Liquid ejector comprising detachable discharge tank

A liquid ejector includes a liquid ejection head, a discharge path, a cap, a pump, a first tank, a second tank, a first valve, and a second valve. The liquid ejection head ejects liquid through a nozzle. The cap covers the nozzle. The pump sucks the liquid from the liquid ejection head through the cap and the nozzle and conveys the liquid to a downstream end of the discharge path. The first tank communicates with the outside air, and temporarily stores the liquid in the discharge path. The second tank is detachably attached to the liquid ejector and is connected to the downstream end of the discharge path. The first valve switches the state of the first tank between open to and cut off from the outside air. The second valve switches the state of the first tank between connection to and cut off from the second tank.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2007-308203, which was filed on Nov. 29, 2007, the disclosure of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid ejector which ejects a liquid from a nozzle.

2. Description of Related Art

Japanese Unexamined Patent Publication No. 2007-8156 recites an inkjet recording apparatus in which a suction pump connected to a suction cap is driven while a nozzle of the inkjet head is sealed with the suction cap, with the result that suction purge by which ink is sucked through the nozzle is performed and the sucked ink is absorbed by an waste-liquid foam.

SUMMARY OF THE INVENTION

This inkjet recording apparatus recited in Japanese Unexamined Patent Publication No. 2007-8156, however, is disadvantageous in that suction purge cannot be performed any more when the waste-liquid foam is saturated with the absorbed ink because of repeated suction purge. Consequently the inkjet recording apparatus becomes unavailable even if components other than the waste-liquid foam, such as an inkjet head, are still usable. This results in shortened life of the inkjet recording apparatus.

An object of the present invention is to provide a liquid ejector with long life.

According to the first aspect of the present invention there is provided a liquid ejector including a liquid ejection head, a discharge path, a cap, a pump, a first tank, a second tank, a first valve, a second valve, and a control unit. The liquid ejection head ejects a liquid through a nozzle. The discharge path is used for discharging the liquid from the liquid ejection head. The cap is connected to an upstream end of the discharge path and covers the nozzle. The pump is provided in the middle of the discharge path. The pump sucks the liquid from the liquid ejection head through the cap and the nozzle and conveys the liquid from the upstream end to a downstream end of the discharge path. The first tank is provided downstream of the pump on the discharge path, communicates with the outside air, and temporarily stores the liquid in the discharge path. The second tank is detachably attached to the liquid ejector and is connected to the downstream end of the discharge path when the second tank is attached to the liquid ejector. The first valve switches the state of the first tank between open to the outside air and cut off from the outside air. The second valve switches the state of the first tank between connection to and cut off from the second tank. The control unit controls the pump, the first valve, and the second valve.

In the first aspect of the present invention, the pump is driven while the first valve does not cut off the first tank from the outside air whereas the second valve cuts off the first tank from the second tank. With this, via the cap, the liquid in the liquid ejection head is sucked through the nozzle and conveyed to the first tank. In the meanwhile, the pump is driven while the first valve cuts off the first tank from the outside air whereas the second valve does not cut off the first tank from the second tank. With this, the liquid stored in the first tank is conveyed to the second tank. The amount of the liquid in the first tank is reduced as a result, and hence a space for storing liquid is created in the first tank. It therefore becomes possible to continue the operation of sucking a liquid from the liquid ejection head and conveying the liquid to the first tank through the discharge path. This elongates the life of the liquid ejector.

Furthermore, as discussed above, the pump can function as not only a power source for sucking the liquid in the liquid ejection head through the nozzle and conveying the liquid to the first tank but also for conveying the liquid from the first tank to the second tank, because of the switching by the first valve and the second valve. Therefore it is unnecessary to provide different power sources and hence the structure of the liquid ejector is kept simple.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes a preferred embodiment of the present invention.

FIG. 1is a schematic diagram of a printer of the present invention.FIG. 2illustrates an ink discharge path which has the upstream end connected to a later-detailed suction cap7ofFIG. 1and the downstream end connected to a second cartridge attaching unit13. As shown inFIGS. 1 and 2, the printer1includes components such as a carriage2, an inkjet head3, a sheet feeding roller4, a first cartridge attaching unit5, tubes6, a suction cap7, a switching unit8, a pump9, a storage tank10, and the second cartridge attaching unit13. The operation of the printer1is controlled by the control unit100.

The carriage2is driven by an unillustrated driver so as to reciprocate along the scanning directions in parallel to the crosswise direction inFIG. 1, i.e. reciprocate in the scanning directions along two guides21extending perpendicular to a predetermined direction of the present invention. These two guides21extend, in both scanning directions, beyond the boundaries of a sheet conveyance path41on which later-described record sheets P are carried. This allows the carriage2to reciprocate in the scanning directions beyond the boundaries of the sheet conveyance path41.

The inkjet head3is disposed on the lower surface of the carriage2. The inkjet head3has plural nozzles31on its lower surface, and ejects ink from the nozzles31by pressurizing, by using an unillustrated piezoelectric actuator, ink in an unillustrated pressure chamber which communicates with the nozzles31. The nozzles31are aligned along a sheet feeding direction in parallel to the vertical directions inFIG. 1, so as to constitute nozzle strings32. Four nozzle strings32are aligned in parallel to the scanning directions. From the leftmost string to the rightmost string inFIG. 1, these four nozzle strings32respectively eject black, yellow, cyan, and magenta inks from the nozzles31constituting each of them.

Along the sheet conveyance path41, the sheet feeding roller4, which is a liquid target medium carrier unit, carries a record sheet P which is a liquid target medium in a sheet feeding direction toward the bottom ofFIG. 1, i.e. in a predetermined direction. In the printer1, ink is ejected from the nozzles31of the inkjet head3reciprocating in the scanning directions along with the carriage2to a record sheet P carried in the sheet feeding direction by the sheet feeding roller4, so that the ink lands on the record sheet P. In this way printing is done on the record sheet P.

The first cartridge attaching unit5is disposed to be adjacent to the lower right end of the sheet conveyance path41inFIG. 1. To the first cartridge attaching unit5, it is possible to attach ink cartridges25filled respectively with black, yellow, cyan, and magenta inks. The ink cartridge25attached to the first cartridge attaching unit5is equivalent to a third tank of the present invention. The third tank is attachable/detachable to/from the printer1(apparatus).

Now, the first cartridge attaching unit5and the ink cartridges25attached to the first cartridge attaching unit5are detailed.FIG. 3Ais a profile of the first cartridge attaching unit5, when no ink cartridge25is attached.FIG. 3Bis a profile of the first cartridge attaching unit5, when an ink cartridge25in which a predetermined amount or more of ink remains is attached.FIG. 3Cis a profile of the first cartridge attaching unit5, when an ink cartridge25in which the amount of remaining ink is lower than the predetermined amount is attached.

As illustrated inFIGS. 3A to 3C, the first cartridge attaching unit5has a cartridge storage space51, an ink flow path52, an air hole53, a light emitting unit54, a light receiving unit55, an attaching sensor56, and a lid57. The cartridge storage space51is a space which is open to the left side inFIGS. 3A to 3C. An ink cartridge25is inserted into the cartridge storage space51through the opening on the left side ofFIGS. 3A to 3C.

The ink flow path52extends to the right inFIGS. 3A to 3Cfrom the vicinity of the lower end of the right wall of the cartridge storage space51inFIGS. 3A to 3C. The right end of the ink flow path52is connected to the inkjet head3via the tube6. The air hole53extends to the right inFIGS. 3A to 3Cfrom the vicinity of the upper end of the right wall of the cartridge storage space51inFIGS. 3A to 3C. This air hole53is open to the outside air.

The light emitting unit54and the light receiving unit55oppose each other in the direction perpendicular to the surfaces ofFIGS. 3A to 3C. The light emitting unit54emits laser light towards the light receiving unit55. The light receiving unit55receives laser light from the light emitting unit54. As discussed later, whether a remaining amount of ink in the ink cartridge25attached to the first cartridge attaching unit5is smaller than a predetermined remaining amount is detectable based on whether the light receiving unit55receives laser light from the light emitting unit54.

The attaching sensor56is disposed in the wall which defines the upper face of the cartridge storage space51. From the lower end of this sensor56, the lever56aextends so as to reach the inside of the cartridge storage space51. As illustrated inFIG. 3BandFIG. 3C, the attaching sensor56detects that an ink cartridge25is attached to the first cartridge attaching unit5, when the attaching sensor56detects that a lever56ais lifted up because the ink cartridge25is attached to the first cartridge attaching unit5.

The lid57is used for closing the opening of the cartridge storage space51, which is on the left side inFIGS. 3A to 3C. The lid57is rotatable about a fulcrum57awhich is provided at the lower end thereof. InFIGS. 3A to 3C, the lid57covers the aforesaid opening of the cartridge storage space51. The lid57in this state is rotated anticlockwise for about 180° so that the opening of the cartridge storage space51is uncovered, and through this opening an ink cartridge25is inserted into the cartridge storage space51. An ink cartridge25is attached to the cartridge storage space51in this way. As shown inFIG. 3BandFIG. 3C, when the ink cartridge25is attached to the cartridge storage space51and the lid57covers the opening of the cartridge storage space51, the lid57pushes the left-side wall of the ink cartridge25inFIGS. 3A to 3Ctoward the right edge of each figure. This ensures the adhesion between the ink flow path52and an ink supplying unit62and between the air hole53and an outside-air passage unit63.

The ink cartridge25has a substantially cuboid shape and includes an ink storage space61, the ink supplying unit62, an outside-air passage unit63, and a rotating component64. The ink storage space61is filled with ink which is to be supplied to the inkjet head3. The ink supplying unit62is disposed in the vicinity of the lower end of the right-side wall of the ink storage space61inFIGS. 3A to 3C. The ink supplying unit62is connected to the ink flow path52when the ink cartridge25is attached to the first cartridge attaching unit5. The ink supplying unit62has an unillustrated valve. This valve is opened only when the ink cartridge25is attached to the first cartridge attaching unit5, and the ink storage space61communicates with the ink flow path52when the valve is open. When the valve is open, ink in the ink storage space61is supplied to the inkjet head3through the ink flow path52and the tube6.

The outside-air passage unit63is disposed in the vicinity of the upper end of the right-side wall of the ink cartridge25inFIGS. 3A to 3C. The outside-air passage unit63is connected to the air hole53when the ink cartridge25is attached to the first cartridge attaching unit5. The outside-air passage unit63has an unillustrated valve which is opened only when the ink cartridge25is attached to the first cartridge attaching unit5. When the ink inside the ink storage space61flows out through the ink flow path52, air is introduced into the ink storage space61through the outside-air passage unit63as much as the ink flowing out.

The rotating component64is provided inside the ink storage space61. The rotating component64is supported at a fulcrum64aso as to be rotatable in clockwise and anticlockwise directions inFIGS. 3A to 3C. At the left hand end of the rotating component64inFIGS. 3A to 3C, a float64bis provided. As an amount of ink inside the ink storage space61changes (i.e. the height of the liquid level changes), the ink provides buoyancy to the float64bso that the rotating component64rotates.

In the meanwhile, at the right hand end of the rotating component inFIGS. 3A to 3C, a light blocking section64cis formed. As illustrated inFIG. 3B, this light blocking section64cis positioned to block laser light emitted from the light emitting unit54, when an amount of ink in the ink cartridge25is not smaller than a predetermined remaining amount. In this state the light receiving unit55does not receive laser light. The rotating component64rotates as the amount of ink inside the ink cartridge25decreases. When the amount of ink inside the ink cartridge25becomes smaller than the predetermined remaining amount, the light blocking section64cmoves to a position of not blocking laser light emitted from the light emitting unit54, as illustrated inFIG. 3C. In this state the light receiving unit55receives laser light emitted from the light emitting unit54. It is therefore possible, by detecting whether the light receiving unit55receives laser light or not, to detect whether an amount of ink in the ink cartridge25attached to the first cartridge attaching unit5is smaller than a predetermined remaining amount, i.e. to detect whether the ink cartridge25is in the empty state or not.

Back toFIGS. 1 and 2, the tube6connects the first cartridge attaching unit5with the inkjet head3. The ink inside the ink cartridge25attached to the first cartridge attaching unit5is therefore supplied to the inkjet head3through the tube6.

The suction cap7is disposed to face the carriage2when the carriage2is at the rightmost position inFIG. 1, which position is to the right of the sheet conveyance path41. The suction cap7is connected to the upstream end of the ink discharge path. The suction cap7includes: a first cap unit7aused to cover the nozzles31which constitute the leftmost nozzle string32inFIG. 1and eject black ink; and a second cap unit7bused to cover the nozzles31which constitute the second leftmost to the rightmost nozzle strings32inFIG. 1and eject color inks, i.e. yellow, cyan, and magenta inks. In addition to the above, the suction cap7is arranged to be movable in the vertical directions inFIG. 2. This makes it possible to cover the corresponding nozzles31by the cap units7aand7bby raising the suction cap7after the carriage2is moved to the position where the inkjet head3faces the suction cap7.

The switching unit8is provided in the middle of the ink discharge path, and selectively connects at least one of the first cap unit7aand the second cap unit7bof the suction cap7with the pump9. The pump9is disposed downstream of the switching unit8which is in the middle of the ink discharge path. The pump9is a known pump such as a tube pump. The pump9sucks ink from the inkjet head3through the nozzles31, via the at least one of the first cap unit7aand the second cap unit7bwith which the pump9is connected via the switching unit8. The pump9then conveys the sucked ink toward the storage tank10, i.e. conveys the ink from the upstream to the downstream of the ink discharge path. Thickened portions of the ink and contaminants in the ink are removed from the inkjet head3as a result, and hence clogging of the nozzles31is prevented.

The storage tank10which is a first tank is disposed downstream of the pump9in the ink discharge path. The storage tank10is fixed to the printer1and not detachable therefrom. The storage tank10temporarily stores ink sucked from the inkjet head3, i.e. ink ejected from the inkjet head3to the ink discharge path. The storage tank10has a connection hole10awhich is open to the outside air. The connection hole10ais provided with a first valve11. The first valve11switches the state of the storage tank10between open to the outside air and cutoff from the outside air. Provided in the vicinity of the storage tank10is a liquid level sensor14which can detect whether the liquid level of the ink in the storage tank10is higher than a predetermined height. This makes it possible to detect whether an amount of ink stored in the storage tank10is not smaller than a predetermined reference storage amount.

The second cartridge attaching unit13is connected to the downstream end of the ink discharge path. To/from this second cartridge attaching unit13, a used ink cartridge25which is in the empty state is attachable/detachable. Therefore an ink cartridge25attached to the second cartridge attaching unit13is connected to the downstream end of the ink discharge path. Ink in the ink discharge path is, as discussed later, discharged to the ink cartridge25attached second cartridge attaching unit13. In this way, a used ink cartridge25is effectively recycled by attaching it to the second cartridge attaching unit13. It is noted that the ink cartridge25attached to the second cartridge attaching unit13is equivalent to the second tank of the present invention, and the second tank is attachable/detachable to/from the printer1. It is also noted that the second tank of the present invention is a used third tank.

Now, details of the second cartridge attaching unit13are given. It is noted that the description is given usingFIGS. 3A to 3Cbecause the second cartridge attaching unit13is substantially identical with the first cartridge attaching unit5. InFIGS. 3A to 3C, the numbers in parentheses indicate the respective components of the second cartridge attaching unit13.

The second cartridge attaching unit13includes a cartridge storage space71, an ink flow path72, an air hole73, a light emitting unit74, a light receiving unit75, an attaching sensor76, and a lid77. The cartridge storage space71is a space where a used ink cartridge25is inserted. This space71is arranged to be identical with the cartridge storage space51. The ink flow path72is identical with the ink flow path52, and the right hand end of the path72is connected to the storage tank10. The ink conveyed from the storage tank10to the downstream of the ink discharge path flows through the ink flow path72into the ink storage space61of the ink cartridge25attached to the cartridge storage space71. The air hole73is identical with the air hole53in terms of the structure. When the ink flows into the ink storage space61, air is discharged to the outside from the ink storage space61through the outside-air passage unit63and the air hole73as much as the ink flowing in.

Detailed descriptions of the light emitting unit74, the light receiving unit75, the attaching sensor76, and the lid77are not given because they are identical with the air hole53, the light emitting unit54, the light receiving unit55, the attaching sensor56, and the lid57, respectively.

Back toFIGS. 1,2, the second cartridge attaching unit13is disposed to the right of the sheet conveyance path41in the scanning directions, along with the suction cap7, the switching unit8, the pump9, and the storage tank10. In other words, with respect to the sheet conveyance path41, the second cartridge attaching unit13is on the same side as the suction cap7, the switching unit8, the pump9, and the storage tank10. This results in the suction cap7, the switching unit8, the pump9, the storage tank10, and the second cartridge attaching unit13being close to one another, and hence the later-detailed conveyance of ink on the ink discharge path is easily done, including the later-detailed conveyance of ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13.

Between the storage tank10and the second cartridge attaching unit13, disposed is a second valve12. The second valve12switches the state of the storage tank10between connection to and cutoff from the second cartridge attaching unit13, more specifically, between connection to and cutoff from the ink cartridge25attached to the second cartridge attaching unit13.

In the printer1, the pump9is driven while the aforesaid first valve11does not cut off the storage tank10from the outside air whereas the second valve12cuts off the storage tank10from the second cartridge attaching unit13. With this, ink in the inkjet head3is sucked through the nozzles31and conveyed to the storage tank10(first conveyance mode).

On the other hand, the pump9is driven while the first valve11cuts off the storage tank10from the outside air whereas the second valve12does not cut off the storage tank10from the second cartridge attaching unit13. With this, ink stored in the storage tank10is conveyed to the ink cartridge25attached to the second cartridge attaching unit13(second conveyance mode).

In this way, in the present embodiment the pump9functions not only as a power source for sucking ink from the inkjet head3through the nozzles31and conveying the same to the storage tank10but also a power source for conveying ink stored in the storage tank10to the second cartridge attaching unit13, more specifically to the ink cartridge25attached to the second cartridge attaching unit13. Therefore it is unnecessary to provide different power sources and hence the structure of the printer1is kept simple. In addition to the above, the aforesaid first and second conveyance modes are easily switchable by (i) switching the state of the storage tank10between connection to and cut off from the outside air by the first valve11and (ii) switching, by the second valve12, the state of the storage tank10between connection to and cut off from the second cartridge attaching unit13, more specifically connection to and cut off from the ink cartridge25attached to the second cartridge attaching unit13.

The following describes the control unit100which controls the operation of the printer1.FIG. 4is a block diagram of the control unit100ofFIG. 1.

The control unit100is constituted by components such as a CPU (Central Processing Unit), a ROM (Read only Memory), and a RAM (Random Access Memory). As shown inFIG. 4, these components function as a head control unit111, a carriage control unit112, cap control unit109, a first attachment detector113, a first empty detector114, a second attachment detector115, a second empty detector116, a storage amount detector117, a pump control unit118, a pump counter119, a power-on detector120, and a valve control unit121.

The head control unit111controls the operation of the inkjet head3when it ejects ink from the nozzles31. The carriage control unit112controls the movement of the carriage2. The cap control unit109controls the vertical movement of the suction cap7. The first attachment detector113detects whether an ink cartridge25is attached to the first cartridge attaching unit5by detecting whether the lever56aof the attaching sensor56is lifted up by the ink cartridge25. When the first attachment detector113has detected that an ink cartridge25is attached to the first cartridge attaching unit5, the first empty detector114detects whether that ink cartridge is in the empty state by detecting whether the light receiving unit55receives laser light.

The second attachment detector115detects whether an ink cartridge25is attached to the second cartridge attaching unit13by detecting whether the lever76aof the attaching sensor76is lifted up by the ink cartridge25. When the second attachment detector115has detected that an ink cartridge25is attached to the second cartridge attaching unit13, the second empty detector116detects whether that ink cartridge25is in the empty state by detecting whether the light receiving unit75receives laser light.

The storage amount detector117detects whether an amount of ink stored in the storage tank10is not smaller than a reference storage amount by causing the liquid level sensor14to detect whether the liquid level of the ink in the storage tank10is at a predetermined height or higher. The pump control unit118controls the operation of the pump9. The pump counter119counts how many times the pump9is driven. The power-on detector120detects whether the printer1is powered on. The valve control unit121controls the operations of the first valve11and the second valve12.

Now, described with reference to the flow chart ofFIG. 5andFIG. 2,FIG. 6,FIG. 7, andFIG. 8AtoFIG. 8Care the operations of the printer1of the present embodiment, which are the operation to suck ink in the inkjet head3through the nozzles31and convey the ink to the storage tank10and the operation to convey ink stored in the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13.FIG. 5is a flowchart of the aforesaid operations of the printer1.FIG. 6is equivalent toFIG. 2and shows a case where ink is sucked from the inkjet head3through the nozzles31and conveyed to the storage tank10.FIG. 7is equivalent toFIG. 2and shows a case where ink is conveyed from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13.FIGS. 8A to 8Cshow the second cartridge attaching unit13and the ink cartridge25attached to the second cartridge attaching unit13, during the aforesaid operations.

As illustrated inFIG. 2, when power is off, the printer1is arranged such that the first valve11cuts off the storage tank10from the outside air and the second valve12cuts off the storage tank10from the second cartridge attaching unit13. This prevents ink from overflowing from the storage tank10. The operations illustrated in the flowchart ofFIG. 5start when the printer1is powered on.

As illustrated inFIG. 5, when the printer1is powered on, the first valve11stops cutting off the storage tank10from the outside air under the control of the valve control unit121, as illustrated inFIG. 6(step S101, hereinafter referred to simply as S101, for example). At this point, the second valve12is kept to cut off the storage tank10from the second cartridge attaching unit13.

Subsequently, when it is necessary to suck ink from the inkjet head3because of reasons such as poor ejection of ink from the nozzles31, the carriage2is moved under the control of the carriage control unit112to the position where the inkjet head3opposes the suction cap7, and then the suction cap7is moved up so as to cover the nozzles31, under the control of the cap control unit109. In this condition, the pump control unit118drives the pump9. Thickened portions of the ink and contaminants in the ink are sucked through the nozzles31from the inkjet head3as a result, and the sucked matter is conveyed to the storage tank10. (S102). In short, the mode is switched to the first conveyance mode. The ink conveyed to the storage tank10is stored therein.

Until an amount of ink stored in the storage tank10becomes equal to or larger than a reference storage amount (S103:NO), the step S102is repeated. When the storage amount detector117detects that an amount of ink stored in the storage tank10is equal to or larger than the reference storage amount (S103:YES), the second attachment detector115detects whether an ink cartridge25is attached to the second cartridge attaching unit13(S104). If no ink cartridge25is attached (S104:NO), a warning is given for example and the operation is stopped.

On the other hand, when an ink cartridge25is attached to the second cartridge attaching unit13(S104:YES), the second empty detector116detects whether that ink cartridge25is in the empty state (S105). If the attached ink cartridge25is not in the empty state (S105:NO), a warning is given for example and the operation is stopped.

In the meanwhile, when as illustrated inFIG. 8Athe ink cartridge25attached to the second cartridge attaching unit13is in the empty state (S105:YES), as illustrated inFIG. 7, the first valve11cuts off the storage tank10from the outside air and the second valve12stops cutting off the storage tank10from the second cartridge attaching unit13, under the control of the valve control unit121(S106), and then the pump control unit118drives the pump9(S107). This results in conveying the ink in the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13. In short, the mode is switched to the second conveyance mode. An amount of the ink in the aforesaid ink cartridge25increases.

Thereafter, until the second empty detector116detects that the ink in the ink cartridge25attached to the second cartridge attaching unit13has increased and the ink cartridge25is no longer in the empty state (S108:YES), the conveyance of the ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13is continued. Subsequently, as illustrated inFIG. 8B, when the second empty detector116detects that an amount of ink in the ink cartridge25attached to the second cartridge attaching unit13has increased to the predetermined remaining amount and the ink cartridge25is no longer in the empty state (S108:NO), the pump counter119starts to count how many times the pump9is driven (s109).

Until the number of times the pump9is driven, which is counted by the pump counter119, reaches a predetermined number (S110:YES), the conveyance of the ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13is continued. When the number of times the pump9is driven counted by the pump counter119reaches the predetermined number (S110:NO), the pump control unit118detects, as illustrated inFIG. 8C, that an amount of ink in the ink cartridge25attached to the second cartridge attaching unit13reaches the limit. When this is the case, the pump control unit118causes the pump counter119to stop the counting of how many times the pump9is driven (S111) and stops the pump9(S112) so as to discontinue the conveyance of the ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13.

In regard to the conveyance of ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13, an amount of ink conveyed by driving the pump9once is predetermined. Therefore, an amount of ink conveyed to the ink cartridge attached to the second cartridge attaching unit13corresponds to the number of times the pump9is driven after the ink cartridge25becomes no longer empty. For this reason the ink conveyed from the storage tank10does not overflow from the ink cartridge25if the number of times the pump9is driven is properly set. Thereafter the process returns to the aforesaid S101.

At the point above, an amount of the ink in the storage tank10is smaller than the reference storage amount because the ink has been conveyed from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13as a result of the above-described S106to S110. The printer1can therefore suck the ink from the inkjet head3through the nozzles31and convey the sucked ink to the storage tank10, by performing the above-described S101to S103.

In addition to the above, in case where the ink cartridge25attached to the second cartridge attaching unit13is replaced with another ink cartridge25which is a used cartridge, when an amount of ink in the storage tank10becomes equal to or larger than the reference storage amount in the above-described S103(S103:YES), it is detected in the above-described S104that the ink cartridge25is attached to the second cartridge attaching unit13(S104:YES) and it is detected in S105that the ink cartridge25is in the empty state (S105:YES). Thereafter the above-described S106to S112are carried out.

In this way, it becomes possible to continue the operation of sucking ink from the inkjet head3and conveying the ink to the storage tank10when the ink cartridge25attached to the second cartridge attaching unit13is replaced with another ink cartridge25and ink is conveyed from the storage tank10to the new ink cartridge25attached to the second cartridge attaching unit13. This elongates the life of the printer1.

In addition to the above, the printer1is arranged so that the power-on detector120detects that the printer1is powered off. When power-off is detected, the valve control unit121causes the first valve11to cut off the storage tank10from the outside air and causes the second valve to cut off the storage tank10from the second cartridge attaching unit13. This prevents ink from overflowing from the storage tank10when the printer1is powered off. As a matter of course, if the printer1is powered off in the middle of the operation ofFIG. 5, the operation ofFIG. 5is discontinued and the aforesaid blocking operation is carried out by the first valve11and the second valve12.

According to the above-described embodiment, the pump9is driven while the first valve11does not cut off the storage tank10from the outside air whereas the second valve12cuts off the storage tank10from the second cartridge attaching unit13, more specifically from the used ink cartridge25attached to the second cartridge attaching unit13. With this, via the suction cap7, ink in the inkjet head3is sucked through the nozzles31and conveyed to the storage tank10(first conveyance mode).

Furthermore, the pump9is driven while the first valve11cuts off the storage tank10from the outside air whereas the second valve12does not cut off the storage tank10from the second cartridge attaching unit13, more specifically from the used ink cartridge25attached to the second cartridge attaching unit13. With this, ink stored in the storage tank10is conveyed to the ink cartridge25attached to the second cartridge attaching unit13(second conveyance mode). The amount of the ink in the storage tank10is reduced as a result, and hence a space for storing ink is created in the storage tank10.

In this way, it becomes possible to continue the operation of sucking ink from the inkjet head3and conveying the ink to the storage tank10when the used ink cartridge25attached to the second cartridge attaching unit13is replaced with another ink cartridge25and ink is conveyed from the storage tank10to the new ink cartridge25attached to the second cartridge attaching unit13. This elongates the life of the printer1.

Furthermore, the pump9functions not only as a power source for sucking ink from the inkjet head3through the nozzles31and conveying the same to the storage tank10but also a power source for conveying ink stored in the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13, because the connection and cutoff between the storage tank10and the outside air are switched by the first valve11and the connection and cutoff between the storage tank10and the second cartridge attaching unit13, more specifically between the storage tank10and the ink cartridge25attached to the second cartridge attaching unit13are switched by the second valve12. Therefore it is unnecessary to provide different power sources and hence the structure of the printer1is kept simple.

Furthermore, to/from this second cartridge attaching unit13, a used ink cartridge25which is in the empty state is attachable/detachable. This makes it possible to effectively recycle used ink cartridges25.

Furthermore, the suction cap7, the switching unit8, the pump9, the storage tank10, and the second cartridge attaching unit13are disposed to the right of the sheet conveyance path41inFIG. 1in the scanning directions. Therefore these components are disposed to be close to one another, and hence the conveyance of ink on the ink discharge path is easily done, including the conveyance of ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13.

In addition to the above, when the printer1is powered off, the first valve11cuts off the storage tank10from the outside air and the second valve12cuts off the storage tank10from the second cartridge attaching unit13, more specifically from the ink cartridge25attached to the second cartridge attaching unit13. This makes it possible to prevent ink from overflowing from the storage tank10, when the printer1is powered off.

The following discusses a variation in which various modifications are made to the embodiment above. It is noted that the same structural elements as those explained in the embodiment above will be assigned with the same reference numerals and the detailed explanations thereof will be suitably omitted.

In the variation, as illustrated inFIG. 9, a first cartridge attaching unit205is disposed to the left of the sheet conveyance path41so that, in the scanning directions, the first cartridge attaching unit205opposes the second cartridge attaching unit13over the sheet conveyance path41, more specifically an ink cartridge25which is a third tank attached to the first cartridge attaching unit205opposes an ink cartridge25which is a second tank attached to the second cartridge attaching unit13, over the sheet conveyance path41(variation1).

In the embodiment above, both the first cartridge attaching unit5and the second cartridge attaching unit13are disposed to the right of the sheet conveyance path41, and the suction cap7, the switching unit8, the pump9, and the storage tank10are also disposed to the right of the sheet conveyance path41. The printer1is therefore required to have a space where the aforesaid components are disposed to the right of the sheet conveyance path41. This may require the printer1to be large in size.

In this regard, the embodiment above is arranged so that the guides21extend beyond the boundaries of a sheet conveyance path41in both scanning directions, in such a way as to allow the carriage2to reciprocate in the scanning directions beyond the boundaries of the sheet conveyance path41. The printer1therefore has spaces to the right and left of the sheet conveyance path41.

In the variation1, the first cartridge attaching unit205is disposed in the space to the left of the sheet conveyance path41. It is therefore possible to downsize the printer1by, for example, as illustrated inFIG. 9, disposing the second cartridge attaching unit13in the space where the first cartridge attaching unit5is originally disposed and disposing the components such as the switching unit8, the pump9, and the storage tank10in the space where the second cartridge attaching unit13is originally disposed.

It is noted that a similar effect is achieved when the second cartridge attaching unit is disposed to the left of the sheet conveyance path41, instead of disposing the first cartridge attaching unit in the space to the left of the sheet conveyance path41. In this case, however, since the path that connects the storage tank10with the second cartridge attaching unit must be disposed to cross over the sheet conveyance path41, it is necessary to contemplate the arrangement of that path. Also in the case above, since the path connecting the storage tank10with the second cartridge attaching unit is long, it is necessary to set the pressure of the pump9to be high enough to convey ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit.

In the embodiment above, the second cartridge attaching unit13is connected to the downstream end of the ink discharge path and a used ink cartridge25is attached to the second cartridge attaching unit13. The invention, however, is not limited to this. For example, the second cartridge attaching unit13may be arranged to be connectable with not a used ink cartridge25but a dedicated cartridge. Alternatively, the present invention may be configured so that the second cartridge attaching unit13is not provided and a tank (second tank) which is detachable to the printer1is detachably attached directly to the downstream end of the ink discharge path.

In the embodiment above, the first valve11cuts off the storage tank10from the outside air and the second valve12cuts off the storage tank10from the second cartridge attaching unit13when the printer1is powered off. Alternatively, when the printer1is powered off, the first valve11and the second valve12may not be operated and is kept in the state before the power-off.

In the embodiment above, ink is conveyed from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13when an amount of ink in the storage tank10becomes equal to or larger than the reference storage amount. Alternatively, for example, ink may be periodically conveyed from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13irrespective of an amount of ink stored in the storage tank10.

In the embodiment above, an amount of ink conveyed from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13is adjusted in such a way that, after the conveyance of ink from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13is started and the ink cartridge25becomes no longer in the empty state, the pump9is further driven for a predetermined number of times, so that ink is conveyed from the storage tank10to the ink cartridge25. The present invention, however, is not limited to this. For example, an amount of ink conveyed from the storage tank10to the ink cartridge25attached to the second cartridge attaching unit13may be adjusted in such a way that a sensor or the like which detects an amount of ink in the storage tank10is provided in place of the liquid level sensor14which detects only whether an amount of ink in the storage tank10is not smaller than the reference storage amount, and an amount of ink conveyed from the storage tank10to the ink cartridge25is adjusted based on the amount of the ink in the storage tank10detected by the sensor.

In the explanation above, the present invention is used in a printer having an inkjet head which ejects ink onto a record sheet through nozzles. Alternatively, the present invention may be used in a liquid ejector which ejects a liquid other than ink.