EP1070592A1

EP1070592A1 - Ink jet printer and method for operating the same

Info

Publication number: EP1070592A1
Application number: EP00115461A
Authority: EP
Inventors: Koyama Sadami; Kaga Ichiki; Haruyama Mikita
Original assignee: Mutoh Industries Ltd
Current assignee: Mutoh Industries Ltd
Priority date: 1999-07-23
Filing date: 2000-07-18
Publication date: 2001-01-24
Also published as: KR20010015416A

Abstract

An ink jet printer and a method for operating the same are proposed. In order to improve the cleaning of an ink passage inside a recording head, a cleaning liquid are alternately supplied to the recording head through an electromagnetic valve. <IMAGE>

Description

The present invention relates to an ink jet printer or plotter according to the preamble of claim 1 and to a method according to the preamble of claim 6.

In ink jet printers, in case of cleaning the inside of a recording head and the inside of a tube connected to the head, a process employed is to apply liquid under pressure to the tube and to discharge the cleaning liquid at a discharge outlet of a purge box from an ink discharge hole of a nozzle of the recording head through the inside of the recording head.

When the cleaning liquid flows inside of the tube, as shown in Fig. 8(A), the flow velocity of the cleaning liquid is fast in a central portion of the tube 4 while the velocity is slow in a portion closer to an inner wall surface of the tube 4. For this reason, a significant amount of ink 6 remains on the inner wall surface of the tube 4. As shown in Fig. 8(B), the amount of remaining ink 6 increases even though the cleaning liquid 8 is made to flow, and the ink passage at the inside of the tube 4 or the recording head is blocked, and such a phenomenon has been a problem.

Furthermore, when the ink passage at the inside of the recording head is cleaned with cleaning liquid, a liquid droplet mixed with the ink adheres to the lower surface of the recording head to which the nozzle opens, the droplet splashes to stain the periphery of the purge box, and such a phenomenon has been a problem.

Particularly, when a color print plotting is carried out with a recording head of four colors of KCMY (black K, cyan C, magenta M, yellow Y or data for printing according to Euro scale), the liquid droplet splashing from the recording head adheres to a cap for covering a nozzle that is provided on the purge box. When ink of an other color adheres to this cap, the color of the ink discharging from the nozzle discolors at the time of plotting, and the picture quality of the color print plotting is deteriorated, and such a phenomenon has been a problem.

Object of the present invention is to solve or minimize the foregoing problems and to provide an ink jet printer and a method for operating an ink jet printer, in particular with improved printing quality and/or with improved cleaning features.

The above object is achieved by an ink jet printer according to claim 1 or a method according to claim 6. Preferred embodiments are subject of the sub-claims.

The present invention is to perform effectively the cleaning of the ink passage of the inside of the recording head and of the ink passage communicating with the recording head, and to keep clear of the ink on the tube wall of the ink passage after the cleaning.

The recording head is connected to an electromagnetic valve through the tube, and air, ink and cleaning liquid are selectively supplied to the tube through the electromagnetic valve. At the plotting time by the recording head, the recording head discharges a rich supply of ink droplets from the nozzle in a range of the plotting to a plotting medium in a controllable manner whereby the plotting is applied to the plotting or printing medium. At the cleaning time of the inside of the recording head, the air and the cleaning liquid are alternately fed under pressure to the recording head through the electromagnetic valve, and the ink remaining in the tube and the recording head is discharged from the nozzle of the recording head at a discharge outlet along with the air and the cleaning liquid.

Further aspects, features and advantages of the present invention will be explained with reference to the enclosed drawing of preferred embodiments. It shows:

Fig. 1: an explanatory drawing of the present invention;
Fig. 2: a flow chart for explanation of an operation of the present invention;
Fig. 3: a general view of an ink jet printer;
Fig. 4: a piping explanatory drawing showing an ink supply system of the ink jet printer;
Fig. 5: a flow chart showing an another embodiment of the cleaning operation of the recording head of the ink jet printer;
Fig. 6: an operation explanatory drawing of another embodiment of the present invention;
Fig. 7: an operation explanatory thawing of the other embodiment of the present invention; and
Fig. 8: an explanatory thawing of the conventional technology.

In Fig. 3, reference numeral 22 denotes legs (illustration of the other is omitted) disposed at right and left of a base plate 26 of an ink jet printer 24, and the base plate 26 is fixed to upper ends of the legs. The legs 22 and the base plate 26 constitute a structure of the ink jet printer 24.

On the upper part of the legs 22 an axial holder 28 is fixed, and an axial portion of a rolled paper holder 32 is rotatably and detachably journalled on the axial holder 28.

A roll portion 30a of a plotting medium 30 wound in a roll type is detachably retained on the paper holder 32.

A platen 34 (paper guide plate) is fixed to the base plate 26, and a guide roller 36 having a width and a length almost same with those of the plotting medium 30 that extends in a Y-axis direction is disposed in the vicinity of an upper flow end of the platen 34. The guide roller 36 is disposed in the upper part of the roll portion 30a of the rolled paper 30, and both ends of the guide roller 36 are rotatably journalled on the base plate 26 by means of a bracket. Reference numeral 38 denotes a Y axis rail, and is disposed horizontally in the upper part of the platen 34, and both ends are journalled on the base plate 26 by means of the bracket.

A Y cursor 40 (carriage) is shiftably mounted on the Y axis rail 38, and the carriage 40 is connected to a Y axis drive device (not shown in the drawing) disposed on the base plate 26 by means of a steel belt 42 spanned endlessly between pulleys or the like. A slit is formed on the platen 34 along the Y axis direction, and a drive roller 44 is disposed on the slit.

Both ends of the drive roller 44 are rotatably journalled on the base plate 26 by means of the bracket, and the drive roller 44 is connected to an X axis drive device (illustration is omitted) that is disposed on the base plate 26. A pinch roller shaft 46 is liftably mounted on the Y axis rail 38 by means of a resilient mechanism (illustration is omitted), and pinch rollers are rotatably fitted on the pinch roller shaft 46. The pinch roller shaft 46 is constructed so that it can be set on an either condition, a condition where it is separated from the surface of the drive roller 44 and a condition where it is in resilient state in horizontal to the surface.

A head base 50 is fixed to one side of the carriage 40 and from ink jet recording heads 52 with four nozzles for four colors are mounted on the head base 50. The bottom surface disposed on mutually identical planes of four rows of the recording heads 52 is formed in an elongate rectangular shape, and the nozzles are disposed on the bottom surface to be slightly projected therefrom which have a plurality of ink discharge holes in a row.

Each of the recording heads 52 of the four rows is disposed in parallel horizontally and mutually at a predetermined interval, and each of the bottom surfaces 52b is arranged with an angle alpha to an X axis forming a right angle to the Y axis rail 38. On the other side of the carriage 40, sub-tanks 54 for solvent ink of four colors (black K, cyanogen C, magenta M, and yellow Y) whose number is identical with the number of the recording heads 52 are mounted, and three-way electromagnetic valves 56 are respectively mounted on upper covers of the sub-tanks 54.

On each sub-tank 54, a sensor for detection of the level of the ink is provided. The insides of the ink supply passages, namely tubes 53 between the recording heads 52 and the corresponding sub-tanks 54 are maintained at negative pressure, in that the liquid upper surface of the sub-tanks 54 is disposed lower than the ink discharge outlet of the corresponding recording head 52.

Reference numeral 58 denotes a main tank case disposed on the base plate 26, and main tanks 60 (illustration of three pieces are omitted) for four color solvent inks whose number is identical with the number of sub-tanks 54, and for a cleaning liquid tank 62 are detachably housed in the main tank case 58. Each

tank

60 and 62 is supported by a spring, and is constructed in such way that the remaining quantities of the ink and the cleaning liquid are detected by

sensors

136 and 138 consisting of limit switches disposed under each

tank

60 and 62.

The main tanks 60 and the sub-tanks 54 are communicated by tube cables by means of the electromagnetic valve.

Reference numeral 64 denotes a control box mounted on the base plate 26 and is built in with a pump 66 and

electromagnetic valves

68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 101, and furthermore, an electronic control circuit unit for controlling these electronic equipments is provided. Also, on the base plate 26 of the printer 24, a controller (illustration is omitted) is provided for controlling the X and Y axis drive devices and the recording head 52 and the like.

Reference numeral 2 denotes a wiping device for cleaning the nozzle peripheral portions of the bottom surfaces of the recording heads 52 and the discharge outlets of the nozzles, and a rubber made wiper is arranged to be reciprocally operated in an X axial direction by a wiper motor 102 (refer to Fig. 4). The wiper is formed with a V-groove, and when the nozzle at the lower surface of a recording head 52 is positioned in the V groove, it is possible to wipe the lower surface of the periphery of the nozzle of the recording head 52 excluding the nozzle by the wiper, and when the recording head is shifted to slide the V groove from the nozzle, the nozzle can be wiped by the wiper.

Reference numeral 106 denotes a purge box having rubber caps 108 and a liquid discharge outlet 110 for covering the discharge outlets of a nozzles of the recording heads 52 alternately. The purge box 106 is disposed at the side of the base plate which is the outside of the plotting range and also, in the transfer range of the recording heads 52. It can be lifted by a motor 112 (refer to Fig. 4). The rubber caps 108 have an opening for receiving a liquid such as ink and the like.

Each cap 108 and the discharge outlet 110 of the purge box 106 are connected to a collection pipe 120 fixed to the base plate 26 by means of the tube and the electromagnetic valve.

Reference numeral 114 denotes a motor for stirring the ink in the

main tanks

60, and 116 denotes a waste liquid tank case mounted on the

leg

22, and 118 denotes a waste liquid tank.

The waste liquid tank 118 is supported by a spring housed in the case 116, and is constructed in such a way that the quantity of the waste liquid is detected by a sensor 134 (refer to Fig. 4) consisting of limit switches disposed between the bottom surface of the tank 118 and the upper surface of the case 116.

At the bottom portion of each main tank 60, a rotor made of magnetic material is rotatably journalled, and when a magnet (illustration is omitted) rotates by the drive of the motor 114, the rotor in the main tank rotates, and the ink in each main tank 60 is arranged to stir.

Each component part and the device are connected by piping with tube as shown in FIG. 4. The recording heads 52 can be shifted to a position immediately above the purge box 106 which is off the plotting range by the transfer of the carriage 40 along the Y axis rail 38.

The operation of the preferred embodiment of the present invention will be described in the following.

In order to set the plotting medium 30 such as paper on the platen 34, the pinch rollers are lifted and the plotting medium 30 is drawn from the roll portion 30a and inserted between the drive roller 44 and the pinch rollers through a guide roller 36, and thereafter, the pinch rollers 48 are descented and made to resiliently contact the drive roller 44 from the upper part of the plotting medium 30.

By the foregoing arrangement, a setting of the plotting medium 30 is completed. When the setting of the plotting medium is completed and the printer enters the plotting mode, the controller performs an ink filling operation, and thereafter, shifts to the plotting operation. When the plotting or printing starts, a feed portion of the plotting medium 30 is carried in the X axis direction, namely, the arrow direction C over the platen 34 by the intermittent rotation of one direction of the drive roller 44.

Furthermore, a piezo element (nozzle drive actuator) of the respective recording head 52 or the like is operated on the basis of an image information by the control of the controller, and the ink is discharged from the nozzle, and the plotting medium 30 is scanned along the Y axis by a reciprocating transfer of the carriage 40 along the Y axis rail 38, and the image information developed in a memory of the controller is visualized on the plotting medium 30.

When the piezo element of the recording head 52 or the like discharges ink, the piezo element operates so that the ink is automatically absorbed or sucked from the sub-tank 54 which corresponds to the quantity of the discharged ink. In this case, unless the sub-tank 54 is not set at the negative pressure, the recording head 52 absorbs or receives ink excessively to result in the overflow of the ink. In order to set the sub-tank 52 at a negative pressure, in this embodiment, the level of the bottom surface of the sub-tank 54 is set at a lower part against the ink discharge outlet of the recording head 52.

When the plotting operation is completed, the controller judges if there is ink in the sub-tanks 54 by the signal of the sensor, and if it is judged that ink is missing, the controller moves to the ink makeup operation. After the makeup of the ink, or in case it is judged that no ink is missing, it is judged if a predetermined time has elapsed or not, and in case it is judged affirmative, the controller shifts to the cleaning operation. After the cleaning or the predetermined time has not elapsed after the plotting, it judges if the plotting is completed or a predetermined time has elapsed in the standby condition, and when it is judged negative, it returns to the plotting operation.

Furthermore, in case it is judged affirmative, it sequentially shifts to an ink recovery operation and head cleaning operation.

The head cleaning operation will be described in the following by referring to the flow chart of Fig. 2.

In the first place, the controller judges if there is the remaining quantity or not in the cleaning liquid tank 62 on the basis of the signal of the respective sensor 138, and in case the remaining quantity is none, the display unit shows no remaining quantity in the cleaning liquid tank 62 and performs a processing of error.

In case it is judged as there is a remaining quantity, a recording head 52 shifts to a position immediately above the discharge outlet 110 of the purge box 106. Next, pump

electromagnetic valves

68, 70 are changed over in the pressure feeding direction.

Next, in the head cleaning operation, in order to effect an instant pressure feeding of the cleaning liquid, the cleaning liquid tank 62 is applied with air pressure (step 1) for 60 seconds. This pressure application operation causes the changeover of the

electromagnetic valves

72, 74, 76 between the pump and the main tank in the direction of the cleaning liquid tank and drives the pump 66 and feeds air into the cleaning liquid tank 62.

Next, the controller changes over the head air

electromagnetic valves

74, 88 in the air feeding direction, and changes over the head electromagnetic valve 56 in the air feeding direction to drive the pump 66 and applies the pressure feeding of air into the recording head 52 for 20 seconds. By this operation, the ink is forced out by the air supplied from the three-way electromagnetic valve 56 to the recording head 52 and is discarded to the outlet 110 from the nozzle. Next, the controller changes over the

electromagnetic valves

74, 76 in the direction of the cleaning liquid tank, and changes over the cleaning liquid tank

electromagnetic valves

78, 88 and the head electromagnetic valve 56 in the direction of the cleaning liquid tank to drive the pump 66 and applies the pressure feeding of the cleaning liquid to the recording head 52 for 20 seconds to clean the inside of the recording head 52 with the cleaning liquid (step 3).

Next, the controller applies the pressure feeding of air to the recording head 52 for 30 seconds, and as shown in Fig. 1, the amount 10 of the cleaning liquid in the tube 53 between the nozzle of the three-way electromagnetic valve 56 and the recording head 52 and the filter and the recording head 52 is pushed out with the amount 12 of air. Next, the controller causes the recording head 52 to shift to a position immediately above the wiping device 2 and performs the wiping of the bottom portion of the recording head 52 namely, performing the wiping operation (step 5). Next, the controller applies the pressure feeding of the cleaning liquid to the recording head 52 for 20 seconds and fills the inside of the recording head 52 again with air (step 6).

The foregoing operations are carried out for each of the recording heads 52 by the controller. Preferably, the recording heads 52 are cleaned subsequently one after the other. However, it is also possible to clean all heads 52 at the same time.

Next, the controller recovers (step 7) the liquid accumulated in a collecting pipe 120 by setting a waste liquid tank 118 in the negative pressure for 5 seconds. Next, the controller releases the cleaning liquid tank 62 to the atmosphere, and cancels the application of the pressure to the cleaning liquid tank 62.

In the foregoing embodiment, as shown in Fig. 1, when the mass 12 of the air and the mass 10 of the cleaning liquid are fed to the ink passage alternately between the threeway electromagnetic valve 56 and the recording head 52, the mass 10 of the cleaning liquid flows at a high velocity in the portion closer to the pipe wall of the ink passage, and the remaining ink at the pipe wall of the ink passage is effectively washed out by the cleaning liquid.

In the foregoing embodiment, the pressure feeding of air and cleaning liquid is alternately repeated twice preferably at an interval of 20 seconds or 30 seconds. If the pressure feeding of air and cleaning liquid is repeated for example 10 times alternately preferably at intervals of 5 seconds, the remaining ink in the ink passage between the three-way electromagnetic valves 56 and the recording heads 52 can be discharged, even more effectively.

Another embodiment of the head cleaning operation will be described in the following by referring to the flow chart of Fig. 5.

Firstly, the controller of the printer judges (step 1) on the basis of the signal of the sensor 138 as to whether there is any remaining quantity in the cleaning liquid tank 62 or not, and in case that the remaining quantity is nill or not enough, performs a processing for error (step 3) by displaying (step 2) the remaining quantity being none in the cleaning liquid tank on a display unit (illustration is omitted) of the operation panel of the printer.

In case that there is any (or enough) remaining quantity, pressure is applied to the cleaning liquid tank 62 (step 4) by feeding air to the cleaning liquid tank 62, and pressure is applied (step 5) to the inside of the cleaning liquid tank 62 at a high level. The operation of the pressure application changes over the

electromagnetic valves

72, 74, 76 between the pump and the main tank in the condition where the electromagnetic valve 78 is closed in the direction of the cleaning liquid tank, and drives the pump 66 and feeds air into the cleaning liquid tank 62. Next, the controller shifts (step 6) the respective recording head 52 as shown in Fig. 6 to a position immediately above the discharge outlet 110 of the purge box 106, namely, the purge position. For reference, Fig. 6 illustrates only one of the recording heads 52 among the four recording heads 52 for convenience of description, and displays a part of the purge box 106.

Next, the controller opens the electromagnetic valve 78 and changes over the electromagnetic valve 88 and the electromagnetic valve 56 of the recording head 52 of the first row which is the subject in the direction of the cleaning liquid tank, and performs the pressure feeding (step 7) of cleaning liquid at a high pressure for about 5 seconds to the nozzle of the recording head 52 and the corresponding tube 53 which are the subjects while driving the nozzle drive actuator (piezo element) of the recording head 52 at high speed with a frequency of preferably about 1 kHz. Next, the controller closes the electromagnetic valve 78 and changes over the head air

electromagnetic valves

74, 88 in the direction of the air feeding, and changes over the electromagnetic valve 56 of the recording head 52 that is the subject in the direction of the air feeding and applies the pressure feeding (step 8) of air at high pressure for about 10 seconds to the nozzle of the recording head 52 and the corresponding tube 53 which are the subjects while driving the nozzle drive actuator of the recording head 52 at a high speed with a frequency of preferably about 1 kHz.

The remaining ink in the pipe wall of the ink passage between the inside of the recording head 52 and the tube 53 is peeled off and is pushed out in the ink passage and is discharged from the nozzle by the alternate pressure feeding operation of the high pressure cleaning liquid feeding and the high pressure air feeding.

Next, the controller judges (step 9) whether or not the alternate pressure feeding operation of the high pressure cleaning liquid feeding and the high pressure air feeding to the subject recording head 52 is carried out by a predetermined number of times (in this embodiment, once) and in case if the operation is not carried out by the predetermined number of times, it returns to the step 7, and if the operation is carried out by the predetermined number of times, it positions (step 10) the subject recording head 52 to a position immediately above the cap 108 of the purge box 106 namely the capping position.

Next, the controller performs the pressure feeding of air for about 10 seconds to the subject recording head 52 and executes (step 11) the cleaning of the cap portion by blowing the air from the nozzle of the recording head 52. Next, the controller returns (step 12) the subject recording head 52 to the purge position. Next, the controller performs the alternate pressure feeding operation of the high pressure feeding (step 13) of the cleaning liquid for about 5 seconds while driving at high speed the nozzle drive actuator of the recording head with a frequency of preferably about 1 kHz and thereafter, of the air high pressure feeding (step 14) for about 10 seconds. The remaining ink in the subject recording head 52 and the tube 53 is pushed to flow by the pressure feeding operation.

Next, the controller judges (step 15) whether or not the alternate pressure feeding operation of the high pressure cleaning liquid feeding and the high pressure air feeding to the subject recording head 52 is carried out by the predetermined number of times (in this embodiment, once) and when it is judged negative, it returns to the step 13, and if it is judged affirmative, the operations of the step 13 and the step 14 to the subject recording head 52 are completed. The operations of the steps 13, 14, 15 for each of the four pieces of the recording head 52 are carried out, and when the high pressure feeding operation of the steps 13, 14, 15 to all the recording heads 52 is completed, the controller sets the waste liquid tank 118 at negative pressure and recovers (step 16) the waste liquid such as the cleaning liquid accumulated in the collecting pipe 120 in the waste liquid tank 118.

Next, the controller performs (step 17) the pressure feeding of the air of high pressure to the subject one recording head 52 or about 40 seconds, and then, shifts the recording head 52 to the capping position, and returns (step 18) the recording head 52 to the purge position. This operation is executed for each of the four recording heads 52 of KMCY. When the air is discharged from the nozzle of a recording head 52, the liquid droplet adhered to the lower surface of the recording head 52 is dried and the liquid droplet is decreased, and the periphery of the discharge outlet 110 is cleaned.

Thereafter, the recording head 52 shifts from the purge position to the capping position and returns to the purge position instantly whereby the liquid droplet mixed with the ink that remains on the lower surface of the recording head is thrown off by the inertia of the recording head 52, and this liquid droplet drops to the liquid discharge outlet 110 of the purge box 106 or the receiving opening of the cap 108 and is stored in the collecting pipe 120.

Next, the controller judges (step 19) whether or not the liquid droplet shaking operation is carried out by the predetermined number of times (in this embodiment, twice) for each of the four pieces of the recording head 52, and when it is judged negative, it returns to the step 17 and when it is judged affirmative, the controller turns the vacuum device (illustration is omitted) for generating the suction power on the platen 34 ON, and causes the paper to adhere (step 20) to the platen 34.

Next, the controller shifts (step 21) the recording head 52 to a position immediately above the wiping device 2 namely, the wiping position.

Next, the controller performs the pressure feeding of the air to the subject recording head 52 and drives the wiper motor 102 while blowing the air from the nozzle of the recording head 52, and shifts the rubber made wiper in one direction of one-way, and wipes (step 22) the nozzle portion of the subject recording head 52 with the wiper. Next, the controller suspends the air pressure feeding to the subject recording head 52. Next, the controller slides the recording head 52 slightly to the wiper and reciprocates the wiper to the subject recording head 52 by the drive of the motor 102, and performs the wiping (step 23) of the peripheral portion of the nozzle excluding the nozzle of the subject recording head 52 with the wiper.

The controller performs the wiping operation on each of the KMCY recording heads 52.

Next, the controller changes over the electromagnetic valve 76 to the atmosphere side, and releases (step 24) the cleaning liquid tank 62 to the atmosphere. Next, the controller reduces the pressure in the waste liquid tank 118 and recovers (step 25) the waste liquid to the waste liquid tank 118, and recovers (step 26) the waste liquid of the cap portion of the purge box 106.

Next, the controller changes over the electromagnetic valve 101 to the atmosphere side, and releases (step 27) the waste liquid tank 118 to the atmosphere, and completes the cleaning operation of the recording head 52. For reference, during the pressure feeding operation in the first stage from the step 5-16 and the second stage from the step 17-19, the release of the main tank 54 to the atmosphere is not executed. The reason for this is that the high pressure cleaning liquid or the high pressure air does not counterflow to the tube of the side of the sub-tank 54 at the changeover time of the head-sub-tank electromagnetic valve 56. For reference, the high pressure feeding of the cleaning liquid and the air is carried out while driving the piezo element that is the nozzle drive actuator of the recording head as described in the foregoing, but the embodiment is not particularly limited to the pressure feeding conducted while driving the piezo element with the high frequency drive signal.

In the operation of the second stage of the embodiment, the recording head 52 is caused to shift between the purge position and the capping position in order to shake off any liquid droplet adhered to the under surface of the recording head 52 but the operation of shaking off the liquid droplet is not limited particularly to the foregoing embodiment, and as shown in Fig. 7, the recording head 52 may be vibrated at the purge position, and the liquid droplet may be dropped to the liquid discharge outlet 110.

In the present embodiment, as described in the foregoing, cleaning liquid and air are arranged to be pressure fed alternately to the recording head so that the ink in the recording head and the tube can be effectively peeled off and can be pushed to flow to the outside. For this reason, the consuming quantity of the cleaning liquid is minimized, and the economy is extremely high. Furthermore, during the cleaning, since the operation of vibrating the recording head is set up, any liquid droplet mixed with the ink at the bottom surface of the recording head can be positively dropped to the required location, giving no chance for staining the periphery of the purge box.

The present invention can effectively clean the ink passage including the inside of the recording head.

Claims

Ink jet printer (24) with at least one recording head (52) for discharging ink droplets to a printing or plotting medium (30), wherein the recording head (52) is connected via a tube (53) to an electromagnetic valve (56) so that ink or a cleaning liquid can be selectively supplied through the tube (53) to the recording head (52),
characterized in
that the ink jet printer (24) is constructed such that air and cleaning liquid can be alternately fed under pressure to the recording head (52) through the electromagnetic valve (56) for cleaning the tube (53) and/or the recording head (52).
Ink jet printer according to claim 1, characterized in that the pressure feeding of air and cleaning liquid is alternately carried out about 10 times for 5 seconds each time.
Ink jet printer according to claim 1 or 2, characterized in that when the inside of the recording head (52) is cleaned, high pressure cleaning liquid and high pressure air are alternately fed under pressure to the recording head (52) through the electromagnetic valve (56).
Ink jet printer according to any one of the preceding claims, characterized in that the recording head (52) is driven or arranged to vibrate to shake off any liquid droplet adhered to the bottom surface of the recording head (52) after the operation of the pressure feeding of cleaning liquid and/or air.
Ink jet printer according to any one of the preceding claims, characterized in that a plurality of the recording heads (52) are connected to respective electromagnetic valves (56) by means of tubes (53), and that air and ink and cleaning liquid are selectively supplied to the plurality of the recording heads (52) through the tubes (53), and/or that when the inside of the recording heads (52) is cleaned, the recording heads (52) are preferably respectively shifted over a purge box (106) provided with at least one cap (108) and/or a discharge outlet (110) for covering a liquid outlet and/or nozzles of at least one recording head (52), and the high pressure cleaning liquid and the high pressure air are alternately fed under pressure to at least one recording head (52) through the respective electromagnetic valves (56) and cleaning liquid is discharged to the corresponding cap (108) or outlet (110) from the nozzles of the respective recording head (52), and air is fed under pressure to the respective recording head (52) after the pressure feeding of cleaning liquid in the air, and/or that thereafter the recording heads (52) are vibrated to shake off any liquid droplet mixed with the adhered to the recording heads (52) to the discharge outlet (110).
Method for operating an ink jet printer (24) with at least one recording head (52) which can be cleaned inside by supplying a cleaning liquid,
characterized in
that cleaning liquid and air are alternately supplied to the recording head (52) for cleaning the inside of the recording head (52) and/or of an associated tube (53).