Abstract:
A fluid pathway is configured to selectively fluidically couple a printing fluid supply container to a printhead. The pathway includes a fail safe valve that that is configured to open as a result of movement of a moveable carriage and to thereafter remain open based on the availability of an electrical power signal.

Description:
RELATED PATENT APPLICATIONS 
   This patent application is related to U.S. patent application Ser. No. 11/261,681 titled “Fluid Delivery System For Printing Device”, filed Oct. 28, 2005. 
   This patent application is related to U.S. patent application Ser. No. 11/261,680 titled “Free Flow Fluid Delivery System For Printing Device”, filed Oct. 28, 2005. 
   This patent application is related to U.S. patent application Ser. No. 11/261,679, titled “Free Flow Fluid Delivery System For Printing Device”, filed Oct. 28, 2005. 
   BACKGROUND 
   Some printing devices include a printhead or pen that is configured to controllably direct drops of ink(s) or other like printing fluid(s) towards a sheet of paper or other like print medium. The inks or printing fluids are typically supplied by to the printhead by a fluid delivery system. Some fluid delivery systems are located “on-axis” with the printhead while others also include “off-axis” components. The fluid delivery system may include, for example, one or more containers that act as reservoirs to supply the fluids to the printhead through one or more fluidic channels. 
   In certain printing devices, the fluid delivery system is configured to maintain a backpressure force on the printing fluid so as to prevent the printing fluid from simply draining out through the ejection nozzles of the printhead. Accordingly, as the printing fluid is ejected during printing the fluid delivery system is usually configured to adapt to the reduced volume of printing fluid in some manner so as to maintain the backpressure force within applicable limits. For example, some fluid delivery systems include foam or other like capillary members within an on-axis container. The foam acts like a sponge in holding the printing fluid while also allowing the fluid to be used for printing. The capillary action of the foam provides the backpressure force. As the printing fluid is consumed air is allowed to enter into the container and into the foam. 
   In other exemplary printing devices, the printing fluid is delivered from on-axis and/or off-axis containers that do not include foam. Some of these containers include a bag-accumulator arrangement or the like that provides the desired backpressure force. Some of these containers include a bubbler feature that is configured to allow air to bubble into the container through the printing fluid to maintain the desired backpressure force. Some off-axis implementations also include additional containers adjacent the printhead. 
   In some implementations, a pump may also be provided to move the printing fluid in one or both directions between the container and the printhead. 
   There is a need for methods and apparatuses that can control the flow of printing fluid between the container and the printhead during certain instances. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following detailed description refers to the accompanying figures. 
       FIG. 1  is a block diagram illustrating certain features of a printing device including a fluid delivery system having a container and a fail safe valve, in accordance with certain exemplary implementations. 
       FIGS. 2A-B  are cross-sectional diagrams illustrating a portion of a fluid delivery system having a fail safe valve, in accordance with certain exemplary implementations. 
       FIGS. 3A-C  are block diagrams illustrating the operation of a fail safe valve features, in accordance with certain exemplary implementations, 
       FIG. 4  is a schematic illustration of another embodiment of the fluid delivery system of  FIG. 1  according to an example embodiment. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a block diagram of an exemplary printing device  100  having a printhead  102  with a plurality of nozzles  104  for forming an image on a print medium  120  using selectively ejected droplets of at least one printing fluid  106 . Printing fluid  106  is supplied to printhead  102  by a printing fluid delivery system  108  that includes a supply of printing fluid  106  in a container  110 . Printhead  102  may be arranged “on-axis” with regard to the printing process by way of a moving carriage  122  or the like. Container  110  may be arranged “off-axis” and operatively coupled to printhead  102  through a pathway of one or more fluidic couplings (not shown) such as, for example, channels, tubes, pipes, fittings, etc. Container  110  includes a printing fluid port  112  through which printing fluid  106  exits container  110 . In certain implementations, printing fluid  106  and/or gas may also enter into container  110  through printing fluid port  112 . 
   A double bubbler  114  may be included in printing fluid delivery system  108  to regulate gas pressure within container  110 , for example, based on the gas pressure of the atmosphere outside of container  110 . In this example, double bubbler  114  is bi-directional in that it is configured to allow gas within container  110  to escape into the atmosphere and to allow gas from the atmosphere to enter into container  110  based on a pressure difference between the gas in the container and gas in the atmosphere. Thus, for example, when the absolute value or magnitude of the pressure difference reaches a threshold level then double bubbler  114  will permit gas to enter or exit container  110 , flowing or bubbling from the higher pressure side to the lower pressure side. Exemplary double bubbler methods and apparatuses are presented in more detail in the related patent application titled “Fluid Delivery System For Printing Device”, which is incorporated, in its entirely, by reference herein. 
   Printing fluid delivery system  108  may supply printing fluid  106  to printhead  102  through a pathway that uses the ejecting action of nozzles  104  to urge printing fluid  106  from container  110  through printing fluid port  112 . Printing fluid delivery system  108  may also or alternatively supply printing fluid  106  to printhead  102  through a pathway that uses a pump  132  to urge printing fluid  106  from container  110  through printing fluid port  112 . In certain implementations, pump  132  may instead or also urge printing fluid  106  from printhead  102  back through the pathway and fluid port  112  into container  110 . 
   Printing fluid delivery system  108  also includes a fail safe valve  130  within the pathway between container  110  and printhead  102 . Fail safe valve  130  is configured to automatically prevent printing fluid  106  from flowing in either direction between container  110  and printhead  102  when the printer is non-operational, for example, due to a loss of electrical power to printing device  100 . 
   In  FIG. 1 , fail safe valve  130  is illustrated in a bypass position with regard to (optional) pump  132 , such that printing fluid  106  may flow between container  110  and printhead  102  without being urged by pump  132  when fail safe valve,  130  is open. 
   Fail safe valve  130  is a normally closed electrically operated valve that can be mechanically opened. For example, fail safe valve  130  may be configured to stay open only when adequate electrical power is available to printing device  100  to prevent potential leaking of printing fluid  106  out of nozzles  104  when adequate electrical power is unavailable to the printing device (e.g., a power switch is turned off, the printing. device is unplugged, electrical power is out, etc.). In certain implementations, for example, fail safe valve  130  may include a solenoid, electromagnet or other electrically activated switching mechanism that closes when power is no longer available. 
   Attention is drawn next to  FIG. 2A , which illustrates in more details an exemplary fail safe valve  130  and pump  132  in accordance with certain implementations of the present invention. 
   Here, container  110  is coupled to pathway tubing  218  which enters fail safe valve  130  at a first port  202  and pump  132 , illustrated in this example as being a peristaltic pump. Pathway tubing  218  is coupled to fail safe valve  130  at a second port  204  and continues on to the printhead. 
   Pump  132  includes a housing portion  224  that is configured to contact tubing  218  as rollers  222  attached to a wheel portion  220  roll and press tubing  218  closed in a manner that urges the printing fluid within tubing  218  to flow in the direction of rotation of wheel portion  220 . Such pumps are well known. Other types of pumps may also be used. 
   In this example, fail safe valve  130  includes a sealing member  205  in the form of a flexible member  206  and control member  208 . In  FIG. 2A , sealing member  205  is in a closed position such that ports  202  and  204  are not fluidically coupled together. Flexible member  202  has been urged by control member  208  into housing  200  by a closing force applied by a resilient member  212 , which in this example is a coil spring. 
   Control member  208  extends beyond housing  200  in this example. Control member  208  is configured to allow flexible member  206  to resiliently return to an open shape when fail safe valve is in an open position, for example, as illustrated in  FIG. 2B . As illustrated in  FIG. 2B , when moved to the open position, flexible member  206  is shaped to fluidically couple first port  202  and second port  204  together. Thus, the first and second ports met to form a chamber  240  inside housing  200 . 
   Control member  208  is acted upon by an opening force that is opposed to and greater than the closing force. The resulting force differential causes control member to pivot about an axle  210  so as to be brought close enough to an electrically controlled mechanism  214  (e.g., an electromagnet or the like) that fail safe valve  130  remains in the open position. Electrically controlled mechanism  214  applies a holding force to control member  208  that is opposed to and equal to or greater than the closing force. Control member  208  may include, for example, ferromagnetic material that is attracted by a magnetic field produced by electrically controlled mechanism  214 . An electrical power source  216  is shown as being operatively coupled to electrically controlled mechanism  214 . 
     FIGS. 3A-C  further illustrate the operation fail safe valve  130 . In  FIG. 3A , fail safe valve  130  is shown in its normally closed position. Control member  208  includes a contact surface  302  which contacts flexible member  206  in this closed position. Control member  208  also includes a pivoting portion represented here by an axle  306 . Control member  208  pivots about a pivot point with pivoting portion  314 . Control member  208  includes a distal portion  304  that includes a material that is attracted to the magnetic field of electrically controlled mechanism  214 . 
   The resilient member is represented in this example by a closing force  300  which causes contact surface  302  to force flexible member  206  into housing  200  and against a surface surrounding first port  202  thereby fluidically sealing first port  202 . Flexible member  206  is resilient itself and/or has shape memory properties that allow it to change its shape once closing force  300  is overcome by either an opening force  306  and/or holding force  308  of proper magnitude. 
   In  FIG. 3B , an opening force  306  is applied to the distal portion  304  of control member  208 . Here, opening force  306  acts in opposition to closing force  300  as a result of the pivoting portion. When opening force  306  as applied to control member  208  is greater than closing force  300 , then control member  208  will move (pivot) allowing flexible member  206  to change shape and unseal first port  202 . Force  306  may be provided by one or more mechanically moving portions of the printing device. For example, in certain implementations, a portion of the carriage  122  ( FIG. 1 ) is moved to physically contact control member  208 . 
   Once fail safe valve  130  is open, then holding force  308  maintains the valve in the open position. In certain implementations, the holding force may also serve as or otherwise assist in providing some of the opening force. 
   As schematically shown in  FIG. 4 , in certain implementations, fluid delivery system  308 , another embodiment of system  108 , may supply a plurality of printing fluids to printhead  102 . In such systems, a corresponding plurality of containers  110 , fail safe valves  130  and passageway elements may be provided. The fail safe valves  130  may share a common housing  310  with multiple chambers  312 . The control members may be connected together in some manner, for example, by a single axle or the like, such that all of the fail safe valves  130  operate together. In such implementations, a single resilient member and/or a single electrically controlled mechanism may be used. 
   Although the above disclosure has been described in language specific to structural/functional features and/or methodological acts, it is to be understood that the appended claims are not limited to the specific features or acts described. Rather, the specific features and acts are exemplary forms of implementing this disclosure.