Patent Publication Number: US-10308029-B2

Title: Liquid holding unit and liquid ejection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2016-116155, filed on Jun. 10, 2016, and Japanese Patent Application No. 2016-216150, filed on Nov. 4, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present invention relates to a liquid holding unit, which holds liquid supplied to a liquid ejector of a liquid ejection device, and a liquid ejection device. 
     JP-A-2016-000504 discloses an example of a liquid ejection device (liquid consumption device) including a liquid ejector that ejects liquid onto a target such as paper. The liquid ejection device is provided with a liquid holding unit that includes a tank (one example of liquid holder), a cap (one example of plug), and a cover. The tank holds ink (one example of liquid) that is supplied to the liquid ejector. The cap opens and closes an inlet of the tank. The cover opens and closes an opening of a compartment that accommodates the tank. An inner side of the cover includes a holding portion to hold the cap, which has been removed by the user, when the cover is located at an open position. When the cap is held by the holding portion, the cap is located in a movement region (movement path) of the cover that extends from the open position to a close position. This restricts movement of the cover to the close position and avoids a situation in which the user forgets to plug the inlet with the cap, which has been removed from the inlet by the user. 
     In the liquid ejection device of Japanese Laid-Open Patent Publication No. 2016-000504, the user holds the cap between fingers to remove the cap from the inlet. As a result, ink may be applied from the cap to the fingers and smear the hand of the user. A liquid holding unit that supplies the liquid ejector with liquid other than ink also has the same shortcoming. 
     SUMMARY 
     It is an object of the present invention to provide a liquid holding unit and a liquid ejection device that reduces the frequency in which liquid is applied from the plug to the fingers when the user opens and closes the inlet with the plug. 
     In one aspect of the present disclosure, a liquid holding unit supplies liquid to a liquid ejector of a liquid ejection device. The liquid holding unit includes a liquid holder, a housing, an inlet, a shaft, and an engagement portion. The liquid holder is capable of holding the liquid. The housing accommodates the liquid holder. The inlet is used to fill the liquid holder with the liquid. The plug is configured to open and close the inlet. The plug includes an elastically deformable plug body that covers the inlet and a holding member that holds the plug body and has higher rigidity than the plug body. The shaft is arranged on one of the housing and the plug. The plug is pivotal about the shaft. The engagement portion is arranged on the other one of the housing and the plug. The engagement portion is engaged with the shaft. 
     With this structure, when the user opens and closes the plug to fill the liquid holder with liquid, the frequency in which liquid is applied from plug body to the fingers or the like of the user is reduced. Further, the plug is pivoted about the shaft to open and close the inlet. Thus, when holding an end part, which is located at the end of the holding member at the opposite side of the shaft, the law of the lever reduces the force required to open or close the plug. 
     Preferably, the holding member includes a first end, a second end, and a side end that intersects the first end and the second end. The holding member further includes a tab arranged on the first end. The tab is held to open and close the inlet. 
     With this structure, the user may hold the tab to open or close the plug. This facilitates opening and closing of the plug and further reduces the frequency in which liquid is applied from plug body to the fingers or the like of the user. 
     Preferably, the plug body is located between the tab and the second end on the holding member. 
     This structure further easily avoids a situation in which the user inadvertently touches the portion of the plug body located at the side where the inlet is located when opening or closing the plug resulting in the application of liquid from the plug body to the fingers or the like of the user. 
     Preferably, the liquid holder is one of a plurality of liquid holders, the plug is one of a plurality of plugs, and each of the plugs is arranged on a corresponding one of the liquid holders and includes the plug body for the corresponding one of the liquid holders. 
     In this structure, each liquid holder is provided with a plug. Thus, compared to a structure in which multiple plug bodies are formed integrally with one another, this reduces the frequency in which liquid is applied from the plug body to the fingers or the like of the user when opening and closing the plug body. 
     Preferably, the holding member is elongated in one direction and configured to hold the plug body so that the plug body is movable in a longitudinal direction of the holding member. 
     With this structure, the plug body of the plug has a certain degree of freedom in the longitudinal direction of the holding member. Thus, when the plug body is fitted to or comes into contact with inlet, the plug body is moved relative to the holding member and positioned relative to the inlet. This ensures that the inlet is sealed and reduces the frequency in which defective sealing of the inlet occurs. For example, the entrance of foreign matter into the liquid holder and the evaporation or volatilization of liquid out of the liquid holder that would result from defective sealing of the inlet is reduced. 
     Preferably, the liquid holding unit further includes a positioning guide including a projection and a recess. The positioning guide is configured to guide and position the plug relative to the inlet by inserting the projection into the recess in a state in which the inlet is closed by the plug. The holding member includes one of the projection and the recess. The liquid holder or the housing includes the other one of the projection and the recess. 
     With this structure, when moving the plug from the open position to the close position, the projection is inserted into the recess. This positions the plug at the proper position and ensures that the plug body seals the inlet. Thus, the entrance of foreign matter into the liquid holder and the evaporation or volatilization of liquid out of the liquid holder that would result from defective sealing of the inlet is reduced. 
     Preferably, the liquid holding unit further includes a cover that covers the plug. The cover or the housing includes a restriction portion that contacts the holding member in a state in which the holding member is pivoted in a direction opening the inlet to restrict a pivot range of the holding member. 
     With this structure, the pivot range of the holding member is restricted when opening the plug. This limits the liquid that is applied from the plug body to the fingers or the like of the user when opening and closing the plug as compared with when, for example, the holding member has no restricted pivot range and is pivoted by approximately 180 degrees to an open position where the holding member lies horizontally. Thus, the liquid applied from the plug body to the fingers or the like of the user is further reduced. 
     Preferably, the liquid holding unit further includes a cover that covers the plug. The cover includes a pushing portion that is capable of pushing the plug toward the inlet. 
     With this structure, the pushing portion pushes the plug toward the inlet when closing the cover. This restricts separation of plug from the inlet and prevents evaporation and volatilization of liquid. 
     The holding member includes a through hole into which at least part of the plug body is fitted. Preferably, a covering covers an opening of the through hole at an opposite side of the plug body. The covering is in correspondence with a color of the liquid held in the liquid holder. 
     With this structure, the covering functions to conceal the through hole of the holding member and to indicate a color. This improves the aesthetic appeal of the plug and allows the user to check the color by looking at the covering when opening the plug. Thus, situations are reduced in which the liquid holder is filled with liquid of the wrong color. 
     Preferably, the holding member includes a first piece located toward a first end of the holding member and provided with the plug body, a second piece located toward a second end of the holding member, and a pivot located between the first piece and the second piece. In a state in which the plug is located at an open position, the holding member takes a bent formation in which the first piece is pivoted about the pivot relative to the second piece in a direction in which the plug body approaches the inlet. In a state in which the plug is located at a close position, the holding member takes a straight formation in which the first piece and the second piece are arranged straight. 
     With this structure, the holding member takes the straight formation when the plug closes the inlet at the close position. Thus, the plug body seals the inlet. Further, the holding member takes the bent formation so that the plug body is directed toward the inlet when the plug opens the inlet and is located at the open position. This limits the liquid that is applied from the plug body to the fingers or the like of the user. Thus, the frequency in which liquid is applied from the plug body to the fingers or the like of the user is further reduced. 
     Preferably, the holding member further includes an urging member that urges the holding member in a direction that bends the holding member from the straight formation to the bent formation. 
     With this structure, the holding member is urged in the direction in which the holding member takes the bent formation. Thus, when opening the plug, the holding member takes the bent formation without the need for the user to adjust the force applied to bend the holding member. This further reduces the frequency in which liquid is applied from the plug body to the fingers or the like of the user when opening and closing the plug. 
     Preferably, the liquid holding unit further includes a cover, which is configured to open and close so that the cover exposes the plug in an open state and covers the plug in a closed state, and a formation holding mechanism, which that contacts at least one of the first piece and the second piece when the cover is in the closed state to hold the holding member in the straight formation and keep the plug body at the close position. 
     With this structure, when closing the cover after closing the plug, the formation holding mechanism contacts at least one of the first piece and the second piece to hold the holding member in the straight formation. Thus, even though the holding member is urged in a direction in which the holding member takes the bent formation, the plug may be kept at the close position when the cover is closed. This reduces the occurrence of defective sealing that would be caused by the urging force of the urging member that moves the plug body away from the inlet. Thus, for example, the entrance of foreign matter into the liquid holder and the evaporation or volatilization of liquid out of the liquid holder that would result from defective sealing of the inlet foreign matter are limited. 
     In a further aspect of the present disclosure, a liquid holding unit supplies liquid to a liquid ejector of a liquid ejection device. The liquid holding unit includes a liquid holder, a housing, an inlet, a plug, and a guide. The liquid holder is capable of holding the liquid. The housing accommodates the liquid holder. The inlet is used to fill the liquid holder with the liquid. The plug is configured to open and close the inlet. The plug includes an elastically deformable plug body that covers the inlet and a holding member that holds the plug body and has higher rigidity than the plug body. The guide is included in the liquid holder or the housing. The guide is configured to hold the holding member of plug so that the holding member is slidable. 
     With this structure, the plug slides to open and close the inlet. Thus, the plug body does not have to be pulled when removed from the inlet. This reduces the force needed to open or close the plug. 
     Preferably, the holding member is elongated in one direction and configured to hold the plug body so that the plug body is movable in a longitudinal direction of the holding member. 
     With this structure, the plug has a certain degree of freedom in the position of the plug body relative to the holding member in the longitudinal direction of the holding member. This ensures that the inlet is sealed. Thus, for example, the entrance of foreign matter into the liquid holder and the evaporation or volatilization of liquid out of the liquid holder that would result from defective sealing of the inlet foreign matter are limited. 
     Preferably, the liquid holder or the housing includes a restriction portion that contacts the holding member to restrict a slide range of the holding member. 
     With this structure, a situation may be avoided in which the plug falls out of the liquid holder or the housing when moving the plug along the guide. This avoids a situation in which liquid is applied to the location where the plug falls. 
     Preferably, the holding member includes a through hole into which at least part of the plug body is fitted. The liquid holding unit further includes a covering that covers an opening of the through hole at an opposite side of the plug body. The covering is in correspondence with a color of the liquid held in the liquid holder. 
     With this structure, the covering functions to conceal the through hole of the holding member and to indicate a color. This improves the aesthetic appeal of the plug and allows the user to check the color by looking at the covering. Thus, situations are reduced in which the liquid holder is filled with liquid of the wrong color. 
     Another aspect of the present disclosure is a liquid injection device including the liquid holding unit and a liquid ejector that ejects liquid supplied from the liquid holder of the liquid holding unit. 
     With this structure, the liquid injection device includes the liquid holding unit. Thus, the advantages of the liquid holding unit are obtained. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a perspective view showing an all-in-one machine including a liquid ejection device of a first embodiment; 
         FIG. 2  is a perspective view showing the all-in-one machine of  FIG. 1  in a state in which covers of an image reader and a liquid holding unit are open; 
         FIG. 3  is a perspective view showing a liquid holding unit of the all-in-one machine of  FIG. 1  in a state in which the cover of the liquid holding unit is open; 
         FIG. 4  is a perspective view showing the liquid holding unit of  FIG. 3  in a state in which an upper housing is removed; 
         FIG. 5  is a perspective view showing, in part, a liquid holder of the liquid holding unit of  FIG. 4 ; 
         FIG. 6  is a perspective view showing a portion of a housing to which a plug is coupled in the liquid holding unit of  FIG. 3 ; 
         FIG. 7  is a perspective view showing, in part, the liquid holder and the plug in the liquid holding unit of  FIG. 3 ; 
         FIG. 8  is cross-sectional side view showing, in part, the plug when sealing an inlet in the liquid holding unit of  FIG. 3 ; 
         FIG. 9  is a perspective view illustrating a structure coupling a holding member and a plug body in the plug of the liquid holding unit shown in  FIG. 3 ; 
         FIG. 10  is a perspective view illustrating the structure coupling the holding member and the plug body in the plug of the liquid holding unit in the same manner as  FIG. 9 ; 
         FIG. 11  is a perspective view illustrating the structure coupling the holding member and the plug body in the plug of the liquid holding unit in the same manner as  FIGS. 9 and 10 ; 
         FIG. 12  is a cross-sectional view illustrating another plugging structure of the holding member and the plug body; 
         FIG. 13  is a cross-sectional view illustrating a plugging structure, which differs from that of  FIG. 12 , of the holding member and the plug body; 
         FIG. 14  is a perspective view showing coverings coupled to plugs in the liquid holding unit of  FIG. 3 ; 
         FIG. 15  is an exploded perspective view showing a structure for coupling the covering in the plug of  FIG. 14 ; 
         FIG. 16  is a perspective view showing the plugs to which coverings that differ from those of  FIG. 14  are coupled; 
         FIG. 17  is an exploded perspective view showing a structure for coupling a covering that differs from that of  FIG. 15 ; 
         FIG. 18  is a cross-sectional side view showing a structure for restricting the plug of the liquid holding unit of  FIG. 3  at an open position; 
         FIG. 19  is cross-sectional side view showing a structure for restricting the plug at the open position in a modified example of a liquid holding unit that does not include the cover; 
         FIG. 20  is a perspective view showing a portion of a housing to which a plug is coupled in a liquid holding unit of a second embodiment; 
         FIG. 21  is a plan view showing the plug of  FIG. 20 ; 
         FIG. 22  is a cross-sectional view taken along line F 22 -F 22  in  FIG. 21 ; 
         FIG. 23  is a cross-sectional view taken along line F 23 -F 23  in  FIG. 20 ; 
         FIG. 24  is a cross-sectional side view showing a modified example of a liquid holding unit that does not include a positioning guide; 
         FIG. 25  is a cross-sectional side view showing a modified example of a plug that includes the covering; 
         FIG. 26  is a cross-sectional side view schematically showing a liquid holding unit in a third embodiment; 
         FIG. 27  is a cross-sectional side view schematically showing an example of a plug including an urging member; 
         FIG. 28  is a cross-sectional side view schematically showing another structure of a liquid holding unit; 
         FIG. 29  is a perspective view showing, in part, a liquid holding unit in a fourth embodiment; 
         FIG. 30  is a cross-sectional view taken along line F 30 -F 30  in  FIG. 29 ; 
         FIG. 31  is a cross-sectional view taken along line F 31 -F 31  in  FIG. 29 ; 
         FIG. 32  is a perspective view showing a liquid holding unit in a modified example; 
         FIG. 33  is a perspective view showing a liquid holding unit in a modified example that differs from that of  FIG. 32 ; 
         FIG. 34  is a cross-sectional side view showing a modified example of a structure coupling the holding member and the plug body; 
         FIG. 35  is a cross-sectional side view schematically showing a liquid holding unit in a modified example that differs from that of  FIG. 33 ; and 
         FIG. 36  is a cross-sectional side view schematically showing a liquid holding unit in a modified example that differs from that of  FIG. 35 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     An all-in-one machine including a liquid ejection device (e.g., printer) will now be described with reference to the drawings. The liquid ejection device of the present embodiment is configured by an inkjet printer that performs printing by ejecting liquid, such as ink, onto a medium, such as paper. A serial printer that performs printing by moving a liquid ejector in a scanning direction X (hereinafter referred to as the widthwise direction X), which intersects a transfer direction Y of the medium, will be described as an example of a liquid ejection device. 
     As shown in  FIG. 1 , an all-in-one machine  11  includes a liquid ejection device  12  that ejects liquid and an image reading device  13  that has a reading function. The liquid ejection device  12  includes a box-shaped enclosure  14 . The image reading device  13  is located at the upper side of the enclosure  14 . 
     An operation panel  15  is arranged on the enclosure  14 . The operation panel  15  includes an operation unit  16  and a display unit  17 . The operation unit  16  includes, for example, a power button  16   a  and an operation button  16   b . The display unit  17  is formed by a touch panel type liquid crystal display screen or the like. 
     A front cover  18  is pivotal about the front lower end of the enclosure  14  to open and close the front surface of the enclosure  14 . A medium cassette  19  and a discharge port  20  are arranged at a rear side of the front cover  18 . The discharge port  20  discharges medium M that has undergone printing. The medium M fed from the medium cassette  19  is reversed at an inner position and then transferred in the transfer direction Y along a predetermined transfer path. 
     As shown in  FIG. 1 , the enclosure  14  includes a liquid ejector  21  that ejects liquid onto the medium M, which is transferred in the transfer direction Y. To perform, for example, printing, the liquid ejector  21  performs a liquid ejection operation by ejecting liquid toward the medium M at an intermediate position in the transfer path of the medium M. The medium M that has undergone printing is discharged from the discharge port  20  as shown by the double-dashed line in  FIG. 1 . The discharged medium M is placed on a slide-type stacker (discharge tray, not shown). The stacker extends toward the front of the enclosure  14 , which corresponds to the downstream side in the transfer direction of where printing starts. In this example in which the liquid ejection device  12  is a serial printer, the liquid ejector  21  includes a carriage  22  that is movable back and forth in the scanning direction X, which intersects the transfer direction Y. The liquid ejector  21  includes a nozzle (not shown) that allows liquid to be ejected to a portion opposing the transfer path of the medium M. In an example in which the liquid ejection device  12  is a line printer, the liquid ejector  21  is elongated and has a length that allows liquid to be ejected over an entire liquid-ejected region in a widthwise direction X that intersects the transfer direction Y. 
     As shown in  FIG. 1 , the liquid ejection device  12  includes a liquid holding unit  30  that supplies the liquid ejector  21  with liquid. In the present example, the liquid holding unit  30  is located at one of the two ends of the enclosure  14  in the widthwise direction X. A communication unit  23  including communication connectors  23   a  and  23   b  is located at the other one of the two ends of the enclosure  14  in the widthwise direction X. Thus, the liquid holding unit  30  and the communication unit  23  are located at opposite ends in the widthwise direction X. In the example shown in  FIG. 1 , a case  31  forming part of the enclosure  14  (outer shell) covers one side of the liquid holding unit  30 . A cover  32  covers an upper opening of the case  31 . The liquid holding unit  30  will be described in detail later. 
     The image reading device  13  shown in  FIG. 1  includes a document cover  13   a  and an image scanner (not shown). The document cover  13   a  is located at an upper portion of the image reading device  13  and is freely opened and closed. The document cover  13   a  covers a document table of a glass plate (not shown) when the document cover  13   a  is closed. A document (not shown) is placed on the glass plate and covered by the document cover  13   a . Then, the image scanner reads an image of the document from the lower side. The image reading device  13  is movable relative to the enclosure  14  between a close position shown in  FIG. 1  and an open position shown in  FIG. 2 . For example, to perform maintenance on the liquid ejection device  12  such as when removing jammed media out of the liquid ejection device  12 , the image reading device  13  is moved from the close position to the open position to expose the inside of the enclosure  14  to the outside. When refilling the liquid holding unit  30  with liquid, the cover  32  is opened. In the liquid ejection device  12  of the present example, the image reading device  13  is located at the close position that is in the movement path of the cover  32  between the open position and the close position. Thus, the cover  32  is moved from the close position shown in  FIG. 1  to the open position shown in  FIG. 2  under a situation in which the image reading device  13  is located at the open position. In  FIG. 2 , to facilitate illustration, the liquid ejector  21 , which should be arranged at a standby position as shown in  FIG. 1  when the image reading device  13  is located at the open position, is located at a middle position in the movement path of the liquid ejector  21 . The cover  32  may be omitted. In such a case, a portion of the image reading device  13  may be used to close the upper opening of the liquid holding unit  30 . Alternatively, the upper opening of the liquid holding unit  30  may be kept open. 
     Referring to  FIG. 2 , when the cover  32  of the liquid holding unit  30  is moved to the open position, which is located at an open angle in a range from 90 to 170 degrees, from the close position, further movement in the opening direction is restricted. The liquid holding unit  30  includes liquid holders  40  that hold liquid. The liquid holders  40 , the number of which is the same as the number of the types of liquids (e.g., color types of ink) that can be ejected from the liquid ejector  21 , are arranged in the case  31 . The liquid ejector  21  of the present example is capable of ejecting multiple types of liquid. Thus, multiple liquid holders  40  are arranged in the liquid holding unit  30  to supply the multiple types of liquid. 
     Further, the liquid holding unit  30  includes plugs  50  that open and close inlets  43  (refer to  FIG. 5 ) of the liquid holders  40 , respectively. In the present example, a plug  50  is provided for each liquid holder  40  arranged in the housing  33 . A user opens the plug  50  corresponding to the liquid holder  40  with which the user wishes to fill liquid with. Then, the user fills the liquid holder  40  with liquid from a liquid bottle (not shown). The liquid holding unit  30  does not have to be formed by part of the enclosure  14  as shown in  FIGS. 1 and 2 . For example, the liquid holding unit  30  may be attached to the outer wall (e.g., side wall) of the enclosure  14  or be a body that is separated from the enclosure  14  but connected by liquid supply tubes to the enclosure  14 . As long as the liquid holding unit  30  is capable of supplying the liquid ejector  21  with liquid through a liquid supply passage, the liquid holding unit  30  may be located inside or outside the enclosure  14 . 
     The liquid holding unit will now be described in detail with reference to  FIGS. 3 to 5 .  FIG. 3  shows a state in which the case  31  is removed from the enclosure  14  and the cover  32  is open. As shown in  FIG. 3 , the liquid holding unit  30  includes the housing  33  that accommodates the liquid holders  40 . The liquid holders  40  are arranged in the housing  33 . The plugs  50  are pivotally supported by an upper surface of the housing  33  at positions corresponding to the liquid holders  40 . In this manner, each of the plugs  50  are arranged in correspondence with each of the liquid holder  40 . 
     As shown in  FIG. 3 , the housing  33  includes a lower housing  34 , which is hollow and has a closed bottom, and an upper housing  35 , which is hollow.  FIG. 4  shows the liquid holding unit  30  without the upper housing  35 .  FIG. 5  shows the upper portion of the liquid holder  40 .  FIG. 6  shows the upper housing  35  and the plug  50 . 
     As shown in  FIG. 4 , the lower housing  34  includes partition plates  36  that define arrangement regions of the liquid holders  40 . The liquid holders  40  are arranged in the corresponding arrangement regions defined by the partition plates  36  in the widthwise direction X. At least a portion of a side wall  40   a  of each liquid holder  40 , for example, an edge  40   b  shown in  FIG. 5 , is fitted to an opening  36   a  in the corresponding partition plate  36  to position the liquid holder  40  in the front-rear direction and the vertical direction of the housing  33 . 
     Referring to  FIGS. 3 and 4 , the liquid holders  40  of the present example are of different sizes (volumes). When the liquid ejection device  12  is in, for example, a first liquid ejection mode, the liquid ejector  21  ejects liquid (first type of liquid) supplied from a single liquid holder. When the liquid ejection device  12  is in a second liquid ejection mode, the liquid ejector  21  ejects liquid (second type of liquid) supplied from multiple liquid holders  40 . Thus, the liquid holder  40  holding the first type of liquid has a relatively large volume, and the liquid holders  40  holding the second type of liquid each have a relatively small volume. In an example in which a liquid ejection operation is a printing operation, the first liquid ejection mode corresponds to a gray scale printing mode, and the second liquid ejection mode corresponds to a color printing mode. For example, the liquid holder  40  that holds black ink is wider than the other liquid holders  40 . 
     In the example shown in  FIG. 4 , the liquid holder  40  having the maximum volume is arranged at a position located at the end in the arrangement direction (widthwise direction X). A tube  42  of the liquid holder  40  having the maximum volume is located closer to the other liquid holders  40  in the widthwise direction X so that the plugs  50  are arranged at generally equal intervals in the widthwise direction X. The liquid holders  40  may all have the same size (volume) or have different sizes. Further, the combination of liquid holders  40  having different sizes may be changed. 
     As shown in  FIG. 4 , each liquid holder  40  includes an upper portion and a lower portion that is, for example, longer toward the rear than the upper portion. Thus, the liquid holding unit  30  avoids the arrangement area of the image reading device  13  or the like, and the liquid holders  40  have relatively large volumes. As shown in  FIGS. 4 and 5 , each liquid holder  40  includes a holder body  41  and the tube  42 , which is used to fill the liquid holder  40  with liquid. The tube  42  projects from one of an upper surface and a side surface (upper surface in example of  FIGS. 4 and 5 ) of the holder body  41  in a direction intersecting that surface. As shown in  FIG. 5 , each liquid holder  40  includes the inlet  43 . Liquid enters the inlet  43  when filling the liquid holder  40  with the liquid. In the example of  FIG. 5 , the open distal end of the tube  42  defines the inlet  43 . Further, each liquid holder  40  includes a front surface that at least partially includes a transparent portion (not shown). The height of the liquid surface in the liquid holder  40  is visible from the outside through the transparent portion. The liquid holder  40  does not have to be shaped so that the lower portion of the holder body  41  is longer than the upper portion of the holder body  41  and may be shaped so that a portion in the widthwise direction has a height that differs from other portions. Further, the liquid holder  40  may have the form of a box, a quadrangular post, a triangular post, or an elliptical post. 
     As shown in  FIG. 6 , the upper housing  35  includes a hollow housing  35 A that is rectangular and a lid  35 B that has the form of a plate and at least partially covers the upper opening of the hollow housing  35 A. The plugs  50  are coupled to the upper surface of the lid  35 B on the housing  33  (specifically, the upper housing  35 ). In detail, the upper surface of the housing  33  includes a rear end where shafts  37  are arranged. The two axial ends of each shaft  37  are held by supports  37   a  having a larger diameter than the shaft  37 . Thus, each shaft  37  is held between the supports  37   a  extending in the widthwise direction X of the liquid holders  40 . As shown in  FIG. 6 , each plug  50  includes a holding member  51  and a plug body  52  for the corresponding liquid holder  40 . The upper surface of the housing  33  shown in  FIG. 6  includes a recess  33   a  that is wide enough to allow the insertion of the plug body  52 . In a state in which the upper housing  35  is coupled to the lower housing  34  in which the liquid holders  40  are arranged, the tube  42  of each liquid holder  40  projects upward through a round hole (not shown) extending through the bottom portion of the corresponding the recess  33   a.    
     Further, as shown in  FIG. 6 , the front surface of the housing  33  includes a window  33   b  that has a predetermined height and a width corresponding to width of the liquid holders  40 . The case  31  includes a transparent window (not shown) at a portion opposing the window  33   b . Thus, the user can check the liquid surface height (liquid level) of each liquid holder  40  by looking through the transparent window of the case  31  and the window  33   b . Further, as shown in  FIG. 6 , two hinges  38  project from the rear end of the housing  33 . The cover  32  is coupled to the hinges  38 . 
     As shown in  FIGS. 6 and 7 , the plug  50  includes the elastically deformable plug body  52 , which covers the corresponding inlet  43  (refer to  FIG. 5 ), and the holding member  51 , which holds the plug body  52 . The holding member  51  is elongated in one direction. As shown in  FIG. 7 , the holding member  51  includes a first end  511  (one end), a second end  512  (other end), and side ends  513 , which intersects the first end  511  (one end) and the second end  512  (other end). More specifically, the side ends  513  intersect the first end  511  and the second end  512  and extend between the first end  511  and the second end  512 . In the example of  FIGS. 6 and 7 , the holding member  51  has the form of a rectangular plate elongated in one direction. Further, the holding member  51  includes the first end  511  defined by a distal end that extends in a short-side direction and the second end  512  defined by a basal end that extends in the short-side direction. The holding member  51  further includes the two side ends  513  defined by the end surfaces extending in the longitudinal direction of the holding member  51  and intersecting both of the end surface (distal end surface) of the first end  511  and the end surface (basal end surface) of the second end  512 . 
     As shown in  FIG. 7 , the first end  511  of the holding member  51  includes a tab  53  held by the user. The tab  53  projects from the surface of the holding member  51  in a direction (forward direction) extending from the second end  512  toward the first end  511  and in a direction (upward direction as viewed in  FIG. 7 ) extending from the surface (lower surface) of the holding member  51  located at the side of the plug body  52  toward the surface (upper surface) located at the opposite side.  FIG. 7  shows an example of the tab  53  that is L-shaped in a cross-sectional side view. The second end  512  of the holding member  51  includes an engagement portion  54  that is engageable with the corresponding shaft  37 . The engagement portion  54  has a widthwise length that is slightly shorter than the axial length of each shaft  37 . The engagement portion  54  has a C-shaped cross section obtained by cutting part of a ring. The opening of the engagement portion  54  is pressed against the corresponding shaft  37  so that the shaft  37  engages the engagement portion  54 . 
     As shown in  FIG. 7 , in a state in which the engagement portion  54  is engaged with the shaft  37 , the two axial sides of the engagement portion  54  are held between the two corresponding supports  37   a . This restricts displacement of the plug  50  in the widthwise direction X. Thus, movement of the plug  50  from the open position to the close position positions the plug body  52  relative to the tube  42  in the widthwise direction X. In  FIG. 7 , to facilitate illustration, a gap extends between each support  37   a  and the engagement portion  54 . However, the actual gap is extremely small or an axial displacement restriction spacer (not shown) extends from at least one of the support  37   a  and the engagement portion  54  to restrict displacement of the plug  50  in the widthwise direction X. This structure is also applied to the other embodiments. 
     As shown in  FIG. 7 , the plug body  52  is located between the tab  53  at the first end of the holding member  51  and the engagement portion  54  at the second end of the holding member  51 . The user holds the tab  53 , which is located closer to the first end of the holding member  51  than the plug body  52 , between fingers to open or close the plug  50 . Thus, liquid of the plug body  52  is not applied to the fingers. The plug  50  is arranged so that the longitudinal direction of the holding member  51  coincides with the longitudinal direction (front-rear direction) of the surface of the corresponding liquid holder  40  including the inlet  43  (tube  42 ). 
     The holding member  51  shown in  FIGS. 6 and 7  has higher rigidity than the plug body  52 . The holding member  51  is formed by a non-flexible member, and the plug body  52  is formed by a flexible member. The material of the non-flexible member may be plastic, metal, or the like. The material of the flexible member may be rubber, elastomer, or the like. The shafts  37 , the housing  33 , and the liquid holders  40  are formed by non-flexible members. Preferably, the material of the liquid holders  40  is selected from materials that are compatible with the properties of the held liquid (e.g., ink) and realize the functions required for the liquid holders  40 . The holding member  51 , the shafts  37 , and the housing  33  may be formed from the same material or from different materials. 
     Various coupling structures may be used to couple the plug body  52  to the holding member  51  shown in  FIG. 7 . The present example employs the coupling mechanism  60  to facilitate the coupling of the plug body  52  to the holding member  51 . As shown in  FIGS. 7, 8, and 9 , the holding member  51  includes a through hole  51   a  at a location where the plug body  52  is coupled. In the present example, the plug body  52  is at least partially fitted into the through hole  51   a . The plug body  52  includes a plug portion  61 , two projections  62  (keys), a fitted portion  63 , and a stopper  63   a . The plug portion  61  is tubular and has a closed end. The projections  62  project from opposite sides of the plug portion  61  in the radial direction. The fitted portion  63  project in the axial direction (upward direction as viewed in  FIGS. 7 to 9 ) from the side of the plug portion  61  opposite to the opening. The distal end of the fitted portion  63  includes a stopper  63   a  having the form of a truncated cone. 
     As shown in  FIGS. 7 to 9 , the rear surface of the holding member  51  includes two grooves  64  (key grooves) located near the through hole  51   a . The two projections  62  can be fitted (inserted) into the two grooves  64 , respectively. The two grooves  64  each define a groove passage that is arcuate, concentric with the through hole  51   a , and has one open end and another closed end. The coupling mechanism  60  includes a fastening portion (not shown) that fastens the two projections  62  and the two grooves  64  when the projections  62  are completely fitted into the grooves  64 . 
     A method for coupling the plug body  52  to the holding member  51  will now be described with reference to  FIGS. 9 to 11 . First, referring to  FIG. 9 , in a state in which the two projections  62  are shifted from the two grooves  64  in a rotation direction, the fitted portion  63  of the plug body  52  is fitted into the through hole  51   a  of the holding member  51 . As shown in  FIG. 10 , the plug body  52  is temporarily coupled to the holding member  51  with the stopper  63   a  fastened to the through hole  51   a  and the basal part of the fitted portion  63  loosely fitted in the through hole  51   a . Then, the plug body  52  is rotated in the counterclockwise direction to insert the two projections  62  into the two grooves  64 . As shown in  FIG. 11 , when the two projections  62  reach the terminal ends of the two grooves  64 , the two projections  62  are engaged with the two grooves  64 . In this manner, as shown in  FIGS. 8 and 11 , the plug body  52  is fixed to the holding member  51  by engagement of a key and key groove. 
     Referring to  FIG. 8 , the plug portion  61  is fitted onto the tube  42  to seal the corresponding inlet  43  with the plug body  52  in a liquid-tight state. The distal side of the plug portion  61  includes a guide surface  61   a  defined by an inclined inner circumferential surface that expands as the distal end becomes closer. Thus, even when the axis of the plug body  52  is slightly separated from the axis of the tube  42 , the guide surface  61   a , which comes into contact with the tube  42 , is guided along the tube  42  so that the axis of the plug body  52  approaches the axis of the tube  42 . This positions the plug portion  61  that is fitted to the tube  42  and seals the inlet  43 . The plugging structure in which the plug body  52  plugs the tube  42  is not limited to the above structure. 
       FIGS. 12 and 13  show examples of other plugging structures. The plug body  52  shown in  FIG. 12  is of a type that contacts the tube  42 . The plug body  52  is formed by a flexible member. The portion of the plug body  52  that contacts the inlet  43  of the tube  42  defines a plug portion  52   a  that is semispherical and bulged outward. As shown in  FIG. 12 , the semispherical plug portion  52   a  contacts the open end of the tube  42  and seals the inlet  43  in a liquid-tight manner. 
     The plug body  52  shown in  FIG. 13  is of a type fitted into the tube  42 . The plug body  52  is formed by a flexible member and includes a tubular or cylindrical plug portion  52   a . The plug portion  52   a  is fitted into the tube  42  to seal the inlet  43  in a liquid-tight manner. The plug  50  of each of the examples shown in  FIGS. 12 and 13  also couples the plug body  52  to the holding member  51  with the coupling mechanism  60  shown in  FIGS. 8 to 11 . More specifically, the plug body  52  is fixed to the holding member  51  by the engagement of the two projections  62  (keys) with the two grooves  64  (key grooves). In the coupling mechanism  60  shown in  FIGS. 8 to 13 , the stopper  63   a  may be omitted from the fitted portion  63 . 
     In the examples shown in  FIGS. 8 to 13 , part of the plug body  52  (fitted portion  63  and the like) is exposed from the through hole  51   a  in the surface of the holding member  51 . Thus, as shown in  FIGS. 14 to 17 , it is preferred that a structure for concealing exposed structures in the through hole  51   a  be employed. 
     In the example shown in  FIG. 14 , the opening (upper opening) of the through hole  51   a  in the holding member  51  at the side opposite to the plug body  52  is covered by a covering  65 . The covering  65  is in correspondence with the type of the liquid held in the corresponding liquid holder  40 . In the present example, the covering  65  is in correspondence with the color of the liquid. In other words, the covering  65  indicates the type of the liquid held in the liquid holder  40 . In the present example, the covering  65  indicates the color of liquid. In this manner, at least a portion of the surface (upper surface) of the covering  65  located at the side opposite to the surface facing the through hole  51   a  indicates the type of the liquid held in the liquid holder  40 , which is plugged by the plug  50  including the covering  65 . In the present example, the upper surface of the covering  65  indicates the color of the liquid. The color of the liquid may be indicated by entirely or partially coloring the plug  50  in accordance with the color of the liquid. Alternatively, the color of the liquid may be indicated by information related to the color, e.g. color name or color code (serial number). As another option, the color of the liquid may be indicated by both of the color name and the color information. 
     In the example shown in  FIG. 15 , the covering  65  is formed by a cap  66  that has a shape (e.g., shape of disk or tube having closed end) allowing the cap  66  to be fitted into the through hole  51   a  from the upper opening. The cap  66  is, for example, colored with the same color as the liquid held in the corresponding liquid holder  40 . The cap  66  is fitted into the through hole  51   a  from the upper opening to cover the upper opening. Thus, even when the plugs  50  are arranged next to one another as shown in  FIG. 14 , the user can recognize the color of the liquid from at least the coloring of the cap  66  or the color information indicated on the cap  66 . This allows the user to check the type (color) of the liquid held in each liquid holder  40  when filling the liquid holder  40  with liquid. This reduces errors in which the liquid holders  40  are filled with liquid of the wrong colors. 
     In the example shown in  FIG. 16 , the covering  65  is formed by a label  67  that covers the upper opening of the through hole  51   a . The label  67  indicates the type of the liquid held in the corresponding liquid holder  40  that is plugged by the plug  50  to which the label  67  is applied. In the present example, the label  67  indicates the color of the liquid. 
     As shown in  FIG. 17 , the label  67  is applied to the upper surface of the holding member  51  so as to cover the upper opening of the through hole  51   a . Thus, even when the plugs  50  are arrange next to one another as shown in  FIG. 16 , the user can recognize the color of the liquid from the color indicated on the label  67  applied to each plug  50 , that is, one of the coloring and the color information. This allows the user to check the type (color) of the liquid held in each liquid holder  40  when filling the liquid holder  40  with liquid. This reduces errors in which the liquid holders  40  are filled with liquid of the wrong colors. 
     Preferably, the pivot range of the plug  50  is restricted as shown in  FIG. 18 . In the example shown in  FIG. 18 , the plug  50  contacts the cover  32  that is located at the open position. This restricts the pivot range of the plug  50 . A restriction portion  39  is arranged in the cover  32 . In a state in which the cover  32  is located at the open position, the restriction portion  39  contacts the holding member  51  when the plug  50  is moved to the open position. This restricts the pivot range of the holding member  51 . The cover  32  includes a thin portion  32   a  and a thick portion  32   b . In the radial direction extending outward from the portion of the cover  32  coupled to the hinges  38 , the thin portion  32   a  is proximate to the coupled portion and the thick portion  32   b  is distant from the coupled portion. The cover  32  includes a bent portion at the boundary of the thin portion  32   a  and the thick portion  32   b . The inner side of the bent portion functions as the restriction portion  39 . The cover  32  contacts, for example, a restriction portion  14   a  of the enclosure  14  at the open position. This restricts the pivot range of the cover  32  and holds the cover  32  at a predetermined open angle. In a state in which the cover  32  is located at the open position, when opening the plug  50 , the corresponding holding member  51  contacts the restriction portion  39 . This restricts further movement of the plug  50  in the opening direction and holds the plug  50  at the open position. 
     The open angle of the plug  50  at the open position from the close position, or reference position (0 degrees) is set to be greater than or equal to the minimum angle at which the plug  50  can remain at the open position without falling to the close position because of its weight and set to be less than or equal to the maximum angle that obtains a sufficient gap (e.g., 5 mm or greater) allowing the user to push the distal end of the tab  53  and close the plug  50  from the open position. Preferably, the open angle of the plug  50  is set to a predetermined angle, for example, in the range from 95 to 170 degrees. In particular, the preferred open angle is 100 degrees or greater since such an angle will ensure that the plug  50  remains at the open position without falling to the close position because of its weight. As the open angle of the plug  50  increases, when closing the plug  50 , the fingers used to hold the tab  53  of the plug  50  at the open position comes into contact more easily with the bottom portion of the plug body  52 . In this regard, it is preferred that the open angle of the plug  50  be less than or equal to 150 degrees. Thus, it is preferred that the open angle of the plug  50  be set to a predetermined angle that is in the range from 100 to 150 degrees. In the example of  FIG. 18 , the tab  53  contacts the restriction portion  39 . However, other portions of the holding member  51  may contact the restriction portion  39 . Further, the location of the restriction portion  39  in the cover  32  relative to the plug  50  may also be changed. 
     Referring to  FIG. 19 , the cover  32  may be omitted from the housing  33 . As shown in  FIG. 19 , the housing  33  includes a restriction portion  33   c  that contacts the holding member  51  when the plug  50  opens to restrict the pivot range of the holding member  51 . The open angle of the plug  50  is, for example, preferably in the range from 95 to 170 degrees and more preferably in the range from 100 to 150 degrees. Further, as shown in  FIG. 19 , the plug  50  may include a projection that extends from the holding member  51  in a direction opposite to the tab  53 . The projection may function as a tab  153  that is held by the user. In this example, the distal end of the holding member  51  is bifurcated to form the tab  53  and the tab  153 . A tab may be located at any position on the holding member  51  as long as the tab can be held by the user. In a structure that includes the cover  32 , the holding member  51  may contact the restriction portion  33   c  to restrict the pivot range of the plug  50 . 
     The operation of the liquid holding unit  30  and the liquid ejection device  12  will now be described. 
     In the liquid ejection device  12 , the medium M fed from the medium cassette  19  is transferred in the transfer direction Y. Further, the liquid ejector  21  ejects liquid onto the medium M when the medium M is being transferred to print, for example, an image on the medium M. A controller (not shown) of the liquid ejection device  12  stores the present liquid amount of each liquid holder  40  remaining from the previous operation. The controller subtracts the consumed liquid amount of each liquid holder  40  from the previous liquid amount of the liquid holder  40 . When the liquid amount of a liquid holder  40  becomes less than a threshold value for the lower limit of the liquid amount (e.g., near end), the controller shows a message on the display unit  17  indicating such a situation and prompts the user to fill the liquid holder  40  with liquid. The user fills the liquid holders  40  indicated on the display unit  17  with liquid. 
     When filling the liquid holders  40  with liquid, the user first opens the image reading device  13  and then opens the cover  32 . This exposes the plugs  50  of the liquid holders  40  to the outside. In the examples in which the covering  65  of the holding member  51  of the plug  50  indicates the liquid color ( FIGS. 14 to 17 ), the plug  50  corresponding to the liquid holder  40  that is to be filled with liquid can be located based on, for example, the color indicated by the covering  65 , namely, the coloring or the color information. Thus, the user selects and opens the appropriate one of the plugs  50 . The user can hold the tab  53  of the selected plug  50  to open the plug  50 . The tab  53  allows for easy opening of the plug  50 . Further, the tab  53  is located closer to the first end (distal end) of the holding member  51  than the plug body  52 . Thus, application of liquid from the plug body  52  to the fingers is limited. The user moves the appropriate plug  50  to open the corresponding inlet  43  and fills the liquid holder  40  with liquid through the inlet  43 . 
     When filling the liquid holder  40  with liquid, the user checks the liquid surface height (liquid level) from the outer side of liquid holding unit  30  and pours the liquid until reaching, for example, an upper limit position. When the filling of the liquid holder  40  with liquid is completed, the user closes the plug  50 . Here, the plug  50 , which is located at the open position when filling the liquid holder  40  with liquid, is in contact with the restriction portion  39  or  33   c  so that further movement of the plug  50  is restricted. At the open position, the plug  50  is held at a predetermined open angle (e.g., predetermined angle in range from 90 to 170 degrees), preferably, at a predetermined open angle in the range from 95 to 150 degrees (refer to  FIGS. 18 and 19 ). Thus, when closing the plug  50  held at the open angle, contact of the fingers holding the tab  53  with the bottom portion of the plug body  52  is limited. This limits the liquid that is applied to the fingers. Further, the holding member  51  of the plug  50  is tilted at the predetermined open angle. This easily avoids situations in which the user inadvertently places his or her hand on the plug  50  and breaks the plug  50  as compared with when the plug  50  lies horizontally at an open angle of approximately 180 degrees. Particularly, in the structure in which contact of the plug  50  with the restriction portion  39  inside the cover  32  restricts the pivot range, the open angle is easily set to the preferred range from 100 to 150 degrees in order to further limit the liquid applied from the plug body  52  to the fingers and further reduce the breaking frequency of the plug  50 . 
     The holding member  51  has higher rigidity than the flexible plug body  52  and resists deformation when opening the plug  50 . This limits the liquid applied from the plug body  52  to the fingers. For example, when the rigidity of holding member is less than or equal to the flexible plug body, the holding member  51  deforms when opening or closing the plug  50  and vibrates the plug body  52 . In such a case, liquid is easily applied from the plug body  52  to the fingers of the user. In the present embodiment, the holding member  51 , which has higher rigidity than the plug body  52 , resists deformation when opening or closing the plug  50 , and limits vibration of the plug body  52 . This limits the liquid that is applied from the plug body  52  to the fingers or the like and easily positions the plug body  52  relative to the inlet  43 . Further, when the distal side of the plug body  52  includes the guide surface  61   a  (refer to  FIG. 8 ) that corresponds to the tube  42 , the plug body  52  securely closes the tube  42  even when the plug body  52  and the tube  42  are slightly misaligned from each other. In addition, the plug body  52  is formed from an elastically deformable member. This ensures that the plug body  52  seals the inlet  43 . 
     Further, the engagement of the shaft  37  with the engagement portion  54  allows the plug  50  to be pivotal relative to the housing  33  or the corresponding liquid holder  40 . Thus, when holding the distal end of the holding member  51  (e.g., tab  53 ) to open or close the plug  50 , the law of the lever reduces the force required to open or close the plug  50 . This allows the plug  50  to be easily opened or closed with a relatively small force. 
     In each plug  50  shown in  FIGS. 7 to 13 , the coupling mechanism  60  that couples the two projections  62  (keys) and the two grooves  64  (key grooves) are employed to couple the holding member  51  and the plug body  52 . Thus, when coupling the plug body  52  to the holding member  51  in a manufacturing plant, the fitted portion  63  of the plug body  52  is fitted into the through hole  51   a  in the holding member  51  of the plug body  52 . Then, the plug body  52  is rotated so that the two projections  62  engage the two grooves  64 . This couples the holding member  51  and the plug body  52 , which are formed by members that differ from each other in rigidity, in a relatively simple manner. Thus, the plug  50  is manufactured in a relatively simple manner. 
     The first embodiment has the advantages described below. 
     (1) The liquid holding unit  30 , which supplies liquid to the liquid ejector  21  of the liquid ejection device  12 , includes the liquid holders  40  holding liquid, the housing  33  that accommodates the liquid holders  40 , the inlets  43  used to fill the corresponding liquid holders  40  with liquid, and the plugs  50  that open and close the corresponding inlets  43 . Each plug  50  includes the elastically deformable plug body  52  that covers the corresponding inlet  43  and the holding member  51  that has higher rigidity than the plug body  52  and holds the plug body  52 . Thus, when the user opens or closes the plug  50  to fill the corresponding liquid holder  40  with liquid, the frequency is reduced in which the liquid is applied from the plug body  52  to the fingers or the like of the user. 
     (2) The holding member  51  includes the first end  511 , the second end  512 , and the side ends  513  that intersect the first end  511  and the second end  512 . The first end  511  includes the tab  53  used to open or close the corresponding inlet  43 . Thus, the user holds the tab  53  between fingers to open or close the plug  50 . This facilitates the opening and closing of the plug  50  and further reduces the frequency liquid is applied from the plug body  52  to the fingers when opening and closing the plug body  52 . 
     (3) The plug body  52  is located between the tab  53  and the second end  512  of the holding member  51 . Thus, when the user opens or closes the plug  50 , situations are reduced in which the user inadvertently touches the portion of the plug body  52  at the side that seals the inlet  43 . This further avoids the application of liquid from the plug body  52  to the fingers of the user. 
     (4) The liquid holding unit  30  includes the plugs  50  respectively corresponding to the liquid holders  40 . Each of the plugs  50  includes a single plug body  52  for the corresponding liquid holder  40 . Since each liquid holder  40  is independently opened and closed by the corresponding plug  50 , the frequency is further reduced in which liquid is applied from the plug body  52  to the fingers of the user when opening or closing the plug  50  as compared to a structure in which multiple plugs are formed integrally with one another. This also reduces the evaporation or volatilization of liquid from the liquid holders  40  other than the one that is filled with liquid. 
     (5) The liquid holding unit  30  includes the shafts  37  that are used to pivot the corresponding plugs  50  and the engagement portions  54  that are engaged with the corresponding shafts  37 . The housing  33  includes either one of the shafts  37  and the engagement portions  54 , and the plugs  50  include the other one of the shafts  37  and the engagement portions  54 . Thus, when the user opens or closes a plug  50  while holding the distal end of the corresponding holding member  51 , the law of the lever reduces the force required to open or close the plug  50 . 
     (6) The cover  32  includes the restriction portion  39 , and the housing  33  includes the restriction portion  33   c . In a state in which each holding member  51  is pivoted in a direction that opens the corresponding inlet  43 , the restriction portion  39  or  33   c  contacts the holding member  51  and restricts the pivot range of the holding member  51 . Such a structure reduces the application of liquid from the plug body  52  to the fingers or the like of the user when opening or closing the plug  50  compared to when, for example, a structure in which the pivot range of the holding member  51  is not restricted and the plug  50  is pivoted by approximately 180 degrees lying horizontally at the open position. This further reduces the frequency in which liquid is applied from the plug body  52  to the fingers or the like of the user. Further, the opening and closing amount of the plug  50  is relatively decreased, and the liquid holder  40  is easily filled with liquid. Moreover, in a structure in which a plug lies horizontally at the open position, the user may inadvertently place his or her hand on the plug and break the plug. However, in the present example, the plug  50  is held at a tilted position at the open position (e.g., position where open angle is 95 to 170 degrees). This decreases the possibility of the user inadvertently placing his or her hand on the plug  50  and reduces situations in which the user inadvertently breaks the plug  50 . 
     (7) The holding member  51  includes the covering  65  that covers the upper opening of the through hole  51   a  and is in correspondence with the color of the liquid held in the corresponding liquid holder  40 . The covering  65  functions to conceal the through hole  51   a  of the holding member  51  and indicate the color. This improves the aesthetic appeal of the plug  50 . Further, the user can check the color of the liquid by looking at the covering  65 . This reduces errors in which the liquid holders  40  are filled with liquid of the wrong colors. 
     (8) The liquid ejection device  12  includes the liquid holding unit  30  and the liquid ejector  21  that ejects the liquid supplied from the liquid holders  40  in the liquid holding unit  30 . When the consumption of liquid by the liquid ejector  21  results in the need to fill the liquid holders  40  with liquid, the liquid ejection device  12  has the advantages of the liquid holding unit  30 . 
     Second Embodiment 
     A liquid holding unit of a second embodiment will now be described with reference to the drawings. Same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described in detail. The description hereafter will focus on differences from the first embodiment. 
     As shown in  FIG. 20 , the liquid holding unit  30  includes a positioning guide  70  for each plug  50 . The positioning guide  70  includes a projection  71  and a recess  72 . In a state in which the inlet  43  is closed by the corresponding plug  50  (refer to  FIG. 22 ), the projection  71  is inserted into the recess  72  to guide and position the plug  50  relative to the inlet  43 . The holding member  51  includes one of the projection  71  and the recess  72 , and the corresponding liquid holder  40  or the housing  33  includes the other one of the projection  71  and the recess  72 . In the example shown in  FIGS. 20 to 23 , the holding member  51  includes the projection  71 , and the housing  33  includes the recess  72 . In detail, as shown in  FIG. 20 , the surface of the holding member  51  opposing the housing  33  includes the projection  71 , and the upper surface of the housing  33  includes the recess  72 . The projection  71  is inserted in the recess  72  when the plug  50  is located at the close position. As shown in  FIGS. 20 and 21 , the holding member  51  of the plug  50  is elongated in a single direction in the same manner as the first embodiment. 
     As shown in  FIG. 22 , the projection  71  includes a tapered guide surface  71   a  having a dimension in the longitudinal direction of the holding member  51  that decreases toward the distal side. Thus, when closing the plug  50 , the plug  50  is guided and positioned in the longitudinal direction of the plug  50  as the projection  71  enters the recess  72 . As shown in  FIG. 23 , the projection  71  includes the tapered guide surface  71   b  having a dimension in the widthwise direction X that decreases toward the distal side. Thus, when closing the plug  50 , the plug  50  is guided and positioned in the widthwise direction X as the projection  71  enters the recess  72 . In this manner, when closing the plug  50 , the plug body  52 , which is held by the holding member  51 , is positioned relative to the tube  42  of the corresponding liquid holder  40 . This ensures that the plug body  52  is fitted onto the tube  42 . Instead of the projection  71 , the inner surfaces of the recess  72  may form the guide surface. Further, the positioning guide  70  need only include at least one of a guide surface that guides the holding member  51  in the longitudinal direction and a guide surface that guides the holding member  51  in the widthwise direction X. For example, the positioning guide  70  may include only one of the guide surfaces. 
     The positioning guide  70  guides and positions the plug body  52 . However, when the position where the holding member  51  is coupled or the position where the plug body  52  and the holding member  51  are coupled differs from the intended position, the plug body  52  may be displaced and separated from the inlet  43  even though the positioning guide  70  guides and positions the plug body  52 . Thus, in the plug  50  of the present embodiment, the plug body  52  is held so as to be movable relative to the holding member  51  in the longitudinal direction. 
     As shown in  FIGS. 21 and 22 , the plug body  52  includes a rod  55  that projects from the plug body  52  at the side opposite to the portion that seals the corresponding inlet  43 . The rod  55  includes two rod guides  55   a  (refer to  FIG. 21 ) that project from opposites sides of the rod  55  in the widthwise direction X. The holding member  51  includes a rectangular guide hole  51   c  (through hole) and two recesses  51   d . The guide hole  51   c  guides the rod  55  in the longitudinal direction of the holding member  51  in a state in which the rod  55  is inserted into the guide hole  51   c . The recesses  51   d  are located at opposite sides of the guide hole  51   c  in the widthwise direction X and extend in the longitudinal direction of the holding member  51 . The plug body  52  is coupled to the holding member  51  in a state in which the rod  55  is inserted into the guide hole  51   c  and the two rod guides  55   a  are placed on the bottom surfaces of the corresponding recesses  51   d . The rod  55  is movable along the guide hole  51   c  in the longitudinal direction of the holding member  51 . This provides a certain degree of freedom for the position of the plug body  52  in the longitudinal direction of the holding member  51 . Further, in the present example, the width of the guide hole  51   c  is slightly greater than the outer diameter of the rod  55 , and the plug body  52  is movable in the widthwise direction X relative to the holding member  51 . This provides a certain degree of freedom for the position of the plug body  52  in the widthwise direction X relative to the holding member  51 . 
     When closing the plug  50 , the projection  71 , which is inserted into the recess  72 , positions the holding member  51  in the longitudinal direction of the holding member  51  and in the widthwise direction X. Thus, even if the plug body  52  is displaced by a maximum amount relative to the tube  42 , when the plug body  52  is moved in the closing direction, the guide surface  61   a  of the plug body  52 , which contacts the tube  42 , guides and positions the plug body  52  in the longitudinal direction of the holding member  51  and the widthwise direction X so that the plug body  52  is fitted onto the tube  42 . 
     When closing the plug  50  in this manner, the insertion of the projection  71  into the recess  72  positions the plug  50  at the proper position in at least one of the longitudinal direction and the widthwise direction X. Further, the plug body  52  is movable relative to the holding member  51  and is provided with a certain degree of freedom in position relative to the corresponding inlet  43 . This ensures that the plug body  52  seals the inlet  43 . More specifically, when closing the inlet  43  with the plug  50 , the projection  71 , which is inserted in the recess  72 , guides and positions the plug  50  relative to the inlet  43 . This obviates the entrance of foreign matter into the liquid holder  40  and the evaporation or volatilization of liquid out of the liquid holder  40  that would result from defective sealing of the inlet  43 . 
     The positioning guide  70  may be omitted as shown in  FIG. 24 . In this structure, the plug body  52  is movable along the guide hole  51   c  relative to the holding member  51 . Further, the plug body  52  is provided with a certain degree of freedom in position in at least one of the longitudinal direction of the holding member  51  and the widthwise direction X. Thus, engagement of the guide surface  61   a  with the tube  42  moves the plug body  52  relative to the holding member  51  and guides and positions the plug body  52  relative to the holding member  51 . This ensures that the plug body  52  seals the corresponding inlet  43 . 
     Further, as shown in  FIG. 25 , the guide hole  51   c  of the holding member  51  may be covered by the covering  65 . In the example of  FIG. 25 , as one example of the covering  65 , the cap  66  is fitted into the guide hole  51   c . The rod  55  is formed to contact the inner wall surface  65   a  of the cap  66 . This obtains a fitting margin for the cap  66  and restricts the movement range of the plug body  52 . In the present example, the movable range of the plug body  52  set by the inner wall surface  65   a  of the cap  66 , which is fitted in the guide hole  51   c , is the same in the structure of  FIGS. 21 to 24  that does not have the cap  66 . Instead of the cap  66 , the label  67  shown in  FIGS. 16 and 17  may be applied as the covering  65  to the holding member  51 . 
     In addition to advantages (1) to (8), the second embodiment has the advantages described below. 
     (9) The holding member  51  is elongated in one direction and holds the plug body  52  so that the plug body  52  is movable in the longitudinal direction of the holding member  51 . This provides the plug  50  with a certain degree of freedom in position relative to the holding member  51  in the longitudinal direction of the holding member  51 . Thus, when the plug body  52  is fitted to the corresponding inlet  43  or when the plug body  52  contacts the inlet  43 , the plug body  52  is moved relative to the holding member  51  and guided and positioned relative to the inlet  43  to ensure that the inlet  43  is sealed. This reduces the frequency in which defective sealing of the inlet  43  occur and obviates, for example, the entrance of foreign matter into the liquid holder  40  and the evaporation or volatilization of liquid out of the liquid holder  40  that would result from defective sealing of the inlet  43 . 
     (10) The liquid holding unit  30  includes the positioning guide  70 . The positioning guide  70  includes the projection  71  and the recess  72  that guide and position the plug  50  relative to the inlet  43  when the projection  71  is inserted into the recess  72  in a state in which the inlet  43  is closed by the plug  50 . The holding member  51  includes one of the projection  71  and the recess  72 , and the liquid holder  40  or the housing  33  includes the other one of the projection  71  and the recess  72 . Thus, when moving the plug  50  from the open position to the close position and inserting the projection  71  into the recess  72 , the plug  50  is positioned at the proper position. This ensures that the plug body  52  seals the corresponding inlet  43  and obviates the entrance of foreign matter into the liquid holder  40  and the evaporation or volatilization of liquid out of the liquid holder  40  that would result from defective sealing of the inlet  43 . 
     Third Embodiment 
     A liquid holding unit of a third embodiment will now be described with reference to the drawings. Same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described in detail. The description hereafter will focus on differences from the first embodiment. 
     As shown in  FIG. 26 , the holding member  51  of the plug  50  is bendable. In detail, the holding member  51  includes a first piece  81 , a second piece  82 , and a pivot  83 . The first piece  81  is located toward a first end (distal end) of the holding member  51  and includes the plug body  52 . The second piece  82  is located closer to the second end (basal end) of the holding member  51  than the first piece  81 . The pivot  83  is located between the first piece  81  and the second piece  82  to pivot the first piece  81  relative to the second piece  82 . 
     As shown in  FIG. 26 , in a state in which the plug  50  is located at the open position, the first piece  81  is pivoted relative to the second piece  82  about the pivot  83  by a predetermined angle in the direction in which the plug body  52  approaches the corresponding inlet  43 , and the holding member  51  is in a bent formation as shown by the solid lines in  FIG. 26 . The state in which the plug  50  is located at the open position refers to a state in which the plug  50  opens the inlet  43 . In a state in which the plug  50  is located at the close position, the first piece  81  and the second piece  82  are arranged straight about the pivot  83 , and the holding member  51  is in a straight formation as shown by the double-dashed lines in  FIG. 26 . The state in which the plug  50  is located at the close position refers to a state in which the plug  50  is sealing the inlet  43 . As shown in  FIG. 26 , when the first piece  81  is bent toward the inlet  43  by angle about the pivot  83  from a state in which the first piece  81  is flush with the second piece  82  as shown by the single-dashed line, a restriction portion (not shown) restricts further pivoting (bending) of the first piece  81 . When the holding member  51  is in the straight formation as shown by the double-dashed line in  FIG. 26 , a restriction portion (not shown) restricts pivoting (bending) of the first piece  81  so that the first piece  81  does not move away from the inlet  43 . In this manner, the first piece  81  is bendable relative to the second piece  82  within an angular range set between the straight formation shown by the double-dashed lines in FIG.  26  and the bent formation shown by the solid lines in  FIG. 26 . In a state in which the holding member  51  is located at the open position as shown by the solid lines in  FIG. 26 , the second piece  82  is in contact with a restriction portion of the cover  32  or the housing  33 . This holds the second piece  82  at a predetermined open angle as shown in  FIG. 26 . 
     When the plug  50  is located at the close position, the first piece  81  and the second piece  82  are in the straight formation as shown by the double-dashed lines in  FIG. 26 , and the plug body  52  seals the inlet  43 . As the user holds the first end (distal end) of the holding member  51  between his or her fingers and moves the plug  50  from the close position to the open position, the force applied from the fingers to the first piece  81  pivots (bends) the first piece  81  relative to the second piece  82  and transforms the holding member  51  from the straight formation to the bent formation. In the bent formation, the plug body  52  is directed diagonally downward. This limits the liquid applied from the plug body  52  to the fingers or the like of the user. 
     Preferably, as shown in the example of  FIG. 27 , an urging member  84  is arranged on the holding member  51  to urge the first piece  81  relative to the second piece  82  in a direction in which the holding member  51  bends from the straight formation to the bent formation. In this structure, when the user opens the plug  50 , the urging force of the urging member  84  automatically transforms the holding member  51  from the straight formation to the bent formation, and there is no need to adjust the force that is applied to bend the holding member  51  from the straight formation to the bent formation. As a result, when opening and closing the plug  50 , the application of liquid from the plug body  52  to the fingers or the like is further limited. The urging member  84  may be a torsion spring as shown in  FIG. 27 . Alternatively, a coil spring, a rubber member, or the like may be used as the urging member  84 . Further, the urging member  84  need not be arranged between the first piece  81  and the second piece  82  and may be arranged between the first piece  81  and the housing  33  or between the first piece  81  and the liquid holder  40 . 
     In this case, preferably, as shown in  FIG. 28 , the liquid holding unit  30  includes the cover  32  that covers the plug  50  in a closed state shown in  FIG. 28  and exposes the plug  50  in an open state. The cover  32  includes a formation holding mechanism  85  that contacts at least one of the first piece  81  and the second piece  82  in a state in which the plug  50  seals the corresponding inlet  43  to hold the holding member  51  in the straight formation. In the example shown in  FIG. 28 , the formation holding mechanism  85  includes one or more abutment portions. 
     In detail, as shown in  FIG. 28 , the formation holding mechanism  85  includes a first rib  86  and a second rib  87  that serve as examples of abutment portions. When the plug  50  is located at the close position, the first rib  86  contacts the surface (lower surface) of the first piece  81  that opposes the inlet  43 . When the cover  32  is in the closed state, the second rib  87  contacts the surface (upper surface) of the second piece  82  that is opposite to the rear surface. More specifically, the first rib  86  contacts the first piece  81  from below in the vertical direction, and the second rib  87  contacts the second piece  82  from above in the vertical direction. In the example shown in  FIG. 28 , the liquid holder  40  includes the first rib  86 , and the cover  32  includes the second rib  87 . The formation holding mechanism  85  may be formed by a single abutment portion that contacts the surface of the first piece  81  at the opposite side of the surface (rear surface) opposing the inlet  43  or be formed by just one second rib  87 . Further, in  FIG. 28 , the cover  32  may include the first rib  86  that contacts the upper surface of the first piece  81 . Further, the abutment portion that contacts at least one of the first piece  81  and the second piece  82  is not limited to a rib and may be a projection other than a rib, the inner surface of the cover  32 , a portion of the liquid holder  40  other than a rib, a rib of the housing  33 , or a portion of the housing  33  other than a rib. 
     In this manner, the plug  50  is held in the straight formation when the cover  32  is closed. This maintains the plug  50  in the closed state against the urging force of the urging member  84 . Thus, for example, the urging force of the urging member  84  does not move the plug  50  in the opening direction after the cover  32  is closed. This avoids situations in which the plug  50  moves and opens the corresponding inlet  43 . Although not shown in the examples of  FIGS. 26 to 28 , the holding member  51  preferably includes the tab  53  of the first embodiment at the first end (distal end). Further, when holding the plug body  52  on the holding member  51  with the same coupling structure as the first embodiment, it is preferred that the first piece  81  of the holding member  51  include the covering  65  that covers the upper opening of the through hole  51   a.    
     In addition to advantages (1) to (8) of the first embodiment, the third embodiment has the advantages described below. 
     (11) The holding member  51  includes the first piece  81  located toward the first end of the holding member  51  and provided with the plug body  52 , the second piece  82  located closer to the second end of the holding member  51  than the first piece  81 , and the pivot  83  located between the first piece  81  and the second piece  82 . In a state in which the plug  50  is located at the open position, the holding member  51  is in the bent formation in which the first piece  81  is pivoted relative to the second piece  82  about the pivot  83  in the direction in which the plug body  52  approaches the corresponding inlet  43 . In a state in which the plug  50  is located at the close position, the holding member  51  is in the straight formation in which the first piece  81  and the second piece  82  are arranged straight. When opening the plug  50 , the holding member  51  takes the bent formation so that the plug body  52  is directed toward the inlet  43 . Thus, when opening and closing the plug  50 , the application of liquid from the plug body  52  to the fingers of the user is limited. Thus, when opening and closing the plug  50  to fill the liquid holder  40  with liquid, the frequency is further reduced in which liquid is applied from the plug body  52  to the fingers or the like of the user. 
     (12) The holding member  51  includes the urging member  84  that urges the holding member  51  in a direction in which the holding member  51  bends from the straight formation to the bent formation. Thus, when opening the plug  50 , the holding member  51  is arranged in the bending formation without the need for the user to adjust the force applied to the holding member  51  to bend the holding member  51 . This further reduces the frequency in which liquid is applied from the plug body  52  to the fingers or the like of the user when opening and closing the plug  50 . 
     (13) The liquid holding unit  30  includes the cover  32 , which opens to expose the plug  50  and closes to cover the plug  50 , and the formation holding mechanism  85 , which contacts at least one of the first piece  81  and the second piece  82  when the cover  32  is closed to hold the holding member  51  in the straight formation at the close position. Thus, even when the urging member  84  is urged in a direction in which the holding member  51  takes the bent formation, when closing the cover  32  after the plug  50  is arranged at the close position, the formation holding mechanism  85  contacts at least one of the first piece  81  and the second piece  82  to hold the holding member  51  in the straight formation and keep the holding member  51  closed. This reduces the occurrence of defective sealing that result from the urging force of the urging member  84  that acts to remove the plug body  52  from the inlet  43 . This obviates the entrance of foreign matter into the liquid holder  40  and the evaporation or volatilization of liquid out of the liquid holder  40  that would result from defective sealing of the inlet  43 . 
     Fourth Embodiment 
     A liquid holding unit of a fourth embodiment will now be described with reference to the drawings. Same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described in detail. The description hereafter will focus on differences from the first embodiment.  FIGS. 29 to 31  show the plug  50  of only one of the liquid holders  40  in the liquid holding unit  30 . The description hereafter will focus on the shown plug  50  that is identical to the other plugs  50 . 
     Referring to  FIG. 29 , in the present embodiment, the plug  50  is slidable. The housing  33  or the liquid holder  40  (refer to  FIG. 5 ) includes guides  91  that hold the holding member  51  of the plug  50  in a slidable manner. The guides  91  hold the holding member  51  in a slidable manner. In the example shown in  FIG. 29 , the housing  33  includes the guides  91 , and the holding member  51  is held to be slidable relative to the housing  33 . In detail, as shown in  FIGS. 29 to 31 , the lid  35 B of the housing  33  includes a through hole  92  that is rectangular and elongated in the longitudinal direction of the holding member  51 . The through hole  92  is defined by two inner walls that oppose each other in the widthwise direction X. Each inner wall is recessed and defines one of the two guide  91 . 
     The holding member  51  has higher rigidity than the elastically deformable plug body  52  and is elongated in one direction. The two sides of the holding member  51  in the widthwise direction X are partially inserted into the two guides  91  and held in a manner slidable relative to the housing  33 . The plug body  52  moves together with the holding member  51  in a sliding direction. Referring to  FIGS. 30 and 31 , the direction in which the holding member  51  and the plug body  52  are slidable is parallel to the plane of the opening of the inlet  43 . The guides  91  may be projections instead of grooves, and the side walls of the holding member  51  may include grooves. In such a case, the guides  91  are engaged with the grooves to hold the holding member  51  in a slidable manner. Alternatively, the guides  91  may be rails, and the holding member  51  may slide on the rails. As another option, the holding member  51  may include rollers that roll on such rails. 
     Referring to  FIGS. 30 and 31 , the plug body  52  is fixed to the holding member  51 . The plug body  52  is of the type shown in  FIG. 12  that contacts and seals the inlets  43 . Thus, even in a structure in which the holding member  51  slides, the plug body  52  seals the inlet  43  without interfering with the tube  42 . One end (first end) of the holding member  51  includes the tab  53 . The plug body  52  is located on the holding member  51  between the tab  53  and the outer end (second end). Preferably, as shown in  FIGS. 29 to 31 , the upper opening of the through hole  51   a , into which the plug body  52  is partially fitted, is covered by the covering  65 . In this case, the covering  65  is in correspondence with the color of the liquid held in the corresponding liquid holder  40  in the same manner as the first to third embodiments. The covering  65  may be the cap  66  shown in  FIGS. 29 to 31  or the label  67  shown in  FIGS. 16 and 17 . 
     As shown in  FIGS. 29 and 30 , the liquid holding unit  30  includes restriction portions  93  and  94  that contact the holding member  51  and restrict the sliding range of the holding member  51 . The restriction portions  93  and  94  may be arranged on the housing  33  or the liquid holder  40 . In the present example in which the holding member  51  is slidable relative to the housing  33 , the housing  33  includes the restriction portions  93  and  94 . As shown in  FIGS. 29 and 30 , one of the restriction portions  93  and  94  (restriction portion  93  in  FIGS. 29 and 30 ) is formed by part of the housing  33 . The other one of the restriction portions  93  and  94  (restriction portion  94  in  FIGS. 29 and 30 ) is attached in a removable manner to the housing  33  at a location corresponding to the longitudinal end of the guides  91 . This allows the plug  50  to be coupled to the housing  33  along the guides  91  when the restriction portion  94  is removed from the housing  33 . The restriction portion  94  is attached to the housing  33  after coupling the plug  50 . This holds the plug  50  in a slidable manner with the slide range restricted. When the holding member  51  is held by the liquid holder  40  and slidable on the guides  91 , it is preferred that the liquid holder  40  includes the restriction portions  93  and  94 . However, the housing  33  may include at least one of the restriction portions  93  and  94 . 
     When the user slides the plug  50  to open the inlet  43 , the holding member  51  contacts the restriction portion  94 . This restricts separation of the plug  50  from the guides  91 . When the user slides the plug  50  to close the inlet  43 , the holding member  51  contacts the restriction portion  93 . This restricts separation of the plug  50  from the guides  91  and positions the plug body  52  at the close position where the inlet  43  can be sealed. In other words, the plug body  52  seals the inlet  43  by closing the holding member  51  until the holding member  51  contacts the restriction portion  93 . For example, if the plug  50  falls out of the holding member  51 , liquid may smear the location where the plug  50  falls. However, in the present embodiment, separation of the holding member  51  is restricted. Thus, the area around the liquid holding unit  30  is not smeared with liquid. One of the restriction portions  93  and  94  may be omitted. Even when, for example, one of the restriction portions  93  and  94  is omitted, the holding member  51  that slides will contact the remaining one of the restriction portions  93  and  94 . This restricts separation of the holding member  51 . 
     In addition to advantages (1) to (4), (7), and (8) of the first embodiment, the fourth embodiment has the advantages described below. 
     (14) In the liquid holding unit  30 , the liquid holder  40  or the housing  33  includes the guides  91  that hold the holding member  51  of the plug  50  in a slidable manner. The guides  91  hold the holding member  51  in a slidable manner. The plug  50  slides to open or close the inlet  43 . Thus, the plug body  52  does not have to be pulled off from the inlet  43 , and the force required to open and close the plug  50  may be decreased. When opening the plug  50 , the portion of the plug body  52  located at the side of the inlet  43  is not exposed to the outside. Thus, liquid is not applied to the fingers or the like of the user. 
     (15) The holding member  51  of the liquid holding unit  30  is elongated in one direction and holds the plug body  52  so that the plug body  52  is movable in the longitudinal direction of the holding member  51 . Thus, the plug  50  provides a certain degree of freedom for the position of the plug body  52  in the longitudinal direction of the holding member  51 . This ensures that the plug body  52  seals the inlet  43  and obviates, for example, the entrance of foreign matter into the liquid holder  40  and the evaporation or volatilization of liquid out of the liquid holder  40  that would result from defective sealing of the inlet  43 . 
     (16) The liquid holder  40  or the housing  33  includes the restriction portions  93  and  94  that contact the holding member  51  and restrict the sliding range of the holding member  51 . This avoids situations in which the plug  50  falls out of the liquid holder  40  or the housing  33  and smears the area where the plug  50  falls with liquid when moving the plug  50  along the guides  91 . 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     The liquid holder  40  or the housing  33  includes one of the shaft, which is used to pivot the plug, and the engagement portion, which is engaged with the shaft. The plug  50  includes the other one of the shaft and the engagement portion. For example, as shown in the modified example of  FIG. 32 , the liquid holder  40  may include a shaft  44 , and the second end (basal end) of the plug  50  may include the engagement portion  54 . The shaft  44  is supported by two supports  45  that extend from the holder body  41  of the liquid holder  40 . Further, as shown in the modified example of  FIG. 33 , the second end (basal end) of the plug  50  may include a shaft  56 , and the housing  33  or the liquid holder  40  may include an engagement portion  96  that engages the shaft  56 . The engagement portion  96  is supported by two supports  97  extending from the holder body  41  or the housing  33  at positions opposing the shaft  56  of the plug  50  in a closed state. In  FIG. 32 or 33 , an axial displacement restriction portion restricts displacement of the holding member  51  in the axial direction of the shaft. 
     The structure coupling the plug body  52  and the holding member  51  is not limited to the structures described in the above embodiments. For example, referring to  FIG. 34 , the plug body  52  may be partially fitted into the through hole  51   a  of the holding member  51 . As shown in  FIG. 34 , the plug body  52  includes the fitted portion  63  at the opposite side of the plug portion  61 , which seals the inlet  43 . The fitted portion  63  is larger in diameter than the through hole  51   a . The distal end of the fitted portion  63  includes the stopper  63   a . The stopper  63   a  is inserted through the through hole  51   a , and the basal portion of the stopper  63   a  is fitted to the through hole  51   a.    
     As shown in  FIGS. 35 and 36 , in the liquid holding unit  30  that includes the cover  32 , a pushing portion  321  may be arranged on the rear surface of the cover  32  to push the plug  50  toward the inlet  43  when closing the cover  32 . The pushing portion  321  is retrofitted on the cover  32  or formed integrally with the cover  32 . In the liquid holding unit  30  having such a structure, when the cover  32  is pivoted in the direction shown by the arrow in  FIG. 35 , the pushing portion  321  pushes the plug  50  in the closing direction. Thus, when the plug  50  is arranged above the closing position, the plug  50  is moved to the closing position. Additionally, once the cover  32  is closed, the plug  50  does not move away from the closing position even when force acting in the opening direction is applied to the plug  50 . Thus, movement of the plug  50  from the closing position is limited. This prevents evaporation and volatilization of liquid. Further, when viewing the liquid ejection device  12  from the front (left side in  FIGS. 35 and 36 ), the formation of a gap is limited between the cover  32  and the housing  33 . This improves the aesthetic appeal of the liquid holding unit  30 . In the liquid holding unit  30  shown in  FIG. 36 , an engagement member  322  is arranged on the cover  32 . In a state in which the cover  32  is closed, the engagement member  322  engages the housing  33 . More specifically, the engagement member  322 , which is fixed to the distal end of the cover  32 , includes an engagement projection  323 . The housing  33  includes an engagement recess  331  at a portion corresponding to the engagement projection  323 . The engagement recess  331  is engageable with the engagement projection  323 . The cover  32  is pivoted and closed in the direction shown by the arrow in  FIG. 36 . As a result, the engagement projection  323  of the engagement member  322  is engaged with the recess  331  of the housing  33 . This structure holds the cover  32  in a closed state and further limits movement of the plug  50  from the close position since the cover  32  is kept at the close position. Further, evaporation and volatilization of liquid are prevented. Moreover, when viewing the liquid ejection device  12  from the front (left side in  FIGS. 35 and 36 ), the formation of a gap is limited between the cover  32  and the housing  33 . This improves the aesthetic appeal of the liquid holding unit  30 . 
     The housing may be formed integrally with the enclosure of the liquid ejection device. 
     The plug body  52  may be entirely fitted to the through hole  51   a  of the holding member  51 . 
     In the first to third embodiments, the enclosure  14  may include a restriction portion that contacts the holding member  51  to restrict the pivot range of the plug  50 . 
     In the first to third embodiments, a structure including a tubular shaft and rod-shaped engagement portions that are insertable into the two hollow ends of the shaft may be employed to pivotally hold the holding member  51 . The engagement portions may be recessed or tubular so as to be engageable with the two ends of the shaft. The engagement portion of the holding member may be a tube, and a shaft may be inserted into and engaged with the tube. Such structures also pivotally hold the holding member  51 . 
     The holding member  51  may be pivoted along a plane parallel to a plane lying along the opening of the inlet  43 . In this case, the plug body  52  shown in  FIG. 12  that contacts the inlet  43  may be used in the same manner as a slide-type. In the same manner as a slide-type, this structure reduces the force required to open and close the plug  50  and reduces the frequency in which liquid is applied from the plug body  52  to fingers or the like. 
     In the first to third embodiments, the holding member  51  may be pivoted about one side end. In this case, it is preferred that the tab be arranged on the other side end. 
     In the third embodiment, there may be more than one pivot  83 , and the holding member  51  may be bent at multiple locations. More specifically, the holding member  51  may include the first piece  81 , the second piece  82 , and at least one further piece such as a third piece. The three or more pieces are connected in series by the pivots  83  and configured to take a straight formation in a closed state and a bent formation in the closed state. In the bent formation, the holding member  51  is bent in the direction in which the plug body  52  approaches the inlet  43 . Preferably, the urging member  84  that urges the holding member  51  from the straight formation to the bent formation is arranged on at least one of the pivots  83 . In this case, it is preferred that the formation holding mechanism  85  be used to hold the holding member  51  in the straight formation when the cover  32  is closed. The formation holding mechanism  85  includes a contact portion that contacts one of the two pieces located at opposite sides of the pivot where the urging member  84  is arranged to hold the holding member  51  in the straight formation. 
     In the fourth embodiment, the holding member  51  may be held to be slidable in the widthwise direction X. Further, the holding member  51  may be pulled to slide from the close position and open the inlet  43 , and the holding member  51  may be pushed to slide from the open position and close the inlet  43 . 
     The plug body  52  may be entirely fitted into the through hole  51   a  of the holding member  51 . In this structure, if the inlet  43  opens at the distal end of the tube  42 , the plug body  52  is fitted onto the tube  42  to seal the inlet  43 . 
     The inlet  43  may be located in any surface of the liquid holder  40 . For example, the inlet  43  may be located in the front surface of the liquid holder  40 . In this case, the plug  50  may be pivotal about the lower end (second end) of the holding member  51  or be held to be slidable in the vertical direction (longitudinal direction) of the holding member  51 . 
     The housing  33  only needs to be able to accommodate one or more of the liquid holders  40  in a predetermined direction. For example, the housing may have a small depth and cover only the lower portion (e.g., lower half) of the liquid holders  40 . Alternatively, the housing may be a frame-shaped housing having front, rear, left, and right surfaces that are open. Further, the window  33   b  may be omitted from the housing  33 . 
     In each of the above embodiments, the cover  32  may be omitted. Further, there may be only one liquid holder  40 . 
     The liquid ejection device  12  does not have to form part of the all-in-one machine  11  and may be a printer dedicated to printing. 
     The liquid ejected from the liquid ejector  21  is not limited to ink and may be, for example, a liquid body formed by dispersing or mixing particles of a functional material. For example, the liquid may be a liquid body in which electrode material or color material (pixel material) is dispersed or dissolved. Such a material is used to manufacture a liquid crystal display, an electroluminescence (EL) display, or a planar light-emitting display. In this manner, the liquid ejection device may eject a liquid body in which material, such as an electrode material or a color material, used to manufacture the above types of displays is dispersed or dissolved. The liquid ejection device may also eject an ultraviolet curing resin liquid or a liquid including a functional material. 
     The medium M onto which the liquid ejection device ejects liquid is not limited to paper and may be a plastic film or sheet, a thin plate, metal foil, laminate film, a circuit board, or a cloth used in a cloth printing device. The medium M may also be clothing having any shape such as a T-shirt or a three-dimensional object having any shape such as dishware or stationery. 
     The liquid ejection device may be a three-dimensional liquid ejection device that molds a three-dimensional object by ejecting resin liquid using a liquid ejection technique (e.g., inkjet technique). 
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.