Patent Publication Number: US-10766269-B2

Title: Printer having accommodating portion for accommodating printing agent supplied from cartridge

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2018-057319 filed Mar. 24, 2018. The entire content of the priority application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a printer provided with a print execution device that executes printing operations using a printing agent supplied from an ink cartridge, and a system that includes this printer. 
     BACKGROUND 
     An image-forming apparatus known in the art on which is mounted a cartridge accommodating toner is provided with a reserve tank that temporarily stores toner supplied from the cartridge. The image-forming apparatus can execute printing operations even after the cartridge has been removed, in a case where the reserve tank still contains toner. 
     SUMMARY 
     Since the conventional image-forming apparatus can execute printing operations using residual toner in the reserve tank even when the cartridge has been removed, there is potential for the cartridge to be removed without careful consideration, for example. However, removing the cartridge without careful consideration could lead to missing cartridges or other problems. 
     In view of the foregoing it is an object of the present disclosure to provide a technique for suppressing a cartridge that accommodates a printing agent from being removed without careful consideration. 
     In order to attain the above and other objects, the disclosure provides a printer. The printer includes a mount portion, a print execution device, and a processor. The first cartridge storing printing agent is mountable on the mount portion. The accommodating portion is configured to accommodate the printing agent supplied from the first cartridge. The print execution device is configured to perform printing with the printing agent supplied from the accommodating portion. The processor is configured to perform: acquiring first information concerning a residual quantity of the printing agent remaining in the first cartridge; acquiring second information concerning a preparation of a second cartridge to be replaced with the first cartridge on the mount portion; if the residual quantity of the printing agent remaining in the first cartridge is below a reference quantity and if the second information is acquired, allowing the print execution device to perform printing under a cartridge removed state where the first cartridge is removed from the mount portion; and if the residual quantity of the printing agent remaining in the first cartridge is larger than or equal to the reference quantity or if the second information is not acquired, prohibiting the print execution device from printing under the cartridge removed state. 
     According to another aspect, the disclosure provides a system. The system includes a printer and an apparatus communicable with the printer. The printer includes a mount portion, a print execution device, and a first processor. The first cartridge storing printing agent is mountable on the mount portion. The accommodating portion is configured to accommodate the printing agent supplied from the first cartridge. The print execution device is configured to perform printing with the printing agent supplied from the accommodating portion. The first processor is configured to perform: acquiring first information concerning a residual quantity of the printing agent remaining in the first cartridge; acquiring second information concerning a preparation of a second cartridge to be replaced with the first cartridge on the mount portion; if the residual quantity of the printing agent remaining in the first cartridge is below a reference quantity and if the second information is acquired, allowing the print execution device to perform printing under a cartridge removed state where the first cartridge is removed from the mount portion; and if the residual quantity of the printing agent remaining in the first cartridge is larger than or equal to the reference quantity or if the second information is not acquired, prohibiting the print execution device from printing under the cartridge removed state. The apparatus includes a second processor configured to perform: a preparation process for preparing the second cartridge; transmitting the second information to the printer in a case where the preparation process is performed. 
     According to still another aspect, the disclosure provides a non-transitory computer readable storage medium storing a set of program instructions for a printer having: a mount portion on which a first cartridge storing printing agent is mountable; an accommodating portion configured to accommodate the printing agent supplied from the first cartridge; a print execution device configured to perform printing with the printing agent supplied from the accommodating portion; and a processor. The set of program instructions includes: acquiring first information concerning a residual quantity of the printing agent remaining in the first cartridge; acquiring second information concerning a preparation of a second cartridge to be replaced with the first cartridge on the mount portion; if the residual quantity of the printing agent remaining in the first cartridge is below a reference quantity and if the second information is acquired, allowing the print execution device to perform printing under a cartridge removed state where the first cartridge is removed from the mount portion; and if the residual quantity of the printing agent remaining in the first cartridge is larger than or equal to the reference quantity or if the second information is not acquired, prohibiting the print execution device from printing under the cartridge removed state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the disclosure as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating a structure of a system according to an embodiment; 
         FIG. 2(A)  is a schematic diagram showing structures of a print execution device and an ink supply portion when a storage state of ink is a first storage state; 
         FIG. 2(B)  is a schematic diagram showing structures of the print execution device and the ink supply portion when the storage state is a second storage state; 
         FIG. 3(A)  is a table illustrating an example of an information database according to the embodiment; 
         FIG. 3(B)  is a table illustrating an example of a management database according to the embodiment; 
         FIG. 4  is a flowchart illustrating a residual quantity management process performed by a management server according to the embodiment; 
         FIG. 5  is a graph showing a relation between a residual quantity of ink and acquisition date; 
         FIG. 6  is a flowchart illustrating an order management process performed by the management server according to the embodiment; 
         FIG. 7  is a sequence diagram illustrating an overall cartridge management process according to the embodiment; 
         FIG. 8  is a flowchart illustrating a print management process performed by a printer according to the embodiment; 
         FIG. 9  is a flowchart illustrating a print management process performed by the printer according to the embodiment; and 
         FIG. 10  is a flowchart illustrating a print management process performed by a printer according to a variation. 
     
    
    
     DETAILED DESCRIPTION 
     A. Embodiment 
     A-1. Structure of a System  1000   
       FIG. 1  is a block diagram showing the structure of a system  1000 . The system  1000  is provided with printers  100 A and  100 B, a management server  300 , and a delivery server  400 . The printers  100 A and  100 B are connected to a local area network NT. The management server  300 , the delivery server  400 , and the local area network NT are connected to an internet IT. The printers  100 A and  100 B and the management server  300  can communicate with each other via the local area network NT and the internet IT. The management server  300  and the delivery server  400  can communicate with each other over the internet IT. 
     Since the printers  100 A and  100 B have the same structure, the following description will focus on the structure of the printer  100 A. The printer  100 A includes a CPU  110  constituting the controller of the printer  100 A; a volatile storage  120 , such as DRAM; a nonvolatile storage  130 , such as a hard disk drive or a flash memory; a display  140 , such as a liquid crystal display that displays images; an operation interface  150 , such as a touchscreen and buttons designed to acquire operations performed by the user; a print execution device  160 ; an ink supply portion  170 ; and a communication interface  180 . 
     The communication interface  180  functions to connect the printer  100 A to an external apparatus such as the management server  300  via the local area network NT. Specifically, the communication interface  180  is a wired interface conforming to Ethernet (registered trademark), or a wireless interface conforming to the Wi-Fi technology (based on the IEEE (Institute of Electrical and Electronics Engineers, Inc.) 802.11 standard or a standard based on this standard, such as one of the versions 802.11a, 11b, 11g, and 11n). 
     The CPU  110  is a processor that performs data processing. The volatile storage  120  provides a buffer region that temporarily stores various intermediate data generated when the CPU  110  performs processes. The nonvolatile storage  130  stores a computer program PG 1  for controlling the printer, and an information database IB described later. 
     In the embodiment, the computer program PG 1  may be pre-stored in the nonvolatile storage  130  when the printer  100 A is manufactured. Alternatively, the computer program PG 1  may be made available through download from a server connected to the printer  100 A over the internet IT, or may be provided in a recorded format, such as on a CD-ROM. 
     By executing the computer program PG 1 , the CPU  110  executes a printing process for controlling the print execution device  160  to print images. Also by executing the computer program PG 1 , the CPU  110  executes a cartridge management process described later in cooperation with the management server  300  and the delivery server  400 . In addition, by executing the computer program PG 1  the CPU  110  executes a print management process A for controlling whether printing is allowed in a state where an ink cartridge  200  is removed, and a print management process B for controlling whether printing is allowed in a state where an ink cartridge  200  is mounted. The cartridge management process will be described later for both print management processes A and B. 
     The print execution device  160  executes printing operations under control of the CPU  110 . The ink supply portion  170  supplies an ink Ik as the printing agent to the print execution device  160 .  FIGS. 2(A) and 2(B)  are schematic diagrams showing the structures of the print execution device  160  and the ink supply portion  170 . 
     The print execution device  160  is an inkjet-type printing mechanism that prints images on paper constituting the printing medium using ink supplied from an ink cartridge  200  as the printing agent. Specifically, the print execution device  160  forms images on paper by ejecting ink onto the paper from nozzles formed in a print head (not shown) to form dots on the paper. In the embodiment, the print execution device  160  is a monochromatic printing mechanism using a single color of ink (black (K), for example). 
     As shown in  FIGS. 2(A) and 2(B) , the ink supply portion  170  is provided with a mount portion  172  in which the ink cartridge  200  is mounted, an ink supply opening  174 , an intermediate tank  175 , and an ink channel section  177 . 
     Formed in the ink cartridge  200  are a main storage chamber  210  for accommodating ink Ik, an air hole  220 , and an ink outlet  230 . The air hole  220  is an opening providing communication between the main storage chamber  210  and the external air. The ink outlet  230  is an opening through which the ink Ik is supplied from the main storage chamber  210  to the ink supply portion  170 . The ink outlet  230  is provided near the bottom of the main storage chamber  210  so as to be capable of supplying all of the ink Ik in the main storage chamber  210  into the ink supply portion  170 . 
     A chip  250  is mounted on the outer surface of the ink cartridge  200 . The chip  250  has a memory for storing various information about the ink cartridge  200 . The information stored in the memory of the chip  250  in the embodiment includes information specifying an initial ink volume constituting the quantity of ink Ik accommodated in a new ink cartridge  200 , and identification information (a serial number) identifying the ink cartridge  200 . 
     The mount portion  172  is a holder, for example, in which the ink cartridge  200  is detachably mountable. The ink supply opening  174  is in connection with the ink outlet  230  of the ink cartridge  200  mounted in the mount portion  172 , and the intermediate tank  175  communicates with the main storage chamber  210  via the ink supply opening  174  and the ink outlet  230 . The ink Ik in the main storage chamber  210  is supplied into the ink supply portion  170  through the ink supply opening  174 . The mount portion  172  has a contact CM that contacts an electrode on the chip  250  of the ink cartridge  200  when the ink cartridge  200  is mounted in the mount portion  172 . The printer  100 A (the CPU  110 ) can read information stored in the memory of the chip  250  or write information to the memory through the contact CM. 
     A mounting sensor AS is provided in the mount portion  172  for detecting whether the ink cartridge  200  is mounted in the mount portion  172 . The mounting sensor AS is provided with a light-emitting portion for emitting light, and a light-receiving portion for receiving the light, for example. When the ink cartridge  200  is mounted in the mount portion  172 , a rib (not shown) formed on the housing of the ink cartridge  200  is disposed in a position at which the rib blocks light traveling from the light-emitting portion toward the light-receiving portion. The light-receiving portion of the mounting sensor AS outputs an electric signal to the CPU  110  indicating whether light has been received. The electric signal specifying that light is received is a signal indicating that the ink cartridge  200  is not mounted (hereinafter called an unmounted signal), while the electric signal specifying that light is not received is a signal indicating that the ink cartridge  200  is mounted (hereinafter called a mounted signal). Various other configurations may be applied to the mounting sensor AS, such as a configuration for detecting that the contact CM is in contact with the electrode of the chip  250 , for example. 
     An auxiliary storage chamber  179  for accommodating the ink Ik and an air hole  178  are formed in the intermediate tank  175 . The air hole  178  is an opening providing communication between the auxiliary storage chamber  179  and the external air. The auxiliary storage chamber  179  communicates with the main storage chamber  210  mounted in the mount portion  172  via the ink supply opening  174 , and stores ink Ik supplied from the ink cartridge  200  through the ink supply opening  174 . 
     Hereinafter, “upstream” and “downstream” are used with respect to an ink supply direction from the ink cartridge  200  to the print execution device  160 . The upstream end of the ink channel section  177  is connected to the intermediate tank  175  near the bottom surface of the auxiliary storage chamber  179  and is in communication with the auxiliary storage chamber  179 . The downstream end of the ink channel section  177  is connected to the print head (not shown) of the print execution device  160 . With this configuration, ink Ik in the auxiliary storage chamber  179  is supplied to the print execution device  160  through the ink channel section  177 . 
     As is clear from the above description, the intermediate tank  175  is disposed along the path of ink Ik flowing from the ink cartridge  200  mounted in the mount portion  172  to the print execution device  160 . 
     This type of ink supply method that provides an intermediate tank along the flow path of the ink Ik leading from the ink cartridge to the print execution device  160 , as in the ink supply portion  170  of the printer  100 A, will be called a double-chamber supply method.  FIG. 2(A)  depicts the ink supply portion  170  when a state of stored ink Ik (hereinafter, referred to the storage state) is a first storage state S 1 , while  FIG. 2(B)  depicts the ink supply portion  170  when the storage state is a second storage state S 2 . In the first storage state S 1 , ink Ik remains in the ink cartridge  200  (in the main storage chamber  210 ) and in the intermediate tank  175  (in the auxiliary storage chamber  179 ). In the second storage state S 2 , ink Ik remains in the intermediate tank  175  (the auxiliary storage chamber  179 ), but no longer remains in the ink cartridge  200  (the main storage chamber  210 ). 
     The main storage chamber  210  in the ink cartridge  200  communicates with the atmosphere through the air hole  220 , while the auxiliary storage chamber  179  in the intermediate tank  175  communicates with the atmosphere through the air hole  178 . The auxiliary storage chamber  179  of the intermediate tank  175  includes a section positioned lower (below in  FIG. 2 ) than the lower end (the bottom) of the main storage chamber  210  formed in the ink cartridge  200 , and a section positioned higher than the bottom of the main storage chamber  210 . Thus, when a new ink cartridge  200  is mounted in the mount portion  172 , some of the ink Ik in the ink cartridge  200  transfers from the main storage chamber  210  into the auxiliary storage chamber  179  through the ink supply opening  174 . Consequently, the level ISm of ink Ik in the main storage chamber  210  and the level ISs of ink Ik in the auxiliary storage chamber  179  are adjusted to the same height (see  FIG. 2(A) ). 
     As ink Ik is consumed through printing by the print execution device  160 , the levels ISm and ISs drop while remaining at the same level to each other. Once the levels ISm and ISs reach a vertical position EL corresponding to the bottom of the main storage chamber  210  (hereinafter called an “empty level EL”), ink Ik no longer remains in the main storage chamber  210 . Hence, the state of the ink Ik shifts from the first storage state S 1  in  FIG. 2(A)  to the second storage state S 2  in  FIG. 2(B) . Here, the state in which ink Ik no longer remains in the main storage chamber  210  of the ink cartridge  200  signifies that ink Ik no longer transfers from the main storage chamber  210  into the auxiliary storage chamber  179  and includes the state in which some ink Ik remains deposited on the inner walls of the main storage chamber  210 . 
     The print execution device  160  can continue to print even after the storage state of the ink Ik has shifted to the second storage state S 2 , in a case where ink Ik remains in the auxiliary storage chamber  179 . If the ink cartridge  200  is replaced with a new ink cartridge after the storage state has shifted to the second storage state S 2 , ink Ik will not be wasted since no ink Ik remains in the old ink cartridge  200  being replaced. Hence, the double-chamber supply method is advantageous in that the ink cartridge  200  can be replaced while printing is still possible, without wasting any ink Ik. 
     In the double-chamber supply method, a liquid level sensor SS is provided in the intermediate tank  175  for detecting whether the level ISs of ink Ik in the auxiliary storage chamber  179  has reached the empty level EL. With this arrangement, the CPU  110  can detect whether ink Ik remains in the ink cartridge  200 . The liquid level sensor SS may be configured with a float having a smaller specific gravity than that of the ink Ik. With this configuration, the position of the float moves downward after the level ISs reaches the empty level EL, making it possible to detect when the level ISs has reached the empty level EL by detecting movement of the float. The liquid level sensor SS outputs a signal based on the residual quantity of ink Ik in the ink cartridge  200 . For example, the liquid level sensor SS outputs an OFF signal when the level ISs of the ink Ik is at or above the empty level EL and outputs an ON signal when the level ISs of the ink Ik below the empty level EL. In other words, the liquid level sensor SS detects whether the storage state of ink is the first storage state S 1  or the second storage state S 2 . Other methods known in the art may be employed as the liquid level sensor SS, such as a method of measuring the electrical resistance of the ink Ik or a method of using a prism to vary the diffraction of light. The ink cartridge  200  need not be provided with the liquid level sensor SS when using the double-chamber supply method in the embodiment. Accordingly, the double-chamber supply method is also advantageous in that the structure of the ink cartridge  200  can be simplified. 
     The ink volume corresponding to the boundary between the first storage state S 1  and the second storage state S 2  will be called a boundary volume BV. The boundary volume BV in the embodiment may be considered the volume of ink in the auxiliary storage chamber  179  when the level ISs in the auxiliary storage chamber  179  has dropped to the empty level EL. The boundary volume BV may also be considered the maximum ink volume in the second storage state S 2 . The boundary volume BV is a value dependent on the structure and size of the intermediate tank  175  and is specific to each model of printer. 
       FIGS. 3(A) and 3(B)  show examples of the information database D 3  and the management database PD (described later). The information database D 3  in  FIG. 3(A)  stores printer information related to the printer  100 A. The printer information includes information specifying the serial number and model name of the printer  100 A and the IP address assigned to the printer  100 A, for example. The printer information also includes an identification number for the ink cartridge  200  currently being used (hereinafter called the “current cartridge ID number”), and the identification number for an ink cartridge  200  that has been ordered and is expected to be used next (hereinafter called the “next cartridge ID number”). The printer information also includes information specifying the residual quantity of ink Ik. The residual quantity of ink Ik is the sum of the ink Ik remaining in the ink cartridge  200  having the current cartridge ID number and the ink Ik remaining in the intermediate tank  175 . The residual quantity of ink Ik is calculated by subtracting from the initial ink volume the quantity of ink Ik consumed between the time the ink cartridge  200  was last replaced and the present time for the ink cartridge  200 . The printer  100 A (the CPU  110 ) updates the residual quantity of ink Ik stored in the information database IB each time a printing operation is executed, for example. The information database IB includes other information, such as information about the printing history. However, the information database IB shown in the example of  FIG. 3(A)  shows only information used in the description of the embodiment. 
     The management server  300  is a computer and is used to manage printers targeted for management, such as the printers  100 A and  100 B. As shown in  FIG. 1 , the management server  300  is provided with a CPU  310  serving as the controller of the management server  300 ; a volatile storage  320 , such as DRAM; a nonvolatile storage  330 , such as a hard disk drive or a flash memory; and a communication interface  380 . 
     The communication interface  380  functions to connect the management server  300  to external devices (the printers  100 A and  100 B and the delivery server  400 , for example) via the internet IT. As with the communication interface  180 , the communication interface  380  is a wired interface conforming to Ethernet (registered trademark), or a wireless interface conforming to Wi-Fi technology or a standard based on this technology. 
     The CPU  310  is a processor that performs data processes. The volatile storage  320  provides a buffer region for temporarily storing various intermediate data generated when the CPU  310  performs processes. The nonvolatile storage  330  stores a computer program PG 2 , and a management database PD. 
     The computer program PG 2  is an application program provided in a downloadable format from a vendor server. Here, the vendor server is a server provided by the company that manages the system  1000  or the vendor that manufactures the printers  100 A and  100 B. Alternatively, the computer program PG 2  may be provided in a recorded format, such as on a CD-ROM, or may be pre-stored in the nonvolatile storage  330  when the management server  300  is manufactured. 
     By executing the computer program PG 2 , the management server  300  (the CPU  310 ) can execute the cartridge management process described later in cooperation with the printers  100 A and  100 B and the delivery server  400 . 
     The management server  300  collects printer information and records the collected printer information in the management database PD.  FIG. 3(B)  shows an example of the management database PD according to the embodiment. As shown in  FIG. 3(B) , the management database PD includes entries EN 1  and EN 2  corresponding to the printers  100 A and  100 B under management. 
     The entry EN 1  that corresponds to the printer  100 A includes a plurality of printer information items for the printer  100 A, and specifically the serial number, the model name, the IP address, and ink-related information for the ink Ik. The ink-related information includes the current cartridge ID number and the next cartridge ID number described above, an estimated order date, and ink history information. 
     The estimated order date is the date on which an order process will likely be executed to order the next ink cartridge  200 . The ink history information includes information specifying residual quantities of ink Ik acquired from the printer  100 A and recorded in association with the dates acquired (acquisition dates). The ink history information includes information specifying a plurality of residual quantities of ink Ik, and information specifying the plurality of corresponding acquisition dates. 
     The delivery server  400  is operated by the distributor of the ink cartridges  200 . In the cartridge management process described later, the delivery server  400  receives order information for ink cartridges  200  and transmits ID numbers for ordered ink cartridges  200 . 
     A-2. Operations of the System  1000   
     A-2-1. Cartridge Management Process 
     The cartridge management process is concerned with the ordering and delivery of cartridges based on residual quantities of ink Ik in the printers  100 A and  100 B. The printers  100 A and  100 B, the management server  300 , and the delivery server  400  execute the cartridge management process in concert. 
     First, the process performed on the management server  300  (the CPU  310 ) will be described. The management server  300  receives residual ink information periodically transmitted from the printers  100 A and  100 B under management. For example, each of the printers  100 A and  100 B transmits residual ink information one time per day at a predetermined time. Alternatively, the printers  100 A and  100 B may transmit residual ink information each time a fixed quantity of printing has been executed. The residual ink information includes the serial number of the printer  100 A, the current cartridge ID number, and the current residual ink quantity described above that are recorded in the information database IB (see  FIG. 3(A) ), for example. 
     The management server  300  executes a residual quantity management process to set an estimated order date for ordering an ink cartridge  200  for each printer under management based on the residual ink information for the respective printer.  FIG. 4  is a flowchart illustrating steps in the residual quantity management process. The management server  300  continuously repeats the residual quantity management process (every few seconds, for example) as long as the management server  300  is running, for example. 
     In S 110  at the beginning of the process in  FIG. 4 , the management server  300  (the CPU  310 ) determines whether residual ink information was received. The CPU  310  executes the subsequent steps S 120 -S 150  when residual ink information was received (S 110 : YES) and ends the residual quantity management process when residual ink information was not received (S 110 : NO). In this way, the process from S 120  to S 150  is executed each time residual ink information is received. 
     In S 120  the CPU  310  confirms the cartridge ID number included in the residual ink information. For example, the CPU  310  references the management database PD based on the serial number included in the residual ink information and the source IP address of the residual ink information to identify the source printer of the residual ink information (or, to identify an entry (EN 1  or EN 2 )). In the following description, it will be assumed that the source printer is the printer  100 A. The CPU  310  confirms whether the current or next cartridge ID number of the printer  100 A recorded in the management database PD matches the cartridge ID number included in the residual ink information. Although not illustrated in the flowchart, the CPU  310  may execute a prescribed error process and subsequently end the residual quantity management process when neither the current nor next cartridge ID number for the printer  100 A matches the cartridge ID number included in the residual ink information, for example. In the error process, the CPU  310  may transmit an error notification to the printer  100 A, for example. The CPU  310  continues to S 130  when the current cartridge ID number matches the cartridge ID number included in the residual ink information. When the next cartridge ID number matches the cartridge ID number included in the residual ink information, it may be assumed that the ink cartridge  200  was replaced. In this case, the CPU  310  records the next cartridge ID number in the management database PD as the new current cartridge ID number with the field for recording the next cartridge ID number left as a null field, and advances to S 130 . 
     In S 130  the CPU  310  records the residual quantity of ink Ik specified in the residual ink information in the ink history information of the entry EN 1  for the printer  100 A in association with the acquisition date for this residual quantity. The acquisition date is the date on which the residual ink information was received. 
     In S 140  the CPU  310  sets the estimated order date.  FIG. 5  illustrates a sample method of setting the estimated order date. In the graph of  FIG. 5 , the vertical axis represents the residual quantity of ink, and the horizontal axis represents the acquisition date for the residual quantity of ink Ik. A plurality of black dots P in the graph indicates a plurality of residual quantities of ink Ik acquired from the printer  100 A to date. The CPU  310  sets an approximation line L 1  indicating the transition of residual quantities of ink Ik over time based on the residual quantities of ink Ik acquired to date. The CPU  310  sets an expected cartridge replacement date BD to the date at which the residual quantity of ink Ik will reach the boundary volume BV described above based on the approximation line L 1 . The date on which the residual quantity of ink Ik reaches the boundary volume BV may be considered the date on which the storage state of ink Ik shifts from the first storage state S 1  in  FIG. 2(A)  to the second storage state S 2  in  FIG. 2(B) . The CPU  310  sets the estimated order date OD to the date prior to the expected cartridge replacement date BD by a prescribed number of days AD. The prescribed number of days AD is set based on a reference number of days required for a new ink cartridge  200  to be delivered to the user of the printer  100 A after the ink cartridge  200  has been ordered. 
     In S 150  the CPU  310  records or overwrites the estimated order date in the management database PD and subsequently ends the residual quantity management process. As described above, the estimated order date can be updated each time residual ink information is acquired. 
     The CPU  310  also executes an order management process concerned with ordering ink cartridges  200 .  FIG. 6  is a flowchart illustrating steps in the order management process. The CPU  310  repeatedly executes the order management process (every few seconds, for example) as long as the CPU  310  is running, for example. 
     In S 210  at the beginning of the process in  FIG. 6 , the CPU  310  determines for each printer under the management whether the estimated order date OD recorded in the printer has arrived. If the estimated order date OD has arrived (S 210 : YES), the CPU  310  executes the process from S 220  to S 260 . If no estimated order date OD has arrived (S 210 : NO), the CPU  310  ends the order management process. In this way, the process of S 220 -S 260  is executed each time an estimated order date OD has arrived. In the following description, it will be assumed that the estimated order date OD for the printer  100 A has arrived. 
     In S 220  the CPU  310  transmits order information to the delivery server  400  for ordering an ink cartridge  200  for a printer whose estimated order date has arrived (the printer  100 A in this example). The order information includes a code specifying the type of the ink cartridge  200  being ordered, and information specifying the delivery destination for the ink cartridge  200 , for example. Upon receiving the order information, the delivery server  400  executes a delivery process. Specifically, the delivery server  400  sets an ID number for the ink cartridge  200  to be shipped, and transmits this ID number to the management server  300 . The ID number for the ink cartridge  200  being shipped may be selected from an inventory list for ink cartridges  200  managed by the delivery server  400 , for example. The delivery server  400  transmits delivery instructions including the ID number and delivery destination for the ink cartridge  200  to an email address for a delivery manager, for example. In response to these instructions, the delivery manager delivers the ink cartridge  200  having the specified ID number to the delivery destination, i.e., the user of the printer  100 A in this example. As another example, the delivery server  400  may receive an ID number that the packaging manager obtains by reading a bar code associated with the ink cartridge  200  when packaging the ink cartridge  200  to be shipped, and may transmit this ID number to the management server  300 . 
     In S 230  the CPU  310  receives the ID number for the ink cartridge  200  being shipped from the delivery server  400  as the next cartridge ID number described above. In S 240  the CPU  310  records the next cartridge ID number received in S 230  in the management database PD (the entry EN 1 ). 
     In S 250  the CPU  310  transmits this next cartridge ID number to the printer  100 A. Note that after the new ink cartridge  200  reaches the user of the printer  100 A and the user replaces the used ink cartridge  200  with the new ink cartridge  200 , the delivery manager may collect the used ink cartridge  200 . In this case, the driver of the delivery vehicle records the ID number for the collected ink cartridge  200  in a collection list managed by the delivery server  400 . The delivery server  400  transmits the ID number of the collected ink cartridge  200  to the CPU  310 . In S 260  the CPU  310  receives the ID number for the collected ink cartridge  200  from the delivery server  400 . Here, a considerable amount of time (several days to several weeks, for example) may elapse between execution of steps S 250  and S 260 . In S 270  the CPU  310  determines whether the ID number for the collected ink cartridge  200  matches the ID number for the ink cartridge  200  in the printer  100 A at the time the order process in S 220  was executed, and subsequently ends the order management process. If step S 260  is not executed for more than a prescribed period after execution of step S 260 , the CPU  310  may determine that the used ink cartridge  200  was not collected. 
     Next, the overall cartridge management process including the processes described above will be described with reference to the sequence chart in  FIG. 7 . The sequence chart in  FIG. 7  illustrates the sequence of processes executed by the printer  100 A, the management server  300 , and the delivery server  400  in the cartridge management process. 
     In S 10  the printer  100 A (the CPU  110 ) transmits registration information to the management server  300 . The registration information may include such items obtained from the printer information recorded in the information database IB described above as the serial number, the model name, and the IP address. 
     Upon receiving this registration information, in S 14  the management server  300  executes a registration process for registering the printer target for management. Specifically, the CPU  310  creates a new entry in the management database PD and records the registration information received from the printer  100 A (the serial number, the model name, and the IP address) in this new entry. As a rule, steps S 10  and S 14  are executed at the beginning of the cartridge management process for each printer under management. 
     In S 16  and S 18 , the printer  100 A registered as a printer under management periodically transmits residual ink information to the management server  300  as described above. Since the management server  300  executes the residual quantity management process of  FIG. 4  each time the management server  300  receives residual ink information, in S 17  and S 19  the management server  300  records an estimated order date (S 150  of  FIG. 4 ). 
     When the estimated order date subsequently arrives, in S 20  the management server  300  determines that the estimated order date has arrived (S 210 : YES of  FIG. 6 ). In S 22  the management server  300  transmits order information to the delivery server  400  (S 220  of  FIG. 6 ). Upon receiving this order information, in S 26  the delivery server  400  transmits the next cartridge ID number (the ID number of the ink cartridge  200  shipped or to be shipped) to the management server  300 . Upon receiving the next cartridge ID number (S 230  of  FIG. 6 ), in S 28  the management server  300  transmits this next cartridge ID number to the printer  100 A (S 250  of  FIG. 6 ). 
     When the printer  100 A receives the next cartridge ID number from the management server  300 , in S 30  the printer  100 A records this next cartridge ID number in the information database IB ( FIG. 3(A) ). Although an ID number is not recorded in the field for the next cartridge ID number in the example of  FIG. 3(A) , in this step the next cartridge ID number will be recorded in this field. 
     Once the next ink cartridge  200  to be used reaches the user of the printer  100 A, the user replaces the old ink cartridge  200  in the printer  100 A with the new ink cartridge  200 . After the user replaces the ink cartridge  200 , in S 32  the printer  100 A detects that the ink cartridge  200  was replaced and in S 34  updates the current cartridge ID number recorded in the information database IB. Specifically, the printer  100 A records the next cartridge ID number in the information database IB as the new current cartridge ID number. In other words, the printer  100 A sets the field of the current cartridge ID number to a number which is presently stored in the field of the next cartridge ID number. The printer  100 A also sets the field in the information database D 3  for the next cartridge ID number to a null field. 
     Subsequently, the company operating the delivery server  400  collects the used ink cartridge  200 , at which time the ID number for the collected ink cartridge  200  is recorded in the collection list on the delivery server  400 . In S 36  the delivery server  400  transmits the cartridge ID number for the collected ink cartridge  200  to the management server  300 , and then the management server  300  receives the ID number for the cartridge  200  (S 260 ). 
     On the system  1000  described above, the same cartridge management process is also executed by the printer  100 B, the management server  300 , and the delivery server  400 . According to the system  1000  of the embodiment, an ink cartridge  200  is delivered to the user of the printer  100 A at a suitable timing. By delivering an ink cartridge  200  at a suitable timing, the user of the printer  100 A need not have an excess stock of ink cartridges  200 , while the printer  100 A is unlikely to run out of ink and become unable to print. 
     A-2-2. Processes Performed by the Printers  100 A and  100 B 
     As described above, the printers  100 A and  100 B in the embodiment both employ a double-chamber supply method. Therefore, the printers  100 A and  100 B can continue printing even after the ink cartridges  200  have been removed by using ink Ik remaining in the intermediate tanks  175 , provided that there are no restrictions placed on printing executed by the printers  100 A and  100 B. For this reason, the ink cartridge  200  may be easily removed from the printers  100 A and  100 B. However, the printers  100 A and  100 B in the embodiment have been configured to prevent the ink cartridge  200  from being removed too easily, i.e., without some consideration. Next, a print management process A and a print management process B executed by the printer  100 A to prevent the ink cartridge  200  from being easily removed will be described. A description of the processes executed by the printer  100 B has been omitted since the processes are the same as those executed by the printer  100 A. 
       FIG. 8  is a flowchart illustrating steps in the print management process A. The printer  100 A (the CPU  110 ) repeatedly executes the print management process A (every 0.1 seconds, for example) while the printer  100 A is running, for example. 
     In S 310  the CPU  110  of the printer  100 A determines whether the ink cartridge  200  has been removed. The CPU  110  determines that the ink cartridge  200  was removed when detecting that the electric signal outputted by the mounting sensor AS has changed from the mounted signal to the unmounted signal. The CPU  110  advances to S 320  when determining that the ink cartridge  200  was removed (S 310 : YES). If the CPU  110  determines that the ink cartridge  200  was not removed (S 310 : NO), the CPU  110  ends the print management process A. Accordingly, the process from S 320  is executed each time the ink cartridge  200  is removed. 
     In S 320  the CPU  110  determines whether the output signal from the liquid level sensor SS is the ON signal. An ON signal outputted from the liquid level sensor SS signifies that the storage state of ink Ik is the second storage state S 2 , as described above, and specifically that the residual quantity of ink Ik has dropped below the boundary volume BV. A residual quantity of ink Ik below the boundary volume BV signifies that ink Ik no longer remains in the ink cartridge  200  removed from the printer  100 A, i.e., that the residual quantity of ink Ik in the ink cartridge  200  is 0. 
     If the output signal from the liquid level sensor SS is the ON signal (S 320 : YES), in S 330  the CPU  110  determines whether a next cartridge ID number has been received. Specifically, the printer  100 A determines that a next cartridge ID number was received when an ID number is stored in the field of the information database IB for the next cartridge ID number, and determines that a next cartridge ID number was not received when the field is a null field. 
     If a next cartridge ID number was received (S 330 : YES), in S 340  the CPU  110  allows printing in a state where the ink cartridge  200  is removed and subsequently ends the print management process A. Specifically, the CPU  110  sets a first printing control flag to ON. 
     However, if the output signal from the liquid level sensor SS is the OFF signal (S 320 : NO) or if a next cartridge ID number was not received (S 330 : NO), in S 350  the CPU  110  prohibits printing in a state where the ink cartridge  200  is removed and subsequently ends the print management process A. Specifically, the CPU  110  sets the first printing control flag to OFF. 
     In the state where the first printing control flag is set to OFF, the CPU  110  displays an error message on the display  140  and does not execute printing operations according to any print commands acquired in the state where the ink cartridge  200  is removed. The error message prompts the user to mount an ink cartridge  200 , for example. On the other hand, in the state where the first printing control flag is set to ON, the CPU  110  controls the print execution device  160  to execute a printing operation in accordance with any print command acquired in the state where the ink cartridge  200  is removed. 
     Next, the print management process B will be described with reference to the flowchart in  FIG. 9 . As with the print management process A, the printer  100 A (the CPU  110 ) repeatedly executes the print management process B (every 0.1 seconds, for example) while the printer  100 A is running, for example. 
     In S 410  the CPU  110  of the printer  100 A determines whether an ink cartridge  200  was mounted. The CPU  110  determines that an ink cartridge  200  was mounted when detecting that the electric signal outputted from the mounting sensor AS changed from the unmounted signal to the mounted signal. The CPU  110  advances to S 420  when determining that an ink cartridge  200  was mounted (S 410 : YES), and ends the print management process B when determining that an ink cartridge  200  was not mounted (S 410 : NO). In this way, the process beginning from S 420  is executed each time an ink cartridge  200  is mounted. 
     In S 420  the CPU  110  acquires the ID number of the mounted ink cartridge  200  from the chip  250  on the ink cartridge  200 . In S 430  the CPU  110  determines whether the ID number for the mounted ink cartridge  200  matches the current cartridge ID number recorded in the information database D 3 . If the ID number of the mounted ink cartridge  200  matches the current cartridge ID number (S 430 : YES), the CPU  110  determines that the ink cartridge  200  was remounted and advances to S 460 . 
     If the CPU  110  determines that the ID number of the mounted ink cartridge  200  does not match the current cartridge ID number (S 430 : NO), in S 440  the CPU  110  determines whether the ID number of the mounted ink cartridge  200  matches the next cartridge ID number recorded in the information database IB. 
     If the ID number for the mounted ink cartridge  200  matches the next cartridge ID number (S 440 : YES), the CPU  110  can determine that the ink cartridge  200  was replaced. In other words, the CPU  110  detects the replacement of the ink cartridge  200  in this case (equivalent to S 32  of  FIG. 7 ). Therefore, in S 450  the CPU  110  sets the field of the current cartridge ID number to the number which is presently recorded in the field of the next cartridge ID number. That is, the CPU  110  copies the number in the field of the next cartridge ID number to the field (or the memory area) of the information database D 3  used to specify the current cartridge ID number. In S 455  the CPU  110  deletes the next cartridge ID number recorded in the information database D 3  and advances to S 460 . Here, the CPU  110  sets the field in the information database D 3  for the next cartridge ID number to a null field. Steps S 450  and S 455  are equivalent to updating the current ID number in S 34  of  FIG. 7 . 
     If the ID number for the mounted ink cartridge  200  does not match the next cartridge ID number (S 440 : NO) in S 470  the CPU  110  prohibits printing in a state where the ink cartridge  200  is mounted and subsequently ends the print management process B. Specifically, the CPU  110  sets a second printing control flag to OFF. 
     In S 460  the CPU  110  allows printing in a state where the ink cartridge  200  is mounted and subsequently ends the print management process B. Specifically, the CPU  110  sets the second printing control flag to ON. 
     In the state where the second printing control flag is set to OFF, the CPU  110  displays an error message on the display  140  and does not execute any printing operations in accordance with print commands acquired in the state where the ink cartridge  200  is mounted. The error message indicates that the currently mounted ink cartridge is not a suitable cartridge, for example. On the other hand, in the state where the second printing control flag is set to ON, the CPU  110  controls the print execution device  160  to execute printing operations in accordance with print commands acquired in the state where the ink cartridge  200  is mounted. 
     Here, an ink cartridge  200  having the current cartridge ID number recorded in the information database IB will be called a first cartridge and an ink cartridge  200  having the next cartridge ID number recorded in the information database IB will be called a second cartridge. The second cartridge is the ink cartridge to be used following the first cartridge. According to the embodiment described above, the CPU  110  allows the print execution device  160  to execute printing operations in the state where the first cartridge is removed from the mount portion  172  (S 340  of  FIG. 8 ) if the residual quantity of ink Ik in the first cartridge is less than a reference (0 in the embodiment) as determined from the output signal of the liquid level sensor SS (S 320 : YES in  FIG. 8 ) and the ID number for the second cartridge (the next cartridge ID number) has been acquired (S 330 : YES in  FIG. 8 ). The CPU  110  prohibits the print execution device  160  from executing printing operations in the state where the first cartridge is removed from the mount portion  172  if the residual quantity of ink Ik in the first cartridge is greater than or equal to the reference as determined based on the output signal from the liquid level sensor SS (S 320 : NO in  FIG. 8 ) or if the ID number for the second cartridge has not been acquired (S 330 : NO in  FIG. 8 ). 
     Here, the need to replace the first cartridge with the second cartridge is high when the residual quantity of ink Ik in the first cartridge is less than the reference. If the ID number for the second cartridge has been acquired, there is a high probability that the second cartridge is available and that the first cartridge can be replaced with the second cartridge. In the embodiment, the printer allows printing in the state where the first cartridge is removed from the mount portion  172  if the need to replace the first cartridge with the second cartridge is high and the probability that the first cartridge can be replaced with the second cartridge is high, thereby suppressing the first cartridge from being removed from the printer  100 A without careful consideration. Thus, this method can suppress problems arising when the first cartridge is carelessly removed despite the need for and possibility of replacing the cartridge being low, for example. 
     If printing were allowed in a state where the first cartridge is removed despite the first cartridge containing ink Ik greater than or equal to the reference (greater than or equal to 0 in the embodiment), there is a great possibility of the first cartridge being removed at this time and being left out. If the first cartridge is removed at this time, problems such as the first cartridge being lost or accidentally discarded may occur despite the residual ink Ik in the first cartridge being greater than or equal to the reference. In such a case, the unused ink Ik will be wasted. In addition, if printing were allowed in the state where the first cartridge is removed at this time, the printer would be unable to continue printing after all ink Ik remaining in the intermediate tank  175  is consumed, despite there being residual ink Ik in the first cartridge. However, the embodiment described above can suppress such problems from occurring. 
     Further, if printing were allowed in the state where the first cartridge is removed while a cartridge ID number for a second cartridge has not yet been acquired, despite the residual ink Ik in the first cartridge being less than the reference (0 in the embodiment), the first cartridge will likely remain removed at this time. If the first cartridge is removed at this time, the first cartridge cannot be replaced by a second cartridge because a second cartridge has not yet been prepared, and the first cartridge will simply remain removed. In such a case, the first cartridge may be lost before being replaced by a second cartridge, preventing the first cartridge from being collected. The embodiment described above can suppress the occurrence of such problems. 
     If the residual ink Ik in the first cartridge is less than the reference and a cartridge ID number has been acquired for the second cartridge, printing is allowed in the state where the first cartridge is removed. Hence, printing can be executed at this time using residual ink Ik in the intermediate tank  175 , even when the first cartridge is removed. Thus, if the first cartridge is removed an appropriate period of time before the second cartridge arrives and is stored in a predetermined location, for example, the delivery manager will be able to collect the first cartridge easily without any printing restrictions being imposed on the printer  100 A, thereby improving the recovery rate of first cartridges. 
     According to the embodiment described above, if an ink cartridge  200  is mounted in the printer but the ID number for the ink cartridge  200  does not match the current cartridge ID number or the next cartridge ID number recorded in the information database IB (S 430 : NO and S 440 : NO in  FIG. 9 ), the printer  100 A is restricted from printing (S 470  of  FIG. 9 ), despite an ink cartridge  200  being mounted in the printer  100 A. This method can suppress an ink cartridge  200  from being mounted in a different printer than the intended printer  100 A (a printer not requiring ink cartridge replacement, for example). 
     In the embodiment described above, an ID number identifying the second cartridge is used in the print management process A as information related to preparation of the second cartridge. If an ID number has been set for the second cartridge, it is likely that the second cartridge will be delivered and acquired within a suitable time period. Accordingly, the printer  100 A can allow printing while the first cartridge is removed from the mount portion  172 , in a case where the second cartridge can be obtained within the suitable time period. Hence, this method more effectively suppresses the first cartridge from being removed without careful consideration. 
     In the embodiment, the printer  100 A, acquires an ID number for the second cartridge from the management server  300  via the communication interface  180  (S 28  of  FIG. 7 ). Thus, the printer  100 A can easily acquire the ID number for the second cartridge while placing less burden on the user than if the user were required to input the ID number for the second cartridge. 
     The printer  100 A transmits residual ink information specifying the residual quantity of ink Ik in the first cartridge to the management server  300  (S 16  of  FIG. 7 ). The printer  100 A acquires the ID number for a second cartridge from the management server  300  (S 28  of  FIG. 7 ) at a timing set based on this residual ink information (the estimated order date OD in the embodiment). Thus, the printer  100 A can acquire the ID number for the second cartridge at a suitable timing (a timing earlier than the expected cartridge replacement date BD by a prescribed number of days AD in the embodiment), thereby more effectively suppressing the first cartridge from being removed without careful consideration. If the ID number for the second cartridge were acquired too early, printing in the state where the first cartridge is removed could be allowed at too soon before the timing at which the first cartridge can be replaced by the second cartridge. In such a case, the user of the printer  100 A might remove the first cartridge without careful consideration. 
     When the printer  100 A detects that the first cartridge was replaced by the second cartridge in the embodiment described above (S 440 : YES in  FIG. 9 ), the printer  100 A sets the ID number for the second cartridge as the current cartridge ID number in place of the ID number for the first cartridge (S 450 ) and sets the field for recording the next cartridge ID number to a null field (S 455 ). Since the next cartridge ID number has not yet been received at this point, the printer  100 A prevents printing in the state where the currently mounted second cartridge is removed in the print management process A of  FIG. 8  (S 330 : NO, S 350  in  FIG. 8 ). That is, if the printer  100 A detects that the second cartridge has been mounted in the mount portion while printing is being allowed in a state where the first cartridge is removed from the mount portion  172 , i.e., when the first cartridge is replaced by the second cartridge, the printer  100 A prevents printing in the state where the second cartridge is removed. Thus, the printer  100 A can suppress the second cartridge from being removed too readily after the first cartridge was replaced by the second cartridge. 
     In the embodiment described above, if the first cartridge was removed from the mount portion  172  and subsequently remounted in the mount portion  172 , in S 430  of  FIG. 9  the printer  100 A detects that the ID number of the mounted first cartridge matches the current cartridge ID number recorded in the information database IB (S 430 : YES in  FIG. 9 ). In this case, the printer  100 A allows printing in the state where the first cartridge is mounted (S 460  of  FIG. 9 ). Thus, printing is allowed when the first cartridge is remounted despite printing being prohibited in the state where the first cartridge was removed from the mount portion  172 , thereby suppressing printing from being excessively restricted. 
     As described in the print management process A of  FIG. 8  according to the embodiment, printing is prohibited in the state where the first cartridge is removed until the condition that the residual quantity of ink Ik in the first cartridge is less than the reference (S 320  of  FIG. 8 ) and the condition that an ID number for the second cartridge is received (S 330  of  FIG. 8 ) are both satisfied. In other words, if the residual quantity of ink Ik in the first cartridge is greater than or equal to the reference when the second cartridge is acquired, the printer  100 A prevents printing in the state where the first cartridge is removed until the residual quantity of ink Ik in the first cartridge is less than the reference, and allows printing in the state where the first cartridge is removed after the residual quantity of ink Ik in the first cartridge is below the reference. Thus, the first cartridge is suppressed from being easily removed until the residual quantity of ink Ik in the first cartridge drops below the reference, even if the second cartridge is available and it is likely that the first cartridge can be replaced with the second cartridge. Hence, this method suppresses the first cartridge from being removed while ink Ik remains in the first cartridge. 
     In the embodiment described above, the management server  300  sets the timing at which the ID number for the second cartridge is transmitted to the printer  100 A (and specifically the estimated order date OD) based on the residual ink information received from the printer  100 A (S 140  of  FIG. 4 ,  FIG. 5 ). The management server  300  transmits the ID number for the second cartridge to the printer  100 A at this timing (S 210 : YES, S 250  in  FIG. 6 ). Thus, since the ID number for the second cartridge is transmitted from the management server  300  to the printer  100 A at a suitable timing, the first cartridge is more effectively suppressed from being removed without careful consideration. 
     In the embodiment, the management server  300  receives the ID number for the first cartridge when the first cartridge is collected from the user of the printer  100 A (S 260  of  FIG. 6 ). Thus, the operator of the management server  300  can confirm whether collection of the first cartridge was successful. 
     In the above description, the output signal of the liquid level sensor SS is an example of the first information, and the information specifying the residual quantity of ink Ik in the first cartridge recorded in the information database IB is an example of the third information. The identification information for the second cartridge is an example of the second information. The process executed by the management server  300  for transmitting order information for a second cartridge to the delivery server  400  (S 220  of  FIG. 6 ) is an example of the preparatory process for preparing the second cartridge. 
     B. Variations of the Embodiment 
     (1)  FIG. 10  is a flowchart illustrating steps in a variation of the print management process A. The print management process A in  FIG. 10  differs from that of the embodiment (see  FIG. 8 ) in that step S 320 B is executed in place of step S 320  of  FIG. 8 . The remainder of the process in  FIG. 10  is identical to that in  FIG. 8  and, hence, all other steps in  FIG. 10  are assigned the same step numbers used in  FIG. 8 . 
     In S 320 B the CPU  110  of the printer  100 A references the information database IB to determine whether the residual quantity of ink Ik recorded in the information database IB is less than the boundary volume BV. The CPU  110  advances to S 330  when the residual quantity of ink Ik recorded in the information database IB is less than the boundary volume BV (S 320 B: YES) and advances to S 350  when the residual quantity of ink Ik is greater than or equal to the boundary volume BV (S 320 B: NO). 
     In this way, the determination regarding whether the residual quantity of ink Ik is less than the boundary volume BV is not limited to a determination using the liquid level sensor SS. Further, the determination in S 320  of the embodiment is based on the output signal of the liquid level sensor SS at the point in time that step S 320  is executed, but the printer  100 A may record the detected output signal from the liquid level sensor SS in the information database IB each time a printing operation is performed. Subsequently in S 320  the CPU  110  may determine whether the residual quantity of ink Ik is less than the boundary volume BV based on the detected result recorded in the information database IB. 
     (2) In the embodiment described above, printing is allowed in the state where the first cartridge is removed as long as the condition that the residual quantity of ink Ik in the first cartridge is less than the reference (S 320  of  FIG. 8 : YES) and the condition that an ID number for the second cartridge has been received (S 330  of  FIG. 8 : YES) are both satisfied. As an alternative, the printer  100 A may prohibit printing in the state where the first cartridge is removed if the residual quantity of ink Ik in the first cartridge is greater than or equal to the reference. In this alternative, the printer  100 A may allow printing in the state where the first cartridge is removed if the residual quantity is less than the reference even if an ID number for the second cartridge has not been received. In this case, the printer  100 A can suppress the first cartridge from being removed without careful consideration despite the first cartridge containing a quantity of residual ink Ik greater than or equal to the reference. Further, since printing is allowed in the state where the first cartridge is removed if the residual quantity of ink in the first cartridge is less than or equal to the reference, even if an ID number for the second cartridge has not been received, the printer  100 A can execute a printing operation when the first cartridge is removed to be replaced with an ink cartridge other than the second cartridge, for example. In this case, in the print management process B the printer  100 A may allow printing in a state where a cartridge is mounted even if the ID number for the mounted ink cartridge does not match the next cartridge ID number recorded in the information database IB (S 440 : NO in  FIG. 9 ). In this case, the management server  300  may not transmit the ID number for the second cartridge to the printer  100 A, the printer  100 A need not record the ID number for the second cartridge in the information database IB, and the printer  100 A may not perform the determination in S 330  of  FIG. 8 . 
     (3) The printer  100 A may prohibit printing in the state where the first cartridge is removed if an ID number for a second cartridge has not been received. The printer  100 A may allow printing in the state where the first cartridge is removed if an ID number has been received for the second cartridge, even if the residual quantity of ink Ik in the first cartridge is greater than or equal to the reference. In this way, the printer  100 A can suppress the first cartridge from being removed haphazardly despite an ID number not being received for a second cartridge (despite a second cartridge not being ordered in the embodiment). In this case, the printer  100 A allows printing in the state where the first cartridge is removed, in a case where an ID number has been received for the second cartridge, even if the residual quantity of ink Ik in the first cartridge is greater than the reference. Thus, if the first cartridge is removed to be replaced when the second cartridge has arrived, for example, the printer  100 A can execute a printing operation despite there being a certain amount of residual ink Ik in the first cartridge. 
     (4) In the embodiment described above, the ID number for the second cartridge is used as information related to the preparation of the second cartridge. However, the information related to preparation of the second cartridge may be information specifying that the second cartridge has been ordered and need not include an ID number for the second cartridge. Alternatively, information related to preparation of the second cartridge may be information specifying that the second cartridge has been delivered (or (to be) shipped) or may be information specifying the order date or delivery date for the second cartridge. 
     (5) In the embodiment described above, the printer  100 A acquires an ID number for the second cartridge from the management server  300 . As an alternative, the printer  100 A may acquire (receive) the ID number for the second cartridge from the delivery server  400  without passing through the management server  300 . The printer  100 A may also acquire the ID number for the second cartridge via the operation interface  150 . In this case, the ID number for the second cartridge may be transmitted to a terminal device of the user, for example, and the user may input this ID number for the second cartridge into the printer  100 A via the operation interface  150 . 
     (6) In the embodiment described above, the printer  100 A transmits residual ink information specifying the residual quantity of ink Ik to the management server  300  (S 16  and S 18  of  FIG. 7 ). Here, the information transmitted to the management server  300  may be other information related to the residual quantity of ink Ik, such as information specifying the residual rate (percentage) of ink Ik in the first cartridge or information specifying the number of sheets that can be printed using the residual ink Ik in the first cartridge. Alternatively, the information transmitted to the management server  300  may be information specifying the cumulative number of sheets that have been printed to date since the ink cartridge was last replaced or may be information specifying the quantity of ink Ik consumed to date since the ink cartridge was last replaced. Based on this information and a predetermined initial quantity of ink Ik in the first cartridge, the management server  300  can identify the residual quantity of ink Ik in the first cartridge. An average quantity of ink Ik per sheet may be used for identifying the residual quantity of ink Ik. 
     (7) In the embodiment described above, the printer  100 A determines whether the residual quantity of ink Ik in the first cartridge is less than the reference based on the residual quantity of ink Ik recorded in the information database IB (S 320  of  FIG. 8 ). However, the printer  100 A may determine whether the residual quantity of ink Ik in the first cartridge is less than the reference based on other information related to the residual quantity of ink Ik. Such other information includes any of the information listed in variation (6) described above. In this case, information to be used in place of the residual quantity of ink Ik may be recorded in the information database IB or the information to be used may be calculated based on the residual quantity of ink Ik recorded in the information database IB. Further, the information related to the residual quantity of ink Ik used for determining whether the residual quantity of ink Ik in the first cartridge is less than the reference may be of a different type than the information related to the residual quantity of ink Ik transmitted to the management server  300 . 
     (8) In the embodiment described above, the management server  300  sets the estimated order date OD based on residual ink information received from the printer  100 A. However, the management server  300  may instead set the estimated order date OD to a predetermined date (a predetermined day of the month) if the amount of consumed ink Ik on the printer  100 A is stable. Specifically, the management server  300  sets a predetermined day of each month (fifth day for each month, for example) as a candidate day for the estimated order date. When the cartridge replacement date BD (see  FIG. 5 ) is calculated, the management server  300  sets the estimated order date to a predetermined day of a specific month which is closest to the cartridge replacement date BD among candidate days before the cartridge replacement date BD. The predetermined day of the specific month may be latest one of the candidate days prior to the cartridge replacement day BD more than the prescribed number of days AD. 
     (9) In the embodiment described above, the printer  100 A allows printing in the state where the first cartridge is mounted if printing was allowed in the state where the first cartridge was removed and the removed first cartridge was remounted in the mount portion  172 . However, the printer  100 A may prohibit printing in the state where the first cartridge is mounted if the first cartridge was previously removed and subsequently remounted in the mount portion  172 . In this way, the printer  100 A can more effectively suppress the first cartridge from being removed without careful consideration. 
     (10) To avoid a complex description, the printer  100 A in the embodiment described above is provided with a monochromatic print execution device  160  employing a single ink color (black (K), for example). However, the printer  100 A may be provided with a printing mechanism using multiple colors of ink Ik, such as a print execution device capable of printing color images using ink in the four colors cyan (C), magenta (M), yellow (Y), and black (K). In this case, four ink cartridges  200  corresponding to the four colors of ink can be mounted in the printer  100 A. Here, the printer  100 A may manage the residual quantities of ink Ik and cartridge ID numbers independently for each of the four ink cartridges  200  and may execute the print management processes A and B in  FIGS. 8 and 9  independently for each of the four ink cartridges  200 . Further, the management server  300  may manage the residual quantities of ink Ik, the cartridge ID numbers, and the estimated order dates OD independently for each of the four ink cartridges  200  and may execute the residual quantity management process of  FIG. 4  and the order management process of  FIG. 6  independently for each of the four ink cartridges  200 . 
     (11) The printer  100 A used as an example of the target printer in the embodiment is provided with an inkjet-type print execution device  160 . However, the printer  100 A may instead be provided with a printing mechanism employing an electrophotographic system (laser system, for example) for printing images using toner as the printing agent. In this case, the printer may be provided with a supply portion in which a toner cartridge is mountable, an intermediate tank (a subtank for temporarily storing toner, for example) that accommodates toner supplied from the toner cartridge mounted in the supply portion, and a print execution device that executes printing using toner accommodated in the intermediate tank. The processes described in the embodiment may be applied to this type of printer when the printer is provided with a double-chamber supply method for supplying toner. 
     (12) While the management server  300  and the delivery server  400  in the embodiment are separate devices, a single server may be used to perform the functions of both devices. In this case, the communications between the management server  300  and the delivery server  400  shown in  FIG. 7  may be omitted. 
     (13) While the management server  300  is connected to the internet IT in the embodiment, the management server  300  may be connected to the local area network NT instead. In this case, the management server  300  may acquire residual ink information from the printers  100 A and  100 B by periodically requesting such information using the Simple Network Management Protocol (SNMP). 
     (14) The management server  300  and/or the delivery server  400  may be a cloud server, for example, that includes a plurality of computers capable of communicating with each other over a network. 
     (15) In the embodiment described above, part of the configuration implemented in hardware may be replaced with software and, conversely, all or part of the configuration implemented in software may be replaced with hardware. 
     (16) When all or some of the functions of the present disclosure are implemented with computer programs, the programs may be stored on a computer-readable storage medium (a non-temporary storage medium, for example). The programs may be used on the same storage medium on which they were supplied or may be transferred to a different storage medium (a computer-readable storage medium). The “computer-readable storage medium” may be a portable storage medium, such as a memory card or CD-ROM; an internal storage built into the computer, such as any of various ROM or the like; or an external storage, such as a hard disk drive, connected to the computer. 
     While the disclosure has been described in detail with reference to the above embodiments, it would be apparent to those skilled in the art that various changes and modifications may be made thereto.