Patent Publication Number: US-7909430-B2

Title: Liquid ejection apparatus and wax gap sealing member

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Japanese Patent Application No. 2006-266475, filed Sep. 29, 2006, the entire subject matter and disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a liquid ejection apparatus such as an inkjet printing apparatus having a plurality of inkjet heads configured to eject ink droplets. 
     2. Description of Related Art 
     A known inkjet printing apparatus includes four inkjet heads arranged adjacently to each other in a direction where a recording sheet is fed, e.g., a sheet feed direction, and a maintenance unit configured to perform maintenance of the inkjet heads. The maintenance unit includes a blade or wiper configured to wipe ink adhering to a nozzle surface, e.g., a liquid ejection surface of each inkjet head. When the maintenance unit is in a purge position, the heads are purged. While the maintenance unit moves from the purge position to a withdrawal position, ink adhering to the nozzle surface during purging is wiped by the blade, and maintenance of the inkjet heads is performed. 
     However, as the four inkjet heads are arranged only adjacently to each other in the inkjet printing apparatus, minute gaps are formed between the nozzle surfaces of the heads. When ink mist and airborne dust in the inkjet printing apparatus and ink adhering to the nozzle surfaces are collected by the blade, they spread in a direction perpendicular to a moving direction of the blade, and ester and remain in the gaps. Ink and foreign matter collected in the gaps may drop down from the gaps. If the in drops down front the gaps during printing, it may soil a recording sheet, and reduce print quality. In addition, if the ink is accumulated in the gaps, ink may be spread onto the nozzle surfaces when the nozzle surfaces are wiped by the blade, and the nozzle surfaces may be soiled, reducing print quality. 
     SUMMARY OF THE INVENTION 
     Aspects of the invention provide an inkjet printing apparatus configured to minimize foreign matter lodged between liquid ejection surfaces of a plurality of liquid ejection heads. 
     In an embodiment of the invention, a liquid ejection apparatus comprises a plurality of liquid ejection heads. Each liquid ejection head comprises a liquid ejection surface formed with a plurality of nozzles, and a particular gap is formed between the plurality of liquid ejection heads. A particular sealing member is disposed in the particular gap, and the particular sealing member forms a particular surface. The particular sealing member joins the liquid ejection surface of at least one of the plurality of liquid ejection heads to an adjacent liquid ejection surface of at least another of the plurality of liquid ejection heads and a wiper is configured to wipe each liquid ejection surface of the plurality of liquid ejection heads and the particular surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention now are described with reference to the accompanying drawings, which are given by way of example only, and are not intended to limit the present invention. 
         FIG. 1  is a schematic cross-sectional view of an inkjet printer according to an embodiment of the invention. 
         FIG. 2  is a schematic plan view of a main part of the inkjet printer according to an embodiment of the invention. 
         FIG. 3  is a cross-sectional view taken along a line III-III of  FIG. 2 . 
         FIG. 4A  is a bottom view of four inkjet heads. 
         FIG. 4B  is a cross-sectional view taken along a line IV-IV of  FIG. 4A . 
         FIG. 5A  illustrates that the inkjet head moves from a printing position to a head maintenance position and a tray of a maintenance unit moves to a maintenance position. 
         FIG. 5B  illustrates that ink adhering to an ink ejection surface is wiped by an ink receiving member and a wiper. 
         FIG. 6A  illustrates that the maintenance unit moves to the maintenance position. 
         FIG. 6B  illustrates that an annular protrusion of a cap is in contact with the ink ejection surface. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention, and their features and advantages, may be understood by referring to accompanying drawings, like numerals being used for corresponding parts in the various drawings. 
     As shown in  FIG. 1 , a liquid ejection apparatus e.g., an inkjet printer  1  may be a color inkjet printer having a plurality of, e.g., four, liquid ejection heads, e.g., inkjet heads  2 . Inkjet printer  1  may be provided with a sheet supply mechanism  11  and a sheet ejection portion  12 . Inkjet printer  1  may be formed with a sheet feed path, in which a recording sheet may be fed from sheet supply mechanism  11  to sheet ejection portion  12 . Sheet supply mechanism  11  may include a pickup roller  22  configured to pick up and feed an uppermost recording sheet of a stack of recording sheets stored in a sheet tray  21 . The recording sheet nay be fed from left to right when inkjet printer  1  is positioned as shown in  FIG. 1 , by the pickup roller  22 . Two belt rollers  6 ,  7 , and an endless conveyor belt  8 , stretched between the belt rollers  6 ,  7 , may be disposed substantially in the sheet feed path. An outer surface of conveyor belt  8 , or a feeding surface  8   a , may be treated with a substance, e.g., silicon, to increase the adhesion of the outer surface. 
     A presser roller  5  may be positioned facing Y conveyer belt  8 , directly downstream of sheet supply mechanism  11 . Presser roller  5  may hold the recording sheet fed from the sheet supply mechanism  11 , down to the feeding surface  8   a  of the conveyor belt  8 . Thus, the recording sheet held down to feeding surface  8   a  may be fed to a downstream side, while being substantially adhered to feeding surface  8   a . At this time, belt roller  6 , disposed on a downstream side with respect to the sheet feed direction, may be driven by a drive force from a drive motor (not shown), causing belt roller  6  to rotate clockwise, e.g., in an arrow direction A in  FIG. 1 . 
     A separation member  13  may be disposed along the sheet feed direction, directly downstream of the conveyor belt  8 . Separation member  13  may be configured to separate the recording sheet held by feeding surface  8   a  of conveyor belt  8  from feeding surface  8   a , and feed the recording sheet to sheet ejection portion  12 . A platen  9 , having a substantially rectangular solid shape, may be disposed in an area enclosed by conveyor belt  8 . Platen  9  may contact a lower surface of conveyor belt  8 , at a position where an upper portion of conveyor belt  8  may face inkjet heads  2 , supporting conveyor belt  8  from its inner circumferential side. 
     Inkjet printer  1  may be a line-type printer. Inkjet heads  2  may correspond to a plurality, e.g., four, colors of ink, such as magenta, yellow, cyan, and black, respectively, and, referring to  FIG. 2 , may be arranged in a line along sheet feed direction B, e.g., a direction from down to up. As shown in  FIG. 2 , inkjet heads  2  may be elongated in a direction perpendicular to sheet feed direction B, and may have a substantially rectangular solid shape. Referring now to  FIGS. 1 and 3 , each inkjet head  2  may include a head body  3  on a bottom end. Head body  3  may be a laminated body, in which a flow path unit and actuators may be bonded. The flow path unit may be formed with ink paths, including pressure chambers, and the actuators may be configured to apply pressure to ink in the pressure chambers. 
     A reservoir unit  10  may be fixed to an upper surface of each head body  3 . Reservoir unit  10  may be partially covered by a cover  14  and may be configured to temporarily store ink. Reservoir unit  10  may be connected to a tube joint  10   a  fixed to an upper surface of the cover  14 . An ink reservoir that may store ink supplied from the tube joint  10   a  may be formed inside. As shown in  FIG. 4A , a number of liquid ejection ports, e.g., minute diameter nozzles  3   b , may be arranged on a bottom surface of each head body  3 . The bottom surface may be an ink ejection surface, e.g., liquid ejection surface  3   a , and may face feeding surface  8   a . Each reservoir unit  10  may be formed longer than head body  3 , with respect to the direction perpendicular to sheet feed direction B. Each reservoir unit  10  may include head fixing portions  10   b  extending toward both ends of head body  3  in the longitudinal direction. Head fixing portions  10   b  may be designed to fix reservoir unit  10  to a frame  4 . Ink in the reservoir unit  10  may be supplied to an ink flow path (not shown) of head body  3 . 
     Head body  3  may be disposed such that ink ejection surface  3   a  is parallel to feeding surface  3   a  of conveyor belt  8 , and such that there may be a small gap between ink ejection surface  3   a  and feeding surface  8   a . The gap may be part of the sheet feed path. With this structure, when the recording sheet fed on conveyor belt  8  passes directly under head bodies  3 , each color of ink is ejected from nozzles  3   b  toward an upper surface, or a print surface, of the recording sheet, thereby forming a desired color image on the recording sheet. 
     Referring to  FIG. 2 , inkjet heads  2  may be arranged adjacently along sheet feed direction B, and may be fixed by frame  4 . Referring again to  FIGS. 3 and 4 , frame  4  may include supporting portions  4   a  extending outward to face head fixing portions  10   b  of reservoir unit  10 . Supporting portions  4   a  and head fixing portions  10   b  of reservoir unit  10  may be fixed by screws  50 . In this manner, inkjet heads  2  may be enclosed by and fixed to the frame  4 . In an embodiment, a surrounding surface, e.g., lower surface  4   d  of frame  4  may be disposed on an imaginary plane extending along ink ejection surfaces  3   a . In other words, ink ejection surfaces  3   a  of inkjet heads  2  may be disposed substantially level, or coplanar, with lower surface  4   d  of frame  4 . Ink ejection surfaces  3   a  also may be exposed from the opening of frame  4 , as shown in  FIG. 3 . 
     As shown in  FIGS. 4A and 4B , minute gaps  3   c  may be formed among the ink ejection surfaces  3   a  in frame  4 . Gaps  3   c  may be filled with sealing members  15 . Sealing members  15  may be disposed so that surface  15   a  of sealing member  15  may be flush with inkjet ejection surfaces  3   a , and surface  15   a  may be in the same plane as inkjet ejection surfaces  3   a . Thus, inkjet ejection surfaces  3   a  may be smoothly wiped by wiper  72 . 
     Minute gaps  4   b  may be formed between the inkjet ejection surfaces  3   a  at each end of frame  4 , in sheet feed direction B, and lower surface  4   d  of frame  4 , extending along the longitudinal direction thereof. Gaps  4   b  may be filled with further sealing members, e.g., sealing members  16 . Minute gaps  4   c  may be formed between ink ejection surfaces  3   a  and supporting portions  4   a . Gaps  4   c  may be filled with further sealing members, e.g., sealing members  17 . Sealing members  16 ,  17  may be disposed so that farther surfaces  16   a ,  17   a , of sealing members  16 ,  17 , may be flush with the inkjet ejection surfaces  3   a  and lower surface  4   d  of frame  4 , and further surfaces  16   a ,  17   a , may be in the same plane as inkjet ejection surfaces  3   a  and lower surface  4   d  of frame  4 . 
     In this manner, sealing members  15 ,  16 ,  17  may be disposed in all gaps  3   c ,  4   b ,  4   c , existing between lower surface  4   d  of frame  4  and ink ejection surfaces  3   a , and among ink ejection surfaces  3   a . Thus, all gaps  3   c ,  4   b ,  4   c  formed between frame  4  and the lower end of head bodies  3 , comprised of four inkjet heads  2 , may be filled, and therefore, removed. 
     In an embodiment, sealing members  15 ,  16 ,  17 , may be made of a wax, e.g., a wax manufactured by Nikka Seiko. Co. Ltd., and may be melted by heating the wax to a temperature of greater than or equal to a temperature at which the wax hardens. In an embodiment of the invention, the wax hardens at temperatures under 40° C. In an embodiment, if inkjet head  2  is out of order, it easily may be replaced with a new inkjet head by melting sealing members  15 ,  16 ,  17 . In an embodiment of the invention, sealing members  15 ,  16 , and  17  do not melt under 40° C. Even if the temperature in inkjet printer  1  rises, the temperature rarely exceeds 40° C., thus the way may not melt during the use of inkjet printer  1 . In another embodiment, the wax may be liquid at room temperature, and may become solidified when an agent, e.g., an organic agent, included in the wax, is volatilized in air. In yet another embodiment, the wax may always be solid at room temperature Wax in the form of a liquid may be filled in a gap using a dispenser. Wax in the form of a solid may be filled in a gap by melting, e.g. by using a heat gun. In an embodiment, sealing members  15 ,  16 ,  17 , may be formed of the same material. In another embodiment, sealing members  15 , and sealing members  16 ,  17 , may be formed of different materials. 
     In an embodiment of the invention, the wax melts between 40° C. and 70° C. For example, when one inkjet head  2  is removed from the frame  4  due to malfunction, the wax may not be heated to greater than or equal to 70° C. Thus, by maintaining a temperature lower than 70° C. electronic components mounted on other inkjet heads  2  have a lower likelihood of failure due to thermal effects. Alternatively, if only the wax surrounding the inkjet head to be replaced is heated, the wax may melt when heated to greater than or equal to 70° C. In this case, heat effect may occur only in electronic parts mounted on the inkjet head to be replaced, and electronic parts mounted on the other inkjet heads may not be affected. Sealing members  15 ,  16 ,  17  may be made of different materials, as long as the material melts when heated to greater than or equal to 40° C. 
     Referring again to  FIGS. 2 and 3 , frame  4  may be supported by a pair of frame moving mechanisms  51  provided in printer  1 , so as to move vertically when the frame is positioned as shown in  FIGS. 2 and 3 . Frame moving mechanisms  51  may be disposed outside inkjet heads  2 , as shown in  FIG. 2 . Each frame moving mechanism  51  may include a drive motor  52  as a drive source to move frame  4  vertically, a pinion gear  53  fixed to a shaft of drive motor  52 , a rack gear  54  disposed uprightly in frame  4 , and configured to mesh with pinion gear  53 , and a guide  56  disposed in a position to hold rack gear  54  with pinion gear  53 . Two drive motors  52  may be disposed facing each other, in sheet feed direction B, and fixed to body frame  1   a  of inkjet printer  1 . Two rack gears  54  may extend vertically, and may be fixed to the periphery of frame  4  at the lower ends of rack gears  54 . Rack gears  54  may slidingly contact guides  56 , on an opposite side from pinion gears  53 , and guides  56  may be fixed to the body frame  1   a . In an embodiment, two drive motors  52  may be synchronized with each other, so as to rotate pinion gears  53  in either a normal or a reverse direction, causing the rack gears  54  move vertically. Along with the vertical movement of rack gears  54 , frame  4  and inkjet heads  2  may move vertically. 
     Guide units  59  may be disposed on both sides of inkjet heads  2  with respect to the longitudinal direction. Each guide unit  59  may include a bar-shaped member  58  positioned between a pair of guides  57 . As shown in  FIG. 3 , in each guide unit  59 , pair of guides  57  may extend vertically, and may be fixed to one of body frames  1   b , facing each other in the direction perpendicular to sheet feed direction B. Bar-shaped member  58  may extend vertically as with the guides  57 , and may be fixed to a side of frame  4  and disposed in parallel with body frame  1   b . Bar-shaped member  58  may be slidingly disposed between pair of guides  57 . Guide units  59  may prevent ink ejection surfaces  3   a  of inkjet heads  2  from including with respect to feeding surface  8   a  when frame  4  is moved vertically by frame moving mechanisms  51 . In other words, ink ejection surfaces  3   a  may be parallel with opposing feeding surface  8   a  even if frame  4  and inkjet heads  2  are moved vertically by frame moving mechanisms  51 . As a result, the accuracy of ink droplets directed toward the recording sheet during printing may be improved. 
     As shown in  FIG. 3 , frame  4  may be disposed in a print position in which inkjet heads  2  may eject ink droplets onto the recording sheet. When performing maintenance of inkjet heads  2 , frame  4  may be moved by frame moving mechanisms  51  to a head maintenance position, where inkjet heads  2  may be disposed above the print position. In an embodiment, maintenance may be performed when a purging operation to forcibly eject ink from inkjet heads  2  may be performed, ink adhering to ink ejection surface  3   a  may be wiped, and ink ejection surfaces  3   a  may be covered with a cap. Maintenance unit  70 , configured to perform maintenance on inkjet heads  2 , may be disposed on the left of inkjet heads  2  in inkjet printer  1  when inkjet printer  1  is positioned as shown in  FIGS. 2 and 3 . Referring again to  FIG. 3 , maintenance unit  70  may include two trays  71 ,  75 , that may be horizontally movable. The tray  71  may have a substantially rectangular box shape, may open upward, and may be configured to hold tray  75  therein. Trays  71 ,  75  may be coupled to each other via engaging devices, and may be configured to be coupled to and removed from each other as needed, e.g., for maintenance. 
     As shown in  FIG. 3 , tray  71  may be open at a side surface opposite from the surface that inkjet heads  2  face. During purging operation, for example, tray  71  may be movable only with tray  75 , held in tray  71 , remaining. Regardless of an engagement condition of the engaging unit, frame  4  may move upward, e.g., in a direction shown by arrow C in  FIG. 3 , to the head maintenance position, so that a space for maintenance unit  70  may be provided between ink ejection surfaces  3   a  and feeding surface  8   a , when maintenance unit  70  moves horizontally. After frame  4  moves upward, maintenance unit  70  may move horizontally, e.g., in a direction shown by arrow D in  FIG. 3 . 
     A waste ink receiving tray  77  may be disposed directly under maintenance unit  70 . Waste ink receiving tray  77  may have a size larger than tray  71  in a plan view, and may have a shape which allows ink receiving tray  77  to overlap an end portion of tray  71 , opposite inkjet heads  2 , even when tray  71  moves to the right end of the inkjet printer, when the inkjet printer is positioned as shown in  FIG. 2 . Waste ink receiving tray  77  may be formed with an ink discharge hole  77   a  at an end close to inkjet heads  2 . Ink discharge hole  77   a  may pass through the bottom surface of waste ink receiving tray  77 . Ink discharge hole  77   a  may allow ink flowing into waste ink receiving tray  77  to flow into a waste ink reservoir (not shown). 
     Tray  71  may include a wiper  72 , an ink receiving member  73 , and tray  75 . Wiper  72 , ink receiving member  73 , and tray  75  may be positioned inside tray  71 , and may be arranged in order, beginning closest to inkjet heads  2 , which may be disposed in parallel with sheet feed direction B. Tray  75  may include inside a plurality, of caps  76 , e.g., four caps  76 . Referring to  FIG. 2 , each cap  76  may have a rectangular plane shape. Referring again to  FIG. 3 , caps  76  may be arranged in association with ink ejection surfaces  3   a  of inkjet heads  2 . Caps  76  may be disposed in parallel to inkjet heads  2  with respect to the longitudinal direction, and at the same intervals of inkjet heads  2  in sheet feed direction B. Each cap  76  may have an annular protrusion  76   a  protruding upward from a bottom portion  76   b . Each cap  76  may be recessed, and may create a hermetically sealed space when annular protrusion  76   a  contacts corresponding ink ejection surface  3   a.    
     Caps  76  may be capable of covering ink ejection surfaces  3   a  in this manner, thus preventing the drying of ink in the nozzles. Caps  76  may be made of an elastic material, e.g., rubber. Thus, ink ejection surfaces  3   a , and annular protrusions  76   a , easily may adhere to each other. This adhesion may allow each cap  76  and corresponding ink ejection surface  3   a , to maintain air tightness in an area enclosed by cap  76  and corresponding ink ejection surface  3   a . In addition, the ink ejection surfaces  3   a  may be prevented from damage. 
     As shown in  FIG. 6B , each cap  76  may be supported at the bottom surface of tray  75  and may be urged upward by a plurality of, e.g., two, springs  88 . Springs  88  may reduce an impactive force generated when annular protrusion  76   a  of cap  76  contacts ink ejection surface  3   a . Springs  88  also may elastically hold cap  76  and ink ejection surface  3   a  by causing annular protrusion  76   a  of cap  76  to contact ink ejection surface  3   a . Even if ink ejection surface  3   a  and cap  76  are not aligned exactly parallel, the cap  76  may be capable of conforming with the inclination of ink ejection surface  3   a . As a result, the area enclosed by cap  76  and ink ejection surface  3   a  may be hermitically sealed. 
     Referring again to  FIG. 2 , a holding member  74  may be fixed to tray  71  at an end closest to inkjet heads  2 , and may have a square bracket shape when viewed in a plan view. Wiper  72  and ink receiving member  73  may be held in holding member  74 , along sheet feed direction B. Engaging, portions, e.g., recessed portion  74   a , may be formed on ends of holding member  74 , extending in the direction perpendicular to sheet feed direction B. 
     As shown in  FIGS. 2 and 3 , ink receiving member  73  may have thin plates  73   a , that may be slightly longer than a total of the widths of four arranged inkjet heads  2 . Thin plates  73   a  may be disposed in parallel to each other, at intervals which permit a capillary action of ink to occur. As with thin plates  73   a , wiper  72  also may be slightly longer than a total of the widths of four arranged inkjet heads  2 , and may be disposed so that its longitudinal direction may be parallel to sheet feed direction B. Wiper  72  may be made of an elastic material, e.g., rubber. 
     Trays  71 ,  75  may be coupled to each other via the engaging devices. The engaging devices may be disposed substantially at the top and bottom ends of trays  71 ,  75 , when trays  71 ,  75  are viewed in a plan view as shown in  FIG. 2 . The engaging devices may include recessed portions  74  provided in holding member  74 , and hook members  83  rotatably supported by tray  75 . Hook members  83  may extend in the direction perpendicular to sheet feed direction B, and may be rotatably supported substantially at their center. Each hook member  83  may include a hook portion  83   a  at an end of hook member  83  closest to the inkjet heads  2 . Hook portion  83   a  may be configured to engage corresponding recessed portion  74   a . Contact members  84  may be rotatably supported by maintenance unit  70 . Contact members  84  may be configured to contact ends  83   b  of hook member  83  located furthest front inkjet heads  2 . When contact members  84  rotate in contact with ends  83   b , hook portions  83   a  may be disengaged from recessed portions  74   a . When contact members  84  separate from ends  83   b , hook portions  83   a  may be engaged with recessed portions  74   a , as shown in  FIG. 3 . 
     When maintenance is not performed, maintenance unit  70  may stand still at a withdrawal position, which may be far from inkjet heads  2 , as shown in  FIGS. 2 and 3 , e.g., in  FIG. 21  the left side, including maintenance unit  70 , does not face inkjet heads  2 . When maintenance may be performed, maintenance unit  70  may move horizontally from the withdrawal position to a maintenance position. At the maintenance position, maintenance unit  70  may face ink ejection surfaces  3   a  of inkjet heads  2 . At this time, as inkjet heads  2  are located in the maintenance position, wiper  72 , and the tips of annular protrusions  76   a  may not contact ink ejection surfaces  3   a . Ink receiving member  73  may be designed to provide a small gap, e.g., 0.5 mm, between ink receiving member  73  and ink ejection surfaces  3   a , with wiper  72  in contact with ink ejection surfaces  3   a.    
     In maintenance, for example, during a purging operation, tray  75  may be left at the withdrawal position, and tray  71  may be moved under the inkjet heads  2  from the withdrawal position to receive discharged ink. When ink ejection surfaces  3   a  may be covered with caps  76 , trays  71 ,  75  may be coupled to each other via the engaging devices, and may be moved to the maintenance position. Trays  71 ,  75  may be movably supported by a pair of guide shafts  96   a ,  96   b  extending in the direction perpendicular to sheet feed direction B, as shown in  FIG. 2 . Tray  71  may be provided with two bearing members  97   a ,  97   b  that protrude from the top and bottom sides of holding member  74 . Tray  75  may be provided with two bearing members  98   a ,  98   b  that may protrude from the top and bottom sides of tray  75 . Guide shafts  96   a ,  96   b  may be fixed to body frames  1   b ,  1   d , at their ends, respectively, and disposed in parallel to each other between frames  1   b ,  1   d . In an embodiment, guide shafts  96   a ,  96   b  may be fixed by a fastening member, e.g., screws. With this configuration, trays  71 ,  75  may be moved along guide shafts  96   a ,  96   b  leftward, in an arrow direction D, as shown in  FIG. 3 . 
     A horizontal moving mechanism  91  may be configured to move trays  71 ,  75  horizontally. As shown in  FIG. 2 , horizontal moving mechanism  91  may include a motor  92 , a motor pulley  93 , an idle pulley  94 , a timing belt  95 , and guide shafts  96   a ,  96   b . Motor  92  may be fixed, e.g. attached to an attaching part  1   c  formed at an end of body frame  1   b  extending parallel to sheet feed direction B. Motor pulley  93  may be connected to motor  92 , and may rotate along with the drive of motor  92 . Idle pulley  94  may be rotatably supported by body frame  1   d , located on the left side when inkjet printer  1  is positioned as shown in  FIG. 2 . Timing belt  95  may be disposed in parallel to guide shaft  96   a , and may be stretched between motor pulley  93  and idle pulley  94 . Timing pulley  95  may be coupled to bearing member  97   a , provided in holding member  74 . 
     With this configuration, when motor  92  may be driven, motor pulley  93  may rotate in a normal or reverse direction, and timing belt  95  may run accordingly. Tray  71  may be connected to timing belt  95  via bearing member  97   a , and may be moved to the withdrawal position or the maintenance position, e.g., to the left or to the right, respectively, when inkjet printer  1  is positioned as shown in  FIG. 2 . When hook portions  83   a  are engaged in recessed portions  74   a  of holding member  74 , wiper  72  and ink receiving member  73  provided in tray  71 , and caps  76  disposed in tray  75  may be moved together to the withdrawal position or to the maintenance position. When hook portions  83   a  are disengaged from recessed portions  74   a , wiper  72  and ink receiving member  74  disposed in tray  71  may be moved to the withdrawal position or to the maintenance position. 
     Operations of the maintenance unit  70  will be described with reference to  FIGS. 5A ,  5 B,  6 A and  6 B. When a purging operation is performed to restore inkjet head  2  when inkjet head  2  has an ejection problem, frame  4  may be moved upward by frame moving mechanisms  51 . At this time, two drive motors  52  may be synchronized with each other so as to rotate pinion gears  53  in the normal direction, e.g., clockwise when pinion gears are arranged as shown in  FIG. 3 . Along the rotation of pinion gears  53 , rack gears  54  may move upward. Frame  4 , which may be fixed to rack gears  54 , may move upward, along with inkjet heads  2 . When frame  4  and inkjet heads  2  arrive at the maintenance position, drive motors  52  may be stopped, thus providing a space for disposing maintenance unit  70  between ink ejection surfaces  3   a  and conveyor belt  8 . Thus, ink ejection surfaces  3   a  of inkjet heads  2  in the maintenance position and the bottom surface of frame  4  may be located at positions which do not contact wiper  72  and the tips of annular protrusions  76   a  when maintenance unit  70  is moved to the maintenance position. 
     Contact members  84  may be brought into contact with ends  83   b  of hook members  83 , so that hook portions  83   a  may be disengaged from recessed portions  74   a , uncoupling trays  71 ,  75 . With trays  71 ,  75  uncoupled, motor  92  of horizontal moving mechanism  91  drives timing belt  95 , and the running of timing belt  95  causes tray  71  to move to the maintenance position. When tray  71  arrives at the maintenance position, as shown in  FIG. 5A , motor  92  may be stopped. A pump (not shown) to force ink in the ink tank (not shown) to flow into inkjet heads  2  may be driven to perform a purging operation, for ejecting ink from nozzles  3   b  of inkjet heads  2  to tray  71 . Due to the purging operation, ejection problems at nozzles  3   b , such as clogging, and increased viscosity of ink may be solved. Ink purged into tray  71  may move along the bottom surface of the tray  71 , e.g., in a leftward direction when tray  71  is positioned as shown in  FIG. 5A , and may flow into waste ink receiving tray  77 . The purged ink may be discharged from ink discharge hole  77   a  of waste ink receiving tray  77 , but the purged ink may partially remain on ink ejection surfaces  3   a , in the form of ink droplets. 
     Inkjet heads  2  may be moved downward by frame moving mechanisms  51 . When tray  71  may be moved to the withdrawal position, e.g., leftward when tray  71  is positioned as shown in  FIG. 5 , inkjet heads  2  may be located in positions where the upper end of wiper  72  is capable of contacting ink ejection surfaces  3   a  and lower surface  4   d  of frame  4 , e.g., a 0.5 mm gap may be formed between ink ejection surfaces  3   a  and thin plates  73   a  of ink receiving member  73 . As shown in  FIG. 5B , tray  71  may be moved leftward, i.e., moved from the maintenance position to the withdrawal position, by horizontal moving mechanism  91 , and wiping is performed. 
     At this time, the upper end of wiper  72  may be located higher than lower surface  4   d  of frame  4 . Thus, wiper  72  may contact lower surface  4   d  of frame  4  and ink ejection surfaces  3   a  while being bent, and wiper  72  may wipe the purged ink adhering to ink ejection surfaces  3   a . The upper ends of thin plates  73   a  of ink receiving member  73  may be located in proximity to ink ejection surfaces  3   a , leaving a minute gap. Thus, relatively large ink droplets adhering to ink ejection surfaces  3   a  may move in between thin plates  73   a  of ink receiving member  73  by capillarity action. Even when wiper  72 , contacting lower, surface  4   d  of frame  4 , passes sealing members  15 ,  16 ,  17 , wiper  72  can wipe ink ejection surfaces  3   a  smoothly because surfaces  15   a ,  16   a ,  17   a  are disposed coplanar with, e.g., in the same plane as, ink ejection surfaces  3   a  and lower surface  4   d  of frame  4 . As sealing members  16 ,  17  may be disposed between frame  4  and ink ejection surfaces  3   a , when wiper  72  moves from frame  4  to ink ejection surfaces  3   a , wiper  72  does not contact a corner of head body  3 , thus reducing the likelihood of damage to wiper  72 . 
     The inkjet heads  2  having ink ejection problems may be restored by purging, and ink adhering to the ink ejection surfaces  3   a  may be wiped. In this manner, maintenance may be finished. As lower surface  4   d  of frame  4  may be level with ink ejection surfaces  3   a , wiper  72  may wipes lower surface  4   d  of frame  4  in addition to ink ejection surfaces  3   a , while tray  71  is moved to the withdrawal position. 
     While printer  1  may be out of action for a prolonged period of time in which printing onto recording sheets is not performed, ink ejection surfaces  3   a  may be covered with caps  76 . Similarly to the above description, inkjet heads  2  may be moved from the print position to the maintenance position by frame moving mechanisms  51 . As shown in  FIG. 6A , trays  71 ,  75  may be moved to the maintenance position by horizontal moving mechanism  91 , with trays  71 ,  75  coupled via hook members  83 . At this time, annular protrusion  76   a  of each cap  76  may be disposed facing a circumference of an area where nozzles  3   b  may be formed on corresponding ink ejection surface  3   a . Referring now to  FIG. 6B , teach inkjet head  2  may be moved downward by frame moving mechanisms  51 , so that the top of annular protrusion  76   a  may be brought into contact with ink ejection surface  3   a , allowing ink ejection surface  3   a  to be hermetically sealed by cap  76 , to prevent drying of ink in nozzles  3   b.    
     According to inkjet printer  1  of an embodiment, as sealing members  15  may be filled in minute gaps  3   c  formed between ink ejection surfaces  3   a , foreign matters, e.g., ink wiped from ink ejection surfaces  3   a  by wiper  72 , ink mist in air, and dust, may be prevented from entering gaps  3   c . If gaps  3   c  are not filled with sealing members  15 , ink may enter gaps  3   c , fall down from gaps  3   c  to the recording sheet, and smudge the recording sheet, or ink may be scraped out from gaps  3   c  by wiper  72  and adhere to ink ejection surfaces  3   a . However, sealing members  15  may reduce the likelihood of these events occurring. 
     According to an embodiment, sealing members  15 ,  16 ,  17  may be made of wax. However, in other embodiments, sealing members  15 ,  16 ,  17  may be made of adhesive and structural members made of resin may be fitted in the gaps  3   c  instead. In other words; frame  4  and sealing members  16 ,  17  may be omitted. If inkjet heads  2  are directly fixed to the printer body, any objects that can fill the gaps to prevent foreign matters may be disposed between ink ejection surfaces  3   a  of inkjet heads  2 . Sealing members  15 ,  16 ,  17  may not be level with ink ejection surfaces  3   a.    
     The above embodiment is an example of the invention that may be applied to an inkjet printer having inkjet heads configured to eject ink from nozzles. However, the invention is not limited to embodiments containing inkjet heads. The invention may be applied to various kinds of liquid jetting apparatuses, having a plurality of liquid jetting heads for multiple applications, e.g., forming fine wiring patterns on a substrate by ejecting conductive paste, making a high-definition display by ejecting organic light emitting member on a substrate, or forming microelectronic devices such as optical waveguides by ejecting optical plastics on a substrate. 
     Although embodiments of the invention have been described in detail herein, the scope of the invention is not limited to these embodiments. It will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the invention. Accordingly, the embodiments disclosed herein are merely exemplary, and are not intended to define the scope of the invention. It is to be understood that the scope of the invention is not to be limited thereby, but is to be determined by the claims which follow.