Abstract:
An ink delivery and recovery system includes a first reservoir for containing ink for delivery to a plurality of ink jets of an imaging device, a second reservoir spaced apart from the first reservoir for containing ink for delivery to the first reservoir, and a third reservoir for capturing ink emitted from the plurality of ink jets. A first conduit is connected to the first reservoir and configured to permit flow of ink in a single direction toward the first reservoir. A second conduit is connected to the third reservoir and configured to permit flow of ink in a single direction away from the third reservoir. A third conduit is connected between the second reservoir and the first conduit and second conduit, the third conduit being configured to permit bidirectional flow of ink from the second reservoir toward the first and second conduits and from the first and second conduits toward the second reservoir. A bidirectional pump is associated with the third conduit.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to phase change ink imaging devices, and, and, in particular, to the delivery and recovery of melted phase change ink in such phase change ink imaging devices. 
       BACKGROUND 
       [0002]    In general, ink jet printing machines or printers include at least one printhead that ejects drops or jets of liquid ink onto a recording or image forming media. A phase change ink jet printer employs phase change inks that are solid at ambient temperature, but transition to a liquid phase at an elevated temperature. The molten ink can then be ejected onto a printing media by a printhead directly onto an image receiving substrate, or indirectly onto an intermediate imaging member before the image is transferred to an image receiving substrate. Once the ejected ink is on the image receiving substrate, the ink droplets quickly solidify to form an image. 
         [0003]    In various modes of operation, ink may be purged from the printheads to ensure proper operation of the printhead. When a solid ink printer is initially turned on, the solid ink is melted or remelted and purged through the printhead to clear air bubbles and/or contaminants from the printhead. The word “printer” as used herein encompasses any apparatus, such as digital copier, bookmaking machine, facsimile machine, multi-function machine, etc. that performs a print outputting function for any purpose. When ink is purged through the printhead, the ink flows down and off the face of the printhead typically to a waste ink tray or container positioned below the printhead where the waste ink is allowed to cool and re-solidify. The waste ink collection container is typically positioned in a location conveniently accessible so that the container may be removed and the waste ink discarded. 
         [0004]    As an alternative to removing and discarding the waste phase change ink, some previously known systems have been configured to recycle the waste ink by directing it back to the melt reservoir that supplies the printhead with the melted phase change ink for jetting onto the image receiving substrate. Such systems typically use both positive and negative air pressure for pressurizing the reservoirs to force ink through the system in the desired direction. 
       SUMMARY 
       [0005]    As an alternative to using positive and negative air pressure to deliver melted phase change ink from a remote reservoir to the printheads and to recover waste ink from a waste ink collector back to the remote reservoir, a phase change ink delivery and recovery system has been developed that enables both ink delivery and recovery operations to be performed using a single pumping system. Such a system utilizes a bidirectional rotary displacement pump in a fluid path that connects a remote reservoir to both the on-board printhead reservoir and the waste ink collector. The bidirectional rotary pump is configured to pump ink in a first direction or a second direction based on the rotational direction of the pump. For example, the rotary displacement pump is configured to rotate in a first direction which displaces melted phase change ink in a direction from the remote reservoir toward the on-board printhead reservoir and to rotate in a second direction which displaces ink in a direction from the waste ink collector toward the remote reservoir. 
         [0006]    In one embodiment, an ink delivery and recovery system includes a first reservoir for containing ink for delivery to a plurality of ink jets of an imaging device, a second reservoir spaced apart from the first reservoir for containing ink for delivery to the first reservoir, and a third reservoir for capturing ink emitted from the plurality of ink jets. The system includes a first conduit connected between the first reservoir and a conduit junction that is configured to permit flow of ink in a single direction toward the first reservoir. The system also includes a second conduit connected between the third reservoir and the conduit junction that is configured to permit flow of ink in a single direction away from the third reservoir. A third conduit is connected between the second reservoir and the junction. The junction fluidly connects the first, second, and third conduits. A bidirectional pump is associated with the third conduit for pumping ink in a first direction and a second direction in the third conduit, the first direction causing ink to flow from the second reservoir toward the junction. 
         [0007]    In another embodiment, a method of operating a phase change ink imaging device is provided. The method includes connecting a first conduit to an on-board printhead reservoir of a phase change ink imaging device; connecting a second conduit between a remote reservoir of the phase change ink imaging device and the first conduit; and connecting a third conduit between a purged ink collecting reservoir of the phase change ink imaging device and the second conduit. A bidirectional pump is positioned in the second conduit that is configured to pump ink in a first direction in the second conduit and to pump ink in a second direction in the second conduit opposite the first direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is block diagram of a phase change ink image producing machine. 
           [0009]      FIG. 2  is a schematic diagram of the ink delivery and recovery system of the device of  FIG. 1 . 
           [0010]      FIG. 3  is a schematic view of an embodiment of a rotary displacement pump for use with the system of  FIG. 2 . 
           [0011]      FIG. 4  is a schematic view of an embodiment of an ink delivery and recovery system with the junction adjacent the printhead. 
           [0012]      FIG. 5  is a schematic view of the ink delivery and recovery system shown as a modular unit that may be stand-alone or combined with the melt reservoir. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    For a general understanding of the present embodiments, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. 
         [0014]    As used herein, the terms “printer” or “imaging device” generally refer to a device for applying an image to print media and may encompass any apparatus, such as a digital copier, bookmaking machine, facsimile machine, multi-function machine, etc. which performs a print outputting function for any purpose. “Print media” can be a usually non rigid physical sheet of paper, plastic, or other suitable physical print media substrate for images. A “print job” or “document” is normally a set of related sheets, usually one or more collated copy sets copied from a set of original print job sheets or electronic document page images, from a particular user, or otherwise related. As used herein, the term “consumable” refers to anything that is used or consumed by an imaging device during operations, such as print media, marking material, transfer fluid, and the like. An image generally may include information in electronic form which is to be rendered on the print media by the image forming device and may include text, graphics, pictures, and the like. The operation of applying images to print media, for example, graphics, text, photographs, etc., is generally referred to herein as printing or marking. 
         [0015]    Referring now to  FIG. 1 , an embodiment of an imaging device  10  of is shown. As depicted, the device  10  includes a frame  11  to which are mounted directly or indirectly all its operating subsystems and components, as described below. In the embodiment of  FIG. 1 , imaging device  10  is an indirect marking device that includes an intermediate imaging member  12  that is shown in the form of a drum, but can equally be in the form of a supported endless belt. The imaging member  12  has an image receiving surface  14  that is movable in the direction  16 , and on which phase change ink images are formed. A transfer roller  19  rotatable in the direction  17  is loaded against the surface  14  of drum  12  to form a transfer nip  18 , within which ink images formed on the surface  14  are transferred onto a media sheet  49 . In alternative embodiments, the imaging device may be a direct marking device in which the ink images are formed directly onto a receiving substrate such as a media sheet or a continuous web of media. 
         [0016]    In one embodiment, the ink utilized in the imaging device  10  is a “phase-change ink,” by which is meant that the ink is substantially solid at room temperature and substantially liquid when heated to a phase change ink melting temperature for jetting onto an imaging receiving surface, also referred to as solid ink sticks or blocks. Accordingly, the imaging device  10  includes a solid ink loading system  20  that is configured to receive phase change ink in solid or substantially solid form, and a phase change ink melting system  30  ( FIG. 2 ) that is configured to melt the solid ink into a liquid form for jetting onto the imaging member  12 . 
         [0017]    As depicted in  FIG. 1 , the ink loading system  20  includes at least one solid ink receiving station, such as receiving station  22 , that is configured to receive at least one color or shade of solid ink stick. Because the imaging device  10  is a multicolor imaging device, the ink loading system includes four receiving stations  22 ,  24 ,  26 ,  28 , representing four different colors CYMK (cyan, yellow, magenta, black) of ink. In one embodiment, the receiving stations comprise insertion openings that permit ink sticks to be inserted into an appropriate delivery channel or chute. The feed channels guide ink sticks to a corresponding melt assembly  30 . A separate feed channel (not shown) and melt assembly (not shown) may be associated with each color or shade of ink utilized in the device  10 . Each ink melting assembly  30  is configured to heat the solid phase change ink to a melting temperature that phase changes, i.e., melts, the solid ink to its liquid or melted form for jetting onto the imaging member by the printhead assemblies. 
         [0018]    The phase change ink melting temperature may be any suitable temperature based on such factors as ink formulation, environmental conditions, desired flow rate of the ink, etc. In one embodiment, the phase change ink melting temperate is in the range of approximately 100° C. to 140° C. Although the ink for use with the imaging device of  FIG. 1  has been described as phase change ink, in alternative embodiments, the ink utilized in the imaging device may be any suitable type of ink that is capable of being jetted or otherwise deposited onto the imaging member. For example, the ink may comprise liquid or substantially liquid ink, such as aqueous ink, UV curable ink, wax-based inks, and the like. 
         [0019]    The imaging device includes at least one printhead assembly configured to receive molten ink from a corresponding melting assembly and to jet the molten ink to form images on the imaging drum. Each printhead assembly extends substantially across the width of the imaging drum in the cross-process direction. In embodiments, the imaging device  10  may include a separate printhead assembly for each color or shade of ink utilized in the device. For example, in the case of the four colors of ink CMYK, the imaging device may include four printhead assemblies. For simplicity, only two printhead assemblies  32 ,  34  are depicted in  FIG. 1 . Each printhead assembly is associated with a molten ink delivery and recovery system  100  ( FIG. 2 ). A molten ink delivery and recovery system for a printhead assembly is configured to receive molten ink of the appropriate color from a corresponding ink melting assembly  30 . As explained below, a molten ink delivery and recovery system  100  is configured to hold quantities of the appropriately colored molten ink and to deliver it as needed to the associated printhead assembly for jetting onto the imaging drum. 
         [0020]    As further shown, the imaging device  10  includes a media supply and handling system  40 . The media supply and handling system  40 , for example, may include sheet or substrate supply sources  42 ,  44 ,  46 ,  48 , of which supply source  48 , for example, is a high capacity paper supply or feeder for storing and supplying image receiving substrates in the form of cut sheets  49 , for example. The substrate supply and handling system  40  also includes a substrate or sheet heater or pre-heater assembly  52 . The imaging device  10  as shown may also include an original document feeder  70  that has a document holding tray  72 , document sheet feeding and retrieval devices  74 , and a document exposure and scanning system  76 . 
         [0021]    Operation and control of the various subsystems, components and functions of the machine or printer  10  are performed with the aid of a controller or electronic subsystem (ESS)  80 . The ESS or controller  80  for example is a self-contained, dedicated mini-computer having a central processor unit (CPU)  82 , electronic storage  84 , and a display or user interface (UI)  86 . The ESS or controller  80  for example includes sensor input and control means  88  as well as a pixel placement and control means  89 . In addition the CPU  82  reads, captures, prepares and manages the image data flow between image input sources such as the scanning system  76 , or an online or a work station connection  90 , and the printhead assemblies. As such, the ESS or controller  80  is the main multi-tasking processor for operating and controlling all of the other machine subsystems and functions, including the machine&#39;s printing operations. 
         [0022]    In operation, image data for an image to be produced is sent to the controller  80  from either the scanning system  76  or via the online or work station connection  90  for processing and output to the printhead assemblies. Additionally, the controller determines and/or accepts related subsystem and component controls, for example from operator inputs via the user interface  86 , and accordingly executes such controls. As a result, appropriately colored phase change ink is melted and delivered to the printhead assemblies. Additionally, pixel placement control is exercised relative to the imaging surface  14  thus forming desired images per such image data, and receiving substrates are supplied by anyone of the sources  42 ,  44 ,  46 ,  48  in timed registration with image formation on the surface  14 . Finally, the image is transferred within the transfer nip  92 , from the surface  14  onto the receiving substrate. 
         [0023]    Referring now to  FIG. 2 , a schematic diagram of an embodiment of a molten ink delivery and recovery system  100  for the imaging device  10  is shown. The molten ink delivery and recovery system  100  of  FIG. 2  includes at least one remote molten ink reservoir  104  for receiving molten ink  106  from an associated ink melting assembly  30  of the imaging device  10 . Melt reservoir  104  includes a housing  108  that defines a receptacle  110  for receiving the molten ink from the melt assembly  30 . An ink level sensor  112  may be provided in the receptacle area for detecting the level of ink therein. Any suitable type of ink level sensor may be used. In operation, the melt assembly is activated to melt ink based on the ink level sensor output to provide and maintain a desired amount of molten ink in the melt reservoir  104 . 
         [0024]    The reservoir also includes a heating system to maintain the received ink at a suitable temperature for delivery to the printhead assembly  32 . For example, in embodiments, the housing formed of a suitable thermally conductive material, such as metal or thermally conductive plastic, to which a suitable heater is mounted. The heater heats the housing which in turn transfers the heat to the ink contained therein. In alternative embodiments, the housing may be formed of a thermally insulative material, and suitable heating may be generated by mounting a heating device internal to the housing. The thermally insulative housing then operates to prevent or limit heat loss from the interior of the housing. 
         [0025]    The melt reservoirs  104  are configured to transport the molten ink to at least one printhead assembly, such as printhead assembly  32 , as needed via a molten ink delivery path. The molten ink received in the remote reservoir  104  is directed to the printhead  32  via an ink delivery path  114 . The ink delivery path  114  may be any suitable device or apparatus capable of transporting fluid such as molten ink from the remote ink reservoir  104  to the printhead  32 . In one embodiment, the ink delivery path  114  comprises an enclosed conduit, such as a tube, duct, or similar structure that confines the ink therein as it is being guided from the melt reservoir to the printhead. 
         [0026]    In one embodiment, the ink delivery path  114  from remote ink reservoir  104  directs melted phase change ink to an on-board ink reservoir  116  of the printhead  32 . The on-board reservoir  116  is configured to hold a quantity of melted phase change ink for delivery to the ink jets (not shown) of the printhead for ejection onto the imaging member  12 . The on-board reservoir  116  may be provided with an ink level sensor  113  configured to detect or indicate the level of ink in the on-board reservoir  116 . Any suitable type of ink level sensor may be used. As used herein, the term “reservoir” may be used to refer to any device, apparatus, or structure that is capable of containing a quantity of melted phase change ink therein, such as the remote reservoir, the on-board reservoir, and purged ink reservoir (described below). The term remote as used herein and as applicable to ink reservoirs refers to a reservoir that is separate or independent from the printhead on-board reservoir which feeds ink through passages to the image forming jets or nozzles. The “remote” reservoir relationship referred to herein may relate to a physical distance separation or may be integrated in a single unit with the printhead and purge reservoirs such that the reservoir functions are “remote” though in close proximity and in a common assembly. 
         [0027]    The imaging device  10  includes a maintenance system for periodically purging ink through the nozzles of the ink jets in the ejecting face  32   a  of the printhead  32 . Ink may be purged through the ink jets in any suitable manner. For example, a positive air pressure may be introduced into the on-board reservoir  116  from a suitable air pressure source (not shown). Solenoid valve  119  may be operably coupled to the on-board reservoir  116  to control the pressure in the on-board reservoir  116  in a suitable manner. The ink flows down the ejecting face  32   a  of the printhead via gravity where it is collected in by a gutter  123  which directs the ink to a purged ink reservoir, also referred to as a purged ink sump or collector  122 . The system may also include a scraper or wiper blade  118  which is configured to be drawn across (e.g., in the direction indicated by the arrow  120 ) the ink ejecting face  32   a  of the printhead  32  to wipe any excess liquid phase change ink, as well as any paper, dust or other debris that has collected on the ejecting face down towards the gutter  123  and sump  122 . 
         [0028]    In the embodiment of  FIG. 2 , the purged ink collector  122  comprises a sump chamber that is incorporated into the printhead assembly  32 . The sump chamber  122  is located in the printhead assembly  32  below the on-board printhead reservoir  116 . In alternative embodiments, the ink collector  122  may be separate from the printhead. Molten ink captured in the ink collector  122 , or sump, is directed back to the remote reservoir  104  via an ink return path  124 . In one embodiment, the ink return path  124  comprises an enclosed conduit, such as a tube, duct, or similar structure that confines the ink therein as it is being guided from the sump to the printhead. One or more filters (not shown) may be positioned at various locations for filtering gross contaminants, such as paper debris and dust, from the purged ink prior to the purged ink being recovered into the remote reservoir. 
         [0029]    To maintain the ink in liquid form during supply and recovery operations, the reservoirs and conduits used to hold and transport ink may be selectively heated by a suitable heating system to maintain an appropriate ink temperature range and such heating control may include temperature monitoring and adjustment of heating power and/or timing. Heater may be any suitable type of heating system and can rely on radiant, conductive, or convective heat to bring the ink in the reservoirs and conduits to at least the phase change melting temperature. By incorporating the purged ink collector  122  into the printhead assembly  32 , the purged ink collected in the sump may be heated to a phase change ink melting temperature by the same heating system for maintaining the ink in the on-board reservoir in liquid phase, e.g. at or above the phase change ink melting temperature. In embodiments in which the purged ink is collected in a chamber separate from the printhead assembly, a dedicated heater may be provided to heat the waste ink in the collection chamber to at least the phase change ink melting temperature. A dedicated heater, however, may also be provided in the sump chamber of the printhead assembly if desired. 
         [0030]    In previously known systems, ink delivery and recovery was controlled using two pumping systems, i.e., one for pumping ink from the remote reservoir  104  to the on-board reservoir  116  of the printhead and a second for pumping ink from the ink collector  122  back to the remote reservoir  104 . Such pumping systems were typically implemented using a positive air pressure source and/or a negative air pressure source. Molten ink was delivered to the on-board reservoir by applying a positive pressure to the remote reservoir to force ink out of the reservoir, through the supply conduit, and into the on-board reservoir or by applying a negative pressure to the on-board reservoir which draws ink from the remote reservoir to the on-board reservoir via the supply conduit. 
         [0031]    As an alternative to the use of a positive and negative air pressure source for pumping molten ink through the supply and return conduits, the molten ink delivery and recovery system  100  is configured to use a single bidirectional rotary displacement pump  128  for providing both the supply and recovery pumping operations. To enable the use of a bidirectional displacement pump  128  for pumping ink, the remote reservoir receptacle  110  is fluidly coupled to a single conduit or tube  130  that extends from the remote reservoir. The conduit or tube  130  is configured to serve as a bidirectional fluid path through which molten ink flows either in a supply direction S from the melt reservoir  104  toward the printhead on-board reservoir  116  or in a recovery direction R from the purged ink reservoir  122  toward the remote reservoir  104 . The bidirectional pump assembly  128  is positioned along the bidirectional fluid path  130  to provide the pumping force for pumping the molten ink in both the supply S and recovery R directions. 
         [0032]    The bidirectional conduit, the supply conduit, and the return conduit are fluidly connected at a conduit junction  148 . As depicted in  FIG. 2 , the bidirectional pump assembly is coupled to the reservoir  104  by bidirectional conduit portion  130   a  and to the junction  148  by the bidirectional conduit portion  130   b . The junction  148  may be provided at any suitable position relative to the melt reservoir  104  and the on-board printhead reservoir  116 . For example,  FIG. 2  schematically shows the junction as being adjacent the melt reservoir  104 .  FIG. 4  shows an embodiment in which the junction is provided adjacent the printhead  32 . 
         [0033]    Referring now to  FIGS. 3A and 3B , an embodiment of a bidirectional rotary displacement pump assembly  128  is shown. In particular,  FIG. 3A  shows the bidirectional pump being operated to pump ink in a first direction, e.g., in the supply direction, and  FIG. 3B  shows the bidirectional pump being operated to pump ink in a second or opposite direction, e.g., in the recovery direction. The rotary displacement pump of  FIGS. 3A and 3B  comprises a rotary gear pump assembly that includes a housing  131  defining a chamber in which at least one gear is rotatably supported. As depicted in  FIGS. 3A and 3B , the gear pump comprises an external gear pump having a pair of meshed gears  132 ,  134 . In other embodiments, any suitable type of bidirectional displacement pump may be utilized including internal gear pumps, gerotors, screw pumps, peristaltic pumps, and the like. In the embodiment of  FIGS. 3A and 3B , the pair of meshed gears  132 ,  134  includes a drive gear  132  and driven gear  134 . Drive gear  132  is mounted on a drive shaft  136  that extends through the chamber  138 . Drive shaft  136  is operably connected to a suitable motor  140  for rotating the drive shaft  136  and drive gear  132  of the gear pump in response to commands received from a controller  142 . Driven gear  134  is mounted on an axle for idle rotation and meshed with the drive gear  132  so that it may be rotated by the drive gear  132 . Controller  142  may be implemented as part of system controller  80  of the device  10  or may comprise a standalone controller, such as an ASIC or other suitable type of microcontroller. 
         [0034]    The pump housing  131  has a pair of diametrically opposed openings  144 ,  146  which, depending on the direction of flow of the molten ink, are configured to serve as inlet and outlet openings for the gear pump  128  through which molten ink flows into and out of the chamber  138 . The first opening  144  is fluidly coupled to the bidirectional fluid path  130   a  to receive molten ink from the remote reservoir  104  during supply operations and to direct recovered ink to the remote reservoir  104  during recovery operations. Similarly, the second opening  146  is fluidly coupled to the bidirectional fluid path  130   b  to direct molten ink toward the on-board printhead reservoir  116  during supply operations and receive recovered ink from the ink collector, e.g., sump,  122  during recovery operations. 
         [0035]    The delivery and recovery conduits are provided with a suitable flow path restriction, such as a valve system or other suitable back flow prevention means, which prevents molten ink from traveling in the wrong direction along either the supply conduit or recovery conduit. For example, delivery conduit  114  includes a flow restriction  150  configured to enable flow in a single direction S toward the on-board reservoir  116  and to substantially prevent the flow of molten ink in direction R. Similarly, recovery conduit  124  includes a flow restriction  152  configured to enable flow in a single direction R toward the remote reservoir  104  and to substantially prevent the flow of ink in direction S toward the ink collector  122 . The flow restrictions  150  and  152  may be located at any suitable position along the respective flow paths or conduits  114  and  124 . For example, the flow restrictions may be positioned at or near the ends of the conduits  114 ,  124  that connect to the junction  148 , at or near the ends of the conduits  114 ,  124  that connect to the respective reservoirs  116 ,  122 , or substantially anywhere between the ends of the conduits  114 ,  124 . In one embodiment, the flow restrictions  150  and  152  comprise one-way check valves. As an alternative to the use of check valves as the flow restrictions for the delivery and return conduits, directional flow control may be provided at least in part dams or weirs, as they are known in the art, positioned in the supply and return paths. For instance, a dam or weir used in conjunction with a filter may be configured to serve as a one-way check valve. An example of such a system is disclosed, for example, in commonly assigned U.S. Patent Publication No. 20080122901 to Platt et al., which is hereby incorporated by reference in its entirety. Flow path restrictions or check valves may be passive or controllably actuated and may include biasing mechanisms such as springs to ensure that the valves open or close appropriately for the given flow rate or pressure in the lines. 
         [0036]    The molten ink delivery and recovery system  100 , and in particular, the bidirectional pump  128 , may be operated in any suitable manner to provide molten ink to the on-board reservoir  116  and to recover molten ink from the purged ink reservoir  122 . In embodiments, molten ink may be provided to the on-board reservoir based on the ink level indicated by the ink level sensor  113  of the on-board reservoir  116 . For example, the ink level sensor  113  may be configured to at least indicate when the ink in the on-board reservoir has reached or passed below a predetermined level, i.e., the ink level has reached a “Low” level. In one embodiment, the ink level sensor is configured as a binary sensor that provides output indicative of whether or not the sensor is in contact with ink. Thus, an ink low condition is indicated when the sensor does not detect ink. The sensor  113 , however, may be any suitable type of sensor or system capable of indicating when the on-board reservoir has reached an ink low condition. 
         [0037]    The bidirectional pump is configured such that the pump is activated to pump ink in the supply direction S when the ink level sensor  113  indicates a low ink condition in the reservoir  116 . With reference to  FIG. 3A , when the ink level sensor indicates that the ink level is low, the motor  140  is activated to control gears  132 ,  134  so that, for example, gear  132  rotates in direction T which in turn causes gear  134  to rotate in complementary direction T′ at a predetermined rate of speed so that ink is moved in the supply direction S. The first  144  and second openings  146  in the pump housing  130  are positioned with respect to the gears such that as the gears  132 ,  134  rotate they separate at position  154  in front of the first opening  144 , creating a void and suction which is filled by molten ink from the remote reservoir  104  (via bidirectional conduit  130 ). The molten ink is carried by the gears  132 ,  134  toward the opposite side  156  of the housing where the gears  132 ,  134  displace the molten ink through the second opening  146 . The ink then travels to the junction  148  at which point the flow restriction  150  permits the ink to travel to the reservoir  116 , and flow restriction  152  prevents ink from being transported toward the purged ink collector  122 . In one embodiment, the gears  132 ,  134  are rotated until the ink level sensor  113  indicates that the reservoir  116  has a desired level of ink. For example, with the binary sensor embodiment described above, the sensor may indicate when it is in contact with the ink at which point the gears are deactivated so that they no longer rotate to pump ink in the supply direction S. 
         [0038]    With reference to  FIG. 3B , when it is desired to recover purged ink from the ink collector  122 , the gears  132  and  134  are activated by the motor  140 , in response to commands from controller  142 , for example, to rotate gear  132  in direction T′ which in turn causes gear  134  to rotate in complementary direction T. In this embodiment, the rotating gears  132 ,  134  create the voids at position  156  in front of the second opening  146  that draws ink from the ink collector  122  and displace ink toward the first opening  144  towards the remote reservoir  104 . Molten ink is drawn toward the melt reservoir  104  from the junction  148 . The flow restriction  152  allows ink to travel from the purged ink collector  122  toward the junction while the flow restriction  150  prevents ink from being drawn from the on-board reservoir  116 . 
         [0039]    The gears may be rotated at a predetermined rate of speed for a predetermined duration to deliver purged ink from the ink collector  122  back to the remote reservoir  104 . In alternative embodiments, the purged ink collector may be provided with an ink level sensor for indicating when the collected ink has reached a predetermined level at which point recovery operations should be performed. The rotational speed of the gears  132 ,  134  for the supply and recovery operations may be any suitable speed and may be selected based on such factors as the gear sizes, fluid path dimensions, ink flow characteristics, and the like so that a desired amount of ink is pumped through the system at a desired rate. 
         [0040]    Although each of the components of the ink delivery and recovery system  100  may be provided and installed separately, in some embodiments, the ink delivery and recovery system  100  may be provided as a self-contained unit that may be inserted into an imaging device and connected between a remote reservoir  104  and a printhead  32  as a single unit. For example, a schematic diagram of an embodiment of a modular ink delivery and recovery system  100  is shown in  FIG. 5 . As depicted, the ink delivery and recovery system  100  may be provided in a housing or frame  158  that supports the delivery  114  and return  124  conduits and bidirectional pump  128  in an operable relationship with respect to each other. The housing  158  may include suitable features that enable the supply  114  and return  124  conduits to be connected to the printhead reservoir  116  and sump  122  without requiring conduits or flow paths exterior to the housing  160  although exterior conduits and connections may be used. In another embodiment, the remote reservoir and the ink delivery and recovery system  100  may be provided as a single combined unit. For example, as depicted schematically in  FIG. 5 , the remote reservoir  104  and the ink delivery and recovery system  100  may be provided in a housing or frame  160  that enables the reservoir  104  and supply and recovery system  100  to be operably connected between the melt assembly and the printhead reservoir. 
         [0041]    Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.