Patent Publication Number: US-10308031-B2

Title: Tank, tank unit, and liquid ejection system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a National Stage of International Application No. PCT/JP2016/000537, filed Feb. 3, 2016; which claims priority from Japanese Patent Application No. 2015-049473 filed on Mar. 12, 2015, the contents of both of which are hereby incorporated by reference into this application. 
     TECHNICAL FIELD 
     The present invention relates to a tank, a tank unit, and a liquid ejection system. 
     BACKGROUND ART 
     As a type of liquid ejection system, an inkjet printer (hereinafter also referred to simply as “printer”) is known that forms an image by discharging ink onto print paper. Some printers include an ink tank that is attached thereto and into which ink can be injected via an injection inlet (for example, Patent Literatures 1 and 2 listed below, and the like). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1 JP-A-2012-20495 
     Patent Literature 2 JP-A-2014-184594 
     SUMMARY OF INVENTION 
     Technical Problem 
     Usually, an ink tank is provided with an atmospheric air communication path for introducing atmospheric air into the ink tank as ink is consumed. The ink tank is problematic in that the ink contained in the ink tank may leak out through the atmospheric air communication path when the ink tank is set in an orientation different from an ordinarily expected orientation, or when the ink tank is installed in an ordinarily expected environment, or the like. 
     Solution to Problem 
     The present invention has been made to solve the above-described problem encountered not only with an ink tank but also at least a tank that can contain a liquid that is supplied to a liquid ejection head, and the invention can be implemented in the following implementations. 
     Advantageous Effects of Invention 
     [1] A first implementation according to the present invention provides a tank. The tank is capable of supplying a liquid to a liquid ejection head, and may include a liquid containing portion, a liquid injection portion, and an atmospheric air introducing portion. The liquid containing portion may be configured so as to be capable of containing the liquid. The liquid injection portion may be configured such that the liquid can be injected into the liquid containing portion therethrough. The atmospheric air introducing portion may be configured such that atmospheric air can be introduced into the liquid containing portion therethrough. The atmospheric air introducing portion may include a buffer chamber that is capable of containing atmospheric air and an atmospheric air communication path that communicates between the buffer chamber and the liquid containing portion. The atmospheric air communication path may include an atmospheric air introducing inlet in an area where the atmospheric air communication path intersects with the liquid containing portion. The buffer chamber may be provided with a first communication inlet that is connected to the atmospheric air communication path and a second communication inlet through which external atmospheric air can be introduced into the buffer chamber. When the tank is in a first orientation in which the liquid is injected into the liquid containing portion via the liquid injection portion, the atmospheric air introducing inlet may be located on an upper end side of the liquid containing portion. The atmospheric air communication path may have: (i) a first portion that is located in a height position between an upper end portion of the liquid containing portion and a midpoint between the upper end portion of the liquid containing portion and a lower end portion of the liquid containing portion when the tank is in the first orientation; (ii) a second portion that is located in a height position between an upper end portion of the liquid containing portion and a midpoint between the upper end portion of the liquid containing portion and a lower end portion of the liquid containing portion when the tank is in a second orientation in which the tank has been rotated by 90° in a predetermined direction from the first orientation; and (iii) a third portion that is located in a height position between an upper end portion of the liquid containing portion and a midpoint between the upper end portion of the liquid containing portion and a lower end portion of the liquid containing portion when the tank is in a third orientation in which the tank has been rotated by 180° in the predetermined direction from the first orientation. The second communication inlet may be located above a lower end portion of the buffer chamber when the tank is in the second orientation and in which the atmospheric air introducing inlet is located on a lower end side, and when the tank is in the third orientation. With the tank according to this implementation, even when the orientation of the tank is rotated from the first orientation, it is possible to suppress a situation in which the liquid reaches the buffer chamber via the atmospheric air communication path. Also, even if the liquid reaches the buffer chamber, the liquid can be stored in the buffer chamber, and it is therefore possible to suppress a situation in which the liquid leaks to the outside via the second communication inlet. Accordingly, the occurrence of leakage of the liquid from the tank is suppressed. 
     [2] In the tank according to the implementation described above, the atmospheric air communication path may include a first path portion, a second path portion, a third path portion, and a fourth path portion, and when the tank is in the first orientation, the first path portion may extend on an upper side or a lower side of the buffer chamber, the second path portion may extend downward from the first path portion, the third path portion may extend upward from a lower end of the second path portion, and the fourth path portion may extend in a direction that intersects with an up-down direction of the tank from an upper end of the third path portion on the upper end side of the liquid containing portion. With the tank according to this implementation, a situation is suppressed in which the liquid passes through each path portion of the atmospheric air communication path and reaches the buffer chamber. 
     [3] The tank according to the implementation described above may include a reference amount specifying portion that specifies an amount of the liquid contained in the liquid containing portion to a predetermined reference amount, and a relationship represented by the following expression may be satisfied: Va×α−Vb&lt;V&lt;Va×α, where V represents a capacity of the buffer chamber, Va represents a difference between a capacity of the liquid containing portion and a volume of the liquid in the reference amount at room temperature, Vb represents a capacity of the atmospheric air communication path, and α is a predetermined coefficient of 1 or less. With the tank according to this implementation, when the tank is in a state in which the atmospheric air introducing inlet is located on a lower side and the liquid containing portion is filled with the liquid, even if the liquid is forced out into the atmospheric air introducing portion due to air in the liquid containing portion expanding, the forced-out liquid can be stored in the buffer chamber. Also, the buffer chamber is prevented from being made to be larger more than necessary. 
     [4] In the tank according to the implementation described above, the predetermined coefficient α may be a value to which an air expansion coefficient is reflected. With the tank according to this implementation, leakage of the liquid caused by the expansion of the air in the liquid containing portion is more reliably suppressed. 
     [5] In the tank according to the implementation described above, the atmospheric air communication path may include an intermediate buffer portion, the intermediate buffer portion may include a first opening that is in communication with the liquid containing portion side and a second opening that is in communication with the buffer chamber side, and when the tank is in the third orientation, the first opening and the second opening may be located above a lower end of the intermediate buffer portion. With the tank according to this implementation, even when the tank is brought into the third orientation, the liquid can be stored in the intermediate buffer portion, and thus leakage of the liquid when the tank is in the third orientation is further suppressed. 
     [6] In the tank according to the implementation described above, the atmospheric air communication path may be a first atmospheric air communication path, and the tank may further include a second atmospheric air communication path that is connected to the second communication inlet. With the tank according to this implementation, the liquid can also be stored in the second atmospheric air communication path provided downstream of the buffer chamber, and thus leakage of the liquid is further suppressed. 
     [7] In the tank according to the implementation described above, the buffer chamber may be a first buffer chamber, and the second atmospheric air communication path may include a second buffer chamber that is capable of containing atmospheric air to be introduced into the first buffer chamber. With the tank according to this implementation, the liquid is stored in the second buffer chamber as well in addition to the first buffer chamber, and thus leakage of the liquid is further suppressed. 
     [8] In the tank according to the implementation described above, the first orientation may be an orientation in which the liquid is supplied from the tank to the liquid ejection head, and when the tank is in the first orientation, the first communication inlet may be located in a lower end of the buffer chamber. With the tank according to this implementation, the liquid that has flowed into the buffer chamber is guided in a direction back toward the liquid containing portion along with the liquid being supplied to the liquid ejection head, and thus leakage of the liquid is further suppressed. 
     [9] The tank according to the implementation described above may include a case member that is a box having an opening in one direction; and a sheet member that is bonded so as to be capable of sealing the opening of the case member, and the liquid containing portion and the atmospheric air introducing portion may be formed between the case member and the sheet member, and each of the first orientation, the second orientation, and the third orientation may be an orientation in which a direction of the opening of the case member is perpendicular to a vertical direction. With the tank according to this implementation, it is possible to achieve simplification of the configuration, weight reduction, and cost reduction of the tank and facilitation of production. 
     [10] A second implementation according to the present invention provides a tank unit. The tank unit according to this implementation may include a first tank, a second tank, and an outer jacket. The first tank and the second tank may be the tanks according to the above-described implementation. The outer jacket may be capable of housing the first tank and the second tank. The first tank and the second tank may have different widths in the direction of the opening of the case member such that the liquid containing portions of the first tank and the second tank have different capacities. The first tank and the second tank may be the tank according to the implementation described above. With this tank unit, leakage of the liquid from each tank is suppressed. Also, a plurality of types of tanks having different capacities are provided, and it is therefore possible to enhance the adaptability for the pattern of consumption of the liquid in the liquid ejection system. 
     [11] A third implementation according to the present invention provides a tank unit. The tank unit according to this implementation may include a tank and an outer jacket. The tank may be the tank according to the above-described implementation. The outer jacket may be capable of housing the tank. With this tank unit, the occurrence of leakage of the liquid from the tank is suppressed. 
     [12] A fourth implementation according to the present invention provides a liquid ejection system. The liquid ejection system according to this implementation may include a tank unit and a liquid ejection apparatus. The tank unit may be the tank unit according to the above-described implementation. The liquid ejection apparatus may include the liquid ejection head, and the tank unit may be connected to the liquid ejection apparatus. With the liquid ejection system according to this implementation, the occurrence of leakage of the liquid from the tank is suppressed. In addition, the liquid ejection apparatus and the tank unit are configured as separate bodies, and it is therefore possible to enhance the ease of maintenance of the liquid ejection apparatus and the tank unit. 
     [13] A fifth implementation according to the present invention provides a liquid ejection system. The liquid ejection system according to this implementation may include a tank, a liquid ejection head, and an outer jacket. The tank may be the tank according to the above-described implementation. The outer jacket may be capable of housing the tank and the liquid ejection head. With the liquid ejection system according to this implementation, the occurrence of leakage of the liquid from the tank is suppressed. Also, because the liquid ejection head and the tank are integrated, the installation efficiency of the liquid ejection system is enhanced. 
     Note that not all of a plurality of constituent elements of each implementation of the present invention are essential, and in order to solve some or all of the above-described problems or achieve some or all of the effects described in the specification, some of the plurality of constituent elements may be changed, removed or replaced with additional other constituent elements as appropriate, or some of the limitations may be partially removed as appropriate. Also, in order to solve some or all of the above-described problems or achieve some or all of the effects described in the specification, it is also possible to combine some or all of the technical features included in one implementation of the present invention with some or all of the technical features included in another implementation of the present invention so as to form a single independent implementation of the present invention. 
     The present invention can also be implemented as various types of implementations other than a tank capable of supplying a liquid to a liquid ejection head, a tank unit including the tank, and a liquid ejection system including the tank. For example, the present invention can be implemented as a tank capable of supplying a liquid to an apparatus other than a liquid ejection head, a tank unit including the tank, and a system including the tank. In addition thereto, the present invention can be implemented as a fluid flow path structure for use in a tank. The term “system” as used in this specification refers to a set of a plurality of constituent elements provided in an integrated or dispersed manner and combined such that their respective functions directly or indirectly interact with each other, so as to implement at least one function. Accordingly, the system as used in this specification also encompasses an “apparatus” in which a plurality of constituent elements are integrally combined. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram showing a configuration of an inkjet printer. 
         FIG. 2  is a schematic exploded perspective view of an ink tank. 
         FIG. 3  is a schematic cross-sectional view of the ink tank. 
         FIG. 4  is a schematic cross-sectional view of the ink tank. 
         FIGS. 5A, 5B, 5C, and 5D  show schematic diagrams illustrating the states of ink contained in the ink tank when the ink tank is rotated from a reference orientation. 
         FIG. 6  is a schematic diagram for illustrating a mechanism that suppresses ink leakage. 
         FIG. 7  is a schematic diagram for illustrating a mechanism that suppresses ink leakage. 
         FIG. 8  is a schematic cross-sectional view showing a configuration of an ink tank according to a second embodiment. 
         FIG. 9  is an exploded perspective view showing a configuration of an ink tank according to a third embodiment. 
         FIG. 10  is a schematic front view showing a configuration of the ink tank according to the third embodiment. 
         FIG. 11  is a schematic cross-sectional view showing a configuration of the ink tank according to the third embodiment. 
         FIG. 12  is a schematic diagram for illustrating a mechanism that suppresses ink leakage. 
         FIG. 13  is a schematic diagram for illustrating a mechanism that suppresses ink leakage. 
         FIG. 14  is a schematic diagram for illustrating a mechanism that suppresses ink leakage. 
         FIG. 15  is a schematic diagram showing a configuration of a tank unit included in a printer according to a fourth embodiment. 
         FIG. 16  is a schematic exploded perspective view of a second ink tank. 
         FIG. 17  is a schematic diagram showing an internal configuration of the second ink tank. 
         FIG. 18  is a schematic diagram showing a configuration of a printer according to a fifth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. First Embodiment 
     Configuration of Printer 
       FIG. 1  is a schematic diagram showing a configuration of an inkjet printer  10  (hereinafter referred to simply as “printer  10 ”) including an ink tank  25  according to a first embodiment of the present invention. In  FIG. 1 , an arrow G indicating the direction of gravity (vertical direction) when the printer  10  is in a normal state of use is shown. In the following description, unless otherwise stated, the terms “up” and “down” refer to the up-down direction with respect to the direction of gravity. Also, in  FIG. 1 , arrows X, Y, and Z indicating three directions that are mutually perpendicular with respect to the ink tank  25  are shown. The directions indicated by the arrows X, Y, and Z will be described later. The arrows G, X, Y, and Z are also shown as appropriate in the diagrams which will be referred to in connection with the following description. 
     The printer  10  is one aspect of a liquid ejection system, and forms images by discharging ink droplets onto print paper PP (indicated by a dash dot line), which is a print medium. The printer  10  includes a tank unit  20  and a printing portion  30 . The tank unit  20  includes a casing portion  21  (indicated by a broken line), which is an outer jacket, a plurality of ink tanks  25 , and a plurality of tubes  26 . The plurality of ink tanks  25  correspond to a subordinate concept of the tank according to the present invention, and contain inks of mutually different colors. The inks contained in the ink tanks  25  are supplied to the printing portion  30  via the flexible resin tubes  26  connected to the ink tanks  25  in a one-to-one correspondence. A description of a configuration of the ink tanks  25  will be given later. 
     In the tank unit  20 , the ink tanks  25  are linearly aligned in a direction indicated by the arrow X, which will be described later, and in this state, they are fixed in an internal space  21   s  of the casing portion  21 . The casing portion  21  includes a cover portion  22 . The cover portion  22  is connected to the main body of the casing portion  21  by a hinge mechanism  28 , and is configured to be opened and closed by being swung in a direction indicated by an arrow RD. By opening the cover portion  22 , the user of the printer  10  can perform operations such as attaching or detaching the ink tank  25  to or from the tank unit  20 , and loading ink into the ink tank  25 , which will be described later. In addition thereto, the tank unit  20  may be provided with an electric circuit and wiring for exchanging electric signals representing ink information such as the remaining amounts of ink in the ink tanks  25  with the printing portion  30 . 
     The printing portion  30  includes a control portion  31 , a print head portion  32 , a conveyance mechanism  33  for conveying the print paper PP, and a casing portion  35 . The casing portion  35  serves as the outer jacket of the printing portion  30 , and houses therein a print head portion  32 , a conveyance mechanism  33 , and a control portion  31 . The control portion  31  is implemented by, for example, a microcomputer including a central processing unit and a main storage device. As a result of the central processing unit reading various programs to the main storage device and executing the programs, the control portion  31  provides at least a function of controlling the printing portion  30  to execute print processing based on externally input print data. 
     The print head portion  32  is provided so as to be capable of reciprocal movement in a main scanning direction SD on a conveyance path along which the print paper PP is conveyed. The print head portion  32  is connected to the ink tanks  25  of the tank unit  20  via the above-described tubes  26 , and is capable of discharging ink supplied from the ink tanks  25 . The print head portion  32  corresponds to a subordinate concept of the liquid ejection head according to the present invention. 
     The conveyance mechanism  33  is capable of conveying the print paper PP in a conveyance direction TD that intersects the main scanning direction SD by driving conveyance rollers to rotate. At the time of printing, under control of the control portion  31 , the conveyance mechanism  33  conveys the print paper PP, and the print head portion  32  discharges ink droplets while reciprocally moving in the main scanning direction SD, whereby a print image is formed on the print surface of the print paper PP. The printing portion  30  corresponds to a subordinate concept of the liquid ejection apparatus according to the present invention. 
     In the present embodiment, the casing portion  21  of the tank unit  20  and the casing portion  35  of the printing portion  30  are connected so as to be capable of detachment and rotation (illustration omitted). In this way, because the tank unit  20  and the printing portion  30  are configured as separate bodies, it is possible to separately maintain the tank unit  20  and the printing portion  30 , and thus the ease of maintenance of the printer  10  is enhanced. 
     Configuration of Ink Tank 
     A configuration of an ink tank  25  will be described with reference to  FIGS. 2 to 4 , in addition to  FIG. 1 .  FIG. 2  is a schematic exploded perspective view of an ink tank  25 .  FIG. 3  is a schematic cross-sectional view of the ink tank  25  taken along the line A-A shown in  FIG. 2 , and  FIG. 4  is a schematic cross-sectional view of the ink tank  25  taken along the line B-B shown in  FIG. 2 .  FIGS. 3 and 4  show a state in which ink IN is stored in an ink containing portion  120 . 
     The ink tank  25  is configured as a hollow container including six surface portions  101  to  106 . The six surface portions  101  to  106  will be described based on an orientation of the ink tank  25  in a state of use as a reference. As used herein, the expression “the ink tank  25  in a state of use” encompasses a state in which the ink tank  25  is attached to the tank unit  20  of the printer  10  ( FIG. 1 ), a state in which the ink tank  25  is supplying ink to the printer  10 , and a state in which ink is loaded by the user. Hereinafter, the orientation of the ink tank  25  in a state of use will also be referred to as “reference orientation”. The reference orientation corresponds to a subordinate concept of the first orientation according to the present invention. In the following description, unless otherwise stated, the orientation of the ink tank  25  is in the reference orientation. 
     In the ink tank  25 , a first surface portion  101  constitutes a bottom surface portion that faces downward, and a second surface portion  102  constitutes an upper surface portion that faces upward ( FIGS. 1 and 2 ). A third surface portion  103  intersects with the first surface portion  101  and the second surface portion  102 , and constitutes a front surface portion that faces toward the user when the cover portion  22  of the casing portion  21  of the tank unit  20  is opened. A fourth surface portion  104  intersects with the first surface portion  101  and the second surface portion  102 , and constitutes a rear surface portion that faces in a direction opposite to the third surface portion  103 . A fifth surface portion  105  intersects with each of the four surface portions  101  to  104 , and constitutes a left side surface portion that is located on the left as viewed from directly in front of the third surface portion  103 . A sixth surface portion  106  intersects with each of the four surface portions  101  to  104 , and constitutes a right side surface portion that is located on the right, which is the side opposite to the fifth surface portion  105 , as viewed from directly in front of the third surface portion  103 . In this specification, the term “intersect” used to indicate that two surface portions intersect with each other refers to one of the following states: a state in which two surface portions actually intersect with each other; a state in which an extended surface of one surface portion intersects with another surface portion; and a state in which two surface portions intersect with each other. 
     Next is a description of the arrows X, Y, and Z indicating three directions with respect to the ink tank  25 . The arrow X indicates a direction parallel to a width direction (right-left direction) of the ink tank  25 , the direction extending from the fifth surface portion  105  toward the sixth surface portion  106 . In the following description, the term “right” refers to the side in the direction of the arrow X, and the term “left” refers to the side in a direction opposite to the direction of the arrow X. The arrow Y indicates a direction parallel to a depth direction (front-rear direction) of the ink tank  25 , the direction extending from the fourth surface portion  104  toward the third surface portion  103 . In the following description, the term “front” refers to the side in the direction of the arrow Y, and the term “rear” refers to the side in a direction opposite to the direction of the arrow Y. The arrow Z indicates a height direction (up-down direction) of the ink tank  25 , the direction extending from the first surface portion  101  toward the second surface portion  102 . In the reference orientation, the arrow Z points in a direction opposite to the direction of gravity. 
     The ink tank  25  includes a case member  110 , a sheet member  111 , and a cap member  112  ( FIG. 2 ). The case member  110  is a hollow box constituting the main body of the ink tank  25 . The case member  110  is entirely open in the direction of the arrow X on the sixth surface portion  106  side, and the outer walls surrounding an internal space of the case member  110  respectively constitute five surface portions  101  to  105  excluding the sixth surface portion  106 . The case member  110  is produced by, for example, integral molding using a synthetic resin such as nylon or polypropylene. 
     The second surface portion  102  of the case member  110  is provided with an ink injection portion  113  and a buffer chamber housing portion  114 . The ink injection portion  113  corresponds to a subordinate concept of the liquid injection portion according to the present invention, and is a part that is in communication with an ink containing portion  120  (described later) included in the ink tank  25  such that ink can be injected therethrough. In the present embodiment, the ink injection portion  113  is configured as a cylindrical part protruding upward and has an opening. 
     The ink injection portion  113  is provided at a position close to the third surface portion  103  so that the user can easily access the ink tank  25  when it is attached to the tank unit  20 . The cap member  112  is usually hermetically attached to an opening  115  of the ink injection portion  113 . The user can load ink into the ink tank  25  via the ink injection portion  113  by detaching the cap member  112  therefrom. 
     The buffer chamber housing portion  114  is a hollow part having a substantially rectangular parallelepiped shape protruding upward on the rear side of the ink injection portion  113 . An internal space of the buffer chamber housing portion  114  constitutes a buffer chamber  122 , which will be described later. 
     In the present embodiment, a wall portion of the third surface portion  103  of the case member  110  is partially or entirely configured to be transparent or translucent so as to allow the user to view the position of the surface of the ink contained in the ink tank  25 . Also, a mark portion  116  is provided on the wall surface of the third surface portion  103 . The mark portion  116  indicates the position of the ink surface when a predetermined reference amount of ink is contained in the ink tank  25  when the ink tank  25  is in the reference orientation. That is, in the ink tank  25 , the maximum amount (reference amount) of ink that needs to be contained in the ink tank  25  is specified by the indication of the mark portion  116 . The mark portion  116  corresponds to a subordinate concept of the reference amount specifying portion according to the present invention. 
     In the ink tank  25  according to the present embodiment, the mark portion  116  is formed at a height position lower than an atmospheric air introducing inlet  132  (described later) provided in the ink containing portion  120 . With this configuration, a situation is suppressed in which the surface of ink stored in the ink containing portion  120  reaches an ink injection inlet  125  when the user injects the ink by using the position of the mark portion  116  as the reference. The mark portion  116  may be formed as, for example, a protrusion or a recess on the wall surface portion of the third wall portion  103 , or may be formed by printing or attaching a label. 
     The sheet member  111  is a member in the form of a thin film, and constitutes the sixth surface portion  106  of the ink tank  25  by being bonded to the case member  110  so as to seal the entirety of an opening of the case member  110 . The sheet member  111  is made of a film member formed using, for example, a synthetic resin such as nylon or polypropylene. The sheet member  111  is bonded to the case member  110  through, for example, melt adhesion. In this way, with the case member  110  and the sheet member  111 , the ink tank  25  according to the present embodiment is configured to be simple and lightweight. 
     In the ink tank  25 , the internal space of the case member  110  is partitioned by an inner wall portion  107 , and thereby an ink containing portion  120  and an atmospheric air introducing portion  121  are formed between the case member  110  and the sheet member  111 . The ink containing portion  120  is a space in which ink can be stored. The atmospheric air introducing portion  121  is a flow path space for introducing atmospheric air outside of the ink tank  25  into the ink containing portion  120 . The ink tank  25  is configured such that atmospheric air is introduced into the ink containing portion  120  via the atmospheric air introducing portion  121  along with the ink stored in the ink containing portion  120  being supplied to the print head portion  32  and consumed. 
     The ink containing portion  120  is formed so as to extend over the width direction and the front-rear direction of the ink tank  25  ( FIGS. 2 and 3 ). The ink containing portion  120  is an internal space in which an ink can be stored. The ink containing portion  120  corresponds to a subordinate concept of the liquid containing portion according to the present invention. The ink containing portion  120  is connected to the ink injection portion  113  in an upper area of the ink containing portion  120  ( FIG. 3 ). An opening serving as an ink injection inlet  125  is formed in an area of an upper surface of the ink containing portion  120  where the upper surface of the ink containing portion  120  intersects with the ink injection portion  113 . 
     At a lower end portion of the fourth surface portion  104  of the ink tank  25 , an ink supply portion  117  for supplying ink to the print head portion  32  is provided. The ink supply portion  117  is configured as a cylindrical part having an opening and protruding from a wall surface of the fourth surface portion  104  toward the rear side. A tube  26  is hermetically connected to the ink supply portion  117 , the tube  26  being connected to the print head portion  32  ( FIG. 1 ). The ink supply portion  117  has a cylindrical hole  117   h  that is in communication with a lower end portion of the ink containing portion  120 . An opening serving as an ink supply inlet  118  is formed in an area of a bottom surface of the ink containing portion  120  where the bottom surface of the ink containing portion  120  intersects with the ink supply portion  117 . In the ink containing portion  120 , a sensor portion for detecting an out-of-ink state, and the like may be housed. 
     The atmospheric air introducing portion  121  ( FIGS. 2 and 4 ) includes a buffer chamber  122  and an atmospheric air communication path  123 . The buffer chamber  122  is a space capable of containing atmospheric air. As described above, the buffer chamber  122  is provided in the buffer chamber housing portion  114  of the second surface portion  102 , and is located above the ink containing portion  120 . The buffer chamber  122  is formed as an internal space having a greater depth in the direction of the arrow X than the atmospheric air communication path  123 . The buffer chamber  122  is in communication with the outside of the ink tank  25  via an atmospheric air intake portion  124 . The atmospheric air intake portion  124  is configured as a cylindrical part having an opening and protruding from the wall surface of the fourth surface portion  104  toward the rear side. The atmospheric air intake portion  124  has a cylindrical hole  124   h  that is in communication with a lower end portion of the buffer chamber  122 . An opening serving as an atmospheric air intake inlet  130  is formed in an area where the buffer chamber  122  and the atmospheric air intake portion  124  intersect with each other. 
     The atmospheric air communication path  123  is a flow path that connects the buffer chamber  122  and the ink containing portion  120  ( FIG. 4 ). The atmospheric air communication path  123  includes a first path portion  123   a , a second path portion  123   b , a third path portion  123   c , and a fourth path portion  123   d . In an end portion of the buffer chamber  122  that is on the third surface portion  103  side, the first path portion  123   a  is connected to the buffer chamber  122  via a communication inlet  131 . The communication inlet  131  is open in the direction of the arrow Z in a bottom surface of the buffer chamber  122 . At a position below the buffer chamber  122 , the first path portion  123   a  extends to an end portion that is on the fourth surface portion  104  side in parallel to the direction of the arrow Y. In the present embodiment, the communication inlet  131  that is in communication with the buffer chamber  122  corresponds to a subordinate concept of the first communication inlet according to the present invention, and the atmospheric air intake inlet  130  corresponds to a subordinate concept of the second communication inlet according to the present invention. 
     In the end portion that is on the fourth surface portion  104  side, the second path portion  123   b  is bent downward from the first path portion  123   a  and extends to an end portion of the ink tank  25  that is on the first surface portion  101  side. The third path portion  123   c  is bent upward from a lower end portion of the second path portion  123   b , extends in parallel to the second path portion  123   b  to a position below the first path portion  123   a , and is connected to the fourth path portion  123   d  located in an upper end portion of the ink containing portion  120 . The fourth path portion  123   d  extends in the direction of the arrow Y to an end portion that is on the third surface portion  103  side, and is connected to the ink containing portion  120 . In the upper surface of the ink containing portion  120  where the atmospheric air communication path  123  and the ink containing portion  120  intersect with each other, an atmospheric air introducing inlet  132  that is open in the direction of the arrow Z is formed. When the ink tank  25  is in the reference orientation, the atmospheric air introducing inlet  132  is located on an upper end side that is closer to the upper end portion of the ink containing portion  120  rather than to the lower end portion of the ink containing portion  120 . 
     In the ink tank  25  according to the present embodiment, the atmospheric air communication path  123  is formed as a groove in the case member  110  so as to face the sheet member  111 . The second path portion  123   b , the third path portion  123   c , and the fourth path portion  123   d  of the atmospheric air communication path  123  are formed at positions overlapping the ink containing portion  120  as viewed in the direction of the arrow X ( FIGS. 3 and 4 ). Also, the communication inlet  131  of the buffer chamber  122  and the atmospheric air introducing inlet  132  of the ink containing portion  120  are formed as spaces between the sheet member  111  and gaps of the inner wall portion  107  of the case member  110 . 
     The ink tank  25  with ink being contained therein may be oriented at various angles when, for example, the printer  10  is transported. Accordingly, depending on the orientation of the ink tank  25 , the ink contained in the ink containing portion  120  may flow into the atmospheric air introducing portion  121 . In particular, as described above, the ink tank  25  is configured such that the amount of ink contained in the ink containing portion  120  is specified to the reference amount that is less than a completely full state, and thus air is usually present in an upper portion of the ink containing portion  120 . For this reason, there is a possibility that the flow of ink into the atmospheric air introducing portion  121  may be facilitated by the influence of the air. With the ink tank  25 , even if the ink contained in the ink containing portion  120  flows into the atmospheric air introducing portion  121 , the above-described flow path configuration of the atmospheric air introducing portion  121  suppresses the occurrence of leakage from the atmospheric air introducing portion  121  to the outside in the manner described below. 
     The mechanism that suppresses ink leakage in the ink tank  25  will be described by making reference to  FIGS. 5 to 7  in sequence. In  FIG. 5 , (a) to (d) show the states of an ink IN contained in the ink tank  25  when the ink tank  25  is rotated from the reference orientation in a predetermined first or second direction. As used herein, the term “first direction” refers to a clockwise direction when the ink tank  25  is viewed in the direction of the arrow X. The term “second direction” refers to a counter-clockwise direction when the ink tank  25  is viewed in the direction of the arrow X. 
     When the ink tank  25  is in the reference orientation ((a) in  FIG. 5 ), the surface of the ink IN stored in the ink containing portion  120  is located below the atmospheric air introducing inlet  132  unless the user injects the ink IN in an amount more than the reference amount, and thus a situation is suppressed in which the ink IN stored in the ink containing portion  120  flows from the atmospheric air introducing inlet  132  into the atmospheric air introducing portion  121 . 
     When the ink tank  25  is rotated by 90° in the first direction from the reference orientation, the third surface portion  103  faces up, and the fourth surface portion  104  faces down ((b) in  FIG. 5 ). This orientation corresponds to an aspect of the second orientation according to the present invention. Hereinafter, the orientation will also be referred to as “90° rotated-right orientation”. When the ink tank  25  is in the 90° rotated-right orientation, the atmospheric air introducing inlet  132  is located in an upper end of the ink containing portion  120 . Accordingly, a situation is suppressed in which the ink IN stored in the ink containing portion  120  flows from the atmospheric air introducing inlet  132  into the atmospheric air introducing portion  121 . 
     Also, in this orientation, the second path portion  123   b  and the third path portion  123   c  are located in a lower end of the ink tank  25 , and the first path portion  123   a  extends upward to the communication inlet  131  located in an upper end of the buffer chamber  122 . Accordingly, even if a portion of the ink IN stored in the ink containing portion  120  flows into the atmospheric air communication path  123 , a situation is suppressed in which the ink reaches the buffer chamber  122 . 
     When the ink tank  25  is rotated by 90° in the second direction from the reference orientation, the fourth surface portion  104  faces up, and the third surface portion  103  faces down ((c) in  FIG. 5 ). This orientation also corresponds to an aspect of the second orientation according to the present invention. Hereinafter, the orientation will also be referred to as “90° rotated-left orientation”. When the ink tank  25  is in the 90° rotated-left orientation, the fourth path portion  123   d  extends from the atmospheric air introducing inlet  132  located in a lower end of the ink containing portion  120  to a height position of the upper end of the ink containing portion  120 . Accordingly, a situation is suppressed in which the ink IN stored in the ink containing portion  120  passes through the fourth path portion  123   d  and reaches the third path portion  123   c  and the second path portion  123   b  located above the third path portion  123   c.    
     When the ink tank  25  is rotated by 180° in the first direction or the second direction from the reference orientation, the first surface portion  101  faces up, and the second surface portion  102  faces down ((d) in  FIG. 5 ). This orientation corresponds to an aspect of the third orientation according to the present invention. Hereinafter, the orientation will also be referred to as “180° rotated orientation”. When the ink tank  25  is in the 180° rotated orientation, the turn-back position where the second path portion  123   b  and the third path portion  123   c  communicate with each other is located above the fourth path portion  123   d , and is located in a height position of the upper end of the ink containing portion  120 . Accordingly, a situation is suppressed in which the ink IN that has flowed into the fourth path portion  123   d  from the ink containing portion  120  via the ink injection inlet  125  passes through the third path portion  123   c  and flows into the second path portion  123   b.    
     In the orientations of the ink tank  25  as shown in (a) to (d) in  FIG. 5 , a region between the height position of the upper end portion of the ink containing portion  120  and a height position of a midpoint between the height position of the upper end portion and the height position of the lower end portion of the ink containing portion  120  will be referred to as “the upper region HA of the ink tank  25 ”. The expression “the upper end portion of the ink containing portion  120 ” refers to an area located at the highest height position of the ink containing portion  120 , and the expression “the lower end portion of the ink containing portion  120 ” refers to an area located at the lowest height position of the ink containing portion  120 . The upper region HA of the ink tank  25  also includes upper wall surfaces of the upper end portion of the ink containing portion  120 . 
     In the ink tank  25  according to the present embodiment, as will be described below, when the ink tank  25  is in any of the above-described orientations, at least a portion of the atmospheric air communication path  123  is located in a height position of the upper end portion of the ink containing portion  120 . As long as at least a portion of the atmospheric air communication path  123  is located in the upper region HA of the ink tank  25 , it is possible to obtain an ink leakage suppression effect, which will be described later. 
     When the ink tank  25  according to the present embodiment is in the reference orientation ((a) in  FIG. 5 ), a portion of the second path portions  123   b  and the third path portion  123   c  is located in the upper region HA. In the present embodiment, this portion of the second path portions  123   b  and the third path portion  123   c  corresponds to a subordinate concept of the first portion according to the present invention. 
     When the ink tank  25  is in the 90° rotated-right orientation ((b) in  FIG. 5 ), a portion of the fourth path portion  123   d  is located in the upper region HA. When the ink tank  25  is in the 90° rotated-left orientation ((c) in  FIG. 5 ), a portion of the first path portion  123   a , the second path portion  123   b , the third path portion  123   c , and a portion of the fourth path portion  123   d  are located in the upper region HA. In the present embodiment, the portions of the path portions  123   a  to  123   d  correspond to a subordinate concept of the second portion according to the present invention. When the ink tank  25  is in the 180° rotated orientation ((d) in  FIG. 5 ), a portion of the second path portion  123   b  and a portion of the third path portion  123   c  are located in the upper region HA. In the present embodiment, the portions of the second path portion  123   b  and the third path portion  123   c  correspond to a subordinate concept of the third portion according to the present invention. 
     As described above, in the ink tank  25  according to the present embodiment, when the ink tank  25  is in any of the above-described orientations, at least a portion of the atmospheric air communication path  123  is located in the upper region HA. As a result, under the action of gravity, a situation is suppressed in which the ink IN stored in the ink containing portion  120  reaches the buffer chamber  122  via the atmospheric air communication path  123 . Accordingly, even if the ink tank  25  is rotated in the first direction or the second direction from the reference orientation, a situation is suppressed in which the ink IN leaks to the outside via the atmospheric air introducing portion  121 . In particular, in the ink tank  25  according to the present embodiment, when the ink tank  25  is in any of the orientations, at least a portion of the atmospheric air communication path  123  is located at a height position of the upper end portion of the ink containing portion  120 , and it is therefore possible to obtain a higher ink leakage suppression effect. 
       FIG. 6  schematically shows an internal state of the ink tank  25  when the ink tank  25  is in a 90° rotated-left orientation similar to that shown in (c) in  FIG. 5 .  FIG. 7  schematically shows an internal state of the ink tank  25  when the ink tank  25  is in a 180° rotated orientation similar to that shown in (d) in  FIG. 5 . When the ink tank  25  is in either of the orientations shown in  FIGS. 6 and 7 , the atmospheric air introducing inlet  132  is located in the lower end of the ink containing portion  120 , and therefore quite a large amount of the ink IN stored in the ink containing portion  120  flows from the atmospheric air introducing inlet  132  to the fourth path portion  123   d  of the atmospheric air communication path  123  due to gravity. Also, unless the ink tank  25  contains the ink IN in an amount more than the capacity of the ink containing portion  120 , air is present above the surface of the ink IN in the ink containing portion  120 . If the air in the ink containing portion  120  expands along with an increase in the outside temperature, a decrease in the outside pressure, or the like, the ink IN stored in the ink containing portion  120  is forced out and may reach the buffer chamber  122  via the atmospheric air communication path  123 . 
     In contrast, with the ink tank  25  according to the present embodiment, the atmospheric air intake inlet  130  that is in communication with the outside is located in the upper end portion of the buffer chamber  122 . As a result of the atmospheric air intake inlet  130  being located above the lower end portion of the buffer chamber  122  as described above, quite a large amount of the ink IN that has been forced out from the atmospheric air communication path  123  due to the air in the ink containing portion  120  expanding is stored in the buffer chamber  122 . Accordingly, leakage of the ink IN from the ink tank  25  is suppressed. 
     The amount of the ink IN forced out to the buffer chamber  122  from the ink containing portion  120  by the expansion of the air in the ink containing portion  120  corresponds to an amount obtained by subtracting the capacity of the atmospheric air communication path  123  from the volume of air increased by expansion in the ink containing portion  120 . Accordingly, in order to reliably store, in the buffer chamber  122 , the ink IN forced out due to the air expanding due to changes in the air pressure and temperature of the ink containing portion  120 , it is desirable that the buffer chamber  122  has a capacity that satisfies a relationship represented by the following inequality expression (1):
 
 V&gt;Va×α−Vb   (1).
 
     In the inequality expression (1) given above, V represents the capacity of the buffer chamber  122 . Va is a value obtained by subtracting, from the capacity of the ink containing portion  120 , the volume of the predetermined reference amount of the ink IN specified by the mark portion  116  at room temperature at an altitude of 0 meters. In other words, Va corresponds to the volume of air contained in the ink containing portion  120  when the ink containing portion  120  contains a predetermined reference amount of the ink IN. Vb corresponds to the capacity of the atmospheric air communication path  123 . 
     α is a predetermined coefficient of 1 or less. It is desirable that α is a value in which an air expansion coefficient is reflected so that Va×α represents the volume of air increased by expansion in the ink containing portion  120 . As used herein, the term “air expansion coefficient” refers to the proportion of the range of variations in the volume of air with respect to the range of altitude and the range of operation temperature in a usage environment specified in advance for the ink tank  25 . That is, the air expansion coefficient refers to the proportion of the range of variations in the volume of air with respect to the range of altitude and the range of ambient temperature (for example, about −10 to 50° C.) in which the ink tank  25  is expected to be installed. To be specific, α is preferably a value within a range of 0.1 or more and 0.5 or less, and more preferably a value within a range of 0.15 or more and 0.3 or less. 
     In order to reduce the size of the ink tank  25 , it is preferable that the buffer chamber  122  and the atmospheric air communication path  123  have a small capacity. In order to store the ink forced out from the ink containing portion  120  due to the air expanding, the buffer chamber  122  only need to have a capacity corresponding to the amount of expansion of the air in the ink containing portion  120 , given that the capacity of the atmospheric air communication path  123  is negligibly small. Accordingly, the buffer chamber  122  preferably has a capacity that satisfies a relationship represented by the following inequality expression (2):
 
 V&gt;Va×α   (2).
 
     As described above, in the ink tank  25  according to the present embodiment, the ink that has flowed into the atmospheric air introducing portion  121  is stored in the buffer chamber  122 , and thus the occurrence of leakage of the ink to the outside is suppressed. In addition, when the ink tank  25  according to the present embodiment is in the reference orientation, the communication inlet  131  that communicates between the buffer chamber  122  and the atmospheric air communication path  123  is located in the lower end portion of the buffer chamber  122 . Accordingly, even if the ink accidentally flows into the buffer chamber  122 , the ink is guided from the buffer chamber  122  to the atmospheric air communication path  123  by gravity and airflow. Accordingly, the occurrence of leakage of the ink from the buffer chamber  122  is further suppressed. 
     Summary 
     As described above, with the ink tank  25  according to the first embodiment, with the flow path configuration of the atmospheric air communication path  123 , a situation is suppressed in which the ink leaks to the outside from the ink containing portion  120  via the atmospheric air introducing portion  121 . Also, even when the ink tank  25  is placed under an environment where the air in the ink containing portion  120  expands, a situation is suppressed in which the ink contained in the ink tank  25  is forced to the outside via the atmospheric air introducing portion  121  by expansion of the air. 
     B. Second Embodiment 
       FIG. 8  is a schematic diagram showing a configuration of an ink tank  25 A according to a second embodiment of the present invention. The ink tank  25 A according to the second embodiment has substantially the same configuration as the ink tank  25  according to the first embodiment, except that an atmospheric air communication path  123 A has a different configuration. In the following description and the diagrams that will be referred to, the same constituent elements as those described in the first embodiment or corresponding constituent elements are given the same reference numerals as those used in the first embodiment. 
     The atmospheric air communication path  123 A according to the second embodiment is substantially the same as the atmospheric air communication path  123  according to the first embodiment, except that a first path portion  123   a A is provided instead of the first path portion  123   a . The first path portion  123   a A is configured as a flow path that passes through an upper end side of the buffer chamber  122 , rather than a lower end side of the buffer chamber  122 , when the ink tank  25  is in the reference orientation. The first path portion  123   a A extends upward from the communication inlet  131  provided in a lower end portion of the buffer chamber  122  that is on the third surface portion  103  side, also extends along an outer periphery of the buffer chamber  122 , is bent downward at an end portion that is on the fourth surface portion  104  side, and is connected to the second path portion  123   b.    
     With the ink tank  25 A according to the second embodiment as well, when it is in any of the following orientations: 90° rotated-right orientation; 90° rotated-left orientation; and 180° rotated orientation, at least a portion of the atmospheric air communication path  123 A is located in the upper region HA ( FIG. 5 ) of the ink containing portion  120  described with reference to  FIG. 5 . Accordingly, as in the ink tank  25  according to the first embodiment, the occurrence of ink leakage caused by the orientation of the ink tank  25 A being rotated is suppressed. Also, in the ink tank  25 A according to the second embodiment as well, when it is in an orientation in which the atmospheric air introducing inlet  132  is located on a lower end side of the ink containing portion  120 , the atmospheric air intake inlet  130  of the buffer chamber  122  is located above the lower end portion of the buffer chamber  122 . Accordingly, as in the ink tank  25  according to the first embodiment, even if the air in the ink containing portion  120  expands, a situation is suppressed in which quite a large amount of ink that has been forced out is stored in the buffer chamber  122  and leaks out to the outside. In addition, the ink tank  25 A according to the second embodiment can provide the same advantageous effects as the ink tank  25  according to the first embodiment. 
     C. Third Embodiment 
     A configuration of an ink tank  25 B according to a third embodiment of the present invention will be described with reference to  FIGS. 9 to 11 .  FIG. 9  is a schematic exploded perspective view of the ink tank  25 B in which the case member  110  and the sheet member  111  are separately shown.  FIG. 10  is a schematic front view of the ink tank  25 B as viewed in a direction opposite to the direction of the arrow Y.  FIG. 11  is a schematic cross-sectional view of the ink tank  25 B taken along the line C-C shown in  FIG. 10 . In the following description and the diagrams that will be referred to, the same constituent elements as those described in the first embodiment or the second embodiment or corresponding constituent elements are given the same reference numerals as those used in the first embodiment or the second embodiment. 
     As in the ink tank according to the first embodiment, in the ink tank  25 B according to the third embodiment, the opening of the case member  110  that is on the sixth surface portion  106  side is sealed through melt adhesion of the sheet member  111  ( FIGS. 9 and 10 ). Inside the ink tank  25 B, an ink containing portion  120  and an atmospheric air introducing portion  121 B are formed (FIGS.  9  and  11 ). Inside the ink containing portion  120 , a plurality of reinforcing ribs  108  are provided upright parallel to the direction of the arrow X. The reinforcing ribs  108  may be omitted. 
     The atmospheric air introducing portion  121 B includes a first buffer chamber  200 , a second buffer chamber  201 , and an atmospheric air communication path  203  ( FIG. 11 ). The first buffer chamber  200  is a space corresponding to the buffer chamber  122  of the ink tank  25 A according to the second embodiment. It is desirable that the first buffer chamber  200  has a capacity V that satisfies the relationships represented by two inequality expressions (1) and (2) described in the first embodiment. The second buffer chamber  201  is formed in a position adjacent to the first buffer chamber  200  with an inner wall portion  210  interposed therebetween. The first buffer chamber  200  is in communication with the second buffer chamber  201  via a communication inlet  211 . The communication inlet  211  is formed as a gap space between the inner wall portion  210  and the sheet member  111  in the lower end of the inner wall portion  210 . In the third embodiment, the communication inlet  211  of the first buffer chamber  200  corresponds to a subordinate concept of the second communication inlet according to the present invention. 
     The depth in the direction of the arrow X and the height in the direction of the arrow Z of the second buffer chamber  201  are substantially the same as those of the first buffer chamber  200 . However, the width in the direction of the arrow Y of the second buffer chamber  201  is smaller than that of the first buffer chamber  200 . The second buffer chamber  201  has a capacity smaller than that of the first buffer chamber  200 . The second buffer chamber  201  is connected to the atmospheric air intake portion  124 , and has an opening serving as an atmospheric air intake inlet  130  on an upper wall surface of the second buffer chamber  201 . When the atmospheric air communication path  203  is regarded as a first atmospheric air communication path, the atmospheric air intake portion  124  and the second buffer chamber  201  can be seen as constituting a second atmospheric air communication path through which atmospheric air can be introduced into the first buffer chamber  200 . 
     The atmospheric air communication path  203  includes a first path portion  203   a , a second path portion  203   b , a third path portion  203   c , and a fourth path portion  203   d . The first path portion  203   a  is an atmospheric air flow path formed in a position corresponding to the first path portion  123   a A of the ink tank  25 A according to the second embodiment ( FIG. 8 ). The first path portion  203   a  extends upward from the communication inlet  131  provided in the lower end portion of the first buffer chamber  200 . Then, the first path portion  203   a  extends in a direction opposite to the direction of the arrow Y along an upper outer peripheral end portion of the first buffer chamber  200  and the second buffer chamber  201  and a bent flow path portion  204  (described later) of the fourth path portion  203   d , is bent downward at an end portion that is on the fourth surface portion  104  side, and is connected to the second path portion  203   b.    
     The second path portion  203   b  and the third path portion  203   c  are atmospheric air flow paths formed at positions corresponding to the second path portion  123   b  and the third path portion  123   c  of the ink tank  25 A according to the second embodiment. The second path portion  203   b  extends from the first path portion  203   a  that is on the fourth surface portion  104  side toward the lower end portion of the ink containing portion  120 , and extends to a point short of where the ink supply inlet  118  is formed. The third path portion  203   c  is bent at the lower end portion of the second path portion  203   b  and extends in parallel to the second path portion  203   b  to a position below the first path portion  203   a.    
     The fourth path portion  203   d  is formed at a position corresponding to the fourth path portion  123   d  of the ink tank  25 A according to the second embodiment, and extends in the direction of the arrow Y on the upper end side of the ink containing portion  120 . The fourth path portion  203   d  includes the bent flow path portion  204 , four buffer portions  205   a  to  205   d , and a connecting path portion  206 . 
     The bent flow path portion  204  is a flow path extending in the direction of the arrow Y with the flow path direction having a plurality of turns in the direction of the arrow Z, and is formed in an area connecting to the third path portion  203   c . In the bent flow path portion  204 , a flow path wall  212  that has one end portion connected to an upper wall surface and is parallel in the direction of the arrow Z and a flow path wall  212  that has one end portion connected to a lower wall surface and is parallel to the direction of the arrow Z are alternately disposed in the direction of the arrow Y. With the bent flow path portion  204 , it is possible to extend the path length between the ink containing portion  120  and the first buffer chamber  200 , and thus a situation is suppressed in which the ink that has flowed from the ink containing portion  120  into the fourth path portion  203   d  reaches the first buffer chamber  200 . 
     The four buffer portions  205   a  to  205   d  are formed as internal spaces having a greater depth in the direction of the arrow X than the other parts of the fourth path portion  203   d . Among the four buffer portions  205   a  to  205   d , the first buffer portion  205   a , the second buffer portion  205   b , and the third buffer portion  205   c  are disposed adjacent to each other in the direction of the arrow Y. 
     The first buffer portion  205   a  is connected to the bent flow path portion  204  via a communication inlet  221  formed in an upper end portion thereof. The first buffer portion  205   a  and the second buffer portion  205   b  are connected via a communication inlet  223  formed in a lower end portion of a boundary wall  222  therebetween. The second buffer portion  205   b  and the third buffer portion  205   c  have substantially the same size, and are formed in positions below the first buffer chamber  200  and the second buffer chamber  201 . The second buffer portion  205   b  is connected to the third buffer portion  205   c  via a communication inlet  225  formed in a lower end portion of a boundary wall  224  between the second buffer portion  205   b  and the third buffer portion  205   c . The two communication inlets  223  and  225  are formed between a gap formed in the boundary wall  222  and the sheet member  111  and between a gap formed in the boundary wall  224  and the sheet member  111 , respectively. 
     The third buffer portion  205   c  is connected to the connecting path portion  206  via a communication inlet  226  formed in a lower end portion thereof. The connecting path portion  206  is a cranked flow path, and includes two flow paths extending in the direction of the arrow Y and an intermediate flow path that extends in the up-down direction and connects the two flow paths on a lower side and an upper side thereof. The buffer portions  205   a  to  205   c  function as storage portions for storing ink when the ink tank  25 B is in the 180° rotated orientation, a detail of which will be described later. 
     The fourth buffer portion  205   d  is located at an end portion that is on the third surface portion  103  side, and is connected to the upper flow path of the connecting path portion  206  via a communication inlet  228  formed in an upper end portion thereof. Also, the fourth buffer portion  205   d  is in communication with the ink containing portion  120  via an atmospheric air introducing inlet  132  in its bottom surface. 
     Here, if, for example, the ink tank  25 B is rocked when it is in the reference orientation, the ink contained in the ink containing portion  120  may accidentally flow into the fourth buffer portion  205   d  via the atmospheric air introducing inlet  132 . Even in such a case, the fourth buffer portion  205   d  includes, as described above, the communication inlet  228  that is located on the upper end side and is in communication with the connecting path portion  206 . Accordingly, a situation is suppressed in which the ink that has flowed into the fourth buffer portion  205   d  from the ink containing portion  120  flows further into an area beyond the fourth buffer portion  205   d.    
     The mechanism that suppresses ink leakage in the ink tank  25 B according to the third embodiment will be described with reference to  FIGS. 12 to 14 .  FIG. 12  shows an internal state of the ink tank  25 B when it is in the 90° rotated-left orientation.  FIG. 13  shows an internal state of the ink tank  25 B when it is in the 90° rotated-left orientation.  FIG. 14  shows an internal state of the ink tank  25 B when it is in the 180° rotated orientation. 
     In the ink tank  25 B according to the third embodiment, even when it is rotated by 90° or 180° in the first direction or the second direction from the reference orientation, at least a portion of the atmospheric air communication path  123 B is located in the upper region HA of the ink containing portion  120  ( FIGS. 12 to 14 ). Accordingly, as in the ink tank  25 A according to the second embodiment, the occurrence of ink leakage caused by the orientation of the ink tank  25 B being rotated is suppressed. 
     In the ink tank  25 B according to the third embodiment, when it is in an orientation in which the atmospheric air introducing inlet  132  is located on a lower end side of the ink containing portion  120  ( FIGS. 13 and 14 ), the communication inlet  211  of the first buffer chamber  200  is located above the lower end portion of the first buffer chamber  200 . Accordingly, as in the ink tank  25 A according to the second embodiment, even if the air in the ink containing portion  120  expands, the ink can be stored in the first buffer chamber  200 , and thus the occurrence of leakage of the ink to the outside is suppressed. 
     Also, in the ink tank  25 B according to the third embodiment, the second buffer chamber  201  for storing ink is provided adjacent to the first buffer chamber  200 , and thus the occurrence of ink leakage is further suppressed. Particularly when the ink tank  25 B is in the 90° rotated-left orientation ( FIG. 13 ), the atmospheric air intake inlet  130  connected to the second buffer chamber  201  is upwardly open in the upper end portion of the second buffer chamber  201 . Accordingly, the ink can be stored by using the entire space of the second buffer chamber  201 , and thus the occurrence of leakage of the ink to the outside is further suppressed. 
     In addition, in the ink tank  25 B according to the third embodiment, when it is in the 180° rotated orientation, the communication inlets  223 ,  225 , and  226  of the three buffer portions  205   a  to  205   c  of the fourth path portion  203   d  are located at the upper end of the fourth path portion  203   d  ( FIG. 14 ). Accordingly, the entire interior of the buffer portions  205   a  to  205   c  can be used as ink storage spaces, and thus the occurrence of ink leakage is further suppressed. At least one of the three buffer portions  205   a  to  205   c  corresponds to a subordinate concept of the intermediate buffer portion according to the present invention, and the communication inlets  223 ,  225 , and  226  correspond to a subordinate concept of the first opening or the second opening. 
     As described above, with the ink tank  25 B according to the third embodiment, a situation is suppressed in which the ink leaks to the outside when the ink tank  25 B is rotated from the reference orientation and brought into another orientation. In addition, the ink tank  25 B according to the third embodiment can provide the same advantageous effects as the ink tank  25  according to the first embodiment and the ink tank  25 A according to the second embodiment. 
     D. Fourth Embodiment 
       FIG. 15  is a schematic diagram showing a configuration of a tank unit  20 C included in a printer  10 C according to a fourth embodiment of the present invention. The printer  10 C according to the fourth embodiment has substantially the same configuration as that of the printer  10  according to the first embodiment, except that a tank unit  20 C is included instead of the tank unit  20 . The tank unit  20 C includes three first ink tanks  25 B and one second ink tank  25 C. The ink tanks  25 B and  25 C are linearly aligned in the direction of the arrow X such that their third surface portions  103  are flush with each other, and in this state they are detachably housed in an internal space  21   s  of a casing portion  21  (indicated by a broken line). 
     The first ink tanks  25 B have substantially the same configuration as that of the ink tank  25 B according to the third embodiment, and thus a description thereof is omitted here. The second ink tank  25 C has a capacity different from the ink capacity of the first ink tanks  25 B, and is capable of containing a larger amount of ink than the first ink tanks  25 B, which will be described later. In the printer  10 C, for example, black ink, which is consumed in a large amount, is allocated to the second ink tank  25 C, and other color inks such as cyan, magenta, and yellow are allocated to the first ink tanks  25 B. 
     A configuration of the second ink tank  25 C will be described with reference to  FIGS. 16 and 17 , in addition to  FIG. 15 .  FIG. 16  is a schematic exploded perspective view of the second ink tank  25 C.  FIG. 17  is a schematic diagram showing an internal configuration of the second ink tank  25 C.  FIG. 17  shows the inside of a case member  110  as viewed in a direction opposite to the direction of the arrow X. In the following description and the diagrams that will be referred to, the same constituent elements as those described in the third embodiment or corresponding constituent elements are given the same reference numerals as those used in the third embodiment. 
     The second ink tank  25 C has a greater width in the direction of the arrow X than that of the first ink tanks  25 B ( FIG. 15 ). Accordingly, in the second ink tank  25 C, an ink containing portion  120  and two buffer chambers  200  and  201  have capacities larger than those of the first ink tanks  25 B. Thus, the second ink tank  25 C has an ink capacity larger than that of the first ink tanks  25 B. An atmospheric air introducing portion  121 C of the second ink tank  25 C has substantially the same configuration as that of the first ink tanks  25 B ( FIGS. 16 and 17 ). The configuration of the second ink tank  25 C other than the above is substantially the same as that of the first ink tanks  25 B. 
     As described above, in the printer  10 C according to the fourth embodiment, the tank unit  20 C includes a first ink tank  25 B and a second ink tank  25 C that have different sizes. For this reason, it is possible to install a plurality of types of ink according to the pattern of consumption of the inks in the printing portion  30 . Accordingly, the adaptability for the characteristics of the printing portion  30  is enhanced, and user convenience is enhanced. Also, the ink tanks  25 B and  25 C included in the printer  10 C according to the fourth embodiment can provide the same advantageous effects as those described in the third embodiment such as suppressing ink leakage. 
     E. Fifth Embodiment 
       FIG. 18  is a schematic diagram showing a configuration of a printer  10 D according to a fifth embodiment of the present invention. The printer  10 D according to the fifth embodiment has substantially the same configuration as that of the printer  10  according to the first embodiment, except that a plurality of ink tanks  25  are housed in a casing portion  35 D (indicated by a broken line) of the printer  10 D together with a printing portion  30 . The casing portion  35 D of the printer  10 D is provided with a cover portion  22  that is similar to that provided in the casing portion  21  of the tank unit  20  according to the first embodiment ( FIG. 1 ) so that the user can access the ink tanks  25 . 
     With the printer  10 D according to the fifth embodiment, because the ink tanks  25  are integrally housed in the main body, the installation efficiency of the printer  10 D is enhanced. Also, the ink tanks  25  included in the printer  10 D according to the fifth embodiment can provide the same advantageous effects as those described in the first embodiment such as suppressing ink leakage. In the printer  10 D according to the fifth embodiment, instead of the ink tank  25 , it is possible to use the ink tank  25 A according to the second embodiment, the ink tank  25 B according to the third embodiment, or the two types of ink tanks  25 B and  25 C. 
     F. Variations 
     F1. Variation 1 
     The flow path configurations of the atmospheric air communication paths  123 ,  123 A, and  203  described in the embodiments given above are merely examples, and thus the flow path configuration is not limited to those described in the embodiments given above. The atmospheric air communication paths  123 ,  123 A, and  203  may have a different flow path configuration. The atmospheric air communication path  123  of the ink tank  25  according to the first embodiment described above has a flow path configuration that includes four path portions  123   a  to  123   d . However, the atmospheric air communication path  123  may include a path portion other than the four path portions  123   a  to  123   d . For example, the atmospheric air communication path  123  may include an additional return path portion that extends in the direction of the arrow Z between the third path portion  123   c  and the fourth path portion  123   d , or may include an additional path portion that extends in the direction of the arrow X in the second path portion  123   b , the third path portion  123   c , or at some midpoint of the fourth path portion  123   d . Also, in the atmospheric air communication path  123  according to the first embodiment, the second path portion  123   b  and the third path portion  123   c  extend between the first surface portion  101  and the second surface portion  102 , and the fourth path portion  123   d  extends between the third surface portion  103  and the fourth surface portion  104 . However, the second path portion  123   b  and the third path portion  123   c  may be configured to extend to some midpoint between the first surface portion  101  and the second surface portion  102 , and the fourth path portion  123   d  may be configured to extend to some midpoint between the third surface portion  103  and the fourth surface portion  104 . The same applies to the other embodiments. In the atmospheric air communication paths  203  of the ink tanks  25 B and  25 C according to the third embodiment and the fourth embodiment, the bent flow path portion  204  and the buffer portions  205   a  to  205   d  may be omitted. The atmospheric air communication paths  123 ,  123 A, and  203  of the embodiments given above only need to be configured such that at least a portion of the atmospheric air communication paths  123 ,  123 A, and  203  is located in the upper region HA when the ink tank is at least in the reference orientation, either of the 90° rotated-right orientation or the 90° rotated-left orientation, and the 180° rotated orientation. 
     F2. Variation 2 
     In the embodiments given above, the ink tanks  25 ,  25 A,  25 B and  25 C are configured to include a case member  110  and a sheet member  111 . However, the ink tanks  25 ,  25 A,  25 B, and  25 C need not be configured to include a case member  110  and a sheet member  111 . The ink tanks  25 ,  25 A,  25 B, and  25 C may be entirely configured with, for example, a resin member such as a plastic member. Alternatively, the ink tanks  25 ,  25 A,  25 B, and  25 C may be configured with a combination of a container that constitutes the ink containing portion  120 , a container that constitutes the buffer chamber  122 , and a tube member that constitutes the atmospheric air communication path  123  that connects these containers. 
     F3. Variation 3 
     With the ink tanks  25 ,  25 A,  25 B, and  25 C of the embodiments given above, when the ink tank is in an orientation in which the atmospheric air introducing inlet  132  is located on the lower end side closer to the lower end portion of the ink containing portion  120  rather than the upper end portion, the atmospheric air intake inlet  130  of the buffer chamber  122  or the communication inlet  211  of the buffer chamber  200  is located in the upper end portion of the buffer chamber  122  or  200 . However, the atmospheric air intake inlet  130  or the communication inlet  211  need not be located in the upper end portion of the buffer chamber  122  or  200  when the ink tank  25 ,  25 A,  25 B and  25 C are in the above-described orientation. It is only necessary that the atmospheric air intake inlet  130  or the communication inlet  211  is located above the lower end portion of the buffer chamber  122  or  200 . 
     F4. Variation 4 
     In the ink tanks  25 ,  25 A,  25 B, and  25 C of the embodiments given above, the communication inlet  131  is formed at an end portion of the buffer chamber  122  or  200  in the direction of the arrow Y. However, the communication inlet  131  only need to be connected to the atmospheric air communication path  123 ,  123 A or  123 B, and the communication inlet  131  may be formed in a different position. For example, the communication inlet  131  may be formed in a position between two end portions in the direction of the arrow Y. 
     F5. Variation 5 
     The reference orientation of the ink tanks  25 ,  25 A,  25 B, and  25 C according to the embodiments given above is an orientation in which the ink tanks  25 ,  25 A,  25 B, and  25 C are in use, and in which the first surface portion  101  faces toward the bottom surface. The reference orientation of the ink tanks  25 ,  25 A,  25 B and  25 C need not be the orientation in which the first surface portion  101  faces toward the bottom surface. It is only necessary that the reference orientation of the ink tanks  25 ,  25 A,  25 B, and  25 C is an orientation in which the ink tanks  25 ,  25 A,  25 B, and  25 C are in use, to be specific, an orientation in which at least ink is injected to the ink containing portion  120  via the ink injection portion  113 . That is, for example, in the case where ink is loaded from the ink injection portion  113  when the ink tank is in an orientation in which the third surface portion  103  faces downward in the direction of gravity, this orientation is defined as the reference orientation, and corresponds to a subordinate concept of the first orientation according to the present invention. 
     F6. Variation 6 
     The atmospheric air communication paths  123 ,  123 A, and  203  of the embodiments given above are configured as grooves that are open on the sixth surface portion  106  side. However, the atmospheric air communication paths  123 ,  123 A, and  203  of the embodiments given above need not be configured as the grooves of the case member  110 , and may be configured as, for example, tunnel-shaped flow paths passing through a wall portion constituting the case member  110 . 
     F7. Variation 7 
     The ink tanks  25 ,  25 A,  25 B, and  25 C of the embodiments given above are housed in the casing portion  21  of the tank unit  20  or  20 C, or in the casing portion  31 D of the printer  10 D. However, the ink tanks  25 ,  25 A,  25 B, and  25 C of the embodiments given above may, instead of being housed in the casing portion  21  or  31 D, be connected to the print head portion  32  via the tube  26 , with the entire ink tank being exposed to the outside or being held by a cage-like holding member or the like. 
     F8. Variation 8 
     In the embodiments given above, the ink tanks  25 ,  25 A,  25 B, and  25 C contain an ink to be supplied to the print head portion  32  of the printer  10  or  10 C. However, the configuration of the ink tanks  25 ,  25 A,  25 B, and  25 C of the embodiments given above may be applied to a tank that contains a liquid to be supplied to a liquid ejection system other than a printer. For example, the configuration may be applied to a cleaning agent tank for supplying a cleaning agent in the form of a liquid to a cleaning agent ejection apparatus that ejects the cleaning agent. 
     The present invention is not limited to the embodiments, examples and variations described above, and can be implemented with various configurations within a scope that does not depart from the spirit and scope of the present invention. For example, the technical features in the embodiments, examples and variations that correspond to the technical features in respective implementations described in Summary of Invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems or achieve some or all of the above-described effects. Also, a technical feature that is not described as essential in the specification may be omitted as appropriate. 
     REFERENCE SIGNS LIST 
       10 ,  10 C,  10 D . . . printer 
       20 ,  20 C . . . tank unit 
       21  . . . casing portion 
       21   s  . . . internal space 
       22  . . . cover portion 
       25 ,  25 A,  25 B,  25 C . . . ink tank 
       26  . . . tube 
       30  . . . printing portion 
       31  . . . control portion 
       32  . . . print head portion 
       33  . . . conveyance mechanism 
       35 ,  35 D . . . casing portion 
       101  to  106  . . . surface portion 
       107  . . . inner wall portion 
       108  . . . reinforcing rib 
       110  . . . case member 
       111  . . . sheet member 
       112  . . . cap member 
       113  . . . ink injection portion 
       114  . . . buffer chamber housing portion 
       115  . . . opening 
       116  . . . mark portion 
       117  . . . ink supply portion 
       117   h  . . . cylindrical hole 
       118  . . . ink supply inlet 
       120  . . . ink containing portion 
       121 ,  121 A,  121 B . . . atmospheric air introducing portion 
       122  . . . buffer chamber 
       123 ,  123 A,  123 B . . . atmospheric air communication path 
       123   a  to  123   d ,  123   a A . . . path portion 
       124  . . . atmospheric air intake portion 
       124   h  . . . cylindrical hole 
       125  . . . ink injection inlet 
       130  . . . atmospheric air intake inlet 
       131  . . . communication inlet 
       132  . . . atmospheric air introducing inlet 
       200  . . . first buffer chamber 
       201  . . . second buffer chamber 
       203  . . . atmospheric air communication path 
       203   a  to  203   d  . . . path portion 
       204  . . . bent flow path portion 
       205   a  to  205   d  . . . buffer portion 
       221 ,  223 ,  225 ,  226 ,  228  . . . communication inlet 
       222 ,  224  . . . boundary wall