Abstract:
An inkjet storage container sealing mechanism is comprised of a cover, a receptacle, a gasket compressed normal to its insertion and a support member to maintain a seal that is resistant to ink and air penetration. The receptacle has sidewalls that form an opening. A gasket is stretched over a portion the cover, then the gasket and the portion of the cover is inserted into the opening of the receptacle. The gasket forms a seal between the cover and the receptacle. The compressive forces acting on the gasket to form the seal do not contribute additional forces to a mechanical joining mechanism, which attaches the cover to the receptacle. The support member prevents the sidewalls of the receptacle from deflecting to help maintain the seal.

Description:
BACKGROUND OF THE INVENTION 
     This invention generally relates to inkjet printing. More particularly, this invention relates to the sealing and assembly of a container used to store and deliver ink to an inkjet printhead, by which the invention provides a robust solution to needs for today&#39;s products, such as replacing or repairing ink delivery systems. 
     Many printers today use inkjet pens to produce recorded media. The inkjet pens have a container used to store and deliver ink to the printhead. The containment of the ink is usually done at a partial vacuum in the range of 0.5 to 9.0 inches of water column to prevent leakage of ink from the printhead. It is undesirable to allow ink to penetrate a seal between different pen parts that create this containment body. Likewise, it is also undesirable to allow air to intrude the containment body through the seal. In addition, the seal technique used should not be permitted to degrade the ink within the container, such as by the seal corroding due to a reaction with the ink. To allow for easy maintenance of assembly processes, it is desirable to have the sealing function be highly consistent and reliable in its manufacture. An additional feature desired in a seal design is the ability to seal, unseal and reseal without degradation of the seal&#39;s properties. This feature would permit new processes to be used to repair or modify an inkjet pen. 
     One current approach to sealing members on inkjet pens is to use an adhesive. 
     However, most adhesives and their resultant seals degrade when exposed to the ink. In addition, many adhesives have also been shown to contaminate the ink. Other manufacturing problems are related to the time it takes adhesives to cure, thus limiting throughput, and the inconsistency of seals on separate containers due to the variation of adhesive formulations from lot to lot. Although using heat can accelerate the curing time of an adhesive, the heat often causes other parts of the pen to become damaged. In addition, damage to the sealing members occurs when the adhesive joint is broken, thus preventing one from repairing a malfunctioning inkjet pen. 
     Ultrasonic welding is a second approach used on contemporary inkjet pens to seal members. This technique requires the materials of the two parts being sealed to be ultrasonically compatible which is not always desirable or even possible for a given application. The high frequency energy, used to heat and melt the plastic, often causes damage to other parts of the pen. To perform the ultrasonic welding properly, the parts need to be precisely supported during the weld thereby requiring expensive tooling fixtures. In addition, to ensure consistency and quality of the weld joints, there must be significant planarity between the welding surfaces, which requires tight part tolerances, thus making them more expensive. Many times energy directors are molded into the plastic to increase the likelihood of welding a good seal. These energy directors are usually delicate part features that are easily damaged. Once an ultrasonic seal is broken, it is virtually impossible to reseal properly and this prevents repairing a malfunctioning inkjet pen. 
     A third approach used is a face seal gasket between the mating parts. The face seal gasket requires that the mechanical joining function of the mating parts react to a constantly applied load from the face seal gasket. This force requires the surfaces on each side of the face seal gasket be smooth and rigid, thus increasing the part cost. In addition, there must be a continuous attachment mechanism or one that has frequent points of attachment to keep the joining surfaces flat. If the attachment mechanisms are exposed to the ink, they may degrade. In addition, if there is a preexisting stress in an attachment point, it may fail after a prolonged period in which it has been subjected to the gasket force, thus causing an early failure of the seal. 
     There is a need for an attachment and sealing process that is suitable for low cost, high volume manufacturing processes such as those used in assembling inkjet pens. A new seal design must allow for less expensive components, more efficient processes, and high volume manufacturing that provides better consistency, quality and reliability of the finished product. The ability to make repeated seals and reseals without degradation would allow an inkjet pen to be repaired or modified. Furthermore, a new seal design also needs to: allow for parts having looser tolerances; withstand attack from many different types of ink; allow for the attachment joint to not be in contact with the ink; and be virtually independent to the use of different plastic molding material. Other concerns a new seal design should address are: saving capital tooling costs required to build production lines, minimizing the size of production lines, and preventing process induced damage to other parts of the pen which might go undetected during manufacturing and later become field failures. 
     SUMMARY OF THE INVENTION 
     An inkjet storage container sealing mechanism is comprised of a cover, a receptacle, a gasket compressed normal to its insertion and a support member to maintain a seal that is resistant to ink and air penetration. The receptacle has sidewalls that form an opening. The gasket is stretched over a portion of the cover; then the gasket and the portion of the cover are inserted into the opening of the receptacle. The gasket forms a seal between the cover and the receptacle. The compressive forces acting on the gasket to form the seal do not contribute additional forces to a mechanical joining mechanism, which attaches the cover to the receptacle. The support member of the cover prevents the sidewalls of the receptacle from deflecting. This support member helps maintain the gasket seal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically depicts an exemplary embodiment of a printing system. 
     FIG. 1A is an isometric drawing showing an exemplary inkjet cartridge using heat stake attachment of members. 
     FIG. 1B is a schematic cross-sectional drawing illustrating an exemplary inkjet cartridge employing the preferred embodiment of the invention along the AA view of FIG.  1 A. 
     FIG. 2A is a drawing illustrating a non-uniform cross-sectional gasket such as that used in FIG. 1B, between two members of the cartridge where the gasket is specially molded to conform to the member parts. 
     FIG. 2B is a drawing illustrating a uniform cross- section gasket such as that used in FIG. 1B, between two members of the cartridge in which the members are molded to conform to the uniform gasket. 
     FIG. 3A is a drawing illustrating the assembly of the two members of the cartridge of FIG. 1B with a gasket and a heat staking method of attaching the two members. 
     FIG. 3B is a drawing illustrating the assembly of the two members of the cartridge of FIG. 1B with a gasket and a heatstaking method of attaching the two members with an alternative design for limiting sidewall deflection. 
     FIG. 3C is a drawing illustrating the assembly of the two members of FIG. 1B with a gasket and the preferred attachment scheme using a snap lock mechanism method of attaching the two members. 
     FIG. 3D is a drawing illustrating the assembly of the two members of FIG. 1B with a gasket and an alternative attachment scheme using a screw method of attaching the two members. 
     FIG. 4A illustrates the receiving detail in one member of the ink jet cartridge used in a snap joint attaching mechanism. 
     FIG. 4B illustrates the snap detail in one member of the ink jet cartridge used in a snap joint attaching mechanism. 
     FIG. 4C illustrates the receiving and snap details when mating the two members. 
     FIG. 4D illustrates an alternative snap lock mechanism. 
     FIG. 5A-5C schematically illustrate a process of disabling an existing ink delivery system and for providing a new ink delivery system. 
     FIG. 5A illustrates the dis-attachment of an inkjet cartridge. 
     FIG. 5B illustrates removal of an old ink delivery system from an inkjet cartridge. 
     FIG. 5C illustrates the insertion of a new ink delivery system into an inkjet cartridge. 
     FIG. 5D illustrates the re-attachment of a new ink delivery system to an inkjet cartridge. 
     FIG. 6A illustrates an electronically controlled valve ink delivery system connected to an inkjet cartridge. 
     FIG. 6B illustrates a gravity regulated ink delivery system connected to an inkjet cartridge. 
     FIG. 6C illustrates a removable type ink delivery system using the gasket sealing mechanism of the preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 schematically depicts an exemplary embodiment of a printing system  16  for which the present invention can be employed. Printing system  16  includes an inkjet cartridge  10  that is fluidically connected to an ink supply  70  via conduit  68 . Inkjet cartridge  10  includes a printhead  20  that receives signals from printing system control electronics  30  and selectively deposits ink onto media (not shown) in response. 
     In this exemplary embodiment, print cartridge  10  is an assembly including a receptacle  22  and a cover  28  which comprise printhead housing  36 . Receptacle  22  has an inner cavity  32  that is fluidically connected to printhead  20 . Inner cavity  32  forms an opening  18 . Cover  28  is positioned in opening  18 . Cover  28  includes an ink inlet  104  that is fluidically coupled to conduit  68 . Cover  28  also includes a valve  72  that fluidically couples ink inlet  104  to inner cavity  32 . 
     The combination of ink supply  70 , conduit  68 , and cover  28  can be referred to as an ink delivery system (IDS) for printhead  20 . When valve  72  is open, ink flows from ink supply  70 , through conduit  68 , to valve  72 , and into inner cavity  32 . During operation of printhead  20 , a pressure regulator actuator  48  opens and closes valve  72  in response to pressure changes in inner cavity  32  to regulate the pressure of ink supplied to printhead  20 . It is important that the pressure in inner cavity  32  be maintained within a printhead operating range (typically a negative 0.5 to 9.0 inches of water) to assure a stable negative operating pressure in inner cavity  32 . 
     If cover  28  has a pressure regulator actuator attached to it, it is difficult to use ultrasonic welding between cover  28  and receptacle  22 . This difficulty is caused by the difficulty in directing the ultrasonic energy only to the sealing surface and not to the regulator portions. If the regulator parts are damaged during ultrasonic welding, the damage is difficult to detect. Thus, parts may be only slightly damaged yet still function when the unit is tested. The damaged parts may prevent optimum performance or fail later causing consumer displeasure and warranty replacements. An additional concern with using ultrasonics is that the cover  28  and receptacle  22  must both be made of a material that is compatible with each other to form an ultrasonic seal. 
     When a conventional adhesive is used for sealing the cover  28  and receptacle  22 , the amount of time needed to cure the adhesive prevents the process from being practical for mass production. Heating the adhesive during curing can shorten the process time needed to cure the adhesive. The heat, if not carefully controlled, can melt, deform or damage portions of the regulator mechanism. An additional concern with an adhesive is that the cover  28  and receptacle  22  must both be made of a material that is compatible with the adhesive used. Often times, the design criteria for the cover  28  and receptacle  22  will require that they be made of different materials, thus limiting the type of adhesive, indeed if any acceptable choices of adhesive are available that also are compatible with the ink stored in the container. 
     One aspect of the present invention concerns a means of sealing an ink containment vessel such as inkjet cartridge  10 . In the preferred embodiment, the sealing means is a compressed gasket  120  that is located between cover  28  and receptacle  22 . This sealing means can be accomplished without costly adhesive curing processes or ultrasonic welding processes that may damage the materials used to fabricate inkjet cartridge  10 . 
     Another aspect of the invention concerns a means of changing the ink delivery system to accommodate different printing requirements. In the preferred embodiment, gasket  120  provides an advantageous way of changing the ink delivery system without damage to receptacle  22 . This can be done by disabling the ink delivery system and then connecting a new ink delivery system to printhead  20 . In the preferred embodiment, this is done by removing cover  28  from receptacle  22  and then connecting a new ink delivery system to inner cavity  32 . Before discussing this second aspect of the invention, it is useful to discuss the first aspect with respect to FIGS. 1A-4D. 
     FIG. 1A depicts an isometric view of an ink containment vessel such as inkjet cartridge  10  that includes only details pertaining to the assembly of inkjet cartridge  10 . A cover such as cover  28  is secured to a receptacle such as receptacle  22  via attachment features  24 . In the preferred embodiment, attachment features  24  comprise snap features, however, other embodiments might use heat stake pins as in FIGS. 1A and 1B, or screws, staples, or clips which are discussed later. 
     FIG. 1A shows the outside of an inkjet cartridge  10 . Cover  28  and receptacle  22  (either piece comprised of polyphenylene sulfide, liquid crystal polymer, syndiotactic polystyrene or polyethylene napthalate, but preferably polyphenylene sulfide material in the preferred embodiment) are attached using attachment features  24 . Ink inlet  104  is used to connect the inkjet cartridge  10  with the rest of the printing system  16 . The ink is expelled from ink cartridge  10  through printhead  20 . As ink is expelled, air enters screw air vent  26  to operate the pressure regulator actuator  48 . 
     FIG. 1B is a cross-sectional schematic representation of the exemplary inkjet cartridge  10  of FIG. 1A along the AA perspective that utilizes the preferred embodiment. The cover  28  is sealed to receptacle  22  using a gasket  120 . Gasket  120  is compressed in a direction normal to the direction in which cover  28  is assembled to receptacle  22 . Support member  110  prevents the sidewall deflection of receptacle  22  ensuring that gasket  120  is not under-compressed, which would compromise the fluid seal between the cover  28  and receptacle  22 . Maintaining a proper seal is critical to the stable operation of inkjet cartridge  10 . 
     As described with respect to FIG. 1, inkjet cartridge  10  includes a means of maintaining a stable operating pressure in inner cavity  32 . Valve  72  is formed by a seal between a lever  126  and a valve outlet portion  108 . Lever  126  is pivotally mounted to cover  28  such that the rotational motion of lever  126  opens and closes valve outlet portion  108 . An expandable bag  124  is located adjacent to lever  126 . Expandable bag  124  has an inner surface that is fluidically connected to outside atmosphere through screw air vent  26 . As the printhead  20  ejects ink droplets, the pressure in inner cavity  32  become more negative. In response, expandable bag  124  expands, pressing on lever  126  to allow ink to flow into inner cavity  32  as discussed with respect to FIG.  1 . 
     The inkjet cartridge  10  when assembled holds an ink supply  122 . Ink supply  122  is refilled by the use of an fluid regulator type ink delivery system (IDS), for pressure regulator actuator  48 , comprised of expandable bag  124 , moment arm  128 , valve moment arm  126 , spring  132  and screw air vent  26 . When ink supply  122  is reduced, expandable bag  124  expands causing valve moment arm  126  to rotate causing valve seat  108  to open which allows ink in from an ink inlet  104 . Ink is drawn out of the inkjet cartridge through ink filter  134  and out of printhead  20  when printing onto an external surface. 
     In the preferred embodiment, the inkjet cartridge  10  is assembled by mounting the gasket  120  so that it circumscribes a gasket receiving area  90  of cover  28 . To make assembly of cover  28  into receptacle  22  easier, the gasket  120  can be pre-coated with polyethylene glycol (PEG). Alternatively, the seal area of the receptacle  22  can be pre-coated with PEG. An alternative approach is to use a gasket that is molded with a lubricant (such as PEG, or Teflon, preferably Teflon) to reduce the amount of process steps in manufacturing and to provide consistent results. After gasket  120  is mounted on cover  28 , cover  28  is inserted into receptacle  22 . During insertion, gasket  120  is compressed by features of cover  28  and receptacle  22 . At the completion of insertion, gasket  120  is compressed in a direction that is normal (orthogonal) to the direction of insertion. This form of compression causes gasket  120  to form a seal between cover  28  and receptacle  22  whereby the compressive force from gasket  120  is directed to the sidewalls of receptacle  22  and cover  28 . Further, this form of compression prevents compression forces from acting in a direction that would separate cover  28  and receptacle  22 , thereby minimizing stress on attachment features  24 . 
     Gasket  120  can be fabricated by two different methods to provide an effective seal. A uniform cross-sectional gasket is the easiest to fabricate, however, the design of the molded cover  28  and receptacle  22  must accommodate the gasket shape. Often times, for other design decisions, the use of a uniform cross-sectional gasket is not desired. In these cases, a non-uniform cross-sectional gasket can be made to precisely mate with existing molded parts of cover  28  and receptacle  22 . 
     FIG. 2A shows the detail of how a non-uniform gasket  44  is made to conform to the dimensions of cover  28  and receptacle  22 . Non-uniform gasket  44  has for each corner an inner radius  42 , which is shaped to fit the curvature of cover  28 . The corner also has an outer radius  40 , which is shaped to fit the curvature of receptacle  22 . By using non-uniform gasket  44 , the seal formed by compression of the gasket can be performed with parts that have a preexisting or required physical design. 
     Alternatively, FIG. 2B shows the detail of uniform gasket  46 , which is molded such that it has a consistent uniform cross-sectional profile. The advantage of this approach is a simpler tool design for the molding of uniform gasket  46 . This approach is possible if cover  28  and receptacle  22  can be molded to accept uniform gasket  46 . 
     Gasket  120 , representing either uniform gasket  46  or non-uniform gasket  44 , has compressive forces that do not interact with the attachment of cover  28  to receptacle  22 , and several alternative methods for this attachment exist. In order to prevent excessive compression or non-compression during periods of unforeseen stress (i.e. dropping, squeezing, etc.) the cover  28  has molded into it a flange support member  110  to limit deflection of the sidewalls of receptacle  22 . The attachment method and support member  110  can be accomplished several ways of which FIGS. 3A through 3D show representative samples. Those skilled in the art will appreciate that different methods of attachment for the cover  28  and receptacle  22  could be used and still meet the spirit and scope of the invention. 
     FIG. 3A shows an embodiment in which the receptacle  22 , having an inside surface  52 , an outside surface  54 , a peripheral lip  56  with heat stake posts  80  that are formed to hold cover  28  in place. Cover  28  has an inside surface  60  and an outside surface  58 . The heat applied to heat stake posts  80  is localized and very temporary, thus preventing the heat related problems that occur with a heat curing adhesive. Also shown is a beveled edge  50  on receptacle  22  that helps to slowly compress gasket  120  as cover  28  is inserted into receptacle  22 . Gasket  120  contacts gasket receiving area  90  on cover  28  and gasket seal area  92  on receptacle  22 . Gasket receiving area  90  and gasket seal area  92  are molded to have essentially zero degrees of draft. This lack of inclination keeps the compressive forces applied directly inward to the gasket  120  and limits the forces applied to the gasket that are not directed inward to the gasket  120  to prevent its movement after the inkjet cartridge  10  is assembled. The support member  110 , in this exemplary embodiment, is formed as a flange around the outside surface  58  of cover  28 . 
     FIG. 3B shows an alternative embodiment for a heat stake attachment scheme in which an additional support member  62  is formed in cover  28  such that it also supports holding gasket  120  to prevent gasket  120  from becoming dislodged during the manufacturing process. Support member  110  prevents outward flexing of the sidewalls of receptacle  22 . Heat stake post  80  is molded into receptacle  22 . 
     FIG. 3C shows the preferred embodiment using a snap lock mechanism  94  for attachment. Further detail of the snap lock is shown in FIGS. 4A-4C. Receptacle  22  is molded to provide a barrier to gasket  120  and to provide a stop  63  for support member  110  that is molded into cover  28 . 
     FIG. 3D shows an alternative embodiment in which a screw  98  is used to attach cover  28  to receptacle  22 . Support member  110  is used to limit sidewall deflection of receptacle  22  thus maintaining a seal with gasket  120  when external forces are applied to the inkjet cartridge  10 . 
     FIG. 4A shows the receiving portion of the snap lock mechanism  94  used in FIG.  3 C. The receiver area  88  is molded into first member  28 . An incline  87  is used to slowly glide the snaps ( 86  on FIG. 4B) until the snaps  86  rest on shelf  89 . FIG. 4B shows the snap portion of the snap lock mechanism  94  with snaps  86  molded into second member  22 . FIG. 4C shows the receiver area  88  and snap  86  when they are mated. 
     FIG. 4D illustrates an alternate snap lock mechanism  94  where a snap  86  is molded as part of cover  28 . This snap  86  mates into a receiver area  88  of receptacle  22 , securing cover  28  to receptacle  22 . Two or more snap lock mechanisms  94  are molded into cover  28  as required. Those skilled in the art will appreciate that other snap feature shapes are possible which could latch on the inside of receptacle  22  or the outside of receptacle  22  as illustrated and still meet the spirit and scope of the invention. 
     In regard to FIGS. 5A-5D, a method for modifying the ink delivery system of printing system  16  (FIG. 1) is described. This enables printing system  16  to accommodate a variety of spatial configurations and ink use rate requirements. The ink delivery system is replaced by disabling the first ink delivery system and connecting a second ink delivery system to printhead housing  36 . 
     In the preferred embodiment, a first ink delivery system is disabled by unsealing and removing cover  28  from receptacle  22  as depicted by FIGS. 5A and 5B. Specifically, FIGS. 5A-5D illustrate a method to remove and replace an ink-delivery subassembly (IDS), such as the regulator type shown in FIG.  1 B and represented in FIGS. 5A and 5B as a box and described as old IDS  96 . Therefore, if an IDS is defective, the print cartridge can be repaired. In addition, new designs, which have new features or benefits, can replace the existing IDS. Having this flexibility allows the inkjet cartridge  10  to be manufactured for high volumes, and at the same time, accommodate the printhead  20  in receptacle  22  for use in lower volume applications. 
     As indicated by FIG. 5A, the attachment features  24  (FIG. 1A) are first disabled. In the case wherein the attachment features are heat stake posts  80  as depicted by FIG. 3B, the heat stake posts  80  may be sheared or otherwise broken. Next, cover  28  is removed in a direction that is substantially perpendicular to a plane defined by gasket  120 . In FIG. 5B, this cover motion is used to remove the old IDS  96 , further comprising cover  28 , gasket  120 , and ink inlet  104 , from the printhead housing  36 , which further comprises a gasket seal area  92 , printhead  20  and receptacle  22 , which has an inner cavity  32  with opening  18 . As this motion is done, the seal formed by gasket  120  with respect to receptacle  22  and cover  28  is broken. 
     Next in FIG. 5C, a new IDS, or a portion  97  of it, of a similar or different type than old IDS  96 , discussed in FIGS. 1 and 1B, is oriented such that it can be positioned into the printhead housing  36  through opening  18 . In the preferred embodiment, the same gasket arrangement is used to provide the seal as was discussed with respect to FIGS.  1 B and  2 A- 2 B. However, provided it can be tolerated by the new ink delivery system, alternative sealing arrangements could be used such as adhesives and ultrasonic welding. In this preferred embodiment, the new IDS portion  97  is preferably moved into position in a direction substantially perpendicular to a plane defined by the gasket sealing surfaces, as depicted by FIG.  5 C. New IDS portion  97  has a gasket  120  thereon that is similar to the gasket structure discussed with respect to FIGS.  1 B and  2 A- 2 B. When the new IDS portion  97  is properly positioned in inner cavity  32 , as indicated by FIG. SD, gasket  120  forms a compression seal between portion  97  and receptacle  22 . After positioning the new IDS portion  97 , an additional means of attachment may be used to secure new IDS portion  97  to receptacle  22 , such as the attachment features indicated in FIG. 1A, or snaps, adhesives, rivets, crimp rings, screws, or other suitable means. 
     After attaching a new IDS portion  97 , a flow of ink can be established between an ink supply  70  (see FIG. 1) and printhead  20 . The new IDS portion  97 , the ink supply  70 , and any conduit  68  in-between, forms a new ink delivery system (IDS). During a printing operation, the new IDS  100  provides pressure regulation in inner cavity  32  that enables stable operation of printhead  20 . 
     Although a particular way of disabling the old IDS  96  and connecting the new IDS  100  was shown, other options are possible. For example, the old IDS  96  is disabled to not provide ink to the ink delivery system, such as by cutting off the flow of ink between the old ink supply  70  and inner cavity  32 . Next, an orifice  84  is formed in the side of receptacle  22  with a process such as drilling and tapping. Next, a new IDS  100  is fluidically coupled to the orifice. However, the gasket method described above is advantageous because it does not require machining or damaging receptacle  22 . 
     In FIGS. 5C and 5D, the new IDS portion  97  was generically shown, without reference to a specific form of ink delivery system. This is because portion  97  can be part of any number of IDS configurations as indicated by FIGS. 6A-6C. 
     Usually, the same gasket seal area  92  (FIG. 5B) on the inner perimeter of the inner cavity  32 , where the gasket was seated for the original seal, is used to form the new seal. However, one new sealing method might be to use an adhesive  116 , since in a low volume—no heat process, the previously stated limitations of using an adhesive can be avoided. Similarly, if the new IDS portion  97  replacement can tolerate it, the new IDS portion  97  and printhead housing  36  can be sealed using ultrasonic welding. Generally, the new IDS portion  97  will provide the ultrasonic welding features to facilitate the welding process. 
     When the gasket  120  is engaged between the new IDS portion  97  and printhead housing  36 , as illustrated in FIG.  5 D and attached using adhesive  116 , the same gasket or an identical replacement may be used to create a new seal. However, a totally new type of gasket  120  or other type of sealant could be used between the new IDS portion  97  and printhead housing  36 , such as an adhesive  116 , another resilient member, or other sealant known to those skilled in the art and still meet the spirit and scope of the invention. 
     Finally, the assembled inkjet cartridge  10  should be primed with ink and any remaining air inside the printhead module purged. Several methods of performing such steps are known to those skilled in the art. 
     Several methods of providing pressure regulation of the ink in an IDS are available. A common type is to use capillary action such as that using foam, for example Erturk et al., “Ink Retention in a Color Thermal Inkjet Pen”, Hewlett-Packard Journal, August 1988, pp.41-45. Another method is active regulation in which a pressure valve opens and closes in response to a pressure change in the printhead housing; see Cowger, “The Optimization of Deliverable Ink from a Disposable Print Cartridge”, IS&amp;T&#39;s Eighth International Congress on Advances in Non-Impact Printing Technologies”, 1992, pp.312-317. A simple method is to just provide passive regulation where the height of the ink source relative to the printhead level regulates the pressure. Those skilled in the art will realize that other pressure regulating systems exist and still fall within the spirit and scope of the invention. 
     Several embodiments of ink delivery systems (IDS), which can use gasket  120  and printhead housing  36 , are now described that demonstrate the usefulness of the invention. 
     FIG. 6A illustrates a first embodiment of an IDS that utilizes electronically controlled pressure regulation and which includes an ink supply  70 , a electronically actuated valve  72 , a pressure sensor  76 , and printing system control electronics  74 . Pressure sensor  76  provides signals to printing system control electronics  74  indicative of pressure changes in printhead housing  36 . Printing system control electronics  74  opens and closes valve  72  in response to regulate fluid pressure in printhead housing  36 . 
     FIG. 6B illustrates a second embodiment of an IDS which includes an ink supply  70 , a conduit  68 , and a cover  28  used to couple the conduit  68  entering ink inlet  104  to the interior of the printhead housing  36 . In this second embodiment, a gravity regulated IDS, the pressure within printhead housing  36  is regulated via the height difference  78  between the printhead  20  and the ink supply  70  center of mass. 
     FIG. 6C illustrates a third embodiment of an IDS, referred to as a removable IDS  82 , such as illustrated in commonly assigned U.S. Pat. Nos. 5,642,144 and 5,680,164. In this embodiment, the IDS includes a resilient sealing device, such as the gasket  120 , to provide a perimeter seal between the removable IDS  82  and the printhead housing  36 . The removable IDS  82  contains a reservoir to hold the ink and a regulator mechanism such as foam, or spring bags, but other known regulator mechanisms could be used and still meet the spirit and scope of the invention. A needle  130  mounted in printhead housing  36  punctures though a septum  118  in the removable IDS  82  to allow the ink within removable IDS  82  to flow to the printhead  20  through ink filter  134 .