Manually replaceable printhead servicing module for each different inkjet printhead

Abstract

A replaceable inkjet printhead service module is provided for each separate inkjet printhead. When the printhead for a particular color ink such as cyan has reached the end of its life cycle and requires replacement, the corresponding printhead service module can also be replaced. The printhead service module includes a handle to facilitate manual mounting in a service station carriage which includes identical individual spring-loaded slots with datum guides for securely holding the service module. The service station carriage moves from a user-accessible position for mounting/removing the service module, to various other printhead servicing positions in the path of the printhead carriage.

Description

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 “CONTINUOUS REFILL OF SPRING BAG RESERVOIR IN AN INK-JET SWATH PRINTER/PLOTTER” 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 “take a gulp” 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 “full” 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 “pulled” into the pen from the reservoir.

A replaceable inkjet printhead service module is provided for each separate inkjet printhead. When the printhead for a particular color ink such as cyan has reached the end of its life cycle and requires replacement, the corresponding printhead service module can also be replaced. The printhead service module includes a handle to facilitate manual mounting in a service station carriage which includes identical individual spring-loaded slots with datum guides for securely holding the service module. The service station carriage moves from a user-accessible position for mounting/removing the service module, to various other printhead servicing positions in the path of the printhead carriage.

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 is 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 position.

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.

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 94 A, 94 B. 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 . FIGS. 16 and 17 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 (shown also in FIG. 16 ) 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 '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 92 A, 92 B. 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, with 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 an 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'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 '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 '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 114 . 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 cartridge 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 172 B ( FIG. 5 ) which engage against the outer housing of the valve body 120 A. The structure is biased into the lock position by integral spring member 172 A (FIGS. 7 and 8 ). By exerting force on structure 170 at point 170 C ( FIGS. 7 and 8 ) the spring is compressed, moving surface 172 B 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 '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 80 A- 86 A 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 platform 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, 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 hat 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 printer 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 256 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 pane 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 291 A, a new service station module 293 A in a plastic storage bag 295 , and a new ink supply module 296 A. As shown in the self-explanatory sequence of drawings of FIG. 20 , an old print cartridge 293 B 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 296 B 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 296 B can then be replaced with a new ink supply module 296 A. 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 293 B, and then pull it out all the way as indicated by arrow 312 , followed by installation of a new service station module 293 A.

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 383 .

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.

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.

Claims

1. An inkjet printhead servicing system for use with an inkjet printer having a plurality of inkjet printheads mounted in a printer carriage which moves from a print zone where ink drops are applied to media to a service zone for performing various printhead servicing functions, the system comprising:a plurality of service modules, a separate service module for servicing each printhead, each service module having waste ink receptacles and printhead servicing means thereon for performing a plurality of servicing functions; a carriage having separate module reception slots therein for holding separate ones of said service modules, the carriage including datum surfaces extending in a plane for abutting engagement with portions of said service modules extending in said plane to position said service modules in said slots on the carriage; guide walls on said carriage for guiding said service modules when positioning said service modules in said slots; and a chassis on which said carriage is mounted for arcuate movement toward and away from a path of movement of a printer carriage in a path extending generally normal to the path of movement of said printer carriage between a manually accessible position and various printhead servicing positions in which different types of said printhead servicing means are engageable with individual printheads to be serviced to perform different types of said servicing functions.

2. The inkjet printhead servicing system of claim 1 wherein each of said separate service modules have printhead servicing means thereon for performing the same plurality of servicing functions.

3. The inkjet printhead servicing system of claim 1 wherein said carriage is arcuately moveable to an access window to allow manual replacement of said separate service modules.

4. The inkjet printhead servicing system of claim 1 wherein said guide walls form separate ones of said slots for each of said separate service modules to allow each separate service module to be independently removably from said carriage.

5. The inkjet printhead servicing system of claim 4 including a separate spring member in each of said separate slots, respectively, for securely positioning said service modules in said slots.

6. The inkjet printhead servicing system of claim 1 wherein each of said service modules includes a manually grippable handle for installing or removing said service modules from said carriage.

7. The inkjet printhead servicing system of claim 1 wherein said datum surfaces include a set of datum surfaces for providing positional restraint in a direction parallel to the surfaces of the guide walls.

8. The inkjet printhead servicing system of claim 7 wherein said datum surfaces further include a second set of datum surfaces for providing positional restraint in a direction parallel to the surfaces of the guide walls and substantially perpendicular to the direction in which the first set of datum surfaces provide positional restraint.

9. The inkjet printhead servicing system of claim 7, wherein each of said service modules includes an end portion for engagement with a datum surface of said carriage for providing positional restraint in a direction parallel to the surfaces of the guide walls and substantially perpendicular to the direction in which said first set of datum surfaces provides positional restraint.

10. The inkjet printhead servicing system of claim 1 wherein the inkjet printer includes separate printheads for at least three different color inks, the system including three separate printhead servicing modules associated with said at least three different color inks, respectively.

11. The inkjet printhead servicing system of claim 10 wherein the inkjet printer includes printheads for yellow, cyan, magenta and black color inks, the system including four separate printhead servicing modules associated therewith, respectively.

12. The inkjet printhead servicing system of claim 1 wherein each of said service modules includes an elongated ledge for engagement with a datum surface of said carriage for providing positional restraint in a direction parallel to the surfaces of the guide walls.

13. The inkjet printhead servicing system of claim 1 wherein each of said service modules includes an elongated ledge on each of two opposite sides of said module for engagement with a corresponding pair of datum surfaces of said carriage for providing positional restraint in a direction parallel to the surfaces of the guide walls.

14. A method of installing a printhead service module in an inkjet printer, comprising the steps of:arcuately moving a support carriage from a plurality of printhead servicing positions to a position which is manually accessible; sliding a printhead service module in a first direction into a matching slot on the support carriage; engaging a spring located in the matching slot with a surface of the service module to push the service module in a second direction that is substantially perpendicular to the first direction to engage an opposing datum surface of the support carriage; pushing the service module to an end of the matching slot; moving the service module in the second direction so that a surface of the service module extending in a plane engages an opposing datum surface of the support carriage extending in said plane; and arcuately moving said support carriage and service module from said manually accessible position to selected ones of said plurality of printhead servicing positions.

15. The method of claim 14 including the steps of returning said carriage and service module from said printhead servicing position to said manually accessible position in an arcuate path and removing the service module from the support carriage.

16. The method of claim 14 including the step of leaving a handle extending out of the support carriage after performing said pushing and moving steps.

17. The method of claim 14 including the step of closing a cover door to prevent access to the support carriage during operation of the printer and using said door to push a partially installed service module forwardly the rest of the way into the slot.

18. The method of claim 17 wherein said step of closing also includes bringing a stop plate on said door into close proximity to the matching slot to push said partially installed service module forwardly the rest of the way into the slot.

19. A set of printhead service modules corresponding to a plurality of inkjet printheads mountable on a printer carriage, wherein each printhead service module is removably mountable in a matching slot of a servicing carriage on a printer, each service module comprising:a central body portion having longitudinally aligned printhead servicing means on a surface of said module and interior portions defined therein for collecting ink during operation of the printer; an end portion of said central body portion engaging a matching surface inside said matching slot when said service module is mounted in said matching slot so that said service module is retained in said matching slot; datum ledges on said central body portion for engagement with datum ridges in a slot in said carriage; and a handle which extends outwardly from said carriage when said service module is mounted in said matching slot for removing said module from said carriage in the direction of said longitudinally aligned printhead servicing means.