Patent Publication Number: US-8534817-B2

Title: Melt reservoir housing

Description:
PRIORITY CLAIM 
     This application claims priority from U.S. patent application having Ser. No. 12/241,452, which is entitled “Melt Reservoir Housing,” was filed on Sep. 30, 2008, and will issue as U.S. Pat. No. 8,042,927 on Oct. 25, 2011. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to phase change ink printers, and in particular, to ink reservoirs for maintaining a supply of phase change ink in liquid form for delivery to one or more printheads of the phase change ink printers. 
     BACKGROUND 
     Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are typically inserted through an insertion opening of an ink loader for the printer, and the ink sticks are pushed or slid along the feed channel by a feed mechanism and/or gravity toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a melt reservoir. 
     The melt reservoir is configured to maintain a quantity of melted ink in liquid or melted form and to communicate the melted ink to one or more printheads as needed. Thermal energy is applied to the melt reservoir to maintain the phase change ink stored therein at a substantially constant temperature which is above the freezing point, or solidification point, of the melted phase change ink. One issue faced in maintaining the melt reservoirs of a phase change ink printer at the melted ink temperature is heat loss. Heat loss from the melt reservoir requires more thermal energy input to the reservoirs to maintain the ink at the melted ink temperature which, in turn, increases the energy consumption of the printer. 
     SUMMARY 
     In order to prevent or limit heat loss from the melt reservoirs of a phase change ink imaging device, an ink storage and supply assembly has been developed that includes at least one ink reservoir positioned in an imaging device. The at least one ink reservoir has an opening configured to receive liquid ink, and a chamber configured to hold a quantity of the ink received through the opening. The at least one ink reservoir is configured to communicate the liquid ink in the chamber to at least one printhead of the imaging device. A housing at least partially encloses the at least one ink reservoir. The housing includes a top positioned above the at least one ink reservoir, a bottom positioned below that at least one ink reservoir, and a plurality of side walls extending vertically between the top and the bottom of the housing. The plurality of side walls are formed of mica panels and are spaced from the at least one reservoir to define a first air gap between each of the side walls and the at least one reservoir. At least one the side walls includes an inner wall and an outer wall spaced from each other to define a second air gap therebetween. The top and bottom of the housing includes locating grooves for receiving edges of the plurality of side walls and for positioning the side walls to provide the first air gap and the second air gap. 
     In another embodiment, an ink storage and supply assembly comprises at least one ink reservoir positioned in an imaging device. The at least one ink reservoir has an opening configured to receive liquid ink, and a chamber configured to hold a quantity of the ink received through the opening. The at least one ink reservoir is configured to communicate the liquid ink in the chamber to at least one printhead of the imaging device. A housing at least partially encloses the at least one ink reservoir. The housing includes a top positioned above the at least one ink reservoir, a bottom positioned below that at least one ink reservoir, and a plurality of side walls extending vertically between the top and the bottom of the housing. The plurality of side walls are spaced from the at least one reservoir to define a first air gap between each of the side walls and the at least one reservoir. 
     In yet another embodiment, an imaging device is provided that includes at least one printhead for ejecting ink onto an ink receiver. The imaging device includes at least one ink reservoir configured to hold liquid ink and to deliver ink to the at least one print head. The at least one ink reservoir includes a housing that at least partially encloses the at least one ink reservoir. The housing includes a top positioned above the at least one ink reservoir, a bottom positioned below that at least one ink reservoir, and a plurality of side walls extending vertically between the top and the bottom of the housing. At least one of the side walls in the plurality is spaced from the at least one reservoir defining an air gap therebetween. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is block diagram of a phase change ink image producing machine; 
         FIG. 2  is top view of four ink sources and a melter assembly having four melter plates of the phase change ink image producing machine of  FIG. 1 ; 
         FIG. 3  is front side view of the four melter plates and the ink melting and control assembly; 
         FIG. 4  is a side cross-sectional view of a dual reservoir of the ink melting and control assembly; 
         FIG. 5  is a front perspective view of the ink melting and control assembly showing the insulated housing; 
         FIG. 6  is a back perspective view of the ink melting and control assembly showing the insulated housing; 
         FIG. 7  is an end cross-sectional view of the ink melting and control assembly showing the panel spacing and air gaps between the panels and between the panels and the reservoirs; and 
         FIG. 8  is an enlarged view of a portion of the end cross-sectional view of the ink melting and control assembly shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For a general understanding of the system disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the word “printer,” “imaging device,” “image producing machine,” etc. encompasses any apparatus that performs a print outputting function for any purpose, such as a digital copier, bookmaking machine, facsimile machine, a multi-function machine, etc. 
     Referring now to  FIG. 1 , there is illustrated an image producing machine, such as the high-speed phase change ink image producing machine or printer  10  of the present invention. As illustrated, the machine  10  includes a frame  11  to which are mounted directly or indirectly all its operating subsystems and components, as will be described below. To start, the high-speed phase change ink image producing machine or printer  10  includes an 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 imaging surface  14  that is movable in the direction  16 , and on which phase change ink images are formed. 
     The high-speed phase change ink image producing machine or printer  10  also includes a phase change ink system  20  that has at least one source  22  of one color phase change ink in solid form. Since the phase change ink image producing machine or printer  10  is a multicolor image producing machine, the ink system  20  includes for example four (4) sources  22 ,  24 ,  26 ,  28 , representing four (4) different colors CYMK (cyan, yellow, magenta, black) of phase change inks. The phase change ink system  20  also includes a phase change ink melting and control assembly  100  ( FIG. 2 ), for melting or phase changing the solid form of the phase change ink into a liquid form. Thereafter, the phase change ink melting and control assembly  100  then controls and supplies the molten liquid form of the ink towards a printhead system  30  including at least one printhead assembly  32 . Since the phase change ink image producing machine or printer  10  is a high-speed, or high throughput, multicolor image producing machine, the printhead system includes for example four (4) separate printhead assemblies  32 ,  34 ,  36  and  38  as shown. 
     As further shown, the phase change ink image producing machine or printer  10  includes a substrate supply and handling system  40 . The substrate supply and handling system  40  for example may include 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 for example. The substrate supply and handling system  40  in any case includes a substrate handling and treatment system  50  that has a substrate pre-heater  52 , substrate and image heater  54 , and a fusing device  60 . The phase change ink image producing machine or printer  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 . 
     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  32 ,  34 ,  36 ,  38 . 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. 
     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  32 ,  34 ,  36 ,  38 . 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, appropriate color solid forms of phase change ink are 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  and handled by means  50  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 for subsequent fusing at fusing device  60 . 
     Referring now to  FIGS. 2 and 3 , there is shown the ink delivery system  100  and ink storage and supply assembly  400  of the imaging device. The ink delivery system  100  of the present example includes four ink sources  22 ,  24 ,  26 ,  28 , each holding a different phase change ink in solid form, such as for example inks of different colors. However, the ink delivery system  100  may include any suitable number of ink sources, each capable of holding a different phase change ink in solid form. The different solid inks are referred to herein by their colors as CYMK, including cyan  122 , yellow  124 , magenta  126 , and black  128 . Each ink source can include a housing (not shown) for storing each solid ink separately from the others. The solid inks are typically in block form, though the solid phase change ink may be in other formats, including but not limited to, pellets and granules, among others. 
     The ink delivery system  100  includes a melter assembly, shown generally at  102 . The melter assembly  102  includes a melter, such as a melter plate, connected to the ink source for melting the solid phase change ink into the liquid phase. In the example provided herein, the melter assembly  102  includes four melter plates,  112 ,  114 ,  116 ,  118  each corresponding to a separate ink source  22 ,  24 ,  26  and  28  respectively, and connected thereto. As shown in  FIG. 3 , each melter plate  112 ,  114 ,  116 ,  118  includes an ink contact portion  130  and a drip point portion  132  extending below the ink contact portion and terminating in a drip point  134  at the lowest end. The drip point portion  132  can be a narrowing portion terminating in the drip point. 
     The melter plates  112 ,  114 ,  116 ,  118  can be formed of a thermally conductive material, such as metal, among others, that is heated in a known manner. In one embodiment, solid phase change ink is heated to about 100° C. to 140° C. to melt the phase change ink to liquid form for supplying to the liquid ink storage and supply assembly  400 . As each color ink melts, the ink adheres to its corresponding melter plate  112 ,  114 ,  116   118 , and gravity moves the liquid ink down to the drip point  134  which is disposed lower than the contact portion. The liquid phase change ink then drips from the drip point  134  in drops shown at  144 . The melted ink from the melters may be directed gravitationally or by other means to the ink storage and supply assembly  400 . The ink storage and supply system  400  includes reservoirs  404  configured to hold quantities of melted ink from the corresponding ink sources/melters and to communicate the melted ink to one or more printheads (not shown) as needed. Each reservoir  404  of the ink storage and supply system  400  includes an opening  402  positioned below the corresponding melt plate configured to receive the melted ink and a chamber  406  below the opening configured to hold a volume of the melted ink received from the corresponding melt plate. 
     In one embodiment, the ink storage and supply system  400  may incorporate a dual reservoir system.  FIG. 4  shows a simplified side cross-sectional view of an exemplary embodiment of a dual reservoir of an ink storage and supply assembly  400 . In this embodiment, each reservoir  404  of the ink storage and control assembly  400  includes a primary reservoir  408  and a secondary reservoir  410  for each ink source and corresponding ink melter of the ink delivery system. Only one dual reservoir is shown in  FIG. 4 , but it is to be understood that each reservoir  404  of the ink storage and control assembly  400  may be configured as a dual reservoir as depicted in  FIG. 4 . In the embodiment of  FIG. 4 , each primary reservoir  408  comprises a low pressure reservoir (LPR) configured to receive molten ink from a corresponding ink melt plate (for example, melt plate  112 ) of the ink delivery system. Each LPR  408  includes an opening  414  at or near a bottom portion of the LPR  408  through which ink may flow to a corresponding secondary reservoir  410 . Gravity, or liquid ink height, may serve as the driving force for causing the molten ink to exit a respective LPR  408  through the opening and into the corresponding secondary reservoir  410 . To prevent backflow of ink from a secondary reservoir  410  to the corresponding primary reservoir (LPR)  408 , the openings  414  in the LPR&#39;s may be provided with one-way check valves  418  that permit ink to flow gravitationally from the LPR  408  into the secondary reservoir  410 . 
     The secondary reservoirs  410  comprise high pressure reservoirs (HPR). Each HPR  410  includes at least one discharge outlet  420  through which molten ink may flow to an ink routing assembly (not shown) for directing ink to one or more printheads (not shown) of the printhead assembly. Each HPR may include a plurality of discharge outlets  420  for supplying ink to a plurality of printheads. For example, in a system that includes four printheads for each color of ink, each HPR may include four discharge outlets, each outlet being configured to supply ink to a different printhead. When charging a printhead with ink, pressure is applied to the ink in a corresponding HPR using, for example, an air pump  424  through a dosing valve  428  or other suitable pressurization means to causing the ink to discharge through the one or more discharge outlets  420  of the HPR. The discharge outlet(s) of the HPR may include check valve(s)  430  or other suitable backflow prevention means that are configured to open to permit the flow of molten ink from the secondary reservoir to the printhead when the HPR is pressurized while preventing backflow of the ink through the opening  420  back into the HPR  410 . In addition, the valve  418  in the opening  414  is configured to prevent backflow of ink from the secondary reservoir to the primary reservoir when the secondary reservoir is pressurized. 
     The primary and secondary reservoirs are configured to maintain the phase change ink stored therein at a substantially constant melted ink temperature that is above a freezing point, or solidification point, of the phase change ink in order to maintain the ink in liquid or melted form for delivery to one or more printheads of the printhead assembly. Accordingly, the primary  408  and secondary reservoirs  410  of the melt reservoir system  400  are formed of a thermally conductive material such as aluminum although any suitable material, such as magnesium, may be used. The development of thermal energy in the primary and secondary reservoirs to maintain the phase change ink at the melted ink temperature may be accomplished in any suitable manner. For example, the ink storage and supply assembly  400  may include one or more heating elements (not shown), such as silicon heaters, that are disposed adjacent to the primary  408  and/or the secondary reservoirs  410  that are configured to heat the primary and second reservoirs to a temperature suitable to maintain the phase change ink at the melted ink temperature. 
     One issue faced in ink handling in an imaging device is maintaining the temperature of the ink at the desired temperature. For example, in the phase change ink imaging device described above, it is desired that the phase change ink in the reservoirs be maintained at the melted ink temperature for delivery to the print heads. A difficulty faced in maintaining phase change ink at the melted ink temperature is heat loss. Heat loss in the primary and secondary reservoirs requires more thermal energy input to the reservoirs to maintain the ink at the melted ink temperature which increases the energy consumption of the printer which, in turn, is undesirable in today&#39;s “green” climate as well as being an impediment to meeting energy star and other regulatory operation objectives. Temperature control of ink may also be an issue in imaging devices that utilize other types of ink. In imaging devices that utilize ink, such as aqueous ink, it may be desired to maintain the ink at a room temperature of approximately 18° C. to 25° C. The environment in which the imaging device is located, however, may provide additional sources of heating and/or cooling that may have an affect on the ink temperature in the imaging device. In addition, the internal components of an imaging device may generate heat that may also affect ink temperature in an imaging device. 
     In order to minimize heat loss and/or heat gain in the ink storage and supply assembly, the ink storage and supply assembly includes an insulated housing assembly configured to surround the primary and secondary reservoirs of the ink storage and supply assembly to minimize heat loss and/or heat gain.  FIGS. 5 and 6  show front and back perspective views of an embodiment of an ink storage and control assembly  400  that shows an exemplary insulated housing assembly. In particular, the insulated housing includes a top portion  450 , a bottom portion  454 , and a plurality of side walls or panels  458 ,  460 ,  464 ,  468  that surround and enclose the primary and secondary reservoirs (not shown in  FIGS. 5 and 6 ) of the ink storage and supply assembly  400 . As seen in  FIGS. 5 and 6 , the top portion  450  of the housing may include an ink collector  470  configured to collect and direct the molten ink received from the melt plates to the corresponding low pressure reservoirs  408 . The ink collector  470  may be formed of an insulating material such as plastic and includes an opening  474  positioned above each low pressure reservoir that is configured to collect the molten ink as it drips from the corresponding ink melter and to funnel the ink through a filter  478  and into the corresponding low pressure ink reservoir. The bottom  454  of the housing is positioned below the reservoirs of the ink storage and supply assembly  400 . The side walls  458 ,  460 ,  464 ,  468  of the housing are oriented substantially vertically about the sides of the ink storage and supply assembly extending between the top and the bottom of the housing. In the embodiment of  FIGS. 5 and 6 , the side walls include a pair of end side walls  458 ,  460  and a pair of longitudinal side walls  464 ,  468 . 
     In one embodiment, the top, bottom, and side panels of the reservoir housing comprise a glass-filled plastic. Plastic molded parts are relatively easy to fashion in the desired shape and can include features for attachment. However, the downside to this approach is the plastic parts are not optimal as an insulator or as a low cost solution. As an alternative to using plastics for the insulated housing of the ink storage and supply assembly, the insulated housing of the ink storage and supply assembly may include mica panels to reduce cost and reduce heat loss. In particular, in one embodiment, at least the side panels  458 ,  460 ,  464 ,  468  of the insulated housing may be formed of mica sheets, also known as muscovite. The thickness of the mica panels utilized in the housing may be any suitable thickness. In one embodiment, the mica panels are provided with a thickness of about 0.030″. 
     The top  450  and bottom portions  454  of the housing may be formed of a suitable thermally resistant material such as plastic which enables the formation of locating and attachment features, such as guide grooves or slots, for positioning the mica side panels relative to the melt reservoirs and to each other.  FIG. 7  shows a simplified side cross-sectional view of the ink storage and supply assembly  400  showing the top portion  450 , bottom portion  454 , and longitudinal side walls  464 ,  468 . As seen in  FIG. 7 , the top  450  and bottom portions  454  of the housing may include guide grooves or slots  480  that are configured to receive the top and bottom edges, respectively, of the side walls  464 ,  468 . Although not depicted in  FIG. 7 , the top and bottom portions of the housing includes guide grooves or slots that are configured to receive the top and bottom edges, respectively, of the end side walls  458 ,  460 . Although not necessary in every embodiment, the panels may be secured and sealed to the top and bottom portions of the housing as well as to adjacent or overlapping panels using a suitable sealing material such as tape, or a thermally cured adhesive. By confining the locating and attachment features to the top and bottom portions of the housing, the mica side panels may be formed of simple stamped mica sheets. For example, the raw material for the mica panels comes in sheets at the thickness desired, and the panels may be formed, for example, by stamping out the profile with a single blanking die. 
     To further minimize heat loss or heat gain in the ink storage and supply assembly  400 , the housing of the ink storage and supply assembly  400  is configured to make use of trapped air to enhance the thermal insulating properties of the housing. As is known in the art, the insulating properties of the air far exceed those of a solid. The housing of the ink storage and supply assembly  400  is configured to use trapped air as insulation by spacing one or more or all of the side walls  458 ,  460 ,  464 ,  468  from the heated reservoirs  404  of the ink storage and supply assembly  400  to provide an air gap  484  between the heated reservoirs and the housing walls. The top and bottom portions of the housing and/or the reservoirs  404  may also be provided with positioning and/or locating features such as standoffs (not shown) that allow precise positioning of the top, bottom and side walls of the housing with respect to the reservoirs  404  so that air gaps may be provided between the heated reservoirs and the top and bottom portions of the housing as well as between the side walls and the reservoirs. Air gaps provided between the housing walls and the reservoirs  404  may have any suitable width. In one embodiment, the air gap  484  between the side walls of the housing and the reservoirs may be approximately 0.080″ although any suitable air gap width may be provided. 
     As depicted in  FIG. 7 , select one or more of the side walls of the housing may be provided with two or more layers of mica panels. Multi-layer housing walls or panels that include multiple layers of mica may also be configured to make use of entrapped air to decrease the thermal conductivity of the particular housing wall. In the embodiment of  FIG. 7 , each of the side walls  464 ,  468  of the housing are provided with two mica panels  488 ,  490  that are positioned with respect to each other to provide an air gap  494  therebetween. In particular, as shown in  FIG. 8 , the side walls  464 ,  468  (only side  464  depicted in  FIG. 8 ) may be provided with an inner panel  488  and an outer panel  490  that are spaced from each other to provide the air gap  494 . The distance between the mica panels  488 ,  490  of the double layer sidewalls of the housing that defines the air gap  494  may be any suitable distance. In one embodiment, the width of the air gap between the mica panels of the double layer sidewalls may be approximately 0.080″ although the air gap may have any suitable width. 
     The housing of the ink storage and supply assembly has been described as having one or more side walls with two mica panels that utilize trapped air to enhance the ability of the housing to reduce heat loss, more than two mica panels may be provided in one or more of the side walls with an air gap between each mica panel. In addition, although not depicted, mica panels may be incorporated into the top and bottom portions of the housing. For example, the bottom portion of the housing may be provided with a mica panel that is configured to be sandwiched between the bottom of the ink storage and supply assembly and the plastic bottom portion of the housing. In addition, the top and bottom portions of the housing may be formed of other materials besides plastic and/or may include suitable fillers that are configured to further increase the ability of the housing to prevent or limit heat loss. 
     It will be appreciated that various of the above-disclosed and other features, and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.