Abstract:
Example continuous ink supply apparatus, systems and methods are disclosed. An example apparatus includes a housing; a printhead; and a regulator including a lever, a spring coupling the lever to the housing, a bladder, and a valve, a position of the lever relative to the housing being controlled by the bladder, the bladder being inflatable to urge the lever away from a surface of the housing and a plug of the valve to move away from a valve seat to enable fluid to flow through the aperture and into the housing, the regulator to enable a pressure within the housing to be maintained below a threshold pressure to substantially prevent fluid from inadvertently dispensing from the printhead.

Description:
RELATED APPLICATION 
     This patent arises from a continuation of U.S. patent application Ser. No. 14/002,972, entitled “Continuous Ink Supply Apparatus, System and Method,” which was filed on Sep. 3, 2013, which is a U.S. national stage filing of PCT Application Serial No. PCT/US11/28369 filed on Mar. 14, 2011. Priority to U.S. patent application Ser. No. 14/002,972 and PCT Application Serial No. PCT/US11/28369 is hereby claimed. U.S. patent application Ser. No. 14/002,972 and PCT Application Serial No. PCT/US11/28369 are hereby incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Inkjet printers and related inkjet devices have proven to be reliable, efficient, and generally cost effective means for the accurate delivery of precisely controlled amounts of ink and other related liquid materials onto various substrates such as, but not limited to, glass, paper, cloth, transparencies and related polymer films. For example, modern inkjet printers for consumer market digital printing on paper offer printing resolutions in excess of 2400 dots per inch (DPI), provide printing speeds greater than 60 sheets per minute, and deliver individual droplets of ink in a ‘drop-on-demand’ method that are often measured in picoliters. The relatively low costs, high print quality and generally vivid color output provided by these modern inkjet printers has made these printers among the most common digital printers in the consumer market. 
     A potential drawback of many inkjet printers is a limited usage rate and a concomitant high intervention rate associated with on-axis ink supplies. Specifically, on-axis ink supplies are necessarily limited in how much ink is available due to a trade-off with scan speed and other mechanical considerations of the printhead in the printer. A solution is to provide an off-axis ink supply that either augments or completely supplants the on-axis supply. Such an off-axis ink supply, often referred to as a continuous ink supply (CIS) system, facilitates both providing larger reservoirs of ink and replenishing ink supplies without a need to interrupt ongoing printer operations (e.g., a current print job). Unfortunately, incorporation of a CIS system in modern printers is generally not as simple as adding an off-axis supply and running tubes to the printhead. Consideration of numerous issues involving connections, locations, air management and maintenance, for example, with respect to the printer render incorporation of CIS systems a non-trivial problem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features of examples may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, where like reference numerals designate like structural elements, and in which: 
         FIG. 1  illustrates a block diagram of a continuous ink supply (CIS) apparatus, according to an example of the principles described herein. 
         FIG. 2A  illustrates a schematic cross sectional view of a one-way valve built into an ink cartridge, according to an example of the principles described herein. 
         FIG. 2B  illustrates a schematic cross sectional view of the one-way valve of  FIG. 2A  in an open configuration, according to an example of the principles described herein. 
         FIG. 2C  illustrates a schematic cross sectional view of the one-way valve of  FIG. 2A  in a closed configuration, according to an example of the principles described herein. 
         FIG. 3  illustrates a perspective view of a continuous ink supply (CIS) apparatus, according to another example of the principles described herein. 
         FIG. 4  illustrates a block diagram of a continuous ink supply (CIS) printer system, according to an example of the principles described herein. 
         FIG. 5  illustrates a flow chart of a method of continuous ink supply (CIS) used with a printer, according to an example of the principles described herein. 
     
    
    
     Certain examples have other features that are one of in addition to and in lieu of the features illustrated in the above-referenced figures. These and other features are detailed below with reference to the preceding drawings. 
     DETAILED DESCRIPTION 
     Examples in accordance with the principles described herein provide a continuous ink supply for an ink deposition system that employs ink. In particular, the continuous ink supply one of augments or replaces an on-axis ink reservoir of the ink deposition system. For examples, the ink reservoir may be an ink reservoir of a printhead in a printer. The continuous ink supply may replace the augment or replace the ink reservoir of the printhead (e.g., the on-axis ink reservoir) to one or both of facilitate performing bigger print jobs and significantly increasing a service interval of the printhead. Examples of the continuous ink supply described herein may be employed to retrofit or modify existing ink deposition systems such as printers to provide the printer with a continuous ink supply. In other examples, a manufacturer may provide the ink deposition system with the continuous ink supply as either standard or optional equipment. 
     Herein, the term ‘liquid ink’ or simply ‘ink’ is defined as a fluid and includes either any liquid medium or a combination of a liquid carrier and substantially solid particles that is or may be deposited in a particular pattern or image by an ink deposition system such as a printer. Herein, ‘continuous ink supply’ is defined as a supply of liquid ink that is substantially uninterrupted in delivery to a printer. In some examples, the continuous ink supply may be replenished without halting a printing operation of the printer. Herein, ‘drooling’ with reference to a printhead is an adverse tendency for ink to leak or drip from the printhead. Drooling may be reduced, or in some examples, substantially minimized or substantially prevented, by maintaining a negative pressure in the ink supply of the printhead. For example, if the ink within a reservoir that services the printhead is maintained at a pressure that is negative relative to an ambient pressure outside of the printhead, the printhead may not exhibit drooling. 
     Also herein, a ‘one-way’ valve is defined as a valve that substantially limits, or in some examples substantially prevents, flow of a fluid in one direction while allowing flow in another direction. In particular, fluid may flow through the one-way valve in a first or downstream direction (i.e., also sometimes called the ‘forward’ direction). However, fluid flow in a second or upstream direction is largely prevented through the one-way valve. One-way valves are also sometimes referred to as check valves. 
     In some examples, one-way valves may further limit fluid flow in the downstream direction. In particular, in some examples one-way valves have a minimum activation pressure in the downstream direction. The minimum activation pressure is also sometimes referred to as cracking pressure and represents a pressure that activates the one-way valve to facilitate fluid flow in the downstream direction. In some examples, the minimum activation pressure is characterized by a pressure difference or differential pressure across the one-way valve. Fore example, the minimum activation pressure may be defined in terms of a pressure difference between the upstream side and the downstream side of the valve. However, when a pressure on a first side of the one-way valve is substantially zero relative to an ambient pressure, the minimum activation pressure may be equivalently characterized by a particular pressure at a second side (i.e., different from the first side) of the one-way valve. In particular, if a pressure on an upstream side of the one-way valve is substantially zero relative to the ambient pressure, the minimum activation pressure may be defined only in terms of the pressure also relative to the ambient pressure on a downstream side. Such a characterization is employed herein and the minimum activation pressure is referred to as a ‘minimum negative activation pressure.’ 
     Specifically, herein the minimum negative activation pressure of a one-way valve is defined as a minimum or lowest negative pressure of a fluid downstream of the one-way valve at which the one-way valve may open to allow fluid to flow. By ‘negative’ it is meant that the fluid pressure has a negative value (i.e., is less than zero). Also, as used herein all pressures are defined as being relative to an ambient pressure outside of a structure that confines and holds the fluid (e.g., outside of a fluid conduit connected to the downstream side of the one-way valve). As such, when a pressure of the fluid downstream of the one-way valve is more negative than the minimum negative activation pressure (i.e., when the downstream fluid pressure has both a negative value and a magnitude that is greater than a magnitude of the minimum negative activation pressure), the one-way valve opens and fluid is able to flow through the one-way valve. Alternatively, when the downstream fluid pressure is less negative than the minimum negative activation pressure (i.e., closer to zero than the minimum negative activation pressure), the fluid is substantially prevented from flowing in the forward or downstream direction. Note that fluid flow in both directions is also substantially prevented when the fluid pressure downstream of the one-way valve is positive (i.e., equal to or greater than zero) given the one-way nature of the one-way valve. 
     Further herein, a ‘memory circuit’ is defined as a circuit, typically implemented as an integrated circuit (IC) or ‘chip,’ that provides information to the printer regarding characteristics of the ink supply. Characteristics to which the information pertains may include, but are not limited to, one or more of an initial quantity of ink, a remaining quantity of ink, a type of ink, an ink color, and an ink cartridge identification number (e.g., model number, serial number, etc.). 
     Further, as used herein, the article ‘a’ is intended to have its ordinary meaning in the patent arts, namely ‘one or more’. For example, ‘a printhead’ means one or more printheads and as such, ‘the printhead’ means ‘the printhead(s)’ herein. Also, any reference herein to ‘top’, ‘bottom’, ‘upper’, ‘lower’, ‘up’, ‘down’, ‘front’, back′, ‘left’ or ‘right’ is not intended to be a limitation herein. Herein, the term ‘about’ when applied to a value generally means plus or minus 10% unless otherwise expressly specified. Moreover, examples herein are intended to be illustrative only and are presented for discussion purposes and not by way of limitation. 
       FIG. 1  illustrates a block diagram of continuous ink supply (CIS) apparatus  100 , according to an example of the principles described herein. The CIS apparatus  100  may be used to supply liquid ink to an ink deposition system. The ink deposition system  102  may deposit the supplied liquid ink in a specific or directed pattern on a substrate. The specific pattern may be one or more of a 2-dimensional pattern, a 3-dimensional pattern (e.g., built up in layers), or a 2-dimensional pattern on a 3-dimensional substrate (e.g., a non-planar substrate), according to various examples. 
     In particular, the ink deposition system  102  may be a printer  102  and the CIS apparatus  100  may be employed to supply liquid ink for use by the printer  102 , according to some examples. For example, the printer  102  may be an inkjet printer and the liquid ink may be inkjet ink. In various examples, the printer  102  comprises a printhead  104  that includes a liquid ink ejector to eject the liquid ink as either droplets or a continuous stream. In various examples, the liquid ink ejector of the printhead  104  may eject the liquid ink according to any of a variety of techniques including, but not limited to, thermal resistance (e.g., thermal inkjet), piezoelectric deformation, and an ink pump to form the pattern on a substrate  106 . The printer  102  may be used to print the pattern on a substrate  106  such as, but not limited to, paper, cardboard, cloth, plastic film (e.g., polyimide film, polyester film, polypropylene film, etc.), metal sheets, various ceramics, oxides, or semiconductor wafers, and a variety of non-planar structures (e.g., cans and bottles). For example, the pattern may comprise one or both of an image and text that is printed on a paper substrate  106  by the printer  102 . 
     As illustrated, the CIS apparatus  100  comprises an off-axis ink supply  110 . The off-axis ink supply  110  is configured to source liquid ink to the printhead  104  of the printer  102 . As employed herein, the term ‘off-axis’ with respect to an ink source or supply is defined as not collocated with the printhead  104 . In particular, the off-axis ink supply  110  is a supply of liquid ink that is not located on a moving assembly that carries and moves the printhead  104  relative to the substrate  106 . 
     For example, the off-axis ink supply  110  may comprise one or more containers of liquid ink located adjacent to the printer  102 . In another example, the off-axis ink supply  110  may comprise an ink reservoir built into a frame of the printer  102  but not collocated with the printhead  104 . In various examples, the off-axis ink supply  110  facilitates replenishment of the liquid ink while the printer  102  is performing a printing job or task, e.g., printing a pattern. In particular, liquid ink may be added to the ink supply  110  without halting the print job of the printer  102 , for example. 
     The off-axis ink supply  110  is connected to and in fluid communication with the printhead  104  by a fluid conduit  112 . In some examples, the fluid conduit  112  comprises a tube. The tube may be a flexible tube to accommodate motion of the printhead  104 , for example. The tube may be one of a plurality of tubes, each tube of the plurality supplying a different color or type of liquid ink, for example. In particular, the individual tubes of the plurality may supply liquid ink to different ones of a plurality of printheads  104  of the printer  102 , for example. 
     The CIS apparatus  100  further comprises a one-way valve  120 . The one-way valve  120  is positioned between the off-axis ink supply  110  and the printhead  104  along flow path of the liquid ink. In some examples, the one-way valve  120  is located along the fluid conduit  112 . For example, the one-way valve  120  may be located at a terminus of the tube adjacent to the printhead  104 . In another example, the one-way valve  120  is located at a beginning of the fluid conduit  112 . In yet another example, the one-way valve  120  is located within the tube away from either the terminus or the beginning of the fluid conduit  112 . In other examples, the one-way valve  120  is located in portion of the fluid conduit  112  other than the tube. For example, the one-way valve  120  may be integral to a housing of a fluid reservoir of the printhead  104 , as described below. 
     According to various examples, the one-way valve  120  acts as a check valve to substantially limit, or substantially prevent in some examples, liquid ink from flowing in an upstream direction from the printhead  104  to the off-axis ink supply  110 . In  FIG. 1 , a direction of flow of liquid ink established by the check valve action of the one-way valve  120  is indicated by an arrow  122 , which points in a forward or downstream direction, as illustrated. In addition to acting as a check valve, the one-way valve  120  has a minimum negative activation pressure at a printhead side (i.e., downstream side) of the one-way valve. 
     In some examples, the minimum negative activation pressure of the one-way valve  120  is equivalent to a pressure of the ink at the printhead  104  that substantially minimizes, and in some examples substantially precludes, the liquid ink from leaking or ‘drooling’ from an ejection orifice of the printhead  104 . In other words, the minimum negative activation pressure is more negative than an ink pressure at which printhead drooling is likely to take place or is considered to be a problem. In some example printers  102 , an ink pressure of between about minus 1.0 and about minus 2.5 kilopascals (kPa) is sufficient to substantially preclude drooling. Thus, in some examples, the minimum negative activation pressure of the one-way valve  120  is selected to be less than or equal to about minus 1.0 kPa. In some examples, the minimum negative activation pressure is selected to be less than or equal to about minus 2.5 kPa. In some examples, the minimum negative activation pressure may be minus 3.0 kPa or less (i.e., a larger negative value). 
     Note, that the minimum negative activation pressure as defined and used herein is a lower bound on the negative activation pressure measured relative to the ambient pressure. Thus, the one-way valve  120  having a minimum negative activation pressure that is more negative than the minimum negative activation pressure that substantially prevents drooling is still within a scope defined herein. In other words, a one-way valve  120  having a minimum negative activation pressure of minus 1.75 kPa is explicitly within the scope of a minimum activation pressure of about minus 1.0 kPa, for example. In another example, a minimum negative activation pressure of minus 3.75 kPa is within the scope defined by a minimum activation pressure of about minus 2.5 kPa, and so on. 
     In various examples, the one-way valve  120  may have a structure selected from a number of structures for implementing one-way or check valves provided that the structure also accommodates the establishment of the minimum negative activation pressure. For example, the one-way valve  120  may be implemented as any of, but not limited to, a ball check valve, a diaphragm check valve, a swing or tilting disc check valve, and a duckbill check valve. Various means for selecting and establishing the minimum activation pressure of such check valves including, but not limited to, selecting a spring constant of a spring or another means of biasing an element of the check valve, may be employed. For example, a spring constant of a spring used to retain a sphere or spherical ball in an opening of a ball check valve may be used to establish a minimum negative activation pressure of the ball check valve when employed as the one-way valve  120 . 
     In some examples as mentioned above, the one-way valve  120  may be integral to a fluid reservoir of the printhead  104 . For example, the one-way valve  120  may be built into an ink cartridge or a similar structure that houses the fluid reservoir of the printhead  104 . The built-in one-way valve  120  within the ink cartridge may be located in part of in whole within the fluid reservoir, for example. A portion of the one-way valve  120  may further extend into a housing of the ink cartridge to provide fluid communication between the fluid reservoir and an exterior of the ink cartridge. The fluid conduit  112 , in turn, may comprise a tube that is connected to the portion of the one-way valve that passes through a wall of the housing as a valve port of the integral one-way valve  120 , for example. 
     In other examples, the one-way valve  120  may be located along and within the fluid conduit  112  itself (e.g., an inline one-way valve), but outside or at least substantially outside of the ink cartridge. For example, the fluid conduit  112  may comprise a tube that is connected either to a housing of the ink cartridge or to a printhead assembly (PHA) that holds the printhead  104  in an absence of the ink cartridge (e.g., when the ink cartridge is removed). In these examples, the one-way valve  120  may be positioned somewhere along the tube, but is not integral with the housing or built in to the ink cartridge, for example. In another example, the one-way valve  120  is positioned somewhere along the tube and the tube with a terminus of the tube being connected to an ink reservoir (e.g., the ink reservoir of the ink cartridge). 
       FIG. 2A  illustrates a schematic cross sectional view of a one-way valve  120  built into an ink cartridge  130 , according to an example of the principles described herein. As illustrated in  FIG. 2A , the one-way valve  120  is closed.  FIG. 2B  illustrates a schematic cross sectional view of the one-way valve  120  of  FIG. 2A  in an open configuration, according to an example of the principles described herein.  FIG. 2C  illustrates a schematic cross sectional view of the one-way valve  120  of  FIG. 2A  in another closed configuration, according to an example of the principles described herein. 
     In particular,  FIGS. 2A-2C  illustrate a cross section of the ink cartridge  130  associated with the printhead  104 . As illustrated the ink cartridge  130  is separable from the printhead  104  at a connector  108 . The connector  108  may serve as a liquid ink port of the printhead  104 , for example. In other examples (not illustrated), the printhead  104  and the ink cartridge  130  may be substantially or even permanently connected. For example, the ink cartridge  130  may include the printhead  104 . 
     The ink cartridge  130  comprises a fluid reservoir  132  that is configured to hold liquid ink for use by the printhead  104 . A housing  134  substantially encloses and, in some examples, substantially defines the fluid reservoir  132 . The ink cartridge  130  further comprises a variable chamber  136  within the housing  134  in fluid communication with the fluid reservoir  132 . The variable chamber  136  is configured to expand and contract in response to pressure changes in the liquid ink within the fluid reservoir  132 . Specifically, the variable chamber  136  expands when a pressure of the ink decreases and contracts as the ink pressure increases relative to an ambient pressure outside of the housing  134  and the fluid reservoir  132 . 
     As illustrated in  FIGS. 2A-2C , the one-way valve  120  is substantially located within the fluid reservoir  132  and comprises a valve port  124  formed through a wall of the housing  134  to access an exterior of the print cartridge  130 . In some examples (e.g., as illustrated), the housing  134  provides or serves as a structural member of the one-way valve  120 . As such, the one-way valve  120  is also integral to the housing  134 , and by extension, is also integral to the ink cartridge  130 . 
     Further illustrated in  FIGS. 2A-2C , the fluid conduit  112  comprises a tube  112  connected to the valve port  124 . In some examples, the valve port  124  may be located on a side of the ink cartridge  130  that is adjacent to another ink cartridge when installed in a printer  102 , for example. A connection between the tube  112  and the valve port  124  may be configured to accommodate a relatively small spacing between adjacent ink cartridges in the printer  102 . For example, the tube  112  may be connected to the valve port  124  using a low-profile, right-angle connector, to facilitate accessing the valve port  124  when the ink cartridge  130  is inserted in the printer  102  adjacent to other print cartridges. 
     The one-way valve  120  further comprises a lever  126  configured to move in response to an expansion and a contraction of the variable chamber  136  within the fluid reservoir  132 . In particular, as the variable chamber  136  expands, the lever  126  is moved away from an upper wall  134   a  and toward a lower wall  134   b  of the housing  134 , as illustrated by a double-headed arrow in  FIG. 2B . The variable chamber  136  may expand in response to a decrease in ink pressure within the ink reservoir  132 . The decrease in ink pressure may be produced as ink is consumed by the printhead  104 , for example. A motion of the lever  126  in cooperation with the expansion and contraction of the variable chamber  136  may be constrained or resisted by a spring  127  or a similar bias element that acts against the movement of the lever  126  away from the upper wall  134   a , for example. The lever may rest on and rotate about a fulcrum  129 , in some examples. 
     The one-way valve  120  further comprises a sealing member  128  located between the lever  126  and an opening  138  in the housing  134  that leads to the valve port  124 . The sealing member  128  is movable by or in response to movement of the lever  126 . Specifically, the sealing member  128  is movable between a first position (see for example  FIG. 2A ) in which the opening  138  is substantially sealed (e.g., blocked by the sealing member  128 ) and a second position (see for example  FIG. 2B ) in which the opening  138  is unsealed. When sealed, fluid is prevented from passing through the opening  138  while when unsealed, fluid may pass therethrough. In some examples, the sealing member  128  is further movable into the first position by a positive ink pressure within the fluid reservoir  132  at a printhead side of the one-way valve  120 . In particular, positive ink pressure moves the sealing member  128  into the first position and seals the opening  138 , irrespective of a position of the lever  126  (see for example  FIG. 2C ). Positive pressure may be provided by using a pump (e.g., an air pump) to expand the variable chamber  136  as illustrated in  FIG. 2C , for example. 
     In some examples, the sealing member  128  may comprise a substantially spherical ball (e.g., as illustrated in  FIGS. 2A-2C ). When the sealing member  128  is a spherical ball, the opening  138  may be a circular hole in the housing  134 , for example. In the first position, the ball-shaped sealing member  128  may be pressed into and seal against a circular rim of the opening  128 . In such examples, the housing  134  provides a structural member (e.g., the opening  138 ) of the one-way valve  120 . In these examples, the one-way valve  120  is integral the to the housing  134 . In other examples (not illustrated), the opening  138  (e.g., circular opening  138 ) may be provided by a structural member that is provided separately from the housing  134  and then affixed and sealed into the housing  134 . When affixed and sealed to the housing  134 , the separately provided structural member may be considered to be integral to the housing  134 , for example. 
     In other examples, a size and a shape of the opening  138  depends on a size and a shape of the sealing member  128 . In some examples, one or both of the sealing member  128  and a rim or other contact surface between the sealing member  128  and the opening  138  may comprise a hydrophilic material. The hydrophilic material may be a coating, for example. In other examples, one or both of the sealing member  128  and the rim or other contact surface may be formed from the hydrophilic material. The hydrophilic material may provide a lower bubble pressure at an interface between the sealing member  128  and opening  138 , for example. The bubble pressure may be lower than the interface without the hydrophilic material, for example. 
       FIG. 3  illustrates a perspective view of a continuous ink supply (CIS) apparatus  100 , according to another example of the principles described herein. In particular, the example illustrated in  FIG. 3  represents a ‘cartridge-less’ configuration. For example, the cartridge-less configuration may be used with a printer  102  (not illustrated in  FIG. 3 ) having printheads  104  supported by a printhead assembly  106 . The printhead assembly  106  may be configured to accept print cartridges (not illustrated). However, when the CIS apparatus  100  is used with the printer, the ink cartridges are removed and the fluid conduit  112 , illustrated as a plurality of tubes  112 , is connected directly to a liquid ink port of the printhead assembly  106 . The liquid ink port may be an input port of or associated with the printhead  104 , for example. In such an arrangement, the fluid reservoir described above may be substantially absent. For example, the fluid reservoir may be located in the removed and absent ink cartridge. As illustrated in  FIG. 3 , the one-way valve  120  is positioned at a terminus of the tube  112  adjacent to the liquid ink port (e.g., within a connector attached to the liquid ink port). Alternative example locations for the one-way valve  120  include within a connector  120   a  in a mid-section of the tube  112  and at a beginning  120   b  of the tube  112  adjacent to the off-axis ink supply  110 . 
     As liquid ink is consumed by the printhead  104 , liquid ink flows from the off-axis ink supply  110  through the fluid conduit  112 , through the one-way valve  120  and into the printhead  104  via the liquid ink port of the printhead assembly  106 . An arrow illustrated next to the fluid conduit  112  (e.g., tubes  112 ) indicates a forward or downstream flow direction of the liquid ink to resupply the printhead  104 . 
     As described above, the one-way valve  120  illustrated in  FIG. 3  prevents liquid ink from flowing in an upstream direction away from the printhead  104 . For example, if the off-axis ink supply  110  is placed below a level of the printhead  104 , the one-way valve  120  prevents gravity from causing the liquid ink to flow from the printhead  104 , upstream along the fluid conduit  112  and back into the off-axis ink supply  110 . Also as above, the minimum negative activation pressure of the one-way valve  120  substantially prevents drooling from the printhead  104 . For example, if the off-axis ink supply  110  is located above a level of the printhead  104 , gravity will not cause the liquid ink flowing through the one-way valve to increase an ink pressure at the printhead side of the one-way valve  120  to a point that may lead to drooling. 
     In some examples, the CIS apparatus  100  further comprises a memory circuit  140 . The memory circuit  140  is associated with the off-axis ink supply  110  and is configured by definition to provide information comprising one or both of an ink type and a remaining quantity of the liquid ink in the off-axis ink supply  110 , for example. For example, the information may be provided to and used by the printer to display the ink type and the remaining quantity of the liquid ink to a user of the printer  102 . In another example, the provided information may be used by the printer  102  to determine whether or not to conduct a printing operation and in some instances, which printhead  104  among a plurality of the printheads to employ given the ink type information. For example, the printer  102  may make a decision on conducting a print operation depending on whether or not enough ink remains to complete the print operation. In other examples, the memory circuit may contain information that indicates whether or not the CIS apparatus  100  is recognized and approved for use by the printer  102 . In yet other examples, the memory circuit  140  may provide a variety of additional information to the printer  102  to facilitate printing when employing the CIS apparatus  100 . 
     In some examples, the memory circuit  140  is implemented as an integrated circuit (IC) such as, but not limited to an application specific integrated circuit (ASIC). In some examples the memory circuit  140  resides or is physically located at the off-axis ink supply  110  (e.g., as indicated by dashed arrow  142 ). The memory circuit  140  may communicate to the printer via a communication channel, for example. In some examples, the communication channel comprises a plurality of wires (e.g., a wire harness) that connect between the printer  102  and the off-axis ink supply  110 . For example, the wires (not illustrated) may follow or be routed along the fluid conduit  112  and ultimately plug into one or more connectors at the printhead assembly  106 . In another example, the wires may simply connect into a connector somewhere else on the printer  102 . In another example, the communications channel may comprise a wireless network channel between the off-axis ink supply  110  and the printer  102 . For example, the communications channel may employ one or more of several wireless communication systems including, but not limited to, Bluetooth™ and IEEE 802.11 (e.g., WiFi) as a wireless communications channel. Bluetooth™ is a registered trademark of Bluetooth SIG, Inc., Bellevue, Wash., USA. IEEE 802.11 is a wireless communications standard promulgated by the Institute of Electrical and Electronic Engineers, Inc., Piscataway, N.J., USA. 
     In some examples, the memory circuit  140  (i.e., also referred to as an ‘memory chip’) one of augments and replaces information from a similar memory circuit or chip normally provided by an ink cartridge of the printhead assembly  106 . For example, as illustrated in  FIG. 3 , the ink cartridge of the printhead assembly  106  is removed and the memory circuit  140  replaces the information from the similar memory circuit of the ink cartridge. 
     In some examples, the CIS apparatus  100  further comprises an adapter  150  supported by the printhead assembly  106 . For example, the adapter  150  may be a single bar-shaped adapter  150 , as illustrated. In other examples, a plurality of adapters may be employed (not illustrated). The adapter  150  facilitates connecting the communications channel to the printer  102  in place of the ink cartridge memory circuit, according to some examples. In particular, the adapter  150  may connect to a connector of the printer  102  or the printhead assembly  106  that normally serves as a connection point for the ink cartridge memory circuit connector. In some examples, the adapter  150  is connected to wires (not illustrated) that provide the communication channel between the off-axis ink supply  110  and the printer  102 . In other examples, the adapter  150  may carry a circuit that provides the wireless network channel to the memory circuit  140  at the off-axis ink supply  110 . 
     In yet other examples (not illustrated), the memory circuit  140  may be located at and carried by the adapter  150  itself (e.g., as indicated by dashed arrow  144 ). In some of these examples, a communications channel to the off-axis ink supply  110  may not be required. In other of these examples, the communications channel may be used to relay only certain, supply-specific data (e.g., ink level measurements) from the off-axis ink supply to the memory circuit  140  on the adapter  150 , for example. Other functions of the memory circuit  140  may be performed at the adapter  150  without communication with the off-axis ink supply  110 , for example. 
     In another example (not illustrated), the connecting wires from the memory circuit  140  of the off-axis ink supply  110  may plug into an auxiliary port of the printer while the ink cartridge remains connected to or installed in the printhead assembly  106 . For example, when the fluid conduit  112  connects to the valve port  124  of the one-way valve  120  that is integral to the ink cartridge (illustrated in  FIGS. 2A-2C ), an auxiliary port may be provided to receive and connect with wires that provide the communications channel with the memory circuit  140  associated with the off-axis ink supply. The auxiliary port may be provided on the ink cartridge for example and the communication channel wires may connect to the printer  102  through the ink cartridge. As such, the information from the memory circuit  140  may augment instead of replace the information provided by the memory circuit of the ink cartridge, for example. 
       FIG. 4  illustrates a block diagram of a continuous ink supply (CIS) printer system  200 , according to an example of the principles described herein. The CIS printer system  200  comprises a printer  210 . The printer  210  has a printhead  212  to receive liquid ink. In some examples, the printer  210  and printhead  212  may be substantially similar to the printer  102  and printhead  104 , described above with respect to the CIS apparatus  100 . The liquid ink is provided to the printhead  212  by an off-axis ink supply  220  using a fluid conduit  222 , for example. The fluid conduit  222  may comprise one or more tubes, for example. In some examples, the off-axis ink supply  220  and associated fluid conduit  212  may be substantially similar to the off-axis ink supply  110  and the fluid conduit  112 , respectively, as described above with reference to the CIS apparatus  100 . According to some examples, the CIS printer system  200  may further comprise the off-axis ink supply  220 . 
     The CIS printer system  200  further comprises a one-way valve  230 . The one-way valve  230  is configured to control a flow of the liquid ink to the printhead  212  through the fluid conduit  222 . In some examples, the one-way valve  230  is substantially similar to the one-way valve  120  described above with respect to the CIS apparatus  100 . In particular, the one-way valve  230  has a minimum negative activation pressure that is selected to substantially minimize printhead drooling. In some examples, the minimum negative activation pressure is at least about minus 1.0 kPa at a printhead side of the one-way valve  230 . In some examples, the one-way valve  230  is located one of along the fluid conduit  222  (e.g., as illustrated) and integral to a housing wall of an ink cartridge (not illustrated) adjacent to the printhead  212 . 
     In some examples, the CIS printer system  200  further comprises a memory circuit  240  associated with the off-axis ink supply  220 , according to some examples. The memory circuit  240  is configured to provide information comprising characteristics of the liquid ink of the off-axis ink supply  220 , in some examples. For example, the characteristics may include, but are not limited to, one or more of an ink type, an ink color, and an amount of ink remaining in the off-axis supply  220 . In some examples, the provided information is transmitted to the printer  210  by way of a communication channel to one of augment and replace information from a similar memory circuit normally provided by an ink cartridge used with the printer  210 . The information may be employed to facilitate printer operation. For example, the information may be employed by the printer  210  to report status to a user of the printer  210 . In some examples, the memory circuit  240  and the communications channel are substantially similar to the memory circuit  140  and the communication channel described above with respect to the CIS apparatus  100 . 
     In some examples, the CIS printer system  200  further comprises a pump  250 . The pump  250  is configured to provide positive ink pressure between the printhead  212  and the one-way valve  230  in support of air management and printhead maintenance functions of the printer  210 . For example, the positive ink pressure may be employed to expel and thereby remove air that may become trapped or entrained in the printhead  212  and associated fluid pathways. In another example, the positive ink pressure may be used to prime the printhead  212  by pushing liquid ink into a firing chamber of the printhead  212 . The one-way valve  230  acts to substantially prevent liquid ink from flowing upstream, i.e., away from the printhead, for example to the off-axis ink supply  220  during instances where the pump  250  is providing the positive ink pressure, for example. 
       FIG. 5  illustrates a flow chart of a method  300  of continuous ink supply (CIS) used with a printer, according to an example of the principles described herein. Method  300  of CIS comprises providing  310  liquid ink in an off-axis ink supply. The liquid ink and the off-axis ink supply may be substantially similar to the liquid ink and off-axis ink supplies  110 ,  220  described above with respect to either of the CIS apparatus  100  and the CIS printer system  200 , according to some examples. 
     The method  300  of CIS further comprises sourcing  320  the liquid ink from the off-axis ink supply to a printhead of a printer. The liquid ink is sourced  320  through a fluid conduit using a one-way valve positioned along the fluid conduit between the off-axis ink supply and the printhead. Specifically, the liquid ink is sourced  230  by passing through and being acted upon by the one-way valve. In some examples, the one-way valve is substantially similar to the one-way valve  120 ,  230  described above with respect to either of the CIS apparatus  100  and the CIS printer system  200 . In particular, the one-way valve has a minimum negative activation pressure at a printhead side (i.e., downstream side) of the one-way valve. The minimum negative activation pressure substantially prevents drooling of the printhead, for example. The one-way valve further substantially prevents liquid ink from flowing upstream when a positive ink pressure exists at the downstream side of the one-way valve, for example. According to some examples, the minimum negative activation pressure of the one-way valve is less than or equal to about minus 1.0 kPa, or less than or equal to about minus 2.5 kPa, or within a range of about minus 1.0 kPa and about minus 3.75 kPa. 
     In some examples, the method  300  of CIS further comprises one of connecting  330   a  the fluid conduit to a pressure relief valve of an ink cartridge that supplies ink to the printhead and removing  330   b  the ink cartridge from the printhead and connecting the fluid conduit to the printhead. When the fluid conduit is connected  330   a  to the pressure relief valve of the ink cartridge, the one-way valve comprises the pressure relief valve. In other words, the pressure relief valve provides the operational characteristics of the one-way valve, for example. In the examples where the ink cartridge is removed  330   b , the one-way valve may be positioned along the fluid conduit, for example at a location where the fluid conduit is connected to the printhead or a location upstream of where the fluid conduit is connected to the printhead. The connection to the printhead may be by way of a liquid ink port of a printhead assembly that supports the printhead, for example. In yet another example (not illustrated in  FIG. 5 ), connecting the fluid conduit comprises inserting the fluid conduit having the one-way valve into the ink cartridge by means other than connecting to the pressure relief valve. 
     In some examples, the method  300  of CIS further comprises providing  340  information to the printer regarding characteristics of the off-axis liquid ink supply. The information is provided  340  to one of augment and replace information normally provided by an ink cartridge of the printer. In some examples, the information is provided  340  by a memory circuit associated with the off-axis ink supply. The memory circuit may be substantially equivalent to the memory circuit  140 ,  240  described above with respect to either of the CIS apparatus  100  and the CIS printer system  200 . In some examples, providing  340  information comprises transmitting the information to the printer by way of a communication channel. In various examples, the communications channel may be either a wired communications channel or a wireless communications channel (e.g., WiFi, Bluetooth™, etc.). 
     In some examples, the method  300  further comprises providing  350  positive ink pressure between the printhead and the one-way valve. The positive pressure may be provided using a pump for example. In some examples, the provided  350  positive pressure supports air management and printhead maintenance functions of the printer. Generally, providing  350  positive pressure may be performed only intermittently and may be performed either prior to (not illustrated) or following providing  340  information, for example. For example, air management may be an issue only when air becomes entrained or trapped in the printhead or in associated fluid pathways thereof. 
     An example continuous ink supply (CIS) apparatus includes an off-axis ink supply to source liquid ink to a printhead of a printer; and a one-way valve positioned along a fluid conduit between the off-axis ink supply and the printhead, the one-way valve having a minimum negative activation pressure at a printhead side of the one-way valve, the minimum negative activation pressure being at least enough to substantially preclude drooling from the printhead. In some examples, the minimum negative activation pressure is more negative than about minus 1.0 kilopascals (kPa). In some examples, the one-way valve is integral to a fluid reservoir of the printhead, and wherein the fluid conduit comprises a tube connected to a valve port of the one-way valve, the valve port being through a wall that houses the fluid reservoir. 
     In some examples, the one-way valve includes a lever to move in response to an expansion and a contraction of a variable chamber within the housing of the fluid reservoir; and a sealing member located between the lever and an opening in the housing, the sealing member being movable by movement of the lever between a first position in which the opening is sealed and a second position in which the opening is unsealed, the sealing member is further movable into the first position by a positive ink pressure within the fluid reservoir at a printhead side of the one-way valve. In some examples, the fluid conduit comprises a tube that is one of connected to a housing of an ink cartridge that houses a fluid reservoir of the printhead and connected to a printhead assembly that holds the printhead in an absence of the fluid reservoir, the one-way valve being positioned along the tube. In some examples, the CIS apparatus includes a memory circuit associated with the off-axis ink supply, the memory circuit to provide information comprising one or both of an ink type in the off-axis ink supply and remaining quantity of the liquid ink in the off-axis ink supply. 
     In some examples, an printer employs the example CIS apparatus, the printer comprising the printhead mounted in a movable printhead assembly to support and position the printhead, the printer further comprising a pump to provide positive ink pressure at the printhead side of the one-way valve, wherein the positive pressure supports air management and printhead maintenance functions of the printer. In some examples, the fluid conduit of the CIS apparatus connects to the printhead in the printhead assembly in place of an ink cartridge of the printer, the CIS apparatus further comprising a memory circuit associated with the off-axis ink supply, the memory circuit providing information regarding characteristics of the liquid ink in the off-axis ink supply, wherein the provided information replaces information from a memory circuit normally provided by the ink cartridge. 
     An example continuous ink supply (CIS) printer system includes a printer having a printhead to receive liquid ink from an off-axis ink source through a fluid conduit; and a one-way valve to control a flow of the liquid ink to the printhead through the fluid conduit, the one-way valve having a minimum negative activation pressure of less than or equal to about minus 1.0 kilopascals (kPa) at a printhead side of the one-way valve, wherein the one-way valve is located one of along the fluid conduit and integral to an ink reservoir in fluid communication with the printhead. In some examples, the CIS printer system includes the off-axis ink source; and a memory circuit associated with the off-axis ink source, the memory circuit providing information comprising characteristics of the liquid ink provided by the off-axis ink source, the provided information is transmitted to the printer by way of a communication channel to one of augment and replace information from a memory circuit of an ink cartridge used with the printer. 
     In some examples, the printer includes a movable printhead assembly to support and position the printhead; and a pump to provide positive ink pressure between the printhead and the one-way valve, the positive pressure to support air management and printhead maintenance functions of the printer. In some examples, the CIS printer system includes a memory circuit associated with the off-axis ink source, the memory circuit providing information comprising one or both of ink type and remaining quantity of the liquid ink in the off-axis ink source, wherein the provided information is employed by the printer to report status to a user of the printer; and an adapter to connect to the movable printhead assembly, the adapter carrying the memory circuit. In some examples, the one-way valve is built into an ink cartridge that provides the ink reservoir and wherein the fluid conduit comprises a tube connected to a valve port of the one-way valve that extends through a housing of the ink cartridge, the one-way valve includes a lever to move in response to an expansion and a contraction of a variable chamber within the housing of the ink cartridge; and a sealing member located between the lever and an opening in the housing that connects to the valve port, the sealing member being movable by movement of the lever between a first position in which the opening is sealed and a second position in which the opening is unsealed, the sealing member is further movable into the first position by a positive pressure ink pressure at a printhead side of the one-way valve. 
     An example method of continuous ink supply (CIS), the method includes providing liquid ink in an off-axis ink supply; sourcing the liquid ink from the off-axis ink supply to a printhead of a printer through a fluid conduit using a one-way valve positioned along the fluid conduit between the off-axis ink supply and the printhead, the one-way valve having a minimum negative activation pressure at a printhead side of the one-way valve that is at least enough to substantially preclude drooling from the printhead. In some examples, the method includes one or more of: providing information to the printer regarding characteristics of the liquid ink supply to one of augment and replace information normally provided by an ink cartridge of the printer, wherein providing information comprises transmitting the information to the printer by way of a communication channel; providing a positive ink pressure between the printhead and the one-way valve using a pump, the positive pressure supporting air management and printhead maintenance functions of the printer; and one of (a) connecting the fluid conduit to a pressure relief valve of an ink cartridge that supplies ink to the printhead, the one-way valve comprising the pressure relief valve, and (b) removing the ink cartridge from the movable printhead assembly and connecting the fluid conduit to the printhead. 
     An example continuous ink supply (CIS) apparatus includes an off-axis ink supply to source liquid ink to a printhead of a printer; and a one-way valve positioned along a fluid conduit between the off-axis ink supply and an input port of the printhead to control a flow of the liquid ink to the printhead through the fluid conduit, the one-way valve is directly connected to the input port of the printhead and provides a minimum negative activation pressure at a printhead side of the one-way valve, the minimum negative activation pressure being at least enough to substantially preclude drooling from the printhead. In some examples, the minimum negative activation pressure is more negative than about minus 1.0 kilopascals (kPa). In some examples, the one-way valve is integral to a fluid reservoir of the printhead, and wherein the fluid conduit comprises a tube connected to a valve port of the one-way valve, the valve port being through a wall that houses the fluid reservoir, and wherein the minimum negative activation pressure of the one-way valve is equal to or more negative than minus 3.0 kilopascals (kPa). 
     In some examples, the one-way valve includes a lever to move in response to an expansion and a contraction of a variable chamber within the housing of the fluid reservoir; and a sealing member located between the lever and an opening in the housing, the sealing member being movable by movement of the lever between a first position in which the opening is sealed and a second position in which the opening is unsealed, the sealing member is further movable into the first position by a positive ink pressure within the fluid reservoir at a printhead side of the one-way valve. In some examples, the fluid conduit comprises a tube that is one of connected to a housing of an ink cartridge that houses a fluid reservoir of the printhead and connected to a printhead assembly that holds the printhead in an absence of the fluid reservoir, the one-way valve being positioned along the tube. In some examples, the CIS apparatus includes a memory circuit associated with the off-axis ink supply, the memory circuit to provide information comprising one or both of an ink type in the off-axis ink supply and remaining quantity of the liquid ink in the off-axis ink supply. 
     An example printer that employs the example CIS apparatus where the printer includes the printhead mounted in a movable printhead assembly to support and position the printhead, the printer further comprising a pump to provide positive ink pressure at the printhead side of the one-way valve, wherein the positive pressure supports air management and printhead maintenance functions of the printer. In some examples, the fluid conduit of the CIS apparatus connects to the printhead in the printhead assembly in place of an ink cartridge of the printer, the CIS apparatus further comprising a memory circuit associated with the off-axis ink supply, the memory circuit providing information regarding characteristics of the liquid ink in the off-axis ink supply, the provided information replaces information from a memory circuit normally provided by the ink cartridge. 
     An example continuous ink supply (CIS) printer system includes a printer having a printhead to receive liquid ink from an off-axis ink source through a fluid conduit; and a one-way valve to control a flow of the liquid ink to the printhead through the fluid conduit, the one-way valve having a minimum negative activation pressure of less than or equal to about minus 1.0 kilopascals (kPa) at a printhead side of the one-way valve, the one-way valve is located along the fluid conduit that is directly connected to an input port of the printhead to replace an ink reservoir in fluid communication with the printhead. In some examples, the CIS printer system includes the off-axis ink source; and a memory circuit associated with the off-axis ink source, the memory circuit providing information comprising characteristics of the liquid ink provided by the off-axis ink source, the provided information is transmitted to the printer by way of a communication channel to one of augment and replace information from a memory circuit of an ink cartridge used with the printer. 
     In some examples, the printer includes a movable printhead assembly to support and position the printhead; and a pump to provide positive ink pressure between the printhead and the one-way valve, the positive pressure to support air management and printhead maintenance functions of the printer. 
     In some examples, the CIS printer system includes a memory circuit associated with the off-axis ink source, the memory circuit providing information comprising one or both of ink type and remaining quantity of the liquid ink in the off-axis ink source, wherein the provided information is employed by the printer to report status to a user of the printer; and an adapter to connect to the movable printhead assembly, the adapter carrying the memory circuit. 
     An example method of continuous ink supply (CIS), the method includes providing liquid ink in an off-axis ink supply; sourcing the liquid ink from the off-axis ink supply to a printhead of a movable printhead assembly of a printer through a fluid conduit using a one-way valve positioned along the fluid conduit between the off-axis ink supply and an input port of the printhead, the one-way valve is directly connected to the input port of the printhead and provides a minimum negative activation pressure at a printhead side of the one-way valve that is equal to or more negative than minus 1.0 kilopascals (kPa). In some examples, the method of CIS used with a printer includes one or more of: providing information to the printer regarding characteristics of the liquid ink supply to one of augment and replace information normally provided by an ink cartridge of the printer, wherein providing information comprises transmitting the information to the printer by way of a communication channel; providing a positive ink pressure between the printhead and the one-way valve using a pump, the positive pressure supporting air management and printhead maintenance functions of the printer; and one of (a) connecting the fluid conduit to a pressure relief valve of an ink cartridge that supplies ink to the printhead, the one-way valve comprising the pressure relief valve, and (b) removing the ink cartridge from the movable printhead assembly and connecting the fluid conduit to the printhead. 
     In some examples, the method of CIS of claim  14 , includes (a) connecting the fluid conduit to a pressure relief valve of an ink cartridge that supplies ink to the printhead, the one-way valve comprising the pressure relief valve; and (b) removing an ink cartridge from the movable printhead assembly of the printer and directly connecting the fluid conduit to the printhead. In some examples, the minimum negative activation pressure of the one-way valve is equal to or more negative than minus 3.0 kilopascals (kPa). In some examples, the minimum negative activation pressure of the one-way valve is equal to or more negative than minus 3.0 kilopascals (kPa). 
     An example continuous ink supply (CIS) apparatus, a CIS printer system and a method of CIS employ a one-way valve having a minimum negative activation pressure. The apparatus includes an off-axis ink supply to source liquid ink to a printhead of a printer. The one-way valve is positioned between the off-axis ink supply and the printhead. The minimum negative activation pressure at a printhead side of the one-way valve is at least enough to substantially precludes drooling from the printhead. 
     Thus, there have been described examples of a continuous ink supply (CIS) apparatus, a CIS printer system and a method of CIS that employ a one-way valve having a minimum negative activation pressure. It should be understood that the above-described examples are merely illustrative of some of the many specific examples that represent the principles described herein. Clearly, those skilled in the art can readily devise numerous other arrangements without departing from the scope as defined by the following claims.