Abstract:
An ink jet printing system comprises multiple print cartridges each containing a different ink and having a plurality of printhead nozzle arrays scanning across printing media in a printing zone. After a specified amount of ink has been dispensed, an ink jet printhead carriage is moved to a refill station for ink replenishment. A label on a print head service module displays encoded visual indicia which are sensed by an optical sensor on the ink jet printhead carriage. The optical sensor is used to read pre-encoded information as well as on the fly information which is recorded on a label when the carriage moves along a traverse path to the printhead service station.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     A previously filed co-pending commonly assigned application related this application is Ser. No. 08/454,975 filed May 31, 1995 by Joseph E. Scheffelin et al. (the &#34;&#39;975 application&#34;) entitled CONTINUOUS REFILL OF SPRING BAG RESERVOIR IN AN INK-JET SWATH PRINTER/PLOTTER now U.S. Pat. No. 5,745,137, which is incorporated herein by reference. 
     Other more recent co-pending commonly assigned related applications are U.S. patent application Ser. No. 08/726,587 entitled INKJET CARTRIDGE FILL PORT ADAPTOR now U.S. Pat. No. 5,874,976 filed Oct. 7, 1996 by Max S. Gunther, et al.; U.S. patent application Ser. No. 08/810,485 entitled INKJET PRINTING WITH REPLACEABLE SET OF INK-RELATED COMPONENTS etc. filed Mar. 3, 1997 by Rick Becker, et al.; U.S. patent application Ser. No. 08/805,859 entitled REPLACEABLE INK SUPPLY MODULE (BAG/BOX/TUBE/VALVE) etc. filed Mar. 3, 1997 by Elizabeth Zapata, et al.; U.S. patent application Ser. No. 08/805,860 entitled SPACE EFFICIENT ENCLOSURE SHAPE FOR NESTING TOGETHER A PLURALITY OF REPLACEABLE INK SUPPLY BAGS filed Mar. 3, 1997 by Erich Coiner, et al.; U.S. patent application Ser. No. 08/810,840 entitled PRINTING SYSTEM WITH SINGLE ON/OFF CONTROL VALVE etc. U.S. Pat. No. 5,929,883 filed Mar. 3, 1997 by Max S. Gunther, et al; U.S. patent application Ser. No. 08/805,861 entitled APPARATUS FOR PERIODIC AUTOMATED CONNECTION OF INK SUPPLY VALVES etc. filed Mar. 3, 1997 by Ignacio Olazabal, et al.; U.S. patent application Ser. No. 08/806,749 entitled VARIABLE PRESSURE CONTROL FOR INK REPLENISHMENT etc. now U.S. Pat. No. 5,992,985 filed Mar. 3, 1997 by Mark Young, et al.; and Ser. No. 08/719,606 entitled CALIBRATION TECHNIQUE FOR MIS-DIRECTED INKJET PRINTHEAD NOZZLES filed Sep. 25, 1996 by Robert W. Beauchamp et al., now U.S. Pat. No. 5,835,108 all of which are incorporated herein by reference. 
    
    
     This invention relates to ink-jet printers/plotters, and more particularly to techniques in varying off-axis ink cartridge reservoir height to decrease on-carriage print cartridge refill time, ensure ink refill volume reliability and set print cartridge vacuum pressure. 
     BACKGROUND OF THE INVENTION 
     A printing system is described in the commonly assigned patent application entitled &#34;CONTINUOUS REFILL OF SPRING BAG RESERVOIR IN AN INK-JET SWATH PRINTER/PLOTTER&#34; which employs off-carriage ink reservoirs connected to on-carriage print cartridges through flexible tubing. The off-carriage reservoirs continuously replenish the supply of ink in the internal reservoirs of the on-carriage print cartridges, and maintain the back pressure in a range which results in high print quality. While this system has many advantages, there are some applications in which the relatively permanent connection of the off-carriage and on-carriage reservoirs via tubing is undesirable. 
     A new ink delivery system (IDS) for printer/plotters has been developed, wherein the on-carriage spring reservoir of the print cartridge is only intermittently connected to the off-carriage reservoir to &#34;take a gulp&#34; and is then disconnected from the off-carriage reservoir. No tubing permanently connecting the on-carriage and off-carriage elements is needed. The above-referenced applications describe certain features of this new ink delivery system. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention optimizes the performance of this new off-carriage, take-a-gulp ink delivery system. In this type of IDS, a pen cartridge that uses an internal spring to provide vacuum pressure is intermittently connected to an ink reservoir located off the scanning carriage axis. Starting with a &#34;full&#34; pen cartridge, the printer will print a variety of plots while monitoring the amount of ink used. After a specified amount of ink has been dispensed, the pen carriage is moved to a refill station for ink replenishment. In the refill station, a valve is engaged into the pen, thus connecting the ink reservoir to pen cartridge and opening a path for ink to flow freely. Using only the vacuum pressure present in the pen cartridge, ink is &#34;pulled&#34; into the pen from the reservoir. 
     An optical sensor on an inkjet scanning carriage is used to read pre-encoded information as well as &#34;on the fly&#34; information which is recorded on a status label on a printhead service module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     These and other features and advantages of the present invention will become more apparent from the following detailed description of an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: 
     FIG. 1 is an isometric view of a large format printer/plotter system employing the invention. 
     FIG. 2 is an enlarged view of a portion of the system of FIG. 1, showing the refill station. 
     FIG. 3 is a top view showing the printer carriage and refill station. 
     FIG. 4 is an isometric view of an ink-jet print cartridge usable in the system of FIG. 1, with a refill platform housing portion, a needle valve, and supply tube in exploded view. 
     FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4, showing the valve structure in a disengaged position relative to a refill port on the print cartridge. 
     FIG. 6 is a cross-sectional view similar to FIG. 5, but showing the valve structure in an engaged position relative to the refill port of the print cartridge. 
     FIG. 7 is a cross-sectional view taken along line 7--7 of FIG. 6 and showing structure of the needle valve and locking structure for locking the valve in the refill socket at the refill station. 
     FIG. 8 is a cross-sectional view similar to FIG. 7, showing the lock in a released position. 
     FIG. 9 is an enlarged view showing the mechanism for moving the valve structure, without any valves mounted thereon. 
     FIG. 10 shows an off-carriage ink supply module incorporating the present invention. 
     FIG. 11 is a schematic representation showing a plurality of off-carriage ink supply modules connected to the valve structure. 
     FIG. 12 is a detailed side view showing the mechanism for moving the valve structure in disengaged position with a print cartridge. 
     FIG. 13 is a detailed side view showing the mechanism for moving the valve structure in engaged position with a print cartridge. 
     FIGS. 14A and 14B show an isometric and a side view, respectively of a service station module incorporating the present invention. 
     FIG. 15 is an isometric view of a carriage for removably mounting the service station module of FIGS. 14A-14B. 
     FIG. 16 is an isometric view of a carriage moving across a print zone. 
     FIG. 17 shows the carriage of FIG. 16 in position at the refill station, with the valve structure in disengaged positon. 
     FIGS. 18A and 18B show the printer with the refill station and service station doors in closed and open positions, respectively. 
     FIG. 19 is an exploded schematic view showing the integrated ink delivery system component of the invention (print cartridge, ink supply module and service station module) incorporated into a single package. 
     FIG. 20 shows six exemplary steps for replacing the print cartridge of the present invention. 
     FIG. 21 shows five exemplary steps for replacing the ink supply module of the present invention. 
     FIG. 22 shows five exemplary steps for replacing the service station module of the present invention. 
     FIG. 23 is an exploded isometric view of the service station module of FIGS. 14A-14B. 
     FIG. 24 is an isometric view looking down at the back of a service station unit with a service station carriage installed thereon for utilizing the service station module of FIG. 23. 
     FIG. 25 is an isometric view looking down at a front portion of the service station unit of FIG. 24, without any carriage installed. 
     FIG. 26 is a top plan view of the service station module. 
     FIG. 27 is a partially schematic end view from the right side of the printer showing a carriage aligned for optical reading of encoded information on a service station module. 
     FIG. 28 is a partially schematic end view from the left side of the printer showing a carriage aligned for nozzle spitting into a spittoon on the service station module. 
     FIG. 29 is an enlarged schematic representation of label format used for encoding information on the service station module. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An exemplary application for the invention is in a swath plotter/printer for large format printing (LFP) applications. FIG. 1 is a perspective view of a thermal ink-jet large format printer/plotter 50. The printer/plotter 50 includes a housing 52 mounted on a stand 54 with left and right covers 56 and 58. A carriage assembly 60 is adapted for reciprocal motion along a carriage bar, shown in phantom under cover 58. A print medium such as paper is positioned along a vertical or media axis by a media axis drive mechanism (not shown). As is common in the art, the media drive axis is denoted as the `x` axis and the carriage scan axis is denoted as the `y` axis. 
     FIG. 3 is a top view diagrammatic depiction of the carriage assembly 60, and the refill station. The carriage assembly 60 slides on slider rods 94A, 94B. The position of the carriage assembly 60 along a horizontal or carriage scan axis is determined by a carriage positioning mechanism with respect to an encoder strip 92. The carriage positioning mechanism includes a carriage position motor 404 (FIG. 16) which drives a belt 96 attached to the carriage assembly. The position of the carriage assembly along the scan axis is determined precisely by the use of the encoder strip. An optical encoder 406 (FIG. 15) is disposed on the carriage assembly and provides carriage position signals which are utilized to achieve optimal image registration and precise carriage positioning. Additional details of a suitable carriage positioning apparatus are given in the above-referenced &#39;975 application. 
     The printer 50 has four ink-jet print cartridges 70, 72, 74, and 76 that store ink of different colors, e.g., black, yellow, magenta and cyan ink, respectively, in internal spring-bag reservoirs. As the carriage assembly 60 translates relative to the medium along the y axis, selected nozzles in the ink-jet cartridges are activated and ink is applied to the medium. 
     The carriage assembly 60 positions the print cartridges 70-76, and holds the circuitry required for interface to the heater circuits in the cartridges. The carriage assembly includes a carriage 62 adapted for the reciprocal motion on the front and rear sliders 92A, 92B. The cartridges are secured in a closely packed arrangement, and may each be selectively removed from the carriage for replacement with a fresh pen. The carriage includes a pair of opposed side walls, and spaced short interior walls, which define cartridge compartments. The carriage walls are fabricated of a rigid engineering plastic. The print heads of the cartridges are exposed through openings in the cartridge compartments facing the print medium. 
     As mentioned above, full color printing and plotting requires that the colors from the individual cartridges be applied to the media. This causes depletion of ink from the internal cartridge reservoirs. The printer 50 includes four take-a-gulp IDSs to meet the ink delivery demands of the printing system. Each IDS includes three components, an off-carriage ink reservoir, an on-carriage print cartridge, and a head cleaner. The ink reservoir includes a bag holding 350 ml of ink, with a short tube and refill valve attached. Details of a ink reservoir bag structure suitable for the purpose are given in co-pending U.S. patent application Ser. No. 08/805,860, SPACE-EFFICIENT ENCLOSURE SHAPE FOR NESTING TOGETHER A PLURALITY OF REPLACEABLE INK SUPPLY BAGS, filed Mar. 3, 1997 by Erich Coiner et al. These reservoirs are fitted on the left-hand side of the printer (behind the door of the left housing 58) and the valves attach to a refill arm 170, also behind the left door, as will be described below. The print cartridge in this exemplary embodiment includes a 300-nozzle, 600 dpi printhead, with an orifice through which it is refilled. The head cleaner includes a spittoon for catching ink used when servicing and calibrating the printheads, a wiper used to wipe the face of the printhead, and a cap (used to protect the printhead when it is not in use). These three components together comprise the IDS for a given color and are replaced as a set by the user. 
     The proper location of each component is preferably identified by color. Matching the color on the replaced component with that on the frame that accepts that component will ensure the proper location of that component. All three components will be in the same order, with, in an exemplary embodiment, the yellow component to the far left, the cyan component in the center-left position, the magenta component in the center-right position and the black component in the far-right position. 
     The ink delivery systems are take-a-gulp ink refill systems. The system refills all four print cartridges 70-76 simultaneously when any one of the print cartridge internal reservoir&#39;s ink volume has dropped below a threshold value. A refill sequence is initiated immediately after completion of the print that caused the print cartridge reservoir ink volume to drop below the threshold and thus a print should never be interrupted for refilling (except when doing a long-axis print that uses more than 5 ccs of ink of any color). 
     The &#39;975 application describes a negative pressure, spring-bag print cartridge which is adapted for continuous refilling. FIGS. 4-8 show an ink-jet print cartridge 100, similar to the cartridges described in the &#39;975 application, but which is adapted for intermittent refilling by addition of a self-sealing refill port in the grip handle of the cartridge. The cartridge 100 illustrates the cartridges 70-76 of the system of FIG. 1. The cartridge 100 includes a housing 102 which encloses an internal reservoir 104 for storing ink. A printhead 106 with ink-jet nozzles is mounted to the housing. The printhead receives ink from the reservoir 104 and ejects ink droplets while the cartridge scans back and forth along a print carriage during a printing operation. A protruding grip 108 extends from the housing enabling convenient installation and removal from a print carriage within an ink-jet printer. The grip is formed on an external surface of the housing. 
     FIGS. 4-8 show additional detail of the grip 108. The grip includes two connectors 110, 112 on opposing sides of a cylindrical port 114 which communicates with the reservoir 104. The port is sealed by a septum 116 formed of an elastomeric material. The septum 116 has a small opening 118 formed therein. The grip with its port 114 is designed to intermittently engage with a needle valve structure 120 connected via a tube 122 to an off-carriage ink reservoir such as one of the reservoirs 80-86 of the system of FIG. 1. FIG. 5 shows the valve structure 120 adjacent but not engaged with the port 116. FIG. 6 shows the valve structure 120 fully engaged with the port. As shown in FIG. 6, the structure 120 includes hollow needle 122 with a closed distal end, but with a plurality of openings 124 formed therein adjacent the end. A sliding valve collar 128 tightly fits about the needle, and is biased by a spring 126 to a valve closed position shown in FIG. 5. When the structure 120 is forced against the port 116, the collar is pressed up the length of the needle, allowing the needle tip to slide into the port opening 118, as shown in FIG. 6. In this position, ink can flow through the needle openings 124 between the reservoir 104 and the tube 130. Thus, with the carriage 100 connected to an off-carriage ink reservoir via a valve structure such as 120, a fluid path is established between the print cartridge and the off-carriage reservoir. Ink can flow between the off-carriage ink reservoir to the cartridge reservoir 104. When the structure 120 is pulled away from the handle 108, the valve structure 120 automatically closes as a result of the spring 126 acting on the collar 128. The opening 118 will close as well due to the elasticity of the material 116, thereby providing a self-sealing refill port for the print cartridge. 
     FIGS. 4-8 illustrate a locking structure 172 for releasably locking the valve 120 into the refill arm 170 at socket 174. The structure 172 has locking surfaces 172B (FIG. 5) which engage against the outer housing of the valve body 120A. The structure is biased into the lock position by integral spring member 172A (FIGS. 7 and 8). By exerting force on structure 170 at point 170C (FIGS. 7 and 8) the spring is compressed, moving surface 172B out of engagement with the valve body, and permitting the valve to be pulled out of the refill arm socket 174. This releasing lock structure enables the valve and reservoir to be replaced quickly as a unit. 
     The print cartridges 70-76 each comprise a single chamber body that utilizes a negative pressure spring-bag ink delivery system, more particularly described in the &#39;975 application. 
     In the exemplary system of FIG. 1, the refill platform 150 is in the left housing 56 of the printer 50 as shown in FIG. 2. The four off-carriage ink reservoirs 80-86 are supported on the platform 150. Short flexible tubes 152, 154, 156 and 158 connect between ports 80A-86A of corresponding reservoirs 80-86 and needle valve structures 160, 162, 164 and 166 supported at a refill station housing 170. These needle valve structures each correspond to the valve structure 120 of FIGS. 4-8. 
     The refill platform 150 is an elevator that holds the four reservoirs and can be moved up and down 
     To perform a refill the carriage assembly 60 is moved to the refill station where the four off-carriage reservoirs 80-86 are connected to the corresponding print cartridges 70-76 via the shut-off valves 160-166. The connection of the reservoirs is accomplished by turning a stepper motor 200 that advances a lever 202 on which the valve structures and refill station housing 170 are mounted, as shown in FIGS. 3 and 12-13. A system suitable for moving the valves into and out of engagement with the refill ports is more fully described in co-pending application Ser. No. 08/805,861 filed Mar. 3, 1997, APPARATUS FOR PERIODIC AUTOMATED CONNECTION OF INK SUPPLY VALVES WITH MULTIPLE PRINTHEADS, by Ignacio Olazabal et al. While the valves are engaged in the refill ports of the print cartridges, ink is pulled into the print cartridge reservoir due to the slight vacuum pressure (back pressure) in it. This back pressure is known to decrease with increasing ink volume. This results in a self regulating refill process where, as more ink is introduced into the print cartridge, the back pressure decreases to a point where the print cartridge can no longer pull additional ink into the cartridge and the refill stops. The pressure at which the flow of ink stops is governed by the distance offsetting the print cartridge and the off-carriage reservoir. The farther below the print cartridge the reservoir is located, the greater the final pressure in the print cartridge and the lower the resulting volume of ink in the print cartridge internal reservoir. 
     As best shown in FIG. 16, the present invention does not require the specifications of the carriage to be redesigned due to the drag and interference that results from typical off-carriage ink systems where ink supply tubes remain constantly connected with the cartridges on the carriage during a printing operation. In contrast, the carriage shown in the drawings can move back and forth across the print zone without any supply tube connection whatsoever. Moreover, there is no need to account for the additional carriage mass that typically results from having a replaceable supplemental ink supply mounted directly on the carriage. 
     Additional details of the apparatus which provides the periodic connection/disconnection at the refill station between the print cartridge fill port and the off-carriage ink supply valve will now be described. Referring to FIGS. 9, 12-13 and 17, a bracket holding the ink supply valves supports the motor 200 which turns gears 210 to move gear arms 212 back and forth between a position of engagement of the supply valves with their respective fill ports on the print cartridges, and a position of disengagement. Primary stabilizing arms 214 on the bracket as well as secondary stabilizing arms 215 on the carriage provide the necessary restraint required to minimize an undue stress on the cartridges which might otherwise displace their precise positioning in the carriage. The beginning and end points of the engagement/disengagement are defined by an optical sensor 216. 
     In the presently preferred embodiment of the invention, all four ink supply valves move together as a unit as they are held in fixed position in their apertures 218 by individual locking buttons 219 that allow each valve to be separately replaced whenever the expected life of the integrated IDS has expired for that particular color of ink. When replacement is required, an arrow-shaped orientation key 222 mates with a matching orientation slot 224 by easy manual manipulation through a valve handle 226. 
     A unique narrow replaceable service station module 230 for each color ink is an important part of the IDS. Referring to FIGS. 14A-14B and 15, this service station module includes a protruding handle 232 on one end, and a group of printhead servicing components which are combined together in a relatively small area on top of the module. At one end are dual wipers 234 and at the other a spittoon 238 with a nozzle plate cap 236 at an intermediate position. An external primer port 240 in the module is connected through an interior passage to the cap 236, and in the opposite direction through a circular seal 242 to a vacuum source. A service station carriage 251 includes separate slots 244, 246, 248, 250 for each service station module (also sometimes called a printhead cleaner). 
     A spring-loaded datum system provides for the service station module to be easily but precisely positioned in the service station carriage. Along a top portion of each slot is a z-datum ridge 252 which engages a corresponding datum ledge 254 along both top edges of the module. An upwardly biased spring arm 260 assures a tight fit along these datum surfaces. A horizontal positioning is provided in each slot by a pair of protruding corners which act as latches against matching stops 258 on the module. Although not required, a biasing arm 262 may be employed in a rear wall of each slot. 
     FIG. 10 shows the basic exterior structure of an ink supply module before installation, and FIG. 11 shows how four such modules are grouped together on a refill platform on the printer with their valves manually installed on the valve bracket. 
     FIGS. 18A and 18B illustrate the accessability required for replacement of the three basic components parts of the IDS. The front of the printer unit typically includes a roll feed unit 270, a control panel 272 and a print zone access door 274 adjacent an elongated frame member 275. The service station is located at the right end of the carriage scan axis, and a refill station 278 at the opposite end. Simple friction latches such as indicated at 280 are provided to assure proper closure of doors which are mounted on pivot hinges such as 281. A pusher plate 284 contacts and helps to position any incompletely mounted service station modules upon closure of a service station door 282. A similar door 286 closes off the refill station during normal operation of the printer. The refill station includes space 287 for an ink supply platform, and an access hole 288 from the platform to carriage-mounted printheads. 
     An installation procedure will now be described in conjunction with FIGS. 19-22. An ink delivery system is preferably packaged as a unit in a carton 290 which holds a new print cartridge 291A, a new service station module 293A in a plastic storage bag 295, and a new ink supply module 296A. As shown in the self-explanatory sequence of drawings of FIG. 20, an old print cartridge 293B is easily removed and replaced with a new one. As shown in the self-explanatory sequence of drawings of FIG. 21, a depleted ink supply module 296B is removed without difficulty by first opening the ink door as shown by arrow 302, then pushing down on the lock button as shown by arrow 304 and at the same time pulling out the valve as shown by arrow 306. The depleted ink module 296B can then be replaced with a new ink supply module 296A. Finally as shown in the self-explanatory sequence of drawings of FIG. 22, after the access door is opened a user can push down on the handle in the direction shown by arrow 310 thereby dislodging an old service station module 293B, and then pull it out all the way as indicated by arrow 312, followed by installation of a new service station module 293A. 
     Accordingly it will be appreciated by those skilled in the art that the basic features of the unique take-a-gulp ink replenishment system of the present invention provides a unique but relatively simple way of providing for unattended printing through automated ink replenishment. Furthermore, all ink-related components can be replaced for a particular color of ink by a user, without the need of special tools and without the need of calling a specialized service person. 
     Additional details of the service station module 230 are shown in FIG. 23 in conjunction with FIGS. 14A-14B. A unitary body portion defines various internal chambers and passages as well as providing a support for a top plate 380 which extends all the way across a top opening in the body portion. The spittoon 238 is in a raised position at one end of the top plate. The cap 236 is positioned and secured on the top plate with the help of a mounting tab 381, and both wipers 234 are incorporated in a single unitary part also mounted on the top plate. A drain 378 next to the wipers feeds ink from the wipers into a waste chamber 379 located in the body portion. 
     The primer port 240 connects through passages in the body portion to the cap. A main ink collection chamber 382 is directly under the cap and is separated from a secondary chamber 383 by a baffle 384 extending down from the top plate. In order to help prevent undue ink buildup, a larger absorbent foam block 386 is employed in the bottom of a spittoon collection chamber 385 and a similar smaller absorbent foam block 388 is placed in the bottom of the chamber 382. 
     Additional details of the service station mechanism on the printer are shown in FIGS. 24-25. The service station carriage 251 has primer tubes 389 attached from the rear to the respective primer ports 240. A motor 390 is provided to move a platform 391 along slide rods 392 as part of various servicing operations as well as to position the carriage for installation or removal of individual modules by a user. The entire service station mechanism is supported by a chassis 394, and the platform includes a rear access 95 for the primer tubes 389 as well as a front access 96 to facilitate the aforementioned installation or removal of individual modules from the service station carriage. 
     It is to be understood that certain features of the service station module and the service station carriage are optional and are not required in order to obtain the benefits of the invention. For example, the foam inserts are helpful but not required in order in the ink collection chambers inside of the service station module. Similarly, while some form of restraint is desirable to assure secure positioning of the module in the carriage, it is not necessary to have positive biasing forces in all of the X, Y and Z axis directions. In a currently preferred form, only a biasing spring in the Z axis direction is to be employed in a proposed commercial embodiment of the invention, thus relying on a somewhat snug mechanical fit in the other axis directions. Also, such spring need not be a plastic extension of the carriage as presently used in a preferred embodiment, but could be a separate spring of different material. And other holding techniques could also be employed rather than a spring in order to stabilize the service station component sufficiently to perform its various functions relating to the cleaning, maintenance, enhancement and protection of the printhead. 
     Thus, once the service station modules are securely positioned in the service station carriage, all of the various important servicing functions (wiping, capping, priming, spitting, or selected sub-groups thereof) required for reliable operation of an inkjet printhead can be done in conjunction with a single module or cleaner which is dedicated solely to a single printhead and which can be removed and replaced at the same time that the associated printhead is removed. Thus the coordination of expected life of the service station module, ink supply module and printhead is an important feature of the invention. When a different ink supply such as UV ink for outdoor usage is required, an entire ink delivery system (including ink and ink-related components) can be easily replaced. 
     Additional details of the service station module are shown in FIGS. 26-29. A scan path of carriage leads on the right side of the printer to a service station where the various functional components of the service station as shown in FIG. 26 can interact with the printhead. The motor of the service station mechanism can move the service station carriage and its service station modules back and forth in order to align the appropriate component (e.g., wipers, or cap) with a print cartridge 409. An optical sensor 410 on the printer carriage assembly 60 (FIG. 16) is used to facilitate orientation of the service station module for its various functions. The details of the optical sensor are disclosed in commonly assigned copending application Ser. No. 08/551,022 filed Oct. 31, 1995 entitled OPTICAL PATH OPTIMIZATION FOR LIGHT TRANSMISSION AND REFLECTION IN A CARRIAGE-MOUNTED INKJET PRINTER SENSOR, which is incorporated herein by reference. 
     Such orientation is measured from reference line 415 of white marker 411 on the service station carriage (see FIG. 15) by the optical sensor which passes directly over the marker while traversing in scan direction 413 (also called the Y axis for large format printers/plotters). When a service station module is mounted in the service station carriage, a label 412 is directly aligned in the scan direction with the marker. This label serves to provide a space for recording and reading encoded information related to the service station functions. 
     The label is large enough to service multiple functions. It can indicate the type of ink system intended for use with this particular module, as for example indicated by the distance 416. Also, it can indicate &#34;on the fly&#34; information about the module such as the extent of use and the remaining intended like, indicated by the quantity, width and/or location of central markings shown as wide black bar 420 and additional markings shown as narrow black bars 422 on the central white space 418 between black end portions 419. System information can be applied at the time of manufacture or by the ink nozzles 414 at the beginning or during operation. Updated information can be applied at any appropriate time during operation by the ink nozzles. Thus the label acts as an information label or in some instances as a gauge as to the remaining useful life of the service station components or other components in an integrated ink delivery system. When certain negative information is sensed by the optical sensor, warning signals or messages can be displayed to the user, or in some instances certain operations of the service station can be temporarily de-activated to prevent damage to the printer, printhead, user or to the printout in progress. 
     This updated information is particularly important where an off-carriage ink system is designed to extend the useful life of a printhead. Wipers may wear out, ink waste chambers in the service station module may overflow. 
     The on-carriage sensor has previously been used primarily for alignment of multiple print cartridges in the carriage, but this new use of reading encoded information on the service module has opened new opportunities for improving the reliability of printers which are intended for long sessions of unattended printing. Thus, the number of marks, their relative positions, the particular area marked or left unmarked, or combinations thereof can all be used. With different color marks, a printer with sensitive optical processing can improve both the quality and quantity of the encoded information. In this regard, to increase the reliability of the label, the edges of the end portions 419 that extend downwardly on both ends are colored black to provide greater contrast for the optical sensor. 
     The invention contemplates using other built-in features of the service station module such as holes, differences in color, differences in height, differences in light reflectance, differences in shape, and the like for storing and conveying information. 
     While a preferred embodiment of the invention has been shown and described, it will be appreciated by those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention as defined by the following claims.