Pressure retaining device, pressure retaining system, and ink jet printer

A pressure retaining device for retaining a pressure in a communication passage which are communicated between a supply tank for supplying a first fluid and a nozzle for ejecting the first fluid, comprises a compressing unit provided across an intermediate of the communication passage for compressing the first fluid transferred from the supply tank to the nozzle, and a pump for supplying to the compressing unit a second fluid on which a pressure is loaded thereby. In the construction above, the second fluid is supplied by the pump to the compressing unit to compress the first fluid in the compressing unit, and the first fluid in the nozzle is then compressed by a pressure loaded on the first fluid in the compressing unit.

CROSS-REFERENCE OF RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-350720 in Japan on Dec. 5, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present invention relates to a pressure retaining device, a pressure retaining system, and an ink jet printer.

A conventional maintenance (pressure retaining) mechanism comprises, for example as shown inFIG. 1, a printing head101having a set of nozzles arranged in rows, an ink cartridge102for storing ink to be supplied to the printing head101, an air pump103for pumping compressed air, and a charge tank104connected across an air passage between the ink cartridge102and the air pump103for temporarily storing the compressed air. The conventional maintenance mechanism further includes, for example, an open/close relief valve105connected across an air passage between the charge tank104and the air pump103and a compressing open/close valve106connected across an air passage between the ink cartridge102and the charge tank104, thus allowing the compressed air generated by the air pump103to be applied to the ink in the ink cartridge102for positive pressure purging and then exposure to the atmosphere after a predetermined length of time.

When employed in an ink jet recording apparatus, the conventional maintenance mechanism may be accompanied with a carriage which carries a printing head and a sub tank unit. The conventional maintenance mechanism also includes an ink cartridge connected by a supply tube to the printing head, an air pump for supplying the ink cartridge with compressed air, a pressure regulator, and a switching valve. When the storage of ink in the sub tank becomes smaller, the switching valve is turned on for communicating between the air pump and an ink bag in the ink cartridge. This permits the compressed air to be delivered from the air pump via the pressure regulator and the switching valve to the ink bag from which the ink is transferred to the printing head or the sub tank (See Japanese Patent Application Laid-Open No. 10-138506, Paragraphs 0030 to 0037 and FIGS. 3 and 4).

However, in the prior arts shown inFIG. 1and depicted in the Japanese Patent Application Laid-Open No. 10-138506, as the relief valve and the pressure regulator are connected between the (air) pressure pump and the ink tank (ink cartridge), they are actuated for controlling the compressed air delivered from the (air) pressure pump to the ink tank (ink cartridge). Accordingly, since its space for installing a large part such as the relief valve or the pressure regulator is essential, the ink jet printer will become large in the overall size and be increased in the production cost. Also, since the flow of the compressed air to be delivered to the ink cartridge is determined by the volume of the pressure regulator provided at the front side (the upstream side) of the ink cartridge, its pressure applied to the printing head will be varied depending on the remaining amount of the ink in the ink cartridge.

For controlling the compressed air with ease and less cost, a mechanism has been proposed where an orifice is provided in the air supply conduit extending from the air pump to the air chamber of the ink cartridge for discharging the compressed air generated by the air pump from the orifice to control the pressure and conduct the purging action (For example, see Japanese Patent Application Laid-Open No. 2004-58348, Paragraphs 0031 to 0035 and FIG. 6).

SUMMARY

As the ink in the ink cartridge is consumed, the air in the ink cartridge will increase. It is hence necessary for conducting the purging action consistently regardless of an increase in the air and holding the printing head at a stable, uniform level of the pressure to modify the charge of air to be supplied to the charge tank in response to the consumption of the ink in the ink cartridge. This may hardly be consulted by the prior art disclosed in the Japanese Patent Application Laid-Open No. 2004-58348.

When the ink cartridge is large in volume, its contained air will be varied significantly from the start to the end of the consumption of the ink. It is hence needed to increase the volume of the charge tank correspondingly. It is also needed for charging the charge tank with a large amount of air to have the air pump of a large sized, high pumping capacity type. As the result, the printer will be increased in the overall size.

It is hence an object to provided a pressure retaining device, a pressure retaining system, and an ink jet printer which are capable of decreasing the charging volume and keeping the purging discharge substantially uniform throughout the consumption of ink from the start to the end, whereby the overall size can be minimized. It is also another object to provide a pressure retaining device, a pressure retaining system, and an ink jet printer which are capable of conducting the purging action with the use of a desired level of the pressure regardless of the remaining amount of ink.

For achievement of the above object, there is provided a pressure retaining device according to an aspect for retaining a pressure in a communication passage which are communicated between a supply tank for supplying a first fluid and a nozzle for ejecting the first fluid, comprising:a compressing unit provided across an intermediate of the communication passage for compressing the first fluid transferred from the supply tank to the nozzle; anda pump for supplying to the compressing unit a second fluid on which a pressure is loaded thereby, whereinthe second fluid is supplied by the pump to the compressing unit to compress the first fluid in the compressing unit, andthe first fluid in the nozzle is then compressed by a pressure loaded on the first fluid in the compressing unit.

The compressing unit may be of either a type for directly compressing the first fluid (ink) in the compressing unit by the action of the second fluid or a type for compressing the ink with the use of an intermediate membrane such as a film.

As set forth above, the aspect allows the compressing units to be provided across the ink passages between the supply tanks (ink cartridges) and the nozzles (in the printing head) for distributing the ink from the ink cartridges to the printing head. Since the compressing units are supplied with the compressed air from the pump, their contained ink is compressed, thus exerting the pressure over the ink in the nozzles of the printing head. As the result, the charging size can be minimized while a switching mechanism such as a switching valve is not needed, hence advantageously encouraging the space saving. Also, the ink cartridges are not loaded with a back pressure and their purging action can be substantially uniform in the discharge throughout the service period from the start to the end.

DETAILED DESCRIPTION

An embodiment will be described referring the relevant drawings.

FIG. 2is a schematic structural view of an ink jet printer according to the embodiment.

As shown inFIG. 2, the ink jet printer5includes a printing head14equipped with a plurality of nozzles, an ink cartridge (supply tank)21for storing ink to be delivered to the printing head14, and a positive pressure recovering means23for applying a pressure to the ink in the nozzles of the printing head14in the direction of blow. The positive pressure recovering means23has a compressing unit24provided across an ink passage22between the ink cartridge21and the printing head14, thus allowing the ink to delivered from the ink cartridge21across the compressing unit24to the printing head14. The positive pressure recovering means23also includes, in addition to the compressing unit24, a air pump25(e.g., a tube pump) for acting as a pumping means to deliver compressed air to the pressuring unit24, a charge tank (reservoir)26for temporarily saving the compressed air received from the air pump25, a compressing solenoid valve (control valve, regulating valve)28for transferring the compressed air from the charge tank26to the compressing unit24, and an atmospheric exhaust solenoid valve (relief valve)32for discharging the compressed air in the charge tank26to the atmosphere. The charge tank26and the compressing solenoid valve28are connected in this order from the upstream between the air pump25and the compressing unit24. An air passage33across which the atmospheric exhaust solenoid valve32is provided is communicated to the air passage between the charge tank26and the compressing solenoid valve28. The atmospheric exhaust solenoid valve32may be connected directly to the charge tank26. A check valve29is connected between the ink cartridge21and the compressing unit24for inhibiting the ink from flowing back from the compressing unit24to the ink cartridge21. Accordingly, the transfer of pressure to the printing head during the positive pressure purging can be improved in the efficiency.

The positive pressure recovering means23is arranged for, during the positive pressure purging, shutting up the compressing solenoid valve28to temporarily save the compressed air in the charge tank26and then opening the compressing solenoid valve28to transfer the compressed air to the compressing unit24where the ink is compressed before released from the nozzles of the printing head14. The positive pressure recovering means23is arranged for, after the purging action, opening the atmospheric exhaust solenoid valve32to communicate the charge tank26by the air passage33to the atmosphere.

This allows the amount of the ink in the compressing unit24(sub tank) to remain uniform, hence minimizing a change in the air amount in the compressing unit24. As the result, the ink to be released from the nozzles of the printing head14can stay at a uniform level of the pressure.

Since the compressing unit24is reduced in the volumetric size, the volumetric size of the charge tank26and the dimensions of the air pump25can be minimized.

In addition, the ink cartridge21is, unlike that of the prior art, not loaded with a back pressure, and can thus be increased in the freedom of design. In other words, the ink cartridge will be not limited in the mass capacity.

The two solenoid valves28and32may be replaced by manually opening/closing valves.

The application of the ink jet printer to a multi-function copier (MFC)1which has a printer function, a copier function, a scanner function, and a facsimile function will now be described.

FIG. 3is a perspective view of the MFC where the ink jet printer of the embodiment is commonly installed andFIG. 4is a schematic structural view of the ink jet printer.

As shown inFIGS. 3 and 4, the MFC1includes a main housing2where a paper feeder3is mounted at the read end. The interior of the main housing2is largely separated into two, upper and lower, sections depending on the installed functions. An original reader4having the copier function and the facsimile function is mounted at the upper section of the main housing2. The ink jet printer denoted by5′ having the printer function is mounted at the lower section or lower half of the main housing2while a paper discharge tray6for receiving sheets of recording medium or paper P on which a record is printed and discharged is mounted at the front of the ink jet printer5′.

Although not specifically shown, the original reader4is mounted to the rear end for upward and downward pivotal movement about the horizontal axis. In action, when a cover4ais pulled upwardly for opening, the original table glass on which an original is placed is exposed under which an image scanner for reading the original is disposed.

The ink jet printer5′ has the head holder13movably mounted as a carriage on a pair of guide shafts11and12which extend in parallel to each other in the main housing2. The printing head14is downwardly mounted to the head holder13for releasing a jet of the ink from its nozzles towards a sheet of recording paper A. The head holder13(with the printing head14) is joined to an endless belt16which is driven by a motor15for circular traveling80that it can move forward and backward along the two guide shafts11and12for printing.

A wiper means17for wiping out the openings of the nozzles with its wiper member and a flushing tank (waste tank)18for receiving and saving the remaining of the ink subjected to the purging and the flushing are disposed at one end of the stroke of the forward and backward movement. At the other end, a storage cap means19is provided for protecting the nozzles of the printing head14with its storage cap in a non-printing state.

In the ink jet printer5′, four ink cartridges21M,21C,21B, and21Y for storing magenta color ink, cyan color ink, black color ink, and yellow color ink respectively to be supplied to the printing head14are installed at this side of the center. The four ink cartridges21M,21C,21B, and21Y can be exposed and replaced with new ones, as necessary, through upwardly pivoting the original reader4to open the main housing2.

The four ink cartridges21M,21C,21B, and21Y are communicated by four ink passages22M,22C,22B, and22Y respectively to a tube joint13A in the head holder13for supplying the printing head14with their respective colors of the ink. Also, the four ink cartridges21M,21C,21B, and21Y are communicated with a positive pressure recovering means23′ for exerting a positive pressure in the direction of jetting on the ink in the nozzles of the printing head14.

The positive pressure recovering means23′ is similar to the positive pressure recovering means23described previously. The positive pressure recovering means23′ comprises four compressing units24M,24C,24B, and24Y which are connected across their respective ink passages22M,22C,22B, and22Y between the ink cartridges (supply tanks)21M,21C,21B, and21Y and the printing head14(at the tube joint13A) and an air pump25(the pumping means) for delivering the compressed air to the compressing units24M,24C,24B, and24Y. The pressuring units24M,24C,24B, and24Y serve as portions of the ink passages for conveying their respective colors of the ink from the four ink cartridges21M,21C,21B, and21Y to the printing head14. The compressed air produced by the action of the air pump25is exerted on the ink of the different colors in their respective compressing units24M,24C,24B, and24Y as well as the ink of the different colors in the nozzles of the printing head14. A charge tank (reservoir)26for reserving the compressed air is connected commonly with the four compressing units24M,24C,24B, and24Y.

The four compressing units24M,24C,24B, and24Y include their respective sub tanks where the ink is present simultaneously with the compressed air. The sub tank is separated into an air chamber and an ink chamber. More particularly, the sub tank24Maof the pressuring unit24M, for example as shown inFIG. 5, is separated by a flexible film (flexible member)24Mbinto an air chamber24Mcfor receiving the compressed air and an ink chamber24Mdthrough which the color ink is conveyed from the ink cartridge (supply tank)21M to the printing head14(with the nozzles). In other words, the flexible film (flexible member)24Mbacts as a partition between the air chamber24Mcand the ink chamber24Md. The sub tank24Mahas a second tank member24Mabwith an ink passage fitted into a first tank member24Maawhich provides a region of the air chamber24c. The flexible film24Mbis water-tightly bonded at the circumferential edge to the second tank member24Mab. The air chamber24Mcis defined between the two tank members24Maaand24Mabwhich are joined tightly to each other. The flexible film24Mbacts as a wall of the air chamber24Mc. The first tank member24Maahas a port P11provided therein for communicating with the air passage27M to supply the compressed air. The second tank member24Mabhas two ports P12and P13provided therein for delivering the ink to the printing head14. The sub tank24Mapermits the compressed air and the ink to be present simultaneously as separated by the flexible film24Mb. Each of the four compressing units24M,24C,24B, and24Y is arranged where the air chamber is located lower along the direction of gravity than the ink chamber, whereby the flexible film24Mbcan downwardly be biased when at least some of the ink remains in the ink chamber.

The compressed air received from the air pump25is temporarily saved in the common charge tank (reservoir)26before distributed to the compressing units24M,24C,24B, and24Y respectively. Four compressing solenoid valves28M,28C,28B, and28Y for being opened at the positive pressure purging action are provided across their respective air passages27M,27C,27B, and27Y between the charge tank26and the compressing units24M,24C,24B, and24Y. The opening of the valves28M,28C,28B, and28Y allow the compressing units24M,24C,24B, and24Y to receive the compressed air. At the time, flexible film24Mbseparating between the air chamber and the ink chamber is biased upwardly to deliver the color ink in the ink chamber to the printing head14. As the air passages27M,27C,27B, and27Y are branched from the air output line27at the downstream of the common charge tank26. The air output line27is also communicated with an air passage33across which an atmospheric exhaust solenoid valve32. Four check valves29M,29C,29B, and29Y are disposed across their respective ink passages22M,22C,223, and22Y between the compressing units24M,24C,24B, and24Y and the ink cartridges21M,21C,21B, and21Y respectively for prohibiting the corresponding colors of the ink from running back from the compressing units24M,24C,24B, and24Y to the ink cartridges21M,21C,21B, and21Y.

For controlling the action of the air pump25, the atmospheric exhaust solenoid valve32, and the compressing solenoid valves28M,28C,28B, and28Y, a recovery controlling means (controller)31is provided which may preferably be a microcomputer. The recovery controlling means31shuts up the atmospheric exhaust solenoid valve32and the compressing solenoid valves28M,28C,28B, and28Y for the positive pressure recovering action and then the air pump25starts rotating to increase the pressure of air and supply the charge tank (reservoir)26and the air passages with the compressed air. In this embodiment, the air pump25remains driven until the pressure increases up to a predetermined level. This is followed by opening one or more the compressing solenoid valves28M,28C,28B, and28Y for a desired length of time in order to exert the pressure on their corresponding colors of the ink in the nozzles of the printing head14. The discharge of the compressed air from the charge tank26depends on the arrangement of the air chamber of each compressing unit and its upstream passage. Accordingly, the pressure to be exerted can remain uniform regardless of the remaining amounts of the ink in the ink cartridges21M,21C,21B, and21Y.

When the desired length of time has elapsed, the atmospheric exhaust solenoid valve (relief valve)32is opened and the compressed air in the charge tank (reservoir)26is discharged under the controlling action. The purging action over the nozzle for a selected color ink is then followed by the flushing action in which all the compressing solenoid valves28M,28C,28B, and28Y remain opened.

As the result, the pressure in the charge tank26is increased to a predetermined level. Then, the compressed air from the charge tank26is exerted on the ink of the different colors in the nozzles of the printing head14for conducting the positive pressure purging action.

Next, the controlling action of the recovery controlling means (controller)31will be described referring toFIG. 6.

For example, when the action of printing down has been completed; a command for starting the purging action is received as programmed. In response, the printing head14on the head holder13is moved to its purging position which faces the flushing tank18(Step S1). The compressing solenoid valves (control valves, regulating valves)28M,28C,28B, and28Y and the atmospheric exhaust solenoid valve (relief valve)32is shifted from the opening position to the closing position or remain closed (Step S2). This is followed by starting the air pump25(Step S3). Then, the charge tank26is filled with the compressed air.

The pressure is gradually increased and reaches at its predetermined level in the charge tank26(Step S4) and the action of the air pump25is canceled (Step S5). As the air pump25is deactivated, the compressing solenoid valves (regulating valves)28M,28C,28B, and28Y are opened (Step S6). This allows the compressing units24,24C,24B, and24Y to be loaded with the compressed air, hence exerting a back pressure over the ink of the different colors in the ink cartridges21M,21C,21B, and21Y and exhausting the flushing tank18through the positive pressure purging action. When the positive pressure purging action is intended to a selected color of the ink in the nozzle, the compressing solenoid valve corresponding to the nozzle for the ink only is opened. When the positive pressure purging action is intended to all the colors of the ink in the nozzles, all the four compressing solenoid valves28M,28C,28B, and28Y are opened up.

As a predetermined length of time Tsec has elapsed (Step S7), the atmospheric exhaust solenoid valve (relief valve)32is opened (Step S8), the wiper member of the wiper means17is lifted up (Step S9), and its wiping action is carried out as the printing head14moves (Step S10). The paragraph “as the predetermined length of time Tsec has elapsed” may be replaced by “when the action of the air pump25has conducted a predetermined number of revolutions”. When the positive pressure purging action is intended to the selected color of the ink in the nozzle, not corresponding ones of the compressing solenoid valves remain closed. However, the pressure in the charge tank26returns back to the atmospheric level during the wiping action.

After the wiping action for the nozzle of the selected color ink subjected to the positive pressure purging action, the not corresponding ones of the compressing solenoid valves are opened. After the wiping action for all the nozzles of the colors of the ink, the procedure simply advances to the succeeding step. The printing head14is moved again to the purging position and the flushing action is carried out for preventing no mixture of the different colors of the ink (Step S11). This is followed by the printing head14moving to the standby position (neutral position) which faces the storage cap means19(Step S12) and being covered with the storage caps of the storage cap means19(Step S13) before the procedure is ended.

The foregoing arrangement may be modified as follows.

(i) While the ink cartridges21M,21C,21B, and21Y are communicated to the common charge tank26in the above embodiment, they may be accompanied with their respective charge tanks on the one-by-one basis. In the latter case, since the ink cartridges21M,21C,21B, and21Y are connected to the four is corresponding charge tank, the storage size of each charge tank is hence equal to ¼ the size of the common charge tank26. Accordingly, the air passages27can be simplified in the construction for communication thus contributing to the improvement of the space saving and minimizing the number of the relevant components.

(ii) While the recovery controlling means (controller) in the embodiment is arranged to exert a uniform level of the pressure (so-called charging pressure) on the ink in the nozzles of the printing head, it may drive the positive pressure recovering means to, in response to a degree of printing error (fault in the delivery of the ink), modify the pressure (so-called charging pressure) to be exerted on the ink in the nozzles of the printing head to a higher level when the degree of printing error is crucial than when the degree of printing error is not crucial throughout the duration of time A from the opening of the compressing solenoid valves to the end of the period Tsec. If the charging pressure remains uniform but not modified, the printing head remains consistent under the pressure regardless of the degree of printing error (crucial or not) and may thus increase the consumption of the ink in vain.

The degree of printing error (fault in the delivery of the ink) may be examined by a user judging and entering the result of the judgment (crucial or not) with a manual switch or by an imaging means such as a CCD camera shooting the sheet of recording paper and subjecting its image output signal to a known image processing action.

In practice, the recovery controlling means (controller) can modify the pressure through varying the compressed air saved in the charge tank, changing the length of the air passage, or adjusting the supply of air to be received by the compressing units24M,24C,24B, and24Y with the action of the pump25.

(iii) The sub tank may be adjusted to a desired storage size depending on the resistance in the air passages connected thereto. More particularly, when the resistance in the air passages is high, the storage size of the sub tank is reduced thus to hasten the increase of the air pressure. Alternatively, when the resistance in the air passages is low, the storage size of the sub tank is increased thus to retard the increase of the air pressure. Also, the sub tanks for all the colors of the ink may be set substantially equal in the internal pressure. In other words, the ink chamber and the air chamber in each sub tank are determined in the storage size depending on the resistance in the ink passage connected to the compressing unit.

(iv) While all the compressing solenoid valves31M,31C,31B, and31Y are opened with the nozzles for all the colors of the ink to be subjected to the purging action in the embodiment, they may be opened one by one in a sequence for subjecting the nozzles for each color of the ink to the positive pressure purging action or conducting the positive pressure purging action over the nozzles for all the colors of the ink.

(v) While the embodiment is applied as an ink jet printer in a multi-function copier (MFC), it may be utilized in any common ink jet printer where the recovery controlling means is provided in the form of an external recovery controlling means in a personal computer.

According to the embodiment, the compressing units are provided across the ink passage between the ink cartridge and the printing head in the embodiment for conveying the ink from the ink cartridge to the printing head, loaded with the compressed air produced by the pumping means, and actuated for compressing the ink in the compressing units and thus supplying the nozzles of the printing head with the compressed ink by the compressing units. It is therefore unnecessary to increase the internal size of the compressing units, thus minimizing the charging size. More specifically, the recovery for delivery can be improved, the consumption of the ink can be decreased, and the time required for the purging action can be shortened. Also, since a switching mechanism such as a switching valve is not needed, the embodiment can be advantageous in the space saving.

In addition, the embodiment permits each compressing unit across the ink passage between the ink cartridge and the printing head to be loaded with a pressure, unlike the prior art where a back pressure is applied to the ink cartridge. Accordingly, the pressure to be applied remains almost uniform regardless of the remaining amount of the ink in the ink cartridge, hence ensuring the purging action with substantially a uniform discharge throughout the start to the end of the consumption in the ink cartridge. In particular, since the compressing units are low in the change of the air volume, variations of the discharge in the purging action can advantageously be suppressed.

According to the embodiment, the return of the ink from the compressing units to the ink cartridges is inhibited by the action of the check valves, thus allowing the force of pressure exerted on the ink in the compressing units by the compressed air from the pumping means to be not received by the ink cartridges. As the result, the transfer of the pressure to the printing head will be improved in the efficiency.

According to the embodiment, the force of pressure introduced to the air chamber by the compressed air is transferred to the ink in the ink chamber by the biasing action of the flexible film before exerted on the ink in the nozzles of the printing head. In particular, since the ink chamber is isolated by the flexible film, no ink leakage from the ink chamber will be permitted.

According to the embodiment, the positive pressure purging action, the wiping action, and the flushing action are conducted at one end of the stroke of the forward and backward movement of the printing head during the purging action. When the printing action has been ceased, the printing head is held at the other end of the stroke of its forward and backward movement and its nozzles are protected with the storage cap.

According to the embodiment, the positive pressure recovering action can be carried out through controlling the compressing solenoid valves and the atmospheric exhaust solenoid valve with no use of a switching mechanism such as a switching valve.

According to the embodiment, the compressing units are provided for their respective ink cartridges and the printing head and loaded with a pressure for exerting the pressure on the ink in the nozzles of the printing head separately, allowing the common charge tank to remain not increased in the storage size.

According to the embodiment, the pressure in the charge tank can be increased to a desired level within a given period of time regardless of the resistance in the ink passages connected to the charge tank.

According to the embodiment, the positive pressure recovering action can be conducted depending on the degree of printing error, thus permitting no unwanted, wasteful consumption of the ink.

According to the embodiment, the compressed air to be supplied to the compressing units can be modified thus to conduct the positive pressure recovering action at optimum simply and easily depending on the degree of printing error.

According to the embodiment, the recovery controlling means may be implemented by a built-in microcomputer or an external device in a personal computer. This allows the ink jet printer to employ no recovery controlling means.