Patent Publication Number: US-8991955-B2

Title: Inkjet printer having bypass line

Description:
This application is a continuation application of U.S. application Ser. No. 13/921,886 filed on Jun. 18, 2013, which is a continuation application of U.S. application Ser. No. 13/108,728 filed on May 16, 2011, now issued as U.S. Pat. No. 8,485,619, which is a non-provisional of U.S. Application No. 61/345,552 filed May 17, 2010. 
    
    
     FIELD OF INVENTION 
     The invention relates to fluid systems, apparatus, and methods for distributing fluid within a printing environment and to the configuration and arrangement of the components of such systems and apparatus. In particular, the fluid is a printing fluid, such as ink or ink fixing agent, as is distributed to and from a fluid ejection printhead, such as an inkjet printhead. More particularly, fluid distribution to an inkjet media width printhead is provided. 
     CO-PENDING APPLICATIONS 
     The following applications have been filed by the Applicant simultaneously with the present application: 
                                                    13107961   13107963   13107964   13107965   13107967   13107968       13107970   13107972   13107976   13107979   13107988   13107990       13107992   13107995   13107998   13108002   13108575   13108594       13108611   13108618   13108640   13108647   13108667   13108673       13108692   13108695   13108706   13108714   13108724   13108741       13108745   13108760   13108763   13108778   13108781   13108797       13108800   13108804   13108810   13108814   13108818   13108827       13108830   13108840   13108842   13108849   13108851   13108861       13108866   13108790   13108799   13108802   13108812   13108815       13108823   13108832   13108809   13108816   13108825   13108834       13108841   13108846   13108853   13108839   13108845   13108855       13108863   13108862   13108870   13107971   13107975   13107978       13107980   13107982   13107984   13107985   13107989   13107993       13107996   13107977   13107981   13107983   13107987   13107991       13107994   13107997   1310800    13108001                    
The disclosures of these co-pending applications are incorporated herein by reference. The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned.
 
     BACKGROUND OF INVENTION 
     Most inkjet printers have a scanning printhead that reciprocates across the printing width as the media incrementally advances along the media feed path. This allows a compact and low cost printer arrangement. However, scanning printhead based printing systems are mechanically complex and slow in light of accurate control of the scanning motion and time delays from the incremental stopping and starting of the media with each scan. Media width printheads resolve this issue by providing a stationary printhead spanning the media. 
     Larger printheads help to increase print speeds regardless of whether the printhead is a conventional scanning type or a media width printhead. However, larger printheads require a higher ink supply flow rate and the pressure drop in the ink from the ink inlet on the printhead to nozzles remote from the inlet can change the drop ejection characteristics. Large supply flow rates necessitate large ink tanks which exhibit a large pressure drop when the ink level in low compared to the hydrostatic pressure generated when the ink tank is full. Individual pressure regulators integrated into each printhead is unwieldy and expensive for multi-color printheads, particularly those carrying four or more inks. For example, a system with five inks would require 25 regulators. 
     Inkjet printers that can prime, deprime and purge air bubbles from the printhead offer the user distinct advantages. Removing a depleted printhead can cause inadvertent spillage of residual ink if it has not been de-primed before decoupling from the printer. 
     Air bubbles trapped in printheads are a perennial problem and a common cause of print artifacts. Actively and rapidly removing air bubbles from the printhead allows the user to rectify print problems without replacing the printhead. Active priming, de-priming and air purging typically use a lot of ink, particularly if the ink is drawn through the nozzles by vacuum or the like. This is exacerbated by large arrays of nozzles as more ink is lost as the number of nozzles increases. 
     Thus, there is a need to have a fluid distribution solution that is simpler, more reliable and more effective for media wide printing systems. 
     SUMMARY OF INVENTION 
     In one aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a first fluid container; 
     a fluid connector for connection to a fluid input of the printhead; and 
     a second fluid container connected between the first container and the connector for delivering fluid from the first container to the connector, 
     wherein the second container is located relative to the first container and the connector so that a fluid pressure difference between fluid contained within the second container and fluid at the connector is independent of the amount of fluid contained within the first container. 
     Optionally, a fluid pressure at fluid ejection nozzles of the printhead is a negative fluid pressure. 
     Optionally, during fluid ejection at the nozzles of the printhead fluid is drawn from the second container to the printhead via the fluid connector. 
     Optionally, as fluid is drawn from the second container the second container draws fluid from the first container so as to maintain a predetermined fluid level in the second container. 
     Optionally, the second container comprises a valve connected between an inlet of the second container and a fluid path interconnecting the first and second containers, the valve being operated to allow fluid flow from the first to the second container when a fluid level in the second container is less than the predetermined fluid level. 
     Optionally, the first container is at a position higher than the second container and the printhead. 
     Optionally, the second container is positioned lower than the printhead. 
     In another aspect, the invention provides a method of controlling fluid pressure at a printhead with a fluid distribution arrangement, the method comprising: 
     providing the fluid distribution arrangement with a first fluid container, a fluid connector for connection to a fluid input of the printhead, and a second fluid container connected between the first container and the connector for delivering fluid from the first container to the connector; and 
     locating the second container relative to the first container and the connector so that a fluid pressure difference between fluid contained within the second container and fluid at the connector is independent of the amount of fluid contained within the first container. 
     Optionally, a fluid pressure at fluid ejection nozzles of the printhead is a negative fluid pressure. 
     Optionally, during fluid ejection at the nozzles of the printhead fluid is drawn from the second container to the printhead via the fluid connector. 
     Optionally, as fluid is drawn from the second container the second container draws fluid from the first container so as to maintain a predetermined fluid level in the second container. 
     Optionally, the second container comprises a valve connected between an inlet of the second container and a fluid path interconnecting the first and second containers, the method comprising operating the valve to allow fluid flow from the first to the second container when a fluid level in the second container is less than the predetermined fluid level. 
     Optionally, the first container is at a position higher than the second container and the printhead. 
     Optionally, the second container is located so as to be lower than the printhead. 
     In another aspect, the invention provides a printing system comprising: 
     a first fluid container; 
     a printhead; and 
     a second fluid container connected between the first container and the printhead for delivering fluid from the first container to the printhead, 
     wherein the second container is located relative to the first container and the printhead so that a fluid pressure difference between fluid contained within the second container and fluid at the printhead is independent of the amount of fluid contained within the first container. 
     Optionally, a fluid pressure at fluid ejection nozzles of the printhead is a negative fluid pressure. 
     Optionally, during fluid ejection at the nozzles of the printhead fluid is drawn from the second container to the printhead. 
     Optionally, as fluid is drawn from the second container the second container draws fluid from the first container so as to maintain a predetermined fluid level in the second container. 
     Optionally, the second container comprises a valve connected between an inlet of the second container and a fluid path interconnecting the first and second containers, the valve being operated to allow fluid flow from the first to the second container when a fluid level in the second container is less than the predetermined fluid level. 
     Optionally, the first container is at a position higher than the second container and the printhead. 
     Optionally, the second container is positioned lower than the printhead. 
     In another aspect, the invention provides a method of distributing fluid pressure in a printing system, the method comprising: 
     providing the printing system with a first fluid container, a printhead having fluid ejection nozzles, and a second fluid container connected between the first container and the printhead for delivering fluid from the first container to the printhead; and 
     locating the first container above the printhead and the second container and locating the second container below the printhead such that negative fluid pressure is provided at the nozzles of the printhead and positive fluid pressure is provided at the second container. 
     Optionally, during fluid ejection at the nozzles of the printhead, fluid is drawn from the second container to the printhead. 
     Optionally, as fluid is drawn from the second container, the second container draws fluid from the first container so as to maintain a predetermined fluid level in the second container. 
     Optionally, the second container comprises a valve connected between an inlet of the second container and a fluid path interconnecting the first and second containers, the method comprising operating the valve operated to allow fluid flow from the first to the second container when a fluid level in the second container is less that the predetermined fluid level. 
     Optionally, the printhead is a media width printhead. 
     In another aspect, the invention provides a fluid distribution system comprising: 
     a first fluid container having a fluid outlet; 
     a second fluid container having a fluid inlet; 
     a fluid line interconnecting the outlet of the first container and the inlet of the second container; 
     an inverted umbrella valve between the fluid line and the inlet, said valve arranged to allow fluid flow from the first container to the second container via the fluid line; and 
     a restrictor for restricting said allowed fluid flow through the fluid line. 
     Optionally, the inlet is defined on a body of the second container, the umbrella valve comprises an umbrella-shaped disc mounted within the inlet so that the umbrella-shape is inverted and a connector connected to the fluid line and enclosing the disc relative to the body. 
     Optionally, the connector is sealingly mounted on the body. 
     Optionally, the second container comprises a valve actuator within the inlet, the disc being mounted on the valve actuator. 
     Optionally, the valve actuator causes the disc to move between positions where a periphery of the disc seals against the body and the disc is spaced from the body. 
     Optionally, the restrictor is mounted on the fluid line in proximity of the umbrella valve. 
     Optionally, the restrictor comprises a resilient member mounted on an exterior of the fluid line, the resilient member being configured to compress the fluid line. 
     Optionally, the connector incorporates the restrictor as an obstruction to fluid flow into the connector from the fluid line. 
     In another aspect, the invention provides an ink container for an inkjet printhead, the ink container comprising: 
     a body for containing ink to a predetermined capacity; 
     an ink inlet on the body; 
     a float member within the body for floating on ink contained in the body; 
     a valve at the inlet; and 
     a valve actuator for selectively opening and closing the valve, 
     wherein the float member is pivotally attached to the valve actuator so that the float member causes the valve actuator to close the valve when the body contains ink at said predetermined capacity and to open the valve otherwise. 
     Optionally, the valve comprises an umbrella-shaped disc mounted within the inlet so that the umbrella-shape is inverted and a connector connected to a fluid line and enclosing the disc relative to the body. 
     Optionally, the connector is sealingly mounted on the body. 
     Optionally, the disc is mounted on the valve actuator. 
     Optionally, the valve actuator causes the disc to move between positions where the disc is spaced from the body and a periphery of the disc seals against the body in order to open and close the valve. 
     Optionally, the float member is attached to the valve actuator with a pin about which the float member pivots. 
     Optionally, the container further comprises an air vent in the body, the float member being located between the air vent and the contained ink. 
     Optionally, the air vent comprises a filter. 
     Optionally, the filter comprises hydrophobic material. 
     Optionally, the hydrophobic material is expanded polytetrafluoroethylene. 
     Optionally, the air vent comprises a tortuous liquid path from the interior of the body to the exterior of the body. 
     Optionally, the tortuous liquid path is a serpentine path. 
     In another aspect, the invention provides a system for distributing fluid to a printhead, the system comprising: 
     a printhead; 
     a first fluid container; and 
     a second fluid container for distributing fluid from the first container to the printhead, the second container having a body for containing the fluid to a predetermined capacity, an inlet connected to the first container, a valve at the inlet, and an outlet connected to the printhead, 
     wherein the valve is operated so that the valve is closed when the body contains fluid at said predetermined capacity and is open when fluid is distributed to the printhead via the outlet. 
     Optionally, the second container further has a float member within the body for floating on the fluid contained in the body which is pivotally attached to the valve so that the float member causes the valve to close when the body contains fluid at said predetermined capacity and to open otherwise. 
     Optionally, the valve comprises: 
     an umbrella-shaped disc mounted within the inlet so that the umbrella-shape is inverted; and 
     a connector which is connected to a fluid line connected to the first container and encloses the disc relative to the body. 
     Optionally, the connector is sealingly mounted on the body. 
     Optionally, the second container further has a valve actuator for selectively opening and closing valve via which the valve is pivotally attached to the float member, and the disc is mounted on the valve actuator. 
     Optionally, the valve actuator causes the disc to move between positions where the disc is spaced from the body and a periphery of the disc seals against the body in order to open and close the valve. 
     Optionally, the float member is attached to the valve actuator with a pin about which the float member pivots. 
     Optionally, the container further comprises an air vent in the body, the float being located between the air vent and the contained ink. 
     In another aspect, the invention provides an ink distribution system for a printhead, the system comprising: 
     a first ink container having an ink outlet; 
     a second ink container having an ink inlet; 
     an ink line interconnecting the outlet of the first container and the inlet of the second container; and 
     a gas vent on the ink line. 
     Optionally, the ink inlet of the second container has a valve, ink from the first container being drawn into the second container when the valve is open. 
     Optionally, the gas vent is disposed on the ink line so that a first portion of the ink line is between the first container and the gas vent, and a second portion of the ink line is between the gas vent and the second container. 
     Optionally, the gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the ink line. 
     Optionally, the filter comprises expanded polytetrafluoroethylene. 
     In another aspect, the invention provides a fluid container comprising: 
     a body for containing fluid; 
     a fluid outlet on a first wall of the body at which said contained fluid exits the body; and 
     a filter arranged within the body adjoining the first wall so that said contained fluid passes through the filter before exiting the outlet, 
     wherein the filter is inclined relative to the first wall so that filtered fluid is contained in the body between the filter and the outlet. 
     Optionally, a second wall of the body beneath the filter adjoins the first wall and is substantially parallel to the filter. 
     Optionally, the outlet is higher than a lowest point of the second wall. 
     Optionally, the filter comprises a polyester mesh. 
     Optionally, the polyester mesh has a pore size of one micron. 
     Optionally, an angle between the filter and the first wall is about 10 degrees. 
     In another aspect, the invention provides a system for distributing filtered ink to an inkjet printhead, the system comprising: 
     an ink container having a body for containing the ink, am ink outlet on a first wall of the body at which said contained ink exits the body, and a filter arranged within the body adjoining the first wall so that said contained ink passes through the filter before exiting the outlet; 
     an inkjet printhead having an ink inlet; and 
     an ink line connecting the outlet of the container to the inlet of the printhead, 
     wherein the filter is inclined relative to the first wall so that filtered ink is contained in the body between the filter and the outlet which is distributed to the printhead. 
     Optionally, a second wall of the body of the container beneath the filter adjoins the first wall and is substantially parallel to the filter. 
     Optionally, the outlet of the container is higher than a lowest point of the second wall. 
     Optionally, the filter of the container comprises a polyester mesh. 
     Optionally, the polyester mesh has a pore size of one micron. 
     Optionally, an angle between the filter and the first wall is about 10 degrees. 
     In another aspect, the invention provides a fluid container comprising: 
     a body for containing fluid; 
     a fluid outlet on a first wall of the body at which said contained fluid exits the body; and 
     a filter arranged within the body substantially parallel to, and spaced from, a second wall of the body, 
     wherein the second wall adjoins the first wall with the outlet in the space between the filter and the second wall so that said contained fluid passes through the filter before exiting the outlet, and 
     the second wall declines from the adjoined first wall when the container is disposed with the filter above the second wall. 
     Optionally, the container further comprises a fluid inlet on a third wall of the body at which fluid enters the body to be contained therein, the inlet being disposed higher than the filter when the container is disposed with the filter above the second wall. 
     Optionally, the second and third walls are interconnected by a fourth wall of the body, the second, third and fourth walls defining a floor of the body when the container is disposed with the filter above the second wall. 
     Optionally, the second wall inclines from the adjoined fourth wall to the adjoined first wall when the container is disposed with the filter above the second wall. 
     Optionally, the inlet is disposed in the third wall so that the entering fluid is caused to flow along the third wall, then pass through the filter, and then flow along the second wall up the incline from the third wall to the first wall when the container is disposed with the filter above the second wall. 
     In another aspect, the invention provides a printing system comprising: 
     a fluid source; 
     a first fluid path connecting the fluid source to a first fluid port of the printhead; 
     a second fluid path connecting the fluid source to a second fluid port of the printhead, 
     wherein the first and second paths are configured so that fluid from the fluid source flows between the first and second paths via the printhead. 
     Optionally, the system further comprises a valve connecting the first path to the printhead. 
     Optionally, the fluid source has a first source port connected to the first path and a second source port connected to the second path. 
     Optionally, the first and second paths, printhead and fluid source form a closed fluid flow loop in which fluid flows to and from the fluid source in either direction of the loop. 
     Optionally, the system further comprises a bi-directional pump on the first or second paths for driving said fluid flows to and from the fluid source in either direction of the loop. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a first fluid path connected to a first fluid port of the printhead; 
     a second fluid path connected to a second fluid port of the printhead; 
     a third fluid path interconnecting the first and second paths, 
     wherein the first, second and third paths are configured so that fluid flows between the first and second paths via the printhead and via the third fluid path. 
     Optionally, the system further comprises a multi-path valve connecting the first path to the printhead and the third path. 
     Optionally, the multi-path valve is operable to selectively provide fluid flow through the printhead and the third path. 
     Optionally, the system further comprises a fluid source having a first source port connected to the first path and a second source port connected to the second path. 
     Optionally, the first, second and third paths, printhead and fluid source form a closed fluid flow loop in which fluid flows to and from the fluid source in either direction of the loop. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead having a first fluid port at one longitudinal end of the media width and a second fluid port at the other longitudinal end of the media width; 
     a first fluid path connected to the first fluid port of the printhead; 
     a second fluid path connected to the second fluid port of the printhead; 
     a third fluid path interconnecting the first and second paths, 
     wherein the first, second and third paths are configured so that fluid flows between the first and second paths via the printhead and via the third fluid path. 
     Optionally, the system further comprises a multi-path valve connecting the first path to the printhead and the third path. 
     Optionally, the multi-path valve is operable to selectively provide fluid flow through the printhead and the third path. 
     Optionally, the system further comprises a fluid source having a first source port connected to the first path and a second source port connected to the second path. 
     Optionally, the first, second and third paths, printhead and fluid source form a closed fluid flow loop in which fluid flows to and from the fluid source in either direction of the loop. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a fluid container; 
     a first fluid path interconnecting the container and a first fluid port of the printhead; 
     a second fluid path interconnecting the container and a second fluid port of the printhead; a third fluid path interconnecting the first and second paths, 
     wherein the first, second and third paths are configured so that fluid from the container flows between the first and second paths via the printhead and via the third fluid path. 
     Optionally, the system further comprises a multi-path valve connecting the first path to the printhead and the third path. 
     Optionally, the multi-path valve is operable to selectively provide fluid flow through the printhead and the third path. 
     In another aspect, the invention provides a printing system comprising: 
     a fluid container; 
     a media width printhead having a first fluid port at one longitudinal end of the media width and a second fluid port at the other longitudinal end of the media width; 
     a first fluid path interconnecting the container and the first fluid port of the printhead; 
     a second fluid path interconnecting the container and the second fluid port of the printhead; 
     a third fluid path interconnecting the first and second paths, 
     wherein the first, second and third paths are configured so that fluid from the container flows between the first and second paths via the printhead and via the third fluid path. 
     Optionally, the system further comprises a multi-path valve connecting the first path to the printhead and the third path. 
     Optionally, the multi-path valve is operable to selectively provide fluid flow through the printhead and the third path. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a bypass fluid path bypassing the printhead on said closed loop; and 
     a multi-path valve on said closed loop for selectively allowing fluid flow along said closed loop via the printhead and the bypass path. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the bypass path bridges across the printhead between the first and second paths. 
     Optionally, the valve is located on the first path. 
     Optionally, said closed loop and bypass path comprise fluid hoses. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a bypass fluid path bypassing the printhead on said closed loop; and 
     a multi-path valve on said closed loop for selectively allowing fluid flow along said closed loop via the printhead and the bypass path. 
     Optionally, said closed loop comprises a first path between the container and one longitudinal end of the media width of the printhead and a second path between the container and the other longitudinal end of the media width of the printhead. 
     Optionally, the bypass path bridges across the printhead between the first and second paths. 
     Optionally, the valve is located on the first path. 
     Optionally, said closed loop and bypass path comprise fluid hoses. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of closed fluid flow loops; 
     a plurality of bypass fluid paths bypassing the printhead, each bypass path being associated with a respective one of the closed loops; and 
     a multi-path, multi-channel valve for selectively allowing fluid flow along each of the closed loops via the printhead and the respective bypass paths. 
     Optionally, the printhead is an elongate printhead spanning a media width, each of the closed loops comprising a first path between the respective container and a first longitudinal end of the printhead and a second path between the respective container and a second longitudinal end of the printhead. 
     Optionally, each bypass path bridges across the printhead between the respective first and second paths. 
     Optionally, the valve is located on the first path of each closed loop. 
     Optionally, each closed loop and bypass path comprises fluid hoses. 
     Optionally, five fluid flow loops are provided between five fluid containers and the printhead. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of closed fluid flow loops; 
     a plurality of bypass fluid paths bypassing the printhead, each bypass path being associated with a respective one of the closed loops; and 
     a multi-path, multi-channel valve for selectively allowing fluid flow along each of the closed loops via the printhead and the respective bypass paths. 
     Optionally, each of the closed loops comprises a first path between the respective container and a first longitudinal end of the printhead and a second path between the respective container and a second longitudinal end of the printhead. 
     Optionally, each bypass path bridges across the printhead between the respective first and second paths. 
     Optionally, the valve is located on the first path of each closed loop. 
     Optionally, each closed loop and bypass path comprises fluid hoses. 
     Optionally, five fluid flow loops are provided between five fluid containers and the printhead. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a gas vent on said closed loop; and 
     a multi-path valve on said closed loop for selectively allowing venting of gas in said closed loop via the gas vent. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the gas vent and the valve are located on the first path. 
     Optionally, the gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the first path. 
     Optionally, the filter comprises expanded polytetrafluoroethylene 
     Optionally, said closed loop and vent line comprise fluid hoses. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a gas vent on said closed loop; and 
     a multi-path valve on said closed loop for selectively allowing venting of gas in said closed loop via the gas vent. 
     Optionally, said closed loop comprises a first path between the container and one longitudinal end of the media width of the printhead and a second path between the container and the other longitudinal end of the media width of the printhead. 
     Optionally, the gas vent and the valve are located on the first path. 
     Optionally, the gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the first path. 
     Optionally, the filter comprises expanded polytetrafluoroethylene 
     Optionally, said closed loop and vent line comprise fluid hoses. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of closed fluid flow loops; 
     a plurality of gas vents, each gas vent being associated with a respective one of the closed loops; and 
     a multi-path, multi-channel valve for selectively allowing venting of gas in each of the closed loops via the gas vents. 
     Optionally, the printhead is an elongate printhead spanning a media width, each closed loop comprising a first path between the respective container and a first longitudinal end of the printhead and a second path between the respective container and a second longitudinal end of the printhead. 
     Optionally, the gas vents are located on the respective first paths. 
     Optionally, the valve is located on the first path. 
     Optionally, each gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the respective first path. 
     Optionally, the filters comprise expanded polytetrafluoroethylene 
     Optionally, each closed loop and vent line comprise fluid hoses. 
     Optionally, five fluid flow loops are provided between five fluid containers and the printhead. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of closed fluid flow loops; 
     a plurality of gas vents, each gas vent being associated with a respective one of the closed loops; and 
     a multi-path, multi-channel valve for selectively allowing venting of gas in each of the closed loops via the gas vents. 
     Optionally, each closed loop comprises a first path between the respective container and a first longitudinal end of the printhead and a second path between the respective container and a second longitudinal end of the printhead. 
     Optionally, the gas vents are located on the respective first paths. 
     Optionally, the valve is located on the first path. 
     Optionally, each gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the respective first path. 
     Optionally, the filters comprise expanded polytetrafluoroethylene 
     Optionally, each closed loop and vent line comprise fluid hoses. 
     Optionally, five fluid flow loops are provided between five fluid containers and the printhead. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a bypass fluid path bypassing the printhead on said closed loop; 
     a gas vent on said closed loop; and 
     a four-way valve on said closed loop for selectively allowing fluid flow along said closed loop via the printhead and the bypass path and venting of gas in said closed loop via the gas vent. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the bypass path bridges across the printhead between the first and second paths. 
     Optionally, the gas vent and the valve are located on the first path. 
     Optionally, the gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the first path. 
     Optionally, the filter comprises expanded polytetrafluoroethylene 
     Optionally, said closed loop, bypass path and vent line comprise fluid hoses. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a bypass fluid path bypassing the printhead on said closed loop; 
     a gas vent on said closed loop; and 
     a four-way valve on said closed loop for selectively allowing fluid flow along said closed loop via the printhead and the bypass path and venting of gas in said closed loop via the gas vent. 
     Optionally, said closed loop comprises a first path between the container and one longitudinal end of the media width of the printhead and a second path between the container and the other longitudinal end of the media width of the printhead. 
     Optionally, the bypass path bridges across the printhead between the first and second paths. 
     Optionally, the gas vent and the valve are located on the first path. 
     Optionally, the gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the first path. 
     Optionally, the filter comprises expanded polytetrafluoroethylene 
     Optionally, said closed loop, bypass path and vent line comprise fluid hoses. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of closed fluid flow loops; 
     a plurality of bypass fluid paths bypassing the printhead, each bypass path being associated with a respective one of the closed loops; and 
     a plurality of gas vents, each gas vent being associated with a respective one of the closed loops; and 
     a multi-channel four-way valve for selectively allowing fluid flow along each closed loop via the printhead and the bypass paths and venting of gas in each closed loop via the gas vents. 
     Optionally, the printhead is an elongate printhead spanning a media width, each closed loop comprising a first path between the respective container and a first longitudinal end of the printhead and a second path between the respective container and a second longitudinal end of the printhead. 
     Optionally, each bypass path bridges across the printhead between the respective first and second paths. 
     Optionally, the gas vents are located on the respective first paths. 
     Optionally, the valve is located on the first path. 
     Optionally, each gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the respective first path. 
     Optionally, the filters comprise expanded polytetrafluoroethylene 
     Optionally, each closed loop, bypass path and vent line comprise fluid hoses. 
     Optionally, five fluid flow loops are provided between five fluid containers and the printhead. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of closed fluid flow loops; 
     a plurality of bypass fluid paths bypassing the printhead, each bypass path being associated with a respective one of the closed loops; and 
     a plurality of gas vents, each gas vent being associated with a respective one of the closed loops; and 
     a multi-channel four-way valve for selectively allowing fluid flow along each closed loop via the printhead and the bypass paths and venting of gas in each closed loop via the gas vents. 
     Optionally, the printhead is an elongate printhead spanning a media width, each closed loop comprising a first path between the respective container and a first longitudinal end of the printhead and a second path between the respective container and a second longitudinal end of the printhead. 
     Optionally, each bypass path bridges across the printhead between the respective first and second paths. 
     Optionally, the gas vents are located on the respective first paths. 
     Optionally, the valve is located on the first path. 
     Optionally, each gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the respective first path. 
     Optionally, the filters comprise expanded polytetrafluoroethylene 
     Optionally, each closed loop, bypass path and vent line comprise fluid hoses. 
     Optionally, five fluid flow loops are provided between five fluid containers and the printhead. 
     In another aspect, the invention provides a fluid distribution system for a printhead, the system comprising: 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop, the fluid being drawn from the container in a first direction around the closed loop by the printhead during printing; and 
     a pump on said closed loop, the pump being operational to draw fluid from the container in an opposite, second direction around said closed loop. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the pump is located on the second path. 
     Optionally, the second path connects with the container at a point higher than a point at which the first path connects with the container. 
     Optionally, the pump is a peristaltic pump. 
     In another aspect, the invention provides a method of priming a media width printhead, the method comprising: 
     controlling operation of the printhead, with a controller of a printing system comprising the printhead, to draw fluid in a first direction around a closed fluid flow loop from a fluid container to the printhead; and 
     controlling operation of a pump on said closed loop, with the controller, to draw fluid from the container in an opposite, second direction around said closed loop. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the pump is located on the second path. 
     Optionally, the second path connects with the container at a point higher than a point at which the first path connects with the container. 
     Optionally, the pump is a peristaltic pump. 
     In another aspect, the invention provides a system for priming and de-priming a printhead, the system comprising: 
     a fluid container fluidically interconnected with the printhead via a closed fluid flow loop; 
     a gas inlet on said closed loop; and 
     a valve on said closed loop for selectively allowing gas to enter said closed loop via the gas inlet; and 
     a pump on said closed loop, 
     wherein the pump is operational to draw fluid from the container in a first direction around said closed loop to prime the printhead with fluid from the container, and 
     the vent is operational to cause fluid in said closed loop and the printhead to de-prime to the container in a second direction around said closed loop. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the pump is located on the second path. 
     Optionally, the second path connects with the container at a point higher than a point at which the first path connects with the container. 
     Optionally, the gas inlet and the valve are located on the first path. 
     Optionally, the gas inlet comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the first path. 
     Optionally, the filter comprises expanded polytetrafluoroethylene. 
     Optionally, said closed loop and vent line comprise fluid hoses. 
     Optionally, the pump is a peristaltic pump. 
     In another aspect, the invention provides a method of priming and de-priming a media width printhead, the method comprising: 
     controlling operation, with a controller of a printing system comprising the printhead, of a pump on a closed fluid flow loop interconnecting a fluid container to the printhead to draw fluid from the container in a first direction around said closed loop to prime the printhead with fluid from the container; and 
     controlling operation of a valve on said closed loop, with the controller, to allow gas to enter said closed loop via a gas inlet to cause fluid in said closed loop and the printhead to de-prime to the container in a second direction around said closed loop. 
     Optionally, the printhead is an elongate printhead spanning a media width, said closed loop comprising a first path between the container and a first longitudinal end of the printhead and a second path between the container and a second longitudinal end of the printhead. 
     Optionally, the pump is located on the second path. 
     Optionally, the second path connects with the container at a point higher than a point at which the first path connects with the container. 
     Optionally, the gas inlet and the valve are located on the first path. 
     Optionally, the gas inlet comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the first path. 
     Optionally, the pump is a peristaltic pump. 
     In another aspect, the invention provides a fluid distribution system for a media width printhead, the system comprising: 
     a fluid container having a gas vent; 
     a first fluid path interconnecting the container and a first fluid port at one longitudinal end of the media width of the printhead; 
     a second fluid path interconnecting the container and a second fluid port at the other longitudinal end of the media width of the printhead; 
     a third fluid path interconnecting the first and second paths, 
     a pump on the second path, the pump being operational to draw fluid from the container through the first and second paths via the printhead and via the third fluid path to flush gas in said paths to the container for venting via the gas vent. 
     Optionally, the system further comprises a multi-path valve connecting the first path to the printhead and the third path. 
     Optionally, the multi-path valve is operable to selectively provide fluid flow through the printhead and the third path. 
     Optionally, the second path connects with the container at a point higher than a point at which the first path connects with the container. 
     Optionally, the pump is a peristaltic pump. 
     In another aspect, the invention provides a multi-path valve for a media width inkjet printhead, the printhead being connected to an ink source via a closed ink flow loop, the valve comprising: 
     a body; 
     a first port on the body for connection to the ink source; 
     a second port on the body for connection to the printhead; 
     a third port on the body for connection to a bypass ink path which bypasses the printhead on said closed loop; 
     a fourth port on the body for connection to a gas vent on said closed loop; 
     a chamber within the body via which the first, second, third and fourth ports are able to be interconnected; and 
     a selection device for selectively establishing interconnection between the first, second, third and fourth ports to allow ink flow therebetween. 
     Optionally: said closed loop comprises a first path between the ink source and one longitudinal end of the media width of the printhead and a second path between the ink source and the other longitudinal end of the media width of the printhead; the bypass path bridges across the printhead between the first and second paths; and the valve is configured to be located on the first path. 
     Optionally, said closed loop and bypass path comprise fluid hoses, the first, second, third and fourth ports being configured to connect with the fluid hoses. 
     Optionally, the selection device comprises a driven shaft and selection members on the shaft, the selection members being rotated by driven rotation of the shaft so as to selectively establishing the interconnections between the first, second, third and fourth ports. 
     Optionally, the selection members define seals for respective ones of the first, second, third and fourth ports. 
     In another aspect, the invention provides a multi-channel valve for a media width inkjet printhead, the printhead being connected to a plurality of ink supplies via a plurality of ink flow channels, the valve comprising: 
     a body; 
     a plurality of sealed chambers within the body; 
     a plurality of groups of ports on the body, each port group being associated with a respective one of the chambers and having individual ports for respective connection to the printhead and a respective one of the ink supplies; and 
     a selection device for selectively establishing interconnection between the ports of each port group to allow ink flow therebetween for each of the channels. 
     Optionally, the selection device comprises a driven shaft and selection members on the shaft, the selection members being rotated by driven rotation of the shaft so as to selectively establishing the interconnections between the ports. 
     Optionally, the selection members define seals for respective ones of the ports. 
     Optionally, five ink channels are provided between five ink supplies and the printhead, the valve comprising five of the sealed chambers and five associated port groups. 
     In another aspect, the invention provides a diaphragm valve for distributing ink from an ink source to a media width inkjet printhead, the valve comprising: 
     a body; 
     a plurality of ports on the body for connection to the ink source and printhead; 
     a chamber within the body via which the ports are able to be interconnected; 
     a diaphragm pad having seals for sealing respective ones of the ports; and 
     a selection device for manipulating the diaphragm pad to selectively seal and un-seal the ports to establish interconnection between the ports thereby allowing ink flow therebetween. 
     Optionally, the selection device comprises a driven shaft and selection members on the shaft, the selection members being rotated by driven rotation of the shaft so as to manipulate the diaphragm pad. 
     Optionally, the selection members comprise eccentric cams mounted on the shaft. 
     Optionally, the selection members comprises cantilevered fingers mounted within the body so that each finger is aligned with a respective one of the eccentric cams. 
     Optionally, the diaphragm pad is arranged so that rotation of the eccentric cams selectively presses the fingers into and out of contact with the diaphragm pad thereby discretely deforming the diaphragm pad to seal and un-seal the ports. 
     Optionally, the valve further comprises a sealing film sealingly located between the diaphragm pad and the fingers. 
     Optionally, the plurality of ports comprises a first port for connection to the ink source, a second port for connection to the printhead, a third port for connection to a bypass ink path which bypasses the printhead on a closed ink flow loop interconnecting the printhead and ink source, and a fourth port for connection to a gas vent on said closed loop. 
     Optionally: said closed loop comprises a first path between the ink source and one longitudinal end of the media width of the printhead and a second path between the ink source and the other longitudinal end of the media width of the printhead; the bypass path bridges across the printhead between the first and second paths; and the valve is configured to be located on the first path. 
     Optionally, said closed loop and bypass path comprise fluid hoses, the first, second, third and fourth ports being configured to connect with the fluid hoses. 
     In another aspect, the invention provides a multi-channel diaphragm valve for distributing ink from a plurality of ink supplies to a media width inkjet printhead via a plurality of ink flow channels, the valve comprising: 
     a body; 
     a plurality of sealed chambers within the body; 
     a plurality of groups of ports on the body, each port group being associated with a respective one of the chambers and having individual ports for respective connection to the printhead and a respective one of the ink supplies; and 
     a plurality of diaphragm pads having seals for sealing respective ones of the ports; and 
     a selection device for manipulating the diaphragm pad to selectively seal and un-seal the ports to establish interconnection between the ports of each port group to allow ink flow therebetween for each of the channels. 
     Optionally, five ink channels are provided between five ink supplies and the printhead, the valve comprising five of the sealed chambers and five associated port groups. 
     Optionally, the selection device comprises a driven shaft and selection members on the shaft, the selection members being rotated by driven rotation of the shaft so as to manipulate the diaphragm pads. 
     Optionally, the selection members comprise eccentric cams mounted on the shaft. 
     Optionally, the selection members comprises cantilevered fingers mounted within the body so that each finger is aligned with a respective one of the eccentric cams. 
     Optionally, the diaphragm pads are arranged so that rotation of the eccentric cams selectively presses the fingers into and out of contact with the diaphragm pads thereby discretely deforming the diaphragm pads to seal and un-seal the ports. 
     Optionally, the valve further comprises sealing films sealingly located between the respective diaphragm pads and fingers. 
     Optionally, a plurality of groups of the eccentric cams are arranged so that each cam group corresponds to a port group, the cams of each group being arranged so that eccentric features of the cams are offset relative to each other cam in that group and are aligned to a corresponding cam in each other cam group. 
     Optionally, each port group comprises a first port for connection to the ink source, a second port for connection to the printhead, a third port for connection to a bypass ink path which bypasses the printhead on the respective ink flow channel, and a fourth port for connection to a gas vent on said ink flow channel 
     Optionally: each ink flow channel comprises a first path between the ink source and one longitudinal end of the media width of the printhead and a second path between the ink source and the other longitudinal end of the media width of the printhead; each bypass path bridges across the printhead between the first and second paths of the respective ink flow channel; and the valve is configured to be located on the first path of each ink flow channel 
     Optionally, each ink flow channel and bypass path comprise fluid hoses, the first, second, third and fourth ports being configured to connect with the fluid hoses. 
     In another aspect, the invention provides a rotary valve for distributing ink from an ink source to a media width inkjet printhead, the valve comprising: 
     a body; 
     a shaft rotatably mounted to the body; 
     a channel cylinder arranged on the shaft to be rotatable therewith, the channel cylinder having a channel defined along its circumference; 
     a port cylinder fixed to the body relative to the shaft so as to concentrically and sealingly enclose the channel cylinder, the port cylinder having a plurality of ports defined therethrough along its circumference for respective connection to the printhead and ink source, each port being aligned with a portion of the channel; and 
     a selection device for selectively rotating the shaft to establish interconnection between the ports and the channel thereby allowing ink flow between the ports via the channel 
     Optionally, the channel has a serpentine form. 
     Optionally, the ports are aligned relative to the channel of the channel cylinder so that alignment of the ports with a straight portion of the serpentine form of the channel provides interconnection between those ports. 
     Optionally, the plurality of ports comprises a first port for connection to the ink source, a second port for connection to the printhead, a third port for connection to a bypass ink path which bypasses the printhead on a closed ink flow loop interconnecting the printhead and ink source, and a fourth port for connection to a gas vent on said closed loop. 
     Optionally: said closed loop comprises a first path between the ink source and one longitudinal end of the media width of the printhead and a second path between the ink source and the other longitudinal end of the media width of the printhead; the bypass path bridges across the printhead between the first and second paths; and the valve is configured to be located on the first path. 
     Optionally, said closed loop and bypass path comprise fluid hoses, the first, second, third and fourth ports being configured to connect with the fluid hoses. 
     In another aspect, the invention provides a multi-channel rotary valve for distributing ink from a plurality of ink supplies to a media width inkjet printhead via a plurality of ink flow channels, the valve comprising: 
     a body; 
     a shaft rotatably mounted to the body; 
     a cylindrical channel arrangement mounted on the shaft to be rotatable therewith, the channel arrangement having a plurality of individual channels defined along its circumference; 
     a cylindrical port arrangement fixed to the body relative to the shaft so as to concentrically and sealingly enclose the channel arrangement, the port arrangement having a plurality of groups of ports defined therethrough along its circumference for respective connection to the printhead and a respective one of the ink supplies, each port groups being aligned with a portion of a respective one of the channels in the channel arrangement; and 
     a selection device for selectively rotating the shaft to establish interconnection between the ports of each port group via the respective channels to allow ink flow therebetween for each of the ink flow channels. 
     Optionally, five ink flow channels are provided between five ink supplies and the printhead, the valve comprising five of the channels and five associated port groups. 
     Optionally, each channel has a serpentine form. 
     Optionally, the ports are aligned relative to the respective channels of the channel arrangement so that alignment of the ports with a straight portion of the serpentine form of the respective channel provides interconnection between those ports. 
     Optionally, each port group comprises a first port for connection to the ink source, a second port for connection to the printhead, a third port for connection to a bypass ink path which bypasses the printhead on the respective ink flow channel, and a fourth port for connection to a gas vent on said ink flow channel 
     Optionally: each ink flow channel comprises a first path between the ink source and one longitudinal end of the media width of the printhead and a second path between the ink source and the other longitudinal end of the media width of the printhead; each bypass path bridges across the printhead between the first and second paths of the respective ink flow channel; and the valve is configured to be located on the first path of each ink flow channel 
     Optionally, each ink flow channel and bypass path comprise fluid hoses, the first, second, third and fourth ports being configured to connect with the fluid hoses. 
     In another aspect, the invention provides a multi-channel valve arrangement for distributing ink from a plurality of ink supplies to a media width inkjet printhead via a plurality of ink tubes each defining an individual ink flow channel, the valve comprising: 
     a body; 
     a plurality of ports defined through the body, each port being configured to receive a respective one of the ink tubes therethrough; 
     a movable pinch element extending across the ports; and 
     a pinch drive arrangement for selectively moving the pinch element into and out of pinching contact with the ink tubes so as to respectively block and allow ink flow through the ink tubes. 
     Optionally, the valve further comprises a plate fixedly mounted to the body Optionally, the pinch element is mounted to the plate by springs. 
     Optionally, the springs are configured to bias the pinch element away from the fixed plate. 
     Optionally, the springs are compression springs. 
     Optionally, four springs are symmetrically arranged about the pinch element and plate. 
     Optionally, the pinch drive arrangement comprises a shaft rotatably mounted to the body and eccentric cams fixedly mounted on the shaft, the eccentric cams being configured so that rotation of the shaft causes selective contact between the cams and the pinch element thereby selectively forcing the pinch element towards the plate. 
     Optionally, the pinch element comprises roller bearings arranged to selectively contact the cams. 
     Optionally, five ink flow channels are provided between five ink supplies and the printhead, the valve comprising five of the ports. 
     Optionally, each ink flow channel comprises a first path between the ink source and one longitudinal end of the media width of the printhead and a second path between the ink source and the other longitudinal end of the media width of the printhead, and the valve is configured to be located on the first path of each ink flow channel. 
     In another aspect, the invention provides a printing system comprising: 
     a media width printhead; 
     a plurality of fluid containers fluidically interconnected with the printhead via a respective plurality of fluid tubes each defining an individual closed fluid flow loop; 
     a first multi-channel valve arrangement for selectively allowing fluid flow along each closed loop via the printhead by selectively moving a pinch element into and out of pinching contact with the fluid tubes so as to respectively block and allow fluid flow through the fluid tubes; 
     a plurality of gas vents, each gas vent being associated with a respective one of the closed loops; and 
     a second multi-channel valve arrangement for selectively allowing venting of gas in each closed loop via the gas vents. 
     Optionally, the first multi-channel valve arrangement comprises: 
     a body; 
     a plurality of ports defined through the body, each port being configured to receive a respective one of the ink tubes therethrough; and 
     a pinch drive arrangement for selectively moving the pinch element. 
     Optionally, the first multi-channel valve arrangement comprises a plate fixedly mounted to the body Optionally, the pinch element is mounted to the plate by springs. 
     Optionally, the springs are configured to bias the pinch element away from the fixed plate. 
     Optionally, the springs are compression springs. 
     Optionally, four springs are symmetrically arranged about the pinch element and plate. 
     Optionally, the pinch drive arrangement comprises a shaft rotatably mounted to the body and eccentric cams fixedly mounted on the shaft, the eccentric cams being configured so that rotation of the shaft causes selective contact between the cams and the pinch element thereby selectively forcing the pinch element towards the plate. 
     Optionally, the pinch element comprises roller bearings arranged to selectively contact the cams. 
     Optionally: each gas vent comprises a filter disposed at one end of a vent line, the opposed end of the vent line joining the respective first path; and the second multi-channel valve arrangement comprises a plurality of check valves, each check valve being located on a respective one of the vent lines. 
     Optionally, the filters comprise expanded polytetrafluoroethylene 
     Optionally, five fluid flow loops are provided between five containers and the printhead. 
     In another aspect, the invention provides a liquid container for supplying liquid to a printer, the liquid container comprising: 
     a body having an interior space for containing liquid to a predetermined capacity; 
     a port through the body for delivery of liquid into the body to said predetermined capacity; 
     an aperture through the body at which the interior space of the body is in communication with atmosphere external to the fluid container; and 
     a fluid pressure changing member between the aperture and the interior space of the body, the member being configured so that contact with the liquid being delivered via the port causes a change in the fluid pressure at the port. 
     Optionally, the port and aperture are located through an upper surface of the body so that the liquid being delivered into the interior space of the body fills said interior space from a lower surface of the body to said upper surface. 
     Optionally, the member comprises a hydrophobic film located between the interior space and the aperture. 
     Optionally, the member comprises a protrusion within an opening of the aperture in an interior surface of the body. 
     Optionally, the aperture has a gas vent on an exterior surface of the body, the gas vent being configured to be closed to atmosphere until the container is installed in the printer. 
     Optionally the container comprises a valve within the aperture, the valve being biased closed and having an engagement portion which engages with the printer so as to open valve against said bias when the container is installed in the printer. 
     In another aspect, the invention provides a system for sensing a predetermined pressure change at a port of a liquid container for supplying liquid to a printer, the system comprising a liquid delivery apparatus connected to a liquid container via a fluid line and a sensing arrangement connected to the fluid line, 
     wherein the liquid container comprises an internal fluid pressure changing member configured so that contact with liquid being delivered by the liquid delivery apparatus causes said predetermined pressure change in the fluid line, and 
     the sensing arrangement is configured to sense said predetermined pressure change in the fluid line. 
     Optionally, the liquid container further comprises: 
     a body having an interior space for containing liquid to a predetermined capacity; 
     a port through the body connected to the fluid line for delivery of the liquid from the liquid delivery apparatus into the body to said predetermined capacity; and 
     an aperture through the body at which the interior space of the body is in communication with atmosphere external to the fluid container, 
     wherein the fluid pressure changing member is arranged between the aperture and the interior space of the body. 
     Optionally, the port and aperture are located through an upper surface of the body so that the liquid being delivered into the interior space of the body fills said interior space from a lower surface of the body to said upper surface. 
     Optionally, the member comprises a hydrophobic film located between the interior space and the aperture. 
     Optionally, the member comprises a protrusion within an opening of the aperture in an interior surface of the body. 
     Optionally, the aperture has a gas vent on an exterior surface of the body, the gas vent being configured to be closed to atmosphere until the container is installed in the printer. 
     Optionally, the container comprises a valve within the aperture, the valve being biased closed and having an engagement portion which engages with the printer so as to open valve against said bias when the container is installed in the printer. 
     In another aspect, the invention provides a liquid container for supplying liquid to a printer, the liquid container comprising: 
     a body having an interior space for containing liquid to a predetermined capacity; 
     a port through the body for delivery of liquid into the body to said predetermined capacity; 
     an aperture through the body at which the interior space of the body is in communication with atmosphere external to the fluid container; and 
     a hydrophobic film between the aperture and the interior space of the body, the film being configured so that contact with the liquid being delivered via the port causes a change in the fluid pressure at the port. 
     Optionally, a material of the hydrophobic film is expanded polytetrafluoroethylene. 
     Optionally, the aperture comprises a tortuous path to liquid. 
     Optionally, the tortuous path is a serpentine channel formed through the body. 
     Optionally, the tortuous path has a gas vent on an exterior surface of the body, the gas vent being covered by a piercable air impervious film. Optionally, the port and aperture are located through an upper surface of the body so that the liquid being delivered into the interior space of the body fills said interior space from a lower surface of the body to said upper surface. 
     In another aspect, the invention provides a coupling for distributing fluid to a printhead, the coupling comprising: 
     a housing; 
     a port plate movably mounted on the housing by a shaft, the port plate having a plurality of ports for receiving respective fluid spouts of the printhead; 
     a seal member mounted on the housing between the housing and the port plate, the seal member having a plurality of seals which align with respective ones of the ports of the port plate; and 
     a compression spring mounted on the shaft by a washer so as to be compressed between the washer and the port plate. 
     Optionally, the seal member is received in a recess of the housing. 
     Optionally, the seal member has linking portions which link the seals together. 
     Optionally, the seals are circular and the linking portions define an arc between each seal, and the recess comprises circular recesses into which the circular seals are received and curved recesses between the circular recesses into which the linking portions are received. 
     Optionally, the recess has slots across the curved recesses which serve to capture and wick away any fluid present in the recess. 
     Optionally, the port plate has rims about the ports for compressing the respective seals of the seal member when pressed thereagainst. 
     Optionally, the washer is a groove-less ring press-on fitted on a reduced section of a cylindrical portion of the shaft. 
     In another aspect, the invention provides a method of assembling a coupling for distributing fluid to a printhead, the method comprising: 
     mounting a seal member on a housing; 
     inserting a shaft through a hole in the housing and the seal member; 
     positioning a compression spring on the shaft; and 
     mounting a port plate on the shaft using a washer about the shaft so that the spring is compressed between the port plate and the housing and a plurality of ports in the port plate align with respective ones of a plurality of seals of the seal member for receiving respective fluid spouts of the printhead. 
     Optionally, the seal member is mounted into a recess of the housing. 
     Optionally, the seal member has linking portions which link the seals together. 
     Optionally, the seals are circular and the linking portions define an arc between each seal, and the recess comprises circular recesses into which the circular seals are received and curved recesses between the circular recesses into which the linking portions are received. 
     Optionally, the recess has slots across the curved recesses which serve to capture and wick away any fluid present in the recess. 
     Optionally, the port plate has rims about the ports for compressing the respective seals of the seal member when pressed thereagainst. 
     Optionally, the washer is a groove-less ring which is press-on fitted on a reduced section of a cylindrical portion of the shaft. 
     In another aspect, the invention provides a coupling assembly for distributing fluid to a printhead, the coupling assembly comprising: 
     a housing; 
     a seal member received in a recess of the housing; 
     a port plate movably mounted on the housing by a washer which is press-on mounted to a shaft through the port plate and housing; and 
     a tube retainer mounted within a groove of the housing for retaining fluid distribution tubes, the retainer having a plurality of holes aligned with respective ones of a plurality of ports in the port plate and a plurality of seals of the seal member for fluidically connecting the retained fluid distribution tubes with respective fluid spouts of the printhead, 
     wherein mounting of each of the seal member, port plate and retainer to the housing is achieved in a non-fastened manner. 
     Optionally, the seal member has linking portions which link the seals together. 
     Optionally, the seals are circular and the linking portions define an arc between each seal, and the recess comprises circular recesses into which the circular seals are received and curved recesses between the circular recesses into which the linking portions are received. 
     Optionally, the recess has slots across the curved recesses which serve to capture and wick away any fluid present in the recess. 
     Optionally, the port plate has rims about the ports for compressing the respective seals of the seal member when pressed thereagainst by the spring. 
     Optionally, the washer is a groove-less ring press-on mounted on a reduced section of a cylindrical portion of the shaft. 
     Optionally, the retainer is formed from resiliently flexible material. 
     Optionally, the retainer has a rim about its circumferential edge having details, the rim being resiliently received within the groove of the housing and the details engaging with slots formed across the groove. 
     In another aspect, the invention provides a method of assembling a coupling for distributing fluid to a printhead, the method comprising: 
     mounting a seal member in a recess of a housing; 
     inserting a shaft through a hole in the housing and the seal member; 
     mounting a port plate on the shaft using a washer which is press-on mounted to the shaft; and 
     mounting a tube retainer for retaining fluid distribution tubes within a groove of the housing, the retainer having a plurality of holes aligned with respective ones of a plurality of ports in the port plate and a plurality of seals of the seal member for fluidically connecting the retained fluid distribution tubes with respective fluid spouts of the printhead, 
     wherein the mounting of each of the seal member, port plate and retainer to the housing is achieved in a non-fastened manner. 
     Optionally, the seal member has linking portions which link the seals together. 
     Optionally, the seals are circular and the linking portions define an arc between each seal, and the recess comprises circular recesses into which the circular seals are received and curved recesses between the circular recesses into which the linking portions are received. 
     Optionally, the recess has slots across the curved recesses which serve to capture and wick away any fluid present in the recess. 
     Optionally, the port plate has rims about the ports for compressing the respective seals of the seal member when pressed thereagainst by the spring. 
     Optionally, the washer is a groove-less ring which is press-on fitted on a reduced section of a cylindrical portion of the shaft. 
     Optionally, the retainer is formed from resiliently flexible material. 
     Optionally, the retainer has a rim about its circumferential edge having details, the rim being resiliently received within the groove of the housing and the details engaging with slots formed across the groove. 
     In another aspect, the invention provides a system for coupling a media width printhead to a fluid supply, the system comprising: 
     a printhead having a fluid inlet printhead coupling at one longitudinal end of the media width and a fluid outlet printhead coupling at the other longitudinal end of the media width, the printhead couplings each having a plurality of fluid ports; 
     an inlet supply coupling having a plurality of fluid ports defined in a port plate for engagement with the fluid ports of the inlet printhead coupling; 
     an outlet supply coupling having a plurality of fluid ports defined in a port plate for engagement with the fluid ports of the outlet printhead coupling; and 
     a coupling drive mechanism connected to the port plates of the supply couplings via pre-compressed compression springs, the coupling drive mechanism being operational to move the port plates relative to the printhead so as to drive the ports of the supply couplings into engagement with the respective ports of the printhead couplings. 
     Optionally, the coupling drive mechanism has a housing in which the supply couplings are housed. 
     Optionally, the housing has generally cylindrical sockets in which the generally cylindrical supply couplings are positioned so that the port plates are exposed for engagement with the respective printhead couplings. 
     Optionally, the sockets have slots which receive wings on two, opposite sides of the respective supply coupling. 
     Optionally, the wings are formed as cantilevered leaf springs which flex within the slots. 
     Optionally, each supply coupling comprises a movable shaft which passes through an apertured projection in the respective port plate, each compression spring being mounted on the shaft by a washer so as to be compressed between washer and the projection of the port plate. 
     Optionally, the coupling drive arrangement is connected to the shafts and drives movement of the shafts relative to each supply coupling body. 
     Optionally, arms are pivotally connected between each shaft and the coupling drive arrangement. 
     Optionally, the coupling drive arrangement has cam arms which are rotationally driven by a cam mechanism, each arm being connected to the respective cam arm so that rotation of the cam arms moves the supply couplings within the sockets. 
     In another aspect, the invention provides a coupling assembly for distributing fluid to a printhead, the coupling assembly comprising: 
     a housing; 
     a port plate movably mounted to a shaft which passes through the port plate and housing; 
     a compression spring mounted on the shaft by a washer so as to be compressed between the washer and the port plate; and 
     an arm pivotally connected to the shaft at one of its longitudinal ends and pivotally connected to a coupling drive mechanism at its other longitudinal end 
     Optionally, the arm has first and second pairs of beams interconnected by a bridge portion, the first beam pair being pivotally connected to the shaft and the second beam pair being pivotally connected to the coupling drive mechanism. 
     Optionally, the first beam pair are tapered in the vicinity of the bridge portion. 
     Optionally, the distal ends of the first beam pair relative to the bridge have a wall thickness greater than a wall thickness of the rest of the first beam pair. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The exemplary features, best mode and advantages of the invention will be understood by the description herein with reference to accompanying drawings, in which: 
         FIG. 1  is a block diagram of the main system components of a printer; 
         FIG. 2  is a perspective view of a printhead of the printer; 
         FIG. 3  illustrates the printhead with a cover removed; 
         FIG. 4  is an exploded view of the printhead; 
         FIG. 5  is an exploded view of the printhead without inlet or outlet couplings; 
         FIG. 6  illustrates an isometric view of the printer with most components other than those of a fluid distribution system for the printer omitted; 
         FIG. 7  illustrates an opposite isometric view of the printer as illustrated in  FIG. 6 ; 
         FIG. 8  schematically illustrates one embodiment of the fluid distribution system; 
         FIG. 9  illustrates an accumulator tank of the fluid distribution system; 
         FIG. 10  illustrates an exploded view of the accumulator tank; 
         FIG. 11  illustrates a cross-sectional view of the accumulator tank taken through line A-A in  FIG. 9 ; 
         FIG. 12  illustrates a first exploded view of the accumulator tank; 
         FIG. 13  illustrates a second exploded view of the accumulator tank; 
         FIG. 14  illustrate the accumulator tank in perspective; 
         FIG. 15  illustrates a partial sectional view of the accumulator tank; 
         FIGS. 16A to 16C  illustrate operation stages of the valve; 
         FIG. 17  illustrates a sensing arrangement of the accumulator tank; 
         FIG. 18  illustrates an air chimney arrangement of the accumulator tank; 
         FIG. 19  illustrates a power up priming procedure of the fluid distribution system; 
         FIG. 20  illustrates a priming procedure of the fluid distribution system; 
         FIG. 21  illustrates a bypass flush procedure of the fluid distribution system; 
         FIG. 22  illustrates a printhead flush procedure of the fluid distribution system; 
         FIG. 23  illustrates a dual flush procedure of the fluid distribution system; 
         FIG. 24  illustrates a pressure prime procedure of the fluid distribution system; 
         FIG. 25  illustrates a de-prime procedure of the fluid distribution system; 
         FIG. 26A  illustrates an isometric view of an exemplary diaphragm multi-channel valve of the fluid distribution system; 
         FIG. 26B  illustrates another isometric view of the diaphragm valve; 
         FIG. 26C  illustrates a top view of the diaphragm valve; 
         FIG. 27  illustrates an exploded view of the diaphragm valve; 
         FIG. 28A  illustrates a diaphragm port arrangement for one fluid channel of the diaphragm valve; 
         FIG. 28B  illustrate an exploded view of the diaphragm port arrangement shown in  FIG. 28A ; 
         FIG. 29A  illustrates operation of a cam drive arrangement of the diaphragm valve; 
         FIG. 29B  illustrates a first position of a single cam disc of the cam drive arrangement; 
         FIG. 29C  illustrates a second position of the single cam disc of  FIG. 29B ; 
         FIG. 30A  illustrates a perspective view of an exemplary rotary multi-channel valve of the fluid distribution system; 
         FIG. 30B  illustrates another perspective view of the rotary valve; 
         FIG. 31  illustrates an exploded view of the diaphragm valve; 
         FIGS. 32A and 32B  illustrate different views of a cylinder port arrangement for one fluid channel of the rotary valve; 
         FIGS. 33A and 33B  illustrate different views of a port cylinder of the rotary valve; 
         FIGS. 34A and 34B  illustrate different views of a channel cylinder of the rotary valve; 
         FIG. 35  illustrates a cross-sectional view of O-ring seal ridges of the port cylinder; 
         FIG. 36  illustrates a cross-sectional view of the rotary valve; 
         FIG. 37  schematically illustrates another embodiment of the fluid distribution system; 
         FIGS. 38A and 38B  illustrates different views of an exemplary pinch valve of the fluid distribution system of  FIG. 37 ; 
         FIG. 39  illustrates an exploded view of the pinch valve; 
         FIG. 40A  illustrates a cross-sectional view along line B-B in  FIG. 38A  of the pinch valve in an open (non-pinched) state; 
         FIG. 40B  illustrates the cross-sectional view of  FIG. 40A  with the pinch valve in a closed (pinched) state; 
         FIG. 41A  illustrates a cross-sectional view along line C-C in  FIG. 38A  of the pinch valve in the open state; 
         FIG. 41B  illustrates the cross-sectional view of  FIG. 41A  with the pinch valve in the closed state; 
         FIG. 42A  illustrates one exemplary cam drive arrangement of the pinch valve; 
         FIG. 42B  illustrates another exemplary cam drive arrangement of the pinch valve; 
         FIG. 43A  illustrates an end view of the pinch valve in the open state; 
         FIG. 43B  illustrates the end view of  FIG. 43A  with the pinch valve in the closed state; 
         FIG. 44  illustrates an alternative priming procedure of the fluid distribution system; 
         FIG. 45  illustrates an alternative printhead flush procedure of the fluid distribution system; 
         FIG. 46  illustrates an alternative pressure prime procedure of the fluid distribution system; 
         FIG. 47  illustrates an alternative de-prime procedure of the fluid distribution system; 
         FIG. 48  illustrates a supply tank of the fluid distribution system; 
         FIG. 49  illustrates the supply tank in a different view than that of  FIG. 48 ; 
         FIG. 50  illustrates a cross-sectional view of the supply tank taken along line D-D in  FIG. 49  within a receiving bay of the printer; 
         FIG. 51  illustrates an cross-sectional view of an alternative supply tank of the fluid distribution system; 
         FIG. 52  illustrates a system diagram for sensing pressure changes during refilling of the supply tank; 
         FIGS. 53A and 53B  illustrate different views of a fluid supply coupling of the fluid distribution system; 
         FIGS. 54A and 54B  illustrate exploded views of the different views of  FIGS. 53A and 53B ; 
         FIG. 55  illustrates the supply coupling with a port plate omitted; 
         FIGS. 56A and 56B  illustrate different exploded views of supply couplings including a coupling drive mechanism; 
         FIGS. 57A-57E  illustrate, in cross-section, different coupling operational steps of the supply coupling; and 
         FIG. 58  illustrates, in isolation, an arm of the supply coupling. 
     
    
    
     One of ordinary skill in the art will appreciate that the invention is not limited in its application to the details of construction, the arrangements of components, and the arrangement of steps set forth in the description herein and/or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or being carried out in various other ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An exemplary block diagram of the main system components of a printer  100  is illustrated in  FIG. 1 . The printer  100  has a printhead  200 , fluid distribution system  300 , maintenance system  600  and electronics  800 . 
     The printhead  200  has fluid ejection nozzles for ejecting printing fluid, such as ink, onto passing print media. The fluid distribution system  300  distributes ink and other fluids for ejection by the nozzles of the printhead  200 . The maintenance system  600  maintains the nozzles of the printhead  200  so that reliable and accurate fluid ejection is provided. 
     The electronics  800  operatively interconnects the electrical components of the printer  100  to one another and to external components/systems. The electronics  800  has control electronics  802  for controlling operation of the connected components. An exemplary configuration of the control electronics  802  is described in US Patent Application Publication No. 20050157040, the contents of which are hereby incorporated by reference. 
     The printhead  200  may be provided as a media width printhead cartridge removable from the printer  100 , as described in US Patent Application Publication No. 20090179940, the contents of which are hereby incorporated by reference. This exemplary printhead cartridge includes a liquid crystal polymer (LCP) molding  202  supporting a series of printhead ICs  204 , as illustrated in  FIGS. 2-5 , which extends the width of media substrate to be printed. When mounted to the printer  100 , the printhead  200  therefore constitutes a stationary, full media width printhead. 
     The printhead ICs  204  each comprise ejection nozzles for ejecting drops of ink and other printing fluids onto the passing media substrate. The nozzles may be MEMS (micro electro-mechanical) structures printing at true 1600 dpi resolution (that is, a nozzle pitch of 1600 nozzles per inch), or greater. The fabrication and structure of suitable printhead ICs  204  are described in detail in US Patent Application Publication No. 20070081032, the contents of which are hereby incorporated by reference. 
     The LCP molding  202  has main channels  206  extending the length of the LCP molding  202  between associated inlet ports  208  and outlet ports  210 . Each main channel  206  feeds a series of fine channels (not shown) extending to the other side of the LCP molding  202 . The fine channels supply ink to the printhead ICs  204  through laser ablated holes in the die attach film via which the printhead ICs are mounted to the LCP molding, as discussed below. 
     Above the main channel  206  is a series of non-priming air cavities  214 . These cavities  214  are designed to trap a pocket of air during printhead priming. The air pockets give the system some compliance to absorb and damp pressure spikes or hydraulic shocks in the printing fluid. The printers are high speed pagewidth or media width printers with a large number of nozzles firing rapidly. This consumes ink at a fast rate and suddenly ending a print job, or even just the end of a page, means that a column of ink moving towards (and through) the printhead  200  must be brought to rest almost instantaneously. Without the compliance provided by the air cavities  214 , the momentum of the ink would flood the nozzles in the printhead ICs  204 . Furthermore, the subsequent ‘reflected wave’ could otherwise generate sufficient negative pressure to erroneously deprime the nozzles. 
     The printhead cartridge has a top molding  216  and a removable protective cover  218 . The top molding  216  has a central web for structural stiffness and to provide textured grip surfaces  220  for manipulating the printhead cartridge during insertion and removal with respect to the printer  100 . Movable caps  222  are provided at a base of the cover and are movable to cover an inlet printhead coupling  224  and an outlet printhead coupling  226  of the printhead  200  prior to installation in the printer. The terms “inlet” and “outlet” are used to specify the usual direction of fluid flow through the printhead  200  during printing. However, the printhead  200  is configured so that fluid entry and exit can be achieved in either direction along the printhead  200 . 
     The base of the cover  218  protects the printhead ICs  204  and electrical contacts  228  of the printhead prior to installation in the printer and is removable, as illustrated in  FIG. 3 , to expose the printhead ICs  204  and the contacts  228  for installation. The protective cover may be discarded or fitted to a printhead cartridge being replaced to contain leakage from residual ink therein. 
     The top molding  216  covers an inlet manifold  230  of the inlet coupling  224  and an outlet manifold  232  of the outlet coupling  226  together with shrouds  234 , as illustrated in  FIG. 4 . The inlet and outlet manifolds  230 , 232  respectively have inlet and outlet spouts  236 , 238 . Five each of the inlet and outlet ports or spouts  236 , 238  are shown in the illustrated embodiment of the printhead  200 , which provide for five ink channels, e.g., CYMKK or CYMKIR. Other arrangements and numbers of the spouts are possible to provide different printing fluid channel configurations. For example, instead of a multi-channel printhead printing multiple ink colors, several printheads could be provided each printing one or more ink colors. 
     Each inlet spout  236  is fluidically connected to a corresponding one of the inlet ports  208  of the LCP molding  202 . Each outlet spout  238  is fluidically connected to a corresponding one of the outlet ports  210  of the LCP molding  202 . Thus, for each ink color, supplied ink is distributed between one of the inlet spouts  236  and a corresponding one of the outlet spouts  238  via a corresponding one of the main channels  206 . 
     From  FIG. 5  it can be seen that the main channels  206  are formed in a channel molding  240  and the associated air cavities  214  are formed in a cavity molding  242 . Adhered to the channel molding  240  is a die attach film  244 . The die attach film  244  mounts the printhead ICs  204  to the channel molding  240  such that the fine channels, which are formed within the channel molding  240 , are in fluid communication with the printhead ICs  204  via small laser ablated holes  245  through the film  244 . 
     The channel and cavity moldings  240 , 244  are mounted together with a contact molding  246  containing the electrical contacts  228  for the printhead ICs and a clip molding  248  in order to form the LCP molding  202 . The clip molding  248  is used to securely clip the LCP molding  202  to the top molding  216 . 
     LCP is the preferred material of the molding  202  because of its stiffness, which retains structural integrity along the media width length of the molding, and its coefficient of thermal expansion which closely matches that of silicon used in the printhead ICs, which ensures good registration between the fine channels of the LCP molding  202  and the nozzles of the printhead ICs  204  throughout operation of the printhead  200 . However, other materials are possible so long as these criteria are met. 
     The fluid distribution system  300  may be arranged as illustrated in  FIGS. 6 and 7 , which show the printer  100  with most components other than those of the fluid distribution system  300  omitted for clarity. The fluid distribution system  300  is described in detail below. 
     The maintenance system  600  may be configured as described in the Applicant&#39;s U.S. Provisional Patent Application No. 61/345,559 
     One embodiment of the system  300  for distributing ink and other fluids for ejection by the printhead  200  is schematically illustrated in  FIG. 8  for a single fluid channel, e.g., a single colored ink or other printing fluid, such as ink fixing agent (fixative). The fluid distribution system  300  of  FIG. 8  and its various components are now described in detail. 
     A first sealed container  302  (herein termed a supply tank) which contains ink or other fluid/liquid for supply to the printhead  200  is coupled to a second sealed container  304  (herein termed an accumulator tank) by a coupling  306  and associated fluid line  308 . The fluid line is in the form of tubing, and is preferably tubing which exhibits low shedding and spallation in an ink environment. Thermoplastic elastomer tubing is therefore suitable, such as Tygoprene® XL-60. 
     The coupling allows releasable engagement of the supply tank  302  in a manner understood by one of ordinary skill in the art. For example, the coupling may be provided in two engageable parts with one part connected to, or part of, the supply tank (‘supply side’) and the other part connected to the fluid line (‘delivery side’). 
     The fluid line is connected to the accumulator tank  304  via a valve  310 . The valve  310  is in the form of an inverted umbrella valve (relative to the orientation illustrated in  FIG. 8 ) which has an umbrella-shaped disc  312  mounted within an inlet  314  on the body  316  of the accumulator tank  304  so that the umbrella-shape is inverted and seals against the inlet. The disc  312  is preferably formed of a resilient material which is inert in an ink environment, such as ethylene propylene diene monomer (EPDM). The disc  312  is enclosed relative to the accumulator tank body by a connector  318  which connects to the fluid line and seals against the accumulator tank body. This arrangement is illustrated in  FIG. 11 . 
     Ink is supplied from the supply tank to the accumulator tank through the fluid line in accordance with a position of the umbrella disc relative to the inlet  314 . In particular, when the umbrella disc is not sealed against the inlet fluid flows from the supply tank to the accumulator tank. This fluid flow is provided under gravitational pressure by locating the supply tank above the printhead and the accumulator tank so that a positive fluid pressure is present at the inlet  314 . On the other hand, when the umbrella disc is sealed against the inlet such fluid flow is prevented. 
     In order to control the level of positive fluid pressure present at the inlet  314 , a restrictor  320  is disposed on the fluid line proximate the inlet  314 , as schematically illustrated in  FIG. 8 . In one example, the restrictor  320  can be provided as a resilient member mounted on the exterior of the fluid line configured to compress the fluid line by an amount which restricts fluid flow therethrough but does not prevent fluid flow. 
     Alternatively, the connector  318  can incorporate the restrictor by forming an obstruction  322  in a fluid passage  324  of the connector through which fluid from the connected fluid line flows into the connector. In the example illustrated in  FIG. 11 , the obstruction  322  is a portion of the fluid passage which has an inner diameter less than the inner diameter of the rest of the fluid passage and which opens into a funnel  326 . 
     The umbrella valve is operated by means of a valve actuator  328  mounted within the inlet  314 . As shown in  FIGS. 12-14 , the valve actuator is a hollow valve pin  328  which protrudes from the inlet and the umbrella disc  312  is pressed into the valve pin (see also  FIG. 11 ). To complete this assembly, the connector  318  is mounted to a mounting ring  330  on the accumulator tank body. In order to provide a reliable seal, the connector can be ultrasonically welded to the mounting ring. 
     The valve pin  328  is pivotally mounted to a float member  332  located within the accumulator tank  304 . The float in turn has pins  334  on arms  336  which locate within recesses  338  formed in the interior of the accumulator tank body to pivot thereabout. This arrangement for one of the pins  334  is shown in  FIG. 15 . 
     By this structure, pivoting of the float relative to the accumulator tank body causes sliding movement of the valve pin within the inlet, which in turn causes the opening and closing of the umbrella valve through movement of the umbrella disc. This operation is shown in  FIGS. 16A to 16C . 
     The pivoting of the float is caused by ink entering the interior of the accumulator tank. In particular, the float is arranged so that when the accumulator tank is empty the umbrella valve is open, as shown in  FIG. 12 . As ink enters the accumulator through the umbrella valve the ink begins the fill the accumulator tank, as shown in  FIG. 16A . 
     As more ink enters the float begins to pivot upward due to buoyancy of the float, as shown in  FIG. 16B . The buoyancy of the float is provided by configuring the float with a hollow interior  340  which is enclosed by a lid  342  so as to contain air within the float (see  FIG. 10 ). One of ordinary skill in the art understands that other configurations of the float are possible to provide buoyancy however. 
     As ink continues to enter the accumulator tank, this upward pivoting of the float continues until the umbrella valve is closed preventing further ink entry, as shown in  FIG. 16C . The interior of the accumulator tank and the relative size of the float are configured so that the accumulator tank has a predetermined fluid containing capacity. The use of the float actuated valve in the accumulator tank ensures that whilst sufficient fluid is available at the inlet of the accumulator tank, the accumulator tank contains fluid at a level which consistently fills this predetermined capacity. 
     The accumulator tank has an outlet  344  and a port  346  through which the fluid contained in the accumulator tank can be drawn in a controlled manner through a closed fluid loop  348  (see  FIG. 8 ) which enables the fluid to be contained in the accumulator tank in a stable manner. This operation is discussed in detail later. 
     The interior of the accumulator tank is sealed with respect to liquids by a lid  350 . The lid  350  incorporates a gas vent  352  and a tortuous liquid path  354  for allowing gases, such as ambient air and internal vapours, to pass into and out of the accumulator tank. This arrangement allows the internal gas pressure of the accumulator tank to be equalized to external ambient conditions. 
     The gas vent  352  is formed with a hydrophobic material which ensures that liquid is retained in the interior whilst allowing gas transit. Preferably, the hydrophobic material of the gas vent  352  is expanded polytetrafluoroethylene (ePTFE, known as Gore-Tex® fabric) which has these gas transit properties. The use of the term “hydrophobic” is to be understood as meaning that any liquid, not only water, is repelled by the material which is said to be “hydrophobic”. 
     The accumulator tank, including the lid  350 , is preferably formed of a material which is inert in ink environments, has a low water vapor transmission rate (WVTR) and can allow ultrasonic welding of connected components, such as the connector  318  and the lid  350 . Such a material is polyethylene terephthalate (PET). The float  332 , including the lid  342 , is preferably formed of a material which is inert in ink, can be ultrasonically welded, and is not susceptible to sympathetic ultrasonic welding when the lid  350  is ultrasonically welded to the body  316  of the accumulator tank. Such a material is a combination of polyphenylene ether and polystyrene, such as Noryl 731. 
     A filter  356  is located at the outlet  344  of the accumulator tank so that the ink contained in the accumulator tank passes through the filter before exiting through the outlet  344  and ultimately to the printhead  200  through the closed loop  348 . The filter  356  is used to filter contaminants from the ink so that the ink reaching the printhead  200  is substantially contaminant-free. The filter is formed of a material which allows fluid transfer through the filter but prevents particulate transfer and is compatible with ink. Preferably, the filter is a polyester mesh having a pore size of one micron. Such a mesh filter  356  is preferably mounted on a flange  357  within the accumulator tank by heat staking or the like. 
     Providing the accumulator tank with an internal filter obviates the need for filtration within the closed fluid path loop  348  which incorporates the printhead  200 , as will be discussed later. 
     As illustrated schematically in  FIG. 8 , the filter  356  is preferably arranged in the accumulator tank to be below the inlet  314  and to be at an angle relative to the outlet  344  with the lower side of the filter  356  at the inlet  314  side (i.e., at the right in  FIG. 16A ) and the higher side of the filter  356  at the outlet  344  side (i.e., at the left in  FIG. 16A ). This arrangement forms a filter compartment  358  comprising the walls of the accumulator tank below the filter  356  and the inclined angle assists in removing air locks within the accumulator tank for reliable and efficient delivery of fluid to the printhead  200 . 
     That is, when the accumulator tank is empty, as ink  359  begins to enter the accumulator tank the filter  356  is wetted from lower side to the higher side so that any air in the filter compartment  358  is trapped beneath the wetted filter  356  and is purged from the filter compartment  358  through the outlet  344  and into the closed loop  348 . This air in the closed loop  348  is purged from the fluid distribution system  300  in a number of ways which are discussed in detail later. 
     This gas purging through the outlet  344  is enhanced by forming the lower wall  360  of the accumulator tank to be substantially parallel to the filter  356  with the outlet  344  at the higher side of the angled lower wall  360 . This allows ink to fill the filter compartment  358  from the lower side to the higher side thereby pushing air up the inclined slope of the lower wall  360  and along the underside of the wetted filter  356  to be purged from the outlet  344 . 
     The angle of the filter  356 , and lower wall  360 , is preferably about 10 degrees from the horizontal. As seen in  FIGS. 16A to 16C , the lower wall  362  of the float  332  is also angled to conform with the angle of the filter  356 , which assists in the floating operation of the float  332 . 
     Providing the filter compartment  358  below the filter  356  and the inlet  314  of the accumulator tank keeps fluid within this filter compartment  358  during normal use, which assists in preventing air re-entering this space and causing air locks. Further, the skewed profile of the filter compartment  358  assists in purging air from this space which may enter due to movement of the printer  100  and therefore the accumulator tank. 
     The amount of fluid within the accumulator tank is monitored by a sensing arrangement  364 . The sensing arrangement  364  senses the level of fluid contained within the accumulator tank and outputs the sensing result to the control electronics  802  of the printer  100 . For example, the sensing result can be stored in a quality assurance (QA) device of the accumulator tank which interconnects with a QA device of the control electronics  802 , as described in previously referenced and incorporated US Patent Application Publication No. 20050157040. 
     An exemplary configuration of the sensing arrangement  364  is illustrated in  FIGS. 15 and 17 . In this example, the sensing arrangement  364  has a prism  366  incorporated within the body  316  of the accumulator tank at a position which accords to a fluid level providing the predetermined fluid containing capacity of the accumulator tank. The sensing arrangement  364  further has a sensor  368  mounted on the body  316  adjacent the prism  366 . The sensor  368  emits light of a certain wavelength into the prism  366  and detects returning light and the wavelength of the returning light. 
     When fluid is present in the accumulator tank at the level providing the predetermined fluid containing capacity (herein termed “full level”), the light emitted by the sensor  368  is refracted by the prism  366  back to the sensor  368  as returning light at a first wavelength. In this case, the sensor  368  provides a signal which indicates a “full” fluid level to the control electronics  802 . 
     When fluid is present in the accumulator tank at a first level less than the full level (herein termed the “low level”), the light emitted by the sensor  368  is refracted by the prism  366  back to the sensor  368  as returning light at a second wavelength different than the first wavelength. In this case, the sensor  368  provides a signal which indicates a “low” fluid level to the control electronics  802 . 
     When fluid is present in the accumulator tank at a second level less than the first level (herein termed the “out level”), the light emitted by the sensor  368  passes through the prism  366  such that no returning light is sensed by the sensor  368 . In this case, the sensor  368  provides a signal which indicates an “out” fluid level to the control electronics  802 . 
     As discussed above, whilst ink is available for supply from the supply tank to the accumulator tank, the level of ink in the accumulator tank is maintained at a substantially constant level by the float activated valve, i.e., the full level, which also serves to effectively isolate the supply tank from the printhead. That is, as schematically illustrated in  FIG. 8  and diagrammatically illustrated in  FIGS. 6 and 7 , the supply tank is positioned above the printhead and the accumulator tank, which results in positive fluid pressure at the inlet  314  of the accumulator tank, as discussed above. Further, as illustrated, the accumulator tank is positioned below the printhead. By this arrangement, the fluid pressure difference between the accumulator tank and the printhead is independent of the fluid pressure difference between the supply tank and accumulator tank. Negative fluid pressure at the nozzles of the printhead, which prevents ink leakage from the nozzles, is also provided by this arrangement. Furthermore, this negative fluid pressure is maintained during ordinary operation of the printer by maintaining the substantially constant level of ink in the accumulator tanks. 
     When the supply tank is depleted of ink, the drawing of ink from the accumulator tank into the closed loop  348  reduces the level of ink within the accumulator tank from the full level to the low level and then the out level. Relaying of this ink level reduction to the control electronics  802  allows printing by the printhead  200  to be controlled to eliminate low quality prints, such as partially printed pages and the like. 
     For example, at the full indicator, the control electronics  802  allows normal printing to be carried out. At the low ink level indicator, the control electronics  802  allows reduced capacity printing to be carried out, such as subsequent printing of only a certain number of pages of certain ink quantity requirements. And at the out level indicator, the control electronics  802  prevents further printing until the supply tank is refilled or replaced with a full tank, such as through prompting of a user of the printer  100 . 
     The out fluid level is set to be an amount below the full fluid level which retains fluid within the accumulator tank, rather than letting the accumulator tank empty completely. For example, the full level is set at about 19 to 22 milliliters, the low level is set at about 13 milliliters, and the out level is set at about 11 milliliters. This lower fluid level causes the umbrella valve  310  to open slightly but since the supply tank and the fluid line  308  are higher than the accumulator tank positive fluid pressure is retained at the umbrella valve  310  and ink does not leak from the fluid line  308 . 
     This ensures that the closed fluid path loop  348  and the printhead  200  remains primed with ink, which eliminates the re-introduction of air into the system. The priming and de-priming of the fluid distribution system  300  is described in detail later. This also allows the fluid pressure difference between the accumulator tank and the printhead to be constrained within a tolerable range for maintaining the necessary negative fluid pressure at the nozzles of the printhead discussed above. 
     When the out fluid level is reached, replacement or refilling of the supply tank is necessary to re-establish ink supply. In the example shown in the drawings, the supply tank is replaced by de-coupling the supply tank from the coupling  306  and then coupling either a new supply tank at full ink capacity or the same supply tank which has been refilled to full ink capacity. Alternatively, the coupling  306  may be provided as a valve which is closed during refilling of the supply tank, such that the supply tank is not physically removed from the system  300  and can be refilled in situ. 
     This process is assisted by maintaining ink within coupling  306  when the supply tank is emptied and then removed so that air locks are not present when the supply tank is re-coupled, which would hamper re-priming of the fluid line  308 . Ink is maintained in the coupling  306  by locating a gas vent  370  (termed herein as “air chimney”) on the fluid line  308  between the coupling  306  and the accumulator tank  304 . 
     The air chimney  370  incorporates a vent line  372  and a filter  374 . The vent line  372  has one end connected to the fluid line  308  by a connector  376  and has the filter  374  disposed at the other end. As such the fluid line  308  has a portion  308   a  between the coupling  306  and the connector  376  and a portion  308   b  between the connector  376  and the accumulator tank  304 , as schematically illustrated in  FIG. 18 . 
     The vent line  372  is preferably vertically disposed, as is the portion  308   b  of the fluid line  308 , and the portion  308   a  of the fluid line  308  is preferably horizontally disposed so that fluid within the fluid line  308  is discouraged from entering the vent line  372  and so that when the supply tank empties of ink reduced ink pressure occurs in the fluid line  308  at the connector  376  which causes air to rush into the portion  308   b  of the fluid line  308  from the air chimney  370 . This in-rush of air leaves the portion  308   a  of the fluid line  308  primed with ink when the supply tank is de-coupled. 
     When the supply tank is re-coupled or refilled in situ, the ink pressure at the connector  376  increases causing ink to be drawn into the portion  308   b  of the fluid line  308  and a predetermined amount of ink is drawn from the outlet  344  of the accumulator tank by operation of a pump  378  on the closed loop  348  (see  FIG. 8 ) so as to draw the ink in the fluid line  308  into the accumulator tank through the open umbrella valve  310  pushing the air into the accumulator tank which is vented through the gas vent  352  of the accumulator tank. This operation ensures that the fluid line  308  is fully primed with ink so that no air is present in the fluid line during printing. Operation of the pump  378  is further discussed later. 
     By disposing the air chimney  370  at the intersection of the fluid line  308  where the horizontal portion  308   b  becomes the vertical portion  308   a  air bubbles induced at the coupling  306  are able to vent out of the fluid line  308 , which prevents air locks in the system  300 . 
     The filter  374  of the air chimney  370  is preferably formed of a hydrophobic material, such as ePTFE, so that air exclusive of water vapor and the like is able to enter the vent line  372  from the ambient environment. 
     The closed loop  348  provides a fluid path between the accumulator tank and the printhead  200 . This fluid path is provided as a closed loop so that fluid can be primed into the fluid path and the printhead from the accumulator tank, the primed fluid can be printed by the printhead and the fluid can be de-primed from the printhead and the fluid path back to the accumulator tank so that de-primed fluid is not wasted, which is a problem with conventional fluid distribution systems for printers. The closed loop  348  also allows periodic recirculation of fluid within the fluid distribution system  300  to be carried out so that the viscosity of the fluid, such as ink, is retained within specified tolerances for printing. 
     In the embodiment of  FIG. 8 , the closed loop  348  is comprised of plural fluid lines. A print fluid line  380  is provided between the accumulator tank outlet  344  and the printhead  200 . A pump fluid line  382  is provided between the printhead  200  and the accumulator tank priming port  346 . A bypass fluid line  384  is provided connecting the print and pump lines independent of the printhead  200 . By the arrangement of these fluid lines, the closed loop  348  actually constitutes two interconnected closed loops: a printhead loop  348   a ; and a bypass loop  348   b.    
     The fluid lines of the closed loop  348  are in the form of tubing, and are preferably tubing which exhibits low shedding and spallation in an ink environment. Thermoplastic elastomer tubing is therefore suitable, such as Norprene® A-60-G. The combined length of the fluid lines is preferably about 1600 to about 2200 millimeters and the internal diameter of the tubing is preferably about 3 millimeters, providing a combined fluid volume of about 14 to 19 millimeters. The pump  378  is preferably a peristaltic pump so that contamination of the pumped ink is prevented and so that pumping amounts of about 0.26 milliliters per revolution of the pump are possible. However, one of ordinary skill in the art understands that other fluid lines dimensions and types of pumps can be used. 
     On one side of the printhead  200  (i.e., at the right side in  FIG. 8 , herein termed “pump side”) the pump and bypass lines are interconnected by a connector (not shown). At the other side of the printhead  200 , the print and bypass lines are interconnected by a multi-path valve  386  on the print line. The valve  386  also interconnects portions  380   a  and  380   b  of the print line with the portion  380   a  being between the accumulator tank  304  and valve  386 , and the portion  380   b  being between the accumulator tank  304  and a fluid supply coupling  388 , as illustrated in  FIG. 8 . Another supply coupling  388  is disposed on the pump side of printhead  200  at which the pump line terminates. 
     In the example shown in  FIG. 8 , the valve  386  further interconnects a gas vent  390  (herein termed “de-prime vent”) to the print and bypass lines. The de-prime vent  390  incorporates a vent line  392  and a filter  394 . The vent line  392  has one end connected to the valve  386  and has the filter  394  disposed at the other end. 
     The valve  386  is a 4-way valve having four ports, termed herein as the “air”, “printhead”, “bypass” and “ink” ports. The air port is connected to the vent line  392 , the printhead port is connected to the print line portion  380   b , the bypass port is connected to the bypass line  384 , and the ink port is connected to the print line portion  380   a . These ports of the 4-way valve  386  are selectively opened and closed to provide selective interconnection of, and fluid flow between, the multiple fluid paths for priming, printing and de-priming procedures for the fluid distribution system  300 . 
     The states of the ports of the valve  386  are shown in Table 1. In Table 1, an “O” indicates that the associated port is open and a blank indicates that the associated port is closed. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 4-way valve states 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 STATE 
                 AIR 
                 PRINTHEAD 
                 BYPASS 
                 INK 
               
               
                   
               
               
                   
                 PRIME 1 
                   
                   
                 O 
                 O 
               
               
                   
                 PRIME 2 
                   
                 O 
                   
                 O 
               
               
                   
                 PRINT 
                   
                 O 
                 O 
                 O 
               
               
                   
                 STANDBY 
                   
                 O 
                 O 
                 O 
               
               
                   
                 PULSE 
                   
                 O 
                 O 
                   
               
               
                   
                 DEPRIME 1 
                 O 
                   
                 O 
                   
               
               
                   
                 NULL 
                   
                   
                   
                   
               
               
                   
                 DEPRIME 2 
                 O 
                 O 
               
               
                   
               
            
           
         
       
     
     The manner in which these state settings of the valve  386  are used is now discussed with respect to the schematic outlay illustrated in  FIG. 8 . 
     At the first power up of the printer  100 , the fluid distribution system  300 , excluding the printhead  200 , is primed and it is ensured that the pump  378  is fully wetted prior to beginning any further volumetric pumping procedures. As is illustrated in  FIG. 19 , in this power up priming procedure the valve  386  is set to PRIME 1 and the pump is operated in the clockwise direction for 88 revolutions at 100 rpm so that ink is moved from the accumulator tank outlet  344  to the accumulator tank priming port  346  via the print line portion  380   a , bypass line  384  and pump line  382  priming the bypass loop  384   b . Then, the valve  386  is set to STANDBY. 
     At times subsequent to first power up of the printer  100  when priming is required, the bypass line  384  and the printhead are primed in sequence. As is illustrated in  FIG. 20 , in this priming procedure the valve  386  is first set to PRIME 1 and the pump is operated in the clockwise direction for 42 revolutions at 150 rpm so that ink is moved from the accumulator tank outlet  344  to the end of the bypass line  384 . Then, the valve  386  is set to PRIME 2 and the pump is operated in clockwise direction for the 63 revolutions at 60 rpm so that the printhead is primed with ink and air that was in the printhead is displaced to the accumulator tank  304  via the priming port  346 . Then, the valve  386  is set to STANDBY. 
     When printing is to be carried out, the valve  386  is set to PRINT and ejection of ink from the nozzles causes ink flow from the accumulator tank to the printhead via the print line  380 . After printing, the valve  386  is set to STANDBY. Allowing fluid flow through the bypass line  384  and through the printhead  200  from the side of the printhead connected to the print line  380  (i.e., at the left side in  FIG. 8 , herein termed “supply side”) to the pump side, provides uniform fluid pressure across the printhead during printing. This uniform fluid pressure ensures that fluid is delivered to each nozzle of the printhead at substantially the same fluid pressure which enables substantially constant print quality across the media width of the printhead. 
     At times it is necessary to flush gas bubbles that might form in the bypass line  384  over time. As is illustrated in  FIG. 21 , in this bypass flush procedure the valve  386  is first set to PRIME 1 and the pump is operated in the clockwise direction for 50 revolutions at 150 rpm to move any gas bubbles to the accumulator tank via the priming port  346 . Then, the valve  386  is set to STANDBY. 
     At times it is necessary to recover the printhead from mild dehydration of ink at the nozzles as well to flush back channel gas bubbles from the printhead. As is illustrated in  FIG. 22 , in this printhead flush procedure the valve  386  is set to PRIME 2 and the pump is operated in the clockwise direction for 100 revolutions at 150 rpm to move fresh ink into the printhead and to move any gas bubbles to the accumulator tank via the priming port  346 . Then, the valve  386  is set to STANDBY. 
     The Applicant has found that printhead flushing can result in mixing of the different colored inks of the printhead, which if not cleared could result in cross-contamination of the separate ink color nozzles of the printhead. This color mixing is due to the flushed ink causing the menisci of the nozzles to pulsate from the action of the pump. Clearing of this color mixing can be achieved by setting the valve  386  to PRINT, prior to setting the valve  386  to STANDBY in the printhead flush procedure, and operating the printhead so that each nozzle ejects  500  drops. This “spitting” operation of the printhead is carried out in relation to an absorber or wick element of the maintenance system  600 , described in incorporated description of the co-filed US provisional patent application filed under Applicant&#39;s U.S. Provisional Patent Application No. 61/345,559. 
     This spitting procedure equates to about 0.03 milliliters of ink being spat out by the entire printhead when the ejection drop size of each nozzle is about one picoliter. 
     As an alternative to the printhead flush procedure, it is possible to recover the printhead from mild dehydration by flushing the bypass line  384  and the printhead simultaneously. As illustrated in  FIG. 23 , in this dual flush procedure the valve  386  is set to PRINT and the pump is operated in the clockwise direction for 50 revolutions at 150 rpm to move fresh ink into the bypass line  384  and the printhead, and to move any gas bubbles to the accumulator tank via the priming port  346 . Then, the valve  386  is set to STANDBY. 
     At times it is necessary to recover the printhead from heavy dehydration and/or remove air bubbles trapped within the fine ink delivery structure of the printhead  200  by priming the printhead at increased fluid pressure. As illustrated in  FIG. 24 , in this pressure prime procedure the valve  386  is first set to PULSE and the pump is operated in the anticlockwise direction for 2 revolutions at 200 rpm to cause ink to be egested from the nozzles of the printhead. Then, the maintenance system  600  is operated to wipe the ejection face of the printhead so as to remove the egested ink, as described in the incorporated description of the co-filed US provisional patent application filed under Applicant&#39;s U.S. Provisional Patent Application No. 61/345,559. Then, the valve  386  is set to PRINT and the printhead is operated so that each nozzle ejects  5000  drops. This “spitting” operation of the printhead is carried out in relation to an absorber or wick element of the maintenance system  600 , described in the incorporated description of the co-filed US provisional patent application filed under Applicant&#39;s U.S. Provisional Patent Application No. 61/345,559. Then, the valve  386  is set to STANDBY. 
     It is important to note in this pressure prime procedure that the printhead wipe is performed before moving the valve  386  from the PULSE setting to the PRINT setting. This is to prevent the ink on the ejection face of the printhead being sucked into the nozzles due to the negative fluid pressure at the nozzles which is established when the accumulator tank is reconnected to the printhead via the print line portion  308   a  when the ink port of the valve  386  is opened. 
     The Applicant has found that the pressure priming can result in color mixing. The spitting of 5000 drops from each nozzle of the printhead has been found by the Applicant to sufficiently clear this color mixing. This spitting procedure equates to about 0.35 milliliters of ink being spat out by the entire printhead when the ejection drop size of each nozzle is about one picoliter. 
     When the printhead  200  is to be removed from the fluid distribution system  300 , long term storage of the printer  100  is desired or an empty supply tank is not replaced or refilled within a certain period (e.g., 24 hours), it is necessary to de-prime the printhead and the bypass line  384 . As illustrated in  FIG. 25 , in this de-prime procedure the valve  386  is first set to DEPRIME 1 and the pump is operated in the clockwise direction for 13 revolutions at 150 rpm to de-prime the bypass line  384  by allowing air to enter the bypass line  384  from the de-prime vent  390  which pushes the ink from the bypass line  384  into the accumulator tank via the pump line  382 . 
     Then, the valve  386  is set to DEPRIME 2 and the pump is operated in the clockwise direction for 29 revolutions at 150 rpm to de-prime the printhead, the print line portion  380   b  and the pump line  382  by allowing air to pass through the printhead from the de-prime vent  390  which pushes the ink from the print line portion  380   b , the printhead  200  and the pump line  382  into the accumulator tank so that the ink is moved into the pump line  382  to at least a leak safe location downstream of the pump relative to the printhead. Then, the valve  386  is set to NULL, which closes all ports of the valve  386  and thereby allows leak safe removal of the printhead or the like. 
     The above-described values for the pump operation in the various priming and de-priming procedures are approximate and other values are possible for carrying out the described procedures. Further, other procedures are possible and those described are exemplary. The levels of uncertainty in the described values, where appropriate, are shown in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 pump operation value ranges 
               
            
           
           
               
               
               
               
               
            
               
                 Procedure 
                 Pump Action 
                 RPM 
                 No. of Revs. 
                 Time 
               
               
                   
               
               
                 Power up prime 
                 prime bypass loop 
                 100 +/− 20 
                  88 +/− 8 
                 52.8 s 
               
               
                 Prime 
                 prime bypass line 
                 150 +/− 50 
                  42 +/− 4 
                 16.8 s 
               
               
                   
                 prime printhead 
                  60 +/− 50 
                  63 +/− 6 
                 25.2 s 
               
               
                 Bypass flush 
                 bubble flush  
                 150 +/− 50 
                 50 
                   20 s 
               
               
                   
                 bypass line 
                   
                   
                   
               
               
                 Printhead flush 
                 bubble flush the  
                 150 +/− 50 
                 100 +/− 50 
                   40 s 
               
               
                   
                 printhead 
                   
                   
                   
               
               
                 Dual flush 
                 bubble flush  
                 150 +/− 50 
                  50 +50/− 25 
                   20 s 
               
               
                   
                 printhead and  
                   
                   
                   
               
               
                   
                 bypass line 
                   
                   
                   
               
               
                 Pressure prime 
                 push ink out  
                 200 +/− 50 
                  2 +2/− 0 
                  0.8 s 
               
               
                   
                 through nozzles 
                   
                   
                   
               
               
                 De-prime 
                 de-prime bypass line 
                 150 +/− 50 
                  13 +/− 2 
                  5.2 s 
               
               
                   
                 de-prime printhead 
                 150 +/− 50 
                  29 +/− 3 
                 11.6 s 
               
               
                   
               
            
           
         
       
     
     The above discussion has been made in relation to a fluid distribution system for a single fluid channel, e.g., an ink of one color, arranged as shown in  FIG. 8 . In order to deliver more than one fluid to the printhead  200  or multiple printheads each printing one or more ink colors, the fluid distribution system  300  is replicated for each fluid. That is, separate supply tanks  302  and accumulator tanks  304  for each fluid are provided which are interconnected by an associated fluid line  308  with an air chimney  370  and are connected to the printhead  200  via an associated closed fluid path loop  348 . 
     Certain components of these separate systems can be configured to be shared. For example, the supply couplings  388 , the 4-way valve  386  and the pump  378  can each be configured as multiple fluid channel components, and a single or separate de-prime vents  390  can be used for the multi-channel 4-way valve  386 . An exemplary arrangement of these multiple fluid paths is illustrated in  FIGS. 6 and 7 . 
     For an exemplary printhead  200  having five ink flow channels, e.g., CYMKK or CYMKIR, as discussed above, the pump  378  is a five channel pump which independently pumps the ink in each channel. The structure and operation of such a multi-channel pump is understood by one of ordinary skill in the art. 
     Using the multi-channel 4-way valve  386  facilitates efficient manufacture and operation of this component. Exemplary structures of the multi-channel valve  386  are now described. 
       FIGS. 26A to 29C  illustrate an exemplary diaphragm multi-channel 4-way valve  386  (herein termed “diaphragm valve”) for use with the multi-channel fluid distribution system. 
     The diaphragm valve  386  has five port arrangements  396  in series along a frame  397  providing five fluid channels. Each port arrangement  396  has four ports  398 , respectively labelled  398 - 1 ,  398 - 2 ,  398 - 3  and  398 - 4 , associated with a corresponding chamber  400  defined in the frame. Each port  398  has opposite, connected ends, with an external end projecting from the chamber  400  and an internal end projecting into the chamber  400 . By this arrangement, the four ports  398  of each port arrangement  396  are in selective fluid communication (as detailed below) with one another via the corresponding chamber  400 . 
     The external ends of the ports  398 - 1 ,  398 - 2  and  398 - 3  are formed as tubing connectors for connection to the tubing of the closed loop  348 . In particular, the portion  380   a  of each print line  380  connects to the external end of the port  398 - 1  of the corresponding port arrangement  396 , the portion  380   b  of each print line  380  connects to the external end of the port  398 - 2  of the corresponding port arrangement  396 , and the bypass line  384  connects to the external end of the port  398 - 3  of the corresponding port arrangement  396 . 
     The vent line  392  of each (or a single) de-prime vent  390  connects to the external end of the port  398 - 4  of the corresponding port arrangement  396 . In the example illustrated in the drawings, five de-prime vents  390  are incorporated into the structure of the diaphragm valve itself, with each port arrangement  396  having an associated de-prime vent  390 . 
     Accordingly, the ports  398 - 1 ,  398 - 2 ,  398 - 3  and  398 - 4  respectively correspond to the previously described “ink”, “printhead”, “bypass” and “air” ports. 
     A single of the port arrangement  396  as sectioned from the other port arrangement  396  is illustrated in  FIG. 28 . The internal end of each port  398  cooperates with an associated seal  402 . The seals  402  are provided on corresponding resiliently flexible flaps  404  of a diaphragm pad  406 . The diaphragm pad  406  is mounted to the chamber  400  and a sealing film  408  is mounted thereon to fluidically seal the chamber  400 . The sealing film  308  is preferably a thin laminated film which is resiliently flexible. 
     The assembled frame  397  is supported within a body  410  of the diaphragm valve. A finger plate  410  is mounted within the diaphragm valve body to be located over the sealing film. The finger plate has cantilevered fingers  412  which each align with a corresponding one of the flaps  404  of each diaphragm pad through the sealing film. 
     This assembly therefore has the seals  402  spaced from the internal ends of the ports  398  and the fingers  412  spaced from the seals  402 . A cam member  416  is mounted within the diaphragm valve body to selectively act on protrusions  418  of each of the fingers  412  of the finger plate so as to cause relative movement of the fingers and flaps thereby closing these spaces and selectively sealing the ports  398 . The fluid flow between the ports  398  in each port arrangement depends upon which of the ports  398  are un-sealed and/or sealed. 
     The flaps  404  are preferably formed of titanium. However, other materials may be used provided they are inert to ink and able to allow the flaps to be either resiliently planar so as to be moved out of plane to seal and then spring back into plane to unseal or resiliently bent out of plane so as to be moved into plane to seal and then spring back out of plane to un-seal. 
     The fingers  412  are preferably formed of stainless steel and the seal  402  is preferably formed of rubber. The sealing film  408  preferably has four layers laminated together. The four layers in sequence are preferably formed of: polyethylene terephthalate (PET) for the outer layer facing the finger plate; vacuum deposited aluminium for the first inner layer; polypropylene for the next inner layer; and polypropylene for the outer layer facing the flaps. 
     The cam member  416  has a shaft  420  rotatably mounted to the diaphragm valve body and five cams  422  mounted on the cam shaft  420 . Each cam  422  has selection members in the form of four cams or discs  422 - 1 ,  422 - 2 ,  422 - 3  and  422 - 4  which have eccentric cam profiles whose eccentricity is offset from one another but aligned with the eccentric cam profiles of the corresponding discs of the other cams  422  for each ink flow channel, as illustrated in  FIG. 29A . The cams  422  may be molded with the discs integrally formed. The cam shaft  420  has a motor gear  424  mounted at one end and an encoder gear  426  mounted at the other end. The motor gear  424  couples with a motor  428  to be rotated in the direction of arrow A in  FIG. 29A , and the encoder gear  426  is part of an encoder  430  for sensing a rotated position of the cam shaft  420 . However, other sensing or operational arrangements for controlling the rotated position of the cam shaft  420  are possible. 
     The associated seals  402 , diaphragm pad  406 , sealing film  408 , finger plate  410 , cam member  416 , motor  428  and encoder  430  form a selection device for selecting the valve states detailed above by selectively sealing and unsealing the ink, printhead, bypass and air ports  398 - 1 ,  398 - 2 ,  398 - 3  and  398 - 4  through manipulation of the diaphragm pad  406 . 
     The encoder  430  has a structure well understood by one of ordinary skill in the art and outputs the sensing result to the control electronics  802  of the printer  100  so that operation of the motor  428  can be controlled by the control electronics  802  to select the necessary cam profiles of the cam member  416  for establishing a selected valve state. 
     The motor  428  is preferably a stepper motor with uni-directional operation so that the cam shaft  420  and the cams  422  are rotated in the one direction to effect the various port state changes. However, other arrangements are possible, such as a bi-directional motor which allows both clockwise and anti-clockwise rotation of the shaft  420 . 
     The operation states of this cam drive arrangement of the cam member  416  with respect to a single disc of one of the cams  422  are illustrated in  FIGS. 29B and 29C . 
     As illustrated in  FIG. 29B , when the cam profile of the disc  422  is not engaged with the protrusion  418  of the finger  412 , the finger  412  is spaced from the flap  404  and as such the seal  402  is not pressed into the port  398 . As illustrated in  FIG. 29C , when the cam profile of the disc  422  is rotated in the direction of arrow A to engage the protrusion  418  of the finger  412 , the finger  412  engages with the flap  404  which discretely deforms the diaphragm pad  406  at the seal  402  to urge the seal  402  into the port  398 . 
     The offsets of the cam profiles of the discs  422 - 1 ,  422 - 2 ,  422 - 3 ,  422 - 4  in each cam  422  are provided so that as the cams  422  are rotated by the cam drive arrangement each of the valve states of Table 1 can be simultaneously selected for the plural fluid channels. 
     In the illustrated embodiment, each port arrangement  396  has an independently formed diaphragm pad  406  and finger plate  410 , whilst the sealing film  408  is formed as a single member which is mounted to the frame  397  to cover all of the port arrangements  396 . However, other arrangements are possible in which the individual port arrangements are integrally formed and the individual finger plates are also integrally formed. 
       FIGS. 30A to 36  illustrate an exemplary rotary multi-channel 4-way valve  386  (herein termed “rotary valve”) for use with the multi-channel fluid distribution system. 
     The rotary valve  386  has five groups of ports or port arrangements  431  in series along a shaft  434 . Each port arrangement  431  has a port cylinder  435  concentrically enclose a selection member in the form of a channel cylinder  436  which is mounted on the shaft  434 . Each port cylinder  435  has four ports  432 , respectively labelled  432 - 1 ,  432 - 2 ,  432 - 3  and  432 - 4 , around along the circumference of the cylinder. Each port  432  has opposite, connected ends, with an external end projecting from the port cylinder  435  and an internal end opening into a channel  438  defined along the circumference of the channel cylinder  436 . By this arrangement, the four ports  432  of each port cylinder  435  are in selective fluid communication (as detailed below) with one another via the channel or chamber  438  of the corresponding channel cylinder  436 . 
     The external ends of the ports  432  are formed as tubing connectors for connection to the tubing of the closed loop  348 . In particular, the portion  380   a  of each print line  380  connects to the external end of the port  432 - 1  of the corresponding port arrangement  432 , the portion  380   b  of each print line  380  connects to the external end of the port  432 - 2  of the corresponding port arrangement  431 , the bypass line  384  connects to the external end of the port  432 - 3  of the corresponding port arrangement  432 , and the vent line  392  of each (or a single) de-prime vent  390  connects to the external end of the port  432 - 4  of the corresponding port arrangement  431 . 
     Accordingly, the ports  432 - 1 ,  432 - 2 ,  432 - 3  and  432 - 4  respectively correspond to the previously described “ink”, “printhead”, “bypass” and “air” ports. 
     Referring to the single port arrangement  431  illustrated in  FIGS. 32A to 34B , the port cylinder  435  has a housing  440  in which tubing connectors  442  of the external ends of the ports  432  are formed and a body  444  which is mounted within the housing  440  and in which apertures  446  are defined as the internal ends of the ports  432 . The body  444  is formed of a resilient material, such as elastomer, so that the assembled housing  440  and body  444  seal against one another. 
     The internal cylindrical surface of the body  444  has inner circumferential ridges  448  at either edge which contact the outer surface of the channel cylinder  436  (see  FIG. 35 ). Due to the resiliency of the body  444 , the ridges  448  act as O-ring seals between the port and channel cylinders thereby sealing the channel  438 . 
     The housing  440  of each of the port cylinders  435  has pins  450  and holes  452  on opposite sides of projections  454 . The pins  450  and the holes  452  are aligned with one another and are dimensioned so that the pins  450  fit within the holes  452 . When the port and channel cylinders are assembled onto the shaft  434 , the port cylinders are brought into contact with one another so that the pins  450  and the holes  452  of the adjacent port cylinders engage one another. End plates  456  and  458  are positioned over the shaft  434  at either end of the adjacently arranged port and channel cylinders. 
     The end plate  456  has pins  450  which engage the holes  452  of the adjacent end port cylinder and the other end plate  458  has holes  452  which engages the pins  450  of the adjacent end port cylinder. By this assembly, the series of independently sealed channels  438  in selective fluid communication with their associated ports  432  is provided, with the ports being fixedly mounted to the body channels. 
     The tubing connectors  442  of the ports  432  are connected with the tubing of the closed loop  348  within a housing  102  of the printer  100 . The rotary valve is mounted to the housing  102  so that in this connected state of the rotary valve, the end plates and the port cylinders, connected together by the engaged pins and holes, are held in place whilst the channel cylinders are free to rotate with the shaft  434 . 
     This is facilitated by providing the shaft  434  with a square spline section  434   a  which conforms with, and fits snugly into, an internal corresponding square spline form  455  of the channel cylinders  436 , whilst positioning the end plate  456  over a gap  434   b  in the square spline section  434   a  and positioning the end plate  458  beyond the square spline section  434   a , as illustrated in  FIGS. 31 and 32B . In the drawings, an E-clip is shown as holding the end plate  456  in position over the gap  434   b  and a bushing is shown as holding the end plate  458  in position beyond the square spline section  434   a , however other holding means are possible. 
     Rotation of the shaft  434  is provided through a cylinder drive arrangement  460 . The cylinder drive arrangement  460  has a motor coupling  462  mounted at one end of the shaft  434  and an encoder disc  464  mounted at the other end of the shaft  434 . The motor coupling  462  couples with a motor  466  to be rotated and the encoder disc  464  is part of an encoder  468  for sensing a rotated position of the shaft  434 . However, other sensing or operational arrangements for controlling the rotated position of the shaft  434  are possible. 
     The encoder  468  has a structure well understood by one of ordinary skill in the art and outputs the sensing result to the control electronics  802  of the printer  100  so that operation of the motor  466  can be controlled by the control electronics  802  to select predetermined rotated positions of the channel cylinders  436  for selecting the valve states of Table 1. The motor  466  is preferably a stepper motor with uni-directional operation so that the shaft  434  and channel cylinders  436  are rotated in the one direction to effect the various port state changes. However, other arrangements are possible, such as a bi-directional motor which allows both clockwise and anti-clockwise rotation of the shaft  434 . 
     The associated channel cylinders  436 , shaft  434 , motor  466  and encoder  468  form a selection device for selecting the valve states detailed above by selectively sealing and unsealing the ink, printhead, bypass and air ports  432 - 1 ,  432 - 2 ,  432 - 3  and  432 - 4  through rotation of the channel cylinders  436 . 
     This is achieved, by snugly and sealingly fitting the port cylinders  435  over the associated the channel cylinders  436  and by forming the channel  438  of each channel cylinder  436  with a serpentine form as shown in  FIGS. 34A and 34B  so that depending upon the rotated position of the channel cylinders  436  relative to the port cylinders  435  some or all of the ports  432  in the port cylinders are aligned with a straight portion of the serpentine form of the associated channels  438  thereby allowing fluid flow therebetween, and the other or all of the ports  432  are blocked by the portions of the associated channel cylinders  436  at which the channels  438  are not present. In this way, as the channel cylinders  436  are rotated by the cylinder drive arrangement  460  each of the valve states of Table 1 can be simultaneously selected for the plural fluid channels 
     In the illustrated embodiment, the ports and the straight portion of the serpentine form of the channels are arranged generally normal to the rotation direction of the channel cylinders on the shaft. Other arrangement are possible however, such as the ports being offset from each other and this normal direction and/or the channels being oblique relative this normal direction. 
     The use of the O-ring seals  448  between the port and channel cylinders eliminates the need to use lubrication materials, such as silicone, within the port arrangements  431  for providing the relative rotation between the port and channel cylinders. Accordingly, the amount of possible fluid contaminants within the fluid distribution system are reduced and compatibility with the fluids, such as ink, in the system is increased. 
     In the illustrated embodiment, individual port cylinders  435  are mounted over the individual channel cylinders  436  between the end plates  456 , 458 . However, other arrangements are possible in which the individual port cylinders are integrally formed as a port arrangement and the individual channel cylinders are also integrally formed as a channel arrangement. 
     The above described diaphragm and rotary multi-path valves provide simple and effective structures for the automatic selection of the valve states of Table 1. Different structures or different drive mechanisms for driving the above described structures are possible however, so long as selection of the various valve states is provided. 
     In the above described embodiment of the fluid distribution system  300  of  FIG. 8 , the use of the 4-way valve and bypass line in the closed fluid path loop  348  assists in maintaining fluid pressure differentials across the printhead  200 . However, the fluid distribution system can be configured so that fluid pressure differentials within tolerable levels can be obtained without use of the 4-way valve and bypass line. 
       FIG. 37  schematically illustrates an alternative embodiment of the fluid distribution system  300  for a single fluid, i.e., a single colored ink or other printing fluid, in which the bypass line and 4-way valve are omitted and an alternative valve arrangement is used. 
     In the embodiment of  FIG. 37  all components labelled with the same reference numbers as in  FIG. 8  are the same components described in relation to the embodiment of  FIG. 8 , including their material and dimensional selections. The embodiment of  FIG. 37  differs from the embodiment of  FIG. 8  only in that the valve  386  and the bypass line  384  are omitted and a multi-channel valve arrangement  470  is added. 
     The closed loop  348  of  FIG. 37  comprises the printhead loop  348   a  of the print fluid line  380  between the accumulator tank outlet  344  and the printhead  200  and the pump fluid line  382  between the printhead  200  and the accumulator tank priming port  346 . The valve arrangement  470  has a pinch valve  472  on the print line  380  and a check valve  474  which interconnects the de-prime vent  390  and print line. The vent line  392  of the de-prime vent  390  has one end connected to the check valve  474  and has the filter  394  disposed at the other end. 
     The state of the check valve  474  is controlled by the control electronics  802  of the printer  100  so that in the closed state of the check valve  474 , the vent line  392  is isolated from the print line  380 , and in the open state of the check valve  474 , air can enter the system  300  via the de-prime vent  390 . The check valve  474  has a structure and function well understood by one of ordinary skill in the art. A single check valve  474  can be provided for a single de-prime vent  390  in the system  300 , or if the system has multiple de-prime vents  390 , such as the five discussed earlier, a separate check valve  474  can be provided for each de-prime vent  390 . 
     The exemplary pinch valve  472  illustrated in  FIGS. 38A to 43B , like the 4-way valve  386 , is a multi-channel valve. The pinch valve  472  has five port or aperture groups  476 , respectively labelled  476 - 1 ,  476 - 2 ,  476 - 3 ,  476 - 4  and  476 - 5 , in series along a body or housing  478  providing five fluid channels when the tubing of the five print lines  380  are inserted through the respective aperture groups  476 . A pinch element  480  is disposed in the housing  478  extending across the aperture groups  476 . The pinch element  480  has a feature  482  configured to be brought into and out of contact with the print line tubing to selectively “pinch” the tubing and thereby selectively obstruct and allow fluid flow through the print lines, respectively. 
     In the illustrated example, the feature  482  has a semi-cylindrical form and a corresponding semi-cylindrical feature  482  of the housing  478  is aligned therewith. This provides a pinch zone on the tubing of two half-rounds, which minimizes the pinch force required to cease fluid flow through the pinched print lines (see  FIGS. 40A and 40B ). 
     The movement of the pinch element  480 , which effects this pinching contact, is provided by a pinch drive arrangement  484  disposed in the housing  478 . The pinch drive arrangement  484  has a shaft  486  rotatably mounted to the housing  478  on which two eccentric cams  488  are fixedly mounted in parallel, a plate  490  fixedly mounted to the housing  478 , springs  492  disposed between, and interconnecting, the pinch element  480  and the plate  490 , and an optical interrupt element  494 . The shaft  486  has a square spline section  487  which cooperates with an internal corresponding square spline form  489  of the cams  488  which conforms with, and fits snugly onto, the square spline section  487  of the shaft  486 . This cooperation ensures that the cams  488  are accurately rotated with rotation of the shaft  486 . 
     The springs  492  are configured to bias the pinch element  480  away from the securely mounted plate  490 . The springs  492  are preferably compression springs and there are preferably four springs symmetrically arranged about the pinch element and plate as illustrated in the drawings, but other arrangements are possible. 
     As illustrated in the cross-sectional views of  FIGS. 41A and 41B , the shaft  486  passes through a channel  480   a  in the pinch element  480  so as to be located within the pinch element  480  and between the aperture groups  476  and the springs  492 . One each of the two cams  488  is mounted at either longitudinal end of the shaft  486  so as to be located within a recess  480   b  on opposite sides of the pinch element  480 . The pinch element  480  has engagement faces  480   c  within the recesses  480   b  which are aligned with, and selectively engage, the cams  488  due to the eccentricity of the cams  488  and the biasing of the springs  492 . 
     When the pinch valve  472  is in the open (non-pinched) state, the feature  482  of the housing  478  is not in the pinch zone so that no obstruction of the print line tubing is made. The open state is provided by rotating the shaft  486  so that the cams  488  engage the engagement faces  480   a  of the pinch element  480  and force the pinch element  480  toward the plate  490  against the bias of the springs  492 , as illustrated in  FIGS. 40A and 41A . 
     When the pinch valve  472  is in the closed (pinched) state, the feature  482  of the housing  478  is in the pinch zone so that the print line tubing is obstructed. The closed state is provided by rotating the shaft  486  so that the cams  488  disengage the engagement faces  480   a  of the pinch element  480  thereby allowing the pinch element  480  to be forced away from the plate  490  with the bias of the springs  492  and into contact with the print line tubing, as illustrated in  FIGS. 40B and 41B . 
     This arrangement of the cams  488  contacting the engagement faces  480   c  of the pinch element  480  directly in the closed state of the pinch valve  472  is illustrated in isolation in  FIG. 42A . Similar operation is provided by arranging roller bearings  480   d  in the engagement faces  480   c  of the pinch element  480 . One roller bearing  480   d  is illustrated in  FIG. 42B . These roller bearings  480   d  contact the cams  488  in the closed state of the pinch valve  472  and facilitate smooth rolling of the cams  488  during the rotation of the shaft  486 . 
     The pinch drive arrangement  484  further has a motor  496  which is coupled at one end of the shaft  486  by a motor coupling  498  to provide the rotation of the shaft  486 . The motor coupling  497  is provided with a projection  498   a  with which the optical interrupt element  494  cooperates to sense a rotated position of the shaft  486 . 
     In particular, the projection  498   a  is preferably a half-circular disc dimensioned to pass between an optical emitter and optical sensor of the optical interrupt element  494 , and the optical interrupt element  494  is disposed as illustrated in  FIGS. 43A and 43B  so that when the pinch valve  472  is open the projection  498   a  does not obstruct the emitter and sensor of the optical interrupt element  494  (see  FIG. 43A ) and when the pinch valve  472  is closed the projection  498   a  obstructs the emitter and sensor of the optical interrupt element  494 . However, other sensing or operational arrangements for controlling the rotated position of the shaft  486  are possible. 
     The pinch element  480  and pinch drive arrangement  484  form a selection device for selecting the valve states detailed below by selectively closing and opening the pinch valve. 
     The optical interrupt element  494  has a structure well understood by one of ordinary skill in the art and outputs the sensing result to the control electronics  802  of the printer  100  so that operation of the motor  496  can be controlled by the control electronics  802  to select predetermined rotated positions of the cams  488  for selecting the pinch valve states of Table 3. The motor  496  is preferably a stepper motor with uni-directional operation so that the shaft  486  and cams  488  are rotated in the one direction to effect movement of the pinch element  480  relative to the plate  490  and print line tubing. However, other arrangements are possible, such as a bi-directional motor which allows both clockwise and anti-clockwise rotation of the shaft  486 . 
     In the above described embodiment of the pinch valve, the housing  478 , pinch element  480 , plate  490  and motor coupling  498  are each preferably formed of a plastics material, such as 20% glass fibre reinforced acrylonitrile butadiene styrene (ABS) for the housing and plate, Acetal copolymer for the pinch element, and 30% glass fibre reinforced ABS for the motor coupling. Further, the cam shaft  486  and cams  488  are preferably formed of a metal, such as aluminium. 
     The states of the check and pinch valves of the valve arrangement  470  are shown in Table 3. In Table 3, an “X” indicates that the associated state is selected and a blank indicates that the associated state is not selected. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 pinch and check valve states 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 PINCH VALVE 
                 CHECK VALVE 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 STATE 
                 Open 
                 closed 
                 open 
                 closed 
               
               
                   
               
               
                   
                 PRIME 
                 X 
                   
                   
                 X 
               
               
                   
                 PRINT 
                 X 
                   
                   
                 X 
               
               
                   
                 FLUSH 
                 X 
                   
                   
                 X 
               
               
                   
                 STANDBY 
                 X 
                   
                   
                 X 
               
               
                   
                 PULSE 
                   
                 X 
                   
                 X 
               
               
                   
                 NULL 
                   
                 X 
                   
                 X 
               
               
                   
                 DEPRIME 
                   
                 X 
                 X 
               
               
                   
               
            
           
         
       
     
     The manner in which these state settings of the valve arrangement  470  are used is now discussed with respect to the schematic outlay illustrated in  FIG. 37 . 
     At the first power up of the printer  100  and at times subsequent to first power up when priming is required, the fluid distribution system  300  is primed, air in the printhead  200  is displaced to the accumulator tank via the priming port  346 , and it is ensured that the pump  378  is fully wetted prior to beginning any further volumetric pumping procedures. As is illustrated in  FIG. 44 , in this priming procedure the valves  472  and  474  are set to PRIME and the pump is operated in the clockwise direction for 88 revolutions at 100 rpm so that ink is moved from the accumulator tank outlet  344  to the accumulator tank priming port  346  via the print line  380 , printhead  200  and pump line  382  priming the closed loop  348 . Then, the valves  472  and  474  are set to STANDBY. 
     When printing is to be carried out, the valves  472  and  474  are set to PRINT and ejection of ink from the nozzles causes ink flow from the accumulator tank to the printhead via the print line  380 . After printing, the valves  472  and  474  are set to STANDBY. 
     At times it is necessary to recover the printhead from mild dehydration of ink at the nozzles as well to flush back channel gas bubbles from the printhead. As is illustrated in  FIG. 45 , in this printhead flush procedure the valves  472  and  474  are set to FLUSH and the pump is operated in the clockwise direction for 100 revolutions at 150 rpm to move fresh ink into the printhead and to move any gas bubbles to the accumulator tank via the priming port  346 . Then, the valves  472  and  474  are set to STANDBY. 
     At times it is necessary to recover the printhead from heavy dehydration and/or remove air bubbles trapped within the fine ink delivery structure of the printhead  200  by priming the printhead at increased fluid pressure. As illustrated in  FIG. 46 , in this pressure prime procedure the valves  472  and  474  are first set to PULSE and the pump is operated in the anticlockwise direction for 2 revolutions at 200 rpm to cause ink to be egested from the nozzles of the printhead. Then, the maintenance system  600  is operated to wipe the ejection face of the printhead so as to remove the egested ink, as described in the incorporated description of the co-filed US provisional patent application filed under Applicant&#39;s U.S. Provisional Patent Application No. 61/345,559. Then, the valves  472  and  474  are set to PRINT and the printhead is operated so that each nozzle ejects  5000  drops. This “spitting” operation of the printhead is carried out in relation to an absorber of the maintenance system  600 , described in the incorporated description of the co-filed US provisional patent application filed under Applicant&#39;s U.S. Provisional Patent Application No. 61/345,559. Then, the valves  472  and  474  are set to STANDBY. 
     It is important to note in this pressure prime procedure that the printhead wipe is performed before moving the valves  472  and  474  from the PULSE setting to the PRINT setting. This is to prevent the ink on the ejection face of the printhead being sucked into the nozzles due to the negative fluid pressure at the nozzles which is established when the accumulator tank is reconnected to the printhead via the printhead loop  348   a  when the valve  472  is opened. 
     The Applicant has found that the pressure priming can result in color mixing. The spitting of 5000 drops from each nozzle of the printhead has been found by the Applicant to sufficiently clear this color mixing. This spitting procedure equates to about 0.35 milliliters of ink being spat out by the entire printhead when the ejection drop size of each nozzle is about one picoliter. 
     When the printhead  200  is to be removed from the fluid distribution system  300 , long term storage of the printer  100  is desired or an empty supply tank is not replaced or refilled within a certain period (e.g., 24 hours), it is necessary to de-prime the printhead. As illustrated in  FIG. 47 , in this de-prime procedure the valves  472  and  474  are set to DEPRIME and the pump is operated in the clockwise direction for 29 revolutions at 150 rpm to de-prime the print line  380 , printhead  200  and pump line  382  by allowing air to pass through the printhead from the de-prime vent  390  which pushes the ink from the print line  380 , the printhead and the pump line  382  into the accumulator tank so that the ink is moved into the pump line  382  to at least a leak safe location downstream of the pump relative to the printhead. Then, the valves  472  and  474  are set to NULL, which closes the valves  472  and  474  and thereby allows leak safe removal of the printhead or the like. 
     The above described values for the pump operation in the various priming and de-priming procedures are approximate and other values are possible for carrying out the described procedures. Further, other procedures are possible and those described are exemplary. The levels of uncertainty in the described values, where appropriate, are shown in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 pump operation value ranges 
               
            
           
           
               
               
               
               
               
            
               
                 Procedure 
                 Pump Action 
                 RPM 
                 No. of Revs. 
                 Time 
               
               
                   
               
               
                 (Power up) prime 
                 prime printhead 
                 100 +/− 20 
                  88 +/− 8 
                 52.8 s 
               
               
                 Printhead flush 
                 bubble flush  
                 150 +/− 50 
                 100 +/− 50 
                   40 s 
               
               
                   
                 the printhead 
                   
                   
                   
               
               
                 Pressure prime 
                 push ink out  
                 200 +/− 50 
                  2 +2/− 0 
                  0.8 s 
               
               
                   
                 through nozzles 
                   
                   
                   
               
               
                 De-prime 
                 de-prime 
                 150 +/− 50 
                  29 +/− 3 
                 11.6 s 
               
               
                   
                 printhead 
               
               
                   
               
            
           
         
       
     
     The above described de-prime procedures of the multi-path valve clears the printhead of ink with about 1.8 milliliters of ink being left in the printhead, which was determined by the Applicant through relative weight measures of the printhead prior to first priming and after de-priming. This is considered the dry-weight of the printhead. 
     The described diaphragm and rotary valves and the pinch valve arrangement for the fluid distribution system are exemplary, and other alternative arrangements are possible to provide selective fluid communication within the closed fluid loop of the system, such as the dual pinch valve arrangement described in the Applicant&#39;s U.S. Provisional Patent Application No. 61/345,572, the entire contents of which is hereby incorporated by reference. 
     Some requirements for the functional attributes of the valve arrangement for ink distribution and air intake that are met by the described diaphragm and rotary valves and the pinch valve arrangement, and which should be met by any alternative arrangement, are shown in Table 5. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 valve specification requirements 
               
            
           
           
               
               
               
            
               
                 ITEM 
                 SPECIFICATION 
                 NOTE 
               
               
                   
               
               
                 pressure loss at  
                 less than 10 mm at 
                 allowable flow loss of ink 
               
               
                 max flow rate 
                 15 mL/min per channel 
                 flowing through the valve 
               
               
                   
                   
                 in open condition 
               
               
                 ink leak rate @  
                 0.1 cc/min @ 10 psi 
                 leak rate of ink across the 
               
               
                 pressure 
                   
                 ink sealing surfaces 
               
               
                 air leak rate 
                 0.05 cc/day 
                 air leak rate into the ink 
               
               
                   
                   
                 lines 
               
               
                 life 
                 50000 cycles over  
                   
               
               
                   
                 three years 
                   
               
               
                 physical size 
                 50 × 42 × 100 mm 
                 envelope to fit the five 
               
               
                   
                   
                 valve assembly and drive 
               
               
                   
                   
                 components 
               
               
                 burst pressure 
                 150 KPa (22 psi) 
                 maximum pressure valve 
               
               
                   
                   
                 can survive 
               
               
                 trapped air 
                 less than 0.05 cc of  
                 amount of air allowed in 
               
               
                   
                 air per channel 
                 the ink path of the valve 
               
               
                   
                   
                 after priming 
               
               
                 barb size of tubing 
                 3.18 mm 
                   
               
               
                 connectors 
                   
                   
               
               
                 valve actuation 
                 automatically actuated 
                 requires motor 
               
               
                   
                 with feedback for  
                 transmission and 
               
               
                   
                 valve states 
                 sensor/encoder 
               
               
                 transition time 
                 two seconds to change 
                   
               
               
                   
                 from standby state to  
                   
               
               
                   
                 print state 
               
               
                   
               
            
           
         
       
     
     As discussed above, upon depletion, the supply tanks  302  are disconnected from the system  300  at the coupling  306 , either replaced or refilled either in situ or remote from the system  300 , and then reconnected to the system  300  via the coupling  306 . 
     In the exemplary supply tank  302  illustrated in  FIGS. 48 to 51 , refilling of the supply tank  302  is provided by connecting a refill port  500  through an upper surface of a body  302   a  of the supply tank  302  with a refilling station or the like. For example, the refill port  500  may comprise a ball valve  502 , as illustrated in  FIGS. 49 and 50 , or other valve arrangement, which is actuated to open by the refilling station and refilling is carried out under gravity. 
     The lower surface of the supply tank body  302   a  incorporates an outlet coupling  504  as an outlet from the tank body  302   a , which constitutes the aforementioned supply side of the coupling  306 . When the supply tank  302  is installed in the printer  100 , the outlet coupling  504  is coupled with the aforementioned delivery side of the coupling  306  so as to be in fluid communication with the fluid line  308 . Ink from the supply tank  302  is drawn into the fluid line  308  under gravity. This is facilitated by an air chimney  506  in the supply tank body  302   a  which is open to atmosphere, thereby allowing air to enter the supply tank  302 . The air chimney  506  is closed to atmosphere prior to installation of the supply tank  302  in the printer  100  in order to prevent leakage of ink from the tank and potential ink drying. Different exemplary arrangements of the air chimney  506  are illustrated in  FIGS. 50 and 51 . 
     In the example of  FIG. 50 , the air chimney  506  is located in the upper surface of the supply tank body  302   a  and vents to atmosphere from the interior fluid containing space of the supply tank body  302   a  via a tortuous liquid path  508  which allows air to enter the supply tank  302  whilst discouraging liquid ink to pass through the air chimney  506 . The path  508  may be provided as an aperture through the upper surface of the supply tank body  302   a  having a serpentine channel between a gas vent in the interior wall of the body and a gas vent  512  in the external wall of the body. 
     The path  508 , and therefore the air chimney  506 , is closed to atmosphere by an air impervious film  510  covering the vent  512  of the air chimney  506 . The film  510  may, for example, be adhesively attached to the upper surface of the supply tank, and is piercable by a pin  104  or like member incorporated in a cover  106  of a receiving bay  107  for the supply tank of the printer  100  to open the air chimney  506  to atmosphere upon installation of the supply tank in the printer  100 . Upon refilling of the ink supply tank  302  of  FIG. 50 , a complete film  510  may be replaced over the vent  512  at the refill station. 
     In the example of  FIG. 51 , the air chimney  506  is defined by a mechanically actuated valve  514 . The valve  514  has a movable body  516  which is biased by a spring  518  so that a seal portion  516   a  of the movable body  516  sealingly rests against a seat  520  to position the valve  514  in a normally closed position. An end portion  516   b  of the movable body  516  is exposed at a gas vent  521  on the body  302   a  through which the end portion  516   b  engages with an actuation feature (not shown) in the receiving bay of the printer  100  upon installation of the supply tank in the printer  100 . This engagement causes the movable body  516  to be urged against the bias of the spring  518  which de-seats the seal portion  516   a  from the seat  520  thereby opening the valve  514  and opening the interior of the supply tank  302  to atmosphere via the gas vent  521  and an aperture  522  within the supply tank. 
     During refilling, determination of when the supply tank  302  has reached its full state can be provided in a number of ways. By “full state” it is meant that the supply tank contains liquid to a predetermined capacity. For example, a measured amount of ink or other printing fluid can be refilled into the supply tank consistent with the supply tank capacity. However, some ink may remain in the supply tank upon depletion, and the amount of this remaining ink is difficult to determine. Thus, refilling such measured amounts may result in some ink being egested from the supply tank during refilling, which is a waste of ink. 
     Alternatively, the full state can be sensed within the supply tank. This can be achieved by internalising a member within the supply tank which causes a change in fluid pressure at the refill port when the full state is reached. This pressure change can be sensed by a sensing arrangement SA (see  FIG. 52 ) thereby providing a means to detect the full state. Alternative exemplary arrangements of such a fluid pressure changing member are illustrated in  FIGS. 50 and 51 . 
     In the arrangement of  FIG. 50 , a hydrophobic film  524  is positioned at an aperture of the path  508  within the interior of the supply tank  302 . The hydrophobic material of the film  524  is selected so as to allow gas transit whilst preventing ink entering the path  508 . A suitable hydrophobic material is expanded polytetrafluoroethylene. 
     The Applicant has found that the hydrophobic nature of the film  524  causes a change in the fluid pressure within the supply tank when the ink or other liquid being refilled into the supply tank  302  via the refill port  500  comes into contact with the underside of the film  524  as the ink fills the supply tank from its lower to upper surfaces. This pressure change is a pressure spike caused by a sudden increase in back pressure experienced at the refill port  500 . This change in back pressure can be easily detected by a sensing arrangement in a manner well understood by those skilled in the art and used as a determination that the full state of the supply tank  302  has been reached. 
     In the alternative arrangement of  FIG. 51 , a protrusion  526  from the movable body  516  is located within the aperture  522  so as to provide a small restriction within a chamber  528  below the seat  520  and movable body  516 . This small restriction, of the order of millimeters, results in a change in the fluid pressure within the supply tank when the ink or other liquid being refilled into the supply tank  302  via the refill port  500  comes into contact with the aperture  522  as the ink fills the supply tank from its lower to upper surfaces. This pressure change is a pressure spike caused by a sudden increase in back pressure experienced at the refill port  500 . This change in back pressure can be easily detected in a manner well understood by those skilled in the art and used as a determination that the full state of the supply tank  302  has been reached. Movement of the protrusion  526  as the movable body  516  is moved assists in clearing the aperture  522  of any dried ink, thereby enhancing the reliability of the full state detection provided by the valve  514 . 
     An exemplary system for sensing the pressure changes provided by the above described embodiments is illustrated in  FIG. 52 . In this exemplary system, a refilling station RS as a liquid delivery apparatus is connected to the refill port  500  of the supply tank  302  to refill liquid  530  into the supply tank  302  such that the liquid  530  fills the supply tank  302  in the direction of arrow B. The sensing arrangement SA is connected to a fluid line  532  between the refilling station RS and the supply tank  302 . The sensing arrangement SA is configured to monitor the fluid pressure within the fluid line. As discussed above, once the liquid  530  contacts pressure changing member  534  a change in fluid pressure occurs in the fluid line  532  which is detected by the sensing arrangement SA. 
     The amount of pressure change at which the full state has been actually reached can be measured experimentally and quantified as a predetermined pressure change. Accordingly, the fluid pressure can be monitored for this predetermined pressure change and supply of the refilling liquid can be ceased by closing a valve V or the like on the fluid line  532  when the predetermined pressure change is detected. This reduces false full state detection caused by unrelated pressure spikes due to normal or anomalous fluctuations in the fluid pressure during refilling. 
     The above-described embodiments of the supply tank  302  illustrate a supply tank for connection to a single fluid line  308  thereby supplying ink of a single color to the connected fluid line  308 . Accordingly, to provide the five fluid channels of the illustrated embodiment of the printhead  200 , five of the supply tanks  302  are provided. Alternatively, in applications where one or more of the ink channels provides the same ink color, e.g., CYMKK, it is possible to configure the respective supply tank  302  for the repeated ink color channels as a double or two-channel supply tank. Such an alternative configuration is illustrated in  FIGS. 6 and 7 . 
     The double supply tank  302  has the same configuration as the single supply tank  302  with respect to having a single refill port  500  and air chimney  506 , and associated components, however either a single outlet coupling  504  can be provided for connection to a single fluid line  308  which connects to two of the accumulator tanks  304  or two outlet couplings  504  can be provided for connection to two fluid lines  308  which connects to two of the accumulator tanks  304 . 
     As discussed above, the supply couplings  388  couple with the printhead  200  on both the print and pump line sides to connect the printhead  200  within the fluid distribution system  300 . The supply couplings  388  are configured to couple with the inlet and outlet printhead couplings  224 , 226  of the printhead  200  as illustrated in  FIGS. 53A-57E . 
     The supply coupling  388  has ports  536  which receive the inlet and outlet spouts  236 , 238  of the printhead  200 . Five of the ports  536  are shown in the illustrated embodiment of the supply coupling  388  to provide for the aforementioned five ink channels. The ports  536  are connected to the either the print lines  380  or the pump lines  382  depending on the respective side of the printhead  200  and the respective ink colour being distributed. 
     In order to ensure reliable sealed connections between the various components, the supply couplings  388  and their ports  536  are assembled from the minimum number of parts possible. Accordingly, in the illustrated embodiment, each of the ports  536  have four assembled parts: a port plate  538 , a seal member  540 , a housing  542  and a retainer  544 . In the coupling assembly, the port plate  538 , seal member  540  and retainer  544  are mounted to the housing  542  in a non-fastened manner, as explained below, which again reduces the number of assembled parts. 
     The seal member  540  is formed as a ring which is received in a recess  546  of the housing  542 , and the port plate  538  is mounted thereover so that sealed printhead ports  536   a  are formed for receiving the spouts  236 , 238  of the printhead  200 . 
     The housing recess has apertures  546  which project into the housing to form apertured pins  546   a . The retainer  544  is received within the housing by holes  548  in the retainer  544  being received over the pins  546   a  so that sealed distribution ports  536   b  are formed for receiving the tubing of the fluid lines of the closed loop  348  (i.e., the print and pump lines  380 , 382 ). The circumferential edge of the retainer  544  is formed as a rim  550  having cylindrical details  552 . The retainer  544  is formed from resiliently flexible material, such as being molded from rubber, so that the rim  550  is resiliently received within a groove or slot  554  in an interior wall  542   a  of the housing  542  and the details  552  engage with slots  556  formed across the circular slot  554 . This arrangement allows the retainer to be mounted to the housing in a self-fastening manner, however screws or the like could alternatively be used for this purpose. 
     The resiliency of the retainer  544  serves not only to provide mounting of the retainer  544  in the housing  542  but also to frictionally and sealingly hold the tubing of the fluid lines of the closed loop  348  in engagement over the apertured pins  546   a . The level of resilient hold provided by the retainer  544  is selected to resist fluid leakage, tube pressure blow-off and accidental pulling-off of the tubing. Other configurations are possible to assist in retaining the tubing such as clipping and crimping arrangements. 
     The seal ring  540  has a seal portion  540   a  for each fluid channel joined together by linking portions  540   b . This simplifies assembly and manufacture of the seal ring as the seal and linking portions can be integrally molded from a resilient, compressible material which is inert to ink, such as rubber, and also ensures that the seal portions of each seal ring are from the same manufactured batch such that the relative sizes and thickness are uniform across the seals. As illustrated, the seal portions  540   a  are circular and the linking portions  540   b  define arcs between the respective seal portions  540   a  about the seal ring  540 . 
     The apertures  546  of the housing  542  are provided with circular recesses  546   b  into which the circular seal portions  540   a  are received and with curved recesses  546   c  between the circular recesses  546   a  into which the curved linking portions  540   b  are received. This arrangement is illustrated in  FIG. 55  and assists in providing a seal at the printhead side of the coupling  388 . As shown, slots  558  are further provided across the curved recesses  546   c  which serve to capture and wick away any fluid which may leak from the apertures  546 , thereby reducing the possibility of cross-contamination of fluids between the individual fluid channels. 
     The port plate  538  has holes  560  through which the spouts  236 , 238  of the printhead  200  pass. Alignment of the holes  560  and the apertures  546  is facilitated by bosses  538   a  on the port plate  538  being received in between the adjacent peripheries of the apertures  546 , as illustrated in  FIG. 53B . 
     The holes  560  are provided with circumferential rims  560   a  which are configured to compress the seal portions  540   a  of the seal ring  540  when pressed thereagainst, which provides a complete seal against the outer surfaces of the spouts  236 , 238 . Accordingly, the coupling  388  is required to press against the inlet and outlet manifolds  230 , 232  of the inlet and outlet couplings  224 , 226  of the printhead  200  to provide this pressing action. 
     For example, this releasable pressing engagement could be achieved by clipping the couplings together in a manner well understood by one of ordinary skill in the art. Alternatively, in the illustrated embodiment, a coupling drive mechanism  562  is used to provide the necessary releasable pressing engagement, as described below. 
     In the illustrated embodiment, the apertures  546  are radially arranged about a central hole  564  in the housing  542  so as to coincide with the radially arranged spouts  236 , 238  of the printhead  200 . The central hole  564  receives an apertured projection  566  in the port plate  538  about which the holes  560  are similarly radially arranged. A shaft  568  is received within an aperture  566   a  of the projection  566  so that a distal end  568   a  of the shaft  568  projects from the aperture  566   a  on the printhead side of the port plate  538 . On this printhead side, a circular recess  538   b  is formed in the port plate  538  about the aperture  566   a  for receiving a washer or ring  570  which is pressed fitted onto the distal end  568   a  of the shaft  568 . 
     The distal end  568   a  is a reduced section of a cylindrical portion  568   b  of the shaft  568  which is configured to receive the ring  570 . The ring  570  is formed as a groove-less metal ring, which strengthens and simplifies the press-on mounting on the shaft  568 . In this regard, the shaft  568  is preferably formed from die-cast metal so that the shaft withstands the notch load from the groove-less ring. Alternative arrangements to the press-on ring for mounting the shaft can be used, such as screws or other fasteners. 
     A compression spring  572  is positioned on the cylindrical portion  568   b  of the shaft  568  and is compressed between the ring  570  and the projection  566  of the port plate  538 . The projection  566  is contacted by a hub  568   c  of the shaft  568  under this compression so as to retain the port plate  538  on the housing  542  in a non-fastened manner. Pins  568   d  projecting from two, opposite sides of the hub  568   c  mount an arm  574  to the shaft  568 . The arm  574  has two pairs of beams  576  and  578  interconnected by a bridge portion  577 . The pair of beams  576  have holes  576   a  at their distal ends relative to the bridge  577  which are configured to snap fit onto the pins  568   d  of the shaft  568 . This arrangement eliminates the need for E-clips or other fastening means, which reduces potential de-linkage of the arm  574  from the shaft  568 . The arm  574  projects through a hole  579  in the retainer  544 . 
     The arm  574  is used as a ‘conrod’ between the port plate  538  and the coupling drive mechanism  562  so that the supply coupling  388  is effectively driven as a piston into sealed engagement with the printhead  200 . This is achieved in the manner illustrated in  FIGS. 57A-57E , as described below. 
     As illustrated in  FIGS. 56A and 56B , the coupling drive mechanism  562  has a housing  580  in which the supply couplings  388  are housed. The housing  580  has generally cylindrical sockets  582  into which the generally cylindrical supply couplings  388  are positioned so that the port plates  538  are exposed for engagement with the respective couplings  224 , 226  of the printhead  200  and so that the second pair of beams  578  of the arm  574  project into the housing  580 . In  FIGS. 57A-57E , one of the sockets is illustrated with the respective supply coupling received therein, however it is understood that the coupling drive mechanism is used to simultaneously drive the supply couplings into engagement with the corresponding printhead couplings. 
     The beams  578  of the arm  574  engage with a cam arm  584  provided on a rod  586  which is rotationally mounted within the socket  582 . The beams  578  have holes  578   a  at their distal ends relative to the bridge  577  which snap fit onto pins  584   a  of the cam arm  584 . in this way, the arm  574  is pivotally connected to both the cam arm  584  and the shaft  568  via the respective pin and hole arrangements. 
     The rod  586  is rotationally driven by a cam mechanism  587  upon rotation of a lever  580   a  rotationally mounted to the housing  580  so as to rotate the cam arm  584  and thereby move the supply coupling  388  within the socket  582  from a fully retracted position relative to the printhead  200  to an engagement position at which the ports  536  supply coupling  388  engage and seal with the spouts  236 , 238  of the printhead  200 . 
       FIG. 57A  illustrates a cross-sectional view of the supply coupling  388  at the fully retracted position.  FIGS. 57B and 57C  illustrates a cross-sectional view of the supply coupling  388  at a partly retracted position.  FIGS. 57D and 57E  illustrate alternative cross-sectional views of the supply coupling  388  at the engagement position. The hole  579  of the retainer  544  is configured so that full, unobstructed motion of the arm  574  and the cam arm  584  throughout these operative positions is provided. 
     At the engagement position, the circumferential rims  560   a  of the holes  560  in the port plate  538  compress the seal portions  540   a  of the seal ring  540  against the outer surfaces of the spouts  236 , 238 , as described earlier. The pre-compression of the spring  572  between the ring  570  and the hub  568   c  of the shaft  568  causes the arm  574  to move along a constrained path with the cam arm  584  rotating through a fixed angle. This constrained movement means that the supply coupling is driven into the engagement position by the coupling drive mechanism without over-stressing the cam features, including the arm beams, cam arm, cam rod or cam mechanism which are typically molded and/or assembled from plastics materials, such as a crystalline thermoplastic, like 25% glass fibre reinforced Acetal copolymer (POM), which could otherwise cause failure of sealed engagement between the couplings of the fluid distribution system  300  and the printhead  200 . 
     Additional protection against over-stressing of the arm  574  is provided by tapering the beams  576  in the vicinity of the bridge  577 , i.e., at point A illustrated in  FIG. 58 , which provides more uniform stress through the beams  576 , by forming the distal ends of the beams  576  relative to the bridge  577 , i.e., at point B illustrated in  FIG. 58 , with walls thicker than the rest of the beams  576  to strengthen weld lines and provide a relatively large surface area for mating with the shaft  568 , and by forming the interconnection of the bridge  577  and the beams  578 , i.e., at point C illustrated in  FIG. 58 , with relatively large bends to eliminate stress risers, provide uniform walls and better mold flow during molding of the arm  574 . 
     Alternative configurations of the arm to those described and illustrated are possible, as too are alternative coupling drive mechanisms, so long as constrained movement of the supply couplings into and out of engagement with the coupling of the printhead is provided. 
     As illustrated in  FIGS. 57C and 57E , slots  588  within the socket  582  receive wings  590  on two, opposite sides of the supply coupling  388 . This slotted engagement provides proper alignment between the ports  536  of the supply couplings  388  and the spouts  236 , 238  of the couplings  224 , 226  of the printhead  200 . The wings  590  are formed as cantilevered leaf springs which flex within the slots  588  to provide stability in this alignment throughout movement of the supply coupling  388 . In the illustrated embodiment, two wings are provided on two sides of the supply coupling, however fewer or more wings can be provided on fewer or more sides of each coupling so long as stable movement of the couplings is achieved. 
     While the present invention has been illustrated and described with reference to exemplary embodiments thereof, various modifications will be apparent to and might readily be made by those skilled in the art without departing from the scope and spirit of the present invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but, rather, that the claims be broadly construed.