Patent Publication Number: US-2023138040-A1

Title: Nozzle surface recovery device, liquid discharge device, and inkjet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to  35  U.S.C. §119(a) to Japanese Patent Application No. 2021-178082, filed on Oct. 29, 2021, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present embodiment relates to a nozzle surface recovery device, a liquid discharge device, and an inkjet printer. 
     Related Art 
     An inkjet printer as a liquid discharge apparatus includes a plurality of liquid discharge devices (C, M, Y, and K) that discharge ink while facing a conveyance drum and a conveyance belt that convey a recording medium. These liquid discharge devices each include a plurality of liquid discharge heads constituting a line head, and the nozzle surface of each liquid discharge head is always maintained in a preferable state by a nozzle surface recovery device so that clogging or the like will not occur with the lapse of time. 
     SUMMARY 
     A nozzle surface recovery device includes: a cap configured to cap a nozzle surface of a liquid discharge head; a guide configured to guide the cap in a first direction; and a first position adjuster configured to adjust a position of the cap with respect to the nozzle surface in a second direction orthogonal to the first direction, and the first position adjuster including: a first roller rotatable along the guide to move the cap in the first direction between a capping position at which the cap caps the nozzle surface and a retraction position at which the cap is retracted from the capping position; and a first adjustment plate coupled to the first roller, the first adjustment plate configured to adjust the position of the cap with respect to the guide in the second direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG.  1    is a schematic view of an inkjet printer according to the present embodiment; 
         FIG.  2    is a plan view of a liquid discharge device as viewed from the opposite side of nozzle surfaces; 
         FIG.  3    is a plan view of the liquid discharge device as viewed from the side of the nozzle surfaces; 
         FIG.  4    is a front view of a conveyance drum; 
         FIG.  5 A  is a perspective view of a nozzle surface recovery device; 
         FIG.  5 B  is a simplified plan view of the nozzle surface recovery device; 
         FIG.  5 C  is a simplified front view of the nozzle surface recovery device; 
         FIG.  6 A  is a perspective view of the nozzle surface recovery device moved below the liquid discharge devices; 
         FIG.  6 B  is a front view of the nozzle surface recovery device moved below the liquid discharge devices; 
         FIG.  7 A  is a perspective view of a first position adjuster  300  for rollers to be used in the nozzle surface recovery device; 
         FIG.  7 B  is an exploded perspective view of the first position adjuster  300  for rollers to be used in the nozzle surface recovery device; 
         FIG.  8 A  is a perspective view of a second position adjuster  400  for rollers to be used in the nozzle surface recovery device; 
         FIG.  8 B  is a plan view of the second position adjuster  400  for rollers to be used in the nozzle surface recovery device; 
         FIGS.  9 A and  9 B  are a perspective view and a front view of the liquid discharge devices at lowered positions and the nozzle surface recovery device at a retraction position, respectively; 
         FIGS.  9 C and  9 D  are a perspective view and a front view of the liquid discharge devices at lifted positions and the nozzle surface recovery device at the retraction position, respectively; 
         FIGS.  9 E and  9 F  are a perspective view and a front view of the liquid discharge devices at lifted positions and the nozzle surface recovery device at a capping position, respectively; 
         FIG.  9 G  is a graph illustrating the relationship between the angle of rotation of first adjustment plates and the amount of displacement of first rollers; and 
         FIG.  10    is a perspective view of liquid discharge devices and a nozzle surface recovery device of a comparative example. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. 
     DETAILED DESCRIPTION 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve similar results. 
     Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable. 
     Referring now to the drawings, embodiments of the present disclosure are described below. In the drawings for explaining the following embodiments, the same reference codes are allocated to elements (members or components) having the same function or shape and redundant descriptions thereof are omitted below. 
     Inkjet Printer 
     The following is a description of the present embodiment, with reference to the accompanying drawings.  FIG.  1    is a schematic view of a line-head-type inkjet printer  1  as a liquid discharge apparatus. The inkjet printer  1  includes a feeder  10  that introduces a sheet material P as an application target (a recording medium) to which liquids are to be applied, a pretreatment device  20 , a printer  30 , a dryer  40 , a sheet receiver  50 , and a reversing mechanism  60 . 
     The inkjet printer  1  gives (applies) a pretreatment liquid to the sheet material P conveyed (supplied) from the feeder  10  with the pretreatment device  20 , as necessary. After that, liquids are applied to the sheet material P with the printer  30  to perform required printing. After drying the liquids adhering to the sheet material P with the dryer  40 , the sheet material P is ejected to the sheet receiver  50 . 
     The feeder  10  includes feed trays  11  (a lower feed tray  11 A and an upper feed tray  11 B) that store a plurality of sheet materials P, and feeding devices  12  ( 12 A and  12 B) that separate and feed the sheet materials P one by one from the feed trays  11 . The sheet materials P are supplied from the feeder  10  to the pretreatment device  20 . The pretreatment device  20  includes an applicator  21  that is a treatment liquid applicator that aggregates the coloring material of ink, for example, and applies a treatment liquid having the effect of preventing the ink from bleeding through the sheet, onto the printing surface of the sheet material P. 
     The printer  30  includes a conveyance drum  31  that is a carrying member (a rotating member) that carries the sheet material P on its peripheral surface and rotates, and a droplet discharger  32  that discharges liquids toward the sheet material P being carried by the conveyance drum  31 . The printer  30  also includes a transfer cylinder  34  that receives the sheet material P sent from the pretreatment device  20  and transfers the sheet material P to the conveyance drum  31 , and a transfer cylinder  35  that receives the sheet material P conveyed by the conveyance drum  31  and transfers the sheet material P to the dryer  40 . 
     The sheet material P conveyed from the pretreatment device  20  to the printer  30  is gripped at the top edge by a gripper (a sheet gripper) provided on the transfer cylinder  34 , and is conveyed as the transfer cylinder  34  rotates. The sheet material P conveyed by the transfer cylinder  34  is transferred to the conveyance drum  31  at a position where the sheet material P faces the conveyance drum  31 . 
     A gripper (a sheet gripper) is also provided on the surface of the conveyance drum  31 , and the sheet material P is gripped at the top edge by the gripper (sheet gripper). A plurality of suction holes is dispersedly formed in the surface of the conveyance drum  31 , and a suction airflow directed inward from predetermined suction holes of the conveyance drum  31  is generated by a suction means. The sheet material P transferred from the transfer cylinder  34  to the conveyance drum  31  is then gripped at the top edge by the sheet gripper, and is attracted and carried on the conveyance drum  31  by the suction airflow generated by the suction means. The sheet material P is further conveyed as the conveyance drum  31  rotates. 
     The droplet discharger  32  includes four liquid discharge devices  33  ( 33 A to  33 D) that discharge droplets. The liquid discharge devices  33  ( 33 A to  33 D) are arranged radially, at equal intervals, and symmetrically in  FIG.  1   , along the upper outer periphery of the conveyance drum  31 . 
     The liquid discharge device  33 A can discharge a cyan (C) liquid, the liquid discharge device  33 B can discharge a magenta (M) liquid, the liquid discharge device  33 C can discharge a yellow (Y) liquid, and the liquid discharge device  33 D can discharge a black (K) liquid. It is also possible to use a liquid discharge device that discharges a special liquid such as a white or gold (silver) liquid. 
     A discharge operation of each of the liquid discharge devices  33  of the droplet discharger  32  is controlled by a drive signal corresponding to print information. When the sheet material P carried on the conveyance drum  31  passes through the region facing the droplet discharger  32 , the liquids of the respective colors are discharged from the liquid discharge devices  33 , and an image corresponding to the print information is printed. 
     The sheet material P onto which the liquids have been applied by the droplet discharger  32  is transferred from the conveyance drum  31  to the transfer cylinder  35 , and the sheet material P received by the transfer cylinder  35  is then transferred to a conveyance mechanism  41  and is conveyed to the dryer  40  (a heater). The dryer  40  dries the liquids that have been applied onto the sheet material P by the printer  30 . As a result, the liquid component such as moisture in the liquids evaporates, and the colorants contained in the liquids are fixed onto the sheet material P. Also, curling of the sheet material P is prevented. 
     The reversing mechanism  60  is a mechanism that reverses the sheet material P in a switchback manner when double-sided printing is performed on the sheet material P that has passed through the dryer  40 . The reversed sheet material P is reversely sent to the upstream side of the transfer cylinder  34  through a conveyance path  61  in the printer  30 . 
     The sheet receiver  50  includes a sheet catch tray  51  on which a plurality of sheet materials P is stacked, and a sheet conveyance device  502 . The sheet materials P conveyed through the reversing mechanism  60  are sequentially stacked and stored in a stacker  501 . 
     Liquid Discharge Devices 
     Next, the liquid discharge devices  33  described above are further described.  FIG.  2    is a plan view of a liquid discharge device  33  as viewed from the nozzle surface side.  FIG.  3    is a plan view of the liquid discharge device  33  as viewed from the side opposite to the nozzle surface.  FIG.  4    is a view of a plurality of liquid discharge devices  33  disposed on the outer periphery of the conveyance drum  31 . 
     The liquid discharge device  33  is formed by arranging a plurality of heads  100  that discharge a liquid on a head mounting member  302  in a staggered manner (a line head type). One of the rows of heads  100  arranged in a staggered manner is referred to as a head row  100 A, and the other row is referred to as a head row  100 B. The present embodiment can also be applied in a case where the head mounting member  302  has one head row, instead of a staggered layout of heads. 
     A head  100  includes a plurality of nozzle rows in which a plurality of nozzles  104  that discharge a liquid is arranged (there are two rows herein, but the number of rows is not limited to two). Here, a “liquid discharge head” is a functional component that discharges/jets a liquid from nozzles. The liquid to be discharged is not limited to any particular liquid as long as the liquid has viscosity or surface tension to allow the liquid to be discharged from the head. However, the viscosity of the liquid is preferably not higher than 30 mPa’s at ordinary temperatures and pressures, or by heating or cooling. 
     More specific examples of the liquid include a solution, a suspension, or an emulsion that contains a solvent such as water or an organic solvent, a colorant such as dye or pigment, a functional material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as deoxyribonucleic acid (DNA), amino acid, protein, or calcium, or an edible material such as a natural colorant. 
     Such a solution, a suspension, or an emulsion is used for inkjet ink, a surface treatment solution, a liquid for forming components of an electronic element and a light-emitting element or a resist pattern of an electronic circuit, or a material solution for three-dimensional molding, for example. 
     Examples of the energy source that generates the energy for discharging a liquid include piezoelectric actuators (stacked piezoelectric elements and thin-film piezoelectric elements), thermal actuators that use thermoelectric conversion elements such as heating resistors, and static actuators each including a diaphragm and opposed electrodes. 
     In the present application. a “liquid discharge apparatus” is an apparatus that includes liquid discharge heads or liquid discharge units, and drives the liquid discharge heads to discharge a liquid. Examples of the “liquid discharge apparatus” include not only apparatuses capable of discharging a liquid to a material to which a liquid can adhere, but also apparatuses that discharge a liquid into a gas or into a liquid. 
     The “liquid discharge apparatus” may include means relating to feeding, conveyance, and sheet ejection of a material to which a liquid can adhere, and also include a pretreatment device and a posttreatment device. 
     For example, the “liquid discharge apparatus” may be an image forming apparatus that forms an image on a paper sheet by discharging ink, or a three-dimensional molding apparatus that discharges a molding liquid to a powder layer in which powder materials are formed in layers, so as to mold a three-dimensional object. 
     The “liquid discharge apparatus” is not necessarily an apparatus that discharges a liquid to visualize meaningful images, such as letters or figures. For example, the “liquid discharge apparatus” may be an apparatus that forms meaningless images such as meaningless patterns, or an apparatus that molds three-dimensional images. 
     The above “material to which a liquid can adhere” means a material to which a liquid can adhere at least temporarily, a material to which a liquid adheres and is fixed, or a material into which a liquid adheres and permeates. Specific examples of the “material to which a liquid can adhere” include a recording medium such as a paper sheet, recording paper, a recording sheet of paper, a film, or cloth, an electronic component such as an electronic substrate or a piezoelectric element, and a medium such as layered powder, an organ model, or a testing cell. Examples of the “material to which a liquid can adhere” include any material to which a liquid adheres, unless particularly specified. 
     The above-mentioned “material to which a liquid can adhere” may be any material to which a liquid can temporarily adhere, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, or ceramics. 
     Meanwhile, a “liquid” may be any liquid that has viscosity or surface tension so that the liquid can be discharged from the head. However, the viscosity of the liquid is preferably not greater than 30 mPa·s at ordinary temperatures and pressures, or by heating or cooling. 
     More specific examples of the liquid include a solution, a suspension, or an emulsion that contains a solvent such as water or an organic solvent, a colorant such as dye or pigment, a functional material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as deoxyribonucleic acid (DNA), amino acid, protein, or calcium, or an edible material such as a natural colorant. 
     Such a solution, a suspension, or an emulsion is used for inkjet ink, a surface treatment solution, a liquid for forming components of an electronic element and a light-emitting element or a resist pattern of an electronic circuit, or a material solution for three-dimensional molding, for example. 
     The “liquid discharge apparatus” is an apparatus in which a liquid discharge head and a material to which a liquid can adhere move relative to each other, but is not limited to this. Specific examples of such apparatuses include a serial-type apparatus that moves liquid discharge heads, a line-type apparatus that does not move liquid discharge heads, and the like. 
     Examples of the “liquid discharge apparatus” further include a treatment liquid applying apparatus that discharges a treatment liquid to a sheet to apply the treatment liquid onto a sheet surface so as to reform the sheet surface, and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is discharged through nozzles to granulate fine particles of the raw materials. 
     Nozzle Surface Recovery Device 
     Next, a nozzle surface recovery device  200  according to the present embodiment is described, with reference to  FIGS.  4  to  9   . As illustrated in  FIG.  4   , the nozzle surface recovery device  200  is moved in the axial direction of the conveyance drum  31  (the forward/backward direction in the paper surface of  FIG.  4   ), to be inserted into a gap between the liquid discharge devices  33  and the outer peripheral surface of the conveyance drum  31 . 
     As illustrated in  FIGS.  5 A to  5 C , the nozzle surface recovery device  200  includes an elongated rectangular substrate  210 , a plurality of caps  240  that are attached to and cover (cap) the nozzle surfaces  101  of the liquid discharge devices  33 , and wipers  250  and webs  260  that wipe the nozzles of the liquid discharge devices  33 . 
     The number of the caps  240  provided therein is the same as the number of the nozzle surfaces  101  of the liquid discharge devices  33 . As for the nozzle surfaces  101  of the liquid discharge devices  33 , each head  100  has two adjacent surfaces, the surfaces are arranged at six locations in two rows in a staggered manner as illustrated in  FIG.  3   . Like the nozzle surfaces  101  in the staggered layout, each two caps  240  forms a pair, and the caps  240  are arranged at six locations in two rows in a staggered manner. 
     Each cap  240  is connected to a waste liquid tank via a waste liquid pump. In a state where the caps  240  are attached to and cover the nozzle surfaces  101  of the liquid discharge devices  33 , ink is discharged from the nozzles into the caps  240 , to clean clogging of the nozzles and the like. The discharged ink is sent to the waste liquid tank via the waste liquid pump. 
     The wipers  250  are formed with a pair of right and left elastic plates that vertically stand on the substrate  210 . These wipers  250  are disposed on the front end side of the caps  240  at six locations in two rows. 
     The webs  260  are formed with a pair of right and left non-woven fabric members or the like that are disposed on the substrate  210  and have liquid absorbing properties. These webs  260  are disposed on the front side of the wipers  250 . 
     Both sides (the long sides) of the substrate  210  are bent upward into an L shape, to form a pair of vertical side plates  211 . Both ends of one of the side plates  211  in the longitudinal direction are partially cut and are horizontally extended outward to form bracket portions  212 . 
     First rollers  220  for supporting the nozzle surface recovery device  200  in the height direction are pivotally supported at both longitudinal ends of the right and left side plates  211 . Also, the rotating shafts  231  of second rollers  230  for supporting the nozzle surface recovery device  200  in the transverse direction are pivotally supported by the bracket portions  212  of the one of the side plates  211 . The first rollers  220  and the second rollers  230  form guided members to be guided by guide rails  280  and  290  described later. 
     These first rollers  220  and the second rollers  230  can roll along a pair of right and left guide rails  280  and  290  that are guide members illustrated in  FIGS.  6 A and  6 B . The guide rails  280  and  290  are fixed to the machine frame of the printer  30  illustrated in  FIG.  1   . The longitudinal direction of the guide rails  280  and  290  is parallel to the axial direction of the conveyance drum  31  (the forward/backward direction of the paper surface of  FIG.  4   ). The nozzle surface recovery device  200  can move back and forth along the pair of right and left guide rails  280  and  290 . 
     Specifically, as illustrated in  FIGS.  5 B and  5 C , the first rollers  220  are capable of rolling on the horizontal bottom plate portions of the right and left guide rails  280  and  290  each having an L-shaped cross section, and the second rollers  230  are capable of rolling on the inside surface of the vertical side plate of the guide rail  290  on one side. In  FIGS.  5 B and  5 C , the wipers  250  and the webs  260  are not illustrated. 
     As illustrated in  FIGS.  5 B and  5 C , a plate spring  270  that is in sliding contact with the inside surface  281  of the vertical side plate of the guide rail  280  can be attached to the outside surface of the side plate  211  on the opposite side of the second rollers  230 , as necessary. The top edge of the plate spring  270  pushes the inside surface  28   1  of the vertical side plate of the guide rail  280 , so that the second rollers  230  can be prevented from floating up from the guide rail  290 , regardless of the direction of tilt of the nozzle surface recovery device  200  in  FIG.  4   . 
     When the second rollers  230  of the nozzle surface recovery device  200  are disposed on one side in the direction of gravity as illustrated in  FIGS.  4  and  5   , the second rollers  230  can be pressed against the guide rail  290  by the weight of the nozzle surface recovery device  200 , even without the plate spring  270 . As a result, a positional shift of the caps  240  in a direction that is parallel to the nozzle surfaces  101  of the liquid discharge devices  33  and is perpendicular to the guide rails  280  and  290  can be accurately adjusted by second adjustment plates  232  of a second position adjuster  400  described later. 
     As illustrated in  FIGS.  6 A and  6 B , the nozzle surface recovery device  200  is disposed so that the upper end positions of the caps  240  of the nozzle surface recovery device  200  accurately match the positions of the nozzle surfaces  101  (lower surfaces) of the liquid discharge devices  33  raised in the height direction. Accordingly, the nozzle surface recovery device  200  is moved in an A5 direction in  FIG.  6 A , so that the caps  240  of the nozzle surface recovery device  200  can be attached to and cover the nozzle surfaces  101  of the liquid discharge devices  33  without any gap. The caps  240  and the nozzle surfaces  101  are aligned by first and second position adjuster  400   s  described later. 
     The upper end positions of the wipers  250  and the webs  260  are set slightly higher than the upper end positions of the caps  240 . Accordingly, when the nozzle surface recovery device  200  is moved from the retraction position to the capping position as illustrated in  FIGS.  9 B and  9 C  described later, the webs  260  and the wipers  250  wipe the plurality of nozzle surfaces  101  of the liquid discharge devices  33 . 
     First Position Adjuster  300   
     The positions of the first rollers  220  disposed at the four corners (the front right, rear right, front left, and rear left corners) of the nozzle surface recovery device  200  in  FIGS.  5 A and  5 B  can be adjusted in the height direction (A3 direction) by the first position adjuster  300  as illustrated in  FIGS.  7 A and  7 B . Specifically, an eccentric shaft  220   a  integrally connected to the rotating shaft of a first roller  220  is fitted in a shaft hole  2   11   b  formed in the corresponding side plate  211  of the substrate  210 . The axis of the rotating shaft of the first roller  220  is eccentric with respect to the axis of the eccentric shaft  220   a  by a predetermined distance. 
     The end portion of the eccentric shaft  220   a  on the opposite side of the first roller  220  is cut in a D-like shape, to be rotationally joined to a fan-shaped first adjustment plate  221 . The eccentric shaft  220   a  cut in a D-like shape is then inserted into and joined to a D-shaped shaft hole  221   a  of the first adjustment plate  221 . 
     An arc-like elongated hole  221   b  centered on the shaft hole  221   a  is formed in the arcuate portion of the fan-shaped first adjustment plate  221 . As a fixing screw  222  inserted in this elongated hole  221   b  is screwed into a screw hole  211   c  of the side plate  211 , the rotational position of the first adjustment plate  221  about the eccentric shaft  220   a  can be secured. 
     On the inside surface of the side plate  211 , an arc-like adjustment scale  211   a  is formed by engraving or printing along the arcuate portion of the first adjustment plate  221 . Meanwhile, a triangular mark  221   c  is formed in the arcuate portion of the first adjustment plate  221 , so that the rotational position of the first adjustment plate  221  can be checked with the position indicated by the triangular mark  221   c  on the adjustment scale  211   a . 
     Since the eccentric shaft  220   a  is eccentric with respect to the rotating shaft (the shaft center) of the first roller  220 , the eccentric shaft  220   a  and the first adjustment plate  221  are rotationally moved, so that the height position of the first roller  220  in the A3 direction in  FIG.  7 A  can be checked and adjusted. That is, the first adjustment plates  221  constitute the first position adjuster  300  that moves the first rollers  220  serving as guided member, so as to adjust the relative heights of the nozzle surfaces  101  and the caps  240 . 
     Second Position Adjuster  400   
     The rotating shafts of the second rollers  230  described above can be pivotally supported directly by the bracket portions  212  as described with reference to  FIG.  5 A , but can also be supported so as to be positionally adjustable in a lateral direction (A4 direction) by the second position adjuster  400  having second adjustment plates  232  as illustrated in  FIGS.  8 A and  8 B . Specifically, the second adjustment plates  232  are provided in place of the bracket portions  212  of a side plate  211  of the substrate  210 , and the rotating shafts  231  of the second rollers  230  are pivotally supported by the second adjustment plates  232 . Part of the outer peripheral portion of a second roller  230  protrudes from a cutout portion  211   d  formed in the side plate  211  to the outside of the substrate  210 , and is in contact with the inside surface of the vertical side plate of the guide rail  290 . 
     A second adjustment plate  232  has a pair of elongated holes  232   a  and a linear sloped portion  232   b . Screws  234  are inserted into the pair of elongated holes  232   a  and are fastened to the substrate  210 , so that the second adjustment plate  232  can be secured to the substrate  210 . 
     The sloped portion  232   b  is tilted with respect to the moving direction (a vertical direction in  FIG.  8 B ) of the nozzle surface recovery device  200 . The direction of this tilt may be the reverse. Meanwhile, a pair of guide pins  233  is fixedly disposed on the substrate  210 . The sloped portion  232   b  of the second adjustment plate  232  slides with the pair of guide pins  233  in a state where the screws  234  is loosened, so that the second adjustment plate  232  can move in the direction of the sloped portion  232   b . The guide pins  233  are also referred to as a “plate guide”. 
     An adjustment scale  210   a  is formed by engraving or printing on the surface of the substrate  210  between the pair of guide pins  233 . Meanwhile, a triangular mark  232   c  is formed at the center in the longitudinal direction of the sloped portion  232   b  of the second adjustment plate  232 . 
     The slide position of the second adjustment plate  232  and the position of the second roller  230  in the A4 direction can be checked and adjusted in accordance with the position indicated by this triangular mark  232   c  on the adjustment scale  210   a . That is, the second adjustment plates  232  constitute the second position adjuster  400  that moves the second rollers  230  serving as guided members, so as to adjust a positional shift of the caps  240  in a direction that is parallel to the nozzle surfaces  101  and is perpendicular to the guide rails  280  and  290 . 
     Nozzle Surface Recovery Process 
     The nozzle surface recovery device  200  is designed as described above, and the nozzle surfaces  101  of the liquid discharge devices  33  are recovered (cleaned) with the nozzle surface recovery device  200 . The procedures in the recovery process are as follows. 
     While the inkjet printer  1  is operating (performing printing), the nozzle surface recovery device  200  is located at a retraction position at the ends of the guide rails  280  and  290  as illustrated in  FIGS.  9 A and  9 B . At this retraction position, the nozzle surface recovery device  200  is separated from the gap between the liquid discharge devices  33  and the conveyance drum  31  toward the front side in the axial direction of the conveyance drum  31 . 
     In the state illustrated in  FIGS.  9 A and  9 B , liquids (inks) discharged from the nozzles of the liquid discharge devices  33  are discharged toward a recording medium held on the outer peripheral surface of the conveyance drum  31 , and required printing is performed. The distance between the nozzle surface recovery device  200  at the retraction position and the liquid discharge devices  33  may be the shortest necessary distance to minimize the length of the guide rails  280  and  290 , and miniaturize the nozzle surface recovery device  200 . 
     When the nozzles of the liquid discharge devices  33  are cleaned, the rotation of the conveyance drum  31  is stopped, and the liquid discharge devices  33  are first lifted up (in an A6 direction) by a lifting mechanism as illustrated in  FIGS.  9 C and  9 D . This lifting operation is performed to form a space into which the nozzle surface recovery device  200  can be inserted, between the liquid discharge devices  33  and the outer peripheral surface of the conveyance drum  31 . 
     After the liquid discharge devices  33  are lifted up, the nozzle surface recovery device  200  is moved (slid) forward in an A7 direction toward the space formed between the liquid discharge devices  33  and the outer peripheral surface of the conveyance drum  31 . At this point of time, the distance by which the nozzle surface recovery device  200  is moved forward is substantially the length in the moving direction of the nozzle surface recovery device  200 . During the forward movement of the nozzle surface recovery device  200 , the plurality of nozzle surfaces  101  of the liquid discharge devices  33  can be preliminarily wiped with the webs  260  and the wipers  250 . 
     When the forward movement of the nozzle surface recovery device  200  is completed, the liquid discharge devices  33  are slightly lowered in an A8 direction as illustrated in  FIGS.  9 E and  9 F . As a result, the caps  240  of the nozzle surface recovery device  200  can be attached to and cover the respective nozzle surfaces  101  of the liquid discharge devices  33  without any gap. 
     The nozzle surfaces  101  and the caps  240  may be aligned beforehand by the first position adjuster  300  illustrated in  FIGS.  7 A and  7 B  described above, or by the second position adjuster  400  illustrated in  FIGS.  8 A and  8 B  described above. As the height of the first rollers  220  disposed at the four corners of the nozzle surface recovery device  200  can be adjusted by the first position adjuster  300 , the nozzle surfaces  101  and the caps  240  can be accurately aligned in the height direction. Also, as the second rollers  230  disposed on one side of the nozzle surface recovery device  200  can be laterally moved and adjusted by the second position adjuster  400 , the caps  240  can be accurately aligned in a direction parallel to the nozzle surfaces  101 . 
     When the height of the first rollers  220  is adjusted, it is possible to smoothly adjust the height by taking advantage of the relationship between the angle of rotation of the first adjustment plates  221  and the amount of displacement of the first rollers  220  illustrated in  FIG.  9 G . The relationship between the angle of rotation and the amount of displacement varies depending on the eccentricity of the rotating shafts of the first rollers  220 . As the eccentricity increases, the slope of the curve in  FIG.  9 G  becomes steeper. 
     The straight line portion at the center of the curve in  FIG.  9 G  can be expressed by an approximation equation (the amount of displacement = the angle of ax rotation, “a” being a constant). Accordingly, by forming the adjustment scale  211   a  in the form corresponding to the necessary amount of movement (the amount of displacement) of the first rollers  220 , it is possible to promptly adjust the first rollers  220  to the target amount of movement. Likewise, the adjustment scale  210   a  of the second position adjuster  400  can also be formed in the form corresponding to the necessary amount of movement (the amount of displacement) of the second rollers  230 . 
     In a state where the caps  240  are attached to and cover the nozzle surfaces  101  of the liquid discharge devices  33  as illustrated in (a) and (b) of  FIG.  9 C , the waste liquid pump connected to the caps  240  is operated, and ink is discharged from the nozzles into tire caps  240 . As a result, the nozzle surface recovery (cleaning) process can be performed by sucking excessive ink and foreign matters on the nozzle surfaces  101 . The discharged ink is sent to the waste liquid tank via the waste liquid pump. 
     When the nozzle surface recovery process is completed, the nozzle surface recovery device  200  is retracted to the original retraction position by procedures that are the reverse of the procedures described above. The liquid discharge devices  33  are then lowered as illustrated in  FIG.  9 A , and are set in a printable state. 
     In a case where the inkjet printer  1  is not used for a long period of time, the nozzle surface recovery device  200  is moved forward to the capping position as illustrated in  FIG.  9 C . The caps  240  are then attached to and cover the nozzle surfaces  101  of the liquid discharge devices  33 , to prevent drying of the nozzle surfaces  101 . 
     Although the present embodiment has been specifically described based on embodiments, the present embodiment is not limited to the above, and it is understood that various modifications can be made to it within the scope of the technical idea disclosed in the claims. For example, in the inkjet printer  1  described above, a plurality of heads  100  is arranged in a staggered manner. However, it is also possible to linearly arrange a plurality of heads having a plurality of sloped nozzle rows. 
     In the above embodiment, the first rollers  220  and the second rollers  230  are used as the guided members. However, the guided members are not necessarily rollers, and guide pins or the like may be used. In short, the guided members may be any members that can slide with low friction along tire guide rails  280  and  290  serving as the guide members. 
     Further, the first and second position adjuster  400   s  are not limited to the embodiment illustrated in  FIGS.  7 A to  8 B . For example, the first rollers  220  may be supported by the second adjustment plates  232  as illustrated in  FIGS.  8 A and  8 B , and the second rollers  230  may be supported by the eccentric shafts  220   a  as illustrated in  FIGS.  7 A and  7 B . In this manner, various mechanisms having similar functions can be adopted as the position adjustment mechanisms. 
       FIG.  10    illustrates a state in which a nozzle surface recovery device C according to a comparative example is at the retraction position. This nozzle surface recovery device C is normally retracted to the front side of a conveyance belt B as illustrated in  FIG.  10   . When a recovery process is performed on nozzle surfaces  101 , a liquid discharge device H is lifted up in an A1 direction, and the nozzle surface recovery device C is then slid in an A2 direction to be located (the capping position) below the liquid discharge device H. In this state, the liquid discharge device H is slightly lowered, and the nozzle surfaces  101  of the liquid discharge device H are pressed against caps of the nozzle surface recovery device C. Thus, a recovery process (cleaning) is performed. 
     The nozzle surfaces  101  of the liquid discharge device H are positioned with high accuracy. If the accuracy in positioning the nozzle surface recovery device C at the time of the recovery process is low, on the other hand, capping of the nozzle surfaces  101  becomes incomplete, and the recovery process is hindered. The sliding movement of the nozzle surface recovery device C is caused when pins Pn serving as guided members protruding from a side surface of the nozzle surface recovery device C are guided by a guide groove formed in a guide plate. Therefore, it is difficult to achieve a high accuracy in positioning the nozzle surface recovery device C due to dimension errors between components. 
     Unlike the comparative example, the present embodiment can improve the accuracy in positioning a nozzle surface recovery device by providing position adjustment mechanisms for guided members. 
     Aspect 1 
     A nozzle surface recovery device includes: a cap configured to cap a nozzle surface of a liquid discharge head: a guide configured to guide the cap in a first direction; and a first position adjuster configured to adjust a position of the cap with respect to the nozzle surface in a second direction orthogonal to the first direction, and the first position adjuster including: a first roller rotatable along the guide to move the cap in the first direction between a capping position at which the cap caps the nozzle surface and a retraction position at which the cap is retracted from the capping position; and a first adjustment plate coupled to the first roller, the first adjustment plate configured to adjust the position of the cap with respect to the guide in the second direction. 
     Aspect 2 
     The nozzle surface recovery device according to Aspect 1, further includes: a second position adjuster including: a second roller rotatable along the guide to move the cap in the first direction between the capping position and the retraction position; and a second adjustment plate coupled to the second roller, tire second adjustment plate configured to adjust the position of the cap with respect to the guide in a third direction orthogonal to the first direction and the second direction. 
     Aspect 3 
     In the nozzle surface recovery device according to Aspect 2, the first position adjuster is adjustable a height of the cap with respect to the nozzle surface in the second direction, and the second position adjuster is adjustable a positional shift of the cap with respect to the nozzle surface in the third direction. 
     Aspect 4 
     In the nozzle surface recovery device according to Aspect 3, the first position adjuster includes: an eccentric shaft connecting the first roller and the first adjustment plate, and the first adjustment plate is rotated to rotate the eccentric shaft to adjust the height of the cap with respect to the nozzle surface in the second direction. 
     Aspect 5 
     In the nozzle surface recovery device according to Aspect 4, the first position adjuster has a scale indicating an amount of rotation of the eccentric shaft. 
     Aspect 6 
     In the nozzle surface recovery device according to Aspect 3, the second adjustment plate of the second position adjuster is movable in the first direction to adjust the positional shift of the cap with respect to the nozzle surface in the third direction. 
     Aspect 7 
     In the nozzle surface recovery device according to Aspect 6, the second adjustment plate has a sloped side in sliding contact with a plate guide, and the sloped side of the second adjustment plate is movable along the plate guide in the first direction. 
     Aspect 8 
     In the nozzle surface recovery device according to Aspect 7, the second position adjuster has a scale indicating an amount of movement of the second adjustment plate. 
     Aspect 9 
     The nozzle surface recovery device according to Aspect 3, further includes a substrate on which the cap is mounted, the substrate including side plates on both sides of the substrate in the third direction. The first roller includes multiple rollers, the multiple roller are attached to the side plates of the substrate, and the guide includes two guide rails disposed parallel with each other to guide the multiple rollers in the first direction. 
     Aspect 10 
     In the nozzle surface recovery device according to Aspect 9, further includes: an elastic member configured to push the substrate toward one of the two guide rails in the third direction. The second roller is attached to one of the side plates of the substrate and rotates to move along said one of the two guide rails in the first direction. 
     Aspect 11 
     A liquid discharge device includes: a liquid discharge head configured to discharge a liquid from a nozzle in the nozzle surface: and the nozzle surface recovery device according to Aspect 2. 
     Aspect 12 
     An inkjet printer includes the liquid discharge device according to Aspect 11, and the liquid discharge head includes multiple heads arrayed in a direction orthogonal to each of the first direction and the second direction. 
     Aspect 13 
     The inkjet printer according to Aspect 12, further includes: a drum configured to hold a recording medium on a peripheral surface of the drum and rotate to convey the recording medium, and the nozzle surface recovery device includes multiple nozzle surface recovery devices, and the multiple heads and the multiple nozzle surface recovery devices are radially disposed to face an outer periphery of the drum. 
     Aspect 14 
     In the inkjet printer according to Aspect 13, the second roller is disposed on one side in a direction of gravity of the plurality of the nozzle surface recovery devices arranged radially. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the above teachings, the present disclosure may be practiced otherwise than as specifically described herein. With some embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present disclosure and appended claims, and all such modifications are intended to be included within the scope of the present disclosure and appended claims.