wax-like material can be a high molecular weight PEG and the encapsulated liquid can be another treatment fluid, for example one which has low solubility in PEG, and this other treatment fluid is dispersed and entrained in liquid PEG at an elevated temperature, for example by high-shear mixing. After cooling the mix the liquid treatment fluid is micro-encapsulated in a solid PEG matrix.
Heating the treatment fluid to liquify it before use in servicing a printhead 30 can be done in a number of ways. In one embodiment illustrated by
Alternatively, as illustrated in
In another embodiment shown in
As shown in
In further embodiments shown in
In another embodiment shown in
With reference to
Turning now to
With reference to
After the treatment fluid 74 has been thrown onto the printhead 30 the printhead is moved along its axis of travel to a second position to be wiped by an offset tumbler-mounted wiper 70. This is best appreciated with reference to FIG. 39.
With reference to
With reference to all the embodiments described herein the application of a treatment fluid in the printhead wiping process add one more parameter (the treatment fluid itself) that can be varied to keep the printhead 30 clean, resulting in better print quality over the life of the printer 10, and lower operating costs and reduction of wasted resources due to improper printhead function attributable to inadequate cleaning, particularly where pigment-based, quick drying and waterfast inks are employed. By machining the chemical and physical characteristics of the ink, orifice plate surface 40 and wiper 70 with a complementary treatment fluid, optimization of pen cleanliness, wiper life and servicing speed is possible. These considerations are especially important if a given printhead is used for a long period of time. Moreover, the results of the invention can be obtained using configurations that are maintenance-free throughout the life of the printer 10. These considerations result in overall improved performance at tow additional cost to purchasers.
Persons skilled in the art will readily appreciate that various modifications can be made from the presently preferred embodiments of the invention disclosed herein and that the scope of protection is intended to be defined only by the limitations of the appended claims.
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|U.S. Classification||347/28, 347/32, 347/33|
|Cooperative Classification||B41J2/16538, B41J2/16552, B41J2/16541|
|European Classification||B41J2/165C3, B41J2/165C2B|
|Sep 30, 2003||AS||Assignment|
Owner name: HEWLETT-PACKARD DEVELOPMENT COMPANY L.P., TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HEWLETT-PACKARD COMPANY;REEL/FRAME:014061/0492
Effective date: 20030926
Owner name: HEWLETT-PACKARD DEVELOPMENT COMPANY L.P.,TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HEWLETT-PACKARD COMPANY;REEL/FRAME:014061/0492
Effective date: 20030926
|Dec 13, 2006||REMI||Maintenance fee reminder mailed|
|May 27, 2007||LAPS||Lapse for failure to pay maintenance fees|