Patent Publication Number: US-8523313-B2

Title: Inkjet cartridge

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 12/125,126, filed on May 22, 2008 now U.S. Pat. No. 8,091,993, the entire disclose of which is herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     An embodiment of the invention pertains to inkjet printers and inkjet cartridges. More specifically, an embodiment of the invention relates to ink containment systems or ink reservoirs used to store ink in an inkjet cartridge. 
     BACKGROUND OF THE INVENTION 
     Typically, an inkjet cartridge comprises an outer housing within which an ink containment system or ink reservoir is disposed in fluid communication with an inkjet printhead. A mechanism linked to the ink reservoir generates a negative pressure or backpressure that is maintained within a sufficient range to prevent ink from leaking from the printhead, but also allow injection of ink for printing. 
     Controlling the internal pressure within the ink reservoir has been the subject patents for more that twenty years. Earlier now expired patents including U.S. Pat. Nos. 4,422,084 (the &#39;084 patent); 4,509,062; and, 4,500,895 (the &#39;895 patent) disclose a variety of mechanisms used to generate and control a negative pressure in an ink reservoir. The &#39;084 and &#39;895 patents disclose pouch, bag or bladder-like configurations that rely on the elasticity of the materials composing the reservoirs to generate the negative pressure. The &#39;084 patent also discloses using a biasing means disposed within the ink reservoir to urge walls of the reservoir apart from one another, or moving one wall apart from another fixed wall. 
     To that end, the &#39;084 patent discloses an ink containment system that incorporates a single flexible membrane secured within a cartridge housing and forming an ink reservoir with the walls of the cartridge. A spring is not disposed within the reservoir, but outside the reservoir and biases the flexible membrane away from the cartridge walls to generate a negative pressure in the ink reservoir. A similar such design is disclosed in the &#39;062 patent. 
     In later issued patents there is disclosed cartridges that have two moveable sidewalls that form the ink reservoir and a biasing means disposed between the sidewalls to create negative pressure. For example in U.S. Pat. Nos. 5,325,119; 5,440,333; 5,737,002; 5,767,882; and, 6,053,607, there is disclosed inkjet cartridges having two flexible sidewalls secured to an internal frame structure to form an ink reservoir. Each of the moveable sidewalls comprises a plate member covered by a flexible membrane. The peripheral edge of each membrane is secured to an internal frame structure attached to the walls of the cartridge housing thereby forming the ink reservoir or ink bag. A pressure regulator is disposed within the ink bag and includes two side plates and a spring disposed between the plates biasing the two plates apart from one another and toward the membranes. The spring disclosed in most of these patents is a bow or leaf spring; however, the &#39;119 patent shows an embodiment with a helical spring. As ink is ejected from the cartridge the reservoir collapses including both sidewalls moving toward one another. The spring biases the sidewalls apart to generate the negative pressure. 
     A drawback in this design is that the plates, especially metal plates, the flexible membrane may have a tendency to tear at the points or lines of engagement of the membrane against edges of the plate. The &#39;333 patent offers a way of preventing the tearing the membranes by securing a protective cover layer between the plate and the membrane. The membrane is heat bonded to the cover layer in a centrally located rectangular area of the side membrane, cover layer and plate. However, such a system adds additional steps to the manufacturing process that may be avoided using different materials that may be more compatible with one another. The &#39;333 patent offers an alternative embodiment in which the membrane is bonded directly to the plate in the absence of the cover layer, which embodiment may still expose the membrane to the edges of the plates; however, this embodiment is not linked to the bonding means as claimed. 
     In these above cited patents, and other patents owned by the same assignee, Hewlett Packard, methods and materials are disclosed for manufacturing inkjet cartridges For example, in the &#39;002 patent there is disclosed an inkjet cartridge having an ink bag design similar to that disclosed in the &#39;333 patent. The &#39;002 patent is directed to materials used to fabricate components of the inkjet cartridge. More specifically, the inkjet cartridge includes an external frame member having an internal frame member mounted thereon for attachment of the ink bag. The external frame member is composed of a first plastic material and the internal frame member is composed of a second plastic material. An ink bag in the cartridge includes two membranes each of which is composed of a third plastic material. The second plastic material and third plastic material are compatible with another so the membranes may be bonded to the internal frame member to form the ink bag. 
     In addition, the external and internal frame members are fabricated using what is known as a “two-shot” molding process. The external frame member is formed using an injection molding process, which is the “first shot”, which is then inserted into a second mold for where the second plastic material is molded to the external frame member to form the internal frame member. 
     In the above referenced patents assigned to Hewlett Packard, and the U.S. Pat. No. 6,206,515 (the &#39;515 patent), a printhead is mounted onto a snout portion of the cartridge. The snout is incorporated as an integral component of the external frame member as compared to fabricating the snout as a component separate from the external frame and mounting the snout to the frame member. 
     In U.S. Pat. No. 5,450,112 (the &#39;112 patent) there is disclosed an ink bag for an inkjet cartridge that includes two flexible membranes bonded to an internal frame member to form the ink bag. Requirements for materials composing the membrane include flexibility, gas/moisture barrier, chemical resistance, mechanical toughness, heat sealability and cost. A laminate structure is disclosed to apparently meet these requirements. The membranes include a laminate structure including two laminated layers adhered to one another. Each laminated layer includes a carrier layer, a barrier layer affixed on a first surface of the carrier layer and a sealant layer affixed to a second surface of the carrier layer. The barrier layers for each of the laminated layers are affixed one another by an adhesive form the laminated structure. The barrier layer disclosed is an aluminum film on a surface of the carrier layer. 
     Sidewalls including a flexible membrane and plate members are also disclosed in U.S. Pat. Nos. 6,773,099; 6,830,324 (the &#39;324 patent); 7,004,572; 7,077,514; and, 7,104,640. In each case there is disclosed a single moveable member secured against walls of a cartridge housing forming an ink reservoir. The moveable member includes a preformed flexible membrane for receiving a plate member. A spring is disposed in the ink reservoir between the housing and plate member biasing the moveable member away from the housing wall to create a negative pressure. In other embodiments, the spring is disposed with the cartridge housing between the moveable member and a wall of the cartridge outside of the ink reservoir. As ink is depleted from the ink reservoir, the moveable member collapses along a periphery of the plate. As noted above, the flexible membrane is preformed having a centrally located area on the membrane for receiving the plate, which may create additional steps and costs in the manufacture of the cartridge. 
     Additional components have been provided to inkjet cartridges, in addition to the above-described mechanism for generating and controlling a constant negative pressure in an ink reservoir. In the &#39;099, &#39;572, &#39;514 and &#39;640 patents, a one-way valve is placed in fluid communication with the ink reservoir. A flexible membrane and plate member open and close openings in the valve in response to changes in pressure within the ink reservoir. If the pressure exceeds a limit, the one-way valve opens to introduce ambient air into the reservoir to decrease the negative pressure so that ink may be effectively ejected from the printhead. 
     In addition, pressure chambers disposed outside of the ink reservoir have been utilized in lieu of, or in addition to biasing means disposed within the ink reservoir for maintaining a constant negative pressure in an ink reservoir. In U.S. Pat. No. 5,764,259 there is disclosed an inkjet cartridge having negative pressure regulating chamber disposed within the cartridge to maintain a constant negative pressure in the ink reservoir. A bellows-type contracting and expanding wall is attached to a cartridge wall and a regulating plate. The ink reservoir constitutes the remaining interior of the cartridge outside the pressure regulating chamber. In addition, the chamber is in fluid communication with the atmosphere via an aperture in the cartridge wall. 
     When ink fills the reservoir, the plate and wall constrict in a retracted position. As ink empties from reservoir during printing operations, wall expands against the resistance from the wall creating the negative pressure in the reservoir. When the wall of the pressure regulating chamber reaches a maximum expansion, air is introduced into the chamber in the form of air bubbles through an aperture in the cartridge wall outside the pressure chamber an in the ink reservoir. The negative pressure is maintained within a predetermined range by the capillary force at the aperture. 
     U.S. Pat. No. 7,033,007 discloses a pump mechanism that presses against the bias of a spring in an ink chamber pressurizes the chamber at a suitable pressure for drawing ink from the chamber. When the chamber is depleted of ink, the pumping mechanism is released and the spring biases the chamber in a direction to draw ink from a reserve ink supply. However, such valves and pumping mechanism increase the complexity, cost and repair of the cartridges. 
     In published applications U.S. 2005/0157040 A1 and U.S. 2005/0157030 A1 there is disclosed an inkjet cartridge that includes a collapsible reservoir including an annular flexible membrane (bag) secured at each end to plates. One plate is fixed and the other plate slides within a frame having struts as the bag collapses from depletion of ink or expands as it is filled with ink. Negative pressure is created by a spring attached to the moveable plate and the frame outside of the ink reservoir. 
     A published application, U.S. 2006/0221153 A1, discloses a stress dampening unit disposed between a collapsible ink cartridge and the wall of the cartridge housing. The stress dampening unit includes a flexible cylindrical membrane attached to the flexible membrane of the ink reservoir. A compression spring is disposed within the ink reservoir. In addition, a second compression spring may be disposed in the dampening unit. An orifice in the wall of the cartridge at the dampening unit provides fluid communication between the dampening unit and atmospheric air. As the ink reservoir collapses as a result of an impact, such as may occur if the ink reservoir is dropped or hit against a desk, the dampening unit may minimize the collapse of the ink reservoir. In addition, the dampening unit may be used to control the increase of negative pressure in the ink reservoir. 
     Systems that utilize springs and flexible membranes are not limited to positioning the spring within the ink reservoir. Some cartridges have mechanisms disposed outside of the ink reservoir, attached to a collapsible wall and pulling on the wall to generate the negative pressure, as compared to systems that have an internally mounted spring, which systems push a moveable wall away from another wall forming the reservoir. A spring mounted external of the ink reservoir is shown U.S. Pat. No. 6,505,924, which discloses cantilevered spring plates mounted externally relative to the ink reservoir. An externally mounted cantilevered spring is also shown in U.S. Pat. No. 6,908,180. 
     Some cartridges utilize bag-like or bladder-like pouches to form a collapsible reservoir. Examples of such ink reservoirs may be seen in U.S. Pat. Nos. 6,736,497; 6,412,894 (FIG. 5); 6,364,474; and U.S. Publication No. 2006/0098063 A1. 
     Some systems or devices used to generate negative pressure in an ink reservoir include a porous material such as a sponge or foam core disposed within the cartridge housing. In such cases, the walls of the housing define the ink reservoir which is connected to a printhead, and the absorption of the ink in the sponge acts to generate the negative pressure. 
     Inkjet cartridges typically incorporate systems, devices or methods for detecting an ink level in a cartridge or ink reservoir. Inkjet cartridges have a minimum level or volume of ink at which the inkjet cartridge may effectively operate. If the volume of ink drops below the minimum level the cartridge risks blank ejections, which may damage the printhead. Prior patents disclose various ink level sensing techniques, including systems employing optical sensing devices, systems that test the electrical conductivity or transparency of the ink to determine an ink level and systems that require visual inspection of components to determine an ink volume remaining in the cartridge. 
     In those patents disclosing optical sensors, a part is connected to a flexible membrane of a collapsible ink reservoir. The devices are configured so that once the flexible membrane collapses to a predetermined level or position in the ink reservoir the sensor is activated. U.S. Pat. No. 4,342,042 discloses a reflective dot on the membrane and detector including a light emitting diode and photo-transistor. As the reflective dot moves up and down with the change in the ink volume, the photo-transistor detects more or less reflected light. 
     U.S. Pat. No. 4,604,633 discloses an ink level detecting system that includes light shielding plate connected to a flexible membrane and moves up and down with movement of the membrane as ink is emptied from or injected into the ink reservoir. The shielding plate is disposed between a light emitting element and a light receiving element. The movement of the flexible membrane causes movement of the light shielding plate, which is detected by the light emitting and light receiving elements to indicate a remaining volume of ink in the ink reservoir. 
     U.S. Pat. No. 5,757,390 discloses an ink level sensing system and method for sensing an ink level that includes the use of a cartridge having two slots, each slot is positioned on opposing walls and aligned to form a light beam path. A light source is mounted on a carriage to generate a light beam, and a detector is mounted on the carriage to generate a signal if it detects light from the light beam. As the cartridge moves on the carriage through the light beam, the ink level may interrupt the beam for detecting a level of remaining ink. The amount of ink is determined by comparing the position of the ink level and the position of the cartridge on the carriage. 
     U.S. Pat. No. 5,997,121 is directed to an ink level and cartridge detection system that includes two light reflectors formed as an integral part of the cartridge wall. The reflectors are used in conjunction with a two light sources and a photosensor. One light source is a roof mirror that reflects light when the cartridge is positioned on the carriage. The second reflector is a faceted prism used to reflect light to determine an ink level of the cartridge. A similar such ink level and cartridge detection system is disclosed in the U.S. Pat. No. 6,234,603. 
     The system for detecting an ink supply disclosed in U.S. Pat. No. 5,844,579 is directed to cartridge that has a pump to force ink from a reservoir. An actuator drives the pump. A sensor associated with the pump detects when the actuator is in a position that represents the ink in the reservoir is depleted. 
     As mentioned above, some ink level detecting systems utilize the electrical conductivity of the ink as component of an ink level sensing system. The sensing system disclosed in U.S. Pat. No. 4,977,413 is directed to an ink remain detector that is disposed in a fluid path from an ink tank to a recording head. The detector includes a pair of electrodes connected to a first alarm and a pair of electrodes connected to a second alarm. Both pairs of electrodes are fixed within an interior of the cartridge; and, conductive plates move responsive to movement of the flexible membrane between the pairs of electrodes to determine a remaining ink volume. Alarms connected to the electrodes sound when the connector plates come in contact with the electrodes. 
     In U.S. Pat. No. 6,554,382 there is disclosed an ink level sensing system in an inkjet cartridge that includes a first and second resistance probe mounted in respective ports that protrude from a bottom of a cartridge. The ports and probes are in fluid communication with an ink reservoir. When the reservoir and ports are filled with ink, the resistance across the probes is high. When ink is drawn from the reservoir and one or both of the probes, the resistance is low indicating that the ink level is low. 
     A patent that discloses an ink level sensing device that includes a visual inspection by an operator is U.S. Pat. No. 4,935,751. The &#39;751 patent discloses a rigid plate attached to one side of a collapsible bag. The cartridge has a window on an end of the cartridge housing. As the ink bag collapses, an end of the plate comes into view within the window. The position of the plate relative to the window indicates a remaining ink volume. The window may also include indicia representing a volume measurement of ink. 
     Still other patents that use a visual indicator incorporate indicial strips outside the cartridge that move responsive to movement of a collapsible reservoir. One such example is found in U.S. Pat. No. 5,359,353. The strip is attached to a flexible ink bag. As the flexible bag deflates with exhaustion of ink, an indicia on the strip moves in or out of view through a window which is on second strip that overlaps the indicia strip. U.S. Pat. No. 6,736,497 discloses an ink level sensing system that uses a flexible strip attached to a collapsible reservoir bag. Portions of the strip extend outside of the cartridge and are covered by panels with a window. As the bag collapses the strip portions move past the window showing indicia indicative of a remaining ink volume. 
     Some inkjet cartridges incorporate a technology known as “ink drop counting.” A controller is placed in communication with a printhead on the cartridge and counts the number of ink drops that are ejected from the printhead. Generally, the controller includes a database and/or look up table that includes data relative to one or more ink volumes that are associated with an ink drop count to determine a remaining ink volume. Some ink level systems may use ink drop counting in combination with other detection systems to more accurately determine an ink volume. Others may factor in printhead characteristics such as nozzle temperature to determine an ink drop size and volume. Still others may compare the ink drop data taken over multiple ranges to calculate a remaining ink volume. 
     In U.S. Pat. No. 4,121,222 there is disclosed a drop counter ink replenishing system for an inkjet printer that discloses a main ink tank and a supply ink tank. The system also includes an ink drop counter that counts the ink drops expelled from a printhead. When the ink drop count reaches a predetermined number, a flow control means is actuated and ink from the supply tank is supplied to the main ink tank. Similarly, U.S. Pat. No. 5,068,806 discloses a system that counts ink drops to determine an ink level within an inkjet cartridge. In the &#39;806 patent, the disclosed system is used with disposable cartridges such that when the ink drop count reaches a predetermined number the cartridge is disposed of and replaced. 
     U.S. Pat. No. 6,151,039 is directed to an inkjet printing system and method of determining an amount of ink in an ink container that incorporates ink drop counting and sensors that detect remaining ink volume and provide an accurate estimate of ink remaining in a cartridge. An information storage device estimates a volume of ink over a first volumetric range using ink drop count data. The device or method also utilizes a sensing circuit that detects an ink level at a predetermined volume. This sensed volume is used to estimate the ink volume over a second volume range that is different than the first range. The sensed volume is combined with count drop data over the second volumetric range to estimate the remaining ink volume. 
     In U.S. Pat. No. 6,676,237 there is disclosed a method for correcting calculations of ink amount consumed in a cartridge. The method uses ink drop counting to calculate an amount of ink consumed. A sensor/monitor monitors an ink level to generate a signal when the ink levels falls to a predetermined value. The data from this monitoring is used to correct a residual ink count determined by the ink drop count. 
     A method and apparatus for detecting a remaining ink in an inkjet cartridge using a sensor/detector and ink drop counting is disclosed in U.S. Pat. No. 6,969,137. The cartridge includes a sensor to detect ink level at a predetermined threshold. If ink drop counting calculates that the volume of ink exceeds the predetermined threshold a correction is made by adding the predetermined amount to the amount remaining as determined by the ink drop count. 
     Ink level sensing systems may factor in characteristics of or events happening at the inkjet printhead. With respect to U.S. Pat. No. 5,414,452 there is disclosed an ink jet cartridge and ink level sensing system that provides a correction in determining the volume of ink remaining in an ink reservoir. More specifically, the system estimates the volume of ink that evaporates over a predetermined time period and then adds that number to the ink drop count. U.S. Pat. No. 6,820,955 discloses an inkjet printing system that controls ink level in a cartridge by factoring the temperature at the printhead. 
     With respect to U.S. Pat. No. 6,431,673 there is disclosed a method of determining a volume of ink remaining in an ink jet cartridge by associating the drop count with the weight of the ink spelled. Drop weight estimates are made during intervals using temperature and printing frequency data for each interval. U.S. Pat. No. 6,382,764 discloses a printing method and apparatus for ink drop counting that factor in ink drops that are accumulated in a recovery suction operation. 
     In addition, inkjet cartridges may also be equipped with memory devices that store data relative to an ink drop count, or remaining volume of ink in an ink reservoir. U.S. Pat. No. 5,788,388 is for an inkjet cartridge with ink level detection means. A chip on the cartridge stores ink depletion data. When the ink level reaches a predetermined threshold a sensor sends a signal to the chip which generates an ink depletion signal. The chip can be reset if the cartridge is filled. 
     Although not directed to an inkjet cartridge, but to an ink reservoir, U.S. Pat. No. 5,365,312 discloses to an ink reservoir that has thereon an electronic memory means that contains data relative to a fill status of the reservoir. In addition, the memory may contain a counter for determining an expiration of the reservoir. 
     Still other ink level sensing systems may factor in the movement or position of an inkjet cartridge on a carriage to determine an ink volume. For example, U.S. Pat. No. 5,136,309 is directed to a residual ink quantity detecting means that includes a detection device that detects when ink in an ink supply is low and generates a responsive signal. This first signal is received by a signal output means, which generates a second signal when the pulse width is greater than a predetermined pulse width, and generates a signal indicative of low ink. The printer includes electronic circuitry that enables the signal output means to alter the first detection signal during certain printer operations, such as when the cartridge is making a left or right carriage turn, when the detection device may erroneously generate a signal indicative of a low ink supply due to movement of ink in the ink reservoir. 
     BRIEF DESCRIPTION OF THE INVENTION 
     An ink containment system for an inkjet cartridge, for storing ink for printing, comprises a housing having a plurality of walls. A rigid basin member and a rigid moveable plate are disposed within the housing and the basin member. A flexible membrane is affixed to a surface of the basin member and to a surface of the plate forming an ink reservoir within the basin member, plate and flexible membrane. A spring-biased mechanism is disposed between the basin member and plate, for biasing the plate apart from the basin member, generating a negative pressure within the ink reservoir and the basin member remains stationary relative to the movement of the plate. 
     In one embodiment the flexible membrane may have an annular configuration with a first peripheral edge affixed to a surface of the plate and a second peripheral edge affixed to a surface of the basin member. The plate may have an annular groove formed therein for receiving a first end of the spring-biased mechanism. A raised portion may be disposed within the housing and ink reservoir over which a second end of the spring biased mechanism is seated. In another embodiment, the raised portion may be disposed on a section of the basin member. 
     Another embodiment of the invention may also have an ink level sensing system for detecting when an ink level has reached a predetermined volume remaining in the ink reservoir. A sensor is provided to detect a detection flag that is connected to the plate at a position in the housing that is indicative of a predetermined volume of ink remaining in the ink reservoir. The detection flag is disposed relative to the plate and in the housing having a longitudinal axis that is disposed at an angle of about 45° to a horizontal axis and vertical axis of the cartridge when the printhead is in a horizontal or vertical printing position. 
     In a further embodiment, after the sensor detects the presence of the detection flag a signal is transmitted to a controller which is programmed to count the ink drops ejected during printer operations. Data representative of a total number of ink drops associated with the predetermined remaining volume of ink is stored in the system. After the total number of ink drops is counted as being used, a signal is generated indicating that the ink reservoir is empty of ink. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings. 
         FIG. 1  is a first perspective view of an inkjet cartridge with printhead and sensor. 
         FIG. 2  is a second perspective view of an inkjet cartridge with a printhead and aperture to an internal fill port. 
         FIG. 3A  is an exploded view of a first embodiment the inkjet cartridge and internal components. 
         FIG. 3B  is an exploded view of a second embodiment of the inkjet cartridge and internal components. 
         FIG. 4A  is a sectional view of the inkjet cartridge with an ink reservoir in an expanded position. 
         FIG. 4B  is a sectional view of the inkjet cartridge with an ink reservoir in a collapsed position. 
         FIG. 4C  is a sectional view of the inkjet cartridge with an ink reservoir in an expanded position. 
         FIG. 4D  is a sectional view of the inkjet cartridge with an ink reservoir in a collapsed position. 
         FIG. 5  is a perspective sectional view of the inkjet cartridge including a snout attached to the cartridge housing. 
         FIG. 6A  is an elevational view of the basin of the ink reservoir showing a fill port and an aperture leading to the snout. 
         FIG. 6B  is a rear perspective view of the snout ring and tabs for attachment to the basin member and housing. 
         FIG. 7A  is an exploded perspective view of the snout aligned for attachment to the basin member. 
         FIG. 7B  a perspective view of the snout aligned for attachment to the basin. 
         FIG. 7C  is a perspective view of the basin member showing a channel, chute and fill port. 
         FIG. 8  is a sectional view of the cartridge showing the fill port of the basin aligned with an aperture in cartridge housing for filling the ink reservoir with ink. 
         FIG. 9  is a sectional view of the inkjet cartridge with the ink reservoir illustrating the flexible membrane collapsed over the channel. 
         FIG. 10A  is a sectional view of the cartridge with the ink reservoir shown in an expanded ink-filled position and illustrating the position of a detection flag and a sensor. 
         FIG. 10B  is a sectional view of the cartridge with the ink reservoir collapsed and the detection flag positioned in the cartridge for detection by the sensor mounted in the housing. 
         FIG. 10C  is a schematic illustration of a detector in the ink level sensing system for an embodiment of the invention. 
         FIG. 11A  is a planar view of the cartridge with a cover removed and the snout and printhead disposed in a vertical printing position. 
         FIG. 11B  is a planar view of the cartridge with a cover removed and the snout and printhead disposed in a horizontal printing position. 
         FIG. 12  is schematic illustration of a first embodiment of a laminate structure for a flexible membrane of the ink reservoir. 
         FIG. 13  is a schematic illustration of a second embodiment of a laminate structure for a flexible membrane of the ink reservoir. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the embodiments consistent with the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings and refer to the same or like parts. 
     An inkjet cartridge  10  shown in  FIGS. 1 and 2  may be mounted on a moveable or stationary carrier for printing and has a printhead  16  in fluid communication with an ink reservoir  19  encased within housing  11 . Responsive to printing commands from a controller (not shown), the printhead  16  discharges ink from the ink reservoir  19  onto a print medium (not shown). The housing  11  comprises a sidewall  12 , a first cover plate  13  and a second cover plate  14 . For purposes of assembling the cartridge  10 , either the first cover plate  13  or second cover plate  14  may be integrally formed with the sidewall  12 . The other cover plate  13  or  14  is then affixed to the sidewall  12  encasing an ink reservoir  19  within housing  11 . Alternatively, both cover plates  13  and  14  may be fabricated as components separate and apart from the sidewall  12 , and then affixed to the sidewall  12 . 
     A snout  15 , attached to the housing  11 , includes the printhead  16  mounted thereon and nozzles (not shown) in fluid communication with the ink reservoir  19  to eject ink from the cartridge per printing commands. As explained in more detail below, the snout  15  is attached to the housing  11  as a separate component and is not integrally formed with the sidewall  12  as disclosed in U.S. Pat. No. 6,206,515 (the &#39;515 patent), which describes a snout as an integral component of an external frame member. The external frame member is a component of an outer casing of the inkjet cartridge disclosed in the &#39;515 patent. 
     As shown in  FIG. 1 , an aperture  34  is formed in the housing  11  and aligned with a fill port  33  of the ink reservoir  19 , which are described below in more detail. In addition, a sensor  18  is mounted in the housing  11  for use in an ink level sensing system incorporated in the cartridge  10 . A handle  17  is disposed on the sidewall  12  of the housing  11  opposite the snout  15 . In the embodiment disclosed herein the sidewall  12  is generally rectilinear with the snout  15  and handle  17  disposed on opposite corners of the housing  11 . 
     The ink reservoir  19  and the components making up the ink reservoir  19  are described in more detail with respect to  FIGS. 3A ,  4 A and  4 B. The ink reservoir  19  is generally defined by a rigid basin member  20 , a rigid moveable plate  21  and a flexible membrane  22  that is affixed to both the basin membrane  20  and the moveable plate  21 . A spring  23  is disposed between the basin member  20  and the plate  21 , and biases the plate  21  away from the basin member  20  to generate a negative or back pressure in the ink reservoir  19  to prevent ink from drooling from the nozzles on the printhead  16 . As ink is ejected during printing and other operations, the flexible membrane  22  collapses towards the basin member  20 , thereby causing the plate  21  to move towards the basin member  20 . The spring  23  biasing force against the plate  21  generates the negative pressure in the ink reservoir  19 . 
     As described above, only the plate  21  is moveable as the basin member  20  remains fixed within the housing  11 . In addition, the reservoir  19  includes only a single flexible membrane  22 , which is distinguishable from those patents U.S. Pat. Nos. 5,325,119; 5,440,333 (the &#39;333 patent); 5,737,002; 5,767,882; and, 6,053,607 that disclose the use of two flexible membrane sheets that have peripheral edges secured to an internal frame member. The flexible membranes disclosed in these patents are rectangular sheets and each covers a respective moveable side plate with the peripheral edges of the flexible membranes sealed to the internal frame member, so the moveable side plates are disposed within an ink reservoir. The internal frame member is affixed to an external frame member, which is described as a rectilinear member and does not include cover plates of the cartridge. In these prior art references, a spring is disposed between the side plates and biases the plates apart from one another; whereby, both plates move relative to one another to generate a negative pressure in an ink reservoir. 
     In contrast, in embodiments of the invention disclosed herein, the plate  21  moves relative to the stationary basin  20 , which is secured against the first cover plate  13 . The flexible membrane  22  may have the annular configuration shown in  FIG. 3A , having a first peripheral edge  22 A sealed against the basin member  20  and a second peripheral edge  22 B sealed against the moveable plate  21 . Annular membranes attached to periphery of moveable plates are shown in the expired &#39;084 patent; however, the &#39;084 patent does not disclose a stationary basin member disposed within an ink reservoir. In an embodiment illustrated in  FIG. 4A , the flexible membrane  22  is attached to a surface of the plate  21  that is disposed toward an exterior of the ink reservoir  19 , between the moveable  21  and an ink level sensing component described below in more detail. The plate  21  may have beveled edge  21 A to prevent the flexible membrane  22  from tearing or being punctured during shipping, handling or operation. 
     The above-referenced &#39;333 patent discloses a means for bonding a membrane to a side plate by first adhesively bonding a protective guard to a surface of a side plate that faces away from an interior of the ink reservoir. The flexible membrane covers the protective guard and side plate and is heat bonded to the side of the plate at an area centrally located on the side plate, so the side plate is disposed within the ink reservoir. The protective guard is formed of plastic sheet material that is wider and longer than the side plate to prevent the edges of the side plate from puncturing or tearing the flexible membranes. 
     In contrast, the flexible membrane  22  of the disclosed embodiments of the subject invention is affixed to the plate  21  along a periphery of the plate  21  or about a central area of the plate  21  and defines a portion of the periphery thereof. As illustrated, the plate  21  has an annular protrusion  24  forming groove  47  for receiving a first end of the spring  23 . The annular protrusion  24  is centrally located on the plate  21 ; therefore the flexible membrane cannot be bonded to the center of the plate  21 , but may be secured by suitable means such as welding to one or more points about the protrusion  24 . 
     A second end of the spring  23  is disposed over a raised portion  27  formed on the basin member  20  and disposed within the ink reservoir  19 . This portion  27  is raised in the sense that it has a surface  27 A that is displaced toward the plate  21  relative to a floor  20 A of the basin member  20 . In addition, a recess  26  formed on the plate  21  within area defined by the annular protrusion  24  or within the annular groove  47  receives the raised portion  27  on the basin member  20  when the ink reservoir is in a collapsed position. In  FIG. 4A , there is shown an ink reservoir  19  in an expanded position filled with ink, which is represented by the stippling. As ink is ejected from nozzles and through the printhead  16 , the spring  23  biases the plate  21  away from the basin member  20 , which is affixed to the cover plate  13 , creating negative pressure in the ink reservoir  19 . 
     In an embodiment, the spring  23  may be a helical spring. Given the configuration of the moveable plate  21 , the basin  20  and the connection of the spring  23  between the two, embodiments of the invention can not incorporate bow springs as disclosed in U.S. Pat. No. 5,541,632. 
     The basin member  20  may be fabricated from a relatively stiff or rigid plastic material such as polyethylene. As shown in  FIGS. 3 ,  4 A and  4 B, the basin member  20  has a bowl-like configuration including outwardly sloping walls  44  projecting to a ledge  45  that has a substantially flat surface on which the flexible membrane  22  is sealed or welded. With respect to  FIG. 4B , the ink reservoir  19  has collapsed. As shown, the bowl-like configuration of the basin member  20  allows the flexible membrane  22  to collapse along or against a surface of the basin member  20  to prevent folding or wrinkling of the membrane  22  that may eventually cause the membrane  22  to tear. In addition, as shown in  FIG. 4B , the recess  26  in the plate  21  receives the raised portion  27  on the basin member  20  and spring  23  folds into the groove  47  so the ink reservoir  19  can collapse with the flexible membrane  22  and the plate  21  is generally flush with the basin member  20  to empty as much ink as possible from the reservoir  19 . 
     Accordingly, one or more recesses are disposed within the ink reservoir, which recesses have a sufficient depth dimension for receiving the spring  23  when the ink reservoir  19  collapses as ink is ejected from the cartridge. A recess may be disposed on the basin member  20  or the moveable plate  21 . With respect to  FIGS. 4C and 4D , an embodiment of the invention is shown having a first groove  47 A formed in moveable plate  21  in which a first end  23 A of the spring  23  is seated and a second groove  47 B formed in the basin member  20  in which a second end  23 B of the spring  23  is seated. The grooves  47 A and  47 B are generally annular recesses for embodiments incorporating a helical spring. The grooves  47 A and  47 B may be aligned with one another so when the ink reservoir  19  collapses the grooves  47 A and  47 B have a combined depth dimension to receive the spring  23 . In this manner the moveable plate  21  may be generally flush against the basin member  20  to empty as much ink as possible from the reservoir  19  when the reservoir  19  collapses as ink is ejected from the cartridge  10 . 
     Embodiments of the present invention differ from the inkjet cartridge disclosed in U.S. Pat. No. 5,737,002 (the &#39;002 patent), which discloses two flexible membranes affixed to an “internal frame member.” The cartridge disclosed and claimed in the &#39;002 patent includes a frame structure which is defined as a continuous rectilinear loop structure. This frame structure does not include the covers therefor, which are independently identified. The frame structure includes an external frame member and an internal frame member. The membranes are joined to the internal frame member to form together with the frame structure, the ink reservoir. 
     As noted above, the flexible membrane  22  of the described embodiments of this invention is affixed to the basin member  20 . However, the basin member  20  is not a component of the housing  11  or sidewall  12  as disclosed in the &#39;002 patent. With respect to embodiments of the present invention disclosed herein, the basin member  20  (including the ledge  45  to which the flexible membrane  22  is sealed) is not attached to the sidewall  12 , but may be affixed to the first cover plate  13  or otherwise secured within housing  11 . Accordingly, the sidewall  12  of the subject cartridge  10  does not form the ink reservoir  19  with the membrane  22 ; it is the basin  20  that forms the ink reservoir  19  with the membrane  22  and moveable plate member  21 . More particularly in the present inventions, inkjet cartridge  10  does not include a frame structure that together with a flexible membrane forms the ink reservoir. 
     The attachment of the basin member  20  and ink reservoir  19  within the housing  11  is now described. Tabs  29  are disposed along the ledge  45  of the basin  20  to secure the basin  20  to the first cover plate  13  of the housing  11 . More specifically, the tabs  29  have apertures for receiving ends of posts  28  affixed to the first cover plate  13 . The posts  28  may be formed as integral components of the first cover plate  13 . As shown in FIGS. Projections  32  depending from the second cover plate  14  abut the tabs  29  and posts  28  to secure the basin  20  against the first cover plate  13  of the housing  11 . 
     In the assembly of the cartridge  10 , the ink reservoir  19 , including the basin member  20 , plate  21 , flexible membrane  22  and spring  23 , are placed in the housing  11  with the second cover plate  14  removed. The tabs  29  are aligned with posts  28  on the first cover plate  13 , and the fill port  33  is aligned with the aperture  32  on the housing  11 . The second cover plate  14  is then snapped into place with the projections  32  aligned to abut against tabs  29  on the basin member  20  and posts  28  to secure the basin member  20  and ink reservoir  19  in the housing  11 . The components of the housing  11 , including the sidewall  12 , first cover plate  13  and second cover plate  14  may be composed of a durable plastic material such as polyethylene terepthalate glycol, or other plastic materials of suitable durability to serve as a protective casing for the ink reservoir  19 . 
     In another embodiment, the housing  11  may include the “clam-shell” configuration illustrated in  FIG. 3B  wherein the housing  11  includes a first half  11 A affixed to a second half  11 B. The halves  11 A and  11 B each include cover plates  13  and  14  respectively and portions of the sidewall  12  to form the housing  11 . The cover plates  13 ,  14  and respective sidewalls form the housing  11 . The halves  11 A,  11 B can be secured to one another using methods such as screwing the halves together, ultrasonically welding the halves together, or bonding the halves together using a suitable or other bonding agent. In addition, in either embodiment illustrated in  FIG. 3A  or  3 B, the basin member  20  is secured against one of the halves  11 A or  11 B, or one of the cover plates  13  or  14 . More specifically, both the basin member  20  and housing  11  may have support ribs that engage one another to minimize any lateral movement of the basin member  20  or the ink reservoir  19  in the housing  11 . In either embodiment, the basin member  20  is secured within the housing  11  and remains stationary relative to movement of the plate  21 . 
     In an embodiment, the basin member  20  and plate  21  are composed of the same rigid plastic material such as polyethylene, and the flexible membrane is composed of a different plastic material that is pliable enough to allow the plate  21  to move relative to the stationary basin member  20 , durable enough to prevent tearing and compatible with the plastic material of the basin member  20  and plate  21  so the flexible membrane  22  may adequately sealed to the basin member  20  and plate  21 . As described in more detail below, the flexible membrane  22  may comprise a laminate structure that includes a polyethylene carrier layer, a polypropylene sealant layer and a metallized plastic layer. 
     The inkjet cartridge disclosed in the &#39;002 patent, describes and claims the composition of some of the components in terms of a first plastic material, second plastic material and third plastic material. More specifically, there is disclosed a cartridge that includes an external frame member that is fabricated from a first rigid plastic material and an interior frame member fabricated from a second plastic material that is different than the first plastic material, and two membranes composed of a third plastic material. The second and third plastic materials are compatible with one another to form a leak-proof joinder. In the specification of the &#39;002 patent at column 3, lines 21-23, an example of the first plastic material is a glass-filled modified polyphenylene oxide sold under a trademark NORYL. An example of the second plastic material is a polyolefin alloy or ten percent glass-filled polyethylene, which was chosen in part because it adheres to the NORYL. An example of the third plastic material for the membranes is listed as ethylene-vinyl acetate. Thus both of the membranes disclosed in the &#39;002 patent are composed of the same third plastic material, which is different than the first and second plastic materials. 
     Embodiments of the present invention disclosed herein include the housing  11  that is composed of a first plastic material and the ledge  45  of the basin member  20 , on which the flexible membrane  22  is sealed, is composed of a second plastic material. However, the remaining portion of the basin member  20  is composed of the same second plastic material. In addition, the flexible membrane  22  is composed of a material, including the plastic laminate structure that is different than the remaining portion of the basin member  20 . 
     The flexible membrane  22 , of the present invention, may require barrier characteristics to prevent the migration of solvents of the ink from the reservoir. For example, the flexible membrane  22  may be composed of a laminate structure having including two laminate layers affixed to one another. As shown in  FIG. 12 , each of a first and second laminate layers  54  and  55  respectively includes a carrier layer ( 54 A,  55 A), a barrier layer ( 54 B,  55 B) affixed to the carrier layer ( 55 A,  55 B) and a sealant layer ( 54 C,  55 C) affixed to the barrier layer ( 54 B,  54 B) sandwiching the barrier layer ( 54 B,  54 B) between carrier ( 54 A,  55 A), and sealant layers ( 54 C,  55 C). The laminate layers  54  and  55  are affixed to one another at their respective carrier layers ( 54 A,  55 A) by an adhesive  58 . A flexible membrane  22  with the above described laminate structure may be acquired through packaging manufacturer Curwood, located in Oshkosh, Wis. 
     Such a laminate structure differs from the laminate structure disclosed in U.S. Pat. No. 5,450,112, which includes laminate materials having the carrier layer sandwiched between the barrier layer and a sealant. In addition, in the &#39;112 patent, the barrier layer for each respective laminate layer is affixed to one another to form the laminate structure. Such a laminate structure differs from the present invention, which has the carrier layers ( 54 A,  55 A) affixed to one another to form the laminate structure. 
     In another embodiment, as shown in  FIG. 13 , the laminate structure includes first and second laminate layers  56  and  57 . The first laminate layer includes a carrier layer  56 A and a sealant layer  56 B. The second laminate layer  57  includes a carrier layer  57 A and a sealant layer  57 B with a barrier layer  57 C disposed there between. The first and second laminated layers  56 ,  57  are affixed to one another by an adhesive  58 . In either of the above described laminate materials, the carrier layer may be composed of polyethylene and the sealant may be composed of a material such as polypropylene, which is compatible with the polyethylene comprising the basin member  20  and plate  21  for attaching the flexible membrane  22 . The barrier layer may be composed of ethylene vinyl alcohol or other plastic material coated with a metal such as aluminum. 
     The above described laminate structure provides a membrane  22 , while inelastic, is flexible. In the assembly of the cartridge  10 , after the membrane has been welded to the basin member  20  and the moveable plate  21 , and the spring  23  having been seated in the reservoir  19 , the membrane  22  is collapsed into the basin membrane  20 . As a result of the inelastic characteristic of the membrane  22  a wrinkle pattern is formed or a flexing memory is created in the membrane  22 . In this manner, the membrane  22  and spring  23  can be expanded to maximize the volume of the ink reservoir  19 . In addition, when the membrane  22  collapses during printing operations, the membrane  22  may more readily conform to the shape of the basin member  22 . Accordingly, the expansion/contraction stroke of the spring  23  is maximized so the negative pressure in the ink reservoir  19  is effectively maintained to drain ink from the ink reservoir, and thereby extending the life of the cartridge  10 . As described above, the membrane  22  is not preformed by the thermal forming methods disclosed in the &#39;324 patent. 
     A more detailed description of the basin member  20 , snout  15  and their components is provided. More specifically, with respect to  FIG. 5 , a channel  35  is formed in the basin member  20  and leads to the snout  15 . A support member  39  is integrally formed with the basin member  20  and connects the snout  15  to the basin member  20 . The channel  35  extends through the support member  39  providing fluid communication between the ink reservoir  19  and the snout  15 . A standpipe  38  disposed in the snout  15  between the channel  35  and printhead  16 , connects the printhead  16  and nozzles (not shown) in fluid communication with the ink reservoir  19 . 
     The snout  15  is fabricated as a component independent of the housing  11  and basin member  20 , and may be composed of any durable plastic and dimensionally stable plastic material such as a glass-filled polyphenylene sulfide resin. As shown in  FIGS. 3A and 3B , tabs  50  on the housing  11 , snout  15  and basin member  20  are aligned relative to one another and pins  53  are inserted through the tabs  50  to secure the snout  15  to the housing  11  and basin member  20 . With respect to  FIGS. 6A and 6B  respectively, the support member  39  is illustrated having a hub  48  for receiving the ring  49  on the snout  15  and positioning the standpipe  38  relative to the channel  35 . An o-ring  59  is disposed between the hub  48  and ring  49 . In  FIG. 5 , a screen  37  is disposed between the support member  39  and snout  15  to filter air bubbles, debris etc. from ink traveling from the ink reservoir  19  through the channel  35  to the standpipe  38  and printhead  16 . 
     Also with respect to  FIGS. 5 and 7C , there is formed in the wall  44  of the basin member  20  a chute  36  that extends between the floor  20 A of the basin  20  and the channel  35 . The chute  36  allows for ink from the reservoir  19  to continue to be supplied to the printhead  16  when plate  21  and flexible membrane  22  are collapsing. As illustrated in  FIG. 9 , when the flexible membrane  22  is collapsing into the basin  20 , the membrane  22  may block the opening to the channel  35 ; however, ink may still travel to the channel  35  and to the printhead  16  via the chute  36 . In this manner, a maximum volume of ink can be withdrawn from the reservoir  19  minimizing the wasting of ink, especially if the cartridge is disposable. 
     In the basin member  20  there is also provided a fill port  33  through which ink is injected into the ink reservoir  19 . As shown, in  FIG. 8 , an aperture  34  in housing  11  is aligned with the fill port  33  to fill the ink reservoir  19  after it has been mounted within the housing  11 , and the snout  15  is attached to the basin  20  and housing  11 . With respect  FIG. 3A , tabs  50 ,  51  and  52  on the snout  15 , housing  11  and basin  20  respectively, are positioned with respect to one another to secure to secure the snout  15  to the basin  20  and the housing  11 . Pins  53  inserted through the tabs  50 ,  51  and  52  secure the snout  15 , basin  20  and housing  11  to one another. 
     The ink reservoir  19  may be filled after it is installed in the housing  11 , and after the snout is attached to the basin member  20  and housing  11 . A plug or stopper may be inserted in the fill port  33  after filling the reservoir  19  with ink, and the aperture  34  may be covered with a cap, tape, label or other suitable means to close off the interior of the cartridge  10 . Filling the ink reservoir  19  may be done by using techniques known to those skilled in the art. For example, a gravimetric or vented fill may be used wherein a needle is inserted through aperture  34  on the housing  11  and into fill port  33  with the ink reservoir  19  in an expanded state. Ink is injected into the reservoir  19  through the fill port  33 . Displaced air may escape through spacing between the needle and fill port  33 . Any remaining air may be removed when the inkjet cartridge  10  is primed by providing a vacuum suction to the printhead  16  and nozzles. Another known method for filling the ink reservoir. The nozzles on printhead  16  are plugged. A needle is connected to a vacuum source and an ink source. A vacuum is first pulled to collapse the ink reservoir and a valve is turned and a predetermined amount of ink is injected into the reservoir  19 . The cartridges is then primed via drawing a vacuum through nozzles to remove any excess air within the reservoir. 
     Ink Level Sensing System 
     Embodiments of the inkjet cartridge may include an ink level sensing system to monitor the volume or level of ink within the ink reservoir. With respect to  FIGS. 3 ,  10 A,  10 B,  11 A and  11 B, the sensing system may comprise an optical position sensor  18 , a detection flag  60  mounted to the moveable plate  21  and a controller  70  programmed to count ink drops ejected from the printhead  16  and nozzles. The detection flag  60  is mounted to the moveable plate  21  so as the flexible membrane  22  collapses and the moveable plate  21  moves toward the basin member  20 , the detection flag  60  also moves in the same direction as plate  21 . 
     The sensor  18  is preferably not mounted to the cartridge housing  11 , but is mounted to a printing system pocket (not shown) within which the inkjet cartridge  10  is positioned for printing. When the cartridge  10  is mounted in the pocket for printing the sensor  18  is positioned adjacent apertures  74  to detect the presence of the detection flag  60  as it advances by the sensor  18 . The position of the flag  60  when detected is representative of a predetermined volume of ink remaining in the reservoir. 
     When the sensor  18  detects the flag  60 , a signal is generated and transmitted to the controller  70 , which signal is representative of the predetermined volume of ink remaining in the ink reservoir  19 . Embodiments of the present invention count ink droplets over a single volumetric range, which is distinguishable from those ink level sensing systems that count ink droplets over multiple ranges such as in U.S. Pat. Nos. 6,151,039 and 6,456,802. A database or memory is available having stored data representative of a total number of ink drops that is associated with the predetermined ink volume remaining in the ink reservoir. When the controller  70  receives the signal from the sensor  18 , the controller  70  begins counting the number of ink droplets ejected during various printer operations. The controller  70  may incorporate programming or software used to count ink droplets that is known to those skilled in the art. When the controller  70  has completed the ink drop counting one or more signals may be transmitted to generate an alarm or indicator that the ink reservoir  19  is empty so the cartridge can be replaced or refilled. To that end the controller  70  may be linked to a display panel that may provide a visual display of the status of the ink volume, which display may include a graphic symbol such as a gauge or an alphanumeric symbol for example. 
     As illustrated in  FIGS. 3 ,  10 A and  10 B, the flag  60  includes a base member  61  affixed to a surface of the moveable plate  21  exterior of the ink reservoir. The base member  61  has an outer edge  61 A that is substantially coextensive with an outer edge  21 A of the moveable plate  21 . A ring  62  on the base member  61  is coaxially aligned with the annular protrusion  24  on the moveable plate  21  for receiving the protrusion  24 . An arm  64  extends from the base member  61  toward the housing  11 . A flag tip  65  depends from an end of the arm  64  distal the base member  61  and has a bottom edge  65 A that is substantially coplanar with the surface of the plate  21  that faces the interior of the ink reservoir. In addition the flag tip  65  has a generally planar configuration that is disposed parallel to a surface of the printhead  16  when the printhead  16  is positioned in either a vertical printing position ( FIG. 11A ) or a horizontal printing position ( FIG. 11B ). 
     In as much as the basin member  20  is a stationary rigid component having the bowl-like configuration, the arm  64  extends obtusely relative to the basin member  20 . Therefore, as the flexible membrane  22  and moveable plate  21  collapse into the basin member  20  the flag tip  65  drops between the sidewall  12  and the basin member  20  so the sensor  18  detects the flag tip  65  when the ink level drops to the predetermined volume. The sensor  18  may include a light emitting element and a light detection element. Light reflectors  75 A and  75 B are disposed at angles of 45° relative to the sidewall  12  to create light path (designated by dashed lines) so that light enters and exits the cartridge  10  along the path shown in  FIG. 10C . The sensor  18  may be programmed such that as long as the sensor  18  detects light during printing operations no signal is transmitted to the controller  70 . However, when the flag tip  65  drops between the reflective surface  75 A and the sensor  18  and interrupts the light path, the sensor  18  transmits a signal  76  to the controller  70 , which signal  76  is indicative of a predetermined ink volume remaining in the ink reservoir  19 . At that point, the controller  70  begins the ink drop count as described above. 
     The components, including the base member  61 , ring  62 , arm  64  and flag  60  are preferably composed of a metal or sufficiently rigid plastic material such as polycarbonate, and may be integrally formed as a unitary piece. As described above, the configuration of the base member  61  is preferably coextensive with that of the plate  21 , or covers a portion of the plate  21 . The counter-acting forces of the negative pressure and spring  23  in the ink reservoir  19  may cause the plate  21  to bend or warp during operation. Such deformation of the plate  21  may effect the disposition of the flag tip  65  relative to the sensor  18 , which may result in the sensor  18  detecting the flag tip  65  at a point that does not accurately represent the predetermined volume of ink remaining in the reservoir  19 . The base member  61 , including the ring  62  and ribs  66  may prevent or minimize warping or bending of the plate  21 . 
     With respect to  FIG. 11A , the inkjet cartridge  10  is shown with the snout  15  and printhead  16  positioned to print in a vertical position. The dashed vertical line  73  beginning from point  81  represents the path that ink droplets may travel vertically downward toward a horizontally disposed print medium  77 . In  FIG. 11B , the inkjet cartridge  10  is shown with the snout  15  and printhead  16  positioned to print in a horizontal position. The dashed horizontal line  72  represents the path that ink droplets may travel horizontally toward a vertically disposed print medium  78 , and dashed also happens to represent an elevation of the point  81  from which a fluid height is measured as referred to below. The detection flag  60  is connected to the plate  21  and disposed in the housing having a longitudinal axis that is disposed at an angle of about 45° to a horizontal axis and vertical axis of the cartridge when the printhead is in either horizontal or vertical printing position. 
     As may be appreciated in previously referenced figures the cartridge housing  11 , basin member  20 , flexible membrane  22  and moveable plate  22  have a generally square configuration. In such a design configuration the fluid head pressure at the nozzles on the printhead  16  is substantially the same when the printhead  16  is disposed in either a horizontal or vertical printing position. The fluid head pressure at the nozzles is the summation of the negative pressure generated in the ink reservoir  19  and the hydrostatic pressure of the ink against the nozzles. The hydrostatic pressure is a function of the fluid height of the ink in reservoir  19  relative to the printhead  16  or nozzles. In  FIG. 11A  the dashed line  79  represents the fluid height of ink in the reservoir measured from dashed line  72  representing the point  81 , which is the center point of the nozzles on the printhead  16 . The diagonal 45° line  71  represents an axis of symmetry of the ink reservoir  19  taken from the point  81 , which is the center of the printhead  16  or nozzles. With respect to  FIG. 11B , the cartridge  10  or ink reservoir  19  has been rotated about line  71  (the axis of symmetry) so the printhead  16  is now disposed in a horizontal printing position as represented by line  72 . The fluid height in  FIG. 11B  of the ink in the ink reservoir  19  is represented by line  79  and measured from the point  81  which represents a center nozzle or center of the printhead  16  and referenced by the dashed line  72 . 
     As can be appreciated from a comparison of  FIGS. 11A and 11B , the fluid height of the ink in the ink reservoir  19  is the same when the printhead  16  is in either a vertical or horizontal printing position. Accordingly, the hydrostatic pressure of the ink against the nozzles will be the same in both printing orientations. Moreover, the different orientations of the cartridge  10  or ink reservoir  19  does not affect the performance of the spring  23  biasing the plate  21  away from the basing member  20 , so the negative pressure is the same in either orientation. Therefore the fluid head pressure at the nozzles is the same in either the vertical or horizontal printing position. This translates into the same fluidic performance of the ink in either printing position, so ink drops are ejected through nozzles effectively and consistently in both printing positions and the cartridge  10  can print in either position. It is noted that embodiments of the invention are not limited components and the ink reservoir  19  having a generally square or rectangular shaped periphery, but may include any such shape that provide the symmetry necessary to achieve that consistent fluid head pressure at the different printing orientations. 
     In addition, the ink level sensing system performs consistently in either printing position. When the cartridge  10  is disposed in either the vertical or horizontal position, gravity may cause ink to slightly settle in the ink reservoir  19  toward the snout  15 , printhead  16  and adjacent side of the basin member  20 . The flexible membrane  22  may bulge at that general area, which may cause the flag  60  or flag tip  65  to slightly tilt. However, because the arm  64  is disposed along the diagonal line  71  (axis of symmetry) and the flag tip  65  is positioned at corner of the cartridge  10  opposite the corner where the printhead  16  is positioned, the flag tip  65  may tilt opposite the bulge in the reservoir in either printing orientation. Therefore, the ink level sensing system will act consistently in either printing orientation. 
     Printhead and Electrical Interconnect 
     Yet another novel feature of the present invention is the disposition of an electrical interconnect  82  on the snout  15  relative to the printhead  16 . As shown in  FIGS. 1 and 2 , the printhead  16  is affixed to the snout  15  in fluid communication with the ink reservoir  19 . The electrical interconnect  82  is also affixed to the snout  15  for receiving print command signals from a printing controller (not shown). The printhead  16  and electrical interconnect  82  are preferably fabricated on a single flexible substrate that is affixed to a first surface (or an ejection surface)  15 A of the snout  15  with printhead  16  in fluid communication with the ink reservoir  19 , and the electrical interconnect  82  is wrapped around the snout  15  and affixed to a second surface  15 B of the snout  15 . When the cartridge  10  is mounted in a printing system for printing the electrical interconnect  82  is aligned with and placed in contact with electrical leads from the printing system for transmitting printing commands to the printhead  16 . 
     The surfaces  15 A and  15 B of the snout  15  are positioned relative to one another such that the electrical interconnect  82  is disposed at an acute angle relative to the printhead  16 . In the embodiments disclosed herein, the second surface  15 B is disposed an angle greater than 90° to the first surface  15 A in a counterclockwise direction and at an angle of less than 90° to the first surface  15 A in a clockwise direction. In an embodiment, the angle of the second surface  15 B relative to the first surface  15 A may be about 135° in a counterclockwise direction and about 45° in a clockwise direction. Prior art cartridges have the electrical interconnect on a cartridge surface that is disposed at an angle of 90° relative to a printhead surface. At such an angle, ink ejected from a printhead may splatter when it hits a print medium, land on the electrical interconnect  82 , thereby fouling or interrupting the electrical communication between the printhead  16  and a printer controller. In this described embodiment, the electrical interconnect  82  is out of range of ink splatter because it is disposed at an acute angle relative to the printhead  16 . 
     With the cartridge  10  disposed in a horizontal printing orientation, the configuration of the snout  15 , the disposition of the electrical interconnection  82  at an acute angle relative to the printhead  16  provides an advantage over prior art cartridges. More specifically, in production line printing systems one or more inkjet cartridges are positioned relative to a conveyor and a product packaging print medium for printing symbols, bar codes or other data on the medium. The cartridge is typically stationary as the packaging passes the cartridge on the conveyor, and is positioned to print an image on an end (usually a bottom end) of the packaging that is on the conveyor. Accordingly, a low deck height is desirable wherein the deck height is measured from the conveyor to a lowest nozzle on the cartridge, or nozzle closest to the conveyor. Often times however, conveyor or printing system components limit positioning of the cartridge relative to the conveyor to minimize the cartridge deck height. Embodiments of the invention in which the electrical interconnect  82  is disposed at an acute angle relative to the printhead  16  provide spacing to avoid conveyor or printing system components to minimize the cartridge deck height. In addition, the printhead  16  may be positioned closer to print medium  77  or  78  because of the disposition of the electrical interconnect  82  relative to the printhead  16 ; and, as described above, in this embodiment the electrical interconnect  82  is out of range of ink splatter because it is disposed at an acute angle relative to the printhead  16 . 
     While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only and not of limitation. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the teaching of the present invention. Accordingly, it is intended that the invention be interpreted within the full spirit and scope of the appended claims.