Patent Publication Number: US-9849681-B2

Title: Structure for printhead having multiple air channels

Description:
BACKGROUND 
     In certain liquid dispensers, printheads are part of a discrete assembly separate from detachable containers, in which a liquid is held in a block of foam or other capillary material inside the container. Known examples of such dispensers and detachable containers are printers and ink containers, respectively. The liquid holding chamber in these foam based containers is vented to the atmosphere through a hole in the top of the container. The container vent hole is sealed during storage and shipment to prevent evaporation from the ink chamber. The container vent is sometimes not functional when the container is installed in a printhead assembly, for example when the user fails to sufficiently remove the vent seal. The printer will not print properly with a malfunctioning container vent. 
    
    
     
       DRAWINGS 
         FIG. 1  is a block diagram illustrating an example inkjet printer. 
         FIGS. 2 and 3  are perspective views illustrating an example structure with an ink container in connected state. 
         FIG. 4  is an exploded top side perspective view of the example structure of  FIGS. 2 and 3 . 
         FIG. 5  is a top view illustrating the example structure of  FIGS. 2-4  with the tower seals removed to expose air holes. 
         FIG. 6  is an exploded bottom side perspective view of the example structure of  FIGS. 2-5 . 
         FIG. 7  is a bottom plan view of the example structure of  FIGS. 2-6  with the manifold cover and printheads removed to expose the air channels along the underside of the substrate. 
         FIG. 8  is a section view of the example structure of  FIGS. 2-7  taken along the line  8 - 8  in  FIG. 5  illustrating a vent path from the ink container outlet through the structure. 
         FIG. 9  is a detail view of the structure and container illustrated in  FIG. 8 . 
         FIG. 10  is a perspective top side view of an example cover for a structure of  FIGS. 2-9 . 
         FIG. 11  is a detail view of the example cover of  FIG. 10 . 
         FIG. 12  is a cross sectional view of a detail of an example structure having an air channel with additional narrow slots formed between the substrate and cover. 
         FIG. 13  is a cross sectional view of the example structure detail of  FIG. 12 , before the substrate and cover are attached. 
         FIG. 14  is a perspective bottom view of the substrate of the example structure of  FIGS. 12 and 13 . 
     
    
    
     The same part numbers designate the same or similar parts throughout the figures. 
     DESCRIPTION 
     A vent through a structure of a printhead assembly has been developed as an addition or alternative to the conventional vent on a detachable ink container. The new vent allows the container to supply ink to the printhead assembly even if the vent on the ink container malfunctions, for example if the user fails to remove the tape sealing the vent or if there is a defect in the vent that prevents air from reaching the ink chamber inside the container. In one example of the new vent, an air hole is formed through a substrate of a printhead support structure near the ink inlet so that the container ink outlet is exposed to the air hole when the container outlet is engaged with the ink inlet of the printhead support structure, that is, when the ink container is installed on the structure. Separate, unique air channels on the back side of the substrate connect each of the air holes to the atmosphere, thus venting the ink container to the atmosphere through the printhead support structure when the container is installed in the support structure. Each unique air channel is associated with a different liquid inlet to prevent that different liquids of ink could mix near the ink inlet. 
     Examples of the structure are described with reference to ink containers for an inkjet printer but are not limited to ink containers or inkjet printers. Examples of the structure might also be implemented in other types of liquid dispensers, such as pharmaceutical liquid dispensers, digital titration devices, laboratory equipment or three dimensional printing devices. For example, besides ink, liquids other than ink can be used such as pharmaceutical liquids, chemical agents, etc. 
     As used in this document, “liquid” means a fluid not composed primarily of a gas or gases; and a “printhead” means that part of a printer or other type dispenser that dispenses liquid from at least one nozzle, for example as drops or streams. In an example a printhead may contain multiple nozzle arrays wherein each nozzle array may dispense at least one color ink. For example one printhead includes at least one nozzle array to dispense black and another printhead includes multiple nozzle arrays to dispense Cyan, Magenta and Yellow. In this disclosure a printhead assembly means that part of the printer that includes at least one printhead. The printhead assembly is part of the overall support structure. Although the figures illustrate a scanning type support structure, the invention can also apply to a fixed array printhead assemblies. Where appropriate, a printhead assembly may be abbreviated by PHA in the description and figures. 
       FIG. 1  is a block diagram illustrating an inkjet printer  10  with a printhead assembly carrying structure  50  implementing one example of new container vents  14 .  FIGS. 2-9  illustrate in detail one example of a printhead assembly structure  50  with such vents  14  such as might be used in the printer shown in  FIG. 1 . Referring first to  FIG. 1 , a printer  10  includes a structure  50  carrying a printhead assembly (PHA)  12  and detachable ink containers  18 ,  20 ,  22 , and  24  that supply ink to the printhead assembly  12 . An interior, ink holding chamber of each container  18 - 24  is vented to the atmosphere through unique vents  14  in the printhead assembly  12 . In the example shown in  FIG. 1 , container vent  14  includes four separate vents  14 A,  14 B,  14 C and  14 D that separately vent each of the ink containers  18 ,  20  and  22 ,  24 , respectively. 
     The printhead assembly  12  includes at least one printhead  46 ,  48  through which ink from the multiple containers  18 - 24  is to be ejected. A print media transport mechanism  26  is to advance a sheet of paper or other print media  28  past structure  50  and printhead assembly  12 . A controller  30  is operatively connected to printhead assembly  12  and media transport  26 . Here, the controller  30  represents generally a processor and associated memory, instructions stored on the memory, and the electronic circuitry and other components needed to control the operative elements of printer  10 . 
     Referring now to  FIGS. 2 and 3 , the structure  50  includes bays  32 ,  34 ,  36 , and  38  for receiving detachable ink containers  18 - 24 , respectively, for example each of a different ink type such as black, cyan, magenta and yellow. Only one ink container  18  is shown installed in the structure  50  in  FIGS. 2 and 3  to better illustrate some of the features of the structure  50 . The structure  50  includes ink inlets  40  for receiving ink from a corresponding ink outlet  42  on each detachable ink container  18 - 24 . Each ink inlet  40  is configured as a tower that is surrounded by an annular seal  44  that seals against the bottom of each container outlet  42  when the container is installed in the structure  50 . In the example shown, the printhead assembly  12  includes two printheads  46  and  48 . For example, ink from color ink containers  18 - 22  is ejected from a first printhead  46  and ink from a black ink container  24  is ejected from a second printhead  48 . 
       FIGS. 4 and 5  are an exploded top side perspective view and a top view, respectively, of the structure  50 . For illustrative purposes the annular seal  44  is lifted in  FIG. 4  and omitted in  FIG. 5 .  FIGS. 6 and 7  are an exploded bottom side perspective view and a bottom view, respectively, of the structure  50 . The printheads  46 ,  48  and the manifold cover are omitted in  FIG. 7  for illustrative purposes.  FIGS. 8 and 9  are sectional side views of the vent features near the ink inlet  40  with the ink container  18  in a connected state. 
     Referring to  FIGS. 4-9 , the support structure  50  supports the printheads  46 ,  48  and other parts. The ink inlet towers  40  protrude from a generally planar substrate  52  of the support structure  50 . While in one example the structure  50  will be installed in the printer so that the substrate  52  is horizontal during printing operations, as shown in the figures, a horizontal substrate  52  is not required. Indeed, substrate  52  alone or integrated into a structure  50  might have different orientations during manufacturing, packaging, storing, shipping, and printing. The ink inlet towers  40  protrude from a first side  54  of the substrate  52 . Printheads  46 ,  48  are mounted to a second side  56  of the substrate  52  opposite to the first side  54 . A manifold cover may be disposed between the substrate  52  and the printheads  46 ,  48 . An ink hole  58  in the substrate  52  inside each inlet tower  40  allows ink to flow through each container outlet  42  to a respective printhead  46  or  48  along a corresponding ink channel  60  formed along the second side  56  of the substrate  52 . An air hole  62  in the substrate  52  near each inlet tower  40  exposes each container outlet  42  to the atmosphere through a respective unique air channel  64  formed in the second side  56  of the substrate  52 , so that none of the inlet towers  40  share one air channel  64 . At a distal end  72  of each air channel  64  the air channel  64  communicates with ambient air. 
     In the example shown in the figures, the individual air channels  64  each include a respective air plenum  66  that connects the air hole  62  with a labyrinth portion of the air channel  64 . Each plenum  66  is defined by a separate enclosed space along the second side  56  of the substrate enveloping air holes  62  as best seen in  FIG. 7 . A first, proximal end  70  of the labyrinth portion of each air channel  64  is open to each of the plenums  66  and the opposite distal end  72  of the air channel  64  is open to the atmosphere. Also, in the example shown in the figures, walls  73  defining the ink channels  60 , air channels  64 , and plenums  66  are formed in the second side  56  of the substrate  52 . In this example, three sides of each enclosed space are formed in the substrate  52  and the fourth side is formed by a cover  74  affixed to the substrate  52 . The cover  74  effectively seals the ink and air channels  60 ,  64  while connecting the ink inlets  40  with the respective printheads  46 ,  48  through the ink channels  60 . The cover  74  is sometimes called a manifold or manifold cover because it helps define the ink distribution manifold formed by the ink channels  60  into the printhead assembly  12 . 
     As illustrated in  FIG. 7 , each of the air channels  64  is isolated from the other air channels  64  by the walls  73 . Isolating the air channels  64  reduces a possibility that under certain circumstances ink would enter one of the air holes  62  and exit another one of the air holes  62  whereby different colors ink could be mixed near one of the ink inlets  40 . 
     In the illustrated examples, the air channels  64  are defined by labyrinths having a length vs. diameter ratio that reduces water or vapor loss while allowing for a desired air flow. In one example the depth of each of the labyrinth air channels  64  is between approximately 0.1 and approximately 1 millimeters, for example between approximately 0.2 and approximately 0.6 millimeters. For example the length of each of the labyrinth air channels  64  is at least approximately 50 millimeters, for example at least approximately 100 millimeters, or for example at least approximately 120 millimeters. In one specific example the length of the labyrinth is approximately 132 millimeter. As illustrated the configuration of the different air and ink channels  64 ,  60  is such that all ink channels  60  and all individual air channels  64  fit on the second side  56  of the substrate  52 . The labyrinths have a serpentine shape. For example each of the labyrinths makes at least five turns that are sharper than 90 degrees, for example 180 degrees turns, providing for an extended air path within a relatively small surface. For example the distal ends  72  of the air channels  64  open into respective enclosed air chambers  100 , from where air is vented to and from ambient air. The air chambers  100  at the distal ends are enclosed by the walls  73  of the labyrinths and/or additional migration preventing walls  73 B. The additional migration preventing walls  73 B can be provided to split the air chambers  100 , so that two distal ends  72  or respective air channels  64  do not open into the same air chambers  100 . 
     For example the air holes  62  associated with each inlet  40  may have a size and shape that depends on the available space on the substrate  52 . In the illustrated example the air holes  62  have different shapes. For example the air holes  62  are sized as large as possible. 
     Referring now to  FIGS. 8 and 9 , each ink inlet tower  40  is surrounded by a seal  44 . In connected state, the bottom of each container outlet  42  is pressed into a corresponding seal  44  to make a fluid tight seal that prevents air from escaping between the container outlet  42  and the inlet  40 . Seal  44  forms an interior cavity  76  surrounding at least part of the inlet tower  40 . The air hole  62  opens into the cavity  76 . The outer surface  78  of the inlet tower  40  is recessed at the location of the air hole  62  so that air can move from the cavity  76  past the seal  44  to the container outlet  42 . In the example shown, multiple recesses  80  are formed along the outer surface  78  of the inlet tower  40  to achieve the desired air flow between the cavity  76  and the container outlet  42 . 
     For illustrative purposes an example ink container will be described while referring to  FIGS. 8 and 9 . Each ink container  18 - 24  includes a housing  82  that forms an interior chamber  84  for holding ink. For convenience, only one ink container  18  is called out in the following description. Ink in the chamber  84  is held in foam or other suitable capillary material  86 . In certain examples, a conventional vent  88  on the container  18  vents the ink chamber  84  to the atmosphere. Such vent  88  usually includes an opening  90  in the container housing  82  and a small winding channel  92  covered by an adhesive label  94 . The label  94  is shown in phantom lines on container  18  in  FIG. 2 . A wick  96  in the container outlet  42  forms the fluidic interface between ink container  22  and printhead assembly  12 . 
     When the ink container  18  is installed in the structure  50 , the wick  96  engages a corresponding inlet tower  40 , for example through a filter  98 , to establish the operative fluidic connection between the ink container  18  and printhead assembly  12 . When the container  18  is installed in the printhead assembly  12  but not vented correctly through the vent  88 , the flow of ink from the container  18  into the printhead assembly  12  during printing and priming would create a high vacuum inside the ink chamber  84 , which could lead to starvation of the printheads for ink. The disclosed vents  14  in the structure  50  could allow air to pass around and through the wick  96  into the ink chamber  84  to prevent high vacuums inside the container  18 , even if the vent  88  would fail. 
     Thus, the structure  50  allows for unique paths from the distal ends  72  of the respective air channels  64 , through the enclosed chambers  100 , along the air channels  64  to respective plenums  66 , through the air holes  62  in the substrate  52  to the cavity  76  between the seal  44  and the inlet tower  40 , then past the inlet tower  40  along recesses  80  to the wick  96  of a container outlet  42 . The air holes  62  in the substrate  52  and the recesses  80  along the inlet tower  40  may be sized and shaped to achieve the desired venting and, where appropriate, to facilitate manufacturing. Printhead support structure  50  usually will be a molded plastic part. In fact, the structure  50  as illustrated in  FIG. 7  may be defined by a single cast. Multiple air holes  62  around an inlet tower  40 , as shown in  FIG. 5 , may be used instead of a single larger hole as necessary or desirable, for example to maintain the rigidity of inlet tower  40  to substrate  52 . 
       FIG. 10  illustrates a perspective top side view on an example of a cover  74 . For example, the cover  74  has a substantially flat top surface  101  to be attached to the second side  56  of the structure  50 . In an example the cover  74  includes at least one air vent hole  102 ,  103  to vent air from and to one of the air channels  64 . At least one of the vent holes  102  comprises a through hole. At other locations the air can be vented along a side wall of the cover  74 . Here, the vent holes  103  are defined by inward curving, bay shaped edges of the cover  74 . The air vent holes  102 ,  103  allow for air to be vented from or to the respective distal ends  72  of the air channels  64 , for example through the enclosed air chambers  100 . As illustrated, the cover  74  also includes ink interconnect holes  104  to fluidically connect each of the ink channels  60  with the printheads  46 ,  48 . 
     As illustrated in  FIG. 10 , and as illustrated in detail in  FIG. 11 , the cover  74  includes ink traps  106 . In an assembled condition of the cover  74 , each ink trap  106  may communicate directly with a first, proximal end  70  of a respective air channel  64  and an air hole  62 . The ink traps  106  may be arranged near the air plenums  66 . The ink traps  106  include a recess  108  and an ink retain feature  110 . The ink retain feature  110  may be defined by a wall spanning a width of the recess  108 . In an example the wall does not span a full height of the recess  108 . The ink traps  106  will retain ink that accidentally enters the air hole  62 . Such ink may flow into the recess  108  whereby the retain feature  110  prevents the ink from flowing into the air channel  64 . The recesses  108  may be substantially wider than the diameter of the air channels  64  to allow for enough ink to be trapped during the lifetime of the printer. 
     In a further example that is illustrated in  FIG. 12  the air channels  64  include narrow elongate slots  118  that extend along a length of the air channels  64 .  FIG. 12  illustrates the structure  50  in an upside-down orientation, that is, in a normal operational state. For example the slot  118  extends at the side, or at each side of the air channel  64 , and at the base of the air channel  64 . For example, the height of the slot  118  is chosen to pull ink by capillary force, to prevent blocking of the air channel  64  by ink. In certain examples the slot has a height of between approximately 10 and 130 micron. The height of the slot  118  may depend on the height of the air channel  64 . 
     In a further example a narrow, large surface slot  118 B is provided to allow for more trapping of ink. For example ink that enters an air channel  64  may be pulled into the first mentioned slot  118  and eventually pulled into the large surface slot  118 B that allows for even more ink storage, by capillary force. Therefore, the side slots  118 ,  118 B may have a varying width wherein both desired trapped ink storage and available space may play a role. 
     As best illustrated in  FIGS. 13 and 14 , again showing the substrate  52  and cover  74  in upside-down orientation, the slots  118  can be formed between the substrate  52  and the cover  74 . For example, the air channels  64  formed in the substrate  52  include a first tier  120  defined by a bottom surface of the air channel wall  73 , and a second tier  122  that is defined by a step in between. During manufacture, the cover  74  is pressed against the substrate  52  for attaching the two parts. The cover presses into the first tier  120  while deforming the wall  73 . Thereby the flat surface  101  of the cover  74  closes in on the second tier  122 , without touching the second tier  122 , shaping the narrow slot  118 . In an example the height difference between the first and the second tier  120 ,  122  and the pressing force for attaching the cover  74  to the substrate  52  are chosen to obtain a desired final slot height.  FIG. 13  illustrates the substrate  52  and cover  74  before said slot formation step and  FIG. 12  illustrates the substrate  52  and cover  74  after said slot formation step, that is, in a deformed, final condition.  FIG. 14  illustrates the substrate  52  including the air channels with the first tier  120  as defined by a bottom surface of the air channel walls  73  and the second tier  122  in between said bottom surface and air channel base. A large surface second tier portion  122 B is illustrated, disposed along the air channel  64  and interrupting normal second tier portions  122 , for forming the earlier mentioned ink trapping large surface slot  118 B illustrated in  FIG. 12 . 
     Some of the mentioned examples allow for venting an ink container even when the ink container vent itself does not work. Some of the mentioned examples allow for said venting while preventing mixing of inks that accidentally enter an air hole or air channel. In some of the examples, if ink from one inlet enters one of the air channels or the air plenum  66  it will not flow to another inlet because the air channels are mutually separate. Furthermore, at least one ink trap can be provided to prevent ink from flowing into or out of the ink channels, and to prevent blocking the air channels. While ink containers generally have a shorter lifetime, some of the described vent and ink trap features can remain in function over the lifetime of the printer, spanning several ink container lifetimes. 
     As noted at the beginning of this description, the examples shown in the figures and described above illustrate but do not limit the invention. Other examples are possible. Therefore, the foregoing description should not be construed to limit the scope of the invention, which is defined in the following claims.